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Sample records for hg matrix study

  1. STATISTICAL EVALUATION OF PROCESSING DATA FROM THE RH RU HG MATRIX STUDY

    SciTech Connect

    Koopman, D

    2009-04-17

    An evaluation of the statistical significance of Rh, Ru, and Hg on DWPF Sludge Receipt and Adjustment Tank (SRAT) cycle catalytic hydrogen generation and process chemistry was conducted by the Savannah River National Laboratory (SRNL) using a full-factorial experimental design. This test design can identify significant interactions between these three species in addition to individual effects. Statistical modeling of data from the Rh-Ru-Hg matrix study has been completed. Preliminary data and conclusions were given in an earlier report. This final report concludes the work on the Rh-Ru-Hg matrix study. Modeling results are summarized below. Rhodium was found to: Promote increased total hydrogen mass; Promote an increase in the maximum hydrogen generation rate; Promote an increase in the hydrogen generation rate shortly after acid addition; Shorten the elapsed time between acid addition and the maximum hydrogen generation rate; Increase formate loss; Inhibit NO{sub 2} and total NO{sub x} off-gas species formation; and Reduce nitrite-to-nitrate conversion. Ruthenium was found to: Promote increased total hydrogen mass; Promote an increase in the maximum hydrogen generation rate; Promote an increase in the hydrogen generation rate in the second half of the SRAT cycle; Promote an increase in total CO{sub 2} generated; Increase formate loss; Promote NO{sub 2} and total NO{sub x} off-gas species formation; and Reduce nitrite-to-nitrate conversion. Mercury was found to: Inhibit total hydrogen mass produced; Promote an increase in total CO{sub 2} generated; Promote NO{sub 2} off-gas species formation; and Inhibit total NO{sub x} off-gas species formation. Results confirmed qualitative observations that Rh was activating before Ru for hydrogen generation. An interaction between Rh and Ru was present in the model for the total hydrogen generated during the SRAT, perhaps because the total combined contributions from two separate episodes of hydrogen generation. The first

  2. Studies of the 198Hg(d,d') and 198Hg(d,p) reactions

    NASA Astrophysics Data System (ADS)

    Diaz Varela, A.; Garrett, P. E.; Bildstein, V.; Laffoley, A. T.; Maclean, A. D.; Rand, E. T.; Svensson, C. E.; Ball, G. C.; Faestermann, T.; Hertenberger, R.; Wirth, H.-F.

    2014-09-01

    Limits on the electric dipole moment (EDM) continue to decrease for 199Hg, the most stringent upper limit for a nuclear EDM to date. The experimental limit on the observed atomic EDM for 199Hg is converted to limits on fundamental CP-odd interactions via a calculation of the nuclear Schiff moment, requiring knowledge of the nuclear structure of 199Hg. The E 3 and E 1 strength distributions to the ground state of 199Hg, and E 2 transitions amongst excited states, would be ideal information to further constrain 199Hg Schiff moment theoretical models. The high level density of 199Hg makes those determinations challenging, however similar information can be obtained from exploring surrounding even-even Hg isotopes. As part of a campaign to study the Hg isotopes near 199Hg, two reactions, 198Hg(d,d')198 Hg and 198Hg(d,p)199Hg were studied using the Q3D spectrograph at the Maier-Leibnitz Laboratory (MLL) at Garching, Germany. A 22 MeV deuterium beam was used to impinge a 198Hg32S target. The (d,d') reaction allows us to probe the desired E 2 and E 3 matrix elements, while the (d,p) reaction provides information on the neutron single-particle states of 199Hg.

  3. Hg(II) Coordination Studies in Penicillamine Enantiomers by 199mHg-TDPAC

    NASA Astrophysics Data System (ADS)

    Tröger, W.; ISOLDE Collaboration

    2001-11-01

    In order to study the binding of the toxic heavy metal ion Hg2+ to penicillamine, complexes with the D- and L-enantiomers of penicillamine were investigated by the nuclear quadrupole interaction of 199Hg monitored by time differential perturbed angular correlation spectroscopy. It was found that bound Hg(II) occurs in two-fold, three-fold and four-fold coordinations.

  4. Superdeformation studies in {sup 191}Hg

    SciTech Connect

    Carpenter, M.P.; Janssens, R.V.F.; Crowell, B.

    1995-08-01

    Superdeformation in the A {approximately} 190 region was first observed in {sup 191}Hg from an experiment performed at ATLAS using the Argonne Notre Dame {gamma}-ray facility. We recently revisited the study of superdeformation in this nucleus using Gammasphere and the {sup 160}Gd({sup 36}S,5n) and {sup 174}Yb({sup 22}Ne,5n) reactions at 172 and 120 MeV in order to populate and measure states in the second well. The goal of the experiment was to identify new bands in the data, and thus allow us to gain understanding on the relative placement of single particle orbitals near the N = 112 SD shell gap. From an analysis of the data, the three previously identified SD bands were extended, and their feeding into the yrast states delineated. Two new SD bands were observed and preliminary evidence for a third new band was obtained as well.

  5. Investigation of the E2 and E3 matrix elements in 200Hg using direct nuclear reactions

    NASA Astrophysics Data System (ADS)

    Rand, Evan; Bildstein, Vinzenz; Diaz Varela, Alejandra; Garrett, Paul; Hadinia, Baharak; Jamieson, Drew; Jigmeddorj, Badamsambuu; Laffoley, Alex; Leach, Kyle; Maclean, Andrew; Svensson, Carl; Ball, Gordon; Faestermann, Thomas; Hertenberger, Ralf; Wirth, Hans-Friedrich

    2014-09-01

    To date, 199Hg provides the most stringent limit on an atomic electric dipole moment (EDM). The existence of a permanent EDM would be a clear signal of CP violation from new physics beyond the Standard Model. Theoretical nuclear-structure calculations for 199Hg are challenging, and give varied predictions for the excited-state spectrum. Understanding the E2 and E3 strengths in 198 , 199 , 200Hg will make it possible to develop a nuclear structure model for the Schiff strength based on these matrix elements, and thereby constrain present models that predict the contribution of octupole collectivity to the Schiff moment of the nucleus. This work comprises two experiments using the Q3D magnetic spectrograph at the Maier-Leibnitz Laboratory. These experiments utilized a 22 MeV deuteron beam incident on a target of 200Hg32S. The first experiment accesses the E 2 and E 3 matrix elements in 200Hg via inelastic deuteron scattering. The second experiment, 200Hg(d , t) 199Hg, yields important information on the single-particle nature of 199Hg. Preliminary results will be presented. To date, 199Hg provides the most stringent limit on an atomic electric dipole moment (EDM). The existence of a permanent EDM would be a clear signal of CP violation from new physics beyond the Standard Model. Theoretical nuclear-structure calculations for 199Hg are challenging, and give varied predictions for the excited-state spectrum. Understanding the E2 and E3 strengths in 198 , 199 , 200Hg will make it possible to develop a nuclear structure model for the Schiff strength based on these matrix elements, and thereby constrain present models that predict the contribution of octupole collectivity to the Schiff moment of the nucleus. This work comprises two experiments using the Q3D magnetic spectrograph at the Maier-Leibnitz Laboratory. These experiments utilized a 22 MeV deuteron beam incident on a target of 200Hg32S. The first experiment accesses the E 2 and E 3 matrix elements in 200Hg via

  6. Assessment of modified matrix solid-phase dispersion as sample preparation for the determination of CH3Hg+ and Hg2+ in fish.

    PubMed

    Duarte, Fabio A; Soares, Bruno M; Vieira, Augusto A; Pereira, Ederson R; Maciel, Juliana V; Caldas, Sergiane S; Primel, Ednei G

    2013-05-21

    This paper reports, for the first time, the development of an analytical method employing modified matrix solid-phase dispersion (MSPD) for the extraction of CH3Hg(+) and Hg(2+) species from fish samples. Separation and determination of mercury species were performed by gas chromatography coupled to mass spectrometry (GC/MS). Important MSPD parameters, such as sample mass, type and mass of solid support, concentration of extraction solution (HCl and NaCl), and stirring time, were investigated by the response surface methodology. The derivatization step and the separation of mercury species were also evaluated for the determination by GC/MS. Quantitative recoveries were obtained with 0.2 g of fish sample, 0.5 g of SiO2 as the solid support, 0.5 mol L(-1) NaCl and 4.2 mol L(-1) HCl as the extraction solution, and 1 min stirring time. The MSPD method showed to be suitable for the extraction and determination of mercury species in certified reference materials of dogfish liver (DOLT-3) and dogfish muscle (DORM-2). It had good agreement (about 99%) with the certified values, and the relative standard deviation was lower than 9.5%. The limits of detection were 0.06 and 0.12 μg g(-1), for CH3Hg(+) and Hg(2+), respectively. A matrix effect was observed, and the quantification was carried out by the matrix-matched calibration. The method was applied to tuna fish ( Thunnus thynnus ), angel shark ( Squatina squatina ), and guitarfish ( Rhinobatos percellens ) samples. The results of the mercury speciation by MPSD and GC/MS were compared to the total mercury concentration determined by flow injection cold vapor generation inductively coupled plasma mass spectrometry, after microwave-assisted digestion. Agreement ranged from 102% to 105%. PMID:23614538

  7. Matrixed business support comparison study.

    SciTech Connect

    Parsons, Josh D.

    2004-11-01

    The Matrixed Business Support Comparison Study reviewed the current matrixed Chief Financial Officer (CFO) division staff models at Sandia National Laboratories. There were two primary drivers of this analysis: (1) the increasing number of financial staff matrixed to mission customers and (2) the desire to further understand the matrix process and the opportunities and challenges it creates.

  8. Electronic properties of liquid Hg-In alloys : Ab-initio molecular dynamics study

    NASA Astrophysics Data System (ADS)

    Sharma, Nalini; Thakur, Anil; Ahluwalia, P. K.

    2016-05-01

    Ab-initio molecular dynamics simulations are performed to study the structural properties of liquid Hg-In alloys. The interatomic interactions are described by ab-initio pseudopotentials given by Troullier and Martins. Three liquid Hg-In alloys (Hg10In90, Hg30In70,. Hg50In50, Hg70In30, and Hg90Pb10) at 299 K are considered. The calculated results for liquid Hg (l-Hg) and lead (l-In) are also drawn. Along with the calculated results of considered five liquid alloys of Hg-In alloy. The results obtained from electronic properties namely total density of state and partial density of states help to find the local arrangement of Hg and In atoms and the presence of liquid state in the considered five alloys.

  9. How to Study a Matrix

    ERIC Educational Resources Information Center

    Jairam, Dharmananda; Kiewra, Kenneth A.; Kauffman, Douglas F.; Zhao, Ruomeng

    2012-01-01

    This study investigated how best to study a matrix. Fifty-three participants studied a matrix topically (1 column at a time), categorically (1 row at a time), or in a unified way (all at once). Results revealed that categorical and unified study produced higher: (a) performance on relationship and fact tests, (b) study material satisfaction, and…

  10. Study of atomic structure of liquid Hg-In alloys using ab-initio molecular dynamics

    SciTech Connect

    Sharma, Nalini; Ahluwalia, P. K.; Thakur, Anil

    2015-05-15

    Ab-initio molecular dynamics simulations are performed to study the structural properties of liquid Hg-In alloys. The interatomic interactions are described by ab-initio pseudopotentials given by Troullier and Martins. Five liquid Hg-In mixtures (Hg{sub 10}In{sub 90}, Hg{sub 30}In{sub 70}, Hg{sub 50}In{sub 50}, Hg{sub 70}In{sub 30} and Hg{sub 90}In{sub 10}) at 299K are considered. The radial distribution function g(r) and structure factor S(q) of considered alloys are compared with respective experimental results for liquid Hg (l-Hg) and (l-In). The radial distribution function g(r) shows the presence of short range order in the systems considered. Smooth curves of Bhatia-Thornton partial structure factors factor shows the presence of liquid state in the considered alloys.

  11. 13C and 199Hg nuclear magnetic resonance spectroscopic study of alkenemercurinium ions: Effect of methyl substituents on 199Hg chemical shifts

    PubMed Central

    Olah, George A.; Garcia-Luna, Armando

    1980-01-01

    The long-lived ethylene, cyclohexene, and norbornenemercurinium ions prepared in superacidic, low-nucleophilic media have been studied by 13C and 199Hg NMR spectroscopy. The norbornenemercurinium ion shows temperature-dependent 13C and 199Hg NMR spectra, consistent with equilibration via rapid hydride and Wagner-Meerwin shifts. The 199Hg NMR shifts of a series of alkylmercury bromides were also obtained in order to elucidate the effect of methyl substituents on 199Hg NMR chemical shifts. PMID:16592870

  12. Understanding natural semiquinone radicals--multifrequency EPR and relativistic DFT studies of the structure of Hg(II) complexes.

    PubMed

    Witwicki, Maciej; Jerzykiewicz, Maria; Ozarowski, Andrzej

    2015-01-01

    Multifrequency EPR spectroscopy and DFT calculations were used to investigate Hg(II) complexes with semiquinone radical ligands formed in a direct reaction between the metal ions and tannic acid (a polyphenol closely related to tannins). Because of the intricate structure of tannic acid a vast array of substituted phenolic compounds were tested to find a structural model mimicking its ability to react with Hg(II) ions. The components of the g matrix (the g tensor) determined from the high field (208 GHz) EPR spectra of the Hg(II) complexes with the radical ligands derived from tannic acid and from the model compounds were analogous, indicating a similar coordination mode in all the studied Hg(II) complexes. Since catechol (1,2-dihydroxybenzene) was the simplest compound undergoing the reaction with Hg(II) it was selected for DFT studies which were aimed at providing an insight into the structural properties of the investigated complexes. Various coordination numbers and different conformations and protonation states of the ligands were included in the theoretical analyses. g Matrices were computed for all the DFT optimized geometries. A good agreement between the theoretical and experimental values was observed only for the model with the Hg(II) ion tetracoordinated by two ligands, one of the ligands being monoprotonated with the unpaired electron mainly localized on it. PMID:25108678

  13. Overcoming phytoremediation limitations. A case study of Hg contaminated soil

    NASA Astrophysics Data System (ADS)

    Barbafieri, Meri

    2013-04-01

    Phytoremediation is a broad term that comprises several technologies to clean up water and soil. Despite the numerous articles appearing in scientific journals, very few field applications of phytoextraction have been successfully realized. The research here reported on Phytoextraction, the use the plant to "extract" metals from contaminated soil, is focused on implementations to overcome two main drawbacks: the survival of plants in unfavorable environmental conditions (contaminant toxicity, low fertility, etc.) and the often lengthy time it takes to reduce contaminants to the requested level. Moreover, to overcome the imbalance between the technology's potential and its drawbacks, there is growing interest in the use of plants to reduce only the fraction that is the most hazardous to the environment and human health, that is to target the bioavailable fractions of metals in soil. Bioavailable Contaminant Stripping (BCS) would be a remediation approach focused to remove the bioavailable metal fractions. BCS have been used in a mercury contaminated soil from Italian industrial site. Bioavailable fractions were determined by sequential extraction with H2O and NH4Cl.Combined treatments of plant hormone and thioligand to strength Hg uptake by crop plants (Brassica juncea and Helianthus annuus) were tested. Plant biomass, evapotranspiration, Hg uptake and distribution following treatments were compared. Results indicate the plant hormone, cytokinine (CK) foliar treatment, increased evapotranspiration rate in both tested plants. The Hg uptake and translocation in both tested plants increased with simultaneous addition of CK and TS treatments. B. juncea was the most effective in Hg uptake. Application of CK to plants grown in TS-treated soil lead to an increase in Hg concentration of 232% in shoots and 39% in roots with respect to control. While H. annuus gave a better response in plant biomass production, the application of CK to plants grown in TS-treated soil lead to

  14. Hydrogen-Te antisite complex impurity (H-TeHg) in Hg0.75Cd0.25Te: First-principles study

    NASA Astrophysics Data System (ADS)

    Xue, L.; Zhou, P.; Zhang, C. X.; Sun, L. Z.; Zhong, Jianxin

    2013-08-01

    Using first-principles method within the framework of the density functional theory, we study the formation energies and the binding energies of hydrogen-telluride antisite complex impurities (n H-TeHg, n=1,2) in Hg0.75Cd0.25Te. We find that telluride antisite impurity (TeHg) in Hg0.75Cd0.25Te is a double donor. When Te antisite and an interstitial hydrogen move close to each other, the interaction between them leads to the creation of a stable 1H-TeHg complex with a binding energy of 0.33 eV. In this case, the donor effects induced by Te antisite are partially passivated. As the hydrogen concentration increases, the binding energy of the 2H-TeHg forming from combining H-TeHg with interstitial hydrogen is only 0.005 eV. Namely, 2H-TeHg is unstable in Hg0.75Cd0.25Te and hydrogenation cannot fully neutralize Te antisite defects.

  15. Using X-ray microscopy and Hg L3 XANES to study Hg binding in the rhizosphere of Spartina cordgrass.

    PubMed

    Patty, Cynthia; Barnett, Brandy; Mooney, Bridget; Kahn, Amanda; Levy, Silvio; Liu, Yijin; Pianetta, Piero; Andrews, Joy C

    2009-10-01

    San Francisco Bay has been contaminated historically by mercury from mine tailings as well as contemporary industrial sources. Native Spartina foliosa and non-native S. alterniflora-hybrid cordgrasses are dominant florae within the SF Bay estuary environment. Understanding mercury uptake and transformations in these plants will help to characterize the significance of their roles in mercury biogeochemical cycling in the estuarine environment. Methylated mercury can be biomagnified up the food web, resulting in levels in sport fish up to 1 million times greater than in surrounding waters and resulting in advisories to limit fish intake. Understanding the uptake and methylation of mercury in the plant rhizosphere can yield insight into ways to manage mercury contamination. The transmission X-ray microscope on beamline 6-2 at the Stanford Synchrotron Radiation Lightsource (SSRL) was used to obtain absorption contrast images and 3D tomography of Spartina foliosa roots that were exposed to 1 ppm Hg (as HgCl2) hydroponically for 1 week. Absorption contrast images of micrometer-sized roots from S. foliosa revealed dark particles, and dark channels within the root, due to Hg absorption. 3D tomography showed that the particles are on the root surface, and slices from the tomographic reconstruction revealed that the particles are hollow, consistent with microorganisms with a thin layer of Hg on the surface. Hg L3 XANES of ground-up plant roots and Hg L3 micro-XANES from microprobe analysis of micrometer-sized roots (60-120 microm in size) revealed three main types of speciation in both Spartina species: Hg-S ligation in a form similar to Hg(II) cysteine, Hg-S bonding as in cinnabar and metacinnabar, and methylmercury-carboxyl bonding in a form similar to methylmercury acetate. These results are interpreted within the context of obtaining a "snapshot" of mercury methylation in progress. PMID:19848152

  16. Investigation of the signal behavior at diagnostic energies of prototype, direct detection, active matrix, flat-panel imagers incorporating polycrystalline HgI2

    PubMed Central

    Du, Hong; El-Mohri, Youcef; Zhao, Qihua; Su, Zhong; Yamamoto, Jin; Wang, Yi

    2009-01-01

    Active matrix, flat-panel x-ray imagers based on a-Si:H thin film transistors offer many advantages and are widely utilized in medical imaging applications. Unfortunately, the detective quantum efficiency (DQE) of conventional flat-panel imagers incorporating scintillators or a-Se photoconductors is significantly limited by their relatively modest signal to noise ratio, particularly in applications involving low x-ray exposures or high spatial resolution. For this reason, polycrystalline HgI2 is of considerable interest by virtue of its low effective work function, high atomic number, and the possibility of large-area deposition. In this study, a detailed investigation of the properties of prototype, flat-panel arrays coated with two forms of this high-gain photoconductor are reported. Encouragingly, high x-ray sensitivity, low dark current, and spatial resolution close to the theoretical limits were observed from a number of prototypes. In addition, input-quantum-limited DQE performance was measured from one of the prototypes at relatively low exposures. However, high levels of charge trapping, lag, and polarization, as well as pixel-to-pixel variations in x-ray sensitivity are of concern. While the results of the current study are promising, further development will be required to realize prototypes exhibiting the characteristics necessary to allow practical implementation of this approach. PMID:18296765

  17. Hg-Cu-Bearing Metal-Sulfide Assemblage in the H3 Chondrite Tieschitz: Important Carriers of Pristine Hg and Possibly Cd-Isotopic Signatures in the Early Solar System

    NASA Astrophysics Data System (ADS)

    Caillet-Komorowski, C.; El Goresy, A.; Miyahara, M.; Boudouma, O.; Ma, C.

    2012-09-01

    The study of a unique assemblage consisting of metallic Hg, HgS, Cu-sulfide and native Cu in the matrix of Tieschitz allows for the first time to determine the isotopic abundance of the Hg isotopes both in matrix and chondrules (and potentially Cd).

  18. Investigation of 198,200Hg isotopes

    NASA Astrophysics Data System (ADS)

    Diaz Varela, A.; Rand, E. T.; Garrett, P. E.; Bildstein, V.; Burbadge, C.; Hadinia, B.; Jamieson, D. S.; Jimeddorj, B.; Laffoley, A. T.; Leach, K. G.; Maclean, A. D.; Radich, A.; Svensson, C. E.; Ball, G. C.; Faestermann, T.; Hertenberger, R.; Wirth, H.-F.; Rebeiro, B.; Triambak, S.

    2015-10-01

    Limits on the electric dipole moment (EDM) continue to decrease for 199Hg, which provides the most stringent upper limit for a nuclear EDM to date. The E 3 and E 1 strength distributions to the ground state of 199Hg, and E 2 transitions among excited states, would be ideal information to constrain theoretical models of the 199Hg Schiff moment. The high level density of 199Hg makes those determinations challenging, however similar information can be obtained from exploring surrounding even-even Hg isotopes. As part of a campaign to study the 198,200Hg isotopes, a number of experiments have been performed using the Q3D spectrograph at the Maier-Leibnitz Laboratory, with 22 MeV deuteron beams impinging on enriched Hg32S targets. Inelastic scattering allows us to probe the desired E 2 and E 3 matrix elements, while the 198Hg (d , p) and 200Hg (d , t) reactions provide information on the neutron single-particle states of 199Hg.

  19. Numerical study of near-, mid-, and long-infrared photon trapping in crystalline and amorphous HgCdTe metamaterials

    NASA Astrophysics Data System (ADS)

    Jung, Young Uk; Bendoym, Igor; Crouse, David T.

    2016-04-01

    Recently, mercury cadmium telluride (HgCdTe) films have been extensively studied for the metamaterial applications. Crystalline HgCdTe (c-HgCdTe) films attracted people's attention for the spectral detection when used as metasurfaces and demonstrated reduced volume size, increased operating temperature, and improved quantum efficiency. Amorphous HgCdTe (a-HgCdTe) films also have been studied due to their interesting properties. Such properties include film deposition on any substrate, direct growth on device, and higher operating temperatures with the low dark current. Hence, in this work, for the first time, we investigate and compare the use of c-HgCdTe and a-HgCdTe for the photon sorting metasurfaces in near-, mid-, and long-IR spectral range in the sensor applications.

  20. [Matrix Support: a bibliographical study].

    PubMed

    Iglesias, Alexandra; Avellar, Luziane Zacché

    2014-09-01

    This article presents a bibliographical review of matrix support in mental health. A search was conducted in the Virtual Health Library and the LILACS, SciELO and Google Scholar databases using the key words: "matrix support in mental health." Fourteen articles were located with the desired characteristics, which indicates that only a restricted number of publications are in circulation. The articles were analyzed with respect to their structural and methodological aspects, which revealed the absolute predominance of the use of qualitative methods and health professionals as the target research population. The same articles were then analyzed for their theoretical discussions. Among other issues, the importance of matrix support to enhance the primary health care teams provided to people suffering from psychic distress is highlighted. However, there is still considerable confusion regarding the proposal of the matrix support and shared responsibilities between teams of reference and mental health professionals, which emphasizes the need for training of these professionals, as well as better coordination and organization of the mental health care network. PMID:25184584

  1. Study of asymmetric fission yield behavior from neutron-deficient Hg isotope

    SciTech Connect

    Perkasa, Y. S.; Waris, A. Kurniadi, R. Su'ud, Z.

    2014-09-30

    A study of asymmetric fission yield behavior from a neutron-deficient Hg isotope has been conducted. The fission yield calculation of the neutron-deficient Hg isotope using Brownian Metropolis shape had showed unusual result at decreasing energy. In this paper, this interesting feature will be validated by using nine degree of scission shapes parameterization from Brosa model that had been implemented in TALYS nuclear reaction code. This validation is intended to show agreement between both model and the experiment result. The expected result from these models considered to be different due to dynamical properties that implemented in both models.

  2. Spectral, thermal, electrochemical and analytical studies on Cd(II) and Hg(II) thiosemicarbazone complexes

    NASA Astrophysics Data System (ADS)

    El-Asmy, A. A.; El-Gammal, O. A.; Saleh, H. S.

    2008-11-01

    The coordination characteristic of the investigated thiosemicarbazones towards hazard pollutants, Cd(II) and Hg(II), becomes the first goal. Their complexes have been studied by microanalysis, thermal, electrochemical and spectral (electronic, IR and MS) studies. The substitutent (salicylaldehyde, acetophenone, benzophenone, o-hydroxy- p-methoxybenzophenone or diacetylmonoxime) plays an important role in the complex formation. The coordination sites were the S for thiosemicarbazide (HTS); NN for benzophenone thiosemicarbazone (HBTS); NS for acetophenone thiosemicarbazone (HATS) and salicylaldehyde thiosemicarbazone (H 2STS); NNS or NSO for diacetylmonoxime thiosemicarbazone (H 2DMTS). The stability constants of Hg(II) complexes were higher than Cd(II). The kinetic and thermodynamic parameters for the different thermal decomposition steps in the complexes have been evaluated. The activation energy values of the first step ordered the complexes as: [Cd(H 2STS)Cl 2]H 2O > [Cd(H 2DAMTS)Cl 2] > [Cd(HBTS) 2Cl 2]2H 2O > [Cd(HATS) 2Cl 2]. The CV of [Cd(H 2STS)Cl 2]H 2O and [Hg(HBTS)Cl 2] were recorded. The use of H 2DMTS as a new reagent for the separation and determination of Cd(II) ions from water and some synthetic samples using flotation technique is aimed to be discussed.

  3. Spectrophotometric study of the system Hg(II)-thymol blue-H2O and its evidence through electrochemical means.

    PubMed

    Balderas-Hernández, P; Rojas-Hernández, A; Galván, M; Ramírez-Silva, M T

    2004-02-01

    The detailed analysis of the experimental spectrophotometric data obtained from solutions containing the acid-base indicator thymol blue (TB) and mercury(II) (Hg(II)) coupled with data processing by means of the SQUAD program, a chemical model was determined that includes the formation of complexes indicator-metal ion (HgTB and HgOTB), dimer species (H3TB2 and H4TB2) and monomer species (HTB and TB). The values of the overall formation constants (log beta) were calculated for the chemical equilibria involved: TB+Hg<-->HgTB log beta=16.047 +/- 0.043, TB+Hg+H2O<-->HgOHTB+H log beta=7.659 +/- 0.049, 2TB+4H<-->H4TB2 log beta=31.398 +/- 0.083, 2TB+3H<-->H3TB2 log beta=29.953 +/- 0.084 and H+TB<-->HTB-log beta=8.900. To compliment the present research, the values of the absorptivity coefficients are included for all the species involved, within a wide range of wavelengths (250-700 nm). The latter were used subsequently to carry simulations of the absorption spectra at various pH values, thus corroborating that the chemical model proposed is fully capable to describe the experimental information. Voltammetric study performed evidenced the formation of a complex with a 1:1 stoichiometry Hg(II):TB. PMID:14747081

  4. Hg-1212 and Hg-1223 single crystals: Synthesis and characterisation

    NASA Astrophysics Data System (ADS)

    Gatt, R.; Olsson, E.; Morawski, A.; Lada, T.; Paszewin, A.; Bryntse, I.; Grishin, A. M.; Eeltsev, Yu.; Berastegui, P.; Johansson, L.-G.

    1997-02-01

    Single crystals of HgBa 2CaCu 2O 6+δ (Hg-1212) and HgBa 2Ca 2Cu 3O 8+δ (Hg-1223) were grown from the melt at an argon pressure of 10 kbar. Electron microscopy, as well as single crystal X-ray diffraction studies show that the crystals are well ordered. The EDS analysis indicates the presence of a minor amount of other cations replacing Hg, Ba and Ca in the structure. Refined fractional coordinates and thermal parameters are given for a crystal of Hg-1223 type. Magnetic and resistive measurements show a Tc of 133 K for the Hg-1223 phase.

  5. One-step green synthesis and characterization of plant protein-coated mercuric oxide (HgO) nanoparticles: antimicrobial studies

    NASA Astrophysics Data System (ADS)

    Das, Amlan Kumar; Marwal, Avinash; Sain, Divya; Pareek, Vikram

    2015-03-01

    The present study demonstrates the bioreductive green synthesis of nanosized HgO using flower extracts of an ornamental plant Callistemon viminalis. The flower extracts of Callistemon viminalis seem to be environmentally friendly, so this protocol could be used for rapid production of HgO. Till date, there is no report of synthesis of nanoparticles using flower extract of Callistemon viminalis. Mercuric acetate was taken as the metal precursor in the present experiment. The flower extract was found to act as a reducing as well as a stabilizing agent. The phytochemicals present in the flower extract act as reducing agent which include proteins, saponins, phenolic compounds, phytosterols, and flavonoids. FT-IR spectroscopy confirmed that the extract had the ability to act as a reducing agent and stabilizer for HgO nanoparticles. The formation of the plant protein-coated HgO nanoparticles was first monitored using UV-Vis absorption spectroscopy. The UV-Vis spectroscopy revealed the formation of HgO nanoparticles by exhibiting the typical surface plasmon absorption maxima at 243 nm. The average particle size formed ranges from 2 to 4 nm. The dried form of synthesized nanoparticles was further characterized using TGA, XRD, TEM, and FTIR spectroscopy. FT-IR spectra of synthesized HgO nanoparticles were performed to identify the possible bio-molecules responsible for capping and stabilization of nanoparticles, which confirm the formation of plant protein-coated HgO nanoparticles that is further corroborated by TGA study. The optical band gap of HgO nanoparticle was measured to be 2.48 eV using cutoff wavelength which indicates that HgO nanoparticles can be used in metal oxide semiconductor-based photovoltaic cells. A possible core-shell structure of the HgO nanobiocomposite has been proposed.

  6. Heterogeneous Reduction Pathways for Hg(II) Species on Dry Aerosols: A First-Principles Computational Study.

    PubMed

    Tacey, Sean A; Xu, Lang; Mavrikakis, Manos; Schauer, James J

    2016-04-01

    The atmospheric lifetime of mercury is greatly impacted by redox chemistry resulting from the high deposition rate of reactive mercury (Hg(II)) compared to elemental mercury (Hg(0)). Recent laboratory and field studies have observed the reduction of Hg(II), but the chemical mechanism for this reaction has not been identified. Recent experimental work has shown that the reduction reaction is heterogeneous and can occur on iron and sodium chloride aerosol surfaces. This study explores the use of density functional theory calculations to discern the reduction pathways of HgCl2, HgBr2, Hg(NO3)2, and HgSO4 on clean Fe(110), NaCl(100), and NaCl(111)(Na) surfaces. Potential energy surfaces were prepared for the various reduction pathways, indicating that the reduction pathway leading to the production of gas-phase elemental mercury is highly favorable on Fe(110) and NaCl(111)(Na). Moreover, the Fe(110) surface requires an external energy source of ∼0.5 eV to desorb the reduced mercury, whereas the NaCl(111)(Na) surface requires no energy input. The results indicate that a number of mercury species can be reduced on metallic iron and sodium chloride surfaces, which are known aerosol components, and that a photochemical reaction involving the aerosol surface is likely needed for the reaction to be catalytic. PMID:27014805

  7. Electronic structure and optical properties of Cs2HgI4: Experimental study and band-structure DFT calculations

    NASA Astrophysics Data System (ADS)

    Lavrentyev, A. A.; Gabrelian, B. V.; Vu, V. T.; Shkumat, P. N.; Myronchuk, G. L.; Khvyshchun, M.; Fedorchuk, A. O.; Parasyuk, O. V.; Khyzhun, O. Y.

    2015-04-01

    High-quality single crystal of cesium mercury tetraiodide, Cs2HgI4, has been synthesized by the vertical Bridgman-Stockbarger method and its crystal structure has been refined. In addition, electronic structure and optical properties of Cs2HgI4 have been studied. For the crystal under study, X-ray photoelectron core-level and valence-band spectra for pristine and Ar+-ion irradiated surfaces have been measured. The present X-ray photoelectron spectroscopy (XPS) results indicate that the Cs2HgI4 single crystal surface is very sensitive with respect to Ar+ ion-irradiation. In particular, Ar+ bombardment of the single crystal surface alters the elemental stoichiometry of the Cs2HgI4 surface. To elucidate peculiarities of the energy distribution of the electronic states within the valence-band and conduction-band regions of the Cs2HgI4 compound, we have performed first-principles band-structure calculations based on density functional theory (DFT) as incorporated in the WIEN2k package. Total and partial densities of states for Cs2HgI4 have been calculated. The DFT calculations reveal that the I p states make the major contributions in the upper portion of the valence band, while the Hg d, Cs p and I s states are the dominant contributors in its lower portion. Temperature dependence of the light absorption coefficient and specific electrical conductivity has been explored for Cs2HgI4 in the temperature range of 77-300 K. Main optical characteristics of the Cs2HgI4 compound have been elucidated by the first-principles calculations.

  8. Pressure makes mercury a transition metal: a first-principles study of HgF4 solid phases

    NASA Astrophysics Data System (ADS)

    Wang, Xiaoli; Lin, Haiqing; Ma, Yanming; Miao, Maosheng

    2012-02-01

    Mercury is considered as a post-transition metal, because its d shell is filled and does not involve in forming chemical bonds. Yet, because the large relativistic effect pushes up the outmost d level, there is a high expectation that Hg can be stabilized in a higher oxidation state. The HgF4 molecule has been predicted by calculations, and an evidence of such molecule is shown by IR absorption recently. However, there is neither computation nor experiment report on possible high oxidation state of Hg in solid. By using first-principles density functional theory and a structure-searching method, we studied the structural change of a solid system of Hg and F under pressures from 0 to 300 GPa. We found that at lower pressure, the stable structure consists of HgF2 and F2 molecules. At about 25 GPa, the system undergoes a structural change and forms HgF4 planar molecules featuring d8 configuration. The calculations show that the d orbitals of Hg involve in chemical bonding, which is the signature of a transition metal.

  9. Spectrophotometric study of the system Hg(II)-thymol blue-H 2O and its evidence through electrochemical means

    NASA Astrophysics Data System (ADS)

    Balderas-Hernández, P.; Rojas-Hernández, A.; Galván, M.; Ramírez-Silva, M. T.

    2004-02-01

    The detailed analysis of the experimental spectrophotometric data obtained from solutions containing the acid-base indicator thymol blue (TB) and mercury(II) (Hg(II)) coupled with data processing by means of the SQUAD program, a chemical model was determined that includes the formation of complexes indicator-metal ion (HgTB and HgOTB), dimer species (H 3TB 2 and H 4TB 2) and monomer species (HTB and TB). The values of the overall formation constants (log β) were calculated for the chemical equilibria involved: TB+Hg↔HgTB log β=16.047±0.043, TB+Hg+H 2O↔HgOHTB+H log β=7.659±0.049, 2TB+4H↔H 4TB 2 log β=31.398±0.083, 2TB+3H↔H 3TB 2 log β=29.953±0.084 and H+TB↔HTB-log β=8.900. To compliment the present research, the values of the absorptivity coefficients are included for all the species involved, within a wide range of wavelengths (250-700 nm). The latter were used subsequently to carry simulations of the absorption spectra at various pH values, thus corroborating that the chemical model proposed is fully capable to describe the experimental information. Voltammetric study performed evidenced the formation of a complex with a 1:1 stoichiometry Hg(II):TB.

  10. Ab-initio study of pressure effects and hydrogen impurity in HgO

    NASA Astrophysics Data System (ADS)

    Choi, Minseok; Park, Chul-Hong

    2016-06-01

    Through ab-initio pseudopotential calculations, we investigated the deformation potential of HgO semiconductors and the structural stabilities of various crystal structures under pressure. We also investigated the microscopic structure of the hydrogen (H) impurity in HgO. Especially the state of hydrogen atoms captured by an acceptor-like Hg-vacancy (V Hg ) is focused on. The location of H is found to be very different from the original Hg-site, forming a strong H-O bond. The capture two H atoms by V Hg is found to be energetically favorable: the binding energy for one H and the second H are 1.01 eV and 0.07 eV, respectively.

  11. [Study on Kinetic of Hg2+ from Wastewater Absorbed by Lemon Residues].

    PubMed

    Shen, Wang-qing; Wang, Miao; Yang, Ting

    2016-03-01

    With low price and its superior adsorption performance after modification, currently agricultural waste is used as adsorbent of heavy metals in wastewater, which has become a hot research topic. To study on Hg2+ from wastewater absorbed by lemon residues that has been modified by 15% concentration of sulphuric acid. The pore volume, pore size and other properties of the adsorbent were test. The samples were characterized by differential thermal analysis, IR, electron microscopy and spectroscopy. The result showed that the adsorption rate was controlled by membrane diffusion kinetics that was viewed as the first order kinetics equation of the Lagergren, which was physically absorbed. The adsorption properties of modified lemon residues were improved greatly, and the pore size distribution mainly was medium. There were three losses-weight process. There was a endothermic peak around 66 degrees C and two exotherm near 316 degrees C and 494 degrees C. Basic framework of Lemon residues was not changed and structure of Lemon residues was amorphous; the surface of modified lemon residues loosen and many pores formed, and Hg2+ have been adsorbed effectively. PMID:27400525

  12. Fabrication, photoemission studies, and sensor of Hg nanoparticles templated on plasmid DNA

    SciTech Connect

    Majumder, Subrata; Umananda, M.; Satyam, P. V.; Varma, Shikha; Priyadarshini, M.; Subudhi, U.; Chainy, G. B. N.

    2009-02-16

    Fabrication of Hg nanoparticles (NPs) templated on plasmid DNA has been investigated here. The Hg NPs get embedded inside the DNA scaffold through local melting of double helix due to the strong and exclusive interaction of the NPs with the nitrogen of the nucleic acid bases. The interaction of the Hg NPs with the guanine-cytosine base pair sites is responsible for the formation of two Hg metal-base complexes that can find application as the signature of ion-DNA interactions. The modifications in the transport properties of metal conjugated DNA can be utilized as sensor for mercury contamination.

  13. Study of Hg(II) species removal from aqueous solution using hybrid ZnCl2-MCM-41 adsorbent

    NASA Astrophysics Data System (ADS)

    Raji, F.; Pakizeh, M.

    2013-10-01

    A novel ZnCl2-MCM-41 adsorbent was prepared by method of solvent dispersion in toluene and characterized using XRD, N2 adsorption-desorption, FTIR and TGA techniques. The synthesized ZnCl2-MCM-41 sorbent possessed high specific surface area (602.3 m2 g-1), narrow pore size distribution (2.37 nm) and total pore volume (0.46 cm3 g-1). The hybrid sorbent was applied for the removal of Hg(II) from aqueous solution under different experimental conditions by varying contact time, initial concentration of Hg(II), pH, presence of interfering ions and solution temperature. It was found that amount of Hg(II) sorption increased with enhancement of Hg(II) initial concentration, contact time and pH but decreased as the temperature increased. Optimum conditions obtained were 20 °C, pH 10 and contact time of 30 min. Effects of foreign anions and cations on Hg(II) removal were studied and it was found that chloride ion affected strongly on adsorption. For experimental data the Langmuir isotherm showed a better fit and maximum adsorption capacity was obtained 204.1 mg g-1 for an initial concentration range 2-50 mg L-1. From the D-R isotherm, the mean free energy was calculated as 9.128 kJ mol-1 indicating that the sorption of Hg(II) was taken place by chemical reaction.

  14. EBIC study of resistive photosensitive elements based on HgCdTe

    SciTech Connect

    Vergeles, P. S.; Krapukhin, V. V.; Yakimov, E. B.

    2007-02-15

    Photosensitive resistive elements based on HgCdTe with decreased photosensitivity as a result of prolonged operation are studied by the method of electron-beam-induced current in a scanning electron microscope. It is shown that the degradation processes in these elements are related to the appearance of regions with a lowered sensitivity in the vicinity of contacts. Distribution of the induced current for these inhomogeneous elements was simulated. It is shown that a comparison of the measured and calculated distributions of the induced-current signal makes it possible to reveal the most probable causes of the inhomogeneous decrease in the photosensitivity. The comparison performed showed that the most likely cause of a decrease in the photosensitivity of the elements under study was an increase in the donor concentration in the near-contact regions.

  15. Quantum chemical study of the interaction of elemental Hg with small neutral, anionic and cationic Au{sub n} (n = 1–6) clusters

    SciTech Connect

    Siddiqui, Shamoon Ahmad; Bouarissa, Nadir; Rasheed, Tabish; Al-Assiri, M.S.

    2013-03-15

    Graphical abstract: Binding energies as a function of cluster size for Au{sub n}Hg, Au{sub n}Hg{sup +} and Au{sub n}Hg{sup −} complexes. Highlights: ► Hg adsorption of neutral and charged Au{sub n} (n = 1–6) clusters has been discussed. ► Size and charged state of cluster significantly affect the Hg adsorption. ► Transfer of electron mainly found from s orbital of Hg to s orbital of Au. - Abstract: Adsorption of elemental mercury (Hg) on small neutral, cationic and anionic gold clusters (Au{sub n}, n = 1–6) has been studied by using the density functional theory (DFT). Results of this investigation show that frontier molecular orbital theory is a useful tool to predict the selectivity of Hg adsorption. It is found that adsorption of Hg on neutral, cationic and anionic Au{sub n} (n = 1–6) clusters are thermodynamically favorable. The binding energies of Hg on the cationic Au{sub n} clusters are greater than those on the neutral and anionic clusters. Natural bond orbital (NBO) analysis indicates that the flow of electrons in the neutral and charged clusters is mainly due to the s orbitals of Hg and Au. Results of NBO analysis also indicate that the binding energy of Hg with Au{sub n} clusters is directly proportional to the charge transfer, i.e. greater is the charge transfer, higher is the binding energy.

  16. Novel bimetallic thiocyanate-bridged Cu(II)-Hg(II) compounds-synthesis, X-Ray studies and magnetic properties

    SciTech Connect

    Machura, B.; Switlicka, A.; Zwolinski, P.; Mrozinski, J.; Kalinska, B.; Kruszynski, R.

    2013-01-15

    Seven novel heterobimetallic Cu/Hg polymers based on thiocyanate bridges have been synthesised and characterised by means of IR, EPR, magnetic measurements and single crystal X-Ray. Three of them, [Cu(pzH){sub 4}Hg(SCN){sub 4}]{sub n} (1) [Cu(indH){sub 4}Hg(SCN){sub 4}]{sub n} (2) and [Cu(ampy){sub 2}Hg(SCN){sub 4}]{sub n} (3), have one-dimensional coordination structure. Two compounds [Cu(pzH){sub 2}Hg(SCN){sub 4}]{sub n} (4) and [Cu(abzimH)Hg(SCN){sub 4}]{sub n} (5) form two-dimensional nets, whereas the complexes [Cu(pyCN){sub 2}Hg(SCN){sub 4}]{sub n} (6) and [Cu(pyCH(OH)(OMe)){sub 2}Hg(SCN){sub 4}]{sub n} (7) are three-dimensional coordination polymers. The chains of 1 are connected by the intermolecular N-H Bullet Bullet Bullet N hydrogen bonds to the three dimensional net. In 2 the N-H Bullet Bullet Bullet S hydrogen bonds link the polymeric chains to the two dimensional layer extending along crystallographic (0 0 1) plane. The polymeric chains of compound 3 are joined by the intermolecular N-H Bullet Bullet Bullet N and N-H Bullet Bullet Bullet S hydrogen bonds to the three dimensional net. The polymeric layers of 4 are connected by the intermolecular N-H Bullet Bullet Bullet N hydrogen bonds to the three dimensional net. - Graphical abstract: Novel bimetallic thiocyanate-bridged Cu(II)-Hg(II) compound-synthesis,X-Ray studies and magnetic properties. Highlights: Black-Right-Pointing-Pointer Novel heterobimetallic Cu/Hg coordination polymers were synthesised. Black-Right-Pointing-Pointer The multidimensional structures have been proved by single X-ray analysIs. Black-Right-Pointing-Pointer A variation in the crystalline architectures was observed depending on auxiliary ligands. Black-Right-Pointing-Pointer Magnetic measurements indicate weak exchange interaction between Cu(II) in the crystal lattices below 10 K.

  17. The theoretical studies of topology electronic states in HgTe Hall Bar and Quantum Dot

    NASA Astrophysics Data System (ADS)

    Qu, Jin-Xian; Zhang, Shu-Hui; Yang, Wen

    In recent years, there is an extensive attention on the new properties of topology materials and their potential applications. Our interest is on the physics in the quantum confined systems based on topology materials. To consider two such systems, i.e., quantum dot and Hall bar constructed on the HgTe quantum well, we study the electronic properties and their dependence on various material parameters with and without an in-plane electric field. For both systems, we find that 1) the exotic edge states appear in bulk energy gap, resulting from the non-trivial topological property of quantum well system. 2) by the magnetic doping, there are tunable phase transitions, e.g., transition from trivial insulating phase to topological insulating phase or anomalous quantum Hall insulating phase. 3) the in-plane electric field can introduce effective control on the electronic states.

  18. Further studies of anisotropy in the T1u⊗hg Jahn-Teller system

    NASA Astrophysics Data System (ADS)

    Qiu, Q. C.; Dunn, J. L.; Bates, C. A.; Liu, Y. M.

    1998-08-01

    In the linear T1u⊗hg Jahn-Teller system, the adiabatic potential energy surface (APES) is a trough. However, in real systems, quadratic coupling will be present, which warps the APES to give wells of either D3d or D5d symmetry. The degeneracy of the vibrations within the wells is also lifted. This anisotropy has recently been investigated in the T1u⊗hg system, and expressions for the frequencies in both types of wells obtained in the strong coupling limit using the method of Öpik and Pryce. A scale transformation procedure was then used to incorporate these results into expressions for the states in the wells and their associated energies. However, this calculation did not allow for second-order perturbation effects and is only valid in the strong coupling limit. In this paper, a revised scale transformation procedure is developed for the D5d wells, which allows expressions for the anisotropic frequencies to be obtained without employing the Öpik and Pryce procedure. An expression is obtained for the phonon overlap that is correct to second-order and is not restricted to the strong coupling limit. Results are then obtained for the ground-state energies and inversion splitting. For D3d wells, the previous results are improved by application of a modified scale transformation procedure and overlaps correct to second order obtained. The results obtained in this paper are of interest in studies of the C-60 anion state of the C60 molecule, which is known to occupy a T1u orbital ground state.

  19. [Using atomic fluorescence spectrometry to study the spatial distribution of As and Hg in orchard soils].

    PubMed

    Zhao, Xi-Mei; Lü, Chun-Yan; Liu, Qing; Zhu, Xi-Cun

    2014-02-01

    Aqua regia digestion, double channels-atomic fluorescence spectrometry method was used to determine the concentrations of As and Hg in orchard soils of Qixia City - the main apple production area of Shandong province. Validate The detection limitation, accuracy and precision of the method were validated, the spatial distribution was analyzed, and the characteristics of As and Hg pollution in Qixia orchard soils were assessed. The results showed that the range of As concentration in Qixia soils is between 2.79 and 20.93 mg x kg(-1), the average concentration is 10.59 mg x kg(-1), the range of Hg concentration in Qixia soil is between 0.01 and 0.79 mg x kg(-1), the average concentration is 0.12 mg x kg(-1). The variation of As concentration in soils is small, whereas that of Hg concentration is large. Frequency distribution graphics of As and Hg showed that the concentration of As in soils is according with the normal distribution approximately and the concentrations are mostly between 7 and 15 mg x kg(-1), the concentration of Hg in soil isn't according with the normal distribution and the concentrations are mostly between 0.03 and 0.21 mg x kg(-1). The correlations between the concentrations of As or Hg in soils and the nutrient are not significant and there is no significant correlation even between As and Hg. Based on the environmental technical terms for green food production area, the As concentration in orchard soil of Qixia City is at clean level, but there are 4.76% of sample points with Hg pollution index exceeding 1, and this should be attracted the attention of the administrators. PMID:24822435

  20. Examining Mechanisms of Groundwater Hg(II) Treatment by Reactive Materials: An EXAFS Study

    SciTech Connect

    Gibson, Blair D.; Ptacek, Carol J.; Lindsay, Matthew B.J.; Blowes, David W.

    2012-02-07

    Laboratory batch experiments were conducted to examine mechanisms of Hg(II) removal by reactive materials proposed for groundwater treatment. These materials included granular iron filings (GIF), 1:1 (w/w) mixtures of metallurgical granular Fe powder + elemental S (MGI+S) and elemental Cu + elemental S (Cu+S), granular activated carbon (GAC), attapulgite clay (ATP), ATP treated with 2-amino-5-thiol-1,3,4-thiadiazole (ATP-a), and ATP treated with 2,5-dimercapto-1,3,4-thiadiazole (ATP-d). Following treatment of simulated groundwater containing 4 mg L{sup -1} Hg for 8 or 16 days, the solution pH values ranged from 6.8 to 8.8 and Eh values ranged from +400 to -400 mV. Large decreases in aqueous Hg concentrations were observed for ATP-d (>99%), GIF (95%), MGI+S (94%), and Cu+S (90%). Treatment of Hg was less effective using ATP (29%), ATP-a (69%), and GAC (78%). Extended X-ray absorption fine structure (EXAFS) spectra of Hg on GIF, MGI+S, and GAC indicated the presence of an Hg-O bond at 2.04-2.07 {angstrom}, suggesting that Hg was bound to GIF corrosion products or to oxygen complexes associated with water sorbed to activated carbon. In contrast, bond lengths ranging from 2.35 to 2.48 {angstrom} were observed for Hg in Cu+S, ATP-a, and ATP-d treatments, suggesting the formation of Hg-S bonds.

  1. Mercury (Hg) accumulation in terrestrial carbon (C) reservoirs: magnitude, spatial patterns, fate upon C losses, and implications of global change

    NASA Astrophysics Data System (ADS)

    Obrist, D.; Johnson, D. W.; Lindberg, S. E.; Luo, Y.

    2012-04-01

    Terrestrial ecosystems are strong natural reservoirs that retain the bulk of atmospheric Hg deposition. As a result, a long-term legacy of past and present Hg pollution is sequestered in surface litter and soil pools. Hg shows a particular affinity to—and hence tends to accumulate in—terrestrial organic C. We present a summary of a comprehensive five-year investigation where we quantified: (i) relationships between Hg and C across 14 forests sites to assess the affinity of Hg to C accumulation across spatial scales; (ii) the degree to which C determines net retention and spatial accumulation of Hg; (iii) the fate of Hg upon losses of C, including losses though wildfires and mineralization; (iv) the coupling of gaseous Hg losses to CO2 respiration; and (v) the potential sensitivity of climate-change induced changes in C on terrestrial Hg sequestration. Results show that continental-scale spatial distribution of Hg in soils and litter is strongly related to C, and that old terrestrial C pools (as determined by C/N ratios) are particularly prone to Hg enrichment. The correlation of Hg and C is likely responsible for increasing Hg levels (concentrations and pools of total Hg, as well as methylated Hg) with higher latitude, which we attribute to a legacy of Hg sequestration in C-rich layers of northern ecosystems. Experimental studies and field observations to address fate of Hg sequestered in organic C show that: (i) fires leads to up-to-complete Hg losses in either gaseous elemental or particulate-bound form; (ii) litter decomposition also leads to evasion losses of Hg in the range of 50% of initial Hg, but little Hg is subject to runoff as dissolved Hg; (iii) soils effectively retain Hg with only about 3% of Hg subject to volatilization upon C loss during respiration; (iv) no links between CO2 and gaseous Hg concentrations are observed in soil depth profiles in the field, indicating that fate and movement of gaseous Hg is decoupled from that of CO2. We calculate

  2. Tuning the electronic structure in nearly gapless HgCdTe with temperature: infrared magneto-spectroscopy study

    NASA Astrophysics Data System (ADS)

    Moon, Seongphill; Marcinkiewicz, M.; Consejo, C.; Ruffenach, S.; Knap, W.; Teppe, F.; Ludwig, J.; Thirunavukkuarasu, K.; Smirnov, D.; Krishtopenko, S.; Gavrilenko, V. I.; Dvoretskii, S. A.; Mikhailov, N. N.

    Replace this text with your abstract body. Recently, a temperature-induced transition from a conventional two-dimensional semiconductor to a topological insulator has been demonstrated through magneto transport studies on HgTe/CdHgTe quantum wells [Wiedmann, S. et al. Phys. Rev. B 91, 205311 (2015)]. Here we report on a temperature-driven semiconductor-to-semimetal transition in 3-dimensional CdxHg1-xTe (x =0.15) revealed by infrared magneto-spectroscopy. We show that changing the temperature from 4K to 120K enables continuous tuning of the band structure from inverted to normal alignment through a critical gapless state realized at ~80K, where the inter-Landau level transitions exhibit a characteristic sqrt(B) dependence intersecting at zero energy. Using an effective Dirac model, we determine the effective mass and the Fermi velocity for the studied temperature range.

  3. Shape coexistence in {sup 180}Hg studied through the {beta} decay of {sup 180}Tl

    SciTech Connect

    Elseviers, J.; Bree, N.; Diriken, J.; Huyse, M.; Ivanov, O.; Van den Bergh, P.; Van Duppen, P.; Andreyev, A. N.; Antalic, S.; Barzakh, A.; Fedorov, D.; Cocolios, T. E.; Seliverstov, M.; Comas, V. F.; Heredia, J. A.; Fedosseyev, V. N.; Marsh, B. A.; Franchoo, S.; Page, R. D.

    2011-09-15

    The {beta}{sup +}/EC decay of {sup 180}Tl and excited states in the daughter nucleus {sup 180}Hg have been investigated at the CERN On-Line Isotope Mass Separator (ISOLDE) facility. Many new low-lying energy levels were observed in {sup 180}Hg, of which the most significant are the 0{sub 2}{sup +} at 419.6 keV and the 2{sub 2}{sup +} at 601.3 keV. The former is the bandhead of an excited band in {sup 180}Hg assumed originally to be of prolate nature. From the {beta} feeding to the different states in {sup 180}Hg, the ground-state spin of {sup 180}Tl was deduced to be (4{sup -},5{sup -}).

  4. Theoretical Study of Midwave Infrared HgCdTe nBn Detectors Operating at Elevated Temperatures

    NASA Astrophysics Data System (ADS)

    Akhavan, Nima Dehdashti; Jolley, Gregory; Umana-Membreno, Gilberto A.; Antoszewski, Jarek; Faraone, Lorenzo

    2015-09-01

    We report a theoretical study of mercury cadmium telluride (HgCdTe) unipolar n-type/barrier/ n-type (nBn) detectors for midwave infrared (MWIR) applications at elevated temperatures. The results obtained indicate that the composition, doping, and thickness of the barrier layer in MWIR HgCdTe nBn detectors can be optimized to yield performance levels comparable with those of ideal HgCdTe p- n photodiodes. It is also shown that introduction of an additional barrier at the back contact layer of the detector structure (nBnn+) leads to substantial suppression of the Auger generation-recombination (GR) mechanism; this results in an order-of-magnitude reduction in the dark current level compared with conventional nBn or p- n junction-based detectors, thus enabling background-limited detector operation above 200 K.

  5. First principles study on electronic structure and elastic properties of LaCd and LaHg

    SciTech Connect

    Devi, Hansa E-mail: gita-pagare@yahoo.co.in; Pagare, Gitanjali E-mail: gita-pagare@yahoo.co.in; Chouhan, S. S. E-mail: gita-pagare@yahoo.co.in; Sanyal, Sankar P.

    2014-04-24

    Full -potential linearized augmented plane wave method (FP- LAPW) has been used for the comparative study of electronic structure and elastic properties of CsCl-type LaCd and LaHg intermetallic compounds using generalized gradient approximation (GGA). The density of states at the Fermi Level, N (E{sub F}), is found to be 0.06 and 3.03 states/eV for LaCd and LaHg respectively. We report elastic constants for these compounds for the first time. The ductility/brittleness of these compounds has been analyzed using Pugh rule and Cauchy’s pressure.

  6. Methylation of Hg downstream from the Bonanza Hg mine, Oregon

    USGS Publications Warehouse

    Gray, John E.; Hines, Mark E.; Krabbenhoft, David P.; Thoms, Bryn

    2012-01-01

    Speciation of Hg and conversion to methyl-Hg were evaluated in stream sediment, stream water, and aquatic snails collected downstream from the Bonanza Hg mine, Oregon. Total production from the Bonanza mine was >1360t of Hg, during mining from the late 1800s to 1960, ranking it as an intermediate sized Hg mine on an international scale. The primary objective of this study was to evaluate the distribution, transport, and methylation of Hg downstream from a Hg mine in a coastal temperate climatic zone. Data shown here for methyl-Hg, a neurotoxin hazardous to humans, are the first reported for sediment and water from this area. Stream sediment collected from Foster Creek flowing downstream from the Bonanza mine contained elevated Hg concentrations that ranged from 590 to 71,000ng/g, all of which (except the most distal sample) exceeded the probable effect concentration (PEC) of 1060ng/g, the Hg concentration above which harmful effects are likely to be observed in sediment-dwelling organisms. Concentrations of methyl-Hg in stream sediment collected from Foster Creek varied from 11 to 62ng/g and were highly elevated compared to regional baseline concentrations (0.11-0.82ng/g) established in this study. Methyl-Hg concentrations in stream sediment collected in this study showed a significant correlation with total organic C (TOC, R2=0.62), generally indicating increased methyl-Hg formation with increasing TOC in sediment. Isotopic-tracer methods indicated that several samples of Foster Creek sediment exhibited high rates of Hg-methylation. Concentrations of Hg in water collected downstream from the mine varied from 17 to 270ng/L and were also elevated compared to baselines, but all were below the 770ng/L Hg standard recommended by the USEPA to protect against chronic effects to aquatic wildlife. Concentrations of methyl-Hg in the water collected from Foster Creek ranged from 0.17 to 1.8ng/L, which were elevated compared to regional baseline sites upstream and downstream

  7. Synthesis, Characterization and Thermal Studies of Zn(II), Cd(II) and Hg(II) Complexes of N-Methyl-N-Phenyldithiocarbamate: The Single Crystal Structure of [(C6H5)(CH3)NCS2]4Hg2

    PubMed Central

    Onwudiwe, Damian C.; Ajibade, Peter A.

    2011-01-01

    Zn(II), Cd(II) and Hg(II) complexes of N-methyl-N-phenyl dithiocarbamate have been synthesized and characterized by elemental analysis and spectral studies (IR, 1H and 13C-NMR). The single crystal X-ray structure of the mercury complex revealed that the complex contains a Hg centre with a distorted tetrahedral coordination sphere in which the dinuclear Hg complex resides on a crystallographic inversion centre and each Hg atom is coordinated to four S atoms from the dithiocarbamate moiety. One dithiocarbamate ligand acts as chelating ligand while the other acts as chelating bridging ligand between two Hg atoms, resulting in a dinuclear eight-member ring. The course of the thermal degradation of the complexes has been investigated using thermogravimetric and differential thermal analyses techniques. Thermogravimetric analysis of the complexes show a single weight loss to give MS (M = Zn, Cd, Hg) indicating that they might be useful as single source precursors for the synthesis of MS nanoparticles and thin films. PMID:21673933

  8. Surface studies on bimetallic thiocyanate ligand based single crystals of MnHg(SCN) 4, CdHg(SCN) 4 and ZnCd(SCN) 4

    NASA Astrophysics Data System (ADS)

    Rajesh Kumar, T.; Jeyasekaran, R.; Ravi Kumar, S. M.; Vimalan, M.; Sagayaraj, P.

    2010-12-01

    Bimetallic SCN ligand based single crystals of manganese mercury thiocyanate (MMTC), cadmium mercury thiocyanate (CMTC) and zinc cadmium thiocyanate (ZCTC) are grown by slow solvent evaporation technique. The growth mechanism and surface features are investigated by optical microscopic techniques such as scanning electron microscopy (SEM) and atomic force microscopy (AFM). The laser induced surface damage measurements were carried out using a Q-switched Nd:YAG laser at 1064 nm with laser beam of 1.0 Hz and pulse duration 25 ps. The laser damage threshold values of MMTC, CMTC and ZCTC are found to be 15.9, 22.9 and 19.7 GW/cm 2, respectively. The SEM analysis of MMTC reveals the formation of elongated dendrite growth pattern caused by the fluctuations of Mn and Hg metal ligands when thiocyanate (SCN) bridges them. The etching study indicates the occurrence of different types of etch pit patterns like terraced triangles, pillars, pyramids and rods. The AFM images confirm the formation of three major hillocks with cavities in MMTC. The measured roughness values for CMTC crystal are very much lower than that of MMTC.

  9. μSR study on multi-layered HgBa 2Ca 4Cu 5O y (Hg-1245) superconductor

    NASA Astrophysics Data System (ADS)

    Tokiwa, K.; Ito, S.; Okumoto, H.; Higemoto, W.; Nishiyama, K.; Iyo, A.; Tanaka, Y.; Watanabe, T.

    2003-05-01

    We have carried out zero-field muon spin relaxation (ZF-μSR) measurements in multi-layered HgBa2Ca4Cu5Oy (Hg-1245) superconductor with Tc of 108 K. The variation of ZF-μSR time spectra from Gaussian-type to exponential-type behavior was observed with decreasing temperature below 60 K and the muon precessions were also observed below 45 K. These results indicate the appearance of a static magnetic order of Cu moments at muon sites below Tc. Compared with the results of NMR measurements, they suggest that this magnetic order is caused in three under-doped inner planes of five CuO2 planes in Hg-1245.

  10. First-principles study of HgTe/CdTe heterostructures under perturbations preserving time-reversal symmetry

    NASA Astrophysics Data System (ADS)

    Anversa, Jonas; Piquini, Paulo; Fazzio, Adalberto; Schmidt, Tome M.

    2014-11-01

    The observation of the quantum spin Hall effect without the need of an external magnetic field in HgTe/CdTe heterostructures triggered the study of materials exhibiting persistent spin-polarized electronic currents at their interfaces. These Dirac-like spin states are predicted to be topologically protected against perturbations preserving time-reversal symmetry. However, nonmagnetic (time-reversal preserving) perturbations will certainly affect these interface states. In this work, the density functional theory is used to characterize the topologically protected states of the (001) HgTe/CdTe heterostructure as well as to understand the influence of external adiabatic parameters as pressure and electric fields on these states. The intrasite Hubbard U term is seen to be important to correctly describe the HgTe bulk band structure. It is shown that, differently from the three-dimensional topological insulators, the HgTe/CdTe interface states present fully in-plane Rashba-like spin texture. Further, biaxial external pressures and electric fields perpendicular to the interfaces are seen to change the energetics and dispersion of the protected states, modifying the energy ordering of the crossing of the polarized interface states inside the band structure, and altering their Fermi velocities while not changing the topological quantum phase. These adiabatic variables can then be used to tune the topologically protected states with respect to the Fermi level.

  11. A comparative DFT study of the adsorption of H2O molecules at Bi, Hg, and Ga surfaces

    NASA Astrophysics Data System (ADS)

    Ivaništšev, Vladislav; Nazmutdinov, Renat R.; Lust, Enn

    2013-03-01

    Adsorption of a H2O molecule on Bi, Ga and Hg electrode surfaces is studied in the framework of cluster model at the density functional theory (DFT) level. At bismuth(111) single crystal plane the hollow site is energetically more preferable for the H2O adsorption (- 31.1 kJ mol- 1), while the adsorption at top site of Hg and Ga metal surfaces is confirmed to be energetically the most preferable (- 35.6 and - 24.7 kJ mol- 1, respectively). The calculations for Bi(111), Hg, and Ga are further extended to include the effect of external electrical field, and data analysis is completed with the help of the mean field approximation in order to model adsorbed water behaviour in the H2O molecules' bilayer. An associate of 13 H2O molecules is modelled in order to address the influence of lateral interactions in a water bilayer. The Ga surface is argued to be more hydrophilic than the Bi(111) and Hg surfaces. Despite the weaker adsorption energy of a single H2O molecule at the Ga surface, water molecules at the Ga/water interface are additionally stabilized by stronger hydrogen bonds. We stress the important role of the H2O bilayer at a metal electrode surface, which depends on the atomic corrugation of a metal surface.

  12. Theoretical study of heavy metal Cd, Cu, Hg, and Ni(II) adsorption on the kaolinite(0 0 1) surface

    NASA Astrophysics Data System (ADS)

    Zhao, Jian; He, Man-Chao

    2014-10-01

    Heavy metal pollution is currently of great concern because it has been recognized as a potential threat to air, water, and soil. Adsorption was one of the most popular methods for the removal of heavy metal. The adsorption of heavy metal Cd, Cu, Hg, and Ni(II) atoms on the hydroxylated (0 0 1) surface of kaolinite was investigated using density-functional theory within the generalized gradient approximation and a supercell approach. The coverage dependence of the adsorption structures and energetics were systematically studied for a wide range of coverage Θ [from 0.11 to 1.0 monolayers (ML)] and adsorption sites. The most stable among all possible adsorption sites for Cd(II) atom was the two-fold bridge site followed by the one-fold top site, and the top site was the most favorite adsorption site for Cu and Ni(II) atoms, while the three-fold hollow site was the most stable adsorption site for Hg(II) atom followed by the two-fold bridge site. The adsorption energy increases with the coverage for Cd, Cu, and Hg(II) atoms, thus indicating the higher stability of surface adsorption and a tendency to the formation of adsorbate islands (clusters) with increasing the coverage. However, the adsorption energy of Ni(II) atoms decreases when increasing the coverage. The adsorption capabilities of the kaolinite clay for the heavy metal atoms were in the order of Ni > Cu > Cd > Hg(II). The other properties of the Cd, Cu, Hg, and Ni(II)/kaolinite(0 0 1) system including the different charge distribution, the lattice relaxation, and the electronic density of states were also studied and discussed in detail.

  13. PILOT STUDY: CCQM-P39.1: As, Hg, Pb, Se and methylmercury in salmon

    NASA Astrophysics Data System (ADS)

    Aregbe, Y.; Taylor, P. D. P.

    2006-01-01

    CCQM-P39.1 was organized as a follow-up pilot study in parallel to the key comparison CCQM-K43 after the previous pilot study on tuna fish. CCQM-P39.1 was an activity of the Inorganic Analysis Working Group (IAWG) of CCQM and was coordinated by the Joint Research Centre-Institute for Reference Materials and Measurements (IRMM, Geel, Belgium) of the European Commission (EC). In CCQM-P39.1 the amount contents of As, Hg, Pb, Se and methylmercury (CH3Hg) in salmon (muscle and skin) were the measurands under investigation. Besides the national metrology institutes (NMIs) also non-IAWG members, expert laboratories for mercury and methylmercury measurements, were invited to participate in this pilot study. Results were reported by six IAWG members and six expert laboratories. During the CCQM-IAWG autumn meeting in Berlin, October 2005, it was agreed that in CCQM-K43 the KCRV is calculated as the mixture model median (MM-median) of all reported results. Therefore in CCQM-P39.1 the reported results are presented graphically with the KCRV from CCQM-K43. The reported results of the IAWG members fall within a range of +/-4% for arsenic and lead relative to the CCQM-K43 KCRV. For mercury, the spread was +/-2%, but one IAWG member reported a very large uncertainty on the measurement result. For selenium the spread of IAGW members is +/-2% deviation from the CCQM-K43 KCRV. Including the reported results from the invited expert laboratories, the spread of results increased for arsenic, lead and mercury to +/-8%. The reported results including the experts fall within a range of +/-20% for selenium and +/-30% for methylmercury. The methods applied were isotope dilution mass spectrometry (IDMS) using sector field or quadrupole inductively coupled plasma-mass spectrometry (ICP-MS), external calibration or standard addition using ICP-MS, atomic absorption spectrometry (AAS), atomic fluorescence spectrometry (AFS), atomic emission detection (AED) and electron capture detection (ECD

  14. PILOT STUDY: CCQM-P39: As, Hg, Pb, Se and methylmercury in tuna fish

    NASA Astrophysics Data System (ADS)

    Aregbe, Y.; Quétel, C.; Taylor, P. D. P.

    2004-01-01

    CCQM-P39 was an activity of the Inorganic Analysis Working Group (IAWG) of CCQM and was organised by the Institute for Reference Materials and Measurements (IRMM, Geel, Belgium) of the European Commission (EC). In CCQM-P39 the amount contents of As, Hg, Pb, Se and methylmercury (CH3Hg) in tuna fish muscle were the measurands under investigation. Besides the National Metrology Institutes (NMIs) who are IAWG members, non-IAWG members, expert laboratories for mercury and methylmercury measurements, were also invited to participate in this pilot study. Finally, results were reported by 13 NMIs and 8 expert laboratories. The results of the IAWG members for arsenic and selenium fall within a range of +/-10% with respect to the mixture model median (MM-median). For lead, the spread was within 2% and for mercury within 4% deviation from the MM-median. Also, for methlymercury the majority of the participating NMIs reported results within 4% deviation from the MM-median. Including the reported results from the invited expert laboratories, the spread of results increased for arsenic, lead, selenium and methlymercury up to 20%-40%. Except for mercury, for this analyte the spread of all the reported results of the IAWG members and the invited expert laboratories was within 4%. The methods applied were isotope dilution mass spectrometry (IDMS) using sector field or quadrupole inductively coupled plasma mass spectrometry (ICP-MS), external calibration using time-of-flight MS, atomic absorption spectrometry (AAS) or atomic fluorescence spectrometry (AFS). Instrumental neutron activation analysis (INAA) and k0-neutron activation analysis (k0-NAA) were also used as analytical techniques. Each of the five analytes under investigation was measured with at least three of these analytical techniques. IAEA reported two results for arsenic, lead and selenium. They were measured with ICP-MS and AAS, respectively. This report presents the participants’ results in CCQM-P39 for all analytes

  15. Electrical and Optical Studies of Defect Structure of HgCdTe Films Grown by Molecular Beam Epitaxy

    NASA Astrophysics Data System (ADS)

    Świątek, Z.; Ozga, P.; Izhnin, I. I.; Fitsych, E. I.; Voitsekhovskii, A. V.; Korotaev, A. G.; Mynbaev, K. D.; Varavin, V. S.; Dvoretsky, S. A.; Mikhailov, N. N.; Yakushev, M. V.; Bonchyk, A. Yu.; Savytsky, H. V.

    2016-07-01

    Electrical and optical studies of defect structure of HgCdTe films grown by molecular beam epitaxy (MBE) are performed. It is shown that the peculiarity of these films is the presence of neutral defects formed at the growth stage and inherent to the material grown by MBE. It is assumed that these neutral defects are the Te nanocomplexes. Under ion milling, they are activated by mercury interstitials and form the donor centers with the concentration of 1017 cm-3, which makes it possible to detect such defects by measurements of electrical parameters of the material. Under doping of HgCdTe with arsenic using high temperature cracking, the As2 dimers are present in the arsenic flow and block the neutral Te nanocomplexes to form donor As2Te3 complexes. The results of electrical studies are compared with the results of studies carried out by micro-Raman spectroscopy.

  16. Comparative study of the trophic transfer of two mercury compounds--HgCl/sub 2/ and CH/sub 3/HgCl--between Chlorella vulgaris and Daphnia magna. Influence of temperature

    SciTech Connect

    Baudou, A.; Ribeyre, F.

    1981-12-01

    A comparative study is presented of the transfer of HgCl/sub 2/ and CH/sub 3/HgCl between a species representative of the ''producer'' level -- Chlorella vulgaris -- and a primary consumer -- Daphnia magna. The experiment was carried out at two temperatures, 10 and 18/sup 0/C, and the concentration of metal in the environment was 1 ..mu..g.l/sup -1/ (1 ppb). Results seem to indicate that the two contaminants, which are first introduced into the environment and then fixed by the unicellular algae, retain their specific property of crossing the digestive barrier of the consumer link.

  17. Study to improve the low frequency noise characteristics of (Hg,Cd)Te detectors

    NASA Technical Reports Server (NTRS)

    Broudy, R. M.

    1973-01-01

    Efforts made to identify and reduce the sources of l/f noise in 15 micron n-type (Hg,Cd)Te detectors operating at 77 K are reported. The investigation covered: evaluation of the influence of material properties and detector processing techniques, determination of the relative importance of surfaces, volumes, regions, and contracts, and generation of theoretical models for guidance of the experimental work.

  18. Parametric Study Of A Ceramic-Fiber/Metal-Matrix Composite

    NASA Technical Reports Server (NTRS)

    Murthy, P. L. N.; Hopkins, D. A.; Chamis, C. C.

    1992-01-01

    Report describes computer-model parametric study of effects of degradation of constituent materials upon mechanical properties of ceramic-fiber/metal-matrix composite material. Contributes to understanding of weakening effects of large changes in temperature and mechanical stresses in fabrication and use. Concerned mainly with influences of in situ fiber and matrix properties upon behavior of composite. Particular attention given to influence of in situ matrix strength and influence of interphase degradation.

  19. Studies of fiber-matrix adhesion on compression strength

    NASA Technical Reports Server (NTRS)

    Bascom, Willard D.; Nairn, John A.; Boll, D. J.

    1991-01-01

    A study was initiated on the effect of the matrix polymer and the fiber matrix bond strength of carbon fiber polymer matrix composites. The work includes tests with micro-composites, single ply composites, laminates, and multi-axial loaded cylinders. The results obtained thus far indicate that weak fiber-matrix adhesion dramatically reduces 0 degree compression strength. Evidence is also presented that the flaws in the carbon fiber that govern compression strength differ from those that determine fiber tensile strength. Examination of post-failure damage in the single ply tests indicates kink banding at the crack tip.

  20. X-ray study of the anomalous thermal hystereses of the modulation wavevectors in Cs2HgCl4

    NASA Astrophysics Data System (ADS)

    Bagautdinov, Bagautdin; Shaw, Zachery; Orlov, Andrii; Aliev, Marat A.

    2016-05-01

    A rich sequence of structural modulations in Cs2HgCl4 as a function of temperature was studied by means of X-ray diffraction. Accurate satellite-position measurements on the cooling and heating paths of the crystal revealed abnormal thermal hystereses for incommensurate phases and coexistences of neighboring commensurate phases. A well-defined X-ray picture of the a-axis modulated phases in the range of 221-184 K were observed on the heating path, while the c-axis modulated phases existing below 184 K were definitely detected on the cooling path. The proper conditions for a precise phase diagram of Cs2HgCl4 can be correlated with relatively defect-free transformations of a-axis modulations at heating and of c-axis modulations at cooling. The peculiarity of Cs2HgCl4 to switch modulation direction among the a- and c-axes at 184 K allows us deliberately accumulate and thus control a majority of mobile defects on the mutually perpendicular (100) or (001) planes by possessing crystal within temperature domain of a- or c-axes modulations, respectively.

  1. Synchrotron X-ray study reveals oxygen chains in HgBa2CuO4+δ

    NASA Astrophysics Data System (ADS)

    Tabis, Wojciech

    2012-02-01

    X-ray scattering work shows that the double-layer high-Tc superconductors YBa2Cu3O8+d and Bi2Sr2CaCu2O6+δ are intrinsically inhomogeneous [1-3], with short-range lattice modulations driven by oxygen dopants. HgBa2CuO4+δ(Hg1201) has a simpler (tetragonal) structure and the highest Tc (at optimal doping) among all single-layer cuprates. It is thus a very good candidate system to address the issue of charge modulations. Using synchrotron X-ray scattering and high-quality single crystals, we have observed a short-range lattice modulations in Hg1201. Careful analysis of the diffuse intensity pattern, and a study of the doping and temperature dependence, point toward the formation of local one-dimensional order in the form of uncorrelated oxygen chains in the charge-reservoir layer. The chains exist at intermediate and high doping, form along [100], and have typical lengths of 15-30 lattice constants [4]. *Z. Islam et al. PRL 93 157008 (2004) *J. Strempfer et al. PRL 93, 157007 (2004) *J. P. Castellan et al. PRB 73, 174505 (2006) *G. Chabot-Couture, W. Tabis, J. N. Hancock Z. Islam, L. Lu, G. Yu, Y. Li, X. Zhao, Y. Ren, A. Mehta, M. Greven, (unpublished)

  2. Dissolved Organic Matter Enhances Hg Bioavailability to a Hg-Methylating Bacterium Under Mildly Sulfidic Conditions

    NASA Astrophysics Data System (ADS)

    Graham, A. M.; Gilmour, C. C.

    2011-12-01

    Field studies have demonstrated a strong linkage between dissolved organic matter (DOM) quantity and quality and in-situ methylmercury (MeHg) production. The biogeochemical basis for these field observations is unknown however. Here, we investigate the roles of DOM and sulfide in controlling Hg bioavailability to the Hg-methylating bacterium Desulfovibrio desulfuricans ND132 in short-term washed cell assays. At environmentally relevant Hg/DOM ratios (2-4300 ng Hg/mg DOM), MeHg production increased linearly with increasing Suwannee River humic acid (SRHA) concentration, even in the presence of sulfide concentrations (5-10 μM) sufficient to outcompete SRHA for inorganic Hg. The DOM-dependent enhancement in Hg-methylation cannot be attributed to an enhancement of ND132 metabolic activity or alteration of Hg sorption to cells or bottle walls. Equilibrium speciation calculations indicated that cell suspensions were supersaturated with respect to metacinnabar (β-HgS(s)) and that Hg-DOM thiol complexes were relatively minor species. Notably, SRHA addition had no effect on Hg methylation in solutions where Hg-cysteine species predominated and β-HgS(s) precipitation was not predicted. We hypothesize that DOM enhances Hg-methylation by stabilizing HgS(s) colloids or nanoparticles against aggregation and/or by reducing the crystallinty of HgS(s) particles, and that such HgS(s) colloids are bioavailable to Hg-methylating bacteria. Ongoing work in the laboratory is evaluating the role of DOM character (size, aromaticity, reduced S content, etc.) in controlling the extent of the enhancement in MeHg production. These findings highlight the limits of equilibrium speciation approaches to predicting Hg bioavailability to methylating bacteria given the demonstrated significance of Hg-DOM-sulfide interactions in the anoxic environments where methylation occurs. Our laboratory experiments provide additional insight into the role that DOM plays in determining spatial and temporal

  3. Relativistic coupled cluster study of diatomic compounds of Hg, Cn, and Fl

    SciTech Connect

    Borschevsky, A.; Pershina, V.; Eliav, E.; Kaldor, U.

    2014-08-28

    The structure and energetics of eight diatomic heavy-atom molecules are presented. These include the species MAu, M{sub 2}, and MHg, with M standing for the Hg, Cn (element 112), and Fl (element 114) atoms. The infinite-order relativistic 2-component Hamiltonian, known to closely reproduce 4-component results at lower computational cost, is used as framework. High-accuracy treatment of correlation is achieved by using the coupled cluster scheme with single, double, and perturbative triple excitations in large converged basis sets. The calculated interatomic separation and bond energy of Hg{sub 2}, the only compound with known experimental data, are in good agreement with measurements. The binding of Fl to Au is stronger than that of Cn, predicting stronger adsorption on gold surfaces. The bond in the M{sub 2} species is strongest for Fl{sub 2}, being of chemical nature; weaker bonds appear in Cn{sub 2} and Hg{sub 2}, which are bound by van der Waals interactions, with the former bound more strongly due to the smaller van der Waals radius. The same set of calculations was also performed using the relativistic density functional theory approach, in order to test the performance of the latter for these weakly bound systems with respect to the more accurate coupled cluster calculations. It was found that for the MAu species the B3LYP functional provides better agreement with the coupled cluster results than the B88/P86 functional. However, for the M{sub 2} and the MHg molecules, B3LYP tends to underestimate the binding energies.

  4. Relativistic coupled cluster study of diatomic compounds of Hg, Cn, and Fl.

    PubMed

    Borschevsky, A; Pershina, V; Eliav, E; Kaldor, U

    2014-08-28

    The structure and energetics of eight diatomic heavy-atom molecules are presented. These include the species MAu, M2, and MHg, with M standing for the Hg, Cn (element 112), and Fl (element 114) atoms. The infinite-order relativistic 2-component Hamiltonian, known to closely reproduce 4-component results at lower computational cost, is used as framework. High-accuracy treatment of correlation is achieved by using the coupled cluster scheme with single, double, and perturbative triple excitations in large converged basis sets. The calculated interatomic separation and bond energy of Hg2, the only compound with known experimental data, are in good agreement with measurements. The binding of Fl to Au is stronger than that of Cn, predicting stronger adsorption on gold surfaces. The bond in the M2 species is strongest for Fl2, being of chemical nature; weaker bonds appear in Cn2 and Hg2, which are bound by van der Waals interactions, with the former bound more strongly due to the smaller van der Waals radius. The same set of calculations was also performed using the relativistic density functional theory approach, in order to test the performance of the latter for these weakly bound systems with respect to the more accurate coupled cluster calculations. It was found that for the MAu species the B3LYP functional provides better agreement with the coupled cluster results than the B88/P86 functional. However, for the M2 and the MHg molecules, B3LYP tends to underestimate the binding energies. PMID:25173008

  5. Polymer matrix and graphite fiber interface study

    NASA Technical Reports Server (NTRS)

    Adams, D. F.; Zimmerman, R. S.; Odom, E. M.

    1985-01-01

    Hercules AS4 graphite fiber, unsized, or with EPON 828, PVA, or polysulfone sizing, was combined with three different polymer matrices. These included Hercules 3501-6 epoxy, Hercules 4001 bismaleimide, and Hexcel F155 rubber toughened epoxy. Unidirectional composites in all twelve combinations were fabricated and tested in transverse tension and axial compression. Quasi-isotropic laminates were tested in axial tension and compression, flexure, interlaminar shear, and tensile impact. All tests were conducted at both room temperature, dry and elevated temperature, and wet conditions. Single fiber pullout testing was also performed. Extensive scanning electron microphotographs of fracture surfaces are included, along with photographs of single fiber pullout failures. Analytical/experimental correlations are presented, based on the results of a finite element micromechanics analysis. Correlations between matrix type, fiber sizing, hygrothermal environment, and loading mode are presented. Results indicate that the various composite properties were only moderately influenced by the fiber sizings utilized.

  6. HgL(3) XANES Study of Mercury Methylation in Shredded Eichhornia Crassipes

    SciTech Connect

    Rajan, M.; Darrow, J.; Hua, M.; Barnett, B.; Mendoza, M.; Greenfield, B.K.; Andrews, J.C.

    2009-05-21

    Eichhornia crassipes (water hyacinth) is a non-native plant found in abundance in the Sacramento-San Joaquin River Delta (hereafter called Delta). This species has become a problem, clogging waterways and wetlands. Water hyacinth are also known to accumulate mercury. Recent attempts to curb its proliferation have included shredding with specialized boats. The purpose of this research is to better understand the ability of water hyacinth to phytoremediate mercury and to determine the effect of shredding and anoxic conditions on mercury speciation in plant tissue. In the field assessment, total mercury levels in sediment from the Dow Wetlands in the Delta were found to be 0.273 {+-} 0.070 ppm Hg, and levels in hyacinth roots and shoots from this site were 1.17 {+-} 0.08 ppm and 1.03 {+-} 0.52 ppm, respectively, indicating bioaccumulation of mercury. Plant samples collected at this site were also grown in nutrient solution with 1 ppm HgCl{sub 2} under (1) aerobic conditions, (2) anaerobic conditions, and (3) with shredded plant material only. The greatest accumulation was found in the roots of whole plants. Plants grown in these conditions were also analyzed at Stanford Synchrotron Radiation Laboratory using Hg L{sub 3} X-ray Absorption Near Edge Spectroscopy (XANES), a method to examine speciation that is element-specific and noninvasive. Least-squares fitting of the XANES data to methylated and inorganic mercury(II) model compounds revealed that in plants grown live and aerobically, 5 {+-} 3% of the mercury was in the form of methylmercury, in a form similar to methylmercury cysteine. This percentage increased to 16 {+-} 4% in live plants grown anaerobically and to 22 {+-} 6% in shredded anaerobic plants. We conclude that shredding of the hyacinth plants and, in fact, subjection of plants to anaerobic conditions (e.g., as in normal decay, or in crowded growth conditions) increases mercury methylation. Mechanical removal of the entire plant is significantly more

  7. Stable isotope (N, C, Hg) study of methylmercury sources and trophic transfer in the northern gulf of Mexico.

    PubMed

    Senn, David B; Chesney, Edward J; Blum, Joel D; Bank, Michael S; Maage, Amund; Shine, James P

    2010-03-01

    We combined N, C, and Hg stable isotope measurements to identify the most important factors that influence MeHg accumulation in fish from the northern Gulf of Mexico (nGOM), and to determine if coastal species residing in the Mississippi River (MR) plume and migratory oceanic species derive their MeHg from the same, or different, sources. In six coastal species and two oceanic species (blackfin and yellowfin tuna), trophic position as measured by delta(15)N explained most of the variance in log[MeHg] (r(2) approximately 0.8), but coastal species and tuna fell along distinct, nearly parallel lines with significantly different intercepts. The tuna also had significantly higher delta(202)Hg (0.2-0.5 per thousand) and Delta(201)Hg ( approximately 1.5 per thousand) than the coastal fish (delta(202)Hg = 0 to -1.0 per thousand; Delta(201)Hg approximately 0.4 per thousand). The observations can be best explained by largely disconnected food webs rooted in different baseline delta(15)N signatures (MR-plume vs oceanic) and isotopically distinct MeHg sources, with oceanic MeHg having undergone substantial photodegradation ( approximately 50%) before entering the base of the food web. Given the MR's large, productive footprint in the nGOM and the potential for exporting prey and MeHg to the adjacent oligotrophic GOM, the disconnected food webs and different MeHg sources are consistent with recent evidence in other systems of important oceanic MeHg sources. PMID:20104887

  8. Experimental study on Hg0 removal from flue gas over columnar MnOx-CeO2/activated coke

    NASA Astrophysics Data System (ADS)

    Xie, Yine; Li, Caiting; Zhao, Lingkui; Zhang, Jie; Zeng, Guangming; Zhang, Xunan; Zhang, Wei; Tao, Shasha

    2015-04-01

    Mn-Ce mixed oxides supported on commercial columnar activated coke (MnCe/AC) were employed to remove elemental mercury (Hg0) at low temperatures (100-250 °C) without the assistance of HCl in flue gas. The samples were characterized by X-ray diffraction (XRD), Brunauer-Emmett-Teller (BET), X-ray photoelectron spectroscopy (XPS) and temperature programmed desorption (TPD). Effects of some factors, including Mn-Ce loading values, active component, reaction temperatures and flue gas components (O2, SO2, NO, H2O), on Hg0 removal efficiency were investigated. Results indicated that the optimal Mn-Ce loading value and reaction temperature were 6% and 190 °C, respectively. Considerable high Hg0 removal efficiency (>90%) can be obtained over MnCe6/AC under both N2/O2 atmosphere and simulated flue gas atmosphere at 190 °C. Besides, it was observed that O2 and NO exerted a promotional effect on Hg0 removal, H2O exhibited a suppressive effect, and SO2 hindered Hg0 removal seriously when in the absence of O2. Furthermore, the XPS spectra of Hg 4f and Hg-TPD results showed that the captured mercury were existed as Hg0 and HgO on the MnCe6/AC, and HgO was the major species, which illustrated that adsorption and catalytic oxidation process were included for Hg0 removal over MnCe6/AC, and catalytic oxidation played the critical role. What's more, both lattice oxygen and chemisorbed oxygen or OH groups on MnCe6/AC contributed to Hg0 oxidation. MnCe6/AC, which exhibited excellent performance on Hg0 removal in the absence of HCl, appeared to be promising in industrial application, especially for low-rank coal fired flue gas.

  9. Evidence to Maintain the Systolic Blood Pressure Treatment Threshold at 140 mm Hg for Stroke Prevention: The Northern Manhattan Study.

    PubMed

    Dong, Chuanhui; Della-Morte, David; Rundek, Tatjana; Wright, Clinton B; Elkind, Mitchell S V; Sacco, Ralph L

    2016-03-01

    In 2014, the Eighth Joint National Committee revised the target maximum systolic blood pressure (SBP) from 140 to 150 mm Hg in patients aged ≥60 years without diabetes mellitus or chronic kidney disease. The evidence from cohort studies supporting this change was sparse, particularly among US minority populations. In the Northern Manhattan Study, 1750 participants aged ≥60 years and free of stroke, diabetes mellitus, and chronic kidney disease had SBP measured at baseline and were annually followed up for incident stroke. Mean age at baseline was 72±8 years, 63% were women, 48% Hispanic, 25% non-Hispanic white, and 25% non-Hispanic black. Among all participants, 40% were on antihypertensive medications; 43% had SBP <140 mm Hg, 20% had 140 to 149 mm Hg, and 37% had ≥150 mm Hg. Over a median follow-up of 13 years, 182 participants developed stroke. The crude stroke incidence was greater among individuals with SBP≥150 mm Hg (10.8 per 1000 person-years) and SBP 140 to 149 (12.3) than among those with SBP<140 (6.2). After adjusting for demographics, vascular risk factors, diastolic BP, and medication use, participants with SBP 140 to 149 mm Hg had an increased risk of stroke (hazard ratio, 1.7; 95% confidence interval, 1.2-2.6) compared with those with SBP <140 mm Hg. The increased stroke risk was most notable among Hispanics and non-Hispanic blacks. Raising the SBP threshold from 140 to 150 mm Hg as a new target for hypertension treatment in older individuals without diabetes mellitus or chronic kidney disease could have a detrimental effect on stroke risk reduction, especially among minority US populations. PMID:26831192

  10. Conformational isomerism of pyridoxal. Infrared matrix isolation and theoretical studies

    NASA Astrophysics Data System (ADS)

    Kwiatek, Anna; Mielke, Zofia

    2015-01-01

    A combined matrix isolation FTIR and theoretical DFT/B3LYP/6-311++G(2p,2d) study of pyridoxal was performed. The calculations resulted in five stable PLHB conformers stabilized by intramolecular Osbnd H⋯O bonding between phenolic OH and carbonyl Cdbnd O groups and another thirteen conformers in which OH or/and aldehyde groups are rotated by 180° around CO or/and CC bonds leading, respectively, to formation of PLO, PLA and PLOA conformers. The analysis of the spectra of the as-deposited matrix indicated that two most stable PLHB1 and PLHB2 conformers with intramolecular hydrogen bond are present in the matrix. The exposure of the PL/Ar matrix to mercury lamp radiation (λ > 345 nm) induced conformational change of PLHB isomers to PLOA ones.

  11. Conformational isomerism of pyridoxal. Infrared matrix isolation and theoretical studies.

    PubMed

    Kwiatek, Anna; Mielke, Zofia

    2015-01-25

    A combined matrix isolation FTIR and theoretical DFT/B3LYP/6-311++G(2p,2d) study of pyridoxal was performed. The calculations resulted in five stable PLHB conformers stabilized by intramolecular O-H⋯O bonding between phenolic OH and carbonyl C=O groups and another thirteen conformers in which OH or/and aldehyde groups are rotated by 180° around CO or/and CC bonds leading, respectively, to formation of PLO, PLA and PLOA conformers. The analysis of the spectra of the as-deposited matrix indicated that two most stable PLHB1 and PLHB2 conformers with intramolecular hydrogen bond are present in the matrix. The exposure of the PL/Ar matrix to mercury lamp radiation (λ>345 nm) induced conformational change of PLHB isomers to PLOA ones. PMID:25173527

  12. Kinetic and thermodynamic studies of Hg(II) adsorption onto MCM-41 modified by ZnCl2

    NASA Astrophysics Data System (ADS)

    Raji, Foad; Pakizeh, Majid

    2014-05-01

    Kinetics and thermodynamics of mercury ions sorption onto ZnCl2-MCM-41 sorbent were studied. Several rate models in the form of two main classes of mathematic kinetic models (adsorption reaction models and adsorption diffusion models) were investigated. Pseudo-first-order, pseudo-second-order, Elovich, film and intraparticle diffusion models were used to analyze the kinetic data. Results showed that the pseudo-second order model can well describe the adsorption kinetic data. The thermodynamic parameters, such as Gibb's free energy change (ΔG°), standard enthalpy change (ΔH°) and standard entropy change (ΔS°) were also evaluated. Negative value of free energy at temperature range of 20-55 °C, indicates the spontaneous nature of Hg(II) sorption by ZnCl2-MCM-41 sorbent. The adsorption capacity which was found to decrease with temperature showed the exothermic nature of the mercury sorption process (ΔH° = -49.4 kJ mol-1). The negative ΔS° value (-148.9 J mol-1 K-1) revealed a decrease in the randomness at the solid/solution interface and also indicated the fast adsorption of the Hg(II) onto active sites.

  13. Study of HgCdTe/CdTe interface structure grown by metal-organic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Ma, Ke J.; Yu, Zhen Z.; Yanh, Jian R.; Shen, Shou Z.; He, Jin; Chen, Wei M.; Song, Xiangyun

    1991-11-01

    The interface of HgCdTe/CdTe thin film growth by MOCVD were investigated by high resolution electron microscope (HREM). It is shown that there is no monolayer abrupt interface between HgCdTe and CdTe films. The interface of HgCdTe/CdTe contains a lot of small and random distributed disorder regions. The disorder areas can be transformed into order one under long time electron beam irradiation.

  14. An anion induced multisignaling probe for Hg(2+) and its application for fish kidney and liver tissue imaging studies.

    PubMed

    Mandal, Sandip; Banerjee, Arnab; Ghosh, Debasree; Mandal, Dipak Kumar; Safin, Damir A; Babashkina, Maria G; Robeyns, Koen; Mitoraj, Mariusz P; Kubisiak, Piotr; Garcia, Yann; Das, Debasis

    2015-08-01

    3',6'-Bis(diethylamino)-2-(pyridin-2-ylmethyl)spiro[isoindoline-1,9'-xanthen]-3-one () was synthesized for the selective fluorescence and colorimetric recognition of Hg(2+) at pH 6.0. In addition, was useful for imaging Hg(2+) in fish kidney and liver tissues using a fluorescence microscope. Spirolactam ring opening of for Hg(2+) recognition is strongly influenced by the nature of the mercury salt and found to be NO3(-)-induced. Other mercury salts such as HgCl2, Hg(CH3COO)2 and Hg(ClO4)2 failed to induce fluorescence and colorimetric response of under the same experimental conditions. For instance, the former salt does not exhibit spirolactam ring opening but forms a new ionic compound (H3L)2[Hg6Cl18]·2H2O (), whose structure has been elucidated by single crystal X-ray diffraction. This might be explained by (1) the higher covalent nature of Hg(2+) and, hence, the lower acidity of the metal center and its inability to induce the ring opening reaction, and (2) the bulky anion, in the case of Hg(ClO4)2, which is also ionic, faces steric hindrance to accommodate within the N(Et)2 group upon spirolactam ring opening. PMID:26110738

  15. Modification-free and N-acetyl-L-cysteine-induced colorimetric response of AuNPs: A mechanistic study and sensitive Hg(2+) detection.

    PubMed

    Tang, Jie; Wu, Peng; Hou, Xiandeng; Xu, Kailai

    2016-10-01

    A facile yet sensitive and selective method was proposed for Hg(2+) detection based on N-acetyl-L-cysteine(NAC)-induced colorimetric response of AuNPs. The proposed method can be easily performed by introducing the premixing of NAC and Hg(2+) into as-prepared citrate-capped AuNPs solution. A combination of experimental and theoretical studies was applied to illustrate the mechanism of this AuNPs colorimetric system. The strong interaction of NAC and AuNPs through Au-S bond could lead to the aggregation of AuNPs, but the formation of NAC-Hg-NAC complex decreased the affinity between NAC and AuNPs and resulted in an anti-aggregation effect. Therefore, the color of the AuNPs solution would progress from purple to red with the increase of Hg(2+) concentration. The proposed method had a high sensitivity with a limit of detection of 9.9nM. Coexistent metal ions, including Cd(2+), Mn(2+), Al(3+), Ag(+), K(+), Mg(2+), Ca(2+), Cr(3+), Cu(2+), Fe(3+), Pb(2+), Ni(2+) and Zn(2+), did not interfere with the detection of Hg(2+). This method can be used to monitor Hg(2+) in tap water. PMID:27474283

  16. Defect study in molecular beam epitaxy-grown HgCdTe films with activated and unactivated arsenic

    SciTech Connect

    Izhnin, I. I.; Dvoretsky, S. A.; Mikhailov, N. N.; Varavin, V. S.; Mynbaev, K. D.; Fitsych, O. I.; Pociask-Bialy, M.; Sheregii, E.; Voitsekhovskii, A. V.

    2014-04-28

    A defect study was performed on molecular beam epitaxy-grown HgCdTe films in situ doped with arsenic. Doping was performed from either effusion cell or cracker cell, and studied were both as-grown samples and samples subjected to arsenic activation annealing. Electrical properties of the films were investigated with the use of ion milling as a means of “stirring” defects in the material. As a result of the study, it was confirmed that the most efficient incorporation of electrically active arsenic occurs at the cracking zone temperature of 700 °C. Interaction between arsenic and tellurium during the growth was observed and is discussed in the paper.

  17. Interfacial studies in fiber-reinforced thermoplastic-matrix composites

    SciTech Connect

    Brady, R.L.

    1989-01-01

    The major theme of this dissertation is structure/property relationships in fiber-reinforced thermoplastic-matrix composites. Effort has been focused on the interface: interfacial crystallization and fiber/matrix adhesion. Included are investigations on interfacial nucleation and morphology, measurement of fiber/matrix adhesion, effects of interfacial adsorption and crystallization on fiber/matrix adhesion, and composites reinforced with thermotropic liquid crystal copolyester fibers. Crystallization of a copolyester and polybutylene terephthalate with glass, carbon, or aramid fibers has been studied with regard to interfacial morphology. Techniques employed included hot-stage optical microscopy and differential scanning calorimetry. Nucleation by the fibers was found to be a general phenomenon. Morphology could be varied by changing the cooling rate. In order to better monitor fiber /matrix adhesion, a buckled plate test has been developed. The test measures transverse toughness as the parameter characterizing interfacial adhesion in unidirectional, continuous-fiber composites. The test is simple to perform yet has advantages over other interfacial evaluation techniques. The buckled plate test was found to be a sensitive measure of fiber/matrix adhesion. The buckled plate test has been used along with the transverse tensile test to examine how interfacial adsorption and crystallization affect fiber/matrix adhesion in polycarbonate/carbon fiber composites. Adsorption was found to be of primary importance in developing adhesion, while crystallization is a secondary effect. The toughness data have been fit successfully for annealing time and temperature dependence. The dependence of adsorption and transverse toughness on matrix molecular weight was found to be large, with higher molecular weights adsorbing more effectively.

  18. The MATRIX study: evaluating the data in older adults.

    PubMed

    Newman, Diane K

    2008-01-01

    In summary, the MATRIX study evaluated the use of OXY-TDS in older adults residing in community settings. Although it was a community-based study, a large segment of those studied had traits similar to those residing in long-term care settings--699 patients were aged 75 years or older; many had comorbid diseases; and many had a long history of OAB. MATRIX found that the transdermal form of oxybutynin was a safe and effective method to manage OAB in this older population. Adverse events reported were minor and local, with the most common event being local skin irritation. The transdermal formulation improved the symptoms associated with OAB and improved QOL. Although nursing home residents were not studied in MATRIX, it appears that the transdermal formulation of oxybutynin would be an agent of choice in older adults. PMID:19343887

  19. Novel bimetallic thiocyanate-bridged Cu(II)-Hg(II) compounds—synthesis, X-Ray studies and magnetic properties

    NASA Astrophysics Data System (ADS)

    Machura, B.; Świtlicka, A.; Zwoliński, P.; Mroziński, J.; Kalińska, B.; Kruszynski, R.

    2013-01-01

    Seven novel heterobimetallic Cu/Hg polymers based on thiocyanate bridges have been synthesised and characterised by means of IR, EPR, magnetic measurements and single crystal X-Ray. Three of them, [Cu(pzH)4Hg(SCN)4]n (1) [Cu(indH)4Hg(SCN)4]n (2) and [Cu(ampy)2Hg(SCN)4]n (3), have one-dimensional coordination structure. Two compounds [Cu(pzH)2Hg(SCN)4]n (4) and [Cu(abzimH)Hg(SCN)4]n (5) form two-dimensional nets, whereas the complexes [Cu(pyCN)2Hg(SCN)4]n (6) and [Cu(pyCH(OH)(OMe))2Hg(SCN)4]n (7) are three-dimensional coordination polymers. The chains of 1 are connected by the intermolecular N-H•••N hydrogen bonds to the three dimensional net. In 2 the N-H•••S hydrogen bonds link the polymeric chains to the two dimensional layer extending along crystallographic (0 0 1) plane. The polymeric chains of compound 3 are joined by the intermolecular N-H•••N and N-H•••S hydrogen bonds to the three dimensional net. The polymeric layers of 4 are connected by the intermolecular N-H•••N hydrogen bonds to the three dimensional net.

  20. Photo-induced athermal phase transitions of HgX (X = S, Se, Te) by ab initio study

    NASA Astrophysics Data System (ADS)

    Da-hua, Ren; Xin-lu, Cheng; Hong, Zhang

    2016-07-01

    Ab initio calculations of lattice constants, lattice stabilities of HgX (X = S, Se, Te) at different electronic temperatures (T e) have been performed within the density functional theory (DFT). We find that the lattice constants of HgX increase and the phonon frequencies reduce as T e increases. Especially the transverse-acoustic (TA) phonon frequencies of HgX gradually become negative with the elevation of the electron temperature. That is to say ultrafast intense laser induces lattice instabilities of HgX and athermal melting appears for the increase of laser intensity. What is more, with the X atom number increasing, the critical electronic temperatures of HgX are decreased in sequence. This result would be helpful for understanding the athermal melting processes for femtosecond laser micromachining. Project supported by the National Natural Science Foundation of China (Grant Nos. 11374217 and 11176020).

  1. Photoacoustic Spectral Study of Lanthanide Complexes Doped in Silica Matrix

    NASA Astrophysics Data System (ADS)

    Yang, Y. T.; Gao, B.; Zhang, S. Y.; Liu, X. J.

    2015-06-01

    Lanthanide phenanthroline (phen) complexes and were incorporated into a silica matrix by an ultrasonic assisted sol-gel method. In the region of ligand absorption, the photoacoustic (PA) intensity for a lanthanide complex is the same as in wet gels. Upon heat treatment at 120C, however, the PA intensity of a O-doped sample is much larger than that of a O-doped sample. The characteristic emissions of complex-doped samples were used to interpret the stability of the complex in silica matrices. The luminescence spectra are consistent with the PA results. The study indicates that phen can only coordinate with lanthanide ions in a silica matrix after a suitable heat treatment. Moreover, the covalency parameters and PA bands of f-f transionts of have been used to study the formation of the complex in a silica matrix.

  2. Optical and Electrical Studies of the Double Acceptor Levels of the Mercury Vacancies in HgCdTe

    NASA Astrophysics Data System (ADS)

    Gemain, F.; Robin, I. C.; Brochen, S.; De Vita, M.; Gravrand, O.; Lusson, A.

    2012-10-01

    Correlations between photoluminescence and temperature-dependent Hall measurements were carried out on unintentionally doped HgCdTe epilayers with cadmium composition of 32.7%. These films were grown by liquid-phase epitaxy and post-annealed under different conditions as follows: a p-type annealing was used to control the mercury vacancy concentration, and an n-type annealing under saturated mercury atmosphere was used to fill the mercury vacancies. Comparison of the results obtained by these two characterization techniques allowed us to identify the two acceptor energy levels of the mercury vacancy. Moreover, the "U-negativity" of the vacancy was evidenced: the ionized state V- is stabilized under the neutral state V0 by the dominance of the Jahn-Teller effect over Coulombic repulsion. Finally, three epilayers with different cadmium compositions were also characterized to complete this study.

  3. Study of Morphological Defects on Dual-Band HgCdTe on CdZnTe

    NASA Astrophysics Data System (ADS)

    Reddy, M.; Radford, W. A.; Lofgreen, D. D.; Olsson, K. R.; Peterson, J. M.; Johnson, S. M.

    2014-08-01

    HgCdTe dual-band epitaxial layers on lattice-matched CdZnTe substrates often have morphological defects. These defects, unlike normal void and microvoid defects, do not contain a polycrystalline core and, therefore, do not offer a good contrast for observation using optical and electron microscopes. This paper reports a way of identifying these defects by using a Nomarski optical microscopy image overlay on focused ion beam microscopy images for preparation of thin cross-sectional foils of these defects. Transmission electron microscopy was used to study the defect cross-sections to identify the origin and evolution of the morphological defects and their effect on the epitaxial layer. This paper reports cross-sectional analysis of four morphological defects of different shape and size.

  4. Cross-Sectional Study of Macrodefects in MBE Dual-Band HgCdTe on CdZnTe

    NASA Astrophysics Data System (ADS)

    Reddy, M.; Lofgreen, D. D.; Jones, K. A.; Peterson, J. M.; Radford, W. A.; Benson, J. D.; Johnson, S. M.

    2013-11-01

    HgCdTe dual-band mid-wave infrared/long-wave infrared focal-plane arrays on CdZnTe are a key component in advanced electrooptic sensor applications. Molecular beam epitaxy (MBE) has been used successfully for growth of dual-band layers on larger CdZnTe substrates. However, the macrodefect density, which is known to reduce the pixel operability and its run-to-run variation, is larger when compared with layers grown on Si substrate. This paper reports the macrodefect density versus size signature of a well-optimized MBE dual-band growth and a cross-sectional study of a macrodefect that represents the most prevalent class using focused ion beam, scanning transmission electron microscopy, and energy-dispersive x-ray spectroscopy. The results show that the macrodefect originates from a void, which in turn is associated with a pit on the CdZnTe substrate.

  5. Decellularized myocardial matrix hydrogels: In basic research and preclinical studies.

    PubMed

    Wang, Raymond M; Christman, Karen L

    2016-01-15

    A variety of decellularized materials have been developed that have demonstrated potential for treating cardiovascular diseases and improving our understanding of cardiac development. Of these biomaterials, decellularized myocardial matrix hydrogels have shown great promise for creating cellular microenvironments representative of the native cardiac tissue and treating the heart after a myocardial infarction. Decellularized myocardial matrix hydrogels derived from porcine cardiac tissue form a nanofibrous hydrogel once thermally induced at physiological temperatures. Use of isolated cardiac extracellular matrix in 2D and 3D in vitro platforms has demonstrated the capability to provide tissue specific cues for cardiac cell growth and differentiation. Testing of the myocardial matrix hydrogel as a therapy after myocardial infarction in both small and large animal models has demonstrated improved left ventricular function, increased cardiac muscle, and cellular recruitment into the treated infarct. Based on these results, steps are currently being taken to translate these hydrogels into a clinically used injectable biomaterial therapy. In this review, we will focus on the basic science and preclinical studies that have accelerated the development of decellularized myocardial matrix hydrogels into an emerging novel therapy for treating the heart after a myocardial infarction. PMID:26056717

  6. A study of the convective flow as a function of external parameters in a high-pressure metal halide discharge lamp (HgDyI3)

    NASA Astrophysics Data System (ADS)

    Hajji, S.; HadjSalah, S.; Benhalima, A.; Charrada, K.; Zissis, G.

    2016-06-01

    This paper deals with the modelling of the convection processes in metal-halide lamp discharges (HgDyI3). For this, we realized a 3D model, a steady, direct current powered and time-depending model for the solution of conservation equations relative to mass, momentum, and energy. After validation, this model was applied to the study of the effect of some parameters that have appeared on major transport phenomena of mass and energy in studying the lamp. Indeed, the electric current, the atomic ratio (Hg/Dy), and the effect of the convective transport have been studied.

  7. Trace elements profiles, notably Hg, from a preliminary study of the Apollo 15 deep-drill core.

    NASA Technical Reports Server (NTRS)

    Jovanovic, S.; Reed, G. W., Jr.

    1972-01-01

    The possible thermal gradient near the surface during a lunation is considered together with the heat flow from the interior, the physical process of Hg migration, the results from core and trench samples from previous missions, and other temperature sensitive phenomena that may help understand the processes. U, Os, and Ru concentrations in the deep drill core samples are of potential interest and are summarized in a table. The Os tends to parallel the Hg profile with depth.

  8. Thermal studies and vibrational analyses of m-methylaniline complexes of Zn(II), Cd(II) and Hg(II) bromides

    NASA Astrophysics Data System (ADS)

    Golcuk, K.; Altun, A.; Kumru, M.

    2003-06-01

    The complexes having the MBr2L2 (M: Zn, Cd and Hg; L: m-methylaniline) formulae have been prepared and characterized by their elemental analyses, thermogravimetric analyses, IR and Raman spectral studies. IR and Raman bands of the complexes have been assigned as compared with the free ligand. Coordination effects on the internal modes of m-methylaniline have been discussed. Vibrational spectra propose that the [ZnBr2(mMA)2] complex is in a tetrahedral environment around Zn(II) ion with C2v symmetry whereas Cd(II) and Hg(II) complexes have 5-coordinate polymeric bromide bridged structures.

  9. Experimental study on mechanical behavior of fiber/matrix interface in metal matrix composite

    SciTech Connect

    Wang, Q.; Chiang, F.P.

    1994-12-31

    The technique SIEM(Speckle Interferometry with Electron Microscopy) was employed to quantitatively measure the deformation on the fiber/matrix interface in SCS-6/Ti-6-4 composite at a microscale level. The displacement field within the fiber/matrix interphase zone was determined by in-situ observation with sensitivity of 0.003({micro}m). The macro-mechanical properties were compared with micro-mechanical behavior. It is shown that the strength in the interphase zone is weaker than the matrix tensile strength. The deformation process can be characterized by the uniform deformation, interface strain concentration and debond, and matrix plastic deformation.

  10. Matrix isolation as a tool for studying interstellar chemical reactions

    NASA Technical Reports Server (NTRS)

    Ball, David W.; Ortman, Bryan J.; Hauge, Robert H.; Margrave, John L.

    1989-01-01

    Since the identification of the OH radical as an interstellar species, over 50 molecular species were identified as interstellar denizens. While identification of new species appears straightforward, an explanation for their mechanisms of formation is not. Most astronomers concede that large bodies like interstellar dust grains are necessary for adsorption of molecules and their energies of reactions, but many of the mechanistic steps are unknown and speculative. It is proposed that data from matrix isolation experiments involving the reactions of refractory materials (especially C, Si, and Fe atoms and clusters) with small molecules (mainly H2, H2O, CO, CO2) are particularly applicable to explaining mechanistic details of likely interstellar chemical reactions. In many cases, matrix isolation techniques are the sole method of studying such reactions; also in many cases, complexations and bond rearrangements yield molecules never before observed. The study of these reactions thus provides a logical basis for the mechanisms of interstellar reactions. A list of reactions is presented that would simulate interstellar chemical reactions. These reactions were studied using FTIR-matrix isolation techniques.

  11. The effect of microscale pore structure on matrix diffusion—a site-specific study on tonalite

    NASA Astrophysics Data System (ADS)

    Siitari-Kauppi, M.; Lindberg, A.; Hellmuth, K. H.; Timonen, J.; Väätäinen, K.; Hartikainen, J.; Hartikainen, K.

    1997-04-01

    The matrix diffusion of non-sorbing tracers was studied in rocks from the Syyry area, Central Finland (SY1). The effect of alteration and weathering on rock matrix porosity and on the available pore space, which affects diffusivity, are discussed. The main rock type in the crystalline bedrock of Syyry is a slightly foliated, gray tonalite with mica gneiss inclusions as well as minor, more mafic inclusions. The total porosity and the spatial porosity distribution and microstructure of the rocks were investigated using infiltration of carbon- 14-methylmethacrylate, electron microscopy and Hg-porosimetry. The laboratory-scale diffusion experiments were performed using (1) the out-leaching technique of methylmethacrylate (MMA), (2) the through-diffusion of tritiated water (HTO) and chloride in the liquid phase and (3) the through-diffusion of helium in the gas phase. The results of structure investigations indicate that alteration and weathering create micrometric-scale pore apertures, visible as fissures and cracks. These migration pathways dominate in laboratory-scale diffusion experiments and result in high effective porosities and effective diffusivities. Alteration also creates spherical pores, smaller than 1 μm, especially in heavily altered biotite and plagioclase minerals. The altered mineral phases act as quasi dead-end pores hindering the diffusion of non-sorbing tracers. The heterogeneity of the matrix is increased. The heterogeneous spatial pore structure of altered and weathered rock samples causes uncertainty in the diffusion coefficients owing to an assumed homogeneous matrix in Fickian diffusion models.

  12. New adamantane-like mercury-chalcogen cages. Synthetic and multinuclear (/sup 31/P, /sup 77/Se, /sup 199/Hg) NMR study of ((. mu. -ER)/sub 6/(HgL)/sub 4/)/sup 2 +/ (E = S or Se; L = tertiary phosphine or arsine) and related species with mixed ligands

    SciTech Connect

    Dean, P.A.W.; Vittal, J.J.; Trattner, M.H.

    1987-12-16

    Reaction between HgL/sub 2/(ClO/sub 4/)/sub 2/, Hg(ER)/sub 2/, and L in a 1:3:2 ratio produces the isolable salts ((..mu..-ER)/sub 6/(HgL)/sub 4/)(ClO/sub 4/)/sub 2/ (L = PPh/sub 3/, ER = SePh, SPh, SMe, or SEt; L = AsPh/sub 3/, ER = SPh; L = PEt/sub 3/, ER = SePh or SPh). Multinuclear (/sup 31/P, /sup 77/Se, /sup 199/Hg) NMR was used to demonstrate the adamantanoid structure of the cations in these salts as well as in those with L = PPh/sub 3/ and ER = S-n-Pr, S-n-Bu, or S-n-C/sub 5/H/sub 11/, which were studied in situ. To confirm that the new cations contain the hitherto unobserved (..mu..-ER)/sub 6/Hg/sub 4/ core, several series of clusters with mixed ligands were investigated (as ClO/sub 4//sup -/ salts) by the multinuclear NMR technique also. The systems ((..mu..-ER)/sub 6/(HgL)/sub 4/)/sup 2 +/-((..mu..-ER)/sub 6/(HgL')/sub 4/)/sup 2 +/ (ER = SePh, L = PPh/sub 3/, L' = PEt/sub 3/; ER = SPh, L = PPh/sub 3/, L' = PEt/sub 3/ or AsPh/sub 3/) give the series ((..mu..-ER)/sub 6/(HgL)/sub 4-n/(HgL')/sub n/)/sup 2 +/ (n = 0-4). The related species ((..mu..-SPh)/sub 6/(HgPPh/sub 3/)/sub 4-n/(HgSbPh/sub 3/)/sub n/)/sup 2 +/ (n = 0-2 and possibly 3) were produced from Hg(PPhh/sub 3/)/sub 2/(ClO/sub 4/)/sub 2/, Hg(SPh)/sub 2/, and SbPh/sub 3/. From the notably rich /sup 31/P and /sup 199/Hg NMR spectra of the system ((..mu..-SPh)/sub 6/(HgPPh/sub 3/)/sub 4/)/sup 2 +/-((..mu..-SePh)/sub 6/(HgPPh/sub 3/)/sub 4/)/sup 2 +/ it was possible to demonstrate the existence of every possible mixed-chalcogen core in the series ((..mu..-SPh)/sub 6-m/(..mu..-SePh)/sub m/(HgPPh/sub 3/)/sub 4/)/sup 2 +/ (m = 0-6). The new (..mu..-SR)/sub 6/Hg/sub 4/ cages are possible models for the proposed Hg/sub 4/(Cys)/sub 11/ cluster in Hg/sub 7/-metallothionein. 46 references, 3 figures, 2 tables.

  13. Search for parity and time reversal violating effects in HgH: Relativistic coupled-cluster study

    NASA Astrophysics Data System (ADS)

    Sasmal, Sudip; Pathak, Himadri; Nayak, Malaya K.; Vaval, Nayana; Pal, Sourav

    2016-03-01

    The high effective electric field (Eeff) experienced by the unpaired electron in an atom or a molecule is one of the key ingredients in the success of electron electric dipole moment (eEDM) experiment and its precise calculation requires a very accurate theory. We, therefore, employed the Z-vector method in the relativistic coupled-cluster framework and found that HgH has a very large Eeff value (123.2 GV/cm) which makes it a potential candidate for the next generation eEDM experiment. Our study also reveals that it has a large scalar-pseudoscalar (S-PS) P,T -violating interaction constant, Ws = 284.2 kHz. To judge the accuracy of the obtained results, we have calculated parallel and perpendicular magnetic hyperfine structure (HFS) constants and compared with the available experimental values. The results of our calculation are found to be in nice agreement with the experimental values. Therefore, by looking at the HFS results, we can say that both Eeff and Ws values are also very accurate. Further, We have derived the relationship between these quantities and the ratio which will help to get model independent value of eEDM and S-PS interaction constant.

  14. Search for parity and time reversal violating effects in HgH: Relativistic coupled-cluster study.

    PubMed

    Sasmal, Sudip; Pathak, Himadri; Nayak, Malaya K; Vaval, Nayana; Pal, Sourav

    2016-03-28

    The high effective electric field (Eeff) experienced by the unpaired electron in an atom or a molecule is one of the key ingredients in the success of electron electric dipole moment (eEDM) experiment and its precise calculation requires a very accurate theory. We, therefore, employed the Z-vector method in the relativistic coupled-cluster framework and found that HgH has a very large Eeff value (123.2 GV/cm) which makes it a potential candidate for the next generation eEDM experiment. Our study also reveals that it has a large scalar-pseudoscalar (S-PS) P,T-violating interaction constant, Ws = 284.2 kHz. To judge the accuracy of the obtained results, we have calculated parallel and perpendicular magnetic hyperfine structure (HFS) constants and compared with the available experimental values. The results of our calculation are found to be in nice agreement with the experimental values. Therefore, by looking at the HFS results, we can say that both Eeff and Ws values are also very accurate. Further, We have derived the relationship between these quantities and the ratio which will help to get model independent value of eEDM and S-PS interaction constant. PMID:27036448

  15. Collagen matrix as a tool in studying fibroblastic cell behavior.

    PubMed

    Kanta, Jiří

    2015-01-01

    Type I collagen is a fibrillar protein, a member of a large family of collagen proteins. It is present in most body tissues, usually in combination with other collagens and other components of extracellular matrix. Its synthesis is increased in various pathological situations, in healing wounds, in fibrotic tissues and in many tumors. After extraction from collagen-rich tissues it is widely used in studies of cell behavior, especially those of fibroblasts and myofibroblasts. Cells cultured in a classical way, on planar plastic dishes, lack the third dimension that is characteristic of body tissues. Collagen I forms gel at neutral pH and may become a basis of a 3D matrix that better mimics conditions in tissue than plastic dishes. PMID:25734486

  16. Collagen matrix as a tool in studying fibroblastic cell behavior

    PubMed Central

    Kanta, Jiří

    2015-01-01

    Type I collagen is a fibrillar protein, a member of a large family of collagen proteins. It is present in most body tissues, usually in combination with other collagens and other components of extracellular matrix. Its synthesis is increased in various pathological situations, in healing wounds, in fibrotic tissues and in many tumors. After extraction from collagen-rich tissues it is widely used in studies of cell behavior, especially those of fibroblasts and myofibroblasts. Cells cultured in a classical way, on planar plastic dishes, lack the third dimension that is characteristic of body tissues. Collagen I forms gel at neutral pH and may become a basis of a 3D matrix that better mimics conditions in tissue than plastic dishes. PMID:25734486

  17. Numerical studies of fibrous composites from the view point of fiber-matrix interface and fiber-matrix bonding

    NASA Astrophysics Data System (ADS)

    Yilmaz, Yahya Ilyas

    In the present research, the micromechanics of fibrous composites was studied numerically. The effects of the fiber/matrix interphase region and fiber/matrix bonding were the main goals of this research. Throughout the research NASTRAN finite element analyses were used. First we investigated the effect of the interphase region on the stress field by varying the thickness of the interphase region and the material properties in the interphase region. Second, we numerically simulated the bonding qualities between the fiber and the matrix by the implementation of the fiber/matrix interphase region. The change for bonding between the fiber and the matrix were simulated through a periodic material property change in the interphase region. Third, we developed a bi-dimensional concentric cylindrical model for stress transfer between the fiber and the matrix model in case of a broken fiber or short fiber composites. This model is unique in accounting for the real non-linear stress-strain relationship for the matrix material. The stress transfer between the fiber and the matrix was also analyzed by finite element models. Toward this end finite element analysis proved a useful tool to help us evaluate key model parameters, most importantly the radius of fiber influence. This parameter is also a key parameter of simple models upon which the new model is based. Finally we applied our stress transfer model to analyze single fiber fragmentation test data obtained at Kansas State University.

  18. X-ray Structure of a Hg2+ Complex of Mercuric Reductase (MerA) and Quantum Mechanical/Molecular Mechanical Study of Hg2+ Transfer between the C-Terminal and Buried Catalytic Site Cysteine Pairs

    PubMed Central

    2015-01-01

    Mercuric reductase, MerA, is a key enzyme in bacterial mercury resistance. This homodimeric enzyme captures and reduces toxic Hg2+ to Hg0, which is relatively unreactive and can exit the cell passively. Prior to reduction, the Hg2+ is transferred from a pair of cysteines (C558′ and C559′ using Tn501 numbering) at the C-terminus of one monomer to another pair of cysteines (C136 and C141) in the catalytic site of the other monomer. Here, we present the X-ray structure of the C-terminal Hg2+ complex of the C136A/C141A double mutant of the Tn501 MerA catalytic core and explore the molecular mechanism of this Hg transfer with quantum mechanical/molecular mechanical (QM/MM) calculations. The transfer is found to be nearly thermoneutral and to pass through a stable tricoordinated intermediate that is marginally less stable than the two end states. For the overall process, Hg2+ is always paired with at least two thiolates and thus is present at both the C-terminal and catalytic binding sites as a neutral complex. Prior to Hg2+ transfer, C141 is negatively charged. As Hg2+ is transferred into the catalytic site, a proton is transferred from C136 to C559′ while C558′ becomes negatively charged, resulting in the net transfer of a negative charge over a distance of ∼7.5 Å. Thus, the transport of this soft divalent cation is made energetically feasible by pairing a competition between multiple Cys thiols and/or thiolates for Hg2+ with a competition between the Hg2+ and protons for the thiolates. PMID:25343681

  19. Theoretical study of HgCr2Se3.5Te0.5: a doping-site-dependent semimetal.

    PubMed

    Yu, Xiang-Long; Jin, Yuan-Jun; Wu, Jiansheng

    2016-01-01

    Weyl semimetals have recently attracted enormous attention due to their unusual features. So far, this novel state has been predicted theoretically and confirmed experimentally in several materials, such as HgTe, LaPtBi, Y2Ir2O7, TaAs, TaP, NbAs, NbP and HgCr2Se4. Doping plays an important role in the research of condensed-matter materials. However, its influence on the Weyl semimetal has been little investigated. Here, we present detailed first-principles and theoretical studies on HgCr2Se4 with doping of Te atoms at the Se sites. A special case where only one pair of crossing points locates at the Fermi level is realized in HgCr2Se3.5Te0.5 where one of the Se atoms in the primitive unit cell is replaced by a Te atom. A further study of k·p theory shows that the two points constitute a pair of Weyl nodes with opposite chiralities in the momentum space, and only one edge state and one single Fermi arc are obtained at each boundary of a film. Moreover, through investigations and analyses of different doping cases of HgCr2Se3.5Te0.5, we find that when the type of doping induces inversion symmetry or positional disorder, the Weyl nodes transform into Dirac points resulting in a change from a Weyl semimetal to a Dirac semimetal. PMID:27480923

  20. Theoretical study of HgCr2Se3.5Te0.5: a doping-site-dependent semimetal

    PubMed Central

    Yu, Xiang-Long; Jin, Yuan-Jun; Wu, Jiansheng

    2016-01-01

    Weyl semimetals have recently attracted enormous attention due to their unusual features. So far, this novel state has been predicted theoretically and confirmed experimentally in several materials, such as HgTe, LaPtBi, Y2Ir2O7, TaAs, TaP, NbAs, NbP and HgCr2Se4. Doping plays an important role in the research of condensed-matter materials. However, its influence on the Weyl semimetal has been little investigated. Here, we present detailed first-principles and theoretical studies on HgCr2Se4 with doping of Te atoms at the Se sites. A special case where only one pair of crossing points locates at the Fermi level is realized in HgCr2Se3.5Te0.5 where one of the Se atoms in the primitive unit cell is replaced by a Te atom. A further study of k·p theory shows that the two points constitute a pair of Weyl nodes with opposite chiralities in the momentum space, and only one edge state and one single Fermi arc are obtained at each boundary of a film. Moreover, through investigations and analyses of different doping cases of HgCr2Se3.5Te0.5, we find that when the type of doping induces inversion symmetry or positional disorder, the Weyl nodes transform into Dirac points resulting in a change from a Weyl semimetal to a Dirac semimetal. PMID:27480923

  1. First-principles study of structure and nonlinear optical properties of CdHg(SCN)4 crystal

    NASA Astrophysics Data System (ADS)

    Zhang, Peng; Kong, Chui-Gang; Zheng, Chao; Wang, Xin-Qiang; Ma, Yue; Feng, Jin-Bo; Jiao, Yu-Qiu; Lu, Gui-Wu

    2015-02-01

    The geometric structure, electronic structure, and optical properties of CdHg(SCN)4 crystal are calculated by using the density functional perturbation theory and Green function screening Coulomb interaction approximation. The band gap of CdHg(SCN)4 crystal is calculated to be 3.198 eV, which is in good agreement with the experimental value 3.265 eV. The calculated second-order nonlinear optical coefficients are d14 = 1.2906 pm/V and d15 = 5.0928 pm/V, which are in agreement with the experimental results (d14 = (1.4 ± 0.6)pm/V and d15 = (6.0 ± 0.9 pm/V). Moreover, it is found that the contribution to the valence band mainly comes from Cd-4d, Hg-5d states, and the contributions to the valence band top and the conduction band bottom predominantly come from C-2p, N-2p, and S-3p states. The second-order nonlinear optical effect of CdHg(SCN)4 crystal results mainly from the internal electronic transition of (SCN)-. Project supported by the National Natural Science Foundation of China (Grant No. 51372140), the Youth Scientist Fund of Shandong Province, China (Grant No. BS2011CL025), and the Basic Discipline Research Fund of China University of Petroleum, Beijing, China (Grant No. 01JB0169).

  2. Random matrix study for a three-terminal chaotic device

    SciTech Connect

    Martínez-Argüello, A. M.; Castaño, E.; Martínez-Mares, M.

    2014-01-14

    We perform a study based on a random-matrix theory simulation for a three-terminal device, consisting of chaotic cavities on each terminal. We analyze the voltage drop along one wire with two chaotic mesoscopic cavities, connected by a perfect conductor, or waveguide, with one open mode. This is done by means of a probe, which also consists of a chaotic cavity that measure the voltage in different configurations. Our results show significant differences with respect to the disordered case, previously considered in the literature.

  3. INITIAL CHARACTERIZATIONS AND SRAT SIMULATIONS OF FOUR SLUDGE MATRIX STUDY SIMULANTS

    SciTech Connect

    Koopman,D.; Lambert, D.

    2009-12-10

    -to-nitrate conversion were found that can be used in the acid calculations for future sludge matrix process simulations. A reasonable determination of the minimum acid requirement for nitrite destruction was found to be slightly less than 105% of the Koopman minimum stoichiometric acid equation prediction for all four simulants at the low noble metal concentrations. The Koopman minimum stoichiometric acid equation is based on supernate carbonate, plus total Mg and Ca, in addition to the usual DWPF inputs such as base equivalents and Mn. This group of four tests extends the range of bulk insoluble solids concentrations over which the new Koopman minimum stoichiometric acid equation has been validated. The low iron-low manganese case appeared to have somewhat more excess acid than the other three combinations. Preliminary results of the initial testing indicate: (1) Hydrogen generation rate was not an issue in these tests. (2) Mercury stripping was less efficient than expected at about 1000 g steam/g mercury stripped. Only about 25% of the initial concentration of 1.5 wt% Hg in the total solids was removed in 13-14 hours of boiling, when 70% needed to be removed to meet the DWPF SRAT product specification of 0.45 wt% in the total solids. (3) Foaminess was not an issue using the nominal antifoam addition strategy in these tests. (4) Ammonia generation was not an issue based on off-gas condensate analyses. (5) One of the SRAT products (an HM-type simulant) was much more viscous than the other three SRAT products even though it had the lowest wt% insoluble solids. More comprehensive results concerning the impact of insoluble solids composition on processing, melt rate, etc. must await completion of the full sludge matrix study experimental scope.

  4. Shock Interaction Studies on Glass Fibre Reinforced Epoxy Matrix Composites

    NASA Astrophysics Data System (ADS)

    Reddy, K. P. J.; Jagadeesh, G.; Jayaram, V.; Reddy, B. Harinath; Madhu, V.; Reddy, C. Jaya Rami

    Glass fibre reinforced polymer matrix composites are being extensively used for structural applications both in civil and defense sectors, owing to their high specific strength, stiffness and good energy absorbing capability. Understanding the dynamic response of these composites on shock loading is very essential for effective design of structures resistant to blast loads. In the present study, E- glass/epoxy composite laminate has been fabricated and evaluated for their mechanical properties such as tensile strength, flexural strength and inter laminar shear strength (ILSS). Further, dynamic response of E-glass laminates is presently studied by shock loading. When E-glass composite subjected to peak shock reflected pressure of 7.2 MPa and estimated temperature of about 14000 K for short duration, it underwent surface discolorations and charring of epoxy matrix. Post test analysis of the composite sample was carried out to study the damage analysis using Scanning Electron Microscope (SEM), changes in thermal properties of composites using Dynamic Mechanical Analyzer (DMA) and Thermo-Gravimetric Analyzer (TGA). The results of these investigations are discussed in this paper.

  5. Consortium studies of matrix of light gray breccia 73215

    NASA Technical Reports Server (NTRS)

    James, O. B.; Brecher, A.; Blanchard, D. P.; Haskin, L. A.; Jacobs, J. W.; Brannon, J. C.; Korotev, R. L.; Higuchi, H.; Morgan, J. W.; Anders, E.

    1975-01-01

    A description is presented of the preliminary results of interdisciplinary studies of matrix samples. The significance of the 73215 studies is considered and the relationship of 73215 to other Apollo 17 highland breccias is discussed. According to a tentative hypothesis 73215 is an aggregate of fragments plus melt generated in a very large impact, possibly the Serenitatis basin-forming event. If this is correct, studies of this sample will make it possible to date the Serenitatis event and will provide an insight into the breccia-forming processes associated with such events. Studies of the clasts in the breccia will provide an opportunity to formulate a partial characterization of the preimpact source terrain. An investigation of the deep lunar crust might perhaps also be possible.

  6. Investigation of uptake and retention of atmospheric Hg(II) by boreal forest plants using stable Hg isotopes

    USGS Publications Warehouse

    Graydon, J.A.; St. Louis, V.L.; Hintelmann, H.; Lindberg, S.E.; Sandilands, K.A.; Rudd, J.W.M.; Kelly, C.A.; Tate, M.T.; Krabbenhoft, D.P.; Lehnherr, I.

    2009-01-01

    Although there is now a general consensus among mercury (Hg) biogeochemists that increased atmospheric inputs of inorganic Hg(II) to lakes and watersheds can result in increased methylmercury (MeHg) concentrations in fish, researchers still lack kinetic data describing the movement of Hg from the atmosphere, through watershed and lake ecosystems, and into fish. The use of isotopically enriched Hg species in environmental studies now allows experimentally applied new Hg to be distinguished from ambient Hg naturally present in the system. Four different enriched stable Hg(II) isotope "spikes" were applied sequentially over four years to the ground vegetation of a microcatchment at the Experimental Lakes Area (ELA) in the remote boreal forest of Canada to examine retention of Hg(II) following deposition. Areal masses of the spikes and ambient THg (all forms of Hg in a sample) were monitored for eight years, and the pattern of spike retention was used to estimate retention of newly deposited ambient Hg within the ground vegetation pool. Fifty to eighty percent of applied spike Hg was initially retained by ground vegetation. The areal mass of spike Hg declined exponentially over time and was best described by a first-order process with constants (k) ranging between 9.7 ?? 10-4 day -1 and 11.6 ?? 10-4 day-1. Average half-life (t1/2) of spike Hg within the ground vegetation pool (??S.D.) was 704 ?? 52 days. This retention of new atmospheric Hg(II) by vegetation delays movement of new Hg(II) into soil, runoff, and finally into adjacent lakes. Ground-applied Hg(II) spikes were not detected in tree foliage and litterfall, indicating that stomatal and/or root uptake of previously deposited Hg (i.e., "recycled" from ground vegetation or soil Hg pools) were likely not large sources of foliar Hg under these experimental conditions. ?? 2009 American Chemical Society.

  7. Raman scattering and electrical studies of the phase stability in the Hg1-xCdxTe

    NASA Astrophysics Data System (ADS)

    Singh, Anand; Shukla, A. K.; Pal, R.

    2016-05-01

    Raman scattering is performed to access phase stability in the boron-implanted Hg0.7Cd0.3Te with fluences ranging from 1 × 1012 to 1 × 1015 cm-2. Threshold fluence for the formation of an amorphous phase is invoked here using Thomas-Fermi statistical model. Asymmetric broadening and red shift of the Raman active HgTe-like LO phonon mode are observed with varying fluencies. Electrical properties such as sheet carrier concentration and mobility are also changed with the fluence and reach their saturated values beyond threshold fluence of 5 × 1013 cm-2. Threshold fluence for the formation of amorphous phase is also validated by the Raman measurements and electrical transport properties in the implanted layers. The excess free energy of 6.8 kJ/mole is found corresponding to the threshold fluence for phase transition.

  8. Magnetotransmission of unpolarized infrared radiation in Hg1 - x Cd x Cr2Se4 (0 ≤ x ≤ 1) single crystals studied using the voigt geometry

    NASA Astrophysics Data System (ADS)

    Sukhorukov, Yu. P.; Telegin, A. V.; Bebenin, N. G.; Patrakov, E. I.; Naumov, S. V.; Fedorov, V. A.; Menshchikova, T. K.

    2013-11-01

    The features characterizing the behavior of magnetotransmission in Hg1 - x Cd x Cr2Se4 single crystals are studied using natural light in the infrared spectral range. The relation between the changes in the magneto-optical properties and in the electron band structure is found. It is shown that the most significant changes in the magnetotransmission spectrum and the band structure occur within the 0.1 < x < 0.25 range.

  9. Multi-Pollutant Emissions Control: Pilot Plant Study of Technologies for Reducing Hg, SO3, NOx and CO2 Emissions

    SciTech Connect

    Michael L. Fenger; Richard A. Winschel

    2005-08-31

    A slipstream pilot plant was built and operated to investigate technology to adsorb mercury (Hg) onto the existing particulate (i.e., fly ash) by cooling flue gas to 200-240 F with a Ljungstrom-type air heater or with water spray. The mercury on the fly ash was then captured in an electrostatic precipitator (ESP). An alkaline material, magnesium hydroxide (Mg(OH){sub 2}), is injected into flue gas upstream of the air heater to control sulfur trioxide (SO{sub 3}), which prevents acid condensation and corrosion of the air heater and ductwork. The slipstream was taken from a bituminous coal-fired power plant. During this contract, Plant Design and Construction (Task 1), Start Up and Maintenance (Task 2), Baseline Testing (Task 3), Sorbent Testing (Task 4), Parametric Testing (Task 5), Humidification Tests (Task 6), Long-Term Testing (Task 7), and a Corrosion Study (Task 8) were completed. The Mercury Stability Study (Task 9), ESP Report (Task 11), Air Heater Report (Task 12) and Final Report (Task 14) were completed. These aspects of the project, as well as progress on Public Outreach (Task 15), are discussed in detail in this final report. Over 90% mercury removal was demonstrated by cooling the flue gas to 200-210 F at the ESP inlet; baseline conditions with 290 F flue gas gave about 26% removal. Mercury removal is sensitive to flue gas temperature and carbon content of fly ash. At 200-210 F, both elemental and oxidized mercury were effectively captured at the ESP. Mg(OH){sub 2} injection proved effective for removal of SO{sub 3} and eliminated rapid fouling of the air heater. The pilot ESP performed satisfactorily at low temperature conditions. Mercury volatility and leaching tests did not show any stability problems. No significant corrosion was detected at the air heater or on corrosion coupons at the ESP. The results justify larger-scale testing/demonstration of the technology. These conclusions are presented and discussed in two presentations given in July and

  10. Nuclear magnetic resonance study of the collagen matrix in tendon

    NASA Astrophysics Data System (ADS)

    Krasnosselskaia, Lada Vadimovna

    Understanding of complex interactions of water with macromolecules is a prerequisite for quantitative musculoskeletal imaging and this dissertation presents a study on NMR characteristics of water in anisotropic environment of the collagen extracellular matrix of tendon. The first chapter of the dissertation analyzes a "magic angle" effect, a well known in clinical practice artifact of a sudden signal increase in normal tendons and ligaments at the orientation of 55° with respect to the static magnetic field of an MRI scanner. The physical basis of the orientation dependence of the free induction decay is studied in ex-vivo mammalian tissue at the field strength of 2 Tesla. Obtained quantitative measures are related to the model of heterogeneous water phases in the collagen extracellular matrix of tendon. A novel effect of central frequency shift of the water signal is reported and hypothesis on the origin of the effect is put forward. Clinical applications of NMR and MRI constantly benefit from adopting methods and techniques from the field of NMR of liquids, solids and liquid crystals. In the second chapter, a pseudo solid echo technique is evaluated for the purpose of detecting slow motions in the collagen matrix at different hydration and temperatures, at the field strength of 11.74 Tesla (500 MHz). The pseudo solid echo is shown capable in detecting motions on the scale of 10-3-10-6 seconds. 1H spin-lattice relaxation study at different levels of hydration and temperatures is presented in the third chapter. Predictions of the molecular model of collagen hydration are verified at the field strength of 11.74 Tesla (500 MHz) and temperature of 6°C, 26°C and 37°C. In the fourth chapter, an efficient adaptive mesh numerical code is developed on the basis of the octal tree data structure for assessment of the bulk magnetic susceptibility effects. The code allows calculation of the microscopic magnetic field as "seen by the nucleus" for uniformly magnetized

  11. Feasibility study on the use of soil washing to remediate the As-Hg contamination at an ancient mining and metallurgy area.

    PubMed

    Sierra, C; Menéndez-Aguado, J M; Afif, E; Carrero, M; Gallego, J R

    2011-11-30

    Soils in abandoned mining sites generally present high concentrations of trace elements, such as As and Hg. Here we assessed the feasibility of washing procedures to physically separate these toxic elements from soils affected by a considerable amount of mining and metallurgical waste ("La Soterraña", Asturias, NW Spain). After exhaustive soil sampling and subsequent particle-size separation via wet sieving, chemical and mineralogical analysis revealed that the finer fractions held very high concentrations of As (up to 32,500 ppm) and Hg (up to 1600 ppm). These elements were both associated mainly with Fe/Mn oxides and hydroxides. Textural and geochemical data were correlated with the geological substrate by means of a multivariate statistical analysis. In addition, the Hg liberation size (below 200 μm) was determined to be main factor conditioning the selection of suitable soil washing strategies. These studies were finally complemented with a specific-gravity study performed with a C800 Mozley separator together with a grindability test, both novel approaches in soil washing feasibility studies. The results highlighted the difficulties in treating "La Soterraña" soils. These difficulties are attributed to the presence of contaminants embedded in the soil and spoil heap aggregates, caused by the meteorization of gangue and ore minerals. As a result of these two characteristics, high concentrations of the contaminants accumulate in all grain-size fractions. Therefore, the soil washing approach proposed here includes the grinding of particles above 125 μm. PMID:21943924

  12. Identification of Atmospheric Mercury Input to Ecosystems From Precipitation Using Coupled Δ200Hg and Δ204Hg Fractionation

    NASA Astrophysics Data System (ADS)

    Blum, J. D.; Johnson, M. W.

    2015-12-01

    Mercury has seven stable isotopes, and during most biogeochemical reactions all of the isotopes fractionate mass dependently (MDF; relative to δ202/198Hg). The odd isotopes also fractionate mass independently (MIF) during reactions involving the magnetic isotope and nuclear volume effects. In 2010 we first reported MIF of 200Hg in precipitation (Gratz et al), and in 2013 we reported MIF of 204Hg in precipitation (Demers et al). Measurements of Δ200Hg are becoming more common and several studies have now used Δ200Hg as a tracer of Hg(II) deposited from the atmosphere (Chen et al, 2012; Strok et al 2015). Δ204Hg is much less commonly measured and reported, but sheds additional light on the mechanisms that might cause even isotope MIF. We observe Δ204Hg to be of opposite sign and ~2x the magnitude of Δ200Hg. The presence of coupled Δ200Hg and Δ204Hg is most useful for detecting precipitation inputs of Hg to ecosystems. We have measured Δ200Hg and Δ204Hg in hundreds of samples of precipitation, invertebrates, fish, moss, lichen, ice crystals and GEM at many locations in North America and Hawaii. When average values for each sample type at each study location are plotted as Δ200Hg versus Δ204Hg they fall on a linear array with slope=0.57 and R2=0.92. Samples of sediment, coal, various rock-types, and point-source contaminants have contrasting Δ200Hg and Δ204Hg indistinguishable from zero. We also use combined Δ200Hg and Δ204Hg to explore mechanisms leading to even isotope MIF. Ghosh et al (2012) measured nuclear volume fractionation and found even MIF to be undetectable. Mead et al (2013) calculated even mass MIF from nuclear self-shielding and it does not fit our observations of Δ200Hg/Δ204Hg in natural samples; they also measured MIF caused by implantation of Hg into glass in compact fluorescent lights (CFLs) and this is consistent with Δ200Hg/Δ204Hg in atmospheric Hg(II), suggesting the possibility of a common fractionation mechanism.

  13. Fibre-matrix bond strength studies of glass, ceramic, and metal matrix composites

    NASA Technical Reports Server (NTRS)

    Grande, D. H.; Mandell, J. F.; Hong, K. C. C.

    1988-01-01

    An indentation test technique for compressively loading the ends of individual fibers to produce debonding has been applied to metal, glass, and glass-ceramic matrix composites; bond strength values at debond initiation are calculated using a finite-element model. Results are correlated with composite longitudinal and interlaminar shear behavior for carbon and Nicalon fiber-reinforced glasses and glass-ceramics including the effects of matrix modifications, processing conditions, and high-temperature oxidation embrittlement. The data indicate that significant bonding to improve off-axis and shear properties can be tolerated before the longitudinal behavior becomes brittle. Residual stress and other mechanical bonding effects are important, but improved analyses and multiaxial interfacial failure criteria are needed to adequately interpret bond strength data in terms of composite performance.

  14. Pathways of CH3Hg and Hg Ingestion in Benthic Organisms: An Enriched Isotope Approach

    PubMed Central

    2015-01-01

    Mercury is a widespread contaminant in marine food webs, and identifying uptake pathways of mercury species, CH3Hg+ and Hg2+, into low trophic level organisms is important to understanding its entry into marine food webs. Enriched stable isotope tracers were used to study benthic vs. pelagic pathways of CH3Hg+ and Hg2+ uptake via food to the infaunal estuarine amphipod, Leptocheirus plumulosus. Algal cells differentially labeled with isotopically enriched CH3Hg+ or Hg2+ were added simultaneously to the sediment and water column of microcosms, and Hg species were monitored in amphipods and in sediment and water compartments. Methylation of Hg2+ occurred during the course of the experiment, enhancing the uptake of Hg2+ spikes. Trophic transfer of Hg from algae added to the water column was determined to be the major uptake route for amphipods, suggesting inputs of contaminated organic matter from the pelagic zone are important to mercury bioaccumulation even in organisms living in sediments. PMID:24678910

  15. Insight On Colorectal Carcinoma Infiltration by Studying Perilesional Extracellular Matrix

    PubMed Central

    Nebuloni, Manuela; Albarello, Luca; Andolfo, Annapaola; Magagnotti, Cinzia; Genovese, Luca; Locatelli, Irene; Tonon, Giovanni; Longhi, Erika; Zerbi, Pietro; Allevi, Raffaele; Podestà, Alessandro; Puricelli, Luca; Milani, Paolo; Soldarini, Armando; Salonia, Andrea; Alfano, Massimo

    2016-01-01

    The extracellular matrix (ECM) from perilesional and colorectal carcinoma (CRC), but not healthy colon, sustains proliferation and invasion of tumor cells. We investigated the biochemical and physical diversity of ECM in pair-wised comparisons of healthy, perilesional and CRC specimens. Progressive linearization and degree of organization of fibrils was observed from healthy to perilesional and CRC ECM, and was associated with a steady increase of stiffness and collagen crosslinking. In the perilesional ECM these modifications coincided with increased vascularization, whereas in the neoplastic ECM they were associated with altered modulation of matrisome proteins, increased content of hydroxylated lysine and lysyl oxidase. This study identifies the increased stiffness and crosslinking of the perilesional ECM predisposing an environment suitable for CRC invasion as a phenomenon associated with vascularization. The increased stiffness of colon areas may represent a new predictive marker of desmoplastic region predisposing to invasion, thus offering new potential application for monitoring adenoma with invasive potential. PMID:26940881

  16. Synthesis, characterization, DFT and biological studies of isatinpicolinohydrazone and its Zn(II), Cd(II) and Hg(II) complexes

    NASA Astrophysics Data System (ADS)

    El-Gammal, O. A.; Rakha, T. H.; Metwally, H. M.; Abu El-Reash, G. M.

    2014-06-01

    Isatinpicolinohydrazone (H2IPH) and its Zn(II), Cd(II) and Hg(II) complexes have been synthesized and investigated using physicochemical techniques viz. IR, 1H NMR, 13C NMR, UV-Vis spectrometric methods and magnetic moment measurements. The investigation revealed that H2IPH acts as binegative tetradentate in Zn(II), neutral tridentate in Cd(II) and as neutral bidentate towards Hg(II) complex. Octahedral geometry is proposed for all complexes. The bond length, bond angle, chemical reactivity, energy components (kcal/mol), binding energy (kcal/mol) and dipole moment (Debyes) for all the title compounds were evaluated by DFT and also MEP for the ligand is shown. Theoretical infrared intensities of H2IPH and also the theoretical electronic spectra of the ligand and its complexes were calculated. The thermal behavior and the kinetic parameters of degradation were determined using Coats-Redfern and Horowitz-Metzger methods. The in vitro antibacterial studies of the complexes proved them as growth inhibiting agents. The DDPH antioxidant of the compounds have been screened. Antitumor activity, carried out in vitro on human mammary gland (breast) MCF7, have shown that Hg(II) complex exhibited potent activity followed by Zn(II), Cd(II) complexes and the ligand.

  17. Electronic and magnetic studies of {kappa}-(BEDT-TTF){sub 2}Hg(SCN){sub 2}Cl.

    SciTech Connect

    Yasin, S.; Rose, E.; Dumm, M.; Drichko, N.; Dressel, M.; Schlueter, J. A.; Zhilyaeva, E. I.; Torunova, S.; Lyubovskaya, R. N.

    2012-06-01

    DC resistivity and electron spin resonance (ESR) measurements have been performed on the two-dimensional organic conductor {kappa}-(BEDT-TTF){sub 2}Hg(SCN){sub 2}Cl. Due to electronic correlations, the compound undergoes a transition from a metallic to an insulating state at T{sub MI} = 34 K. The ESR parameters exhibit a drastic change below T{sub afm} = 27 K that evidences a magnetic phase transition. In this low-temperature state, we observe the characteristics of antiferromagnetic resonances in the angular dependence of the g-value.

  18. Homogeneity study of candidate reference material in fish matrix

    NASA Astrophysics Data System (ADS)

    Ulrich, J. C.; Sarkis, J. E. S.; Hortellani, M. A.

    2015-01-01

    A material is perfectly homogeneous with respect to a given characteristic, or composition, if there is no difference between the values obtained from one part to another. Homogeneity is usually evaluated using analysis of variance (ANOVA). However, the requirement that populations of data to be processed must have a normal distribution and equal variances greatly limits the use of this statistical tool. A more suitable test for assessing the homogeneity of RMs, known as "sufficient homogeneity", was proposed by Fearn and Thompson. In this work, we evaluate the performance of the two statistical treatments for assessing homogeneity of methylmercury (MeHg) in candidate reference material of fish tissue.

  19. Decellularization of porcine skeletal muscle extracellular matrix for the formulation of a matrix hydrogel: a preliminary study.

    PubMed

    Fu, Yuehe; Fan, Xuejiao; Tian, Chunxiang; Luo, Jingcong; Zhang, Yi; Deng, Li; Qin, Tingwu; Lv, Qing

    2016-04-01

    Extracellular matrix (ECM) hydrogels are used as scaffolds to facilitate the repair and reconstruction of tissues. This study aimed to optimize the decellularization process of porcine skeletal muscle ECM and to formulate a matrix hydrogel scaffold. Five multi-step methods (methods A-E) were used to generate acellular ECM from porcine skeletal muscle [rinsing in SDS, trypsin, ethylenediaminetetraacetic acid (EDTA), Triton X-100 and/or sodium deoxycholate at 4-37°C]. The resulting ECM was evaluated using haematoxylin and eosin, 4-6-diamidino-2-phenylindole (DAPI) staining, and DNA quantification. Acellular matrix was dissolved in pepsin and gelled at 37°C. Hydrogel response to temperature was observed in vivo and in vitro. ECM components were assessed by Masson, Sirius red, and alcian blue staining, and total protein content. Acellular porcine skeletal muscle exhibited a uniform translucent white appearance. No intact nuclear residue was detected by haematoxylin and eosin staining, while DAPI staining showed a few nuclei in the matrixes produced by methods B, C, and D. Method A generated a gel that was too thin for gelation. However, the matrix obtained by rinsing in 0.2% trypsin/0.1% EDTA, 0.5% Triton X-100, and 1% Triton X-100/0.2% sodium deoxycholate was nuclei-free and produced a viscous solution that formed a structurally stable white jelly-like hydrogel. The residual DNA content of this solution was 49.37 ± 0.72 ng/mg, significantly less than in fresh skeletal muscle, and decreased to 19.22 ± 0.85 ng/mg after gelation (P < 0.05). The acellular matrix was rich in collagen and glycosaminoglycan, with a total protein concentration of 64.8 ± 6.9%. An acellular ECM hydrogel from porcine skeletal muscle was efficiently produced. PMID:26781342

  20. GLYCOLIC-FORMIC ACID FLOWSHEET SLUDGE MATRIX STUDY

    SciTech Connect

    Lambert, D.; Koopman, D.

    2011-06-30

    Testing was completed to demonstrate the viability of the newly developed glycolic acid/formic acid flowsheet on processing in the Defense Waste Processing Facility's (DWPF) Chemical Process Cell (CPC). The Savannah River National Laboratory (SRNL) initiated a sludge matrix study to evaluate the impact of changing insoluble solid composition on the processing characteristics of slurries in DWPF. Four sludge simulants were prepared to cover two compositional ranges in the waste. The first was high iron/low aluminum versus low iron/high aluminum (referred to as HiFe or LoFe in this report). The second was high calcium-manganese/low nickel, chromium, and magnesium versus low calcium-manganese/high nickel, chromium, and magnesium (referred to as HiMn or LoMn in this report). These two options can be combined to form four distinct sludge compositions. The sludge matrix study called for testing each of these four simulants near the minimum acid required for nitrite destruction (100% acid stoichiometry) and at a second acid level that produced significant hydrogen by noble metal catalyzed decomposition of formic acid (150% acid stoichiometry). Four simulants were prepared based on the four possible combinations of the Al/Fe and Mn-Ca/Mg-Ni-Cr options. Preliminary simulant preparation work has already been documented. The four simulants were used for high and low acid testing. Eight planned experiments (GF26 to GF33) were completed to demonstrate the viability of the glycolic-formic flowsheet. Composition and physical property measurements were made on the SRAT product. Composition measurements were made on the condensate from the Mercury Water Wash Tank (MWWT), Formic Acid Vent Condenser (FAVC), ammonia scrubber and on SRAT samples pulled throughout the SRAT cycle. Updated values for formate loss and nitrite-tonitrate conversion were found that can be used in the acid calculations for future sludge matrix process simulations with the glycolic acid/formic acid flowsheet

  1. Accumulation and translocation of 198Hg in four crop species.

    PubMed

    Cui, Liwei; Feng, Xinbin; Lin, Che-Jen; Wang, Xinming; Meng, Bo; Wang, Xun; Wang, Heng

    2014-02-01

    The uptake and transport of mercury (Hg) through vegetation play an important role in the biogeochemical cycling of Hg. However, quantitative information regarding Hg translocation in plants is poorly understood. In the present study, Hg uptake, accumulation, and translocation in 4 crops-rice (Oryza.sativa L.), wheat (Triticum L.), corn (Zea mays L.), and oilseed rape (Brassica campestris L.)-grown in Hoagland solution were investigated using a stable isotope ((198)Hg) tracing technique. The distribution of (198)Hg in root, stem, and leaf after uptake was quantified, and the release of (198)Hg into the air from crop leaf was investigated. It was found that the concentration of Hg accumulated in the root, stem, and leaf of rice increased linearly with the spiked (198)Hg concentration. The uptake equilibrium constant was estimated to be 2.35 mol Hg/g dry weight in rice root per mol/L Hg remaining in the Hoagland solution. More than 94% of (198)Hg uptake was accumulated in the roots for all 4 crops examined. The translocation to stem and leaf was not significant because of the absence of Hg(2+) complexes that facilitate Hg transport in plants. The accumulated (198)Hg in stem and leaf was not released from the plant at air Hg(0) concentration ranging from 0 ng/m(3) to 10 ng/m(3). Transfer factor data analysis showed that Hg translocation from stems to leaves was more efficient than that from roots to stems. PMID:24173818

  2. Expression of genes encoding extracellular matrix proteins: A macroarray study

    PubMed Central

    FUTYMA, KONRAD; MIOTŁA, PAWEŁ; RÓŻYŃSKA, KRYSTYNA; ZDUNEK, MAŁGORZATA; SEMCZUK, ANDRZEJ; RECHBERGER, TOMASZ; WOJCIEROWSKI, JACEK

    2014-01-01

    Endometrial cancer (EC) is one of the most common gynecological malignancies in Poland, with well-established risk factors. Genetic instability and molecular alterations responsible for endometrial carcinogenesis have been systematically investigated. The aim of the present study was to investigate, by means of cDNA macroarrays, the expression profiles of genes encoding extracellular matrix (ECM) proteins in ECs. Tissue specimens were collected during surgical procedures from 40 patients with EC, and control tissue was collected from 9 patients with uterine leiomyomas. RNA was isolated and RT-PCR with radioisotope-labeled cDNA was performed. The levels of ECM protein gene expression in normal endometrial tissues were compared to the expression of these genes in EC specimens. Statistically significant differences in gene expression, stratified by clinical stage of the ECs, were detected for aggrecan, vitronectin, tenascin R, nidogen and two collagen proteins: type VIII chain α1 and type XI chain α2. All of these proteins were overexpressed in stage III endometrial carcinomas compared to levels in stage I and II uterine neoplasms. In conclusion, increased expression of genes encoding ECM proteins may play an important role in facilitating accelerated disease progression of human ECs. PMID:25231141

  3. Study on micro-crystallization, growth, optical properties and defects of a nonlinear optical crystal: MnHg(SCN) 4

    NASA Astrophysics Data System (ADS)

    Liu, Xitao; Wang, Xinqiang; Sun, Zhihua; Lin, Xiaojing; Zhang, Guanghui; Xu, Dong

    2011-02-01

    High optical quality single crystals of a nonlinear optical material, manganese mercury thiocyanate, MnHg(SCN) 4 (MMTC), with dimensions up to 21×14×13 mm 3 have been grown by the solvent evaporation method. The growth habit of MMTC crystal crystallized under different conditions was investigated by means of micro-crystallization method. Two typical growth morphologies of the crystal were indexed and compared with the morphology deduced from the single crystal structure data. The results show that two novel {1 0 0} and {1 1 2} facets appear during the crystal growth. Powder second harmonic generation and spectral transmittance measurements were also performed. The results indicate that MMTC is phase-matchable and the UV transparency cutoff occurs at 373 nm. Various defects were found in MMTC crystal. Their formation mechanisms and the methods to eliminate these defects are discussed.

  4. Methylmercury (MeHg)

    Integrated Risk Information System (IRIS)

    Methylmercury ( MeHg ) ; CASRN 22967 - 92 - 6 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarci

  5. Theoretical studies on the Knight shifts for the tetragonal Cu2+ site in HgBa2CuO4+δ

    NASA Astrophysics Data System (ADS)

    Li, Guo-Liang; Wu, Shao-Yi; Kuang, Min-Quan; Hu, Xian-Fen

    2015-08-01

    The Knight shifts for the tetragonal Cu2+ site in HgBa2CuO4+δ are theoretically studied from the high order perturbation formulas of the Knight shifts for a tetragonally elongated octahedral 3d9 cluster. The significant anisotropy of the Knight shifts is attributable to the obvious tetragonal elongation distortion of the Cu2+ site. The anisotropic g factors of this system are uniformly analyzed, and the calculation results and the local structure of the copper site are also discussed.

  6. Thermal Studies of Zn(II), Cd(II) and Hg(II) Complexes of Some N-Alkyl-N-Phenyl-Dithiocarbamates

    PubMed Central

    Onwudiwe, Damian C.; Ajibade, Peter A.

    2012-01-01

    The thermal decomposition of Zn(II), Cd(II) and Hg(II) complexes of N-ethyl-N-phenyl and N-butyl-N-phenyl dithiocarbamates have been studied using thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC). The products of the decomposition, at two different temperatures, were further characterized by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). The results show that while the zinc and cadmium complexes undergo decomposition to form metal sulphides, and further undergo oxidation forming metal oxides as final products, the mercury complexes gave unstable volatiles as the final product. PMID:22949811

  7. Relativistic unitary coupled-cluster study of the electric quadrupole moment and magnetic dipole hyperfine constants of {sup 199}Hg{sup +}

    SciTech Connect

    Sur, Chiranjib; Chaudhuri, Rajat K.

    2007-09-15

    Searching for an accurate optical clock which can serve as a better time standard than the present-day atomic clock is highly demanding from several areas of science and technology. Several attempts have been made to build more accurate clocks with different ion species. In this paper, we discuss the electric quadrupole and hyperfine shifts in the 5d{sup 9}6s{sup 2} {sup 2}D{sub 5/2}(F=0,m{sub F}=0){r_reversible}5d{sup 10}6s {sup 2}S{sub 1/2}(F=2,m{sub F}=0) clock transition in {sup 199}Hg{sup +}, one of the most promising candidates for next-generation optical clocks. We have applied Fock-space unitary coupled-cluster theory to study the electric quadrupole moment of the 5d{sup 9}6s{sup 2} {sup 2}D{sub 5/2} state and magnetic dipole hyperfine constants of 5d{sup 9}6s{sup 2} {sup 2}D{sub 3/2,5/2} and 5d{sup 10}6s{sup 1} {sup 2}S{sub 1/2} states, respectively, of {sup 199}Hg{sup +}. We have also compared our results with available data. To the best of our knowledge, this is the first time a variant of coupled-cluster theories has been applied to study these kinds of properties of Hg{sup +} and is the most accurate estimate of these quantities to date.

  8. Study of the essential spectrum of a matrix operator

    NASA Astrophysics Data System (ADS)

    Rasulov, T. Kh.

    2010-07-01

    We consider a matrix operator H corresponding to a system with a nonconserved finite number of particles on a lattice. We describe the structure of the essential spectrum of the operator H and prove that the essential spectrum is a union of at most four intervals.

  9. Supersymmetry and 198Hg

    NASA Astrophysics Data System (ADS)

    Bernards, Christian; Heinze, Stefan; Jolie, Jan; Fransen, Christoph; Linnemann, Andreas; Radeck, Désirée

    2009-01-01

    The energy spectrum and electromagnetic transition properties of the supermultiplet members with two proton fermions can be constructed using the dynamical Uv(6/12)⊗Uπ(6/4) extended supersymmetry. In order to investigate predictions of the two proton fermion—four neutron boson supermultiplet member 198Hg, an experiment with the HORUS cube γ-ray spectrometer at the Cologne TANDEM accelerator was performed using the 196Pt(α,2n)198Hg reaction. By analyzing γγ coincidence spectra and γγ angular correlations, the required experimental data—level and decay energies, level spins and multipole mixing ratios—could be obtained. For the low-energy states, the experimental data show good agreement with theory.

  10. Hg(+) Frequency Standards

    NASA Technical Reports Server (NTRS)

    Prestage, John D.; Tjoelker, Robert L.; Maleki, Lute

    2000-01-01

    In this paper we review the development of Hg(+) microwave frequency standards for use in high reliability and continuous operation applications. In recent work we have demonstrated short-term frequency stability of 3 x 10(exp -14)/nu(sub tau) when a cryogenic oscillator of stability 2-3 x 10(exp 15) was used a the local oscillator. The trapped ion frequency standard employs a Hg-202 discharge lamp to optically pump the trapped Hg(+)-199 clock ions and a helium buffer gas to cool the ions to near room temperature. We describe a small Hg(+) ion trap based frequency standard with an extended linear ion trap (LITE) architecture which separates the optical state selection region from the clock resonance region. This separation allows the use of novel trap configurations in the resonance region since no optical pumping is carried out there. A method for measuring the size of an ion cloud inside a linear trap with a 12-rod trap is currently being investigated. At approx. 10(exp -12), the 2nd order Doppler shift for trapped mercury ion frequency standards is one of the largest frequency offsets and its measurement to the 1% level would represent an advance in insuring the very long-term stability of these standards to the 10(exp -14) or better level. Finally, we describe atomic clock comparison experiments that can probe for a time variation of the fine structure constant, alpha = e(exp 2)/2(pi)hc, at the level of 10(exp -20)/year as predicted in some Grand Unified String Theories.

  11. Study of LWIR and VLWIR Focal Plane Array Developments: Comparison Between p-on- n and Different n-on- p Technologies on LPE HgCdTe

    NASA Astrophysics Data System (ADS)

    Gravrand, O.; Mollard, L.; Largeron, C.; Baier, N.; Deborniol, E.; Chorier, Ph.

    2009-08-01

    The very long infrared wavelength (>14 μm) is a very challenging range for the design of mercury cadmium telluride (HgCdTe) large focal plane arrays (FPAs). The need (mainly expressed by the space industry) for very long wave FPAs appears very difficult to fulfil. High homogeneity, low defect rate, high quantum efficiency, low dark current, and low excess noise are required. Indeed, for such wavelength, the corresponding HgCdTe gap becomes smaller than 100 meV and each step from the metallurgy to the technology becomes critical. This paper aims at presenting a status of long and very long wave FPAs developments at DEFIR (LETI-LIR/Sofradir joint venture). This study will focus on results obtained in our laboratory for three different ion implanted technologies: n-on- p mercury vacancies doped technology, n-on- p extrinsic doped technology, and p-on- n arsenic on indium technology. Special focus is given to 15 μm cutoff n/ p FPA fabricated in our laboratory demonstrating high uniformity, diffusion and shot noise limited photodiodes at 50 K.

  12. Modeling atmospheric concentrations and deposition of Hg

    SciTech Connect

    Shannon, J.D.

    1994-06-01

    The deleterious effects on ecosystems of mercury pollution are well established and fish advisories are in effect for many lakes in North America. Because methylation and other transformation processes in ecosystems can alter the original speciation of deposited Hg, a decrease in atmospheric loading of Hg in all forms is highly desirable. The contribution to Hg deposition by emissions from current anthropogenic activities relative to the deposition contribution by emissions from natural processes must be estimated to establish what fraction of atmospheric loading to watersheds and ecosystems is at least potentially amenable to control actions. Additional modeling questions concern source-receptor relationships (SRR) for major point sources and for emissions aggregated over geopolitical regions or emission sectors, because of the usefulness of SRR in comparing effectiveness of alternate control strategies. Modeling of atmospheric Hg is less advanced than that of some other widespread air pollution problems such as acid deposition. Nonetheless, several promising studies have been made for northern Europe and North America. For this study of Hg deposition in eastern North America we extend modeling techniques used extensively and successfully during the last 15 years for concentrations and deposition of SO{sub x} and NO{sub x} over regional scales, with parameterization rates adjusted to suitable values for Hg transformation and removal.

  13. Studies of interdiffusion, chemical bonding, and intermolecular interactions in fiber-matrix adhesion

    SciTech Connect

    Chou, Chiate.

    1990-01-01

    A study of the key factors involved in adhesion was conducted to determine a quantitative relation between the underlying physicochemical mechanisms of adhesion and the adhesive performance at the fiber-matrix interface. Aramid fiber was modified by attaching pendent chains to its surface to change the nature of its interaction with matrix materials. The relative importance of the three fundamental factors of adhesion (interdiffusion, intermolecular interactions, and chemical bonding) was studied by evaluating the fiber-matrix adhesive performance of these modified fiber-matrix systems.

  14. Cu(N-N){sub 2}Cl{sub 2} and Cu(N-N-N)Cl{sub 2} and HgCl{sub 2} building blocks in the synthesis of coordination compounds-X-ray studies and magnetic properties

    SciTech Connect

    Machura, B.; Switlicka, A.; Nawrot, I.; Mrozinski, J.; Kruszynski, R.; Kusz, J.

    2010-09-15

    A series of complexes containing Cu(N-N){sub 2}Cl{sub 2} (N-N=bis(pyrazol-1-yl)methane (bpzm), bis(3,5dimethylpyrazol-1-yl)methane (bdmpzm), 2,2-dipyridylamine (dpa), 5,6-diphenyl-3-(2-pyridyl)-1,2,4-trazine (dppt) and 2,2'-bipyridine (bipy)), Cu(N-N-N)Cl{sub 2} (N-N-N=2,2':6',2''-terpyridine (terpy)) and HgCl{sub 2} building blocks have been synthesized and structurally characterized. Increase in structural dimensionality is observed for [Cu(bpzm){sub 2}][HgCl{sub 4}], [Cu(dpa){sub 2}][HgCl{sub 3}]{sub 2} and [Cu(terpy)({mu}-Cl)HgCl{sub 3}] compounds. No coordination polymers have formed in the case of bis(3,5dimethylpyrazol-1-yl)methane, 5,6-diphenyl-3-(2-pyridyl)-1,2,4-trazine and 2,2'-bipyridine. The [Cu(bpzm){sub 2}][HgCl{sub 4}] and [Cu(terpy)({mu}-Cl)HgCl{sub 3}] complexes have been studied by magnetic measurements. - Graphical abstract: N-N: bis(3,5dimethylpyrazol-1-yl)methane (bdmpzm), 2,2-dipyridylamine (dpa), 5,6-diphenyl-3-(2-pyridyl)-1,2,4-trazine (dppt) and 2,2'-bipyridine (bipy), 6',2''-terpyridine (terpy).

  15. New adamantane-like mercury-chalcogen cages. 2. Synthetic and multinuclear ( sup 31 P, sup 77 Se, sup 125 Te, sup 199 Hg) magnetic resonance study of tellurolate-bridged mercury(III) clusters ((. mu. -TeR) sub 6 (HgPR prime sub 3 ) sub 4 ) sup 2+ and ((. mu. -TeR) sub 6 (Hg)(HgPR prime sub 3 ) sub 3 ) sup 2+ and related species with mixed-bridging chalcogenates

    SciTech Connect

    Dean, P.A.W.; Manivannan, V.; Vittal, J.J. )

    1989-06-14

    The salts (({mu}-TePh){sub 6}(HgPR{prime}{sub 3}){sub 3}(Hg))(ClO{sub 4}){sub 2} (R{prime} = Ph, 4-C{sub 6}H{sub 4}Me, 4-C{sub 6}H{sub 4}Cl) are preparable from Hg(TePh){sub 2}, Mg(PR{prime}{sub 3}){sub 2}(ClO{sub 4}){sub 2}, and PR{prime}P{sub 3} in a 3:1:1 ratio in CH{sub 2}Cl{sub 2} or CHCl{sub 3}. The new cations have been characterized in CH{sub 2}Cl{sub 2} and DMF by multinuclear ({sup 31}P, {sup 125}Te, {sup 199}Hg) magnetic resonance and shown to be of adamantanoid structure with novel tellurolate bridging. These spectra provide clear evidence for preferential formation of one (R{prime} = Ph) or a mixture of both (R{prime} = 4-C{sub 6}H{sub 4}Cl, in DMF solution) of the two C{sub 3} isomers that are possible for adamantane-like ({mu}-TeR){sub 6}M{sub 4} as a result of inversion at the pyramidal Te atoms. Such preferential isomer formation has not been demonstrated previously for any adamantanoid chalcogenate-bridge ({mu}-ER){sub 6}M{sub 4} in solution. Isomer formation at various temperatures is reported. For the cations with R = Ph, the rate of inversion at Te varies with R{prime} in the order alkyl > 4-C{sub 6}H{sub 4}Me > Ph > 4-C{sub 6}H{sub 4}Cl. When R = Ph, R{prime} = 4-C{sub 6}H{sub 4}Me, NMR spectra ({sup 31}P, {sup 77}Se, {sup 125}Te, {sup 199}Hg) of mixtures of ((TeR){sub 6}(HgPR{prime}{sub 3}){sub 4}){sup 2+} and (({mu}-ER){sub 6}(HgPR{prime}{sub 3}){sub 4}){sup 2+} (E = S, Se) provide evidence for the formation of the mixed-chalcogen cores ({mu}-Te){sub 6-m}({mu}-E){sub m}Hg{sub 4}. 35 refs., 8 figs., 3 tabs.

  16. Stable Hg isotope signatures in creek sediments impacted by a former Hg mine.

    PubMed

    Smith, Robin S; Wiederhold, Jan G; Jew, Adam D; Brown, Gordon E; Bourdon, Bernard; Kretzschmar, Ruben

    2015-01-20

    The goal of this study was to investigate the Hg stable isotope signatures of sediments in San Carlos Creek downstream of the former Hg mine New Idria, CA, USA and to relate the results to previously studied Hg isotope signatures of unroasted ore waste and calcine materials in the mining area. New Idria unroasted ore waste was reported to have a narrow δ(202)Hg range (−0.09 to 0.16‰), while roasted calcine materials exhibited a very large variability in δ(202)Hg (−5.96 to 14.5‰). In this study, creek sediment samples were collected in the stream bed from two depths (0–10 and 10–20 cm) at 10 locations between the mine adit and 28 km downstream. The sediment samples were size-fractionated into sand, silt, and (if possible) clay fractions as well as hand-picked calcine pebbles. The sediment samples contained highly elevated Hg concentrations (8.2 to 647 μg g(–1)) and displayed relatively narrow mass-dependent fractionation (MDF, δ(202)Hg; ± 0.08‰, 2SD) ranges (−0.58 to 0.24‰) and little to no mass-independent fractionation (MIF, Δ(199)Hg; ± 0.04‰, 2SD) (0.00 to 0.10‰), similar to what was observed previously for the unroasted ore waste. However, due to the highly variable and overlapping δ(202)Hg signatures of the calcines, they could not be ruled out as source of Hg to the creek sediments. Overall, our results suggest that analyzing creek sediments downstream of former Hg mines can provide a more reliable Hg isotope source signature for tracing studies at larger spatial scales, than analyzing the isotopically highly heterogeneous tailing piles typically found at former mining sites. Creek sediments carry an integrated isotope signature of Hg transported away from the mine with runoff into the creek, eventually affecting ecosystems downstream. PMID:25489982

  17. Hg0 absorption in potassium persulfate solution*

    PubMed Central

    Ye, Qun-feng; Wang, Cheng-yun; Wang, Da-hui; Sun, Guan; Xu, Xin-hua

    2006-01-01

    The aqueous phase oxidation of gaseous elemental mercury (Hg0) by potassium persulfate (KPS) catalyzed by Ag+ was investigated using a glass bubble column reactor. Concentration of gaseous mercury and potassium persulfate were measured by cold vapor atom absorption (CVAA) and ion chromatograph (IC), respectively. The effects of pH value, concentration of potassium persulfate and silver nitrate (SN), temperature, Hg0 concentration in the reactor inlet and tertiary butanol (TBA), free radical scavenger, on the removal efficiency of Hg0 were studied. The results showed that the removal efficiency of Hg0 increased with increasing concentration of potassium persulfate and silver nitrate, while temperature and TBA were negatively effective. Furthermore, the removal efficiency of Hg0 was much better in neutral solution than in both acidic and alkaline solution. But the influence of pH was almost eliminated by adding AgNO3. High Hg0 concentration has positive effect. The possible reaction mechanism of gaseous mercury was also discussed. PMID:16615172

  18. Hg(0) absorption in potassium persulfate solution.

    PubMed

    Ye, Qun-feng; Wang, Cheng-yun; Wang, Da-hui; Sun, Guan; Xu, Xin-hua

    2006-05-01

    The aqueous phase oxidation of gaseous elemental mercury (Hg(0)) by potassium persulfate (KPS) catalyzed by Ag(+) was investigated using a glass bubble column reactor. Concentration of gaseous mercury and potassium persulfate were measured by cold vapor atom absorption (CVAA) and ion chromatograph (IC), respectively. The effects of pH value, concentration of potassium persulfate and silver nitrate (SN), temperature, Hg(0) concentration in the reactor inlet and tertiary butanol (TBA), free radical scavenger, on the removal efficiency of Hg(0) were studied. The results showed that the removal efficiency of Hg(0) increased with increasing concentration of potassium persulfate and silver nitrate, while temperature and TBA were negatively effective. Furthermore, the removal efficiency of Hg(0) was much better in neutral solution than in both acidic and alkaline solution. But the influence of pH was almost eliminated by adding AgNO(3). High Hg(0) concentration has positive effect. The possible reaction mechanism of gaseous mercury was also discussed. PMID:16615172

  19. Stable mercury isotope ratios as tracers for Hg cycling at the inoperative New Idria Hg mine, California

    NASA Astrophysics Data System (ADS)

    Wiederhold, J. G.; Jew, A. D.; Brown, G. E.; Bourdon, B.; Kretzschmar, R.

    2010-12-01

    The seven stable isotopes of Hg are fractionated in the environment as a result of mass-dependent (MDF) and mass-independent (MIF) fractionation processes that can be studied in parallel by analyzing the ratios of even and odd mass Hg isotopes. MDF and MIF Hg isotope signatures of natural samples may provide a new tool to trace sources and transformations in environmental Hg cycling. However, the mechanisms controlling the extent of kinetic and equilibrium Hg isotope fractionations are still only partially understood. Thus, development of this promising tracer requires experimental calibration of relevant fractionation factors as well as assessment of natural variations of Hg isotope ratios under different environmental conditions. The inoperative Hg mine in New Idria (California, USA) represents an ideal case study to explore Hg isotope fractionation during Hg transformation and transport processes. More than a century of Hg mining and on-site thermal refining to obtain elemental Hg until 1972 produced large volumes of contaminated mine wastes which now represent sources of Hg pollution for the surrounding ecosystems. Here, we present Hg isotope data from various materials collected at New Idria using Cold-Vapor-MC-ICPMS with a long-term δ202Hg reproducibility of ±0.1‰ (2SD). Uncalcined mine waste samples were isotopically similar to NIST-3133 and did not exhibit any MIF signatures. In contrast, calcine samples, which represent the residue of the thermal ore processing at 700°C, had significantly heavier δ202Hg values of up to +1.5‰. In addition, we observed small negative MIF anomalies of the odd-mass Hg isotopes in the calcine samples, which could be caused either by nuclear volume fractionation or a magnetic isotope effect during or after the roasting process. The mass-dependent enrichment of heavy Hg isotopes in the calcine materials indicates that light Hg isotopes were preferentially removed during the roasting process, in agreement with a previous

  20. Effective management of major lower extremity wounds using an acellular regenerative tissue matrix: a pilot study.

    PubMed

    Brigido, Stephen A; Boc, Steven F; Lopez, Ramon C

    2004-01-01

    Wound healing is a significant problem in orthopedics. Graftjacket tissue matrix (Wright Medical Technology, Inc, Arlington, Tenn), a novel acellular regenerative tissue matrix, has been designed to aid wound closure. A prospective, randomized study was initiated to determine the efficacy of this tissue product in wound repair compared with conventional treatment. Lower extremity wounds are refractile to healing in patients with diabetes mellitus. Therefore, researchers used diabetic foot ulcers to evaluate the efficacy of GraftJacket tissue matrix in wound repair. Only a single administration of the tissue matrix was required. After 1 month of treatment, preliminary results demonstrate that this novel tissue matrix promotes faster healing at a statistically significant rate over conventional treatment. Because wounds in this series of patients are deep and circulation around the wound is poor, the preliminary results suggest that this tissue matrix will be applicable to other types of orthopedic wounds. PMID:14763548

  1. Fluctuation studies in the infinite interval matrix representations of operator products and their decompositions

    SciTech Connect

    Baykara, N. A.; Guervit, Ercan; Demiralp, Metin

    2012-12-10

    In this work a study on finite dimensional matrix approximations to products of quantum mechanical operators is conducted. It is emphasized that the matrix representation of the product of two operators is equal to the product of the matrix representation of each of the operators when all the fluctuation terms are ignored. The calculation of the elements of the matrices corresponding to the matrix representation of various operators, based on three terms recursive relation is defined. Finally it is shown that the approximation quality depends on the choice of higher values of n, namely the dimension of Hilbert space.

  2. Anaerobic oxidation of Hg(0) and methylmercury formation by Desulfovibrio desulfuricans ND132

    NASA Astrophysics Data System (ADS)

    Colombo, Matthew J.; Ha, Juyoung; Reinfelder, John R.; Barkay, Tamar; Yee, Nathan

    2013-07-01

    The transformation of inorganic mercury (Hg) to methylmercury (MeHg) plays a key role in determining the amount of Hg that is bioaccumulated in aquatic food chains. An accurate knowledge of Hg methylation mechanisms is required to predict the conditions that promote MeHg production in aquatic environments. In this study, we conducted experiments to examine the oxidation and methylation of dissolved elemental mercury [Hg(0)] by the anaerobic bacterium Desulfovibrio desulfuricans ND132. Anoxic cultures of D. desulfuricans ND132 were exposed to Hg(0) in the dark, and samples were collected and analyzed for the loss of Hg(0), formation of non-purgeable Hg, and formation of MeHg over time. We found that D. desulfuricans ND132 rapidly transformed dissolved gaseous mercury into non-purgeable Hg, with bacterial cultures producing approximately 40 μg/L of non-purgeable Hg within 30 min, and as much as 800 μg/L of non-purgeable Hg after 36 h. Derivatization of the non-purgeable Hg in the cell suspensions to diethylmercury and analysis of Hg(0)-reacted D. desulfuricans ND132 cells using X-ray absorption near edge structure (XANES) spectroscopy demonstrated that cell-associated Hg was dominantly in the oxidized Hg(II) form. Spectral comparisons and linear combination fitting of the XANES spectra indicated that the oxidized Hg(II) was covalently bonded to cellular thiol functional groups. MeHg analyses revealed that D. desulfuricans ND132 produced up to 118 μg/L of methylmercury after 36 h of incubation. We found that a significant fraction of the methylated Hg was exported out of the cell and released into the culture medium. The results of this work demonstrate a previously unrecognized pathway in the mercury cycle, whereby anaerobic bacteria produce MeHg when provided with dissolved Hg(0) as their sole Hg source.

  3. Matrix Training of Receptive Language Skills with a Toddler with Autism Spectrum Disorder: A Case Study

    ERIC Educational Resources Information Center

    Curiel, Emily S. L.; Sainato, Diane M.; Goldstein, Howard

    2016-01-01

    Matrix training is a systematic teaching approach that can facilitate generalized language. Specific responses are taught that result in the emergence of untrained responses. This type of training facilitates the use of generalized language in children with autism spectrum disorder (ASD). This study used a matrix training procedure with a toddler…

  4. Three-Dimensional-Engineered Matrix to Study Cancer Stem Cells and Tumorsphere Formation: Effect of Matrix Modulus

    PubMed Central

    Yang, Xiaoming; Sarvestani, Samaneh K.; Moeinzadeh, Seyedsina; He, Xuezhong

    2013-01-01

    Maintenance of cancer stem cells (CSCs) is regulated by the tumor microenvironment. Synthetic hydrogels provide the flexibility to design three-dimensional (3D) matrices to isolate and study individual factors in the tumor microenvironment. The objective of this work was to investigate the effect of matrix modulus on tumorsphere formation by breast cancer cells and maintenance of CSCs in an inert microenvironment without the interference of other factors. In that regard, 4T1 mouse breast cancer cells were encapsulated in inert polyethylene glycol diacrylate hydrogels and the effect of matrix modulus on tumorsphere formation and expression of CSC markers was investigated. The gel modulus had a strong effect on tumorsphere formation and the effect was bimodal. Tumorsphere formation and expression of CSC markers peaked after 8 days of culture. At day 8, as the matrix modulus was increased from 2.5 kPa to 5.3, 26.1, and 47.1 kPa, the average tumorsphere size changed from 37±6 μm to 57±6, 20±4, and 12±2 μm, respectively; cell number density in the gel changed from 0.8±0.1×105 cells/mL to 1.7±0.2×105, 0.4±0.1×105, and 0.2±0.1×105 cells/mL after initial encapsulation of 0.14×105 cells/mL; and the expression of CD44 breast CSC marker changed from 17±4-fold to 38±9-, 3±1-, and 2±1-fold increase compared with the initial level. Similar results were obtained with MCF7 human breast carcinoma cells. Mouse 4T1 and human MCF7 cells encapsulated in the gel with 5.3 kPa modulus formed the largest tumorspheres and highest density of tumorspheres, and had highest expression of breast CSC markers CD44 and ABCG2. The inert polyethylene glycol hydrogel can be used as a model-engineered 3D matrix to study the role of individual factors in the tumor microenvironment on tumorigenesis and maintenance of CSCs without the interference of other factors. PMID:23013450

  5. Hg-Mask Coronagraph

    NASA Astrophysics Data System (ADS)

    Bourget, P.; Veiga, C. H.; Vieira Martins, R.; Assus, P.; Colas, F.

    In order to optimize the occulting process of a Lyot coronagraph and to provide a high dynamic range imaging, a new kind of occulting disk has been developed at the National Observatory of Rio de Janeiro. A mercury (Hg) drop glued onto an optical window by molecular cohesion and compressed by a pellicle film is used as the occulting disk. The minimum of the superficial tension potential function provides an optical precision (lambda/100) of the toric free surface of the mercury. This process provides a size control for the adaptation to the seeing conditions and to the apparent diameter of a resolved object, and in the case of adaptive optics, to the Airy diameter fraction needed. The occultation is a three dimensional process near the focal plane on the toric free surface that provides an apodization of the occultation. The Hg-Mask coronagraph has been projected for astrometric observations of faint satellites near to Jovian planets and works since 2000 at the 1.6 m telescope of the Pico dos Dias Observatory (OPD - Brazil).

  6. An Evaluation of Matrix-Containing and Humanised Matrix-Free 3-Dimensional Cell Culture Systems for Studying Breast Cancer

    PubMed Central

    Roberts, Grace C.; Morris, Paul G.; Moss, Marcus A.; Maltby, Sarah L.; Palmer, Chelsea A.; Nash, Claire E.; Smart, Emily; Holliday, Deborah L.; Speirs, Valerie

    2016-01-01

    Background 3D cell cultures are emerging as more physiologically meaningful alternatives to monolayer cultures for many biological applications. They are attractive because they more closely mimic in vivo morphology, especially when co-cultured with stromal fibroblasts. Methodology/Principal Findings We compared the efficacy of 3 different 3D cell culture systems; collagen I, low attachment culture vessels and a modification of Fibrolife®, a specialised humanised cell culture medium devoid of animal-derived components, using breast cancer cell lines representative of the different molecular subtypes of breast cancer, cultured alone or with human mammary fibroblasts with a view to developing matrix-free humanised systems. 3D collagen I culture supported the growth of a range of breast cancer cell lines. By modifying the composition of Fibrolife® to epiFL, matrix-free cell culture was possible. During sequential transfer to epiFL breast cancer cells gradually detached from the flask, growing progressively as spheroids. Phenotype was stable and reversible with cells remaining actively proliferating and easily accessible throughout culture. They could also be revived from frozen stocks. To achieve co-culture with fibroblasts in epiFL required use of low attachment culture vessels instead of standard plastic as fibroblasts remained adherent in epiFL. Here, cancer cell spheroids were allowed to form before adding fibroblasts. Immunohistochemical examination showed fibroblasts scattered throughout the epithelial spheroid, not dissimilar to the relationship of tumour stroma in human breast cancer. Conclusions Because of its ease of handling, matrix-free 3D cell culture may be a useful model to study the influence of fibroblasts on breast cancer epithelial cells with use of epiFL culture medium taking this a step further towards a fully humanised 3D model. This methodology could be applied to other types of cancer cell lines, making this a versatile technique for cancer

  7. Genome-Wide Association Study of Resistance to Soybean Cyst Nematode (Heterodera glycines) HG Type 2.5.7 in Wild Soybean (Glycine soja)

    PubMed Central

    Zhang, Hengyou; Li, Chunying; Davis, Eric L.; Wang, Jinshe; Griffin, Joshua D.; Kofsky, Janice; Song, Bao-Hua

    2016-01-01

    Soybean cyst nematode (SCN) is the most destructive soybean pest worldwide. Host plant resistance is the most environmentally friendly and cost-effective way of mitigating SCN damage to soybeans. However, overuse of the resistant soybean [Glycine max (L.) Merr.] cultivars from limited genetic resources has resulted in SCN race shifts in many soybean-growing areas. Thus, exploration of novel sources of SCN resistance and dissection of the genetic basis are urgently needed. In this study, we screened 235 wild soybean (Glycine soja Sieb. & Zucc.) accessions to identify genotypes resistant to SCN HG Type 2.5.7 (race 5), a less investigated type but is prevalent in the southeastern US. We also dissected the genetic basis of SCN resistance using a genome-wide association study with SNPs genotyped by SoySNP50k iSelect BeadChip. In total, 43 resistant accessions (female index < 30) were identified, with 10 SNPs being significantly associated with SCN HG 2.5.7 resistance in this wild species. Furthermore, four significant SNPs were localized to linked regions of the known quantitative trait locus (QTL) rhg1 on chromosome 18. The other four SNPs on chromosome 18 and two SNPs on chromosome 19 are novel. Genes encoding disease resistance-related proteins with a leucine-rich region, a mitogen-activated protein kinase (MAPK) on chromosome 18, and a MYB transcription factor on chromosome 19 were identified as promising candidate genes. The identified SNPs and candidate genes will benefit future marker-assisted breeding and dissection of the molecular mechanisms underlying the soybean-SCN interaction. PMID:27582748

  8. Genome-Wide Association Study of Resistance to Soybean Cyst Nematode (Heterodera glycines) HG Type 2.5.7 in Wild Soybean (Glycine soja).

    PubMed

    Zhang, Hengyou; Li, Chunying; Davis, Eric L; Wang, Jinshe; Griffin, Joshua D; Kofsky, Janice; Song, Bao-Hua

    2016-01-01

    Soybean cyst nematode (SCN) is the most destructive soybean pest worldwide. Host plant resistance is the most environmentally friendly and cost-effective way of mitigating SCN damage to soybeans. However, overuse of the resistant soybean [Glycine max (L.) Merr.] cultivars from limited genetic resources has resulted in SCN race shifts in many soybean-growing areas. Thus, exploration of novel sources of SCN resistance and dissection of the genetic basis are urgently needed. In this study, we screened 235 wild soybean (Glycine soja Sieb. & Zucc.) accessions to identify genotypes resistant to SCN HG Type 2.5.7 (race 5), a less investigated type but is prevalent in the southeastern US. We also dissected the genetic basis of SCN resistance using a genome-wide association study with SNPs genotyped by SoySNP50k iSelect BeadChip. In total, 43 resistant accessions (female index < 30) were identified, with 10 SNPs being significantly associated with SCN HG 2.5.7 resistance in this wild species. Furthermore, four significant SNPs were localized to linked regions of the known quantitative trait locus (QTL) rhg1 on chromosome 18. The other four SNPs on chromosome 18 and two SNPs on chromosome 19 are novel. Genes encoding disease resistance-related proteins with a leucine-rich region, a mitogen-activated protein kinase (MAPK) on chromosome 18, and a MYB transcription factor on chromosome 19 were identified as promising candidate genes. The identified SNPs and candidate genes will benefit future marker-assisted breeding and dissection of the molecular mechanisms underlying the soybean-SCN interaction. PMID:27582748

  9. Wear and Reactivity Studies of Melt infiltrated Ceramic Matrix Composite

    NASA Technical Reports Server (NTRS)

    Jarmon, David C.; Ojard, Greg; Brewer, David N.

    2013-01-01

    As interest grows in the use of ceramic matrix composites (CMCs) for critical gas turbine engine components, the effects of the CMCs interaction with the adjoining structure needs to be understood. A series of CMC/material couples were wear tested in a custom elevated temperature test rig and tested as diffusion couples, to identify interactions. Specifically, melt infiltrated silicon carbide/silicon carbide (MI SiC/SiC) CMC was tested in combination with a nickel-based super alloy, Waspaloy, a thermal barrier coating, Yttria Stabilized Zirconia (YSZ), and a monolithic ceramic, silicon nitride (Si3N4). To make the tests more representative of actual hardware, the surface of the CMC was kept in the as-received state (not machined) with the full surface features/roughness present. Test results include: scanning electron microscope characterization of the surfaces, micro-structural characterization, and microprobe analysis.

  10. Matrix population models from 20 studies of perennial plant populations

    USGS Publications Warehouse

    Ellis, Martha M.; Williams, Jennifer L.; Lesica, Peter; Bell, Timothy J.; Bierzychudek, Paulette; Bowles, Marlin; Crone, Elizabeth E.; Doak, Daniel F.; Ehrlen, Johan; Ellis-Adam, Albertine; McEachern, Kathryn; Ganesan, Rengaian; Latham, Penelope; Luijten, Sheila; Kaye, Thomas N.; Knight, Tiffany M.; Menges, Eric S.; Morris, William F.; den Nijs, Hans; Oostermeijer, Gerard; Quintana-Ascencio, Pedro F.; Shelly, J. Stephen; Stanley, Amanda; Thorpe, Andrea; Tamara, Ticktin; Valverde, Teresa; Weekley, Carl W.

    2012-01-01

    Demographic transition matrices are one of the most commonly applied population models for both basic and applied ecological research. The relatively simple framework of these models and simple, easily interpretable summary statistics they produce have prompted the wide use of these models across an exceptionally broad range of taxa. Here, we provide annual transition matrices and observed stage structures/population sizes for 20 perennial plant species which have been the focal species for long-term demographic monitoring. These data were assembled as part of the 'Testing Matrix Models' working group through the National Center for Ecological Analysis and Synthesis (NCEAS). In sum, these data represent 82 populations with >460 total population-years of data. It is our hope that making these data available will help promote and improve our ability to monitor and understand plant population dynamics.

  11. Matrix population models from 20 studies of perennial plant populations

    USGS Publications Warehouse

    Ellis, Martha M.; Williams, Jennifer L.; Lesica, Peter; Bell, Timothy J.; Bierzychudek, Paulette; Bowles, Marlin; Crone, Elizabeth E.; Doak, Daniel F.; Ehrlen, Johan; Ellis-Adam, Albertine; McEachern, Kathryn; Ganesan, Rengaian; Latham, Penelope; Luijten, Sheila; Kaye, Thomas N.; Knight, Tiffany M.; Menges, Eric S.; Morris, William F.; den Nijs, Hans; Oostermeijer, Gerard; Quintana-Ascencio, Pedro F.; Shelly, J. Stephen; Stanley, Amanda; Thorpe, Andrea; Tamara, Ticktin; Valverde, Teresa; Weekley, Carl W.

    2012-01-01

    Demographic transition matrices are one of the most commonly applied population models for both basic and applied ecological research. The relatively simple framework of these models and simple, easily interpretable summary statistics they produce have prompted the wide use of these models across an exceptionally broad range of taxa. Here, we provide annual transition matrices and observed stage structures/population sizes for 20 perennial plant species which have been the focal species for long-term demographic monitoring. These data were assembled as part of the "Testing Matrix Models" working group through the National Center for Ecological Analysis and Synthesis (NCEAS). In sum, these data represent 82 populations with >460 total population-years of data. It is our hope that making these data available will help promote and improve our ability to monitor and understand plant population dynamics.

  12. Precision Study of Excited State Effects in Nucleon Matrix Elements

    SciTech Connect

    Simon Dinter, Constantia Alexandrou, Martha Constantinou, Vincent Drach, Karl Jansen, Dru B. Renner

    2011-10-01

    We present a dedicated precision analysis of the influence of excited states on the calculation of several nucleon matrix elements. This calculation is performed at fixed values of the lattice spacing, volume and pion mass that are typical of contemporary lattice computations. We focus on the nucleon axial charge, g{sub A}, for which we use 7,500 measurements, and on the average momentum of the unpolarized isovector parton distribution, x{sub u-d}, for which we use 23,000 measurements. All computations are done employing N{sub f}=2+1+1 maximally-twisted-mass Wilson fermions and non-perturbatively calculated renormalization factors. We find that excited state effects are negligible for g{sub A} and lead to a O(10%) downward shift for x{sub u-d}.

  13. Persistent Hg contamination and occurrence of Hg-methylating transcript (hgcA) downstream of a chlor-alkali plant in the Olt River (Romania).

    PubMed

    Bravo, Andrea G; Loizeau, Jean-Luc; Dranguet, Perrine; Makri, Stamatina; Björn, Erik; Ungureanu, Viorel Gh; Slaveykova, Vera I; Cosio, Claudia

    2016-06-01

    Chlor-alkali plants using mercury (Hg) cell technology are acute point sources of Hg pollution in the aquatic environment. While there have been recent efforts to reduce the use of Hg cells, some of the emitted Hg can be transformed to neurotoxic methylmercury (MeHg). Here, we aimed (i) to study the dispersion of Hg in four reservoirs located downstream of a chlor-alkali plant along the Olt River (Romania) and (ii) to track the activity of bacterial functional genes involved in Hg methylation. Total Hg (THg) concentrations in water and sediments decreased successively from the initial reservoir to downstream reservoirs. Suspended fine size particles and seston appeared to be responsible for the transport of THg into downstream reservoirs, while macrophytes reflected the local bioavailability of Hg. The concentration and proportion of MeHg were correlated with THg, but were not correlated with bacterial activity in sediments, while the abundance of hgcA transcript correlated with organic matter and Cl(-) concentration, indicating the importance of Hg bioavailability in sediments for Hg methylation. Our data clearly highlights the importance of considering Hg contamination as a legacy pollutant since there is a high risk of continued Hg accumulation in food webs long after Hg-cell phase out. PMID:26662302

  14. Chronologically matched toenail-Hg to hair-Hg ratio: temporal analysis within the Japanese community (U.S.)

    PubMed Central

    2012-01-01

    Background Toenail-Hg levels are being used as a marker of methylmercury (MeHg) exposure in efforts to associate exposure with effects such as cardiovascular disease. There is a need to correlate this marker with more established biomarkers that presently underlie existing dose–response relationships in order to compare these relationships across studies. Methods As part of the Arsenic Mercury Intake Biometric Study, toenail clippings were collected at three time points over a period of one year amongst females from within the population of Japanese living near Puget Sound in Washington State (US). Variability in temporal intra-individual toenail-Hg levels was examined and chronologically matched hair and toenail samples were compared to more accurately define the toxicokinetic variability of Hg levels observed between the two compartments. Results Mean toenail-Hg values (n=43) for the 1st, 2nd and 3rd visits were 0.60, 0.60 and 0.56 ng/mg. Correlations were as follows: r=0.92 between 1st and 2nd clinic visits, r=0.75 between 1st and 3rd visits and r=0.87 between 2nd and 3rd visits. With few exceptions, toenail-Hg values from any visit were within 50-150% of the individual’s mean toenail-Hg level. Nearly all participants had less than a two-fold change in toenail-Hg levels across the study period. A regression model of the relationship between toenail-Hg and hair-Hg (n = 41) levels representing the same time period of exposure, gave a slope (Hg ng/mg) of 2.79 for hair relative to toenail (r=0.954). Conclusions A chronologically matched hair-Hg to toenail-Hg ratio has been identified within a population that consumes fish regularly and in quantity. Intra-individual variation in toenail-Hg levels was less than two-fold and may represent dietary-based fluctuations in body burden for individuals consuming various fish species with different contaminant levels. The chronologically matched ratio will be useful for relating MeHg exposure and dose–response derived

  15. Theoretical study of the formation of mercury (Hg2+) complexes in solution using an explicit solvation shell in implicit solvent calculations.

    PubMed

    Afaneh, Akef T; Schreckenbach, Georg; Wang, Feiyue

    2014-09-25

    The structures and harmonic vibrational frequencies of water clusters (H2O)n, n = 1-10, have been computed using the M06-L/, B3LYP/, and CAM-BLYP/cc-pVTZ levels of theories. On the basis of the literature and our results, we use three hexamer structures of the water molecules to calculate an estimated "experimental" average solvation free energy of [Hg(H2O)6](2+). Aqueous formation constants (log K) for Hg(2+) complexes, [Hg(L)m(H2O)n](2-mq), L = Cl(-), HO(-), HS(-), and S(2-), are calculated using a combination of experimental (solvation free energies of ligands and Hg(2+)) and calculated gas- and liquid-phase free energies. A combined approach has been used that involves attaching n explicit water molecules to the Hg(2+) complexes such that the first coordination sphere is complete, then surrounding the resulting (Hg(2+)-Lm)-(OH2)n cluster by a dielectric continuum, and using suitable thermodynamic cycles. This procedure significantly improves the agreement between the calculated log K values and experiment. Thus, for some neutral and anionic Hg(II) complexes, particularly Hg(II) metal ion surrounded with homo- or heteroatoms, augmenting implicit solvent calculations with sufficient explicit water molecules to complete the first coordination sphere is required-and adequate-to account for strong short-range hydrogen bonding interactions between the anion and the solvent. Calculated values for formation constants of Hg(2+) complexes with S(2-) and SH(-) are proposed. Experimental measurements of these log K values have been lacking or controversial. PMID:25076413

  16. Adsorption of Hg on lunar samples

    SciTech Connect

    Reed, G.W. Jr.; Jovanovic, S.

    1985-01-01

    Understanding the presence, migration mechanisms and trapping of indigneous gases and volatiles on the moon is the objective of this study. The rare gases Ar and Xe and highly volatile Hg/sup 0/ and Br/sup 0/ (and/or their compounds) have been determined to be present in the lunar regolith. Evidence for these elements in the moon was recently reviewed. Studies of the sorption behavior of Xe on lunar material have been carried out. We report here preliminary results of a study designed to rationalize the behavior of Hg in lunar material.

  17. Material and structural studies of metal and polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Signorelli, R. A.; Serafini, T. T.; Johns, R. H.

    1973-01-01

    Fiber-reinforced composites and design analysis methods for these materials are being developed because of the vast potential of composites for decreasing weight and/or increasing use temperature capability in aerospace systems. These composites have potential for use in airbreathing engine components as well as aeronautical and space vehicle structures. Refractory wire-superalloy composites for use up to 2200 F or more and metal-matrix composites for lower temperature applications such as aerospace structures and turbojet fan and compressor blades are under investigation and are discussed. The development of a number of resin systems, including the polyimides and polyphenylquinoxalines, is described and their potential for use at temperatures approaching 315 C (600 F) is indicated. Various molecular modifications that improve processability and/or increase thermal and oxidative resistance of the resins are also described. Structural analysis methods are discussed for determining the stresses and deformations in complex composite systems. Consideration is also given to residual stresses resulting from the curing process and to the foreign object damage problem in fan blade applications.

  18. In vitro studies to show sequestration of matrix metalloproteinases by silver-containing wound care products.

    PubMed

    Walker, Michael; Bowler, Philip G; Cochrane, Christine A

    2007-09-01

    Excess or "uncontrolled" proteinase activity in the wound bed has been implicated as one factor that may delay or compromise wound healing. One proteinase group--matrix metalloproteinases--includes collagenases, elastase, and gelatinases and can be endogenous (cell) or exogenous (bacterial) in origin. A study was conducted to assess the ability of five silver-containing wound care products to reduce a known matrix metalloproteinase supernatant concentration in vitro. Four silver-containing wound dressings (a carboxy-methyl cellulose, a nanocrystalline, a hydro-alginate, and a collagen/oxidized regenerated cellulose composite dressing), along with a 0.5% aqueous silver nitrate [w/v] solution and controls for matrix metalloproteinase-2 and matrix metalloproteinase-9 sourced from ex vivo dermal tissue and blood monocytes, respectively, were used. Extracts were separated and purified using gelatine-Sepharose column chromatography and dialysis and polyacrylamide gel electrophoretic zymography was used to analyze specific matrix metalloproteinase activity. All dressings and the solution were shown to sequester both matrix metalloproteinases. The silver-containing carboxy-methyl cellulose dressing showed significantly greater sequestration for matrix metalloproteinase-2 at 6 and 24 hours (P< 0.001) compared to the other treatments. For matrix metalloproteinase-9, both the carboxy-methyl cellulose dressing and the oxidized regenerated cellulose dressing achieved significant sequestration when compared to the other treatments at 24 hours (P <0.001), which was maintained to 48 hours (P < 0.001). Results from this study show that silver-containing dressings are effective in sequestering matrix metalloproteinase-2 and -9 and that this can be achieved without a sacrificial protein (eg, collagen). Although the varying ability of wound dressings to sequester matrix metalloproteinases has been shown in vitro, further in vivo evidence is required to confirm these findings. PMID

  19. Analysis of RFSA Campaign No.2 Dissolver Solution for Hg(I) and Hg(II)

    SciTech Connect

    Holcomb, H.P.

    2001-05-17

    TA 2-1083, under which RFSA processing is conducted, calls for a nominal mercuric ion concentration in the dissolver solution of 0.006M with a maximum of 0.01 M. The second RFSA campaign operated according to these guidelines with the initial Hg(II) concentration being 0.0068 M. Part of this study is to ascertain optimum excess Hg(I) for chloride removal.

  20. One-pot synthesis of two-sized clusters for ratiometric sensing of Hg2+.

    PubMed

    Chen, Tzu-Heng; Lu, Chi-Yu; Tseng, Wei-Lung

    2013-12-15

    This paper presents a discussion of a one-pot approach for preparing lyszoyme type VI (Lys VI) stabilized clusters, including small (Au7Ag and Au8) and large (Au24Ag) clusters, for ratiometric fluorescence sensing of Hg(2+). Our previous study (Chen and Tseng, Small 8 (2012) 1912) showed the formation of intermediate Au8 clusters in the conversion of Au(+)-Lys VI protein complexes to Au25 clusters. The presence of Ag(+) in the precursor solution slowed this conversion, thereby forming two-sized clusters. With an increase in Ag(+) content, a systematic blue shift in the first exciton absorption and fluorescence peaks indicated the formation of Au-Ag bimetallic clusters. The prepared Ag(+)/Au(3+) molar ratio of 2:8 resulted in the formation of two-sized clusters, with dual emission bands centered at 471 and 613 nm. After these clusters are separated by a membrane filter, matrix-assisted laser desorption/ionization time-of-flight mass spectrometry was used to determine the composition of Au24Ag clusters. By monitoring the intensity ratio of the two emission wavelengths, the solution consisting of Hg(2+)-insensitive small clusters (Au7Ag and Au8) and Hg(2+)-sensitive Au24Ag clusters exhibited a ratiometric fluorescence response toward Hg(2+), and provided a built-in correction for photobleaching; the limit of detection at a signal-to-noise ratio of three for Hg(2+) was estimated to be 1 nM. This probe was successfully applied to ratiometric fluorescence sensing of Hg(2+) in tap water. PMID:24209338

  1. Combined tween 20-stabilized gold nanoparticles and reduced graphite oxide-Fe3O4 nanoparticle composites for rapid and efficient removal of mercury species from a complex matrix.

    PubMed

    Shih, Ya-Chen; Ke, Chen-Yi; Yu, Cheng-Ju; Lu, Chi-Yu; Tseng, Wei-Lung

    2014-10-22

    This study describes a simple method for removing mercuric ions (Hg(2+)) from a high-salt matrix based on the use of Tween-20-stabilized gold nanoparticles (Tween 20-Au NPs) as Hg(2+) adsorbents and composites of reduced graphite oxide and Fe3O4 NPs as NP collectors. Citrate ions adsorbed on the surface of the Tween 20-Au NPs reduced Hg(2+) to Hg(0), resulting in the deposition of Hg(0) on the surface of the NPs. To circumvent time-consuming centrifugation and transfer steps, the Hg(0)-containing gold NPs were collected using reduced graphite oxide-Fe3O4 NP composites. Compared with the reported NP-based methods for removing Hg(2+), Tween 20-Au NPs offered the rapid (within 30 min), efficient (>99% elimination efficiency), durable (>10 cycles), and selective removal of Hg(2+), CH3Hg(+), and C2H5Hg(+) in a high-salt matrix without the interference of other metal ions. This was attributed to the fact that the dispersed Tween 20-Au NPs exhibited large surface-area-to-volume ratio to bind Hg(2+) through Hg(2+)-Au(+) metallophilic interactions in a high-salt matrix. The formation of graphite oxide sheets and reduced graphite oxide-Fe3O4 NP composites was demonstrated using X-ray diffraction, X-ray photoelectron spectroscopy, Raman spectroscopy, Fourier transform infrared spectrometry, and transmission electron microscopy. The mechanism of interaction between Tween 20-Au NPs and Hg(2+) was studied using visible spectroscopy, transmission electron microscopy, and X-ray photoelectron spectroscopy. PMID:25238563

  2. Distribution and excretion of Cd, Hg, methyl-Hg and ZS in the predatory beetle Pterostichus niger (Coleoptera: Carabidae)

    SciTech Connect

    Lindqvist, L.; Block, M.; Tjaelve, H.

    1995-07-01

    Excretion and distribution of cadmium (Cd), and mercury (Hg), methylmercury (methyl-Hg), and zinc (Zn) were studied in the predatory beetle, Pterostichus niger. Specimens of P. niger were fed with insect larvae containing {sup 109}Cd, {sup 203}Hg, methyl-{sup 203}Hg, or {sup 65}Zn. After ingestion of the larvae, the metal contents in the beetles were measured daily for 30 d by {gamma}-spectrometry. Additional beetles were used for autoradiography 5, 15, and 19 d after ingestion of the metals. Excretion of the metals was fast during an initial interval but occurred thereafter at a slow rate. After 2 weeks, the contents of Cd and inorganic Hg had decreased to approximately 1% of the ingested amounts. For Zn and methyl-Hg, higher levels were retained in the beetles. Thus after 30 d, Zn content was 20% of the ingested amount, whereas for methyl-Hg 60% was retained in the body. Autoradiography showed high levels of all metals in the gut. For methyl-Hg, in contrast to inorganic Hg, there was also an evenly distributed labelling in most body tissues. This labelling was also seen for Zn, although at a lower lever than for methyl-Hg. Cadmium showed a localization in the integument, which was not seen for the other metals. The results show that patterns of uptake and excretion of the examined metals in P. niger vary considerably and that the distribution picture show specific features for the individual metals.

  3. Effects of fulvic substances on the distribution and migration of Hg in landfill leachate.

    PubMed

    Xiaoli, Chai; Guixiang, Liu; Jun, Wu; Huanhuan, Tong; Rong, Ji; Youcai, Zhao

    2011-05-01

    Mercury (Hg) distribution and migration in different landfill stabilization processes were evaluated in this study. Wide ranges of Hg concentrations were observed because of the heterogeneity and variability of landfill refuse. In addition, temporally variable conditions, including pH, organic matter, and vegetation cover, which influence Hg migration in landfills, may also affect the temporal distribution of Hg in landfill refuse. The main fraction of Hg, elemental Hg, decreased with time, while the stable fractions of Hg increased. The fulvic acid (FA) extracted from the landfill leachate had much lower overall Hg-complexation stability constants, which suggests that organic S groups might have been rapidly saturated by small amounts of Hg while leaving oxygen functional groups, such as carboxylic functional or phenolic groups, acting as the primary binding sites for Hg. PMID:21468428

  4. Highly efficient ultrasonic-assisted removal of Hg(II) ions on graphene oxide modified with 2-pyridinecarboxaldehyde thiosemicarbazone: Adsorption isotherms and kinetics studies.

    PubMed

    Tadjarodi, Azadeh; Moazen Ferdowsi, Somayeh; Zare-Dorabei, Rouholah; Barzin, Ahmad

    2016-11-01

    A novel adsorbent, based on modifying graphene oxide (GO) chemically with 2-pyridinecarboxaldehyde thiosemicarbazone (2-PTSC) as ligand, was designed by facile process for removal of Hg(II) from aqueous solution. Characterization of the adsorbent was performed using various techniques, such as FT-IR, XRD, XPS, SEM and AFM analysis. The adsorption capacity was affected by variables such as adsorbent dosage, pH solution, Hg(2+) initial concentration and sonicating time. These variables were optimized by rotatable central composite design (CCD) under response surface methodology (RSM). The predictive model for Hg(II) adsorption was constructed and applied to find the best conditions at which the responses were maximized. In this conditions, the adsorption capacity of this adsorbent for Hg(2+) ions was calculated to be 309mgg(-1) that was higher than that of GO. Appling the ultrasound power combined with adsorption method was very efficient in shortening the removal time of Hg(2+) ions by enhancing the dispersion of adsorbent and metal ions in solution and effective interactions among them. The adsorption process was well described by second-order kinetic and Langmuir isotherm model in which the maximum adsorption capacity (Qm) was found to be 555mgg(-1) for adsorption of Hg(2+) ions over the obtained adsorbent. The performance of adsorbent was examined on the real wastewaters and confirmed the applicability of adsorbent for practical applications. PMID:27245963

  5. Determination of elemental constituents in different matrix materials and flow injection studies by the electrolyte cathode glow discharge technique with a new design

    SciTech Connect

    Shekhar, R.; Karunasagar, D.; Ranjit, M.; Arunachalam, J.

    2009-10-15

    An open-to-air type electrolyte cathode discharge (ELCAD) has been developed with a new design. The present configuration leads to a stable plasma even at low flow rates (0.96 mL/min). Plasma fluctuations arising from the variations in the gap between solid anode and liquid cathode were eliminated by providing a V-groove to the liquid glass-capillary. Cathode (ground) connection is given to the solution at the V-groove itself. Interfaced to atomic emission spectrometry (AES), its analytical performance is evaluated. The optimized molarity of the solution is 0.2 M. The analytical response curves for Ca, Cu, Cd, Pb, Hg, Fe, and Zn demonstrated good linearity. The limit of detections of Ca, Cu, Cd, Pb, Hg, Fe, and Zn are determined to be 17, 11, 5, 45, 15, 28, and 3 ng mL{sup -1}. At an integration time of 0.3 s, the relative standard deviation (RSD) values of the acid blank solutions are found to be less than 10% for the elements Ca, Cu, Cd, Hg, Fe, and Zn and 18% for Pb. The method is applied for the determination of the elemental constituents in different matrix materials such as tuna fish (IAEA-350), oyster tissue (NIST SRM 1566a), and coal fly ash (CFA SRM 1633b). The obtained results are in good agreement with the certified values. The accuracy is found to be between 7% and 0.6% for major to trace levels of constituent elements and the precision between 11% and 0.6%. For the injection of 100 {mu} L of 200 ng mL{sup -1} mercury solution at the flow rate of 0.8 mL/min, the flow injection studies resulted in the relative standard deviation (RSD) of 8%, concentration detection limit of 10 ng/mL, and mass detection limit of 1 ng for mercury.

  6. Determination of elemental constituents in different matrix materials and flow injection studies by the electrolyte cathode glow discharge technique with a new design.

    PubMed

    Shekhar, R; Karunasagar, D; Ranjit, Manjusha; Arunachalam, J

    2009-10-01

    An open-to-air type electrolyte cathode discharge (ELCAD) has been developed with a new design. The present configuration leads to a stable plasma even at low flow rates (0.96 mL/min). Plasma fluctuations arising from the variations in the gap between solid anode and liquid cathode were eliminated by providing a V-groove to the liquid glass-capillary. Cathode (ground) connection is given to the solution at the V-groove itself. Interfaced to atomic emission spectrometry (AES), its analytical performance is evaluated. The optimized molarity of the solution is 0.2 M. The analytical response curves for Ca, Cu, Cd, Pb, Hg, Fe, and Zn demonstrated good linearity. The limit of detections of Ca, Cu, Cd, Pb, Hg, Fe, and Zn are determined to be 17, 11, 5, 45, 15, 28, and 3 ng mL(-1). At an integration time of 0.3 s, the relative standard deviation (RSD) values of the acid blank solutions are found to be less than 10% for the elements Ca, Cu, Cd, Hg, Fe, and Zn and 18% for Pb. The method is applied for the determination of the elemental constituents in different matrix materials such as tuna fish (IAEA-350), oyster tissue (NIST SRM 1566a), and coal fly ash (CFA SRM 1633b). The obtained results are in good agreement with the certified values. The accuracy is found to be between 7% and 0.6% for major to trace levels of constituent elements and the precision between 11% and 0.6%. For the injection of 100 microL of 200 ng mL(-1) mercury solution at the flow rate of 0.8 mL/min, the flow injection studies resulted in the relative standard deviation (RSD) of 8%, concentration detection limit of 10 ng/mL, and mass detection limit of 1 ng for mercury. PMID:19715301

  7. Microtubes and corrugations fabricated from strained ZnTe/CdHgTe/HgTe/CdHgTe heterofilms with 2D electron-hole gas in the HgTe quantum well

    NASA Astrophysics Data System (ADS)

    Mutilin, S. V.; Soots, R. A.; Vorob'ev, A. B.; Ikusov, D. G.; Mikhailov, N. N.; Prinz, V. Ya

    2014-07-01

    Variously shaped shells were fabricated from strained ZnTe/CdTe/CdHgTe/HgTe/CdHgTe heterofilms that contained a HgTe quantum well populated simultaneously with electrons and holes. The radius of curvature of formed tubes proved to be 12 µm and the period of corrugations about 20 µm. Such a curvature induces a 1.2% deformation in the HgTe layer sufficient for the occurrence of notable band-edge shifts in this layer and causes a transition of the band structure from a semiconductor to a semi-metal state. Curved HgTe-based films offer potential in studying surfaces where topological insulating states are interfaced with semiconductor states.

  8. Ruditapes philippinarum and Ruditapes decussatus under Hg environmental contamination.

    PubMed

    Velez, Cátia; Galvão, Petrus; Longo, Renan; Malm, Olaf; Soares, Amadeu M V M; Figueira, Etelvina; Freitas, Rosa

    2015-08-01

    The native species Ruditapes decussatus and the invasive species Ruditapes philippinarum have an important ecological role and socio-economic value, from the Atlantic and Mediterranean to the Indo-Pacific region. In the aquatic environment, they are subjected to the presence of different contaminants, such as mercury (Hg) and its methylated form, methylmercury (MeHg). However, few studies have assessed the impacts of Hg on bivalves under environmental conditions, and little is known on bivalve oxidative stress patterns due to Hg contamination. Therefore, this study aims to assess the Hg contamination in sediments as well as the concentration of Hg and MeHg in R. decussatus and R. philippinarum, and to identify the detoxification strategies of both species living in sympatry, in an aquatic system with historical Hg contamination. The risk to human health due to the consumption of clams was also evaluated. The results obtained demonstrated that total Hg concentration found in sediments from the most contaminated area was higher than the maximum levels established by Sediment Quality Guidelines. This study further revealed that the total Hg and MeHg accumulation in both species was strongly correlated with the total Hg contamination of the sediments. Nonetheless, the THg concentration in both species was lower than maximum permissible limits (MPLs) of THg defined by international organizations. R. decussatus and R. philippinarum showed an increase in lipid peroxidation levels along with the increase of THg accumulation by clams. Nevertheless, for both species, no clear trend was obtained regarding the activity of antioxidant (superoxide dismutase, catalase) and biotransformation (glutathione S-transferase) enzymes and metallothioneins with the increase of THg in clams. Overall, the present work demonstrated that both species can be used as sentinel species of contamination and that the consumption of these clams does not constitute a risk for human health. PMID

  9. Quasiparticle excitations in superdeformed {sup 192}Hg

    SciTech Connect

    Lauritsen, T.; Carpenter, M.P.; Janssens, R.V.F.

    1995-08-01

    The nucleus {sup 192}Hg plays a pivotal role for superdeformation in the mass 190 region, since calculations of single-particle levels show large shell-gaps for the superdeformed (SD) shape at N = 112 and Z = 80. As a result, {sup 192}Hg is referred to as the doubly magic SD nucleus for the A = 190 region. In previous studies, only one superdeformed band was observed in this nucleus, and this fact was cited as indirect evidence that large shell gaps do indeed exist at the proposed particle numbers.

  10. Oxidative stress in MeHg-induced neurotoxicity

    SciTech Connect

    Farina, Marcelo; Aschner, Michael; Rocha, Joao B.T.

    2011-11-15

    Methylmercury (MeHg) is an environmental toxicant that leads to long-lasting neurological and developmental deficits in animals and humans. Although the molecular mechanisms mediating MeHg-induced neurotoxicity are not completely understood, several lines of evidence indicate that oxidative stress represents a critical event related to the neurotoxic effects elicited by this toxicant. The objective of this review is to summarize and discuss data from experimental and epidemiological studies that have been important in clarifying the molecular events which mediate MeHg-induced oxidative damage and, consequently, toxicity. Although unanswered questions remain, the electrophilic properties of MeHg and its ability to oxidize thiols have been reported to play decisive roles to the oxidative consequences observed after MeHg exposure. However, a close examination of the relationship between low levels of MeHg necessary to induce oxidative stress and the high amounts of sulfhydryl-containing antioxidants in mammalian cells (e.g., glutathione) have led to the hypothesis that nucleophilic groups with extremely high affinities for MeHg (e.g., selenols) might represent primary targets in MeHg-induced oxidative stress. Indeed, the inhibition of antioxidant selenoproteins during MeHg poisoning in experimental animals has corroborated this hypothesis. The levels of different reactive species (superoxide anion, hydrogen peroxide and nitric oxide) have been reported to be increased in MeHg-exposed systems, and the mechanisms concerning these increments seem to involve a complex sequence of cascading molecular events, such as mitochondrial dysfunction, excitotoxicity, intracellular calcium dyshomeostasis and decreased antioxidant capacity. This review also discusses potential therapeutic strategies to counteract MeHg-induced toxicity and oxidative stress, emphasizing the use of organic selenocompounds, which generally present higher affinity for MeHg when compared to the classically

  11. Biphasic release of indomethacin from HPMC/pectin/calcium matrix tablet: I. Characterization and mechanistic study.

    PubMed

    Wu, Baojian; Chen, Zhukang; Wei, Xiuli; Sun, Ningyun; Lu, Yi; Wu, Wei

    2007-11-01

    Calcium-induced crosslinking of pectin acts as the dominating factor controlling drug release from pectin-based matrices. The same interaction was employed to modify indomethacin release from HPMC/pectin/calcium matrix in this study. The aim was to characterize the release profiles, and to study the formulation variables and the underlying mechanisms. The matrix tablet was made up of pectin HM 70, calcium chloride and HPMC K4M, and prepared by the wet granulation method. In vitro release was performed in water and characterized by the power law. Matrix erosion was evaluated by studying the weight loss and pectin release. Biphasic release of indomethacin from the HPMC/pectin/calcium matrix tablet was observed, and extraordinary power law exponent n values of over 1.0 were observed. Increase in calcium amount led to more significant retardation on drug release. The two power law parameters, n and K, correlated to the amount of calcium in the matrix. A lag time of over 4 h can be achieved at HPMC/pectin/calcium chloride amount of 100 mg/100 mg/100 mg. Both matrix weight loss and pectin release were linearly correlated to indomethacin release, indicating erosion-controlled drug release mechanisms. The hybrid matrix showed retarded erosion and hydration rate, which served as the basis for retarded indomethacin release. It is concluded that the pectin/calcium interaction can be employed to modify drug release from HPMC/pectin/calcium matrix tablet with biphasic release patterns for potential timed or site-specific drug delivery. PMID:17540549

  12. Elemental Mercury in Natural Waters: Occurrence and Determination of Particulate Hg(0).

    PubMed

    Wang, Yongmin; Li, Yanbin; Liu, Guangliang; Wang, Dingyong; Jiang, Guibin; Cai, Yong

    2015-08-18

    Elemental mercury, Hg(0), is ubiquitous in water and involved in key Hg biogeochemical processes. It is extensively studied as a purgeable dissolved species, termed dissolved gaseous mercury (DGM). Little information is available regarding nonpurgeable particulate Hg(0) in water, Hg(0) bound to suspended particulate matter (SPM), which is presumably present due to high affinity of Hg(0) adsorption on solids. By employing stable isotope tracer and isotope dilution (ID) techniques, we investigated the occurrence and quantification of particulate Hg(0) after Hg(0) being spiked into natural waters, aiming to provide firsthand information on particulate Hg(0) in water. A considerable fraction of (201)Hg(0) spiked in water (about 70% after 4 h equilibration) was bound to SPM and nonpurgeable, suggesting the occurrence of particulate Hg(0) in natural waters. A scheme, involving isotope dilution, purge and trap, and inductively coupled plasma mass spectrometry detection, was proposed to quantify particulate Hg(0) by the difference between DGM and total Hg(0), determined immediately and at equilibration after spiking ID Hg isotope, respectively. The application of this newly established method revealed the presence of particulate Hg(0) in Florida Everglades water, as the determined DGM levels (0.14 to 0.22 ng L(-1)) were remarkably lower than total Hg(0) (0.41 to 0.75 ng L(-1)). PMID:26196077

  13. Importance of Dissolved Neutral Hg-Sulfides, Energy Rich Organic Matter and total Hg Concentrations for Methyl Mercury Production in Sediments

    NASA Astrophysics Data System (ADS)

    Drott, A.; Skyllberg, U.

    2007-12-01

    Methyl mercury (MeHg) is the mercury form that biomagnifies to the greatest extent in aquatic food webs. Therefore information about factors determining MeHg concentrations is critical for accurate risk assessment of contaminated environments. The concentration of MeHg in wetlands and sediments is the net result of: 1) methylation rates, 2) demethylation rates, and 3) input/output processes. In this study, the main controls on Hg methylation rates and total concentrations of MeHg, were investigated at eight sites in Sweden with sediments that had been subjected to local Hg contamination either as Hg(0), or as phenyl-Hg. Sediments were selected to represent a gradient in total Hg concentration, temperature climate, salinity, primary productivity, and organic C content and quality. Most sediments were high in organic matter content due to wood fibre efflux from pulp and paper industry. The pore water was analysed for total Hg, MeHg, DOC, H2S(aq), pH, DOC, Cl and Br. The chemical speciation of Hg(II) and MeHg in pore water was calculated using equilibrium models. Potential methylation and demethylation rates in sediments were determined in incubation experiments at 23° C under N2(g) for 48 h, after addition of isotopically enriched 201Hg(II) and Me204Hg. In all surface (0-20 cm) sediments there was a significant (p<0.001) positive relationship between the experimentally determined specific potential methylation rate constant (Km, day-1) and % MeHg (concentrations of MeHg normalized to total Hg) in the sediment. This indicates that MeHg production overruled degradation and input/output processes of MeHg in surface sediments, and that % MeHg in surface sediments may be used as a proxy for net production of MeHg. To our knowledge, these are the first data showing significant positive relationships between short term (48 h) MeHg production and longer term accumulation of MeHg, across a range of sites with different properties (1). If MeHg was not normalized to total Hg

  14. Study of uranium matrix interference on ten analytes using inductively coupled plasma atomic emission spectrometry

    NASA Astrophysics Data System (ADS)

    Ghazi, A. A.; Qamar, Sajid; Atta, M. A.

    1993-08-01

    Maximum allowable concentrations of 12 elements in uranium hexafluoride feed for enrichment to reactor grade material (about 3%), vary from 1 to 100 ppm ( μg/g). Using an inductively coupled plasma atomic emission spectrometer, 51 lines of ten of these elements (B, Cr, Mo, P, Sb, Si, Ta, Ti, V and W) have been studied with a uranium matrix to investigate the matrix interference on the basis of signal to background (SBR), and background to background ratios (BBR). Detection limits and limits of quantitative determination (LQDs) were calculated for these elements in a uranium matrix using SBR and relative standard deviation of the background signal (RSD B) approach. In almost all cases, the uranium matrix interference reduces the SBRs to the extent that direct trace analysis is impossible. A uranium sample having known concentrations of impurities (around LQDs) was directly analysed with results that showed reasonable accuracy and precision.

  15. Study of the nucleation and growth of antibiotic labeled Au NPs and blue luminescent Au8 quantum clusters for Hg2+ ion sensing, cellular imaging and antibacterial applications

    NASA Astrophysics Data System (ADS)

    Khandelwal, Puneet; Singh, Dheeraj K.; Sadhu, Subha; Poddar, Pankaj

    2015-11-01

    Herein, we report a detailed experimental study supported by DFT calculations to understand the mechanism behind the synthesis of cefradine (CFD - an antibiotic) labeled gold nanoparticles (Au NPs) by employing CFD as both a mild reducing and capping agent. The analysis of the effect of growth conditions reveals that a higher concentration of HAuCl4 results in the formation of an increasing fraction of anisotropic structures, higher temperature leads to the formation of quasi-spherical particles instead of anisotropic ones, and larger pH leads to the formation of much smaller particles. The cyclic voltammetry (CV) results show that when the pH of the reaction medium increases from 4 to 6, the reduction potential of CFD increases which leads to the synthesis of nanoparticles (in a pH 4 reaction) to quantum clusters (in a pH 6 reaction). The MALDI-TOF mass spectrometry results of supernatant of the pH 6 reaction indicate the formation of [Au8(CFD)2S6] QCs which show fluorescence at ca. 432 nm with a Stokes shift of ca. 95 nm. The blue luminescence from Au8 QCs was applied for sensing of Hg2+ ions on the basis of an aggregation-induced fluorescence quenching mechanism and offers good selectivity and a high sensitivity with a limit of detection ca. 2 nM which is lower than the detection requirement of 10 nM by the U.S. EPA and 30 nM by WHO for drinking water. We have also applied the sensing probe to detect Hg2+ ions in bacterial samples. Further, we have investigated the antibacterial property of as-synthesized Au NPs using MIC, growth curve and cell survival assay. The results show that Au NPs could reduce the cell survival very efficiently rather than the cell growth in comparison to the antibiotic itself. The scanning electron microscopy study shows the degradation and blebbing of the bacterial cell wall upon exposure with Au NPs which was further supported by fluorescence microscopy results. These Au NPs did not show reactive oxygen species generation. We believe

  16. An in-depth evaluation of accuracy and precision in Hg isotopic analysis via pneumatic nebulization and cold vapor generation multi-collector ICP-mass spectrometry.

    PubMed

    Rua-Ibarz, Ana; Bolea-Fernandez, Eduardo; Vanhaecke, Frank

    2016-01-01

    Mercury (Hg) isotopic analysis via multi-collector inductively coupled plasma (ICP)-mass spectrometry (MC-ICP-MS) can provide relevant biogeochemical information by revealing sources, pathways, and sinks of this highly toxic metal. In this work, the capabilities and limitations of two different sample introduction systems, based on pneumatic nebulization (PN) and cold vapor generation (CVG), respectively, were evaluated in the context of Hg isotopic analysis via MC-ICP-MS. The effect of (i) instrument settings and acquisition parameters, (ii) concentration of analyte element (Hg), and internal standard (Tl)-used for mass discrimination correction purposes-and (iii) different mass bias correction approaches on the accuracy and precision of Hg isotope ratio results was evaluated. The extent and stability of mass bias were assessed in a long-term study (18 months, n = 250), demonstrating a precision ≤0.006% relative standard deviation (RSD). CVG-MC-ICP-MS showed an approximately 20-fold enhancement in Hg signal intensity compared with PN-MC-ICP-MS. For CVG-MC-ICP-MS, the mass bias induced by instrumental mass discrimination was accurately corrected for by using either external correction in a sample-standard bracketing approach (SSB) or double correction, consisting of the use of Tl as internal standard in a revised version of the Russell law (Baxter approach), followed by SSB. Concomitant matrix elements did not affect CVG-ICP-MS results. Neither with PN, nor with CVG, any evidence for mass-independent discrimination effects in the instrument was observed within the experimental precision obtained. CVG-MC-ICP-MS was finally used for Hg isotopic analysis of reference materials (RMs) of relevant environmental origin. The isotopic composition of Hg in RMs of marine biological origin testified of mass-independent fractionation that affected the odd-numbered Hg isotopes. While older RMs were used for validation purposes, novel Hg isotopic data are provided for the

  17. HgCdTe heterostructures on Si (310) substrates for midinfrared focal plane arrays

    SciTech Connect

    Yakushev, M. V. Brunev, D. V.; Varavin, V. S.; Vasilyev, V. V.; Dvoretskii, S. A.; Marchishin, I. V.; Predein, A. V.; Sabinina, I. V.; Sidorov, Yu. G.; Sorochkin, A. V.

    2011-03-15

    Results of studies of the molecular beam epitaxial growth of HgCdTe alloys on Si substrates as large as 100 mm in diameter are presented. Optimum conditions for obtaining HgCdTe/Si(310) heterostructures of the device quality for the spectral range of 3-5 {mu}m are determined. The results of measurements and discussion of photoelectric parameters of an infrared photodetector of a format of 320 Multiplication-Sign 256 elements with a step of 30 {mu}m based on a hybrid assembly of a matrix photosensitive cell with a Si multiplexer are presented. A high stability of photodetector parameters to thermocycling from room temperature to liquid-nitrogen temperature is shown.

  18. ADAPTATION OF AQUATIC MICROBIAL COMMUNITIES TO HG(2+) STRESS

    EPA Science Inventory

    The mechanism of adaptation to Hg(2+) in four aquatic habitats was studied by correlating microbially mediated Hg(2+) volatilization with the adaptive state of the exposed communities. Structural and functional parameters indicated that adaptation of all four communities was stim...

  19. Material and structural studies of metal and polymer matrix composites.

    NASA Technical Reports Server (NTRS)

    Signorelli, R. A.; Serafini, T. T.; Johns, R. H.

    1972-01-01

    Research directed toward the application of fiber composites to aeronautical and space vehicle systems indicates that resin/fiber composites can be developed for service at 315 C for several thousand hours and at 370 C for a few hundred hours. The retention of resin/fiber strength at these high temperatures can be achieved by modifying the polymer molecular structure or by developing new processing techniques, or both. Carbon monofilament with attractive strength values has been produced and fabrication studies to reinforce aluminum with such monofilaments have been initiated. Refractory wire-superalloy composites have demonstrated sufficiently high strength and impact values to suggest that they have potential for application to turbine blades at temperatures to 1200 C and above.

  20. Photolysis of astrophysically relevant acrylonitrile: a matrix experimental study.

    PubMed

    Toumi, A; Couturier-Tamburelli, I; Chiavassa, T; Piétri, N

    2014-04-01

    This report documents the photochemical study of H2C ═ C(H)CN (acrylonitrile) trapped in low-temperature argon matrices and irradiated with a microwave-discharge hydrogen-flow lamp (λ > 120 nm). We succeeded in identifying H2C ═ C(H)NC (isoacrylonitrile) as a photoproduct. HC3N (cyanoacetylene), C2H2:HCN (acetylene:hydrogen cyanide), and C2H2:HNC (acetylene:hydrogen isocyanide) complexes, which are molecules detected in molecular clouds or in the Titan atmosphere, were also identified. No imine product was observed, but other compounds coming from the HC3N photolysis have been found. Fourier transform infrared measurements and (2)H substitution experiments coupled with density functional theory calculations (B3LYP/6-31G**) were performed to confirm the spectral assignments of the photochemical products and intermediate species. PMID:24621153

  1. Material and structural studies of metal and polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Signorelli, R. A.; Serafini, T. T.; Johns, R. H.

    1972-01-01

    The application of fiber composites to aeronautical and space vehicle systems indicates the following: It appears quite probable that resin/fiber composites can be developed for service at 315 C for several thousand hours and at 370 C for a few hundred hours. The retention of resin/fiber strength at these high temperatures can be achieved by modifying the polymer molecular structure or by developing new processing techniques, or both. Carbon monofilament with attractive strength values has been produced and fabrication studies to reinforce aluminum with such monofilaments have been initiated. Refractory wire-superalloy composites have demonstrated sufficiently high strength and impact values to suggest that they have potential for application to turbine blades at temperatures to 1200 C and above.

  2. Determination of acute Hg emissions from solidified/stabilized cement waste forms

    SciTech Connect

    Hamilton, W.P.; Bowers, A.R.

    1997-12-31

    The chemical form of mercury in wastes to be solidified/stabilized may lead to volatile losses from the finished solidified/stabilized monolith. Elemental mercury vapor (Hg vapor) was detected in the headspace of batch reactors that contained solidified/stabilized ordinary Portland cement doped with mercuric oxide (HgO) or liquid elemental mercury [Hg{degree}(1)]. Vapor concentrations increased as a function of time and temperature; the headspace over the HgO samples was saturated in about one hour, while the samples containing Hg{degree}(1) reached approx. 20% of saturation in about two hours. Increased temperatures due to cement hydrolysis lead to increased Hg vapor evolution. Mercury solidified/stabilized as mercuric sulfide (HgS, black) emitted no Hg vapor. Data for the HgO and Hg{degree}(1) experiments were fit to a reversible first-order rate expression. Samples containing HgO displayed the greatest volatility as a result of the rapid dissolution of HgO and the subsequent formation of a strong driving force across the air-water interface. The evolution of Hg vapor from samples solidified/stabilized as Hg{degree}(1) is limited by mass transfer resistances that kinetically limit the dissolution of Hg{degree}(1) into the aqueous phase. The inert character of HgS prevents the evolution of detectable Hg in wastes solidified/stabilized as HgS. The findings of these studies may be important when considering treatment and disposal scenarios for Hg-containing wastes.

  3. Dynamic studies of proton diffusion in mesoscopic heterogeneous matrix

    PubMed Central

    Gutman, M.; Nachliel, E.; Kiryati, S.

    1992-01-01

    The thin water layer, as found in chloroplast or mitochondria, is confined between low dielectric amphypathic surfaces a few nm apart. The physical properties of this mesoscopic space, and how its dimensions affect the rate of chemical reactions proceeding in it, is the subject for this study. The method selected for this purpose is time resolved fluorometry which can monitor the reversible dissociation of a proton from excited molecule of pyranine (8 hydroxy pyrene 1,3,6 tri sulfonate) trapped in thin water layers of a multilamellar vesicle made of neutral or slightly charged phospholipids. The results were analyzed by a computer program of N. Agmon (Pines, E., D. Huppert, and N. Agmon. 1988. J. Am. Chem. Soc. 88:5620-5630) that simulates the diffusion of a proton, subjected to electrostatic attraction, in a thin water layer enclosed between low affinity, proton binding surfaces. The analysis determines the diffusion coefficient of the proton, the effective dielectric constant of the water and the water accessibility of the phosphomoieties of the lipids. These parameters were measured for various lipids [egg-phosphatidylcholine (egg PC), dipalmitoyl phosphatidylcholine (DPPC), cholesterol + DPPC (1:1) and egg PC plus phosphatidyl serine (9:1)] and under varying osmotic pressure which reduces the width of the water layer down to ∼10 ∼ across. We found that: (a) The effective dielectric constant of the aqueous layer, depending on the lipid composition, is ∼40. (b) The diffusion coefficient of the proton in the thin layer (30-10 ∼ across) is that measured in bulk water D = 9.3 10-5 cm2/s, indicating that the water retains its normal liquid state even on contact with the membrane. (c) The reactivity of the phosphomoiety, quantitated by rate of its reaction with proton, diminishes under lateral pressure which reduces the surface area per lipid. We find no evidence for abnormal dynamics of proton transfer at the lipid water interface which, by any mechanism

  4. Seasonal and Diurnal Variations of Hg(0) Over New England

    NASA Astrophysics Data System (ADS)

    Mao, H.; Talbot, R.; Sigler, J.; Sive, B.; Hegarty, J.

    2007-12-01

    Diurnal to interannual variability of Hg° over New England was investigated using multiple years of Hg° measurements at two inland sites, Thompson Farm (TF, 43.11° N, 70.95° W, 24 m, 25 km inland) and Pac Monadnock (PM, 42.86° N, 71.88° W, 700 m, 180 km inland), and one summer of measurements from a marine site, Appledore Island (AI, 42.97° N, 70.62° W, sea level), from the University of New Hampshire AIRMAP observing network. Possible sources were identified via a thorough examination of relationships between Hg° and a number of trace gases, e.g., CO, CO2, CH4, NOy, NO, SO2, and VOCs. The measurements of Hg at TF showed distinct seasonality with an annual maxima in late winter - early spring and a minima in early fall, with large day-to-day variation. A decreasing trend in the mixing ratio of Hg over the time period of March - September occurred at a rate of 0.5 - 0.6 ppqv d-1 for all years except 2004 (0.3 ppqv d-1). Measurements of Hg° at the elevated site PM exhibited much smaller daily and annual variation, particularly reflected in the slower warm season decline (relative to TF) of 0.2 and 0.3 ppqv d-1 in 2005 and 2006 respectively. The AI data appeared to track the variation observed at TF albeit with much higher minima. Hg° was correlated most strongly with CO and NOy in winter suggesting that anthropogenic emissions were the primary source of Hg° . Applying the Hg° - CO relationship, we found that the seasonally averaged Hg° mixing ratio of ~160 ppqv at PM can be considered the regional background level. The positive Hg° -NOy correlation along the lower boundary of all data points indicated dry deposition as a stronger sink for Hg° than suggested by previous studies. We estimated a dry deposition velocity for Hg° of 0.17 - 0.20 cm s-1, and a lifetime of ~11 days in the local PBL at TF. Correlation between Hg° and CHBr3 at both TF and AI suggested a role of the oceanic source influencing the ambient levels of Hg° in the marine and coastal

  5. Cd and Hg ions stimulate cell membrane potassium conductance

    SciTech Connect

    Jungwirth, A.; Paulmichl, M.; Lang, F. )

    1989-02-09

    Intracellular microelectrodes have been applied to study the effect of cadmium (Cd) and mercury (Hg) ions on cultured renal epitheloid Madin Darby Canine Kidney (MDCK) cells. Within 10 seconds Cd and within 50 seconds Hg hyperpolarize the cell membrane from - 53 {plus minus} 1 mV to - 68 {plus minus} 1 mV and - 67 {plus minus} 1 mV, resp., increase the potassium selectivity of the cell membrane (tk) from 0.33 {plus minus} 0.02 to 0.64 {plus minus} 0.03 and 0.77 {plus minus} 0.02, resp., and reduce the apparent cell membrane resistance from 40 {plus minus} 2 MOhm to 27 {plus minus} 2 MOhm and 22 {plus minus} 2 MOhm, resp.. Thus, both, Cd and Hg hyperpolarize the cell membrane by enhancement of the potassium conductance. The concentration required to elicit half maximal hyperpolarization is some 400 nmol/1 for either, Cd or Hg. Barium (1 mmol/1) depolarizes the cell membrane to - 34 {plus minus} 1 mV and virtually abolishes tk in the absence of Cd and Hg. In the presence of barium Cd leads to a transient, Hg to a sustained reappearance of tk and hyperpolarization. Thus, the Cd induced potassium conductance is blocked by barium with delay, the Hg induced potassium conductance is insensitive to barium. Quinidine (1 mmol/1) depolarizes the cell membrane to - 3 {plus minus}1 mV and abolishes the effect of both, Cd and Hg. In the nominal absence of extracellular calcium Cd leads to transient, Hg to sustained increase of tk and hyperpolarization of the cell membrane. In conclusion, both, CD and Hg at the low concentrations encountered during Cd and Hg intoxication enhance potassium conductance of MDCK cell membranes. However, the channels activated apparently differ.

  6. Parametric studies to determine the effect of compliant layers on metal matrix composite systems

    NASA Technical Reports Server (NTRS)

    Caruso, J. J.; Chamis, C. C.; Brown, H. C.

    1990-01-01

    Computational simulation studies are conducted to identify compliant layers to reduce matrix stresses which result from the coefficient of thermal expansion mismatch and the large temperature range over which the current metal matrix composites will be used. The present study includes variations of compliant layers and their properties to determine their influence on unidirectional composite and constituent response. Two simulation methods are used for these studies. The first approach is based on a three-dimensional linear finite element analysis of a 9 fiber unidirectional composite system. The second approach is a micromechanics based nonlinear computer code developed to determine the behavior of metal matrix composite system for thermal and mechanical loads. The results show that an effective compliant layer for the SCS 6 (SiC)/Ti-24Al-11Nb (Ti3Al + Nb) and SCS 6 (SiC)/Ti-15V-3Cr-3Sn-3Al (Ti-15-3) composite systems should have modulus 15 percent that of the matrix and a coefficient of thermal expansion of the compliant layer roughly equal to that of the composite system without the CL. The matrix stress in the longitudinal and the transverse tangent (loop) direction are tensile for the Ti3Al + Nb and Ti-15-3 composite systems upon cool down from fabrication. The fiber longitudinal stress is compressive from fabrication cool down. Addition of a recommended compliant layer will result in a reduction in the composite modulus.

  7. Calculation of the energetics for the oligomerization of gas phase HgO and HgS and for the solvolysis of crystalline HgO and HgS.

    PubMed

    Tossell, J A

    2006-02-23

    Recent experimental studies indicate that gaseous elemental Hg (GEM) is rapidly oxidized to Hg(II) compounds, known collectively as reactive gaseous Hg (RGM), in Arctic and Antarctic regions after polar sunrise. The reduction in GEM is correlated with a reduction in surface O(3) concentration, which is thought to be caused by photochemically initiated catalytic reactions involving halogen species, particularly Br and BrO. Initially, the reaction of Hg(0) and BrO to produce HgO and Br was thought to be the dominant reaction, but recent theoretical studies have decisively shown that this reaction is highly endoergic due to the low stability of monomeric gas-phase HgO. This result is in conflict with experimental data on the energetics of the species existing in the vapor over heated HgO (s). One possible explanation for this discrepancy is the existence of highly stable oligomers formed from HgO. Recent high-level quantum calculations on the dimers of HgO and HgS support this concept. In the present work, we systematically examine the structures, stabilities, and other properties of closed (HgX)(n)() ring-type oligomers, n = 2, 3, 4, and 6, X = O, S, as well as infinite one-dimensional (1D) polymers of HgX (studied by using the periodic boundary condition DFT implementation in GAUSSIAN03). We find that the HgX ring oligomers become systematically more stable (per HgX unit) as n increases but that this stability levels off around n = 4-6. We also find that the 1D chain polymers are only marginally more stable than the n = 6 oligomers. To estimate the energies of interaction between the chains in the 3-dimensional (3D) crystal structures of HgX (s), we adopt a cluster model and use the MP2 method to describe the interchain dispersion interactions. We have also obtained optimized geometries for open chain triplets for the dimers, finding them to be substantially more stable than the closed ringlike dimeric species previously described. Trends in relative energies and

  8. Crystal Growth and Electronic Raman Scattering Study of Model High-Tc Cuprate HgBa2 CaCu2 O6 +Ä

    NASA Astrophysics Data System (ADS)

    Wang, Lichen; Li, Yuan; Luo, Xiangpeng; Li, Jiarui; Yuan Li's group in ICQM Team

    In this talk, I will report our recent progress on crystal growth of HgBa2CaCu2O6 +x (Hg1212), which possesses a simple tetragonal crystal structure and the highest ambient-pressure Tc (128 K) among all cuprate superconductors with two CuO2 sheets in the primitive cell. Improvement in single-crystal synthesis was made possible by using self-designed high-pressure furnaces and a two-layer encapsulation method, and we demonstrate that the hole concentration can be homogeneously tuned in the underdoped region by post-growth annealing. Our electronic Raman scattering experiments reveal that the maximum of the d-wave superconducting gap increases from single-layer HgBa2CuO4 +x to double-layer Hg1212. In the same spectra, it is found that the characteristic energy of spin excitations, as manifested by the energy of the two-magnon signal, also increases in a nearly proportional fashion. This result is consistent with the idea that magnetic interactions are closely related to the Cooper pairing mechanism.

  9. Thermo-oxidative stability studies of PMR-15 polymer matrix composites reinforced with various fibers

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.

    1990-01-01

    An experimental study was conducted to measure the thermo-oxidative stability of PMR-15 polymer matrix composites reinforced with various fibers and to observe differences in the way they degrade in air. The fibers that were studied included graphite and the thermally stable Nicalon and Nextel ceramic fibers. Weight loss rates for the different composites were assessed as a function of mechanical properties, specimen geometry, fiber sizing, and interfacial bond strength. Differences were observed in rates of weight loss, matrix cracking, geometry dependency, and fiber-sizing effects. It was shown that Celion 6000 fiber-reinforced composites do not exhibit a straight-line Arrhenius relationship at temperatures above 316 C.

  10. A feasibility study for producing an egg matrix candidate reference material for the polyether ionophore salinomycin.

    PubMed

    Ferreira, Rosana Gomes; Monteiro, Mychelle Alves; Pereira, Mararlene Ulberg; da Costa, Rafaela Pinto; Spisso, Bernardete Ferraz; Calado, Veronica

    2016-08-01

    The aim of this work was to study the feasibility of producing an egg matrix candidate reference material for salinomycin. Preservation techniques investigated were freeze-drying and spray drying dehydration. Homogeneity and stability studies of the produced batches were conducted according to ISO Guides 34 and 35. The results showed that all produced batches were homogeneous and both freeze-drying and spray drying techniques were suitable for matrix dehydrating, ensuring the material stability. In order to preserve the material integrity, it must be transported within the temperature range of -20 up to 25°C. The results constitute an important step towards the development of an egg matrix reference material for salinomycin is possible. PMID:27216677

  11. In vitro characterization and release study of Ambroxol hydrochloride matrix tablets prepared by direct compression.

    PubMed

    Abd-Elbary, A; Haider, M; Sayed, S

    2012-01-01

    A series of either hydrophilic or hydrophobic polymers were used to prepare controlled release Ambroxol hydrochloride (AMX) matrix tablets by direct compression. Both the compatibility and flow properties of AMX/polymer mixtures were investigated. The effect of the amount and type of polymer on the physical properties and in vitro drug release was studied and compared to commercially available Ambroxol(®) SR capsules. A kinetic study of the release profile of AMX from the prepared matrix tablets was performed. All excipients used in the study were compatible with the model drug. AMX/drug mixtures containing sodium alginate (NA) and hydroxypropylmethyl cellulose (HPMC) showed better flow properties than other polymers used in the study. The in vitro drug release studies showed that matrix tablets formulae containing 10% HPMC (S7) or a combination of 30% NA and 5% HPMC (Ah) exhibited a higher ability to control the release of AMX. The kinetic study revealed that a diffusion controlled mechanism prevailed except when carbopol was used. Formula Ah followed a non-fickian diffusion mechanism similar to Ambroxol(®) SR capsules. Both formulae S7 and Ah could be considered as potential candidates for formulation of AMX controlled release matrix tablets. PMID:21428699

  12. A Novel Biodegradable Polyurethane Matrix for Auricular Cartilage Repair: An In Vitro and In Vivo Study.

    PubMed

    Iyer, Kartik; Dearman, Bronwyn L; Wagstaff, Marcus J D; Greenwood, John E

    2016-01-01

    Auricular reconstruction poses a challenge for reconstructive and burns surgeons. Techniques involving cartilage tissue engineering have shown potential in recent years. A biodegradable polyurethane matrix developed for dermal reconstruction offers an alternative to autologous, allogeneic, or xenogeneic biologicals for cartilage reconstruction. This study assesses such a polyurethane matrix for this indication in vivo and in vitro. To evaluate intrinsic cartilage repair, three pigs underwent auricular surgery to create excisional cartilage ± perichondrial defects, measuring 2 × 3 cm in each ear, into which acellular polyurethane matrices were implanted. Biopsies were taken at day 28 for histological assessment. Porcine chondrocytes ± perichondrocytes were cultured and seeded in vitro onto 1 × 1 cm polyurethane scaffolds. The total culture period was 42 days; confocal, histological, and immunohistochemical analyses of scaffold cultures were performed on days 14, 28, and 42. In vivo, the polyurethane matrices integrated with granulation tissue filling all biopsy samples. Minimal neocartilage invasion was observed marginally on some samples. Tissue composition was identical between ears whether perichondrium was left intact, or not. In vitro, the polyurethane matrix was biocompatible with chondrocytes ± perichondrocytes and supported production of extracellular matrix and Type II collagen. No difference was observed between chondrocyte culture alone and chondrocyte/perichondrocyte scaffold coculture. The polyurethane matrix successfully integrated into the auricular defect and was a suitable scaffold in vitro for cartilage tissue engineering, demonstrating its potential application in auricular reconstruction. PMID:26284639

  13. Adhesion strength study between plasma treated polyester fibres and a rubber matrix

    NASA Astrophysics Data System (ADS)

    Krump, H.; Šimor, M.; Hudec, I.; Jaššo, M.; Luyt, A. S.

    2005-02-01

    In this work, the adhesion strength between poly(ethylene terephthalate) (PET) fibres and styrene-butadiene rubber (SBR) was studied. The effects of atmospheric plasma treatment, used to increase adhesion strength between PET fibres and the rubber matrix, were investigated and compared. It was confirmed that lubricants on the fibres caused a decrease in adhesion strength between the plasma treated reinforcing PET fibres and the SBR rubber matrix. These lubricants can be removed by acetone. When washed and treated in plasma, a substantial improvement in adhesion strength was observed. No ageing in air before combination with the rubber matrix was observed. This confirmed that the plasma streamers caused the creation of a new, relatively stable chemical species on the polymer surface. It suggests that the surface modification of PET fibres by plasma treatment at atmospheric gas pressure is a suitable and technologically applicable method for the improvement of adhesion strength of polyester reinforcing materials to rubber.

  14. The Use of Polyacrylamide Hydrogels to Study the Effects of Matrix Stiffness on Nuclear Envelope Properties.

    PubMed

    Minaisah, Rose-Marie; Cox, Susan; Warren, Derek T

    2016-01-01

    Matrix-derived mechanical cues influence cell proliferation, motility, and differentiation. Recent findings clearly demonstrate that the nuclear envelope (NE) adapts and remodels in response to mechanical signals, including matrix stiffness, yet a plethora of studies have been performed on tissue culture plastic or glass that have a similar stiffness to cortical bone. Using methods that allow modulation of matrix stiffness will provide further insight into the role of the NE in physiological conditions and the impact of changes in stiffness observed during ageing and disease on cellular function. In this chapter, we describe the polyacrylamide hydrogel system, which allows fabrication of hydrogels with variable stiffness to better mimic the environment experienced by cells in most tissues of the body. PMID:27147046

  15. Study of matrix cracking and delamination in glass/epoxy laminates

    NASA Technical Reports Server (NTRS)

    Caslini, Massimo; Zanotti, Carlo; O'Brien, T. Kevin

    1987-01-01

    This study focused on characterizing matrix cracking and delamination behavior in multidirectional laminates. Static tension and tension-tension fatigue tests were conducted on two different layups. Damage onset, accumulation, and residual properties were measured. Matrix cracking was shown to have a considerable influence on residual stiffness of glass epoxy laminates, and could be predicted reasonably well for cracks in 90 deg piles using a simple shear lag analysis. A fracture mechanics analysis for the strain energy release rate associated with 90 deg ply-matrix crack formation was developed and was shown to correlate the onset of 90 deg ply cracks in different laminates. The linear degradation of laminate modulus with delamination area, previously observed for graphite epoxy laminates, was predicted for glass epoxy laminates using a simple rule of mixtures analysis. The strain energy release rate associated with edge delamination formation under static and cyclic loading was difficult to analyze because of the presence of several contemporary damage phenomena.

  16. Selective optical scattering characterisation of tissue malignancy using Mueller matrix polarimetry: a simulation study

    NASA Astrophysics Data System (ADS)

    Fathima, Adeeba; Sujatha, N.

    2016-04-01

    Quantitative Mueller polarimetry optically characterizes a medium and is reflected upon by the ultrastructural changes in it. Tissue morphology changes occur during advent of diseases like cancer neoplasia. This alters the Mueller matrix characterizing the tissue as an optical element. The nucleus size undergoes an approximate doubling during the development of cancer. Cell crowding during cancer increases the number density of the nuclei per unit volume. Modeling the cell nuclei as main scattering centers, a systematic computational study on how Mueller matrix elements vary for an increase in scatterer size and number density is performed. Simulation on polarized light transport of wavelength 633nm through a slab of size 3 mm comprising of spherical scatterers in a medium of refractive index 1.33 is carried out. Light propagation is modeled using Monte Carlo method and meridian plane method is adopted for tracking the polarization state change. The stokes vector of the outgoing light is tracked to calculate the Mueller matrix images of the light backscattered from the slab. The Mueller matrix elements as well as depolarization factors are derived. The depolarization index increases with scatterer size. Along with nucleus size, change in the cell number density is also expected in the different stages of the cancer growth. Volume fraction of the scatterers in medium is varied as an indicator of this number density change. Behavior of Mueller matrix with respect to change in scattering coefficient due to variation in scatterer size and volume fraction is studied. It is observed that the depolarization index derived from Mueller matrix has selective discrimination towards the change in scattering coefficient caused due to size change and volume fraction change respectively.

  17. School Television for Social Studies: A Competency-Based Matrix, Grade 5.

    ERIC Educational Resources Information Center

    North Carolina State Dept. of Public Instruction, Raleigh.

    This matrix keys school films to the social studies competency-based curriculum cbjectives for grade 5. Three television series are included. Emphasis is placed on geography, people, and the economy, but the themes are also related to history and government. The first series, "Across Cultures," focuses on the people of North America, South…

  18. Method Modification Study for the Thermo Scientific SureTect™ Listeria Species Assay-Matrix Extension.

    PubMed

    Cloke, Jonathan; Evans, Katharine; Crabtree, David; Hughes, Annette; Simpson, Helen; Holopainen, Jani; Wickstrand, Nina; Kauppinen, Mikko; Leon-Velarde, Carlos; Larson, Nathan; Dave, Keron; Chen, Yi; Ryser, Elliot; Carter, Mark

    2016-01-01

    The Thermo Scientific™ SureTect™ Listeria species assay is a new real-time PCR assay for the detection of all species of Listeria in food and environmental samples. The assay was originally certified as Performance Tested Methods(SM) (PTM) 071304 in 2013. This report details the method modification study undertaken to extend the performance claims of the assay for matrixes of raw ground turkey, raw ground pork, bagged lettuce, raw pork sausages, pasteurized 2% fat milk, raw cod, pasteurized brie cheese, and ice cream. The method modification study was conducted using the AOAC Research Institute (RI) PTM program to validate the SureTect PCR assay in comparison to the reference method detailed in ISO 11290-1:1996 including amendment 1:2004. All matrixes were tested by Thermo Fisher Scientific (Basingstoke, United Kingdom). In addition, three matrixes (raw cod, bagged lettuce, and pasteurized brie cheese) were analyzed independently as part of the AOAC RI-controlled independent laboratory study by the University of Guelph, Canada. Using probability of detection statistical analysis, there was no significant difference in the performance between the SureTect assay and the International Organization for Standardization reference method for any of the matrixes analyzed in this study. PMID:27103105

  19. Hg2+ reduction and re-emission from simulated wet flue gas desulfurization liquors.

    PubMed

    Wo, Jingjing; Zhang, Meng; Cheng, Xiaoya; Zhong, Xiaohang; Xu, Jiang; Xu, Xinhua

    2009-12-30

    In this study, considering that Hg(2+) in wet flue gas desulfurization (FGD) systems can easily be reduced and then released into atmosphere, causing secondary pollution, the researches about Hg(2+) reduction and Hg(0) re-emission mechanism were carried out. The effects of several experimental parameters on the reduction were studied, including initial pH, temperature, and concentrations of Cl(-) and S(IV). Our experimental results indicated that Cl(-) had a restraining effect on the Hg(2+) reduction and Hg(0) re-emission, after 24h reaction, only 20.5% of Hg(2+) was reduced with 100mM Cl(-) in simulated desulfurization solution. Cl(-) can slow Hg(2+) reduction and Hg(0) re-emissions dramatically through changing reaction mechanism, with formation of new intermediate: ClHgSO(3)(-), which can decompose to Hg(0), but much more slowly than Hg(SO(3))(2)(2-) or HgSO(3). Simulating the conditions of the practical application (initial pH 5, T=50 degrees C, S(IV)=5 mM, Cl(-)=100 mM), we also found that Ca(2+), NO(3)(-), F(-), etc. all had obvious effects on reduction rates. Based on the material balance and characteristic of the reactants, the reduction emission mechanism of Hg(2+) has been established, providing theoretical basis for industrial application of mercury control in wet FGD systems. PMID:19699584

  20. Long-distance transport of Hg, Sb, and As from a mined area, conversion of Hg to methyl-Hg, and uptake of Hg by fish on the Tiber River basin, west-central Italy

    USGS Publications Warehouse

    Gray, John E.; Rimondi, Valentina; Costagliola, Pilario; Vaselli, Orlando; Lattanzi, Pierfranco

    2014-01-01

    guideline. Data in this study indicate some conversion of inorganic Hg to methyl-Hg and uptake of Hg in fish on the Paglia River, but less methylation of Hg and Hg uptake by freshwater fish in the larger Tiber River.

  1. A relativistic periodic DFT study on interaction of superheavy elements 112 (Cn) and 114 (Fl) and their homologs Hg and Pb, respectively, with a quartz surface.

    PubMed

    Pershina, V

    2016-06-29

    Relativistic periodic calculations of adsorption energies of group-12 elements Hg and Cn and group-14 elements Pb and Fl on a hydroxylated (001) α-quartz surface at different adsorbate coverage have been performed using the ADF-BAND program. Results for the (4 × 4) supercell, being in good agreement with gas-phase chromatography experimental data for adsorption of Hg and Pb on quartz at zero coverage, indicate that Cn and Fl should not interact with the silicon oxide at room temperature. However, their moderately strong interaction with gold is expected. The reason for the non-interaction of Cn and Fl with SiO2 is strong relativistic effects on their valence electron shells. PMID:27315587

  2. Photoluminescence study of PVP capped CdS nanoparticles embedded in PVA matrix

    SciTech Connect

    Pattabi, Manjunatha . E-mail: manjupattabi@yahoo.com; Saraswathi Amma, B.; Manzoor, K.

    2007-05-03

    Photoluminescence properties of polyvinyl pyrrolidone (PVP) capped cadmium sulphide (CdS) nanoparticles embedded in polyvinyl alcohol matrix (PVA) are reported. The PVP-CdS nanoparticles are prepared by non-aqueous method wherein cadmium nitrate is used as the cadmium source and hydrogen sulphide as the sulphur source. The synthesized nanoparticles are dispersed in polyvinyl alcohol (PVA) matrix and cast as self-standing flexible (PVP-CdS)-PVA films. The nanocomposites are characterized by optical absorption spectroscopy, X-ray diffraction (XRD) and transmission electron microscopy (TEM) studies. XRD and TEM studies show the formation of cubic CdS particles with average size {approx}3-5 nm. Thermal studies, carried out to observe the changes in PVA matrix due to the incorporation of PVP-CdS nanoparticles show strong interaction between the polymer matrix and nanoparticles. The photoluminescence emission spectra of the nanocomposites show two peaks, at 502 and 636 nm, which are attributed to the band edge and surface defects respectively, of CdS nanoparticles. Effective surface capping with optimum concentration of polyvinyl pyrrolidone leads to the quenching of surface defect-related emission.

  3. Numerical study of the intrinsic recombination carriers lifetime in extended short-wavelength infrared detector materials: A comparison between InGaAs and HgCdTe

    NASA Astrophysics Data System (ADS)

    Wen, Hanqing; Bellotti, Enrico

    2016-05-01

    Intrinsic carrier lifetime due to radiative and Auger recombination in HgCdTe and strained InGaAs has been computed in the extended short-wavelength infrared (ESWIR) spectrum from 1.7 μm to 2.7 μm. Using the Green's function theory, both direct and phonon-assisted indirect Auger recombination rates as well as the radiative recombination rates are calculated for different cutoff wavelengths at 300 K with full band structures of the materials. In order to properly model the full band structures of strained InGaAs, an empirical pseudo-potential model for the alloy is fitted using the virtual crystal approximation with spin-orbit coupling included. The results showed that for InxGa1-xAs grown on InP substrate, the compressive strain, which presents in the film when the cutoff wavelength is longer than 1.7 μm, leads to decrease of Auger recombination rate and increase of radiative recombination rate. Since the dominant intrinsic recombination mechanism in this spectral range is radiative recombination, the overall intrinsic carrier lifetime in the strained InGaAs alloys is shorter than that in the relaxed material. When compared to the relaxed HgCdTe, both relaxed and compressively strained InGaAs alloys show shorter intrinsic carrier lifetime at the same cutoff wavelength in room temperature which confirms the potential advantage of HgCdTe as wide-band infrared detector material. While HgCdTe offers superior performance, ultimately the material of choice for ESWIR application will also depend on material quality and cost.

  4. Growth, Characterization and Theoretical Study of a Novel Organometallic Nonlinear Optical Crystal: CdHg(SCN)4(C2H5NO)2

    NASA Astrophysics Data System (ADS)

    Liu, X. T.; Wang, X. Q.; Lin, X. J.; Sun, G. H.; Zhang, G. H.; Xu, D.

    2012-06-01

    A novel potentially useful second harmonic generation (SHG) organometallic nonlinear optical (NLO) crystal: cadmium mercury thiocyanate bis( N-methylformamide), CdHg(SCN)4(C2H5NO)2 (CMTN), has been prepared, and large high-optical-quality single crystals with dimensions up to 30 ×27×9 mm3 have been grown by the temperature-lowering method. Its structural, physicochemical and optical properties are characterized by elemental analyses, X-ray powder diffraction, Fourier transform infrared and Raman spectroscopy, thermal analysis, powder SHG measurements and UV/Vis/NIR transmission. The specific heat has been determined to be 515.5 J mol-1 K-1 at 300 K. CMTN possesses good physicochemical stability up to 128.5∘C, exhibits powder SHG efficiencies 0.8 times that of urea and its UV transparency cutoff is 358 nm. By the use of the DFT/B3LYP/6-31G(d) method, the microscopic second order NLO behavior of CMTN has been investigated by computing the first-order hyperpolarizability together with that of CdHg(SCN)4 (CMTC) and CdHg(SCN)4(C3H8O2) (CMTG) crystals. The results have been explained based on their crystal structures.

  5. A study of the influence of Hg(6(3)P2) population in a low-pressure discharge on mercury ion emission at 194.2 nm

    NASA Technical Reports Server (NTRS)

    Maleki, L.; Blasenheim, B. J.; Janik, G. R.

    1990-01-01

    A low-pressure mercury-argon discharge, similar to the type existing in the mercury lamp for the trapped-ion standard, is probed with a new technique of laser spectroscopy to determine the influence of the Hg(6 3P(sub 2)) population on discharge emission. The discharge is excited with inductively coupled rf power. Variations in the intensity of emission lines in the discharge were examined as lambda = 546.1 nm light from a continuous wave (CW) laser excited the Hg(6 3P(sub 2)) to (7 3S (sub 1)) transition. The spectrum of the discharge viewed in the region of laser irradiation showed increased emission in lambda = 546.1, 435.8, 404.7, 253.7, and 194.2 nm lines. Other lines in Hg I exhibited a decrease in emission. When the discharge was viewed outside the region of laser irradiation, all lines exhibited an increased emission. Based on these results, it is concluded that the dominant mechanism for the excitation of higher lying levels of mercury is the the electron-impact excitation via the 3P(sub 2) level. The depopulation of this metastable is also responsible for the observed increase in the electron temperature when the laser irradiates the discharge. It is also concluded that the 3P(sub 2) metastable level of mercury does not play a significant role in the excitation of the 3P(sub 1/2) level of mercury ion.

  6. Maternal-fetal distribution of mercury ( sup 203 Hg) released from dental amalgam fillings

    SciTech Connect

    Vimy, M.J.; Takahashi, Y.; Lorscheider, F.L. )

    1990-04-01

    In humans, the continuous release of Hg vapor from dental amalgam tooth restorations is markedly increased for prolonged periods after chewing. The present study establishes a time-course distribution for amalgam Hg in body tissues of adult and fetal sheep. Under general anesthesia, five pregnant ewes had twelve occlusal amalgam fillings containing radioactive 203Hg placed in teeth at 112 days gestation. Blood, amniotic fluid, feces, and urine specimens were collected at 1- to 3-day intervals for 16 days. From days 16-140 after amalgam placement (16-41 days for fetal lambs), tissue specimens were analyzed for radioactivity, and total Hg concentrations were calculated. Results demonstrate that Hg from dental amalgam will appear in maternal and fetal blood and amniotic fluid within 2 days after placement of amalgam tooth restorations. Excretion of some of this Hg will also commence within 2 days. All tissues examined displayed Hg accumulation. Highest concentrations of Hg from amalgam in the adult occurred in kidney and liver, whereas in the fetus the highest amalgam Hg concentrations appeared in liver and pituitary gland. The placenta progressively concentrated Hg as gestation advanced to term, and milk concentration of amalgam Hg postpartum provides a potential source of Hg exposure to the newborn. It is concluded that accumulation of amalgam Hg progresses in maternal and fetal tissues to a steady state with advancing gestation and is maintained. Dental amalgam usage as a tooth restorative material in pregnant women and children should be reconsidered.

  7. Elevated levels of matrix metalloprotein-3 in patients with coronary aneurysm: A case control study

    PubMed Central

    Tengiz, Istemihan; Ercan, Ertugrul; Aliyev, Emil; Sekuri, Cevad; Duman, Can; Altuglu, Imre

    2004-01-01

    Background Matrix metalloproteinases (MMPs) have been implicated in the pathogenesis of arterial aneurysms through increased proteolysis of extracellular matrix proteins. Increased proteolysis due to elevated matrix degrading enzyme activity in the arterial wall may act as a susceptibility factor for the development of coronary aneurysms. The aim of this study was to investigate the association between MMPs and presence of coronary aneurysms. Methods Thirty patients with aneurysmal coronary artery disease and stable angina were enrolled into study (Group 1). Fourteen coronary artery disease patients with stable angina were selected as control group (Group 2). MMP-1, MMP-3 and C-reactive protein (CRP) were measured in peripheral venous blood and matched between the groups. Results Serum MMP-3 level was higher in patients with aneurismal coronary artery disease compared to the control group (20.23 ± 14.68 vs 11.45 ± 6.55 ng/ml, p = 0.039). Serum MMP-1 (13.63 ± 7.73 vs 12.15 ± 6.27 ng/ml, p = 0.52) and CRP levels (4.78 ± 1.47 vs 4.05 ± 1.53 mg/l, p = 0.13) were not significantly different between the groups. Conclusion MMPs can cause arterial wall destruction. MMP-3 may play role in the pathogenesis of coronary aneurysm development through increased proteolysis of extracellular matrix proteins. PMID:15482602

  8. Hg bioavailability and impact on bacterial communities in a long-term polluted soil.

    PubMed

    Ruggiero, P; Terzano, R; Spagnuolo, M; Cavalca, L; Colombo, M; Andreoni, V; Rao, M A; Perucci, P; Monaci, E

    2011-01-01

    Different soil samples characterised by a long-term Hg-pollution were studied for Hg total content, fractionation, phytotoxicity and influence on the bacterial community. Hg pollution ranged from 1 to 50 mg kg(-1) and most of it was speciated in scarcely soluble forms. In agreement with this, the biochemical quality indexes were investigated (biomass, enzyme activities) and the bacterial community (viable heterotrophic (VH) bacteria, functional diversity) apparently was not influenced by the degree of Hg pollution. In particular, the investigated soils exhibited a low percentage of Hg-resistant (Hg(R)) bacteria ranging from less than 0.001% to 0.25% of the VH and the addition of available Hg in the form of HgCl(2) induced an enrichment of resistant Hg(R) populations. The general biodiversity of the bacterial community was evaluated by denaturing gradient gel electrophoresis of DNA of Hg spiked soil microcosms and of control soils. Hg(R) bacteria capable to grow in a minimal medium containing HgCl(2) were also isolated and identified. MerA and merB gene PCR fragments were obtained from different Hg(R) strains and the range of similarities at the DNA level and at the deduced amino acid level showed that they carried mercuric reductase and lyase. Differently from bacteria, some influence of soil Hg content on seeds' germination and root elongation was observed for Lepidium sativum L. and Solanum lycopersicum L. In conclusion, most of the Hg in these long-term polluted soils was scarcely mobile and available and did not significantly influence the soil bacterial community. The risk of potential Hg remobilization over time, that could be naturally favoured by the activity of plant roots or other inorganic processes occurring in soil, can be extenuated since bacterial community was resistant and resilient to subsequent Hg stress. PMID:21060931

  9. 40 CFR 60.4112 - Changing Hg designated representative and alternate Hg designated representative; changes in...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Changing Hg designated representative and alternate Hg designated representative; changes in owners and operators. 60.4112 Section 60.4112... Generating Units Hg Designated Representative for Hg Budget Sources § 60.4112 Changing Hg...

  10. New thermodynamic data on the Hg-O-S system: With application to the thermal processing of mercury containing wastes

    SciTech Connect

    Fredrickson, G.L.; Hager, J.P.

    1996-12-31

    A modified transpiration reactor was used to measure the composition of the equilibrium gas phase formed above compounds in the Hg-O-S system at high temperatures (600 to 900K). A thermodynamic database ({Delta}G{degrees}{sub f}, {Delta}H{degrees}{sub f}, {Delta}S{degrees}{sub f}) for HgO, HgS, HgSO{sub 4}, Hg{sub 2}SO{sub 4}, HgSO{sub 4}-HgO, and HgSO{sub 4}{circ}2HgO was developed based on the experimental results. Prior to this study, only estimated data were available in the literature for the sulfates and oxysulfates at temperatures above 298K. A series of vapor pressure / stability diagrams were constructed from 473 to 973K with isobars of Hg(g), HgO(g), S{sub 2}(g), and SO{sub 3}(g). These diagrams were found to be significantly different than those available previously and do provide insight to the phase relations of importance during the thermal processing of Hg-containing wastes. The thermodynamic results were used to conduct a series of Gibbs energy minimization calculations for a thermal processor / afterburner system for the treatment of HgS-containing wastes. The retention of Hg in the discharge calcine was examined as a function of temperature and excess air. Hg was found to report to the calcine as HgSO{sub 4}, Hg{sub 2}SO{sub 4}, or HgSO{sub 4}-HgO depending on the process conditions, and Hg retention occurs at temperatures as high as 930K. The precipitation of Hg-containing phases from cooled afterburner discharge gas starts at approximately 900K and the cooling of the gas an additional 30K (to 870K) results in over 50% of the Hg being precipitated as HgSO{sub 4}-HgO. It was also determined that for small amounts of Hg present in sulfide concentrates during roasting, the Hg will be retained as HgSO{sub 4} or HgSO{sub 4}-HgO at temperatures as high as 870K. 8 refs., 30 figs., 3 tabs.

  11. Magnetic fields of HgMn stars⋆

    NASA Astrophysics Data System (ADS)

    Hubrig, S.; González, J. F.; Ilyin, I.; Korhonen, H.; Schöller, M.; Savanov, I.; Arlt, R.; Castelli, F.; Lo Curto, G.; Briquet, M.; Dall, T. H.

    2012-11-01

    Context. The frequent presence of weak magnetic fields on the surface of spotted late-B stars with HgMn peculiarity in binary systems has been controversial during the two last decades. Recent studies of magnetic fields in these stars using the least-squares deconvolution (LSD) technique have failed to detect magnetic fields, indicating an upper limit on the longitudinal field between 8 and 15 G. In these LSD studies, assumptions were made that all spectral lines are identical in shape and can be described by a scaled mean profile. Aims: We re-analyse the available spectropolarimetric material by applying the moment technique on spectral lines of inhomogeneously distributed elements separately. Furthermore, we present new determinations of the mean longitudinal magnetic field for the HgMn star HD 65949 and the hotter analog of HgMn stars, the PGa star HD 19400, using FORS 2 installed at the VLT. We also give new measurements of the eclipsing system AR Aur with a primary star of HgMn peculiarity, which were obtained with the SOFIN spectropolarimeter installed at the Nordic Optical Telescope. Methods: We downloaded from the European Southern Observatory (ESO) archive the publically available HARPS spectra for eight HgMn stars and one normal and one superficially normal B-type star obtained in 2010. Out of this sample, three HgMn stars belong to spectroscopic double-lined systems. The application of the moment technique to the HARPS and SOFIN spectra allowed us to study the presence of the longitudinal magnetic field, the crossover effect, and quadratic magnetic fields. Results for the HgMn star HD 65949 and the PGa star HD 19400 are based on a linear regression analysis of low-resolution spectra obtained with FORS 2 in spectropolarimetric mode. Results: Our measurements of the magnetic field with the moment technique using spectral lines of several elements separately reveal the presence of a weak longitudinal magnetic field, a quadratic magnetic field, and the

  12. The Upside to Hg-DOM Associations for Water Quality: Removal of Hg from Solution Using Coagulaion with Metal-Based Salts

    NASA Astrophysics Data System (ADS)

    Henneberry, Y.; Kraus, T. E.; Fleck, J.; Krabbenhoft, D. P.; Horwath, W. R.

    2011-12-01

    This study assessed the potential use of metal-based coagulants to remove dissolved mercury (Hg) from natural waters and provides information regarding the importance of Hg associations with the dissolved organic matter (DOM) fraction and metal hydroxides. Previous research indicated coagulants were not effective at removing Hg from solution; however those studies used high concentrations of Hg, which did not reflect naturally occurring concentrations of Hg. Filtered water collected from an agricultural drain in the Sacramento-San Joaquin Delta (Delta) was treated with three industrial-grade coagulants (ferric chloride, ferric sulfate, and polyaluminum chloride) to determine their efficacy in removing both inroganic (IHg) and methylmercury (MeHg) from the water column. The Delta suffers from elevated surface water Hg concentrations and as a result is listed as an imparied water body. Coagulants removed up to 85% of DOM from solution. In the absence of DOM, all three coagulants released IHg into solution, however in the presence of DOM the coagulants removed up to 97% of IHg and 80% of MeHg. Results suggest that the removal of Hg is mediated by DOM-coagulant interactions. There was a preferential association of IHg with the more aromatic, higher molecular weight fraction of DOM but no such relationship was found for MeHg. This study offers new fundamental insights regarding large-scale removal of Hg at environmentally relevant concentrations. Research using isotopically labeled Hg is providing insight into whether coagulation can remove recently added Hg (e.g. atmospheric deposition) from solution and whether once formed, the floc can remove additional Hg from the water column.

  13. Theoretical studies of 63Cu2+ orbital Knight shifts of HgBa2Ca2Cu3O8+δ

    NASA Astrophysics Data System (ADS)

    Kuang, Min-Quan; Wu, Shao-Yi; Hu, Xian-Fen

    2014-08-01

    The orbital Knight shifts and g factors for the tetragonal 63Cu2+ site in HgBa2Ca2Cu3O8+δ at 133 and 115 K are theoretically investigated based on the high-order perturbation formulae of these quantities for a 3d9 ion situated into tetragonally elongated octahedra. The theoretical results reveal good agreement with the observed values. The significant anisotropies of the Knight shifts are illustrated as the considerable local tetragonal elongation distortions of the five-coordinated Cu2+ sites. The results at different temperatures are also discussed in view of the local structure of the Cu2+ sites.

  14. General population job exposure matrix applied to a pooled study of prevalent carpal tunnel syndrome.

    PubMed

    Dale, Ann Marie; Zeringue, Angelique; Harris-Adamson, Carisa; Rempel, David; Bao, Stephen; Thiese, Matthew S; Merlino, Linda; Burt, Susan; Kapellusch, Jay; Garg, Arun; Gerr, Fred; Hegmann, Kurt T; Eisen, Ellen A; Evanoff, Bradley

    2015-03-15

    A job exposure matrix may be useful for the study of biomechanical workplace risk factors when individual-level exposure data are unavailable. We used job title-based exposure data from a public data source to construct a job exposure matrix and test exposure-response relationships with prevalent carpal tunnel syndrome (CTS). Exposures of repetitive motion and force from the Occupational Information Network were assigned to 3,452 active workers from several industries, enrolled between 2001 and 2008 from 6 studies. Repetitive motion and force exposures were combined into high/high, high/low, and low/low exposure groupings in each of 4 multivariable logistic regression models, adjusted for personal factors. Although force measures alone were not independent predictors of CTS in these data, strong associations between combined physical exposures of force and repetition and CTS were observed in all models. Consistent with previous literature, this report shows that workers with high force/high repetition jobs had the highest prevalence of CTS (odds ratio = 2.14-2.95) followed by intermediate values (odds ratio = 1.09-2.27) in mixed exposed jobs relative to the lowest exposed workers. This study supports the use of a general population job exposure matrix to estimate workplace physical exposures in epidemiologic studies of musculoskeletal disorders when measures of individual exposures are unavailable. PMID:25700886

  15. General Population Job Exposure Matrix Applied to a Pooled Study of Prevalent Carpal Tunnel Syndrome

    PubMed Central

    Dale, Ann Marie; Zeringue, Angelique; Harris-Adamson, Carisa; Rempel, David; Bao, Stephen; Thiese, Matthew S.; Merlino, Linda; Burt, Susan; Kapellusch, Jay; Garg, Arun; Gerr, Fred; Hegmann, Kurt T.; Eisen, Ellen A.; Evanoff, Bradley

    2015-01-01

    A job exposure matrix may be useful for the study of biomechanical workplace risk factors when individual-level exposure data are unavailable. We used job title–based exposure data from a public data source to construct a job exposure matrix and test exposure-response relationships with prevalent carpal tunnel syndrome (CTS). Exposures of repetitive motion and force from the Occupational Information Network were assigned to 3,452 active workers from several industries, enrolled between 2001 and 2008 from 6 studies. Repetitive motion and force exposures were combined into high/high, high/low, and low/low exposure groupings in each of 4 multivariable logistic regression models, adjusted for personal factors. Although force measures alone were not independent predictors of CTS in these data, strong associations between combined physical exposures of force and repetition and CTS were observed in all models. Consistent with previous literature, this report shows that workers with high force/high repetition jobs had the highest prevalence of CTS (odds ratio = 2.14–2.95) followed by intermediate values (odds ratio = 1.09–2.27) in mixed exposed jobs relative to the lowest exposed workers. This study supports the use of a general population job exposure matrix to estimate workplace physical exposures in epidemiologic studies of musculoskeletal disorders when measures of individual exposures are unavailable. PMID:25700886

  16. A transfer-matrix study of directed lattice animals and directed percolation on a square lattice

    NASA Astrophysics Data System (ADS)

    Knežević, Dragica; Knežević, Milan

    2016-03-01

    We studied the large-scale properties of directed lattice animals and directed percolation on a square lattice. Using a transfer-matrix approach on strips of finite widths, we generated relatively long sequences of estimates for effective values of critical fugacity, percolation threshold and correlation length critical exponents. We applied two different extrapolation methods to obtain estimates for infinite systems. The precision of our final estimates is comparable to (or better than) the precision of the best currently available results.

  17. Neurobehavioral effects, c-Fos/Jun expression and tissue distribution in rat offspring prenatally co-exposed to MeHg and PFOA: PFOA impairs Hg retention.

    PubMed

    Cheng, Jinping; Fujimura, Masatake; Zhao, Wenchang; Wang, Wenhua

    2013-05-01

    Exposure to methylmercury (MeHg) and perfluorooctanoic acid (PFOA) can occur simultaneously as both contaminants are found in the same food sources, especially fish, seafood, marine mammals and milk. The aim of this study was to assess the effects of exposure to MeHg (10 μg mL(-1) in drinking water) and PFOA (10 μg mL(-1) in drinking water) from gestational day 1 to postnatal day (PND) 21, alone and in combination, on neurobehavioral development and the expression of c-Fos/Jun in different brain regions in the offspring. Our findings showed that exposure to MeHg alone, and exposure to MeHg combined with PFOA significantly induced cliff avoidance reflexes and negative geotaxis reflexes. And these effects appeared to be greater following exposure to MeHg alone. MeHg and/or PFOA exposure did not significantly impair motor coordination functions, or cause significant changes in c-Fos expression in the hippocampus and cerebellum, and spatial learning tests were similar to those in the controls, thus it was impossible to determine whether combined exposure to MeHg and PFOA had any additional effects on both hippocampus and cerebellum regions. However, a significant increase in the frequency of line crossing was observed in rats treated with MeHg or PFOA alone, and there were no significant differences between the MeHg+PFOA-treated group and the controls, suggesting that PFOA was antagonistic to MeHg toxicity in the locomotor activity test. Co-exposure to MeHg and PFOA decreased all tissue Hg concentrations in pups compared to the group exposed to MeHg only, suggesting that PFOA impaired Hg retention in different tissues. PMID:23490179

  18. Studies on the optimization of deformation processed metal metal matrix composites

    SciTech Connect

    Ellis, T.W.

    1994-01-04

    A methodology for the production of deformation processed metal metal matrix composites from hyper-eutectic copper-chromium alloys was developed. This methodology was derived from a basic study of the precipitation phenomena in these alloys encompassing evaluation of microstructural, electrical, and mechanical properties. The methodology developed produces material with a superior combination of electrical and mechanical properties compared to those presently available in commercial alloys. New and novel alloying procedures were investigated to extend the range of production methods available for these material. These studies focused on the use of High Pressure Gas Atomization and the development of new containment technologies for the liquid alloy. This allowed the production of alloys with a much more refined starting microstructure and lower contamination than available by other methods. The knowledge gained in the previous studies was used to develop two completely new families of deformation processed metal metal matrix composites. These composites are based on immissible alloys with yttrium and magnesium matrices and refractory metal reinforcement. This work extends the physical property range available in deformation processed metal metal matrix composites. Additionally, it also represents new ways to apply these metals in engineering applications.

  19. 3D printed nanocomposite matrix for the study of breast cancer bone metastasis.

    PubMed

    Zhu, Wei; Holmes, Benjamin; Glazer, Robert I; Zhang, Lijie Grace

    2016-01-01

    Bone is one of the most common metastatic sites of breast cancer, but the underlying mechanisms remain unclear, in part due to an absence of advanced platforms for cancer culture and study that mimic the bone microenvironment. In the present study, we integrated a novel stereolithography-based 3D printer and a unique 3D printed nano-ink consisting of hydroxyapatite nanoparticles suspended in hydrogel to create a biomimetic bone-specific environment for evaluating breast cancer bone invasion. Breast cancer cells cultured in a geometrically optimized matrix exhibited spheroid morphology and migratory characteristics. Co-culture of tumor cells with bone marrow mesenchymal stem cells increased the formation of spheroid clusters. The 3D matrix also allowed for higher drug resistance of breast cancer cells than 2D culture. These results validate that our 3D bone matrix can mimic tumor bone microenvironments, suggesting that it can serve as a tool for studying metastasis and assessing drug sensitivity. From the Clinical Editor: Cancer remains a major cause of mortality for patients in the clinical setting. For breast cancer, bone is one of the most common metastatic sites. In this intriguing article, the authors developed a bone-like environment using 3D printing technology to investigate the underlying biology of bone metastasis. Their results would also allow a new model for other researchers who work on cancer to use. PMID:26472048

  20. Characteristics of Hg-resistant bacteria isolated from Minamata Bay sediment

    SciTech Connect

    Nakamura, K.; Fujisaki, T.; Tamashiro, H.

    1986-06-01

    Seventy-two strains of Hg-resistant bacteria (Pseudomonas) were isolated on agar plates containing 40 micrograms/ml of HgCl2 from Minamata Bay sediment, which was heavily polluted with mercury (45.8 micrograms/g). The minimal inhibitory concentrations (MICs) of mercurial compounds were determined for the Hg-resistant pseudomonads and 65 strains (Pseudomonas sp., Bacillus sp., Vibrio sp., and Corynebacterium sp.) isolated from Sendai Bay sediment (1 microgram/g of mercury) as control. The MICs to HgCl/sub 2/, CH/sub 3/HgCl, C/sub 2/H/sub 5/HgCl, C/sub 3/H/sub 7/HgCl, and C/sub 6/H/sub 5/HgOCOCH/sub 3/ for the Hg-resistant pseudomonads from Minamata Bay were significantly higher than those of strains from Sendai Bay. The volatilization from liquid culture containing 20 micrograms/ml of HgCl2 was observed in all of the Hg-resistant pseudomonads from Minamata Bay (70 strains). The mean loss of mercury from liquid culture was 60.4 +/- 17.3%. Further study is warranted to determine what role the Hg-resistant bacteria, particularly the Pseudomonas species, play in the mercury cycle in Minamata Bay.

  1. MicroCT vs. Hg porosimetry: microporosity in commercial stones

    NASA Astrophysics Data System (ADS)

    Fusi, N.; Martinez-Martinez, J.; Barberini, V.; Galimberti, L.

    2009-04-01

    Decay of rocks, due both to extrinsic and intrinsic factors, can show up in several different forms, such as neoformation of minerals, decohesion of grains and/or crystals, magnification of previous defects, new discontinuities, etc. Intrinsic factors include the type of material, its properties and microstructure, in particular porosity and microporosity. Extrinsic factors relate to atmosphere and usage of the material itself. Rock degradation has several heavy consequences for commercial stones, such as increase of permeability, loss of material, loss of mechanical strength; these consequences are of crucial importance for conservation of historical buildings. Aim of this study is to compare microporosity of some massive commercial stones by means of X ray microtomography, a non destructive technique, and Hg porosimetry. Nine of the most used Spanish limestones and dolostones have been analysed. The lithotypes have been chosen for their homogeneous mineralogical composition (calcitic or dolomitic) and for their low porosity; some of them have been widely used in Spain for historical buildings. Different lithotypes have been described in thin section: Ambarino (A) and Beige Serpiente (BS): brecciated dolostone, composed by microcrystalline dolomitic clasts, in a dolomitic and/or calcitic microcrystalline matrix. Amarillo Triana (AT): yellow dolomitic marble, with fissures filled up by calcite and Fe oxides. Blanco Alconera (BA): a white-pink homogeneous limestone, with veins. Blanco Tranco (BT): a homogeneous white calcitic marble, without any fissures and/or fractures. Crema Valencia (CV): a pinkish limestone, characterized by abundant stilolythes, filled mainly by quartz (80%) and kaolin (11%). Gris Macael (GM): a calcitic marble wiht darker and lighter beds, conferring a strong anisotropy. Rojo Cehegin (RC): a red fossiliferous limestone with white calcitic veins. Travertino Blanco (TB): a massive white calcitic travertine. Prismatic samples of about 2x1x1 cm

  2. Carbonate aquifers with hydraulically non-active matrix: A case study from Poland

    NASA Astrophysics Data System (ADS)

    Rzonca, Bartłomiej

    2008-06-01

    SummaryThe Devonian carbonate (karst) rocks of the Holy Cross Mountains (Góry Świętokrzyskie) in Poland, which constitute a major water supply for the region, are the subject of the presented study. Using standard laboratory methods, the matrix hydrogeological properties (open porosity, permeability and specific yield) of the limestones and dolomites were determined. The test results showed very low open porosities of the samples, as well as an extremely low permeability. The specific yield in all the cases was zero. There was a very slight correlation between the permeability (represented by the hydraulic conductivity) and the open porosity for limestones - and no correlation for dolomites. The measured parameters do not depend on the structure of the rock matrix (classified as pelite, sparite or crystalline) nor does the occurrence of fractures. Differences in open porosity (but not in hydraulic conductivity) were observed between the samples from different structural units.

  3. Experimental study of the fracture toughness of a ceramic/ceramic-matrix composite sandwich structure

    SciTech Connect

    Li, Z.; Taya, M.; Dunn, M.L.; Watanabe, Ryuzo

    1995-06-01

    A hybrid experimental-numerical approach has been used to measure the fracture resistance of a sandwich structure consisting of a 304 stainless steel/partially stabilized zirconia ceramic-matrix composite crack-arresting layer embedded in a partially stabilized zirconia ceramic specimen. The mode 1 fracture toughness increases significantly when the crack propagates from the ceramic into the ceramic-matrix composite region. The increased toughening due to the stainless steel particles is explained reasonably well by a toughening model based on processing-induced thermal residual stresses. In addition, several experimental modifications were made to the chevron-notch wedge-loaded double cantilever beam specimen to overcome numerous problems encountered in generating a precrack in the small, brittle specimens used in this study.

  4. Association weight matrix: a network-based approach towards functional genome-wide association studies.

    PubMed

    Reverter, Antonio; Fortes, Marina R S

    2013-01-01

    In this chapter we describe the Association Weight Matrix (AWM), a novel procedure to exploit the results from genome-wide association studies (GWAS) and, in combination with network inference algorithms, generate gene networks with regulatory and functional significance. In simple terms, the AWM is a matrix with rows represented by genes and columns represented by phenotypes. Individual {i, j}th elements in the AWM correspond to the association of the SNP in the ith gene to the jth phenotype. While our main objective is to provide a recipe-like tutorial on how to build and use AWM, we also take the opportunity to briefly reason the logic behind each step in the process. To conclude, we discuss the impact on AWM of issues like the number of phenotypes under scrutiny, the density of the SNP chip and the choice of contrast upon which to infer the cause-effect regulatory interactions. PMID:23756904

  5. Transient and diffusion analysis of HgCdTe

    NASA Technical Reports Server (NTRS)

    Clayton, J. C.

    1982-01-01

    Solute redistribution during directional solidification of HgCdTe is addressed. Both one-dimensional and two-dimensional models for solute redistribution are treated and model results compared to experiment. The central problem studied is the cause of radial inhomogeneities found in directionally solidified HgCdTe. A large scale gravity-driven interface instability, termed shape instability, is postulated to be the cause of radial inhomogeneities. Recommendations for future work, along with appropriate computer programs, are included.

  6. In vitro studies on human periodontal ligament stem cell sheets enhanced by enamel matrix derivative.

    PubMed

    Wang, Zhongshan; Feng, Zhihong; Wu, Guofeng; Bai, Shizhu; Dong, Yan; Zhao, Yimin

    2016-05-01

    Numerous preclinical and clinical studies have focused on the periodontal regenerative functions of enamel matrix derivative (EMD), a heat-treated preparation derived from enamel matrix proteins (EMPs) of developing porcine teeth. In this study, periodontal ligament (PDL) stem cells (PDLSCs) were isolated, and the effects of EMD on the extracorporeal induction process and the characteristics of PDLSC sheets were investigated for their potential as a more effective stem-cell therapy. EMD-enhanced cell sheets could be induced by complete medium supplemented with 50 μg/mL vitamin C and 100 μg/mL EMD. The EMD-enhanced cell sheets appeared thicker and more compact than the normal PDLSC sheets, demonstrated more layers of cells (3-7 layers), secreted richer extracellular matrix (ECM), showed varying degrees of increases in mRNA expression of periodontal tissue-specific genes (COL I, POSTN), calcification-related genes (RUNX2, OPN, OCN) and a cementum tissue-specific gene (CAP), and possessed a better mineralization ability in terms of osteogenic differentiation in vitro. These EMD-enhanced cell sheets may represent a potential option for stem-cell therapy for PDL regeneration. PMID:26844646

  7. Expression of extracellular matrix proteins in cervical squamous cell carcinoma--a clinicopathological study.

    PubMed Central

    Goldberg, I; Davidson, B; Lerner-Geva, L; Gotlieb, W H; Ben-Baruch, G; Novikov, I; Kopolovic, J

    1998-01-01

    AIM: To evaluate the intracellular and peritumoral expression of matrix proteins in squamous cell carcinoma of the uterine cervix using immunohistochemistry. METHODS: 71 squamous cell carcinomas and 10 controls were stained for laminin, fibronectin, and collagen IV. Cytoplasmic staining in tumour cells and peritumoral deposition of matrix proteins were evaluated. The association between staining results and patient age, tumour stage, histological grade, and survival was studied. RESULTS: Positive cytoplasmic staining for laminin, fibronectin, and collagen IV was observed in 17 (23.9%), 27 (38%), and 10 (14.1%) cases, respectively. Staining for laminin was most pronounced in the invasive front of tumour islands, while for fibronectin and collagen IV it appeared to be diffuse. Peritumoral staining for laminin and collagen IV was detected in 12 cases (16.9%). Early stage (Ia1-Ia2) tumours were uniformly negative for all three proteins. Cytoplasmic staining for laminin correlated with positive staining for fibronectin and collagen IV, and with the presence of a peritumoral deposition of collagen IV and laminin. There was no correlation with any of the three markers between staining results and patient age, stage, grade, or survival. CONCLUSIONS: Expression of extracellular matrix proteins in some cervical squamous cell carcinomas might reflect the enhanced ability of these tumours to modify the peritumoral stroma. This ability seems to be absent in early stage tumours. The correlation between intracytoplasmic and peritumoral expression of matrix proteins supports the evidence of their synthesis by tumour cells. However, this property did not correlate with disease outcome in this study. Images PMID:10023343

  8. Supersymmetry and {sup 198}Hg

    SciTech Connect

    Bernards, Christian; Heinze, Stefan; Jolie, Jan; Fransen, Christoph; Linnemann, Andreas; Radeck, Desiree

    2009-01-28

    The energy spectrum and electromagnetic transition properties of the supermultiplet members with two proton fermions can be constructed using the dynamical U{sub v}(6/12) x U{sub {pi}}(6/4) extended supersymmetry. In order to investigate predictions of the two proton fermion--four neutron boson supermultiplet member {sup 198}Hg, an experiment with the HORUS cube {gamma}-ray spectrometer at the Cologne TANDEM accelerator was performed using the {sup 196}Pt({alpha},2n){sup 198}Hg reaction. By analyzing {gamma}{gamma} coincidence spectra and {gamma}{gamma} angular correlations, the required experimental data--level and decay energies, level spins and multipole mixing ratios--could be obtained. For the low-energy states, the experimental data show good agreement with theory.

  9. Mercury isotope signatures as tracers for Hg cycling at the New Idria Hg mine.

    PubMed

    Wiederhold, Jan G; Smith, Robin S; Siebner, Hagar; Jew, Adam D; Brown, Gordon E; Bourdon, Bernard; Kretzschmar, Ruben

    2013-06-18

    Mass-dependent fractionation (MDF) and mass-independent fractionation (MIF) of Hg isotopes provides a new tool for tracing Hg in contaminated environments such as mining sites, which represent major point sources of Hg pollution into surrounding ecosystems. Here, we present Hg isotope ratios of unroasted ore waste, calcine (roasted ore), and poplar leaves collected at a closed Hg mine (New Idria, CA, U.S.A.). Unroasted ore waste was isotopically uniform with δ(202)Hg values from -0.09 to 0.16‰ (± 0.10‰, 2 SD), close to the estimated initial composition of the HgS ore (-0.26‰). In contrast, calcine samples exhibited variable δ(202)Hg values ranging from -1.91‰ to +2.10‰. Small MIF signatures in the calcine were consistent with nuclear volume fractionation of Hg isotopes during or after the roasting process. The poplar leaves exhibited negative MDF (-3.18 to -1.22‰) and small positive MIF values (Δ(199)Hg of 0.02 to 0.21‰). Sequential extractions combined with Hg isotope analysis revealed higher δ(202)Hg values for the more soluble Hg pools in calcines compared with residual HgS phases. Our data provide novel insights into possible in situ transformations of Hg phases and suggest that isotopically heavy secondary Hg phases were formed in the calcine, which will influence the isotope composition of Hg leached from the site. PMID:23662941

  10. Mercury methylation and demethylation in Hg-contaminated lagoon sediments (Marano and Grado Lagoon, Italy)

    NASA Astrophysics Data System (ADS)

    Hines, Mark E.; Poitras, Erin N.; Covelli, Stefano; Faganeli, Jadran; Emili, Andrea; Žižek, Suzana; Horvat, Milena

    2012-11-01

    Mercury (Hg) transformation activities and sulfate (SO42-) reduction were studied in sediments of the Marano and Grado Lagoons in the Northern Adriatic Sea region as part of the "MIRACLE" project. The lagoons, which are sites of clam (Tapes philippinarum) farming, have been receiving excess Hg from the Isonzo River for centuries. Marano Lagoon is also contaminated from a chlor-alkali plant. Radiotracer methods were used to measure mercury methylation (230Hg, 197Hg), methylmercury (MeHg) demethylation (14C-MeHg) and SO42- reduction (35S) in sediment cores collected in autumn, winter and summer. Mercury methylation rate constants ranged from near zero to 0.054 day-1, generally decreased with depth, and were highest in summer. Demethylation rate constants were much higher than methylation reaching values of ˜0.6 day-1 in summer. Demethylation occurred via the oxidative pathway, except in winter when the reductive pathway increased in importance in surficial sediments. Sulfate reduction was also most active in summer (up to 1600 nmol mL-1 day-1) and depth profiles reflected seasonally changing redox conditions near the surface. Methylation and demethylation rate constants correlated positively with SO42- reduction and pore-water Hg concentrations, and inversely with Hg sediment-water partition coefficients indicating the importance of SO42- reduction and Hg dissolution on Hg cycling. Hg transformation rates were calculated using rate constants and concentrations of Hg species. In laboratory experiments, methylation was inhibited by amendments of the SO42--reduction inhibitor molybdate and by nitrate. Lagoon sediments displayed a dynamic seasonal cycle in which Hg dissolution in spring/summer stimulated Hg methylation, which was followed by a net loss of MeHg in autumn from demethylation. Sulfate-reducing bacteria (SRB) tended to be responsible for methylation of Hg and the oxidative demethylation of MeHg. However, during winter in surficial sediments, iron

  11. Fabrication and microstructure of Hg-1223 tape

    NASA Astrophysics Data System (ADS)

    Meng, R. L.; Wang, Y. Q.; Lewis, K.; Garcia, C.; Gao, L.; Xue, Y. Y.; Chu, C. W.

    1997-08-01

    A two-step spray/press process for the fabrication of Hg-1223 tape on a flexible Ni-substrate coated with Cr/(Ag,Pd) has been developed by using the mechanically aligned c-axis oriented Hg-1212 micrograins as the nucleation sites for the large c-axis oriented Hg-1223 grain growth. The self-field Jc of Hg-1223 tapes so reproducibly obtained is 7×104 A/cm2 at 77 K.

  12. Long wavelength photochemistry of ozone and n-butylferrocene: A matrix isolation study

    NASA Astrophysics Data System (ADS)

    Pinelo, Laura F.; Ault, Bruce S.

    2016-07-01

    The photochemical reaction of ozone and n-butylferrocene has been studied using a combination of argon-matrix isolation, infrared spectroscopy, and theoretical calculations. The dark deposition produced a vivid green matrix that, when irradiated with red light, turned a brownish-red color. This green matrix as well as slightly red-shifted O3 infrared absorptions are indicative of the formation an initial charge transfer complex between ozone and n-butylferrocene. The spectral results support the photodissociation of the complexed ozone with red light (λ ≥ 600 nm) producing an oxygen atom, O(3P), and a dioxygen molecule, O2(3Σ). The O(3P) then reacts with n-butylferrocene to form products consisting of an iron atom with a coordinated n-butylcyclopentadienyl or cyclopentadienyl ring and either: (1) a pyran, (2) an aldehyde, or (3) a bidentate cyclic aldehyde with a seven-membered ring including the iron atom. The photochemical products were characterized with FT-IR spectroscopy, 18O-labeled O3 experiments, and DFT calculations using the B3LYP functional with the 6-311++G(d, 2p) basis set. A possible mechanism for the photochemical reaction is discussed.

  13. Thermal cycling damage of metal matrix composites. Analytical study on dimensional change

    SciTech Connect

    Taya, Minoru ); Armstrong, W.D. ); Dunn, M. )

    1993-05-01

    An analytical model to predict dimensional changes in thermal cycled metal matrix composites (MMCs) with and without constant stress is proposed. The present model assumes that the temperature-time relation to simulate thermal cycling is of a step-function type and the matrix metal deforms as elastic/plastic/creep material while the fiber remains elastic throughout thermal cycling. The model can explain well the experimental results of W-ThO[sub 2]/FeC[sub r]AlY composite during the early stage of cycling and those of the previous works. The present model is then compared with the existing ones including our previous model. Another model is also constructed to simulate the later stage of thermal cycling damage where the debonding of the matrix-fiber interface would presumably take place progressively with number of cycles. This model with a progressive debonded interface was found to explain reasonably well the later stage of dimensional changes observed in W-ThO[sub 2]/FeCrAlY composite. Then, the dimensional change in thermal cycled MMC under constant stress loading is studied by use of the above model for early (first) stage of thermal cycling that is modified to account for applied stress. This model can explain well the experimental results of W/Cu composite. 20 refs., 15 figs., 1 tab.

  14. Long wavelength photochemistry of ozone and n-butylferrocene: A matrix isolation study

    NASA Astrophysics Data System (ADS)

    Pinelo, Laura F.; Ault, Bruce S.

    2016-07-01

    The photochemical reaction of ozone and n-butylferrocene has been studied using a combination of argon-matrix isolation, infrared spectroscopy, and theoretical calculations. The dark deposition produced a vivid green matrix that, when irradiated with red light, turned a brownish-red color. This green matrix as well as slightly red-shifted O3 infrared absorptions are indicative of the formation an initial charge transfer complex between ozone and n-butylferrocene. The spectral results support the photodissociation of the complexed ozone with red light (λ ≥ 600 nm) producing an oxygen atom, O(3P), and a dioxygen molecule, O2(3Σ). The O(3P) then reacts with n-butylferrocene to form products consisting of an iron atom with a coordinated n-butylcyclopentadienyl or cyclopentadienyl ring and either: (1) a pyran, (2) an aldehyde, or (3) a bidentate cyclic aldehyde with a seven-membered ring including the iron atom. The photochemical products were characterized with FT-IR spectroscopy, 18O-labeled O3 experiments, and DFT calculations using the B3LYP functional with the 6-311++G(d, 2p) basis set. A possible mechanism for the photochemical reaction is discussed.

  15. Synthesis and characterization of zirconia-magnesia inert matrix fuel: Uranium homolog studies

    SciTech Connect

    Holliday, Kiel; Hartmann, Thomas; Poineau, Frederic; Kennedy, J Rory; Czerwinski, Ken

    2009-10-21

    X-ray powder diffraction, X-ray fluorescence, microscopy, X-ray absorption fine structure, and electron probe microanalysis were used to characterize ZrO2–MgO inert matrix fuel containing UO2 (as a fissile element and a Pu homolog) and Er2O3 as a burnable poison. A large composition range of MgO and ZrO2 was evaluated to determine total concentrations, local environment, phases present, phase mixing, and phase composition. It was found that most compositions of the material consist of two phases: MgO (periclase) and ZrO2 (cubic zirconia). The zirconia phase incorporates up to 5% (wt/wt) MgO and up to 20% and 10% (wt/wt) UO2 and Er2O3 respectively. This allows the fissile material and burnable poison to be incorporated into the zirconia crystal structure and defines the limits of this isomorphic substitution. The bond deformation due to the isomorphic substitution of uranium was determined by X-ray absorption fine structure. The MgO phase remains pure, which will enable design optimization of the overall thermophysical properties of the inert matrix fuel in regard to thermal diffusivity and thermal conductivity. This characterization data will be used in future studies to correlate the dissolution behavior of inert matrix material containing plutonium.

  16. Thermo-oxidative stability studies of PMR-15 polymer matrix composites reinforced with various continuous fibers

    NASA Technical Reports Server (NTRS)

    Bowles, Kenneth J.

    1990-01-01

    An experimental study was conducted to measure the thermooxidative stability of PMR-15 composites reinforced with various fibers and to observe differences in the way they degrade in air. The fibers studied include graphite and the thermally stable Nicalon and Nextel ceramic fibers. Weight-loss rates for the different composites were assessed as a function of mechanical properties, specimen geometry, fiber sizing, and interfacial bond strength. Differences were observed in rates of weight loss, matrix cracking, geometry dependency, and fiber sizing effects. It was shown that Celion 6000 fiber-reinforced composites do not exhibit a straight-line Arrhenius relationship at temperatures above 316 C.

  17. Transfer matrix method-based approach to study the bi-gyrotropic magnetic materials

    NASA Astrophysics Data System (ADS)

    Zamani, Mehdi; Hajesmaeili, Hamidreza Nezhad; Zandi, Mohammad Hossein

    2016-08-01

    Optical and magneto-optical (MO) responses in magnetic multilayer systems are calculated by transfer matrix method (TMM). In a bi-gyrotropic medium, electric permittivity (ε) and magnetic permeability (μ) coefficients are in the form of non-diagonal tensors, synchronously, which their non-diagonal elements refer to the existence of anisotropy in such medium. In the present study, in addition to present a TMM based-approach for bi-gyrotropic medium, numerical simulations for studying the amount of optical and MO parameters of the bi-gyrotropic Yttrium Iron Garnet (YIG) material, in both transmission and reflection configurations, have been done.

  18. HCN Producing Bacteria Enable Sensing Of Non-Bioavailable Hg Species by the Whole Cell Biosensor

    NASA Astrophysics Data System (ADS)

    Horvat, M.; Rijavec, T.; Koron, N.; Lapanje, A.

    2015-12-01

    Bacteria play an important role in Hg transformation reactions. The production of cyanide (HCN) and other secondary metabolites seems to be key elements involved in these transformations. Current hypotheses link the role of HCN production to growth inhibition of nonHCN producing competitor organisms (role of an antimicrobial agent). Our past investigations showed that HCN production did not correlate with antimicrobial activity and since pK value of HCN is very high (pK = 9,21), it can be expected that most of the produced HCN is removed from the microenvironment. This way, the expected inhibitory concentrations can hardly be reached. Accordingly, we proposed a new concept, where the ability of complexation of transient metals by HCN served as a regulation process for the accessibility of micro-elements. In our study, we focused on the presence of HCN producing bacteria and carried it out in the Hg contaminated environment connected to the Idrija Mercury Mine, Slovenia. We characterised the isolates according to the presence of Hg resistance (HgR), level of HCN production and genetic similarities. In laboratory setups, using our merR whole cell based biosensor, we determined the transformation of low bioavailable Hg0 and HgS forms into bioavailable Hg by these HCN producing bacteria. We observed that HgR strains producing HCN had the highest impact on increased Hg bioavailability. In the proposed ecological strategy HgR HCN producing bacteria increase their competitive edge over non-HgR competitors through the increase of Hg toxicity. Due to their activity, Hg is made available to other organisms as well and thus enters into the ecosystem. Finally, using some of the characteristics of bacteria (e.g. Hg resistance genetic elements), we developed a fully automated sensing approach, combining biosensorics and mechatronics, to measure the bioavailability of Hg in situ.

  19. Engineering topological surface states: HgS, HgSe, and HgTe.

    PubMed

    Virot, François; Hayn, Roland; Richter, Manuel; van den Brink, Jeroen

    2013-10-01

    Using density functional electronic structure calculations, we establish the consequences of surface termination and modification on protected surface states of metacinnabar (β-HgS). Whereas we find that the Dirac cone is isotropic and well separated from the valence band for the (110) surface, it is highly anisotropic at the pure (001) surface. We demonstrate that the anisotropy is modified by surface passivation because the topological surface states include contributions from dangling bonds. Such dangling bonds exist on all pure surfaces within the whole class HgX with X=S, Se, or Te and directly affect the properties of the Dirac cone. Surface modifications also alter the spatial location (depth and decay length) of the topologically protected edge states, which renders them essential for the interpretation of photoemission data. PMID:24138263

  20. Magneto-optical transitions between subbands with different quantum numbers in narrow gap HgTe-CdTe superlattices

    NASA Astrophysics Data System (ADS)

    Luo, H.; Yang, G. L.; Furdyna, J. K.; Ram-Mohan, L. R.

    1991-10-01

    Magneto-optical transitions induced by the coupling between the conduction and the valence bands through the momentum matrix element, and by the coupling terms between light and heavy holes resulting from an applied magnetic field are studied theoretically in narrow gap HgTe-CdTe superlattices. Selection rules and transition probabilities for the above transitions are presented and compared with allowed transitions. The numerical results for the transition probabilities show that some of the interband transitions with ΔN=±1 are significant and have to be considered in the studies of interband magneto-optical spectra of narrow gap superlattices.

  1. Total Hg and methyl Hg distribution in sediments of selected Louisiana water bodies.

    PubMed

    Delaune, Ronald D; Gambrell, Robert P; Devai, Istvan; Jugsujinda, Aroon; Kongchum, Manoch

    2009-05-01

    Sediment samples (543) collected from selected Louisiana streams and lakes were analyzed for total Hg and methyl Hg content. The average total Hg content among 543 samples was 92.3 +/- 95.1 microg kg(-1). The average methyl Hg content in the samples was 0.68 +/- 0.80 microg kg(-1). Methyl Hg accounted for an average of 0.73% of the total Hg in sediment. Linear regression analysis of total Hg versus methyl Hg content of the sediment showed methyl Hg content was significantly correlated to total Hg content of sediment (P > 0.01, n = 537) and sediment organic matter content. (P > 0.01, n = 536) Methyl Hg was also positively correlated to clay (P > 0.01, n = 537) and inversely correlated to sand content of sediment (P > 0.01, n = 537). Total Hg and methyl Hg content in these sediments was within the normal range reported elsewhere indicating no significant industrial or municipal Hg contamination. A comparison of selected water bodies with fishing advisories showed no relationship to total Hg and methyl Hg in sediment. PMID:19337918

  2. Mercury profiles in sediment from the marginal high of Arabian Sea: an indicator of increasing anthropogenic Hg input.

    PubMed

    Chakraborty, Parthasarathi; Vudamala, Krushna; Chennuri, Kartheek; Armoury, Kazip; Linsy, P; Ramteke, Darwin; Sebastian, Tyson; Jayachandran, Saranya; Naik, Chandan; Naik, Richita; Nath, B Nagender

    2016-05-01

    Total Hg distributions and its speciation were determined in two sediment cores collected from the western continental marginal high of India. Total Hg content in the sediment was found to gradually increase (by approximately two times) towards the surface in both the cores. It was found that Hg was preferentially bound to sulfide under anoxic condition. However, redox-mediated reactions in the upper part of the core influenced the total Hg content in the sediment cores. This study suggests that probable increase in authigenic and allogenic Hg deposition attributed to the increasing Hg concentration in the surface sediment in the study area. PMID:26797942

  3. An Experimental Study of Penny-shaped Fluid-driven Cracks in an Elastic Matrix

    NASA Astrophysics Data System (ADS)

    Stone, Howard

    2015-11-01

    When a pressurized fluid is injected into an elastic matrix, the fluid generates a fracture that grows along a plane and forms a fluid-filled disc-like shape. For example, such problems occur in various natural and industrial applications involving the subsurface of Earth, such as hydraulic fracturing operations. We report a laboratory study of such a fluid-driven crack in a gelatin matrix, study the crack shape as a function of time, and investigate the influence of different experimental parameters such as the injection flow rate, Young's modulus of the matrix, and fluid viscosity. We find that the crack radius increases with time as a power law, which has been predicted both for the limit where viscous effects in the flow along the crack opening control the rate of crack propagation, as well as the limit where fracture toughness controls crack propagation. We vary experimental parameters to probe the physical limits and highlight that for our typical parameters both effects can be significant. Also, we measure the time evolution of crack shape, which has not been studied before. The rescaled crack shapes collapse at longer times, based on an appropriate scaling argument, and again we compare the scaling arguments in different physical limits. The gelatin system provides a useful laboratory model for further studies of fluid-driven cracks, some of which we will mention as they are inspired by the physics of hydraulic fracturing. This work is part of the PhD thesis of Ching-Yao Lai and is a collaboration with Drs. Zhong Zheng and Jason Wexler (Princeton University) and Professor Emilie Dressaire (NYU). Department of Mechanical and Aerospace Engineering.

  4. Ligational behavior of clioquinol antifungal drug towards Ag(I), Hg(II), Cr(III) and Fe(III) metal ions: Synthesis, spectroscopic, thermal, morphological and antimicrobial studies

    NASA Astrophysics Data System (ADS)

    El-Megharbel, Samy M.; Refat, Moamen S.

    2015-04-01

    This article presents a synthesis, characterization, theoretical and biological (anti-bacterial, and anti-fugal) evaluation studies of Ag(I), Hg(II), Cr(III) and Fe(III) complexes of clioquinol (CQ) drug ligand. Structures of the titled complexes cited herein were discussed using elemental analyses and spectral measurements e.g., IR, 1H NMR, and electronic studies. The results confirmed the formation of the clioquinol complexes by three molar ratios (1:1) for Ag(I), (1:2) for Hg(II) and (1:3) for both Cr(III) and Fe(III) metal ions. The clioquinol reacts as a bidentate chelate bound to all respected metal ions through the oxygen and nitrogen of quinoline-8-ol. The metal(II) ions coordinated to clioquinol ligand through deprotonation of sbnd OH terminal group. Infrared and 1H NMR spectral data confirm that coordination is via the oxygen of phenolic group and nitrogen atom of quinoline moiety. The molar conductance measurements of the CQ complexes in DMSO correspond to be non-electrolyte nature. Thus, these complexes may be formulated as [Ag(CQ)(H2O)2] H2O, [Hg(CQ)2]ṡ2H2O, [Cr(CQ)3] and [Fe(CQ)3]H2O. The Coats-Redfern method, the kinetic thermodynamic parameters like activation energies (E∗), entropies (ΔS∗), enthalpies (ΔH∗), and Gibbs free energies (ΔG∗) of the thermal decomposition reactions have been deduced from thermogravimetric curves (TG) with helpful of differential thermo gravimetric (DTG) curves. The narrow size distribution in nano-scale range for the clioquinol complexes have been discussed using X-ray powder diffraction (XRD), scanning electron microscope (SEM), and X-ray energy dispersive spectrometer (EDX) analyzer.

  5. Porcine acellular lung matrix for wound healing and abdominal wall reconstruction: A pilot study

    PubMed Central

    Fernandez-Moure, Joseph S; Van Eps, Jeffrey L; Rhudy, Jessica R; Cabrera, Fernando J; Acharya, Ghanashyam S; Tasciotti, Ennio; Sakamoto, Jason; Nichols, Joan E

    2016-01-01

    Surgical wound healing applications require bioprosthetics that promote cellular infiltration and vessel formation, metrics associated with increased mechanical strength and resistance to infection. Porcine acellular lung matrix is a novel tissue scaffold known to promote cell adherence while minimizing inflammatory reactions. In this study, we evaluate the capacity of porcine acellular lung matrix to sustain cellularization and neovascularization in a rat model of subcutaneous implantation and chronic hernia repair. We hypothesize that, compared to human acellular dermal matrix, porcine acellular lung matrix would promote greater cell infiltration and vessel formation. Following pneumonectomy, porcine lungs were processed and characterized histologically and by scanning electron microscopy to demonstrate efficacy of the decellularization. Using a rat model of subcutaneou implantation, porcine acellular lung matrices (n = 8) and human acellular dermal matrices (n = 8) were incubated in vivo for 6 weeks. To evaluate performance under mechanically stressed conditions, porcine acellular lung matrices (n = 7) and human acellular dermal matrices (n = 7) were implanted in a rat model of chronic ventral incisional hernia repair for 6 weeks. After 6 weeks, tissues were evaluated using hematoxylin and eosin and Masson’s trichrome staining to quantify cell infiltration and vessel formation. Porcine acellular lung matrices were shown to be successfully decellularized. Following subcutaneous implantation, macroscopic vessel formation was evident. Porcine acellular lung matrices demonstrated sufficient incorporation and showed no evidence of mechanical failure after ventral hernia repair. Porcine acellular lung matrices demonstrated significantly greater cellular density and vessel formation when compared to human acellular dermal matrix. Vessel sizes were similar across all groups. Cell infiltration and vessel formation are well-characterized metrics of incorporation

  6. Porcine acellular lung matrix for wound healing and abdominal wall reconstruction: A pilot study.

    PubMed

    Fernandez-Moure, Joseph S; Van Eps, Jeffrey L; Rhudy, Jessica R; Cabrera, Fernando J; Acharya, Ghanashyam S; Tasciotti, Ennio; Sakamoto, Jason; Nichols, Joan E

    2016-01-01

    Surgical wound healing applications require bioprosthetics that promote cellular infiltration and vessel formation, metrics associated with increased mechanical strength and resistance to infection. Porcine acellular lung matrix is a novel tissue scaffold known to promote cell adherence while minimizing inflammatory reactions. In this study, we evaluate the capacity of porcine acellular lung matrix to sustain cellularization and neovascularization in a rat model of subcutaneous implantation and chronic hernia repair. We hypothesize that, compared to human acellular dermal matrix, porcine acellular lung matrix would promote greater cell infiltration and vessel formation. Following pneumonectomy, porcine lungs were processed and characterized histologically and by scanning electron microscopy to demonstrate efficacy of the decellularization. Using a rat model of subcutaneou implantation, porcine acellular lung matrices (n = 8) and human acellular dermal matrices (n = 8) were incubated in vivo for 6 weeks. To evaluate performance under mechanically stressed conditions, porcine acellular lung matrices (n = 7) and human acellular dermal matrices (n = 7) were implanted in a rat model of chronic ventral incisional hernia repair for 6 weeks. After 6 weeks, tissues were evaluated using hematoxylin and eosin and Masson's trichrome staining to quantify cell infiltration and vessel formation. Porcine acellular lung matrices were shown to be successfully decellularized. Following subcutaneous implantation, macroscopic vessel formation was evident. Porcine acellular lung matrices demonstrated sufficient incorporation and showed no evidence of mechanical failure after ventral hernia repair. Porcine acellular lung matrices demonstrated significantly greater cellular density and vessel formation when compared to human acellular dermal matrix. Vessel sizes were similar across all groups. Cell infiltration and vessel formation are well-characterized metrics of incorporation

  7. Fiber-matrix interface studies on bioabsorbable composite materials for internal fixation of bone fractures. I. Raw material evaluation and measurement of fiber-matrix interfacial adhesion.

    PubMed

    Slivka, M A; Chu, C C; Adisaputro, I A

    1997-09-15

    The objective of this study was to characterize and evaluate the performance of various fiber-matrix composite systems by studying the mechanical, thermal, and physical properties of the fiber and matrix components, and by studying the fiber-matrix interface adhesion strength using both microbond and fragmentation methods. The composites studies were poly(L-lactic acid) (PLLA) matrix reinforced with continuous fibers of either nonabsorbable AS4 carbon (C), absorbable calcium phosphate (CaP), poly(glycolic acid) (PGA), or chitin. Carbon and CaP single fibers had high Young's moduli and failed in a brittle manner. PGA and chitin single fibers had relatively lower Young's moduli and relatively higher ductility. Upon in vitro hydrolysis, CaP fibers retained 17% of their tensile strength and 39% of their Young's modulus after 12 h, PCA fibers retained 10% of their tensile strength and 52% of their Young's modulus after 16 days, and chitin fibers retained 87% of their tensile strength and 130% of their Young's modulus after 25 days. PLLA films had much lower strength and Young's moduli, but much higher ductility relative to the single fibers. Using the microbond method, the initial fiber-matrix interfacial shear strength (IFSS) of C/PLLA and CaP/PLLA microcomposites was 33.9 and 12.6 MPa, respectively. Upon in vitro hydrolysis, C/PLLA retained 49% of IFSS after 15 days and CaP/PLLA retained 46% of IFSS after 6 h. Using a fiber fragmentation method, the initial IFSS of C/PLLA, CaP/PLLA, and chitin/ PLLA was 22.2, 15.6, and 28.3 MPa, respectively. The performance of carbon fibers and C/PLLA composites was superior to the other fibers and fiber/PLLA systems, but the carbon fiber was nonabsorbable. CaP had the most suitable modulus of the absorbable fibers for fixing cortical bone fracture, but its rapid deterioration of mechanical properties and loss of IFSS limits its use. PGA and chitin fibers had suitable mechanical properties and their retention for fixing cancellous

  8. Synthesis, spectroscopic, antimicrobial and DNA cleavage studies of new Co(II), Ni(II), Cu(II), Cd(II), Zn(II) and Hg(II) complexes with naphthofuran-2-carbohydrazide Schiff base

    NASA Astrophysics Data System (ADS)

    Halli, Madappa B.; Sumathi, R. B.

    2012-08-01

    A series of Co(II), Ni(II), Cu(II), Cd(II), Zn(II) and Hg(II) complexes have been synthesized with newly synthesized Schiff base derived from naphthofuran-2-carbohydrazide and cinnamaldehyde. The elemental analyses of the complexes are confined to the stoichiometry of the type MLCl2 [M = Co(II) and Cu(II)], ML2Cl2 [M = Ni(II), Cd(II), Zn(II) and Hg(II)] respectively, where L is Schiff base ligand. Structures have been proposed from elemental analyses, IR, electronic, mass, 1H NMR, ESR spectral data, magnetic, and thermal studies. The measured low molar conductance values in DMF indicate that the complexes are non-electrolytes. Spectroscopic studies suggest coordination occurs through azomethine nitrogen and carbonyl oxygen of the ligand with the metal ions. The Schiff base and its complexes have been screened for their antibacterial (Escherichia coli, Staphylococcus aureus, Bacillus subtilis and Salmonella typhi) and antifungal (Aspergillus niger, Aspergillus flavus, Cladosporium and Candida albicans) activities by minimum inhibitory concentration (MIC) method. The DNA cleavage studies by agarose gel electrophoresis method was studied for all the complexes.

  9. Experimental studies of nuclear matrix elements for neutrino-less ββ decays

    SciTech Connect

    Ejiri, H.

    2013-12-30

    Nuclear matrix elements M{sup 0ν} for neutrino less double beta decays (0νββ) are crucial for neutrino studies in 0νββ experiments. The neutrino mass to be studied is sensitive to M{sup 0ν}, while theoretical calculations for M{sup 0ν} are hard. Thus experimental studies of nuclear structures and single β matrix elements M{sub β} associated with 0νββ are useful to confirm and help the theoretical calculations. This reports briefly experimental methods and recent charge exchange reaction studies for M{sub β}. The single β elements for M{sup ±}(2{sup −}) associated with M{sup 0ν}(2{sup −}), which is the major component of M{sup 0ν}, are found to be reduced (quenched) much by the spin isospin correlation and the nuclear medium (non-nucleonic isobar) effect. The present result suggests that the spin isospin components of M{sup 0ν} is fairly reduced (quenched)

  10. Electron-H2 Collisions Studied Using the Finite Element Z-Matrix Method

    NASA Technical Reports Server (NTRS)

    Huo, Winifred M.; Brown, David; Langhoff, Stephen R. (Technical Monitor)

    1997-01-01

    We have applied the Z-matrix method, using a mixed basis of finite elements and Gaussians, to study e-H2 elastic and inelastic collisions. Special attention is paid to the quality of the basis set and the treatment of electron correlation. The calculated cross sections are invariant, to machine accuracy, with respect to the choice of parameters a, b, d, e as long as they satisfy Equation (3). However, the log derivative approach, i.e., the choice a = -e = 1, b = d = 0 appears to converge slightly faster than other choices. The cross sections agree well with previous theoretical results. Comparison will be made with available experimental data.

  11. R-matrix study of ionization in barium via two-photon interfering routes

    NASA Astrophysics Data System (ADS)

    Aymar, M.; Luc-Koenig, E.; Lecomte, J. M.; Millet, M.; Lyras, A.

    2000-02-01

    A quantitative analysis of part of the experimental data reported by Wang, Chen and Elliott [1,3] who studied in barium coherent control through two-color resonant interfering paths is reported. Dynamics of the two-color photoionization process, described as an adiabatic process in the rotating wave approximation, is governed by the coherent excitation of the 6s6p and 6s7p 1P1 intermediate states. Interference effects are found to play a minor role. The required atomic parameters are obtained from a theoretical approach based on a combination of jj-coupled eigenchannel R-matrix and Multichannel Quantum Defect Theory.

  12. Mercury isotope fractionation during precipitation of metacinnabar (β-HgS) and montroydite (HgO).

    PubMed

    Smith, Robin S; Wiederhold, Jan G; Kretzschmar, Ruben

    2015-04-01

    To utilize stable Hg isotopes as a tracer for Hg cycling and pollution sources in the environment, it is imperative that fractionation factors for important biogeochemical processes involving Hg are determined. Here, we report experimental results on Hg isotope fractionation during precipitation of metacinnabar (β-HgS) and montroydite (HgO). In both systems, we observed mass-dependent enrichments of light Hg isotopes in the precipitates relative to the dissolved Hg. Precipitation of β-HgS appeared to follow equilibrium isotope fractionation with an enrichment factor ε(202)Hg(precipitate-supernatant) of -0.63‰. Precipitation of HgO resulted in kinetic isotope fractionation, which was described by a Rayleigh model with an enrichment factor of -0.32‰. Small mass-independent fractionation was observed in the HgS system, presumably related to nuclear volume fractionation. We propose that Hg isotope fractionation in the HgS system occurred in solution during the transition of O- to S-coordination of Hg(II), consistent with theoretical predictions. In the HgO system, fractionation was presumably caused by the faster precipitation of light Hg isotopes, and no isotopic exchange between solid and solution was observed on the timescale investigated. The results of this work emphasize the importance of Hg solution speciation and suggest that bonding partners of Hg in solution complexes may control the overall isotope fractionation. The determined fractionation factor and mechanistic insights will have implications for the interpretation of Hg isotope signatures and their use as an environmental tracer. PMID:25782104

  13. Study of barrier height and trap centers of Au/n-Hg{sub 3}In{sub 2}Te{sub 6} Schottky contacts by current-voltage (I-V) characteristics and deep level transient spectroscopy

    SciTech Connect

    Li, Yapeng; Fu, Li Sun, Jie; Wang, Xiaozhen

    2015-02-28

    The temperature-dependent electrical characteristics of the Au/n-Hg{sub 3}In{sub 2}Te{sub 6} Schottky contact have been studied at the temperature range of 140 K–315 K. Based on the thermionic emission theory, the ideality factor and Schottky barrier height were calculated to decrease and increase from 3.18 to 1.88 and 0.39 eV to 0.5 eV, respectively, when the temperature rose from 140 K to 315 K. This behavior was interpreted by the lateral inhomogeneities of Schottky barrier height at the interface of Au/n-Hg{sub 3}In{sub 2}Te{sub 6} contact, which was shown by the plot of zero-bias barrier heights Φ{sub bo} versus q/2kT. Meanwhile, it was found that the Schottky barrier height with a Gaussian distribution was 0.67 eV and the standard deviation σ{sub 0} was about 0.092 eV, indicating that the uneven distribution of barrier height at the interface region. In addition, the mean value of Φ{sup ¯}{sub b0} and modified Richardson constant was determined to be 0.723 eV and 62.8 A/cm{sup 2}K{sup 2} from the slope and intercept of the ln(I{sub o}/T{sup 2}) – (qσ{sub 0}{sup 2}/2k{sup 2}T{sup 2}) versus q/kT plot, respectively. Finally, two electron trap centers were observed at the interface of Au/n-Hg{sub 3}In{sub 2}Te{sub 6} Schottky contact by means of deep level transient spectroscopy.

  14. Detection Feasibility of Magnetic Fields and HG Abundances in HgMn Stars

    NASA Astrophysics Data System (ADS)

    Takada-Hidai, M.; Sakaue, A.; Kotake, J.

    We analyzed two Fe II lines at 6147.7 AA and 6149.2 AA observed in 14 HgMn stars with the purpose to examine the feasibility of detecting magnetic fields in HgMn stars based on Mathys' empirical relation between the strengths of the Fe II lines and magnetic fields (Mathys 1990, A&A 232, 151). Takada-Hidai & Jugaku (1992, PASP 104, 106) found that the Fe II 6149 AA is strongly blended with the Hg II 6149.5 AA line in the typical HgMn star mu Lep. To investigate the blending effect of the Hg II line, we measured the strengths of Fe II lines in the sample stars with the Hg abundances of 4 < log Hg < 7 and obtained Hg abundaces from the blending Hg II lines. Most of the resulting Hg abundances were found to agree with the previously determined values within about 0.6 dex. We also found, from a comparison between the strengths of Fe II lines with Hg abundances, that the blending effect of the Hg II line seems to be negligible for the Hg abundances of about < 5 dex, and therefore magnetic fields may possibly be detected with Mathys' empirical relation in case of HgMn stars with such Hg abundances as < 5 dex.

  15. Body Burden of Hg in Different Bio-Samples of Mothers in Shenyang City, China

    PubMed Central

    Xu, Jian; Du, Juan; Yan, Chong-huai

    2014-01-01

    Hg is an accumulative and neuro-toxic heavy metal which has a wide range of adverse effects in human health. However, few studies are available on body burden of Hg level in different bio-samples of pregnant women in Chinese population. Therefore, this study evaluated Hg levels in different maternal bio-samples in Shenyang city, China and investigated the correlation of Hg levels in different bio-samples. From October to December 2008, 200 pregnant women about to deliver their babies at ShengJing Hospital (Shenyang city, northeast of China) participated in this study. The geometric mean (GM) of Hg levels in cord blood, maternal venous blood, breast milk, and maternal urine were 2.18 µg/L, 1.17 µg/L, 1.14 µg/L, and 0.73 µg/L, respectively, and the GM of maternal hair Hg level was 404.45 µg/kg. There was a strong correlation between cord blood and maternal blood total Hg level (r = 0.713, P<0.001). Frequency of fish consumption more than or equal to 3 times per week during pregnancy was suggested as a significant risk factor of prenatal Hg exposure (unadjusted OR 3.5, adjusted OR 2.94, P<0.05). This study provides evidence about Hg burden of mothers and the risk factors of prenatal Hg exposure in Shenyang city, China. PMID:24858815

  16. Knight Shift vs Hole Concentration in Hg1201 and Hg1212

    NASA Astrophysics Data System (ADS)

    Itoh, Yutaka

    We studied the hole concentration dependences of 63Cu Knight shifts in single-CuO2-layer high-Tc cuprate superconductors HgBa2CuO4+δ and double-layer HgBa2CaCu2O6+δ. We found that the spin Knight shift at room temperature as a function of the hole concentration in the single-layer superconductor is different from that in the double-layer superconductor. Two type relations between the spin Knight shift and the hole doping level serve to estimate the individual hole concentrations of the non-equivalent CuO2 planes in a unit cell.

  17. Matrix Isolation Studies of Carbonic Acid—The Vapor Phase above the β-Polymorph

    PubMed Central

    2013-01-01

    Twenty years ago two different polymorphs of carbonic acid, α- and β-H2CO3, were isolated as thin, crystalline films. They were characterized by infrared and, of late, by Raman spectroscopy. Determination of the crystal structure of these two polymorphs, using cryopowder and thin film X-ray diffraction techniques, has failed so far. Recently, we succeeded in sublimating α-H2CO3 and trapping the vapor phase in a noble gas matrix, which was analyzed by infrared spectroscopy. In the same way we have now investigated the β-polymorph. Unlike α-H2CO3, β-H2CO3 was regarded to decompose upon sublimation. Still, we have succeeded in isolation of undecomposed carbonic acid in the matrix and recondensation after removal of the matrix here. This possibility of sublimation and recondensation cycles of β-H2CO3 adds a new aspect to the chemistry of carbonic acid in astrophysical environments, especially because there is a direct way of β-H2CO3 formation in space, but none for α-H2CO3. Assignments of the FTIR spectra of the isolated molecules unambiguously reveal two different carbonic acid monomer conformers (C2v and Cs). In contrast to the earlier study on α-H2CO3, we do not find evidence for centrosymmetric (C2h) carbonic acid dimers here. This suggests that two monomers are entropically favored at the sublimation temperature of 250 K for β-H2CO3, whereas they are not at the sublimation temperature of 210 K for α-H2CO3. PMID:23631554

  18. Study of the influence of alkalizing components on matrix pellets prepared by extrusion/spheronization.

    PubMed

    Hamedelniel, Elnazeer I; Bajdik, János; Kása, Péter; Pintye-Hódi, Klára

    2012-01-01

    The aim of this study was to investigate the effects of alkalizing components and the nature of the wetting liquid on the properties of matrix pellets prepared by extrusion and spheronization. Atenolol was used as an active pharmaceutical ingredient, ethylcellulose as a matrix former, microcrystalline cellulose as a filler and disodium phosphate anhydrous and trisodium phosphate dodecahydrate as alkalizing materials. Water and a water-ethanol mixture served as granulation liquids. Pellet formation was evaluated via mechanical, dissolution and morphological studies. In order to enhance the dissolution of Atenolol from the pellets, alkalizing components were used and the influence of these components on the pH was tested. Investigations of the breaking hardness, the morphology and the dissolution revealed that the pellets containing trisodium phosphate dodecahydrate and prepared with a higher amount of water as binding liquid displayed the best physico-chemical parameters and uniform dissolution. In in vitro experiments, the dissolution release complied with the texture of the pellets and the effect of pH. The pellets have suitable shape and very good hardness for the coating process and are appropriate for subsequent in vivo experiments. PMID:21067337

  19. A Flowable Placental Tissue Matrix Allograft in Lower Extremity Injuries: A Pilot Study.

    PubMed

    Lullove, Eric

    2015-06-01

    Damaged connective tissue commonly leads to lower extremity injuries. These injuries can result in inflammation, reduced mobility, and chronic pain. Conservative treatment may include orthotics, offloading the injury, physical therapy, and/or NSAIDs. If conservative treatment fails, surgical intervention may be required. Even after successful surgery, these procedures often result in reduced joint mobility and tendon or ligament strength. A novel flowable tissue matrix allograft, derived from human placental connective tissue, has recently been made available for minimally invasive treatment of damaged or inadequate tissue  (PX50®, Human Regenerative Technologies LLC, Redondo Beach, CA). Based on the universal role of connective tissue in the body, and its reported antimicrobial, anti-adhesive, and anti-inflammatory properties, we assessed the effects of using this placental tissue matrix in the treatment of a series of lower extremity injuries. In this pilot study, 9 of 10 patients reported pain levels of 2 or less by week four using the VAS pain scale. This short-term pilot study effectively shows that injectable, flowable amniotic allografts can be used for orthopedic sports injuries of the lower extremities. PMID:26180699

  20. Human articular cartilage in osteoarthrosis. I. The matrix. Transmission electron microscopic study.

    PubMed

    Montella, A; Manunta, A; Espa, E; Gasparini, G; De Santis, E; Gulisano, M

    1992-01-01

    The present research has been carried out with the aim of contributing to the understanding of morphological changes in human articular cartilage during osteoarthrosis and to evaluate the usefulness of TEM in this application. Only the matrix was examined in this first phase of study. Fragments from the femoral head of 20 patients subjected total hip arthroplasis, were studied by TEM after treatment with current procedures. The images obtained were considered observing the division of cartilage into superficial, intermediate and deep layers. Patients were divided according to the gravity of their clinical conditions. The least severe forms of pathology seem to involve only the superficial layer, which quickly loses the lamina splendens and may be affected by rarefactions of the matrix, which becomes fissured, while the deep layers are only slightly involved. During the later stages, the pathology progresses with irregularity of disposition and size of the collagen fibres and an increase in the number and size of fissures. The intermediate layer shows architectural disorder in the collagen fibres, even reaching the deep layer. The interfibrillar distance appears greater. As pathology progresses, the superficial layer tends to disappear, while the successive layers undergo progressive alteration in disposition and size of the collagen fibres. Globular aggregations of various dimensions and electron density similar to collagen are present in the deep layer. PMID:1288443

  1. Impacts of forest harvesting on mobilization of Hg and MeHg in drained peatland forests on black schist or felsic bedrock.

    PubMed

    Ukonmaanaho, Liisa; Starr, Mike; Kantola, Marjatta; Laurén, Ari; Piispanen, Juha; Pietilä, Heidi; Perämäki, Paavo; Merilä, Päivi; Fritze, Hannu; Tuomivirta, Tero; Heikkinen, Juha; Mäkinen, Jari; Nieminen, Tiina M

    2016-04-01

    Forest harvesting, especially when intensified harvesting method as whole-tree harvesting with stump lifting (WTHs) are used, may increase mercury (Hg) and methylmercury (MeHg) leaching to recipient water courses. The effect can be enhanced if the underlying bedrock and overburden soil contain Hg. The impact of stem-only harvesting (SOH) and WTHs on the concentrations of Hg and MeHg as well as several other variables in the ditch water was studied using a paired catchment approach in eight drained peatland-dominated catchments in Finland (2008-2012). Four of the catchments were on felsic bedrock and four on black schist bedrock containing heavy metals. Although both Hg and MeHg concentrations increased after harvesting in all treated sites according to the randomized intervention analyses (RIAs), there was only a weak indication of a harvest-induced mobilization of Hg and MeHg into the ditches. Furthermore, no clear differences between WTHs and SOH were found, although MeHg showed a nearly significant difference (p = 0.06) between the harvesting regimes. However, there was a clear bedrock effect, since the MeHg concentrations in the ditch water were higher at catchments on black schist than at those on felsic bedrock. The pH, suspended solid matter (SSM), dissolved organic carbon (DOC), and iron (Fe) concentrations increased after harvest while the sulfate (SO4-S) concentration decreased. The highest abundances of sulfate-reducing bacteria (SRB) were found on the sites with high MeHg concentrations. The biggest changes in ditch water concentrations occurred first 2 years after harvesting. PMID:26979172

  2. Matching of beams on the MAPPER MATRIX tool: a simulation study

    NASA Astrophysics Data System (ADS)

    Belledent, J.; Berglund, G. Z. M.; Brandt, P. L.; Bérard-Bergery, S.; Wieland, M. J.; Pain, L.

    2013-03-01

    So far, the CMOS technology roadmap has been consistent with Moore's law, even if manufacturing photolithography tools are now operating beyond their resolution limit. This has been made feasible at the expense of an intensive joint work between designers and process people who have successfully enabled double patterning processes. Tools that can provide photo lithographers with some relief are on their way although not yet in production. Among them, massively parallel mask-less electron beam lithography stands out as a serious candidate since it can achieve the required resolution at the right cost of ownership provided targeted throughput performance is reached. This paper focuses on this latter technique and more precisely, reports on simulation works performed using an emulator of the high volume manufacturing tool being developed by MAPPER Lithography, called MATRIX. In a nutshell, the MATRIX tool will operate using more than 13,000 beams, each one writing a stripe 2μm wide. Each beam itself will be composed of 49 individual sub-beams that can be blanked independently in order to write pixels onto the wafer. The residual placement errors and any current mismatch between the beams will be measured in-situ and corrected through the data path. In order to validate that this concept can actually work, the authors have built an off-line emulator of the data treatment performed down to the information sent to the blanker. It has then been plugged into an electron beam simulator such that the performance on real designs can be tested. In this paper, the methodology used for the corrections is explained as well as the validation process applied. The results of an extensive statistical study are presented showing CD, placement and residual scaling errors simulated on a set of predefined key structures assuming current and misplacement ranges within the MATRIX tool specifications, applying various correction solutions. Based on the collected data, it is shown that CD

  3. Structural studies on some dithiophosphonato complexes of Ni(II), Cd(II), Hg(II) and theoretical studies on a dithiophosphonato Ni(II) complex using density functional theory

    NASA Astrophysics Data System (ADS)

    Sağlam, Ertuğrul Gazi; Ebinç, Ahmet; Zeyrek, Celal Tuğrul; Ünver, Hüseyin; Hökelek, Tuncer

    2015-11-01

    In this study, three dithiophosphonic acid complexes, namely, trans-bis-[O-3-methylbutyl (4-methoxyphenyl)dithiophosphonato]nickel(II), Ni(L)2; bis-{bis-[O-3-phenylpropyl (4-methoxyphenyl)dithiophosphonato]cadmium(II)}, [Cd(L)2]2 and bis-{bis-[O-3-methylbutyl (4-methoxyphenyl)dithiophosphonato]mercury(II)}, [Hg(L)2]2 were prepared. The compounds were characterized by elemental analysis; MS; FTIR and Raman spectroscopies and were also investigated by 1H-, 13C- and 31P- NMR. The Ni(L)2 complex was elucidated by X-ray crystallography, molecular characterization and density functional modelling studies. The molecular structure obtained from X-ray single-crystal analysis of the Ni(L)2 complex in the ground state has been compared using density functional theory (DFT), B3LYP functional with 6-311G(d,p) basis set. In addition to the optimized geometrical structures, atomic charges and nonlinear optical (NLO) effects have been investigated by using DFT. The experimental (spectroscopic) and calculated vibrational frequencies (using DFT) of the Ni(L)2 have been compared. There exists a good correlation between experimental and theoretical data for the Ni(L)2 complex.

  4. Co(II), Cd(II), Hg(II) and U(VI)O2 complexes of o-hydroxyacetophenone[N-(3-hydroxy-2-naphthoyl)] hydrazone: Physicochemical study, thermal studies and antimicrobial activity

    NASA Astrophysics Data System (ADS)

    Zaky, R. R.; Yousef, T. A.; Ibrahim, K. M.

    2012-11-01

    The o-Hydroxy acetophenone [N-(3-hydroxy-2-naphthoyl)] hydrazone (H2o-HAHNH) has been prepared and its structure is confirmed by elemental analysis, IR, 1H NMR and 13C NMR spectroscopy. It has been used to produce diverse complexes with Co(II), Cd(II), Hg(II) and U(VI)O2 ions. The isolated complexes have been investigated by elemental analysis, magnetic measurements, molar conductivity, thermal (TG, DTG) and spectral (1H NMR, 13C NMR, IR, UV-visible, MS) studies. Infrared spectra suggested H2o-HAHNH acts as a bidentate and/or tridentate ligand. The electronic spectrum of [Co(Ho-HAHNH)2] complex as well as its magnetic moments suggesting octahedral geometry around Co(II) center. The TG analyses suggest high stability for most complexes followed by thermal decomposition in different steps. Moreover, the kinetic and thermodynamic parameters (Ea, A, ΔH∗, ΔS∗ and ΔG∗) for the different decomposition steps of the [Co(Ho-HAHNH)2] and [Cd(Ho-HAHNH)2] complexes were calculated using the Coats-Redfern and Horowitz-Metzger methods. Moreover, the antibacterial and antifungal activities of the isolated compounds were studied using a wide spectrum of bacterial and fungal strains.

  5. Acellular dermal matrix allograft used alone and in combination with enamel matrix protein in gingival recession: histologic study in dogs.

    PubMed

    de Oliveira, Cristiane Aparecida; Spolidório, Luís Carlos; Cirelli, Joni Augusto; Marcantonio, Roseemary Adriana Chiérici

    2005-12-01

    Gingival recession was created in six mongrel dogs. The dogs were divided into two groups based on treatment: group 1--AlloDerm only, group 2--AlloDerm + Emdogain. The histologic results were compared. At the end of the study, the mean values were, for groups 1 and 2, respectively: 0.06 and 0.32 mm for cementum regeneration; -0.75 and -0.86 mm for bone regeneration; -2.15 and -3.11 mm for attachment level; and 4.90 and 5.51 mm for defect extent. The epithelial formation parameter was 2.88 mm in group 1 and 2.15 mm in group 2, which was a statistically significant difference. It could be concluded that Emdogain did not result in beneficial effects when associated with AlloDerm. PMID:16353534

  6. Supramolecular aggregation of Ni(salen) with (C6F5)2Hg and [o-C6F4Hg]3.

    PubMed

    Tsunoda, Mitsukimi; Fleischmann, Martin; Jones, J Stuart; Bhuvanesh, Nattamai; Scheer, Manfred; Gabbaï, François P

    2016-03-15

    As part of our ongoing interest in the supramolecular chemistry of fluorinated organomercurials, we have investigated the interaction of bis(pentafluorophenyl)mercury ((C6F5)2Hg), and trimeric (perfluoro-o-phenylene)mercury ([o-C6F4Hg]3), with nickel(ii) N,N'-bis(salicylidene)ethylenediamine) (Ni(salen)). While solution studies monitored by UV-VIS spectroscopy suggest that Ni(salen) interacts with the trinuclear mercury complex in solution, the 1 : 1 adduct (Ni(salen)-(C6F5)2Hg) and the 1 : 1 adducts Ni(salen)-[o-C6F4Hg]3 and [Ni(salen)-[o-C6F4Hg]3-THF-H2O] can be obtained by slow evaporation of solutions containing the two building blocks. While arene-fluoroarene and hydrogen bonding interactions, as well as interactions between mercury and the salen ligand are the predominant forces responsible for the formation of these adducts, Ni(salen)-[o-C6F4Hg]3 and [Ni(salen)-[o-C6F4Hg]3-THF-H2O] also display short Ni-Hg separations consistent with the presence of metallophilic interactions. Quantum theory of atoms in molecules (QTAIM) analyses of the Ni-Hg interactions in these adducts finds that these interactions are dominated by electrostatic and dispersion forces, despite featuring non-negligible covalent contributions. PMID:26865181

  7. DFT study and crystal structure analysis of a new nano-structure five coordinated Hg(II) complex involving C-H⋯O, N⋯O and π⋯π interactions in a supra-molecular structure.

    PubMed

    Montazerozohori, M; Musavi, S A; Masoudiasl, A; Hojjati, A; Assoud, A

    2015-08-01

    In this research, template synthesis and crystal structure of a new HgLI₂ complex are presented (L=N(1)-(4-nitrobenzylidene)-N(2)-(2-((E)-(4-nitrobenzylidene)amino)ethyl)ethane-1,2-diamine). The mercury complex crystallizes in the triclinic system with space group of P1¯. The crystal structure of the complex shows a distorted trigonal bipyramidal geometry around the mercury(II) center; including two I and an N atoms of Schiff base ligand in equatorial plane and two iminic N atoms in axial positions. Two five membered mercury containing rings [Hg(-N-C-C-N-)] are found in the structure. Some C-H⋯O, N⋯O and π⋯π intermolecular interactions causes a supra-molecular network in the solid-state. In addition to crystal structure analysis, density functional theory (DFT) study at the B3LYP/LanL2DZ level of theory has been also performed on the structure. Thereafter some theoretical structural and spectral data were compared with experimental results. Furthermore, total energy levels of HOMO and LUMO orbitals, molecular electrostatic potential, Mullikan atomic charges, thermodynamic and polarizability properties of the complex were calculated. Finally the mercury complex was prepared in nano-structure size confirmed by SEM and XRD analyses. The particles size of the titled complex was evaluated under 40 nm based on Sherrer's formula. PMID:25835377

  8. DFT study and crystal structure analysis of a new nano-structure five coordinated Hg(II) complex involving C-H⋯O, N⋯O and π⋯π interactions in a supra-molecular structure

    NASA Astrophysics Data System (ADS)

    Montazerozohori, M.; Musavi, S. A.; Masoudiasl, A.; Hojjati, A.; Assoud, A.

    2015-08-01

    In this research, template synthesis and crystal structure of a new HgLI2 complex are presented (L = N1-(4-nitrobenzylidene)-N2-(2-((E)-(4-nitrobenzylidene)amino)ethyl)ethane-1,2-diamine). The mercury complex crystallizes in the triclinic system with space group of P 1 bar . The crystal structure of the complex shows a distorted trigonal bipyramidal geometry around the mercury(II) center; including two I and an N atoms of Schiff base ligand in equatorial plane and two iminic N atoms in axial positions. Two five membered mercury containing rings [Hg(-N-C-C-N-)] are found in the structure. Some C-H⋯O, N⋯O and π⋯π intermolecular interactions causes a supra-molecular network in the solid-state. In addition to crystal structure analysis, density functional theory (DFT) study at the B3LYP/LanL2DZ level of theory has been also performed on the structure. Thereafter some theoretical structural and spectral data were compared with experimental results. Furthermore, total energy levels of HOMO and LUMO orbitals, molecular electrostatic potential, Mullikan atomic charges, thermodynamic and polarizability properties of the complex were calculated. Finally the mercury complex was prepared in nano-structure size confirmed by SEM and XRD analyses. The particles size of the titled complex was evaluated under 40 nm based on Sherrer's formula.

  9. On the FCNS ⇆ FC(NS) reaction: A matrix isolation and theoretical study

    NASA Astrophysics Data System (ADS)

    Tajti, Attila; Mück, Leonie Anna; Farkas, Ádám László; Krebsz, Melinda; Pasinszki, Tibor; Tarczay, György; Szalay, Péter G.

    2015-04-01

    The FCNS ⇆ FC(NS) photoisomerization process is a simple model system for molecular switches. Here, we examined the switching processes by experimental and theoretical methods. Prior matrix-isolation IR spectroscopic studies were complemented by matrix-isolation UV spectroscopic measurements to assist the interpretation of the mechanism of the ring closure and opening processes and to verify the accuracy of the computations on the vertical excitation energies. Vertical excitation energies were computed by the EOMEE-CCSD, MCSCF, and MR-CISD methods. Conical intersections were also searched for and three conical intersections along the reaction path FCNS → FC(NS) were located, one conical intersection between the 2A‧ and 1A″ state, one between the 1A″ and 1A‧ state and one where all three states intersect. The ring opening and closing processes were simulated by non-adiabatic dynamics propagation with the trajectory surface hopping method. The combined computational and experimental results suggest that upon 365 nm irradiation the ring closure FCNS → FC(NS) occurs under participation of all three conical intersections, while 254 nm irradiation causes ring opening FC(NS) → FCNS. Both processes, especially the ring opening, are accompanied by fragmentation into FCN+S.

  10. Study of spin-density matrix in exclusive electroproduction of ω meson at HERMES

    NASA Astrophysics Data System (ADS)

    Manaenkov, S. I.

    2016-02-01

    Exclusive electroproduction of ω mesons on unpolarized hydrogen and deuterium targets is studied in the kinematic region of Q2 > 1.0 GeV2, 3.0 GeV < W < 6.3 GeV, and -t' < 0.2 GeV2. The data were accumulated with the HERMES forward spectrometer during the 1996-2007 running period using the 27.6 GeV longitudinally polarized electron or positron beam of HERA. Spin-density matrix elements are presented in projections of Q2 or -t'. Violation of s-channel helicity conservation is observed for some of these elements. A sizable contribution from unnatural-parity-exchange amplitudes is established for special combinations of spin-density matrix elements. The determination of the virtual-photon longitudinal-to- transverse cross-section ratio reveals that a dominant part of the cross section arises from transversely polarized photons. Good agreement is found between the HERMES proton data and results of a pQCD-inspired Goloskokov-Kroll model that includes pion-pole contributions.

  11. Study of extracellular matrix in vocal fold biomechanics using a two-phase model

    PubMed Central

    Li, Nicole Y. K.; Avazmohammadi, Reza; Thibeault, Susan L.; Mongrain, Rosaire; Mongeau, Luc

    2014-01-01

    The extracellular matrix (ECM) of the vocal fold tissue consists primarily of fibrous and interstitial proteins. The purpose of this study was to investigate the effects of selective enzymatic digestion of two ECM proteins, namely elastin and versican, on the elasticity of rabbit vocal fold tissue. Quasi-static, sinusoidal, uniaxial tensile tests were performed. The data were analyzed within the framework of a model of the ECM as a two-phase composite material consisting of collagen fibrils as the reinforcing fibers and noncollagenous ECM proteins as the matrix. To validate the two-phase model, the regression parameters for the fibers’ volume fraction and shear modulus in a different animal model were compared with corresponding published data. The proposed model was then used to analyze rabbit vocal fold tissues. The mean value and the standard deviation of the fiber volume fraction were found to be 8.49 ±3.75% for the control samples (n =4), 0.59 ±1.13 % after elastin removal (n =4), and 8.22 ±1.06% after versican removal (n =4). The results suggest that elastin removal may lead to a reduction in tissue stiffness, through counteracting the reinforcement of collagen fibrils. PMID:24792897

  12. Study of extracellular matrix in vocal fold biomechanics using a two-phase model.

    PubMed

    Miri, Amir K; Li, Nicole Y K; Avazmohammadi, Reza; Thibeault, Susan L; Mongrain, Rosaire; Mongeau, Luc

    2015-01-01

    The extracellular matrix (ECM) of the vocal fold tissue consists primarily of fibrous and interstitial proteins. The purpose of this study was to investigate the effects of selective enzymatic digestion of two ECM proteins, namely elastin and versican, on the elasticity of rabbit vocal fold tissue. Quasi-static, sinusoidal, uniaxial tensile tests were performed. The data were analyzed within the framework of a model of the ECM as a two-phase composite material consisting of collagen fibrils as the reinforcing fibers and noncollagenous ECM proteins as the matrix. To validate the two-phase model, the regression parameters for the fibers' volume fraction and shear modulus in a different animal model were compared with corresponding published data. The proposed model was then used to analyze rabbit vocal fold tissues. The mean value and the standard deviation of the fiber volume fraction were found to be 8.49 ± 3.75 % for the control samples (n = 4), 0.59 ± 1.13 % after elastin removal (n = 4), and 8.22 ± 1.06 % after versican removal (n = 4). The results suggest that elastin removal may lead to a reduction in tissue stiffness, through counteracting the reinforcement of collagen fibrils. PMID:24792897

  13. A Study of Groundwater Matrix Effects for the Destruction of Trichloroethylene Using Fe/Pd Nanoaggregates.

    PubMed

    Meyer, D E; Hampson, S; Ormsbee, L; Bhattacharyya, D

    2009-01-30

    Iron nanoaggregates have been prepared using the sodium borohydride reduction method and post-coated with Pd using aqueous phase electro-deposition. The Fe/Pd nanoaggregates were used to examine dechlorination of trichloroethylene (TCE) with regard to matrix effects using materials representative of a potential zero-valent metal remediation site surrounding the Paducah gaseous diffusion plant in Paducah, KY. A surface-area-normalized first-order rate constant of 1.4 x 10(-1) L m(-2) h(-1) was obtained for the case of ideal dechlorination of 19.6 mg L(-1) TCE at room temperature and pH 6.2 using 0.5 g L(-1) Fe/Pd (0.42 wt % Pd) loading. This value decreases by an order of magnitude to 1.9 x 10(-2) L m(-2) h(-1) when the reaction is carried out in a realistic background matrix when the pH is high (8.8). For all variables tested, Pd content has the most impact on reaction rates. Circulating batch-column experiments are used to study dechlorination under flow conditions and demonstrate the ability of nonstabilized Fe/Pd nanoaggregates to remove significant amounts of TCE (80-90%) over a broad range of groundwater velocities (12.9-83 ft per day) using moderate metal loadings (0.23-0.5 g L(-1)). PMID:20526423

  14. FT-Raman spectroscopy study of organic matrix degradation in nanofilled resin composite.

    PubMed

    Soares, Luís Eduardo Silva; Nahórny, Sídnei; Martin, Airton Abrahão

    2013-04-01

    This in vitro study evaluated the effect of light curing unit (LCU) type, mouthwashes, and soft drink on chemical degradation of a nanofilled resin composite. Samples (80) were divided into eight groups: halogen LCU, HS--saliva (control); HPT--Pepsi Twist®; HLC--Listerine®; HCP--Colgate Plax®; LED LCU, LS--saliva (control); LPT--Pepsi Twist®; LLC--Listerine®; LCP--Colgate Plax®. The degree of conversion analysis and the measure of the peak area at 2,930 cm-1 (organic matrix) of resin composite were done by Fourier-transform Raman spectroscopy (baseline, after 7 and 14 days). The data were subjected to multifactor analysis of variance (ANOVA) at a 95% confidence followed by Tukey's HSD post-hoc test. The DC ranged from 58.0% (Halogen) to 59.3% (LED) without significance. Differences in the peak area between LCUs were found after 7 days of storage in S and PT. A marked increase in the peak intensity of HLC and LLC groups was found. The soft-start light-activation may influence the chemical degradation of organic matrix in resin composite. Ethanol contained in Listerine® Cool Mint mouthwash had the most significant degradation effect. Raman spectroscopy is shown to be a useful tool to investigate resin composite degradation. PMID:23388411

  15. A Study of Groundwater Matrix Effects for the Destruction of Trichloroethylene Using Fe/Pd Nanoaggregates

    PubMed Central

    Meyer, D.E.; Hampson, S.; Ormsbee, L.; Bhattacharyya, D.

    2010-01-01

    Iron nanoaggregates have been prepared using the sodium borohydride reduction method and post-coated with Pd using aqueous phase electro-deposition. The Fe/Pd nanoaggregates were used to examine dechlorination of trichloroethylene (TCE) with regard to matrix effects using materials representative of a potential zero-valent metal remediation site surrounding the Paducah gaseous diffusion plant in Paducah, KY. A surface-area-normalized first-order rate constant of 1.4 × 10–1 L m–2 h–1 was obtained for the case of ideal dechlorination of 19.6 mg L–1 TCE at room temperature and pH 6.2 using 0.5 g L–1 Fe/Pd (0.42 wt % Pd) loading. This value decreases by an order of magnitude to 1.9 × 10–2 L m–2 h–1 when the reaction is carried out in a realistic background matrix when the pH is high (8.8). For all variables tested, Pd content has the most impact on reaction rates. Circulating batch-column experiments are used to study dechlorination under flow conditions and demonstrate the ability of nonstabilized Fe/Pd nanoaggregates to remove significant amounts of TCE (80–90%) over a broad range of groundwater velocities (12.9–83 ft per day) using moderate metal loadings (0.23–0.5 g L–1). PMID:20526423

  16. Conformations of 1,1-diethoxyethane: A matrix isolation infrared and ab initio study

    NASA Astrophysics Data System (ADS)

    Venkatesan, V.; Viswanathan, K. S.

    2011-03-01

    Conformations of 1,1-diethoxyethane (DEE) were studied using matrix isolation infrared spectroscopy. Infrared features of the lowest energy, G∓G±(tt) conformer and the first higher energy, TG-(tt) conformer of matrix-isolated DEE were observed for the first time. The experiments were supported by ab initio computations performed at the HF and B3LYP levels, using a 6-31++G** basis set. The computed vibrational wavenumbers at the B3LYP/6-31++G** level for the G∓G±(tt) and TG-(tt) conformers, were found to agree well with the experimentally observed features, leading to a definitive assignment of the infrared features of these conformers of DEE. At the B3LYP/6-31++G** level, the energy of TG-(tt) conformer was found to be 0.42 kcal/mol above the ground state G∓G±(tt) conformer. AIM calculations were also performed to understand the role of intramolecular Csbnd H⋯O interaction in the conformational preferences in DEE.

  17. DFT study of Hg adsorption on M-substituted Pd(1 1 1) and PdM/γ-Al2O3(1 1 0) (M = Au, Ag, Cu) surfaces

    NASA Astrophysics Data System (ADS)

    Wang, Jiancheng; Yu, Huafeng; Geng, Lu; Liu, Jianwen; Han, Lina; Chang, Liping; Feng, Gang; Ling, Lixia

    2015-11-01

    The adsorption of Hgn (n = 1-3) on the Au-, Ag-, Cu-substituted Pd(1 1 1) surfaces as well as the PdM/γ-Al2O3(1 1 0) (M = Au, Ag, Cu) surfaces has been investigated using spin-polarized density functional theory calculations. It is found that M-substituted Pd(1 1 1) surfaces show as good Hg adsorption capacity as the perfect Pd(1 1 1) at low Hg coverage, while the Hg adsorption capacity is only slightly weakened at high Hg coverage. On the basis of stepwise adsorption energies analysis, it is concluded that M-substituted Pd(1 1 1) surfaces can contribute to the binding of Hg atom on the surfaces at high Hg coverage. The electronic properties of the second metal atoms are the main factor contributes to the Hg adsorption capacity. Gas phase Pd2 shows better Hg adsorption capacity than Pd2/γ-Al2O3, while PdM/γ-Al2O3 can adsorb Hg more efficiently than bare PdM clusters. It suggests that the γ-Al2O3 support can enhance the activity of PdM for Hg adsorption and reduces the activity of Pd2. It is also found that Pd is the main active composition responsible for the interaction of mercury with the surface for PdM/γ-Al2O3 sorbent. Taking Hg adsorption capacity and economic costs into account, Cu addition is a comparatively good candidate for Hg capture.

  18. Structure of isothiocyanic acid dimers. Theoretical and FTIR matrix isolation studies

    NASA Astrophysics Data System (ADS)

    Krupa, Justyna; Wierzejewska, Maria

    2016-05-01

    A quantum mechanical study of the potential energy surface for the HNCS dimer is reported. The calculations were performed using DFT and ab initio MP2 methods. The most stable is a cyclic form with a double N-H⋯S interaction and the interaction energy in the range of 16.91-18.92 kJ mol-1. An open HNCS dimer bound by the N-H⋯N hydrogen bond is by ca 3.3-5.1 kJ mol-1 less stable. Experimental FTIR matrix isolation studies of HNCS/N2 system show that exclusively less stable open dimer is formed in solid nitrogen. Possible reasons for the observed discrepancy between theory and experiment are discussed.

  19. A study of the composition and microstructure of aluminum matrix composites reinforced with alumina fibers

    NASA Astrophysics Data System (ADS)

    Zolotova, D.; Serpova, V.; Prokofiev, M.; Rabinskiy, L.; Shavnev, A.

    2016-04-01

    This article presents the results of a study of the microstructure and the composition of aluminum-based metal matrix composites (MMC) reinforced with continuous alumina fibers. An Al-Mg-Cu alloy similar to that of AA 2024 was used. X-ray diffraction and X-ray fluorescence analyses were used for investigation of a probable volume fraction of a spinel phase in MMC. Scanning electron microscopy and an X-ray microanalysis were used to study a change of the elemental composition of the composites microstructure on the polished cross sections. The constant mass fractions of magnesium (0.65 wt. %) and copper (1.25 wt. %) were found in the interphase area within radius of 1 μm around fibers.

  20. Organ-specific accumulation, transportation, and elimination of methylmercury and inorganic mercury in a low Hg accumulating fish.

    PubMed

    Peng, Xiaoyan; Liu, Fengjie; Wang, Wen-Xiong

    2016-08-01

    Low mercury (Hg) concentrations down to several nanograms Hg per gram of wet tissue are documented in certain fish species such as herbivorous fish, and the underlying mechanisms remain speculative. In the present study, bioaccumulation and depuration patterns of inorganic Hg(II) and methylmercury (MeHg) in a herbivorous rabbitfish Siganus canaliculatus were investigated at organ and subcellular levels following waterborne or dietary exposures. The results showed that the efflux rate constants of Hg(II) and MeHg were 0.104 d(-1) and 0.024 d(-1) , respectively, and are probably the highest rate constants recorded in fish thus far. The dietary MeHg assimilation efficiency (68%) was much lower than those in other fish species (∼90%). The predominant distribution of MeHg in fish muscle was attributable to negligible elimination of MeHg from muscle (< 0) and efficient elimination of MeHg from gills (0.12 d(-1) ), liver (0.17 d(-1) ), and intestine (0.20 d(-1) ), as well as efficient transportation of MeHg from other organs into muscle. In contrast, Hg(II) was much more slowly distributed into muscle but was efficiently eliminated by the intestine (0.13 d(-1) ). Subcellular distribution indicated that some specific membrane proteins in muscle were the primary binding pools for MeHg, and both metallothionein-like proteins and Hg-rich granules were the important components in eliminating both MeHg and Hg(II). Overall, the present study's results suggest that the low tissue Hg concentration in the rabbitfish was partly explained by its unique biokinetics. Environ Toxicol Chem 2016;35:2074-2083. © 2016 SETAC. PMID:26756981

  1. Benthic flux measurements of Hg species in a northern Adriatic lagoon environment (Marano and Grado Lagoon, Italy)

    NASA Astrophysics Data System (ADS)

    Emili, Andrea; Acquavita, Alessandro; Koron, Neža; Covelli, Stefano; Faganeli, Jadran; Horvat, Milena; Žižek, Suzana; Fajon, Vesna

    2012-11-01

    As part of the "MIRACLE" project, the biogeochemical cycling of mercury (Hg) at the sediment-water interface was studied in the field in the Marano and Grado Lagoon (Northern Adriatic Sea). Seasonal investigations were conducted at selected experimental sites, where Manila Clams (Tapes philippinarum) were previously seeded. Measurements were performed seasonally during three campaigns, using two benthic chambers, one transparent and one dark, to evaluate the effect of light on Hg cycling. Total dissolved Hg (THg), methylmercury (MeHg), and dissolved gaseous Hg (DGM) species were considered. Diurnal benthic fluxes were found to significantly exceed the diffusive fluxes at all stations. The assessment of the annual recycling of Hg species from sediments to the water column showed that up to 99% of MeHg is recycled annually to the water column, while Hg recycling ranges from 30 to 60%. MeHg poses the higher risk for potential bioaccumulation in clams, but it is partially mitigated by Hg reduction, which seems to be an important process leading to evasion losses of Hg from these environments. Estimated benthic fluxes suggest that Hg recycling at the sediment-water interface is more active in the Grado sector. Hence, based on the estimated release of MeHg from sediments, it is suggested that the western sector seems to be more suitable for clam farming and the extension of rearing activities.

  2. A portable optical emission spectroscopy-cavity ringdown spectroscopy dual-mode plasma spectrometer for measurements of environmentally important trace heavy metals: Initial test with elemental Hg

    SciTech Connect

    Sahay, Peeyush; Scherrer, Susan T.; Wang Chuji

    2012-09-15

    A portable optical emission spectroscopy-cavity ringdown spectroscopy (OES-CRDS) dual-mode plasma spectrometer is described. A compact, low-power, atmospheric argon microwave plasma torch (MPT) is utilized as the emission source when the spectrometer is operating in the OES mode. The same MPT serves as the atomization source for ringdown measurements in the CRDS mode. Initial demonstration of the instrument is carried out by observing OES of multiple elements including mercury (Hg) in the OES mode and by measuring absolute concentrations of Hg in the metastable state 6s6p {sup 3}P{sub 0} in the CRDS mode, in which a palm-size diode laser operating at a single wavelength 405 nm is incorporated in the spectrometer as the light source. In the OES mode, the detection limit for Hg is determined to be 44 parts per 10{sup 9} (ppb). A strong radiation trapping effect on emission measurements of Hg at 254 nm is observed when the Hg solution concentration is higher than 50 parts per 10{sup 6} (ppm). The radiation trapping effect suggests that two different transition lines of Hg at 253.65 nm and 365.01 nm be selected for emission measurements in lower (<50 ppm) and higher concentration ranges (>50 ppm), respectively. In the CRDS mode, the detection limit of Hg in the metastable state 6s6p {sup 3}P{sub 0} is achieved to be 2.24 parts per 10{sup 12} (ppt) when the plasma is operating at 150 W with sample gas flow rate of 480 mL min{sup -1}; the detection limit corresponds to 50 ppm in Hg sample solution. Advantage of this novel spectrometer has two-fold, it has a large measurement dynamic range, from a few ppt to hundreds ppm and the CRDS mode can serve as calibration for the OES mode as well as high sensitivity measurements. Measurements of seven other elements, As, Cd, Mn, Ni, P, Pb, and Sr, using the OES mode are also carried out with detection limits of 1100, 33, 30, 144, 576, 94, and 2 ppb, respectively. Matrix effect in the presence of other elements on Hg measurements

  3. Gamma scintigraphic study of the hydrodynamically balanced matrix tablets of Metformin HCl in rabbits.

    PubMed

    Razavi, Mahboubeh; Karimian, Hamed; Yeong, Chai Hong; Sarji, Sazilah Ahmad; Chung, Lip Yong; Nyamathulla, Shaik; Noordin, Mohamed Ibrahim

    2015-01-01

    The purpose of this study is to evaluate the in vitro and in vivo performance of gastro-retentive matrix tablets having Metformin HCl as model drug and combination of natural polymers. A total of 16 formulations were prepared by a wet granulation method using xanthan, tamarind seed powder, tamarind kernel powder and salep as the gel-forming agents and sodium bicarbonate as a gas-forming agent. All the formulations were evaluated for compendial and non-compendial tests and in vitro study was carried out on a USP-II dissolution apparatus at a paddle speed of 50 rpm. MOX2 formulation, composed of salep and xanthan in the ratio of 4:1 with 96.9% release, was considered as the optimum formulation with more than 90% release in 12 hours and short floating lag time. In vivo study was carried out using gamma scintigraphy in New Zealand White rabbits, optimized formulation was incorporated with 10 mg of (153)Sm for labeling MOX2 formulation. The radioactive samarium oxide was used as the marker to trace transit of the tablets in the gastrointestinal tract. The in vivo data also supported retention of MOX2 formulation in the gastric region for 12 hours and were different from the control formulation without a gas and gel forming agent. It was concluded that the prepared floating gastro-retentive matrix tablets had a sustained-release effect in vitro and in vivo, gamma scintigraphy played an important role in locating the oral transit and the drug-release pattern. PMID:26124637

  4. Use of Synthetic Peptides to Study Structure-Function Relationships of Matrix Metalloproteinases and Their Substrates.

    NASA Astrophysics Data System (ADS)

    Netzel-Arnett, Sarah Joann

    The matrix metalloproteinases (MMPs) are a family of zinc proteinases that is collectively capable of degrading the major components of the extracellular matrix. A variety of synthetic peptides has been prepared which are models for the human MMP and their substrates to study structure -function relationships in this enzyme-substrate system. To elucidate the sequence specificity of the MMP, the k _{cat}/K_ M values for the hydrolysis of over 50 synthetic octapeptides has been investigated. Similarities, as well as distinct differences have been found between the individual MMP with the largest differences occurring at subsites P_1, P_1^' and P_3 ^'. Based on these data, quenched -fluorescence substrates with optimized sequences have been developed for five human MMP. The key features of these heptapeptides are a tryptophan on the P_ n^' side and a dinitrophenol quenching group on the amino terminus. To assess the role of the triple helical conformation in the collagenase-collagen system, a series of triple helical peptides has been prepared and shown to compete with collagen in collagenase assays. This provides evidence for the existence of a triple helical recognition site distinct from the active site. All of the MMP are secreted as zymogens and it has been postulated that the portion of the propeptide surrounding a critical cysteine is responsible for maintaining latency. Conformational energy calculations and mutagenesis studies have suggested that this region adopts a specific conformation that stabilizes the latent form. Peptide models of this region of the propeptide have been prepared and shown to inhibit the MMP. CD and NMR studies, however, have failed to provide evidence for the predicted peptide conformation. Thus, the observed inhibition may reflect their propensity to adopt the propeptide conformation upon binding to the enzyme.

  5. Gamma scintigraphic study of the hydrodynamically balanced matrix tablets of Metformin HCl in rabbits

    PubMed Central

    Razavi, Mahboubeh; Karimian, Hamed; Yeong, Chai Hong; Sarji, Sazilah Ahmad; Chung, Lip Yong; Nyamathulla, Shaik; Noordin, Mohamed Ibrahim

    2015-01-01

    The purpose of this study is to evaluate the in vitro and in vivo performance of gastro-retentive matrix tablets having Metformin HCl as model drug and combination of natural polymers. A total of 16 formulations were prepared by a wet granulation method using xanthan, tamarind seed powder, tamarind kernel powder and salep as the gel-forming agents and sodium bicarbonate as a gas-forming agent. All the formulations were evaluated for compendial and non-compendial tests and in vitro study was carried out on a USP-II dissolution apparatus at a paddle speed of 50 rpm. MOX2 formulation, composed of salep and xanthan in the ratio of 4:1 with 96.9% release, was considered as the optimum formulation with more than 90% release in 12 hours and short floating lag time. In vivo study was carried out using gamma scintigraphy in New Zealand White rabbits, optimized formulation was incorporated with 10 mg of 153Sm for labeling MOX2 formulation. The radioactive samarium oxide was used as the marker to trace transit of the tablets in the gastrointestinal tract. The in vivo data also supported retention of MOX2 formulation in the gastric region for 12 hours and were different from the control formulation without a gas and gel forming agent. It was concluded that the prepared floating gastro-retentive matrix tablets had a sustained-release effect in vitro and in vivo, gamma scintigraphy played an important role in locating the oral transit and the drug-release pattern. PMID:26124637

  6. Electronic properties of Hg1-xCdxSe lens-shaped quantum dots under external fields

    NASA Astrophysics Data System (ADS)

    Herrera, J. R.; Gutierrez, W.; Miranda, D. A.

    2016-02-01

    Hg1-xCdxSe are II-VI semiconductors alloys with optoelectronic properties that depend upon the molar fraction x, which can be further controlled by nanostructuring. In this work one electron confined in a zero-dimensional lens-shaped nanostructure of Hg1-xCdxSe surrounded by a matrix of different molar fraction is analyzed and its electronic properties are studied under external magnetic and electric fields. Our system was modeled by means of the 3D Schrodinger equation in the framework of the effective mass approximation, which was solved using a finite element method. The model is described by a discontinuous space with Ben Daniel-Duke boundary conditions. We calculated the energy spectrum and the corresponding probability density of the electron for some low-lying energy levels as a function of: electric field strength on plane and magnetic field strength applied along the growth direction. Also, the effect of finite confinement potential was studied in presence of a uniform magnetic field. Our results shown that the electronic properties of Hg1-xCdxSe quantum dots are highly sensitive to a threading magnetic field because the degenerate energy levels are split. On the other hand, the effect of electric and magnetic fields applied simultaneously on a quantum dot can increase the system stability against external perturbation, e.g. thermal interactions.

  7. MicroCT vs. Hg porosimetry: microporosity in commercial stones

    NASA Astrophysics Data System (ADS)

    Fusi, N.; Martinez-Martinez, J.; Barberini, V.; Galimberti, L.

    2009-04-01

    Decay of rocks, due both to extrinsic and intrinsic factors, can show up in several different forms, such as neoformation of minerals, decohesion of grains and/or crystals, magnification of previous defects, new discontinuities, etc. Intrinsic factors include the type of material, its properties and microstructure, in particular porosity and microporosity. Extrinsic factors relate to atmosphere and usage of the material itself. Rock degradation has several heavy consequences for commercial stones, such as increase of permeability, loss of material, loss of mechanical strength; these consequences are of crucial importance for conservation of historical buildings. Aim of this study is to compare microporosity of some massive commercial stones by means of X ray microtomography, a non destructive technique, and Hg porosimetry. Nine of the most used Spanish limestones and dolostones have been analysed. The lithotypes have been chosen for their homogeneous mineralogical composition (calcitic or dolomitic) and for their low porosity; some of them have been widely used in Spain for historical buildings. Different lithotypes have been described in thin section: Ambarino (A) and Beige Serpiente (BS): brecciated dolostone, composed by microcrystalline dolomitic clasts, in a dolomitic and/or calcitic microcrystalline matrix. Amarillo Triana (AT): yellow dolomitic marble, with fissures filled up by calcite and Fe oxides. Blanco Alconera (BA): a white-pink homogeneous limestone, with veins. Blanco Tranco (BT): a homogeneous white calcitic marble, without any fissures and/or fractures. Crema Valencia (CV): a pinkish limestone, characterized by abundant stilolythes, filled mainly by quartz (80%) and kaolin (11%). Gris Macael (GM): a calcitic marble wiht darker and lighter beds, conferring a strong anisotropy. Rojo Cehegin (RC): a red fossiliferous limestone with white calcitic veins. Travertino Blanco (TB): a massive white calcitic travertine. Prismatic samples of about 2x1x1 cm

  8. A New Technique for Quantification of Elemental Hg in Mine Wastes and Its Implications for Mercury Evasion Into the Atmosphere

    PubMed Central

    JEW, ADAM D.; KIM, CHRISTOPHER S.; RYTUBA, JAMES J.; GUSTIN, MAE S.; BROWN, GORDON E.

    2010-01-01

    Mercury in the environment is of prime concern to both ecosystem and human health. Determination of the molecular-level speciation of Hg in soils and mine wastes is important for understanding its sequestration, mobility, and availability for methylation. Extended x-ray absorption fine structure (EXAFS) spectroscopy carried out under ambient P-T conditions has been used in a number of past studies to determine Hg speciation in complex mine wastes and associated soils. However, this approach cannot detect elemental (liquid) mercury in Hg-polluted soils and sediments due to the significant structural disorder of liquid Hg at ambient-temperature. A new sample preparation protocol involving slow cooling through the crystallization temperature of Hg(0) (234K) results in its transformation to crystalline α-Hg(0). The presence and proportion of Hg(0), relative to other crystalline Hg-bearing phases, in samples prepared in this way can be quantified by low-temperature (77K) EXAFS spectroscopy. Using this approach, we have determined the relative concentrations of liquid Hg(0) in Hg mine wastes from several sites in the California Coast Range and have found that they correlate well with measured fluxes of gaseous Hg released during light and dark exposure of the same samples, with higher evasion ratios from samples containing higher concentrations of liquid Hg(0). Two different linear relationships are observed in plots of the ratio of Hg emission under light and dark conditions vs. % Hg(0), corresponding to silica-carbonate- and hot springs-type Hg deposits, with the hot springs-type samples exhibiting higher evasion fluxes than silica-carbonate type samples at similar Hg(0) concentrations. Our findings help explain significant differences in Hg evasion data for different mine sites in the California Coast Range. PMID:21121657

  9. Photoreduction of Hg(ii) and photodemethylation of methylmercury: the key role of thiol sites on dissolved organic matter.

    PubMed

    Jeremiason, Jeffrey D; Portner, Joshua C; Aiken, George R; Hiranaka, Amber J; Dvorak, Michelle T; Tran, Khuyen T; Latch, Douglas E

    2015-11-01

    This study examined the kinetics of photoreduction of Hg(ii) and photodemethylation of methylmercury (MeHg(+)) attached to, or in the presence of, dissolved organic matter (DOM). Both Hg(ii) and MeHg(+) are principally bound to reduced sulfur groups associated with DOM in many freshwater systems. We propose that a direct photolysis mechanism is plausible for reduction of Hg(ii) bound to reduced sulfur groups on DOM while an indirect mechanism is supported for photodemethylation of MeHg(+) bound to DOM. UV spectra of Hg(ii) and MeHg(+) bound to thiol containing molecules demonstrate that the Hg(ii)-S bond is capable of absorbing UV-light in the solar spectrum to a much greater extent than MeHg(+)-S bonds. Experiments with chemically distinct DOM isolates suggest that concentration of DOM matters little in the photochemistry if there are enough reduced S sites present to strongly bind MeHg(+) and Hg(ii); DOM concentration does not play a prominent role in photodemethylation other than to screen light, which was demonstrated in a field experiment in the highly colored St. Louis River where photodemethylation was not observed at depths ≥ 10 cm. Experiments with thiol ligands yielded slower photodegradation rates for MeHg(+) than in experiments with DOM and thiols; rates in the presence of DOM alone were the fastest supporting an intra-DOM mechanism. Hg(ii) photoreduction rates, however, were similar in experiments with only DOM, thiols plus DOM, or only thiols suggesting a direct photolysis mechanism. Quenching experiments also support the existence of an intra-DOM photodemethylation mechanism for MeHg(+). Utilizing the difference in photodemethylation rates measured for MeHg(+) attached to DOM or thiol ligands, the binding constant for MeHg(+) attached to thiol groups on DOM was estimated to be 10(16.7). PMID:26420634

  10. New technique for quantification of elemental hg in mine wastes and its implications for mercury evasion into the atmosphere

    USGS Publications Warehouse

    Jew, A.D.; Kim, C.S.; Rytuba, J.J.; Gustin, M.S.; Brown, Gordon E., Jr.

    2011-01-01

    Mercury in the environment is of prime concern to both ecosystem and human health. Determination of the molecular-level speciation of Hg in soils and mine wastes is important for understanding its sequestration, mobility, and availability for methylation. Extended X-ray absorption fine structure (EXAFS) spectroscopy carried out under ambient P-T conditions has been used in a number of past studies to determine Hg speciation in complex mine wastes and associated soils. However, this approach cannot detect elemental (liquid) mercury in Hg-polluted soils and sediments due to the significant structural disorder of liquid Hg at ambient-temperature. A new sample preparation protocol involving slow cooling through the crystallization temperature of Hg(0) (234 K) results in its transformation to crystalline ??-Hg(0). The presence and proportion of Hg(0), relative to other crystalline Hg-bearing phases, in samples prepared in this way can be quantified by low-temperature (77 K) EXAFS spectroscopy. Using this approach, we have determined the relative concentrations of liquid Hg(0) in Hg mine wastes from several sites in the California Coast Range and have found that they correlate well with measured fluxes of gaseous Hg released during light and dark exposure of the same samples, with higher evasion ratios from samples containing higher concentrations of liquid Hg(0). Two different linear relationships are observed in plots of the ratio of Hg emission under light and dark conditions vs % Hg(0), corresponding to silica-carbonate- and hot springs-type Hg deposits, with the hot springs-type samples exhibiting higher evasion fluxes than silica-carbonate type samples at similar Hg(0) concentrations. Our findings help explain significant differences in Hg evasion data for different mine sites in the California Coast Range. ?? 2011 American Chemical Society.

  11. Accelerated hydration reaction of an unsymmetrical tolan evidenced by a Hg(ii)-trapped macrocycle and its application as a Hg(ii)-selective indicator.

    PubMed

    Hong, Jung-Ho; Kurapati, Sathish; Jo, Yunhee; Shin, June-Ho; Cho, Dong-Gyu

    2016-09-14

    Hg(ii)-mediated hydration reactions of unsymmetrical quinoline type tolans were studied. The observed accelerated reactions of the tolans rely on the additional binding motifs of the tolan, as supported by the X-ray structure of the macrocycle (2b). The analyte-specific reaction allows us to detect Hg(ii) in buffered media. PMID:27510469

  12. New concepts for HgI2 scintillator gamma ray spectroscopy

    NASA Technical Reports Server (NTRS)

    Iwanczyk, Jan S.

    1994-01-01

    The primary goals of this project are development of the technology for HgI2 photodetectors (PD's), development of a HgI2/scintillator gamma detector, development of electronics, and development of a prototype gamma spectrometer. Work on the HgI2 PD's involved HgI2 purification and crystal growth, detector surface and electrical contact studies, PD structure optimization, encapsulation and packaging, and testing. Work on the HgI2/scintillator gamma detector involved a study of the optical - mechanical coupling for the optimization of CsI(Tl)/HgI2 gamma ray detectors and determination of the relationship between resolution versus scintillator type and size. The development of the electronics focused on low noise amplification circuits using different preamp input FET's and the use of a coincidence technique to maximize the signal, minimize the noise contribution in the gamma spectra, and improve the overall system resolution.

  13. Study of mould design and forming process on advanced polymer-matrix composite complex structure

    NASA Astrophysics Data System (ADS)

    Li, S. J.; Zhan, L. H.; Bai, H. M.; Chen, X. P.; Zhou, Y. Q.

    2015-07-01

    Advanced carbon fibre-reinforced polymer-matrix composites are widely applied to aviation manufacturing field due to their outstanding performance. In this paper, the mould design and forming process of the complex composite structure were discussed in detail using the hat stiffened structure as an example. The key issues of the moulddesign were analyzed, and the corresponding solutions were also presented. The crucial control points of the forming process such as the determination of materials and stacking sequence, the temperature and pressure route of the co-curing process were introduced. In order to guarantee the forming quality of the composite hat stiffened structure, a mathematical model about the aperture of rubber mandrel was introduced. The study presented in this paper may provide some actual references for the design and manufacture of the important complex composite structures.

  14. STUDY OF DUAL MATRIX TABLETS CONTAINING HYPROMELLOSE OF DIFFERENT VISCOSITY DEGREE AND GLYCERYL DIBEHENATE.

    PubMed

    Mužíková, Jitka; Holubová, Katerina; Komersová, Alena; Lochar, Václav

    2016-01-01

    Studies are described on the compressibility of directly compressible tableting materials containing two viscosity types of hypromellose in two concentrations and tableting materials containing additional glyceryl dibehenate, also in two concentrations. Compressibility is evaluated by means of the energy profile of the compression process and determination of tensile strength of tablets. Dissolution test examines the rate of release of the active ingredient from matrix tablets, which is subsequently evaluated mathematically. Increased concentrations of both hypromelloses and an addition of glyceryl dibehenate into tablets with both types of hypromellose improved compressibility. The rate of drug release was decreased with increasing viscosity degree of hypromellose and its increasing concentration. An addition of glyceryl dibehenate exerted the same influence on release as increased concentrations of the pertinent hypromellose. PMID:27180439

  15. Study of degraded neutron spectra through metal matrix composites using CR-39 films

    NASA Astrophysics Data System (ADS)

    Gopalani, Deepak; Kumar, S.; Ramaseshu, P.; Sundaram, V. K.; Mehta, S. K.

    1998-06-01

    Considerable interest has grown in the last decade in the use of CR-39 films in routine neutron monitoring and dosimetry. In addition, work in neutron spectrometry has been undertaken by various workers ( Decossas et al., 1984; Faermann et al., 1983; Fews et al., 1984; Turner et al., 1984). In the present study metal matrix composites (MMC) samples of Pb-Li, Pb-Cd, Al-Li and Al-B 4C were prepared by using powder metallurgy and alloying elements techniques. The density was obtained for these MMC samples in the range of 80-90% of the metal density. Degraded neutron spectra were obtained by exposing these samples to a 252Cf source housed in a camera and the detector used was CR-39 films covered with a 1 mm PE radiator. These spectra have also been validated through Monte Carlo Neutron and Photon Transport Code (1983).

  16. Functionalized Graphene Sheets As Immobilization Matrix for Fenugreek β-Amylase: Enzyme Kinetics and Stability Studies

    PubMed Central

    Srivastava, Garima; Singh, Kritika; Talat, Mahe; Srivastava, Onkar Nath; Kayastha, Arvind M.

    2014-01-01

    β-Amylase finds application in food and pharmaceutical industries. Functionalized graphene sheets were customised as a matrix for covalent immobilization of Fenugreek β-amylase using glutaraldehyde as a cross-linker. The factors affecting the process were optimized using Response Surface Methodology based Box-Behnken design of experiment which resulted in 84% immobilization efficiency. Scanning and Transmission Electron Microscopy (SEM, TEM) and Fourier Tansform Infrared (FTIR) spectroscopy were employed for the purpose of characterization of attachment of enzyme on the graphene. The enzyme kinetic studies were carried out for obtaining best catalytic performance and enhanced reusability. Optimum temperature remained unchanged, whereas optimum pH showed shift towards acidic range for immobilized enzyme. Increase in thermal stability of immobilized enzyme and non-toxic nature of functionalized graphene can be exploited for production of maltose in food and pharmaceutical industries. PMID:25412079

  17. Functionalized graphene sheets as immobilization matrix for Fenugreek β-amylase: enzyme kinetics and stability studies.

    PubMed

    Srivastava, Garima; Singh, Kritika; Talat, Mahe; Srivastava, Onkar Nath; Kayastha, Arvind M

    2014-01-01

    β-Amylase finds application in food and pharmaceutical industries. Functionalized graphene sheets were customised as a matrix for covalent immobilization of Fenugreek β-amylase using glutaraldehyde as a cross-linker. The factors affecting the process were optimized using Response Surface Methodology based Box-Behnken design of experiment which resulted in 84% immobilization efficiency. Scanning and Transmission Electron Microscopy (SEM, TEM) and Fourier Tansform Infrared (FTIR) spectroscopy were employed for the purpose of characterization of attachment of enzyme on the graphene. The enzyme kinetic studies were carried out for obtaining best catalytic performance and enhanced reusability. Optimum temperature remained unchanged, whereas optimum pH showed shift towards acidic range for immobilized enzyme. Increase in thermal stability of immobilized enzyme and non-toxic nature of functionalized graphene can be exploited for production of maltose in food and pharmaceutical industries. PMID:25412079

  18. Biomolecular papain thin films grown by matrix assisted and conventional pulsed laser deposition: A comparative study

    NASA Astrophysics Data System (ADS)

    György, E.; Pérez del Pino, A.; Sauthier, G.; Figueras, A.

    2009-12-01

    Biomolecular papain thin films were grown both by matrix assisted pulsed laser evaporation (MAPLE) and conventional pulsed laser deposition (PLD) techniques with the aid of an UV KrF∗ (λ =248 nm, τFWHM≅20 ns) excimer laser source. For the MAPLE experiments the targets submitted to laser radiation consisted on frozen composites obtained by dissolving the biomaterial powder in distilled water at 10 wt % concentration. Conventional pressed biomaterial powder targets were used in the PLD experiments. The surface morphology of the obtained thin films was studied by atomic force microscopy and their structure and composition were investigated by Fourier transform infrared spectroscopy. The possible physical mechanisms implied in the ablation processes of the two techniques, under comparable experimental conditions were identified. The results showed that the growth mode, surface morphology as well as structure of the deposited biomaterial thin films are determined both by the incident laser fluence value as well as target preparation procedure.

  19. Environmental/Thermal Barrier Coatings for Ceramic Matrix Composites: Thermal Tradeoff Studies

    NASA Technical Reports Server (NTRS)

    Murthy, Pappu L. M.; Brewer, David; Shah, Ashwin R.

    2007-01-01

    Recent interest in environmental/thermal barrier coatings (EBC/TBCs) has prompted research to develop life-prediction methodologies for the coating systems of advanced high-temperature ceramic matrix composites (CMCs). Heat-transfer analysis of EBC/TBCs for CMCs is an essential part of the effort. It helps establish the resulting thermal profile through the thickness of the CMC that is protected by the EBC/TBC system. This report documents the results of a one-dimensional analysis of an advanced high-temperature CMC system protected with an EBC/TBC system. The one-dimensional analysis was used for tradeoff studies involving parametric variation of the conductivity; the thickness of the EBC/TBCs, bond coat, and CMC substrate; and the cooling requirements. The insight gained from the results will be used to configure a viable EBC/TBC system for CMC liners that meet the desired hot surface, cold surface, and substrate temperature requirements.

  20. Low-energy excited states of divanadium: a matrix isolation and MRCI study.

    PubMed

    Hübner, Olaf; Himmel, Hans-Jörg

    2016-06-01

    The ground and excited electronic states of the vanadium dimer (V2) have been studied using Ne matrix isolation experiments and quantum chemical calculations (multireference configuration interaction based on complete active space self-consistent orbitals). In the near infrared absorption spectrum, two vibrational progressions of a new electronic term with a large number of members have been observed with the origin at 1.08 eV and a fundamental vibrational quantum of 475 cm(-1). With the aid of calculations, it has been assigned to a (3)Πu electronic term. The calculations yield potential energy curves for a large number of singlet, triplet, and quintet electronic terms. PMID:27182729

  1. Hybrid-Space Density Matrix Renormalization Group Study of the Two-Dimensional Hubbard Model

    NASA Astrophysics Data System (ADS)

    Ehlers, Georg; Noack, Reinhard M.

    We investigate the ground state of the two-dimensional Hubbard model on a cylinder geometry at intermediate coupling and weak doping. We study properties such as the behavior of the ground-state energy, pair-field correlations, and the appearance of stripes. We find striped ground states generically, with the width of the stripes depending on the filling, the boundary conditions, and the circumference of the cylinder. Furthermore, we analyse the interplay between the different stripe configurations and the decay of the pairing correlations. Our analysis is based on a hybrid-space density matrix renormalization group (DMRG) approach, which uses a momentum-space representation in the transverse and a real-space representation in the longitudinal direction. Exploiting the transverse momentum quantum number makes significant speedup and memory savings compared to the real-space DMRG possible. In particular, we obtain computational costs that are independent of the cylinder width for fixed size of the truncated Hilbert space.

  2. Polymer model with annealed dilution on the square lattice: A transfer-matrix study

    NASA Astrophysics Data System (ADS)

    Serra, Pablo; Stilck, Jürgen F.

    1994-02-01

    We study a lattice model for equilibrium polymerization with annealed dilution. The model considered is an Ising lattice-gas monomer-solvent system where the polymers are represented by mutually and self-avoiding walks constrained to pass through sites occupied by monomers. Numerical results on the square lattice using transfer-matrix techniques and finite-size scaling are reported. The values obtained for the tricitical exponent νt are in agreement with the tricritical Ising exponent (8/11) for high values of the monomer fugacity, but the accuracy we obtained does not rule out the possibility of νt being equal to the critical self-avoiding-walk (SAW) value 3/4. Our results indicate that a crossover occurs in the tricritical behavior of the model. This crossover corroborates the equivalence between a particular limit of the diluted model and the self-attracting polymer system proposed recently.

  3. Analyses of functional polymer-modified nanoparticles for protein sensing by surface-assisted laser desorption/ionization mass spectrometry coupled with HgTe nanomatrices.

    PubMed

    Chang, Hsiang-Yu; Huang, Ming-Feng; Hsu, Chia-Lun; Huang, Chih-Ching; Chang, Huan-Tsung

    2015-06-01

    In this study, we employed HgTe nanostructure-based matrices (nanomartrices; NMs) for surface-assisted laser desorption/ionization mass spectrometry (SALDI-MS) for the analyses of polyethylene glycol (PEG) derivatives as well as thiol-PEG-modified gold nanoparticles (PEG-Au NPs). Relative to common organic matrices, the use of HgTe NMs as the matrix for SALDI-MS resulted in more highly efficient analyses of PEG derivatives, in terms of sensitivity and reproducibility. The symmetric MS profiles of PEG (Mw: ca. 8000 Da) obtained through HgTe NMs/SALDI-MS analysis revealed the absence of polymer degradation during this process. Under optimal conditions, the HgTe NMs/SALDI-MS system enabled the detection of PEG sample as low as 100 pg and with molecular weights of up to approximately 42,000 Da. We also used this approach for the analyses of PEG-Au NPs in which various functional groups (carboxymethyl, amine, biotin) were present at the PEG termini, revealing that the combination of SALDI-MS and HgTe NMs have great potential for use in the characterization of modified polymer-ligands on nanomaterials. We also demonstrated the PEG-Au NPs can be coupled with HgTe NMs/SALDI-MS for characterization of biorecognition events. After avidin, the target protein, had been selectively captured by the biotin-PEG-Au NPs, we found that the desorption/ionization efficiency of biotin-PEG from the Au NP surface was suppressed; accordingly, this novel SALDI-MS approach allows rapid detection of avidin with high specificity and sensitivity. Au NP surfaces functionalized with other functional-PEG ligands might also allow amplification of signals from other biological interactions. PMID:25896538

  4. Effect of doping on electronic properties of HgSe

    NASA Astrophysics Data System (ADS)

    Nag, Abhinav; Sastri, O. S. K. S.; Kumar, Jagdish

    2016-05-01

    First principle study of electronic properties of pure and doped HgSe have been performed using all electron Full Potential Linearized Augmented Plane Wave (FP-LAPW) method using ELK code. The electronic exchange and co-relations are considered using Generalized Gradient Approach (GGA). Lattice parameter, Density of States (DOS) and Band structure calculations have been performed. The total energy curve (Energy vs Lattice parameter), DOS and band structure calculations are in good agreement with the experimental values and those obtained using other DFT codes. The doped material is studied within the Virtual Crystal Approximation (VCA) with doping levels of 10% to 25% of electrons (hole) per unit cell. Results predict zero band gap in undopedHgSe and bands meet at Fermi level near the symmetry point D. For doped HgSe, we found that by electron (hole) doping, the point where conduction and valence bands meet can be shifted below (above) the fermi level.

  5. Effect of Model-dependent Covariance Matrix for Studying Baryon Acoustic Oscillations

    NASA Astrophysics Data System (ADS)

    Labatie, A.; Starck, J. L.; Lachièze-Rey, M.

    2012-12-01

    Large-scale structures in the universe are a powerful tool to test cosmological models and constrain cosmological parameters. A particular feature of interest comes from baryon acoustic oscillations (BAOs), which are sound waves traveling in the hot plasma of the early universe that stopped at the recombination time. This feature can be observed as a localized bump in the correlation function at the scale of the sound horizon rs . As such, it provides a standard ruler and a lot of constraining power in the correlation function analysis of galaxy surveys. Moreover, the detection of BAOs at the expected scale gives strong support to cosmological models. Both of these studies (BAO detection and parameter constraints) rely on a statistical modeling of the measured correlation function \\hat{\\xi }. Usually \\hat{\\xi } is assumed to be Gaussian, with a mean ξθ depending on the cosmological model and a covariance matrix C generally approximated as a constant (i.e., independent of the model). In this article, we study whether a realistic model-dependent C θ changes the results of cosmological parameter constraints compared to the approximation of a constant covariance matrix C. For this purpose, we use a new procedure to generate lognormal realizations of the luminous red galaxy sample of the Sloan Digital Sky Survey Data Release 7 to obtain a model-dependent C θ in a reasonable time. The approximation of C θ as a constant creates small changes in the cosmological parameter constraints on our sample. We quantify this modeling error using a lot of simulations and find that it only has a marginal influence on cosmological parameter constraints for current and next-generation galaxy surveys. It can be approximately taken into account by extending the 1σ intervals by a factor ≈1.3.

  6. EFFECT OF MODEL-DEPENDENT COVARIANCE MATRIX FOR STUDYING BARYON ACOUSTIC OSCILLATIONS

    SciTech Connect

    Labatie, A.; Starck, J. L.

    2012-12-01

    Large-scale structures in the universe are a powerful tool to test cosmological models and constrain cosmological parameters. A particular feature of interest comes from baryon acoustic oscillations (BAOs), which are sound waves traveling in the hot plasma of the early universe that stopped at the recombination time. This feature can be observed as a localized bump in the correlation function at the scale of the sound horizon r{sub s} . As such, it provides a standard ruler and a lot of constraining power in the correlation function analysis of galaxy surveys. Moreover, the detection of BAOs at the expected scale gives strong support to cosmological models. Both of these studies (BAO detection and parameter constraints) rely on a statistical modeling of the measured correlation function {xi}-circumflex. Usually {xi}-circumflex is assumed to be Gaussian, with a mean {xi}{sub {theta}} depending on the cosmological model and a covariance matrix C generally approximated as a constant (i.e., independent of the model). In this article, we study whether a realistic model-dependent C {sub {theta}} changes the results of cosmological parameter constraints compared to the approximation of a constant covariance matrix C. For this purpose, we use a new procedure to generate lognormal realizations of the luminous red galaxy sample of the Sloan Digital Sky Survey Data Release 7 to obtain a model-dependent C {sub {theta}} in a reasonable time. The approximation of C {sub {theta}} as a constant creates small changes in the cosmological parameter constraints on our sample. We quantify this modeling error using a lot of simulations and find that it only has a marginal influence on cosmological parameter constraints for current and next-generation galaxy surveys. It can be approximately taken into account by extending the 1{sigma} intervals by a factor Almost-Equal-To 1.3.

  7. Feasibility study on production of a matrix reference material for cyanobacterial toxins.

    PubMed

    Hollingdale, Christie; Thomas, Krista; Lewis, Nancy; Békri, Khalida; McCarron, Pearse; Quilliam, Michael A

    2015-07-01

    The worldwide increase in cyanobacterial contamination of freshwater lakes and rivers is of great concern as many cyanobacteria produce potent hepatotoxins and neurotoxins (cyanotoxins). Such toxins pose a threat to aquatic ecosystems, livestock, and drinking water supplies. In addition, dietary supplements prepared from cyanobacteria can pose a risk to consumers if they contain toxins. Analytical monitoring for toxins in the environment and in consumer products is essential for the protection of public health. Reference materials (RMs) are an essential tool for the development and validation of analytical methods and are necessary for ongoing quality control of monitoring operations. Since the availability of appropriate RMs for cyanotoxins has been very limited, the present study was undertaken to examine the feasibility of producing a cyanobacterial matrix RM containing various cyanotoxins. The first step was large-scale culturing of various cyanobacterial cultures that produce anatoxins, microcystins, and cylindrospermopsins. After harvesting, the biomass was lyophilized, blended, homogenized, milled, and bottled. The moisture content and physical characteristics were assessed in order to evaluate the effectiveness of the production process. Toxin levels were measured by liquid chromatography with tandem mass spectrometry and ultraviolet detection. The reference material was found to be homogeneous for toxin content. Stability studies showed no significant degradation of target toxins over a period of 310 days at temperatures up to +40 °C except for the anatoxin-a, which showed some degradation at +40 °C. These results show that a fit-for-purpose matrix RM for cyanotoxins can be prepared using the processes and techniques applied in this work. PMID:25929442

  8. Defect structure of Cd{sub x}Hg{sub 1-x}Te films grown by liquid-phase epitaxy, studied by means of low-energy ion treatment

    SciTech Connect

    Izhnin, I. I. Izhnin, A. I.; Fitsych, E. I.; Smirnova, N. A.; Denisov, I. A.; Pociask, M.; Mynbaev, K. D.

    2011-09-15

    Treatment with low-energy ions and measurements of electrical parameters of samples have been used to study the defect structure of Cd{sub x}Hg{sub 1-x}Te films grown by liquid-phase epitaxy. The films contain neutral defects supposedly associated with tellurium nanoinclusions. Ion treatment electrically activates these defects, with a high concentration of donor centers ({approx}10{sup 17} cm{sup -3}) created in the films. These defects decompose in {approx}10{sup 3} min of aging at room temperature. Then the properties of the material are determined by the concentration of residual donors, which is found to be very low (down to {approx}10{sup 14} cm{sup -3}) for the films under study.

  9. Structural, spectral analysis and DNA studies of heterocyclic thiosemicarbazone ligand and its Cr(III), Fe(III), Co(II) Hg(II), and U(VI) complexes

    NASA Astrophysics Data System (ADS)

    Yousef, T. A.; Abu El-Reash, G. M.; El Morshedy, R. M.

    2013-08-01

    The paper presents a combined experimental and computational study of novel Cr(III), Fe(III), Co(II), Hg(II) and U(VI) complexes of (E)-2-((3-hydroxynaphthalen-2-yl)methylene)-N-(pyridin-2-yl)hydrazinecarbothioamide (H2L). The ligand and its complexes have been characterized by elemental analyses, spectral (IR, UV-vis, 1H NMR and 13C NMR), magnetic and thermal studies. IR spectra show that H2L is coordinated to the metal ions in a mononegative bi or tri manner. The structures are suggested to be octahedral for all complexes except Hg(II) complex is tetrahedral. Theoretical calculations have been performed to obtain IR spectra of ligand and its complexes using AM1, MM, Zindo/1, MM+ and PM3, methods. Satisfactory theoretical-experimental agreements were achieved by MM method for the ligand and PM3 for its complexes. DOS calculations carried out by MM (ADF) method for ligand Hg complex from which we concluded that the thiol form of the ligand is more active than thione form and this explains that the most complexation take place in that form. The calculated IR vibrations of the metal complexes, using the PM3 method was the nearest method for the experimental data, and it could be used for all complexes. Also, valuable information are obtained from calculation of molecular parameters for all compounds carried out by the previous methods of calculation (electronegativity of the coordination sites, net dipole moment of the metal complexes, values of heat of formation and binding energy) which approved that the complexes are more stable than ligand. The low value of ΔE could be expected to indicate H2L molecule has high inclination to bind with the metal ions. Furthermore, the kinetic and thermodynamic parameters for the different decomposition steps were calculated using the Coats-Redfern and Horowitz-Metzger methods. Finally, the biochemical studies showed that, complex 2, 4 have powerful and complete degradation effect on DNA. For the foremost majority of cases the

  10. Bioaccumulation of Hg in the mushroom Pleurotus ostreatus

    SciTech Connect

    Bressa, G.; Cima, L.; Costa, P.

    1988-10-01

    The possibility of utilizing industrial, urban, and other wastes for the growth of a product which is directly edible by humans is fascinating. However, it is possible that many wastes containing toxic substances, for example, heavy metals, could reach the food chain and produce adverse effects on human health. To this end, we studied the possibility of bioaccumulation of Hg by a mushroom, Pleurotus ostreatus, grown on an artificial compost containing this element. Concentrations of 0.05, 0.1, and 0.2 mg/kg of Hg as Hg(NO/sub 3/)/sub 2/.H/sub 2/O were added to three groups of the same compost, successively inoculated with the mycelia of the mushroom. Higher concentrations strongly reduced the growth of the mycelia and therefore were not utilized. The concentrations of Hg in the substrate and in the mushroom were evaluated by AAS. The range of the accumulation factor was found to be 65-140, i.e., very marked. This finding suggests that the cultivation of P. ostreatus on substrates containing Hg from industrial and urban wastes could involve possible risks to human health.

  11. Fundamental Studies of Low Velocity Impact Resistance of Graphite Fiber Reinforced Polymer Matrix Composites. Ph.D. Thesis

    NASA Technical Reports Server (NTRS)

    Bowles, K. J.

    1985-01-01

    A study was conducted to relate the impact resistance of graphite fiber reinforced composites with matrix properties through gaining an understanding of the basic mechanics involved in the deformation and fracture process, and the effect of the polymer matrix structure on these mechanisms. It was found that the resin matrix structure influences the composite impact resistance in at least two ways. The integration of flexibilizers into the polymer chain structure tends to reduce the T sub g and the mechanical properties of the polymer. The reduction in the mechanical properties of the matrix does not enhance the composite impact resistance because it allows matrix controlled failure to initiate impact damage. It was found that when the instrumented dropweight impact tester is used as a means for assessing resin toughness, the resin toughness is enhanced by the ability of the clamped specimen to deflect enough to produce sufficient membrane action to support a significant amount of the load. The results of this study indicate that crossplied composite impact resistance is very much dependent on the matrix mechanical properties.

  12. Risk Assessment Study of Fluoride Salts: Probability-Impact Matrix of Renal and Hepatic Toxicity Markers.

    PubMed

    Usuda, Kan; Ueno, Takaaki; Ito, Yuichi; Dote, Tomotaro; Yokoyama, Hirotaka; Kono, Koichi; Tamaki, Junko

    2016-09-01

    The present risk assessment study of fluoride salts was conducted by oral administration of three different doses of sodium and potassium fluorides (NaF, KF) and zinc fluoride tetrahydrate (ZnF2 •4H2O) to male Wistar rats. The rats were divided into control and nine experimental groups, to which oral injections of 0.5 mL distilled water and 0.5 mL of fluoride solutions, respectively, were given. The dosage of fluoride compounds was adjusted to contain 2.1 mg (low-dose group, LG), 4.3 mg (mid-dose group, MG), and 5.4 mg fluoride per 200 g rat body weight (high-dose group, HG) corresponding to 5, 10, and 12.5 % of LD50 values for NaF. The 24-h urine volume, N-acetyl-β-D-glucosaminidase (NAG) and creatinine clearance (Ccr) were measured as markers of possible acute renal impact. The levels of alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were determined in serum samples as markers of acute hepatic impact. The levels of serum and urinary fluoride were determined to evaluate fluoride bioavailability. The results reveal that higher doses of NaF, KF, and ZnF2 induced renal damage as indicated by higher urinary NAG (p < 0.05 with ≥90th percentile of control). High doses of ZnF2 also induced a significant Ccr decrease (p < 0.05 with ≤10th percentile of control). Low doses of NaF and mid-doses of ZnF2 induced polyuria (p < 0.05 with ≥90th percentile of control) while medium doses of NaF and low doses of KF also induced liver damage, as indicated by a high level of AST (p < 0.05 with ≥90th percentile of control). These findings suggest that oral administration of fluoride is a potential, dose-dependent risk factor of renal tubular damage. PMID:26892107

  13. Impacts of Activated Carbon Amendment on Hg Methylation, Demethylation and Microbial Activity in Marsh Soils

    NASA Astrophysics Data System (ADS)

    Gilmour, C. C.; Ghosh, U.; Santillan, E. F. U.; Soren, A.; Bell, J. T.; Butera, D.; McBurney, A. W.; Brown, S.; Henry, E.; Vlassopoulos, D.

    2015-12-01

    In-situ sorbent amendments are a low-impact approach for remediation of contaminants in sediments, particular in habitats like wetlands that provide important ecosystem services. Laboratory microcosm trials (Gilmour et al. 2013) and early field trials show that activated carbon (AC) can effectively increase partitioning of both inorganic Hg and methylmercury to the solid phase. Sediment-water partitioning can serve as a proxy for Hg and MeHg bioavailability in soils. One consideration in using AC in remediation is its potential impact on organisms. For mercury, a critical consideration is the potential impact on net MeHg accumulation and bioavailability. In this study, we specifically evaluated the impact of AC on rates of methylmercury production and degradation, and on overall microbial activity, in 4 different Hg-contaminated salt marsh soils. The study was done over 28 days in anaerobic, sulfate-reducing slurries. A double label of enriched mercury isotopes (Me199Hg and inorganic 201Hg) was used to separately follow de novo Me201Hg production and Me199Hg degradation. AC amendments decreased both methylation and demethylation rate constants relative to un-amended controls, but the impact on demethylation was stronger. The addition of 5% (dry weight) regenerated AC to soil slurries drove demethylation rate constants to nearly zero; i.e. MeHg sorption to AC almost totally blocked its degradation. The net impact was increased solid phase MeHg concentrations in some of the soil slurries with the highest methylation rate constants. However, the net impact of AC amendments was to increase MeHg (and inorganic Hg) partitioning to the soil phase and decrease concentrations in the aqueous phase. AC significantly decreased aqueous phase inorganic Hg and MeHg concentrations after 28 days. Overall, the efficacy of AC in reducing aqueous MeHg was highest in the soils with the highest MeHg concentrations. The AC addition did not significantly impact microbial activity, as

  14. Design, development and permeation studies of nebivolol hydrochloride from novel matrix type transdermal patches

    PubMed Central

    Jatav, Vijay Singh; Saggu, Jitender Singh; Sharma, Ashish Kumar; Sharma, Anil; Jat, Rakesh Kumar

    2013-01-01

    Background: Nebivolol hydrochloride is a third generation β-blocker with highly selective β1-receptor antagonist with antihypertensive properties having plasma half life of 10 h and 12% oral bioavailability. The aim of the present investigation was to form matrix type transdermal patches containing Nebivolol hydrochloride to avoid its extensive hepatic first pass metabolism, lesser side effect and increase bioavailability of drug. Materials and Methods: Matrix type transdermal patches containing Nebivolol hydrochloride were prepared using EudragitRS100, HPMC K100M (2:8) polymers by solvent evaporation technique. Aluminum foil was used as a backing membrane. Polyethylene glycol (PEG) 400 was used as plasticizer and Dimethyl sulfoxide (DMSO) was used as a penetration enhancer. Drug polymer interactions determined by FTIR and standard calibration curve of Nebivolol hydrochloride were determined by using UV estimation. Result: The systems were evaluated physicochemical parameters and drug present in the patches was determined by scanning electron microscopy. All prepared formulations indicated good physical stability. In vitro drug permeation studies of formulations were performed by using Franz diffusion cells using abdomen skin of Wistar albino rat. Result showed best in vitro skin permeation through rat skin as compared to all other formulations prepared with hydrophilic polymer containing permeation enhancer. Conclusions: It was observed that the formulation containing HPMC: EudragitRS100 (8:2) showed ideal higuchi release kinetics. On the basis of in vitro drug release through skin permeation performance, Formulation F1 was found to be better than other formulations and it was selected as the optimized formulation. PMID:24223377

  15. Matrix-isolation study and ab initio calculations of the structure and spectra of hydroxyacetone.

    PubMed

    Sharma, Archna; Reva, Igor; Fausto, Rui

    2008-07-01

    The structure of hydroxyacetone (HA) isolated in an argon matrix (at 12 K) and in a neat solid phase (at 12-175 K) was characterized by using infrared (IR) spectroscopy. The interpretation of the experimental results was supported by high-level quantum chemical calculations, undertaken by using both ab initio (MP2) and density functional theory methods. A potential-energy surface scan, carried out at the MP2/6-311++G(d,p) level of theory, predicted four nonequivalent minima, Cc, Tt, Tg, and Ct, all of them doubly degenerate by symmetry. The energy barriers for conversion between most of the symmetrically related structures and also between some of the nonequivalent minima (e.g., Tg --> Tt and Ct --> Tt) are very small and stay below the zero-point vibrational level associated with the isomerization coordinate in the higher-energy form in each pair. Therefore, only Cc and Tt conformers have physical significance, with populations of 99 and 1%, respectively, in gas phase at room temperature. For the matrix-isolated compound, only the most stable Cc conformer was observed. On the other hand, the polarizable continuum model calculations indicated that in water solution, the population of Tt and Ct conformers might be high enough (ca. 6 and 11%, respectively) to enable their experimental detection, thus supporting the conclusions of a previous IR spectroscopy study [ Spectrochim. Acta A 2005, 61, 477] in which the presence of more than one HA conformer in aqueous solution was postulated. The signatures of these minor conformers, however, do not appear in the spectra of the neat HA crystal, and the crystal structure was rationalized in terms of centrosymmetric hydrogen-bonded dimers consisting of two Cc-like units. Finally, we calculated (1)H, (13)C, and (17)O NMR chemical shifts at different levels of theory and found them to agree with available experimental data. PMID:18537231

  16. Matrix isolation infrared spectroscopic study of the vapor species over heated ReO{sub 3}

    SciTech Connect

    Almond, M.J.; Orrin, R.H.; Ogden, J.S.

    1996-02-01

    The vapor phase species over ReO{sub 3} heated in vacuo to approx 400C have been trapped in argon or nitrogen matrices at approx 12 K. The only species within such matrices detected by infrared spectroscopy is Re{sub 2}O{sub 7}. The bands of matrix-isolated Re{sub 2}O{sub 7} have been assigned by comparison with the spectrum of the gaseous compound. Most of the isolated Re{sub 2}O{sub 7} is shown to be in the monomeric form; thus, an infrared absorption at 916.5 cm{sup {minus}1} (N{sub 2} matrix), which had previously been assigned to an aggregate of Re{sub 2}O{sub 7} may, on the basis of annealing experiments, be attributed to the monomer. The solid remaining in the sample tube following heating of the ReO{sub 3} sample consists of ReO{sub 2} in both the monoclinic and orthorhombic crystal forms alongside some unreacted cubic ReO{sub 3} and a small amount of orthorhombic Re{sub 2}O{sub 7}. Thus, it is found that thermal decomposition of ReO{sub 3} in vacuo at 400 C follows the expected disproportionation route. The authors find no spectroscopic evidence for the existence of other species, such as ReO{sub 3} or HReO{sub 4}, in the vapor above heated ReO{sub 3}. This finding is in contrast to the results of earlier mass spectrometric studies that suggested that molecular ReO{sub 3} was present in the vapor together with Re{sub 2}O{sub 7}.

  17. Raman spectroscopic investigations of Hg-Cd-Te melts

    NASA Technical Reports Server (NTRS)

    Morrobel-Sosa, Anny

    1987-01-01

    Raman scattering measurements are reported for a series of Hg sub1-xCd subxTe (with x less than or =0.2) materials from 295 K (room temperature) to 1126K (up to and above their liquidus temperatures), and for Hg sub1-xCd subxTe (x=0.3) at 285K. The samples were contained in high-temperature optically-flat fused silica cell. Variable temperature measurements were effected in a three-zone, high-temperature furnace equipped with optical windows, and monitored externally by three independently programmable temperature controllers. All studies were made in the backscattering geometry using the 5145 A line of an Ar+ ion laser, with incident power less than 250 mW, as the excitiation source. An intensity enhancement is observed for a mode in each of the compositions studied. The frequency of this mode varies with composition, 142/cm for HgTe, and 128/cm for both the Hg sub1-xCd subxTe (x=0.053 and 0.204) samples. In addition, a shift to lower frequency as a function of temperature is observed in all samples. This shift is most prominent for the x=0.053 sample. The temperature dependence of these modes as the liquidus temperatures are achieved and surpassed for these samples is presented as being associated with a structural transition in the Hg-rich compositions of the Hg sub1-xCd subxTe series. To our knowledge, this is the first reported study of Raman scattering by phonons in the melts of these materials.

  18. Study of 14O as a test of the unitarity of the CKM matrix and the CVC hypothesis

    SciTech Connect

    Burke, Jason Timothy

    2004-06-01

    The study of superallowed beta decay in nuclei, in conjunction with other experiments, provide a test of the unitarity of the quark mixing matrix or CKM matrix. Nonunitarity of the CKM matrix could imply the existence of a fourth generation of quarks, right handed currents in the weak interaction, and/or new exotic fermions. Advances in radioactive beam techniques allow the creation of nearly pure samples of nuclei for beta decay studies. The subject of this thesis is the development of a radioactive beam of 14O and the study of the 14O halflife and branching ratio. The radioactive beam is produced by ionizing 12C14O radioactive gas and then accelerating with an ECR ion source. The 14O nucleus decays via superallowed beta decay with a branching ratio > 99 percent. The low Z of 14O is important for calculating reliable corrections to the beta decay that generally increase in with Z. The > 99 percent branching ratio can be established with modest precision on the complementary branching ratio.When this work began the experimentally determined CKM matrix was nonunitary by 2.5 standard deviations. Recent studies of Kaon, Hyperon, and B meson decays have been used to determine Vus and Vub matrix elements. In this work the halflife and branching ratio of 14O are measured and used to establish Vud. The unitarity of the CKM matrix is then assessed. The halflife of 14O was determined to be 70.683 +- 0.015 s and the GamowTeller branching ratio was found to be 0.643 +- 0.020 percent. Using these results the value of Vud is 0.9738 +- 0.0005. Incorporating the new values for Vus of 0.2272 +- 0.0030 and Vub of 0.0035 +- 0.0015 the squared sum of the first row of the CKM matrix is 0.9999 +- 0.0017 which is consistent with unitarity.

  19. Using the matrix-induced ion suppression method for concentration normalization in cellular metabolomics studies.

    PubMed

    Chen, Guan-Yuan; Liao, Hsiao-Wei; Tsai, I-Lin; Tseng, Yufeng Jane; Kuo, Ching-Hua

    2015-10-01

    Studies of the cell metabolome greatly improve our understanding of cell biology. Currently, most cellular metabolomics studies control only cell numbers or protein content without adjusting the total metabolite concentration, mainly because of the lack of an effective concentration normalization method for cell metabolites. This study proposed a matrix-induced ion suppression (MIIS) method to measure the total amount of cellular metabolites by utilizing flow injection analysis coupled with electrospray ionization mass spectrometry (FIA-ESI-MS).We used series dilutions of HL-60 cell extracts to establish the relationship between cellular metabolite concentration and the degree of ion suppression of the ion suppression indicator, and a good correlation was obtained between 2- and 12-fold dilutions of cell extracts (R(2) = 0.999). Two lung cancer cells, CL1-0 and CL1-5, were selected as the model cell lines to evaluate the efficacy of the MIIS method and the importance of metabolite concentration normalization. Through MIIS analysis, CL1-0 cells were found to contain metabolites at a concentration 2.1 times higher than in CL1-5, and the metastatic properties of CL1-5 could only be observed after 2.1-fold dilution of CL1-0 before metabolomic analysis. Our results demonstrated that the MIIS method is an effective approach for metabolite concentration normalization and that controlling metabolite concentrations can improve data integrity in cellular metabolomics studies. PMID:26359637

  20. First-principles study on magnetism and half-metallicity in bulk and various (001) surfaces of Heusler alloy Zr2VSn with Hg2CuTi-type structure

    NASA Astrophysics Data System (ADS)

    Deng, Zun-Yi; Zhang, Jian-Min

    2016-07-01

    Structural, electronic and magnetic properties in the bulk and five different (001) surfaces (ZrV-, ZrSn-, VV-, ZrZr- and SnSn-terminations) of Zr2 VSn Heusler alloy with Hg2 CuTi -type structure are studied by using first-principles calculations based on density-functional theory. The bulk Zr2 VSn Heusler alloy is ferrimagnetic half-metallicity with equilibrium lattice constant 6.815 Å and total magnetic moment -1.000 μB / f.u . , following the Slater-Pauling rule μt =Zt - 18 . The atoms on different surface layers exhibit different displacements, electronic and magnetic properties. All five (001) surfaces lose the half-metallicity and are not usable in spintronics devices.

  1. Mercury in stream water at five Czech catchments across a Hg and S deposition gradient

    USGS Publications Warehouse

    Navrátil, Tomáš; Shanley, James B.; Rohovec, Jan; Oulehle, Filip; Krám, Pavel; Matoušková, Šárka; Tesař, Miroslav; Hojdová, Maria

    2015-01-01

    The Czech Republic was heavily industrialized in the second half of the 20th century but the associated emissions of Hg and S from coal burning were significantly reduced since the 1990s. We studied dissolved (filtered) stream water mercury (Hg) and dissolved organic carbon (DOC) concentrations at five catchments with contrasting Hg and S deposition histories in the Bohemian part of the Czech Republic. The median filtered Hg concentrations of stream water samples collected in hydrological years 2012 and 2013 from the five sites varied by an order of magnitude from 1.3 to 18.0 ng L− 1. The Hg concentrations at individual catchments were strongly correlated with DOC concentrations r from 0.64 to 0.93 and with discharge r from 0.48 to 0.75. Annual export fluxes of filtered Hg from individual catchments ranged from 0.11 to 13.3 μg m− 2 yr− 1 and were highest at sites with the highest DOC export fluxes. However, the amount of Hg exported per unit DOC varied widely; the mean Hg/DOC ratio in stream water at the individual sites ranged from 0.28 to 0.90 ng mg− 1. The highest stream Hg/DOC ratios occurred at sites Pluhův Bor and Jezeří which both are in the heavily polluted Black Triangle area. Stream Hg/DOC was inversely related to mineral and total soil pool Hg/C across the five sites. We explain this pattern by greater soil Hg retention due to inhibition of soil organic matter decomposition at the sites with low stream Hg/DOC and/or by precipitation of a metacinnabar (HgS) phase. Thus mobilization of Hg into streams from forest soils likely depends on combined effects of organic matter decomposition dynamics and HgS-like phase precipitation, which were both affected by Hg and S deposition histories.

  2. [Experimental Research of Hg (II) Removal from Aqueous Solutions of HgCl2 with Nano-TiO2].

    PubMed

    Zhou, Xiong; Zhang, Jin-yang; Wang, Ding-yong; Qin, Cai-qing; Xu, Feng; Luo Cheng-zhong; Yang, Xi

    2016-01-15

    Mercury removal from aqueous solutions of HgCl2 was studied by indoor simulation experiments, and the effects of three different diameter of particles of Nano-TiO2 ( Nano-Titanium Dioxide) at different dosage, pH, adsorption time and the initial concentration of Hg2+ on the mercury adsorption from simulated wastewater were investigated. The single factor experiments showed that the optimal conditions were: 7.5 g x L(-1) of 5 nm TiO2 or 2.0 g x L(-1) of 100 nm TiO2, pH 8.0, initial concentration of Hg2+ 15 x mg x L(-1) adsorption time 5 min, and under these conditions the adsorption rates reached 99.5% and 99.3%, relatively. When the content of 25 nm TiO2 was 10 g x L(-1), and the other conditions were pH 8.0, initial concentration of Hg2+ 15 mg x L(-1), adsorption time 60 min, the adsorption rate was 62.8%. The Hg(II) removal effects of the TiO2 particles with different diameters followed the order of 100 nm TiO2 > 5 nm TiO2 > 25 nm TiO2. Component adsorption results showed that the 5 nm TiO2 component adsorption effect was superior to its single adsorption effect, while there was little difference between 100 nm TiO2 component adsorption effect and its single adsorption effect. The results of orthogonal experiments indicated that the influencing factors of the adsorption rate followed the order of pH > the initial concentration of Hg2+ > time > dosage. The optimal experiment scheme was: pH 8.0, a dosage of 100 nm Nano-TiO2 of 2.0 g x L(-1) an initial Hg2+ concentration of 25 mg x L(-1) and adsorption time of 10 min. Under the experimental conditions, the maximum adsorption rate reached 99.9%, at the same time, the equilibrium concentration of Hg(II) was 0.033 mg x L(-1) < 0.05 mg x L(-1), below the current enterprise rules of water pollutants in mercury emissions limits. In addition, the maximum adsorptive capacity was 26.95 mg x g(-1). The adsorption isotherm was in line with the Langmuir isotherm equation, indicating that the Hg(II) uptake by 100 nm Nano-TiO2

  3. Special Issue: Environmental Chemicals and Neurotoxicity Oxidative stress in MeHg-induced neurotoxicity

    PubMed Central

    Farina, Marcelo; Aschner, Michael; Rocha, João B. T.

    2011-01-01

    Methylmercury (MeHg) is an environmental toxicant that leads to long-lasting neurological and developmental deficits in animals and humans. Although the molecular mechanisms mediating MeHg-induced neurotoxicity are not completely understood, several lines of evidence indicate that oxidative stress represents a critical event related to the neurotoxic effects elicited by this toxicant. The objective of this review is to summarize and discuss data from experimental and epidemiological studies that have been important in clarifying the molecular events which mediate MeHg-induced oxidative damage and, consequently, toxicity. Although unanswered questions remain, the electrophilic properties of MeHg and its ability to oxidize thiols have been reported to play decisive roles to the oxidative consequences observed after MeHg exposure. However, a close examination of the relationship between low levels of MeHg necessary to induce oxidative stress and the high amounts of sulfhydryl-containing antioxidants in mammalian cells (e.g., glutathione) have led to the hypothesis that nucleophilic groups with extremely high affinities for MeHg (e.g., selenols) might represent primary targets in MeHg-induced oxidative stress. Indeed, the inhibition of antioxidant selenoproteins during MeHg poisoning in experimental animals has corroborated this hypothesis. The levels of different reactive species (superoxide anion, hydrogen peroxide and nitric oxide) have been reported to be increased in MeHg-exposed systems, and the mechanisms concerning these increments seem to involve a complex sequence of cascading molecular events, such as mitochondrial dysfunction, excitotoxicity, intracellular calcium dyshomeostasis and decreased antioxidant capacity. This review also discusses potential therapeutic strategies to counteract MeHg-induced toxicity and oxidative stress, emphasizing the use of organic selenocompounds, which generally present higher affinity for MeHg when compared to the classically

  4. Element spots in HgMn stars

    NASA Astrophysics Data System (ADS)

    Korhonen, H.

    2014-11-01

    A fraction of late B-type stars, the so-called HgMn stars, exhibit enhanced absorption lines of certain chemical elements, notably Hg and Mn, combined with an underabundance of He. For about a decade it has been known that the elements with anomalously high abundances in HgMn stars are distributed inhomogeneously over the stellar surface. Observation of the temporal evolution of those spots has been reported in a few HgMn stars, first of a secular evolution of the mercury spots in α And, and more recently of a fast evolution of yttrium and strontium spots in HD 11753. The fast evolution of spots in HD 11753 is combined with a slower change in the overall abundance of the elements affected. In this paper I review what is known about these ``elemental spots'' in HgMn stars and their secular and fast temporal evolution.

  5. Highly luminescent Ag+ nanoclusters for Hg2+ ion detection

    NASA Astrophysics Data System (ADS)

    Yuan, Xun; Yeow, Teik Jin; Zhang, Qingbo; Lee, Jim Yang; Xie, Jianping

    2012-03-01

    A simple, low-cost and label-free Hg2+ ion sensor has been developed by using novel luminescent Ag+ nanoclusters (NCs) with an excellent optical property (quantum yield = 15%), an ultra-high ratio of active Ag+ species in the NC surface (~100%), and an ultra-short diffusion path length of Hg2+ ions to access the NC surface (~0.5 nm).A simple, low-cost and label-free Hg2+ ion sensor has been developed by using novel luminescent Ag+ nanoclusters (NCs) with an excellent optical property (quantum yield = 15%), an ultra-high ratio of active Ag+ species in the NC surface (~100%), and an ultra-short diffusion path length of Hg2+ ions to access the NC surface (~0.5 nm). Electronic supplementary information (ESI) available: Experimental details of the synthesis of b-Ag NCs; time-resolved evolution of photoemission spectra of the b-Ag NCs in toluene; photoexcitation spectrum of the b-Ag NCs in toluene; comparison of the luminescence of b-Ag NCs at different temperatures (4 and 25 °C) TEM image of the b-Ag NCs in toluene; optical properties of r-Ag NCs obtained by the reduction of b-Ag NCs in toluene; XPS spectra of b-Ag NCs, thiolate-Ag+ complexes, r-Ag NCs, and large Ag nanoparticles; TEM image of the Hg2+-Ag NCs; photostability of the b-Ag NCs; tolerance studies of the b-Ag NCs over other metal ions; tolerance studies of the b-Ag NCs over common thiol ligands (e.g., GSH) and anions; relative luminescence of the b-Ag NCs in different real water samples in the presence of Hg2+ ions; and relative luminescence of the b-Ag NCs in NaCl solution with different concentrations. See DOI: 10.1039/c2nr11999d

  6. Energy density matrix formalism for interacting quantum systems: a quantum Monte Carlo study

    SciTech Connect

    Krogel, Jaron T; Kim, Jeongnim; Reboredo, Fernando A

    2014-01-01

    We develop an energy density matrix that parallels the one-body reduced density matrix (1RDM) for many-body quantum systems. Just as the density matrix gives access to the number density and occupation numbers, the energy density matrix yields the energy density and orbital occupation energies. The eigenvectors of the matrix provide a natural orbital partitioning of the energy density while the eigenvalues comprise a single particle energy spectrum obeying a total energy sum rule. For mean-field systems the energy density matrix recovers the exact spectrum. When correlation becomes important, the occupation energies resemble quasiparticle energies in some respects. We explore the occupation energy spectrum for the finite 3D homogeneous electron gas in the metallic regime and an isolated oxygen atom with ground state quantum Monte Carlo techniques imple- mented in the QMCPACK simulation code. The occupation energy spectrum for the homogeneous electron gas can be described by an effective mass below the Fermi level. Above the Fermi level evanescent behavior in the occupation energies is observed in similar fashion to the occupation numbers of the 1RDM. A direct comparison with total energy differences demonstrates a quantita- tive connection between the occupation energies and electron addition and removal energies for the electron gas. For the oxygen atom, the association between the ground state occupation energies and particle addition and removal energies becomes only qualitative. The energy density matrix provides a new avenue for describing energetics with quantum Monte Carlo methods which have traditionally been limited to total energies.

  7. Studies of matrix vesicle-induced mineralization in a gelatin gel

    NASA Technical Reports Server (NTRS)

    Boskey, A. L.; Boyan, B. D.; Doty, S. B.; Feliciano, A.; Greer, K.; Weiland, D.; Swain, L. D.; Schwartz, Z.

    1992-01-01

    Matrix vesicles isolated from fourth-passage cultures of chondrocytes were tested for their ability to induce hydroxyapatite formation in a gelatin gel in order to gain insight into the function of matrix vesicles in in situ mineralization. These matrix vesicles did not appear to be hydroxyapatite nucleators per se since the extent of mineral accumulation in the gel diffusion system was not altered by the presence of matrix vesicles alone, and in the vesicle containing gels, mineral crystals were formed whether associated with vesicles or not. In gels with these matrix vesicles and beta-glycerophosphate, despite the presence of alkaline phosphatase activity, there was no increase in mineral deposition. This suggested that in the gel system these culture-derived vesicles did not increase local phosphate concentrations. However, when known inhibitors of mineral crystal formation and growth (proteoglycan aggregates [4 mg/ml], or ATP [1 mM], or both proteoglycan and ATP) were included in the gel, more mineral was deposited in gels with the vesicles than in comparable gels without vesicles, indicating that enzymes within these vesicles were functioning to remove the inhibition. These data support the suggestion that one function of the extracellular matrix vesicles is to transport enzymes for matrix modification.

  8. Degradation of connective tissue matrices by macrophages. III. Morphological and biochemical studies on extracellular, pericellular, and intracellular events in matrix proteolysis by macrophages in culture

    SciTech Connect

    Werb, Z.; Bainton, D.F.; Jones, P.A.

    1980-12-01

    The aim of the present study was to determine the localization of macrophage-mediated degradation of matrix proteins. The sites of matrix degradation were examined ultrastructurally, and the effects of modulation of macrophage secretion, endocytosis, and activity of macrophage hydrolases on matrix degradation were monitored biochemically.

  9. Impacts of crab bioturbation and local pollution on sulfate reduction, Hg distribution and methylation in mangrove sediments, Rio de Janeiro, Brazil.

    PubMed

    Correia, Raquel Rose Silva; Guimarães, Jean Remy Davée

    2016-08-15

    Mercury (Hg) and methylmercury (MeHg) are highly toxic and poorly studied in mangroves. Burrowing Uca crabs change sediment topography and biogeochemistry and thus may affect Hg distribution and MeHg formation. We studied added (203)Hg distribution, Me(203)Hg formation and sulfate reduction rates (SRR) in sediment aquariums containing Uca leptodactyla; and analyzed profiles of Me(203)Hg formation and SRR in sediment cores from two mangroves with distinct environmental impacts. MeHg formation and SRR were higher in the top (≤6cm) sediment and there was no significant difference in Hg methylation in more or less impacted mangroves. In aquariums, crab bioturbation favored Hg retention in the sediment. In the treatment without crabs, Hg volatilization and water Hg concentrations were higher. Hg methylation was higher in bioturbated aquariums but SRR were similar in both treatments. These findings suggest that bioturbating activity favors Hg retention in sediment but also promotes MeHg formation near the surface. PMID:27269386

  10. Electronic structures of HgTe and CdTe surfaces and HgTe/CdTe interfaces

    NASA Technical Reports Server (NTRS)

    Schick, J. T.; Bose, S. M.; Chen, A.-B.

    1989-01-01

    A Green's-function method has been used to study the surface and interface electronic structures of the II-VI compounds HgTe and CdTe. Localized surface and resonance states near the cation-terminated (100) surface of CdTe and the anion-terminated surface of HgTe have been found for the ideal surfaces. The energies and strengths of these surface states are altered by surface perturbations. The bulk states near the surface are drastically modified by the creation of the surface, but the band gaps remain unchanged. Numerical evaluation of the local densities of states at the Gamma and J points shows that, at the (100) interface of HgTe/CdTe, the previously observed surface states are no longer present. However, in the interface region, bulk states of one material penetrate some distance into the other material.

  11. The Abundance and Isotopic Composition of Hg in Extraterrestrial Materials

    NASA Technical Reports Server (NTRS)

    Lauretta, D. S.

    2004-01-01

    During the past three year grant period we made excellent progress in our study of the abundances and isotopic compositions of Hg and other volatile trace elements in extraterrestrial materials. As part of my startup package I received funds to construct a state-of-the-art experimental facility to study gas-solid reaction kinetics. Much of our effort was spent developing the methodology to measure the abundance and isotopic composition of Hg at ultratrace levels in solid materials. In our first study, the abundance and isotopic composition of Hg was determined in bulk samples of the Murchison (CM) and Allende (CV) carbonaceous chondrites. We have continued our study of mercury in primitive meteorites and expanded the suite of meteorites to include other members of the CM and CV chondrite group as well as CI and CO chondrites. Samples of the CI chondrite Orgueil, the CM chondrites Murray, Nogoya, and Cold Bokkeveld, the CO chondrites Kainsaz, Omans, and Isna, and the CV chondrites Vigarano, Mokoia, and Grosnaja were tested. We have developed a thermal analysis ICP-MS technique and applied it to the study of a suite of thermally labile elements (Zn, As, Se, Cd, In, Sn, Sb, Te, Hg, Au, Tl, Pb, and Bi) in geologic materials as well.

  12. Anthropogenic Hg in the ocean: Trajectories of change and implications for exposure in the United States

    NASA Astrophysics Data System (ADS)

    Amos, H. M.; Corbitt, E. S.; Bullard, K. T.; Sunderland, E. M.

    2014-12-01

    Humans have been releasing mercury (Hg) to the environment for millenia through activities such as mining and fuel combustion. The result has been an enrichment of the ocean, atmosphere, and terrestrial ecosystems. Consumption of marine fish contaminated with methylmercury (MeHg) is the primary route of exposure in many populations globally. We present an updated analysis of sources of MeHg exposures in the United States that shows the majority (>70%) is from oceanic fish rather than coastal species. Using a fully coupled biogeochemical box model we also estimate Hg accumulation across major ocean basins and show anthropogenic enrichment is highest in the North Atlantic Ocean and lowest in the deep Pacific Ocean. Our results for contemporary ocean concentrations are consistent with recent data from the Pacific, Atlantic, Indian and Southern Oceans measured as part of the CLIVAR repeat hydrography program. Our estimates of natural (i.e., pre-anthropogenic) seawater Hg concentrations are lower than suggested by other studies, implying a greater anthropogenic perturbation in the ocean. Our work suggests total accumulation of anthropogenic Hg in the global oceans is greater than recently derived based on anthropogenic CO2. We compare modeled seawater concentrations since 1980 to observations over this period to evaluate evidence for changes in recent decades and then investigate potential impacts of changing global emissions. To do this, we use a range of historical and future anthropogenic Hg emission inventories. Our previous work using the box model indicates burial of Hg at ocean margins is the single largest global sink of anthropogenic Hg. We will discuss how the magnitude and permanence of this sink affects estimates of enrichment and time scales of recovery in all geochemical Hg reservoirs. Governing time scales of response in each ocean basin are diagnosed using eigenanalysis and discussed in the context of changes in human MeHg exposure resulting from

  13. The Hg isoelectronic defect in ZnO

    NASA Astrophysics Data System (ADS)

    Cullen, J.; Johnston, K.; Dunker, D.; McGlynn, E.; Yakovlev, D. R.; Bayer, M.; Henry, M. O.

    2013-11-01

    We report a study of the luminescence due to Hg in ZnO, concentrating on the main zero phonon line (ZPL) at 3.2766(1) eV and its associated phonon sidebands. For a sample implanted with radioactive 192Hg, the ZPL intensity, normalised to that of shallow bound exciton emission, is observed to decrease with an equivalent half-life of 4.5(1) h, very close to the 4.85(20) h half-life of 192Hg. ZnO implanted with stable Hg impurities produces the same luminescence spectrum. Temperature dependent measurements confirm that the zero phonon line is a thermalizing doublet involving one allowed and one largely forbidden transition from excited states separated by 0.91(1) meV to a common ground state. Uniaxial stress measurements show that the allowed transition takes place from an orbitally degenerate excited state to a non-degenerate ground state in a centre of trigonal (C3v) symmetry while the magneto-optical properties are characteristic of electron-hole pair recombination at an isoelectronic defect. The doublet luminescence is assigned to bound exciton recombination involving exchange-split Γ5 and Γ1,2 excited states (using C6v symmetry labels; Γ3 and Γ1,2 using C3v labels) at isoelectronic Hg impurities substituting for Zn in the crystal. The electron and hole g values deduced from the magneto-optical data indicate that this Hg impurity centre in ZnO is hole-attractive.

  14. The Hg isoelectronic defect in ZnO

    SciTech Connect

    Cullen, J.; McGlynn, E. Henry, M. O.; Johnston, K.; Dunker, D.; Bayer, M.; Yakovlev, D. R.

    2013-11-21

    We report a study of the luminescence due to Hg in ZnO, concentrating on the main zero phonon line (ZPL) at 3.2766(1) eV and its associated phonon sidebands. For a sample implanted with radioactive {sup 192}Hg, the ZPL intensity, normalised to that of shallow bound exciton emission, is observed to decrease with an equivalent half-life of 4.5(1) h, very close to the 4.85(20) h half-life of {sup 192}Hg. ZnO implanted with stable Hg impurities produces the same luminescence spectrum. Temperature dependent measurements confirm that the zero phonon line is a thermalizing doublet involving one allowed and one largely forbidden transition from excited states separated by 0.91(1) meV to a common ground state. Uniaxial stress measurements show that the allowed transition takes place from an orbitally degenerate excited state to a non-degenerate ground state in a centre of trigonal (C{sub 3v}) symmetry while the magneto-optical properties are characteristic of electron-hole pair recombination at an isoelectronic defect. The doublet luminescence is assigned to bound exciton recombination involving exchange-split Γ{sub 5} and Γ{sub 1,2} excited states (using C{sub 6v} symmetry labels; Γ{sub 3} and Γ{sub 1,2} using C{sub 3v} labels) at isoelectronic Hg impurities substituting for Zn in the crystal. The electron and hole g values deduced from the magneto-optical data indicate that this Hg impurity centre in ZnO is hole-attractive.

  15. Laser induced fluorescence (LIF) of Hg2 and Hg3 via dissociation of HgBr2 at 157 nm

    NASA Astrophysics Data System (ADS)

    Skordoulis, C.; Sarantopoulou, E.; Spyrou, S. M.; Kosmidis, C.; Cefalas, A. C.

    1991-06-01

    Laser induced fluorescence of the mercury clusters Hg2 and Hg3 in the spectral range between 300 nm to 510 nm has been obtained from the dissociation of HgBr2 at 7.88 eV (157.5 nm) with an F2 molecular laser, together with fluorescence from mercury atomic transitions from highly excited states. The excitation process involves two photon absorption which dissociates the molecule at 15.76 eV total photon energy with the subsequent formation of the metallic clusters.

  16. 40 CFR 60.4160 - Submission of Hg allowance transfers.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Submission of Hg allowance transfers... Times for Coal-Fired Electric Steam Generating Units Hg Allowance Transfers § 60.4160 Submission of Hg allowance transfers. An Hg authorized account representative seeking recordation of a Hg allowance...

  17. Decellularized skeletal muscle as an in vitro model for studying drug-extracellular matrix interactions.

    PubMed

    Wassenaar, Jean W; Boss, Gerry R; Christman, Karen L

    2015-09-01

    Several factors can affect drug absorption after intramuscular (IM) injection: drug solubility, drug transport across cell membranes, and drug metabolism at the injection site. We found that potential interactions between the drug and the extracellular matrix (ECM) at the injection site can also affect the rate of absorption post-injection. Using decellularized skeletal muscle, we developed a simple method to model drug absorption after IM injection, and showed that the nature of the drug-ECM interaction could be investigated by adding compounds that alter binding. We validated the model using the vitamin B12 analog cobinamide with different bound ligands. Cobinamide is being developed as an IM injectable treatment for cyanide poisoning, and we found that the in vitro binding data correlated with previously published in vivo drug absorption in animals. Commercially available ECM products, such as collagen and GelTrex, did not recapitulate drug binding behavior. While decellularized ECM has been widely studied in fields such as tissue engineering, this work establishes a novel use of skeletal muscle ECM as a potential in vitro model to study drug-ECM interactions during drug development. PMID:26125502

  18. Dispersion/Aggregation of polymer grafted nanorods in a polymer matrix studied by Dissipative Particle Dynamics

    NASA Astrophysics Data System (ADS)

    Maia, Joao; Khani, Shaghayegh

    2015-03-01

    Nanorods are incorporated into polymer matrices for fabricating composite materials with enhanced physical and mechanical properties.The final macroscopic properties of the composites are directly related to the dispersion and organization of the nanoparticles in the matrix. For instance, a significant improvement in the mechanical properties of the nanorod-polymer composites is observed upon formation of a percolating network. One way of controlling the assembly of nanorods in the polymer medium is adjusting the chemical interactions which is done through grafting polymer chains on the surface of the rods. The recent developments in the computational techniques have paved the road for further understanding of the controlled dispersion and aggregation of nanorods in polymer matrices. In this study, Dissipative Particle Dynamics (DPD) is employed in order to investigate the effect of enthalpic and entopic variables on the phase behavior of the abovementioned nanocomposites. In DPD, the interaction parameter between the components of the systems can be mapped onto the Flory-Huggins χ-parameter via well-known Groot-Warren expression. This works studies the effect of the enthalpic and entropic variables on phase transitions. The main goal is to provide a phase diagram than can be used to guide the experiments in designing new materials.

  19. Electron-impact study of PO2 using the R-matrix method

    NASA Astrophysics Data System (ADS)

    Bharadvaja, Anand; Kaur, Savinder; Baluja, K. L.

    2013-06-01

    The R-matrix approach is used to study the electron scattering from PO2 radical at low electron impact energies. The elastic scattering phenomenon is studied in static-exchange, one-state and many-states close-coupling approximation. The elastic differential cross sections, corresponding momentum-transfer cross sections, and collision frequency are calculated in the one-state configuration interaction approximation only. Calculations reveal a stable bound state of PO2- having symmetry 1A1, a configuration of ⋯8a12,⋯2b12,⋯5b22,⋯1a22, and vertical electron affinity of 2.94 eV. The excited state of anion PO2- having symmetry 3B1 is also just bound relative to the ground state of PO2 at its equilibrium geometry. The shape, core-excited, and Feshbach resonances are analyzed in different symmetries up to 7 eV. The partial waves up to l=4 are used to represent continuum electron. The converged cross sections are obtained for the partial waves having l greater than 4 by applying Born correction. Certain interesting spectroscopic properties of radical are also reported.

  20. Density matrix renormalization group study of Y-junction spin systems

    NASA Astrophysics Data System (ADS)

    Guo, Haihui

    Junction systems are important to understand both from the fundamental and the practical point of view, as they are essential components in existing and future electronic and spintronic devices. With the continuous advance of technology, device size will eventual reach the atomic scale. Some of the most interesting and useful junction systems will be strongly correlated. We chose the Density Matrix Renormalization Group method to study two types of Y-junction systems, the Y and YDelta junctions, on strongly correlated spin chains. With new ideas coming from the quantum information field, we have made a very efficient. Y-junction DMRG algorithm, which improves the overall CUB cost from O(m6) to O(m4), where m is the number of states kept per block. We studied the ground state properties, the correlation length, and investigated the degeneracy problem on the Y and YDelta junctions. For the excited states, we researched the existence of magnon bound states for various conditions, and have shown that the bound state exists when the central coupling constant is small.

  1. Parametric study of the cyclic behaviour of a hygroscopic matrix in a desiccant airflow system

    NASA Astrophysics Data System (ADS)

    Ruivo, C. R.; Costa, J. J.; Figueiredo, A. R.

    2011-09-01

    The study of the transport phenomena in desiccant airflow systems has been addressed in numerous research works, some of them concerning combined processes of cooling, dehumidification and energy recovery. In this paper a detailed numerical model is used to simulate the behaviour of a parallel-plate channel, cyclically exposed to two airflows with different inlet conditions, the plate being composed by a substrate and a desiccant porous layer. The modelled channel is considered to be representative of a real channel of a hygroscopic matrix that is operating at steady state regime, like it occurs in desiccant or enthalpy rotors. The numerical results are treated in order to represent the global behaviour of the hygroscopic rotor under steady state conditions. Results of a parametric study are presented as maps of isovalues of the heat and mass transfer rates and of the outlet states of both airflows, considering channels of distinct wall thickness, of different thickness of the desiccant and the subtract layers, together with wide ranges of the rotation speed and of the wheel partition. The mapped results presented provide an overview of the operation characteristics of hygroscopic rotors, allowing a quick determination of the optimum range of values for relevant parameters, such as the rotation speed and the wheel partition. The model is thus an interesting tool for design and manufacture purposes of enthalpy and desiccant wheels.

  2. Density matrix renormalization group study of the Anyon-Hubbard model

    NASA Astrophysics Data System (ADS)

    Arcila-Forero, J.; Franco, R.; Silva-Valencia, J.

    2016-02-01

    Recently optical lattices allow us to observe phase transition without the uncertainty posed by complex materials, and the simulations of these systems are an excellent bridge between materials-based condensed matter physics and cold atoms. In this way, the computational physics related to many-body problems have increased in importance. Using the density matrix renormalization group method, we studied a Hubbard model for anyons, which is an equivalent to a variant of the Bose-Hubbard model in which the bosonic hopping depends on the local density. This is an exact mapping between anyons and bosons in one dimension. The anyons interlope between bosons and fermions. For two anyons under particle exchange, the wave function acquires a fractional phase eiθ . We conclude that this system exhibits two phases: Mott-insulator and superfluid. We present the phase diagram for some angles. The Mott lobe increases with an increase of the statistical. We observed a reentrance phase transition for all lobes. We showed that the model studied is in the same universality class as the Bose-Hubbard model with two-body interactions.

  3. Longitudinal prospective study of matrix metalloproteinase-9 as a serum marker in gliomas.

    PubMed

    Iwamoto, Fabio M; Hottinger, Andreas F; Karimi, Sasan; Riedel, Elyn; Dantis, Jocelynn; Jahdi, Maryam; Panageas, Katherine S; Lassman, Andrew B; Abrey, Lauren E; Fleisher, Martin; Deangelis, Lisa M; Holland, Eric C; Hormigo, Adília

    2011-12-01

    The objective of this study was to evaluate if longitudinal measurements of serum matrix metalloproteinase-9 (MMP-9) correlated with disease status or survival in adults with gliomas. Serum samples were collected prospectively and concurrently with MRI scans at multiple time points during the course of the disease. MMP-9 levels were determined by ELISA and correlated with radiographic disease status and survival. Forty-one patients with low-grade gliomas, 105 with anaplastic gliomas, and 197 with glioblastoma enrolled in this study from August 2002 to September 2008. A total of 1,684 serum samples (97.1% of all MMP-9 samples) had a matching MRI scan. No statistically significant association was observed between levels of serum MMP-9 and radiographic disease status in low-grade gliomas (P = 0.98), anaplastic gliomas (P = 0.39) or glioblastomas (P = 0.33). Among patients with glioblastoma, longitudinal increases in MMP-9 had a weak association with shorter survival (HR = 1.1 per each doubling in MMP-9 levels, 95% CI, 1.0-1.3, P = 0.04) but they were not independently associated with survival when adjusted for age, extent of resection, and performance status. Changes in serum MMP-9 were not associated with survival in the anaplastic glioma cohort. Serum MMP-9 showed no utility in determining glioma disease status and was not a clinically relevant prognostic marker of survival. PMID:21710351

  4. Early Embryonic Vascular Patterning by Matrix-Mediated Paracrine Signalling: A Mathematical Model Study

    PubMed Central

    Köhn-Luque, Alvaro; de Back, Walter; Starruß, Jörn; Mattiotti, Andrea; Deutsch, Andreas; Pérez-Pomares, José María; Herrero, Miguel A.

    2011-01-01

    During embryonic vasculogenesis, endothelial precursor cells of mesodermal origin known as angioblasts assemble into a characteristic network pattern. Although a considerable amount of markers and signals involved in this process have been identified, the mechanisms underlying the coalescence of angioblasts into this reticular pattern remain unclear. Various recent studies hypothesize that autocrine regulation of the chemoattractant vascular endothelial growth factor (VEGF) is responsible for the formation of vascular networks in vitro. However, the autocrine regulation hypothesis does not fit well with reported data on in vivo early vascular development. In this study, we propose a mathematical model based on the alternative assumption that endodermal VEGF signalling activity, having a paracrine effect on adjacent angioblasts, is mediated by its binding to the extracellular matrix (ECM). Detailed morphometric analysis of simulated networks and images obtained from in vivo quail embryos reveals the model mimics the vascular patterns with high accuracy. These results show that paracrine signalling can result in the formation of fine-grained cellular networks when mediated by angioblast-produced ECM. This lends additional support to the theory that patterning during early vascular development in the vertebrate embryo is regulated by paracrine signalling. PMID:21949696

  5. Density-matrix renormalization group study of the extended Kitaev-Heisenberg model

    NASA Astrophysics Data System (ADS)

    Shinjo, Kazuya; Sota, Shigetoshi; Tohyama, Takami

    2015-02-01

    We study an extended Kitaev-Heisenberg model including additional anisotropic couplings by using the two-dimensional density-matrix renormalization group method. Calculating the ground-state energy, entanglement entropy, and spin-spin correlation functions, we make a phase diagram of the extended Kitaev-Heisenberg model around the spin-liquid phase. We find a zigzag antiferromagnetic phase, a ferromagnetic phase, a 120∘ antiferromagnetic phase, and two kinds of incommensurate phases around the Kitaev spin-liquid phase. Furthermore, we study the entanglement spectrum of the model, and we find that entanglement levels in the Kitaev spin-liquid phase are degenerate forming pairs, but those in the magnetically ordered phases are nondegenerate. The Schmidt gap defined as the energy difference between the lowest two levels changes at the phase boundary adjacent to the Kitaev spin-liquid phase. However, we find that phase boundaries between magnetically ordered phases do not necessarily agree with the change of the Schmidt gap.

  6. Shell matrix proteins of the clam, Mya truncata: Roles beyond shell formation through proteomic study.

    PubMed

    Arivalagan, Jaison; Marie, Benjamin; Sleight, Victoria A; Clark, Melody S; Berland, Sophie; Marie, Arul

    2016-06-01

    Mya truncata, a soft shell clam, is presented as a new model to study biomineralization through a proteomics approach. In this study, the shell and mantle tissue were analysed in order to retrieve knowledge about the secretion of shell matrix proteins (SMPs). Out of 67 and 127 shell and mantle proteins respectively, 16 were found in both shell and mantle. Bioinformatic analysis of SMP sequences for domain prediction revealed the presence of several new domains such as fucolectin tachylectin-4 pentraxin-1 (FTP), scavenger receptor, alpha-2-macroglobulin (α2 M), lipocalin and myosin tail along with previously reported SMP domains such as chitinase, carbonic anhydrase, tyrosinase, sushi, and chitin binding. Interestingly, these newly predicted domains are attributed with molecular functions other than biomineralization. These findings suggest that shells may not only act as protective armour from predatory action, but could also actively be related to other functions such as immunity. In this context, the roles of SMPs in biomineralization need to be looked in a new perspective. PMID:27068305

  7. Unique Hg stable isotope signatures of compact fluorescent lamp-sourced Hg.

    PubMed

    Mead, Chris; Lyons, James R; Johnson, Thomas M; Anbar, Ariel D

    2013-03-19

    The recent widespread adoption of compact fluorescent lamps (CFL) has increased their importance as a source of environmental Hg. Stable isotope analysis can identify the sources of environmental Hg, but the isotopic composition of Hg from CFL is not yet known. Results from analyses of CFL with a range of hours of use show that the Hg they contain is isotopically fractionated in a unique pattern during normal CFL operation. This fractionation is large by comparison to other known fractionating processes for Hg and has a distinctive, mass-independent signature, such that CFL Hg could be uniquely identified from other sources. The fractionation process described here may also explain anomalous fractionation of Hg isotopes in precipitation. PMID:23373764

  8. Nanoscale studies of thermal transport: R-matrix theory and thermal transport in strained graphene nanoribbons

    NASA Astrophysics Data System (ADS)

    Gunawardana, K. G. S. H.

    The rapid development of nanotechnology has enabled the fabrication of structures much smaller than the mean free path of electrons and phonons. In modern electronics, miniaturization is desired to increase the transistor density and the clock speed. Electronic transport on the nanoscale has been studied for over three decades and fascinating quantum effects have been observed. Phonon transport on this scale is of significant interest because of the increased power dissipation in nanoelectronics, which undermines the correct functionality of devices and limits their lifetime. Apart from the effort to minimize heat generation, an efficient heat management scheme is necessary. Historically, thermal transport in bulk materials was described by the Fourier's law, in which the thermal conductivity is an intrinsic property of the material. Later a more descriptive model, the Boltzmann approach for thermal transport, was developed and could explain the thermal conductivity down to a 100 nm length scale at high temperatures. At low temperatures and in structures smaller than roughly 100 nm, thermal transport is described by the fully quantum mechanical Landauer- Butticker formalism. In this context, accurate calculation of phonon transmission probabilities is very important. In this dissertation, I develop a continuum model to calculate phonon transmission probabilities between media, which have high contrast in the elastic properties. In this work, we include an interface transition layer between the two media and look for interface properties that improve thermal transport. Secondly, I develop a new theoretical tool based on the R-Matrix theory to calculate phonon transmission probabilities on the atomic scale. R-matrix theory is a well developed theoretical approach commonly used in nuclear and atomic physics to solve scattering problems. Recently, this approach has been successfully developed to calculate electronic scattering in mesoscopic quantum devices. The key

  9. Temporal and spatial trends in Hg deposition monitored by moss analysis.

    PubMed

    Steinnes, E; Berg, T; Sjøbakk, T E

    2003-03-20

    Results for Hg from a nation-wide survey of atmospheric deposition of heavy metals in Norway in 2000 are presented and compared to similar results from 1985, 1990 and 1995. The study is based on sampling of the naturally growing feather moss Hylocomium splendens at approximately 500 sites all over the country. Cold vapor AAS (1985, 1990) or atomic fluorescence spectrometry (1995, 2000) was used for Hg determinations after HNO(3) digestion of the moss samples. As different from the wet deposition of Hg and several other heavy metals in Norway the Hg concentration in moss shows no significant north-south gradient. This is explained by a considerable supply of Hg to the moss from dry deposition of Hg(0) in addition to the retention of Hg(2+) from wet deposition. Presumably the cool summer climate particularly in the middle and northern parts of the country explains that some of the Hg(0) retained in the moss is not lost by re-volatilisation. Whereas the level and geographic distribution of Hg in moss showed only small differences during 1985-1995 the 2000 data are approximately 30% lower. A satisfactory explanation of this difference remains to be found. PMID:12663185

  10. A physiologically based pharmacokinetic (PBPK) model for methyl mercury (MeHg) in monkey and human

    SciTech Connect

    Gearhart, J.M.; Clewall, H.J. III; Shipp, A.M.

    1995-12-31

    A PBPK model for MeHg was developed which coherently describes MeHg pharmacokinetics in the adult rat, monkey and man, and predicts fetal levels of MeHg from in utero exposure. The model includes a description of enterohepatic recirculation of MeHg, conversion to inorganic mercury in tissues and intestinal flora, slowly reversible incorporation of mercury in tissues, and excretion of both organic and inorganic mercury into urine, feces, and hair. The adult submodel includes compartments representing the red blood tells (RBC), plasma, brain, liver, kidney, gut intestinal lumen, gut tissue, hair, richly and slowly perfused tissues, and placenta. The fetal submodel includes compartments representing RBC`s, plasma, brain, and remaining body mass. Two features of the model structure which are critical to prediction of the kinetics of MeHg in different species is the use of separate RBC and plasma compartments, allowing the use of species specific RBC/plasma ratios, and biliary excretion with enterohepatic recirculation. Published tissue and blood MeHg concentrations were used to derive the partition coefficients and RBC/plasma ratios to adjust for species differences in MeHg distribution. Validation involved comparing the model simulations with data from repeated dosing studies in animals and humans, and from accidental human exposures. The model will be used to investigate maternal MeHg intake as it relates to measured blood and hair MeHg concentrations, and to fetal exposure.

  11. Detection of Hg2+ in water environment by fluorescence spectroscopic methods

    NASA Astrophysics Data System (ADS)

    Li, Zhen; Zhang, Jinsong; Hu, Hong; Wan, Ruyi; Yao, Youwei

    2015-08-01

    Inorganic mercury (Hg2+) produces toxic effects even at very low concentration. High sensitive fluorescent probes for Hg2+ detection has been researched and synthesized. A fluorescence detection system is built for Hg2+ detection in water environment with fluorescent probes as the detection reagent. Fiber coupled LED with high brightness is developed and used as excitation light source. And the optimized excitation wavelength is about 520 nm. The measurements of fluorescence spectra is obtained by means of optical fiber spectroscopic techniques. Fluorescence detection experiments are carried out for a range of different concentrations of Hg2+ in aqueous solutions. The center wavelength of the fluorescence spectra is about 580 nm which is unchanged in the experiments. Relationship between Hg2+ concentrations and the fluorescence intensity is studied. A positive correlation exists between the intensity of fluorescence spectrum and the concentrations of Hg2+. The fluorescence intensity grows with increasing the concentration of Hg2+ for the same excitation light. When the concentration of Hg2+ is high enough, the fluorescence intensity increases slowly. And a numerical model is built for the concentration calculating. The detection limit is 0.005 μmol/L in the experiments. The Hg2+ detection system reported has many advantages such as small size, rapid response, high-sensitivity, and can be used for on-site testing of the water quality.

  12. Numerical study of three-parameter matrix eigenvalue problem by Rayleigh quotient method

    NASA Astrophysics Data System (ADS)

    Bora, Niranjan; Baruah, Arun Kumar

    2016-06-01

    In this paper, an attempt is done to find approximate eigenvalues and the corresponding eigenvectors of three-parameter matrix eigenvalue problem by extending Rayleigh Quotient Iteration Method (RQIM), which is generally used to solve generalized eigenvalue problems of the form Ax = λBx. Convergence criteria of RQIM will be derived in terms of matrix 2-norm. We will test the computational efficiency of the Method analytically with the help of numerical examples. All calculations are done in MATLAB software.

  13. A Study of Groundwater Matrix Effects for the Destruction of Trichloroethylene Using Fe/Pd Nanoaggregates

    SciTech Connect

    meyer, D E; Hampson, Steve; ormsbee, Lindelle; Bhattacharyya, Dibakar

    2008-06-01

    Fe nanoaggregates have been prepared using the sodium borohydride reduction method and post-coated with Pd using aqueous phase electro-depostition. The Fe/Pd particles have been used to examine dechlorination of TCE with regard to matrix effects using materials representative of examine dechlorination of TCE with regard to matrix effects using materials representative of a potential zero-valent metal remediation site surrounding the Paducah Gaseous Diffusion Plant in Paducah, KY.

  14. The primitive matrix components of the unique carbonaceous chondrite Acfer 094: a TEM study.

    PubMed

    Greshake, A

    1997-01-01

    The mineralogical and chemical characteristics of the fine-grained matrix (< or = 3 micrometers) of the unique primitive carbonaceous chondrite Acfer 094 have been investigated in detail by scanning electron microscopy (SEM) and analytical transmission electron microscopy (ATEM). Generally, the fine-grained matrix represents a highly unequilibrated assemblage of an amorphous material, small forsteritic olivines (200-300 nm), low Ca-pyroxenes (300-400 nm), and Fe,Ni-sulfides (100-300 nm). The matrix is basically unaffected by secondary processes. Only minor amounts of serpentine and ferrihydrite, as products of hydrous alteration, are present. Texturally, the amorphous material acts as a groundmass to olivines, pyroxenes, and sulfides, mostly exhibiting rounded or elongated morphologies. Only very few clastic mineral grains have been found. The texture and chemical composition of the amorphous material are consistent with an origin by disequilibrium condensation in either the cooling solar nebula or a circumstellar environment. As such, the amorphous material may be considered as a possible precursor of matrix materials in other types of chondrites. The non-clastic matrix olivines (Fo98-99) and pyroxenes (En97-100) are suggested to have formed either by condensation in the solar nebula under highly oxidizing conditions or by recrystallization from the amorphous material. The formation of these grains by fragmentation of chondrule components is unlikely due to chemical and microstructural reasons. Rapid cooling caused the observed intergrowths of clino/orthoenstatite in the Mg-rich matrix pyroxenes. Although some similarities exist comparing the fine-grained matrix of Acfer 094 with the matrices of the unequilibrated CO3 chondrite ALHA77307 and the unique type 3 chondrite Kakangari, Acfer 094 remains unique. Since it contains the highest measured concentrations of circumstellar SiC and the second highest of diamond (highest is Orgueil), it seems reasonable to

  15. Numerical study of a matrix-free trust-region SQP method for equality constrained optimization.

    SciTech Connect

    Heinkenschloss, Matthias; Ridzal, Denis; Aguilo, Miguel Antonio

    2011-12-01

    This is a companion publication to the paper 'A Matrix-Free Trust-Region SQP Algorithm for Equality Constrained Optimization' [11]. In [11], we develop and analyze a trust-region sequential quadratic programming (SQP) method that supports the matrix-free (iterative, in-exact) solution of linear systems. In this report, we document the numerical behavior of the algorithm applied to a variety of equality constrained optimization problems, with constraints given by partial differential equations (PDEs).

  16. Evaluating the role of re-adsorption of dissolved Hg(2+) during cinnabar dissolution using isotope tracer technique.

    PubMed

    Jiang, Ping; Li, Yanbin; Liu, Guangliang; Yang, Guidi; Lagos, Leonel; Yin, Yongguang; Gu, Baohua; Jiang, Guibin; Cai, Yong

    2016-11-01

    Cinnabar dissolution is an important factor controlling mercury (Hg) cycling. Recent studies have suggested the co-occurrence of re-adsorption of the released Hg during the course of cinnabar dissolution. However, there is a lack of feasible techniques that can quantitatively assess the amount of Hg re-adsorbed on cinnabar when investigating cinnabar dissolution. In this study, a new method, based on isotope tracing and dilution techniques, was developed to study the role of Hg re-adsorption in cinnabar dissolution. The developed method includes two key components: (1) accurate measurement of both released and spiked Hg in aqueous phase and (2) estimation of re-adsorbed Hg on cinnabar surface via the reduction in spiked (202)Hg(2+). By adopting the developed method, it was found that the released Hg for trials purged with oxygen could reach several hundred μgL(-1), while no significant cinnabar dissolution was detected under anaerobic condition. Cinnabar dissolution rate when considering Hg re-adsorption was approximately 2 times the value calculated solely with the Hg detected in the aqueous phase. These results suggest that ignoring the Hg re-adsorption process can significantly underestimate the importance of cinnabar dissolution, highlighting the necessity of applying the developed method in future cinnabar dissolution studies. PMID:27322904

  17. A study of rock matrix diffusion properties by electrical conductivity measurements

    SciTech Connect

    Ohlsson, Y.; Neretnieks, I.

    1999-07-01

    Traditional rock matrix diffusion experiments on crystalline rock are very time consuming due to the low porosity and extensive analysis requirements. Electrical conductivity measurements are, on the other hand, very fast and larger samples can be used than are practical in ordinary diffusion experiments. The effective diffusivity of a non-charged molecule is readily evaluated from the measurements, and influences from surface conductivity on diffusion of cations can be studied. A large number of samples of varying thickness can be measured within a short period, and the changes in transport properties with position in a rock core can be examined. In this study the formation factor of a large number of Aespoe diorite samples is determined by electrical conductivity measurements. The formation factor is a geometric factor defined as the ratio between the effective diffusivity of a non-charged molecule, to that of the same molecule in free liquid. The variation of this factor with position among a borecore and with sample length, and its coupling to the porosity of the sample is studied. Also the surface conductivity is studied. This was determined as the residual conductivity after leaching of the pore solution ions. The formation factor of most of the samples is in the range 1E-5 to 1E-4, with a mean value of about 5E-5. Even large samples (4--13 cm) give such values. The formation factor increases with increasing porosity and the change in both formation factor and porosity with position in the borecore can be large, even for samples close to each other. The surface conductivity increases with increasing formation factor for the various samples but the influence on the pore diffusion seems to be higher for samples of lower formation factor. This suggests that the relation between the pore surface area and the pore volume is larger for samples of low formation factor.

  18. Study on Different Molecular Weights of Chitosan as an Immobilization Matrix for a Glucose Biosensor

    PubMed Central

    Ang, Lee Fung; Por, Lip Yee; Yam, Mun Fei

    2013-01-01

    Two chitosan samples (medium molecular weight (MMCHI) and low molecular weight (LMCHI)) were investigated as an enzyme immobilization matrix for the fabrication of a glucose biosensor. Chitosan membranes prepared from acetic acid were flexible, transparent, smooth and quick-drying. The FTIR spectra showed the existence of intermolecular interactions between chitosan and glucose oxidase (GOD). Higher catalytic activities were observed on for GOD-MMCHI than GOD-LMCHI and for those crosslinked with glutaraldehyde than using the adsorption technique. Enzyme loading greater than 0.6 mg decreased the activity. Under optimum conditions (pH 6.0, 35°C and applied potential of 0.6 V) response times of 85 s and 65 s were observed for medium molecular weight chitosan glucose biosensor (GOD-MMCHI/PT) and low molecular weight chitosan glucose biosensor (GOD-LMCHI/PT), respectively. The apparent Michaelis-Menten constant () was found to be 12.737 mM for GOD-MMCHI/PT and 17.692 mM for GOD-LMCHI/PT. This indicated that GOD-MMCHI/PT had greater affinity for the enzyme. Moreover, GOD-MMCHI/PT showed higher sensitivity (52.3666 nA/mM glucose) when compared with GOD-LMCHI/PT (9.8579 nA/mM glucose) at S/N>3. Better repeatability and reproducibility were achieved with GOD-MMCHI/PT than GOD-LMCHI/PT regarding glucose measurement. GOD-MMCHI/PT was found to give the highest enzymatic activity among the electrodes under investigation. The extent of interference encountered by GOD-MMCHI/PT and GOD-LMCHI/PT was not significantly different. Although the Nafion coated biosensor significantly reduced the signal due to the interferents under study, it also significantly reduced the response to glucose. The performance of the biosensors in the determination of glucose in rat serum was evaluated. Comparatively better accuracy and recovery results were obtained for GOD-MMCHI/PT. Hence, GOD-MMCHI/PT showed a better performance when compared with GOD-LMCHI/PT. In conclusion, chitosan membranes shave

  19. Optical and TDPAC spectroscopy of Hg(II)-rubredoxin: model for a mononuclear tetrahedral [Hg(CysS)4]2- center. ISOLDE Collaboration.

    PubMed

    Faller, P; Ctortecka, B; Tröger, W; Butz, T; Vasák, M

    2000-06-01

    Rubredoxins possess a well-defined mononuclear tetrahedral tetrathiolate metal binding site, a feature exploited by several investigations to study the spectroscopic characteristics and the coordination chemistry of different metal ions at this binding site. In the present work, Hg(II)-substituted rubredoxin (Rd) from Desulfovibrio gigas has been studied by electronic absorption, circular dichroism (CD), magnetic circular dichroism (MCD), and time differential perturbed angular correlation of gamma-rays (TDPAC) spectroscopies. The TDPAC spectrum of 199mHg-Rd at pH 8 exhibits a prevailing nuclear quadrupole interaction (NQI) with a precession frequency of omega1=0.09 Grad/s and an asymmetry parameter eta=0, features characteristic of a slightly distorted tetrahedral tetrathiolate metal coordination, i.e, a HgCysS4 center. In addition, three minor populated NQIs have also been detected. They may represent a trigonal HgS3 (omega1=1.13 Grad/s, eta=0.21), a digonal HgS2 (omega1= 1.34 Grad/s, eta =0.20), and a digonal Hg(II) coordination (omega = 1.58 Grad/s, eta =0.18) with unidentified ligands. Since similar studies at pH 2.5 revealed a time-dependent increase of the HgCysS4 population, the low populated sites may represent intermediate Hg(II) complexes formed prior to the generation of the thermodynamically stable structure. The metal-induced absorption envelope of Hg-Rd reveals three distinct transitions with Gaussian-resolved maxima located at 230, 257, and 284 nm, which are paralleled by dichroic features in the corresponding difference CD spectrum of Hg(II)-Rd versus apo-Rd. Based on the optical electronegativity theory of J*rgensen, the lowest energy transition has been attributed to a CysS-Hg(II) charge-transfer excitation. The Td type of metal coordination in Hg-Rd is supported by the presence of an unresolved A-term with a negative lobe at 295 nm in the difference MCD spectrum. These results point to the usefulness of optical and TDPAC spectroscopies for

  20. Effect of carboxylic and thiol ligands (oxalate, cysteine) on the kinetics of desorption of Hg(II) from kaolinite

    SciTech Connect

    Senevirathna, W. U.; Zhang, Hong; Gu, Baohua

    2010-01-01

    Sorption and desorption of Hg(II) on clay minerals can impact the biogeochemical cycle and bio-uptake of Hg in the environment. We studied the kinetics of the desorption of Hg(II) from kaolinite as affected by oxalate and cysteine, representing the ligands with carboxylic and thiol groups of different affinities for Hg(II). The effects of pH (3, 5, and 7), ligand concentration (0.25 and 1.0 mM), and temperature (15 C, 25 C, and 35 C) on the Hg(II) desorption were investigated through desorption kinetics. Our study showed that the Hg(II) desorption was pH dependent. In the absence of any organic ligand, >90% of the previously adsorbed Hg(II) desorbed at pH 3 within 2 h, compared to <10% at pH 7. Similar results were observed in the presence of oxalate, showing that it hardly affected the Hg(II) desorption. Cysteine inhibited the Hg(II) desorption significantly at all the pH tested, especially in the first 80 min with the desorption less than 20%, but the inhibition of the desorption appeared to be less prominent afterwards. The effect of the ligand concentration on the Hg(II) desorption was small, especially in the presence of oxalate. The effect of temperature on the Hg(II) desorption was nearly insignificant. The effect of the organic acids on the Hg(II) sorption and desorption is explained by the formation of the ternary surface complexes involving the mineral, ligand, and Hg(II). The competition for Hg(II) between the cysteine molecules adsorbed on the particle surfaces and in the solution phase probably can also affect the Hg(II) desorption.

  1. From Nano to Macro: Studying the Hierarchical Structure of the Corneal Extracellular Matrix

    PubMed Central

    Quantock, Andrew J.; Winkler, Moritz; Parfitt, Geraint J.; Young, Robert D.; Brown, Donald J.; Boote, Craig; Jester, James V.

    2014-01-01

    In this review, we discuss current methods for studying ocular extracellular matrix (ECM) assembly from the ‘nano’ to the ‘macro’ levels of hierarchical organization. Since collagen is the major structural protein in the eye, providing mechanical strength and controlling ocular shape, the methods presented focus on understanding the molecular assembly of collagen at the nanometer level using x-ray scattering through to the millimeter to centimeter level using nonlinear optical (NLO) imaging of second harmonic generated (SHG) signals. Three-dimensional analysis of ECM structure is also discussed, including electron tomography, serial block face scanning electron microscopy (SBF-SEM) and digital image reconstruction. Techniques to detect non-collagenous structural components of the ECM are also presented, and these include immunoelectron microscopy and staining with cationic dyes. Together, these various approaches are providing new insights into the structural blueprint of the ocular ECM, and in particular that of the cornea, which impacts upon our current understanding of the control of corneal shape, pathogenic mechanisms underlying ectatic disorders of the cornea and the potential for corneal tissue engineering. PMID:25819457

  2. Sorption and diffusion of radionuclides in rock matrix and natural fracture surfaces studied by autoradiography

    SciTech Connect

    Muuronen, S.; Kaemaeraeinen, E.L.; Jaakkola, T.; Pinnioja, S.; Lindberg, A.

    1986-01-01

    A method based on autoradiography was developed to determine the sorption and diffusion of cesium, strontium, cobalt, nickel, iodine and americium into rock matrix. Samples chosen for this study were filled and unfilled natural fracture surfaces and drill cores having a central drilled hole (drill core cups). Rock types were mica gneiss, tonalite and rapakivi granite, which were selected to represent the common rocks and minerals in Finnish bedrock. Distribution coefficients (K/sub a/-values) of cesium and strontium determined for fissure surfaces and drill core cups were of the same order of magnitude. After three months contact time the greatest penetration depth for cesium was 2.5 mm, for a natural fissure surface sample of rapakivi granite. For strontium the penetration depths of 11 mm in three months and 35 mm in twelve months were found for filled natural fissure surface samples of rapakivi granite. The range of D/sub a/-values was 1.5 x 10/sup -15/ - 3.2 x 10/sup -14/ m/sup 2//s and 1.4 x 10/sup -14/ - 2.1 x 10/sup -13/ m/sup 2//s for cesium and strontium, resp. For cobalt the D/sub a/-values of 5 x 10/sup -16/ m/sup 2//s in tonalite was obtained. In six months the penetration depths of nickel, iodine and americium were too low (<0.5 mm) to allow calculation of D/sub a/.

  3. Hyaluronan based hydrogels provide an improved model to study megakaryocyte-matrix interactions.

    PubMed

    Currao, Manuela; Malara, Alessandro; Di Buduo, Christian A; Abbonante, Vittorio; Tozzi, Lorenzo; Balduini, Alessandra

    2016-08-01

    Hyaluronan (HA) is a glycosamminoglican involved in cell biology as well as a relevant polymer for tissue engineering and regenerative medicine. Megakaryocytes (Mks) are immersed in a mesh of extracellular matrix (ECM) components that regulate their maturation in the bone marrow (BM) and the release of platelets into the bloodstream. While fibrous ECMs such as collagens and fibronectin have been demonstrated to differently regulate Mk function and platelet release, the role of HA, that fills the majority of the BM extracellular interstitial space, has not been investigated so far. Here we demonstrated that, although human Mks express HA receptors, they are not affected by HA in terms of in vitro differentiation, maturation and platelet formation. Importantly, chemical properties of HA were exploited to generate hydrogels with entrapped ECMs that represent a useful model to more closely mimic the tridimensional characteristics of the BM environment for studying Mk function. In conclusion, in this work we demonstrated that HA is an ideal candidate for a 3D ex vivo model of human BM ECM component environment. PMID:26027944

  4. Blade system design studies volume II : preliminary blade designs and recommended test matrix.

    SciTech Connect

    Griffin, Dayton A.

    2004-06-01

    As part of the U.S. Department of Energy's Wind Partnerships for Advanced Component Technologies (WindPACT) program, Global Energy Concepts, LLC is performing a Blade System Design Study (BSDS) concerning innovations in materials, processes and structural configurations for application to wind turbine blades in the multi-megawatt range. The BSDS Volume I project report addresses issues and constraints identified to scaling conventional blade designs to the megawatt size range, and evaluated candidate materials, manufacturing and design innovations for overcoming and improving large blade economics. The current report (Volume II), presents additional discussion of materials and manufacturing issues for large blades, including a summary of current trends in commercial blade manufacturing. Specifications are then developed to guide the preliminary design of MW-scale blades. Using preliminary design calculations for a 3.0 MW blade, parametric analyses are performed to quantify the potential benefits in stiffness and decreased gravity loading by replacement of a baseline fiberglass spar with carbon-fiberglass hybrid material. Complete preliminary designs are then presented for 3.0 MW and 5.0 MW blades that incorporate fiberglass-to-carbon transitions at mid-span. Based on analysis of these designs, technical issues are identified and discussed. Finally, recommendations are made for composites testing under Part I1 of the BSDS, and the initial planned test matrix for that program is presented.

  5. Number of CuO2 layers dependence of magnetic quantum criticality in homogeneously doped high-T copper oxides: A 63Cu-NMR study on four-layered high-T compounds HgBa2Ca3Cu4O8+y

    NASA Astrophysics Data System (ADS)

    Itohara, Keita; Shimizu, Sunao; Mukuda, Hidekazu; Kitaoka, Yoshio; Shirage, Parasharam M.; Kito, Hijiri; Iyo, Akira

    2010-12-01

    We report 63Cu-NMR/NQR studies on Hg-based four-layered compounds HgBa2Ca3Cu4 O8+y (Hg-1234) with T=123, 110, and 95 K. The 63Cu Knight shift measurements have revealed that the carrier density (N) monotonously decreases with decreasing T. Although static magnetic order was not observed at N=0.15 for the IP with T=95K, it was revealed that antiferromagnetic correlations critically develop, preventing from observing the NMR spectrum below ˜200 K far above T. Thus, we deduce that a magnetic quantum critical point, where an AFM order collapses, may exist at slightly less than N˜0.15 in the Hg-based four-layered compounds, which is lower than that in Hg-based five-layered compounds, N˜0.17. This result suggests that a magnetic interlayer coupling, which stabilizes an AFM order, becomes weaker in the four-layered compounds than in five-layered compounds.

  6. Quasiparticle band structure of HgSe

    SciTech Connect

    Rohlfing, M.; Louie, S.G.

    1998-04-01

    Motivated by a recent discussion about the existence of a fundamental gap in HgSe [Phys. Rev. Lett. {bold 78}, 3165 (1997)], we calculate the quasiparticle band structure of HgSe within the GW approximation for the electron self-energy. The band-structure results show that HgSe is a semimetal, which is in agreement with most experimental data. We observe a strong wave-vector dependence of the self-energy of the lowest conduction band, leading to an increased dispersion and a small effective mass. This may help to interpret recent photoemission spectroscopy measurements. {copyright} {ital 1998} {ital The American Physical Society}

  7. A Study of Influencing Factors on the Tensile Response of a Titanium Matrix Composite With Weak Interfacial Bonding

    NASA Technical Reports Server (NTRS)

    Goldberg, Robert K.; Arnold, Steven M.

    2000-01-01

    The generalized method of cells micromechanics model is utilized to analyze the tensile stress-strain response of a representative titanium matrix composite with weak interfacial bonding. The fiber/matrix interface is modeled through application of a displacement discontinuity between the fiber and matrix once a critical debonding stress has been exceeded. Unidirectional composites with loading parallel and perpendicular to the fibers are examined, as well as a cross-ply laminate. For each of the laminates studied, analytically obtained results are compared to experimental data. The application of residual stresses through a cool-down process was found to have a significant effect on the tensile response. For the unidirectional laminate with loading applied perpendicular to the fibers, fiber packing and fiber shape were shown to have a significant effect on the predicted tensile response. Furthermore, the interface was characterized through the use of semi-emperical parameters including an interfacial compliance and a "debond stress;" defined as the stress level across the interface which activates fiber/matrix debonding. The results in this paper demonstrate that if architectural factors are correctly accounted for and the interface is appropriately characterized, the macro-level composite behavior can be correctly predicted without modifying any of the fiber or matrix constituent properties.

  8. Growth factor-rich plasma increases tendon cell proliferation and matrix synthesis on a synthetic scaffold: an in vitro study.

    PubMed

    Visser, Lance C; Arnoczky, Steven P; Caballero, Oscar; Kern, Andreas; Ratcliffe, Anthony; Gardner, Keri L

    2010-03-01

    Numerous scaffolds have been proposed for use in connective tissue engineering. Although these scaffolds direct cell migration and attachment, many are biologically inert and thus lack the physiological stimulus to attract cells and induce mitogenesis and matrix synthesis. In the current study, a bioactive scaffold was created by combining a synthetic scaffold with growth factor-rich plasma (GFRP), an autologous concentration of growth factors derived from a platelet-rich plasma preparation. In vitro tendon cell proliferation and matrix synthesis on autologous GFRP-enriched scaffolds, autologous serum-enriched scaffolds, and scaffolds alone were compared. The GFRP preparation was found to have a 4.7-fold greater concentration of a sentinel growth factor (transforming growth factor-beta1) compared with serum. When combined with media containing calcium, the GFRP produced a thin fibrin matrix over and within the GFRP-enriched scaffolds. Cell proliferation assays demonstrated that GFRP-enriched scaffolds significantly enhanced cell proliferation over autologous serum and control groups at both 48 and 72 h. Analysis of the scaffolds at 14, 21, and 28 days revealed that GFRP-enriched scaffolds significantly increased the deposition of a collagen-rich extracellular matrix when compared with the other groups. These results indicate that GFRP can be used to enhance in vitro cellular population and matrix deposition of tissue-engineered scaffolds. PMID:19839921

  9. Mercury (Hg) in meteorites: Variations in abundance, thermal release profile, mass-dependent and mass-independent isotopic fractionation

    NASA Astrophysics Data System (ADS)

    Meier, Matthias M. M.; Cloquet, Christophe; Marty, Bernard

    2016-06-01

    We have measured the concentration, isotopic composition and thermal release profiles of Mercury (Hg) in a suite of meteorites, including both chondrites and achondrites. We find large variations in Hg concentration between different meteorites (ca. 10 ppb to 14,000 ppb), with the highest concentration orders of magnitude above the expected bulk solar system silicates value. From the presence of several different Hg carrier phases in thermal release profiles (150-650 °C), we argue that these variations are unlikely to be mainly due to terrestrial contamination. The Hg abundance of meteorites shows no correlation with petrographic type, or mass-dependent fractionation of Hg isotopes. Most carbonaceous chondrites show mass-independent enrichments in the odd-numbered isotopes 199Hg and 201Hg. We show that the enrichments are not nucleosynthetic, as we do not find corresponding nucleosynthetic deficits of 196Hg. Instead, they can partially be explained by Hg evaporation and redeposition during heating of asteroids from primordial radionuclides and late-stage impact heating. Non-carbonaceous chondrites, most achondrites and the Earth do not show these enrichments in vapor-phase Hg. All meteorites studied here have however isotopically light Hg (δ202Hg = ∼-7 to -1) relative to the Earth's average crustal values, which could suggest that the Earth has lost a significant fraction of its primordial Hg. However, the late accretion of carbonaceous chondritic material on the order of ∼2%, which has been suggested to account for the water, carbon, nitrogen and noble gas inventories of the Earth, can also contribute most or all of the Earth's current Hg budget. In this case, the isotopically heavy Hg of the Earth's crust would have to be the result of isotopic fractionation between surface and deep-Earth reservoirs.

  10. Study of the effect of interface slip and diffusion mechanisms on the creep of metal and intermetallic matrix composites

    NASA Astrophysics Data System (ADS)

    Nimmagadda, Prasad B. R.

    2000-09-01

    Experimental results indicate that, in general, at modest temperatures the creep strength of metal and intermetallic matrix composites is better than that of the matrix material alone. However, at temperatures higher than approximately half the melting temperature of the matrix, the composite strength is limited and in some cases the strengthening imparted by the reinforcements is completely lost despite the absence of any debonding or damage accumulation along the matrix-reinforcement interface. Slip and diffusional flow along the interface, driven by the gradient in the normal stress, are suggested as mechanisms responsible for the loss of strengthening. The composite behavior is investigated by coupling the interface diffusion and slip mechanisms with the power-law creep of the matrix. The steady state creep strength of a continuous fiber composite under transverse loading and a discontinuous fiber composite under axial loading are investigated. In the case of discontinuous fiber reinforced composites with a diffusive interface, the critical fiber aspect ratio needed for the composite to be stronger than the pure matrix is obtained. The two relaxation mechanisms are used to explain the temperature dependence of the strength of gamma-TiAl matrix reinforced with Ti 2AlC particles. A methodology is suggested for extracting the properties of the interface combining the experimental measurements of the composite creep strength with the corresponding finite element based strength predictions. The strength of the leading order singularity and the angular variation of the solution within a constant around the sharp corner of a discontinuous fiber are obtained in an asymptotic study. By comparing the asymptotic and the finite element solutions the value of this constant and the region of dominance for the singular solution are obtained. The region of dominance is found to be only of the order of 5 x 10-4 times the fiber radius. The influence of the two mechanisms on the

  11. Studies of Structure and Phase Transition in [C(NH2)3]HgBr3 and [C(NH2)3]HgI3 by Means of Halogen NQR, 1H NMR, and Single Crystal X-Ray Diffraction

    NASA Astrophysics Data System (ADS)

    Terao, Hiromitsu; Hashimoto, Masao; Hashimoto, Shinichi; Furukawa, Yoshihiro

    2000-02-01

    The crystal structure of [C(NH2)3]HgBr3 was determined at room temperature: monoclinic, space group C2/c, Z = 4, a = 775.0(2), b = 1564.6(2), c = 772.7(2) pm, β = 109.12(2)°. In the crystal, almost planar HgBr3- ions are connected via Hg ··· Br bonds, resulting in single chains of trigonal bipyramidal HgBr5 units which run along the c direction. [C(NH2)3]HgI3 was found to be isomorphous with the bromide at room temperature. The temperature dependence of the halogen NQR frequencies (77 < 77K < ca. 380) and the DTA measurements evidenced no phase transition for the bromide, but a second-order phase transition at (251 ± 1) K (Tc1) and a first-order one at (210 ± 1) K for the iodide. The transitions at Tc2are accompanied with strong supercooling and significant superheating. The room temperature phase (RTP) and the intermediate temperature phase (ITP) of the iodide are characterized by two 127I(m=1/2↔3/2) NQR lines which are assigned to the terminal and the bridging I atoms, respectively. There exist three lines in the lowest temperature phase (LTP), indicating that the resonance line of the bridging atom splits into two. The signal intensities of the 127I(m =1/2↔3/2) NQR lines in the LTP decrease with decreasing temperature resulting in no detection below ca. 100 K. The 127I(m=1/2↔3/2) NQR frequency vs. temperature curves are continuous at Tcl, but they are unusual in the LTP. The T1vs. Tcurves of 1H NMR for the bromide and iodide are explainable by the reorientational motions of the cations about their pseudo three-fold axes. The estimated activation energies of the motions are 35.0 kJ/mol for the bromide, and 24.1, 30.1, and 23.0 kJ/mol for the RTP, FTP, and LTP of the iodide, respectively

  12. A comparative study of matrix remodeling in chronic models for COPD; mechanistic insights into the role of TNF-α.

    PubMed

    Eurlings, Irene M J; Dentener, Mieke A; Mercken, Evi M; de Cabo, Rafael; Bracke, Ken R; Vernooy, Juanita H J; Wouters, Emiel F M; Reynaert, Niki L

    2014-10-01

    Remodeling in chronic obstructive pulmonary disease (COPD) has at least two dimensions: small airway wall thickening and destruction of alveolar walls. Recently we showed comparable alterations of the extracellular matrix (ECM) compounds collagen, hyaluoran, and elastin in alveolar and small airway walls of COPD patients. The aim of this study was to characterize and assess similarities in alveolar and small airway wall matrix remodeling in chronic COPD models. From this comparative characterization of matrix remodeling we derived and elaborated underlying mechanisms to the matrix changes reported in COPD. Lung tissue sections of chronic models for COPD, either induced by exposure to cigarette smoke, chronic intratracheal lipopolysaccharide instillation, or local tumor necrosis factor (TNF) expression [surfactant protein C (SPC)-TNFα mice], were stained for elastin, collagen, and hyaluronan. Furthermore TNF-α matrix metalloproteinase (MMP)-2, -9, and -12 mRNA expression was analyzed using qPCR and localized using immunohistochemistry. Both collagen and hyaluronan were increased in alveolar and small airway walls of all three models. Interestingly, elastin contents were differentially affected, with a decrease in both alveolar and airway walls in SPC-TNFα mice. Furthermore TNF-α and MMP-2 and -9 mRNA and protein levels were found to be increased in alveolar walls and around airway walls only in SPC-TNFα mice. We show that only SPC-TNFα mice show changes in elastin remodeling that are comparable to what has been observed in COPD patients. This reveals that the SPC-TNFα model is a suitable model to study processes underlying matrix remodeling and in particular elastin breakdown as seen in COPD. Furthermore we indicate a possible role for MMP-2 and MMP-9 in the breakdown of elastin in airways and alveoli of SPC-TNFα mice. PMID:25106431

  13. The construction and testing of the portable Hg(2+) ultrasonic calibrator for the control of mercury speciation systems.

    PubMed

    Gorecki, Jerzy; Okonska, Anna

    2016-01-15

    During fuel combustion mercury, as Hg(0) and Hg(2+) forms, is emitted to the atmosphere. Effective reduction of mercury emission requires applying speciation systems for emission control and research. An important part of all mercury determination and speciation systems are the calibrators. Calibrators are responsible for the accuracy of mercury determination and, in consequence, the effective reduction of mercury emission. The aim of the work was to construct a portable HgCl2 calibrator. The purpose of the device was the control of mercury speciation systems for continuous measurements and study of HgCl2 sorption. As a result of previously conducted research, the portable Hg(2+) ultrasonic calibrator was designed, constructed and tested. The ultrasonic calibrator generates a stable stream of HgCl2 (RSD=2.8% for CHg=28µg/m(3)). The correlation between theoretical and reading concentration of HgCl2 was R(2)=0.9983. The average recovery of HgCl2 was 95%. The advantages of the ultrasonic Hg(2+) calibrator are: high accuracy and selectivity, low pressure of HgCl2 stream and very low cost of production. The calibrator was successfully tested, both in the laboratory and in the power plant, during a preliminary study on HgCl2 sorption on a fly ash filter. PMID:26592572

  14. A Biodegradable Polyurethane Dermal Matrix in Reconstruction of Free Flap Donor Sites: A Pilot Study

    PubMed Central

    Wagstaff, Marcus J.D.; Schmitt, Bradley J.; Coghlan, Patrick; Finkemeyer, James P.; Caplash, Yugesh

    2015-01-01

    We have developed a biodegradable temporizing matrix (BTM) capable of supporting secondary split-skin graft-take in animal studies. We report its first long-term implantation and use as a dermal scaffold in humans. This preliminary study assesses its ability to integrate, its ease of delamination, its ability to sustain split-skin graft in complex wounds, the degree of wound contraction, and ultimately the quality of the scar at 1 year postimplantation. Ten patients were recruited, each requiring elective free flap reconstruction. Free flap donor sites created were anterolateral thigh flaps, fibular osseocutaneous flaps, or radial/ulnar forearm (RF/UF) flaps. The BTM was implanted when the flap was detached from its donor site. Dressing changes were performed twice weekly. The time elapsed between implantation and delamination depended on the type of flap and thus the wound bed left. Once integrated, the BTMs were delaminated in theatre, and the surface of the “neodermis” was refreshed by dermabrasion, prior to application of a split-skin graft. The BTM integration occurred in all patients (100% in 6 patients, with 90%, 84%, 76%, and 60% integration in the remainder). Integrated BTM sustained successful graft-take in all patients. Complete take was marred in 2 patients, over areas of BTM that had not integrated and graft application was performed too early. The BTM can be applied into wounds in humans and can integrate, persist in the presence of infection, and sustain split-skin overgrafting, despite the trial group presenting with significant comorbidities. PMID:25987938

  15. Many-body localization and transition by density matrix renormalization group and exact diagonalization studies

    NASA Astrophysics Data System (ADS)

    Lim, S. P.; Sheng, D. N.

    2016-07-01

    A many-body localized (MBL) state is a new state of matter emerging in a disordered interacting system at high-energy densities through a disorder-driven dynamic phase transition. The nature of the phase transition and the evolution of the MBL phase near the transition are the focus of intense theoretical studies with open issues in the field. We develop an entanglement density matrix renormalization group (En-DMRG) algorithm to accurately target highly excited states for MBL systems. By studying the one-dimensional Heisenberg spin chain in a random field, we demonstrate the accuracy of the method in obtaining energy eigenstates and the corresponding statistical results of quantum states in the MBL phase. Based on large system simulations by En-DMRG for excited states, we demonstrate some interesting features in the entanglement entropy distribution function, which is characterized by two peaks: one at zero and another one at the quantized entropy S =ln2 with an exponential decay tail on the S >ln2 side. Combining En-DMRG with exact diagonalization simulations, we demonstrate that the transition from the MBL phase to the delocalized ergodic phase is driven by rare events where the locally entangled spin pairs develop power-law correlations. The corresponding phase diagram contains an intermediate or crossover regime, which has power-law spin-z correlations resulting from contributions of the rare events. We discuss the physical picture for the numerical observations in this regime, where various distribution functions are distinctly different from results deep in the ergodic and MBL phases for finite-size systems. Our results may provide new insights for understanding the phase transition in such systems.

  16. A biodegradable polyurethane dermal matrix in reconstruction of free flap donor sites: a pilot study.

    PubMed

    Wagstaff, Marcus J D; Schmitt, Bradley J; Coghlan, Patrick; Finkemeyer, James P; Caplash, Yugesh; Greenwood, John E

    2015-01-01

    We have developed a biodegradable temporizing matrix (BTM) capable of supporting secondary split-skin graft-take in animal studies. We report its first long-term implantation and use as a dermal scaffold in humans. This preliminary study assesses its ability to integrate, its ease of delamination, its ability to sustain split-skin graft in complex wounds, the degree of wound contraction, and ultimately the quality of the scar at 1 year postimplantation. Ten patients were recruited, each requiring elective free flap reconstruction. Free flap donor sites created were anterolateral thigh flaps, fibular osseocutaneous flaps, or radial/ulnar forearm (RF/UF) flaps. The BTM was implanted when the flap was detached from its donor site. Dressing changes were performed twice weekly. The time elapsed between implantation and delamination depended on the type of flap and thus the wound bed left. Once integrated, the BTMs were delaminated in theatre, and the surface of the "neodermis" was refreshed by dermabrasion, prior to application of a split-skin graft. The BTM integration occurred in all patients (100% in 6 patients, with 90%, 84%, 76%, and 60% integration in the remainder). Integrated BTM sustained successful graft-take in all patients. Complete take was marred in 2 patients, over areas of BTM that had not integrated and graft application was performed too early. The BTM can be applied into wounds in humans and can integrate, persist in the presence of infection, and sustain split-skin overgrafting, despite the trial group presenting with significant comorbidities. PMID:25987938

  17. Ab initio density matrix renormalization group study of magnetic coupling in dinuclear iron and chromium complexes

    SciTech Connect

    Harris, Travis V.; Morokuma, Keiji; Kurashige, Yuki; Yanai, Takeshi

    2014-02-07

    The applicability of ab initio multireference wavefunction-based methods to the study of magnetic complexes has been restricted by the quickly rising active-space requirements of oligonuclear systems and dinuclear complexes with S > 1 spin centers. Ab initio density matrix renormalization group (DMRG) methods built upon an efficient parameterization of the correlation network enable the use of much larger active spaces, and therefore may offer a way forward. Here, we apply DMRG-CASSCF to the dinuclear complexes [Fe{sub 2}OCl{sub 6}]{sup 2−} and [Cr{sub 2}O(NH{sub 3}){sub 10}]{sup 4+}. After developing the methodology through systematic basis set and DMRG M testing, we explore the effects of extended active spaces that are beyond the limit of conventional methods. We find that DMRG-CASSCF with active spaces including the metal d orbitals, occupied bridging-ligand orbitals, and their virtual double shells already capture a major portion of the dynamic correlation effects, accurately reproducing the experimental magnetic coupling constant (J) of [Fe{sub 2}OCl{sub 6}]{sup 2−} with (16e,26o), and considerably improving the smaller active space results for [Cr{sub 2}O(NH{sub 3}){sub 10}]{sup 4+} with (12e,32o). For comparison, we perform conventional MRCI+Q calculations and find the J values to be consistent with those from DMRG-CASSCF. In contrast to previous studies, the higher spin states of the two systems show similar deviations from the Heisenberg spectrum, regardless of the computational method.

  18. Elevated blood Hg at recommended seafood consumption rates in adult seafood consumers.

    PubMed

    Karimi, Roxanne; Silbernagel, Susan; Fisher, Nicholas S; Meliker, Jaymie R

    2014-09-01

    Mercury (Hg) exposure from seafood continues to be a public health concern due to health effects from elevated exposure, increasing worldwide seafood consumption, and continued Hg inputs into the environment. Elevated Hg exposure can occur in populations with specialized diets of sport-caught freshwater fish. However, we need a better understanding of Hg exposure from seafood, the most common exposure source, and from specific seafood types. We examined Hg exposure in avid seafood consumers, and the seafood items and consumption frequency that confer the largest Hg exposure. Adult, avid seafood consumers, in Long Island, NY, USA, with blood total Hg concentrations predicted to exceed the USEPA reference concentration that is considered safe (5.8 μg L(-1)), were eligible for the study; 75% of self-reported avid seafood consumers were eligible to participate. We measured blood total Hg concentrations and seafood consumption in 285 participants. We examined relationships between Hg and seafood consumption using multiple linear regression. Seafood consumption rate for our population (14.4 kg yr(-1)) was >2 times that estimated for the U.S. (6.8 kg yr(-1)), and lower than the worldwide estimate (18.4 kg yr(-1)). Mean blood Hg concentration was 4.4 times the national average, and 42% of participants had Hg concentrations exceeding 5.8 μg L(-1). Elevated Hg exposures occurred at all seafood consumption frequencies, including the recommended frequency of 2 meals per week. Blood Hg concentrations were positively associated with weekly tuna steak or sushi intake (β=6.30 change in blood Hg, μg L(-1)) and monthly (β=2.54) or weekly (β=9.47) swordfish, shark or marlin intake. Our findings show that seafood consumers in this population have elevated Hg exposures even at relatively low seafood consumption rates that are at or below current dietary recommendations. Further study should examine health risks and benefits of avid seafood consumption, and consider modifying

  19. The Hg region: Superdeformation and other shapes

    SciTech Connect

    Janssens, R.V.F.; Carpenter, M.P.; Fernandez, P.B.; Moore, E.F.; Ahmad, I.; Khoo, T.L.; Wolfs, F.L.H. ); Drigert, M.W. ); Ye, D.; Beard, K.B.; Reviol, W. ); Bearden, I.; Benet, P.; Daly, P.J.; Grabowski, Z.W. )

    1990-01-01

    We shall first summarize the present experimental situation concerning {sup 192}Hg, the nucleus regarded as the analog of {sup 152}Dy{sup 8} for this SD region in that shell gaps are calculated {sup 5} to occur at large deformation for Z=80 and N=112. Proton and neutron excitations out of te {sup 192}Hg core will then be reviewed with particular emphasis on {sup 191}Hg and {sup 193}Tl. The implications of the results for pairing at large deformations and the need to consider other degrees of freedom (such as octupole correlations) will be addressed. The presentation will conclude with a brief discussion on other shapes seen in this region, with a particular emphasis on {sup 191}Hg.

  20. Study on the key technology of spectral reflectance reconstruction based on the weighted measurement matrix

    NASA Astrophysics Data System (ADS)

    Leihong, Zhang; Bei, Li; Dong, Liang; Xiuhua, Ma

    2016-07-01

    In order to reconstruct the spectral reflectance accurately, a new method of spectral reflectance reconstruction based on the weighted measurement matrix is proposed in this paper. By optimizing the measurement matrix between spectral reflectance and the response of a camera, the method can improve the reconstruction accuracy. The new method is a combination of three kinds of common reflectance reconstruction methods, which are the pseudo inverse method, the Wiener estimation method and the principal component analysis method. The new measurement matrix can be achieved after weighting the measurement matrices of these three methods to reconstruct the spectral reflectance. What is more, the weights of the three methods can be obtained by minimizing the color difference. Results show that the CIE1976 color difference and RMSE value of the weighted reconstructed spectra are less than that of three common reconstruction methods. The spectral matching accuracy GFC of the method is higher than 0.99 and its reconstruction accuracy is high.

  1. Study on the validity of 3 × 3 Mueller matrix decomposition.

    PubMed

    Wang, Yunfei; Guo, Yihong; Zeng, Nan; Chen, Dongsheng; He, Honghui; Ma, Hui

    2015-06-01

    Using Monte Carlo simulations based on previously developed scattering models consisting of spherical and cylindrical scatterers imbedded in birefringent interstitial medium, we compare the polarization parameters extracted from the 3×3 and 4×4 Mueller matrix decomposition methods in forward and backward scattering directions. The results show that the parameters derived from the 3×3 Mueller matrix decomposition are usually not the same as those from the 4×4 Mueller matrix decomposition but display similar qualitative relations to changes in the microstructure of the sample, such as the density, size, and orientation distributions of the scatterers, and birefringence of the interstitial medium. The simulations are backed up by experiments when suitable samples are available. PMID:26039383

  2. Isotopic Hg in an Allende carbon-rich residue

    NASA Technical Reports Server (NTRS)

    Reed, G. W., Jr.; Jovanovic, S.

    1990-01-01

    A carbon-rich residue from Allende subjected to stepwise heating yielded two isotopically resolvable types of Hg: one with an (Hg-196)/(Hg-202) concentration ratio the same as terrestrial (monitor) Hg; the other enriched in Hg-196 relative to Hg-202 by about 60 percent. Hg with the 202 isotope enriched relative to 196, as is found in bulk Allende, was not observed. Whether the result of mass fractionation or nucleosynthesis, the distinct types of Hg entered different carrier phases and were not thermally mobilized since the accretion of the Allende parent body.

  3. Study on perturbation schemes for achieving the real PMNS matrix from various symmetric textures

    NASA Astrophysics Data System (ADS)

    Wang, Bin; Tang, Jian; Li, Xue-Qian

    2013-10-01

    The Pontecorvo-Maki-Nakawaga-Sakata matrix displays an obvious symmetry but not exact. There are several textures proposed in the literature which possess various symmetry patterns and seem to originate from different physics scenarios at high energy scales. To be consistent with the experimental measurement, however, the symmetry must be broken. Following the schemes given in the literature, we modify the matrices (ten in total) to gain the real Pontecorvo-Maki-Nakawaga-Sakata matrix by perturbative rotations. The results may be useful for future model builders.

  4. Composition dependence of the mercury vacancies energy levels in HgCdTe: Evolution of the ``negative-U'' property

    NASA Astrophysics Data System (ADS)

    Gemain, F.; Robin, I. C.; Feuillet, G.

    2013-12-01

    HgCdTe films grown by liquid phase epitaxy with different Cd compositions were post-annealed to control the Hg vacancy concentration. Then temperature-dependent Hall measurements and photoluminescence measurements allowed us to study the evolution of the Hg vacancy acceptor levels with the cadmium composition. For Cd compositions below 33% the Hg vacancies in HgCdTe present a negative-U property with the ionized state V- stabilized compared to the neutral state V0. For Cd compositions higher than 45%, the Hg vacancies in HgCdTe present a more standard level ordering with the ionized state V- at higher energy than the neutral state V0.

  5. Dosimetric study of 2D ion chamber array matrix for the modern radiotherapy treatment verification.

    PubMed

    Saminathan, Sathiyan; Manickam, Ravikumar; Chandraraj, Varatharaj; Supe, Sanjay S

    2010-01-01

    Intensity-modulated radiotherapy treatment demands stringent quality assurance and accurate dose determination for delivery of highly conformal dose to the patients. Generally 3D dose distributions obtained from a treatment planning system have to be verified by dosimetric methods. Mainly, a comparison of two-dimensional calculated and measured data in several coplanar planes is performed. In principle, there are many possibilities to measure two-dimensional dose distributions such as films, flat-panel electronic portal imaging devices (EPID), ion chambers and ionization chamber arrays, and radiographic and radiochromic films. The flat-panel EPIDs show a good resolution and offer a possibility for real-time measurements: however to convert the signal into dose, a separate commercial algorithm is required. The 2D ion chamber array system offers the real-time measurements. In this study, dosimetric characteristics of 2D ion chamber array matrix were analyzed for verification of radiotherapy treatments. The dose linearity and dose rate effect of the I'matriXX device was studied using 6 MV, 18 MV photons and 12 MeV electrons. The output factor was estimated using I'matriXX device and compared with ion chamber measurements. The ion chamber array system was found to be linear in the dose range of 2-500 cGy and the response of the detector was found to be independent of dose rate between 100 MU/min to 600 MU/min. The estimated relative output factor with I'matriXX was found to match very well with the ion chamber measurements. To check the final dose delivered during IMRT planning, dose distribution patterns such as field-in-field, pyramidal, and chair tests were generated with the treatment planning system (TPS) and the same was executed in the accelerator and measured with the I'matriXX device. The dose distribution pattern measured by the matrix device for field-in-field, pyramidal, and chair test were found to be in good agreement with the calculated dose distribution

  6. Hg Isotopic Compositions of Chimneys and Pelagic Sediments at Active Submarine Hydrothermal Field in the Okinawa Trough, Japan

    NASA Astrophysics Data System (ADS)

    Takeuchi, A.; Marumo, K.; Tomiyasu, T.; Yamamoto, M.; Komuro, K.

    2012-12-01

    Mercury (Hg) is a globally distributed and highly toxic pollutant in the environment. It is known that a submarine hydrothermal activity is one of the natural processes to emit Hg to marine environment. In order to estimate the degree to which the Hg found in the marine environment is from anthropogenic versus natural sources, it is important to characterize the Hg from the hydrothermal vents. Samples of chimneys and a ~20 cm sediment core, collected by a deep-sea remotely operated vehicle, from Iheya North hydrothermal field in Okinawa Trough, Japan, were analyzed for Hg concentrations and Hg isotopic compositions. Total Hg concentrations of chimneys range between 8.2 and 16.9 mg/kg, whereas seafloor sediment total Hg concentrations are from 3.8 to 34.8 mg/kg. Approximately 0.4 to 1.1 μg/kg of monomethyl Hg (MMHg) was detected in the top 6 cm sediment cores. Hg isotopic compositions (δ202Hg) of chimneys are between -0.30 and -0.96 ‰, whereas δ202Hg values of sediment samples range from -0.85 to -1.60 ‰. Neither chimneys nor sediment samples exhibit the significant mass independent fractionations in Hg isotopes (Δ201Hg > ± 0.10). The chimney δ202Hg values are slightly higher than the δ202Hg values of sediments. This may indicate that the heavier Hg isotopes tend to be incorporated with mercury-bearing sulfides in chimneys, and the lighter isotopes tend to be remained in the hydrothermal fluid and distributed in the surrounding sediments. Also, the sediment samples from the upper portion of cores demonstrate approximately 0.4 - 0.5 ‰ lower δ202Hg values than those from the lower part. This isotopic fractionation may be resulted from a demethylated process of MMHg by microbes. Several studies have previously demonstrated the rapid demethylation of MMHg by microbes in Hg-contaminated aquatic sediments, and range of the isotopic fractionation is similar to that of the experimentally determined isotopic fractionation of MMHg by bacterial reduction

  7. Decay from the superdeformed bands in {sup 194}Hg

    SciTech Connect

    Henry, R.G.; Khoo, T.L.; Carpenter, M.P.

    1995-08-01

    Superdeformed bands in {sup 194}H g were studied using the early implementation of Gammasphere. The response functions for the Ge detectors were measured for the first time as part of this experiment. Experiments were performed with both a backed target (where the residue stopped in the Au backing) and a thin target (where the residue recoiled into vacuum). This will permit measurements of the decay times of the quasicontinuum {gamma}rays. The spectrum in coincidence with the yrast SD band in {sup 194}Hg reveals the same features as found in the quasicontinuum structure in {sup 192}Hg. These features include: statistical {gamma}rays feeding the SD band, a pronounced E2 peak from transitions feeding the SD band, a Ml/E2 bump at low energies that is associated with the last stages of feeding of the superdeformed band, and a quasicontinuous distribution from {gamma}rays linking SD and normal states, including a sizable clustering of strength around 1.7 MeV. The remarkable similarity of the spectra coincident with SD bands in {sup 192,194}Hg provides additional support for a statistical process for decay out of the SD states. This similarity contrasts with differences observed in the spectrum coincident with the SD band in the odd-even {sup 191}Hg, confirming the predictions about the role of pairing (in normal states) in influencing the shape of the decay-out spectrum.

  8. Matrix Metalloproteinase Expression in Contusional Traumatic Brain Injury: A Paired Microdialysis Study

    PubMed Central

    Carpenter, Keri L.H.; Helmy, Adel; Pickard, John D.; Menon, David K.; Hutchinson, Peter J.A.

    2015-01-01

    Abstract Matrix metalloproteinases (MMPs) are extracellular enzymes that have been implicated in the pathophysiology of blood–brain barrier (BBB) breakdown, contusion expansion, and vasogenic edema after traumatic brain injury (TBI). Specifically, in focal injury models, increased MMP-9 expression has been observed in pericontusional brain, and MMP-9 inhibitors reduce brain swelling and final lesion volume. The aim of this study was to examine whether there is a similarly localized increase of MMP concentrations in patients with contusional TBI. Paired microdialysis catheters were inserted into 12 patients with contusional TBI (with or without associated mass lesion) targeting pericontusional and radiologically normal brain defined on admission computed tomography scan. Microdialysate was pooled every 8 h and analyzed for MMP-1, -2, -7, -9, and -10 using a multiplex immunoassay. Concentrations of MMP-1, -2, and -10 were similar at both monitoring sites and did not show discernible temporal trends. Overall, there was a gradual increase in MMP-7 concentrations in both normal and injured brain over the monitoring period, although this was not consistent in every patient. MMP-9 concentrations were elevated in pericontusional, compared to normal, brain, with the maximal difference at the earliest monitoring times (i.e., <24 h postinjury). Repeated-measures analysis of variance showed that MMP-9 concentrations were significantly higher in pericontusional brain (p=0.03) and within the first 72 h of injury, compared with later in the monitoring period (p=0.04). No significant differences were found for the other MMPs assayed. MMP-9 concentrations are increased in pericontusional brain early post-TBI and may represent a potential therapeutic target to reduce hemorrhagic progression and vasogenic edema. PMID:25858502

  9. Climate implications of carbonaceous aerosols: An aerosol microphysical study using the GISS/MATRIX climate model

    SciTech Connect

    Bauer, Susanne E.; Menon, Surabi; Koch, Dorothy; Bond, Tami; Tsigaridis, Kostas

    2010-04-09

    Recently, attention has been drawn towards black carbon aerosols as a likely short-term climate warming mitigation candidate. However the global and regional impacts of the direct, cloud-indirect and semi-direct forcing effects are highly uncertain, due to the complex nature of aerosol evolution and its climate interactions. Black carbon is directly released as particle into the atmosphere, but then interacts with other gases and particles through condensation and coagulation processes leading to further aerosol growth, aging and internal mixing. A detailed aerosol microphysical scheme, MATRIX, embedded within the global GISS modelE includes the above processes that determine the lifecycle and climate impact of aerosols. This study presents a quantitative assessment of the impact of microphysical processes involving black carbon, such as emission size distributions and optical properties on aerosol cloud activation and radiative forcing. Our best estimate for net direct and indirect aerosol radiative forcing change is -0.56 W/m{sup 2} between 1750 and 2000. However, the direct and indirect aerosol effects are very sensitive to the black and organic carbon size distribution and consequential mixing state. The net radiative forcing change can vary between -0.32 to -0.75 W/m{sup 2} depending on these carbonaceous particle properties. Assuming that sulfates, nitrates and secondary organics form a coating shell around a black carbon core, rather than forming a uniformly mixed particles, changes the overall net radiative forcing from a negative to a positive number. Black carbon mitigation scenarios showed generally a benefit when mainly black carbon sources such as diesel emissions are reduced, reducing organic and black carbon sources such as bio-fuels, does not lead to reduced warming.

  10. The use of an acellular collagen matrix in penile augmentation: A pilot study in Saudi Arabia

    PubMed Central

    Tealab, Alaa A.; Maarouf, Aref M.; Habous, Mohamed; Ralph, David J.; Abohashem, Safwat

    2013-01-01

    Objectives To assess the use of an acellular collagen matrix (Pelvicol, Bard Medical, Covington, GA, USA), a successful agent for reconstructive surgery, for enhancing penile girth. Patients and methods Between June and December 2011, 18 patients (mean age 24 years, range 19–38) had their penis augmented with Pelvicol; the mean (range) penile circumference was 9.2 (7–13) cm before treatment. They were divided into two groups; the first (10 patients) had a Pelvicol sheet of 8 × 12 cm inserted through a V–Y suprapubic incision and wrapped around the shaft in a bilayer under the dartos fascia, but not covering the urethra, with division of the suspensory ligament. The second group of eight patients had the Pelvicol inserted through a subcoronal degloving incision and placed in one layer. The penile circumference was measured at 6 and 12 months after surgery. Patient satisfaction at 1 year after surgery was assessed as ‘poor’, ‘unsatisfied’, ‘moderately satisfied’, ‘highly satisfied’, or ‘excellent’. Results The mean (range) increase in girth (circumference) was 2.8 (2–3.2) cm in group 1 and 1.7 (1.2–2) cm in group 2. In group 1, two patients were highly satisfied, four moderately satisfied and four unsatisfied; in group 2, three were moderately satisfied and five unsatisfied. Complications were common in both groups, with five patients in group 1 and three in group 2 developing severe penile oedema and ischaemic shaft ulcers. Removal of the graft was required in two patients in each group. Conclusion This pilot study shows that Pelvicol is not an ideal option for enhancing penile girth, and the method of placement did not apparently influence the result. PMID:26558077

  11. The extracellular matrix of Volvox: a comparative study and proposed system of nomenclature.

    PubMed

    Kirk, D L; Birchem, R; King, N

    1986-02-01

    The structure of the extracellular matrix (ECM) of representatives of all four sections of the genus Volvox was examined by a combination of light- and electron-microscopic methods. On the basis of these observations, plus published descriptions of aspects of ECM organization in other members of the order Volvocales, a system of nomenclature is proposed, to facilitate discussion of comparative morphology and phylogeny of the ECM in the order. In this system the ECM is divided into four main zones: the flagellar zone (FZ), which consists of attachments to and specializations of the ECM around the flagella; the boundary zone (BZ), which consists of portions of the ECM that (except in periflagellar regions) are continuous over the surface of the organism and are not structurally continuous with deeper layers; the cellular zone (CZ), which consists of specializations, other than those of the FZ, around individual cells; and the deep zone (DZ), which consists of components that fill the central region of the organism, internal to CZ. An empirically based set of hierarchical subdivisions of these zones is then proposed that permits specific identification of most morphologically distinct ECM components. The fact that not all zones and subzones are present in all members of the order means that this system permits identification of those ECM structures that have been gained or lost during Volvocalean evolution. Species-specific differences in the structure of virtually all aspects of the ECM were seen among the Volvox species examined in this study. However, the fact that such differences cannot always be used as diagnostic characters for the four divisions of the genus was demonstrated by the observation that in certain ECM features two members of the same division (V. carteri f. nagariensis and V. carteri f. weismannia) differ markedly in structure from one another, with one member of the pair resembling a member of another division. Thus many details of ECM

  12. Urban sediment contamination in a former Hg mining district, Idrija, Slovenia.

    PubMed

    Bavec, Spela; Biester, Harald; Gosar, Mateja

    2014-06-01

    Road sediments from gully pots of the drainage system and stream sediments from local streams were investigated for the first time in the urban area of Idrija town, the central part of the second largest and strongly contaminated Hg mining district in the world. Hg concentrations in road sediments were lower than in stream sediments. They ranged from 16 to 110 mg/kg (Md = 29 mg/kg) for <0.125 mm particles and from 7 to 125 mg/kg (Md = 35 mg/kg) for <0.04 mm particles, while Hg concentrations in stream sediments ranged from 10 to 610 mg/kg (Md = 95 mg/kg) for <0.125 particles and from 10 to 440 mg/kg (Md = 105 mg/kg) for <0.04 mm particles. High Hg loadings in stream sediments were successfully linked with identified mercury sources (rocks containing mercury ore, areas of former ore roasting sites, ore residue dumps), because they are located in the drainage areas of streams, from which the sediments were collected. Links between Hg loadings in road sediments and identified mercury sources were not recognized. Solid phases of Hg were determined by thermo-desorption technique and are similar for both types of sediments. Results show the occurrence of three different forms: elemental mercury, mercury bound to matrix components and cinnabar. Approximately 50 % of Hg in samples consist of non-cinnabar fractions. This is important, since they are potentially bioavailable. An interesting new discovery according to previous research of environmental media from Idrija area by solid-phase Hg thermo-desorption technique is that elemental mercury was determined in almost all investigated sediments in minor amounts (Md = 3 %). PMID:24114255

  13. Clams sensitivity towards As and Hg: A comprehensive assessment of native and exotic species.

    PubMed

    Velez, Cátia; Freitas, Rosa; Antunes, Sara C; Soares, Amadeu M V M; Figueira, Etelvina

    2016-03-01

    To assess the environmental impact of As and Hg, bioindicator organisms such as bivalves have been used. Nevertheless, few studies have assessed the impacts of As and Hg in Ruditapes decussatus and Ruditapes philippinarum, which are native and exotic species in Europe, respectively. The main goal of the present study was to assess elements' partitioning and detoxification strategies of R. decussatus and R. philippinarum. Both clams showed a higher capacity to bioconcentrate Hg (BCF 2.29-7.49), when compared to As (0.59-1.09). Furthermore, As accumulation in both species was similar in the soluble and insoluble fractions, while in both species the majority of Hg was found in the insoluble fraction. Clams exposed to As showed different detoxification strategies, since R. decussatus had higher ability to enhance antioxidant enzymes and metallothioneins in order to reduce toxicity, and R.philippinarum increased glutathione S-transferase Ω activity, that catalyzes monomethyl arsenate reduction, the rate-limiting reaction in arsenic biotransformation. When exposed to Hg, R. decussatus presented, higher synthesis of antioxidant enzymes and lower LPO, being able to better tolerate Hg than the exotic species R. philippinarum. Thus under relevant levels of As and Hg contamination our work evidenced the higher ability of R. decussatus to survive and inhabit coastal environments not heavily contaminated by Hg and As. PMID:26655232

  14. Potential of Brass to Remove Inorganic Hg(II) from Aqueous Solution through Amalgamation.

    PubMed

    Wenke, Axel; Bollen, Anne; Richard, Jan-Helge; Biester, Harald

    2016-06-01

    Brass shavings (CuZn45) were tested for their efficiency to remove Hg(II) from contaminated groundwater through amalgamation. The study was focused on long-term retention efficiency, the understanding of the amalgamation process and kinetics, and influences of filter surface alteration. Column tests were performed with brass filters (thickness 3 to 9 cm) flushed with 1000 μg/L Hg solution for 8 hours under different flow rates (300 to 600 mL/h). Brass filters consistently removed >98% of Hg from solution independent of filter thickness and flow rate. In a long-term experiment (filter thickness 2 cm), Hg retention decreased from 96 to 92% within 2000 hours. Batch and column experiments for studying kinetics of Hg removal indicate ~100% Hg removal from solution within only 2 hours. Solid-phase mercury thermo-desorption analysis revealed that Hg(0) diffusion into the brass surface controls kinetics of mercury retention. Brass surface alteration could be observed, but did not influence Hg retention. PMID:27225782

  15. Drug release kinetics and fronts movement studies from methyl methacrylate (MMA) copolymer matrix tablets: effect of copolymer type and matrix porosity.

    PubMed

    Ferrero, C; Bravo, I; Jiménez-Castellanos, M R

    2003-09-19

    Several methyl methacrylate (MMA) copolymers have recently been proposed as an alternative for the formulation of controlled-release matrix tablets. Copolymers were synthesised by free radical copolymerisation of methyl methacrylate with starch or cellulose derivatives and were alternatively dried by oven or freeze-drying techniques. Both the chemical composition and the drying technique were demonstrated to have a considerable influence on the physical properties of the copolymers. The present investigation was focused on the elucidation of the drug release mechanism from MMA copolymer matrices, using anhydrous theophylline as model drug. Drug release experiments were performed from free tablets. Radial drug release and fronts movement were also evaluated using special devices consisting of two Plexiglass discs joined by means of four stainless steel screws. Mathematical analysis of release data was performed using Higuchi, Korsmeyer and Peppas equations and fronts movement was investigated using a colorimetric technique. The drug release rate and the relative positions of the fronts were studied as functions of the type of copolymer and the initial porosity of the tablets. Drug release was controlled mainly by diffusion and the release rate was found to be affected by the drying method and related to the area exposed to the dissolution medium. Three distinct fronts (water uptake, complete wetting, erosion) were observed during the release process and the dynamics of fronts movement confirmed the diffusional mechanism. PMID:14499186

  16. Light-induced structural changes in (HgBr2)3(As4S4)2: An X-ray single-crystal diffraction, Raman spectroscopy and ab initio study

    NASA Astrophysics Data System (ADS)

    Zoppi, M.; Bindi, L.; Rödl, T.; Pielnhofer, F.; Weihrich, R.; Pfitzner, A.; Bonazzi, P.

    2013-09-01

    To investigate the behaviour of the As4S4 molecule within a crystal-chemical environment differing from realgar, α-As4S4, and its high-temperature polymorph, β-As4S4, the effects of the light exposure on the structure of the (HgBr2)3(As4S4)2 adduct have been studied. Differently from the cases previously studied, the action of the light filtered using a 550 nm long-wavelength pass filter did not produce any evident effect on the unit-cell. On the other hand, employing the 440 nm long-wavelength pass filter, remarkable variations of the unit-cell parameters were observed. In particular, an increase of the a, c, and β, and a decrease of the b parameter, producing on the whole an expansion of the unit-cell volume, is observed as a function of the light exposure times. Structure refinements indicated that the increase of the unit-cell volume is to ascribe to the formation of an increasing fraction (up to 20%) of pararealgar-type replacing the realgar-type molecule. Further light-exposure did not cause any further increase of the lattice parameters. On the contrary, a decrease of the unit-cell volume occurred by keeping the crystal in the dark (46 days): due to the loss of the crystallinity, only the core of the crystal, less altered and with smaller unit-cell volume, contributes to the diffraction effects. Micro-Raman spectra were collected on crystals exposed to the above mentioned wavelength light for increasing times. The peak at 275(±1) cm-1 whose intensity increases as a function of the exposure time confirms the transition from a realgar- to a pararealgar-type molecule in the (HgBr2)3(As4S4)2 adduct. Relativistic DFT-GGA ab initio band structure calculations reveal a direct band gap of 2.04 eV and quite flat valence and conduction bands around the Fermi level. According to analyses of the atomic orbital contributions to the electronic band structures the highest occupied states are attributed to non-bonding p-states of As.

  17. Styrene-terminated polysulfone oligomers as matrix material for graphite reinforced composites - An initial study

    NASA Technical Reports Server (NTRS)

    Garcia, Dana; Bowles, Kenneth J.; Vannucci, Raymond D.

    1987-01-01

    Results pertaining to graphite reinforced composites containing styrene-terminated oligomers as the matrix material are summarized. The processing parameters are determined and the properties of the resulting composite are evaluated. In terms of solvent impregnation techniques, CH2Cl2 is the preferred solvent due to its easy removal during the prepreg drying and consolidation steps.

  18. Line-Mixing Relaxation Matrix model for spectroscopic and radiative transfer studies

    NASA Astrophysics Data System (ADS)

    Mendaza, Teresa; Martin-Torres, Javier

    2016-04-01

    We present a generic model to compute the Relaxation Matrix easily adaptable to any molecule and type of spectroscopic lines or bands in non-reactive molecule collisions regimes. It also provides the dipole moment of every transition and level population of the selected molecule. The model is based on the Energy-Corrected Sudden (ECS) approximation/theory introduced by DePristo (1980), and on previous Relaxation Matrix studies for the interaction between molecular ro-vibrational levels (Ben-Rueven, 1966), atoms (Rosenkranz, 1975), linear molecules (Strow and Reuter, 1994; Niro, Boulet and Hartmann, 2004), and symmetric but not linear molecules (Tran et al., 2006). The model is open source, and it is user-friendly. To the point that the user only has to select the wished molecule and vibrational band to perform the calculations. It reads the needed spectroscopic data from the HIgh-resolution TRANsmission molecular absorption (HITRAN) (Rothman et al., 2013) and ExoMol (Tennyson and Yurchenko, 2012). In this work we present an example of the calculations with our model for the case of the 2ν3 band of methane (CH4), and a comparison with a previous work (Tran et al., 2010). The data produced by our model can be used to characterise the line-mixing effects on ro-vibrational lines of the infrared emitters of any atmosphere, to calculate accurate absorption spectra, that are needed in the interpretation of atmospheric spectra, radiative transfer modelling and General Circulation Models (GCM). References [1] A.E. DePristo, Collisional influence on vibration-rotation spectral line shapes: A scaling theoretical analysis and simplification, J. Chem. Phys. 73(5), 1980. [2] A. Ben-Reuven, Impact broadening of microwave spectra, Phys. Rev. 145(1), 7-22, 1966. [3] P.W. Rosenkranz, Shape of the 5 mm Oxygen Band in the Atmosphere, IEEE Transactions on Antennas and Propagation, vol. AP-23, no. 4, pp. 498-506, 1975. [4] Strow, L.L., D.D. Tobin, and S.E. Hannon, A compilation of

  19. Conformations of dimethyl carbonate and its complexes with water: A matrix isolation infrared and ab initio study

    NASA Astrophysics Data System (ADS)

    Kar, Bishnu Prasad; Ramanathan, N.; Sundararajan, K.; Viswanathan, K. S.

    2012-09-01

    Conformations of dimethyl carbonate (DMC) were studied using matrix isolation infrared spectroscopy. Infrared spectra of DMC trapped in inert gas matrixes, using an effusive source at 298 and 423 K, showed evidence of both the ground state (cis-cis), and higher energy (cis-trans) conformers. Experiments were also performed using a supersonic jet source to deposit the matrix, to look for conformational cooling in the expansion process. The structures and vibrational frequencies of these conformers were computed at the B3LYP/6-31++G** level of theory. Natural bond orbital analyses were performed to understand the role of the delocalization interactions in conformational preferences. Complexes of DMC with H2O were also studied. A 1:1 DMC-H2O complex was identified in the matrix isolation experiments, where the carbonyl oxygen of DMC served as the proton acceptor for the hydrogen bonded complex. This observation was corroborated by computations performed on the complex at the B3LYP/6-31++G** level. Our computations also indicated another minimum, corresponding to an alkoxy bonded DMC-H2O complex, which was less exothermic; however, this complex was not identified in our experiments. Atoms-in-molecules theory was also performed to understand the nature of the intermolecular interaction in the DMC-H2O complex.

  20. Design Studies for a Multiple Application Thermal Reactor for Irradiation Experiments (MATRIX)

    SciTech Connect

    Pope, Michael A.; Gougar, Hans D.; Ryskamp, J. M.

    2015-03-01

    The Advanced Test Reactor (ATR) is a high power density test reactor specializing in fuel and materials irradiation. For more than 45 years, the ATR has provided irradiations of materials and fuels testing along with radioisotope production. Should unforeseen circumstances lead to the decommissioning of ATR, the U.S. Government would be left without a large-scale materials irradiation capability to meet the needs of its nuclear energy and naval reactor missions. In anticipation of this possibility, work was performed under the Laboratory Directed Research and Development (LDRD) program to investigate test reactor concepts that could satisfy the current missions of the ATR along with an expanded set of secondary missions. A survey was conducted in order to catalogue the anticipated needs of potential customers. Then, concepts were evaluated to fill the role for this reactor, dubbed the Multi-Application Thermal Reactor Irradiation eXperiments (MATRIX). The baseline MATRIX design is expected to be capable of longer cycle lengths than ATR given a particular batch scheme. The volume of test space in In-Pile-Tubes (IPTs) is larger in MATRIX than in ATR with comparable magnitude of neutron flux. Furthermore, MATRIX has more locations of greater volume having high fast neutron flux than ATR. From the analyses performed in this work, it appears that the lead MATRIX design can be designed to meet the anticipated needs of the ATR replacement reactor. However, this design is quite immature, and therefore any requirements currently met must be re-evaluated as the design is developed further.

  1. Study on the algorithm of computational ghost imaging based on discrete fourier transform measurement matrix

    NASA Astrophysics Data System (ADS)

    Zhang, Leihong; Liang, Dong; Li, Bei; Kang, Yi; Pan, Zilan; Zhang, Dawei; Gao, Xiumin; Ma, Xiuhua

    2016-07-01

    On the basis of analyzing the cosine light field with determined analytic expression and the pseudo-inverse method, the object is illuminated by a presetting light field with a determined discrete Fourier transform measurement matrix, and the object image is reconstructed by the pseudo-inverse method. The analytic expression of the algorithm of computational ghost imaging based on discrete Fourier transform measurement matrix is deduced theoretically, and compared with the algorithm of compressive computational ghost imaging based on random measurement matrix. The reconstruction process and the reconstruction error are analyzed. On this basis, the simulation is done to verify the theoretical analysis. When the sampling measurement number is similar to the number of object pixel, the rank of discrete Fourier transform matrix is the same as the one of the random measurement matrix, the PSNR of the reconstruction image of FGI algorithm and PGI algorithm are similar, the reconstruction error of the traditional CGI algorithm is lower than that of reconstruction image based on FGI algorithm and PGI algorithm. As the decreasing of the number of sampling measurement, the PSNR of reconstruction image based on FGI algorithm decreases slowly, and the PSNR of reconstruction image based on PGI algorithm and CGI algorithm decreases sharply. The reconstruction time of FGI algorithm is lower than that of other algorithms and is not affected by the number of sampling measurement. The FGI algorithm can effectively filter out the random white noise through a low-pass filter and realize the reconstruction denoising which has a higher denoising capability than that of the CGI algorithm. The FGI algorithm can improve the reconstruction accuracy and the reconstruction speed of computational ghost imaging.

  2. A combination of high-resolution X-ray diffractometry and diffraction imaging techniques applied to the study of MOVPE-grown Cd xHg 1-xTe/CdTe on GaAs

    NASA Astrophysics Data System (ADS)

    Keir, A. M.; Barnett, S. J.; Giess, J.; Walsh, T. D.; Astles, M. G.

    1991-06-01

    We have applied a range of high-resolution X-ray diffractometry and diffraction imaging techniques to study the structural properties of Cd xHg 1- xTe (CMT) grown epitaxially on GaAs by MOVPE. In this paper we specifically describe three such techniques and evaluate and compare the results from each. Automated double crystal diffractometry with a mapping facility provides information on the quality and uniformity of the layers. 004 rocking curve widths vary from < 70 arc seconds on the best samples to substantially higher values on poorer material. Study of non-uniform layers shows that lattice tilts are a dominant influence on rocking curve widths and large (up to 2°) misorientations between epilayer and substrate (100) planes are found on some samples. These characteristics are further investigated using triple crystal diffractometry. X-ray topography of the layers shows orientation-contrast features which correlate directly with the GaAs substrate dislocation distribution. A number of layers with varying degrees of structural quality have been examined using a combination of the above techniques. Recent results are reported illustrating the value of each technique and we demonstrate how the application of a combination of X-ray diffraction techniques can be a powerful tool for investigating the nature of structural defects in this highly mismatched heteroepitaxial system.

  3. Kinetic and interface studies for MOCVD CdTe and HgCdTe epilayers grown on GaAs substrates

    NASA Astrophysics Data System (ADS)

    Rui-wu, Peng; Fei, Xu; Yong-qing, Ding

    1991-12-01

    The growth rates of CdTe and CMT on GaAs and on CdTe/GaAs substrates were studied as a function of temperature and gas composition. A Langmuir-Hinshelwood model for surface reaction control region is proposed. The CdTe/GaAs interface was examined by X-ray double crystal diffraction, laser Raman spectroscopy and transmission electron microscopy (TEM). A defect layer was observed at CdTe/GaAs interface. The relationship between the interface qualities and electrical properties of the CMT overlayers was discussed.

  4. A study of low-noise preamplifier systems for use with room temperature mercuric iodide /HgI2/ X-ray detectors

    NASA Technical Reports Server (NTRS)

    Iwanczyk, J. S.; Huth, G. C.; Del Duca, A.; Schnepple, W.; Dabrowski, A. J.

    1981-01-01

    An analysis of different preamplification systems for use with room temperature mercuric iodide X-ray detectors has been performed. Resistor-, drain-, and light-feedback preamplifiers have been studied. Energy resolution values of 295 eV (FWHM) for an Fe-55 source (5.9 keV) and 225 eV (FWHM) for a pulser have been obtained with both the detector and the input FET at room temperature using a pulsed-light feedback preamplifier. Improvement in energy resolution by cooling the input FET using a small Peltier element has been discussed.

  5. A study of low-noise preamplifier systems for use with room temperature mercuric iodide /HgI2/ X-ray detectors

    NASA Astrophysics Data System (ADS)

    Iwanczyk, J. S.; Huth, G. C.; del Duca, A.; Schnepple, W.; Dabrowski, A. J.

    1981-02-01

    An analysis of different preamplification systems for use with room temperature mercuric iodide X-ray detectors has been performed. Resistor-, drain-, and light-feedback preamplifiers have been studied. Energy resolution values of 295 eV (FWHM) for an Fe-55 source (5.9 keV) and 225 eV (FWHM) for a pulser have been obtained with both the detector and the input FET at room temperature using a pulsed-light feedback preamplifier. Improvement in energy resolution by cooling the input FET using a small Peltier element has been discussed.

  6. Theoretical Studies on the Fe-M Interactions and 31P NMR in Fe(CO)3(EtPhPpy)2MX2 (X = NCS, SCN, Cl; M = Zn, Cd, Hg)

    NASA Astrophysics Data System (ADS)

    Huang, Xiao-xuan; Xu, Xuan; Xie, Mei-xiang

    2008-10-01

    To study the Fe-M interactions and their effects on 31P NMR, the structures of Fe(CO)3(EtPhPpy)2 1, Fe(CO)3(EtPhPpy)2M(NCS)2 (2: M = Zn, 3: M = Cd, 4: M = Hg) and Fe(CO)3(EtPhPpy)2CdX2 (5: X = C1, 6: X = SCN) were investigated by density functional theory (DFT) PBE0 method. The stabilities S of complexes follow S(2)>S(3)>S(4) and S(3)approxS(6)>S(5), indicating that 6 is stable and may be synthesized. The complexes with thiocyanate are more stable than that with chloride in Fe(CO)3(EtPhPpy)2CdX2. The strength / of Fe-M interactions follows I(2)approxI(3)Hg atoms in 4. However, in binuclear complexes except 4, the Fe-M interactions act as nFe→nm, σ-Fe→nM and σc-Fe→nM delocalization, and the N-M interactions mainly act as nN→nm delocalization. In binuclear complexes, due to the Fe→M interactions, the strong σFe-c→σ*Fe-P or σFe_Hg→σ*Fe-p delocalization and the charge-transfer, the electron density on P nucleus is increased, and thus upfield 31P chemical shifts are caused (compared with mononuclear complex 1).

  7. Seasonal variations in metallic mercury (Hg0) vapor exchange over biannual wheat - corn rotation cropland in the North China Plain

    NASA Astrophysics Data System (ADS)

    Sommar, J.; Zhu, W.; Shang, L.; Lin, C.-J.; Feng, X. B.

    2015-09-01

    Air-surface gas exchange of Hg0 was measured in five approximately bi-weekly campaigns (in total 87 days) over a wheat-corn rotation cropland located in the North China Plain using the relaxed eddy accumulation (REA) technique. The campaigns were separated over duration of a full year period (201-2013) aiming to capture the flux pattern over essential growing stages of the planting system with a low homogeneous topsoil Hg content (~ 45 ng g-1). Contrasting pollution regimes influenced air masses at the site and corresponding Hg0 concentration means (3.3 in late summer to 6.2 ng m-3 in winter) were unanimously above the typical hemispheric background of 1.5-1.7 ng m-3 during the campaigns. Extreme values in bi-directional net Hg0 exchange were primarily observed during episodes of peaking Hg0 concentrations. In tandem with under-canopy chamber measurements, the above-canopy REA measurements provided evidence for a balance between Hg0 ground emissions and uptake of Hg0 by the developed canopies. During the wheat growing season covering ~ 2/3 of the year at the site, net field-scale Hg0 emission was prevailing for periods of active plant growth until canopy senescence (mean flux: 20.0 ng m-3) disclosing the dominance of Hg0 soil efflux during warmer seasons. In the final vegetative stage of corn and wheat, ground and above-canopy Hg0 flux displayed inversed daytime courses with a near mid-day maximum (emission) and minimum (deposition), respectively. In contrast to wheat, Hg0 uptake of the corn canopy at this stage offset ground Hg0 emissions with additional removal of Hg0 from the atmosphere. Differential uptake of Hg0 between wheat (C3 species) and corn (C4 species) foliage is discernible from estimated Hg0 flux (per leaf area) and Hg content in mature cereal leaves being a factor of > 3 higher for wheat (at ~ 120 ng g-1 dry weight). Furthermore, this study shows that intermittent flood irrigation of the air-dry field induced a short pulse of Hg0 emission due to

  8. High-temperature HgTe/CdTe multiple-quantum-well lasers.

    PubMed

    Vurgaftman, I; Meyer, J

    1998-02-16

    While most previous studies of Hg-based mid-IR lasers have focused on either bulk Hg(1-x)Cd(x)Te alloys or thick (> 100 A) Hg(1-x)Cd(x)Te quantum wells with relatively large x, we show that much thinner (20-30 A) HgTe binary wells may be engineered to suppress both Auger recombination and intervalence free carrier absorption. On the basis of detailed numerical simulations, we predict 4.3 m cw emission at temperatures up to 220 K for optical pumping and 105 K for diode operation. In pulsed mode, we expect maximum lasing temperatures more than 100 K higher than any prior Hg-based mid-IR result. PMID:19377592

  9. Understanding of matrix embedding: a theoretical spectroscopic study of CO interacting with Ar clusters, surfaces and matrices.

    PubMed

    Mahjoubi, K; Benoit, D M; Jaidane, N-E; Al-Mogren, M Mogren; Hochlaf, M

    2015-07-14

    Through benchmark studies, we explore the performance of PBE density functional theory, with and without Grimme's dispersion correction (DFT-D3), in predicting spectroscopic properties for molecules interacting with rare gas matrices. Here, a periodic-dispersion corrected model of matrix embedding is used for the first time. We use PBE-D3 to determine the equilibrium structures and harmonic vibrational frequencies of carbon monoxide in interaction with small Ar clusters (CO-Arn, n = 1, 2, 3), with an Ar surface and embedded in an Ar matrix. Our results show a converging trend for both the vibrational frequencies and binding energies when going from the gas-phase to a fully periodic approach describing CO embedding in Ar. This trend is explained in terms of solvation effects, as CO is expected to alter the structure of the Ar matrix. Due to a competition between CO-Ar interactions and Ar-Ar interactions, perturbations caused by the presence of CO are found to extend over several Å in the matrix. Accordingly, it is mandatory to fully relax rare gas matrices when studying their interaction with embedded molecules. Moreover, we show that the binding energy per Ar is almost constant (∼-130 cm(-1) atom(-1)) regardless of the environment of the CO molecule. Finally, we show that the concentration of the solute into the cold matrix influences the spectroscopic parameters of molecules embedded into cold matrices. We suggest hence that several cautions should be taken before comparing these parameters to gas phase measurements and to theoretical data of isolated species. PMID:26067278

  10. Fe and O EELS Studies of Ion Irradiated Murchison CM2 Carbonaceous Chondrite Matrix

    NASA Technical Reports Server (NTRS)

    Keller, L. P.; Christofferson, R.; Dukes, C. A.; Baragiola, R. A.; Rahman, Z.

    2015-01-01

    Introduction: The physical and chemical response of hydrated carbonaceous chondrite materials to space weathering processes is poorly understood. Improving this understanding is a key part of establishing how regoliths on primitive carbonaceous asteroids respond to space weathering processes, knowledge that supports future sample return missions (Hayabusa 2 and OSIRISREx) that are targeting objects of this type. We previously reported on He+ irradiation of Murchison matrix and showed that the irradiation resulted in amorphization of the matrix phyllosilicates, loss of OH, and surface vesiculation. Here, we report electron energy-loss spectroscopy (EELS) measurements of the irradiated material with emphasis on the Fe and O speciation. Sample and Methods: A polished thin section of the Murchison CM2 carbonaceous chondrite was irradiated with 4 kilovolts He(+) (normal incidence) to a total dose of 1 x 10(exp 18) He(+) per square centimeter. We extracted thin sections from both irradiated and unirradiated regions in matrix using focused ion beam (FIB) techniques with electron beam deposition for the protective carbon strap to minimize surface damage artifacts from the FIB milling. The FIB sections were analyzed using a JEOL 2500SE scanning and transmission electron microscope (STEM) equipped with a Gatan Tridiem imaging filter. EELS spectra were collected from 50 nanometer diameter regions with an energy resolution of 0.7 electronvolts FWHM at the zero loss. EELS spectra were collected at low electron doses to minimize possible artifacts from electron-beam irradiation damage. Results and Discussion: Fe L (sub 2,3) EELS spectra from matrix phyllosilicates in CM chondrites show mixed Fe(2+)/Fe(3+) oxidation states with Fe(3+)/Sigma Fe approximately 0.5. Fe L(sub 2,3) spectra from the irradiated/ amorphized matrix phyllosilicates show higher Fe(2+)/Fe(3+) ratios compared to spectra obtained from pristine material at depths beyond the implantation/amorphization layer. We

  11. Application of novel Polypyrrole/thiol-functionalized zeolite Beta/MCM-41 type mesoporous silica nanocomposite for adsorption of Hg2+ from aqueous solution and industrial wastewater: Kinetic, isotherm and thermodynamic studies

    NASA Astrophysics Data System (ADS)

    Javadian, Hamedreza; Taghavi, Mehdi

    2014-01-01

    Hierarchical zeolite consists of both microporous and unordered mesoporous structures. A composite of Polypyrrole/thiol-functionalized Beta/MCM-41 (PPy/SH-Beta/MCM-41) was prepared, characterized by FE-SEM, FT-IR, XRD, TGA and BET analysis and applied in the investigation of its adsorption characteristics for the removal of Hg2+ ions from aqueous solutions. Thiol-functionalized Beta/MCM-41 (SH-Beta/MCM-41) was prepared by 3-mercaptopropyltrimethoxysilane (MPTMS) in the presence of aerosil-200 as a silica source by two-step hydrothermal crystallization procedure. Batch mode experiments were conducted and three kinetic models were used to describe the adsorption process. The experimental data fitted very well with the Pseudo-second-order kinetic model. The calculated thermodynamic parameters (ΔH, ΔS and ΔG) revealed that the adsorption of Hg2+ onto PPy/SH-Beta/MCM-41 is an endothermic and spontaneous process. It was found that temperature has a positive effect on the removal efficiency and that PPy/SH-Beta/MCM-41 is potentially able to remove Hg2+ ions from aqueous solutions at even high concentrations (400 mg L-1). The recovery of Hg2+ from the PPy/SH-Beta/MCM-41 adsorbent was found to be more than 90% using 0.5 M H2SO4, and the ability of the absorbent to be reused for removal of Hg2+ was investigated.

  12. Mono and binuclear Ag(I), Cu(II), Zn(II) and Hg(II) complexes of a new azo-azomethine as ligand: Synthesis, potentiometric, spectral and thermal studies

    NASA Astrophysics Data System (ADS)

    Ahmed, Ibrahim S.; Moustafa, Moustafa M.; Abd El Aziz, Mohamed. M.

    2011-05-01

    New azo-azomethine dyes were prepared by reaction of p-aminobenzoic acid, o-anisidine, o-nitroaniline, and p-bromoaniline with salicylaldehyde respectively to form azo compounds and then condensation by urea to form 4-(R-arylazo 2-salicylaldene)-urea azo-azomethine derivatives (I a-d). The complexes of these ligands with Ag(I), Cu(II), Zn(II) and Hg(II) metal ions were prepared. The structure of the free ligands and their complexes were characterized by using elemental analysis (C, H, N), 1H NMR, IR and UV-Vis-spectra. The proton dissociation constants of the ligands and the stability constant of their complexes have been determined potentiometrically in 40% (v/v) alcohol-water medium as well as the stoichiometry of complexes were determined conductometrically. The data reveal that the stoichiometries for all complexes were prepared in molar ratios (1:1) and (1:2) (M:L). The electrolytic and nonelectrolytic natures of the complexes were assigned based on molar conductance measurements. The thermogravimetric (TG), and differential thermal analyses (DTA) were studied in nitrogen atmosphere with heating rate 10 °C/min. The kinetic and thermodynamic parameters for thermal decomposition of complexes have been calculated by graphical method using Coats-Redfern (CR) method.

  13. Biomechanics of fibrous proteins of the extracellular matrix studied by Brillouin scattering

    PubMed Central

    Palombo, Francesca; Winlove, C. Peter; Edginton, Ryan S.; Green, Ellen; Stone, Nick; Caponi, Silvia; Madami, Marco; Fioretto, Daniele

    2014-01-01

    Brillouin light scattering (BLS) spectroscopy is a technique that is able to detect thermally excited phonons within a material. The speed of propagation of these phonons can be determined from the magnitude of the Brillouin frequency shift between incident and scattered light, thereby providing a measure of the mechanical properties of the material in the gigahertz range. The mechanical properties of the extracellular matrices of biological tissues and their constituent biopolymers are important for normal tissue function and disturbances in these properties are widely implicated in disease. BLS offers the prospect of measuring mechanical properties on a microscopic scale in living tissues, thereby providing insights into structure–function relationships under normal and pathological conditions. In this study, we investigated BLS in collagen and elastin—the fibrous proteins of the extracellular matrix (ECM). Measurements were made on type I collagen in rat tail tendon, type II collagen in articular cartilage and nuchal ligament elastin. The dependence of the BLS spectrum on fibre orientation was investigated in a backscattering geometry using a reflective substrate. Two peaks, a bulk mode arising from phonon propagation along a quasi-radial direction to the fibre axis and a mode parallel to the surface, depending on sample orientation relative to the fibre axis, could be distinguished. The latter peak was fitted to a model of wave propagation through a hexagonally symmetric elastic solid, and the five components of the elasticity tensor were combined to give axial and transverse Young's, shear and bulk moduli of the fibres. These were 10.2, 8.3, 3.2 and 10.9 GPa, and 6.1, 5.3, 1.9 and 8 GPa for dehydrated type I collagen and elastin, respectively. The former values are close to those previously reported. A microfocused BLS approach was also applied providing selection of single fibres. The moduli of collagen and elastin are much higher than those measured at

  14. Biomechanics of fibrous proteins of the extracellular matrix studied by Brillouin scattering.

    PubMed

    Palombo, Francesca; Winlove, C Peter; Edginton, Ryan S; Green, Ellen; Stone, Nick; Caponi, Silvia; Madami, Marco; Fioretto, Daniele

    2014-12-01

    Brillouin light scattering (BLS) spectroscopy is a technique that is able to detect thermally excited phonons within a material. The speed of propagation of these phonons can be determined from the magnitude of the Brillouin frequency shift between incident and scattered light, thereby providing a measure of the mechanical properties of the material in the gigahertz range. The mechanical properties of the extracellular matrices of biological tissues and their constituent biopolymers are important for normal tissue function and disturbances in these properties are widely implicated in disease. BLS offers the prospect of measuring mechanical properties on a microscopic scale in living tissues, thereby providing insights into structure-function relationships under normal and pathological conditions. In this study, we investigated BLS in collagen and elastin-the fibrous proteins of the extracellular matrix (ECM). Measurements were made on type I collagen in rat tail tendon, type II collagen in articular cartilage and nuchal ligament elastin. The dependence of the BLS spectrum on fibre orientation was investigated in a backscattering geometry using a reflective substrate. Two peaks, a bulk mode arising from phonon propagation along a quasi-radial direction to the fibre axis and a mode parallel to the surface, depending on sample orientation relative to the fibre axis, could be distinguished. The latter peak was fitted to a model of wave propagation through a hexagonally symmetric elastic solid, and the five components of the elasticity tensor were combined to give axial and transverse Young's, shear and bulk moduli of the fibres. These were 10.2, 8.3, 3.2 and 10.9 GPa, and 6.1, 5.3, 1.9 and 8 GPa for dehydrated type I collagen and elastin, respectively. The former values are close to those previously reported. A microfocused BLS approach was also applied providing selection of single fibres. The moduli of collagen and elastin are much higher than those measured at lower

  15. HRTEM study of Popigai impact diamond: heterogeneous diamond nanostructures in native amorphous carbon matrix

    NASA Astrophysics Data System (ADS)

    Kis, Viktoria K.; Shumilova, Tatyana; Masaitis, Victor

    2016-07-01

    High-resolution transmission electron microscopy was applied for the detailed nanostructural investigation of Popigai impact diamonds with the aim of revealing the nature of the amorphous carbon of the matrix. The successful application of two complementary specimen preparation methods, focused ion beam (FIB) milling and mechanical cleavage, allowed direct imaging of nanotwinned nanodiamond crystals embedded in a native amorphous carbon matrix for the first time. Based on its stability under the electron beam, native amorphous carbon can be easily distinguished from the amorphous carbon layer produced by FIB milling during specimen preparation. Electron energy loss spectroscopy of the native amorphous carbon revealed the dominance of sp 2-bonded carbon and the presence of a small amount of oxygen. The heterogeneous size distribution and twin density of the nanodiamond crystals and the structural properties of the native amorphous carbon are presumably related to non-graphitic (organic) carbon precursor material.

  16. Rapid thermal annealing and crystallization mechanisms study of silicon nanocrystal in silicon carbide matrix

    PubMed Central

    2011-01-01

    In this paper, a positive effect of rapid thermal annealing (RTA) technique has been researched and compared with conventional furnace annealing for Si nanocrystalline in silicon carbide (SiC) matrix system. Amorphous Si-rich SiC layer has been deposited by co-sputtering in different Si concentrations (50 to approximately 80 v%). Si nanocrystals (Si-NC) containing different grain sizes have been fabricated within the SiC matrix under two different annealing conditions: furnace annealing and RTA both at 1,100°C. HRTEM image clearly reveals both Si and SiC-NC formed in the films. Much better "degree of crystallization" of Si-NC can be achieved in RTA than furnace annealing from the research of GIXRD and Raman analysis, especially in high-Si-concentration situation. Differences from the two annealing procedures and the crystallization mechanism have been discussed based on the experimental results. PMID:21711625

  17. Immunohistochemical study of cytoskeletal and extracellular matrix components in the notochord and notochordal sheath of amphioxus

    PubMed Central

    Bočina, Ivana; Saraga-Babić, Mirna

    2006-01-01

    A major cytoskeletal and extracellular matrix proteins of the amphioxus notochordal cells and sheath were detected by immunohistochemical techniques. The three-layered amphioxus notochordal sheath strongly expressed fish collagen type I in its outer and middle layers, while in the innermost layer expression did not occur. The amphioxus notochordal sheath was reactive to applied anti-human antibodies for intermediate filament proteins such as cytokeratins, desmin and vimentin, as well as to microtubule components (ß-tubulin), particularly in the area close to the epipharyngeal groove. Alpha-smooth muscle actin was expressed in some notochordal cells and in the area of the notochordal attachment to the sheath. Thus muscular nature of notochordal cells was shown by immunohistochemistry in tissue section. Our results confirm that genes encoding intermediate filament proteins, microtubules and microfilaments are highly conserved during evolution. Collagen type I was proven to be the key extracellular matrix protein that forms the amphioxus notochordal sheath. PMID:16733537

  18. Modelling in-situ matrix diffusion at Palmottu natural analogue study site in SW Finland

    SciTech Connect

    Rasilainen, K.; Suksi, J.

    1993-12-31

    Radioactive disequilibria, between U-238, U-234, and Th-230, in crystalline rock adjacent to a fracture, indicates mass transfer of U and Th between water in the fracture and the rock. The matrix diffusion theory was used to interpret the observed profiles of mobilized nuclides around the natural fracture. The interpretation of the profiles was based on the use of uranium series disequilibrium code, URSE, and migration code FTRANS. The model system was characterized using all available site-specific data, and the system evolution was outlined using the geology of the Palmottu site. The simulated concentration profiles, as a function of depth from the fracture surface, indicate that measured profiles can be modelled by matrix diffusion, assuming realistic initial and boundary conditions and diffusion times of 300,000 years.

  19. Electronic transitions of C5H(+) and C5H: neon matrix and CASPT2 studies.

    PubMed

    Fulara, Jan; Nagy, Adam; Chakraborty, Arghya; Maier, John P

    2016-06-28

    Two electronic transitions at 512.3 and 250 nm of linear-C5H(+) are detected following mass-selective deposition of m/z = 61 cations into a 6 K neon matrix and assigned to the 1 (1)Π←X (1)Σ(+) and 1 (1)Σ(+)←X (1)Σ(+) systems. Five absorption systems of l-C5H with origin bands at 528,7, 482.6, 429.0, 368.5, and 326.8 nm are observed after neutralization of the cations in the matrix and identified as transitions from the X (2)Π to 1 (2)Δ, 1 (2)Σ (-), 1 (2)Σ(+), 2 (2)Π, and 3 (2)Π electronic states. The assignment to specific structures is based on calculated excitation energies, vibrational frequencies in the electronic states, along with simulated Franck-Condon profiles. PMID:27369517

  20. Electronic transitions of C5H+ and C5H: neon matrix and CASPT2 studies

    NASA Astrophysics Data System (ADS)

    Fulara, Jan; Nagy, Adam; Chakraborty, Arghya; Maier, John P.

    2016-06-01

    Two electronic transitions at 512.3 and 250 nm of linear-C5H+ are detected following mass-selective deposition of m/z = 61 cations into a 6 K neon matrix and assigned to the 1 1Π←X 1Σ+ and 1 1Σ+←X 1Σ+ systems. Five absorption systems of l-C5H with origin bands at 528,7, 482.6, 429.0, 368.5, and 326.8 nm are observed after neutralization of the cations in the matrix and identified as transitions from the X 2Π to 1 2Δ, 1 2Σ -, 1 2Σ+, 2 2Π, and 3 2Π electronic states. The assignment to specific structures is based on calculated excitation energies, vibrational frequencies in the electronic states, along with simulated Franck-Condon profiles.

  1. Tungsten wire/FeCrAlY matrix turbine blade fabrication study

    NASA Technical Reports Server (NTRS)

    Melnyk, P.; Fleck, J. N.

    1979-01-01

    The objective was to establish a viable FRS monotape technology base to fabricate a complex, advanced turbine blade. All elements of monotape fabrication were addressed. A new process for incorporation of the matrix, including bi-alloy matrices, was developed. Bonding, cleaning, cutting, sizing, and forming parameters were established. These monotapes were then used to fabricate a 48 ply solid JT9D-7F 1st stage turbine blade. Core technology was then developed and first a 12 ply and then a 7 ply shell hollow airfoil was fabricated. As the fabrication technology advanced, additional airfoils incorporated further elements of sophistication, by introducing in sequence bonded root blocks, cross-plying, bi-metallic matrix, tip cap, trailing edge slots, and impingement inserts.

  2. A study of scandia and rhenium doped tungsten matrix dispenser cathode

    NASA Astrophysics Data System (ADS)

    Wang, Jinshu; Li, Lili; Liu, Wei; Wang, Yanchun; Zhao, Lei; Zhou, Meiling

    2007-10-01

    Scandia and rhenium doped tungsten powders were prepared by solid-liquid doping combined with two-step reduction method. The experimental results show that scandia was distributed evenly on the surface of tungsten particles. The addition of scandia and rhenium could decrease the particle size of doped tungsten, for example, the tungsten powders doped with Sc 2O 3 and Re had the average size of about 50 nm in diameter. By using this kind of powder, scandia and rhenium doped tungsten matrix with the sub-micrometer sized tungsten grains was obtained. This kind of matrix exhibited good anti-bombardment insensitivity at high temperature. The emission property result showed that high space charge limited current densities of more than 60 A/cm 2 at 900 °C could be obtained for this cathode. A Ba-Sc-O multilayer about 100 nm in thickness formed at the surface of cathode after activation led to the high emission property.

  3. Rapid thermal annealing and crystallization mechanisms study of silicon nanocrystal in silicon carbide matrix.

    PubMed

    Wan, Zhenyu; Huang, Shujuan; Green, Martin A; Conibeer, Gavin

    2011-01-01

    In this paper, a positive effect of rapid thermal annealing (RTA) technique has been researched and compared with conventional furnace annealing for Si nanocrystalline in silicon carbide (SiC) matrix system. Amorphous Si-rich SiC layer has been deposited by co-sputtering in different Si concentrations (50 to approximately 80 v%). Si nanocrystals (Si-NC) containing different grain sizes have been fabricated within the SiC matrix under two different annealing conditions: furnace annealing and RTA both at 1,100°C. HRTEM image clearly reveals both Si and SiC-NC formed in the films. Much better "degree of crystallization" of Si-NC can be achieved in RTA than furnace annealing from the research of GIXRD and Raman analysis, especially in high-Si-concentration situation. Differences from the two annealing procedures and the crystallization mechanism have been discussed based on the experimental results. PMID:21711625

  4. Studies on binary lipid matrix based solid lipid nanoparticles of repaglinide: in vitro and in vivo evaluation.

    PubMed

    Rawat, Manoj K; Jain, Achint; Singh, Sanjay

    2011-06-01

    The purpose of present study is to examine effect of binary lipid matrix (combination of lipids) on the entrapment and storage stability of repaglinide (RG) loaded solid lipid nanoparticles (SLN). Solid lipid nanoparticles were prepared by modified solvent injection method for oral delivery to improve the bioavailability of RG, an antidiabetic drug. The stearic acid and tristearin were used to form lipid core materials, and Pluronic-F68 was used as a stabilizer. Nanoparticles were characterized by evaluating their particle size, zeta potential, entrapment efficiency, drug loading, solid-state studies (differential scanning calorimetry, X-ray diffraction), in vitro drug release, particle surface (transmission electron microscopy analysis with electron diffraction pattern), stability study in gastrointestinal fluids (GIFs) and storage stability at 30 °C/65% RH for 3 months. The characterization of SLN suggested that binary lipid matrix based nanoparticles had better drug entrapment and loading, desired release characteristics, stable in GIFs and significantly higher storage stability compared with single lipid formulations. Pharmacodynamic (blood glucose, blood cholesterol, blood triglyceride levels) and pharmacokinetic (AUC, T(max), peak plasma concentrations, K, t(1/2), mean residence time and relative bioavailabilities) studies were performed for the selected formulations. These studies indicate that the formulation based on binary lipid matrix significantly improves the oral bioavailability of RG. PMID:21491449

  5. Ultrastructural response of rat lung to 90 days' exposure to oxygen at 450 mm Hg

    NASA Technical Reports Server (NTRS)

    Harrison, G. A.

    1974-01-01

    Young Sprague-Dawley rats were exposed to 100% oxygen at 450 mm Hg in constant environment capsules for 90 days. Lung tissue examined by electron microscopy revealed a number of changes, many similar to those observed after exposure to oxygen at 760 mm Hg for shorter periods of time. Alterations in vesicle size and number and in mitochondrial matrix and cristae appear in both the endothelial and epithelial cells. Blebbing and rarefication of cytoplasm occur in both cell layers of the alveolo-capillary wall. Also seen are fluid in the basement membrane, platelets in the capillaries, and alveolar fluid and debris. All of these alterations occur at 1 atm exposure. However, after exposure to 450 mm Hg the changes are not as widespread nor as destructive as they are at the higher pressure.

  6. Surface characterization of amalgam made with Hg-In liquid alloy.

    PubMed

    Nakajima, H; Akaiwa, Y; Hashimoto, H; Ferracane, J L; Okabe, T

    1997-01-01

    When amalgam was triturated with Hg-In liquid alloys instead of pure mercury, the resultant amalgams released a significantly smaller amount of mercury vapor during setting. To understand the mechanisms responsible for the drastic decrease in mercury evaporation from the In-containing amalgam, we used Auger Electron Spectroscopy to examine surface oxide films on amalgams made with Hg-10 wt% In or pure mercury. The surface of the In-containing amalgam was rapidly covered with both indium and tin oxide films. Greater amounts of oxygen were found on the gamma 1 Ag-Hg matrix in the In-containing amalgam than in the amalgam without indium. The rapid formation of the oxide film contributes to a reduction in the mercury release from the In-containing amalgam by forming an effective barrier to evaporation. PMID:9042085

  7. Non linear viscoelasticity applied for the study of durability of polymer matrix composites

    NASA Technical Reports Server (NTRS)

    Cardon, A.; Brinson, H. F.; Hiel, C. C.

    1989-01-01

    A methodology is described for the durability analysis of polymer matrix composites, based on nonlinear viscoelasticity theory. The durability analysis is performed on the basis of a certain number of tests carried out on limited and, if possible, short time scale by the use of accelerating factors. The method was applied to thermomatrix composites under uniaxial and biaxial loadings, showing satisfactory agreement between the life-time predictions and the published data on real-time behavior.

  8. Transport coefficients for electrons in Hg vapor

    NASA Astrophysics Data System (ADS)

    Dujko, Sasa; White, Ron; Petrovic, Zoran

    2012-06-01

    Transport coefficients and distribution functions are calculated for electrons in Hg vapor under swarm conditions using a multi term theory for solving the Boltzmann equation, over a range of E/N values and temperatures relevant to lamp discharges. It is shown that for higher E/N the electron distribution is non-thermal for all Hg vapor temperatures considered, and that the speed distribution function significantly deviates from a Maxwellian under these conditions. Our work has been motivated, in part, by recent suggestions that highly accurate data for transport coefficients required as input in fluid models of Hg vapor lamp discharges may significantly improve the existing models. Current models of such lamps require a knowledge of the plasma electrical conductivity, which can be calculated from the cross sections for electron scattering in Hg vapor and mobility coefficients presented in this work. The effect of metastable atoms on the swarm parameters is also discussed. The influence of a magnetic field on electron transport coefficients in Hg vapor is investigated over a range of B/N values and angles between the fields.

  9. HgCdTe barrier infrared detectors

    NASA Astrophysics Data System (ADS)

    Kopytko, M.; Rogalski, A.

    2016-05-01

    In the last decade, new strategies to achieve high-operating temperature (HOT) detectors have been proposed, including barrier structures such as nBn devices, unipolar barrier photodiodes, and multistage (cascade) infrared detectors. The ability to tune the positions of the conduction and valence band edges independently in a broken-gap type-II superlattices is especially helpful in the design of unipolar barriers. This idea has been also implemented in HgCdTe ternary material system. However, the implementation of this detector structure in HgCdTe material system is not straightforward due to the existence of a valence band discontinuity (barrier) at the absorber-barrier interface. In this paper we present status of HgCdTe barrier detectors with emphasis on technological progress in fabrication of MOCVD-grown HgCdTe barrier detectors achieved recently at the Institute of Applied Physics, Military University of Technology. Their performance is comparable with state-of-the-art of HgCdTe photodiodes. From the perspective of device fabrication their important technological advantage results from less stringent surface passivation requirements and tolerance to threading dislocations.

  10. 40 CFR 60.4153 - Recordation of Hg allowance allocations.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Recordation of Hg allowance allocations... Times for Coal-Fired Electric Steam Generating Units Hg Allowance Tracking System § 60.4153 Recordation of Hg allowance allocations. (a) By December 1, 2006, the Administrator will record in the Hg...

  11. 40 CFR 60.4114 - Objections concerning Hg designated representative.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Objections concerning Hg designated... Times for Coal-Fired Electric Steam Generating Units Hg Designated Representative for Hg Budget Sources § 60.4114 Objections concerning Hg designated representative. (a) Once a complete certificate...

  12. 40 CFR 60.4111 - Alternate Hg designated representative.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Alternate Hg designated representative... Times for Coal-Fired Electric Steam Generating Units Hg Designated Representative for Hg Budget Sources § 60.4111 Alternate Hg designated representative. (a) A certificate of representation under §...

  13. 40 CFR 60.45Da - Standard for mercury (Hg).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 6 2010-07-01 2010-07-01 false Standard for mercury (Hg). 60.45Da... for mercury (Hg). (a) For each coal-fired electric utility steam generating unit other than an IGCC... gases that contain mercury (Hg) emissions in excess of each Hg emissions limit in paragraphs...

  14. Dynamic Micro-CT Study of Fracture-Matrix Flow During Capillary Imbibition in Layered Berea Sandstone

    NASA Astrophysics Data System (ADS)

    Karpyn, Z. T.; Halleck, P. M.; Grader, A. S.; Elsworth, D.

    2004-12-01

    Studies concerning flow in fractured rocks have important applications in hydrocarbon recovery, hydrogeology, and environmental remediation of subsurface spills, such as DNAPLs. To properly design immiscible flow processes in those systems, it is crucial to understand fracture-matrix transfer mechanisms. The goal of this work is to provide a mechanistic description of capillary-driven imbibition in fractured media and the effects of fluid occupancy in the fracture and of matrix heterogeneity on saturation distribution. Capillary imbibition experiments where performed in a layered Berea sample, 4.75 cm long and 2.54 cm in diameter, with a single longitudinal fracture. The artificially created fracture was oriented perpendicular to the natural bedding of the rock. The sample was initially vacuum saturated with non-wetting phase. Small amounts of a wetting phase were introduced into the bottom of the fracture, allowing it to imbibe and exchange places with the resident non-wetting phase through the fracture-matrix interface. Progress of the imbibition process was monitored after each injection using high-resolution Micro Computed Tomography (CT). Micro-CT also provided non-destructive means to characterize the fracture structure and rock properties. A series of simulation scenarios were also tested using a commercially available package developed by the Computer Modeling Group (CMG). Experimental observations combined with simulation results indicate that the fracture itself exhibits a strong capillary behavior. Its rough-walled nature, leads to a two-phase flow similar to that in porous media. Experimental observations also show a strong correspondence between fluid invasion in the matrix and variations in porosity in the rock's bedding planes. Our results suggest that different porosities correspond to different permeabilities and capillary pressure curves. Fluid accessibility in the fracture space is also an important factor governing imbibition in fractured media

  15. 46 CFR 53.12-1 - General (modifies HG-600 through HG-640).

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... reference; see 46 CFR 53.01-1) except as noted otherwise in this section. (b) For control systems for... HEATING BOILERS Instruments, Fittings, and Controls (Article 6) § 53.12-1 General (modifies HG-600 through HG-640). (a) The instruments, fittings and controls for heating boilers shall be as indicated in...

  16. 46 CFR 53.12-1 - General (modifies HG-600 through HG-640).

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... reference; see 46 CFR 53.01-1) except as noted otherwise in this section. (b) For control systems for... HEATING BOILERS Instruments, Fittings, and Controls (Article 6) § 53.12-1 General (modifies HG-600 through HG-640). (a) The instruments, fittings and controls for heating boilers shall be as indicated in...

  17. 46 CFR 53.12-1 - General (modifies HG-600 through HG-640).

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... reference; see 46 CFR 53.01-1) except as noted otherwise in this section. (b) For control systems for... HEATING BOILERS Instruments, Fittings, and Controls (Article 6) § 53.12-1 General (modifies HG-600 through HG-640). (a) The instruments, fittings and controls for heating boilers shall be as indicated in...

  18. 46 CFR 53.12-1 - General (modifies HG-600 through HG-640).

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... reference; see 46 CFR 53.01-1) except as noted otherwise in this section. (b) For control systems for... HEATING BOILERS Instruments, Fittings, and Controls (Article 6) § 53.12-1 General (modifies HG-600 through HG-640). (a) The instruments, fittings and controls for heating boilers shall be as indicated in...

  19. 46 CFR 53.12-1 - General (modifies HG-600 through HG-640).

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... reference; see 46 CFR 53.01-1) except as noted otherwise in this section. (b) For control systems for... HEATING BOILERS Instruments, Fittings, and Controls (Article 6) § 53.12-1 General (modifies HG-600 through HG-640). (a) The instruments, fittings and controls for heating boilers shall be as indicated in...

  20. Discovery of Hg-Cu-bearing metal-sulfide assemblages in a primitive H-3 chondrite: Towards a new insight in early solar system processes

    NASA Astrophysics Data System (ADS)

    Caillet Komorowski, Catherine; El Goresy, Ahmed; Miyahara, Masaaki; Boudouma, Omar; Ma, Chi

    2012-10-01

    We report here the discovery of a novel meteoritic paragenesis consisting of sub-micrometric HgS, Cu sulfides, and Hg metal, associated with polycrystalline fine-grained native Cu in opaque mineral aggregates heterogeneously distributed in the matrix of the H-3 Tieschitz unequilibrated ordinary chondrite (UOC). The systematic association of Hg with Cu in Tieschitz chondrite provides a unique opportunity to place robust constraints on the origin of these assemblages either by condensation and sulfidation in a local nebular reservoir of non-solar composition, followed by gentle and fast accretion, or by sublimation of Hg from the hot interior of the asteroid and recondensation in its cold outer regions. The sulfide phase relations support low temperature conditions (<300 °C), implying that subsequent to accretion indigenous hydrothermal processing, oxidation/sulfidation, transportation, or shock-induced thermal processing of the assemblage on the parent body earlier proposed are very unlikely and unrealistic. Origin of HgS by sublimation of Hg from the hotter asteroid interior and precipitation as cinnabar in the colder surface regions is discrepant with our findings and can be ruled out because cinnabar occurs only in Tieschitz matrix in alternating rhythmic intergrowth with Cu-sulfide. The sublimation scenario calls for co-evaporation of both the highly volatile Hg as HgS and Hg metal and the moderately volatile Cu both as Cu metal, or their sulfides and deposition as sulfides in alternating episodes. Our findings provide further ample evidence refuting the repeated claim of formation of native copper in chondritic metal by shock-induced impact melting. Cold accretion is the only reasonable possibility to preserve the delicate accretionary intergrowth textures, the polycrystallinity of FeNi-metal, native Cu, Hg-Cu-sulfides and native Hg globules and the high Hg concentration retained in this meteorite. Our findings strongly suggest that Tieschitz resided near the

  1. Thermodynamics limits the reactivity of BrHg

    NASA Astrophysics Data System (ADS)

    Dibble, Theodore S.; Schwid, Abraham C.

    2016-08-01

    Mercury emissions to the atmosphere primarily consist of Hg(0), which tends not to enter ecosystems until it is oxidized. Atomic bromine initiates oxidation of Hg(0) via the BrHg intermediate, but the further reactions of BrHg are just beginning to be explored. Here we use quantum chemistry to determine that hydrogen abstraction from hydrocarbons by BrHg is so endothermic as to be irrelevant. Bonds between BrHg and carbon atoms are so weak that BrHg addition to carbon-carbon double bonds atoms will be somewhat ineffective in leading to further reactions.

  2. Mechanisms of Hg species induced toxicity in cultured human astrocytes: genotoxicity and DNA-damage response.

    PubMed

    Pieper, Imke; Wehe, Christoph A; Bornhorst, Julia; Ebert, Franziska; Leffers, Larissa; Holtkamp, Michael; Höseler, Pia; Weber, Till; Mangerich, Aswin; Bürkle, Alexander; Karst, Uwe; Schwerdtle, Tanja

    2014-03-01

    The toxicologically most relevant mercury (Hg) species for human exposure is methylmercury (MeHg). Thiomersal is a common preservative used in some vaccine formulations. The aim of this study is to get further mechanistic insight into the yet not fully understood neurotoxic modes of action of organic Hg species. Mercury species investigated include MeHgCl and thiomersal. Additionally HgCl2 was studied, since in the brain mercuric Hg can be formed by dealkylation of the organic species. As a cellular system astrocytes were used. In vivo astrocytes provide the environment necessary for neuronal function. In the present study, cytotoxic effects of the respective mercuricals increased with rising alkylation level and correlated with their cellular bioavailability. Further experiments revealed for all species at subcytotoxic concentrations no induction of DNA strand breaks, whereas all species massively increased H2O2-induced DNA strand breaks. This co-genotoxic effect is likely due to a disturbance of the cellular DNA damage response. Thus, at nanomolar, sub-cytotoxic concentrations, all three mercury species strongly disturbed poly(ADP-ribosyl)ation, a signalling reaction induced by DNA strand breaks. Interestingly, the molecular mechanism behind this inhibition seems to be different for the species. Since chronic PARP-1 inhibition is also discussed to sacrifice neurogenesis and learning abilities, further experiments on neurons and in vivo studies could be helpful to clarify whether the inhibition of poly(ADP-ribosyl)ation contributes to organic Hg induced neurotoxicity. PMID:24549367

  3. Genetic engineering of bacteria and their potential for Hg2+ bioremediation.

    PubMed

    Chen, S; Wilson, D B

    1997-01-01

    Ion exchange or biosorptive processes for metal removal generally lack specificity in metal binding and are sensitive to ambient conditions, e.g. pH, ionic strength and the presence of metal chelators. In this study, cells of a genetically engineered Escherichia coli strain, JM109, which expresses metallothionein and a Hg2+ transport system after induction were evaluated for their selectivity for Hg2+ accumulation in the presence of sodium, magnesium, or cadmium ions and their sensitivity to pH or the presence of metal chelators during Hg2+ bioaccumulation. The genetically engineered E. coli cells in suspension accumulated Hg2+ effectively at low concentrations (0-20 microM) over a broad range of pH (3 to 11). The presence of 400 mM sodium chloride, 200 mM magnesium chloride, or 100 microM cadmium ions did not have a significant effect on the bioaccumulation of 5 microM Hg2+, indicating that this process is not sensitive to high ionic strength and is highly selective against sodium, magnesium, or cadmium ions. Metal chelators usually interfere with ion exchange or biosorptive processes. However, two common metal chelators, EDTA and citrate, had no significant effect on Hg2+ bioaccumulation by the genetically engineered strain. These results suggest that this E. coli strain could be used for selective removal of Hg2+ from waste water or from contaminated solutions which are resistant to common treatments. A second potential application would be to remove Hg2+ from Hg(2+)-contaminated soil, sediment, or particulates by washing them with a Hg2+ chelator and regenerating the chelator by passing the solution through a reactor containing the strain. PMID:9342882

  4. Comparing Linear Sigma Model K-matrix studies of sigma/f0 and the Higgs boson

    SciTech Connect

    A. Abdel-Rehim; Deirdre M. Black; A.H. Fariborz; Salah Nasri; Joseph Schechter

    2003-05-01

    We present a description of the low energy pi pi scattering data using the Linear Sigma Model with K-matrix unitarization. Then we carry out an analogous study of the strongly-coupled minimal Higgs sector of the electroweak theory. We discuss the effect of the unitarization prescription on the WW or ZZ fusion processes and also suggest a related treatment for other Higgs production processes such as gluon fusion.

  5. Biofilm Matrix Proteins

    PubMed Central

    Fong, Jiunn N. C.; Yildiz, Fitnat H.

    2015-01-01

    Proteinaceous components of the biofilm matrix include secreted extracellular proteins, cell surface adhesins and protein subunits of cell appendages such as flagella and pili. Biofilm matrix proteins play diverse roles in biofilm formation and dissolution. They are involved in attaching cells to surfaces, stabilizing the biofilm matrix via interactions with exopolysaccharide and nucleic acid components, developing three-dimensional biofilm architectures, and dissolving biofilm matrix via enzymatic degradation of polysaccharides, proteins, and nucleic acids. In this chapter, we will review functions of matrix proteins in a selected set of microorganisms, studies of the matrix proteomes of Vibrio cholerae and Pseudomonas aeruginosa, and roles of outer membrane vesicles and of nucleoid-binding proteins in biofilm formation. PMID:26104709

  6. Magnetotransport in double quantum well with inverted energy spectrum: HgTe/CdHgTe

    NASA Astrophysics Data System (ADS)

    Yakunin, M. V.; Suslov, A. V.; Popov, M. R.; Novik, E. G.; Dvoretsky, S. A.; Mikhailov, N. N.

    2016-02-01

    We present an experimental study of the double-quantum-well (DQW) system made of two-dimensional layers with inverted energy band spectrum: HgTe. The magnetotransport reveals a considerably larger overlap of the conduction and valence subbands than in known HgTe single quantum wells (QW), which may be regulated here by an applied gate voltage Vg. This large overlap manifests itself in a much higher critical field Bc separating the range above it with a plain behavior of the Hall magnetoresistance ρx y(B ) , where the quantum peculiarities shift linearly with Vg, and the range below with a complicated behavior. In the latter case, specific structures in ρx y(B ) are formed like a double-N -shaped ρx y(B ) , reentrant sign-alternating quantum Hall effect with transitions into a zero-filling-factor state, etc., which are clearly manifested here due to better magnetic quantization at high fields, as compared to the features seen earlier in a single HgTe QW. The coexisting electrons and holes were found in the whole investigated range of positive and negative Vg as revealed (i) from fits to the low-field N -shaped ρx y(B ) , (ii) from the Fourier analysis of oscillations in ρx x(B ) , and (iii) from a specific behavior of ρx y(B ) at high positive Vg. A peculiar feature here is that the found electron density n remains almost constant in the whole range of investigated Vg while the hole density p drops down from the value a factor of 6 larger than n at extreme negative Vg to almost zero at extreme positive Vg passing through the charge-neutrality point. We show that this difference between n and p stems from an order of magnitude larger density of states for holes in the lateral valence subband maxima than for electrons in the conduction subband minimum. We analyze our observations on the basis of a calculated picture of magnetic levels in a DQW and suggest that their specificity is due to (i) a nonmonotonic course of the valence subband magnetic levels and an

  7. Synthesis and Characterization of Sodium Alginate Conjugate and Study of Effect of Conjugation on Drug Release from Matrix Tablet.

    PubMed

    Satheeshababu, B K; Mohamed, I

    2015-01-01

    The aim of the present research work to study the effect of conjugation of the polymer on drug release from the matrix tablets. Sodium alginate L-cysteine conjugate was achieved by covalent attachment of thiol group of L-cysteine with the primary amino group of sodium alginate through the amide bonds formed by primary amino groups of the sodium alginate and the carboxylic acid group of L-cysteine. The synthesised sodium alginate L-cysteine conjugate was characterised by determining of charring point, Fourier transmission-infrared and differential scanning calorimetric analysis. To study the effect of conjugation on drug release pattern, the matrix tablets were prepared using various proportions of sodium alginate and sodium alginate L-cysteine conjugate along with atorvastatin calcium as model drug. The wet granulation technique was adopted and prepared matrix tablets were evaluated for various physical parameters. The in vitro drug release study results suggested that tablet formulated in combination of sodium alginate and sodium alginate L-cysteine conjugate S4 showed 100% after 8 h drug release whereas formulated with only sodium alginate S0 released 40% in 8 h. PMID:26798173

  8. Synthesis and Characterization of Sodium Alginate Conjugate and Study of Effect of Conjugation on Drug Release from Matrix Tablet

    PubMed Central

    Satheeshababu, B. K.; Mohamed, I.

    2015-01-01

    The aim of the present research work to study the effect of conjugation of the polymer on drug release from the matrix tablets. Sodium alginate L-cysteine conjugate was achieved by covalent attachment of thiol group of L-cysteine with the primary amino group of sodium alginate through the amide bonds formed by primary amino groups of the sodium alginate and the carboxylic acid group of L-cysteine. The synthesised sodium alginate L-cysteine conjugate was characterised by determining of charring point, Fourier transmission-infrared and differential scanning calorimetric analysis. To study the effect of conjugation on drug release pattern, the matrix tablets were prepared using various proportions of sodium alginate and sodium alginate L-cysteine conjugate along with atorvastatin calcium as model drug. The wet granulation technique was adopted and prepared matrix tablets were evaluated for various physical parameters. The in vitro drug release study results suggested that tablet formulated in combination of sodium alginate and sodium alginate L-cysteine conjugate S4 showed 100% after 8 h drug release whereas formulated with only sodium alginate S0 released 40% in 8 h. PMID:26798173

  9. A mouse 3T6 fibroblast cell culture model for the study of normal and protein-engineered collagen synthesis and deposition into the extracellular matrix.

    PubMed

    Lamandé, S R; Bateman, J F

    1993-07-01

    Mouse 3T6 fibroblasts deposited an organized collagenous extracellular matrix during long-term culture in the presence of ascorbic acid. The matrix produced by the cells had a similar distribution of collagen types as the mouse dermal matrix, comprising predominantly type I with smaller amounts of types III and V collagens. By day 8 of culture more than 70% of the collagen in the 3T6 matrix was involved in covalent crosslinkages and required pepsin digestion for extraction. Incorporation of NaB3H4 into reducible crosslinks and aldehydes directly demonstrated the involvement of the alpha 1 (I)CB6 and alpha 2(I)CB3.5 in crosslinks. The pattern of reducible crosslinks in the in vitro 3T6 matrix was similar to that in mouse skin suggesting a comparable fibril organization. Processing of procollagen to collagen occurred efficiently throughout the culture period and the rate of collagen production was unaltered during 15 days of culture, indicating that the development of a collagenous matrix does not directly play a role in procollagen processing or biosynthetic regulation. The existence of a preformed matrix did however, increase the efficiency with which newly synthesised collagen was incorporated into the pericellular matrix. At day 0, when there was no measurable matrix present, 29% of the collagen synthesised was deposited, while by day 15, 88% of the collagen was laid down in the matrix. The development of this 3T6 culture system, where collagen is efficiently incorporated into an organized extracellular matrix, will facilitate detailed studies on matrix organization and regulation and provide a system in which protein-engineered mutant collagens can be expressed to determine their effects on the production of a functional extracellular matrix. PMID:8412990

  10. Mercury methylation in rice paddies and its possible controlling factors in the Hg mining area, Guizhou province, Southwest China.

    PubMed

    Zhao, Lei; Qiu, Guangle; Anderson, Christopher W N; Meng, Bo; Wang, Dingyong; Shang, Lihai; Yan, Haiyu; Feng, Xinbin

    2016-08-01

    Understanding mercury (Hg) methylation/demethylation processes and the factors controlling methylmercury (MeHg) production within the rice paddy ecosystem of Hg mining areas is critical to assess the risk of MeHg contamination in rice grain. Two typical Hg-contaminated mining sites, a current-day artisanal site (Gouxi) and an abandoned site (Wukeng), were chosen in this study. We qualified the in situ specific methylation/demethylation rate constants in rice paddy soil during a complete rice-growing season. Our results demonstrate that MeHg levels in rice paddy soil were a function of both methylation and demethylation processes and the net methylation potential in the rice paddy soil reflected the measured MeHg production at any time point. Sulfate stimulating the activity of sulfate-reducing bacteria was a potentially important metabolic pathway for Hg methylation in rice paddies. We suggest that bioavailable Hg derived from new atmospheric deposition appears to be the primary factor regulating net MeHg production in rice paddies. PMID:27176759

  11. Matrix Isolation FTIR and AB Initio Studies on the Conformations of Dimethyl and Diethyl Carbonate and Their Complexes with Water

    NASA Astrophysics Data System (ADS)

    Kar, Bishnu Prasad; Ramanathan, N.; Sundararajan, K.; Viswanathan, K. S.

    2011-06-01

    Dimethyl carbonate (DMC) and diethyl carbonate (DEC) have been studied for their conformations using matrix isolation infrared spectroscopy and ab initio computations. In addition to the above studies, the complexes of the two compounds with water have also been studied. The experiments were corroborated with ab initio calculations at the B3LYP/6-31++G** level. The organic carbonates were trapped in argon and nitrogen matrixes using an effusive source maintained at two different temperatures; i.e. room temperature and 170°C. In addition the matrix was also deposited using a supersonic jet source. These experiments were performed to alter the relative population of the various conformations, to aid us in the assignments of the vibrational features. The conformation of DMC corresponding to the global minimum of DMC was found to be a cis-cis conformer where the two methyl groups are found to be at cis position with respect to the carbonyl oxygen. The next higher energy conformer corresponded to a cis-trans structure with a near trans-near trans structure being the highest energy conformer. In our experimental matrix isolation spectra of DMC, we were able to assign features due to the cis-cis and cis-trans conformers. The features of the higher energy cis-trans conformer was confirmed with our experiments using the elevated temperature effusive source and the supersonic source. DEC displays a richer conformational landscape due to the presence of a longer carbon chain. The computational and experimental indicate that the ground state conformer for this compound is one in which carbon attached to oxygen adopts a cis configuration with respect to the carbonyl oxygen, while the terminal carbon adopts an anti conformation. A detailed study of the conformational picture of DEC will be presented. In addition to the above conformational studies, 1:1 hydrogen bonded complexes of DMC and DEC with water were also observed in the matrix, which was corroborated by our

  12. Aptamer-functionalized porous phospholipid nanoshells for direct measurement of Hg(2+) in urine.

    PubMed

    Li, Zhen; Muhandiramlage, Thusitha P; Keogh, John P; Hall, Henry K; Aspinwall, Craig A

    2015-01-01

    A porous phospholipid nanoshell (PPN) sensor functionalized with a specific aptamer sensor agent was prepared for rapid detection of Hg(2+) in human urine with minimal sample preparation. Aptamer sensors provide an important class of optical transducers that can be readily and reproducibly synthesized. A key limitation of aptamer sensors, and many other optical sensors, is the potential of biofouling or biodegradation when used in complex biological matrices such as serum or urine, particularly when high levels of nucleases are present. We prepared Hg(2+)-responsive, PPN-encapsulated aptamer sensors that overcome these limitations. PPNs provide a protective barrier to encapsulate the aptamer sensor in an aqueous environment free of diffusional restrictions encountered with many polymer nanomaterials. The unique porous properties of the PPN membrane enable ready and rapid transfer of small molecular weight ions and molecules into the sensor interior while minimizing the macromolecular interactions between the transducer and degradants or interferents in the exterior milieu. Using Hg(2+)-responsive, PPN-encapsulated aptamer sensors, we were able to detect sub-100 ppb (chronic threshold limit from urine test) Hg(2+) in human urine with no sample preparation, whereas free aptamer sensors yielded inaccurate results due to interferences from the matrix. The PPN architecture provides a new platform for construction of aptamer-functionalized sensors that target low molecular weight species in complex matrices, beyond the Hg(2+) demonstrated here. PMID:25326888

  13. Degeneracy Lifting Effect in the FTIR Spectrum of Fluoroform Trapped in a Nitrogen Matrix. An Experimental and Car-Parrinello Molecular Dynamics Study.

    PubMed

    Asfin, Ruslan E; Melikova, Sona M; Domanskaya, Alexandra V; Rodziewicz, Paweł; Rutkowski, Konstantin S

    2016-05-26

    The FTIR spectra of fluoroform trapped in argon and nitrogen matrixes are studied at T ∼ 10-30 K. The bands of E symmetry show the splitting effect in a nitrogen matrix, which is absent in an argon matrix. The effect is the most prominent in the case of the ν4 CH bending vibration. It decreases slightly with increasing temperature. Both static and Car-Parrinello molecular dynamic simulations suggest that the degeneracy lifting is due to C3v symmetry lowering caused by interactions between fluoroform and all neighbor N2 matrix molecules. PMID:27149085

  14. Studies of Matrix/Fiber Reinforced Composite Materials for the High Speed Research (HSR) Program

    NASA Technical Reports Server (NTRS)

    Orwoll, Robert A.

    1998-01-01

    The research on the curing mechanism of the phenylethynyl terminated imide matrix resins was the primary focus of this research. The ability to process high performance polymers into useful adhesives and high quality composites has been significantly advanced by synthetic techniques in which oligomers terminated with reactive groups cure or crosslink at elevated temperature after the article has been fabricated. The research used a variety of analytical techniques. Many stable products were isolated, and attempts at identification were made. This research was intended to provide fundamental insight into the molecular structure of these new engineering materials.

  15. Monte Carlo studies of supersymmetric matrix quantum mechanics with sixteen supercharges at finite temperature.

    PubMed

    Anagnostopoulos, Konstantinos N; Hanada, Masanori; Nishimura, Jun; Takeuchi, Shingo

    2008-01-18

    We present the first Monte Carlo results for supersymmetric matrix quantum mechanics with 16 supercharges at finite temperature. The recently proposed nonlattice simulation enables us to include the effects of fermionic matrices in a transparent and reliable manner. The internal energy nicely interpolates the weak coupling behavior obtained by the high temperature expansion, and the strong coupling behavior predicted from the dual black-hole geometry. The Polyakov line asymptotes at low temperature to a characteristic behavior for a deconfined theory, suggesting the absence of a phase transition. These results provide highly nontrivial evidence for the gauge-gravity duality. PMID:18232852

  16. A comparison study of different physical treatments on cartilage matrix derived porous scaffolds for tissue engineering applications

    NASA Astrophysics Data System (ADS)

    Moradi, Ali; Pramanik, Sumit; Ataollahi, Forough; Khalil, Alizan Abdul; Kamarul, Tunku; Pingguan-Murphy, Belinda

    2014-12-01

    Native cartilage matrix derived (CMD) scaffolds from various animal and human sources have drawn attention in cartilage tissue engineering due to the demonstrable presence of bioactive components. Different chemical and physical treatments have been employed to enhance the micro-architecture of CMD scaffolds. In this study we have assessed the typical effects of physical cross-linking methods, namely ultraviolet (UV) light, dehydrothermal (DHT) treatment, and combinations of them on bovine articular CMD porous scaffolds with three different matrix concentrations (5%, 15% and 30%) to assess the relative strengths of each treatment. Our findings suggest that UV and UV-DHT treatments on 15% CMD scaffolds can yield architecturally optimal scaffolds for cartilage tissue engineering.

  17. Noninterventional Study of Transdermal Fentanyl (Fentavera) Matrix Patches in Chronic Pain Patients: Analgesic and Quality of Life Effects

    PubMed Central

    Heim, Manuel

    2015-01-01

    Fentanyl is considered to be an effective, transdermal treatment of chronic, cancer, and noncancer pain. This noninterventional, clinical practice-based study, on 426 patients attending 42 practices, assessed a proprietary, Aloe vera-containing, transdermal fentanyl matrix patch (Fentavera), for its analgesic effects, patients' quality of life (QoL) effects, tolerability, and adhesiveness. Study outcomes were mean changes from baseline of patient (11-point scales) and physician (5-point scales) ratings. After 1 and 2 months treatment, there were significant (P < 0.0001) decreases in patients' ratings of pain intensity, and impairment of walking, general activity, sleep quality, and QoL. For each parameter, the patient response rate was >30% at 2 months (response = 2-point decrease on 11-point rating scale). In a large majority of patients, the physicians rated the matrix patch as good or very good for analgesic effect, systemic and local tolerance, and adhesiveness. There were 30 adverse events in 4.2% of patients and analgesic comedications were reduced during treatment compared to before treatment. It is concluded, from this population-based data, that the proprietary, transdermal fentanyl matrix patch is effective and safe for chronic pain management in clinical practice, with significant positive analgesic and QoL effects, while being well tolerated and exhibiting good or very good adhesiveness. PMID:25861472

  18. Noninterventional study of transdermal fentanyl (fentavera) matrix patches in chronic pain patients: analgesic and quality of life effects.

    PubMed

    Heim, Manuel

    2015-01-01

    Fentanyl is considered to be an effective, transdermal treatment of chronic, cancer, and noncancer pain. This noninterventional, clinical practice-based study, on 426 patients attending 42 practices, assessed a proprietary, Aloe vera-containing, transdermal fentanyl matrix patch (Fentavera), for its analgesic effects, patients' quality of life (QoL) effects, tolerability, and adhesiveness. Study outcomes were mean changes from baseline of patient (11-point scales) and physician (5-point scales) ratings. After 1 and 2 months treatment, there were significant (P < 0.0001) decreases in patients' ratings of pain intensity, and impairment of walking, general activity, sleep quality, and QoL. For each parameter, the patient response rate was >30% at 2 months (response = 2-point decrease on 11-point rating scale). In a large majority of patients, the physicians rated the matrix patch as good or very good for analgesic effect, systemic and local tolerance, and adhesiveness. There were 30 adverse events in 4.2% of patients and analgesic comedications were reduced during treatment compared to before treatment. It is concluded, from this population-based data, that the proprietary, transdermal fentanyl matrix patch is effective and safe for chronic pain management in clinical practice, with significant positive analgesic and QoL effects, while being well tolerated and exhibiting good or very good adhesiveness. PMID:25861472

  19. Spectral matrix analysis for detection of polarized wave arrivals and its application to seismic reflection studies using local earthquake data

    NASA Astrophysics Data System (ADS)

    Moriya, H.

    2009-12-01

    Local earthquakes observed at Sendai, Japan, were analyzed to confirm the validity of a method of polarization analysis using the spectral matrix of seismic wave and its application to seismic reflection studies of the crust using local earthquake data. Reflectors (Bright spots) are known below the Nagamachi-Rifu fault, which caused an M 5.0 class event in 1998. Polarization analysis was applied to earthquake data in and around the fault. Use of the Z-parameter, which is defined using the eigenvalues of the spectral matrix and a statistical value representing the confidence level for the detection of the arrival of polarized waves, allowed detection of linearly and elliptically polarized waves in coda waves. The Z-parameter was also used to image the reflectors by using a migration technique that assumes the P × P and S × S reflection waves travel through a multi-layered velocity structure. Distinct reflectors were detected at depths of around 10 km, 14 km, 17 km, 21-26 km, 35 km and 40 km, that is, from deeper than the fault and the Moho. This study demonstrated the feasibility of using the spectral matrix of three-component seismic signal to detect polarized waves and to image reflectors in the earth's crust and upper mantle.

  20. Bayesian Inference for Multivariate Meta-regression with a Partially Observed Within-Study Sample Covariance Matrix

    PubMed Central

    Yao, Hui; Kim, Sungduk; Chen, Ming-Hui; Ibrahim, Joseph G.; Shah, Arvind K.; Lin, Jianxin

    2015-01-01

    Summary Multivariate meta-regression models are commonly used in settings where the response variable is naturally multi-dimensional. Such settings are common in cardiovascular and diabetes studies where the goal is to study cholesterol levels once a certain medication is given. In this setting, the natural multivariate endpoint is Low Density Lipoprotein Cholesterol (LDL-C), High Density Lipoprotein Cholesterol (HDL-C), and Triglycerides (TG) (LDL-C, HDL-C, TG). In this paper, we examine study level (aggregate) multivariate meta-data from 26 Merck sponsored double-blind, randomized, active or placebo-controlled clinical trials on adult patients with primary hypercholesterolemia. Our goal is to develop a methodology for carrying out Bayesian inference for multivariate meta-regression models with study level data when the within-study sample covariance matrix S for the multivariate response data is partially observed. Specifically, the proposed methodology is based on postulating a multivariate random effects regression model with an unknown within-study covariance matrix Σ in which we treat the within-study sample correlations as missing data, the standard deviations of the within-study sample covariance matrix S are assumed observed, and given Σ, S follows a Wishart distribution. Thus, we treat the off-diagonal elements of S as missing data, and these missing elements are sampled from the appropriate full conditional distribution in a Markov chain Monte Carlo (MCMC) sampling scheme via a novel transformation based on partial correlations. We further propose several structures (models) for Σ, which allow for borrowing strength across different treatment arms and trials. The proposed methodology is assessed using simulated as well as real data, and the results are shown to be quite promising. PMID:26257452

  1. Formulation and in vitro release studies of pegylated mucin based matrix tablets.

    PubMed

    Eraga, Sylvester Okhuelegbe; Arhewoh, Matthew Ikhuoria; Iwuagwu, Magnus Amara; Ukponahiusi, Oyenmwen Enoma

    2015-01-01

    The effects of polymer concentration on the flow properties of granules and in-vitro release profiles from matrix tablets of three model drugs formulated from pegylated mucin base was investigated. Mucin was extracted from the African giant snail and in combination with PEG was used to produce a copolymer matrix base, which was mixed with the model drugs using wet granulation method. The granules and tablets were evaluated according to official and unofficial requirements. Results showed best flow with Acetylsalicylic acid (ASA) and Chloroquine Phosphate (CQ) granules with Hausner ratio of 1.04-1.2, Carr's index of 4.2-17.5% and angle of repose between 19°-26°. The tablets met B.P specifications with respect to tablet weights, friability and drug content. The release profiles showed faster release of the drug with high content of PEG and a slower release with high concentration of mucin. Pegylated mucin base will find useful application in the development of a wide range of formulations. PMID:25553689

  2. Enhanced plasticity in a bulk amorphous matrix composite: macroscopic and microscopic viewpoint studies

    SciTech Connect

    Lee, Jae-Chul . E-mail: jclee001@korea.ac.kr; Kim, Yu-Chan; Ahn, Jae-Pyoung; Kim, Hyoung Seop

    2005-01-03

    We developed the (Cu{sub 60}Zr{sub 30}Ti{sub 10}){sub 0.95}Ta{sub 5} amorphous matrix composite, which is a Cu-based bulk amorphous composite reinforced with a micron-sized Ta-rich crystalline phase. The composite demonstrated an ultimate strength of 2332 MPa with a dramatically enhanced fracture strain of 15.3%. Macroscopic observation of the fractured (Cu{sub 60}Zr{sub 30}Ti{sub 10}){sub 0.95}Ta{sub 5} amorphous composite using scanning electron microscopy showed the presence of multiple shear bands along with numerous secondary shear bands, which spread from the primary shear bands. On the other hand, microscopic observation of the fractured composite using transmission electron microscopy showed that the cracks propagate through the amorphous matrix in a jagged manner. The observed macroscopic and microscopic behaviors, involving shear band formation and crack propagation, are believed to be responsible for the enhanced plasticity. Finite element calculations using the Mohr-Coulomb model of hydrostatic pressure dependent materials were conducted, in order to gain a better understanding of various aspects of the macroscopic deformation behavior, such as the interaction of the shear bands with the crystalline particles, the initiation site of the shear bands, and the formation of multiple shear bands, while the microscopic deformation behavior was explained based on the formation of nanocrystallites that had precipitated under quasistatic compression.

  3. Hg Deposition to Lakes in Northern New England Inferred at Multiple Scales From 210Pb-Dated Sediment Cores

    NASA Astrophysics Data System (ADS)

    Kamman, N. C.; Engstrom, D.

    2004-05-01

    Mercury (Hg) contamination of aquatic systems is recognized to be a problem of global consequence, and Hg bioaccumulation poses significant risks to piscivorous animals and humans who consume gamefish. In order to quantify historical and current Hg deposition to the northern New England landscape, we dated and performed Hg analyses on sediments cores from various lakes at local and regional scales. In this presentation, we contrast results of three studies: a regional assessment of Hg deposition to the VT-NH landscape (10 lakes); a localized study of deposition to the Lye Brook Wilderness of southern VT (four lakes); and the first-ever dated assessment of sediment Hg deposition history for Lake Champlain (three sites + one adjacent inland lake). At the VT-NH scale, total Hg (HgT) fluxes to sediments ranged from 5 to 17 μ g.m-2.yr-1 during pre-industrial times, and from 21 to 83 μ g.m-2.yr-1 presently. Present-day HgT fluxes are between 2.1 to 6.9 times greater than pre-1850 fluxes, and atmospheric Hg deposition to the VT-NH region was estimated at 21 μ g.m-2.yr-1. This agrees well with measured HgT deposition, when re-evasion of Hg is accounted for. Hg fluxes to lake sediments have declined in recent decades, owing to reductions in atmospheric Hg deposition to the lake surfaces. In the high-elevation Lye Brook Wilderness landscape, baseline, peak, and present accumulations were higher than those estimated from the VT-NH dataset, a finding that highlights the roles of elevation, watershed size, and dissolved organic carbon export in mediating Hg transport. Available data from the Lake Champlain Basin show the influence of historical and current watershed sediment delivery due to land cultivation, and more recently to land-use conversion. These studies jointly indicate that watershed export of legacy Hg continues despite declines in present-day deposition rates, contributing to the impression that Hg retention by watershed soils has declined.

  4. Investigation of Substrate Effects on Interface Strain and Defect Generation in MBE-Grown HgCdTe

    NASA Astrophysics Data System (ADS)

    Gu, R.; Lei, W.; Antoszewski, J.; Faraone, L.

    2016-09-01

    Si, Ge, and GaAs have been extensively investigated as alternative substrates for molecular-beam epitaxy (MBE) growth of HgCdTe and, at present, are widely used for HgCdTe-based infrared focal-plane arrays. However, the problem of high dislocation density in HgCdTe layers grown on these lattice-mismatched substrates has yet to be resolved. In this work, we investigated another alternative substrate, GaSb, which has a significantly smaller lattice mismatch with HgCdTe in comparison with Si, Ge, and GaAs, and is readily available as large-area, epiready wafers at much lower cost in comparison with lattice-matched CdZnTe substrates. The resultant stress due to lattice and thermal mismatch between the HgCdTe epilayer and various substrates has been calculated in this work using the elasticity matrix, and the corresponding stress distribution simulated using ANSYS. The simulated structures were matched by experimental samples involving MBE growth of HgCdTe on GaAs, GaSb, and CdZnTe substrates, and were characterized via reflection high-energy electron diffraction and x-ray diffraction analysis, followed by etch pit density (EPD) analysis. In comparison with other alternative substrates, GaSb is shown to have lower interface stress and lower EPD, rendering it an interesting and promising alternative substrate material for HgCdTe epitaxy.

  5. Investigation of Substrate Effects on Interface Strain and Defect Generation in MBE-Grown HgCdTe

    NASA Astrophysics Data System (ADS)

    Gu, R.; Lei, W.; Antoszewski, J.; Faraone, L.

    2016-05-01

    Si, Ge, and GaAs have been extensively investigated as alternative substrates for molecular-beam epitaxy (MBE) growth of HgCdTe and, at present, are widely used for HgCdTe-based infrared focal-plane arrays. However, the problem of high dislocation density in HgCdTe layers grown on these lattice-mismatched substrates has yet to be resolved. In this work, we investigated another alternative substrate, GaSb, which has a significantly smaller lattice mismatch with HgCdTe in comparison with Si, Ge, and GaAs, and is readily available as large-area, epiready wafers at much lower cost in comparison with lattice-matched CdZnTe substrates. The resultant stress due to lattice and thermal mismatch between the HgCdTe epilayer and various substrates has been calculated in this work using the elasticity matrix, and the corresponding stress distribution simulated using ANSYS. The simulated structures were matched by experimental samples involving MBE growth of HgCdTe on GaAs, GaSb, and CdZnTe substrates, and were characterized via reflection high-energy electron diffraction and x-ray diffraction analysis, followed by etch pit density (EPD) analysis. In comparison with other alternative substrates, GaSb is shown to have lower interface stress and lower EPD, rendering it an interesting and promising alternative substrate material for HgCdTe epitaxy.

  6. Measurement of Linear Stark Interference in {sup 199}Hg

    SciTech Connect

    Loftus, T. H.; Swallows, M. D.; Griffith, W. C.; Romalis, M. V.; Heckel, B. R.; Fortson, E. N.

    2011-06-24

    We present measurements of Stark interference in the 6{sup 1}S{sub 0}{yields}6{sup 3}P{sub 1} transition in {sup 199}Hg, a process whereby a static electric field E mixes magnetic dipole and electric quadrupole couplings into an electric dipole transition, leading to E-linear energy shifts similar to those produced by a permanent atomic electric dipole moment (EDM). The measured interference amplitude, a{sub SI}=(a{sub M1}+a{sub E2})=(5.8{+-}1.5)x10{sup -9} (kV/cm){sup -1}, agrees with relativistic, many-body predictions and confirms that earlier central-field estimates are a factor of 10 too large. More importantly, this study validates the capability of the {sup 199}Hg EDM search apparatus to resolve nontrivial, controlled, and sub-nHz Larmor frequency shifts with EDM-like characteristics.

  7. Measurement of linear stark interference in 199Hg.

    PubMed

    Loftus, T H; Swallows, M D; Griffith, W C; Romalis, M V; Heckel, B R; Fortson, E N

    2011-06-24

    We present measurements of Stark interference in the (61)S(0)→6(3)P(1) transition in (199)Hg, a process whereby a static electric field E mixes magnetic dipole and electric quadrupole couplings into an electric dipole transition, leading to E-linear energy shifts similar to those produced by a permanent atomic electric dipole moment (EDM). The measured interference amplitude, a(SI) = (a(M1) + a(E2)) = (5.8 ± 1.5) × 10(-9) (kV / cm)(-1), agrees with relativistic, many-body predictions and confirms that earlier central-field estimates are a factor of 10 too large. More importantly, this study validates the capability of the (199)Hg EDM search apparatus to resolve nontrivial, controlled, and sub-nHz Larmor frequency shifts with EDM-like characteristics. PMID:21770639

  8. Measurement of Linear Stark Interference in Hg199

    NASA Astrophysics Data System (ADS)

    Loftus, T. H.; Swallows, M. D.; Griffith, W. C.; Romalis, M. V.; Heckel, B. R.; Fortson, E. N.

    2011-06-01

    We present measurements of Stark interference in the 6S01→6P13 transition in Hg199, a process whereby a static electric field E mixes magnetic dipole and electric quadrupole couplings into an electric dipole transition, leading to E-linear energy shifts similar to those produced by a permanent atomic electric dipole moment (EDM). The measured interference amplitude, aSI=(aM1+aE2)=(5.8±1.5)×10-9(kV/cm)-1, agrees with relativistic, many-body predictions and confirms that earlier central-field estimates are a factor of 10 too large. More importantly, this study validates the capability of the Hg199 EDM search apparatus to resolve nontrivial, controlled, and sub-nHz Larmor frequency shifts with EDM-like characteristics.

  9. Chemical stabilization and high pressure synthesis of Ba-free Hg-based superconductors, (Hg,M)Sr{sub 2}Ca{sub n-1}Cu{sub n}O{sub y}(N=1{approximately}3)

    SciTech Connect

    Kishio, K. |; Shimoyama, J.; Hahakura, S.

    1994-12-31

    A homologous series of new Hg-based HTSC compounds, (Hg,M)Sr{sub 2}Ca{sub n-1}Cu{sub n}O{sub y} with n=1 to 3, have been synthesized. The stabilization of the pure phases have been accomplished by chemical doping of third elements such as M=Cr, Mo and Re. While the Hg1201(n=1) phase was readily obtained in this way, it was necessary to simultaneously dope Y into the Ca site to stabilize the Hg1212(n=2) phase. On the other hand, single-phase Y-free Hg1212(n=2) and Hg1223(n=3) samples were synthesized only under a high pressure of 6 GPa. In sharp contrast to the Ba-containing compounds, all the samples prepared in the present study have been quite stable during the synthesis and no deterioration in air has been observed after the preparation.

  10. Optical spectroscopic and reverse-phase HPLC analyses of Hg(II) binding to phytochelatins.

    PubMed

    Mehra, R K; Miclat, J; Kodati, V R; Abdullah, R; Hunter, T C; Mulchandani, P

    1996-02-15

    Optical spectroscopy and reverse-phase HPLC were used to investigate the binding of Hg(II) to plant metal-binding peptides (phytochelatins) with the structure (gammaGlu-Cys)2Gly, (gammaGlu-Cys)3Gly and (gammaGlu-Cys)4Gly. Glutathione-mediated transfer of Hg(II) into phytochelatins and the transfer of the metal ion from one phytochelatin to another was also studied using reverse-phase HPLC. The saturation of Hg(II)-induced bands in the UV/visible and CD spectra of (gammaGlu-Cys)2Gly suggested the formation of a single Hg(II)-binding species of this peptide with a stoichiometry of one metal ion per peptide molecule. The separation of apo-(gammaGlu-Cys)2Gly from its Hg(II) derivative on a C18 reverse-phase column also indicated the same metal-binding stoichiometry. The UV/visible spectra of both (gammaGlu-Cys)3Gly and (gammaGlu-Cys)4Gly at pH 7.4 showed distinct shoulders in the ligand-to-metal charge-transfer region at 280-290 mm. Two distinct Hg(II)-binding species, occurring at metal-binding stoichiometries of around 1.25 and 2.0 Hg(II) ions per peptide molecule, were observed for (gammaGlu-Cys)3Gly. These species exhibited specific spectral features in the charge-transfer region and were separable by HPLC. Similarly, two main Hg(II)-binding species of (gammaGlu-Cys)4Gly were observed by UV/visible and CD spectroscopy at metal-binding stoichiometries of around 1.25 and 2.5 respectively. Only a single peak of Hg(II)-(gammaGlu-Cys)4Gly complexes was resolved under the conditions used for HPLC. The overall Hg(II)-binding stoichiometries of phytochelatins were similar at pH 2.0 and at pH 7.4, indicating that pH did not influence the final Hg(II)-binding capacity of these peptides. The reverse-phase HPLC assays indicated a rapid transfer of Hg(II) from glutathione to phytochelatins. These assays also demonstrated a facile transfer of the metal ion from shorter- to longer-chain phytochelatins. The strength of Hg(II) binding to glutathione and phytochelatins followed the

  11. Estimation of Hg 0 exchange between ecosystems and the atmosphere using 222Rn and Hg 0 concentration changes in the stable nocturnal boundary layer

    NASA Astrophysics Data System (ADS)

    Obrist, Daniel; Conen, Franz; Vogt, Roland; Siegwolf, Rolf; Alewell, Christine

    The goal of this study was to test a 222Rn/Hg 0 method to measure exchange fluxes of Hg 0 between ecosystems and the atmosphere complementing gradient-based micrometeorological methods which are difficult to apply when exchange fluxes are very low, during calm nights, and over heterogeneous surfaces. The method is based on absolute concentration changes of Hg 0 and of the trace gas 222Rn over several hours in the stable nocturnal boundary layer (NBL) when absolute gas concentrations change according to the source or sink strength of the underlying landscape. 222Rn accumulations were observed in 28 of 66 measured nights in an urban area and in 14 of the 40 nights at a subalpine grassland. Concurrent and significant increases in atmospheric Hg 0 concentrations were observed 22 times in the urban area and calculated Hg 0 emissions—for the first time measured over a city area—averaged 6.4±0.9 ng m -2 h -1. Concurrent changes in Hg 0 in the stable NBLs at the subalpine site were very small and significant only nine times with calculated Hg 0 fluxes averaging -0.2±0.3 ng m -2 h -1, indicating that the flux of Hg 0 in the grassland was a very small net deposition of atmospheric Hg 0 to the ecosystem. At the subalpine grassland the 222Rn/Hg 0 method compared reasonably well to a modified Bowen ratio (MBR) method applied during turbulent conditions (-1.9±0.2 ng m -2 h -1 [or -1.7±0.4 ng m -2 h -1 during nights only]). The MBR, however, was not applicable in the urban area due to high surface roughness. We conclude that the 222Rn/Hg 0 method—although limited to nighttime periods in our study—can complement gradient-based methods during stable NBL periods and can be used over heterogeneous surfaces when conventional micrometeorological approaches are not applicable.

  12. Hg-contaminated terrestrial spiders pose a potential risk to songbirds at Caddo Lake (Texas/Louisiana, USA).

    PubMed

    Gann, Gretchen L; Powell, Cleveland H; Chumchal, Matthew M; Drenner, Ray W

    2015-02-01

    Methylmercury (MeHg) is an environmental contaminant that can have adverse effects on wildlife. Because MeHg is produced by bacteria in aquatic ecosystems, studies of MeHg contamination of food webs historically have focused on aquatic organisms. However, recent studies have shown that terrestrial organisms such as songbirds can be contaminated with MeHg by feeding on MeHg-contaminated spiders. In the present study, the authors examined the risk that MeHg-contaminated terrestrial long-jawed orb weaver spiders (Tetragnatha sp.) pose to songbirds at Caddo Lake (Texas/Louisiana, USA). Methylmercury concentrations in spiders were significantly different in river, wetland, and open-water habitats. The authors calculated spider-based wildlife values (the minimum spider MeHg concentrations causing physiologically significant doses in consumers) to assess exposure risks for arachnivorous birds. Methylmercury concentrations in spiders exceeded wildlife values for Carolina chickadee (Poecile carolinensis) nestlings, with the highest risk in the river habitat. The present study indicates that MeHg concentrations in terrestrial spiders vary with habitat and can pose a threat to small-bodied nestling birds that consume large amounts of spiders at Caddo Lake. This MeHg threat to songbirds may not be unique to Caddo Lake and may extend throughout the southeastern United States. PMID:25378235

  13. Matrix superpotentials

    NASA Astrophysics Data System (ADS)

    Nikitin, Anatoly G.; Karadzhov, Yuri

    2011-07-01

    We present a collection of matrix-valued shape invariant potentials which give rise to new exactly solvable problems of SUSY quantum mechanics. It includes all irreducible matrix superpotentials of the generic form W=kQ+\\frac{1}{k} R+P, where k is a variable parameter, Q is the unit matrix multiplied by a real-valued function of independent variable x, and P and R are the Hermitian matrices depending on x. In particular, we recover the Pron'ko-Stroganov 'matrix Coulomb potential' and all known scalar shape invariant potentials of SUSY quantum mechanics. In addition, five new shape invariant potentials are presented. Three of them admit a dual shape invariance, i.e. the related Hamiltonians can be factorized using two non-equivalent superpotentials. We find discrete spectrum and eigenvectors for the corresponding Schrödinger equations and prove that these eigenvectors are normalizable.

  14. SEQUESTRATION OF SUBSURFACE ELEMENTAL MERCURY (HG0)

    EPA Science Inventory

    Elemental mercury (Hg0) is a metal with a number of atypical properties, which has resulted in its use in myriad anthropogenic processes. However, these same properties have also led to severe local subsurface contamination at many places where it has been used. As...

  15. Mercuric chloride (HgCl2)

    Integrated Risk Information System (IRIS)

    Mercuric chloride ( HgCl2 ) ; CASRN 7487 - 94 - 7 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Nonc

  16. Beryllium abundances in Hg-Mn stars

    SciTech Connect

    Boesgaard, A.M.; Heacox, W.D.; Wolff, S.C.; Borsenberger, J.; Praderie, F.

    1982-08-15

    The Hg-Mn stars show anomalous line strengths of many chemical elements including Be. We have observed the Be ii resonance doublet at lambdalambda 3130, 3131 at 6.7 A mm/sup -1/ in 43 Hg-Mn stars and 10 normal stars in the same temperature range with the coude spectrograph of the 2.24 m University of Hawaii telescope at Mauna Kea. Measured equivalent widths of the two lines and/or the blend of the doublet have been compared with predictions from (1) LTE model atmospheres and (2) non-LTE line formation on non-LTE model atmospheres. (For strong Be ii lines, the LTE calculations result in more Be by factors of 2 to 4 than do the non-LTE calculations.) Overabundances of factors of 20--2 x 10/sup 4/ relative to solar have been found for 75% of the Hg-Mn stars. The 25% with little or no Be are typically among the cooler Hg-Mn stars, but for the stars with Be excesses, there is only marginal evidence for a correlationi of the size of the overabundance and temperature. It is suggested that diffusion driven by radiation pressure is responsible for the observed Be abundance anomalies.

  17. Multiple-trait genome-wide association study based on principal component analysis for residual covariance matrix

    PubMed Central

    Gao, H; Zhang, T; Wu, Y; Wu, Y; Jiang, L; Zhan, J; Li, J; Yang, R

    2014-01-01

    Given the drawbacks of implementing multivariate analysis for mapping multiple traits in genome-wide association study (GWAS), principal component analysis (PCA) has been widely used to generate independent ‘super traits' from the original multivariate phenotypic traits for the univariate analysis. However, parameter estimates in this framework may not be the same as those from the joint analysis of all traits, leading to spurious linkage results. In this paper, we propose to perform the PCA for residual covariance matrix instead of the phenotypical covariance matrix, based on which multiple traits are transformed to a group of pseudo principal components. The PCA for residual covariance matrix allows analyzing each pseudo principal component separately. In addition, all parameter estimates are equivalent to those obtained from the joint multivariate analysis under a linear transformation. However, a fast least absolute shrinkage and selection operator (LASSO) for estimating the sparse oversaturated genetic model greatly reduces the computational costs of this procedure. Extensive simulations show statistical and computational efficiencies of the proposed method. We illustrate this method in a GWAS for 20 slaughtering traits and meat quality traits in beef cattle. PMID:24984606

  18. Use of regenerative tissue matrix as an oral layer for the closure of recalcitrant anterior palatal fistulae: a pilot study

    PubMed Central

    2016-01-01

    Objectives To evaluate the effectiveness of regenerative tissue matrix (Alloderm) as an oral layer for difficult anterior palatal fistula closure. Materials and Methods The authors have tested the feasibility of a novel surgical technique of adding a regenerative tissue matrix (Alloderm) as an oral layer for closure of recalcitrant large anterior palatal fistulae and report the outcome of the first 12 patients in this pilot study. Patients with recurrent large fistula who otherwise would require either a local pedicled flap, free flap, or an obturator were treated with this technique and followed up for at least 6 months to monitor the progress of healing. Results Of the 12 patients, 8 patients (66.7%) had complete closure of the fistula, and 2 patients (16.7%) showed reduction in size of the fistula to the extent that symptoms were eliminated, for an overall success rate of 83.3% (10/12 patients). Premature graft loss and recurrence of the fistula were noted in 2 patients (16.7%). Conclusion Alloderm provided an adequate barrier allowing healing to occur unimpeded and allowed closure of the palatal fistula. In our experience, this new technique using regenerative tissue matrix as an adjunct to the oral layer in large anterior palatal fistula has an advantage compared to other more invasive complex procedures and has been shown to provide satisfactory results. PMID:27162747

  19. C dbnd N sbnd N dbnd C conformational isomers of 2'-hydroxyacetophenone azine: FTIR matrix isolation and DFT study

    NASA Astrophysics Data System (ADS)

    Grzegorzek, Joanna; Mielke, Zofia; Filarowski, Aleksander

    2010-07-01

    2'-hydroxyacetophenone azine (APA) has been studied by matrix isolation infrared spectroscopy and quantum chemical calculations. The DFT/B3LYP/6-311++G(2d,2p) calculations demonstrated the existence of two conformers for the lowest energy E/ E configuration of APA, a s- trans and a gauche ones. The conformers are characterized by similar energies and differ in the value of a C dbnd N sbnd N dbnd C angle, that was calculated to be 180° for a planar s-trans conformer and 155° for a non-planar gauche one . The calculated barrier for conformational interconversion is also very low, ca. 1 kJ mol -1 for the conversion from a gauche conformer to a trans one. The FTIR spectra of an argon matrix doped with APA from a vapour above solid sample evidence the presence of both conformers that exhibit reversible interconversion at matrix temperatures. The comparison of the theoretical spectra with the experimental ones and reversible temperature dependence of the experimental spectra allowed for unambiguous spectroscopic characterization of the trans and gauche conformers. The experiment also demonstrated that a gauche conformer is more stable than a trans one. The spectra analysis indicates that transformation from a trans conformer to a gauche one weakens the intramolecular O sbnd H⋯N bonds in the molecule.

  20. Cyclotron resonance in HgTe/CdTe-based heterostructures in high magnetic fields.

    PubMed

    Zholudev, Maxim S; Ikonnikov, Anton V; Teppe, Frederic; Orlita, Milan; Maremyanin, Kirill V; Spirin, Kirill E; Gavrilenko, Vladimir I; Knap, Wojciech; Dvoretskiy, Sergey A; Mihailov, Nikolay N

    2012-01-01

    : Cyclotron resonance study of HgTe/CdTe-based quantum wells with both inverted and normal band structures in quantizing magnetic fields was performed. In semimetallic HgTe quantum wells with inverted band structure, a hole cyclotron resonance line was observed for the first time. In the samples with normal band structure, interband transitions were observed with wide line width due to quantum well width fluctuations. In all samples, impurity-related magnetoabsorption lines were revealed. The obtained results were interpreted within the Kane 8·8 model, the valence band offset of CdTe and HgTe, and the Kane parameter EP being adjusted. PMID:23013642

  1. Cyclotron resonance in HgTe/CdTe-based heterostructures in high magnetic fields

    PubMed Central

    2012-01-01

    Cyclotron resonance study of HgTe/CdTe-based quantum wells with both inverted and normal band structures in quantizing magnetic fields was performed. In semimetallic HgTe quantum wells with inverted band structure, a hole cyclotron resonance line was observed for the first time. In the samples with normal band structure, interband transitions were observed with wide line width due to quantum well width fluctuations. In all samples, impurity-related magnetoabsorption lines were revealed. The obtained results were interpreted within the Kane 8·8 model, the valence band offset of CdTe and HgTe, and the Kane parameter EP being adjusted. PMID:23013642

  2. A Method for the Highly Selective, Colorimetric and Ratiometric Detection of Hg(2+) in a 100% Aqueous Solution.

    PubMed

    Liu, Jingkai; Xu, Zhenghe; Xu, Lirong; Bian, Zhen; Sang, Guoqing; Zhu, Baocun

    2016-01-01

    Mercury (Hg) and its derivatives pose a serious threat to the environment and human health. Thus, the development of methods for the selective and sensitive determination of Hg(2+) is very important to understand its distribution, and to implement more detailed toxicological studies. Herein, we developed a new method for the detection of Hg(2+) based on the tricyanoethylene derivative and mercaptoethanol. This method could selectively detect Hg(2+) in a 100% aqueous solution by the naked-eye within the range of 1 - 60 μM. Importantly, this method also could detect Hg(2+) quantitatively by ratiometic absorption spectroscopy in the range of 0.1 - 6 μM with a detection limit of 55 nM. We anticipate that this proposed method will be used widely to monitor Hg(2+) in the environment. PMID:26960619

  3. (Hg, Sb)Ba2Ca2Cu3O8+δ thick films on YSZ substrates

    NASA Astrophysics Data System (ADS)

    Li, J. Q.; Lam, C. C.; Peacock, G. B.; Hyatt, N. C.; Gameson, I.; Edwards, P. P.; Shields, T. C.; Abell, J. S.

    2000-02-01

    Superconducting thick films of (Hg, Sb)Ba2Ca2Cu3O8+icons/Journals/Common/delta" ALT="delta" ALIGN="MIDDLE"/> have been fabricated on polycrystalline yttria-stabilized-zirconia substrates utilizing an Hg-free precursor film reacted with Hg vapour, released from a solid Hg source, in a sealed quartz tube. The resulting films have been studied by x-ray diffraction, scanning electron microscopy, ac susceptibility and resistance measurement techniques. A high quality Hg(Sb)-1223 superconducting thick film on YSZ can be fabricated by using a pre-melted Hg-free precursor film. The zero resistance superconducting transition temperature in the post-growth oxygenated thick film is in excess of 130 K and the transport critical current density for the film is 510 A cm-2 at 77 K.

  4. Excess Ca(2+) does not alleviate but increases the toxicity of Hg(2+) to photosystem II in Synechocystis sp. (Cyanophyta).

    PubMed

    Zhang, Daoyong; Deng, Chunnuan; Pan, Xiangliang

    2013-11-01

    This study demonstrated that excess Ca(2+) increased the toxicity of Hg(2+) to PSII of cyanobacterium Synechocystis sp. using fast rise chlorophyll fluorescence test. Excess Ca(2+) increased the inhibitory effect of Hg(2+) on O2 evolution. Exposure to Hg(2+) caused increase in functional antenna size (ABS/RC), trapping rate of reaction center (TR0/RC), dissipated energy flux per reaction center (DI0/RC) and maximum quantum yield of non-photochemical deexcitation ( [Formula: see text] ), indicating that some reaction centers were transformed to dissipation sinks under Hg(2+) stress. Hg(2+) stress slowed down electron transport on both donor side and acceptor side and caused accumulation of P680(+). Excess Ca(2+) intensified all the Hg(2+) toxic effects on PSII function and led to dysfunction of PSII. The number of reaction centers that were transformed into dissipation sinks increased with increasing Ca(2+) concentration. PMID:23953992

  5. Mode of incorporation of phosphorus in Hg(0.8)Cd(0.2)Te

    NASA Technical Reports Server (NTRS)

    Vydyanath, H. R.; Abbott, R. C.; Nelson, D. A.

    1983-01-01

    Selim and Kroeger (1977) have studied the mode of incorporation of phosphorus in CdTe. According to their findings, phosphorus behaves amphoterically in CdTe acting as an acceptor interstitially and on Te lattice sites, and as a triple donor on Cd lattice sites. The present investigation is concerned with the role of phosphorus in Hg(0.8)Cd(0.2)Te, taking into account Hall-effect and mobility measurements on phosphorus-doped crystals quenched from a temperature in the range from 450 to 600 C subsequent to anneals in different partial pressures of Hg. It is found that the behavior of phosphorus in Hg(0.8)Cd(0.2)Te is similar to that established for CdTe, except that all the electrically active phosphorus defect centers in Hg(0.8)Cd(0.2)Te appear to be only singly ionized. At low Hg pressure, phosphorus is incorporated as a single donor occupying Hg lattice sites, and at high Hg pressure, as a single acceptor on interstitial sites and Te lattice sites.

  6. Binding constants of divalent mercury (Hg2+) in soil humic acids and soil organic matter.

    PubMed

    Khwaja, Abdul R; Bloom, Paul R; Brezonik, Patrick L

    2006-02-01

    Distribution coefficients (K(OC)) for Hg2+ binding by IHSS Pahokee peat humic acid (PHA) and humic acids separated from O-horizons and peats in a northern temperate forest were determined using a competitive ligand-exchange method. All measurements were made at low ratios of added Hg2+ to reduced S. The commonly used chelating agents, EGTA and DTPA, were found to be ineffective competitive ligands; thus, we used DL-penicillamine, a synthetic amino acid with a thiol group. Calculated free [Hg2+] at equilibrium is very low, ranging from 10(-26.4) at pH 1.9 to 10(-36.9) at pH 5.8. Corresponding log Koc values ranged from 22.6 to 32.8. The slope of the plot of pH versus log K(OC) was 2.68, suggesting that two or more protons are released when each Hg2+ is bound. This is consistent with binding of Hg2+ to bidentate thiol sites with some participation of a third weak-acid group, presumably a thiol. The 1:2 stoichiometry is consistent with X-ray spectroscopy data for Hg2+ bound to HA and with other pH-dependency results showing release of two protons with the binding of each Hg2+. Our K(OC) values are much greater than indicated by the data from most previous studies. PMID:16509327

  7. Mode of incorporation of phosphorus in Hg(0.8)Cd(0.2)Te

    NASA Astrophysics Data System (ADS)

    Vydyanath, H. R.; Abbott, R. C.; Nelson, D. A.

    1983-03-01

    Selim and Kroeger (1977) have studied the mode of incorporation of phosphorus in CdTe. According to their findings, phosphorus behaves amphoterically in CdTe acting as an acceptor interstitially and on Te lattice sites, and as a triple donor on Cd lattice sites. The present investigation is concerned with the role of phosphorus in Hg(0.8)Cd(0.2)Te, taking into account Hall-effect and mobility measurements on phosphorus-doped crystals quenched from a temperature in the range from 450 to 600 C subsequent to anneals in different partial pressures of Hg. It is found that the behavior of phosphorus in Hg(0.8)Cd(0.2)Te is similar to that established for CdTe, except that all the electrically active phosphorus defect centers in Hg(0.8)Cd(0.2)Te appear to be only singly ionized. At low Hg pressure, phosphorus is incorporated as a single donor occupying Hg lattice sites, and at high Hg pressure, as a single acceptor on interstitial sites and Te lattice sites.

  8. Hg0 removal from flue gas over different zeolites modified by FeCl3.

    PubMed

    Qi, Hao; Xu, Wenqing; Wang, Jian; Tong, Li; Zhu, Tingyu

    2015-02-01

    The elemental mercury removal abilities of three different zeolites (NaA, NaX, HZSM-5) impregnated with iron(III) chloride were studied on a lab-scale fixed-bed reactor. X-ray diffraction, nitrogen adsorption porosimetry, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and temperature programmed desorption (TPD) analyses were used to investigate the physicochemical properties. Results indicated that the pore structure and active chloride species on the surface of the samples are the key factors for physisorption and oxidation of Hg0, respectively. Relatively high surface area and micropore volume are beneficial to efficient mercury adsorption. The active Cl species generated on the surface of the samples were effective oxidants able to convert elemental mercury (Hg0) into oxidized mercury (Hg2+). The crystallization of NaCl due to the ion exchange effect during the impregnation of NaA and NaX reduced the number of active Cl species on the surface, and restricted the physisorption of Hg0. Therefore, the Hg0 removal efficiencies of the samples were inhibited. The TPD analysis revealed that the species of mercury on the surface of FeCl3-HZSM-5 was mainly in the form of mercuric chloride (HgCl2), while on FeCl3-NaX and FeCl3-NaA it was mainly mercuric oxide (HgO). PMID:25662245

  9. The thermal release of HG from chondrites and their thermal histories

    NASA Astrophysics Data System (ADS)

    Jovanovic, S.; Reed, G. W.

    1985-08-01

    A quantitative treatment and implications of isothermal and linear heating data on Hg in meteorites are given as a sequel to a more qualitative analysis of meteorite thermal histories (Reed and Jovanovic, 1968). Studies of Hg in terrestrial metamorphic rocks establish that thermal events to which meteorites were subjected fall in the same temperature range, of 400-900 C, as exists during terrestrial metamorphism. Hg diffusion parameters based on data from the linear and isothermal heating experiments are calculated. The conclusions are: (1) Meteorites experienced thermal events of the same magnitude as those measured by primarily mineralogical metamorphic indicators reviewed by Dodd (1969); (2) no correspondence with mineralogical-petrological metamorphic grade is evident; (3) Hg data for some chondrites correlate with shock facies (non-thermal) indicators (Dodd and Jarosewich, 1979); (4) small Hg activation energies (6-14 kcal/mole) require that the meteorites must have been stored in closed systems until low temperatures were attained. Hg must be presented as an involatile mineral(s) or as a substituent in a host phase at temperatures below 100 C. Consistent with this interpretation is the fact that despite diffusion times of 100-1,000,000 years at 200 K, Hg was retained in small objects over cosmic ray exposure periods of a hundred-million years.

  10. The thermal release of Hg from chondrites and their thermal histories

    NASA Technical Reports Server (NTRS)

    Jovanovic, S.; Reed, G. W., Jr.

    1985-01-01

    A quantitative treatment and implications of isothermal and linear heating data on Hg in meteorites are given as a sequel to a more qualitative analysis of meteorite thermal histories (Reed and Jovanovic, 1968). Studies of Hg in terrestrial metamorphic rocks establish that thermal events to which meteorites were subjected fall in the same temperature range, of 400-900 C, as exists during terrestrial metamorphism. Hg diffusion parameters based on data from the linear and isothermal heating experiments are calculated. The conclusions are: (1) Meteorites experienced thermal events of the same magnitude as those measured by primarily mineralogical metamorphic indicators reviewed by Dodd (1969); (2) no correspondence with mineralogical-petrological metamorphic grade is evident; (3) Hg data for some chondrites correlate with shock facies (non-thermal) indicators (Dodd and Jarosewich, 1979); (4) small Hg activation energies (6-14 kcal/mole) require that the meteorites must have been stored in closed systems until low temperatures were attained. Hg must be presented as an involatile mineral(s) or as a substituent in a host phase at temperatures below 100 C. Consistent with this interpretation is the fact that despite diffusion times of 100-1,000,000 years at 200 K, Hg was retained in small objects over cosmic ray exposure periods of a hundred-million years.

  11. Density matrix renormalization group study of triangular Kitaev-Heisenberg model

    NASA Astrophysics Data System (ADS)

    Sota, Shigetoshi; Sjinjo, Kazuya; Shirakawa, Tomonori; Tohyama, Takami; Yunoki, Seiji

    2015-03-01

    Topological insulator has been one of the most active subjects in the current condensed matter physics. For most of topological insulators electron correlations are considered to be not essential. However, in the case where electron correlations are strong, novel phases such as a spin liquid phase can emerge in competition with a spin-orbit coupling. Here, using the density matrix renormalization group method, we investigate magnetic phase of a triangular Kitaev-Heisenberg (quantum compass) model that contains a spin-orbital interaction and spin frustration in the antiferromagnetic region. The triangular Kitaev-Heisenberg model is regarded as a dual model of the honeycomb Kitaev-Heisenberg model that is usually employed to discuss A2CuO3 (A=Na, K). Systematically calculating ground state energy, entanglement entropy, entanglement spectrum, and spin-spin correlation functions, we discuss the duality between the triangular and the honeycomb Kitaev-Heisenberg model as well as the ground state magnetic phases.

  12. Study of modal coupling procedures for the shuttle: A matrix method for damping synthesis

    NASA Technical Reports Server (NTRS)

    Hasselman, T. K.

    1972-01-01

    The damping method was applied successfully to real structures as well as analytical models. It depends on the ability to determine an appropriate modal damping matrix for each substructure. In the past, modal damping matrices were assumed diagonal for lack of being able to determine the coupling terms which are significant in the general case of nonproportional damping. This problem was overcome by formulating the damped equations of motion as a linear perturbation of the undamped equations for light structural damping. Damped modes are defined as complex vectors derived from the complex frequency response vectors of each substructure and are obtained directly from sinusoidal vibration tests. The damped modes are used to compute first order approximations to the modal damping matrices. The perturbation approach avoids ever having to solve a complex eigenvalue problem.

  13. Matrix-isolation and ab initio study of HKrCCCl and HXeCCCl

    SciTech Connect

    Zhu, Cheng; Räsänen, Markku; Khriachtchev, Leonid

    2015-12-28

    We report on two new noble-gas molecules, HKrCCCl and HXeCCCl, prepared in low-temperature Kr and Xe matrices. These molecules are made by UV photolysis of HCCCl in the matrices and subsequent thermal annealing. The HCCCl precursor is produced by microwave discharge of a mixture of a matrix gas with trichloroethylene (HClC=CCl{sub 2}). The assignments of the new noble-gas molecules are supported by deuteration experiments and quantum chemical calculations at the MP2(full) and CCSD(T) levels of theory with the def2-TZVPPD basis set. No evidence of ClXeCCH, which is computationally reliably stable, is found in the experiments. ClKrCCH as well as the Ar compounds HArCCCl and ClArCCH are not observed either, which is in agreement with the calculations.

  14. OMC studies for the matrix elements in ββ decay

    SciTech Connect

    Zinatulina, D.; Brudanin, V.; Egorov, V.; Shirchenko, M.; Vasiliev, R.; Yyutlandov, I.; Briançon, Ch.; Petitjean, C.

    2013-12-30

    Energy and time spectra of gamma-rays following μ-capture in natural Kr, Se, Cd and Sm, as well as isotopic enriched {sup 82}Kr, {sup 76}Se, {sup 106}Cd and {sup 150}Sm, have been measured. Total life-times of muons in different isotopes, as well as partial μ-capture rates to the excited states of {sup 48}Sc, {sup 76}As and {sup 106}Ag, were extracted. These results are discussed in the context of the double-beta decay matrix elements. The data are also compared with data from theoretical calculations and with data from charge-exchange reactions on {sup 48}Ti. It is the first time that μ-capture and charge-exchange reaction data are being compared in the context of ββ decay.

  15. Investigation of Praseodymium Fluorides: A Combined Matrix-Isolation and Quantum-Chemical Study.

    PubMed

    Vent-Schmidt, Thomas; Riedel, Sebastian

    2015-12-01

    The chemistry of the lanthanides is mostly dominated by compounds in the oxidation state +III. Only few compounds of Ce, Pr, and Tb are known with the metal in the +IV oxidation state. Removal of the last f-electron on praseodymium +IV would lead to a closed-shell system with formal oxidation state V. In this work we investigated the stability of the PrF5 molecule by theory and matrix-isolation techniques through the reaction of laser-ablated praseodymium atoms with fluorine in excess of neon, argon, krypton, or neat fluorine. Besides the known PrF3 molecule, unreported IR bands for PrF4 could be observed, and there is evidence for the formation of PrF and PrF2 but not for the formation of PrF5. PMID:26544761

  16. Reaction of trimethylsilylacetylenes with antimony pentafluoride under matrix isolation conditions: experimental and computational study.

    PubMed

    Cicak, Helena; Vancik, Hrvoj; Mihalić, Zlatko

    2010-10-15

    Reaction of trimethylsilylacetylenes Me(3)SiC≡CR with SbF(5) in the solid state was investigated using matrix isolation infrared spectroscopy and quantum-mechanical calculations. Two reaction pathways were detected. Replacement of the trimethylsilyl group with SbF(4) produces neutral antimony acetylides F(4)SbC≡CR. Acetylenic bond protonation produces silyl cation 6-R, fully bridged for R = H and SiMe(3). High total charges on the bridging SiMe(3) group and low Me(3)Si-C bond orders to acetylenic moiety, both calculated at the MP4(SDQ)/6-311G(d,p) level of theory, indicate high silyl cation character of these species. PMID:20857942

  17. A study of internal damage of metal matrix composites by neutron diffraction

    SciTech Connect

    Shi, N.; Bourke, M.A.M.; Goldstone, J.A.

    1994-12-31

    Using neutron diffraction, we have measured the elastic phase strains of Al/TiC and Al/SiC composites under uniaxial tensile loading. The phase strains were used to reconstruct the global elastic strain. It has been found that, above macroscopic yield, the global elastic strain response is not linear. A theoretical model shows that the nonlinearity is dictated by changes in the ratio of longitudinal phase stresses. Furthermore, the changes in this ratio resulting from matrix plasticity and reinforcement fracture are different which leads to distinct slope changes in the global elastic strain response that can be used to distinguish the onset of these two processes on the global elastic strain loading curve.

  18. Density-matrix renormalization-group study of current and activity fluctuations near nonequilibrium phase transitions.

    PubMed

    Gorissen, Mieke; Hooyberghs, Jef; Vanderzande, Carlo

    2009-02-01

    Cumulants of a fluctuating current can be obtained from a free-energy-like generating function, which for Markov processes equals the largest eigenvalue of a generalized generator. We determine this eigenvalue with the density-matrix renormalization group for stochastic systems. We