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Sample records for stabilized enzyme solution

  1. 21 CFR 864.9400 - Stabilized enzyme solution.

    Science.gov (United States)

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Stabilized enzyme solution. 864.9400 Section 864... and Blood Products § 864.9400 Stabilized enzyme solution. (a) Identification. A stabilized enzyme... enzyme solutions include papain, bromelin, ficin, and trypsin. (b) Classification. Class II (performance...

  2. Enzyme stabilization by glass-derived silicates in glass-exposed aqueous solutions

    Science.gov (United States)

    Ives, J.A.; Moffett, J.R.; Arun, P.; Lam, D.; Todorov, T.I.; Brothers, A.B.; Anick, D.J.; Centeno, J.; Namboodiri, M.A.A.; Jonas, W.B.

    2010-01-01

    Objectives: To analyze the solutes leaching from glass containers into aqueous solutions, and to show that these solutes have enzyme activity stabilizing effects in very dilute solutions. Methods: Enzyme assays with acetylcholine esterase were used to analyze serially succussed and diluted (SSD) solutions prepared in glass and plastic containers. Aqueous SSD preparations starting with various solutes, or water alone, were prepared under several conditions, and tested for their solute content and their ability to affect enzyme stability in dilute solution. Results: We confirm that water acts to dissolve constituents from glass vials, and show that the solutes derived from the glass have effects on enzymes in the resultant solutions. Enzyme assays demonstrated that enzyme stability in purified and deionized water was enhanced in SSD solutions that were prepared in glass containers, but not those prepared in plastic. The increased enzyme stability could be mimicked in a dose-dependent manner by the addition of silicates to the purified, deionized water that enzymes were dissolved in. Elemental analyses of SSD water preparations made in glass vials showed that boron, silicon, and sodium were present at micromolar concentrations. Conclusions: These results show that silicates and other solutes are present at micromolar levels in all glass-exposed solutions, whether pharmaceutical or homeopathic in nature. Even though silicates are known to have biological activity at higher concentrations, the silicate concentrations we measured in homeopathic preparations were too low to account for any purported in vivo efficacy, but could potentially influence in vitro biological assays reporting homeopathic effects. ?? 2009 The Faculty of Homeopathy.

  3. Enzyme stabilization for pesticide degradation

    Energy Technology Data Exchange (ETDEWEB)

    Rivers, D.B.; Frazer, F.R. III; Mason, D.W.; Tice, T.R.

    1988-01-01

    Enzymes offer inherent advantages and limitations as active components of formulations used to decontaminate soil and equipment contaminated with toxic materials such as pesticides. Because of the catalytic nature of enzymes, each molecule of enzyme has the potential to destroy countless molecules of a contaminating toxic compound. This degradation takes place under mild environmental conditions of pH, temperature, pressure, and solvent. The basic limitation of enzymes is their degree of stability during storage and application conditions. Stabilizing methods such as the use of additives, covalent crosslinking, covalent attachment, gel entrapment, and microencapsulation have been directed developing an enzyme preparation that is stable under extremes of pH, temperature, and exposure to organic solvents. Initial studies were conducted using the model enzymes subtilisin and horseradish peroxidase.

  4. PFP solution stabilization

    International Nuclear Information System (INIS)

    Aftanas, B.L.

    1996-01-01

    This Functional Design Criteria (FDC) addresses remediation of the plutonium-bearing solutions currently in inventory at the Plutonium Finishing Plant (PFP). The recommendation from the Environmental Impact Statement (EIS) is that the solutions be treated thermally and stabilized as a solid for long term storage. For solutions which are not discardable, the baseline plan is to utilize a denitration process to stabilize the solutions prior to packaging for storage

  5. Bacteriophage enzymes for the prevention and treatment of bacterial infections: Stability and stabilization of the enzyme lysing Streptococcus pyogenes cells

    Energy Technology Data Exchange (ETDEWEB)

    Klyachko, N. L.; Dmitrieva, N. F.; Eshchina, A. S.; Ignatenko, O. V.; Filatova, L. Y.; Rainina, Evguenia I.; Kazarov, A. K.; Levashov, A. V.

    2008-06-01

    Recombinant, phage associated lytic enzyme Ply C capable to lyse streptococci of groups A and C was stabilized in the variety of the micelles containing compositions to improve the stability of the enzyme for further application in medicine. It was shown that, in the micellar polyelectrolyte composition M16, the enzyme retained its activity for 2 months; while in a buffer solution under the same conditions ((pH 6.3, room temperature), it completely lost its activity in 2 days

  6. Electro-ultrafiltration of industrial enzyme solutions

    DEFF Research Database (Denmark)

    Enevoldsen, Ann Dorrit; Hansen, Erik Børresen; Jonsson, Gunnar Eigil

    2007-01-01

    To reduce the problems with fouling and concentration polarization during crossflow ultrafiltration of industrial enzyme solutions an electric field is applied across the membrane. The filtration performance during electro-ultrafiltration (EUF) has been tested with several enzymes. Results show...

  7. Computationally designed libraries for rapid enzyme stabilization

    NARCIS (Netherlands)

    Wijma, Hein J.; Floor, Robert J.; Jekel, Peter A.; Baker, David; Marrink, Siewert J.; Janssen, Dick B.

    The ability to engineer enzymes and other proteins to any desired stability would have wide-ranging applications. Here, we demonstrate that computational design of a library with chemically diverse stabilizing mutations allows the engineering of drastically stabilized and fully functional variants

  8. Stability of Enzymes in Granular Enzyme Products for Laundry Detergents

    DEFF Research Database (Denmark)

    Biran, Suzan; Bach, Poul; Simonsen, Ole

    Enzymes have long been of interest to the detergent industry due to their ability to improve the cleaning efficiency of synthetic detergents, contribute to shortening washing times, and reduce energy and water consumption, provision of environmentally friendlier wash water effluents and fabric care....... However, incorporating enzymes in detergent formulations gives rise to numerous practical problems due to their incompatibility with and stability against various detergent components. In powdered detergent formulations, these issues can be partly overcome by physically isolating the enzymes in separate...... particles. However, enzymes may loose a significant part of their activity over a time period of several weeks. Possible causes of inactivation of enzymes in a granule may be related to the release of hydrogen peroxide from the bleaching chemicals in a moisture-containing atmosphere, humidity, autolysis...

  9. Project Management Plan Solution Stabilization

    Energy Technology Data Exchange (ETDEWEB)

    SATO, P.K.

    1999-08-31

    This plan presents the overall objectives, description, justification and planning for the Plutonium Finishing Plant (PFP) Solutions Stabilization subproject. The intent of this plan is to describe how this project will be managed and integrated with other facility stabilization and deactivation activities. This plan supplements the overall integrated plan presented in the Integrated Project Management Plan (IPMP) for the Plutonium Finishing Plant Stabilization and Deactivation Project, HNF-3617. This project plan is the top-level definitive project management document for the PFP Solution Stabilization subproject. It specifies the technical, schedule, requirements and the cost baselines to manage the execution of the Solution Stabilization subproject. Any deviations to the document must be authorized through the appropriate change control process.

  10. Project Management Plan Solution Stabilization

    International Nuclear Information System (INIS)

    SATO, P.K.

    1999-01-01

    This plan presents the overall objectives, description, justification and planning for the Plutonium Finishing Plant (PFP) Solutions Stabilization subproject. The intent of this plan is to describe how this project will be managed and integrated with other facility stabilization and deactivation activities. This plan supplements the overall integrated plan presented in the Integrated Project Management Plan (IPMP) for the Plutonium Finishing Plant Stabilization and Deactivation Project, HNF-3617. This project plan is the top-level definitive project management document for the PFP Solution Stabilization subproject. It specifies the technical, schedule, requirements and the cost baselines to manage the execution of the Solution Stabilization subproject. Any deviations to the document must be authorized through the appropriate change control process

  11. Effect of irradiation on immobilized enzymes compared with that on enzymes in solution

    International Nuclear Information System (INIS)

    Schachinger, L.; Schippel, C.; Altmann, E.; Diepold, B.; Yang, C.; Jaenike, M.; Hochhaeuser, E.

    1985-01-01

    Glucose oxidase and catalase were immobilized by attaching them to nylon fibers that had been treated with triethyloxonium-tetrafluoroborate, diaminohexane and glutaraldialdehyde according to Morris, Campell and Hornby (1975). This method assures that the enzymes are bound to a side chain of the polyamide structure. Enzyme activity (as measured by the O 2 -uptake and by microcalorimetry) was found to be unchanged after 2 years. The apparent Ksub(m)-constants of the immobilized enzymes with glucose were the same as those for enzymes in solution. GOD and catalase immobilized in poly(acrylamide) gel had the same Ksub(m)-value. Despite the high stability during storage, the radiation induced inactivation of enzymes immobilized on gel or chromosorb, an inorganic carrier, was of the same order of magnitude as that of the dissolved enzymes. The enzymes bound to nylon fibers showed a higher radiation sensitivity. This might have been caused by an additional attack on the binding site of the carrier. (orig.)

  12. Enzyme based soil stabilization for unpaved road construction

    Directory of Open Access Journals (Sweden)

    Renjith Rintu

    2017-01-01

    Full Text Available Enzymes as soil stabilizers have been successfully used in road construction in several countries for the past 30 years. However, research has shown that the successful application of these enzymes is case specific, emphasizing that enzyme performance is dependent on subgrade soil type, condition and the type of enzyme used as the stabilizer. A universal standard or a tool for road engineers to assess the performance of stabilized unbound pavements using well-established enzymes is not available to date. The research aims to produce a validated assessment tool which can be used to predict strength enhancement within a generalized statistical framework. The objective of the present study is to identify new materials for developing the assessment tool which supports enzyme based stabilization, as well as to identify the correct construction sequence for such new materials. A series of characterization tests were conducted on several soil types obtained from proposed construction sites. Having identified the suitable soil type to mix with the enzyme, a trial road construction has been performed to investigate the efficiency of the enzyme stabilization along with the correct construction sequence. The enzyme stabilization has showed significant improvement of the road performance as was evidenced from the test results which were based on site soil obtained before and after stabilization. The research will substantially benefit the road construction industry by not only replacing traditional construction methods with economical/reliable approaches, but also eliminating site specific tests required in current practice of enzyme based road construction.

  13. Stabilization of enzymes against thermal stress and freeze-drying by mannosylglycerate

    NARCIS (Netherlands)

    Ramos, A.; Raven, N.; Sharp, R.J.; Bartolucci, S.; Rossi, M.; Cannio, R.; Lebbink, J.; Oost, van der J.; Vos, de W.M.; Santos, H.

    1997-01-01

    2-O-(beta)-Mannosylglycerate, a solute that accumulates in some (hyper)thermophilic organisms, was purified from Pyrococcus furiosus cells, and its effect on enzyme stabilization in vitro was assessed. Enzymes from hyperthermophilic, thermophilic, and mesophilic sources were examined. The

  14. Engineering report (conceptual design) PFP solution stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Witt, J.B.

    1997-07-17

    This Engineering Report (Conceptual Design) addresses remediation of the plutonium-bearing solutions currently in inventory at the Plutonium Finishing Plant (PFP). The recommendation from the Environmental Impact Statement (EIS) is that the solutions be treated thermally and stabilized as a solid for long term storage. For solutions which are not discardable, the baseline plan is to utilize a denitration process to stabilize the solutions prior to packaging for storage.

  15. Engineering report (conceptual design) PFP solution stabilization

    International Nuclear Information System (INIS)

    Witt, J.B.

    1997-01-01

    This Engineering Report (Conceptual Design) addresses remediation of the plutonium-bearing solutions currently in inventory at the Plutonium Finishing Plant (PFP). The recommendation from the Environmental Impact Statement (EIS) is that the solutions be treated thermally and stabilized as a solid for long term storage. For solutions which are not discardable, the baseline plan is to utilize a denitration process to stabilize the solutions prior to packaging for storage

  16. Stability studies of oxytetracycline in methanol solution

    Science.gov (United States)

    Wang, Wei; Wu, Nan; Yang, Jinghui; Zeng, Ming; Xu, Chenshan; Li, Lun; Zhang, Meng; Li, Liting

    2018-02-01

    As one kind of typical tetracycline antibiotics, antibiotic residues of oxytetracycline have been frequently detected in many environmental media. In this study, the stability of oxytetracycline in methanol solution was investigated by high-performance liquid chromatography combined with UV-vis (HPLC-UV). The results show that the stability of oxytetracycline in methanol solution is highly related to its initial concentration and the preserved temperature. Under low temperature condition, the solution was more stable than under room temperature preservation. Under the same temperature preservation condition, high concentrations of stock solutions are more stable than low concentrations. The study provides a foundation for preserving the oxytetracycline-methanol solution.

  17. Stabilization of enzymes in ionic liquids via modification of enzyme charge.

    Science.gov (United States)

    Nordwald, Erik M; Kaar, Joel L

    2013-09-01

    Due to the propensity of ionic liquids (ILs) to inactivate enzymes, the development of strategies to improve enzyme utility in these solvents is critical to fully exploit ILs for biocatalysis. We have developed a strategy to broadly improve enzyme utility in ILs based on elucidating the effect of charge modifications on the function of enzymes in IL environments. Results of stability studies in aqueous-IL mixtures indicated a clear connection between the ratio of enzyme-containing positive-to-negative sites and enzyme stability in ILs. Stability studies of the effect of [BMIM][Cl] and [EMIM][EtSO4 ] on chymotrypsin specifically found an optimum ratio of positively-charged amine-to-negatively-charged acid groups (0.39). At this ratio, the half-life of chymotrypsin was increased 1.6- and 4.3-fold relative to wild-type chymotrypsin in [BMIM][Cl] and [EMIM][EtSO4 ], respectively. The half-lives of lipase and papain were similarly increased as much as 4.0 and 2.4-fold, respectively, in [BMIM][Cl] by modifying the ratio of positive-to-negative sites of each enzyme. More generally, the results of stability studies found that modifications that reduce the ratio of enzyme-containing positive-to-negative sites improve enzyme stability in ILs. Understanding the impact of charge modification on enzyme stability in ILs may ultimately be exploited to rationally engineer enzymes for improved function in IL environments. Copyright © 2013 Wiley Periodicals, Inc.

  18. Chemical stability of oseltamivir in oral solutions.

    Science.gov (United States)

    Albert, K; Bockshorn, J

    2007-09-01

    The stability of oseltamivir in oral aqueous solutions containing the preservative sodium benzoate was studied by a stability indicating HPLC-method. The separation was achieved on a RP-18 ec column using a gradient of mobile phase A (aqueous solution of 50 mM ammonium acetate) and mobile phase B (60% (v/v) acetonitrile/40% (v/v) mobile phase A). The assay was subsequently validated according to the ICH guideline Q2(R1). The extemporaneously prepared "Oseltamivir Oral Solution 15 mg/ml for Adults or for Children" (NRF 31.2.) according to the German National Formulary ("Neues Rezeptur-Formularium") was stable for 84 days if stored under refrigeration. After storage at 25 degrees C the content of oseltamivir decreased to 98.4%. Considering the toxicological limit of 0.5% of the 5-acetylamino derivative (the so-called isomer I) the solution is stable for 46 days. Oseltamivir was less stable in a solution prepared with potable water instead of purified water. Due to an increasing pH the stability of this solution decreased to 14 days. Furthermore a white precipitate of mainly calcium phosphate was observed. The addition of 0.1% anhydrous citric acid avoided these problems and improved the stability of the solution prepared with potable water to 63 days. Sodium benzoate was stable in all oral solutions tested.

  19. Modification of polymer surfaces to enhance enzyme activity and stability

    DEFF Research Database (Denmark)

    Hoffmann, Christian

    Enzyme immobilization is an important concept for the development of improved biocatalytic processes, primarily through facilitated separation procedures. However, enzyme immobilization usually comes at a price of reduced biocatalytic activity. For this reason, different immobilization methods have...... already been developed, combining the same goal to improve enzyme activity, stability and selectivity. Polymer materials have shown, due to their easy processibility and versatile properties, high potential as enzyme support. However, in order to achieve improved enzyme performance, the combination...... on their tailored surface modification in order to obtain improved enzyme-support systems. Firstly, an off-stoichiometric thiol-ene (OSTE) thermosetting material was used for the development of a screening platform allowing the investigation of micro-environmental effects and their impact on the activity...

  20. Stability of tacrolimus solutions in polyolefin containers.

    Science.gov (United States)

    Lee, Jun H; Goldspiel, Barry R; Ryu, Sujung; Potti, Gopal K

    2016-02-01

    Results of a study to determine the stability of tacrolimus solutions stored in polyolefin containers under various temperature conditions are reported. Triplicate solutions of tacrolimus (0.001, 0.01, and 0.1 mg/mL) in 0.9% sodium chloride injection or 5% dextrose injection were prepared in polyolefin containers. Some samples were stored at room temperature (20-25 °C); others were refrigerated (2-8 °C) for 20 hours and then stored at room temperature for up to 28 hours. The solutions were analyzed by stability-indicating high-performance liquid chromatography (HPLC) assay at specified time points over 48 hours. Solution pH was measured and containers were visually inspected at each time point. Stability was defined as retention of at least 90% of the initial tacrolimus concentration. All tested solutions retained over 90% of the initial tacrolimus concentration at all time points, with the exception of the 0.001-mg/mL solution prepared in 0.9% sodium chloride injection, which was deemed unstable beyond 24 hours. At all evaluated concentrations, mean solution pH values did not change significantly over 48 hours; no particle formation was detected. During storage in polyolefin bags at room temperature, a 0.001-mg/mL solution of tacrolimus was stable for 24 hours when prepared in 0.9% sodium chloride injection and for at least 48 hours when prepared in 5% dextrose injection. Solutions of 0.01 and 0.1 mg/mL prepared in either diluent were stable for at least 48 hours, and the 0.01-mg/mL tacrolimus solution was also found to be stable throughout a sequential temperature protocol. Copyright © 2016 by the American Society of Health-System Pharmacists, Inc. All rights reserved.

  1. Thermodynamic stability of radioactivity standard solutions

    International Nuclear Information System (INIS)

    Iroulard, M.G.

    2007-04-01

    The basic requirement when preparing radioactivity standard solutions is to guarantee the concentration of a radionuclide or a radioelement, expressed in the form of activity concentration (Ac = A/m (Bq/g), with A: activity and m: mass of solution). Knowledge of the law of radioactive decay and the half-life of a radionuclide or radioelement makes it possible to determine the activity concentration at any time, and this must be confirmed subsequently by measurement. Furthermore, when radioactivity standard solutions are prepared, it is necessary to establish optimal conditions of thermodynamic stability of the standard solutions. Radioactivity standard solutions are prepared by metrology laboratories from original solutions obtained from a range of suppliers. These radioactivity standard solutions must enable preparation of liquid and/or solid radioactivity standard sources of which measurement by different methods can determine, at a given instant, the activity concentration of the radionuclide or radioelement present in the solution. There are a number of constraints associated with the preparation of such sources. Here only those that relate to the physical and chemical properties of the standard solution are considered, and therefore need to be taken into account when preparing a radioactivity standard solution. These issues are considered in this document in accordance with the following plan: - A first part devoted to the chemical properties of the solutions: - the solubilization media: ultra-pure water and acid media, - the carriers: concentration, oxidation state of the radioactive element and the carrier element. - A second part describing the methodology of the preparation, packaging and storage of standard solutions: - glass ampoules: the structure of glasses, the mechanisms of their dissolution, the sorption phenomenon at the solid-solution interface, - quartz ampoules, - cleaning and packaging: cleaning solutions, internal surface coatings and

  2. Thermodynamic stability of radioactivity standard solutions

    Energy Technology Data Exchange (ETDEWEB)

    Iroulard, M.G

    2007-04-15

    The basic requirement when preparing radioactivity standard solutions is to guarantee the concentration of a radionuclide or a radioelement, expressed in the form of activity concentration (Ac = A/m (Bq/g), with A: activity and m: mass of solution). Knowledge of the law of radioactive decay and the half-life of a radionuclide or radioelement makes it possible to determine the activity concentration at any time, and this must be confirmed subsequently by measurement. Furthermore, when radioactivity standard solutions are prepared, it is necessary to establish optimal conditions of thermodynamic stability of the standard solutions. Radioactivity standard solutions are prepared by metrology laboratories from original solutions obtained from a range of suppliers. These radioactivity standard solutions must enable preparation of liquid and/or solid radioactivity standard sources of which measurement by different methods can determine, at a given instant, the activity concentration of the radionuclide or radioelement present in the solution. There are a number of constraints associated with the preparation of such sources. Here only those that relate to the physical and chemical properties of the standard solution are considered, and therefore need to be taken into account when preparing a radioactivity standard solution. These issues are considered in this document in accordance with the following plan: - A first part devoted to the chemical properties of the solutions: - the solubilization media: ultra-pure water and acid media, - the carriers: concentration, oxidation state of the radioactive element and the carrier element. - A second part describing the methodology of the preparation, packaging and storage of standard solutions: - glass ampoules: the structure of glasses, the mechanisms of their dissolution, the sorption phenomenon at the solid-solution interface, - quartz ampoules, - cleaning and packaging: cleaning solutions, internal surface coatings and

  3. Thermal Stabilization of Enzymes Immobilized within Carbon Paste Electrodes.

    Science.gov (United States)

    Wang, J; Liu, J; Cepra, G

    1997-08-01

    In this note we report on the remarkable thermal stabilization of enzymes immobilized in carbon paste electrodes. Amperometric biosensors are shown for the first time to withstand a prolonged high-temperature (>50 °C) stress. Nearly full activity of glucose oxidase is retained over periods of up to 4 months of thermal stress at 60-80 °C. Dramatic improvements in the thermostability are observed for polyphenol oxidase, lactate oxidase, alcohol oxidase, horseradish peroxidase, and amino acid oxidase. Such resistance to heat-induced denaturation is attributed to the conformational rigidity of these biocatalysts within the highly hydrophobic (mineral oil or silicone grease) pasting liquid. While no chemical stabilizer is needed for attaining such protective action, it appears that low humidity (i.e., low water content) is essential for minimizing the protein mobility. Besides their implications for electrochemical biosensors, such observations should lead to a new generation of thermoresistant enzyme reactors based on nonpolar semisolid supports.

  4. Protein stability and enzyme activity at extreme biological temperatures

    International Nuclear Information System (INIS)

    Feller, Georges

    2010-01-01

    Psychrophilic microorganisms thrive in permanently cold environments, even at subzero temperatures. To maintain metabolic rates compatible with sustained life, they have improved the dynamics of their protein structures, thereby enabling appropriate molecular motions required for biological activity at low temperatures. As a consequence of this structural flexibility, psychrophilic proteins are unstable and heat-labile. In the upper range of biological temperatures, thermophiles and hyperthermophiles grow at temperatures > 100 0 C and synthesize ultra-stable proteins. However, thermophilic enzymes are nearly inactive at room temperature as a result of their compactness and rigidity. At the molecular level, both types of extremophilic proteins have adapted the same structural factors, but in opposite directions, to address either activity at low temperatures or stability in hot environments. A model based on folding funnels is proposed accounting for the stability-activity relationships in extremophilic proteins. (topical review)

  5. Thermal stability of tagatose in solution.

    Science.gov (United States)

    Luecke, Katherine J; Bell, Leonard N

    2010-05-01

    Tagatose, a monosaccharide similar to fructose, has been shown to behave as a prebiotic. To deliver this prebiotic benefit, tagatose must not degrade during the processing of foods and beverages. The objective of this study was to evaluate the thermal stability of tagatose in solutions. Tagatose solutions were prepared in 0.02 and 0.1 M phosphate and citrate buffers at pHs 3 and 7, which were then held at 60, 70, and 80 degrees C. Pseudo-1st-order rate constants for tagatose degradation were determined. In citrate and phosphate buffers at pH 3, minimal tagatose was lost and slight browning was observed. At pH 7, tagatose degradation rates were enhanced. Degradation was faster in phosphate buffer than citrate buffer. Higher buffer concentrations also increased the degradation rate constants. Enhanced browning accompanied tagatose degradation in all buffer solutions at pH 7. Using the activation energies for tagatose degradation, less than 0.5% and 0.02% tagatose would be lost under basic vat and HTST pasteurization conditions, respectively. Although tagatose does breakdown at elevated temperatures, the amount of tagatose lost during typical thermal processing conditions would be virtually negligible. Practical Application: Tagatose degradation occurs minimally during pasteurization, which may allow for its incorporation into beverages as a prebiotic.

  6. Paper Microzone Plates as Analytical Tools for Studying Enzyme Stability: A Case Study on the Stabilization of Horseradish Peroxidase Using Trehalose and SU-8 Epoxy Novolac Resin.

    Science.gov (United States)

    Ganaja, Kirsten A; Chaplan, Cory A; Zhang, Jingyi; Martinez, Nathaniel W; Martinez, Andres W

    2017-05-16

    Paper microzone plates in combination with a noncontact liquid handling robot were demonstrated as tools for studying the stability of enzymes stored on paper. The effect of trehalose and SU-8 epoxy novolac resin (SU-8) on the stability of horseradish peroxidase (HRP) was studied in both a short-term experiment, where the activity of various concentrations of HRP dried on paper were measured after 1 h, and a long-term experiment, where the activity of a single concentration of HRP dried and stored on paper was monitored for 61 days. SU-8 was found to stabilize HRP up to 35 times more than trehalose in the short-term experiment for comparable concentrations of the two reagents, and a 1% SU-8 solution was found to stabilize HRP approximately 2 times more than a 34% trehalose solution in both short- and long-term experiments. The results suggest that SU-8 is a promising candidate for use as an enzyme-stabilizing reagent for paper-based diagnostic devices and that the short-term experiment could be used to quickly evaluate the capacity of various reagents for stabilizing enzymes to identify and characterize new enzyme-stabilizing reagents.

  7. Stability and instability of stationary solutions for sublinear parabolic equations

    Science.gov (United States)

    Kajikiya, Ryuji

    2018-01-01

    In the present paper, we study the initial boundary value problem of the sublinear parabolic equation. We prove the existence of solutions and investigate the stability and instability of stationary solutions. We show that a unique positive and a unique negative stationary solutions are exponentially stable and give the exact exponent. We prove that small stationary solutions are unstable. For one space dimensional autonomous equations, we elucidate the structure of stationary solutions and study the stability of all stationary solutions.

  8. One-electron reduction reactions with enzymes in solution

    International Nuclear Information System (INIS)

    Bisby, R.H.; Cundall, R.B.; Redpath, J.L.; Adams, G.E.

    1976-01-01

    At pH 8 and above, hydrated electrons react with ribonuclease lysozyme and α-chymotrypsin to form transient products whose spectra resemble, but are not identical to, those for the RSSR - radical anion already known for simple disulphides. Assuming a value for the extinction coefficient similar to that for RSSR - in simple disulphides, only a fraction of the hydrated electrons are shown to react with the disulphide bridges: the remainder react at other sites in the protein molecule, such as histidine, tyrosine and, in lysozyme, tryptophan residues, giving rise to comparatively weak optical absorptions between 300 and 400 nm. This has been substantiated by studying the reaction of e - sub(aq) with subtilisin Novo (an enzyme which does not contain disulphide bridges), with enzymes in which the sulphur bridges have been oxidised and with some amino acid derivatives. On lowering the pH of the solution the intensity of the RSSR - absorption diminishes as the protonated histidine residues become the favoured reaction sites. In acid solutions (pH 2 to 3) the transient optical absoptions observed are due to reactions of hydrogen atoms with the aromatic amino acids tyrosine, tryptophan and phenylalanine. The CO - 2 radical anion is only observed to transfer an electron to disulphide groups in ribonuclease, although the effect of repeated pulsing shows that some reaction must occur elsewhere in the protein molecule. In acid solutions, protonation of the electron adduct appears to produce the RSSRH. radical, whose spectrum has a maximum at 340 nm. (author)

  9. Crosslinked Enzyme Aggregates in Hierarchically-Ordered Mesoporous Silica: A Simple and Effective Method for Enzyme Stabilization

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Moon Il; Kim, Jungbae; Lee, Jinwoo; Jia, Hongfei; Na, Hyon Bin; Youn, Jongkyu; Kwak, Ja Hun; Dohnalkova, Alice; Grate, Jay W.; Wang, Ping; Hyeon, Taeghwan; Park, Hyun-Gyu; Chang, Ho Nam

    2007-02-01

    alpha-chymotrypsin (CT) and lipase (LP) were immobilized in hierarchically-ordered mesocellular mesoporous silica (HMMS) in a simple but effective way for the enzyme stabilization, which was achieved by the enzyme adsorption followed by glutaraldehyde (GA) crosslinking. This resulted in the formation of nanometer scale crosslinked enzyme aggregates (CLEAs) entrapped in the mesocellular pores of HMMS (37 nm), which did not leach out of HMMS through narrow mesoporous channels (13 nm). CLEA of alpha-chymotrypsin (CLEA-CT) in HMMS showed a high enzyme loading capacity and significantly increased enzyme stability. No activity decrease of CLEA-CT was observed for two weeks under even rigorously shaking condition, while adsorbed CT in HMMS and free CT showed a rapid inactivation due to the enzyme leaching and presumably autolysis, respectively. With the CLEA-CT in HMMS, however, there was no tryptic digestion observed suggesting that the CLEA-CT is not susceptible to autolysis. Moreover, CLEA of lipase (CLEA-LP) in HMMS retained 30% specific activity of free lipase with greatly enhanced stability. This work demonstrates that HMMS can be efficiently employed as host materials for enzyme immobilization leading to highly enhanced stability of the immobilized enzymes with high enzyme loading and activity.

  10. The stability of the strong gravity solution

    International Nuclear Information System (INIS)

    Baran, S.A.

    1978-01-01

    The perturbation of the classical solution to a strong gravity model given by Salam and Strathdee is investigated. Using the Hamiltonian formalism it is shown that this static and spherically symmetric solution is stable under the odd parity perturbations provided some parameters in the solution are suitably restricted

  11. Protein Stabilization and Enzyme Activation in Ionic Liquids: Specific Ion Effects

    Science.gov (United States)

    Zhao, Hua

    2015-01-01

    There are still debates on whether the hydration of ions perturbs the water structure, and what is the degree of such disturbance; therefore, the origin of Hofmeister effect on protein stabilization continues being questioned. For this reason, it is suggested to use the ‘specific ion effect’ instead of other misleading terms such as Hofmeister effect, Hofmeister series, lyotropic effect, and lyotropic series. In this review, we firstly discuss the controversial aspect of inorganic ion effects on water structures, and several possible contributors to the specific ion effect of protein stability. Due to recent overwhelming attraction of ionic liquids (ILs) as benign solvents in many enzymatic reactions, we further evaluate the structural properties and molecular-level interactions in neat ILs and their aqueous solutions. Next, we systematically compare the specific ion effects of ILs on enzyme stability and activity, and conclude that (a) the specificity of many enzymatic systems in diluted aqueous IL solutions is roughly in line with the traditional Hofmeister series albeit some exceptions; (b) however, the specificity follows a different track in concentrated or neat ILs because other factors (such as hydrogen-bond basicity, nucelophilicity, and hydrophobicity, etc) are playing leading roles. In addition, we demonstrate some examples of biocatalytic reactions in IL systems that are guided by the empirical specificity rule. PMID:26949281

  12. The stability of vacuum solutions in generalised gravity

    Energy Technology Data Exchange (ETDEWEB)

    Madsen, M.S. (Sussex Univ., Brighton (UK). Astronomy Centre); Low, R.J. (Coventry (Lanchester) Polytechnic (UK). Dept. of Mathematics)

    1990-05-10

    The stability of the Ricci-flat solutions of a large class of generalised gravity theories is examined. It is shown by use of complementary methods that all such solutions are stable in a given theory if that theory admits a truncation to a quadratic theory in which the solution is stable. In particular, this means that the exterior Schwarzschild solution is stable in any gravity theory constructed purely from the Ricci scalar, provided that it exists in that theory. (orig.).

  13. The stability of vacuum solutions in generalised gravity

    International Nuclear Information System (INIS)

    Madsen, M.S.; Low, R.J.

    1990-01-01

    The stability of the Ricci-flat solutions of a large class of generalised gravity theories is examined. It is shown by use of complementary methods that all such solutions are stable in a given theory if that theory admits a truncation to a quadratic theory in which the solution is stable. In particular, this means that the exterior Schwarzschild solution is stable in any gravity theory constructed purely from the Ricci scalar, provided that it exists in that theory. (orig.)

  14. Stability and Concentration Verification of Ammonium Perchlorate Dosing Solutions

    National Research Council Canada - National Science Library

    Tsui, David

    1998-01-01

    Stability and concentration verification was performed for the ammonium perchlorate dosing solutions used in the on-going 90-Day Oral Toxicity Study conducted by Springborn Laboratories, Inc. (SLI Study No. 3433.1...

  15. Slope stability and erosion control: Ecotechnological solutions

    NARCIS (Netherlands)

    Norris, J.E.; Stokes, A.; Mickovski, S.B.; Cammeraat, E.; van Beek, R.; Nicoll, B.C.; Achim, A.

    2008-01-01

    This book is designed to assist the civil and geotechnical engineer, geomorphologist, forester, landscape architect or ecologist in choosing ecotechnological solutions for slopes that are prone to a variety of mass movements e.g. shallow failure or erosion. Within this book, the 'engineer' is used

  16. Nanocaged enzymes with enhanced catalytic activity and increased stability against protease digestion

    Science.gov (United States)

    Zhao, Zhao; Fu, Jinglin; Dhakal, Soma; Johnson-Buck, Alexander; Liu, Minghui; Zhang, Ting; Woodbury, Neal W.; Liu, Yan; Walter, Nils G.; Yan, Hao

    2016-01-01

    Cells routinely compartmentalize enzymes for enhanced efficiency of their metabolic pathways. Here we report a general approach to construct DNA nanocaged enzymes for enhancing catalytic activity and stability. Nanocaged enzymes are realized by self-assembly into DNA nanocages with well-controlled stoichiometry and architecture that enabled a systematic study of the impact of both encapsulation and proximal polyanionic surfaces on a set of common metabolic enzymes. Activity assays at both bulk and single-molecule levels demonstrate increased substrate turnover numbers for DNA nanocage-encapsulated enzymes. Unexpectedly, we observe a significant inverse correlation between the size of a protein and its activity enhancement. This effect is consistent with a model wherein distal polyanionic surfaces of the nanocage enhance the stability of active enzyme conformations through the action of a strongly bound hydration layer. We further show that DNA nanocages protect encapsulated enzymes against proteases, demonstrating their practical utility in functional biomaterials and biotechnology. PMID:26861509

  17. Nanocaged enzymes with enhanced catalytic activity and increased stability against protease digestion

    Science.gov (United States)

    Zhao, Zhao; Fu, Jinglin; Dhakal, Soma; Johnson-Buck, Alexander; Liu, Minghui; Zhang, Ting; Woodbury, Neal W.; Liu, Yan; Walter, Nils G.; Yan, Hao

    2016-02-01

    Cells routinely compartmentalize enzymes for enhanced efficiency of their metabolic pathways. Here we report a general approach to construct DNA nanocaged enzymes for enhancing catalytic activity and stability. Nanocaged enzymes are realized by self-assembly into DNA nanocages with well-controlled stoichiometry and architecture that enabled a systematic study of the impact of both encapsulation and proximal polyanionic surfaces on a set of common metabolic enzymes. Activity assays at both bulk and single-molecule levels demonstrate increased substrate turnover numbers for DNA nanocage-encapsulated enzymes. Unexpectedly, we observe a significant inverse correlation between the size of a protein and its activity enhancement. This effect is consistent with a model wherein distal polyanionic surfaces of the nanocage enhance the stability of active enzyme conformations through the action of a strongly bound hydration layer. We further show that DNA nanocages protect encapsulated enzymes against proteases, demonstrating their practical utility in functional biomaterials and biotechnology.

  18. An appraisal of the enzyme stability-activity trade-off.

    Science.gov (United States)

    Miller, Scott R

    2017-07-01

    A longstanding idea in evolutionary physiology is that an enzyme cannot jointly optimize performance at both high and low temperatures due to a trade-off between stability and activity. Although a stability-activity trade-off has been observed for well-characterized examples, such a trade-off is not imposed by any physical chemical constraint. To better understand the pervasiveness of this trade-off, I investigated the stability-activity relationship for comparative biochemical studies of purified orthologous enzymes identified by a literature search. The nature of this relationship varied greatly among studies. Notably, studies of enzymes with low mean synonymous nucleotide sequence divergence were less likely to exhibit the predicted negative correlation between stability and activity. Similarly, a survey of directed evolution investigations of the stability-activity relationship indicated that these traits are often uncoupled among nearly identical yet phenotypically divergent enzymes. This suggests that the presumptive trade-off often reported for investigations of enzymes with high mean sequence divergence may in some cases instead be a consequence of the degeneration over time of enzyme function in unselected environments, rather than a direct effect of thermal adaptation. The results caution against the general assertion of a stability-activity trade-off during enzyme adaptation. © 2017 The Author(s). Evolution © 2017 The Society for the Study of Evolution.

  19. Neutral insulin solutions physically stabilized by addition of Zn2+.

    Science.gov (United States)

    Brange, J; Havelund, S; Hommel, E; Sørensen, E; Kühl, C

    1986-01-01

    Commercial neutral insulin solutions, all of which contain 2-3 zinc atoms per hexameric unit of insulin, have a relatively limited physical stability when exposed to heat and movement, as for example in insulin infusion pumps. Physical stabilization of neutral insulin solutions has been obtained by addition of two extra Zn2+ per hexamer of insulin. This addition stabilizes porcine and human neutral solutions equally well and does not affect the chemical stability of the insulin. The stabilization is probably obtained by a further strengthening of the hexameric structure of insulin, so that the formation of insoluble insulin fibrils (via the dissociation into the insulin monomer or dimer) is impeded or prevented. The addition of an extra 2 Zn2+ has been shown to be without influence on the insulin immunogenicity in rabbits or on the rate of absorption after subcutaneous injection in diabetic patients. It is concluded that neutral insulin solution can be physically stabilized by addition of extra Zn2+ without affecting other qualities of the insulin preparation including chemical stability, immunogenicity, and duration of action after injection.

  20. Stability of core–shell nanowires in selected model solutions

    International Nuclear Information System (INIS)

    Kalska-Szostko, B.; Wykowska, U.; Basa, A.; Zambrzycka, E.

    2015-01-01

    Highlights: • Stability of the core–shell nanowires in environmental solutions were tested. • The most and the least aggressive solutions were determined. • The influence of different solutions on magnetic nanowires core was found out. - Abstract: This paper presents the studies of stability of magnetic core–shell nanowires prepared by electrochemical deposition from an acidic solution containing iron in the core and modified surface layer. The obtained nanowires were tested according to their durability in distilled water, 0.01 M citric acid, 0.9% NaCl, and commercial white wine (12% alcohol). The proposed solutions were chosen in such a way as to mimic food related environment due to a possible application of nanowires as additives to, for example, packages. After 1, 2 and 3 weeks wetting in the solutions, nanoparticles were tested by Infrared Spectroscopy, Atomic Absorption Spectroscopy, Transmission Electron Microscopy and X-ray diffraction methods

  1. Stability of core–shell nanowires in selected model solutions

    Energy Technology Data Exchange (ETDEWEB)

    Kalska-Szostko, B., E-mail: kalska@uwb.edu.pl; Wykowska, U.; Basa, A.; Zambrzycka, E.

    2015-03-30

    Highlights: • Stability of the core–shell nanowires in environmental solutions were tested. • The most and the least aggressive solutions were determined. • The influence of different solutions on magnetic nanowires core was found out. - Abstract: This paper presents the studies of stability of magnetic core–shell nanowires prepared by electrochemical deposition from an acidic solution containing iron in the core and modified surface layer. The obtained nanowires were tested according to their durability in distilled water, 0.01 M citric acid, 0.9% NaCl, and commercial white wine (12% alcohol). The proposed solutions were chosen in such a way as to mimic food related environment due to a possible application of nanowires as additives to, for example, packages. After 1, 2 and 3 weeks wetting in the solutions, nanoparticles were tested by Infrared Spectroscopy, Atomic Absorption Spectroscopy, Transmission Electron Microscopy and X-ray diffraction methods.

  2. Wind energy systems solutions for power quality and stabilization

    CERN Document Server

    Ali, Mohd Hasan

    2012-01-01

    Unlike conventional power plants, wind plants emit no air pollutants or greenhouse gases--and wind energy is a free, renewable resource. However, the induction machines commonly used as wind generators have stability problems similar to the transient stability of synchronous machines. To minimize power, frequency, and voltage fluctuations caused by network faults or random wind speed variations, control mechanisms are necessary. Wind Energy Systems: Solutions for Power Quality and Stabilization clearly explains how to solve stability and power quality issues of wind generator systems. Covering

  3. Enzyme Stability and Activity in Non-Aqueous Reaction Systems: A Mini Review

    Directory of Open Access Journals (Sweden)

    Shihui Wang

    2016-02-01

    Full Text Available Enormous interest in biocatalysis in non-aqueous phase has recently been triggered due to the merits of good enantioselectivity, reverse thermodynamic equilibrium, and no water-dependent side reactions. It has been demonstrated that enzyme has high activity and stability in non-aqueous media, and the variation of enzyme activity is attributed to its conformational modifications. This review comprehensively addresses the stability and activity of the intact enzymes in various non-aqueous systems, such as organic solvents, ionic liquids, sub-/super-critical fluids and their combined mixtures. It has been revealed that critical factors such as Log P, functional groups and the molecular structures of the solvents define the microenvironment surrounding the enzyme molecule and affect enzyme tertiary and secondary structure, influencing enzyme catalytic properties. Therefore, it is of high importance for biocatalysis in non-aqueous media to elucidate the links between the microenvironment surrounding enzyme surface and its stability and activity. In fact, a better understanding of the correlation between different non-aqueous environments and enzyme structure, stability and activity can contribute to identifying the most suitable reaction medium for a given biotransformation.

  4. Evaluation of the effects of enzyme-based liquid chemical stabilizers on subgrade soils

    CSIR Research Space (South Africa)

    Mgangira, Martin B

    2009-07-01

    Full Text Available The purpose of this study was to asses the strength of enzyme treated soil material. Thus the aim of the paper is to present laboratory results on the effects of two enzyme-based liquid chemicals as soil stabilizers. Soil samples were prepared...

  5. Enzyme-assisted extraction of stabilized chlorophyll from spinach.

    Science.gov (United States)

    Özkan, Gülay; Ersus Bilek, Seda

    2015-06-01

    Zinc complex formation with chlorophyll derivatives in spinach pulp was studied by adding 300ppm Zn(2+) for production of stable food colorant, followed by the heating at 110°C for 15min. Zinc complex formation increased at pH values of 7.0 or greater. Pectinex Ultra SP-L was selected for enzyme-assisted release of zinc-chlorophyll derivatives from spinach pulp. Effect of enzyme concentration (1-9%), treatment temperature (30-60°C), and time (30-210min) on total chlorophyll content (TCC) were optimized using response surface methodology. A quadratic regression model (R(2)=0.9486) was obtained from the experimental design. Optimum treatment conditions were 8% enzyme concentration, 45°C, and 30min, which yielded a 50.747mgTCC/100g spinach pulp. Enzymatic treatment was followed by solvent extraction with ethanol at a solvent-to-sample ratio of 2.5:1 at 60°C for 45min for the highest TCC recovery. Pretreatment with enzyme and extraction in ethanol resulted in 39% increase in Zn-chlorophyll derivative yield. Copyright © 2014 Elsevier Ltd. All rights reserved.

  6. Multipoint attachment to a support protects enzyme from inactivation by organic solvents: alpha-Chymotrypsin in aqueous solutions of alcohols and diols.

    Science.gov (United States)

    Mozhaev, V V; Sergeeva, M V; Belova, A B; Khmelnitsky, Y L

    1990-03-25

    Inactivation of alpha-chymotrypsin in aqueous solutions of alcohols and diols proceeds both reversibly and irreversibly. Reversible loss of the specific enzyme activity results from conformational changes (unfolding) of the enzyme detected by fluorescence spectroscopy. Multipoint covalent attachment to the matrix of polyacryl-amide gel by copolymerization method stabilizes alpha-chymotrypsin from denaturation by alcohols, the stabilizing effect increasing with the number of bonds between the protein and the support. Immobilization protects the enzyme also from irreversible inactivation by organic solvents resulting from bimolecular aggregation and autolysis.

  7. On the stability of non-supersymmetric supergravity solutions

    Science.gov (United States)

    Imaanpur, Ali; Zameni, Razieh

    2017-09-01

    We examine the stability of some non-supersymmetric supergravity solutions that have been found recently. The first solution is AdS5 ×M6, for M6 an stretched CP3. We consider breathing and squashing mode deformations of the metric, and find that the solution is stable against small fluctuations of this kind. Next we consider type IIB solution of AdS2 ×M8, where the compact space is a U (1) bundle over N (1 , 1). We study its stability under the deformation of M8 and the 5-form flux. In this case we also find that the solution is stable under small fluctuation modes of the corresponding deformations.

  8. On the stability of non-supersymmetric supergravity solutions

    Directory of Open Access Journals (Sweden)

    Ali Imaanpur

    2017-09-01

    Full Text Available We examine the stability of some non-supersymmetric supergravity solutions that have been found recently. The first solution is AdS5×M6, for M6 an stretched CP3. We consider breathing and squashing mode deformations of the metric, and find that the solution is stable against small fluctuations of this kind. Next we consider type IIB solution of AdS2×M8, where the compact space is a U(1 bundle over N(1,1. We study its stability under the deformation of M8 and the 5-form flux. In this case we also find that the solution is stable under small fluctuation modes of the corresponding deformations.

  9. Non-homologous isofunctional enzymes: a systematic analysis of alternative solutions in enzyme evolution.

    Science.gov (United States)

    Omelchenko, Marina V; Galperin, Michael Y; Wolf, Yuri I; Koonin, Eugene V

    2010-04-30

    Evolutionarily unrelated proteins that catalyze the same biochemical reactions are often referred to as analogous - as opposed to homologous - enzymes. The existence of numerous alternative, non-homologous enzyme isoforms presents an interesting evolutionary problem; it also complicates genome-based reconstruction of the metabolic pathways in a variety of organisms. In 1998, a systematic search for analogous enzymes resulted in the identification of 105 Enzyme Commission (EC) numbers that included two or more proteins without detectable sequence similarity to each other, including 34 EC nodes where proteins were known (or predicted) to have distinct structural folds, indicating independent evolutionary origins. In the past 12 years, many putative non-homologous isofunctional enzymes were identified in newly sequenced genomes. In addition, efforts in structural genomics resulted in a vastly improved structural coverage of proteomes, providing for definitive assessment of (non)homologous relationships between proteins. We report the results of a comprehensive search for non-homologous isofunctional enzymes (NISE) that yielded 185 EC nodes with two or more experimentally characterized - or predicted - structurally unrelated proteins. Of these NISE sets, only 74 were from the original 1998 list. Structural assignments of the NISE show over-representation of proteins with the TIM barrel fold and the nucleotide-binding Rossmann fold. From the functional perspective, the set of NISE is enriched in hydrolases, particularly carbohydrate hydrolases, and in enzymes involved in defense against oxidative stress. These results indicate that at least some of the non-homologous isofunctional enzymes were recruited relatively recently from enzyme families that are active against related substrates and are sufficiently flexible to accommodate changes in substrate specificity.

  10. Detection of microwave radiation of cytochrome CYP102 A1 solution during the enzyme reaction

    Directory of Open Access Journals (Sweden)

    Yu.D. Ivanov

    2016-03-01

    Full Text Available Microwave radiation at 3.4–4.2 GHz frequency of the cytochrome P450 CYP102 A1 (BM3 solution was registered during the lauric acid hydroxylation reaction. The microwave radiation generation was shown to occur following the addition of electron donor NADPH to a system containing an enzyme and a substrate. The radiation occurs for the enzyme solutions with enzyme concentrations of 10−8 and 10−9 М. The microwave radiation effect elicited by the aqueous enzyme solution was observed for the first time. The results obtained can be used to elaborate a new approach to enzyme systems research, including studying of the mechanism of interaction of a functioning enzyme system with microenvironment.

  11. Evaluation of the organophosphorus hydrolase enzyme activity in creams and investigation of its stability

    Directory of Open Access Journals (Sweden)

    Mariye Rajaie

    2016-06-01

    Full Text Available The main purpose of this project is investigation of the organophosphorus hydrolase (OPH enzyme activity in water in oil (w/o and oil in water (o/w creams and investigation of the OPH enzyme stability in formulated creams. OPH enzyme was extracted and purified from strain flavobacterium. The w/o and o/w creams were prepared using different formulations. In order to achieve an emulsion with maximum stability, appropriate percentage of the cream components was selected by studying different formulations and the physical and chemical stability of the produced cream were considered. 5Uenzyme/90gcream enzyme was used for each formulation. To measure the enzyme activity in creams, extraction method was used and enzyme activity was determined based on parathion hydrolysis. The thermal stability of OPH in both types of w/o and o/w creams was studied at 4 and 30  °C for various time periods. The average enzyme activity was about 0.0065 U/gcream and 0.018 U/gcream for w/o and o/w creams respectivly. According to the results, the relative activity at 4 °C was reduced to 50% after 26 and 45 days in w/o and o/w creams, respectivly. The results showed that the OPH enzyme activity in o/w cream was 2.6 times more than that of w/o cream, because of the higher hydrophobicity of o/w cream compared to w/o. The OPH enzyme stability in o/w cream was greater in comparison to w/o cream. The OPH enzyme was active for nearly 2 months on o/w creams at 4 °C .

  12. Stabilizing effect of biochar on soil extracellular enzymes after a denaturing stress.

    Science.gov (United States)

    Elzobair, Khalid A; Stromberger, Mary E; Ippolito, James A

    2016-01-01

    Stabilizing extracellular enzymes may maintain enzymatic activity while protecting enzymes from proteolysis and denaturation. A study determined whether a fast pyrolysis hardwood biochar (CQuest™) would reduce evaporative losses, subsequently stabilizing soil extracellular enzymes and prohibiting potential enzymatic activity loss following a denaturing stress (microwaving). Soil was incubated in the presence of biochar (0%, 1%, 2%, 5%, or 10% by wt.) for 36 days and then exposed to microwave energies (0, 400, 800, 1600, or 3200 J g(-1) soil). Soil enzymes (β-glucosidase, β-d-cellobiosidase, N-acetyl-β-glucosaminidase, phosphatase, leucine aminopeptidase, β-xylosidase) were analyzed by fluorescence-based assays. Biochar amendment reduced leucine aminopeptidase and β-xylosidase potential activity after the incubation period and prior to stress exposure. The 10% biochar rate reduced soil water loss at the lowest stress level (400 J microwave energy g(-1) soil). Enzyme stabilization was demonstrated for β-xylosidase; intermediate biochar application rates prevented a complete loss of this enzyme's potential activity after soil was exposed to 400 (1% biochar treatment) or 1600 (5% biochar treatment) J microwave energy g(-1) soil. Remaining enzyme potential activities were not affected by biochar, and activities decreased with increasing stress levels. We concluded that biochar has the potential to reduce evaporative soil water losses and stabilize certain extracellular enzymes where activity is maintained after a denaturing stress; this effect was biochar rate and enzyme dependent. While biochar may reduce the potential activity of certain soil extracellular enzymes, this phenomenon was not universal as the majority of enzymes assayed in this study were unaffected by exposure to biochar. Copyright © 2015 Elsevier Ltd. All rights reserved.

  13. Stability of Adrenaline in Irrigating Solution for Intraocular Surgery.

    Science.gov (United States)

    Shibata, Yuuka; Kimura, Yasuhiro; Taogoshi, Takanori; Matsuo, Hiroaki; Kihira, Kenji

    2016-01-01

    Intraocular irrigating solution containing 1 µg/mL adrenaline is widely used during cataract surgery to maintain pupil dilation. Prepared intraocular irrigating solutions are recommended for use within 6 h. After the irrigating solution is admistered for dilution, the adrenaline may become oxidized, and this may result in a decrease in its biological activity. However, the stability of adrenaline in intraocular irrigating solution is not fully understood. The aim of this study was to evaluate the stability of adrenaline in clinically used irrigating solutions of varying pH. Six hours after mixing, the adrenaline percentages remaining were 90.6%±3.7 (pH 7.2), 91.1%±2.2 (pH 7.5), and 65.2%±2.8 (pH 8.0) of the initial concentration. One hour after mixing, the percentages remaining were 97.6%±2.0 (pH 7.2), 97.4%±2.7 (pH 7.5), and 95.6%±3.3 (pH 8.0). The degradation was especially remarkable and time dependent in the solution at pH 8.0. These results indicate that the concentration of adrenaline is decreased after preparation. Moreover, we investigated the influence of sodium bisulfite on adrenaline stability in irrigating solution. The percentage adrenaline remaining at 6 h after mixing in irrigating solution (pH 8.0) containing sodium bisulfite at 0.5 µg/mL (concentration in irrigating solution) or at 500 µg/mL (concentration in the undiluted adrenaline preparation) were 57.5 and 97.3%, respectively. Therefore, the low concentration of sodium bisulfite in the irrigating solution may be a cause of the adrenaline loss. In conclusion, intraocular irrigation solution with adrenaline should be prepared just prior to its use in surgery.

  14. Enzyme stability, thermodynamics and secondary structures of α-amylase as probed by the CD spectroscopy.

    Science.gov (United States)

    Kikani, B A; Singh, S P

    2015-11-01

    An amylase of a thermophilic bacterium, Bacillus sp. TSSC-3 (GenBank Number, EU710557) isolated from the Tulsi Shyam hot spring reservoir (Gujarat, India) was purified to the homogeneity in a single step on phenyl sepharose 6FF. The molecular weight of the enzyme was 25kD, while the temperature and pH optima for the enzyme catalysis were 80°C and 7, respectively. The purified enzyme was highly thermostable with broad pH stability and displayed remarkable resistance against surfactants, chelators, urea, guanidine HCl and various solvents as well. The stability and changes in the secondary structure of the enzyme under various extreme conditions were determined by the circular dichroism (CD) spectroscopy. The stability trends and the changes in the α-helices and β-sheets were analyzed by Mean Residual Ellipticity (MRE) and K2D3. The CD data confirmed the structural stability of the enzyme under various harsh conditions, yet it indicated reduced α-helix content and increased β-sheets upon denaturation. The thermodynamic parameters; deactivation rate constant, half-life, changes in entropy, enthalpy, activation energy and Gibb's free energy indicated that the enzyme-substrate reactions were highly stable. The overall profile of the enzyme: high thermostability, alkalitolerance, calcium independent nature, dextrose equivalent values and resistance against chemical denaturants, solvents and surfactants suggest its commercial applications. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. Conductivity and electrochemical stability of concentrated aqueous choline chloride solutions

    Science.gov (United States)

    Grishina, E. P.; Kudryakova, N. O.

    2017-10-01

    The conductivity and electrochemical stability of choline chloride (ChCl) solutions with water contents ranging from 20 to 39 wt % are studied. Exposing ChCl to moist ambient air yields a highly concentrated aqueous solution that, as an electrolyte, exhibits the properties and variations in conductivity with temperature and concentration characteristic of other similar systems. Its electrochemical stability window, determined by cyclic voltammetry, is comparable to that of ChCl-based deep eutectic solvents (DESs). Products of the electrolysis of ChCl‒H2O mixtures seem to be less toxic than those of Reline, Ethaline, and Maline.

  16. Stability and special solutions to the conducting dusty gas model

    International Nuclear Information System (INIS)

    Calmelet, C.J.

    1987-01-01

    Models of the flow of a dusty, conducting and non-conducting gas are examined. Exact solutions for a conducting dusty gas model in the presence of a magnetic field are developed for two different flow domains. The exact solutions are calculated in the cases of negligible and non-negligible induced magnetic field. Stability theorems are developed which depend on the flow parameters of the dusty gas and the magnetic field. In particular, a universal stability theorem is obtained when the dusty gas flow is electrically conducting in the presence of an applied magnetic field, and the dust particles are non-uniformly distributed

  17. On exponential stability and periodic solutions of CNNs with delays

    Science.gov (United States)

    Cao, Jinde

    2000-03-01

    In this Letter, the author analyses further problems of global exponential stability and the existence of periodic solutions of cellular neural networks with delays (DCNNs). Some simple and new sufficient conditions are given ensuring global exponential stability and the existence of periodic solutions of DCNNs by applying some new analysis techniques and constructing suitable Lyapunov functionals. These conditions have important leading significance in the design and applications of globally stable DCNNs and periodic oscillatory DCNNs and are weaker than those in the earlier works [Phys. Rev. E 60 (1999) 3244], [J. Comput. Syst. Sci. 59 (1999)].

  18. Model format for a vaccine stability report and software solutions.

    Science.gov (United States)

    Shin, Jinho; Southern, James; Schofield, Timothy

    2009-11-01

    A session of the International Association for Biologicals Workshop on Stability Evaluation of Vaccine, a Life Cycle Approach was devoted to a model format for a vaccine stability report, and software solutions. Presentations highlighted the utility of a model format that will conform to regulatory requirements and the ICH common technical document. However, there need be flexibility to accommodate individual company practices. Adoption of a model format is premised upon agreement regarding content between industry and regulators, and ease of use. Software requirements will include ease of use and protections against inadvertent misspecification of stability design or misinterpretation of program output.

  19. Stability analysis of the Peregrine solution via squared eigenfunctions

    Science.gov (United States)

    Schober, C. M.; Strawn, M.

    2017-10-01

    A preliminary numerical investigation involving ensembles of perturbed initial data for the Peregrine soliton (the lowest order rational solution of the nonlinear Schrödinger equation) indicates that it is unstable [16]. In this paper we analytically investigate the linear stability of the Peregrine soliton, appealing to the fact that the Peregrine solution can be viewed as the singular limit of a single mode spatially periodic breathers (SPB). The "squared eigenfunction" connection between the Zakharov-Shabat (Z-S) system and the linearized NLS equation is employed in the stability analysis. Specifically, we determine the eigenfunctions of the Z-S system associated with the Peregrine soliton and construct a family of solutions of the associated linearized NLS (about the Peregrine) in terms of quadratic products of components of the eigenfunctions (i.e., the squared eigenfunction). We find there exist solutions of the linearization that grow exponentially in time, thus showing the Peregrine soliton is linearly unstable.

  20. The improved stability of enzyme encapsulated in biomimetic titania particles

    International Nuclear Information System (INIS)

    Jiang Yanjun; Sun Qianyun; Jiang Zhongyi; Zhang Lei; Li Jian; Li Lin; Sun Xiaohui

    2009-01-01

    This study demonstrates a novel biomimetic approach for the entrapment of yeast alcohol dehydrogenase (YADH) within titania nanoparticles to improve its stability. Protamine was as the template and catalyst for the condensation of titanium (IV) bis(ammonium lactato) dihydroxide (Ti-BALDH) into titania nanoparticles in which YADH was trapped. The as-prepared titania/protamine/YADH composites were characterized by scanning electron microscopy (SEM), transmission electron microscopy (TEM), dynamic light scattering (DLS), X-ray powder diffraction (XRD) and X-ray photoelectron spectroscopy (XPS). The mechanism of YADH encapsulation was tentatively proposed from a series of experimental results. The preliminary investigation showed that encapsulated YADH could retain most of its initial activity. Compared to free YADH, encapsulated YADH exhibited significantly improved thermal, pH and recycling stability. After 5 weeks storage, no substantial loss of catalytic activity for encapsulated YADH was observed

  1. Stability of sodium bicarbonate solutions in polyolefin bags.

    Science.gov (United States)

    Wear, Jennifer; McPherson, Timothy B; Kolling, William M

    2010-06-15

    The stability of sodium bicarbonate solutions in sterile water for injection or 5% dextrose injection stored at 21-24 degrees C or 2-4 degrees C was evaluated. Sodium bicarbonate injection was obtained in 50-mL vials of 8.4% (1 meq/mL). A total of 50, 100, or 150 meq of sodium bicarbonate was added to each 1-L polyolefin bag of either sterile water for injection or 5% dextrose injection. All solutions were prepared in a laminar-airflow hood using aseptic technique. Bags were punctured once to remove headspace air and once for the addition of each 50 meq of sodium bicarbonate. Six replicates of each test solution were prepared. The solutions were stored at 21-24 degrees C and 2-4 degrees C. Control solutions (50 and 150 meq) were similarly prepared in triplicate. Control solutions were sparged with either nitrogen gas or oxygen gas before storage. Sodium bicarbonate stability was assessed by measuring solution pH. Bicarbonate content was measured utilizing titration. Both pH and bicarbonate concentrations were measured immediately upon preparation and on days 3, 5, and 7 for both test and control solutions. All 95% confidence interval values for sample solution pH remained within 7.0-8.5 for seven days at 2-4 degrees C. Sodium bicarbonate solutions of 50, 100, and 150 meq in sterile water for injection or 5% dextrose injection were stable for up to seven days when refrigerated. The 50-meq solution was stable for up to 48 hours when stored at room temperature, and the 100- and 150-meq solutions were stable for up to 30 hours when stored at room temperature.

  2. The Local Stability of Solutions for a Nonlinear Equation

    Directory of Open Access Journals (Sweden)

    Haibo Yan

    2014-01-01

    Full Text Available The approach of Kruzkov’s device of doubling the variables is applied to establish the local stability of strong solutions for a nonlinear partial differential equation in the space L1(R by assuming that the initial value only lies in the space L1(R∩L∞(R.

  3. Stabilizing the border steady-state solution of two interacting ...

    African Journals Online (AJOL)

    In this paper, we have successfully developed a feedback control which has been used to stabilize an unstable steady-state solution (0, 3.3534). This convergence has occurred when the values of the final time are 190, 200, 210 and 220 which corresponds to the scenario when the value of the step length of our simulation ...

  4. Non-complexed four cascade enzyme mixture: simple purification and synergetic co-stabilization.

    Directory of Open Access Journals (Sweden)

    Suwan Myung

    Full Text Available Cell-free biosystems comprised of synthetic enzymatic pathways would be a promising biomanufacturing platform due to several advantages, such as high product yield, fast reaction rate, easy control and access, and so on. However, it was essential to produce (purified enzymes at low costs and stabilize them for a long time so to decrease biocatalyst costs. We studied the stability of the four recombinant enzyme mixtures, all of which originated from thermophilic microorganisms: triosephosphate isomerase (TIM from Thermus thermophiles, fructose bisphosphate aldolase (ALD from Thermotoga maritima, fructose bisphosphatase (FBP from T. maritima, and phosphoglucose isomerase (PGI from Clostridium thermocellum. It was found that TIM and ALD were very stable at evaluated temperature so that they were purified by heat precipitation followed by gradient ammonia sulfate precipitation. In contrast, PGI was not stable enough for heat treatment. In addition, the stability of a low concentration PGI was enhanced by more than 25 times in the presence of 20 mg/L bovine serum albumin or the other three enzymes. At a practical enzyme loading of 1000 U/L for each enzyme, the half-life time of free PGI was prolong to 433 h in the presence of the other three enzymes, resulting in a great increase in the total turn-over number of PGI to 6.2×10(9 mole of product per mole of enzyme. This study clearly suggested that the presence of other proteins had a strong synergetic effect on the stabilization of the thermolabile enzyme PGI due to in vitro macromolecular crowding effect. Also, this result could be used to explain why not all enzymes isolated from thermophilic microorganisms are stable in vitro because of a lack of the macromolecular crowding environment.

  5. [Alanine solution as enzyme reaction buffer used in A to O blood group conversion].

    Science.gov (United States)

    Li, Su-Bo; Zhang, Xue; Zhang, Yin-Ze; Tan, Ying-Xia; Bao, Guo-Qiang; Wang, Ying-Li; Ji, Shou-Ping; Gong, Feng; Gao, Hong-Wei

    2014-06-01

    The aim of this study was to investigate the effect of alanine solution as α-N-acetylgalactosaminidase enzyme reaction buffer on the enzymatic activity of A antigen. The binding ability of α-N-acetylgalactosaminidase with RBC in different reaction buffer such as alanine solution, glycine solution, normal saline (0.9% NaCl), PBS, PCS was detected by Western blot. The results showed that the efficiency of A to O conversion in alanine solution was similar to that in glycine solution, and Western blot confirmed that most of enzymes blinded with RBC in glycine or alanine solution, but few enzymes blinded with RBC in PBS, PCS or normal saline. The evidences indicated that binding of enzyme with RBC was a key element for A to O blood group conversion, while the binding ability of α-N-acetylgalactosaminidase with RBC in alanine or glycine solution was similar. It is concluded that alanine solution can be used as enzyme reaction buffer in A to O blood group conversion. In this buffer, the α-N-acetylgalactosaminidase is closely blinded with RBC and α-N-acetylgalactosaminidase plays efficient enzymatic activity of A antigen.

  6. Some reactions of oxidizing radicals with enzymes in aqueous solution

    International Nuclear Information System (INIS)

    Cundall, R.B.; Bisby, R.H.; Hoe, S.T.; Sims, H.E.; Anderson, R.F.

    1979-01-01

    A range of oxidizing radicals including some inorganic radical anions and the superoxide radical, can be generated by radiolysis of aqueous solutions. These radicals are more selective in their reactions with amino acids than the hydroxyl radical. Factors controlling the apparent reactivity of radical anions with proteins, such as free radical equilibria and ion-binding, are described. The superoxide radical inactivates papain by reaction with the cysteine residue. This reaction has been studied in solutions subjected to radiations of varying linear energy transfer. (Auth.)

  7. Stabilization of oil-in-water emulsions by enzyme catalyzed oxidative gelation of sugar beet pectin

    DEFF Research Database (Denmark)

    Abang Zaidel, Dayang Norulfairuz; Chronakis, Ioannis S.; Meyer, Anne S.

    2013-01-01

    Enzyme catalyzed oxidative cross-linking of feruloyl groups can promote gelation of sugar beet pectin (SBP). It is uncertain how the enzyme kinetics of this cross-linking reaction are affected in emulsion systems and whether the gelation affects emulsion stability. In this study, SBP (2.5% w...... larger average particle sizes than the emulsions in which the SBP was homogenized into the emulsion system during emulsion preparation (referred as Mix B). Mix B type emulsions were stable. Enzyme catalyzed oxidative gelation of SBP helped stabilize the emulsions in Mix A. The kinetics of the enzyme...... catalyzed oxidative gelation of SBP was evaluated by small angle oscillatory measurements for horseradish peroxidase (HRP) (EC 1.11.1.7) and laccase (EC 1.10.3.2) catalysis, respectively. HRP catalyzed gelation rates, determined from the slopes of the increase of elastic modulus (G0) with time, were higher...

  8. Stability of Bifurcating Stationary Solutions of the Artificial Compressible System

    Science.gov (United States)

    Teramoto, Yuka

    2018-02-01

    The artificial compressible system gives a compressible approximation of the incompressible Navier-Stokes system. The latter system is obtained from the former one in the zero limit of the artificial Mach number ɛ which is a singular limit. The sets of stationary solutions of both systems coincide with each other. It is known that if a stationary solution of the incompressible system is asymptotically stable and the velocity field of the stationary solution satisfies an energy-type stability criterion, then it is also stable as a solution of the artificial compressible one for sufficiently small ɛ . In general, the range of ɛ shrinks when the spectrum of the linearized operator for the incompressible system approaches to the imaginary axis. This can happen when a stationary bifurcation occurs. It is proved that when a stationary bifurcation from a simple eigenvalue occurs, the range of ɛ can be taken uniformly near the bifurcation point to conclude the stability of the bifurcating solution as a solution of the artificial compressible system.

  9. Electronic origin of strain effects on solute stabilities in iron

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Wei; Li, Xiangyan; Xu, Yichun, E-mail: xuyichun@issp.ac.cn, E-mail: csliu@issp.ac.cn; Liu, C. S., E-mail: xuyichun@issp.ac.cn, E-mail: csliu@issp.ac.cn [Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, P.O. Box 1129, Hefei 230031 (China); Liang, Yunfeng [Environment and Resource System Engineering, Kyoto University, Kyoto 615-8540 (Japan); Key Laboratory of Materials Physics, Institute of Solid State Physics, Chinese Academy of Sciences, P.O. Box 1129, Hefei 230031 (China)

    2016-08-21

    Nonuniform strain fields might induce the segregation of alloying solutes and ultimately lead to the mechanical performance degradation of body-centered-cubic (bcc) Fe based steels serving in extreme environments, which is worthy of investigation. In this paper, two typical volume-conserving strains, shear strain (SS) and normal strain (NS), are proposed to investigate the strain effects on solute stabilities in bcc iron by first-principles calculations. For solutes in each transition metal group, the calculated substitution energy change due to SS exhibits a linear dependence on the valence d radius of the solutes, and the slope decreases in an exponential manner as a function of the absolute difference between the Watson's electronegativity of iron and the averaged value of each transition metal group. This regularity is attributed to the Pauli repulsion between the solutes and the nearest neighboring Fe ions modulated by the hybridization of valence d bands and concluded to be originated from the characteristics of valence d bonding between the transition-metal solutes and Fe ions under SS. For main-group and post transition-metal solutes, the considerable drop of substitution energy change due to NS is concluded to be originated from the low-energy side shift of the widened valence s and p bands of the solutes. Our results indicate that the stabilities of substitutional solutes in iron under volume-conserving strain directly correlate with the intrinsic properties of the alloying elements, such as the valence d radius and occupancy, having or not having valence s and p bands.

  10. Enzyme

    Science.gov (United States)

    Enzymes are complex proteins that cause a specific chemical change in all parts of the body. For ... use them. Blood clotting is another example of enzymes at work. Enzymes are needed for all body ...

  11. Correlation of high-temperature stability of alpha-chymotrypsin with 'salting-in' properties of solution.

    Science.gov (United States)

    Levitsky VYu; Panova, A A; Mozhaev, V V

    1994-01-15

    A correlation between the stability of alpha-chymotrypsin against irreversible thermal inactivation at high temperatures (long-term stability) and the coefficient of Setchenov equation as a measure of salting-in/out efficiency of solutes in the Hofmeister series has been found. An increase in the concentration of salting-in solutes (KSCN, urea, guanidinium chloride, formamide) leads to a many-fold decrease of the inactivation rate of the enzyme. In contrast, addition of salting-out solutes has a small effect on the long-term stability of alpha-chymotrypsin at high temperatures. The effects of solutes are additive with respect to their salting-in/out capacities; the stabilizing action of the solutes is determined by the calculated Setchenov coefficient of solution. The correlation is explained by a solute-driven shift of the conformational equilibrium between the 'low-temperature' native and the 'high-temperature' denatured forms of the enzyme within the range of the kinetic scheme put forward in the preceding paper in this journal: irreversible inactivation of the high-temperature form proceeds much more slowly compared with the low-temperature form.

  12. Physical and chemical stability of pemetrexed in infusion solutions.

    Science.gov (United States)

    Zhang, Yanping; Trissel, Lawrence A

    2006-06-01

    Pemetrexed is a multitargeted, antifolate, antineoplastic agent that is indicated for single-agent use in locally advanced or metastatic non-small-cell lung cancer after prior chemotherapy and in combination with cisplatin for the treatment of malignant pleural mesothelioma not treatable by surgery. Currently, there is no information on the long-term stability of pemetrexed beyond 24 hours. To evaluate the longer-term physical and chemical stability of pemetrexed 2, 10, and 20 mg/mL in polyvinyl chloride (PVC) bags of dextrose 5% injection and NaCl 0.9% injection. Triplicate samples of pemetrexed were prepared in the concentrations and infusion solutions required. Evaluations for physical and chemical stability were performed initially and over 2 days at 23 degrees C protected from light and exposed to fluorescent light, and over 31 days of storage at 4 degrees C protected from light. Physical stability was assessed using turbidimetric and particulate measurement as well as visual observation. Chemical stability was evaluated by HPLC. All pemetrexed solutions remained chemically stable, with little or no loss of pemetrexed over 2 days at 23 degrees C, protected from light and exposed to fluorescent light, and over 31 days of storage at 4 degrees C, protected from light. The room temperature samples were physically stable throughout the 48 hour test period. However, pemetrexed admixtures developed large numbers of microparticulates during refrigerated storage exceeding 24 hours. Pemetrexed is chemically stable for 2 days at room temperature and 31 days refrigerated in dextrose 5% injection and NaCl 0.9% injection. However, substantial numbers of microparticulates may form in pemetrexed diluted in the infusion solutions in PVC bags, especially during longer periods of refrigerated storage. Limiting the refrigerated storage period to the manufacturer-recommended 24 hours will limit particulate formation.

  13. Color stability of ceramic brackets immersed in potentially staining solutions.

    Science.gov (United States)

    Guignone, Bruna Coser; Silva, Ludimila Karsbergen; Soares, Rodrigo Villamarim; Akaki, Emilio; Goiato, Marcelo Coelho; Pithon, Matheus Melo; Oliveira, Dauro Douglas

    2015-01-01

    To assess the color stability of five types of ceramic brackets after immersion in potentially staining solutions. Ninety brackets were divided into 5 groups (n = 18) according to brackets commercial brands and the solutions in which they were immersed (coffee, red wine, coke and artificial saliva). The brackets assessed were Transcend (3M/Unitek, Monrovia, CA, USA), Radiance (American Orthodontics, Sheboygan, WI, USA), Mystique (GAC International Inc., Bohemia, NY, USA) and Luxi II (Rocky Mountain Orthodontics, Denver, CO, USA). Chromatic changes were analyzed with the aid of a reflectance spectrophotometer and by visual inspection at five specific time intervals. Assessment periods were as received from the manufacturer (T0), 24 hours (T1), 72 hours (T2), as well as 7 days (T3) and 14 days (T4) of immersion in the aforementioned solutions. Results were submitted to statistical analysis with ANOVA and Bonferroni correction, as well as to a multivariate profile analysis for independent and paired samples with significance level set at 5%. The duration of the immersion period influenced color alteration of all tested brackets, even though these changes could not always be visually observed. Different behaviors were observed for each immersion solution; however, brackets immersed in one solution progressed similarly despite minor variations. Staining became more intense over time and all brackets underwent color alterations when immersed in the aforementioned solutions.

  14. Color stability of ceramic brackets immersed in potentially staining solutions

    Directory of Open Access Journals (Sweden)

    Bruna Coser Guignone

    2015-08-01

    Full Text Available OBJECTIVE: To assess the color stability of five types of ceramic brackets after immersion in potentially staining solutions.METHODS: Ninety brackets were divided into 5 groups (n = 18 according to brackets commercial brands and the solutions in which they were immersed (coffee, red wine, coke and artificial saliva. The brackets assessed were Transcend (3M/Unitek, Monrovia, CA, USA, Radiance (American Orthodontics, Sheboygan, WI, USA, Mystique (GAC International Inc., Bohemia, NY, USA and Luxi II (Rocky Mountain Orthodontics, Denver, CO, USA. Chromatic changes were analyzed with the aid of a reflectance spectrophotometer and by visual inspection at five specific time intervals. Assessment periods were as received from the manufacturer (T0, 24 hours (T1, 72 hours (T2, as well as 7 days (T3 and 14 days (T4 of immersion in the aforementioned solutions. Results were submitted to statistical analysis with ANOVA and Bonferroni correction, as well as to a multivariate profile analysis for independent and paired samples with significance level set at 5%.RESULTS: The duration of the immersion period influenced color alteration of all tested brackets, even though these changes could not always be visually observed. Different behaviors were observed for each immersion solution; however, brackets immersed in one solution progressed similarly despite minor variations.CONCLUSIONS: Staining became more intense over time and all brackets underwent color alterations when immersed in the aforementioned solutions.

  15. The effect of leachate recirculation with enzyme cellulase addition on waste stability in landfill bioreactor

    Science.gov (United States)

    Saffira, N.; Kristanto, G. A.

    2018-01-01

    Landfill bioreactor with leachate recirculation is known to enhance waste stabilization. However, the composition of waste in Indonesia is comprised by organic waste which is lignocellulosic materials that considered take a long time to degrade under anaerobic condition. To accelerate the degradation process, enzyme addition is ought to do. Cellulase is an enzyme that can catalyse cellulose and other polysaccharide decomposition processes. Therefore, operation of waste degradation using leachate recirculation with a cellulase addition to enhance waste stabilization was investigated using anaerobic bioreactor landfill. The experiment was performed on 2 conditions; leachate recirculation with cellulase addition and recirculation only as a control. The addition of cellulase is reported to be significant in decreasing organic content, represented by volatile solid parameter. The volatile solid reduction in the cellulase augmented reactor and control reactor was 17.86% and 7.90%, respectively. Cellulase addition also resulted in the highest cellulose reduction. Settlement of the landfill in a bioreactor with enzyme addition (32.67%) was reported to be higher than the control (19.33%). Stabilization of landfill review by the decreasing rate constant of the cellulose and lignin ratio parameter was more rapidly achieved by the enzyme addition (0.014 day-1) compared to control (0.002 day-1).

  16. Rational Design of Thermally Stable Novel Biocatalytic Nanomaterials: Enzyme Stability in Restricted Spatial Dimensions

    Science.gov (United States)

    Mudhivarthi, Vamsi K.

    Enzyme stability is of intense interest in bio-materials science as biocatalysts, and as sensing platforms. This is essentially because the unique properties of DNA, RNA, PAA can be coupled with the interesting and novel properties of proteins to produce systems with unprecedented control over their properties. In this article, the very first examples of enzyme/NA/inorganic hybrid nanomaterials and enzyme-Polyacrylic acid conjugates will be presented. The basic principles of design, synthesis and control of properties of these hybrid materials will be presented first, and this will be followed by a discussion of selected examples from our recent research findings. Data show that key properties of biological catalysts are improved by the inorganic framework especially when the catalyst is co-embedded with DNA. Several examples of such studies with various enzymes and proteins, including horseradish peroxidase (HRP), glucose oxidase (GO), cytochrome c (Cyt c), met-hemoglobin (Hb) and met-myoglobin (Mb) will be discussed. Additionally, key insights obtained by the standard methods of materials science including XRD, SEM and TEM as well as biochemical, calorimetric and spectroscopic methods will be discussed. Furthermore, improved structure and enhanced activities of the biocatalysts in specific cases will be demonstrated along with the potential stabilization mechanisms. Our hypothesis is that nucleic acids provide an excellent control over the enzyme-solid interactions as well as rational assembly of nanomaterials. These novel nanobiohybrid materials may aid in engineering more effective synthetic materials for gene-delivery, RNA-delivery and drug delivery applications.

  17. Cell culture media impact on drug product solution stability.

    Science.gov (United States)

    Purdie, Jennifer L; Kowle, Ronald L; Langland, Amie L; Patel, Chetan N; Ouyang, Anli; Olson, Donald J

    2016-07-08

    To enable subcutaneous administration of monoclonal antibodies, drug product solutions are often needed at high concentrations. A significant risk associated with high drug product concentrations is an increase in aggregate level over the shelf-life dating period. While much work has been done to understand the impact of drug product formulation on aggregation, there is limited understanding of the link between cell culture process conditions and soluble aggregate growth in drug product. During cell culture process development, soluble aggregates are often measured at harvest using cell-free material purified by Protein A chromatography. In the work reported here, cell culture media components were evaluated with respect to their impact on aggregate levels in high concentration solution drug product during accelerated stability studies. Two components, cysteine and ferric ammonium citrate, were found to impact aggregate growth rates in our current media (version 1) leading to the development of new chemically defined media and concentrated feed formulations. The new version of media and associated concentrated feeds (version 2) were evaluated across four cell lines producing recombinant IgG4 monoclonal antibodies and a bispecific antibody. In all four cell lines, the version 2 media reduced aggregate growth over the course of a 12 week accelerated stability study compared with the version 1 media, although the degree to which aggregate growth decreased was cell line dependent. © 2016 American Institute of Chemical Engineers Biotechnol. Prog., 32:998-1008, 2016. © 2016 American Institute of Chemical Engineers.

  18. Effect of ionic liquid on activity, stability, and structure of enzymes: a review.

    Science.gov (United States)

    Naushad, Mu; Alothman, Zied Abdullah; Khan, Abbul Bashar; Ali, Maroof

    2012-11-01

    Ionic liquids have shown their potential as a solvent media for many enzymatic reactions as well as protein preservation, because of their unusual characteristics. It is also observed that change in cation or anion alters the physiochemical properties of the ionic liquids, which in turn influence the enzymatic reactions by altering the structure, activity, enatioselectivity, and stability of the enzymes. Thus, it is utmost need of the researchers to have full understanding of these influences created by ionic liquids before choosing or developing an ionic liquid to serve as solvent media for enzymatic reaction or protein preservation. So, in the present review, we try to shed light on effects of ionic liquids chemistry on structure, stability, and activity of enzymes, which will be helpful for the researchers in various biocatalytic applications. Copyright © 2012. Published by Elsevier B.V.

  19. Stability and enzyme inhibition activities of au nanoparticles using an aqueous extract of clove as a reducing and stabilizing agent

    International Nuclear Information System (INIS)

    Hameed, A.; Khan, I.; Naz, S.S.; Islam, N.U.

    2014-01-01

    Gold nanoparticles (AuNPs) were synthesized in one pot using aqueous extract of clove buds (CB) to reduce HAuCl/sub 4/ and stabilize gold in its atomic form at room temperature. To determine the potential of gold nanoparticles with clove buds (AuCB) for in vivo applications, the stability of the nanoparticles was explored as a function of temperature, pH and salt concentration. The suspensions were found to be stable for salt concentrations up to 1 mol/L, temperatures of up to 100 degree C and a pH range of 2-13. Our results indicate that CB exhibited comparable activities to standards of urease and carbonic anhydrase, but its conjugation to Au knocks out the enzyme inhibition activity by about two times. In case of xanthine oxidase activity, CB and its gold Au bio-conjugates (AuCB) are found to be absolutely inactive. (author)

  20. Stability of subsystem solutions in agent-based models

    Science.gov (United States)

    Perc, Matjaž

    2018-01-01

    The fact that relatively simple entities, such as particles or neurons, or even ants or bees or humans, give rise to fascinatingly complex behaviour when interacting in large numbers is the hallmark of complex systems science. Agent-based models are frequently employed for modelling and obtaining a predictive understanding of complex systems. Since the sheer number of equations that describe the behaviour of an entire agent-based model often makes it impossible to solve such models exactly, Monte Carlo simulation methods must be used for the analysis. However, unlike pairwise interactions among particles that typically govern solid-state physics systems, interactions among agents that describe systems in biology, sociology or the humanities often involve group interactions, and they also involve a larger number of possible states even for the most simplified description of reality. This begets the question: when can we be certain that an observed simulation outcome of an agent-based model is actually stable and valid in the large system-size limit? The latter is key for the correct determination of phase transitions between different stable solutions, and for the understanding of the underlying microscopic processes that led to these phase transitions. We show that a satisfactory answer can only be obtained by means of a complete stability analysis of subsystem solutions. A subsystem solution can be formed by any subset of all possible agent states. The winner between two subsystem solutions can be determined by the average moving direction of the invasion front that separates them, yet it is crucial that the competing subsystem solutions are characterised by a proper composition and spatiotemporal structure before the competition starts. We use the spatial public goods game with diverse tolerance as an example, but the approach has relevance for a wide variety of agent-based models.

  1. Stability of biodegradable waterborne polyurethane films in buffered saline solutions.

    Science.gov (United States)

    Lin, Ying Yi; Hung, Kun-Che; Hsu, Shan-Hui

    2015-09-21

    The stability of polyurethane (PU) is of critical importance for applications such as in coating industry or as biomaterials. To eliminate the environmental concerns on the synthesis of PU which involves the use of organic solvents, the aqueous-based or waterborne PU (WBPU) has been developed. WBPU, however, may be unstable in an electrolyte-rich environment. In this study, the authors reported the stability of biodegradable WBPU in the buffered saline solutions evaluated by atomic force microscopy (AFM). Various biodegradable WBPU films were prepared by spin coating on coverslip glass, with a thickness of ∼300 nm. The surface AFM images of poly(ε-caprolactone) (PCL) diol-based WBPU revealed nanoglobular structure. The same feature was observed when 20% molar of the PCL diol soft segment was replaced by polyethylene butylenes adipate diol. After hydration in buffered saline solutions for 24 h, the surface domains generally increased in sizes and became irregular in shape. On the other hand, when the soft segment was replaced by 20% poly(l-lactide) diol, a meshlike surface structure was demonstrated by AFM. When the latter WBPU was hydrated, the surface domains appeared to be disconnected. Results from the attenuated total reflectance infrared spectroscopy and x-ray photoelectron spectroscopy indicated that the surface chemistry of WBPU films was altered after hydration. These changes were probably associated with the neutralization of carboxylate by ions in the saline solutions, resulting in the rearrangements of soft and hard segments and causing instability of the WBPU.

  2. A Study on the Stability of Diluted Bee Venom Solution

    Directory of Open Access Journals (Sweden)

    Mi-Suk Kang

    2003-06-01

    Full Text Available Objective : The purpose of this study was to investigate the stability of bee venom according to the keeping method and period. Method : The author observed microbial contamination of bee venom in nutrient agar, broth, YPD agar and YPD media and antibacterial activity for S. aureus, E. coli manufactured 12, 6 and 3 months ago as the two type of room temperature and 4℃ cold storage. Result : 1. 1:3,000 and 1:4,000 diluted bee venom solution did not show microbial contamination both room temperature and cold storage within twelve months. 2. There was antibacterial activity of diluted bee venom for S. aureus in cold storage within twelve months and there was no antibacterial activity of diluted bee venom for S. aureus in twelve months, room temperature storage. 3. We could not observe the zone of inhibition around paper disc of all for E.coli. in 1:3,000, 1:30,000 and 1:3,000,000 diluted bee venom solution, respectively. According to results, we expect that diluted bee venom solution is stable both cold and room temperature storage within twelve months.

  3. Global stability and exact solution of an arbitrary-solute nonlinear cellular mass transport system.

    Science.gov (United States)

    Benson, James D

    2014-12-01

    The prediction of the cellular state as a function of extracellular concentrations and temperatures has been of interest to physiologists for nearly a century. One of the most widely used models in the field is one where mass flux is linearly proportional to the concentration difference across the membrane. These fluxes define a nonlinear differential equation system for the intracellular state, which when coupled with appropriate initial conditions, define the intracellular state as a function of the extracellular concentrations of both permeating and nonpermeating solutes. Here we take advantage of a reparametrization scheme to extend existing stability results to a more general setting and to a develop analytical solutions to this model for an arbitrary number of extracellular solutes. Copyright © 2014 Elsevier Inc. All rights reserved.

  4. Stability analysis of a pressure-solution surface

    Science.gov (United States)

    Gal, Doron; Nur, Amos; Aharonov, Einat

    We present a linear stability analysis of a dissolution surface subjected to non-hydrostatic stress. A sinusoidal perturbation is imposed on an initially flat solid/fluid interface, and the consequent changes in elastic strain energy and surface energy are calculated. Our results demonstrate that if the far-field lateral stresses are either greater, or much smaller than the fluid pressure, the perturbed configuration has a lower strain energy than the initial one. For wavelengths greater than a critical wavelength this energy decrease may be large enough to offset the increased surface energy. Under these conditions, the perturbation grows unstably. If these conditions are not met, the surface becomes flat. The growth rate and wavelength of the maximally unstable mode depend on the mechanism of matter transport. We conclude that the instability discussed in this paper may account for the formation of stylolites and other pressure-solution phenomena, such as roughening of grain contacts.

  5. Optimization of ultrasound-assisted extraction of pectinase enzyme from guava (Psidium guajava) peel: Enzyme recovery, specific activity, temperature, and storage stability.

    Science.gov (United States)

    Amid, Mehrnoush; Murshid, Fara Syazana; Manap, Mohd Yazid; Islam Sarker, Zaidul

    2016-01-01

    This study aimed to investigate the effects of the ultrasound-assisted extraction conditions on the yield, specific activity, temperature, and storage stability of the pectinase enzyme from guava peel. The ultrasound variables studied were sonication time (10-30 min), ultrasound temperature (30-50 °C), pH (2.0-8.0), and solvent-to-sample ratio (2:1 mL/g to 6:1 mL/g). The main goal was to optimize the ultrasound-assisted extraction conditions to maximize the recovery of pectinase from guava peel with the most desirable enzyme-specific activity and stability. Under the optimum conditions, a high yield (96.2%), good specific activity (18.2 U/mg), temperature stability (88.3%), and storage stability (90.3%) of the extracted enzyme were achieved. The optimal conditions were 20 min sonication time, 40 °C temperature, at pH 5.0, using a 4:1 mL/g solvent-to-sample ratio. The study demonstrated that optimization of ultrasound-assisted process conditions for the enzyme extraction could improve the enzymatic characteristics and yield of the enzyme.

  6. Engineering Enzyme Stability and Resistance to an Organic Cosolvent by Modification of Residues in the Access Tunnel

    Czech Academy of Sciences Publication Activity Database

    Koudeláková, T.; Chaloupková, R.; Březovský, J.; Prokop, Z.; Šebestová, E.; Hesseler, M.; Khabiri, Morteza; Plevaka, M.; Kulik, D.; Kutá-Smatanová, Ivana; Řezáčová, Pavlína; Ettrich, Rüdiger; Bornscheuer, U.T.; Damborský, J.

    2013-01-01

    Roč. 52, č. 7 (2013), s. 1959-1963 ISSN 1433-7851 R&D Projects: GA MŠk(CZ) LC06010 Institutional support: RVO:67179843 ; RVO:68378050 Keywords : directed evolution * enzyme catalysis * enzymes * protein engineering * protein stability Subject RIV: CE - Biochemistry; EB - Genetics ; Molecular Biology (UMG-J) Impact factor: 11.336, year: 2013

  7. Stability estimates for solution of IBVP to fractional parabolic differential and difference equations

    Science.gov (United States)

    Ashyralyev, Allaberen; Cakir, Zafer

    2016-08-01

    In this work, we investigate initial-boundary value problems for fractional parabolic equations with the Neumann boundary condition. Stability estimates for the solution of this problem are established. Difference schemes for approximate solution of initial-boundary value problem are constructed. Furthermore, we give theorem on coercive stability estimates for the solution of the difference schemes.

  8. Experimental measurements of U60 nanocluster stability in aqueous solution

    Science.gov (United States)

    Flynn, Shannon L.; Szymanowski, Jennifer E. S.; Gao, Yunyi; Liu, Tianbo; Burns, Peter C.; Fein, Jeremy B.

    2015-05-01

    In this study, the aqueous behavior of isolated U60 nanoclusters (K16Li25[UO2(O2)OH]60)-19 was studied under several pH conditions and nanocluster concentrations to determine if the nanoclusters exhibit solid phase buffering behavior or if they exhibit behavior more like aqueous complexes. U60 is a cage cluster consisting of 60 (UO2)(O2)2(OH)2 uranyl polyhedral which share OH and O2 groups with their neighboring uranyl polyhedral, resulting in negatively charged cage clusters whose charge is at least partially offset by K+ and Li+ in the aqueous phase. Batch experiments to monitor nanocluster stability were conducted for 16 days at pH 7.5, 8.0 and 8.5 at nanocluster suspension concentrations of 1.4, 2.8 and 6.0 g/L. The aqueous concentrations of U, Li, and K, determined after 10 kDa molecular weight filtration, achieved steady-state with the nanoclusters within 24 h. The steady-state aqueous U, Li, and K concentrations were independent of solution pH, however they increased with increasing nanocluster concentration, indicating that the nanoclusters do not buffer the aqueous activities as a bulk solid phase would, but exhibit behavior that is more characteristic of dissolved aqueous complexes. The ion activity product (I.A.P.) value was calculated using two approaches: (1) treating the nanoclusters as a solid phase with an activity of one, and (2) treating the nanoclusters as aqueous complexes with a non-unit activity equal to their concentration in solution. The I.A.P. values that were calculated with non-unit activity for the nanoclusters exhibited significantly less variation as a function of nanocluster concentration compared to the I.A.P. values calculated with a nanocluster activity of one. The results yield a calculated log dissociation constant for the U60 nanoclusters of 9.2 + 0.2/-0.3 (1σ). Our findings provide a better understanding of the thermodynamic stability and behavior of U60 nanoclusters in aqueous systems, and can be used to estimate the

  9. WEOD-S: Westinghouse expanded operating domain stability solution

    International Nuclear Information System (INIS)

    Rotander, C.; Blaisdell, J.; Anderson, D.; Kumar, V.; Stier, D.; Chu, E.

    2014-01-01

    As Extended Power up-rates (EPUs) are implemented in BWR plants, the flow window at full power decreases due to the extension of the rod line. It is thus desirable to raise load line limits to realize increased power generation at a wider flow range offering operational flexibility and fuel cycle efficiency. However, when load lines are raised, the power/flow operating map is changed in a direction that can cause core power instability at its lower left corner (high power/low flow) if a flow reduction transient (i.e. pump trip) occurs. Unstable operation of the reactor core can result in diverging neutron flux (and power) oscillations, and through the thermal hydraulic/neutronic feedback challenge the Safety Limit Minimum Critical Power Ratio (SLMCPR). In many BWRs the SLMCPR in a power oscillation event is already protected by a detect and suppress system. The methodology to determine the set point of this system, the DIVOM methodology (Delta CPR over Initial MCPR versus Oscillation Magnitude), is defined and applicable up to, but not beyond, the thermal hydraulic stability limit. The DIVOM methodology is used to determine the channel power oscillation magnitude that will challenge the SLMCPR. It is defined as the relationship between ΔCPR/ICPR and the Hot Channel Oscillation Magnitude (HCOM). The DIVOM calculations are typically performed at the end state following a design basis two pump trip from rated power and minimum flow. When approaching the thermal hydraulic (T/H) instability limit, the DIVOM curve can become chaotic and the DIVOM approach breaks down. At T/H-instability, small power fluctuations give rise to large flow oscillations and the non-linear dynamic properties emerge. The newly developed Westinghouse Expanded Operating Domain Stability (WEOD-S) solution proactively prevents entry into the regions of the power/flow map that are vulnerable to thermal hydraulic instability. This is achieved automatically, without any dependence on operator action

  10. TOPICAL REVIEW: Protein stability and enzyme activity at extreme biological temperatures

    Science.gov (United States)

    Feller, Georges

    2010-08-01

    Psychrophilic microorganisms thrive in permanently cold environments, even at subzero temperatures. To maintain metabolic rates compatible with sustained life, they have improved the dynamics of their protein structures, thereby enabling appropriate molecular motions required for biological activity at low temperatures. As a consequence of this structural flexibility, psychrophilic proteins are unstable and heat-labile. In the upper range of biological temperatures, thermophiles and hyperthermophiles grow at temperatures > 100 °C and synthesize ultra-stable proteins. However, thermophilic enzymes are nearly inactive at room temperature as a result of their compactness and rigidity. At the molecular level, both types of extremophilic proteins have adapted the same structural factors, but in opposite directions, to address either activity at low temperatures or stability in hot environments. A model based on folding funnels is proposed accounting for the stability-activity relationships in extremophilic proteins.

  11. Stable preparations of tyrosine hydroxylase provide the solution structure of the full-length enzyme

    Science.gov (United States)

    Bezem, Maria T.; Baumann, Anne; Skjærven, Lars; Meyer, Romain; Kursula, Petri; Martinez, Aurora; Flydal, Marte I.

    2016-01-01

    Tyrosine hydroxylase (TH) catalyzes the rate-limiting step in the biosynthesis of catecholamine neurotransmitters. TH is a highly complex enzyme at mechanistic, structural, and regulatory levels, and the preparation of kinetically and conformationally stable enzyme for structural characterization has been challenging. Here, we report on improved protocols for purification of recombinant human TH isoform 1 (TH1), which provide large amounts of pure, stable, active TH1 with an intact N-terminus. TH1 purified through fusion with a His-tagged maltose-binding protein on amylose resin was representative of the iron-bound functional enzyme, showing high activity and stabilization by the natural feedback inhibitor dopamine. TH1 purified through fusion with a His-tagged ZZ domain on TALON is remarkably stable, as it was partially inhibited by resin-derived cobalt. This more stable enzyme preparation provided high-quality small-angle X-ray scattering (SAXS) data and reliable structural models of full-length tetrameric TH1. The SAXS-derived model reveals an elongated conformation (Dmax = 20 nm) for TH1, different arrangement of the catalytic domains compared with the crystal structure of truncated forms, and an N-terminal region with an unstructured tail that hosts the phosphorylation sites and a separated Ala-rich helical motif that may have a role in regulation of TH by interacting with binding partners. PMID:27462005

  12. GLOBAL STABILITY AND PERIODIC SOLUTION OF A VIRAL DYNAMIC MODEL

    Directory of Open Access Journals (Sweden)

    Erhan COŞKUN

    2009-02-01

    Full Text Available Abstract:In this paper, we consider the classical viral dynamic mathematical model. Global dynamics of the model is rigorously established. We prove that, if the basic reproduction number, the HIV infection is cleared from the T-cell population; if , the HIV infection persists. For an open set of parameter values, the chronic-infection equilibrium can be unstable and periodic solutions may exist. We establish parameter regions for which is globally stable. Keywords: Global stability, HIV infection; CD4+ T cells; Periodic solution Mathematics Subject Classifications (2000: 65L10, 34B05 BİR VİRAL DİNAMİK MODELİN GLOBAL KARARLILIĞI VE PERİYODİK ÇÖZÜMÜ Özet: Bu makalede klasik viral dinamik modeli ele aldık. Modelin global dinamikleri oluşturuldu. Eğer temel üretim sayısı olur ise HIV enfeksiyonu T hücre nüfusundan çıkartılır, eğer olursa HIV enfeksiyonu çıkartılamaz. Parametre değerlerinin açık bir kümesi için kronik enfeksiyon dengesi kararsızdır ve periyodik çözüm oluşabilir. ın global kararlı olduğu parametre bölgeleri oluşturuldu. Anahtar Kelimeler: Global Kararlılık, HIV enfeksiyon, CD4+ T hücreler, Periyodik çözüm

  13. Solutions stability of one-dimensional parametric superconducting magnetic levitation model analysis by the first approximation

    International Nuclear Information System (INIS)

    Shvets', D.V.

    2009-01-01

    By the first approximation analyzing stability conditions of unperturbed solution of one-dimensional dynamic model with magnetic interaction between two superconducting rings obtained. The stability region in the frozen magnetic flux parameters space was constructed.

  14. Stability of furosemide and aminophylline in parenteral solutions

    Directory of Open Access Journals (Sweden)

    Carolina Alves dos Santos

    2011-03-01

    Full Text Available Parenteral solutions (PS are one of the most commonly used drug delivery vehicles. Interactions among the drug, components in the drug's formulation, and the PS can result in the formation of inactive complexes that limit efficacy or increase side effects. The aim of this work was to evaluate possible interactions between the drugs and PS, assess drug stability and to identify degradation products after 20 h at room temperature. Furosemide (FSM and Aminophylline (APN were added to PS containing either 20% mannitol or 0.9% NaCl at pH 6.5-7.5 and 10-11. Their behavior was studied individually and as an admixture, after 1 h oxidation with H2O2, using a spectrophotometer and HPLC. Individually, FSM and APN added to 20% mannitol and 0.9% NaCl solutions had the highest stability at pH 10-11. When FSM and APN were combined, the behavior of FSM was similar to the behavior observed for the drug individually in the same solutions. With the drugs combined in 20% mannitol pH 10-11, HPLC showed that both drugs were stable after a 20 h period yielding two distinct peaks; in oxidized samples, the elution profile showed four peaks with retention times unrelated to the untreated samples.Soluções parenterais de grande volume são frequentemente utilizadas no ambiente hospitalar para a veiculação de fármacos. No entanto, possíveis incompatibilidades entre as estruturas dos fármacos, em diferentes veículos de administração, podem gerar possíveis associações antagônicas ou sinérgicas, resultando em alterações das propriedades físico-químicas, consequentemente, dos efeitos farmacológicos e das respostas clínicas esperadas. Este artigo avaliou a estabilidade e a possível formação de produtos de degradação entre os fármacos furosemida e aminofilina quando estes foram veiculados em soluções parenterais, após o preparo e após o período de 20 h. Furosemida e aminofilina foram adicionadas às soluções de 20% manitol e 0,9% NaCl nos valores

  15. Effects of Straw Incorporation on Soil Nutrients, Enzymes, and Aggregate Stability in Tobacco Fields of China

    Directory of Open Access Journals (Sweden)

    Jiguang Zhang

    2016-07-01

    Full Text Available To determine the effects of straw incorporation on soil nutrients, enzyme activity, and aggregates in tobacco fields, we conducted experiments with different amounts of wheat and maize straw in Zhucheng area of southeast Shandong province for three years (2010–2012. In the final year of experiment (2012, straw incorporation increased soil organic carbon (SOC and related parameters, and improved soil enzyme activity proportionally with the amount of straw added, except for catalase when maize straw was used. And maize straw incorporation was more effective than wheat straw in the tobacco field. The percentage of aggregates >2 mm increased with straw incorporation when measured by either dry or wet sieving. The mean weight diameter (MWD and geometric mean diameter (GMD in straw incorporation treatments were higher than those in the no-straw control (CK. Maize straw increased soil aggregate stability more than wheat straw with the same incorporation amount. Alkaline phosphatase was significantly and negatively correlated with soil pH. Sucrase and urease were both significantly and positively correlated with soil alkali-hydrolysable N. Catalase was significantly but negatively correlated with soil extractable K (EK. The MWD and GMD by dry sieving had significantly positive correlations with SOC, total N, total K, and EK, but only significantly correlated with EK by wet sieving. Therefore, soil nutrients, metabolic enzyme activity, and aggregate stability might be increased by increasing the SOC content through the maize or wheat straw incorporation. Moreover, incorporation of maize straw at 7500 kg·hm−2 was the best choice to enhance soil fertility in the tobacco area of Eastern China.

  16. Stability and square integrability of solutions of nonlinear fourth order differential equations

    Directory of Open Access Journals (Sweden)

    Moussadek Remili

    2016-05-01

    Full Text Available The aim of the present paper is to establish a new result, which guarantees the asymptotic stability of zero solution and square integrability of solutions and their derivatives to nonlinear differential equations of fourth order.

  17. Relationship between sol-gel conditions and enzyme stability: a case study with β-galactosidase/silica biocatalyst for whey hydrolysis.

    Science.gov (United States)

    Escobar, Sindy; Bernal, Claudia; Mesa, Monica

    2015-01-01

    The sol-gel process has been very useful for preparing active and stable biocatalysts, with the possibility of being reused. Especially those based on silica are well known. However, the study of the enzyme behavior during this process is not well understood until now and more, if the surfactant is involved in the synthesis mixture. This work is devoted to the encapsulation of β-galactosidase from Bacillus circulans in silica by sol-gel process, assisted by non-ionic Triton X-100 surfactant. The correlation between enzyme activity results for the β-galactosidase in three different environments (soluble in buffered aqueous reference solution, in the silica sol, and entrapment on the silica matrix) explains the enzyme behavior under stress conditions offered by the silica sol composition and gelation conditions. A stable β-galactosidase/silica biocatalyst is obtained using sodium silicate, which is a cheap source of silica, in the presence of non-ionic Triton X-100, which avoids the enzyme deactivation, even at 40 °C. The obtained biocatalyst is used in the whey hydrolysis for obtaining high value products from this waste. The preservation of the enzyme stability, which is one of the most important challenges on the enzyme immobilization through the silica sol-gel, is achieved in this study.

  18. Sensitizing effect of Z,Z-bilirubin IXα and its photoproducts on enzymes in model solutions

    Science.gov (United States)

    Plavskii, V. Yu.; Mostovnikov, V. A.; Tret'yakova, A. I.; Mostovnikova, G. R.

    2008-05-01

    In model systems, we have studied side effects which may be induced by light during phototherapy of hyperbilirubinemia (jaundice) in newborn infants, with the aim of reducing the Z,Z-bilirubin IXα (Z,Z-BR IXα) level. We have shown that the sensitizing effect of Z,Z-BR IXα, localized at strong binding sites of the human serum albumin (HSA) macromolecule, is primarily directed at the amino acid residues of the carrier protein and does not involve the molecules of the enzyme (lactate dehydrogenase (LDH)) present in the buffer solution. The detected photodynamic damage to LDH is due to sensitization by bilirubin photoisomers, characterized by lower HSA association constants and located (in contrast to native Z,Z-BR IXα) on the surface of the HSA protein globule. Based on study of the spectral characteristics of the photoproducts of Z,Z-BR IXα and comparison of their accumulation kinetics in solution and the enzyme photo-inactivation kinetics, we concluded that the determining role in sensitized damage to LDH is played by lumirubin. The photosensitization effect depends on the wavelength of the radiation used for photoconversion of bilirubin. When (at the beginning of exposure) we make sure that identical numbers of photons are absorbed by the pigment in the different spectral ranges, the side effect is minimal for radiation corresponding to the long-wavelength edge of the bilirubin absorption band. We have shown that for a bilirubin/HSA concentration ratio >2 (when some of the pigment molecules are sorbed on the surface of the protein globule), the bilirubin can act as a photosensitizing agent for the enzyme present in solution. We discuss methods for reducing unfavorable side effects of light on the body of newborn infants during phototherapy of hyperbilirubinemia.

  19. Homogeneous solutions of hydrophilic enzymes in nonpolar organic solvents. New systems for fundamental studies and biocatalytic transformations.

    Science.gov (United States)

    Mozhaev, V V; Poltevsky, K G; Slepnev, V I; Badun, G A; Levashov, A V

    1991-11-04

    A typical hydrophilic enzyme, CT, can be dissolved in nonpolar organic solvents (n-octane, cyclohexane and toluene) up to microM concentrations. In the homogeneous solution obtained, the enzyme possesses catalytic activity and enormously high thermostability. It does not lose this activity even after several hours refluxing in octane (126 degrees C) or cyclohexane (81 degrees C).

  20. Orbital stability of Gausson solutions to logarithmic Schrodinger equations

    Directory of Open Access Journals (Sweden)

    Alex H. Ardila

    2016-12-01

    Full Text Available In this article we prove of the orbital stability of the ground state for logarithmic Schrodinger equation in any dimension and under nonradial perturbations. This general stability result was announced by Cazenave and Lions [9, Remark II.3], but no details were given there.

  1. 49 CFR 173.195 - Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution).

    Science.gov (United States)

    2010-10-01

    ... 49 Transportation 2 2010-10-01 2010-10-01 false Hydrogen cyanide, anhydrous, stabilized... Hazardous Materials Other Than Class 1 and Class 7 § 173.195 Hydrogen cyanide, anhydrous, stabilized (hydrocyanic acid, aqueous solution). (a) Hydrogen cyanide, anhydrous, stabilized, must be packed in...

  2. Stability analysis of solutions to nonlinear stiff Volterra functional differential equations in Banach spaces

    Institute of Scientific and Technical Information of China (English)

    LI Shoufu

    2005-01-01

    A series of stability, contractivity and asymptotic stability results of the solutions to nonlinear stiff Volterra functional differential equations (VFDEs) in Banach spaces is obtained, which provides the unified theoretical foundation for the stability analysis of solutions to nonlinear stiff problems in ordinary differential equations(ODEs), delay differential equations(DDEs), integro-differential equations(IDEs) and VFDEs of other type which appear in practice.

  3. Covalent Immobilization of Cellulase Using Magnetic Poly(ionic liquid) Support: Improvement of the Enzyme Activity and Stability.

    Science.gov (United States)

    Hosseini, Seyed Hassan; Hosseini, Seyedeh Ameneh; Zohreh, Nasrin; Yaghoubi, Mahshid; Pourjavadi, Ali

    2018-01-31

    A magnetic nanocomposite was prepared by entrapment of Fe 3 O 4 nanoparticles into the cross-linked ionic liquid/epoxy type polymer. The resulting support was used for covalent immobilization of cellulase through the reaction with epoxy groups. The ionic surface of the support improved the adsorption of enzyme, and a large amount of enzyme (106.1 mg/g) was loaded onto the support surface. The effect of the presence of ionic monomer and covalent binding of enzyme was also investigated. The structure of support was characterized by various instruments such as FT-IR, TGA, VSM, XRD, TEM, SEM, and DLS. The activity and stability of immobilized cellulase were investigated in the prepared support. The results showed that the ionic surface and covalent binding of enzyme onto the support improved the activity, thermal stability, and reusability of cellulase compared to free cellulase.

  4. Existence and stability of periodic solutions for a delayed prey-predator model with diffusion effects

    Directory of Open Access Journals (Sweden)

    Hongwei Liang

    2016-01-01

    Full Text Available Existence and stability of spatially periodic solutions for a delay prey-predator diffusion system are concerned in this work. We obtain that the system can generate the spatially nonhomogeneous periodic solutions when the diffusive rates are suitably small. This result demonstrates that the diffusion plays an important role on deriving the complex spatiotemporal dynamics. Meanwhile, the stability of the spatially periodic solutions is also studied. Finally, in order to verify our theoretical results, some numerical simulations are also included.

  5. Copper stressed anaerobic fermentation: biogas properties, process stability, biodegradation and enzyme responses.

    Science.gov (United States)

    Hao, He; Tian, Yonglan; Zhang, Huayong; Chai, Yang

    2017-12-01

    The effect of copper (added as CuCl 2 ) on the anaerobic co-digestion of Phragmites straw and cow dung was studied in pilot experiments by investigating the biogas properties, process stability, substrate degradation and enzyme activities at different stages of mesophilic fermentation. The results showed that 30 and 100 mg/L Cu 2+ addition increased the cumulative biogas yields by up to 43.62 and 20.77% respectively, and brought forward the daily biogas yield peak, while 500 mg/L Cu 2+ addition inhibited biogas production. Meanwhile, the CH 4 content in the 30 and 100 mg/L Cu 2+ -added groups was higher than that in the control group. Higher pH values (close to pH 7) and lower oxidation-reduction potential (ORP) values in the Cu 2+ -added groups after the 8th day indicated better process stability compared to the control group. In the presence of Cu 2+ , the degradation of volatile fatty acids (VFAs) and other organic molecules (represented by chemical oxygen demand, COD) generated from hydrolysis was enhanced, and the ammonia nitrogen (NH 4 + -N) concentrations were more stable than in the control group. The contents of lignin and hemicellulose in the substrate declined in the Cu 2+ -added groups while the cellulose contents did not. Neither the cellulase nor the coenzyme F 420 activities could determine the biogas producing efficiency. Taking the whole fermentation process into account, the promoting effect of Cu 2+ addition on biogas yields was mainly attributable to better process stability, the enhanced degradation of lignin and hemicellulose, the transformation of intermediates into VFA, and the generation of CH 4 from VFA.

  6. Stability of time-dependent particle-like solutions of some wave equations

    International Nuclear Information System (INIS)

    Voronov, N.A.

    1978-01-01

    The proof of the nonstability of the one-dimensional periodical localized solutions of the equation with a spontaneously broken symmetry is given. The stability of the one-dimensional oscillating solutions of the sine-Gordon equation was also considered with regard to such perturbations. As it was expected these solutions proved to be stable

  7. Analytical systems as a basis for immobilized enzymes. 3. Use of a glucose enzyme electrode to determine carbohydrates in biological solutions

    Energy Technology Data Exchange (ETDEWEB)

    Kulys, J; Pesliakiene, M

    1981-01-01

    A method is described for determination of glucose, sucrose, and lactose in biological solutions using a glucose enzyme electrode characterized by high sensitivity and selectivity. The enzyme membrane (15 nm thick) is prepared from glucose oxidase isolated from Penicillium vitale. Glucose is determined in one minute (using static currents) or in 12 s (using registered current in a kinetic regime). Phosphate buffer (5-10 mM) is the only reagent required for analysis. Determination of sucrose and lactose require prior hydrolysis with 17.8% HCl at 70 degrees Celcius for O.5 and lO.7 minutes, respectively.

  8. Weak stability of Lagrangian solutions to the semigeostrophic equations

    International Nuclear Information System (INIS)

    Faria, Josiane C O; Lopes Filho, Milton C; Nussenzveig Lopes, Helena J

    2009-01-01

    In (Cullen and Feldman 2006 SIAM J. Math. Anal. 37 137–95), Cullen and Feldman proved the existence of Lagrangian solutions for the semigeostrophic system in physical variables with initial potential vorticity in L p , p > 1. Here, we show that a subsequence of the Lagrangian solutions corresponding to a strongly convergent sequence of initial potential vorticities in L 1 converges strongly in L q , q < ∞, to a Lagrangian solution, in particular extending the existence result of Cullen and Feldman to the case p = 1. We also present a counterexample for Lagrangian solutions corresponding to a sequence of initial potential vorticities converging in BM. The analytical tools used include techniques from optimal transportation, Ambrosio's results on transport by BV vector fields and Orlicz spaces

  9. Stabilization of periodic solutions in a tethered satellite system by damping injection

    DEFF Research Database (Denmark)

    Larsen, Martin Birkelund; Blanke, Mogens

    2009-01-01

    presents a control design for stabilizing these periodic solutions. The design consists of a control law for stabilizing the open-loop equilibrium and a bias term which forces the system trajectory away from the equilibrium. The tether needs to be positioned away from open-loop equilibrium for the tether...... to affect the orbit parameters. An approximation of the periodic solutions of the closed loop system is found as a series expansion in the parameter plane spanned by the controller gain and the bias term. The stability of the solutions is investigated using linear Floquet analysis of the variational...

  10. The storage stability of polyvinylbutyral solutions from an electrospinnability standpoint

    Czech Academy of Sciences Publication Activity Database

    Peer, Petra; Stěnička, M.; Pavlinek, V.; Filip, Petr

    2014-01-01

    Roč. 105, July (2014), s. 134-139 ISSN 0141-3910 R&D Projects: GA ČR(CZ) GAP105/11/2342 Institutional support: RVO:67985874 Keywords : electrospinning * nanofibres * polyvinylbutyral * ageing * stability Subject RIV: BK - Fluid Dynamics Impact factor: 3.163, year: 2014

  11. Maceration enzymes and mannoproteins: a possible strategy to increase colloidal stability and color extraction in red wines.

    Science.gov (United States)

    Guadalupe, Zenaida; Palacios, Antonio; Ayestaran, Belén

    2007-06-13

    Different strategies were adopted to achieve increases in color stability in Tempranillo wines: (i) addition of maceration enzymes directly to the must, (ii) addition of commercial mannoproteins to the must, and (iii) inoculation of must with yeast overexpressed of mannoproteins. The addition of enzymes favored color extraction, and the wines obtained presented higher values of wine color, color intensity, bisulfite-stable color, and visually enhanced color intensity. The enzyme hydrolytic activity produced an increase in the acid polysaccharide content and polyphenol index and yielded to wines with more astringency, tannin, and length. Added mannoproteins had clearer effects on the analyzed parameters than yeast. Contrary to what may be thought, mannoproteins did not maintain the extracted polyphenols in colloidal dispersion and neither ensured color stability. These compounds clearly modified the gustative structure of the wines, enhancing the sweetness and roundness.

  12. Co-Immobilization of Enzymes and Magnetic Nanoparticles by Metal-Nucleotide Hydrogelnanofibers for Improving Stability and Recycling

    Directory of Open Access Journals (Sweden)

    Chunfang Li

    2017-01-01

    Full Text Available In this paper we report a facile method for preparing co-immobilized enzyme and magnetic nanoparticles (MNPs using metal coordinated hydrogel nanofibers. Candida rugosa lipase (CRL was selected as guest protein. For good aqueous dispersity, low price and other unique properties, citric acid-modified magnetic iron oxide nanoparticles (CA-Fe3O4 NPs have been widely used for immobilizing enzymes. As a result, the relative activity of CA-Fe3O4@Zn/AMP nanofiber-immobilized CRL increased by 8-fold at pH 10.0 and nearly 1-fold in a 50 °C water bath after 30 min, compared to free CRL. Moreover, the immobilized CRL had excellent long-term storage stability (nearly 80% releative activity after storage for 13 days. This work indicated that metal-nucleotide nanofibers could efficiently co-immobilize enzymes and MNPs simultaneously, and improve the stability of biocatalysts.

  13. [Regulation of thermal stability of enzymes by changing the composition of media. Native and modified alpha-chymotrypsin].

    Science.gov (United States)

    Levitskiĭ, V Iu; Melik-Nubarov, N S; Slepnev, V I; Shikshnis, V A; Mozhaev, V V

    1990-01-01

    Stabilizing effect of denaturing salts on irreversible thermoinactivation of native and modified alpha-chymotrypsin at elevated temperatures is observed. The effect is caused by a shift of conformational equilibrium, at the primary step of reversible unfolding in the course of thermoinactivation, to a more unfolded form which is not able to refold "incorrectly". The stability of alpha-chymotrypsin is regulated within a wide range by medium alteration: the stabilizing effects are similar to those achieved by multipoint attachment of the enzyme to a support or by hydrophilization of protein by covalent modification.

  14. Optical spectroscopic methods for probing the conformational stability of immobilised enzymes.

    Science.gov (United States)

    Ganesan, Ashok; Moore, Barry D; Kelly, Sharon M; Price, Nicholas C; Rolinski, Olaf J; Birch, David J S; Dunkin, Ian R; Halling, Peter J

    2009-07-13

    We report the development of biophysical techniques based on circular dichroism (CD), diffuse reflectance infrared Fourier transform (DRIFT) and tryptophan (Trp) fluorescence to investigate in situ the structure of enzymes immobilised on solid particles. Their applicability is demonstrated using subtilisin Carlsberg (SC) immobilised on silica gel and Candida antartica lipase B immobilised on Lewatit VP.OC 1600 (Novozyme 435). SC shows nearly identical secondary structure in solution and in the immobilised state as evident from far UV CD spectra and amide I vibration bands. Increased near UV CD intensity and reduced Trp fluorescence suggest a more rigid tertiary structure on the silica surface. After immobilised SC is inactivated, these techniques reveal: a) almost complete loss of near UV CD signal, suggesting loss of tertiary structure; b) a shift in the amide I vibrational band from 1658 cm(-1) to 1632 cm(-1), indicating a shift from alpha-helical structure to beta-sheet; c) a substantial blue shift and reduced dichroism in the far UV CD, supporting a shift to beta-sheet structure; d) strong increase in Trp fluorescence intensity, which reflects reduced intramolecular quenching with loss of tertiary structure; and e) major change in fluorescence lifetime distribution, confirming a substantial change in Trp environment. DRIFT measurements suggest that pressing KBr discs may perturb protein structure. With the enzyme on organic polymer it was possible to obtain near UV CD spectra free of interference by the carrier material. However, far UV CD, DRIFT and fluorescence measurements showed strong signals from the organic support. In conclusion, the spectroscopic methods described here provide structural information hitherto inaccessible, with their applicability limited by interference from, rather than the particulate nature of, the support material.

  15. Existence of Periodic Solutions and Stability of Zero Solution of a Mathematical Model of Schistosomiasis

    Directory of Open Access Journals (Sweden)

    Lin Li

    2014-01-01

    Full Text Available A mathematical model on schistosomiasis governed by periodic differential equations with a time delay was studied. By discussing boundedness of the solutions of this model and construction of a monotonic sequence, the existence of positive periodic solution was shown. The conditions under which the model admits a periodic solution and the conditions under which the zero solution is globally stable are given, respectively. Some numerical analyses show the conditional coexistence of locally stable zero solution and periodic solutions and that it is an effective treatment by simply reducing the population of snails and enlarging the death ratio of snails for the control of schistosomiasis.

  16. ON THE BOUNDEDNESS AND THE STABILITY OF SOLUTION TO THIRD ORDER NON-LINEAR DIFFERENTIAL EQUATIONS

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    In this paper we investigate the global asymptotic stability,boundedness as well as the ultimate boundedness of solutions to a general third order nonlinear differential equation,using complete Lyapunov function.

  17. On the stability of soliton solution in NLS-type general field model

    International Nuclear Information System (INIS)

    Chakrabarti, S.; Nayyar, A.H.

    1982-08-01

    A model incorporating the nonlinear Schroedinger equation and its generalizations is considered and the stability of its periodic-in-time solutions under the restriction of a fixed charge Q is analysed. It is shown that the necessary condition for the stability is given by the inequality deltaQ/deltaν<0, where ν is the parameter of periodicity of the solution in time. In particular, one specific class of Lagrangians is considered and, in addition, the sufficient conditions for the stability of the soliton solutions are also determined. This study thus examines both the necessary and the sufficient conditions for the stability of the solutions of nonlinear Schroedinger equation and some of its generalizations. (author)

  18. Spectroscopic study on the stability of morin in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Bark, Ki Min [Dept. of Chemical Education and Research Institute of Life Science, Gyeongsang National University, Chinju (Korea, Republic of); Im, Seo Eun; Seo, Jung Ja; Park, Ok Hyun; Park, Hyoung Ryun [Dept. of Chemistry, Chonnam National University, Gwangju (Korea, Republic of); Park, Chul Ho [Dept. of Cosmetic Science, Nambu University, Gwangju (Korea, Republic of)

    2015-02-15

    Morin (3,2,4,5,7-pentahydroxyflavone) is a flavonol conjugated to a resorcinol moiety at the C-2 position, different from many other flavonoids. The UV–vis spectrum of morin in neat water reveals two major absorption bands with maxima at 265 and 387 nm. The substance is stable in acidic solution and neat water. However, its absorption maximum at 387 nm continuously shifts to longer wavelengths and new peaks appeared at wavelengths of 312 nm with increasing pH of the solution. The shape of the absorption spectrum of morin depends on the storage time at a given pH, indicating the occurrence of other successive chemical reactions. The fluorescence spectroscopic results also prove that new conjugated double bonds are formed in the deaerated basic solution at the initial state and decompose with time. This behavior indicates that morin is very unstable, and therefore its decomposition occurs by a sequence of multistep reactions in basic solution. Probable reaction pathways for the reaction are suggested based on the spectroscopic results.

  19. Tet Enzymes Regulate Telomere Maintenance and Chromosomal Stability of Mouse ESCs

    Directory of Open Access Journals (Sweden)

    Jiao Yang

    2016-05-01

    Full Text Available Ten-eleven translocation (Tet family proteins convert 5-methylcytosine to 5-hydroxymethylcytosine. We show that mouse embryonic stem cells (ESCs depleted of Tet1 and/or Tet2 by RNAi exhibit short telomeres and chromosomal instability, concomitant with reduced telomere recombination. Tet1 and Tet2 double-knockout ESCs also display short telomeres but to a lesser extent. Notably, Tet1/2/3 triple-knockout ESCs show heterogeneous telomere lengths and increased frequency of telomere loss and chromosomal fusion. Mechanistically, Tets depletion or deficiency increases Dnmt3b and decreases 5hmC levels, resulting in elevated methylation levels at sub-telomeres. Consistently, knockdown of Dnmt3b or addition of 2i (MAPK and GSK3β inhibitors, which also inhibits Dnmt3b, reduces telomere shortening, partially rescuing Tet1/2 deficiency. Interestingly, Tet1/2 double or Tet1/2/3 triple knockout in ESCs consistently upregulates Zscan4, which may counteract telomere shortening. Together, Tet enzymes play important roles in telomere maintenance and chromosomal stability of ESCs by modulating sub-telomeric methylation levels.

  20. Aquifex aeolicus membrane hydrogenase for hydrogen biooxidation: Role of lipids and physiological partners in enzyme stability and activity

    Energy Technology Data Exchange (ETDEWEB)

    Infossi, Pascale; Lojou, Elisabeth; Giudici-Orticoni, Marie-Therese [Unite de Bioenergetique et Ingenierie des Proteines, UPR 9036, Institut de Microbiologie de la Mediterranee - CNRS, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20 (France); Chauvin, Jean-Paul [Institut de Biologie du developpement de Marseille Luminy, UMR 6216, Parc Scientifique de Luminy, 163 Avenue de Luminy, BP 907, 13009 Marseille (France); Herbette, Gaetan [Spectropole FI 1739, Aix-Marseille Universite case 511, Faculte de St Jerome Avenue Escadrille Normandie Niemen, 13397 Marseille Cedex 20 (France); Brugna, Myriam [Unite de Bioenergetique et Ingenierie des Proteines, UPR 9036, Institut de Microbiologie de la Mediterranee - CNRS, 31 Chemin Joseph Aiguier, 13402 Marseille Cedex 20 (France); Universite de Provence, 3 Place Victor Hugo, 13331 Marseille Cedex 03 (France)

    2010-10-15

    Hydrogenase I from the hyperthermophilic bacterium Aquifex aeolicus is a good candidate for biotechnological devices thanks to its ability to oxidize hydrogen at high temperature, even in the presence of oxygen and CO. In order to enhance the enzyme stability and the catalytic efficiency, we investigated the hydrogen oxidation process with hydrogenase I embedded in a physiological-like environment. Hydrogenase I partners in the metabolic chain, namely membrane quinone and cytochrome b, were purified and fully characterized. The complex hydrogenase I-cytochrome b was inserted into liposomes. Surface Plasmon Resonance revealed that quinone took part in the stabilization of the complex. By use of molecular modelization and electrochemistry analysis, enzyme stability has been demonstrated to be stronger and enzymatic efficiency to be five times higher when hydrogenase is embedded into the liposomes. This result raises the possibility of using hydrogenases as biocatalysts in fuel cells. (author)

  1. Antioxidant activity and emulsion-stabilizing effect of pectic enzyme treated pectin in soy protein isolate-stabilized oil/water emulsion.

    Science.gov (United States)

    Huang, Ping-Hsiu; Lu, Hao-Te; Wang, Yuh-Tai; Wu, Ming-Chang

    2011-09-14

    The antioxidant activity of pectic enzyme treated pectin (PET-pectin) prepared from citrus pectin by enzymatic hydrolysis and its potential use as a stabilizer and an antioxidant for soy protein isolate (SPI)-stabilized oil in water (O/W) emulsion were investigated. Trolox equivalent antioxidant capacity (TEAC) was found to be positively associated with molecular weight (M(w)) of PET-pectin and negatively associated with degree of esterification (DE) of PET-pectin. PET-pectin (1 kDa and 11.6% DE) prepared from citrus pectin after 24 h of hydrolysis by commercial pectic enzyme produced by Aspergillus niger expressed higher α,α-diphenyl-β-picrylhydrazyl (DPPH) radical scavenging activity, TEAC, and reducing power than untreated citrus pectin (353 kDa and 60% DE). The addition of PET-pectin could increase both emulsifying activity (EA) and emulsion stability (ES) of SPI-stabilized O/W emulsion. When the SPI-stabilized lipid droplet was coated with the mixture of PET-pectin and pectin, the EA and ES of the emulsion were improved more than they were when the lipid droplet was coated with either pectin or PET-pectin alone. The amount of secondary oxidation products (thiobarbituric acid reactive substances) produced in the emulsion prepared with the mixture of SPI and PET-pectin was less than the amount produced in the emulsion prepared with either SPI or SPI/pectin. These results suggest that PET-pectin has an emulsion-stabilizing effect and lipid oxidation inhibition ability on SPI-stabilized emulsion. Therefore, PET-pectin can be used as a stabilizer as well as an antioxidant in plant origin in SPI-stabilized O/W emulsion and thus prolong the shelf life of food emulsion.

  2. Globally exponential stability and periodic solutions of CNNS with variable coefficients and variable delays

    International Nuclear Information System (INIS)

    Liu Haifei; Wang Li

    2006-01-01

    In this Letter, by using the inequality method and the Lyapunov functional method, we analyze the globally exponential stability and the existence of periodic solutions of a class of cellular neutral networks with delays and variable coefficients. Some simple and new sufficient conditions ensuring the existence and uniqueness of globally exponential stability of periodic solutions for cellular neutral networks with variable coefficients and delays are obtained. In addition, one example is also worked out to illustrate our theory

  3. Globally exponential stability and periodic solutions of CNNS with variable coefficients and variable delays

    Energy Technology Data Exchange (ETDEWEB)

    Liu Haifei [School of Management and Engineering, Nanjing University, Nanjing 210093 (China)]. E-mail: hfliu80@126.com; Wang Li [School of Management and Engineering, Nanjing University, Nanjing 210093 (China)

    2006-09-15

    In this Letter, by using the inequality method and the Lyapunov functional method, we analyze the globally exponential stability and the existence of periodic solutions of a class of cellular neutral networks with delays and variable coefficients. Some simple and new sufficient conditions ensuring the existence and uniqueness of globally exponential stability of periodic solutions for cellular neutral networks with variable coefficients and delays are obtained. In addition, one example is also worked out to illustrate our theory.

  4. Almost Surely Asymptotic Stability of Exact and Numerical Solutions for Neutral Stochastic Pantograph Equations

    Directory of Open Access Journals (Sweden)

    Zhanhua Yu

    2011-01-01

    Full Text Available We study the almost surely asymptotic stability of exact solutions to neutral stochastic pantograph equations (NSPEs, and sufficient conditions are obtained. Based on these sufficient conditions, we show that the backward Euler method (BEM with variable stepsize can preserve the almost surely asymptotic stability. Numerical examples are demonstrated for illustration.

  5. Stability of carotenoids toward UV-irradiation in hexane solution

    Directory of Open Access Journals (Sweden)

    DRAGAN CVETKOVIC

    2008-01-01

    Full Text Available The stabilities of four selected carotenoids dissolved in hexane, two carotenes and two xanthophylls, toward UV-irradiation of three different ranges (UV-A, UV-B and UV-C were studied in this work. The carotenoids underwent bleaching via a probable free radical mediated mechanism following first-order kinetics. The bleaching rates were highly dependent on the input of the involved photons and, although not consistently, on the chemical structures of the investigated compounds. For the two xanthophylls, a possible role of oxygen associated with their bleaching cannot be neglected.

  6. Robust Stability and H∞ Control of Uncertain Piecewise Linear Switched Systems with Filippov Solutions

    DEFF Research Database (Denmark)

    Ahmadi, Mohamadreza; Mojallali, Hamed; Wisniewski, Rafal

    2012-01-01

    This paper addresses the robust stability and control problem of uncertain piecewise linear switched systems where, instead of the conventional Carathe ́odory solutions, we allow for Filippov solutions. In other words, in contrast to the previous studies, solutions with infinite switching in fini...... algorithm is proposed to surmount the aforementioned matrix inequality conditions....... time along the facets and on faces of arbitrary dimensions are also taken into account. Firstly, based on earlier results, the stability problem of piecewise linear systems with Filippov solutions is translated into a number of linear matrix inequality feasibility tests. Subsequently, a set of matrix...... inequalities are brought forward, which determines the asymptotic stability of the Filippov solutions of a given uncertain piecewise linear system. Afterwards, bilinear matrix inequality conditions for synthesizing a robust controller with a guaranteed H∞ per- formance are formulated. Finally, a V-K iteration...

  7. Stabilization of polymer solutions in the presence of oxidizing agents

    Energy Technology Data Exchange (ETDEWEB)

    Mendez, A; Serino, A; Jenkins, D; Lichaa, P M

    1974-01-01

    Many investigators in the field of heavy oil recovery techniques have confirmed the recovery efficiency which, in the miscible displacement method, has utilized polymer solutions as additives to the injection fluids. The viscosity increase of the displacing phase has lowered the mobility ratio with a significant improvement in the sweep efficiency. Recently, others have reported a notable improvement in the recovery of heavy crude by this same method of miscible displacement which causes a mobile fluid bank between the crude and the displacing fluid. There is an intervening oxidation reaction, promoting the in situ formation of surface-active agents on the interface of these 2 fluids. This study describes the effect on degradation of polymer solutions by such oxidizing agents as potassium chromate and potassium permanganate. The degradation of any polymer solution with or without additives is increased materially by an increase in temperature. The presence of NaCl brine is not often of any great significance in the time of gelation, especially with polymers of the polysaccharide type. (18 refs.)

  8. Enzyme-polyelectrolyte complexes in water-ethanol mixtures: negatively charged groups artificially introduced into alpha-chymotrypsin provide additional activation and stabilization effects.

    Science.gov (United States)

    Kudryashova, E V; Gladilin, A K; Vakurov, A V; Heitz, F; Levashov, A V; Mozhaev, V V

    1997-07-20

    Formation of noncovalent complexes between alpha-chymotrypsin (CT) and a polyelectrolyte, polybrene (PB), has been shown to produce two major effects on enzymatic reactions in binary mixtures of polar organic cosolvents with water. (i) At moderate concentrations of organic cosolvents (10% to 30% v/v), enzymatic activity of CT is higher than in aqueous solutions, and this activation effect is more significant for CT in complex with PB (5- to 7-fold) than for free enzyme (1.5- to 2.5-fold). (ii) The range of cosolvent concentrations that the enzyme tolerates without complete loss of catalytic activity is much broader. For enhancement of enzyme stability in the complex with the polycation, the number of negatively charged groups in the protein has been artificially increased by using chemical modification with pyromellitic and succinic anhydrides. Additional activation effect at moderate concentrations of ethanol and enhanced resistance of the enzyme toward inactivation at high concentrations of the organic solvent have been observed for the modified preparations of CT in the complex with PB as compared with an analogous complex of the native enzyme. Structural changes behind alterations in enzyme activity in water-ethanol mixtures have been studied by the method of circular dichroism (CD). Protein conformation of all CT preparations has not changed significantly up to 30% v/v of ethanol where activation effects in enzymatic catalysis were most pronounced. At higher concentrations of ethanol, structural changes in the protein have been observed for different forms of CT that were well correlated with a decrease in enzymatic activity. (c) 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 267-277, 1997.

  9. Stability of Medium-Bridged Twisted Amides in Aqueous Solutions

    Science.gov (United States)

    Szostak, Michal; Yao, Lei; Aubé, Jeffrey

    2012-01-01

    “Twisted” amides containing non-standard dihedral angles are typically hypersensitive to hydrolysis, a feature that has stringently limited their utility in water. We have synthesized a series of bridged lactams that contain a twisted amide linkage but which exhibit enhanced stability in aqueous environments. Many of these compounds were extracted unchanged from aqueous mixtures ranging from the strongly basic to the strongly acidic. NMR experiments showed that tricyclic lactams undergo reversible hydrolysis at extreme pH ranges, but that a number of compounds in this structure class are indefinitely stable under physiologically relevant pH conditions; one bicyclic example was additionally water-soluble. We examined the effect of structure on the reversibility of amide bond hydrolysis, which we attributed to the transannular nature of the amino acid analogs. These data suggest that medium-bridged lactams of these types should provide useful platforms for studying the behavior of twisted amides in aqueous systems. PMID:19178141

  10. Stability studies of lincomycin hydrochloride in aqueous solution and intravenous infusion fluids.

    Science.gov (United States)

    Czarniak, Petra; Boddy, Michael; Sunderland, Bruce; Hughes, Jeff D

    2016-01-01

    The purpose of this study was to evaluate the chemical stability of Lincocin(®) (lincomycin hydrochloride) in commonly used intravenous fluids at room temperature (25°C), at accelerated-degradation temperatures and in selected buffer solutions. The stability of Lincocin(®) injection (containing lincomycin 600 mg/2 mL as the hydrochloride) stored at 25°C±0.1°C in sodium lactate (Hartmann's), 0.9% sodium chloride, 5% glucose, and 10% glucose solutions was investigated over 31 days. Forced degradation of Lincocin(®) in hydrochloric acid, sodium hydroxide, and hydrogen peroxide was performed at 60°C. The effect of pH on the degradation rate of lincomycin hydrochloride stored at 80°C was determined. Lincomycin hydrochloride w as found to maintain its shelf life at 25°C in sodium lactate (Hartmann's) solution, 0.9% sodium chloride solution, 5% glucose solution, and 10% glucose solution, with less than 5% lincomycin degradation occurring in all intravenous solutions over a 31-day period. Lincomycin hydrochloride showed less rapid degradation at 60°C in acid than in basic solution, but degraded rapidly in hydrogen peroxide. At all pH values tested, lincomycin followed first-order kinetics. It had the greatest stability near pH 4 when stored at 80°C (calculated shelf life of 4.59 days), and was least stable at pH 2 (calculated shelf life of 0.38 days). Lincocin(®) injection was chemically found to have a shelf life of at least 31 days at 25°C when added to sodium lactate (Hartmann's) solution, 0.9% sodium chloride solution, 5% glucose solution, and 10% glucose solution. Solutions prepared at approximately pH 4 are likely to have optimum stability.

  11. Rippled shock front solutions for testing hydrodynamic stability simulations

    International Nuclear Information System (INIS)

    Munro, D.H.

    1989-01-01

    The response of a shock front to arbitrary small perturbations can be calculated analytically. Such rippled shock front solutions are useful for determining the accuracy of hydrodynamic simulation codes such as LASNEX [Comments Plasma Phys. Controlled Fusion 2, 51 (1977)], which are used to compute perturbation growth in inertial fusion targets. The LASNEX fractional errors are of order κ 2 L 2 , where κ is the transverse wavenumber of the perturbation, and L is the largest zone dimension. Numerical errors are about 25% for a calculation using 26 zones per transverse wavelength

  12. Contractivity and Exponential Stability of Solutions to Nonlinear Neutral Functional Differential Equations in Banach Spaces

    Institute of Scientific and Technical Information of China (English)

    Wan-sheng WANG; Shou-fu LI; Run-sheng YANG

    2012-01-01

    A series of contractivity and exponential stability results for the solutions to nonlinear neutral functional differential equations (NFDEs) in Banach spaces are obtained,which provide unified theoretical foundation for the contractivity analysis of solutions to nonlinear problems in functional differential equations (FDEs),neutral delay differential equations (NDDEs) and NFDEs of other types which appear in practice.

  13. Stability of oscillatory solutions of differential equations with a general piecewise constant argument

    Directory of Open Access Journals (Sweden)

    Kuo-Shou Chiu

    2011-11-01

    Full Text Available We examine scalar differential equations with a general piecewise constant argument, in short DEPCAG, that is, the argument is a general step function. Criteria of existence of the oscillatory and nonoscillatory solutions of such equations are proposed. Necessary and sufficient conditions for stability of the zero solution are obtained. Appropriate examples are given to show our results.

  14. Stabilization of solutions to higher-order nonlinear Schrodinger equation with localized damping

    Directory of Open Access Journals (Sweden)

    Eleni Bisognin

    2007-01-01

    Full Text Available We study the stabilization of solutions to higher-order nonlinear Schrodinger equations in a bounded interval under the effect of a localized damping mechanism. We use multiplier techniques to obtain exponential decay in time of the solutions of the linear and nonlinear equations.

  15. Existence and exponential stability of almost periodic solution for Hopfield-type neural networks with impulse

    International Nuclear Information System (INIS)

    Zhang Huiying; Xia Yonghui

    2008-01-01

    In this paper, some sufficient conditions are obtained for checking the existence and exponential stability of almost periodic solution for bidirectional associative memory Hopfield-type neural networks with impulse. The approaches are based on contraction principle and Gronwall-Bellman's inequality. This paper is considering the almost periodic solution for impulsive Hopfield-type neural networks

  16. Formulation and stability of an extemporaneous 0.02% chlorhexidine digluconate ophthalmic solution

    Directory of Open Access Journals (Sweden)

    Shu-Chiao Lin

    2015-12-01

    Conclusion: The acetate-buffered 0.02% chlorhexidine digluconate ophthalmic solution stored in light-resistant high-density polyethylene eyedroppers demonstrated excellent stability at 2–25°C for 6 months after being sealed and for 1 month after opening. This finding will enable us to prepare 0.02% chlorhexidine digluconate ophthalmic solutions based on a doctor's prescription.

  17. DUB3 Deubiquitylating Enzymes Regulate Hippo Pathway Activity by Regulating the Stability of ITCH, LATS and AMOT Proteins

    DEFF Research Database (Denmark)

    Nguyen, Thanh Hung; Kugler, Jan-Michael; Cohen, Stephen Michael

    2017-01-01

    /TAZ, is regulated by ubiquitin mediated protein turnover and several ubiquitin ligase complexes have been implicated in human cancer. However, little is known about the deubiquitylating enzymes that counteract these ubiquitin ligases in regulation of the Hippo pathway. Here we identify the DUB3 family...... deubiquitylating enzymes as regulators of Hippo pathway activity. We provide evidence that DUB3 proteins regulate YAP/TAZ activity by controlling the stability of the E3 ligase ITCH, the LATS kinases and the AMOT family proteins. As a novel Hippo pathway regulator, DUB3 has the potential to act a tumor suppressor...

  18. Experimental and theoretical study of solid solution stability under irradiation

    International Nuclear Information System (INIS)

    Cauvin, Richard.

    1981-08-01

    The behavior of dilute alloys (Al-Zn, Al-Ag, Al-Si, Al-Ge and Al-Mg) under 1 MeV electron irradiation has been studied in a high voltage electron microscope. A phenomenon of homogeneous precipitation induced by irradiation in undersaturated solid solutions (Al-Zn, Al-Ag and Al-Si) has been discovered; the observed precipitates are either coherent or incoherent, but never associated with point defect sinks. The solubility limit is a function of irradiation temperature and flux; but, under irradiation, it does not behave as a true thermal solubility limit (without irradiation). The existing theories (kinetic or strictly thermodynamic) do not account for this phenomenon. It is shown that the irreversibility of the mutual recombination between trapped vacancies and mixed interstitials is the driving force of this homogeneous precipitation. Using a dilute solid solution model, we show that, under irradiation, the homogeneous stationary state, stable from a strictly thermodynamic point of view, can be unstable when the recombination reaction is taken into account. The solubility limit under irradiation is calculated with a nucleation-growth model taking account for this effect; it is proportional to the thermal solubility limit without irradiation. This model explains all the experimental observations [fr

  19. Trade-offs with stability modulate innate and mutationally acquired drug-resistance in bacterial dihydrofolate reductase enzymes.

    Science.gov (United States)

    Matange, Nishad; Bodkhe, Swapnil; Patel, Maitri; Shah, Pooja

    2018-06-05

    Structural stability is a major constraint on the evolution of protein sequences. However, under strong directional selection, mutations that confer novel phenotypes but compromise structural stability of proteins may be permissible. During the evolution of antibiotic resistance, mutations that confer drug resistance often have pleiotropic effects on the structure and function of antibiotic-target proteins, usually essential metabolic enzymes. In this study, we show that trimethoprim-resistant alleles of dihydrofolate reductase from Escherichia coli (EcDHFR) harbouring the Trp30Gly, Trp30Arg or Trp30Cys mutations are significantly less stable than the wild type making them prone to aggregation and proteolysis. This destabilization is associated with lower expression level resulting in a fitness cost and negative epistasis with other TMP-resistant mutations in EcDHFR. Using structure-based mutational analysis we show that perturbation of critical stabilizing hydrophobic interactions in wild type EcDHFR enzyme explains the phenotypes of Trp30 mutants. Surprisingly, though crucial for the stability of EcDHFR, significant sequence variation is found at this site among bacterial DHFRs. Mutational and computational analyses in EcDHFR as well as in DHFR enzymes from Staphylococcus aureus and Mycobacterium tuberculosis demonstrate that natural variation at this site and its interacting hydrophobic residues, modulates TMP-resistance in other bacterial DHFRs as well, and may explain the different susceptibilities of bacterial pathogens to trimethoprim. Our study demonstrates that trade-offs between structural stability and function can influence innate drug resistance as well as the potential for mutationally acquired drug resistance of an enzyme. ©2018 The Author(s).

  20. Theoretical calculations of the thermodynamic stability of ionic substitutions in hydroxyapatite under an aqueous solution environment

    International Nuclear Information System (INIS)

    Matsunaga, Katsuyuki; Murata, Hidenobu; Shitara, Kazuki

    2010-01-01

    Defect formation energies in materials generally depend on chemical potentials determined by a chemical equilibrium condition. In particular, an aqueous solution environment is important for biomaterials such as hydroxyapatite studied here. Therefore, a methodology to obtain ionic chemical potentials under chemical equilibrium between solid and aqueous solution was introduced, and was applied to substitutional divalent cations formed via ion exchange with Ca 2+ in hydroxyapatite. The calculated ranking of the stability of substitutional cations in HAp was in good agreement with the experimentally observed trend. The present theoretical approach would be useful to explore the thermodynamic stability of defects in materials subjected to an aqueous solution environment.

  1. Stability and periodicity of solutions for delay dynamic systems on time scales

    Directory of Open Access Journals (Sweden)

    Zhi-Qiang Zhu

    2014-04-01

    Full Text Available This article concerns the stability and periodicity of solutions to the delay dynamic system $$ x^{\\triangle}(t=A(t x(t + F(t, x(t, x(g(t+C(t $$ on a time scale. By the inequality technique for vectors, we obtain some stability criteria for the above system. Then, by using the Horn fixed point theorem, we present some conditions under which our system is asymptotically periodic and its periodic solution is unique. In particular, the periodic solution is positive under proper assumptions.

  2. Multiple solutions and stability of the steady transonic small-disturbance equation

    Directory of Open Access Journals (Sweden)

    Ya Liu

    2017-09-01

    Full Text Available Numerical solutions of the steady transonic small-disturbance (TSD potential equation are computed using the conservative Murman−Cole scheme. Multiple solutions are discovered and mapped out for the Mach number range at zero angle of attack and the angle of attack range at Mach number 0.85 for the NACA 0012 airfoil. We present a linear stability analysis method by directly assembling and evaluating the Jacobian matrix of the nonlinear finite-difference equation of the TSD equation. The stability of all the discovered multiple solutions are then determined by the proposed eigen analysis. The relation of stability to convergence of the iterative method for solving the TSD equation is discussed. Computations and the stability analysis demonstrate the possibility of eliminating the multiple solutions and stabilizing the remaining unique solution by adding a sufficiently long splitter plate downstream the airfoil trailing edge. Finally, instability of the solution of the TSD equation is shown to be closely connected to the onset of transonic buffet by comparing with experimental data.

  3. Valency stabilization of Polyvalent Iron Ions in Solution By some Organic additives during Gamma Irradiation

    International Nuclear Information System (INIS)

    Barakat, M.F.; Abdel Hamid, M.M.

    2012-01-01

    Valency stabilization of polyvalent ions in gamma irradiated aqueous solutions is sometimes necessary for the success of some chemical operations. In some previous publications valency stabilization of some polyvalent ions in solution upon gamma irradiation was achieved by using additives capable of interacting with the oxidizing or reducing species formed by water radiolysis in the medium. The results showed that the duration of valency stabilization depends on the concentration of the additives used.In the present work, a series of some organic additives has been used to investigate their capability in inducing valency stabilization of polyvalent iron ions when subjected to extended gamma irradiation periods. The results showed that the efficiency of valency stabilization depends on the amount and chemical structure of the organic additive used

  4. Estimation of stability constants of metal monoacidocomplexes in aqueous solutions (1:2) of electrolytes

    International Nuclear Information System (INIS)

    Ryazanov, M.A.

    1992-01-01

    On the basis of the concept of the model of isoactive solutions it is shown that osmosis pressure of aqueous solutions (1:2) of electrolytes is well described by the Van-der-Vaals model for ideal associated gas. Stabilisty constants were calculated using osmosis mole parts of interacting particles as a concentrational scale. Stability constants in the scale of osmosis mole parts are equal to thermodynamic contstants, rated for an infinitely diluted solution

  5. THE STABILITY OF THE PERIODIC SOLUTIONS OF SECOND ORDER HAMILTONIAN SYSTEMS

    Institute of Scientific and Technical Information of China (English)

    2000-01-01

    This paper studies the stability of the periodic solutions of the second order Hamiltonian systems with even superquadratic or subquadratic potentials. The author proves that in the subquadratic case, there exist infinite geometrically distinct elliptic periodic solutions, and in the superquadratic case, there exist infinite geometrically distinct periodic solutions with at most one instability direction if they are half period non-degenerate, otherwise they are elliptic.

  6. The linear stability of the Schwarzschild solution to gravitational perturbations in the generalised wave gauge

    OpenAIRE

    Johnson, Thomas

    2018-01-01

    In a recent seminal paper \\cite{D--H--R} of Dafermos, Holzegel and Rodnianski the linear stability of the Schwarzschild family of black hole solutions to the Einstein vacuum equations was established by imposing a double null gauge. In this paper we shall prove that the Schwarzschild family is linearly stable as solutions to the Einstein vacuum equations by imposing instead a generalised wave gauge: all sufficiently regular solutions to the system of equations that result from linearising the...

  7. Stability-indicating HPLC method for the determination of the stability of oxytocin parenteral solutions prepared in polyolefin bags.

    Science.gov (United States)

    Kaushal, G; Sayre, B E; Prettyman, T

    2012-02-01

    Oxytocin is very commonly used in clinical settings and is a nonapeptide hormone that stimulates the contraction of uterine smooth muscles. In this study the stability of extemporaneously compounded oxytocin solutions was investigated in polyolefin bags. The sterile preparations of oxytocin were compounded to the strength of 0.02 U/mL in accordance with United States Pharmacopeia (USP) standards. In order to carry out the stability testing of these parenteral products, the solutions were stored under three different temperature conditions of -20°C (frozen), 2-6°C (refrigerated), and 22-25°C (room temperature). Three solutions from each temperature were withdrawn and were assessed for stability on days 0, 7, 15, 21, and 30 as per the USP guidelines. The assay of oxytocin was examined by an HPLC method at each time point. No precipitation, cloudiness or color change was observed during this study at all temperatures. The assay content by HPLC revealed that oxytocin retains greater than at least 90% of the initial concentrations for 21 days. There was no significant change in pH and absorbance values for 21 days under all the conditions of storage. Oxytocin parenteral solutions in the final concentration of 0.02 U/mL and diluted in normal saline are stable for at least 30 days under frozen and refrigerated conditions for 30 days. At the room temperature, the oxytocin solutions were stable for at least 21 days. The stability analysis results show that the shelf-life of 21 days observed in this study was far better than their recommended expiration dates.

  8. The role of glycosylation and domain interactions in the thermal stability of human angiotensin-converting enzyme.

    Science.gov (United States)

    O'Neill, Hester G; Redelinghuys, Pierre; Schwager, Sylva L U; Sturrock, Edward D

    2008-09-01

    The N and C domains of somatic angiotensin-converting enzyme (sACE) differ in terms of their substrate specificity, inhibitor profiling, chloride dependency and thermal stability. The C domain is thermally less stable than sACE or the N domain. Since both domains are heavily glycosylated, the effect of glycosylation on their thermal stability was investigated by assessing their catalytic and physicochemical properties. Testis ACE (tACE) expressed in mammalian cells, mammalian cells in the presence of a glucosidase inhibitor and insect cells yielded proteins with altered catalytic and physicochemical properties, indicating that the more complex glycans confer greater thermal stabilization. Furthermore, a decrease in tACE and N-domain N-glycans using site-directed mutagenesis decreased their thermal stability, suggesting that certain N-glycans have an important effect on the protein's thermodynamic properties. Evaluation of the thermal stability of sACE domain swopover and domain duplication mutants, together with sACE expressed in insect cells, showed that the C domain contained in sACE is less dependent on glycosylation for thermal stabilization than a single C domain, indicating that stabilizing interactions between the two domains contribute to the thermal stability of sACE and are decreased in a C-domain-duplicating mutant.

  9. Proteolysis of Sardine (Sardina pilchardus and Anchovy (Stolephorus commersonii by Commercial Enzymes in Saline Solutions

    Directory of Open Access Journals (Sweden)

    Chau Minh Le

    2015-01-01

    Full Text Available Fish sauce production is a very long process and there is a great interest in shortening it. Among the different strategies to speed up this process, the addition of external proteases could be a solution. This study focuses on the eff ect of two commercial enzymes (Protamex and Protex 51FP on the proteolysis of two fish species traditionally converted into fish sauce: sardine and anchovy, by comparison with classical autolysis. Hydrolysis reactions were conducted with fresh fish at a temperature of 30 °C and under different saline conditions (from 0 to 30 % NaCl. Hydrolysis degree and liquefaction of the raw material were used to follow the process. As expected, the proteolysis decreased with increasing amount of salt. Regarding the fi sh species, higher rate of liquefaction and higher hydrolysis degree were obtained with anchovy. Between the two proteases, Protex 51FP gave better results with both fi sh types. This study demonstrates that the addition of commercial proteases could be helpful for the liquefaction of fi sh and cleavage of peptide bonds that occur during fi sh sauce production and thus speed up the production process.

  10. Factors affecting emulsion stability and quality of oil recovered from enzyme-assisted aqueous extraction of soybeans.

    Science.gov (United States)

    Jung, S; Maurer, D; Johnson, L A

    2009-11-01

    The objectives of the present study were to assess how the stability of the emulsion recovered from aqueous extraction processing of soybeans was affected by characteristics of the starting material and extraction and demulsification conditions. Adding endopeptidase Protex 6L during enzyme-assisted aqueous extraction processing (EAEP) of extruded soybean flakes was vital to obtaining emulsions that were easily demulsified with enzymes. Adding salt (up to 1.5 mM NaCl or MgCl(2)) during extraction and storing extruded flakes before extraction at 4 and 30 degrees C for up to 3 months did not affect the stabilities of emulsions recovered from EAEP of soy flour, flakes and extruded flakes. After demulsification, highest free oil yield was obtained with EAEP of extruded flakes, followed by flour and then flakes. The same protease used for the extraction step was used to demulsify the EAEP cream emulsion from extruded full-fat soy flakes at concentrations ranging from 0.03% to 2.50% w/w, incubation times ranging from 2 to 90 min, and temperatures of 25, 50 or 65 degrees C. Highest free oil recoveries were achieved at high enzyme concentrations, mild temperatures, and short incubation times. Both the nature of enzyme (i.e., protease and phospholipase), added alone or as a cocktail, concentration of enzymes (0.5% vs. 2.5%) and incubation time (1 vs. 3 h), use during the extraction step, and nature of enzyme added for demulsifying affected free oil yield. The free oil recovered from EAEP of extruded flakes contained less phosphorus compared with conventional hexane-extracted oil. The present study identified conditions rendering the emulsion less stable, which is critical to increasing free oil yield recovered during EAEP of soybeans, an environmentally friendly alternative processing method to hexane extraction.

  11. Phase stability in wear-induced supersaturated Al-Ti solid solution

    Energy Technology Data Exchange (ETDEWEB)

    Watanabe, Y.; Yokoyama, K. [Dept. of Functional Machinery Mechanics Shinshu Univ., Ueda (Japan); Hosoda, H. [Precision and Intelligence Lab., Tokyo Inst. of Tech., Nagatsuta, Midori-ku, Yokohama (Japan)

    2002-07-01

    Al-Ti supersaturated solid solutions were introduced by wear testing and the rapid quenching of an Al/Al{sub 3}Ti composite (part of an Al/Al{sub 3}Ti functionally graded material) that was fabricated using the centrifugal method. The phase stability of the supersaturated solid solution was studied through systematic annealing of the supersaturated solid solution. It was found that the Al-Ti supersaturated solid solution decomposed into Al and Al{sub 3}Ti intermetallic compound phases during the heat treatment. The Al-Ti supersaturated solid solutions fabricated were, therefore, not an equilibrium phase, and thus decomposed into the equilibrium phases during heat treatment. It was also found that heat treatment leads to a significant hardness increase for the Al-Ti supersaturated solid solution. Finally, it was concluded that formation of the wear-induced supersaturated solid solution layer was a result of severe plastic deformation. (orig.)

  12. Global stability and existence of periodic solutions of discrete delayed cellular neural networks

    International Nuclear Information System (INIS)

    Li Yongkun

    2004-01-01

    We use the continuation theorem of coincidence degree theory and Lyapunov functions to study the existence and stability of periodic solutions for the discrete cellular neural networks (CNNs) with delays xi(n+1)=xi(n)e-bi(n)h+θi(h)-bar j=1maij(n)fj(xj(n))+θi(h)-bar j=1mbij(n)fj(xj(n- τij(n)))+θi(h)Ii(n),i=1,2,...,m. We obtain some sufficient conditions to ensure that for the networks there exists a unique periodic solution, and all its solutions converge to such a periodic solution

  13. The Effects of Electroless Nickel Plating Bath Conditions on Stability of Solution and Properties of Deposit

    International Nuclear Information System (INIS)

    Huh, Jin; Lee, Jae Ho

    2000-01-01

    Electroless depositions of nickel were conducted in different bath conditions to find optimum conditions of electroless nickel plating at low operating temperature and pH. The effect of complexing reagent on stability of plating solution was investigated. Sodium citrate complexed plating solution is more stable than sodium pyrophosphate complexed solution. The effects of nickel salt concentration, reducing agent, complexing agent and inhibitor on deposition rate was investigated. The effects of pH on deposition rate and content of phosphorous in deposited nickel were also analyzed. Electroless deposited nickel become crystallized with increasing pH due to lower phosphorous content. In optimum operating bath condition, deposition rate was 7 μm/hr at 60 .deg. C and pH 10.0 without stabilizer. The rate was decreased with stabilizer concentration

  14. Legendre condition and the stabilization problem for classical soliton solutions in generalized Skyrme models

    International Nuclear Information System (INIS)

    Kiknadze, N.A.; Khelashvili, A.A.

    1990-01-01

    The problem on stability of classical soliton solutions is studied from the unique point of view: the Legendre condition - necessary condition of existence of weak local minimum for energy functional (term soliton is used here in the wide sense) is used. Limits to parameters of the model Lagrangians are obtained; it is shown that there is no soliton stabilization in some of them despite the phenomenological achievements. The Jacoby sufficient condition is discussed

  15. Fingering patterns in magnetic fluids: Perturbative solutions and the stability of exact stationary shapes

    Science.gov (United States)

    Anjos, Pedro H. A.; Lira, Sérgio A.; Miranda, José A.

    2018-04-01

    We examine the formation of interfacial patterns when a magnetic liquid droplet (ferrofluid, or a magnetorheological fluid), surrounded by a nonmagnetic fluid, is subjected to a radial magnetic field in a Hele-Shaw cell. By using a vortex-sheet formalism, we find exact stationary solutions for the fluid-fluid interface in the form of n -fold polygonal shapes. A weakly nonlinear, mode-coupling method is then utilized to find time-evolving perturbative solutions for the interfacial patterns. The stability of such nonzero surface tension exact solutions is checked and discussed, by trying to systematically approach the exact stationary shapes through perturbative solutions containing an increasingly larger number of participating Fourier modes. Our results indicate that the exact stationary solutions of the problem are stable, and that a good matching between exact and perturbative shape solutions is achieved just by using a few Fourier modes. The stability of such solutions is substantiated by a linearization process close to the stationary shape, where a system of mode-coupling equations is diagonalized, determining the eigenvalues which dictate the stability of a fixed point.

  16. Formulation and stability of an extemporaneously compounded oral solution of chlorpromazine HCl.

    Science.gov (United States)

    Prohotsky, Daniel L; Juba, Katherine M; Zhao, Fang

    2014-12-01

    Chlorpromazine is a phenothiazine antipsychotic which is often used in hospice and palliative care to treat hiccups, delirium, and nausea. With the discontinuation of the commercial oral solution concentrate, there is a need to prepare this product by extemporaneous compounding. This study was initiated to identify an easy-to-prepare formulation for the compounding pharmacist. A stability study was also conducted to select the proper storage conditions and establish the beyond-use date. Chlorpromazine HCl powder and the Ora-Sweet® syrup vehicle were used to prepare the 100 mg/mL solution. Once the feasibility was established, a batch of the solution was prepared and packaged in amber plastic prescription bottles for a stability study. These samples were stored at refrigeration (2-8°C) or room temperature (20-25°C) for up to 3 months. At each monthly time point, the samples were evaluated by visual inspection, pH measurement, and high performance liquid chromatography (HPLC). A separate forced stability study was conducted to confirm that the HPLC method was stability indicating. A clear and colorless solution of 100 mg/mL chlorpromazine HCl was obtained by dissolving the drug powder in Ora-Sweet® with moderate agitation. The stability study results indicated that this solution product remained unchanged in visual appearance or pH at both refrigeration and room temperature for up to 3 months. The HPLC results also confirmed that all stability samples retained 93.6-101.4% of initial drug concentration. Chlorpromazine HCl solution 100 mg/mL can be compounded extemporaneously by dissolving chlorpromazine HCl drug powder in Ora-Sweet®. The resulting product is stable for at least three months in amber plastic prescription bottles stored at either refrigeration or room temperature.

  17. Stability studies of lincomycin hydrochloride in aqueous solution and intravenous infusion fluids

    Directory of Open Access Journals (Sweden)

    Czarniak P

    2016-03-01

    Full Text Available Petra Czarniak, Michael Boddy, Bruce Sunderland, Jeff D Hughes School of Pharmacy, Curtin University, Perth, WA, Australia Purpose: The purpose of this study was to evaluate the chemical stability of Lincocin® (lincomycin hydrochloride in commonly used intravenous fluids at room temperature (25°C, at accelerated-degradation temperatures and in selected buffer solutions.Materials and methods: The stability of Lincocin® injection (containing lincomycin 600 mg/2 mL as the hydrochloride stored at 25°C±0.1°C in sodium lactate (Hartmann’s, 0.9% sodium chloride, 5% glucose, and 10% glucose solutions was investigated over 31 days. Forced degradation of Lincocin® in hydrochloric acid, sodium hydroxide, and hydrogen peroxide was performed at 60°C. The effect of pH on the degradation rate of lincomycin hydrochloride stored at 80°C was determined.Results: Lincomycin hydrochloride was found to maintain its shelf life at 25°C in sodium lactate (Hartmann’s solution, 0.9% sodium chloride solution, 5% glucose solution, and 10% glucose solution, with less than 5% lincomycin degradation occurring in all intravenous solutions over a 31-day period. Lincomycin hydrochloride showed less rapid degradation at 60°C in acid than in basic solution, but degraded rapidly in hydrogen peroxide. At all pH values tested, lincomycin followed first-order kinetics. It had the greatest stability near pH 4 when stored at 80°C (calculated shelf life of 4.59 days, and was least stable at pH 2 (calculated shelf life of 0.38 days.Conclusion: Lincocin® injection was chemically found to have a shelf life of at least 31 days at 25°C when added to sodium lactate (Hartmann’s solution, 0.9% sodium chloride solution, 5% glucose solution, and 10% glucose solution. Solutions prepared at approximately pH 4 are likely to have optimum stability. Keywords: lincomycin, stability, pH, intravenous fluids, IV additives

  18. Deubiquitylating enzyme UBP64 controls cell fate through stabilization of the transcriptional repressor tramtrack

    NARCIS (Netherlands)

    P.K. Bajpe (Prashanth Kumar); J.A. van der Knaap (Jan); J.A.A. Demmers (Jeroen); K. Bezstarosti (Karel); A. Bassett (Andrew); H.M.M. van Beusekom (Heleen); A.A. Travers (Andrew); C.P. Verrijzer (Peter)

    2008-01-01

    textabstractProtein ubiquitylation plays a central role in multiple signal transduction pathways. However, the substrate specificity and potential developmental roles of deubiquitylating enzymes remain poorly understood. Here, we show that the Drosophila ubiquitin protease UBP64 controls cell fate

  19. Stabilization of red fruit-based smoothies by high-pressure processing. Part A. Effects on microbial growth, enzyme activity, antioxidant capacity and physical stability.

    Science.gov (United States)

    Hurtado, Adriana; Guàrdia, Maria Dolors; Picouet, Pierre; Jofré, Anna; Ros, José María; Bañón, Sancho

    2017-02-01

    Non-thermal pasteurization by high-pressure processing (HPP) is increasingly replacing thermal processing (TP) to maintain the properties of fresh fruit products. However, most of the research on HPP-fruit products only partially addresses fruit-pressure interaction, which limits its practical interest. The objective of this study was to assess the use of a mild HPP treatment to stabilize red fruit-based smoothies (microbial, enzymatic, oxidative and physical stability). HPP (350 MPa/10 °C/5 min) was slightly less effective than TP (85 °C/7 min) in inactivating microbes (mesophilic and psychrophilic bacteria, coliforms, yeasts and moulds) in smoothies kept at 4 °C for up to 28 days. The main limitation of using HPP was its low efficacy in inactivating oxidative (polyphenol oxidase and peroxidase) and hydrolytic (pectin methyl esterase) enzymes. Data on antioxidant status, colour parameters, browning index, transmittance, turbidity and viscosity confirmed that the HPP-smoothies have a greater tendency towards oxidation and clarification, which might lead to undesirable sensory and nutritional changes (see Part B). The microbial quality of smoothies was adequately controlled by mild HPP treatment without affecting their physical-chemical characteristics; however, oxidative and hydrolytic enzymes are highly pressure-resistant, which suggests that additional strategies should be used to stabilize smoothies. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  20. Dynamic stability of self-similar solutions for a plasma pinch

    International Nuclear Information System (INIS)

    Ma, Sifeng.

    1988-01-01

    Linear Magnetohydrodynamic (MHD) stability theory is applied to a class of self-similar solutions which describe implosion, expansion and oscillation of an infinitely conducting plasma column. The equations of perturbation are derived in the Lagrangian coordinate system. Numerical procedures via the finite-element method are formulated, and general aspects of dynamic stability are discussed, The dynamic stability of the column when it is oscillatory is studied in detail using the Floquet theory, and the characteristic exponent is calculated numerically. A-pinch configuration is examined. It is found that self-similar oscillations in general destabilize the continua in the MHD spectrum, and parametric instability results

  1. Radiation stability of colloidal metals in aqueous solutions: silver and other metals

    International Nuclear Information System (INIS)

    Ershov, B.G.

    1998-01-01

    The effect of accelerated electrons and γ-rays of 60N i on the stability of aqueous solutions of colloidal silver was studied. The threshold of absorbed dose, at which the stability dramatically decreases and coagulation of the metal occurs, was found. This critical dose corresponds to the reduction of silver ions determining the electrical potential of the sols. Radiation neutralization was also found for cadmium was not observed in the case of thallium, copper and platinum. A mechanism of the effect of radiation, taking into account the electrostatic factor in the stability of metal sols, was considered. (author)

  2. Physical and chemical stability of proflavine contrast agent solutions for early detection of oral cancer.

    Science.gov (United States)

    Kawedia, Jitesh D; Zhang, Yan-Ping; Myers, Alan L; Richards-Kortum, Rebecca R; Kramer, Mark A; Gillenwater, Ann M; Culotta, Kirk S

    2016-02-01

    Proflavine hemisulfate solution is a fluorescence contrast agent to visualize cell nuclei using high-resolution optical imaging devices such as the high-resolution microendoscope. These devices provide real-time imaging to distinguish between normal versus neoplastic tissue. These images could be helpful for early screening of oral cancer and its precursors and to determine accurate margins of malignant tissue for ablative surgery. Extemporaneous preparation of proflavine solution for these diagnostic procedures requires preparation in batches and long-term storage to improve compounding efficiency in the pharmacy. However, there is a paucity of long-term stability data for proflavine contrast solutions. The physical and chemical stability of 0.01% (10 mg/100 ml) proflavine hemisulfate solutions prepared in sterile water was determined following storage at refrigeration (4-8℃) and room temperature (23℃). Concentrations of proflavine were measured at predetermined time points up to 12 months using a validated stability-indicating high-performance liquid chromatography method. Proflavine solutions stored under refrigeration were physically and chemically stable for at least 12 months with concentrations ranging from 95% to 105% compared to initial concentration. However, in solutions stored at room temperature increased turbidity and particulates were observed in some of the tested vials at 9 months and 12 months with peak particle count reaching 17-fold increase compared to baseline. Solutions stored at room temperature were chemically stable up to six months (94-105%). Proflavine solutions at concentration of 0.01% were chemically and physically stable for at least 12 months under refrigeration. The solution was chemically stable for six months when stored at room temperature. We recommend long-term storage of proflavine solutions under refrigeration prior to diagnostic procedure. © The Author(s) 2014.

  3. Existence and Stability of Solutions for Implicit Multivalued Vector Equilibrium Problems

    Directory of Open Access Journals (Sweden)

    Li Qiuying

    2011-01-01

    Full Text Available A class of implicit multivalued vector equilibrium problems is studied. By using the generalized Fan-Browder fixed point theorem, some existence results of solutions for the implicit multivalued vector equilibrium problems are obtained under some suitable assumptions. Moreover, a stability result of solutions for the implicit multivalued vector equilibrium problems is derived. These results extend and unify some recent results for implicit vector equilibrium problems, multivalued vector variational inequality problems, and vector variational inequality problems.

  4. Identification of parallel and divergent optimization solutions for homologous metabolic enzymes

    Directory of Open Access Journals (Sweden)

    Robert F. Standaert

    2018-06-01

    Full Text Available Metabolic pathway assembly typically involves the expression of enzymes from multiple organisms in a single heterologous host. Ensuring that each enzyme functions effectively can be challenging, since many potential factors can disrupt proper pathway flux. Here, we compared the performance of two enzyme homologs in a pathway engineered to allow Escherichia coli to grow on 4-hydroxybenzoate (4-HB, a byproduct of lignocellulosic biomass deconstruction. Single chromosomal copies of the 4-HB 3-monooxygenase genes pobA and praI, from Pseudomonas putida KT2440 and Paenibacillus sp. JJ-1B, respectively, were introduced into a strain able to metabolize protocatechuate (PCA, the oxidation product of 4-HB. Neither enzyme initially supported consistent growth on 4-HB. Experimental evolution was used to identify mutations that improved pathway activity. For both enzymes, silent mRNA mutations were identified that increased enzyme expression. With pobA, duplication of the genes for PCA metabolism allowed growth on 4-HB. However, with praI, growth required a mutation in the 4-HB/PCA transporter pcaK that increased intracellular concentrations of 4-HB, suggesting that flux through PraI was limiting. These findings demonstrate the value of directed evolution strategies to rapidly identify and overcome diverse factors limiting enzyme activity. Keywords: Lignin, Protocatechuate, Experimental evolution

  5. Identification of parallel and divergent optimization solutions for homologous metabolic enzymes.

    Science.gov (United States)

    Standaert, Robert F; Giannone, Richard J; Michener, Joshua K

    2018-06-01

    Metabolic pathway assembly typically involves the expression of enzymes from multiple organisms in a single heterologous host. Ensuring that each enzyme functions effectively can be challenging, since many potential factors can disrupt proper pathway flux. Here, we compared the performance of two enzyme homologs in a pathway engineered to allow Escherichia coli to grow on 4-hydroxybenzoate (4-HB), a byproduct of lignocellulosic biomass deconstruction. Single chromosomal copies of the 4-HB 3-monooxygenase genes pobA and praI , from Pseudomonas putida KT2440 and Paenibacillus sp. JJ-1B, respectively, were introduced into a strain able to metabolize protocatechuate (PCA), the oxidation product of 4-HB. Neither enzyme initially supported consistent growth on 4-HB. Experimental evolution was used to identify mutations that improved pathway activity. For both enzymes, silent mRNA mutations were identified that increased enzyme expression. With pobA , duplication of the genes for PCA metabolism allowed growth on 4-HB. However, with praI , growth required a mutation in the 4-HB/PCA transporter pcaK that increased intracellular concentrations of 4-HB, suggesting that flux through PraI was limiting. These findings demonstrate the value of directed evolution strategies to rapidly identify and overcome diverse factors limiting enzyme activity.

  6. Carbapenems and SHV-1 β-Lactamase Form Different Acyl-Enzyme Populations in Crystals and Solution

    Science.gov (United States)

    Kalp, Matthew; Carey, Paul R.

    2009-01-01

    The reactions between single crystals of the SHV-1 β-lactamase enzyme and the carbapenems, meropenem, imipenem and ertapenem, have been studied by Raman microscopy. Aided by quantum mechanical calculations, major populations of two acyl-enzyme species, a labile Δ2-pyrroline and a more tightly bound Δ1-pyrroline, have been identified for all three compounds. These isomers differ only in the position of the double bond about the carbapenem nucleus. This discovery is consonant with X-ray crystallographic findings that also identified two populations for meropenem bound in SHV-1: one with the acyl C=O group in the oxyanion hole and the second with the acyl group rotated 180 degrees compared to its expected position [Nukaga, M., Bethel, C. R., Thomson, J. M., Hujer, A. M., Distler, A. M., Anderson, V. E., Knox, J. R., and Bonomo, R. A. (2008) Journal of the American Chemical Society]. When crystals of the Δ1 and Δ2 containing acyl-enzymes were exposed to solutions with no carbapenem, rapid deacylation of the Δ2 species was observed by kinetic Raman experiments. However, no change in the Δ1 population was observed over 1 hour, the effective lifetime of the crystal. These observations lead to the hypothesis that the stable Δ1 species is due to the form seen by X-ray with the acyl carbonyl outside the oxyanion hole, while the Δ2 species corresponds to the form with the carbonyl inside the oxyanion hole. Soak-in and soak-out Raman experiments also demonstrated that tautomeric exchange between the Δ1 and Δ2 forms does not occur on the crystalline enzyme. When meropenem or ertapenem were reacted with SHV-1 in solution, the Raman difference spectra demonstrated that only a major population corresponding to the Δ1 acyl-enzyme could be detected. The 1003 cm-1 mode of the phenyl ring positioned on the C3 side chain of ertapenem acts as an effective internal Raman intensity standard and the ratio of its intensity to that of the 1600 cm-1 feature of Δ1 provides an

  7. Hyperthermophilic enzymes - stability, activity and implementation strategies for high temperature applications

    NARCIS (Netherlands)

    Unsworth, L.D.; Oost, van der J.; Koutsopoulos, S.

    2007-01-01

    Current theories agree that there appears to be no unique feature responsible for the remarkable heat stability properties of hyperthermostable proteins. A concerted action of structural, dynamic and other physicochemical attributes are utilized to ensure the delicate balance between stability and

  8. Direct NMR Monitoring of Phase Separation Behavior of Highly Supersaturated Nifedipine Solution Stabilized with Hypromellose Derivatives.

    Science.gov (United States)

    Ueda, Keisuke; Higashi, Kenjirou; Moribe, Kunikazu

    2017-07-03

    We investigated the phase separation behavior and maintenance mechanism of the supersaturated state of poorly water-soluble nifedipine (NIF) in hypromellose (HPMC) derivative solutions. Highly supersaturated NIF formed NIF-rich nanodroplets through phase separation from aqueous solution containing HPMC derivative. Dissolvable NIF concentration in the bulk water phase was limited by the phase separation of NIF from the aqueous solution. HPMC derivatives stabilized the NIF-rich nanodroplets and maintained the NIF supersaturation with phase-separated NIF for several hours. The size of the NIF-rich phase was different depending on the HPMC derivatives dissolved in aqueous solution, although the droplet size had no correlation with the time for which NIF supersaturation was maintained without NIF crystallization. HPMC acetate and HPMC acetate succinate (HPMC-AS) effectively maintained the NIF supersaturation containing phase-separated NIF compared with HPMC. Furthermore, HPMC-AS stabilized NIF supersaturation more effectively in acidic conditions. Solution 1 H NMR measurements of NIF-supersaturated solution revealed that HPMC derivatives distributed into the NIF-rich phase during the phase separation of NIF from the aqueous solution. The hydrophobicity of HPMC derivative strongly affected its distribution into the NIF-rich phase. Moreover, the distribution of HPMC-AS into the NIF-rich phase was promoted at lower pH due to the lower aqueous solubility of HPMC-AS. The distribution of a large amount of HPMC derivatives into NIF-rich phase induced the strong inhibition of NIF crystallization from the NIF-rich phase. Polymer distribution into the drug-rich phase directly monitored by solution NMR technique can be a useful index for the stabilization efficiency of drug-supersaturated solution containing a drug-rich phase.

  9. EFFECT OF STABILIZERS ON THE CHEMICAL AND PHOTODEGRADATION OF ASCORBIC ACID IN AQUEOUS SOLUTION

    Directory of Open Access Journals (Sweden)

    Iqbal Ahmad

    2016-06-01

    Full Text Available Ascorbic acid (vitamin C is susceptible to light and air and forms various degradation products. A number of stabilizers have been used to study their effect on the degradation of ascorbic acid (AH2 in dark and light at pH 4.0 and 6.0 alone and in combination with citric and tartaric acids. The assay of AH2 in degraded solutions was performed by a specific UV spectrometric method. The degradation product of AH2 at pH 4.0 and 6.0 was identified as dehydroascorbic acid. The degradation of AH2 has been found to follow first-order kinetics. The apparent first-order rate constants, t90 and percent inhibition in rate in the presence of stabilizers and the second-order rate constants for the interaction of stabilizers with AH2 have been determined. The highest stabilizing effect on AH2 was found by sodium metabisulfite, followed by sodium sulfite, sodium bisulfate, sodium thiosulfate and thiourea. The pH of the solutions has also been found to influence the degradation of AH2 as the rates are higher at pH 6.0 compared to those of pH 4.0, probably due to the ionization of AH2. A synergistic effect has been observed when citric or tartaric acid was added to the solutions containing stabilizers where citric acid showed comparatively better effect.

  10. Adsorption of Trametes versicolor laccase to soil iron and aluminum minerals: enzyme activity, kinetics and stability studies.

    Science.gov (United States)

    Wu, Yue; Jiang, Ying; Jiao, Jiaguo; Liu, Manqiang; Hu, Feng; Griffiths, Bryan S; Li, Huixin

    2014-02-01

    Laccases play an important role in the degradation of soil phenol or phenol-like substance and can be potentially used in soil remediation through immobilization. Iron and aluminum minerals can adsorb extracellular enzymes in soil environment. In the present study, we investigated the adsorptive interaction of laccase, from the white-rot fungus Trametes versicolor, with soil iron and aluminum minerals and characterized the properties of the enzyme after adsorption to minerals. Results showed that both soil iron and aluminum minerals adsorbed great amount of laccase, independent of the mineral specific surface areas. Adsorbed laccases retained 26-64% of the activity of the free enzyme. Compared to the free laccase, all adsorbed laccases showed higher Km values and lower Vmax values, indicating a reduced enzyme-substrate affinity and a lower rate of substrate conversion in reactions catalyzed by the adsorbed laccase. Adsorbed laccases exhibited increased catalytic activities compared to the free laccase at low pH, implying the suitable application of iron and aluminum mineral-adsorbed T. versicolor laccase in soil bioremediation, especially in acid soils. In terms of the thermal profiles, adsorbed laccases showed decreased thermal stability and higher temperature sensitivity relative to the free laccase. Moreover, adsorption improved the resistance of laccase to proteolysis and extended the lifespan of laccase. Our results implied that adsorbed T. versicolor laccase on soil iron and aluminum minerals had promising potential in soil remediation. Crown Copyright © 2013. Published by Elsevier B.V. All rights reserved.

  11. STABILITY OF SYNTHESIZED SILVER NANOPARTICLES IN CITRATE AND MIXED GELATIN/CITRATE SOLUTION

    Directory of Open Access Journals (Sweden)

    Jana Kavuličová

    2018-04-01

    Full Text Available The study focuses on an investigation of the influence of both citrate and mixed gelatin/citrate as a reductant and stabilizer on the colloidal stability of silver nanoparticles (AgNPssynthesized by a chemical reduction of Ag+ ions after a short - (7th day - and long - (118th day - term storage. Formed AgNPs were characterized by a UV–vis Spectroscopy, Transmission Electron Microscope (TEM, Dynamic light scattering (DLS and Zeta-potential (ZP. The obtained results revealed that a short-term stability of the synthesized AgNPs was greatly influenced by a citrate stabilizer with the absence of gelatin. Smaller-sized AgNPs (average particle diameter of 3 nm, roughly spherical in a shape, were obtained with a narrow size distribution. The very negative value of the Zeta-potential confirmed a strong stability of the citrate capped AgNPs. However, a surface coating of the AgNPs by a gelatin/citrate stabilizer was found to be a dominant contributor in improving a long-term stability of the AgNPs (average particle diameter of 26 nm. The use of gelatin in mixed stabilizer solution provided the AgNPs with higher monodispersity and a controllable size after both the short and long-term storage.

  12. Global stability of almost periodic solution of shunting inhibitory cellular neural networks with variable coefficients

    International Nuclear Information System (INIS)

    Chen Ling; Zhao Hongyong

    2008-01-01

    The paper investigates the almost periodicity of shunting inhibitory cellular neural networks with delays and variable coefficients. Several sufficient conditions are established for the existence and globally exponential stability of almost periodic solutions by employing fixed point theorem and differential inequality technique. The results of this paper are new and they complement previously known results

  13. Stability and square integrability of derivatives of solutions of nonlinear fourth order differential equations with delay.

    Science.gov (United States)

    Korkmaz, Erdal

    2017-01-01

    In this paper, we give sufficient conditions for the boundedness, uniform asymptotic stability and square integrability of the solutions to a certain fourth order non-autonomous differential equations with delay by using Lyapunov's second method. The results obtained essentially improve, include and complement the results in the literature.

  14. Almost Surely Asymptotic Stability of Numerical Solutions for Neutral Stochastic Delay Differential Equations

    Directory of Open Access Journals (Sweden)

    Zhanhua Yu

    2011-01-01

    convergence theorem. It is shown that the Euler method and the backward Euler method can reproduce the almost surely asymptotic stability of exact solutions to NSDDEs under additional conditions. Numerical examples are demonstrated to illustrate the effectiveness of our theoretical results.

  15. Stability and square integrability of derivatives of solutions of nonlinear fourth order differential equations with delay

    Directory of Open Access Journals (Sweden)

    Erdal Korkmaz

    2017-06-01

    Full Text Available Abstract In this paper, we give sufficient conditions for the boundedness, uniform asymptotic stability and square integrability of the solutions to a certain fourth order non-autonomous differential equations with delay by using Lyapunov’s second method. The results obtained essentially improve, include and complement the results in the literature.

  16. Solutions Stability of Initial Boundary Problem, Modeling of Dynamics of Some Discrete Continuum Mechanical System

    Directory of Open Access Journals (Sweden)

    D. A. Eliseev

    2015-01-01

    Full Text Available The solution stability of an initial boundary problem for a linear hybrid system of differential equations, which models the rotation of a rigid body with two elastic rods located in the same plane is studied in the paper. To an axis passing through the mass center of the rigid body perpendicularly to the rods location plane is applied the stabilizing moment proportional to the angle of the system rotation, derivative of the angle, integral of the angle. The external moment provides a feedback. A method of studying the behavior of solutions of the initial boundary problem is proposed. This method allows to exclude from the hybrid system of differential equations partial differential equations, which describe the dynamics of distributed elements of a mechanical system. It allows us to build one equation for an angle of the system rotation. Its characteristic equation defines the stability of solutions of all the system. In the space of feedback-coefficients the areas that provide the asymptotic stability of solutions of the initial boundary problem are built up.

  17. Large-signal stability analysis of two power converters solutions for DC shipboard microgrid

    NARCIS (Netherlands)

    Bosich, Daniele; Gibescu, Madeleine; Sulligoi, Giorgio

    2017-01-01

    Bus voltage stability is an essential requirement in DC shipboard microgrids. In presence of Constant Power Loads, voltage instability is strictly dependent on RLC filters. This paper evaluates two power converter solutions (Thyristor Converters, TCs, and diode rectifiers + DC-DC Converters, DCs)

  18. On the stability of solutions, compacted to eleven dimensions, with the Euler invariants

    International Nuclear Information System (INIS)

    Fabris, J.C.

    1991-01-01

    The Supergravity Lagrangian at eleven dimensions has been modified by the inclusion of Euler invariants. Compact solutions have been obtained where the space-time is the Minkowski one, preserving, the internal space as a seven-sphere. The stability study of this configuration allows the restriction of the acceptable values for the coupling constants present in this model. (A.C.A.S.)

  19. Existence and global exponential stability of periodic solution of CNNs with impulses

    Energy Technology Data Exchange (ETDEWEB)

    Li Yongkun [Department of Mathematics, Yunnan University, Kunming, Yunnan 650091 (China); Xing Zhiwei [Department of Mathematics, Yunnan University, Kunming, Yunnan 650091 (China)

    2007-08-15

    Sufficient conditions are obtained for the existence and global exponential stability of a unique periodic solution of cellular neural networks with variable time delays and impulses by using Mawhin's continuation theorem of coincidence degree and by means of a method based on delay differential inequality.

  20. Existence and global exponential stability of periodic solution of CNNs with impulses

    International Nuclear Information System (INIS)

    Li Yongkun; Xing Zhiwei

    2007-01-01

    Sufficient conditions are obtained for the existence and global exponential stability of a unique periodic solution of cellular neural networks with variable time delays and impulses by using Mawhin's continuation theorem of coincidence degree and by means of a method based on delay differential inequality

  1. The existence and the stability of solutions for equilibrium problems with lower and upper bounds

    Directory of Open Access Journals (Sweden)

    Congjun Zhang

    2012-12-01

    Full Text Available In this paper, we study a class of equilibrium problems with lower and upper bounds. We obtain some existence results of solutions for equilibrium problems with lower and upper bounds by employing some classical fixed-point theorems. We investigate the stability of the solution sets for the problems, and establish sufficient conditions for the upper semicontinuity, lower semicontinuity and continuity of the solution set mapping $S:Lambda_1imesLambda_2o2^{X}$ in a Hausdorff topological vector space, in the case where a set $K$ and a mapping $f$ are perturbed respectively by parameters $lambda$ and $mu.$

  2. Effects of solute-solute interactions on protein stability studied using various counterions and dendrimers.

    Directory of Open Access Journals (Sweden)

    Curtiss P Schneider

    Full Text Available Much work has been performed on understanding the effects of additives on protein thermodynamics and degradation kinetics, in particular addressing the Hofmeister series and other broad empirical phenomena. Little attention, however, has been paid to the effect of additive-additive interactions on proteins. Our group and others have recently shown that such interactions can actually govern protein events, such as aggregation. Here we use dendrimers, which have the advantage that both size and surface chemical groups can be changed and therein studied independently. Dendrimers are a relatively new and broad class of materials which have been demonstrated useful in biological and therapeutic applications, such as drug delivery, perturbing amyloid formation, etc. Guanidinium modified dendrimers pose an interesting case given that guanidinium can form multiple attractive hydrogen bonds with either a protein surface or other components in solution, such as hydrogen bond accepting counterions. Here we present a study which shows that the behavior of such macromolecule species (modified PAMAM dendrimers is governed by intra-solvent interactions. Attractive guanidinium-anion interactions seem to cause clustering in solution, which inhibits cooperative binding to the protein surface but at the same time, significantly suppresses nonnative aggregation.

  3. Stability of a1 mg/mL oral solution zidovudine

    International Nuclear Information System (INIS)

    Garcia Penna, Caridad Margarita; Morales Lacarrere, Ivan; Martinez Espinosa, Vivian

    2011-01-01

    The carrying out of a high-performance liquid chromatography analytical method was assessed; applicable to stability study of oral solution zidovudine (1 mg/mL) was made. The analytical method was linear, precise, specific and exact in the study concentrations. The stability study of oral solution zidovudine (1 mg/mL) was conducted determining expiring date. The shelf life study was conducted over 24 months at room temperature; whereas that of accelerated stability was conducted with the product under wet and temperature conditions; analysis was carried out over three months. Formula met quality specifications described in Pharmacopeia. Results from the shelf life study demonstrated that product keeps the parameters determining its quality during that time and in accelerated studies there was not significant product degradation. Under above mentioned conditions two years were established as expiring date

  4. Pressure stabilization is not a general property of thermophilic enzymes: the adenylate kinases of Methanococcus voltae, Methanococcus maripaludis, Methanococcus thermolithotrophicus, and Methanococcus jannaschii.

    OpenAIRE

    Konisky, J; Michels, P C; Clark, D S

    1995-01-01

    The application of 50-MPa pressure did not increase the thermostabilities of adenylate kinases purified from four related mesophilic and thermophilic marine methanogens. Thus, while it has been reported that some thermophilic enzymes are stabilized by pressure (D. J. Hei and D. S. Clark, Appl. Environ. Microbiol. 60:932-939, 1994), hyperbaric stabilization is not an intrinsic property of all enzymes from deep-sea thermophiles.

  5. Uranium (VI) complexing by macrocyclic or chelating ligands in aqueous solutions stability, formation kinetics, polarographic properties

    International Nuclear Information System (INIS)

    Brighli, M.

    1984-07-01

    Stability of chelates (with EDTA,N,N ethylenediamine diacetic acid EDDA nitrilotriacetic acid NTA and iminodiacetic acid) of UO 2 2+ and UO 4 species of uranium VI is studied in aqueous solution (NaClO 4 3M at 25 deg celcius). Structure in solution are proposed and discussed for mononuclear species. Only complexing kinetics (formation and acid hydrolysis) of UO 4 with EDDA and NTA are studied by spectrophotometry (other reactions are too fast). Besides UO 2 2+ complexes are formed with crown ethers I5C5 and I8C6 in aqueous solution (TEA ClO 4 M/10 at 25 deg celcius. Complexes are probably stabilized by solvation. Results are confirmed by voltametry and reduction mechanisms of UO 2 2+ and its complexes on mercury drop are proposed. 143 refs [fr

  6. Stability of plane wave solutions of the two-space-dimensional nonlinear Schroedinger equation

    International Nuclear Information System (INIS)

    Martin, D.U.; Yuen, H.C.; Saffman, P.G.

    1980-01-01

    The stability of plane, periodic solutions of the two-dimensional nonlinear Schroedinger equation to infinitesimal, two-dimensional perturbation has been calculated and verified numerically. For standing wave disturbances, instability is found for both odd and even modes; as the period of the unperturbed solution increases, the instability associated with the odd modes remains but that associated with the even mode disappears, which is consistent with the results of Zakharov and Rubenchik, Saffman and Yuen and Ablowitz and Segur on the stability of solitons. In addition, we have identified travelling wave instabilities for the even mode perturbations which are absent in the long-wave limit. Extrapolation to the case of an unperturbed solution with infinite period suggests that these instabilities may also be present for the soliton. In other words, the soliton is unstable to odd, standing-wave perturbations, and very likely also to even, travelling-wave perturbations. (orig.)

  7. Evaluation of the stability of linezolid in aqueous solution and commonly used intravenous fluids

    Directory of Open Access Journals (Sweden)

    Taylor R

    2017-07-01

    Full Text Available Rachel Taylor, Bruce Sunderland, Giuseppe Luna, Petra Czarniak School of Pharmacy, Faculty of Health Sciences, Curtin University, Bentley, WA, Australia Purpose: The aim was to evaluate the stability of linezolid in commonly used intravenous fluids and in aqueous solution to determine the kinetics of degradation and shelf-life values at alkaline pH values. Methods: Forced degradation studies were performed on linezolid in solution to develop a validated high-performance liquid chromatography analysis. Sodium chloride 0.9%, sodium lactate, and glucose 5% and glucose 10% solution containing 2.0 mg/mL linezolid were stored at 25.0°C (±0.1°C for 34 days. The effect of temperature on the stability of linezolid in 0.1 M sodium hydroxide solution was investigated to determine the activation energy. The degradation rates of linezolid at selected pH values at 70.0°C and the influence of ionic strength were also examined. Activation energy data were applied to determine the shelf-life values at selected pH values, and a pH rate profile was constructed over the pH range of 8.7–11.4. The stability of intravenous linezolid (Zyvox® solution was evaluated by storing at 70.0°C for 72 hours. Results: Linezolid was found to maintain >95.0% of its initial concentration after storage at 25.0°C for 34 days in sodium lactate, 0.9% in sodium chloride, and 5% and 10% in glucose solutions. Linezolid was degraded at alkaline pH values by first-order kinetics. Activation energy data showed that temperature, but not ionic strength, influenced the degradation rate significantly. An activation energy of 58.22 kJ/mol was determined for linezolid in 0.1 M sodium hydroxide solution. Linezolid was least stable at high pH values and at elevated temperatures. It was determined that linezolid has adequate stability for the preparation of intravenous fluids for clinical administration. Conclusion: Linezolid was found to have a shelf life of 34 days at 25°C when added to

  8. STABILITY OF A CYLINDRICAL SOLUTE-SOLVENT INTERFACE: EFFECT OF GEOMETRY, ELECTROSTATICS, AND HYDRODYNAMICS.

    Science.gov (United States)

    Li, B O; Sun, Hui; Zhou, Shenggao

    The solute-solvent interface that separates biological molecules from their surrounding aqueous solvent characterizes the conformation and dynamics of such molecules. In this work, we construct a solvent fluid dielectric boundary model for the solvation of charged molecules and apply it to study the stability of a model cylindrical solute-solvent interface. The motion of the solute-solvent interface is defined to be the same as that of solvent fluid at the interface. The solvent fluid is assumed to be incompressible and is described by the Stokes equation. The solute is modeled simply by the ideal-gas law. All the viscous force, hydrostatic pressure, solute-solvent van der Waals interaction, surface tension, and electrostatic force are balanced at the solute-solvent interface. We model the electrostatics by Poisson's equation in which the solute-solvent interface is treated as a dielectric boundary that separates the low-dielectric solute from the high-dielectric solvent. For a cylindrical geometry, we find multiple cylindrically shaped equilibrium interfaces that describe polymodal (e.g., dry and wet) states of hydration of an underlying molecular system. These steady-state solutions exhibit bifurcation behavior with respect to the charge density. For their linearized systems, we use the projection method to solve the fluid equation and find the dispersion relation. Our asymptotic analysis shows that, for large wavenumbers, the decay rate is proportional to wavenumber with the proportionality half of the ratio of surface tension to solvent viscosity, indicating that the solvent viscosity does affect the stability of a solute-solvent interface. Consequences of our analysis in the context of biomolecular interactions are discussed.

  9. The effects of stabilizing and directional selection on phenotypic and genotypic variation in a population of RNA enzymes.

    Science.gov (United States)

    Hayden, Eric J; Bratulic, Sinisa; Koenig, Iwo; Ferrada, Evandro; Wagner, Andreas

    2014-02-01

    The distribution of variation in a quantitative trait and its underlying distribution of genotypic diversity can both be shaped by stabilizing and directional selection. Understanding either distribution is important, because it determines a population's response to natural selection. Unfortunately, existing theory makes conflicting predictions about how selection shapes these distributions, and very little pertinent experimental evidence exists. Here we study a simple genetic system, an evolving RNA enzyme (ribozyme) in which a combination of high throughput genotyping and measurement of a biochemical phenotype allow us to address this question. We show that directional selection, compared to stabilizing selection, increases the genotypic diversity of an evolving ribozyme population. In contrast, it leaves the variance in the phenotypic trait unchanged.

  10. An Investigation into the Gastrointestinal Stability of Exenatide in the Presence of Pure Enzymes, Everted Intestinal Rings and Intestinal Homogenates.

    Science.gov (United States)

    Sun, Yanan; Wang, Mengshu; Sun, Bingxue; Li, Feng; Liu, Shubo; Zhang, Yong; Zhou, Yan; Chen, Yan; Kong, Wei

    2016-01-01

    The purpose of this study was to investigate the gastrointestinal stability of exenatide to determine the key factor(s) contributing to peptide degradation during the oral delivery process. The effects of pH and various digestive enzymes on the degradation kinetics of exenatide were determined. Moreover, the degradation clearances of peptide were also examined using rat everted intestinal rings and intestinal homogenates from various intestinal locations. Exenatide was comparatively stable within a pH range of 1.2-8. However, obvious degradation was observed in the presence of digestive enzymes. The order of enzymes, in terms of ability to degradate exenatide, was chymotrypsin>aminopeptidase N>carboxypeptidase A>trypsin>pepsin. Chymotrypsin showed the greatest ability to degrade exenatide (half-life t1/2, 5.784×10(-2) h), whereas aminopeptidase N and carboxylpeptidase A gave t1/2 values of 3.53 and 10.16 h, respectively. The degradation of exenatide was found to be peptide concentration- and intestinal site-dependent, with a lower clearance in the upper part of the duodenum and the lower part of the ileum. When using intestinal homogenates as enzyme sources, the order, in terms of peptide degradation ability, was ileum>jejunum>duodenum. However, no significant difference was observed in the remaining peptide concentrations throughout 2 h of incubation, which may be due to the involvement of cytosolic enzymes. These results revealed key factors contributing to peptide degradation, and suggest that the inhibition of chymotrypsin and site-specific delivery of exenatide might be advantageous in overcoming metabolic obstacles during its oral delivery.

  11. Physico-chemical stability of eribulin mesylate containing concentrate and ready-to-administer solutions.

    Science.gov (United States)

    Spindeldreier, Kirsten; Thiesen, Judith; Lipp, Hans-Peter; Krämer, Irene

    2014-06-01

    The aim of this study was to determine the stability of commercially available eribulin mesylate containing injection solution as well as diluted ready-to-administer solutions stored under refrigeration or at room temperature. Stability was studied by a novel developed stability-indicating reversed-phase high-performance liquid chromatography (RP-HPLC) assay with ultraviolet detection (detection wavelength 200 nm). Triplicate test solutions of eribulin mesylate containing injection concentrate (0.5 mg/mL) and with 0.9% sodium chloride solution diluted ready-to-administer preparations (0.205 mg/mL eribulin mesylate in polypropylene (PP) syringes, 0.020 mg/mL eribulin mesylate in polypropylene/polyethylene (PE) bags) were stored protected from light either at room temperature (25) or under refrigeration (2-8). Samples were withdrawn on day 0 (initial), 1, 3, 5, 7, 14, 21 and 28 of storage and assayed. Physical stability was determined by measuring the pH value once a week and checking for visible precipitations or colour changes. The stability tests revealed that concentrations of eribulin mesylate remained unchanged over a period of 28 days irrespective of concentration, container material or storage temperature. Neither colour changes nor visible particles have been observed. The pH value varied slightly over time but remained in the stability favourable range of 5-9. Eribulin mesylate injection (0.5 mg/mL) is physico-chemically stable over a period of 28 days after first puncture of the vial. After dilution with 0.9% NaCl vehicle solution, ready-to-administer eribulin mesylate injection solutions (0.205 mg/mL in PP syringe) and infusion solutions (0.02 mg/mL in prefilled PP/PE bags) are physico-chemically stable for a period of at least four weeks either refrigerated or stored at room temperature. For microbiological reasons storage under refrigeration is recommended.

  12. Chemical and physical stability of smectites and illite in electrolyte solutions: experimental study at 150 C

    International Nuclear Information System (INIS)

    Boutiche, M.

    1995-01-01

    Chemical interactions between electrolytic solutions commonly used i drilling muds and clays have been studies under P-T conditions similar to those of drillings (150 deg C) in order to determine the eventual consequences on the stability of clay rich formations. The experimental work has been carried out using several solutions (water, NaOH (pH 8, 10, 12), KCI (0,1, 1 2 mol./l), sea water, and K 2 CO 3 ) and clay minerals with low to high amounts of swelling layers (smectite (Na, Na-Ca, Ca), mixed layered illite-smectite minerals). Run products are studied by X-ray diffraction and electronic microprobe. Smectite layers show series of mineralogical changes (cation exchange in the interlayer site, formation of non-swelling layers, hydrolysis), which, however, do not yield to the formation of new minerals, except in the case of the interaction with K 2 CO 3 at 150 deg C (zeolite crystallisation). Cation exchange in the interlayer depends on the nature of the cation, cation concentration in the solution, exchange constants, and liquid/solid ratio. In dilute solutions ( 1 mol./l), because they favour the collapse of swelling layers, and dispersion. Solutions of K 2 CO 3 at 150 deg C are at the origin of the transformation of smectite to zeolites, and high pH - highly saline solutions are rather aggressive, and would probably not stabilize the argilites. (author)

  13. VMCast: A VM-Assisted Stability Enhancing Solution for Tree-Based Overlay Multicast.

    Directory of Open Access Journals (Sweden)

    Weidong Gu

    Full Text Available Tree-based overlay multicast is an effective group communication method for media streaming applications. However, a group member's departure causes all of its descendants to be disconnected from the multicast tree for some time, which results in poor performance. The above problem is difficult to be addressed because overlay multicast tree is intrinsically instable. In this paper, we proposed a novel stability enhancing solution, VMCast, for tree-based overlay multicast. This solution uses two types of on-demand cloud virtual machines (VMs, i.e., multicast VMs (MVMs and compensation VMs (CVMs. MVMs are used to disseminate the multicast data, whereas CVMs are used to offer streaming compensation. The used VMs in the same cloud datacenter constitute a VM cluster. Each VM cluster is responsible for a service domain (VMSD, and each group member belongs to a specific VMSD. The data source delivers the multicast data to MVMs through a reliable path, and MVMs further disseminate the data to group members along domain overlay multicast trees. The above approach structurally improves the stability of the overlay multicast tree. We further utilized CVM-based streaming compensation to enhance the stability of the data distribution in the VMSDs. VMCast can be used as an extension to existing tree-based overlay multicast solutions, to provide better services for media streaming applications. We applied VMCast to two application instances (i.e., HMTP and HCcast. The results show that it can obviously enhance the stability of the data distribution.

  14. A Pilot Chemical and Physical Stability Study of Extemporaneously Compounded Levetiracetam Intravenous Solution.

    Science.gov (United States)

    Raphael, Chenzira D; Zhao, Fang; Hughes, Susan E; Juba, Katherine M

    2015-01-01

    Levetiracetam is a commonly used antiepileptic medication for tumor-related epilepsy. However, the 100 mL intravenous (IV) infusion volume can be burdensome to imminently dying hospice patients. A reduced infusion volume would improve patient tolerability. The purpose of this study was to evaluate the stability of 1000 mg/25 mL (40 mg/mL) levetiracetam IV solution in sodium chloride 0.9%. We prepared levetiracetam 40 mg/mL IV solution and added it to polyvinyl chloride (PVC) bags, polyolefin bags, and polypropylene syringes. Triplicate samples of each product were stored at refrigeration (2-8°C) and analyzed on days 0, 1, 4, 7, and 14. Samples were subjected to visual inspection, pH measurement, and stability-indicating high-performance liquid chromatography (HPLC) analysis. Over the 2-week storage period, there was no significant change in visual appearance or pH for any of the stability samples. The HPLC results confirmed that all stability samples retained 94.2-101.3% of initial drug concentration and no degradation products or leachable material from the packaging materials were observed. We conclude that levetiracetam 1000 mg/25 mL IV solution in sodium chloride 0.9% is physically and chemically stable for up to 14 days under refrigeration in polypropylene syringes, PVC bags, and polyolefin bags.

  15. Physical and chemical stability of palonosetron HCl in 4 infusion solutions.

    Science.gov (United States)

    Trissel, Lawrence A; Xu, Quanyun A

    2004-10-01

    Palonosetron HCl is a selective 5-HT(3) receptor antagonist used for the prevention of chemotherapy-induced nausea and vomiting. Palonosetron HCl may be diluted in an infusion solution for administraton. Consequently, stability information is needed for palonosetron HCl admixed in common infusion solutions. To evaluate the physical and chemical stability of palonosetron HCl in concentrations of 5 and 30 microg/mL in dextrose 5% injection, NaCl 0.9% injection, dextrose 5% in NaCl 0.45% injection, and dextrose 5% in lactated Ringer's injection. Triplicate test samples of palonosetron HCl at each concentration in each diluent were tested. Samples were stored and evaluated at appropriate intervals for up to 48 hours at room temperature ( approximately 23 degrees C) and 14 days under refrigeration (4 degrees C). Physical stability was assessed using turbidimetric and particulate measurement, as well as visual inspection. Chemical stability was assessed by HPLC. All of the admixtures were initially clear and colorless when viewed in normal fluorescent room light and with a Tyndall beam. Measured turbidity and particulate content were low initially and remained low throughout the study. The drug concentration was unchanged in any of the samples at either temperature throughout the study. Palonosetron HCl is physically and chemically stable in all 4 common infusion solutions for at least 48 hours at room temperature and 14 days under refrigeration.

  16. Effect of γ-rays irradiation and alkali solution pretreatment on hydrolyzing enzyme and microcosmic structure of core straw

    International Nuclear Information System (INIS)

    Tang Hongtao; Wang Feng; Li Weiming; Li An; Ha Yiming; Li Yanjie

    2012-01-01

    To increase yield of reducing sugar enzymatic hydrolyzed from corn straw yield of corn stalk on Enzymatic hydrolysis, γ-rays radiation and NaOH solution pretreatment were used. The changes of microstructure of the corn straw before and after pretreatments were characterized by IR, X-rays diffraction and SEM. The results shows that the γ-rays radiation can significantly decrease the essential concentration of NaOH solution and shorten the immersion time, but it could not affected the yield of reducing sugar remarkably. The scanning electron microscopy (SEM) results show that the sample which was treated at the 200 kGy irradiation dose and NaOH solution circumstance has the biggest surface area increase. The reducing sugar content of enzyme hydrolyzed corn straw treated at 200 kGy irradiation dose and 2% NaOH solution was achieved 48.34%, which provides the theoretical basis for industry ethanol production using enzyme hydrolyzed corn straw. (authors)

  17. Stability of twisted rods, helices and buckling solutions in three dimensions

    KAUST Repository

    Majumdar, Apala; Raisch, Alexander

    2014-01-01

    © 2014 IOP Publishing Ltd & London Mathematical Society. We study stability problems for equilibria of a naturally straight, inextensible, unshearable Kirchhoff rod allowed to deform in three dimensions (3D), subject to terminal loads. We investigate the stability of the twisted, straight state in 3D for three different boundary-value problems, cast in terms of Dirichlet and Neumann boundary conditions for the Euler angles, with and without isoperimetric constraints. In all cases, we obtain explicit stability estimates in terms of the twist, external load and elastic constants and in the Dirichlet case, we compute bifurcation diagrams for the Euler angles as a function of the external load. In the same vein, we obtain explicit stability estimates for a family of prototypical helical equilibria in 3D and demonstrate that they are stable for a range of tensile and compressive forces. We propose a numerical L2-gradient flow model to study the stability and dynamical evolution (in viscous model situations) of Kirchhoff rod equilibria. In Nizette and Goriely 1999 J. Math. Phys. 40 2830-66, the authors construct a family of localized buckling solutions. We apply our L2-gradient flow model to these localized buckling solutions, demonstrate that they are unstable, study their evolution and the simulations demonstrate rich spatio oral patterns that strongly depend on the boundary conditions and imposed isoperimetric constraints.

  18. Stability of twisted rods, helices and buckling solutions in three dimensions

    KAUST Repository

    Majumdar, Apala

    2014-11-03

    © 2014 IOP Publishing Ltd & London Mathematical Society. We study stability problems for equilibria of a naturally straight, inextensible, unshearable Kirchhoff rod allowed to deform in three dimensions (3D), subject to terminal loads. We investigate the stability of the twisted, straight state in 3D for three different boundary-value problems, cast in terms of Dirichlet and Neumann boundary conditions for the Euler angles, with and without isoperimetric constraints. In all cases, we obtain explicit stability estimates in terms of the twist, external load and elastic constants and in the Dirichlet case, we compute bifurcation diagrams for the Euler angles as a function of the external load. In the same vein, we obtain explicit stability estimates for a family of prototypical helical equilibria in 3D and demonstrate that they are stable for a range of tensile and compressive forces. We propose a numerical L2-gradient flow model to study the stability and dynamical evolution (in viscous model situations) of Kirchhoff rod equilibria. In Nizette and Goriely 1999 J. Math. Phys. 40 2830-66, the authors construct a family of localized buckling solutions. We apply our L2-gradient flow model to these localized buckling solutions, demonstrate that they are unstable, study their evolution and the simulations demonstrate rich spatio oral patterns that strongly depend on the boundary conditions and imposed isoperimetric constraints.

  19. Formation and stabilization of anionic metal complexes in concentrated aqueous quaternary ammonium salt solutions

    International Nuclear Information System (INIS)

    Aronson, F.L.; Hwang, L.L.Y.; Ronca, N.; Solomon, N.A.; Steigman, J.

    1985-01-01

    Anionic complexes of transition metals were stabilized in aqueous solutions containing high concentrations of various short-chain quaternary ammonium salts. Compounds with longer paraffin chains were effective in much less concentrated solution. Complex ions were detected spectrophotometrically. FeCl 4 - , which is usually formed in concentrated HCl, was the predominant Fe(III) complex in 30 m choline chloride containing only 0.12 M HCl. A yellow transitory Tc(VII) chloro-addition intermediate, formed in the reduction of TcO 4 - by concentrated HCl, was stabilized when the solution also contained 25 m choline chloride. Its spectrum, as well as the isolation of an already known Tc(VII) bipyridyl complex, is reported. Concentrated organic electrolytes also stabilized Tc(V) oxide halides against disproportionation and Tc(IV) hexahalides against hydrolysis. Halochromates of Cr(VI) were formed and stabilized in dilute acid containing quaternary ammonium salts. Their UV spectra showed the well-resolved vibronic fine structure associated with the symmetric chromium-to-oxygen charge-transfer band. It is known that these progressions are resolved in aprotic solvents, but not in aqueous acidic solution alone, and that the loss of fine structure in aqueous media is due to hydrogen bonding. The stabilization of anionic metal complexes and the resolution of vibronic structure in halochromates are probably consequences of water-structure-enforced ion paring. The present work suggests that the water molecules in immediate contact with the complex anions are more strongly hydrogen bonded to each other than to the complex. 21 references, 4 figures

  20. Extensive Lysine Methylation in Hyperthermophilic Crenarchaea: Potential Implications for Protein Stability and Recombinant Enzymes

    Directory of Open Access Journals (Sweden)

    Catherine H. Botting

    2010-01-01

    Full Text Available In eukarya and bacteria, lysine methylation is relatively rare and is catalysed by sequence-specific lysine methyltransferases that typically have only a single-protein target. Using RNA polymerase purified from the thermophilic crenarchaeum Sulfolobus solfataricus, we identified 21 methyllysines distributed across 9 subunits of the enzyme. The modified lysines were predominantly in α-helices and showed no conserved sequence context. A limited survey of the Thermoproteus tenax proteome revealed widespread modification with 52 methyllysines in 30 different proteins. These observations suggest the presence of an unusual lysine methyltransferase with relaxed specificity in the crenarchaea. Since lysine methylation is known to enhance protein thermostability, this may be an adaptation to a thermophilic lifestyle. The implications of this modification for studies and applications of recombinant crenarchaeal enzymes are discussed.

  1. Formulation and stability of an extemporaneous 0.02% chlorhexidine digluconate ophthalmic solution.

    Science.gov (United States)

    Lin, Shu-Chiao; Huang, Chih-Fen; Shen, Li-Jiuan; Wang, Hsueh-Ju; Lin, Chia-Yu; Wu, Fe-Lin Lin

    2015-12-01

    Acanthamoeba keratitis is difficult to treat because Acanthamoeba cysts are resistant to the majority of antimicrobial agents. Despite the efficacy of 0.02% chlorhexidine in treating Acanthamoeba keratitis, a lack of data in the literature regarding the formulation's stability limits its clinical use. The objective of this study was to develop an optimal extemporaneous 0.02% chlorhexidine digluconate ophthalmic formulation for patients in need. With available active pharmaceutical ingredients, 0.02% chlorhexidine digluconate sample solutions were prepared by diluting with BSS Plus Solution or acetate buffer. Influences of the buffer, type of container, and temperature under daily-open condition were assessed based on the changes of pH values and chlorhexidine concentrations of the test samples weekly. To determine the beyond-use date, the optimal samples were stored at 2-8°C or room temperature, and analyzed at time 0 and at Week 1, Week 2, Week 3, Week 4, Week 5, Week 8, Week 12, and Week 24. Despite chlorhexidine exhibiting better stability in acetate buffer than in BSS solution, its shelf-life was stability at 2-25°C for 6 months after being sealed and for 1 month after opening. This finding will enable us to prepare 0.02% chlorhexidine digluconate ophthalmic solutions based on a doctor's prescription. Copyright © 2014. Published by Elsevier B.V.

  2. Enzyme allocation problems in kinetic metabolic networks: Optimal solutions are elementary flux modes

    Czech Academy of Sciences Publication Activity Database

    Müller, Stefan; Regensburger, G.; Steuer, Ralf

    2014-01-01

    Roč. 347, APR 2014 (2014), s. 182-190 ISSN 0022-5193 R&D Projects: GA MŠk(CZ) EE2.3.20.0256 Institutional support: RVO:67179843 Keywords : metabolic optimization * enzyme kinetics * oriented matroid * elementary vector * conformal sum Subject RIV: EI - Biotechnology ; Bionics Impact factor: 2.116, year: 2014

  3. Evaluation of solution stability for two-component polydisperse systems by small-angle scattering

    Science.gov (United States)

    Kryukova, A. E.; Konarev, P. V.; Volkov, V. V.

    2017-12-01

    The article is devoted to the modelling of small-angle scattering data using the program MIXTURE designed for the study of polydisperse multicomponent mixtures. In this work we present the results of solution stability studies for theoretical small-angle scattering data sets from two-component models. It was demonstrated that the addition of the noise to the data influences the stability range of the restored structural parameters. The recommendations for the optimal minimization schemes that permit to restore the volume size distributions for polydisperse systems are suggested.

  4. Ionic liquids as cosolvents for glycosylation by sucrose phosphorylase: balancing acceptor solubility and enzyme stability

    Czech Academy of Sciences Publication Activity Database

    De Winter, K.; Verlinden, K.; Křen, Vladimír; Weignerová, Lenka; Soetaert, W.; Desmet, T.

    2013-01-01

    Roč. 15, č. 7 (2013), s. 1949-1955 ISSN 1463-9262 R&D Projects: GA MŠk(CZ) 7E11011 Institutional support: RVO:61388971 Keywords : DISACCHARIDE PHOSPHORYLASES * THERMAL-STABILITY * ALPHA-GLUCOSIDASE Subject RIV: CE - Biochemistry Impact factor: 6.852, year: 2013

  5. Aqueous solutions that model the cytosol : studies on polarity, chemical reactivity and enzyme kinetics

    NARCIS (Netherlands)

    Asaad, N.; den Otter, M.J.; Engberts, J.B.F.N.

    2004-01-01

    Concentrated solutions of a series of organic compounds have been prepared and the effects of these solutes on the properties of the solvent system assessed as a function of their concentration and nature. Polarity, as measured by Reichardt's E-T(30) probe, exhibits a linear variation with both

  6. A numerical technique for enhanced efficiency and stability for the solution of the nuclear reactor equation

    International Nuclear Information System (INIS)

    Khotylev, V.A.; Hoogenboom, J.E.

    1996-01-01

    The paper presents new techniques for the solution of the nuclear reactor equation in diffusion approximation, that has enhanced efficiency and stability. The code system based on the new technique solves a number of steady-state and/or transient problems with coupled thermal hydraulics in one-, two-, or three dimensional geometry with reduced CPU time as compared to similar code systems of previous generations if well-posed neutronics problems are considered. Automated detection of ill-posed problem and selection of the appropriate numerical method makes the new code system capable of yielding a correct solution for wider range of problems without user intervention. (author)

  7. A numerical technique for enhanced efficiency and stability for the solution of the nuclear reactor equation

    Energy Technology Data Exchange (ETDEWEB)

    Khotylev, V.A.; Hoogenboom, J.E. [Delft Univ. of Technology, Interfaculty Reactor Inst., Delft (Netherlands)

    1996-07-01

    The paper presents new techniques for the solution of the nuclear reactor equation in diffusion approximation, that has enhanced efficiency and stability. The code system based on the new technique solves a number of steady-state and/or transient problems with coupled thermal hydraulics in one-, two-, or three dimensional geometry with reduced CPU time as compared to similar code systems of previous generations if well-posed neutronics problems are considered. Automated detection of ill-posed problem and selection of the appropriate numerical method makes the new code system capable of yielding a correct solution for wider range of problems without user intervention. (author)

  8. Stability of stationary solutions for inflow problem on the micropolar fluid model

    Science.gov (United States)

    Yin, Haiyan

    2017-04-01

    In this paper, we study the asymptotic behavior of solutions to the initial boundary value problem for the micropolar fluid model in a half-line R+:=(0,∞). We prove that the corresponding stationary solutions of the small amplitude to the inflow problem for the micropolar fluid model are time asymptotically stable under small H1 perturbations in both the subsonic and degenerate cases. The microrotation velocity brings us some additional troubles compared with Navier-Stokes equations in the absence of the microrotation velocity. The proof of asymptotic stability is based on the basic energy method.

  9. The crystallization of a solid solution in a solvent and the stability of a growth interface

    International Nuclear Information System (INIS)

    Malmejac, Yves

    1971-03-01

    The potential uses of germanium-silicon alloys as thermoelectric generators in hitherto unexploited temperature ranges initiated the present study. Many delicate problems are encountered in the classical methods of preparation. An original technique was sought for crystallization in a metallic solvent. The thermodynamic equilibria between the various phases of the ternary System used were studied in order to justify the method used. The conditions (temperature and composition) were determined in which the cooling of a ternary liquid mixture induces the precipitation of a binary solid solution with the desired composition. If large crystals are to be obtained from the solid solution, metallic solvent precipitation must be replaced by a mono-directional solvent crystallization. The combined effect of a certain number of simple physical phenomena on the stability of a crystal liquid interface was studied: the morphological stability of the crystal growth interface is the first step towards obtaining perfect crystals. (author) [fr

  10. Evaluation of the Magnesium Hydroxide Treatment Process for Stabilizing PFP Plutonium/Nitric Acid Solutions

    Energy Technology Data Exchange (ETDEWEB)

    Gerber, Mark A.; Schmidt, Andrew J.; Delegard, Calvin H.; Silvers, Kurt L.; Baker, Aaron B.; Gano, Susan R.; Thornton, Brenda M.

    2000-09-28

    This document summarizes an evaluation of the magnesium hydroxide [Mg(OH)2] process to be used at the Hanford Plutonium Finishing Plant (PFP) for stabilizing plutonium/nitric acid solutions to meet the goal of stabilizing the plutonium in an oxide form suitable for storage under DOE-STD-3013-99. During the treatment process, nitric acid solutions bearing plutonium nitrate are neutralized with Mg(OH)2 in an air sparge reactor. The resulting slurry, containing plutonium hydroxide, is filtered and calcined. The process evaluation included a literature review and extensive laboratory- and bench-scale testing. The testing was conducted using cerium as a surrogate for plutonium to identify and quantify the effects of key processing variables on processing time (primarily neutralization and filtration time) and calcined product properties.

  11. Stability of the trivial solution for linear stochastic differential equations with Poisson white noise

    International Nuclear Information System (INIS)

    Grigoriu, Mircea; Samorodnitsky, Gennady

    2004-01-01

    Two methods are considered for assessing the asymptotic stability of the trivial solution of linear stochastic differential equations driven by Poisson white noise, interpreted as the formal derivative of a compound Poisson process. The first method attempts to extend a result for diffusion processes satisfying linear stochastic differential equations to the case of linear equations with Poisson white noise. The developments for the method are based on Ito's formula for semimartingales and Lyapunov exponents. The second method is based on a geometric ergodic theorem for Markov chains providing a criterion for the asymptotic stability of the solution of linear stochastic differential equations with Poisson white noise. Two examples are presented to illustrate the use and evaluate the potential of the two methods. The examples demonstrate limitations of the first method and the generality of the second method

  12. Multi-stability and almost periodic solutions of a class of recurrent neural networks

    International Nuclear Information System (INIS)

    Liu Yiguang; You Zhisheng

    2007-01-01

    This paper studies multi-stability, existence of almost periodic solutions of a class of recurrent neural networks with bounded activation functions. After introducing a sufficient condition insuring multi-stability, many criteria guaranteeing existence of almost periodic solutions are derived using Mawhin's coincidence degree theory. All the criteria are constructed without assuming the activation functions are smooth, monotonic or Lipschitz continuous, and that the networks contains periodic variables (such as periodic coefficients, periodic inputs or periodic activation functions), so all criteria can be easily extended to fit many concrete forms of neural networks such as Hopfield neural networks, or cellular neural networks, etc. Finally, all kinds of simulations are employed to illustrate the criteria

  13. The study of the antimicrobial activity of colloidal solutions of silver nanoparticles prepared using food stabilizers.

    Science.gov (United States)

    Balandin, G V; Suvorov, O A; Shaburova, L N; Podkopaev, D O; Frolova, Yu V; Ermolaeva, G A

    2015-06-01

    The bactericidal effect of colloidal solutions of silver nanoparticles based on food stabilizers, gum arabic and chitosan, against bacterial cultures of microorganisms in food production is described. The antibacterial activity of nanotechnology products containing different amounts of stabilizing additives when applied to solid pH-neutral substrates is studied. For its evaluation a method making it possible to take into account the capability of nanoparticles to diffuse in solid media was applied. Minimal inhibitory concentrations of nanoparticles used against Erwinia herbicola, Pseudomonas fluorescens, Bacillus subtilis, Sarcina flava were found. A suggestion was made concerning the influence of the spatial structure of bacteria on the antibacterial activity of colloidal solutions of silver nanoparticles. The data concerning the antibacterial activity and minimal inhibiting concentrations of nanoparticles may be used for development of products suppressing activity of microorganisms hazardous for food production.

  14. Method of Lyapunov functions in problems of stability of solutions of systems of differential equations with impulse action

    International Nuclear Information System (INIS)

    Ignat'yev, A O

    2003-01-01

    A system of ordinary differential equations with impulse action at fixed moments of time is considered. The system is assumed to have the zero solution. It is shown that the existence of a corresponding Lyapunov function is a necessary and sufficient condition for the uniform asymptotic stability of the zero solution. Restrictions on perturbations of the right-hand sides of differential equations and impulse actions are obtained under which the uniform asymptotic stability of the zero solution of the 'unperturbed' system implies the uniform asymptotic stability of the zero solution of the 'perturbed' system

  15. Stability of busulfan solutions in polypropylene syringes and infusion bags as determined with an original assay.

    Science.gov (United States)

    Guichard, Nicolas; Bonnabry, Pascal; Rudaz, Serge; Fleury-Souverain, Sandrine

    2017-11-15

    The stability of busulfan solution in 0.9% sodium chloride and stored in polypropylene syringes or infusion bags was evaluated. Busulfan solutions (0.54 mg/mL) were prepared and transferred to 50-mL polypropylene syringes and 100- and 500-mL polypropylene infusion bags and stored at 2-8 and 23-27 °C. Chemical stability was measured using a stability-indicating, ultrahigh performance liquid chromatography coupled to mass spectrometry method. The stability of busulfan was assessed by measuring the percentage of the initial concentration remaining at the end of each time point of analysis. The initial busulfan concentration was defined as 100%. Stability was defined as retention of at least 90% of the initial busulfan concentration. A visual inspection of the samples for particulate matter, clarity, and color without instrumentation of magnification was conducted at each time point of analysis. The visual inspection demonstrated no influence of the storage container when busulfan infusions diluted in 0.9% sodium chloride injection were stored at 23-27 °C. No color change or precipitate was observed at this temperature; however, a rapid decrease of the busulfan content in all containers stored at room temperature was observed. Busulfan in syringes was chemically stable for 12 hours, while busulfan in infusion bags (100 and 500 mL) was stable only for 3 hours at 23-27 °C. Busulfan 0.54-mg/mL solution in 0.9% sodium chloride injection was physically and chemically stable for 30 hours when stored in 50-mL polypropylene syringes at 2-8 °C and protected from light. Copyright © 2017 by the American Society of Health-System Pharmacists, Inc. All rights reserved.

  16. Application of high hydrostatic pressure for increasing activity and stability of enzymes.

    Science.gov (United States)

    Mozhaev, V V; Lange, R; Kudryashova, E V; Balny, C

    1996-10-20

    Elevated hydrostatic pressure has been used to increase catalytic activity and thermal stability of alpha-chymotrypsin (CT). For an anilide substrate, characterized by a negative value of the reaction activation volume (DeltaV( not equal)), an increase in pressure at 20 degrees C results in an exponential acceleration of the hydrolysis rate catalyzed by CT reaching a 6.5-fold increase in activity at 4700 atm (4.7 kbar). Due to a strong temperature dependence of DeltaV( not equal), the acceleration effect of high pressure becomes more pronounced at high temperatures. For example, at 50 degrees C, under a pressure of 3.6 kbar, CT shows activity which is more than 30 times higher than the activity at normal conditions (20 degrees C, 1 atm). At pressures of higher than 3.6 kbar, the enzymatic activity is decreased due to a pressure-induced denaturation.Elevated hydrostatic pressure is also efficient for increasing stability of CT against thermal denaturation. For example, at 55 degrees C, CT is almost instantaneously inactivated at atmospheric pressure, whereas under a pressure of 1.8 kbar CT retains its anilide-hydrolyzing activity during several dozen minutes. Additional stabilization can be achieved in the presence of glycerol, which is most effective for protection of CT at an intermediate concentration of 40% (v/v). There has been observed an additivity in stabilization effects of high pressure and glycerol: thermal inactivation of pressure-stabilized CT can be decelerated in a supplementary manner by addition of 40% (v/v) glycerol. The protection effect of glycerol on the catalytic activity and stability of CT becomes especially pronounced when both extreme factors of temperature and pressure reach critical values. For example, at approximately 55 degrees C and 4.7 kbar, enzymatic activity of CT in the presence of 40% (v/v) glycerol is severalfold higher than in aqueous buffer.The results of this study are discussed in terms of the hypotheses which explain the

  17. Synthesis, characterization and thermal stability of solid solutions Zr (Y, Fe, MoO2

    Directory of Open Access Journals (Sweden)

    Felipe Legorreta-García

    2015-05-01

    Full Text Available The synthesis of Fe3+, Mo4+ and Y3+ fully stabilized zirconia by the nitrate/urea combustion route and thermal stability in air was investigated. The solid solution obtained was characterized by X ray diffraction (XRD, scanning electron microscopy (SEM and used the BET method for determining specific surface. The ceramic powders obtained were calcined at 1473 K in air atmosphere in order to determine their thermal stability. The scanning electron microscopy (SEM results showed a homogeneous grain surface, measuring several tens of micrometers across. The crystallographic study revealed that by this method it was successfully achieved zirconia doped with Fe3+, Mo4+ and Y3+ ions in the zirconia tetragonal monophase, even after calcinations.

  18. Synthesis, characterization and thermal stability of solid solutions Zr (Y, Fe, Mo)O {sub 2}

    Energy Technology Data Exchange (ETDEWEB)

    Legorreta-Garcia, F.; Esperanza Hernandez-Cruz, L.; Villanueva-Ibanez, M.; Flores-Gonzalez, M. A.

    2015-10-01

    The synthesis of Fe{sup 3}+, Mo{sup 4+} and Y{sup 3+} fully stabilized zirconia by the nitrate/urea combustion route and thermal stability in air was investigated. The solid solution obtained was characterized by X ray diffraction (XRD), scanning electron microscopy (SEM) and used the BET method for determining specific surface. The ceramic powders obtained were calcined at 1473 K in air atmosphere in order to determine their thermal stability. The scanning electron microscopy (SEM) results showed a homogeneous grain surface, measuring several tens of micrometers across. The crystallographic study revealed that by this method it was successfully achieved zirconia doped with Fe{sup 3+}, Mo{sup 4+} and Y{sup 3+} ions in the zirconia tetragonal monophase, even after calcinations. (Author)

  19. Stability of periodic steady-state solutions to a non-isentropic Euler-Poisson system

    Science.gov (United States)

    Liu, Cunming; Peng, Yue-Jun

    2017-06-01

    We study the stability of periodic smooth solutions near non-constant steady-states for a non-isentropic Euler-Poisson system without temperature damping term. The system arises in the theory of semiconductors for which the doping profile is a given smooth function. In this stability problem, there are no special restrictions on the size of the doping profile, but only on the size of the perturbation. We prove that small perturbations of periodic steady-states are exponentially stable for large time. For this purpose, we introduce new variables and choose a non-diagonal symmetrizer of the full Euler equations to recover dissipation estimates. This also allows to make the proof of the stability result very simple and concise.

  20. Noether symmetries and stability of ideal gas solutions in Galileon cosmology

    Science.gov (United States)

    Dimakis, N.; Giacomini, Alex; Jamal, Sameerah; Leon, Genly; Paliathanasis, Andronikos

    2017-03-01

    A class of generalized Galileon cosmological models, which can be described by a pointlike Lagrangian, is considered in order to utilize Noether's theorem to determine conservation laws for the field equations. In the Friedmann-Lemaître-Robertson-Walker universe, the existence of a nontrivial conservation law indicates the integrability of the field equations. Because of the complexity of the latter, we apply the differential invariants approach in order to construct special power-law solutions and study their stability.

  1. Existence and stability of periodic solution in impulsive Hopfield neural networks with finite distributed delays

    International Nuclear Information System (INIS)

    Yang Xiaofan; Liao Xiaofeng; Evans, David J.; Tang Yuanyan

    2005-01-01

    In this Letter, we introduce a class of Hopfield neural networks with periodic impulses and finite distributed delays. We then derive a sufficient condition for the existence and global exponential stability of a unique periodic solution of the networks, which assumes neither the differentiability nor the monotonicity of the activation functions. Our condition extends and generalizes a known condition for the global exponential periodicity of continuous Hopfield neural networks with finite distributed delays

  2. Global exponential stability of periodic solution for shunting inhibitory CNNs with delays [rapid communication

    Science.gov (United States)

    Li, Yongkun; Liu, Chunchao; Zhu, Lifei

    2005-03-01

    By using the continuation theorem of coincidence degree theory and constructing suitable Lyapunov functions, we study the existence and stability of periodic solution for shunting inhibitory cellular neural networks (SICNNs) with delays x˙ij(t)=-aij(t)xij(t)-∑Bkl∈Nr(i,j)Bijkl(t)fij(xkl(t))xij(t)-∑Ckl∈Nr(i,j)Cijkl(t)gij(xkl(t-τkl))xij(t)+Lij(t).

  3. Storage stability and improved quality of fish products by enzyme suppression and gamma-irradiation

    International Nuclear Information System (INIS)

    Ninjoor, V.; Doke, S.N.; Nadkarni, G.B.

    1981-01-01

    The occurrence and distribution of lysosomal hydrolases in the skeletal muscle and skin of a variety of fish species have been demonstrated. As compared with the skeletal muscle, the skin contained two to ten times more activity of hydrolytic enzymes. In the case of Bombay duck (Harpodon nehereus), the drip represented a rich source of lysosomal enzymes. The involvement of these hydrolases in accentuating fish spoilage was examined by measuring the release of cathepsin D and accumulated hydrolytic end-products during progressive autolysis. The data showed that the shelf-life of fresh-water fish Tilapia mossambica could be extended by removing the skin, while that of Bombay duck by eliminating drip. Sodium tripolyphosphate (NaTPP) dip treatment was shown to inhibit the activity of lysosomal hydrolases of Bombay duck. Combination treatment consisting of NaTPP dip and irradiation (100 krad) resulted in a two-week extension in the shelf-life of Bombay duck fillets when stored at 0-4 0 C. (author)

  4. Effect of hydrogen peroxide on improving the heat stability of whey protein isolate solutions.

    Science.gov (United States)

    Sutariya, Suresh; Patel, Hasmukh

    2017-05-15

    Whey protein isolate (WPI) solutions (12.8%w/w protein) were treated with varying concentrations of H 2 O 2 in the range of 0-0.144 H 2 O 2 to protein ratios (HTPR) by the addition of the required quantity of H 2 O 2 and deionized water. The samples were analyzed for heat stability, rheological properties, denaturation level of β-lactoglobulin (β-LG) and α-lactalbumin (α-LA). The samples treated with H 2 O 2 concentration >0.072 (HTPR) showed significant improvement in the heat stability, and decreased whey protein denaturation and aggregation. The WPI solution treated with H 2 O 2 (>0.072 HTPR) remained in the liquid state after heat treatment at 120°C, whereas the control samples formed gel upon heat treatment. Detailed analysis of these samples suggested that the improvement in the heat stability of H 2 O 2 treated WPI solution was attributed to the significant reduction in the sulfhydryl-disulfide interchange reaction during denaturation of β-LG and α-LA. Copyright © 2016 Elsevier Ltd. All rights reserved.

  5. Development of bifurcated solutions and study of their stability in damage problems

    International Nuclear Information System (INIS)

    Beaurain, J.

    2011-01-01

    This work is concerned with the development and the implementation of a numerical optimization algorithm in an industrial software for studying the stability of non local gradient damage numerical solutions given by finite elements method. Stability is a fundamental concept, that takes into account the existence of multiple solutions which could emerge due to the softening constitutive laws generally used to represent the irreversible damage of materials like concrete. Among all those solutions, only stable ones, invariant by little perturbations, could be physically observed. The difficulty is to satisfy the irreversible constraint of damage which drives to define a stability criterion by the positivity of the second derivative of the total energy in the direction of increasing damage. It numerically leads to ensure the positivity of the minimum of a quadratic form, using the second derivative matrix and subjected to inequalities constraints. In conclusion, the aim of this work is to implement an efficient and robust numerical constraints minimization algorithm in Code-Aster, adapted to different damage modelling, and to improve it using test cases found in the literature. (author)

  6. Improvement of thermal-stability of enzyme immobilized onto mesoporous zirconia

    Directory of Open Access Journals (Sweden)

    Yuichi Masuda

    2014-03-01

    Thereafter, FDH immobilized on MPZ showed higher catalytic activity than that on MPS. Enhancement of catalytic activity was obtained by improving the substrate affinity derived from interparticle voids of MPZ. In addition, the FDH immobilized on MPZ had a very great higher thermal stability. Further investigation using transmittance Infrared spectroscopy indicated that the high-order structure of the FDH immobilized on MPZ did not get altered after the heat-treatment.

  7. Physical and chemical stability of reconstituted and diluted dexrazoxane infusion solutions.

    Science.gov (United States)

    Zhang, Yan-Ping; Myers, Alan L; Trinh, Van A; Kawedia, Jitesh D; Kramer, Mark A; Benjamin, Robert S; Tran, Hai T

    2014-02-01

    Dexrazoxane is used clinically to prevent anthracycline-associated cardiotoxicity. Hydrolysis of dexrazoxane prior to reaching the cardiac membranes severely hampers its mode of action; therefore, degradation during the preparation and administration of intravenous dexrazoxane admixtures demands special attention. Moreover, the ongoing national shortage of one dexrazoxane formulation in the United States has forced pharmacies to dispense other commercially available dexrazoxane products. However, the manufacturers' limited stability data restrict the flexibility of dexrazoxane usage in clinical practice. The aims of this study are to determine the physical and chemical stability of reconstituted and diluted solutions of two commercially available dexrazoxane formulations. The stability of two dexrazoxane products, brand and generic name, in reconstituted and intravenous solutions stored at room temperature without light protection in polyvinyl chloride bags was determined. The concentrations of dexrazoxane were measured at predetermined time points up to 24 h using a validated reversed phase high-performance liquid chromatography with ultraviolet detection assay. Brand (B-) and generic (G-) dexrazoxane products, reconstituted in either sterile water or 0.167 M sodium lactate (final concentration of 10 mg/mL), were found stable for at least to 8 h. Infusion solutions of B-dexrazoxane, prepared according to each manufacturer's directions, were stable for at least 24 h and 8 h at 1 mg/mL and 3 mg/mL, respectively. Infusion solutions of G-dexrazoxane, prepared in either 5% dextrose or 0.9% sodium chloride following the manufacturer's guidelines, were also stable for at least 24 h and 8 h at 1 mg/mL and 3 mg/mL, respectively. All tested solutions were found physically stable up to 24 h at room temperature. The stability of dexrazoxane infusion solutions reported herein permits advance preparation of dexrazoxane intravenous admixtures, facilitating

  8. Valency stabilization of polyvalent ions during gamma irradiation of their aqueous solutions by sacrificial protection. I- Valency stabilization of Fe (II) ions by sulphate ions

    Energy Technology Data Exchange (ETDEWEB)

    Barakat, M F [Nuclear chemistry department, hot lab. center, Atomic Energy Authority, Cairo, (Egypt); Abdel-Hamid, M M [Arab Atomic Energy Agency, P.O. Box 402 El-Manzah-1004 Tunis, (Tunisia)

    1995-10-01

    Polyvalent ions are very sensitive to gamma irradiation in aqueous solutions. The present work is a part of a more comprehensive study dealing with the stabilization or protection of certain oxidation states of some polyvalent ions during their gamma irradiation in aqueous systems. The behaviour of aqueous acidic Fe (II) solutions during gamma irradiation, in presence the prevailing protection mechanism. The conditions and stabilization limits in the studied case has been found out. 9 figs.

  9. Valency stabilization of polyvalent ions during gamma irradiation of their aqueous solutions by sacrificial protection. I- Valency stabilization of Fe (II) ions by sulphate ions

    International Nuclear Information System (INIS)

    Barakat, M.F.; Abdel-Hamid, M.M.

    1995-01-01

    Polyvalent ions are very sensitive to gamma irradiation in aqueous solutions. The present work is a part of a more comprehensive study dealing with the stabilization or protection of certain oxidation states of some polyvalent ions during their gamma irradiation in aqueous systems. The behaviour of aqueous acidic Fe (II) solutions during gamma irradiation, in presence the prevailing protection mechanism. The conditions and stabilization limits in the studied case has been found out. 9 figs

  10. Solution of non-steady-state substrate concentration in the action of biosensor response at mixed enzyme kinetics

    Science.gov (United States)

    Senthamarai, R.; Jana Ranjani, R.

    2018-04-01

    In this paper, a mathematical model of an amperometric biosensor at mixed enzyme kinetics and diffusion limitation in the case of substrate inhibition has been developed. The model is based on time dependent reaction diffusion equation containing a non -linear term related to non -Michaelis - Menten kinetics of the enzymatic reaction. Solution for the concentration of the substrate has been derived for all values of parameters using the homotopy perturbation method. All the approximate analytic expressions of substrate concentration are compared with simulation results using Scilab/Matlab program. Finally, we have given a satisfactory agreement between them.

  11. Effect of active acidity on the stability of amylolytic enzymes in fermentation of corn mash

    Energy Technology Data Exchange (ETDEWEB)

    Zherebtsov, N A; Mal' tsev, P M

    1957-01-01

    The effect of pH between 6.5 and 3.5 on the activity of ..cap alpha..- and ..beta..-amylases, dextrinase, and on the yield of alcohol in the fermentation of corn mash were investigated. The minimum of unfermented maltose and maximum activity of amylolytic enzymes were found from fermentations between pH 5.5 and 4.9. Under these conditions ..beta..-amylase and dextrinase were unaffected, while ..cap alpha..-amylase activity was reduced to 59.1% initial activity. Considerable inactivation of ..beta..-amylase and dextrinase set in at pH 4.0 and ..cap alpha..-amylase at pH 4.5. The highest yield of alcohol was produced from mash with initial pH 6.0 obtained by addition of sodium hydroxide.

  12. [Physical and chemical stability of fortified ophtalmic ready-to-use solutions: review of literature].

    Science.gov (United States)

    Sourdeau, P; Evrard, J-M; Remy, G; Hecq, J-D

    2012-03-01

    Ophtalmic infections and inflammations are often encountered during hospitalization. They require the preparation of "fortified" ophtalmic solutions, i.e. pharmaceutical ophtalmic solutions which are hyperconcentrated in active substance. The data of physicochemical stabilities are modified and it is therefore essential to gather the results of the various publications devoted to this subject. In 2006, an initial literature review was undertaken to identify the molecules mostly used in the preparation of fortified ophtalmic solutions in hospital. A second review of the literature in 2010 has enriched the knowledge about it. Two new drugs have entered the summary table: amikacin and ticarcillin disodium. Date on 12 molecules already known in 2006 were updated to improve clinical practices. A review of the literature was undertaken in order to collect the results of the molecules mostly used for the preparation of the fortified ophtalmic solutions in hospitals. A summary table, indicating the active substance, its concentration, the assay method, the storage temperature and physicochemical modifications, presents all the results. This review of literature makes it possible to match stability and validity period to these preparations. Copyright © 2011 Elsevier Masson SAS. All rights reserved.

  13. Stability constant determinations for technetium (IV) complexation with selected amino carboxylate ligands in high nitrate solutions

    Energy Technology Data Exchange (ETDEWEB)

    Omoto, Trevor; Wall, Nathalie A. [Washington State Univ., Pullman, WA (United States). Dept. of Chemistry

    2017-10-01

    The stability constants for Tc(IV) complexation with the ligands IDA, NTA, HEDTA, and DTPA were determined in varied nitrate concentrations using liquid-liquid extraction methods. The determined log β{sub 101} stability constants at 0.5 M NaNO{sub 3} were found to be 9.2±0.3, 10.3±0.3, and 15.3±0.3 for IDA, NTA, and HEDTA, respectively. The log β{sub 111} stability constant for DTPA was determined to be 22.0±0.6. These determined stability constants show a slight decrease in magnitude as a function of increasing NaNO{sub 3} concentration. These stability constants were used to model the total dissolution of Tc(IV) in acidic aqueous solutions in the presence of each ligand. The results of these predictive models indicate that amino carboxylic ligands have a high potential for increasing the aqueous dissolution of Tc(IV); at pH 2.3, 0.01 M ligand yield dissolved Tc(IV) concentrations of 1.42.10{sup -5} M, 1.33.10{sup -5} M, 6.07.10{sup -6} M, 9.65.10{sup -7} M, for DTPA, HEDTA, NTA, and IDA, respectively.

  14. Aqueous solutions of acidic ionic liquids for enhanced stability of polyoxometalate-carbon supercapacitor electrodes

    Science.gov (United States)

    Hu, Chenchen; Zhao, Enbo; Nitta, Naoki; Magasinski, Alexandre; Berdichevsky, Gene; Yushin, Gleb

    2016-09-01

    Nanocomposites based on polyoxometalates (POMs) nanoconfined in microporous carbons have been synthesized and used as electrodes for supercapacitors. The addition of the pseudocapacitance from highly reversible redox reaction of POMs to the electric double-layer capacitance of carbon lead to an increase in specific capacitance of ∼90% at 1 mV s-1. However, high solubility of POM in traditional aqueous electrolytes leads to rapid capacity fading. Here we demonstrate that the use of aqueous solutions of protic ionic liquids (P-IL) as electrolyte instead of aqueous sulfuric acid solutions offers an opportunity to significantly improve POM cycling stability. Virtually no degradation in capacitance was observed in POM-based positive electrode after 10,000 cycles in an asymmetric capacitor with P-IL aqueous electrolyte. As such, POM-based carbon composites may now present a viable solution for enhancing energy density of electrical double layer capacitors (EDLC) based on pure carbon electrodes.

  15. Considerable improvement in the stability of solution processed small molecule OLED by annealing

    Energy Technology Data Exchange (ETDEWEB)

    Mao Guilin [Key Laboratory of Photonics Technology for Information, Key Laboratory for Physical Electronics and Devices of the Ministry of Education, School of Electronic and Information Engineering, Xi' an Jiaotong University, Xi' an, 710049 (China); Wu Zhaoxin, E-mail: zhaoxinwu@mail.xjtu.edu.cn [Key Laboratory of Photonics Technology for Information, Key Laboratory for Physical Electronics and Devices of the Ministry of Education, School of Electronic and Information Engineering, Xi' an Jiaotong University, Xi' an, 710049 (China); He Qiang [Key Laboratory of Photonics Technology for Information, Key Laboratory for Physical Electronics and Devices of the Ministry of Education, School of Electronic and Information Engineering, Xi' an Jiaotong University, Xi' an, 710049 (China); Department of UAV, Wuhan Ordnance Noncommissioned Officers Academy, Wuhan, 430075 (China); Jiao Bo; Xu Guojin; Hou Xun [Key Laboratory of Photonics Technology for Information, Key Laboratory for Physical Electronics and Devices of the Ministry of Education, School of Electronic and Information Engineering, Xi' an Jiaotong University, Xi' an, 710049 (China); Chen Zhijian; Gong Qihuang [State Key Laboratory for Mesoscopic Physics and Department of Physics, Peking University, Beijing, 100871 (China)

    2011-06-15

    We investigated the annealing effect on solution processed small organic molecule organic films, which were annealed with various conditions. It was found that the densities of the spin-coated (SC) films increased and the surface roughness decreased as the annealing temperature rose. We fabricated corresponding organic light emitting diodes (OLEDs) by spin coating on the same annealing conditions. The solution processed OLEDs show the considerable efficiency and stability, which were prior or equivalent to the vacuum-deposited (VD) counterparts. Our research shows that annealing process plays a key role in prolonging the lifetime of solution processed small molecule OLEDs, and the mechanism for the improvement of the device performance upon annealing was also discussed.

  16. Hybrid quantum and classical methods for computing kinetic isotope effects of chemical reactions in solutions and in enzymes.

    Science.gov (United States)

    Gao, Jiali; Major, Dan T; Fan, Yao; Lin, Yen-Lin; Ma, Shuhua; Wong, Kin-Yiu

    2008-01-01

    A method for incorporating quantum mechanics into enzyme kinetics modeling is presented. Three aspects are emphasized: 1) combined quantum mechanical and molecular mechanical methods are used to represent the potential energy surface for modeling bond forming and breaking processes, 2) instantaneous normal mode analyses are used to incorporate quantum vibrational free energies to the classical potential of mean force, and 3) multidimensional tunneling methods are used to estimate quantum effects on the reaction coordinate motion. Centroid path integral simulations are described to make quantum corrections to the classical potential of mean force. In this method, the nuclear quantum vibrational and tunneling contributions are not separable. An integrated centroid path integral-free energy perturbation and umbrella sampling (PI-FEP/UM) method along with a bisection sampling procedure was summarized, which provides an accurate, easily convergent method for computing kinetic isotope effects for chemical reactions in solution and in enzymes. In the ensemble-averaged variational transition state theory with multidimensional tunneling (EA-VTST/MT), these three aspects of quantum mechanical effects can be individually treated, providing useful insights into the mechanism of enzymatic reactions. These methods are illustrated by applications to a model process in the gas phase, the decarboxylation reaction of N-methyl picolinate in water, and the proton abstraction and reprotonation process catalyzed by alanine racemase. These examples show that the incorporation of quantum mechanical effects is essential for enzyme kinetics simulations.

  17. Co-immobilization of multiple enzymes by metal coordinated nucleotide hydrogel nanofibers: improved stability and an enzyme cascade for glucose detection.

    Science.gov (United States)

    Liang, Hao; Jiang, Shuhui; Yuan, Qipeng; Li, Guofeng; Wang, Feng; Zhang, Zijie; Liu, Juewen

    2016-03-21

    Preserving enzyme activity and promoting synergistic activity via co-localization of multiple enzymes are key topics in bionanotechnology, materials science, and analytical chemistry. This study reports a facile method for co-immobilizing multiple enzymes in metal coordinated hydrogel nanofibers. Specifically, four types of protein enzymes, including glucose oxidase, Candida rugosa lipase, α-amylase, and horseradish peroxidase, were respectively encapsulated in a gel nanofiber made of Zn(2+) and adenosine monophosphate (AMP) with a simple mixing step. Most enzymes achieved quantitative loading and retained full activity. At the same time, the entrapped enzymes were more stable against temperature variation (by 7.5 °C), protease attack, extreme pH (by 2-fold), and organic solvents. After storing for 15 days, the entrapped enzyme still retained 70% activity while the free enzyme nearly completely lost its activity. Compared to nanoparticles formed with AMP and lanthanide ions, the nanofiber gels allowed much higher enzyme activity. Finally, a highly sensitive and selective biosensor for glucose was prepared using the gel nanofiber to co-immobilize glucose oxidase and horseradish peroxidase for an enzyme cascade system. A detection limit of 0.3 μM glucose with excellent selectivity was achieved. This work indicates that metal coordinated materials using nucleotides are highly useful for interfacing with biomolecules.

  18. Assessment of natural sepiolite on cadmium stabilization, microbial communities, and enzyme activities in acidic soil.

    Science.gov (United States)

    Sun, Yuebing; Sun, Guohong; Xu, Yingming; Wang, Lin; Liang, Xuefeng; Lin, Dasong; Hu, Fazhi

    2013-05-01

    A pot trial was conducted to assess the efficiency of sepiolite-induced cadmium (Cd) immobilization in ultisoils. Under Cd concentrations of 1.25, 2.5, and 5 mg kg(-1), the available Cd in the soil after the application of 1-10 % sepiolite decreased by a maximum of 44.4, 23.0, and 17.0 %, respectively, compared with no sepiolite treatments. The increase in the values of soil enzyme activities and microbial number proved that a certain metabolic recovery occurred after sepiolite treatment. The dry biomass of spinach (Spinacia oleracea) increased with increasing sepiolite concentration in the soil. However, the concentration (dry weight) of Cd in the spinach shoots decreased with the increase in sepiolite dose, with maximum reduction of 92.2, 90.0, and 84.9 %, respectively, compared with that of unamended soils. Under a Cd level of 1.25 mg kg(-1), the Cd concentration in the edible parts of spinach at 1 % sepiolite amendment was lower than 0.2 mg kg(-1) fresh weight, the maximum permissible concentration (MPC) of Cd in vegetable. Even at higher Cd concentrations (2.5 and 5 mg kg(-1)), safe spinach was produced when the sepiolite treatment was up to 5 %. The results showed that sepiolite-assisted remediation could potentially succeed on a field scale by decreasing Cd entry into the food chain.

  19. Stability of a family of travelling wave solutions in a feedforward chain of phase oscillators

    International Nuclear Information System (INIS)

    Lanford, O E III; Mintchev, S M

    2015-01-01

    Travelling waves are an important class of signal propagation phenomena in extended systems with a preferred direction of information flow. We study the generation of travelling waves in unidirectional chains of coupled oscillators communicating via a phase-dependent pulse-response interaction borrowed from mathematical neuroscience. Within the context of such systems, we develop a widely applicable, jointly numerical and analytical methodology for deducing existence and stability of periodic travelling waves. We provide careful numerical studies that support the existence of a periodic travelling wave solution as well as the asymptotic relaxation of a single oscillator to the wave when it is forced with the wave profile. Using this evidence as an assumption, we analytically prove global stability of waves in the infinite chain, with respect to initial perturbations of downstream sites. This rigorous stability result suggests that asymptotic relaxation to the travelling wave occurs even when the forcing is perturbed from the wave profile, a property of the motivating system that is supported by previous work as well as the convergence of the more sophisticated numerical algorithm that we propose in order to compute a high-precision approximation to the solution. We provide additional numerical studies that show that the wave is part of a one-parameter family, and we illustrate the structural robustness of this family with respect to changes in the coupling strength. (paper)

  20. Hammerhead ribozyme activity and oligonucleotide duplex stability in mixed solutions of water and organic compounds

    Directory of Open Access Journals (Sweden)

    Shu-ichi Nakano

    2014-01-01

    Full Text Available Nucleic acids are useful for biomedical targeting and sensing applications in which the molecular environment is different from that of a dilute aqueous solution. In this study, the influence of various types of mixed solutions of water and water-soluble organic compounds on RNA was investigated by measuring the catalytic activity of the hammerhead ribozyme and the thermodynamic stability of an oligonucleotide duplex. The compounds with a net neutral charge, such as poly(ethylene glycol, small primary alcohols, amide compounds, and aprotic solvent molecules, added at high concentrations changed the ribozyme-catalyzed RNA cleavage rate, with the magnitude of the effect dependent on the NaCl concentration. These compounds also changed the thermodynamic stability of RNA base pairs of an oligonucleotide duplex and its dependence on the NaCl concentration. Specific interactions with RNA molecules and reduced water activity could account for the inhibiting effects on the ribozyme catalysis and destabilizing effects on the duplex stability. The salt concentration dependence data correlated with the dielectric constant, but not with water activity, viscosity, and the size of organic compounds. This observation suggests the significance of the dielectric constant effects on the RNA reactions under molecular crowding conditions created by organic compounds.

  1. Stability of interbed for salt cavern gas storage in solution mining considering cusp displacement catastrophe theory

    Directory of Open Access Journals (Sweden)

    Le Yu

    2015-03-01

    Full Text Available Cusp displacement catastrophe theory can be introduced to propose a new method about instability failure of the interbed for gas storage cavern in bedded salt in solution mining. We can calculate initial fracture drawing pace of this interbed to obtain 2D and 3D gas storage shapes at this time. Moreover, Stability evaluation of strength reduction finite element method (FEM based on this catastrophe theory can used to evaluate this interbed stability after initial fracture. A specific example is simulated to obtain the influence of the interbed depth, cavern internal pressure, and cavern building time on stability safety factor (SSF. The results indicate: the value of SSF will be lower with the increase of cavern building time in solution mining and the increase of interbed depth and also this value remains a rise with the increase of cavern internal pressure Especially, we can conclude that the second-fracture of the interbed may take place when this pressure is lower than 6 MPa or after 6 days later of the interbed after initial fracture. According to above analysis, some effective measures, namely elevating the tube up to the top of the interbed, or changing the circulation of in-and-out lines, can be introduced to avoid the negative effects when the second-fracture of the interbed may occur.

  2. Effect of different solutions on color stability of acrylic resin-based dentures

    Directory of Open Access Journals (Sweden)

    Marcelo Coelho Goiato

    2014-01-01

    Full Text Available The aim of this study was to evaluate the effect of thermocycling and immersion in mouthwash or beverage solutions on the color stability of four different acrylic resin-based dentures (Onda Cryl, OC; QC20, QC; Classico, CL; and Lucitone, LU. The factors evaluated were type of acrylic resin, immersion time, and solution (mouthwash or beverage. A total of 224 denture samples were fabricated. For each type of resin, eight samples were immersed in mouthwashes (Plax-Colgate, PC; Listerine, LI; and Oral-B, OB, beverages (coffee, CP; cola, C; and wine, W, and artificial saliva (AS; control. The color change (DE was evaluated before (baseline and after thermocycling (T1, and after immersion in solution for 1 h (T2, 3 h (T3, 24 h (T4, 48 h (T5, and 96 h (T6. The CIE Lab system was used to determine the color changes. The thermocycling test was performed for 5000 cycles. Data were submitted to three-way repeated-measures analysis of variance and Tukey's test (p < 0.05. When the samples were immersed in each mouthwash, all assessed factors, associated or not, significantly influenced the color change values, except there was no association between the mouthwash and acrylic resin. Similarly, when the samples were immersed in each beverage, all studied factors influenced the color change values. In general, regardless of the solution, LU exhibited the greatest DE values in the period from T1 to T5; and QC presented the greatest DE values at T6. Thus, thermocycling and immersion in the various solutions influenced the color stability of acrylic resins and QC showed the greatest color alteration.

  3. Effect of different solutions on color stability of acrylic resin-based dentures.

    Science.gov (United States)

    Goiato, Marcelo Coelho; Nóbrega, Adhara Smith; dos Santos, Daniela Micheline; Andreotti, Agda Marobo; Moreno, Amália

    2014-01-01

    The aim of this study was to evaluate the effect of thermocycling and immersion in mouthwash or beverage solutions on the color stability of four different acrylic resin-based dentures (Onda Cryl, OC; QC20, QC; Classico, CL; and Lucitone, LU). The factors evaluated were type of acrylic resin, immersion time, and solution (mouthwash or beverage). A total of 224 denture samples were fabricated. For each type of resin, eight samples were immersed in mouthwashes (Plax-Colgate, PC; Listerine, LI; and Oral-B, OB), beverages (coffee, CP; cola, C; and wine, W), and artificial saliva (AS; control). The color change (DE) was evaluated before (baseline) and after thermocycling (T1), and after immersion in solution for 1 h (T2), 3 h (T3), 24 h (T4), 48 h (T5), and 96 h (T6). The CIE Lab system was used to determine the color changes. The thermocycling test was performed for 5000 cycles. Data were submitted to three-way repeated-measures analysis of variance and Tukey's test (p<0.05). When the samples were immersed in each mouthwash, all assessed factors, associated or not, significantly influenced the color change values, except there was no association between the mouthwash and acrylic resin. Similarly, when the samples were immersed in each beverage, all studied factors influenced the color change values. In general, regardless of the solution, LU exhibited the greatest DE values in the period from T1 to T5; and QC presented the greatest DE values at T6. Thus, thermocycling and immersion in the various solutions influenced the color stability of acrylic resins and QC showed the greatest color alteration.

  4. Stability of antimicrobial activity of peracetic acid solutions used in the final disinfection process

    Directory of Open Access Journals (Sweden)

    Solange Alves da Silva COSTA

    2015-01-01

    Full Text Available The instruments and materials used in health establishments are frequently exposed to microorganism contamination, and chemical products are used before sterilization to reduce occupational infection. We evaluated the antimicrobial effectiveness, physical stability, and corrosiveness of two commercial formulations of peracetic acid on experimentally contaminated specimens. Stainless steel specimens were contaminated with Staphylococcus aureus, Escherichia coli, Candida albicans, blood, and saliva and then immersed in a ready peracetic acid solution: 2% Sekusept Aktiv (SA or 0.25% Proxitane Alpha (PA, for different times. Then, washes of these instruments were plated in culture medium and colony-forming units counted. This procedure was repeated six times per day over 24 non-consecutive days. The corrosion capacity was assessed with the mass loss test, and the concentration of peracetic acid and pH of the solutions were measured with indicator tapes. Both SA and PA significantly eliminated microorganisms; however, the SA solution was stable for only 4 days, whereas PA remained stable throughout the experiment. The concentration of peracetic acid in the SA solutions decreased over time until the chemical was undetectable, although the pH remained at 5. The PA solution had a concentration of 500-400 mg/L and a pH of 2-3. Neither formulation induced corrosion and both reduced the number of microorganisms (p = 0.0001. However, the differences observed in the performance of each product highlight the necessity of establishing a protocol for optimizing the use of each one.

  5. Stability of antimicrobial activity of peracetic acid solutions used in the final disinfection process.

    Science.gov (United States)

    Costa, Solange Alves da Silva; Paula, Olívia Ferreira Pereira de; Silva, Célia Regina Gonçalves E; Leão, Mariella Vieira Pereira; Santos, Silvana Soléo Ferreira dos

    2015-01-01

    The instruments and materials used in health establishments are frequently exposed to microorganism contamination, and chemical products are used before sterilization to reduce occupational infection. We evaluated the antimicrobial effectiveness, physical stability, and corrosiveness of two commercial formulations of peracetic acid on experimentally contaminated specimens. Stainless steel specimens were contaminated with Staphylococcus aureus, Escherichia coli, Candida albicans, blood, and saliva and then immersed in a ready peracetic acid solution: 2% Sekusept Aktiv (SA) or 0.25% Proxitane Alpha (PA), for different times. Then, washes of these instruments were plated in culture medium and colony-forming units counted. This procedure was repeated six times per day over 24 non-consecutive days. The corrosion capacity was assessed with the mass loss test, and the concentration of peracetic acid and pH of the solutions were measured with indicator tapes. Both SA and PA significantly eliminated microorganisms; however, the SA solution was stable for only 4 days, whereas PA remained stable throughout the experiment. The concentration of peracetic acid in the SA solutions decreased over time until the chemical was undetectable, although the pH remained at 5. The PA solution had a concentration of 500-400 mg/L and a pH of 2-3. Neither formulation induced corrosion and both reduced the number of microorganisms (p = 0.0001). However, the differences observed in the performance of each product highlight the necessity of establishing a protocol for optimizing the use of each one.

  6. Stability of exact solutions describing two-layer flows with evaporation at the interface

    Energy Technology Data Exchange (ETDEWEB)

    Bekezhanova, V B [Institute of Computational Modelling SB RAS, Akademgorodok, 50/44, Krasnoyarsk, 660036 (Russian Federation); Goncharova, O N, E-mail: bekezhanova@mail.ru, E-mail: gon@math.asu.ru [Altai State University, Lenina 61, Barnaul, 656049 (Russian Federation)

    2016-12-15

    A new exact solution of the equations of free convection has been constructed in the framework of the Oberbeck–Boussinesq approximation of the Navier–Stokes equations. The solution describes the joint flow of an evaporating viscous heat-conducting liquid and gas-vapor mixture in a horizontal channel. In the gas phase the Dufour and Soret effects are taken into account. The consideration of the exact solution allows one to describe different classes of flows depending on the values of the problem parameters and boundary conditions for the vapor concentration. A classification of solutions and results of the solution analysis are presented. The effects of the external disturbing influences (of the liquid flow rates and longitudinal gradients of temperature on the channel walls) on the stability characteristics have been numerically studied for the system HFE7100-nitrogen in the common case, when the longitudinal temperature gradients on the boundaries of the channel are not equal. In the system both monotonic and oscillatory modes can be formed, which damp or grow depending on the values of the initial perturbations, flow rates and temperature gradients. Hydrodynamic perturbations are most dangerous under large gas flow rates. The increasing oscillatory perturbations are developed due to the thermocapillary effect under large longitudinal gradients of temperature. The typical forms of the disturbances are shown. (paper)

  7. Magnetically responsive enzyme powders

    Energy Technology Data Exchange (ETDEWEB)

    Pospiskova, Kristyna, E-mail: kristyna.pospiskova@upol.cz [Regional Centre of Advanced Technologies and Materials, Palacky University, Slechtitelu 11, 783 71 Olomouc (Czech Republic); Safarik, Ivo, E-mail: ivosaf@yahoo.com [Regional Centre of Advanced Technologies and Materials, Palacky University, Slechtitelu 11, 783 71 Olomouc (Czech Republic); Department of Nanobiotechnology, Institute of Nanobiology and Structural Biology of GCRC, Na Sadkach 7, 370 05 Ceske Budejovice (Czech Republic)

    2015-04-15

    Powdered enzymes were transformed into their insoluble magnetic derivatives retaining their catalytic activity. Enzyme powders (e.g., trypsin and lipase) were suspended in various liquid media not allowing their solubilization (e.g., saturated ammonium sulfate and highly concentrated polyethylene glycol solutions, ethanol, methanol, 2-propanol) and subsequently cross-linked with glutaraldehyde. Magnetic modification was successfully performed at low temperature in a freezer (−20 °C) using magnetic iron oxides nano- and microparticles prepared by microwave-assisted synthesis from ferrous sulfate. Magnetized cross-linked enzyme powders were stable at least for two months in water suspension without leakage of fixed magnetic particles. Operational stability of magnetically responsive enzymes during eight repeated reaction cycles was generally without loss of enzyme activity. Separation of magnetically modified cross-linked powdered enzymes from reaction mixtures was significantly simplified due to their magnetic properties. - Highlights: • Cross-linked enzyme powders were prepared in various liquid media. • Insoluble enzymes were magnetized using iron oxides particles. • Magnetic iron oxides particles were prepared by microwave-assisted synthesis. • Magnetic modification was performed under low (freezing) temperature. • Cross-linked powdered trypsin and lipase can be used repeatedly for reaction.

  8. Stability of 2 mg/mL Adenosine Solution in Polyvinyl Chloride and Polyolefin Infusion Bags.

    Science.gov (United States)

    DeAngelis, Michael; Ferrara, Alexander; Gregory, Kaleigh; Zammit, Kimberly; Zhao, Fang

    2018-04-01

    Adenosine is a potent endogenous mediator of vasodilation. Compounded sterile solutions of adenosine are used in cardiac catheterization lab to perform stress tests on the heart. These tests are used to determine the fractional flow reserve (FFR) and are commonly used in the management and diagnosis of cardiovascular conditions. The purpose of this study was to assess the physical and chemical stability of 2 mg/mL adenosine in 0.9% Sodium Chloride Injection, USP in polyvinyl chloride [PVC]) and polyolefin infusion bags stored at room temperature (20°C-25°C) and under refrigeration (2°C-8°C). The compounding and analytical methods used in this study were very similar to those described in the prior publications from the authors' laboratory. To ensure a uniform starting concentration of all stability samples, a batch of 2 mg/mL adenosine solution was prepared and then packaged into empty PVC and polyolefin infusion bags. These stability samples were prepared in triplicate for each bag type and storage temperature (a total of 12 samples). The infusion bag samples were assessed for stability immediately after preparation and after 1 day, 3 days, 7 days, and 14 days. At each time point, the infusion bags were first visually inspected against a light background for color change, clarity, and particulates. Aliquots were drawn from each sample at each time point for pH analysis and high-performance liquid chromatography (HPLC) analysis. Over 14 days of storage at room temperature or refrigeration, no considerable change in visual appearance or pH was observed in any bags. All samples retained 90% to 110% of the initial drug concentration. No significant degradation peaks were observed in the HPLC chromatograms.

  9. Model based on GRID-derived descriptors for estimating CYP3A4 enzyme stability of potential drug candidates

    Science.gov (United States)

    Crivori, Patrizia; Zamora, Ismael; Speed, Bill; Orrenius, Christian; Poggesi, Italo

    2004-03-01

    A number of computational approaches are being proposed for an early optimization of ADME (absorption, distribution, metabolism and excretion) properties to increase the success rate in drug discovery. The present study describes the development of an in silico model able to estimate, from the three-dimensional structure of a molecule, the stability of a compound with respect to the human cytochrome P450 (CYP) 3A4 enzyme activity. Stability data were obtained by measuring the amount of unchanged compound remaining after a standardized incubation with human cDNA-expressed CYP3A4. The computational method transforms the three-dimensional molecular interaction fields (MIFs) generated from the molecular structure into descriptors (VolSurf and Almond procedures). The descriptors were correlated to the experimental metabolic stability classes by a partial least squares discriminant procedure. The model was trained using a set of 1800 compounds from the Pharmacia collection and was validated using two test sets: the first one including 825 compounds from the Pharmacia collection and the second one consisting of 20 known drugs. This model correctly predicted 75% of the first and 85% of the second test set and showed a precision above 86% to correctly select metabolically stable compounds. The model appears a valuable tool in the design of virtual libraries to bias the selection toward more stable compounds. Abbreviations: ADME - absorption, distribution, metabolism and excretion; CYP - cytochrome P450; MIFs - molecular interaction fields; HTS - high throughput screening; DDI - drug-drug interactions; 3D - three-dimensional; PCA - principal components analysis; CPCA - consensus principal components analysis; PLS - partial least squares; PLSD - partial least squares discriminant; GRIND - grid independent descriptors; GRID - software originally created and developed by Professor Peter Goodford.

  10. Ferulic acid stabilizes a solution of vitamins C and E and doubles its photoprotection of skin.

    Science.gov (United States)

    Lin, Fu-Hsiung; Lin, Jing-Yi; Gupta, Ravindra D; Tournas, Joshua A; Burch, James A; Selim, M Angelica; Monteiro-Riviere, Nancy A; Grichnik, James M; Zielinski, Jan; Pinnell, Sheldon R

    2005-10-01

    Ferulic acid is a potent ubiquitous plant antioxidant. Its incorporation into a topical solution of 15%l-ascorbic acid and 1%alpha-tocopherol improved chemical stability of the vitamins (C+E) and doubled photoprotection to solar-simulated irradiation of skin from 4-fold to approximately 8-fold as measured by both erythema and sunburn cell formation. Inhibition of apoptosis was associated with reduced induction of caspase-3 and caspase-7. This antioxidant formulation efficiently reduced thymine dimer formation. This combination of pure natural low molecular weight antioxidants provides meaningful synergistic protection against oxidative stress in skin and should be useful for protection against photoaging and skin cancer.

  11. Global stability, periodic solutions, and optimal control in a nonlinear differential delay model

    Directory of Open Access Journals (Sweden)

    Anatoli F. Ivanov

    2010-09-01

    Full Text Available A nonlinear differential equation with delay serving as a mathematical model of several applied problems is considered. Sufficient conditions for the global asymptotic stability and for the existence of periodic solutions are given. Two particular applications are treated in detail. The first one is a blood cell production model by Mackey, for which new periodicity criteria are derived. The second application is a modified economic model with delay due to Ramsey. An optimization problem for a maximal consumption is stated and solved for the latter.

  12. Global exponential stability of periodic solution for shunting inhibitory CNNs with delays

    International Nuclear Information System (INIS)

    Li Yongkun; Liu Chunchao; Zhu Lifei

    2005-01-01

    By using the continuation theorem of coincidence degree theory and constructing suitable Lyapunov functions, we study the existence and stability of periodic solution for shunting inhibitory cellular neural networks (SICNNs) with delays x-bar ij (t)=-a ij (t)x ij (t)--bar B kl -bar Nr(i,j)B ij kl (t)f ij (x kl (t))x ij (t)--bar C kl -bar Nr(i,j)C ij kl (t)g ij (x kl (t-τ kl ))x ij (t)+L ij (t)

  13. Global exponential stability and existence of periodic solutions of CNNs with delays

    Science.gov (United States)

    Dong, Meifang

    2002-07-01

    In this Letter, we establish general sufficient conditions for global exponential stability and existence of periodic solutions of a class of cellular neural networks (CNNs) with delays. The key to proving the sufficient conditions is the construction of a new Lyapunov functional. An elementary inequality, which may be of independent interest, has been employed in the proof. Checking the sufficient conditions is often reduced to checking some algebraic relations among certain set of parameter. Our sufficient conditions recover the known results in literature as special cases. Finally, we give two examples to illustrate the usage of our main results.

  14. Enzyme-based solutions for textile processing and dye contaminant biodegradation-a review.

    Science.gov (United States)

    Chatha, Shahzad Ali Shahid; Asgher, Muhammad; Iqbal, Hafiz M N

    2017-06-01

    The textile industry, as recognized conformist and stake industry in the world's economy, is facing serious environmental challenges. In numerous industries, in practice, various chemical-based processes from initial sizing to final washing are fascinating harsh environment concerns. Some of these chemicals are corrosive to equipment and cause serious damage itself. Therefore, in the twenty-first century, chemical and allied industries quest a paradigm transition from traditional chemical-based concepts to a greener, sustainable, and environmentally friendlier catalytic alternative, both at the laboratory and industrial scales. Bio-based catalysis offers numerous benefits in the context of biotechnological industry and environmental applications. In recent years, bio-based processing has received particular interest among the scientist for inter- and multi-disciplinary investigations in the areas of natural and engineering sciences for the application in biotechnology sector at large and textile industries in particular. Different enzymatic processes such as chemical substitution have been developed or in the process of development for various textile wet processes. In this context, the present review article summarizes current developments and highlights those areas where environment-friendly enzymatic textile processing might play an increasingly important role in the textile industry. In the first part of the review, a special focus has been given to a comparative discussion of the chemical-based "classical/conventional" treatments and the modern enzyme-based treatment processes. Some relevant information is also reported to identify the major research gaps to be worked out in future.

  15. Integrated cellulosic enzymes hydrolysis and fermentative advanced yeast bioconversion solution ready for biomass biorefineries

    Energy Technology Data Exchange (ETDEWEB)

    Kumar, Manoj [DSM Innovation, Inc., San Francisco, CA (United States)

    2011-05-04

    These are slides from this conference. Lignocellulosic biomass is the most abundant, least expensive renewable natural biological resource for the production of biobased products and bioenergy is important for the sustainable development of human civilization in 21st century. For making the fermentable sugars from lignocellulosic biomass, a reduction in cellulase production cost, an improvement in cellulase performance, and an increase in sugar yields are all vital to reduce the processing costs of biorefineries. Improvements in specific cellulase activities for non-complexed cellulase mixtures can be implemented through cellulase engineering based on rational design or directed evolution for each cellulase component enzyme, as well as on the reconstitution of cellulase components. In this paper, we will provide DSM's efforts in cellulase research and developments and focus on limitations. Cellulase improvement strategies based on directed evolution using screening on relevant substrates, screening for higher thermal tolerance based on activity screening approaches such as continuous culture using insoluble cellulosic substrates as a powerful selection tool for enriching beneficial cellulase mutants from the large library. We will illustrate why and how thermostable cellulases are vital for economic delivery of bioproducts from cellulosic biomass using biochemical conversion approach.

  16. Stability of Almost Periodic Solution for a General Class of Discontinuous Neural Networks with Mixed Time-Varying Delays

    Directory of Open Access Journals (Sweden)

    Yingwei Li

    2013-01-01

    Full Text Available The global exponential stability issues are considered for almost periodic solution of the neural networks with mixed time-varying delays and discontinuous neuron activations. Some sufficient conditions for the existence, uniqueness, and global exponential stability of almost periodic solution are achieved in terms of certain linear matrix inequalities (LMIs, by applying differential inclusions theory, matrix inequality analysis technique, and generalized Lyapunov functional approach. In addition, the existence and asymptotically almost periodic behavior of the solution of the neural networks are also investigated under the framework of the solution in the sense of Filippov. Two simulation examples are given to illustrate the validity of the theoretical results.

  17. Method of denitrification and stabilization of radioactive aqueous solutions of radioisotope nitrates

    International Nuclear Information System (INIS)

    Pecak, V.; Matous, V.

    1983-01-01

    The method is solved of denitrification and of the stabilization of aqueous solutions of radioactive isotopes produced during the reprocessing of nuclear fuel. The aqueous solution is first mixed with the vitreous component, most frequently phosphoric acid, ammonium phosphate or boric acid and if needed with the addition of alkalis, possibly with clarifying or anti-foam components, e.g., arsenic trioxide, antimony or cerium oxide. The mixture is further adjusted with ammonia to pH 5 - 9. The liquid mixture is then thermally and pyrolytically processed, e.g., by calcinator or fluid-bed reactor or by pot melting at temperatures of 3O0 to 900 degC while of a powder product or glass melt is formed in the presence of gaseous emissions composed of nitrous oxide - nitrogen. The resulting product is further processed by containerization or is sealed in a metal matrix. (B.S.)

  18. Structural aspects of magnetic fluid stabilization in aqueous agarose solutions

    Energy Technology Data Exchange (ETDEWEB)

    Nagornyi, A.V. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Taras Shevchenko National University of Kyiv, Kyiv (Ukraine); Petrenko, V.I., E-mail: vip@nf.jinr.ru [Joint Institute for Nuclear Research, Dubna (Russian Federation); Taras Shevchenko National University of Kyiv, Kyiv (Ukraine); Avdeev, M.V. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Yelenich, O.V.; Solopan, S.O.; Belous, A.G. [V.I.Vernadsky Institute of General and Inorganic Chemistry of the Ukrainian NAS, Kyiv (Ukraine); Gruzinov, A.Yu. [National Research Centre “Kurchatov Institute”, Moscow (Russian Federation); Ivankov, O.I. [Joint Institute for Nuclear Research, Dubna (Russian Federation); Institute for Safety Problems of Nuclear Power Plants of the Ukrainian NAS, Kyiv (Ukraine); Bulavin, L.A. [Taras Shevchenko National University of Kyiv, Kyiv (Ukraine); Institute for Safety Problems of Nuclear Power Plants of the Ukrainian NAS, Kyiv (Ukraine)

    2017-06-01

    Structure characterization of magnetic fluids (MFs) synthesized by three different methods in aqueous solutions of agarose was done by means of small-angle neutron (SANS) and synchrotron X-ray scattering (SAXS). The differences in the complex aggregation observed in the studied magnetic fluids were related to different stabilizing procedures of the three kinds of MFs. The results of the analysis of the scattering (mean size of single polydisperse magnetic particles, fractal dimensions of the aggregates) are consistent with the data of transmission electron microscopy (TEM). - Highlights: • MFs synthesized by three different methods in agarose solution were studied. • all MFs are agglomerated colloidal systems whose structures are nevertheless stable in time. • differences in the complex aggregation were observed in the studied magnetic fluids. • results of the SAXS and SANS analysis are consistent with TEM data.

  19. First Integrals of Evolution Systems and Nonlinear Stability of Stationary Solutions for the Ideal Atmospheric, Oceanic Hydrodynamical and Plasma Models

    International Nuclear Information System (INIS)

    Gordin, V.A.

    1998-01-01

    First integral of the systems of nonlinear equations governing the behaviour of atmospheric, oceanic and MHD plasma models are determined. The Lyapunov stability conditions for the solutions under small initial disturbances are analyzed. (author)

  20. Stability of silver nanoparticles (nAg) in aqueous solution: the role of particle size and water ionic strength

    CSIR Research Space (South Africa)

    Radebe, N

    2014-01-01

    Full Text Available biota which can arise from the particulates, dissolved species or both forms. However, there is limited and contradicting information on how the nanoparticle and aqueous solution characteristics influence nanoparticle stability and toxicity. This study...

  1. The Colloidal Stabilization of Quantum Dots: Towards Manufacturable, Efficient Solution-Processed Solar Cells

    Science.gov (United States)

    Rollny, Lisa

    Understanding colloidal stabilization can influence the design of optoelectronic devices and enable improvements to their performance and stability. For photovoltaics, important characteristics of the active layer material are high conductivity along with a minimum of recombination centers. In order to capitalize on the benefits of solution-processed materials, it is important to minimize the number of processing steps: ideally, to achieve a low-cost solution, materials would be deposited using a single process step compatible with roll-to-roll manufacturing. Prior to this work, the highest-performing colloidal quantum dots (CQD) solar cells have relied on several deposition steps that are repeated in a layer-by-layer (LBL) fashion. The purpose of these process steps has been to remove the long insulating ligands used in synthesis and replace them with short ligands that allow electrical conduction. The large number of steps combined, typically implemented via spin coating, leads to inefficient materials utilization and fails to show a path to a manufacturable solution. In this work, the first CQD solar cells were designed, built, and characterized combining state-of-art performance with scalable manufacture. Firstly, I report the first automated CQD synthesis to result in CQDs that form high-performance CQD solar cells. I analyze the CQD synthesis and by separating it into two phases---nucleation and growth phase---my insights are used to create higher-quality CQDs exhibiting enhanced monodispersity. I then proceed to develop a CQD ink: a CQD solution ready for direct deposition to form a semiconducting film exhibiting low trap state density. In early trials the CQD ink showed only limited power conversion efficiencies of 2%. I designed a new ink strategy, which I term cleavable hemiketal ligands. This novel two-component ligand strategy enables the combination of colloidal stabilization (via this longer two-component ligand) and cleavability (enabling excellent

  2. Long-Term Stability of Tramadol and Ketamine Solutions for Patient-Controlled Analgesia Delivery.

    Science.gov (United States)

    Gu, Junfeng; Qin, Wengang; Chen, Fuchao; Xia, Zhongyuan

    2015-08-26

    Subanesthetic doses of ketamine as an adjuvant to tramadol in patient-controlled analgesia (PCA) for postoperative pain have been shown to improve the quality of analgesia. However, there are no such commercially available drug mixtures, and the stability of the combination has rarely been assessed. Admixtures were assessed for periods of up to 14 days at 4°C and 25°C. Three different mixtures of tramadol and ketamine (tramadol 5.0 mg/mL + ketamine 0.5 mg/mL, tramadol 5.0 mg/mL + ketamine 1.0 mg/mL, and tramadol 5.0 mg/mL + ketamine 2.0 mg/mL) were prepared in polyolefin bags by combining these 2 drugs with 0.9% sodium chloride (normal saline [NS]). The chemical stability of the admixtures was evaluated by a validated high-performance liquid chromatography (HPLC) method and by measurement of pH values. Solution appearance and color were assessed by observing the samples against black and white backgrounds. Solutions were considered stable if they maintained 90% of the initial concentration of each drug. The percentages of initial concentration of tramadol and ketamine in the various solutions remained above 98% when stored at 4°C or 25°C over the testing period. No changes in color or turbidity were observed in any of the prepared solutions. Throughout this period, pH values remained stable. The results indicate that the drug mixtures of tramadol with ketamine in NS for PCA delivery systems were stable for 14 days when stored in polyolefin bags at 4°C or 25°C.

  3. Stabilization of sputtered gold and silver nanoparticles in PEG colloid solutions

    International Nuclear Information System (INIS)

    Slepička, P.; Elashnikov, R.; Ulbrich, P.; Staszek, M.; Kolská, Z.; Švorčík, V.

    2015-01-01

    In this study, a simple technique for preparation of colloid solution of metal nanoparticles in polyethylene glycol (PEG)/H 2 O is described. By this technique, stable colloidal metal solutions can be prepared ready for use without application of chemical reactions, stabilizers, or reducing agents. The nanoparticles are created by direct sputtering of metal into PEG. The influence of sputter conditions and the concentration of PEG/H 2 O on the properties of nanoparticles was studied. The nanoparticles were characterized by transmission electron microscopy, atomic absorption spectrometry, dynamic light scattering, and UV–Vis spectroscopy. UV–Vis spectra of gold nanoparticle solution exhibit localized surface plasmon resonance characteristic peaks located in the region 513–560 nm (PEG/H 2 O—1/1), 509–535 nm (PEG/H 2 O—1/9), and for silver nanoparticles in the region from 401 to 421 nm. Silver nanoparticles have a broader size distribution compared with gold ones. An appropriate choice of concentration, mixing, and deposition conditions allows preparing the stable solution of gold or silver nanoparticles

  4. Stabilization of sputtered gold and silver nanoparticles in PEG colloid solutions

    Energy Technology Data Exchange (ETDEWEB)

    Slepička, P., E-mail: petr.slepicka@vscht.cz; Elashnikov, R. [University of Chemistry and Technology Prague, Department of Solid State Engineering (Czech Republic); Ulbrich, P. [University of Chemistry and Technology Prague, Department of Biochemistry and Microbiology (Czech Republic); Staszek, M. [University of Chemistry and Technology Prague, Department of Solid State Engineering (Czech Republic); Kolská, Z. [University of J. E. Purkyně, Faculty of Science (Czech Republic); Švorčík, V. [University of Chemistry and Technology Prague, Department of Solid State Engineering (Czech Republic)

    2015-01-15

    In this study, a simple technique for preparation of colloid solution of metal nanoparticles in polyethylene glycol (PEG)/H{sub 2}O is described. By this technique, stable colloidal metal solutions can be prepared ready for use without application of chemical reactions, stabilizers, or reducing agents. The nanoparticles are created by direct sputtering of metal into PEG. The influence of sputter conditions and the concentration of PEG/H{sub 2}O on the properties of nanoparticles was studied. The nanoparticles were characterized by transmission electron microscopy, atomic absorption spectrometry, dynamic light scattering, and UV–Vis spectroscopy. UV–Vis spectra of gold nanoparticle solution exhibit localized surface plasmon resonance characteristic peaks located in the region 513–560 nm (PEG/H{sub 2}O—1/1), 509–535 nm (PEG/H{sub 2}O—1/9), and for silver nanoparticles in the region from 401 to 421 nm. Silver nanoparticles have a broader size distribution compared with gold ones. An appropriate choice of concentration, mixing, and deposition conditions allows preparing the stable solution of gold or silver nanoparticles.

  5. An investigation into the stability and sterility of citric acid solutions used for cough reflex testing.

    Science.gov (United States)

    Falconer, James R; Wu, Zimei; Lau, Hugo; Suen, Joanna; Wang, Lucy; Pottinger, Sarah; Lee, Elaine; Alazawi, Nawar; Kallesen, Molly; Gargiulo, Derryn A; Swift, Simon; Svirskis, Darren

    2014-10-01

    Citric acid is used in cough reflex testing in clinical and research settings to assess reflexive cough in patients at risk of swallowing disorders. To address a lack of knowledge in this area, this study investigated the stability and sterility of citric acid solutions. Triplicate solutions of citric acid (0.8 M) in isotonic saline were stored at 4 ± 2 °C for up to 28 days and analysed by high-performance liquid chromatography. Microbiological sterility of freshly prepared samples and bulk samples previously used for 2 weeks within the hospital was determined using a pour plate technique. Microbial survival in citric acid was determined by inoculating Staphylococcus aureus, Escherichia coli, or Candida albicans into citric acid solution and monitoring the number of colony-forming units/mL over 40 min. Citric acid solutions remained stable at 4 °C for 28 days (98.4 ± 1.8 % remained). The freshly prepared and clinical samples tested were sterile. However, viability studies revealed that citric acid solution allows for the survival of C. albicans but not for S. aureus or E. coli. The microbial survival study showed that citric acid kills S. aureus and E. coli but has no marked effect on C. albicans after 40 min. Citric acid samples at 0.8 M remained stable over the 4-week testing period, with viable microbial cells absent from samples tested. However, C. albicans has the ability to survive in citric acid solution if inadvertently introduced in practice. For this reason, in clinical and research practice it is suggested to use single-use aliquots prepared aseptically which can be stored for up to 28 days at 4 °C.

  6. Stability theory of critical cases and the bifurcation points of the stationary solutions of the Lorenz model

    International Nuclear Information System (INIS)

    Bakasov, A.A.; Govorkov, B.B. Jr.

    1990-08-01

    The critical case in stability theory is the case when it is impossible to study the stability of solutions over the linear part of ordinary differential equations. This situation is usual at the bifurcation points. There exists a powerful and constructive approach to investigate the stability - the theory of critical cases created by Lyapunov. The famous Lorenz model is used in this article as an illustration of the power of the method (new results). (author). 27 refs

  7. Application of a novel enzymatic pretreatment using crude hydrolytic extracellular enzyme solution to microalgal biomass for dark fermentative hydrogen production.

    Science.gov (United States)

    Yun, Yeo-Myeong; Kim, Dong-Hoon; Oh, You-Kwan; Shin, Hang-Sik; Jung, Kyung-Won

    2014-05-01

    In this study, a novel enzymatic pretreatment of Chlorella vulgaris for dark fermentative hydrogen production (DFHP) was performed using crude hydrolytic extracellular enzyme solution (CHEES) extracted from the H2 fermented effluent of food waste. It was found that the enzyme extracted at 52 h had the highest hydrolysis efficiency of microalgal biomass, resulting in the highest H2 yield of 43.1 mL H2/g dry cell weight along with shorter lag periods. Even though a high amount of VFAs was accumulated in CHEES, especially butyrate, the fermentative bacteria on the DFHP was not affected from product inhibition. It also appears that the presence of organic acids, especially lactate and acetate, contained in the CHEES facilitated enhancement of H2 production acted as a co-substrate. Therefore, all of the experimental results suggest that the enhancement of DFHP performance caused by CHEES has a dual role as the hydrolysis enhancer and the co-substrate supplier. Copyright © 2014 Elsevier Ltd. All rights reserved.

  8. Stability-indicating liquid Chromatographic assaymethod for Opthalmic solutions containing combination of Dexamethasone and Chloramphenicol

    International Nuclear Information System (INIS)

    Rao, R.M.; Al-Ashban, R.M.; Shah, A.H.

    2004-01-01

    A selective high-performance chromatographic procedure for the stability monitoring of ophthalmic solutions containing a combination of dexamethasone and chloramphenicolis demonstrated. The separation of the active components and the degradation product of chloramphenicol (1-amino-1-(4-nitrophenyl)-propane-1, 3diol) was achieved on a u-Bondapack C-18 column ( 5 um, 300 mm x 3.9 mm) maintained at ambient temperature (15-20C) by utilizing a mobile phase consisting acidified water (5% actified water with glacial acetic acid ) : acetonitrile : triethyl amine 700 : 300 : 2and pH was adjusted to 5.0 by using 10 M Na OH. The flow rate was 1.5 ml min-1; and elutes were followed with UV-detection at 254 nm. Complete resolution of dexamethasone, chloramphenicol and its hydrolytic product could be attained. The sensitivity, accuracy and specificity were tested. The method was successfully applied in post-marketing stability of the commercial batches of ophthalmic solutions. (author)

  9. In-use stability of enrofloxacin solution for injection in multi-dose containers

    Directory of Open Access Journals (Sweden)

    Šandor Ksenija

    2012-01-01

    Full Text Available The in-use stability study in this paper was designed as far as possible to simulate the practical usage of multi-dose containers products in veterinary practice and to establish the influence of storage conditions on drug's quality. According to literature data, shelf-live of enrofloxacin solutions for injection tested in this study is 28 days after opening. In-use (open container stability testing of enrofloxacin injection solutions was studied during a period of 112 days, and the physical-chemical parameters and microbiological contamination were assessed. A spectrophotometric method was validated for the quantification of enrofloxacin. The validation method yielded good results and included the selectivity, linearity, intra-assay precision (1.26% RSD, inter-assay precision (1.52% RSD, limit of detection (0.18 μg/mL, limit of quantification (0.54 μg/mL and accuracy. The results of spectrophotometric analyses were presented as the mean drug concentration of enrofloxacin vs. time of sampling. The findings of physical, chemical and microbiological parameters were in accordance with the producers' specifications and no extreme changes during prescribed storage occurred. The study was extended from the drug's proposed shelf-life after opening for the next 84 days and in that period no significant changes were recorded.

  10. Design and stability study of an oral solution of amlodipine besylate for pediatric patients.

    Science.gov (United States)

    van der Vossen, A C; van der Velde, I; Smeets, O S N M; Postma, D J; Vermes, A; Koch, B C P; Vulto, A G; Hanff, L M

    2016-09-20

    Amlodipine is an antihypertensive agent recommended for the management of hypertension in children and adolescents. The commercially available tablets of 5 and 10mg do not provide the necessary flexibility in dosing needed for treating children. Our goal was to develop a pediatric oral solution of amlodipine, using a robust manufacturing process suitable for ex-tempora and larger scale production. The parameters API and preservative content, related substances, appearance and pH were studied under four different storage conditions. Samples were analyzed up to 12months. Microbiological quality was studied in an 18-week in-use test based on a two-times daily dosing schedule. The stability of the formulation was influenced by storage conditions and composition. A formulation containing amlodipine besylate, sucrose syrup and methyl paraben remained physically stable for 12months at 4°C with no loss of amlodipine content. Related substances increased during the study but remained below 0.5%. In-use stability was proven up to 18weeks. Storage under refrigerated conditions was necessary to prevent precipitation and to obtain an acceptable shelf-life. In conclusion, we have developed and validated an amlodipine oral solution, suitable for the pediatric population. This liquid formulation is preferred over manipulated commercial dosage forms or non-standardized extemporaneously compounded formulations. Copyright © 2016 Elsevier B.V. All rights reserved.

  11. Brassinosteroid-induced CO{sub 2} assimilation is associated with increased stability of redox-sensitive photosynthetic enzymes in the chloroplasts in cucumber plants

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Yu Ping; Cheng, Fei; Zhou, Yan Hong; Xia, Xiao Jian; Mao, Wei Hua; Shi, Kai [Department of Horticulture, Zijingang Campus, Zhejiang University, Yuhangtang Road 866, Hangzhou 310058 (China); Chen, Zhi Xiang [Department of Horticulture, Zijingang Campus, Zhejiang University, Yuhangtang Road 866, Hangzhou 310058 (China); Department of Botany and Plant Pathology, Purdue University, West Lafayette, IN 47907-2054 (United States); Yu, Jing Quan, E-mail: jqyu@zju.edu.cn [Department of Horticulture, Zijingang Campus, Zhejiang University, Yuhangtang Road 866, Hangzhou 310058 (China); Key Laboratory of Horticultural Plants Growth, Development and Quality Improvement, Ministry of Agriculture of China, Yuhangtang Road 866, Hangzhou 310058 (China)

    2012-09-28

    Highlights: Black-Right-Pointing-Pointer Activity of certain Calvin cycle enzymes and CO{sub 2} assimilation are induced by BRs. Black-Right-Pointing-Pointer BRs upregulate the activity of the ascorbate-glutathione cycle in the chloroplasts. Black-Right-Pointing-Pointer BRs increase the chloroplast thiol reduction state. Black-Right-Pointing-Pointer A BR-induced reducing environment increases the stability of photosynthetic enzymes. -- Abstract: Brassinosteroids (BRs) play important roles in plant growth, development, photosynthesis and stress tolerance; however, the mechanism underlying BR-enhanced photosynthesis is currently unclear. Here, we provide evidence that an increase in the BR level increased the quantum yield of PSII, activities of Rubisco activase (RCA) and fructose-1,6-bisphosphatase (FBPase), and CO{sub 2} assimilation. BRs upregulated the transcript levels of genes and activity of enzymes involved in the ascorbate-glutathione cycle in the chloroplasts, leading to an increased ratio of reduced (GSH) to oxidized (GSSG) glutathione in the chloroplasts. An increased GSH/GSSG ratio protected RCA from proteolytic digestion and increased the stability of redox-sensitive enzymes in the chloroplasts. These results strongly suggest that BRs are capable of regulating the glutathione redox state in the chloroplasts through the activation of the ascorbate-glutathione cycle. The resulting increase in the chloroplast thiol reduction state promotes CO{sub 2} assimilation, at least in part, by enhancing the stability and activity of redox-sensitive photosynthetic enzymes through post-translational modifications.

  12. Brassinosteroid-induced CO2 assimilation is associated with increased stability of redox-sensitive photosynthetic enzymes in the chloroplasts in cucumber plants

    International Nuclear Information System (INIS)

    Jiang, Yu Ping; Cheng, Fei; Zhou, Yan Hong; Xia, Xiao Jian; Mao, Wei Hua; Shi, Kai; Chen, Zhi Xiang; Yu, Jing Quan

    2012-01-01

    Highlights: ► Activity of certain Calvin cycle enzymes and CO 2 assimilation are induced by BRs. ► BRs upregulate the activity of the ascorbate–glutathione cycle in the chloroplasts. ► BRs increase the chloroplast thiol reduction state. ► A BR-induced reducing environment increases the stability of photosynthetic enzymes. -- Abstract: Brassinosteroids (BRs) play important roles in plant growth, development, photosynthesis and stress tolerance; however, the mechanism underlying BR-enhanced photosynthesis is currently unclear. Here, we provide evidence that an increase in the BR level increased the quantum yield of PSII, activities of Rubisco activase (RCA) and fructose-1,6-bisphosphatase (FBPase), and CO 2 assimilation. BRs upregulated the transcript levels of genes and activity of enzymes involved in the ascorbate–glutathione cycle in the chloroplasts, leading to an increased ratio of reduced (GSH) to oxidized (GSSG) glutathione in the chloroplasts. An increased GSH/GSSG ratio protected RCA from proteolytic digestion and increased the stability of redox-sensitive enzymes in the chloroplasts. These results strongly suggest that BRs are capable of regulating the glutathione redox state in the chloroplasts through the activation of the ascorbate–glutathione cycle. The resulting increase in the chloroplast thiol reduction state promotes CO 2 assimilation, at least in part, by enhancing the stability and activity of redox-sensitive photosynthetic enzymes through post-translational modifications.

  13. A Semilinear Wave Equation with a Boundary Condition of Many-Point Type: Global Existence and Stability of Weak Solutions

    Directory of Open Access Journals (Sweden)

    Giai Giang Vo

    2015-01-01

    Full Text Available This paper is devoted to the study of a wave equation with a boundary condition of many-point type. The existence of weak solutions is proved by using the Galerkin method. Also, the uniqueness and the stability of solutions are established.

  14. Analysis of stability and bifurcations of fixed points and periodic solutions of a lumped model of neocortex with two delays

    NARCIS (Netherlands)

    Visser, Sid; Meijer, Hil G.E.; van Putten, Michel J.A.M.; van Gils, Stephan A.

    2012-01-01

    A lumped model of neural activity in neocortex is studied to identify regions of multi-stability of both steady states and periodic solutions. Presence of both steady states and periodic solutions is considered to correspond with epileptogenesis. The model, which consists of two delay differential

  15. Extended stability of intravenous 0.9% sodium chloride solution after prolonged heating or cooling.

    Science.gov (United States)

    Puertos, Enrique

    2014-03-01

    The primary objective of this study was to evaluate the stability and sterility of an intravenous 0.9% sodium chloride solution that had been cooled or heated for an extended period of time. Fifteen sterile 1 L bags of 0.9% sodium chloride solution were randomly selected for this experiment. Five bags were refrigerated at an average temperature of 5.2°C, 5 bags were heated at an average temperature of 39.2°C, and 5 bags were stored at an average room temperature of 21.8°C to serve as controls. All samples were protected from light and stored for a period of 199 days prior to being assayed and analyzed for microbial and fungal growth. There was no clinically significant difference in the mean sodium values between the refrigerated samples, the heated samples, and the control group. There were no signs of microbial or fungal growth for the duration of the study. A sterile intravenous solution of 0.9% sodium chloride that was heated or cooled remained stable and showed no signs of microbial or fungal growth for a period of 199 days. This finding will allow hospitals and emergency medical technicians to significantly extend the expiration date assigned to these fluids and therefore obviate the need to change out these fluids every 28 days as recommended by the manufacturer.

  16. Effect of neohesperidin dihydrochalcone on the activity and stability of alpha-amylase: a comparative study on bacterial, fungal, and mammalian enzymes.

    Science.gov (United States)

    Kashani-Amin, Elaheh; Ebrahim-Habibi, Azadeh; Larijani, Bagher; Moosavi-Movahedi, Ali Akbar

    2015-10-01

    Neohesperidin dihydrochalcone (NHDC) was recently introduced as an activator of mammalian alpha-amylase. In the current study, the effect of NHDC has been investigated on bacterial and fungal alpha-amylases. Enzyme assays and kinetic analysis demonstrated the capability of NHDC to significantly activate both tested alpha-amylases. The ligand activation pattern was found to be more similar between the fungal and mammalian enzyme in comparison with the bacterial one. Further, thermostability experiments indicated a stability increase in the presence of NHDC for the bacterial enzyme. In silico (docking) test locates a putative binding site for NHDC on alpha-amylase surface in domain B. This domain shows differences in various alpha-amylase types, and the different behavior of the ligand toward the studied enzymes may be attributed to this fact. Copyright © 2015 John Wiley & Sons, Ltd.

  17. Stability of therapeutic albumin solutions used for molecular adsorbent recirculating system-based liver dialysis.

    Science.gov (United States)

    De Bruyn, Tom; Meijers, Björn; Evenepoel, Pieter; Laub, Ruth; Willems, Ludo; Augustijns, Patrick; Annaert, Pieter

    2012-01-01

    Mounting evidence suggests beneficial effects of albumin dialysis-based liver support in patients suffering from acute-on-chronic liver failure. Molecular adsorbent recirculating system (MARS) is a nonbiological liver support device, based on the exchange of albumin-bound toxins between the patient's blood and a 20% human serum albumin solution in a secondary circuit. Bound toxins are continuously removed from the circulating albumin by exposure to activated charcoal and an ion-exchange resin. The aim of the present in vitro study was to determine the impact of exposure to charcoal and resin on the ligand binding properties of albumins, containing various levels of stabilizers and obtained from different suppliers (Baxter, CAF-DCF [Red Cross], and Sigma-Aldrich). Albumin binding properties were assessed by measuring equilibrium binding properties of warfarin, diazepam, and salicylate before and after incubation (for up to 7 h) with adsorbing materials; albumin-associated esterase-like activities were also determined. Notable changes in albumin binding upon incubation with adsorbing materials were only observed when using warfarin as a ligand. Affinity of warfarin for the Baxter and Sigma albumins showed a pronounced decrease (higher K(d) ) after the 1-7-h exposure to charcoal or resin. In the absence of adsorbing materials, similar effects were found, indicating that incubation time per se affects albumin binding properties. Following exposure to resin, Baxter albumin binding capacity (B(max)) increased about twofold. For albumin obtained from CAF-DCF, binding affinity and capacity for warfarin were constant under all conditions tested. Esterase-like activities associated with these albumins were either maintained or enhanced (up to 2.5-fold in case of Sigma albumin) following 7-h incubations with adsorbing materials. Our data suggest limited direct influence of the presence of stabilizers in therapeutic albumin solutions on baseline binding properties of human

  18. Formation and thermodynamic stability of (polymer + porphyrin) supramolecular structures in aqueous solutions

    International Nuclear Information System (INIS)

    Costa, Viviana C.P. da; Hwang, Barrington J.; Eggen, Spencer E.; Wallace, Megan J.; Annunziata, Onofrio

    2014-01-01

    Highlights: • Thermodynamic stability of a (polymer + porphyrin) supramolecular structure was characterized. • Isothermal titration calorimetry provided two ways to determine reaction enthalpies. • Exothermic (polymer + porphyrin) binding competes with porphyrin self-association. • (Polymer + porphyrin) binding is entropically favored with respect to porphyrin self-association. • Spectral shifts show importance of porphyrin central hydrogens in polymer binding. - Abstract: Optical properties of porphyrins can be tuned through (polymer + porphyrin) (host + guest) binding in solution. This gives rise to the formation of supramolecular structures. In this paper, the formation, thermodynamic stability and spectroscopic properties of (polymer + porphyrin) supramolecular structures and their competition with porphyrin self-association were investigated by both isothermal titration calorimetry (ITC) and absorption spectroscopy. Specifically, reaction enthalpies and equilibrium constants were measured for meso-tetrakis(4-sulfonatophenyl) porphyrin (TPPS) self-association and TPPS binding to the polymer poly(vinylpyrrolidone) (PVP, 40 kg/mol) in aqueous solutions at pH 7 and three different temperatures (12, 25 and 37 °C). ITC, compared to spectroscopic techniques, provides two independent means to determine reaction enthalpies: direct measurements and Van’t Hoff plot. This was used as a criterion to assess that (1) self-association of TPPS is limited to the formation of dimers and (2) TPPS binds to PVP in its monomeric state only. The formation of TPPS dimers and (PVP + TPPS) supramolecular structures are both enthalpically driven. However, (polymer + porphyrin) binding was found to be entropically favored compared to dimerization. Furthermore, the reaction enthalpies of these two processes significantly depend on temperature. This behavior was attributed to hydrophobic interactions. Finally, the limiting absorption spectra of monomeric, dimeric and polymer

  19. Stability analysis of the soliton solutions for the generalized quintic derivative nonlinear Schrödinger equation

    Directory of Open Access Journals (Sweden)

    Chen Yue

    Full Text Available The propagation of hydrodynamic wave packets and media with negative refractive index is studied in a quintic derivative nonlinear Schrödinger (DNLS equation. The quintic DNLS equation describe the wave propagation on a discrete electrical transmission line. We obtain a Lagrangian and the invariant variational principle for quintic DNLS equation. By using a class of ordinary differential equation, we found four types of exact solutions of the quintic DNLS equation, which are kink-type solitary wave solution, antikink-type solitary wave solution, sinusoidal solitary wave solution, bell-type solitary wave solution. By applying the modulation instability to discuss stability analysis of the obtained solutions. Modulation instabilities of continuous waves and localized solutions on a zero background have been investigated. Keywords: Quintic derivative NLS equation, Solitary wave solutions, Mathematical physics methods, 2000 MR Subject Classification: 35G20, 35Q53, 37K10, 49S05, 76A60

  20. Physico-chemical stability of busulfan in injectable solutions in various administration packages.

    Science.gov (United States)

    Houot, Mélanie; Poinsignon, Vianney; Mercier, Lionel; Valade, Cyril; Desmaris, Romain; Lemare, François; Paci, Angelo

    2013-03-01

    Busulfan is used as part of a conditioning regimen prior to hematopoietic stem cell transplantation for the treatment of certain cancers and immune deficiency syndromes. Due to its instability in aqueous preparations, busulfan for infusion is prepared from a concentrate and has a relatively short shelf life once prepared. The purpose of this study was to identify the most suitable storage container and temperature to maximize the shelf life of busulfan therapeutic infusions prepared from Busilvex(®). Busilvex(®) 6 mg/mL was diluted to 0.55 mg/mL with 0.9 % NaCl and aliquots dispensed into polypropylene syringes, polyvinyl chloride bags, and glass bottles. Three storage temperatures were evaluated: 2-8 °C, 13-15 °C (thermostatically controlled chamber), and room temperature (20 ± 5 °C). At set time points, samples were analysed for busulfan content, using a high-performance liquid chromatography (HPLC) system with ultraviolet detection. The change in pH and osmolarity on storage was also determined, and solutions were inspected visually for formation of a precipitate or colour change. To determine the contribution of precipitation to loss of busulfan content on storage, samples from one time series were treated with the solvent dimethylacetamide prior to HPLC separation and quantitation of busulfan. The results of the active substance content monitoring study over a 48-h period demonstrate that busulfan solution is stable at a 5 % threshold, at 2-8 °C for 16 h in syringes, 14 h in glass bottles, and 6 h in bags. In addition, the period of stability decreases as the temperature increases (4 h at 20 ± 5 °C). The solution is considered to be stable, subject to precipitation liable to be observed regardless of the temperature. The best stability was observed for busulfan solutions placed at 2-8 °C in syringes. This study demonstrated that precipitation, in addition to hydrolysis, has a significant influence on the busulfan content.

  1. The survey of biological absorption of hexavalent chromium from aqueous solutions by Wastewater stabilization pond algae

    Directory of Open Access Journals (Sweden)

    Mohammad Nourisepehr

    2016-06-01

    Full Text Available Background: Contamination of aquatic habitats due to toxicity and accumulation of heavy metals leading to serious damage to organisms and their advance to the food chain. Chrome is one of these heavy metals for the three and six-valence oxides used in industry. Health risks such as carcinogenic hexavalent chromium have been For this reason, removal and reduction of environment is essential. Target of this study hexavalent chromium biosorption by waste stabilization pond algae is of the aquatic environment. Methods: This study was a fundamental applied; In this batch reactor, variables Was investigated pH(3,5,7,9,11, Contact time(30,60,120,180,240,300min, The concentration of hexavalent chromium(0.5,1,5mg And the concentration of algae(0.25, 0.5, 1, 3g. Liquid mixed municipal wastewater treatment stabilization pond was used for insemination. For the investigate the effects of variables pH, contact time, the concentration of hexavalent chromium values in a 250 ml Erlenmeyer flask prepared and various amounts of dried algae (0.25-0.5-1- 3 g were added to it. Then became the shakers. After mixing, the filter paper was passed. The lab temperature was centrifuged for min10-5 rpm 2700 rpm. Then it was read at a wavelength absorbed by 540 nm. . Then collected was data to Excel and SPSS software. Finally was used for hexavalent chromium adsorption isotherm model equation of Langmuir and Freundlich. Results: This study shows that PH, contact time, the concentration of hexavalent chromium and chromium concentrations of algae optimal absorption by algae concentrations, respectively, in5 mg / l, min 120, 0.5 mg / l and is 1gr. Average maximum absorption of chromium Wastewater stabilization ponds by algae 97/2%, respectively. Correlation coefficients absorption curves of these models showed that Cr (VI adsorption isotherm on wastewater stabilization pond algae follows (= R.  Conclusion: The results showed that wastewater stabilization pond algae as a

  2. On the stability of the cosmological solutions in f(R, G) gravity

    International Nuclear Information System (INIS)

    De la Cruz-Dombriz, Álvaro; Sáez-Gómez, Diego

    2012-01-01

    Modified gravity is one of the most promising candidates for explaining the current accelerating expansion of the Universe, and even its unification with the inflationary epoch. Nevertheless, the wide range of models capable of explaining the phenomena of dark energy imposes that current research focuses on a more precise study of the possible effects of modified gravity on both cosmological and local levels. In this paper, we focus on the analysis of a type of modified gravity, the so-called f(R, G) gravity, and we perform a deep analysis on the stability of important cosmological solutions. This not only can help to constrain the form of the gravitational action, but also facilitate a better understanding of the behavior of the perturbations in this class of higher order theories of gravity, which will lead to a more precise analysis of the full spectrum of cosmological perturbations in future. (paper)

  3. Global exponential stability of periodic solution for shunting inhibitory CNNs with delays

    Energy Technology Data Exchange (ETDEWEB)

    Li Yongkun [Department of Mathematics, Yunnan University, Kunming, Yunnan 650091 (China)]. E-mail: yklie@ynu.edu.cn; Liu Chunchao [Department of Mathematics, Yunnan University, Kunming, Yunnan 650091 (China); Zhu Lifei [Department of Mathematics, Yunnan University, Kunming, Yunnan 650091 (China)

    2005-03-28

    By using the continuation theorem of coincidence degree theory and constructing suitable Lyapunov functions, we study the existence and stability of periodic solution for shunting inhibitory cellular neural networks (SICNNs) with delays x-bar {sub ij}(t)=-a{sub ij}(t)x{sub ij}(t)--bar B{sup kl}-bar Nr(i,j)B{sub ij}{sup kl}(t)f{sub ij}(x{sub kl}(t))x{sub ij}(t)--bar C{sup kl}-bar Nr(i,j)C{sub ij}{sup kl}(t)g{sub ij}(x{sub kl}(t-{tau}{sub kl}))x{sub ij}(t)+L{sub ij}(t)

  4. An investigation on the chemical stability and a novel strategy for long-term stabilization of diphenylalanine nanostructures in aqueous solution

    Directory of Open Access Journals (Sweden)

    H. Nezammahalleh

    2015-01-01

    Full Text Available The stability of diphenylalanine (FF microwires and microtubes in phosphate buffer solution was investigated and a novel strategy was developed for their chemical stabilization. This stability investigation was carried out by optical microscopy and by high performance liquid chromatography (HPLC. These microstructures dissolve in the solution depending upon their degree of FF saturation. The dissolution mechanisms of the structures in kinetically limited processes were found by accurately fitting the experimental dissolution data to a theoretical kinetic equation. The dissolution data were well fitted to the particular Avrami-Erofe’ev kinetic expression (R2 > 0.98. These findings suggest that the structures can be stabilized by a decrease in the hydration of the constituent molecules thorough a chemical conformational induced transition upon heat treatment. The stable microtubes were fabricated in a novel three step procedure consisting of the reduction of silver ions in unstable FF microtubes by a citrate reductant, the stabilization by chemical conformational induced transition upon heat treatment, and the consequent oxidation of the reduced silver by a persulfate oxidant. These materials were characterized by electron microscopy and powder X-ray diffraction techniques. The long-term stability of both structures was also confirmed by optical microscopy and HPLC.

  5. Existence, Multiplicity, and Stability of Positive Solutions of a Predator-Prey Model with Dinosaur Functional Response

    Directory of Open Access Journals (Sweden)

    Xiaozhou Feng

    2017-01-01

    Full Text Available We investigate the property of positive solutions of a predator-prey model with Dinosaur functional response under Dirichlet boundary conditions. Firstly, using the comparison principle and fixed point index theory, the sufficient conditions and necessary conditions on coexistence of positive solutions of a predator-prey model with Dinosaur functional response are established. Secondly, by virtue of bifurcation theory, perturbation theory of eigenvalues, and the fixed point index theory, we establish the bifurcation of positive solutions of the model and obtain the stability and multiplicity of the positive solution under certain conditions. Furthermore, the local uniqueness result is studied when b and d are small enough. Finally, we investigate the multiplicity, uniqueness, and stability of positive solutions when k>0 is sufficiently large.

  6. The thermodynamic stability induced by solute co-segregation in nanocrystalline ternary alloys

    Energy Technology Data Exchange (ETDEWEB)

    Liang, Tao; Chen, Zheng; Zhang, Jinyong; Zhang, Ping [China Univ. of Mining and Technology, Xuzhou (China). School of Mateial Science and Engineering; Yang, Xiaoqin [China Univ. of Mining and Technology, Xuzhou (China). School of Chemical Engineering and Technology

    2017-06-15

    The grain growth and thermodynamic stability induced by solute co-segregation in ternary alloys are presented. Grain growth behavior of the single-phase supersaturated grains prepared in Ni-Fe-Pb alloy melt at different undercoolings was investigated by performing isothermal annealings at T = 400 C-800 C. Combining the multicomponent Gibbs adsorption equation and Guttmann's grain boundary segregation model, an empirical relation for isothermal grain growth was derived. By application of the model to grain growth in Ni-Fe-Pb, Fe-Cr-Zr and Fe-Ni-Zr alloys, it was predicted that driving grain boundary energy to zero is possible in alloys due to the co-segregation induced by the interactive effect between the solutes Fe/Pb, Zr/Ni and Zr/Cr. A non-linear relationship rather than a simple linear relation between 1/D* (D* the metastable equilibrium grain size) and ln(T) was predicted due to the interactive effect.

  7. Foam capacity and stability of Sodium Dodecyl Sulfate (SDS) on the presence of contaminant coffee and Cd ions in solution

    Science.gov (United States)

    Haryanto, B.; Chang, C. H.; Kuo, A. T.; Siswarni, M. Z.; Sinaga, T. M. A.

    2018-02-01

    In this study, the effect of the coffee colloidal particle and Cd ion contaminant on the foam capacity and stability of sodium dodecyl sulfate (SDS) solution was investigated. The foam was generated by using a foam generator. The foam capacity of SDS was first evaluated at different concentrations. After the foam capacity reaching a constant value, the foam stability was then measured by flowing to a column. The results showed that the presence the coffee colloidal particles or Cd ions in the solution would decrease the foam capacity and stability of SDS. In addition, the decreased foam capacity and stability was more pronounced in the presence of coffee colloidal particles than Cd ions. The colloidal particles may have stronger interaction with SDS and thus reduce the formation of the foam.

  8. Validation of an analytical method applicable to study of 1 mg/mL oral Risperidone solution stability

    International Nuclear Information System (INIS)

    Abreu Alvarez, Maikel; Garcia Penna, Caridad Margarita; Martinez Miranda, Lissette

    2010-01-01

    A validated analytical method by high-performance liquid chromatography (HPLC) was applicable to study of 1 mg/mL Risperidone oral solution stability. The above method was linear, accurate, specific and exact. A stability study of the 1 mg/mL Risperidone oral solution was developed determining its expiry date. The shelf life study was conducted for 24 months at room temperature; whereas the accelerated stability study was conducted with product under influence of humidity and temperature; analysis was made during 3 months. Formula fulfilled the quality specifications described in Pharmacopeia. The results of stability according to shelf life after 24 months showed that the product maintains the parameters determining its quality during this time and in accelerated studies there was not significant degradation (p> 0.05) in the product. Under mentioned conditions expiry date was of 2 years

  9. Investigations of foam formation and its stabilization in the extraction systems: TBP in kerosene-nitric acid solutions

    International Nuclear Information System (INIS)

    Zielinski, A.

    1980-01-01

    The paper is devoted to studies of foam formation and its stabilization in TBP - kerosene - nitric acid solutions extracting systems. It was experimentally found, that TBP acts as a stabilizator of thin, liquid foam films as well as an emulgator in forming dispersions. The stabilizing effect of fine emulsions w/o on formed foams column was observed. Relevant references on the subject are also reviewed. (author)

  10. Kinetics of the decomposition and the estimation of the stability of 10% aqueous and non-aqueous hydrogen peroxide solutions

    Directory of Open Access Journals (Sweden)

    Zun Maria

    2014-12-01

    Full Text Available In this study, the stability of 10% hydrogen peroxide aqueous and non-aqueous solutions with the addition of 6% (w/w of urea was evaluated. The solutions were stored at 20°C, 30°C and 40°C, and the decomposition of hydrogen peroxide proceeded according to first-order kinetics. With the addition of the urea in the solutions, the decomposition rate constant increased and the activation energy decreased. The temperature of storage also affected the decomposition of substance, however, 10% hydrogen peroxide solutions prepared in PEG-300, and stabilized with the addition of 6% (w/w of urea had the best constancy.

  11. Brightly luminescent colloidal Ag–In–S nanoparticles stabilized in aqueous solutions by branched polyethyleneimine

    Energy Technology Data Exchange (ETDEWEB)

    Raevskaya, Alexandra E.; Ivanchenko, Maria V.; Skoryk, Mykola A.; Stroyuk, Oleksandr L., E-mail: alstroyuk@ukr.net

    2016-10-15

    Silver indium sulfide nanoparticles (NPs) stabilized in water by branched polyethyleneimine (PEI) were produced by a mild and direct synthesis. The Ag–In–S NPs exhibit relatively bright photoluminescence (PL) in the visible spectral range. The key parameters influencing color and intensity of PL are the Ag:In and Ag:S molar ratios and duration of the post-synthesis thermal treatment at ~100 °C. A maximal PL quantum yield, 20%, was observed for the Ag–In–S–PEI NPs produced at a molar Ag:In:S ratio of 1:5:5 and a thermal treatment at ~100 °C for 2 h. Such NPs are characterized by an average hydrodynamic size of around 100 nm. According to SEM each 100-nm globule comprises many smaller Ag–In–S NPs. Reasonably high PL quantum yield, variability of the emission color and self-aggregation of Ag–In–S–PEI NPs into polymer globules that do not scatter light makes such NPs promising for the luminescent bio-labeling applications. The PL band maximum energy of the Ag–In–S–PEI NPs produced in optimal conditions is very close to the band gap derived from the absorption spectra of colloidal solutions indicating that PL originates from the radiative recombination of delocalized or shallowly trapped charge carriers. - Highlights: • Ag–In–S nanoparticles (NPs) stabilized by polyethyleneimine in water were synthesized. • Ag–In–S NPs emit bright visible photoluminescence varying in color from green to red. • Maximal quantum yield of emission, ~20%, is observed at a Ag:In:S ratio of 1:5:5. • Separate Ag–In–S NPs are assembled into ~100-nm polyethyleneimine globules.

  12. A Riccati solution for the ideal MHD plasma response with applications to real-time stability control

    Science.gov (United States)

    Glasser, Alexander; Kolemen, Egemen; Glasser, A. H.

    2018-03-01

    Active feedback control of ideal MHD stability in a tokamak requires rapid plasma stability analysis. Toward this end, we reformulate the δW stability method with a Hamilton-Jacobi theory, elucidating analytical and numerical features of the generic tokamak ideal MHD stability problem. The plasma response matrix is demonstrated to be the solution of an ideal MHD matrix Riccati differential equation. Since Riccati equations are prevalent in the control theory literature, such a shift in perspective brings to bear a range of numerical methods that are well-suited to the robust, fast solution of control problems. We discuss the usefulness of Riccati techniques in solving the stiff ordinary differential equations often encountered in ideal MHD stability analyses—for example, in tokamak edge and stellarator physics. We demonstrate the applicability of such methods to an existing 2D ideal MHD stability code—DCON [A. H. Glasser, Phys. Plasmas 23, 072505 (2016)]—enabling its parallel operation in near real-time, with wall-clock time ≪1 s . Such speed may help enable active feedback ideal MHD stability control, especially in tokamak plasmas whose ideal MHD equilibria evolve with inductive timescale τ≳ 1s—as in ITER.

  13. Effect of Different Irrigation Solutions on the Colour Stability of Three Calcium Silicate-Based Materials

    Directory of Open Access Journals (Sweden)

    Sobhnamayan F

    2017-06-01

    Full Text Available Abstract: Statement of Problem: Previous studies have shown discoloration of mineral trioxide aggregate (MTA in contact with root canal irrigation solutions. However, there are limited data on colour stability of other calcium silicate–based materials (CSMs. Objectives: This in vitro study aimed to evaluate the colour stability of three CSMs in contact with different irrigation solutions. Materials and Methods: Three CSMs including White MTA (wMTA Angelus, calcium enriched mixture (CEM, and Biodentine were assessed in this study. Forty five samples of each material were mixed according to the manufactures’ instructions and then placed in silicone tubes. After 24 hours, the materials were removed from the moulds and 9 samples of each material left dry or immersed in normal saline, 5% sodium hypochlorite (NaOCL, 2% chlorhexidinegluconate (CHX, or 17%EDTA for 24 hours. Colour changes were measured with a spectrophotometer. Data were evaluated with 2-way analysis of variance, one way analysis of variance and Tukey post hoc tests. Results: The highest discoloration of all materials was observed after contact with CHX. In the MTA Angelus and CEM cement groups, significant differences were observed between CHX and NaOCl and also between these two irrigants with the other three irrigants (p < 0.05. In the Biodentine group, CHX created statistically significant discoloration compared to other irrigants (p < 0.05. Only wMTA Angelus showed a significantly higher discoloration in contact with EDTA compared to normal saline and dry condition (p < 0.05. wMTA Angelus showed a significantly higher colour change compared with CEM cement and Biodentine after contact with NaOCl, CHX, and EDTA (p < 0.05. Conclusions: The contact of wMTA, CEM cement, and Biodentine with CHX should be avoided because this leads to severe discoloration. Contact with sodium hypochlorite also leads to discoloration of wMTA and CEM cements. Among of the three tested materials, w

  14. Effect of staining solutions and repolishing on color stability of direct composites

    Directory of Open Access Journals (Sweden)

    Fabrício Mariano Mundim

    2010-06-01

    Full Text Available OBJECTIVES: The purpose of this study was to assess the color change of three types of composite resins exposed to coffee and cola drink, and the effect of repolishing on the color stability of these composites after staining. MATERIALS AND METHODS: Fifteen specimens (15 mm diameter and 2 mm thick were fabricated from microhybrid (Esthet-X; Dentsply and Filtek Z-250; 3M ESPE and high-density hybrid (Surefil; Dentsply composites, and were finished and polished with aluminum oxide discs (Sof-Lex; 3M ESPE. Color of the specimens was measured according to the CIE L*a*b* system in a refection spectrophotometer (PCB 6807; BYK Gardner. After baseline color measurements, 5 specimens of each resin were immersed in different staining solutions for 15 days: G1 - distilled water (control, G2 - coffee, G3 - cola soft drink. Afterwards, new color measurement was performed and the specimens were repolished and submitted to new color reading. Color stability was determined by the difference (ΔE between the coordinates L*, a*, and b* obtained from the specimens before and after immersion into the solutions and after repolishing. RESULTS: There was no statistically signifcant difference (ANOVA, Tukey's test; p>0.05 among the ΔE values for the different types of composites after staining or repolishing. For all composite resins, coffee promoted more color change (ΔE>3.3 than distilled water and the cola soft drink. After repolishing, the ΔE values of the specimens immersed in coffee decreased to clinically acceptable values (ΔE<3.3, but remained signifcantly higher than those of the other groups. CONCLUSIONS: No signifcant difference was found among composite resins or between color values before and after repolishing of specimens immersed in distilled water and cola. Immersing specimens in coffee caused greater color change in all types of composite resins tested in this study and repolishing contributed to decrease staining to clinically acceptable

  15. Existence and Asymptotic Stability of Periodic Solutions of the Reaction-Diffusion Equations in the Case of a Rapid Reaction

    Science.gov (United States)

    Nefedov, N. N.; Nikulin, E. I.

    2018-01-01

    A singularly perturbed periodic in time problem for a parabolic reaction-diffusion equation in a two-dimensional domain is studied. The case of existence of an internal transition layer under the conditions of balanced and unbalanced rapid reaction is considered. An asymptotic expansion of a solution is constructed. To justify the asymptotic expansion thus constructed, the asymptotic method of differential inequalities is used. The Lyapunov asymptotic stability of a periodic solution is investigated.

  16. Major satellite repeat RNA stabilize heterochromatin retention of Suv39h enzymes by RNA-nucleosome association and RNA

    NARCIS (Netherlands)

    Camacho, Oscar Velazquez; Galan, Carmen; Swist-Rosowska, Kalina; Ching, Reagan; Gamalinda, Michael; Karabiber, Fethullah; La Rosa-Velazquez, De Inti; Engist, Bettina; Koschorz, Birgit; Shukeir, Nicholas; Onishi-Seebacher, Megumi; De Nobelen, Van Suzanne; Jenuwein, Thomas

    2017-01-01

    The Suv39h1 and Suv39h2 histone lysine methyltransferases are hallmark enzymes at mammalian heterochromatin. We show here that the mouse Suv39h2 enzyme differs from Suv39h1 by containing an N-terminal basic domain that facilitates retention at mitotic chromatin and provides an additional affinity

  17. On stability of exponential cosmological solutions with non-static volume factor in the Einstein-Gauss-Bonnet model

    Energy Technology Data Exchange (ETDEWEB)

    Ivashchuk, V.D. [VNIIMS, Center for Gravitation and Fundamental Metrology, Moscow (Russian Federation); Peoples' Friendship University of Russia (RUDN University), Institute of Gravitation and Cosmology, Moscow (Russian Federation)

    2016-08-15

    A (n + 1)-dimensional gravitational model with Gauss-Bonnet term and a cosmological constant term is considered. When ansatz with diagonal cosmological metrics is adopted, the solutions with an exponential dependence of the scale factors, a{sub i} ∝ exp(v{sup i}t), i = 1,.., n, are analyzed for n > 3. We study the stability of the solutions with non-static volume factor, i.e. K(v) = sum {sub k=1}{sup n} v{sup k} ≠ 0. We prove that under a certain restriction R imposed solutions with K(v) > 0 are stable, while solutions with K(v) < 0 are unstable. Certain examples of stable solutions are presented. We show that the solutions with v{sup 1} = v{sup 2} = v{sup 3} = H > 0 and zero variation of the effective gravitational constant are stable if the restriction R is obeyed. (orig.)

  18. STABILITY OF DOW CORNING Q2-3183A ANTIFOAM IN IRRADIATED HYDROXIDE SOLUTION

    International Nuclear Information System (INIS)

    White, T.; Crawford, C.; Burket, P.; Calloway, B.

    2009-01-01

    Researchers at the Savannah River National Laboratory (SRNL) examined the stability of Dow Corning Q2-3183A antifoam to radiation and aqueous hydroxide solutions. Initial foam control studies with Hanford tank waste showed the antifoam reduced foaming. The antifoam was further tested using simulated Hanford tank waste spiked with antifoam that was heated and irradiated (2.1 x 10 4 rad/h) at conditions (90 C, 3 M NaOH, 8 h) expected in the processing of radioactive waste through the Waste Treatment and Immobilization Plant (WTP) at Hanford. After irradiation, the concentration of the major polymer components polydimethylsiloxane (PDMS) and polypropylene glycol (PPG) in the antifoam was determined by gel permeation chromatography (GPC). No loss of the major polymer components was observed after 24 h and only 15 wt% loss of PDMS was reported after 48 h. The presence of degradation products were not observed by gas chromatography (GC), gas chromatography mass spectrometry (GCMS) or high performance liquid chromatography mass spectrometry (HPLC-MS). G values were calculated from the GPC analysis and tabulated. The findings indicate the antifoam is stable for 24 h after exposure to gamma radiation, heat, and alkaline simulated waste

  19. First-principles thermodynamics study of phase stability in inorganic halide perovskite solid solutions

    Science.gov (United States)

    Bechtel, Jonathon S.; Van der Ven, Anton

    2018-04-01

    Halide substitution gives rise to a tunable band gap as a function of composition in halide perovskite materials. However, photoinduced phase segregation, observed at room temperature in mixed halide A Pb (IxBr1-x) 3 systems, limits open circuit voltages and decreases photovoltaic device efficiencies. We investigate equilibrium phase stability of orthorhombic P n m a γ -phase CsM (XxY1-x) 3 perovskites where M is Pb or Sn, and X and Y are Br, Cl, or I. Finite-temperature phase diagrams are constructed using a cluster expansion effective Hamiltonian parameterized from first-principles density-functional-theory calculations. Solid solution phases for CsM (IxBr1-x) 3 and CsM (BrxCl1-x) 3 are predicted to be stable well below room temperature while CsM (IxCl1-x) 3 systems have miscibility gaps that extend above 400 K. The height of the miscibility gap correlates with the difference in volume between end members. Also layered ground states are found on the convex hull at x =2 /3 for CsSnBr2Cl ,CsPbI2Br , and CsPbBrCl2. The impact of these ground states on the finite temperature phase diagram is discussed in the context of the experimentally observed photoinduced phase segregation.

  20. Plasma Creatine Kinetics After Ingestion of Microencapsulated Creatine Monohydrate with Enhanced Stability in Aqueous Solutions.

    Science.gov (United States)

    Hone, Michelle; Kent, Robert M; Scotto di Palumbo, Alessandro; Bleiel, Sinead B; De Vito, Giuseppe; Egan, Brendan

    2017-07-04

    Creatine monohydrate represents one of the largest sports supplement markets. Enhancing creatine (CRE) stability in aqueous solutions, such as with microencapsulation, represents innovation potential. Ten physically active male volunteers were randomly assigned in a double-blind design to either placebo (PLA) (3-g maltodextrin; n = 5) or microencapsulated CRE (3-g creatine monohydrate; n = 5) conditions. Experimental conditions involved ingestion of the samples in a 70-mL ready-to-drink format. CRE was delivered in a novel microencapsulation matrix material consisting entirely of hydrolyzed milk protein. Three hours after ingestion, plasma creatine concentrations were unchanged during PLA, and averaged ∼45 μM. During CRE, plasma creatine concentration peaked after 30 min at 101.6 ± 14.9 μM (p creatine concentration gradually trended downwards but remained significantly elevated (∼50% above resting levels) 3 hr after ingestion. These results demonstrate that the microencapsulated form of creatine monohydrate reported herein remains bioavailable when delivered in aqueous conditions, and has potential utility in ready-to-drink formulations for creatine supplementation.

  1. High Pressure Homogenization of Porcine Pepsin Protease: Effects on Enzyme Activity, Stability, Milk Coagulation Profile and Gel Development

    Science.gov (United States)

    Leite Júnior, Bruno Ricardo de Castro; Tribst, Alline Artigiani Lima; Cristianini, Marcelo

    2015-01-01

    This study investigated the effect of high pressure homogenization (HPH) (up to 190 MPa) on porcine pepsin (proteolytic and milk-clotting activities), and the consequences of using the processed enzyme in milk coagulation and gel formation (rheological profile, proteolysis, syneresis, and microstructure). Although the proteolytic activity (PA) was not altered immediately after the HPH process, it reduced during enzyme storage, with a 5% decrease after 60 days of storage for samples obtained with the enzyme processed at 50, 100 and 150 MPa. HPH increased the milk-clotting activity (MCA) of the enzyme processed at 150 MPa, being 15% higher than the MCA of non-processed samples after 60 days of storage. The enzyme processed at 150 MPa produced faster aggregation and a more consistent milk gel (G’ value 92% higher after 90 minutes) when compared with the non-processed enzyme. In addition, the gels produced with the enzyme processed at 150 MPa showed greater syneresis after 40 minutes of coagulation (forming a more compact protein network) and lower porosity (evidenced by confocal microscopy). These effects on the milk gel can be associated with the increment in MCA and reduction in PA caused by the effects of HPH on pepsin during storage. According to the results, HPH stands out as a process capable of changing the proteolytic characteristics of porcine pepsin, with improvements on the milk coagulation step and gel characteristics. Therefore, the porcine pepsin submitted to HPH process can be a suitable alternative for the production of cheese. PMID:25938823

  2. Stability of midazolam hydrochloride injection 1-mg/mL solutions in polyvinyl chloride and polyolefin bags.

    Science.gov (United States)

    Karlage, Kelly; Earhart, Zachary; Green-Boesen, Kelly; Myrdal, Paul B

    2011-08-15

    The stability of midazolam hydrochloride injection 1-mg/mL solutions in polyvinyl chloride (PVC) and polyolefin bags under varying conditions was evaluated. Triplicate solutions of midazolam hydrochloride 1-mg/mL were prepared in polyolefin and PVC i.v. bags by diluting midazolam hydrochloride injection 5 mg/mL with 5% dextrose injection. Bags were then stored under refrigeration (3-4 °C), exposed to light at room temperature (20-25 °C), or protected from light in amber bags at room temperature. Samples were taken immediately after preparation (day 0) and on days 1, 2, 3, 6, 13, 20, and 27 for analysis with a stability-indicating high-performance liquid chromatography assay in order to determine solution concentration. Stability was defined as retention of at least 90% of the initial drug concentration. The pH of each solution was also measured weekly. Sterility of the i.v. bags was determined at the end of the study by microbiological testing with culture in growth media. Differences in concentrations under the various storage conditions and bags used were analyzed using analysis of variance. All solutions retained over 98% of the initial midazolam hydrochloride concentration, with no statistically significant (p ≥ 0.05) change in concentration over the four-week period. Stability was not affected by temperature, exposure to light, or bag type. The pH of all solutions remained between 3.2 and 3.4 throughout the study. Sterility after 28 days was retained. Midazolam hydrochloride 1-mg/mL solutions diluted in 5% dextrose injection remained stable over 27 days in both polyolefin and PVC i.v. bags, regardless of storage condition.

  3. Influence of electric field on the properties of the polymer stabilized luminescent quantum dots in aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Zharkova, Irina S.; Markina, Natalia E. [Saratov State University, Astrakhanskaya 83, 410012 Saratov (Russian Federation); Markin, Alexey V., E-mail: av_markin@mail.ru [Saratov State University, Astrakhanskaya 83, 410012 Saratov (Russian Federation); Drozd, Daniil D.; Speranskaya, Elena S. [Saratov State University, Astrakhanskaya 83, 410012 Saratov (Russian Federation); Goryacheva, Irina Yu. [Saratov State University, Astrakhanskaya 83, 410012 Saratov (Russian Federation); Saint-Petersburg State University, Universitetskii pr. 26, 198504 Petrodvorets, Saint-Petersburg (Russian Federation)

    2016-08-15

    The application of external electric field for verification of quantum dots (QDs) stability in aqueous medium was proposed. Hydrophilic CdSe core-shell nanocrystals were synthesized and used with three polymer-based organic stabilizers, two of which contain PEG chains. An increasing of the stability under applied electric field (EF) was shown for stabilizer containing higher amount of PEG chains and terminal amino-groups: introduction of additional PEG chains allowed reducing degradation of luminescence intensity for about 60%. The changes of QDs solutions after EF treatment were examined by dynamic light scattering measurements, luminescence and absorbance spectroscopy, and conductivity measurements and explained by decreasing of quantum yield of the samples due to degradation of stabilizer coating. - Highlights: • Hydrophilic QDs with three types of stabilizer coatings were prepared and treated by electric field in water environment. • Permanent QDs luminescence quenching in aqueous medium under low electric field strength was observed. • Luminescence stability to EF treatment increases by stabilizer with higher PEG content. • Redox mechanism of luminescence quenching was proved via conductivity, DLS, and UV-visible absorbance measurements.

  4. Global Exponential Stability of Positive Almost Periodic Solutions for a Fishing Model with a Time-Varying Delay

    Directory of Open Access Journals (Sweden)

    Hong Zhang

    2014-01-01

    Full Text Available This paper is concerned with a nonautonomous fishing model with a time-varying delay. Under proper conditions, we employ a novel argument to establish a criterion on the global exponential stability of positive almost periodic solutions of the model with almost periodic coefficients and delays. Moreover, an example and its numerical simulation are given to illustrate the main results.

  5. On parametric domain for asymptotic stability with probability one of zero solution of linear Ito stochastic differential equations

    International Nuclear Information System (INIS)

    Phan Thanh An; Phan Le Na; Ngo Quoc Chung

    2004-05-01

    We describe a practical implementation for finding parametric domain for asymptotic stability with probability one of zero solution of linear Ito stochastic differential equations based on Korenevskij and Mitropolskij's sufficient condition and our sufficient conditions. Numerical results show that all of these sufficient conditions are crucial in the implementation. (author)

  6. Suzuki coupling reactions catalyzed by poly(N-ethyl-4-vinylpyridinium bromide stabilized palladium nanoparticles in aqueous solution

    Directory of Open Access Journals (Sweden)

    2008-04-01

    Full Text Available InIn this work, it was investigated to use of poly(N-ethyl-4-vinylpyridinium bromide stabilized palladium nanoparticles in the Suzuki reaction between phenylboronic acid and aryl halides in aqueous solution. The nanoparticles were isolated and re-used several times with low loss of activity.

  7. Capillary electrophoresis with indirect UV detection for the determination of stabilizers and citrates present in human albumin solutions.

    Science.gov (United States)

    Jaworska, Małgorzata; Cygan, Paulina; Wilk, Małgorzata; Anuszewska, Elzbieta

    2009-08-15

    Sodium caprylate and N-acetyltryptophan are the most frequently used stabilizers that protect the albumin from aggregation or heat induced denaturation. In turn citrates - excipients remaining after fractionation process - can be treated as by-product favoring leaching aluminum out of glass containers whilst albumin solution is stored. With ionic nature these substances have all the markings of a subject for capillary electrophoresis analysis. Thus CE methods were proposed as new approach for quality control of human albumin solution in terms of determination of stabilizers and citrates residue. Human albumin solutions both 5% and 20% from various manufacturers were tested. Indirect detection mode was set to provide sufficient detectability of analytes lacking of chromophores. As being anions analytes were separated with reversed electroosmotic flow. As a result of method optimization two background electrolytes based on p-hydroxybenzoic acid and 2,6-pyridinedicarboxylic acid were selected for stabilizers and citrates separation, respectively. The optimized methods were successfully validated. For citrates that require quantification below 100microM the method demonstrated the precision less than 4% and the limit of detection at 4microM. In order to check the new methods accuracy and applicability the samples were additionally tested with selected reference methods. The proposed methods allow reliable quantification of stabilizers and citrates in human albumin solution that was confirmed by method validation as well as result comparison with reference methods. The CE methods are considered to be suitable for quality control yet simplifying and reducing cost of analysis.

  8. Key factors influencing the stability of silane solution during long-term surface treatment on carbon steel

    International Nuclear Information System (INIS)

    Xian, Xiaochao; Chen, Minglu; Li, Lixin; Lin, Zhen; Xiang, Jun; Zhao, Shuo

    2013-01-01

    Highlights: •The corrosion-resistance time of silane films decreases with increasing cycle numbers. •The morphology of silane films prepared from aged solution is inhomogeneous. •Introduction of contamination ions is one reason for the poor property of aged solution. •Consumption of silane is the other reason for the poor property of aged solution. •Fe 3+ accumulated is the key factor influencing the property of silane solution. -- Abstract: The mixtures of bis-[trimethoxysilylpropyl]amine and vinyltriacetoxysilane were used for surface treatment of carbon steel, aiming to investigate the factors influencing the stability of silane solution during long-term experiment from two aspects. One is the concentrations of contamination ions, and the other is mass of silane consumed per cycle which is calculated according to concentration of Si measured by silicon molybdenum blue photometry. The results indicate that the accumulation of contamination ions, especially Fe 3+ , is the main factor leading to the condensation between the Si–OH groups in silane solution, which is responsible for the downward stability of silane solution

  9. A coupled conductive-convective thermo-poroelastic solution and implications for wellbore stability

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yarlong [Petro-Geotech Inc., Suite no.300, 840-6th Avenue, S.W., Calgary, AB (Canada) T2P 3E5; Dusseault, Maurice B. [Porous Media Research Institute, Department of Earth Sciences, University of Waterloo, Waterloo, ON (Canada) N2L 361

    2003-06-01

    Steam injection is widely used in heavy oil reservoirs to enhance oil recovery; elevated temperatures increase fluid mobility in several ways, but can also generate damage through shearing, crushing of weak grains, and casing impairment by shear, collapse, or buckling. Disposal of cold produced water by injection can generate thermally induced extensional fracturing, increasing the effective wellbore radius. Drilling with long open-hole sections can lead to rock temperature changes as large as 30-40 C at the casing shoe through mud heating at depth and upward mud circulation, dramatically impacting wellbore stability. Clearly, thermal stress analysis of open and cased boreholes is of primary interest for drilling and completion planning, as bottom-hole temperature changes can have as large an impact as bottom-hole pressure changes. Local wellbore stresses are the sum of far-field, pore pressure and thermally induced stresses; they may be highly inhomogeneous because of different rock properties and heat transport processes. These stresses, combined with thermal weakening and pore pressure changes, may lead to phenomena such as formation damage, sand production, shale shrinkage, and various modes of instability (shearing, spalling, fracturing, etc.). Previous studies of thermally induced stresses were primarily based on assumptions of low permeability and heat conduction only; this is inadequate when high-permeability formations are encountered. To analyze induced stresses and formation damage, a geomechanics model that is fully coupled to diffusive transport processes is employed. By assuming a constant wellbore pressure and temperature boundary condition, a closed-form solution including heat conduction and convection is obtained for the stresses near a cylindrical wellbore. The stability of an open-hole subject to non-isothermal, non-hydrostatic in situ loading and various conditions is then investigated. Our studies indicate that maximum tangential stresses are

  10. Effects of intermolecular interactions on the stability of carbon nanotube–gold nanoparticle conjugates in solution

    Directory of Open Access Journals (Sweden)

    Konczak L

    2016-11-01

    Full Text Available Lukasz Konczak,1 Jolanta Narkiewicz-Michalek,2 Giorgia Pastorin,3 Tomasz Panczyk1 1Institute of Catalysis and Surface Chemistry, Polish Academy of Sciences, Cracow, 2Department of Chemistry, Maria Curie-Sklodowska University, Lublin, Poland; 3Department of Pharmacy, National University of Singapore, Singapore Abstract: This work deals with the role of intermolecular interactions in the stability of a carbon nanotube (CNT capped by functionalized gold nanoparticles (AuNPs. The importance of such a system is due to its potential application as a pH-controlled drug carrier. Our preliminary experimental studies showed that fabrication of such a nanobottle/nanocontainer is feasible and it is possible to encapsulate the anticancer drug cisplatin inside the inner space of a CNT and seal its ends by functionalized AuNPs. The expected behavior, that is, detachment of AuNPs at acidic pH and the release of cisplatin, was, however, not observed. On the other hand, our theoretical studies of chemically identical system led to the conclusion that the release of cisplatin at acidic pH should be observed. Therefore, in this work, a deeper theoretical analysis of various factors that could be responsible for the disagreement between experimental and theoretical results were performed. The study found that the major factor is a large dispersion interaction component acting between CNT and AuNP in solution in the case of the experimental system. This factor can be controlled to some extent by tuning the system size or the ratio between AuNP diameter and CNT diameter. Thus, such kind of a pH-sensitive drug carrier is still of great interest, but its structural parameters need to be properly adjusted. Keywords: hydrazone bond, drug delivery, dispersion interactions, cisplatin, acidic pH

  11. Thermodynamic stability of binary systems involving metal ions and the 4-methoxy benzylidenepyruvate in aqueous solution

    International Nuclear Information System (INIS)

    Redigolo, H.

    1989-01-01

    A review on studies previously carried out in this laboratory involving metal ions and benzylidene-pyruvate, in aqueous solutions, is presented; emphasis is mainly placed on complexes comprising 4-Dimethyl-amino-benzylidene-pyruvate (DMBP, p K a 3.79) and 2-Chloro-4-Dimethyl-amino-benzylidene-pyruvate (2 Cl-DMBP, p k a = 3.08). In an endeavour to extend the previous work, the dissociation constant of 4-methoxy-benzylidene-pyruvic acid (H-4-Me O-BP) was determined spectrophotometrically at 25.0 +- 0.1 0 C and ionic strength 0.500 M, held with sodium perchlorate (p k a = 1.473). The complex formation equilibria in M-4-Me O-BP systems, where M = Cu(II), La(III), Pr(III), Sm(III), Lu(III), Sc (III), In(III), Ga(III) or Th(IV) were investigated, also spectrophotometrically, in the above mentioned experimental conditions. In addition, the system involving Sm(III) was reinvestigated at ionic strengths 0.100 and 2.00 M, the remaining experimental conditions being maintained. The study is mostly concerned with the determination of formation constants of 1:1 complex species (β 1 ) and spectrophotometric parameters associated with these species. The investigation of possible higher binary complexes (ML n , n > 1) was prevented by solubility limitations. For all considered metal ions, log β 1 (DMBP) > log β 1 (4-Me O-BP) indicating that the stability is governed, at least in part, by ligand basicity. (author). 121 refs, 36 figs, 20 tabs

  12. The stability of DLC film on nitrided CoCrMo alloy in phosphate buffer solution

    International Nuclear Information System (INIS)

    Zhang, T.F.; Liu, B.; Wu, B.J.; Liu, J.; Sun, H.; Leng, Y.X.; Huang, N.

    2014-01-01

    CoCrMo alloy is often used as the material for metal artificial joint, but metal debris and metal ions are the main concern on tissue inflammation or tissue proliferation for metal prosthesis. In this paper, nitrogen ion implantation and diamond like carbon (DLC) film composite treatment was used to reduce the wear and ion release of biomedical CoCrMo substrate. The mechanical properties and stability of N-implanted/DLC composite layer in phosphate buffer solution (PBS) was evaluated to explore the full potential of N-implanted/DLC composite layer as an artificial joint surface modification material. The results showed that the DLC film on N implanted CoCrMo (N-implanted/DLC composite layer) had the higher surface hardness and wear resistance than the DLC film on virgin CoCrMo alloy, which was resulted from the strengthen effect of the N implanted layer on CoCrMo alloy. After 30 days immersion in PBS, the structure of DLC film on virgin CoCrMo or on N implanted CoCrMo had no visible change. But the adhesion and corrosion resistance of DLC on N implanted CoCrMo (N-implanted/DLC composite layer) was weakened due to the dissolution of the N implanted layer after 30 days immersion in PBS. The adhesion reduction of N-implanted/DLC composite layer was adverse for in vivo application in long term. So researcher should be cautious to use N implanted layer as an inter-layer for increasing CoCrMo alloy load carrying capacity in vivo environment.

  13. Stability of the neurotensin receptor NTS1 free in detergent solution and immobilized to affinity resin.

    Directory of Open Access Journals (Sweden)

    Jim F White

    2010-09-01

    Full Text Available Purification of recombinant membrane receptors is commonly achieved by use of an affinity tag followed by an additional chromatography step if required. This second step may exploit specific receptor properties such as ligand binding. However, the effects of multiple purification steps on protein yield and integrity are often poorly documented. We have previously reported a robust two-step purification procedure for the recombinant rat neurotensin receptor NTS1 to give milligram quantities of functional receptor protein. First, histidine-tagged receptors are enriched by immobilized metal affinity chromatography using Ni-NTA resin. Second, remaining contaminants in the Ni-NTA column eluate are removed by use of a subsequent neurotensin column yielding pure NTS1. Whilst the neurotensin column eluate contained functional receptor protein, we observed in the neurotensin column flow-through misfolded NTS1.To investigate the origin of the misfolded receptors, we estimated the amount of functional and misfolded NTS1 at each purification step by radio-ligand binding, densitometry of Coomassie stained SDS-gels, and protein content determination. First, we observed that correctly folded NTS1 suffers damage by exposure to detergent and various buffer compositions as seen by the loss of [(3H]neurotensin binding over time. Second, exposure to the neurotensin affinity resin generated additional misfolded receptor protein.Our data point towards two ways by which misfolded NTS1 may be generated: Damage by exposure to buffer components and by close contact of the receptor to the neurotensin affinity resin. Because NTS1 in detergent solution is stabilized by neurotensin, we speculate that the occurrence of aggregated receptor after contact with the neurotensin resin is the consequence of perturbations in the detergent belt surrounding the NTS1 transmembrane core. Both effects reduce the yield of functional receptor protein.

  14. Radiation inactivation of angiotensin-converting enzyme in solutions. Communication 3. The effect of NaCl

    International Nuclear Information System (INIS)

    Orlova, M.A.; Kost, O.A.; Nikol'skaya, I.I.; Troshina, N.N.; Binevskij, P.V.

    1999-01-01

    The effect of 0-0.15 M NaCl on the dose response of angiotensin-converting enzyme is described. The data represented at three-dimensional surfaces demonstrate the existence of special areas where definite mechanisms of dose response are predominant. In acidic and alkaline media, the regions of high values of enzyme activation can be emphasized; moreover, the oscillations of enzyme activity can also be detected. At pH 7.5, when angiotensin-converting enzyme conformation is less rigid, activation peaks on the three-dimensional surface are less pronounced indicating the decreasing effect of NaCl on dose response at this pH value [ru

  15. Novel photoluminescence enzyme immunoassay based on supramolecular host-guest recognition using L-arginine/6-aza-2-thiothymine-stabilized gold nanocluster.

    Science.gov (United States)

    Wang, Youmei; Lu, Minghua; Tang, Dianping

    2018-06-30

    A new photoluminescence (PL) enzyme immunoassay was designed for sensitive detection of aflatoxin B 1 (AFB 1 ) via an innovative enzyme substrate, 6-aza-2-thiothymine-stabilized gold nanocluster (AAT-AuNC) with L-arginine. The enzyme substrate with strong PL intensity was formed through supramolecular host-guest assembly between guanidine group of L-arginine and AAT capped on the surface of AuNC. Upon arginase introduction, the captured L-arginine was hydrolyzed into ornithine and urea, thus resulting in the decreasing PL intensity. Based on this principle, a novel competitive-type immunoreaction was first carried out on AFB 1 -bovine serum albumin (AFB 1 -BSA) conjugate-coated microplate, using arginase-labeled anti-AFB 1 antibody as the competitor. Under the optimum conditions, the PL intensity increased with the increment of target AFB 1 , and allowed the detection of the analyte at concentrations as low as 3.2 pg mL -1 (ppt). Moreover, L-arginine-AAT-AuNC-based PL enzyme immunoassay afforded good reproducibility and acceptable specificity. In addition, the accuracy of this methodology, referring to commercial AFB 1 ELISA kit, was evaluated to analyze naturally contaminated or spiked peanut samples, giving well-matched results between two methods, thus representing a useful scheme for practical application in quantitative monitoring of mycotoxins in foodstuff. Copyright © 2018 Elsevier B.V. All rights reserved.

  16. The influences of inoculants from municipal sludge and solid waste on compost stability, maturity and enzyme activities during chicken manure composting.

    Science.gov (United States)

    Li, Shuyan; Li, Jijin; Yuan, Jing; Li, Guoxue; Zang, Bing; Li, Yangyang

    2017-07-01

    The aim of this study was to investigate the influence of inoculants on compost stability, maturity and enzyme activities during composting of chicken manure and cornstalk. Two microbial inoculants (originated from aerobic municipal sludge and municipal solid waste, respectively) were used in composting at the rate of 0.3% of initial raw materials (wet weight). No microbial inoculums were added to the control. The experiment was conducted under aerobic conditions for 53 days. The results show that enzyme activity is an important index to comprehensively evaluate the composting stability and maturity. Microbes originated from sludge works best in terms of composting stability and maturity (C:N ratio decreased from 15.5 to 10, and germination index increased to 109%). Microbial inoculums originated from sludge and municipal solid waste extended the time of thermophilic phase for 11 and 7 days, respectively. Microbial inoculums originated from sludge and MSW significantly increased the average of catalase activity (by 15.0% and 12.1%, respectively), urease activity (by 21.5% and 12.2%, respectively) and cellulase activity (by 32.1% and 26.1%, respectively) during composting.

  17. Controlling Microstructure of Yttria-Stabilized Zirconia Prepared from Suspensions and Solutions by Plasma Spraying with High Feed Rates.

    Czech Academy of Sciences Publication Activity Database

    Mušálek, Radek; Medřický, Jan; Tesař, Tomáš; Kotlan, Jiří; Pala, Zdeněk; Lukáč, František; Illková, Ksenia; Hlína, Michal; Chráska, Tomáš; Sokołowski, P.; Curry, N.

    2017-01-01

    Roč. 26, č. 8 (2017), s. 1787-1803 ISSN 1059-9630 R&D Projects: GA ČR GA15-12145S Institutional support: RVO:61389021 Keywords : hybrid plasma torch * microstructure * solution * precursor spraying * suspension spraying * thermal barrier * coatings (TBCs) * water-stabilized plasma * yttria-stabilized zirconia (YSZ) Subject RIV: JK - Corrosion ; Surface Treatment of Materials OBOR OECD: Coating and films Impact factor: 1.488, year: 2016 https://link.springer.com/ article /10.1007/s11666-017-0622-x

  18. Stability of Benzotriazole Derivatives with Free Cu, Zn, Co and Metal-Containing Enzymes: Binding and Interaction of Methylbenzotriazoles with Superoxide Dismutase and Vitamin B12

    Science.gov (United States)

    Abudalo, R. A.; AbuDalo, M. A.; Hernandez, M. T.

    2018-02-01

    Benzotriazole derivatives form very strong bonds with transition metals, and are the most widely used type of industrial corrosion inhibitor. Some benzotriazole derivatives have been implicated as hormone regulators which also carry the ability to induce uncoupling responses or otherwise inhibit respiration processes in some microorganisms. However, the mechanisms associated with benzotriazole toxicity and inhibition are unknown. Using Differential Pulse Polarography, the stability constants of commercially significant corrosion inhibitors, 4-and 5-methylbenzotriazole, coordinated with free Cu (II) and Co (III), were determined to be 1015 and 108, respectively. Polarographic analyses were extended to confirm that methylbenzotriazole also binds the copper center(s) in the ubiquitous enzyme superoxide dismutase, and the Corrin site in the coenzyme cobalamin (vitamin B12). These results suggest that the metal-chelating ability of this unique class of compounds may confer inhibition to certain enzyme systems.

  19. Existence and global exponential stability of periodic solution of memristor-based BAM neural networks with time-varying delays.

    Science.gov (United States)

    Li, Hongfei; Jiang, Haijun; Hu, Cheng

    2016-03-01

    In this paper, we investigate a class of memristor-based BAM neural networks with time-varying delays. Under the framework of Filippov solutions, boundedness and ultimate boundedness of solutions of memristor-based BAM neural networks are guaranteed by Chain rule and inequalities technique. Moreover, a new method involving Yoshizawa-like theorem is favorably employed to acquire the existence of periodic solution. By applying the theory of set-valued maps and functional differential inclusions, an available Lyapunov functional and some new testable algebraic criteria are derived for ensuring the uniqueness and global exponential stability of periodic solution of memristor-based BAM neural networks. The obtained results expand and complement some previous work on memristor-based BAM neural networks. Finally, a numerical example is provided to show the applicability and effectiveness of our theoretical results. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Conditional Stability of Solitary-Wave Solutions for Generalized Compound KdV Equation and Generalized Compound KdV-Burgers Equation

    International Nuclear Information System (INIS)

    Zhang Weiguo; Dong Chunyan; Fan Engui

    2006-01-01

    In this paper, we discuss conditional stability of solitary-wave solutions in the sense of Liapunov for the generalized compound KdV equation and the generalized compound KdV-Burgers equations. Linear stability of the exact solitary-wave solutions is proved for the above two types of equations when the small disturbance of travelling wave form satisfies some special conditions.

  1. Zirconium-cerin solid solutions: thermodynamic model and thermal stability at high temperature; Solutions solides de zirconium dans la cerine: modele thermodynamique et stabilite thermique a haute temperature

    Energy Technology Data Exchange (ETDEWEB)

    Janvier, C.

    1998-04-02

    The oxides-gaseous dioxygen equilibria and the textural thermal stability of six zirconium-cerin solutions Ce{sub 1-x}Zr{sub x}O{sub 2} (0solutions and the gaseous oxygen by thermal gravimetric analysis at 600 degrees Celsius has shown that these solutions have not a ideal behaviour. A thermodynamic model where the point defects of solutions are included describe them the best. It becomes then possible to know the variations of the concentrations of the point defects in terms of temperature, oxygen pressure and zirconium concentration. A kinetic study (by calcination at 950 degrees Celsius of the solid solutions) of the specific surface area decrease has revealed a minima (0

  2. Biological and physicochemical stability of ceftazidime and aminophylline on glucose parenteral solution

    Directory of Open Access Journals (Sweden)

    Carolina Alves dos Santos

    2012-12-01

    Full Text Available Ceftazidime is a broad spectrum antibiotic administered mainly by the parenteral route, and it is especially effective against Pseudomonas aeruginosa. The period of time in which serum levels exceed the Minimum Inhibitory Concentration (MIC is an important pharmacodynamic parameter for its efficacy. One of the forms to extend this period is to administer the antibiotic by continuous infusion, after prior dilution in a Parenteral Solution (PS. The present work assessed the stability of ceftazidime in 5% glucose PS for 24 hours, combined or not with aminophylline, through High Performance Liquid Chromatography (HPLC. The physicochemical evaluation was accompanied by in vitro antimicrobial activity compared MIC test in the 24-hour period. Escherichia coli and Pseudomonas aeruginosa were the microorganisms chosen for the MIC comparison. The HPLC analysis confirmed ceftazidime and aminophylline individual stability on PS, while the MIC values were slightly higher than the mean described in the literature. When both drugs were associated in the same PS, the ceftazidime concentration by HPLC decreased 25% after 24 hours. Not only did the MIC values show high loss of antibiotic activity within the same period, but also altered MIC values immediately after the preparation, which was not detected by HPLC. Our results indicate that this drug combination is not compatible, even if used right away, and that PS might not be the best vehicle for ceftazidime, emphasizing the importance of the MIC evaluation for drug interactions.Ceftazidima é um antimicrobiano administrado por via parenteral, que apresenta amplo espectro de ação, principalmente contra Pseudomonas aeruginosa. O tempo em que a concentração sérica de ceftazidima permanece acima da concentração mínima inibitória (MIC é um importante parâmetro farmacodinâmico para a determinação da eficácia antimicrobiana e pode ser potencializado através da utilização de infusão contínua em

  3. A DFT study of the stability of SIAs and small SIA clusters in the vicinity of solute atoms in Fe

    Science.gov (United States)

    Becquart, C. S.; Ngayam Happy, R.; Olsson, P.; Domain, C.

    2018-03-01

    The energetics, defect volume and magnetic properties of single SIAs and small SIA clusters up to size 6 have been calculated by DFT for different configurations like the parallel 〈110〉 dumbbell, the non parallel 〈110〉 dumbbell and the C15 structure. The most stable configurations of each type have been further analyzed to determine the influence on their stability of various solute atoms (Ti, V, Cr, Mn, Co, Ni, Cu, Mo, W, Pd, Al, Si, P), relevant for steels used under irradiation. The results show that the presence of solute atoms does not change the relative stability order among SIA clusters. The small SIA clusters investigated can bind to both undersized and oversized solutes. Several descriptors have been considered to derive interesting trends from results. It appears that the local atomic volume available for the solute is the main physical quantity governing the binding energy evolution, whatever the solute type (undersized or oversized) and the cluster configuration (size and type).

  4. Investigation into the temporal stability of aqueous standard solutions of psilocin and psilocybin using high performance liquid chromatography.

    Science.gov (United States)

    Anastos, N; Barnett, N W; Pfeffer, F M; Lewis, S W

    2006-01-01

    This paper reports an investigation into the temporal stability of aqueous solutions of psilocin and psilocybin reference drug standards over a period of fourteen days. This study was performed using high performance liquid chromatography utilising a (95:5% v/v) methanol: 10 mM ammonium formate, pH 3.5 mobile phase and absorption detection at 269 nm. It was found that the exclusion of light significantly prolonged the useful life of standards, with aqueous solutions of both psilocin and psilocybin being stable over a period of seven days.

  5. Chapter 1. Bending the Curve: Ten Scalable Solutions for Carbon Neutrality and Climate Stability

    Directory of Open Access Journals (Sweden)

    V. Ramanathan

    2016-12-01

    Full Text Available We are living in a world of over seven billion people, with annual greenhouse gas emissions of approximately 50 billion tons a year and rising steadily. If continued unabated, the world is on target to warm by about 2 °C in less than 40 years, pushing the climate to a regime unlike any that has been witnessed in the last million years. Nonetheless, we still have time to avert such a catastrophic scenario, or delay its occurrence by several decades to provide human societies and the ecosystem with the time to adjust. In order to mitigate the possibility of climate disruption, we need to recognize that fossil fuel based technologies have become outdated and transform the energy system to that of low-carbon, sustainable and secure energy systems. In addition, we have to mitigate emissions of the four short-lived climate pollutants to bring immediate relief from climate change and protect vulnerable societies. Stability of the climate system involves not only the centrality of scientific and technological advancements and investments, but also necessary shifts in social structure and behavior by individuals, communities and societies worldwide as well as market based instruments, sub-national collaborations and governance structure. Fortunately, living laboratories—such as the State of California and the University of California system, which has pledged to become carbon neutral by 2025—provide demonstrable solutions which hold promise in alleviating the climate warming in the next generation. These jurisdictions are tiny emitters in the global picture, but they offer the potential for leverage through demonstrating (Figure 1 new technologies as well as workable institutions that cut emissions. We outline 10 pragmatic solutions—a “kit of parts” rooted in California but scalable to the world—that taken together, can “bend the curve” of the upward trajectory of human-caused warming trends. Wholesale transformation of our current

  6. Engineering solutions to the long-term stabilization and isolation of uranium mill tailings in the United States

    International Nuclear Information System (INIS)

    Sanders, D.R.; Lommler, J.C.

    1995-01-01

    Engineering solutions to the safe and environmentally protective disposal and isolation of uranium mill tailings in the US include many factors. Cover design, materials selection, civil engineering, erosive forces, and cost effectiveness are only a few of those factors described in this paper. The systems approach to the engineering solutions employed in the US is described, with emphasis on the standards prescribed for the Uranium Mill Tailings Remedial Action Project. Stabilization and isolation of the tailings from humans and the environment are the primary goals of the US uranium mill tailings control standards. The performance of cover designs with respect to water infiltration, radon exhalation, geotechnical stability, erosion protection, human and animal intrusion prevention, and longevity are addressed. The need for and frequency of surveillance efforts to ensure continued disposal system performance are also assessed

  7. Stability of small-amplitude periodic solutions near Hopf bifurcations in time-delayed fully-connected PLL networks

    Science.gov (United States)

    Ferruzzo Correa, Diego P.; Bueno, Átila M.; Castilho Piqueira, José R.

    2017-04-01

    In this paper we investigate stability conditions for small-amplitude periodic solutions emerging near symmetry-preserving Hopf bifurcations in a time-delayed fully-connected N-node PLL network. The study of this type of systems which includes the time delay between connections has attracted much attention among researchers mainly because the delayed coupling between nodes emerges almost naturally in mathematical modeling in many areas of science such as neurobiology, population dynamics, physiology and engineering. In a previous work it has been shown that symmetry breaking and symmetry preserving Hopf bifurcations can emerge in the parameter space. We analyze the stability along branches of periodic solutions near fully-synchronized Hopf bifurcations in the fixed-point space, based on the reduction of the infinite-dimensional space onto a two-dimensional center manifold in normal form. Numerical results are also presented in order to confirm our analytical results.

  8. Heat stability of strawberry anthocyanins in model solutions containing natural copigments extracted from rose (Rosa damascena Mill.) petals.

    Science.gov (United States)

    Shikov, Vasil; Kammerer, Dietmar R; Mihalev, Kiril; Mollov, Plamen; Carle, Reinhold

    2008-09-24

    Thermal degradation and color changes of purified strawberry anthocyanins in model solutions were studied upon heating at 85 degrees C by HPLC-DAD analyses and CIELCh measurements, respectively. The anthocyanin half-life values increased significantly due to the addition of rose (Rosa damascena Mill.) petal extracts enriched in natural copigments. Correspondingly, the color stability increased as the total color difference values were smaller for anthocyanins upon copigment addition, especially after extended heating. Furthermore, the stabilizing effect of rose petal polyphenols was compared with that of well-known copigments such as isolated kaempferol, quercetin, and sinapic acid. The purified rose petal extract was found to be a most effective anthocyanin-stabilizing agent at a molar pigment/copigment ratio of 1:2. The results obtained demonstrate that the addition of rose petal polyphenols slows the thermal degradation of strawberry anthocyanins, thus resulting in improved color retention without affecting the gustatory quality of the product.

  9. Effects of sorbitol and glycerol on the structure, dynamics, and stability of Mycobacterium tuberculosis pyrazinamidase

    Directory of Open Access Journals (Sweden)

    Mehrnoosh Khajehzadeh

    2016-01-01

    Conclusion: It can be concluded that the native conformation of the enzyme was stabilized in the sorbitol and glycerol and tend to exclude from the PZase surface, forcing the enzyme to keep it in the compactly folded conformation. The glycerol molecules stabilized PZase by decreasing the loops flexibility and then compacting the enzyme structure. It appears that more stability of PZase in glycerol solution correlates with its amphiphilic orientation, which decreases the unfavorable interactions of hydrophobic regions.

  10. A Review on the Effects of Supercritical Carbon Dioxide on Enzyme Activity

    Directory of Open Access Journals (Sweden)

    Marie Zarevúcka

    2010-01-01

    Full Text Available Different types of enzymes such as lipases, several phosphatases, dehydrogenases, oxidases, amylases and others are well suited for the reactions in SC-CO2. The stability and the activity of enzymes exposed to carbon dioxide under high pressure depend on enzyme species, water content in the solution and on the pressure and temperature of the reaction system. The three-dimensional structure of enzymes may be significantly altered under extreme conditions, causing their denaturation and consequent loss of activity. If the conditions are less adverse, the protein structure may be largely retained. Minor structural changes may induce an alternative active protein state with altered enzyme activity, specificity and stability.

  11. Simultaneous and continuous stabilization of As and Pb in contaminated solution and soil by a ferrihydrite-gypsum sorbent.

    Science.gov (United States)

    Kameda, Kentaro; Hashimoto, Yohey; Wang, Shan-Li; Hirai, Yasumasa; Miyahara, Hidetaka

    2017-04-05

    For the increasing need of stabilization both cationic and anionic metal(loid)s simultaneously, we newly developed a metal sorbent (FIXALL), consisting mainly of ferrihydrite and gypsum. The objectives of this study were to determine the molecular mechanisms of Pb and As stabilization in an aqueous system and to examine a simultaneous and long-term (up to 754days) effect on Pb and As stabilization in an anthropogenically contaminated soil using the FIXALL sorbent. When the solution contained a low concentration of Pb (5mgL -1 ), the mechanisms of Pb removal by FIXALL were based chiefly on the formation of inner-sphere surface complex with ferrihydrite. In the highly concentrated Pb solution (1200mgL -1 ), contrarily, the removal of Pb by FIXALL was the direct consequence of the dissolution of gypsum and subsequent precipitation of PbSO 4 , which strengthens the drawback of low capability of ferrihydrite for Pb removal. Regardless of initial concentrations, the primary mechanism of FIXALL for As stabilization is attributed to the formation of inner-sphere surface complex with ferrihydrite. A contaminated soil study demonstrated that FIXALL could decrease the concentration of water soluble As and Pb simultaneously and continuously for 754days without notable changes in their chemical species and soil pH. Copyright © 2016 Elsevier B.V. All rights reserved.

  12. Orbital stability of periodic traveling-wave solutions for the log-KdV equation

    Science.gov (United States)

    Natali, Fábio; Pastor, Ademir; Cristófani, Fabrício

    2017-09-01

    In this paper we establish the orbital stability of periodic waves related to the logarithmic Korteweg-de Vries equation. Our motivation is inspired in the recent work [3], in which the authors established the well-posedness and the linear stability of Gaussian solitary waves. By using the approach put forward recently in [20] to construct a smooth branch of periodic waves as well as to get the spectral properties of the associated linearized operator, we apply the abstract theories in [13] and [25] to deduce the orbital stability of the periodic traveling waves in the energy space.

  13. Stabilization of enzymes activities of lipoxygenase pathway by irradiation to improve the production of olive oil aroma

    International Nuclear Information System (INIS)

    Musrati, Imen

    2009-01-01

    The main purpose of this work was to improve the synthesis of volatile compounds leading to green note in olives and olive tree leaves by improving enzymes activities of lipoxygenase pathway. Lipoxygenase (LOX), hydroperoxyde lyase (HPL) and alcohol dehydrogenase (ADH) activities were tested in olives and olive tree leaves during maturation. The gamma irradiation effects on these samples were studied. LOX, HPL and ADH showed maximum activities at black stage for olives and in December for olive leaves. Those activities, from olives and Chemlali olive leaves, were improved after irradiation with 0,5KGy. For the case of Chetoui olive leaves, the irradiation treatment was unfavorable because it causes a loss in enzymes activities. (Author)

  14. Existence and exponential stability of almost periodic solution for stochastic cellular neural networks with delay

    International Nuclear Information System (INIS)

    Huang Zaitang; Yang Qigui

    2009-01-01

    The paper considers the problems of existence of quadratic mean almost periodic and global exponential stability for stochastic cellular neural networks with delays. By employing the Holder's inequality and fixed points principle, we present some new criteria ensuring existence and uniqueness of a quadratic mean almost periodic and global exponential stability. These criteria are important in signal processing and the design of networks. Moreover, these criteria are also applied in others stochastic biological neural systems.

  15. Determination of Required Ion Exchange Solution for Stabilizing Clayey Soils with Various PI

    OpenAIRE

    R. Ziaie Moayed; F. Allahyari

    2012-01-01

    Soil stabilization has been widely used to improve soil strength and durability or to prevent erosion and dust generation. Generally to reduce problems of clayey soils in engineering work and to stabilize these soils additional materials are used. The most common materials are lime, fly ash and cement. Using this materials, although improve soil property , but in some cases due to financial problems and the need to use special equipment are limited .One of the best method...

  16. Stabilization of the solution of a doubly nonlinear parabolic equation

    International Nuclear Information System (INIS)

    Andriyanova, È R; Mukminov, F Kh

    2013-01-01

    The method of Galerkin approximations is employed to prove the existence of a strong global (in time) solution of a doubly nonlinear parabolic equation in an unbounded domain. The second integral identity is established for Galerkin approximations, and passing to the limit in it an estimate for the decay rate of the norm of the solution from below is obtained. The estimates characterizing the decay rate of the solution as x→∞ obtained here are used to derive an upper bound for the decay rate of the solution with respect to time; the resulting estimate is pretty close to the lower one. Bibliography: 17 titles

  17. Structural stability of Riemann solutions for strictly hyperbolic systems with three piecewise constant states

    Directory of Open Access Journals (Sweden)

    Xuefeng Wei

    2016-12-01

    Full Text Available This article concerns the wave interaction problem for a strictly hyperbolic system of conservation laws whose Riemann solutions involve delta shock waves. To cover all situations, the global solutions are constructed when the initial data are taken as three piecewise constant states. It is shown that the Riemann solutions are stable with respect to a specific small perturbation of the Riemann initial data. In addition, some interesting nonlinear phenomena are captured during the process of constructing the solutions, such as the generation and decomposition of delta shock waves.

  18. Low Operational Stability of Enzymes in Dry Organic Solvents: Changes in the Active Site Might Affect Catalysis

    Directory of Open Access Journals (Sweden)

    Gabriel Barletta

    2012-02-01

    Full Text Available The potential of enzyme catalysis in organic solvents for synthetic applications has been overshadowed by the fact that their catalytic properties are affected by organic solvents. In addition, it has recently been shown that an enzyme’s initial activity diminishes considerably after prolonged exposure to organic media. Studies geared towards understanding this last drawback have yielded unclear results. In the present work we decided to use electron paramagnetic resonance spectroscopy (EPR to study the motion of an active site spin label (a nitroxide free radical during 96 h of exposure of the serine protease subtilisin Carlsberg to four different organic solvents. Our EPR data shows a typical two component spectra that was quantified by the ratio of the anisotropic and isotropic signals. The isotropic component, associated with a mobile nitroxide free radical, increases during prolonged exposure to all solvents used in the study. The maximum increase (of 43% was observed in 1,4-dioxane. Based on these and previous studies we suggest that prolonged exposure of the enzyme to these solvents provokes a cascade of events that could induce substrates to adopt different binding conformations. This is the first EPR study of the motion of an active-site spin label during prolonged exposure of an enzyme to organic solvents ever reported.

  19. Influence of biopolymers on the solubility of branched-chain amino acids and stability of their solutions.

    Science.gov (United States)

    Hong, Chi Rac; Lee, Gyu Whan; Paik, Hyun-Dong; Chang, Pahn-Shick; Choi, Seung Jun

    2018-01-15

    This study confirmed the possibility of biopolymer-type stabilizers to increase the saturation concentration of branched-chain amino acids by preventing their crystallization/precipitation. Although microfluidization increased the initial solubility, it failed to increase the saturation concentration of the branched-chain amino acids. The saturation concentration of the branched-chain amino acids increased from 3.81% to 4.42% and 4.85% after the incorporation of food hydrocolloids and proteins, respectively. However, the branched-chain amino acids:stabilizer ratio did not affect the solubility. In the case of food hydrocolloid-based solutions, crystal formation and growth of branched-chain amino acids occurred during storage, resulting in the precipitation of branched-chain amino acid crystals. However, food proteins effectively increased the stability of the solubilized branched-chain amino acids. The improved solubility and stability of the solubilized branched-chain amino acids could be attributed to interactions between the functional groups (carboxyl, amine, sulfate, aliphatic, aromatic, etc.) of the stabilizer and the branched-chain amino acid molecules. Copyright © 2017 Elsevier Ltd. All rights reserved.

  20. Natural Variants of the KPC-2 Carbapenemase have Evolved Increased Catalytic Efficiency for Ceftazidime Hydrolysis at the Cost of Enzyme Stability.

    Directory of Open Access Journals (Sweden)

    Shrenik C Mehta

    2015-06-01

    Full Text Available The spread of β-lactamases that hydrolyze penicillins, cephalosporins and carbapenems among Gram-negative bacteria has limited options for treating bacterial infections. Initially, Klebsiella pneumoniae carbapenemase-2 (KPC-2 emerged as a widespread carbapenem hydrolyzing β-lactamase that also hydrolyzes penicillins and cephalosporins but not cephamycins and ceftazidime. In recent years, single and double amino acid substitution variants of KPC-2 have emerged among clinical isolates that show increased resistance to ceftazidime. Because it confers multi-drug resistance, KPC β-lactamase is a threat to public health. In this study, the evolution of KPC-2 function was determined in nine clinically isolated variants by examining the effects of the substitutions on enzyme kinetic parameters, protein stability and antibiotic resistance profile. The results indicate that the amino acid substitutions associated with KPC-2 natural variants lead to increased catalytic efficiency for ceftazidime hydrolysis and a consequent increase in ceftazidime resistance. Single substitutions lead to modest increases in catalytic activity while the double mutants exhibit significantly increased ceftazidime hydrolysis and resistance levels. The P104R, V240G and H274Y substitutions in single and double mutant combinations lead to the largest increases in ceftazidime hydrolysis and resistance. Molecular modeling suggests that the P104R and H274Y mutations could facilitate ceftazidime hydrolysis through increased hydrogen bonding interactions with the substrate while the V240G substitution may enhance backbone flexibility so that larger substrates might be accommodated in the active site. Additionally, we observed a strong correlation between gain of catalytic function for ceftazidime hydrolysis and loss of enzyme stability, which is in agreement with the 'stability-function tradeoff' phenomenon. The high Tm of KPC-2 (66.5°C provides an evolutionary advantage as

  1. Application of membrane LaF3 electrode in the determination of stability constants of Uranyl Fluoride complex in solution

    International Nuclear Information System (INIS)

    Muzakky; Iswani GS; Mintolo

    1996-01-01

    A membrane electrode LaF 3 has been applied in the determination of uranyl fluoride complex stability constant in solution. The determination is based on the detection of free F ion in solution as a result of hydrolysis reaction (process) of uranyl ions into the uranyl hydroxide form at low pH. The experiment results showed that there was no effect of ammonium carbonate 2 M titran, flow rate on the electrode response. The F release is optimum at pH 1. The free F ion in solution is calculated from the standard curve at pH 1, after the fluoride concentration at the same pH has been corrected. Using the plot of average number of ligand binding (n) versus minus log of free ligand (-log F) the value of β1 = 4.4, β2 = 7.48, β3=9.73, and β4 = 11.67

  2. Stationary solution of the compressible magnetohydrodynamic equation and its stability with respect to initial disturbance

    Directory of Open Access Journals (Sweden)

    WU Renchao

    2016-06-01

    Full Text Available In this paper, we consider three dimensional compressible viscous magnetohydro dynamic equations(MHD with external potentialforce. We first derive the corresponding non-constantstationary solutions. Then we show global well-posedness of the initial value problem for the three dimensional compressible viscous magnetohydrodynamic equations, provided that rescribed initial data is close to the stationary solution.

  3. Stability of Solutions of Parabolic PDEs with Random Drift and Viscosity Limit

    International Nuclear Information System (INIS)

    Deck, T.; Potthoff, J.; Vage, G.; Watanabe, H.

    1999-01-01

    Let u α be the solution of the Ito stochastic parabolic Cauchy problem ∂u/∂t - L =ξ.∇u,u , where ξ is a space-time noise. We prove that u α depends continuously on α , when the coefficients in L α converge to those in L 0 . This result is used to study the diffusion limit for the Cauchy problem in the Stratonovich sense: when the coefficients of L α tend to 0 the corresponding solutions u α converge to the solution u 0 of the degenerate Cauchy problem ∂u 0 /∂t=ξ o ∇u 0 , u o . These results are based on a criterion for the existence of strong limits in the space of Hida distributions (S) * . As a by-product it is proved that weak solutions of the above Cauchy problem are in fact strong solutions

  4. Stability of fortified cefazolin ophthalmic solutions prepared in artificial tears containing surfactant-based versus oxidant-based preservatives.

    Science.gov (United States)

    Rojanarata, Theerasak; Tankul, Junlathip; Woranaipinich, Chayanee; Potawanich, Paweena; Plianwong, Samarwadee; Sakulma, Sirinart; Saehuan, Choedchai

    2010-10-01

    The aim of this study was to investigate the stability of fortified cefazolin sodium ophthalmic solutions (50 mg mL⁻¹) extemporaneously prepared in commercial artificial tears containing 2 different types of preservatives, namely the surfactants and oxidants. Fortified cefazolin sodium solutions were prepared by reconstituting cefazolin for injection with sterile water and further diluted with Tears Naturale II or Natear, 2 commercial artificial tears containing polyquaternium-1 and sodium perborate, respectively, as preservatives. The solutions were then kept at room temperature (28°C) or in the refrigerator (4°C). During the 28-day period, the formulations were periodically examined for the physical appearance, pH, and the remaining drug concentrations. The antibacterial potency was evaluated as the minimal inhibitory concentration against Staphylococcus aureus strain ATCC 29923 by broth dilution technique. The activity of the preservatives was demonstrated by antimicrobial effectiveness tests. On day 28, the microbial contamination in the preparations was tested. The stability profiles of cefazolin solutions prepared in Tears Naturale II, Natear, and water were not different, but they were significantly influenced by the storage temperature. The refrigerated formulations showed no loss of drug and antibacterial potency as well as alteration of physical appearance and pH throughout the 28 days. In contrast, those kept at room temperature showed gradual change in color and odor. The degradation of drug exceeded 10% from day 3 and the decrease of antibacterial potency could be observed at week 3. All cefazolin solutions prepared in artificial tears retained the antimicrobial activity of preservatives and were free from bacterial and fungal contamination throughout the 28-day period of study. Cefazolin sodium ophthalmic solutions can be extemporaneously prepared in Tears Naturale II or Natear without the influence from different types of preservatives used in

  5. The stability of high-Tc BSCCO/Ag superconducting microcomposites in water, some inorganic solutions and organic solvents

    International Nuclear Information System (INIS)

    Gao, W.; Chen, J.; Yang, C.O.; McNabb, D.; Sande, J. vander

    1992-01-01

    Bi(Pb)-Sr-Ca-Cu-O/Ag (BSCCO/Ag) superconducting microcomposites with zero-resistance temperatures from 102 to 108 K and critical current densities of ∝600 A/cm 2 at 77 K were produced by oxidation and annealling of metallic precursor alloys. The stabilities and degradation behavior of BSCCO/Ag specimens in various environments were studied by a combination of mass loss measurement, electrical transport measurement and microstructural observation. The environmental conditions used in the present work were moist air, distilled water, aqueous solutions of NaCl, NaOH and acetic acid, and organic solvents methanol and acetone. Although there is a general tendency toward a decrease in critical current density after a long exposure to most of the testing conditions, the specimens containing a high percent of Ag (≥70 wt.%) showed very little decrease in Tc and J c up to 200 days of exposure in moist air and distilled water, and up to 20 days in NaCl solution, methanol and acetone. It was found that the superconducting ''2223'' phase is stable in water, neutral solutions and the organic solvents, reacts very slowly with basic solutions, and dissolves rapidly in acidic solutions. Some non-superconducting Ca-rich oxides dissolve in water and neutral and basic solutions and therefore damage the connection of the superconducting grains in low-Ag containing specimens. The excellent stability of the BSCCO/Ag superconducting microcomposites containing high Ag provides an important advantage for their potential industrial application. (orig.)

  6. Solid/solution Cu fractionations/speciation of a Cu contaminated soil after pilot-scale electrokinetic remediation and their relationships with soil microbial and enzyme activities

    International Nuclear Information System (INIS)

    Wang Quanying; Zhou Dongmei; Cang Long; Li Lianzhen; Wang Peng

    2009-01-01

    The aim of this study was to investigate the detailed metal speciation/fractionations of a Cu contaminated soil before and after electrokinetic remediation as well as their relationships with the soil microbial and enzyme activities. Significant changes in the exchangeable and adsorbed-Cu fractionations occurred after electrokinetic treatment, while labile soil Cu in the solution had a tendency to decrease from the anode to the cathode, and the soil free Cu 2+ ions were mainly accumulated in the sections close to the cathode. The results of regression analyses revealed that both the soil Cu speciation in solution phase and the Cu fractionations in solid phase could play important roles in the changes of the soil microbial and enzyme activities. Our findings suggest that the bioavailability of soil heavy metals and their ecotoxicological effects on the soil biota before and after electroremediation can be better understood in terms of their chemical speciation and fractionations. - The assessment of the roles of soil solution speciation and solid-phase fractionations in metal bioavailability after electrokinetic remediation deserves close attention.

  7. Physicochemical stability of carfilzomib (Kyprolis®) containing solutions in glass vials, ready-to-administer plastic syringes and infusion bags over a 28-day storage period.

    Science.gov (United States)

    Kim, Sun Hee; Krämer, Irene

    2017-01-01

    Centralized aseptic preparation of ready-to-administer carfilzomib containing parenteral solutions in plastic syringes and polyolefine (PO) infusion bags needs profound knowledge about the physicochemical stability in order to determine the beyond-use-date of the preparations. Therefore, the purpose of this study was to determine the physicochemical stability of carfilzomib solution marketed as Kyprolis® powder for solution for infusion. Reconstituted solutions and ready-to-administer preparations of Kyprolis® stored under refrigeration (2-8℃) or at room temperature (25℃) were analyzed at predetermined intervals over a maximum storage period of 28 days. Chemical stability of carfilzomib was planned to be determined with a stability-indicating reversed-phase high-performance liquid chromatography assay. Physicochemical stability was planned to be determined by visual inspection of clarity and color as well as pH measurement. The study results show that reconstituted carfilzomib containing parenteral solutions are stable in glass vials as well as diluted solutions in plastic syringes and PO infusion bags over a period of at least 28 days when stored light protected under refrigeration. When stored at room temperature, reconstituted and diluted carfilzomib solutions are physicochemically stable over 14 days and 10 days, respectively. The physicochemical stability of carfilzomib infusion solutions allows cost-saving pharmacy-based centralized preparation of ready-to-administer preparations.

  8. Stabilization

    Directory of Open Access Journals (Sweden)

    Muhammad H. Al-Malack

    2016-07-01

    Full Text Available Fuel oil flyash (FFA produced in power and water desalination plants firing crude oils in the Kingdom of Saudi Arabia is being disposed in landfills, which increases the burden on the environment, therefore, FFA utilization must be encouraged. In the current research, the effect of adding FFA on the engineering properties of two indigenous soils, namely sand and marl, was investigated. FFA was added at concentrations of 5%, 10% and 15% to both soils with and without the addition of Portland cement. Mixtures of the stabilized soils were thoroughly evaluated using compaction, California Bearing Ratio (CBR, unconfined compressive strength (USC and durability tests. Results of these tests indicated that stabilized sand mixtures could not attain the ACI strength requirements. However, marl was found to satisfy the ACI strength requirement when only 5% of FFA was added together with 5% of cement. When the FFA was increased to 10% and 15%, the mixture’s strength was found to decrease to values below the ACI requirements. Results of the Toxicity Characteristics Leaching Procedure (TCLP, which was performed on samples that passed the ACI requirements, indicated that FFA must be cautiously used in soil stabilization.

  9. Stabilizers of edaravone aqueous solution and their action mechanisms. 2. Glutathione

    OpenAIRE

    Tanaka, Masahiko; Motomiya, Satsuki; Fujisawa, Akio; Yamamoto, Yorihiro

    2017-01-01

    Edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one) has garnered attention since its approval for amyotrophic lateral sclerosis in Japan (2015) and the United States (2017). Edaravone is administered intravenously, and as such, is distributed in the form of an aqueous solution. However, aqueous solutions of edaravone are very unstable because they present as edaravone anions, which become edaravone radicals when the anion donates an electron to free radicals including oxygen. In this study, gluta...

  10. Stabilizers of edaravone aqueous solution and their action mechanisms. 1. Sodium bisulfite

    OpenAIRE

    Tanaka, Masahiko; Sugimura, Natsuhiko; Fujisawa, Akio; Yamamoto, Yorihiro

    2017-01-01

    Edaravone (3-methyl-1-phenyl-2-pyrazolin-5-one) has been used as a free radical scavenging drug for the treatment of acute ischemic stroke in Japan since 2001. Edaravone is given to patients intravenously; therefore, it is distributed in the form of an aqueous solution. However, aqueous solutions of edaravone are very unstable because it is present as edaravone anion, which is capable of transferring an electron to free radicals including oxygen, and becomes edaravone radical. We observed the...

  11. Stability of antimicrobial activity of peracetic acid solutions used in the final disinfection process

    OpenAIRE

    COSTA,Solange Alves da Silva; PAULA,Olívia Ferreira Pereira de; SILVA,Célia Regina Gonçalves e; LEÃO,Mariella Vieira Pereira; SANTOS,Silvana Soléo Ferreira dos

    2015-01-01

    The instruments and materials used in health establishments are frequently exposed to microorganism contamination, and chemical products are used before sterilization to reduce occupational infection. We evaluated the antimicrobial effectiveness, physical stability, and corrosiveness of two commercial formulations of peracetic acid on experimentally contaminated specimens. Stainless steel specimens were contaminated with Staphylococcus aureus, Escherichia coli, Candida albicans, blood, and sa...

  12. Influence of the extracted solute on the aggregation of malonamide extractant in organic phases: Consequences for phase stability

    International Nuclear Information System (INIS)

    Berthon, L.; Martinet, L.; Testard, F.; Madic, Ch.; Zem, Th.

    2010-01-01

    Due to their amphiphilic properties, malonamide molecules in alkane are organized in reverse micelle type aggregates, composed of a polar core formed by the malonamide polar heads and the extracted solutes, and surrounded by a hydrophobic shell made up of the extractant alkyl chains. The aggregates interact with one another through an attractive potential, leading to the formation of a third phase. This occurs with the splitting of the organic phase into a light phase composed mostly of diluent, and a heavy third phase containing highly concentrated extractant and solutes. In this article, we show that the aggregation (monomer concentration, domain of stability, and attractive potential between micelles) greatly depends on the nature of the extracted solute, whereas the size of aggregate (aggregation number) is only slightly influenced by this. We describe the extraction of water, nitric acid, neodymium nitrate and uranyl nitrate. Strongly polarizable species induce consistently large attraction potentials and a small stability domain for the dispersion of nano-droplets in the solvent. Highly polarizable ions such as lanthanides or uranyl induce more long-range attractive interactions than do protons. (authors)

  13. Effect of finishing and polishing on the color stability of a composite resin immersed in staining solutions

    Directory of Open Access Journals (Sweden)

    Maiara Justo Polli

    2015-01-01

    Full Text Available Objective: To evaluate the influence of finishing/polishing methods and staining solutions using different immersion periods on the color stability of a microhybrid composite resin. Materials and Methods: Ninety specimens were fabricated using a stainless steel mold and polyester strips. The samples were randomly divided into five groups according to the finishing and polishing performed: Control group (no surface treatment was performed, Diamond Pro group, Diamond burs group, Enhance group, and SiC paper group. After finishing and polishing, six samples from each group were immersed in coffee, red wine, or water for 30 days. The color measurements were obtained using digital photography before immersion and after 7, 15, and 30 days of immersion. The red, green, and blue values provided by the Adobe Photoshop software were converted into CIELab values. A three-way analysis of variance and Tukey's test were used for statistical analysis (P ≤ 0.05. Results: The finishing and polishing methods, staining solutions, immersion times, and their interaction had statistically significant effects on the color change (P = 0.00. Coffee and red wine caused intense staining. Among the polishing methods, the highest color change value was observed in the control group (P < 0.05 and the Diamond Pro disks provided the most stain-resistant surfaces (P ≤ 0.05. Conclusion: The finishing and polishing method, staining solution, and immersion time influences the color stability. Finishing and polishing should be applied to obtain a more stain-resistant surface.

  14. Chemical Stability of Cd(II and Cu(II Ionic Imprinted Amino-Silica Hybrid Material in Solution Media

    Directory of Open Access Journals (Sweden)

    Buhani, Narsito, Nuryono, Eko Sri Kunarti

    2015-12-01

    Full Text Available Chemical stability of Cd(II and Cu(II ionic imprinted hybrid material of (i-Cd-HAS and i-Cu-HAS derived from silica modification with active compound (3-aminopropyl-trimethoxysilane (3-APTMS has been studied in solution media. Stability test was performed with HNO3 0.1 M (pH 1.35 to investigate material stability at low pH condition, CH3COONa 0.1 M (pH 5.22 for adsorption process optimum pH condition, and in the water (pH 9.34 for base condition. Material characteristics were carried out with infrared spectrophotometer (IR and atomic absorption spectrophotometer (AAS. At interaction time of 4 days in acid and neutral condition, i-Cd-HAS is more stable than i-Cu-HAS with % Si left in material 95.89 % (acid media, 43.82 % (close to neutral, and 9.39 % (base media.Keywords: chemical stability, amino-silica hybrid, ionic imprinting technique

  15. Chemical Stability of Cd(II and Cu(II Ionic Imprinted Amino-Silica Hybrid Material in Solution Media

    Directory of Open Access Journals (Sweden)

    Buhani Buhani

    2012-02-01

    Full Text Available Chemical stability of Cd(II and Cu(II ionic imprinted amino-silica (HAS material of (i-Cd-HAS and i-Cu-HAS derived from silica modification with active compound (3-aminopropyl-trimethoxysilane (3-APTMS has been studied in solution media.  Stability test was performed with HNO3 0.1 M (pH 1.35 to investigate material stability at low pH condition, acetat buffer at pH 5.22 for adsorption process optimum pH condition, and in the water (pH 9.34 for base condition.  Material characteristics were carried out with infrared spectrophotometer (IR and atomic absorption spectrophotometer (AAS.  At interaction time of 4 days in acid and neutral condition, i-Cd-HAS is more stable than i-Cu-HAS with % Si left in material 95.89 % (acid media, 43.82 % (close to neutral, and 9.39 % (base media.Keywords: chemical stability, amino-silica hybrid, ionic imprinting technique.

  16. Chemical stability of diphenhydramine hydrochloride from an elixir and lidocaine hydrochloride from a viscous solution when mixed together.

    Science.gov (United States)

    Gupta, Vishnu D

    2006-01-01

    The stability of diphenhydramine hydrochloride (from an elixir) and lidocaine hydrochloride (from a viscous solution) in a mixture (1:1) was studied using a stability-indicating high-peformance liquid chromatographic assay method. The concentrations of the drugs were related directly to peak heights and the percent relative standard deviations based on five injections were 1.4 for diphenhydramine and 1.3 for lidocaine. The products of hydrolysis from the both the drugs and a number of excipients present in the dosage forms did not interfere with the developed assay procedure. The mixture was stable for at least 21 days when stored in amber-colored bottles at room temperature. The pH value of the mixture remained constant, and the physical appearance did not change during the study period.

  17. Preparation of polyurethane/montmorillonite nanocomposites by solution: characterization using low-field NMR and study of thermal stability

    International Nuclear Information System (INIS)

    Silva, Marcos Anacleto da; Tavares, Maria Ines B.

    2009-01-01

    Polyurethanes (PU) are important and versatile class of polymer materials, especially because of their desirable properties, such as high abrasion resistance, tear strength, excellent shock absorption, flexibility and elasticity. However, there also exist some disadvantages, for example, low thermal stability and barrier properties. To overcome the disadvantages, research on novel polyurethane/clay nanocomposites has been carried out. The investigation of the structure of polyurethane/clay nanocomposites has been mostly done by X-ray diffraction (XRD) and transmission electron microscopy (TEM). In this work, PU/clay films were prepared by solution, and the obtained nanocomposites were characterized by XRD and low-field nuclear magnetic resonance (NMR). Low field NMR measurements were able to provide important information on molecular dynamics of the polymeric nanocomposites PU/OMMT. In addition, they also confirmed the results obtained by XRD. The thermal stability was determined by thermogravimetric analysis (TGA). (author)

  18. Stability of Hydromorphone-Ketamine Solutions in Glass Bottles, Plastic Syringes, and IV Bags for Pediatric Use.

    Science.gov (United States)

    Ensom, Mary H H; Decarie, Diane; Leung, Karen; Montgomery, Carolyne

    2009-03-01

    To evaluate the stability of mixtures of hydromorphone and ketamine in 0.9% sodium chloride (normal saline [NS]) after storage for up to 7 days at room temperature (25°C). The stability of 3 standard mixtures of hydromorphone and ketamine (hydromorphone 0.2 mg/mL + ketamine 0.2 mg/mL, hydromorphone 0.2 mg/mL + ketamine 0.6 mg/mL, and hydromorphone 0.2 mg/mL + ketamine 1.0 mg/mL) in NS was studied. Portions of each mixture were transferred to 3 brown glass bottles (100 mL), 3 plastic syringes (50 mL), and 3 IV bags (50 mL), which were then stored at room temperature (25°C). Physical characteristics, including pH, colour, and precipitation, were evaluated daily. Three 1.5-mL samples were collected from each bottle, syringe, and IV bag at baseline, at 24, 48, and 72 hours, and on day 7. Samples were analyzed in triplicate by a stability-indicating high-performance liquid chromatography method. Solutions were considered stable if they maintained 90% of the initial concentration of each drug. Samples from syringes and IV bags were subjected to standard sterility testing by incubation for 5 days in an enriched culture media. No notable changes in pH or colour were observed, and no precipitation occurred in any of the solutions. All formulations maintained more than 90% of the initial concentration of each drug on day 7. No bacterial growth was observed in any of the samples tested. Mixtures of hydromorphone and ketamine were stable for up 7 days at 25°C, and the sterility of the preparations was maintained. Because stability alone does not guarantee efficacy, it is recommended that clinical studies be conducted to evaluate the pharmacokinetics and pharmacodynamics of these formulations.

  19. High thermal stability solution-processable narrow-band gap molecular semiconductors.

    Science.gov (United States)

    Liu, Xiaofeng; Hsu, Ben B Y; Sun, Yanming; Mai, Cheng-Kang; Heeger, Alan J; Bazan, Guillermo C

    2014-11-19

    A series of narrow-band gap conjugated molecules with specific fluorine substitution patterns has been synthesized in order to study the effect of fluorination on bulk thermal stability. As the number of fluorine substituents on the backbone increase, one finds more thermally robust bulk structures both under inert and ambient conditions as well as an increase in phase transition temperatures in the solid state. When integrated into field-effect transistor devices, the molecule with the highest degree of fluorination shows a hole mobility of 0.15 cm(2)/V·s and a device thermal stability of >300 °C. Generally, the enhancement in thermal robustness of bulk organization and device performance correlates with the level of C-H for C-F substitution. These findings are relevant for the design of molecular semiconductors that can be introduced into optoelectronic devices to be operated under a wide range of conditions.

  20. Existence and global exponential stability of periodic solutions for n-dimensional neutral dynamic equations on time scales.

    Science.gov (United States)

    Li, Bing; Li, Yongkun; Zhang, Xuemei

    2016-01-01

    In this paper, by using the existence of the exponential dichotomy of linear dynamic equations on time scales and the theory of calculus on time scales, we study the existence and global exponential stability of periodic solutions for a class of n-dimensional neutral dynamic equations on time scales. We also present an example to illustrate the feasibility of our results. The results of this paper are completely new and complementary to the previously known results even in both the case of differential equations (time scale [Formula: see text]) and the case of difference equations (time scale [Formula: see text]).

  1. The existence and global exponential stability of a periodic solution of a class of delay differential equations

    International Nuclear Information System (INIS)

    Tang, X H; Zou, Xingfu

    2009-01-01

    By employing Schauder's fixed point theorem and a non-Liapunov method (matrix theory, inequality analysis), we obtain some new criteria that ensure existence and global exponential stability of a periodic solution to a class of functional differential equations. Applying these criteria to a cellular neural network with time delays (delayed cellular neural network, DCNN) under a periodic environment leads to some new results that improve and generalize many existing ones we know on this topic. These results are of great significance in designs and applications of globally stable periodic DCNNs

  2. Existence and global exponential stability of periodic solution to BAM neural networks with periodic coefficients and continuously distributed delays

    International Nuclear Information System (INIS)

    Zhou Tiejun; Chen Anping; Zhou Yuyuan

    2005-01-01

    By using the continuation theorem of coincidence degree theory and Liapunov function, we obtain some sufficient criteria to ensure the existence and global exponential stability of periodic solution to the bidirectional associative memory (BAM) neural networks with periodic coefficients and continuously distributed delays. These results improve and generalize the works of papers [J. Cao, L. Wang, Phys. Rev. E 61 (2000) 1825] and [Z. Liu, A. Chen, J. Cao, L. Huang, IEEE Trans. Circuits Systems I 50 (2003) 1162]. An example is given to illustrate that the criteria are feasible

  3. Existence and global exponential stability of periodic solution to BAM neural networks with periodic coefficients and continuously distributed delays

    Science.gov (United States)

    Zhou, distributed delays [rapid communication] T.; Chen, A.; Zhou, Y.

    2005-08-01

    By using the continuation theorem of coincidence degree theory and Liapunov function, we obtain some sufficient criteria to ensure the existence and global exponential stability of periodic solution to the bidirectional associative memory (BAM) neural networks with periodic coefficients and continuously distributed delays. These results improve and generalize the works of papers [J. Cao, L. Wang, Phys. Rev. E 61 (2000) 1825] and [Z. Liu, A. Chen, J. Cao, L. Huang, IEEE Trans. Circuits Systems I 50 (2003) 1162]. An example is given to illustrate that the criteria are feasible.

  4. On the stabilization of NbV-solutions by ZrIV and HfIV

    International Nuclear Information System (INIS)

    Soerensen, E.; Bjerre, A.B.

    1987-11-01

    Niobium cannot be separated from zirconium or hafnium when these elements occur together in solution with common anions such as Cl- and SO 4 --. This is ascribed to the copolymerisation of Nb v and the hydrolyzed ionic species of Zr IV v and Hf IV by which the colloidal particles are masked as Zr- and Hf-compounds. In HCl the particles are positively charged as opposed to when they are in sulphate solution where the Zr- and Hf- sulphate complexes confer a negative charge. The two cases are considered separately. (author)

  5. Integrability and structural stability of solutions to the Ginzburg-Landau equation

    Science.gov (United States)

    Keefe, Laurence R.

    1986-01-01

    The integrability of the Ginzburg-Landau equation is studied to investigate if the existence of chaotic solutions found numerically could have been predicted a priori. The equation is shown not to possess the Painleveproperty, except for a special case of the coefficients that corresponds to the integrable, nonlinear Schroedinger (NLS) equation. Regarding the Ginzburg-Landau equation as a dissipative perturbation of the NLS, numerical experiments show all but one of a family of two-tori solutions, possessed by the NLS under particular conditions, to disappear under real perturbations to the NLS coefficients of O(10 to the -6th).

  6. Stabilizing a solution of the 2D Navier-Stokes system in the exterior of a bounded domain by means of a control on the boundary

    International Nuclear Information System (INIS)

    Gorshkov, Aleksei V

    2012-01-01

    The problem of stabilizing a solution of the 2D Navier-Stokes system defined in the exterior of a bounded domain with smooth boundary is investigated. For a given initial velocity field a control on the boundary of the domain must be constructed such that the solution stabilizes to a prescribed vortex solution or trivial solution at the rate of 1/t k . On the way, related questions are investigated, concerning the behaviour of the spectrum of an operator under a relatively compact perturbation and the existence of attracting invariant manifolds. Bibliography: 21 titles.

  7. Rheological and micro-Raman time-series characterization of enzyme sol–gel solution toward morphological control of electrospun fibers

    International Nuclear Information System (INIS)

    Oriero, Dennis A; Weakley, Andrew T; Aston, D Eric

    2012-01-01

    Rheological and micro-Raman time-series characterizations were used to investigate the chemical evolutionary changes of silica sol–gel mixtures for electrospinning fibers to immobilize an enzyme (tyrosinase). Results of dynamic rheological measurements agreed with the expected structural transitions associated with reacting sol–gel systems. The electrospinning sols exhibited shear-thinning behavior typical of a power law model. Ultrafine (200–300 nm diameter) fibers were produced at early and late times within the reaction window of approximately one hour from initial mixing of sol solutions with and without enzyme; diameter distributions of these fibers showed much smaller deviations than expected. The enzyme markedly increased magnitudes of both elastic and viscous moduli but had no significant impact on final fiber diameters, suggesting that the shear-thinning behavior of both sol–gel mixtures is dominant in the fiber elongation process. The time course and scale for the electrospinning batch fabrication show strong correlations between the magnitudes in rheological property changes over time and the chemical functional group evolution obtained from micro-Raman time-series analysis of the reacting sol–gel systems.

  8. Rheological and micro-Raman time-series characterization of enzyme sol–gel solution toward morphological control of electrospun fibers

    Science.gov (United States)

    Oriero, Dennis A; Weakley, Andrew T; Aston, D Eric

    2012-01-01

    Rheological and micro-Raman time-series characterizations were used to investigate the chemical evolutionary changes of silica sol–gel mixtures for electrospinning fibers to immobilize an enzyme (tyrosinase). Results of dynamic rheological measurements agreed with the expected structural transitions associated with reacting sol–gel systems. The electrospinning sols exhibited shear-thinning behavior typical of a power law model. Ultrafine (200–300 nm diameter) fibers were produced at early and late times within the reaction window of approximately one hour from initial mixing of sol solutions with and without enzyme; diameter distributions of these fibers showed much smaller deviations than expected. The enzyme markedly increased magnitudes of both elastic and viscous moduli but had no significant impact on final fiber diameters, suggesting that the shear-thinning behavior of both sol–gel mixtures is dominant in the fiber elongation process. The time course and scale for the electrospinning batch fabrication show strong correlations between the magnitudes in rheological property changes over time and the chemical functional group evolution obtained from micro-Raman time-series analysis of the reacting sol–gel systems. PMID:27877486

  9. Computing the stability of steady-state solutions of mathematical models of the electrical activity in the heart.

    Science.gov (United States)

    Tveito, Aslak; Skavhaug, Ola; Lines, Glenn T; Artebrant, Robert

    2011-08-01

    Instabilities in the electro-chemical resting state of the heart can generate ectopic waves that in turn can initiate arrhythmias. We derive methods for computing the resting state for mathematical models of the electro-chemical process underpinning a heartbeat, and we estimate the stability of the resting state by invoking the largest real part of the eigenvalues of a linearized model. The implementation of the methods is described and a number of numerical experiments illustrate the feasibility of the methods. In particular, we test the methods for problems where we can compare the solutions with analytical results, and problems where we have solutions computed by independent software. The software is also tested for a fairly realistic 3D model. Copyright © 2011 Elsevier Ltd. All rights reserved.

  10. On the stabilization of niobium(V) solutions by zirconium(IV) and hafnium(IV)

    DEFF Research Database (Denmark)

    Sørensen, E.; Bjerre, A.B.

    1992-01-01

    Niobium cannot be separated from zirconium or hafnium when these elements occur together in solution with common anions such as chloride and sulphate. This is ascribed to the co-polymerization of niobium(V) and the hydrolysed ionic species of zirconium(IV) and hafnium(IV) to form colloidal...

  11. Effect of metal chloride solutions on coloration and biaxial flexural strength of yttria-stabilized zirconia

    Science.gov (United States)

    Oh, Gye-Jeong; Lee, Kwangmin; Lee, Doh-Jae; Lim, Hyun-Pil; Yun, Kwi-Dug; Ban, Jae-Sam; Lee, Kyung-Ku; Fisher, John G.; Park, Sang-Won

    2012-10-01

    The effect of three kinds of transition metal dopants on the color and biaxial flexural strength of zirconia ceramics for dental applications was evaluated. Presintered zirconia discs were colored through immersion in aqueous chromium, molybdenum and vanadium chloride solutions and then sintered at 1450 °C. The color of the doped specimens was measured using a digital spectrophotometer. For biaxial flexural strength measurements, specimens infiltrated with 0.3 wt% of each aqueous chloride solution were used. Uncolored discs were used as a control. Zirconia specimens infiltrated with chromium, molybdenum and vanadium chloride solutions were dark brown, light yellow and dark yellow, respectively. CIE L*, a*, and b* values of all the chromium-doped specimens and the specimens infiltrated with 0.1 wt% molybdenum chloride solution were in the range of values for natural teeth. The biaxial flexural strengths of the three kinds of metal chloride groups were similar to the uncolored group. These results suggest that chromium and molybdenum dopants can be used as colorants to fabricate tooth colored zirconia ceramic restorations.

  12. Investigation of factors affecting the stability of lysozyme spray dried from ethanol-water solutions

    DEFF Research Database (Denmark)

    Ji, Shuying; Thulstrup, Peter Waaben; Mu, Huiling

    2017-01-01

    -ethanol mixtures. The effect of formulation additives (trehalose, Tween 20 and phosphate-buffered saline) and processing conditions (inlet temperature and storage time of lysozyme in the feed solution before the spray drying process) on the protein bioactivity was investigated. The results showed...

  13. Post-reconstitution Stability of Telavancin with Commonly Used Diluents and Intravenous Infusion Solutions

    Directory of Open Access Journals (Sweden)

    Zhengtian Gu, PhD

    2015-12-01

    Conclusions: These results are supportive of a total hold time for reconstituted telavancin in vials plus the time in IV infusion solutions in polyvinyl chloride bags to not exceed 12 hours under ambient conditions and 7 days under refrigeration.

  14. Stability properties of solutions to nonlinear models possessing a sign-undefined metric

    International Nuclear Information System (INIS)

    Barashenkov, I.V.

    1983-01-01

    Multicomponent field systems possessing a sign-undefined internal space metric, in particular models with a noncompact global invariance group are investigated. It is shown that the energy cannot have even a conditional relative minimum. It is demonstrated, nevertheless, that the corresponding nonlinear equations of motion are permitted to possess stable particle-like solutions

  15. Stability properties of solutions to nonlinear models possessing a sign-undefined metric

    International Nuclear Information System (INIS)

    Barashenkov, I.V.

    1983-01-01

    Multicomponent field systems possessing a sign-undefined internal space metric, in particular models with a noncompact global invariance group, are investigated. It is shown that the energy cannot have even a conditional relative minimum. It is demonstrated, nevertheless, that the corresponding nonlinear equations of motion are permitted to possess stable particle-like solutions. (Auth.)

  16. A calorimetric study of solute effects on the kinetic stability of a-amylase

    DEFF Research Database (Denmark)

    Olsen, Søren Nymand; Andersen, Kim Bruno; Øgendal, Lars Holm

    2009-01-01

    In this study we evaluated the applications of isothermal titration calorimetry (ITC) to Study solute effects on the kinetics of irreversible protein denaturation. More specifically, denaturation of Bacillus Halmapalus alpha-amylase (BHA) was initiated by addition of EDTA to the calorimetric cell...

  17. Long-term stability of earthen materials in contact with acidic tailings solutions

    International Nuclear Information System (INIS)

    Peterson, S.R.; Erikson, R.L.; Gee, G.W.

    1982-11-01

    The objectives of the studies documented in this report were to use experimental and geochemical computer modeling tools to assess the long-term environmental impact of leachate movement from acidic uranium mill tailings. Liner failure (i.e., an increase in the permeability of the liner material) was not found to be a problem when various acidic tailings solutions leached through liner materials for periods up to 3 years. On the contrary, materials that contained over 30% clay showed a decrease in permeability with time in the laboratory columns. The high clay materials tested appear suitable for lining tailings impoundment ponds. The decreases in permeability are attributed to pore plugging resulting from the precipitation of minerals and solids. This precipitation takes place due to the increase in pH of the tailings solution brought about by the buffering capacity of the soil. Geochemical modeling predicts, and x-ray characterization confirms, that precipitation of solids from solution is occurring in the acidic tailings solution/liner interactions studied. In conclusion the same mineralogical changes and contaminant reactions predicted by geochemical modeling and observed in laboratory studies were found at a drained evaporation pond (Lucky Mc in Wyoming) with a 4 year history of acid attack

  18. Existence and Stability of the Periodic Solution with an Interior Transitional Layer in the Problem with a Weak Linear Advection

    Directory of Open Access Journals (Sweden)

    Nikolay N. Nefedov

    2018-01-01

    Full Text Available In the paper, we study a singularly perturbed periodic in time problem for the parabolic reaction-advection-diffusion equation with a weak linear advection. The case of the reactive term in the form of a cubic nonlinearity is considered. On the basis of already known results, a more general formulation of the problem is investigated, with weaker sufficient conditions for the existence of a solution with an internal transition layer to be provided than in previous studies. For convenience, the known results are given, which ensure the fulfillment of the existence theorem of the contrast structure. The justification for the existence of a solution with an internal transition layer is based on the use of an asymptotic method of differential inequalities based on the modification of the terms of the constructed asymptotic expansion. Further, sufficient conditions are established to fulfill these requirements, and they have simple and concise formulations in the form of the algebraic equation w(x0,t = 0 and the condition wx(x0,t < 0, which is essentially a condition of simplicity of the root x0(t and ensuring the stability of the solution found. The function w is a function of the known functions appearing in the reactive and advective terms of the original problem. The equation w(x0,t = 0 is a problem for finding the zero approximation x0(t to determine the localization region of the inner transition layer. In addition, the asymptotic Lyapunov stability of the found periodic solution is investigated, based on the application of the so-called compressible barrier method. The main result of the paper is formulated as a theorem. 

  19. Stability of the split-band solution and energy gap in the narrow-band region of the Hubbard model

    International Nuclear Information System (INIS)

    Arai, T.; Cohen, M.H.

    1980-01-01

    By inserting quasielectron energies ω calculated from the fully renormalized Green's function of the Hubbard model obtained in the preceding paper into the exact expression of Galitskii and Migdal, the ground-state energy, the chemical potential, and the dynamic- and thermodynamic-stability conditions are calculated in the narrow-band region. The results show that as long as the interaction energy I is finite, electrons in the narrow-band region do not obey the Landau theory of Fermi liquids, and a gap appears between the lowest quasielectron energy ω and the chemical potential μ for any occupation n, regardless of whether the lower band is exactly filled or not. This unusual behavior is possible because, when an electron is added to the system of N electrons, the whole system relaxes due to the strong interaction, introducing a relaxation energy difference between the two quantities. We also show that all previous solutions which exhibit the split-band structure, including Hubbard's work, yield the same conclusion that electrons do not behave like Landau quasiparticles. However, the energy gap is calculated to be negative at least for some occupations n, demonstrating the dynamic instability of those solutions. They also exhibit thermodynamic instability for certain occupations, while the fully renormalized solution, having sufficient electron correlations built in, satisfies the dynamic and thermodynamic stability conditions for all occupations. When the lower band is nearly filled, the nature of the solution is shown to change, making the coherent motion of electrons with fixed k values more difficult. In the pathological limit where I=infinity, however, the gap vanishes, yielding a metallic state

  20. THE EXISTENCE OF THE STABILIZING SOLUTION OF THE RICCATI EQUATION ARISING IN DISCRETE-TIME STOCHASTIC ZERO SUM LQ DYNAMIC GAMES WITH PERIODIC COEFFICIENTS

    Directory of Open Access Journals (Sweden)

    Vasile Dr ̆agan

    2017-06-01

    Full Text Available We investigate the problem for solving a discrete-time periodic gen- eralized Riccati equation with an indefinite sign of the quadratic term. A necessary condition for the existence of bounded and stabilizing solution of the discrete-time Riccati equation with an indefinite quadratic term is derived. The stabilizing solution is positive semidefinite and satisfies the introduced sign conditions. The proposed condition is illustrated via a numerical example.

  1. Effect of morin on pharmacokinetics of piracetam in rats, in vitro enzyme kinetics and metabolic stability assay using rapid UPLC method.

    Science.gov (United States)

    Sahu, Kapendra; Shaharyar, Mohammad; Siddiqui, Anees A

    2013-07-01

    The aim of this study was to investigate the effect of Morin on the pharmacokinetics of Piracetam in rats, in vitro enzyme kinetics and metabolic stability (high throughput) studies using human liver microsomes in UPLC. For pharmacokinetics studies, male Wistar rats were pretreated with Morin (10 mg/kg) for one week and on the last day, a single dose of Piracetam (50 mg/kg) was given orally. In another group, both Morin and Piracetam were co-administered to evaluate the acute effect of Morin on Piracetam. The control group received oral distilled water for one week and administered with Piracetam on the last day. As Morin is an inhibitor of P- Glycoprotein (P-gp) and CYP 3A, it was anticipated to improve the bioavailability of Piracetam. Amazingly, relative to control, the areas under the concentration time curve and peak plasma concentration of Piracetam were 1.50- and 1.45-fold, respectively, greater in the Morin-pretreated group. However, co-administration of Morin had no significant effect on these parameters. Apart from the aforementioned merits, the results of this study are further confirmed by clinical trials; Piracetam dosages should be adjusted to avoid potential drug interaction when Piracetam is used clinically in combination with Morin and Morin-containing dietary supplements. The in vitro enzyme kinetics were performed to determined km, Vmax & CLins . The in vitro metabolic stability executed for the estimation of metabolic rate constant and half-life of Piracetam. These studies also extrapolate to in vivo intrinsic hepatic clearance (Clint, in vivo ) from in vitro intrinsic hepatic clearance (CLint, in vitro ). Copyright © 2012 John Wiley & Sons, Ltd.

  2. The effect of germination and metallic salts on the stability of enzymes of three high yielding varieties of maize (Zea mays L. in respect of Bangladesh

    Directory of Open Access Journals (Sweden)

    Rupa, A.Z.,

    2017-09-01

    Full Text Available The study was conducted with a view to determine the effect of germination and metallic salts on nutritional quality, enzymes activity and their stability of three high yielding varieties of maize (Zea mays L.. The protein content of BHM-3, BHM-5 and BHM-6 were increased 22.37%, 26.48%, and 20.34% respectively at 48 hours then decreased drastically from 72-96 hours of germination. Starch content was increased maximum 29.19% in BHM-6 at 0 hours (non-germinating seeds among the three varieties and then decreased gradually from 48-96 hours of germination. Total sugar and reducing sugar contents of BHM-3, BHM-5 and BHM-6 seeds were maximum at 96 hours than 24-72 hours of germination while BHM-3 showed boosting increase of total sugar (336.97% due to 96 hours of germination. BHM-5 showed a tremendous increase of α-amylase (189.83% and protease (144.44% activity whereas BHM-6 showed maximum invertase activity (175.27% at 48 hours then decreased gradually from 72-96 hours of germination. The activities of enzymes were increased in presence of metallic salts such as Ca2+, Mg2+, and Mn2+ while Fe2+, Zn2+ and Cu2+ inhibited the activities moderately.

  3. Real cause of detrimental carbonation in chemically stabilized layers and possible solutions

    CSIR Research Space (South Africa)

    Botha, PB

    2005-10-01

    Full Text Available to determine the other reaction that may take place in the material. KEYWORDS CARBONATION/ CHEMICAL REACTIONS/ WATER CURING/ NEW TESTING PROTOCOL 1 INTRODUCTION This paper deals with the problems related to the “curing” of the stabilized layers... than CO2 driven. In actually fact the so-called “detrimental carbonation” chemical reaction cannot even take place without free water being available. The water is normally supplied by the specified curing 2 technique to keep the layer moist...

  4. Structural stability and chaotic solutions of perturbed Benjamin-Ono equations

    International Nuclear Information System (INIS)

    Birnir, B.; Morrison, P.J.

    1986-11-01

    A method for proving chaos in partial differential equations is discussed and applied to the Benjamin-Ono equation subject to perturbations. The perturbations are of two types: one that corresponds to viscous dissipation, the so-called Burger's term, and one that involves the Hilbert transform and has been used to model Landau damping. The method proves chaos in the PDE by proving temporal chaos in its pole solutions. The spatial structure of the pole solutions remains intact, but their positions are chaotic in time. Melnikov's method is invoked to show this temporal chaos. It is discovered that the pole behavior is very sensitive to the Burger's perturbation, but is quite insensitive to the perturbation involving the Hilbert transform

  5. Bitumen stabilized ballast: a potential solution for railway track-bed

    OpenAIRE

    D'Angelo, Giacomo; Thom, Nicholas; Lo Presti, Davide

    2016-01-01

    Railway ballast degradation under dynamic loads progressively leads to loss of mechanical performance and geometry of the track, so that maintenance interventions are frequently needed. In order to systematically avoid this issue, recently solutions have been proposed to reinforce track-bed by using polyurethane and/or resins as well as asphalt layers among others. Nonetheless, their main limitations are related to the high initial cost and low productivity.\\ud To cope with these limitations,...

  6. Stability of the isentropic Riemann solutions of the full multidimensional Euler system

    Czech Academy of Sciences Publication Activity Database

    Feireisl, Eduard; Kreml, Ondřej; Vasseur, A.

    2015-01-01

    Roč. 47, č. 3 (2015), s. 2416-2425 ISSN 0036-1410 R&D Projects: GA ČR GA13-00522S EU Projects: European Commission(XE) 320078 - MATHEF Institutional support: RVO:67985840 Keywords : Euler system * isentropic solutions * Riemann problem * rarefaction wave Subject RIV: BA - General Mathematics Impact factor: 1.486, year: 2015 http://epubs.siam.org/doi/abs/10.1137/140999827

  7. Stabilization of solutions of quasilinear second order parabolic equations in domains with non-compact boundaries

    International Nuclear Information System (INIS)

    Karimov, Ruslan Kh; Kozhevnikova, Larisa M

    2010-01-01

    The first mixed problem with homogeneous Dirichlet boundary condition and initial function with compact support is considered for quasilinear second order parabolic equations in a cylindrical domain D=(0,∞)xΩ. Upper bounds are obtained, which give the rate of decay of the solutions as t→∞ as a function of the geometry of the unbounded domain Ω subset of R n , n≥2. Bibliography: 18 titles.

  8. The effect of disinfecting solutions on the dimensional stability of dental alginate impression materials.

    Science.gov (United States)

    Muzaffar, Danish; Braden, Michael; Parker, Sandra; Patel, Mangala P

    2012-07-01

    Dimensional changes occur in set dental alginate impression materials when immersed in disinfecting solutions. In this contribution the dimensional changes of two alginates in two disinfecting solutions, and for two specimen thicknesses, have been studied. The results were analyzed theoretically. The dimensional changes of two commercial alginates (Blueprint Cremix and Hydrogum), have been measured, in distilled water and two disinfecting solutions (Perform ID/sodium hypochlorite), using a traveling microscope, at 5 min intervals over a period of 1h. Samples of simple geometry have been studied, namely rectangular strips with thicknesses of 1.5 and 3mm, respectively. In all cases, both alginates continuously shrank with time, in the three immersion liquids, over the hour of measurement, indicating transfer of water from the alginate into the external water or disinfecting solution. The t(1/2) shrinkage plots were generally linear, but with an intercept on the t(1/2) axis, indicating the possibility of an initial expansion at very short times. In most cases, the ratios of slopes for both thicknesses were 1.33-1.54, in contrast to the theoretical value of 2. Perform ID however gave anomalous results for the 1.5mm thick samples. At 10 min their shrinkage was 1.34-1.72%, compared with -0.42% to 0.67% in the other two media. The effects of thickness observed were not in accord with simple Fickian theory because of the various ions diffusing into and out of the alginate. Moreover, the water content of the alginate decreased consequent on the cross-linking process. Copyright © 2012 Academy of Dental Materials. Published by Elsevier Ltd. All rights reserved.

  9. Microstructural and microchemical studies of phase stability in V-O solid solution

    Energy Technology Data Exchange (ETDEWEB)

    Ghosh, Chanchal, E-mail: chanchal@igcar.gov.in [Metallurgy & Materials Group, Indira Gandhi Centre for Atomic Research, HBNI, Kalpakkam 603102, Tamil Nadu (India); Singh, Akash [Metallurgy & Materials Group, Indira Gandhi Centre for Atomic Research, HBNI, Kalpakkam 603102, Tamil Nadu (India); Basu, Joysurya [Metallurgy & Materials Group, Indira Gandhi Centre for Atomic Research, HBNI, Kalpakkam 603102, Tamil Nadu (India); Department of Metallurgical Engineering, Indian Institute of Technology (BHU), Varanasi 221005, Uttar Pradesh (India); Ramachandran, Divakar; Mohandas, E [Metallurgy & Materials Group, Indira Gandhi Centre for Atomic Research, HBNI, Kalpakkam 603102, Tamil Nadu (India)

    2017-02-15

    Over the last couple of decades vanadium and V-based alloys have received significant attention as a potential structural material for fusion power applications because of their favourable mechanical properties under irradiation and at elevated temperatures. They are also considered as the advanced options of storage materials for hydrogen and its isotopes. However, the higher affinity of V for O, C and N poses critical challenges in its engineering applications since they lead to degradation of mechanical properties. They can further interact with the matrix to produce metallic oxy-carbo-nitride precipitates. To a certain limit, these precipitates are beneficial and can be exploited to enhance the mechanical behaviour of the alloy through suitable microstructural design. However, this requires a prior knowledge of the interaction between the alloy and the impurity solutes. In the present work vanadium specific experiments have been designed and carried out to bring out the V-interstitial solute interaction by charging oxygen in the near surface region of vanadium. Microstructural and microchemical behaviour of the V-O solid solution has been studied through HRTEM (high resolution transmission electron microscopy) and HAADF (high angle annular dark field) coupled with EELS. Quantitative electron microscopy has been carried out to study structural modification of the alloy in atomic level caused by O charging. - Highlights: •Controlled experiments were carried out in pulsed laser ablation set-up to promote V-O interaction. • As a consequence of O dissolution, V transformed into a bct structure which is otherwise a bcc structure. •In V-O solid solution, dissolved O in the V matrix introduces significant amount of lattice strain. • Present work can be extended for introducing interstitial O in other pure transition metals and their alloys.

  10. Effects of mannose, fructose, and fucose on the structure, stability, and hydration of lysozyme in aqueous solution

    DEFF Research Database (Denmark)

    Rahim, Abdoul; Peters, Günther H.J.; Jalkanen, Karl J.

    2013-01-01

    The bio-protective properties of monosaccharaides, namely mannose, fructose and fucose, on the stability and dynamical properties of the NMR determined hen egg-white lysozyme structure have been investigated by means of molecular dynamics simulations at room temperature in aqueous solution and in...... of the solvent and sugar distributions around lysozyme was used to investigate the interfacial solvent and sugar structure near the protein surface.......The bio-protective properties of monosaccharaides, namely mannose, fructose and fucose, on the stability and dynamical properties of the NMR determined hen egg-white lysozyme structure have been investigated by means of molecular dynamics simulations at room temperature in aqueous solution and in 7...... and 13 wt % concentrations of the three sugars. Results are discussed in the framework of the bio-protective phenomena. The three sugars show similar bio-protective behaviours at room temperature (300 K) in the concentration range studied as shown by the small RMSDs of the resulting MD structures from...

  11. Effects of pH on the stability of cyanidin and cyanidin 3-O-β-glucopyranoside in aqueous solution

    Directory of Open Access Journals (Sweden)

    Rakić Violeta P.

    2015-01-01

    Full Text Available The colour variation, colour intensity and stability at various pH values (2.0, 4.0, 7.0 and 9.0 of cyanidin 3-O-β-glucopyranoside (Cy3Glc and its aglycone cyanidin was investigated during a period of 8 hours storage at 25ºC. Our data showed that pH of aqueous solution had impact on spectroscopic profile of cyanidin and Cy3Glc. Beginning with the most acidic solutions, increasing the pH induce bathochromic shifts of absorbance maximum in the visible range for all examined pH values (with the exception pH 4.0 for cyanidin, while the presence of the 3-glucosidic substitution induce hypsochromic shift. Compared to cyanidin, Cy3Glc has higher colour intensity and higher stability in the whole pH range, except at pH 7.0. The 3-glucosidic substitution influences on the colour intensity of Cy3Glc in the alkaline region. After 8-hour incubation of Cy3Glc and cyanidin at pH 2.0 and 25 ºC, 99% of Cy3Glc and only 27% of cyanidin remained unchanged.

  12. Hydration interactions and stability of soluble microbial products in aqueous solutions.

    Science.gov (United States)

    Wang, Ling-Ling; Wang, Long-Fei; Ye, Xiao-Dong; Yu, Han-Qing

    2013-10-01

    Soluble microbial products (SMP) are organic compounds excreted by microorganisms in their metabolism and decay and the main constituents in effluent from biological wastewater treatment systems. They also have an important contribution to the dissolved organic matters in natural aqueous systems. So far the interactions between SMP colloids have not been well explored. In this work, the interactions between SMP colloids in water and salt solutions were studied by using a combination of static and dynamic light scattering, Fourier transform infrared spectra, Zeta potential and acid-base titration techniques. The second osmotic virial coefficient had a larger value in a 750-mM salt solution than that in a 50-mM solution, indicating that repulsion between SMP colloids increased with an increase in salt concentration, which is contrary with the classic Derjaguin, Landau, Verwey, and Overbeek (DLVO) theory. Such a repulsion was attributed to water structuring and enhanced by the accumulation of hydrophilic counter ions around SMP colloids and the formed hydration force. The repulsion and hydration effect led to the dispersing and deeper draining structure, accompanied by a decreased hydrodynamic radius and increased diffusion coefficient. This hydration force was related to so-called ion specific effect, and electrolyte sodium chloride had a more substantial effect on hydration force than KCl, CsCl, NaBr and NaI. Our results provide an experimental approach to explore the SMP structures, inter-colloid interactions and confirm the non-DLVO forces. Copyright © 2013 Elsevier Ltd. All rights reserved.

  13. Pupil size stability of the cubic phase mask solution for presbyopia

    Science.gov (United States)

    Almaguer, Citlalli; Acosta, Eva; Arines, Justo

    2018-01-01

    Presbyopia correction involves different types of studies such as lens design, clinical study, and the development of objective metrics, such as the visual Strehl ratio. Different contact lens designs have been proposed for presbyopia correction, but performance depends on pupil diameter. We will analyze the potential use of a nonsymmetrical element, a cubic phase mask (CPM) solution, to develop a contact or intraocular lens whose performance is nearly insensitive to changes in pupil diameter. We will show the through focus optical transfer function of the proposed element for different pupil diameters ranging from 3 to 7 mm. Additionally, we will show the images obtained through computation and experiment for a group of eye charts with different visual acuities. Our results show that a CPM shaped as 7.07 μm*(Z33-Z3-3)-0.9 μm Z20 is a good solution for a range of clear vision with a visual acuity of at least 0.1 logMar from 0.4 to 6 m for pupil diameters in the 3- to 7-mm range. Our results appear to be a good starting point for further development and study of this kind of CPM solution for presbyopia.

  14. Upper Bound Solution for the Face Stability of Shield Tunnel below the Water Table

    Directory of Open Access Journals (Sweden)

    Xilin Lu

    2014-01-01

    Full Text Available By FE simulation with Mohr-Coulomb perfect elastoplasticity model, the relationship between the support pressure and displacement of the shield tunnel face was obtained. According to the plastic strain distribution at collapse state, an appropriate failure mechanism was proposed for upper bound limit analysis, and the formula to calculate the limit support pressure was deduced. The limit support pressure was rearranged to be the summation of soil cohesion c, surcharge load q, and soil gravity γ multiplied by their corresponding coefficients Nc, Nq, and Nγ, and parametric studies were carried out on these coefficients. In order to consider the influence of seepage on the face stability, the pore water pressure distribution and the seepage force on the tunnel face were obtained by FE simulation. After adding the power of seepage force into the equation of the upper bound limit analysis, the total limit support pressure for stabilizing the tunnel face under seepage condition was obtained. The total limit support pressure was shown to increase almost linearly with the water table.

  15. Stability of the Stevia-Derived Sweetener Rebaudioside A in Solution as Affected by Ultraviolet Light Exposure.

    Science.gov (United States)

    Zhang, Jiewen; Bell, Leonard N

    2017-04-01

    Rebaudioside A is a natural noncaloric high-potency sweetener extracted from the leaves of Stevia rebaudiana. With rebaudioside A use increasing in foods, understanding the factors affecting its stability is necessary. This project evaluated the degradation rate constants of rebaudioside A in water, 0.1 M phosphate buffer, and 0.1 M citrate buffer at pH 3 and 7 as a function of ultraviolet (UV) light intensity (365 nm, 0 μW/cm 2 for dark conditions, 27 μW/cm 2 for low intensity, and 190 μW/cm 2 for high intensity) at 32.5 °C. Rebaudioside A stability was adversely affected by light exposure. The pseudo-1st-order degradation rate constants increased significantly (P < 0.05) with increasing light intensity in all solutions. Under dark conditions, rebaudioside A in phosphate buffers was more susceptible to breakdown than in water and citrate buffers at both pH levels. However, exposure to UV light resulted in rebaudioside A degradation occurring approximately 10 times faster in citrate than in phosphate buffers at both pH levels. The sensitivity of rebaudioside A to UV light was greater in citrate buffers than in water or phosphate buffers. The use of light-protective packaging for beverages containing rebaudioside A will improve its stability. © 2017 Institute of Food Technologists®.

  16. Stability-Indicating HPLC Method for Simultaneous Determination of Chloramphenicol, Dexamethasone Sodium Phosphate and Tetrahydrozoline Hydrochloride in Ophthalmic Solution.

    Science.gov (United States)

    AlAani, Hashem; Alnukkary, Yasmin

    2016-03-01

    A simple stability-indicating RP-HPLC assay method was developed and validated for quantitative determination of Chloramphenicol, Dexamethasone Sodium Phosphate and Tetrahydrozoline Hydrochloride in ophthalmic solution in the presence of 2-amino-1-(4-nitrophenyl)propane-1,3-diol, a degradation product of Chloramphenicol, and Dexamethasone, a degradation product of Dexamethasone Sodium Phosphate. Effective chromatographic separation was achieved using C18 column (250 mm, 4.6 mm i.d., 5 μm) with isocratic mobile phase consisting of acetonitrile - phosphate buffer (pH 4.0; 0.05 M) (30:70, v/v) at a flow rate of 1 mL/minute. The column temperature was maintained at 40°C and the detection wavelength was 230 nm. The proposed HPLC procedure was statistically validated according to the ICH guideline, and was proved to be stability-indicating by resolution of the APIs from their forced degradation products. The developed method is suitable for the routine analysis as well as stability studies.

  17. Full Stability of Locally Optimal Solutions in Second-Order Cone Programs

    Czech Academy of Sciences Publication Activity Database

    Mordukhovich, B. S.; Outrata, Jiří; Sarabi, E.

    2014-01-01

    Roč. 24, č. 4 (2014), s. 1581-1613 ISSN 1052-6234 R&D Projects: GA ČR GAP402/12/1309 Grant - others:Australian Research Council(AU) DP-12092508; Australian Research Council(AU) DP-110102011; Portuguese Foundation of Science and Technologies(PT) MAT/11109; USA National Science Foundation(US) DMS-1007132 Institutional support: RVO:67985556 Keywords : variational analysis * second-order cone programming * full stability of local minimizers * nondegeneracy * strong regularity * quadratic growth * second-order subdifferentials * coderivatives Subject RIV: BA - General Mathematics Impact factor: 1.829, year: 2014 http://library.utia.cas.cz/separaty/2014/MTR/outrata-0434303.pdf

  18. Effects of Pressure on Stability of Biomolecules in Solutions Studied by Neutron Scattering

    Science.gov (United States)

    Bellissent-Funel, Marie-Claire-; Appavou, Marie-Sousai; Gibrat, Gabriel

    Studies of the pressure dependence on protein structure and dynamics contribute not only to the basic knowledge of biological molecules but have also a considerable relevance in full technology, like in food sterilization and pharmacy. Conformational changes induced by pressure as well as the effects on the protein stability have been mostly studied by optical techniques (optical absorption, fluorescence, phosphorescence), and by NMR. Most optical techniques used so far give information related to the local nature of the used probe (fluorescent or phosphorescent tryptophan). Small angle neutron scattering and quasi-elastic neutron scattering provide essential complementary information to the optical data, giving quantitative data on change of conformation of soluble globular proteins such as bovine pancreatic trypsin inhibitor (BPTI) and on the mobility of protons belonging to the protein surface residues.

  19. Reduced Dental Plaque Formation in Dogs Drinking a Solution Containing Natural Antimicrobial Herbal Enzymes and Organic Matcha Green Tea

    Directory of Open Access Journals (Sweden)

    Michael I. Lindinger

    2016-01-01

    Full Text Available The results of an exploratory, multicenter clinical study confirmed the hypothesis that a novel, natural, and safe oral care product (OCP reduced the rate of plaque formation on teeth of dogs consuming the OCP (antimicrobial plant-derived enzymes, organic matcha green tea, cultured dextrose, sodium bicarbonate, and ascorbic acid compared to controls. Healthy dogs without periodontitis, of varying breeds, sex, and age, were recruited and enrolled, using nonrandomized stratification methods, into a control and treatment groups. Treatment group dogs drank only water into which OCP was suspended, for 28 days. Control group dogs drank their normal household water. On day 0 all teeth were cleaned by a veterinarian and gingivitis was assessed. On days 14, 21, and 28 plaque index, plaque thickness, gingivitis, freshness of breath, and general health were assessed. Over the 28 days of study, dogs on the OCP had significant reduction in plaque index and plaque thickness compared to controls. By day 14 OCP reduced plaque formation by 37%; the 28-day reduction in plaque index and coverage averaged 22% with no measurable gingivitis or calculus. Conclusion. Using the OCP attenuated dental plaque formation when consumed as normal drinking water and in the absence of other modes of oral care.

  20. Stability of antibiotics and amino acids in two synthetic L-amino acid solutions commonly used for total parenteral nutrition in children

    DEFF Research Database (Denmark)

    Colding, H; Andersen, G E

    1978-01-01

    The stability and interaction at 29 degrees C of ampicillin, carbenicillin, gentamicin, and polymyxin B were examined in a common electrolyte solution, invertose darrow, and in two synthetic l-amino acid solutions, one commercial (vamin with fructose; Vitrum) and the other a neonatal preparation ...

  1. Effect of temperature on chlorproguanil and proguanil hydrochloride solutions: a chemical stability study.

    Science.gov (United States)

    Kolawole, J A; Mustapha, A; Abdul-Aguye, I; Ochekpe, N

    1996-04-01

    Chlorproguanil and proguanil hydrochloride solutions in 0.5 M hydrochloric acid, water and 1 M ammonium hydroxide were subjected to different temperatures (22-80 degrees C) for 68 h. The decomposition rate constants for chlorproguanil ranged from 1.60 to 47.6 x 10(3) h-1 in acid, 3.5 to 18 x 10(3) h-1 in water and 3.87 to 32.5 x 10(3) h-1 in base, between 50 degrees C and 80 degrees C. The activation energy Ea was 96.5, 52.12 and 62.1 kJ mol-1 in acid, water and base respectively. The proguanil decomposition rate constant ranged from 1.72 to 18.5 x 10(3) h-1 in acid, 1.58 to 9.67 x 10(3) h-1 in water and 2.34 to 15.77 x 10(3) h-1 in base, between 50 degrees C and 80 degrees C, with Ea values of 54.7, 73.3 and 62.5 kJ mol-1. Three unidentified degradation products were separated in the acid solution for each of the compounds. Chlorproguanil and proguanil are stable (t1/2 values over 30 days and up to 287 days respectively) in acid, water and base at temperatures below 22 degrees C.

  2. Asymptotic stability of shear-flow solutions to incompressible viscous free boundary problems with and without surface tension

    Science.gov (United States)

    Tice, Ian

    2018-04-01

    This paper concerns the dynamics of a layer of incompressible viscous fluid lying above a rigid plane and with an upper boundary given by a free surface. The fluid is subject to a constant external force with a horizontal component, which arises in modeling the motion of such a fluid down an inclined plane, after a coordinate change. We consider the problem both with and without surface tension for horizontally periodic flows. This problem gives rise to shear-flow equilibrium solutions, and the main thrust of this paper is to study the asymptotic stability of the equilibria in certain parameter regimes. We prove that there exists a parameter regime in which sufficiently small perturbations of the equilibrium at time t=0 give rise to global-in-time solutions that return to equilibrium exponentially in the case with surface tension and almost exponentially in the case without surface tension. We also establish a vanishing surface tension limit, which connects the solutions with and without surface tension.

  3. Stability-Indicating HPTLC Method for Simultaneous Estimation of Flurbiprofen and Chloramphenicol in Ophthalmic Solution.

    Science.gov (United States)

    Sadakwala, Vaishnavi M; Chauhan, Renu S; Shah, Shailesh A; Shah, Dinesh R

    2016-01-01

    A specific, accurate and reproducible stability-indicating high performance thin layer chromatography (HPTLC) method was developed for the estimation of flurbiprofen and chloramphenicol in the presence of their degradation products. Degradation studies of both the drugs were carried out in acidic, alkaline, neutral, oxidative, photolytic and thermal stress conditions. Separation was performed on thin layer chromatography plate precoated with silica gel 60 F254 using ethyl acetate : n-hexane : methanol : tri-ethyl amine (5 : 4 : 2 : 0.5, v/v/v/v). Spots at retention factor 0.29 and 0.62 were recognized as flurbiprofen and chloramphenicol, respectively, and were quantified through densitometric measurements at wavelength 267 nm. Method was found to be linear over the concentration range 12-60 ng/spot with correlation coefficient of 0.9997 for flurbiprofen and 200-1,000 ng/spot with correlation coefficient of 0.9977 for chloramphenicol. The proposed method was applied to the estimation of flurbiprofen and chloramphenicol in commercial ophthalmic formulation. The developed HPTLC method can be applied for routine analysis of flurbiprofen and chloramphenicol in the presence of their degradation products in their individual as well as combined pharmaceutical formulations. © The Author 2015. Published by Oxford University Press. All rights reserved. For Permissions, please email: journals.permissions@oup.com.

  4. Solution characterization of the extracellular region of CD147 and its interaction with its enzyme ligand cyclophilin-A

    Energy Technology Data Exchange (ETDEWEB)

    Schlegel, Jennifer; Redzic, Jasmina S.; Porter, Christopher; Yurchenko, Vyacheslav; Bukrinsky, Michael; Labeikovsky, Wladimir; Armstrong, Geoffrey S.; Zhang, Fengli; Isern, Nancy G.; Degregori, James; Hodges, Robert; Eisenmesser, Elan Z.

    2009-08-21

    The CD147 receptor plays an integral role in numerous diseases by stimulating the expression of several protein families and serving as the receptor for extracellular cyclophilins, however, neither CD147 nor its interactions with its cyclophilin ligands have been well characterized in solution. CD147 is a unique protein in that it can function both at the cell membrane and after being released from cells where it continues to retain activity. Thus, the CD147 receptor functions through at least two mechanisms that include both cyclophilin-independent and cyclophilin-dependent modes of action. In regard to CD147 cyclophilin-independent activity, CD147 homophilic interactions are thought to underlie its activity. In regard to CD147 cyclophilin-dependent activity, cyclophilin/CD147 interactions may represent a novel means of signaling since cyclophilins are also peptidyl-prolyl isomerases.

  5. Growth kinetics and long-term stability of CdS nanoparticles in aqueous solution under ambient conditions

    International Nuclear Information System (INIS)

    Mullaugh, Katherine M.; Luther, George W.

    2011-01-01

    The ubiquity of naturally occurring nanoparticles in the aquatic environment is now widely accepted, but a better understanding of the conditions that promote their formation and persistence is needed. Using cadmium sulfide (CdS) as a model metal sulfide species, thiolate-capped CdS nanoparticles were prepared in the laboratory to evaluate how aquatic conditions influence metal sulfide nanoparticle growth and stability. This work examines CdS nanoparticle growth directly in aqueous solution at room temperature by utilizing the size-dependent spectroscopic properties of semiconductors detectable by UV/vis. CdS nanoparticle growth was governed by oriented attachment, a non-classical mechanism of crystallization in which small precursor nanoparticles coalesce to form larger nanoparticle products. Nanoparticle growth was slowed with increasing capping agent and decreasing ionic strength. In addition to examining the short-term (hours) growth of the nanoparticles, a long-term study was conducted in which cysteine-capped CdS nanoparticles were monitored over 3 weeks in solutions of various ionic strengths. The long-term study revealed an apparent shift from small nanoparticles to nanoparticles twice their original size, suggesting nanoparticle growth may continue through oriented attachment over longer time scales. High-ionic strength solutions resulted in salt-induced aggregation and eventual settling of nanoparticles within days, whereas low-ionic strength solutions were stable against settling over the course of the experiment. Sulfide recovery from cysteine-capped CdS nanoparticles as acid volatile sulfide was nearly quantitative after 2 weeks in fully oxygenated water, demonstrating significantly slowed oxidation of sulfide when complexed to Cd(II) within CdS nanoparticles. The nanoparticles were also shown to be resistant to oxidation by Fe(III) (hydr)oxide. This study illustrates that aggregation, rather than chemical oxidation, is likely more important to the

  6. Rationally designed turn promoting mutation in the amyloid-β peptide sequence stabilizes oligomers in solution.

    Directory of Open Access Journals (Sweden)

    Jayakumar Rajadas

    Full Text Available Enhanced production of a 42-residue beta amyloid peptide (Aβ(42 in affected parts of the brain has been suggested to be the main causative factor for the development of Alzheimer's Disease (AD. The severity of the disease depends not only on the amount of the peptide but also its conformational transition leading to the formation of oligomeric amyloid-derived diffusible ligands (ADDLs in the brain of AD patients. Despite being significant to the understanding of AD mechanism, no atomic-resolution structures are available for these species due to the evanescent nature of ADDLs that hinders most structural biophysical investigations. Based on our molecular modeling and computational studies, we have designed Met35Nle and G37p mutations in the Aβ(42 peptide (Aβ(42Nle35p37 that appear to organize Aβ(42 into stable oligomers. 2D NMR on the Aβ(42Nle35p37 peptide revealed the occurrence of two β-turns in the V24-N27 and V36-V39 stretches that could be the possible cause for the oligomer stability. We did not observe corresponding NOEs for the V24-N27 turn in the Aβ(21-43Nle35p37 fragment suggesting the need for the longer length amyloid peptide to form the stable oligomer promoting conformation. Because of the presence of two turns in the mutant peptide which were absent in solid state NMR structures for the fibrils, we propose, fibril formation might be hindered. The biophysical information obtained in this work could aid in the development of structural models for toxic oligomer formation that could facilitate the development of therapeutic approaches to AD.

  7. Tank Waste Transport Stability: Summaries of Hanford Slurry and Salt-Solution Studies in FY 2000

    Energy Technology Data Exchange (ETDEWEB)

    Welch, T.D.

    2002-07-08

    This report is a collection of summary articles on FY 2000 studies of slurry transport and salt-well pumping related to Hanford tank waste transfers. These studies are concerned with the stability (steady, uninterrupted flow) of tank waste transfers, a subset of the Department of Energy (DOE) Tanks Focus Area Tank (TFA) Waste Chemistry effort. This work is a collaborative effort of AEA Technology plc, the Diagnostic Instrumentation and Analysis Laboratory at Mississippi State University (DIAL-MSU), the Hemispheric Center for Environmental Technology at Florida International University (HCET-FIU), Numatec Hanford Corporation (NHC), and the Oak Ridge National Laboratory (ORNL). The purpose of this report is to provide, in a single document, an overview of these studies to help the reader identify contacts and resources for obtaining more detailed information and to help promote useful interchanges between researchers and users. Despite over 50 years of experience in transporting radioactive tank wastes to and from equipment and tanks at the Department of Energy's Hanford, Savannah River, and Oak Ridge sites, waste slurry transfer pipelines and process piping become plugged on occasion. At Hanford, several tank farm pipelines are no longer in service because of plugs. At Savannah River, solid deposits in the outlet line of the 2H evaporator have resulted in an unplanned extended downtime. Although waste transfer criteria and guidelines intended to prevent pipeline plugging are in place, they are not always adequate. To avoid pipeline plugging in the future, other factors that are not currently embodied in the transfer criteria may need to be considered. The work summarized here is being conducted to develop a better understanding of the chemical and waste flow dynamics during waste transfer. The goal is to eliminate pipeline plugs by improving analysis and engineering tools in the field that incorporate this understanding.

  8. A stabilized finite element formulation for the solution of the Navier-Stokes equations in axisymmetric geometry

    International Nuclear Information System (INIS)

    Souza, Altivo Monteiro de

    2008-12-01

    The world energy consumption has been increasing strongly in recent years. Nuclear energy has been regarded as a suitable option to supply this growing energy demand in industrial scale. In view of the need of improving the understanding and capacity of analysis of nuclear power plants, modern simulation techniques for flow and heat transfer problems are gaining greater importance. A large number of problems found in nuclear reactor engineering can be dealt assuming axial symmetry. Thus, in this work a stabilized finite element formulation for the solution of the Navier-Stokes and energy equations for axisymmetric problems have been developed and tested. The formulation has been implemented in the NS S OLVER M PI 2 D A program developed at the Parallel Computation Laboratory of the Instituto de Engenharia Nuclear (LCP/IEN) and is now available either for safety analysis or design of nuclear systems. (author)

  9. Solution stabilities of some mixed ligand complexes of UO22+ and Th4+ with complexones and salicylic acids

    International Nuclear Information System (INIS)

    Singh, R.K.; Saxena, M.C.

    1991-01-01

    Formation constants (log Ksub(MAL)sup(MA)) of mixed ligands complexes (MAL), where M = UO 2 2+ or Th 4+ , A = IMDA, NTA, HEDTA, EDTA, CDTA or DTPA, L = salicylic acid (SA) or 5-sulphosalicylic acid (SSA), have been determined by pH titrations using Irving-Rossotti approach at 25 o C and at I =0.2 (mol dm -3 , KNO 3 ). The solution stabilities exhibit the sequence (i) Th 4+ >UO 2 2+ , (ii) IMDA>NTA>HEDTA>EDTA>CDTA>DTPA, and (iii) SA>SSA with respect to metal ions, primary ligands and secondary ligands, respectively. The formation constants log Ksub(ML)sup(M) and log Ksub(ML 2 )sup(ML) have also been determined. The Δlog K values have been found to be negative-increasing numerically with the negative charge on the deprotonated primary ligand (A n- ). (author). 17 refs., 1 tab

  10. Instability of Wind Turbine Converters during Current Injection to Low Voltage Grid Faults and PLL Frequency Based Stability Solution

    DEFF Research Database (Denmark)

    Göksu, Ömer; Teodorescu, Remus; Bak, Claus Leth

    2014-01-01

    In recent grid codes for wind power integration, wind turbines are required to stay connected during grid faults even when the grid voltage drops down to zero; and also to inject reactive current in proportion to the voltage drop. However, a physical fact, instability of grid-connected converters...... during current injection to very low (close to zero) voltage faults, has been omitted, i.e., failed to be noticed in the previous wind power studies and grid code revisions. In this paper, the instability of grid side converters of wind turbines defined as loss of synchronism (LOS), where the wind...... turbines lose synchronism with the grid fundamental frequency (e.g., 50 Hz) during very deep voltage sags, is explored with its theory, analyzed and a novel stability solution based on PLL frequency is proposed; and both are verified with power system simulations and by experiments on a grid...

  11. Clozapine-carboxylic acid plasticized co-amorphous dispersions: Preparation, characterization and solution stability evaluation

    Directory of Open Access Journals (Sweden)

    Ali Ahmed Mahmoud Abdelhaleem

    2015-06-01

    Full Text Available This study addressed the possibility of forming of co-amorphous systems between clozapine (CZ and various carboxylic acid plasticizers (CAPs. The aim was to improve the solubility and oral bioavailability of clozapine. Co-amorphous dispersions were prepared using modified solvent evaporation methodology at drug/plasticizer stoichiometric ratios of 1:1, 1:1.5 and 1:2. Solid state characterization was performed using differential scanning calorimetry, X-ray diffraction and infra red spectroscopy. Highly soluble homogeneous co-amorphous dispersions were formed between clozapine and CAPs via hydrogen bonding. The co-amorphous dispersions formed with tartaric acid (1:2 showed the highest dissolution percentage (> 95 % in 20 minutes compared to pure crystalline CZ (56 %. Highly stable solutions were obtained from co-amorphous CZ-citric and CZ-tartaric acid at 1:1.5 molar ratio. The prepared dispersions suggest the possibility of peroral or sublingual administration of highly soluble clozapine at a reduced dose with the great chance to bypass the first pass metabolism.

  12. Stabilized Discretization in Spline Element Method for Solution of Two-Dimensional Navier-Stokes Problems

    Directory of Open Access Journals (Sweden)

    Neng Wan

    2014-01-01

    Full Text Available In terms of the poor geometric adaptability of spline element method, a geometric precision spline method, which uses the rational Bezier patches to indicate the solution domain, is proposed for two-dimensional viscous uncompressed Navier-Stokes equation. Besides fewer pending unknowns, higher accuracy, and computation efficiency, it possesses such advantages as accurate representation of isogeometric analysis for object boundary and the unity of geometry and analysis modeling. Meanwhile, the selection of B-spline basis functions and the grid definition is studied and a stable discretization format satisfying inf-sup conditions is proposed. The degree of spline functions approaching the velocity field is one order higher than that approaching pressure field, and these functions are defined on one-time refined grid. The Dirichlet boundary conditions are imposed through the Nitsche variational principle in weak form due to the lack of interpolation properties of the B-splines functions. Finally, the validity of the proposed method is verified with some examples.

  13. One-step synthesis and applications of fluorescent Cu nanoclusters stabilized by L-cysteine in aqueous solution

    International Nuclear Information System (INIS)

    Yang, Xiaoming; Feng, Yuanjiao; Zhu, Shanshan; Luo, Yawen; Zhuo, Yan; Dou, Yao

    2014-01-01

    Graphical abstract: An innovative and simple strategy for synthesizing high-fluorescent Cu nanoclusters stabilized with L-cysteine has been successfully established in aqueous solution. Significantly, the Cu nanoclusters were employed for sensitive and selective detections of Hg 2+ , coding and fluorescent staining, suggesting their potential toward various applications. - Highlights: • A novel, one-step strategy for synthesizing water-soluble CuNCs was established. • A simple, selective, and cost-effective assay for Hg 2+ was developed. • CuNCs may broaden ways for fluorescent staining and coding. - Abstract: Herein, an innovative and simple strategy for synthesizing high fluorescent Cu nanoclusters was successfully established while L-cysteine played a role as the stabilizer. Meaningfully, the current Cu nanoclusters together with a quantum yield of 14.3% were prepared in aqueous solution, indicating their extensive applications. Subsequently, the possible fluorescence mechanism was elucidated by fluorescence, UV–vis, HR-TEM, FTIR, XPS, and MS. Additionally, the CuNCs were employed for assaying Hg 2+ on the basis of the interactions between Hg 2+ and L-cysteine; thus facilitating the quenching of their fluorescence. The proposed analytical strategy permitted detections of Hg 2+ in a linear range of 1.0 × 10 −7 mol L −1 × 10 −3 mol L −1 , with a detection limit of 2.4 × 10 −8 mol L −1 at a signal-to-noise ratio of 3. Significantly, this CuNCs described here were further applied for coding and fluorescent staining, suggesting may broaden avenues toward diverse applications

  14. One-step synthesis and applications of fluorescent Cu nanoclusters stabilized by L-cysteine in aqueous solution

    Energy Technology Data Exchange (ETDEWEB)

    Yang, Xiaoming, E-mail: ming4444@swu.edu.cn; Feng, Yuanjiao; Zhu, Shanshan; Luo, Yawen; Zhuo, Yan; Dou, Yao

    2014-10-17

    Graphical abstract: An innovative and simple strategy for synthesizing high-fluorescent Cu nanoclusters stabilized with L-cysteine has been successfully established in aqueous solution. Significantly, the Cu nanoclusters were employed for sensitive and selective detections of Hg{sup 2+}, coding and fluorescent staining, suggesting their potential toward various applications. - Highlights: • A novel, one-step strategy for synthesizing water-soluble CuNCs was established. • A simple, selective, and cost-effective assay for Hg{sup 2+} was developed. • CuNCs may broaden ways for fluorescent staining and coding. - Abstract: Herein, an innovative and simple strategy for synthesizing high fluorescent Cu nanoclusters was successfully established while L-cysteine played a role as the stabilizer. Meaningfully, the current Cu nanoclusters together with a quantum yield of 14.3% were prepared in aqueous solution, indicating their extensive applications. Subsequently, the possible fluorescence mechanism was elucidated by fluorescence, UV–vis, HR-TEM, FTIR, XPS, and MS. Additionally, the CuNCs were employed for assaying Hg{sup 2+} on the basis of the interactions between Hg{sup 2+} and L-cysteine; thus facilitating the quenching of their fluorescence. The proposed analytical strategy permitted detections of Hg{sup 2+} in a linear range of 1.0 × 10{sup −7} mol L{sup −1} × 10{sup −3} mol L{sup −1}, with a detection limit of 2.4 × 10{sup −8} mol L{sup −1} at a signal-to-noise ratio of 3. Significantly, this CuNCs described here were further applied for coding and fluorescent staining, suggesting may broaden avenues toward diverse applications.

  15. Color stability of sealed composite resin restorative materials after ultraviolet artificial aging and immersion in staining solutions.

    Science.gov (United States)

    Catelan, Anderson; Briso, André Luiz Fraga; Sundfeld, Renato Hermann; Goiato, Marcelo Coelho; dos Santos, Paulo Henrique

    2011-04-01

    The color alteration of resin-based materials is one of the most common reasons to replace esthetic dental restorations. This study assessed the influence of surface sealant (Biscover) on the color stability of nanofilled (Supreme XT) and microhybrid (Vit-l-escence and Opallis) composite resins after artificial aging. One hundred disc-shaped (6 × 1.5 mm) specimens were made for each composite resin. After 24 hours, all specimens were polished and sealant was applied to 50 specimens of each material. Baseline color was measured according to the CIE L*a*b* system using a reflection spectrophotometer. Ten specimens of each group were aged for 252 h in an ultraviolet (UV)-accelerated aging chamber or immersed for 4 weeks in cola soft drink, orange juice, red wine staining solutions or distilled water as control. Color difference (ΔE) after aging was calculated based on the color coordinates before (baseline) and after aging/staining treatment. Data were analyzed with 2-way ANOVA and Fisher's test (α=.05). The results showed significant changes in color after artificial aging in all the groups (Paging, and the cola soft drink. The lowest values of ΔE were found for specimens stored in distilled water. All composite resins showed some color alteration after the aging methods. The surface sealant did not alter the color stability of the tested materials. Copyright © 2011 The Editorial Council of the Journal of Prosthetic Dentistry. Published by Mosby, Inc. All rights reserved.

  16. Solution processed transition metal oxide anode buffer layers for efficiency and stability enhancement of polymer solar cells

    Science.gov (United States)

    Ameen, M. Yoosuf; Shamjid, P.; Abhijith, T.; Reddy, V. S.

    2018-01-01

    Polymer solar cells were fabricated with solution-processed transition metal oxides, MoO3 and V2O5 as anode buffer layers (ABLs). The optimized device with V2O5 ABL exhibited considerably higher power conversion efficiency (PCE) compared to the devices based on MoO3 and poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) ABLs. The space charge limited current measurements and impedance spectroscopy results of hole-only devices revealed that V2O5 provided a very low charge transfer resistance and high hole mobility, facilitating efficient hole transfer from the active layer to the ITO anode. More importantly, incorporation of V2O5 as ABL resulted in substantial improvement in device stability compared to MoO3 and PEDOT:PSS based devices. Unencapsulated PEDOT:PSS-based devices stored at a relative humidity of 45% have shown complete failure within 96 h. Whereas, MoO3 and V2O5 based devices stored in similar conditions retained 22% and 80% of their initial PCEs after 96 h. Significantly higher stability of the V2O5-based device is ascribed to the reduction in degradation of the anode/active layer interface, as evident from the electrical measurements.

  17. Numerical solutions of magnetohydrodynamic stability of axisymmetric toroidal plasmas using cubic B-spline finite element method

    International Nuclear Information System (INIS)

    Cheng, C.Z.

    1988-12-01

    A nonvariational ideal MHD stability code (NOVA) has been developed. In a general flux coordinate (/psi/, θ, /zeta/) system with an arbitrary Jacobian, the NOVA code employs Fourier expansions in the generalized poloidal angle θ and generalized toroidal angle /zeta/ directions, and cubic-B spline finite elements in the radial /psi/ direction. Extensive comparisons with these variational ideal MHD codes show that the NOVA code converges faster and gives more accurate results. An extended version of NOVA is developed to integrate non-Hermitian eigenmode equations due to energetic particles. The set of non-Hermitian integro-differential eigenmode equations is numerically solved by the NOVA-K code. We have studied the problems of the stabilization of ideal MHD internal kink modes by hot particle pressure and the excitation of ''fishbone'' internal kink modes by resonating with the energetic particle magnetic drift frequency. Comparisons with analytical solutions show that the values of the critical β/sub h/ from the analytical theory can be an order of magnitude different from those computed by the NOVA-K code. 24 refs., 11 figs., 1 tab

  18. Numerical solutions of magnetohydrodynamic stability of axisymmetric toroidal plasmas using cubic B-spline finite element method

    Energy Technology Data Exchange (ETDEWEB)

    Cheng, C.Z.

    1988-12-01

    A nonvariational ideal MHD stability code (NOVA) has been developed. In a general flux coordinate (/psi/, theta, /zeta/) system with an arbitrary Jacobian, the NOVA code employs Fourier expansions in the generalized poloidal angle theta and generalized toroidal angle /zeta/ directions, and cubic-B spline finite elements in the radial /psi/ direction. Extensive comparisons with these variational ideal MHD codes show that the NOVA code converges faster and gives more accurate results. An extended version of NOVA is developed to integrate non-Hermitian eigenmode equations due to energetic particles. The set of non-Hermitian integro-differential eigenmode equations is numerically solved by the NOVA-K code. We have studied the problems of the stabilization of ideal MHD internal kink modes by hot particle pressure and the excitation of ''fishbone'' internal kink modes by resonating with the energetic particle magnetic drift frequency. Comparisons with analytical solutions show that the values of the critical ..beta../sub h/ from the analytical theory can be an order of magnitude different from those computed by the NOVA-K code. 24 refs., 11 figs., 1 tab.

  19. Potentiometric titration for determining the composition and stability of metal(II) alginates and pectinates in aqueous solutions

    Science.gov (United States)

    Kaisheva, N. Sh.; Kaishev, A. Sh.

    2015-07-01

    The compositions and stabilities of Cu2+, Mn2+, Pb2+, Ca2+, Zn2+, Cd2+, Co2+, and Ni2+ alginates and pectinates are determined in aqueous solutions via titrimetry and potentiometry with calculations performed using Bjerrum's method, the curve intersection technique, and the equilibrium shift method. It is found that the interaction between Cu2+ and polyuronides is a stepwise process and, depending on the ligand concentration and the method of determination, Cu2+ alginate can be characterized by its ML, ML2, and ML3 compositions (where M is the metal ion and L is the structural unit of polyuronide) and stability constants logβ = 2.65, 5.00-5.70, and 7.18-7.80, respectively. The compositions of Cu2+ pectinates are ML and ML2 with logβ = 3.00 and 7.64-7.94, respectively. It is concluded that Pb2+, Ca2+, Mn2+, Zn2+, Cd2+, Co2+, and Ni2+ ions form only alginates and pectinates of ML2 composition with logβ values of 3.45 (Pb2+ alginate), 2.20 (Ca2+ alginate), 1.06 (Mn2+ alginate), 3.51 (Pb2+ pectinate), 2.35 (Ca2+ pectinate), and 1.24 (Mn2+ pectinate). The pectinates are shown to be more stable than the alginates, the most stable compounds being those formed by polyuronides and Cu2+. The least stable are those with Mn2+.

  20. Effect of chitosan on the heat stability of whey protein solution as a function of pH.

    Science.gov (United States)

    Zhao, Zhengtao; Xiao, Qian

    2017-03-01

    Chitosan was reported to interact with proteins through electrostatic interactions. Their interaction was influenced by pH, which was not fully characterized. Further research on the interactions between protein and chitosan at different pH and their influence on the thermal denaturation of proteins is necessary. In this research, the effect of chitosan on the heat stability of whey protein solution at pH 4.0-6.0 was studied. At pH 4.0, a small amount chitosan was able to prevent the heat-induced denaturation and aggregation of whey protein molecules. At higher pH values (5.5 and 6.0), whey proteins complexed with chitosan through electrostatic attraction. The formation of chitosan-whey protein complexes at pH 5.5 improved the heat stability of dispersions and no precipitation could be detected up to 20 days. The dispersion with a medium amount of chitosan (chitosan:whey protein 1:5) produced the most stable particles, which had an average radius of 135 ± 14 nm and a zeta potential value of 36 ± 1 mV. In contrast, at pH 6.0 only the dispersion with a high amount of chitosan (chitosan:whey protein 1:2) showed good shelf stability up to 20 days. It was possible to produce heat-stable whey protein beverages by regulating the interaction between chitosan and whey protein molecules. © 2016 Society of Chemical Industry. © 2016 Society of Chemical Industry.

  1. Existence and stability of periodic solutions of an impulsive differential equation and application to CD8 T-cell differentiation.

    Science.gov (United States)

    Girel, Simon; Crauste, Fabien

    2018-06-01

    Unequal partitioning of the molecular content at cell division has been shown to be a source of heterogeneity in a cell population. We propose to model this phenomenon with the help of a scalar, nonlinear impulsive differential equation (IDE). To study the effect of molecular partitioning at cell division on the effector/memory cell-fate decision in a CD8 T-cell lineage, we study an IDE describing the concentration of the protein Tbet in a CD8 T-cell, where impulses are associated to cell division. We discuss how the degree of asymmetry of molecular partitioning can affect the process of cell differentiation and the phenotypical heterogeneity of a cell population. We show that a moderate degree of asymmetry is necessary and sufficient to observe irreversible differentiation. We consider, in a second part, a general autonomous IDE with fixed times of impulse and a specific form of impulse function. We establish properties of the solutions of that equation, most of them obtained under the hypothesis that impulses occur periodically. In particular, we show how to investigate the existence of periodic solutions and their stability by studying the flow of an autonomous differential equation. Then we apply those properties to prove the results presented in the first part.

  2. Photo-stability study of a solution-processed small molecule solar cell system: correlation between molecular conformation and degradation.

    Science.gov (United States)

    Newman, Michael J; Speller, Emily M; Barbé, Jérémy; Luke, Joel; Li, Meng; Li, Zhe; Wang, Zhao-Kui; Jain, Sagar M; Kim, Ji-Seon; Lee, Harrison Ka Hin; Tsoi, Wing Chung

    2018-01-01

    Solution-processed organic small molecule solar cells (SMSCs) have achieved efficiency over 11%. However, very few studies have focused on their stability under illumination and the origin of the degradation during the so-called burn-in period. Here, we studied the burn-in period of a solution-processed SMSC using benzodithiophene terthiophene rhodamine:[6,6]-phenyl C 71 butyric acid methyl ester (BTR:PC 71 BM) with increasing solvent vapour annealing time applied to the active layer, controlling the crystallisation of the BTR phase. We find that the burn-in behaviour is strongly correlated to the crystallinity of BTR. To look at the possible degradation mechanisms, we studied the fresh and photo-aged blend films with grazing incidence X-ray diffraction, UV-vis absorbance, Raman spectroscopy and photoluminescence (PL) spectroscopy. Although the crystallinity of BTR affects the performance drop during the burn-in period, the degradation is found not to originate from the crystallinity changes of the BTR phase, but correlates with changes in molecular conformation - rotation of the thiophene side chains, as resolved by Raman spectroscopy which could be correlated to slight photobleaching and changes in PL spectra.

  3. Head to head comparison of the formulation and stability of concentrated solutions of HESylated versus PEGylated anakinra.

    Science.gov (United States)

    Liebner, Robert; Meyer, Martin; Hey, Thomas; Winter, Gerhard; Besheer, Ahmed

    2015-02-01

    Although PEGylation of biologics is currently the gold standard for half-life extension, the technology has a number of limitations, most importantly the non-biodegradability of PEG and the extremely high viscosity at high concentrations. HESylation is a promising alternative based on coupling to the biodegradable polymer hydroxyethyl starch (HES). In this study, we are comparing HESylation with PEGylation regarding the effect on the protein's physicochemical properties, as well as on formulation at high concentrations, where protein stability and viscosity can be compromised. For this purpose, the model protein anakinra is coupled to HES or PEG by reductive amination. Results show that coupling of HES or PEG had practically no effect on the protein's secondary structure, and that it reduced protein affinity by one order of magnitude, with HESylated anakinra more affine than the PEGylated protein. The viscosity of HESylated anakinra at protein concentrations up to 75 mg/mL was approximately 40% lower than that of PEG-anakinra. Both conjugates increased the apparent melting temperature of anakinra in concentrated solutions. Finally, HESylated anakinra was superior to PEG-anakinra regarding monomer recovery after 8 weeks of storage at 40°C. These results show that HESylating anakinra offers formulation advantages compared with PEGylation, especially for concentrated protein solutions. © 2014 Wiley Periodicals, Inc. and the American Pharmacists Association.

  4. Defect and phase stability of solid solutions of Mg2X with an antifluorite structure: An ab initio study

    International Nuclear Information System (INIS)

    Viennois, Romain; Jund, Philippe; Colinet, Catherine; Tédenac, Jean-Claude

    2012-01-01

    First principles calculations are done for Mg 2 X (X=Si, Ge or Sn) antifluorite compounds and their solid solutions in order to investigate their pseudo-binary phase diagram. The formation energies of the end-member compounds agree qualitatively with the experiments. For X=Si and Ge, there is a complete solubility, but we observe a miscibility gap in the pseudo-binary phase diagram Mg 2 Si–Mg 2 Sn. This agrees with the most recent experiments and phase diagram assessments. Calculated electronic properties of Mg 2 Si 1−x Sn x alloys qualitatively agree with experiments and in particular the energy bandgap decreases when Si is substituted by Sn. Supercell calculations are also done in order to determine the most stable defects and the doping induced by these defects in the three end-member compounds. We find that the intrinsic n-doping in pure Mg 2 Si can be attributed to the presence of magnesium atoms in interstitial positions. In Mg 2 Ge and Mg 2 Sn, since other defects are stable, they can be also of p-type. - Graphical abstract: Evidence of a miscibility gap from the plot of the formation energy vs x Si (silicon content) for the solid solutions Mg 2 Si–Mg 2 Sn. Highlights: ► First-principles study of the stability of Mg 2 Si–Mg 2 X alloys (X=Ge or Sn) and their defects. ► Mg 2 Si–Mg 2 Ge alloys form a complete series of solid solutions. ► Miscibility gap is found in Mg 2 Si–Mg 2 Sn alloys. ► Interstitial defects are more stable in Mg 2 Si and induce n-doping.

  5. Enhanced electrical stability of nitrate ligand-based hexaaqua complexes solution-processed ultrathin a-IGZO transistors

    Science.gov (United States)

    Choi, C.; Baek, Y.; Lee, B. M.; Kim, K. H.; Rim, Y. S.

    2017-12-01

    We report solution-processed, amorphous indium-gallium-zinc-oxide-based (a-IGZO-based) thin-film transistors (TFTs). Our proposed solution-processed a-IGZO films, using a simple spin-coating method, were formed through nitrate ligand-based metal complexes, and they were annealed at low temperature (250 °C) to achieve high-quality oxide films and devices. We investigated solution-processed a-IGZO TFTs with various thicknesses, ranging from 4 to 16 nm. The 4 nm-thick TFT films had smooth morphology and high-density, and they exhibited excellent performance, i.e. a high saturation mobility of 7.73  ±  0.44 cm2 V-1 s-1, a sub-threshold swing of 0.27 V dec-1, an on/off ratio of ~108, and a low threshold voltage of 3.10  ±  0.30 V. However, the performance of the TFTs degraded as the film thickness was increased. We further performed positive and negative bias stress tests to examine their electrical stability, and it was noted that the operating behavior of the devices was highly stable. Despite a small number of free charges, the high performance of the ultrathin a-IGZO TFTs was attributed to the small effect of the thickness of the channel, low bulk resistance, the quality of the a-IGZO/SiO2 interface, and high film density.

  6. A Comprehensive Strategy to Evaluate Compatible Stability of Chinese Medicine Injection and Infusion Solutions Based on Chemical Analysis and Bioactivity Assay.

    Science.gov (United States)

    Li, Jian-Ping; Liu, Yang; Guo, Jian-Ming; Shang, Er-Xin; Zhu, Zhen-Hua; Zhu, Kevin Y; Tang, Yu-Ping; Zhao, Bu-Chang; Tang, Zhi-Shu; Duan, Jin-Ao

    2017-01-01

    Stability of traditional Chinese medicine injection (TCMI) is an important issue related with its clinical application. TCMI is composed of multi-components, therefore, when evaluating TCMI stability, several marker compounds cannot represent global components or biological activities of TCMI. Till now, when evaluating TCMI stability, method involving the global components or biological activities has not been reported. In this paper, we established a comprehensive strategy composed of three different methods to evaluate the chemical and biological stability of a typical TCMI, Danhong injection (DHI). UHPLC-TQ/MS was used to analyze the stability of marker compounds (SaA, SaB, RA, DSS, PA, CA, and SG) in DHI, UHPLC-QTOF/MS was used to analyze the stability of global components (MW 80-1000 Da) in DHI, and cell based antioxidant capability assay was used to evaluate the bioactivity of DHI. We applied this strategy to assess the compatible stability of DHI and six infusion solutions (GS, NS, GNS, FI, XI, and DGI), which were commonly used in combination with DHI in clinic. GS was the best infusion solution for DHI, and DGI was the worst one based on marker compounds analysis. Based on global components analysis, XI and DGI were the worst infusion solutions for DHI. And based on bioactivity assay, GS was the best infusion solution for DHI, and XI was the worst one. In conclusion, as evaluated by the established comprehensive strategy, GS was the best infusion solution, however, XI and DGI were the worst infusion solutions for DHI. In the compatibility of DHI and XI or DGI, salvianolic acids in DHI would be degraded, resulting in the reduction of original composition and generation of new components, and leading to the changes of biological activities. This is the essence of instability compatibility of DHI and some infusion solutions. Our study provided references for choosing the reasonable infusion solutions for DHI, which could contribute the improvement of safety

  7. The combined effect of food-simulating solutions, brushing and staining on color stability of composite resins

    Science.gov (United States)

    Silva, Tânia Mara Da; Sales, Ana Luísa Leme Simões; Pucci, Cesar Rogerio; Borges, Alessandra Bühler; Torres, Carlos Rocha Gomes

    2017-01-01

    Abstract Objective: This study evaluated the effect of food-simulating media associated with brushing and coffee staining on color stability of different composite resins. Materials and methods: Eighty specimens were prepared for each composite: Grandio SO (Voco), Amaris (Voco), Filtek Z350XT (3M/ESPE), Filtek P90 (3M/ESPE). They were divided into four groups according to food-simulating media for 7 days: artificial saliva (control), heptane, citric acid and ethanol. The composite surface was submitted to 10,950 brushing cycles (200 g load) in an automatic toothbrushing machine. The specimens were darkened with coffee solution at 37 °C for 24 h. After each treatment, color measurements were assessed by spectrophotometry, using CIE L*a*b* system. The overall color change (ΔE) was determined for each specimen at baseline (C1) and after the treatments (food-simulating media immersion/C2, brushing/C3 and dye solution/C4). Data were analyzed by two-way repeated measures ANOVA and Tukey’s tests (p composites (p = .001), time (p = .001) and chemical degradation (p = .002). The mean of ΔE for composites were: Z350XT (5.39)a, Amaris (3.89)b, Grandio (3.75)bc, P90 (3.36)c. According to food-simulating media: heptane (4.41)a, citric acid (4.24)a, ethanol (4.02)ab, artificial saliva (3.76)b. For the treatments: dye solution (4.53)a, brushing (4.26)a, after food-simulating media (3.52)b. Conclusions: The composite resin Filtek Z350XT showed significantly higher staining than all other composite resin tested. The immersion in heptane and citric acid produced the highest color alteration than other food-simulating media. The exposure of samples to brushing protocols and darkening in coffee solution resulted in significant color alteration of the composite resins. PMID:28642926

  8. Simultaneous solution algorithms for Eulerian-Eulerian gas-solid flow models: Stability analysis and convergence behaviour of a point and a plane solver

    International Nuclear Information System (INIS)

    Wilde, Juray de; Vierendeels, Jan; Heynderickx, Geraldine J.; Marin, Guy B.

    2005-01-01

    Simultaneous solution algorithms for Eulerian-Eulerian gas-solid flow models are presented and their stability analyzed. The integration algorithms are based on dual-time stepping with fourth-order Runge-Kutta in pseudo-time. The domain is solved point or plane wise. The discretization of the inviscid terms is based on a low-Mach limit of the multi-phase preconditioned advection upstream splitting method (MP-AUSMP). The numerical stability of the simultaneous solution algorithms is analyzed in 2D with the Fourier method. Stability results are compared with the convergence behaviour of 3D riser simulations. The impact of the grid aspect ratio, preconditioning, artificial dissipation, and the treatment of the source terms is investigated. A particular advantage of the simultaneous solution algorithms is that they allow a fully implicit treatment of the source terms which are of crucial importance for the Eulerian-Eulerian gas-solid flow models and their solution. The numerical stability of the optimal simultaneous solution algorithm is analyzed for different solids volume fractions and gas-solid slip velocities. Furthermore, the effect of the grid resolution on the convergence behaviour and the simulation results is investigated. Finally, simulations of the bottom zone of a pilot-scale riser with a side solids inlet are experimentally validated

  9. Flexible ITO-free organic solar cells applying aqueous solution-processed V2O5 hole transport layer: An outdoor stability study

    Directory of Open Access Journals (Sweden)

    F. Anderson S. Lima

    2016-02-01

    Full Text Available Solution processable semiconductor oxides have opened a new paradigm for the enhancement of the lifetime of thin film solar cells. Their fabrication by low-cost and environmentally friendly solution-processable methods makes them ideal barrier (hole and electron transport layers. In this work, we fabricate flexible ITO-free organic solar cells (OPV by printing methods applying an aqueous solution-processed V2O5 as the hole transport layer (HTL and compared them to devices applying PEDOT:PSS. The transparent conducting electrode was PET/Ag/PEDOT/ZnO, and the OPV configuration was PET/Ag/PEDOT/ZnO/P3HT:PC60BM/HTL/Ag. Outdoor stability analyses carried out for more than 900 h revealed higher stability for devices fabricated with the aqueous solution-processed V2O5.

  10. Stabilization of the norm of the solution of a mixed problem in an unbounded domain for parabolic equations of orders 4 and 6

    International Nuclear Information System (INIS)

    Mukminov, F Kh; Bikkulov, I M

    2004-01-01

    The behaviour as t→∞ of the solution of a mixed problem for parabolic equations in an unbounded domain with two exits to infinity is studied. A certain class of domains is distinguished, in which an estimate characterizing the stabilization of solutions and determined by the geometry of the domain is established. This estimate is proved to be sharp in a certain sense for a broad class of domains with two exits to infinity.

  11. A salt water battery with high stability and charging rates made from solution processed conjugated polymers with polar side chains

    KAUST Repository

    Moia, Davide

    2017-11-28

    We report a neutral salt water based battery which uses p-type and n-type solution processed polymer films as the cathode and the anode of the cell. The specific capacity of the electrodes (approximately 30 mAh cm-3) is achieved via formation of bipolarons in both the p-type and n-type polymers. By engineering ethylene glycol and zwitterion based side chains attached to the polymer backbone we facilitate rapid ion transport through the non-porous polymer films. This, combined with efficient transport of electronic charge via the conjugated polymer backbones, allowed the films to maintain constant capacity at high charge and discharge rates (>1000 C-rate). The electrodes also show good stability during electrochemical cycling (less than 30% decrease in capacity over >1000 cycles) and an output voltage up to 1.4 V. The performance of these semiconducting polymers with polar side-chains demonstrates the potential of this material class for fast-charging, water based electrochemical energy storage devices.

  12. One-step synthesis and applications of fluorescent Cu nanoclusters stabilized by L-cysteine in aqueous solution.

    Science.gov (United States)

    Yang, Xiaoming; Feng, Yuanjiao; Zhu, Shanshan; Luo, Yawen; Zhuo, Yan; Dou, Yao

    2014-10-17

    Herein, an innovative and simple strategy for synthesizing high fluorescent Cu nanoclusters was successfully established while L-cysteine played a role as the stabilizer. Meaningfully, the current Cu nanoclusters together with a quantum yield of 14.3% were prepared in aqueous solution, indicating their extensive applications. Subsequently, the possible fluorescence mechanism was elucidated by fluorescence, UV-vis, HR-TEM, FTIR, XPS, and MS. Additionally, the CuNCs were employed for assaying Hg(2+) on the basis of the interactions between Hg(2+) and L-cysteine; thus facilitating the quenching of their fluorescence. The proposed analytical strategy permitted detections of Hg(2+) in a linear range of 1.0×10(-7) mol L(-1)×10(-3) mol L(-1), with a detection limit of 2.4×10(-8) mol L(-1) at a signal-to-noise ratio of 3. Significantly, this CuNCs described here were further applied for coding and fluorescent staining, suggesting may broaden avenues toward diverse applications. Copyright © 2014 Elsevier B.V. All rights reserved.

  13. Stability of Naturally Relevant Ternary Phases in the Cu–Sn–S system in Contact with an Aqueous Solution

    Directory of Open Access Journals (Sweden)

    Andrea Giaccherini

    2016-07-01

    Full Text Available A relevant research effort is devoted to the synthesis and characterization of phases belonging to the ternary system Cu–Sn–S, mainly for their possible applications in semiconductor technology. Among all ternary phases, kuramite, Cu3SnS4, mohite, Cu2SnS3, and Cu4Sn7S16 have attracted the highest interest. Numerous studies were carried out claiming for the description of new phases in the ternary compositional field. In this study, we revise the existing literature on this ternary system, with a special focus on the phases stable in a temperature range at 25 °C. The only two ternary phases observed in nature are mohite and kuramite. Their occurrence is described as very rare. A numerical modelling of the stable solid phases in contact with a water solution was underwent to define stability relationships of the relevant phases of the system. The numerical modelling of the Eh-pH diagrams was carried out through the phreeqc software with the lnll.dat thermodynamic database. Owing to the complexity of this task, the subsystems Cu–O–H, Sn–O–H, Cu–S–O–H and Sn–S–O–H were firstly considered. The first Pourbaix diagram for the two naturally relevant ternary phases is then proposed.

  14. On stability of the solutions of inverse problem for determining the right-hand side of a degenerate parabolic equation with two independent variables

    Science.gov (United States)

    Kamynin, V. L.; Bukharova, T. I.

    2017-01-01

    We prove the estimates of stability with respect to perturbations of input data for the solutions of inverse problems for degenerate parabolic equations with unbounded coefficients. An important feature of these estimates is that the constants in these estimates are written out explicitly by the input data of the problem.

  15. Stability of ampicillin, piperacillin, cefotaxime, netilmicin and amikacin in an L-amino acid solution prepared for total parenteral nutrition of newborn infants

    DEFF Research Database (Denmark)

    Goldstein, K; Colding, H; Andersen, G E

    1988-01-01

    The stability of ampicillin, piperacillin and cefotaxime, alone or in combination with either netilmicin or amikacin, was tested by microbiological methods at 29 degrees C (ampicillin, also at 22 degrees C) in an L-amino acid solution specially prepared for newborn infants. In the case of ampicil...

  16. Pancreatic Enzymes

    Science.gov (United States)

    ... Contact Us DONATE NOW GENERAL DONATION PURPLESTRIDE Pancreatic enzymes Home Facing Pancreatic Cancer Living with Pancreatic Cancer ... and see a registered dietitian. What are pancreatic enzymes? Pancreatic enzymes help break down fats, proteins and ...

  17. Stability of Hyperthermophilic Proteins

    DEFF Research Database (Denmark)

    Stiefler-Jensen, Daniel

    stability by randomly generate mutants and lengthy screening processes to identify the best new mutants. However, with the increase in available genomic sequences of thermophilic or hyperthermophilic organisms a world of enzymes with intrinsic high stability are now available. As these organisms are adapted...... to life at high temperatures so are their enzymes, as a result the high stability is accompanied by low activity at moderate temperatures. Thus, much effort had been put into decoding the mechanisms behind the high stability of the thermophilic enzymes. The hope is to enable scientist to design enzymes...... in the high stability of hyperthermophilic enzymes. The thesis starts with an introduction to the field of protein and enzyme stability with special focus on the thermophilic and hyperthermophilic enzymes and proteins. After the introduction three original research manuscripts present the experimental data...

  18. Ternary system of dihydroartemisinin with hydroxypropyl-β-cyclodextrin and lecithin: simultaneous enhancement of drug solubility and stability in aqueous solutions.

    Science.gov (United States)

    Wang, Dan; Li, Haiyan; Gu, Jingkai; Guo, Tao; Yang, Shuo; Guo, Zhen; Zhang, Xueju; Zhu, Weifeng; Zhang, Jiwen

    2013-09-01

    The purpose of this study was to simultaneously improve the solubility and stability of dihydroartemisinin (DHA) in aqueous solutions by a ternary cyclodextrin system comprised of DHA, hydroxypropyl-β-cyclodextrin (HP-β-CD) and a third auxiliary substance. Solubility and phase solubility studies were carried out to evaluate the solubilizing efficiency of HP-β-CD in association with various auxiliary substances. Then, the solid binary (DHA-HP-β-CD or DHA-lecithin) and ternary systems were prepared and characterized by Fourier transform infrared (FT-IR), differential scanning calorimetry (DSC) and power X-ray diffraction (PXRD). The effect of the ternary system on the solubility, dissolution and stability of DHA in aqueous solutions was also investigated. As a result, the soybean lecithin was found to be the most promising third component in terms of solubility enhancement. For the solid characterization, the disappearance of the drug crystallinity indicated the formation of new solid phases, implicating the formation of the ternary system. The dissolution rate of the solid ternary system was much faster than that of the drug alone and binary systems. Importantly, compared with binary systems, the ternary system showed a significant improvement in the stability of DHA in Hank's balanced salt solutions (pH 7.4). The solubility and stability of DHA in aqueous solutions were simultaneously enhanced by the ternary system, which might be attributed to the possible formation of a ternary complex. For the ternary interactions, results of molecular docking studies further indicated that the lecithin covered the top of the wide rim of HP-β-CD and surrounded around the peroxide bridging of DHA, providing the possibility for the ternary complex formation. In summary, the ternary system prepared in our study, with simultaneous enhancement of DHA solubility and stability in aqueous solutions, might have an important pharmaceutical potential in the development of a better

  19. Radiation sterilization of enzyme hybrids with biodegradable polymers

    International Nuclear Information System (INIS)

    Furuta, Masakazu; Oka, Masahito; Hayashi, Toshio

    2002-01-01

    Ionizing radiations, which have already been utilized for the sterilization of medical supplies as well as gas fumigation, should be the final candidate to decontaminate 'hybrid' biomaterials containing bio-active materials including enzymes because irradiation induces neither heat nor substances affecting the quality of the materials and our health. In order to check the feasibility of 60 Co-gamma rays on these materials, we selected commercial proteases including papain and bromelain hybridized with commercial activated chitosan beads and demonstrated that these enzyme-hybrids suspended in water showed the significant radiation durability of more than twice as much as free enzyme solution at 25-kGy irradiation. Enhanced thermal and storage stability of the enzyme hybrids were not affected by the same dose level of irradiation, either, indicating that commercial irradiation sterilization method is applicable to enzyme hybrids without modification

  20. CONDENSED MATTER: STRUCTURE, MECHANICAL AND THERMAL PROPERTIES: Molecular Dynamics Study of Stability of Solid Solutions and Amorphous Phase in the Cu-Al System

    Science.gov (United States)

    Yang, Bin; Lai, Wen-Sheng

    2009-06-01

    The relative stability of fcc and bcc solid solutions and amorphous phase with different compositions in the Cu-Al system is studied by molecular dynamics simulations with n-body potentials. For Cu1-xAlx alloys, the calculations show that the fcc solid solution has the lowest energies in the composition region with x 0.72, while the bee solid solution has the lowest energies in the central composition range, in agreement with the ball-milling experiments that a single bcc solid solution with 0.30 < x < 0.70 is obtained. The evolution of structures in solid solutions and amorphous phase is studied by the coordination number (CN) and bond-length analysis so as to unveil the underlying physics. It is found that the energy sequence among three phases is determined by the competition in energy change originating from the bond length and CNs (or the number of bonds).

  1. Existence and Globally Asymptotic Stability of Equilibrium Solution for Fractional-Order Hybrid BAM Neural Networks with Distributed Delays and Impulses

    Directory of Open Access Journals (Sweden)

    Hai Zhang

    2017-01-01

    Full Text Available This paper investigates the existence and globally asymptotic stability of equilibrium solution for Riemann-Liouville fractional-order hybrid BAM neural networks with distributed delays and impulses. The factors of such network systems including the distributed delays, impulsive effects, and two different fractional-order derivatives between the U-layer and V-layer are taken into account synchronously. Based on the contraction mapping principle, the sufficient conditions are derived to ensure the existence and uniqueness of the equilibrium solution for such network systems. By constructing a novel Lyapunov functional composed of fractional integral and definite integral terms, the globally asymptotic stability criteria of the equilibrium solution are obtained, which are dependent on the order of fractional derivative and network parameters. The advantage of our constructed method is that one may directly calculate integer-order derivative of the Lyapunov functional. A numerical example is also presented to show the validity and feasibility of the theoretical results.

  2. Estimation of free acid content in lanthanide salt solution used for pH-potentiometric determination of their stability constants with organic ligands

    International Nuclear Information System (INIS)

    Zheltvaj, I.I.; Tishchenko, M.A.

    1985-01-01

    To improve the pH-potentiometric method for determining complex stability constants the possibility of alkalimetric titration of a free acid in the lanthanide perchlorate solution after binding metal ions by disodium salt of ethylene-diamine-tetraacetic acid is studied. The stability constants were determined from the difference between the total acid content after complexon addition and doubled metal cation content in the solution which has been preliminarily determined by the complexonometric method. It is shown that the alkaline (NaOH) equivalent quantities spent for free acid titration either in the absence or presence of the complexon is different. With increase of free acid content in the solution the difference in determinations with complexon and without it is somewhat reduced. Thus, the use of complexon contributes to a higher accuracy in determining the free acid, and in the first place in case of minor contents

  3. The Influence of pH and Temperature on the Stability of N-[(Piperidinemethylene]daunorubicin Hydrochloride and a Comparison of the Stability of Daunorubicin and Its Four New Amidine Derivatives in Aqueous Solutions

    Directory of Open Access Journals (Sweden)

    Mikołaj Piekarski

    2014-01-01

    Full Text Available The influence of pH and temperature on the stability of N-[(piperidinemethylene]daunorubicin hydrochloride (PPD was investigated. Degradation was studied using an HPLC method. Specific acid-base catalysis of PPD involves hydrolysis of protonated molecules of PPD catalyzed by hydrogen ions and spontaneous hydrolysis under the influence of water zwitterions, unprotonated molecules, and monoanions of PPD. The thermodynamic parameters of these reactions, energy, enthalpy, and entropy, were calculated. Also, the stability of daunorubicin and its new amidine derivatives (piperidine, morpholine, pyrrolidine, and hexahydroazepin-1-yl in aqueous solutions was compared and discussed.

  4. Effect of enzyme location on activity and stability of trypsin and urease immobilized on porous membranes by using layer-by-layer self-assembly of polyelectrolyte

    OpenAIRE

    Guedidi, Sadika; Yürekli, Yılmaz; Deratani, André; Déjardin, Philippe; Innocent, Christophe; Altınkaya, Sacide; Roudesli, Sadok; Yemenicioğlu, Ahmet

    2010-01-01

    The layer-by-layer (LbL) self-assembly of polyelectrolyte is one of the simplest ways to immobilize enzyme on membrane. In this paper, the immobilization of trypsin (TRY) and urease (URE) on polyacrylonitrile based membranes using the LbL assembly technique was presented. The studied systems consisted in bilayered assemblies with the enzyme layer as the outer layer and trilayered assemblies with the enzyme layer as the inner sandwiched layer. The membrane pore size was chosen so that the smal...

  5. Modulation stability and optical soliton solutions of nonlinear Schrödinger equation with higher order dispersion and nonlinear terms and its applications

    Science.gov (United States)

    Arshad, Muhammad; Seadawy, Aly R.; Lu, Dianchen

    2017-12-01

    In optical fibers, the higher order non-linear Schrödinger equation (NLSE) with cubic quintic nonlinearity describes the propagation of extremely short pulses. We constructed bright and dark solitons, solitary wave and periodic solitary wave solutions of generalized higher order NLSE in cubic quintic non Kerr medium by applying proposed modified extended mapping method. These obtained solutions have key applications in physics and mathematics. Moreover, we have also presented the formation conditions on solitary wave parameters in which dark and bright solitons can exist for this media. We also gave graphically the movement of constructed solitary wave and soliton solutions, that helps to realize the physical phenomena's of this model. The stability of the model in normal dispersion and anomalous regime is discussed by using the modulation instability analysis, which confirms that all constructed solutions are exact and stable. Many other such types of models arising in applied sciences can also be solved by this reliable, powerful and effective method.

  6. Problems experiences with the construction of cement and lime stabilized layers and working solutions for these problems

    CSIR Research Space (South Africa)

    Botha, PB

    2005-10-01

    Full Text Available Stabilized layers are used extensively in South-Africa in the construction of roads. The layers are usually stabilized with hydrated road lime, cement, slag, fly-ash, bitumen emulsion, foamed asphalt or a combination of several of these agents...

  7. Influence of calcium chelators on concentrated micellar casein solutions : from micellar structure to viscosity and heat stability

    NARCIS (Netherlands)

    Kort, de E.J.P.

    2012-01-01

    In practice it is challenging to prepare a concentrated medical product with high heat stability
    and low viscosity. Calcium chelators are often added to dairy products to improve heat stability,
    but this may increase viscosity through interactions with the casein proteins. The aim of

  8. Temperature stability of Poly-[hemoglobin-superoxide dismutase-catalase-carbonic anhydrase] in the form of a solution or in the lyophilized form during storage at -80 °C, 4 °C, 25 °C and 37 °C or pasteurization at 70 °C.

    Science.gov (United States)

    Bian, Y Z; Guo, C; Chang, T M S

    2016-01-01

    Polyhemoglobin-superoxide dismutase-catalase-carbonic anhydrase (Poly-[Hb-SOD-CAT-CA]) contains all three major functions of red blood cells (RBCs) at an enhanced level. It transports oxygen, removes oxygen radicals and transports carbon dioxide. Our previous studies in a 90-min 30 mm Hg Mean Arterial Pressure (MAP) sustained hemorrhagic shock rat model shows that it is more effective than blood in the lowering of elevated intracellular pCO2, recovery of ST-elevation and histology of the heart and intestine. This paper is to analyze the storage and temperature stability. Allowable storage time for RBC is about 1 d at room temperature and 42 d at 4 °C. Also, RBC cannot be pasteurized to remove infective agents like HIV and Ebola. PolyHb can be heat sterilized and can be stored for 1 year even at room temperature. However, Poly-[Hb-SOD-CAT-CA] contains both Hb and enzymes and enzymes are particularly sensitive to storage and heat. We thus carried out studies to analyze its storage stability at different temperatures and heat pasteurization stability. Results of storage stability show that lyophilization extends the storage time to 1 year at 4 °C and 40 d at room temperature (compared to respectively, 42 d and 1 d for RBC). After the freeze-dry process, the enzyme activities of Poly-[SFHb-SOD-CAT-CA] was 100 ± 2% for CA, 100 ± 2% for SOD and 93 ± 3.5% for CAT. After heat pasteurization at 70 °C for 2 h, lyophilized Poly-[Hb-SOD-CAT-CA] retained good enzyme activities of CA 97 ± 4%, SOD 100 ± 2.5% and CAT 63.8 ± 4%. More CAT can be added during the crosslinking process to maintain the same enzyme ratio after heat pasteurization. Heat pasteurization is possible only for the lyophilized form of Poly-[Hb-SOD-CAT-CA] and not for the solution. It can be easily reconstituted by dissolving in suitable solutions that continues to have good storage stability though less than that for the lyophilized form. According to the P50 value, Poly-[SFHb-SOD-CAT-CA] retains its

  9. Determination of stability constants of K and Cs nitrate complex with dicyclohexyl-18-crown-6 and dibenzo-18-crown-6 in isopropanol aqueous solutions

    International Nuclear Information System (INIS)

    Myasoedova, T.G.; Ponomareva, A.V.; Zagorets, P.A.; Filippov, E.A.

    1984-01-01

    Total stability constants of K and Cs nitrate complexes with dicyclohexyl-18-crown-6 and dibenzo-18-crown-6 in isopropanol aqueous solutions were determined by the method of low-frequency contact conductometry. Clearly defined K/Cs selectivity is observed for the system with dibenzo-18-crown-6. It is shown that lgβ depends on permittivity of the solvent. The decrease of permittivity of isopropanol aqueous solutions results in reduction of K/Cs selectivity of DB18C6

  10. Determination of stability constants of K and Cs nitrate complex with dicyclohexyl-18-crown-6 and dibenzo-18-crown-6 in isopropanol aqueous solutions

    Energy Technology Data Exchange (ETDEWEB)

    Myasoedova, T G; Ponomareva, A V; Zagorets, P A; Filippov, E A [Moskovskij Khimiko-Tekhnologicheskij Inst. (USSR)

    1984-08-01

    Total stability constants of K and Cs nitrate complexes with dicyclohexyl-18-crown-6 and dibenzo-18-crown-6 in isopropanol aqueous solutions were determined by the method of low-frequency contact conductometry. Clearly defined K/Cs selectivity is observed for the system with dibenzo-18-crown-6. It is shown that lg..beta.. depends on permittivity of the solvent. The decrease of permittivity of isopropanol aqueous solutions results in reduction of K/Cs selectivity of DB18C6.

  11. THE EFFECTS OF 1‰ STABILIZED LIQUID SOLUTION OF CHLORINE DIOXIDE (ClO2 ON SOME FOOD-BORN BACTERIA

    Directory of Open Access Journals (Sweden)

    Sead Hadziabdić

    2014-03-01

    Full Text Available The conducted research gives an overview of the results obtained after the application of 1‰ solution of stabilized liquid chlorine dioxide on some food-born related bacteria - E. coli, Staphylococcus aureus, S. Enteritidis and C. jejuni.  For this purpose,  reference strains of the aforementioned pathogens in decimal dilutions were exposed to 1 ml of 1‰ solution of stabilized liquid chlorine dioxide for one hour. Reduction of bacteria counts per mililitre (CFU/ml has been noticed for all bacteria, with total reduction of C. jejuni and Staphylococcus aureus in the fourth (1:104, and for S. Enteritidis and E. coli in the sixth (1:106 decimal dilution. Key words: chlorine dioxide, E. coli, S. aureus, S. Enteritidis, C. jejuni

  12. Stability of 10 mg/mL cefuroxime solution for intracameral injection in commonly used polypropylene syringes and new ready-to-use cyclic olefin copolymer sterile vials using the LC-UV stability-indicating method.

    Science.gov (United States)

    Feutry, Frédéric; Simon, Nicolas; Genay, Stéphanie; Lannoy, Damien; Barthélémy, Christine; Décaudin, Bertrand; Labalette, Pierre; Odou, Pascal

    2016-01-01

    Injecting intracameral cefuroxime has been found beneficial in reducing the risk of postoperative endophthalmitis but its use has been limited through a lack of approved marketing and of ready-to-use single-units as well as the problem of aseptic compounding. Our aim was to assess a new automated primary packaging system which should ensure a higher level of sterility, thanks to its closed, sterile, ready-to-use polymer vial called "Crystal® vial". The chemical stability of a 10 mg/mL cefuroxime solution was compared in 1 mL Crystal® vials and 1 mL Luer-lock polypropylene syringes (actual reference) to eliminate any potential and specific interactions with its cyclic olefin copolymer (COC) body and elastomer stopper. Cefuroxime solution was introduced into vials and syringes and stored at -20 °C, +5 °C and +25°C/60% Relative Humidity. Cefuroxime concentration and the relative amount of the main degradation product (descarbamoyl-cefuroxime) were both determined by an HPLC/UV method indicating stability. Solutions were considered steady if the concentration remained at over 90% of the initial value. In the adapted storage conditions, the evolution of osmolality, pH and sterility was assessed. Stability profiles were identical between vials and syringes in all storage and temperature conditions. The solution was stable (cefuroxime concentration, pH and osmolality) and still sterile for 365 days at -20°C. The concentration fell below 90% after 21 days at +5 °C and after 16 h at +25°C/60%s relative humidity. The COC and thermoplastic elastomer of the vials had no impact on the degradation process confirming its possible use for a ready-to-use cefuroxime solution single-unit dose.

  13. Effects of Mg doping on the gate bias and thermal stability of solution-processed InGaZnO thin-film transistors

    International Nuclear Information System (INIS)

    Su, Bo-Yuan; Chu, Sheng-Yuan; Juang, Yung-Der; Liu, Ssu-Yin

    2013-01-01

    Graphical abstract: Mg-doped IGZO TFTs showed improved TFT performance and thermal stability due to fewer oxygen deficiencies and less interface electron trapping. Highlights: •We fabricated Mg-doped IGZO TFTs with improved performance using solution-process. •Mg doping reduced the oxygen deficiencies and less interface electron trapping of a-IGZO films. •Mg dope-TFT showed high mobility of 2.35 cm 2 /V s and an on–off current ratio over 10 6 . •For better device stability (gate-bias and thermal stability) was proved. -- Abstract: The effects of magnesium (Mg) doping (molar ratio Mg/Zn = (0–10 at.%)) on solution-processed amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) grown using the sol–gel method are investigated. TFT devices fabricated with Mg-doped films showed an improved field-effect mobility of 2.35 cm 2 /V s and a subthreshold slope (S) of 0.42 V/dec compared to those of an undoped a-IGZO TFT (0.73 cm 2 /V s and 0.74 V/dec, respectively), and an on–off current ratio of over 10 6 . Moreover, the 5 at.% Mg-doped TFT device showed improved gate bias and thermal stability due to fewer oxygen deficiencies, smaller carrier concentration, and less interface electron trapping in the a-IGZO films

  14. Hemoglobin bioconjugates with surface-protected gold nanoparticles in aqueous media: The stability depends on solution pH and protein properties.

    Science.gov (United States)

    Del Caño, Rafael; Mateus, Lucia; Sánchez-Obrero, Guadalupe; Sevilla, José Manuel; Madueño, Rafael; Blázquez, Manuel; Pineda, Teresa

    2017-11-01

    The identification of the factors that dictate the formation and physicochemical properties of protein-nanomaterial bioconjugates are important to understand their behavior in biological systems. The present work deals with the formation and characterization of bioconjugates made of the protein hemoglobin (Hb) and gold nanoparticles (AuNP) capped with three different molecular layers (citrate anions (c), 6-mercaptopurine (MP) and ω-mercaptoundecanoic acid (MUA)). The main focus is on the behavior of the bioconjugates in aqueous buffered solutions in a wide pH range. The stability of the bioconjugates have been studied by UV-visible spectroscopy by following the changes in the localized surface resonance plasmon band (LSRP), Dynamic light scattering (DLS) and zeta-potential pH titrations. It has been found that they are stable in neutral and alkaline solutions and, at pH lower than the protein isoelectric point, aggregation takes place. Although the surface chemical properties of the AuNPs confer different properties in respect to colloidal stability, once the bioconjugates are formed their properties are dictated by the Hb protein corona. The protein secondary structure, as analyzed by Attenuated total reflectance infrared (ATR-IR) spectroscopy, seems to be maintained under the conditions of colloidal stability but some small changes in protein conformation take place when the bioconjugates aggregate. These findings highlight the importance to keep the protein structure upon interaction with nanomaterials to drive the stability of the bioconjugates. Copyright © 2017 Elsevier Inc. All rights reserved.

  15. Use of a screening method to determine excipients which optimize the extent and stability of supersaturated drug solutions and application of this system to solid formulation design.

    Science.gov (United States)

    Vandecruys, Roger; Peeters, Jef; Verreck, Geert; Brewster, Marcus E

    2007-09-05

    Assessing the effect of excipients on the ability to attain and maintain supersaturation of drug-based solution may provide useful information for the design of solid formulations. Judicious selection of materials that affect either the extent or stability of supersaturating drug delivery systems may be enabling for poorly soluble drug candidates or other difficult-to-formulate compounds. The technique suggested herein is aimed at providing a screening protocol to allow preliminary assessment of these factors based on small to moderate amounts of drug substance. A series of excipients were selected that may, by various mechanisms, affect supersaturation including pharmaceutical polymers such as HMPC and PVP, surfactants such as Polysorbate 20, Cremophor RH40 and TPGS and hydrophilic cyclodextrins such as HPbetaCD. Using a co-solvent based method and 25 drug candidates, the data suggested, on the whole, that the surfactants and the selected cyclodextrin seemed to best augment the extent of supersaturation but had variable benefits as stabilizers, while the pharmaceutical polymers had useful effect on supersaturation stability but were less helpful in increasing the extent of supersaturation. Using these data, a group of simple solid dosage forms were prepared and tested in the dog for one of the drug candidates. Excipients that gave the best extent and stability for the formed supersaturated solution in the screening assay also gave the highest oral bioavailability in the dog.

  16. Process for preparing multilayer enzyme coating on a fiber

    Science.gov (United States)

    Kim, Jungbae [Richland, WA; Kwak, Ja Hun [Richland, WA; Grate, Jay W [West Richland, WA

    2009-11-03

    A process for preparing high stability, high activity biocatalytic materials is disclosed and processes for using the same. The process involves coating of a material or fiber with enzymes and enzyme aggregate providing a material or fiber with high biocatalytic activity and stability useful in heterogeneous environments. In one illustrative approach, enzyme "seeds" are covalently attached to polymer nanofibers followed by treatment with a reagent that crosslinks additional enzyme molecules to the seed enzymes forming enzyme aggregates thereby improving biocatalytic activity due to increased enzyme loading and enzyme stability. This approach creates a useful new biocatalytic immobilized enzyme system with potential applications in bioconversion, bioremediation, biosensors, and biofuel cells.

  17. Diluting ferric carboxymaltose in sodium chloride infusion solution (0.9% w/v) in polypropylene bottles and bags: effects on chemical stability.

    Science.gov (United States)

    Philipp, Erik; Braitsch, Michaela; Bichsel, Tobias; Mühlebach, Stefan

    2016-01-01

    This study was designed to assess the physicochemical stability of colloidal ferric carboxymaltose solution (Ferinject) when diluted and stored in polypropylene (PP) bottles and bags for infusion. Two batches of ferric carboxymaltose solution (Ferinject) were diluted (500 mg, 200 mg and 100 mg iron in 100 mL saline) in PP bottles or bags under aseptic conditions. The diluted solutions were stored at 30°C and 75%±5% relative humidity (rH) for 72 h, and samples were withdrawn aseptically at preparation and after 24 h, 48 h and 72 h. Multiple parameters were used to test stability-related measures (pH, total iron and iron (II) content, molecular weight range determination, microbial contamination and particles count ≥10 μm). Overall, Ferinject diluted in 0.9% (w/v) NaCl solution and stored in PP bottles and bags was stable within the specifications for the complex and the acceptability limits set for all assays. In both containers, total iron content remained stable, within 10% of the theoretical iron content, and levels of iron (II) remained far below the threshold of acceptability. All preparations were free from sediments, particle numbers were acceptable and there was no microbial contamination. The molecular weight distribution and polydispersity index were also acceptable. Under the tested experimental conditions, colloidal ferric carboxymaltose solution (Ferinject) diluted in saline in PP infusion bottles or bags demonstrated physical and chemical stability for up to 72 h at 30°C and 75% rH. Because of the lack of additional clinical data, when using ferric carboxymaltose, physicians/pharmacists should refer to the dilution and storing recommendations given in the product's summary of product characteristics.

  18. Artifactual degradation of secondary amine-containing drugs during accelerated stability testing when saturated sodium nitrite solutions are used for humidity control.

    Science.gov (United States)

    Sluggett, Gregory W; Zelesky, Todd; Hetrick, Evan M; Babayan, Yelizaveta; Baertschi, Steven W

    2018-02-05

    Accelerated stability studies of pharmaceutical products are commonly conducted at various combinations of temperature and relative humidity (RH). The RH of the sample environment can be controlled to set points using humidity-controlled stability chambers or via storage of the sample in a closed container in the presence of a saturated aqueous salt solution. Herein we report an unexpected N-nitrosation reaction that occurs upon storage of carvedilol- or propranolol-excipient blends in a stability chamber in the presence of saturated sodium nitrite (NaNO 2 ) solution to control relative humidity (∼60% RH). In both cases, the major products were identified as the corresponding N-nitroso derivatives of the secondary amine drugs based on mass spectrometry, UV-vis and retention time. These degradation products were not observed upon storage of the samples at the same temperature and humidity but in the presence of saturated potassium iodide (KI) solution (∼60% RH) for humidity control. The levels of the N-nitrosamine derivatives varied with the pH of various NaNO 2 batches. The presence of volatile NOx species in the headspace of a container containing saturated NaNO 2 solution was confirmed via the Griess assay. The process for formation of the N-nitrosamine derivatives is proposed to involve volatilization of nitric oxide (NO) from aqueous nitrite solution into the headspace of the container followed by diffusion into the solid drug-excipient blend and subsequent reaction of NOx with the secondary amine. Copyright © 2017 Elsevier B.V. All rights reserved.

  19. Explaining Operational Instability of Amine Transaminases : Substrate-Induced Inactivation Mechanism and Influence of Quaternary Structure on Enzyme-Cofactor Intermediate Stability

    NARCIS (Netherlands)

    Borner, Tim; Ramisch, Sebastian; Reddem, Eswar R.; Bartsch, Sebastian; Vogel, Andreas; Thunnissen, Andy-Mark W. H.; Adlercreutz, Patrick; Grey, Carl

    The insufficient operational stability of amine transaminases (ATA) constitutes a limiting factor for high productivity in chiral amine synthesis. In this work, we investigated the operational stability of a tetrameric ATA with 92% sequence identity to a Pseudomonas sp. transaminase and compared it

  20. Asymptotic behaviour and stability of solutions of a singularly perturbed elliptic problem with a triple root of the degenerate equation

    Science.gov (United States)

    Butuzov, V. F.

    2017-06-01

    We construct and justify asymptotic expansions of solutions of a singularly perturbed elliptic problem with Dirichlet boundary conditions in the case when the corresponding degenerate equation has a triple root. In contrast to the case of a simple root, the expansion is with respect to fractional (non-integral) powers of the small parameter, the boundary-layer variables have another scaling, and the boundary layer has three zones. This gives rise to essential modifications in the algorithm for constructing the boundary functions. Solutions of the elliptic problem are stationary solutions of the corresponding parabolic problem. We prove that such a stationary solution is asymptotically stable and find its global domain of attraction.

  1. Validation of a stability-indicating hydrophilic interaction liquid chromatographic method for the quantitative determination of vitamin k3 (menadione sodium bisulfite) in injectable solution formulation.

    Science.gov (United States)

    Ghanem, Mashhour M; Abu-Lafi, Saleh A; Hallak, Hussein O

    2013-01-01

    A simple, specific, accurate, and stability-indicating method was developed and validated for the quantitative determination of menadione sodium bisulfite in the injectable solution formulation. The method is based on zwitterionic hydrophilic interaction liquid chromatography (ZIC-HILIC) coupled with a photodiode array detector. The desired separation was achieved on the ZIC-HILIC column (250 mm × 4.6 mm, 5 μm) at 25°C temperature. The optimized mobile phase consisted of an isocratic solvent mixture of 200mM ammonium acetate (NH4AC) solution and acetonitrile (ACN) (20:80; v/v) pH-adjusted to 5.7 by glacial acetic acid. The mobile phase was fixed at 0.5 ml/min and the analytes were monitored at 261 nm using a photodiode array detector. The effects of the chromatographic conditions on the peak retention, peak USP tailing factor, and column efficiency were systematically optimized. Forced degradation experiments were carried out by exposing menadione sodium bisulfite standard and the injectable solution formulation to thermal, photolytic, oxidative, and acid-base hydrolytic stress conditions. The degradation products were well-resolved from the main peak and the excipients, thus proving that the method is a reliable, stability-indicating tool. The method was validated as per ICH and USP guidelines (USP34/NF29) and found to be adequate for the routine quantitative estimation of menadione sodium bisulfite in commercially available menadione sodium bisulfite injectable solution dosage forms.

  2. Immobilized enzymes: understanding enzyme - surface interactions at the molecular level.

    Science.gov (United States)

    Hoarau, Marie; Badieyan, Somayesadat; Marsh, E Neil G

    2017-11-22

    Enzymes immobilized on solid supports have important and industrial and medical applications. However, their uses are limited by the significant reductions in activity and stability that often accompany the immobilization process. Here we review recent advances in our understanding of the molecular level interactions between proteins and supporting surfaces that contribute to changes in stability and activity. This understanding has been facilitated by the application of various surface-sensitive spectroscopic techniques that allow the structure and orientation of enzymes at the solid/liquid interface to be probed, often with monolayer sensitivity. An appreciation of the molecular interactions between enzyme and surface support has allowed the surface chemistry and method of enzyme attachement to be fine-tuned such that activity and stability can be greatly enhanced. These advances suggest that a much wider variety of enzymes may eventually be amenable to immobilization as green catalysts.

  3. Modulation stability and dispersive optical soliton solutions of higher order nonlinear Schrödinger equation and its applications in mono-mode optical fibers

    Science.gov (United States)

    Arshad, Muhammad; Seadawy, Aly R.; Lu, Dianchen

    2018-01-01

    In mono-mode optical fibers, the higher order non-linear Schrödinger equation (NLSE) describes the propagation of enormously short light pulses. We constructed optical solitons and, solitary wave solutions of higher order NLSE mono-mode optical fibers via employing modified extended mapping method which has important applications in Mathematics and physics. Furthermore, the formation conditions are also given on parameters in which optical bright and dark solitons can exist for this media. The moment of the obtained solutions are also given graphically, that helps to realize the physical phenomena's of this model. The modulation instability analysis is utilized to discuss the model stability, which verifies that all obtained solutions are exact and stable. Many other such types of models arising in applied sciences can also be solved by this reliable, powerful and effective method. The method can also be functional to other sorts of higher order nonlinear problems in contemporary areas of research.

  4. Technology of Synergy Manifestation in the Research of Solution's Stability of Differential Equations System

    Science.gov (United States)

    Dvoryatkina, Svetlana N.; Melnikov, Roman A. M.; Smirnov, Eugeny I.

    2017-01-01

    Effectiveness of mathematical education as non-linear, composite and open system, formation and development of cognitive abilities of the trainee are wholly defined in the solution of complex tasks by means of modern achievements in science to high school practice adaptation. The possibility of complex tasks solution arises at identification of…

  5. phase formation and thermal stability of fcc (fluorite) Ce1-xTbxO2-d solid solutions

    NARCIS (Netherlands)

    de Vries, Karel Jan; de Vries, K.J.; Meng, G.Y.

    1998-01-01

    Ce1−xTbxO2−δ solid solutions (x = 0.3, 0.4, and 0.5) were synthesized by a coprecipitation method, using ammonia. The formation process of the solid solutions was studied as a function of temperature up to 1200°C by X-ray diffraction, thermogravimetric analysis, and differential scanning

  6. Stability constants of the fluoride complexes of actinides in aqueous solution and their correlation with fundamental properties

    International Nuclear Information System (INIS)

    Chaudhuri, N.K.; Sawant, R.M.

    1997-09-01

    Stability constants of the fluoride complexes of the actinides in different oxidation states measured by potentiometric method using fluoride ion selective electrode have been presented. Procedure and precautions required to overcome certain difficulties particular to actinide ions have been discussed. Literature data from various sources have been compiled. In order to have a reasonable comparison the stability constant (β 1 ) values obtained in diverse ionic strength media are converted to thermodynamic stability constant, β 1 0 , using Davies equation (a modification of Debye-Huckel equation). A correlation of the β 1 0 values with the fundamental properties of the actinide ions using various models available in the literature has been attempted. A semiempirical relation recently developed by Brown, Sylva and Ellis (BSE equation) appears to be most suitable. Using the values of ionic radii and best available values of the stability constants of a large number of metal ions from recent compilations a comparative study of the various models or relations available in the literature has been tried. For metal ions in general, the best correlation is obtained with the BSE equation. In an attempt to accommodate the unusual trend in the stability constants of the tetravalent actinides a modification in a parameter of the BSE equation has been proposed. Good agreement between the theoretically calculated and experimentally determined values for actinides in different oxidation states is then obtained in most of the cases. (author)

  7. Enhanced removal of humic acid from aqueous solution by novel stabilized nano-amorphous calcium phosphate: Behaviors and mechanisms

    Science.gov (United States)

    Jiang, Ling; Li, Yiming; Shao, Yi; Zhang, Yong; Han, Ruiming; Li, Shiyin; Wei, Wei

    2018-01-01

    Stabilized nano-amorphous calcium phosphate (nACP) was prepared using polyethylene glycol as stabilizer to obtain a nanosized amorphous adsorbent. The produced nACP was evaluated by using XRD, FTIR, SEM and X-ray photoelectron spectroscopy (XPS). The sedimentation test demonstrated that nACP exhibited better stability than crystallized hydroxyapatite. The adsorption efficiency of the nACP material for aqueous humic acid (HA) was evaluated from the point of view of medium pH, adsorption time, temperature, and ionic strength, as well as the presences of metal ions. The results of the study showed very good adsorption performance towards aqueous HA. The Sips modeling results revealed that the stabilized nACP adsorbent had a considerably high adsorption capacity (248.3 mg/g) for HA at 298 K. The adsorption data fitted well into pseudo-second order and Elovich kinetic models. XPS analyses indicated that HA retention on nACP material might be due to the surface complexation reaction between oxygen-containing group and calcium of HA and nACP, respectively. Moreover, the HA adsorption capacity of nACP could still keep more than 86% after four adsorption-desorption cycles. By taking into account all results it was concluded that the nACP adsorbent leveraged its stability in combination with its high uptake capacity to offer a great promise for HA adsorption from water.

  8. NMR investigation of acrolein stability in hydroalcoholic solution as a foundation for the valid HS-SPME/GC–MS quantification of the unsaturated aldehyde in beverages

    International Nuclear Information System (INIS)

    Kächele, Martin; Monakhova, Yulia B.; Kuballa, Thomas; Lachenmeier, Dirk W.

    2014-01-01

    Highlights: • Acrolein in hydroalcoholic solution degrades to 1,3,3-propanetriol and 3-hydroxypropionaldehyde. • Hydroquinone (0.2%) at pH 3.0 stabilizes acrolein solutions. • Quantitative HS-SPME/GC–MS determination of acrolein in alcoholic beverages was developed (LOD 14 μg L −1 ). • 6 of 117 samples had acrolein levels above the WHO threshold (1500 μg L −1 ). - Abstract: Acrolein (propenal) is found in many foods and beverages and may pose a health hazard due to its cytotoxicity. Considerable knowledge gaps regarding human exposure to acrolein exist, and there is a lack of reliable analytical methods. Hydroalcoholic dilutions prepared for calibration purposes from pure acrolein show considerable degradation of the compound and nuclear magnetic resonance (NMR) spectroscopy showed that 1,3,3-propanetriol and 3-hydroxypropionaldehyde are formed. The degradation can be prevented by addition of hydroquinone as stabilizer to the calibration solutions, which then show linear concentration-response behaviour required for quantitative analysis. The stabilized calibration solutions were used for quantitative headspace solid-phase microextraction/gas chromatography–mass spectrometry (HS-SPME/GC–MS) determination of acrolein in alcoholic beverages with a detection limit of 14 μg L −1 . Of 117 tested alcoholic beverages, 64 were tested positive with the highest incidence in grape marc spirits and whiskey (100%, mean 252 μg L −1 ), followed by fruit spirits (86%, mean 591 μg/L −1 ), tequila (86%, mean 404 μg L −1 ), Asian spirits (43%, mean 54 μg L −1 ) and wine (9%, mean 0.7 μg L −1 ). Acrolein could not be detected in beer, vodka, absinthe and bottled water. Six of the fruit and grape marc spirits had acrolein levels above the World Health Organization (WHO) provisional tolerable concentration of 1.5 mg L −1

  9. NMR investigation of acrolein stability in hydroalcoholic solution as a foundation for the valid HS-SPME/GC–MS quantification of the unsaturated aldehyde in beverages

    Energy Technology Data Exchange (ETDEWEB)

    Kächele, Martin [Chemisches und Veterinäruntersuchungsamt (CVUA) Karlsruhe, Weissenburger Strasse 3, D-76187 Karlsruhe (Germany); Hochschule Mannheim, Paul-Wittsack-Strasse 10, D-68163 Mannheim (Germany); Monakhova, Yulia B. [Chemisches und Veterinäruntersuchungsamt (CVUA) Karlsruhe, Weissenburger Strasse 3, D-76187 Karlsruhe (Germany); Bruker Biospin GmbH, Silbersteifen, 76287 Rheinstetten (Germany); Department of Chemistry, Saratov State University, Astrakhanskaya Street 83, 410012 Saratov (Russian Federation); Kuballa, Thomas [Chemisches und Veterinäruntersuchungsamt (CVUA) Karlsruhe, Weissenburger Strasse 3, D-76187 Karlsruhe (Germany); Lachenmeier, Dirk W., E-mail: lachenmeier@web.de [Chemisches und Veterinäruntersuchungsamt (CVUA) Karlsruhe, Weissenburger Strasse 3, D-76187 Karlsruhe (Germany); Ministry of Rural Affairs and Consumer Protection, Kernerplatz 10, 70182 Stuttgart (Germany)

    2014-04-01

    Highlights: • Acrolein in hydroalcoholic solution degrades to 1,3,3-propanetriol and 3-hydroxypropionaldehyde. • Hydroquinone (0.2%) at pH 3.0 stabilizes acrolein solutions. • Quantitative HS-SPME/GC–MS determination of acrolein in alcoholic beverages was developed (LOD 14 μg L⁻¹. • 6 of 117 samples had acrolein levels above the WHO threshold (1500 μg L⁻¹). Abstract: Acrolein (propenal) is found in many foods and beverages and may pose a health hazard due to its cytotoxicity. Considerable knowledge gaps regarding human exposure to acrolein exist, and there is a lack of reliable analytical methods. Hydroalcoholic dilutions prepared for calibration purposes from pure acrolein show considerable degradation of the compound and nuclear magnetic resonance (NMR) spectroscopy showed that 1,3,3-propanetriol and 3-hydroxypropionaldehyde are formed. The degradation can be prevented by addition of hydroquinone as stabilizer to the calibration solutions, which then show linear concentration-response behaviour required for quantitative analysis. The stabilized calibration solutions were used for quantitative headspace solid-phase microextraction/gas chromatography–mass spectrometry (HS-SPME/GC–MS) determination of acrolein in alcoholic beverages with a detection limit of 14 μg L⁻¹. Of 117 tested alcoholic beverages, 64 were tested positive with the highest incidence in grape marc spirits and whiskey (100%, mean 252 μg L⁻¹), followed by fruit spirits (86%, mean 591 μg/L⁻¹), tequila (86%, mean 404 μg L⁻¹), Asian spirits (43%, mean 54 μg L⁻¹) and wine (9%, mean 0.7 μg L⁻¹). Acrolein could not be detected in beer, vodka, absinthe and bottled water. Six of the fruit and grape marc spirits had acrolein levels above the World Health Organization (WHO) provisional tolerable concentration of 1.5 mg L⁻¹.

  10. Effect of a surface sealant on the color stability of composite resins after immersion in staining solution.

    Science.gov (United States)

    Pedroso, Lauana Borges; Barreto, Luma Franciélle Cabreira; Miotti, Leonardo Lamberti; Nicoloso, Gabriel Ferreira; Durand, Leticia Brandão

    2016-01-01

    This study evaluated the influence of surface sealants on the color stability of 2 different composite resins after immersion in coffee. Four groups were created (n = 10): microhybrid composite, microhybrid with surface sealant, nanofilled composite, and nanofilled composite with surface sealant. Half of the specimens of each group were immersed in distilled water and half were immersed in coffee for 48 hours. Color was measured before and after immersion. Groups with surface sealants presented less color variation when compared with the groups without surface sealants. The nanofilled resin specimens presented the greatest color variation within the groups without sealant. The surface sealant positively influenced the color stability of composite resin specimens immersed in coffee. When surface sealant was not applied, the microhybrid specimens had better color stability than the nanofilled.

  11. Room temperature synthesis of PbSe quantum dots in aqueous solution: Stabilization by interactions with ligands

    Science.gov (United States)

    Primera-Pedrozo, Oliva M.; Arslan, Zikri; Rasulev, Bakhtiyor; Leszczynski, Jerzy

    2011-01-01

    An aqueous route of synthesis is described for rapid synthesis of lead selenide quantum dots (PbSe QDs) at room temperature in an attempt to produce water-soluble and stable nanocrystals. Several thiol-ligands, including thioglycolic acid (TGA), thioglycerol (TGC), 3-mercaptopropionic acid (MPA), 2-mercaptoethyleamine hydrochloride (MEA), 6-mercaptohexanoic acid (MHA), and L-cysteine (L-cys), were used for capping/stabilization of PbSe QDs. The effects of the ligands on the stability of PbSe QDs were evaluated for a period of two months at room temperature under normal light conditions and at 4 °C in dark. The TGA- and MEA-capped QDs exhibited the highest stability prior to purification, almost two months when kept in dark at 4 °C. However, the stability of TGA-capped QDs was reduced substantially after purification to about 5 days under same conditions, while MEA-capped QDs did not show any significant instability. The stabilization energies of Pb-thiolate complexes determined by theoretical DFT simulations supported the experimental results. The PbSe QDs capped with TGA, MPA and MEA were successfully purified and re-dispersed in water, while those stabilized with TGC, MHA and L-cys aggregated during purification attempts. The purified PbSe QDs possess very susceptible surface resulting in poor stability for about 30 – 45 min after re-dispersion in water. In the presence of an excess of free ligand, the stability increased up to 5 days for TGA-capped QDs at pH 7.19, 9 –12 days for MPA-capped QDs at pH 7.3–7.5 and 45–47 days for MEA-capped QDs at pH 7.35. X-Ray Diffraction (XRD) results showed that the QDs possess a cubic rock salt structure with the most intense peaks located at 2θ = 25.3° (200) and 2θ = 29.2° (100). TEM images showed that the size of the QDs ranges between 5 and 10 nm. ICP-MS results revealed that Pb:Se ratio was 1.26, 1.28, 3.85, 1.18, and 1.31 for the QDs capped with TGA, MPA, MEA, L-Cys, and TGC, respectively. The proposed method

  12. Mutation for nonsyndromic mental retardation in the trans-2-enoyl-CoA reductase TER gene involved in fatty acid elongation impairs the enzyme activity and stability, leading to change in sphingolipid profile.

    Science.gov (United States)

    Abe, Kensuke; Ohno, Yusuke; Sassa, Takayuki; Taguchi, Ryo; Çalışkan, Minal; Ober, Carole; Kihara, Akio

    2013-12-20

    Very long-chain fatty acids (VLCFAs, chain length >C20) exist in tissues throughout the body and are synthesized by repetition of the fatty acid (FA) elongation cycle composed of four successive enzymatic reactions. In mammals, the TER gene is the only gene encoding trans-2-enoyl-CoA reductase, which catalyzes the fourth reaction in the FA elongation cycle. The TER P182L mutation is the pathogenic mutation for nonsyndromic mental retardation. This mutation substitutes a leucine for a proline residue at amino acid 182 in the TER enzyme. Currently, the mechanism by which the TER P182L mutation causes nonsyndromic mental retardation is unknown. To understand the effect of this mutation on the TER enzyme and VLCFA synthesis, we have biochemically characterized the TER P182L mutant enzyme using yeast and mammalian cells transfected with the TER P182L mutant gene and analyzed the FA elongation cycle in the B-lymphoblastoid cell line with the homozygous TER P182L mutation (TER(P182L/P182L) B-lymphoblastoid cell line). We have found that TER P182L mutant enzyme exhibits reduced trans-2-enoyl-CoA reductase activity and protein stability, thereby impairing VLCFA synthesis and, in turn, altering the sphingolipid profile (i.e. decreased level of C24 sphingomyelin and C24 ceramide) in the TER(P182L/P182L) B-lymphoblastoid cell line. We have also found that in addition to the TER enzyme-catalyzed fourth reaction, the third reaction in the FA elongation cycle is affected by the TER P182L mutation. These findings provide new insight into the biochemical defects associated with this genetic mutation.

  13. Enzyme Informatics

    Science.gov (United States)

    Alderson, Rosanna G.; Ferrari, Luna De; Mavridis, Lazaros; McDonagh, James L.; Mitchell, John B. O.; Nath, Neetika

    2012-01-01

    Over the last 50 years, sequencing, structural biology and bioinformatics have completely revolutionised biomolecular science, with millions of sequences and tens of thousands of three dimensional structures becoming available. The bioinformatics of enzymes is well served by, mostly free, online databases. BRENDA describes the chemistry, substrate specificity, kinetics, preparation and biological sources of enzymes, while KEGG is valuable for understanding enzymes and metabolic pathways. EzCatDB, SFLD and MACiE are key repositories for data on the chemical mechanisms by which enzymes operate. At the current rate of genome sequencing and manual annotation, human curation will never finish the functional annotation of the ever-expanding list of known enzymes. Hence there is an increasing need for automated annotation, though it is not yet widespread for enzyme data. In contrast, functional ontologies such as the Gene Ontology already profit from automation. Despite our growing understanding of enzyme structure and dynamics, we are only beginning to be able to design novel enzymes. One can now begin to trace the functional evolution of enzymes using phylogenetics. The ability of enzymes to perform secondary functions, albeit relatively inefficiently, gives clues as to how enzyme function evolves. Substrate promiscuity in enzymes is one example of imperfect specificity in protein-ligand interactions. Similarly, most drugs bind to more than one protein target. This may sometimes result in helpful polypharmacology as a drug modulates plural targets, but also often leads to adverse side-effects. Many cheminformatics approaches can be used to model the interactions between druglike molecules and proteins in silico. We can even use quantum chemical techniques like DFT and QM/MM to compute the structural and energetic course of enzyme catalysed chemical reaction mechanisms, including a full description of bond making and breaking. PMID:23116471

  14. Study of Water-Oil Emulsion Breaking by Stabilized Solution Consisting of Anionic Surface Acting Agent - Soda Ash - Polymer (ASP)

    Science.gov (United States)

    Kulichkov, S. V.; Avtomonov, E. G.; Andreeva, L. V.; Solomennik, S. F.; Nikitina, A. V.

    2018-01-01

    The paper provides a laboratory research of breaking natural water-oil emulsions: - by non-stabilized ASP; by stabilized ASP; by mixture of stabilized and non-stabilized ASP in different proportions and production of refinery water of the required quality with the use of IronGuard 2495 as flocculant. Oil-in-water emulsion is stable. Classic methods are not suitable for residual water treatment: sediment gravity flow; filtration; centrifuge test. Microemulsion formed after ASP application has low boundary tension and high pH. It contributes to transfer of oil phase into a water one, forming oil-in-water emulsion. Alkaline condition has adverse effect on demulsifying ability of agents, flocculation and boundary tension. For breaking of water-oil emulsion at EBU before the interchanger water or water-oil emulsion from the wells that were not APS-treated in ratio of 1:9 shall be delivered. Residual water after EBU must be prepared in water tanks by dilution in great volume.

  15. Alkylarylnitrosoureas--stability in aqueous solution, partition coefficient, alkylating activity and its relationship to SCE induction in Chinese hamster V 79-E cells.

    Science.gov (United States)

    Mendel, J; Thust, R; Schwarz, H

    1982-01-01

    The alkylating activity, chemical stability in aqueous solution (pH 7.0; 37 degrees C), and partition coefficient (octanol/water) of the following compounds were determined: 1-methyl-3-phenyl-1-nitrosourea (MPNU), 1-ethyl-3-phenyl-1-nitrosourea (EPNU), 1-isopropyl-3-phenyl-1-nitrosourea (i-PrPNU), 1-methyl-3-(p-fluorophenyl)-1-nitrosourea (F-MPNU), 1-methyl-3-(p-chlorophenyl)-1-nitrosourea (Cl-MPNU), 1-methyl-3-(p-bromophenyl)-1-nitrosourea (Br-MPNU), 1,3-dimethyl-3-phenyl-1-nitrosourea (DMPNU), and 1-methyl-3-naphthyl-1-nitrosocarbamate (NCA). 1-Methyl-1-nitrosourea (MNU) and 1-ethyl-1-nitrosourea (ENU) were used for the comparison. THe rate of decomposition in aqueous solution is discussed concerning the influences of the substituents at the 1- and 3-N-atom. The mono- and disubstituted N-nitrosoureas showed a coarse correlation between alkylating activity and SCE induction in Chinese hamster V 79-E cells. On the other hand, this correlation is missing in the case of NCA, which is a potent SCE inducer despite relatively low alkylating activity. DMPNU is the strongest SCE inducer, but this compound shows a high stability in aqueous solution and, consequently, we were not able to detect an alkylating activity.

  16. Shelf life stability comparison in air for solution processed pristine PDPP3T polymer and doped spiro-OMeTAD as hole transport layer for perovskite solar cell

    Directory of Open Access Journals (Sweden)

    Ashish Dubey

    2016-06-01

    Full Text Available This data in brief includes forward and reverse scanned current density–voltage (J–V characteristics of perovskite solar cells with PDPP3T and spiro-OMeTAD as HTL, stability testing conditions of perovskite solar cell shelf life in air for both PDPP3T and spiro-OMeTAD as HTL as per the description in Ref. [1], and individual J–V performance parameters acquired with increasing time exposed in ambient air are shown for both type of devices using PDPP3T and spiro-OMeTAD as HTL. The data collected in this study compares the device stability with time for both PDPP3T and spiro-OMeTAD based perovskite solar cells and is directly related to our research article “solution processed pristine PDPP3T polymer as hole transport layer for efficient perovskite solar cells with slower degradation” [2].

  17. Reduction of Charge Traps and Stability Enhancement in Solution-Processed Organic Field-Effect Transistors Based on a Blended n-Type Semiconductor.

    Science.gov (United States)

    Campos, Antonio; Riera-Galindo, Sergi; Puigdollers, Joaquim; Mas-Torrent, Marta

    2018-05-09

    Solution-processed n-type organic field-effect transistors (OFETs) are essential elements for developing large-area, low-cost, and all organic logic/complementary circuits. Nonetheless, the development of air-stable n-type organic semiconductors (OSCs) lags behind their p-type counterparts. The trapping of electrons at the semiconductor-dielectric interface leads to a lower performance and operational stability. Herein, we report printed small-molecule n-type OFETs based on a blend with a binder polymer, which enhances the device stability due to the improvement of the semiconductor-dielectric interface quality and a self-encapsulation. Both combined effects prevent the fast deterioration of the OSC. Additionally, a complementary metal-oxide semiconductor-like inverter is fabricated depositing p-type and n-type OSCs simultaneously.

  18. Comparison of conventional and plant-extract disinfectant solutions on the hardness and color stability of a maxillofacial elastomer after artificial aging.

    Science.gov (United States)

    Guiotti, Aimée Maria; Goiato, Marcelo Coelho; Dos Santos, Daniela Micheline; Vechiato-Filho, Aljomar José; Cunha, Bruno Guandalini; Paulini, Marcela Borghi; Moreno, Amália; de Almeida, Margarete Teresa Gottardo

    2016-04-01

    Silicone elastomers undergo physical and chemical degradation with disinfecting solutions. Phytotherapy may be a suitable solution for disinfection. However, its effect on the properties of the silicone material is unknown. The purpose of this in vitro study was to evaluate the effect of disinfection with conventional and plant-extract solutions and of artificial aging on the hardness and color stability of a facial silicone associated with pigments and an opacifier. Four hundred specimens of silicone (MDX4-4210) were fabricated (5×6 mm). Two pigment shades and 1 dry opacifier were combined in the tested material, and 4 groups (n=10) were obtained: colorless (GI), colorless with opacifier (GII), medium pigment with opacifier (GIII), and black pigment with opacifier (GIV). Specimens were subjected to disinfection (30 days) using saline solution, water, and neutral soap (digital friction, 30 seconds), chlorhexidine 4%, Hydrastis canadensis, and Cymbopogon nardus extracts (immersion, 10 minutes). Shore A hardness (ASTM D2240) and color analyses were performed before and after disinfection. Specimens were then exposed to 1008 hours of artificial aging (ASTM 53) and subjected to final hardness and color readings. The results were analyzed with ANOVA and the Tukey significant difference test (α=.05). The opacifier increased the hardness (GII). For GII, the H. canadensis solution and the friction with water and soap promoted significantly reduced hardness; the friction also promoted a reduction in this property for GIV. The GIII was not affected after disinfection. A significant difference was found between the ΔE values of the specimens disinfected with H. canadensis, C. nardus, and chlorhexidine, and specimens subjected to saline solution and neutral soap. The hardness of MDX4-4210 after the experimental procedure was considered clinically acceptable for facial prostheses. All groups showed clinically unacceptable color alterations regardless of the disinfecting

  19. Effects of Mg doping on the gate bias and thermal stability of solution-processed InGaZnO thin-film transistors

    Energy Technology Data Exchange (ETDEWEB)

    Su, Bo-Yuan [Department of Electrical Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Chu, Sheng-Yuan, E-mail: chusy@mail.ncku.edu.tw [Department of Electrical Engineering, National Cheng Kung University, Tainan 701, Taiwan (China); Center for Micro/Nano Science and Technology Center, National Cheng Kung University, Tainan 701, Taiwan (China); Juang, Yung-Der [Department of Materials Science, National University of Tainan, Tainan 700, Taiwan (China); Liu, Ssu-Yin [Department of Electrical Engineering, National Cheng Kung University, Tainan 701, Taiwan (China)

    2013-12-15

    Graphical abstract: Mg-doped IGZO TFTs showed improved TFT performance and thermal stability due to fewer oxygen deficiencies and less interface electron trapping. Highlights: •We fabricated Mg-doped IGZO TFTs with improved performance using solution-process. •Mg doping reduced the oxygen deficiencies and less interface electron trapping of a-IGZO films. •Mg dope-TFT showed high mobility of 2.35 cm{sup 2}/V s and an on–off current ratio over 10{sup 6}. •For better device stability (gate-bias and thermal stability) was proved. -- Abstract: The effects of magnesium (Mg) doping (molar ratio Mg/Zn = (0–10 at.%)) on solution-processed amorphous InGaZnO (a-IGZO) thin-film transistors (TFTs) grown using the sol–gel method are investigated. TFT devices fabricated with Mg-doped films showed an improved field-effect mobility of 2.35 cm{sup 2}/V s and a subthreshold slope (S) of 0.42 V/dec compared to those of an undoped a-IGZO TFT (0.73 cm{sup 2}/V s and 0.74 V/dec, respectively), and an on–off current ratio of over 10{sup 6}. Moreover, the 5 at.% Mg-doped TFT device showed improved gate bias and thermal stability due to fewer oxygen deficiencies, smaller carrier concentration, and less interface electron trapping in the a-IGZO films.

  20. Effect of various de-anodizing techniques on the surface stability of non-colored and colored nanoporous AAO films in acidic solution

    Energy Technology Data Exchange (ETDEWEB)

    Awad, Ahmed M. [Chemical Engineering & Pilot Plant Department, National Research Centre, Dokki, Giza (Egypt); Shehata, Omnia S. [Physical Chemistry Department, National Research Centre, Dokki, Giza (Egypt); Heakal, Fakiha El-Taib, E-mail: fakihaheakal@yahoo.com [Chemistry Department, Faculty of Science, Cairo University, Giza 12613 (Egypt)

    2015-12-30

    Highlights: • Three de-anodization methods were used during two-step fabrication of nanoporous AAO. • Electrolytic etching (EE), chemical etching with H{sub 3}PO{sub 4} (PE) or NaOH (HE) were adopted. • After the second anodizing step, HE film was the thinnest as compared to EE and HE. • Stability order of nanoporous AAO films in 0.5 M HCl solution was: PE > EE > HE. • For the colored films by electrodeposited Cu atoms, the order was: HE > EE > PE. - Abstract: Anodic aluminum oxide (AAO) is well known as an important nanostructured material, and a useful template in the fabrication of nanostructures. Nanoporous anodic alumina (PAA) with high open porosity was prepared by adopting three de-anodizing regimes following the first anodizing step and preceding the second one. The de-anodizing methods include electrolytic etching (EE) and chemical etching using either phosphoric acid (PE) or sodium hydroxide (HE) solutions. Three of the obtained AAO samples were black colored by electrodeposition of copper nanoparticles in their pores. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques were used to characterize the electrochemical performance of the two sets of the prepared samples. In general, the data obtained in aggressive aerated 0.5 M HCl solution demonstrated dissimilar behavior for the three prepared samples despite that the second anodizing step was the same for all of them. The data indicated that the resistance and thickness of the inner barrier part of nano-PAA film, are the main controlling factors determining its stability. On the other hand, coloring the film decreased its stability due to the galvanic effect. The difference in the electrochemical behavior of the three colored samples was discussed based on the difference in both the pore size and thickness of the outer porous part of PAA film as supported by SEM, TEM and cross-sectional micrographs. These results can thus contribute for better engineering

  1. Solution NMR characterization of Sgf73(1-104) indicates that Zn ion is required to stabilize zinc finger motif

    International Nuclear Information System (INIS)

    Lai, Chaohua; Wu, Minhao; Li, Pan; Shi, Chaowei; Tian, Changlin; Zang, Jianye

    2010-01-01

    Zinc finger motif contains a zinc ion coordinated by several conserved amino acid residues. Yeast Sgf73 protein was identified as a component of SAGA (Spt/Ada/Gcn5 acetyltransferase) multi-subunit complex and Sgf73 protein was known to contain two zinc finger motifs. Sgf73(1-104), containing the first zinc finger motif, was necessary to modulate the deubiquitinase activity of SAGA complex. Here, Sgf73(1-104) was over-expressed using bacterial expression system and purified for solution NMR (nuclear magnetic resonance) structural studies. Secondary structure and site-specific relaxation analysis of Sgf73(1-104) were achieved after solution NMR backbone assignment. Solution NMR and circular dichroism analysis of Sgf73(1-104) after zinc ion removal using chelation reagent EDTA (ethylene-diamine-tetraacetic acid) demonstrated that zinc ion was required to maintain stable conformation of the zinc finger motif.

  2. A salt water battery with high stability and charging rates made from solution processed conjugated polymers with polar side chains

    KAUST Repository

    Moia, Davide; Giovannitti, Alexander; Szumska, Anna A.; Schnurr, Martin; Rezasoltani, Elham; Maria, Iuliana P.; Barnes, Piers R. F.; McCulloch, Iain; Nelson, Jenny

    2017-01-01

    conjugated polymer backbones, allowed the films to maintain constant capacity at high charge and discharge rates (>1000 C-rate). The electrodes also show good stability during electrochemical cycling (less than 30% decrease in capacity over >1000 cycles) and an output voltage up to 1.4 V. The performance of these semiconducting polymers with polar side-chains demonstrates the potential of this material class for fast-charging, water based electrochemical energy storage devices.

  3. Stability analysis solutions and optical solitons in extended nonlinear Schrödinger equation with higher-order odd and even terms

    Science.gov (United States)

    Peng, Wei-Qi; Tian, Shou-Fu; Zou, Li; Zhang, Tian-Tian

    2018-01-01

    In this paper, the extended nonlinear Schrödinger equation with higher-order odd (third order) and even (fourth order) terms is investigated, whose particular cases are the Hirota equation, the Sasa-Satsuma equation and Lakshmanan-Porsezian-Daniel equation by selecting some specific values on the parameters of higher-order terms. We first study the stability analysis of the equation. Then, using the ansatz method, we derive its bright, dark solitons and some constraint conditions which can guarantee the existence of solitons. Moreover, the Ricatti equation extension method is employed to derive some exact singular solutions. The outstanding characteristics of these solitons are analyzed via several diverting graphics.

  4. Structural stability of solutions to the Riemann problem for a non-strictly hyperbolic system with flux approximation

    Directory of Open Access Journals (Sweden)

    Meina Sun

    2016-05-01

    Full Text Available We study the Riemann problem for a non-strictly hyperbolic system of conservation laws under the linear approximations of flux functions with three parameters. The approximated system also belongs to the type of triangular systems of conservation laws and this approximation does not change the structure of Riemann solutions to the original system. Furthermore, it is proven that the Riemann solutions to the approximated system converge to the corresponding ones to the original system as the perturbation parameter tends to zero.

  5. Chaperone-Like Activity of ß-Casein and Its Effect on Residual in Vitro Activity of Food Enzymes

    DEFF Research Database (Denmark)

    Sulewska, Anna Maria

    ABSTRACT Activity of endogenous enzymes may cause browning of fruits and vegetables. These enzymes can be inactivated, for example by heat treatment, but the response of enzymes to heat treatment depends on many factors. Foods are very complex systems and the stability of enzymes......-casein on the enzymatic activity of three targets was tested by monitoring enzyme activity after heat treatment and by measuring the intensity of scattered light during and after heat treatment. β-Casein was shown to interact at elevated temperatures with three selected targets:horseradish peroxidase, tyrosinase from......, residual activity of horseradish peroxidase was lower in samples containing BSA than in samples without any addition. Horseradish peroxidase heated with BSA did not regain activity within one hour after treatment. BSA is often added to enzyme solutions to prevent enzyme adhesion to vial surfaces...

  6. Determination of stability constants for thallium(III) cyanide complexes in aqueous solution by means of 13C and 205Ti NMR

    International Nuclear Information System (INIS)

    Blixt, J.; Gyori, B.; Glaser, J.

    1989-01-01

    In contrast to what is usually assumed, we have found and proved that thallium(III) forms very strong cyanide complexes in aqueous solution. The authors have investigated this system using 205 Tl, 13 C, and 14 N NMR and potentiometry and established the existence of four thallium(III)-cyanide complexes of the composition Tl(CN) n 3-n , n = 1-4. We have measured their chemical shifts and spin-spin coupling constants and determined their formation constants at 25 degree C in dilute (0.05 M) aqueous solution in the ionic medium ([Na + ] = 1 M, [Li + ] + [H + ] = 3 M, [ClO 4 - ] = 4 M). We have also determined the stability constant for HCN in the same ionic medium, log K a = 10.11 (5)

  7. Human Lactoferricin Is Partially Folded in Aqueous Solution and Is Better Stabilized in a Membrane Mimetic Solvent

    Science.gov (United States)

    Hunter, Howard N.; Demcoe, A. Ross; Jenssen, Håvard; Gutteberg, Tore J.; Vogel, Hans J.

    2005-01-01

    Lactoferricins are highly basic bioactive peptides that are released in the stomach through proteolytic cleavage of various lactoferrin proteins. Here we have determined the solution structure of human lactoferricin (LfcinH) by conventional two-dimensional nuclear magnetic resonance methods in both aqueous solution and a membrane mimetic solvent. Unlike the 25-residue bovine lactoferricin (LfcinB), which adopts a somewhat distorted antiparallel β sheet, the longer LfcinH peptide shows a helical content from Gln14 to Lys29 in the membrane mimetic solvent but a nonexistent β-sheet character in either the N- or C-terminal regions of the peptide. The helical characteristic of the LfcinH peptide resembles the conformation that this region adopts in the crystal structure of the intact protein. The LfcinH structure determined in aqueous solution displays a nascent helix in the form of a coiled conformation in the region from Gln14 to Lys29. Numerous hydrophobic interactions create the basis for the better-defined overall structure observed in the membrane mimetic solvent. The 49-residue LfcinH peptide isolated for these studies was found to be slightly longer than previously reported peptide preparations and was found to have an intact peptide bond between residues Ala11 and Val12. The distinct solution structures of LfcinH and LfcinB represent a novel difference in the physical properties of these two peptides, which contributes to their unique physiological activities. PMID:16048952

  8. Enzymes for Enhanced Oil Recovery (EOR)

    Energy Technology Data Exchange (ETDEWEB)

    Nasiri, Hamidreza

    2011-04-15

    Primary oil recovery by reservoir pressure depletion and secondary oil recovery by waterflooding usually result in poor displacement efficiency. As a consequence there is always some trapped oil remaining in oil reservoirs. Oil entrapment is a result of complex interactions between viscous, gravity and capillary forces. Improving recovery from hydrocarbon fields typically involves altering the relative importance of the viscous and capillary forces. The potential of many EOR methods depends on their influence on fluid/rock interactions related to wettability and fluid/fluid interactions reflected in IFT. If the method has the potential to change the interactions favorably, it may be considered for further investigation, i.e. core flooding experiment, pilot and reservoir implementation. Enzyme-proteins can be introduced as an enhanced oil recovery method to improve waterflood performance by affecting interactions at the oil-water-rock interfaces. An important part of this thesis was to investigate how selected enzymes may influence wettability and capillary forces in a crude oil-brine-rock system, and thus possibly contribute to enhanced oil recovery. To investigate further by which mechanisms selected enzyme-proteins may contribute to enhance oil recovery, groups of enzymes with different properties and catalytic functions, known to be interfacially active, were chosen to cover a wide range of possible effects. These groups include (1) Greenzyme (GZ) which is a commercial EOR enzyme and consists of enzymes and stabilizers (surfactants), (2) The Zonase group consists of two types of pure enzyme, Zonase1 and Zonase2 which are protease enzymes and whose catalytic functions are to hydrolyze (breakdown) peptide bonds, (3) The Novozyme (NZ) group consists of three types of pure enzyme, NZ2, NZ3 and NZ6 which are esterase enzymes and whose catalytic functions are to hydrolyze ester bonds, and (4) Alpha-Lactalbumin ( -La) which is an important whey protein. The effect of

  9. Stability of solutions of antineoplastic agents during preparation and storage for in vitro assays. General considerations, the nitrosoureas and alkylating agents.

    Science.gov (United States)

    Bosanquet, A G

    1985-01-01

    In vitro drug sensitivity of tumour biopsies is currently being determined using a variety of methods. For these chemosensitivity assays many drugs are required at short notice, and this in turn means that the drugs must generally be stored in solution. There are, however, a number of potential problems associated with dissolving and storing drugs for in vitro use, which include (a) drug adsorption; (b) effects of freezing; (c) drug stability under the normal conditions of dilution and setting up of an in vitro assay; and (d) insolubility of drugs in normal saline (NS) or phosphate-buffered saline (PBS). These problems are considered in general, and some recommendations for use of solutions of drugs in in vitro assays are suggested. The nitrosoureas and alkylating agents are also investigated in greater detail in this respect. The nitrosoureas are found to be very labile in PBS at pH 7, with 5% degradation (t0.95) occurring in 10-50 min at room temperature. These values are increased about 10-fold on refrigeration and about 5- to 10-fold on reduction of the pH of the medium to pH 4-5. At pH 7 and room temperature, t0.95 is observed in under 1 h with the alkylating agents nitrogen mustard, chlorambucil, melphalan, 2,5-diaziridinyl-3,6-bis(2-hydroxyethylamino)-1,4-benzoquinone (BZQ), dibromodulcitol, dibromomannitol, treosulphan, and procarbazine. Of the other alkylating agents, 4-hydroperoxycylophosphamide (sometimes used in vitro in place of cyclophosphamide), busulphan, dianhydrogalactitol, aziridinylbenzoquinone (AZQ), and dacarbazine have a t0.95 of between 2 and 24 h, while ifosfamide and pentamethylmelamine are both stable in aqueous solution for greater than 7 days. About half the drugs studied in detail have been stored frozen in solution for in vitro use, although very little is known about their stability under these conditions.

  10. Biocatalysis with thermostable enzymes: structure and properties of a thermophilic 'ene'-reductase related to old yellow enzyme.

    Science.gov (United States)

    Adalbjörnsson, Björn V; Toogood, Helen S; Fryszkowska, Anna; Pudney, Christopher R; Jowitt, Thomas A; Leys, David; Scrutton, Nigel S

    2010-01-25

    We report the crystal structure of a thermophilic "ene" reductase (TOYE) isolated from Thermoanaerobacter pseudethanolicus E39. The crystal structure reveals a tetrameric enzyme and an active site that is relatively large compared to most other structurally determined and related Old Yellow Enzymes. The enzyme adopts higher order oligomeric states (octamers and dodecamers) in solution, as revealed by sedimentation velocity and multiangle laser light scattering. Bead modelling indicates that the solution structure is consistent with the basic tetrameric structure observed in crystallographic studies and electron microscopy. TOYE is stable at high temperatures (T(m)>70 degrees C) and shows increased resistance to denaturation in water-miscible organic solvents compared to the mesophilic Old Yellow Enzyme family member, pentaerythritol tetranitrate reductase. TOYE has typical ene-reductase properties of the Old Yellow Enzyme family. There is currently major interest in using Old Yellow Enzyme family members in the preparative biocatalysis of a number of activated alkenes. The increased stability of TOYE in organic solvents is advantageous for biotransformations in which water-miscible organic solvents and biphasic reaction conditions are required to both deliver novel substrates and minimize product racemisation.

  11. Measuring the Enzyme Activity of Arabidopsis Deubiquitylating Enzymes.

    Science.gov (United States)

    Kalinowska, Kamila; Nagel, Marie-Kristin; Isono, Erika

    2016-01-01

    Deubiquitylating enzymes, or DUBs, are important regulators of ubiquitin homeostasis and substrate stability, though the molecular mechanisms of most of the DUBs in plants are not yet understood. As different ubiquitin chain types are implicated in different biological pathways, it is important to analyze the enzyme characteristic for studying a DUB. Quantitative analysis of DUB activity is also important to determine enzyme kinetics and the influence of DUB binding proteins on the enzyme activity. Here, we show methods to analyze DUB activity using immunodetection, Coomassie Brilliant Blue staining, and fluorescence measurement that can be useful for understanding the basic characteristic of DUBs.

  12. New generation of membrane efficient water-based drilling fluids: pragmatic and cost-effective solutions to borehole stability problems

    Energy Technology Data Exchange (ETDEWEB)

    Tare, U.A. [Haliburton, Calgary, AB (Canada); Mody, F.K. [Shell International E and P Inc., Calgary, AB (Canada); Tan, C.P. [CSIRO Petroleum, Kensington, WA (Australia)

    2002-06-01

    Drilling and completion operations in shales often suffer as a result of wellbore instability. Mechanical failure of the rock around a wellbore is the primary cause of shale instability. This process can be exacerbated by physico-chemical interactions between drilling fluids and shales. Water-based drilling fluids are used more and more due to environmental awareness that becomes more prevalent. Wellbore instability problems can however result from an improper application of water-based drilling fluids in those cases where drilling occurs in sensitive clay-rich formations. To meet the requirements of the petroleum industry, considerable collaborative efforts were expanded in the development of innovative environmentally acceptable water-based drilling fluids. In this paper, the authors describe the process that leads to the development of these drilling fluids. It is possible to achieve shale stability through an osmotic outflow of pore fluid and prevention/minimization of mud pressure penetration, as laboratory experiments on shale samples under realistic downhole conditions exposed to these drilling fluids prove. High membrane efficiencies, in excess of 80 per cent, were generated by this new generation of membrane efficient water-based drilling fluids. Drilling objectives resulting from an improved application of water-based drilling fluids are made possible by a fundamental understanding of the main drilling fluid-shale interaction mechanisms for shale stability and the application of experimental data to field conditions. The authors indicate that the achievement of trouble-free drilling of shales and notable reductions in non-productive time is accomplished by following the practical guidelines included in this paper for maintaining shale stability with the new generation of water-based drilling fluids. 8 refs., 2 tabs., 4 figs.

  13. Removal of Nitrate from Aqueous Solutions by Starch Stabilized nano Zero-Valent Iron(nZVI

    Directory of Open Access Journals (Sweden)

    Kaveh Yaghmaeian

    2016-09-01

    Full Text Available Background and Objective: Nitrate is one of the inorganic anions derived as a result of oxidation of elemental nitrogen. Urban and industrial wastewater, animal and vegetable waste products in large cities that have organic nitrogen are excreted along the soil. The primary risk of Nitrate in drinking water occurs when nitrate in the gastrointestinal tract switch to nitrite. Nitrite causes the oxidation of iron in hemoglobin of red blood cells, result in red blood cells could not carry the oxygen, a condition called methemoglobinemia. Therefore, achieving the new technologies for nitrate removal is necessary. Material and Methods: The present study was conducted at laboratory Scale in non-continuous batches. Stabilized adsorbent was produced through reducing Iron sulfate by sodium borohydride (NaBH4 in presence of Starch (0.2W % as a stabilizer. At first, the effect of various parameters such as contact time (10-90min, pH (3-11, adsorbent dose (0.5-3 g/L and initial concentration of arsenate (50-250 mg/L were investigated on process efficiency. Freundlich and Langmuir isotherm model equilibrium constant, were calculated. Residual nitrate were measured by using the DR5000 spectrophotometer. Results: The optimum values based on RSM for pH, absorbent dose, contact time, and initial concentration of nitrate were 5.87, 2.25 g/L, 55.7 min, and 110.35 mg/L respectively. Langmuir isotherm with R2= 0.9932 for nitrate was the best graph for the experimental data. The maximum amount of nitrate adsorption was 138.88mg/g. Conclusion: Stabilized absorbent due to have numerous absorption sites and Fe0 as a reducing agent could have great potential in nitrate removal from water.

  14. Effect of electrolyte valency, alginate concentration and pH on engineered TiO₂ nanoparticle stability in aqueous solution.

    Science.gov (United States)

    Loosli, Frédéric; Le Coustumer, Philippe; Stoll, Serge

    2015-12-01

    Agglomeration and disagglomeration processes are expected to play a key role on the fate of engineered nanoparticles in natural aquatic systems. These processes are investigated here in detail by studying first the stability of TiO2 nanoparticles in the presence of monovalent and divalent electrolytes at different pHs (below and above the point of zero charge of TiO2) and discussing the importance of specific divalent cation adsorption with the help of the DLVO theory as well as the importance of the nature of the counterions. Then the impact of one polysaccharide (alginate) on the stability of agglomerates formed under pH and water hardness representative of Lake Geneva environmental conditions is investigated. In these conditions the large TiO2 agglomerates (diameter>1μm) are positively charged due to Ca(2+) and Mg(2+) specific adsorption and alginate, which is negatively charged, adsorbs onto the agglomerate surface. Our results indicate that the presence of alginate at typical natural organic matter concentration (1-10 mg L(-1)) strongly modifies the TiO2 agglomerate (50 mg L(-1)) stability by inducing their partial and rapid disagglomeration. The importance of disagglomeration is found dependent on the alginate concentration with maximum of disagglomeration obtained for alginate concentration ≥8 mg L(-1) and leading to 400 nm fragments. From an environmental point of view partial restabilization of TiO2 agglomerates in the presence of alginate constitutes an important outcome. Disagglomeration will enhance their transport and residence time in aquatic systems which is an important step in the current knowledge on risk assessment associated to engineered nanoparticles. Copyright © 2015 Elsevier B.V. All rights reserved.

  15. On the calculation of linear stability with the aid of asymptotic solutions of Orr-Sommerfeld equation, 1

    International Nuclear Information System (INIS)

    Fujimura, Kaoru

    1980-11-01

    The numerical treatment of Orr-Sommerfeld equation which is the fundamental equation of linear hydrodynamic stability theory is described. Present calculation procedure is applied to the two-dimensional quasi-parallel flow for which linearized disturbance equation (Orr-Sommerfeld equation) contains one simple turning point and αR >> 1. The numerical procedure for this problem and one numerical example for Jeffery-Hamel flow (J-H III 1 ) are presented. These treatment can be extended to the other velocity profiles by slight midifications. (author)

  16. Investigation of the degradation and stability of acrylamide-based polymers in acid solution: Functional monomer modified polyacrylamide

    Directory of Open Access Journals (Sweden)

    Yuxin Pei

    2016-12-01

    Full Text Available Acrylamide copolymers are often used as acidizing diverting and thickening agents for their advantageous thickening, flocculation, adhesion and resistance reduction properties. Experimental results indicate that the acid concentration greatly affects the properties of acrylamide polymers, which varies from results reported by other researchers. Considering the theoretical and field application value of the present study, four comparable acrylamide-based polymers were synthesized, and their macro- and micro-changes as well as the related changes in viscosity and molecular weight were studied in high-concentration hydrochloric acid. A proposed mechanism of acrylamide copolymer stability and degradation is provided, and further suggestions are made for the modification of acrylamide copolymers.

  17. A Simplified Solution for Calculating the Phreatic Line and Slope Stability during a Sudden Drawdown of the Reservoir Water Level

    Directory of Open Access Journals (Sweden)

    Guanhua Sun

    2018-01-01

    Full Text Available On the basis of the Boussinesq unsteady seepage differential equation, a new simplified formula for the phreatic line of slopes under the condition of decreasing reservoir water level is derived by means of the Laplacian matrix and its inverse transform. In this context, the expression of normal stress on the slip surface under seepage forces is deduced, and a procedure for obtaining the safety factors under hydrodynamic forces is proposed. A case study of the Three Gorges Reservoir is used to analyze the influences of the water level, decreasing velocity and the permeability coefficient on slope stability.

  18. Synthesis of Gold Nanoparticles Stabilized in Dextran Solution by Gamma Co-60 Ray Irradiation and Preparation of Gold Nanoparticles/Dextran Powder

    Directory of Open Access Journals (Sweden)

    Phan Ha Nu Diem

    2017-01-01

    Full Text Available Gold nanoparticles (AuNPs in spherical shape with diameter of 6–35 nm stabilized by dextran were synthesized by γ-irradiation method. The AuNPs were characterized by UV-Vis spectroscopy and transmission electron microscopy. The influence of pH, Au3+ concentration, and dextran concentration on the size of AuNPs was investigated. Results indicated that the smallest AuNPs size (6 nm and the largest AuNPs size (35 nm were obtained for pH of 1 mM Au3+/1% dextran solution of 5.5 and 7.5, respectively. The smaller Au3+ concentration favored smaller size and conversely the smaller dextran concentration favored bigger size of AuNPs. AuNPs powders were prepared by spay drying, coagulation, and centrifugation and their sizes were also evaluated. The purity of prepared AuNPs powders was also examined by energy dispersive X-ray (EDX analysis. Thus, the as-prepared AuNPs stabilized by biocompatible dextran in solution and/or in powder form can be potentially applied in biomedicine and pharmaceutics.

  19. Effect of various de-anodizing techniques on the surface stability of non-colored and colored nanoporous AAO films in acidic solution

    Science.gov (United States)

    Awad, Ahmed M.; Shehata, Omnia S.; Heakal, Fakiha El-Taib

    2015-12-01

    Anodic aluminum oxide (AAO) is well known as an important nanostructured material, and a useful template in the fabrication of nanostructures. Nanoporous anodic alumina (PAA) with high open porosity was prepared by adopting three de-anodizing regimes following the first anodizing step and preceding the second one. The de-anodizing methods include electrolytic etching (EE) and chemical etching using either phosphoric acid (PE) or sodium hydroxide (HE) solutions. Three of the obtained AAO samples were black colored by electrodeposition of copper nanoparticles in their pores. Electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization techniques were used to characterize the electrochemical performance of the two sets of the prepared samples. In general, the data obtained in aggressive aerated 0.5 M HCl solution demonstrated dissimilar behavior for the three prepared samples despite that the second anodizing step was the same for all of them. The data indicated that the resistance and thickness of the inner barrier part of nano-PAA film, are the main controlling factors determining its stability. On the other hand, coloring the film decreased its stability due to the galvanic effect. The difference in the electrochemical behavior of the three colored samples was discussed based on the difference in both the pore size and thickness of the outer porous part of PAA film as supported by SEM, TEM and cross-sectional micrographs. These results can thus contribute for better engineering applications of nanoporous AAO.

  20. Improvement of transistor characteristics and stability for solution-processed ultra-thin high-valence niobium doped zinc-tin oxide thin film transistors

    Energy Technology Data Exchange (ETDEWEB)

    Jeng, Jiann-Shing, E-mail: jsjeng@mail.nutn.edu.tw

    2016-08-15

    Nb-doped Zinc tin oxide (NZTO) channel materials have been prepared by solution process in combination with the spin-coating method. All NZTO thin film transistors (TFTs) are n-type enhancement-mode devices, either without or with Nb additives. High-valence niobium ion (ionic charge = +5) has a larger ionic potential and similar ionic radius to Zn{sup 2+} and Sn{sup 4+} ions. As compared with the pure ZTO device, introducing Nb{sup 5+} ions into the ZTO channel layers can improve the electrical properties and bias stability of TFTs because of the reduction of the oxygen vacancies. This study discusses the connection among the material properties of the NZTO films and the electrical performance and bias stability of NZTO TFTs and how they are influenced by the Nb/(Nb + Sn) molar ratios of NZTO films. - Highlights: • Ultra-thin high-valence niobium doped zinc-tin oxide (NZTO) thin films are prepared using a solution process. • Nb dopants in ZTO films reduce the oxygen vacancy and subgap adsorption of the ZTO films. • The Nb-doping concentration of the NZTO channel layer has a strong influence on the TFT performance.