Sample records for equivalent radiochromic gel

  1. Optical CT scanning of cross-linked radiochromic gel without cylinder wall

    Energy Technology Data Exchange (ETDEWEB)

    Jordan, Kevin [London Regional Cancer Program, London Health Sciences Centre and Department of Medical Biophysics, University of Western Ontario, London, ON (Canada)], E-mail:


    Genipin cross-linked gelatin hydrogels with 0.2 M sulphuric acid are radiochromic and have sufficient sensitivity for investigating doses less than 50 Gray. Because of the gelatine cross-links, these gels have sufficient strength to allow removal from the vessel container in which they were cast. Placing the gels in the same liquid that was used for preparing the gel allows the radiochemistry to the same throughout the gels and provides physical support. In this buoyancy neutral environment the gel has the same shape and the preparation vessel. This allows optical CT scanning without wall artefacts due to reflection, refraction and optical activity. A gel was irradiated to dose of 25 Gray with a 10 MV photon beam of 20 x 20 mm cross section. Full 3D optical CT scanning was performed with a Vista 10 optical cone-beam CT scanner. Central beam axis profiles and depth dose agree with diode and parallel plate ion chamber measurements. These results demonstrate that genipin cross-linked gel can be used for accurate 3D dosimetry, including surface dose measurements.

  2. New radiochromic gel for 3D dosimetry based on Turnbull blue: basic properties (United States)

    Šolc, Jaroslav; Spěváček, Václav


    The recently developed new radiochromic gel dosimeter based on Turnbull blue dye formed by irradiation (the TBG dosimeter) does not exhibit dose pattern degradation due to diffusion effects as observed in the Fricke-gel dosimeter with xylenol orange incorporated into the gel matrix (the FXG dosimeter). The TBG dosimeter can be easily prepared and its optical properties enable evaluation of the gel's response using the cone-beam optical computed tomography technique. The preparation procedure is described in the paper along with the basic characteristics of the gel, including dose response, dose sensitivity, ageing under different storage conditions, diffusion rates of Turnbull blue and gel density. The measurement of diffusion is described in more detail. The same method was applied to the FXG dosimeter for direct comparison. It was found that the diffusion coefficient of the TBG dosimeter stored at 24 °C is less than 4 × 10-3 mm2 h-1 (1σ confidence level), compared to the value of 7.3 × 10-1 mm2 h-1 (1σ) of the FXG dosimeter measured at the same temperature. Although the TBG dosimeter is less sensitive than the FXG dosimeter, its diffusion coefficient is practically negligible and, therefore, it offers large potential as a three-dimensional dosimeter for applications encompassing sharp dose gradients such as high-dose-rate brachytherapy.

  3. Effects of composition interactions on the response of a turnbull blue radiochromic gel dosimeter (United States)

    Shieh, Jiunn-I.; Cheng, Kai-Yuan; Shyu, Huey-Lih; Yu, Yi-Chen; Hsieh, Ling-Ling


    In this study, the Taguchi statistical method was used to design experiments for investigating the effects of interactions among compositions on the performance of a Turnbull blue gel (TBG) radiochromic dosimeter. Four parameters were considered as the design factors: (A) concentration of ferric chloride, (B) concentration of potassium ferricyanide, (C) concentration of sulfuric acid, and (D) amount of gelling agent added. Two levels were selected for each factor. The change in optical absorbance at 695 nm under UVA exposures was monitored to determine the response of the dosimeters. The results showed that the contributions of factors A-D on the absorbance were 20.01%, 23.16%, 27.03%, and 0.49%, respectively. The contributions of significant interaction effects were AC (8.60%), BC (5.61%), and ABC (10.56%). This finding indicated that sulfuric acid (C) was the most influential factor, whereas gelling agent (D) was the least influential factor. Sulfuric acid had an important function in two two-way interactions and one three-way interaction in the response of TBG to UV exposure.

  4. Assessment of radiochromic gel dosimeter based on Turnbull Blue dye for relative output factor measurements of the Leksell Gamma Knife® PerfexionTM (United States)

    Kozubikova, P.; Solc, J.; Novotny, J., Jr.; Pilarova, K.; Pipek, J.; Koncekova, J.


    The aim of the study was to perform assessment of radiochromic gel dosimeter based on Turnbull blue dye formed by irradiation (TB gel dosimeter) for measurement of ROFs for 4 mm and 8 mm collimators for the Leksell Gamma Knife PerfexionTM. All measurements have been carried out using home-made spherical Perspex glass phantom of diameter 160 mm. TB gel dosimeters were scanned using homemade optical CT scanner. The results are compared with vendor recommended Monte Carlo calculated ROFs values of 0.814 and 0.900 for 4 mm and 8 mm collimators, respectively. The comparisons between the gel measurements and the treatment planning system (TPS) calculation are presented in the form of 2D isodoses for the central slices and 1D profile. Measured ROF 0.746 and 0.874 for 4 mm and 8 mm collimators respectively are in a reasonable agreement with vendor recommended values and measured relative dose distribution in a central slice and measured profiles of all shots show excellent correspondence with TPS.

  5. Characterisation of TruView™: a new 3-D reusable radiochromic MethylThymolBlue based gel dosimeter for ionising radiations (United States)

    Colnot, J.; Huet, C.; Clairand, I.


    TruView™ is a new water-equivalent reusable Fricke gel dosimeter based on MethylThymolBlue reactive dye. Details of the characterisation of the TruView™ MTB gel dosimeter by spectrophotometric measurements and of its reading with the Optical-CT Scanner Vista™ are described. In this study, the different parameters influencing TruView™ dose response have been studied and its performances have been compared to chamber and diodes measurements. This gel presents a linear response with dose up to 20 Gy, independent in the investigated range of photon beam energy and dose rate and also a good intra-batch uniformity. Ions diffusion into the matrix homogenizes the gel after a week, losing dosimetric information but allowing a new irradiation to be performed. However, auto-oxidation happens before and after irradiation, degrading the dosimeter response and stability. Storage and reading conditions affect the response as well.

  6. Radiochromic film dosimetry

    CERN Document Server

    Xu Zhi Yong


    Radiochromic film dosimetry was developed to measure ionization irradiation dose for industry and medicine. At this time, there are no comprehensive guideline on the medical application, calibration method and densitometer system for medicine. The review gives update on Radiochromic film dosimetry used for medicine, including principles, film model and material, characteristics, calibration method, scanning densitometer system and medical application

  7. Mango butter emulsion gels as cocoa butter equivalents: physical, thermal, and mechanical analyses. (United States)

    Sagiri, Sai S; Sharma, Vijeta; Basak, Piyali; Pal, Kunal


    The search for cocoa butter equivalents in food and pharmaceutical industries has been gaining importance. In the present study, mango butter was explored as cocoa butter equivalent. Aqueous gelatin solution (20% w/w) containing cocoa butter and mango butter water-in-oil (fat) type emulsion gels were prepared by hot emulsification method. XRD and DSC melting profiles suggested the presence of unstable polymorphic forms (α and β') of fats in the emulsion gels. The crystal size and solid fat content analyses suggested that the presence of aqueous phase might have hindered the transformation of unstable polymorphic forms to stable polymorphic form (β) in the emulsion gels. Fat crystals in the emulsion gels were formed by instantaneous nucleation via either uni- or bidimensional growth (Avrami analysis). The viscoelastic nature of the emulsion gels was evaluated by modified Peleg's analysis (stress relaxation study). Results inferred that the physical, thermal, and mechanical properties of mango butter emulsion gels are comparable to those of cocoa butter emulsion gels. On the basis of preliminary studies, it was suggested that the mango butter emulsion gels may have potential to be used as cocoa butter equivalents.

  8. Dose of radiation enhancement, using silver nanoparticles in a human tissue equivalent gel dosimeter. (United States)

    Hassan, Muhammad; Waheed, Muhammad Mohsin; Anjum, Muhammad Naeem


    To quantify the radiation dose enhancement in a human tissue-equivalent polymer gel impregnated with silver nanoparticles. The case-control study was conducted at the Bahawalpur Institute of Nuclear Medicine and Oncology, Bahawalpur, Pakistan, in January 2014. Silver nanoparticles used in this study were prepared by wet chemical method. Polymer gel was prepared by known quantity of gelatine, methacrylic acid, ascorbic acid, copper sulphate pentahydrate, hydroquinone and water. Different concentrations of silver nanoparticles were added to the gel during its cooling process. The gel was cooled in six plastic vials of 50ml each. Two vials were used as a control sample while four vials were impregnated with silver nanoparticles. After 22 hours, the vials were irradiated with gamma rays by aCobalt-60 unit. Radiation enhancement was assessed by taking magnetic resonance images of the vials. The images were analysed using Image J software. The dose enhancement factor was 24.17% and 40.49% for 5Gy and 10Gy dose respectively. The dose enhancement factor for the gel impregnated with 0.10mM silver nanoparticles was 32.88% and 51.98% for 5Gy and 10Gy dose respectively. The impregnation of a tissue-equivalent gel with silver nanoparticles resulted in dose enhancement and this effect was magnified up to a certain level with the increase in concentration of silver nanoparticles.

  9. SU-F-BRA-11: An Experimental Commissioning Test of Brachytherapy MBDCA Dosimetry, Based On a Commercial Radiochromic Gel/optical CT System

    Energy Technology Data Exchange (ETDEWEB)

    Pappas, E; Karaiskos, P; Zourari, K; Peppa, V; Papagiannis, P [Medical Physics Laboratory, Medical School, University of Athens (Greece)


    Purpose: To implement a 3D dose verification procedure of Model-Based Dose Calculation Algorithms (MBDCAs) for {sup 192}Ir HDR brachytherapy, based on a novel Ferrous Xylenol-orange gel (FXG) and optical CT read-out. Methods: The TruView gel was employed for absolute dosimetry in conjunction with cone-beam optical CT read-out with the VISTA scanner (both from Modus Medical Inc, London, ON, Canada). A multi-catheter skin flap was attached to a cylindrical PETE jar (d=9.6cm, h=16cm) filled with FXG, which served as both the dosimeter and the water equivalent phantom of bounded dimensions. X- ray CT image series of the jar with flap attached was imported to Oncentra Brachy v.4.5. A treatment plan consisting of 8 catheters and 56 dwell positions was generated, and Oncentra-ACE MBDCA as well as TG43 dose results were exported for further evaluation. The irradiation was carried out with a microSelecton v2 source. The FXG dose-response, measured via an electron irradiation of a second dosimeter from the same batch, was linear (R2>0.999) at least up to 12Gy. A MCNP6 input file was prepared from the DICOM-RT plan data using BrachyGuide to facilitate Monte Carlo (MC) simulation dosimetry in the actual experimental geometry. Agreement between experimental (reference) and calculated dose distributions was evaluated using the 3D gamma index (GI) method with criteria (5%-2mm applied locally) determined from uncertainty analysis. Results: The TG-43 GI failed, as expected, in the majority of voxels away from the flap (pass rate 59% for D>0.8Gy, corresponding to 10% of prescribed dose). ACE performed significantly better (corresponding pass rate 92%). The GI evaluation for the MC data (corresponding pass rate 97%) failed mainly at low dose points of increased uncertainty. Conclusion: FXG gel/optical CT is an efficient method for level-2 commissioning of brachytherapy MBDCAs. Target dosimetry is not affected from uncertainty introduced by TG43 assumptions in 192Ir skin brachytherapy

  10. SU-E-T-130: Dosimetric Evaluation of Tissue Equivalent Gel Dosimeter Using Saccharide in Radiotherapy System

    Energy Technology Data Exchange (ETDEWEB)

    Cho, Y [Korea Institute of Radiological and Medical Sciences (KIRAMS), Seoul (Korea, Republic of); Lee, D; Jung, H; Ji, Y; Kim, K; Chang, U [Korea Institute of Radiological and Medical Sciences, Seoul (Korea, Republic of); Kwon, S [Kyonggi University, Suwon-si, Gyeonggi-do (Korea, Republic of)


    Purpose: In this study, the dose responses of the MAGIC gel with various concentrations and type of saccharide are examined to clarify the roles of mono and disaccharide in the polymerization process. Then we focused on the tissue equivalence and dose sensitivity of MAGIC gel dosimeters. Methods: The gel is composed of HPLC, 8% gelatin, 2 × 10-3 M L-ascorbic acid, 1.8 × 10-2 M hydroquinone, 8 × 10-5 M copper(II)sulfate and 9% methacrylic acid, new polymer gels are synthesized by adding glucose(monosaccharide), sucrose(disaccharide) and urea in the concentration range of 5∼35%. For irradiation of the gel, cesium-137 gamma-ray irradiator was used, radiation dose was delivered from 5∼50 Gy. MRI images of the gel were acquired by using a 3.0 T MRI system. Results: When saccharide and urea were added, the O/C, O/N and C/N ratios agreed with those of soft tissue with 1.7%. The dose-response of glucose and sucrose gel have slope-to-intercept ratio of 0.044 and 0.283 respectively. The slope-to-ratio is one important determinant of gel sensitivity. R-square values of glucose and sucrose gel dosimeters were 0.984 and 0.994 respectively. Moreover when urea were added, the slope-to-intercept ratio is 0.044 and 0.073 respectively. R-square values of mono and disaccharide gel were 0.973 and 0.989 respectively. When a saccharide is added into the MAGIC gel dosimeter, dose sensitivity is increased. However when urea were added, dose sensitivity is slightly decreased. Conclusion: In this study, it was possible to obtain the following conclusions by looking at the dose response characteristics after adding mono-, di-saccharide and urea to a MAGIC gel dosimeter. Saccharide was a tendency of increasing dose sensitivity with disaccharide. Sa.ccharide is cost effective, safe, soft tissue equivalent, and can be used under various experimental conditions, making it a suitable dosimeter for some radiotherapy applications.

  11. Polymer gel water equivalence and relative energy response with emphasis on low photon energy dosimetry in brachytherapy. (United States)

    Pantelis, E; Karlis, A K; Kozicki, M; Papagiannis, P; Sakelliou, L; Rosiak, J M


    The water equivalence and stable relative energy response of polymer gel dosimeters are usually taken for granted in the relatively high x-ray energy range of external beam radiotherapy based on qualitative indices such as mass and electron density and effective atomic number. However, these favourable dosimetric characteristics are questionable in the energy range of interest to brachytherapy especially in the case of lower energy photon sources such as 103Pd and 125I that are currently utilized. In this work, six representative polymer gel formulations as well as the most commonly used experimental set-up of a LiF TLD detector-solid water phantom are discussed on the basis of mass attenuation and energy absorption coefficients calculated in the energy range of 10 keV-10 MeV with regard to their water equivalence as a phantom and detector material. The discussion is also supported by Monte Carlo simulation results. It is found that water equivalence of polymer gel dosimeters is sustained for photon energies down to about 60 keV and no corrections are needed for polymer gel dosimetry of 169Yb or 192Ir sources. For 125I and 103Pd sources, however, a correction that is source-distance dependent is required. Appropriate Monte Carlo results show that at the dosimetric reference distance of 1 cm from a source, these corrections are of the order of 3% for 125I and 2% for 103Pd. These have to be compared with corresponding corrections of up to 35% for 125I and 103Pd and up to 15% even for the 169Yb energies for the experimental set-up of the LiF TLD detector-solid water phantom.

  12. A randomized equivalence trial comparing the i-gel and laryngeal mask airway Supreme in children. (United States)

    Jagannathan, Narasimhan; Sommers, Katherine; Sohn, Lisa E; Sawardekar, Amod; Shah, Ravi D; Mukherji, Isabella I; Miller, Steven; Voronov, Polina; Seraphin, Sally


    The laryngeal mask airway Supreme (Supreme) is a new single-use supraglottic device with gastric access capability now available in all sizes for children. To compare the i-gel with the Supreme in children for routine airway maintenance. One hundred and seventy children, aged 3 months to 11 years, 5-50 kg in weight, were randomly assigned to receive either the i-gel or the Supreme. The primary outcome measured was airway leak pressure. Secondary outcomes included the following: ease and time for insertion, insertion success rate, fiberoptic grade of view, ease of gastric tube placement, number of airway manipulations, quality of airway during anesthetic maintenance, and complications. A total of 168 patients were assessed for the outcomes. The median (IQR [range]) airway leak pressure for the i-gel was higher than with the Supreme, 20 (18-25 [9-40]) cm H(2)O vs 17 (14-22 [10-40]) cm H(2)O, respectively (P = 0.001). There were no differences in the time for device insertion, fiberoptic grade of view, quality of airway, and complications. Median (IQR[range]) time of successful insertion of a gastric tube was faster with the Supreme, 12 (9.2-14.3 [5.2-44.2]) s than with the i-gel, 14 (11.9-19 [6.9-75]) s; P = 0.01. The number of airway manipulations during placement was higher with the i-gel than with the laryngeal mask airway Supreme (12 vs 13 patients), P = 0.02. In infants and children, when a single-use supraglottic device with gastric access capabilities is required, the i-gel demonstrated higher airway leak pressures and can be a useful alternative to the Supreme. © 2012 Blackwell Publishing Ltd.

  13. Fundamentals of gel dosimeters (United States)

    McAuley, K. B.; Nasr, A. T.


    Fundamental chemical and physical phenomena that occur in Fricke gel dosimeters, polymer gel dosimeters, micelle gel dosimeters and genipin gel dosimeters are discussed. Fricke gel dosimeters are effective even though their radiation sensitivity depends on oxygen concentration. Oxygen contamination can cause severe problems in polymer gel dosimeters, even when THPC is used. Oxygen leakage must be prevented between manufacturing and irradiation of polymer gels, and internal calibration methods should be used so that contamination problems can be detected. Micelle gel dosimeters are promising due to their favourable diffusion properties. The introduction of micelles to gel dosimetry may open up new areas of dosimetry research wherein a range of water-insoluble radiochromic materials can be explored as reporter molecules.

  14. Iron-based radiochromic systems for UV dosimetry applications (United States)

    Lee, Hannah J.; Alqathami, Mamdooh; Blencowe, Anton; Ibbott, Geoffrey


    Phototherapy treatment using ultraviolet (UV) A and B light sources has long existed as a treatment option for various skin conditions. Quality control for phototherapy treatment recommended by the British Association of Dermatologists and British Photodermatology Group generally focused on instrumentation-based dosimetry measurements. The purpose of this study was to present an alternative, easily prepared dosimeter system for the measurement of UV dose and as a simple quality assurance technique for phototherapy treatments. Five different UVA-sensitive radiochromic dosimeter formulations were investigated and responded with a measurable and visible optical change both in solution and in gel form. Iron(III) reduction reaction formulations were found to be more sensitive to UVA compared to iron(II) oxidation formulations. One iron(III) reduction formulation was found to be especially promising due to its sensitivity to UVA dose, ease of production, and linear response up to a saturation point.

  15. Linearization of dose-response curve of the radiochromic film dosimetry system

    Energy Technology Data Exchange (ETDEWEB)

    Devic, Slobodan; Tomic, Nada; Aldelaijan, Saad; DeBlois, Francois; Seuntjens, Jan; Chan, Maria F.; Lewis, Dave [Medical Physics Unit, McGill University, Montreal, Quebec H3G 1A4 (Canada) and Department of Radiation Oncology, SMBD Jewish General Hospital, McGill University, Montreal, Quebec H3T 1E2 (Canada); Executive Administration for Radiation Protection and Safety Medical Devices Sector, Saudi Food and Drug Authority, Riyadh, Kingdom of Saudi Arabia 13312 (Saudi Arabia); Medical Physics Unit, McGill University, Montreal, Quebec H3G 1A4 (Canada) and Department of Radiation Oncology, SMBD Jewish General Hospital, McGill University, Montreal, Quebec H3T 1E2 (Canada); Medical Physics Unit, McGill University, Montreal, Quebec H3G 1A4 (Canada); Department of Medical Physics, Memorial Sloan-Kettering Cancer Center Basking Ridge, New Jersey 07920 (United States); Ashland Inc., Wayne, New Jersey 07470 (United States)


    Purpose: Despite numerous advantages of radiochromic film dosimeter (high spatial resolution, near tissue equivalence, low energy dependence) to measure a relative dose distribution with film, one needs to first measure an absolute dose (following previously established reference dosimetry protocol) and then convert measured absolute dose values into relative doses. In this work, we present result of our efforts to obtain a functional form that would linearize the inherently nonlinear dose-response curve of the radiochromic film dosimetry system. Methods: Functional form [{zeta}= (-1){center_dot}netOD{sup (2/3)}/ln(netOD)] was derived from calibration curves of various previously established radiochromic film dosimetry systems. In order to test the invariance of the proposed functional form with respect to the film model used we tested it with three different GAFCHROMIC Trade-Mark-Sign film models (EBT, EBT2, and EBT3) irradiated to various doses and scanned on a same scanner. For one of the film models (EBT2), we tested the invariance of the functional form to the scanner model used by scanning irradiated film pieces with three different flatbed scanner models (Epson V700, 1680, and 10000XL). To test our hypothesis that the proposed functional argument linearizes the response of the radiochromic film dosimetry system, verification tests have been performed in clinical applications: percent depth dose measurements, IMRT quality assurance (QA), and brachytherapy QA. Results: Obtained R{sup 2} values indicate that the choice of the functional form of the new argument appropriately linearizes the dose response of the radiochromic film dosimetry system we used. The linear behavior was insensitive to both film model and flatbed scanner model used. Measured PDD values using the green channel response of the GAFCHROMIC Trade-Mark-Sign EBT3 film model are well within {+-}2% window of the local relative dose value when compared to the tabulated Cobalt-60 data. It was also

  16. Linearization of dose-response curve of the radiochromic film dosimetry system. (United States)

    Devic, Slobodan; Tomic, Nada; Aldelaijan, Saad; Deblois, Francois; Seuntjens, Jan; Chan, Maria F; Lewis, Dave


    Despite numerous advantages of radiochromic film dosimeter (high spatial resolution, near tissue equivalence, low energy dependence) to measure a relative dose distribution with film, one needs to first measure an absolute dose (following previously established reference dosimetry protocol) and then convert measured absolute dose values into relative doses. In this work, we present result of our efforts to obtain a functional form that would linearize the inherently nonlinear dose-response curve of the radiochromic film dosimetry system. Functional form [ζ = (-1)[middle dot]netOD((2∕3))∕ln(netOD)] was derived from calibration curves of various previously established radiochromic film dosimetry systems. In order to test the invariance of the proposed functional form with respect to the film model used we tested it with three different GAFCHROMIC™ film models (EBT, EBT2, and EBT3) irradiated to various doses and scanned on a same scanner. For one of the film models (EBT2), we tested the invariance of the functional form to the scanner model used by scanning irradiated film pieces with three different flatbed scanner models (Epson V700, 1680, and 10000XL). To test our hypothesis that the proposed functional argument linearizes the response of the radiochromic film dosimetry system, verification tests have been performed in clinical applications: percent depth dose measurements, IMRT quality assurance (QA), and brachytherapy QA. Obtained R(2) values indicate that the choice of the functional form of the new argument appropriately linearizes the dose response of the radiochromic film dosimetry system we used. The linear behavior was insensitive to both film model and flatbed scanner model used. Measured PDD values using the green channel response of the GAFCHROMIC™ EBT3 film model are well within ±2% window of the local relative dose value when compared to the tabulated Cobalt-60 data. It was also found that criteria of 3%∕3 mm for an IMRT QA plan and 3%∕2

  17. SU-E-T-102: Determination of Dose Distributions and Water-Equivalence of MAGIC-F Polymer Gel for 60Co and 192Ir Brachytherapy Sources

    Energy Technology Data Exchange (ETDEWEB)

    Quevedo, A; Nicolucci, P [University of Sao Paulo, Ribeirao Preto, SP (Brazil)


    Purpose: Analyse the water-equivalence of MAGIC-f polymer gel for {sup 60}Co and {sup 192}Ir clinical brachytherapy sources, through dose distributions simulated with PENELOPE Monte Carlo code. Methods: The real geometry of {sup 60} (BEBIG, modelo Co0.A86) and {sup 192}192Ir (Varian, model GammaMed Plus) clinical brachytherapy sources were modelled on PENELOPE Monte Carlo simulation code. The most probable emission lines of photons were used for both sources: 17 emission lines for {sup 192}Ir and 12 lines for {sup 60}. The dose distributions were obtained in a cubic water or gel homogeneous phantom (30 × 30 × 30 cm{sup 3}), with the source positioned in the middle of the phantom. In all cases the number of simulation showers remained constant at 10{sup 9} particles. A specific material for gel was constructed in PENELOPE using weight fraction components of MAGIC-f: wH = 0,1062, wC = 0,0751, wN = 0,0139, wO = 0,8021, wS = 2,58×10{sup −6} e wCu = 5,08 × 10{sup −6}. The voxel size in the dose distributions was 0.6 mm. Dose distribution maps on the longitudinal and radial direction through the centre of the source were used to analyse the water-equivalence of MAGIC-f. Results: For the {sup 60} source, the maximum diferences in relative doses obtained in the gel and water were 0,65% and 1,90%, for radial and longitudinal direction, respectively. For {sup 192}Ir, the maximum difereces in relative doses were 0,30% and 1,05%, for radial and longitudinal direction, respectively. The materials equivalence can also be verified through the effective atomic number and density of each material: Zef-MAGIC-f = 7,07 e .MAGIC-f = 1,060 g/cm{sup 3} and Zef-water = 7,22. Conclusion: The results showed that MAGIC-f is water equivalent, consequently being suitable to simulate soft tissue, for Cobalt and Iridium energies. Hence, gel can be used as a dosimeter in clinical applications. Further investigation to its use in a clinical protocol is needed.

  18. Comparison of the radiochromic EBT2 responses for 4MV LINACs in calibration processes

    Energy Technology Data Exchange (ETDEWEB)

    Silva, Sabrina D.; Castro, André L.S.; Mendes, Thais M.; Campos, Tarcisio P.R. [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Dept. de Energia Nuclear; Nogueira, Luciana B., E-mail:, E-mail:, E-mail:, E-mail:, E-mail: [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Departamento de Anatomia e Imagem


    Background: Actually, cancer has gained a larger dimension and become a global public health problem. Radiotherapy (RT) is a neoplasia treatment and RT linear accelerators must undergo a strict dose quality control. Pure liquid water or solid water phantoms can be used with this intuit. In recent years, radiochromic films with equivalent tissue composition have been widely used as dosimeters in the medical field. Objective: the proposal was to analyze two distinct radiochromic film responses in water and solid water phantoms, in a distinct LINAC spectra of 4MV beam. Methods: Solid water phantom and EBT2 Radiochromic films were set. Films were exposed to a set of absorbed doses established by distinct monitor units (MU) specified in each RT-center. Mathematical relations between the degree of red-intensity from digitized films and the absorbed dose for both spectra were established. The coefficients of the polynomial function of the calibration curve were determined from the Origin software. The uncertainty of both processes was analyzed. The efficiency of the two calibration processes was set up. Results: The adjustment of the calibration curve provided the coefficients of the second-order equation that relates the dose absorbed with the optical density of the film. The uncertainty regarding the calibration performed in water and solid water and the dose-error accuracy are in agreement with the literature. Conclusion: Both water or solid water were effective in calibration and can be used in routines of quality-control measurements. The results show that EBT2-radiochromic films is suitable to for dose-calibration in RT. (author)

  19. Energy dependence of Fricke-xylenol orange gel and gel based on Turnbull blue for low-energy photons (United States)

    Šolc, Jaroslav; Sochor, Vladimír; Kozubíková, Petra


    The paper describes the energy dependence of two types of radiochromic gels, a Fricke-xylenol orange gel (FX gel) and a gel based on Turnbull blue (TB gel), on low energy photons between 14 and 145 keV. Gel samples were irradiated at reference photon fields at the Czech Metrology Institute and evaluated by two independent optical methods. Measurements revealed that the response of the TB gel is independent on photon energy down to at least 14 keV photons, while the FX gel is energy dependent for photons below roughly 50 keV.

  20. On the re-calibration process in radiochromic film dosimetry. (United States)

    Ruiz-Morales, Carmen; Vera-Sánchez, Juan Antonio; González-López, Antonio


    The accuracy and precision of the dose estimates obtained with radiochromic film dosimetry are investigated in a clinical environment. The improvement in the accuracy of dose estimates reached with corrective methods is analyzed. Two novel re-calibration algorithms for radiochromic film dosimetry are presented. Two different EBT3 lots are evaluated in two different centres. They are calibrated in Varian linacs and read in two different EPSON scaners. Once the lots are calibrated, three films per lot are considered and divided into stripes that are exposed to known doses. Several dosimetry protocols usually employed in radiochromic film dosimetry are used to convert film responses to absorbed doses. These protocols are characterized by different choices of the film responses or different sensitometric curves. Finally, the accuracy and reproducibility of the dose estimates is investigated with and without the corrective methods. The variabilities that affect radiochromic film dosimetry, such as intra-lot variability, inter-scan variability, post-exposure time and film autodevelopment may give rise to inaccuracies in the dose estimates. However, the implementation of re-calibration methods leads to more accurate dose estimates. All the investigated protocols showed more accurate and reproducible results when the re-calibrated methods were employed. So, the novel re-calibration methods may be applied in order to improve the accuracy and reproducibility of radiochromic film dosimetry. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

  1. Radiochromic film calibration for the RQT9 quality beam (United States)

    Costa, K. C.; Gomez, A. M. L.; Alonso, T. C.; Mourao, A. P.


    When ionizing radiation interacts with matter it generates energy deposition. Radiation dosimetry is important for medical applications of ionizing radiation due to the increasing demand for diagnostic radiology and radiotherapy. Different dosimetry methods are used and each one has its advantages and disadvantages. The film is a dose measurement method that records the energy deposition by the darkening of its emulsion. Radiochromic films have a little visible light sensitivity and respond better to ionizing radiation exposure. The aim of this study is to obtain the resulting calibration curve by the irradiation of radiochromic film strips, making it possible to relate the darkening of the film with the absorbed dose, in order to measure doses in experiments with X-ray beam of 120 kV, in computed tomography (CT). Film strips of GAFCHROMIC XR-QA2 were exposed according to RQT9 reference radiation, which defines an X-ray beam generated from a voltage of 120 kV. Strips were irradiated in "Laboratório de Calibração de Dosímetros do Centro de Desenvolvimento da Tecnologia Nuclear" (LCD / CDTN) at a dose range of 5-30 mGy, corresponding to the range values commonly used in CT scans. Digital images of the irradiated films were analyzed by using the ImageJ software. The darkening responses on film strips according to the doses were observed and they allowed obtaining the corresponding numeric values to the darkening for each specific dose value. From the numerical values of darkening, a calibration curve was obtained, which correlates the darkening of the film strip with dose values in mGy. The calibration curve equation is a simplified method for obtaining absorbed dose values using digital images of radiochromic films irradiated. With the calibration curve, radiochromic films may be applied on dosimetry in experiments on CT scans using X-ray beam of 120 kV, in order to improve CT acquisition image processes.

  2. Acrylonitrile Butadiene Styrene (ABS) plastic based low cost tissue equivalent phantom for verification dosimetry in IMRT. (United States)

    Kumar, Rajesh; Sharma, S D; Deshpande, Sudesh; Ghadi, Yogesh; Shaiju, V S; Amols, H I; Mayya, Y S


    A novel IMRT phantom was designed and fabricated using Acrylonitrile Butadiene Styrene (ABS) plastic. Physical properties of ABS plastic related to radiation interaction and dosimetry were compared with commonly available phantom materials for dose measurements in radiotherapy. The ABS IMRT phantom has provisions to hold various types of detectors such as ion chambers, radiographic/radiochromic films, TLDs, MOSFETs, and gel dosimeters. The measurements related to pre-treatment dose verification in IMRT of carcinoma prostate were carried out using ABS and Scanditronics-Wellhoffer RW3 IMRT phantoms for five different cases. Point dose data were acquired using ionization chamber and TLD discs while Gafchromic EBT and radiographic EDR2 films were used for generating 2-D dose distributions. Treatment planning system (TPS) calculated and measured doses in ABS plastic and RW3 IMRT phantom were in agreement within +/-2%. The dose values at a point in a given patient acquired using ABS and RW3 phantoms were found comparable within 1%. Fluence maps and dose distributions of these patients generated by TPS and measured in ABS IMRT phantom were also found comparable both numerically and spatially. This study indicates that ABS plastic IMRT phantom is a tissue equivalent phantom and dosimetrically it is similar to solid/plastic water IMRT phantoms. Though this material is demonstrated for IMRT dose verification but it can be used as a tissue equivalent phantom material for other dosimetry purposes in radiotherapy.

  3. Poster - Thur Eve - 18: Characterization of a camera and LED lightbox imaging system for radiochromic film dosimetry. (United States)

    Alexander, K; Percy, E; Olding, T; Schreiner, L J; Salomons, G


    Radiation therapy treatment modalities continue to develop and have become increasingly complex. With this, dose verification and quality assurance (QA) is of great importance to ensure that a prescribed dose is accurately and precisely delivered to a patient. Radiochromic film dosimetry has been adopted as a convenient option for QA, because it is relatively energy independent, is near tissue equivalent, and has high spatial resolution. Unfortunately, it is not always easy to use. In this study, preliminary work towards developing a novel method of imaging radiochromic film is presented. The setup consists of a camera mounted vertically above a lightbox containing red LEDs, interfaced with computer image acquisition software. Imaging results from this system will be compared with imaging performed using an Epson Expression 10000XL scanner (a device in common clinical use). The lightbox imaging technique with camera readout is much faster relative to a flatbed scanner. The film measurements made using the camera are independent of film orientation, and show reduced artifacts, so that there are fewer corrections required compared to the use of flatbed scanners. Optical scatter also appears to be less of an issue with this design than with the flat bed scanner. While further work needs to be done to optimize the lightbox imaging system, the lightbox system shows great promise for a rapid, simple, and orientation independent setup, improving on existing film scanning systems. © 2012 American Association of Physicists in Medicine.

  4. Characteristics of polyacrylamide gel with THPC and Turnbull Blue gel dosimeters evaluated using optical tomography (United States)

    Pilařová (Vávrů), Kateřina; Kozubíková, Petra; Šolc, Jaroslav; Spěváček, Václav


    The purpose of this study was to compare characteristics of radiochromic gel - Turnbull Blue gel (TB gel) with polymer gel - polyacrylamide gel and tetrakis hydroxymethyl phosphonium chloride (PAGAT) using optical tomography. Both types of gels were examined in terms of dose sensitivity, dose response linearity and background value of spectrophotometric absorbance. The calibration curve was obtained for 60Co irradiation performed on Gammacell 220 at predefined gamma dose levels between 0 and 140 Gy for TBG and 0-15 Gy for PAGAT. To measure relative dose distributions from stereotactic irradiation, dosimeters were irradiated on Leksell Gamma Knife Perfexion. The cylindrical glass housings filled with gel were attached to the stereotactic frame. They were exposed with single shot and 16 mm collimator by 65 Gy to a 50% prescription isodose for TB gel and 4 Gy to a 50% prescription isodose for PAGAT. Evaluations of dosimeters were performed on an UV-vis Spectrophotometer Helios β and an optical cone beam homemade tomography scanner with a 16-bit astronomy CCD camera with a set of color filters. The advantages and potential disadvantages for both types of gel dosimeters were summarized. Dose distribution in central slice and measured profiles of 16 mm shot shows excellent correspondence with treatment planning system Leksell GammaPlan® for both PAGAT and Turnbull Blue gels. Gel dosimeters are suitable for steep dose gradient verification. An optical tomography evaluation method is successful. Dose response characteristics of TB gel and PAGAT gel are presented.

  5. Measurement of gold nanofilm dose enhancement using unlaminated radiochromic film

    Energy Technology Data Exchange (ETDEWEB)

    Rakowski, Joseph T., E-mail:; Snyder, Michael G.; Hillman, Yair [Department of Radiation Oncology, School of Medicine, Wayne State University, Detroit, Michigan 48201 (United States); Laha, Suvra S.; Lawes, Gavin [Department of Physics, Wayne State University, Detroit, Michigan 48201 (United States); Buczek, Matthew G. [Department of Radiation Oncology, School of Medicine, Wayne State University, Detroit, Michigan 48201 and MidMichigan Health, Midland, Michigan 48670 (United States); Tucker, Mark A. [Department of Radiation Oncology, School of Medicine, Wayne State University, Detroit, Michigan 48201 and Missouri Cancer Associates, Columbia, Missouri 65202 (United States); Liu, Fangchao; Mao, Guangzhao [Department of Chemical Engineering and Materials Science, College of Engineering, Wayne State University, Detroit, Michigan 48201 (United States)


    Purpose: Bombarding high-Z material with x-ray radiation releases Auger electrons and Coster–Kronig electrons, along with deeper penetrating fluorescent x-rays and photoelectrons. The Auger and Coster–Kronig electron penetration distance is on the order of nanometers to micrometers in water or tissue, creating a large dose enhancement accompanied by a RBE greater than 1 at the cellular level. The authors’ aim is to measure the gold nanofilm dose enhancement factor (DEF) at the cellular level with unlaminated radiochromic film via primary 50 kVp tungsten x-ray spectrum interaction, similar to an electronic brachytherapy spectrum. Methods: Unlaminated Gafchromic{sup ®} EBT2 film and Monte Carlo modeling were combined to derive DEF models. Gold film of thickness 23.1 ±  4.3 nm and surface roughness of 1.2 ± 0.2 nm was placed in contact with unlaminated radiochromic film in a downstream orientation and exposed to a 50 kVp tungsten bremsstrahlung, mean energy 19.2 keV. Film response correction factors were derived by Monte Carlo modeling of electron energy deposition in the film’s active layer, and by measuring film energy dependence from 4.5 keV to 50 kVp. Results: The measured DEF within a 13.6 μm thick water layer was 0.29 with a mean dose of 94 ± 9.4 cGy from Au emissions and 324 ± 32.4 cGy from the 50 kVp primary beam. Monte Carlo derived correction factors allowed determination of Au contributed dose in shallower depths at 0.25 μm intervals. Maximum DEF of 18.31 was found in the first 0.25 μm water depth. Conclusions: Dose enhancement from Au nanofilm can be measured at the cellular level using unlaminated radiochromic film. Complementing the measured dose value with Monte Carlo calculations allows estimation of dose enhancement at depth increments within the cellular range.

  6. Temperature, humidity and time. Combined effects on radiochromic film dosimeters

    DEFF Research Database (Denmark)

    Abdel-Fattah, A.A.; Miller, A.


    The effects of both relative humidity and temperature during irradiation on the dose response of FWT-60-00 and Riso B3 radiochromic film dosimeters have been investigated in the relative humidity (RH) range 11-94% and temperature range 20-60 degrees C for irradiation by Co-60 photons and 10-Me......V electrons. The results show that humidity and temperature cannot be treated as independent variables, rather there appears to be interdependence between absorbed dose, temperature, and humidity. Dose rate does not seem to play a significant role. The dependence of temperature during irradiation is +0.......25 +/- 0.1% per degrees C for the FWT-60-00 dosimeters and +0.5 +/- 0.1% per degrees C For Riso B3 dosimeters at temperatures between 20 and 50 degrees C and at relative humidities between 20 and 53%. At extreme conditions both with respect to temperature and to humidity, the dosimeters show much stronger...

  7. Non-diffusing radiochromic leuco-crystal violet hydrogel dosimeter (United States)

    Jordan, K. J.; Lindenmaier, T.; Dekker, K. H.


    A systematic study to prepare mixed-micelle, radiochromic hydrogels found that non-diffusing dosimeters can be prepared. Subsequent experiments determined that sodium dodecyl sulfate (SDS) a negatively charged surfactant, binds positively charged crystal violet dye to gelatin below the critical micelle concentration. A typical formulation includes: 4% gelatin by mass, 1 mM hydrogen peroxide, 1 mM SDS, 1 mM leuco crystal violet (LCV) and 25 mM trichloroacetic acid (TCAA). This transparent material has an initial attenuation coefficient of 0.08 cm-1 and dose sensitivity of 0.015 cm-1 Gy-1. Which is a doubling of the dose sensitivity from the initial formulation with uncharged Triton X100 micelles. Reconstructed beam profiles from 3D optical CT scans performed 1, 14 and 85 hours post irradiation demonstrate no diffusion of the recorded dose distribution.

  8. Dose profile study in head CT scans using radiochromic films

    Energy Technology Data Exchange (ETDEWEB)

    Ladino G, A. M.; Prata M, A., E-mail: [Universidade Federal de Minas Gerais, Departamento de Engenharia Nuclear, Av. Pte. Antonio Carlos 6627, 31270-901 Belo Horizonte, Minas Gerais (Brazil)


    Diagnostic images of computed tomography generate higher doses than other methods of diagnostic radiology using X-ray beam attenuation. Clinical applications of CT have been increased by technological advances, what leads to a wide variety of scanner in the Brazilian technological pool. It has been difficult to implement dose reduction strategies because of the lack of proper guidance on computed tomography examinations. However, CT scanners allow adjusting acquisition parameter according to the patients physical profile and diagnostic application for which the scan is intended. The knowledge of the dose distribution is important because changes in image acquisition parameters may provide dose reduction. In this study, it was used a cylindrical head phantom in PMMA with 5 openings, what allows dose measurement in 5 regions. In a GE CT scanner, Discovery model of 64 channels, the central slice of the head phantom was irradiated and the absorbed doses were measured using a pencil ionization chamber. Radiochromic film strips were placed in the peripheral and in the central region of the head phantom and was performed a scan of 10 cm in the phantom central region. The scan was performed using the head scanning protocol of the radiobiology service, with a voltage of 120 kV. After scanning, the radiochromic film strips were digitalized and their digital images were used to have the dose longitudinal profiles. The dose values recorded have variation in a range of 18.66 to 23.57 mGy. In the results it was compared the dose index values obtained by the pencil chamber measurement to the dose longitudinal profiles recorded by the film strips. (Author)

  9. Influence of gelling agents on the dosimetric performance of the Turnbull Blue gel dosimeter (United States)

    Šolc, Jaroslav; Sochor, Vladimír; Spěváček, Václav


    Gelling agents such as agarose, phytagel, and several types of gelatin were used for preparation of Turnbull Blue radiochromic gel dosimeter. Their influence on gel dose response and background value was assessed. It was found that all gelatins cause significant increase of background in a short period of time after gel preparation therefore gelatin is not a suitable gelling agent for this dosimeter. Phytagel and agarose gels exhibit low and stable background and higher dose sensitivity than gelatin gels; however, the disadvantage is increased scattered light intensity in the gel in comparison to gelatin gels. A simple measurement was done demonstrating that the scattered light intensity significantly increases in phytagel and agarose gel in comparison to gelatin gels.

  10. Tetrazolium salt monomers for gel dosimetry I: Principles (United States)

    Penev, Kalin I.; Wang, Meng; Mequanint, Kibret


    Tetrazolium salts (TS) have been previously used for radiochromic dosimetry in solutions, films and three dimensional (3D) gelatine-based gels. However, widespread application for 3D dosimetry has not been achieved due to the required high concentrations and associated high costs of the TS dimer used in prior research. Through careful selection of TS monomer, sensitivity-enhancing additives and inert gel forming material, we report the preparation of a non-diffusing, chemically stable, 3D dosimeter with linear sensitivity between 0 and 80 Gy with submillimolar requirements for the active TS.

  11. Characteristics of modified radiochomic gel Turnbull-Blue (United States)

    Silveira, M. A.; Pavoni, J. F.; Baffa, O.


    This work presents a dosimetric characterization of the modified radiochromic gel Turnbull-Blue (TB). Formaldehyde a cross-link agent was added to the composition. This modification raised the melting point of agarose gel to 55°C, 22°C above the agarose gel matrix. For this new gel formulation the energy, dose-rate dependence and Diffusion coefficient were verified. The modified TB gel showed higher sensitivity in the 6 MV than 15 MV beam. Dose rate dependence was evaluated from 100 to 500 cGy/min using a 15MV linear accelerator. The results show variations in sensitivity for dose rate dependence. The addition of formaldehyde does not affects the diffusion coefficient for the modified Turnbull-Blue.

  12. Calculating Percent Gel For Process Control (United States)

    Webster, Charles Neal; Scott, Robert O.


    Reaction state of thermosetting resin tracked to assure desired properties. Rate of gel determined as function of temperature by measuring time to gel of part of graphite fabric impregnated with Hexcel R120 (or equivalent) phenolic resin.

  13. A method for multichannel dosimetry with EBT3 radiochromic films

    Energy Technology Data Exchange (ETDEWEB)

    Pérez Azorín, Jose Fernando, E-mail: [Hospital Universitario de Cruces, Department of Medical Physics, Plz. Cruces s/n, Barakaldo, 48903 Bizkaia (Spain); Ramos García, Luis Isaac, E-mail: [Clínica Universitaria de Navarra, Department of Oncology, University of Navarre, Av. Pio XII s/n, Pamplona, 31008 Navarre (Spain); Martí-Climent, Josep M., E-mail: [Clínica Universitaria de Navarra, Department of Nuclear Medicine, University of Navarre, Av. Pio XII s/n, Pamplona, 31008 Navarre (Spain)


    Purpose: An improved method for multichannel dosimetry is presented. This method explicitly takes into account the information provided by the unexposed image of the film. Methods: The method calculates the dose by applying a couple of perturbations to the scanned dose, one dependent and the other independent on the color channel. The method has been compared with previous multichannel and two single channel methods (red and green) against measurements using two different tests: first, five percentage depth dose profiles covering a wide range of doses; second, the dose map perpendicular to the beam axis for a 15 × 15cm{sup 2} square field. Finally, the results of 30 IMRT quality assurances tests are presented. All tests have been evaluated using the gamma analysis. Results: The coefficient of variation was found to be similar for all methods in a wide range of doses. The results of the proposed method are more in agreement with the experimental measurements and with the treatment planning system. Furthermore, the differences in the mean gamma pass rates are statistically significant. Conclusions: The improved multichannel dosimetric method is able to remove many of the common disturbances usually present in radiochromic films and improves the gamma analysis results compared with the other three methods.

  14. Computed tomography scan optimization using head phantom and radiochromic films

    Energy Technology Data Exchange (ETDEWEB)

    Fernandes, Lorena C.; Santana, P.C.; Velasquez, Carlos E.; Mourao, Arnaldo P., E-mail:, E-mail:, E-mail:, E-mail: [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte (Brazil). Departamento de Engenharia Nuclear; Centro de Imagem Molecular do INCT-Medicina Molecular (CIMol/UFMG) Belo Horizonte (Brazil); Centro Federal de Educação Tecnológica de Minas Gerais (CEFET-MG), Belo Horizonte (Brazil)


    The research and development in technology applied to computed tomography has been improve in the image quality, resulting in the best identification of diseases, and therefore an increase in the number of exams, among them the head exams can be highlighted. In order to promote a radioprotection and reduction on the dose of the general public some international agencies have stipulated dose limits to be followed and the implementation of the principles of ALARA in all establishments that use ionizing radiation. One of these principles is the optimization that should be treated with substantial attention, because the reduction of radiation doses can be feasible as long as it does not compromise the tomographic images; such practice is difficult to perform due to the lack of proper guidance. In optimization of the CT exams, not only the lowest dose is evaluated to obtain diagnostic image, but also should be knowledge the dose distribution throughout the scanned area. In this work were used a cylindrical head phantom of PMMA, a GE Discovery CT scan with 64 channels, and radiochromic films. The films were positioned in the phantom in their central region for the dose evaluation using the automatic control for the voltages of 80, 100 and 120 kV. The images were acquired from the scan of the phantom and the film readings were obtained through digital images. The results show an evaluation of the longitudinal kerma profiles, dose delivered, and the image noise was also observed using the central slice images. (author)

  15. Commissioning a hobby cutting device for radiochromic film preparation. (United States)

    Zolfaghari, Somayeh; Francis, Kirby E; Kairn, Tanya; Crowe, Scott B


    In addition to a high spatial resolution and well characterised dose response, one of the major advantages of radiochromic film as a dosimeter is that sheets of film can be cut into pieces suitable for use as calibration films, and for in vivo and phantom measurements. The cutting of film is typically done using scissors or a guillotine, and this process can be time-consuming, limited in precision, requires extensive handling and does not allow holes to be cut from the film without cutting from an existing edge. This study investigated the use of a Brother ScanNCut hobby cutting system for EBT3 film preparation. The optimal operating parameters (blade size, pressure, speed) that resulted in precise cuts with minimal delamination at cut edges were identified using test cutting patterns. These parameters were then used to cut a large film insert for a stereotactic head phantom for comparison against an insert cut with scissors. While the hobby cutting system caused a wider region of delamination at the film edge (1.8 mm) compared to scissors (1 mm), the hobby cutting system was found to be able to produce reproducible cuts more efficiently and more accurately than scissors. The use of the hobby cutting system is recommended for complex phantom inserts (containing sharp corners or holes for alignment rods) or in situations where large numbers of film pieces need to be prepared.

  16. Correcting lateral response artifacts from flatbed scanners for radiochromic film dosimetry. (United States)

    Lewis, David; Chan, Maria F


    lateral position response artifact. To validate this method, corrections were applied to several films that were exposed to 15 × 15 cm(2) open fields and large IMRT and VMAT fields and scanned at the extreme edges of the scan window in addition to the central location. Calibration and response data were used to generate dose maps and perform gamma analysis using single- or triple-channel dosimetry with FilmQAPro 2014 software. The authors' study found that calibration curves at the different lateral positions could be correlated by a simple two-point rescaling using the response for unexposed film as well as the response of film exposed at high doses between 800 and 1600 cGy. The coefficients A(L,X) and BL,X for each color channel X were found to be independent of dose at each lateral location L. This made it possible to apply the relationship Response(C, D, X) = A(L,X) + B(L,X) ⋅ Response(L, D, X), to the raw film responses, permitting correction of the response values at any lateral position to an equivalent response, as if that part of the film was located at the center of the scanner. This correction method was validated for several films exposed to open as well as large IMRT and VMAT fields. The work reported elaborates on the process using the correction procedures to eliminate the lateral response artifact and demonstrates improvements in the accuracy of radiochromic film dosimetry for the radiation therapy quality assurance applications.

  17. Radiochromic film dosimetry for UV-C treatments of apple fruit (United States)

    Radiochromic films were evaluated for their suitability to estimate UV-C doses and dose uniformity on apple fruit surface. Parameters investigated included film type, color changes of the films in response to different UV-C doses, color stability of films, UV-C light intensity, and temperature. In...

  18. A prototype quantitative film scanner for radiochromic film dosimetry. (United States)

    Ranade, Manisha K; Li, Jonathan G; Dubose, Ryan S; Kozelka, Jakub; Simon, William E; Dempsey, James F


    We have developed a high resolution, quantitative, two-dimensional optical film scanner for use with a commercial high sensitivity radiochromic film (RCF) for measuring single fraction external-beam radiotherapy dose distributions. The film scanner was designed to eliminate artifacts commonly observed in RCF dosimetry. The scanner employed a stationary light source and detector with a moving antireflective glass film platen attached to a high precision computerized X-Y translation stage. An ultrabright red light emitting diode (LED) with a peak output at 633 nm and full width at half maximum (FWHM) of 16 nm was selected as the scanner light source to match the RCF absorption peak. A dual detector system was created using two silicon photodiode detectors to simultaneously measure incident and transmitted light. The LED light output was focused to a submillimeter (FWHM 0.67 mm) spot size, which was determined from a scanning knife-edge technique for measuring Gaussian optical beams. Data acquisition was performed with a 16-bit A/D card in conjunction with commercial software. The linearity of the measured densities on the scanner was tested using a calibrated neutral-density step filter. Sensitometric curves and three IMRT field scans were acquired with a spatial resolution of 1 mm for both radiographic film and RCF. The results were compared with measurements taken with a commercial diode array under identical delivery conditions. The RCF was rotated by 90 deg and rescanned to study orientation effects. Comparison between the RCF and the diode array measurements using percent dose difference and distance-to-agreement criteria produced average passing rates of 99.0% using 3%/3 mm criteria and 96.7% using 2%/2 mm criteria. The same comparison between the radiographic film and diode array measurements resulted in average passing rates 96.6% and 91.6% for the above two criteria, respectively. No measurable light-scatter or interference scanner artifacts were observed

  19. Characterization of the proton beam from an IBA Cyclone 18/9 with radiochromic film EBT2

    Energy Technology Data Exchange (ETDEWEB)

    Sansaloni, F.; Lagares, J. I.; Arce, P.; Llop, J.; Perez, J. M. [Medical Applications Unit, Technology Department, CIEMAT, Madrid (Spain); Radiochemistry Department, Molecular Imaging unit, CIC-biomaGUNE, San Sebastian (Spain); Technology Department, CIEMAT (Spain)


    The use of radiochromic films is widespread in different areas of medical physics like radiotherapy and hadrontherapy; however, radiochromic films have been scarcely used in the characterization of proton or deuteron beams generated in biomedical cyclotrons. In this paper the radiochromic film EBT2 was used to study the beam size and the proton beam energy of an IBA Cyclone 18/9 cyclotron. The results indicate that the beam size can be easily measured at a very low expense; however, an accurate determination of the beam energy might require the implementation of certain experimental improvements.

  20. Angular dependence on the records of dose in radiochromic films strips

    Energy Technology Data Exchange (ETDEWEB)

    Costa, K. C.; Prata M, A. [Centro Federal de Educacao Tecnologica de Minas Gerais, Centro de Engenharia Biomedica, Av. Amazonas 5253, 30421-169 Nova Suica, Belo Horizonte, Minas Gerais (Brazil); Alonso, T. C. [Centro de Desenvolvimento da Tecnologia Nuclear - CNEN, Av. Pte. Antonio Carlos 6627, 31270-901 Pampulha, Belo Horizonte, Minas Gerais (Brazil); Campo de O, P. M., E-mail: [Universidade Federal de Minas Gerais, Departamento de Anatomia e Imagen, Av. Prof. Alfredo Balena 190, 30130-100 Belo Horizonte, Minas Gerais (Brazil)


    Radiological images have relevant information both the diagnostic results as to treatment decisions. Then, the diagnostic quality of image that allows a proper analysis should be achieved with the lowest possible deposition of dose in a patient. CT scans produce sectional images that allow the observation of internal structures of the human body without overlap. As in conventional radiology, the contrast which allows obtaining CT images results from the difference in X-ray beam absorption, according to the characteristics of each tissue. The increased of the beam absorption by a tissue means that it appears brighter in the image. In CT scanners, X-ray tube rotates around the patient, and this rotation results in a cross-sectional image of the body. From a sectional image series is possible to obtain a 3-dimensional image that can be viewed from different angles. Among the methods of dose measurement is the use of radiochromic films, which record the energy deposition by darkening its emulsion. The radiochromic films show little sensitivity to visible light and respond better to exposure to ionizing radiation. In this work, strips of the radiochromic film GAFCHROMIC XR-QA2 were irradiated at different angular positions for radiation quality RQT8, defining a beam of X-rays generated from a voltage of 100 kV. The response of radiochromic films depending on the doses was assessed through digital images obtained by H P Scan jet G-4050 scanner. Digital images were analyzed using Image-J software, which allowed obtaining numerical values corresponding to the intensity of darkening for each film. The aim of this study is to evaluate the dose deposition in radiochromic film according to the angular variation in order how is affected the record. So, to examine the use of film strips to record doses in Computed Tomography tests. (Author)

  1. Turnbull Blue Gel (TBG) evaluation as optical dosimeter (United States)

    Borguezan Neto, E.; Batistuti, M. R.; Pavoni, J. F.; Bachmann, L.


    The radiochromic Turnbull Blue Gel (TBG) is sensitive to X- and γ-rays. When exposed to high-energy radiation, TBG can simulate biological tissues, so this gel has potential use in ionizing radiation dosimetry. After irradiation, the yellow TBG changes to the blue Turnbull Blue dye. This work aims to evaluate how TBG responds to exposure to ultraviolet, visible, and infrared radiation from the sun. The gel was irradiated with a solar simulator, which sensitized TBG and transformed it into the Turnbull Blue dye; a change in the optical absorption ensued. The fluence values delivered by the source did not provide a linear response, but it was still possible to use TBG as an optical dosimeter. In conclusion, TBG can be applied to detect solar radiation because it is sensitive enough to measure sun exposure values at time intervals of few minutes.

  2. Basic Study on Visibility and Water Equivalency of a New Colorless Transparent Bolus for Electron Radiotherapy. (United States)

    Maruyama, Daiki; Yamazaki, Shinichi; Honda, Emi; Suzuki, Eiji; Hommatsu, Kouji; Oshiba, Ryo; Sato, Noboru


    Boluses used in electron radiotherapy need to have radiation field visibility and water equivalence. In this report, we have examined field visibility and water equivalence of a new colorless transparent bolus. We examined field visibility, water equivalence, and dose profile. Field visibility was evaluated by comparison to conventional bolus. Water equivalence was investigated by a measured fluence scaling factor. The dose profile was measured by using radiochromic film with the bolus and an ionization chamber in water. We confirmed that the irradiation field could clearly be seen through the transparent colorless bolus. The bolus did not cast a field edge as compared with the conventional bolus. The fluence scaling factor was less than 0.8% as compared to water. We confirmed that the colorless transparent bolus was treated as a water equivalent material. The percentage depth dose (PDD) measured by using radiochromic film with the bolus matched the PDD measured with an ionization chamber in water. R50 was less than 1 mm as compared to PDD measured with an ionization chamber. It was confirmed that the colorless transparent bolus can use to set up patient without losing visibility on flat ground planes. The fluence scaling factor and dose profile measured by using the bolus matched the results measured in water. Therefore, the new colorless transparent bolus has feasibility to improve patient setup efficiency and can improve calculation accuracy by using the fluence scaling factor.

  3. Estimation of MSAD values in computed tomography scans using radiochromic films

    Energy Technology Data Exchange (ETDEWEB)

    Oliveira, Bruno Beraldo; Teogenes Augusto da, E-mail: [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil); Mourao, Arnaldo Prata [Centro Federal de Educacao Tecnologica de Minas Gerais (CEFET-MG), Belo Horizonte, MG (Brazil)


    Objective: To evaluate the feasibility of using radiochromic films as an alternative dosimeter to estimate the multiple scan average dose on the basis on kerma profiles. Materials and Methods: The radiochromic films were distributed in cylinders positioned in the center and in four peripheral bores of a standard abdominal phantom utilized for computed tomography dosimetry. Results: Values for multiple scan average dose values corresponded to 13.6 {+-} 0.7, 13.5 {+-} 0.7 and 18.7 {+-} 1.0 mGy for pitch of 0.75, 1.00 and 1.50, respectively. Conclusion: In spite of results showing lower values than the reference level for radiodiagnosis (25 mGy) established by the Brazilian regulations for abdominal studies, it is suggested that there is room to optimize procedures and review the reference level for radiodiagnosis in Brazil. (author)

  4. A unified approach to deconvolution radiation spectra measured by radiochromic films

    CERN Document Server

    Stancic, V; Ljubenov, V


    A method for the evaluation of energy distribution of a radiation source on the basis of measured space distribution of deposited energy is proposed. The measured data were obtained by using radiochromic films. Mathematical modeling is defined as a Fredholm integral equation inversion problem. Negative solutions were treated as an additional condition expressed through undefined energy group boundaries, caused by virtue of the physical phenomenon of statistical uncertainty. Examples are given of the electron source and neutron radiation field.

  5. Proposed linear energy transfer areal detector for protons using radiochromic film

    Energy Technology Data Exchange (ETDEWEB)

    Mayer, Rulon [Henry M. Jackson Foundation for the Advancement of Military Medicine, Bethesda, Maryland 20817 (United States); Lin, Liyong; Fager, Marcus; Douglas, Dan; McDonough, James; Carabe, Alejandro [Department of Radiation Oncology, University of Pennsylvania Medical Center, Philadelphia, Pennsylvania 19104 (United States)


    Radiation therapy depends on predictably and reliably delivering dose to tumors and sparing normal tissues. Protons with kinetic energy of a few hundred MeV can selectively deposit dose to deep seated tumors without an exit dose, unlike x-rays. The better dose distribution is attributed to a phenomenon known as the Bragg peak. The Bragg peak is due to relatively high energy deposition within a given distance or high Linear Energy Transfer (LET). In addition, biological response to radiation depends on the dose, dose rate, and localized energy deposition patterns or LET. At present, the LET can only be measured at a given fixed point and the LET spatial distribution can only be inferred from calculations. The goal of this study is to develop and test a method to measure LET over extended areas. Traditionally, radiochromic films are used to measure dose distribution but not for LET distribution. We report the first use of these films for measuring the spatial distribution of the LET deposited by protons. The radiochromic film sensitivity diminishes for large LET. A mathematical model correlating the film sensitivity and LET is presented to justify relating LET and radiochromic film relative sensitivity. Protons were directed parallel to radiochromic film sandwiched between solid water slabs. This study proposes the scaled-normalized difference (SND) between the Treatment Planning system (TPS) and measured dose as the metric describing the LET. The SND is correlated with a Monte Carlo (MC) calculation of the LET spatial distribution for a large range of SNDs. A polynomial fit between the SND and MC LET is generated for protons having a single range of 20 cm with narrow Bragg peak. Coefficients from these fitted polynomial fits were applied to measured proton dose distributions with a variety of ranges. An identical procedure was applied to the protons deposited from Spread Out Bragg Peak and modulated by 5 cm. Gamma analysis is a method for comparing the calculated

  6. Characterization of radiochromic films EBT3 by means of the scanner Vidar dosimetry Pro Red and Epson 10000-XL use; Caracterizacion de films radiocromicos EBT3 mediante el uso de scanner Vidar dosimetry Pro Red y Epson 10000-XL

    Energy Technology Data Exchange (ETDEWEB)

    Medina, L.; Garrigo, E.; Venencia, D.; Adrada, A.; Filipuzzi, M., E-mail: [Instituto Privado de Radioterapia, Obispo Oro 423, X5000BFI Cordoba (Argentina)


    The Radiochromic film have become an attractive tool for verification of dose distributions in IMRT because these have high spatial resolution film, are near water equivalent and not require revealed, A critical aspect of the use of these film is used for digitizing scanner The purpose of this paper is to characterize EBT3 using two types of scanner. Were employed The Radiochromic film EBT3, was used photon beam 6 MV generated by a linear accelerator Siemens Primus, he films were irradiated at a dose range between 0 Gy a 9 Gy. The stabilization time after irradiation was 24 hours. The films were digitized with a scanner Epson 10000-XL y el VIDAR Dosimetry Pro Red. We used the software for construction of the calibration curve. The resolution of each dosimetry system was analyzed through the results of the spatial response function by analyzing a step pattern. The Epson scanner is most sensitive to the red channel. This is less than that obtained with the Vidar. The Vidar scanner spatial response profiles disturbs not opposed to Epson analyzed. The calibration curves for both dosimetry systems can be employed. However, the sensitivity and repeatability of the system is better than Red Vidar Epson 10000-XL. (author)

  7. Fast protocol for radiochromic film dosimetry using a cloud computing web application. (United States)

    Calvo-Ortega, Juan-Francisco; Pozo, Miquel; Moragues, Sandra; Casals, Joan


    To investigate the feasibility of a fast protocol for radiochromic film dosimetry to verify intensity-modulated radiotherapy (IMRT) plans. EBT3 film dosimetry was conducted in this study using the triple-channel method implemented in the cloud computing application ( We described a fast protocol for radiochromic film dosimetry to obtain measurement results within 1h. Ten IMRT plans were delivered to evaluate the feasibility of the fast protocol. The dose distribution of the verification film was derived at 15, 30, 45min using the fast protocol and also at 24h after completing the irradiation. The four dose maps obtained per plan were compared using global and local gamma index (5%/3mm) with the calculated one by the treatment planning system. Gamma passing rates obtained for 15, 30 and 45min post-exposure were compared with those obtained after 24h. Small differences respect to the 24h protocol were found in the gamma passing rates obtained for films digitized at 15min (global: 99.6%±0.9% vs. 99.7%±0.5%; local: 96.3%±3.4% vs. 96.3%±3.8%), at 30min (global: 99.5%±0.9% vs. 99.7%±0.5%; local: 96.5%±3.2% vs. 96.3±3.8%) and at 45min (global: 99.2%±1.5% vs. 99.7%±0.5%; local: 96.1%±3.8% vs. 96.3±3.8%). The fast protocol permits dosimetric results within 1h when IMRT plans are verified, with similar results as those reported by the standard 24h protocol. Copyright © 2017 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

  8. SU-F-T-550: Radiochromic Plastic Thin Sheet Dosimeter: Initial Performance

    Energy Technology Data Exchange (ETDEWEB)

    Jordan, K [London Regional Cancer Program, London, ON (United Kingdom); Adamovics, J [John Adamovics, Skillman, NJ (United States)


    Purpose: Thin sheets, of a high sensitivity formulation of radiochromic dosimeter, Presage were prepared and evaluated for optical readout. Methods: Sheets of radiochromic polyurethane, 12 cm long, 10 cm wide and 0.2 cm thick were prepared with leuco crystal violet as the reporter molecule. Sample transmission was evaluated at a wavelength of 590 nm with in-house constructed instruments: optical cone beam laser CT scanner, fixed and scanning spot densitometers. Sample sequential irradiations to a total dose of 40 Gy were conducted with a modified, Theratron 60, cobalt radiotherapy machine at dose rates of 1 or 0.25 Gy per minute. Exposure to ambient and readout light was minimized to limit background photochromic signals. Samples were stored at 4°C. Optical activity was assessed from linearly polarized transmission images. Comparison sensitivity measurements with EBT3 film were conducted. Results: Samples were transparent, smooth and pale purple before irradiation. Radiochromic reaction was completed in less than 5 minutes. A linear dose response with a sensitivity of 0.5 cm-1Gy-1 was observed. Micrometer measurements found sheet thickness variations up to 20%. Uniform dose, 2 Gy attenuation images, correlated with local sheet thicknesses. Comparable measurements with EBT3 film were 3 times more sensitive at 1 Gy but above 15 Gy, EBT3 film had lower sensitivity than 0.2 cm thick Presage sheet dosimeter due to its non-linear response. Conclusion: Dose sensitivity provided a 10% decrease in transmission for a 1 Gy dose. Improvements in mold design are expected to allow production of sheets with less than 5% variation in thickness. Above, 10 Gy, Presage sheet dosimeter performance expected to exceed EBT3 film based on linearity, sensitivity, transparency and smoothness of samples. J Adamovics is owner of Heuris Inc.

  9. SU-G-TeP2-06: Development of Novel Radiochromic Films for Radiotherapy Dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Alqathami, M; Lee, H; Ibbott, G [UT MD Anderson Cancer Center, Houston, TX (United States); Won Choi, G [UT MD Anderson Cancer Center, Houston, TX-Texas (United States); Blencowe, A [The University of South Australia, South Australia, SA (Australia); Wen, Z [MD Anderson Cancer Center, Houston, TX (United States); Adamovics, J [Department of Chemistry and Biology, Rider University, Skillman, NJ (United States)


    Purpose: To develop and evaluate novel radiochromic films for quality assurance in radiotherapy dosimetry. Materials and Methods: Novel radiochromic film compositions were formulated using leuco crystal violet (LCV) as a reporting system and tetrabromoethane as a free radical source. The film matrix used consisted of polyurethane polymer mixed with dibutyl phthalate plasticizer (20 wt%). The concentration of the radical initiator was kept constant at 10 wt% and the concentration of the LCV dye varied (1 and 2 wt%). To ensure uniform thickness of the film, its precursors were sandwiched between two pieces of glass separated by a 1 mm gap between during the curing process. The films were cut into pieces and were irradiated with a 6 MV X-ray beam to selected doses. The change in optical density was measured using a flatbed scanner and a spectrophotometer. Results: The results showed that all film formulations exhibited a linear response with dose and an absorption maximum at ∼ 590 nm. The formulation with 2 wt% LCV was ∼ 30% more sensitive to dose than the formulation with 1 wt% LCV. Both films were very deformable. In addition, the radiochromic response of the film was found to bleach over a short period of time (few weeks) allowing the film to be reused for dose verification measurements. Conclusion: Both film formulations displayed excellent sensitivity and linearity to radiation dose and thus can be used for the 2D dosimetry of clinical megavoltage and kilovoltage X-ray beams. In addition, the thickness of the film could easily be increased allowing for their potential use as a deformable bolus material. However, thicker films would need more optimization of the manufacturing procedure to ensure consistent material uniformity and sensitivity are recommended.

  10. Three-dimensional radiochromic film dosimetry for volumetric modulated arc therapy using a spiral water phantom. (United States)

    Tanooka, Masao; Doi, Hiroshi; Miura, Hideharu; Inoue, Hiroyuki; Niwa, Yasue; Takada, Yasuhiro; Fujiwara, Masayuki; Sakai, Toshiyuki; Sakamoto, Kiyoshi; Kamikonya, Norihiko; Hirota, Shozo


    We validated 3D radiochromic film dosimetry for volumetric modulated arc therapy (VMAT) using a newly developed spiral water phantom. The phantom consists of a main body and an insert box, each of which has an acrylic wall thickness of 3 mm and is filled with water. The insert box includes a spiral film box used for dose-distribution measurement, and a film holder for positioning a radiochromic film. The film holder has two parallel walls whose facing inner surfaces are equipped with spiral grooves in a mirrored configuration. The film is inserted into the spiral grooves by its side edges and runs along them to be positioned on a spiral plane. Dose calculation was performed by applying clinical VMAT plans to the spiral water phantom using a commercial Monte Carlo-based treatment-planning system, Monaco, whereas dose was measured by delivering the VMAT beams to the phantom. The calculated dose distributions were resampled on the spiral plane, and the dose distributions recorded on the film were scanned. Comparisons between the calculated and measured dose distributions yielded an average gamma-index pass rate of 87.0% (range, 91.2-84.6%) in nine prostate VMAT plans under 3 mm/3% criteria with a dose-calculation grid size of 2 mm. The pass rates were increased beyond 90% (average, 91.1%; range, 90.1-92.0%) when the dose-calculation grid size was decreased to 1 mm. We have confirmed that 3D radiochromic film dosimetry using the spiral water phantom is a simple and cost-effective approach to VMAT dose verification.

  11. Technical Note: Statistical dependences between channels in radiochromic film readings. Implications in multichannel dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    González-López, Antonio, E-mail: [Hospital Clínico Universitario Virgen de la Arrixaca, Ctra. Madrid-Cartagena, El Palmar, Murcia 30120 (Spain); Vera-Sánchez, Juan Antonio [Servicio de Protección Radiológica y Física Médica Hospital Universitari Sant Joan de Reus, Av. del Dr. Josep Laporte, 2, Reus, Tarragona 43204 (Spain); Ruiz-Morales, Carmen [Hospital IMED Elche, Max Planck No. 3, Elche, Alicante 03203 (Spain)


    Purpose: This note studies the statistical relationships between color channels in radiochromic film readings with flatbed scanners. The same relationships are studied for noise. Finally, their implications for multichannel film dosimetry are discussed. Methods: Radiochromic films exposed to wedged fields of 6 MV energy were read in a flatbed scanner. The joint histograms of pairs of color channels were used to obtain the joint and conditional probability density functions between channels. Then, the conditional expectations and variances of one channel given another channel were obtained. Noise was extracted from film readings by means of a multiresolution analysis. Two different dose ranges were analyzed, the first one ranging from 112 to 473 cGy and the second one from 52 to 1290 cGy. Results: For the smallest dose range, the conditional expectations of one channel given another channel can be approximated by linear functions, while the conditional variances are fairly constant. The slopes of the linear relationships between channels can be used to simplify the expression that estimates the dose by means of the multichannel method. The slopes of the linear relationships between each channel and the red one can also be interpreted as weights in the final contribution to dose estimation. However, for the largest dose range, the conditional expectations of one channel given another channel are no longer linear functions. Finally, noises in different channels were found to correlate weakly. Conclusions: Signals present in different channels of radiochromic film readings show a strong statistical dependence. By contrast, noise correlates weakly between channels. For the smallest dose range analyzed, the linear behavior between the conditional expectation of one channel given another channel can be used to simplify calculations in multichannel film dosimetry.

  12. Investigation of nanoscale structures by small-angle X-ray scattering in a radiochromic dosimeter

    DEFF Research Database (Denmark)

    Skyt, Peter Sandegaard; Jensen, Grethe Vestergaard; Wahlstedt, Isak Hannes


    This study examines the nanoscale structures in a radiochromic dosimeter that was based on leuco-malachite-green dye and the surfactant sodium dodecyl sulfate (SDS) suspended in a gelatin matrix. Small-angle X-ray scattering was used to investigate the structures of a range of compositions...... of the dosimeter. When omitting gelatin, ellipsoidal micelles of SDS were formed with a core radius near 15 Å, an eccentricity of 1.6, and a head-group shell thickness near 7 Å. Gelatin significantly changed the micelles to a cylindrical shape with around three times lower core radius and four times larger shell...

  13. Radiochromic film measurement of spatial uniformity for a laser generated x-ray environment

    Energy Technology Data Exchange (ETDEWEB)

    Fisher, J. H.; Newlander, C. D.; Horton, R.; Fournier, K. B.; Emig, J.; Patterson, R.; Davis, J. F.; Seiler, S.; Jenkins, P. P.


    n existing x-ray source application (XRSA) test cassette was modified to hold multiple x-ray filter materials followed by two radiochromic film types (FWT-60 and HD-810 Gafchromic® film) to qualitatively characterize the spectral-spatial uniformity over the XRSA sample field of view. Multiple sets of film were examined and nominal set was determined. These initial, qualitative measurements suggest a low-energy regime (E < 3 keV) spatial anisotropy and spatial isotropy at higher energies (E > 3 keV).

  14. Dose determination with nitro blue tetrazolium containing radiochromic dye films by measuring absorbed and reflected light

    DEFF Research Database (Denmark)

    Kovács, A.; Baranyai, M.; Wojnárovits, L.


    Tetrazolium salts as heterocyclic organic compounds are known to form highly coloured, water insoluble formazans by reduction, which can be utilized in radiation processing dosimetry. Radiochromic films containing nitro blue tetrazolium dissolved in a polymer matrix were found suitable for dose...... determination in a wide dose range both by absorbance and reflectance measurements. The concept of measuring reflected light from dose labels has been discussed earlier and emerged recently due to the requirement of introducing semiquantitative label dose indicators for quarantine control. The usefulness...

  15. Determining the mechanical properties of a radiochromic silicone-based 3D dosimeter (United States)

    Kaplan, L. P.; Høye, E. M.; Balling, P.; Muren, L. P.; Petersen, J. B. B.; Poulsen, P. R.; Yates, E. S.; Skyt, P. S.


    New treatment modalities in radiotherapy (RT) enable delivery of highly conformal dose distributions in patients. This creates a need for precise dose verification in three dimensions (3D). A radiochromic silicone-based 3D dosimetry system has recently been developed. Such a dosimeter can be used for dose verification in deformed geometries, which requires knowledge of the dosimeter’s mechanical properties. In this study we have characterized the dosimeter’s elastic behaviour under tensile and compressive stress. In addition, the dose response under strain was determined. It was found that the dosimeter behaved as an incompressible hyperelastic material with a non-linear stress/strain curve and with no observable hysteresis or plastic deformation even at high strains. The volume was found to be constant within a 2% margin at deformations up to 60%. Furthermore, it was observed that the dosimeter returned to its original geometry within a 2% margin when irradiated under stress, and that the change in optical density per centimeter was constant regardless of the strain during irradiation. In conclusion, we have shown that this radiochromic silicone-based dosimeter’s mechanical properties make it a viable candidate for dose verification in deformable 3D geometries.

  16. Politico-economic equivalence

    DEFF Research Database (Denmark)

    Gonzalez Eiras, Martin; Niepelt, Dirk


    and a state are equivalent to another such pair if both pairs give rise to the same allocation in politico-economic equilibrium. The equivalence conditions help to identify factors that render institutional change non-neutral and to construct politico-economic equilibria in new policy regimes. We exemplify......Traditional "economic equivalence'' results, like the Ricardian equivalence proposition, define equivalence classes over exogenous policies. We derive "politico-economic equivalence" conditions that apply in environments where policy is endogenous and chosen sequentially. A policy regime...

  17. Radiochromic film for dosimetric measurements in radiation shielding composites synthesized for applied in radiology procedures of high dose

    Energy Technology Data Exchange (ETDEWEB)

    Fontainha, C. C. P. [Universidade Federal de Minas Gerais, Departamento de Engenharia Nuclear, Av. Pte. Antonio Carlos 6627, 31270-901 Belo Horizonte, Minas Gerais (Brazil); Baptista N, A. T.; Faria, L. O., E-mail: [Centro de Desenvolvimento da Tecnologia Nuclear / CNEN, Av. Pte. Antonio Carlos 6627, 31270-901 Belo Horizonte, Minas Gerais (Brazil)


    Full text: Medical radiology offers great benefit to patients. However, although specifics procedures of high dose, as fluoroscopy, Interventional Radiology, Computed Tomography (CT) make up a small percent of the imaging procedures, they contribute to significantly increase dose to population. The patients may suffer tissue damage. The probability of deterministic effects incidence depends on the type of procedure performed, exposure time, and the amount of applied dose at the irradiated area. Calibrated radiochromic films can identify size and distribution of the radiated fields and measure intensities of doses. Radiochromic films are sensitive for doses ranging from 0.1 to 20 c Gy and they have the same response for X-rays effective energies ranging from 20 to 100 keV. New radiation attenuators materials have been widely investigated resulting in dose reduction entrance skin dose. In this work, Bi{sub 2}O{sub 3} and ZrO{sub 2}:8 % Y{sub 2}O{sub 3} composites were obtained by mixing them with P(VDF-Tr Fe) copolymers matrix from casting method and then characterized by Ftir. Dosimetric measurements were obtained with Xr-Q A2 Gafchromic radiochromic films. In this setup, one radiochromic film is directly exposed to the X-rays beam and another one measures the attenuated beam were exposed to an absorbed dose of 10 mGy of RQR5 beam quality (70 kV X-ray beam). Under the same conditions, irradiated Xr-Q A2 films were stored and scanned measurement in order to obtain a more reliable result. The attenuation factors, evaluated by Xr-Q A2 radiochromic films, indicate that both composites are good candidates for use as patient radiation shielding in high dose medical procedures. (Author)

  18. Aerosol gels (United States)

    Sorensen, Christopher M. (Inventor); Chakrabarti, Amitabha (Inventor); Dhaubhadel, Rajan (Inventor); Gerving, Corey (Inventor)


    An improved process for the production of ultralow density, high specific surface area gel products is provided which comprises providing, in an enclosed chamber, a mixture made up of small particles of material suspended in gas; the particles are then caused to aggregate in the chamber to form ramified fractal aggregate gels. The particles should have a radius (a) of up to about 50 nm and the aerosol should have a volume fraction (f.sub.v) of at least 10.sup.-4. In preferred practice, the mixture is created by a spark-induced explosion of a precursor material (e.g., a hydrocarbon) and oxygen within the chamber. New compositions of matter are disclosed having densities below 3.0 mg/cc.

  19. SU-E-T-516: Investigation of a Novel Radiochromic Radiation Reporting System Utilizing the Reduction of Ferric Ion

    Energy Technology Data Exchange (ETDEWEB)

    Lee, H; Alqathami, M; Wang, J; Ibbott, G [UT MD Anderson Cancer Center, Houston, TX (United States); Blencowe, A [The University of South Australia, South Australia, SA (Australia)


    Purpose To introduce and characterize a new “reverse-Fricke” radiation reporting system utilizing the reduction of ferric ions (Fe{sup 3+}) to ferrous ions (Fe{sup 2+}). Methods Two formulations of the radiochromic reporting system, referred to as A and B, were prepared for investigation. Formulation-A consisted of 14 mM 1,10-phenanthroline, 42 mM ethanol, and 57 mM ammonium ferric oxalate in water. Formulation-B consisted of 27 mM 1,10-phenanthroline, 42 mM ethanol, and 28 mM ammonium ferric oxalate in water. Solutions were prepared immediately prior to irradiation with a Cobalt-60 unit with radiation doses of 0, 1, 5, 10, 15, 20, and 25 Gy. The change in optical density over the visible range of 450–650 nm was measured using a spectrophotometer immediately after irradiation. The effective atomic numbers of the formulations were calculated using Mayneord’s formula. Results Ionizing radiation energy absorbed in the solutions causes the reduction of ferric ions (Fe{sup 3+}) into ferrous ions (Fe{sup 2+}), which then forms a 1:3 red colored complex with 1,10-phenanthroline ([(C{sub 1} {sub 2}H{sub 8}N{sup 2}){sub 3}Fe]{sup 2+}) that can be measured spectrophotometrically. The absorbance spectra of the resulting complex displayed a peak maximum at 512 nm with a greater change in absorbance for Formulation-B after receiving comparable radiation doses. The change in absorbance relative to dose exhibited a linear response up to 25 Gy for both Formulation-A (R{sup 2} = 0.98) and Formulation-B (R{sup 2} = 0.97). The novel formulations were also nearly water equivalent (Zeff = 7.42) with effective atomic numbers of 7.65 and 7.52 and mass densities within 0.2% of water. Conclusion Both formulations displayed visible Fe{sup 2+} complex formation with 1,10-phenanthroline after irradiation using a Cobalt-60 source. The higher sensitivity measured for Formulation-B is attributed to the increase in 1,10-phenanthroline concentration and the increase in the 1

  20. Development and characterization of a three-dimensional radiochromic film stack dosimeter for megavoltage photon beam dosimetry. (United States)

    McCaw, Travis J; Micka, John A; DeWerd, Larry A


    Three-dimensional (3D) dosimeters are particularly useful for verifying the commissioning of treatment planning and delivery systems, especially with the ever-increasing implementation of complex and conformal radiotherapy techniques such as volumetric modulated arc therapy. However, currently available 3D dosimeters require extensive experience to prepare and analyze, and are subject to large measurement uncertainties. This work aims to provide a more readily implementable 3D dosimeter with the development and characterization of a radiochromic film stack dosimeter for megavoltage photon beam dosimetry. A film stack dosimeter was developed using Gafchromic(®) EBT2 films. The dosimeter consists of 22 films separated by 1 mm-thick spacers. A Virtual Water™ phantom was created that maintains the radial film alignment within a maximum uncertainty of 0.3 mm. The film stack dosimeter was characterized using simulations and measurements of 6 MV fields. The absorbed-dose energy dependence and orientation dependence of the film stack dosimeter were investigated using Monte Carlo simulations. The water equivalence of the dosimeter was determined by comparing percentage-depth-dose (PDD) profiles measured with the film stack dosimeter and simulated using Monte Carlo methods. Film stack dosimeter measurements were verified with thermoluminescent dosimeter (TLD) microcube measurements. The film stack dosimeter was also used to verify the delivery of an intensity-modulated radiation therapy (IMRT) procedure. The absorbed-dose energy response of EBT2 film differs less than 1.5% between the calibration and film stack dosimeter geometries for a 6 MV spectrum. Over a series of beam angles ranging from normal incidence to parallel incidence, the overall variation in the response of the film stack dosimeter is within a range of 2.5%. Relative to the response to a normally incident beam, the film stack dosimeter exhibits a 1% under-response when the beam axis is parallel to the film

  1. Development of radiochromic film for spatially quantitative dosimetric analysis of indirect ionizing radiation fields (United States)

    Brady, Samuel Loren

    Two types of radiochromic films (RCF) were characterized for this work: EBT and XRQA film. Both films were investigated for: radiation interaction with film structure; light interaction with film structure for optimal film readout (densitometry) sensitivity; range of absorbed dose measurements; dependence of film dose measurement response as a function of changing radiation energy; fractionation and dose rate effects on film measurement response; film response sensitivity to ambient factors; and stability of measured film response with time. EBT film was shown to have the following properties: near water equivalent atomic weight (Zeff); dynamic dose range of 10 -1-102 Gy; 3% change in optical density (OD) response for a single exposure level when exposed to radiation energies from (75-18,000) kV; and best digitized using transmission densitometry. XRQA film was shown to have: a Zeff of ˜25; a 12 fold increase in sensitivity at lower photon energies for a dynamic dose range of 10-3-100 Gy, a difference of 25% in OD response when comparing 120 kV to 320 kV, and best digitized using reflective densitometry. Both XRQA and EBT films were shown to have: a temporal stability (DeltaOD) of ˜1% for t > 24 hr post film exposure for up to ˜20 days; a change in dose response of ˜0.03 mGy hr-1 when exposed to fluorescent room lighting at standard room temperature and humidity levels; a negligible dose rate and fractionation effect when operated within the optimal dose ranges; and a light wavelength dependence with dose for film readout. The flat bed scanner was chosen as the primary film digitizer due to its availability, cost, OD range, functionality (transmission and reflection scanning), and digitization speed. As a cost verses functionality comparison, the intrinsic and operational limitations were determined for two flat bed scanners. The EPSON V700 and 10000XL exhibited equal spatial and OD accuracy. The combined precision of both the scanner light sources and CCD

  2. Radiochromic Plastic Films for Accurate Measurement of Radiation Absorbed Dose and Dose Distributions

    DEFF Research Database (Denmark)

    McLaughlin, W. L.; Miller, Arne; Fidan, S.


    Thin radiochromic dye films are useful for measuring large radiation absorbed doses (105–108 rads) and for high-resolution imaging of dose patterns produced by penetrating radiation beams passing through non-homogeneous media. Certain types of amino-substituted triarylmethane cyanides dissolved...... in polymeric solutions can be cast into flexible free-standing thin films of uniform thickness and reproducible response to ultraviolet and ionizing radiation. The increase in optical density versus energy deposited by radiation is linear over a wide range of doses and is for practical purposes independent...... of dose rate (1–1014 rad s−1). Upon irradiation of the film, the profile of the radiation field is registered as a permanent colored image of the dose distribution. Unlike most other types of dyed plastic dose meters, the optical density produced by irradiation is in most cases stable for periods...

  3. Novel radiochromic dosimeters based on Calcein dye for high dose applications (United States)

    Aldweri, Feras M.; Rabaeh, Khalid A.; Al-Ahmad, Kefaia N.


    New compositions of radio-chromic solutions and polyvinyl alcohol (PVA) films containing different concentrations of Calcein dye have been introduced as high dose dosimeter. The dosimeters were irradiated with gamma rays from 60C o source at doses from 5 to 30 kGy for film and from 0.25 to 1 kGy for solution. UV/vis spectrophotometry was used to investigate the absorbance (optical density) of unirradiated and irradiated films and solutions in terms of absorbance at 493 nm for film and 496 nm for solution. The effects of scan temperature, relative humidity and stability of the response of films and solutions after irradiation were investigated. The results show that these films could be used as dosimeter in industrial radiation processing. The useful dose range of developed Calcein-PVA film and solution dosimeters is in the range of 5-20 kGy and 0.25-1 kGy respectively

  4. Chemically tuned linear energy transfer dependent quenching in a deformable, radiochromic 3D dosimeter

    DEFF Research Database (Denmark)

    Høye, Ellen Marie; Skyt, Peter Sandegaard; Balling, Peter


    Most solid-state detectors, including 3D dosimeters, show lower signal in the Bragg peak than expected, a process termed quenching. The purpose of this study was to investigate how variation in chemical composition of a recently developed radiochromic, silicone-based 3D dosimeter influences...... the observed quenching in proton beams. The dependency of dose response on linear energy transfer, as calculated through Monte Carlo simulations of the dosimeter, was investigated in 60 MeV proton beams. We found that the amount of quenching varied with the chemical composition: peak-to-plateau ratios (1cm...... into the plateau) ranged from 2.2 to 3.4, compared to 4.3 using an ionization chamber. The dose response, and thereby the quenching, was predominantly influenced by the curing agent concentration, which determined the dosimeter’s deformation properties. The dose response was found to be linear at all depths. All...

  5. Comparison of the responses of TLD-100 and radiochromic films exposed to X-rays of low energy in a radiodiagnostic clinical treatment

    Energy Technology Data Exchange (ETDEWEB)

    Castro, M.; Mesa, F.; Sosa, M. [Physics Institute, University of Guanajuato, Loma del Bosque 103, Lomas del Campestre, 37150 Leon, Guanajuato (Mexico)


    Full text: In this work a comparison of the responses of a TLD-100 and a radiochromic film exposed to a low energy X-ray beam is presented. X-rays in the range of 20 to 120 KV from a clinical machine at the radiodiagnostic unit of the IMSS-Tl hospital in Leon were used. The processes of calibration of both the TLD-100 and the radiochromic films are also discussed. (Author)

  6. SU-E-T-485: In Vivo Dosimetry with EBT3 Radiochromic Films for TBI Treatments

    Energy Technology Data Exchange (ETDEWEB)

    Lozares, S; Gracia, M; Olasolo, J; Gallardo, N; Fuentemilla, N; Pellejero, S; Miquelez, S; Maneru, F; Martin, M; Bragado, L; Rubio, A [Complejo Hospitalario de Navarra, Pamplona, Navarra (Spain)


    Purpose: Total body irradiation (TBI) is a technique that requires special equipment to control “in vivo” the dose to the patient because it is a complex technique performed in extraordinary conditions. There are several devices to perform this task (diodes, TLDs, ionization chambers, MOSFET). In this paper we study the possibility of performing these measurements with radiochromic films EBT3 properly calibrated. This method has been compared to the PTW diodes system for TBI. Methods: Once made the TC to the patients, we measured different thicknesses of the relevant areas of the body (head, neck, chest with or without arms, umbilicus area, knees and ankles); for each of these thicknesses we measured dose rate (cGy / UM) in RW3 phantom, in TBI conditions, with ionization chamber in the center; in turn, the input diode and the output of each configuration is placed to assign dose to each set of diodes. Movie calibration is performed according to manufacturer’s recommendations but TBI conditions. The dose at the center of each thickness compared to a linear interpolation of the dose at the entrance and exit, resulting in an adequate approximation. Finally in each session for each patient put a piece of film (2×2 cm2) at the entrance and another at the exit in each area, obtaining these readings and interpolating the estimated center dose, as with the diodes. Results: These results show a greater homogeneity in the distribution for use with film and validate the use of the same for this task and, if necessary, to avoid purchasing diode group if they have not. Conclusion: By using radiochromic films for this technique gives us a proper calculation of the dose received by the patient in the absence of other methods, or gives us a second additional track that already used normally.

  7. Radiochromic film-based quality assurance for CT-based high-dose-rate brachytherapy. (United States)

    Asgharizadeh, Saeid; Bekerat, Hamed; Syme, Alasdair; Aldelaijan, Saad; DeBlois, François; Vuong, Té; Evans, Michael; Seuntjens, Jan; Devic, Slobodan


    In the past, film dosimetry was developed into a powerful tool for external beam radiotherapy treatment verification and quality assurance. The objective of this work was the development and clinical testing of the EBT3 model GafChromic film based brachytherapy quality assurance (QA) system. Retrospective dosimetry study was performed to test a patient-specific QA system for preoperative endorectal brachytherapy that uses a radiochromic film dosimetry system. A dedicated phantom for brachytherapy applicator used for rectal cancer treatment was fabricated enabling us to compare calculated-to-measured dose distributions. Starting from the same criteria used for external beam intensity-modulated radiation therapy QA (3%, 3 mm), passing criteria for high- and low-dose gradient regions were subsequently determined. Finally, we investigated the QA system's sensitivity to controlled source positional errors on selected patient plans. In low-dose gradient regions, measured dose distributions with criteria of 3%, 3 mm barely passed the test, as they showed 95% passing pixels. However, in the high-dose gradient region, a more stringent condition could be established. Both criteria of 2%, 3 mm and 3%, 2 mm with gamma function calculated using normalization to the same absolute dose value in both measured and calculated dose distributions, and matrix sizes rescaled to match each other showed more than 95% of pixels passing, on average, for 15 patient plans analyzed. Although the necessity of the patient-specific brachytherapy QA needs yet to be justified, we described a radiochromic film dosimetry-based QA system that can be a part of the brachytherapy commissioning process, as well as yearly QA program. Copyright © 2015 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

  8. A practical tool to evaluate dose distributions using radiochromic film in radiation oncology. (United States)

    Tamponi, M; Bona, R; Poggiu, A; Marini, P


    Triple channel algorithm and specific procedures make more reliable radiochromic dosimetry for treatment planning verification and quality assurance in radiation therapy. A tool to obtain radiochromic dose distributions and compare them with the ones resulting from a treatment planning system was developed and applied. The tool was developed as Microsoft Excel macro; it builds dose calibration curves against net optical density of Gafchromic EBT3 film, produces axial, coronal and sagittal dose maps and allows to evaluate them against dose distributions calculated by the Varian treatment planning system Eclipse using gamma index and gamma angle. The net optical density standard errors of estimate of calibration curves at 6 MV Varian DBX600 linac energy were 0.2%, 0.4% and 0.2% for the red, green and blue channels. Tests of these curves by means of three independent eight dose points measurement series, at 15 MV and 6 MV Varian 2100C linac and at 6 MV DBX600 linac energies, showed less than 2% of dose errors for the red channel and less than 3% for the green channel in the range 100-450 cGy. The comparisons between dose distributions from Gafchromic EBT3 triple channel algorithm and the ones from Eclipse analytic anisotropic algorithm (AAA) showed values of gamma index 95th percentile between 0.6 and 1.0. The obtained results encourage the application of this tool in radiation therapy quality assurance. Copyright © 2014 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

  9. SU-E-CAMPUS-T-06: Radiochromic Film Analysis Based On Principal Components

    Energy Technology Data Exchange (ETDEWEB)

    Wendt, R [UT MD Anderson Cancer Center, Houston, TX (United States)


    Purpose: An algorithm to convert the color image of scanned EBT2 radiochromic film [Ashland, Covington KY] into a dose map was developed based upon a principal component analysis. The sensitive layer of the EBT2 film is colored so that the background streaks arising from variations in thickness and scanning imperfections may be distinguished by color from the dose in the exposed film. Methods: Doses of 0, 0.94, 1.9, 3.8, 7.8, 16, 32 and 64 Gy were delivered to radiochromic films by contact with a calibrated Sr-90/Y-90 source. They were digitized by a transparency scanner. Optical density images were calculated and analyzed by the method of principal components. The eigenimages of the 0.94 Gy film contained predominantly noise, predominantly background streaking, and background streaking plus the source, respectively, in order from the smallest to the largest eigenvalue. Weighting the second and third eigenimages by −0.574 and 0.819 respectively and summing them plus the constant 0.012 yielded a processed optical density image with negligible background streaking. This same weighted sum was transformed to the red, green and blue space of the scanned images and applied to all of the doses. The curve of processed density in the middle of the source versus applied dose was fit by a twophase association curve. A film was sandwiched between two polystyrene blocks and exposed edge-on to a different Y-90 source. This measurement was modeled with the GATE simulation toolkit [Version 6.2, OpenGATE Collaboration], and the on-axis depth-dose curves were compared. Results: The transformation defined using the principal component analysis of the 0.94 Gy film minimized streaking in the backgrounds of all of the films. The depth-dose curves from the film measurement and simulation are indistinguishable. Conclusion: This algorithm accurately converts EBT2 film images to dose images while reducing noise and minimizing background streaking. Supported by a sponsored research

  10. Total skin electron therapy (TSET): a reimplementation using radiochromic films and IAEA TRS-398 code of practice. (United States)

    Schiapparelli, P; Zefiro, D; Massone, F; Taccini, G


    The aim of this work is to present an updated implementation of total skin electron therapy (TSET) using IAEA TRS-398 code of practice for absolute dosimetry and taking advantage of the use of radiochromic films. The optimization of quality control tests is also included. A Varian 2100 C/D linear accelerator equipped with the special procedure HDTSe- (high dose rate total skin electron mode, E=6 MeV) was employed to perform TSET irradiations using the modified Stanford technique. The commissioning was performed following the AAPM report 23 recommendations. In particular, for dual-field beams irradiation, the optimal tilt angle was investigated and the dose distribution in the treatment plane was measured. For a complete six dual-field beams irradiation, the treatment skin dose on the surface of a cylindrical phantom was evaluated by radiochromic films and the B factor which relates the single dual-field skin dose to the six dual-field skin dose was assessed. Since the TRS-398 reference conditions do not meet the requirements of TSET absolute dosimetry, GafChromic EBT films were also employed to check and validate the application of the protocol. Simplified procedures were studied to verify beam constancy in PMMA phantoms without the more difficult setup of total skin irradiation. The optimized geometrical setup for dual-field beams was: Tilt angle = +/- 19 degrees, SSD=353 cm, and the beam degrader (200 x 100 X 1 cm3) placed at 320 cm from the source. As regards to dose homogeneity in the treatment plane, for dual-field beams irradiation, the mean relative dose value was 97% +/- 5% (normalizing to 100% at the calibration point level). For six dual-field beams irradiation, the multiplication factor B was 2.63. In addition, beam quality, dose rate, and bremsstrahlung contribution were also suitable for TSET treatments. The TRS-398 code of practice was used for TSET dosimetry, as dose measurements performed by ionization chamber and radiochromic film agreed within 2

  11. Radiological properties of normoxic polymer gel dosimeters. (United States)

    Venning, A J; Nitschke, K N; Keall, P J; Baldock, C


    The radiological properties of the normoxic polymer gel dosimeters MAGIC, MAGAS, and MAGAT [methacrylic and ascorbic acid in gelatin initiated by copper; methacrylic acid gelatine gel with ascorbic acid; and methacrylic acid gelatine and tetrakis (hydroxymethyl) phosphonium chloride, respectively] have been investigated. The radiological water equivalence was determined by comparing the polymer gel macroscopic photon and electron interaction cross sections over the energy range from 10 keV to 20 MeV and by Monte Carlo modeling of depth doses. Normoxic polymer gel dosimeters have a high gelatine and monomer concentration and therefore mass density (kg m(-3)) up to 3.8% higher than water. This results in differences between the cross-section ratios of the normoxic polymer gels and water of up to 3% for the attenuation, energy absorption, and collision stopping power coefficient ratios through the Compton dominant energy range. The mass cross-section ratios were within 2% of water except for the mass attenuation and energy absorption coefficients ratios, which showed differences with water of up to 6% for energies less than 100 keV. Monte Carlo modeling was undertaken for the polymer gel dosimeters to model the electron and photon transport resulting from a 6 MV photon beam. The absolute percentage differences between gel and water were within 1% and the relative percentage differences were within 3.5%. The results show that the MAGAT gel formulation is the most radiological water equivalent of the normoxic polymer gel dosimeters investigated due to its lower mass density measurement compared with MAGAS and MAGIC gels.

  12. Response of radiochromic dye films to low energy heavy charged particles

    CERN Document Server

    Buenfil, A E; Gamboa-Debuen, I; Aviles, P; Avila, O; Olvera, C; Robledo, R; Rodriguez-Ponce, M; Mercado-Uribe, H; Rodriguez-Villafuerte, M; Brandan, M E


    We have studied the possible use of radiochromic dye films (RCF) as heavy charged particle dosemeters. We present the results of irradiating two commercial RCF (GafChromic HD-810 and MD-55-1) with 1.5, 2.9 and 4.4 MeV protons, 1.4, 2.8, 4.7, 5.9, 6.8 MeV sup 4 He ions and 8.5 and 12.4 MeV sup 1 sup 2 C ions, at proton doses from about 1 Gy up to 3 kGy, helium ions doses from 3 Gy to 5 kGy and carbon ion doses from 30 Gy to 20 kGy. The films were scanned and digitized using commercial equipment. For a given particle, the response per unit dose at different energies indicates an energy dependence of the sensitivity, which is discussed. Comparison was made for the use of a standard spectrophotometer to obtain optical density readings versus a white light scanner.

  13. Chemically tuned linear energy transfer dependent quenching in a deformable, radiochromic 3D dosimeter. (United States)

    Høye, Ellen Marie; Skyt, Peter S; Balling, Peter; Muren, Ludvig P; Taasti, Vicki T; Swakoń, Jan; Mierzwińska, Gabriela; Rydygier, Marzena; Bassler, Niels; Petersen, Jørgen B B


    Most solid-state detectors, including 3D dosimeters, show lower signal in the Bragg peak than expected, a process termed quenching. The purpose of this study was to investigate how variation in chemical composition of a recently developed radiochromic, silicone-based 3D dosimeter influences the observed quenching in proton beams. The dependency of dose response on linear energy transfer, as calculated through Monte Carlo simulations of the dosimeter, was investigated in 60 MeV proton beams. We found that the amount of quenching varied with the chemical composition: peak-to-plateau ratios (1 cm into the plateau) ranged from 2.2 to 3.4, compared to 4.3 using an ionization chamber. The dose response, and thereby the quenching, was predominantly influenced by the curing agent concentration, which determined the dosimeter's deformation properties. The dose response was found to be linear at all depths. All chemical compositions of the dosimeter showed dose-rate dependency; however this was not dependent on the linear energy transfer. Track-structure theory was used to explain the observed quenching effects. In conclusion, this study shows that the silicone-based dosimeter has potential for use in measuring 3D-dose-distributions from proton beams.

  14. EBT-XD Radiochromic Film Sensitivity Calibrations Using Proton Beams from a Pelletron Accelerator (United States)

    Stockler, Barak; Grun, Alexander; Brown, Gunnar; Klein, Matthew; Wood, Jacob; Cooper, Anthony; Ward, Ryan; Freeman, Charlie; Padalino, Stephen; Regan, S. P.; Sangster, T. C.


    Radiochromic film (RCF) is a transparent detector film that permanently changes color following exposure to ionizing radiation. RCF is used frequently in medical applications, but also has been used in a variety of high energy density physics diagnostics. RCF is convenient to use because it requires no chemical processing and can be scanned using commercially available document scanners. In this study, the sensitivity of Gafchromic™ EBT-XD RCF to protons and x-rays was measured. Proton beams produced by the SUNY Geneseo Pelletron accelerator were directed into an evacuated target chamber where they scattered off a thin gold foil. The scattered protons were incident on a sample of RCF which subtended a range of angles around the scattering center. A new analysis method, which relies on the variation in scattered proton fluence as a function of scattering angle in accordance with the Rutherford scattering law, is currently being developed to speed up the proton calibrations. Samples of RCF were also exposed to x-ray radiation using an X-RAD 160 x-ray irradiator, allowing the sensitivity of RCF to X-rays to be measured. This work was funded in part by a Grant from the DOE through the Laboratory for Laser Energetics as well as the NSF.

  15. Gel dosimetry for conformal radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Gambarini, G. [Department of Physics of the University and INFN, Milan (Italy)]. e-mail:


    With the continuum development of conformal radio therapies, aimed at delivering high dose to tumor tissue and low dose to the healthy tissue around, the necessities has appeared of suitable improvement of dosimetry techniques giving the possibility of obtaining dose images to be compared with diagnostic images. Also if wide software has been developed for calculating dose distributions in the fields of various radiotherapy units, experimental verifications are necessary, in particular in the case of complex geometries in conformal radiotherapy. Gel dosimetry is a promising method for imaging the absorbed dose in tissue-equivalent phantoms, with the possibility of 3D reconstruction of the spatial dose distribution, with milli metric resolution. Optical imaging of gel dosimeters, based on visible light absorbance analysis, has shown to be a reliable technique for achieving dose distributions. (Author)

  16. System equivalent model mixing

    NARCIS (Netherlands)

    Klaassen, Steven W.B.; van der Seijs, M.V.; de Klerk, D.


    This paper introduces SEMM: a method based on Frequency Based Substructuring (FBS) techniques that enables the construction of hybrid dynamic models. With System Equivalent Model Mixing (SEMM) frequency based models, either of numerical or experimental nature, can be mixed to form a hybrid model.

  17. Equivalent Quantum Circuits


    Garcia-Escartin, Juan Carlos; Chamorro-Posada, Pedro


    Quantum algorithms and protocols are often presented as quantum circuits for a better understanding. We give a list of equivalence rules which can help in the analysis and design of quantum circuits. As example applications we study quantum teleportation and dense coding protocols in terms of a simple XOR swapping circuit and give an intuitive picture of a basic gate teleportation circuit.

  18. Dose Distribution According to the Tissue Composition Using Wedge Filter by Radiochromic Film

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Yon Lae [Dept. of Radiologic Technology, Choonhae College of Health Sciences, Ulsan (Korea, Republic of); Lee, Jeong Woo; Park, Byung Moon [Dept. of Radiation Oncology, Konku University Hospital, Seoul (Korea, Republic of); Jung, Jae Yong; Park, Ji Yeon; Suh, Tae Suk [Dept. of Biomedical Engineering, Catholic University, Seoul (Korea, Republic of)


    The purpose of this study is to analyze the dose distribution when wedge filter is used in the various tissue electron density materials. The dose distribution was assessed that the enhanced dynamic wedge filter and physical wedge filter were used in the solid water phantom, cork phantom, and air cavity. The film dosimetry was suitable simple to measure 2D dose distribution. Therefore, the radiochromic films (Gafchromic EBT2, ISP, NJ, USA) were selected to measure and to analyze the dose distributions. A linear accelerator using 6 MV photon were irradiated to field size of 10 x10 cm{sup 2} with 400 MUs. The dose distributions of EBT2 films were analyzed the in-field area and penumbra regions by using dose analysis program. In the dose distributions of wedge field, the dose from a physical wedge was higher than that from a dynamic wedge at the same electron density materials. A dose distributions of wedge type in the solid water phantom and the cork phantom were in agreements with 2%. However, the dose distribution in air cavity showed the large difference with those in the solid water phantom or cork phantom dose distributions. Dose distribution of wedge field in air cavity was not shown the wedge effect. The penumbra width, out of the field of thick and thin, was observed larger from 1 cm to 2 cm at the thick end. The penumbra of physical wedge filter was much larger average 6% than the dynamic wedge filter. If the physical wedge filter is used, the dose was increased to effect the scatter that interacted with photon and physical wedge. In the case of difference in electron like the soft tissue, lung, and air, the transmission, absorption, and scattering were changed in the medium at high energy photon. Therefore, the treatment at the difference electron density should be inhomogeneity correction in treatment planning system.

  19. Mycosis Fungoides electron beam absorbed dose distribution using Fricke xylenol gel dosimetry (United States)

    da Silveira, Michely C.; Sampaio, Francisco G. A.; Petchevist, Paulo C. D.; de Oliveira, André L.; Almeida, Adelaide de


    Radiotherapy uses ionizing radiation to destroy tumor cells. The absorbed dose control in the target volume is realized through radiation sensors, such as Fricke dosimeters and radiochromic film, which permit to realize bi-dimensional evaluations at once and because of that, they will be used in this study as well. Among the several types of cancer suitable for ionizing radiation treatment, the Mycosis Fungoides, a lymphoma that spreads on the skin surface and depth, requires for its treatment total body irradiation by high-energy electrons. In this work the Fricke xylenol gel (FXG) was used in order to obtain information about the absorbed dose distribution induced by the electron interactions with the irradiated tissues and to control this type of treatment. FXG can be considered as an alternative dosimeter, since up to now only films have been used. FXG sample cuvettes, simulating two selected tomos (cranium and abdomen) of the Rando anthropomorphic phantom, were positioned along with radiochromic films for comparison. The phantom was subjected to Stanford total body irradiation using 6 MeV electrons. Tomographic images were acquired for both dosimeters and evaluated through horizontal and vertical profiles along the tomographic centers. These profiles were obtained through a Matlab routine developed for this purpose. From the obtained results, one could infer that, for a superficial and internal patient irradiation, the FXG dosimeter showed an absorbed dose distribution similar to the one of the film. These results can validate the FXG dosimeter as an alternative dosimeter for the Mycosis Fungoides treatment planning.

  20. Establishing Substantial Equivalence: Metabolomics (United States)

    Beale, Michael H.; Ward, Jane L.; Baker, John M.

    Modern ‘metabolomic’ methods allow us to compare levels of many structurally diverse compounds in an automated fashion across a large number of samples. This technology is ideally suited to screening of populations of plants, including trials where the aim is the determination of unintended effects introduced by GM. A number of metabolomic methods have been devised for the determination of substantial equivalence. We have developed a methodology, using [1H]-NMR fingerprinting, for metabolomic screening of plants and have applied it to the study of substantial equivalence of field-grown GM wheat. We describe here the principles and detail of that protocol as applied to the analysis of flour generated from field plots of wheat. Particular emphasis is given to the downstream data processing and comparison of spectra by multivariate analysis, from which conclusions regarding metabolome changes due to the GM can be assessed against the background of natural variation due to environment.

  1. From equivalence to adaptation

    Directory of Open Access Journals (Sweden)

    Paulina Borowczyk


    Full Text Available The aim of this paper is to illustrate in which cases the translators use the adaptation when they are confronted with a term related to sociocultural aspects. We will discuss the notions of equivalence and adaptation and their limits in the translation. Some samples from Arte TV news and from the American film Shrek translated into Polish, German and French will be provided as a support for this article.

  2. A new implementation of multichannel radiochromic film dosimetry; Una nueva implementacion del analisis multicanal para la dosimetria mediante peliculas radiocromicas

    Energy Technology Data Exchange (ETDEWEB)

    Rodriguez Rodriguez, C.; Martin Martin, G.; Bermudez Luna, R.; Lopez Fernandez, A.; Tores Olombrada, M. V. de


    The aims of this paper are to carry out a new implementation of the multichannel radiochromic film dosimetry (Micke A, Lewis D, Yu X. Multichannel film dosimetry with nonuniformity correction. Med Phys 2011;38:2523-34), to quantify the variation in gamma index as compared to the single channel film dosimetry, and to determine if the procedure achieves similar results by means of a different scanner that the one used by Micke et al. Radiochromic EBT2 films and a Microtek 9000 XL scanner were used. Our procedure simplifies the system calibration splitting it into two factors, manufactured batch and digitalization specific. Absorbed dose spatial distributions from an open radiotherapy beam without any modulation and 20 IMRT treatments were determined. Their gamma index maps were calculated and a comparison of the results from single channel and multichannel dosimetry was performed. A 5% mean increase in concordance was obtained by using the multichannel film dosimetry. Our results are similar to those reported by Micke et al. even though we are using a different scanner. (Author)

  3. Validation of the entire 2D array Octavius by radiochromic films; Validacion del conjunto Octavius 2D array mediante peliculas radiocromicas

    Energy Technology Data Exchange (ETDEWEB)

    Iriondo Igerabide, U.; Former Forner, A.; Otal Palacin, A.; Martin Albina, M. L.; Lozares Cordero, S.; Maneru Camara, F.; Pellejero Pellejero, S.; Miquelez Alonso, S.; Soto Prados, P. M.; Rubio Arroniz, A.


    We have validated the 2D-array Octavius set for verification of IMRT plans complete, radiating with the same angles of incidence in the patient's actual plan. This has been taken as reference measurements with radiochromic films, since they are almost isotropic response, higher resolution and we already have experience with them.

  4. Comparison of calibration curve of radiochromic films EBT2 and EBT; Comparacion de la curva de calibracion de las peliculas radiocromica EBT2 y EBT

    Energy Technology Data Exchange (ETDEWEB)

    Parra Osorio, V.; Martin-Viera Cueto, J. A.; Galan Montenegro, P.; Benitez Villegas, E. M.; Casado Villalon, F. F.; Bodineau Gil, C.


    The aim is to compare the quality of the fit to calibrate two radiochromic films batches, one model and another of EBT3 EBT2, using both experimental settings as phenomenological expression as of the calibration curve depends on the precision and accuracy of the estimate of absorbed dose. (Author)

  5. Evolution, present state and future of the radiochromic dyeing films; Evolucion, estado actual y futuro de las peliculas de tinte radiocromico

    Energy Technology Data Exchange (ETDEWEB)

    Villarreal B, J.E. [Instituto Nacional de Investigaciones Nucleares, A.P. 18-1027, 11801 Mexico D.F. (Mexico)


    The evolution of radiochromic films, their present state and their developing future are the object of this work. For this purpose a review of the evolution was realized and also of the present state of using the radiochromic dyeing films as tools to determine the absorbed doses distribution produces by beta emissor sources, beta-gamma, electrons and X-rays. In particular it is presented the development of radiochromic films type GafChromic that by their quality in terms of reproducibility, sensibility and high spatial resolution they have been converted in those films of greatest use so dominating market. Since one of the application fields more important of this type of films is clinical dosimetry, the more eminent applications in this area are presented, which the high resolution dosimetry that use GafChromic has been converted in a basic tool. On the other hand the scopes of this type of dosimetry and the possible development lines of dosimetry with radiochromic dyeing films are discussed. (Author)

  6. Comments on TNT Equivalence

    Energy Technology Data Exchange (ETDEWEB)

    Cooper, P.W.


    The term ``TNT Equivalence`` is used throughout the explosives and related industries to compare the effects of the output of a given explosive to that of TNT. This is done for technical design reasons in scaling calculation such as for the prediction of blast waves, craters, and structural response, and is also used as a basis for government regulations controlling the shipping, handling and storage of explosive materials, as well as for the siting and design of explosive facilities. TNT equivalence is determined experimentally by several different types of tests, the most common of which include: plate dent, ballistic mortar, trauzl, sand crush, and air blast. All of these tests do not necessarily measure the same output property of the sample explosive. As examples of this, some tests depend simply upon the CJ pressure, some depend upon the PV work in the CJ zone and in the Taylor wave behind the CJ plane, some are functions of the total work which includes that from secondary combustion in the air mixing region of the fireball and are acutely effected by the shape of the pressure-time profile of the wave. Some of the tests incorporate systematic errors which are not readily apparent, and which have a profound effect upon skewing the resultant data. Further, some of the tests produce different TNT Equivalents for the same explosive which are a function of the conditions at which the test is run. This paper describes the various tests used, discusses the results of each test and makes detailed commentary on what the test is actually measuring, how the results may be interpreted, and if and how these results can be predicted by first principals based calculations. Extensive data bases are referred to throughout the paper and used in examples for each point in the commentaries.

  7. Skin dose measurements using radiochromic films, TLDS and ionisation chamber and comparison with Monte Carlo simulation. (United States)

    Alashrah, Saleh; Kandaiya, Sivamany; Maalej, Nabil; El-Taher, A


    Estimation of the surface dose is very important for patients undergoing radiation therapy. The purpose of this study is to investigate the dose at the surface of a water phantom at a depth of 0.007 cm as recommended by the International Commission on Radiological Protection and International Commission on Radiation Units and Measurement with radiochromic films (RFs), thermoluminescent dosemeters and an ionisation chamber in a 6-MV photon beam. The results were compared with the theoretical calculation using Monte Carlo (MC) simulation software (MCNP5, BEAMnrc and DOSXYZnrc). The RF was calibrated by placing the films at a depth of maximum dose (d(max)) in a solid water phantom and exposing it to doses from 0 to 500 cGy. The films were scanned using a transmission high-resolution HP scanner. The optical density of the film was obtained from the red component of the RGB images using ImageJ software. The per cent surface dose (PSD) and percentage depth dose (PDD) curve were obtained by placing film pieces at the surface and at different depths in the solid water phantom. TLDs were placed at a depth of 10 cm in a solid water phantom for calibration. Then the TLDs were placed at different depths in the water phantom and were exposed to obtain the PDD. The obtained PSD and PDD values were compared with those obtained using a cylindrical ionisation chamber. The PSD was also determined using Monte Carlo simulation of a LINAC 6-MV photon beam. The extrapolation method was used to determine the PSD for all measurements. The PSD was 15.0±3.6% for RF. The TLD measurement of the PSD was 16.0±5.0%. The (0.6 cm(3)) cylindrical ionisation chamber measurement of the PSD was 50.0±3.0%. The theoretical calculation using MCNP5 and DOSXYZnrc yielded a PSD of 15.0±2.0% and 15.7±2.2%. In this study, good agreement between PSD measurements was observed using RF and TLDs with the Monte Carlo calculation. However, the cylindrical chamber measurement yielded an overestimate of the PSD

  8. Patient-Specific QA of Spot-Scanning Proton Beams using Radiochromic Film. (United States)

    Chan, Maria F; Chen, Chin-Cheng; Shi, Chengyu; Li, Jingdong; Tang, Xiaoli; Li, Xiang; Mah, Dennis


    Radiochromic film for spot-scanning QA provides high spatial resolution and efficiency gains from one-shot irradiation for multiple depths. However, calibration can be a tedious procedure which may limit widespread use. Moreover, since there may be an energy dependence, which manifests as a depth dependence, this may require additional measurements for each patient. We present a one-scan protocol to simplify the procedure. A calibration using an EBT3 film, exposed by a 6-level step-wedge plan on a Proteus ® PLUS proton system (IBA, Belgium), was performed at depths of 18, 20, 24cm using Plastic Water ® (CIRS, Norfolk, VA). The calibration doses ranged from 65-250 cGy(RBE) (relative biological effectiveness) for proton energies of 170-200 MeV. A clinical prostate+nodes plan was used for validation. The planar doses at selected depths were measured with EBT3 films and analyzed using One-scan protocol (one-scan digitization of QA film and at least one film exposed to a known dose). The gamma passing rates, dose-difference maps, and profiles of 2D planar doses measured with EBT3 film and IBA MatriXX-PT, versus the RayStation TPS calculations were analyzed and compared. The EBT3 film measurement results matched well with the TPS calculation data with an average passing rate of ~95% for 2%/2mm and slightly lower passing rates were obtained from an ion chamber array detector. We were able to demonstrate that the use of a proton step-wedge provided clinically acceptable results and minimized variations between film-scanner orientation, inter-scan, and scanning conditions. Furthermore, for relative dosimetry (calibration is not done at the time of experiment) it could be derived from no more than two films exposed to known doses (one could be zero) for rescaling the master calibration curve at each depth. The sensitivity of the calibration to depth variations has been explored. One-scan protocol results appear to be comparable to that of the ion chamber array detector

  9. Radiochromic film dosimetry: considerations on precision and accuracy for EBT2 and EBT3 type films. (United States)

    Dreindl, Ralf; Georg, Dietmar; Stock, Markus


    Gafchromic® EBT2 film is a widely used dosimetric tool for quality assurance in radiation therapy. In 2012 EBT3 was presented as a replacement for EBT2 films. The symmetric structure of EBT3 films to reduce face-up/down dependency as well as the inclusion of a matte film surface to frustrate Newton Ring artifacts present the most prominent improvements of EBT3 films. The aim of this study was to investigate the characteristics of EBT3 films, to benchmark the films against the known EBT2-features and to evaluate the dosimetric behavior over a time period greater than 6 months. All films were irradiated to clinical photon beams (6 MV, 10 MV and 18 MV) on an Elekta Synergy Linac equipped with a Beam Modulator MLC in solid water phantom slabs. Film digitalization was done with a flatbed transparency scanner (Type Epson Expression 1680 Pro). MATLAB® was used for further statistical calculations and image processing. The investigations on post-irradiation darkening, film orientation, film uniformity and energy dependency resulted in negligible differences between EBT2 and EBT3 film. A minimal improvement in face-up/down dependence was found for EBT3. The matte film surface of EBT3 films turned out to be a practical feature as Newton rings could be eliminated completely. Considering long-term behavior (> 6 months) a shift of the calibration curve for EBT2 and EBT3 films due to changes in the dynamic response of the active component was observed. In conclusion, the new EBT3 film yields comparable results to its predecessor EBT2. The general advantages of radiochromic film dosimeters are completed by high film homogeneity, low energy dependence for the observed energy range and a minimized face-up/down dependence. EBT2 dosimetry-protocols can also be used for EBT3 films, but the inclusion of periodical recalibration-interval (e.g. once a quarter) is recommended for protocols of both film generations. Copyright © 2013. Published by Elsevier GmbH.

  10. Equivalence, commensurability, value

    DEFF Research Database (Denmark)

    Albertsen, Niels


    Deriving value in Capital Marx uses three commensurability arguments (CA1-3). CA1 establishes equivalence in exchange as exchangeability with the same third commodity. CA2 establishes value as common denominator in commodities: embodied abstract labour. CA3 establishes value substance...... as commonality of labour: physiological labour. Tensions between these logics have permeated Marxist interpretations of value. Some have supported value as embodied labour (CA2, 3), others a monetary theory of value and value as ‘pure’ societal abstraction (ultimately CA1). They all are grounded in Marx....

  11. Transport Phenomena in Gel

    Directory of Open Access Journals (Sweden)

    Masayuki Tokita


    Full Text Available Gel becomes an important class of soft materials since it can be seen in a wide variety of the chemical and the biological systems. The unique properties of gel arise from the structure, namely, the three-dimensional polymer network that is swollen by a huge amount of solvent. Despite the small volume fraction of the polymer network, which is usually only a few percent or less, gel shows the typical properties that belong to solids such as the elasticity. Gel is, therefore, regarded as a dilute solid because its elasticity is much smaller than that of typical solids. Because of the diluted structure, small molecules can pass along the open space of the polymer network. In addition to the viscous resistance of gel fluid, however, the substance experiences resistance due to the polymer network of gel during the transport process. It is, therefore, of importance to study the diffusion of the small molecules in gel as well as the flow of gel fluid itself through the polymer network of gel. It may be natural to assume that the effects of the resistance due to the polymer network of gel depends strongly on the network structure. Therefore, detailed study on the transport processes in and through gel may open a new insight into the relationship between the structure and the transport properties of gel. The two typical transport processes in and through gel, that is, the diffusion of small molecules due to the thermal fluctuations and the flow of gel fluid that is caused by the mechanical pressure gradient will be reviewed.

  12. Establishing Substantial Equivalence: Proteomics (United States)

    Lovegrove, Alison; Salt, Louise; Shewry, Peter R.

    Wheat is a major crop in world agriculture and is consumed after processing into a range of food products. It is therefore of great importance to determine the consequences (intended and unintended) of transgenesis in wheat and whether genetically modified lines are substantially equivalent to those produced by conventional plant breeding. Proteomic analysis is one of several approaches which can be used to address these questions. Two-dimensional PAGE (2D PAGE) remains the most widely available method for proteomic analysis, but is notoriously difficult to reproduce between laboratories. We therefore describe methods which have been developed as standard operating procedures in our laboratory to ensure the reproducibility of proteomic analyses of wheat using 2D PAGE analysis of grain proteins.

  13. Development and clinical implementation of a global software use and analysis of radiochromic s films; Desarrollo e implementacion clinica de un software global de uso y analisis de peliculas radiocromicas

    Energy Technology Data Exchange (ETDEWEB)

    Gimeno Olmos, J.; Martinez Fernandez, J. M.; Pastor Sanchis, V.; Gonzalez Perez, V.; Guardino de la Flor, C.; Dolores Alemany, V. de los; Crispin Contreras, V.


    The aim of this study was to gather information in one solution the different processes that occur with the use of radiochromic films: calibration, reading, corrections, step-absorbed dose, dose distribution analysis and comparison with reference distributions.

  14. Enhancement of the optical properties of a new radiochromic dosimeter based on aliphatic-aromatic biodegradable polymers

    Energy Technology Data Exchange (ETDEWEB)

    Schimitberger, Thiago, E-mail: [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Escola de Engenharia. Departamento de Engenharia Nuclear; Faria, Luiz O., E-mail: [Centro de desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)


    The development of a dosimeter that is of low cost, easy to process without dependence on expensive complex instruments and environment friendly is a challenging in irradiation quality control. Recently, an aliphatic-aromatic biodegradable polymer has been proposed as radiochromic dosimeter. The dosimeter is based on biodegradable poly(butylene adipate-co-terephthalate) copolymers (PBAT). In order to improve the photoluminescence (PL) properties of PBAT, increasing its range of applicability (50 kGy to 1000 kGy), this work investigates the influence of solution concentration in the dose response. Films with thickness of c.a. 80 μm were produce by wirebar coating, a simple deposition method for preparing large areas of organic films at low cost. The irradiation of samples was performed at room temperature using a Co-60 source at dose rate of 20 kGy/h. The films were exposed to doses ranging from 501 kGy to 1000 kGy. A 405 nm LED light source was used to excite the films. The USB2000 spectrometer made by Ocean Optics was used to collect the emission spectra of the luminescent films. The photoluminescent intensity captured by the spectrometer present linear radiation dose dependence. The maximum PL for the film sample made from a 0.05 g.mL{sup -1} solution is 1.5 (a.u.) while it is about 3.5 (a.u.) for a film sample made from a 0.2 mg.mL{sup -1} solution, when irradiated with 1000 kGy. These results indicate that PBAT films have great potential to be used as a high gamma dose radiochromic dosimeter over a wide dose range, expanding its applicability for different radiations process. (author)

  15. Adherens junction proteins are expressed in collagen corneal equivalents produced in vitro with human cells


    Giasson, Claude J.; Deschambeault, Alexandre; Carrier, Patrick; Germain, Lucie


    Purpose To test whether adherens junction proteins are present in the epithelium and the endothelium of corneal equivalents. Methods Corneal cell types were harvested from human eyes and grown separately. Stromal equivalents were constructed by seeding fibroblasts into a collagen gel on which epithelial and endothelial cells were added on each side. Alternatively, bovine endothelial cells were used. At maturity, sections of stromal equivalents were processed for Masson's trichrome or indirect...


    Energy Technology Data Exchange (ETDEWEB)

    Randall S. Seright


    This report describes work performed during the second year of the project, ''Conformance Improvement Using Gels.'' The project has two objectives. The first objective is to identify gel compositions and conditions that substantially reduce flow through fractures that allow direct channeling between wells, while leaving secondary fractures open so that high fluid injection and production rates can be maintained. The second objective is to optimize treatments in fractured production wells, where the gel must reduce permeability to water much more than that to oil. Pore-level images from X-ray computed microtomography were re-examined for Berea sandstone and porous polyethylene. This analysis suggests that oil penetration through gel-filled pores occurs by a gel-dehydration mechanism, rather than a gel-ripping mechanism. This finding helps to explain why aqueous gels can reduce permeability to water more than to oil. We analyzed a Cr(III)-acetate-HPAM gel treatment in a production well in the Arbuckle formation. The availability of accurate pressure data before, during, and after the treatment was critical for the analysis. After the gel treatment, water productivity was fairly constant at about 20% of the pre-treatment value. However, oil productivity was stimulated by a factor of 18 immediately after the treatment. During the six months after the treatment, oil productivity gradually decreased to approach the pre-treatment value. To explain this behavior, we proposed that the fracture area open to oil flow was increased substantially by the gel treatment, followed by a gradual closing of the fractures during subsequent production. For a conventional Cr(III)-acetate-HPAM gel, the delay between gelant preparation and injection into a fracture impacts the placement, leakoff, and permeability reduction behavior. Formulations placed as partially formed gels showed relatively low pressure gradients during placement, and yet substantially reduced the

  17. SU-E-T-799: Verification of a Simultaneous Treatment of Multiple Brain Metastases Using VMAT Technique by a Composite Alanine-Gel Dosimeter Phantom

    Energy Technology Data Exchange (ETDEWEB)

    Pavoni, J; Silveira, M; Filho, O Baffa [University of Sao Paulo, Ribeirao Preto, Sao Paulo (Brazil); Neves, W; Ramos, P; Haddad, C [Sirio Libanes Hospital, Sao Paulo, Sao Paulo (Brazil)


    Purpose: This work presents an end-to-end test using a Gel-Alanine phantom to validate the three-dimensional (3D) dose distribution (DD) delivered by a single isocenter VMAT technique on the simultaneous treatment of multiple brain metastases. Methods: Three cylindrical phantons containing MAGIC-f gel dosimeter were used to measure the 3D DD of a VMAT treatment, the first two were filled with the gel dosimeter (Gel 1 and 2) and the third one was filled with gel and 12 alanine dosimeters distributed along it (Gel 3). Gels 1 and 3 were irradiated and gel 2 was used to map the magnetic resonance image (MRI) scanner field inomogeneities. A CT scan of gel 3 was used for the VMAT treatment planning and 5 alanine pellets were chosen as lesions, around them a PTV was grown and different dose prescriptions were assigned for each one, varying from 5 to 9Gy. Before treatment, the plan was approved in a QA based on an ionization chamber absolute dose measurement, a radiochromic film planar dose measurement and a portal dosimetry per field verification; and also the phantons positioning were verified by ExacTrac 6D correction and OBI kV Cone Beam CT. The gels were irradiated, the MRIs were acquired 24 hours after irradiation and finally, the alanine dosimeters were analysed in a X-band Electron Spin Resonance spectrometer. Results: The association of the two detectors enabled the 3D dose evaluation by gel and punctually inside target volumes by alanine. In the gamma analyses (3%/3mm) comparing the 5 PTVs’ central images DD with TPS expected DD more than 95% of the points were approved. The alanine absolute dose measurements were in agreement with TPS by less than 5%. Conclusion: The gel-alanine phantom enabled the dosimetric validation of multiple brain metastases treatment using VMAT, being an almost ideal tool for this application. This work is partially supported by FAPESP.

  18. Biomonitoring Equivalents for selenium. (United States)

    Hays, Sean M; Macey, Kristin; Nong, Andy; Aylward, Lesa L


    Selenium is an essential nutrient for human health with a narrow range between essentiality and toxicity. Selenium is incorporated into several proteins that perform important functions in the body. With insufficient selenium intake, the most notable effect is Keshan disease, an endemic cardiomyopathy in children. Conversely, excessive selenium intake can result in selenosis, manifested as brittle nails and hair and gastro-intestinal disorders. As such, guidance values have been established to protect against both insufficient and excessive selenium exposures. Dietary Reference Intakes (DRIs) have been established as standard reference values for nutritional adequacy in North America. To protect against selenosis resulting from exposure to excessive amounts of selenium, several government and non-governmental agencies have established a range of guidance values. Exposure to selenium is primarily through the diet, but monitoring selenium intake is difficult. Biomonitoring is a useful means of assessing and monitoring selenium status for both insufficient and excessive exposures. However, to be able to interpret selenium biomonitoring data, levels associated with both DRIs and toxicity guidance values are required. Biomonitoring Equivalents (BEs) were developed for selenium in whole blood, plasma and urine. The BEs associated with assuring adequate selenium intake (Estimated Average Requirements - EAR) are 100, 80 and 10μg/L in whole blood, plasma and urine, respectively. The BEs associated with protection against selenosis range from 400 to 480μg/L in whole blood, 180-230μg/L in plasma, and 90-110μg/L in urine. These BE values can be used by both regulatory agencies and public health officials to interpret selenium biomonitoring data in a health risk context. Copyright © 2014 Elsevier Inc. All rights reserved.

  19. Characterization of Destrins with Different Dextrose Equivalents

    Directory of Open Access Journals (Sweden)

    Guanglei Li


    Full Text Available Dextrins are widely used for their functional properties and prepared by partial hydrolysis of starch using acid, enzymes, or combinations of both. The physiochemical properties of dextrins are dependent on their molecular distribution and oligosaccharide profiles. In this study, scanning electron microscopy (SEM, X-ray diffractometry (XRD, rapid viscoanalysis (RVA, high-performance Liquid Chromatography (HPLC and gel permeation chromatography (GPC were used to characterize dextrins prepared by common neutral and thermostable α-amylase hydrolysis. The dextrin granules displayed irregular surfaces and were badly damaged by the enzyme treatment. They displayed A-type X-ray diffraction patterns with a decrease of intensity of the characteristic diffraction peaks. The RVA profiles showed that the viscosity of dextrin decreased with the increase of its Dextrose Equivalent (DE value. According to HPLC analysis, the molecular weight, degree of polymerization and the composition of oligosaccharides in dextrins were different.

  20. Radiological properties of MAGIC normoxic polymer gel dosimetry (United States)

    Aljamal, M.; Zakaria, A.; Shamsuddin, S.


    For a polymer gel dosimeter to be of use in radiation dosimetry, it should display water-equivalent radiological properties. In this study, the radiological properties of the MAGIC (Methacrylic and Ascorbic acid in Gelatin Initiated by Copper) normoxic polymer gels were investigated. The mass density (ρ) was determined based on Archimedes' principle. The weight fraction of elemental composition and the effective atomic number (Zeff) were calculated. The electron density was also measured with 90° scattering angle at room temperature. The linear attenuation coefficient (μ) of unirradiated gel, irradiated gel, and water were determined using Am-241 based on narrow beam geometry. Monte Carlo simulation was used to calculate the depth doses response of MAGIC gel and water for 6MV photon beam. The weight fractions of elements composition of MAGIC gel were close to that for water. The mass density was found to be 1027 ± 2 kg m-3, which is also very close to mass density of muscle tissue (1030 kg m-3) and 2.7% higher than that of water. The electron density (ρe) and atomic number (Zeff) were found to be 3.43 × 1029 e m-3 and 7.105, respectively. The electron density measured was 2.6% greater than that for water. The atomic number was very close to that for water. The prepared MAGIC gel was found to be water equivalent based on the study of element composition, mass density, electron density and atomic number. The linear attenuation coefficient of unirradiated gel was very close to that of water. The μ of irradiated gel was found to be linear with dose 2-40 Gy. The depth dose response for MAGIC gel from a 6 MV photon beam had a percentage dose difference to water of less than 1%. Therefore it satisfies the criteria to be a good polymer gel dosimeter for radiotherapy.

  1. Modeling chemoresponsive polymer gels. (United States)

    Kuksenok, Olga; Deb, Debabrata; Dayal, Pratyush; Balazs, Anna C


    Stimuli-responsive gels are vital components in the next generation of smart devices, which can sense and dynamically respond to changes in the local environment and thereby exhibit more autonomous functionality. We describe recently developed computational methods for simulating the properties of such stimuli-responsive gels in the presence of optical, chemical, and thermal gradients. Using these models, we determine how to harness light to drive shape changes and directed motion in spirobenzopyran-containing gels. Focusing on oscillating gels undergoing the Belousov-Zhabotinksy reaction, we demonstrate that these materials can spontaneously form self-rotating assemblies, or pinwheels. Finally, we model temperature-sensitive gels that encompass chemically reactive filaments to optimize the performance of this system as a homeostatic device for regulating temperature. These studies could facilitate the development of soft robots that autonomously interconvert chemical and mechanical energy and thus perform vital functions without the continuous need of external power sources.

  2. Equivalence principle and gravitational redshift. (United States)

    Hohensee, Michael A; Chu, Steven; Peters, Achim; Müller, Holger


    We investigate leading order deviations from general relativity that violate the Einstein equivalence principle in the gravitational standard model extension. We show that redshift experiments based on matter waves and clock comparisons are equivalent to one another. Consideration of torsion balance tests, along with matter-wave, microwave, optical, and Mössbauer clock tests, yields comprehensive limits on spin-independent Einstein equivalence principle-violating standard model extension terms at the 10(-6) level.

  3. Evaluation of different calibration curves QA of IMRT plans with radiochromic films; Evaluacion de diversas curvas de calibracion QA de planes de IMRT con peliculas radiocromicas

    Energy Technology Data Exchange (ETDEWEB)

    Hernandez Rodriguez, J.; Martin Rincon, C.; Garcia Repiso, S.; Ramos Paheo, J. A.; Verde Velasco, J. M.; Sena Espinel, E. de


    The non-linear relationship between dose and the optical density, characteristic plates radiochromic Gafchromic EBT and EBT2, has been studied by various authors, whose publications are proposed different functional forms that fit the specific values measured curves that allow the full range of useful dose calibration. The objective of the work focuses on evaluating the influence of the use of different calibration curves in the dose measurement for quality control of IMRT treatments. (Author)

  4. Testing statistical hypotheses of equivalence

    CERN Document Server

    Wellek, Stefan


    Equivalence testing has grown significantly in importance over the last two decades, especially as its relevance to a variety of applications has become understood. Yet published work on the general methodology remains scattered in specialists' journals, and for the most part, it focuses on the relatively narrow topic of bioequivalence assessment.With a far broader perspective, Testing Statistical Hypotheses of Equivalence provides the first comprehensive treatment of statistical equivalence testing. The author addresses a spectrum of specific, two-sided equivalence testing problems, from the

  5. Estimating equivalence with quantile regression (United States)

    Cade, B.S.


    Equivalence testing and corresponding confidence interval estimates are used to provide more enlightened statistical statements about parameter estimates by relating them to intervals of effect sizes deemed to be of scientific or practical importance rather than just to an effect size of zero. Equivalence tests and confidence interval estimates are based on a null hypothesis that a parameter estimate is either outside (inequivalence hypothesis) or inside (equivalence hypothesis) an equivalence region, depending on the question of interest and assignment of risk. The former approach, often referred to as bioequivalence testing, is often used in regulatory settings because it reverses the burden of proof compared to a standard test of significance, following a precautionary principle for environmental protection. Unfortunately, many applications of equivalence testing focus on establishing average equivalence by estimating differences in means of distributions that do not have homogeneous variances. I discuss how to compare equivalence across quantiles of distributions using confidence intervals on quantile regression estimates that detect differences in heterogeneous distributions missed by focusing on means. I used one-tailed confidence intervals based on inequivalence hypotheses in a two-group treatment-control design for estimating bioequivalence of arsenic concentrations in soils at an old ammunition testing site and bioequivalence of vegetation biomass at a reclaimed mining site. Two-tailed confidence intervals based both on inequivalence and equivalence hypotheses were used to examine quantile equivalence for negligible trends over time for a continuous exponential model of amphibian abundance. ?? 2011 by the Ecological Society of America.

  6. Magnetic fields are causing small, but significant changes of the radiochromic EBT3 film response to 6 MV photons. (United States)

    Delfs, Björn; Schoenfeld, Andreas A; Poppinga, Daniela; Kapsch, Ralf-Peter; Jiang, Ping; Harder, Dietrich; Poppe, Björn; Looe, Hui Khee


    The optical density (OD) of EBT3 radiochromic films (Ashland Specialty Ingredients, Bridgewater, NJ, USA) exposed to absorbed doses to water up to D  =  20 Gy in magnetic fields of B  =  0.35 and 1.42 T was measured in the three colour channels of an Epson Expression 10000XL flatbed scanner. A 7 cm wide water phantom with fixed film holder was placed between the pole shoes of a constant-current electromagnet with variable field strength and was irradiated by a 6 MV photon beam whose axis was directed at right angles with the field lines. The doses at the film position at water depth 5 cm were measured with a calibrated ionization chamber when the magnet was switched off and were converted to the doses in presence of the magnetic field via the monitor units and by a Monte Carlo-calculated correction accounting for the slight change of the depth dose curves in magnetic fields. In the presence of the 0.35 and 1.42 T fields small negative changes of the OD values at given absorbed doses to water occurred and just significantly exceeded the uncertainty margin given by the stochastic and the uncorrected systematic deviations. This change can be described by a  +2.1% change of the dose values needed to produce a given optical density in the presence of a 1.42 T field. The thereby modified OD versus D function remained unchanged irrespective of whether the original short film side-the preference direction of the monomer crystals of the film-was directed parallel or orthogonal to the magnetic field. The 'orientation effect', the difference between the optical densities measured in the 'portrait' or 'landscape' film positions on the scanner bed caused by the reflection of polarised light in the scanner's mirror system, remained unaltered after EBT3 film exposure in magnetic fields. An independent optical bench investigation of EBT3 films exposed to doses of 10 and 20 Gy at 0.35 and 1.42 T showed that the direction of the electric vector of polarised

  7. Dosimetric validation of a magnetic resonance image gated radiotherapy system using a motion phantom and radiochromic film. (United States)

    Lamb, James M; Ginn, John S; O'Connell, Dylan P; Agazaryan, Nzhde; Cao, Minsong; Thomas, David H; Yang, Yingli; Lazea, Mircea; Lee, Percy; Low, Daniel A


    Magnetic resonance image (MRI) guided radiotherapy enables gating directly on the target position. We present an evaluation of an MRI-guided radiotherapy system's gating performance using an MRI-compatible respiratory motion phantom and radiochromic film. Our evaluation is geared toward validation of our institution's clinical gating protocol which involves planning to a target volume formed by expanding 5 mm about the gross tumor volume (GTV) and gating based on a 3 mm window about the GTV. The motion phantom consisted of a target rod containing high-contrast target inserts which moved in the superior-inferior direction inside a body structure containing background contrast material. The target rod was equipped with a radiochromic film insert. Treatment plans were generated for a 3 cm diameter spherical planning target volume, and delivered to the phantom at rest and in motion with and without gating. Both sinusoidal trajectories and tumor trajectories measured during MRI-guided treatments were used. Similarity of the gated dose distribution to the planned, motion-frozen, distribution was quantified using the gamma technique. Without gating, gamma pass rates using 4%/3 mm criteria were 22-59% depending on motion trajectory. Using our clinical standard of repeated breath holds and a gating window of 3 mm with 10% target allowed outside the gating boundary, the gamma pass rate was 97.8% with 3%/3 mm gamma criteria. Using a 3 mm window and 10% allowed excursion, all of the patient tumor motion trajectories at actual speed resulting in at least 95% gamma pass rate at 4%/3 mm. Our results suggest that the device can be used to compensate respiratory motion using a 3 mm gating margin and 10% allowed excursion results in conjunction with repeated breath holds. Full clinical validation requires a comprehensive evaluation of tracking performance in actual patient images, outside the scope of this study. © 2017 The Authors. Journal of Applied Clinical Medical Physics

  8. SU-E-I-42: Measurement of X-Ray Beam Width and Geometric Efficiency in MDCT Using Radiochromic Films. (United States)

    Liillau, T; Liebmann, M; von Boetticher, H; Poppe, B


    The purpose of this work was to measure the x-ray beam width and geometric efficiency (GE) of a multi detector computed tomography scanner (MDCT) for different beam collimations using radiochromic films. In MDCT, the primary beam width extends the nominal beam collimation to irradiate the active detector elements uniformly (called 'over-beaming') which contributes to increased radiation dose to the patient compared to single detector CT. Therefore, the precise determination of the primary beam width and GE is of value for any CT dose calculation using Monte Carlo or analytical methods. Single axial dose profiles free in air were measured for 6 different beam collimations nT for a Siemens SOMATOM Sensation 64 Scanner with Gafchromic XR-QA2 films. The films were calibrated relative to the measured charge of a PTW semiflex ionization chamber (type: 31010) for a single rotation in the CT scanner at the largest available beam collimation of 28.8 mm. The beam energy for all measurements in this work was set to 120 kVp. For every measured dose profile and beam collimation the GEin-air and the full-width-at-half- maximum value (FWHM) as a value for the x-ray beam width was determined. Over-beaming factors FWHM / nT were calculated accordingly. For MDCT beam collimations from 7.2 (12×0.6 mm) to 28.8 (24×1.2 mm) the geometric efficiency was between 58 and 85 %. The over- beaming factor ranged from 1.43 to 1.11. For beam collimations of 1×5 mm and 1×10 mm the GE was 77 % and 84 % respectively. The over-beaming factors were close to 1, as expected. This work has shown that radiochromic films can be used for accurate x-ray beam width and geometric efficiency measurements due to their high spatial resolution. The measured free-in-air geometric efficiency and the over-beaming factor depend strongly on beam collimation. © 2012 American Association of Physicists in Medicine.

  9. Mechanically induced gel formation

    NARCIS (Netherlands)

    van Herpt, Jochem T.; Stuart, Marc C. A.; Browne, Wesley R.; Feringa, Ben L.


    Mechanical triggering of gelation of an organic solution by a carbazole-based bisurea organogelator is described. Both the duration of the mechanical stimulation and the gelator concentration control the gelation process and the characteristics of the gel obtained.

  10. Radiochromic and radiofluorogenic 3D solid polymer dosimeter: initial results for high doses

    DEFF Research Database (Denmark)

    Bernal Zamorano, Maria del Rocio; Sanders, Nicolai Højer; Lindvold, Lars René


    The complexity of dose distributions has increased with the advent of intensity modulated radiation therapy (IMRT). For that reason, experimental measurements using 3D dosimeters with high spatial resolution are required to check the delivered dose. In this study a new 3D solid polymer dosimeter...... with absorbance and fluorescence responses to radiation is presented. Measuring fluorescence instead of absorbance improves the spatial resolution and eases the read out of the dosimeter. The proposed dosimeter is tissue-equivalent and can be moulded in any shape by a controllable and fast photopolymerization...

  11. Preparation of chitosan gel


    Lagerge S.; Ben Salem R.; Elaloui E.; Mnasri N.; Moussaoui Y.; de Menorval L. C.


    Aerogel conditioning of the chitosan makes it possible to prepare porous solids of significant specific surface. The increase in the chitosan concentration or the degree of acetylation decreases the specific surface of the synthesized chitosan gel. Whereas drying with supercritical CO2 more effectively makes it possible to preserve the volume of the spheres of gel and to have a more significant specific surface in comparison with evaporative drying.

  12. Mechanochromic photonic gels. (United States)

    Chan, Edwin P; Walish, Joseph J; Urbas, Augustine M; Thomas, Edwin L


    Polymer gels are remarkable materials with physical structures that can adapt significantly and quite rapidly with changes in the local environment, such as temperature, light intensity, electrochemistry, and mechanical force. An interesting phenomenon observed in certain polymer gel systems is mechanochromism - a change in color due to a mechanical deformation. Mechanochromic photonic gels are periodically structured gels engineered with a photonic stopband that can be tuned by mechanical forces to reflect specific colors. These materials have potential as mechanochromic sensors because both the mechanical and optical properties are highly tailorable via incorporation of diluents, solvents, nanoparticles, or polymers, or the application of stimuli such as temperature, pH, or electric or strain fields. Recent advances in photonic gels that display strain-dependent optical properties are discussed. In particular, this discussion focuses primarily on polymer-based photonic gels that are directly or indirectly fabricated via self-assembly, as these materials are promising soft material platforms for scalable mechanochromic sensors. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Adapalene gel 0.1%: effective and well tolerated in the topical treatment of acne vulgaris in Chinese patients. (United States)

    Zhu, X J; Tu, P; Zhen, J; Duan, Y Q


    Acne vulgaris is a common dermatologic disease in Asian populations, as well as in Caucasians. Our objective was to evaluate the safety and efficacy of adapalene gel 0.1% in comparison with tretinoin gel 0.025% in Chinese patients with acne vulgaris. We used an 8-week, multicenter, randomized, controlled, investigator-masked, parallel group design study of adapalene gel 0.1% and tretinoin gel 0.025% in 150 Chinese patients with mild-to-moderate acne vulgaris. Our results showed that adapalene gel 0.1% had efficacy equivalent to tretinoin gel 0.025% against acne lesions in Chinese patients, with a more acceptable tolerability profile.


    Energy Technology Data Exchange (ETDEWEB)

    Randall S. Seright


    This report describes work performed during the third and final year of the project, ''Conformance Improvement Using Gels.'' Corefloods revealed throughput dependencies of permeability reduction by polymers and gels that were much more prolonged during oil flow than water flow. This behavior was explained using simple mobility ratio arguments. A model was developed that quantitatively fits the results and predicts ''clean up'' times for oil productivity when production wells are returned to service after application of a polymer or gel treatment. X-ray computed microtomography studies of gels in strongly water-wet Berea sandstone and strongly oil-wet porous polyethylene suggested that oil penetration through gel-filled pores occurs by a gel-dehydration mechanism, rather than gel-ripping or gel-displacement mechanisms. In contrast, analysis of data from the University of Kansas suggests that the gel-ripping or displacement mechanisms are more important in more permeable, strongly water-wet sandpacks. These findings help to explain why aqueous gels can reduce permeability to water more than to oil under different conditions. Since cement is the most commonly used material for water shutoff, we considered when gels are preferred over cements. Our analysis and experimental results indicated that cement cannot be expected to completely fill (top to bottom) a vertical fracture of any width, except near the wellbore. For vertical fractures with apertures less than 4 mm, the cement slurry will simply not penetrate very far into the fracture. For vertical fractures with apertures greater than 4 mm, the slurry may penetrate a substantial distance into the bottom part of the fracture. However, except near the wellbore, the upper part of the fracture will remain open due to gravity segregation. We compared various approaches to plugging fractures using gels, including (1) varying polymer content, (2) varying placement (extrusion) rate

  15. Polymer gel dosimeters with PVA-GA matrix. (United States)

    Abtahi, Seyed Mohammad Mahdi; Sadeghi Abandansari, Hamid


    Properties of a new polymer gel with cross-linked polyvinyl alcohol as a gelatinous matrix were investigated. The new polymer gel dosimeter was named PVABAT. The irradiation was performed using a calibrated 60Co beam. The dose responses of the PVABAT formulations were quantified with MRI transverse relaxation rate (R2) measurements. The results show that the PVABAT gel responds linearly to the absorbed dose for doses from 30 up to 45 Gy. The maximal amount of [Formula: see text] of PVABAT polymer gel dosimeter was about 0.19 Gy which was indicated on a better resolution in comparison with previously reported acrylamide-based polymer gel dosimeters formulations. Furthermore, the gel response remains stable in the investigated time (192 h) after the irradiation. The effective atomic number and electron density of the new gel showed a maximum difference of 3.2 and 2% with soft tissue respectively. The melting point also increased significantly for new formulation. Furthermore, the new gel formulation has an elemental tissue equivalency for dosimetry applications involving nuclear reactions.

  16. Full Static Output Feedback Equivalence

    Directory of Open Access Journals (Sweden)

    Aristotle G. Yannakoudakis


    Full Text Available We present a constructive solution to the problem of full output feedback equivalence, of linear, minimal, time-invariant systems. The equivalence relation on the set of systems is transformed to another on the set of invertible block Bezout/Hankel matrices using the isotropy subgroups of the full state feedback group and the full output injection group. The transformation achieving equivalence is calculated solving linear systems of equations. We give a polynomial version of the results proving that two systems are full output feedback equivalent, if and only if they have the same family of generalized Bezoutians. We present a new set of output feedback invariant polynomials that generalize the breakaway polynomial of scalar systems.

  17. The paradox of energy equivalence


    Isaac, Nick J. B.; Storch, David; Carbone, Chris


    Energy equivalence, the notion that population energy flux is independent of body mass, has become a key concept in ecology. We argue that energy equivalence is not an ecological ‘rule’, as claimed, but a flawed concept beset by circular reasoning. In fact, the independence of mass and energy flux is a null hypothesis. We show that our mechanistic understanding of size–density relationships (SDRs) follows directly from this null model and the assumption that energy limits abundance. Paradoxic...

  18. SU-E-T-150: The Basic Dosimetric Properties of NIPAM Polymer Gel Dosimeter. (United States)

    Pak, F; Farajollahi, A; Miabi, Z


    To asses a series of basic dosimetric properties such as reproducibility, linearity, tissue equivalency, dose rate and energy independency for NIPAM polymer gel dosimeter. The NIPAM gel was manufactured according to the method, described by senden et al (2006). The gels were irradiated approximately 2 h after manufacturing and MR images of the gel were made 24 h after irradiation. Transverse relaxation rates (R2=T2?1 ) were obtained from the signal decay data using the proper data analyzer. In order to investigate the absorbed dose response reproducibility, the experiment was repeated three times using the same batch of monomer, irradiation method, scanning parameters and conditions, also with analyzing two set of the gel with different batches of chemical the effect of different batches were investigated . For assessing if the NIPAM gel dosimeter response is dependent on different photon energies, two sets of NIPAM gel were irradiated using a 9 MV linear accelerator and a 60co. The effect of different dose rate on gel response was studied in SSD of 80, 90, 100, 110 and 120 and radiation beam were calibrated to give 5Gy in each SSD. To investigate the linearity of the gel, the vials were irradiated from 1 to 35 Gy. In order to verify tissue equivalency, effective atomic number and relative electron density of NIPAM dosimeter were calculated using CT number, and compared with tissue. This polymer gel found to be tissue equivalent. The results showed that the dose response of NIPAM polymer gel is highly reproducible in same and different batches of chemical and its response was linear up to 26 Gy. Energy and dose rate had no effect on NIPAM gel response. NIPAM gel dosimeter appears to be a promising dosimeter in all aspects of dosimetric properties which were assessed in this study. © 2012 American Association of Physicists in Medicine.

  19. Spatially resolved multicomponent gels (United States)

    Draper, Emily R.; Eden, Edward G. B.; McDonald, Tom O.; Adams, Dave J.


    Multicomponent supramolecular systems could be used to prepare exciting new functional materials, but it is often challenging to control the assembly across multiple length scales. Here we report a simple approach to forming patterned, spatially resolved multicomponent supramolecular hydrogels. A multicomponent gel is first formed from two low-molecular-weight gelators and consists of two types of fibre, each formed by only one gelator. One type of fibre in this ‘self-sorted network’ is then removed selectively by a light-triggered gel-to-sol transition. We show that the remaining network has the same mechanical properties as it would have done if it initially formed alone. The selective irradiation of sections of the gel through a mask leads to the formation of patterned multicomponent networks, in which either one or two networks can be present at a particular position with a high degree of spatial control.

  20. Gel electrolytes and electrodes

    Energy Technology Data Exchange (ETDEWEB)

    Fleischmann, Sven; Bunte, Christine; Mikhaylik, Yuriy V.; Viner, Veronika G.


    Gel electrolytes, especially gel electrolytes for electrochemical cells, are generally described. In some embodiments, the gel electrolyte layers comprise components a) to c). Component a) may be at least one layer of at least one polymer comprising polymerized units of: a1) at least one monomer containing an ethylenically unsaturated unit and an amido group and a2) at least one crosslinker. Component b) may be at least one conducting salt and component c) may be at least one solvent. Electrodes may comprise the components a), d) and e), wherein component a) may be at least one layer of at least one polymer as described herein. Component d) may be at least one electroactive layer and component e) may be at least one ceramic layer. Furthermore, electrochemical cells comprising component a) which may be at least one layer of at least one polymer as described herein, are also provided.

  1. Active Polymer Gel Actuators

    Directory of Open Access Journals (Sweden)

    Shuji Hashimoto


    Full Text Available Many kinds of stimuli-responsive polymer and gels have been developed and applied to biomimetic actuators or artificial muscles. Electroactive polymers that change shape when stimulated electrically seem to be particularly promising. In all cases, however, the mechanical motion is driven by external stimuli, for example, reversing the direction of electric field. On the other hand, many living organisms can generate an autonomous motion without external driving stimuli like self-beating of heart muscles. Here we show a novel biomimetic gel actuator that can walk spontaneously with a wormlike motion without switching of external stimuli. The self-oscillating motion is produced by dissipating chemical energy of oscillating reaction. Although the gel is completely composed of synthetic polymer, it shows autonomous motion as if it were alive.

  2. Spatially resolved multicomponent gels. (United States)

    Draper, Emily R; Eden, Edward G B; McDonald, Tom O; Adams, Dave J


    Multicomponent supramolecular systems could be used to prepare exciting new functional materials, but it is often challenging to control the assembly across multiple length scales. Here we report a simple approach to forming patterned, spatially resolved multicomponent supramolecular hydrogels. A multicomponent gel is first formed from two low-molecular-weight gelators and consists of two types of fibre, each formed by only one gelator. One type of fibre in this 'self-sorted network' is then removed selectively by a light-triggered gel-to-sol transition. We show that the remaining network has the same mechanical properties as it would have done if it initially formed alone. The selective irradiation of sections of the gel through a mask leads to the formation of patterned multicomponent networks, in which either one or two networks can be present at a particular position with a high degree of spatial control.

  3. Antibacterial Inhibitory Effects ofPunica GranatumGel on Cariogenic Bacteria: Anin vitroStudy. (United States)

    Millo, Grazielle; Juntavee, Apa; Ratanathongkam, Ariya; Nualkaew, Natsajee; Peerapattana, Jomjai; Chatchiwiwattana, Supaporn


    This study evaluated the in vitro antibacterial effects of the formulated Punica granatum (PG) gel against Streptococcus mutans, Streptococcus sanguinis, and Lactobacillus casei. The PG extract was dissolved in water at 500 mg/mL. High performance liquid chromatography (HPLC) was used for identification and quantification of chemical marker punicalagin. Minimum bactericidal concentration (MBC) and time-kill assay (TKA) were investigated. Antibacterial activities of the formulated PG gel, 2% chlorhexidine (CHX) gel and blank gel were tested by measuring the zones of inhibition through agar well diffusion method. The HPLC results showed presence of punicalagin at 2023.58 ± 25.29 pg/mL in the aqueous PG extract and at 0.234% (w/w) in the formulated PG gel. The MBC for S. mutans, S. Sanguinis, and L. casei were 250, 125, and 500 mg/mL respectively. The TKA of 500 mg/mL aqueous PG extract showed total inhibition of S. mutans, S. Sanguinis, and L. casei at 6, 1, and 24 hours contact time respectively. Agar well diffusion revealed that for S. mutans, CHX gel > PG gel > blank gel; for S. sanguinis, CHX gel = PG gel > blank gel; for L. casei, CHX gel > PG gel = blank gel. Comparison of the PG gel potency showed that S. sanguinis = S. mutans > L. casei. The PG gel equivalent to 0.234% punicalagin (w/w) inhibited S. mutans and S. sanguinis but not L. casei within 24 hours incubation period and has the potential to be used for caries prevention. Millo G, Juntavee A, Ratanathongkam A, Nualkaew N, Peerapattana J, Chatchiwiwattana S. Antibacterial Inhibitory Effects of Punica Granatum Gel on Cariogenic Bacteria: An in vitro Study. Int J Clin Pediatr Dent 2017;10(2):152-157.

  4. Matching of equivalent field regions

    DEFF Research Database (Denmark)

    Appel-Hansen, Jørgen; Rengarajan, S.B.


    screen, having the same homogeneous medium on both sides and an impressed current on one aide, an alternative procedure is relevant. We make use of the fact that in the aperture the tangential component of the magnetic field due to the induced currents in the screen is zero. The use of such a procedure......In aperture problems, integral equations for equivalent currents are often found by enforcing matching of equivalent fields. The enforcement is made in the aperture surface region adjoining the two volumes on each side of the aperture. In the case of an aperture in a planar perfectly conducting...... shows that equivalent currents can be found by a consideration of only one of the two volumes into which the aperture plane divides the space. Furthermore, from a consideration of an automatic matching at the aperture, additional information about tangential as well as normal field components...

  5. Equivalent linearization of nonlinear forces (United States)

    Meng, Guang; Xue, Zhongqing


    A method used for equivalent linearization of the two orthogonal squeeze-film forces is extended here to the general case of n degrees of freedom and n components of nonlinear forces, and the expressions for equivalent linear coefficients are derived. Nonlinear forces can be linearized by the methods of Fourier expansion, active and reactive powers, or mean-square error. The n components of nonlinear forces can all be expressed formally as the sum of an average force, a linear spring force, and a linear damping force. This paper also gives a flow chart for calculating the steady-state responses of a nonlinear system with many degrees of freedom, using the method of equivalent linearization. The resulting saving in computation time is demonstrated by a numerical example of a flexible rotor-bearing system with a noncentralized squeeze-film damper.

  6. In vivo dosimetry in intraoperative electron radiotherapy. microMOSFETs, radiochromic films and a general-purpose linac

    Energy Technology Data Exchange (ETDEWEB)

    Lopez-Tarjuelo, Juan; Marco-Blancas, Noelia de; Santos-Serra, Agustin; Quiros-Higueras, Juan David [Consorcio Hospitalario Provincial de Castellon, Servicio de Radiofisica y Proteccion Radiologica, Castellon de la Plana (Spain); Bouche-Babiloni, Ana; Morillo-Macias, Virginia; Ferrer-Albiach, Carlos [Consorcio Hospitalario Provincial de Castellon, Servicio de Oncologia Radioterapica, Castellon de la Plana (Spain)


    In vivo dosimetry is desirable for the verification, recording, and eventual correction of treatment in intraoperative electron radiotherapy (IOERT). Our aim is to share our experience of metal oxide semiconductor field-effect transistors (MOSFETs) and radiochromic films with patients undergoing IOERT using a general-purpose linac. We used MOSFETs inserted into sterile bronchus catheters and radiochromic films that were cut, digitized, and sterilized by means of gas plasma. In all, 59 measurements were taken from 27 patients involving 15 primary tumors (seven breast and eight non-breast tumors) and 12 relapses. Data were subjected to an outliers' analysis and classified according to their compatibility with the relevant doses. Associations were sought regarding the type of detector, breast and non-breast irradiation, and the radiation oncologist's assessment of the difficulty of detector placement. At the same time, 19 measurements were carried out at the tumor bed with both detectors. MOSFET measurements (D = 93.5 %, s{sub D} = 6.5 %) were not significantly shifted from film measurements (D = 96.0 %, s{sub D} = 5.5 %; p = 0.109), and no associations were found (p = 0.526, p = 0.295, and p = 0.501, respectively). As regards measurements performed at the tumor bed with both detectors, MOSFET measurements (D = 95.0 %, s{sub D} = 5.4 %) were not significantly shifted from film measurements (D = 96.4 %, s{sub D} = 5.0 %; p = 0.363). In vivo dosimetry can produce satisfactory results at every studied location with a general-purpose linac. Detector choice should depend on user factors, not on the detector performance itself. Surgical team collaboration is crucial to success. (orig.) [German] Die In-vivo-Dosimetrie ist wuenschenswert fuer die Ueberpruefung, Registrierung und die eventuelle Korrektur der Behandlungen in der IOERT (''Intraoperative Electron Radiation Therapy''). Unser Ziel ist die Veroeffentlichung unserer Erfahrungen beim

  7. Calibration in water films GAFCHROMIC EBT radiochromic-2. Effects of Drying; Calibracion en agua de las peliculas radiocromicas Gafchromic EBT-2. Efectos de Secado

    Energy Technology Data Exchange (ETDEWEB)

    Herrero, C.; Perez-Alija, J.; Alaman, C.; Almansa, J.; Vilches, M.


    Recent studies [1] show that immersion in water GAFCHROMIC EBT radiochromic film-2 has on these two effects: a progressive diffusion of water across its borders (fact which tells us the manufacturer and the effect of which we can avoid choosing a proper analysis region) and a uniform moisture through the polyester film, producing a variation in the measurement of optical density (OD) of the film. The latter effect is negligible for immersion times of less than 30 minutes. We study the effect of hydration and drying in these films when they have been submerged for 24 hours.

  8. SU-F-T-573: Evaluation of EBT-XD Radiochromic Films for Verification of SBRT and SRS Treatment Delivery

    Energy Technology Data Exchange (ETDEWEB)

    Aubry, J; Zerouali, K [Centre hospitalier de l’Universite de Montreal, Montreal, Quebec (Canada)


    Purpose: To evaluate the accuracy and precision of radiochromic films EBT-XD for quality control of stereotaxic body radiation therapy (SBRT) and stereotactic radiosurgery (SRS) plan delivery. Methods: A film cut in 3×10 cm2 strips was irradiated from 0 to 20 Gy in increments of 1 to 1.5 Gy using a 15 MeV electron beam. Triple-channel film calibration was completed 24 hours later by scanning the film strips on an Epson 10000XL scanner using a well-defined protocol. Several dose measurements of increasing complexity were subsequently performed with Varian iX accelerators. Pieces of films were first irradiated in a solid water phantom with 6 MV photon beams and a static gantry to doses spanning the calibration range, either in a single field or multiple fields setup. High dose (>15 Gy per fraction) IMRT plans were then measured. Finally films were irradiated with volumetric modulated arc therapy (VMAT) plans of lung and spinal lesions with prescribed doses per fraction between 8 and 20 Gy. The dose measured with the films was compared to the calculated dose from the Eclipse planning system using the Anisotropic Analytical Algorithm (AAA). Results: 77 dose measurements were compared to either ion chamber measurements or dose calculations (reference). The average dose difference between film measurements and reference was 0.7 % and the standard deviation was 1.3%. The maximum and minimum dose differences were +3.5% and −2% in the 4 Gy to 20 Gy range. Measured dose profiles of lung and vertebra treatment plans agreed very well with the calculations. Conclusion: EBT-XD films are a useful dosimeter for quality control of SBRT and SRS plan delivery. The measurement of a full 2D dose plane with high spatial resolution and acceptable dose accuracy make it an advantageous choice compared to other detectors such as ion chambers or diodes.

  9. Comparison of small photon beams measured using radiochromic and silver-halide films in solid water phantoms. (United States)

    Zeidan, Omar A; Li, Jonathan G; Low, Daniel A; Dempsey, James F


    In this study, we compared the dosimetric properties of four of the most commonly used films for megavoltage photon-beam dosimetry when irradiated under identical conditions by small multileaf-collimator (MLC) defined beamlets. Two silver-halide films (SHFs), Kodak XV2 and EDR2, and two radiochromic films (RCFs), Gafchromic HS and MD55-2, were irradiated by MLC-defined 1 x 1 cm2 beamlets from a Varian 2100 C/D linac equipped with a 120-leaf MLC. The beamlets were delivered with the accelerator gantry set laterally (90 degrees rotation) upon a solid-water compression film phantom at 100 cm source-to-surface distance which was positioned with the films parallel to the beam axis. Beamlets were delivered at central axis, 5.0 cm, and 10.5 cm off-axis for both leaf-end and leaf-side defined beamlets. The film dosimetry was performed using a quantitative optical density (OD) imaging system that was validated in a previous study. No significant differences between SHF and RCF measurements were observed in percentage depth doses, horizontal depth profiles, or two-dimension spatial isodose distributions in both the central axis and off-axis measurements. We found that regardless of the type of film used, RCF or SHF, a consistent data set for small beam dose modeling was generated. Previous validation studies based on the use of RCF and OD imaging system would indicate that all film produce an accurate result for small beam characterization.

  10. SU-E-T-44: Angular Dependence of Surface Dose Enhancement Measured On Several Inhomogeneities Using Radiochromic EBT3 Films

    Energy Technology Data Exchange (ETDEWEB)

    Jansen, A; Schoenfeld, A; Poppinga, D; Chofor, N; Poppe, B [University of Oldenburg, Oldenburg (Germany); Pius Hospital Oldenburg, Oldenburg (Germany)


    Purpose: The quantification of the relative surface dose enhancement in dependence on the angle of incidence and the atomic number Z of the surface material. Methods: Experiments were performed with slabs made of aluminum, titanium, copper, silver, dental gold and lead. The metal slabs with equal sizes of 1.0×8.0×8.8mm{sup 3} were embedded in an Octavius 4D phantom (PTW Freiburg, Germany). Radiochromic EBT3 films were used to measure the surface dose for angles of incidence ranging from 0° to 90°. The setup with the metals slabs at the isocenter was irradiated with acceleration voltages of 6MV and 10MV. Water reference measurements were taken under equal conditions. Results: The surface dose enhancement is highest for angles of incidence below 30° and drops significantly for higher. The surface dose enhancement produced by lead and dental gold at 6MV showed a peak of 65%. At 90°, the surface dose enhancement dropped to 15% for both materials. The surface dose enhancements for silver, copper, titanium and aluminum were 45%, 32%, 22% and 12% at 0°, respectively. At an angle of incidence of 80°, the values dropped to 22%, 18%, 12% und 6%. The values for 10MV were very similar. Lead and dental gold showed peaks of 65% und 60%. Their values dropped to 18% at an angle of 90°. The surface dose enhancements for silver, copper, titanium and aluminum were 45%, 30%, 20% and 8% at 0°. At 80° the values dropped to 30%, 20%, 12% and 5%. A dependence of the magnitude of the surface dose enhancement on the atomic number of the surface material can be seen, which is in consistence with literature. Conclusion: The results show that the surface dose enhancements near implant materials with high Z-values should be taken into consideration in radio therapy, even when the angle of incidence is flat.

  11. TNT Equivalency of Bulk Nitrocellulose (United States)


    Whien Dato Enlotod) &,1W SUMMARY Nitrocellulose, 13.157 nitrogen MIL-N-244A Grade C (Lot number RAD78F0015027) was detonated in configurations...weight factored out, the calculated TNT equivalencies were tabularized and plotted as functions of sample scaled distance. TEST RESULTS Data sheets for

  12. Comments on field equivalence principles

    DEFF Research Database (Denmark)

    Appel-Hansen, Jørgen


    It is pointed Out that often-used arguments based on a short-circuit concept in presentations of field equivalence principles are not correct. An alternative presentation based on the uniqueness theorem is given. It does not contradict the results obtained by using the short-circuit concept...


    Directory of Open Access Journals (Sweden)

    Cristina, Chifane


    Full Text Available This paper aims at highlighting the fact that “equivalence” represents a concept worth revisiting and detailing upon when tackling the translation process of economic texts both from English into Romanian and from Romanian into English. Far from being exhaustive, our analysis will focus upon the problems arising from the lack of equivalence at the word level. Consequently, relevant examples from the economic field will be provided to account for the following types of non-equivalence at word level: culturespecific concepts; the source language concept is not lexicalised in the target language; the source language word is semantically complex; differences in physical and interpersonal perspective; differences in expressive meaning; differences in form; differences in frequency and purpose of using specific forms and the use of loan words in the source text. Likewise, we shall illustrate a number of translation strategies necessary to deal with the afore-mentioned cases of non-equivalence: translation by a more general word (superordinate; translation by a more neutral/less expressive word; translation by cultural substitution; translation using a loan word or loan word plus explanation; translation by paraphrase using a related word; translation by paraphrase using unrelated words; translation by omission and translation by illustration.

  14. Biopolymer gels containing fructooligosaccharides. (United States)

    Silva, Karen Cristina Guedes; Sato, Ana Carla Kawazoe


    The influence of the addition of fructooligosaccharide (FOS) in an external gelated alginate/gelatin biopolymer matrix, was evaluated in order to produce biopolymeric structures with functional effects. Solutions were characterized regarding their rheological properties, macrogels regarding their microstructure and mechanical properties and microgels were characterized in relation to their particle size distribution and morphology. Close relationship was found between the microstructure, rheological and mechanical properties of the biopolymeric systems. An increased viscosity and accentuated elastic and pseudoplastic behavior were associated to denser microstructures. The FOS addition caused changes in the evaluated properties, resulting in more cohesive structures, with smaller pores and higher viscosity, compared to alginate-gelatin gels. The addition of 3% FOS to biopolymeric system provided an optimal condition, allowing the formation of stronger gels, with smaller pores and beads with smaller sizes, indicating the potential use of these functional systems as texture modifiers or encapsulation systems. Copyright © 2017 Elsevier Ltd. All rights reserved.

  15. GelTouch

    DEFF Research Database (Denmark)

    Miruchna, Viktor; Walter, Robert; Lindlbauer, David


    activation techniques: 1) Indium Tin Oxide (ITO) as a heating element that enables tactile feedback through individually addressable taxels; 2) predefined tactile areas of engraved ITO, that can be layered and combined; 3) complex arrangements of resistance wire that create thin tactile edges. We present...... a tablet with 6x4 tactile areas, enabling a tactile numpad, slider, and thumbstick. We show that the gel is up to 25 times stiffer when activated and that users detect tactile features reliably (94.8%)....

  16. Chiromagnetic nanoparticles and gels (United States)

    Yeom, Jihyeon; Santos, Uallisson S.; Chekini, Mahshid; Cha, Minjeong; de Moura, André F.; Kotov, Nicholas A.


    Chiral inorganic nanostructures have high circular dichroism, but real-time control of their optical activity has so far been achieved only by irreversible chemical changes. Field modulation is a far more desirable path to chiroptical devices. We hypothesized that magnetic field modulation can be attained for chiral nanostructures with large contributions of the magnetic transition dipole moments to polarization rotation. We found that dispersions and gels of paramagnetic Co3O4 nanoparticles with chiral distortions of the crystal lattices exhibited chiroptical activity in the visible range that was 10 times as strong as that of nonparamagnetic nanoparticles of comparable size. Transparency of the nanoparticle gels to circularly polarized light beams in the ultraviolet range was reversibly modulated by magnetic fields. These phenomena were also observed for other nanoscale metal oxides with lattice distortions from imprinted amino acids and other chiral ligands. The large family of chiral ceramic nanostructures and gels can be pivotal for new technologies and knowledge at the nexus of chirality and magnetism.

  17. Equivalent statistics and data interpretation. (United States)

    Francis, Gregory


    Recent reform efforts in psychological science have led to a plethora of choices for scientists to analyze their data. A scientist making an inference about their data must now decide whether to report a p value, summarize the data with a standardized effect size and its confidence interval, report a Bayes Factor, or use other model comparison methods. To make good choices among these options, it is necessary for researchers to understand the characteristics of the various statistics used by the different analysis frameworks. Toward that end, this paper makes two contributions. First, it shows that for the case of a two-sample t test with known sample sizes, many different summary statistics are mathematically equivalent in the sense that they are based on the very same information in the data set. When the sample sizes are known, the p value provides as much information about a data set as the confidence interval of Cohen's d or a JZS Bayes factor. Second, this equivalence means that different analysis methods differ only in their interpretation of the empirical data. At first glance, it might seem that mathematical equivalence of the statistics suggests that it does not matter much which statistic is reported, but the opposite is true because the appropriateness of a reported statistic is relative to the inference it promotes. Accordingly, scientists should choose an analysis method appropriate for their scientific investigation. A direct comparison of the different inferential frameworks provides some guidance for scientists to make good choices and improve scientific practice.

  18. Verification of an algorithm of cono collapsed through the IAEA TECDOC 1583 protocol and dosimetry with radiochromic films; Verificacion de un algoritmo de cono colapso mediante en protocolo IAEA TECDOC 1583 y dosimetria con peliculas radiocromicas

    Energy Technology Data Exchange (ETDEWEB)

    Martin-Viera Cueto, J. A.; Benitez Villegas, E. M.; Bodineau Gil, C.; Parra Osorio, V.; Garcia Pareja, S.; Casado Villalon, F. J.


    The objective of this study is to verify the characterization of the collapsed cone algorithm of an SP using this Protocol. In addition, given that it only offers details of dose values measured at discrete points, measures are complemented by a gamma test distributions 2D of doses in different cases using film radiochromic. (Author)

  19. Dosimetric comparison between a planning system and Radiochromic-EBT2 films in surface brachytherapy treatments of high rate; Comparacion dosimetrica entre un sistema de planificacion y peliculas radiocromicas EBT2 en tratamientos de braquiterapia superficial de alta tasa

    Energy Technology Data Exchange (ETDEWEB)

    Gutierrez Ramos, S. M.; Carrasco Herrera, M. a.; Vicent, D.; Rodriguez, C.; Herrador, M.


    The objective of this work is to study a situation in which, the accuracy of the calculation of the planner may be limited, superficial brachytherapy treatment. It has relative to the dose obtained with the planner with that obtained with film radiochromic EBT2. (Author)

  20. Assessment of the factors field for fields small of a throttle lineal multienergetic by diodes and radiochromic film; Evaluacion de los factores campo pra campos pequalos de un acelerador lineal multienergetico mediante diodos y pelicul radiocromica

    Energy Technology Data Exchange (ETDEWEB)

    Ramirez-Ros, J.; Garcia-Marcos, R.; Huertas Martinez, M. c.; Hurtado Sanchez, A.


    We discuss the field factors obtained for a linear accelerator electron multi energetic with irradiation standard modes and flatter unfiltered. We compared the values obtained with several diodes, two chambers of ionization and film radiochromic We obtain correction factors for diodes and. Finally, we evaluate the Daisy-Chain method, depending on the detector and the field of step. (Author)

  1. Equivalence relations of AF-algebra extensions

    Indian Academy of Sciences (India)

    In this paper, we consider equivalence relations of *-algebra extensions and describe the relationship between the isomorphism equivalence and the unitary equivalence. We also show that a certain group homomorphism is the obstruction for these equivalence relations to be the same.

  2. SU-F-T-570: Comparison of Synthetic Diamond, Microionization Chamber, and Radiochromic Film for Absolute Dosimetry of VMAT Radiosurgery

    Energy Technology Data Exchange (ETDEWEB)

    Popple, R; Wu, X; Kraus, J; Thomas, E; Brezovich, I [The University of Alabama at Birmingham, Birmingham, AL (United States)


    Purpose: Patient specific quality assurance of stereotactic radiosurgery (SRS) plans is challenging because of small target sizes and high dose gradients. We compared three detectors for dosimetry of VMAT SRS plans. Methods: The dose at the center of seventeen targets was measured using a synthetic diamond detector (2.2 mm diameter, 1 µm thickness), a 0.007 cm{sup 3} ionization chamber, and radiochromic film. Measurements were made in a PMMA phantom in the clinical geometry – all gantry and table angles were delivered as planned. The diamond and chamber positions were offset by 1 cm from the film plane, so the isocenter was shifted accordingly to place the center of the target at the detector of interest. To ensure accurate detector placement, the phantom was positioned using kV images. To account for the shift-induced difference in geometry and differing prescription doses between plans, the measurements were normalized to the expected dose calculated by the treatment planning system. Results: The target sizes ranged from 2.8 mm to 34.8 mm (median 14.8 mm). The mean measurement-to-plan ratios were 1.054, 1.076, and 1.023 for RCF, diamond, and chamber, respectively. The mean difference between the chamber and film was −3.2% and between diamond and film was 2.2%. For targets larger than 15 mm, the mean difference relative to film was −0.8% and 0.1% for chamber and diamond, respectively, whereas for targets smaller than 15 mm, the difference was −5.3% and 4.2% for chamber and diamond, respectively. The difference was significant (p=0.005) using the two-sample Kolmogorov-Smirnov test. Conclusion: The detectors agree for target sizes larger than 15 mm. Relative to film, for smaller targets the diamond detector over-responds, whereas the ionization chamber under-responds. Further work is needed to characterize detector response in modulated SRS fields.

  3. SU-E-T-122: Dose Response Analysis of Radiochromic Films in Regions of Low Dose Using Separation Color Components. (United States)

    Marini, G; Nicolucci, P


    To evaluate the dose response of EBT2 films in regions of low dose using the decomposition of the image's color channels (RGB, Red, Green and Blue). Doses ranging from 1 Gy to 60 Gy were used to calibrate the dose response of Gafchromic ® EBT2 films irradiated in 6MV photons beams. Segments of film with dimensions of 8.5 cm × 8.5 cm were used. Another segment of film with dimensions 8.5 cm × 20.25 cm was also irradiated with a maximum dose of 4Gy to determine the percentage depth dose (PDD). The films were digitized by a LaserJet M1132 MFP - HP ® scanner in standard resolution of 150dpi and analyzed by a routine created in MatLab to convert the image to gray levels as well as assess the desired color components from the image. The green component presented the higher sensitivity (17.8 a.u./Gy) when the separated color channels and the shades of gray analysis are compared. The red component presented the highest signal to noise ratio in the low dose range (63% at 1Gy). The blue component presented low sensitivity (0.66 a.u./Gy) in the entire dose range. A linear fitting (r=0.998) was used to the green and gray components until a dose of 4 Gy. The red component presented a non-linear behavior in the entire dose range. The useful dose range found was from 1 Gy to 15 Gy. The maximum differences between the reference PDD, measured with ionization chamber in a water phantom, and the PDDs determined with film were 6%, 9% and 14% for the green, gray and red components, respectively. This work results show that the use of radiochromic films on planning verification procedures in low dose ranges can be benefit from the analysis of the image's separated color components. © 2012 American Association of Physicists in Medicine.

  4. SU-F-BRF-13: Investigating the Feasibility of Accurate Dose Measurement in a Deforming Radiochromic Dosimeter

    Energy Technology Data Exchange (ETDEWEB)

    Juang, T [Medical Physics Graduate Program, Duke University Medical Center, Durham, NC (United States); Adamovics, J [Rider University, Skillman, NJ (United States); Oldham, M [Duke University Medical Center, Durham, NC (United States)


    Purpose: Presage-Def, a deformable radiochromic 3D dosimeter, has been previously shown to have potential for validating deformable image registration algorithms. This work extends this effort to investigate the feasibility of using Presage-Def to validate dose-accumulation algorithms in deforming structures. Methods: Two cylindrical Presage-Def dosimeters (8cm diameter, 4.5cm length) were irradiated in a water-bath with a simple 4-field box treatment. Isocentric dose was 20Gy. One dosimeter served as control (no deformation) while the other was laterally compressed during irradiation by 21%. Both dosimeters were imaged before and after irradiation with a fast (∼10 minutes for 1mm isotropic resolution), broad beam, high resolution optical-CT scanner. Measured dose distributions were compared to corresponding distributions calculated by a commissioned Eclipse planning system. Accuracy in the control was evaluated with 3D gamma (3%/3mm). The dose distribution calculated for the compressed dosimeter in the irradiation geometry cannot be directly compared via profiles or 3D gamma to the measured distribution, which deforms with release from compression. Thus, accuracy under deformation was determined by comparing integral dose within the high dose region of the deformed dosimeter distribution versus calculated dose. Dose profiles were used to study temporal stability of measured dose distributions. Results: Good dose agreement was demonstrated in the control with a 3D gamma passing rate of 96.6%. For the dosimeter irradiated under compression, the measured integral dose in the high dose region (518.0Gy*cm3) was within 6% of the Eclipse-calculated integral dose (549.4Gy*cm3). Elevated signal was noted on the dosimeter edge in the direction of compression. Change in dosimeter signal over 1.5 hours was ≤2.7%, and the relative dose distribution remained stable over this period of time. Conclusion: Presage-Def is promising as a 3D dosimeter capable of accurately

  5. An apparent threshold dose response in ferrous xylenol-orange gel dosimeters when scanned with a yellow light source (United States)

    Babic, Steven; Battista, Jerry; Jordan, Kevin


    Freshly prepared radiochromic ferrous xylenol-orange (FX) gels optically scanned with a light source exhibit a threshold dose response that is thermally and wavelength dependent. Correction for this threshold dose leads to accurate dose calibration and better reproducibility in multiple fraction radiation exposures. The objective of this study was to determine the cause of the threshold dose effect and to control it through improved dose calibration procedures. The results of a systematic investigation into the chemical cause revealed that impurities within the various FX gel constituents (i.e. xylenol-orange, gelatin, sulfuric acid and ferrous ammonium sulfate) were not directly responsible for the threshold dose. Rather, it was determined that the threshold dose response stems from a spectral sensitivity to different chemical complexes that are formed at different dose levels in FX gels between ferric (Fe(III)) ions and xylenol-orange (XO), i.e. Fe(III)i:XOj. A double Fe(III)2:XO1 complex preferentially absorbs at longer wavelengths (i.e. yellow), while at shorter wavelengths (i.e. green) the sensitivity is biased toward the single Fe(III)1:XO1 complex. As a result, when scanning with yellow light, freshly prepared FX gels require a minimum concentration of Fe(III) ions to shift the equilibrium concentration to favor the predominant production of the double Fe(III)2:XO1 complex at low doses. This can be accomplished via pre-irradiation of freshly prepared gels to a priming dose of ~0.5 Gy or allowing auto-oxidation to generate the startup concentration of Fe(III) ions required to negate the apparent threshold dose response.

  6. Carbon Equivalent and Maximum Hardness


    Haruyoshi, Suzuki; Head Office, Nippon Steel Corporation


    The accuracy of formulae for estimating the maximum hardness values of the HAZ from chemical composition and cooling time for welds in high strength steel is discussed and a new formula. NSC-S, is proposed which uses only C%, Pcm% and cooling time for the purpose of satisfactory accuracy. IIW CE and Ito-Bessyo Pcm carbon equivalent alone are not satisfactory in establishing Hmax values. The former is good only for slow cooling, t8/5 longer than 10 seconds, while the latter is good only for fa...

  7. [Lscr]0-equivalence of maps (United States)

    Gaffney, Terence


    We use the theory of the integral closure of an ideal to study the equivalence of map-germs under C0 coordinate changes in the target. We also derive a formula for the number of double points of a map germ from Cn [rightward arrow] C2n in terms of the Segre number of dimension 0 of an ideal associated to the double point locus of f, and the number of Whitney umbrellas of the composition of f with a generic projection to C2n[minus sign]1.

  8. Rheology and Relaxation Timescales of ABA Triblock Polymer Gels (United States)

    Peters, Andrew; Lodge, Timothy

    When dissolved in a midblock selective solvent, ABA polymers form gels composed of aggregated end block micelles bridged by the midblocks. While much effort has been devoted to the study of the structure of these systems, the dynamics of these systems has received less attention. We examine the underlying mechanism of shear relaxation of ABA triblock polymer gels, especially as a function of chain length, composition, and concentration. Recent work using time-resolved small-angle neutron scattering of polystyrene (PS)-block-poly(ethylene-alt-propylene) (PEP) in squalane has elucidated many aspects of the dynamics of diblock chain exchange. By using rheology to study bulk relaxation phenomena of the triblock equivalent, PS-PEP-PS, we apply the knowledge gained from the chain exchange studies to bridge the gap between the molecular and macroscopic relaxation phenomena in PS-PEP-PS triblock gels.

  9. SU-C-201-02: Dosimetric Verification of SBRT with FFF-VMAT Using a 3-D Radiochromic/Optical-CT Dosimetry System

    Energy Technology Data Exchange (ETDEWEB)

    Na, Y; Black, P; Wuu, C [Columbia University, New York, NY (United States); Adamovics, J [Department of Chemistry and Biology, Rider University, Skillman, NJ (United States)


    Purpose: With an increasing use of small field size and high dose rate irradiation in the advances of radiotherapy techniques, such as stereotactic body radiotherapy (SBRT) and stereotactic radiosurgery (SRS), an in-depth quality assurance (QA) system is required. The purpose of this study is to investigate a high resolution optical CT-based 3D radiochromic dosimetry system for SBRT with intensity modulated radiotherapy (IMRT) and flattening filter free (FFF) volumetric modulated arc therapy (VMAT). Methods: Cylindrical PRESAGE radiochromic dosimeters of 10cm height and 11cm diameter were used to validate SBRT. Four external landmarks were placed on the surface of each dosimeter to define the isocenter of target. SBRT plans were delivered using a Varian TrueBeam™ linear accelerator (LINAC). Three validation plans, SBRT with IMRT (6MV 600MU/min), FFF-VMAT (10MV 2400MU/min), and mixed FFF-VMAT (6MV 1400MU/min, 10MV 2400MU/min), were delivered to the PRESAGE dosimeters. Each irradiated PRESAGE dosimeter was scanned using a single laser beam optical CT scanner and reconstructed with a 1mm × 1mm high spatial resolution. The comparison of measured dose distributions of irradiated PRESAGE dosimeters to those calculated by Pinnacle{sup 3} treatment planning system (TPS) were performed with a 10% dose threshold, 3% dose difference (DD), and 3mm distance-to-agreement (DTA) Gamma criteria. Results: The average pass rates for the gamma comparisons between PRESAGE and Pinnacle{sup 3} in the transverse, sagittal, coronal planes were 94.6%, 95.9%, and 96.4% for SBRT with IMRT, FFF-VMAT, and mixed FFF-VMAT plans, respectively. A good agreement of the isodose distributions of those comparisons were shown at the isodose lines 50%, 70%, 80%, 90% and 98%. Conclusion: This study demonstrates the feasibility of the high resolution optical CT-based 3D radiochromic dosimetry system for validation of SBRT with IMRT and FFF-VMAT. This dosimetry system offers higher precision QA with 3D

  10. Hydrodynamics of active permeating gels

    Energy Technology Data Exchange (ETDEWEB)

    Callan-Jones, A C [Laboratoire Charles Coulomb, UMR 5521 CNRS-UM2, Universite Montpellier II, 34095 Montpellier Cedex 5 (France); Juelicher, F, E-mail: [Max-Planck-Institut fuer Physik komplexer Systeme, Noethnitzerstrasse 38, 01187 Dresden (Germany)


    We develop a hydrodynamic theory of active permeating gels with viscoelasticity in which a polymer network is embedded in a background fluid. This situation is motivated by active processes in the cell cytoskeleton in which motor molecules generate elastic stresses in the network, which can drive permeation flows of the cytosol. Our approach differs from earlier ones by considering the elastic strain in the polymer network as a slowly relaxing dynamical variable. We first present the general ideas for the case of a passive, isotropic gel and then extend this description to a polar, active gel. We discuss two specific cases to illustrate the role of permeation in active gels: self-propulsion of a thin slab of gel relative to a substrate driven by filament polymerization and depolymerization; and non-equilibrium deswelling of a gel driven by molecular motors.


    Directory of Open Access Journals (Sweden)

    Grubnik I.M., Gladukh Ye.V., Chernyaev S.V.


    Full Text Available The article presents the results of studies on the functional properties of carrageenan, depending on the concentration of sodium chloride and xanthan in gels. It is established that the main factors in the syneresis of carrageenan gels are its concentration, the presence of ions and gums in solution. If using sodium chloride there is a change in the structure of mesh of the resulting gel, which leads to an increase in syneresis.

  12. Polyoxometalate-based Supramolecular Gel (United States)

    He, Peilei; Xu, Biao; Liu, Huiling; He, Su; Saleem, Faisal; Wang, Xun


    Self-assemblyings of surfactant-encapsulated Wells-Dawson polyoxometalates (SEPs) nanobuilding blocks in butanone and esters yielded supramolecular gels showing thermo and photo responsive properties. The gels can be further polymerized if unsaturated esters were used and subsequently electrospinned into nanowires and non-woven mats. The as-prepared non-woven mats have a Young's modulus as high as 542.55 MPa. It is believed that this supramolecular gel is a good platform for polyoxometalates processing.

  13. Adherens junction proteins are expressed in collagen corneal equivalents produced in vitro with human cells. (United States)

    Giasson, Claude J; Deschambeault, Alexandre; Carrier, Patrick; Germain, Lucie


    To test whether adherens junction proteins are present in the epithelium and the endothelium of corneal equivalents. Corneal cell types were harvested from human eyes and grown separately. Stromal equivalents were constructed by seeding fibroblasts into a collagen gel on which epithelial and endothelial cells were added on each side. Alternatively, bovine endothelial cells were used. At maturity, sections of stromal equivalents were processed for Masson's trichrome or indirect immunofluorescence using antibodies against pan-, N-, or E-cadherins or α- or β-catenins. Alternatively, stromal equivalents were dissected, to separate the proteins from the epithelium, endothelium, and stroma with sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Western blots of the transferred proteins exposed to these primary antibodies were detected with chemiluminescence. Native corneas were processed similarly. Three or four layers of epithelial cells reminiscent of the native cornea (basal cuboidal and superficial flatter cells) lay over a stromal construct containing fibroblastic cells under which an endothelium is present. Western blots and indirect immunofluorescence revealed that, similarly to the native cornea, the epithelium reacted positively to antibodies against catenins (α and β) and E-cadherin. The endothelium of corneal constructs, whether of human or bovine origin, reacted mildly to catenins and N-cadherin. This collagen-based corneal equivalent simulated the native cornea. Cells from the epithelial and endothelial layers expressed adherens junction proteins, indicating the presence of cell-cell contacts and the existence of polarized morphology of these layers over corneal equivalents.

  14. Brimonidine gel: Systemic cardiovascular effects

    National Research Council Canada - National Science Library


    Safety News United Kingdom - The MHRA has informed health care professionals that systemic cardiovascular effects including bradycardia, hypotension and dizziness have been reported after application of brimonidine gel...

  15. Gel polymer electrolytes for batteries (United States)

    Balsara, Nitash Pervez; Eitouni, Hany Basam; Gur, Ilan; Singh, Mohit; Hudson, William


    Nanostructured gel polymer electrolytes that have both high ionic conductivity and high mechanical strength are disclosed. The electrolytes have at least two domains--one domain contains an ionically-conductive gel polymer and the other domain contains a rigid polymer that provides structure for the electrolyte. The domains are formed by block copolymers. The first block provides a polymer matrix that may or may not be conductive on by itself, but that can soak up a liquid electrolyte, thereby making a gel. An exemplary nanostructured gel polymer electrolyte has an ionic conductivity of at least 1.times.10.sup.-4 S cm.sup.-1 at C.

  16. Analysis of the response dependence of Ebt3 radiochromic film with energy, dose rate, wavelength, scanning mode and humidity; Analisis de la dependencia de la respuesta de la pelicula radiocromica EBT3 con la energia, tasa de dosis, longitud de onda, modo de escaneo y con la humedad

    Energy Technology Data Exchange (ETDEWEB)

    Leon M, E. Y.; Camacho L, M. A. [Universidad Autonoma del Estado de Mexico, Facultad de Medicina, Laboratorio de Fotomedicina, Biofotonica y Espectroscopia Laser de Pulsos Ultracortos, Jesus Carranza y Paseo Tollocan s/n, 50120 Toluca, Estado de Mexico (Mexico); Herrera G, J. A.; Garcia G, O. A. [Instituto Nacional de Neurologia y Neurocirugia, Laboratorio de Fisica Medica y Unidad de Radiocirugia, 14269 Ciudad de Mexico (Mexico); Villarreal B, J. E., E-mail: [University of Calgary, Department of Oncology, Tom Baker Cancer Centre, 1331 29th street NW Calgary, Alberta T2N 4N2 (Canada)


    With the development of new modalities in radiotherapy treatments, the use of radiochromic films has increased considerably. Because the characteristics that presented, they are suitable for quality control and dose measurement. In this work and analysis of the dependence of the response of Ebt3 radiochromic films with energy, dose rate, wavelength, scan mode and humidity, for a dose range of 0-70 Gy is presented. According to the results, the response of Ebt3 radiochromic films has low dependence on energy, dose rate, scan mode and humidity. However, the sensitivity of the response Ebt3 radiochromic films has a high dependence on the wavelength of the optical system used for reading. (Author)


    Directory of Open Access Journals (Sweden)

    Dr. Stefan DUMITRU


    Full Text Available In this study we set forth to present several of the most important aspects regarding the contrastive analysis of a well-defined number of Latin idioms in parallel with their Romanic counterparts (in French, Italian, Spanish and Romanian. Our intent was not to discover, in the Romanic space, all the equivalents of the phrases that form the corpus we work with, for reasons pertaining to material restrictions, but to discuss, based on a certain number of units, the different types of issues they may point to. The most important is to establish the relation between the idiomatic expressions in Latin and their correspondents in the above mentioned languages, regarding their inner form, their meaning and their structure.

  18. Expanding the Interaction Equivalency Theorem

    Directory of Open Access Journals (Sweden)

    Brenda Cecilia Padilla Rodriguez


    Full Text Available Although interaction is recognised as a key element for learning, its incorporation in online courses can be challenging. The interaction equivalency theorem provides guidelines: Meaningful learning can be supported as long as one of three types of interactions (learner-content, learner-teacher and learner-learner is present at a high level. This study sought to apply this theorem to the corporate sector, and to expand it to include other indicators of course effectiveness: satisfaction, knowledge transfer, business results and return on expectations. A large Mexican organisation participated in this research, with 146 learners, 30 teachers and 3 academic assistants. Three versions of an online course were designed, each emphasising a different type of interaction. Data were collected through surveys, exams, observations, activity logs, think aloud protocols and sales records. All course versions yielded high levels of effectiveness, in terms of satisfaction, learning and return on expectations. Yet, course design did not dictate the types of interactions in which students engaged within the courses. Findings suggest that the interaction equivalency theorem can be reformulated as follows: In corporate settings, an online course can be effective in terms of satisfaction, learning, knowledge transfer, business results and return on expectations, as long as (a at least one of three types of interaction (learner-content, learner-teacher or learner-learner features prominently in the design of the course, and (b course delivery is consistent with the chosen type of interaction. Focusing on only one type of interaction carries a high risk of confusion, disengagement or missed learning opportunities, which can be managed by incorporating other forms of interactions.

  19. Model changes EBT2 radiochromic film from its predecessor EBT; Cambios del modelo EBT2 de peliculas radiocromicas respecto a su predecesora EBT

    Energy Technology Data Exchange (ETDEWEB)

    Carrasco Herrera, M. A.; Perucha Ortega, M.; Baeza Trujillo, M.; Luis Simon, F. J.; Herrador Cordoba, M.


    The model EBT2 Gafchromic radiochromic film is significantly different from its predecessor EBT. The presence of a yellow pigment in the active layer results in a reduced sensitivity to ambient light, on the other hand, this pigment can apply a correction to the measured signal to compensate for changes due to differences in the thickness of the active layer, there by improving a priori, the homogeneity of the response of the film. Another new feature they present is the lack of symmetry of the layers that make up the film, leading to the emergence of a new unit of the pixel value obtained with the orientation of the film to scan: heads or tails. (Author)

  20. Enhancement of radiation effects by bismuth oxide nanoparticles for kilovoltage x-ray beams: A dosimetric study using a novel multi-compartment 3D radiochromic dosimeter (United States)

    Alqathami, M.; Blencowe, A.; Yeo, U. J.; Franich, R.; Doran, S.; Qiao, G.; Geso, M.


    The aim of this study is to present the first experimental validation and quantification of the dose enhancement capability of bismuth oxide nanoparticles (Bi2O3-Nps). A recently introduced multi-compartment 3D radiochromic dosimeter for measuring radiation dose enhancement produced from the interaction of X-rays with metal nanoparticles was employed to investigate the 3D spatial distribution of ionizing radiation dose deposition. Dose-enhancement factor for the dosimeters doped with Bi2O3-NPs was ~1.9 for both spectrophotometry and optical CT analyses. Our results suggest that bismuth-based nanomaterials are efficient dose enhancing agents and have great potential for application in clinical radiotherapy.

  1. Equivalence of recursive specifications in process algebra

    NARCIS (Netherlands)

    A.J. van der Poorten (Alf); Y.S. Usenko (Yaroslav)


    textabstractWe define an equivalence relation on recursive specifications in process algebra that is model-independent and does not involve an explicit notion of solution. Then we extend this equivalence to the specification language $mu$CRL.

  2. Equivalent damage of loads on pavements

    CSIR Research Space (South Africa)

    Prozzi, JA


    Full Text Available This report describes a new methodology for the determination of Equivalent Damage Factors (EDFs) of vehicles with multiple axle and wheel configurations on pavements. The basic premise of this new procedure is that "equivalent pavement response...

  3. Behavioural equivalence for infinite systems - Partially decidable!

    DEFF Research Database (Denmark)

    Sunesen, Kim; Nielsen, Mogens


    languages with two generalizations based on traditional approaches capturing non-interleaving behaviour, pomsets representing global causal dependency, and locality representing spatial distribution of events. We first study equivalences on Basic Parallel Processes, BPP, a process calculus equivalent...

  4. Commissioning of applicator-guided stereotactic body radiation therapy boost with high-dose-rate brachytherapy for advanced cervical cancer using radiochromic film dosimetry. (United States)

    Aldelaijan, Saad; Wadi-Ramahi, Shada; Nobah, Ahmad; Moftah, Belal; Devic, Slobodan; Jastaniyah, Noha

    To describe an EBT3 GAFCHROMIC film-based dosimetry method to be used in commissioning of a combined HDR brachytherapy (HDRB) and stereotactic body radiation therapy (SBRT) boost for treatment of advanced cervical cancer involving extensive residual disease after external beam treatment. A cube phantom was designed to firmly fit an intrauterine tandem applicator and EBT3 radiochromic film pieces. A high-risk clinical target volume (CTVHR, Total) was contoured with an extended arm at one side. The HDRB treatment was planned to cover the proximal CTVHR, Total with 7 Gy and the distal volume, referred to as CTVHR, Distal, was planned by SBRT for dose augmentation. After HDRB treatment delivery, SBRT treatment was delivered within 1 hour by image guidance using the applicator geometry. Intentional 1D and 2D misalignments were introduced to evaluate the effect on target volumes. In addition, effect of film reirradiation at different time gaps and dose levels was evaluated. Film dosimetric accuracy, with up to 2 hours gap between irradiations, was shown to be unaffected. A 2%/2 mm gamma analysis between measured and planned doses showed agreement of >99%. Misalignments of more than 2 mm between applicator and SBRT isocenter resulted in suboptimal dose-volume histogram affecting mostly D98% and D90% of CTVHR, Distal. Visualizing how target dose-volume metrics are affected by minor misalignments between SBRT and HDRB dose gradients, in light of achievable phantom-based experimental quality assurance level, encourages the clinical applicability of this technique. Radiochromic film was shown to be a valuable tool to commission procedures combining two different treatment planning systems and modalities with varying dose rates and energy ranges. Copyright © 2017 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

  5. Dose comparison between TG-43-based calculations and radiochromic film measurements of the Freiburg flap applicator used for high-dose-rate brachytherapy treatments of skin lesions. (United States)

    Aldelaijan, Saad; Bekerat, Hamed; Buzurovic, Ivan; Devlin, Phillip; DeBlois, Francois; Seuntjens, Jan; Devic, Slobodan

    Current high-dose-rate brachytherapy skin treatments with the Freiburg flap (FF) applicator are planned with treatment planning systems based on the American Association of Physicists in Medicine TG-43 data sets, which assume full backscatter conditions in dose calculations. The aim of this work is to describe an experimental method based on radiochromic film dosimetry to evaluate dose calculation accuracy during surface treatments with the FF applicator at different depths and bolus thicknesses. Absolute doses were measured using a reference EBT3 radiochromic film dosimetry system within a Solid Water phantom at different depths (0, 0.5, 1, 2, and 3 cm) with respect to the phantom surface. The impact of bolus (up to 3-cm thickness) placed on top of the applicator was investigated for two clinical loadings created using Oncentra MasterPlan: 5 cm × 5 cm and 11 cm × 11 cm. For smaller loading and depths beyond 2 cm and for larger loading and depths beyond 1 cm, the dose difference was less than 3% (±4%). At shallower depths, differences of up to 6% (±4%) at the surface were observed if no bolus was added. The addition of 2-cm bolus for the smaller loading and 1 cm for larger loading minimized the difference to less than 3% (±4%). For typical FF applicator loading sizes, the actual measured dose was 6% (±4%) lower at the skin level when compared with TG-43. Additional bolus above the FF was shown to decrease the dose difference. The consideration of change in clinical practice should be carefully investigated in light of clinical reference data. Copyright © 2017 American Brachytherapy Society. Published by Elsevier Inc. All rights reserved.

  6. SU-F-T-583: Comparison of EBT3 Radiochromic Film Densitometry with Narrow Bandwidth LED Source in Point, Slot and Full Aperture Geometries

    Energy Technology Data Exchange (ETDEWEB)

    Jordan, K [London Regional Cancer Program (United Kingdom); University of Western Ontario, London, ON, CA (United States)


    Purpose: Film densitometers optimized for radiochromic EBT3 film are not commercially available and flatbed document scanners are limited by broad spectral overlap of the red green and blue channels and polarization effects. Non-polarized, narrow bandwith, intensity stabilized light emitting diode (LED) light sources were constructed and transmission measurements compared for point, slot and full aperture geometries. Methods: LED’s with 10 nm bandwidths were focused to 1 mm spots for point scanning. The LED’s back-illuminated a 6 mm diameter diffuser near the focal point of a 25 cm diameter Fresnel lens for slot and full aperture transmission imaging. Films were located at the aperture plane, 15 cm from the lens and imaged with a 16 bit digital camera with 50 mm lens. Sheets, 10×8 cm, were irradiated to 25 Gy with a 4×4 cm 6 MV photon beam. Transmission measurements with a 633nm, linearly polarized laser were used as lowacceptance angle reference geometry. Results: LED intensity stabilized to <1% within one minute of startup. The useful transmission range increased as the acceptance angle decreased, laser(∼2%)> spot(∼3%)> slot(∼5%)> full aperture(∼10%). The Fresnel lens introduced a 4-fold polarization symmetry that increased radially causing a 2% change in transmission at 10 cm from the optic axis for EBT3 film. Polarized spot densitometer and laser transmission were similar. Conclusion: Spectrally filtered LED sources were effective for transmission measurements of radiochromic films. Because of polarization sensitivity of EBT3 film, the scanning spot geometry is the most general for measuring unpolarised transmission of larger film sizes, ie > 15×15 cm. Due to EBT3 film scatter, spot scanning should provide the most accurate profiles of high dose gradients, for a given acceptance angle. The spot scanning densitometer provided useful transmission to ∼5, 25, >25 Gy with 635, 590 and 530 nm light respectively.

  7. SU-E-T-257: Development of a New Endorectal Balloon with An Unfoldable Radiochromic Film for In-Vivo Rectal Dosimetry During Prostate Cancer Radiotherapy

    Energy Technology Data Exchange (ETDEWEB)

    Jeang, E; Lim, Y; Cho, K; Hwang, U; Jeong, J; Kim, H; Kim, S; Lee, S; Shin, D; Park, J; Kim, J [National Cancer Center, Goyang-si, Gyeonggi-do (Korea, Republic of); Kwak, J [Asan Medical Center, Seoul (Korea, Republic of); Choi, S [Korea institute of Radiological and Medical Sciences, Seoul (Korea, Republic of)


    Purpose: We developed an endorectal balloon for in-vivo rectal dosimetry in two-dimensions, and evaluated its dosimetric properties for the radiation treatment of prostate cancer. Methods: The endorectal balloon for in-vivo rectal dosimetry is equipped with a radiochromic film so that two-dimensional dose distribution can be measured in the rectal wall. The film is unrolled as the balloon is inflated, and it is rolled as the balloon is deflated. The outer diameter of the balloon is about 14 mm before inflating it, but its outer diameter can be increased up to about 50 mm after inflating it with 80 ml distilled water. The size of the film is 80(L) x 64(W) mm2, so large as to measure a dose distribution of an anterior half of the rectal wall. After it was inserted into a fabricated rectal phantom, the phantom was scanned by a CT scanner and 5 Gy was delivered to a target inside the phantom with a 15 MV photon beam in AP direction. Finally, the dose distribution measured in the endorectal balloon was compared with that of the treatment plan. Results: The two dose distributions were compared each other in the parallel and the perpendicular directions along an axis of the balloon. The two dose profiles analyzed from the radiochromic film agreed well with the plan within 3% for 15 MV photon beam. Conclusion: An endorectal balloon for two-dimensional in-vivo rectal dosimetry was developed and its dosimetric effectiveness was evaluated for the radiation treatment of prostate cancer. The measured dose distributions showed good agreement with the plans.

  8. Discovering Classes of Strongly Equivalent Logic Programs


    Chen, Y.; Lin, F.


    In this paper we apply computer-aided theorem discovery technique to discover theorems about strongly equivalent logic programs under the answer set semantics. Our discovered theorems capture new classes of strongly equivalent logic programs that can lead to new program simplification rules that preserve strong equivalence. Specifically, with the help of computers, we discovered exact conditions that capture the strong equivalence between a rule and the empty set, between two rules, between t...

  9. Rheology and structure of milk protein gels

    NARCIS (Netherlands)

    Vliet, van T.; Lakemond, C.M.M.; Visschers, R.W.


    Recent studies on gel formation and rheology of milk gels are reviewed. A distinction is made between gels formed by aggregated casein, gels of `pure` whey proteins and gels in which both casein and whey proteins contribute to their properties. For casein' whey protein mixtures, it has been shown

  10. Nanocrystal/sol-gel nanocomposites (United States)

    Petruska, Melissa A [Los Alamos, NM; Klimov, Victor L [Los Alamos, NM


    The present invention is directed to solid composites including colloidal nanocrystals within a sol-gel host or matrix and to processes of forming such solid composites. The present invention is further directed to alcohol soluble colloidal nanocrystals useful in formation of sol-gel based solid composites


    African Journals Online (AJOL)

    prepared using Ca"w_froni two dt_'/]'erent sources (chloride and lactate). The G' o'/"calcium alginate gels was st'_z;Iii/ieaiitt'y reduced (5 I -- 95%) when prepared with sodium alginate and calcium solu- tions autoelaved at 121 °C_/or 15 min. The longer the autoclaving time the jlreater the reduction in the G' ofthe gels.

  12. Electrochemical Light-Emitting Gel

    Directory of Open Access Journals (Sweden)

    Nobuyuki Itoh


    Full Text Available Light-emitting gel, a gel state electroluminescence material, is reported. It is composed of a ruthenium complex as the emitter, an ionic liquid as the electrolyte, and oxide nanoparticles as the gelation filler. Emitted light was produced via electrogenerated chemiluminescence. The light-emitting gel operated at low voltage when an alternating current was passed through it, regardless of its structure, which is quite thick. The luminescence property of the gel is strongly affected by nanoparticle materials. TiO2 nanoparticles were a better gelation filler than silica or ZnO was, with respect to luminescence stability, thus indicating a catalytic effect. It is demonstrated that the light-emitting gel device, with quite a simple fabrication process, flashes with the application of voltage.

  13. Silica reinforced triblock copolymer gels

    DEFF Research Database (Denmark)

    Theunissen, E.; Overbergh, N.; Reynaers, H.


    The effect of silica and polymer coated silica particles as reinforcing agents on the structural and mechanical properties of polystyrene-poly(ethylene/butylene)-polystyrene (PS-PEB-PS) triblock gel has been investigated. Different types of chemically modified silica have been compared in order...... to evaluate the influence of the compatibility between gel and filler. Time-resolved SANS and small-angle X-ray scattering (SAXS) shows that the presence of silica particles affects the ordering of the polystyrene domains during gelsetting. The scattering pattern of silica-reinforced gels reveals strong...... scattering at very low q, but no structure and formfactor information. However, on heating above the viscoelastic to plastic transition, the 'typical' scattering pattern of the copolymer gel builds-up. All reinforced gels are strengthened by the addition of the reinforcing agent. The transitions from...

  14. Methylthymol blue in Fricke gels (United States)

    Penev, K. I.; Mequanint, K.


    The initial trial of methylthymol blue (MTB) as a chelator for ferric iron in Fricke gel dosimeters, used for three-dimensional (3D) dosimetry in cancer radiotherapy, is reported. MTB is a structural analogue of the conventionally used xylenol orange (XO); however, the absorbance spectrum of the ferric-MTB complex is shifted to higher wavelengths, which should allow for lower amount of light scattering during gel scanning. In this study, two gelatin substrates, two sources of XO and one source of MTB have been compared. The MTB- containing gels exhibited similar dose response and diffusion coefficient to the XO-containing gels at their wavelengths of maximum absorption (620 and 585 nm, respectively). In addition, the MTB gels gave an excellent dose response at 633 nm, which is an important wavelength that is already used with other 3D dosimeters.

  15. Living bacteria in silica gels (United States)

    Nassif, Nadine; Bouvet, Odile; Noelle Rager, Marie; Roux, Cécile; Coradin, Thibaud; Livage, Jacques


    The encapsulation of enzymes within silica gels has been extensively studied during the past decade for the design of biosensors and bioreactors. Yeast spores and bacteria have also been recently immobilized within silica gels where they retain their enzymatic activity, but the problem of the long-term viability of whole cells in an inorganic matrix has never been fully addressed. It is a real challenge for the development of sol-gel processes. Generic tests have been performed to check the viability of Escherichia coli bacteria in silica gels. Surprisingly, more bacteria remain culturable in the gel than in an aqueous suspension. The metabolic activity of the bacteria towards glycolysis decreases slowly, but half of the bacteria are still viable after one month. When confined within a mineral environment, bacteria do not form colonies. The exchange of chemical signals between isolated bacteria rather than aggregates can then be studied, a point that could be very important for 'quorum sensing'.

  16. QCM studies of gel spreading: Kraton gels on polystyrene surfaces. (United States)

    Nunalee, F Nelson; Shull, Kenneth R


    Contact of a polymer gel made from a styrene/ethylene-butene/styrene triblock copolymer in mineral oil was investigated by bringing the gel into contact with the coated surface of a quartz crystal microbalance (QCM). The experimental apparatus enabled simultaneous measurement of the load, displacement, and contact area, in addition to the resonant frequency and dissipation of the oscillating quartz crystal. The QCM response was determined by the linear viscoelastic properties of the gel at the frequency of oscillation. A geometric correction factor involving the contact area provided a means for quantitatively determining these viscoelastic parameters as the gel spread over the QCM surface. When the gel was removed from the surface, a thin solvent layer was left behind. The thickness of this solvent layer was determined from the QCM response and was compared to predictions from a simple model involving the disjoining pressure of the film and the osmotic pressure of the gel. Qualitative agreement with the model required that tensile, adhesive forces at the perimeter of the gel/QCM contact area were taken into account when calculating the film thickness.

  17. An Equivalent Fracture Modeling Method (United States)

    Li, Shaohua; Zhang, Shujuan; Yu, Gaoming; Xu, Aiyun


    3D fracture network model is built based on discrete fracture surfaces, which are simulated based on fracture length, dip, aperture, height and so on. The interesting area of Wumishan Formation of Renqiu buried hill reservoir is about 57 square kilometer and the thickness of target strata is more than 2000 meters. In addition with great fracture density, the fracture simulation and upscaling of discrete fracture network model of Wumishan Formation are very intense computing. In order to solve this problem, a method of equivalent fracture modeling is proposed. First of all, taking the fracture interpretation data obtained from imaging logging and conventional logging as the basic data, establish the reservoir level model, and then under the constraint of reservoir level model, take fault distance analysis model as the second variable, establish fracture density model by Sequential Gaussian Simulation method. Increasing the width, height and length of fracture, at the same time decreasing its density in order to keep the similar porosity and permeability after upscaling discrete fracture network model. In this way, the fracture model of whole interesting area can be built within an accepted time.

  18. Aqueous sulfomethylated melamine gel-forming compositions and methods of use

    Energy Technology Data Exchange (ETDEWEB)

    Meltz, C.N.; Guetzmacher, G.D.; Chang, P.W.


    A method is described for the selective modification of the permeability of the strata of a subterranean bydrocarbon-containing reservoir consisting of introducing into a well in, communication with the reservoir; an aqueous gel-forming composition, comprising a 1.0-60.0 weight percent sulfomethylated melamine polymer solution. The solution is prepared with a 1.0 molar equivalent of a malemine, reacted with 3.0-6.7 molar equivalents of formaldehyde or a 2-6 carbon atom containing dialdehyde; 0.25-1.25 molar equivalents of an alkali metal or ammonium salt of surfurous acid; and 0.01-1.5 molar equivalents of a gel-modifying agent.

  19. Quality assurance in RapidArc with Alderson anthropomorphic phantom using radiochromic film in comparison to MATLAB; Controle de qualidade em RapidArc com simulador de corpo humano antropomorfico Alderson utilizando filme radiocromico em comparacao ao MATLAB

    Energy Technology Data Exchange (ETDEWEB)

    Garcia, Paulo L.; Silva, Leonardo P.; Santos, Maira R.; Trindade, Cassia; Martins, Lais P.; Batista, Delano V.S., E-mail: [Instituto Nacional de Cancer (INCA), Rio de Janeiro, RJ (Brazil); Alves, Victor G. [Instituto Nacional de Cancer (SQRIS/INCA), Rio de Janeiro, RJ (Brazil). Servico de Qualidade em Radiacoes Ionizantes


    This paper presented the quality control for RapidArc using an Alderson human body phantom and radiochromic film as an alternative system to approve the treatment plan for brain tumor. Thus, it was comprised the dose distributions provided by the treatment planning system with those measured by the film radiochromic. The gamma index (Γ) analysis, to verify the acceptability of the dose distribution, was 95% of approved points, with the mostly non-compliance points in regions near the PTV’s edges. These non-compliance points may be associated to transmission blades aspects, because the regions near the edges present significant losses compared to the central areas. Also, MATLAB has proved an effective tool for that measurements and it can be used in quality assurance programs. (author)

  20. Mechanical Failure in Colloidal Gels (United States)

    Kodger, Thomas Edward

    When colloidal particles in a dispersion are made attractive, they aggregate into fractal clusters which grow to form a space-spanning network, or gel, even at low volume fractions. These gels are crucial to the rheological behavior of many personal care, food products and dispersion-based paints. The mechanical stability of these products relies on the stability of the colloidal gel network which acts as a scaffold to provide these products with desired mechanical properties and to prevent gravitational sedimentation of the dispersed components. Understanding the mechanical stability of such colloidal gels is thus of crucial importance to predict and control the properties of many soft solids. Once a colloidal gel forms, the heterogeneous structure bonded through weak physical interactions, is immediately subject to body forces, such as gravity, surface forces, such as adhesion to a container walls and shear forces; the interplay of these forces acting on the gel determines its stability. Even in the absence of external stresses, colloidal gels undergo internal rearrangements within the network that may cause the network structure to evolve gradually, in processes known as aging or coarsening or fail catastrophically, in a mechanical instability known as syneresis. Studying gel stability in the laboratory requires model colloidal system which may be tuned to eliminate these body or endogenous forces systematically. Using existing chemistry, I developed several systems to study delayed yielding by eliminating gravitational stresses through density matching and cyclic heating to induce attraction; and to study syneresis by eliminating adhesion to the container walls, altering the contact forces between colloids, and again, inducing gelation through heating. These results elucidate the varied yet concomitant mechanisms by which colloidal gels may locally or globally yield, but then reform due to the nature of the physical, or non-covalent, interactions which form

  1. Surface grafted chitosan gels. Part II. Gel formation and characterization

    DEFF Research Database (Denmark)

    Liu, Chao; Thormann, Esben; Claesson, Per M.


    cross-linking the chitosan present in the polyelectrolyte multilayer, poly(acrylic acid) is partly removed by exposing the multilayer structure to a concentrated carbonate buffer solution at a high pH, leaving a surface-grafted cross-linked gel. Chemical cross-linking enhances the gel stability against......Responsive biomaterial hydrogels attract significant attention due to their biocompatibility and degradability. In order to make chitosan based gels, we first graft one layer of chitosan to silica, and then build a chitosan/poly(acrylic acid) multilayer using the layer-by-layer approach. After......-linking density. The amount of poly(acrylic acid) trapped inside the surface grafted films was found to decrease with decreasing cross-linking density, as confirmed in situ using TIRR, and ex situ by Fourier transform infrared (FTIR) measurements on dried films. The responsiveness of the chitosan-based gels...

  2. Synergetic effect of green tea on polymer gel dosimeter and determination of optimal wavelength to choose light source for optical computed tomography

    Directory of Open Access Journals (Sweden)

    Sathiya Raj


    Full Text Available Purpose: The ultimate aim of this study is to observe the effect of Green tea as a co-antioxidant in PAGAT gel dosimeter and evaluate the appropriate light source for scanning the PAGAT and NIPAM polymer gel.Methods: Both PAGAT (Poly Acrylamide Gelatin Tetrakis hydroxyl phosphonium chloride and NIPAM (N-Isopropyl acrylamide gel were prepared in normoxic condition. The green tea extract (GTE was prepared and tested only on PAGAT. Co-60 teletherapy machine has been used for irradiation purpose, and the gel samples were scanned using UV-Visible spectrophotometer. Water equivalency of the gel has been tested in terms of their electron density, effective atomic number and Ratio of oxygen and hydrogen (O/H. We have used NIST XCOM database to test the water equivalency.Results: In this study we found that the GTE added to the gel do not respond to the given doses. By adding sugar we can enhance the sensitivity of the gel. Further investigations are required to use Green tea as a co antioxidant concentration of THPC (Tetrakis hydroxymethyl phosphonium chloride. The optimal wavelength with different region for scanning the PAGAT is 450 to 480 nm (Blue region, for NIPAM it is 540 nm and 570 nm (Green and yellow region. The PAGAT and NIPAM showed better sensitivity at 510 nm. Both gels have their effective atomic number closer to water (NIPAM-7.2, PAGAT-7.379.Conclusion: As per our results, we concluded that GTE alone is not an effective co-antioxidant for polymer gels. When the GTE is combined with sugar and THPC, it protects the gel from pre-polymerization. This study strongly suggests that the blue light is an optimal source for scanning the PAGAT and green to yellow light for NIPAM gel. Though both gels were considered as water equivalent, the PAGAT is equivalent to water and the temporal stability of this gel is higher than NIPAM.

  3. The effective theory of Borel equivalence relations

    DEFF Research Database (Denmark)

    Fokina, E.B.; Friedman, S.-D.; Törnquist, Asger Dag


    equality on ω is above equality on P (ω), the power set of ω, and any Borel equivalence relation strictly above equality on the reals is above equality modulo finite on P (ω). In this article we examine the effective content of these and related results by studying effectively Borel equivalence relations......The study of Borel equivalence relations under Borel reducibility has developed into an important area of descriptive set theory. The dichotomies of Silver [20] and Harrington, Kechris and Louveau [6] show that with respect to Borel reducibility, any Borel equivalence relation strictly above...... under effectively Borel reducibility. The resulting structure is complex, even for equivalence relations with finitely many equivalence classes. However use of Kleene's O as a parameter is sufficient to restore the picture from the noneffective setting. A key lemma is that of the existence of two...

  4. Grafting of venous leg ulcers. An intraindividual comparison between cultured skin equivalents and full-thickness skin punch grafts

    NARCIS (Netherlands)

    Mol, M. A.; Nanninga, P. B.; van Eendenburg, J. P.; Westerhof, W.; Mekkes, J. R.; van Ginkel, C. J.


    Skin equivalents that consisted of a noncontracted collagen gel populated with allogeneic fibroblasts and covered with autologous cultured keratinocytes were used for grafting venous leg ulcers. The results were compared in the same patient with those obtained with a routinely used standard method

  5. The Complexity of Identifying Large Equivalence Classes

    DEFF Research Database (Denmark)

    Skyum, Sven; Frandsen, Gudmund Skovbjerg; Miltersen, Peter Bro


    We prove that at least 3k−4/k(2k−3)(n/2) – O(k)equivalence tests and no more than 2/k (n/2) + O(n) equivalence tests are needed in the worst case to identify the equivalence classes with at least k members in set of n elements. The upper bound is an improvement by a factor 2 compared to known res...

  6. Accuracy of nimodipine gel extraction. (United States)

    Oyler, Douglas R; Stump, Sarah E; Cook, Aaron M


    Until recently, use of nimodipine in aneurysmal subarachnoid hemorrhage patients unable to swallow required extraction of gel from inside the commercially available capsule. Despite the Black-Box warning against inadvertent intravenous administration, bedside extraction of the gel from the capsule continues to be a common practice in some institutions. The accuracy of bedside extraction has not been formally evaluated. Twenty-eight nurses from the neurology and neurosurgical ICUs at a single center attempted to extract nimodipine gel from 2 capsules, each using the method currently approved by the US FDA. The primary outcome was mean weight of extracted gel per capsule, which was compared to both gel weight from batch compounded pharmacy syringes and a pre-calculated appropriate weight for 30 mg nimodipine gel. Simulated bedside extraction provided lower yield than pharmacy-compounded syringes (22.6 ± 4.6 mg vs 30.4 ± 0.59 mg, p = 0.001). Bedside extraction provided inconsistent and low yield (75.4 ± 15.32 % of possible dose extracted, p = 0.0001 for comparison of means between bedside extraction syringes and predicted gel weight). Pharmacy-compounded syringes provided consistent high yield (101.3 ± 2.0 % of possible dose extracted, p = 0.14 for comparison of means between pharmacy syringes and predicted gel weight). Combined with reports of significant patient harm and death with inadvertent intravenous administration, this study suggests that there is no role for bedside extraction of nimodipine in clinical practice.

  7. 21 CFR 26.9 - Equivalence determination. (United States)


    ... RECOGNITION OF PHARMACEUTICAL GOOD MANUFACTURING PRACTICE REPORTS, MEDICAL DEVICE QUALITY SYSTEM AUDIT REPORTS... Specific Sector Provisions for Pharmaceutical Good Manufacturing Practices § 26.9 Equivalence determination...

  8. 21 CFR 26.6 - Equivalence assessment. (United States)


    ... OF PHARMACEUTICAL GOOD MANUFACTURING PRACTICE REPORTS, MEDICAL DEVICE QUALITY SYSTEM AUDIT REPORTS... Specific Sector Provisions for Pharmaceutical Good Manufacturing Practices § 26.6 Equivalence assessment...

  9. SU-F-J-151: Evaluation of a Magnetic Resonance Image Gated Radiotherapy System Using a Motion Phantom and Radiochromic Film

    Energy Technology Data Exchange (ETDEWEB)

    Lamb, J; Ginn, J; O’Connell, D; Thomas, D; Agazaryan, N; Cao, M; Yang, Y; Low, D [UCLA, Los Angeles, CA (United States)


    Purpose: Magnetic resonance image (MRI) guided radiotherapy enables gating directly on target position for soft-tissue targets in the lung and abdomen. We present a dosimetric evaluation of a commercially-available FDA-approved MRI-guided radiotherapy system’s gating performance using a MRI-compatible respiratory motion phantom and radiochromic film. Methods: The MRI-compatible phantom was capable of one-dimensional motion. The phantom consisted of a target rod containing high-contrast target inserts which moved inside a body structure containing background contrast material. The target rod was equipped with a radiochromic film insert. Treatment plans were generated for a 3 cm diameter spherical target, and delivered to the phantom at rest and in motion with and without gating. Both sinusoidal and actual tumor trajectories (two free-breathing trajectories and one repeated-breath hold) were used. Gamma comparison at 5%/3mm was used to measure fidelity to the static target dose distribution. Results: Without gating, gamma pass rates were 24–47% depending on motion trajectory. Using our clinical standard of repeated breath holds and a gating window of 3 mm with 10% of the target allowed outside the gating boundary, the gamma pass rate was 99.6%. Relaxing the gating window to 5 mm resulted in gamma pass rate of 98.6% with repeated breath holds. For all motion trajectories gated with 3 mm margin and 10% allowed out, gamma pass rates were between 64–100% (mean:87.5%). For a 5 mm margin and 10% allowed out, gamma pass rates were between 57–98% (mean: 82.49%), significantly lower than for 3 mm by paired t-test (p=0.01). Conclusion: We validated the performance of respiratory gating based on real-time cine MRI images with the only FDA-approved MRI-guided radiotherapy system. Our results suggest that repeated breath hold gating should be used when possible for best accuracy. A 3 mm gating margin is statistically significantly more accurate than a 5 mm gating margin.

  10. Characterization of calibration curves and energy dependence GafChromic{sup TM} XR-QA2 model based radiochromic film dosimetry system

    Energy Technology Data Exchange (ETDEWEB)

    Tomic, Nada, E-mail:; Quintero, Chrystian; Aldelaijan, Saad; Bekerat, Hamed; Liang, LiHeng; DeBlois, François; Devic, Slobodan [Medical Physics Unit, McGill University, Montréal, Québec H3G 1A4, Canada and Department of Radiation Oncology, SMBD Jewish General Hospital, McGill University, Montréal, Québec H3T 1E2 (Canada); Whiting, Bruce R. [Department of Radiology, University of Pittsburgh, Pittsburgh, Pennsylvania 15213 (United States); Seuntjens, Jan [Medical Physics Unit, McGill University, Montréal, Québec H3G 1A4 (Canada)


    Purpose: The authors investigated the energy response of XR-QA2 GafChromic{sup TM} film over a broad energy range used in diagnostic radiology examinations. The authors also made an assessment of the most suitable functions for both reference and relative dose measurements. Methods: Pieces of XR-QA2 film were irradiated to nine different values of air kerma in air, following reference calibration of a number of beam qualities ranging in HVLs from 0.16 to 8.25 mm Al, which corresponds to effective energy range from 12.7 keV to 56.3 keV. For each beam quality, the authors tested three functional forms (rational, linear exponential, and power) to assess the most suitable function by fitting the delivered air kerma in air as a function of film response in terms of reflectance change. The authors also introduced and tested a new parameterχ = netΔR·e{sup m} {sup netΔR} that linearizes the inherently nonlinear response of the film. Results: The authors have found that in the energy range investigated, the response of the XR-QA2 based radiochromic film dosimetry system ranges from 0.222 to 0.420 in terms of netΔR at K{sub air}{sup air} = 8 cGy. For beam qualities commonly used in CT scanners (4.03–8.25 mm Al), the variation in film response (netΔR at K{sub air}{sup air} = 8 cGy) amounts to ± 5%, while variation in K{sub air}{sup air} amounts to ± 14%. Conclusions: Results of our investigation revealed that the use of XR-QA2 GafChromic{sup TM} film is accompanied by a rather pronounced energy dependent response for beam qualities used for x-ray based diagnostic imaging purposes. The authors also found that the most appropriate function for the reference radiochromic film dosimetry would be the power function, while for the relative dosimetry one may use the exponential response function that can be easily linearized.

  11. Characterization of an extrapolation chamber and radiochromic films for verifying the metrological coherence among beta radiation fields; Caracterizacao de uma camara de extrapolacao e filmes radiocromicos para verificacao da coerencia metrologica entre campos padroes de radiacao beta

    Energy Technology Data Exchange (ETDEWEB)

    Castillo, Jhonny Antonio Benavente


    The metrological coherence among standard systems is a requirement for assuring the reliability of dosimetric quantities measurements in ionizing radiation field. Scientific and technologic improvements happened in beta radiation metrology with the installment of the new beta secondary standard BSS2 in Brazil and with the adoption of the internationally recommended beta reference radiations. The Dosimeter Calibration Laboratory of the Development Center for Nuclear Technology (LCD/CDTN), in Belo Horizonte, implemented the BSS2 and methodologies are investigated for characterizing the beta radiation fields by determining the field homogeneity, the accuracy and uncertainties in the absorbed dose in air measurements. In this work, a methodology to be used for verifying the metrological coherence among beta radiation fields in standard systems was investigated; an extrapolation chamber and radiochromic films were used and measurements were done in terms of absorbed dose in air. The reliability of both the extrapolation chamber and the radiochromic film was confirmed and their calibrations were done in the LCD/CDTN in {sup 90}Sr/{sup 90}Y, {sup 85}Kr and {sup 147}Pm beta radiation fields. The angular coefficients of the extrapolation curves were determined with the chamber; the field mapping and homogeneity were obtained from dose profiles and isodose with the radiochromic films. A preliminary comparison between the LCD/CDTN and the Instrument Calibration Laboratory of the Nuclear and Energy Research Institute / Sao Paulo (LCI/IPEN) was carried out. Results with the extrapolation chamber measurements showed in terms of absorbed dose in air rates showed differences between both laboratories up to de -I % e 3%, for {sup 90}Sr/{sup 90}Y, {sup 85}Kr and {sup 147}Pm beta radiation fields, respectively. Results with the EBT radiochromic films for 0.1, 0.3 and 0.15 Gy absorbed dose in air, for the same beta radiation fields, showed differences up to 3%, -9% and -53%. The beta

  12. Evaluation of hyaluronan gel (Gengigel(®) ) as a topical applicant in the treatment of gingivitis. (United States)

    Sapna, Nadiger; Vandana, Kharidi Laxman


      To clinically and histopathologically evaluate the anti-inflammatory effect of 0.2% hyaluronan gel alone and with mechanical therapy on gingivitis. The argyrophilic nucleolar organizer region staining technique was attempted to routinely determine its diagnostic and prognostic dependability for periodontal lesions.   In each of the 28 gingivitis patients, the four quadrants were subjected to different treatments: scaling, scaling + topical hyaluronan gel, only topical hyaluronan gel, and topical + intrasulcular hyaluronan gel. Clinical parameters were recorded at baseline, and on days 7, 14, and 21. Biopsies were taken from each quadrant, inflammatory infiltrates were graded, and the argyrophilic nucleolar organizer region count was measured before and after treatment.   A significant reduction was seen in clinical parameters, inflammatory infiltrates, and the argyrophilic nucleolar organizer region count within the groups. The effect of topical + intrasulcular gel was equivalent to scaling (P > 0.05). Topical + intrasulcular hyaluronan gel application demonstrated a better reduction than topical hyaluronan gel alone.   Hyaluronan gel is an effective topical agent for treating gingivitis, along with scaling and intrasulcular application. The argyrophilic nucleolar organizer region count can be used as a histopathological indicator in cases of non-responsive gingivitis to assess the severity of gingival inflammation. © 2011 Blackwell Publishing Asia Pty Ltd.

  13. Catalytically Initiated Gel-in-Gel Printing of Composite Hydrogels. (United States)

    Basu, Amrita; Saha, Abhijit; Goodman, Cassandra; Shafranek, Ryan T; Nelson, Alshakim


    Herein, we describe a method to 3D print robust hydrogels and hydrogel composites via gel-in-gel 3D printing with catalytically activated polymerization to induce cross-linking. A polymerizable shear-thinning hydrogel ink with tetramethylethylenediamine as catalyst was directly extruded into a shear-thinning hydrogel support bath with ammonium persulfate as initiator in a pattern-wise manner. When the two gels came into contact, the free radicals generated by the catalyst initiated the free-radical polymerization of the hydrogel ink. Unlike photocuring, a catalyst-initiated polymerization is suitable for printing hydrogel composites of varying opacity, since it does not depend upon light penetration through the sample. The hydrogel support bath also exhibited a temperature-responsive behavior in which the gel "melted" upon cooling below 16 °C. Therefore, the printed object was easily removed by cooling the gel to a liquid state. Hydrogel composites with graphene oxide and multiwalled carbon nanotubes (MWCNTs) were successfully printed. The printed composites with MWCNTs afforded photothermally active objects, which have utility as stimuli-responsive actuators.

  14. Investigation of radiological properties and water equivalency of PRESAGE dosimeters. (United States)

    Gorjiara, Tina; Hill, Robin; Kuncic, Zdenka; Adamovics, John; Bosi, Stephen; Kim, Jung-Ha; Baldock, Clive


    PRESAGE formulations with lower halogen content are more radiologically water equivalent overall than the original formulation. This indicates that the new PRESAGE formulations are better suited to clinical applications and are more accurate dosimeters and phantoms than the original PRESAGE formulation. While correction factors are still needed to convert the dose measured by the dosimeter to an absorbed dose in water in the kilovoltage energy range, these correction factors are considerably smaller for the new PRESAGE formulations compared to the original PRESAGE and the existing polymer gel dosimeters.

  15. 46 CFR 176.930 - Equivalents. (United States)


    ...) INSPECTION AND CERTIFICATION International Convention for Safety of Life at Sea, 1974, as Amended (SOLAS) § 176.930 Equivalents. As outlined in Chapter I (General Provisions) Regulation 5, of SOLAS, the... required by SOLAS regulations if satisfied that such equivalent is at least as effective as that required...

  16. 46 CFR 115.930 - Equivalents. (United States)


    ... International Convention for Safety of Life at Sea, 1974, as Amended (SOLAS) § 115.930 Equivalents. In accordance with Chapter I (General Provisions) Regulation 5, of SOLAS, the Commandant may accept an... the SOLAS regulations if satisfied that such equivalent is at least as effective as that required by...

  17. Flow equivalence and isotopy for subshifts

    DEFF Research Database (Denmark)

    Boyle, Mike; Carlsen, Toke Meier; Eilers, Søren


    We study basic properties of flow equivalence on one-dimensional compact metric spaces with a particular emphasis on isotopy in the group of (self-) flow equivalences on such a space. In particular, we show that such an orbit-preserving map is not always an isotopy, but that this always is the case...

  18. What is Metaphysical Equivalence? | Miller | Philosophical Papers

    African Journals Online (AJOL)

    In this paper I argue that if we are judiciously to resolve disputes about whether theories are equivalent or not, we need to develop testable criteria that will give us epistemic access to the obtaining of the relation of metaphysical equivalence holding between those theories. I develop such 'diagnostic' criteria. I argue that ...

  19. What is Metaphysical Equivalence? | Miller | Philosophical Papers

    African Journals Online (AJOL)

    Theories are metaphysically equivalent just if there is no fact of the matter that could render one theory true and the other false. In this paper I argue that if we are judiciously to resolve disputes about whether theories are equivalent or not, we need to develop testable criteria that will give us epistemic access to the obtaining ...

  20. 49 CFR 38.2 - Equivalent facilitation. (United States)


    ... 49 Transportation 1 2010-10-01 2010-10-01 false Equivalent facilitation. 38.2 Section 38.2 Transportation Office of the Secretary of Transportation AMERICANS WITH DISABILITIES ACT (ADA) ACCESSIBILITY SPECIFICATIONS FOR TRANSPORTATION VEHICLES General § 38.2 Equivalent facilitation. Departures from particular...

  1. Beyond Language Equivalence on Visibly Pushdown Automata

    DEFF Research Database (Denmark)

    Srba, Jiri


    We study (bi)simulation-like preorder/equivalence checking on the class of visibly pushdown automata and its natural subclasses visibly BPA (Basic Process Algebra) and visibly one-counter automata. We describe generic methods for proving complexity upper and lower bounds for a number of studied...... preorders and equivalences like simulation, completed simulation, ready simulation, 2-nested simulation preorders/equivalences and bisimulation equivalence. Our main results are that all the mentioned equivalences and preorders are EXPTIME-complete on visibly pushdown automata, PSPACE-complete on visibly...... one-counter automata and P-complete on visibly BPA. Our PSPACE lower bound for visibly one-counter automata improves also the previously known DP-hardness results for ordinary one-counter automata and one-counter nets. Finally, we study regularity checking problems for visibly pushdown automata...

  2. Equivalence in Ventilation and Indoor Air Quality

    Energy Technology Data Exchange (ETDEWEB)

    Sherman, Max; Walker, Iain; Logue, Jennifer


    We ventilate buildings to provide acceptable indoor air quality (IAQ). Ventilation standards (such as American Society of Heating, Refrigerating, and Air-Conditioning Enginners [ASHRAE] Standard 62) specify minimum ventilation rates without taking into account the impact of those rates on IAQ. Innovative ventilation management is often a desirable element of reducing energy consumption or improving IAQ or comfort. Variable ventilation is one innovative strategy. To use variable ventilation in a way that meets standards, it is necessary to have a method for determining equivalence in terms of either ventilation or indoor air quality. This study develops methods to calculate either equivalent ventilation or equivalent IAQ. We demonstrate that equivalent ventilation can be used as the basis for dynamic ventilation control, reducing peak load and infiltration of outdoor contaminants. We also show that equivalent IAQ could allow some contaminants to exceed current standards if other contaminants are more stringently controlled.

  3. A model of ideal elastomeric gels for polyelectrolyte gels. (United States)

    Li, Jianyu; Suo, Zhigang; Vlassak, Joost J


    The concept of the ideal elastomeric gel is extended to polyelectrolyte gels and verified using a polyacrylamide-co-acrylic acid hydrogel as a model material system. A comparison between mixing and ion osmosis shows that the mixing osmosis is larger than the ion osmosis for small swelling ratios, while the ion osmosis dominates for large swelling ratios. We show further that the non-Gaussian chain effect becomes important in the elasticity of the polymer network at the very large swelling ratios that may occur under certain conditions of pH and salinity. We demonstrate that the Gent model captures the non-Gaussian chain effect well and that it provides a good description of the free energy associated with the stretching of the network. The model of ideal elastomeric gels fits the experimental data very well.

  4. Thixotropic gel for vadose zone remediation (United States)

    Riha, Brian D.


    A thixotropic gel suitable for use in subsurface bioremediation is provided along with a process of using the gel. The thixotropic gel provides a non-migrating injectable substrate that can provide below ground barrier properties. In addition, the gel components provide for a favorable environment in which certain contaminants are preferentially sequestered in the gel and subsequently remediated by either indigenous or introduced microorganisms.

  5. Equilibrium gels of limited valence colloids


    Sciortino, Francesco; Zaccarelli, Emanuela


    Gels are low-packing arrested states of matter which are able to support stress. On cooling, limited valence colloidal particles form open networks stabilized by the progressive increase of the interparticle bond lifetime. These gels, named equilibrium gels, are the focus of this review article. Differently from other types of colloidal gels, equilibrium gels do not require an underlying phase separation to form. Oppositely, they form in a region of densities deprived of thermodynamic instabi...

  6. Dose-response curve of EBT, EBT2, and EBT3 radiochromic films to synchrotron-produced monochromatic x-ray beams

    CERN Document Server

    Brown, Thomas A D; Alvarez, Diane; Matthews, Kenneth L; Ham, Kyungmin; Dugas, Joseph P; 10.1118/1.4767770


    This work investigates the dose-response curves of GAFCHROMIC EBT, EBT2, and EBT3 radiochromic films using synchrotron-produced monochromatic x-ray beams. EBT2 film is being utilized for dose verification in photoactivated Auger electron therapy at the Louisiana State University CAMD synchrotron facility. Monochromatic beams of 25, 30, and 35 keV were generated on the tomography beamline at CAMD. Ion chamber depth-dose measurements were used to determine the dose delivered to films irradiated at depths from 0.7 to 8.5 cm in a 10x10x10-cm3 PMMA phantom. AAPM TG-61 protocol was applied to convert measured ionization into dose. Films were digitized using an Epson 1680 Professional flatbed scanner and analyzed using the net optical density (NOD) derived from the red channel. A dose-response curve was obtained at 35 keV for EBT film, and at 25, 30, and 35 keV for EBT2 and EBT3 films. Calibrations of films for 4 MV x-rays were obtained for comparison using a radiotherapy accelerator at Mary Bird Perkins Cancer Cent...

  7. Studies on the Neutron Radiation Damage Equivalence

    Directory of Open Access Journals (Sweden)

    ZOU De-hui


    Full Text Available To establish a unified standard of the evaluation of different sources of radiation damage, the neutron radiation damage equivalent standard source was determined both at home and abroad, and a lot of equivalence research work was done for making weapons anti neutron radiation performance examination and acceptance basis. The theoretical research progress was combed according to the relationship between the displacement damage function and the radiation source spectra ,and the experimental research progress was combed from the basic experimental methods, the controlling trend of effect parameters and field parameters. The experiment method to reduce the uncertainty was discussed, and present the research directions of radiation damage equivalence.

  8. Dose integration and dose rate characteristics of a NiPAM polymer gel MRI dosimeter system (United States)

    Waldenberg, C.; Karlsson Hauer, A.; Gustafsson, C.; Ceberg, S.


    The normoxic polymer gel dosimeter based on N-isopropyl acrylamide (NiPAM) is a promising full 3D-dosimeter with high spatial resolution and near tissue equivalency. NiPAM gel samples were irradiated to different doses using a linear accelerator. The absorbed dose was evaluated using MRI and statistical significance of the analysed data was calculated. The analysis was carried out using an in-house developed software. It was found that the gel dosimeter responded linearly to the absorbed dose. The gel exhibited a dose rate dependence, as well as a dependence on the sequential beam irradiation scheme. A higher dose rate, as well as a higher dose per sequential beam, resulted in a lower dose response.

  9. A prospective randomized multicentre study comparing vaginal progesterone gel and vaginal micronized progesterone tablets for luteal support after in vitro fertilization/intracytoplasmic sperm injection

    DEFF Research Database (Denmark)

    Bergh, Christina; Lindenberg, Svend; Al Humaidan, Peter Samir Heskjær


    SUMMARY QUESTION: Is vaginal progesterone gel equivalent to vaginal micronized progesterone tablets concerning ongoing pregnancy rate and superior concerning patient convenience when used for luteal support after IVF/ICSI? SUMMARY ANSWER: Equivalence of treatments in terms of ongoing live intraut...

  10. Distinguishing Provenance Equivalence of Earth Science Data (United States)

    Tilmes, Curt; Yesha, Ye; Halem, M.


    Reproducibility of scientific research relies on accurate and precise citation of data and the provenance of that data. Earth science data are often the result of applying complex data transformation and analysis workflows to vast quantities of data. Provenance information of data processing is used for a variety of purposes, including understanding the process and auditing as well as reproducibility. Certain provenance information is essential for producing scientifically equivalent data. Capturing and representing that provenance information and assigning identifiers suitable for precisely distinguishing data granules and datasets is needed for accurate comparisons. This paper discusses scientific equivalence and essential provenance for scientific reproducibility. We use the example of an operational earth science data processing system to illustrate the application of the technique of cascading digital signatures or hash chains to precisely identify sets of granules and as provenance equivalence identifiers to distinguish data made in an an equivalent manner.

  11. Nuclear Regulatory Commission equivalency evaluation report

    Energy Technology Data Exchange (ETDEWEB)

    Garvin, L.J.


    This paper provides the basis for concluding that using the seismic design criteria, defined in DOE order 4580.28, Natural Phenomena Hazards Mitigation, and its implementing standards provides safety equivalent to NRC criteria.

  12. Equivalence Principle, Higgs Boson and Cosmology

    Directory of Open Access Journals (Sweden)

    Mauro Francaviglia


    Full Text Available We discuss here possible tests for Palatini f(R-theories together with their implications for different formulations of the Equivalence Principle. We shall show that Palatini f(R-theories obey the Weak Equivalence Principle and violate the Strong Equivalence Principle. The violations of the Strong Equivalence Principle vanish in vacuum (and purely electromagnetic solutions as well as on short time scales with respect to the age of the universe. However, we suggest that a framework based on Palatini f(R-theories is more general than standard General Relativity (GR and it sheds light on the interpretation of data and results in a way which is more model independent than standard GR itself.

  13. Equivalence principle and bound kinetic energy. (United States)

    Hohensee, Michael A; Müller, Holger; Wiringa, R B


    We consider the role of the internal kinetic energy of bound systems of matter in tests of the Einstein equivalence principle. Using the gravitational sector of the standard model extension, we show that stringent limits on equivalence principle violations in antimatter can be indirectly obtained from tests using bound systems of normal matter. We estimate the bound kinetic energy of nucleons in a range of light atomic species using Green's function Monte Carlo calculations, and for heavier species using a Woods-Saxon model. We survey the sensitivities of existing and planned experimental tests of the equivalence principle, and report new constraints at the level of between a few parts in 10(6) and parts in 10(8) on violations of the equivalence principle for matter and antimatter.

  14. REFractions: The Representing Equivalent Fractions Game (United States)

    Tucker, Stephen I.


    Stephen Tucker presents a fractions game that addresses a range of fraction concepts including equivalence and computation. The REFractions game also improves students' fluency with representing, comparing and adding fractions.

  15. Dark matter and the equivalence principle (United States)

    Frieman, Joshua A.; Gradwohl, Ben-Ami


    A survey is presented of the current understanding of dark matter invoked by astrophysical theory and cosmology. Einstein's equivalence principle asserts that local measurements cannot distinguish a system at rest in a gravitational field from one that is in uniform acceleration in empty space. Recent test-methods for the equivalence principle are presently discussed as bases for testing of dark matter scenarios involving the long-range forces between either baryonic or nonbaryonic dark matter and ordinary matter.

  16. Screening effect on nanostructure of charged gel

    DEFF Research Database (Denmark)

    Sugiyama, M; Annaka, M; Hino, M


    Charge screening effects on nanostructures of N-isopropylacrylamide-sodium acrylate (NIPA-SA) and -acrylic acid (NIPA-AAc) gels are investigated with small-angle neutron scattering. The NIPA-SA and NIPA-AAc gels with low water content exhibit microphase separations with different dimensions....... The dehydrated NIPA-SA gel also makes the microphase separation but the dehydrated NIPA-AAc gel does not. These results indicate that ionic circumstance around charged bases strongly affects the nanostructures both of the dehydrated gel and the gel with low water content. (C) 2004 Elsevier B. V. All rights...

  17. Nonlinear elasticity in biological gels

    NARCIS (Netherlands)

    Storm, C.; Pastore, J. J.; Mac Kintosh, F.C.; Lubensky, T. C.; Janmey, P.A.


    The mechanical properties of soft biological tissues are essential to their physiological function and cannot easily be duplicated by synthetic materials. Unlike simple polymer gels, many biological materials-including blood vessels, mesentery tissue, lung parenchyma, cornea and blood clots-stiffen

  18. Fluoride Rinses, Gels and Foams

    DEFF Research Database (Denmark)

    Twetman, Svante; Keller, Mette K


    AIM: The aim of this conference paper was to systematically review the quality of evidence and summarize the findings of clinical trials published after 2002 using fluoride mouth rinses, fluoride gels or foams for the prevention of dental caries. METHODS: Relevant papers were selected after an el...... brushing with fluoride toothpaste....

  19. Q A IMRT comparison specific patient by means of radiochromic films, radiographic films and ionization chambers arrangement; Comparacion de QA IMRT paciente especifico mediante films radiocromicos, films radiograficos y arreglo de camaras de ionizacion

    Energy Technology Data Exchange (ETDEWEB)

    Medina, L.; Venencia, D.; Garrigo, E., E-mail: [Instituto Privado de Radioterapia, Obispo Oro 423, X5000BFI Cordoba (Argentina)


    IMRT uses radiation beams of nonuniform intensity. Quality assurance (Q A) specific patient is mandatory in this treatment modality. The purpose of this study is to compare results of patient specific Q A IMRT dose distributions of the total plan and individual fields using different dosimetric systems. We used a photon beam 6 MV generated for linear accelerator PRIMUS, were used planning systems iPLAN and Konrad for IMRT inverse planning with modality Step and Shoot. For plans total dose distributions were measured with radiographic films EDR2 and Radiochromic Film EBT3. For individual fields the dose distributions were measured with radiographic films X-Omat-V, Radiochromic Film EBT3 and PTW 2D-Array. We used a scanner VIDAR Dosimetry Pro Red and software Rit v6.1 for analysis, was used Gamma index [Γ] for comparison of measured and calculated dose recording the number of pixels with Γ> 1. We analyzed 50 plan dose distributions total 50 individual fields. For the total plan the number of pixels with Γ>1 (3%-3m m) was 0.7%±1.2 [0.1%; 2.82%] for EBT3 y 1%±1.8 [0.2%; 3%] for EDR2. For individual fields (5%-3m m) was obtained 0.97%±1,7 [0%, 3%] for X-Omat-V, 0.84%±1.1[0.3%,3.1%] for EBT3 and 2.6%±1.9 [0.01%,6.8%] PTW 2D-Array. All three methods can be used. Radiochromic Films revealed the advantage and disadvantage of the cost. Both systems are slightly better film to PTW 2D-Array. (author)

  20. Silicone Gel-Filled Breast Implants (United States)

    ... Medical Procedures Implants and Prosthetics Breast Implants Silicone Gel-Filled Breast Implants Share Tweet Linkedin Pin it ... options Linkedin Pin it Email Print Description: Silicone gel-filled breast implants have a silicone outer shell ...

  1. 21 CFR 866.4900 - Support gel. (United States)


    ... IMMUNOLOGY AND MICROBIOLOGY DEVICES Immunology Laboratory Equipment and Reagents § 866.4900 Support gel. (a) Identification. A support gel for clinical use is a device that consists of an agar or agarose preparation that...

  2. Radiochromic film calibration EBT2 Gafchromic-R for the evaluation of skin dose in interventional radiology; Calibracion de la pelicula radiocromica Gafchromic EBT2 para la evaluacion de la dosis en piel en radiologia intevencionista

    Energy Technology Data Exchange (ETDEWEB)

    Manano Herrera, J. A.; Roldan Arjona, J. M.; Martinez-Luna, R. J.; Soler Cantos, M. M.


    The estimate of the dose in the entrance surface (DSE) in interventional radiology procedures is of interest to identify those which by their nature may lead to skin lesions. The purpose of this paper is to analyze the possibility of use of radiochromic film GAFCHROMICrEBT2 in the estimation of the DSE in these procedures. This is a calibration curve obtained in the dose range of this type of scans proving its validity in relation to the dose given in Perspex phantom exposed to similar values ??of fluoroscopy time and number of acquisitions of employees in the above proceedings.

  3. A method for labeling polyacrylamide gels




    Have you ever struggled with the identification of your polyacrylamide gels after running a few of them at once? Here is a new method for labeling gels which is easy, free and does not interfere with your protein samples. You will be intrigued once you learn how you can add a label to your laboratory-made gels and will have no problem identifying your gels any more.

  4. Yield stress determination of a physical gel

    DEFF Research Database (Denmark)

    Hvidt, Søren


    Pluronic F127 solutions form gels in water with high elastic moduli. Pluronic gels can, however, only withstand small deformations and stresses. Different steady shear and oscillatory methods traditionally used to determine yield stress values are compared. The results show that the yield stresses...... values of these gels depend on test type and measurement time, and no absolute yield stress value can be determined for these physical gels....

  5. The principle of equivalence reconsidered: assessing the relevance of the principle of equivalence in prison medicine. (United States)

    Jotterand, Fabrice; Wangmo, Tenzin


    In this article we critically examine the principle of equivalence of care in prison medicine. First, we provide an overview of how the principle of equivalence is utilized in various national and international guidelines on health care provision to prisoners. Second, we outline some of the problems associated with its applications, and argue that the principle of equivalence should go beyond equivalence to access and include equivalence of outcomes. However, because of the particular context of the prison environment, third, we contend that the concept of "health" in equivalence of health outcomes needs conceptual clarity; otherwise, it fails to provide a threshold for healthy states among inmates. We accomplish this by examining common understandings of the concepts of health and disease. We conclude our article by showing why the conceptualization of diseases as clinical problems provides a helpful approach in the delivery of health care in prison.

  6. The incidence of the different sources of noise on the uncertainty in radiochromic film dosimetry using single channel and multichannel methods (United States)

    González-López, Antonio; Vera-Sánchez, Juan Antonio; Ruiz-Morales, Carmen


    The influence of the various sources of noise on the uncertainty in radiochromic film (RCF) dosimetry using single channel and multichannel methods is investigated in this work. These sources of noise are extracted from pixel value (PV) readings and dose maps. Pieces of an RCF were each irradiated to different uniform doses, ranging from 0 to 1092 cGy. Then, the pieces were read at two resolutions (72 and 150 ppp) with two flatbed scanners: Epson 10000XL and Epson V800, representing two states of technology. Noise was extracted as described in ISO 15739 (2013), separating its distinct constituents: random noise and fixed pattern (FP) noise. Regarding the PV maps, FP noise is the main source of noise for both models of digitizer. Also, the standard deviation of the random noise in the 10000XL model is almost twice that of the V800 model. In the dose maps, the FP noise is smaller in the multichannel method than in the single channel ones. However, random noise is higher in this method, throughout the dose range. In the multichannel method, FP noise is reduced, as a consequence of this method’s ability to eliminate channel independent perturbations. However, the random noise increases, because the dose is calculated as a linear combination of the doses obtained by the single channel methods. The values of the coefficients of this linear combination are obtained in the present study, and the root of the sum of their squares is shown to range between 0.9 and 1.9 over the dose range studied. These results indicate the random noise to play a fundamental role in the uncertainty of RCF dosimetry: low levels of random noise are required in the digitizer to fully exploit the advantages of the multichannel dosimetry method. This is particularly important for measuring high doses at high spatial resolutions.

  7. 21 CFR 520.1452 - Moxidectin gel. (United States)


    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Moxidectin gel. 520.1452 Section 520.1452 Food and..., FEEDS, AND RELATED PRODUCTS ORAL DOSAGE FORM NEW ANIMAL DRUGS § 520.1452 Moxidectin gel. (a) Specifications. Each milliliter of gel contains 20 milligrams (2 percent) moxidectin. (b) Sponsor. See No. 000856...

  8. Permeability of gels is set by the impulse applied on the gel

    NARCIS (Netherlands)

    Urbonaite, V.; Jongh, de H.H.J.; Linden, van der E.; Pouvreau, L.A.M.


    To better understand sensory perception of foods, water exudation studies on protein-based gels are of a high importance. It was aimed to study the interplay of gel coarseness and gel stiffness on water holding (WH) and water flow kinetics from the gel once force is applied onto the material.

  9. Relation between gel stiffness and water holding for coarse and fine-stranded protein gels

    NARCIS (Netherlands)

    Urbonaite, V.; Kaaij, van der S.; Jongh, de H.H.J.; Scholten, E.; Ako, K.; Linden, van der E.; Pouvreau, L.


    The sensory perception of foods is directly related to gel morphology. The aim of this research was to investigate the relationship between gel water holding and stiffness for gels with a different morphology. Whey protein gels were prepared by varying ionic strength to create fine and

  10. Orientifold Planar Equivalence: The Chiral Condensate

    DEFF Research Database (Denmark)

    Armoni, Adi; Lucini, Biagio; Patella, Agostino


    in SU($N$) Yang-Mills in the large $N$ limit. Then, we compute numerically those quenched condensates for $N$ up to 8. After separating the even from the odd corrections in $1/N$, we are able to show that our data support the equivalence; however, unlike other quenched observables, subleading terms......The recently introduced orientifold planar equivalence is a promising tool for solving non-perturbative problems in QCD. One of the predictions of orientifold planar equivalence is that the chiral condensates of a theory with $N_f$ flavours of Dirac fermions in the symmetric (or antisymmetric......) representation and $N_f$ flavours of Majorana fermions in the adjoint representation have the same large $N$ value for any value of the mass of the (degenerate) fermions. Assuming the invariance of the theory under charge conjugation, we prove this statement on the lattice for staggered quenched condensates...

  11. Anion-responsive supramolecular gels. (United States)

    Maeda, Hiromitsu


    Supramolecular gels that change their state or structure in response to anion stimuli have been highlighted. Only a few examples exist of such supramolecular gels, the structures and properties of which can be controlled and modulated by interactions with anions. To form anion-responsive dimensionally-controlled organized structures, the constituent low-molecular-weight gelator molecules must act as anion receptors by possessing one or more of van der Waals interaction units (aliphatic chains), stacking pi planes, hydrogen-bonding sites, and metal-coordination units. This Concept focuses on the gelation and transition behaviors of amide- and urea-based anion-stimulated systems, metal-coordinated systems, and novel acyclic pi-conjugated oligopyrroles that act as "molecular flippers."

  12. The Swelling of Olympic Gels (United States)

    Lang, Michael; Fischer, Jakob; Werner, Marco; Sommer, Jens-Uwe


    The swelling equilibrium of Olympic gels is studied by Monte Carlo Simulations. We observe that gels consisting of flexible cyclic molecules of a higher degree of polymerization N show a smaller equilibrium swelling degree Q ~N - 0 . 28φ0- 0 . 72 for the same monomer volume fraction φ0 at network preparation. This observation is explained by a disinterpenetration process of overlapping non-concatenated polymers upon swelling. In the limit of a sufficiently large number of concatenations per cyclic molecule we expect that the equilibrium degree of swelling becomes proportional to φ0- 1 / 2 independent of N. Our results challenge current textbook models for the equilibrium degree of swelling of entangled polymer networks. Now at: Bio Systems Analysis Group, Jena Centre for Bioinformatics (JCB) and Department for Mathematics and Computer Sciences, Friedrich Schiller University of Jena, 07743 Jena, Germany.

  13. The Sol-Gel Process

    Directory of Open Access Journals (Sweden)

    Khalid Suliman Aboodh


    Full Text Available Abstract An increasingly important application of liquid jets is the disintegration of the jet to form droplets of liquid containing nuclear fuel. These droplets are then dried and sintered to form ceramic micro spheres for use in fuel elements in nuclear reactors. The total operations required to form the droplets convert them to solids and fire them to ceramic bodies comprise what are known as Sol-Gel processes Reference 13.

  14. Equivalent circuit analysis of terahertz metamaterial filters

    KAUST Repository

    Zhang, Xueqian


    An equivalent circuit model for the analysis and design of terahertz (THz) metamaterial filters is presented. The proposed model, derived based on LMC equivalent circuits, takes into account the detailed geometrical parameters and the presence of a dielectric substrate with the existing analytic expressions for self-inductance, mutual inductance, and capacitance. The model is in good agreement with the experimental measurements and full-wave simulations. Exploiting the circuit model has made it possible to predict accurately the resonance frequency of the proposed structures and thus, quick and accurate process of designing THz device from artificial metamaterials is offered. ©2011 Chinese Optics Letters.

  15. Fiscal adjustments in Europe and Ricardian equivalence

    Directory of Open Access Journals (Sweden)



    Full Text Available According to the ‘Ricardian’ equivalence hypothesis, consumption is dependent on permanent disposable income and current deficits are equivalent to future tax payments. This hypothesis is tested on 14 European countries in the 1990s. The relationships between private sector savings and general government deficit, and the GDP growth rate and the unemployment rate are determined. The results show the change in consumers' behaviour with respect to government deficit, and that expectations of an increase in future wealth are no longer associated with a decrease in deficit.


    Directory of Open Access Journals (Sweden)

    I Made Sena Darmasetiyawan


    Full Text Available This article aims at describing the translation methods of this tool through equivalence and context consideration which also suggest the account of language database within. The data was taken from Google Translate because it is one of the most reliable tools of translation through internet service. Results showed that there are three basic reference methods of frequency, graphology, and contextual matching database in the translation. Context in discourse and equivalence in translation are used in order to analyze the extent of this consideration.

  17. A Logical Characterisation of Static Equivalence

    DEFF Research Database (Denmark)

    Hüttel, Hans; Pedersen, Michael D.


    The work of Abadi and Fournet introduces the notion of a frame to describe the knowledge of the environment of a cryptographic protocol. Frames are lists of terms; two frames are indistinguishable under the notion of static equivalence if they satisfy the same equations on terms. We present a first......-order logic for frames with quantification over environment knowledge which, under certain general conditions, characterizes static equivalence and is amenable to construction of characteristic formulae. The logic can be used to reason about environment knowledge and can be adapted to a particular application...

  18. High School Equivalency Testing in Arizona. Forum: Responding to Changes in High School Equivalency Testing (United States)

    Hart, Sheryl


    For decades, the state of Arizona has used the General Educational Development (GED) Test to award the Arizona High School Equivalency (HSE) Diploma, as the GED Test was the only test available, recognized and accepted in the United States as the measure by which adults could demonstrate the educational attainment equivalent to high school…

  19. Fuel Cell Equivalent Electric Circuit Parameter Mapping

    DEFF Research Database (Denmark)

    Jeppesen, Christian; Zhou, Fan; Andreasen, Søren Juhl

    In this work a simple model for a fuel cell is investigated for diagnostic purpose. The fuel cell is characterized, with respect to the electrical impedance of the fuel cell at non-faulty conditions and under variations in load current. Based on this the equivalent electrical circuit parameters can...

  20. Identifiability and Equivalence of GLLIRM Models (United States)

    Revuelta, Javier


    The generalized logit-linear item response model (GLLIRM) is a linearly constrained nominal categories model (NCM) that computes the scale and intercept parameters for categories as a weighted sum of basic parameters. This paper addresses the problems of the identifiability of the basic parameters and the equivalence between different GLLIRM…

  1. Confluence Modulo Equivalence in Constraint Handling Rules

    DEFF Research Database (Denmark)

    Christiansen, Henning; Kirkeby, Maja Hanne


    Previous results on confluence for Constraint Handling Rules, CHR, are generalized to take into account user-defined state equivalence relations. This allows a much larger class of programs to enjoy the ad- vantages of confluence, which include various optimization techniques and simplified corre...

  2. interpratation: of equivalences and cultural untranslatability

    African Journals Online (AJOL)


    interpretation?; How does lack of equivalences affect interpretation? Key words: Sign Language, Interpretation, Translation, linguistics, context ... World Federation of the Deaf (WFD's) vision 2020 in which it envisions that by the year ... sign 1b) can mean MANY or A LOT: 1c) can have three meaning i.e. FOR EXAMPLE,.

  3. An Equivalent Circuit for Landau Damping

    DEFF Research Database (Denmark)

    Pécseli, Hans


    An equivalent circuit simulating the effect of Landau damping in a stable plasma‐loaded parallel‐plate capacitor is presented. The circuit contains a double infinity of LC components. The transition from stable to unstable plasmas is simulated by the introduction of active elements into the circuit....

  4. On Behavioral Equivalence of Rational Representations

    NARCIS (Netherlands)

    Trentelman, Harry L.; Willems, JC; Hara, S; Ohta, Y; Fujioka, H


    This article deals with the equivalence of representations of behaviors of linear differential systems In general. the behavior of a given linear differential system has many different representations. In this paper we restrict ourselves to kernel representations and image representations Two kernel

  5. Equivalence domination in graphs | Arumugam | Quaestiones ...

    African Journals Online (AJOL)

    Click on the link to view the abstract. Keywords: Equivalence domination, total domination, P3-forming set. Quaestiones Mathematicae 36(2013), 331-340. Full Text: EMAIL FULL TEXT EMAIL FULL TEXT · DOWNLOAD FULL TEXT DOWNLOAD FULL TEXT · · AJOL African ...

  6. A Criticism of Healthy-years Equivalents

    NARCIS (Netherlands)

    P.P. Wakker (Peter)


    textabstractThe following questions describe the scope of this paper. When decision trees are used to analyze optimal decisions, should end nodes be evaluated on the basis of QALYs or on the basis of healthy-years equivalents? Which measures should be used in communications with others, e.g.,

  7. A criticism of healthy-years equivalents

    NARCIS (Netherlands)

    Wakker, P.P.


    The following questions describe the scope of this paper. When decision trees are used to analyze optimal decisions, should end nodes be evaluated on the basis of QALYs or on the basis of healthy-years equivalents? Which measures should be used in communication with others, e.g., patients? Which of

  8. Conservation Laws, Equivalence Principle and Forbidden Radiation ...

    Indian Academy of Sciences (India)

    Home; Journals; Resonance – Journal of Science Education; Volume 17; Issue 3. Conservation Laws, Equivalence Principle and Forbidden Radiation Modes. Cihan Saçlioğlu. General ... Author Affiliations. Cihan Saçlioğlu1. Faculty of Engineering and Natural Sciences, Sabanci University, 81474 Tuzla, Istanbul, Turkey.

  9. Conservation Laws, Equivalence Principle and Forbidden Radiation ...

    Indian Academy of Sciences (India)

    There are standard proofs showing there can be no monopole electromagnetic radiation and no dipole gravitational radiation. We supplement these with a global topological argument for the former, and a local argument based directly on the principle of equivalence for the latter. 1. Introduction: Wave and Particle Pictures ...

  10. Bilingual Dictionaries and Communicative Equivalence for a ...

    African Journals Online (AJOL)

    Speakers in a multilingual society often employ a bilingual dictionary as the only instrument to meet their lexicographic needs. This implies that a bilingual dictionary becomes a poly functional instrument, presenting more information than just translation equivalents. This article focuses on the contents and the presentation ...

  11. Stimulus Equivalence in Rudimentary Reading and Spelling. (United States)

    Mackay, Harry A.


    Programs were designed to teach three severely retarded adolescents to use individual anagram letters to construct the appropriate color words when shown color patches. After learning visual equivalences between colors and printed words, Ss demonstrated auditory reading-comprehension (matching printed words to dictated words) and oral reading…

  12. 21 CFR 26.39 - Equivalence assessment. (United States)



  13. CP Violation, Neutral Currents, and Weak Equivalence (United States)

    Fitch, V. L.


    Within the past few months two excellent summaries of the state of our knowledge of the weak interactions have been presented. Correspondingly, we will not attempt a comprehensive review but instead concentrate this discussion on the status of CP violation, the question of the neutral currents, and the weak equivalence principle.

  14. Confluence Modulo Equivalence in Constraint Handling Rules

    DEFF Research Database (Denmark)

    Christiansen, Henning; Kirkeby, Maja Hanne


    Previous results on confluence for Constraint Handling Rules, CHR, are generalized to take into account user-defined state equivalence relations. This allows a much larger class of programs to enjoy the advantages of confluence, which include various optimization techniques and simplified...

  15. interpratation: of equivalences and cultural untranslatability

    African Journals Online (AJOL)


    communicative situation – this involves not only linguistic and cultural competence but ... Diversity in language use – how does it affect interpretation? ; Does direct and indirect use of language, social customs and relationships, how people express emotions have any ..... 1.3.3 Grammatical- Syntactical Equivalences.

  16. Chemical equivalence assessment of three brands of ...

    African Journals Online (AJOL)

    Assay for content of active ingredients is a critical test of drug quality; failure to meet up the standard for content of active ingredients will result to sub therapeutic quantities. Three brands (A, B and C) of carbamazepine were assayed to determine their chemical equivalence as well as their anticonvulsant activities. This was ...

  17. Four equivalent lot-sizing models

    NARCIS (Netherlands)

    W. van den Heuvel (Wilco); A.P.M. Wagelmans (Albert)


    textabstractWe study the following lot-sizing models that recently appeared in the literature: a lot-sizing model with a remanufacturing option, a lot-sizing model with production time windows, and a lot-sizing model with cumulative capacities. We show the equivalence of these models with a

  18. Contextual dependencies in a stimulus equivalence paradigm

    NARCIS (Netherlands)

    Dibbets, P.; Maes, J.H.R.; Vossen, J.M.H.


    Two experiments with human subjects assessed contextual dependencies in a stimulus equivalence paradigm. Subjects learned to form two sets of stimuli in a matching-to-sample training procedure. Each set was presented against one of two different background colours, the contextual cues. At test, the

  19. Radiochromic film use to record dose profile variations in chest CT scan; Utilizacao do filme radiocromico para registro da variacao do perfil de dose em varredura de TC de torax

    Energy Technology Data Exchange (ETDEWEB)

    Mourao, Arnaldo P.; Santana, Priscila C., E-mail: [Universidade Federal de Minas Gerais (UFMG), Belo Horizonte, MG (Brazil). Departamento de Engenharia Nuclear; Silva, Teogenes A. da; Alonso, Thessa C. [Centro de Desenvolvimento da Tecnologia Nuclear (CDTN/CNEN-MG), Belo Horizonte, MG (Brazil)


    The CT scans generate higher doses in patients than those caused by other types of diagnostic radiology using the attenuation of X-ray beams. Technological advances have increased the clinical applications of computed tomography (CT) and consequently the demand for these exams. Dose reduction strategies are difficult to implement because of a lack of proper guidance on the CT scanning. However, CT offers the possibility of adjusting the image acquisition parameters according to the patient physical profile and the diagnostic application for which it is intended to scan. Knowledge of the dose distribution is important when thinking about varying the acquisition parameters to reduce the dose. In this work was used a PMMA chest phantom to observe the dose deposition in 5 areas. Radiochromic film strips were placed inside the chest phantom, in peripheral and in the central region. The phantom was placed in the scanner isocenter and it was performed the irradiation of its central region using a chest acquisition protocol. After the phantom CT scan the radiochromic film strips were processed for obtaining digital images. Digital images were reworked to obtain the dose variation profiles for each position. The results showed a wide variation in absorbed dose by the phantom, either within a same position along the length of the film strip, as in the comparison among the five regions which the strips are placed. In this second case the dose variations were even greater. (author)

  20. Experimental comparison of profiles of acquired small fields with ionization chambers, diodes, radiochromic s and TLD films; Comparacion experimental de perfiles de campos pequenos adquiridos con camaras de ionizacion, diodos, peliculas radiocromicas y TLD

    Energy Technology Data Exchange (ETDEWEB)

    Venencia, D.; Garrigo, E. [Instituto Privado de Radioterapia, Obispo Oro 423, X5000BFI Cordoba (Argentina); Filipuzzi, M. [Instituto Balseiro, Centro Atomico Bariloche, Av. Bustillo 9500, 8400 Bariloche - Rio Negro (Argentina); Germanier, A., E-mail: [Centro de Excelencia en Productos y Procesos, Santa Maria de Punilla, 5164 Cordoba (Argentina)


    The use of radiation small fields, introduced by new techniques, can bring a considerable uncertainty in the precision of the acquired profiles, due to the conditions of lateral electronic non-equilibrium and the perturbations introduced by the detectors (volume effect and alteration of the charged particles flowing) [Das et al., 2007]. The development of new miniature detectors looks to diminish the uncertainty created by the material and the size of the sensitive volume of the dosimeter. For this reason, comparative measurements for three sizes of square field were carried out (20 mm, 10 mm and 5 mm, of side) using a detectors series: 3 ionization chambers (PTW-31003, IBA-CC04, PTW-31016), 2 diodes (PTW-60012, IBA-Sfd), thermoluminescent detectors micro-cubes of 1 mm of edge (TLD-700) and radiochromic s films EBT-3. These last two were used as reference detectors, due to their spatial high resolution and similar performance with Monte Carlo simulations [Francescon et al., 1998]. So much the thermoluminescent detectors as the radiochromic films resolved the profiles in a similar way. Both diodes responded correctly, but the rest of the detectors overestimated the gloom of the fields, which allows conclude that the used TLD (and both diodes) can resolve field sizes correctly, usually utilized in radio-surgery, without producing significant alterations in the acquired data. (author)

  1. Evaluation of the use of radiochromic films alongside of the ionization chamber and TLDs in measuring peripheral doses; Avaliacao do uso de filmes radiocromicos ao lado de camara de ionizacao e TLDs na mensuracao de doses perifericas

    Energy Technology Data Exchange (ETDEWEB)

    Soboll, Danyel S.; Wolter, Brenda Von; Nascimento, Josiane Q., E-mail: [Universidade Tecnologica Federal do Parana (UTFPR), Curitiba, PR (Brazil); Viamonte, Alfredo; Alves, Victor G.L., E-mail: [Instituto Nacional de Cancer (PQRT/INCA), Rio de Janeiro, RJ (Brazil). Programa de Qualidade em Radioterapia


    The objective of this work is to submit radiochromic films, thermoluminescent dosimeters and ionization chamber to identical situations irradiation, in order to assess their capabilities in measuring peripheral doses. The growing number of survivors of childhood cancer has created the need to investigate the cause of the sequelae of treatment. Measurements of peripheral radiation to the radiotherapy target region increment the knowledge of the subject and assist in the development of protection methods. As the periphery of the radiation spectrum is different from that in the beam, the energy independence supposedly provided in radiochromic films can overcome the energy dependence found of ionization and TLD chambers, in order to discard the necessity of correction of the values if films are used. In this work the three dosimeters were exposed to doses arising from the issuance of 6 MV beams, field 10 cm x 10 cm and 500 UM. The dosimeters were placed at 0, 10, 17.5 and 30 cm from the central ray, always under 5 cm of water. The results showed that the figures reported by the films have high average standard deviation and for more conclusive results is necessary to proceed with the radiations, employing more intense beams.

  2. Verification of the 3D dose distribution in spinal radiosurgery by using a BANG3 polymer gel dosimeter

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Dae-Hong; Kim, Hee-Joung [Yonsei University, Wonju (Korea, Republic of); Lee, Dong-Joon [Inje University, Goyang (Korea, Republic of)


    In intensity-modulated radiosurgery (IMRS) treatment, radiation delivery techniques require the ability to accurately verify complex three-dimensional (3D) dose distributions. This study was designed to evaluate and verify dosimetry generated from gels, films, and treatment planning systems. In this study, commercially available BANG3 polymer gel was used to confirm the accuracy of the treatment plan and to assess the dosimetric uncertainty of the radiosurgery procedure. BANG3 gels that are read with R{sub 2} magnetic resonance (MR) imaging mapping are useful options. The gel is a tissue equivalent, and the relaxation ratio measured using MR imaging is proportional to the dose absorbed in the gel. A cylindrical container (5 inch deep, 7 inch high) filled with BANG3 gel was mounted in a cubic phantom (The EASY CUBE, Euromechanics, Schwarzenbruck, Germany). We then carried out the same process using the gel and gafchromic film as would be used for a patient with metastatic T-spine cancer by using a Novalis Radiosurgery system (Brain LAB Inc., Germany). Our experimental results provided the dose distribution and the radiation delivery precision. Comparisons of the measured and the calculated relative dose distributions showed good agreement in the high-dose region with differences of 2 mm. BANG3 polymer gel dosimetry can be useful for the verification of clinical treatment radiosurgery plans.


    Directory of Open Access Journals (Sweden)

    Prima Astuti Handayani


    Full Text Available Sekam padi merupakan salah satu sumber penghasil silika terbesar, berpotensi sebagai bahan pembuatan silika gel. Abu sekam padi mengandung silika sebanyak 87%-97% berat kering. Sintesis silika gel dari abu sekam padi dilakukan dengan mereaksikan abu sekam padi menggunakan larutan NaOH 1N pada suhu 800C selama 1 jam dan dilanjutkan dengan penambahan larutan asam hingga pH=7. Gel yang dihasilkan selanjutnya didiamkan selama 18 jam kemudian dikeringkan pada suhu dikeringkan menggunakan oven pada suhu 800C hingga beratnya konstan. Hasil percobaan diperoleh bahwa silika gel dengan penambahan CH3COOH menghasilkan yield yang lebih besar dibandingkan penambahan HCl. Berdasarkan analisis FT-IR silika gel yang diperoleh memiliki gugus Si-O-Si dan gugus Si-OH. Silika gel dengan penambahan HCl memiliki surface area sebesar 65,558 m2/g, total pore volume 0,1935 cc/g, dan average pore size sebesar 59,0196 Å. Sedangkan silika gel dengan penambahan CH3COOH memiliki surface area sebesar 9,685 m2/g, total pore volume 0,02118 cc/g, dan average pore size sebesar 43,7357Å. Silika gel dengan penambahanCH3COOH memiliki kemampuan menyerap kelembaban udara yang lebih baik dibanding silika gel dengan penambahan HCl. Rice hull ash (RHA is one of the biggest source of silica, potential for sintesis silica gel. RHA contains silica as many as 87 % -97 %. Synthesis of silica gel from rice hull ash was done by reaction using NaOH solution at temperature 800C for 1 hour and followed by the addition of an acid solution until pH=7. The gel were rested with time aging 18 hour, and then dried using oven at temperature 800C until constant weigh. The results obtained that the silica gel with the addition of CH3COOH produce higher yields than the addition of HCl. Based on FT-IR analysis, silica gel has a group of silanol (Si-`OH and siloxan (Si-O-Si group. Silica gel with the addition of HCl has a surface area 65,558 m2/g, a total pore volume 0,1935 cc/g, and average pore size 59

  4. Rheological characterization of Poloxamer 407 nimesulide gels

    Directory of Open Access Journals (Sweden)

    M. N. Freitas


    Full Text Available The thermal gelling property of Poloxamer 407- nimesulide gels was characterized by rheological studies. Nimesulide, a local anti-inflammatory and anesthetic drug used for the treatment of acute and chronic pain, has a short duration of action and a long-acting single-dose injection would be of clinical importance. Thus a poloxamer 407 gel applied intramuscularly could prolong the release and action of nimesulide. In this study, aqueous gels with nimesulide, containing three different concentrations of Poloxamer 407, were prepared. Viscosity measurements were performed by rheologial studies to obtain the optimal sol-gel transition temperature . Poloxamer 407 gels are pseudoplastic and viscoelastic materials, which have an elastic modulus (G', characteristic of the solid, and a viscous modulus (G'', characteristic of the liquid material. Moreover, being pseudoplastic gels, when they are deformed by shearing, their viscosity decreases. Increase of the polymer concentration increased the viscosity of the gels, which could affect the releasing process of nimesulide. Furthermore, the presence of nimesulide led to a lowering of the sol-gel transition temperature. Keywords: Poloxamer 407 gels; nimesulide; rheological characterization; viscosity; sol-gel transition temperature.

  5. Bacterial cellulose gels with high mechanical strength. (United States)

    Numata, Yukari; Sakata, Tadanori; Furukawa, Hidemitsu; Tajima, Kenji


    A composite structure was formed between polyethylene glycol diacrylate (PEGDA) and bacterial cellulose (BC) gels swollen in polyethylene glycol (PEG) as a solvent (BC/PEG gel) to improve the mechanical strength of the gels. The mechanical strength under compression and the rheostatic properties of the gels were evaluated. The compression test results indicated that the mechanical strength of the gels depended on the weight percent of cross-linked PEGDA in the gel, the chain length between the cross-linking points, and the cross-linking density of PEGDA polymers. The PEGDA polymers around the cellulose fibers were resistant to pressure; thus, the BC/PEG-PEGDA gel was stronger than the BC/PEG gel under compression. The results of transmittance measurements and thermomechanical analysis showed that the rheostatic properties of the gels were retained even after composite structure formation. BC/PEG-PEGDA gels, which are expected to be biocompatible, may be useful for clinical applications as a soft material. Copyright © 2014 Elsevier B.V. All rights reserved.

  6. Metal-silica sol-gel materials (United States)

    Stiegman, Albert E. (Inventor)


    The present invention relates to a single phase metal-silica sol-gel glass formed by the co-condensation of a transition metal with silicon atoms where the metal atoms are uniformly distributed within the sol-gel glass as individual metal centers. Any transition metal may be used in the sol-gel glasses. The present invention also relates to sensor materials where the sensor material is formed using the single phase metal-silica sol-gel glasses. The sensor materials may be in the form of a thin film or may be attached to an optical fiber. The present invention also relates to a method of sensing chemicals using the chemical sensors by monitoring the chromatic change of the metal-silica sol-gel glass when the chemical binds to the sensor. The present invention also relates to oxidation catalysts where a metal-silica sol-gel glass catalyzes the reaction. The present invention also relates to a method of performing oxidation reactions using the metal-silica sol-gel glasses. The present invention also relates to organopolymer metal-silica sol-gel composites where the pores of the metal-silica sol-gel glasses are filled with an organic polymer polymerized by the sol-gel glass.

  7. SU-E-T-121: Investigating the Optimal Scanning Resolution for Radiochromic EBT-2 Films Using an Epson 10000XL Flatbed Scanner. (United States)

    Schoenfeld, A; Poppinga, D; Chofor, N; Poppe, B


    The purpose of this work is to determine the optimal scanner resolution of an Epson 10000XL scanner for the analysis of radiochromic EBT-2 films. Using Fourier analysis and the Nyquist-Shanon sampling theory, the highest frequency component required to sufficiently reproduce a previously measured step dose profile was investigated. A setup was created, in which one half of a 6×6cm2 EBT-2 film was shielded on exposure using a 15×5×10cm3 lead block to obtain sharp step dose profiles. The film itself was placed between two 6cm RW3 stacks on top of which the lead block was placed. Using a Siemens Primus linear accelerator operating at 6/15MV nominal energies, the setup was exposed to 400MUs at 6MV and 500MUs at 15MV respectively. Preliminary investigations were performed without RW3 between the lead and film. Initial image acquisition was performed at 600dpi to minimize information loss. Using the average of five line profiles, a uniformity correction algorithm provided by the manufacturer was implemented prior to the Fast Fourier Transform (FFT) operation. In an iterative process, all frequency components above a cut-off frequency wcut were successively removed and the original image reconstructed with the inverse FFT operation. The goodness of fit was evaluated by comparing the change in penumbra width on image reconstruction. The minimum scanning resolution required to analyze the step dose profiles created without build-up material was 52dpi for 6MV and 30dpi for 15MV. By adding build-up material, in the areas of secondary electron equilibrium the required resolution reduces to 12dpi for 6MV and 8dpi for 15MV. For sufficient image reproduction within any information loss, resolutions as low as 52dpi at 6MV and 30dpi at 15MV are sufficient for evaluating EBT-2 films. This is in compliance with 50dpi recommended by the manufacturer. © 2012 American Association of Physicists in Medicine.

  8. Equivalent configurations of optical transformation media. (United States)

    Chen, Tungyang; Cheng, Shen-Wen; Weng, Chung-Ning


    We demonstrate that a medium consisting of two adjoining distinct layers of transformation materials, corresponding respectively to two linear coordinate transformations, can behave effectively as that of the same region transformed by another linear transformation. The equivalence means that, irrespective of the direction of incident wave, the fields of the medium exterior to the transformed regions of the two configurations are exactly the same. This property can also apply to a domain that is transformed by a piecewise linear transformation function, and to a medium that is mapped by a general curved function. This proof is shown analytically based on a rigorous Fourier-Bessel analysis. The equivalence suggests that, for a given transformed domain, one can find an infinite number of complementary media that altogether can give a desired effective response of certain transformation path.

  9. Orientifold Planar Equivalence: The Quenched Meson Spectrum

    CERN Document Server

    Lucini, Biagio; Patella, Agostino; Rago, Antonio


    A numerical study of Orientifold Planar Equivalence is performed in SU(N) Yang-Mills theories for N=2,3,4,6. Quenched meson masses are extracted in the antisymmetric, symmetric and adjoint representations for the pseudoscalar and vector channels. An extrapolation of the vector mass as a function of the pseudoscalar mass to the large-N limit shows that the numerical results agree within errors for the three theories, as predicted by Orientifold Planar Equivalence. As a byproduct of the extrapolation, the size of the corrections up to O(1/N^3) are evaluated. A crucial prerequisite for the extrapolation is the determination of an analytical relationship between the corrections in the symmetric and in the antisymmetric representations, order by order in a 1/N expansion.

  10. Thevenin Equivalent Method for Dynamic Contingency Assessment

    DEFF Research Database (Denmark)

    Møller, Jakob Glarbo; Jóhannsson, Hjörtur; Østergaard, Jacob


    A method that exploits Thevenin equivalent representation for obtaining post-contingency steady-state nodal voltages is integrated with a method of detecting post-contingency aperiodic small-signal instability. The task of integrating stability assessment with contingency assessment is challenged...... by the cases of unstable post-contingency conditions. For unstable postcontingency conditions there exists no credible steady-state which can be used for basis of a stability assessment. This paper demonstrates how Thevenin Equivalent methods can be applied in algebraic representation of such bifurcation...... points which may be used in assessment of post-contingency aperiodic small-signal stability. The assessment method is introduced with a numeric example....

  11. Underlining some aspects of the equivalence principle (United States)

    Benedetto, E.; Feoli, A.


    We want to shed light on some discussed aspects of the principle of equivalence. We consider two different phases in the evolution of the principle. We pay attention to the fact that some textbooks do not dwell on the mathematical meaning of ‘locally flat spacetime’, which can confuse students and, occasionally, can also lead to misinterpretations. For example, the non-eliminability of tidal forces, not even locally, may suggest that the equivalence principle is wrong. By contrast, we want to show that this is in perfect agreement with the Einstein geometrical interpretation of spacetime. Finally, in order to check the approximations used in the Gedankenexperiment of an elevator, we estimate explicitly the magnitude of the deflection of light and the effects of tidal forces in a ‘real lift’.

  12. On equivalent resistance of electrical circuits (United States)

    Kagan, Mikhail


    While the standard (introductory physics) way of computing the equivalent resistance of nontrivial electrical circuits is based on Kirchhoff's rules, there is a mathematically and conceptually simpler approach, called the method of nodal potentials, whose basic variables are the values of the electric potential at the circuit's nodes. In this paper, we review the method of nodal potentials and illustrate it using the Wheatstone bridge as an example. We then derive a closed-form expression for the equivalent resistance of a generic circuit, which we apply to a few sample circuits. The result unveils a curious interplay between electrical circuits, matrix algebra, and graph theory and its applications to computer science. The paper is written at a level accessible by undergraduate students who are familiar with matrix arithmetic. Additional proofs and technical details are provided in appendices.

  13. Testing the Equivalence of Regular Languages

    Directory of Open Access Journals (Sweden)

    Marco Almeida


    Full Text Available The minimal deterministic finite automaton is generally used to determine regular languages equality. Antimirov and Mosses proposed a rewrite system for deciding regular expressions equivalence of which Almeida et al. presented an improved variant. Hopcroft and Karp proposed an almost linear algorithm for testing the equivalence of two deterministic finite automata that avoids minimisation. In this paper we improve the best-case running time, present an extension of this algorithm to non-deterministic finite automata, and establish a relationship between this algorithm and the one proposed in Almeida et al. We also present some experimental comparative results. All these algorithms are closely related with the recent coalgebraic approach to automata proposed by Rutten.

  14. Quantum mechanics from an equivalence principle

    Energy Technology Data Exchange (ETDEWEB)

    Faraggi, A.E. [Univ. of Florida, Gainesville, FL (United States). Inst. for Fundamental Theory; Matone, M. [Univ. of Padova (Italy)


    The authors show that requiring diffeomorphic equivalence for one-dimensional stationary states implies that the reduced action S{sub 0} satisfies the quantum Hamilton-Jacobi equation with the Planck constant playing the role of a covariantizing parameter. The construction shows the existence of a fundamental initial condition which is strictly related to the Moebius symmetry of the Legendre transform and to its involutive character. The universal nature of the initial condition implies the Schroedinger equation in any dimension.

  15. Derived equivalences induced by good silting complexes


    Breaz, Simion; Modoi, George Ciprian


    Consider a (possibly big) silting object $U$ in a derived category over a (dg-)algebra $A$. Under some fairly general appropriate hypotheses, we show that it induces derived equivalences between the derived category over $A$ and a localization of the derived category of dg-endomorphism algebra $B$ of $U$. If, in addition, $U$ is small then this localization is the whole derived category over $B$.

  16. Global equivalent magnetization of the oceanic lithosphere (United States)

    Dyment, J.; Choi, Y.; Hamoudi, M.; Lesur, V.; Thebault, E.


    As a by-product of the construction of a new World Digital Magnetic Anomaly Map over oceanic areas, we use an original approach based on the global forward modeling of seafloor spreading magnetic anomalies and their comparison to the available marine magnetic data to derive the first map of the equivalent magnetization over the World's ocean. This map reveals consistent patterns related to the age of the oceanic lithosphere, the spreading rate at which it was formed, and the presence of mantle thermal anomalies which affects seafloor spreading and the resulting lithosphere. As for the age, the equivalent magnetization decreases significantly during the first 10-15 Myr after its formation, probably due to the alteration of crustal magnetic minerals under pervasive hydrothermal alteration, then increases regularly between 20 and 70 Ma, reflecting variations in the field strength or source effects such as the acquisition of a secondary magnetization. As for the spreading rate, the equivalent magnetization is twice as strong in areas formed at fast rate than in those formed at slow rate, with a threshold at ∼40 km/Myr, in agreement with an independent global analysis of the amplitude of Anomaly 25. This result, combined with those from the study of the anomalous skewness of marine magnetic anomalies, allows building a unified model for the magnetic structure of normal oceanic lithosphere as a function of spreading rate. Finally, specific areas affected by thermal mantle anomalies at the time of their formation exhibit peculiar equivalent magnetization signatures, such as the cold Australian-Antarctic Discordance, marked by a lower magnetization, and several hotspots, marked by a high magnetization.

  17. APTE: An Algorithm for Proving Trace Equivalence


    Cheval, Vincent


    This paper presents APTE, a new tool for automatically proving the security of cryptographic protocols. It focuses on proving trace equivalence between processes, which is crucial for specifying privacy type properties such as anonymity and unlinkability.\\ud \\ud The tool can handle protocols expressed in a calculus similar to the applied-pi calculus, which allows us to capture most existing protocols that rely on classical cryptographic primitives. In particular, APTE handles private channels...

  18. Two Tests for the Equivalence Principle (United States)

    Harpaz, Amos


    The question: "Is the equivalence principle (EP) a general principle" is examined by analyzing solutions to two cases: 1. The Twin Paradox, and 2. Does a static charge located in a gravitational field radiate? The solutions to these two cases are given first by using EP, and then by physical analysis of the system involved. The fact that the two methods yield the same solutions, may be considered as test cases for the validity of the EP.

  19. Equivalent Lagrangians: Generalization, Transformation Maps, and Applications

    Directory of Open Access Journals (Sweden)

    N. Wilson


    Full Text Available Equivalent Lagrangians are used to find, via transformations, solutions and conservation laws of a given differential equation by exploiting the possible existence of an isomorphic algebra of Lie point symmetries and, more particularly, an isomorphic Noether point symmetry algebra. Applications include ordinary differential equations such as the Kummer equation and the combined gravity-inertial-Rossbywave equation and certain classes of partial differential equations related to multidimensional wave equations.

  20. Capacitors with low equivalent series resistance (United States)

    Fleig, Patrick Franz (Inventor); Lakeman, Charles D. E. (Inventor); Fuge, Mark (Inventor)


    An electric double layer capacitor (EDLC) in a coin or button cell configuration having low equivalent series resistance (ESR). The capacitor comprises mesh or other porous metal that is attached via conducting adhesive to one or both the current collectors. The mesh is embedded into the surface of the adjacent electrode, thereby reducing the interfacial resistance between the electrode and the current collector, thus reducing the ESR of the capacitor.

  1. Determining sample size when assessing mean equivalence. (United States)

    Asberg, Arne; Solem, Kristine B; Mikkelsen, Gustav


    When we want to assess whether two analytical methods are equivalent, we could test if the difference between the mean results is within the specification limits of 0 ± an acceptance criterion. Testing the null hypothesis of zero difference is less interesting, and so is the sample size estimation based on testing that hypothesis. Power function curves for equivalence testing experiments are not widely available. In this paper we present power function curves to help decide on the number of measurements when testing equivalence between the means of two analytical methods. Computer simulation was used to calculate the probability that the 90% confidence interval for the difference between the means of two analytical methods would exceed the specification limits of 0 ± 1, 0 ± 2 or 0 ± 3 analytical standard deviations (SDa), respectively. The probability of getting a nonequivalence alarm increases with increasing difference between the means when the difference is well within the specification limits. The probability increases with decreasing sample size and with smaller acceptance criteria. We may need at least 40-50 measurements with each analytical method when the specification limits are 0 ± 1 SDa, and 10-15 and 5-10 when the specification limits are 0 ± 2 and 0 ± 3 SDa, respectively. The power function curves provide information of the probability of false alarm, so that we can decide on the sample size under less uncertainty.

  2. Self-Pumping Active Gel (United States)

    Wu, Kun-Ta; Hishamunda, Jean Bernard; Fraden, Seth; Dogic, Zvonimir

    Isotropic active gels are the network which is consist of cross-linked building blocks and the structure of which changes randomly and isotropically with time. Dogic et. al. show that pairs of anti-parallel microtubules form extensile bundles, which merge, extend, and buckle. In an unconfined system, the dynamics of these bundles causes spontaneous turbulent-like flow driven by motion of microscopic molecular motors. We found that confining these active gels in a millimeter sized toroids causes a transition into a new dynamical state characterized by circulation currents persisting for hours until ATP is depleted. We show how toroid dimensions impact the properties of self-organized circular currents, how directions of circulation can be designed by engineering ratchet-shaped boundaries, and how circulations of connected toroids can be either synchronized or antisynchronized. Furthermore, we demonstrate that the flow rate in the circulation is independent of curvature and length of flow path. The flow rate persists for centimeters without decay, disregarding conventional pipe flow resistance. Such findings pave the path to self-pumping pipe transport and performing physical work with biological system.

  3. Microfluidics of soft granular gels (United States)

    Nixon, Ryan; Bhattacharjee, Tapomoy; Sawyer, W. Gregory; Angelini, Thomas E.

    Microfluidic methods for encapsulating cells and particles typically involve drop making with two immiscible fluids. The main materials constraint in this approach is surface tension, creating inherent instability between the two fluids. We can eliminate this instability by using miscible inner and outer phases. This is achieved by using granular micro gels which are chemically miscible but physically do not mix. These microgels are yield stress materials, so they flow as solid plugs far from shear gradients, and fluidize where gradients are generated - near an injection nozzle for example. We have found that tuning the yield stress of the material by varying polymer concentration, device performance can be controlled. The solid like behavior of the gel allows us to produces infinitely stable jets that maintain their integrity and configuration over long distances and times. These properties can be combined and manipulated to produce discrete particulate bunches of an inner phase, flowing inside of an outer phase, well enough even to print a Morse code message suspended within flow chambers about a millimeter in diameter moving at millimeters a second.

  4. GEM printer: 3D gel printer for free shaping of functional gel engineering materials (United States)

    Furukawa, Hidemitsu; Muroi, Hisato; Yamamoto, Kouki; Serizawa, Ryo; Gong, Jin


    In the past decade, several high-strength gels have been developed. These gels are expected to use as a kind of new engineering materials in the fields of industry and medical as substitutes to polyester fibers, which are materials of artificial blood vessels. The gels have both low surface friction and well permeability due to a large amount of water absorbed in the gels, which are superiority of the gels compering to the polyester fibers. It is, however, difficult for gels to be forked structure or cavity structure by using cutting or mold. Consequently, it is necessary to develop the additive manufacturing device to synthesize and mode freely gels at the same time. Here we try to develop an optical 3D gel printer that enables gels to be shaped precisely and freely. For the free forming of high-strength gels, the 1st gels are ground to particles and mixed with 2nd pregel solution, and the mixed solution is gelled by the irradiation of UV laser beam through an optical fiber. The use of the optical fiber makes one-point UV irradiation possible. Since the optical fiber is controlled by 3D-CAD, the precise and free molding in XYZ directions is easily realized. We successfully synthesized tough gels using the gel printer.

  5. Stabilized aqueous gels and uses thereof

    Energy Technology Data Exchange (ETDEWEB)

    Swanson, B.L.


    New improved aqueous gels, and methods of using same in contacting subterranean formations, are provided. The gels are prepared by gelling an aqueous brine having incorporated therein a water-soluble cellulose ether such as a carboxymethylcellulose (CMC), and are rendered more stable to decomposition by incorporating a sulfoalkylated tannin stabilizing agent, such as a sulfomethylated quebracho (SMQ), in the gel during the preparation thereof.

  6. Crystal structure of thermally reversible maltodextrin gels

    Energy Technology Data Exchange (ETDEWEB)

    Reuther, F.; Schierbaum, F. (Akademie der Wissenschaften der DDR, Potsdam. Zentralinstitut fuer Ernaehrung); Gernat, C.; Damaschun, G. (Akademie der Wissenschaften der DDR, Berlin. Zentralinstitut fuer Molekularbiologie)


    Aqueous solutions of starch solidify at room temperature to form thermally irreversible gels. These gels exhibit the wide angle X-ray pattern of B-starch. In thermally reversible gels of a special digestion product of starch the B-pattern of starch is also observed. The property of thermal reversibility therefore is not due to amorphous or different crystalline structures, but is a consequence of smaller macromolecules.

  7. Ionic liquid based multifunctional double network gel (United States)

    Ahmed, Kumkum; Higashihara, Tomoya; Arafune, Hiroyuki; Kamijo, Toshio; Morinaga, Takashi; Sato, Takaya; Furukawa, Hidemitsu


    Gels are a promising class of soft and wet materials with diverse application in tissue engineering and bio-medical purpose. In order to accelerate the development of gels, it is required to synthesize multi-functional gels of high mechanical strength, ultra low surface friction and suitable elastic modulus with a variety of methods and new materials. Among many types of gel ionic gel made from ionic liquids (ILs) could be used for diverse applications in electrochemical devices and in the field of tribology. IL, a promising materials for lubrication, is a salt with a melting point lower than 100 °C. As a lubricant, ILs are characterized by an extremely low vapor pressure, high thermal stability and high ion conductivity. In this work a novel approach of making double network DN ionic gel using IL has been made utilizing photo polymerization process. A hydrophobic monomer Methyl methacrylate (MMA) has been used as a first network and a hydrophobic IL monomer, N,N-diethyl-N-(2-mthacryloylethyl)-N-methylammonium bistrifluoromethylsulfonyl)imide (DEMM-TFSI) has been used as a second network using photo initiator benzophenon and crosslinker triethylene glycol dimethacrylate (TEGDMA). The resulting DN ionic gel shows transparency, flexibility, high thermal stability, good mechanical toughness and low friction coefficient value which can be a potential candidate as a gel slider in different mechanical devices and can open a new area in the field of gel tribology.

  8. Conducting polymer electrodes for gel electrophoresis.

    Directory of Open Access Journals (Sweden)

    Katarina Bengtsson

    Full Text Available In nearly all cases, electrophoresis in gels is driven via the electrolysis of water at the electrodes, where the process consumes water and produces electrochemical by-products. We have previously demonstrated that π-conjugated polymers such as poly(3,4-ethylenedioxythiophene (PEDOT can be placed between traditional metal electrodes and an electrolyte to mitigate electrolysis in liquid (capillary electroosmosis/electrophoresis systems. In this report, we extend our previous result to gel electrophoresis, and show that electrodes containing PEDOT can be used with a commercial polyacrylamide gel electrophoresis system with minimal impact to the resulting gel image or the ionic transport measured during a separation.

  9. Fabrication of thermal sensitive folic acid based supramolecular hybrid gels for injectable drug release gels. (United States)

    Song, Yahui; Gao, Jianping; Xu, Xiaoyang; Zhao, Huilin; Xue, Ruinan; Zhou, Jingkuo; Hong, Wei; Qiu, Haixia


    Thermal sensitive supramolecular hybrid gels for injectable drug release were prepared by adding different amounts of agar into folic acid (FA) gelator. The gelation temperature was modulated in order to form injectable gel with body temperature (37°C). Such kind of folic acid-agar (FAG) hybrid gel makes it possible to use supramolecular gel as injectable drug loaded gels for drug release. FT-IR and UV-vis spectra indicate that agar macromolecules involve in the self-assembly process through intermolecular H-bonding and π-π stacking interactions with FA molecules. The SEM and TEM images demonstrate that the fiber diameter of FAG hybrid gel is about 20nm, much smaller than that of FA gel (40nm). However, FAG hybrid has a denser nano-fibrous network structure than FA gels. Moreover, FAG hybrid gel is endowed with a more ordered network structure and a little better crystallization capability by adding agar. FAG hybrid gel also shows a shear-thinning behavior but the shear viscosity is about 2 times higher than that of FA gel. Compared with FA gel, the storage (G') and loss (G″) moduli of the FAG gel are higher, which implies an enhanced gel strength. At the same time, both FA and FAG gels are facilely affected by some external factors such as acid, base and salts. In acidic or basic conditions, the strength became weak and the gelation temperature (Tg) decreased. While, within certain concentrations, the salt (NaCl) increased the gel strength and Tg. FAG gel suffered lower mass loss and owned better stability in different pH solutions compared with pure FA gel. The release behavior of the FA and injectable FAG gels was investigated by using Rhodamine B as a mimic model drug. FAG hybrid gel shows a long release profile and the release time is 3 times longer than that of FA gel, up to 30h, and the accumulative release amount reaches about 86%. So it is a potential injectable gel for sustained release drug delivery system. Copyright © 2017 Elsevier B.V. All rights

  10. Electron Beam Quality Determination Through Fricke Xylenol Gel Dosimeter (United States)

    Petchevist, P. C. D.; Moreira, M. V.; de Almeida, A.


    According to the IAEA TRS-398 protocol, a parallel plate ionization chamber is recommended to be used in electron dosimetry. The important dosimetric parameters such as R100 and R50, inferred from the percentage depth dose (PDD) curve, allow to obtain the electron beam average energy at the water phantom surface (material equivalent to the soft tissue). In this work, a chemical dosimeter based on the Fe(II) to Fe(III) oxidation was used to obtain the average energies from electrons beams (from nominal energies of 5, 8 and 10 MeV) and related parameters of R100, R50 and zref. These energies obtained through the Fricke Xylenol Gel (FXG) were compared to those with a parallel plate ionization chamber, following the cited protocol, which showed no significant differences. From these measurements one can conclude the FXG applicability for R100, R50 and electron beam average energy determination.

  11. Effect of gel structure on the gastric digestion of whey protein emulsion gels. (United States)

    Guo, Qing; Ye, Aiqian; Lad, Mita; Dalgleish, Douglas; Singh, Harjinder


    This study aimed to characterize and determine the disintegration of emulsion gels in a human gastric simulator (HGS) and the physicochemical characteristics of gastric digesta. Using thermal treatment at 90 °C, whey protein emulsion gels with different structures and gel strengths were formed by varying the ionic strength. Simulated boluses of soft (containing 10 mM NaCl) and hard (200 mM NaCl) gels, which had similar particle sizes to those of human subjects, were created for gastric digestion. Soft gels disintegrated faster than hard gels in the HGS. The boluses of both gels gradually disintegrated into particles of size ∼10 μm. With further digestion, the protein matrix of the soft gel particles dissolved, the proteins were disrupted mainly by proteolysis and large quantities of oil droplets were released. In contrast, for the hard gel particles, although all proteins were hydrolysed after 240 min the breakdown of the particles was slow and no oil droplets were released after 300 min. The differences in the breakdown of soft and hard gels in the HGS were attributed to the structures of the emulsion gel, which may result in different sets of peptides in the digestion. In addition, coalescence of the oil droplets was observed only for the soft gel.

  12. Chitosan: Gels and Interfacial Properties

    Directory of Open Access Journals (Sweden)

    Julie Nilsen-Nygaard


    Full Text Available Chitosan is a unique biopolymer in the respect that it is abundant, cationic, low-toxic, non-immunogenic and biodegradable. The relative occurrence of the two monomeric building units (N-acetyl-glucosamine and d-glucosamine is crucial to whether chitosan is predominantly an ampholyte or predominantly a polyelectrolyte at acidic pH-values. The chemical composition is not only crucial to its surface activity properties, but also to whether and why chitosan can undergo a sol–gel transition. This review gives an overview of chitosan hydrogels and their biomedical applications, e.g., in tissue engineering and drug delivery, as well as the chitosan’s surface activity and its role in emulsion formation, stabilization and destabilization. Previously unpublished original data where chitosan acts as an emulsifier and flocculant are presented and discussed, showing that highly-acetylated chitosans can act both as an emulsifier and as a flocculant.

  13. Equivalent Circuit Modeling of Hysteresis Motors

    Energy Technology Data Exchange (ETDEWEB)

    Nitao, J J; Scharlemann, E T; Kirkendall, B A


    We performed a literature review and found that many equivalent circuit models of hysteresis motors in use today are incorrect. The model by Miyairi and Kataoka (1965) is the correct one. We extended the model by transforming it to quadrature coordinates, amenable to circuit or digital simulation. 'Hunting' is an oscillatory phenomenon often observed in hysteresis motors. While several works have attempted to model the phenomenon with some partial success, we present a new complete model that predicts hunting from first principles.

  14. Real Options Valuation Based on Certainty Equivalents

    Directory of Open Access Journals (Sweden)

    Cecilia Maya Ochoa


    Full Text Available This purpose of this research is to identify appropriate rates to discount the flows from real options in situations in which the risk-free rate does not apply, in particular, in incomplete markets.  A methodology is proposed for valuing real options based on certainty equivalence, which requires as a principal condition the consideration of preferences represented with utility functions.  A constant relative risk aversion (CRRA utility function is used to represent these preferences. The results indicate that this methodology adequately reflects how the value of a real option changes in accordance with an investor´s preferences.

  15. Applicability constraints of the equivalence theorem

    Energy Technology Data Exchange (ETDEWEB)

    Dobado, A.; Pelaez, J.R. [Departamento de Fisica Teorica, Universidad Complutense, 28040 Madrid (Spain); Urdiales, M.T. [Departamento de Fisica Teorica, Universidad Autonoma, 28049 Madrid (Spain)


    In this work we study the applicability of the equivalence theorem, either for unitary models or within an effective Lagrangian approach. There are two types of limitations: the existence of a validity energy window and the use of the lowest order in the electroweak constants. For the first kind, we consider some methods, based on dispersion theory or the large N limit, that allow us to extend the applicability. For the second, we obtain numerical estimates of the effect of neglecting higher orders in the perturbative expansion. {copyright} {ital 1997} {ital The American Physical Society}

  16. Open maps, behavioural equivalences, and congruences

    DEFF Research Database (Denmark)

    Cheng, Allan; Nielsen, Mogens


    Spans of open maps have been proposed by Joyal, Nielsen, and Winskel as a way of adjoining an abstract equivalence, P-bisimilarity, to a category of models of computation M, where P is an arbitrary sub-category of observations. Part of the motivation was to recast and generalise Milner's well...... viewed as functors preserve P-bisimilarity? We define the notion of functors being P -factorisable, show how this ensures that P-bisimilarity is a congruence with respect to such functors. Guided by the definition of P-factorisability we show how it is possible to parametrise proofs of functors being P...

  17. Galilean equivalence for galactic dark matter. (United States)

    Kesden, Michael; Kamionkowski, Marc


    Satellite galaxies are tidally disrupted as they orbit the Milky Way. If dark matter (DM) experiences a stronger self-attraction than baryons, stars will preferentially gain rather than lose energy during tidal disruption, leading to an enhancement in the trailing compared to the leading tidal stream. The Sgr dwarf galaxy is seen to have roughly equal streams, challenging models in which DM and baryons accelerate differently by more than 10%. Future observations and a better understanding of DM distribution should allow detection of equivalence violation at the percent level.

  18. Equivalent Circuit for Magnetoelectric Read and Write


    Camsari, Kerem Y.; Faria, Rafatul; Hassan, Orchi; Sutton, Brian M.; Datta, Supriyo


    We describe an equivalent circuit model applicable to a wide variety of magnetoelectric phenomena and use SPICE simulations to benchmark this model against experimental data. We use this model to suggest a different mode of operation where the "1" and "0'" states are not represented by states with net magnetization (like $m_x$, $m_y$ or $m_z$) but by different easy axes, quantitatively described by ($m_x^2 - m_y^2$) which switches from "0" to "1" through the write voltage. This change is dire...

  19. European Equivalencies in Legal Interpreting and Translation

    DEFF Research Database (Denmark)

    Corsellis, Ann; Hertog, Erik; Martinsen, Bodil


    Within Europe there is increasing freedom of movement between countries and increasing inward migration. As a result, equivalent standards of legl interpreting and translation are required to allow reliable communication for judicial cooperation between member states, for criminal and civil matters...... which cross national borders and for the needs of multilingual populations. The European Convention of Human Rights (article 6, paragrph 3) is one of the main planks of relevant legislation. This international, two year project has been funded by the EU Grotius programme to set out what is required...

  20. Silica gel matrix immobilized Chlorophyta hydrodictyon africanum ...

    African Journals Online (AJOL)



    Aug 5, 2015 ... Chlorophyta hydrodictyon africanum was immobilized on a silica gel matrix to improve its mechanical properties. The algae-silica gel adsorbent was used for batch sorption studies of a cationic dye, methylene blue (MB). Optimum adsorption was obtained with a dosage of 0.8 g bio sorbent. Results.

  1. Sodium Dedecyl Suphate Polyacrilamide Gel Electrophosis of ...

    African Journals Online (AJOL)

    Sodium Dedecyl Suphate Polyacrilamide Gel Electrophosis of Campylobacter coli. S.I. Smith, M.M. Ibrahim, V.N. Ezeobi, K.S. Oyedeji, K.A. Akinsinde, A.O Coker. Abstract. Campylobacter coli were characterized using sodium dodecyl sulphate-polyacrilamide gel electrophoresis (SDS-PAGE). The isolates were obtained ...

  2. Using Greener Gels to Explore Rheology (United States)

    Garrett, Brendan; Matharu, Avtar S.; Hurst, Glenn A.


    A laboratory experiment was developed to investigate the rheological properties of a green calcium-cross-linked alginate gel as an alternative to the traditional borax-cross-linked poly(vinyl alcohol) gel. As borax is suspected of damaging fertility and the unborn child, a safe, green alternative is necessary. The rheological properties of a…

  3. Development and Evaluation of Ibuprofen Transdermal Gel ...

    African Journals Online (AJOL)


    1Dubai Pharmacy College, Dubai, UAE, 2Helwan University, Helwan, Egypt. Abstract. Purpose: To develop an ibuprofen transdermal gel with a capability for both topical and systemic drug delivery. Methods: Ibuprofen gel formulations, incorporating various permeation enhancers, were prepared using chitosan as a gelling ...

  4. Responsive molecular gels. : Surface Chemistry and Colloids

    NARCIS (Netherlands)

    de Jong, Jaap J. D.; Feringa, Bernard; van Esch, Jan


    A review discusses the chemo-responsive gels and physico-responsive gels. Phys. low mol. mass responsive gelators are interesting mols. with many potential applications in areas such as catalysis, sensor and sepn. technol., drug delivery, and biomedicine. In a relatively short period, a wide variety

  5. Silica gel matrix immobilized Chlorophyta hydrodictyon africanum ...

    African Journals Online (AJOL)

    Chlorophyta hydrodictyon africanum was immobilized on a silica gel matrix to improve its mechanical properties. The algae-silica gel adsorbent was used for batch sorption studies of a cationic dye, methylene blue (MB). Optimum adsorption was obtained with a dosage of 0.8 g bio sorbent. Results from sorption studies ...

  6. Recrystallization of amylopectin in concentrated starch gels

    NARCIS (Netherlands)

    Keetels, CJAM; Oostergetel, GT; vanVliet, T

    The relation between the recrystallization of amylopectin and the increase in stiffness of starch gels during storage was studied by various techniques. From transmission electron microscopy it was concluded that the size of the crystalline domains in retrograded 30% w/w potato starch gels was about

  7. Preparation of Alginate Gel Beads Containing Metformin ...

    African Journals Online (AJOL)

    A new emulsion gelation method was used to prepare gel beads for a highly water-soluble drug metformin hydrochloride using sodium alginate as the polymer. The gel beads containing oil was prepared by gently mixing or homogenizing oil and water phase containing sodium alginate which was then extruded into calcium ...

  8. An in vitro and in vivo toxicologic evaluation of a stabilized aloe vera gel supplement drink in mice. (United States)

    Sehgal, Inder; Winters, Wallace D; Scott, Michael; Kousoulas, Konstantine


    Aloe vera gel is increasingly consumed as a beverage dietary supplement. The purpose of this study was to determine potential toxicity of a stabilized aloe vera gel derived from the inner gel fillet and marketed as a drink. The gel juice was assessed through assays of genotoxicity in vivo and acute and subchronic toxicity in B6C3F1 mice. Aloe vera did not increase the SOS DNA repair response in Escherichia coli and at 1× and 0.25× it did not increase mutagenesis of Salmonella TA100 resulting in histidine biosynthesis. At 3 and 14days following acute exposure, male and female mice gavaged with the stabilized aloe gel had daily appearances, total body weight gain, selected organ weights, necropsy and hematology tests similar to control mice gavaged with water. After a 13-week aloe gel feed study, male and female mice evaluated by the same criteria as the acute study plus feed consumption and serum chemistry tests were found to be equivalent to control groups. These data indicate that a commercial stabilized aloe gel consumed as a beverage was not genotoxic or toxic in vivo. These results contrast with those obtained using preparations containing aloe latex phenolic compounds such as anthraquinones. Copyright © 2013 Elsevier Ltd. All rights reserved.

  9. Analysis of traumatic ulcer healing time under the treatment of the Mauli banana (Musa acuminata 25% stem extract gel

    Directory of Open Access Journals (Sweden)

    Dewi Puspitasari


    Full Text Available ABSTRACT Introduction: Traumatic ulcer is one of oral disorders that often occur. The prevalence is quite high, between 3-24% of population. Therapy of traumatic ulcer is symptomatic. People usually use Aloe vera extract gel. Previous research showed that the Aloe vera gel is equivalent with ethanol extract of 25% Mauli banana (Musa acuminata stem in accelerating wound healing based on the number of macrophages and neovascular. The objective of the study is to find out the time difference of traumatic ulcer healing using 25% Musa acuminata stem extract gel compared to a gel containing Aloe vera extract. Methods: The research was post test design. Subjects were patients of Oral Medicine Installation in Gusti Hasan Aman Dental Hospital Banjarmasin with diagnosis of traumatic ulcer using completely random sampling method. Eight patients as samples were determined by the formula of Lemeshow. Results: there was no significant difference with p=0,724 (p>0,05 between healing time using Aloe vera gel and 25% Musa acuminata stem extract. Conclusion: At the concentration of 25% Musa acuminata stem extract gel concentration has the same healing time with Aloe vera gel, therefore can be recommended as a topical use for traumatic ulcer healing. Keywords: Musa acuminata stem, Healing time, Traumatic ulcer

  10. Integrable topological billiards and equivalent dynamical systems (United States)

    Vedyushkina, V. V.; Fomenko, A. T.


    We consider several topological integrable billiards and prove that they are Liouville equivalent to many systems of rigid body dynamics. The proof uses the Fomenko-Zieschang theory of invariants of integrable systems. We study billiards bounded by arcs of confocal quadrics and their generalizations, generalized billiards, where the motion occurs on a locally planar surface obtained by gluing several planar domains isometrically along their boundaries, which are arcs of confocal quadrics. We describe two new classes of integrable billiards bounded by arcs of confocal quadrics, namely, non-compact billiards and generalized billiards obtained by gluing planar billiards along non-convex parts of their boundaries. We completely classify non-compact billiards bounded by arcs of confocal quadrics and study their topology using the Fomenko invariants that describe the bifurcations of singular leaves of the additional integral. We study the topology of isoenergy surfaces for some non-convex generalized billiards. It turns out that they possess exotic Liouville foliations: the integral trajectories of the billiard that lie on some singular leaves admit no continuous extension. Such billiards appear to be leafwise equivalent to billiards bounded by arcs of confocal quadrics in the Minkowski metric.

  11. Equivalent Relaxations of Optimal Power Flow

    Energy Technology Data Exchange (ETDEWEB)

    Bose, S; Low, SH; Teeraratkul, T; Hassibi, B


    Several convex relaxations of the optimal power flow (OPF) problem have recently been developed using both bus injection models and branch flow models. In this paper, we prove relations among three convex relaxations: a semidefinite relaxation that computes a full matrix, a chordal relaxation based on a chordal extension of the network graph, and a second-order cone relaxation that computes the smallest partial matrix. We prove a bijection between the feasible sets of the OPF in the bus injection model and the branch flow model, establishing the equivalence of these two models and their second-order cone relaxations. Our results imply that, for radial networks, all these relaxations are equivalent and one should always solve the second-order cone relaxation. For mesh networks, the semidefinite relaxation and the chordal relaxation are equally tight and both are strictly tighter than the second-order cone relaxation. Therefore, for mesh networks, one should either solve the chordal relaxation or the SOCP relaxation, trading off tightness and the required computational effort. Simulations are used to illustrate these results.

  12. Free fall and the equivalence principle revisited (United States)

    Pendrill, Ann-Marie


    Free fall is commonly discussed as an example of the equivalence principle, in the context of a homogeneous gravitational field, which is a reasonable approximation for small test masses falling moderate distances. Newton’s law of gravity provides a generalisation to larger distances, and also brings in an inhomogeneity in the gravitational field. In addition, Newton’s third law of action and reaction causes the Earth to accelerate towards the falling object, bringing in a mass dependence in the time required for an object to reach ground—in spite of the equivalence between inertial and gravitational mass. These aspects are rarely discussed in textbooks when the motion of everyday objects are discussed. Although these effects are extremely small, it may still be important for teachers to make assumptions and approximations explicit, to be aware of small corrections, and also to be prepared to estimate their size. Even if the corrections are not part of regular teaching, some students may reflect on them, and their questions deserve to be taken seriously.

  13. Photoswitchable gel assembly based on molecular recognition (United States)

    Yamaguchi, Hiroyasu; Kobayashi, Yuichiro; Kobayashi, Ryosuke; Takashima, Yoshinori; Hashidzume, Akihito; Harada, Akira


    The formation of effective and precise linkages in bottom-up or top-down processes is important for the development of self-assembled materials. Self-assembly through molecular recognition events is a powerful tool for producing functionalized materials. Photoresponsive molecular recognition systems can permit the creation of photoregulated self-assembled macroscopic objects. Here we demonstrate that macroscopic gel assembly can be highly regulated through photoisomerization of an azobenzene moiety that interacts differently with two host molecules. A photoregulated gel assembly system is developed using polyacrylamide-based hydrogels functionalized with azobenzene (guest) or cyclodextrin (host) moieties. Reversible adhesion and dissociation of the host gel from the guest gel may be controlled by photoirradiation. The differential affinities of α-cyclodextrin or β-cyclodextrin for the trans-azobenzene and cis-azobenzene are employed in the construction of a photoswitchable gel assembly system. PMID:22215078

  14. On shear rheology of gel propellants

    Energy Technology Data Exchange (ETDEWEB)

    Rahimi, Shai; Peretz, Arie [RAFAEL, MANOR Propulsion and Explosive Systems Division, Haifa (Israel); Natan, Benveniste [Faculty of Aerospace Engineering, Technion - Israel Institute of Technology, Haifa (Israel)


    Selected fuel, oxidizer and simulant gels were prepared and rheologically characterized using a rotational rheometer. For fuel gelation both organic and inorganic gellants were utilized, whereas oxidizers and simulants were gelled with addition of silica and polysaccharides, respectively. The generalized Herschel-Bulkley constitutive model was found to most adequately represent the gels studied. Hydrazine-based fuels, gelled with polysaccharides, were characterized as shear-thinning pseudoplastic fluids with low shear yield stress, whereas inhibited red-fuming nitric acid (IRFNA) and hydrogen peroxide oxidizers, gelled with silica, were characterized as yield thixotropic fluids with significant shear yield stress. Creep tests were conducted on two rheological types of gels with different gellant content and the results were fitted by Burgers-Kelvin viscoelastic constitutive model. The effect of temperature on the rheological properties of gel propellant simulants was also investigated. A general rheological classification of gel propellants and simulants is proposed. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

  15. Polymer architecture of magnetic gels: a review (United States)

    Weeber, Rudolf; Hermes, Melissa; Schmidt, Annette M.; Holm, Christian


    In this review article, we provide an introduction to ferrogels, i.e. polymeric gels with embedded magnetic particles. Due to the interplay between magnetic and elastic properties of these materials, they are promising candidates for engineering and biomedical applications such as actuation and controlled drug release. Particular emphasis will be put on the polymer architecture of magnetic gels since it controls the degrees of freedom of the magnetic particles in the gel, and it is important for the particle-polymer coupling determining the mechanisms available for the gel deformation in magnetic fields. We report on the different polymer architectures that have been realized so far, and provide an overview of synthesis strategies and experimental techniques for the characterization of these materials. We further focus on theoretical and simulational studies carried out on magnetic gels, and highlight their contributions towards understanding the influence of the gels’ polymer architecture.

  16. Catalytic control over supramolecular gel formation (United States)

    Boekhoven, Job; Poolman, Jos M.; Maity, Chandan; Li, Feng; van der Mee, Lars; Minkenberg, Christophe B.; Mendes, Eduardo; van Esch, Jan H.; Eelkema, Rienk


    Low-molecular-weight gels show great potential for application in fields ranging from the petrochemical industry to healthcare and tissue engineering. These supramolecular gels are often metastable materials, which implies that their properties are, at least partially, kinetically controlled. Here we show how the mechanical properties and structure of these materials can be controlled directly by catalytic action. We show how in situ catalysis of the formation of gelator molecules can be used to accelerate the formation of supramolecular hydrogels, which drastically enhances their resulting mechanical properties. Using acid or nucleophilic aniline catalysis, it is possible to make supramolecular hydrogels with tunable gel-strength in a matter of minutes, under ambient conditions, starting from simple soluble building blocks. By changing the rate of formation of the gelator molecules using a catalyst, the overall rate of gelation and the resulting gel morphology are affected, which provides access to metastable gel states with improved mechanical strength and appearance despite an identical gelator composition.

  17. A new polymer gel dosimeter composed of methacrylic acid, agarose gel and THPC with gelatin

    Energy Technology Data Exchange (ETDEWEB)

    Yoshioka, M; Hayashi, S; Usui, S; Haneda, K; Tominaga, T [Department of Clinical Radiology, Faculty of Health Sciences, Hiroshima International University, Higashi-Hiroshima, Hiroshima, 739-2695 (Japan); Numasaki, H; Teshima, T [Department of Medical Physics and Engineering, Osaka University Graduate School of Medicine, Suita, Osaka, 565-0871 (Japan)], E-mail:


    In this paper, a new type of methacrylic acid based gel dosimeter is presented. This gel contains both agarose and gelatin with deferent roles respectively. The agarose conducts itself as a gelling agent, while the gelatin relates to the graft reaction of methacrylic acid. This new type of gel excels in the long-term stability of R{sub 2} after irradiation. The characteristics of this gel were studied by the measurements of R{sub 2} with MRI and the direct measurements of temperature in the gel during the irradiation.

  18. Initial experiments with gel-water: towards MRI-linac dosimetry and imaging. (United States)

    Alnaghy, Sarah J; Gargett, Maegan; Liney, Gary; Petasecca, Marco; Begg, Jarrad; Espinoza, Anthony; Newall, Matthew K; Duncan, Mitchell; Holloway, Lois; Lerch, Michael L F; Lazea, Mircea; Rosenfeld, Anatoly B; Metcalfe, Peter


    Tracking the position of a moving radiation detector in time and space during data acquisition can replicate 4D image-guided radiotherapy (4DIGRT). Magnetic resonance imaging (MRI)-linacs need MRI-visible detectors to achieve this, however, imaging solid phantoms is an issue. Hence, gel-water, a material that provides signal for MRI-visibility, and which will in future work, replace solid water for an MRI-linac 4DIGRT quality assurance tool, is discussed. MR and CT images of gel-water were acquired for visualisation and electron density verification. Characterisation of gel-water at 0 T was compared to Gammex-RMI solid water, using MagicPlate-512 (M512) and RMI Attix chamber; this included percentage depth dose, tissue-phantom ratio (TPR20/10), tissue-maximum ratio (TMR), profiles, output factors, and a gamma analysis to investigate field penumbral differences. MR images of a non-powered detector in gel-water demonstrated detector visualisation. The CT-determined gel-water electron density agreed with the calculated value of 1.01. Gel-water depth dose data demonstrated a maximum deviation of 0.7% from solid water for M512 and 2.4% for the Attix chamber, and by 2.1% for TPR20/10 and 1.0% for TMR. FWHM and output factor differences between materials were ≤0.3 and ≤1.4%. M512 data passed gamma analysis with 100% within 2%, 2 mm tolerance for multileaf collimator defined fields. Gel-water was shown to be tissue-equivalent for dosimetry and a feasible option to replace solid water.

  19. Gelatin increases the coarseness of whey protein gels and impairs water exudation from the mixed gel at low temperatures

    NARCIS (Netherlands)

    Martin, A.H.; Bakhuizen, E.; Ersch, C.; Urbonaite, V.; Jongh, H.H.J. de; Pouvreau, L.


    To understand the origin of water holding of mixed protein gels, a study was performed on water exudation from mixed whey protein (WP)-gelatin gels upon applied pressure. Mixed gels were prepared with varying WP and gelatin concentration and gelatin type to obtain gels with a wide range of gel

  20. Randomised, controlled trial of the efficacy and safety of adapalene gel 0.1% and tretinoin cream 0.05% in patients with acne vulgaris. (United States)

    Cunliffe, William J; Danby, F William; Dunlap, Frank; Gold, Michael H; Gratton, David; Greenspan, Alan


    Previous clinical trials have shown that adapalene gel produces less irritation than tretinoin gels and tretinoin 0.025% cream. Short term results have shown that adapalene is less irritating than tretinoin gels and creams. This study is the first to compare the 0.1% formulation of adapalene gel with the 0.05% strength of tretinoin cream in a formal clinical trial. To investigate the efficacy and tolerability of adapalene gel 0.1% compared with tretinoin cream 0.05% in patients with mild-to-moderate acne vulgaris. Ten-week, multicentre, randomised, investigator-masked, active-controlled, parallel group study in 409 patients with acne vulgaris. Adapalene gel 0.1% demonstrated equivalent efficacy in reduction of acne lesion counts and global improvement of acne severity over 10 weeks' treatment and was significantly better tolerated than tretinoin cream 0.05% in terms of erythema, dryness, desquamation and stinging/burning. Adapalene gel 0.1% showed equivalent efficacy and was significantly better tolerated than tretinoin cream 0.05% in patients with mild-to-moderate acne vulgaris.

  1. Premetric equivalent of general relativity: Teleparallelism (United States)

    Itin, Yakov; Hehl, Friedrich W.; Obukhov, Yuri N.


    In general relativity (GR), the metric tensor of spacetime is essential since it represents the gravitational potential. In other gauge theories (such as electromagnetism), the so-called premetric approach succeeds in separating the purely topological field equation from the metric-dependent constitutive law. We show here that GR allows for a premetric formulation, too. For this purpose, we apply the teleparallel approach of gravity, which represents GR as a gauge theory based on the translation group. We formulate the metric-free topological field equation and a general linear constitutive law between the basic field variables. The requirement of local Lorentz invariance turns the model into a full equivalent of GR. Our approach opens a way for a natural extension of GR to diverse geometrical structures of spacetime.

  2. Expressivism, Relativism and the analytic equivalence test

    Directory of Open Access Journals (Sweden)

    Maria J. Frapolli


    Full Text Available The purpose of this paper is to show that, pace (Field 2009, 252, MacFarlane’s assessment relativism and expressivism should be sharply distinguished. We do so by arguing that relativism and expressivism exemplify two very different approaches to context-dependence. Relativism, on the one hand, shares with other contemporary approaches a bottom-up, building block, model, while expressivism is part of a different tradition, one that might include Lewis’ epistemic contextualism and Frege’s content individuation, with which it shares an organic model to deal with context-dependence. The building-block model and the organic model, and thus relativism and expressivism, are set apart with the aid of a particular test: only the building-block model is compatible with the idea that there might be analytically equivalent, and yet different, propositions.

  3. Expressivism, Relativism, and the Analytic Equivalence Test. (United States)

    Frápolli, Maria J; Villanueva, Neftalí


    The purpose of this paper is to show that, pace (Field, 2009), MacFarlane's assessment relativism and expressivism should be sharply distinguished. We do so by arguing that relativism and expressivism exemplify two very different approaches to context-dependence. Relativism, on the one hand, shares with other contemporary approaches a bottom-up, building block, model, while expressivism is part of a different tradition, one that might include Lewis' epistemic contextualism and Frege's content individuation, with which it shares an organic model to deal with context-dependence. The building-block model and the organic model, and thus relativism and expressivism, are set apart with the aid of a particular test: only the building-block model is compatible with the idea that there might be analytically equivalent, and yet different, propositions.

  4. Theoretical Aspects of the Equivalence Principle

    CERN Document Server

    Damour, Thibault


    We review several theoretical aspects of the Equivalence Principle (EP). We emphasize the unsatisfactory fact that the EP maintains the absolute character of the coupling constants of physics while General Relativity, and its generalizations (Kaluza-Klein,..., String Theory), suggest that all absolute structures should be replaced by dynamical entities. We discuss the EP-violation phenomenology of dilaton-like models, which is likely to be dominated by the linear superposition of two effects: a signal proportional to the nuclear Coulomb energy, related to the variation of the fine-structure constant, and a signal proportional to the surface nuclear binding energy, related to the variation of the light quark masses. We recall the various theoretical arguments (including a recently proposed anthropic argument) suggesting that the EP be violated at a small, but not unmeasurably small level. This motivates the need for improved tests of the EP. These tests are probing new territories in physics that are related t...

  5. Framework for Application of the Toxicity Equivalence ... (United States)

    Polychlorinated dibenzo-p-dioxins (PCDDs), dibenzofurans (PCDFs), and biphenyls (PCBs) are persistent contaminants found widely in the environment. Several of these compounds bioaccumulate in the tissues of fish, birds, and mammals and have been shown to cause mortality and adverse effects on reproduction, development, and the immune system. EPA has developed a framework intended to assist Agency scientists in using a method known as the toxicity equivalence methodology to evaluate the ecological risks of these chemicals. The methodology offers a means to derive a single exposure estimate from multiple chemical concentrations found in environmental mixtures so that risk assessors can consider their cumulative impacts. This framework helps to clarify this methodology’s strengths, limitations, and role within the broader context of ecological risk assessment.

  6. Experimental and Calculated Effectiveness of a Radiochromic Dye Film to Stopping 21 MeV 7Li- and 64 MeV 16O Ions

    DEFF Research Database (Denmark)

    Olsen, Kjeld J; Hansen, Johnny


    Relative radiation effectiveness, RE, of 21 MeV 7Li and 64 MeV 16O ions being completely stopped in a tissue equivalent film dose meter has been measured as a function of penetration depth and energy, and the results have been compared with calculations based on a δ-ray theory for heavy charged...... in the detector, which are important parameters in the theoretical model, does not improve the overall correlation between theory and experiment. It is concluded that disagreement between theoretical and experimental RE-values below 1.5 MeV/amu is partly due to lack of equivalence between the δ-ray spectrum...

  7. Halogen-bonding-triggered supramolecular gel formation (United States)

    Meazza, Lorenzo; Foster, Jonathan A.; Fucke, Katharina; Metrangolo, Pierangelo; Resnati, Giuseppe; Steed, Jonathan W.


    Supramolecular gels are topical soft materials involving the reversible formation of fibrous aggregates using non-covalent interactions. There is significant interest in controlling the properties of such materials by the formation of multicomponent systems, which exhibit non-additive properties emerging from interaction of the components. The use of hydrogen bonding to assemble supramolecular gels in organic solvents is well established. In contrast, the use of halogen bonding to trigger supramolecular gel formation in a two-component gel (‘co-gel’) is essentially unexplored, and forms the basis for this study. Here, we show that halogen bonding between a pyridyl substituent in a bis(pyridyl urea) and 1,4-diiodotetrafluorobenzene brings about gelation, even in polar media such as aqueous methanol and aqueous dimethylsulfoxide. This demonstrates that halogen bonding is sufficiently strong to interfere with competing gel-inhibitory interactions and create a ‘tipping point’ in gel assembly. Using this concept, we have prepared a halogen bond donor bis(urea) gelator that forms co-gels with halogen bond acceptors.

  8. Pterygium inversum unguis secondary to gel polish. (United States)

    Cervantes, J; Sanchez, M; Eber, A E; Perper, M; Tosti, A


    Pterygium inversum unguis (PIU) is characterized by the abnormal adherence of the hyponychium to the ventral surface of the nail plate. It can be both unsightly and painful, resulting in morbidity for patients. Gel polish is a popular nail cosmetic that has been reported to cause several complications. PIU may be another adverse outcome. To highlight a newly recognized adverse effect of a popular beauty technique. This retrospective and prospective case series reports 17 women who developed PIU after gel polish use. All study-related activities occurred at a University of Miami dermatology outpatient clinic. All 17 subjects developed PIU after two to five years of gel polish application. Nine of 17 patients reported using both UVA and LED light to cure gel polish. Of the remaining eight, five used LED light only and three did not know or could not remember. All but two patients had a resolution of PIU a few weeks after switching from gel polish to regular polish manicures. While it remains undiscerned whether PIU is related to chemicals present in the gel polish or to the application and/or removal process of such, patients and dermatologists should be aware of the potential risks of gel manicures. © 2017 European Academy of Dermatology and Venereology.

  9. Muddy marine sediments are gels (United States)

    Dorgan, K. M.; Clemo, W. C.; Barry, M. A.; Johnson, B.


    Marine sediments cover 70% of the earth's surface, are important sites of carbon burial and nutrient regeneration, and provide habitat for diverse and abundant infaunal communities. The majority of these sediments are muds, in which bioturbation affects sediment structure and geochemical gradients. How infaunal activites result in particle mixing depends on the mechanical properties of muddy sediments. At the scale of burrowing animals, muds are elastic solids. Animals move through these elastic muds by extending crack-shaped burrows by fracture. The underlying mechanism driving this elasticity, however, has not been explicitly illustrated. Here, we test the hypothesis that the elastic behavior of muddy sediments is disrupted by removal of organic material by measuring fracture toughness and stiffness of manipulated and control sediments. Our results indicate that the mechanical responses of sediments to forces are governed by the muco-polymeric matrix of organic material. Similar effects of organic material oxidation were not observed in sands, indicating a clear mechanical distinction between fine- and coarse-grained sediments. Muddy sediments are gels, not fluids or granular materials, and models of how sediments respond to forces imposed by, e.g., organisms, gases, and ambient water should explicitly consider the role of organic material.

  10. Auditory Stimulus Equivalence and Non-Arbitrary Relations

    National Research Council Canada - National Science Library

    Stewart, Ian; Lavelle, Niamh


    This study extended previous research on stimulus equivalence with all auditory stimuli by using a methodology more similar to conventional match-to-sample training and testing for three 3-member equivalence relations...

  11. Control of Drug Diffusion Behavior of Xanthan and Locust Bean Gum Gel by Agar Gel. (United States)

    Hishikawa, Yoshihiro; Kakino, Yukari; Tsukamoto, Hoshi; Tahara, Kohei; Onodera, Risako; Takeuchi, Hirofumi


    Oral gel formulations are known as easy to administer drug products for patients who have problems taking drugs including those with conditions such as dysphagia. In addition, there are numerous commercially available oral gel products, most of which are immediate-release formulation that release their pharmaceutical ingredient content by diffusion. This study is focused on developing oral gel formulations that reduce the dosing frequency and dosage compared to the conventional types. This is with the aim of facilitating the use of gel formulations for producing pharmaceutical agents with different dose regimens, thereby enhancing patient convenience. Here, we used naturally derived high-molecular-weight agar (Ag), xanthan gum (Xa), and locust bean gum (Lo) as gel bases to prepare a variety of gel membranes, and evaluated the diffusion coefficient of the model substances. The result revealed that the Ag content in the Xa-Lo combination gel concentration-dependently increased the diffusion coefficient. Moreover, these findings were applied in an attempt to mask the taste of intensely bitter levofloxacin. The results indicated that the Xa-Lo combination gel exhibited a significantly superior masking effect to that of the Ag gel. This study demonstrates the feasibility of using oral gel formulations to modulate the controlled-release functionality of pharmaceutical agents.

  12. Pulsed field gel electrophoresis a practical guide

    CERN Document Server

    Birren, Bruce


    Pulsed Field Gel Electrophoresis: A Practical Guide is the first laboratory manual to describe the theory and practice of this technique. Based on the authors' experience developing pulsed field gel instruments and teaching procedures, this book provides everything a researcher or student needs to know in order to understand and carry out pulsed field gel experiments. Clear, well-tested protocols assume only that users have a basic familiarity with molecular biology. Thorough coverage of useful data, theory, and applications ensures that this book is also a lasting resource for more adv

  13. 49 CFR 391.33 - Equivalent of road test. (United States)


    ... 49 Transportation 5 2010-10-01 2010-10-01 false Equivalent of road test. 391.33 Section 391.33... AND LONGER COMBINATION VEHICLE (LCV) DRIVER INSTRUCTORS Tests § 391.33 Equivalent of road test. (a) In place of, and as equivalent to, the road test required by § 391.31, a person who seeks to drive a...

  14. Approaches to the treatment of zero equivalence in a bilingual ...

    African Journals Online (AJOL)

    The absence of equivalents in the TL is marked by two symbols: Ø (a complete absence of any equivalent) and # (equivalence at the level of the entire message rather than at word level). Sixty-five lemmata in the ESD contain a slashed zero, a hash or both, but one and the same entry can contain more than one symbol.

  15. Tests of the weak equivalence principle (United States)

    Speake, C. C.; Will, C. M.


    The Einstein equivalence principle is the foundation for general relativity and all metric theories of gravity. Of its three tenets—the equality of acceleration of test bodies, or weak equivalence principle; the validity of Lorentz invariance in local freely falling frames; and the position invariance of local physical laws—the weak equivalence principle has played the most important role historically, and continues to be a focus of intense theoretical and experimental investigation. From the probably apocryphal 16th century demonstrations by Galileo at Pisa's leaning tower to the sensitive torsion-balance measurements of today (both pictured on the cover of this issue), this principle, dubbed WEP, has been crucial to the development of gravitation theory. The universality of the rate of acceleration of all types of matter in a gravitational field can be taken as evidence that gravitation is fundamentally determined by the geometry, or metric, of spacetime. Newton began his magnum opus 'The Principia' with a discussion of WEP and his experiments to verify it, while Einstein took WEP for granted in his construction of general relativity, never once referring to the epochal experiments by Baron Eötvös. The classic 1964 experiment of Roll, Krotkov and Dicke ushered in the modern era of high-precision tests, and the search for a 'fifth force' during the late 1980s (instigated, ironically, by purported anomalies in Eötvös's old data) caused the enterprise to pivot from pure tests of the foundation of GR to searches for new physics beyond the standard model of the non-gravitational interactions. Today, the next generation of experimental tests of WEP are being prepared for launch or are being developed, with the goal of reaching unprecedented levels of sensitivity, in search of signatures of interactions inspired by string theory, extra dimensions and other concepts from the world of high-energy physics. At the same time observations continue using lunar laser

  16. Fricke xylenol gel energy dependence

    Energy Technology Data Exchange (ETDEWEB)

    Costa, Rosangela T.; Moreira, Marcos V.; Almeida, Adelaide de, E-mail: dalmeida@ffclrp.usp.b, E-mail: [Universidade de Sao Paulo (USP), Ribeirao Preto, SP (Brazil). Faculdade de Filosofia, Ciencias e Letras. Dept. de Fisica e Matematica


    The advancement of technology has increasingly use the of ionizing radiation mainly in the areas of medicine, industry and research. The development of instruments and methods for an effective performance for detection and measurement of each radiation area was crucial. The literature have demonstrated the effectiveness of the Fricke Xylenol Gel (FXG) as an adequate chemical sensor to be used for dosimetry, once its effective atomic number and density are near to those of the soft tissue. The use of photon beams for therapeutic purpose requires knowledge of their characteristics that can vary for each equipment. Therefore, is important to know all parameters involved for the patient irradiation as the total geometry involved, type of radiation, target material composition and beam energy, that have to be taken into account in the beam dosimetry for the treatment success being the energy parameter is one of the most important. This work was developed to study the energetic dependence of the FXG dosimeter. This chemical solution is made with gelatine 300 Bloom, ferrous ammonium sulfate, xylenol orange, sulfuric acid and Milli-Q water and is based on the Fe{sup +2} oxidation to Fe{sup +3}, due to the ionizing radiation leading to the xylenol orange - ferric complex formation, that is linear depend on the absorbed dose. The FXG samples were irradiated with photons of different energies and the absorbance measurements were done with the spectrophotometric technique at the 585 nm, FXG highest absorption peak. The energetic dependence results presented a stronger dependence for low energies and almost independence for high energies, as expected by the interaction of radiation with matter. (author)

  17. Sol-gel deposited electrochromic coatings

    Energy Technology Data Exchange (ETDEWEB)

    Ozer, N.; Lampert, C.M.


    Electrochromic devices have increasing application in display devices, switchable mirrors and smart windows. A variety of vacuum deposition technologies have been used to make electrochromic devices. The sol- gel process offers an alternative approach to the synthesis of optical quality and low cost electrochromic device layers. This study summarizes the developments in sol-gel deposited electrochromic films. The sol-gel process involves the formation of oxide networks upon hydrolysis-condensation of alkoxide precursors. In this study we cover the sol-gel deposited oxides of WO[sub 3], V[sub 2]O[sub 5], TiO[sub 2], Nb[sub 2]O[sub 5], and NiO[sub x].

  18. Maize Arabinoxylan Gels as Protein Delivery Matrices

    Directory of Open Access Journals (Sweden)

    Ana Luisa Martínez-López


    Full Text Available The laccase induced gelation of maize bran arabinoxylans at 2.5% (w/v in the presence of insulin or β-lactoglobulin at 0.1% (w/v was investigated. Insulin and β-lacto-globulin did not modify either the gel elasticity (9 Pa or the cross-links content (0.03 and 0.015 mg di- and triferulic acids/mg arabinoxylan, respectively. The protein release capability of the gel was also investigated. The rate of protein release from gels was dependent on the protein molecular weight. The apparent diffusion coefficient was 0.99 × 10-7 and 0.79 × 10-7 cm2/s for insulin (5 kDa and β-lactoglobulin (18 kDa, respectively. The results suggest that maize bran arabinoxylan gels can be potential candidates for the controlled release of proteins.

  19. Stable Liquid Jets Bouncing off Soft Gels (United States)

    Daniel, Dan; Yao, Xi; Aizenberg, Joanna


    A liquid jet can stably bounce off a sufficiently soft gel by following the contour of the dimple created upon impact. This new phenomenon is insensitive to the wetting properties of the gels and was observed for different liquids over a wide range of surface tensions, γ =24 -72 mN /m . In contrast, other jet rebound phenomena are typically sensitive to γ : only a high γ jet rebounds off a hard solid (e.g. superhydrophobic surface) and only a low γ jet bounces off a liquid bath. This is because an air layer must be stabilized between the two interfaces. For a soft gel, no air layer is necessary and the jet rebound remains stable even when there is direct liquid-gel contact.

  20. Manual control of catalytic reactions: Reactions by an apoenzyme gel and a cofactor gel (United States)

    Kobayashi, Yuichiro; Takashima, Yoshinori; Hashidzume, Akihito; Yamaguchi, Hiroyasu; Harada, Akira


    Enzymes play a vital role in catalysing almost all chemical reactions that occur in biological systems. Some enzymes must form complexes with non-protein molecules called cofactors to express catalytic activities. Although the control of catalytic reactions via apoenzyme–cofactor complexes has attracted significant attention, the reports have been limited to the microscale. Here, we report a system to express catalytic activity by adhesion of an apoenzyme gel and a cofactor gel. The apoenzyme and cofactor gels act as catalysts when they form a gel assembly, but they lose catalytic ability upon manual dissociation. We successfully construct a system with switchable catalytic activity via adhesion and separation of the apoenzyme gel with the cofactor gel. We expect that this methodology can be applied to regulate the functional activities of enzymes that bear cofactors in their active sites, such as the oxygen transport of haemoglobin or myoglobin and the electron transport of cytochromes. PMID:26537172

  1. Frictional properties of gel engineering materials with laser surface texturing (United States)

    Yamada, Naoya; Gong, Jin; Kabir, M. Hasnat; Makino, Masato; Maekawa, Keisuke; Wada, Masato; Furukawa, Hidemitsu


    Several synthesis methods have been devised to improve the mechanical strength of gels extraordinarily after 2001. It was a trigger to use gels as a new industrial materials, since gels had been considered difficult for industrial materials because of their weakness. In a recent study, we had designed transparency shape memory gels for the first time. Shape memory gels are one of the gels with characteristic networks, and have a shape memory function by copolymerizing an acrylic monomer with a hydrophobic long alkyl side group. It is well known that the mechanical properties such as Young's modulus and friction coefficient of shape memory gels depend on temperature. In this study, we tried to change the frictional properties of shape memory gels by laser surface texturing. Two types of processed surface were prepared. The hexagonal close packed pattern and the square close packed pattern of dimples were formed on the surface of gel sheets with CO2 laser. The intensity of laser was optimized to avoid cutting gels. The friction coefficients of unprocessed gels and two types of processed gels were measured by ball-on-disk method. Measurement partner material was sodalime glass ball. The measurement results of processed gels showed clear differences from unprocessed gels. The friction coefficients of processed gels were larger than unprocessed gels. However, these results specifically showed the velocity dependence. It indicates that surface texturing enable to control the friction coefficient of polymer gels by surface pattern and velocity.

  2. Improving calibration accuracy in gel dosimetry (United States)

    Oldham, M.; McJury, M.; Baustert, I. B.; Webb, S.; Leach, M. O.


    A new method of calibrating gel dosimeters (applicable to both Fricke and polyacrylamide gels) is presented which has intrinsically higher accuracy than current methods, and requires less gel. Two test-tubes of gel (inner diameter 2.5 cm, length 20 cm) are irradiated separately with a field end-on in a water bath, such that the characteristic depth-dose curve is recorded in the gel. The calibration is then determined by fitting the depth-dose measured in water, against the measured change in relaxivity with depth in the gel. Increased accuracy is achieved in this simple depth-dose geometry by averaging the relaxivity at each depth. A large number of calibration data points, each with relatively high accuracy, are obtained. Calibration data over the full range of dose (1.6-10 Gy) is obtained by irradiating one test-tube to 10 Gy at dose maximum , and the other to 4.5 Gy at . The new calibration method is compared with a `standard method' where five identical test-tubes of gel were irradiated to different known doses between 2 and 10 Gy. The percentage uncertainties in the slope and intercept of the calibration fit are found to be lower with the new method by a factor of about 4 and 10 respectively, when compared with the standard method and with published values. The gel was found to respond linearly within the error bars up to doses of 7 Gy, with a slope of and an intercept of Gy. For higher doses, nonlinear behaviour was observed.

  3. Droplet Burning of JP-8/Silica Gels


    Arnold, R.; Anderson, W. E.


    For future high performance rocket launchers, gelled propellants have the potential to replace conventional solid and liquid fuels by combining the individual advantages of both systems and neglecting the most disadvantages at the same time. Since gels show different atomization, spray and combustion behavior in comparison to liquid propellants, the investigation of single droplet vaporization and combustion is fundamental for the understanding of designing a gel operated injector system. Bas...

  4. Notes on The Energy Equivalence of Information. (United States)

    Matta, Chérif F; Massa, Lou


    Maxwell's demon makes observations and thereby collects information. As Brillouin points out such information is the negative of entropy (negentropy) and is the equivalent of a cost in energy. The energy cost of information can be quantified in the relationship E = kT ln 2, where k is the Boltzmann constant, T is the absolute temperature, and the factor ln 2 arises from the existence of two possibilities for a "yes/no" circumstance, as, for example, in the passage of a proton through a barrier controlled by a Maxwell's demon. This paper considers further conclusions that follow from the quantification of the energy cost of information. First, consideration of the minimum uncertainty in the measurement of energy cost of information leads to an expression for the uncertainty in the corresponding time of the measurement, which depends inversely upon temperature at which the measurements occur. Second, because of the universal connection between energy and mass, an almost imperceptible mass accompanies the accumulation of information. And third, to account for the total free energy change that describes the action of adenosine triphosphate (ATP) synthase, an additional term is suggested to be appended to the Mitchell chemiosmotic equation, which describes this process. The additional term accounts for the energy cost of sorting away from background ions those protons allowed to enter the ATP synthase.

  5. Testing the equivalence principle on a trampoline (United States)

    Reasenberg, Robert D.; Phillips, James D.


    We are developing a Galilean test of the equivalence principle in which two pairs of test mass assemblies (TMA) are in free fall in a comoving vacuum chamber for about 0.9 s. The TMA are tossed upward, and the process repeats at 1.2 s intervals. Each TMA carries a solid quartz retroreflector and a payload mass of about one-third of the total TMA mass. The relative vertical motion of the TMA of each pair is monitored by a laser gauge working in an optical cavity formed by the retroreflectors. Single-toss precision of the relative acceleration of a single pair of TMA is 3.5×10-12 g. The project goal of Δg/g = 10-13 can be reached in a single night's run, but repetition with altered configurations will be required to ensure the correction of systematic error to the nominal accuracy level. Because the measurements can be made quickly, we plan to study several pairs of materials.

  6. Challenging a culture of racial equivalence. (United States)

    Song, Miri


    We live at a time when our understandings and conceptualizations of 'racism' are often highly imprecise, broad, and used to describe a wide range of racialized phenomena. In this article, I raise some important questions about how the term racism is used and understood in contemporary British society by drawing on some recent cases of alleged racism in football and politics, many of which have been played out via new media technologies. A broader understanding of racism, through the use of the term 'racialization', has been helpful in articulating a more nuanced and complex understanding of racial incidents, especially of people's (often ambivalent) beliefs and behaviours. However, the growing emphasis upon 'racialization' has led to a conceptualization of racism which increasingly involves multiple perpetrators, victims, and practices without enough consideration of how and why particular interactions and practices constitute racism as such. The trend toward a growing culture of racial equivalence is worrying, as it denudes the idea of racism of its historical basis, severity and power. These frequent and commonplace assertions of racism in the public sphere paradoxically end up trivializing and homogenizing quite different forms of racialized interactions. I conclude that we need to retain the term 'racism', but we need to differentiate more clearly between 'racism' (as an historical and structured system of domination) from the broader notion of 'racialization'. © London School of Economics and Political Science 2014.

  7. Mathematical Equivalence of Evolution and Design

    Directory of Open Access Journals (Sweden)

    Leonid Perlovsky


    Full Text Available "Every one who is seriously involved in the pursuit of science becomes convinced that a spirit is manifest in the laws of the Universe." This Einsteinian statement remains outside of science. Our current understanding of the mind mechanisms have come close to explaining spirituality from the scientific point of view. In this paper a theory is presented which is a mathematical breakthrough, overcoming decades of limitations in AI, pattern recognition, neural networks, and other attempts to model the brain-mind. Solutions to engineering problems are presented that have overcome previous difficulties in terms of computational complexity. These solutions result in orders of magnitude improvement in detection, prediction, tracking, fusion, and learning situations. The theory is also extended to higher cognitive functions. It models the knowledge instinct operating in the hierarchy of the human brain-mind. At the top are concepts unifying our entire knowledge; we perceive them as concepts of the meaning and purpose of our existence. This theory is formulated mathematically as dynamic and equivalently as teleological. Experimental results supporting the theory are discussed. The theory overcomes various difficulties, including reductionism, which, in the past, interfered with the acceptance of scientific explanations of the spiritual.

  8. Pengaruh Natrium Hialuronat terhadap Penetrasi Kofein Sebagai Antiselulit dalam Sediaan Hidrogel, Hidroalkoholik Gel, dan Emulsi Gel

    Directory of Open Access Journals (Sweden)

    Joshita Djajadisastra


    Full Text Available Anticellulite topical gel preparation with caffeine as an active ingredient needs a penetration enhancer to reach subcutaneous layer. Sodium hyaluronate (NaHA, the sodium salt of hyaluronic acid, is a hydrophilic polysaccharide derivative polymer. It has an ability to enhance percutaneous penetration by loosening the dense of the compact substance of stratum corneum. The aim of this research was to observe the effects of NaHA on caffeine penetration as an anticellulite active agent in three types of gel preparation: hydrogel, hydroalcoholic gel, and gel emulsion. Each gel type contained caffeine 1,5% and was varied into three formulas. Formula 1 contained HPMC 2% as gel basis; formula 2 contained HPMC 2% and NaHA 0,5% as gel basis; formula 3 contained NaHA 2% as gel basis. Caffeine penetration properties were analyzed by Franz diffusion cell in vitro test using rat skin as membrane. Percent caffeine penetration of hydrogel formula 1, 2, 3 were 9,41 ± 0,01%; 11,74 ± 0,13%; 16,32 ± 0,03%, respectively. Percent caffeine penetration of hydroalcoholic gel formula 1, 2, 3 were 19,54 ± 0,02%; 22,99 ± 0,23%; 7,42 ± 0,08%, respectively. Percent caffeine penetration of gel emulsion formula 1, 2, 3 were 10,47 ± 0,19%; 13,41 ± 0,12%; 18,42 ± 0,06%, respectively. The result showed that NaHA enhanced the caffeine percutaneous penetration properties in various gel preparations, except hidroalkoholic gel formula 3.

  9. The microrheology of sickle hemoglobin gels. (United States)

    Zakharov, Mikhail N; Aprelev, Alexey; Turner, Matthew S; Ferrone, Frank A


    Sickle cell disease is a rheological disease, yet no quantitative rheological data exist on microscopic samples at physiological concentrations. We have developed a novel method for measuring the microrheology of sickle hemoglobin gels, based on magnetically driven compression of 5- to 8-microm-thick emulsions containing hemoglobin droplets approximately 80 microm in diameter. Using our method, by observing the expansion of the droplet area as the emulsion is compressed, we were able to resolve changes in thickness of a few nanometers with temporal resolution of milliseconds. Gels were formed at various initial concentrations and temperatures and with different internal domain structure. All behaved as Hookean springs with Young's modulus from 300 to 1500 kPa for gels with polymerized hemoglobin concentration from 6 g/dl to 12 g/dl. For uniform, multidomain gels, Young's modulus mainly depended on the terminal concentration of the gel rather than the conditions of formation. A simple model reproduced the quadratic dependence of the Young's modulus on the concentration of polymerized hemoglobin. Partially desaturated samples also displayed quadratic concentration dependence but with a smaller proportionality coefficient, as did samples that were desaturated in steps; such samples were significantly less rigid than gels formed all at once. The magnitude of the Young's modulus provides quantitative support for the dominant models of sickle pathophysiology. 2010 Biophysical Society. Published by Elsevier Inc. All rights reserved.

  10. Study of nuclear glasses alteration gel and synthesis of some model gels; Etude du gel d`alteration des verres nucleaires et synthese de gels modeles

    Energy Technology Data Exchange (ETDEWEB)

    Ricol, S.


    This work deals with the general problem of alteration of the reference nuclear glass R7T7. Attention is paid particularly to the altered layer formed at the glass surface during alteration process. In opposition to previous works, related essentially to glass dissolution kinetics based on chemical analyses of lixiviated elements, this thesis deals with alteration problems through structural studies of the reference glass and derived gel. This approach allows the determination of mechanisms for the gel formation and a better understanding of the behaviour of glasses towards lixiviation. Both approaches appeared complementary. Based on several spectroscopic techniques, this work showed the particular role of cations such as calcium, zirconium and iron. Studies of silica-based synthetic gels showed the synergic effect of formers cation and of one highly coordinated cation. The variation of the wavenumber related to Si-O-Si asymmetric stretching vibration can be correlated to O/Si ratio for ternary systems Si/Na/Zr. On the contrary, the Si losses of the materials depend on the number of non-bridging oxygen atoms. In the perspective of long-term behaviour, the alteration gel presents better characteristics than initial glass. It is therefore a highly stable material in static conditions. In the same way, synthetic gels are materials with very low solubilities (much lower than the alteration gel) and could be used as confining matrices. (authors). refs., 71 figs., 37 tabs.

  11. Swelling instabilities in patterned, microscale gels (United States)

    Toomey, Ryan; Dupont, Samuel


    Hydrogels facilitate reconfigurable structures with response integrated at the material level. Response is engendered by a competing mechanism: the elasticity of the network ounterbalances expansion by the solvent. If the strength of expansion can be controlled by an environmental cue, the hydrogel can be adjusted in situ. The equilibrium state occurs when the osmotic stress exerted by the solvent in the gel equals the osmotic pressure of the solvent outside the gel. For a free structure, the equilibrium state corresponds to homogenous swelling. If a free surface of the gel is mechanically constrained, however, the dimensions available for the relief of the osmotic stress are reduced, resulting in non-uniform or inhomogeneous swelling. In this study, we demonstrate how mechanical constraints impose differential gel swelling and buckling in patterned gels. Depending on the initial geometry of the constrained gel, three general modes of swelling-induced deformation can be observed: lateral differential swelling, bulk sinusoidal buckling, and surface wrinkling. Through confocal microscopy and 3D image rendering, the mechanics of swelling has been evaluated in the context of linear elasticity theory.

  12. Gel nano-particulates against radioactivity; Des nanoparticules en gel contre la radioactivite

    Energy Technology Data Exchange (ETDEWEB)

    Deroin, Ph


    The Argonne research center (USA) has developed a 'super-gel' compound, a polymer close to those used in baby's diapers, which can reach a 90% efficiency in the radioactive decontamination of porous materials, like bricks or concrete. The contaminated materials are sprayed with a mixture of polymer gel and wetting agent with nano-particulates in suspension. Under the action of the wetting agent, radioactivity migrates from the pores to the gel and is trapped by the nano-particulates. The drying and recycling of the gel allows to reduce the volume of radioactive wastes. Short paper. (J.S.)

  13. Analysis of energy dependence of the film radiochromic XRQA2 for seven spectra of X-ray standard in diagnostic radiology; Analisis de la dependencia energetica de la pelicula radiogromica XRQA2 para siete espectros de rayos X habituales en radiodiagnostico

    Energy Technology Data Exchange (ETDEWEB)

    Vicent Granado, D.; Gutierrez Ramos, S. M.; Sanchez Carmona, G.; Santos Rubio, A. J.; Herrador Cordoba, M.


    The response of the radiochromic film XRQA2 depends on the peak voltage, as well as filtration and measurement with or without backscatter. The common method of using a calibration from the kerma in air to measure the dose at the entrance of patients is not the most advisable for this film in this dose range. Whenever possible should be the calibration with the spectrum of X rays for which will be the measurement of absorbed dose. (Author)

  14. Uncertainty in 3D gel dosimetry (United States)

    De Deene, Yves; Jirasek, Andrew


    Three-dimensional (3D) gel dosimetry has a unique role to play in safeguarding conformal radiotherapy treatments as the technique can cover the full treatment chain and provides the radiation oncologist with the integrated dose distribution in 3D. It can also be applied to benchmark new treatment strategies such as image guided and tracking radiotherapy techniques. A major obstacle that has hindered the wider dissemination of gel dosimetry in radiotherapy centres is a lack of confidence in the reliability of the measured dose distribution. Uncertainties in 3D dosimeters are attributed to both dosimeter properties and scanning performance. In polymer gel dosimetry with MRI readout, discrepancies in dose response of large polymer gel dosimeters versus small calibration phantoms have been reported which can lead to significant inaccuracies in the dose maps. The sources of error in polymer gel dosimetry with MRI readout are well understood and it has been demonstrated that with a carefully designed scanning protocol, the overall uncertainty in absolute dose that can currently be obtained falls within 5% on an individual voxel basis, for a minimum voxel size of 5 mm3. However, several research groups have chosen to use polymer gel dosimetry in a relative manner by normalizing the dose distribution towards an internal reference dose within the gel dosimeter phantom. 3D dosimetry with optical scanning has also been mostly applied in a relative way, although in principle absolute calibration is possible. As the optical absorption in 3D dosimeters is less dependent on temperature it can be expected that the achievable accuracy is higher with optical CT. The precision in optical scanning of 3D dosimeters depends to a large extend on the performance of the detector. 3D dosimetry with X-ray CT readout is a low contrast imaging modality for polymer gel dosimetry. Sources of error in x-ray CT polymer gel dosimetry (XCT) are currently under investigation and include inherent

  15. On the Equivalence of HLLE and LTSA. (United States)

    Zhang, Sumin; Ma, Zhengming; Tan, Hengliang


    Among the representative algorithms of manifold learning, Hessian locally linear embedding (HLLE) and local tangent space alignment (LTSA) algorithms haven been regarded as two different algorithms. However, in practice, the effects of these two algorithms are very similar and LTSA performs better than HLLE in some applications. This paper tries to account for this phenomenon from a mathematical point of view. There are only two differences between HLLE and LTSA. First, LTSA includes a data point into its neighborhood, while HLLE does not. Second, HLLE and LTSA use different methods to align the local coordinates of manifold. In this paper, we show that, the first difference between HLLE and LTSA is not essential. However, from the viewpoint of data utilization, LTSA does better than HLLE in the neighborhood construction. This may account for why LTSA can perform better than HLLE in some applications. As for the second difference between HLLE and LTSA, we first prove that, the alignment equations used by HLLE and LTSA are exactly the same. Second, we prove that, although HLLE and LTSA uses different methods to solve the alignment equation, their solutions are exactly the same, provided that HLLE adopts the same method as LTSA to construct the neighborhoods. Based on these arguments, we claim that HLLE and LTSA are equivalent to each other. This conclusion can also be verified experimentally by using manifold learning MATLAB demo (MANI), a widely-used experimental platform of manifold learning. When testing HLLE on MANI, if HLLE adopts the same method as LTSA to construct the neighborhoods, the experimental results presented by MANI will be the same as those of LTSA.

  16. General Dynamic Equivalent Modeling of Microgrid Based on Physical Background

    Directory of Open Access Journals (Sweden)

    Changchun Cai


    Full Text Available Microgrid is a new power system concept consisting of small-scale distributed energy resources; storage devices and loads. It is necessary to employ a simplified model of microgrid in the simulation of a distribution network integrating large-scale microgrids. Based on the detailed model of the components, an equivalent model of microgrid is proposed in this paper. The equivalent model comprises two parts: namely, equivalent machine component and equivalent static component. Equivalent machine component describes the dynamics of synchronous generator, asynchronous wind turbine and induction motor, equivalent static component describes the dynamics of photovoltaic, storage and static load. The trajectory sensitivities of the equivalent model parameters with respect to the output variables are analyzed. The key parameters that play important roles in the dynamics of the output variables of the equivalent model are identified and included in further parameter estimation. Particle Swarm Optimization (PSO is improved for the parameter estimation of the equivalent model. Simulations are performed in different microgrid operation conditions to evaluate the effectiveness of the equivalent model of microgrid.

  17. Fabricating porous materials using interpenetrating inorganic-organic composite gels (United States)

    Seo, Dong-Kyun; Volosin, Alex


    Porous materials are fabricated using interpenetrating inorganic-organic composite gels. A mixture or precursor solution including an inorganic gel precursor, an organic polymer gel precursor, and a solvent is treated to form an inorganic wet gel including the organic polymer gel precursor and the solvent. The inorganic wet gel is then treated to form a composite wet gel including an organic polymer network in the body of the inorganic wet gel, producing an interpenetrating inorganic-organic composite gel. The composite wet gel is dried to form a composite material including the organic polymer network and an inorganic network component. The composite material can be treated further to form a porous composite material, a porous polymer or polymer composite, a porous metal oxide, and other porous materials.

  18. Dose verification in HDR brachytherapy and IMRT with Fricke gel-layer dosimeters

    Energy Technology Data Exchange (ETDEWEB)

    Gambarini, G.; Negri, A.; Bartesaghi, G.; Pirola, L. [Department of Physics, Universita degli Studi di Milano, Italy (Italy); Carrara, M.; Gambini, I.; Tomatis, S.; Fallai, C.; Zonca, G. [Fondazione IRCCS Istituto Nazionale dei Tumori, Milano, Italy (Italy); Stokucova, J. [Faculty Hospital Na Bulovce, Prague, Czech Republic (Czech Republic)


    At the Department of Physics of the Universita degli Studi di Milano in collaboration with the Medical Physics Unit and the Radiotherapy Unit of the Fondazione IRCCS Istituto Nazionale dei Tumori di Milano the research of a dosimetric technique based on Fricke gel layers and optical analysis in under study. In fact, Fricke gel layer dosimeters (FGLD) have various advantages such as the tissue-equivalence for photons in the clinical energy interval, the possibility to obtain the spatial information about continuous dose distribution and not only a point dose distribution as it is for example in the case of ionization chambers, TLD or diodes and the possibility to obtain the information about 3D dose distributions. In this work, specific applications of FGLD to absolute dosimetry in radiotherapy have been studied, i.e. in-phantom measurements of complex intensity modulated radiation therapy fields (IMRT) and complex brachytherapy fields. (Author)

  19. Determining the optomechanical properties of accommodating gel for lens refilling surgery using finite element analysis and numerical ray-tracing (United States)

    Mohammad-Pour, Hooman; Kanapathipillai, Sangarapillai; Manns, Fabrice; Ho, Arthur


    A key step in the design of an accommodating gel to replace the natural contents of the presbyopic human crystalline lens is to find the equivalent homogeneous mechanical and material properties of the gel that yield comparable optical response as the lens with gradient properties. This process is compounded by the interplay between the mechanical and optical gradient. In order to find uniform properties of the lens both gradients need to be considered. In this paper, numerical ray-tracing and finite element method (FEM) are implemented to investigate the effects of varying the uniform elasticity and refractive index on the accommodative amplitude. Our results show that the accommodative amplitude be expressed as a function of gel refractive index and Young's modulus of elasticity. In other words infinite sets of elasticity and refractive index exist that yield a certain amount of accommodation.

  20. Investigation into response characteristics of the chitosan gel artificial muscle (United States)

    Zhao, Gang; Yang, Junjie; Wang, Yujian; Zhao, Honghao; Fu, Yu; Zhang, Guangli; Yu, Shuqin; Wu, Yuda; Wei, Chengye; Liu, Xuxiong; Wang, Zhijie


    Bionic artificial muscle made from chitosan gel is an emerging type of the ionic electro active polymer with advantages of large deformation, low cost and environmental protection etc, which leads to a research focus and wide application in the fields of bionic engineering and intelligence material recently. In this paper, effects and improvement mechanisms of the direct casting and genipin cross-linking processes on response speed properties of the chitosan gel artificial muscle (CGAM) were mainly studied. Based on in-depth analysis of the CGAM response mechanism, a platform was built for testing the response performance of the CGAM, then its equivalent circuit and mathematical models were also established. Furthermore, control experiments were carried out to test and analyze several performances of the CGAM on response speed, electrical conductivity, mechanical properties and microstructure with different control variables. The experimental results illustrated that the CGAM assembled by direct casting enabled its electric actuating membrane and non-metallic electrode membrane tightly attached together with low contact resistance, which dramatically promoted the electrical conductivity of the CGAM resulting in nearly doubled response speed. Besides, different concentrations of genipin were adopted to cross-link the CGAM actuating membranes, and then it was found that the response speed of the uncross-linked CGAM was fast in the initial stage, but as time increased, it declined rapidly with poor steadiness. While there was no obvious decrease over time on the response speed of the CGAM cross-linked with low genipin concentration. Namely, its stability was getting better and better. In addition, the response speed of the CGAM cross-linked with low concentration of genipin was roughly the same as uncross-linked CGAM, which was quicker than that of high concentration. In this work, its internal mechanisms, feasible assembly technique and green modification method were

  1. Supramolecular Gel-Templated In Situ Synthesis and Assembly of CdS Quantum Dots Gels (United States)

    Zhu, Lili; He, Jie; Wang, Xiaoliang; Li, Dawei; He, Haibing; Ren, Lianbing; Jiang, Biwang; Wang, Yong; Teng, Chao; Xue, Gi; Tao, Huchun


    Although many studies have attempted to develop strategies for spontaneously organizing nanoparticles (NPs) into three-dimensional (3D) geometries, it remains a fascinating challenge. In this study, a method for in situ synthesis and self-assembly of a CdS quantum dots (QDs) gel using a Cd supramolecular gel as a scaffold was demonstrated. During the QDs formation process, the Cd ions that constituted the Cd gels served as the precursors of the CdS QDs, and the oleic acid (OA) that ligated with the Cd in the supramolecular gels was capped on the surface of the CdS QDs in the form of carboxylate. The OA-stabilized CdS QDs were in situ synthesized in the entangled self-assembled fibrillar networks (SAFIN) of the Cd gels through reactions between the gelator and H2S. As a result, the QDs exactly replicated the framework of the SAFIN in the CdS QD gels instead of simply assembling along the SAFIN of the supramolecular gels. Moreover, the CdS QDs showed extraordinary sensitivity in the fluorescence detection of IO4 - anions. The facile one-step method developed here is a new approach to assembling nanostructured materials into 3D architectures and has general implications for the design of low molecular mass gelators to bring desired functionality to the developed supramolecular gels.

  2. Preparation of continuous alumina gel fibres by aqueous sol–gel ...

    Indian Academy of Sciences (India)

    Abstract. Continuous alumina gel fibres were prepared by sol–gel method. The spinning sol was prepared by mixing aluminum nitrate, lactic acid and polyvinylpyrrolidone with a mass ratio of 10:3:1·5. Thermogravimetry– differential scanning calorimetry (TG–DSC), Fourier transform infrared (FTIR) spectra, X-ray diffraction ...

  3. Evolution of gel structure during thermal processing of Na-geopolymer gels. (United States)

    Duxson, Peter; Lukey, Grant C; van Deventer, Jannie S J


    The present work examines how the gel structure and phase composition of Na-geopolymers derived from metakaolin with varied Si/Al ratio evolve with exposure to temperatures up to 1000 degrees C. Gels were thermally treated and characterized using quantitative XRD, DTA, and FTIR to elucidate the changes in gel structure, phase composition, and porosity at each stage of heating. It is found that the phase stability, defined by the amount and onset temperature of crystallization, is improved at higher Si/Al ratios. Two different mechanisms of densification have been isolated by FTIR, related to viscous flow and collapse of the highly distributed pore network in the gel. Gels with low Si/Al ratio only experience viscous flow that correlates with low thermal shrinkage. Gels at a higher Si/Al ratio, which have a homogeneous microstructure composed of a highly distributed porosity, undergo both densification processes corresponding to a large extent of thermal shrinkage during densification. This work elucidates the intimate relationship between gel microstructure, chemistry, and thermal evolution of Na-geopolymer gels.

  4. Reprogramming cellular phenotype by soft collagen gels. (United States)

    Ali, M Yakut; Chuang, Chih-Yuan; Saif, M Taher A


    A variety of cell types exhibit phenotype changes in response to the mechanical stiffness of the substrate. Many cells excluding neurons display an increase in the spread area, actin stress fiber formation and larger focal adhesion complexes as substrate stiffness increases in a sparsely populated culture. Cell proliferation is also known to directly correlate with these phenotype changes/changes in substrate stiffness. Augmented spreading and proliferation on stiffer substrates require nuclear transcriptional regulator YAP (Yes associated protein) localization in the cell nucleus and is tightly coupled to larger traction force generation. In this study, we show that different types of fibroblasts can exhibit spread morphology, well defined actin stress fibers, and larger focal adhesions even on very soft collagen gels (modulus in hundreds of Pascals) as if they are on hard glass substrates (modulus in GPa, several orders of magnitude higher). Strikingly, we show, for the first time, that augmented spreading and other hard substrate cytoskeleton architectures on soft collagen gels are not correlated with the cell proliferation pattern and do not require YAP localization in the cell nucleus. Finally, we examine the response of human colon carcinoma (HCT-8) cells on soft collagen gels. Recent studies show that human colon carcinoma (HCT-8) cells form multicellular clusters by 2-3 days when cultured on soft polyacrylamide (PA) gels with a wide range of stiffness (0.5-50 kPa) and coated with an extracellular matrix, ECM (collagen monomer/fibronectin). These clusters show limited spreading/wetting on PA gels, form 3D structures at the edges, and eventually display a remarkable, dissociative metastasis like phenotype (MLP), i.e., epithelial to rounded morphological transition after a week of culture on PA gels only, but not on collagen monomer coated stiff polystyrene/glass where they exhibit enhanced wetting and form confluent monolayers. Here, we show that HCT-8 cell


    Energy Technology Data Exchange (ETDEWEB)



    Physical and chemical agents in the environment, those used in clinical applications, or encountered during recreational exposures to sunlight, induce damages in DNA. Understanding the biological impact of these agents requires quantitation of the levels of such damages in laboratory test systems as well as in field or clinical samples. Alkaline gel electrophoresis provides a sensitive (down to {approx} a few lesions/5Mb), rapid method of direct quantitation of a wide variety of DNA damages in nanogram quantities of non-radioactive DNAs from laboratory, field, or clinical specimens, including higher plants and animals. This method stems from velocity sedimentation studies of DNA populations, and from the simple methods of agarose gel electrophoresis. Our laboratories have developed quantitative agarose gel methods, analytical descriptions of DNA migration during electrophoresis on agarose gels (1-6), and electronic imaging for accurate determinations of DNA mass (7-9). Although all these components improve sensitivity and throughput of large numbers of samples (7,8,10), a simple version using only standard molecular biology equipment allows routine analysis of DNA damages at moderate frequencies. We present here a description of the methods, as well as a brief description of the underlying principles, required for a simplified approach to quantitation of DNA damages by alkaline gel electrophoresis.

  6. Tretinoin microsphere gel in younger acne patients. (United States)

    Jorizzo, Joseph; Grossman, Rachel; Nighland, Marge


    Facial acne is common in adolescents and can have a significant psychosocial impact. Treatments prescribed should not add stress by causing excessive localized irritation. To determine whether the lowest concentration of tretinoin microsphere gel (TMG) currently available (0.04%) provides an acceptable balance of efficacy and tolerability for adolescents with moderate facial acne. The findings of 2 multicenter, randomized, double-blind, vehicle-controlled trials of TMG 0.04% applied once nightly for 12 weeks in 245 adolescents ages 11 to 16 years with moderate facial acne were combined. Patients were evaluated via changes in acne lesion counts and the occurrence of cutaneous and other adverse effects. Tretinoin microsphere gel 0.04% reduced total, noninflammatory, and inflammatory lesion counts to a significantly greater extent than the vehicle gel at 12 weeks (PTretinoin microsphere gel 0.04% was tolerated well, with over 70% of patients experiencing no cutaneous adverse events (AEs). Tretinoin microsphere gel 0.04% is effective in significantly reducing all types of acne lesions in adolescents with moderate facial acne ages 11 to 16 years, and has a low incidence of cutaneous AEs.

  7. Polymethacrylate microparticles gel for topical drug delivery. (United States)

    Labouta, Hagar Ibrahim; El-Khordagui, Labiba K


    Evaluating the potentials of particulate delivery systems in topical drug delivery. Polymethacrylate microparticles (MPs) incorporating verapamil hydrochloride (VRP) as a model hydrophilic drug with potential topical clinical uses, using Eudragit RS100 and Eudragit L100 were prepared for the formulation of a composite topical gel. The effect of initial drug loading, polymer composition, particularly the proportion of Eudragit L100 as an interacting polymer component and the HLB of the dispersing agent on MPs characteristics was investigated. A test MPs formulation was incorporated in gel and evaluated for drug release and human skin permeation. MPs showed high % incorporation efficiency and % yield. Composition of the hybrid polymer matrix was a main determinant of MPs characteristics, particularly drug release. Factors known to influence drug release such as MPs size and high drug solubility were outweighed by strong VRP-Eudragit L100 interaction. The developed MPs gel showed controlled VRP release and reduced skin retention compared to a free drug gel. Topical drug delivery and skin retention could be modulated using particulate delivery systems. From a practical standpoint, the VRP gel developed may offer advantage in a range of dermatological conditions, in response to the growing off-label topical use of VRP.

  8. Reconfigurable assemblies of active, autochemotactic gels (United States)

    Dayal, Pratyush; Kuksenok, Olga; Balazs, Anna C.


    Using computational modeling, we show that self-oscillating Belousov–Zhabotinsky (BZ) gels can both emit and sense a chemical signal and thus drive neighboring gel pieces to spontaneously self-aggregate, so that the system exhibits autochemotaxis. To the best of our knowledge, this is the closest system to the ultimate self-recombining material, which can be divided into separated parts and the parts move autonomously to assemble into a structure resembling the original, uncut sample. We also show that the gels’ coordinated motion can be controlled by light, allowing us to achieve selective self-aggregation and control over the shape of the gel aggregates. By exposing the BZ gels to specific patterns of light and dark, we design a BZ gel “train” that leads the movement of its “cargo.” Our findings pave the way for creating reconfigurable materials from self-propelled elements, which autonomously communicate with neighboring units and thereby actively participate in constructing the final structure. PMID:23271807


    Directory of Open Access Journals (Sweden)

    Melnik AL


    , food and water consumption, the dynamics of body weight, hematological and biochemical parameters of blood. Clinical observations of the animals was performed daily during the experiment, registering changes in their general condition, behavior, food and water consumption. Clinical and biochemical parameters studied using a reagent kit of "Felicity Diagnostics" (Ukraine and conventional methods. Body weight of animals recorded in dynamics. The animals were weighed before the experiment, then 7 and 14 days. Results and discussion. Results of the study parameters acute toxicity gel with carbon dioxide Humulus lupulus extract showed that intragastric administration to mice at a dose of 2.0 g/kg caused no clinical symptoms of intoxication. Animals calmly reacted to the introduction of the sample gel, their general condition and behavior remained unchanged. Animal deaths and abnormalities in their general condition and behavior during the observation period were noted. Impact analysis of the sample of gel on the dynamics of body mass animal experiments showed that a single injection of a gel to mice at a dose of 2.0 g/kg did not significantly affect the dynamics of body weight. In experiments on rats were studied subacute toxicity gel with carbon dioxide Humulus lupulus extract. The results of 14 days intragastric introduction gel and reference drug studies at subacute toxicity showed that daily administration of no effect on the general condition, appearance (state of the skin and mucous membranes and the behavior of rats. Consumption of food and water in animal experimental and control groups had no differences from each other. During the experiment animal deaths were not reported. Data characterizing the dynamics of increase in body weight of rats showed that the animals of experimental groups and the control group by the end of the experiment had equivalent, statistically significant weight gain compared with the output data: males – p ≤ 0. 0001 females – from p

  10. Investigation of the electrical properties of agarose gel: characterization of concentration using nyquist plot phase angle and the implications of a more comprehensive in vitro model of the brain. (United States)

    Pomfret, Roland; Sillay, Karl; Miranpuri, Gurwattan


    The electrical properties of agarose gel, namely impedance and capacitance, are relatively unexplored. Agarose gels are used as in vitro models in studies across numerous disciplines, including imaging, radiotherapy, infusion, and neurosurgery. In this study, we seek to characterize the impedance response of low concentration agarose gels by relating the gel concentrations to Nyquist Plot phase in order to establish a baseline with which to modify the response of the gel to simulate that of in vivo brain tissue. This information is relevant to areas such as deep brain stimulation, and could have a significant impact on in vitro model design for such studies in the future. Ten agarose gels spanning four different concentrations were subjected to impedance spectroscopy using a Model 3387 DBS electrode. Phase angles were calculated and Cartesian Nyquist plots generated from the data. Results suggest that an inverse relationship exists between agarose gel concentration and phase angle. In addition, the results indicate that agarose gel reasonably emulates a constant phase element, which portrays the electrode-electrolyte interface impedance of some equivalent circuit models of brain tissue. The data shows that agarose gel is a suitable substrate for a deep brain stimulation in vitro model, but requires modification. In the future, we plan to utilize this data to determine the modifications necessary in the current agarose gel model to make it scientifically applicable to studies of both deep brain stimulation and infusion due to their overlapping variables.

  11. Dynamic equivalence relation on the fuzzy measure algebras

    Directory of Open Access Journals (Sweden)

    Roya Ghasemkhani


    Full Text Available The main goal of the present paper is to extend classical results from the measure theory and dynamical systems to the fuzzy subset setting. In this paper, the notion of  dynamic equivalence relation is introduced and then it is proved that this relation is an equivalence relation. Also, a new metric on the collection of all equivalence classes is introduced and it is proved that this metric is complete.

  12. Equivalent Viscous Damping Models in Displacement Based Seismic Design

    Directory of Open Access Journals (Sweden)

    Raul Zaharia


    Full Text Available The paper reviews some equivalent viscous damping models used in the displacement based seismic design considering the equivalent linearization. The limits of application of the models are highlighted, based on comparison existing in the literature. The study is part of research developed by author, aimed to determine the equivalent linear parameters in order to predict the maximum displacement response for earthquakes compatible with given response spectra.

  13. Equivalence of Deterministic Nested Word to Word Transducers (United States)

    Staworko, Sławomir; Laurence, Grégoire; Lemay, Aurélien; Niehren, Joachim

    We study the equivalence problem of deterministic nested word to word transducers and show it to be surprisingly robust. Modulo polynomial time reductions, it can be identified with 4 equivalence problems for diverse classes of deterministic non-copying order-preserving transducers. In particular, we present polynomial time back and fourth reductions to the morphism equivalence problem on context free languages, which is known to be solvable in polynomial time.

  14. Efficacy of 1.23% APF gel applications on incipient carious lesions: a double-blind randomized clinical trial

    Directory of Open Access Journals (Sweden)

    Maria Laura Menezes Bonow


    Full Text Available The aim of this double-blind randomized clinical trial was to evaluate the efficacy of 1.23% APF gel application on the arrest of active incipient carious lesions in children. Sixty 7- to 12-year-old children, with active incipient lesions were included in the study. Children were divided randomly into 2 groups: 1.23% APF gel and placebo gel applications. Each group received 8 weekly applications of treatment. The lesions were re-evaluated at the 4th and 8th appointments. Poisson regression analysis was used to estimate relative risks of the presence of active white spot lesions. Groups showed similar results (PR = 1.67; CI 95% 0.69–3.98. The persistence of at least 1 active lesion was associated with a higher number of lesions in the baseline (PR = 2.67; CI 95% 1.19–6.03, but not with sugar intake (PR = 1.06; CI 95% 0.56–2.86 and previous exposure to fluoride dentifrice (PR = 1.26; CI 95% 0.49–2.29. The trial demonstrates the equivalence of the treatments. The use of the APF gel showed no additional benefits in this sample of children exposed to fluoridated water and dentifrice. The professional dental plaque removal in both groups may also account for the resulting equivalence of the treatments.

  15. Approximate Testing Equivalence Based on Time, Probability, and Observed Behavior

    Directory of Open Access Journals (Sweden)

    Alessandro Aldini


    Full Text Available Several application domains require formal but flexible approaches to the comparison problem. Different process models that cannot be related by behavioral equivalences should be compared via a quantitative notion of similarity, which is usually achieved through approximation of some equivalence. While in the literature the classical equivalence subject to approximation is bisimulation, in this paper we propose a novel approach based on testing equivalence. As a step towards flexibility and usability, we study different relaxations taking into account orthogonal aspects of the process observations: execution time, event probability, and observed behavior. In this unifying framework, both interpretation of the measures and decidability of the verification algorithms are discussed.

  16. Electron Beam Dosimetry in Heterogeneous Phantoms Using a MAGIC Normoxic Polymer Gel

    Directory of Open Access Journals (Sweden)

    Ruhollah Ghahraman Asl


    cold spots at deeper depths, are compensated with the contributions of scattered electrons. Our study showed that normoxic polymer gels are reliable detectors for determination of electron dose distributions due to their characteristics such as tissue equivalence, energy independence, and 2D and 3D dose visualization capabilities.

  17. Catenane Crosslinked Mechanically Adaptive Polymer Gel. (United States)

    Xing, Hao; Li, Zhengtao; Wu, Zi Liang; Huang, Feihe


    A new strategy is introduced to prepare an adaptive polymer gel that has a unique adaptability in response to environmental stimuli. This gel is prepared by the thiol-ene "click" reaction between a bisvinyl [2]catenane and a poly(ethylene glycol) derivative containing multiple thiol groups. The catenane crosslinker is responsive to external stimuli due to the existence of intercomponent hydrogen bonding (IHB). The strong IHB restricts the rotation and movement of the crosslinker, giving it a rigid feature; however, the crosslinker becomes flexible when the IHB is destroyed. In consequence, the resulting gel can be reversibly switched between tough and soft states under stimulations. © 2017 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  18. Ordering phenomena in ABA triblock copolymer gels

    DEFF Research Database (Denmark)

    Reynders, K.; Mischenko, N.; Kleppinger, R.


    Temperature and concentration dependencies of the degree of order in ABA triblock copolymer gels are discussed. Two factors can influence the ordering phenomena: the conformation of the midblocks (links of the network) and the polydispersity of the endblock domains (nodes of the network). The lat......Temperature and concentration dependencies of the degree of order in ABA triblock copolymer gels are discussed. Two factors can influence the ordering phenomena: the conformation of the midblocks (links of the network) and the polydispersity of the endblock domains (nodes of the network...... crystalline lattice with close-packed spheres or with cubic (presumably BCC) equilibrium morphology. The appearance of the latter is never detected in the gels with a stretched conformation of the midblock....

  19. Blue native-gel electrophoresis proteomics. (United States)

    Andringa, Kelly; King, Adrienne; Bailey, Shannon


    The importance of the mitochondrion in maintaining normal cellular physiology has long been appreciated. Recently there has been an upsurge in mitochondrial research due to increased recognition that a number of diseases are caused by defective functioning of this key intracellular organelle. Given this, along with advances made in proteomics technologies, the mitochondrion is clearly recognized as a top candidate for proteomics analysis. However, mitochondrial proteomics is not a trivial undertaking due to physicochemical properties that impair the resolution of inner mitochondrial membrane proteins when using conventional proteomic gel electrophoresis procedures. To circumvent such problems, many laboratories have adapted blue native-gel electrophoresis (BN-PAGE), a specialized type of native-gel electrophoresis, to generate high-resolution proteomic maps of the oxidative phosphorylation system. In this short overview the concepts and methods of BN-PAGE are presented, which demonstrate the power of using this complementary proteomics approach to identify alterations in the mitochondrial proteome that contribute to disease.

  20. Matching Two-dimensional Gel Electrophoresis' Spots

    DEFF Research Database (Denmark)

    Dos Anjos, António; AL-Tam, Faroq; Shahbazkia, Hamid Reza


    This paper describes an approach for matching Two-Dimensional Electrophoresis (2-DE) gels' spots, involving the use of image registration. The number of false positive matches produced by the proposed approach is small, when compared to academic and commercial state-of-the-art approaches. This ar......This paper describes an approach for matching Two-Dimensional Electrophoresis (2-DE) gels' spots, involving the use of image registration. The number of false positive matches produced by the proposed approach is small, when compared to academic and commercial state-of-the-art approaches...

  1. Connectivity in sol-gel silica glasses

    Directory of Open Access Journals (Sweden)

    Wander L. Vasconcelos


    Full Text Available In this work it is carried out a review on structural parameters related to the evaluation of pore connectivity of nanostructures. The work describes parameters and methods of evaluation of geometric parameters. The concepts of connectivity are applied to silica gels and glasses obtained from sol-gel process. The study of pores connectivity was carried out using a combination of geometric modeling and experimental evaluation of specific surface area and pore volume. The permeability of the pore structure is evaluated and a permeability geometric factor, Pg, is proposed.

  2. Abnormal gel flotation caused by contrast media during adrenal vein sampling. (United States)

    Lima-Oliveira, Gabriel; Lippi, Giuseppe; Salvagno, Gian Luca; Gelati, Matteo; Bassi, Antonella; Contro, Alberto; Pizzolo, Francesca; Guidi, Gian Cesare


    During adrenal venous sampling (AVS) procedure, radiologists administer a contrast agent via the catheter to visualize the proper catheter position. A patient with primary aldosteronism diagnostic-hypothesis was admitted for AVS. A venogram was performed to
confirm the catheter's position with 2mL of Iopamidol 300 mg/mL. Samples were collected with syringe connected to a hydrophilic coated catheter by low-pressure aspiration from each of the four collection sites: inferior vena cava in the suprarenal portion, inferior vena cava in the infrarenal portion, left adrenal vein, and right adrenal vein; then immediately transferred from syringe to tubes with gel separator. All tubes were centrifuged at 1200 x g for 10 minutes. At the end of centrifugation process, primary blood tubes containing blood from inferior vena cava and left adrenal vein exhibited the standard gel separator barrier, while tubes from right adrenal vein showed abnormal flotation of gel separator. The radiologist confirmed the usage of 2.6 mL instead of 2.0 mL of Iopamidol 300 mg/mL. This iodinated contrast media, with 1.33 g/cm 3 of density, was used close to the right adrenal vein due to some difficulty to access it. The abnormal flotation of gel separator in samples taken from right adrenal vein can be explained by the usage of the iodinated
contrast media. We suggest using plain-tubes (without gel separator) for AVS in order to avoid preanalytical nonconformities. Moreover, a blood volume equivalent to twice the catheter extension should be discarded to eliminate residual contrast media before collection of samples for laboratory assays.

  3. Characterization of a team intraoperative Radiation therapy and measurement of dose in skin with film radiochromic; Caracterizacion de un equipo de radioterapia intraoperatoria y medida de la dosis en piel con pelicula radiocromica

    Energy Technology Data Exchange (ETDEWEB)

    Onses Segarra, A.; Sancho Kolster, I.; Eraso Urien, A.; Pla Farnos, M. J.; Picon Olmos, C.


    This paper presents the results of the initial reference state of intraoperative radiotherapy equipment lntraBeam, for performing breast treatments are analyzed. To the initial reference team was established for the following dosimetric and geometric beam parameters: percentage depth dose, beam quality, isotropy, linearity and mechanical and geometric integrity for both the source RX as for different spherical applicators of the team. Based on these checks, a program of periodic quality control was established. One of the exclusion criteria for this treatment is that the tumor is less than l cm of the skin, yaque give doses received in this organ can be high. For this reason it is important to know exactly the absorbed dose in skin during these treatments. In this regard we have implemented a system for measuring the skin dose during treatment with Radiochromic film, placing 4 film segments in fixed positions of the skin around the surgical incision. It .ha obtained calibration curve of sterilized films and compared the results with a calibration beam megavoltage. The results of the skin dose measurements are compared with theoretical estimates given by the planning system equipment. The results indicate the need to measure individually the skin dose for these treatments. (Author)

  4. Methodological questions of creating tissue-equivalent phantoms (United States)

    Kolodkin, A. V.; Popov, V. I.; Sychkov, M. A.; Nikl, I.; Erdei, M.; Eyben, O.


    On the basis of analysis and generalization of literature data, the composition of tissue equivalent plastic was justified, parameters of a standard man were determined, plaster and metal forms were created for casting dummies, and an experimental model was produced from tissue equivalent material.

  5. On the equivalence of brushlet and wavelet bases

    DEFF Research Database (Denmark)

    Nielsen, Morten; Borup, Lasse


    We prove that the Meyer wavelet basis and a class of brushlet systems associated with exponential type partitions of the frequency axis form a family of equivalent (unconditional) bases for the Besov and Triebel-Lizorkin function spaces. This equivalence is then used to obtain new results...

  6. On the equivalence of brushlet and wavelet bases

    DEFF Research Database (Denmark)

    Borup, Lasse; Nielsen, Morten

    We prove that the Meyer wavelet basis and a class of brushlet systems associated with exponential type partitions of the frequency axis form a family of equivalent (unconditional) bases for the Besov and Triebel-Lizorkin function spaces. This equivalence is then used to obtain new results...

  7. 40 CFR 133.105 - Treatment equivalent to secondary treatment. (United States)


    ... 40 Protection of Environment 21 2010-07-01 2010-07-01 false Treatment equivalent to secondary treatment. 133.105 Section 133.105 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) WATER PROGRAMS SECONDARY TREATMENT REGULATION § 133.105 Treatment equivalent to secondary treatment...

  8. When is a background equivalent? Sparse chromatic context revisited

    NARCIS (Netherlands)

    Brenner, E; Cornelissen, FW

    Jenness and Shevell (Vision Res 1995,35:797-805) reported that a red background with white dots scattered on it has a different influence on a target's apparent colour than an equivalent uniform background. We show that this finding depends on what one considers an equivalent background. Jenness and

  9. Students' Conceptions of Models of Fractions and Equivalence (United States)

    Jigyel, Karma; Afamasaga-Fuata'i, Karoline


    A solid understanding of equivalent fractions is considered a steppingstone towards a better understanding of operations with fractions. In this article, 55 rural Australian students' conceptions of equivalent fractions are presented. Data collected included students' responses to a short written test and follow-up interviews with three students…

  10. An equivalent problem to the Twin Prime Conjecture


    Balestrieri, F.


    In this short paper we will show, via elementary arguments, the equivalence of the Twin Prime Conjecture to a problem which might be simpler to prove. Some conclusions are drawn, and it is shown that proving the Twin Prime Conjecture is equivalent to proving that there cannot be an infinite string of consecutive natural numbers satisfying some specified equations.

  11. Unitary equivalence classes of one-dimensional quantum walks II (United States)

    Ohno, Hiromichi


    This study investigated the unitary equivalence classes of one-dimensional quantum walks with and without initial states. We determined the unitary equivalence classes of one-dimensional quantum walks, two-phase quantum walks with one defect, complete two-phase quantum walks, one-dimensional quantum walks with one defect and translation-invariant one-dimensional quantum walks.

  12. Theoretical equivalence in classical mechanics and its relationship to duality (United States)

    Teh, Nicholas J.; Tsementzis, Dimitris


    As a prolegomenon to understanding the sense in which dualities are theoretical equivalences, we investigate the intuitive 'equivalence' of hyper-regular Lagrangian and Hamiltonian classical mechanics. We show that the symplectification of these theories (via Tulczyjew's Triple) provides a sense in which they are (1) isomorphic, and (2) mutually and canonically definable through an analog of 'common definitional extension'.

  13. Assessment Battery for Communication: Development of Two Equivalent Forms (United States)

    Bosco, Francesca M.; Angeleri, Romina; Zuffranieri, Marco; Bara, Bruno G.; Sacco, Katiuscia


    The aim of this paper was to develop and test two equivalent forms of the Assessment Battery for Communication (ABaCo), a tool for evaluating pragmatic abilities in patients with neuropsychological and psychiatric disorders. The equivalent forms were created using the data from a sample of 390 children, then tested in a sample of 30 patients with…

  14. Basis for equivalent fluence concept in space solar cells (United States)

    Meulenberg, A.


    The equivalent fluence concept is defined, and its use and potential problems are noted. Silicon and GaAs solar cells are compared in a radiation environment. The analysis indicates that valid equivalent fluence values may be easier to obtain in GaAs than in silicon.

  15. 49 CFR 538.8 - Gallon Equivalents for Gaseous Fuels. (United States)


    ... VEHICLES § 538.8 Gallon Equivalents for Gaseous Fuels. The gallon equivalent of gaseous fuels, for purposes... Natural Gas 0.823 Liquefied Natural Gas 0.823 Liquefied Petroleum Gas (Grade HD-5)* 0.726 Hydrogen 0.259...

  16. Physicochemical equivalence of some brands of Nifedipine retard ...

    African Journals Online (AJOL)



    Feb 22, 2010 ... Full Length Research Paper. Physicochemical equivalence of some brands of ... Nigeria. Accepted 9 November, 2009. This research evaluated the physicochemical equivalence of some samples of Nifedipine 20 mg Retard ... Tel: +23408052742521. dicarboxylate. It is light sensitive and its photo-reaction.

  17. On the equivalence of two fundamental theta identities

    NARCIS (Netherlands)

    Koornwinder, T.H.


    Two fundamental theta identities, a three-term identity due to Weierstrass and a five-term identity due to Jacobi, both with products of four theta functions as terms, are shown to be equivalent. One half of the equivalence was already proved by R. J. Chapman in 1996. The history and usage of the

  18. Estimation of U.S. Timber Harvest Using Roundwood Equivalents (United States)

    James Howard


    This report details the procedure used to estimate the roundwood products portion of U.S. annual timber harvest levels by using roundwood equivalents. National-level U.S. forest products data published by trade associations and State and Federal Government organizations were used to estimate the roundwood equivalent of national roundwood products production. The...

  19. Mechanical Equivalent of Heat--Software for a Thermistor (United States)

    Boleman, Michael


    The Mechanical Equivalent of Heat Apparatus from PASCO scientific provides the means for doing a simple experiment to determine the mechanical equivalent of heat, "J." A necessary step of this experiment is to determine the temperature of an aluminum cylinder. By measuring the resistance of a thermistor embedded in the cylinder, one is able to…

  20. New scale-down methodology from commercial to lab scale to optimize plant-derived soft gel capsule formulations on a commercial scale. (United States)

    Oishi, Sana; Kimura, Shin-Ichiro; Noguchi, Shuji; Kondo, Mio; Kondo, Yosuke; Shimokawa, Yoshiyuki; Iwao, Yasunori; Itai, Shigeru


    A new scale-down methodology from commercial rotary die scale to laboratory scale was developed to optimize a plant-derived soft gel capsule formulation and eventually manufacture superior soft gel capsules on a commercial scale, in order to reduce the time and cost for formulation development. Animal-derived and plant-derived soft gel film sheets were prepared using an applicator on a laboratory scale and their physicochemical properties, such as tensile strength, Young's modulus, and adhesive strength, were evaluated. The tensile strength of the animal-derived and plant-derived soft gel film sheets was 11.7 MPa and 4.41 MPa, respectively. The Young's modulus of the animal-derived and plant-derived soft gel film sheets was 169 MPa and 17.8 MPa, respectively, and both sheets showed a similar adhesion strength of approximately 4.5-10 MPa. Using a D-optimal mixture design, plant-derived soft gel film sheets were prepared and optimized by varying their composition, including variations in the mass of κ-carrageenan, ι-carrageenan, oxidized starch and heat-treated starch. The physicochemical properties of the sheets were evaluated to determine the optimal formulation. Finally, plant-derived soft gel capsules were manufactured using the rotary die method and the prepared soft gel capsules showed equivalent or superior physical properties compared with pre-existing soft gel capsules. Therefore, we successfully developed a new scale-down methodology to optimize the formulation of plant-derived soft gel capsules on a commercial scale. Copyright © 2017 Elsevier B.V. All rights reserved.

  1. Sol-Gel Processing Science Using a Sol-Gel Optics Research Facility (SGORF) (United States)


    Far. Soc. 61, 962, 975, (1965); 65, 1741 (1969). 11. L. Gengembre, A Chaperton, B. Vandorpe, C. R. Acad. Sc. Paris, Serie C, 284, 541 (1977); J. Chimie ...temperatures as low as 500°C 1]. However, when the Na20 content was more than 20 molZ the gel-derived glass had very poor durability and little usefulness...the preparation, properties and durability of largeI monolithic Na20-SiO2 gels. This is especially so for chemically durable gels in which the Na2O

  2. Multiple-phase behavior and memory effect of polymer gel

    CERN Document Server

    Annaka, M; Nakahira, T; Sugiyama, M; Hara, K; Matsuura, T


    A poly(4-acrylamidosalicylic acid) gel (PASA gel) exhibits multiple phases as characterized by distinct degrees of swelling; the gel can take one of four different swelling values, but none of the intermediate values. The gel has remarkable memory: the phase behavior of the gel depends on whether the gel has experienced the most swollen phase or the most collapsed phase in the immediate past. The information is stored and reversibly erased in the form of a macroscopic phase transition behavior. The structure factors corresponding to these four phases were obtained by SANS, which indicated the presence of characteristic structures depending on pH and temperature, particularly in the shrunken state. (orig.)

  3. The mechanism and properties of acid-coagulated milk gels

    Directory of Open Access Journals (Sweden)

    Chanokphat Phadungath


    Full Text Available Acid-coagulated milk products such as fresh acid-coagulated cheese varieties and yogurt areimportant dairy food products. However, little is known regarding the mechanisms involved in gel formation, physical properties of acid gels, and the effects of processing variables such as heat treatment and gelation temperature on the important physical properties of acid milk gels. This paper reviews the modern concepts of possible mechanisms involved in the formation of particle milk gel aggregation, along with recent developments including the use of techniques such as dynamic low amplitude oscillatory rheology to observe the gel formation process, and confocal laser scanning microscopy to monitor gel microstructure.

  4. Iron(II)- or vanadium(IV)-containing siliceous gels


    Hutter, Frank; Schmidt, Helmut K.; Scholze, Horst


    Iron(II)-containing SiO2 gels can be prepared by the hydrolysis and condensation of tetramethoxysilane in methanolic solutions of iron(II) chloride. These gels show an absorption at 1000 nm indicating the presence of iron(II). In opposition to that, iron(II) cannot be introduced into organically modified gels of the 3-glycidyloxypropyltrimethoxysilane type. Vanadium(IV) can be incorporated into both gels. Unlike the SiO2 gels, the organically modified gels are compact and elastic. The spectra...

  5. Multiple-phase behavior and memory effect of polymer gel

    Energy Technology Data Exchange (ETDEWEB)

    Annaka, M.; Motokawa, R.; Nakahira, T. [Department of Materials Technology, Chiba University, Chiba 263-8522 (Japan); Sugiyama, M. [Department of Physics, Kyushu University, Fukuoka 812-8581 (Japan); Hara, K. [Institute of Environmental Systems, Kyushu University, Fukuoka 812-8581 (Japan); Matsuura, T. [Department of Ophtalmology, Nava Medical University, Nava 634-8522 (Japan)


    A poly(4-acrylamidosalicylic acid) gel (PASA gel) exhibits multiple phases as characterized by distinct degrees of swelling; the gel can take one of four different swelling values, but none of the intermediate values. The gel has remarkable memory: the phase behavior of the gel depends on whether the gel has experienced the most swollen phase or the most collapsed phase in the immediate past. The information is stored and reversibly erased in the form of a macroscopic phase transition behavior. The structure factors corresponding to these four phases were obtained by SANS, which indicated the presence of characteristic structures depending on pH and temperature, particularly in the shrunken state. (orig.)

  6. Protein electrophoretic migration data from custom and commercial gradient gels

    Directory of Open Access Journals (Sweden)

    Andrew J. Miller


    Full Text Available This paper presents data related to the article “A method for easily customizable gradient gel electrophoresis” (A.J. Miller, B. Roman, E.M. Norstrom, 2016 [1]. Data is presented on the rate of electrophoretic migration of proteins in both hand-poured and commercially acquired acrylamide gradient gels. For each gel, migration of 9 polypeptides of various masses was measured upon completion of gel electrophoresis. Data are presented on the migration of proteins within separate lanes of the same gel as well as migration rates from multiple gels.

  7. Adhesion and Disintegration Phenomena on Fractal Agar Gel Surfaces. (United States)

    Kudo, Ayano; Sato, Marika; Sawaguchi, Haruna; Hotta, Jun-Ichi; Mayama, Hiroyuki; Nonomura, Yoshimune


    In the present study, mechanical phenomena on fractal agar gel were analyzed to understand the interfacial properties of hydrophilic biosurfaces. The evaluation of adhesion strength between the fractal agar gel surfaces showed that the fractal structure inhibits the adhesion between the agar gel surfaces. In addition, when the disintegration behavior of an agar gel block was observed between fractal agar gel substrates, the rough structure prevented the sliding of an agar gel block. These findings are useful for understanding the biological significance of rough structure on the biological surfaces.

  8. Initial investigation of a novel light-scattering gel phantom for evaluation of optical CT scanners for radiotherapy gel dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Bosi, Stephen [Institute of Medical Physics, School of Physics, University of Sydney, NSW 2006 (Australia); Naseri, Pourandokht [Institute of Medical Physics, School of Physics, University of Sydney, NSW 2006 (Australia); Puran, Alicia [Institute of Medical Physics, School of Physics, University of Sydney, NSW 2006 (Australia); Davies, Justin [Institute of Medical Physics, School of Physics, University of Sydney, NSW 2006 (Australia); Baldock, Clive [Institute of Medical Physics, School of Physics, University of Sydney, NSW 2006 (Australia)


    There is a need for stable gel materials for phantoms used to validate optical computerized tomography (CT) scanners used in conjunction with radiation-induced polymerizing gel dosimeters. Phantoms based on addition of light-absorbing dyes to gelatine to simulate gel dosimeters have been employed. However, to more accurately simulate polymerizing gels one requires phantoms that employ light-scattering colloidal suspensions added to the gel. In this paper, we present the initial results of using an optical CT scanner to evaluate a novel phantom in which radiation-exposed polymer gels are simulated by the addition of colloidal suspensions of varying turbidity. The phantom may be useful as a calibration transfer standard for polymer gel dosimeters. The tests reveal some phenomena peculiar to light-scattering gels that need to be taken into account when calibrating polymer gel dosimeters.

  9. Inter Digital Transducer Modelling through Mason Equivalent Circuit Model

    DEFF Research Database (Denmark)

    Mishra, Dipti; Singh, Abhishek; Hussain, Dil muhammed Akbar


    The frequency reliance of inter-digital transducer is analyzed with the help of MASON’s Equivalent circuit which is based on Smith’s Equivalent circuit which is further based on Foster’sNetwork. An inter-digital transducer has been demonstratedas a RLC network. The circuit is simulated by Simulat......The frequency reliance of inter-digital transducer is analyzed with the help of MASON’s Equivalent circuit which is based on Smith’s Equivalent circuit which is further based on Foster’sNetwork. An inter-digital transducer has been demonstratedas a RLC network. The circuit is simulated...... by Simulation program with Integrated Circuit Emphasis (HSPICE), a well-liked electronic path simulator. The acoustic wave devices are not suitable to simulation through circuit simulator.In this paper, an electrical model of Mason’s Equivalent electricalcircuit for an inter-digital transducer (IDT...

  10. Inter digital transducer modelling through Mason equivalent circuit model

    DEFF Research Database (Denmark)

    Mishra, Dipti; Singh, Abhishek; Hussain, Dil muhammed Akbar


    The frequency reliance of inter-digital transducer is analyzed with the help of MASON's Equivalent circuit which is based on Smith's Equivalent circuit which is further based on Foster's Network. An inter-digital transducer has been demonstrated as a RLC network. The circuit is simulated by Simul......The frequency reliance of inter-digital transducer is analyzed with the help of MASON's Equivalent circuit which is based on Smith's Equivalent circuit which is further based on Foster's Network. An inter-digital transducer has been demonstrated as a RLC network. The circuit is simulated...... by Simulation program with Integrated Circuit Emphasis (HSPICE), a well-liked electronic path simulator. The acoustic wave devices are not suitable to simulation through circuit simulator. In this paper, an electrical model of Mason's Equivalent electrical circuit for an inter-digital transducer (IDT...

  11. On identifying name equivalences in digital libraries. Name equivalence, Surname matching, Author identification, Databases

    Directory of Open Access Journals (Sweden)

    Dror G. Feitelson


    Full Text Available The services provided by digital libraries can be much improved by correctly identifying variants of the same name. For example, this will allow for better retrieval of all the works by a certain author. We focus on variants caused by abbreviations of first names, and show that significant achievements are possible by simple lexical analysis and comparison of names. This is done in two steps: first a pairwise matching of names is performed, and then these are used to find cliques of equivalent names. However, these steps can each be performed in a variety of ways. We therefore conduct an experimental analysis using two real datasets to find which approaches actually work well in practice. Interestingly, this depends on the size of the repository, as larger repositories may have many more similar names.

  12. Reduction of artefacts caused by missing ray-sum data in optical-CT imaging of implants in gel dosimeters (United States)

    Asena, A.; Smith, S. T.; Kairn, T.; Crowe, S. B.; Franich, R. D.; Trapp, J. V.


    This study demonstrates the degradation in image quality, and subsequent dose evaluation inaccuracies, that are encountered when an optical-CT system reconstructs an image slice of a gel dosimeter containing an opaque implant, and evaluates the feasibility of a simple correction method to improve the accuracy of radiotherapy dose distribution measurements under these circumstances. MATLAB was used to create a number of different virtual phantoms and treatment plans along with their synthetic projections and reconstructed data sets. The results have illustrated that accurately evaluating 3D gel dose distributions in the vicinity of high-Z interfaces is not possible using the filtered back projection method, without correction, as there are serious artefacts throughout the dose volume that are induced by the missing ray-sum data. Equivalent artefacts were present in physical measurements of irradiated PAGAT gel containers when read by an optical-CT system. An interpolation correction performed prior to reconstruction via the filtered back projection algorithm has been shown to significantly improve dose evaluation accuracy to within approximately 15 mm of the opacity. With careful placement of the implant within the gel sample, and use of the linear interpolation method described in this study, there is the potential for more accurate optical CT imaging of gels containing opaque objects.

  13. Benchmarking sample preparation/digestion protocols reveals tube-gel being a fast and repeatable method for quantitative proteomics. (United States)

    Muller, Leslie; Fornecker, Luc; Van Dorsselaer, Alain; Cianférani, Sarah; Carapito, Christine


    Sample preparation, typically by in-solution or in-gel approaches, has a strong influence on the accuracy and robustness of quantitative proteomics workflows. The major benefit of in-gel procedures is their compatibility with detergents (such as SDS) for protein solubilization. However, SDS-PAGE is a time-consuming approach. Tube-gel (TG) preparation circumvents this drawback as it involves directly trapping the sample in a polyacrylamide gel matrix without electrophoresis. We report here the first global label-free quantitative comparison between TG, stacking gel (SG), and basic liquid digestion (LD). A series of UPS1 standard mixtures (at 0.5, 1, 2.5, 5, 10, and 25 fmol) were spiked in a complex yeast lysate background. TG preparation allowed more yeast proteins to be identified than did the SG and LD approaches, with mean numbers of 1979, 1788, and 1323 proteins identified, respectively. Furthermore, the TG method proved equivalent to SG and superior to LD in terms of the repeatability of the subsequent experiments, with mean CV for yeast protein label-free quantifications of 7, 9, and 10%. Finally, known variant UPS1 proteins were successfully detected in the TG-prepared sample within a complex background with high sensitivity. All the data from this study are accessible on ProteomeXchange (PXD003841). © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Drying and Rehydration of Calcium Alginate Gels

    NARCIS (Netherlands)

    Vreeker, R.; Li, L.; Fang, Y.; Appelqvist, I.; Mendes, E.


    In this paper, we study the rehydration properties of air-dried calcium alginate gel beads. Rehydration is shown to depend on alginate source (i.e. mannuronic to guluronic acid ratio) and the salt concentration in the rehydration medium. Rehydration curves are described adequately by the empirical

  15. Electrophoretic Porosimetry of Sol-Gels (United States)

    Snow, L. A.; Smith, D. D.; Sibille, L.; Hunt, A. J.; Ng, J.; Rose, M. Franklin (Technical Monitor)


    It has been hypothesized that gravity has an effect on the formation and resulting microstructure of sol-gels. In order to more clearly resolve the effect of gravity, pores may be non-destructively analyzed in the wet gel, circumventing the shrinkage and coarsening associated with the drying procedure. We discuss the development of an electrophoretic technique, analogous to affinity chromatography, for the determination of pore size distribution and its application to silica gels. Specifically a monodisperse charged dye is monitored by an optical densitometer as it moves through the wet gel under the influence of an electric field. The transmittance data (output) represents the convolution of the dye concentration profile at the beginning of the run (input) with the pore size distribution (transfer function), i.e. linear systems theory applies. Because of the practical difficulty in producing a delta function input dye profile we prefer instead to use a step function. Average pore size is then related to the velocity of this dye front, while the pore size distribution is related to the spreading of the front. Preliminary results of this electrophoretic porosimetry and its application to ground and space-grown samples will be discussed.

  16. Gels for the conservation of cultural heritage. (United States)

    Baglioni, Piero; Dei, Luigi; Carretti, Emiliano; Giorgi, Rodorico


    Gels are becoming one of the most important tools for the conservation of cultural heritage. They are very versatile systems and can be easily adapted to the cleaning and consolidation of works of art. This perspective reviews the major achievements in the field and suggests possible future developments.

  17. Chemomechanical Characterization of Autonomic Polyacrylamide Gels (United States)

    Smith, Matthew; Heitfeld, Kevin; Kramb, Ryan; Tchoul, Maxim; Gallagher, Daniel; Vaia, Richard


    Autonomic behavior is a distinctive attribute of complex biological systems. Like biological tissue, self-oscillating hydrogels driven by the Belousov-Zhabotinsky (BZ) reaction can convert chemical signals into a mechanical response. Under appropriate conditions BZ gels exhibit sustained mechanical swell-deswell oscillations; and arrays of these gels have the potential to form networks of coupled oscillators. One of the key challenges to developing criteria for device design and assessing practical performance limits of these materials is the need for detailed knowledge of the chemomechanical characteristics of the BZ gels at various states of autonomic behavior. Recently we developed an easily synthesized BZ gel system based on polyacrylamide. Here in, the swell-deswell amplitude, mechanical forces produced during uniform oscillations, and the chemical response to external loads are discussed in context with current poly(N-isopropylacrylamide)-based systems. These studies establish the parameter space leading to robust chemomechanical oscillations and provide an experimental foundation to refine currently available theoretical models to guide the design of autonomic materials and devices.

  18. Sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS ...

    African Journals Online (AJOL)

    Four strains of eri, Samia cynthia ricini Lepidoptera: Saturniidae that can be identified morphologically and maintained at North East Institute of Science and Technology, Jorhat were characterized based on their protein profile by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE) and DNA by random ...

  19. Screening of mucoadhesive vaginal gel formulations

    Directory of Open Access Journals (Sweden)

    Ana Ochoa Andrade


    Full Text Available Rational design of vaginal drug delivery formulations requires special attention to vehicle properties that optimize vaginal coating and retention. The aim of the present work was to perform a screening of mucoadhesive vaginal gels formulated with carbomer or carrageenan in binary combination with a second polymer (carbomer, guar or xanthan gum. The gels were characterised using in vitroadhesion, spreadability and leakage potential studies, as well as rheological measurements (stress and frequency sweep tests and the effect of dilution with simulated vaginal fluid (SVF on spreadability. Results were analysed using analysis of variance and multiple factor analysis. The combination of polymers enhanced adhesion of both primary gelling agents, carbomer and carrageenan. From the rheological point of view all formulations presented a similar behaviour, prevalently elastic and characterised by loss tangent values well below 1. No correlation between rheological and adhesion behaviour was found. Carbomer and carrageenan gels containing the highest percentage of xanthan gum displayed good in vitro mucoadhesion and spreadability, minimal leakage potential and high resistance to dilution. The positive results obtained with carrageenan-xanthan gum-based gels can encourage the use of natural biocompatible adjuvants in the composition of vaginal products, a formulation field that is currently under the synthetic domain.

  20. Sol–gel processing of carbidic glasses

    Indian Academy of Sciences (India)


    Abstract. Carbon incorporation into the silicate network results in the formation of rigid carbidic glasses with improved physical, mechanical and thermal properties. This generated great interest in the development of these heteroatom structured materials through different processing routes. In the present studies, sol–gel.

  1. Sol–gel processing of carbidic glasses

    Indian Academy of Sciences (India)

    Carbon incorporation into the silicate network results in the formation of rigid carbidic glasses with improved physical, mechanical and thermal properties. This generated great interest in the development of these heteroatom structured materials through different processing routes. In the present studies, sol–gel processing ...

  2. Gel bead composition for metal adsorption (United States)

    Scott, Charles D.; Woodward, Charlene A.; Byers, Charles H.


    The invention is a gel bead comprising propylene glycol alginate and bone gelatin and is capable of removing metals such as Sr and Cs from solution without adding other adsorbents. The invention could have application to the nuclear industry's waste removal activities.

  3. Effectiveness of Gel Repellents on Feral Pigeons

    Directory of Open Access Journals (Sweden)

    Birte Stock


    Full Text Available Millions of feral pigeons (Columba livia live in close association with the human population in our cities. They pose serious health risks to humans and lead to high economic loss due to damage caused to buildings. Consequently, house owners and city authorities are not willing to allow pigeons on their buildings. While various avian repellents are regularly introduced onto the market, scientific proof of efficacy is lacking. This study aimed at testing the effectiveness of two avian gel repellents and additionally examined their application from animal welfare standpoint. The gels used an alleged tactile or visual aversion of the birds, reinforced by additional sensory cues. We mounted experimental shelves with the installed repellents in a pigeon loft and observed the behavior of free-living feral pigeons towards the systems. Both gels showed a restricted, transient repellent effect, but failed to prove the claimed complete effectiveness. Additionally, the gels’ adhesive effect remains doubtful in view of animal welfare because gluing of plumage presents a risk to feral pigeons and also to other non-target birds. This study infers that both gels lack the promised complete efficacy, conflict with animal welfare concerns and are therefore not suitable for feral pigeon management in urban areas.

  4. The Sol-Gel-Xerogel Transition (United States)


    relative mobili- ty are supported by the ESR (Electron Spin Resonance) studies of * * * Ikoma et al. [301 demonstrating that polyamine copper(II) chelates...deactivation of the triplet state of the molecule in the case of RTP. Recent studies on the photoisomerization of azobenzene in sol-gel glass films by

  5. Fast Dissolving Tablets of Aloe Vera Gel

    African Journals Online (AJOL)


    combined effect of two formulation variables - amounts of microcrystalline cellulose and mannitol. Results: The results of multiple regression analysis revealed that in order to obtain a fast dissolving tablet of the Aloe vera gel, an optimum concentration of mannitol and a higher content of microcrystalline cellulose should be ...

  6. The charge transport in polymeric gel electrolytes

    CERN Document Server

    Reiche, A


    The aim of the present thesis consisted in the study of the charge transport in gel electrolytes, which were obtained by photopolymerization of oligo(ethylene glycol) sub n -dimethacrylates with n=3, 9, and 23, and the survey of structure and property relations for the optimization of the electrolyte composition. The pressure dependence of the electric conductivity was measured. (HSI)

  7. Disulfide-Functionalized Diblock Copolymer Worm Gels. (United States)

    Warren, Nicholas J; Rosselgong, Julien; Madsen, Jeppe; Armes, Steven P


    Two strategies for introducing disulfide groups at the outer surface of RAFT-synthesized poly(glycerol monomethacrylate)-poly(2-hydroxypropyl methacrylate) (PGMA-PHPMA, or Gx-Hy for brevity) diblock copolymer worms are investigated. The first approach involved statistical copolymerization of GMA with a small amount of disulfide dimethacrylate (DSDMA, or D) comonomer to afford a G54-D0.50 macromolecular chain transfer agent (macro-CTA); this synthesis was conducted in relatively dilute solution in order to ensure mainly intramolecular cyclization and hence the formation of linear chains. Alternatively, a new disulfide-based bifunctional RAFT agent (DSDB) was used to prepare a G45-S-S-G45 (or (G45-S)2) macro-CTA. A binary mixture of a non-functionalized G55 macro-CTA was utilized with each of these two disulfide-based macro-CTAs in turn for the RAFT aqueous dispersion polymerization of 2-hydroxypropyl methacrylate (HPMA). By targeting a PHPMA DP of 130 and systematically varying the molar ratio of the two macro-CTAs, a series of disulfide-functionalized diblock copolymer worm gels were obtained. For both formulations, oscillatory rheology studies confirmed that higher disulfide contents led to stronger gels, presumably as a result of inter-worm covalent bond formation via disulfide/thiol exchange. Using the DSDB-based macro-CTA led to the strongest worm gels, and this formulation also proved to be more effective in suppressing the thermosensitive behavior that is observed for the nondisulfide-functionalized control worm gel. However, macroscopic precipitation occurred when the proportion of DSDB-based macro-CTA was increased to 50 mol %, whereas the DSDMA-based macro-CTA could be utilized at up to 80 mol %. Finally, the worm gel modulus could be reduced to that of a nondisulfide-containing worm gel by reductive cleavage of the inter-worm disulfide bonds using excess tris(2-carboxyethyl)phosphine (TCEP) to yield thiol groups. These new biomimetic worm gels are

  8. Embedding memories in colloidal gels though oscillatory shear (United States)

    Schwen, Eric; Ramaswamay, Meera; Jan, Linda; Cheng, Chieh-Min; Cohen, Itai

    While gels are ubiquitous in applications from food products to filtration, their mechanical properties are usually determined by self-assembly. We use oscillatory shear to train colloidal gels, embedding memories of the training protocol in rheological responses such as the yield strain and the gel network structures. When our gels undergo shear, the particles are forced to rearrange until they organize into structures that can locally undergo reversible shear cycles. We utilize a high-speed confocal microscope and a shear cell to image a colloidal gel while simultaneously straining the gel and measuring its shear stresses. By comparing stroboscopic images of the gel, we quantify the decrease in particle rearrangement as the gel develops reversible structures. We analyze and construct a model for the rates at which different regions in the gel approach reversible configurations. Through characterizing the gel network, we determine the structural origins of these shear training memories in gels. These results may allow us to use shear training protocols to produce gels with controllable yield strains and to better understand changes in the microstructure and rheology of gels that undergo repeated shear through mixing or flowing. This research was supported in part by NSF CBET 1509308 and Xerox Corporation.

  9. Investigations of the small-scale thermal behavior of sol-gel thermites.

    Energy Technology Data Exchange (ETDEWEB)

    Warren, Mial E.; Farrow, Matthew; Tappan, Alexander Smith


    Sol-gel thermites, formulated from nanoporous oxides and dispersed fuel particles, may provide materials useful for small-scale, intense thermal sources, but understanding the factors affecting performance is critical prior to use. Work was conducted on understanding the synthesis conditions, thermal treatments, and additives that lead to different performance characteristics in iron oxide sol-gel thermites. Additionally, the safety properties of sol-gel thermites were investigated, especially those related to air sensitivity. Sol-gel thermites were synthesized using a variety of different techniques and there appear to be many viable routes to relatively equivalent thermites. These thermites were subjected to several different thermal treatments under argon in a differential scanning calorimeter, and it was shown that a 65 C hold for up to 200 minutes was effective for the removal of residual solvent, thus preventing boiling during the final thermal activation step. Vacuum-drying prior to this heating was shown to be even more effective at removing residual solvent. The addition of aluminum and molybdenum trioxide (MoO{sub 3}) reduced the total heat release per unit mass upon exposure to air, probably due to a decrease in the amount of reduced iron oxide species in the thermite. For the thermal activation step of heat treatment, three different temperatures were investigated. Thermal activation at 200 C resulted in increased ignition sensitivity over thermal activation at 232 C, and thermal activation at 300 C resulted in non-ignitable material. Non-sol-gel iron oxide did not exhibit any of the air-sensitivity observed in sol-gel iron oxide. In the DSC experiments, no bulk ignition of sol-gel thermites was observed upon exposure to air after thermal activation in argon; however ignition did occur when the material was heated in air after thermal treatment. In larger-scale experiments, up to a few hundred milligrams, no ignition was observed upon exposure to air

  10. The biased reptation model of DNA gel electrophoresis: mobility vs molecular size and gel concentration. (United States)

    Slater, G W; Noolandi, J


    The biased reptation model provides a good framework for interpreting the results of continuous field DNA electrophoresis experiments performed in agarose gels. Here we discuss the main features of the mobility-molecular size and mobility-gel concentration diagrams as obtained from new extensive computer simulations of the model. Our aim is to suggest a global and coherent picture of this widely used yet poorly understood experimental technique, and to point out the areas where a systematic experimental study is still needed.

  11. Simplified riboprobe purification using translucent straws as gel tubes. (United States)

    Kol, S; Ben-Shlomo, I; Adashi, E Y; Rohan, R M


    Gel purification of radioactive riboprobes enhances the quality of the ribonuclease protection assay. A simple and effective method for riboprobe purification is described. The method uses acrylamide gels in plastic tubes to achieve electrophoretic separation of the RNA polymerase products.

  12. Image noise in X-ray CT polymer gel dosimetry

    Energy Technology Data Exchange (ETDEWEB)

    Hilts, M [Medical Physics, BC Cancer Agency, Vancouver Centre (Canada); Department of Physics and Astronomy, University of British Columbia, Vancouver, BC (Canada); Duzenli, C [Medical Physics, BC Cancer Agency, Vancouver Centre (Canada)


    This work investigates factors which affect image noise in CT polymer gel dosimetry, discusses techniques that can be used to further improve image noise and provides overall recommendations for the CT imaging of polymer gels.

  13. Gel-expanded to gel-condensed transition in neurofilament networks revealed by direct force measurements (United States)

    Beck, Roy; Deek, Joanna; Jones, Jayna B.; Safinya, Cyrus R.


    Neurofilaments (NF)-the principal cytoskeletal constituent of myelinated axons in vertebrates-consist of three molecular-weight subunit proteins NF-L (low), NF-M (medium) and NF-H (high), assembled to form mature filaments with protruding unstructured C-terminus side arms. Liquid-crystal gel networks of side-arm-mediated neurofilament assemblies have a key role in the mechanical stability of neuronal processes. Disruptions of the neurofilament network, owing to neurofilament over-accumulation or incorrect side-arm interactions, are a hallmark of motor-neuron diseases including amyotrophic lateral sclerosis. Using synchrotron X-ray scattering, we report on a direct measurement of forces in reconstituted neurofilament gels under osmotic pressure (P). With increasing pressure near physiological salt and average phosphorylation conditions, NF-LMH, comprising the three subunits near in vivo composition, or NF-LH gels, undergo for P>Pc~10kPa, an abrupt non-reversible gel-expanded to gel-condensed transition. The transition indicates side-arm-mediated attractions between neurofilaments consistent with an electrostatic model of interpenetrating chains. In contrast, NF-LM gels remain in a collapsed state for PPc. These findings, which delineate the distinct roles of NF-M and NF-H in regulating neurofilament interactions, shed light on possible mechanisms for disruptions of optimal mechanical network properties.

  14. Spaces of homotopy self-equivalences a survey

    CERN Document Server

    Rutter, John W


    This survey covers groups of homotopy self-equivalence classes of topological spaces, and the homotopy type of spaces of homotopy self-equivalences. For manifolds, the full group of equivalences and the mapping class group are compared, as are the corresponding spaces. Included are methods of calculation, numerous calculations, finite generation results, Whitehead torsion and other areas. Some 330 references are given. The book assumes familiarity with cell complexes, homology and homotopy. Graduate students and established researchers can use it for learning, for reference, and to determine the current state of knowledge.

  15. Theory of Covariance Equivalent ARMAV Models of Civil Engineering Structures

    DEFF Research Database (Denmark)

    Andersen, P.; Brincker, Rune; Kirkegaard, Poul Henning


    In this paper the theoretical background for using covariance equivalent ARMAV models in modal analysis is discussed. It is shown how to obtain a covariance equivalent ARMA model for a univariate linear second order continous-time system excited by Gaussian white noise. This result is generalized...... for multi-variate systems to an ARMAV model. The covariance equivalent model structure is also considered when the number of channels are different from the number of degrees offreedom to be modelled. Finally, it is reviewed how to estimate an ARMAV model from sampled data....

  16. Theory of Covariance Equivalent ARMAV Models of Civil Engineering Structures

    DEFF Research Database (Denmark)

    Andersen, P.; Brincker, Rune; Kirkegaard, Poul Henning

    In this paper the theoretical background for using covariance equivalent ARMAV models in modal analysis is discussed. It is shown how to obtain a covariance equivalent ARMA model for a univariate linear second order continuous-time system excited by Gaussian white noise. This result is generalized...... for multivariate systems to an ARMAV model. The covariance equivalent model structure is also considered when the number of channels are different from the number of degrees of freedom to be modelled. Finally, it is reviewed how to estimate an ARMAV model from sampled data....

  17. Gel-forming reagents and uses thereof for preparing microarrays (United States)

    Golova, Julia; Chernov, Boris; Perov, Alexander


    New gel-forming reagents including monomers and cross-linkers, which can be applied to gel-drop microarray manufacturing by using co-polymerization approaches are disclosed. Compositions for the preparation of co-polymerization mixtures with new gel-forming monomers and cross-linker reagents are described herein. New co-polymerization compositions and cross-linkers with variable length linker groups between unsaturated C.dbd.C bonds that participate in the formation of gel networks are disclosed.

  18. Methods of Manufacturing Bioactive Gels from Extracellular Matrix Material (United States)

    Kentner, Kimberly (Inventor); Stuart, Katherine A. (Inventor); Janis, Abram D. (Inventor)


    The present invention is directed to methods of manufacturing bioactive gels from ECM material, i.e., gels which retain bioactivity, and can serve as scaffolds for preclinical and clinical tissue engineering and regenerative medicine approaches to tissue reconstruction. The manufacturing methods take advantage of a new recognition that bioactive gels from ECM material can be created by digesting particularized ECM material in an alkaline environment and neutralizing to provide bioactive gels.

  19. Sol-gel modification of wood substrates to retard weathering (United States)

    Mandla A Tshabalala; Sam Williams


    Wood specimens were treated with sol-gel systems based on metalorganic precursors of silicon (Si), iron (Fe), zirconium (Zr), and titanium (Ti). The effect of these sol-gel systems on weathering properties of wood was investigated. These sol-gel systems were found to have a positive effect on surface color stability and water vapor resistance of the specimens. Under...

  20. Outdoor weathering of sol-gel-treated wood (United States)

    Mandla A Tshabalala; Ryan Libert; Nancy Ross Sutherland


    Outdoor weathering of wood specimens treated with sol-gel formulations based on methyltrimethoxysilane (MTMOS), hexadecyltrimethoxysilane (HDTMOS), and ferric-zirconia-titania (Fe-Zr-Ti) sol was evaluated. The sol-gel process allowed deposition of a thin film of hybrid inorganic-organic networks (gel) in the wood cell wall that resulted in improved outdoor weathering...

  1. 21 CFR 520.1453 - Moxidectin and praziquantel gel. (United States)


    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Moxidectin and praziquantel gel. 520.1453 Section 520.1453 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... and praziquantel gel. (a) Specifications. Each milliliter of gel contains 20 milligrams (mg) (2.0...

  2. 21 CFR 520.1242f - Levamisole hydrochloride gel. (United States)


    ... 21 Food and Drugs 6 2010-04-01 2010-04-01 false Levamisole hydrochloride gel. 520.1242f Section 520.1242f Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES... Levamisole hydrochloride gel. (a) Specifications. The drug is a gel containing 11.5 percent levamisole...

  3. Evaluation and Selection of Gel Base for the Formulation of ...

    African Journals Online (AJOL)

    Results: The flow curves of the gels with Carbopol 980 and Ultrez 10 showed pseudoplastic flow. Lutrol F 127 gels presented thixotropic behaviour. The consistency of the studied gels was in the following rank order: Lutrol F 127 > Ultrez 10 > Carbopol 980. In vitro results showed that dexpanthenol was released in lower ...

  4. Based Mucoadhesive Gel for Nasal Delivery of Rizatriptan Benzoate

    African Journals Online (AJOL)

    Purpose: To develop a safe mucoadhesive gel for nasal drug delivery using okra polysaccharide. Methods: Rizatriptan benzoate nasal gel was developed using natural polysaccharide obtained from the Abelmoschus esculentus. The gel formulation was characterized for pH, viscosity, mucoadhesion, and in vitro ...

  5. Formulation and method for preparing gels comprising hydrous hafnium oxide (United States)

    Collins, Jack L; Hunt, Rodney D; Montgomery, Frederick C


    Formulations useful for preparing hydrous hafnium oxide gels contain a metal salt including hafnium, an acid, an organic base, and a complexing agent. Methods for preparing gels containing hydrous hafnium oxide include heating a formulation to a temperature sufficient to induce gel formation, where the formulation contains a metal salt including hafnium, an acid, an organic base, and a complexing agent.

  6. Formulation and method for preparing gels comprising hydrous cerium oxide (United States)

    Collins, Jack L; Chi, Anthony


    Formulations useful for preparing hydrous cerium oxide gels contain a metal salt including cerium, an organic base, and a complexing agent. Methods for preparing gels containing hydrous cerium oxide include heating a formulation to a temperature sufficient to induce gel formation, where the formulation contains a metal salt including cerium, an organic base, and a complexing agent.

  7. Formulation and method for preparing gels comprising hydrous aluminum oxide (United States)

    Collins, Jack L.


    Formulations useful for preparing hydrous aluminum oxide gels contain a metal salt including aluminum, an organic base, and a complexing agent. Methods for preparing gels containing hydrous aluminum oxide include heating a formulation to a temperature sufficient to induce gel formation, where the formulation contains a metal salt including aluminum, an organic base, and a complexing agent.

  8. Agarose Gel Size Selection for DNA Sequencing Libraries. (United States)

    Mardis, Elaine; McCombie, W Richard


    Agarose gel electrophoresis may be used to purify fragmented genomic DNA after ligation of adaptors. After electrophoresis, the region of the gel containing the desired size range of DNA is excised, and the DNA is subsequently extracted from the gel and purified by passage through a spin column. © 2017 Cold Spring Harbor Laboratory Press.

  9. 21 CFR 872.1730 - Electrode gel for pulp testers. (United States)


    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Electrode gel for pulp testers. 872.1730 Section... (CONTINUED) MEDICAL DEVICES DENTAL DEVICES Diagnostic Devices § 872.1730 Electrode gel for pulp testers. (a) Identification. An electrode gel for pulp testers is a device intended to be applied to the surface of a tooth...

  10. Improvement in Tensile Strength of Bamboo Knitted Fabric by Sol-Gel Coating

    Directory of Open Access Journals (Sweden)

    Awais Khatri


    Full Text Available Textiles made of bamboo regenerated fibre are reported to have lower tensile strength than the other cellulosic fibres, due to high porosity of the fibre. This paper was aimed to modify the bamboo knitted fabric by the sol-gel coating to improve the tensile strength with minimum effect on its inherent morphology and ultimate relevant properties such as good absorbency and air permeability. The paddry- bake process was employed for the coating where tetraethyl-orthosilicate and nano-titanium-dioxide were used as the active ingredients. The treated fabrics were tested for the tensile behaviour in terms of breaking strength and elongation and the sol-gel process recipe and parameters were optimised. The absorbency, air-permeability and washing durability of the coating were also tested for the optimised process. Results showed the increase in tensile strength of the fabric by sol-gel coating, whereas absorbency and air-permeability were almost unaffected. The coating results were unaffected even after a washing treatment (equivalent to 5 industrial washings. Additionally, the wrinkle recovery angle of the coated fabric was also tested and found improved.

  11. Guidelines for the communication of Biomonitoring Equivalents: report from the Biomonitoring Equivalents Expert Workshop. (United States)

    LaKind, Judy S; Aylward, Lesa L; Brunk, Conrad; DiZio, Stephen; Dourson, Michael; Goldstein, Daniel A; Kilpatrick, Michael E; Krewski, Daniel; Bartels, Michael J; Barton, Hugh A; Boogaard, Peter J; Lipscomb, John; Krishnan, Kannan; Nordberg, Monica; Okino, Miles; Tan, Yu-Mei; Viau, Claude; Yager, Janice W; Hays, Sean M


    Biomonitoring Equivalents (BEs) are screening tools for interpreting biomonitoring data. However, the development of BEs brings to the public a relatively novel concept in the field of health risk assessment and presents new challenges for environmental risk communication. This paper provides guidance on methods for conveying information to the general public, the health care community, regulators and other interested parties regarding how chemical-specific BEs are derived, what they mean in terms of health, and the challenges and questions related to interpretation and communication of biomonitoring data. Key communication issues include: (i) developing a definition of the BE that accurately captures the BE concept in lay terms, (ii) how to compare population biomonitoring data to BEs, (iii) interpreting biomonitoring data that exceed BEs for a specific chemical, (iv) how to best describe the confidence in chemical-specific BEs, and (v) key requirements for effective communication with health care professionals. While the risk communication literature specific to biomonitoring is sparse, many of the concepts developed for traditional risk assessments apply, including transparency and discussions of confidence and uncertainty. Communication of BEs will require outreach, education, and development of communication materials specific to several audiences including the lay public and health care providers.

  12. Efficacy of leukocyte‐ and platelet‐rich plasma gel (L‐PRP gel) in treating osteomyelitis in a rabbit model

    National Research Council Canada - National Science Library

    Li, Guang‐Yi; Yin, Ji‐Min; Ding, Hao; Jia, Wei‐Tao; Zhang, Chang‐Qing


    Leukocyte‐ and platelet‐rich plasma gel (L‐PRP gel), a new autologous product which was previously utilized in several surgical procedures to enhance tissue healing, is now increasingly used as a promising treatment method for infections...

  13. Thiourea-tagged poly(octadecyl acrylate) gels as fluoride and acetate responsive polymer gels through selective complexation. (United States)

    Krishnamurthi, Janakiraman; Ono, Toshikazu; Amemori, Shogo; Komatsu, Hiromu; Shinkai, Seiji; Sada, Kazuki


    Fluoride and acetate-responsive polymer gels were prepared by incorporation of p-nitrophenylthiourea into poly(octadecyl acrylate) gels, and the colours and volumes were changed selectively in the presence of these ions by complexation in THF.

  14. Affine equivalence of cubic homogeneous rotation symmetric Boolean functions

    CERN Document Server

    Cusick, Thomas W


    Homogeneous rotation symmetric Boolean functions have been extensively studied in recent years because of their applications in cryptography. Little is known about the basic question of when two such functions are affine equivalent. The simplest case of quadratic rotation symmetric functions which are generated by cyclic permutations of the variables in a single monomial was only settled in 2009. This paper studies the much more complicated cubic case for such functions. A new concept of \\emph{patterns} is introduced, by means of which the structure of the smallest group G_n, whose action on the set of all such cubic functions in $n$ variables gives the affine equivalence classes for these functions under permutation of the variables, is determined. We conjecture that the equivalence classes are the same if all nonsingular affine transformations, not just permutations, are allowed. This conjecture is verified if n < 22. Our method gives much more information about the equivalence classes; for example, in t...

  15. Analysis of equivalent antenna based on FDTD method

    Directory of Open Access Journals (Sweden)

    Yun-xing Yang


    Full Text Available An equivalent microstrip antenna used in radio proximity fuse is presented. The design of this antenna is based on multilayer multi-permittivity dielectric substrate which is analyzed by finite difference time domain (FDTD method. Equivalent iterative formula is modified in the condition of cylindrical coordinate system. The mixed substrate which contains two kinds of media (one of them is airtakes the place of original single substrate. The results of equivalent antenna simulation show that the resonant frequency of equivalent antenna is similar to that of the original antenna. The validity of analysis can be validated by means of antenna resonant frequency formula. Two antennas have same radiation pattern and similar gain. This method can be used to reduce the weight of antenna, which is significant to the design of missile-borne antenna.

  16. Equivalence principle and quantum mechanics: quantum simulation with entangled photons (United States)

    Longhi, S.


    Einstein`s equivalence principle states the complete physical equivalence of a gravitational field and corresponding inertial field in an accelerated reference frame. However, to what extent the equivalence principle remains valid in non-relativistic quantum mechanics is a controversial issue. To avoid violation of the equivalence principle, Bargmann`s superselection rule forbids a coherent superposition of states with different masses. Here we suggest a quantum simulation of non-relativistic Schr\\"odinger particle dynamics in non-inertial reference frames, which is based on propagation of polarization-entangled photon pairs in curved and birefringent optical waveguides and Hong-Ou-Mandel quantum interference measurement. The photonic simulator can emulate superposition of mass states, which would lead to violation of the EP.

  17. Aldehydes as alkyl carbanion equivalents for additions to carbonyl compounds (United States)

    Wang, Haining; Dai, Xi-Jie; Li, Chao-Jun


    Nucleophilic addition reactions of organometallic reagents to carbonyl compounds for carbon-carbon bond construction have played a pivotal role in modern chemistry. However, this reaction's reliance on petroleum-derived chemical feedstocks and a stoichiometric quantity of metal have prompted the development of many carbanion equivalents and catalytic metal alternatives. Here, we show that naturally occurring carbonyls can be used as latent alkyl carbanion equivalents for additions to carbonyl compounds, via reductive polarity reversal. Such 'umpolung' reactivity is facilitated by a ruthenium catalyst and diphosphine ligand under mild conditions, delivering synthetically valuable secondary and tertiary alcohols in up to 98% yield. The unique chemoselectivity exhibited by carbonyl-derived carbanion equivalents is demonstrated by their tolerance to protic reaction media and good functional group compatibility. Enantioenriched tertiary alcohols can also be accessed with the aid of chiral ligands, albeit with moderate stereocontrol. Such carbonyl-derived carbanion equivalents are anticipated to find broad utility in chemical bond formation.

  18. ESA GlobSnow Snow Water Equivalent (SWE) (United States)

    National Aeronautics and Space Administration — The European Space Agency (ESA) Global Snow Monitoring for Climate Research (GlobSnow) snow water equivalent (SWE) v2.0 data record contains snow information derived...

  19. Problems of Equivalence in Shona- English Bilingual Dictionaries

    African Journals Online (AJOL)


    translation equivalents in Shona-English dictionaries where lexicographers will be dealing with divergent languages and cultures, traditional practices of lexicography and the absence of reliable corpora. Keywords: BILINGUAL LEXICOGRAPHY, CORPUS, CULTURE, CULTURE-BOUND,. CULTURAL GAP, DICTIONARY ...

  20. On conjugate points and the Leitmann equivalent problem approach

    NARCIS (Netherlands)

    Wagener, F.O.O.


    This article extends the Leitmann equivalence method to a class of problems featuring conjugate points. The class is characterised by the requirement that the set of indifference points of a given problem forms a finite stratification.

  1. Approved Drug Products with Therapuetic Equivalence Evaluations (Orange Book) (United States)

    U.S. Department of Health & Human Services — The publication Approved Drug Products with Therapeutic Equivalence Evaluations (the List, commonly known as the Orange Book) identifies drug products approved on...

  2. Therapeutic equivalence study of two formulations (innovator v ...

    African Journals Online (AJOL)

    Therapeutic equivalence study of two formulations (innovator v. generic) of beclomethasone dipropionate in adult asthmatic patients. Haylene Nell, Charlene M. Louw, Helen Cyster, Zelda Williams, Philip G. Bardin, James R. Joubert ...

  3. Solvent induced supramolecular anisotropy in molecular gels

    Energy Technology Data Exchange (ETDEWEB)

    Rogers, Michael A., E-mail: [Department of Food Science, University of Guelph, Guelph, Ontario, N3C3X9 (Canada); Corradini, Maria G. [Department of Food Science, University of Massachusetts Amherst, Amherst, MA, 01003 (United States); Emge, Thomas [Department of Chemistry and Biochemistry, Rutgers University, New Brunswick, NJ, 08901 (United States)


    Herein is the first report of solvent induced anisotropy in 12-hydroxystearic acid self-assembled fibrillar networks. Increasing the chain length of polar solvent, such as nitriles and ketones, tailored the anisotropy of the fibrillar aggregates. 12HSA molecular gels, comprised of alkanes, exhibited an isotropic fibrillar network irrespective of the alkane chain length. In polar solvents, anisotropy, observed using 2D powder x-ray diffraction profiles, is correlated to a fibrillar supramolecular morphologies in long chain nitriles and ketones while sphereulitic crystals are correlated to x-ray diffraction patterns with an isotropic scatter intensity in short chain ketones and nitriles. These changes directly modify the final physical properties of the gels. - Highlights: • 12-HSA self-assembles into crystalline supramolecular morphologies depending on the solvent. • Alkanes, short chain nitriles and ketones led to 12-HSA displaying supramolecular isotropy. • In long chain nitriles and ketones, 12-HSA displays supramolecular anisotropy.

  4. Spontaneous exfoliation of a drying gel. (United States)

    Chung, Jun Young; Regev, Ido; Mahadevan, L


    Wet starch cracks when it dries inhomogeneously, while hot glass cracks when it cools non-uniformly. In both cases, differential shrinkage induced by drying/cooling from the surface causes superficial cracks to grow perpendicular to the surface in different patterns. In contrast with these observations of bulk cracking in brittle materials, when a soft and homogeneously swollen polymer gel dries, differential strains lead to the peeling of a thin layer that spontaneously tears away from the bulk. Continued drying leads to the process repeating itself, forming a peeled-layered structure. The emergent thickness of the exfoliated layer is a function of both the geometry of the original gel and the physical parameters associated with the drying rate and external temperature. We characterize the experimental conditions under which layer peeling can arise, and use simulations to corroborate these observations. Finally, a minimal theory explains the scaling of the peel thickness, consistent with our experiments.

  5. Polyphosphate gel/methyl orange supramolecular composites (United States)

    Galembeck, André; Silva, Sidicleia B. C.; Silva, José Augusto P.; Del Nero, J.


    The aims of this work were to investigate theoretically the optical properties of methyl orange (MO) and the synthesis of new supramolecular composites based on the incorporation of this dye in an aluminum polyphosphate gel network. The theoretical methodology was based in semiempirical (AM1 and INDO/S-CI) and ab initio (3-21G*) methods. Our results reveal the existence of different electronic patterns for the acidic and basic forms of these molecules. Also, we present a theoretical spectroscopic study for the molecules including interactions with water molecules. MO was successfully incorporated in its acidic form within the host matrix, leading to pink-red transparent self-standing films. The dye could be converted to its basic form upon exposure to ammonia vapor. The spectrum of MO basic form within the gel network differs from its behavior in aqueous solution.

  6. Gel Fabrication of Molybdenum “Beads”

    Energy Technology Data Exchange (ETDEWEB)

    Lowden, Richard Andrew [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Armstrong, Beth L. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division; Cooley, Kevin M. [Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States). Materials Science and Technology Division


    Spherical molybdenum particles or “beads” of various diameters are of interest as feedstock materials for the additive manufacture of targets and assemblies used in the production of 99Mo medical isotopes using accelerator technology. Small metallic beads or ball bearings are typically fabricated from wire; however, small molybdenum spheres cannot readily be produced in this manner. Sol-gel processes are often employed to produce small dense microspheres of metal oxides across a broad diameter range that in the case of molybdenum could be reduced and sintered to produce metallic spheres. These Sol-gel type processes were examined for forming molybdenum oxide beads; however, the molybdenum trioxide was chemically incompatible with commonly used gelation materials. As an alternative, an aqueous alginate process being assessed for the fabrication of oxide spheres for catalyst applications was employed to form molybdenum trioxide beads that were successfully reduced and sintered to produce small molybdenum spheres.

  7. Structural Hierarchy Governs Fibrin Gel Mechanics (United States)

    Piechocka, Izabela K.; Bacabac, Rommel G.; Potters, Max; MacKintosh, Fred C.; Koenderink, Gijsje H.


    Abstract Fibrin gels are responsible for the mechanical strength of blood clots, which are among the most resilient protein materials in nature. Here we investigate the physical origin of this mechanical behavior by performing rheology measurements on reconstituted fibrin gels. We find that increasing levels of shear strain induce a succession of distinct elastic responses that reflect stretching processes on different length scales. We present a theoretical model that explains these observations in terms of the unique hierarchical architecture of the fibers. The fibers are bundles of semiflexible protofibrils that are loosely connected by flexible linker chains. This architecture makes the fibers 100-fold more flexible to bending than anticipated based on their large diameter. Moreover, in contrast with other biopolymers, fibrin fibers intrinsically stiffen when stretched. The resulting hierarchy of elastic regimes explains the incredible resilience of fibrin clots against large deformations. PMID:20483337

  8. Calcium Impact on Milk Gels Formation

    DEFF Research Database (Denmark)

    Koutina, Glykeria

    Calcium is one of the several elements that can be found in milk distributed between the micellar and the serum milk phase. Calcium is important from a nutritional point of view, but its contribution to the functional and structural properties of dairy products has only recently been...... acknowledgement. The presence of calcium in a dynamic equilibrium between the serum and the micellar milk phase make the distribution susceptible to certain physicochemical conditions and to technological treatments of milk resulting in fluctuations in pH and temperature and also sensitive to addition of calcium...... salts. The perturbation of calcium equilibria by these factors will affect the final properties of acid, calcium and rennet milk gels. By decreasing the pH from 6.0 to 5.2 (acid gels), the calcium equilibrium was significantly affected by temperature (4, 20, 30, 40 oC), and different combinations...

  9. Influence of Gravitation on Mass-Energy Equivalence Relation


    Pandya, R. V. R.


    We study influence of gravitational field on the mass-energy equivalence relation by incorporating gravitation in the physical situation considered by Einstein (Ann. Physik, 17, 1905, English translation in ref. [1]) for his first derivation of mass-energy equivalence. In doing so, we also refine Einstein's expression (Ann. Physik, 35, 1911, English translation in ref. [3]) for increase in gravitational mass of the body when it absorbs E amount of radiation energy.

  10. Human skin equivalent as an alternative to animal testing


    Mertsching, Heike; Weimer, Michaela; Kersen, Silke; Brunner, Herwig


    The 3-D skin equivalent can be viewed as physiologically comparable to the natural skin and therefore is a suitable alternative for animal testing. This highly differentiated in vitro human skin equivalent is used to assess the efficacy and mode of action of novel agents. This model is generated from primary human keratinocytes on a collagen substrate containing human dermal fibroblasts. It is grown at the air-liquid interface which allows full epidermal stratification and epidermal-dermal in...

  11. Equivalence Between Out-of-Sample Forecast Comparisons and Wald

    DEFF Research Database (Denmark)

    Hansen, Peter Reinhard; Timmermann, Allan

    We establish the equivalence between a commonly used out-of-sample test of equal predictive accuracy and the difference between two Wald statistics. This equivalence greatly simplifies the computational burden of calculating recursive out-of-sample tests and evaluating their critical values. Our r...... results shed new light on many aspects of the test and establishes certain weaknesses associated with using out-of-sample forecast comparison tests to conduct inference about nested regression models....

  12. Noise equivalent circuit of a semiconductor laser diode


    Harder, Christoph; Katz, Joseph; Margalit, S.; Shacham, J.; Yariv, A.


    The noise equivalent circuit of a semiconductor laser diode is derived from the rate equations including Langevin noise sources. This equivalent circuit allows a straightforward calculation of the noise and modulation characteristics of a laser diode combined with electronic components. The intrinsic junction voltage noise spectrum and the light intensity fluctuation of a current driven laser diode are calculated as a function of bias current and frequency.

  13. Equivalence of Quantum Resource Measures for X States (United States)

    Huang, Zhiming; Zhang, Cai; Zhang, Wei; Zhao, Lianghui


    In this paper, we investigate some X states, quantum resource measures of which are equivalent. We find that for a class of X states, trace norm geometric quantum discord (TGQD), trace norm measurement-induced nonlocality (TMIN) and l 1 norm quantum coherence (L1QC) are all equal, and for some special states, therein two measures are equal. We also exemplify relative application of the equivalent relations.

  14. Dose Equivalents for Antipsychotic Drugs: The DDD Method. (United States)

    Leucht, Stefan; Samara, Myrto; Heres, Stephan; Davis, John M


    Dose equivalents of antipsychotics are an important but difficult to define concept, because all methods have weaknesses and strongholds. We calculated dose equivalents based on defined daily doses (DDDs) presented by the World Health Organisation's Collaborative Center for Drug Statistics Methodology. Doses equivalent to 1mg olanzapine, 1mg risperidone, 1mg haloperidol, and 100mg chlorpromazine were presented and compared with the results of 3 other methods to define dose equivalence (the "minimum effective dose method," the "classical mean dose method," and an international consensus statement). We presented dose equivalents for 57 first-generation and second-generation antipsychotic drugs, available as oral, parenteral, or depot formulations. Overall, the identified equivalent doses were comparable with those of the other methods, but there were also outliers. The major strength of this method to define dose response is that DDDs are available for most drugs, including old antipsychotics, that they are based on a variety of sources, and that DDDs are an internationally accepted measure. The major limitations are that the information used to estimate DDDS is likely to differ between the drugs. Moreover, this information is not publicly available, so that it cannot be reviewed. The WHO stresses that DDDs are mainly a standardized measure of drug consumption, and their use as a measure of dose equivalence can therefore be misleading. We, therefore, recommend that if alternative, more "scientific" dose equivalence methods are available for a drug they should be preferred to DDDs. Moreover, our summary can be a useful resource for pharmacovigilance studies. © The Author 2016. Published by Oxford University Press on behalf of the Maryland Psychiatric Research Center. All rights reserved. For permissions, please email:

  15. Steganographic Capacity of Images, based on Image Equivalence Classes

    DEFF Research Database (Denmark)

    Hansen, Klaus; Hammer, Christian; Andersen, Jens Damgaard


    The problem of hiding information imperceptibly can be formulated as the problem of determining if a given image is a member of a sufficiently large equivalence class of images which to the Human Visual System appears to be the same image. This makes it possible to replace the given image...... with a modified image similar in appearance but carrying imperceptibly coded information. This paper presents a framework and an experimental algorithm to estimate upper bounds for the size of an equivalence class....

  16. On the Equivalence of Euler-Lagrange and Noether Equations

    Energy Technology Data Exchange (ETDEWEB)

    Faliagas, A. C., E-mail: [University of Athens, Department of Mathematics (Greece)


    We prove that, under the condition of nontriviality, the Euler-Lagrange and Noether equations are equivalent for a general class of scalar variational problems. Examples are position independent Lagrangians, Lagrangians of p-Laplacian type, and Lagrangians leading to nonlinear Poisson equations. As applications we prove certain propositions concerning the nonlinear Poisson equation and its generalisations, and the equivalence of admissible and inner variations for the systems under consideration.

  17. Neutral theory and the evolution of ecological equivalence. (United States)

    Hubbell, Stephen P


    Since the publication of the unified neutral theory in 2001, there has been much discussion of the theory, pro and con. The hypothesis of ecological equivalence is the fundamental yet controversial idea behind neutral theory. Assuming trophically similar species are demographically alike (symmetric) on a per capita basis is only an approximation, but it is equivalent to asking: How many of the patterns of ecological communities are the result of species similarities, rather than of species differences? The strategy behind neutral theory is to see how far one can get with the simplification of assuming ecological equivalence before introducing more complexity. In another paper, I review the empirical evidence that led me to hypothesize ecological equivalence among many of the tree species in the species-rich tropical forest on Barro Colorado Island (BCI). In this paper, I develop a simple model for the evolution of ecological equivalence or niche convergence, using as an example evolution of the suite of life history traits characteristic of shade tolerant tropical tree species. Although the model is simple, the conclusions from it seem likely to be robust. I conclude that ecological equivalence for resource use are likely to evolve easily and often, especially in species-rich communities that are dispersal and recruitment limited. In the case of the BCI forest, tree species are strongly dispersal- and recruitment-limited, not only because of restricted seed dispersal, but also because of low recruitment success due to heavy losses of the seedling stages to predators and pathogens and other abiotic stresses such as drought. These factors and the high species richness of the community strongly reduce the potential for competitive exclusion of functionally equivalent or nearly equivalent species.

  18. Mesoscale symmetries explain dynamical equivalence of food webs


    Aufderheide, Helge; Rudolf, Lars; Gross, Thilo


    A present challenge in complex systems is to identify mesoscale structures that have distinct dynamical implications. In this paper we present a detailed investigation of a previously observed dynamical equivalence of certian ecological food webs. We show that this equivalence is rooted in mesoscale symmetries that exist in these webs. Certain eigenvectors of the Jacobian describing dynamical modes of the system, such as specific instabilities or responses to perturbations, localize on these ...

  19. Feedback equivalence of convolutional codes over finite rings

    Directory of Open Access Journals (Sweden)

    DeCastro-García Noemí


    Full Text Available The approach to convolutional codes from the linear systems point of view provides us with effective tools in order to construct convolutional codes with adequate properties that let us use them in many applications. In this work, we have generalized feedback equivalence between families of convolutional codes and linear systems over certain rings, and we show that every locally Brunovsky linear system may be considered as a representation of a code under feedback convolutional equivalence.

  20. Gel Evolution in Oil Based Drilling Fluids


    Sandvold, Ida


    Drilling fluids make up an essential part of the drilling operation. Successful drilling operations rely on adequate drilling fluid quality. With the development of new drilling techniques such as long deviated sections and drilling in ultra-deep waters, the standard of required performance of the drilling fluids continue to increase. Narrow pressure margins and low tolerance for barite sag requires accurate prediction of the gel evolution in drilling fluids. Increased knowledge of how dri...

  1. The Microrheology of Sickle Hemoglobin Gels


    Zakharov, Mikhail N.; Aprelev, Alexey; Turner, Matthew S.; Ferrone, Frank A.


    Sickle cell disease is a rheological disease, yet no quantitative rheological data exist on microscopic samples at physiological concentrations. We have developed a novel method for measuring the microrheology of sickle hemoglobin gels, based on magnetically driven compression of 5- to 8-μm-thick emulsions containing hemoglobin droplets ∼80 μm in diameter. Using our method, by observing the expansion of the droplet area as the emulsion is compressed, we were able to resolve changes in thickne...

  2. Epoxy Sol-Gel Hybrid Thermosets

    Directory of Open Access Journals (Sweden)

    Angels Serra


    Full Text Available Sol-gel methodologies are advantageous in the preparation of hybrid materials in front of the conventional addition of nanoparticles, because of the fine dispersion of the inorganic phase that can be reached in epoxy matrices. In addition, the use of organoalkoxysilanes as coupling agents allows covalent linkage between organic and inorganic phases, which is the key point in the improvement of mechanical properties. The sol-gel process involves hydrolysis and condensation reactions under mild conditions, starting from hydrolysable metal alkoxides, generally alkoxy silanes. Using the sol-gel procedure, the viscosity of the formulation is maintained, which is an important issue in coating applications, whereas the transparency of the polymer matrix is also maintained. However, only the proper combination of the chemistries and functionalities of both organic and inorganic structures leads to thermosets with the desired characteristics. The adequate preparation of hybrid epoxy thermosets enables their improvement in characteristics such as mechanical properties (modulus, hardness, scratch resistance, thermal and flame resistance, corrosion and antimicrobial protection, and even optical performance among others.

  3. Formation of Colloidal Nanocellulose Glasses and Gels. (United States)

    Nordenström, Malin; Fall, Andreas; Nyström, Gustav; Wågberg, Lars


    Nanocellulose (NC) suspensions can form rigid volume-spanning arrested states (VASs) at very low volume fractions. The transition from a free-flowing dispersion to a VAS can be the result of either an increase in particle concentration or a reduction in interparticle repulsion. In this work, the concentration-induced transition has been studied with a special focus on the influence of the particle aspect ratio and surface charge density, and an attempt is made to classify these VASs. The results show that for these types of systems two general states can be identified: glasses and gels. These NC suspensions had threshold concentrations inversely proportional to the particle aspect ratio. This dependence indicates that the main reason for the transition is a mobility constraint that, together with the reversibility of the transition, classifies the VASs as colloidal glasses. If the interparticle repulsion is reduced, then the glasses can transform into gels. Thus, depending on the preparation route, either soft and reversible glasses or stiff and irreversible gels can be formed.

  4. The formation and structure of Olympic gels. (United States)

    Fischer, J; Lang, M; Sommer, J-U


    Different methods for creating Olympic gels are analyzed using computer simulations. First ideal reference samples are obtained from freely interpenetrating semi-dilute solutions and melts of cyclic polymers. The distribution of pairwise concatenations per cyclic molecule is given by a Poisson-distribution and can be used to describe the elastic structure of the gels. Several batches of linear chains decorated with different selectively binding groups at their ends are mixed in the "DNA Origami" technique and network formation is realized. While the formation of cyclic molecules follows mean field predictions below overlap of the precursor molecules, an enhanced ring formation above overlap is found that is not explained by mean field arguments. The "progressive construction" method allows to create Olympic gels with a single reaction step from a concentrated mixture of large compressed rings with a low weight fraction of short chains that are below overlap concentration. This method, however, is limited by the difficulty to obtain a sufficiently high degree of polymerization of the large rings.

  5. Calcium Impact on Milk Gels Formation

    DEFF Research Database (Denmark)

    Koutina, Glykeria

    salts. The perturbation of calcium equilibria by these factors will affect the final properties of acid, calcium and rennet milk gels. By decreasing the pH from 6.0 to 5.2 (acid gels), the calcium equilibrium was significantly affected by temperature (4, 20, 30, 40 oC), and different combinations...... of temperature and pH may result in different final structure properties in dairy products such as cheese. A significant amount of calcium remained in the micelles between pH 4.8 and 4.6, this can contribute to the final strength of acid milk gels, such as in yogurt or in cream cheeses. After the gelation point......, a sudden solubilization of micellar calcium was observed at 50 oC and 60 oC, which revealed an interesting role of calcium during acidification at elevated temperatures. After enrichment of milk with calcium D-lactobionate, the added calcium was distributed between the micellar and serum milk phase at pH 6...

  6. Exploratory data analysis groupware for qualitative and quantitative electrophoretic gel analysis over the Internet-WebGel. (United States)

    Lemkin, P F; Myrick, J M; Lakshmanan, Y; Shue, M J; Patrick, J L; Hornbeck, P V; Thornwal, G C; Partin, A W


    Many scientists use quantitative measurements to compare the presence and amount, of various proteins and nucleotides among series of one- and two-dimensional (1-D and 2-D) electrophoretic gels. These gels are often scanned into digital image files. Gel spots are then quantified using stand-alone analysis software. However, as more research collaborations take place over the Internet, it has become useful to share intermediate quantitative data between researchers. This allows research group members to investigate their data and share their work in progress. We developed a World Wide Web group-accessible software system, WebGel, for interactively exploring qualitative and quantitative differences between electrophoretic gels. Such Internet databases are useful for publishing quantitative data and allow other researchers to explore the data with respect to their own research. Because intermediate results of one user may be shared with their collaborators using WebGel, this form of active data-sharing constitutes a groupware method for enhancing collaborative research. Quantitative and image gel data from a stand-alone gel image processing system are copied to a database accessible on the WebGel Web server. These data are then available for analysis by the WebGel database program residing on that server. Visualization is critical for better understanding of the data. WebGel helps organize labeled gel images into montages of corresponding spots as seen in these different gels. Various views of multiple gel images, including sets of spots, normalization spots, labeled spots, segmented gels, etc. may also be displayed. These displays are active and may be used for performing database operations directly on individual protein spots by simply clicking on them. Corresponding regions between sets of gels may be visually analyzed using Flicker-comparison (Electrophoresis 1997, 18, 122-140) as one of the WebGel methods for qualitative analysis. Quantitative exploratory data

  7. Technical note: Influence of the phantom material on the absorbed-dose energy dependence of the EBT3 radiochromic film for photons in the energy range 3 keV-18 MeV. (United States)

    Hermida-López, M; Lüdemann, L; Flühs, A; Brualla, L


    Water is the reference medium for radiation therapy dosimetry, but for film dosimetry it is more practical to use a solid phantom. As the composition of solid phantoms differs from that of water, the energy dependence of film exposed within solid phantoms may also differ. The energy dependence of a radiochromic film for a given beam quality Q (energy for monoenergetic beams) has two components: the intrinsic energy dependence and the absorbed-dose energy dependence f(Q), the latter of which can be calculated through a Monte Carlo simulation of radiation transport. The authors used Monte Carlo simulations to study the influence of the phantom material on the f(Q) of the EBT3 radiochromic film (Ashland Specialty Ingredients, Wayne, NJ) for photon beams with energies between 3 keV and 18 MeV. All simulations were carried out with the general-purpose Monte Carlo code penelope 2011. The geometrical model consisted of a cylindrical phantom, with the film positioned at different depths depending on the initial photon energy. The authors simulated monoenergetic parallel photon beams and x-ray beams from a superficial therapy system. To validate their choice of simulation parameters, they also calculated f(Q) for older film models, EBT and EBT2, comparing with published results. In addition to water, they calculated f(Q) of the EBT3 film for solid phantom materials commonly used for film dosimetry: RW1 and RW3 (PTW-Freiburg, Freiburg, Germany), Solid Water (Gammex-RMI, Madison, WI), and PMMA. Finally, they combined their calculated f(Q) with published overall energy response data to obtain the intrinsic energy dependence of the EBT3 film in water. The calculated f(Q) for EBT and EBT2 films was statistically compatible with previously published data. Between 10 keV and 18 MeV, the variation found in f(Q) of the EBT3 film for water was within 2.3%, with a standard statistical uncertainty less than 1%. If the quantity dose-to-water in the phantom is considered, which is the

  8. Technical Note: Influence of the phantom material on the absorbed-dose energy dependence of the EBT3 radiochromic film for photons in the energy range 3 keV–18 MeV

    Energy Technology Data Exchange (ETDEWEB)

    Hermida-López, M., E-mail: [NCTeam, Strahlenklinik, Universitätsklinikum Essen, Hufelandstraße 55, Essen D-45122, Germany and Servei de Física i Protecció Radiològica, Hospital Universitari Vall d’Hebron, Pg. Vall d’Hebron 119-129, Barcelona 08035 (Spain); Lüdemann, L.; Flühs, A. [Medical Physics, Strahlenklinik, Universitätsklinikum Essen, Hufelandstraße 55, Essen D-45122 (Germany); Brualla, L. [NCTeam, Strahlenklinik, Universitätsklinikum Essen, Hufelandstraße 55, Essen D-45122 (Germany)


    Purpose: Water is the reference medium for radiation therapy dosimetry, but for film dosimetry it is more practical to use a solid phantom. As the composition of solid phantoms differs from that of water, the energy dependence of film exposed within solid phantoms may also differ. The energy dependence of a radiochromic film for a given beam quality Q (energy for monoenergetic beams) has two components: the intrinsic energy dependence and the absorbed-dose energy dependence f(Q), the latter of which can be calculated through a Monte Carlo simulation of radiation transport. The authors used Monte Carlo simulations to study the influence of the phantom material on the f(Q) of the EBT3 radiochromic film (Ashland Specialty Ingredients, Wayne, NJ) for photon beams with energies between 3 keV and 18 MeV. Methods: All simulations were carried out with the general-purpose Monte Carlo code PENELOPE 2011. The geometrical model consisted of a cylindrical phantom, with the film positioned at different depths depending on the initial photon energy. The authors simulated monoenergetic parallel photon beams and x-ray beams from a superficial therapy system. To validate their choice of simulation parameters, they also calculated f(Q) for older film models, EBT and EBT2, comparing with published results. In addition to water, they calculated f(Q) of the EBT3 film for solid phantom materials commonly used for film dosimetry: RW1 and RW3 (PTW-Freiburg, Freiburg, Germany), Solid Water (Gammex-RMI, Madison, WI), and PMMA. Finally, they combined their calculated f(Q) with published overall energy response data to obtain the intrinsic energy dependence of the EBT3 film in water. Results: The calculated f(Q) for EBT and EBT2 films was statistically compatible with previously published data. Between 10 keV and 18 MeV, the variation found in f(Q) of the EBT3 film for water was within 2.3%, with a standard statistical uncertainty less than 1%. If the quantity dose-to-water in the phantom is

  9. Evaluation of radiochromic films EBT3 for in-vivo dosimetry in radiotherapy treatments with photons; Evaluacion de peliculas radiocromicas EBT3 para dosimetria in vivo en tratamientos de radioterapia con fotones

    Energy Technology Data Exchange (ETDEWEB)

    Galvan de la C, O. O.; Rivera M, T. [IPN, Centro de Investigacion en Ciencia Aplicada y Tecnologia Avanzada, Av. Legaria No. 694, Col. Irrigacion, 11500 Mexico D. F. (Mexico); Garcia G, O. A.; Larraga G, J. M., E-mail: [Instituto Nacional de Neurologia y Neurocirugia, Laboratorio de Fisica Medica, Insurgentes Sur 3877, Col. La Fama, 14269 Mexico D. F. (Mexico)


    Full text: In-vivo dosimetry is a challenge in radiotherapy due to the measures are carried out in reference conditions outside; there is no balance of charged particle and beam consists of photons own and contamination electrons. Detectors that are useful for such measures should be sufficiently small and thin so they do not disturb the beam and do not alter the dose on target. In this paper the radiochromic films Gafchromic model EBT3 are evaluated as potential detectors for in-vivo dosimetry; measurements were carried out in solid water phantom on the surface, with films of dimensions 3 x 3 cm{sup 2}. Irradiations were performed with a linear accelerator Novalis of 6 MV. Comparison between dose values found with a diode type Sfd detector (IBA dosimetry, Germany) and a diamond detector CVD (PTW-Freiburg) for 2 different sized of field (5 x 5 cm{sup 2} and 10 x 10 cm{sup 2}) on the surface of a water phantom scanning was realized. The total spreading factor (Tsf) measured on surface was of 0.831 ± 4.6%; which is greater 12.9% than Tsf measured at a depth of maximum dose. This difference may be due to the contribution of scattered electrons to the beam exit. The measures must be corroborated with Monte Carlo simulations, which they will be validated on surface by the Abdel-Rahman [et al.] method; this mechanism will determine if the films are useful detectors for in-vivo dosimetry clinically. (Author)

  10. Gel Encapsulation of Glucose Nanosensors for Prolonged In Vivo Lifetime (United States)

    Balaconis, Mary K.; Clark, Heather A.


    Background Fluorescent glucose-sensitive nanosensors have previously been used in vivo to track glucose concentration changes in interstitial fluid. However, this technology was limited because of loss of fluorescence intensity due to particle diffusion from the injection site. In this study, we encapsulated the nanosensors into injectable gels to mitigate nanosensor migration in vivo. Methods Glucose-sensitive nanosensors were encapsulated in two different commercially available gelling agents: gel 1 and gel 2. Multiple formulations of each gel were assessed in vitro for their nanosensor encapsulation efficiency, permeability to glucose, and nanosensor retention over time. The optimal formulation for each gel, as determined from the in vitro assessment, was then tested in mice, and the lifetime of the encapsulated nanosensors was compared with controls of nanosensors without gel. Results Five gel formulations had encapsulation efficiencies of the nanosensors greater than 90%. Additionally, they retained up to 20% and 40% of the nanosensors over 24 h for gel 1 and gel 2, respectively. In vivo, both gels prevented diffusion of glucose nanosensors at least three times greater than the controls. Conclusions Encapsulating glucose nanosensors in two injectable gels prolonged nanosensor lifetime in vivo; however, the lifetime must still be increased further to be applicable for diabetes monitoring. PMID:23439160

  11. Gel encapsulation of glucose nanosensors for prolonged in vivo lifetime. (United States)

    Balaconis, Mary K; Clark, Heather A


    Fluorescent glucose-sensitive nanosensors have previously been used in vivo to track glucose concentration changes in interstitial fluid. However, this technology was limited because of loss of fluorescence intensity due to particle diffusion from the injection site. In this study, we encapsulated the nanosensors into injectable gels to mitigate nanosensor migration in vivo. Glucose-sensitive nanosensors were encapsulated in two different commercially available gelling agents: gel 1 and gel 2. Multiple formulations of each gel were assessed in vitro for their nanosensor encapsulation efficiency, permeability to glucose, and nanosensor retention over time. The optimal formulation for each gel, as determined from the in vitro assessment, was then tested in mice, and the lifetime of the encapsulated nanosensors was compared with controls of nanosensors without gel. Five gel formulations had encapsulation efficiencies of the nanosensors greater than 90%. Additionally, they retained up to 20% and 40% of the nanosensors over 24 h for gel 1 and gel 2, respectively. In vivo, both gels prevented diffusion of glucose nanosensors at least three times greater than the controls. Encapsulating glucose nanosensors in two injectable gels prolonged nanosensor lifetime in vivo; however, the lifetime must still be increased further to be applicable for diabetes monitoring. © 2013 Diabetes Technology Society.

  12. Time-dependent gel to gel transformation of a peptide based supramolecular gelator. (United States)

    Baral, Abhishek; Basak, Shibaji; Basu, Kingshuk; Dehsorkhi, Ashkan; Hamley, Ian W; Banerjee, Arindam


    A dipeptide with a long fatty acid chain at its N-terminus gives hydrogels in phosphate buffer in the pH range 7.0-8.5. The hydrogel with a gelator concentration of 0.45% (w/v) at pH 7.46 (physiological pH) provides a very good platform to study dynamic changes within a supramolecular framework as it exhibits remarkable change in its appearance with time. Interestingly, the first formed transparent hydrogel gradually transforms into a turbid gel within 2 days. These two forms of the hydrogel have been thoroughly investigated by using small angle X-ray scattering (SAXS), powder X-ray diffraction (PXRD), field emission scanning electron microscopic (FE-SEM) and high-resolution transmission electron microscopic (HR-TEM) imaging, FT-IR and rheometric analyses. The SAXS and low angle PXRD studies substantiate different packing arrangements for the gelator molecules for these two different gel states (the freshly prepared and the aged hydrogel). Moreover, rheological studies of these two gels reveal that the aged gel is stiffer than the freshly prepared gel.

  13. Characterization of silica gel prepared by using sol-gel process (United States)

    Besbes, M.; Fakhfakh, N.; Benzina, M.


    We studied the preparation of silica gels from sodium silicate solution mixed with hydrochloric acid by sol-gel process. The obtained gel is washed with water to obtain a 'hydrogel'. The immersion of the last one in alcohol, gives an 'alcogel'. A Hoke D6 experimental design was followed in order to limit the number of tests. pH and the silica concentration represent the most significant factors which control the obtaining of a significant specific surface and thus a great capacity of adsorption. A second order polynomial model was adopted in order to represent the results in the form of three-dimensional surfaces. These results are also topographically illustrated as isoresponses lines. The results showed that the pH effect is more significant than the silica concentration one. We obtained gels with great microporosity and presenting specific surfaces of 657 m2.g-1 when pH is equal to 2. The prepared gel without alcohol presents interesting characteristics for a potential industrial use since its production cost is lowest and has a high specific surface.

  14. Antioxidant effect of green tea on polymer gel dosimeter (United States)

    Samuel, E. J. J.; Sathiyaraj, P.; Deena, T.; Kumar, D. S.


    Extract from Green Tea (GTE) acts as an antioxidant in acrylamide based polymer gel dosimeter. In this work, PAGAT gel was used for investigation of antioxidant effect of GTE.PAGAT was called PAGTEG (Polyacrylamide green tea extract gel dosimeter) after adding GTE. Free radicals in water cause pre polymerization of polymer gel before irradiation. Polyphenols from GTE are highly effective to absorb the free radicals in water. THPC is used as an antioxidant in polymer gel dosimeter but here we were replaced it by GTE and investigated its effect by spectrophotometer. GTE added PAGAT samples response was lower compared to THPC added sample. To increase the sensitivity of the PAGTEG, sugar was added. This study confirmed that THPC was a good antioxidant for polymer gel dosimeter. However, GTE also can be used as an antioxidant in polymer gel if use less quantity (GTE) and add sugar as sensitivity enhancer.

  15. Anion-switchable supramolecular gels for controlling pharmaceutical crystal growth (United States)

    Foster, Jonathan A.; Piepenbrock, Marc-Oliver M.; Lloyd, Gareth O.; Clarke, Nigel; Howard, Judith A. K.; Steed, Jonathan W.


    We describe the use of low-molecular-weight supramolecular gels as media for the growth of molecular crystals. Growth of a range of crystals of organic compounds, including pharmaceuticals, was achieved in bis(urea) gels. Low-molecular-weight supramolecular gelators allow access to an unlimited range of solvent systems, in contrast to conventional aqueous gels such as gelatin and agarose. A detailed study of carbamazepine crystal growth in four different bis(urea) gelators, including a metallogelator, is reported. The crystallization of a range of other drug substances, namely sparfloxacin, piroxicam, theophylline, caffeine, ibuprofen, acetaminophen (paracetamol), sulindac and indomethacin, was also achieved in supramolecular gel media without co-crystal formation. In many cases, crystals can be conveniently recovered from the gels by using supramolecular anion-triggered gel dissolution; however, crystals of substances that themselves bind to anions are dissolved by them. Overall, supramolecular gel-phase crystallization offers an extremely versatile new tool in pharmaceutical polymorph screening.

  16. Gel-Bead Delivery of Eimeria oocysts protects chickens against coccidiosis. (United States)

    Jenkins, Mark C; Parker, Carolyn; Klopp, Spangler; O'Brien, Celia; Miska, Katarzyna; Fetterer, Raymond


    Vaccines composed of either virulent or attenuated Eimeria spp. oocysts have been developed as an alternative to medication of feed with ionophore drugs or synthetic chemicals. The purpose of this study was to evaluate the use of gel-beads containing a mixture of Eimeria acervulina, Eimeria maxima, and Eimeria tenella oocysts as a vaccine against coccidiosis. Newly hatched chicks (Gallus gallus domesticus) were either sprayed with an aqueous suspension of Eimeria oocysts or were allowed to ingest feed containing Eimeria oocysts-incorporated gel-beads. Control day-old chicks were given an equivalent number of Eimeria oocysts (10(4) total) by oral gavage. After 3 days, chicks were randomly assigned to individual cages, and feces were collected between days 5 and 8 postinfection. All samples were processed for total Eimeria oocysts. At 4 wk of age, all chickens and a control nonimmunized group received a high-dose E acervulina, E maxima, and E. tenella challenge infection. Oocyst excretion by chicks fed gel-beads or inoculated by oral gavage was 10- to 100-fold greater than that of chicks spray-vaccinated with the Eimeria oocysts mixture (log 6.3-6.6 vs. log 4.8). Subsequent protection against challenge as measured by weight gain and feed conversion efficiency was significantly greater (P 0.05) in weight gain and feed conversion efficiency compared with nonchallenged controls. These findings indicate that incorporation of Eimeria spp. oocysts in gel-beads may represent an effective way to deliver live oocyst vaccines to day-old chicks for preventing subsequent outbreaks of coccidiosis in the field.

  17. Autologous platelet-poor plasma gel for injection laryngoplasty. (United States)

    Woo, Seung Hoon; Kim, Jin Pyeong; Park, Jung Je; Chung, Phil-Sang; Lee, Sang-Hyuk; Jeong, Han-Sin


    To overcome the potential disadvantages of the use of foreign materials and autologous fat or collagen, we introduce here an autologous plasma gel for injection laryngoplasty. The purpose of this study was to present a new injection material, a plasma gel, and to discuss its clinical effectiveness. From 2 mL of blood, the platelet poor serum layer was collected and heated at 100°C for 12 min to form a plasma gel. The plasma gel was then injected into a targeted site; the safety and efficacy thereof were evaluated in 30 rats. We also conducted a phase I/II clinical study of plasma gel injection laryngoplasty in 11 unilateral vocal fold paralysis patients. The plasma gel was semi-solid and an easily injectable material. Of note, plasma gel maintains the same consistency for up to 1 year in a sealed bottle. However, exposure to room air causes the plasma gel to disappear within 1 month. In our animal study, the autologous plasma gel remained in situ for 6 months in animals with minimal inflammation. Clinical study showed that vocal cord palsy was well compensated for with the plasma gel in all patients at two months after injection with no significant complications. Jitter, shimmer, maximum, maximum phonation time (MPT) and mean voice handicap index (VHI) also improved significantly after plasma gel injection. However, because the injected plasma gel was gradually absorbed, 6 patients needed another injection, while the gel remained in place in 2 patients. Injection laryngoplasty with autologous plasma gel may be a useful and safe treatment option for temporary vocal cord palsy.


    Directory of Open Access Journals (Sweden)

    V. S. Safaryan


    Full Text Available The article considers experimental and analytical determination of the asynchronous machine equivalent-circuit parameters with application of the reference data. Transient processes investigation of the asynchronous machines necessitates the equivalent circuit parameters (resistance impedance, inductances and coefficient of the stator-rotor contours mutual inductance that help form the transitory-process mathematical simulation model. The reference books do not provide those parameters; they instead give the rated ones (active power, voltage, slide, coefficient of performance and capacity coefficient as well as the ratio of starting and nominal currents and torques. The noted studies on the asynchronous machine equivalent-circuits parametrization fail to solve the problems ad finem or solve them with admissions. The paper presents experimental and analytical determinations of the asynchronous machine equivalent-circuit parameters: the experimental one based on the results of two measurements and the analytical one where the problem boils down to solving a system of nonlineal algebraic equations. The authors investigate the equivalent asynchronous machine input-resistance properties and adduce the dependence curvatures of the input-resistances on the slide. They present a symbolic model for analytical parameterization of the asynchronous machine equivalent-circuit that represents a system of nonlineal equations and requires one of the rotor-parameters arbitrary assignment. The article demonstrates that for the asynchronous machine equivalent-circuit experimental parameterization the measures are to be conducted of the stator-circuit voltage, current and active power with two different slides and arbitrary assignment of one of the rotor parameters. The paper substantiates the fact that additional measurement does not discard the rotor-parameter choice arbitrariness. The authors establish that in motoring mode there is a critical slide by which the

  19. The Biophysical Properties of Basal Lamina Gels Depend on the Biochemical Composition of the Gel (United States)

    Pflieger, Kerstin; Boettcher, Kathrin; Zahler, Stefan; Lieleg, Oliver


    The migration of cells within a three-dimensional extracellular matrix (ECM) depends sensitively on the biochemical and biophysical properties of the matrix. An example for a biological ECM is given by reconstituted basal lamina gels purified from the Engelbreth-Holm-Swarm sarcoma of mice. Here, we compare four different commercial variants of this ECM, which have all been purified according to the same protocol. Nevertheless, in those gels, we detect strong differences in the migration behavior of leukocyte cells as well as in the Brownian motion of nanoparticles. We show that these differences correlate with the mechanical properties and the microarchitecture of the gels which in turn arise from small variations in their biochemical composition. PMID:25689062

  20. Sol-gel synthesis of hydroxyapatite; Sintese de hidroxiapatita via sol-gel

    Energy Technology Data Exchange (ETDEWEB)

    Zupanski, M.D.; Lucena, M.P.P.; Bergmann, C.P., E-mail: [Universidade Federal do Rio Grande do Sul (UFRGS), Porto Alegre, RS (Brazil)


    Hydroxyapatite (HAp) has been established as the calcium phosphate based compound with most applications in the biological field. Among the numerous techniques for synthesis of HAp, the sol-gel processing route affords great control over purity and formed phases using low processing temperatures. In addition, the sol-gel approach offers an option for homogeneous HAp coating on metal substrates, as well as the ability to generate nanocrystalline powders. In this work, the sol-gel synthesis of HAp was investigated employing triethyl phosphate and calcium nitrate tetrahydrate as phosphorous and calcium precursors, respectively. The aging effect on phase composition and powder morphology of the final product was studied in terms of temperature and aging time. The powders were studied by using X-ray diffraction, Fourier transform infrared spectroscopy, particle size distribution by laser diffraction and scanning electron microscopy. (author)