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N B Singh - One of the best experts on this subject based on the ideXlab platform.
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processing of Mercurous Chloride in space
Optical Science Engineering and Instrumentation '97, 1997Co-Authors: C Watson, N B Singh, A W Thomas, A E Nelson, T O Rolin, J Griffin, Glen B Haulenbeek, N Daniel, J Seaquist, C CacioppoAbstract:Mercurous Chloride is an acoustical optical material with an unusually low acoustic velocity and high acousto-optical figure of merit, which makes it an interesting candidate for optical delay lines and Bragg cells for optical signal processors. It also has a broad range of spectral transmissivity which makes it an ideal candidate for wide band acoustically tuned optical filter (ATOF) applications. Single crystals of this material can be readily grown in normal gravity by closed-tube physical vapor transport, but the crystals appear to contain structural inhomogeneities which degrade the optical performance. The nature of these defects is not known, but their degree appears to correlate with the Rayleigh number that characterizes their growth; hence, it is suspected that uncontrolled convection may play a role in the defect structure. This prompted a space flight experiment to determine if these defects could be further reduced by virtually eliminating the buoyancy-driven convective flows which are always present to a degree in normal gravity. Single crystals of Mercurous Chloride (Hg2Cl2) were grown in the Space Experiment Facility (SEF) transparent furnace developed by the University of Alabama in Huntsville, Consortium for Materials Development in Space. The Northrop- Grumman Science and Technology Center provided the highly purified starting material and analyzed the crystals that were grown. This experiment was flown on Spacehab 4 (STS-77) in May 1996. The SEF is a transparent furnace which allowed the progress of the growth to be recorded by video. Extensive furnace profiling and modeling has been carried out to relate the growth front location to the thermal environment and to the crystal quality. The results of the flight experiment as well as the ground control experiments are presented.© (1997) COPYRIGHT SPIE--The International Society for Optical Engineering. Downloading of the abstract is permitted for personal use only.
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physical vapor transport of Mercurous Chloride crystals design of a microgravity experiment
Journal of Crystal Growth, 1997Co-Authors: W M B Duval, N B Singh, M E GlicksmanAbstract:Flow field characteristics predicted from a computational model show that the dynamical state of the flow, for practical crystal growth conditions of Mercurous Chloride, can range from steady to unsteady. Evidence that the flow field can be strongly dominated by convection for ground-based conditions is provided by the prediction of asymmetric velocity profiles bv the model which show reasonable agreement with laser Doppler velocimetry experiments in both magnitude and planform. Unsteady flow is shown to be correlated with a degradation of crystal quality as quantified by light scattering pattern measurements, A microgravity experiment is designed to show that an experiment performed with parameters which yield an unsteady flow becomes steady (diffusive-advective) in a microgravity environment of 10(exp -3) g(sub 0) as predicted by the model, and hence yields crystals with optimal quality.
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thermal convective effects on physical vapor transport growth of Mercurous Chloride hg2cl2 crystals for axisymmetric 2d cylindrical enclosure
Modelling and Simulation in Materials Science and Engineering, 1995Co-Authors: G T Kim, W M B Duval, M E Glicksman, N B SinghAbstract:The effects of thermal convection are investigated for the physical vapor transport (PVT) crystal growth process of Hg2Cl2. These effects may lead to increased defect densities and reduced optical homogeneity of the resultant crystals. A two-dimensional axisymmetrical model has been developed and applied to simulate the fluid flow, temperature, and mass concentration distribution in closed ampoules during PVT crystal growth. The numerical parametric studies show that the growth rate increases with the one-quarter power of the Raleigh number, Ra0.25, for 0
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performance of Mercurous Chloride acousto optic devices
Optical Materials, 1993Co-Authors: N B Singh, M Gottlieb, R Mazelsky, Anastasios P Goutzoulis, W M B DuvalAbstract:Abstract The suitability of Mercurous Chloride for commercial applications was examined by fabricating Bragg cells and acousto-optic tunable filters (AOTF). The acoustic attenuation measurements showed that for operation at a center frequency of 30 MHz, it should be possible to build a Bragg cell with over 8000 resolution elements. For a frequency of 50 MHz, 6000 resolution elements can be achieved with an aperture smaller than 10 cm which is a significant advancement in the state of the art, and is superior to that tellurium dioxide. The AOTF was tested by measuring the transmission at 3.39 μm. The peak response was observed at 18.9 MHz and the fwhm was about 0.58 MHz, corresponding to a 3% of center wavelength resolution, which were excellent agreement with the theory.
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physical vapor transport growth of Mercurous Chloride crystals
Progress in Crystal Growth and Characterization of Materials, 1993Co-Authors: N B Singh, M Gottlieb, R H Hopkins, R Mazelsky, W M B Duval, M E GlicksmanAbstract:Abstract We have carried out experiments to derive a quantitative understanding of the physical vapor transport (PVT) process and to identify convective effects on the crystal growth process. The experimental growth velocity was several orders of magnitude lower than the theoretically predicted value. The effusion holes were used to disturb the impurity boundary layers. We observed a change of 18% (not an order of magnitude) in growth velocities. The Arrhenius behavior of growth rate with temperature was used to derive the sticking coefficient. Experimental result on growth velocity as the aspect ratio was varied showed that with increasing convection, the growth rate increased up to a certain value and then dropped to a constant value. This indicated that a bifurcation had occured with a resulting change in transport behavior. Growth velocity measurements for the PVT process as a function of orientation of the g-vector were also made. The experimental results clearly showed that the growth velocity varied with g-vector for a particular temperature profile. The effects of convection on crystal quality were studied by varying the thermal conditions (source and crystal temperatures) which affects thermal convection during PVT. The results showed that crystals grown at low Rayleight numbers had better homogeneity. While no microgravity experiments were conducted, computation of mass flux for the horizontal orientation for various gravitational levels showed two distinct regions; above 10-3 g where the flow was convective and strong circulating cells appeared, and also below 10-3 g, where the flow was purely diffusive and no circulating cells were predicted. Therefore it is postulated that for the conditions of growth considered, space flight experiments with acceleration less than 10-3 g could yield crystals grown under diffusive transport.
H V Aposhian - One of the best experts on this subject based on the ideXlab platform.
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dmps 2 3 dimercaptopropane 1 sulfonate dimaval decreases the body burden of mercury in humans exposed to Mercurous Chloride
Journal of Pharmacology and Experimental Therapeutics, 1998Co-Authors: Diego Gonzalezramirez, M Zunigacharles, Katherine M Hurlbut, Richard C Dart, A Narrojuarez, Y Molinarecio, H V AposhianAbstract:DMPS (2,3-dimercaptopropane-1-sulfonate, Na salt), when used as a challenge test for mercury in workers involved in the production of a calomel skin-bleaching lotion and in direct contact with Mercurous Chloride, elevated urine levels of mercury. A DMPS treatment regimen was devised and initiated. Three days after the challenge test, DMPS was administered p.o. (400 mg per day) for 8 days, followed by a no-treatment period of five days. A new cycle of DMPS treatment for 7 days was initiated and followed by 5 days without treatment. A third period of treatment was begun for 6 days, followed by a 5-day no-treatment period. The urinary mercury greatly increased during those periods when DMPS was administered (1754, 314, and 173 μg/24 h for the periods 1, 2 and 3, compared with 106, 48 and 53 μg/24 h on the corresponding no-treatment periods). One of the workers presented signs of drug intolerance and was discharged after receiving the first cycle of treatment. DMPS treatment was effective in lowering the body burden of mercury and in decreasing the urinary mercury concentration to normal levels.
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sodium 2 3 dimercaptopropane 1 sulfonate challenge test for mercury in humans iii urinary mercury after exposure to Mercurous Chloride
Journal of Pharmacology and Experimental Therapeutics, 1996Co-Authors: R M Maiorino, Diego Gonzalezramirez, M Zunigacharles, Katherine M Hurlbut, Mary M Aposhian, Richard C Dart, James S Woods, Patricia Ostroskywegman, Maria E Gonsebatt, H V AposhianAbstract:The sodium salt of 2,3-dimercaptopropane-1-sulfonic acid (Dimaval; DMPS) challenge test has been given previously to humans exposed to elemental mercury (vapor) or mercuric salts, but not Mercurous salts. The test (300 mg p.o., after an 11-hr fast) was given to 11 factory workers who make a skin lotion that contains Mercurous Chloride, eight users of the skin lotion and nine controls. Urines were analyzed for total mercury by using cold vapor atomic absorption spectrophotometry. The mercury excreted for 6 hr before and 6 hr after DMPS treatment was 113 micrograms +/- 26 and 5037 micrograms +/- 682 S.E.M. for the skin lotion makers; 16.2 micrograms +/- 3.4 and 1410 micrograms +/- 346 S.E.M. for the skin lotions users; and 0.49 micrograms +/- 0.11 and 18.4 micrograms +/- 7.1 S.E.M. for the controls, respectively. The increases in urinary mercury resulting from the DMPS challenge test were 45-, 87- and 38-fold, respectively. The results demonstrate that, in humans exposed to Mercurous Chloride, DMPS increases the urinary excretion of mercury and that the DMPS/mercury challenge test is of value for a more realistic estimation of mobilizable mercury. An attempt to associate genotoxicity, as indicated by micronuclei content in buccal cells, with mercury exposure was inconclusive, perhaps because of the small number of subjects.
W M B Duval - One of the best experts on this subject based on the ideXlab platform.
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thermal convection in physical vapour transport of Mercurous Chloride for rectangular enclosures
Modelling and Simulation in Materials Science and Engineering, 1997Co-Authors: G T Kim, W M B Duval, M E GlicksmanAbstract:The convective flow structures in the physical vapour transport process for Mercurous Chloride are investigated for two-dimensional rectangular enclosures at various aspect ratios (width-to-transport length) and two different wall boundary conditions: conducting and insulating. For a low aspect ratio of 0.124, the core of the flow is dominated by a unicellular convective structure at a Rayleigh number for conducting walls. For increasing Rayleigh number, the flow field bifurcates to asymmetric multicells. In contrast to conducting wall boundary conditions, the insulating wall boundary conditions tend to suppress the formation of secondary cells. As the aspect ratio decreases, the Rayleigh number at which transient convective flow arises decreases.
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physical vapor transport of Mercurous Chloride crystals design of a microgravity experiment
Journal of Crystal Growth, 1997Co-Authors: W M B Duval, N B Singh, M E GlicksmanAbstract:Flow field characteristics predicted from a computational model show that the dynamical state of the flow, for practical crystal growth conditions of Mercurous Chloride, can range from steady to unsteady. Evidence that the flow field can be strongly dominated by convection for ground-based conditions is provided by the prediction of asymmetric velocity profiles bv the model which show reasonable agreement with laser Doppler velocimetry experiments in both magnitude and planform. Unsteady flow is shown to be correlated with a degradation of crystal quality as quantified by light scattering pattern measurements, A microgravity experiment is designed to show that an experiment performed with parameters which yield an unsteady flow becomes steady (diffusive-advective) in a microgravity environment of 10(exp -3) g(sub 0) as predicted by the model, and hence yields crystals with optimal quality.
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thermal convective effects on physical vapor transport growth of Mercurous Chloride hg2cl2 crystals for axisymmetric 2d cylindrical enclosure
Modelling and Simulation in Materials Science and Engineering, 1995Co-Authors: G T Kim, W M B Duval, M E Glicksman, N B SinghAbstract:The effects of thermal convection are investigated for the physical vapor transport (PVT) crystal growth process of Hg2Cl2. These effects may lead to increased defect densities and reduced optical homogeneity of the resultant crystals. A two-dimensional axisymmetrical model has been developed and applied to simulate the fluid flow, temperature, and mass concentration distribution in closed ampoules during PVT crystal growth. The numerical parametric studies show that the growth rate increases with the one-quarter power of the Raleigh number, Ra0.25, for 0
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performance of Mercurous Chloride acousto optic devices
Optical Materials, 1993Co-Authors: N B Singh, M Gottlieb, R Mazelsky, Anastasios P Goutzoulis, W M B DuvalAbstract:Abstract The suitability of Mercurous Chloride for commercial applications was examined by fabricating Bragg cells and acousto-optic tunable filters (AOTF). The acoustic attenuation measurements showed that for operation at a center frequency of 30 MHz, it should be possible to build a Bragg cell with over 8000 resolution elements. For a frequency of 50 MHz, 6000 resolution elements can be achieved with an aperture smaller than 10 cm which is a significant advancement in the state of the art, and is superior to that tellurium dioxide. The AOTF was tested by measuring the transmission at 3.39 μm. The peak response was observed at 18.9 MHz and the fwhm was about 0.58 MHz, corresponding to a 3% of center wavelength resolution, which were excellent agreement with the theory.
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physical vapor transport growth of Mercurous Chloride crystals
Progress in Crystal Growth and Characterization of Materials, 1993Co-Authors: N B Singh, M Gottlieb, R H Hopkins, R Mazelsky, W M B Duval, M E GlicksmanAbstract:Abstract We have carried out experiments to derive a quantitative understanding of the physical vapor transport (PVT) process and to identify convective effects on the crystal growth process. The experimental growth velocity was several orders of magnitude lower than the theoretically predicted value. The effusion holes were used to disturb the impurity boundary layers. We observed a change of 18% (not an order of magnitude) in growth velocities. The Arrhenius behavior of growth rate with temperature was used to derive the sticking coefficient. Experimental result on growth velocity as the aspect ratio was varied showed that with increasing convection, the growth rate increased up to a certain value and then dropped to a constant value. This indicated that a bifurcation had occured with a resulting change in transport behavior. Growth velocity measurements for the PVT process as a function of orientation of the g-vector were also made. The experimental results clearly showed that the growth velocity varied with g-vector for a particular temperature profile. The effects of convection on crystal quality were studied by varying the thermal conditions (source and crystal temperatures) which affects thermal convection during PVT. The results showed that crystals grown at low Rayleight numbers had better homogeneity. While no microgravity experiments were conducted, computation of mass flux for the horizontal orientation for various gravitational levels showed two distinct regions; above 10-3 g where the flow was convective and strong circulating cells appeared, and also below 10-3 g, where the flow was purely diffusive and no circulating cells were predicted. Therefore it is postulated that for the conditions of growth considered, space flight experiments with acceleration less than 10-3 g could yield crystals grown under diffusive transport.
Alfredo Pineyrolopez - One of the best experts on this subject based on the ideXlab platform.
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urinary mercury in twelve cases of cutaneous Mercurous Chloride calomel exposure effect of sodium 2 3 dimercaptopropane 1 sulfonate dmps therapy
Clinical Toxicology, 1997Co-Authors: Lourdes Garzaocanas, Oscar Torresalanis, Alfredo PineyrolopezAbstract:AbstractObjective: To evaluate clinical symptoms and urinary mercury before and after chelation therapy in subjects with chronic cutaneous Mercurous Chloride (HgCl; calomel) exposure. Subjects: Twelve women from 19–45 years who had used a facial cream which contained HgCl (5.9%) for 2 to 10 years. Design: Twenty-four hour urine samples were collected for basal urine mercury. All the subjects received a 5-day cycle of oral sodium 2,3-dimercaptopropane-1-sulfonate (Dimaval capsules 100 mg) 200 mg/d on an outpatient basis. The urine mercury excretion was monitored 24 hours after the first dose and 72 hours after the last dose in eight subjects. Result: Exanthem and tremor were detected in two of 12 subjects. The range of urine mercury was 180 to 1876 μg/g creatinine. A significant increase in the urinary mercury excretion was observed in the first 24 hours after beginning sodium 2,3-dimercaptopropane-1-sulfonate. Conclusion: Chronic topical application of 5.9% HgCl cream was associated with clinical mercuria...
M E Glicksman - One of the best experts on this subject based on the ideXlab platform.
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thermal convection in physical vapour transport of Mercurous Chloride for rectangular enclosures
Modelling and Simulation in Materials Science and Engineering, 1997Co-Authors: G T Kim, W M B Duval, M E GlicksmanAbstract:The convective flow structures in the physical vapour transport process for Mercurous Chloride are investigated for two-dimensional rectangular enclosures at various aspect ratios (width-to-transport length) and two different wall boundary conditions: conducting and insulating. For a low aspect ratio of 0.124, the core of the flow is dominated by a unicellular convective structure at a Rayleigh number for conducting walls. For increasing Rayleigh number, the flow field bifurcates to asymmetric multicells. In contrast to conducting wall boundary conditions, the insulating wall boundary conditions tend to suppress the formation of secondary cells. As the aspect ratio decreases, the Rayleigh number at which transient convective flow arises decreases.
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physical vapor transport of Mercurous Chloride crystals design of a microgravity experiment
Journal of Crystal Growth, 1997Co-Authors: W M B Duval, N B Singh, M E GlicksmanAbstract:Flow field characteristics predicted from a computational model show that the dynamical state of the flow, for practical crystal growth conditions of Mercurous Chloride, can range from steady to unsteady. Evidence that the flow field can be strongly dominated by convection for ground-based conditions is provided by the prediction of asymmetric velocity profiles bv the model which show reasonable agreement with laser Doppler velocimetry experiments in both magnitude and planform. Unsteady flow is shown to be correlated with a degradation of crystal quality as quantified by light scattering pattern measurements, A microgravity experiment is designed to show that an experiment performed with parameters which yield an unsteady flow becomes steady (diffusive-advective) in a microgravity environment of 10(exp -3) g(sub 0) as predicted by the model, and hence yields crystals with optimal quality.
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thermal convective effects on physical vapor transport growth of Mercurous Chloride hg2cl2 crystals for axisymmetric 2d cylindrical enclosure
Modelling and Simulation in Materials Science and Engineering, 1995Co-Authors: G T Kim, W M B Duval, M E Glicksman, N B SinghAbstract:The effects of thermal convection are investigated for the physical vapor transport (PVT) crystal growth process of Hg2Cl2. These effects may lead to increased defect densities and reduced optical homogeneity of the resultant crystals. A two-dimensional axisymmetrical model has been developed and applied to simulate the fluid flow, temperature, and mass concentration distribution in closed ampoules during PVT crystal growth. The numerical parametric studies show that the growth rate increases with the one-quarter power of the Raleigh number, Ra0.25, for 0
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physical vapor transport growth of Mercurous Chloride crystals
Progress in Crystal Growth and Characterization of Materials, 1993Co-Authors: N B Singh, M Gottlieb, R H Hopkins, R Mazelsky, W M B Duval, M E GlicksmanAbstract:Abstract We have carried out experiments to derive a quantitative understanding of the physical vapor transport (PVT) process and to identify convective effects on the crystal growth process. The experimental growth velocity was several orders of magnitude lower than the theoretically predicted value. The effusion holes were used to disturb the impurity boundary layers. We observed a change of 18% (not an order of magnitude) in growth velocities. The Arrhenius behavior of growth rate with temperature was used to derive the sticking coefficient. Experimental result on growth velocity as the aspect ratio was varied showed that with increasing convection, the growth rate increased up to a certain value and then dropped to a constant value. This indicated that a bifurcation had occured with a resulting change in transport behavior. Growth velocity measurements for the PVT process as a function of orientation of the g-vector were also made. The experimental results clearly showed that the growth velocity varied with g-vector for a particular temperature profile. The effects of convection on crystal quality were studied by varying the thermal conditions (source and crystal temperatures) which affects thermal convection during PVT. The results showed that crystals grown at low Rayleight numbers had better homogeneity. While no microgravity experiments were conducted, computation of mass flux for the horizontal orientation for various gravitational levels showed two distinct regions; above 10-3 g where the flow was convective and strong circulating cells appeared, and also below 10-3 g, where the flow was purely diffusive and no circulating cells were predicted. Therefore it is postulated that for the conditions of growth considered, space flight experiments with acceleration less than 10-3 g could yield crystals grown under diffusive transport.