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Sample records for release rates based

  1. Relationship among reaction rate, release rate and efficiency of nanomachine-based targeted drug delivery.

    Science.gov (United States)

    Zhao, Qingying; Li, Min; Luo, Jun

    2017-12-04

    In nanomachine applications towards targeted drug delivery, drug molecules released by nanomachines propagate and chemically react with tumor cells in aqueous environment. If the nanomachines release drug molecules faster than the tumor cells react, it will result in loss and waste of drug molecules. It is a potential issue associated with the relationship among reaction rate, release rate and efficiency. This paper aims to investigate the relationship among reaction rate, release rate and efficiency based on two drug reception models. We expect to pave a way for designing a control method of drug release. We adopted two analytical methods that one is drug reception process based on collision with tumors and another is based on Michaelis Menten enzymatic kinetics. To evaluate the analytical formulations, we used the well-known simulation framework N3Sim to establish simulations. The analytical results of the relationship among reaction rate, release rate and efficiency is obtained, which match well with the numerical simulation results in a 3-D environment. Based upon two drug reception models, the results of this paper would be beneficial for designing a control method of nanomahine-based drug release.

  2. Release rate of diazinon from microcapsule based on melamine formaldehyde

    Science.gov (United States)

    Noviana Utami C., S.; Rochmadi

    2018-04-01

    The microcapsule containing diazinon as the core material and melamine formaldehyde as the membrane material have been synthesized by in situ polymerization method. The microcapsule membrane in this research is melamine formaldehyde (MF). This research aims to study the effect of pH and temperature on the release rate of diazinon from microcapsule based on melamine formaldehyde in aqueous medium. The results showed that pH and temperature has little effect on the release rate of diazinon from microcapsule based on melamine formaldehyde. This is due to the diffusion through the microcapsule membrane is not influenced by the pH and temperature of the solution outside of microcapsule.

  3. Diffusion rates for elevated releases

    International Nuclear Information System (INIS)

    Ramsdell, J.V.

    1983-11-01

    A search of the literature related to diffusion from elevated sources has determined that an adequate data base exists for use in developing parameterizations for estimating diffusion rates for material released from free standing stacks at nuclear power plants. A review of published data analyses indicates that a new parameterization of horizontal diffusion rates specifically for elevated releases is not likely to significantly change the magnitudes of horizontal diffusion coefficients on the average. However, the uncertainties associated with horizontal diffusion coefficient estimates under any given set of atmospheric conditions could be reduced by a new parameterization. Similarly, a new parameterization of vertical diffusion rates would be unlikely to significantly alter the magnitudes of diffusion coefficients for unstable atmospheric conditons. However, for neutral and stable atmospheric conditions, a new parameterization of vertical diffusion rates might increase vertical diffusion coefficients significantly. The increase would move ground-level time-integrated concentration maxima closer to the plant and would increase the maxima. 55 references, 2 figures, 4 tables

  4. The surface-forming energy release rate versus the local energy release rate

    OpenAIRE

    Xiao, Si; Wang, He-ling; Landis, Chad M; Hwang, Keh-Chih; Liu, Bin

    2016-01-01

    This paper identifies two ways to extract the energy (or power) flowing into a crack tip during propagation based on the power balance of areas enclosed by a stationary contour and a comoving contour. It is very interesting to find a contradiction that two corresponding energy release rates (ERRs), a surface-forming ERR and a local ERR, are different when stress singularity exists at a crack tip. Besides a rigorous mathematical interpretation, we deduce that the stress singularity leads to an...

  5. An atomistic methodology of energy release rate for graphene at nanoscale

    International Nuclear Information System (INIS)

    Zhang, Zhen; Lee, James D.; Wang, Xianqiao

    2014-01-01

    Graphene is a single layer of carbon atoms packed into a honeycomb architecture, serving as a fundamental building block for electric devices. Understanding the fracture mechanism of graphene under various conditions is crucial for tailoring the electrical and mechanical properties of graphene-based devices at atomic scale. Although most of the fracture mechanics concepts, such as stress intensity factors, are not applicable in molecular dynamics simulation, energy release rate still remains to be a feasible and crucial physical quantity to characterize the fracture mechanical property of materials at nanoscale. This work introduces an atomistic simulation methodology, based on the energy release rate, as a tool to unveil the fracture mechanism of graphene at nanoscale. This methodology can be easily extended to any atomistic material system. We have investigated both opening mode and mixed mode at different temperatures. Simulation results show that the critical energy release rate of graphene is independent of initial crack length at low temperature. Graphene with inclined pre-crack possesses higher fracture strength and fracture deformation but smaller critical energy release rate compared with the graphene with vertical pre-crack. Owing to its anisotropy, graphene with armchair chirality always has greater critical energy release rate than graphene with zigzag chirality. The increase of temperature leads to the reduction of fracture strength, fracture deformation, and the critical energy release rate of graphene. Also, higher temperature brings higher randomness of energy release rate of graphene under a variety of predefined crack lengths. The energy release rate is independent of the strain rate as long as the strain rate is small enough

  6. Radionuclide release rate inversion of nuclear accidents in nuclear facility based on Kalman filter

    International Nuclear Information System (INIS)

    Tang Xiuhuan; Bao Lihong; Li Hua; Wan Junsheng

    2014-01-01

    The rapidly and continually back-calculating source term is important for nuclear emergency response. The Gaussian multi-puff atmospheric dispersion model was used to produce regional environment monitoring data virtually, and then a Kalman filter was designed to inverse radionuclide release rate of nuclear accidents in nuclear facility and the release rate tracking in real time was achieved. The results show that the Kalman filter combined with Gaussian multi-puff atmospheric dispersion model can successfully track the virtually stable, linear or nonlinear release rate after being iterated about 10 times. The standard error of inversion results increases with the true value. Meanwhile extended Kalman filter cannot inverse the height parameter of accident release as interceptive error is too large to converge. Kalman filter constructed from environment monitoring data and Gaussian multi-puff atmospheric dispersion model can be applied to source inversion in nuclear accident which is characterized by static height and position, short and continual release in nuclear facility. Hence it turns out to be an alternative source inversion method in nuclear emergency response. (authors)

  7. Silica-Based and Borate-Based, Titania-Containing Bioactive Coatings Characterization: Critical Strain Energy Release Rate, Residual Stresses, Hardness, and Thermal Expansion

    Directory of Open Access Journals (Sweden)

    Omar Rodriguez

    2016-12-01

    Full Text Available Silica-based and borate-based glass series, with increasing amounts of TiO2 incorporated, are characterized in terms of their mechanical properties relevant to their use as metallic coating materials. It is observed that borate-based glasses exhibit CTE (Coefficient of Thermal Expansion closer to the substrate’s (Ti6Al4V CTE, translating into higher mode I critical strain energy release rates of glasses and compressive residual stresses and strains at the coating/substrate interface, outperforming the silica-based glasses counterparts. An increase in the content of TiO2 in the glasses results in an increase in the mode I critical strain energy release rate for both the bulk glass and for the coating/substrate system, proving that the addition of TiO2 to the glass structure enhances its toughness, while decreasing its bulk hardness. Borate-based glass BRT3, with 15 mol % TiO2 incorporated, exhibits superior properties overall compared to the other proposed glasses in this work, as well as 45S5 Bioglass® and Pyrex.

  8. Development of polymer film dosage forms of lidocaine for buccal administration. I. Penetration rate and release rate.

    Science.gov (United States)

    Okamoto, H; Taguchi, H; Iida, K; Danjo, K

    2001-12-13

    We examined the penetration rate of lidocaine (LC) through excised oral mucosa from hamster cheek pouch and the in vitro release rate of LC from film dosage forms with hydroxypropylcellulose (HPC) as a film base. Addition of glycyrrhizic acid (GL) to the HPC films increased the LC release rate almost GL-content-dependently, while an optimum GL content was observed for the LC penetration rate. No LC penetration was observed from an acidic aqueous solution (pH 3.4) of LC, suggesting only unionized LC can substantially penetrate through the mucosa. A significant relationship between the penetration rate of LC and the release rate of unionized LC was found, suggesting that the in vitro dissolution study is a useful tool to predict the penetration rate taking the unionized drug fraction into consideration.

  9. Heat release rate of wood-plastic composites

    Science.gov (United States)

    N. M. Stark; R. H. White; C. M. Clemons

    1997-01-01

    Wood-plastic composites are becoming more important as a material that fulfills recycling needs. In this study, fire performance tests were conducted on several compositions of wood and plastic materials using the Ohio State University rate of heat release apparatus. Test results included five-minute average heat release rate in kW/m2 (HRR avg) and maximum heat release...

  10. Hindered disulfide bonds to regulate release rate of model drug from mesoporous silica.

    Science.gov (United States)

    Nadrah, Peter; Maver, Uroš; Jemec, Anita; Tišler, Tatjana; Bele, Marjan; Dražić, Goran; Benčina, Mojca; Pintar, Albin; Planinšek, Odon; Gaberšček, Miran

    2013-05-01

    With the advancement of drug delivery systems based on mesoporous silica nanoparticles (MSNs), a simple and efficient method regulating the drug release kinetics is needed. We developed redox-responsive release systems with three levels of hindrance around the disulfide bond. A model drug (rhodamine B dye) was loaded into MSNs' mesoporous voids. The pore opening was capped with β-cyclodextrin in order to prevent leakage of drug. Indeed, in absence of a reducing agent the systems exhibited little leakage, while the addition of dithiothreitol cleaved the disulfide bonds and enabled the release of cargo. The release rate and the amount of released dye were tuned by the level of hindrance around disulfide bonds, with the increased hindrance causing a decrease in the release rate as well as in the amount of released drug. Thus, we demonstrated the ability of the present mesoporous systems to intrinsically control the release rate and the amount of the released cargo by only minor structural variations. Furthermore, an in vivo experiment on zebrafish confirmed that the present model delivery system is nonteratogenic.

  11. In situ release rates of Cu and Zn from commercial antifouling paints at different salinities.

    Science.gov (United States)

    Lagerström, Maria; Lindgren, J Fredrik; Holmqvist, Albin; Dahlström, Mia; Ytreberg, Erik

    2018-02-01

    Antifouling paints are environmentally risk assessed based on their biocidal release rates to the water phase. In situ release rates of copper (Cu) and zinc (Zn) were derived for five commercial paints in two recreational marinas with different salinities (5 and 14 PSU) using an X-Ray Fluorescence spectrometer (XRF). Salinity was found to significantly affect the Cu release, with twice the amount of Cu released at the higher salinity, while its influence on the Zn release was paint-specific. Site-specific release rates for water bodies with salinity gradients, e.g. the Baltic Sea, are therefore necessary for more realistic risk assessments of antifouling paints. Furthermore, the in situ release rates were up to 8 times higher than those generated using standardized laboratory or calculation methods. The environmental risk assessment repeated with the field release rates concludes that it is questionable whether the studied products should be allowed on the Swedish market. Copyright © 2017 The Authors. Published by Elsevier Ltd.. All rights reserved.

  12. Research on release rate of volatile organic compounds in typical vessel cabin

    Directory of Open Access Journals (Sweden)

    ZHANG Jinlan

    2018-02-01

    Full Text Available [Objectives] Volatile Organic Compounds (VOC should be efficiently controlled in vessel cabins to ensure the crew's health and navigation safety. As an important parameter, research on release rate of VOCs in cabins is required. [Methods] This paper develops a method to investigate this parameter of a ship's cabin based on methods used in other closed indoor environments. A typical vessel cabin is sampled with Tenax TA tubes and analyzed by Automated Thermal Desorption-Gas Chromatography-Mass Spectrometry (ATD-GC/MS. The lumped mode is used and the release rate of Benzene, Toluene, Ethylbenzene and Xylene (BTEX, the typical representatives of VOCs, is obtained both in closed and ventilated conditions. [Results] The results show that the content of xylene and Total Volatile Organic Compounds (TVOC exceed the indoor environment standards in ventilated conditions. The BTEX release rate is similar in both conditions except for the benzene. [Conclusions] This research builds a method to measure the release rate of VOCs, providing references for pollution character evaluation and ventilation and purification system design.

  13. Influence of the ionic character of a drug on its release rate from hydrogels based on 2-hydroxyethylmethacrylate and acrylamide synthesized by photopolymerization

    Directory of Open Access Journals (Sweden)

    M. L. Gomez

    2012-03-01

    Full Text Available The influence of the ionic character of a specific drug on its release rate from a hydrogel based on 2-hydroxyethylmethacrylate (HEMA and acrylamide (AAm is analyzed. The hydrogel was synthesized by photopolymerization employing visible light, safranine O (Saf, as sensitizer, and a silsesquioxane functionalized with amine and methacrylate groups (SFMA, as co-initiator and crosslinker. Safranine O (Saf was employed as a model of a cationic drug and the anionic form of resorufin (Rf as a model of an anionic drug. Saf exhibited a larger affinity with functional groups of the hydrogel than that of Rf. This produced a lower loading and a faster release rate of Rf with respect to Saf. Besides, the release rate of Rf followed a Fickian behavior, while that of Saf exhibited a non-Fickian behavior. By hydrolyzing the hydrogel at pH = 13, amide groups supplied by AAm were irreversibly converted into carboxylic acid groups. Higher loadings and slower release rates of Saf from the hydrolyzed hydrogels were observed, making them particularly suitable for the slow drug-delivery of cationic drugs.

  14. A unified model of hydride cracking based on elasto-plastic energy release rate over a finite crack extension

    International Nuclear Information System (INIS)

    Zheng, X.J.; Metzger, D.R.; Sauve, R.G.

    1995-01-01

    A fracture criterion based on energy balance is proposed for elasto-plastic cracking at hydrides in zirconium, assuming a finite length of crack advance. The proposed elasto-plastic energy release rate is applied to the crack initiation at hydrides in smooth and notched surfaces, as well as the subsequent delayed hydride cracking (DHC) considering limited crack-tip plasticity. For a smooth or notched surface of an elastic body, the fracture parameter is related to the stress intensity factor for the initiated crack. For DHC, a unique curve relates the non-dimensionalized elasto-plastic energy release rate with the length of crack extension relative to the plastic zone size. This fracture criterion explains experimental observations concerning DHC in a qualitative manner. Quantitative comparison with experiments is made for fracture toughness and DHC tests on specimens containing certain hydride structures; very good agreement is obtained. ((orig.))

  15. H2S release rate assessment guidelines and audit forms

    International Nuclear Information System (INIS)

    Johnson, S.; Wilson, T.; Long, R.; Shewan, K.; Nchkalo, H.; Nelson, R.; Morand, M.

    1998-01-01

    Development of a process to evaluate and calculate potential hydrogen sulfide release has been recommended by the Canadian Association of Petroleum Producers' Drilling and Completion Committee, and the Alberta Energy and Utilities Board. To facilitate the process, CAPP has released guidelines describing a methodology and standard for the industry to calculate the potential hydrogen sulfide release rates of a well, and a standardized format for the documentation and retention of data. The Guidelines describe a four-step process, with each step having an increasing degree of complexity. Step One describes the zone hydrogen sulfide exclusion area maps, defining when reporting is to be used (based on well location and distance from inhabited areas). Step Two provides details of the recommended method for determining hydrogen sulfide release through a data search process. Step Three consists of a series of instructions in the use of geologic analogs, data editing and wellbore design to further refine the cumulative hydrogen sulfide release rate. Step Four contains information designed to assist in detailed geological and reservoir modeling. It is not necessary to use all four steps in all cases. The user, however, is advised to use sound engineering judgement and due diligence in the calculation decisions. Sample calculations are provided for a variety of different situations. Measurement techniques are described in an appendix. A completed example of an audit form is attached. 10 + 6 refs., tabs

  16. Translational and extensional energy release rates (the J- and M-integrals) for a crack layer in thermoelasticity

    Science.gov (United States)

    Chudnovsky, A.; Gommerstadt, B.

    1985-01-01

    A number of papers have been presented on the evaluation of energy release rate for thermoelasticity and corresponding J integral. Two main approaches were developed to treat energy release rate in elasticity. The first is based on direct calculation of the potential energy rate with respect to crack length. The second makes use of Lagrangian formalism. The translational and expansional energy release rates in thermoelasticity are studied by employing the formalism of irreversible thermodynamics and the Crack Layer Approach.

  17. Release rates from waste packages in a salt repository

    International Nuclear Information System (INIS)

    Chambre, P.L.; Hwang, Y.; Lee, W.W.L.; Pigford, T.H.

    1987-06-01

    In this report we present estimates of radionuclide release rates from waste packages into salt. This conservative and bounding analysis shows that release rates from waste packages in salt are well below the US Nuclear Regulatory Commission's performance objectives for the engineered barrier system. 2 refs., 2 figs

  18. Comparison of the Heat Release Rate from the Mass Loss Calorimeter to the Cone Calorimeter for Wood-based Materials

    Science.gov (United States)

    Laura E. Hasburgh; Robert H. White; Mark A. Dietenberger; Charles R. Boardman

    2015-01-01

    There is a growing demand for material properties to be used as inputs in fi re behavior models designed to address building fire safety. This comparative study evaluates using the mass loss calorimeter as an alternative to the cone calorimeter for obtaining heat release rates of wood-based materials. For this study, a modified mass loss calorimeter utilized an...

  19. Heat release rate from the combustion of uranium

    International Nuclear Information System (INIS)

    Solbrig, C.W.

    1995-01-01

    Fuel treatment is planned at the Argonne National Laboratory on EBR-II spent fuel. The electrochemical treatment process is carried out in a cell with an argon atmosphere to prevent any reaction. The amount of fuel processed at any time is limited by the amount of energy which could be released by metal combustion if air is inadvertently allowed into the cell since the heat release would increase the cell pressure. The cell pressure is required to be below atmospheric even if combustion occurs to ensure no cell gas/aerosol is released to the environment. Metal fires can release large amounts of heat. In certain configurations such as fine particulate, metal can be pyrophoric at room temperature. When the metal is a nuclear fuel, it is important to be able to predict the reaction/heat release rate if the metal is inadvertently exposed to air. A realistic combustion model is needed to predict heat release rates for the many different flow and transport configurations which exist in the various fuel processing steps. A model for the combustion of uranium is developed here which compares satisfactorily to experimental data

  20. Determination of the sterile release rate for stopping growing age-structured populations

    International Nuclear Information System (INIS)

    Barclay, Hugh John

    2016-01-01

    A freely-growing age-structured population was modelled for growth and control by sterile male releases. Equilibrium populations yield critical sterile male release rates that would hold the population at equilibrium. It is shown here that these rates may be different from the release rates required to stop a growing population and bring it to an equilibrium. A computer simulation was constructed of this population and a parameter sensitivity analysis graphed the effects on the required sterile male release rate of fertility, mating delay in adult females, net juvenile survivorship, three adult survivorship curves, the time spent in the juvenile stages, and total life span. The adult survivorship curves had the greatest effect on the required sterile release rate for population elimination. The required release rate was also determined for Ceratitis capitata (Wiedemann) using survivorship and fertility data from a laboratory strain. The concepts of over-flooding ratio and release ratio were discussed and quantified for the cases above. (author)

  1. Fracture patterns and the energy release rate of phosphorene.

    Science.gov (United States)

    Liu, Ning; Hong, Jiawang; Pidaparti, Ramana; Wang, Xianqiao

    2016-03-14

    Phosphorene, also known as monolayer black phosphorus, has been enjoying popularity in electronic devices due to its superior electrical properties. However, it's relatively low Young's modulus, low fracture strength and susceptibility to structural failure have limited its application in mechanical devices. Therefore, in order to design more mechanically reliable devices that utilize phosphorene, it is necessary to explore the fracture patterns and energy release rate of phosphorene. In this study, molecular dynamics simulations are performed to investigate phosphorene's fracture mechanism. The results indicate that fracture under uniaxial tension along the armchair direction is attributed to a break in the interlayer bond angles, while failure in the zigzag direction is triggered by the break in both intra-layer angles and bonds. Furthermore, we developed a modified Griffith criterion to analyze the energy release rate of phosphorene and its dependence on the strain rates and orientations of cracks. Simulation results indicate that phosphorene's energy release rate remains almost unchanged in the armchair direction while it fluctuates intensively in the zigzag direction. Additionally, the strain rate was found to play a negligible role in the energy release rate. The geometrical factor α in the Griffith's criterion is almost constant when the crack orientation is smaller than 45 degree, regardless of the crack orientation and loading direction. Overall, these findings provide helpful insights into the mechanical properties and failure behavior of phosphorene.

  2. Radionuclide release rates from spent fuel for performance assessment modeling

    International Nuclear Information System (INIS)

    Curtis, D.B.

    1994-01-01

    In a scenario of aqueous transport from a high-level radioactive waste repository, the concentration of radionuclides in water in contact with the waste constitutes the source term for transport models, and as such represents a fundamental component of all performance assessment models. Many laboratory experiments have been done to characterize release rates and understand processes influencing radionuclide release rates from irradiated nuclear fuel. Natural analogues of these waste forms have been studied to obtain information regarding the long-term stability of potential waste forms in complex natural systems. This information from diverse sources must be brought together to develop and defend methods used to define source terms for performance assessment models. In this manuscript examples of measures of radionuclide release rates from spent nuclear fuel or analogues of nuclear fuel are presented. Each example represents a very different approach to obtaining a numerical measure and each has its limitations. There is no way to obtain an unambiguous measure of this or any parameter used in performance assessment codes for evaluating the effects of processes operative over many millennia. The examples are intended to suggest by example that in the absence of the ability to evaluate accuracy and precision, consistency of a broadly based set of data can be used as circumstantial evidence to defend the choice of parameters used in performance assessments

  3. Radioisotopic composition of yellowcake: an estimation of stack release rates

    International Nuclear Information System (INIS)

    Momeni, M.H.; Kisieleski, W.E.; Rayno, D.R.; Sabau, C.S.

    1979-12-01

    Uranium concentrate (yellowcake) composites from four mills (Anaconda, Kerr-McGee, Highland, and Uravan) were analyzed for U-238, U-235, U-234, Th-230, Ra-226, and Pb-210. The ratio of specific activities of U-238 to U-234 in the composites suggested that secular radioactive equilibrium exists in the ore. The average activity ratios in the yellowcake were determined to be 2.7 x 10 -3 (Th-230/U-238), 5 x 10 -4 (Ra-226/U-238) and 2 x 10 -4 (Pb-210/U-238). Based on earlier EPA measurements of the release rates from the stacks, the amount of yellowcake released was determined to be 0.1% of the amount processed

  4. A new method for calculating energy release rate in tunnel excavation subjected to high in situ stress

    Directory of Open Access Journals (Sweden)

    Xiao Qinghua

    2016-03-01

    Full Text Available Based on energy theory, energy release rate (EER and local energy release rate (LEER, a new index called FERR (Fractional Energy Release Rate is proposed, and this method can not only evaluate the risk of rock burst, but also can point out the location of high risk and the scale of rockburst. The FERR index is applied to the TBM assembling tunnel in Jinping Hydro Power Station II to evaluate the scale and intensity of rockburst, as well as the location where rockburst occurs. With FDM method adopted, the energy release rate of 3 excavation plans are calculated and the scale and risk of rockburst is evaluated, and the location of high risk of rockburst is also mapped. With FERR used in the evaluation, the rockburst is nicely controlled which ensured the safety and construction schedule of the project.

  5. Controlling Object Heat Release Rate using Geometrical Features

    OpenAIRE

    Kraft, Stefan Marc

    2017-01-01

    An experimental study was conducted to determine the effect of complex geometries on the burning rate of materials made using additive manufacturing. Controlling heat release rate has applicability in limiting fire hazards as well as for designing fuels for optimal burning rate. The burning rate of a structure is a function of the material properties as well as the airflow through it, which is dictated by the geometry. This burning rate is generally proportional to the porosity for obj...

  6. Measurement of semiochemical release rates with a dedicated environmental control system

    Science.gov (United States)

    Heping Zhu; Harold W. Thistle; Christopher M. Ranger; Hongping Zhou; Brian L. Strom

    2015-01-01

    Insect semiochemical dispensers are commonly deployed under variable environmental conditions over a specified period. Predictions of their longevity are hampered by a lack of methods to accurately monitor and predict how primary variables affect semiochemical release rate. A system was constructed to precisely determine semiochemical release rates under...

  7. Swelling, erosion and drug release characteristics of salbutamol sulfate from hydroxypropyl methylcellulose-based matrix tablets.

    Science.gov (United States)

    Chaibva, Faith A; Khamanga, Sandile M M; Walker, Roderick B

    2010-12-01

    Hydrophilic matrix formulations are important and simple technologies that are used to manufacture sustained release dosage forms. Hydroxypropyl methylcellulose-based matrix tablets, with and without additives, were manufactured to investigate the rate of hydration, rate of erosion, and rate and mechanism of drug release. Scanning electron microscopy was used to assess changes in the microstructure of the tablets during drug release testing and whether these changes could be related to the rate of drug release from the formulations. The results revealed that the rate of hydration and erosion was dependent on the polymer combination(s) used, which in turn affected the rate and mechanism of drug release from these formulations. It was also apparent that changes in the microstructure of matrix tablets could be related to the different rates of drug release that were observed from the test formulations. The use of scanning electron microscopy provides useful information to further understand drug release mechanisms from matrix tablets.

  8. Release rates of soluble species at Yucca Mountain

    International Nuclear Information System (INIS)

    Lee, W.W.-L.; Pigford, T.H.

    1989-02-01

    Experimental leaching of spent fuel shows that some fission product species are preferentially released upon contact with water. We analyze the conservative case of bare spent fuel in contact with saturated tuff using diffusional mass transfer analysis. For the parameter values used, the USNRC release rate limit is not exceeded, except for 99 Tc. The presence of a container and the distribution of water contact over time will assist in meeting this criterion. 6 figs., 2 tabs

  9. Phenazopyridine-phthalimide nano-cocrystal: Release rate and oral bioavailability enhancement.

    Science.gov (United States)

    Huang, Yu; Li, Jin-Mei; Lai, Zhi-Hui; Wu, Jun; Lu, Tong-Bu; Chen, Jia-Mei

    2017-11-15

    Both cocrystal and nanocrystal technologies have been widely used in the pharmaceutical development for poorly soluble drugs. However, the synergistic effects due to the integration of these two technologies have not been well investigated. The aim of this study is to develop a nano-sized cocrystal of phenazopyridine (PAP) with phthalimide (PI) to enhance the release rate and oral bioavailability of PAP. A PAP-PI nano-cocrystal with particle diameter of 21.4±0.1nm was successfully prepared via a sonochemical approach and characterized by powder X-ray diffraction (PXRD), differential scanning calorimetry (DSC), scanning electron microscopy (SEM) and dynamic light scattering (DLS) analysis. An in vitro release study revealed a significant release rate enhancement for PAP-PI nano-cocrystal as compared to PAP-PI cocrystal and PAP hydrochloride salt. Further, a comparative oral bioavailability study in rats indicated significant improvement in C max and oral bioavailability (AUC 0-∞ ) by 1.39- and 2.44-fold, respectively. This study demonstrated that this novel nano-cocrystal technology can be a new promising option to improve release rate and absorption of poorly soluble compounds in the pharmaceutical industry. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Short-term Outcomes following Concussion in the NFL: An 11-year Retrospective Study of Player Release Rate and Financial Loss

    Science.gov (United States)

    Ramkumar, Prem; Navarro, Sergio Michael

    2017-01-01

    Objectives: The primary goal of this study was to assess the short-term outcomes among National Football League (NFL) players following concussion in terms of: (1) DNP protocol activation, (2) release rate at one and three years, and (3) mean salary reduction. A secondary goal of the study was to stratify the post-concussive release rate by franchise and player position. Methods: NFL player transaction records and publicly available weekly injury reports from August 2005 to January 2016 for NFL players were analyzed. All players immediately sustaining recorded concussions were evaluated for a change to inactive or do-not-play (DNP) status. The one-year and three-year release rate following concussion was defined as any player transitioning to inactivation, retirement, free agency, or any failure to return for a successive season on the same team’s active roster after one or three years from the initial concussion. Student’s t-test was used to compare release rates between non-concussed and concussed players at one and three years. Mean salary reduction per year following concussion was calculated using publicly available player contracts. Additionally, franchise-level and position-based analyses of the release rate were performed. Results: Of the total 5,451 NFL players retrospectively analyzed over the 11-year period, 373 sustained publicly reported concussions resulting in DNP protocol activation. The release rate of the post-concussive versus non-concussive player was 26% vs. 20% at 1 year (pfranchise to release an athlete following concussion within one and three years. Table 1 reports a position-based analysis in terms of concussion rate, mean salary reduction, and NFL career longevity. Conclusion: Our retrospective study demonstrates that NFL concussions resulting in DNP protocol activation leads to a statistically greater release rate among concussed NFL players than non-concussed players. Released players suffered reduction in year-over-year accumulated

  11. Development of theophylline sustained release dosage form based on Kollidon SR.

    Science.gov (United States)

    Reza, Md Selim; Quadir, Mohiuddin Abdul; Haider, Syed Shabbir

    2002-01-01

    Sustained release theophylline matrix tablets constituting Kollidon SR (Polyvinyl acetate and povidone based matrix retarding polymer) were developed in this study in an attempt to design a dosage form that manifests desirable release profile and thorough adherence to official monographs. Four matrix tablet formulations were prepared by dry blending and direct compression of Kollidon SR and HPMC-15cps (hydroxypropylmethylcellulose) in varying proportion with fixed percentage of theophylline. Tablets containing only Kollidon SR with the active ingredient demonstrated a rapid rate of drug release with an initial burst effect. Incorporation of HPMC-15cps in the matrix tablet prolonged the release of drug with subsequent minimization of burst effect as confirmed by mean dissolution time, T50 and Higuchi release rate data. Among the batches containing HPMC-15 cps, a direct relationship was obtained between release rate and the percentage of HPMC used. A suitable controlled release profile was obtained with the matrix tablets containing 20% Kollidon SR and 30% HPMC-15cps. The formulation showed close resemblance to commercial products and compliance with USP specification. The results were explored and explained by the difference of physico-chemical property and hydration characteristics of the polymers. In addition to this result, the exponential model was applied to characterize the drug release behaviour from polymeric systems. It was found that, Fickian release is predominant in tablets containing Kollidon SR alone and non-Fickian mechanism plays an important role in the release of drug from HPMC containing tablets with a trend towards zero-order or case II release. In vitro release profile of two commercial brands were also undertaken for comparison and modulation of the experimental batches.

  12. Tritium breeding and release-rate kinetics from neutron-irradiated lithium oxide

    International Nuclear Information System (INIS)

    Quanci, J.F.

    1989-01-01

    The research encompasses the measurement of the tritium breeding and release-rate kinetics from lithium oxide, a ceramic tritium-breeding material. A thermal extraction apparatus which allows the accurate measurement of the total tritium inventory and release rate from lithium oxide samples under different temperatures, pressures and carrier-gas compositions with an uncertainty not exceeding 3% was developed. The goal of the Lithium Blanket Module program was to determine if advanced computer codes could accurately predict the tritium production in the lithium oxide blanket of a fusion power plant. A fusion blanket module prototype, was built and irradiated with a deuterium-tritium fusion-neutron source. The tritium production throughout the module was modeled with the MCNP three dimensional Monte Carlo code and was compared to the assay of the tritium bred in the module. The MCNP code accurately predicted tritium-breeding trends but underestimated the overall tritium breeding by 30%. The release rate of tritium from small grain polycrystalline sintered lithium oxide with a helium carrier gas from 300 to 450 C was found to be controlled by the first order surface desorption of mono-tritiated water. When small amounts of hydrogen were added to the helium carrier gas, the first order rate constant increased from the isotopic exchange of hydrogen for tritium at the lithium oxide surface occurring in parallel with the first order desorption process. The isotopic-exchange first order rate constant temperature dependence and hydrogen partial pressure dependence were evaluated. Large single crystals of lithium oxide were fabricated by the vacuum fusion technique. The release rate of tritium from the large single crystals was found to be controlled by diffusion, and the mixed diffusion-desorption controlled release regime

  13. Measurement of very low release rates of corrosion products in high temperature water

    International Nuclear Information System (INIS)

    Hermansson, H.-P.; Falk, I.

    1984-01-01

    A radiotracer technique has been developed for the measurement of release rates from nuclear reactor materials and it has been tested in a number of experiments. THis article, which forms the first part in a series, describes the experimental loop, the experimental technique and the preliminary results. Experiments were carried out on 18Cr8Ni stainless steel and on Inconel X750 in BWR primary system and feed water environments. The result show that a steady state in the release rate is achieved after operation for approximately 600 h. The release rate depends on the elemental concentration in the material and on the chemical and physical environments. Typical release rates for an 18Cr8Ni stainless steel and Inconel X750 in a BWR primary system environment were found to be 5 mdm and 8 mdm respectively. (Authors)

  14. Inverse modelling of radionuclide release rates using gamma dose rate observations

    Science.gov (United States)

    Hamburger, Thomas; Evangeliou, Nikolaos; Stohl, Andreas; von Haustein, Christoph; Thummerer, Severin; Wallner, Christian

    2015-04-01

    Severe accidents in nuclear power plants such as the historical accident in Chernobyl 1986 or the more recent disaster in the Fukushima Dai-ichi nuclear power plant in 2011 have drastic impacts on the population and environment. Observations and dispersion modelling of the released radionuclides help to assess the regional impact of such nuclear accidents. Modelling the increase of regional radionuclide activity concentrations, which results from nuclear accidents, underlies a multiplicity of uncertainties. One of the most significant uncertainties is the estimation of the source term. That is, the time dependent quantification of the released spectrum of radionuclides during the course of the nuclear accident. The quantification of the source term may either remain uncertain (e.g. Chernobyl, Devell et al., 1995) or rely on estimates given by the operators of the nuclear power plant. Precise measurements are mostly missing due to practical limitations during the accident. The release rates of radionuclides at the accident site can be estimated using inverse modelling (Davoine and Bocquet, 2007). The accuracy of the method depends amongst others on the availability, reliability and the resolution in time and space of the used observations. Radionuclide activity concentrations are observed on a relatively sparse grid and the temporal resolution of available data may be low within the order of hours or a day. Gamma dose rates, on the other hand, are observed routinely on a much denser grid and higher temporal resolution and provide therefore a wider basis for inverse modelling (Saunier et al., 2013). We present a new inversion approach, which combines an atmospheric dispersion model and observations of radionuclide activity concentrations and gamma dose rates to obtain the source term of radionuclides. We use the Lagrangian particle dispersion model FLEXPART (Stohl et al., 1998; Stohl et al., 2005) to model the atmospheric transport of the released radionuclides. The

  15. Radiation preparation of drug carriers based on poly(N-isopropylacrylamide) hydrogels, their loading capacities and controlled release rates for dexamethasone and tegafur

    International Nuclear Information System (INIS)

    Hoang Dang Sang; Nguyen Van Binh; Tran Bang Diep; Nguyen Thi Thom; Hoang Phuong Thao; Pham Duy Duong; Tran Minh Quynh

    2015-01-01

    Thermo-sensitive hydrogels have great potential in some applications. In order to use as the drug delivery systems, the hydrogels should be biocompatibility. New polymers with more biocompatibility and better biodegradability, and environmental friendly crosslinking agents would be necessary for the successful drug carriers. Poly (N-isopropylacrylamide-co-dimethylacrylamide) based hydrogels have been prepared from the admixture solutions of N-isopropylacrylamide (NIPA) and N,N’-dimethyl acrylamide (DMA) by radiation copolymerization and crosslinking at radiation dose of 20 kGy as reported in our previous study. Water swelling behaviour of the resulting hydrogels were much depended on their nature such as initial ratio of NIPA and DMA. The drug-loaded hydrogels were prepared by merging hydrogel in the solutions containing corresponding drugs. Loading capacity of the hydrogels were about 48.6 and 95.7 mg per g dried hydrogel for dexamethasone and tegafur. The release studies showed that the presence of ions in simulated body fluid and temperature of the solution much affecting to in vitro release behaviors of hydrogels for dexamethasone and tegafur. The release rates were fast for both drug models. The result also revealed that these drug carriers were biocompatibility without skin irritation, suggested the drug-loaded hydrogels may be used as controlled release drug delivery systems. (author)

  16. The burning and smoke release rates of sodium pool fires

    International Nuclear Information System (INIS)

    Newman, R.N.; Payne, J.F.B.

    1976-10-01

    The burning rates and smoke release fractions of sodium pool fires have been measured over the pool temperature range 250 0 C to 750 0 C. A theoretical model is derived which satisfactorily predicts the burning rate over the above temperature range. The theory further predicts that the burning rate should be independent of pool diameter, a prediction supported by a comparison of burning rate data from this study and available data from other studies. (author)

  17. LEAK: A source term generator for evaluating release rates from leaking vessels

    International Nuclear Information System (INIS)

    Clinton, J.H.

    1994-01-01

    An interactive computer code for estimating the rate of release of any one of several materials from a leaking tank or broken pipe leading from a tank is presented. It is generally assumed that the material in the tank is liquid. Materials included in the data base are acetonitrile, ammonia, carbon tetrachloride, chlorine, chlorine trifluoride, fluorine, hydrogen fluoride, nitric acid, nitrogen tetroxide, sodium hydroxide, sulfur hexafluoride, sulfuric acid, and uranium hexafluoride. Materials that exist only as liquid and/or vapor over expected ranges of temperature and pressure can easily be added to the data base file. The Fortran source code for LEAK and the data file are included with this report

  18. Preparation and Characterization of Azadirachtin Alginate-Biosorbent Based Formulations: Water Release Kinetics and Photodegradation Study.

    Science.gov (United States)

    Flores-Céspedes, Francisco; Martínez-Domínguez, Gerardo P; Villafranca-Sánchez, Matilde; Fernández-Pérez, Manuel

    2015-09-30

    The botanical insecticide azadirachtin was incorporated in alginate-based granules to obtain controlled release formulations (CRFs). The basic formulation [sodium alginate (1.47%) - azadirachtin (0.28%) - water] was modified by the addition of biosorbents, obtaining homogeneous hybrid hydrogels with high azadirachtin entrapment efficiency. The effect on azadirachtin release rate caused by the incorporation of biosorbents such as lignin, humic acid, and olive pomace in alginate formulation was studied by immersion of the granules in water under static conditions. The addition of the biosorbents to the basic alginate formulation reduces the rate of release because the lignin-based formulation produces a slower release. Photodegradation experiments showed the potential of the prepared formulations in protecting azadirachtin against simulated sunlight, thus improving its stability. The results showed that formulation prepared with lignin provided extended protection. Therefore, this study provides a new procedure to encapsulate the botanical insecticide azadirachtin, improving its delivery and photostability.

  19. Tritium breeding and release-rate kinetics from neutron-irradiated lithium oxide

    International Nuclear Information System (INIS)

    Quanci, J.F.

    1989-01-01

    The research encompasses the measurement of the tritium breeding and release-rate kinetics from lithium oxide, a ceramic tritium-breeding material. A thermal extraction apparatus which allows the accurate measurement of the total tritium inventory and release rate from lithium oxide samples under different temperatures, pressures and carrier-gas compositions with an uncertainty not exceeding 3% was developed. The goal of the Lithium Blanket Module program was to determine if advanced computer codes could accurately predict the tritium production in the lithium oxide blanket of a fusion power plant. A fusion blanket module prototype was built and irradiated with a deuterium-tritium fusion-neutron source. The tritium production throughout the module was modeled with the MCNP three dimensional Monte Carlo code and was compared to the assay of the tritium bred in the module. The MCNP code accurately predicted tritium-breeding trends but underestimated the overall tritium breeding by 30%. The release rate of tritium from small grain polycrystalline sintered lithium oxides with a helium carrier gas from 300 to 450 C was found to be controlled by the first order surface desorption of monotritiated water. When small amounts of hydrogen were added to the helium carrier gas, the first order rate constant increased from the isotopic exchange of hydrogen for tritium at the lithium oxide surface occurring in parallel with the first order desorption process. The isotopic-exchange first order rate constant temperature dependence and hydrogen partial pressure dependence were evaluated

  20. Radioactive Release from Aluminum-Based Spent Nuclear Fuel in Basin Storage

    Energy Technology Data Exchange (ETDEWEB)

    Sindelar, R.L.

    1999-10-21

    The report provides an evaluation of: (1) the release rate of radionuclides through minor cladding penetrations (breaches) on aluminum-based spent nuclear fuel (AL SNF), and (2) the consequences of direct storage of breached AL SNF relative to the authorization basis for SRS basin operation.

  1. Radioactive Release from Aluminum-Based Spent Nuclear Fuel in Basin Storage

    International Nuclear Information System (INIS)

    Sindelar, R.L.

    1999-01-01

    The report provides an evaluation of: (1) the release rate of radionuclides through minor cladding penetrations (breaches) on aluminum-based spent nuclear fuel (AL SNF), and (2) the consequences of direct storage of breached AL SNF relative to the authorization basis for SRS basin operation

  2. Preparation and Characterization of Controlled-Release Avermectin/Castor Oil-Based Polyurethane Nanoemulsions.

    Science.gov (United States)

    Zhang, Hong; Qin, He; Li, Lingxiao; Zhou, Xiaoteng; Wang, Wei; Kan, Chengyou

    2017-06-12

    Avermectin (AVM) is a low-toxic and high-active biopesticide, but it can be easily degraded by UV light. In this paper, biodegradable castor oil-based polyurethanes (CO-PU) are synthesized and used as carriers to fabricate a new kind of AVM/CO-PU nanoemulsion through an emulsion solvent evaporation method, and the chemical structure, colloidal property, AVM loading capacity, controlled-release behavior, foliar adhesion, and photostability of the AVM/CO-PU drug delivery systems are investigated. Results show that AVM is physically encapsulated in the CO-PU carrier nanospheres, the diameter of the AVM/CO-PU nanoparticles is 85%. The release profiles indicate that the release rate is relatively high at the early stage and then slows, which can be adjusted by loaded AVM content, temperature, and pH of the release medium. The foliar pesticide retention of the AVM/CO-PU nanoemulsions is improved, and the photolysis rate of AVM in the AVM/CO-PU nanoparticles is significantly slower than that of the free AVM. A release mechanism of the AVM/CO-PU nanoemulsions is proposed, which is controlled by both diffusion and matrix erosion.

  3. Sensitivity of the engineered barrier system (EBS) release rate to alternative conceptual models of advective release from waste packages under dripping fractures

    International Nuclear Information System (INIS)

    Lee, J.H.; Atkins, J.E.; McNeish, J.A.; Vallikat, V.

    1996-01-01

    Simulations were conducted to analyze the sensitivity of the engineered barrier system (EBS) release rate to alternative conceptual models of the advective release from waste packages under dripping fractures. The first conceptual model assumed that dripping water directly contacts the waste form inside the 'failed' waste package, and radionuclides are released from the EBS by advection. The second conceptual model assumed that dripping water is diverted around the 'failed' waste package (because of the presence of corrosion products plugging the perforations) and dripping water is prevented from directly contacting the waste form. In the second model, radionuclides were assumed to transport through the perforations by diffusion, and, once outside the waste package, to be released from the EBS by advection. The second model was to incorporate more realism into the EBS release calculations. For the case with the second EBS release model, most radionuclides had significantly lower peak EBS release rates (from at least one to several orders of magnitude) than with the first EBS release model. The impacts of the alternative EBS release models were greater for the radionuclides with a low solubility (or solubility-limited radionuclides) than for the radionuclides with a high solubility (or waste form dissolution-limited radionuclides). The analyses indicated that the EBS release model representing advection through a 'failed' waste package (the first EBS release model) may be too conservative in predicting the EBS performance. One major implication from this sensitivity study was that a 'failed' waste package container with multiple perforations may still be able to perform effectively as an important barrier to radionuclide release. (author)

  4. Calcium release rates from tooth enamel treated with dentifrices containing whitening agents and abrasives.

    Science.gov (United States)

    Araujo, Danilo Barral; Silva, Luciana Rodrigues; de Araujo, Roberto Paulo Correia

    2010-01-01

    Tooth whitening agents containing hydrogen peroxide and carbamide peroxide are used frequently in esthetic dental procedures. However, lesions on the enamel surface have been attributed to the action of these products. Using conventional procedures for separating and isolating biological structures, powdered enamel was obtained and treated with hydrogen peroxide, carbamide peroxide, and sodium bicarbonate, ingredients typically found in dentifrices. The enamel was exposed to different pH levels, and atomic emission spectrometry was used to determine calcium release rates. As the pH level increased, the rate of calcium release from enamel treated with dentifrices containing whitening agents decreased. Carbamide peroxide produced the lowest amount of decalcification, while sodium bicarbonate produced the highest release rates at all pH levels.

  5. Ultraviolet enhancement of DNA base release by bleomycin

    International Nuclear Information System (INIS)

    Kakinuma, J.; Tanabe, M.; Orii, H.

    1984-01-01

    The effect of UV irradiation on base-releasing activity of bleomycin was studied on bleomycin A 2 -DNA reaction mixture in the presence of Fe(II) and 2-mercaptoethanol. This effect was measured by the release of free bases from calf thymus DNA with high-performance liquid chromatography. UV irradiation enhanced DNA base-releasing activity of bleomycin and simultaneously caused disappearance of fluorescence emission maximum at 355 nm assigned to bithiazole rings and increase in the intensity of a peak at 400 nm. UV irradiation at 295 nm, the UV absorption maximum of bleomycin, is the most effective in releasing free bases and in changing fluorescence emission patterns. From these results, we suggest that some alterations in the bithiazole group of bleomycin molecule were initiated by UV irradiation and contributed to increased base-releasing activity of bleomycin through a yet unexplained mechanism, presumably through bleomycin dimer formation. (orig.)

  6. Synthesis and characterization of a HAp-based biomarker with controlled drug release for breast cancer

    Energy Technology Data Exchange (ETDEWEB)

    González, Maykel [Dept. of Molecular Engineering of Materials, Center of Applied Physics and Advanced Technology, National Autonomous University of Mexico (CFATA-UNAM), Boulevard Juriquilla 3001, Santiago de Querétaro, Querétaro 76230 (Mexico); Merino, Ulises [Dept. of Molecular Engineering of Materials, Center of Applied Physics and Advanced Technology, National Autonomous University of Mexico (CFATA-UNAM), Boulevard Juriquilla 3001, Santiago de Querétaro, Querétaro 76230 (Mexico); University of the Valley of Mexico (UVM), Boulevard Villas del Mesón 1000, Juriquilla, Santiago de Querétaro, Querétaro 76320 (Mexico); Vargas, Susana [Dept. of Molecular Engineering of Materials, Center of Applied Physics and Advanced Technology, National Autonomous University of Mexico (CFATA-UNAM), Boulevard Juriquilla 3001, Santiago de Querétaro, Querétaro 76230 (Mexico); Quintanilla, Francisco [University of the Valley of Mexico (UVM), Boulevard Villas del Mesón 1000, Juriquilla, Santiago de Querétaro, Querétaro 76320 (Mexico); Rodríguez, Rogelio, E-mail: rogelior@unam.mx [Dept. of Molecular Engineering of Materials, Center of Applied Physics and Advanced Technology, National Autonomous University of Mexico (CFATA-UNAM), Boulevard Juriquilla 3001, Santiago de Querétaro, Querétaro 76230 (Mexico)

    2016-04-01

    A biocompatible hybrid porous polymer–ceramic material was synthesized to be used as a biomarker in the treatment of breast cancer. This device was equipped with the capacity to release medicaments locally in a controlled manner. The biomaterial was Hydroxyapatite(HAp)-based and had a controlled pore size and pore volume fraction. It was implemented externally using a sharp end and a pair of barbed rings placed opposite each other to prevent relative movement once implanted. The biomarker was impregnated with cis-diamine dichloride platinum (II) [Cl{sub 2}-Pt-(NH{sub 3}){sub 2}]; the rate of release was obtained using inductively coupled plasma atomic emission spectroscopy (ICP-AES), and release occurred over the course of three months. Different release profiles were obtained as a function of the pore volume fraction. The biomaterial was characterized using scanning electron microscopy (SEM) and Raman spectroscopy. - Highlights: • A novel biocompatible hybrid porous polymer–ceramic material was synthesized. • The polymer–ceramic (HAp-based) material was used to prepare a biomarker. • The biomarker was impregnated with cis-diamine dichloride platinum (II). • The rate of cisplatin release was determined using inductively coupled plasma. • The kinetics of the cisplatin release was studied varying the biomarker porosity.

  7. Synthesis and characterization of a HAp-based biomarker with controlled drug release for breast cancer

    International Nuclear Information System (INIS)

    González, Maykel; Merino, Ulises; Vargas, Susana; Quintanilla, Francisco; Rodríguez, Rogelio

    2016-01-01

    A biocompatible hybrid porous polymer–ceramic material was synthesized to be used as a biomarker in the treatment of breast cancer. This device was equipped with the capacity to release medicaments locally in a controlled manner. The biomaterial was Hydroxyapatite(HAp)-based and had a controlled pore size and pore volume fraction. It was implemented externally using a sharp end and a pair of barbed rings placed opposite each other to prevent relative movement once implanted. The biomarker was impregnated with cis-diamine dichloride platinum (II) [Cl_2-Pt-(NH_3)_2]; the rate of release was obtained using inductively coupled plasma atomic emission spectroscopy (ICP-AES), and release occurred over the course of three months. Different release profiles were obtained as a function of the pore volume fraction. The biomaterial was characterized using scanning electron microscopy (SEM) and Raman spectroscopy. - Highlights: • A novel biocompatible hybrid porous polymer–ceramic material was synthesized. • The polymer–ceramic (HAp-based) material was used to prepare a biomarker. • The biomarker was impregnated with cis-diamine dichloride platinum (II). • The rate of cisplatin release was determined using inductively coupled plasma. • The kinetics of the cisplatin release was studied varying the biomarker porosity.

  8. Preliminary calculations of release rates from spent fuel in a tuff repository

    International Nuclear Information System (INIS)

    Apted, M.J.; O'Connell, W.J.; Lee, K.H.; MacIntyre, A.T.; Ueng, T.S.; Pigford, T.H.; Lee, W.W.L.

    1991-01-01

    Time-dependent release rates of Tc-99, I-129, Cs-135, and Np-237 have been calculated for wet-drip and moist-continuous release modes from the engineered barrier system of a potential nuclear waste repository in unsaturated tuff, representative of a possible repository at Yucca Mountain in southern Nevada. We describe the modes of water contact and of release of dissolved radionuclides to the surrounding intact rock, and the corresponding calculational models. We list the parameter values adopted, and then present numerical results, conclusions, and recommendations. 21 refs., 5 figs., 2 tabs

  9. Liquid-Phase Heat-Release Rates of the Systems Hydrazine-Nitric Acid and Unsymmetrical Dimethylhydrazine-Nitric Acid

    Science.gov (United States)

    Somogyi, Dezso; Feiler, Charles E.

    1960-01-01

    The initial rates of heat release produced by the reactions of hydrazine and unsymmetrical dimethylhydrazine with nitric acid were determined in a bomb calorimeter under conditions of forced mixing. Fuel-oxidant weight ratio and injection velocity were varied. The rate of heat release apparently depended on the interfacial area between the propellants. Above a narrow range of injection velocities representing a critical amount of interfacial area, the rates reached a maximum and were almost constant with injection velocity. The maximum rate for hydrazine was about 70 percent greater than that for unsymmetrical dimethylhydrazine. The total heat released did not vary with mixture ratio over the range studied.

  10. Impaired sarcoplasmic reticulum Ca(2+) release rate after fatiguing stimulation in rat skeletal muscle

    DEFF Research Database (Denmark)

    Ørtenblad, Niels; Sjøgaard, G; Madsen, Klavs

    2000-01-01

    during the first 0.5-1 h the metabolic state recovered to resting levels, and a slow phase from 1-3 h characterized by a rather slow recovery of the mechanical properties. The recovery of SR Ca(2+) release rate was closely correlated to +dF/dt during the slow phase of recovery (r(2) = 0.51; P ... to 66% that persisted for 1 h, followed by a gradual recovery to 87% of prefatigue release rate at 3 h recovery. Tetanic force and rate of force development (+dF/dt) and relaxation (-dF/dt) were depressed by approximately 80% after stimulation. Recovery occurred in two phases: an initial phase, in which......The purpose of the study was to characterize the sarcoplasmic reticulum (SR) function and contractile properties before and during recovery from fatigue in the rat extensor digitorum longus muscle. Fatiguing contractions (60 Hz, 150 ms/s for 4 min) induced a reduction of the SR Ca(2+) release rate...

  11. Evaluation of chitosan–anionic polymers based tablets for extended-release of highly water-soluble drugs

    Directory of Open Access Journals (Sweden)

    Yang Shao

    2015-02-01

    Full Text Available The objective of this study is to develop chitosan–anionic polymers based extended-release tablets and test the feasibility of using this system for the sustained release of highly water-soluble drugs with high drug loading. Here, the combination of sodium valproate (VPS and valproic acid (VPA were chosen as the model drugs. Anionic polymers studied include xanthan gum (XG, carrageenan (CG, sodium carboxymethyl cellulose (CMC-Na and sodium alginate (SA. The tablets were prepared by wet granulation method. In vitro drug release was carried out under simulated gastrointestinal condition. Drug release mechanism was studied. Compared with single polymers, chitosan–anionic polymers based system caused a further slowdown of drug release rate. Among them, CS–xanthan gum matrix system exhibited the best extended-release behavior and could extend drug release for up to 24 h. Differential scanning calorimetry (DSC and Fourier transform infrared spectroscopy (FTIR studies demonstrated that polyelectrolyte complexes (PECs were formed on the tablet surface, which played an important role on retarding erosion and swelling of the matrix in the later stage. In conclusion, this study demonstrated that it is possible to develop highly water-soluble drugs loaded extended-release tablets using chitosan–anionic polymers based system.

  12. Controlled release from aspirin based linear biodegradable poly(anhydride esters) for anti-inflammatory activity.

    Science.gov (United States)

    Dasgupta, Queeny; Movva, Sahitya; Chatterjee, Kaushik; Madras, Giridhar

    2017-08-07

    This work reports the synthesis of a novel, aspirin-loaded, linear poly (anhydride ester) and provides mechanistic insights into the release of aspirin from this polymer for anti-inflammatory activity. As compared to conventional drug delivery systems that rely on diffusion based release, incorporation of bioactives in the polymer backbone is challenging and high loading is difficult to achieve. In the present study, we exploit the pentafunctional sugar alcohol (xylitol) to provide sites for drug (aspirin) attachment at its non-terminal OH groups. The terminal OH groups are polymerized with a diacid anhydride. The hydrolysis of the anhydride and ester bonds under physiological conditions release aspirin from the matrix. The resulting poly(anhydride ester) has high drug loading (53%) and displays controlled release kinetics of aspirin. The polymer releases 8.5 % and 20%, of the loaded drug in one and four weeks, respectively and has a release rate constant of 0.0035h -0.61 . The release rate is suitable for its use as an anti-inflammatory agent without being cytotoxic. The polymer exhibits good cytocompatibility and anti-inflammatory properties and may find applications as injectable or as an implantable bioactive material. The physical insights into the release mechanism can provide development of other drug loaded polymers. Copyright © 2017 Elsevier B.V. All rights reserved.

  13. Dynamic energy release rate in couple-stress elasticity

    International Nuclear Information System (INIS)

    Morini, L; Piccolroaz, A; Mishuris, G

    2013-01-01

    This paper is concerned with energy release rate for dynamic steady state crack problems in elastic materials with microstructures. A Mode III semi-infinite crack subject to loading applied on the crack surfaces is considered. The micropolar behaviour of the material is described by the theory of couple-stress elasticity developed by Koiter. A general expression for the dynamic J-integral including both traslational and micro-rotational inertial contributions is derived, and the conservation of this integral on a path surrounding the crack tip is demonstrated

  14. Evaluation of rate of swelling and erosion of verapamil (VRP) sustained-release matrix tablets.

    Science.gov (United States)

    Khamanga, Sandile M; Walker, Roderick B

    2006-01-01

    Tablets manufactured in-house were compared to a marketed sustained-release product of verapamil to investigate the rate of hydration, erosion, and drug-release mechanism by measuring the wet and subsequent dry weights of the products. Swelling and erosion rates depended on the polymer and granulating fluid used, which ultimately pointed to their permeability characteristics. Erosion rate of the marketed product was highest, which suggests that the gel layer that formed around these tablets was weak as opposed to the robust and resistant layers of test products. Anomalous and near zero-order transport mechanisms were dominant in tests and commercial product, respectively.

  15. Fouling Release Coatings Based on Polydimethylsiloxane with the Incorporation of Phenylmethylsilicone Oil

    Directory of Open Access Journals (Sweden)

    Miao Ba

    2018-04-01

    Full Text Available In this study, phenylmethylsilicone oil (PSO with different viscosity was used for research in fouling release coatings based on polydimethylsiloxane (PDMS. The surface properties and mechanical properties of the coatings were investigated, while the leaching behavior of PSO from the coatings was studied. Subsequently, the antifouling performance of the coatings was investigated by the benthic diatom adhesion test. The results showed that the coatings with high-viscosity PSO exhibited high levels of hydrophobicity and PSO leaching, while the high PSO content significantly decreased the elastic modulus of the coatings and prolonged the release time of PSO. The antifouling results indicated that the incorporation of PSO into coatings enhanced the antifouling performance of the coating by improving the coating hydrophobicity and decreasing the coating elastic modulus, while the leaching of PSO from the coatings improved the fouling removal rate of the coating. This suggests a double enhancement effect on the antifouling performance of fouling release coatings based on PDMS with PSO incorporated.

  16. Influence of Strain Rate on Heat Release under Quasi-Static Stretching of Metals. Experiment

    Science.gov (United States)

    Zimin, B. A.; Sventitskaya, V. E.; Smirnov, I. V.; Sud'enkov, Yu. V.

    2018-04-01

    The paper presents the results of experimental studies of energy dissipation during a quasi-static stretching of metals and alloys at room temperature. The strain rates varied in the range of 10-3-10-2 s-1. Samples of M1 copper, AZ31B magnesium alloy, BT6 titanium, 12Cr18Ni10Ti steel, and D16AM aluminum alloy were analyzed. The experimental results demonstrated a significant dependence of the heat release on the strain rate in the absence of its influence on stress-strain diagrams for all the metals studied in this range of strain rates. The correlation of the changes in the character of heat release with the processes of structural transformations at various stages of plastic flow is shown on the qualitative level. A difference in the nature of the processes of heat release in materials with different ratios of the plasticity and strength is noted.

  17. Effect of crack-microcracks interaction on energy release rates

    Science.gov (United States)

    Chudnovsky, A.; Wu, Shaofu

    1990-01-01

    The energy release rates associated with the main crack advancing into its surrounding damage zone, and the damage zone translation relative to the main crack, as well as the energy of interaction between the crack and the damage zone are analyzed. The displacement and stress fields for this crack-damage interaction problem are reconstructed by employing a semi-empirical stress analysis which involves experimental evaluation of the average microcrack density in the damage zone.

  18. Poly lactic acid based injectable delivery systems for controlled release of a model protein, lysozyme.

    Science.gov (United States)

    Al-Tahami, Khaled; Meyer, Amanda; Singh, Jagdish

    2006-02-01

    The objective of this study was to evaluate the critical formulation parameters (i.e., polymer concentration, polymer molecular weight, and solvent nature) affecting the controlled delivery of a model protein, lysozyme, from injectable polymeric implants. The conformational stability and biological activity of the released lysozyme were also investigated. Three formulations containing 10%, 20%, and 30% (w/v) poly lactic acid (PLA) in triacetin were investigated. It was found that increasing polymer concentration in the formulations led to a lower burst effect and a slower release rate. Formulation with a high molecular weight polymer showed a greater burst effect as compared to those containing low molecular weight. Conformational stability and biological activity of released samples were studied by differential scanning calorimeter and enzyme activity assay, respectively. The released samples had significantly (P solution kept at same conditions). Increasing polymer concentration increased both the conformational stability and the biological activity of released lysozyme. In conclusion, phase sensitive polymer-based delivery systems were able to deliver a model protein, lysozyme, in a conformationally stable and biologically active form at a controlled rate over an extended period.

  19. Development of controlled release formulations of azadirachtin-A employing poly(ethylene glycol) based amphiphilic copolymers.

    Science.gov (United States)

    Kumar, Jitendra; Shakil, Najam A; Singh, Manish K; Singh, Mukesh K; Pandey, Alka; Pandey, Ravi P

    2010-05-01

    Controlled release (CR) formulations of azadirachtin-A, a bioactive constituent derived from the seed of Azadirachta indica A. Juss (Meliaceae), have been prepared using commercially available polyvinyl chloride, polyethylene glycol (PEG) and laboratory synthesized poly ethylene glycol-based amphiphilic copolymers. Copolymers of polyethylene glycol and various dimethyl esters, which self assemble into nano micellar aggregates in aqueous media, have been synthesized. The kinetics of azadirachtin-A, release in water from the different formulations was studied. Release from the commercial polyethylene glycol (PEG) formulation was faster than the other CR formulations. The rate of release of encapsulated azadirachtin-A from nano micellar aggregates is reduced by increasing the molecular weight of PEG. The diffusion exponent (n value) of azadirachtin-A, in water ranged from 0.47 to 1.18 in the tested formulations. The release was diffusion controlled with a half release time (t(1/2)) of 3.05 to 42.80 days in water from different matrices. The results suggest that depending upon the polymer matrix used, the application rate of azadirachtin-A can be optimized to achieve insect control at the desired level and period.

  20. Calculation of the Fission Product Release for the HTR-10 based on its Operation History

    International Nuclear Information System (INIS)

    Xhonneux, A.; Druska, C.; Struth, S.; Allelein, H.-J.

    2014-01-01

    Since the first criticality of the HTR-10 test reactor in 2000, a rather complex operation history was performed. As the HTR-10 is the only pebble bed reactor in operation today delivering experimental data for HTR simulation codes, an attempt was made to simulate the whole reactor operation up to the presence. Special emphasis was put on the fission product release behaviour as it is an important safety aspect of such a reactor. The operation history has to be simulated with respect to the neutronics, fluid mechanics and depletion to get a detailed knowledge about the time-dependent nuclide inventory. In this paper we report about such a simulation with VSOP 99/11 and our new fission product release code STACY. While STACY (Source Term Analysis Code System) so far was able to calculate the fission product release rates in case of an equilibrium core and during transients, it now can also be applied to running-in-phases. This coupling demonstrates a first step towards an HCP Prototype. Based on the published power histogram of the HTR-10 and additional information about the fuel loading and shuffling, a coupled neutronics, fluid dynamics and depletion calculation was performed. Special emphasis was put on the complex fuel-shuffling scheme within both VSOP and STACY. The simulations have shown that the HTR-10 up to now generated about 2580 MWd while reshuffling the core about 2.3 times. Within this paper, STACY results for the equilibrium core will be compared with FRESCO-II results being published by INET. Compared to these release rates, which are based on a few user defined life histories, in this new approach the fission product release rates of Ag-110m, Cs-137, Sr-90 and I-131 have been simulated for about 4000 tracer pebbles with STACY. For the calculation of the HTR-10 operation history time-dependent release rates are being presented as well. (author)

  1. Effects of Sediment Chemical Properties on Phosphorus Release Rates in the Sediment-Water Interface of the Steppe Wetlands.

    Science.gov (United States)

    He, Jing; Su, Derong; Lv, Shihai; Diao, Zhaoyan; Xie, Jingjie; Luo, Yan

    2017-11-22

    Rising temperature causes a process of phosphorus release, which can be characterized well using phosphorus release rates (V P ). The objective of the present study was to investigate the major factors affecting sediment phosphorus release rates through a wetland habitat simulation experiment. The results showed that the V P of different wetland sediments were different and changed with the order of W-R (river wetland) > W-L (lake wetland) > W-M (grassy marsh wetland) > W-A (reservoir wetland). The main driving factors which influenced sediment phosphorus flux velocity in the sediment-water interface were sediment B-SO₄ 2- , B-MBN and A-MBP content. Path analysis and determination coefficient analysis indicated the standard multiple regression equation for sediment phosphorus release rates in the sediment-water interface, and each main factor was Y = -0.105 + 0.096X₁ + 0.275X₂ - 0.010X₃ ( r = 0.416, p phosphorus release rates; X₁ is sediment B-SO₄ 2- content; X₂ is sediment B-MBN; and X₃ is sediment A-MBP content. Sediment B-SO₄ 2- , B-MBN and A-MBP content and the interaction between them were the main factors affecting sediment phosphorus release rates in the sediment-water interface. Therefore, these results suggest that soil chemical properties and microbial activities likely play an important role in phosphorus release rates in the sediment-water interface. We hope to provide effective scientific management and control methods for relevant environmental protection departments.

  2. Electron transfer rates and energy releases during denitrification of municipal wastewater

    DEFF Research Database (Denmark)

    Abdul-Talib, S.; Ujang, Z; Vollertsen, J.

    2004-01-01

    could be simplified by a two-stage process. In the first stage, nitrate was utilised with significant accumulation of nitrite. In the second stage nitrite was utilised when nitrate depleted. Denitrification rates during the two stages were expressed in terms of electron equivalents (e-eq.) in order...... to compare the process when differennt electron acceptors namlely, nitrate and nitrite were utilised. The energy release rates during the two stages were calculated and compared....

  3. Sensitivity of the engineered barrier system (EBS) release rate to alternative conceptual models of advective release from waste packages under dripping fractures

    International Nuclear Information System (INIS)

    Lee, J.H.; Atkins, J.E.; McNeish, J.A.; Vallikat, V.

    1996-01-01

    The first model assumed that dripping water directly contacts the waste form inside the ''failed'' waste package and radionuclides are released from the EBS by advection. The second model assumed that dripping water is diverted around the package (because of corrosion products plugging the perforations), thereby being prevented from directly contacting the waste form. In the second model, radionuclides were assumed to diffuse through the perforations, and, once outside the waste package, to be released from the EBS by advection. For the case with the second EBS release model, most radionuclides had lower peak EBS release rates than with the first model. Impacts of the alternative EBS release models were greater for the radionuclides with low solubility. The analysis indicated that the EBS release model representing advection through a ''failed'' waste package (the first model) may be too conservative; thus a ''failed'' waste package container with multiple perforations may still be an important barrier to radionuclide release

  4. Influence of ceramic dental crown coating substrate thickness ratio on strain energy release rate

    Science.gov (United States)

    Khasnulhadi, K.; Daud, R.; Mat, F.; Noor, S. N. F. M.; Basaruddin, K. S.; Sulaiman, M. H.

    2017-10-01

    This paper presents the analysis of coating substrate thickness ratio effect on the crown coating fracture behaviour. The bi-layer material is examined under four point bending with pre-crack at the bottom of the core material by using finite element. Three different coating thickness of core/substrate was tested which is 1:1, 1:2 and 2:1. The fracture parameters are analysed based on bilayer and homogenous elastic interaction. The result shows that the ratio thickness of core/veneer provided a significant effect on energy release rate.

  5. Effects of Sediment Chemical Properties on Phosphorus Release Rates in the Sediment-Water Interface of the Steppe Wetlands

    Directory of Open Access Journals (Sweden)

    Jing He

    2017-11-01

    Full Text Available Rising temperature causes a process of phosphorus release, which can be characterized well using phosphorus release rates (VP. The objective of the present study was to investigate the major factors affecting sediment phosphorus release rates through a wetland habitat simulation experiment. The results showed that the VP of different wetland sediments were different and changed with the order of W–R (river wetland > W–L (lake wetland > W–M (grassy marsh wetland > W–A (reservoir wetland. The main driving factors which influenced sediment phosphorus flux velocity in the sediment–water interface were sediment B-SO42−, B-MBN and A-MBP content. Path analysis and determination coefficient analysis indicated the standard multiple regression equation for sediment phosphorus release rates in the sediment–water interface, and each main factor was Y = −0.105 + 0.096X1 + 0.275X2 − 0.010X3 (r = 0.416, p < 0.01, n = 144, where Y is sediment phosphorus release rates; X1 is sediment B-SO42− content; X2 is sediment B-MBN; and X3 is sediment A-MBP content. Sediment B-SO42−, B-MBN and A-MBP content and the interaction between them were the main factors affecting sediment phosphorus release rates in the sediment–water interface. Therefore, these results suggest that soil chemical properties and microbial activities likely play an important role in phosphorus release rates in the sediment–water interface. We hope to provide effective scientific management and control methods for relevant environmental protection departments.

  6. Applications of energy-release-rate techniques to part-through cracks in experimental pressure vessels

    International Nuclear Information System (INIS)

    Bass, B.R.; Bryan, R.H.; Bryson, J.W.; Merkle, J.G.

    1982-01-01

    In nonlinear applications of computational fracture mechanics, energy release rate techniques are used increasingly for computing stress intensity parameters of crack configurations. Recently, deLorenzi used the virtual-crack-extension method to derive an analytical expression for the energy release rate that is better suited for three-dimensional calculations than the well-known J-integral. Certain studies of fracture phenomena, such as pressurized-thermal-shock of cracked structures, require that crack tip parameters be determined for combined thermal and mechanical loads. A method is proposed here that modifies the isothermal formulation of deLorenzi to account for thermal strains in cracked bodies. This combined thermo-mechanical formulation of the energy release rate is valid for general fracture, including nonplanar fracture, and applies to thermo-elastic as well as deformation plasticity material models. Two applications of the technique are described here. In the first, semi-elliptical surface cracks in an experimental test vessel are analyzed under elastic-plastic conditions using the finite element method. The second application is a thick-walled test vessel subjected to combined pressure and thermal shock loadings

  7. Different magnesium release profiles from W/O/W emulsions based on crystallized oils.

    Science.gov (United States)

    Herzi, Sameh; Essafi, Wafa

    2018-01-01

    Water-in-oil-in-water (W/O/W) double emulsions based on crystallized oils were prepared and the release kinetics of magnesium ions from the internal to the external aqueous phase was investigated at T=4°C, for different crystallized lipophilic matrices. All the emulsions were formulated using the same surface-active species, namely polyglycerol polyricinoleate (oil-soluble) and sodium caseinate (water-soluble). The external aqueous phase was a lactose or glucose solution at approximately the same osmotic pressure as that of the inner droplets, in order to avoid osmotic water transfer phenomena. We investigated two types of crystallized lipophilic systems: one based on blends of cocoa butter and miglyol oil, exploring a solid fat content from 0 to 90% and the other system based on milk fat fractions for which the solid fat content varies between 54 and 86%. For double emulsions based on cocoa butter/miglyol oil, the rate of magnesium release was gradually lowered by increasing the % of fat crystals i.e. cocoa butter, in agreement with a diffusion/permeation mechanism. However for double emulsions based on milk fat fractions, the rate of magnesium release was independent of the % of fat crystals and remains the one at t=0. This difference in diffusion patterns, although the solid content is of the same order, suggests a different distribution of fat crystals within the double globules: a continuous fat network acting as a physical barrier for the diffusion of magnesium for double emulsions based on cocoa butter/miglyol oil and double globule/water interfacial distribution for milk fat fractions based double emulsions, through the formation of a crystalline shell allowing an effective protection of the double globules against diffusion of magnesium to the external aqueous phase. Copyright © 2017 Elsevier Inc. All rights reserved.

  8. On the Ni-Ion release rate from surfaces of binary NiTi shape memory alloys

    Science.gov (United States)

    Ševčíková, Jana; Bártková, Denisa; Goldbergová, Monika; Kuběnová, Monika; Čermák, Jiří; Frenzel, Jan; Weiser, Adam; Dlouhý, Antonín

    2018-01-01

    The study is focused on Ni-ion release rates from NiTi surfaces exposed in the cell culture media and human vascular endothelial cell (HUVEC) culture environments. The NiTi surface layers situated in the depth of 70 μm below a NiTi oxide scale are affected by interactions between the NiTi alloys and the bio-environments. The finding was proved with use of inductively coupled plasma mass spectrometry and electron microscopy experiments. As the exclusive factor controlling the Ni-ion release rates was not only thicknesses of the oxide scale, but also the passivation depth, which was two-fold larger. Our experimental data strongly suggested that some other factors, in addition to the Ni concentration in the oxide scale, admittedly hydrogen soaking deep below the oxide scale, must be taken into account in order to rationalize the concentrations of Ni-ions released into the bio-environments. The suggested role of hydrogen as the surface passivation agent is also in line with the fact that the Ni-ion release rates considerably decrease in NiTi samples that were annealed in controlled hydrogen atmospheres prior to bio-environmental exposures.

  9. Isoniazid release from suppositories compounded with selected bases.

    Science.gov (United States)

    Hudson, Kristofer C; Asbill, C Scott; Webster, Andrew A

    2007-01-01

    There is an increasing need for an alternative route of isoniazid adminstration for prophylaxis and treatment of tuberculosis in children. The purpose of this study is to evaluate the in vitro release of isoniazid from extemporaneously compounded isoniazid suppositories with a goal of optimizing the suppository dosage form for this indication. Suppositories were compounded using three different base formulations (cocoa butter, Witepsol H15 Base F, and a combination of polyethylene glycols 3350, 1000, and 400). The release profiles of six compounded suppositories with isoniazid (100 mg) were tested with a United States Pharmacopeial Convention-approved dissolution apparatus. Isoniazid concentrations at predetermined time points were determined using high-performance liquid chromatographic analysis. The results show that drug release from the water-solutble base (mixed polyethylene glycols) was significantly greater than that from the lipophilic bases (cocoa butter and Witepsol H15). The percentage of isoniazid release form the polyethylene glycol suppository formulation (70 +/- 1.4 mg/mL) was greater than that from the cocoa butter (55 +/- 1.1 mg/mL) and Witepsol H15 Base F (18 +/- 0.36 mg/mL) suppository formulations.

  10. Mechanism-Based Modeling of Gastric Emptying Rate and Gallbladder Emptying in Response to Caloric Intake

    DEFF Research Database (Denmark)

    Guiastrennec, B; Sonne, David Peick; Hansen, M

    2016-01-01

    Bile acids released postprandially modify the rate and extent of absorption of lipophilic compounds. The present study aimed to predict gastric emptying (GE) rate and gallbladder emptying (GBE) patterns in response to caloric intake. A mechanism-based model for GE, cholecystokinin plasma concentr......Bile acids released postprandially modify the rate and extent of absorption of lipophilic compounds. The present study aimed to predict gastric emptying (GE) rate and gallbladder emptying (GBE) patterns in response to caloric intake. A mechanism-based model for GE, cholecystokinin plasma...... concentrations, and GBE was developed on data from 33 patients with type 2 diabetes and 33 matched nondiabetic individuals who were administered various test drinks. A feedback action of the caloric content entering the proximal small intestine was identified for the rate of GE. The cholecystokinin...

  11. Development of novel diclofenac potassium controlled release tablets by wet granulation technique and the effect of co-excipients on in vitro drug release rates.

    Science.gov (United States)

    Shah, Shefaatullah; Khan, Gul Majid; Jan, Syed Umer; Shah, Kifayatullah; Hussain, Abid; Khan, Haroon; Khan, Haroon; Khan, Haroon; Khan, Kamran Ahmad

    2012-01-01

    The aim of the present study was the formulation and evaluation of controlled release polymeric tablets of Diclofenac Potassium by wet granulation method for the release rate, release pattern and the mechanism involved in drug release. Formulations having three grades of polymer Ethocel (7P; 7FP, 10P, 10FP, 100P, 100FP) in several drugs to polymer ratios (10:3 and 10:1) were compressed into tablets using wet granulation method. Co-excipients were added to some selected formulations to investigate their enhancement effect on in vitro drug release patterns. In vitro drug release studies were performed using USP Method-1 (Rotating Basket method) and Phosphate buffer (pH 7.4) was used as a dissolution medium. The similarities and dissimilarities of release profiles of test formulations with reference standard were checked using f2 similarity factor and f1 dissimilarity factor. Mathematical/Kinetic models were employed to determine the release mechanism and drug release kinetics.

  12. Evaluation of olibanum and its resin as rate controlling matrix for controlled release of diclofenac

    OpenAIRE

    Chowdary KPR; Mohapatra P; Murali Krishna M

    2006-01-01

    Olibanum and its resin and carbohydrate fractions were evaluated as rate controlling matrix materials in tablets for controlled release of diclofenac. Diclofenac matrix tablets were formulated employing olibanum and its resin and carbohydrate fractions in different concentrations and the tablets were evaluated for various tablet characters including drug release kinetics and mechanism. Olibanum and its resin component exhibited excellent retarding effect on drug release from the matrix tablet...

  13. Structural and functional analysis of a FeoB A143S G5 loop mutant explains the accelerated GDP release rate.

    Science.gov (United States)

    Guilfoyle, Amy P; Deshpande, Chandrika N; Vincent, Kimberley; Pedroso, Marcelo M; Schenk, Gerhard; Maher, Megan J; Jormakka, Mika

    2014-05-01

    GTPases (G proteins) hydrolyze the conversion of GTP to GDP and free phosphate, comprising an integral part of prokaryotic and eukaryotic signaling, protein biosynthesis and cell division, as well as membrane transport processes. The G protein cycle is brought to a halt after GTP hydrolysis, and requires the release of GDP before a new cycle can be initiated. For eukaryotic heterotrimeric Gαβγ proteins, the interaction with a membrane-bound G protein-coupled receptor catalyzes the release of GDP from the Gα subunit. Structural and functional studies have implicated one of the nucleotide binding sequence motifs, the G5 motif, as playing an integral part in this release mechanism. Indeed, a Gαs G5 mutant (A366S) was shown to have an accelerated GDP release rate, mimicking a G protein-coupled receptor catalyzed release state. In the present study, we investigate the role of the equivalent residue in the G5 motif (residue A143) in the prokaryotic membrane protein FeoB from Streptococcus thermophilus, which includes an N-terminal soluble G protein domain. The structure of this domain has previously been determined in the apo and GDP-bound states and in the presence of a transition state analogue, revealing conformational changes in the G5 motif. The A143 residue was mutated to a serine and analyzed with respect to changes in GTPase activity, nucleotide release rate, GDP affinity and structural alterations. We conclude that the identity of the residue at this position in the G5 loop plays a key role in the nucleotide release rate by allowing the correct positioning and hydrogen bonding of the nucleotide base. © 2014 FEBS.

  14. Setting accelerated dissolution test for PLGA microspheres containing peptide, investigation of critical parameters affecting drug release rate and mechanism.

    Science.gov (United States)

    Tomic, I; Vidis-Millward, A; Mueller-Zsigmondy, M; Cardot, J-M

    2016-05-30

    The objective of this study was development of accelerated in vitro release method for peptide loaded PLGA microspheres using flow-through apparatus and assessment of the effect of dissolution parameters (pH, temperature, medium composition) on drug release rate and mechanism. Accelerated release conditions were set as pH 2 and 45°C, in phosphate buffer saline (PBS) 0.02M. When the pH was changed from 2 to 4, diffusion controlled phases (burst and lag) were not affected, while release rate during erosion phase decreased two-fold due to slower ester bonds hydrolyses. Decreasing temperature from 45°C to 40°C, release rate showed three-fold deceleration without significant change in release mechanism. Effect of medium composition on drug release was tested in PBS 0.01M (200 mOsm/kg) and PBS 0.01M with glucose (380 mOsm/kg). Buffer concentration significantly affected drug release rate and mechanism due to the change in osmotic pressure, while ionic strength did not have any effect on peptide release. Furthermore, dialysis sac and sample-and-separate techniques were used, in order to evaluate significance of dissolution technique choice on the release process. After fitting obtained data to different mathematical models, flow-through method was confirmed as the most appropriate for accelerated in vitro dissolution testing for a given formulation. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Phytosterol-based oleogels self-assembled with monoglyceride for controlled volatile release.

    Science.gov (United States)

    Yang, Dan-Xia; Chen, Xiao-Wei; Yang, Xiao-Quan

    2018-01-01

    Oleogels have recently emerged as a subject of growing interest among industrial and academic researchers as an alternative to saturated/trans-fat and delivery of functional ingredients. Phytosterols, comprising plant-derived natural steroid compounds, are preferred for oleogel production because they are both natural and healthy. In the present study, phytosterol-based oleogels self-assembled with monoglyceride were studied with respect to tuning volatile release. Microscopy images of the bicomponent oleogels of β-sitosterol and monoglyceride showed the formation of a new three-dimensional network of entangled crystals and a controllable microstructure. Our analysis from differential scanning calorimetry and small angle X-ray scattering results suggests the self-assembly of β-sitosterol and monoglyceride via intermolecular hydrogen bonds into spherulitic microstructures. The results showed that the release rate (v 0 ), maximum headspace concentrations (C max ) and partition coefficients (k a/o ) for oleogels showed a significantly controlled release and were tunable via the microstructure of phytosterol-based oleogels under both dynamic and static conditions. In addition, the solid-like oleogels had interesting thixotropic and thermoresponsive behaviors, probably as a result of intermolecular hydrogen bonding. The self-assembly of phytosterol-based oleogels with monoglyceride was attributed to intermolecular hydrogen and is demonstrated to be a promising tunable and functional strategy for delivering flavor compounds. © 2017 Society of Chemical Industry. © 2017 Society of Chemical Industry.

  16. Comodulation masking release in bit-rate reduction systems

    DEFF Research Database (Denmark)

    Vestergaard, Martin David; Rasmussen, Karsten Bo; Poulsen, Torben

    1999-01-01

    It has been suggested that the level dependence of the upper masking slope be utilized in perceptual models in bit-rate reduction systems. However, comodulation masking release (CMR) phenomena lead to a reduction of the masking effect when a masker and a probe signal are amplitude modulated...... with the same frequency. In bit-rate reduction systems the masker would be the audio signal and the probe signal would represent the quantization noise. Masking curves have been determined for sinusoids and 1-Bark-wide noise maskers in order to investigate the risk of CMR, when quantizing depths are fixed...... in accordance with psycho-acoustical principles. Masker frequencies of 500 Hz, 1 kHz, and 2 kHz have been investigated, and the masking of pure tone probes has been determined in the first four 1/3 octaves above the masker. Modulation frequencies between 6 and 20 Hz were used with a modulation depth of 0...

  17. Carrageenan-based semi-IPN nanocomposite hydrogels: Swelling kinetic and slow release of sequestrene Fe 138 fertilizer

    Directory of Open Access Journals (Sweden)

    Mohammad Kazem Bahrami

    2016-09-01

    Full Text Available Nanocomposite hydrogels based on kappa-carrageenan were synthesized by incorporating natural sodium montmorillonite (Cloisite nanoclay. Acrylamide (AAm and methylenebisacrylamide (MBA were used as a monomer and a crosslinker, respectively. Effects of reaction variables on the swelling kinetics were studied. The results revealed that the rate of swelling for nanocomposites with high content of MBA was higher than those of nanocomposites consisting of low content of MBA. Similar to the effect of MBA, the rate of swelling enhanced as the carrageenan content was decreased. The influence of clay content on swelling rate was not remarkable. The experimental swelling data were evaluated by pseudo-first-order and pseudo-second-order kinetic models. The swelling data described well by pseudo-second-order kinetic model. Sequestrene Fe 138 (Sq as an agrochemical was loaded into nanocomposites and releasing of this active agent from nanocomposites was studied. The clay-free hydrogel released the whole loaded Sq; whereas the presence of clay restricted the release of Sq.

  18. Size-fractionated characterization and quantification of nanoparticle release rates from a consumer spray product containing engineered nanoparticles

    Energy Technology Data Exchange (ETDEWEB)

    Hagendorfer, Harald, E-mail: Harald.Hagendorfer@empa.c [EMPA, Swiss Federal Laboratories for Materials Testing and Research (Switzerland); Lorenz, Christiane, E-mail: Christiane.Lorenz@chem.ethz.c [ETHZ, Swiss Federal Institute of Technology Zurich (Switzerland); Kaegi, Ralf, E-mail: Ralf.Kaegi@eawag.ch; Sinnet, Brian, E-mail: Brian.Sinnet@eawag.c [EAWAG, Swiss Federal Institute of Aquatic Science and Technology (Switzerland); Gehrig, Robert, E-mail: Robert.Gehrig@empa.c [EMPA, Swiss Federal Laboratories for Materials Testing and Research (Switzerland); Goetz, Natalie V., E-mail: Natalie.vonGoetz@chem.ethz.ch; Scheringer, Martin, E-mail: Martin.Scheringer@chem.ethz.c [ETHZ, Swiss Federal Institute of Technology Zurich (Switzerland); Ludwig, Christian, E-mail: Christian.Ludwig@psi.c [PSI, Paul Scherrer Institue (Switzerland); Ulrich, Andrea, E-mail: Andrea.Ulrich@empa.c [EMPA, Swiss Federal Laboratories for Materials Testing and Research (Switzerland)

    2010-09-15

    This study describes methods developed for reliable quantification of size- and element-specific release of engineered nanoparticles (ENP) from consumer spray products. A modified glove box setup was designed to allow controlled spray experiments in a particle-minimized environment. Time dependence of the particle size distribution in a size range of 10-500 nm and ENP release rates were studied using a scanning mobility particle sizer (SMPS). In parallel, the aerosol was transferred to a size-calibrated electrostatic TEM sampler. The deposited particles were investigated using electron microscopy techniques in combination with image processing software. This approach enables the chemical and morphological characterization as well as quantification of released nanoparticles from a spray product. The differentiation of solid ENP from the released nano-sized droplets was achieved by applying a thermo-desorbing unit. After optimization, the setup was applied to investigate different spray situations using both pump and gas propellant spray dispensers for a commercially available water-based nano-silver spray. The pump spray situation showed no measurable nanoparticle release, whereas in the case of the gas spray, a significant release was observed. From the results it can be assumed that the homogeneously distributed ENP from the original dispersion grow in size and change morphology during and after the spray process but still exist as nanometer particles of size <100 nm. Furthermore, it seems that the release of ENP correlates with the generated aerosol droplet size distribution produced by the spray vessel type used. This is the first study presenting results concerning the release of ENP from spray products.

  19. Size-fractionated characterization and quantification of nanoparticle release rates from a consumer spray product containing engineered nanoparticles

    International Nuclear Information System (INIS)

    Hagendorfer, Harald; Lorenz, Christiane; Kaegi, Ralf; Sinnet, Brian; Gehrig, Robert; Goetz, Natalie V.; Scheringer, Martin; Ludwig, Christian; Ulrich, Andrea

    2010-01-01

    This study describes methods developed for reliable quantification of size- and element-specific release of engineered nanoparticles (ENP) from consumer spray products. A modified glove box setup was designed to allow controlled spray experiments in a particle-minimized environment. Time dependence of the particle size distribution in a size range of 10-500 nm and ENP release rates were studied using a scanning mobility particle sizer (SMPS). In parallel, the aerosol was transferred to a size-calibrated electrostatic TEM sampler. The deposited particles were investigated using electron microscopy techniques in combination with image processing software. This approach enables the chemical and morphological characterization as well as quantification of released nanoparticles from a spray product. The differentiation of solid ENP from the released nano-sized droplets was achieved by applying a thermo-desorbing unit. After optimization, the setup was applied to investigate different spray situations using both pump and gas propellant spray dispensers for a commercially available water-based nano-silver spray. The pump spray situation showed no measurable nanoparticle release, whereas in the case of the gas spray, a significant release was observed. From the results it can be assumed that the homogeneously distributed ENP from the original dispersion grow in size and change morphology during and after the spray process but still exist as nanometer particles of size <100 nm. Furthermore, it seems that the release of ENP correlates with the generated aerosol droplet size distribution produced by the spray vessel type used. This is the first study presenting results concerning the release of ENP from spray products.

  20. Evaluating release alternatives for a long-lived bird species under uncertainty about long-term demographic rates

    Science.gov (United States)

    Moore, Clinton T.; Converse, Sarah J.; Folk, Martin J.; Runge, Michael C.; Nesbitt, Stephen A.

    2012-01-01

    The release of animals to reestablish an extirpated population is a decision problem that is often attended by considerable uncertainty about the probability of success. Annual releases of captive-reared juvenile Whooping Cranes (Grus americana) were begun in 1993 in central Florida, USA, to establish a breeding, non-migratory population. Over a 12-year period, 286 birds were released, but by 2004, the introduced flock had produced only four wild-fledged birds. Consequently, releases were halted over managers' concerns about the performance of the released flock and uncertainty about the efficacy of further releases. We used data on marked, released birds to develop predictive models for addressing whether releases should be resumed, and if so, under what schedule. To examine the outcome of different release scenarios, we simulated the survival and productivity of individual female birds under a baseline model that recognized age and breeding-class structure and which incorporated empirically estimated stochastic elements. As data on wild-fledged birds from captive-reared parents were sparse, a key uncertainty that confronts release decision-making is whether captive-reared birds and their offspring share the same vital rates. Therefore, we used data on the only population of wild Whooping Cranes in existence to construct two alternatives to the baseline model. The probability of population persistence was highly sensitive to the choice of these three models. Under the baseline model, extirpation of the population was nearly certain under any scenario of resumed releases. In contrast, the model based on estimates from wild birds projected a high probability of persistence under any release scenario, including cessation of releases. Therefore, belief in either of these models suggests that further releases are an ineffective use of resources. In the third model, which simulated a population Allee effect, population persistence was sensitive to the release decision

  1. The variation of health effects based on the scenarios considering release parameters and meteorological data

    International Nuclear Information System (INIS)

    Jeong, Jong Tae; Ha, Jae Joo

    2000-01-01

    The variation of health effects resulting from the severe accidents of the YGN 3 and 4 nuclear power plants was examined based on scenarios considering the release parameters and meteorological data. The release parameters and meteorological data considered in making basic scenarios are release height, heat content, release time, warning time, wind speed, rainfall rate, and atmospheric stability class. The seasonal scenarios were also made in order to estimate the seasonal variation of health effects by considering seasonal characteristics of Korea. According to the results, there are large differences in consequence analysis from scenario to although an equal amount of radioactive materials is released to the atmosphere. Also, there are large differences in health effects from season to season due to distinct seasonal characteristics of Korea. Therefore, it is necessary to consider seasonal characteristics in developing optimum emergency response strategies

  2. Nanoscale architectural tuning of parylene patch devices to control therapeutic release rates

    International Nuclear Information System (INIS)

    Pierstorff, Erik; Lam, Robert; Ho, Dean

    2008-01-01

    The advent of therapeutic functionalized implant coatings has significantly impacted the medical device field by enabling prolonged device functionality for enhanced patient treatment. Incorporation of drug release from a stable, biocompatible surface is instrumental in decreasing systemic application of toxic therapeutics and increasing the lifespan of implants by the incorporation of antibiotics and anti-inflammatories. In this study, we have developed a parylene C-based device for controlled release of Doxorubicin, an anti-cancer chemotherapy and definitive read-out for preserved drug functionality, and further characterized the parylene deposition condition-dependent tunability of drug release. Drug release is controlled by the deposition of a layer of 20-200 nm thick parylene over the drug layer. This places a porous layer above the Doxorubicin, limiting drug elution based on drug accessibility to solvent and the solvent used. An increase in the thickness of the porous top layer prolongs the elution of active drug from the device from, in the conditions tested, the order of 10 min to the order of 2 d in water and from the order of 10 min to no elution in PBS. Thus, the controlled release of an anti-cancer therapeutic has been achieved via scalably fabricated, parylene C-encapsulated drug delivery devices.

  3. 19 CFR 142.50 - Line Release data base corrections or changes.

    Science.gov (United States)

    2010-04-01

    ... 19 Customs Duties 2 2010-04-01 2010-04-01 false Line Release data base corrections or changes. 142...; DEPARTMENT OF THE TREASURY (CONTINUED) ENTRY PROCESS Line Release § 142.50 Line Release data base corrections... numbers or bond information on a Line Release Data Loading Sheet as soon as possible. Notification shall...

  4. Quantification of Kinetic Rate Law Parameters of Uranium Release from Sodium Autunite as a Function of Aqueous Bicarbonate Concentrations

    Energy Technology Data Exchange (ETDEWEB)

    Gudavalli, Ravi; Katsenovich, Yelena; Wellman, Dawn M.; Lagos, Leonel; Tansel, Berrin

    2013-09-05

    ABSTRACT: Hydrogen carbonate is one of the most significant components within the uranium geochemical cycle. In aqueous solutions, hydrogen carbonate forms strong complexes with uranium. As such, aqueous bicarbonate may significantly increase the rate of uranium release from uranium minerals. Quantifying the relationship of aqueous hydrogen carbonate solutions to the rate of uranium release during dissolution is critical to understanding the long-term fate of uranium within the environment. Single-pass flow-through (SPTF) experiments were conducted to estimate the rate of uranium release from Na meta-autunite as a function of bicarbonate solutions (0.0005-0.003 M) under the pH range of 6-11 and temperatures of 5-60oC. Consistent with the results of previous investigation, the rate of uranium release from sodium autunite exhibited minimal dependency on temperature; but were strongly dependent on pH and increasing concentrations of bicarbonate solutions. Most notably at pH 7, the rate of uranium release exhibited 370 fold increases relative to the rate of uranium release in the absence of bicarbonate. However, the effect of increasing concentrations of bicarbonate solutions on the release of uranium was significantly less under higher pH conditions. It is postulated that at high pH values, surface sites are saturated with carbonate, thus the addition of more bicarbonate would have less effect on uranium release. Results indicate the activation energies were unaffected by temperature and bicarbonate concentration variations, but were strongly dependent on pH conditions. As pH increased from 6 to 11, activation energy values were observed to decrease from 29.94 kJ mol-1 to 13.07 kJ mol-1. The calculated activation energies suggest a surface controlled dissolution mechanism.

  5. Dual turn-on fluorescence signal-based controlled release system for real-time monitoring of drug release dynamics in living cells and tumor tissues.

    Science.gov (United States)

    Kong, Xiuqi; Dong, Baoli; Song, Xuezhen; Wang, Chao; Zhang, Nan; Lin, Weiying

    2018-01-01

    Controlled release systems with capabilities for direct and real-time monitoring of the release and dynamics of drugs in living systems are of great value for cancer chemotherapy. Herein, we describe a novel dual turn-on fluorescence signal-based controlled release system ( CDox ), in which the chemotherapy drug doxorubicin ( Dox ) and the fluorescent dye ( CH ) are conjugated by a hydrazone moiety, a pH-responsive cleavable linker. CDox itself shows nearly no fluorescence as the fluorescence of CH and Dox is essentially quenched by the C=N isomerization and N-N free rotation. However, when activated under acidic conditions, CDox could be hydrolyzed to afford Dox and CH , resulting in dual turn-on signals with emission peaks at 595 nm and 488 nm, respectively. Notably, CDox exhibits a desirable controlled release feature as the hydrolysis rate is limited by the steric hindrance effect from both the Dox and CH moieties. Cytotoxicity assays indicate that CDox shows much lower cytotoxicity relative to Dox , and displays higher cell inhibition rate to cancer than normal cells. With the aid of the dual turn-on fluorescence at different wavelengths, the drug release dynamics of CDox in living HepG2 and 4T-1 cells was monitored in double channels in a real-time fashion. Importantly, two-photon fluorescence imaging of CDox in living tumor tissues was also successfully performed by high-definition 3D imaging. We expect that the unique controlled release system illustrated herein could provide a powerful means to investigate modes of action of drugs, which is critical for development of much more robust and effective chemotherapy drugs.

  6. Variable temperature effects on release rates of readily soluble nuclides

    International Nuclear Information System (INIS)

    Kim, C.-L.; Light, W.B.; Lee, W.W.-L.; Chambre, P.L.; Pigford, T.H.

    1988-09-01

    In this paper we study the effect of temperature on the release rate of readily soluble nuclides, as affected by a time-temperature dependent diffusion coefficient. In this analysis ground water fills the voids in the waste package at t = 0 and one percent of the inventories of cesium and iodine are immediately dissolved into the void water. Mass transfer resistance of partly failed container and cladding is conservatively neglected. The nuclides move through the void space into the surrounding rock under a concentration gradient. We use an analytic solution to compute the nuclide concentration in the gap or void, and the mass flux rate into the porous rock. 8 refs., 4 figs

  7. Evaluation of fuel release rate and mechanism tests under RBCB conditions

    International Nuclear Information System (INIS)

    Adamson, M.G.

    1981-09-01

    This task includes theoretical evaluation of fuel/fission product release behavior from failed LMFBR fuel elements as well as an on-going experimental investigation of the mechanism of oxide fuel dispersal into flowing liquid sodium. The primary objectives of this work are to develop a fuel source term that can be used in predictive models for primary heat transfer system contamination and to understand the separate influences of important system variables (such as flow rate, oxygen impurity level) on this source term. The present report is written in two parts: the first, in condensed form, is an updated evaluation of fuel (U,Pu) and fission product release data, and the second describes the current status of supporting experimental work at General Electric's Vallecitos Laboratory

  8. Unexpectedly high catch-and-release rates in European marine recreational fisheries: implications for science and management

    DEFF Research Database (Denmark)

    Ferter, Keno; Weltersbach, Marc Simon; Strehlow, Harry Vincent

    2013-01-01

    Unexpectedly high catch-and-release rates in European marine recreational fisheries: implications for science and management. – ICES Journal of Marine Science, 70: .While catch-and-release (C&R) is a well-known practice in several European freshwater recreational fisheries, studies on the magnitu...

  9. Review of tellurium release rates from LWR fuel elements under accident conditions

    International Nuclear Information System (INIS)

    Lorenz, R.A.; Beahm, E.C.; Wichner, R.P.

    1983-01-01

    Although fission product tellurium presents a potentially significant radiohazard, its release and transport in source-term experiments is frequently overlooked because it does not possess a readily measurable, gamma emission; moreover, a recent study emphasized noble gas, iodine and cesium release from LWR fuel elements because of the large data base that exists for these materials. Some new tests show that in some cases tellurium may be held up in core material to a greater degree than previously assumed - an observation that prompts a careful reappraisal of the existing tellurium-release data and its chemical foundation

  10. Conversion factors for estimating release rate of gaseous radioactivity by an aerial survey

    International Nuclear Information System (INIS)

    Saito, Kimiaki; Moriuchi, Shigeru

    1988-02-01

    Conversion factors necessary for estimating release rate of gaseous radioactivity by an aerial survey are presented. The conversion factors were determined based on calculation assuming a Gaussian plume model as a function of atmospheric stability, down-wind distance and flight height. First, the conversion factors for plumes emitting mono-energy gamma rays were calculated, then, conversion factors were constructed through convolution for the radionuclides essential in an accident of a nuclear reactor, and for mixtures of these radionuclides considering elapsed time after shutdown. These conversion factors are shown in figures, and also polynomial expressions of the conversion factors as a function of height have been decided with the least-squares method. A user can easily obtain proper conversion factors from data shown here. (author)

  11. Static and dynamic strain energy release rates in toughened thermosetting composite laminates

    Science.gov (United States)

    Cairns, Douglas S.

    1992-01-01

    In this work, the static and dynamic fracture properties of several thermosetting resin based composite laminates are presented. Two classes of materials are explored. These are homogeneous, thermosetting resins and toughened, multi-phase, thermosetting resin systems. Multi-phase resin materials have shown enhancement over homogenous materials with respect to damage resistance. The development of new dynamic tests are presented for composite laminates based on Width Tapered Double Cantilevered Beam (WTDCB) for Mode 1 fracture and the End Notched Flexure (ENF) specimen. The WTDCB sample was loaded via a low inertia, pneumatic cylinder to produce rapid cross-head displacements. A high rate, piezo-electric load cell and an accelerometer were mounted on the specimen. A digital oscilloscope was used for data acquisition. Typical static and dynamic load versus displacement plots are presented. The ENF specimen was impacted in three point bending with an instrumented impact tower. Fracture initiation and propagation energies under static and dynamic conditions were determined analytically and experimentally. The test results for Mode 1 fracture are relatively insensitive to strain rate effects for the laminates tested in this study. The test results from Mode 2 fracture indicate that the toughened systems provide superior fracture initiation and higher resistance to propagation under dynamic conditions. While the static fracture properties of the homogeneous systems may be relatively high, the apparent Mode 2 dynamic critical strain energy release rate drops significantly. The results indicate that static Mode 2 fracture testing is inadequate for determining the fracture performance of composite structures subjected to conditions such as low velocity impact. A good correlation between the basic Mode 2 dynamic fracture properties and the performance is a combined material/structural Compression After Impact (CAI) test is found. These results underscore the importance of

  12. Aerosol material release rates from zircaloy-4 at temperatures from 2000 to 22000C

    International Nuclear Information System (INIS)

    Mulpuru, S.R.; Wren, D.J.; Rondeau, R.K.

    1987-01-01

    During some postulated severe accidents involving loss of coolant and loss of emergency coolant injection, the temperatures in a CANDU reactor fuel channel become high enough to cause failure and melting of the Zircaloy fuel cladding. At such high temperatures, vapors of fission products and structural (fuel and cladding) materials will be released into the coolant steam and hydrogen mixture. These vapors will condense as cooler conditions are encountered downstream. The vapors from structural materials are relatively involatile; therefore, they will condense readily into aerosol particles. These particles, in turn, will provide sites for the condensation of the more volatile fission products. The aerosol transport of fission products in the primary heat transport system (PHTS) will thus be influenced by the structural material release rates. As part of an ongoing program to develop predictive tools for aerosol and associated fission product transport through the PHTS, experiments have been conducted to measure the vapor mass release rates of the alloying elements from Zircaloy-4 at high temperatures. The paper presents the results and analysis of these experiments

  13. Characterization and optimization of GMO-based gels with long term release for intraarticular administration.

    Science.gov (United States)

    Réeff, J; Gaignaux, A; Goole, J; Siepmann, J; Siepmann, F; Jerome, C; Thomassin, J M; De Vriese, C; Amighi, K

    2013-07-15

    Osteoarthritis is characterized by slow degenerative processes in the articular cartilage within synovial joints. It could be interesting to develop a sustained-release formulation that could be effective on both pain/inflammation and restoration of mechanical integrity of the joint. Recently, an injectable system based on glycerol monooleate (GMO), containing clonidine as a model hydrophilic analgesic/anti-inflammatory drug and hyaluronic acid as a viscoelastic scaffold, showed promising potential as a biodegradable and biocompatible preparation to sustain the drug activity. However, drug release from the system is relatively fast (complete within 1 week) and the underlying drug release mechanisms not fully understood. The aims of this study were: (i) to significantly improve this type of local controlled drug delivery system by further sustaining clonidine release, and (ii) to elucidate the underlying mass transport mechanisms. The addition of FDA-approved inactive ingredients such as sodium oleate or purified soybean oil was found to be highly effective. The release rate could be substantially reduced (e.g., 50% release after 10 days), due to the increased hydrophobicity of the systems, resulting in slower and reduced water uptake and reduced drug mobility. Interestingly, Fick's second law of diffusion could be used to quantitatively describe drug release. Copyright © 2013. Published by Elsevier B.V.

  14. Controlled release of diuron from an alginate-bentonite formulation: water release kinetics and soil mobility study.

    Science.gov (United States)

    Fernández-Pérez, M; Villafranca-Sánchez, M; González-Pradas, E; Flores-Céspedes, F

    1999-02-01

    The herbicide diuron was incorporated in alginate-based granules to obtain controlled release (CR) properties. The standard formulation (alginate-herbicide-water) was modified by the addition of different sorbents. The effect on diuron release rate caused by incorporation of natural and acid-treated bentonites in alginate formulation was studied by immersion of the granules in water under static conditions. The release of diuron was diffusion-controlled. The time taken for 50% release of active ingredient to be released into water, T(50), was calculated for the comparison of formulations. The addition of bentonite to the alginate-based formulation produced the higher T(50) values, indicating slower release of the diuron. The mobility of technical and formulated diuron was compared by using soil columns. The use of alginate-based CR formulations containing bentonite produced a less vertical distribution of the active ingredient as compared to the technical product and commercial formulation. Sorption capacities of the various soil constituents for diuron were also determined using batch experiments.

  15. Isopleths of surface air concentration and surface air kerma rate due to a radioactive cloud released from a stack (3)

    International Nuclear Information System (INIS)

    Tachibana, Haruo; Kikuchi, Masamitsu; Sekita, Tsutomu; Yamaguchi, Takenori

    2004-06-01

    This report is a revised edition of 'Isopleths of Surface Air Concentration and Surface Air Absorbed Dose Rate due to a Radioactive Cloud Released from a Stack(II) '(JAERI-M 90-206) and based on the revised Nuclear Safety Guidelines reflected the ICRP1990 Recommendation. Characteristics of this report are the use of Air Karma Rate (Gy/h) instead of Air Absorbed Dose Rate (Gy/h), and the record of isopleths of surface air concentration and surface air karma rate on CD-ROM. These recorded data on CD-ROM can be printed out on paper and/or pasted on digital map by personal computer. (author)

  16. Fabrication and evaluation of a sustained-release chitosan-based scaffold embedded with PLGA microspheres

    International Nuclear Information System (INIS)

    Song, Kedong; Liu, Yingchao; Macedo, Hugo M.; Jiang, Lili; Li, Chao; Mei, Guanyu; Liu, Tianqing

    2013-01-01

    Nutrient depletion within three-dimensional (3D) scaffolds is one of the major hurdles in the use of this technology to grow cells for applications in tissue engineering. In order to help in addressing it, we herein propose to use the controlled release of encapsulated nutrients within polymer microspheres into chitosan-based 3D scaffolds, wherein the microspheres are embedded. This method has allowed maintaining a stable concentration of nutrients within the scaffolds over the long term. The polymer microspheres were prepared using multiple emulsions (w/o/w), in which bovine serum albumin (BSA) and poly (lactic-co-glycolic) acid (PLGA) were regarded as the protein pattern and the exoperidium material, respectively. These were then mixed with a chitosan solution in order to form the scaffolds by cryo-desiccation. The release of BSA, entrapped within the embedded microspheres, was monitored with time using a BCA kit. The morphology and structure of the PLGA microspheres containing BSA before and after embedding within the scaffold were observed under a scanning electron microscope (SEM). These had a round shape with diameters in the range of 27–55 μm, whereas the chitosan-based scaffolds had a uniform porous structure with the microspheres uniformly dispersed within their 3D structure and without any morphological change. In addition, the porosity, water absorption and degradation rate at 37 °C in an aqueous environment of 1% chitosan-based scaffolds were (92.99 ± 2.51) %, (89.66 ± 0.66) % and (73.77 ± 3.21) %, respectively. The studies of BSA release from the embedded microspheres have shown a sustained and cumulative tendency with little initial burst, with (20.24 ± 0.83) % of the initial amount released after 168 h (an average rate of 0.12%/h). The protein concentration within the chitosan-based scaffolds after 168 h was found to be (11.44 ± 1.81) × 10 −2 mg/mL. This novel chitosan-based scaffold embedded with PLGA microspheres has proven to be a

  17. Fabrication and evaluation of a sustained-release chitosan-based scaffold embedded with PLGA microspheres

    Energy Technology Data Exchange (ETDEWEB)

    Song, Kedong, E-mail: kedongsong@dlut.edu.cn [Dalian R and D Center for Stem Cell and Tissue Engineering, State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 (China); Liu, Yingchao [Dalian R and D Center for Stem Cell and Tissue Engineering, State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 (China); Macedo, Hugo M. [Biological Systems Engineering Laboratory, Department of Chemical Engineering, Department of Chemical Engineering, South Kensington Campus, London SW7 2AZ (United Kingdom); Jiang, Lili; Li, Chao; Mei, Guanyu [Dalian R and D Center for Stem Cell and Tissue Engineering, State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 (China); Liu, Tianqing, E-mail: liutq@dlut.edu.cn [Dalian R and D Center for Stem Cell and Tissue Engineering, State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian 116024 (China)

    2013-04-01

    Nutrient depletion within three-dimensional (3D) scaffolds is one of the major hurdles in the use of this technology to grow cells for applications in tissue engineering. In order to help in addressing it, we herein propose to use the controlled release of encapsulated nutrients within polymer microspheres into chitosan-based 3D scaffolds, wherein the microspheres are embedded. This method has allowed maintaining a stable concentration of nutrients within the scaffolds over the long term. The polymer microspheres were prepared using multiple emulsions (w/o/w), in which bovine serum albumin (BSA) and poly (lactic-co-glycolic) acid (PLGA) were regarded as the protein pattern and the exoperidium material, respectively. These were then mixed with a chitosan solution in order to form the scaffolds by cryo-desiccation. The release of BSA, entrapped within the embedded microspheres, was monitored with time using a BCA kit. The morphology and structure of the PLGA microspheres containing BSA before and after embedding within the scaffold were observed under a scanning electron microscope (SEM). These had a round shape with diameters in the range of 27–55 μm, whereas the chitosan-based scaffolds had a uniform porous structure with the microspheres uniformly dispersed within their 3D structure and without any morphological change. In addition, the porosity, water absorption and degradation rate at 37 °C in an aqueous environment of 1% chitosan-based scaffolds were (92.99 ± 2.51) %, (89.66 ± 0.66) % and (73.77 ± 3.21) %, respectively. The studies of BSA release from the embedded microspheres have shown a sustained and cumulative tendency with little initial burst, with (20.24 ± 0.83) % of the initial amount released after 168 h (an average rate of 0.12%/h). The protein concentration within the chitosan-based scaffolds after 168 h was found to be (11.44 ± 1.81) × 10{sup −2} mg/mL. This novel chitosan-based scaffold embedded with PLGA microspheres has proven to be a

  18. Can nanofluidic chemical release enable fast, high resolution neurotransmitter-based neurostimulation?

    Directory of Open Access Journals (Sweden)

    Peter D Jones

    2016-03-01

    Full Text Available Artificial chemical stimulation could provide improvements over electrical neurostimulation. Physiological neurotransmission between neurons relies on the nanoscale release and propagation of specific chemical signals to spatially-localized receptors. Current knowledge of nanoscale fluid dynamics and nanofluidic technology allows us to envision artificial mechanisms to achieve fast, high resolution neurotransmitter release. Substantial technological development is required to reach this goal. Nanofluidic technology — rather than microfluidic — will be necessary; this should come as no surprise given the nanofluidic nature of neurotransmission.This perspective reviews the state of the art of high resolution electrical neuroprostheses and their anticipated limitations. Chemical release rates from nanopores are compared to rates achieved at synapses and with iontophoresis. A review of microfluidic technology justifies the analysis that microfluidic control of chemical release would be insufficient. Novel nanofluidic mechanisms are discussed, and we propose that hydrophobic gating may allow control of chemical release suitable for mimicking neurotransmission. The limited understanding of hydrophobic gating in artificial nanopores and the challenges of fabrication and large-scale integration of nanofluidic components are emphasized. Development of suitable nanofluidic technology will require dedicated, long-term efforts over many years.

  19. Isopleths of surface concentration and surface exposure rate due to a radioactive cloud released from a stack

    International Nuclear Information System (INIS)

    Kobayashi, Hideo; Yabuta, Hajimu; Katagiri, Hiroshi; Obata, Kazuichi; Kokubu, Morinobu

    1982-03-01

    Various calculations are made to estimate the distributions of concentration and γ-exposure rate due to a radioactive cloud released from a point source to the atmosphere. In this report, the isopleths of concentration and γ-exposure rate which were calculated are given in graphs to enable rapid prediction of the influence of released radioactive material in the emergency situation. Recently there are facilities which are equipped with a system to display the calculation results on CRT; but such practice is rather rare. By placing the calculated isopleths of reduction scale 1/25000 or 1/50000 on the usual map, any facilities without the CRT system can readily estimate the influence of an accidental release. The graphs of isopleths are given with the release height (11 values of 0 to 200 m at about 20 m intervals) and the atmospheric stability (6 classes) as parameters. Calculations of γ-exposure rates were made using the computer code GAMPUL developed by T. Hayashi and T. Shiraishi. In the calculation of radioactive concentrations and γ-exposure rates, the vertical diffusion depths, σsub(z), exceeding 1000 m are taken to be 1000 m according to the Meteorological Guide for the Safety Analysis of Power Reactor (J.AEC). The comparison between with and without this limitation in σsub(z) is made in the case of downwind axial surface distributions. (author)

  20. Airborne release fractions/rates and respirable fractions for nonreactor nuclear facilities. Volume 2, Appendices

    International Nuclear Information System (INIS)

    1994-12-01

    This document contains compiled data from the DOE Handbook on Airborne Release Fractions/Rates and Respirable Fractions for Nonreactor Nuclear facilities. Source data and example facilities utilized, such as the Plutonium Recovery Facility, are included

  1. Fabrication and evaluation of a sustained-release chitosan-based scaffold embedded with PLGA microspheres.

    Science.gov (United States)

    Song, Kedong; Liu, Yingchao; Macedo, Hugo M; Jiang, Lili; Li, Chao; Mei, Guanyu; Liu, Tianqing

    2013-04-01

    Nutrient depletion within three-dimensional (3D) scaffolds is one of the major hurdles in the use of this technology to grow cells for applications in tissue engineering. In order to help in addressing it, we herein propose to use the controlled release of encapsulated nutrients within polymer microspheres into chitosan-based 3D scaffolds, wherein the microspheres are embedded. This method has allowed maintaining a stable concentration of nutrients within the scaffolds over the long term. The polymer microspheres were prepared using multiple emulsions (w/o/w), in which bovine serum albumin (BSA) and poly (lactic-co-glycolic) acid (PLGA) were regarded as the protein pattern and the exoperidium material, respectively. These were then mixed with a chitosan solution in order to form the scaffolds by cryo-desiccation. The release of BSA, entrapped within the embedded microspheres, was monitored with time using a BCA kit. The morphology and structure of the PLGA microspheres containing BSA before and after embedding within the scaffold were observed under a scanning electron microscope (SEM). These had a round shape with diameters in the range of 27-55 μm, whereas the chitosan-based scaffolds had a uniform porous structure with the microspheres uniformly dispersed within their 3D structure and without any morphological change. In addition, the porosity, water absorption and degradation rate at 37 °C in an aqueous environment of 1% chitosan-based scaffolds were (92.99±2.51) %, (89.66±0.66) % and (73.77±3.21) %, respectively. The studies of BSA release from the embedded microspheres have shown a sustained and cumulative tendency with little initial burst, with (20.24±0.83) % of the initial amount released after 168 h (an average rate of 0.12%/h). The protein concentration within the chitosan-based scaffolds after 168 h was found to be (11.44±1.81)×10(-2) mg/mL. This novel chitosan-based scaffold embedded with PLGA microspheres has proven to be a promising technique

  2. Ultrasound enhanced release of therapeutics from drug-releasing implants based on titania nanotube arrays.

    Science.gov (United States)

    Aw, Moom Sinn; Losic, Dusan

    2013-02-25

    A non-invasive and external stimulus-driven local drug delivery system (DDS) based on titania nanotube (TNT) arrays loaded with drug encapsulated polymeric micelles as drug carriers and ultrasound generator is described. Ultrasound waves (USW) generated by a pulsating sonication probe (Sonotrode) in phosphate buffered saline (PBS) at pH 7.2 as the medium for transmitting pressure waves, were used to release drug-loaded nano-carriers from the TNT arrays. It was demonstrated that a very rapid release in pulsatile mode can be achieved, controlled by several parameters on the ultrasonic generator. This includes pulse length, time, amplitude and power intensity. By optimization of these parameters, an immediate drug-micelles release of 100% that spans a desirable time of 5-50 min was achieved. It was shown that stimulated release can be generated and reproduced at any time throughout the TNT-Ti implant life, suggesting considerable potential of this approach as a feasible and tunable ultrasound-mediated drug delivery system in situ via drug-releasing implants. It is expected that this concept can be translated from an in vitro to in vivo regime for therapeutic applications using drug-releasing implants in orthopedic and coronary stents. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.

  3. Sustained Release Drug Delivery Applications of Polyurethanes

    Directory of Open Access Journals (Sweden)

    Michael B. Lowinger

    2018-05-01

    Full Text Available Since their introduction over 50 years ago, polyurethanes have been applied to nearly every industry. This review describes applications of polyurethanes to the development of modified release drug delivery. Although drug delivery research leveraging polyurethanes has been ongoing for decades, there has been renewed and substantial interest in the field in recent years. The chemistry of polyurethanes and the mechanisms of drug release from sustained release dosage forms are briefly reviewed. Studies to assess the impact of intrinsic drug properties on release from polyurethane-based formulations are considered. The impact of hydrophilic water swelling polyurethanes on drug diffusivity and release rate is discussed. The role of pore formers in modulating drug release rate is examined. Finally, the value of assessing mechanical properties of the dosage form and approaches taken in the literature are described.

  4. Iron oxide nanoparticle-based magnetic resonance method to monitor release kinetics from polymeric particles with high resolution.

    Science.gov (United States)

    Chan, Minnie; Schopf, Eric; Sankaranarayanan, Jagadis; Almutairi, Adah

    2012-09-18

    A new method to precisely monitor rapid release kinetics from polymeric particles using super paramagnetic iron oxide nanoparticles, specifically by measuring spin-spin relaxation time (T(2)), is reported. Previously, we have published the formulation of logic gate particles from an acid-sensitive poly-β-aminoester ketal-2 polymer. Here, a series of poly-β-aminoester ketal-2 polymers with varying hydrophobicities were synthesized and used to formulate particles. We attempted to measure fluorescence of released Nile red to determine whether the structural adjustments could finely tune the release kinetics in the range of minutes to hours; however, this standard technique did not differentiate each release rate of our series. Thus, a new method based on encapsulation of iron oxide nanoparticles was developed, which enabled us to resolve the release kinetics of our particles. Moreover, the kinetics matched the relative hydrophobicity order determined by octanol-water partition coefficients. To the best of our knowledge, this method provides the highest resolution of release kinetics to date.

  5. On the energy release rate in a turbulent current sheet on the Sun

    International Nuclear Information System (INIS)

    Bardakov, V.M.

    1986-01-01

    It is shown that turbulent current sheets on the Sun, realizing in the form of the Parker - Sweet flow, are in quasilinear regime of turbulence (or in the regime of instability threshold). The energy release rate in such sheets does not exceed 10 26 erg/s for typical plasma parameters in active regions

  6. Sill intrusion driven fluid flow and vent formation in volcanic basins: Modeling rates of volatile release and paleoclimate effects

    Science.gov (United States)

    Iyer, Karthik; Schmid, Daniel

    2016-04-01

    Evidence of mass extinction events in conjunction with climate change occur throughout the geological record and may be accompanied by pronounced negative carbon isotope excursions. The processes that trigger such globally destructive changes are still under considerable debate. These include mechanisms such as poisoning from trace metals released during large volcanic eruptions (Vogt, 1972), CO2 released from lava degassing during the formation of Large Igneous Provinces (LIPs) (Courtillot and Renne, 2003) and CH4 release during the destabilization of sub-seafloor methane (Dickens et al., 1995), to name a few. Thermogenic methane derived from contact metamorphism associated with magma emplacement and cooling in sedimentary basins has been recently gaining considerable attention as a potential mechanism that may have triggered global climate events in the past (e.g. Svensen and Jamtveit, 2010). The discovery of hydrothermal vent complexes that are spatially associated with such basins also supports the discharge of greenhouse gases into the atmosphere (e.g. Jamtveit et al., 2004; Planke et al., 2005; Svensen et al., 2006). A previous study that investigated this process using a fluid flow model (Iyer et al., 2013) suggested that although hydrothermal plume formation resulting from sill emplacement may indeed release large quantities of methane at the surface, the rate at which this methane is released into the atmosphere is too slow to trigger, by itself, some of the negative δ13C excursions observed in the fossil record over short time scales observed in the fossil record. Here, we reinvestigate the rates of gas release during sill emplacement in a case study from the Harstad Basin off-shore Norway with a special emphasis on vent formation. The presented study is based on a seismic line that crosses multiple sill structures emplaced around 55 Ma within the Lower Cretaceous sediments. A single well-defined vent complex is interpreted above the termination of the

  7. Metallic ion release from biocompatible cobalt-based alloy

    Directory of Open Access Journals (Sweden)

    Dimić Ivana D.

    2014-01-01

    Full Text Available Metallic biomaterials, which are mainly used for the damaged hard tissue replacements, are materials with high strength, excellent toughness and good wear resistance. The disadvantages of metals as implant materials are their susceptibility to corrosion, the elastic modulus mismatch between metals and human hard tissues, relatively high density and metallic ion release which can cause serious health problems. The aim of this study was to examine metallic ion release from Co-Cr-Mo alloy in artificial saliva. In that purpose, alloy samples were immersed into artificial saliva with different pH values (4.0, 5.5 and 7.5. After a certain immersion period (1, 3 and 6 weeks the concentrations of released ions were determined using Inductively Coupled Plasma - Mass Spectrophotometer (ICP-MS. The research findings were used in order to define the dependence between the concentration of released metallic ions, artificial saliva pH values and immersion time. The determined released metallic ions concentrations were compared with literature data in order to describe and better understand the phenomenon of metallic ion release from the biocompatible cobalt-based alloy. [Projekat Ministarstva nauke Republike Srbije, br. III 46010 i br. ON 174004

  8. Evaluation of Ocimum basilicum L. seed mucilage as rate controlling matrix for sustained release of propranolol HCl

    Directory of Open Access Journals (Sweden)

    Majid Saeedi

    2015-01-01

    Full Text Available Polysaccharide mucilage derived from the seeds of Ocimum basilicum L. (family Lamiaceae was investigated for use in matrix formulations containing propranolol hydrochloride. Basil mucilage was extracted and several tablets were formulated. The effect of mucilage on drug release rate was evaluated in comparison with tablets containing two kinds of hydroxypropyl methylcellulose (HPMC K4M and HPMC K100M as standard polymer. The release data were fitted to several models for kinetic evaluation. The results showed that hardness decreased and friability of tablets increased as the concentration of mucilage increased. The rate of release of propranolol HCl from O. basilicm mucilage matrices was mainly controlled by the drug: mucilage ratio. Drug release was slower from the HPMC K4M and HPMCK100M containing tablets compared to the mucilage containing matrices than the drug release from matrices containing O. basilicum seed mucilage in similar ratios.  Formulations containing O. basilicm mucilage were found to exhibit suitable release pattern. The results of kinetic analysis showed that in tablets containing O. basilicm mucilage the highest correlation coefficient was achieved with the zero order model. The swelling and erosion studies revealed that, as the proportion of mucilage in tablets was increased, there was a corresponding increase in percent swelling and a decrease in percent erosion of tablets.

  9. Possibilities for in-vitro testing of controlled-release parenterals.

    OpenAIRE

    Kožák, Jan

    2014-01-01

    The objective of this study was to start with the development of a gel-based medium simulating intramuscular environment for in-vitro drug release testing as an alternative to currently used water-based media. A pork meat was selected as a model of the muscle tissue. At the first part of the study, diffusion rate was proposed as the most determining factor of drug release in gel-based medium. Consequently, the diffusion rate of sodium fluorescein in pork meat was compared with the diffusion r...

  10. Selective attenuation of norepinephrine release and stress-induced heart rate increase by partial adenosine A1 agonism.

    Directory of Open Access Journals (Sweden)

    Lorenz Bott-Flügel

    Full Text Available The release of the neurotransmitter norepinephrine (NE is modulated by presynaptic adenosine receptors. In the present study we investigated the effect of a partial activation of this feedback mechanism. We hypothesized that partial agonism would have differential effects on NE release in isolated hearts as well as on heart rate in vivo depending on the genetic background and baseline sympathetic activity. In isolated perfused hearts of Wistar and Spontaneously Hypertensive Rats (SHR, NE release was induced by electrical stimulation under control conditions (S1, and with capadenoson 6 · 10(-8 M (30 µg/l, 6 · 10(-7 M (300 µg/l or 2-chloro-N(6-cyclopentyladenosine (CCPA 10(-6 M (S2. Under control conditions (S1, NE release was significantly higher in SHR hearts compared to Wistar (766+/-87 pmol/g vs. 173+/-18 pmol/g, p<0.01. Capadenoson led to a concentration-dependent decrease of the stimulation-induced NE release in SHR (S2/S1  =  0.90 ± 0.08 with capadenoson 6 · 10(-8 M, 0.54 ± 0.02 with 6 · 10(-7 M, but not in Wistar hearts (S2/S1  =  1.05 ± 0.12 with 6 · 10(-8 M, 1.03 ± 0.09 with 6 · 10(-7 M. CCPA reduced NE release to a similar degree in hearts from both strains. In vivo capadenoson did not alter resting heart rate in Wistar rats or SHR. Restraint stress induced a significantly greater increase of heart rate in SHR than in Wistar rats. Capadenoson blunted this stress-induced tachycardia by 45% in SHR, but not in Wistar rats. Using a [(35S]GTPγS assay we demonstrated that capadenoson is a partial agonist compared to the full agonist CCPA (74+/-2% A(1-receptor stimulation. These results suggest that partial adenosine A(1-agonism dampens stress-induced tachycardia selectively in rats susceptible to strong increases in sympathetic activity, most likely due to a presynaptic attenuation of NE release.

  11. Evaporation release behavior of volatile fission products from liquid sodium pool to the inert cover gas

    Energy Technology Data Exchange (ETDEWEB)

    Nakagiri, T; Miyahara, S [Oarai Engineering Center, Power Reactor and Nuclear Fuel Development Corp., Oaraimachi, Ibaraki (Japan)

    1996-12-01

    In fuel failure of sodium cooled fast breeder reactors, released volatile fission products (VFPs) such as iodine and cesium from the fuel will be dissolved into the liquid sodium coolant and transferred to the cover vaporization. In the cover gas system of the reactor, natural convection occurs due to temperature differences between the sodium pool and the gas phase. The release rates of VFPs together with sodium vaporization are considered to be controlled by the convection. In this study, three analytical models are developed and examined to calculate the transient release rates using the equilibrium partition coefficients of VFPs. The calculated release rates are compared with experimental results for sodium and sodium iodide. The release rate of sodium is closest to the calculation by the heterogeneous nucleation theory. The release rate of sodium iodide obtained from the experiment is between the release rates calculated by the model based on heat-and-mass transfer analogy and the Hill`s theory. From this study, it is confirmed that the realistic release rate of sodium is able to be calculated by the model based on the heterogeneous nucleation theory. The conservative release rate of sodium iodide is able to be calculated by the model based on the Hill`s theory using the equilibrium partition coefficient of sodium iodide. (author) 7 figs., 1 tab., 3 refs.

  12. Electric-field triggered controlled release of bioactive volatiles from imine-based liquid crystalline phases.

    Science.gov (United States)

    Herrmann, Andreas; Giuseppone, Nicolas; Lehn, Jean-Marie

    2009-01-01

    Application of an electric field to liquid crystalline film forming imines with negative dielectric anisotropy, such as N-(4-methoxybenzylidene)-4-butylaniline (MBBA, 1), results in the expulsion of compounds that do not participate in the formation of the liquid crystalline phase. Furthermore, amines and aromatic aldehydes undergo component exchange with the imine by generating constitutional dynamic libraries. The strength of the electric field and the duration of its application to the liquid crystalline film influence the release rate of the expelled compounds and, at the same time, modulate the equilibration of the dynamic libraries. The controlled release of volatile organic molecules with different chemical functionalities from the film was quantified by dynamic headspace analysis. In all cases, higher headspace concentrations were detected in the presence of an electric field. These results point to the possibility of using imine-based liquid crystalline films to build devices for the controlled release of a broad variety of bioactive volatiles as a direct response to an external electric signal.

  13. Controlled release profiles of dipyridamole from biodegradable microspheres on the base of poly(3-hydroxybutyrate.

    Directory of Open Access Journals (Sweden)

    2007-12-01

    Full Text Available Novel biodegradable microspheres on the base of poly(3-hydroxybutyrate (PHB designed for controlled release of antithrombotic drug, namely dipyridamole (DPD, have been kinetically studied. The profiles of release from the microspheres with different diameters 4, 9, 63, and 92 µm present the progression of nonlinear and linear stages. Diffusionkinetic equation describing both linear (PHB hydrolysis and nonlinear (diffusion stages of the DPD release profiles from the spherical subjects has been written down as the sum of two terms: desorption from the homogeneous sphere in accordance with diffusion mechanism and the zero-order release. In contrast to the diffusivity dependence on microsphere size, the constant characteristics (k of linearity are scarcely affected by the diameter of PHB microparticles. The view of the kinetic profiles as well as the low rate of DPD release are in satisfactory agreement with kinetics of weight loss measured in vitro for the PHB films. Taking into account kinetic results, we suppose that the degradation of both films and PHB microspheres is responsible for the linear stage of DPD release profiles. In the nearest future, combination of biodegradable PHB and DPD as a representative of proliferation cell inhibitors will give possibility to elaborate the novel injectable therapeutic system for a local, long-term, antiproliferative action.

  14. Model-based computer-aided design for controlled release of pesticides

    DEFF Research Database (Denmark)

    Muro Sunè, Nuria; Gani, Rafiqul; Bell, G.

    2005-01-01

    In the field of controlled release technology for pesticides or active ingredients (AI), models that can predict its delivery during application are important for purposes of design and marketing of the pesticide product. Appropriate models for the controlled release of pesticides, if available, ...... extended models have been developed and implemented into a computer-aided system. The total model consisting of the property models embedded into the release models are then employed to study the release of different combinations of AIs and polymer-based microcapsules.......In the field of controlled release technology for pesticides or active ingredients (AI), models that can predict its delivery during application are important for purposes of design and marketing of the pesticide product. Appropriate models for the controlled release of pesticides, if available...

  15. Numerical Studies on Heat Release Rate in Room Fire on Liquid Fuel under Different Ventilation Factors

    Directory of Open Access Journals (Sweden)

    N. Cai

    2012-01-01

    Full Text Available Heat release rate (HRR of the design fire is the most important parameter in assessing building fire hazards. However, HRR in room fire was only studied by computational fluid dynamics (CFD in most of the projects determining fire safety provisions by performance-based design. In contrast to ten years ago, officers in the Far East are now having better knowledge of CFD. Two common questions are raised on CFD-predicted results on describing free boundaries; and on computing grid size. In this work, predicting HRR by the CFD model was justified with experimental room pool fire data reported earlier. The software fire dynamics simulator (FDS version 5 was selected as the CFD simulation tool. Prescribed input heating rate based on the experimental results was used with the liquid fuel model in FDS. Five different free boundary conditions were investigated to predict HRR. Grid sensitivity study was carried out using one stretched mesh and multiple uniform meshes with different grid sizes. As it is difficult to have the entire set of CFD predicted results agreed with experiments, macroscopic flow parameters on the mass flow rate through door opening predicted by CFD were also justified by another four conditions with different ventilation factors.

  16. Detection of low-level environmental exposure rates due to noble gas releases from the Muehleberg nuclear power plant

    International Nuclear Information System (INIS)

    Czarnecki, J.; Volkle, H.; Pretre, S.

    1980-01-01

    The increase of radiation doses in the vicinity of the Swiss Nuclear Power Stations due to airborne releases is generally expected to be below one mrem/year (about one percent of the natural radiation dose). To prove this expected rate, long term measurements with pressure ionization chambers in the vicinity of the Muhleberg plant (BWR) were conducted. Two of these chambers were installed at places where the greatest dose rates from the noble gas plumes were expected in the two prevailing wind directions. The local dose rates were continuously registered on magnetic tape to allow minicomputer evaluation. After the fuel change in the summer of 1976 the noble gas releases from Muhleberg dropped considerably. From that time the noble gas releases consisted of a very low continuous component and some rare short-time spike compoments resulting from turbine and reactor trips. The dose due to the low continuous component was determined by correlating the dose rates at the measuring points with the release measure--ments at the stack and with weather conditions, and by subtracting the natural background. The short noble gas spikes lasted from minutes to some hours and caused small dose rate increases which were easily measured with the ionization chambers, and usually amounted to doses of some microroentgens. By further correlating these dose peaks with wind direction and stack emission measurements, determination of short time atmospheric dilution factors for existing weather situations became possible. By this process, the very low annual environmental doses in the range of 1 mrem per year were determined. (author)

  17. Satellite-based constraints on explosive SO2 release from Soufrière Hills Volcano, Montserrat

    Science.gov (United States)

    Carn, Simon A.; Prata, Fred J.

    2010-09-01

    Numerous episodes of explosive degassing have punctuated the 1995-2009 eruption of Soufrière Hills volcano (SHV), Montserrat, often following major lava dome collapses. We use ultraviolet (UV) and infrared (IR) satellite measurements to quantify sulfur dioxide (SO2) released by explosive degassing, which is not captured by routine ground-based and airborne gas monitoring. We find a total explosive SO2 release of ˜0.5 Tg, which represents ˜6% of total SO2 emissions from SHV since July 1995. The majority of this SO2 (˜0.4 Tg) was vented following the most voluminous SHV dome collapses in July 2003 and May 2006. Based on our analysis, we suggest that the SO2 burden measured following explosive disruption of lava domes depends on several factors, including the instantaneous lava effusion rate, dome height above the conduit, and the vertical component of directed explosions. Space-based SO2 measurements merit inclusion in routine gas monitoring at SHV and other dome-forming volcanoes.

  18. Effect of detention basin release rates on flood flows - Application of a model to the Blackberry Creek Watershed in Kane County, Illinois

    Science.gov (United States)

    Soong, David T.; Murphy, Elizabeth A.; Straub, Timothy D.

    2009-01-01

    The effects of stormwater detention basins with specified release rates are examined on the watershed scale with a Hydrological Simulation Program - FORTRAN (HSPF) continuous-simulation model. Modeling procedures for specifying release rates from detention basins with orifice and weir discharge configurations are discussed in this report. To facilitate future detention modeling as a tool for watershed management, a chart relating watershed impervious area to detention volume is presented. The report also presents a case study of the Blackberry Creek watershed in Kane County, Ill., a rapidly urbanizing area seeking to avoid future flood damages from increased urbanization, to illustrate the effects of various detention basin release rates on flood peaks and volumes and flood frequencies. The case study compares flows simulated with a 1996 land-use HSPF model to those simulated with four different 2020 projected land-use HSPF model scenarios - no detention, and detention basins with release rates of 0.08, 0.10, and 0.12 cubic feet per second per acre (ft3/s-acre), respectively. Results of the simulations for 15 locations, which included the downstream ends of all tributaries and various locations along the main stem, showed that a release rate of 0.10 ft3/s-acre, in general, can maintain postdevelopment 100-year peak-flood discharge at a similar magnitude to that of 1996 land-use conditions. Although the release rate is designed to reduce the 100-year peak flow, reduction of the 2-year peak flow is also achieved for a smaller proportion of the peak. Results also showed that the 0.10 ft3/s-acre release rate was less effective in watersheds with relatively high percentages of preexisting (1996) development than in watersheds with less preexisting development.

  19. INVESTIGATION OF DRUG RELEASE FROM BIODEGRADABLE PLG MICROSPHERES: EXPERIMENT AND THEORY

    Energy Technology Data Exchange (ETDEWEB)

    ANDREWS, MALCOLM J. [Los Alamos National Laboratory; BERCHANE, NADER S. [Los Alamos National Laboratory; CARSON, KENNETH H. [Los Alamos National Laboratory; RICE-FICHT, ALLISON C. [Los Alamos National Laboratory

    2007-01-30

    Piroxicam containing PLG microspheres having different size distributions were fabricated, and in vitro release kinetics were determined for each preparation. Based on the experimental results, a suitable mathematical theory has been developed that incorporates the effect of microsphere size distribution and polymer degradation on drug release. We show from in vitro release experiments that microsphere size has a significant effect on drug release rate. The initial release rate decreased with an increase in microsphere size. In addition, the release profile changed from first order to concave-upward (sigmoidal) as the system size was increased. The mathematical model gave a good fit to the experimental release data.

  20. Combustion Heat Release Rate Comparison of Algae Hydroprocessed Renewable Diesel to F-76 in a Two-Stroke Diesel Engine

    Science.gov (United States)

    2013-06-01

    was recorded. Figure 14 shows the gauge on the rocker arm during calibration . Figure 14. Mechanical Injector Rocker Arm Strain Gauge. D. DATA...RELEASE RATE COMPARISON OF ALGAE HYDROPROCESSED RENEWABLE DIESEL TO F-76 IN A TWO-STROKE DIESEL ENGINE by John H. Petersen June 2013 Thesis...RELEASE RATE COMPARISON OF ALGAE HYDROPROCESSED RENEWABLE DIESEL TO F-76 IN A TWO-STROKE DIESEL ENGINE 5. FUNDING NUMBERS 6. AUTHOR(S) John H

  1. An efficient and accurate method for computation of energy release rates in beam structures with longitudinal cracks

    DEFF Research Database (Denmark)

    Blasques, José Pedro Albergaria Amaral; Bitsche, Robert

    2015-01-01

    This paper proposes a novel, efficient, and accurate framework for fracture analysis of beam structures with longitudinal cracks. The three-dimensional local stress field is determined using a high-fidelity beam model incorporating a finite element based cross section analysis tool. The Virtual...... Crack Closure Technique is used for computation of strain energy release rates. The devised framework was employed for analysis of cracks in beams with different cross section geometries. The results show that the accuracy of the proposed method is comparable to that of conventional three......-dimensional solid finite element models while using only a fraction of the computation time....

  2. Drug release from enzyme-mediated in situ-forming hydrogel based on gum tragacanth-tyramine conjugate.

    Science.gov (United States)

    Dehghan-Niri, Maryam; Tavakol, Moslem; Vasheghani-Farahani, Ebrahim; Ganji, Fariba

    2015-05-01

    In the present study, injectable hydrogels based on gum tragacanth-tyramine conjugate were prepared by enzymatic oxidation of tyramine radicals in the presence of hydrogen peroxide. Then, in vitro release of bovine serum albumin and insulin as model protein drugs from this polymeric network was investigated. Also, to improve the properties of this hydrogel, a blended hydrogel composed of tyramine-conjugated gelatin and tyramine-conjugated tragacanth was prepared. Experimental results showed that the gelation time ranged from 3 to 28 s depending on the polymer and enzyme concentrations. Results of morphological investigation of hydrogels indicated that the average pore size of hydrogels varied from 120 to 160 µm. Swelling degree of hydrogels and the rate of drug release decreased by increasing of hydrogen peroxide and polymer concentrations. The release profile of drug from hydrogels followed Higuchi and Fickian diffusion mechanism. Finally, it was shown that the swelling characteristics and drug release behavior of this polymeric network could be improved by blending it with tyramine-conjugated gelatin. © The Author(s) 2015 Reprints and permissions: sagepub.co.uk/journalsPermissions.nav.

  3. PHEBUS FP release analysis using a microstructure-based code

    International Nuclear Information System (INIS)

    Carlucci, L.N.

    1992-03-01

    The results of pre-test fission-product (FP) release analyses of the first two PHEBUS FP experiments, FPT0 and FPT1, indicate that the FREEDOM microstructure-based code predicts significant differences in both the timing and percent of gaseous FP releases for the two tests. To provide an indication of its predictive capability, FREEDOM was also used to model the high-burnup fuel tested in the Oak Ridge National Laboratory experiments VI-2 and VI-3. For these, the code was found to overpredict releases during the early stages of the tests and to underpredict releases during the later stages. The release kinetics in both tests were reasonably predicted, however. In view of the above, it is likely that the FREEDOM predictions of the final cumulative releases for the first two PHEBUS FP tests are lower-bound estimates. However, the significant difference in the predicted timing of initial releases for the two tests is felt to be indicative of what will occur. Therefore, this difference should be considered in the planning and conduct of the two tests, particularly aspects related to on-line measurements

  4. Influence of the oil globule fraction on the release rate profiles from multiple W/O/W emulsions.

    Science.gov (United States)

    Bonnet, Marie; Cansell, Maud; Placin, Frédéric; Monteil, Julien; Anton, Marc; Leal-Calderon, Fernando

    2010-06-15

    Water-in-oil-in-water (W/O/W) double emulsions were prepared and the kinetics of release of magnesium ions from the internal to the external water phase was investigated as a function of the formulation and the globule volume fraction. All the emulsions were formulated using the same surface-active species (polyglycerol polyricinoleate and sodium caseinate). Also, the internal droplet and oil globule diameters were almost identical for all the systems. Two types of W/O/W emulsions were prepared based either on a synthetic oil (miglyol) or on an edible oil (olive oil). The globule volume fraction varied from 11% to 72%. At constant temperature (T=25 degrees C) and irrespective of the oil type, the percentage of magnesium released was lowered by increasing the globule fraction. In all cases, magnesium leakage occurred without film rupturing (no coalescence). Thus, the experimental data were interpreted within the frame of a model based on diffusion. The rate of release was determined by the permeation coefficient of magnesium across the oil phase and by the binding (chelation) of magnesium by caseinate molecules. The data could be adequately fitted by considering a time-dependant permeation coefficient. The better retention of magnesium at high globule fractions could account for two distinct phenomena: (i) the reduction of the relative volume of the outer phase, and (ii) the attenuation of the permeation coefficient over time induced by interfacial magnesium binding, all the more important than the globule fraction increased. Copyright 2010 Elsevier B.V. All rights reserved.

  5. Tunable volatile release from organogel-emulsions based on the self-assembly of β-sitosterol and γ-oryzanol.

    Science.gov (United States)

    Chen, Xiao-Wei; Chen, Ya-Jun; Wang, Jin-Mei; Guo, Jian; Yin, Shou-Wei; Yang, Xiao-Quan

    2017-04-15

    A current challenge in the area of food emulsion is the design of microstructure that provides controlled release of volatile compounds during storage and consumption. Here, a new strategy addressed this problem at the fundamental level by describing the design of organogel-based emulsion from the self-assembly of β-sitosterol and γ-oryzanol that are capable of tuning volatile release. The results showed that the release rate (v 0 ), maximum headspace concentrations (C max ) and partition coefficients (k a / e ) above structured emulsions were significantly lower than unstructured emulsions and controlled release doing undergo tunable though the self-assembled interface and core fine microstructure from internal phase under dynamic and static condition. This result provides an understanding of how emulsions can behave as delivery system to better design novel food products with enhanced sensorial and nutritional attributes. Copyright © 2016 Elsevier Ltd. All rights reserved.

  6. Simulation of short-term fluctuations in gamma exposure rate due to radioactive cloud released from nuclear power plant

    International Nuclear Information System (INIS)

    Ichikawa, Yoichi; Shikata, Hiroshi; Ishida, Kenji; Ohba, Tachimori.

    1981-01-01

    The measured γ-exposure rate around nuclear power plants is due mainly to natural causes and radioactive clouds emitted from the plants. An exposure calculation method based on puff model has been already proposed to identify the plant contributions and to estimate values in response to short-term fluctuations of meteorological condition and the release rate. However, the calculation method by this model consumes a lot of computer time, since the calculation requires a three-dimensional integration of the distribution of the concentration from each puff. Hence, we propose a simplified method using approximate polynominal equations and interpolations. The computer time needed for the calculation with the simplified method is reduced to 1/30 of that required by the previous method. The calculation results by simplified method are compared with those by the previous method and with the measured exposure rate less natural background. The results of two different methods are in good agreement. The calculated exposure rate is within the range from half to twice as much as the measured exposure rate less background. (author)

  7. Drug release kinetic analysis and prediction of release data via polymer molecular weight in sustained release diltiazem matrices.

    Science.gov (United States)

    Adibkia, K; Ghanbarzadeh, S; Mohammadi, G; Khiavi, H Z; Sabzevari, A; Barzegar-Jalali, M

    2014-03-01

    This study was conducted to investigate the effects of HPMC (K4M and K100M) as well as tragacanth on the drug release rate of diltiazem (DLTZ) from matrix tablets prepared by direct compression method.Mechanism of drug transport through the matrices was studied by fitting the release data to the 10 kinetic models. 3 model independent parameters; i. e., mean dissolution time (MDT), mean release rate (MRR) and release rate efficacy (RE) as well as 5 time point approaches were established to compare the dissolution profiles. To find correlation between fraction of drug released and polymer's molecular weight, dissolution data were fitted into two proposed equations.All polymers could sustain drug release up to 10 h. The release data were fitted best to Peppas and Higuchi square root kinetic models considering squared correlation coefficient and mean percent error (MPE). RE and MRR were decreased when polymer to drug ratio was increased. Conversely, t60% was increased with raising polymer /drug ratio. The fractions of drug released from the formulations prepared with tragacanth were more than those formulated using the same amount of HPMC K4M and HPMC K100M.Preparation of DLTZ matrices applying HPMCK4M, HPMC K100M and tragacanth could effectively extend the drug release. © Georg Thieme Verlag KG Stuttgart · New York.

  8. Chitosan/alginate based multilayers to control drug release fromophthalmic lens

    OpenAIRE

    Silva, Diana; Pinto, Luís F. V.; Bozukova, Dimitriya; Santos, Luís F.; Serro, Ana Paula; Saramago, Benilde

    2016-01-01

    In this study we investigated the possibility of using layer-by-layer deposition, based in natural polymers (chitosan and alginate), to control the release of different ophthalmic drugs from three types of lens materials: a silicone-based hydrogel recently proposed by our group as drug releasing soft contact lens (SCL) material and two commercially available materials: CI26Y for intraocular lens (IOLs) and Definitive 50 for SCLs. The optimised coating, consisting in one double layer of (algin...

  9. Operational control of material release and discharges from nuclear power plant

    International Nuclear Information System (INIS)

    Szabo, I. C.; Ranga, T.; Daroczi, L.; Deme, S.; Kerekes, A.

    2003-01-01

    The operational control of radioactive materials during atmospheric release and aquatic discharge from nuclear power plant is a licensing criterion for NPPs. Originally at the Paks NPP the release control was based on activity limits for four groups of elements. These groups were noble gases, long living radio-aerosols, radioiodine and radiostrontium for atmospheric release and specified activity limit for beta emitters, strontium and tritium for aquatic discharge into Danube. These groups were controlled with proper sampling and/or measuring instrumentation. The limit for atmospheric release was given as a 30-day moving average, for liquid discharges the annual limit was stipulated. The new release and discharge limitation system is based on the environmental dose limitation. The dose constraint for Paks NPP is 90 Sv/year of the critical group for all release pathways and the investigation dose limit is equal to 27 Sv/year. The regulation did not subdivide the dose limit for atmospheric and liquid components but for operational control subdivision of dose limits for atmospheric release and aquatic discharge and shorter time period (one day-one month) seems to be useful. The subdivision can be based on past release data and/or previous activity limits. To satisfy dose below the investigation dose limit there should be a proper operation control level for each separately measured component and pathway belonging to reasonable time interval significantly shorter than one year. The main task of the NPP staff is elaboration of reasonable control levels and reference time intervals for different radionuclide and element groups to be used in operational control. Operational control levels are based on measured daily or monthly release rates. In case of noble gases, aerosols and iodine the daily release rates have several sharp peaks per year. Operational control levels give opportunity to detect these peaks for internal investigation purposes. Investigation release limits

  10. Kinetic and theoretical studies of novel biodegradable thermo-sensitive xerogels based on PEG/PVP/silica for sustained release of enrofloxacin

    Science.gov (United States)

    Ebadi, Azra; Rafati, Amir Abbas; Bavafa, Sadeghali; Mohammadi, Masoumah

    2017-12-01

    This study involves the synthesis of a new silica-based colloidal hybrid system. In this new hybrid system, poly (ethylene glycol) (PEG) and thermo-sensitive amphiphilic biocompatible poly (vinyl pyrrolidone) (PVP) were used to create suitable storage for hydrophobic drugs. The possibility of using variable PVP/PEG molar ratios to modulate drug release rate from silica nanoparticles was a primary goal of the current research. In addition, an investigation of the drug release kinetic was conducted. To achieve this, silica nanoparticles were synthesized in poly (ethylene glycol) (PEG) and poly (vinyl pyrrolidone) (PVP) solution incorporated with enrofloxacin (EFX) (as a model hydrophobic drug), using a simple synthetic strategy of hybrid materials which avoided waste and multi-step processes. The impacts of PVP/PEG molar ratios, temperature, and pH of the release medium on release kinetic were investigated. The physicochemical properties of the drug-loaded composites were studied by Fourier transform infrared (FT-IR) spectra, scanning electron microscopy (SEM), and thermogravimetric analysis (TGA). In vitro drug release studies demonstrated that the drug release rate, which was evaluated by analyzing the experimental data with seven kinetic models in a primarily non-Fickian diffusion-controlled process, aligned well with both Ritger-Peppas and Sahlin-Peppas equations.

  11. The Relationship between Toxics Release Inventory Discharges and Mortality Rates in Rural and Urban Areas of the United States

    Science.gov (United States)

    Hendryx, Michael; Fedorko, Evan

    2011-01-01

    Background: Potential environmental exposures from chemical manufacturing or industrial sites have not been well studied for rural populations. The current study examines whether chemical releases from facilities monitored through the Toxics Release Inventory (TRI) program are associated with population mortality rates for both rural and urban…

  12. Investigation on the ion pair amphiphiles and their in vitro release of amantadine drug based on PLGA–PEG–PLGA gel

    International Nuclear Information System (INIS)

    Yang, Xiaoxia; Ji, Xiaoqing; Shi, Chunhuan; Liu, Jing; Wang, Haiyang; Luan, Yuxia

    2014-01-01

    The amantadine drug and oleic acid surfactant are used to form amantadine-based ion pair amphiphiles based on proton transfer reaction between the drug and the surfactant molecules. The ion pair amphiphiles are characterized by 1 H-nuclear magnetic resonance, Fourier transform infrared spectroscopy, and X-ray diffraction. Self-assembly properties of amantadine-based ion pair amphiphiles are studied by surface tension determination, transmission electron microscopy, zeta potential, and dynamic light scattering. The aggregation behavior studies indicate that the as-prepared ion pair amphiphiles can self-assemble into vesicles with the size of 200–300 nm in aqueous solution. The drug release results show that the amantadine release rate could be well controlled by incorporating the amantadine-based ion pair vesicles in poly (lactic-co-glycolic acid)-poly (ethylene glycol)-poly (lactic-co-glycolic acid) (PLGA–PEG–PLGA) copolymer hydrogel. The drug release from the AT–OA vesicle-loaded PLGA–PEG–PLGA hydrogel is significantly inhibited in comparison with the AT-loaded PLGA–PEG–PLGA hydrogel. The present work thus demonstrates that the vesicle-loaded hydrogel is a good candidate for the drug delivery system with long-term controlled drug release behavior

  13. Effective Anti-miRNA Oligonucleotides Show High Releasing Rate of MicroRNA from RNA-Induced Silencing Complex.

    Science.gov (United States)

    Ariyoshi, Jumpei; Matsuyama, Yohei; Kobori, Akio; Murakami, Akira; Sugiyama, Hiroshi; Yamayoshi, Asako

    2017-10-01

    MicroRNAs (miRNAs) regulate gene expression by forming RNA-induced silencing complexes (RISCs) and have been considered as promising therapeutic targets. MiRNA is an essential component of RISC for the modulation of gene expression. Therefore, the release of miRNA from RISC is considered as an effective method for the inhibition of miRNA functions. In our previous study, we reported that anti-miRNA oligonucleotides (AMOs), which are composed of the 2'-O-methyl (2'-OMe) RNA, could induce the release of miRNA from RISC. However, the mechanisms underlying the miRNA-releasing effects of chemically modified AMOs, which are conventionally used as anti-cancer drugs, are still unclear. In this study, we investigated the relationship between the miRNA releasing rate from RISC and the inhibitory effect on RISC activity (IC 50 ) using conventional chemically modified AMOs. We demonstrated that the miRNA-releasing effects of AMOs are directly proportional to the IC 50 values, and AMOs, which have an ability to promote the release of miRNA from RISC, can effectively inhibit RISC activity in living cells.

  14. Influence of the rate of conversion of HT and HTO on projected radiation doses from release of molecular tritium

    International Nuclear Information System (INIS)

    Jacobs, D.G.; Easterly, C.E.; Phillips, J.E.

    1979-01-01

    Releases of tritium in the past have been largely in the form of tritiated water, and the projected radiation doses could be estimated by assuming tritium behaviour to parallel that of water. There is increasing interest in potential releases of tritium in the form of HT because of significant recent advances in fusion reactor research. Several recent studies have shown that bacteria containing the enzyme hydrogenase can catalyse the conversion of HT to HTO at rates several orders of magnitude faster than the rates measured in atmospheric systems. Rates of conversion in the soil have been combined with estimates of rates of permeation of HT into the soil and with global and local models depicting tritium transport and cycling. The results suggest that for the expected conversion rates, the impact on projected radiation doses should be relatively minor. (author)

  15. Study on crack propagation of adhesively bonded DCB for aluminum foam using energy release rate

    Energy Technology Data Exchange (ETDEWEB)

    Bang, Hye Jin; Lee, Sang Kyo; Cho, Chong Du [Inha University, Incheon (Korea, Republic of); Cho, Jae Ung [Kongju National University, Choenan (Korea, Republic of)

    2015-01-15

    Aluminum foam with initial crack, which has a closed cell form adhesively bonded, is studied to compare and analyze the crack propagation behavior by using both experimental and finite element analysis techniques. The specimen is loaded in Mode I type of fracture as 15 mm/min speed of a displacement control method. The experimental results were used to accommodate the finite element analysis performed with commercial software ABAQUS 6.10. First, using a video recording, five steps of experiment were selected at random and then the energy release rate was calculated. The estimated energy release rate was then used as fracture energy into the finite element analysis. Comparing the experimental axial load-displacement graphs and the finite element analysis results, roughly equivalent peak values were observed in the cohesive strength of the aluminum foam double cantilever beam. However, force versus displacement patterns showed somewhat different: little deformation was observed in aluminum foam, whereas adhesive parts in double cantilever beam were significantly deformed.

  16. Organic-Inorganic Hybrid Hollow Mesoporous Organosilica Nanoparticles for Efficient Ultrasound-Based Imaging and Controlled Drug Release

    Directory of Open Access Journals (Sweden)

    Xiaoqin Qian

    2014-01-01

    Full Text Available A novel anticancer drug delivery system with contrast-enhanced ultrasound-imaging performance was synthesized by a typical hard-templating method using monodispersed silica nanoparticles as the templates, which was based on unique molecularly organic/inorganic hybrid hollow periodic mesoporous organosilicas (HPMOs. The highly dispersed HPMOs show the uniform spherical morphology, large hollow interior, and well-defined mesoporous structures, which are very beneficial for ultrasound-based theranostics. The obtained HPMOs exhibit excellent performances in contrast-enhanced ultrasonography both in vitro and in vivo and can be used for the real-time determination of the progress of lesion tissues during the chemotherapeutic process. Importantly, hydrophobic paclitaxel- (PTX- loaded HPMOs combined with ultrasound irradiation show fast ultrasound responsiveness for controlled drug release and higher in vitro and in vivo tumor inhibition rates compared with free PTX and PTX-loaded HPMOs, which is due to the enhanced ultrasound-triggered drug release and ultrasound-induced cavitation effect. Therefore, the achieved novel HPMOs-based nanoparticle systems will find broad application potentials in clinically ultrasound-based imaging and auxiliary tumor chemotherapy.

  17. WATER HYACINTH: A POSSIBLE ALTERNATIVE RATE RETARDING NATURAL POLYMER USED IN SUSTAINED RELEASE TABLET DESIGN

    Directory of Open Access Journals (Sweden)

    Sabera eKhatun

    2014-06-01

    Full Text Available In recent years natural polymers have been widely used, because of their effectiveness and availability over synthetic polymers. In this present investigation matrix tablets of Metformin hydrochloride were formulated using Water hyacinth powder and its rate retardant activity was studied. Tablets were prepared using wet granulation method with 8% starch as granulating agent and 5%, 10%, 15%, 20%, 25% and 30% of Water hyacinth powder to the drug. In preformulation study, angle of repose, Carr’s Index and Hausner ratio were calculated. Fourier Transform Infrared Spectroscopy (FTIR, Differential Scanning Calorimetry (DSC and Scanning Electron Microscopy (SEM studies were performed and no interactions were found between drug and excipients. Weight variation, friability, hardness, thickness, diameter, and in vitro release study were performed with the prepared matrix tablets. Dissolution studies were conducted using USP type II apparatus at a speed of 100 rpm at 37oC ± 0.5 temperature, for 8 hours. All the formulations comply with both BP and USP requirements, but among all the formulations F-1 (5% of Water hyacinth was the best fitted formula. The drug release patterns were explained in different kinetic models such as Zero order, First order, Higuchi, Hixson Crowell and Korsmeyer-Peppas equations. The current investigation implies that Water hyacinth has the potential to be used as a rate-retarding agent in sustained release drug formulations.

  18. Water hyacinth: a possible alternative rate retarding natural polymer used in sustained release tablet design.

    Science.gov (United States)

    Khatun, Sabera; Sutradhar, Kumar B

    2014-01-01

    In recent years natural polymers have been widely used because of their effectiveness and availability over synthetic polymers. In this present investigation matrix tablets of Metformin hydrochloride were formulated using Water hyacinth powder and its rate retardant activity was studied. Tablets were prepared using wet granulation method with 8% starch as granulating agent and 5, 10, 15, 20, 25 and 30% of Water hyacinth powder to the drug. In preformulation study, angle of repose, Carr's Index and Hausner ratio were calculated. Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), and Scanning Electron Microscopy (SEM) studies were performed and no interactions were found between drug and excipients. Weight variation, friability, hardness, thickness, diameter, and in vitro release study were performed with the prepared matrix tablets. Dissolution studies were conducted using USP type II apparatus at a speed of 100 rpm at 37°C ± 0.5 temperature for 8 h. Though all the formulations comply with both BP and USP requirements, formulation F-1 (5% of Water hyacinth) was the best fitted formula. The drug release patterns were explained in different kinetic models such as Zero order, First order, Higuchi, Hixson Crowell, and Korsmeyer-Peppas equations. The current investigation implies that Water hyacinth has the potential to be used as a rate-retarding agent in sustained release drug formulations.

  19. Oxidation of siloxanes during biogas combustion and nanotoxicity of Si-based particles released to the atmosphere.

    Science.gov (United States)

    Tansel, Berrin; Surita, Sharon C

    2014-01-01

    Siloxanes have been detected in the biogas produced at municipal solid waste landfills and wastewater treatment plants. When oxidized, siloxanes are converted to silicon oxides. The objectives of this study were to evaluate the transformation of siloxanes and potential nanotoxicity of Si-based particles released to the atmosphere from the gas engines which utilize biogas. Data available from nanotoxicity studies were used to assess the potential health risks associated with the inhalation exposure to Si-based nanoparticles. Silicon dioxide formed from siloxanes can range from 5 nm to about 100 nm in diameter depending on the combustion temperature and particle clustering characteristics. In general, silicon dioxide particles formed during from combustion process are typically 40-70 nm in diameter and can be described as fibrous dusts and as carcinogenic, mutagenic, astmagenic or reproductive toxic (CMAR) nanoparticles. Nanoparticles deposit in the upper respiratory system, conducting airways, and the alveoli. Size ranges between 5 and 50 nm show effective deposition in the alveoli where toxic effects are higher. In this study the quantities for the SiO₂ formed and release during combustion of biogas were estimated based on biogas utilization characteristics (gas compositions, temperature). The exposure to Si-based particles and potential effects in humans were analyzed in relation to their particle size, release rates and availability in the atmosphere. The analyses showed that about 54.5 and 73 kg/yr of SiO₂ can be released during combustion of biogas containing D4 and D5 at 14.1 mg/m(3) (1 ppm) and 15.1 mg/m(3) (1ppm), respectively, per MW energy yield. Copyright © 2013 Elsevier B.V. All rights reserved.

  20. Study on Thermal Degradation Characteristics and Regression Rate Measurement of Paraffin-Based Fuel

    Directory of Open Access Journals (Sweden)

    Songqi Hu

    2015-09-01

    Full Text Available Paraffin fuel has been found to have a regression rate that is higher than conventional HTPB (hydroxyl-terminated polybutadiene fuel and, thus, presents itself as an ideal energy source for a hybrid rocket engine. The energy characteristics of paraffin-based fuel and HTPB fuel have been calculated by the method of minimum free energy. The thermal degradation characteristics were measured for paraffin, pretreated paraffin, HTPB and paraffin-based fuel in different working conditions by the using differential scanning calorimetry (DSC and a thermogravimetric analyzer (TGA. The regression rates of paraffin-based fuel and HTPB fuel were tested by a rectangular solid-gas hybrid engine. The research findings showed that: the specific impulse of paraffin-based fuel is almost the same as that of HTPB fuel; the decomposition temperature of pretreated paraffin is higher than that of the unprocessed paraffin, but lower than that of HTPB; with the increase of paraffin, the initial reaction exothermic peak of paraffin-based fuel is reached in advance, and the initial reaction heat release also increases; the regression rate of paraffin-based fuel is higher than the common HTPB fuel under the same conditions; with the increase of oxidizer mass flow rate, the regression rate of solid fuel increases accordingly for the same fuel formulation.

  1. Maximum permissible continuous release rates of phosphorus-32 and sulphur-35 to atmosphere in a milk producing area

    Energy Technology Data Exchange (ETDEWEB)

    Bryant, P M

    1963-01-01

    A method is given for calculating, for design purposes, the maximum permissible continuous release rates of phosphorus-32 and sulphur-35 to atmosphere with respect to milk contamination. In the absence of authoritative advice from the Medical Research Council, provisional working levels for the concentration of phosphorus-32 and sulphur-35 in milk are derived, and details are given of the agricultural assumptions involved in the calculation of the relationship between the amount of the nuclide deposited on grassland and that to be found in milk. The agricultural and meteorological conditions assumed are applicable as an annual average to England and Wales. The results (in mc/day) for phosphorus-32 and sulphur-35 for a number of stack heights and distances are shown graphically; typical values, quoted in a table, include 20 mc/day of phosphorus-32 and 30 mc/day of sulfur-35 as the maximum permissible continuous release rates with respect to ground level releases at a distance of 200 metres from pastureland.

  2. Particle emission rates during electrostatic spray deposition of TiO2 nanoparticle-based photoactive coating

    DEFF Research Database (Denmark)

    Koivisto, Antti J.; Jensen, Alexander C. Ø.; Kling, Kirsten I.

    2017-01-01

    Here, we studied the particle release rate during Electrostatic spray deposition of anatase-(TiO2)-based photoactive coating onto tiles and wallpaper using a commercially available electrostatic spray device. Spraying was performed in a 20.3m3 test chamber while measuring concentrations of 5.6nm ...

  3. Releasable activity and maximum permissible leakage rate within a transport cask of Tehran Research Reactor fuel samples

    Directory of Open Access Journals (Sweden)

    Rezaeian Mahdi

    2015-01-01

    Full Text Available Containment of a transport cask during both normal and accident conditions is important to the health and safety of the public and of the operators. Based on IAEA regulations, releasable activity and maximum permissible volumetric leakage rate within the cask containing fuel samples of Tehran Research Reactor enclosed in an irradiated capsule are calculated. The contributions to the total activity from the four sources of gas, volatile, fines, and corrosion products are treated separately. These calculations are necessary to identify an appropriate leak test that must be performed on the cask and the results can be utilized as the source term for dose evaluation in the safety assessment of the cask.

  4. Synthesis of bio-based nanocomposites for controlled release of antimicrobial agents in food packaging

    Science.gov (United States)

    DeGruson, Min Liu

    The utilization of bio-based polymers as packaging materials has attracted great attention in both scientific and industrial areas due to the non-renewable and nondegradable nature of synthetic plastic packaging. Polyhydroxyalkanoate (PHA) is a biobased polymer with excellent film-forming and coating properties, but exhibits brittleness, insufficient gas barrier properties, and poor thermal stability. The overall goal of the project was to develop the polyhydroxyalkanoate-based bio-nanocomposite films modified by antimicrobial agents with improved mechanical and gas barrier properties, along with a controlled release rate of antimicrobial agents for the inhibition of foodborne pathogens and fungi in food. The ability for antimicrobial agents to intercalate into layered double hydroxides depended on the nature of the antimicrobial agents, such as size, spatial structure, and polarity, etc. Benzoate and gallate anions were successfully intercalated into LDH in the present study and different amounts of benzoate anion were loaded into LDH under different reaction conditions. Incorporation of nanoparticles showed no significant effect on mechanical properties of polyhydroxybutyrate (PHB) films, however, significantly increased the tensile strength and elongation at break of polyhydroxybutyrate-co-valerate (PHBV) films. The effects of type and concentration of LDH nanoparticles (unmodified LDH and LDH modified by sodium benzoate and sodium gallate) on structure and properties of PHBV films were then studied. The arrangement of LDH in the bio-nanocomposite matrices ranged from exfoliated to phase-separated depending on the type and concentration of LDH nanoparticles. Intercalated or partially exfoliated structures were obtained using modified LDH, however, only phase-separated structures were formed using unmodified LDH. The mechanical (tensile strength and elongation at break) and thermo-mechanical (storage modulus) properties were significantly improved with low

  5. Sustained release of radioprotective agents

    International Nuclear Information System (INIS)

    Shani, J.

    1980-11-01

    New pharmaceutical formulations for the sustained release into the G.I. tract of radioprotective agents have been developed by the authors. The experimental method initially consisted in the production of methylcellulose microcapsules. This method failed apparently because of the premature ''explosion'' of the microcapsules and the consequent premature release of massive amounts of the drug. A new method has been developed which consists in drying and pulverising cysteamine and cysteine preparations, mixing them in various proportions with stearic acid and ethylcellulose as carriers. The mixture is then compressed into cylindrical tablets at several pressure values and the leaching rate of the radioprotective agents is then measured by spectrophotometry. The relation between the concentration of the active drug and its rate of release, and the effect on the release rate of the pressure applied to the tablet during its formation were also investigated. Results indicating that the release rate was linearly related to the square root of ''t'' seem to be in agreement with what is predictable, according to Higuchi's equation, save for the very initial and terminal phases. A clear correlation was also established between the stearic acid/ethylcellulose ratios and the release of 20% cysteine, namely a marked decrease in the rate of cysteine release was observed with increasing concentrations of stearic acid. Finally, it was observed that a higher formation pressure results in quicker release of the drug

  6. Evaluation of Radionuclide Release from Aluminum-Based SNF in Basin Storage

    International Nuclear Information System (INIS)

    Sindelar, R.L.; Burke, S.D.; Howell, J.P.

    1998-09-01

    This report provides an evaluation of the release rates of radionuclides from breached A1-SNF assemblies and evaluates the effect of direct storage of breached fuel at a conservative upper bound reference condition on the SRS basin water activity levels

  7. Nuclide release from the near-field of a L/ILW repository

    International Nuclear Information System (INIS)

    Karlsson, L.G.; Hoeglund, L.O.; Pers, K.

    1986-12-01

    For Project Gewaehr 1985, the release of nuclides from a repository for low- and intermediate-level radioactive waste is calculated. The calculations are made for a reference design repository located in the marl host rock at the Oberbauen Stock reference site. The results are limited to the release of the nuclides from the waste through the engineered barriers into the surrounding host rock and will, therefore, constitute a source term for the far-field and biosphere calculations. The most probable nuclide transport mechanism is diffusion and releases are thus influenced by the nuclide diffusivities in the barriers, nuclide sorption and nuclide solubility limits. Degradation of the engineered concrete barriers is taken into account. The effects of convective flow through the barriers are described elsewhere. A near-field release model is presented. It consists of a set of computer programs suited to handel different repository designs, solubility limitations and the different waste categories. The release calculations were made for a base case in which best estimates of the parameters were used. Sensitivity to the choice of the most important parameters was tested by parameter variations. The numerical models used were checked by comparative calculations with different codes and similar data. The results of the base calculations show that near-field barriers will cause both a delay of the release to the far-field and a reduced rate of release. The sorbed nuclides, comprising the actinides and some activation and fission products, will be delayed by 10'000 years and have a maximum release rate of less than 10 -3 Ci/a each. The non-sorbed nuclides are delayed by only about 100 years and the maximum release rate is less than 10 -2 Ci per year and nuclide. The parameter variations and the design model tests gave only limited deviations from the base case results. (author)

  8. Joint release rate estimation and measurement-by-measurement model correction for atmospheric radionuclide emission in nuclear accidents: An application to wind tunnel experiments.

    Science.gov (United States)

    Li, Xinpeng; Li, Hong; Liu, Yun; Xiong, Wei; Fang, Sheng

    2018-03-05

    The release rate of atmospheric radionuclide emissions is a critical factor in the emergency response to nuclear accidents. However, there are unavoidable biases in radionuclide transport models, leading to inaccurate estimates. In this study, a method that simultaneously corrects these biases and estimates the release rate is developed. Our approach provides a more complete measurement-by-measurement correction of the biases with a coefficient matrix that considers both deterministic and stochastic deviations. This matrix and the release rate are jointly solved by the alternating minimization algorithm. The proposed method is generic because it does not rely on specific features of transport models or scenarios. It is validated against wind tunnel experiments that simulate accidental releases in a heterogonous and densely built nuclear power plant site. The sensitivities to the position, number, and quality of measurements and extendibility of the method are also investigated. The results demonstrate that this method effectively corrects the model biases, and therefore outperforms Tikhonov's method in both release rate estimation and model prediction. The proposed approach is robust to uncertainties and extendible with various center estimators, thus providing a flexible framework for robust source inversion in real accidents, even if large uncertainties exist in multiple factors. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. Shape memory-based actuators and release mechanisms therefrom

    Science.gov (United States)

    Vaidyanathan, Rajan (Inventor); Snyder, Daniel W. (Inventor); Schoenwald, David K. (Inventor); Lam, Nhin S. (Inventor); Watson, Daniel S. (Inventor); Krishnan, Vinu B. (Inventor); Noebe, Ronald D. (Inventor)

    2012-01-01

    SM-based actuators (110) and release mechanisms (100) therefrom and systems (500) including one or more release mechanisms (100). The actuators (110) comprise a SM member (118) and a deformable member (140) mechanically coupled to the SM member (118) which deforms upon a shape change of the SM member triggered by a phase transition of the SM member. A retaining element (160) is mechanically coupled to the deformable member (140), wherein the retaining element (160) moves upon the shape change. Release mechanism (100) include an actuator, a rotatable mechanism (120) including at least one restraining feature (178) for restraining rotational movement of the retaining element (160) before the shape change, and at least one spring (315) that provides at least one locked spring-loaded position when the retaining element is in the restraining feature and at least one released position that is reached when the retaining element is in a position beyond the restraining feature (178). The rotatable mechanism (120) includes at least one load-bearing protrusion (310). A hitch (400) is for mechanically coupling to the load, wherein the hitch is supported on the load bearing protrusion (310) when the rotatable mechanism is in the locked spring-loaded position.

  10. Controlled release of potassium chloride from radiation-polymerized copolymer matrices

    International Nuclear Information System (INIS)

    Yoshida, Masaru; Kumakura, Minoru; Kaetsu, Isao

    1979-01-01

    Release behavior of potassium chloride (KCl) from the flat circular copolymer composites, obtained by radiation-induced polymerization at low temperatures, was studied. The release rate agreed with the first-order kinetics based on the Noyes-Whitney equation in relation to the swelling of the composites. Release profiles of KCl from copolymer composites was affected by monomer composition between hydroxyethyl acrylate (HEA) and polyfunctional glass-forming monomers such as 2-hydroxyethyl methacrylate (HEMA), diethylene glycol dimethacrylate (DGDA), and trimethylolpropane trimethacrylate (TMPT) owing to change of swelling property of copolymers. The release rate decreased at HEA-poor composition in any system. In the case of hydrophobic comonomer system such as glycidyl methacrylate (GMA) and DGDA, release profile of KCl showed a minimum at 50% GMA-50% DGDA monomer composition. (author)

  11. Impacts of external convection on release rates in metal hydride storage tanks. Paper no. IGEC-1-080

    International Nuclear Information System (INIS)

    MacDonald, B.; Rowe, A.; Tomlinson, J.; Ho, J.

    2005-01-01

    Reversible metal hydrides can be used to store hydrogen at relatively low pressures, with very high volumetric density. The rate hydrogen can be drawn from a given tank is strongly influenced by the rate heat can be transferred to the reaction zone. Because of this, enhancing and controlling heat transfer is a key area of research in the development of metal hydride storage tanks. In this work, the impacts of external convection resistance on hydrogen release rates are examined. A one-dimensional resistive analysis determines the thermal resistances in the system based on one case where no external heat transfer enhancements are used, and a second case where external fins are used. A two-dimensional, transient model, developed in FEMLAB, is used to determine the impact of the external fins on the mass flow rate of hydrogen in more detail. For the particular metal hydride alloy (LaNi 4.8 Sn 0.2 ) and tank geometry studied, it was found that the fins have a large impact on the hydrogen flow rate during the initial stages of desorption. The flow rate with no fins is only 20% of the flow rate with fins for a full tank, 57% when the tank is 33% full, and 74% when the tank is 5% full. As the reaction proceeds, the resistance of the metal hydride alloy within the tank increases and becomes dominant. Therefore, the impact of the fins becomes less significant as the tank empties. (author)

  12. Atmospheric modeling of Mars CH4 subsurface clathrates releases mimicking SAM and 2003 Earth-based detections

    Science.gov (United States)

    Pla-García, J.; Rafkin, S. C.

    2017-12-01

    The aim of this work is to establish the amount of mixing during all martian seasons to test whether CH4 releases inside or outside of Gale crater are consistent with MSL-SAM observations. Several modeling scenarios were configured, including instantaneous and steady releases, both inside and outside the crater. A simulation to mimic the 2003 Earth-based detections (Mumma et al. 2009 or M09) was also performed. In the instantaneous release inside Gale experiments, Ls270 was shown to be the faster mixing season when air within and outside the crater was well mixed: all tracer mass inside the crater is diluted after just 8 hours. The mixing of near surface crater air with the external environment in the rest of the year is potentially rapid but slower than Ls270.In the instantaneous release outside Gale (NW) experiment, in just 12 hours the CH4 that makes it to the MSL landing location is diluted by six orders of magnitude. The timescale of mixing in MRAMS experiments is on the order of 1 sol regardless of season. The duration of the CH4 peak observed by SAM is 100 sols. Therefore there is a steady release inside the crater, or there is a very large magnitude steady release outside the crater. In the steady release Gale experiments, CH4 flux rate from ground is 1.8 kg m-2 s-1 (derived from Gloesener et al. 2017 clathrates fluxes) and it is not predictive. In these experiments, 200 times lower CH4 values detected by SAM are modeled around MSL location. There are CH4 concentration variations of orders of magnitude depending on the hour, so timing of SAM measurements is important. With a larger (but further away) outside crater release area compared to inside, similar CH4 values around MSL are modeled, so distance to source is important. In the steady experiments mimicking M09 detection release area, only 12 times lower CH4 values detected by SAM are modeled around MSL. The highest value in the M09 modeled scenario (0.6 ppbv) is reached in Ls270. This value is the

  13. Development of controlled drug release systems based on thiolated polymers.

    Science.gov (United States)

    Bernkop-Schnürch, A; Scholler, S; Biebel, R G

    2000-05-03

    The purpose of the present study was to generate mucoadhesive matrix-tablets based on thiolated polymers. Mediated by a carbodiimide, L-cysteine was thereby covalently linked to polycarbophil (PCP) and sodium carboxymethylcellulose (CMC). The resulting thiolated polymers displayed 100+/-8 and 1280+/-84 micromol thiol groups per gram, respectively (means+/-S.D.; n=6-8). In aqueous solutions these modified polymers were capable of forming inter- and/or intramolecular disulfide bonds. The velocity of this process augmented with increase of the polymer- and decrease of the proton-concentration. The oxidation proceeded more rapidly within thiolated PCP than within thiolated CMC. Due to the formation of disulfide bonds within thiol-containing polymers, the stability of matrix-tablets based on such polymers could be strongly improved. Whereas tablets based on the corresponding unmodified polymer disintegrated within 2 h, the swollen carrier matrix of thiolated CMC and PCP remained stable for 6.2 h (mean, n=4) and more than 48 h, respectively. Release studies of the model drug rifampicin demonstrated that a controlled release can be provided by thiolated polymer tablets. The combination of high stability, controlled drug release and mucoadhesive properties renders matrix-tablets based on thiolated polymers useful as novel drug delivery systems.

  14. Ispaghula Husk-Based Extended Release Tablets of Diclofenac ...

    African Journals Online (AJOL)

    Purpose: To formulate extended-release tablets of diclofenac sodium based on ispaghula husk. Methods: Tablets with varying proportions of diclofenac sodium and ispaghula husk were formulated by wet granulation technique at a fixed compression force of 10 kN. The formulated tablets were evaluated for ...

  15. Release rates of Al from inorganic and organic compounds in a sandy podzol, during laboratory experiments

    NARCIS (Netherlands)

    Salm, van der C.; Westerveld, J.W.; Verstraten, J.M.

    2000-01-01

    Research with respect to release rates of Al and Al concentrations in the soil solution has led to two contrasting hypotheses, stressing either the importance of kinetically constrained dissolution reactions or the role of complexation of Al to soil organic matter. The existence of two contrasting

  16. Antifouling composites with self-adaptive controlled release based on an active compound intercalated into layered double hydroxides

    Science.gov (United States)

    Yang, Miaosen; Gu, Lianghua; Yang, Bin; Wang, Li; Sun, Zhiyong; Zheng, Jiyong; Zhang, Jinwei; Hou, Jian; Lin, Cunguo

    2017-12-01

    This paper reports a novel method to prepare the antifouling composites with properties of self-adaptive controlled release (defined as control the release rate autonomously and adaptively according to the change of environmental conditions) by intercalation of sodium paeonolsilate (PAS) into MgAl and ZnAl layered double hydroxide (LDH) with the molar ratio (M2+/M3+) of 2:1 and 3:1, respectively. The powder X-ray diffraction (XRD) and Fourier transform infrared spectroscopy (FT-IR) confirm the intercalation of PAS into the galleries of LDH. The controlled release behavior triggered by temperature for the PAS-LDH composites has been investigated, and the results show that the release rate of all PAS-LDH composites increases as the increase of temperature. However, the MgAl-PAS-LDH composites (Mg2Al-PAS-LDH and Mg3Al-PAS-LDH) exhibit the increased release rate of 0.21 ppm/°C from 15 to 30 °C in 3.5% NaCl solution, more than three times of the ZnAl-PAS-LDH composites (0.06 ppm/°C), owing to the confined microenvironment influenced by metal types in LDH layers. In addition, a possible diffusion-controlled process with surface diffusion, bulk diffusion and heterogeneous flat surface diffusion has been revealed via fitting four kinetic equations. Moreover, to verify the practical application of the PAS-LDH composites, a model coating denoted as Mg2Al-PAS-LDH coating was fabricated. The release result displays that the release rate increases or decreases as temperature altered at 15 and 25 °C alternately, indicating its self-adaptive controlled release behavior with temperature. Moreover, the superior resistance to the settlement of Ulva spores at 15 and 25 °C was observed for the Mg2Al-PAS-LDH coating, as a result of the controllable release of antifoulant. Therefore, this work provides a facile and effective method for the fabrication of antifouling composites with self-adaptive controlled release behavior in response to temperature, which can be used to prolong

  17. Rapid Retinal Release from a Cone Visual Pigment Following Photoactivation*

    Science.gov (United States)

    Chen, Min-Hsuan; Kuemmel, Colleen; Birge, Robert R.; Knox, Barry E.

    2012-01-01

    As part of the visual cycle, the retinal chromophore in both rod and cone visual pigments undergoes reversible Schiff base hydrolysis and dissociation following photobleaching. We characterized light-activated retinal release from a short-wavelength sensitive cone pigment (VCOP) in 0.1% dodecyl maltoside using fluorescence spectroscopy. The half-time (t1/2) of retinal release from VCOP was 7.1 s, 250-fold faster than rhodopsin. VCOP exhibited pH-dependent release kinetics, with the t1/2 decreasing from 23 s to 4 s with pH 4.1 to 8, respectively. However, the Arrhenius activation energy (Ea) for VCOP derived from kinetic measurements between 4° and 20°C was 17.4 kcal/mol, similar to 18.5 kcal/mol for rhodopsin. There was a small kinetic isotope (D2O) effect in VCOP, but less than that observed in rhodopsin. Mutation of the primary Schiff base counterion (VCOPD108A) produced a pigment with an unprotonated chromophore (⌊max = 360 nm) and dramatically slowed (t1/2 ~ 6.8 min) light-dependent retinal release. Using homology modeling, a VCOP mutant with two substitutions (S85D/ D108A) was designed to move the counterion one alpha helical turn into the transmembrane region from the native position. This double mutant had a UV-visible absorption spectrum consistent with a protonated Schiff base (⌊max = 420 nm). Moreover, VCOPS85D/D108A mutant had retinal release kinetics (t1/2 = 7 s) and Ea (18 kcal/mol) similar to the native pigment exhibiting no pH-dependence. By contrast, the single mutant VCOPS85D had a ~3-fold decrease in retinal release rate compared to the native pigment. Photoactivated VCOPD108A had kinetics comparable to a rhodopsin counterion mutant, RhoE113Q, both requiring hydroxylamine to fully release retinal. These results demonstrate that the primary counterion of cone visual pigments is necessary for efficient Schiff base hydrolysis. We discuss how the large differences in retinal release rates between rod and cone visual pigments arise, not from

  18. Controlled Pesticide Release from Porous Composite Hydrogels Based on Lignin and Polyacrylic Acid

    Directory of Open Access Journals (Sweden)

    Yajie Sun

    2016-01-01

    Full Text Available For the controlled release of pesticides, a novel composite porous hydrogel (LBPAA was prepared based on lignin and polyacrylic acid for use as the support frame of a pore structure for water delivery. The LBPAA was analyzed to determine its water-swelling and slow release properties. The controlled release properties of LBPAA were evaluated through experiments in relation to the cumulative release of pesticides, with particular emphasis on environmental effects and release models. The porous LBPAA hydrogel showed improved properties compared to polyacrylic acid, and could therefore be considered an efficient material for application in controlled release systems in agriculture.

  19. The in Vitro Release of Indomethacin from Suppositories: Effects of Bases and Comparison of Different Dissolution Methods.

    Science.gov (United States)

    Mori, Kenji; Hori, Seiichi; Kawata, Tsubasa; Kogure, Sanae; Matsumoto, Kaori; Hasegawa, Tetsuya; Akimoto, Masayuki

    2017-01-01

    The suitability of apparatuses for the quality control of indomethacin (IND, 50 mg) compounded suppositories was evaluated and the effects of the type of suppository base on release profiles was investigated. The release characteristics of hydrophilic and lipophilic suppositories containing IND were compared using four types of dissolution methods: basket (RB), paddle (PD), dialysis tubing (DT) and flow-through cell (FTC). The release process was evaluated using the following model independent parameters: the mean dissolution time (MDT), cumulative percent of drug released (Q) at the end of the sampling time, and dissolution efficiency (DE). The fastest and most reproducible release profiles were observed for a hydrophilic base (macrogols), which resulted in more than 90% of the drug being released in 30 min using PD, RB and FTC. After 90 min, 90% of the total amount of the drug was released from a mixture of hydrophilic bases with a lipophilic base (macrogols and hard fat) in compendial dissolution methods and the mixture base was the second fastest only to the hydrophilic base. The slowest release profiles in each method were observed for the lipophilic base (hard fat). Poor drug release from any type of suppository base was noted using DT. Based on the results of the present study, FTC may be regarded as an adequate technique allowing sufficient discriminating power for the quality control of IND compounded suppositories.

  20. Impact of change of matrix crystallinity and polymorphism on ovalbumin release from lipid-based implants.

    Science.gov (United States)

    Duque, Luisa; Körber, Martin; Bodmeier, Roland

    2018-05-30

    The objectives of this study were to prepare lipid-based implants by hot melt extrusion (HME) for the prolonged release of ovalbumin (OVA), and to relate protein release to crystallinity and polymorphic changes of the lipid matrix. Two lipids, glycerol tristearate and hydrogenated palm oil, with different composition and degree of crystallinity were studied. Solid OVA was dispersed within the lipid matrixes, which preserved its stability during extrusion. This was partially attributed to a protective effect of the lipidic matrix. The incorporation of OVA decreased the mechanical strength of the implants prepared with the more crystalline matrix, glycerol tristearate, whereas it remained comparable for the hydrogenated palm oil because of stronger physical and non-covalent interactions between the protein and this lipid. This was also the reason for the faster release of OVA from the glycerol tristearate matrix when compared to the hydrogenated palm oil (8 vs. 28 weeks). Curing induced and increased crystallinity, and changes in the release rate, especially for the more crystalline matrix. In this case, both an increase and a decrease in release, were observed depending on the tempering condition. Curing at higher temperatures induced a melt-mediated crystallization and solid state transformation of the glycerol tristearate matrix and led to rearrangements of the inner structure with the formation of larger pores, which accelerated the release. In contrast, changes in the hydrogenated palm oil under the same curing conditions were less noticeable leading to a more robust formulation, because of less polymorphic changes over time. This study helps to understand the effect of lipid matrix composition and crystallinity degree on the performance of protein-loaded implants, and to establish criteria for the selection of a lipid carrier depending on the release profile desired. Copyright © 2018. Published by Elsevier B.V.

  1. Improved design and characterization of PLGA/PLA-coated Chitosan based micro-implants for controlled release of hydrophilic drugs.

    Science.gov (United States)

    Manna, Soumyarwit; Donnell, Anna M; Kaval, Necati; Al-Rjoub, Marwan F; Augsburger, James J; Banerjee, Rupak K

    2018-05-29

    Repetitive intravitreal injections of Methotrexate (MTX), a hydrophilic chemotherapeutic drug, are currently used to treat selected vitreoretinal (VR) diseases, such as intraocular lymphoma. To avoid complications associated with the rapid release of MTX from the injections, a Polylactic acid (PLA) and Chitosan (CS)-based MTX micro-implant prototype was fabricated in an earlier study, which showed a sustained therapeutic release rate of 0.2-2.0 µg/day of MTX for a period ∼1 month in vitro and in vivo. In the current study, different combinations of Poly(lactic-co-glycolic) acid (PLGA)/PLA coatings were used for lipophilic surface modification of the CS-MTX micro-implant, such as PLGA 5050, PLGA 6535 and PLGA 7525 (PLA: PGA - 50:50, 65:35, 75:25, respectively; M.W: 54,400 - 103,000) and different PLA, such as PLA 100 and PLA 250 (MW: 102,000 and 257,000, respectively). This improved the duration of total MTX release from the coated CS-MTX micro-implants to ∼3-5 months. With an increase in PLA content in PLGA and molecular weight of PLA, a) the initial burst of MTX and the mean release rate of MTX can be reduced; and b) the swelling and biodegradation of the micro-implants can be delayed. The controlled drug release mechanism is caused by a combination of diffusion process and hydrolysis of the polymer coating, which can be modulated by a) PLA content in PLGA and b) molecular weight of PLA, as inferred from Korsmeyer Peppas model, Zero order, First order and Higuchi model fits. This improved micro-implant formulation has the potential to serve as a platform for controlled release of hydrophilic drugs to treat selected VR diseases. Copyright © 2018. Published by Elsevier B.V.

  2. Development and evaluation of a new prototype P&T system to determine in-heading gas release rate.

    CSIR Research Space (South Africa)

    Van Zyl, FJ

    2001-11-01

    Full Text Available In order to quantify the potential methane hazard in underground coal mines, it is necessary to determine the in-seam methane content and an expected gas release rate during production. Various methods for estimating this have been proposed, ranging...

  3. Forest soil mineral weathering rates: use of multiple approaches

    Science.gov (United States)

    Randy K. Kolka; D.F. Grigal; E.A. Nater

    1996-01-01

    Knowledge of rates of release of base cations from mineral dissolution (weathering) is essential to understand ecosystem elemental cycling. Although much studied, rates remain enigmatic. We compared the results of four methods to determine cation (Ca + Mg + K) release rates at five forested soils/sites in the northcentral U.S.A. Our premise was that multiple...

  4. Quantifying methane emission from fugitive sources by combining tracer release and downwind measurements – A sensitivity analysis based on multiple field surveys

    DEFF Research Database (Denmark)

    Mønster, Jacob; Samuelsson, Jerker; Kjeldsen, Peter

    2014-01-01

    Using a dual species methane/acetylene instrument based on cavity ring down spectroscopy (CRDS), the dynamic plume tracer dispersion method for quantifying the emission rate of methane was successfully tested in four measurement campaigns: (1) controlled methane and trace gas release with differe...

  5. Release of Tenofovir from Carrageenan-Based Vaginal Suppositories

    Directory of Open Access Journals (Sweden)

    Toral Zaveri

    2014-07-01

    Full Text Available Microbicides are an active area of research for HIV prevention, being developed as a woman-initiated method of prevention during unprotected coitus. Along with safety and efficacy, assessing and improving compliance is a major area of research in microbicide development. We have produced microbicide prototypes in the form of semisoft vaginal suppositories prepared from carrageenan and conducted both qualitative and quantitative studies using these prototypes to determine the physical properties that drive acceptability and possibly adherence. In order to ensure that the suppositories function as effective drug delivery vehicles, we have conducted in vitro dissolution studies in water, vaginal simulant fluid (VSF and semen simulant fluid (SSF with suppositories loaded with the antiretroviral drug, tenofovir (TFV. TFV was released via diffusion and matrix erosion in water or by diffusion out of the matrix in VSF and SSF. Diffusion studies were conducted in two different volumes of VSF and SSF. The volume of VSF/SSF into which TFV diffused and the size of the suppositories determined the rate of diffusion from the suppositories. About 45%–50% of the encapsulated TFV diffused out of the suppositories within the first two hours, irrespective of suppository size, diffusion medium (VSF/SSF and the volume of medium. Prior work indicates that a short waiting period between insertion and coitus is highly desired by women; present data suggest our microbicide prototypes have rapid initial release followed by a slow release curve over the first 24 h.

  6. Kinetic coupling of phosphate release, force generation and rate-limiting steps in the cross-bridge cycle.

    Science.gov (United States)

    Stehle, Robert; Tesi, Chiara

    2017-08-01

    A basic goal in muscle research is to understand how the cyclic ATPase activity of cross-bridges is converted into mechanical force. A direct approach to study the chemo-mechanical coupling between P i release and the force-generating step is provided by the kinetics of force response induced by a rapid change in [P i ]. Classical studies on fibres using caged-P i discovered that rapid increases in [P i ] induce fast force decays dependent on final [P i ] whose kinetics were interpreted to probe a fast force-generating step prior to P i release. However, this hypothesis was called into question by studies on skeletal and cardiac myofibrils subjected to P i jumps in both directions (increases and decreases in [P i ]) which revealed that rapid decreases in [P i ] trigger force rises with slow kinetics, similar to those of calcium-induced force development and mechanically-induced force redevelopment at the same [P i ]. A possible explanation for this discrepancy came from imaging of individual sarcomeres in cardiac myofibrils, showing that the fast force decay upon increase in [P i ] results from so-called sarcomere 'give'. The slow force rise upon decrease in [P i ] was found to better reflect overall sarcomeres cross-bridge kinetics and its [P i ] dependence, suggesting that the force generation coupled to P i release cannot be separated from the rate-limiting transition. The reasons for the different conclusions achieved in fibre and myofibril studies are re-examined as the recent findings on cardiac myofibrils have fundamental consequences for the coupling between P i release, rate-limiting steps and force generation. The implications from P i -induced force kinetics of myofibrils are discussed in combination with historical and recent models of the cross-bridge cycle.

  7. Toxic chemical considerations for tank farm releases. Revision 1

    Energy Technology Data Exchange (ETDEWEB)

    Van Keuren, J.C.

    1995-11-01

    This document provides a method of determining the toxicological consequences of accidental releases from Hanford Tank Farms. A determination was made of the most restrictive toxic chemicals that are expected to be present in the tanks. Concentrations were estimated based on the maximum sample data for each analyte in all the tanks in the composite. Composite evaluated were liquids and solids from single shell tanks, double shell tanks, flammable gas watch list tanks, as well as all solids, all liquids, head space gases, and 241-C-106 solids. A sum of fractions of the health effects was computed for each composite for unit releases based emergency response planning guidelines (ERPGs). Where ERPGs were not available for chemical compounds of interest, surrogate guidelines were established. The calculation method in this report can be applied to actual release scenarios by multiplying the sum of fractions by the release rate for continuous releases, or the release amount for puff releases. Risk guidelines are met if the product is less than for equal to one.

  8. Toxic chemical considerations for tank farm releases. Revision 1

    International Nuclear Information System (INIS)

    Van Keuren, J.C.

    1995-11-01

    This document provides a method of determining the toxicological consequences of accidental releases from Hanford Tank Farms. A determination was made of the most restrictive toxic chemicals that are expected to be present in the tanks. Concentrations were estimated based on the maximum sample data for each analyte in all the tanks in the composite. Composite evaluated were liquids and solids from single shell tanks, double shell tanks, flammable gas watch list tanks, as well as all solids, all liquids, head space gases, and 241-C-106 solids. A sum of fractions of the health effects was computed for each composite for unit releases based emergency response planning guidelines (ERPGs). Where ERPGs were not available for chemical compounds of interest, surrogate guidelines were established. The calculation method in this report can be applied to actual release scenarios by multiplying the sum of fractions by the release rate for continuous releases, or the release amount for puff releases. Risk guidelines are met if the product is less than for equal to one

  9. Building an Efficient Model for Afterburn Energy Release

    Energy Technology Data Exchange (ETDEWEB)

    Alves, S; Kuhl, A; Najjar, F; Tringe, J; McMichael, L; Glascoe, L

    2012-02-03

    Many explosives will release additional energy after detonation as the detonation products mix with the ambient environment. This additional energy release, referred to as afterburn, is due to combustion of undetonated fuel with ambient oxygen. While the detonation energy release occurs on a time scale of microseconds, the afterburn energy release occurs on a time scale of milliseconds with a potentially varying energy release rate depending upon the local temperature and pressure. This afterburn energy release is not accounted for in typical equations of state, such as the Jones-Wilkins-Lee (JWL) model, used for modeling the detonation of explosives. Here we construct a straightforward and efficient approach, based on experiments and theory, to account for this additional energy release in a way that is tractable for large finite element fluid-structure problems. Barometric calorimeter experiments have been executed in both nitrogen and air environments to investigate the characteristics of afterburn for C-4 and other materials. These tests, which provide pressure time histories, along with theoretical and analytical solutions provide an engineering basis for modeling afterburn with numerical hydrocodes. It is toward this end that we have constructed a modified JWL equation of state to account for afterburn effects on the response of structures to blast. The modified equation of state includes a two phase afterburn energy release to represent variations in the energy release rate and an afterburn energy cutoff to account for partial reaction of the undetonated fuel.

  10. Dose rates as a function of time due to postulated radionuclide releases from the U.S. Yucca Mountain high-level radioactive waste repository

    International Nuclear Information System (INIS)

    Moeller, Dade W.; Sun, Lin-Shen C.; Cherry, Robert

    2008-01-01

    The Yucca Mountain repository, which is located in a remote area in the State of Nevada, is being constructed for the long-term care and disposal of spent nuclear fuel and vitrified high-level radioactive waste. In accordance with U.S. law, the U.S. Environmental Protection Agency (USEPA) promulgated Standards that limit the dose rates to members of the public due to the consumption of ground water, alone, and the consumption of ground water plus agricultural products irrigated with the contaminated ground water, and other exposures, such as those from external sources and the inhalation of airborne radioactive materials. As part of this exercise, the USEPA identified eight specific radionuclides to which their Standards are to apply. These are: 14 C, 99 Tc, 129 I, 226 Ra, 228 Ra, 237 Np, 239 Pu, and 241 Am. For purposes of the associated dose rate estimates, a range of conservative assumptions have been applied, all of which are designed to assure that the estimated dose rates are well above what might be expected under 'real-world' conditions. As a first step, it was assumed that: (1) at 10 4 year after repository closure, a fractional release of 10 -5 of the entire repository radionuclide inventory occurred; (2) the only prior reduction in the inventory was that due to radioactive decay; and (3) the sole path of exposure to neighboring population groups was through the consumption of 2 L d -1 of contaminated ground water. The accompanying analyses revealed that, of the eight radionuclides, only 226 Ra, 237 Np, and 239 Pu, will represent a significant source of dose at that time. To provide perspective and insights, the next step was to estimate the committed effective dose rates for all eight radionuclides based on an assumed fractional release each year of 10 -5 of the inventory from the time of repository closure up through the 10 6 year. For purposes of providing perspective, it was assumed that each dose rate estimate was independent, that is, no releases

  11. Correlation between Ni base alloys surface conditioning and cation release mitigation in primary coolant

    Energy Technology Data Exchange (ETDEWEB)

    Clauzel, M.; Guillodo, M.; Foucault, M. [AREVA NP SAS, Technical Centre, Le Creusot (France); Engler, N.; Chahma, F.; Brun, C. [AREVA NP SAS, Chemistry and Radiochemistry Group, Paris La Defense (France)

    2010-07-01

    The mastering of the reactor coolant system radioactive contamination is a real stake of performance for operating plants and new builds. The reduction of activated corrosion products deposited on RCS surfaces allows minimizing the global dose integrated by workers which supports the ALARA approach. Moreover, the contamination mastering limits the volumic activities in the primary coolant and thus optimizes the reactor shutdown duration and environment releases. The main contamination sources on PWR are due to Co-60 and Co-58 nuclides which come respectively Co-59 and Ni-58, naturally present in alloys used in the RCS. Co is naturally present as an impurity in alloys or as the main component of hardfacing materials (Stellites™). Ni is released mainly by SG tubes which represent the most important surface of the RCS. PWR steam generators (SG), due to the huge wetted surface are the main source of corrosion products release in the primary coolant circuit. As corrosion products may be transported throughout the whole circuit, activated in the core, and redeposited all over circuit surfaces, resulting in an increase of activity buildup, it is of primary importance to gain a better understanding of phenomenon leading to corrosion product release from SG tubes before setting up mitigation measures. Previous studies have shown that SG tubing made of the same material had different release rates. To find the origin of these discrepancies, investigations have been performed on tubes at the as-received state and after exposure to a nominal primary chemistry in titanium recirculating loop. These investigations highlighted the existence of a correlation between the inner surface metallurgical properties and the release of corrosion products in primary coolant. Oxide films formed in nominal primary chemistry are always protective, their morphology and their composition depending strongly on the geometrical, metallurgical and physico-chemical state of the surface on which they

  12. Release behavior and stability of encapsulated D-limonene from emulsion-based edible films.

    Science.gov (United States)

    Marcuzzo, Eva; Debeaufort, Frédéric; Sensidoni, Alessandro; Tat, Lara; Beney, Laurent; Hambleton, Alicia; Peressini, Donatella; Voilley, Andrée

    2012-12-12

    Edible films may act as carriers of active molecules, such as flavors. This possibility confers to them the status of active packaging. Two different film-forming biopolymers, gluten and ι-carrageenans, have been compared. D-Limonene was added to the two film formulations, and its release kinetics from emulsion-based edible films was assessed with HS-SPME. Results obtained for edible films were compared with D-limonene released from the fatty matrix called Grindsted Barrier System 2000 (GBS). Comparing ι-carrageenans with gluten-emulsified film, the latter showed more interesting encapsulating properties: in fact, D-limonene was retained by gluten film during the process needed for film preparation, and it was released gradually during analysis time. D-Limonene did not show great affinity to ι-carrageenans film, maybe due to high aroma compound hydrophobicity. Carvone release from the three different matrices was also measured to verify the effect of oxygen barrier performances of edible films to prevent D-limonene oxidation. Further investigations were carried out by FT-IR and liquid permeability measurements. Gluten film seemed to better protect D-limonene from oxidation. Gluten-based edible films represent an interesting opportunity as active packaging: they could retain and release aroma compounds gradually, showing different mechanical and nutritional properties from those of lipid-based ingredients.

  13. 47 CFR 65.800 - Rate base.

    Science.gov (United States)

    2010-10-01

    ... 47 Telecommunication 3 2010-10-01 2010-10-01 false Rate base. 65.800 Section 65.800 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) COMMON CARRIER SERVICES (CONTINUED) INTERSTATE RATE OF RETURN PRESCRIPTION PROCEDURES AND METHODOLOGIES Rate Base § 65.800 Rate base. The rate base shall...

  14. Investigating the in vitro drug release kinetics from controlled release diclofenac potassium-ethocel matrix tablets and the influence of co-excipients on drug release patterns.

    Science.gov (United States)

    Shah, Shefaat Ullah; Shah, Kifayat Ullah; Rehman, Asimur; Khan, Gul Majid

    2011-04-01

    The objective of the study was to formulate and evaluate controlled release polymeric tablets of Diclofenac Potassium for the release rate, release patterns and the mechanism involved in the release process of the drug. Formulations with different types and grades of Ethyl Cellulose Ether derivatives in several drug-to-polymer ratios (D:P) were compressed into tablets using the direct compression method. In vitro drug release studies were performed in phosphate buffer (pH 7.4) as dissolution medium by using USP Method-1 (Rotating Basket Method). Similarity factor f2 and dissimilarity factor f1 were applied for checking the similarities and dissimilarities of the release profiles of different formulations. For the determination of the release mechanism and drug release kinetics various mathematical/kinetic models were employed. It was found that all of the Ethocel polymers could significantly slow down the drug release rate with Ethocel FP polymers being the most efficient, especially at D:P ratios of 10:03 which lead towards the achievement of zero or near zero order release kinetics.

  15. SOURCE TERM ESTIMATION BASED on PLANT STATUS and on GAMMA DOSE RATES Measured by an ON-line environmental Monitoring Network

    International Nuclear Information System (INIS)

    Stubna, M.; Bujan, A.; Duranova, T.

    1997-01-01

    A number of severe accident analyses for reactor unit with WWER-440 (213) has been performed in order to evaluate the source term and radiological consequences. As a tool for these analyses the WWER modified version of Source Term Code Package and Real Time Accident Release Consequences codes have been used. A set of emergency procedures - manuals for quick estimation of the source term and countermeasures introduction during early -pre-release phase of severe accident progression has been developed at Nuclear Power Plants Research Institute Trnava, Inc. These manuals are subdivided into three groups: 1.) evaluation of the barriers integrity, 2.) source term estimation and 3.) estimation of the distances for the countermeasures introduction. A methodology and computer module for interpretation of environmental data - source term assessment during post-release phase from on-line environmental network has been developed at Nuclear Power Plants Research Institute Trnava, Inc. The method is based on the conversion of measured dose rates to the source term,i.e. airborne radioactivity release rate, taking into account real meteorological data and location of the measure points. The bootstrap method for the estimation of the mean value of source term Q as integral value of the release and confidence interval of Q has been selected. The methodology of Q distribution into fission product groups according to code Real Time Accident Release Consequences needs is based on known plant status, i.e. on the results of pre calculated accident sequences. The paper describes the methodologies introduced above and the way of their application

  16. Planar Diamond-Based Multiarrays to Monitor Neurotransmitter Release and Action Potential Firing: New Perspectives in Cellular Neuroscience.

    Science.gov (United States)

    Carabelli, Valentina; Marcantoni, Andrea; Picollo, Federico; Battiato, Alfio; Bernardi, Ettore; Pasquarelli, Alberto; Olivero, Paolo; Carbone, Emilio

    2017-02-15

    High biocompatibility, outstanding electrochemical responsiveness, inertness, and transparency make diamond-based multiarrays (DBMs) first-rate biosensors for in vitro detection of electrochemical and electrical signals from excitable cells together, with potential for in vivo applications as neural interfaces and prostheses. Here, we will review the electrochemical and physical properties of various DBMs and how these devices have been employed for recording released neurotransmitter molecules and all-or-none action potentials from living cells. Specifically, we will overview how DBMs can resolve localized exocytotic events from subcellular compartments using high-density microelectrode arrays (MEAs), or monitoring oxidizable neurotransmitter release from populations of cells in culture and tissue slices using low-density MEAs. Interfacing DBMs with excitable cells is currently leading to the promising opportunity of recording electrical signals as well as creating neuronal interfaces through the same device. Given the recent increasingly growing development of newly available DBMs of various geometries to monitor electrical activity and neurotransmitter release in a variety of excitable and neuronal tissues, the discussion will be limited to planar DBMs.

  17. Chitosan/alginate based multilayers to control drug release from ophthalmic lens.

    Science.gov (United States)

    Silva, Diana; Pinto, Luís F V; Bozukova, Dimitriya; Santos, Luís F; Serro, Ana Paula; Saramago, Benilde

    2016-11-01

    In this study we investigated the possibility of using layer-by-layer deposition, based in natural polymers (chitosan and alginate), to control the release of different ophthalmic drugs from three types of lens materials: a silicone-based hydrogel recently proposed by our group as drug releasing soft contact lens (SCL) material and two commercially available materials: CI26Y for intraocular lens (IOLs) and Definitive 50 for SCLs. The optimised coating, consisting in one double layer of (alginate - CaCl2)/(chitosan+glyoxal) topped with a final alginate-CaCl2 layer to avoid chitosan degradation by tear fluid proteins, proved to have excellent features to control the release of the anti-inflammatory, diclofenac, while keeping or improving the physical properties of the lenses. The coating leads to a controlled release of diclofenac from SCL and IOL materials for, at least, one week. Due to its high hydrophilicity (water contact angle≈0) and biocompatibility, it should avoid the use of further surface treatments to enhance the useŕs comfort. However, the barrier effect of this coating is specific for diclofenac, giving evidence to the need of optimizing the chemical composition of the layers in view of the desired drug. Copyright © 2016 Elsevier B.V. All rights reserved.

  18. Interaction between fed and gastric media (ensure Plus) and different hypromellose based caffeine controlled release tablets; comparison and mechanistic study of caffeine release in fed and fasted media versus water using USP dissolution apparatus 3

    DEFF Research Database (Denmark)

    Franek, Frans; Holm, Per; Larsen, Frank

    2014-01-01

    , which decreases erosion rate in 100 mPa s viscosity tablets, swelling in 15,000 mPa s viscosity tablets and caffeine release from both tablets. This observed interaction between Ensure Plus® and the HPMC tablets may translate into decreased drug release rate in the fed stomach, which may decrease...... using factorial designed experiments. Furthermore, the mechanism of release in Ensure Plus®, a nutrition drink similar in composition to the FDA standard meal, was investigated by studying tablet swelling using texture analysis. Altering dip speed has negligible effect on release and erosion rates...... the amount of drug available for absorption in the small intestine and thus reduce systemic drug exposure and maximum plasma concentration....

  19. Release kinetics of tocopherol and quercetin from binary antioxidant controlled-release packaging films.

    Science.gov (United States)

    Chen, Xi; Lee, Dong Sun; Zhu, Xuntao; Yam, Kit L

    2012-04-04

    This paper investigated the feasibility of manipulating packaging polymers with various degrees of hydrophobicity to release two antioxidants, tocopherol and quercetin, at rates suitable for long-term inhibition of lipid oxidation in food. For example, one antioxidant can be released at a fast rate to provide short-term/intermediate protection, whereas the other antioxidant can be released at a slower rate to provide intermediate/long-term protection of lipid oxidation. Controlled-release packaging films containing tocopherol and quercetin were produced using ethylene vinyl alcohol (EVOH), ethylene vinyl acetate (EVA), low-density polyethylene (LDPE), and polypropylene (PP) polymers; the release of these antioxidants to 95% ethanol (a fatty food simulant) was measured using UV-vis spectrophotometry, and Fickian diffusion models with appropriate initial and boundary conditions were used to fit the data. For films containing only quercetin, the results show that the release of quercetin was much faster but lasted for a much shorter time for hydrophilic polymers (EVOH and EVA) than for hydrophobic polymers (LDPE and PP). For binary antioxidant films containing tocopherol and quercetin, the results show that tocopherol released more rapidly but for a shorter period of time than quercetin in LDPE and EVOH films, and the difference is more pronounced for LDPE films than EVOH films. The results also show the presence of tocopherol can accelerate the release of quercetin. Although none of the films produced is acceptable for long-term lipid oxidation inhibition, the study provides encouraging results suggesting that acceptable films may be produced in the future using polymer blend films.

  20. Releasable Kinetic Energy-Based Inertial Control of a DFIG Wind Power Plant

    DEFF Research Database (Denmark)

    Lee, Jinsik; Muljadi, Eduard; Sørensen, Poul Ejnar

    2016-01-01

    Wind turbine generators (WTGs) in a wind power plant (WPP) contain different levels of releasable kinetic energy (KE) because of the wake effects. This paper proposes a releasable KE-based inertial control scheme for a doubly fed induction generator (DFIG) WPP that differentiates the contributions....... The proposed scheme adjusts the two loop gains in a DFIG controller depending on its rotor speed so that a DFIG operating at a higher rotor speed releases more KE. The performance of the proposed scheme was investigated under various wind conditions. The results clearly indicate that the proposed scheme...

  1. Evaluation of Plantago major L. seed mucilage as a rate controlling matrix for sustained release of propranolol hydrochloride.

    Science.gov (United States)

    Saeedi, Majid; Morteza-Semnani, Katayoun; Sagheb-Doust, Mehdi

    2013-03-01

    Polysaccharide mucilage derived from the seeds of Plantago major L. (family Plantaginaceae) was investigated for use in matrix formulations containing propranolol hydrochloride. HPMC K4M and tragacanth were used as standards for comparison. The hardness, tensile strength, and friability of tablets increased as the concentration of mucilage increased, indicating good compactibility of mucilage powders. The rate of release of propranolol hydrochloride from P. major mucilage matrices was mainly controlled by the drug/mucilage ratio. Formulations containing P. major mucilage were found to exhibit a release rate comparable to HPMC containing matrices at a lower drug/polymer ratio (drug/HPMC 2:1). These results demonstrated that P. major mucilage is a better release retardant compared to tragacanth at an equivalent content. The results of kinetic analysis showed that in F3 (containing 1:2 drug/mucilage) the highest correlation coefficient was achieved with the zero order model. The swelling and erosion studies revealed that as the proportion of mucilage in tablets was increased, there was a corresponding increase in percent swelling and a decrease in percent erosion of tablets. The DSC and FT-IR studies showed that no formation of complex between the drug and mucilage or changes in crystallinity of the drug had occurred.

  2. Increased survival rate by local release of diclofenac in a murine model of recurrent oral carcinoma

    Directory of Open Access Journals (Sweden)

    Will OM

    2016-10-01

    Full Text Available Olga Maria Will,1,* Nicolai Purcz,2,* Athena Chalaris,3 Carola Heneweer,4,5 Susann Boretius,1 Larissa Purcz,2 Lila Nikkola,6 Nureddin Ashammakhi,6 Holger Kalthoff,7 Claus-Christian Glüer,1 Jörg Wiltfang,2 Yahya Açil,2 Sanjay Tiwari1 1Section Biomedical Imaging, Clinic for Radiology and Neuroradiology, MOIN CC, 2Department of Oral and Maxillofacial Surgery, University Hospital Schleswig-Holstein, 3Institute of Biochemistry, Christian-Albrechts-Universität zu Kiel, 4Clinic for Radiology and Neuroradiology, University Hospital Schleswig-Holstein, Kiel, 5Institute for Diagnostic and Interventional Radiology, University Hospital Cologne, Cologne, Germany; 6Department of Biomedical Engineering, Tampere University of Technology, Tampere, Finland; 7Institute for Experimental Cancer Research, University Hospital Schleswig-Holstein, Kiel, Germany *These authors contributed equally to this work Abstract: Despite aggressive treatment with radiation and combination chemotherapy following tumor resection, the 5-year survival rate for patients with head and neck cancer is at best only 50%. In this study, we examined the therapeutic potential of localized release of diclofenac from electrospun nanofibers generated from poly(d,l-lactide-co-glycolide polymer. Diclofenac was chosen since anti-inflammatory agents that inhibit cyclooxygenase have shown great potential in their ability to directly inhibit tumor growth as well as suppress inflammation-mediated tumor growth. A mouse resection model of oral carcinoma was developed by establishing tumor growth in the oral cavity by ultrasound-guided injection of 1 million SCC-9 cells in the floor of the mouth. Following resection, mice were allocated into four groups with the following treatment: 1 no treatment, 2 implanted scaffolds without diclofenac, 3 implanted scaffolds loaded with diclofenac, and 4 diclofenac given orally. Small animal ultrasound and magnetic resonance imaging were utilized for longitudinal

  3. Encapsulation of Volatile Citronella Essential Oil by Coacervation: Efficiency and Release Study

    Science.gov (United States)

    Manaf, M. A.; Subuki, I.; Jai, J.; Raslan, R.; Mustapa, A. N.

    2018-05-01

    The volatile citronella essential oil was encapsulated by simple coacervation and complex coacervation using Arabic gum and gelatin as wall material. Glutaraldehyde was used in the methodology as crosslinking agent. The citronella standard calibration graph obtained with R2 of 0.9523 was used for the accurate determination of encapsulation efficiency and release study. The release kinetic was analysed based on Fick"s law of diffusion for polymeric system and linear graph of Log fraction release over Log time was constructed to determine the release rate constant, k and diffusion coefficient, n. Both coacervation methods in the present study produce encapsulation efficiency around 94%. The produced capsules for both coacervation processes were discussed based on the capsules morphology and release kinetic mechanisms.

  4. Dissolution rates of aluminum-based spent fuels relevant to geological disposal

    International Nuclear Information System (INIS)

    Mickalonis, J.I.

    2000-01-01

    The Department of Energy is pursuing the option of direct disposal of a wide variety of spent nuclear fuels under its jurisdiction. Characterization of the various types of spent fuel is required prior to licensing by the Nuclear Regulatory Commission and acceptance of the fuel at a repository site. One category of required data is the expected rate of radionuclide and fissile release to the environment as a result of exposure to groundwater after closure of the repository. To provide this type of data for four different aluminum-based spent fuels, tests were conducted using a flow through method that allows the dissolution rate of the spent fuel matrix to be measured without interference by secondary precipitation reactions that would muddle interpretation of the results. Similar tests had been conducted earlier with light water reactor spent fuel, thereby allowing direct comparisons

  5. Uniformity of Peptide Release Is Maintained by Methylation of Release Factors

    Directory of Open Access Journals (Sweden)

    William E. Pierson

    2016-09-01

    Full Text Available Termination of protein synthesis on the ribosome is catalyzed by release factors (RFs, which share a conserved glycine-glycine-glutamine (GGQ motif. The glutamine residue is methylated in vivo, but a mechanistic understanding of its contribution to hydrolysis is lacking. Here, we show that the modification, apart from increasing the overall rate of termination on all dipeptides, substantially increases the rate of peptide release on a subset of amino acids. In the presence of unmethylated RFs, we measure rates of hydrolysis that are exceptionally slow on proline and glycine residues and approximately two orders of magnitude faster in the presence of the methylated factors. Structures of 70S ribosomes bound to methylated RF1 and RF2 reveal that the glutamine side-chain methylation packs against 23S rRNA nucleotide 2451, stabilizing the GGQ motif and placing the side-chain amide of the glutamine toward tRNA. These data provide a framework for understanding how release factor modifications impact termination.

  6. Improving release completeness from PLGA-based implants for the acid-labile model protein ovalbumin.

    Science.gov (United States)

    Duque, Luisa; Körber, Martin; Bodmeier, Roland

    2018-03-01

    The objectives of this study were to assess the feasibility of hot melt extrusion (HME) for the preparation of PLGA-based ovalbumin-loaded implants as well as to characterize and improve protein release from the implants. Ovalbumin (OVA) was stable during extrusion, which was attributed to a protective effect of the biodegradable matrix. OVA release was characterized by a low burst, a slow release up to day 21, which plateaued thereafter resulting in incomplete release for all evaluated protein loadings. Release incompleteness was accompanied by the formation of an insoluble residual mass. Further characterization of this mass indicated that it consisted of non-covalent protein aggregates and polymer, where ovalbumin was ionically bound as the pH inside the degrading matrix decreased below the pI of the protein. Although higher protein release was obtained with the inclusion of weak bases because of their neutralizing effect, OVA aggregation and release incompleteness were not fully avoided. With the use of shellac, a well-known enteric and biocompatible polymer, as protective excipient, a distinct late release phase occurred and release completeness was increased to more than 75% cumulative release. Shellac apparently protected the protein against the acidic microclimate due to its low solubility at low pH. Protected OVA was thus released once the pH increased due to a declining PLGA-oligomer formation. The result was a triphasic release profile consisting of an initial burst, a slow diffusion phase over about 7 weeks, and an erosion-controlled dissolution phase over the next 3 weeks. An acid-labile protein like OVA was thus feasibly protected from interactions with PLGA and its degradation products, resulting in a controlled delivery of more than 85% of the original payload. Copyright © 2018 Elsevier B.V. All rights reserved.

  7. Design and evaluation of nicorandil extended-release tablet

    Directory of Open Access Journals (Sweden)

    Ju-Young Kim

    2015-04-01

    Full Text Available The aim of this study was to design and evaluate extended-release formulations of a model drug, nicorandil, in order to achieve the desired steady-state plasma concentration of drug in vivo. Simulation was employed to estimate optimum dissolution and absorption rate of nicorandil. The dissolution test was employed using pH 1.2, 4.0, 6.8 buffer solution, or water, to measure the in vitro release behaviors of nicorandil formulations. A single dose (15 mg of each formulation was orally administered to four beagle dogs under fasted conditions, and the pharmacokinetic parameters were calculated. The in vitro/in vivo relationship of the extended-release formulation was confirmed using in vitro dissolution profiles and plasma concentrations of drug in beagle dogs. Nicorandil was released completely within 30 min from the immediate-release tablets and released for 24 h from the extended-release tablets. The nicorandil plasma concentration could be modified by adjusting the drug release rate from the extended-release formulation. The release rate of nicorandil was the rate-limiting step in the overall absorption of drug from the extended-release formulations. These results highlight the potential of a nicorandil extended-release formulation in the treatment of angina pectoris.

  8. Study of the ionization rate of the released deuterium in vacuum arc discharges with metal deuteride cathodes

    Science.gov (United States)

    Liu, Fei-Xiang; Long, Ji-Dong; Zheng, Le; Dong, Pan; Li, Chen; Chen, Wei

    2018-02-01

    The ionization rate of the released deuterium from a metal deuteride cathode in vacuum arc discharges is investigated by both experiments and modeling analysis. Experimental results show that the deuterium ionization rate increases from 2% to 30% with the increasing arc current in the range of 2-100 A. Thus the full ionization assumption, as is widely used in arc plasma simulations, is not satisfied for the released deuterium at low discharge current. According to the modeling results, the neutral-to-ion conversion efficiency for the deuterium traveling across the cathodic spot region can be significantly less than one, due to the fast plasma expansion and rarefaction in the vacuum. In addition, the model also reveals that, unlike the metal atoms which are mainly ionized in the sheath region and flow back to the cathode, the deuterium ionization primarily occurs in the quasi-neutral region and moves towards the anode. Consequently, the cathodic sheath layer acts like a filter that increases the deuterium fraction beyond the sheath region.

  9. Ingenious pH-sensitive dextran/mesoporous silica nanoparticles based drug delivery systems for controlled intracellular drug release.

    Science.gov (United States)

    Zhang, Min; Liu, Jia; Kuang, Ying; Li, Qilin; Zheng, Di-Wei; Song, Qiongfang; Chen, Hui; Chen, Xueqin; Xu, Yanglin; Li, Cao; Jiang, Bingbing

    2017-05-01

    In this work, dextran, a polysaccharide with excellent biocompatibility, is applied as the "gatekeeper" to fabricate the pH-sensitive dextran/mesoporous silica nanoparticles (MSNs) based drug delivery systems for controlled intracellular drug release. Dextran encapsulating on the surface of MSNs is oxidized by NaIO 4 to obtain three kinds of dextran dialdehydes (PADs), which are then coupled with MSNs via pH-sensitive hydrazone bond to fabricate three kinds of drug carriers. At pH 7.4, PADs block the pores to prevent premature release of anti-cancer drug doxorubicin hydrochloride (DOX). However, in the weakly acidic intracellular environment (pH∼5.5) the hydrazone can be ruptured; and the drug can be released from the carriers. The drug loading capacity, entrapment efficiency and release rates of the drug carriers can be adjusted by the amount of NaIO 4 applied in the oxidation reaction. And from which DOX@MSN-NH-N=C-PAD 10 is chosen as the most satisfactory one for the further in vitro cytotoxicity studies and cellular uptake studies. The results demonstrate that DOX@MSN-NH-N=C-PAD 10 with an excellent pH-sensitivity can enter HeLa cells to release DOX intracellular due to the weakly acidic pH intracellular and kill the cells. In our opinion, the ingenious pH-sensitive drug delivery systems have application potentials for cancer therapy. Copyright © 2017 Elsevier B.V. All rights reserved.

  10. Design of tablets for the delayed and complete release of poorly water-soluble weak base drugs using SBE7M-β-CD as a solubilizing agent.

    Science.gov (United States)

    Rao, Venkatramana M; Zannou, Erika A; Stella, Valentino J

    2011-04-01

    The challenge of designing a delayed-release oral dosage form is significantly increased when the drug substance is poorly water soluble. This manuscript describes the design and characterization of a novel controlled-release film-coated tablet for the pH-triggered delayed and complete release of poorly water-soluble weak base drugs. Delivery of weak bases is specifically highlighted with the use of dipyridamole and prazosin as model compounds. Tailored delayed release is achieved with a combination of an insoluble but semipermeable polymer and an enteric polymer, such as cellulose acetate and hydroxypropyl cellulose phthalate, respectively, as coatings. The extent of the time lag prior to complete release depends on the film-coating composition and thickness. Complete release is achieved by the addition of a cyclodextrin, namely SBE7M-β-CD with or without a pH modifier added to the tablet core to ensure complete solubilization and release of the drug substance. The film-coating properties allow the complex formation/solubilization to occur in situ. Additionally, the drug release rate can be modulated on the basis of the cyclodextrin to drug molar ratio. This approach offers a platform technology for delayed release of potent but poorly soluble drugs and the release can be modulated by adjusting the film-coating composition and thickness and/or the cyclodextrin and pH modifier, if necessary. Copyright © 2010 Wiley-Liss, Inc.

  11. Base Rates: Both Neglected and Intuitive

    Science.gov (United States)

    Pennycook, Gordon; Trippas, Dries; Handley, Simon J.; Thompson, Valerie A.

    2014-01-01

    Base-rate neglect refers to the tendency for people to underweight base-rate probabilities in favor of diagnostic information. It is commonly held that base-rate neglect occurs because effortful (Type 2) reasoning is required to process base-rate information, whereas diagnostic information is accessible to fast, intuitive (Type 1) processing…

  12. Reduced rates of controlled-release fertilizer lower potential nitrogen leaching from a Wisconsin bare-root tree nursery

    Science.gov (United States)

    Ryosuke Fujinuma; Nick J. Balster; Hyung-Kyung. Lee

    2011-01-01

    Controlled-release fertilizer (CRF) typically increases nitrogen (N) fertilizer uptake and lowers N lost from the rooting zone via leaching. However, questions remain as to whether lower rates of CRF could further increase this efficiency, especially in sandy bare-root nurseries in Wisconsin. We hypothesized that: 1) a reduced CRF application at 60 percent of the...

  13. Vapour HF release of airgap-based UV-visible optical filters

    NARCIS (Netherlands)

    Ghaderi, M.; Ayerden, N.P.; De Graaf, G.; Wolffenbuttel, R.F.

    2015-01-01

    The design and CMOS-compatible fabrication of airgap-based optical filters in a surface micromachining process with sacrificial release using thevapour phase is presented. An airgap-dielectric layer combination offers a higher refractive index contrast, as compared to the conventional

  14. Drug release from non-aqueous suspensions. II. The release of methylxanthines from paraffin suspensions

    NARCIS (Netherlands)

    Blaey, C.J. de; Fokkens, J.G.

    1984-01-01

    The release of 3 methylxanthines, i.e. caffeine, theobromine and theophylline, from suspensions in liquid paraffin to an aqueous phase was determined in an in vitro apparatus. The release rates were determined as a function of the pH of the aqueous phase. It was proved that the release process was

  15. Helium release from radioisotope heat sources

    Energy Technology Data Exchange (ETDEWEB)

    Peterson, D.E.; Early, J.W.; Starzynski, J.S.; Land, C.C.

    1984-05-01

    Diffusion of helium in /sup 238/PuO/sub 2/ fuel was characterized as a function of the heating rate and the fuel microstructure. The samples were thermally ramped in an induction furnace and the helium release rates measured with an automated mass spectrometer. The diffusion constants and activation energies were obtained from the data using a simple diffusion model. The release rates of helium were correlated with the fuel microstructure by metallographic examination of fuel samples. The release mechanism consists of four regimes, which are dependent upon the temperature. Initially, the release is controlled by movement of point defects combined with trapping along grain boundaries. This regime is followed by a process dominated by formation and growth of helium bubbles along grain boundaries. The third regime involves volume diffusion controlled by movement of oxygen vacancies. Finally, the release at the highest temperatures follows the diffusion rate of intragranular bubbles. The tendency for helium to be trapped within the grain boundaries diminishes with small grain sizes, slow thermal pulses, and older fuel.

  16. Helium release from radioisotope heat sources

    International Nuclear Information System (INIS)

    Peterson, D.E.; Early, J.W.; Starzynski, J.S.; Land, C.C.

    1984-05-01

    Diffusion of helium in 238 PuO 2 fuel was characterized as a function of the heating rate and the fuel microstructure. The samples were thermally ramped in an induction furnace and the helium release rates measured with an automated mass spectrometer. The diffusion constants and activation energies were obtained from the data using a simple diffusion model. The release rates of helium were correlated with the fuel microstructure by metallographic examination of fuel samples. The release mechanism consists of four regimes, which are dependent upon the temperature. Initially, the release is controlled by movement of point defects combined with trapping along grain boundaries. This regime is followed by a process dominated by formation and growth of helium bubbles along grain boundaries. The third regime involves volume diffusion controlled by movement of oxygen vacancies. Finally, the release at the highest temperatures follows the diffusion rate of intragranular bubbles. The tendency for helium to be trapped within the grain boundaries diminishes with small grain sizes, slow thermal pulses, and older fuel

  17. Rates of opioid dispensing and overdose after introduction of abuse-deterrent extended-release oxycodone and withdrawal of propoxyphene.

    Science.gov (United States)

    Larochelle, Marc R; Zhang, Fang; Ross-Degnan, Dennis; Wharam, J Frank

    2015-06-01

    In the second half of 2010, abuse-deterrent extended-release oxycodone hydrochloride (OxyContin; Purdue Pharma) was introduced and propoxyphene was withdrawn from the US market. The effect of these pharmaceutical market changes on opioid dispensing and overdose rates is unknown. To evaluate the association between 2 temporally proximate changes in the opioid market and opioid dispensing and overdose rates. Claims from a large national US health insurer were analyzed, using an interrupted time series study design. Participants included an open cohort of 31.3 million commercially insured members aged 18 to 64 years between January 1, 2003, and December 31, 2012, with median follow-up of 20 months (last follow-up, December 31, 2012). Introduction of abuse-deterrent OxyContin (resistant to crushing or dissolving) on August 9, 2010, and market withdrawal of propoxyphene on November 19, 2010. Standardized opioid dispensing rates and prescription opioid and heroin overdose rates were the primary outcomes. We used segmented regression to analyze changes in outcomes from 30 quarters before to 8 quarters after the 2 interventions. Two years after the opioid market changes, total opioid dispensing decreased by 19% from the expected rate (absolute change, -32.2 mg morphine-equivalent dose per member per quarter [95% CI, -38.1 to -26.3]). By opioid subtype, the absolute change in dispensing by milligrams of morphine-equivalent dose per member per quarter at 2 years was -11.3 (95% CI, -12.4 to -10.1) for extended-release oxycodone, 3.26 (95% CI, 1.40 to 5.12) for other long-acting opioids, -8.19 (95% CI, -9.30 to -7.08) for propoxyphene, and -16.2 (95% CI, -18.8 to -13.5) for other immediate-release opioids. Two years after the market changes, the estimated overdose rate attributed to prescription opioids decreased by 20% (absolute change, -1.10 per 100,000 members per quarter [95% CI, -1.47 to -0.74]), but heroin overdose increased by 23% (absolute change, 0.26 per 100

  18. Predicting red wolf release success in the southeastern United States

    Science.gov (United States)

    van Manen, Frank T.; Crawford, Barron A.; Clark, Joseph D.

    2000-01-01

    Although the red wolf (Canis rufus) was once found throughout the southeastern United States, indiscriminate killing and habitat destruction reduced its range to a small section of coastal Texas and Louisiana. Wolves trapped from 1973 to 1980 were taken to establish a captive breeding program that was used to repatriate 2 mainland and 3 island red wolf populations. We collected data from 320 red wolf releases in these areas and classified each as a success or failure based on survival and reproductive criteria, and whether recaptures were necessary to resolve conflicts with humans. We evaluated the relations between release success and conditions at the release sites, characteristics of released wolves, and release procedures. Although <44% of the variation in release success was explained, model performance based on jackknife tests indicated a 72-80% correct prediction rate for the 4 operational models we developed. The models indicated that success was associated with human influences on the landscape and the level of wolf habituation to humans prior to release. We applied the models to 31 prospective areas for wolf repatriation and calculated an index of release success for each area. Decision-makers can use these models to objectively rank prospective release areas and compare strengths and weaknesses of each.

  19. Drug Release Studies from Caesalpinia pulcherrima Seed Polysaccharide.

    Science.gov (United States)

    Jeevanandham, Somasundaram; Dhachinamoorthi, Duraiswamy; Bannoth Chandra Sekhar, Kothapalli

    2011-01-01

    This study examines the controlled release behavior of both water-soluble (acetaminophen, caffeine, theophylline and salicylic acid) and water insoluble (indomethacin) drugs derived from Caesalpinia pulcherrima seed Gum isolated from Caesalpinia pulcherrima kernel powder. It further investigates the effect of incorporating diluents such as microcrystalline cellulose and lactose on caffeine release. In addition the effect the gum's (polysaccharide) partial cross-linking had on release of acetaminophen was examined. Applying the exponential equation, the soluble drugs mechanism of release was found to be anomalous. The insoluble drugs showed a near case II or zero order release mechanism. The rate of release in descending order was caffeine, acetaminophen, theophylline, salicylic acid and indomethacin. An increase in the release kinetics of the drug was observed on blending with diluents. However, the rate of release varied with the type and amount of blend within the matrix. The mechanism of release due to effect of diluents was found to be anomalous. The rate of drug release decreased upon partial cross-linking and the mechanism of release was found to be of super case II.

  20. A vacuum microgripping tool with integrated vibration releasing capability

    Energy Technology Data Exchange (ETDEWEB)

    Rong, Weibin; Fan, Zenghua, E-mail: zenghua-fan@163.com; Wang, Lefeng; Xie, Hui; Sun, Lining [State Key Laboratory of Robotics and System, Harbin Institute of Technology, Harbin, Heilongjiang (China)

    2014-08-01

    Pick-and-place of micro-objects is a basic task in various micromanipulation demands. Reliable releasing of micro-objects is usually disturbed due to strong scale effects. This paper focuses on a vacuum micro-gripper with vibration releasing functionality, which was designed and assembled for reliable micromanipulation tasks. Accordingly, a vibration releasing strategy of implementing a piezoelectric actuator on the vacuum microgripping tool is presented to address the releasing problem. The releasing mechanism was illustrated using a dynamic micro contact model. This model was developed via theoretical analysis, simulations and pull-off force measurement using atomic force microscopy. Micromanipulation experiments were conducted to verify the performance of the vacuum micro-gripper. The results show that, with the assistance of the vibration releasing, the vacuum microgripping tool can achieve reliable release of micro-objects. A releasing location accuracy of 4.5±0.5 μm and a successful releasing rate of around 100% (which is based on 110 trials) were achieved for manipulating polystyrene microspheres with radius of 35–100 μm.

  1. A vacuum microgripping tool with integrated vibration releasing capability

    International Nuclear Information System (INIS)

    Rong, Weibin; Fan, Zenghua; Wang, Lefeng; Xie, Hui; Sun, Lining

    2014-01-01

    Pick-and-place of micro-objects is a basic task in various micromanipulation demands. Reliable releasing of micro-objects is usually disturbed due to strong scale effects. This paper focuses on a vacuum micro-gripper with vibration releasing functionality, which was designed and assembled for reliable micromanipulation tasks. Accordingly, a vibration releasing strategy of implementing a piezoelectric actuator on the vacuum microgripping tool is presented to address the releasing problem. The releasing mechanism was illustrated using a dynamic micro contact model. This model was developed via theoretical analysis, simulations and pull-off force measurement using atomic force microscopy. Micromanipulation experiments were conducted to verify the performance of the vacuum micro-gripper. The results show that, with the assistance of the vibration releasing, the vacuum microgripping tool can achieve reliable release of micro-objects. A releasing location accuracy of 4.5±0.5 μm and a successful releasing rate of around 100% (which is based on 110 trials) were achieved for manipulating polystyrene microspheres with radius of 35–100 μm

  2. Controlled Release of Indomethacin from Smart Starch-Based Hydrogels Prepared Acrylic Acid and b-Cyclodextrin as a Nanocarrier

    Directory of Open Access Journals (Sweden)

    Hossein Ghasemzadeh Mohammadi

    2017-01-01

    Full Text Available Controlled release of drugs can reduce the undesired effects of drug level fluctuations, and diminish the side effects as well as improve the therapeutic outcome of the drugs. In recent year, the scope of the drug delivery systems has been greatly expanded by the development of various hydrogels. The present work has focused on the design of a pH sensitive drug delivery system (DDS based on starch, acrylic acid (AA and β-cyclodextrins for controlled delivery of indomethacin. The hydrogels were prepared via graft polymerization of acrylic acid (AA onto starch and β-cyclodextrins backbones by a free radical polymerization technique. Cyclodextrins are able to form water-soluble complexes with many lipophilic water-insoluble drugs. In aqueous solutions, the drug molecules located in the central cavity of the cyclodextrin are in a dynamic equilibrium with free drug molecules. The interaction of drug with the polymer was evidenced by FTIR spectroscopy and thermal gravimetric analysis (TGA. The morphology of the samples was examined by scanning electron microscopy (SEM. The results showed that the hydrogels have good porosity and provided high surface area for the loading and release of drugs. Drug release behavior was carried out at physiological conditions of phosphate buffer, pH 8. In basic pH (like the intestine medium the hydrogels released the indomethacin, but in acidic pH (like the stomach medium there was no tendency to drug release. By increasing the amount of cyclodextrin, the rate of drug loading and release increased due to the dynamic equilibrium and interaction between the loaded drug and the cyclodextrin. This study has demonstrated that the hydrogel matrices are potentially suitable for controlled-release systems.

  3. Uptake and release of glucose by the human kidney. Postabsorptive rates and responses to epinephrine.

    Science.gov (United States)

    Stumvoll, M; Chintalapudi, U; Perriello, G; Welle, S; Gutierrez, O; Gerich, J

    1995-11-01

    Despite ample evidence that the kidney can both produce and use appreciable amounts of glucose, the human kidney is generally regarded as playing a minor role in glucose homeostasis. This view is based on measurements of arteriorenal vein glucose concentrations indicating little or no net release of glucose. However, inferences from net balance measurements do not take into consideration the simultaneous release and uptake of glucose by the kidney. Therefore, to assess the contribution of release and uptake of glucose by the human kidney to overall entry and removal of plasma glucose, we used a combination of balance and isotope techniques to measure renal glucose net balance, fractional extraction, uptake and release as well as overall plasma glucose appearance and disposal in 10 normal volunteers under basal postabsorptive conditions and during a 3-h epinephrine infusion. In the basal postabsorptive state, there was small but significant net output of glucose by the kidney (66 +/- 22 mumol.min-1, P = 0.016). However, since renal glucose fractional extraction averaged 2.9 +/- 0.3%, there was considerable renal glucose uptake (2.3 +/- 0.2 mumol.kg-1.min-1) which accounted for 20.2 +/- 1.7% of systemic glucose disposal (11.4 +/- 0.5 mumol.kg-1.min-1). Renal glucose release (3.2 +/- 0.2 mumol.kg-1.min-1) accounted for 27.8 +/- 2.1% of systemic glucose appearance (11.4 +/- 0.5 mumol.kg-1.min-1). Epinephrine infusion, which increased plasma epinephrine to levels observed during hypoglycemia (3722 +/- 453 pmol/liter) increased renal glucose release nearly twofold (5.2 +/- 0.5 vs 2.8 +/- 0.1 mol.kg-1.min-1, P = 0.01) so that at the end of the infusion, renal glucose release accounted for 40.3 +/- 5.5% of systemic glucose appearance and essentially all of the increase in systemic glucose appearance. These observations suggest an important role for the human kidney in glucose homeostasis.

  4. Effect of temperature and ph on the drug release rate from a polymer conjugate system

    International Nuclear Information System (INIS)

    Kenawy, E.; Abdel-Hay, F.I.; El-Newehy, M.H.; Ottenbrite, R.M.

    2005-01-01

    Hydroximide and A-methylhydroxamic acid of poly(ethylene-altmaleic anhydride) (average MW 100-500 k) were used as a carrier for a new drug delivery system. The synthesis of the hydroximide and N methylhydroxamic acid of poly(ethylene-alt-maleic anhydride) were carried out by chemical modification of poly(ethylene-alt-maleic anhydride) with hydroxylamine and N-methyl hydroxylamine, respectively, in N,N- dimethylformamide at room temperature to yield water soluble copolymer. Ketoprofen was reacted with hydroximide and N-methylhydroxamic acid derivatives of poly(ethylene-alt-maleic anhydride) using dicyclohexylcarbodiimide as condensation agent at -5 degree C to yield water insoluble ketoprofen conjugates. All products were characterized by elemental analysis, FTIR and 1HNMR spectra. The in-vitro ketoprofen release was carried out by UV spectrophotometer at max =260 nm. The results demonstrated the effectiveness of hydroximide and N-methylhydroxamic acid of polyethylene-alt-maleic anhydride) as a drug delivery system. The release rates were studied at various ph and temperatures. The copolymer-drug adducts released the drug very slowly at the low ph found in the stomach thus protecting the drug from the action of high concentrations of digestive acids. These results showed the usefulness of hydroxamic acid polymer-drug conjugates as a new drug delivery system for drugs to be targeted to sites in the GI system

  5. Modulation of drug release kinetics of shellac-based matrix tablets by in-situ polymerization through annealing process.

    Science.gov (United States)

    Limmatvapirat, Sontaya; Limmatvapirat, Chutima; Puttipipatkhachorn, Satit; Nunthanid, Jurairat; Luangtana-anan, Manee; Sriamornsak, Pornsak

    2008-08-01

    A new oral-controlled release matrix tablet based on shellac polymer was designed and developed, using metronidazole (MZ) as a model drug. The shellac-based matrix tablets were prepared by wet granulation using different amounts of shellac and lactose. The effect of annealing temperature and pH of medium on drug release from matrix tablets was investigated. The increased amount of shellac and increased annealing temperature significantly affected the physical properties (i.e., tablet hardness and tablet disintegration) and MZ release from the matrix tablets. The in-situ polymerization played a major role on the changes in shellac properties during annealing process. Though the shellac did not dissolve in acid medium, the MZ release in 0.1N HCl was faster than in pH 7.3 buffer, resulting from a higher solubility of MZ in acid medium. The modulation of MZ release kinetics from shellac-based matrix tablets could be accomplished by varying the amount of shellac or annealing temperature. The release kinetics was shifted from relaxation-controlled release to diffusion-controlled release when the amount of shellac or the annealing temperature was increased.

  6. Use of OND-86 recommendations for calculation of the Shelter radioactive release

    International Nuclear Information System (INIS)

    Bogatov, S.A.

    2000-01-01

    A model of radioactive release from the Shelter has been considered under current operation conditions. Integral assessment of current dust release has been done on the base of natural ventilation rate. Model predictions are consistent (20% accuracy) with experimental results of air contamination measurements at the earth surface. 12 refs., 1 tab., 6 figs

  7. Radionuclide release from low-level waste in field lysimeters

    International Nuclear Information System (INIS)

    Oblath, S.B.

    1986-01-01

    A field program has been in operation for 8 years at the Savannah River Plant (SRP) to determine the leaching/migration behavior of low-level radioactive waste using lysimeters. The lysimeters are soil-filled caissons containing well characterized wastes, with each lysimeter serving as a model of a shallow land burial trench. Sampling and analysis of percolate water and vegetation from the lysimeters provide a determination of the release rates of the radionuclides from the waste/soil system. Vegetative uptake appears to be a major pathway for migration. Fractional release rates from the waste/soil system are less than 0.01% per year. Waste-to-soil leach rates up to 10% per year have been determined by coring several of the lysimeters. The leaching of solidified wasteforms under unsaturated field conditions has agreed well with static, immersion leaching of the same type waste in the laboratory. However, releases from the waste/soil system in the lysimeter may be greater than predicted based on leaching alone, due to complexation of the radionuclides by other components leached from the wastes to form mobile, anionic species

  8. Reaction rate estimation of controlled-release antifouling paint binders: Rosin-based systems

    DEFF Research Database (Denmark)

    Meseguer Yebra, Diego; Kiil, Søren; Dam-Johansen, Kim

    2005-01-01

    Biofouling on ship hulls is prevented by the use of antifouling (A/F) paints. Typically, sea water soluble rosin or rosin-derivatives are used as the primary means of adjusting the polishing rate of the current chemically active self-polishing paint systems to a suitable value. Previous studies h...

  9. Influence of Groundwater Flow Rate on Nuclide Releases from Pyro-processed Waste Repository

    International Nuclear Information System (INIS)

    Lee, Youn Myoung; Jeong, Jong Tae

    2011-01-01

    Since the early 2000s several template programs for the safety assessment of a high-level radioactive waste repository as well as a low- and intermediate level radioactive waste repository systems have been developed by utilizing GoldSim and AMBER at KAERI. Very recently, another template program for a conceptual hybrid-typed repository system, called 'A-KRS' in which two kinds of pyroprocessed radioactive wastes, low-level metal wastes and ceramic high-level wastes that arise from pyroprocessing of PWR nuclear spent fuels has been developed and are to be disposed of by separate disposal strategies. The A-KRS is considered to be constructed at two different depths in geological media: 200m depth, at which a possible human intrusion is considered to be limited after closure, for the pyroprocessed metal wastes with lower or no decay heat producing nuclides, and 500m depth, believed to be in the reducing condition for nuclides with a rather higher radioactivity and heat generation rate. This program is ready for total system performance assessment which is able to evaluate nuclide release from the repository and farther transport into the geosphere and biosphere under various normal, disruptive natural and manmade events, and scenarios that can occur after a failure of waste package and canister. To quantify a nuclide release and transport through the possible various pathways especially in the near-fields of the A-KRS repository system, some illustrative evaluations have been made through the study. Even though all parameter values associated with the A-KRS were assumed for the time being, the illustrative results should be informative since the evaluation of such releases is very important not only in view of the safety assessment of the repository, but also for design feedback of its performance

  10. Comparative evaluation of carbamazepine release from single and ...

    African Journals Online (AJOL)

    In the present study the release rate and kinetics of carbamazepine as a model drug from various single and bi-polymeric matrices were studied. Matrices containing different percentages of hydroxylpropyl methylcellulose (HPMC), ethylcellulose (EC), Eudragit RS (EuRS) or various ratios of polymer blends based on HPMC ...

  11. Effect of buffer thickness on the retardation of radionuclide release from the high-level waste repository

    International Nuclear Information System (INIS)

    Cho, Won Jin; Lee, Jae Owan; Kang, Chul Hyung; Han, Kyung Won

    2000-12-01

    The radionuclide release from buffer in the high-level waste repository to the surrounding host rock was assessed, and the effect of the radial buffer thickness on the release rate was analyzed. The total release rates decrease sharply with increasing radial buffer thickness up to 0.25 m, and decrease moderately at the buffer thickness between 0.25 m and 0.5 m. But increasing the radial buffer thickness beyond 0.5 m has little effect in reducing radionuclide release. Therefore a radial buffer thickness between 0.25 m and 0.5 m is sufficient based on the viewpoint of radionuclide retention

  12. Surface displacements and energy release rates for constant stress drop slip zones in joined elastic quarter spaces

    Science.gov (United States)

    Rodgers, Michael J.; Wen, Shengmin; Keer, Leon M.

    2000-08-01

    A three-dimensional quasi-static model of faulting in an elastic half-space with a horizontal change of material properties (i.e., joined elastic quarter spaces) is considered. A boundary element method is used with a stress drop slip zone approach so that the fault surface relative displacements as well as the free surface displacements are approximated in elements over their respective domains. Stress intensity factors and free surface displacements are calculated for a variety of cases to show the phenomenological behavior of faulting in such a medium. These calculations showed that the behavior could be distinguished from a uniform half-space. Slip in a stiffer material increases, while slip in a softer material decreases the energy release rate and the free surface displacements. Also, the 1989 Kalapana earthquake was located on the basis of a series of forward searches using this method and leveling data. The located depth is 8 km, which is the closer to the seismically inferred depth than that determined from other models. Finally, the energy release rate, which can be used as a fracture criterion for fracture at this depth, is calculated to be 11.1×106 J m-2.

  13. Fouling release nanostructured coatings based on PDMS-polyurea segmented copolymers

    KAUST Repository

    Fang, Jason

    2010-05-01

    The bulk and surface characteristics of a series of coatings based on PDMS-polyurea segmented copolymers were correlated to their fouling release performance. Incorporation of polyurea segments to PDMS backbone gives rise to phase separation with the extensively hydrogen bonded hard domains creating an interconnected network that imparts mechanical rigidity. Increasing the compositional complexity of the system by including fluorinated or POSS-functionalized chain extenders or through nanoclay intercalation, confers further thermomechanical improvements. In analogy to the bulk morphology, the surface topography also reflects the compositional complexity of the materials, displaying a wide range of motifs. Investigations on settlement and subsequent removal of Ulva sporelings on those nanostructured surfaces indicate that the work required to remove the microorganisms is significantly lower compared to coatings based on standard PDMS homopolymer. All in all, the series of materials considered in this study demonstrate advanced fouling release properties, while exhibiting superior mechanical properties and, thus, long term durability. © 2010 Elsevier Ltd.

  14. Fission gas release of MOX with heterogeneous structure

    International Nuclear Information System (INIS)

    Nakae, N.; Akiyama, H.; Kamimura, K; Delville, R.; Jutier, F.; Verwerft, M.; Miura, H.; Baba, T.

    2015-01-01

    It is very useful for fuel integrity evaluation to accumulate knowledge base on fuel behavior of uranium and plutonium mixed oxide (MOX) fuel used in light water reactors (LWRs). Fission gas release is one of fuel behaviors which have an impact on fuel integrity evaluation. Fission gas release behavior of MOX fuels having heterogeneous structure is focused in this study. MOX fuel rods with a heterogeneous fuel microstructure were irradiated in Halden reactor (IFA-702) and the BR-3/BR-2 CALLISTO Loop (CHIPS program). The 85 Kr gamma spectrometry measurements were carried out in specific cycles in order to examine the concerned LHR (Linear Heat Rate) for fission gas release in the CHIPS program. The concerned LHR is defined in this paper to be the LHR at which a certain additional fission gas release thermally occurs. Post-irradiation examination was performed to understand the fission gas release behavior in connection with the pellet microstructure. The followings conclusions can be made from this study. First, the concerned LHR for fission gas release is estimated to be in the range of 20-23 kW/m with burnup over 37 GWd/tM. It is moreover guessed that the concerned LHR for fission gas release tends to decrease with increasing burnup. Secondly It is observed that FGR (fission gas release rate) is positively correlated with LHR when the LHR exceeds the concerned value. Thirdly, when burnup dependence of fission gas release is discussed, effective burnup should be taken into account. The effective burnup is defined as the burnup at which the LHR should be exceed the concerned value at the last time during all the irradiation period. And fourthly, it appears that FGR inside Pu spots is higher than outside and that retained (not released) fission gases mainly exist in the fission gas bubbles. Since fission gases in bubbles are considered to be easily released during fuel temperature increase, this information is very important to estimate fission gas release behavior

  15. Predicting hydrocarbon release from soil

    International Nuclear Information System (INIS)

    Poppendieck, D.; Loehr, R.C.

    2002-01-01

    'Full text:' The remediation of hazardous chemicals from soils can be a lengthy and costly process. As a result, recent regulatory initiatives have focused on risk-based corrective action (RBCA) approaches. Such approaches attempt to identify the amount of chemical that can be left at a site with contaminated soil and still be protective of human health and the environment. For hydrocarbons in soils to pose risk to human heath and the environment, the hydrocarbons must be released from the soil and accessible to microorganisms, earthworms, or other higher level organisms. The sorption of hydrocarbons to soil can reduce the availability of the hydrocarbon to receptors. Typically in soils and sediments, there is an initial fast release of a hydrocarbon from the soil to the aqueous phase followed by a slower release of the remaining hydrocarbon to the aqueous phase. The rate and extent of slow release can influence aqueous hydrocarbon concentrations and the fate and transport of hydrocarbons in the subsurface. Once the fast fraction of the chemical has been removed from the soil, the remaining fraction of a chemical may desorb at a rate that natural mechanisms can attenuate the released hydrocarbon. Hence, active remediation may be needed only until the fast fraction has been removed. However, the fast fraction is a soil and chemical specific parameter. This presentation will present a tier I type protocol that has been developed to quickly estimate the fraction of hydrocarbons that are readily released from the soil matrix to the aqueous phase. Previous research in our laboratory and elsewhere has used long-term desorption (four months) studies to determine the readily released fraction. This research shows that a single short-term (less than two weeks) batch extraction procedure provides a good estimate of the fast released fraction derived from long-term experiments. This procedure can be used as a tool to rapidly evaluate the release and bioavailability of

  16. Changes in cortisol release and heart rate and heart rate variability during the initial training of 3-year-old sport horses.

    Science.gov (United States)

    Schmidt, Alice; Aurich, Jörg; Möstl, Erich; Müller, Jürgen; Aurich, Christine

    2010-09-01

    Based on cortisol release, a variety of situations to which domestic horses are exposed have been classified as stressors but studies on the stress during equestrian training are limited. In the present study, Warmblood stallions (n=9) and mares (n=7) were followed through a 9 respective 12-week initial training program in order to determine potentially stressful training steps. Salivary cortisol concentrations, beat-to-beat (RR) interval and heart rate variability (HRV) were determined. The HRV variables standard deviation of the RR interval (SDRR), RMSSD (root mean square of successive RR differences) and the geometric means standard deviation 1 (SD1) and 2 (SD2) were calculated. Nearly each training unit was associated with an increase in salivary cortisol concentrations (pHRV variables SDRR, RMSSD and SD1 decreased in response to training and lowest values were reached during mounting of a rider (pHRV variables increased again. In contrast, SD2 increased with the beginning of lunging (p<0.05) and no changes in response to mounting were detectable. In conclusion, initial training is a stressor for horses. The most pronounced reaction occurred in response to mounting by a rider, a situation resembling a potentially lethal threat under natural conditions. Copyright (c) 2010 Elsevier Inc. All rights reserved.

  17. Effect of rearing diet on the infection rate in flies released for the control of tsetse populations by sterile males

    International Nuclear Information System (INIS)

    Maudlin, I.

    1990-01-01

    In areas where sleeping sickness is endemic, it is the practice of sterile insect technique (SIT) programmes to give sterilized males a bloodmeal before release into the wild in order to reduce the risk of these released flies acting as disease vectors. This strategy has been adopted because of experimental evidence which showed that it was essential to infect flies at their first feed to establish a Tripanosoma brucei gambiense or T. b rhodesiense infection in tsetse flies. The aim of the work was to test artificial tsetse diets produced in the IAEA Laboratory at Seibersdorf in order to determine whether they were as effective as whole blood in inhibiting T. brucei sensu lato (sl) infections in flies. Seven artificial diets were tested with T.b. rhodesiense; Glossina morsitans morsitans males were fed one meal of the diet and then starved for 3 days before the infective feed. None of these diets significantly altered the infection rate of the treated flies and the seven groups produced statistically homogeneous results, with a mean midgut rate of 16% (control flies fed pig blood: 17%). Flies infected as tenerals with the same trypanosome stock produced midgut rates of 61%. Three of the diets were also tested with a T. congolense stock. There were no significant differences between flies fed artificial (mean midgut infection rate: 15%) and whole blood diets (19%). G. m. morsitans infected as tenerals with this trypanosome stock produced midgut rates of 66%. As with T. brucei sl infections, teneral flies were far more likely to develop a T. congolense infection than fed flies; this result suggests that all the tsetse flies used in SIT programmes should be fed before release in order to reduce the risk both to man and his livestock. Artificial diets are as effective as whole blood in inhibiting trypanosome infections. The effect of bloodmeal on the fly infection rates is discussed in relation to lectin production in fed flies. (author). 13 refs, 2 tabs

  18. Radionuclide releases from natural analogues of spent nuclear fuel

    International Nuclear Information System (INIS)

    Curtis, D.B.; Fabryka-Martin, J.; Dixon, P.; Aguilar, R.; Rokop, D.; Cramer, J.

    1993-01-01

    Measures of 99 Tc, 129 I, 239 Pu and U concentrations in rock samples from uranium deposits at Cigar Lake and Koongarra have been used to study processes of radionuclide release from uranium minerals. Rates of release have been immeasurably slow at Cigar Lake. At Koongarra release rates appear to have been faster, producing small deficiencies of 99 Tc, and larger ones of 129 I. The inferred differences in radionuclide release rates are consistent with expected differences in uranium mineral degradation rates produced by the differing hydrogeochemical environments at the two sites

  19. Formulation and release of alaptide from cellulose-based hydrogels

    Directory of Open Access Journals (Sweden)

    Zbyněk Sklenář

    2012-01-01

    Full Text Available The modern drug alaptide, synthetic dipeptide, shows regenerative effects and effects on the epitelisation process. A commercial product consisting of 1% alaptide hydrophilic cream is authorised for use in veterinary practice. This study focuses on the formulation of alaptide into semi-synthetic polymer-based hydrogels. The aim of the present study is to prepare hydrogels and to evaluate the liberation of alaptide from hydrogels. The hydrogels were prepared on the basis of three gel-producing substances: methylcellulose, hydroxyethylcellulose and hydroxypropylcellulose. To enhance the drug release from hydrogel humectants, glycerol, propylene glycol and ethanol in various concentrations were evaluated. The permeation of the alaptide from gels into the acceptor solution was evaluated with the use of the permeable membrane neprophane. The amount of drug released from prepared hydrogels was determined spectrophotometrically. Hydrogels with optimal alaptide liberation properties were subjected to the study of rheological properties in the next phase. The optimal composition of hydrogel as established in this study was 1% alaptide + 3% hydroxyethylcellulose with the addition of 10% glycerol as humectant. Due to the advantageous properties of hydrogels in wounds, alaptide could be incorporated into a hydrogel base for use in veterinary medicine.

  20. Ispaghula Husk-Based Extended Release Tablets of Diclofenac ...

    African Journals Online (AJOL)

    1Vels College of Pharmacy, Pallavaram, Chennai, India, 2Jeffrey Cheah School of Medicine and Health Sciences, Monash University, ... Keywords: Ispaghula husk, Extended release tablet, Diclofenac sodium, Release kinetics. .... release, i.e., Qt vs t, log (Q0-Qt) vs t and Qt vs .... Wallis TE, Textbook of Pharmacognosy, CBS.

  1. PWR-GALE, Radioactive Gaseous Release and Liquid Release from PWR

    International Nuclear Information System (INIS)

    Chandrasekaran, T.; Lee, J.Y.; Willis, C.A.

    1988-01-01

    1 - Description of program or function: The PWR-GALE (Boiling Water Reactor Gaseous and Liquid Effluents) Code is a computerized mathematical model for calculating the release of radioactive material in gaseous and liquid effluents from pressurized water reactors (PWRs). The calculations are based on data generated from operating reactors, field tests, laboratory tests, and plant-specific design considerations incorporated to reduce the quantity of radioactive materials that may be released to the environment. 2 - Method of solution: GALE calculates expected releases based on 1) standardized coolant activities derived from ANS Standards 18.1 Working Group recommendations, 2) release and transport mechanisms that result in the appearance of radioactive material in liquid and gaseous waste streams, 3) plant-specific design features used to reduce the quantities of radioactive materials ultimately released to the environs, and 4) information received on the operation of nuclear power plants. 3 - Restrictions on the complexity of the problem: The liquid release portion of GALE uses subroutines taken from the ORIGEN (CCC-217) to calculate radionuclide buildup and decay during collection, processing, and storage of liquid radwaste. Memory requirements for this part of the program are determined by the large nuclear data base accessed by these subroutines

  2. Gas Release as a Deformation Signal

    Energy Technology Data Exchange (ETDEWEB)

    Bauer, Stephen J. [Sandia National Lab. (SNL-NM), Albuquerque, NM (United States)

    2017-09-01

    Radiogenic noble gases are contained in crustal rock at inter and intra granular sites. The gas composition depends on lithology, geologic history, fluid phases, and the aging effect by decay of U, Th, and K. The isotopic signature of noble gases found in rocks is vastly different than that of the atmosphere which is contributed by a variety of sources. When rock is subjected to stress conditions exceeding about half its yield strength, micro-cracks begin to form. As rock deformation progresses a fracture network evolves, releasing trapped noble gases and changing the transport properties to gas migration. Thus, changes in gas emanation and noble gas composition from rocks could be used to infer changes in stress-state and deformation. The purpose of this study has been to evaluate the effect of deformation/strain rate upon noble gas release. Four triaxial experiments were attempted for a strain rate range of %7E10-8 /s (180,000s) to %7E 10-4/s (500s); the three fully successful experiments (at the faster strain rates) imply the following: (1) helium is measurably released for all strain rates during deformation, this release is in amounts 1-2 orders of magnitude greater than that present in the air, and (2) helium gas release increases with decreasing strain rate.

  3. Cargo Release from Polymeric Vesicles under Shear

    Directory of Open Access Journals (Sweden)

    Yingying Guo

    2018-03-01

    Full Text Available In this paper we study the release of cargo from polymeric nano-carriers under shear. Vesicles formed by two star block polymers— A 12 B 6 C 2 ( A B C and A 12 B 6 A 2 ( A B A —and one linear block copolymer— A 14 B 6 ( A B , are investigated using dissipative particle dynamics (DPD simulations. A - and C -blocks are solvophobic and B -block is solvophilic. The three polymers form vesicles of different structures. The vesicles are subjected to shear both in bulk and between solvophobic walls. In bulk shear, the mechanisms of cargo release are similar for all vesicles, with cargo travelling through vesicle membrane with no preferential release location. When sheared between walls, high cargo release rate is only observed with A B C vesicle after it touches the wall. For A B C vesicle, the critical condition for high cargo release rate is the formation of wall-polymersome interface after which the effect of shear rate in promoting cargo release is secondary. High release rate is achieved by the formation of solvophilic pathway allowing cargo to travel from the vesicle cavity to the vesicle exterior. The results in this paper show that well controlled target cargo release using polymersomes can be achieved with polymers of suitable design and can potentially be very useful for engineering applications. As an example, polymersomes can be used as carriers for surface active friction reducing additives which are only released at rubbing surfaces where the additives are needed most.

  4. Pharmacokinetic-pharmacodynamic analysis of antipsychotics-induced extrapyramidal symptoms based on receptor occupancy theory incorporating endogenous dopamine release.

    Science.gov (United States)

    Matsui-Sakata, Akiko; Ohtani, Hisakazu; Sawada, Yasufumi

    2005-06-01

    We aimed to analyze the risks of extrapyramidal symptoms (EPS) induced by typical and atypical antipsychotic drugs using a common pharmacokinetic-pharmacodynamic (PK-PD) model based on the receptor occupancy. We collected the data for EPS induced by atypical antipsychotics, risperidone, olanzapine and quetiapine, and a typical antipsychotic, haloperidol from literature and analyzed the following five indices of EPS, the ratio of patients obliged to take anticholinergic medication, the occurrence rates of plural extrapyramidal symptoms (more than one of tremor, dystonia, hypokinesia, akathisia, extrapyramidal syndrome, etc.), parkinsonism, akathisia, and extrapyramidal syndrome. We tested two models, i.e., a model incorporating endogenous dopamine release owing to 5-HT2A receptor inhibition and a model not considering the endogenous dopamine release, and used them to examine the relationship between the D2 receptor occupancy of endogenous dopamine and the extent of drug-induced EPS. The model incorporating endogenous dopamine release better described the relationship between the mean D2 receptor occupancy of endogenous dopamine and the extent of EPS than the other model, as assessed by the final sum of squares of residuals (final SS) and Akaike's Information Criteria (AIC). Furthermore, the former model could appropriately predict the risks of EPS induced by two other atypical antipsychotics, clozapine and ziprasidone, which were not incorporated into the model development. The developed model incorporating endogenous dopamine release owing to 5-HT2A receptor inhibition may be useful for the prediction of antipsychotics-induced EPS.

  5. Potential of phytase-mediated iron release from cereal-based foods: a quantitative view

    DEFF Research Database (Denmark)

    Nielsen, Anne Veller Friis; Tetens, Inge; Meyer, Anne S.

    2013-01-01

    The major part of iron present in plant foods such as cereals is largely unavailable for direct absorption in humans due to complexation with the negatively charged phosphate groups of phytate (myo-inositol (1,2,3,4,5,6)-hexakisphosphate). Human biology has not evolved an efficient mechanism...... to naturally release iron from iron phytate complexes. This narrative review will evaluate the quantitative significance of phytase-catalysed iron release from cereal foods. In vivo studies have shown how addition of microbially derived phytases to cereal-based foods has produced increased iron absorption via...... phytate complexes, and (3) the extent of phytate dephosphorylation required for iron release from inositol phosphates is warranted. Phytase-mediated iron release can improve iron absorption from plant foods. There is a need for development of innovative strategies to obtain better effects....

  6. The Influence of Polyethylene Glycol Solution on the Dissolution Rate of Sustained Release Morphine.

    Science.gov (United States)

    Hodgman, Michael; Holland, Michael G; Englich, Ulrich; Wojcik, Susan M; Grant, William D; Leitner, Erich

    2016-12-01

    Whole bowel irrigation (WBI) is a management option for overdose of medications poorly adsorbed to activated charcoal, with modified release properties, or for body packers. Polyethylene glycol (PEG) is a mixture of ethylene oxide polymers of varying molecular weight. PEG with an average molecular weight of 3350 g/mol is used for WBI. PEG electrolyte lavage solution has been shown in vitro to hasten the dissolution of acetaminophen. The impact of PEG on the pharmacokinetics of extended release pharmaceuticals is unknown. Lower average molecular weight PEG mixtures are used as solvents and excipients. We sought to investigate the impact of PEG on the release of morphine from several extended release morphine formulations. An in vitro gastric model was developed. To test the validity of our model, we first investigated the previously described interaction of ethanol and Avinza®. Once demonstrated, we then investigated the effect of PEG with several extended release morphine formulations. In the validation portion of our study, we confirmed an ethanol Avinza® interaction. Subsequently, we did not observe accelerated release of morphine from Avinza® or generic extended release morphine in the presence of PEG. The use of PEG for gastric decontamination following ingestion of these extended release morphine formulations is unlikely to accelerate morphine release and aggravate intoxication.

  7. Derived release limits for airborne effluents at TRIGA - INR Reactor

    International Nuclear Information System (INIS)

    Toma, A.; Dulama, C.; Hirica, O.; Mihai, S.; Oprea, I.

    2008-01-01

    Beginning from fulfilling the purposes of dose limitation system recommended by ICRP, and now accepted in radiation protection, this paper presents an environmental transfer model to calculate derived release limits for airborne and gaseous radioactive effluents at TRIGA-INR, 14 MW Steady State Reactor, in function on INR-Pitesti site. The methodology consists in determination of the principal exposure pathways for different groups of population and dose calculations for each radionuclide. The characterization of radionuclides transfer to environment was made using the compartmental model. The parameter transfer concept was used to describe the distribution of radionuclides between the different compartments. Atmospheric dispersion was very carefully treated, because it is the primary mechanism of the transfer of radionuclides in the environment and it determines all exposure pathways. Calculation of the atmospheric dispersion was made using ORION-II computer code based on the Gaussian plume model which takes account of site's specific climate and relief conditions. Default values recommended by literature were used to calculate some of the parameters when specific site values were not available. After identification of all transfer parameters which characterize the most important exposure pathways, the release rate corresponding to the individual dose rate limit was calculated. This maximum release rate is the derived release limit for each radionuclide and source. In the paper, the derived release limits are calculated for noble gases, radioiodine and other airborne particulate radionuclides, which can be released on the TRIGA-INR reactor stack, and are important to radiation protection. (authors)

  8. Modulating release of ranibizumab and aflibercept from thiolated chitosan-based hydrogels for potential treatment of ocular neovascularization.

    Science.gov (United States)

    Moreno, Miguel; Pow, Poh Yih; Tabitha, Tan Su Teng; Nirmal, Sonali; Larsson, Andreas; Radhakrishnan, Krishna; Nirmal, Jayabalan; Quah, Soo Tng; Geifman Shochat, Susana; Agrawal, Rupesh; Venkatraman, Subbu

    2017-08-01

    This paper describes the synthesis of thiolated chitosan-based hydrogels with varying degrees of crosslinking that has been utilized to modulate release kinetics of two clinically relevant FDA-approved anti-VEGF protein drugs, ranibizumab and aflibercept. These hydrogels have been fabricated into disc shaped structures for potential use as patches on ocular surface. Protein conformational changes and aggregation after loading and release was evaluated by circular dichroism (CD), steady-state tryptophan fluorescence spectroscopy, electrophoresis and size-exclusion chromatography (SEC). Finally, the capacity of both released proteins to bind to VEGF was tested by ELISA and surface plasmon resonance (SPR) technology. The study demonstrates the versatility of thiolated chitosan-based hydrogels for delivering proteins. The effect of various parameters of the hydrogel on protein release kinetics and mechanism of protein release was studied using the Korsmeyer-Peppas release model. Furthermore, we have studied the stability of released proteins in detail while comparing it with non-entrapped proteins under physiological conditions to understand the effect of formulation conditions on protein stability. The disc-shaped thiolated chitosan-based hydrogels provide a potentially useful platform to deliver ranibizumab and aflibercept for the treatments of ocular diseases such as wet AMD, DME and corneal neovascularization.

  9. Gas retention and release behavior in Hanford single-shell waste tanks

    International Nuclear Information System (INIS)

    Stewart, C.W.; Brewster, M.E.; Gauglitz, P.A.; Mahoney, L.A.; Meyer, P.A.; Recknagle, K.P.; Reid, H.C.

    1996-12-01

    This report describes the current understanding of flammable gas retention and release in Hanford single-shell waste tanks based on theory, experimental results, and observations of tank behavior. The single-shell tanks likely to pose a flammable gas hazard are listed and described, and photographs of core extrusions and the waste surface are included. The credible mechanisms for significant flammable gas releases are described, and release volumes and rates are quantified as much as possible. The only mechanism demonstrably capable of producing large (∼100 m 3 ) spontaneous gas releases is the buoyant displacement, which occurs only in tanks with a relatively deep layer of supernatant liquid. Only the double-shell tanks currently satisfy this condition. All release mechanisms believed plausible in single-shell tanks have been investigated, and none have the potential for large spontaneous gas releases. Only small spontaneous gas releases of several cubic meters are likely by these mechanisms. The reasons several other postulated gas release mechanisms are implausible or incredible are also given

  10. Microemulsion-Based Mucoadhesive Buccal Wafers: Wafer Formation, In Vitro Release, and Ex Vivo Evaluation.

    Science.gov (United States)

    Pham, Minh Nguyet; Van Vo, Toi; Tran, Van-Thanh; Tran, Phuong Ha-Lien; Tran, Thao Truong-Dinh

    2017-10-01

    Microemulsion has the potentials to enhance dissolution as well as facilitate absorption and permeation of poorly water-soluble drugs through biological membranes. However, its application to govern a controlled release buccal delivery for local treatment has not been discovered. The aim of this study is to develop microemulsion-based mucoadhesive wafers for buccal delivery based on an incorporation of the microemulsion with mucoadhesive agents and mannitol. Ratio of oil to surfactant to water in the microemulsion significantly impacted quality of the wafers. Furthermore, the combination of carbopol and mannitol played a key role in forming the desired buccal wafers. The addition of an extra 50% of water to the formulation was suitable for wafer formation by freeze-drying, which affected the appearance and distribution of carbopol in the wafers. The amount of carbopol was critical for the enhancement of mucoadhesive properties and the sustained drug release patterns. Release study presented a significant improvement of the drug release profile following sustained release for 6 h. Ex vivo mucoadhesive studies provided decisive evidence to the increased retention time of wafers along with the increased carbopol content. The success of this study indicates an encouraging strategy to formulate a controlled drug delivery system by incorporating microemulsions into mucoadhesive wafers.

  11. Tritium transport and release from lithium ceramic breeder materials

    International Nuclear Information System (INIS)

    Johnson, C.E.; Kopasz, J.P.; Tam, S.W.

    1994-01-01

    In an operating fusion reactor,, the tritium breeding blanket will reach a condition in which the tritium release rate equals the production rate. The tritium release rate must be fast enough that the tritium inventory in the blanket does not become excessive. Slow tritium release will result in a large tritium inventory, which is unacceptable from both economic and safety viewpoints As a consequence, considerable effort has been devoted to understanding the tritium release mechanism from ceramic breeders and beryllium neutron multipliers through theoretical, laboratory, and in-reactor studies. This information is being applied to the development of models for predicting tritium release for various blanket operating conditions

  12. Development of a cell-based bioassay for phospholipase A2-triggered liposomal drug release

    DEFF Research Database (Denmark)

    Arouri, Ahmad; Trojnar, Jakub; Schmidt, Steffen

    2015-01-01

    models, the pattern of sPLA2-assisted drug release is unknown due to the lack of a suitable bio-relevant model. We report here on the development of a novel bioluminescence living-cell-based luciferase assay for the monitoring of sPLA2-triggered release of luciferin from liposomes. To this end, we...

  13. Effect of synchronizing the rate of degradation of dietary energy and nitrogen release on growth performance in Brahman cattle

    Directory of Open Access Journals (Sweden)

    Virote Pattarajinda

    2006-01-01

    Full Text Available The objective of this research was to determine the effect of synchronizing the rate of degradation of dietary energy and nitrogen release on growth performance in Brahman beef cattle. Fifteen Brahman cattle, 1.5 years old, with an average initial body weight of 184.8±11.1 kg were assigned to one of three treatments according to a randomized complete block design. Dietary treatments contained 3 levels of synchrony index (0.39, 0.56 and 0.74 that were derived from laboratory chemical composition analysis and degradation kinetics using nylon bag technique. Diets were fed at the rate of 2.5% BW by separate concentrate and roughage. Average daily gain increased linearly (P<0.05 with increase levels of synchrony index in the diets. The digestibility of dry matter, organic matter and neutral detergent fiber increased linearly (P<0.01. The digestibility of acid detergent fiber increased linearly (P<0.05. Ruminal total volatile fatty acids concentration increased linearly (P<0.05 at 6 h post feeding. Higher concentration and fluctuation of ruminal ammonia nitrogen and blood urea nitrogen were observed in animals that received lower synchrony index in their diets. Rumen microbial population tended to increase with diets having higher levels of synchrony index. The results indicated that synchronized rate of dietary energy and nitrogen degradation improved ruminal fermentation and digestibility, thus this increased the growth rate in Brahman cattle fed with ricestraw- based diets.

  14. Biodegradable protein-based rockets for drug transportation and light-triggered release.

    Science.gov (United States)

    Wu, Zhiguang; Lin, Xiankun; Zou, Xian; Sun, Jianmin; He, Qiang

    2015-01-14

    We describe a biodegradable, self-propelled bovine serum albumin/poly-l-lysine (PLL/BSA) multilayer rocket as a smart vehicle for efficient anticancer drug encapsulation/delivery to cancer cells and near-infrared light controlled release. The rockets were constructed by a template-assisted layer-by-layer assembly of the PLL/BSA layers, followed by incorporation of a heat-sensitive gelatin hydrogel containing gold nanoparticles, doxorubicin, and catalase. These rockets can rapidly deliver the doxorubicin to the targeted cancer cell with a speed of up to 68 μm/s, through a combination of biocatalytic bubble propulsion and magnetic guidance. The photothermal effect of the gold nanoparticles under NIR irradiation enable the phase transition of the gelatin hydrogel for rapid release of the loaded doxorubicin and efficient killing of the surrounding cancer cells. Such biodegradable and multifunctional protein-based microrockets provide a convenient and efficient platform for the rapid delivery and controlled release of therapeutic drugs.

  15. Phytantriol based liquid crystal provide sustained release of anticancer drug as a novel embolic agent.

    Science.gov (United States)

    Qin, Lingzhen; Mei, Liling; Shan, Ziyun; Huang, Ying; Pan, Xin; Li, Ge; Gu, Yukun; Wu, Chuanbin

    2016-01-01

    Phytantriol has received increasing amount of attention in drug delivery system, however, the ability of the phytantriol based liquid crystal as a novel embolic agent to provide a sustained release delivery system is yet to be comprehensively demonstrated. The purpose of this study was to prepare a phytantriol-based cubic phase precursor solution loaded with anticancer drug hydroxycamptothecine (HCPT) and evaluate its embolization properties, in vitro drug release and cytotoxicity. Phase behavior of the phytantriol-solvent-water system was investigated by visual inspection and polarized light microscopy, and no phase transition was observed in the presence of HCPT within the studied dose range. Water uptake by the phytantriol matrices was determined gravimetrically, suggesting that the swelling complied with the second order kinetics. In vitro evaluation of embolic efficacy indicated that the isotropic solution displayed a satisfactory embolization effect. In vitro drug release results showed a sustained-release up to 30 days and the release behavior was affected by the initial composition and drug loading. Moreover, the in vitro cytotoxicity and anticancer activity were evaluated by MTT assay. No appreciable mortality was observed for NIH 3T3 cells after 48 h exposure to blank formulations, and the anticancer activity of HCPT-loaded formulations to HepG2 and SMMC7721 cells was strongly dependent on the drug loading and treatment time. Taken together, these results indicate that phytantriol-based cubic phase embolic gelling solution is a promising potential carrier for HCPT delivery to achieve a sustained drug release by vascular embolization, and this technology may be potential for clinical applications.

  16. The critical release rates for the dissociating gas N204/N02/N0

    International Nuclear Information System (INIS)

    Porter, W.H.L.

    1979-03-01

    Dissociating vapour systems have certain characteristics which make them attractive as coolants, notably a large effective specific heat which is significantly greater than that for the individual components of the gas mixture, and also an enhanced boundary layer heat transfer coefficient resulting from the physical characteristics of thermal dissociation. In part these effects ensure that a dissociating gas has a greatly improved thermal capacity and heat transfer capability when compared with most inert gases. In this report the critical release rates for the dissociating vapour system N 2 0 4 -N0 2 -N0 are established, principally in the two phase region, and the thermodynamics of nitrogen tetroxide are examined. (U.K.)

  17. Evaluation of hydrophobic materials as matrices for controlled-release drug delivery.

    Science.gov (United States)

    Quadir, Mohiuddin Abdul; Rahman, M Sharifur; Karim, M Ziaul; Akter, Sanjida; Awkat, M Talat Bin; Reza, Md Selim

    2003-07-01

    The present study was undertaken to evaluate the effect of different insoluble and erodable wax-lipid based materials and their content level on the release profile of drug from matrix systems. Matrix tablets of theophylline were prepared using carnauba wax, bees wax, stearic acid, cetyl alcohol, cetostearyl alcohol and glyceryl monostearate as rate-retarding agents by direct compression process. The release of theophylline from these hydrophobic matrices was studied over 8-hours in buffer media of pH 6.8. Statistically significant difference was found among the drug release profile from different matrices. The release kinetics was found to be governed by the type and content of hydrophobic materials in the matrix. At lower level of wax matrices (25%), a potential burst release was observed with all the materials being studied. Bees wax could not exert any sustaining action while an extensive burst release was found with carnauba wax at this hydrophobic load. Increasing the concentration of fat-wax materials significantly decreased the burst effect of drug from the matrix. At higher hydrophobic level (50% of the matrix), the rate and extent of drug release was significantly reduced due to increased tortuosity and reduced porosity of the matrix. Cetostearyl alcohol imparted the strongest retardation of drug release irrespective of fat-wax level. Numerical fits indicate that the Higuchi square root of time model was the most appropriate one for describing the release profile of theophylline from hydrophobic matrices. The release mechanism was also explored and explained with biexponential equation. Application of this model indicates that Fickian or case I kinetics is the predominant mechanism of drug release from these wax-lipid matrices. The mean dissolution time (MDT) was calculated for all the formulations and the highest MDT value was obtained with cetostearyl matrix. The greater sustaining activity of cetostearyl alcohol can be attributed to some level of

  18. Controlled release of isoproturon, imidacloprid, and cyromazine from alginate-bentonite-activated carbon formulations.

    Science.gov (United States)

    Garrido-Herrera, F J; Gonzalez-Pradas, E; Fernandez-Pérez, M

    2006-12-27

    Different alginate-based systems of isoproturon, imidacloprid, and cyromazine have been investigated in order to obtain controlled release (CR) properties. The basic formulation [sodium alginate (1.50%), pesticide (0.30%), and water] was modified using different amounts of bentonite and activated carbon. The higher values of encapsulation efficiency corresponded to those formulations prepared with higher percentages of activated carbon, showing higher encapsulation efficiency values for isoproturon and imidacloprid than for cyromazine, which has a higher water solubility. The kinetic experiments of imidacloprid/isoproturon release in water have shown us that the release rate is higher in imidacloprid systems than in those prepared with isoproturon. Moreover, it can be deduced that the use of bentonite and/or activated carbon sorbents reduces the release rate of the isoproturon and imidacloprid in comparison with the technical product and with alginate formulation without modifying agents. The highest decrease in release rate corresponds to the formulations prepared with the highest percentage of activated carbon. The water uptake, permeability, and time taken for 50% of the active ingredient to be released into water, T50, were calculated to compare the formulations. On the basis of a parameter of an empirical equation used to fit the pesticide release data, the release of isoproturon and imidacloprid from the various formulations into water is controlled by a diffusion mechanism. The sorption capacity of the sorbents and the permeability of the formulations were the most important factors modulating pesticide release. Finally, a linear correlation of the T50 values and the content of activated carbon in formulations were obtained.

  19. A model for the release of low-volatility fission products in oxidizing conditions

    International Nuclear Information System (INIS)

    Cox, D.S.; Hunt, C.E.L.; Liu, Z.; Keller, N.A.; Barrand, R.D.; O'Connor, R.F.

    1991-07-01

    A thermodynamic and kinetic model has been developed for calculating low-volatility fission-product releases from UO 2 at high temperatures in oxidizing conditions. Volatilization of the UO 2 matrix is assumed to be the rate controlling process. Oxidation kinetics of the UO 2 are modelled by either interfacial rate control, gas phase oxidant transport control, or solid-state diffusion of oxygen. The vapour pressure of UO 3 in equilibrium with the oxidizing fuel is calculated from thermodynamic data, and volatilization rates are determined using a model for forced convective mass transport. Low-volatility fission-product releases are calculated from the volume of vapourized fuel. Model calculations are conservative compared to experimental data for Zr, La, Ce and Nb fission-product releases from irradiated UO 2 exposed to air at 1973-2350 K. The implications of this conservatism are discussed in terms of possible rate control by processes other than convective mass transport of UO 3 . Coefficients for effective surface area (based on experimental data) and for heterogeneous rate controlling reaction kinetics are introduced to facilitate agreement between calculations and the experimental data.

  20. The effect of explosive percentage on underwater explosion energy release of hexanitrohexaazaisowurtzitane and octogen based aluminized explosives

    Directory of Open Access Journals (Sweden)

    Qingjie Jiao

    2018-03-01

    Full Text Available To control the explosion energy output by optimizing explosive components is a key requirement in a number of different application areas. The effect of different Al/O Ratio on underwater explosion of aluminized explosives has been studied detailedly. However, the effect of explosive percentage in the same Al/O Ratio is rarely researched, especially for Hexanitrohexaazaisowurtzitane (CL-20 based aluminized explosives. In this study, we performed the underwater explosion experiments with 1.2-kilogram explosives in order to investigate the explosion energy released from CL-20 and Octogen (HMX based aluminized explosives. The percentage of the explosive varied from 5% to 30% and it is shown that: the shockwave peak pressure (pm grows gradually; shock wave energy (Es continues increasing, bubble energy (Eb increases then decreases peaking at 15% for both formulas, and the total energy (E and energy release rate (η peak at 20% for CL-20 and 15% for HMX. This paper outlines the physical mechanism of Eb change under the influence of an aluminium initial reaction temperature and reaction active detonation product percentage coupling. The result shows that CL-20 is superior as a new high explosive and has promising application prospects in the regulation of explosive energy output for underwater explosives.

  1. The effect of explosive percentage on underwater explosion energy release of hexanitrohexaazaisowurtzitane and octogen based aluminized explosives

    Science.gov (United States)

    Jiao, Qingjie; Wang, Qiushi; Nie, Jianxin; Guo, Xueyong; Zhang, Wei; Fan, Wenqi

    2018-03-01

    To control the explosion energy output by optimizing explosive components is a key requirement in a number of different application areas. The effect of different Al/O Ratio on underwater explosion of aluminized explosives has been studied detailedly. However, the effect of explosive percentage in the same Al/O Ratio is rarely researched, especially for Hexanitrohexaazaisowurtzitane (CL-20) based aluminized explosives. In this study, we performed the underwater explosion experiments with 1.2-kilogram explosives in order to investigate the explosion energy released from CL-20 and Octogen (HMX) based aluminized explosives. The percentage of the explosive varied from 5% to 30% and it is shown that: the shockwave peak pressure (pm) grows gradually; shock wave energy (Es) continues increasing, bubble energy (Eb) increases then decreases peaking at 15% for both formulas, and the total energy (E) and energy release rate (η) peak at 20% for CL-20 and 15% for HMX. This paper outlines the physical mechanism of Eb change under the influence of an aluminium initial reaction temperature and reaction active detonation product percentage coupling. The result shows that CL-20 is superior as a new high explosive and has promising application prospects in the regulation of explosive energy output for underwater explosives.

  2. Rain-rate data base development and rain-rate climate analysis

    Science.gov (United States)

    Crane, Robert K.

    1993-01-01

    The single-year rain-rate distribution data available within the archives of Consultative Committee for International Radio (CCIR) Study Group 5 were compiled into a data base for use in rain-rate climate modeling and for the preparation of predictions of attenuation statistics. The four year set of tip-time sequences provided by J. Goldhirsh for locations near Wallops Island were processed to compile monthly and annual distributions of rain rate and of event durations for intervals above and below preset thresholds. A four-year data set of tropical rain-rate tip-time sequences were acquired from the NASA TRMM program for 30 gauges near Darwin, Australia. They were also processed for inclusion in the CCIR data base and the expanded data base for monthly observations at the University of Oklahoma. The empirical rain-rate distributions (edfs) accepted for inclusion in the CCIR data base were used to estimate parameters for several rain-rate distribution models: the lognormal model, the Crane two-component model, and the three parameter model proposed by Moupfuma. The intent of this segment of the study is to obtain a limited set of parameters that can be mapped globally for use in rain attenuation predictions. If the form of the distribution can be established, then perhaps available climatological data can be used to estimate the parameters rather than requiring years of rain-rate observations to set the parameters. The two-component model provided the best fit to the Wallops Island data but the Moupfuma model provided the best fit to the Darwin data.

  3. A REVIEW ON CONTROLLED DRUG RELEASE FORMULATION: SPANSULES

    OpenAIRE

    Rinky Maurya; Dr. Pramod Kumar Sharma; Rishabha Malviya

    2014-01-01

    Spansules are a dosage form which was considered as one of the Advanced Drug Delivery System. Multidrug preparations can be delivered easily by spansules or granules in capsule technology. This type of delivery system designed to release a drug or a medicament at two or more different rates or in different span of time. A quick/slow release system provides an initial release of drug followed by a constant rate of drug release over a extended period or a defined period of time and in slow/quic...

  4. Development of thermosensitive poly(n-isopropylacrylamide-co-((2-dimethylamino) ethyl methacrylate))-based nanoparticles for controlled drug release

    Energy Technology Data Exchange (ETDEWEB)

    Peng, Cheng-Liang; Luo, Tsai-Yueh; Lin, Wuu-Jyh [Isotope Application Division, Institute of Nuclear Energy Research, PO Box 3-27, Longtan Taoyuan 325, Taiwan (China); Tsai, Han-Min; Yang, Shu-Jyuan; Lin, Chia-Fu; Shieh, Ming-Jium, E-mail: soloman@ntu.edu.tw [Institute of Biomedical Engineering, College of Medicine and College of Engineering, National Taiwan University, No 1, Section 1, Jen-Ai Road, Taipei 10051, Taiwan (China)

    2011-07-01

    Thermosensitive nanoparticles based on poly(N-isopropylacrylamide-co-((2-dimethylamino)ethylmethacrylate)) (poly(NIPA-co-DMAEMA)) copolymers were successfully fabricated by free radical polymerization. The lower critical solution temperature (LCST) of the synthesized nanoparticles was 41 deg. C and a temperature above which would cause the nanoparticles to undergo a volume phase transition from 140 to 100 nm, which could result in the expulsion of encapsulated drugs. Therefore, we used the poly(NIPA-co-DMAEMA) nanoparticles as a carrier for the controlled release of a hydrophobic anticancer agent, 7-ethyl-10-hydroxy-camptothecin (SN-38). The encapsulation efficiency and loading content of SN-38-loaded nanoparticles at an SN-38/poly(NIPA-co-DMAEMA) ratio of 1/10 (D/P = 1/10) were about 80% and 6.293%, respectively. Moreover, the release profile of SN-38-loaded nanoparticles revealed that the release rate at 42 deg. C (above LCST) was higher than that at 37 deg. C (below LCST), which demonstrated that the release of SN-38 could be controlled by increasing the temperature. The cytotoxicity of the SN-38-loaded poly(NIPA-co-DMAEMA) nanoparticles was investigated in human colon cancer cells (HT-29) to compare with the treatment of an anticancer drug, Irinotecan (CPT-11). The antitumor efficacy evaluated in a C26 murine colon tumor model showed that the SN-38-loaded nanoparticles in combination with hyperthermia therapy efficiently suppressed tumor growth. The results indicate that these thermo-responsive nanoparticles are potential carriers for controlled drug delivery.

  5. Approach and issues toward development of risk-based release standards for radioactive scrap metal recycle and reuse

    International Nuclear Information System (INIS)

    Chen, S.Y.; Nieves, L.A.; Nabelssi, B.K.; LePoire, D.J.

    1994-01-01

    The decontamination and decommissioning of nuclear facilities is expected to generate large amounts of slightly radioactive scrap metal (RSM). It is likely that some of these materials will be suitable for recycling and reuse. The amount of scrap steel from DOE facilities, for instance, is estimated to be more than one million tons (Hertzler 1993). However, under current practice and without the establishment of acceptable recycling standards, the RSM would be disposed of primarily as radioactive low-level waste (LLW). In the United States, no specific standards have been developed for the unrestricted release of bulk contaminated materials. Although standards for unrestricted release of radioactive surface contamination (NRC 1974) have existed for about 20 years, the release of materials is not commonly practiced because of the lack of risk-based justifications. Recent guidance from international bodies (IAEA 1988) has established a basis for deriving risk-based release limits for radioactive materials. It is important, therefore, to evaluate the feasibility of recycling and associated issues necessary for the establishment of risk-based release limits for the radioactive metals

  6. Release of Water Soluble Drugs from Dynamically Swelling POLY(2-HYDROXYETHYL Methacrylate - CO - Methacrylic Acid) Hydrogels.

    Science.gov (United States)

    Kou, Jim Hwai-Cher

    In this study, ionizable copolymers of HEMA and methacrylic acid (MA) are investigated for their potential use in developing pH dependent oral delivery systems. Because of the MA units, these gels swell extensively at high pH. Since solute diffusion in the hydrophilic polymers depends highly on the water content of the matrix, it is anticipated that the release rate will be modulated by this pH induced swelling. From a practical point of view, the advantage of the present system is that one can minimize drug loss in the stomach and achieve a programmed release in intestine. This approach is expected to improve delivery of acid labile drugs or drugs that cause severe gastrointestinal side effects. This work mainly focuses on the basic understanding of the mechanism involved in drug release from the poly(HEMA -co- MA) gels, especially under dynamic swelling conditions. Equilibrium swelling is first characterized since water content is the major determinant of transport properties in these gels. Phenylpropanolamine (PPA) is chosen as the model drug for the release study and its diffusion characteristics in the gel matrix determined. The data obtained show that the PPA diffusivity follows the free volume theory of Yasuda, which explains the accelerating effect of swelling on drug release. A mathematical model based on a diffusion mechanism has been developed to describe PPA release from the swelling gels. Based on this model, several significant conclusions can be drawn. First, the release rate can be modulated by the aspect ratio of the cylindrical geometry, and this has a practical implication in dosage form design. Second, the release rate can be lowered quite considerably if the dimensional increase due to swelling is significant. Consequently, it is the balance between the drug diffusivity increase and the gel dimensional growth that determines the release rate from the swelling matrix. Third, quasi-steady release kinetics, which are characteristic of swelling

  7. Zein-alginate based oral drug delivery systems: Protection and release of therapeutic proteins.

    Science.gov (United States)

    Lee, Sungmun; Kim, Yeu-Chun; Park, Ji-Ho

    2016-12-30

    Reactive oxygen species (ROS) play an important role in the development of inflammatory bowel diseases. Superoxide dismutase (SOD) has a great therapeutic potential by scavenging superoxide that is one of ROS; however, in vivo application is limited especially when it is orally administered. SOD is easily degraded in vivo by the harsh conditions of gastrointestinal tract. Here, we design a zein-alginate based oral drug delivery system that protects SOD from the harsh conditions of gastrointestinal tract and releases it in the environment of the small intestine. SOD is encapsulated in zein-alginate nanoparticles (ZAN) via a phase separation method. We demonstrate that ZAN protect SOD from the harsh conditions of the stomach or small intestine condition. ZAN (200:40) at the weight ratio of 200mg zein to 40mg of alginate releases SOD in a pH dependent manner, and it releases 90.8±1.2% of encapsulated SOD at pH 7.4 in 2h, while only 11.4±0.4% of SOD was released at pH 1.3. The encapsulation efficiency of SOD in ZAN (200:40) was 62.1±2.0%. SOD in ZAN (200:40) reduced the intracellular ROS level and it saved 88.9±7.5% of Caco-2 cells from the toxic superoxide in 4 hours. Based on the results, zein-alginate based oral drug delivery systems will have numerous applications to drugs that are easily degradable in the harsh conditions of gastrointestinal tract. Copyright © 2016 Elsevier B.V. All rights reserved.

  8. Externally controlled triggered-release of drug from PLGA micro and nanoparticles.

    Directory of Open Access Journals (Sweden)

    Xin Hua

    Full Text Available Biofilm infections are extremely hard to eradicate and controlled, triggered and controlled drug release properties may prolong drug release time. In this study, the ability to externally control drug release from micro and nanoparticles was investigated. We prepared micro/nanoparticles containing ciprofloxacin (CIP and magnetic nanoparticles encapsulated in poly (lactic-co-glycolic acid PLGA. Both micro/nanoparticles were observed to have narrow size distributions. We investigated and compared their passive and externally triggered drug release properties based on their different encapsulation structures for the nano and micro systems. In passive release studies, CIP demonstrated a fast rate of release in first 2 days which then slowed and sustained release for approximately 4 weeks. Significantly, magnetic nanoparticles containing systems all showed ability to have triggered drug release when exposed to an external oscillating magnetic field (OMF. An experiment where the OMF was turned on and off also confirmed the ability to control the drug release in a pulsatile manner. The magnetically triggered release resulted in a 2-fold drug release increase compared with normal passive release. To confirm drug integrity following release, the antibacterial activity of released drug was evaluated in Pseudomonas aeruginosa biofilms in vitro. CIP maintained its antimicrobial activity after encapsulation and triggered release.

  9. Externally controlled triggered-release of drug from PLGA micro and nanoparticles.

    Science.gov (United States)

    Hua, Xin; Tan, Shengnan; Bandara, H M H N; Fu, Yujie; Liu, Siguo; Smyth, Hugh D C

    2014-01-01

    Biofilm infections are extremely hard to eradicate and controlled, triggered and controlled drug release properties may prolong drug release time. In this study, the ability to externally control drug release from micro and nanoparticles was investigated. We prepared micro/nanoparticles containing ciprofloxacin (CIP) and magnetic nanoparticles encapsulated in poly (lactic-co-glycolic acid) PLGA. Both micro/nanoparticles were observed to have narrow size distributions. We investigated and compared their passive and externally triggered drug release properties based on their different encapsulation structures for the nano and micro systems. In passive release studies, CIP demonstrated a fast rate of release in first 2 days which then slowed and sustained release for approximately 4 weeks. Significantly, magnetic nanoparticles containing systems all showed ability to have triggered drug release when exposed to an external oscillating magnetic field (OMF). An experiment where the OMF was turned on and off also confirmed the ability to control the drug release in a pulsatile manner. The magnetically triggered release resulted in a 2-fold drug release increase compared with normal passive release. To confirm drug integrity following release, the antibacterial activity of released drug was evaluated in Pseudomonas aeruginosa biofilms in vitro. CIP maintained its antimicrobial activity after encapsulation and triggered release.

  10. A Three-Pulse Release Tablet for Amoxicillin: Preparation, Pharmacokinetic Study and Physiologically Based Pharmacokinetic Modeling.

    Science.gov (United States)

    Li, Jin; Chai, Hongyu; Li, Yang; Chai, Xuyu; Zhao, Yan; Zhao, Yunfan; Tao, Tao; Xiang, Xiaoqiang

    2016-01-01

    Amoxicillin is a commonly used antibiotic which has a short half-life in human. The frequent administration of amoxicillin is often required to keep the plasma drug level in an effective range. The short dosing interval of amoxicillin could also cause some side effects and drug resistance, and impair its therapeutic efficacy and patients' compliance. Therefore, a three-pulse release tablet of amoxicillin is desired to generate sustained release in vivo, and thus to avoid the above mentioned disadvantages. The pulsatile release tablet consists of three pulsatile components: one immediate-release granule and two delayed release pellets, all containing amoxicillin. The preparation of a pulsatile release tablet of amoxicillin mainly includes wet granulation craft, extrusion/spheronization craft, pellet coating craft, mixing craft, tablet compression craft and film coating craft. Box-Behnken design, Scanning Electron Microscope and in vitro drug release test were used to help the optimization of formulations. A crossover pharmacokinetic study was performed to compare the pharmacokinetic profile of our in-house pulsatile tablet with that of commercial immediate release tablet. The pharmacokinetic profile of this pulse formulation was simulated by physiologically based pharmacokinetic (PBPK) model with the help of Simcyp®. Single factor experiments identify four important factors of the formulation, namely, coating weight of Eudragit L30 D-55 (X1), coating weight of AQOAT AS-HF (X2), the extrusion screen aperture (X3) and compression forces (X4). The interrelations of the four factors were uncovered by a Box-Behnken design to help to determine the optimal formulation. The immediate-release granule, two delayed release pellets, together with other excipients, namely, Avicel PH 102, colloidal silicon dioxide, polyplasdone and magnesium stearate were mixed, and compressed into tablets, which was subsequently coated with Opadry® film to produce pulsatile tablet of

  11. Pressure releasing device for reactor container

    International Nuclear Information System (INIS)

    Takeda, Mika.

    1994-01-01

    In the present invention, dose rate to public caused by radioactive rare gases can be decreased. That is, a reactor container contains a reactor pressure vessel incorporating a reactor core. There are disposed a pressure releasing system for releasing the pressure in the reactor pressure vessel to the outside, and a burning device for burning gases released from the pressure releasing system. An exhaustion pipe is disposed to the pressure releasing system. A burning device is disposed to the exhaustion pipe. It is effective to dispose a ventilation port at a portion of the exhaustion pipe upstream of the burning device. In addition, the burning device may preferably be disposed in a multi-stage in the axial direction of the exhaustion pipe. With such procedures, hydrogen in gases discharged along with the release of the pressure in the container is burned. Buoyancy is caused to the exhaustion gases by heat energy upon burning. Since the exhaustion gases can reach a higher level by the buoyancy, the dose rate due to the rare gases can be reduced. (I.S.)

  12. Temporal trend of carpal tunnel release surgery: a population-based time series analysis.

    Directory of Open Access Journals (Sweden)

    Naif Fnais

    Full Text Available BACKGROUND: Carpal tunnel release (CTR is among the most common hand surgeries, although little is known about its pattern. In this study, we aimed to investigate temporal trends, age and gender variation and current practice patterns in CTR surgeries. METHODS: We conducted a population-based time series analysis among over 13 million residents of Ontario, who underwent operative management for carpal tunnel syndrome (CTS from April 1, 1992 to March 31, 2010 using administrative claims data. RESULTS: The primary analysis revealed a fairly stable procedure rate of approximately 10 patients per 10,000 population per year receiving CTRs without any significant, consistent temporal trend (p = 0.94. Secondary analyses revealed different trends in procedure rates according to age. The annual procedure rate among those age >75 years increased from 22 per 10,000 population at the beginning of the study period to over 26 patients per 10,000 population (p<0.01 by the end of the study period. CTR surgical procedures were approximately two-fold more common among females relative to males (64.9% vs. 35.1 respectively; p<0.01. Lastly, CTR procedures are increasingly being conducted in the outpatient setting while procedures in the inpatient setting have been declining steadily - the proportion of procedures performed in the outpatient setting increased from 13% to over 30% by 2010 (p<0.01. CONCLUSION: Overall, CTR surgical-procedures are conducted at a rate of approximately 10 patients per 10,000 population annually with significant variation with respect to age and gender. CTR surgical procedures in ambulatory-care facilities may soon outpace procedure rates in the in-hospital setting.

  13. FACTORS AFFECTING THE RELEASE RATE OF A HIGHLY SOLUBLE DRUG FROM A PROGRAMMED RELEASE MEGALOPOROUS SYSTEM

    NARCIS (Netherlands)

    VANDERVEEN, C; MENGER, NR; LERK, CF

    The present study reports on the successful incorporation of a highly soluble drug, procaine HCl, in a programmed-release megaloporous system. This solid two-phase system is composed of housing phase matrix granules (HMG), controlling liquid penetration into the system, and of restraining phase

  14. Should repository release criteria be based on collective dose, release limits, or individual doses?

    International Nuclear Information System (INIS)

    Channell, J.K.; Neill, R.H.

    1999-01-01

    The advantages and disadvantages of using each of 3 alternative methods (collective dose, release limits, and individual dose) as release criteria for determining long-term high level or transuranic waste repository performance of naturally occurring releases or man-made intrusions are evaluated. Each of the alternative approaches have positive aspects and each has uncertainties that require some arbitrary assumptions. A comparison of the numerical results from evaluating the three alternatives at WIPP leads to the conclusion that a collective dose is preferable because it is more site specific and allows consideration of the full effects of human intrusion. The main objection to release limits is they do not use site specific criteria to determine the radiological effect on local and regional populations. Individual dose criteria used and recommended in the United States have ignored doses to drillers and the public from wastes brought to the surface by human intrusion because these doses can be greater than acceptable limits. Also, there is disagreement about defining the location and lifestyle of the individual

  15. A poly(glycerol sebacate)-coated mesoporous bioactive glass scaffold with adjustable mechanical strength, degradation rate, controlled-release and cell behavior for bone tissue engineering.

    Science.gov (United States)

    Lin, Dan; Yang, Kai; Tang, Wei; Liu, Yutong; Yuan, Yuan; Liu, Changsheng

    2015-07-01

    Various requirements in the field of tissue engineering have motivated the development of three-dimensional scaffold with adjustable physicochemical properties and biological functions. A series of multiparameter-adjustable mesoporous bioactive glass (MBG) scaffolds with uncrosslinked poly(glycerol sebacate) (PGS) coating was prepared in this article. MBG scaffold was prepared by a modified F127/PU co-templating process and then PGS was coated by a simple adsorption and lyophilization process. Through controlling macropore parameters and PGS coating amount, the mechanical strength, degradation rate, controlled-release and cell behavior of the composite scaffold could be modulated in a wide range. PGS coating successfully endowed MBG scaffold with improved toughness and adjustable mechanical strength covering the bearing range of trabecular bone (2-12MPa). Multilevel degradation rate of the scaffold and controlled-release rate of protein from mesopore could be achieved, with little impact on the protein activity owing to an "ultralow-solvent" coating and "nano-cavity entrapment" immobilization method. In vitro studies indicated that PGS coating promoted cell attachment and proliferation in a dose-dependent manner, without affecting the osteogenic induction capacity of MBG substrate. These results first provide strong evidence that uncrosslinked PGS might also yield extraordinary achievements in traditional MBG scaffold. With the multiparameter adjustability, the composite MBG/PGS scaffolds would have a hopeful prospect in bone tissue engineering. The design considerations and coating method of this study can also be extended to other ceramic-based artificial scaffolds and are expected to provide new thoughts on development of future tissue engineering materials. Copyright © 2015 Elsevier B.V. All rights reserved.

  16. A mRNA-Responsive G-Quadruplex-Based Drug Release System

    Directory of Open Access Journals (Sweden)

    Hidenobu Yaku

    2015-04-01

    Full Text Available G-quadruplex-based drug delivery carriers (GDDCs were designed to capture and release a telomerase inhibitor in response to a target mRNA. Hybridization between a loop on the GDDC structure and the mRNA should cause the G-quadruplex structure of the GDDC to unfold and release the bound inhibitor, anionic copper(II phthalocyanine (CuAPC. As a proof of concept, GDDCs were designed with a 10-30-mer loop, which can hybridize with a target sequence in epidermal growth factor receptor (EGFR mRNA. Structural analysis using circular dichroism (CD spectroscopy showed that the GDDCs form a (3 + 1 type G-quadruplex structure in 100 mM KCl and 10 mM MgCl2 in the absence of the target RNA. Visible absorbance titration experiments showed that the GDDCs bind to CuAPC with Ka values of 1.5 × 105 to 5.9 × 105 M−1 (Kd values of 6.7 to 1.7 μM at 25 °C, depending on the loop length. Fluorescence titration further showed that the G-quadruplex structure unfolds upon binding to the target RNA with Ka values above 1.0 × 108 M−1 (Kd values below 0.01 μM at 25 °C. These results suggest the carrier can sense and bind to the target RNA, which should result in release of the bound drug. Finally, visible absorbance titration experiments demonstrated that the GDDC release CuAPC in response to the target RNA.

  17. Calcein AM release-based cytotoxic cell assay for fish leucocytes.

    Science.gov (United States)

    Iwanowicz, Luke R; Densmore, Christine L; Ottinger, Christopher A

    2004-02-01

    A non-specific cytotoxic cell assay for fish is presented that is based on the release of the activated fluorochrome calcein AM from lysed carp epithelioma papulosum cyprini (EPC) cells. To establish the suitability of treating EPC cells with calcein AM the uptake and spontaneous release of the calcein AM by the EPC cells was evaluated. Incubation of 5 microM calcein AM in culture medium with 1x10(5)EPC cells well(-1)for a minimum of 3 h provided sufficient labelling. Spontaneous release of fluorescence from the labelled EPC cells during 10 h of post labelling incubation ranged from 30 to 39% of the total observed fluorescence. Cytotoxic activity of trout leucocytes was evaluated at three leucocyte to target cell ratios (10:1, 2:1 and 1:1) following incubation (4, 6, 8, and 10 h) with calcein AM-labelled EPC cells at 15 degrees C. In some instances, the monoclonal antibody specific for the NCC surface receptor NCCRP-1 (MAb5C.6) was included in the cultures. The activity of NCC cells was significantly inhibited in the presence of 0.25 microg well(-1)of MAb5C.6 relative to no antibody (Prelease assay.

  18. Lignin based controlled release coatings

    NARCIS (Netherlands)

    Mulder, W.J.; Gosselink, R.J.A.; Vingerhoeds, M.H.; Harmsen, P.F.H.; Eastham, D.

    2011-01-01

    Urea is a commonly used fertilizer. Due to its high water-solubility, misuse easily leads to excess nitrogen levels in the soil. The aim of this research was to develop an economically feasible and biodegradable slow-release coating for urea. For this purpose, lignin was selected as coating

  19. Development of DUST: A computer code that calculates release rates from a LLW disposal unit

    International Nuclear Information System (INIS)

    Sullivan, T.M.

    1992-01-01

    Performance assessment of a Low-Level Waste (LLW) disposal facility begins with an estimation of the rate at which radionuclides migrate out of the facility (i.e., the disposal unit source term). The major physical processes that influence the source term are water flow, container degradation, waste form leaching, and radionuclide transport. A computer code, DUST (Disposal Unit Source Term) has been developed which incorporates these processes in a unified manner. The DUST code improves upon existing codes as it has the capability to model multiple container failure times, multiple waste form release properties, and radionuclide specific transport properties. Verification studies performed on the code are discussed

  20. [Construction of multiple drug release system based on components of traditional Chinese medicine].

    Science.gov (United States)

    Liu, Dan; Jia, Xiaobin; Yu, Danhong; Zhang, Zhenhai; Sun, E

    2012-08-01

    With the development of the modernization drive of traditional Chinese medicine (TCM) preparations, new-type TCM dosage forms research have become a hot spot in the field. Because of complexity of TCM components as well as uncertainty of material base, there is still not a scientific system for modern TCM dosage forms so far. Modern TCM preparations inevitably take the nature of the multi-component and the general function characteristics of multi-link and multi-target into account. The author suggests building a multiple drug release system for TCM using diverse preparation techniques and drug release methods at levels on the basis the nature and function characteristics of TCM components. This essay expounds elaborates the ideas to build the multiple traditional Chinese medicine release system, theoretical basis, preparation techniques and assessment system, current problems and solutions, in order to build a multiple TCM release system with a view of enhancing the bioavailability of TCM components and provide a new form for TCM preparations.

  1. Sensitivity of performance assessment of the engineered barriers to nuances of release rate criteria

    International Nuclear Information System (INIS)

    Oliver, D.L.R.

    1987-01-01

    The United States Nuclear Regulatory Commission (NRC) has established criteria for the long-term performance of proposed high-level waste repositories. As with any regulation, the criteria may be interpreted in several ways. Due to the high capital costs and the emotional political climate associated with any high-level radioactive waste repository, it is important that there be an early consensus regarding interpretations of the criteria, and what assumptions may be used to demonstrate compliance with them. This work uses analytic solutions of mass transport theory to demonstrate how sensitive performance analyses are to various nuances of the NRC release rate criterion for the engineered barriers. The analysis is directed at the proposed repository in basalt at the Hanford site in Washington State

  2. Radioactive release during nuclear accidents in Chernobyl and Fukushima

    Science.gov (United States)

    Nur Ain Sulaiman, Siti; Mohamed, Faizal; Rahim, Ahmad Nabil Ab

    2018-01-01

    Nuclear accidents that occurred in Chernobyl and Fukushima have initiated many research interests to understand the cause and mechanism of radioactive release within reactor compound and to the environment. Common types of radionuclide release are the fission products from the irradiated fuel rod itself. In case of nuclear accident, the focus of monitoring will be mostly on the release of noble gases, I-131 and Cs-137. As these are the only accidents have been rated within International Nuclear Events Scale (INES) Level 7, the radioactive release to the environment was one of the critical insights to be monitored. It was estimated that the release of radioactive material to the atmosphere due to Fukushima accident was approximately 10% of the Chernobyl accident. By referring to the previous reports using computational code systems to model the release rate, the release activity of I-131 and Cs-137 in Chernobyl was significantly higher compare to Fukushima. The simulation code also showed that Chernobyl had higher release rate of both radionuclides on the day of accident. Other factors affecting the radioactive release for Fukushima and Chernobyl accidents such as the current reactor technology and safety measures are also compared for discussion.

  3. Enhancement of radiation-induced base release from nucleosides in alkaline solution: essential role of the O.- radical

    International Nuclear Information System (INIS)

    Scholes, M.L.; Schuchmann, M.N.; Sonntag, C. von

    1992-01-01

    The effect of pH on base release in the γ-radiolysis of N 2 O-saturated solutions of a number of nucleosides (including uridine, 3-methyluridine, 2', 3' -O-isopropylidene-uridine, and adenosine) has been investigated. For all these nucleosides, independent of the base or sugar moiety, base release is very low at pH below 10 (G∼(0.3-0.7) x 10 -7 mol J -1 ), but increases drastically to G∼(3-4) x 10 -7 mol J -1 at pH ≥ 13. It is concluded that the increase in base release at high pH is caused by the increasing participation of O .- , which, unlike . OH, attacks the nucleosides preferentially at their sugar moieties, and is not due to an OH - -induced radical transfer from the base to the sugar moiety. (author)

  4. Gas retention and release behavior in Hanford single-shell waste tanks

    Energy Technology Data Exchange (ETDEWEB)

    Stewart, C.W.; Brewster, M.E.; Gauglitz, P.A.; Mahoney, L.A.; Meyer, P.A.; Recknagle, K.P.; Reid, H.C.

    1996-12-01

    This report describes the current understanding of flammable gas retention and release in Hanford single-shell waste tanks based on theory, experimental results, and observations of tank behavior. The single-shell tanks likely to pose a flammable gas hazard are listed and described, and photographs of core extrusions and the waste surface are included. The credible mechanisms for significant flammable gas releases are described, and release volumes and rates are quantified as much as possible. The only mechanism demonstrably capable of producing large ({approximately}100 m{sup 3}) spontaneous gas releases is the buoyant displacement, which occurs only in tanks with a relatively deep layer of supernatant liquid. Only the double-shell tanks currently satisfy this condition. All release mechanisms believed plausible in single-shell tanks have been investigated, and none have the potential for large spontaneous gas releases. Only small spontaneous gas releases of several cubic meters are likely by these mechanisms. The reasons several other postulated gas release mechanisms are implausible or incredible are also given.

  5. Evaluation of particle release from montmorillonite gel by flowing groundwater based on the DLVO theory

    International Nuclear Information System (INIS)

    Kurosawa, Susumu; Nagasaki, Shinya; Tanaka, Satoru

    2007-01-01

    Theoretical study has been performed to clarify the ability of colloid release form the montmorillonite gel by the flowing groundwater. Evaluation of montmorillonite colloidal particles release from the bentonite buffer material is important for the performance assessment of radioactive waste disposal because the colloids may influence the radionuclide transport. In this study, the minimum groundwater flow rate required to tear off montmorillonite particles from surface of bentonite buffer was estimated from the shear stress on the gel front, which was calculated by the DLVO theory. The estimated shear force was converted to corresponding groundwater velocity by using Stoke's equation. The results indicated that groundwater velocity in a range of about 10 -5 to 10 -4 m/s would be necessary to release montmorillonite particles. This range is higher than the groundwater flow velocity found generally in deep geological media in Japan. This study suggests that the effect of montmorillonite particles release from the bentonite buffer on radionuclide transport is likely to be negligible in the performance assessment of high-level radioactive waste geological disposal. (author)

  6. Formulation and in-vitro evaluation of directly compressed controlled release matrices of Losartan Potassium using Ethocel Grade 100 as rate retarding agent.

    Science.gov (United States)

    Khan, Kamran Ahmad; Khan, Gul Majid; Zeeshan Danish, Muhammad; Akhlaq; Khan, Haroon; Rehman, Fazal; Mehsud, Saifullah

    2015-12-30

    Current study was aimed to develop 200mg controlled release matrix tablets of Losartan Potassium using Ethocel 100 Premium and Ethocel 100 FP Premium as rate controlling polymer. In-vitro studies were performed according to USP Method-I in phosphate buffer (PH 6.8) using pharma test dissolution apparatus. The temperature of the dissolution medium was kept constant at 37±0.5°C at 100rpm. Flow properties, physical quality control tests, effect of polymer size and drug-to-polymers ratios were studied using different kinetics models such as 1st-order, zero-order, Hixon Crowell model, Highuchi model and Power law. Difference factor f1 and similarity factor f2 were applied for dissolution profiles against Cardaktin® tablets used as a reference formulation. The matrices with polymer ethocel 100 FP Premiums have prolonged the drug release rate as compared to polymer ethocel 100 Premiums. The n values matrices with polymer ethocel grade 100 ranged from 0.603 to 0.857 indicating that the drug release occurred by anomalous non fickian diffusion kinetics while then value of reference Cardaktin® tablet was measured as 0.125 indicating that these tablets do not follow power law. The dissolution profiles of test formulations were different than that of reference Cardaktin®. This suggests the polymer Ethocel grade 100 can be proficiently incorporated in fabrication and development of once a day controlled release matrix tablets. Copyright © 2015. Published by Elsevier B.V.

  7. Quantifying MTBE biodegradation in the Vandenberg Air Force Base ethanol release study using stable carbon isotopes

    Science.gov (United States)

    McKelvie, Jennifer R.; Mackay, Douglas M.; de Sieyes, Nicholas R.; Lacrampe-Couloume, Georges; Sherwood Lollar, Barbara

    2007-12-01

    Compound-specific isotope analysis (CSIA) was used to assess biodegradation of MTBE and TBA during an ethanol release study at Vandenberg Air Force Base. Two continuous side-by-side field releases were conducted within a preexisting MTBE plume to form two lanes. The first involved the continuous injection of site groundwater amended with benzene, toluene and o-xylene ("No ethanol lane"), while the other involved the continuous injection of site groundwater amended with benzene, toluene and o-xylene and ethanol ("With ethanol lane"). The δ 13C of MTBE for all wells in the "No ethanol lane" remained constant during the experiment with a mean value of - 31.3 ± 0.5‰ ( n = 40), suggesting the absence of any substantial MTBE biodegradation in this lane. In contrast, substantial enrichment in 13C of MTBE by 40.6‰, was measured in the "With ethanol lane", consistent with the effects of biodegradation. A substantial amount of TBA (up to 1200 μg/L) was produced by the biodegradation of MTBE in the "With ethanol lane". The mean value of δ 13C for TBA in groundwater samples in the "With ethanol lane" was - 26.0 ± 1.0‰ ( n = 32). Uniform δ 13C TBA values through space and time in this lane suggest that substantial anaerobic biodegradation of TBA did not occur during the experiment. Using the reported range in isotopic enrichment factors for MTBE of - 9.2‰ to - 15.6‰, and values of δ 13C of MTBE in groundwater samples, MTBE first-order biodegradation rates in the "With ethanol lane" were 12.0 to 20.3 year - 1 ( n = 18). The isotope-derived rate constants are in good agreement with the previously published rate constant of 16.8 year - 1 calculated using contaminant mass-discharge for the "With ethanol lane".

  8. Synthesis of attapulgite/N-isopropylacrylamide and its use in drug release

    Energy Technology Data Exchange (ETDEWEB)

    Li, Xiaomo [Jiangsu Key Laboratory for Chemistry of Low-Dimensional Materials, School of Chemistry and Chemical Engineering, Huaiyin Normal University, Huaian 223300 (China); Faculty of Chemistry, Northeast Normal University, Changchun 130024, Jilin (China); Zhong, Hui, E-mail: huizhong@hytc.edu.cn [Jiangsu Key Laboratory for Chemistry of Low-Dimensional Materials, School of Chemistry and Chemical Engineering, Huaiyin Normal University, Huaian 223300 (China); Faculty of Chemistry, Northeast Normal University, Changchun 130024, Jilin (China); Li, Xiaorong, E-mail: lxr206206@163.com [Jiangsu Key Laboratory for Chemistry of Low-Dimensional Materials, School of Chemistry and Chemical Engineering, Huaiyin Normal University, Huaian 223300 (China); Jia, Feifei [Jiangsu Key Laboratory for Chemistry of Low-Dimensional Materials, School of Chemistry and Chemical Engineering, Huaiyin Normal University, Huaian 223300 (China); Faculty of Chemistry, Northeast Normal University, Changchun 130024, Jilin (China); Cheng, Zhipeng; Zhang, Lili; Yin, Jingzhou; An, Litao [Jiangsu Key Laboratory for Chemistry of Low-Dimensional Materials, School of Chemistry and Chemical Engineering, Huaiyin Normal University, Huaian 223300 (China); Guo, Liping, E-mail: guolp078@nenu.edu.cn [Faculty of Chemistry, Northeast Normal University, Changchun 130024, Jilin (China)

    2014-12-01

    Environmentally sensitive hydrogels as one of the most potential drug delivery systems have gained considerable interest in recent years. In the present study, we synthesized a newly temperature-responsive composite hydrogel based on attapulgite (ATP) and poly (N-isopropylacrylamide) (PNIPAM) as the localized drug carriers for drug delivery. The as-prepared ATP/PNIPAM hydrogel has large aperture which significantly improved the quantity of adsorption of drugs, exhibiting the excellent properties of drug release. The scanning electron microscope (SEM), Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), and X-ray diffraction (XRD) were used to characterize the ATP/PNIPAM. The swelling/deswelling behaviors and the release of ciprofloxacin lactate were studied. When the temperature was below the low critical solution temperature (LCST), the swelling property of hydrogels was excellent and the swelling rate was large. And, the drug release rate increased with the increase of the content of attapulgite in the composite hydrogel when it was put in the buffer solution (pH 7.38) at 37.0 °C. Therefore, the composite hydrogels might be very useful for its application in biomedical fields. - Highlights: • Attapulgite/N-isopropylacrylamide hydrogels were synthesized and characterized. • The swelling property of hydrogels was excellent when temperature was below 34.0 °C. • The composite hydrogels were used for the release of ciprofloxacin lactate. • The drug release rate increased with the increase of the content of attapulgite.

  9. Method and apparatus for controlling accidental releases of tritium

    International Nuclear Information System (INIS)

    Galloway, T.R.

    1980-01-01

    An improvement in a tritium control system based on a catalytic oxidation reactor is provided wherein accidental releases of tritium into room air are controlled by flooding the catalytic oxidation reactor with hydrogen when the tritium concentration in the room air exceeds a specified limit. The sudden flooding with hydrogen heats the catalyst to a high temperature within seconds, thereby greatly increasing the catalytic oxidation rate of tritium to tritiated water vapor. Thus, the catalyst is heated only when needed. In addition to the heating effect, the hydrogen flow also swamps the tritium and further reduces the tritium release

  10. Method and apparatus for controlling accidental releases of tritium

    Science.gov (United States)

    Galloway, Terry R. [Berkeley, CA

    1980-04-01

    An improvement in a tritium control system based on a catalytic oxidation reactor wherein accidental releases of tritium into room air are controlled by flooding the catalytic oxidation reactor with hydrogen when the tritium concentration in the room air exceeds a specified limit. The sudden flooding with hydrogen heats the catalyst to a high temperature within seconds, thereby greatly increasing the catalytic oxidation rate of tritium to tritiated water vapor. Thus, the catalyst is heated only when needed. In addition to the heating effect, the hydrogen flow also swamps the tritium and further reduces the tritium release.

  11. Investigating the role of ion-pair strategy in regulating nicotine release from patch: Mechanistic insights based on intermolecular interaction and mobility of pressure sensitive adhesive.

    Science.gov (United States)

    Li, Qiaoyun; Wan, Xiaocao; Liu, Chao; Fang, Liang

    2018-07-01

    The aim of this study was to prepare a drug-in-adhesive patch of nicotine (NIC) and use ion-pair strategy to regulate drug delivery rate. Moreover, the mechanism of how ion-pair strategy regulated drug release was elucidated at molecular level. Formulation factors including pressure sensitive adhesives (PSAs), drug loading and counter ions (C 4 , C 6 , C 8 , C 10 , and C 12 ) were screened. In vitro release experiment and in vitro transdermal experiment were conducted to determine the rate-limiting step in drug delivery process. FT-IR and molecular modeling were used to characterize the interaction between drug and PSA. Thermal analysis and rheology study were conducted to investigate the mobility variation of PSA. The optimized patch prepared with NIC-C 8 had the transdermal profile fairly close to that of the commercial product (p > 0.05). The release rate constants (k) of NIC, NIC-C 4 and NIC-C 10 were 21.1, 14.4 and 32.4, respectively. Different release rates of NIC ion-pair complexes were attributed to the dual effect of ion-pair strategy on drug release. On one hand, ion-pair strategy enhanced the interaction between drug and PSA, which inhibited drug release. On the other hand, using ion-pair strategy improved the mobility of PSA, which facilitated drug release. Drug release behavior was determined by combined effect of two aspects above. These conclusions provided a new idea for us to regulate drug release behavior from patch. Copyright © 2018 Elsevier B.V. All rights reserved.

  12. Pore geometry of ceramic device: The key factor of drug release kinetics

    Directory of Open Access Journals (Sweden)

    Čolović B.

    2013-01-01

    Full Text Available Release kinetics of tigecycline, a potential antibiotic in treatment of osteomyelitis, from calcium hydroxyapatite (CHA, as one of the most important ceramic materials in bone tissue engineering, was investigated in this study. Tigecycline, in solid state, was mixed with CHA powder and the obtained mixture was compressed into tablets using two different pressures. These tablets were immersed in a phosphate-buffered saline solution and tigecycline release was measured by a UV-VIS spectrophotometer. The total release time was 5 or 28 days, depending on the pressure applied during compression. It was shown that there is a close relationship between pore sizes and drug release rate. The drug release kinetics was interpreted on the base of pore sizes and pore size distribution. [Projekat Ministarstva nauke Republike Srbije, br. 172026

  13. Numerical Analysis of Inlet Gas-Mixture Flow Rate Effects on Carbon Nanotube Growth Rate

    Directory of Open Access Journals (Sweden)

    B. Zahed

    2013-01-01

    Full Text Available The growth rate and uniformity of Carbon Nano Tubes (CNTs based on Chemical Vapor Deposition (CVD technique is investigated by using a numerical model. In this reactor, inlet gas mixture, including xylene as carbon source and mixture of argon and hydrogen as  carrier gas enters into a horizontal CVD reactor at atmospheric pressure. Based on the gas phase and surface reactions, released carbon atoms are grown as CNTs on the iron catalysts at the reactor hot walls. The effect of inlet gas-mixture flow rate, on CNTs growth rate and its uniformity is discussed. In addition the velocity and temperature profile and also species concentrations throughout the reactor are presented.

  14. Modelling and assessment of accidental oil release from damaged subsea pipelines.

    Science.gov (United States)

    Li, Xinhong; Chen, Guoming; Zhu, Hongwei

    2017-10-15

    This paper develops a 3D, transient, mathematical model to estimate the oil release rate and simulate the oil dispersion behavior. The Euler-Euler method is used to estimate the subsea oil release rate, while the Eulerian-Lagrangian method is employed to track the migration trajectory of oil droplets. This model accounts for the quantitative effect of backpressure and hole size on oil release rate, and the influence of oil release rate, oil density, current speed, water depth and leakage position on oil migration is also investigated in this paper. Eventually, the results, e.g. transient release rate of oil, the rise time of oil and dispersion distance are determined by above-mentioned model, and the oil release and dispersion behavior under different scenarios is revealed. Essentially, the assessment results could provide a useful guidance for detection of leakage positon and placement of oil containment boom. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. Continuous-release formulation for environmental doses to moving receptors

    International Nuclear Information System (INIS)

    Piepho, M.G.

    1981-01-01

    Atmospheric dispersion models frequently assume a puff release or several puff releases, each of which are described separately. A dispersion model should better describe a continuous release as more puffs are assumed, but the computational cost and bookkeeping difficulty increases with additional puffs. A new formulism is derived in this work which replaces the puff approximation. With the new continuous release formulation, radioactive dose calculations to moving receptors are more accurately calculated without any great additional computation. There are several advantages of a continuous release formulation. With this formulation, a dose rate to a moving receptor is calculated as a function of time. The dose-rate will increase (decrease) as the bulk of the release gets closer (farther) to (from) the receptor which is at position x(t), y(t). The receptor may follow any x, y trajectory as a function of time, and the dose rate will be calculated along the path

  16. Rheological behaviour and physical properties of controlled-release gluten-based bioplastics.

    Science.gov (United States)

    Gómez-Martínez, D; Partal, P; Martínez, I; Gallegos, C

    2009-03-01

    Bioplastics based on glycerol, water and wheat gluten have been manufactured in order to determine the effect that mechanical processing and further thermal treatments exert on different thermo-mechanical properties of the biomaterials obtained. An "active agent", KCl was incorporated in these matrices to develop controlled-release formulations. Oscillatory shear, dynamic mechanical thermal analysis (DMTA), diffusion and water absorption tests were carried out in order to study the influence of the above-mentioned treatments on the physico-chemical characteristics and rheological behaviour of these bioplastic samples. Wheat gluten protein-based bioplastics studied in this work present a high ability for thermosetting modification, due to protein denaturation, which may favour the development of a wide variety of biomaterials. Bioplastic hygroscopic properties depend on plasticizer nature and processing procedure, and may be a key factor for industrial applications where water absorption is required. On the other hand, high water absorption and slow KCl release from bioplastic samples (both of them suitable properties in agricultural applications) may be obtained by adding citric acid to a given formulation, at selected processing conditions.

  17. Estimation of cobalt release from feed water heater tubes of BWRs

    International Nuclear Information System (INIS)

    Uchida, S.; Kitamura, M.; Ozawa, Y.

    1983-01-01

    To evaluate the release source of cobalt from heater tubes of the feed water line, release rate measurements were carried out by detecting 60 Co released from irradiated stainless steel in contact with neutral water at an oxygen concentration of 20 ppb. The dependences of cobalt release rate on temperature, flow velocity and exposure time were studied after 670 hours of release experiments, and an empirical equation (which is presented) was obtained in the temperature range from 150 to 240 deg C. A decrease in the cobalt release rate above 250 deg C was considered due to the formation of a protective oxide layer. From these data, the amount of cobalt released from individual feed water heaters was evaluated. It was demonstrated that low cobalt containing stainless steel was economically applied only in the higher temperature region of the heater (20% of the total surface) to reduce cobalt feed rate into the reactor (to approx. 1/2). (author)

  18. Effects of Symmetrically Arranged Heat Sources on the Heat Release Performance of Extruded-Type Heat Sinks

    Energy Technology Data Exchange (ETDEWEB)

    Ku, Min Ye [Chonbuk National Univ., Chonju (Korea, Republic of)

    2016-02-15

    In this study we investigated the effects of symmetrically arranged heat sources on the heat release performances of extruded-type heat sinks through experiments and thermal fluid simulations. Also, based on the results we suggested a high-efficiency and cost-effective heat sink for a solar inverter cooling system. In this parametric study, the temperatures between heaters on the base plate and the heat release rates were investigated with respect to the arrangements of heat sources and amounts of heat input. Based on the results we believe that the use of both sides of the heat sink is the preferred method for releasing the heat from the heat source to the ambient environment rather than the use of a single side of the heat sink. Also from the results, it is believed that the symmetric arrangement of the heat sources is recommended to achieve a higher rate of heat transfer. From the results of the thermal fluid simulation, it was possible to confirm the qualitative agreement with the experimental results. Finally, quantitative comparison with respect to mass flow rates, heat inputs, and arrangements of the heat source was also performed.

  19. The smart aerial release machine, a universal system for applying the sterile insect technique.

    Directory of Open Access Journals (Sweden)

    Ruben Leal Mubarqui

    Full Text Available Beyond insecticides, alternative methods to control insect pests for agriculture and vectors of diseases are needed. Management strategies involving the mass-release of living control agents have been developed, including genetic control with sterile insects and biological control with parasitoids, for which aerial release of insects is often required. Aerial release in genetic control programmes often involves the use of chilled sterile insects, which can improve dispersal, survival and competitiveness of sterile males. Currently available means of aerially releasing chilled fruit flies are however insufficiently precise to ensure homogeneous distribution at low release rates and no device is available for tsetse.Here we present the smart aerial release machine, a new design by the Mubarqui Company, based on the use of vibrating conveyors. The machine is controlled through Bluetooth by a tablet with Android Operating System including a completely automatic guidance and navigation system (MaxNav software. The tablet is also connected to an online relational database facilitating the preparation of flight schedules and automatic storage of flight reports. The new machine was compared with a conveyor release machine in Mexico using two fruit flies species (Anastrepha ludens and Ceratitis capitata and we obtained better dispersal homogeneity (% of positive traps, p<0.001 for both species and better recapture rates for Anastrepha ludens (p<0.001, especially at low release densities (<1500 per ha. We also demonstrated that the machine can replace paper boxes for aerial release of tsetse in Senegal.This technology limits damages to insects and allows a large range of release rates from 10 flies/km2 for tsetse flies up to 600,000 flies/km2 for fruit flies. The potential of this machine to release other species like mosquitoes is discussed. Plans and operating of the machine are provided to allow its use worldwide.

  20. Social media release increases dissemination of original articles in the clinical pain sciences.

    Science.gov (United States)

    Allen, Heidi G; Stanton, Tasha R; Di Pietro, Flavia; Moseley, G Lorimer

    2013-01-01

    A barrier to dissemination of research is that it depends on the end-user searching for or 'pulling' relevant knowledge from the literature base. Social media instead 'pushes' relevant knowledge straight to the end-user, via blogs and sites such as Facebook and Twitter. That social media is very effective at improving dissemination seems well accepted, but, remarkably, there is no evidence to support this claim. We aimed to quantify the impact of social media release on views and downloads of articles in the clinical pain sciences. Sixteen PLOS ONE articles were blogged and released via Facebook, Twitter, LinkedIn and ResearchBlogging.org on one of two randomly selected dates. The other date served as a control. The primary outcomes were the rate of HTML views and PDF downloads of the article, over a seven-day period. The critical result was an increase in both outcome variables in the week after the blog post and social media release. The mean ± SD rate of HTML views in the week after the social media release was 18±18 per day, whereas the rate during the other three weeks was no more than 6±3 per day. The mean ± SD rate of PDF downloads in the week after the social media release was 4±4 per day, whereas the rate during the other three weeks was less than 1±1 per day (psocial media reach, engagement or virality related to either outcome variable, nor to citation count one year later (p>0.3 for all). We conclude that social media release of a research article in the clinical pain sciences increases the number of people who view or download that article, but conventional social media metrics are unrelated to the effect.

  1. Social media release increases dissemination of original articles in the clinical pain sciences.

    Directory of Open Access Journals (Sweden)

    Heidi G Allen

    Full Text Available A barrier to dissemination of research is that it depends on the end-user searching for or 'pulling' relevant knowledge from the literature base. Social media instead 'pushes' relevant knowledge straight to the end-user, via blogs and sites such as Facebook and Twitter. That social media is very effective at improving dissemination seems well accepted, but, remarkably, there is no evidence to support this claim. We aimed to quantify the impact of social media release on views and downloads of articles in the clinical pain sciences. Sixteen PLOS ONE articles were blogged and released via Facebook, Twitter, LinkedIn and ResearchBlogging.org on one of two randomly selected dates. The other date served as a control. The primary outcomes were the rate of HTML views and PDF downloads of the article, over a seven-day period. The critical result was an increase in both outcome variables in the week after the blog post and social media release. The mean ± SD rate of HTML views in the week after the social media release was 18±18 per day, whereas the rate during the other three weeks was no more than 6±3 per day. The mean ± SD rate of PDF downloads in the week after the social media release was 4±4 per day, whereas the rate during the other three weeks was less than 1±1 per day (p0.3 for all. We conclude that social media release of a research article in the clinical pain sciences increases the number of people who view or download that article, but conventional social media metrics are unrelated to the effect.

  2. Effects of magnesium-based hydrogen storage materials on the thermal decomposition, burning rate, and explosive heat of ammonium perchlorate-based composite solid propellant.

    Science.gov (United States)

    Liu, Leili; Li, Jie; Zhang, Lingyao; Tian, Siyu

    2018-01-15

    MgH 2 , Mg 2 NiH 4 , and Mg 2 CuH 3 were prepared, and their structure and hydrogen storage properties were determined through X-ray photoelectron spectroscopy and thermal analyzer. The effects of MgH 2 , Mg 2 NiH 4 , and Mg 2 CuH 3 on the thermal decomposition, burning rate, and explosive heat of ammonium perchlorate-based composite solid propellant were subsequently studied. Results indicated that MgH 2 , Mg 2 NiH 4 , and Mg 2 CuH 3 can decrease the thermal decomposition peak temperature and increase the total released heat of decomposition. These compounds can improve the effect of thermal decomposition of the propellant. The burning rates of the propellant increased using Mg-based hydrogen storage materials as promoter. The burning rates of the propellant also increased using MgH 2 instead of Al in the propellant, but its explosive heat was not enlarged. Nonetheless, the combustion heat of MgH 2 was higher than that of Al. A possible mechanism was thus proposed. Copyright © 2017. Published by Elsevier B.V.

  3. A comparison of measured radionuclide release rates from Three Mile Island Unit-2 core debris for different oxygen chemical potentials

    International Nuclear Information System (INIS)

    Baston, V.F.; Hofstetter, K.J.; Ryan, R.F.

    1987-01-01

    Chemical and radiochemical analyses of reactor coolant samples taken during defueling of the Three Mile Island Unit-2 (TMI-2) reactor provide relevant data to assist in understanding the solution chemistry of the radionuclides retained within the TMI-2 reactor coolant system. Hydrogen peroxide was added to various plant systems to provide disinfection for microbial contamination and has provided the opportunity to observe radionuclide release under different oxygen chemical potentials. A comparison of the radionuclide release rates with and without hydrogen peroxide has been made for these separate but related cases, i.e., the fuel transfer canal and connecting spent-fuel pool A with the TMI-2 reactor plenum in the fuel transfer canal, core debris grab sample laboratory experiments, and the reactor vessel fluid and associated core debris. Correlation and comparison of these data indicate a physical parameter dependence (surface-to-volume ratio) affecting all radionuclide release; however, selected radionuclides also demonstrate a chemical dependence release under the different oxygen chemical potentials. Chemical and radiochemical analyses of reactor coolant samples taken during defueling of the Three Mile Island Unit-2 (TMI-2) reactor provide relevant data to assist in understanding the solution chemistry of the radionuclides retained within the TMI-2 reactor coolant system

  4. On the Impact of the Fuel Dissolution Rate Upon Near-Field Releases From Nuclear Waste Disposal

    Directory of Open Access Journals (Sweden)

    A Pereira

    2016-09-01

    Full Text Available Calculations of the impact of the dissolution of spent nuclear fuel on the release from a damaged canister in a KBS-3 repository are presented. The dissolution of the fuel matrix is a complex process and the dissolution rate is known to be one of the most important parameters in performance assessment models of the near-field of a geological repository. A variability study has been made to estimate the uncertainties associated with the process of fuel dissolution. The model considered in this work is a 3D model of a KBS-3 copper canister. The nuclide used in the calculations is Cs-135. Our results confirm that the fuel degradation rate is an important parameter, however there are considerable uncertainties associated with the data and the conceptual models. Consequently, in the interests of safety one should reduce, as far as possible, the uncertainties coupled to fuel degradation.

  5. Effect of tunnel cross section on gas temperatures and heat fluxes in case of large heat release rate

    International Nuclear Information System (INIS)

    Fan, Chuan Gang; Li, Ying Zhen; Ingason, Haukur; Lönnermark, Anders

    2016-01-01

    Highlights: • The effect of tunnel cross section together with ventilation velocity was studied. • Ceiling temperature varies clearly with tunnel height, but little with tunnel width. • Downstream temperature decreases with increasing tunnel dimensions. • HRR is an important factor that influences decay rate of excess gas temperature. • An equation considering both tunnel dimensions and HRR was developed. - Abstract: Tests with liquid and solid fuels in model tunnels (1:20) were performed and analysed in order to study the effect of tunnel cross section (width and height) together with ventilation velocity on ceiling gas temperatures and heat fluxes. The model tunnel was 10 m long with varying width (0.3 m, 0.45 m and 0.6 m) and height (0.25 m and 0.4 m). Test results show that the maximum temperature under the ceiling is a weak function of heat release rate (HRR) and ventilation velocity for cases with HRR more than 100 MW at full scale. It clearly varies with the tunnel height and is a weak function of the tunnel width. With a lower tunnel height, the ceiling is closer to the base of continuous flame zone and the temperatures become higher. Overall, the gas temperature beneath the ceiling decreases with the increasing tunnel dimensions, and increases with the increasing longitudinal ventilation velocity. The HRR is also an important factor that influences the decay rate of excess gas temperature, and a dimensionless HRR integrating HRR and other two key parameters, tunnel cross-sectional area and distance between fuel centre and tunnel ceiling, was introduced to account for the effect. An equation for the decay rate of excess gas temperature, considering both the tunnel dimensions and HRR, was developed. Moreover, a larger tunnel cross-sectional area will lead to a smaller heat flux.

  6. Ni-Cr based dental alloys; Ni release, corrosion and biological evaluation

    Energy Technology Data Exchange (ETDEWEB)

    Reclaru, L., E-mail: lucien.reclaru@pxgroup.com [PX Holding S.A., Dep R and D Corrosion and Biocompatibility Group, Bd. des Eplatures 42, CH-2304 La Chaux-de-Fonds (Switzerland); Unger, R.E.; Kirkpatrick, C.J. [Institute for Pathology, REPAIR Lab, University Medical Center, Johannes Gutenberg University Mainz, Langenbeckstr.1, D-55101 Mainz (Germany); Susz, C.; Eschler, P.-Y.; Zuercher, M.-H. [PX Holding S.A., Dep R and D Corrosion and Biocompatibility Group, Bd. des Eplatures 42, CH-2304 La Chaux-de-Fonds (Switzerland); Antoniac, I. [Materials Science and Engineering Faculty, Politehnica of Bucharest, 060042 Bucharest (Romania); Luethy, H. [Institute of Dental Materials Science and Technology, University of Basel, Hebelstrasse 3, CH-4056 Basel (Switzerland)

    2012-08-01

    In the last years the dental alloy market has undergone dramatic changes for reasons of economy and biocompatibility. Nickel based alloys have become widely used substitute for the much more expensive precious metal alloys. In Europe the prevalence of nickel allergy is 10-15% for female adults and 1-3% for male adults. Despite the restrictions imposed by the EU for the protection of the general population in contact dermatitis, the use of Ni-Cr dental alloys is on the increase. Some questions have to be faced regarding the safety risk of nickel contained in dental alloys. We have collected based on many EU markets, 8 Ni-Cr dental alloys. Microstructure characterization, corrosion resistance (generalized, crevice and pitting) in saliva and the quantities of cations released in particular nickel and CrVI have been evaluated. We have applied non parametric classification tests (Kendall rank correlation) for all chemical results. Also cytotoxicity tests and an evaluation specific to TNF-alpha have been conducted. According to the obtained results, it was found that their behavior to corrosion was weak but that nickel release was high. The quantities of nickel released are higher than the limits imposed in the EU concerning contact with the skin or piercing. Surprisingly the biological tests did not show any cytotoxic effect on Hela and L929 cells or any change in TNF-alpha expression in monocytic cells. The alloys did not show any proinflammatory response in endothelial cells as demonstrated by the absence of ICAM-1 induction. We note therefore that there is really no direct relationship between the in vitro biological evaluation tests and the physico-chemical characterization of these dental alloys. Clinical and epidemiological studies are required to clarify these aspects. - Highlights: Black-Right-Pointing-Pointer Nickel released was higher than the limits imposed in EU in contact with the skin. Black-Right-Pointing-Pointer No direct relationship between the

  7. The release code package REVOLS/RENONS for fission product release from a liquid sodium pool into an inert gas atmosphere

    International Nuclear Information System (INIS)

    Starflinger, J.; Scholtyssek, W.; Unger, H.

    1994-12-01

    For aerosol source term considerations in the field of nuclear safety, the investigation of the release of volatile and non-volatile species from liquid surfaces into a gas atmosphere is important. In case of a hypothetical liquid metal fast breeder reactor accident with tank failure, primary coolant sodium with suspended or solved fuel particles and fission products may be released into the containment. The computer code package REVOLS/RENONS, based on a theoretical mechanistic model with a modular structure, has been developed for the prediction of sodium release as well as volatile and non-volatile radionuclide release from a liquid pool surface into the inert gas atmosphere of the inner containment. Hereby the release of sodium and volatile fission products, like cesium and sodium iodide, is calculated using a theoretical model in a mass transfer coefficient formulation. This model has been transposed into the code version REVOLS.MOD1.1, which is discussed here. It enables parameter analysis under highly variable user-defined boundary conditions. Whereas the evaporative release of the volatile components is governed by diffusive and convective transport processes, the release of the non-volatile ones may be governed by mechanical processes which lead to droplet entrainment from the wavy pool surface under conditions of natural or forced convection into the atmosphere. The mechanistic model calculates the liquid entrainment rate of the non-volatile species, like the fission product strontium oxide and the fuel (uranium dioxide) from a liquid pool surface into a parallel gas flow. The mechanistic model has been transposed into the computer code package REVOLS/RENONS, which is discussed here. Hereby the module REVOLS (RElease of VOLatile Species) calculates the evaporative release of the volatile species, while the module RENONS (RElease of NON-Volatile Species) computes the entrainment release of the non-volatile radionuclides. (orig./HP) [de

  8. Role of various natural, synthetic and semi-synthetic polymers on drug release kinetics of losartan potassium oral controlled release tablets.

    Science.gov (United States)

    Jayasree, J; Sivaneswari, S; Hemalatha, G; Preethi, N; Mounika, B; Murthy, S Vasudeva

    2014-10-01

    The objective of the present work was to formulate and to characterize controlled release matrix tablets of losartan potassium in order to improve bioavailability and to minimize the frequency of administration and increase the patient compliance. Losartan potassium controlled release matrix tablets were prepared by direct compression technique by the use of different natural, synthetic and semisynthetic polymers such as gum copal, gum acacia, hydroxypropyl methyl cellulose K100 (HPMC K100), eudragit RL 100 and carboxy methyl ethyl cellulose (CMEC) individually and also in combination. Studies were carried out to study the influence of type of polymer on drug release rate. All the formulations were subjected to physiochemical characterization such as weight variation, hardness, thickness, friability, drug content, and swelling index. In vitro dissolution studies were carried out simulated gastric fluid (pH 1.2) for first 2 h and followed by simulated intestinal fluid (pH 6.8) up to 24 h, and obtained dissolution data were fitted to in vitro release kinetic equations in order to know the order of kinetics and mechanism of drug release. Results of physiochemical characterization of losartan potassium matrix tablets were within acceptable limits. Formulation containing HPMC K100 and CMEC achieved the desired drug release profile up to 24 h followed zero order kinetics, release pattern dominated by Korsmeyer - Peppas model and mechanism of drug release by nonfickian diffusion. The good correlation obtained from Hixson-Crowell model indicates that changes in surface area of the tablet also influences the drug release. Based on the results, losartan potassium controlled release matrix tablets prepared by employing HPMC K100 and CMEC can attain the desired drug release up to 24 h, which results in maintaining steady state concentration and improving bioavailability.

  9. Sequential multi-nuclide emission rate estimation method based on gamma dose rate measurement for nuclear emergency management

    International Nuclear Information System (INIS)

    Zhang, Xiaole; Raskob, Wolfgang; Landman, Claudia; Trybushnyi, Dmytro; Li, Yu

    2017-01-01

    Highlights: • Sequentially reconstruct multi-nuclide emission using gamma dose rate measurements. • Incorporate a priori ratio of nuclides into the background error covariance matrix. • Sequentially augment and update the estimation and the background error covariance. • Suppress the generation of negative estimations for the sequential method. • Evaluate the new method with twin experiments based on the JRODOS system. - Abstract: In case of a nuclear accident, the source term is typically not known but extremely important for the assessment of the consequences to the affected population. Therefore the assessment of the potential source term is of uppermost importance for emergency response. A fully sequential method, derived from a regularized weighted least square problem, is proposed to reconstruct the emission and composition of a multiple-nuclide release using gamma dose rate measurement. The a priori nuclide ratios are incorporated into the background error covariance (BEC) matrix, which is dynamically augmented and sequentially updated. The negative estimations in the mathematical algorithm are suppressed by utilizing artificial zero-observations (with large uncertainties) to simultaneously update the state vector and BEC. The method is evaluated by twin experiments based on the JRodos system. The results indicate that the new method successfully reconstructs the emission and its uncertainties. Accurate a priori ratio accelerates the analysis process, which obtains satisfactory results with only limited number of measurements, otherwise it needs more measurements to generate reasonable estimations. The suppression of negative estimation effectively improves the performance, especially for the situation with poor a priori information, where it is more prone to the generation of negative values.

  10. Sequential multi-nuclide emission rate estimation method based on gamma dose rate measurement for nuclear emergency management

    Energy Technology Data Exchange (ETDEWEB)

    Zhang, Xiaole, E-mail: zhangxiaole10@outlook.com [Institute for Nuclear and Energy Technologies, Karlsruhe Institute of Technology, Karlsruhe, D-76021 (Germany); Institute of Public Safety Research, Department of Engineering Physics, Tsinghua University, Beijing, 100084 (China); Raskob, Wolfgang; Landman, Claudia; Trybushnyi, Dmytro; Li, Yu [Institute for Nuclear and Energy Technologies, Karlsruhe Institute of Technology, Karlsruhe, D-76021 (Germany)

    2017-03-05

    Highlights: • Sequentially reconstruct multi-nuclide emission using gamma dose rate measurements. • Incorporate a priori ratio of nuclides into the background error covariance matrix. • Sequentially augment and update the estimation and the background error covariance. • Suppress the generation of negative estimations for the sequential method. • Evaluate the new method with twin experiments based on the JRODOS system. - Abstract: In case of a nuclear accident, the source term is typically not known but extremely important for the assessment of the consequences to the affected population. Therefore the assessment of the potential source term is of uppermost importance for emergency response. A fully sequential method, derived from a regularized weighted least square problem, is proposed to reconstruct the emission and composition of a multiple-nuclide release using gamma dose rate measurement. The a priori nuclide ratios are incorporated into the background error covariance (BEC) matrix, which is dynamically augmented and sequentially updated. The negative estimations in the mathematical algorithm are suppressed by utilizing artificial zero-observations (with large uncertainties) to simultaneously update the state vector and BEC. The method is evaluated by twin experiments based on the JRodos system. The results indicate that the new method successfully reconstructs the emission and its uncertainties. Accurate a priori ratio accelerates the analysis process, which obtains satisfactory results with only limited number of measurements, otherwise it needs more measurements to generate reasonable estimations. The suppression of negative estimation effectively improves the performance, especially for the situation with poor a priori information, where it is more prone to the generation of negative values.

  11. Effects of geometric non-linearity on energy release rates in a realistic wind turbine blade cross section

    DEFF Research Database (Denmark)

    Eder, Martin Alexander; Bitsche, Robert; Belloni, Federico

    2015-01-01

    Most wind turbine rotor blades comprise several adhesively connected sub-components typically made from glass fibre reinforced polymer composite materials. It is a well-known fact that wind turbine blades are prone to fail in their adhesive joints. However, owing to the complexity...... of their structural behaviour, little is known about the root causes of adhesive joint failure. This paper investigates the effects of geometrical non-linearity on energy release rates (ERRs) of transversely oriented cracks present in the adhesive joints of a wind turbine rotor blade. Utilising a computationally...

  12. Study of benzene release from Savannah River in-tank precipitation process slurry simulant

    International Nuclear Information System (INIS)

    Rappe, K.G.; Gauglitz, P.A.

    1998-08-01

    At the Savannah River Site, the in-tank precipitation (ITP) process uses sodium tetraphenylborate (NaTPB) to precipitate radioactive cesium from alkaline wastes. During this process, potassium is also precipitated to form 4-wt% KTPB/CsTPB slurry. Residual NaTPB decomposes to form benzene, which is retained by the waste slurry. The retained benzene is also readily released from the waste during subsequent waste processing. While the release of benzene certainly poses flammability and toxicological safety concerns, the magnitude of the hazard depends on the rate of release. Currently, the mechanisms controlling the benzene release rates are not well understood, and predictive models for estimating benzene release rates are not available. The overall purpose of this study is to obtain quantitative measurements of benzene release rates from a series of ITP slurry simulants. This information will become a basis for developing a quantitative mechanistic model of benzene release rates. The transient benzene release rate was measured from the surface of various ITP slurry (solution) samples mixed with benzene. The benzene release rate was determined by continuously purging the headspace of a sealed sample vessel with an inert gas (nitrogen) and analyzing that purged headspace vapor for benzene every minute

  13. Mesoporous hydroxyapatite: Preparation, drug adsorption, and release properties

    Energy Technology Data Exchange (ETDEWEB)

    Gu, Lina; He, Xiaomei; Wu, Zhenyu, E-mail: zhenyuwuhn@sina.com

    2014-11-14

    Mesoporous hydroxyapatite (HA) was synthesized through gas–liquid chemical precipitation method at ambient temperature without any template. Structure, morphology and pore size distribution of HA were analyzed via X-ray powder diffraction, scanning electron microscopy, transmission electron microscopy, high-resolution electron microscopy and N{sub 2} adsorption/desorption. The chemotherapeutic agent doxorubicin (DOX) was used to investigate the drug adsorption and release behavior of HA. The kinetics of DOX adsorption on HA followed the pseudo-second-order rate expression. Adsorption isotherms at various temperatures were obtained, and the equilibrium data fitted the Langmuir model. The values of thermodynamic parameters (Gibbs free energy, entropy, and enthalpy changes) demonstrated that the adsorption process was spontaneous and endothermic. In vitro pH-responsive (pH = 7.4, 5.8) controlled release was investigated. DOX-loaded HA showed a slow, long-term, and steady release rate. The release rate at pH5.8 was larger than that at pH7.4. Consequently, the as-prepared mesoporous HA has potential applications in controlled drug delivery systems. - Highlights: • Mesoporous HA was synthesized by a simple precipitation method without any template. • The kinetics of adsorption followed the pseudo-second-order rate expression. • Thermodynamics investigation showed that adsorption was spontaneous and endothermic. • DOX-loaded HA showed a long-term, steady, and pH-controlled release rate.

  14. Electrosprayed nanoparticle delivery system for controlled release

    Energy Technology Data Exchange (ETDEWEB)

    Eltayeb, Megdi, E-mail: megdi.eltayeb@sustech.edu [Department of Biomedical Engineering, Sudan University of Science and Technology, PO Box 407, Khartoum (Sudan); Stride, Eleanor, E-mail: eleanor.stride@eng.ox.ac.uk [Institute of Biomedical Engineering, Department of Engineering Science, University of Oxford, Old Road Campus Research Building, Headington OX3 7DQ (United Kingdom); Edirisinghe, Mohan, E-mail: m.edirisinghe@ucl.ac.uk [Department of Mechanical Engineering, University College London, Torrington Place, London WC1E 7JE (United Kingdom); Harker, Anthony, E-mail: a.harker@ucl.ac.uk [London Centre for Nanotechnology, Gordon Street, London WC1H 0AH (United Kingdom); Department of Physics & Astronomy, University College London, Gower Street, London WC1E 6BT (United Kingdom)

    2016-09-01

    This study utilises an electrohydrodynamic technique to prepare core-shell lipid nanoparticles with a tunable size and high active ingredient loading capacity, encapsulation efficiency and controlled release. Using stearic acid and ethylvanillin as model shell and active ingredients respectively, we identify the processing conditions and ratios of lipid:ethylvanillin required to form nanoparticles. Nanoparticles with a mean size ranging from 60 to 70 nm at the rate of 1.37 × 10{sup 9} nanoparticles per minute were prepared with different lipid:ethylvanillin ratios. The polydispersity index was ≈ 21% and the encapsulation efficiency ≈ 70%. It was found that the rate of ethylvanillin release was a function of the nanoparticle size, and lipid:ethylvanillin ratio. The internal structure of the lipid nanoparticles was studied by transmission electron microscopy which confirmed that the ethylvanillin was encapsulated within a stearic acid shell. Fourier transform infrared spectroscopy analysis indicated that the ethylvanillin had not been affected. Extensive analysis of the release of ethylvanillin was performed using several existing models and a new diffusive release model incorporating a tanh function. The results were consistent with a core-shell structure. - Highlights: • Electrohydrodynamic spraying is used to produce lipid-coated nanoparticles. • A new model is proposed for the release rates of active components from nanoparticles. • The technique has potential applications in food science and medicine. • Electrohydrodynamic processing controlled release lipid nanoparticles.

  15. Outpacing the Anthropocene: New Constraints for the Rate of Carbon Release at the Paleocene-Eocene Thermal Maximum

    Science.gov (United States)

    Wright, J. D.; Schaller, M. F.

    2012-12-01

    The Paleocene/Eocene Thermal Maximum (PETM) Carbon Isotope Excursion (CIE) is linked to benthic foraminiferal extinction and excursion taxa in planktonic foraminifera and calcareous nannofossils. Previous studies have used integrated bio-magneto-stratigraphies, cycle counting, and extraterrestrial 3He accumulation rates to produce a range of estimates for the duration of the initial onset of the PETM CIE between 750 years to 30 kyr. Durations for the total release time (onset to initiation of recovery) range from 45 to 95 kyr. Uncertainty in the timing of the onset of the PETM CIE prevents the identification of a causal mechanism, and hence understanding the biological responses. Recent work on the Paleocene/Eocene Marlboro Clay has unveiled the presence of regular couplets (~2 cm) expressed in multiple cores and exposures throughout the Atlantic Coastal Plain. Specifically, the Millville and newly recovered Wilson Lake B cores contain 750 and 660 layers through the CIE, respectively. These couplets have corresponding oxygen stable isotope cycles, arguing for a climatic origin. Orbital and millennial periodicities are far too long to explain the ~750 layers identified in the Millville core. Seasonal insolation is the only regular climate cycle that can plausibly account for the observed δ18O amplitudes (~1‰, with some cycles up to 2‰) and layer counts. Seasonal freshwater input can also augment the cyclic oscillations in δ18O, but the majority of the variability is most plausibly ascribed to temperature. Wilson Lake B and Millville have total δ13C excursions of -5 and -4.5‰ respectively, as well as highly expanded sections of the PETM CIE. In the Millville core, high-resolution, bulk stable isotope records show a 3.5‰ δ13C decrease over 12 layers across the PETM CIE onset. Concomitant with this δ13C decrease is a sharp drop in CaCO3. Decreases in both proxies require a large, sudden release of isotopically light carbon. The couplet chronology indicates

  16. Release mechanism of doxazosin from carrageenan matrix tablets: Effect of ionic strength and addition of sodium dodecyl sulphate.

    Science.gov (United States)

    Kos, Petra; Pavli, Matej; Baumgartner, Saša; Kogej, Ksenija

    2017-08-30

    The polyelectrolyte matrix tablets loaded with an oppositely charged drug exhibit complex drug-release mechanisms. In this study, the release mechanism of a cationic drug doxazosin mesylate (DM) from matrix tablets based on an anionic polyelectrolyte λ-carrageenan (λ-CARR) is investigated. The drug release rates from λ-CARR matrices are correlated with binding results based on potentiometric measurements using the DM ion-sensitive membrane electrode and with molecular characteristics of the DM-λ-CARR-complex particles through hydrodynamic size measurements. Experiments are performed in solutions with different ionic strength and with the addition of an anionic surfactant sodium dodecyl sulphate (SDS). It is demonstrated that in addition to swelling and erosion of tablets, the release rates depend strongly on cooperative interactions between DM and λ-CARR. Addition of SDS at concentrations below its critical micelle concentration (CMC) slows down the DM release through hydrophobic binding of SDS to the DM-λ-CARR complex. On the contrary, at concentrations above the CMC SDS pulls DM from the complex by forming mixed micelles with it and thus accelerates the release. Results involving SDS show that the concentration of surfactants that are naturally present in gastrointestinal environment may have a great impact on the drug release process. Copyright © 2017 Elsevier B.V. All rights reserved.

  17. Risk-informed assessment of radionuclide release from dissolution of spent nuclear fuel and high-level waste glass

    Energy Technology Data Exchange (ETDEWEB)

    Ahn, Tae M., E-mail: tae.ahn@nrc.gov

    2017-06-15

    Highlights: • Dissolution of HLW waste form was assessed with long-term risk informed approach. • The radionuclide release rate decreases with time from the initial release rate. • Fast release radionuclides can be dispersed with discrete container failure time. • Fast release radionuclides can be restricted by container opening area. • Dissolved radionuclides may be further sequestered by sorption or others means. - Abstract: This paper aims to detail the different parameters to be considered for use in an assessment of radionuclide release. The dissolution of spent nuclear fuel and high-level nuclear waste glass was considered for risk and performance insights in a generic disposal system for more than 100,000 years. The probabilistic performance assessment includes the waste form, container, geology, and hydrology. Based on the author’s previous extended work and data from the literature, this paper presents more detailed specific cases of (1) the time dependence of radionuclide release, (2) radionuclide release coupled with container failure (rate-limiting process), (3) radionuclide release through the opening area of the container and cladding, and (4) sequestration of radionuclides in the near field after container failure. These cases are better understood for risk and performance insights. The dissolved amount of waste form is not linear with time but is higher at first. The radionuclide release rate from waste form dissolution can be constrained by container failure time. The partial opening area of the container surface may decrease radionuclide release. Radionuclides sequestered by various chemical reactions in the near field of a failed container may become stable with time as the radiation level decreases with time.

  18. Observed Barium Emission Rates

    Science.gov (United States)

    Stenbaek-Nielsen, H. C.; Wescott, E. M.; Hallinan, T. J.

    1993-01-01

    The barium releases from the CRRES satellite have provided an opportunity for verifying theoretically calculated barium ion and neutral emission rates. Spectra of the five Caribbean releases in the summer of 1991 were taken with a spectrograph on board a U.S. Air Force jet aircraft. Because the line of sight release densities are not known, only relative rates could be obtained. The observed relative rates agree well with the theoretically calculated rates and, together with other observations, confirm the earlier detailed theoretical emission rates. The calculated emission rates can thus with good accuracy be used with photometric observations. It has been postulated that charge exchange between neutral barium and oxygen ions represents a significant source for ionization. If so. it should be associated with emissions at 4957.15 A and 5013.00 A, but these emissions were not detected.

  19. Recombinant human bone morphogenetic protein-2 released from polyurethane-based scaffolds promotes early osteogenic differentiation of human mesenchymal stem cells

    International Nuclear Information System (INIS)

    Kim, Jinku; Hollinger, Jeffrey O

    2012-01-01

    The purposes of this study were to determine the pharmacokinetics of recombinant human bone morphogenetic protein-2 (rhBMP-2) from a polyurethane (PUR)-based porous scaffold and to determine the biological responses of human mesenchymal stem cells (hMSCs) to the rhBMP-2 released from those scaffolds. The rhBMP-2 was incorporated into the PUR three-dimensional (3D) porous scaffolds and release profiles were determined using enzyme-linked immunosorbent assay. The bioactivity of the rhBMP-2 containing releasates was determined using hMSCs and compared with exogenous rhBMP-2. Release of rhBMP-2 from PUR-based systems was bi-phasic and characterized by an initial burst followed by a sustained release for up to 21 days. Expression of alkaline phosphatase activity by hMSCs treated with the rhBMP-2 releasates was significantly greater than the cells alone (control) throughout the time periods. Furthermore, after 14 days of culture, the hMSCs cultured with rhBMP-2 releasate had a greater amount of mineralization compared to exogenous rhBMP-2. Overall, the rhBMP-2 release from the PUR-based scaffolds was sustained for 21 days and the releasates appeared to be bioactive and promoted earlier osteogenic differentiation and mineralization of hMSCs than the exogenous rhBMP-2. (paper)

  20. Multiscale numerical modeling of Ce3+-inhibitor release from novel corrosion protection coatings

    International Nuclear Information System (INIS)

    Trenado, Carlos; Wittmar, Matthias; Veith, Michael; Strauss, Daniel J; Rosero-Navarro, Nataly C; Aparicio, Mario; Durán, Alicia; Castro, Yolanda

    2011-01-01

    A novel hybrid sol–gel coating has recently been introduced as an alternative to high toxic chromate-based corrosion protection systems. In this paper, we propose a multiscale computational model to estimate the amount and time scale of inhibitor release of the active corrosion protection coating. Moreover, we study the release rate under the influence of parameters such as porosity and viscosity, which have recently been implicated in the stability of the coating. Numerical simulations obtained with the model predicted experimental release tests and recent findings on the compromise between inhibitor concentration and the stability of the coating

  1. Deuterium isotope effects on toluene metabolism. Product release as a rate-limiting step in cytochrome P-450 catalysis

    International Nuclear Information System (INIS)

    Ling, K.H.; Hanzlik, R.P.

    1989-01-01

    Liver microsomes from phenobarbital-induced rats oxidize toluene to a mixture of benzyl alcohol plus o-, m- and p-cresol (ca. 69:31). Stepwise deuteration of the methyl group causes stepwise decreases in the yield of benzyl alcohol relative to cresols (ca. 24:76 for toluene-d3). For benzyl alcohol formation from toluene-d3 DV = 1.92 and D(V/K) = 3.53. Surprisingly, however, stepwise deuteration induces stepwise increases in total oxidation, giving rise to an inverse isotope effect overall (DV = 0.67 for toluene-d3). Throughout the series (i.e. d0, d1, d2, d3) the ratios of cresol isomers remain constant. These results are interpreted in terms of product release for benzyl alcohol being slower than release of cresols (or their epoxide precursors), and slow enough to be partially rate-limiting in turnover. Thus metabolic switching to cresol formation causes a net acceleration of turnover

  2. Calculation of the inventory and near-field release rates of radioactivity from neutron-activated metal parts discharged from the high flux isotope reactor and emplaced in solid waste storage area 6 at Oak Ridge National Laboratory

    Energy Technology Data Exchange (ETDEWEB)

    Kelmers, A.D.; Hightower, J.R.

    1987-05-01

    Emplacement of contaminated reactor components involves disposal in lined and unlined auger holes in soil above the water table. The radionuclide inventory of disposed components was calculated. Information on the composition and weight of the components, as well as reasonable assumptions for the neutron flux fueling use, the time of neutron exposure, and radioactive decay after discharge, were employed in the inventory calculation. Near-field release rates of /sup 152/Eu, /sup 154/Eu, and /sup 155/Eu from control plates and cylinders were calculated for 50 years after emplacement. Release rates of the europium isotopes were uncertain. Two release-rate-limiting models were considered and a range of reasonable values were assumed for the time-to-failure of the auger-hole linear and aluminum cladding and europium solubility in SWSA-6 groundwater. The bounding europium radionuclide near-field release rates peaked at about 1.3 Ci/year total for /sup 152,154,155/Eu in 1987 for the lower bound, and at about 420 Ci/year in 1992 for the upper bound. The near-field release rates of /sup 55/Fe, /sup 59/Ni, /sup 60/Co, and /sup 63/Ni from stainless steel and cobalt alloy components, as well as of /sup 10/Be, /sup 41/Ca, and /sup 55/Fe from beryllium reflectors, were calculated for the next 100 years, assuming bulk waste corrosion was the release-rate-limiting step. Under the most conservative assumptions for the reflectors, the current (1986) total radionuclide release rate was calculated to be about 1.2 x 10/sup -4/ Ci/year, decreasing by 1992 to a steady release of about 1.5 x 10/sup -5/ Ci/year due primarily to /sup 41/Ca. 50 refs., 13 figs., 8 tabs.

  3. Variation of the energy release rate as a crack approaches and passes through an elastic inclusion

    Science.gov (United States)

    Li, Rongshun; Chudnovsky, A.

    1993-01-01

    The variation of the energy release rate (ERP) at the tip of a crack penetrating an elastic inclusion is analyzed using an approach involving modeling the random array of microcracks or other defects by an elastic inclusion with effective elastic properties. Computations are carried out using a finite element procedure. The eight-noded isoparametric serendipity element with the shift of the midpoint to the quarter-point is used to simulate the singularity at the crack tip, and the crack growth is accommodated by implementing a mesh regeneration technique. The ERP values were calculated for various crack tip positions which simulate the process of the crack approaching and penetrating the inclusion.

  4. Steady-State Flammable Gas Release Rate Calculation And Lower Flammability Level Evaluation For Hanford Tank Waste

    International Nuclear Information System (INIS)

    Meacham, J.E.

    2008-01-01

    This report assesses the steady state flammability level under off normal ventilation conditions in the tank headspace for 28 double-shell tanks (DST) and 149 single shell-tanks (SST) at the Hanford Site. Flammability was calculated using estimated gas release rates, Le Chatelier's rule, and lower flammability limits of fuels in an air mixture. This revision updates the hydrogen generation rate input data for al1 177 tanks using waste composition information from the Best Basis Inventory Detail Report (data effective as of August 4,2008). Assuming only barometric breathing, the shortest time to reach 25% of the lower flammability limit is 13 days for DSTs (i.e., tank 241-AZ-102) and 36 days for SSTs (i.e., tank 241-B-203). Assuming zero ventilation, the shortest time to reach 25% of the lower flammability limit is 12 days for DSTs (i.e., tank 241-AZ-102) and 34 days for SSTs (i.e., tank 241-B-203).

  5. Steady-State Flammable Gas Release Rate Calculation And Lower Flammability Level Evaluation For Hanford Tank Waste

    International Nuclear Information System (INIS)

    Meacham, J.E.

    2009-01-01

    This report assesses the steady state flammability level under off normal ventilation conditions in the tank headspace for 28 double-shell tanks (DST) and 149 single shell-tanks (SST) at the Hanford Site. Flammability was calculated using estimated gas release rates, Le Chatelier's rule, and lower flammability limits of fuels in an air mixture. This revision updates the hydrogen generation rate input data for all 177 tanks using waste composition information from the Best Basis Inventory Detail Report (data effective as of August 4,2008). Assuming only barometric breathing, the shortest time to reach 25% of the lower flammability limit is 11 days for DSTs (i.e., tank 241-AZ-10l) and 36 days for SSTs (i.e., tank 241-B-203). Assuming zero ventilation, the shortest time to reach 25% of the lower flammability limit is 10 days for DSTs (i.e., tank 241-AZ-101) and 34 days for SSTs (i.e., tank 241-B-203).

  6. Controlled release of insect sex pheromones from paraffin wax and emulsions.

    Science.gov (United States)

    Atterholt, C A; Delwiche, M J; Rice, R E; Krochta, J M

    1999-02-22

    Paraffin wax and aqueous paraffin emulsions can be used as controlled release carriers for insect sex pheromones for mating disruption of orchard pests. Paraffin can be applied at ambient temperature as an aqueous emulsion, adheres to tree bark or foliage, releases pheromone for an extended period of time, and will slowly erode from bark and biodegrade in soil. Pheromone emulsions can be applied with simple spray equipment. Pheromone release-rates from paraffin were measured in laboratory flow-cell experiments. Pheromone was trapped from an air stream with an adsorbent, eluted periodically, and quantified by gas chromatography. Pheromone release from paraffin was partition-controlled, providing a constant (zero-order) release rate. A typical paraffin emulsion consisted of 30% paraffin, 4% pheromone, 4% soy oil, 1% vitamin E, 2% emulsifier, and the balance water. Soy oil and vitamin E acted as volatility suppressants. A constant release of oriental fruit moth pheromone from paraffin emulsions was observed in the laboratory for more than 100 days at 27 degreesC, with release-rates ranging from 0.4 to 2 mg/day, depending on the concentration and surface area of the dried emulsion. The use of paraffin emulsions is a viable method for direct application of insect pheromones for mating disruption. Sprayable formulations can be designed to release insect pheromones to the environment at a rate necessary for insect control by mating disruption. At temperatures below 38 degreesC, zero-order release was observed. At 38 degreesC and higher, pheromone oxidation occurred. A partition-controlled release mechanism was supported by a zero-order pheromone release-rate, low air/wax partition coefficients, and pheromone solubility in paraffin.

  7. Potential of Phytase-Mediated Iron Release from Cereal-Based Foods: A Quantitative View

    Science.gov (United States)

    Nielsen, Anne V. F.; Tetens, Inge; Meyer, Anne S.

    2013-01-01

    The major part of iron present in plant foods such as cereals is largely unavailable for direct absorption in humans due to complexation with the negatively charged phosphate groups of phytate (myo-inositol (1,2,3,4,5,6)-hexakisphosphate). Human biology has not evolved an efficient mechanism to naturally release iron from iron phytate complexes. This narrative review will evaluate the quantitative significance of phytase-catalysed iron release from cereal foods. In vivo studies have shown how addition of microbially derived phytases to cereal-based foods has produced increased iron absorption via enzyme-catalysed dephosphorylation of phytate, indicating the potential of this strategy for preventing and treating iron deficiency anaemia. Despite the immense promise of this strategy and the prevalence of iron deficiency worldwide, the number of human studies elucidating the significance of phytase-mediated improvements in iron absorption and ultimately in iron status in particularly vulnerable groups is still low. A more detailed understanding of (1) the uptake mechanism for iron released from partially dephosphorylated phytate chelates, (2) the affinity of microbially derived phytases towards insoluble iron phytate complexes, and (3) the extent of phytate dephosphorylation required for iron release from inositol phosphates is warranted. Phytase-mediated iron release can improve iron absorption from plant foods. There is a need for development of innovative strategies to obtain better effects. PMID:23917170

  8. The ability of retention, drug release and rheological properties of nanogel bioadhesives based on cellulose derivatives.

    Science.gov (United States)

    Keshavarz, M; Kaffashi, B

    2014-12-01

    The rheological and drug release behavior of biopolymer nanocomposite gels based on the cellulose derivatives, formulated as the bioadhesive drug delivery platforms, were investigated. The bioadhesive gel is composed of the microcrystalline cellulose, sodium carboxymethyl cellulose and phosphate buffered saline (pH = 7.4 at 20 °C) as the dissolution and release medium. The reinforcing nanofillers such as MMT-clay, fumed porous silica and porous starch were used as additives in the nanogel bioadhesive. The constant steady state viscosities of this nanogels upon incorporation of various nanofillers into the systems is the sign of structural stability. Hence, this system is suitable for use in the controlled drug delivery systems in contact with the biological tissues. Based on the rheological measurements, the shear flow properties (i.e. zero shear viscosity and yield stress) were influenced by the concentration of polymers and nanoparticles. The results indicate that the nonlinear rheological data are fitted properly by the Giesekus model. Furthermore, the results showed that the nonlinear viscoelastic parameters (λ and α) are highly affected by the biogel and nanoparticles concentrations. Finally, the drug release was measured, and the results indicated that the biopolymer-clay nanocomposites have appropriate release pattern as the release is better controlled compared to the other nanogel formulations.

  9. Strand breaks, base release and post-irradiation changes in DNA γ-irradiated in dilute O2-saturated aqueous solution

    International Nuclear Information System (INIS)

    Ward, J.F.; Kuo, I.

    1976-01-01

    Gamma irradiation of DNA in dilute O 2 -saturated aqueous solution releases free bases and damaged bases from the macromolecule. The yields of these products were measured after column chromatographic separation. For double stranded DNA the immediate yield of bases varies from G = 0.012 for cytosine to G = 0.033 for adenine. The yields of released bases increase with post-irradiation time (the majority of the increase occurs in the first 2 hrs.) to yields in the range of G = 0.07 +- 0.012. Yields of two released damaged thymine radiation products from γ-irradiated 3 H thymine labelled DNA also increased with post-irradiation time. Strand breaks were measured in γ-irradiated single stranded DNA the initial yield G = 0.02 was low but increased with time to G = 0.07. No direct correlation between strand-break production and release of low molecular weight products is possible. The findings are discussed in terms of damage to DNA in vivo and its enzymatic repair

  10. A method of surface area measurement of fuel materials by fission gas release at low temperature

    International Nuclear Information System (INIS)

    Kaimal, K.N.G.; Naik, M.C.; Paul, A.R.; Venkateswarlu, K.S.

    1989-01-01

    The present report deals with the development of a method for surface area measurement of nuclear fuel as well as fissile doped materials by fission gas release study at low temperature. The method is based on the evaluation of knock-out release rate of fission 133 Xe from irradiated fuel after sufficient cooling to decay the short lived activity. The report also describes the fabrication of an ampoule breaker unit for such study. Knock-out release rate of 133 Xe has been studied from UO 2 powders having varying surface area 'S' ranging from 270 cm 2 /gm to 4100 cm 2 /gm at two fissioning rates 10 12 f/cm 3 . sec. and 3.2x10 10 f/cm.sec. A relation between K and A has been established and discussed in this report. (author). 6 refs

  11. Release time of residual oxygen after dental bleaching with 35% hydrogen peroxide: effect of a catalase-based neutralizing agent.

    Science.gov (United States)

    Guasso, Bárbara; Salomone, Paloma; Nascimento, Paulo Cícero; Pozzobon, Roselaine Terezinha

    2016-01-01

    This article assessed the effect of a catalase-based agent on residual oxygen (O2) release from teeth exposed to 35% hydrogen peroxide (H2O2). The use of the catalase-based neutralizer agent for 2-3 minutes was able to release residual O2 5 days after exposure to a 35% H2O2-based bleaching gel.

  12. Dose-rate conversion factors for external exposure to photon and electron radiation from radionuclides occurring in routine releases from nuclear fuel cycle facilities

    International Nuclear Information System (INIS)

    Kocher, D.C.

    1980-01-01

    Dose-rate conversion factors for external exposure to photon and electron radiation are calculated for 240 radionuclides of potential importance in routine releases from nuclear fuel cycle facilities. Exposure modes considered are immersion in contaminated air, immersion in contaminated water, and irradiation from a contaminated ground surface. For each exposure mode, dose-rate conversion factors for photons and electrons are calculated for tissue-equivalent material at the body surface of an exposed individual. Dose-rate conversion factors for photons only are calculated for 22 body organs. (author)

  13. Starch derivative-based superabsorbent with integration of water-retaining and controlled-release fertilizers.

    Science.gov (United States)

    Zhong, Kang; Lin, Zuan-Tao; Zheng, Xi-Liang; Jiang, Gang-Biao; Fang, Yu-Sheng; Mao, Xiao-Yun; Liao, Zong-Wen

    2013-02-15

    Phosphate rock (PHR), a traditional fertilizer, is abundant, but is hard to be utilized by plants. To improve the utilization of PHR, and to integrate water-retaining and controlled-release fertilizers, an agricultural superabsorbent polymer based on sulfonated corn starch/poly (acrylic acid) embedding phosphate rock (SCS/PAA/PHR) was prepared. PHR can be suspended and well-dispersed in SCS/PAA by sulfonated corn starch (SCS). PHR and KOH were mixed in acrylic acid solution to provide phosphorus (P) and potassium (K) nutrients, respectively. Impacts on water absorption capacity of the superabsorbent were investigated. The maximum swelling capacity in distilled water or 0.9 wt.% (weight percent) NaCl solution reached 498 g g(-1) and 65 g g(-1) (water/prepared dry superabsorbent) respectively. Moreover, release behaviours of P and K in SCS/PAA/PHR were also investigated. The results showed that SCS/PAA/PHR possessed excellent sustained-release property of plant nutrient, and the SCS/PAA could improve the P release greatly. Besides, the XPS analysis was employed to study the relationship between PHR and superabsorbent polymer. Copyright © 2012 Elsevier Ltd. All rights reserved.

  14. Applications of energy-release-rate techniques to part-through cracks in plates and cylinders. Volume 2. ORVIRT: a finite element program for energy release rate calculations for 2-dimensional and 3-dimensional crack models

    International Nuclear Information System (INIS)

    Bass, B.R.; Bryson, J.W.

    1983-02-01

    Certain studies of fracture phenomena, such as pressurized-thermal-shock of cracked structures, require that crack tip parameters be determined for combined thermal and mechanical loads. A method is proposed here that modifies the isothermal formulation of deLorenzi to account for thermal strains in cracked bodies. The formulation has been implemented in the virtual-crack-extension program ORVIRT (Oak Ridge VIRTual-Crack-Extension). Program ORVIRT performs energy release rate calculations for both 2- and 3-dimensional nonlinear models of crack configurations in engineering structures. Two applications of the ORVIRT program are described. In the first, semielliptical surface cracks in an experimental test vessel are analyzed under elastic-plastic conditions using the finite element method. The second application is a thick-walled test vessel subjected to combined pressure and thermal shock loading

  15. Role of hemolysis in potassium release by iodinated contrast medium

    Energy Technology Data Exchange (ETDEWEB)

    Hayakawa, K.; Nakamura, T.; Shimizu, Y. [Department of Radiology, Kyoto City Hospital (Japan)

    1999-09-01

    It has been demonstrated that an iodinated contrast medium (CM) causes release of potassium into blood vessel lumina, resulting in an increase in serum potassium. The purpose of the present study was to assess whether this potassium release is due to hemolysis. Fresh human blood was mixed in vitro with CM at a ratio of 10:2. Potassium release rates were determined, and serum haptoglobin and free hemoglobin were measured after 30 min of exposure to CM. To compare the potassium release curve between CM exposure and true hemolysis induced by distilled water, fresh human blood was also mixed with distilled water. The level of serum haptoglobin decreased due to hemodilution. Changes in haptoglobin were not correlated with potassium release rates. The serum free hemoglobin level did not increase significantly, and there was no correlation between changes in the free hemoglobin level and the rate of potassium release. Hemolysis caused by water occurred instantaneously, whereas potassium release caused by CM was a slow response, which was linearly correlated with exposure time. Potassium release from blood cannot be explained by hemolysis. (orig.) With 4 figs., 4 tabs., 3 refs.

  16. Modeling of container failure and radionuclide release from a geologic nuclear waste repository

    International Nuclear Information System (INIS)

    Kim, Chang Lak; Kim, Jhin Wung; Choi, Kwang Sub; Cho, Chan Hee

    1989-02-01

    Generally, two processes are involved in leaching and dissolution; (1) chemical reactions and (2) mass transfer by diffusion. The chemical reaction controls the dissolution rates only during the early stage of exposure to groundwater. The exterior-field mass transfer may control the long-term dissolution rates from the waste solid in a geologic repository. Masstransfer analyses rely on detailed and careful application of the governing equations that describe the mechanistic processes of transport of material between and within phases. We develop analytical models to predict the radionuclide release rate into the groundwater with five different approaches: a measurement-based model, a diffusion model, a kinetics model, a diffusion-and-kinetics model, and a modified diffusion model. We also collected experimental leaching data for a partial validation of the radionuclide release model based on the mass transfer theory. Among various types of corrosions, pitting is the most significant because of its rapid growth. The failure time of the waste container, which also can be interpreted as the containment time, is a milestone of the performance of a repository. We develop analytical models to predict the pit growth rate on the container surface with three different approaches: an experimental method, a statistical method, and a mathematical method based on the diffusion theory. (Author)

  17. Risk assessment based on current release standards for radioactive surface contamination

    International Nuclear Information System (INIS)

    Chen, S.Y.

    1993-09-01

    Standards for uncontrolled releases of radioactive surface contamination have been in existence in the United States for about two decades. Such standards have been issued by various agencies, including the US Department of Energy. This paper reviews the technical basis of published standards, identifies areas in need of revision, provides risk interpretations based on current technical knowledge and the regulatory environment, and offers suggestions for improvements

  18. Low molecular weight polylactic acid as a matrix for the delayed release of pesticides.

    Science.gov (United States)

    Zhao, Jing; Wilkins, Richard M

    2005-05-18

    Low molecular weight polylactic acid (LMW PLA) was used as a matrix to formulate biodegradable matrix granules and films with bromacil using a melt process. The compatibility of the PLA with bromacil was evaluated. The release characteristics of the formulations were investigated in vitro. The degradation and erosion of the formulations were monitored by pH and gravimetric analysis during the course of release. Various granules and films had similar biphasic release patterns, a delayed release followed by an explosive release. The release rates were independent of bromacil content in the matrix, but varied with the geometry of matrices. The mechanisms of diffusion and erosion were involved in the release. The delayed release of the formulations was dominantly governed by the degradation and erosion of PLA. LMW PLA underwent bulk erosion. LMW PLA-based matrix formulations could thus be useful for the application of pesticides to sensitive targets such as seed treatment.

  19. Breeding blanket development. Tritium release from breeder

    International Nuclear Information System (INIS)

    Tsuchiya, Kunihiko; Kawamura, Hiroshi; Nagao, Yoshiharu

    2006-01-01

    Engineering data on neutron irradiation performance of tritium breeders are needed to design the breeding blanket of fusion reactor. In this study, tritium release experiments of the breeders were carried out to examine the effects of various parameters (such as sweep gas flow rate, hydrogen content in sweep gas, irradiation temperature and thermal neutron flux) on tritium generation and release behavior. Lithium titanate (Li 2 TiO 3 ) is considered as a candidate tritium breeder in the blanket design of International Thermonuclear Experimental Reactor (ITER). As for the shape of the breeder material, a small spherical form is preferred to reduce the thermal stress induced in the breeder. Li 2 TiO 3 pebbles of about 170g in total weight and with 0.3 and 2 mm in diameter were manufactured by a wet process, and an assembly packed with the binary Li 2 TiO 3 pebbles was irradiated in Japan Materials Testing Reactor (JMTR). The tritium was generated in the Li 2 TiO 3 pebble bed and released from the pebble bed, and was swept downstream using the sweep gas for on-line analysis of tritium content. Concentration of total tritium and gaseous tritium (HT or T 2 gas) released from the Li 2 TiO 3 pebble bed were measured by ionization chambers, and the ratio of (gaseous tritium)/(total tritium) was evaluated. The sweep gas flow rate was changed from 100 to 900cm 3 /min, and hydrogen content in the sweep gas was changed from 100 to 10000 ppm. Furthermore, thermal neutron flux was changed using a window made of hafnium (Hf) neutron absorber. The irradiation temperature at an outer region of the Li 2 TiO 3 pebble bed was held between 200 and 400degC. The main results of this experiment are summarized as follows. 1) When the temperature at the outside edge of the Li 2 TiO 3 pebble bed exceeded 100degC, the tritium release from the Li 2 TiO 3 pebble bed started. The ratio of the tritium release rate and the tritium generation rate (normalized tritium release rate: R/G) reached

  20. Mathematical modeling of radionuclide release through a borehole in a radioactive waste repository

    International Nuclear Information System (INIS)

    Choi, Heui Joo

    1996-02-01

    The effects of inadvertent human intrusion as a form of direct drilling into a radioactive waste repository are discussed in this thesis. It has been mentioned that the inadvertent direct drilling into the repository could provide a release pathway for radionuclides even with its low occurrence probability. The following analyses are carried out regarding the problem. The maximum concentration in a water-filled borehole penetrating a repository is computed with a simple geometry. The modeling is based upon the assumption of the diffusive mass transfer in the waste forms and the complete mixing in the borehole. It is shown that the maximum concentrations of six radionuclides in the borehole could exceed the Maximum Permissible Concentration. Also, the diffusive mass transport in a water-filled borehole is investigated with a solubility-limited boundary condition. An analytic solution is derived for this case. Results show that the diffusive mass transport is fast enough to justify the assumption of the complete mixing compared with the considered time span. The axial diffusive mass transport along a water-filled borehole is modeled to compute the release rate taking account of the rock matrix diffusion. The results show that the release of short-lived radionuclides are negligible due to the low concentration gradient in early time and the rock matrix diffusion. The release rates of four long-lived radionuclides are computed. It is also shown that the model developed could be applied to a borehole at a non-cylindrically shaped repository and the off-center drilling of a cylindrical repository. The release rates of long-lived nuclides through a porous material-filled borehole are computed. The results show that the release of all the long-lived nuclides is negligible up to half million years in the case that the borehole is filled with the porous material. The radiological effects of the nuclides released through the borehole penetrating the repository are computed

  1. Experiments to determine the rate of beta energy release following fission of Pu239 andU235 in a fast reactor

    International Nuclear Information System (INIS)

    Murphy, M.F.; Taylor, W.H.; Sweet, D.W.; March, M.R.

    1979-02-01

    Measurements have been made of the rate of beta energy release from Pu239 and U235 fission fragments over a period of 107 seconds following a 105 second irradiation in the zero-power fast reactor Zebra. Results are compared with predictions using the UKFPDD-1 decay data file and two different sets of fission product yield data. (author)

  2. Rate based failure detection

    Science.gov (United States)

    Johnson, Brett Emery Trabun; Gamage, Thoshitha Thanushka; Bakken, David Edward

    2018-01-02

    This disclosure describes, in part, a system management component and failure detection component for use in a power grid data network to identify anomalies within the network and systematically adjust the quality of service of data published by publishers and subscribed to by subscribers within the network. In one implementation, subscribers may identify a desired data rate, a minimum acceptable data rate, desired latency, minimum acceptable latency and a priority for each subscription. The failure detection component may identify an anomaly within the network and a source of the anomaly. Based on the identified anomaly, data rates and or data paths may be adjusted in real-time to ensure that the power grid data network does not become overloaded and/or fail.

  3. PIXE investigation of in vitro release of chloramphenicol across polyvinyl alcohol/acrylamide hydrogel

    International Nuclear Information System (INIS)

    Rihawy, M.S.; Alzier, A.; Allaf, A.W.

    2011-01-01

    Hydrogels based on polyvinyl alcohol and different amounts of acrylamide monomer were prepared by thermal cross-linking in the solid state. The hydrogels were investigated for drug delivery system applications. Chloramphenicol was adopted as a model drug to study its release behavior. Particle induced X-ray emission was utilized to study the drug release behavior across the hydrogels and a comparison study with ultraviolet measurements was performed. Fourier Transform Infrared measurements were carried out for molecular characterization. The releasing behavior of the drug exhibits a decrease and a subsequent increase in the release rate, as the acrylamide monomer increases. Characterization of the hydrogels has shown a competitive behavior between crosslinking with AAm acrylamide monomer or oligomerized version, depending on the amount added to prepare the hydrogels.

  4. Drug release into hydrogel-based subcutaneous surrogates studied by UV imaging

    DEFF Research Database (Denmark)

    Ye, Fengbin; Larsen, Susan Weng; Yaghmur, Anan

    2012-01-01

    of the performance of drug delivery systems based on in vitro experiments. The objective of this study was to evaluate a UV imaging-based method for real-time characterization of the release and transport of piroxicam in hydrogel-based subcutaneous tissue mimics/surrogates. Piroxicam partitioning from medium chain...... upon the injection of aqueous or MCT solutions into an agarose-based hydrogel were investigated by UV imaging. The spatial distribution of piroxicam around the injection site in the gel matrix was monitored in real-time. The disappearance profiles of piroxicam from the injected aqueous solution were...... obtained. This study shows that the UV imaging methodology has considerable potential for characterizing transport properties in hydrogels, including monitoring the real-time spatial concentration distribution in vitro after administration by injection....

  5. Influence of ionic complexation on release rate profiles from multiple water-in-oil-in-water (W/O/W) emulsions.

    Science.gov (United States)

    Bonnet, Marie; Cansell, Maud; Placin, Frédéric; David-Briand, Elisabeth; Anton, Marc; Leal-Calderon, Fernando

    2010-07-14

    Water-in-oil-in-water (W/O/W) double emulsions were prepared, and the kinetics of release of magnesium ions from the internal to the external water phase was followed. Different chelating agents (phosvitin and gluconate) were used to bind magnesium within the prospect of improving the ion retention in the internal aqueous droplets. Magnesium release was monitored for 1 month of storage, for each formulation, with and without chelation, at two storage temperatures (4 and 25 degrees C). Leakage occurred without film rupturing (coalescence) and was mainly due to entropically driven diffusion/permeation phenomena. The experimental results revealed a clear correlation between the effectiveness of chelating agents to delay the delivery and their binding capacity characterized by the equilibrium affinity constant. The kinetic data (percent released versus time curves) were interpreted within the framework of a kinetic model based on diffusion and taking into account magnesium chelation.

  6. Preparation of ionic-crosslinked chitosan-based gel beads and effect of reaction conditions on drug release behaviors.

    Science.gov (United States)

    Chen, Shilan; Liu, Mingzhu; Jin, Shuping; Wang, Bin

    2008-02-12

    Drug-loaded chitosan (CS) beads were prepared under simple and mild condition using trisodium citrate as ionic crosslinker. The beads were further coated with poly(methacrylic acid) (PMAA) by dipping the beads in PMAA aqueous solution. The surface and cross-section morphology of these beads were observed by scanning electron microscopy and the observation showed that the coating beads had core-shell structure. In vitro release of model drug from these beads obtained under different reaction conditions was investigated in buffer medium (pH 1.8). The results showed that the rapid drug release was restrained by PMAA coating and the optimum conditions for preparing CS-based drug-loaded beads were decided through the effect of reaction conditions on the drug release behaviors. In addition, the drug release mechanism of CS-based drug-loaded beads was analyzed by Peppa's potential equation. According to this study, the ionic-crosslinked CS beads coated by PMAA could serve as suitable candidate for drug site-specific carrier in stomach.

  7. A simple fluorescence based assay for quantification of human immunodeficiency virus particle release

    Directory of Open Access Journals (Sweden)

    Heuser Anke-Mareil

    2010-04-01

    Full Text Available Abstract Background The assembly and release of human immunodeficiency virus (HIV particles from infected cells represent attractive, but not yet exploited targets for antiretroviral therapy. The availability of simple methods to measure the efficiency of these replication steps in tissue culture would facilitate the identification of host factors essential for these processes as well as the screening for lead compounds acting as specific inhibitors of particle formation. We describe here the development of a rapid cell based assay for quantification of human immunodeficiency virus type 1 (HIV-1 particle assembly and/or release. Results Using a fluorescently labelled HIV-derivative, which carries an eYFP domain within the main viral structural protein Gag in the complete viral protein context, the release of virus like particles could be monitored by directly measuring the fluorescence intensity of the tissue culture supernatant. Intracellular Gag was quantitated in parallel by direct fluorescence analysis of cell lysates, allowing us to normalize for Gag expression efficiency. The assay was validated by comparison with p24 capsid ELISA measurements, a standard method for quantifying HIV-1 particles. Optimization of conditions allowed the robust detection of particle amounts corresponding to 50 ng p24/ml in medium by fluorescence spectroscopy. Further adaptation to a multi-well format rendered the assay suitable for medium or high throughput screening of siRNA libraries to identify host cell factors involved in late stages of HIV replication, as well as for random screening approaches to search for potential inhibitors of HIV-1 assembly or release. Conclusions The fast and simple fluorescence based quantification of HIV particle release yielded reproducible results which were comparable to the well established ELISA measurements, while in addition allowing the parallel determination of intracellular Gag expression. The protocols described here

  8. Bactericidal strontium-releasing injectable bone cements based on bioactive glasses.

    Science.gov (United States)

    Brauer, Delia S; Karpukhina, Natalia; Kedia, Gopal; Bhat, Aditya; Law, Robert V; Radecka, Izabela; Hill, Robert G

    2013-01-06

    Strontium-releasing injectable bone cements may have the potential to prevent implant-related infections through the bactericidal action of strontium, while enhancing bone formation in patients suffering from osteoporosis. A melt-derived bioactive glass (BG) series (SiO2–CaO–CaF2–MgO) with 0–50% of calcium substituted with strontium on a molar base were produced. By mixing glass powder, poly(acrylic acid) and water, cements were obtained which can be delivered by injection and set in situ, giving compressive strength of up to 35 MPa. Strontium release was dependent on BG composition with increasing strontium substitution resulting in higher concentrations in the medium. Bactericidal effects were tested on Staphylococcus aureus and Streptococcus faecalis; cell counts were reduced by up to three orders of magnitude over 6 days. Results show that bactericidal action can be increased through BG strontium substitution, allowing for the design of novel antimicrobial and bone enhancing cements for use in vertebroplasty or kyphoplasty for treating osteoporosis-related vertebral compression fractures.

  9. The Dynamics of Pheromone Gland Synthesis and Release: a Paradigm Shift for Understanding Sex Pheromone Quantity in Female Moths.

    Science.gov (United States)

    Foster, Stephen P; Anderson, Karin G; Casas, Jérôme

    2018-05-10

    Moths are exemplars of chemical communication, especially with regard to specificity and the minute amounts they use. Yet, little is known about how females manage synthesis and storage of pheromone to maintain release rates attractive to conspecific males and why such small amounts are used. We developed, for the first time, a quantitative model, based on an extensive empirical data set, describing the dynamical relationship among synthesis, storage (titer) and release of pheromone over time in a moth (Heliothis virescens). The model is compartmental, with one major state variable (titer), one time-varying (synthesis), and two constant (catabolism and release) rates. The model was a good fit, suggesting it accounted for the major processes. Overall, we found the relatively small amounts of pheromone stored and released were largely a function of high catabolism rather than a low rate of synthesis. A paradigm shift may be necessary to understand the low amounts released by female moths, away from the small quantities synthesized to the (relatively) large amounts catabolized. Future research on pheromone quantity should focus on structural and physicochemical processes that limit storage and release rate quantities. To our knowledge, this is the first time that pheromone gland function has been modeled for any animal.

  10. Analysis of fission gas release-to-birth ratio data from the AGR irradiations

    International Nuclear Information System (INIS)

    Einerson, Jeffrey J.; Pham, Binh T.; Scates, Dawn M.; Maki, John T.; Petti, David A.

    2016-01-01

    A series of advanced gas reactor (AGR) irradiation tests is being conducted in the advanced test reactor (ATR) at Idaho National Laboratory (INL) in support of development and qualification of tristructural isotropic (TRISO) fuel used in the High temperature gas-cooled reactor (HTGR). Each AGR test consists of multiple independent capsules containing fuel compacts placed in a graphite cylinder shrouded by a steel shell. These capsules are instrumented with thermocouples (TC) embedded in the graphite enabling temperature control. For AGR-1, the first US irradiation of modern TRISO fuel completed in 2009, there were no particle failures detected. For AGR-2, a few exposed kernels existed in the fuel compacts based upon quality control data. For the AGR-3/4 experiment, particle failures in all capsules were expected because of the use of designed-to-fail (DTF) fuel particles whose kernels are identical to the driver fuel kernels and whose coatings are designed to fail under irradiation. The release-rate-to-birth-rate ratio (R/B) for each of krypton and xenon isotopes is calculated from release rates measured by the germanium detectors used in the AGR fission product monitoring (FPM) system installed downstream from each irradiated capsule. Birth rates are calculated based on the fission power in the experiment and fission product generation models. Thus, this R/B is a measure of the ability of fuel particle coating layers and compact matrix to retain fission gas atoms preventing their release into the sweep gas flow. The major factors that govern gaseous diffusion and release processes are found to be fuel material diffusion coefficient, temperature, and isotopic decay constant. To compare the release behavior among the AGR capsules and historic experiments, the R/B per failed particle is used. HTGR designers use this parameter in their fission product behavior models. For the U.S. TRISO fuel, a regression analysis is performed to establish functional relationships

  11. Analysis of Fission Gas Release-to-Birth Ratio Data from the AGR Irradiations

    International Nuclear Information System (INIS)

    Einerson, Jeffrey J.; Pham, Binh T.; Scates, Dawn M.; Maki, John T.; Petti, David A.

    2014-01-01

    A series of Advanced Gas Reactor (AGR) irradiation tests is being conducted in the Advanced Test Reactor (ATR) at Idaho National Laboratory (INL) in support of development and qualification of tristructural isotropic (TRISO) fuel used in the High Temperature Gas-cooled Reactor (HTGR). Each AGR test consists of multiple independent capsules containing fuel compacts placed in a graphite cylinder shrouded by a steel shell. These capsules are instrumented with thermocouples (TC) embedded in the graphite enabling temperature control. For AGR-1, the first US irradiation of modern TRISO fuel completed in 2009, there were no particle failures detected. For AGR-2, a few exposed kernels existed in the fuel compacts based upon quality control data. For the AGR-3/4 experiment, particle failures in all capsules were expected because of the use of designed-to-fail (DTF) fuel particles whose kernels are identical to the driver fuel kernels and whose coatings are designed to fail under irradiation. The release-rate-to-birth-rate ratio (R/B) for each of krypton and xenon isotopes is calculated from release rates measured by the germanium detectors used in the AGR Fission Product Monitoring (FPM) System installed downstream from each irradiated capsule. Birth rates are calculated based on the fission power in the experiment and fission product generation models. Thus, this R/B is a measure of the ability of fuel particle coating layers and compact matrix to retain fission gas atoms preventing their release into the sweep gas flow. The major factors that govern gaseous diffusion and release processes are found to be fuel material diffusion coefficient, temperature, and isotopic decay constant. To compare the release behavior among the AGR capsules and historic experiments, the R/B per failed particle is used. HTGR designers use this parameter in their fission product behavior models. For the U.S. TRISO fuel, a regression analysis is performed to establish functional relationships

  12. Analysis of fission gas release-to-birth ratio data from the AGR irradiations

    Energy Technology Data Exchange (ETDEWEB)

    Einerson, Jeffrey J., E-mail: jeffrey.einerson@inl.gov; Pham, Binh T.; Scates, Dawn M.; Maki, John T.; Petti, David A.

    2016-09-15

    A series of advanced gas reactor (AGR) irradiation tests is being conducted in the advanced test reactor (ATR) at Idaho National Laboratory (INL) in support of development and qualification of tristructural isotropic (TRISO) fuel used in the High temperature gas-cooled reactor (HTGR). Each AGR test consists of multiple independent capsules containing fuel compacts placed in a graphite cylinder shrouded by a steel shell. These capsules are instrumented with thermocouples (TC) embedded in the graphite enabling temperature control. For AGR-1, the first US irradiation of modern TRISO fuel completed in 2009, there were no particle failures detected. For AGR-2, a few exposed kernels existed in the fuel compacts based upon quality control data. For the AGR-3/4 experiment, particle failures in all capsules were expected because of the use of designed-to-fail (DTF) fuel particles whose kernels are identical to the driver fuel kernels and whose coatings are designed to fail under irradiation. The release-rate-to-birth-rate ratio (R/B) for each of krypton and xenon isotopes is calculated from release rates measured by the germanium detectors used in the AGR fission product monitoring (FPM) system installed downstream from each irradiated capsule. Birth rates are calculated based on the fission power in the experiment and fission product generation models. Thus, this R/B is a measure of the ability of fuel particle coating layers and compact matrix to retain fission gas atoms preventing their release into the sweep gas flow. The major factors that govern gaseous diffusion and release processes are found to be fuel material diffusion coefficient, temperature, and isotopic decay constant. To compare the release behavior among the AGR capsules and historic experiments, the R/B per failed particle is used. HTGR designers use this parameter in their fission product behavior models. For the U.S. TRISO fuel, a regression analysis is performed to establish functional relationships

  13. Dam Breach Release of Non-Cohesive Sediments: Channel Response and Recovery Rates

    Science.gov (United States)

    Collins, M. J.; Boardman, G.; Banks, W.; Andrews, M.; Conlon, M.; Dillow, J. J. A.; Gellis, A.; Lowe, S.; McClain, S.; Miller, A. J.; Snyder, N. P.; Wilcock, P. R.

    2014-12-01

    Dam removals featuring unchecked releases of non-cohesive sediments are excellent opportunities to learn more about stream channel response to abrupt increases in bed material supply that can occur deliberately or by natural processes like landslides and volcanic eruptions. Understanding channel response to sediment pulses, including response rates, is essential because human uses of river channels and floodplains are impacted by these events as are aquatic habitats. We had the opportunity to study a dam removal site at the Simkins Dam in Maryland, USA, that shares many important geophysical attributes of another well-studied dam removal in the humid northeast United States [Merrimack Village Dam, New Hampshire; Pearson et al., 2011]. The watershed sizes are the same order of magnitude (102 km2), and at both sites relatively low head dams were removed (~ 3-4 m) and ~60,000 m3 of dominantly sand-sized sediments discharged to low-gradient reaches immediately downstream. Analyzing four years of repeat morphometry and bed sediment grain size surveys at the Simkins site on the Patapsco River, as well as continuous discharge and suspended sediment gaging data, we clearly document a two-phase response in the upstream reach as described by Pearson et al. [2011] for their New Hampshire site and noted at other dam removals [e.g., Major et al., 2012]. In the early phase, approximately 50% of the impounded sediment mass was eroded rapidly over a period of about three months when flows were very modest (Figure 1). After incision to base level and channel widening in the former impoundment, a second phase began when further erosion depended on floods large enough to access impounded sediments more distant from the newly-formed channel. We also found important differences in the upstream responses at the Maryland and New Hampshire sites that appear to be related to valley type (non-glaciated versus glaciated, respectively). Response variances immediately downstream between the

  14. Fabrication of Hyperbranched Block-Statistical Copolymer-Based Prodrug with Dual Sensitivities for Controlled Release.

    Science.gov (United States)

    Zheng, Luping; Wang, Yunfei; Zhang, Xianshuo; Ma, Liwei; Wang, Baoyan; Ji, Xiangling; Wei, Hua

    2018-01-17

    Dendrimer with hyperbranched structure and multivalent surface is regarded as one of the most promising candidates close to the ideal drug delivery systems, but the clinical translation and scale-up production of dendrimer has been hampered significantly by the synthetic difficulties. Therefore, there is considerable scope for the development of novel hyperbranched polymer that can not only address the drawbacks of dendrimer but maintain its advantages. The reversible addition-fragmentation chain transfer self-condensing vinyl polymerization (RAFT-SCVP) technique has enabled facile preparation of segmented hyperbranched polymer (SHP) by using chain transfer monomer (CTM)-based double-head agent during the past decade. Meanwhile, the design and development of block-statistical copolymers has been proven in our recent studies to be a simple yet effective way to address the extracellular stability vs intracellular high delivery efficacy dilemma. To integrate the advantages of both hyperbranched and block-statistical structures, we herein reported the fabrication of hyperbranched block-statistical copolymer-based prodrug with pH and reduction dual sensitivities using RAFT-SCVP and post-polymerization click coupling. The external homo oligo(ethylene glycol methyl ether methacrylate) (OEGMA) block provides sufficient extracellularly colloidal stability for the nanocarriers by steric hindrance, and the interior OEGMA units incorporated by the statistical copolymerization promote intracellular drug release by facilitating the permeation of GSH and H + for the cleavage of the reduction-responsive disulfide bond and pH-liable carbonate link as well as weakening the hydrophobic encapsulation of drug molecules. The delivery efficacy of the target hyperbranched block-statistical copolymer-based prodrug was evaluated in terms of in vitro drug release and cytotoxicity studies, which confirms both acidic pH and reduction-triggered drug release for inhibiting proliferation of He

  15. Release of DNA from polyelectrolyte multilayers fabricated using 'charge-shifting' cationic polymers: tunable temporal control and sequential, multi-agent release.

    Science.gov (United States)

    Sun, Bin; Lynn, David M

    2010-11-20

    We report an approach to the design of multilayered polyelectrolyte thin films (or 'polyelectrolyte multilayers', PEMs) that can be used to provide tunable control over the release of plasmid DNA (or multiple different DNA constructs) from film-coated surfaces. Our approach is based upon methods for the layer-by-layer assembly of DNA-containing thin films, and exploits the properties of a new class of cationic 'charge-shifting' polymers (amine functionalized polymers that undergo gradual changes in net charge upon side chain ester hydrolysis) to provide control over the rates at which these films erode and release DNA. We synthesized two 'charge-shifting' polymers (polymers 1 and 2) containing different side chain structures by ring-opening reactions of poly(2-alkenyl azlactone)s with two different tertiary amine functionalized alcohols (3-dimethylamino-1-propanol and 2-dimethylaminoethanol, respectively). Subsequent characterization revealed large changes in the rates of side chain ester hydrolysis for these two polymers; whereas the half-life for the hydrolysis of the esters in polymer 1 was ~200 days, the half-life for polymer 2 was ~6 days. We demonstrate that these large differences in side chain hydrolysis make possible the design of PEMs that erode and promote the surface-mediated release of DNA either rapidly (e.g., over ~3 days for films fabricated using polymer 2) or slowly (e.g., over ~1 month for films fabricated using polymer 1). We demonstrate further that it is possible to design films with release profiles that are intermediate to these two extremes by fabricating films using solutions containing different mixtures of these two polymers. This approach can thus expand the usefulness of these two polymers and achieve a broader range of DNA release profiles without the need to synthesize polymers with new structures or properties. Finally, we demonstrate that polymers 1 and 2 can be used to fabricate multilayered films with hierarchical structures that

  16. Bactericidal strontium-releasing injectable bone cements based on bioactive glasses

    OpenAIRE

    Brauer, Delia S.; Karpukhina, Natalia; Kedia, Gopal; Bhat, Aditya; Law, Robert V.; Radecka, Izabela; Hill, Robert G.

    2013-01-01

    Strontium-releasing injectable bone cements may have the potential to prevent implant-related infections through the bactericidal action of strontium, while enhancing bone formation in patients suffering from osteoporosis. A melt-derived bioactive glass (BG) series (SiO2–CaO–CaF2–MgO) with 0–50% of calcium substituted with strontium on a molar base were produced. By mixing glass powder, poly(acrylic acid) and water, cements were obtained which can be delivered by injection and set in situ, gi...

  17. Forms and rates of release of Cs-137 in 2 peat soils

    International Nuclear Information System (INIS)

    Livens, F.R.; Howe, M.T.; Hemingway, J.D.; Goulding, K.W.T.; Howard, B.J.; IACR Rothamsted, Harpenden; Liverpool Univ.; Institute of Terrestrial Ecology, Grange-on-Sands

    1996-01-01

    Cation exchange resin saturated with H+ and Ca2+ was used to extract Cs-137 from peat soil at two sites in Britain affected by Cs-137 deposition following the Chernobyl accident. The technique identified three classes of Cs-137, similar to those observed for K+ in soils: ''Fast'', ''Intermediate'' and ''Slow''. These classes are probably related to the selectivity for Cs-137 of the cation exchange sites on the organic matter and the clay minerals, and to the structure of the soil. With one exception, most Cs-137 was in the ''Slow'' form and was only very slowly released to the resins, if at all. However, there was enough Cs-137 in the ''Fast'' and ''Intermediate'' forms to contaminate pasture and thus grazing animals for some years. Based on the resin technique, it is estimated that contamination will persist for several decades in uplands contaminated at these activity concentrations. (Author)

  18. The Fukushima releases: an inverse modelling approach to assess the source term by using gamma dose rate observations

    Science.gov (United States)

    Saunier, Olivier; Mathieu, Anne; Didier, Damien; Tombette, Marilyne; Quélo, Denis; Winiarek, Victor; Bocquet, Marc

    2013-04-01

    The Chernobyl nuclear accident and more recently the Fukushima accident highlighted that the largest source of error on consequences assessment is the source term estimation including the time evolution of the release rate and its distribution between radioisotopes. Inverse modelling methods have proved to be efficient to assess the source term due to accidental situation (Gudiksen, 1989, Krysta and Bocquet, 2007, Stohl et al 2011, Winiarek et al 2012). These methods combine environmental measurements and atmospheric dispersion models. They have been recently applied to the Fukushima accident. Most existing approaches are designed to use air sampling measurements (Winiarek et al, 2012) and some of them use also deposition measurements (Stohl et al, 2012, Winiarek et al, 2013). During the Fukushima accident, such measurements are far less numerous and not as well distributed within Japan than the dose rate measurements. To efficiently document the evolution of the contamination, gamma dose rate measurements were numerous, well distributed within Japan and they offered a high temporal frequency. However, dose rate data are not as easy to use as air sampling measurements and until now they were not used in inverse modelling approach. Indeed, dose rate data results from all the gamma emitters present in the ground and in the atmosphere in the vicinity of the receptor. They do not allow one to determine the isotopic composition or to distinguish the plume contribution from wet deposition. The presented approach proposes a way to use dose rate measurement in inverse modeling approach without the need of a-priori information on emissions. The method proved to be efficient and reliable when applied on the Fukushima accident. The emissions for the 8 main isotopes Xe-133, Cs-134, Cs-136, Cs-137, Ba-137m, I-131, I-132 and Te-132 have been assessed. The Daiichi power plant events (such as ventings, explosions…) known to have caused atmospheric releases are well identified in

  19. The smart aerial release machine, a universal system for applying the sterile insect technique: Manuscript Draft

    International Nuclear Information System (INIS)

    Mubarqui, Leal Ruben; Perez, Rene Cano; Klad, Roberto Angulo; Lopez, Jose L. Zavale; Parker, Andrew; Seck, Momar Talla; Sall, Baba; Bouyer, Jeremy

    2014-01-01

    Beyond insecticides, alternative methods to control insect pests for agriculture and vectors of diseases are needed. Management strategies involving the mass-release of living control agents have been developed, including genetic control with sterile insects and biological control with parasitoids, for which aerial release of insects is often required. Aerial release in genetic control programmes often involves the use of chilled sterile insects, which can improve dispersal, survival and competitiveness of sterile males. Currently available means of aerially releasing chilled fruit flies are however insufficiently precise to ensure homogeneous distribution at low release rates and no device is available for tsetse. Here we present the smart aerial release machine, a new design by the Mubarqui Company, based on the use of vibrating conveyors. The machine is controlled through Bluetooth by a tablet with Android Operating System including a completely automatic guidance and navigation system (MaxNav software). The tablet is also connected to an online relational database facilitating the preparation of flight schedules and automatic storage of flight reports. The new machine was compared with a conveyor release machine in Mexico using two fruit flies species (Anastrepha ludens and Ceratitis capitata) and we obtained better dispersal homogeneity (% of positive traps, p < 0.001) for both species and better recapture rates for Anastrepha ludens (p < 0.001), especially at low release densities (<1500 per ha). We also demonstrated that the machine can replace paper boxes for aerial release of tsetse in Senegal.This technology limits damages to insects and allows a large range of release rates from 10 flies/km"2 for tsetse flies up to 600 000 flies/km"2 for fruit flies. The potential of this machine to release other species like mosquitoes is discussed. Plans and operating of the machine are provided to allow its use worldwide.

  20. Photoimages and the release characteristics of lipophilic matrix tablets containing highly water-soluble potassium citrate with high drug loadings.

    Science.gov (United States)

    Cao, Qing-Ri; Kim, Tae-Wan; Lee, Beom-Jin

    2007-07-18

    Two types of the carnauba wax-based lipophilic matrix tablet using spray-dried granules (SDT) or directly compressible powdered mixtures (DCT) were prepared for sustained release. The model drug was a highly water-soluble potassium citrate and loaded about 74% of the total tablet weight. The SDT slowly eroded and disintegrated during the release study without showing sustained release when the hydrophilic excipients were added. In contrast, the DCT was more efficient for sustained release. The release rate decreased with increasing carnauba wax concentration. In particular, the sustained release rate was markedly pronounced when the lipophilic stearyl alcohol and stearic acid were combined with the carnauba wax. The surface of the intact DCT appeared to be smooth and rusty. The DCT rose to the surface from the bottom of the vessel during the release test, and numerous pores and cracks with no signs of disintegration were also observed after the release test. The release profile was dependent on the formulation composition and preparation method of the matrix tablet. Diffusion-controlled leaching through the channels of the pores and cracks of the lipophilic matrix tablet (DCT) is a key to the sustained release.

  1. Validation of kinetic modeling of progesterone release from polymeric membranes

    Directory of Open Access Journals (Sweden)

    Analia Irma Romero

    2018-01-01

    Full Text Available Mathematical modeling in drug release systems is fundamental in development and optimization of these systems, since it allows to predict drug release rates and to elucidate the physical transport mechanisms involved. In this paper we validate a novel mathematical model that describes progesterone (Prg controlled release from poly-3-hydroxybutyric acid (PHB membranes. A statistical analysis was conducted to compare the fitting of our model with six different models and the Akaike information criterion (AIC was used to find the equation with best-fit. A simple relation between mass and drug released rate was found, which allows predicting the effect of Prg loads on the release behavior. Our proposed model was the one with minimum AIC value, and therefore it was the one that statistically fitted better the experimental data obtained for all the Prg loads tested. Furthermore, the initial release rate was calculated and therefore, the interface mass transfer coefficient estimated and the equilibrium distribution constant of Prg between the PHB and the release medium was also determined. The results lead us to conclude that our proposed model is the one which best fits the experimental data and can be successfully used to describe Prg drug release in PHB membranes.

  2. Controlled release of tocopherols from polymer blend films

    Science.gov (United States)

    Obinata, Noe

    Controlled release packaging has great potential to increase storage stability of foods by releasing active compounds into foods continuously over time. However, a major limitation in development of this technology is the inability to control the release and provide rates useful for long term storage of foods. Better understanding of the factors affecting active compound release is needed to overcome this limitation. The objective of this research was to investigate the relationship between polymer composition, polymer processing method, polymer morphology, and release properties of active compounds, and to provide proof of principle that compound release is controlled by film morphology. A natural antioxidant, tocopherol was used as a model active compound because it is natural, effective, heat stable, and soluble in most packaging polymers. Polymer blend films were produced from combination of linear low density polyethylene (LLDPE) and high density polyethylene (HDPE), polypropylene (PP), or polystyrene (PS) with 3000 ppm mixed tocopherols using conventional blending method and innovative blending method, smart blending with a novel mixer using chaotic advection. Film morphologies were visualized with scanning electron microscopy (SEM). Release of tocopherols into 95% ethanol as a food simulant was measured by UV/Visible spectrophotometry or HPLC, and diffusivity of tocopherols in the polymers was estimated from this data. Polymer composition (blend proportions) and processing methods have major effects on film morphology. Four different types of morphologies, dispersed, co-continuous, fiber, and multilayer structures were developed by either conventional extrusion or smart blending. With smart blending of fixed polymer compositions, different morphologies were progressively developed with fixed polymer composition as the number of rod rotations increased, providing a way to separate effects of polymer composition and morphology. The different morphologies

  3. A simple operational gas release and swelling model. Pt. 1

    International Nuclear Information System (INIS)

    Wood, M.H.; Matthews, J.R.

    1980-01-01

    A new and simple model of fission gas release and swelling has been developed for oxide nuclear fuel under operational conditions. The model, which is to be incorporated into a fuel element behaviour code, is physically based and applicable to fuel at both thermal and fast reactor ratings. In this paper we present that part of the model describing the behaviour of intragranular gas: a future paper will detail the treatment of the grain boundary gas. The results of model calculations are compared with recent experimental observations of intragranular bubble concentrations and sizes, and gas release from fuel irradiated under isothermal conditions. Good agreement is found between experiment and theory. (orig.)

  4. Aqueous studies of hydrogen sulfide releases from a heavy water extraction facility

    International Nuclear Information System (INIS)

    Kiser, D.L.

    1979-03-01

    Upsets in the operation of the wastewater strippers in the 400 Area of the Savannah River Plant have released hydrogen sulfide in quantities as large as 1800 kg to the effluent stream. Fish kills in the swamp area of Beaver Dam Creek have occurred following the large releases. A literature survey revealed volatilization and oxidation as the major loss mechanisms of H 2 S. Laboratory investigations supported the literature survey. The computer code for pollutant transport in a stream, LODIPS, has an option to account for sink-source effects in a stream. Volatilization and oxidation rate constants were developed for the sink option from two H 2 S releases (18 kg and 118 kg) and results were predicted with LODIPS. Based on the predicted concentration-time profiles for various hypothetical cases, releases as small as 568 kg if discharged over a 30-minute period or releases as large as 1818 kg if discharged over a 360-minute period or less are lethal to swamp fish

  5. Microfluidic Device for Controllable Chemical Release via Field-Actuated Membrane Incorporating Nanoparticles

    Directory of Open Access Journals (Sweden)

    Xiang Wang

    2013-01-01

    Full Text Available We report a robust magnetic-membrane-based microfluidic platform for controllable chemical release. The magnetic membrane was prepared by mixing polydimethylsiloxane (PDMS and carbonyl-iron nanoparticles together to obtain a flexible thin film. With combined, simultaneous regulation of magnetic stimulus and mechanical pumping, the desired chemical release rate can easily be realized. For example, the dose release experimental data was well fitted by a mathematical sigmoidal model, exhibiting a typical dose-response relationship, which shows promise in providing significant guidance for on-demand drug delivery. To test the platform’s feasibility, our microfluidic device was employed in an experiment involving Escherichia coli culture under controlled antibiotic ciprofloxacin exposure, and the expected outcomes were successfully obtained. Our experimental results indicate that such a microfluidic device, with high accuracy and easy manipulation properties, can legitimately be characterized as active chemical release system.

  6. Microfluidic Device for Controllable Chemical Release via Field-Actuated Membrane Incorporating Nanoparticles

    KAUST Repository

    Wang, Xiang; Li, Shunbo; Wang, Limu; Yi, Xin; Hui, Yu Sanna; Qin, Jianhua; Wen, Weijia

    2013-01-01

    We report a robust magnetic-membrane-based microfluidic platform for controllable chemical release. The magnetic membrane was prepared by mixing polydimethylsiloxane (PDMS) and carbonyl-iron nanoparticles together to obtain a flexible thin film. With combined, simultaneous regulation of magnetic stimulus and mechanical pumping, the desired chemical release rate can easily be realized. For example, the dose release experimental data was well fitted by a mathematical sigmoidal model, exhibiting a typical dose-response relationship, which shows promise in providing significant guidance for on-demand drug delivery. To test the platform’s feasibility, our microfluidic device was employed in an experiment involving Escherichia coli culture under controlled antibiotic ciprofloxacin exposure, and the expected outcomes were successfully obtained. Our experimental results indicate that such a microfluidic device, with high accuracy and easy manipulation properties, can legitimately be characterized as active chemical release system.

  7. Microfluidic Device for Controllable Chemical Release via Field-Actuated Membrane Incorporating Nanoparticles

    KAUST Repository

    Wang, Xiang

    2013-01-01

    We report a robust magnetic-membrane-based microfluidic platform for controllable chemical release. The magnetic membrane was prepared by mixing polydimethylsiloxane (PDMS) and carbonyl-iron nanoparticles together to obtain a flexible thin film. With combined, simultaneous regulation of magnetic stimulus and mechanical pumping, the desired chemical release rate can easily be realized. For example, the dose release experimental data was well fitted by a mathematical sigmoidal model, exhibiting a typical dose-response relationship, which shows promise in providing significant guidance for on-demand drug delivery. To test the platform’s feasibility, our microfluidic device was employed in an experiment involving Escherichia coli culture under controlled antibiotic ciprofloxacin exposure, and the expected outcomes were successfully obtained. Our experimental results indicate that such a microfluidic device, with high accuracy and easy manipulation properties, can legitimately be characterized as active chemical release system.

  8. Multi-kinetics and site-specific release of gabapentin and flurbiprofen from oral fixed-dose combination: in vitro release and in vivo food effect.

    Science.gov (United States)

    Sonvico, Fabio; Conti, Chiara; Colombo, Gaia; Buttini, Francesca; Colombo, Paolo; Bettini, Ruggero; Barchielli, Marco; Leoni, Barbara; Loprete, Luca; Rossi, Alessandra

    2017-09-28

    In this work, a fixed-dose combination of gabapentin and flurbiprofen formulated as multilayer tablets has been designed, developed and studied in vitro and in vivo. The aim was to construct a single dosage form of the two drugs, able to perform a therapeutic program involving three release kinetics and two delivery sites, i.e., immediate release of gabapentin, intra-gastric prolonged release of gabapentin and intestinal (delayed) release of flurbiprofen. An oblong three-layer tablet was manufactured having as top layer a floating hydrophilic polymeric matrix for gastric release of gabapentin, as middle layer a disintegrating formulation for immediate release of a gabapentin loading dose and as bottom layer, an uncoated hydrophilic polymeric matrix, swellable but insoluble in gastric fluids, for delayed and prolonged release of flurbiprofen in intestinal environment. The formulations were studied in vitro and in vivo in healthy volunteers. The in vitro release rate assessment confirmed the programmed delivery design. A significant higher bioavailability of gabapentin administered 30min after meal, compared to fasting conditions or to dose administration 10min before meal, argued in favor of the gastro-retention of gabapentin prolonged release layer. The two drugs were delivered at different anatomical sites, since the food presence prolonged the gastric absorption of gabapentin from the floating layer and delayed the flurbiprofen absorption. The attainment of a successful delayed release of flurbiprofen was realized by a matrix based on a polymers' combination. The combined use of three hydrophilic polymers with different pH sensitivity provided the dosage form layer containing flurbiprofen with gastro-resistant characteristics without the use of film coating. Copyright © 2017 Elsevier B.V. All rights reserved.

  9. TOXRISK, Toxic Gas Release Accident Analysis

    International Nuclear Information System (INIS)

    Bennett, D.E.; Chanin, D.I.; Shiver, A.W.

    1993-01-01

    1 - Description of program or function: TOXRISK is an interactive program developed to aid in the evaluation of nuclear power plant control room habitability in the event of a nearby toxic material release. The program uses a model which is consistent with the approach described in the NRC Regulatory Guide 1.78. Release of the gas is treated as an initial puff followed by a continuous plume. The relative proportions of these as well as the plume release rate are supplied by the user. Transport of the gas is modeled as a Gaussian distribution and occurs through the action of a constant velocity, constant direction wind. Great flexibility is afforded the user in specifying the release description, meteorological conditions, relative geometry of the accident and plant, and the plant ventilation system characteristics. Two types of simulation can be performed: multiple case (parametric) studies and probabilistic analyses. Upon execution, TOXRISK presents a menu, and the user chooses between the Data Base Manager, the Multiple Case program, and the Probabilistic Study Program. The Data Base Manager provides a convenient means of storing, retrieving, and modifying blocks of data required by the analysis programs. The Multiple Case program calculates resultant gas concentrations inside the control room and presents a summary of information that describes the event for each set of conditions given. Optimally, a time history profile of inside and outside concentrations can also be produced. The Probabilistic Study program provides a means for estimating the annual probability of operator incapacitation due to toxic gas accidents on surrounding transportation routes and storage sites. 2 - Method of solution: Dispersion or diffusion of the gas during transport is described by modified Pasquill-Gifford dispersion coefficients

  10. Guidance for Evaluating the Safety of Experimental Releases of Mosquitoes, Emphasizing Mark-Release-Recapture Techniques.

    Science.gov (United States)

    Benedict, Mark Q; Charlwood, J Derek; Harrington, Laura C; Lounibos, L Philip; Reisen, William K; Tabachnick, Walter J

    2018-01-01

    Experimental releases of mosquitoes are performed to understand characteristics of populations related to the biology, ability to transmit pathogens, and ultimately their control. In this article, we discuss considerations related to the safety of experimental releases of living mosquitoes, applying principles of good practice in vector biology that protect human health and comfort. We describe specific factors of experimental releases of mosquitoes that we believe are critical to inform institutional biosafety committees and similar review boards to which proposals to conduct mosquito release experiments have been submitted. In this study, "experimental releases" means those that do not significantly increase vector capacity or nuisance biting relative to the unperturbed natural baseline. This document specifically does not address releases of mosquitoes for ongoing control programs or trials of new control methods for which broader assessments of risk are required. It also does not address releases of transgenic or exotic (non-native) mosquito species, both of which require particular regulatory approval. Experimental releases may include females and males and evaluation must consider their effects based on the number released, their genotype and phenotype, the environment into which they are released, and postrelease collection activities. We consider whether increases of disease transmission and nuisance biting might result from proposed experimental releases against the backdrop of natural population size variation. We recommend that experimental releases be conducted in a manner that can be reasonably argued to have insignificant negative effects. Reviewers of proposals for experimental releases should expect applicants to provide such an argument based on evidence from similar studies and their planned activities. This document provides guidance for creating and evaluating such proposals.

  11. Risk based In Vitro Performance Assessment of Extended Release Abuse Deterrent Formulations

    Science.gov (United States)

    Xu, Xiaoming; Gupta, Abhay; Al-Ghabeish, Manar; Calderon, Silvia N.; Khan, Mansoor A.

    2016-01-01

    High strength extended release opioid products, which are indispensable tools in the management of pain, are associated with serious risks of unintentional and potentially fatal overdose, as well as of misuse and abuse that might lead to addiction. The issue of drug abuse becomes increasingly prominent when the dosage forms can be readily manipulated to release a high amount of opioid or to extract the drug in certain products or solvents. One approach to deter opioid drug abuse is by providing novel abuse deterrent formulations (ADF), with properties that may be viewed as barriers to abuse of the product. However, unlike regular extended release formulations, assessment of ADF technologies are challenging, in part due to the great variety of formulation designs available to achieve deterrence of abuse by oral, parenteral, nasal and respiratory routes. With limited prior history or literature information, and lack of compendial standards, evaluation and regulatory approval of these novel drug products become increasingly difficult. The present article describes a risk-based standardized in-vitro approach that can be utilized in general evaluation of abuse deterrent features for all ADF products. PMID:26784976

  12. On-Line Fission Gas Release Monitoring System in the High Flux Reactor Petten

    International Nuclear Information System (INIS)

    Laurie, M.; Fuetterer, M. A.; Appelman, K.H.; Lapetite, J.-M.; Marmier, A.; Knol, S.; Best, J.

    2013-06-01

    For HTR fuel irradiation tests in the HFR Petten a specific installation was designed and installed dubbed the 'Sweep Loop Facility' (SLF). The SLF is tasked with three functions, namely temperature control by gas mixture technique, surveillance of safety parameters (temperature, pressure, radioactivity etc.) and analysis of fission gas release for three individual capsules in two separate experimental rigs. The SLF enables continuous and independent surveillance of all gas circuits. The release of volatile fission products (FP) from the in-pile experiments is monitored by continuous gas purging. The fractional release of these FP, defined as the ratio between release rate of a gaseous fission isotope (measured) to its instantaneous birth rate (calculated), is a licensing-relevant test for HTR fuel. The developed gamma spectrometry station allows for higher measurement frequencies, thus enabling follow-up of rapid and massive release transients. The designed stand-alone system was tested and fully used through the final irradiation period of the HFR-EU1 experiment which was terminated on 18 February 2010. Its robustness allowed the set up to be used as extra safety instrumentation. This paper describes the gas activity measurement technique based on HPGe gamma spectrometry and illustrates how qualitative and quantitative analysis of volatile FP can be performed on-line. (authors)

  13. On the rate determining step in fission gas release from high burn-up water reactor fuel during power transients

    International Nuclear Information System (INIS)

    Walker, C.T.; Mogensen, M.

    1987-01-01

    The radial distribution of grain boundary gas in a PWR and a BWR fuel is reported. The measurements were made using a new approach involving X-ray fluorescence analysis and electron probe microanalysis. In both fuels the concentration of grain boundary gas was much higher than hitherto suspected. The gas was mainly contained in the bubble/pore structure. The factors that determined the fraction of gas released from the grains and the level of gas retention on the grain boundaries are identified and discussed. The variables involved are the local fuel stoichiometry, the amount of open porosity, the magnitude of the local compressive hydrostatic stress and the interaction of metallic precipitates with gas bubbles on the grain faces. It is concluded that under transient conditions the interlinkage of gas bubbles on the grain faces and the subsequent formation of grain edge tunnels is the rate determining step for gas release; at least when high burn-up fuel is involved. (orig.)

  14. Emulsion-based encapsulation and delivery of nanoparticles for the controlled release of alkalinity within the subsurface environment

    Science.gov (United States)

    Ramsburg, C. A.; Muller, K.; Gill, J.

    2012-12-01

    Many current approaches to managing groundwater contamination rely on further advances in amendment delivery in order to initiate and sustain contaminant degradation or immobilization. In fact, limited or ineffective delivery is often cited when treatment objectives are not attained. Emulsions, specifically oil-in-water emulsions, have demonstrated potential to aid delivery of remediation amendments. Emulsions also afford opportunities to control the release of active ingredients encapsulated within the droplets. Our research is currently focused on the controlled release of nanoparticle-based buffering agents using oil-in-water emulsions. This interest is motivated by the fact that chemical and biological processes employed for the remediation and stewardship of contaminated sites often necessitate control of pH during treatment and, in some cases, long thereafter. Alkalinity-release nanoparticles (e.g., CaCO3, MgO) were suspended within soybean oil and subsequently encapsulated by through the creation of oil-in-water emulsions. These oil-in-water emulsions are designed to have physical properties which are favorable for subsurface delivery (nominal properties: 1 g/mL density; 10 cP viscosity; and 1.5 μm droplet diameter). Buffer capacity titrations suggest that MgO particles are moderately more accessible within the oil phase and nearly twice as effective (on a per mass basis) at releasing alkalinity (as compared to the CaCO3 particles). Results from experiments designed to assess the release kinetics suggest that a linear driving force model is capable of describing the release process and mass transfer coefficients are constant through the reactive life of the emulsion. The release kinetics in emulsions containing MgO particles were found to be three orders of magnitude faster than those quantified for emulsions containing CaCO3. The slower release kinetics of the emulsions containing CaCO3 particles may prove beneficial when considering pH control at sites

  15. Protein Nanocage-Based Photo-Controlled Nitric Oxide Releasing Platform.

    Science.gov (United States)

    Li, Xiao; Zhang, Yajie; Sun, Jian; Chen, Weijian; Wang, Xuewei; Shao, Fenli; Zhu, Yuyu; Feng, Fude; Sun, Yang

    2017-06-14

    A photoactive NO releasing system was constructed by incorporation of NO-bound Fe-S clusters into horse spleen apoferritin cavities with high loading efficacy. The composites retained intact core-shell structure and indicated advantages such as enhanced stability, reduced cytotoxicity, efficient cellular uptake, and photocontrolled NO releasing property.

  16. Analysis and evaluation of the ASTEC model basis on fission product and aerosol release phenomena from melts. 3. Technical report

    International Nuclear Information System (INIS)

    Agethen, K.; Koch, M.K.

    2016-04-01

    The present report is the 3 rd Technical Report within the research project ''ASMO'' founded by the German Federal Ministry for Economic Affairs and Energy (BMWi 1501433) and projected at the Chair of Energy Systems and Energy Economics (LEE) within the workgroup Reactor Simulation and Safety at the Ruhr-Universitaet Bochum (RUB). The focus in this report is set on the release of fission products and the contribution to the source term, which is formed in the late phase after failure of the reactor pressure vessel during MCCI. By comparing the RUB simulation results including the fission product release rates with further simulations of GRS and VEIKI it can be indicated that the simulations have a high sensitivity in respect to the melting point temperature. It can be noted that the release rates are underestimated for most fission product species with the current model. Especially semi-volatile fission products and the lanthanum release is underestimated by several orders of magnitude. Based on the ACE experiment L2, advanced considerations are presented concerning the melt temperature, the gas temperature, the segregation and a varied melt configuration. Furthermore, the influence of the gas velocity is investigated. This variation of the gas velocity causes an underestimation of the release rates compared to the RUB base calculation. A model extension to oxidic species for lanthanum and ruthenium shows a significant improvement of the simulation results. In addition, the MEDICIS module has been enhanced to document the currently existing species, are displayed in a *.ist-file. This expansion shows inconsistencies between the melt composition and the fission product composition. Based on these results, there are still some difficulties regarding the release of fission products in the MEDICIS module and the interaction with the material data base (MOB) which needs further investigation.

  17. In Vitro Investigation of Self-Assembled Nanoparticles Based on Hyaluronic Acid-Deoxycholic Acid Conjugates for Controlled Release Doxorubicin: Effect of Degree of Substitution of Deoxycholic Acid

    Directory of Open Access Journals (Sweden)

    Wen-Hao Wei

    2015-03-01

    Full Text Available Self-assembled nanoparticles based on a hyaluronic acid-deoxycholic acid (HD chemical conjugate with different degree of substitution (DS of deoxycholic acid (DOCA were prepared. The degree of substitution (DS was determined by titration method. The nanoparticles were loaded with doxorubicin (DOX as the model drug. The human cervical cancer (HeLa cell line was utilized for in vitro studies and cell cytotoxicity of DOX incorporated in the HD nanoparticles was accessed by the 3-(4,5-dimethylthiazol-2-yl-2,5-diphenyltetrazolium bromide (MTT assay. In addition, cellular uptake of fluorescently labeled nanoparticles was also investigated. An increase in the degree of deoxycholic acid substitution reduced the size of the nanoparticles and also enhanced their drug encapsulation efficiency (EE, which increased with the increase of DS. A higher degree of deoxycholic acid substitution also lead to a lower release rate and an initial burst release of doxorubicin from the nanoparticles. In summary, the degree of substitution allows the modulation of the particle size, drug encapsulation efficiency, drug release rate, and cell uptake efficiency of the nanoparticles. The herein developed hyaluronic acid-deoxycholic acid conjugates are a good candidate for drug delivery and could potentiate therapeutic formulations for doxorubicin–mediated cancer therapy.

  18. Characterization of a poly(ether urethane)-based controlled release membrane system for delivery of ketoprofen

    International Nuclear Information System (INIS)

    Macocinschi, Doina; Filip, Daniela; Vlad, Stelian; Oprea, Ana Maria; Gafitanu, Carmen Anatolia

    2012-01-01

    Highlights: ► Ketoprofen incorporation in poly(ether urethane) microporous membrane. ► Moisture sorption properties of as-cast membrane. ► Drug release mechanisms in function of pH and composition of membranes. - Abstract: A poly(ether urethane) based on polytetrahydrofuran containing hydroxypropyl cellulose for biomedical applications was tested for its biocompatibility. Ketoprofen was incorporated (3% and 6%) in the polyurethane matrix as an anti-inflammatory drug. Kinetic and drug release mechanisms were studied. The pore size and pore size distribution of the polyurethane membranes were investigated by scanning electron microscopy. Surface tension characteristics as well as moisture sorption properties such as diffusion coefficients and equilibrium moisture contents of the membrane material were studied. It was found that kinetics and release mechanisms are in function of medium pH, composition of polymer–drug system, pore morphology and pore size distribution. Prolonged nature of release of ketoprofen is assured by low amount of drug in polyurethane membrane and physiological pH.

  19. Pest persistence and eradication conditions in a deterministic model for sterile insect release.

    Science.gov (United States)

    Gordillo, Luis F

    2015-01-01

    The release of sterile insects is an environment friendly pest control method used in integrated pest management programmes. Difference or differential equations based on Knipling's model often provide satisfactory qualitative descriptions of pest populations subject to sterile release at relatively high densities with large mating encounter rates, but fail otherwise. In this paper, I derive and explore numerically deterministic population models that include sterile release together with scarce mating encounters in the particular case of species with long lifespan and multiple matings. The differential equations account separately the effects of mating failure due to sterile male release and the frequency of mating encounters. When insects spatial spread is incorporated through diffusion terms, computations reveal the possibility of steady pest persistence in finite size patches. In the presence of density dependence regulation, it is observed that sterile release might contribute to induce sudden suppression of the pest population.

  20. Particle emission rates during electrostatic spray deposition of TiO2 nanoparticle-based photoactive coating.

    Science.gov (United States)

    Koivisto, Antti J; Jensen, Alexander C Ø; Kling, Kirsten I; Kling, Jens; Budtz, Hans Christian; Koponen, Ismo K; Tuinman, Ilse; Hussein, Tareq; Jensen, Keld A; Nørgaard, Asger; Levin, Marcus

    2018-01-05

    Here, we studied the particle release rate during Electrostatic spray deposition of anatase-(TiO 2 )-based photoactive coating onto tiles and wallpaper using a commercially available electrostatic spray device. Spraying was performed in a 20.3m 3 test chamber while measuring concentrations of 5.6nm to 31μm-size particles and volatile organic compounds (VOC), as well as particle deposition onto room surfaces and on the spray gun user hand. The particle emission and deposition rates were quantified using aerosol mass balance modelling. The geometric mean particle number emission rate was 1.9×10 10 s -1 and the mean mass emission rate was 381μgs -1 . The respirable mass emission-rate was 65% lower than observed for the entire measured size-range. The mass emission rates were linearly scalable (±ca. 20%) to the process duration. The particle deposition rates were up to 15h -1 for deposited particles consisted of mainly TiO 2 , TiO 2 mixed with Cl and/or Ag, TiO 2 particles coated with carbon, and Ag particles with size ranging from 60nm to ca. 5μm. As expected, no significant VOC emissions were observed as a result of spraying. Finally, we provide recommendations for exposure model parameterization. Copyright © 2017 The Author(s). Published by Elsevier B.V. All rights reserved.

  1. A Web Based Framework for Pre-release Testing of Mobile Applications

    Directory of Open Access Journals (Sweden)

    Hamdy Abeer

    2016-01-01

    Full Text Available Mobile applications are becoming an integral part of daily life and of business’s marketing plan. They are helpful in promoting for the business, attracting and retaining customers. Software testing is vital to ensure the delivery of high quality mobile applications that could be accessed across different platforms and meet business and technical requirements. This paper proposes a web based tool, namely Pons, for the distribution of pre-release mobile applications for the purpose of manual testing. Pons facilities building, running, and manually testing Android applications directly in the browser. It gets the developers and end users engaged in testing the applications in one place, alleviates the tester’s burden of installing and maintaining testing environments, and provides a platform for developers to rapidly iterate on the software and integrate changes over time. Thus, it speeds up the pre-release testing process, reduces its cost and increases customer satisfaction.

  2. Crustacean zooplankton release copious amounts of dissolved organic matter as taurine in the ocean.

    Science.gov (United States)

    Clifford, Elisabeth L; Hansell, Dennis A; Varela, Marta M; Nieto-Cid, Mar; Herndl, Gerhard J; Sintes, Eva

    2017-11-01

    Taurine (Tau), an amino acid-like compound, is present in almost all marine metazoans including crustacean zooplankton. It plays an important physiological role in these organisms and is released into the ambient water throughout their life cycle. However, limited information is available on the release rates by marine organisms, the concentrations and turnover of Tau in the ocean. We determined dissolved free Tau concentrations throughout the water column and its release by abundant crustacean mesozooplankton at two open ocean sites (Gulf of Alaska and North Atlantic). At both locations, the concentrations of dissolved free Tau were in the low nM range (up to 15.7 nM) in epipelagic waters, declining sharply in the mesopelagic to about 0.2 nM and remaining fairly stable throughout the bathypelagic waters. Pacific amphipod-copepod assemblages exhibited lower dissolved free Tau release rates per unit biomass (0.8 ± 0.4 μmol g -1 C-biomass h -1 ) than Atlantic copepods (ranging between 1.3 ± 0.4 μmol g -1 C-biomass h -1 and 9.5 ± 2.1 μmol g -1 C-biomass h -1 ), in agreement with the well-documented inverse relationship between biomass-normalized excretion rates and body size. Our results indicate that crustacean zooplankton might contribute significantly to the dissolved organic matter flux in marine ecosystems via dissolved free Tau release. Based on the release rates and assuming steady state dissolved free Tau concentrations, turnover times of dissolved free Tau range from 0.05 d to 2.3 d in the upper water column and are therefore similar to those of dissolved free amino acids. This rapid turnover indicates that dissolved free Tau is efficiently consumed in oceanic waters, most likely by heterotrophic bacteria.

  3. Nanocomposites for controlled release of nitrogen fertilizer

    International Nuclear Information System (INIS)

    Silva, Viviane J.M. da; Visconte, Leila L.Y.; Nascimento, Regina Sandra V.

    2009-01-01

    The study aimed at the development of nano structured materials capable of reducing the rate of release of nitrogen in the soil from an agricultural nitrogen fertilizer. Four different systems of polymer composites were prepared: (1) montmorillonite clay/fertilizer, (2) montmorillonite clay/thermoplastic starch and fertilizer, (3) montmorillonite clay/fertilizer, thermoplastic starch and low-density polyethylene (LDPE) and also (4) montmorillonite clay/fertilizer, thermoplastic starch and polycaprolactone. It was confirmed the formation of nano structured materials by elemental analysis (CHN) and X-ray diffraction (XRD). The kinetics of nitrogen release was detected by enzymatic colorimetric analysis and spectroscopy in the ultraviolet/visible. The results showed that all materials evaluated were able to reduce the rate of release of nitrogen in the fertilizers. (author)

  4. Tellurium release and deposition during the TMI-2 accident

    International Nuclear Information System (INIS)

    Vinjamuri, K.; Osetek, D.J.; Hobbins, R.R.; Jessup, J.S.

    1984-09-01

    The estimated behavior of tellurium during and after the accident at the Three Mile Island Unit-2 is presented. The behavior is based on all available measurement data for /sup 129m/Te, 132 Te, stable tellurium ( 126 Te, 128 Te and 130 Te), and best estimate calculations of tellurium release and transport. The predicted release was calculated using current techniques that relate release rate to fuel temperature and holdup of tellurium in zircaloy until significant oxidation occurs. The calculated release fraction was low, approx. 7%, but the total measured release for samples analyzed to date is about 5.8%. Of the measured tellurium about 2.4, 1.8, 0.88, 0.42, 0.17 and 0.086% of core inventory were in the containment sump water, upper plenum assembly surfaces, containment solids in the sump water, makeup and purification demineralizer, containment inside surface, and the reactor primary coolant, respectively. A significant fraction (54%) of the tellurium calculated to be retained on the upper plenum surfaces (4.61% of the core inventory) was deposited during the high pressure injection of coolant at about 200 min after the reactor scram. Comparison of tellurium behavior with in-pile and out-of-pile tests strongly suggests that zircaloy holds tellurium until significant cladding oxidation occurs

  5. Regenerated cellulose micro-nano fiber matrices for transdermal drug release

    International Nuclear Information System (INIS)

    Liu, Yue; Nguyen, Andrew; Allen, Alicia; Zoldan, Janet; Huang, Yuxiang; Chen, Jonathan Y.

    2017-01-01

    In this work, biobased fibrous membranes with micro- and nano-fibers are fabricated for use as drug delivery carries because of their biocompatibility, eco-friendly approach, and potential for scale-up. The cellulose micro-/nano-fiber (CMF) matrices were prepared by electrospinning of pulp in an ionic liquid, 1-butyl-3-methylimidazolium chloride. A model drug, ibuprofen (IBU), was loaded on the CMF matrices by a simple immersing method. The amount of IBU loading was about 6% based on the weight of cellulose membrane. The IBU-loaded CMF matrices were characterized by Fourier-transform infrared spectroscopy, thermal gravimetric analysis, and scanning electron microscopy. The test of ibuprofen release was carried out in an acetate buffer solution of pH 5.5 and examined by UV–Vis spectroscopy. Release profiles from the CMF matrices indicated that the drug release rate could be determined by a Fickian diffusion mechanism. - Highlights: • Cellulose micro-nano fiber matrix was prepared by dry-wet electrospinning. • Ibuprofen was loaded on the matrix by a simple immersing method. • The drug loaded matrix showed a biphasic release profile. • The drug release was determined by a Fickian diffusion mechanism.

  6. Regenerated cellulose micro-nano fiber matrices for transdermal drug release

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Yue [School of Human Ecology, The University of Texas at Austin, Austin, TX (United States); Department of Chemistry, School of Science, Tianjin University, Tianjin (China); Nguyen, Andrew; Allen, Alicia; Zoldan, Janet [Department of Biomedical Engineering, The University of Texas at Austin, Austin, TX (United States); Huang, Yuxiang [School of Human Ecology, The University of Texas at Austin, Austin, TX (United States); Chen, Jonathan Y., E-mail: jychen2@austin.utexas.edu [School of Human Ecology, The University of Texas at Austin, Austin, TX (United States)

    2017-05-01

    In this work, biobased fibrous membranes with micro- and nano-fibers are fabricated for use as drug delivery carries because of their biocompatibility, eco-friendly approach, and potential for scale-up. The cellulose micro-/nano-fiber (CMF) matrices were prepared by electrospinning of pulp in an ionic liquid, 1-butyl-3-methylimidazolium chloride. A model drug, ibuprofen (IBU), was loaded on the CMF matrices by a simple immersing method. The amount of IBU loading was about 6% based on the weight of cellulose membrane. The IBU-loaded CMF matrices were characterized by Fourier-transform infrared spectroscopy, thermal gravimetric analysis, and scanning electron microscopy. The test of ibuprofen release was carried out in an acetate buffer solution of pH 5.5 and examined by UV–Vis spectroscopy. Release profiles from the CMF matrices indicated that the drug release rate could be determined by a Fickian diffusion mechanism. - Highlights: • Cellulose micro-nano fiber matrix was prepared by dry-wet electrospinning. • Ibuprofen was loaded on the matrix by a simple immersing method. • The drug loaded matrix showed a biphasic release profile. • The drug release was determined by a Fickian diffusion mechanism.

  7. Influence of PCL on the material properties of collagen based biocomposites and in vitro evaluation of drug release

    International Nuclear Information System (INIS)

    Kanungo, Ivy; Fathima, Nishter Nishad; Rao, Jonnalagadda Raghava; Nair, Balachandran Unni

    2013-01-01

    Formulation of biodegradable collagen–poly-ε-caprolactone (PCL) based biomaterials for the sustained release of insulin is the main objective of the present work. PCL has been employed to modulate the physico-chemical behavior of collagen to control the drug release. Designed formulations were employed to statistically optimize insulin release parameter profile at different collagen to PCL molar ratios. Circular dichroism, thermoporometry, FTIR, impedance and scanning electron microscopy techniques have been employed to investigate the effect of PCL on hydration dynamics of the collagen molecule, which in turn changes the dissolution parameters of the drug from the systems. Drug entrapment efficiency has been found to be maximum for collagen to PCL molar ratio of 1:2 (> 90%). In vitro dissolution test reveals that 99% of the drug was released from composite at collagen to PCL molar ratio of 1:3 and 1:4 within 2 h, which indicates that hydrophobicity of the matrix results in weak interaction between lipophilic drug and carrier materials. The least burst release was observed for collagen to PCL molar ratio at 1:2 as synergistic interactions between collagen and PCL was maximum at that particular polymer–polymer ratios. The drug release data indicates super case-II transport of drug (n > 1.0). - Graphical abstract: Collagen–poly-ε-caprolactone based biomaterials for the sustained release of insulin were formulated. Circular dichroism, thermoporometry, FTIR, impedance and scanning electron microscopy techniques have been employed to elucidate the effect of PCL on the structure of the collagen and in vitro drug release. The drug release data fitted to the kinetic model indicates super case-II transport due to the combination of diffusion and polymer relaxation/dissolution (n > 1.0). - Highlights: • Poly-ε-caprolactone influences physico-chemical behavior of collagen. • Poly-ε-caprolactone influences in vitro drug release mechanism from biocomposites.

  8. Change regularity of water quality parameters in leakage flow conditions and their relationship with iron release.

    Science.gov (United States)

    Liu, Jingqing; Shentu, Huabin; Chen, Huanyu; Ye, Ping; Xu, Bing; Zhang, Yifu; Bastani, Hamid; Peng, Hongxi; Chen, Lei; Zhang, Tuqiao

    2017-11-01

    The long-term stagnation in metal water supply pipes, usually caused by intermittent consumption patterns, will cause significant iron release and water quality deterioration, especially at the terminus of pipelines. Another common phenomenon at the terminus of pipelines is leakage, which is considered helpful by allowing seepage of low-quality drinking water resulting from long-term stagnation. In this study, the effect of laminar flow on alleviating water quality deterioration under different leakage conditions was investigated, and the potential thresholds of the flow rate, which can affect the iron release process, were discussed. Based on a galvanized pipe and ductile cast iron pipe pilot platform, which was established at the terminus of pipelines, this research was carried out by setting a series of leakage rate gradients to analyze the influence of different leakage flow rates on iron release, as well as the relationship with chemical and biological parameters. The results showed that the water quality parameters were obviously influenced by the change in flow velocity. Water quality was gradually improved with an increase in flow velocity, but its change regularity reflected a diversity under different flow rates (p water distribution system, when the bulk water was at the critical laminar flow velocity, the concentration of total iron, the quantity and rate of total iron release remain relatively in an ideal and safe situation. Copyright © 2017. Published by Elsevier Ltd.

  9. Phototoxicity free quantum dot-based niosome formulation for controlled drug release and its monitoring

    Science.gov (United States)

    Kumar, Sunil; Kang, T. W.; Bala, Suman; Kamboj, Sunil; Jeon, H. C.

    2018-04-01

    A novel niosomes-based system composed of Hypromellose (HPMC) functionalized fluorescent, biocompatible ZnS:Mn quantum dots (QDs), and anti-HIV drug Tenofovir disoproxil fumarate (TDF) was designed. An appropriate ratio of surfactant Sorbitan Monostearate (SPAN-60) and cholesterol was used to obtain an optimal entrapment efficiency. Initially, after observing the successful interaction of HPMC with SPAN-60, the noisome formulation including (QDs + drug) and HPMC-coated QDs was synthesized by a wet chemical route and characterized by X-ray diffraction (XRD), Transmission electron microscope (TEM) and Selected Electron Diffraction (SAED). Secondly, (QDs + drug) loaded niosome formulations were studied by varying the ratio of SPAN-60 and cholesterol. Multiple studies were done to characterize the shape, size, viscosity, colloidal stability, and entrapment efficiency of (QDs + drug) loaded niosomes. Lastly, pH-dependent (QDs + drug) release profiles were studied by a spectroscopic technique considering the pH of the human gastrointestinal region to obtain the formulation stability of (QDs + drug) release from the niosome vesicles. These studies also include pH-dependent photo-stability measurements based on laser-induced multiphoton excitation technique in the Infrared region. The multiphoton time-resolved studies were completed to avoid the UV induced phototoxicity in the drug delivery modules. Current studies on the formulation of niosomes-based (QDs + drug) system laid a foundation to make a complete phototoxicity free system for tracking controlled drug release and its imaging.

  10. The physical properties and ion release of CPP-ACP-modified calcium silicate-based cements.

    Science.gov (United States)

    Dawood, A E; Manton, D J; Parashos, P; Wong, Rhk; Palamara, Jea; Stanton, D P; Reynolds, E C

    2015-12-01

    This study investigated the physical properties and ion release of casein phosphopeptide-amorphous calcium phosphate (CPP-ACP)-modified calcium silicate-based cements (CSCs) and compared the properties of a trial mineral trioxide aggregate (MTA) with two commercially available CSCs, Biodentine(™) and Angelus(®) MTA. The setting time, solubility, compressive strength and Vickers surface microhardness of the three CSCs incorporated with 0%, 0.5%, 1.0%, 2.0% and 3.0% (w/w) CPP-ACP were investigated. Release of calcium (Ca(2+) ), phosphate ions (Pi ) and pH of the test cements were measured after 24, 72, 168 and 336 h of storage. The addition of up to 1.0% CPP-ACP into Biodentine(™) and 0.5% into the other cements did not adversely affect their physical properties except for the setting time. The addition of 0.5% CPP-ACP increased Ca(2+) released from Biodentine(™) (after 168 and 336 h), Angelus(®) MTA (after 168 h) and the trial MTA (after 72 h). The addition of 1.0-3.0% CPP-ACP increased Ca(2+) and Pi released from all the cements. Biodentine(™) released more Ca(2+) particularly in the early stages and showed shorter setting time and higher mechanical properties than the other cements. The mechanical properties of Angelus(®) MTA and the trial MTA were similar. All the cements produced highly alkaline storage solutions. Up to 1.0% CPP-ACP in Biodentine(™) improves Ca(2+) and Pi release and 0.5% CPP-ACP in Angelus(®) MTA and the trial MTA improves Ca(2+) release without altering the mechanical properties and solubility. The addition of CPP-ACP into CSCs prolonged the setting time. © 2015 Australian Dental Association.

  11. Controlled Release Formulation of Indomethacin Prepared With Bee ...

    African Journals Online (AJOL)

    Erah

    2010-12-27

    Dec 27, 2010 ... Results: The results show that, although the release rate of formulations F1 - F7 did not show any ... Keywords: Propolis (bee glue), Indomethacin, Controlled release, Zero order kinetics, Waxy materials ... focus of interest.

  12. Controlling Release of Integral Lipid Nanoparticles Based on Osmotic Pump Technology.

    Science.gov (United States)

    Tian, Zhiqiang; Yu, Qin; Xie, Yunchang; Li, Fengqian; Lu, Yi; Dong, Xiaochun; Zhao, Weili; Qi, Jianping; Wu, Wei

    2016-08-01

    To achieve controlled release of integral nanoparticles by the osmotic pump strategy using nanostructured lipid carriers (NLCs) as model nanoparticles. NLCs was prepared by a hot-homogenization method, transformed into powder by lyophilization, and formulated into osmotic pump tablets (OPTs). Release of integral NLCs was visualized by live imaging after labeling with a water-quenching fluorescent probe. Effects of formulation variables on in vitro release characteristics were evaluated by measuring the model drug fenofibrate. Pharmacokinetics were studied in beagle dogs using the core tablet and a micronized fenofibrate formulation as references. NLCs are released through the release orifices of the OPTs as integral nanoparticles. Near zero-order kinetics can be achieved by optimizing the influencing variables. After oral administration, decreased C max and steady drug levels for as long as over 24 h are observed. NLC-OPTs show an oral bioavailability of the model drug fenofibrate similar to that of the core tablets, which is about 1.75 folds that of a fast-release formulation. Controlled release of integral NLCs is achieved by the osmotic pump strategy.

  13. Controlled Release Kinetics in Hydroxy Double Salts: Effect of Host Anion Structure

    Directory of Open Access Journals (Sweden)

    Stephen Majoni

    2014-01-01

    Full Text Available Nanodimensional layered metal hydroxides such as layered double hydroxides (LDHs and hydroxy double salts (HDSs can undergo anion exchange reactions releasing intercalated anions. Because of this, these metal hydroxides have found applications in controlled release delivery of bioactive species such as drugs and pesticides. In this work, isomers of hydroxycinnamate were used as model compounds to systematically explore the effects of anion structure on the rate and extent of anion release in HDSs. Following intercalation and subsequent release of the isomers, it has been demonstrated that the nature and position of substituent groups on intercalated anions have profound effects on the rate and extent of release. The extent of release was correlated with the magnitude of dipole moments while the rate of reaction showed strong dependence on the extent of hydrogen bonding within the layers. The orthoisomer showed a more sustained and complete release as compared to the other isomers.

  14. Thermoresponsive latexes for fragrance encapsulation and release.

    Science.gov (United States)

    Popadyuk, N; Popadyuk, A; Kohut, A; Voronov, A

    2016-04-01

    To synthesize cross-linked latex particles protecting the encapsulated fragrance at ambient temperatures and facilitating the release of cargo at the temperature of the surface of the skin that varies in different regions of the body between 33.5 and 36.9°C. Poly(stearyl acrylate) (PSA), a polymer with long crystallizable alkyl side chains (undergoes order-disorder transitions at 45°C), was chosen as the main component of the polymer particles. As a result, new thermoresponsive polymer particles for fragrance encapsulation were synthesized and characterized, including assessing the performance of particles in triggered release by elevated temperature. To obtain network domains of various crystallinity, stearyl acrylate was copolymerized with dipropylene glycol acrylate caprylate (DGAC) (comonomer) in the presence of a dipropylene glycol diacrylate sebacate (cross-linker) using the miniemulsion process. Comonomers and a cross-linker were mixed directly in a fragrance during polymerization. Fragrance release was evaluated at 25, 31, 35 and 39°C to demonstrate a new material potential in personal/health care skin-related applications. Particles protect the fragrance from evaporation at 25°C. The fragrance release rate gradually increases at 31, 35 and 39°C. Two slopes were found on release plots. The first slope corresponds to a rapid fragrance release. The second slope indicates a subsequent reduction in the release rate. Crystalline-to-amorphous transition of PSA triggers the release of fragrances from cross-linked latex particles at elevated temperatures. The presence of the encapsulated fragrance, as well as the inclusion of amorphous fragments in the polymer network, reduces the particle crystallinity and enhances the release. Release profiles can be tuned by temperature and controlled by the amount of loaded fragrance and the ratio of comonomers in the feed mixture. © 2015 Society of Cosmetic Scientists and the Société Française de Cosmétologie.

  15. Uranium Release from Acidic Weathered Hanford Sediments: Single-Pass Flow-Through and Column Experiments.

    Science.gov (United States)

    Wang, Guohui; Um, Wooyong; Wang, Zheming; Reinoso-Maset, Estela; Washton, Nancy M; Mueller, Karl T; Perdrial, Nicolas; O'Day, Peggy A; Chorover, Jon

    2017-10-03

    The reaction of acidic radioactive waste with sediments can induce mineral transformation reactions that, in turn, control contaminant fate. Here, sediment weathering by synthetic uranium-containing acid solutions was investigated using bench-scale experiments to simulate waste disposal conditions at Hanford's cribs (Hanford, WA). During acid weathering, the presence of phosphate exerted a strong influence over uranium mineralogy and a rapidly precipitated, crystalline uranium phosphate phase (meta-ankoleite [K(UO 2 )(PO 4 )·3H 2 O]) was identified using spectroscopic and diffraction-based techniques. In phosphate-free system, uranium oxyhydroxide minerals such as K-compreignacite [K 2 (UO 2 ) 6 O 4 (OH) 6 ·7H 2 O] were formed. Single-pass flow-through (SPFT) and column leaching experiments using synthetic Hanford pore water showed that uranium precipitated as meta-ankoleite during acid weathering was strongly retained in the sediments, with an average release rate of 2.67 × 10 -12 mol g -1 s -1 . In the absence of phosphate, uranium release was controlled by dissolution of uranium oxyhydroxide (compreignacite-type) mineral with a release rate of 1.05-2.42 × 10 -10 mol g -1 s -1 . The uranium mineralogy and release rates determined for both systems in this study support the development of accurate U-release models for the prediction of contaminant transport. These results suggest that phosphate minerals may be a good candidate for uranium remediation approaches at contaminated sites.

  16. Uranium Release from Acidic Weathered Hanford Sediments: Single-Pass Flow-Through and Column Experiments

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Guohui [Pacific Northwest National Laboratory, Richland, Washington 99354, United States; Um, Wooyong [Pacific Northwest National Laboratory, Richland, Washington 99354, United States; Pohang University of Science and Technology (POSTECH), Pohang, South Korea; Wang, Zheming [Pacific Northwest National Laboratory, Richland, Washington 99354, United States; Reinoso-Maset, Estela [Sierra; Washton, Nancy M. [Pacific Northwest National Laboratory, Richland, Washington 99354, United States; Mueller, Karl T. [Pacific Northwest National Laboratory, Richland, Washington 99354, United States; Perdrial, Nicolas [Department; Department; O’Day, Peggy A. [Sierra; Chorover, Jon [Department

    2017-09-21

    The reaction of acidic radioactive waste with sediments can induce mineral transformation reactions that, in turn, control contaminant fate. Here, sediment weathering by synthetic uranium-containing acid solutions was investigated using bench-scale experiments to simulate waste disposal conditions at Hanford’s cribs, USA. During acid weathering, the presence of phosphate exerted a strong influence over uranium mineralogy and a rapidly precipitated, crystalline uranium phosphate phase (meta-ankoleite [K(UO2)(PO4)·3H2O]) was identified using spectroscopic and diffraction-based techniques. In phosphate-free system, uranium oxyhydroxide minerals such as K-compreignacite [K2(UO2)6O4(OH)6·7H2O] were formed. Single-pass flow-through (SPFT) and column leaching experiments using synthetic Hanford pore water showed that uranium precipitated as meta-ankoleite during acid weathering was strongly retained in the sediments, with an average release rate of 2.67E-12 mol g-1 s-1. In the absence of phosphate, uranium release was controlled by dissolution of uranium oxyhydroxide (compreignacite-type) mineral with a release rate of 1.05-2.42E-10 mol g-1 s-1. The uranium mineralogy and release rates determined for both systems in this study support the development of accurate U-release models for prediction of contaminant transport. These results suggest that phosphate minerals may be a good candidate for uranium remediation approaches at contaminated sites.

  17. Development of a general model to predict the rate of radionuclide release (source term) from a low-level waste shallow land burial facility

    International Nuclear Information System (INIS)

    Sullivan, T.M.; Kempf, C.R.; Suen, C.J.; Mughabghab, S.M.

    1988-01-01

    Federal Code of Regulations 10 CFR 61 requires that any near surface disposal site be capable of being characterized, analyzed, and modeled. The objective of this program is to assist NRC in developing the ability to model a disposal site that conforms to these regulations. In particular, a general computer model capable of predicting the quantity and rate of radionuclide release from a shallow land burial trench, i.e., the source term, is being developed. The framework for this general model has been developed and consists of four basic compartments that represent the major processes that influence release. These compartments are: water flow, container degradation, release from the waste packages, and radionuclide transport. Models for water flow and radionuclide transport rely on the use of the computer codes FEMWATER and FEMWASTE. These codes are generally regarded as being state-of-the-art and required little modification for their application to this project. Models for container degradation and release from waste packages have been specifically developed for this project. This paper provides a brief description of the models being used in the source term project and examples of their use over a range of potential conditions. 13 refs

  18. Macroscopic calculational model of fission gas release from water reactor fuels

    International Nuclear Information System (INIS)

    Uchida, Masaki

    1993-01-01

    Existing models for estimating fission gas release rate usually have fuel temperature as independent variable. Use of fuel temperature, however, often brings an excess ambiguity in the estimation because it is not a rigorously definable quantity as a function of heat generation rate and burnup. To derive a mathematical model that gives gas release rate explicitly as a function of design and operational parameters, the Booth-type diffusional model was modified by changing the character of the diffusion constant from physically meaningful quantity into a mere mathematical parameter, and also changing its temperature dependency into power dependency. The derived formula was found, by proper choice of arbitrary constants, to satisfactorily predict the release rates under a variety of irradiation histories up to a burnup of 60,000 MWd/t. For simple power histories, the equation can be solved analytically by defining several transcendental functions, which enables simple calculation of release rate using graphs. (author)

  19. In-vitro release of diclofenac diethylammonium from lipid-based formulations.

    Science.gov (United States)

    Parsaee, Siamak; Sarbolouki, Mohammad N; Parnianpour, Mohamad

    2002-07-08

    This article presents the preparation and topical performance of some new lipid-based formulations of diclofenac, namely (a) a diclofenac aqueous gel containing mixed micelles (sodium cholate:egg lecithin molar ratio 0.55); (b) diclofenac lotion that contains soya lecithin, ethanol and buffer; and (c) diclofenac lipogel containing egg lecithin, isopropyl myristate, propylene glycol and ethanol. Gel formulations were prepared using Carbomer 934. Release of diclofenac from all formulations was monitored via dialysis through Spectra/por membrane into phosphate buffer (0.2 M pH=7.4) using a Franz cell. Drug release profile and diffusion coefficients were compared with brand formulation (Geigy's Vlotaren Emulgel). Statistical analysis of data show that the diffusion coefficient of the drug from these formulations rank according to the following order: Diclofenac lotion (D=5.308x10(-7) cm(2)/s) >lipogel (D=2.102 x 10(-7) cm(2)/s) >Voltaren Emulgel (1.518 x 10(-7) cm(2)/s) >aqueous gel mixed micelle (0.966 x 10(-7) cm(2)/s). These results show that diclofenac lotion and lipogel maybe more suitable formulations than the conventional topical dosage form.

  20. Preparation and Application of Sustained-Release Potassium Ferrate(VI

    Directory of Open Access Journals (Sweden)

    Xuan Xu

    2014-01-01

    Full Text Available In this study, a composite system for the sustained release of potassium ferrate(VI (sustained-release K2FeO4 was prepared and applied for water treatment. The objective of this research was to maximize the effectiveness of K2FeO4 for water treatment by enhancing its stability using diatomite. The sustained-release K2FeO4 was characterized using X-ray diffraction, scanning electron microscopy, and Fourier transform infrared spectroscopy. The results indicated that no new crystal phase was formed during the preparation and some K2FeO4 crystals entered the pores of the diatomite. From K2FeO4 release experiments, we found that the decomposition rate of K2FeO4 was obviously decreased, which greatly improved the contact rate between released K2FeO4 and pollutants. Via degradation of methyl orange, which was used as a model pollutant, the influential factor of K2FeO4 content within the complete sustained-release K2FeO4 system was studied. The optimal K2FeO4 content within the sustained-release K2FeO4 system was approximately 70%. In natural water samples, sustained-release K2FeO4 at a dosage of 0.06 g/L and with a reaction time of 20 minutes removed 36.84% of soluble microbial products and 17.03% of simple aromatic proteins, and these removal rates were better than those observed after traditional chlorine disinfection.

  1. Fuel morphology effects on fission product release

    International Nuclear Information System (INIS)

    Osetek, D.J.; Hartwell, J.K.; Cronenberg, A.W.

    1986-01-01

    Results are presented of fission product release behavior observed during four severe fuel damage tests on bundles of UO 2 fuel rods. Transient temperatures up to fuel melting were obtained in the tests that included both rapid and slow cooldown, low and high (36 GWd/t) burnup fuel and the addition of Ag-In-Cd control rods. Release fractions of major fission product species and release rates of noble gas species are reported. Significant differences in release behavior are discussed between heatup and cooldown periods, low and high burnup fuel and long- and short-lived fission products. Explanations for the observed differences are offered that relate fuel morphology changes to the releases

  2. Development and Validation of a National System for Routine Monitoring of Mortality in People Recently Released from Prison.

    Directory of Open Access Journals (Sweden)

    Stuart A Kinner

    Full Text Available People released from prison are at increased risk of death. However, no country has established a system for routine monitoring of mortality in this population. The aims of this study were to (a evaluate a system for routine monitoring of deaths after release from prison in Australia and (b estimate the number of deaths annually within 28 and 365 days of prison release from 2000 to 2013.Persons released from prison and deaths were identified in records held by Centrelink, Australia's national provider of unemployment benefits. Estimates generated in this manner were compared with those from a study that probabilistically linked correctional records with the National Death Index (NDI, for each calendar year 2000 to 2007. Using Centrelink data, national estimates of mortality within 28 and 365 days of release were produced for each calendar year 2000 to 2013.Compared with estimates based on linkage with the NDI, the estimated crude mortality rate based on Centrelink records was on average 52% lower for deaths within 28 days of release and 24% lower for deaths within 365 days of release. Nationally, over the period 2000 to 2013, we identified an average of 32 deaths per year within 28 days of release and 188 deaths per year within 365 days of release. The crude mortality rate for deaths within both 28 and 365 days of release increased over this time.Using routinely collected unemployment benefits data we detected the majority of deaths in people recently released from prison in Australia. These data may be sufficient for routine monitoring purposes and it may be possible to adopt a similar approach in other countries. Routine surveillance of mortality in ex-prisoners serves to highlight their extreme vulnerability and provides a basis for evaluating policy reforms designed to reduce preventable deaths.

  3. Design of a new type of coating for the controlled release of heparin

    NARCIS (Netherlands)

    Hinrichs, W.L.J.; Hinrichs, W.L.J.; ten Hoopen, Hermina W.M.; Wissink, M.J.B.; Engbers, G.H.M.; Feijen, Jan

    1997-01-01

    Thrombus formation at the surface of blood contacting devices can be prevented by local release of heparin. Preferably, the release rate should be constant for prolonged periods of time. The minimum heparin release rate to achieve thromboresistance will be different for various applications and

  4. In-pile test of tritium release from tritium breeding materials (VOM-21H experiment)

    International Nuclear Information System (INIS)

    Kurasawa, Toshimasa; Takeshita, Hidefumi; Watanabe, Hitoshi; Yoshida, Hiroshi.

    1986-10-01

    Material development and blanket design of lithium-based ceramics such as lithium oxide, lithium aluminate, lithium silicate and lithium zirconate have been performed in Japan, United State of America and Europian Communities. Lithium oxide is a most attractive candidate for tritium breeding materials because of its high lithium density, high thermal conductivity and good tritium release performance. This work has been done to clarify the characteristics of tritium release and recovery from Li 2 O by means of in-situ tritium release measurement. The effects of temperature and sweep gas composition on the tritium release were investigated in this VOM-21H Experiment. Good measurement of tritium release was achieved but there were uncertainties in reproduciblity of data. The experimental results show that the role of surface adsorption/desorption makes a significant contribution to the tritium release and tritium inventory. Also, it is necessary to define the rate limiting process either diffusion or surface adsorption/desorption. (author)

  5. Pilot power based rate control in CDMA 2000 1x EV-DO Rev-A

    Institute of Scientific and Technical Information of China (English)

    LIU Xiao-feng; GU Jian; YANG Hong-wen

    2008-01-01

    This article proposes a new algorithm to improvethe rate control efficiency of enhanced reverse link mediumaccess control (RLMAC) in the code division multiple access(CDMA) lx EV-DO release A(Rev. A) system. The newalgorithm brings reverse access terminal (AT) pilot power tothe RLMAC rate control procedure and makes it easier for alow pilot power user to increase its data rate when the systemis slightly loaded and harder to decrease its date rate when thesystem is heavily loaded. Numerical results of system levelsimulations show that the new algorithm can bring highersystem throughput, lower AT transmission power, and lowersystem load.

  6. Tetrapeptide-coumarin conjugate 3D networks based on hydrogen-bonded charge transfer complexes: gel formation and dye release.

    Science.gov (United States)

    Guo, Zongxia; Gong, Ruiying; Jiang, Yi; Wan, Xiaobo

    2015-08-14

    Oligopeptide-based derivatives are important synthons for bio-based functional materials. In this article, a Gly-(L-Val)-Gly-(L-Val)-coumarin (GVGV-Cou) conjugate was synthesized, which forms 3D networks in ethanol. The gel nanostructures were characterized by UV-vis spectroscopy, FT-IR spectroscopy, X-ray diffraction (XRD), SEM and TEM. It is suggested that the formation of charge transfer (CT) complexes between the coumarin moieties is the main driving force for the gel formation. The capability of the gel to encapsulate and release dyes was explored. Both Congo Red (CR) and Methylene Blue (MB) can be trapped in the CT gel matrix and released over time. The present gel might be used as a functional soft material for guest encapsulation and release.

  7. Release of polyaromatic hydrocarbons from coal tar contaminated soils

    International Nuclear Information System (INIS)

    Priddy, N.D.; Lee, L.S.

    1996-01-01

    A variety of process wastes generated from manufactured gas production (MGP) have contaminated soils and groundwater at production and disposal sites. Coal tar, consisting of a complex mixture of hydrocarbons present as a nonaqueous phase liquid, makes up a large portion of MGP wastes. Of the compounds in coal tar, polyaromatic hydrocarbons (PAHs) are the major constituents of environmental concern due to their potential mutagenic and carcinogenic hazards. Characterization of the release of PAHs from the waste-soil matrix is essential to quantifying long-term environmental impacts in soils and groundwater. Currently, conservative estimates for the release of PAHs to the groundwater are made assuming equilibrium conditions and using relationships derived from artificially contaminated soils. Preliminary work suggests that aged coal tar contaminated soils have much lower rates of desorption and a greater affinity for retaining organic contaminants. To obtain better estimates of desorption rates, the release of PAHs from a coal tar soil was investigated using a flow-interruption, miscible displacement technique. Methanol/water solutions were employed to enhance PAH concentrations above limits of detection. For each methanol/water solution employed, a series of flow interrupts of varying times was invoked. Release rates from each methanol/water solution were estimated from the increase in concentration with duration of flow interruption. Aqueous-phase release rates were then estimated by extrapolation using a log-linear cosolvency model

  8. Nanostructured Diclofenac Sodium Releasing Material

    Science.gov (United States)

    Nikkola, L.; Vapalahti, K.; Harlin, A.; Seppälä, J.; Ashammakhi, N.

    2008-02-01

    Various techniques have been developed to produce second generation biomaterials for tissue repair. These include extrusion, molding, salt leaching, spinning etc, but success in regenerating tissues has been limited. It is important to develop porous material, yet with a fibrous structure for it to be biomimetic. To mimic biological tissues, the extra-cellular matrix usually contains fibers in nano scale. To produce nanostructures, self-assembly or electrospinning can be used. Adding a drug release function to such a material may advance applications further for use in controlled tissue repair. This turns the resulting device into a multifunctional porous, fibrous structure to support cells and drug releasing properties in order to control tissue reactions. A bioabsorbable poly(ɛ-caprolactone-co-D,L lactide) 95/5 (PCL) was made into diluted solution using a solvent, to which was added 2w-% of diclofenac sodium (DS). Nano-fibers were made by electrospinning onto substrate. Microstructure of the resulting nanomat was studied using SEM and drug release profiles with UV/VIS spectroscopy. Thickness of the electrospun nanomat was about 2 mm. SEM analysis showed that polymeric nano-fibers containing drug particles form a highly interconnected porous nano structure. Average diameter of the nano-fibers was 130 nm. There was a high burst peak in drug release, which decreased to low levels after one day. The used polymer has slow a degradation rate and though the nanomat was highly porous with a large surface area, drug release rate is slow. It is feasible to develop a nano-fibrous porous structure of bioabsorbable polymer, which is loaded with test drug. Drug release is targeted at improving the properties of biomaterial for use in controlled tissue repair and regeneration.

  9. A fission gas release model for MOX fuel and its verification

    International Nuclear Information System (INIS)

    Koo, Y.H.; Sohn, D.S.; Strijov, P.

    2000-01-01

    A fission gas release model for MOX fuel has been developed based on a model for UO 2 fuel. Using the concept of equivalent cell, the model considers the uneven distribution of Pu within the fuel matrix and a number of Pu-rich particles that could lead to a non-uniform fission rate and fission gas distribution across the fuel pellet. The model has been incorporated into a code, COSMOS, and some parametric studies were made to analyze the effect of the size and Pu content of Pu-rich agglomerates. The model was then applied to the experimental data obtained from the FIGARO program, which consisted of the base irradiation of MOX fuels in the BEZNAU-1 PWR and the subsequent irradiation of four refabricated fuel segments in the Halden reactor. The calculated gas releases show good agreement with the measured ones. In addition, the present analysis indicates that the microstructure of the MOX fuel used in the FIGARO program is such that it has produced little difference in terms of gas release compared with UO 2 fuel. (author)

  10. Characteristics of CO2 release from forest soil in the mountains near Beijing.

    Science.gov (United States)

    Sun, Xiang Yang; Gao, Cheng Da; Zhang, Lin; Li, Su Yan; Qiao, Yong

    2011-04-01

    CO2 release from forest soil is a key driver of carbon cycling between the soil and atmosphere ecosystem. The rate of CO2 released from soil was measured in three forest stands (in the mountainous region near Beijing, China) by the alkaline absorption method from 2004 to 2006. The rate of CO2 released did not differ among the three stands. The CO2 release rate ranged from - 341 to 1,193 mg m(-2) h(-1), and the mean value over all three forests and sampling times was 286 mg m(-2) h(-1). CO2 release was positively correlated with soil water content and the soil temperature. Diurnally, CO2 release was higher in the day than at night. Seasonally, CO2 release was highest in early autumn and lowest in winter; in winter, negative values of CO2 release suggested that CO2 was absorbed by soil.

  11. Kinetics of extracellular release of 14C-labelled organic carbon by submerged macrophytes

    International Nuclear Information System (INIS)

    Soendergaard, M.

    1981-01-01

    The release of extracellular organic carbon (EOC) by six submerged freswater macrophytes was measured in time course studies with a 14 C-technique. Incubation in light in an open water-flow system made it possible to assay the time courses of 14 C-fixation and the simultaneous release of labelled EOC. Heterotrophic utilization of the released products by epiphytic communities was measured. Two patterns of release kinetics were found: (1) Constant rates of release occurred during the incubations, (2) The rates still increased after 24 h of incubation. During the first hours of incubation the rates of release increased in all species. Elodea reached constant rates after 2-4 h and Littorella and Ceratophyllum demersum after about 20 h. In the experiments with C. submersum and Nitella the rates of release increased almost linearly during the entire incubation period. The kinetics of release were in agreement with the molecular weight distribution of the dissolved EOC measured with gel chromatography. Low molecular weight products ( 10000 Daltons) dominated the dissolved EOC released by C. submersum and Nitella. A large fraction (18-60%) of the total EOC could be recovered on filters with a pore size of 0.2 μm. This particulate fraction probably represents some abiotic removal. The quantities of relase were low in all species and did not exceed 0.9% of the photosynthetic carbon fixation. Heterotrophic uptake by the epiphytic communities was less than 10% of the EOC released. The results emphasize that the 14 C-labelling of extracellular products is a time dependent process. (author)

  12. Effluent release limits, sources and control

    International Nuclear Information System (INIS)

    Swindell, G.E.

    1977-01-01

    Objectives of radiation protection in relation to releases. Environmental transfer models for radionuclides. Relationship between releases, environmental levels and doses to persons. Establishment of release limits: Limits based on critical population group concept critical pathway analysis and identification of critical group. Limits based on optimization of radiation protection individual dose limits, collective doses and dose commitments 1) differential cost benefit analysis 2) authorized and operational limits taking account of future exposures. Monitoring of releases to the environment: Objectives of effluent monitoring. Typical sources and composition of effluents; design and operation of monitoring programmes; recording and reporting of monitoring results; complementary environmental monitoring. (orig.) [de

  13. Thermal ramp rate effects on mixed-oxide fuel swelling/gas release

    International Nuclear Information System (INIS)

    Hinman, C.A.; Randklev, E.H.

    1979-01-01

    Macroscopic swelling behavior of PNL-10 was compared to that of PNL-2 fuel and it was found that the swelling-threshold behavior is similar for similar thermal conditions. Transient fission gas release for the PNL-10 fuel is very similar to that observed for the PNL-2 fuel for similar thermal conditions

  14. Hydrogen peroxide release and acid-base status in exhaled breath condensate at rest and after maximal exercise in young, healthy subjects.

    Science.gov (United States)

    Marek, E; Platen, P; Volke, J; Mückenhoff, K; Marek, W

    2009-12-07

    Exhaled breath condensate (EBC) contains among a large number of mediators hydrogen peroxide (H2O2) as a marker of airway inflammation and oxidative stress. Similarly EBC pH also changes in respiratory diseases. It was the aim of our investigation to prove if hydrogen peroxide release and changes in pH of EBC changes with exercise. EBC was collected from 100 litres exhaled air along with samples of arterialized blood of 16 healthy subjects (9 males, 7 females, age 23 +/- 1 years). EBC hydrogen peroxide was analyzed with EcoCheck amperometer (FILT, Berlin). The rate of H(2)O(2) release was calculated from the concentration and collection time. pH and PCO(2) in blood and in EBC were measured with the Radiometer blood gas analyzer, EBC was equilibrated with a gas mixture (5% CO(2) in O(2)). The bicarbonate concentration was calculated according to the law of mass action for CO(2) and HCO(3)(-) (pK = 6.1). H(2)O(2) concentration in EBC was 190 +/- 109 nmol/l, and H (2)O(2) release at rest was 31.0 +/- 18.3 pmol/min. At maximal exercise, the H(2)O(2) concentration in EBC increased to 250 +/- 120 nmol/l, and H(2)O(2) release significantly increased at maximal exercise to 84.4 +/- 39.9 pmol/min (Pexercise, pH 6.18 +/- 0.17 and [HCO(3)(-)] 1.23 +/- 0.30 mmol/l remained almost unaltered. The rate of H(2)O(2) release in EBC increased during exhausting exercise (external load: 300 Watt) by a factor of 2, whereas the pH and the bicarbonate concentration of the EBC, equilibrated with 5% CO(2) at 37 degrees C were not significantly altered. It has to be proven by further experiments whether there is a linear relationship between the rates of H(2)O(2) release in EBC in graded submaximal exercise.

  15. [Effect of the interaction of microorganisms and iron oxides on arsenic releasing into groundwater in Chinese Loess].

    Science.gov (United States)

    Xie, Yun-Yun; Chen, Tian-Hu; Zhou, Yue-Fei; Xie, Qiao-Qin

    2013-10-01

    A large part of groundwater in the Chinese Loess Plateau area is characterized by high arsenic concentration. Anaerobic bacteria have been considered to play key roles in promoting arsenic releasing from loess to groundwater. However, this hypothesis remains unconfirmed. Based on modeling experiments, this study investigated the speciation of arsenic in loess, and then determined the release rates and quantities of arsenic with the mediation of anaerobic bacteria. The results showed that arsenic contents in loess were between 23 mg.kg-1 and 30 mg.kg-1. No obvious arsenic content difference among loess samples was observed. The ratios for specific adsorbed, iron oxides co-precipitated and silicate co-precipitated arsenic were 37.76% , 36. 15% and 25. 69% , respectively. Indigenous microorganisms, dissimilatory iron reducing bacteria (DIRB) and sulfate reducing bacteria (SRB) could all promote the release of arsenic from loess. Organic matters highly affected the release rates. More than 100 mg.L-1 sodium lactate was required for all bacterial experiments to facilitate obvious arsenic release. Considering the redox condition in loess, the contribution of SRB to arsenic release in loess area was less feasible than that of DIRB and indigenous microorganisms.

  16. Experimental weathering rates of aluminium silicates

    International Nuclear Information System (INIS)

    Gudbrandsson, Snorri

    2013-01-01

    release rates estimated from the sum of the volume fraction normalized dissolution rates of plagioclase, pyroxene, and olivine are within one order of magnitude of those measured in this study. In addition, these experimental results show that during injection of CO 2 -charged waters with pH close to 3.6, crystalline basalt preferentially releases Mg and Fe relative to Ca to the fluid phase. The injection of acidic CO 2 -charged fluids into crystalline basaltic rocks may therefore favour the formation of Mg and Fe carbonates rather than calcite at acidic to neutral conditions. Plagioclase is the most abundant phase in crystalline basalts and thus influences strongly its reactivity. Plagioclase dissolution rates based on Si release show a common U-shaped behaviour as a function of pH where rates decrease with increasing pH at acid condition but increase with increasing pH at alkaline conditions. Constant pH plagioclase dissolution rates increase with increasing anorthite content at acid conditions, in agreement with literature findings. Interpretation and data fitting suggests that plagioclase dissolution rates are consistent with their control by the detachment of Si-rich activated complexes formed by the removal of Al from the mineral framework. Most notably, compared with previous assumptions, plagioclase dissolution rates are independent of plagioclase composition at alkaline conditions, e.g. anorthite-rich plagioclase dissolution rates increase with increasing pH at alkaline conditions. At such conditions rapid plagioclase dissolution rates likely dominate divalent metal release from crystalline basalts to the fluids phase due to its high Ca content. Gibbsite is commonly the first mineral formed during low temperature dissolution of plagioclase. Gibbsite is an aluminium-hydroxide that is found in various soils as well as the dominant phase in many bauxite ores. Gibbsite precipitation rates were measured in closed system reactors at alkaline condition, both at 25 C and

  17. Influence of factors on release of antimicrobials from antimicrobial packaging materials.

    Science.gov (United States)

    Wu, Yu-Mei; Wang, Zhi-Wei; Hu, Chang-Ying; Nerín, Cristina

    2018-05-03

    Antimicrobial packaging materials (films or coatings) (APMs) have aroused great interest among the scientists or the experts specialized in material science, food science, packaging engineering, biology and chemistry. APMs have been used to package the food, such as dairy products, poultry, meat (e.g., beef), salmon muscle, pastry dough, fresh pasta, bakery products, fruits, vegetables and beverages. Some materials have been already commercialized. The ability of APMs to extend the shelf-life of the food depends on the release rate of the antimicrobials (AMs) from the materials to the food. The optimum rate is defined as target release rate (TRR). To achieve TRR, the influencing factors of the release rate should be considered. Herein we reviewed for the first time these factors and their influence on the release. These factors mainly include the AMs, food (or food simulant), packaging materials, the interactions among them, the temperature and environmental relative humidity (RH).

  18. Measurement of fission gas release, internal pressure and cladding creep rate in the fuel pins of PHWR bundle of normal discharge burnup

    Energy Technology Data Exchange (ETDEWEB)

    Viswanathan, U.K. [Post Irradiation Examination Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Sah, D.N., E-mail: dnsah@barc.gov.i [Post Irradiation Examination Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India); Rath, B.N.; Anantharaman, S. [Post Irradiation Examination Division, Bhabha Atomic Research Centre, Trombay, Mumbai 400085 (India)

    2009-08-01

    Fuel pins of a Pressurised Heavy Water Reactor (PHWR) fuel bundle discharged from Narora Atomic Power Station unit no. 1 after attaining a fuel burnup of 7528 MWd/tU have been subjected to two types of studies, namely (i) puncture test to estimate extent of fission gas release and internal pressure in the fuel pin and (ii) localized heating of the irradiated fuel pin to measure the creep rate of the cladding in temperature range 800 deg. C - 900 deg. C. The fission gas release in the fuel pins from the outer ring of the bundle was found to be about 8%. However, only marginal release was found in fuel pins from the middle ring and the central fuel pin. The internal gas pressure in the outer fuel pin was measured to be 0.55 +- 0.05 MPa at room temperature. In-cell isothermal heating of a small portion of the outer fuel pins was carried out at 800 deg. C, 850 deg. C and 900 deg. C for 10 min and the increase in diameter of the fuel pin was measured after heat treatment. Creep rates of the cladding obtained from the measurement of the diameter change of the cladding due to heating at 800 deg. C, 850 deg. C and 900 deg. C were found respectively to be 2.4 x 10{sup -5} s{sup -1}, 24.6 x 10{sup -5} s{sup -1} and 45.6 x 10{sup -5} s{sup -1}.

  19. Carboxymethyl starch/montmorillonite composite microparticles: Properties and controlled release of isoproturon.

    Science.gov (United States)

    Wilpiszewska, Katarzyna; Spychaj, Tadeusz; Paździoch, Waldemar

    2016-01-20

    Preparation of novel high substituted carboxymethyl starch-based microparticles containing sodium montmorillonite (MMT) by crosslinking with Al(3+) was described. For preparing nanocomposite granules carboxymethyl starch (CMS) from native potato starch as well as CMS from amylopectin has been used. The hydrophilic CMS/MMT composite systems were used for herbicide, i.e. isoproturon encapsulation (ca. 75% encapsulation efficiency). The herbicide release rate from CMS/MMT composites in water was significantly reduced when compared to commercial isoproturon: 95% released after ca. 700 h and ca. 24h, respectively. Leaching in soil from composite systems was relatively slower than release in water. After a series of eight irrigations leached about 10% of isoproturon loaded. The CMS/MMT carriers could reduce the potential leaching of herbicide and beneficially reduce pollution of the environment. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Preparation and physical characterization of calcium sulfate cement/silica-based mesoporous material composites for controlled release of BMP-2

    Directory of Open Access Journals (Sweden)

    Tan H

    2015-07-01

    Full Text Available Honglue Tan,1 Shengbing Yang,2 Pengyi Dai,1 Wuyin Li,1 Bing Yue2 1Luoyang Orthopedics and Traumatology Institution, Luoyang Orthopedic-Traumatological Hospital, Luoyang, 2Shanghai Key Laboratory of Orthopedic Implants, Department of Orthopedic Surgery, Shanghai Ninth People’s Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, People’s Republic of China Abstract: As a commonly used implant material, calcium sulfate cement (CSC, has some shortcomings, including low compressive strength, weak osteoinduction capability, and rapid degradation. In this study, silica-based mesoporous materials such as SBA-15 were synthesized and combined with CSC to prepare CSC/SBA-15 composites. The properties of SBA-15 were characterized by X-ray diffraction, transmission electron microscopy, and nitrogen adsorption–desorption isotherms. SBA-15 was blended into CSC at 0, 5, 10, and 20 wt%, referred to as CSC, CSC-5S (5% mass ratio, CSC-10S (10% mass ratio, and CSC-20S (20% mass ratio, respectively. Fourier-transform infrared spectroscopy and compression tests were used to determine the structure and mechanical properties of the composites, respectively. The formation of hydroxyapatite on composite surfaces was analyzed using scanning electron microscopy and X-ray diffraction after soaking in simulated body fluid. BMP-2 was loaded into the composites by vacuum freeze-drying, and its release characteristics were detected by Bradford protein assay. The in vitro degradation of the CSC/SBA-15 composite was investigated by measuring weight loss. The results showed that the orderly, nanostructured, mesoporous SBA-15 possessed regular pore size and structure. The compressive strength of CSC/SBA-15 increased with the increase in SBA-15 mass ratio, and CSC-20S demonstrated the maximum strength. Compared to CSC, hydroxyapatite that formed on the surfaces of CSC/SBA-15 was uniform and compact. The degradation rate of CSC/SBA-15 decreased with increasing

  1. Controlled release of biofunctional substances by radiation-induced polymerization

    International Nuclear Information System (INIS)

    Yoshida, M.; Kumakura, M.; Kaetsu, I.

    1978-01-01

    The release behaviour of a drug from flat circular capsules obtained by radiation-induced polymerization at low temperatures and with different hydrophilic properties has been studied. The effect of various factors on release property was investigated. The release process could be divided into three parts, an initial quick release stage, stationary state release stage and a retarded release stage. Release behaviour in the stationary state was examined using Noyes-Whitney and Higuchi equations. It was shown that the hydrophilic property of polymer matrix expressed by water content was the most important effect on diffusion and release rate. Rigidity of the polymer may also affect diffusivity. The first quick release step could be attributed to rapid dissolution of drug in the matrix surface due to polymer swelling. (author)

  2. The effect of additives on release and in vitro skin retention of flavonoids from emulsion and gel semisolid formulations.

    Science.gov (United States)

    Dyja, R; Jankowski, A

    2017-08-01

    To assess the effect of two different additives (propylene glycol (PG) and polyethylene glycol 400 (PEG 400)) on release and in vitro skin retention of quercetin and chrysin from semisolid bases (amphiphilic creams and acidic carbomer gels). For obtaining semisolid formulations, flavonoids were pre-dissolved in the liquid (PG or PEG 400) or directly suspended in the semisolid base. Three chrysin formulations ('cream 0', 'PG-cream' and 'PEG 400-cream') and five quercetin formulations ('cream 0', 'PG cream', 'PEG 400 cream', 'gel 0' and 'PG gel') were prepared. The release studies were carried out in Franz diffusion cells by means of a cellulose membrane. The porcine ear skin was used in in vitro skin retention studies. The dissolution was a prerequisite to increase the release rates of tested flavonoids from obtained semisolid formulations. The cumulative amount of chrysin released after 6 h from 'PEG 400 cream' containing partly dissolved form of that flavonoid was higher than that from 'cream 0' or 'PG cream' containing its suspended form. The formulations containing quercetin dissolved in PG ('PG cream', 'PG gel') or PEG 400 ('PEG 400 cream') exhibited higher release rates of that flavonoid than corresponding semisolid suspensions ('cream 0' or 'gel 0'). The effects of both liquid additives (PG and PEG 400) on the cumulative amount of quercetin released after 6 h were comparable. However, there was no correlation between the release rate and the skin retention. The amounts of the flavonoids found in the skin were strongly affected by the type of the used solvent. While PG increased the skin retention of both flavonoids, PEG 400 had no effect on chrysin skin retention and delayed quercetin skin absorption. The proper choice of the solvent added to the semisolid base is crucial for enhanced skin delivery of the tested flavonoids. PG is more efficient absorption promoter than PEG 400 of both chrysin and quercetin. © 2017 Society of Cosmetic Scientists and the Soci

  3. Field study of the long-term release of block copolymers from fouling-release coatings

    DEFF Research Database (Denmark)

    Noguer, Albert Camós; Olsen, A.; Hvilsted, Søren

    2017-01-01

    The addition of block copolymers (i.e. oils) is a common technique to enhance the biofouling-resistance properties of poly(dimethylsiloxane) (PDMS)-based fouling-release coatings. These copolymers diffuse from the bulk to the surface of the coating, thus modifying the properties of the surface an...... fouling-release coatings. Finally, the potential of long-term field-studies is discussed, as compared to short-term laboratory experiments usually performed within fouling-release coatings studies....

  4. Radionuclide release calculations for SAR-08

    International Nuclear Information System (INIS)

    Thomson, Gavin; Miller, Alex; Smith, Graham; Jackson, Duncan

    2008-04-01

    Following a review by the Swedish regulatory authorities of the post-closure safety assessment of the SFR 1 disposal facility for low and intermediate waste (L/ILW), SAFE, the SKB has prepared an updated assessment called SAR-08. This report describes the radionuclide release calculations that have been undertaken as part of SAR-08. The information, assumptions and data used in the calculations are reported and the results are presented. The calculations address issues raised in the regulatory review, but also take account of new information including revised inventory data. The scenarios considered include the main case of expected behaviour of the system, with variants; low probability releases, and so-called residual scenarios. Apart from these scenario uncertainties, data uncertainties have been examined using a probabilistic approach. Calculations have been made using the AMBER software. This allows all the component features of the assessment model to be included in one place. AMBER has been previously used to reproduce results the corresponding calculations in the SAFE assessment. It is also used in demonstration of the IAEA's near surface disposal assessment methodology ISAM and has been subject to very substantial verification tests and has been used in verifying other assessment codes. Results are presented as a function of time for the release of radionuclides from the near field, and then from the far field into the biosphere. Radiological impacts of the releases are reported elsewhere. Consideration is given to each radionuclide and to each component part of the repository. The releases from the entire repository are also presented. The peak releases rates are, for most scenarios, due to organic C-14. Other radionuclides which contribute to peak release rates include inorganic C-14, Ni-59 and Ni-63. (author)

  5. Radionuclide release calculations for SAR-08

    Energy Technology Data Exchange (ETDEWEB)

    Thomson, Gavin; Miller, Alex; Smith, Graham; Jackson, Duncan (Enviros Consulting Ltd, Wolverhampton (United Kingdom))

    2008-04-15

    Following a review by the Swedish regulatory authorities of the post-closure safety assessment of the SFR 1 disposal facility for low and intermediate waste (L/ILW), SAFE, the SKB has prepared an updated assessment called SAR-08. This report describes the radionuclide release calculations that have been undertaken as part of SAR-08. The information, assumptions and data used in the calculations are reported and the results are presented. The calculations address issues raised in the regulatory review, but also take account of new information including revised inventory data. The scenarios considered include the main case of expected behaviour of the system, with variants; low probability releases, and so-called residual scenarios. Apart from these scenario uncertainties, data uncertainties have been examined using a probabilistic approach. Calculations have been made using the AMBER software. This allows all the component features of the assessment model to be included in one place. AMBER has been previously used to reproduce results the corresponding calculations in the SAFE assessment. It is also used in demonstration of the IAEA's near surface disposal assessment methodology ISAM and has been subject to very substantial verification tests and has been used in verifying other assessment codes. Results are presented as a function of time for the release of radionuclides from the near field, and then from the far field into the biosphere. Radiological impacts of the releases are reported elsewhere. Consideration is given to each radionuclide and to each component part of the repository. The releases from the entire repository are also presented. The peak releases rates are, for most scenarios, due to organic C-14. Other radionuclides which contribute to peak release rates include inorganic C-14, Ni-59 and Ni-63. (author)

  6. Novel Injectable Pentablock Copolymer Based Thermoresponsive Hydrogels for Sustained Release Vaccines.

    Science.gov (United States)

    Bobbala, Sharan; Tamboli, Viral; McDowell, Arlene; Mitra, Ashim K; Hook, Sarah

    2016-01-01

    The need for multiple vaccinations to enhance the immunogenicity of subunit vaccines may be reduced by delivering the vaccine over an extended period of time. Here, we report two novel injectable pentablock copolymer based thermoresponsive hydrogels made of polyethyleneglycol-polycaprolactone-polylactide-polycaprolactone-polyethyleneglycol (PEG-PCL-PLA-PCL-PEG) with varying ratios of polycaprolactone (PCL) and polylactide (PLA), as single shot sustained release vaccines. Pentablock copolymer hydrogels were loaded with vaccine-encapsulated poly lactic-co-glycolic acid nanoparticles (PLGA-NP) or with the soluble vaccine components. Incorporation of PLGA-NP into the thermoresponsive hydrogels increased the complex viscosity of the gels, lowered the gelation temperature, and minimized the burst release of antigen and adjuvants. The two pentablock hydrogels stimulated both cellular and humoral responses. The addition of PLGA-NP to the hydrogels sustained immune responses for up to 49 days. The polymer with a higher ratio of PCL to PLA formed a more rigid gel, induced stronger immune responses, and stimulated effective anti-tumor responses in a prophylactic melanoma tumor model.

  7. Combining rate-based and cap-and-trade emissions policies

    International Nuclear Information System (INIS)

    Fischer, Carolyn

    2003-12-01

    Rate-based emissions policies (like tradable performance standards, TPS) fix average emissions intensity, while cap-and-trade (CAT) policies fix total emissions. This paper shows that unfettered trade between rate-based and cap-and-trade programs always raises combined emissions, except when product markets are related in particular ways. Gains from trade are fully passed on to consumers in the rate-based sector, resulting in more output and greater emissions allocations. We consider several policy options to offset the expansion, including a tax, an 'exchange rate' to adjust for relative permit values, output-based allocation (OBA) for the rate-based sector, and tightening the cap. A range of combinations of tighter allocations could improve situations in both sectors with trade while holding emissions constant

  8. Preparation and characterization of smart magnetic hydrogels and its use for drug release

    International Nuclear Information System (INIS)

    Liu, T.-Y.; Hu, S.-H.; Liu, K.-H.; Liu, D.-M.; Chen, S.-Y.

    2006-01-01

    The magnetic hydrogels were successfully fabricated by chemically cross-linking of gelatin hydrogels and Fe 3 O 4 nanoparticles (ca. 40-60 nm) through genipin (GP) as cross-linking agent. The cross-sectional SEM observation demonstrates that the Fe 3 O 4 nanoparticles were fairly uniformly distributed in the gelatin matrix. Moreover, in vitro release data reveal that drug release profile of the resulting hydrogels is controllable by switching on or off mode of a given magnetic field. While applying magnetic fields to the magnetic hydrogels, the release rate of vitamin B 12 of the hydrogels was considerably decreased as compared with those when the field was turned off, suggesting a close configuration of the hydrogels as a result of the aggregation of Fe 3 O 4 nanoparticles. Based on this on- and -off mechanism, the smart magnetic hydrogels based on the gelatin-ferrite hybrid composites can be potentially developed for application in novel drug delivery systems

  9. Fluoride release and recharge behavior of a nano-filled resin-modified glass ionomer compared with that of other fluoride releasing materials.

    Science.gov (United States)

    Mitra, Sumita B; Oxman, Joe D; Falsafi, Afshin; Ton, Tiffany T

    2011-12-01

    To compare the long-term fluoride release kinetics of a novel nano-filled two-paste resin-modified glass-ionomer (RMGI), Ketac Nano (KN) with that of two powder-liquid resin-modified glass-ionomers, Fuji II LC (FLC) and Vitremer (VT) and one conventional glass-ionomer, Fuji IX (FIX). Fluoride release was measured in vitro using ion-selective electrodes. Kinetic analysis was done using regression analysis and compared with existing models for GIs and compomers. In a separate experiment the samples of KN and two conventional glass-ionomers, FIX and Ketac Molar (KM) were subjected to a treatment with external fluoride source (Oral-B Neutra-Foam) after 3 months of fluoride release and the recharge behavior studied for an additional 7-day period. The cumulative amount of fluoride released from KN, VT and FLC and the release profiles were statistically similar but greater than that for FIX at P coating of KN with its primer and of DY with its adhesive did not significantly alter the fluoride release behavior of the respective materials. The overall rate for KN was significantly higher than for the compomer DY. DY showed a linear rate of release vs. t and no burst effect as expected for compomers. The nanoionomer KN showed fluoride recharge behavior similar to the conventional glass ionomers FIX and KM. Thus, it was concluded that the new RMGI KN exhibits fluoride ion release behavior similar to typical conventional and RMGIs and that the primer does not impede the release of fluoride.

  10. Formulation and characterization of modified release tablets containing isoniazid using swellable polymers.

    Science.gov (United States)

    Akhtar, M F; Rabbani, M; Sharif, A; Akhtar, B; Saleem, A; Murtaza, G

    2011-01-01

    The aim of this work was to develop swellable modified release (MR) isoniazid tablets using different combinations of polyvinyl acetate (PVAc) and sodium-carboxymethylcellulose (Na-CMC). Granules were prepared by moist granulation technique and then compressed into tablets. In vitro release studies for 12 hr were carried out in dissolution media of varying pH i.e. pH 1.2, 4.5, 7.0 and 7.5. Tablets of all formulations were found to be of good physical quality with respect to appearance (width and thickness), content uniformity, hardness, weight variation and friability. In vitro release data showed that increasing total polymer content resulted in more retarding effect. Formulation with 35% polymer content exhibited zero order release profile and it released 35% of the drug in first hr, later on, controlled drug release was observed upto the 12(th) hour. Formulations with PVAc to Na-CMC ratio 20:80 exhibited zero order release pattern at levels of studied concentrations, which suggested that this combination can be used to formulate zero order release tablets of water soluble drugs like isoniazid. Korsmeyer-Peppas modeling of drug release showed that non-Fickian transport is the primary mechanism of isoniazid release from PVAc and Na-CMC based tablets. The value of mean dissolution time decreased with the increase in the release rate of drug clearly showing the retarding behavior of the swellable polymers. The application of a mixture of PVAc to Na-CMC in a specific ratio may be feasible to formulate zero order release tablets of water soluble drugs like isoniazid.

  11. Encapsulation of naproxen in lipid-based matrix microspheres: characterization and release kinetics.

    Science.gov (United States)

    Bhoyar, P K; Morani, D O; Biyani, D M; Umekar, M J; Mahure, J G; Amgaonkar, Y M

    2011-04-01

    The objective of this study was to microencapsulate the anti-inflammatory drug (naproxen) to provide controlled release and minimizing or eliminating local side effect by avoiding the drug release in the upper gastrointestinal track. Naproxen was microencapsulated with lipid-like carnauba wax, hydrogenated castor oil using modified melt dispersion (modified congealable disperse phase encapsulation) technique. Effect of various formulation and process variables such as drug-lipid ratio, concentration of modifier, concentration of dispersant, stirring speed, stirring time, temperature of external phase, on evaluatory parameters such as size, entrapment efficiency, and in vitro release of naproxen were studied. The microspheres were characterized for particle size, scanning electron microscopy (SEM), FT-IR spectroscopy, drug entrapment efficiency, in vitro release studies, for in vitro release kinetics. The shape of microspheres was found to be spherical by SEM. The drug entrapment efficiency of various batches of microspheres was found to be ranging from 60 to 90 %w/w. In vitro drug release studies were carried out up to 24 h in pH 7.4 phosphate buffer showing 50-65% drug release. In vitro drug release from all the batches showed better fitting with the Korsmeyer-Peppas model, indicating the possible mechanism of drug release to be by diffusion and erosion of the lipid matrix.

  12. Extended release formulations for local anaesthetic agents.

    Science.gov (United States)

    Weiniger, C F; Golovanevski, L; Domb, A J; Ickowicz, D

    2012-08-01

    Systemic toxicity through overdose of local anaesthetic agents is a real concern. By encapsulating local anaesthetics in biodegradable carriers to produce a system for prolonged release, their duration of action can be extended. This encapsulation should also improve the safety profile of the local anaesthetic as it is released at a slower rate. Work with naturally occurring local anaestheticss has also shown promise in the area of reducing systemic and neurotoxicity. Extended duration local anaesthetic formulations in current development or clinical use include liposomes, hydrophobic based polymer particles such as Poly(lactic-co-glycolic acid) microspheres, pasty injectable and solid polymers like Poly(sebacic-co-ricinoleic acid) P(SA:RA) and their combination with synthetic and natural local anaesthetic. Their duration of action, rationale and limitations are reviewed. Direct comparison of the different agents is limited by their chemical properties, the drug doses encapsulated and the details of in vivo models described. Anaesthesia © 2012 The Association of Anaesthetists of Great Britain and Ireland.

  13. Controlled release of phenytoin for epilepsy treatment from titania and silica based materials

    International Nuclear Information System (INIS)

    Lopez, Tessy; Ortiz, Emma; Meza, Doraliz; Basaldella, Elena; Bokhimi, Xim; Magana, Carlos; Sepulveda, Antonio; Rodriguez, Francisco; Ruiz, Javier

    2011-01-01

    Research highlights: → Template technique was used to obtain well ordered nanostructured materials: SBA-15 and titania tubes. → Phenytoin (PH), a drug used in epilepsy treatment, was loaded in these materials to used como PH release. → Loaded PH showed a good stability inside the used materials as observed by spectroscopy analysis. → The load-release PH are faster in nanostructured TiO2 tubes than in mesoporous silica matrix. → There is an inverse effect of the surface area of the structured materials on the amount of released PH. - Abstract: Template technique was used to obtain well ordered nanostructured materials: mesoporous silica and nanostructured titania tubes. This technique permits the synthesis of solids with controlled mesoporosity, where a large variety of molecules that have therapeutic activity can be hosted and further released to specific sites. In this work phenytoin (PH), a drug used in epilepsy treatment, was loaded in ordered mesoporous silica (SBA 15) and nanostructured titania tubes (TiO 2 ). The pure materials and those containing PH were characterized by X-ray diffraction, FTIR spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and N 2 adsorption-desorption at 77 K. In order to determine the loading capacity of the antiepileptic drug on these silica- and titania-based materials, the loading and release of PH was investigated using UV-vis spectroscopy. Tubular structures were found for the titania samples, for which the X-ray diffractograms showed to be formed by anatase and rutile phases. On the other hand, an amorphous phase was found in the silica sample. A highly ordered hexagonal structure of 1D cylindrical channels was also observed for this material. Loaded PH showed a good stability inside the used materials as observed by spectroscopy analysis. The adsorption and desorption of PH are faster in nanostructured TiO 2 tubes than in mesoporous silica matrix.

  14. Preparation and release study of Triclosan in polyethylene/Triclosan anti-bacterial blend.

    Science.gov (United States)

    Kamalipour, Jamshid; Masoomi, Mahmood; Khonakdar, Hossein Ali; Razavi, Seyed Mohammad Reza

    2016-09-01

    In this study, medium density polyethylene (MDPE) incorporated with Triclosan antibacterial substance has been prepared and Triclosan release rate was investigated. The crystallinity level and matrix polarity, as two significant parameters in antibacterial release control, were studied. Triclosan, a well-established widespread antibacterial agent, was incorporated into medium density polyethylene (MDPE) and Maleic anhydride grafted polyethylene (PE-g-MA) was used to change the polarity of the MDPE matrix. A masterbatch of 10wt% Triclosan incorporated with the MDPE and various PE-g-MA concentrations were prepared using an internal mixer. Then the masterbatch was diluted in the MDPE matrix to produce compounds with 0.1, 0.5, and1wt% Triclosan via twin screw extruder. The compounds were molded by compression molding method and then were cooled in three different cooling rate methods: isothermal cooling (I), quenching (Q),and moderate 5-10°C/min cooling rate (M). Cooling rate effects on crystallinity level were investigated applying sample density measurement. UV-vis absorption spectroscopy was used to probe the release of Triclosan. Antibacterial properties of the compounds against Escherichia coli, Klebsiella pneumoniae, and Staphylococcus aureus were measured. The results showed that by addition of PE-g-MA, Triclosan release rate was increased. It was confirmed that the sample crystallinity was decreased by the cooling rate enhancement. The results also showed that quenched samples indicated higher release of Triclosan. Cooling rate reduction and raising the polarity increased the release of Triclosan and improved the antibacterial properties of the compounds. Copyright © 2016 Elsevier B.V. All rights reserved.

  15. Controlled release of tetracycline-HCl from halloysite-polymer composite films.

    Science.gov (United States)

    Ward, Christopher J; Song, Shang; Davis, Edward W

    2010-10-01

    The first direct comparison between two common methods for loading halloysite with a small molecule for controlled release is presented. While the methods differ in the degree of simplicity, they provide essentially the same level of loading and release kinetics. A tentative explanation of the "burst" effect often seen in the release of low molecular weight molecules from halloysite is provided. The ability of halloysite to mediate the release rate of a water soluble drug, tetracycline, from solution cast polyvinyl alcohol and polymethyl methacrylate films was evaluated. In some films, montmorillonite was also incorporated. The addition of montmorillonite to solutions used to cast tetracycline containing films significantly reduced the release rate from the dried films. The same overall effect was seen when the drug was loaded into halloysite prior to preparation of the films. In both cases, the release was best fit with the simple Higuchi model. However, when montmorillonite was added to solutions of polyvinyl alcohol and drug loaded halloysite the release profiles were better fit by the Ritgar-Peppas model for anomalous transport. Release from polymethyl methacrylate was reduced by a factor of three by incorporating the drug in halloysite prior to producing the films.

  16. Interim report: Study of benzene release from Savannah River in-tank precipitation process slurry simulant

    International Nuclear Information System (INIS)

    Rappe, K.G.; Gauglitz, P.A.

    1997-09-01

    At the Savannah River Site, the in-tank precipitation (ITP) process uses sodium tetraphenylborate (NaTPB) to precipitate radioactive cesium from alkaline wastes. During this process, potassium is also precipitated to form a 4-wt% KTPB/CsTPB slurry. Residual NaTPB decomposes to form benzene, which is retained by the waste slurry. The retained benzene is also readily released from the waste during subsequent waste processing. While the release of benzene certainly poses both flammability and toxicological safety concerns, the magnitude of the hazard depends on the rate of release. Currently, the mechanisms controlling the benzene release rates are not well understood, and predictive models for estimating benzene release rates are not available. The overall purpose of this study is to obtain quantitative measurements of benzene release rates from a series of ITP slurry stimulants. This information will become a basis for developing a quantitative mechanistic model of benzene release rates. The transient benzene release rate was measured from the surface of various ITP slurry (solution) samples mixed with benzene. The benzene release rate was determined by continuously purging the headspace of a sealed sample vessel with an inert gas (nitrogen) and analyzing that purged headspace vapor for benzene every 3 minutes. The following 75-mL samples were measured for release rates: KTPB slurry with 15,000 ppm freshly added benzene that was gently mixed with the slurry, KTPB slurry homogenized (energetically mixed) with 15,000 ppm and 5,000 ppm benzene, clear and filtered KTPB salt solution saturated with benzene (with and without a pure benzene layer on top of the solution), and a slurry sample from a large demonstration experiment (DEMO slurry) containing-benzene generated in situ

  17. Trigger release mechanism for release of mine water to Magela Creek

    International Nuclear Information System (INIS)

    McQuade, C.V.; McGill, R.A.

    1988-01-01

    The Ranger Uranium Mine is surrounded by a World Heritage National Park. The strict environmental controls under which the mine operates are based on scientific and social requirements. Release of non-process storm runoff water to the Magela Creek during flood discharge and under controlled conditions has been identified as best practicable technology for the operation of the water management system. Social and political factors have limited this release to a wet season with an annual exceedance probability of one in ten. The first-generation trigger mechanism was based on a percentile analysis of monthly rainfall. The second-generation trigger is based on cumulative monthly volume increase in the retention ponds and is considered to be more applicable to the operation of the mine water management system. 6 figs., 2 tabs

  18. Real-time UV imaging of nicotin release from transdermal patch

    DEFF Research Database (Denmark)

    Østergaard, Jesper; Meng-Lund, Emil; Larsen, Susan Weng

    2010-01-01

    PURPOSE: This study was conducted to characterize UV imaging as a platform for performing in vitro release studies using Nicorette® nicotine patches as a model drug delivery system. METHODS: The rate of nicotine release from 2 mm diameter patch samples (Nicorette®) into 0.067 M phosphate buffer, p......H 7.40, was studied by UV imaging (Actipix SDI300 dissolution imaging system) at 254 nm. The release rates were compared to those obtained using the paddle-over-disk method. RESULTS: Calibration curves were successfully established which allowed temporally and spatially resolved quantification...... of nicotine. Release profiles obtained from UV imaging were in qualitative agreement with results from the paddle-over-disk release method. CONCLUSION: Visualization as well as quantification of nicotine concentration gradients was achieved by UV imaging in real time. UV imaging has the potential to become...

  19. Assessing the influence of media composition and ionic strength on drug release from commercial immediate-release and enteric-coated aspirin tablets.

    Science.gov (United States)

    Karkossa, Frank; Klein, Sandra

    2017-10-01

    The objective of this test series was to elucidate the importance of selecting the right media composition for a biopredictive in-vitro dissolution screening of enteric-coated dosage forms. Drug release from immediate-release (IR) and enteric-coated (EC) aspirin formulations was assessed in phosphate-based and bicarbonate-based media with different pH, electrolyte composition and ionic strength. Drug release from aspirin IR tablets was unaffected by media composition. In contrast, drug release from EC aspirin formulations was affected by buffer species and ionic strength. In all media, drug release increased with increasing ionic strength, but in bicarbonate-based buffers was delayed when compared with that in phosphate-based buffers. Interestingly, the cation species in the dissolution medium had also a clear impact on drug release. Drug release profiles obtained in Blank CarbSIF, a new medium simulating pH and average ionic composition of small intestinal fluid, were different from those obtained in all other buffer compositions studied. Results from this study in which the impact of various media parameters on drug release of EC aspirin formulations was systematically screened clearly show that when developing predictive dissolution tests, it is important to simulate the ionic composition of intraluminal fluids as closely as possible. © 2017 Royal Pharmaceutical Society.

  20. PIXE investigation of in-vitro release of chloramphenicol across polyvinyl alcohol/ acrylamide hydrogel

    International Nuclear Information System (INIS)

    Rihawi, M.; Al-Zeer, A.; Allaf, A.

    2012-01-01

    Hydrogels based on polyvinyl alcohol (PVA) and different amounts of acrylamide monomer (AAm) were prepared by thermal crosslinking process in solid state. The PVA/AAm hydrogels were investigated for drug delivery system applications. Chloramphenicol was adopted as a model drug to study its release behaviour across the prepared hydrogels. Particle induced X-ray emission (PIXE) analytical technique was utilized to study the drug release behaviour across the hydrogels. A comparison study between PIXE and UV measurements was performed. FTIR measurements were carried out to perform the molecular characterization. The releasing behaviour of the drug across the hydrogels demonstrates a decrease and a subsequent increase in the drug release rate, as the AAm amount increases. The FTIR characterization of the prepared hydrogels has shown a competitive behaviour between the crosslinking of PVA with AAm monomer or oligomerized AAm, depending on the amount of AAm added to prepare the PVA/AAm hydrogels. (author)

  1. Host-Guest Recognition-Assisted Electrochemical Release: Its Reusable Sensing Application Based on DNA Cross Configuration-Fueled Target Cycling and Strand Displacement Reaction Amplification.

    Science.gov (United States)

    Chang, Yuanyuan; Zhuo, Ying; Chai, Yaqin; Yuan, Ruo

    2017-08-15

    In this work, an elegantly designed host-guest recognition-assisted electrochemical release was established and applied in a reusable electrochemical biosensor for the detection of microRNA-182-5p (miRNA-182-5p), a prostate cancer biomarker in prostate cancer, based on the DNA cross configuration-fueled target cycling and strand displacement reaction (SDR) amplification. With such a design, the single target miRNA input could be converted to large numbers of single-stranded DNA (S1-Trp and S2-Trp) output, which could be trapped by cucurbit[8]uril methyl viologen (CB-8-MV 2+ ) based on the host-guest recognition, significantly enhancing the sensitivity for miRNA detection. Moreover, the nucleic acids products obtained from the process of cycling amplification could be utilized sufficiently, avoiding the waste and saving the experiment cost. Impressively, by resetting a settled voltage, the proposed biosensor could release S1-Trp and S2-Trp from the electrode surface, attributing that the guest ion methyl viologen (MV 2+ ) was reduced to MV +· under this settled voltage and formed a more-stable CB-8-MV +· -MV +· complex. Once O 2 was introduced in this system, MV +· could be oxidized to MV 2+ , generating the complex of CB-8-MV 2+ for capturing S1-Trp and S2-Trp again in only 5 min. As a result, the simple and fast regeneration of biosensor for target detection was realized on the base of electrochemical redox-driven assembly and release, overcoming the challenges of time-consuming, burdensome operations and expensive experimental cost in traditional reusable biosensors and updating the construction method for a reusable bisensor. Furthermore, the biosensor could be reused for more than 10 times with a regeneration rate of 93.20%-102.24%. After all, the conception of this work provides a novel thought for the construction of effective reusable biosensor to detect miRNA and other biomarkers and has great potential application in the area requiring the release of

  2. Consequences of severe radioactive releases to Nordic Marine environment

    Energy Technology Data Exchange (ETDEWEB)

    Iosjpe, M. [Norwegian Radiation Protection Authority (NRPA) (Norway); Isaksson, M. [Univ. of Gothenburg (Sweden); Joensen, H.P. [Froskaparsetur Foeroya. Faroe Islands, Torshavn (Denmark); Lahtinen, J. [Radiation and Nuclear Safety Authority (Finland); Logemann, K. [Univ. of Iceland (Iceland); Palsson, S.E. [Geislavarnir Rikisins (Iceland); Roos, P. [Technical Univ. of Denmark. Risoe DTU, Roskilde (Denmark); Suolanen, V. [Technical Research Centre of Finland (Finland)

    2013-02-15

    chosen release fractions in the study were: iodine 20% (of the total core inventory), caesium 10%, tellurium 10%, strontium 0.5%, ruthenium 0.5%. The considered release event to marine environment were assumed to start ten hours after shutdown of the reactor. Total released amounts of the most important nuclides were estimated to be: 4.85{center_dot}10{sup 17} Bq (I-131), 7.29{center_dot}10{sup 16} Bq (Cs-134) and 4.17{center_dot}10{sup 16} Bq (Cs-137). Due to the highly contaminated sea food, the arising doses to human from a hypothetical severe nuclear power plant accident would be high especially in local sea area. Based on preliminary results, annual individual doses could be ten to some hundreds of millisieverts from local sea area. The most important nuclides were Cs-134, Cs-137 and I-131 causing 96% of the total ingestion dose. In the Baltic Sea area, the arising doses from a severe nuclear power plant accident assumed to happen e.g. at Gulf of Finland, would be about 1/10000 compared to doses in the local sea area. Thus the arising maximum annual individual dose for fish pathway is in the level of 0.1 mSv in the Baltic Sea area. Submarine accident assumed to happen at Icelandic waters, has been analysed in the study. The calculated collective dose rates to man as well as doses to a critical group are significantly lower than doses from natural sources. However, in local considerations dose-rates are significantly higher than the negligible component to the annual individual dose obtained from natural sources (UNSCEAR, 2000) and, therefore, have to be taken into consideration during evaluation of the accident consequences. (Author)

  3. Consequences of severe radioactive releases to Nordic Marine environment

    International Nuclear Information System (INIS)

    Iosjpe, M.; Isaksson, M.; Joensen, H.P.; Lahtinen, J.; Logemann, K.; Palsson, S.E.; Roos, P.; Suolanen, V.

    2013-02-01

    release fractions in the study were: iodine 20% (of the total core inventory), caesium 10%, tellurium 10%, strontium 0.5%, ruthenium 0.5%. The considered release event to marine environment were assumed to start ten hours after shutdown of the reactor. Total released amounts of the most important nuclides were estimated to be: 4.85·10 17 Bq (I-131), 7.29·10 16 Bq (Cs-134) and 4.17·10 16 Bq (Cs-137). Due to the highly contaminated sea food, the arising doses to human from a hypothetical severe nuclear power plant accident would be high especially in local sea area. Based on preliminary results, annual individual doses could be ten to some hundreds of millisieverts from local sea area. The most important nuclides were Cs-134, Cs-137 and I-131 causing 96% of the total ingestion dose. In the Baltic Sea area, the arising doses from a severe nuclear power plant accident assumed to happen e.g. at Gulf of Finland, would be about 1/10000 compared to doses in the local sea area. Thus the arising maximum annual individual dose for fish pathway is in the level of 0.1 mSv in the Baltic Sea area. Submarine accident assumed to happen at Icelandic waters, has been analysed in the study. The calculated collective dose rates to man as well as doses to a critical group are significantly lower than doses from natural sources. However, in local considerations dose-rates are significantly higher than the negligible component to the annual individual dose obtained from natural sources (UNSCEAR, 2000) and, therefore, have to be taken into consideration during evaluation of the accident consequences. (Author)

  4. The biowaiver extension for BCS class III drugs: the effect of dissolution rate on the bioequivalence of BCS class III immediate-release drugs predicted by computer simulation.

    Science.gov (United States)

    Tsume, Yasuhiro; Amidon, Gordon L

    2010-08-02

    The Biopharmaceutical Classification System (BCS) guidance issued by the FDA allows waivers for in vivo bioavailability and bioequivalence studies for immediate-release (IR) solid oral dosage forms only for BCS class I drugs. However, a number of drugs within BCS class III have been proposed to be eligible for biowaivers. The World Health Organization (WHO) has shortened the requisite dissolution time of BCS class III drugs on their Essential Medicine List (EML) from 30 to 15 min for extended biowaivers; however, the impact of the shorter dissolution time on AUC(0-inf) and C(max) is unknown. The objectives of this investigation were to assess the ability of gastrointestinal simulation software to predict the oral absorption of the BCS class I drugs propranolol and metoprolol and the BCS class III drugs cimetidine, atenolol, and amoxicillin, and to perform in silico bioequivalence studies to assess the feasibility of extending biowaivers to BCS class III drugs. The drug absorption from the gastrointestinal tract was predicted using physicochemical and pharmacokinetic properties of test drugs provided by GastroPlus (version 6.0). Virtual trials with a 200 mL dose volume at different drug release rates (T(85%) = 15 to 180 min) were performed to predict the oral absorption (C(max) and AUC(0-inf)) of the above drugs. Both BCS class I drugs satisfied bioequivalence with regard to the release rates up to 120 min. The results with BCS class III drugs demonstrated bioequivalence using the prolonged release rate, T(85%) = 45 or 60 min, indicating that the dissolution standard for bioequivalence is dependent on the intestinal membrane permeability and permeability profile throughout the gastrointestinal tract. The results of GastroPlus simulations indicate that the dissolution rate of BCS class III drugs could be prolonged to the point where dissolution, rather than permeability, would control the overall absorption. For BCS class III drugs with intestinal absorption patterns

  5. Impact of sodium caseinate concentration and location on magnesium release from multiple W/O/W emulsions.

    Science.gov (United States)

    Bonnet, Marie; Cansell, Maud; Placin, Frédéric; Anton, Marc; Leal-Calderon, Fernando

    2010-06-15

    Water-in-oil-in-water (W/O/W) double emulsions were prepared and the rate of release of magnesium ions from the internal to the external aqueous phase was followed. Sodium caseinate was used not only as a hydrophilic surface-active species but also as a chelating agent able to bind magnesium ions. The release occurred without film rupturing (no coalescence). The kinetics of the release process depended on the location (in only one or in both aqueous compartments) and on the concentration of sodium caseinate. The rate of release increased with the concentration of sodium caseinate in the external phase and decreased when sodium caseinate was present in the inner droplets. The experiments were interpreted within the frame of a mean-field model based on diffusion, integrating the effect of ion binding. The data could be adequately fitted by considering a time-dependent permeation coefficient of the magnesium ions across the oil phase. Our results suggested that ion permeability was influenced by the state of the protein interfacial layers which itself depended on the extent of magnesium binding.

  6. Effects of administration of gonadotropin-releasing hormone at artificial insemination on conception rates in dairy cows.

    Science.gov (United States)

    Shephard, R W; Morton, J M; Norman, S T

    2014-01-10

    A controlled trial investigating the effect on conception of administration of 250 μg of gonadotropin-releasing hormone (GnRH) at artificial insemination (AI) in dairy cows in seasonal or split calving herds was conducted. Time of detection of estrus, body condition, extent of estrous expression, treatment, breed, age and milk production from the most recent herd test of the current lactation was recorded. Cows were tested for pregnancy with fetal aging between 35 and 135 days after AI. Sixteen herds provided 2344 spring-calved cows and 3007 inseminations. Logistic regression adjusting for clustering at herd level was used to examine the effect of treatment for first (2344) and second (579) inseminations separately. For first AI, treatment significantly improved conception rate in cows with milk protein concentrations of 3.75% or greater and for cows with milk protein concentrations between 3.00% and 3.50% and less than 40 days calved; increased conception rate from 41.2% to 53.4%. Treatment reduced conception rates in cows with milk protein concentrations of 2.75% or less. Treating only cows identified as responding positively to treatment (11% of all study cows) was estimated to increase first service conception rate in herds from 48.1% to 49.4%. There was no significant effect of treatment on conception to second AI, nor any significant interactions. These findings indicate that GnRH at AI should be limited to the sub-group cows most likely to respond. The positive effect of GnRH at AI may be mediated through improved oocyte maturation and/or improved luteal function, rather than by reducing AI-to-ovulation intervals. Copyright © 2013 Elsevier B.V. All rights reserved.

  7. Modelling biocide release based on coating properties

    NARCIS (Netherlands)

    Erich, S.J.F.; Baukh, V.

    2016-01-01

    Growth of micro-organisms on coated substrates is a common problem, since it reduces the performance of materials, in terms of durability as well as aesthetics. In order to prevent microbial growth biocides are frequently added to coatings. Unfortunately, early release of these biocides reduces the

  8. SMA-Based System for Environmental Sensors Released from an Unmanned Aerial Vehicle

    Directory of Open Access Journals (Sweden)

    Lorenzo Pellone

    2017-01-01

    Full Text Available In the work at hand, a shape memory alloy (SMA-based system is presented. The system, conceived for releasing environmental sensors from ground or small unmanned aerial vehicles, UAV (often named UAS, unmanned aerial system, is made of a door, integrated into the bottom of the fuselage, a device distributor, operated by a couple of antagonistic SMA springs, and a kinematic chain, to synchronize the deployment operation with the system movement. On the basis of the specifications (weight, available space, energy supply, sensors size, etc., the system design was addressed. After having identified the main system characteristics, a representative mock-up was manufactured, featuring the bottom part of the reference fuselage. Functionality tests were performed to prove the system capability to release the sensors; a detailed characterization was finally carried out, mainly finalized at correlating the kinematic chain displacement with the SMA spring temperature and the supplied electrical power. A comparison between theoretical predictions and experimental outcomes showed good agreement.

  9. Computational Studies of Drug Release, Transport and Absorption in the Human Intestines

    Science.gov (United States)

    Behafarid, Farhad; Brasseur, J. G.; Vijayakumar, G.; Jayaraman, B.; Wang, Y.

    2016-11-01

    Following disintegration of a drug tablet, a cloud of particles 10-200 μm in diameter enters the small intestine where drug molecules are absorbed into the blood. Drug release rate depends on particle size, solubility and hydrodynamic enhancements driven by gut motility. To quantify the interrelationships among dissolution, transport and wall permeability, we apply lattice Boltzmann method to simulate the drug concentration field in the 3D gut released from polydisperse distributions of drug particles in the "fasting" vs. "fed" motility states. Generalized boundary conditions allow for both solubility and gut wall permeability to be systematically varied. We apply a local 'quasi-steady state' approximation for drug dissolution using a mathematical model generalized for hydrodynamic enhancements and heterogeneity in drug release rate. We observe fundamental differences resulting from the interplay among release, transport and absorption in relationship to particle size distribution, luminal volume, motility, solubility and permeability. For example, whereas smaller volume encourages higher bulk concentrations and reduced release rate, it also encourages higher absorption rate, making it difficult to generalize predictions. Supported by FDA.

  10. Nanodiamond-based injectable hydrogel for sustained growth factor release: Preparation, characterization and in vitro analysis.

    Science.gov (United States)

    Pacelli, Settimio; Acosta, Francisca; Chakravarti, Aparna R; Samanta, Saheli G; Whitlow, Jonathan; Modaresi, Saman; Ahmed, Rafeeq P H; Rajasingh, Johnson; Paul, Arghya

    2017-08-01

    Nanodiamonds (NDs) represent an emerging class of carbon nanomaterials that possess favorable physical and chemical properties to be used as multifunctional carriers for a variety of bioactive molecules. Here we report the synthesis and characterization of a new injectable ND-based nanocomposite hydrogel which facilitates a controlled release of therapeutic molecules for regenerative applications. In particular, we have formulated a thermosensitive hydrogel using gelatin, chitosan and NDs that provides a sustained release of exogenous human vascular endothelial growth factor (VEGF) for wound healing applications. Addition of NDs improved the mechanical properties of the injectable hydrogels without affecting its thermosensitive gelation properties. Biocompatibility of the generated hydrogel was verified by in vitro assessment of apoptotic gene expressions and anti-inflammatory interleukin productions. NDs were complexed with VEGF and the inclusion of this complex in the hydrogel network enabled the sustained release of the angiogenic growth factor. These results suggest for the first time that NDs can be used to formulate a biocompatible, thermosensitive and multifunctional hydrogel platform that can function both as a filling agent to modulate hydrogel properties, as well as a delivery platform for the controlled release of bioactive molecules and growth factors. One of the major drawbacks associated with the use of conventional hydrogels as carriers of growth factors is their inability to control the release kinetics of the loaded molecules. In fact, in most cases, a burst release is inevitable leading to diminished therapeutic effects and unsuccessful therapies. As a potential solution to this issue, we hereby propose a strategy of incorporating ND complexes within an injectable hydrogel matrix. The functional groups on the surface of the NDs can establish interactions with the model growth factor VEGF and promote a prolonged release from the polymer network

  11. Once daily, extended release ciprofloxacin for complicated urinary tract infections and acute uncomplicated pyelonephritis.

    Science.gov (United States)

    Talan, David A; Klimberg, Ira W; Nicolle, Lindsay E; Song, James; Kowalsky, Steven F; Church, Deborah A

    2004-02-01

    We assessed the efficacy and safety of 1,000 mg extended release ciprofloxacin orally once daily vs conventional 500 mg ciprofloxacin orally twice daily, each for 7 to 14 days, in patients with a complicated urinary tract infection (cUTI) or acute uncomplicated pyelonephritis (AUP). In this prospective, randomized, double-blind, North American multicenter clinical trial adults were stratified based on clinical presentation of cUTI or AUP and randomized to extended release ciprofloxacin or ciprofloxacin twice daily. Efficacy valid patients had positive pretherapy urine cultures (105 or greater cFU/ml) and pyuria within 48 hours of study entry. Bacteriological and clinical outcomes were assessed at the test of cure visit (5 to 11 days after therapy) and the late followup visit (28 to 42 days after therapy). The intent to treat population comprised 1,035 patients (extended release ciprofloxacin in 517 and twice daily in 518), of whom 435 were efficacy valid (cUTI in 343 and AUP in 92). For efficacy valid patients (cUTI and AUP combined) bacteriological eradication rates at test of cure were 89% (183 of 206) vs 85% (195 of 229) (95% CI -2.4%, 10.3%) and clinical cure rates were 97% (198 of 205) vs 94% (211 of 225) (95% CI -1.2%, 6.9%) for extended release vs twice daily ciprofloxacin. Late followup outcomes were consistent with test of cure findings. Eradication rates for Escherichia coli, which accounted for 58% of pathogens, were 97% or greater per group. Drug related adverse event rates were similar for extended release and twice daily ciprofloxacin (13% and 14%, respectively). Extended release ciprofloxacin at a dose of 1,000 mg once daily was as safe and effective as conventional treatment with 500 mg ciprofloxacin twice daily, each given orally for 7 to 14 days in adults with cUTI or AUP. It provides a convenient, once daily, empirical treatment option.

  12. Heat release from wood wall assemblies using oxygen consumption method

    Science.gov (United States)

    Hao C. Tran; Robert E. White

    1990-01-01

    The concept of heat release rate is gaining acceptance in the evaluation of fire performance of materials and assemblies. However, this concept has not been incorporated into fire endurance testing such as the ASTM E-119 test method. Heat release rate of assemblies can be useful in determining the time at which the assemblies start to contribute to the controlled fire...

  13. Piroxicam loaded alginate beads obtained by prilling/microwave tandem technique: morphology and drug release.

    Science.gov (United States)

    Aquino, Rita P; Auriemma, Giulia; d'Amore, Matteo; D'Ursi, Anna Maria; Mencherini, Teresa; Del Gaudio, Pasquale

    2012-07-01

    This paper presents a tandem technique, based on the combination of prilling and microwave (MW) assisted treatments, to produce biodegradable alginate carriers of piroxicam with different drug controlled release behaviours. Results showed that alginate/piroxicam beads demonstrated high encapsulation efficiency and very narrow dimensional distribution. Beads dried by MW retained shape and size distribution of the hydrated particles while drying rate was strongly increased compared to convective drying processes. Moreover, different MW irradiation regimes promoted interactions between the drug and alginate matrix, affected drug polymorphism as well as inner and surface matrix structure leading to different piroxicam release profiles. High level MW irradiation led to beads with highly porous and swellable matrix able to release piroxicam in few minutes in the intestine while convective drying produced gastro-resistant beads that exhibit sustained piroxicam release (total release in 5.5h) in intestinal environment. On these results the tandem technique prilling/MW irradiation appears to be promising to obtain alginate carrier with tailored NSAIDs release depending on drug characteristics and MW irradiation. Copyright © 2012 Elsevier Ltd. All rights reserved.

  14. A modified SILCS contraceptive diaphragm for long-term controlled release of the HIV microbicide dapivirine.

    Science.gov (United States)

    Major, Ian; Boyd, Peter; Kilbourne-Brook, Maggie; Saxon, Gene; Cohen, Jessica; Malcolm, R Karl

    2013-07-01

    There is considerable interest in developing new multipurpose prevention technologies to address women's reproductive health needs. This study describes an innovative barrier contraceptive device--based on the SILCS diaphragm--that also provides long-term controlled release of the lead candidate anti-HIV microbicide dapivirine. Diaphragm devices comprising various dapivirine-loaded polymer spring cores overmolded with a nonmedicated silicone elastomer sheath were fabricated by injection molding processes. In vitro release testing, thermal analysis and mechanical characterization were performed on the devices. A diaphragm device containing a polyoxymethylene spring core loaded with 10% w/w dapivirine provided continuous and controlled release of dapivirine over a 6-month period, with a mean in vitro daily release rate of 174 mcg/day. The mechanical properties of the new diaphragm were closely matched to the SILCS diaphragm. The study demonstrates proof of concept for a dapivirine-releasing diaphragm with daily release quantities potentially capable of preventing HIV transmission. In discontinuous clinical use, release of dapivirine may be readily extended over 1 or more years. Copyright © 2013 Elsevier Inc. All rights reserved.

  15. RAVEN Beta Release

    International Nuclear Information System (INIS)

    Rabiti, Cristian; Alfonsi, Andrea; Cogliati, Joshua Joseph; Mandelli, Diego; Kinoshita, Robert Arthur; Wang, Congjian; Maljovec, Daniel Patrick; Talbot, Paul William

    2016-01-01

    This documents the release of the Risk Analysis Virtual Environment (RAVEN) code. A description of the RAVEN code is provided, and discussion of the release process for the M2LW-16IN0704045 milestone. The RAVEN code is a generic software framework to perform parametric and probabilistic analysis based on the response of complex system codes. RAVEN is capable of investigating the system response as well as the input space using Monte Carlo, Grid, or Latin Hyper Cube sampling schemes, but its strength is focused toward system feature discovery, such as limit surfaces, separating regions of the input space leading to system failure, using dynamic supervised learning techniques. RAVEN has now increased in maturity enough for the Beta 1.0 release.

  16. RAVEN Beta Release

    Energy Technology Data Exchange (ETDEWEB)

    Rabiti, Cristian [Idaho National Lab. (INL), Idaho Falls, ID (United States); Alfonsi, Andrea [Idaho National Lab. (INL), Idaho Falls, ID (United States); Cogliati, Joshua Joseph [Idaho National Lab. (INL), Idaho Falls, ID (United States); Mandelli, Diego [Idaho National Lab. (INL), Idaho Falls, ID (United States); Kinoshita, Robert Arthur [Idaho National Lab. (INL), Idaho Falls, ID (United States); Wang, Congjian [Idaho National Lab. (INL), Idaho Falls, ID (United States); Maljovec, Daniel Patrick [Idaho National Lab. (INL), Idaho Falls, ID (United States); Talbot, Paul William [Idaho National Lab. (INL), Idaho Falls, ID (United States)

    2016-02-01

    This documents the release of the Risk Analysis Virtual Environment (RAVEN) code. A description of the RAVEN code is provided, and discussion of the release process for the M2LW-16IN0704045 milestone. The RAVEN code is a generic software framework to perform parametric and probabilistic analysis based on the response of complex system codes. RAVEN is capable of investigating the system response as well as the input space using Monte Carlo, Grid, or Latin Hyper Cube sampling schemes, but its strength is focused toward system feature discovery, such as limit surfaces, separating regions of the input space leading to system failure, using dynamic supervised learning techniques. RAVEN has now increased in maturity enough for the Beta 1.0 release.

  17. Effects of compost age on the release of nutrients

    Directory of Open Access Journals (Sweden)

    Bilal B. Al-Bataina

    2016-09-01

    Full Text Available Composted organic materials are applied to help restore disturbed soils, speed revegetation, and control erosion; these changes are generally beneficial for stormwater quality. Ensuring that nutrient release from compost is adequate for plant needs without degrading stormwater quality is important since composts release nitrogen at variable rates (1–3% of total N/yr and the leaching process can extend for many years. The aim of this work was to understand the effect of compost age on the extent and rates of nitrogen release by conducting detailed rainfall simulation studies of one compost type at three different ages. Models describing temporal changes in nitrogen release to runoff during a single storm and across multiple storms were developed and applied to the runoff data. Nitrogen content (% and bulk density of compost increased with the increase in compost age and total nitrogen release decreased with increasing compost age. The three rain simulations (storms performed on each of the three compost ages show that nitrogen release declined each day of the repeated daily storms. A first-order kinetic model was used to estimate the amount of nitrogen remaining on compost after several storms.

  18. 3D finite element analysis of stress distributions and strain energy release rates for adhesive bonded flat composite lap shear joints having pre-existing delaminations

    Energy Technology Data Exchange (ETDEWEB)

    Parida, S. K.; Pradhan, A. K. [Indian Institute of Technology, Bhubaneswar (India)

    2014-02-15

    The rate of propagation of embedded delamination in the strap adherend of lap shear joint (LSJ) made of carbon/epoxy composites has been evaluated employing three-dimensional non-linear finite elements. The delamination has been presumed to pre-exist in the thin resin layer between the first and second plies of the strap adherend. The inter-laminar peel and shear stress distributions have been studied in details and are seen to be predominantly three-dimensional in nature. The components of strain energy release rate (SERR) corresponding to the opening, sliding and cross sliding modes of delamination are significantly different at the two fronts of the embedded delamination. The sequential release of multi-point constraint (MPC) finite elements in the vicinity of the delamination fronts enables to simulate the growth of the delamination at either ends. This simulation procedure can be utilized effectively for evaluation of the status of the structural integrity of the bonded joints.

  19. An investigation of effects of modification processes on physical properties and mechanism of drug release for sustaining drug release from modified rice

    Energy Technology Data Exchange (ETDEWEB)

    Ngo, Vuong Duy; Luu, Thinh Duc; Van Vo, Toi [Pharmaceutical Engineering Laboratory, Biomedical Engineering Department, International University, Vietnam National University, Ho Chi Minh City (Viet Nam); Tran, Van-Thanh [Faculty of Pharmacy, University of Medicine and Pharmacy, Ho Chi Minh City (Viet Nam); Duan, Wei [School of Medicine, Deakin University, Pigdons Road, Waurn Ponds, Victoria (Australia); Tran, Phuong Ha-Lien, E-mail: phuong.tran1@deakin.edu.au [School of Medicine, Deakin University, Pigdons Road, Waurn Ponds, Victoria (Australia); Tran, Thao Truong-Dinh, E-mail: ttdthao@hcmiu.edu.vn [Pharmaceutical Engineering Laboratory, Biomedical Engineering Department, International University, Vietnam National University, Ho Chi Minh City (Viet Nam)

    2016-10-01

    The aim of this study was to investigate the effect of modification processes on physical properties and explain the mechanism of sustained drug release from modified rice (MR). Various types of Vietnamese rice were introduced in the study as the matrices of sustained release dosage form. Rice was thermally modified in water for a determined temperature at different times with a simple process. Then tablets containing MR and isradipine, the model drug, were prepared to investigate the capability of sustained drug release. Scanning electron microscopy (SEM) was used to determine different morphologies between MR formulations. Flow property of MR was analyzed by Hausner ratio and Carr's indices. The dissolution rate and swelling/erosion behaviors of tablets were evaluated at pH 1.2 and pH 6.8 at 37 ± 0.5 °C. The matrix tablet containing MR showed a sustained release as compared to the control. The SEM analyses and swelling/erosion studies indicated that the morphology as well as swelling/erosion rate of MR were modulated by modification time, drying method and incubation. It was found that the modification process was crucial because it could highly affect the granule morphologies and hence, leading to the change of flowability and swelling/erosion capacity for sustained release of drug. - Highlights: • Modification process affected granule morphologies and flowability of modified rice. • Modification process affected swelling/erosion capacity for drug sustained release. • Freeze-drying could decrease the erosion as well as increase the swelling rate.

  20. An investigation of effects of modification processes on physical properties and mechanism of drug release for sustaining drug release from modified rice

    International Nuclear Information System (INIS)

    Ngo, Vuong Duy; Luu, Thinh Duc; Van Vo, Toi; Tran, Van-Thanh; Duan, Wei; Tran, Phuong Ha-Lien; Tran, Thao Truong-Dinh

    2016-01-01

    The aim of this study was to investigate the effect of modification processes on physical properties and explain the mechanism of sustained drug release from modified rice (MR). Various types of Vietnamese rice were introduced in the study as the matrices of sustained release dosage form. Rice was thermally modified in water for a determined temperature at different times with a simple process. Then tablets containing MR and isradipine, the model drug, were prepared to investigate the capability of sustained drug release. Scanning electron microscopy (SEM) was used to determine different morphologies between MR formulations. Flow property of MR was analyzed by Hausner ratio and Carr's indices. The dissolution rate and swelling/erosion behaviors of tablets were evaluated at pH 1.2 and pH 6.8 at 37 ± 0.5 °C. The matrix tablet containing MR showed a sustained release as compared to the control. The SEM analyses and swelling/erosion studies indicated that the morphology as well as swelling/erosion rate of MR were modulated by modification time, drying method and incubation. It was found that the modification process was crucial because it could highly affect the granule morphologies and hence, leading to the change of flowability and swelling/erosion capacity for sustained release of drug. - Highlights: • Modification process affected granule morphologies and flowability of modified rice. • Modification process affected swelling/erosion capacity for drug sustained release. • Freeze-drying could decrease the erosion as well as increase the swelling rate.

  1. Lecithin-based microemulsions for targeted delivery of ceramide AP into the stratum corneum: formulation, characterizations, and in vitro release and penetration studies.

    Science.gov (United States)

    Sahle, Fitsum F; Metz, Hendrik; Wohlrab, Johannes; Neubert, Reinhard H H

    2013-02-01

    To improve the solubility and penetration of Ceramide AP (CER [AP]) into the stratum corneum that potentially restores the barrier function of aged and affected skin. CER [AP] microemulsions (MEs) were formulated using lecithin, Miglyol® 812 (miglyol) and water-1,2 pentandiol (PeG) mixture as amphiphilic, oily and hydrophilic components, respectively. The nanostructure of the MEs was revealed using electrical conductivity, differential scanning calorimeter (DSC) and electron paramagnetic resonance (EPR) techniques. Photon correlation spectroscopy (PCS) was used to measure the sizes and shape of ME droplets. The release and penetration of the CER into the stratum corneum was investigated in vitro using a multi-layer membrane model. The MEs exhibited excellent thermodynamic stability (>2 years) and loading capacity (0.5% CER [AP]). The pseudo-ternary phase diagrams of the MEs were obtained and PCS results showed that the droplets are spherical in shape and bigger in size. In vitro investigations showed that the MEs exhibited excellent rate and extent of release and penetration. Stable lecithin-based CER [AP] MEs that significantly enhance the solubility and penetration of CER [AP] into the stratum corneum were developed. The MEs also have better properties than the previously reported polyglycerol fatty acid surfactant-based CER [AP] MEs.

  2. Fission product release from defected nuclear reactor fuel elements

    International Nuclear Information System (INIS)

    Lewis, B.J.

    1983-01-01

    The release of gaseous (krypton and xenon) and iodine radioactive fission products from defective fuel elements is described with a semi-empirical model. The model assumes precursor-corrected 'Booth diffusional release' in the UO 2 and subsequent holdup in the fuel-to-sheath gap. Transport in the gap is separately modelled with a phenomenological rate constant (assuming release from the gap is a first order rate process), and a diffusivity constant (assuming transport in the gap is dominated by a diffusional process). Measured release data from possessing various states of defection are use in this analysis. One element (irradiated in an earlier experiment by MacDonald) was defected with a small drilled hole. A second element was machined with 23 slits while a third element (fabricated with a porous end plug) displayed through-wall sheath hydriding. Comparison of measured release data with calculated values from the model yields estimates of empirical diffusion coefficients for the radioactive species in the UO 2 (1.56 x 10 -10 to 7.30 x 10 -9 s -1 ), as well as escape rate constants (7.85 x 10 -7 to 3.44 x 10 -5 s -1 ) and diffusion coefficients (3.39 x 10 -5 to 4.88 x 10 -2 cm 2 /s) for these in the fuel-to-sheath gap. Analyses also enable identification of the various rate-controlling processes operative in each element. For the noble gas and iodine species, the rate-determining process in the multi-slit element is 'Booth diffusion'; however, for the hydrided element an additional delay results from diffusional transport in the fuel-to-heath gap. Furthermore, the iodine species exhibit an additional holdup in the drilled element because of significant trapping on the fuel and/or sheath surfaces. Using experimental release data and applying the theoretical results of this work, a systematic procedure is proposed to characterize fuel failures in commercial power reactors (i.e., the number of fuel failures and average leak size)

  3. Metal lost and found: dissipative uses and releases of copper in the United States 1975-2000.

    Science.gov (United States)

    Lifset, Reid J; Eckelman, Matthew J; Harper, E M; Hausfather, Zeke; Urbina, Gonzalo

    2012-02-15

    Metals are used in a variety of ways, many of which lead to dissipative releases to the environment. Such releases are relevant from both a resource use and an environmental impact perspective. We present a historical analysis of copper dissipative releases in the United States from 1975 to 2000. We situate all dissipative releases in copper's life cycle and introduce a conceptual framework by which copper dissipative releases may be categorized in terms of intentionality of use and release. We interpret our results in the context of larger trends in production and consumption and government policies that have served as drivers of intentional copper releases from the relevant sources. Intentional copper releases are found to be both significant in quantity and highly variable. In 1975, for example, the largest source of intentional releases was from the application of copper-based pesticides, and this decreased more than 50% over the next 25 years; all other sources of intentional releases increased during that period. Overall, intentional copper releases decreased by approximately 15% from 1975 to 2000. Intentional uses that are unintentionally released such as copper from roofing, increased by the same percentage. Trace contaminant sources such as fossil fuel combustion, i.e., sources where both the use and the release are unintended, increased by nearly 50%. Intentional dissipative uses are equivalent to 60% of unintentional copper dissipative releases and more than five times that from trace sources. Dissipative copper releases are revealed to be modest when compared to bulk copper flows in the economy, and we introduce a metric, the dissipation index, which may be considered an economy-wide measure of resource efficiency for a particular substance. We assess the importance of dissipative releases in the calculation of recycling rates, concluding that the inclusion of dissipation in recycling rate calculations has a small, but discernible, influence, and should

  4. A description of bubble growth and gas release of helium implanted tungsten

    International Nuclear Information System (INIS)

    Sharafat, S.; Hu, Q.; Ghoniem, N.; Tkahashi, A.

    2007-01-01

    Full text of publication follows: Bubble growth and gas release during annealing of helium implanted tungsten is described using a Kinetic Monte Carlo approach. The implanted spatial profiles of stable bubble nuclei are first determined using the Kinetic Rate Theory based helium evolution code, HEROS. The effects of implantation energy, temperature, and bias forces, such as temperature- and stress gradients on bubble migration and coalescence are investigated to explain experimental gas release measurements. This comprehensive helium bubble evolution and release model, demonstrates the impact of near surface (< 1 um) versus deep helium implantation on bubble evolution. Near surface implanted helium bubbles readily attain large equilibrium sizes, while matrix bubbles remain small with high helium pressures. Using the computer simulation, the various stages of helium bubble nucleation, growth, coalescence, and migration are demonstrated and compared with available experimental results. (authors)

  5. Alternate source term models for Yucca Mountain performance assessment based on natural analog data and secondary mineral solubility

    International Nuclear Information System (INIS)

    Murphy, W.M.; Codell, R.B.

    1999-01-01

    Performance assessment calculations for the proposed high level radioactive waste repository at Yucca Mountain, Nevada, were conducted using the Nuclear Regulatory Commission Total-System Performance Assessment (TPA 3.2) code to test conceptual models and parameter values for the source term based on data from the Pena Blanca, Mexico, natural analog site and based on a model for coprecipitation and solubility of secondary schoepite. In previous studies the value for the maximum constant oxidative alteration rate of uraninite at the Nopal I uranium body at Pena Blanca was estimated. Scaling this rate to the mass of uranium for the proposed Yucca Mountain repository yields an oxidative alteration rate of 22 kg/y, which was assumed to be an upper limit on the release rate from the proposed repository. A second model was developed assuming releases of radionuclides are based on the solubility of secondary schoepite as a function of temperature and solution chemistry. Releases of uranium are given by the product of uranium concentrations at equilibrium with schoepite and the flow of water through the waste packages. For both models, radionuclides other than uranium and those in the cladding and gap fraction were modeled to be released at a rate proportional to the uranium release rate, with additional elemental solubility limits applied. Performance assessment results using the Pena Blanca oxidation rate and schoepite solubility models for Yucca Mountain were compared to the TPA 3.2 base case model, in which release was based on laboratory studies of spent fuel dissolution, cladding and gap release, and solubility limits. Doses calculated using the release rate based on natural analog data and the schoepite solubility models were smaller than doses generated using the base case model. These results provide a degree of confidence in safety predictions using the base case model and an indication of how conservatism in the base case model may be reduced in future analyses

  6. Alternate source term models for Yucca Mountain performance assessment based on natural analog data and secondary mineral solubility

    Energy Technology Data Exchange (ETDEWEB)

    Murphy, W.M.; Codell, R.B.

    1999-07-01

    Performance assessment calculations for the proposed high level radioactive waste repository at Yucca Mountain, Nevada, were conducted using the Nuclear Regulatory Commission Total-System Performance Assessment (TPA 3.2) code to test conceptual models and parameter values for the source term based on data from the Pena Blanca, Mexico, natural analog site and based on a model for coprecipitation and solubility of secondary schoepite. In previous studies the value for the maximum constant oxidative alteration rate of uraninite at the Nopal I uranium body at Pena Blanca was estimated. Scaling this rate to the mass of uranium for the proposed Yucca Mountain repository yields an oxidative alteration rate of 22 kg/y, which was assumed to be an upper limit on the release rate from the proposed repository. A second model was developed assuming releases of radionuclides are based on the solubility of secondary schoepite as a function of temperature and solution chemistry. Releases of uranium are given by the product of uranium concentrations at equilibrium with schoepite and the flow of water through the waste packages. For both models, radionuclides other than uranium and those in the cladding and gap fraction were modeled to be released at a rate proportional to the uranium release rate, with additional elemental solubility limits applied. Performance assessment results using the Pena Blanca oxidation rate and schoepite solubility models for Yucca Mountain were compared to the TPA 3.2 base case model, in which release was based on laboratory studies of spent fuel dissolution, cladding and gap release, and solubility limits. Doses calculated using the release rate based on natural analog data and the schoepite solubility models were smaller than doses generated using the base case model. These results provide a degree of confidence in safety predictions using the base case model and an indication of how conservatism in the base case model may be reduced in future analyses.

  7. Intuitive Understanding of Base Rates

    DEFF Research Database (Denmark)

    Austin, Laurel

    Purpose: This study examines whether physicians and other adults intuitively understand that the probability a positive test result is a true positive (positive predictive value, PPV) depends on the base rate of disease in the population tested. In particular, this research seeks to examine perce...

  8. On the exfoliating polymeric cellular dosage forms for immediate drug release.

    Science.gov (United States)

    Blaesi, Aron H; Saka, Nannaji

    2016-06-01

    The most prevalent pharmaceutical dosage forms at present-the oral immediate-release tablets and capsules-are granular solids. Though effective in releasing drug rapidly, development and manufacture of such dosage forms are fraught with difficulties inherent to particulate processing. Predictable dosage form manufacture could be achieved by liquid-based processing, but cast solid dosage forms are not suitable for immediate drug release due to their resistance to fluid percolation. To overcome this limitation, we have recently introduced cellular dosage forms that can be readily prepared from polymeric melts. It has been shown that open-cell structures comprising polyethylene glycol 8000 (PEG 8k) excipient and a drug exfoliate upon immersion in a dissolution medium. The drug is then released rapidly due to the large specific surface area of the exfoliations. In this work, we vary the molecular weight of the PEG excipient and investigate its effect on the drug release kinetics of structures with predominantly open-cell topology. We demonstrate that the exfoliation rate decreases substantially if the excipient molecular weight is increased from 12 to 100kg/mol, which causes the drug dissolution time to increase by more than a factor of ten. A model is then developed to elucidate the exfoliation behavior of cellular structures. Diverse transport processes are considered: percolation due to capillarity, diffusion of dissolution medium through the cell walls, and viscous flow of the saturated excipient. It is found that the lower exfoliation rate and the longer dissolution time of the dosage forms with higher excipient molecular weight are primarily due to the greater viscosity of the cell walls after fluid penetration. Copyright © 2016 Elsevier B.V. All rights reserved.

  9. The role of a detailed aqueous phase source release model in the LANL area G performance assessment

    Energy Technology Data Exchange (ETDEWEB)

    Vold, E.L.; Shuman, R.; Hollis, D.K. [Los Alamos National Lab., NM (United States)] [and others

    1995-12-31

    A preliminary draft of the Performance Assessment for the Los Alamos National Laboratory (LANL) low-level radioactive waste disposal facility at Area G is currently being completed as required by Department of Energy orders. A detailed review of the inventory data base records and the existing models for source release led to the development of a new modeling capability to describe the liquid phase transport from the waste package volumes. Nuclide quantities are sorted down to four waste package release categories for modeling: rapid release, soil, concrete/sludge, and corrosion. Geochemistry for the waste packages was evaluated in terms of the equilibrium coefficients, Kds, and elemental solubility limits, Csl, interpolated from the literature. Percolation calculations for the base case closure cover show a highly skewed distribution with an average of 4 mm/yr percolation from the disposal unit bottom. The waste release model is based on a compartment representation of the package efflux, and depends on package size, percolation rate or Darcy flux, retardation coefficient, and moisture content.

  10. Polymer based microspheres of aceclofenac as sustained release parenterals for prolonged anti-inflammatory effect

    Energy Technology Data Exchange (ETDEWEB)

    Kaur, Manpreet; Sharma, Sumit; Sinha, VR, E-mail: sinha_vr@rediffmail.com

    2017-03-01

    Poly(lactic-co-glycolic acid) (PLGA) (75:25) and polycaprolactone (PCL) microspheres were fabricated for prolonged release of aceclofenac by parenteral administration. Microspheres encapsulating aceclofenac were designed to release the drug at controlled rate for around one month. Biodegradable microspheres were prepared by solvent emulsification evaporation method in different polymer:drug ratios (1:1, 2:1 and 3:1). After drug loading, PLGA and PCL microspheres showed a controlled size distribution with an average size of 11.75 μm and 3.81 μm respectively and entrapment efficiency in the range of 90 ± 0.72% to 91.06 ± 4.01% with PLGA and 83.01 ± 2.13% to 90.4 ± 2.11% with PCL. Scanning electron microscopy has confirmed good spherical structures of microspheres. The percent yield of biodegradable polymeric microspheres ranged between 30.95 ± 10.14% to 92.84 ± 3.15% and 47.33 ± 4.72% to 80 ± 3.60% for PLGA and PCL microspheres respectively. PLGA microspheres followed Higuchi release pattern while Korsmeyer-Peppas explained the release pattern of PCL microspheres. Stability studies of microspheres were also carried out by storing the preparations at 2-8 °C for 30, 60 and 90 days and evaluating them for entrapment efficiency, residual drug content and polymer drug compatability. In-vivo studies showed significant anti-inflammatory activity of microspheres upto 48 hours using the carrageenan induced rat paw oedema model. - Highlights: • PLGA and PCL polymeric microspheres for parenteral prolonged drug delivery system were formulated. • Polymeric microspheres were characterized physically and drug excipient incompatability. • Three months accelerated stability studies were carried for drug loaded polymeric microspheres. • Pharmacodynamic studies prove the rationality of sustained therapeutic effect of designed drug delivery system.

  11. Hydrogen peroxide release and acid-base status in exhaled breath condensate at rest and after maximal exercise in young, healthy subjects

    Directory of Open Access Journals (Sweden)

    Marek E

    2009-12-01

    Full Text Available Abstract Objective Exhaled breath condensate (EBC contains among a large number of mediators hydrogen peroxide (H2O2 as a marker of airway inflammation and oxidative stress. Similarly EBC pH also changes in respiratory diseases. It was the aim of our investigation to prove if hydrogen peroxide release and changes in pH of EBC changes with exercise. Methods EBC was collected from 100 litres exhaled air along with samples of arterialized blood of 16 healthy subjects (9 males, 7 females, age 23 ± 1 years. EBC hydrogen peroxide was analyzed with EcoCheck amperometer (FILT, Berlin. The rate of H2O2 release was calculated from the concentration and collection time. pH and PCO2 in blood and in EBC were measured with the Radiometer blood gas analyzer, EBC was equilibrated with a gas mixture (5% CO2 in O2. The bicarbonate concentration was calculated according to the law of mass action for CO2 and HCO3- (pK = 6.1. Results H2O2 concentration in EBC was 190 ± 109 nmol/l, and H2O2 release at rest was 31.0 ± 18.3 pmol/min. At maximal exercise, the H2O = concentration in EBC increased to 250 ± 120 nmol/l, and H2O2 release significantly increased at maximal exercise to 84.4 ± 39.9 pmol/min (P 2 equilibrated EBC was at 6.08 ± 0.23 and the [HCO3 -] was 1.03 ± 0.40 mmol/l. At maximum exercise, pH 6.18 ± 0.17 and [HCO3-] 1.23 ± 0.30 mmol/l remained almost unaltered. Conclusions The rate of H2O2 release in EBC increased during exhausting exercise (external load: 300 Watt by a factor of 2, whereas the pH and the bicarbonate concentration of the EBC, equilibrated with 5% CO2 at 37°C were not significantly altered. It has to be proven by further experiments whether there is a linear relationship between the rates of H2O2 release in EBC in graded submaximal exercise.

  12. Modulating drug release from gastric-floating microcapsules through spray-coating layers.

    Directory of Open Access Journals (Sweden)

    Wei Li Lee

    Full Text Available Floating dosage forms with prolonged gastric residence time have garnered much interest in the field of oral delivery. However, studies had shown that slow and incomplete release of hydrophobic drugs during gastric residence period would reduce drug absorption and cause drug wastage. Herein, a spray-coated floating microcapsule system was developed to encapsulate fenofibrate and piroxicam, as model hydrophobic drugs, into the coating layers with the aim of enhancing and tuning drug release rates. Incorporating fenofibrate into rubbery poly(caprolactone (PCL coating layer resulted in a complete and sustained release for up to 8 h, with outermost non-drug-holding PCL coating layer serving as a rate-controlling membrane. To realize a multidrug-loaded system, both hydrophilic metformin HCl and hydrophobic fenofibrate were simultaneously incorporated into these spray-coated microcapsules, with metformin HCl and fenofibrate localized within the hollow cavity of the capsule and coating layer, respectively. Both drugs were observed to be completely released from these coated microcapsules in a sustained manner. Through specific tailoring of coating polymers and their configurations, piroxicam loaded in both the outer polyethylene glycol and inner PCL coating layers was released in a double-profile manner (i.e. an immediate burst release as the loading dose, followed by a sustained release as the maintenance dose. The fabricated microcapsules exhibited excellent buoyancy in simulated gastric fluid, and provided controlled and sustained release, thus revealing its potential as a rate-controlled oral drug delivery system.

  13. Production of an experimental bonding agent containing doxycyicline as matrix metalloproteinase inhibitor, and its release rate

    Directory of Open Access Journals (Sweden)

    Ghavam M

    2010-01-01

    Full Text Available Background and Aims: In spite of the advances achieved in the field of dentin adhesives, the longevity of bond to dentin is still a challenge. According to recent studies, Matrix Metaloproteinase (MMP inhibitors can increase clinical longevity of bonding and decrease leakage. The aim of this study was to evaluate the amount and pattern of doxycycline release from an experimental dentin adhesive containing this MMP inhibitor. Materials and Methods: In this experimental study, specimens containing 0.25 and 0.5 loading percent of doxycycline in an experimental monomer were prepared in cylindrical moulds of 12 mm diameter and 2 mm thickness. The adhesive monomer was composed of 12 wt% Bis-GMA, 10 wt% TMPTMA, 28 wt% HEMA and 50 wt% ethanol. Camphorquinone and amine were used as initiators. Results: Addition of 0.25 and 0.5 w% doxycycline showed linear release in both groups. Increasing the loading percent of doxycycline caused more release. The release continued during the test period. Conclusion: Doxycycline release was observed from the experimental adhesive. Further studies in this field will help in preparing adhesive systems with more clinical longevity.

  14. Workload Control with Continuous Release

    NARCIS (Netherlands)

    Phan, B. S. Nguyen; Land, M. J.; Gaalman, G. J. C.

    2009-01-01

    Workload Control (WLC) is a production planning and control concept which is suitable for the needs of make-to-order job shops. Release decisions based on the workload norms form the core of the concept. This paper develops continuous time WLC release variants and investigates their due date

  15. Decomposition and nutrient release of leguminous plants in coffee agroforestry systems

    Directory of Open Access Journals (Sweden)

    Eduardo da Silva Matos

    2011-02-01

    Full Text Available Leguminous plants used as green manure are an important nutrient source for coffee plantations, especially for soils with low nutrient levels. Field experiments were conducted in the Zona da Mata of Minas Gerais State, Brazil to evaluate the decomposition and nutrient release rates of four leguminous species used as green manures (Arachis pintoi, Calopogonium mucunoides, Stizolobium aterrimum and Stylosanthes guianensis in a coffee agroforestry system under two different climate conditions. The initial N contents in plant residues varied from 25.7 to 37.0 g kg-1 and P from 2.4 to 3.0 g kg-1. The lignin/N, lignin/polyphenol and (lignin+polyphenol/N ratios were low in all residues studied. Mass loss rates were highest in the first 15 days, when 25 % of the residues were decomposed. From 15 to 30 days, the decomposition rate decreased on both farms. On the farm in Pedra Dourada (PD, the decomposition constant k increased in the order C. mucunoides < S. aterrimum < S. guianensis < A. pintoi. On the farm in Araponga (ARA, there was no difference in the decomposition rate among leguminous plants. The N release rates varied from 0.0036 to 0.0096 d-1. Around 32 % of the total N content in the plant material was released in the first 15 days. In ARA, the N concentration in the S. aterrimum residues was always significantly higher than in the other residues. At the end of 360 days, the N released was 78 % in ARA and 89 % in PD of the initial content. Phosphorus was the most rapidly released nutrient (k values from 0.0165 to 0.0394 d-1. Residue decomposition and nutrient release did not correlate with initial residue chemistry and biochemistry, but differences in climatic conditions between the two study sites modified the decomposition rate constants.

  16. Amphiphilic polymer based on fluoroalkyl and PEG side chains for fouling release coating

    Science.gov (United States)

    Cong, W. W.; Wang, K.; Yu, X. Y.; Zhang, H. Q.; Lv, Z.; Gui, T. J.

    2017-12-01

    Under static conditions, fouling release coating could not express good release property to marine organisms. Amphiphilic polymer with mixture of fluorinated monomer and short side group of polyethylene glycol (PEG) was synthesized. And also we studied the ability of amphiphilic polymer to influence the surface properties and how it controlled the adhesion of marine organisms to coated surfaces. By incorporating fluorinated monomer and PEG side chain into the polymer, the effect of incorporating both polar and non-polar groups on fouling-release coating could be studied. The dry surface was characterized by three-dimensional digital microscopy and scanning electron microscopy (SEM), and the morphology of the amphiphilic fouling release coating showed just like flaky petal. The amphiphilic polymer in fouling release coating tended to reconstruct in water, and the ability was examined by static contact angle, which was smaller than the PDMS (polydimethylsiloxane) fouling release coating. Also surface energy was calculated by three solvents, and surface energy of amphiphilic fouling release coating was higher than that of the PDMS fouling release coating. To understand more about its fouling release property, seawater exposure method was adopted in gulf of Qingdao port. Fewer diatoms Navicula were found in biofilm after using amphiphilic fouling release coating. In general, coating containing both PEG and fluorinated side chain possessed certain fouling release property.

  17. Combined Effects of Supersaturation Rates and Doses on the Kinetic-Solubility Profiles of Amorphous Solid Dispersions Based on Water-Insoluble Poly(2-hydroxyethyl methacrylate) Hydrogels.

    Science.gov (United States)

    Schver, Giovanna C R M; Lee, Ping I

    2018-05-07

    Under nonsink dissolution conditions, the kinetic-solubility profiles of amorphous solid dispersions (ASDs) based on soluble carriers typically exhibit so-called "spring-and-parachute" concentration-time behaviors. However, the kinetic-solubility profiles of ASDs based on insoluble carriers (including hydrogels) are known to show sustained supersaturation during nonsink dissolution through a matrix-regulated diffusion mechanism by which the supersaturation of the drug is built up gradually and sustained over an extended period without any dissolved polymers acting as crystallization inhibitors. Despite previous findings demonstrating the interplay between supersaturation rates and total doses on the kinetic-solubility profiles of soluble amorphous systems (including ASDs based on dissolution-regulated releases from soluble polymer carriers), the combined effects of supersaturation rates and doses on the kinetic-solubility profiles of ASDs based on diffusion-regulated releases from water-insoluble carriers have not been investigated previously. Thus, the objective of this study is to examine the impacts of total doses and supersaturation-generation rates on the resulting kinetic-solubility profiles of ASDs based on insoluble hydrogel carriers. We employed a previously established ASD-carrier system based on water-insoluble-cross-linked-poly(2-hydroxyethyl methacrylate) (PHEMA)-hydrogel beads and two poorly water soluble model drugs: the weakly acidic indomethacin (IND) and the weakly basic posaconazole (PCZ). Our results show clearly for the first time that by using the smallest-particle-size fraction and a high dose (i.e., above the critical dose), it is indeed possible to significantly shorten the duration of sustained supersaturation in the kinetic-solubility profile of an ASD based on a water-insoluble hydrogel carrier, such that it resembles the spring-and-parachute dissolution profiles normally associated with ASDs based on soluble carriers. This generates

  18. Control of drug releasing from biodegradable polymer drug delivery system by gamma-ray irradiation

    International Nuclear Information System (INIS)

    Yoshioka, Sumie; Aso, Yukio; Kojima, Shigeo

    1999-01-01

    In order to introduce the drug to the target organ, we developed a gel to control the drug releasing velocity by response to change of temperature by means of γ-ray irradiation to gelatin-GMA modified dextran mixture aqueous solution. A certain level of molecular weight of drug is necessary. The response to the temperature (change of drug releasing velocity) was affected by the concentration of gelatin and the modification rate of GMA. The Higuchi equation was applied to the releasing of β-galactosidase from gelatin-dextran gel and the releasing velocity was calculated. The releasing velocity decreased with increasing GMA modification rate at 37degC and 15degC. The releasing velocity of β-galactosidase decreased with increasing the concentration of gelatin at 15degC, but the velocity increased with increasing the concentration at 37degC. These results indicated that the good drug releasing conditions are obtained by controlling the GMA modification rate and the concentration of gelatin. (S.Y.)

  19. Controlled Release of Damascone from Poly(styrene-co-maleic anhydride-based Bioconjugates in Functional Perfumery

    Directory of Open Access Journals (Sweden)

    Andreas Herrmann

    2013-02-01

    Full Text Available Poly(styrene-co-maleic anhydrides were modified with poly(propylene oxide (PO-co-ethylene oxide (EO side chains (Jeffamine® with different EO/PO molar ratios, varying between 0.11 and 3.60. These copolymers were then further functionalized with a β-mercapto ketone of δ-damascone. The obtained poly(maleic acid monoamide-based β-mercapto ketones were then studied as delivery systems for the controlled release of δ-damascone by retro 1,4-addition. The release of δ-damascone, a volatile, bioactive molecule of the family of rose ketones, was studied by dynamic headspace analysis above a cotton surface after deposition of a cationic surfactant containing fabric softening formulation, as a function of the ethylene oxide (EO/propylene oxide (PO molar ratio of the grafted copolymer side chains. The polarity of the EO/PO side chain influenced the release efficiency of the damascone in a typical fabric softening application. PO-rich copolymers and the corresponding poly(styrene-co-maleic anhydride without Jeffamine® side chains were found to be less efficient for the desired fragrance release than the corresponding bioconjugate with a EO/PO ratio of 3.60 in the side chain. This copolymer conjugate seemed to represent a suitable balance between hydrophilicity and hydrophobicity to favor the release of the δ-damascone and to improve the deposition of the conjugate from an aqueous environment onto a cotton surface.

  20. CRRIS, Health Risk Assessment from Atmospheric Releases of Radionuclides

    International Nuclear Information System (INIS)

    1999-01-01

    1 - Description of program or function: CRRIS consists of eight fully integrated computer codes which calculate environmental transport of atmospheric releases of radionuclides and resulting doses and health risks to individuals or populations. Each code may be used alone for various assessment applications. Because of its modular structure, CRRIS allows assessments to be tailored to the user's needs. Radionuclides are handled by CRRIS either in terms of the released radionuclides or the exposure radionuclides which consist of both the released nuclides and decay products that build up during environmental transport. Atmospheric dispersion calculations are performed by the ANEMOS computer code for distances less than 100 km and the RETADD-II computer code regional-scale distances. Both codes estimate annual-average air concentrations and ground deposition rates by location. SUMIT will translate and scale multiple ANEMOS runs onto a master grid. TERRA reads radionuclide air concentrations and deposition rates to estimate concentrations of radionuclides in food and surface soil. Radiologic decay and ingrowth, soil leaching, and transport through the food chain are included in the calculations. MLSOIL computes an effective radionuclide ground-surface concentration to be used in computing external health effects. The five-layer model of radionuclide transport through soil in MLSOIL provides an alternative to the single-layer model used in TERRA. DFSOIL computes dose factors used in MLSOIL to compute doses from the five soil layers and from the ground surface. ANDROS reads environmental concentrations of radionuclides computed by the other CRRIS codes and produces tables of doses and risks to individuals or populations from atmospheric releases of radionuclides. 2 - Method of solution: SUMIT performs geometric interpolation. TERRA and MLSOIL are terrestrial transport compartment models. DFSOIL computes soil-layer-specific dose factors based on the point-kernel method

  1. Local sustained-release delivery systems of the antibiofilm agent thiazolidinedione-8 for prevention of catheter-associated urinary tract infections.

    Science.gov (United States)

    Shenderovich, Julia; Feldman, Mark; Kirmayer, David; Al-Quntar, Abed; Steinberg, Doron; Lavy, Eran; Friedman, Michael

    2015-05-15

    Thiazolidinedione-8 (TZD-8) is an anti-quorum-sensing molecule that has the potential to effectively prevent catheter-associated urinary tract infections, a major healthcare challenge. Sustained-release drug-delivery systems can enhance drugs' therapeutic potential, by maintaining their therapeutic level and reducing their side effects. Varnishes for sustained release of TZD-8 based on ethylcellulose or ammonio methacrylate copolymer type A (Eudragit(®) RL) were developed. The main factors affecting release rate were found to be film thickness and presence of a hydrophilic or swellable polymer in the matrix. The release mechanism of ethylcellulose-based systems matched the Higuchi model. Selected varnishes were retained on catheters for at least 8 days. Sustained-release delivery systems of TZD-8 were active against Candida albicans biofilms. The present study demonstrates promising results en route to developing applications for the prevention of catheter-associated infections. Copyright © 2015 Elsevier B.V. All rights reserved.

  2. Swelling and drug release behavior of poly(2-hydroxyethyl methacrylate/itaconic acid) copolymeric hydrogels obtained by gamma irradiation

    International Nuclear Information System (INIS)

    Tomic, S.Lj.; Micic, M.M.; Filipovic, J.M.; Suljovrujic, E.H.

    2007-01-01

    The new copolymeric hydrogels based on 2-hydroxyethyl methacrylate (HEMA) and itaconic acid (IA) were prepared by gamma irradiation, in order to examine the potential use of these hydrogels in controlled drug release systems. The influence of IA content in the gel on the swelling characteristics and the releasing behavior of hydrogels, and the effect of different drugs, theophylline (TPH) and fenethylline hydrochloride (FE), on the releasing behavior of P(HEMA/IA) matrix were investigated in vitro. The diffusion exponents for swelling and drug release indicate that the mechanisms of buffer uptake and drug release are governed by Fickian diffusion. The swelling kinetics and, therefore, the release rate depends on the matrix swelling degree. The drug release was faster for copolymeric hydrogels with a higher content of itaconic acid. Furthermore, the drug release for TPH as model drug was faster due to a smaller molecular size and a weaker interaction of the TPH molecules with(in) the P(HEMA/IA) copolymeric networks

  3. [In vitro drug release behavior of carrier made of porous glass ceramics].

    Science.gov (United States)

    Wang, De-ping; Huang, Wen-hai; Zhou, Nai

    2002-09-01

    To conduct the in vitro test on drug release of rifampin encapsulated in a carrier made of porous phosphate glass ceramics and to analyze main factors which affect the drug release rate. A certain quantitative of rifampin was sealed in a hollow cylindrical capsule which consisted of chopped calcium phosphate crystal fiber obtained from glass crystallization. The rifampin concentration was measured in the simulated physiological solution in which the capsule soaked. Rifampin could be released in a constant rate from the porous glass ceramic carrier in a long time. The release rate was dependent on the size of crystal fiber and the wall thickness of the capsule. This kind of calcium phosphate glass ceramics can be a candidate of the carrier materials used as long term drug therapy after osteotomy surgery.

  4. Biomimetic synthesized chiral mesoporous silica: Structures and controlled release functions as drug carrier

    Energy Technology Data Exchange (ETDEWEB)

    Li, Jing; Xu, Lu, E-mail: xl2013109@163.com; Yang, Baixue; Bao, Zhihong; Pan, Weisan; Li, Sanming, E-mail: li_sanming2013@163.com

    2015-10-01

    This work initially illustrated the formation mechanism of chiral mesoporous silica (CMS) in a brand new insight named biomimetic synthesis. Three kinds of biomimetic synthesized CMS (B-CMS, including B-CMS1, B-CMS2 and B-CMS3) were prepared using different pH or stirring rate condition, and their characteristics were tested with transmission electron microscope and small angle X-ray diffraction. The model drug indomethacin was loaded into B-CMS and drug loading content was measured using ultraviolet spectroscopy. The result suggested that pH condition influenced energetics of self-assembly process, mainly packing energetics of the surfactant, while stirring rate was the more dominant factor to determine particle length. In application, indomethacin loading content was measured to be 35.3%, 34.8% and 35.1% for indomethacin loaded B-CMS1, indomethacin loaded B-CMS2 and indomethacin loaded B-CMS3. After loading indomethacin into B-CMS carriers, surface area, pore volume and pore diameter of B-CMS carriers were reduced. B-CMS converted crystalline state of indomethacin to amorphous state, leading to the improved indomethacin dissolution. B-CMS1 controlled drug release without burst-release, while B-CMS2 and B-CMS3 released indomethacin faster than B-CMS1, demonstrating that the particle length, the ordered lever of multiple helixes, the curvature degree of helical channels and pore diameter greatly contributed to the release behavior of indomethacin loaded B-CMS. - Highlights: • Chiral mesoporous silica was synthesized using biomimetic method. • pH influenced energetics of self-assembly process of chiral mesoporous silica. • Stirring rate determined the particle length of chiral mesoporous silica. • Controlled release behaviors of chiral mesoporous silica varied based on structures.

  5. Biomimetic synthesized chiral mesoporous silica: Structures and controlled release functions as drug carrier

    International Nuclear Information System (INIS)

    Li, Jing; Xu, Lu; Yang, Baixue; Bao, Zhihong; Pan, Weisan; Li, Sanming

    2015-01-01

    This work initially illustrated the formation mechanism of chiral mesoporous silica (CMS) in a brand new insight named biomimetic synthesis. Three kinds of biomimetic synthesized CMS (B-CMS, including B-CMS1, B-CMS2 and B-CMS3) were prepared using different pH or stirring rate condition, and their characteristics were tested with transmission electron microscope and small angle X-ray diffraction. The model drug indomethacin was loaded into B-CMS and drug loading content was measured using ultraviolet spectroscopy. The result suggested that pH condition influenced energetics of self-assembly process, mainly packing energetics of the surfactant, while stirring rate was the more dominant factor to determine particle length. In application, indomethacin loading content was measured to be 35.3%, 34.8% and 35.1% for indomethacin loaded B-CMS1, indomethacin loaded B-CMS2 and indomethacin loaded B-CMS3. After loading indomethacin into B-CMS carriers, surface area, pore volume and pore diameter of B-CMS carriers were reduced. B-CMS converted crystalline state of indomethacin to amorphous state, leading to the improved indomethacin dissolution. B-CMS1 controlled drug release without burst-release, while B-CMS2 and B-CMS3 released indomethacin faster than B-CMS1, demonstrating that the particle length, the ordered lever of multiple helixes, the curvature degree of helical channels and pore diameter greatly contributed to the release behavior of indomethacin loaded B-CMS. - Highlights: • Chiral mesoporous silica was synthesized using biomimetic method. • pH influenced energetics of self-assembly process of chiral mesoporous silica. • Stirring rate determined the particle length of chiral mesoporous silica. • Controlled release behaviors of chiral mesoporous silica varied based on structures

  6. Evaluation of Controlled Release Urea on the Dynamics of Nitrate, Ammonium, and Its Nitrogen Release in Black Soils of Northeast China

    Directory of Open Access Journals (Sweden)

    Xin Tong

    2018-01-01

    Full Text Available Controlled release urea (CRU is considered to enhance crop yields while alleviating negative environmental problems caused by the hazardous gas emissions that are associated with high concentrations of ammonium (NH4+ and nitrate (NO3− in black soils. Short-term effects of sulfur-coated urea (SCU and polyurethane-coated urea (PCU, compared with conventional urea, on NO3− and NH4+ in black soils were studied through the buried bag experiment conducted in an artificial climate chamber. We also investigated nitrogen (N release kinetics of CRU and correlations between the cumulative N release rate and concentrations of NO3− and NH4+. CRU can reduce concentrations of NO3− and NH4+, and PCU was more effective in maintaining lower soil NO3−/NH4+ ratios than SCU and U. Parabolic equation could describe the kinetics of NO3− and NH4+ treated with PCU. The Elovich equation could describe the kinetics of NO3− and NH4+ treated with SCU. The binary linear regression model was established to predict N release from PCU because of significant correlations between the cumulative N release rate and concentrations of NO3− and NH4+. These results provided a methodology and data support for characterizing and predicting the N release from PCU in black soils.

  7. PEG modulated release of etanidazole from implantable PLGA/PDLA discs.

    Science.gov (United States)

    Wang, Fangjing; Lee, Timothy; Wang, Chi-Hwa

    2002-09-01

    In this work, etanidazole (one type of hypoxic radiosensitizer) is encapsulated into spray dried poly(D),L-lactide-co-glycolide) (PLGA) microspheres and then compressed into discs for controlled release applications. Etanidazole is characterized by intracellular glutathione depletion and glutathione transferases inhibition, thereby enhancing sensitivity to radiation. It is also cytotoxic to tumor cells and can chemosensitize some alkylating agents by activating their tumor cell killing capabilities. We observed the release characteristics of etanidazole in the dosage forms of microspheres and discs, subjected to different preparation conditions. The release characteristics, morphology changes, particle size, and encapsulation efficiency of microspheres are also investigated. The release rate of etanidazole from implantable discs (13 mm in diameter, 1 mm in thickness, fabricated by a press) is much lower than microspheres due to the reduced specific surface. After the initial burst of 1% release for the first day, the cumulative release within the first week is less than 2% until a secondary burst of release (caused by polymer degradation) occurs after one month. Some key preparation conditions such as drug loadings, disc thickness and diameter, and compression pressure can affect the initial burst of etanidazole from the discs. However, none of them can significantly make the release more uniform. In contrast, the incorporation of polyethylene glycol (PEG) can greatly enhance the release rate of discs and also reduces the secondary burst effect, thereby achieving a sustained release for about 2 months.

  8. In Vivo Imaging of the Stability and Sustained Cargo Release of an Injectable Amphipathic Peptide-Based Hydrogel.

    Science.gov (United States)

    Oyen, Edith; Martin, Charlotte; Caveliers, Vicky; Madder, Annemieke; Van Mele, Bruno; Hoogenboom, Richard; Hernot, Sophie; Ballet, Steven

    2017-03-13

    Hydrogels are promising materials for biomedical applications such as tissue engineering and controlled drug release. In the past two decades, the peptide hydrogel subclass has attracted an increasing level of interest from the scientific community because of its numerous advantages, such as biocompatibility, biodegradability, and, most importantly, injectability. Here, we report on a hydrogel consisting of the amphipathic hexapeptide H-FEFQFK-NH 2 , which has previously shown promising in vivo properties in terms of releasing morphine. In this study, the release of a small molecule, a peptide, and a protein cargo as representatives of the three major drug classes is directly visualized by in vivo fluorescence and nuclear imaging. In addition, the in vivo stability of the peptide hydrogel system is investigated through the use of a radiolabeled hydrogelator sequence. Although it is shown that the hydrogel remains present for several days, the largest decrease in volume takes place within the first 12 h of subcutaneous injection, which is also the time frame wherein the cargos are released. Compared to the situation in which the cargos are injected in solution, a prolonged release profile is observed up to 12 h, showing the potential of our hydrogel system as a scaffold for controlled drug delivery. Importantly, this study elucidates the release mechanism of the peptide hydrogel system that seems to be based on erosion of the hydrogel providing a generally applicable controlled release platform for small molecule, peptide, and protein drugs.

  9. Nitrogen and phosphorus release from organic wastes and suitability as bio-based fertilizers in a circular economy.

    Science.gov (United States)

    Case, S D C; Jensen, L S

    2017-11-22

    The drive to a more circular economy has created increasing interest in recycling organic wastes as bio-based fertilizers. This study screened 15 different manures, digestates, sludges, composts, industry by-products, and struvites. Nitrogen (N) and phosphorous (P) release was compared following addition to soil. Three waste materials were then 'upgraded' using heating and pressure (105°C at 220 kPa), alkalinization (pH 10), or sonification to modify N and P release properties, and compared in a second soil incubation. Generally, maximum N release was negatively correlated with the CN ratio of the material (r = -0.6). Composted, dried, or raw organic waste materials released less N (mean of 10.8 ± 0.5%, 45.3 ± 7.2%, and 47.4 ± 3.2% of total N added respectively) than digestates, industry-derived organic fertilizer products, and struvites (mean of 58.2 ± 2.8%, 77.7 ± 6.0%, and 100.0 ± 13.1% of total N added respectively). No analyzed chemical property or processing type could explain differences in P release. No single upgrading treatment consistently increased N or P release. However, for one raw biosolid, heating at a low temperature (105°C) with pressure did increase N release as a percentage of total N added to soil from 30% to 43%.

  10. Staff background paper on performance-based rate making

    International Nuclear Information System (INIS)

    Fraser, J.; Brownell, B.

    1998-10-01

    An alternative to the traditional cost of service (COS) regulation for electric utilities in British Columbia has been proposed. The alternative to pure COS regulation is performance-based rate making (PBR). PBR partially decouples a utility's rates from its costs and ties utility profits to performance relative to specific benchmarks. The motivation underlying PBR is that ideally, it provides incentives for utilities to cost-effectively achieve pre-defined goals. This report describes the design of PBR mechanisms, base rate PBR formulas, base rate PBR in other jurisdictions including New York, California, Maine and New Jersey. The report also describes gas procurement PBR in other jurisdictions, as well as British Columbia Utilities' Commission's own experience with PBR. In general, PBR has the potential to provide resource efficiency, allocative efficiency, support for introduction of new services, and reduced regulatory administrative costs. 15 refs., 4 tabs

  11. Corrosion Tests of LWR Fuels - Nuclide Release

    International Nuclear Information System (INIS)

    P.A. Finn; Y. Tsai; J.C. Cunnane

    2001-01-01

    Two BWR fuels [64 and 71 (MWd)/kgU], one of which contained 2% Gd, and two PWR fuels [30 and 45 (MWd)/kgU], are tested by dripping groundwater on the fuels under oxidizing and hydrologically unsaturated conditions for times ranging from 2.4 to 8.2 yr at 90 C. The 99 Tc, 129 I, 137 Cs, 97 Mo, and 90 Sr releases are presented to show the effects of long reaction times and of gadolinium on nuclide release. This investigation showed that the five nuclides at long reaction times have similar fractional release rates and that the presence of 2% Gd reduced the 99 Tc cumulative release fraction by about an order of magnitude over that of a fuel with a similar burnup

  12. Tritium releases, birth defects and infant deaths

    International Nuclear Information System (INIS)

    1991-01-01

    The AECB has published a report 'Tritium releases from the Pickering Nuclear Generating Station and Birth Defects and Infant Mortality in Nearby Communities 1971-1988' (report number INFO-0401). This presents the results of a detailed analysis of deaths and birth defects occurring in infants born to mothers living in the area (25 Km radius) of the Pickering nuclear power plant, over an 18-year period. The analysis looked at the frequency of these defects and deaths in comparison to the general rate for Ontario, and also in relation to airborne and waterborne releases of tritium from the power plant. The overall conclusion was that the rates of infant death and birth defects were generally not higher in the study population than in all of Ontario. There was no prevalent relationship between these deaths and defects and tritium releases measured either at the power plant or by ground monitoring stations t some distance from the facility

  13. Sustained release nimesulide microparticles: evaluation of release modifying property of ethy

    International Nuclear Information System (INIS)

    Khan, S.A.; Ahmed, M.; Nisar-ur-Rehman; Madni, A.U.; Aamir, M.N.; Murtaza, G.

    2011-01-01

    Microencapsulated controlled-release preparations of nimesulide were formulated. Microparticles were prepared by modified phase separation (non-solvent addition) technique using different ratios of ethylcellulose. The microparticles (M/sub 1/, M/sub 2/, and M/sub 3/) were yellow, free flowing and spherical in shape with the particle size varying from 93.62 +- 14.15 to 104.19 +- 18.15 mu m. The t/sub 60%/of nimesulide release from microparticles was found to be 3 +- 0.6, 5 +- 0.6 and 8 +- 0.8 h for formulations M/sub 1/, M/sub 2/, and M/sub 3/, respectively. FT-IR, XRD, and thermal analysis were done which showed that there is no interaction between the polymer and drug. The mechanism of drug release from nimesulide microparticles was studied by using Higuchi and Korsmeyer-Peppas models. The value of coefficient of determination (R/sup 2/) for M/sub 1/, M/sub 2/, and M/sub 3/ indicates anomalous and case-II transport release mechanism. The dissolution data of designed system verified its ability to maintain plasma concentration without the need of frequent dosing. The Nimesulide microparticles prolonged drug release for 12 hours or longer. Based on the results of release studies, M/sub 3/ was opted as a suitable microparticulate formulation allowing the controlled release of nimesulide over a prolonged period of time. Moreover, its encapsulation efficiency was also comparable to the other two formulations (M/sub 1/ and M/sub 2/). In conclusion, the influence of polymer concentration should be considered during formulation development. (author)

  14. Exploring the correlation between the sequence composition of the nucleotide binding G5 loop of the FeoB GTPase domain (NFeoB) and intrinsic rate of GDP release.

    Science.gov (United States)

    Guilfoyle, Amy P; Deshpande, Chandrika N; Schenk, Gerhard; Maher, Megan J; Jormakka, Mika

    2014-12-12

    GDP release from GTPases is usually extremely slow and is in general assisted by external factors, such as association with guanine exchange factors or membrane-embedded GPCRs (G protein-coupled receptors), which accelerate the release of GDP by several orders of magnitude. Intrinsic factors can also play a significant role; a single amino acid substitution in one of the guanine nucleotide recognition motifs, G5, results in a drastically altered GDP release rate, indicating that the sequence composition of this motif plays an important role in spontaneous GDP release. In the present study, we used the GTPase domain from EcNFeoB (Escherichia coli FeoB) as a model and applied biochemical and structural approaches to evaluate the role of all the individual residues in the G5 loop. Our study confirms that several of the residues in the G5 motif have an important role in the intrinsic affinity and release of GDP. In particular, a T151A mutant (third residue of the G5 loop) leads to a reduced nucleotide affinity and provokes a drastically accelerated dissociation of GDP.

  15. Mechanisms of iodine release from iodoapatite in aqueous solution

    Science.gov (United States)

    Zhang, Z.; Wang, J.

    2017-12-01

    Immobilization of iodine-129 with waste forms in geological setting is challenging due to its extremely long half-life and high volatility in the environment. To evaluate the long-term performance of waste form, it is imperative to determine the release mechanism of iodine hosted in the waste form materials. This study investigated the iodine released from apatite structured waste form Pb9.85 (VO4)6 I1.7 to understand how diffusion and dissolution control the durability of apatite waste form. A standard semi-dynamic leach test was adopted in this study. Samples were exposed in fresh leachant periodically and the leachant was replaced after each interval. Each experiment was carried out in cap-sealed Teflon vessels under constant temperature (e.g. 90 °C). ICP-MS analysis on the reacted leachates shows that Pb and V were released constantly and congruently with the stoichiometric ratio of Pb/V. However, iodine release is incongruent and time dependent. The iodine release rate starts significantly higher than the corresponding stoichiometric value and gradually decreases, approaching the stoichiometric value. Therefore, a dual-mode mechanism is proposed to account for the iodine release from apatite, which is dominated by short-term diffusion and long-term dissolution processes. Additional tests show that the element release rates depend on a number of test parameters, including sample surface to solution volume ratio (m-1), interval (day), temperature (°C), and solution pH. This study provides a quantitative characterization of iodine release mechanism. The activation energy of iodine leaching 21±1.6 kJ/mol was obtained by varying the test temperature. At the test conditions of to neutral pH and 90 °C, the long-term iodine release rate 3.3 mg/(m2 • day) is projected by normalizing sample surface area to solution volume ratio (S/V) to 1.0 m-1 and interval to 1 day. These findings demonstrate i) the feasibility of our approach to quantify the release mechanism

  16. Release characteristics of tritium from high-purity lithium oxide

    International Nuclear Information System (INIS)

    O'Kula, K.R.; Vogelsang, W.F.

    1985-01-01

    Rates of tritium release from neutronirradiated lithium oxide were determined from isothermal release experiments. High-purity, monocrystalline lithium oxide was purged ex-reactor with helium and helium-hydrogen gas streams. Overall release was found to be controlled by solid-phase diffusion, and was predominantly in the form of condensible species. The result of an independent concentration profile analysis at 923 K was in agreement with the gas release diffusion coefficient. Sweeping the Li 2 O with hydrogen-containing gas was found to enhance tritium removal during the early stage of each run

  17. Energy release rate analysis on the interface cracks of enamel-cement-bracket fracture using virtual crack closure technique

    Science.gov (United States)

    Samshuri, S. F.; Daud, R.; Rojan, M. A.; Mat, F.; Basaruddin, K. S.; Hassan, R.

    2017-10-01

    This paper presents the energy method to evaluate fracture behavior of enamel-cement-bracket system based on cement thickness. Finite element (FE) model of enamel-cement-bracket was constructed by using ANSYS Parametric Design Language (APDL). Three different thickness were used in this study, 0.05, 0.2, and 0.271 mm which assigned as thin, medium and thick for both enamel-cement and cement bracket interface cracks. Virtual crack closure technique (VCCT) was implemented as a simulation method to calculated energy release rate (ERR). Simulation results were obtained for each thickness are discussed by using Griffith’s energy balance approach. ERR for thin thickness are found to be the lowest compared to medium and thick. Peak value of ERR also showed a significant different between medium and thick thickness. Therefore, weakest bonding occurred at low cement thickness because less load required to produce enough energy to detach the bracket. For medium and thick thickness, both increased rapidly in energy value at about the mid-point of the enamel-cement interface. This behavior occurred because of the increasing in mechanical and surface energy when the cracks are increasing. However, result for thick thickness are higher at mid-point compared to thin thickness. In conclusion, fracture behavior of enamel cracking process for medium most likely the safest to avoid enamel fracture and withstand bracket debonding.

  18. Controlled release of phenytoin for epilepsy treatment from titania and silica based materials

    Energy Technology Data Exchange (ETDEWEB)

    Lopez, Tessy, E-mail: tessy3@prodigy.net.mx [Universidad Autonoma Metropolitana-Xochimilco. Departamento de Microbiologia. Calzada del Hueso 1100, Col. Villa Quietud, Coyoacan, C.P. 04960, Mexico D.F. Mexico (Mexico); Instituto Nacional de Neurologia y Neurocirugia ' MVS' . Laboratorio de Nanotecnologia. Av. Insurgentes Sur 3877, Col. La Fama, Tlalpan, 14269, Mexico, D.F. Mexico (Mexico); Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, LA 70118 (United States); Ortiz, Emma [Instituto Nacional de Neurologia y Neurocirugia ' MVS' . Laboratorio de Nanotecnologia. Av. Insurgentes Sur 3877, Col. La Fama, Tlalpan, 14269, Mexico, D.F. Mexico (Mexico); Meza, Doraliz [Universidad Autonoma Metropolitana-Iztapalapa, Departamento de Quimica, Av. San Rafael Atlixco 186, A.P. 55-534, Mexico D.F., C.P. 09340 (Mexico); Basaldella, Elena [CIC-CINDECA - Universidad Nacional de La Plata - Calle 47 No 257 - La Plata (Argentina); Bokhimi, Xim; Magana, Carlos [Instituto de fisica, UNAM. Circuito de la Investigacion s/n. C.U. Mexico D.F. 01000 (Mexico); Sepulveda, Antonio; Rodriguez, Francisco; Ruiz, Javier [Departamento de Quimica Inorganica, Universidad de Alicante. Apartado 99, E-03080 Alicante, Espana Spain (Spain)

    2011-04-15

    Research highlights: {yields} Template technique was used to obtain well ordered nanostructured materials: SBA-15 and titania tubes. {yields} Phenytoin (PH), a drug used in epilepsy treatment, was loaded in these materials to used como PH release. {yields} Loaded PH showed a good stability inside the used materials as observed by spectroscopy analysis. {yields} The load-release PH are faster in nanostructured TiO2 tubes than in mesoporous silica matrix. {yields} There is an inverse effect of the surface area of the structured materials on the amount of released PH. - Abstract: Template technique was used to obtain well ordered nanostructured materials: mesoporous silica and nanostructured titania tubes. This technique permits the synthesis of solids with controlled mesoporosity, where a large variety of molecules that have therapeutic activity can be hosted and further released to specific sites. In this work phenytoin (PH), a drug used in epilepsy treatment, was loaded in ordered mesoporous silica (SBA 15) and nanostructured titania tubes (TiO{sub 2}). The pure materials and those containing PH were characterized by X-ray diffraction, FTIR spectroscopy, transmission electron microscopy (TEM), scanning electron microscopy (SEM) and N{sub 2} adsorption-desorption at 77 K. In order to determine the loading capacity of the antiepileptic drug on these silica- and titania-based materials, the loading and release of PH was investigated using UV-vis spectroscopy. Tubular structures were found for the titania samples, for which the X-ray diffractograms showed to be formed by anatase and rutile phases. On the other hand, an amorphous phase was found in the silica sample. A highly ordered hexagonal structure of 1D cylindrical channels was also observed for this material. Loaded PH showed a good stability inside the used materials as observed by spectroscopy analysis. The adsorption and desorption of PH are faster in nanostructured TiO{sub 2} tubes than in mesoporous silica

  19. PREPARATION, CHARACTERIZATION, AND PHARMACEUTICAL APPLICATION OF LINEAR DEXTRIN .3. DRUG-RELEASE FROM FATTY SUPPOSITORY BASES CONTAINING AMYLODEXTRIN

    NARCIS (Netherlands)

    TEWIERIK, GHP; EISSENS, AC; LERK, CF

    Drug release from fatty suppository bases containing a solid dispersion of diazepam with amylodextrin or a complex of prednisolone with amylodextrin was analyzed in a flow-through model. Being present as a suspension in the fatty base, particles of complex or solid dispersion are transported to the

  20. Correlation for boron carbide helium release in fast reactors

    International Nuclear Information System (INIS)

    Basmajian, J.A.; Pitner, A.L.

    1977-04-01

    An empirical helium correlation for the helium release from boron carbide has been developed. The correlation provides a good fit to the experimental data in the temperature range from 800 to 1350 0 K, and burnup levels up to 80 x 10 20 captures/cm 3 . The correlation has the capability of extrapolation to 2200 0 K (3500 0 F) and 200 x 10 20 captures/cm 3 . In this range the helium release rate will not exceed the generation rate

  1. PEG-PE/clay composite carriers for doxorubicin: Effect of composite structure on release, cell interaction and cytotoxicity.

    Science.gov (United States)

    Kohay, Hagay; Sarisozen, Can; Sawant, Rupa; Jhaveri, Aditi; Torchilin, Vladimir P; Mishael, Yael G

    2017-06-01

    A novel drug delivery system for doxorubicin (DOX), based on organic-inorganic composites was developed. DOX was incorporated in micelles (M-DOX) of polyethylene glycol-phosphatidylethanolamine (PEG-PE) which in turn were adsorbed by the clay, montmorillonite (MMT). The nano-structures of the PEG-PE/MMT composites of LOW and HIGH polymer loadings were characterized by XRD, TGA, FTIR, size (DLS) and zeta measurements. These measurements suggest that for the LOW composite a single layer of polymer intercalates in the clay platelets and the polymer only partially covers the external surface, while for the HIGH composite two layers of polymer intercalate and a bilayer may form on the external surface. These nanostructures have a direct effect on formulation stability and on the rate of DOX release. The release rate was reversely correlated with the degree of DOX interaction with the clay and followed the sequence: M-DOX>HIGH formulation>LOW formulation>DOX/MMT. Despite the slower release from the HIGH formulation, its cytotoxicity effect on sensitive cells was as high as the "free" DOX. Surprisingly, the LOW formulation, with the slowest release, demonstrated the highest cytotoxicity in the case of Adriamycin (ADR) resistant cells. Confocal microscopy images and association tests provided an insight into the contribution of formulation-cell interactions vs. the contribution of DOX release rate. Internalization of the formulations was suggested as a mechanism that increases DOX efficiency, particularly in the ADR resistant cell line. The employment of organic-inorganic hybrid materials as drug delivery systems, has not reached its full potential, however, its functionality as an efficient tunable release system was demonstrated. DOX PEG-PE/clay formulations were design as an efficient drug delivery system. The main aim was to develop PEG-PE/clay formulations of different structures based on various PEG-PE/clay ratios in order to achieve tunable release rates, to control

  2. Xylitol vs glucose: Effect on the rate of gastric emptying and motilin, insulin, and gastric inhibitory polypeptide release

    International Nuclear Information System (INIS)

    Salminen, E.K.; Salminen, S.J.; Porkka, L.; Kwasowski, P.; Marks, V.; Koivistoinen, P.E.

    1989-01-01

    The effect of xylitol and glucose on the rate of gastric emptying and intestinal transit and on motilin, gastric inhibitory polypeptide (GIP), and insulin release were studied in human volunteers. A single oral dose of 200 mL water containing 30 g glucose or 30 g xylitol, mixed with a 99m technetium-tin (99mTc-Sn) colloid, was used. Similar dosing without the label was used in motilin, GIP, and insulin studies. Xylitol decreased the rate of gastric emptying but concomitantly accelerated intestinal transit compared with glucose. The half-times for gastric emptying were 77.5 +/- 4.6 and 39.8 +/- 3.4 min after ingestion of xylitol and glucose solutions, respectively. Glucose suppressed motilin and stimulated GIP secretion; xylitol stimulated motilin secretion but had no effect on GIP, which is currently the main candidate for the role of enterogastrone. The accelerated intestinal transit and increase in plasma motilin observed after xylitol ingestion were thought to be causally related to the diarrhea and gastrointestinal discomfort produced by it

  3. Diclofenac sodium entrapment and release from halloysite nanotubules.

    Science.gov (United States)

    Krejčová, Kateřina; Deasy, Patrick B; Rabišková, Miloslava

    2013-02-01

    Halloysite was found to have interesting nanotubular geometry viable for the entrapment of various active agents. In this experiment, the ability of hollow halloysite cylinders to entrap the anionic model drug diclofenac sodium and to retard drug dissolution rate was investigated. Drugs could be incorporated into layered tubules via three different mechanisms: adsorption, intercalation and tubular entrapment. Based on the adsorption studies, some diclofenac sodium was shown to be adsorbed to the polyionic mineral surface despite its permanent negative charge. The X-ray powder diffraction analysis (XRPD) results did not prove any intercalation reaction to occur. The most important drug-loading mechanism involved the tubular entrapment with encapsulation efficiency 48.1%. The drug release from halloysite was prolonged in comparison with the dissolution of pure drug. Halloysite itself as well as halloysite loaded with the drug proved to be appropriate material to form pellets by extrusion /spheronization method. halloysite diclofenac sodium drug entrapment pellets prolonged drug release.

  4. Controlled release of biofunctional substances by radiation-induced polymerization

    International Nuclear Information System (INIS)

    Yoshida, M.; Kumakura, M.; Kaetsu, I.

    1978-01-01

    The controlled release of potassium chloride from flat circular matrices made by radiation-induced polymerization of a glass-forming monomer at low temperatures has been studied. The water-particle phase content formed in a poly(diethylene glycol dimethacrylate) matrix was controlled by the addition of polyethylene glycol 600. The dispersed water-particle phase content in the matrix was estimated directly and by scanning electron microscopic observations. The release of potassium chloride from the matrix increased linearly with the square root of time. The water content of the matrix had an important effect on the release rate which increases roughly in proportion to water content. This effect can be attributed to the apparent increase of the rate of drug diffusion. (author)

  5. Aerosols released from solvent fire accidents in reprocessing plants

    International Nuclear Information System (INIS)

    Jordan, S.; Lindner, W.

    1985-01-01

    Thermodynamic, aerosol characterizing and radiological data of solvent fires in reprocessing plants have been established in experiments. These are the main results: Depending on the ventilation in the containment, kerosene-TBP mixtures burn at a rate up to 120 kg/m 2 h. The aqueous phase of inorganic-organic mixtures might be released during the fire. The gaseous reaction products contain unburnable acidic compounds. Solvents with TBP-nitrate complex shows higher (up to 25%) burning rates than pure solvents (kerosene-TBP). The nitrate complex decomposes violently at about 130 0 C with a release of acid and unburnable gases. Up to 20% of the burned kerosene-TBP solvents are released during the fire in the form of soot particles, phosphoric acid and TBP decomposition products. The particles have an aerodynamic mass median diameter of about 0.5 μm and up to 1.5% of the uranium fixed in the TBP-nitrate complex is released during solvent fires. (orig.)

  6. A Self-Peeling Vat for Improved Release Capabilities During DLP Materials Processing

    DEFF Research Database (Denmark)

    Pedersen, David Bue; Zhang, Yang; Nielsen, Jakob Skov

    2016-01-01

    for an eased release of the manufactured part from the vat by means of a flexible membrane system. A membrane of fluorinated ethylene polymer will through elastic deformation automatically peel off the part as the part is lifted during layer changes. Peeling has been qualified by means of a truncated inverted...... cone as test geometry. As the cross-sectional diameter of the cone increase throughout the build-job, the geometry will release from the glass based build platform at the point where the peeling force exceed the adhesion force between platform and part. At failure point the lateral surface area...... of the top and bottom of the truncated cone is used as a measure of the performance of the vat with respect to release-capability. This has been tested at increasing manufacturing rates. The new self-peeling vat outperformed industrial state-of-the-art vats by 814% percent....

  7. Sustained-release diclofenac potassium-loaded solid lipid microparticle based on solidified reverse micellar solution: in vitro and in vivo evaluation.

    Science.gov (United States)

    Chime, Salome Amarachi; Attama, Anthony Amaechi; Builders, Philip F; Onunkwo, Godswill C

    2013-01-01

    To formulate sustained-release diclofenac potassium-loaded solid lipid microparticles (SLMs) based on solidified reverse micellar solution (SRMS) and to evaluate the in vitro and in vivo properties. SRMS consisting of mixtures of Phospholipon® 90H and Softisan® 154 were used to formulate diclofenac potassium-loaded SLMs. Characterization based on the particle size and morphology, stability and encapsulation efficiency (EE%) were carried out on the SLMs. In vitro release was carried out in simulated intestinal fluid (pH 7.5). Anti-inflammatory and ulcerogenic properties were studied using rats. Maximum EE% of 95%, 94% and 93% were obtained for SLMs formulated with SRMS 1:1, 2:1 and 1:2, respectively. In vitro release showed about 85-90% drug release at 13 h. Diclofenac potassium-loaded SLMs showed good anti-inflammatory and gastro-protective properties. Diclofenac potassium-loaded SLMs based on SRMS could be used orally or parenterally under controlled conditions, for once daily administration.

  8. Budget impact of switching from an immediate-release to a prolonged-release formulation of tacrolimus in renal transplant recipients in the UK based on differences in adherence

    Directory of Open Access Journals (Sweden)

    Muduma G

    2014-03-01

    Full Text Available Gorden Muduma,1 Isaac Odeyemi,1 Jayne Smith-Palmer,2 Richard F Pollock21Astellas Pharma Europe, Chertsey, UK; 2Ossian Health Economics and Communications, Basel, SwitzerlandBackground and aims: Advagraf is a once-daily prolonged-release formulation of tacrolimus with proven noninferiority to Prograf, a twice-daily immediate-release formulation of tacrolimus, in biopsy-proven acute rejection, graft survival and patient survival in renal transplant recipients. Advagraf is associated with improved adherence compared with Prograf, which may ultimately improve long-term outcomes. The present study assessed the budget impact of switching patients from Prograf to Advagraf in the UK.Materials and methods: A budget-impact model was constructed based on published data on acute rejection, graft failure, and mortality in the UK setting. Patients were assumed to convert from Prograf to Advagraf on a 1:1 milligram:milligram basis. In a study comparing the adherence rates between once-daily versus twice-daily formulations of tacrolimus, the proportion of patients taking the prescribed number of daily doses was 88.2% in Advagraf patients and 78.8% in Prograf patients. The model applied a relative risk of graft failure of 3.47 to nonadherent patients based on data from a 2004 meta-analysis (based on graft-failure rates of 1.3%–40.0% in adherent patients, compared with 6.1%–100% in nonadherent patients. Cost data were taken from the March 2013 British National Formulary and 2012–2013 National Health Service tariff information. The analysis was performed over a 5-year time horizon and future costs were not discounted, in line with International Society for Pharmacoeconomics and Outcomes Research guidelines.Results: Over a 5-year time horizon, the mean cost per patient (including tacrolimus, concomitant immunosuppressive medications, dialysis after graft failure, and treatment for acute rejection was £29,328 (standard deviation [SD] £2,844 for Advagraf

  9. Prodigiosin release from an implantable biomedical device: kinetics of localized cancer drug release

    International Nuclear Information System (INIS)

    Danyuo, Y.; Obayemi, J.D.; Dozie-Nwachukwu, S.; Ani, C.J.; Odusanya, O.S.; Oni, Y.; Anuku, N.; Malatesta, K.; Soboyejo, W.O.

    2014-01-01

    This paper presents an implantable encapsulated structure that can deliver localized heating (hyperthermia) and controlled concentrations of prodigiosin (a cancer drug) synthesized by bacteria (Serratia marcesce (subsp. marcescens)). Prototypical Poly-di-methyl-siloxane (PDMS) packages, containing well-controlled micro-channels and drug storage compartments, were fabricated along with a drug-storing polymer produced by free radical polymerization of Poly(N-isopropylacrylamide)(PNIPA) co-monomers of Acrylamide (AM) and Butyl-methacrylate (BMA). The mechanisms of drug diffusion of PNIPA-base gels were elucidated. Scanning Electron Microscopy (SEM) was also used to study the heterogeneous porous structure of the PNIPA-based gels. The release exponents, n, of the gels were found to between 0.5 and 0.7. This is in the range expected for Fickian (n = 0.5). Deviation from Fickian diffusion was also observed (n > 0.5) diffusion. The gel diffusion coefficients were shown to vary between 2.1 × 10 −12 m 2 /s and 4.8 × 10 −6 m 2 /s. The implications of the results are then discussed for the localized treatment of cancer via hyperthermia and the controlled delivery of prodigiosin from encapsulated PNIPA-based devices. - Highlights: • Fabricated thermo-sensitive hydrogels for localized drug release from an implantable biomedical device. • Determined the cancer drug diffusion mechanisms of PNIPA-co-AM copolymer hydrogel. • Encapsulated PNIPA-based hydrogels in PDMS capsules for controlled drug delivery. • Established the kinetics of drug release from gels and channels in an implantable biomedical device. • Demonstrated the potential for the controlled release of prodigiosin (PG) as an anticancer drug

  10. Prodigiosin release from an implantable biomedical device: kinetics of localized cancer drug release

    Energy Technology Data Exchange (ETDEWEB)

    Danyuo, Y.; Obayemi, J.D.; Dozie-Nwachukwu, S. [Department of Materials Science and Engineering, African University of Science and Technology (AUST), Abuja, Federal Capital Territory (Nigeria); Ani, C.J. [Department of Theoretical Physics, African University of Science and Technology (AUST), Abuja, Federal Capital Territory (Nigeria); Odusanya, O.S. [Biotechnology and Genetic Engineering Advanced Laboratory, Sheda Science and Technology Complex (SHESTCO), Abuja, Federal Capital Territory (Nigeria); Oni, Y. [Department of Chemistry, Bronx Community College, New York, NY (United States); Anuku, N. [Department of Chemistry, Bronx Community College, New York, NY (United States); Princeton Institute for the Science and Technology of Materials (PRISM), 70 Prospect Street, Princeton, NJ 08544 (United States); Malatesta, K. [Department of Chemistry, Bronx Community College, New York, NY (United States); Soboyejo, W.O., E-mail: soboyejo@princeton.edu [Department of Materials Science and Engineering, African University of Science and Technology (AUST), Abuja, Federal Capital Territory (Nigeria); Princeton Institute for the Science and Technology of Materials (PRISM), 70 Prospect Street, Princeton, NJ 08544 (United States); Department of Mechanical and Aerospace Engineering 1 Olden Street, Princeton, NJ 08544 (United States)

    2014-09-01

    This paper presents an implantable encapsulated structure that can deliver localized heating (hyperthermia) and controlled concentrations of prodigiosin (a cancer drug) synthesized by bacteria (Serratia marcesce (subsp. marcescens)). Prototypical Poly-di-methyl-siloxane (PDMS) packages, containing well-controlled micro-channels and drug storage compartments, were fabricated along with a drug-storing polymer produced by free radical polymerization of Poly(N-isopropylacrylamide)(PNIPA) co-monomers of Acrylamide (AM) and Butyl-methacrylate (BMA). The mechanisms of drug diffusion of PNIPA-base gels were elucidated. Scanning Electron Microscopy (SEM) was also used to study the heterogeneous porous structure of the PNIPA-based gels. The release exponents, n, of the gels were found to between 0.5 and 0.7. This is in the range expected for Fickian (n = 0.5). Deviation from Fickian diffusion was also observed (n > 0.5) diffusion. The gel diffusion coefficients were shown to vary between 2.1 × 10{sup −12} m{sup 2}/s and 4.8 × 10{sup −6} m{sup 2}/s. The implications of the results are then discussed for the localized treatment of cancer via hyperthermia and the controlled delivery of prodigiosin from encapsulated PNIPA-based devices. - Highlights: • Fabricated thermo-sensitive hydrogels for localized drug release from an implantable biomedical device. • Determined the cancer drug diffusion mechanisms of PNIPA-co-AM copolymer hydrogel. • Encapsulated PNIPA-based hydrogels in PDMS capsules for controlled drug delivery. • Established the kinetics of drug release from gels and channels in an implantable biomedical device. • Demonstrated the potential for the controlled release of prodigiosin (PG) as an anticancer drug.

  11. Impacts of accidental radioactive releases to the hydrosphere from floating and land-based nuclear power plants

    International Nuclear Information System (INIS)

    Vollmer, R.H.

    1978-01-01

    To assess the impacts of accidental radioactive releases to the hydrosphere from floating and land-based nuclear power plants, the Liquid Pathway Generic Study was initiated. The objective of this study was to compare the risks associated with releases through the liquid pathway from accidents that may reasonably be expected and those that are very improbable. Consequences were estimated in terms of radiation dose to man from drinking water ingestion, shell-fish and fish flesh consumption, and direct exposure (swimming, beach) as well as long-term effects, such as genetic effects or aquatic species degradation. (author)

  12. Arduino-based noise robust online heart-rate detection.

    Science.gov (United States)

    Das, Sangita; Pal, Saurabh; Mitra, Madhuchhanda

    2017-04-01

    This paper introduces a noise robust real time heart rate detection system from electrocardiogram (ECG) data. An online data acquisition system is developed to collect ECG signals from human subjects. Heart rate is detected using window-based autocorrelation peak localisation technique. A low-cost Arduino UNO board is used to implement the complete automated process. The performance of the system is compared with PC-based heart rate detection technique. Accuracy of the system is validated through simulated noisy ECG data with various levels of signal to noise ratio (SNR). The mean percentage error of detected heart rate is found to be 0.72% for the noisy database with five different noise levels.

  13. Analysis of drug effects on neurotransmitter release

    International Nuclear Information System (INIS)

    Rowell, P.; Garner, A.

    1986-01-01

    The release of neurotransmitter is routinely studied in a superfusion system in which serial samples are collected and the effects of drugs or other treatments on the amount of material in the superfusate is determined. With frequent sampling interval, this procedure provides a mechanism for dynamically characterizing the release process itself. Using automated data collection in conjunction with polyexponential computer analysis, the equation which describes the release process in each experiment is determined. Analysis of the data during the nontreated phase of the experiment allows an internal control to be used for accurately assessing any changes in neurotransmitter release which may occur during a subsequent treatment phase. The use of internal controls greatly improves the signal to noise ratio and allows determinations of very low concentrations of drugs on small amounts of tissue to be made. In this presentation, the effects of 10 μM nicotine on 3 H-dopamine release in rat nucleus accumbens is described. The time course, potency and efficacy of the drug treatment is characterized using this system. Determinations of the exponential order of the release as well as the rate constants allow one to study the mechanism of the release process. A description of 3 H-dopamine release in normal as well as Ca ++ -free medium is presented

  14. In vitro studies of copper release from powder particles in synthetic biological media

    International Nuclear Information System (INIS)

    Midander, Klara; Wallinder, Inger Odnevall; Leygraf, Christofer

    2007-01-01

    The aim of this paper is to provide quantitative data on copper release from powder particles of different copper materials, including artificial copper patina, Cu 2 O and metallic Cu, when exposed to different synthetic biological media to simulate an inhalation scenario and/or skin contact. Generated data may contribute in risk assessment of potential health effects following exposure to and handling of various copper materials. All tests were performed in vitro to determine total copper concentrations, release rates of total copper, and to elucidate its time-dependence. The copper release process was interpreted in terms of specific surface area, surface morphology-, and composition. All powder materials show a time-dependent release process with total copper release rates less than 3 μg/cm 2 per hour at steady state conditions, for all media investigated. The importance of using relevant test media when simulating different interstitial lung conditions and difficulties encountered when comparing powder particles of essentially different properties are thoroughly discussed. - Copper release rates from particles are essential to assess potential health aspects

  15. Floating matrix tablets based on low density foam powder: effects of formulation and processing parameters on drug release.

    Science.gov (United States)

    Streubel, A; Siepmann, J; Bodmeier, R

    2003-01-01

    The aim of this study was to develop and physicochemically characterize single unit, floating controlled drug delivery systems consisting of (i). polypropylene foam powder, (ii). matrix-forming polymer(s), (iii). drug, and (iv). filler (optional). The highly porous foam powder provided low density and, thus, excellent in vitro floating behavior of the tablets. All foam powder-containing tablets remained floating for at least 8 h in 0.1 N HCl at 37 degrees C. Different types of matrix-forming polymers were studied: hydroxypropyl methylcellulose (HPMC), polyacrylates, sodium alginate, corn starch, carrageenan, gum guar and gum arabic. The tablets eroded upon contact with the release medium, and the relative importance of drug diffusion, polymer swelling and tablet erosion for the resulting release patterns varied significantly with the type of matrix former. The release rate could effectively be modified by varying the "matrix-forming polymer/foam powder" ratio, the initial drug loading, the tablet geometry (radius and height), the type of matrix-forming polymer, the use of polymer blends and the addition of water-soluble or water-insoluble fillers (such as lactose or microcrystalline cellulose). The floating behavior of the low density drug delivery systems could successfully be combined with accurate control of the drug release patterns.

  16. Evaluating conditional release in not guilty by reason of insanity acquittees: a prospective follow-up study in Virginia.

    Science.gov (United States)

    Vitacco, Michael J; Vauter, Rebecca; Erickson, Steven K; Ragatz, Laurie

    2014-08-01

    Detailed research on treatment and risk management approaches with not guilty by reason of insanity acquittees (NGRI) during their conditional release is needed as states increasingly use community-based services for these individuals. Grounded in case law, and supported by follow-up studies demonstrating low recidivism rates, states have been encouraged in their efforts to conditionally release NGRI acquittees. The authors evaluated a state-wide sample of 127 NGRI acquittees released into the community after spending a mean of 61.63 months (SD = 76.54) in the hospital. One hundred individuals were committed to the hospital for lengthier treatment (M hospital time = 77.23 months, SD = 79.84), but 27 individuals were released to the community after a relatively short hospital stay (M hospital time = 5.60 months, SD = 3.01). Regarding release, 96 individuals (75.6%) maintained their conditional release. After evaluating a host of demographic and standardized risk data, the following variables predicted revocation on conditional release: previous failure on conditional release, nonadherence with hospital treatment, dangerousness to others, and previous violent charges. A multivariate survival analysis determined criminal behavior and previous failure on conditional release predicted time to revocation. The results of this study demonstrate the importance of considering standardized risk variables in the community-based management of forensic patients. In addition, the data are supportive of continued attempts at moving insanity acquittees from the hospital to the community via conditional release.

  17. A Model of Exchange-Rate-Based Stabilization for Turkey

    OpenAIRE

    Ozlem Aytac

    2008-01-01

    The literature on the exchange-rate-based stabilization has focused almost exclusively in Latin America. Many other countries however, such as Egypt, Lebanon and Turkey; have undertaken this sort of programs in the last 10-15 years. I depart from the existing literature by developing a model specifically for the 2000-2001 heterodox exchange-rate-based stabilization program in Turkey: When the government lowers the rate of crawl, the rate of domestic credit creation is set equal to the lower r...

  18. Dams release methane even in temperate zoned

    International Nuclear Information System (INIS)

    Lemarchand, F.

    2010-01-01

    The Wohlen lake (near Bern) is a retaining dam built 90 years ago that has undergone a campaign to measure the quantity of methane released. The campaign lasted 1 year and the result was unexpected: 0.15 g/m 2 *day which one of the highest release rates in temperate zones. This result is all the more stunning since water stays only 2 days in average in the reservoir and that the drowned area is not important. In fact the river Aar that feeds the lake is loaded with organic matter coming from humane activities: agriculture and 3 sewage plants. This organic matter decays in the lake releasing methane. (A.C.)

  19. Effect of co-administration of probiotics with polysaccharide based colon targeted delivery systems to optimize site specific drug release.

    Science.gov (United States)

    Prudhviraj, G; Vaidya, Yogyata; Singh, Sachin Kumar; Yadav, Ankit Kumar; Kaur, Puneet; Gulati, Monica; Gowthamarajan, K

    2015-11-01

    Significant clinical success of colon targeted dosage forms has been limited by their inappropriate release profile at the target site. Their failure to release the drug completely in the colon may be attributed to changes in the colonic milieu because of pathological state, drug effect and psychological stress accompanying the diseased state or, a combination of these. Alteration in normal colonic pH and bacterial picture leads to incomplete release of drug from the designed delivery system. We report the effectiveness of a targeted delivery system wherein the constant replenishment of the colonic microbiota is achieved by concomitant administration of probiotics along with the polysaccharide based drug delivery system. Guar gum coated spheroids of sulfasalazine were prepared. In the dissolution studies, these spheroids showed markedly higher release in the simulated colonic fluid. In vivo experiments conducted in rats clearly demonstrated the therapeutic advantage of co-administration of probiotics with guar gum coated spheroids. Our results suggest that concomitant use of probiotics along with the polysaccharide based delivery systems can be a simple strategy to achieve satisfactory colon targeting of drugs. Copyright © 2015 Elsevier B.V. All rights reserved.

  20. STEADY STATE FLAMMABLE GAS RELEASE RATE CALCULATION AND LOWER FLAMMABILITY LEVEL EVALUATION FOR HANFORD TANK WASTE

    Energy Technology Data Exchange (ETDEWEB)

    HU TA

    2009-10-26

    Assess the steady-state flammability level at normal and off-normal ventilation conditions. The hydrogen generation rate was calculated for 177 tanks using the rate equation model. Flammability calculations based on hydrogen, ammonia, and methane were performed for 177 tanks for various scenarios.