Science.gov

Sample records for ag cd sb

  1. Particulate contacts to Si and CdTe: Al, Ag, Hg-Cu-Te, and Sb-Te

    NASA Astrophysics Data System (ADS)

    Schulz, Douglas L.; Ribelin, Rosine; Curtis, Calvin J.; Ginley, David S.

    1999-03-01

    Our team has been investigating the use of particle-based contacts in both Si and CdTe solar cell technologies. First, in the area of contacts to Si, powders of Al and Ag prepared by an electroexplosion process have been characterized by transmission electron microscopy (TEM), TEM elemental determination X-ray spectroscopy (TEM-EDS), and TEM electron diffraction (TEM-ED). These Al and Ag particles were slurried and tested as contacts to p- and n-type silicon wafers, respectively. Linear current-voltage (I-V) was observed for Ag on n-type Si, indicative of an ohmic contact, whereas the Al on p-type Si sample was non-ideal. A wet-chemical surface treatment was performed on one Al sample and TEM-EDS indicated a substantial decrease in the O contaminant level. The treated Al on p-type Si films exhibited linear I-V after annealing. Second, in the area of contacts to CdTe, particles of Hg-Cu-Te and Sb-Te have been applied as contacts to CdTe/CdS/SnO2 heterostructures prepared by the standard NREL protocol. First, Hg-Cu-Te and Sb-Te were prepared by a metathesis reaction. After CdCl2 treatment and NP etch of the CdTe layer, particle contacts were applied. The Hg-Cu-Te contacted cells exhibited good electrical characteristics, with Voc>810 mV and efficiencies > 11.5% for most cells. Although Voc>800 mV were observed for the Sb-Te contacted cells, efficiencies in these devices were limited to 9.1% presumably by a large series resistance (>20 Ω) observed in all samples.

  2. A rapid, partial leach and organic separation for the sensitive determination of Ag, Bi, Cd, Cu, Mo, Pb, Sb, and Zn in surface geologic materials by flame atomic absorption

    USGS Publications Warehouse

    Viets, J.G.; Clark, J.R.; Campbell, W.L.

    1984-01-01

    A solution of dilute hydrochloric acid, ascorbic acid, and potassium iodide has been found to dissolve weakly bound metals in soils, stream sediments, and oxidized rocks. Silver, Bi, Cd, Cu, Mo, Pb, Sb, and Zn are selectively extracted from this solution by a mixture of Aliquat 336 (tricaprylyl methyl ammonium chloride) and MIBK (methyl isobutyl ketone). Because potentially interfering major and minor elements do not extract, the organic separation allows interference-free determinations of Ag and Cd to the 0.05 ppm level, Mo, Cu, and Zn to 0.5 ppm, and Bi, Pb, and Sb to 1 ppm in the sample using flame atomic absorption spectroscopy. The analytical absorbance values of the organic solution used in the proposed method are generally enhanced more than threefold as compared to aqueous solutions, due to more efficient atomization and burning characteristics. The leaching and extraction procedures are extremely rapid; as many as 100 samples may be analyzed per day, yielding 800 determinations, and the technique is adaptable to field use. The proposed method was compared to total digestion methods for geochemical reference samples as well as soils and stream sediments from mineralized and unmineralized areas. The partial leach showed better anomaly contrasts than did total digestions. Because the proposed method is very rapid and is sensitive to pathfinder elements for several types of ore deposits, it should be useful for reconnaissance surveys for concealed deposits. ?? 1984.

  3. Laser ablation of AgSbS(2) and cluster analysis by time-of-flight mass spectrometry.

    PubMed

    Houska, Jan; Peña-Méndez, Eladia Maria; Kolár, Jakub; Frumar, Miloslav; Wágner, Tomás; Havel, Josef

    2009-06-01

    Thin films of AgSbS(2) are important for phase-change memory applications. This solid is deposited by various techniques, such as metal organic chemical vapour deposition or laser ablation deposition, and the structure of AgSbS(2)(s), as either amorphous or crystalline, is already well characterized. The pulsed laser ablation deposition (PLD) of solid AgSbS(2) is also used as a manufacturing process. However, the processes in plasma have not been well studied. We have studied the laser ablation of synthesized AgSbS(2)(s) using a nitrogen laser of 337 nm and the clusters formed in the laser plume were identified. The ablation leads to the formation of various single charged ternary Ag(p)Sb(q)S(r) clusters. Negatively charged AgSbS(4) (-), AgSb(2)S(3) (-), AgSb(2)S(4) (-), AgSb(2)S(5) (-) and positively charged ternary AgSbS(+), AgSb(2)S(+), AgSb(2)S(2) (+), AgSb(2)S(3) (+) clusters were identified. The formation of several singly charged Ag(+), Ag(2) (-), Ag(3) (-), Sb(3) (+), Sb(3) (-), S(8) (+) ions and binary Ag(p)S(r) clusters such as AgSb(2) (-), Ag(3)S(-), SbS(r) (-) (r = 1-5), Sb(2)S(-), Sb(2)S(2) (-), Sb(3)S(r) (-) (r = 1-4) and AgS(2) (+), SbS(+), SbS(2) (+), Sb(2)S(+), Sb(2)S(2) (+), Sb(3)S(r) (+) (r = 1-4), AgSb(2) (+) was also observed. The stoichiometry of the clusters was determined via isotopic envelope analysis and computer modeling. The relation of the composition of the clusters to the crystal structure of AgSbS(2) is discussed. PMID:19434598

  4. Predicting the optimized thermoelectric performance of MgAgSb

    NASA Astrophysics Data System (ADS)

    Sheng, C. Y.; Liu, H. J.; Fan, D. D.; Cheng, L.; Zhang, J.; Wei, J.; Liang, J. H.; Jiang, P. H.; Shi, J.

    2016-05-01

    Using first-principles method and Boltzmann theory, we provide an accurate prediction of the electronic band structure and thermoelectric transport properties of α-MgAgSb. Our calculations demonstrate that only when an appropriate exchange-correlation functional is chosen can we correctly reproduce the semiconducting nature of this compound. By fine tuning the carrier concentration, the thermoelectric performance of α-MgAgSb can be significantly optimized, which exhibits a strong temperature dependence and gives a maximum ZT value of 1.7 at 550 K. We also provide a simple map by which one can efficiently find the best doping atoms and optimal doping content.

  5. Sign of the electric-field gradient at /sup 111/Cd in Zr and Sb

    SciTech Connect

    Kaufmann, E.N.; Krien, K.; Pielen, W.; Vianden, R.

    1983-01-01

    The ..beta..-..gamma.. TDPAC technique was applied to /sup 111/Ag implanted in Zr and Sb metal single crystals in order to determine sign and magnitude of the quadrupole interaction at the site of /sup 111/Cd in these metals. An analysis of the data taken at 293K yielded nu/sub Q/ = +15.4(6) MHz for /sup 111/Cd in Zr and nu/sub Q/ = -107.5(20) MHz for /sup 111/Cd in Sb. From these values electric field gradients of +7.3(8)x10/sup 16/ V/cm/sup 2/ and -5.56(62)x10/sup 17/ V/cm/sup 2/ for Cd in Zr and Sb are derived respectively.

  6. Enhanced thermoelectric performance of CdO : Ag nanocomposites.

    PubMed

    Gao, Linjie; Wang, Shufang; Liu, Ran; Zha, Xinyu; Sun, Niefeng; Wang, Shujie; Wang, Jianglong; Fu, Guangsheng

    2016-07-26

    CdO : Ag nanocomposites with metallic Ag nanoparticles embedded in the polycrystalline CdO matrix were synthesized by the solid-state reaction method. The addition of Ag led to increased grain boundaries of CdO and created numerous CdO/Ag interfaces. By incorporating Ag into the CdO matrix, the power factor was increased which was probably due to the carrier energy filtering effect induced by the enhanced energy-dependent scattering of electrons. In addition, reduced thermal conductivity was also achieved by stronger phonon scattering from grain boundaries, CdO/Ag interfaces and Ag nanoparticles. These concomitant effects resulted in enhanced ZT values for all CdO : Ag nanocomposites, demonstrating that the strategy of introducing metallic Ag nanoparticles into the CdO host was very effective in optimizing the thermoelectric performance. PMID:27411573

  7. First-principles study of Sb adsorption on Ag (110)(2×2)

    SciTech Connect

    Nie, JL; Xiao, H Y.; Zu, Xiaotao; Gao, Fei

    2006-08-01

    The adsorption of antimony atom on the Ag(110) surface has been studied within the density functional theory framework. It was turned out that Sb-Ag surface alloy was formed in which Sb atoms substitute Ag atom in the outermost layer and subsurface site absorption was not preferred, suggesting that Sb is well segregated to the surface. Geometric analysis showed that rumpling between substitutional Sb and Ag in the alloy surface is negligible. These results are found to agree well with the experimental finding of Nascimento et al. [Surf. Sci. 572 (2004) 337]. In addition, investigation of the diffusion of Ag atom on bare and Sb-covered Ag(110) surface showed that Ag adatoms will jump along the so call in-channel direction and Sb substitution has little effect on the diffusion of Ag adatoms on Ag(110) surface. Such diffusion behavior was found to be different from that of Ag adatoms on Ag(111) surface, where the diffusion energy barrier was reported to be significantly increased upon Sb substitution [Phys. Rev. Lett. 73 (1993) 2437].

  8. The crystal structures of Hg 4Sb 2I 3 and Cd 4Sb 2I 3

    NASA Astrophysics Data System (ADS)

    Shevelkov, A. V.; Dikarev, E. V.; Popovkin, B. A.

    1991-08-01

    The crystal structures of Hg 4Sb 2I 3 and Cd 4Sb 2I 3 have been solved by X-ray single crystal techniques. Hg 4Sb 2I 3 and Cd 4Sb 2I 3 are isostructural and crystallize in the cubic system, space group Pa3, Z = 8, with cell dimensions a = 13.4392(6) Å for Hg 4Sb 2I 3 and a = 13.4876(5) Å for Cd 4Sb 2I 3. The compounds have a three-dimensional array built from six-membered rings containing mercury (cadmium), antimony, and iodine atoms. One-half of the antimony atoms are bound into Sb 4-2 pairs with an SbSb distance of 2.75 Å. The absence of HgHg (or CdCd) and SbI bonding was determined.

  9. The new Zintl phases Eu21Cd4Sb18 and Eu21Mn4Sb18

    NASA Astrophysics Data System (ADS)

    Wang, Yi; Darone, Gregory M.; Bobev, Svilen

    2016-06-01

    Crystals of two new Zintl compounds, Eu21Mn4Sb18 and Eu21Cd4Sb18 have been synthesized using the molten metal flux method, and their structures have been established by single-crystal X-ray diffraction. Both compounds are isotypic and crystallize in the monoclinic space group C2/m (No. 12, Z=4). The structures are based on edge- and corner-shared MnSb4 or CdSb4 tetrahedra, which make octameric [Mn8Sb22] or [Cd8Sb22] polyanions. Homoatomic Sb-Sb bonds are present in both structures. The Eu atoms take the role of Eu2+cations with seven unpaired 4f electrons, as suggested by the temperature-dependent magnetization measurements. The magnetic susceptibilities of Eu21Mn4Sb18 and Eu21Cd4Sb18 indicate that both phases order anti-ferromagnetically with Néel temperatures of ca. 7 K and ca. 10 K, respectively. The unpaired 3d electrons of the Mn atoms in Eu21Mn4Sb18 do contribute to the magnetic response, however, the bulk magnetization measurements do not provide evidence for long-range ordering of the Mn spins down to 5 K. Electrical resistivity measurements suggest that both compounds are narrow band gap semiconductors.

  10. Thermoelectric Generators from AgBiTe and AgSbTe Thin Films Modified by High-Energy Beam

    NASA Astrophysics Data System (ADS)

    Budak, S.; Guner, S.; Muntele, C.; Ila, D.

    2015-06-01

    The ternary chalcogenides AgBiTe2 and AgSbTe2 belong to the family of semiconductors with disordered NaCl cubic structure in which Ag and Sb occupy metal sublattices. Both compounds are very interesting due to their thermoelectric properties. We have grown single-layer AgBiTe and AgSbTe thin films on silicon (Si) and fused silica (Suprasil) substrates using electron beam deposition. High-energy (MeV) Si-ion bombardment was performed on the thin-film samples at five different fluences between 5 × 1013 ions/cm2 and 7 × 1015 ions/cm2. We have measured the thermoelectric efficiency (figure of merit, ZT) of the fabricated thermoelectric devices by measuring the cross-plane thermal conductivity using the third-harmonic (3 ω) method, the cross-plane Seebeck coefficient, and the in-plane electrical conductivity using the van der Pauw method before and after MeV Si-ion bombardment. Rutherford backscattering spectrometry and the Rutherford Universal Manipulation Program (RUMP) simulation package were used to analyze the elemental composition and thickness of the deposited materials on the substrates. The RUMP simulation gave thicknesses for the AgBiTe and AgSbTe thin films of 270 nm and 188 nm, respectively. The figure of merit for AgBiTe started to decrease from the value of 0.37 for the virgin sample after bombardment. We saw similar decreasing behavior for the AgSbTe thin-film system. The figure of merit for AgSbTe started to decrease from the value of 0.88 for the virgin sample after bombardment. MeV Si-ion bombardment caused changes in the thermoelectric properties of the thin films.

  11. Nanoscale structure in AgSbTe2 determined by diffuse elastic neutron scattering

    SciTech Connect

    Specht, Eliot D; Ma, Jie; Delaire, Olivier A; Budai, John D; May, Andrew F; Karapetrova, Evguenia A.

    2015-01-01

    Diffuse elastic neutron scattering measurements confirm that AgSbTe2 has a hierarchical structure, with defects on length scales from nanometers to microns. While scattering from mesoscale structure is consistent with previously-proposed structures in which Ag and Sb order on a NaCl lattice, more diffuse scattering from nanoscale structure suggests a structural rearrangement in which hexagonal layers form a combination of (ABC), (ABA), and (AAB) stacking sequences. The AgCrSe2 structure is the best-fitting model for the local atomic arrangements.

  12. Facile synthesis of hybrid nanorods with the Sb2Se3/AgSbSe2 heterojunction structure for high performance photodetectors.

    PubMed

    Chen, Shuo; Qiao, Xvsheng; Wang, Fengxia; Luo, Qun; Zhang, Xianghua; Wan, Xia; Xu, Yang; Fan, Xianping

    2016-01-28

    An effective colloidal process involving the hot-injection method is developed to synthesize uniform single-crystalline Sb2Se3 nanorods in high yields. The photoconductive characteristics of the as-synthesized Sb2Se3 nanorods are investigated by developing a film-based photodetector and this device displays a remarkable response to visible light with an "ON/OFF" ratio as high as 50 (with an incident light density of 12.05 mW cm(-2)), short response/recovery times and long-term durability. To overcome the challenge of the intrinsic low electrical conductivity of Sb2Se3, hybrid nanorods with the Sb2Se3/AgSbSe2 heterojunction structure having a type-II band alignment are firstly prepared. The electric current of the photodetector based on the Sb2Se3/AgSbSe2 hybrid nanorod film has been significantly increased both in the dark and under light illumination. The responsivity of the photodetector based on the Sb2Se3/AgSbSe2 hybrid nanorod film is about 4.2 times as much as that of the photodetector based on the Sb2Se3 nanorod film. This improvement can be considered as an important step to promote Sb2Se3 based semiconductors for applications in high performance photodetectors. PMID:26743461

  13. The antimony-group 11 chemical bond: Dissociation energies of the diatomic molecules CuSb, AgSb, and AuSb

    SciTech Connect

    Carta, V.; Ciccioli, A. E-mail: andrea.ciccioli@uniroma1.it; Gigli, G. E-mail: andrea.ciccioli@uniroma1.it

    2014-02-14

    The intermetallic molecules CuSb, AgSb, and AuSb were identified in the effusive molecular beam produced at high temperature under equilibrium conditions in a double-cell-like Knudsen source. Several gaseous equilibria involving these species were studied by mass spectrometry as a function of temperature in the overall range 1349–1822 K, and the strength of the chemical bond formed between antimony and the group 11 metals was for the first time measured deriving the following thermochemical dissociation energies (D{sub 0}{sup ∘}, kJ/mol): 186.7 ± 5.1 (CuSb), 156.3 ± 4.9 (AgSb), 241.3 ± 5.8 (AuSb). The three species were also investigated computationally at the coupled cluster level with single, double, and noniterative quasiperturbative triple excitations (CCSD(T)). The spectroscopic parameters were calculated from the potential energy curves and the dissociation energies were evaluated at the Complete Basis Set limit, resulting in an overall good agreement with experimental values. An approximate evaluation of the spin-orbit effect was also performed. CCSD(T) calculations were further extended to the corresponding group 11 arsenide species which are here studied for the first time and the following dissociation energies (D{sub 0}{sup ∘}, kJ/mol): 190 ± 10 (CuAs), 151 ± 10 (AgAs), 240 ± 15 (AuAs) are proposed. Taking advantage of the new experimental and computational information here presented, the bond energy trends along group 11 and 4th and 5th periods of the periodic table were analyzed and the bond energies of the diatomic species CuBi and AuBi, yet experimentally unobserved, were predicted on an empirical basis.

  14. Pressure and field tuning in the heavy fermion ferromagnet CeAgSb2

    NASA Astrophysics Data System (ADS)

    Logg, Peter; Feng, Zhuo; Ebihara, Takao; Goh, Swee K.; Alireza, Patricia; Grosche, F. Malte

    2012-12-01

    The intermetallic compound CeAgSb2 is an unusual example of a ferromagnetically ordered heavy fermion system. Ferromagnetism sets in below the Curie temperature Tc=9.6 K at ambient pressure. We have investigated the magnetisation of CeAgSb2 under applied hydrostatic pressure of up to 45 kbar. Tc is suppressed rapidly, and at pressures > 35 kbar it is replaced by an unidentified ordered phase, possibly antiferromagnetism. The ordered magnetic moment in CeAgSb2 is aligned along the c-axis. We investigate the effect of transverse field tuning on Tc, and show that magnetic order at low temperature is suppressed by in-plane fields exceeding about 3 T.

  15. Elastic Constants of the β1-AgCd Alloy

    NASA Astrophysics Data System (ADS)

    Matsuo, Yoshie; Makita, Tomoko; Suzuki, Toshiharu; Nagasawa, Akira

    1981-04-01

    The elastic constants of single crystal of β1-AgCd alloy with 47.9± 0.1 at.%Cd have been measured in a temperature range between 180 K and 360 K, using a ultrasonic pulse-cho overlapping method. It is found that with increasing temperature, the elastic constants CL{=}(C11+C12+2C44)/2 and C44 decrease linearly but C'{=}(C11-C12)/2 increases. In addition, this alloy shows a high elastic anisotropy in comparison with other Ag-based β1-phase alloys such as AgMg and AgZn.

  16. Atomistic Structure and Nucleation of Nanoprecipitates in Thermoelectric PbTe- AgSbTe Composite

    SciTech Connect

    Ke, Xuezhi; Chen, Changfeng; Yang, Jihui; Wu, Lijun; Zhou, Juan; Li, Qiang; Zhu, Yimei; Kent, Paul R

    2009-01-01

    Many recent advances in thermoelectric (TE) materials are attributed to their nanoscale constituents. Determination of the nanocomposite structures has represented a major experimental and computational challenge and eluded previous attempts. Here we present the first atomically resolved structures of high performance TE material PbTe-AgSbTe2 by transmission electron microscopy imaging and density functional theory calculations. The results establish an accurate structural characterization for PbTe-AgSbTe2 and identify the interplay of electric dipolar interactions and strain fields as the driving mechanism for nanoprecipitate nucleation and aggregation.

  17. Synthesis and high temperature thermoelectric properties of Yb0.25Co4Sb12-(Ag2Te)x(Sb2Te3)1-x nanocomposites

    NASA Astrophysics Data System (ADS)

    Zheng, Jin; Peng, Jiangying; Zheng, Zhexin; Zhou, Menghan; Thompson, Emily; Yang, Junyou; Xiao, Wanli

    2015-09-01

    Nanocomposites are becoming a new paradigm in thermoelectric study: by incorporating nanophase(s) into a bulk matrix, a nanocomposite often exhibits unusual thermoelectric properties beyond its constituent phases. To date most nanophases are binary, while reports on ternary nanoinclusions are scarce. In this work, we conducted an exploratory study of introducing ternary (Ag2Te)x(Sb2Te3)1-x inclusions in the host matrix of Yb0.25Co4Sb12. Yb0.25Co4Sb12 - 4wt% (Ag2Te)x(Sb2Te3)1-x nanocomposites were prepared by a melting-milling-hot-pressing process. Microstructural analysis showed that poly-dispersed nanosized Ag-Sb-Te inclusions are distributed on the grain boundaries of Yb0.25Co4Sb12 coarse grains. Compared to the pristine nanoinclusion-free sample, the electrical conductivity, Seebeck coefficient, and thermal conductivity were optimized simultaneously upon nanocompositing, while the carrier mobility was largely remained. A maximum ZT of 1.3 was obtained in Yb0.25Co4Sb12-4wt% (Ag2Te)0.42(Sb2Te3)0.58 at 773 K, a ~ 40% increase compared to the pristine sample. The electron and phonon mean-free-path were estimated to help quantify the observed changes in the carrier mobility and lattice thermal conductivity.

  18. Inherent instability by antibonding coupling in AgSbTe2

    NASA Astrophysics Data System (ADS)

    Shinya, Hikari; Masago, Akira; Fukushima, Tetsuya; Katayama-Yoshida, Hiroshi

    2016-04-01

    In the present paper, an inherent instability in the ternary chalcogenide compound AgSbTe2 is described from the electronic structure viewpoint. Our calculations, which are based on the cluster expansion method, suggest nine stable crystal structures involving the most stable structure with Fd\\bar{3}m symmetry. The effective pair interactions calculated by the generalized perturbation method point out that the stability of these structures originates from the number of linear arrangements of the Ag-Te-Sb atomic bonds. Moreover, it is found that AgSbTe2 has a special electronic structure, where the dominant components of the top of the valence band are the Te-5p antibonding states. Such an antibonding contribution leads to an inherent instability, such that the system spontaneously forms various mutation phases caused by charge-compensated defect complexes. We propose that these mutation phases play an important role in the thermal conductivity and thermoelectric efficiency in AgSbTe2.

  19. Thermoelectric properties of AgSbTe₂ from first-principles calculations

    SciTech Connect

    Rezaei, Nafiseh; Akbarzadeh, Hadi; Hashemifar, S. Javad

    2014-09-14

    The structural, electronic, and transport properties of AgSbTe₂ are studied by using full-relativistic first-principles electronic structure calculation and semiclassical description of transport parameters. The results indicate that, within various exchange-correlation functionals, the cubic Fd3⁻m and trigonal R3⁻m structures of AgSbTe₂ are more stable than two other considered structures. The computed Seebeck coefficients at different values of the band gap and carrier concentration are accurately compared with the available experimental data to speculate a band gap of about 0.1–0.35 eV for AgSbTe₂ compound, in agreement with our calculated electronic structure within the hybrid HSE (Heyd-Scuseria-Ernzerhof) functional. By calculating the semiclassical Seebeck coefficient, electrical conductivity, and electronic part of thermal conductivity, we present the theoretical upper limit of the thermoelectric figure of merit of AgSbTe₂ as a function of temperature and carrier concentration.

  20. Thermoelectric properties of AgSbTe2 from first-principles calculations

    NASA Astrophysics Data System (ADS)

    Rezaei, Nafiseh; Hashemifar, S. Javad; Akbarzadeh, Hadi

    2014-09-01

    The structural, electronic, and transport properties of AgSbTe2 are studied by using full-relativistic first-principles electronic structure calculation and semiclassical description of transport parameters. The results indicate that, within various exchange-correlation functionals, the cubic F d 3 ¯ m and trigonal R 3 ¯ m structures of AgSbTe2 are more stable than two other considered structures. The computed Seebeck coefficients at different values of the band gap and carrier concentration are accurately compared with the available experimental data to speculate a band gap of about 0.1-0.35 eV for AgSbTe2 compound, in agreement with our calculated electronic structure within the hybrid HSE (Heyd-Scuseria-Ernzerhof) functional. By calculating the semiclassical Seebeck coefficient, electrical conductivity, and electronic part of thermal conductivity, we present the theoretical upper limit of the thermoelectric figure of merit of AgSbTe2 as a function of temperature and carrier concentration.

  1. Natural nanostructure and superlattice nanodomains in AgSbTe{sub 2}

    SciTech Connect

    Carlton, Christopher E.; De Armas, Ricardo; Shao-Horn, Yang E-mail: shaohorn@mit.edu; Ma, Jie; May, Andrew F.; Delaire, Olivier E-mail: shaohorn@mit.edu

    2014-04-14

    AgSbTe{sub 2} has long been of interest for thermoelectric applications because of its favorable electronic properties and its low lattice thermal conductivity of ∼0.7 W/mK. In this work, we report new findings from a high-resolution transmission electron microscopy study revealing two nanostructures in single crystal Ag{sub 1−x}Sb{sub 1+x}Sb{sub 2+x} (with x = 0, 0.1, 0.2); (i) a rippled natural nanostructure with a period of ∼2.5–5 nm and (ii) superlattice ordered nanodomains consistent with cation ordering predicted in previous density functional theory studies. These nanostructures, combined with point-defects, probably serve as sources of scattering for phonons, thereby yielding a low lattice thermal conductivity over a wide temperature range.

  2. Contrasting the Role of Mg and Ba Doping on the Microstructure and Thermoelectric Properties of p-Type AgSbSe2.

    PubMed

    Liu, Zihang; Shuai, Jing; Geng, Huiyuan; Mao, Jun; Feng, Yan; Zhao, Xu; Meng, Xianfu; He, Ran; Cai, Wei; Sui, Jiehe

    2015-10-21

    Microstructure has a critical influence on the mechanical and functional properties. For thermoelectric materials, deep understanding of the relationship of microstructure and thermoelectric properties will enable the rational optimization of the ZT value and efficiency. Herein, taking AgSbSe2 as an example, we first report a different role of alkaline-earth metal ions (Mg(2+) and Ba(2+)) doping in the microstructure and thermoelectric properties of p-type AgSbSe2. For Mg doping, it monotonously increases the carrier concentration and then reduces the electrical resistivity, leading to a substantially enhanced power factor in comparison to those of other dopant elements (Bi(3+), Pb(2+), Zn(2+), Na(+), and Cd(2+)) in the AgSbSe2 system. Meanwhile, the lattice thermal conductivity is gradually suppressed by point defects scattering. In contrast, the electrical resistivity first decreases and then slightly rises with the increased Ba-doping concentrations due to the presence of BaSe3 nanoprecipitates, exhibiting a different variation tendency compared with the corresponding Mg-doped samples. More significantly, the total thermal conductivity is obviously reduced with the increased Ba-doping concentrations partially because of the strong scattering of medium and long wavelength phonons via the nanoprecipitates, consistent with the theoretical calculation and analysis. Collectively, ZT value ∼1 at 673 K and calculated leg efficiency ∼8.5% with Tc = 300 K and Th = 673 K are obtained for both AgSb0.98Mg0.02Se2 and AgSb0.98Ba0.02Se2 samples. PMID:26434693

  3. Some electrical and structural properties of Cd/CdS/n-Si/Au-Sb sandwich structure

    NASA Astrophysics Data System (ADS)

    Güzeldir, Betül; Sağlam, Mustafa; Ateş, Aytunc

    2012-09-01

    In view of CdS growth is very impotent for technological importance especially solar applications; synthesis of this material remains a topic of great interest for researchers by means of an economically and technically viable method. In the present paper, Cd/CdS/n-Si/Au-Sb sandwich structure has been grown by Successive Ionic Layer Adsorption and Reaction (SILAR) technique. For investigating the structural properties, X-ray diffraction (XRD), scanning electron microscopy (SEM) and energy dispersive X-ray analysis (EDAX) measurements have been performed and it has been seen that films exhibit polycrystalline behavior. The capacitance-voltage (C-V) and conductance/w-voltage (G/w-V) characteristics of Cd/CdS/n-Si/Au-Sb structure have been investigated by considering series resistance and interface states effects. These measurements have been done in the -4 V, 4 V voltage range and in the frequency range of 10 kHz-3 MHz at room temperature. It is seen that, the series resistance (Rs) and interface state density have been strongly depend on frequency. The barrier height, donor concentration, diffusion potential parameters have been determined from the linear C-2-V plot. The barrier height values are obtained between 0.495 and 0.796 eV and doping density values have been ranged from 1.455 × 1014 to 1.999 × 1014 cm-3respectively. The capacitance-frequency (C-f) and conductance/w-frequency (G/w-f) characteristics of Cd/CdS/n-Si/Au-Sb structures have been measured at the various biases 0.00-0.14 V at room temperature. The energy distribution of the interface states (Nss) and their relaxation time (τ) have been determined from the forward bias capacitance-frequency characteristics. The Nss and τ values have ranged from 2.01 × 1012 cm-2 eV-1and 9.68 × 10-4 s in (Ec-0.45) eV-2.86 × 1013 cm-2 eV-1 and 3.81 × 10-4 s in (Ec-0.75) eV, respectively.

  4. A Simple Sb2Te3 Back-Contact Process for CdTe Solar Cells

    NASA Astrophysics Data System (ADS)

    Siepchen, B.; Späth, B.; Drost, C.; Krishnakumar, V.; Kraft, C.; Winkler, M.; König, J.; Bartholomé, K.; Peng, S.

    2015-10-01

    CdTe solar technology has proved to be a cost-efficient solution for energy production. Formation of the back contact is an important and critical step in preparing high-efficiency, stable CdTe solar cells. In this paper we report a simple CdTe solar cell (Sb2Te3) back contact-formation process. The CdS and CdTe layers were deposited by close-space sublimation. After CdCl2 annealing treatment, the CdTe surface was etched by use of a mixture of nitric and phosphoric acids to obtain a Te-rich surface. Elemental Sb was sputtered on the etched surface and successive post-annealing treatment induced Sb2Te3 alloy formation. Structural characterization by x-ray diffraction analysis confirmed formation of the Sb2Te3 phase. The performance of solar cells with nanoalloyed Sb2Te3 back contacts was comparable with that of reference solar cells prepared with sputtered Sb2Te3 back contact from a compound sputter target.

  5. Spin pumping and inverse Rashba-Edelstein effect in NiFe/Ag/Bi and NiFe/Ag/Sb

    SciTech Connect

    Zhang, Wei Jungfleisch, Matthias B.; Jiang, Wanjun; Pearson, John E.; Hoffmann, Axel

    2015-05-07

    The Rashba effect is an interaction between the spin and the momentum of electrons induced by the spin-orbit coupling in surface or interface states. We measured the inverse Rashba-Edelstein effect via spin pumping in Ag/Bi and Ag/Sb interfaces. The spin current is injected from the ferromagnetic resonance of a NiFe layer towards the Rashba interfaces, where it is further converted into a charge current. Using spin pumping theory, we quantify the conversion parameter of spin to charge current to be 0.11 ± 0.02 nm for Ag/Bi and a factor of ten smaller for Ag/Sb. The relative strength of the effect is in agreement with spectroscopic measurements and first principles calculations. We also vary the interlayer materials to study the voltage output in relation to the change of the effective spin mixing conductance. The spin pumping experiment offers a straight-forward approach of using spin current as an efficient probe for detecting interface Rashba splitting.

  6. Extranuclear dynamics of 111Ag(→111Cd) doped in AgI nanoparticles

    NASA Astrophysics Data System (ADS)

    Sato, W.; Mizuuchi, R.; Irioka, N.; Komatsuda, S.; Kawata, S.; Taoka, A.; Ohkubo, Y.

    2014-08-01

    Dynamic behavior of the extranuclear field relative to the 111Ag(→111Cd) probe nucleus introduced in a superionic conductor silver iodide (AgI) was investigated by means of the time-differential perturbed angular correlation technique. For poly-N-vinyl-2-pyrrolidone (PVP)-coated AgI nanoparticles, we observed nuclear spin relaxation of the probe at room temperature. This result signifies that Ag+ ions in the polymer-coated sample make hopping motion from site to site at this low temperature. The activation energy for the dynamic motion was successfully estimated to be 46(10) meV. The first atomic-level observation of the temperature-dependent dynamic behavior of Ag+ ions in the polymer-coated AgI is reported.

  7. Structural, elastic, electronic, and thermodynamic properties of MgAgSb investigated by density functional theory

    NASA Astrophysics Data System (ADS)

    Wang, Jun-Fei; Fu, Xiao-Nan; Zhang, Xiao-Dong; Wang, Jun-Tao; Li, Xiao-Dong; Jiang, Zhen-Yi

    2016-08-01

    The structural, elastic, electronic, and thermodynamic properties of thermoelectric material MgAgSb in γ,β,α phases are studied with first-principles calculations based on density functional theory. The optimized lattice constants accord well with the experimental data. According to the calculated total energy of the three phases, the phase transition order is determined from α to γ phase with cooling, which is in agreement with the experimental result. The physical properties such as elastic constants, bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, and anisotropy factor are also discussed and analyzed, which indicates that the three structures are mechanically stable and each has a ductile feature. The Debye temperature is deduced from the elastic properties. The total density of states (TDOS) and partial density of states (PDOS) of the three phases are investigated. The TDOS results show that the γ phase is most stable with a pseudogap near the Fermi level, and the PDOS analysis indicates that the conduction band of the three phases is composed mostly of Mg-3s, Ag-4d, and Sb-5p. In addition, the changes of the free energy, entropy, specific heat, thermal expansion of γ-MgAgSb with temperature are obtained successfully. The obtained results above are important parameters for further experimental and theoretical tuning of doped MgAgSb as a thermoelectric material at high temperature. Project supported by the National Natural Science Foundation of China (Grant No. 11504088), the Fund from Henan University of Technology, China (Grant Nos. 2014YWQN08 and 2013JCYJ12), the Natural Science Fund from the Henan Provincial Education Department, China (Grant No. 16A140027), the Natural Science Foundation of Shaanxi Province of China (Grant Nos. 2013JQ1018 and 15JK1759), and the Science Foundation of Northwest University of China (Grant No. 14NW23).

  8. Nucleation of AgInSbTe films employed in phase-change media

    SciTech Connect

    Ziegler, Stefan; Wuttig, Matthias

    2006-03-15

    In phase-change technology small volumes of a chalcogenide material are switched between amorphous and crystalline states by local heating with a short laser or current pulses. AgInSbTe is an alloy frequently used in optical data storage, which could also be applied in electronic data storage. For those applications it is crucial to understand the reliability and reproducibility of the switching process. In this work the first crystallization of an AgInSbTe alloy has been studied on a microsecond time scale using a focused laser beam. The experiments show that nucleation is a process governed by statistics. A correlation between the success of a nucleation event with the probability of nucleation is established. By measuring the nucleation probability as a function of laser pulse duration, the incubation time is determined to 11 {mu}s. The results are compared to measurements of the growth velocity of this material. The analysis of the temperature dependence of the growth velocity explains why AgInSbTe shows growth-dominated recrystallization. The implications of these findings to the application of such growth-dominated materials in electronic data storage are discussed.

  9. Photoluminescence and upconversion on Ag/CdTe quantum dots

    NASA Astrophysics Data System (ADS)

    Ragab, A. E.; Gadallah, A.-S.; Mohamed, M. B.; Azzouz, I. M.

    2014-11-01

    Different sizes of aqueous CdTe QDs have been prepared by microwave via controlling the temperature and time of irradiation. To study the plasmonic effect on CdTe QDs, Silver NPs were prepared by using a chemical reduction method. Structure characterization of the nanocrystals (Ag NPs and CdTe QDs) was determined by transmission electron microscopy “TEM”. For optical characterization, the absorption and photolumincence (PL) spectra were measured. It has been found that there are two opposite behaviors (quenching and enhancement) in the fluorescence spectra based on the spectral coupling strength between Ag NPs and CdTe QDs. When there is strong overlapping, PL enhancement of CdTe QDs has been observed. On the other hand, when the overlapping is weak, the PL quenching was predominant at all Ag NPS concentrations. Input-output PL intensity dependence was also studied. Upconversion photoluminescence with low excitation intensity was observed in our CdTe QDs with a standard spectrofluorometer at excitation wavelength of 800 nm. Thermally assisted surface state mechanism has been proposed to be responsible for the upconverion process.

  10. Temperature-dependent thermal expansion of cast and hot-pressed LAST (Pb-Sb-Ag-Te) thermoelectric materials

    SciTech Connect

    Ren, Fei; Hall, Bradley D.; Case, Eldon D; Timm, Edward J; Trejo, Rosa M; Meisner, Roberta Ann; Lara-Curzio, Edgar

    2009-01-01

    The thermal expansion for two compositions of cast and hot-pressed LAST (Pb Sb Ag Te) n-type thermoelectric materials has been measured between room temperature and 673K via thermomechanical analysis (TMA). In addition, using high-temperature X-ray diffraction (HT-XRD), the thermal expansion for both cast and hot-pressed LAST materials was determined from the temperature-dependent lattice parameters measured between room temperature and 623 K. The TMA and HT-XRD determined values of the coefficient of thermal expansion (CTE) for the LAST compositions ranged between 20106K1 and 24106K1, which is comparable to the CTE values for other thermoelectric materials including PbTe and Bi2Te3. The CTE of the LAST specimens with a higher Ag content (Ag0.86Pb19Sb1.0Te20) exhibited a higher CTE value than that of the LAST material with a lower Ag content (Ag0.43Pb18Sb1.2Te20). In addition, a peak in the temperature-dependent CTE was observed between room temperature and approximately 450K for both the cast and hot-pressed LAST with the Ag0.86Pb19Sb1.0Te20 composition, whereas the CTE of the Ag0.43Pb18Sb1.2Te20 specimen increased monotonically with temperature.

  11. Cladding technique for development of Ag In Cd decoupler

    NASA Astrophysics Data System (ADS)

    Teshigawara, M.; Harada, M.; Saito, S.; Kikuchi, K.; Kogawa, H.; Ikeda, Y.; Kawai, M.; Kurishita, H.; Konashi, K.

    2005-08-01

    To develop a Ag (silver)-In (indium)-Cd (cadmium) alloy decoupler, a method is needed to bond the decoupler between two plates of the Al alloy (A6061-T6). We found that a better HIP condition was temperature, pressure and holding time at 803 K, 100 MPa and 1 h, respectively, for small test pieces ( ϕ 22 mm in diam. × 5 mm in height). Especially, a sandwich case (a Ag-In plate with thickness of 0.5 mm between two Ag-Cd plates with thickness of 1.25 mm) gave easier (or better) bonding results. Though a hardened layer is found in the bonding layer, the rupture strength of the bonding layer is more than 30 MPa, which is higher than the design stress in our application.

  12. New CuM 2/3Sb 1/3O 2 and AgM 2/3Sb 1/3O 2 compounds with the delafossite structure

    NASA Astrophysics Data System (ADS)

    Nagarajan, R.; Uma, S.; Jayaraj, M. K.; Tate, J.; Sleight, A. W.

    2002-05-01

    Several new compounds have been prepared with the delafossite structure: CuMn 2/3Sb 1/3O 2, CuCo 2/3Sb 1/3O 2, CuNi 2/3Sb 1/3O 2, CuZn 2/3Sb 1/3O 2, CuMg 2/3Sb 1/3O 2, AgNi 2/3Sb 1/3O 2, and AgZn 2/3Sb 1/3O 2. The structures of the CuM 2/3Sb 1/3O 2 compounds are generally based on 2H stacking along the c axis, and the M 2+ and Sb 5+ cations can be ordered or disordered. The structures of the AgM 2/3Sb 1/3O 2 compounds are based on 3R stacking along c with the M 2+ and Sb 5+ cations disordered. The structures of CuMn 2/3Sb 1/3O 2 (disordered) and CuMg 2/3Sb 1/3O 2 (ordered) were refined from single crystal X-ray diffraction data. Pellets and transparent thin films of CuNi 2/3Sb 1/3O 2 with 10% Sn doping for Sb showed p-type electronic conduction.

  13. Nanodopant-Induced Band Modulation in AgPbmSbTe2+m-Type Nanocomposites

    SciTech Connect

    Zhang, Yi; Ke, Xuezhi; Chen, Changfeng; Yang, Jihui; Kent, Paul R

    2011-01-01

    We elucidate the fundamental physics of nanoscale dopants in narrow band-gap thermoelectric nanocomposites XPbmYTe2+m (X=Ag,Na; Y=Sb,Bi) using first-principles calculations. Our re- sults unveil distinct band-structure modulations, most notably a sizable band-gap widening driven by nanodopant-induced lattice strain and a band split-off at the conduction band minimum caused by the spin-orbit interaction of the dopant Sb or Bi atoms. Boltzmann transport calculations demon- strate that these band modulations have significant but competing effects on high-temperature elec- tron transport behavior. These results offer insights for understanding recent experimental findings and suggest principles for optimizing thermoelectric properties of narrow band-gap semiconductors.

  14. Dielectric relaxation studies in Se90Cd8Sb2 glassy alloy

    NASA Astrophysics Data System (ADS)

    Shukla, Nitesh; Rao, Vandita; Dwivedi, D. K.

    2016-05-01

    Se90Cd8Sb2 chalcogenide semiconducting alloy was prepared by melt quench technique. The prepared glassy alloy has been characterized by techniques such as scanning electron microscopy (SEM) and energy dispersive X-ray (EDAX).Dielectric properties of Se90Cd8Sb2 chalcogenide semiconductor have been studied using impedance spectroscopic technique in the frequency range 5×102Hz - 1×105Hz and in temperature range 303-318K. It is found that dielectric constant ɛ' and dielectric loss factor ɛ″ are dependent on frequency and temperature.

  15. Electrical and photoconductivity studies on AgSbSe2 thin films

    NASA Astrophysics Data System (ADS)

    Namitha Asokan, T.; Urmila, K. S.; Pradeep, B.

    2015-02-01

    Silver antimony selenide thin films have been deposited on ultrasonically cleaned glass substrate at a vacuum of 10-5 torr using reactive evaporation technique. The preparative parameters like substrate temperature and incident fluxes have been properly controlled in order to get highly reproducible compound films. The polycrystalline nature of the sample is confirmed using XRD. The dependence of the electrical conductivity on the temperature has also been studied. The prepared AgSbSe2 samples show p-type conductivity. The samples show a little photoresponse.

  16. Comparative modular analysis of two complex sulfosalt structures: sterryite, Cu(Ag,Cu)3Pb19(Sb,As)22(As-As)S56, and parasterryite, Ag4Pb20(Sb,As)24S58.

    PubMed

    Moëlo, Yves; Guillot-Deudon, Catherine; Evain, Michel; Orlandi, Paolo; Biagioni, Cristian

    2012-10-01

    The crystal structures of two very close, but distinct complex minerals of the lead sulfosalt group have been solved: sterryite, Cu(Ag,Cu)(3)Pb(19)(Sb,As)(22)(As-As)S(56), and parasterryite, Ag(4)Pb(20)(Sb,As)(24)S(58). They are analyzed and compared according to modular analysis. The fundamental building block is a complex column centred on a Pb(6)S(12) triangular prismatic core, with two additional long and short arms. The main chemical and topological differences relate to the short arm, which induces a relative a/4 shift (~2 Å along the elongation parameter) of the constitutive rod layers, as illustrated by distinct cell settings within the same space group (P2(1)/n and P2(1)/c, respectively). Selection of the shortest (i.e. strongest) (Sb,As)-S bonds permitted to enhance the polymeric organization of (Sb,As) atoms with triangular pyramidal coordination. These two quasi-homeotypic structures are expanded derivatives of owyheeite, Ag(3)Pb(10)Sb(11)S(28). The hierarchy of organization levels from zero- to three-dimensional entities is subordinated to building operators, which appear as the driving force for the construction of such complex structures. Minor cations (Ag, Cu) or the As-As pair in sterryite secure the final locking, which favours the formation of one or the other compound. PMID:22992793

  17. Effect of Pressure and Chemical Substitutions on the Charge-Density-Wave in LaAgSb2

    SciTech Connect

    Budko,S.; Weiner, T.; Ribeiro, R.; Canfield, P.; Lee, Y.; Vogt, T.; Lacerda

    2006-01-01

    We present data on the crystal structure and evolution of the electrical resistivity in lightly doped La{sub 1-x}R{sub x}AgSb{sub 2} (R=Gd, Y, Ce, and Nd) at ambient pressure and in LaAgSb{sub 2} under hydrostatic pressure. The upper charge density wave transition is suppressed by both doping and pressure with substitution-related disorder being the dominant mechanism for this suppression in the former case and the anisotropic pressure dependence of the unit cell dimensions (as seen in the c/a ratio) prevailing in the latter case.

  18. Structural studies of GeTe-AgSbTe2 alloys

    SciTech Connect

    Thompson, A. J.; Sharp, Jeff; Rawn, Claudia J; Chakoumakos, Bryan C

    2008-01-01

    GeTe, a small bandgap semiconductor that has native p-type defects due to Ge vacancies, is an important constituent in the thermoelectric material known as 'TAGS' [1]. TAGS is an acronym for alloys of GeTe with AgSbTe2, and compositions are normally designated as TAGS-x, where x is the fraction of GeTe. TAGS-85 is the most important with regard to applications, and there also is commercial interest in TAGS-80. The crystal structure of GeTe1+d has a composition-dependent phase transformation at a temperature ranging from 430 C (d = 0) to {approx} 400 C (d = 0.02) [2]. The high temperature form is cubic. The low temperature form is rhombohedral for d < 0.01, as is the case for good thermoelectric performance. Addition of AgSbTe2 shifts the phase transformation to lower temperatures, and one of the goals of this work is a systematic study of the dependence of transformation temperature on the parameter x. We present results on phase transformations and associated instabilities in TAGS compositions in the range of 70-85 at.% GeTe.

  19. Measurements of the energy band gap and valence band structure of AgSbTe2

    NASA Astrophysics Data System (ADS)

    Jovovic, V.; Heremans, J. P.

    2008-06-01

    The de Haas-van Alphen effect, galvanomagnetic and thermomagnetic properties of high-quality crystals of AgSbTe2 are measured and analyzed. The transport properties reveal the material studied here to be a very narrow-gap semiconductor (Eg≈7.6±3meV) with ˜5×1019cm-3 holes in a valence band with a high density of states and thermally excited ˜1017cm-3 high-mobility (2200cm2/Vs) electrons at 300 K. The quantum oscillations are measured with the magnetic field oriented along the ⟨111⟩ axis. Taken together with the Fermi energy derived from the transport properties, the oscillations confirm the calculated valence band structure composed of 12 half-pockets located at the X -points of the Brillouin zone, six with a density-of-states effective mass mda∗≫0.21me and six with mdb∗≫0.55me , giving a total density-of-states effective mass, including Fermi pocket degeneracy, of md∗≈1.7±0.2me ( me is the free electron mass). The lattice term dominates the thermal conductivity, and the electronic contribution in samples with both electrons and holes present is in turn dominated by the ambipolar term. The low thermal conductivity and very large hole mass of AgSbTe2 make it a most promising p -type thermoelectric material.

  20. A dry method to synthesize dendritic Ag2Se nanostructures utilizing CdSe quantum dots and Ag thin films.

    PubMed

    Hu, Lian; Zhang, Bingpo; Xu, Tianning; Li, Ruifeng; Wu, Huizhen

    2015-01-01

    Dendritic Ag2Se nanostructures are synthesized in a dry environment by UV irradiating the hybrids composed of CdSe quantum dots (QDs) and silver (Ag). UV irradiation on CdSe QDs induces a photooxidation effect on the QD surface and leads to the formation of SeO2 components. Then SeO2 reacts with the Ag atoms in either Ag film or QD layer to produce the Ag2Se. The growth mechanism of Ag2Se dendrites on solid Ag films is explored and explained by a diffusion limited aggregation model in which the QD layer provides enough freedom for Ag2Se motion. Since the oxidation of the CdSe QDs is the critical step for the Ag2Se dendrites formation this dry chemical interaction between QDs and Ag film can be applied in the study of the QD surface chemical properties. With this dry synthesis method, the Ag2Se dendrites can also be facilely formed at the designed area on Ag substrates. PMID:25483981

  1. A dry method to synthesize dendritic Ag2Se nanostructures utilizing CdSe quantum dots and Ag thin films

    NASA Astrophysics Data System (ADS)

    Hu, Lian; Zhang, Bingpo; Xu, Tianning; Li, Ruifeng; Wu, Huizhen

    2015-01-01

    Dendritic Ag2Se nanostructures are synthesized in a dry environment by UV irradiating the hybrids composed of CdSe quantum dots (QDs) and silver (Ag). UV irradiation on CdSe QDs induces a photooxidation effect on the QD surface and leads to the formation of SeO2 components. Then SeO2 reacts with the Ag atoms in either Ag film or QD layer to produce the Ag2Se. The growth mechanism of Ag2Se dendrites on solid Ag films is explored and explained by a diffusion limited aggregation model in which the QD layer provides enough freedom for Ag2Se motion. Since the oxidation of the CdSe QDs is the critical step for the Ag2Se dendrites formation this dry chemical interaction between QDs and Ag film can be applied in the study of the QD surface chemical properties. With this dry synthesis method, the Ag2Se dendrites can also be facilely formed at the designed area on Ag substrates.

  2. Ag{sub 1.75}InSb{sub 5.75}Se{sub 11}: A new noncentrosymmetric compound with congruent-melting behavior

    SciTech Connect

    Hao, Wenyu; Han, Yemao; Huang, Rongjin; Feng, Kai; Yin, Wenlong; Yao, Jiyong; Wu, Yicheng

    2014-10-15

    A new type of quaternary selenide Ag{sub 1.75}InSb{sub 5.75}Se{sub 11} has been synthesized. It crystallizes in the non-centrosymmetric space group Cm of monoclinic system, with a=13.419 (1) Å, b=4.084 (1) Å, and c=19.165 (2) Å, Z=2. The compound has a new three-dimensional layer structure which consists of infinite {sup 2}{sub ∞}[AgSb{sub 2}Se{sub 4}] layers and {sup 2}{sub ∞}[Ag1(Sb6)Ag3InSb{sub 3}Se{sub 8}] layers. The band gap of Ag{sub 1.75}InSb{sub 5.75}Se{sub 11} is 0.94(2) eV, which agrees with its dark gray color. Moreover, the compound exhibits congruent-melting behavior. - Graphical abstract: Ag{sub 1.75}InSb{sub 5.75}Se{sub 11} has a new three-dimensional layer structure which consists of infinite {sup 2}{sub ∞}[AgSb{sub 2}Se{sub 4}] layers and {sup 2}{sub ∞}[Ag1(Sb6)Ag3InSb{sub 3}Se{sub 8}] layers. - Highlights: • The new quaternary selenide Ag{sub 1.75}InSb{sub 5.75}Se{sub 11} has been synthesized. • It crystallizes in non-centrosymmetric space group Cm and has a new layer structure. • The structure consists of {sup 2}{sub ∞}[AgSb{sub 2}Se{sub 4}] layers and {sup 2}{sub ∞}[Ag1(Sb6)Ag3InSb{sub 3}Se{sub 8}] layers. • The band gap of Ag{sub 1.75}InSb{sub 5.75}Se{sub 11} is 0.94(2) eV. • The compound exhibits congruent-melting behavior.

  3. Influence of root temperature on phytoaccumulation of As, Ag, Cr, and Sb in potato plants (Solanum tuberosum L. var. Spunta).

    PubMed

    Baghour, M; Moreno, D A; Hernández, J; Castilla, N; Romero, L

    2001-01-01

    Three consecutive years of field experiments were carried out to investigate the effect of root temperatures induced by the application of mulches for phytoextraction of As, Ag, Cr and Sb using potato plants (roots, tubers, stems and leaflets). Four different plastic covers were used (T1: transparent polyethylene; T2: white polyethylene; T3: white and black coextruded polyethylene; and T4: black polyethylene), taking uncovered plants as control (T0). The different treatments had a significant effect on mean root temperatures (T0 = 16 degrees C, T1 = 20 degrees C, T2 = 23 degrees C, T3 = 27 degrees C and T4 = 30 degrees C) and induced a significantly different response in the As, Ag, Cr and Sb phytoaccumulation. The T3 treatment gave rise to the greatest phytoaccumulation of As, Ag, Cr and Sb in the roots, leaflets and tubers. In terms of the relative distribution of the phytoaccumulated metals (with respect to the total of the plant), As accumulated mainly in the roots and leaflets whereas Ag, Cr and Sb accumulated primarily in the tubers, establishing a close relationship between biomass development of each organ and phytoaccumulation capacity of elements in response to temperature in the root zone. With regard to phytoremediation using the potato plant, it is necessary to ascertain the influence and include the control of the thermal regime of the soil to optimize the phytoextraction of pollutants. PMID:11545361

  4. Thermoelectric device including an alloy of GeTe and AgSbTe as the P-type element

    DOEpatents

    Skrabek, Emanuel Andrew; Trimmer, Donald Smith

    1976-01-01

    Improved alloys suitable for thermoelectric applications and having the general formula: (AgSbTe.sub.2).sub.1.sub.-x + (GeTe).sub.x wherein x has a value of about 0.80 and 0.85, have been found to possess unexpectedly high thermoelectric properties such as efficiency index, as well as other improved physical properties.

  5. Internally consistent database for sulfides and sulfosalts in the system Ag 2S-Cu 2S-ZnS-Sb 2S 3-As 2S 3

    NASA Astrophysics Data System (ADS)

    Sack, Richard O.

    2000-11-01

    An updated thermodynamic database for Ag 2S-Cu 2S-ZnS-Sb 2S 3-As 2S 3 sulfides and sulfosalts applicable to temperatures above 119°C is developed to calculate phase relations for polybasite-pearceite- and fahlore-bearing assemblages. It is based on pre-existing and new constraints on activity-composition, Ag-Cu and As-Sb partitioning, and other relations, and on experiments (200-300°C, evacuated silica tubes) conducted to define the stability of the polybasite-pearceite [(Ag 1- x,Cu x) 16(Sb 1- y,As y) 2S 11] + ZnS sphalerite assemblage with respect to assemblages containing (Ag,Cu) 2S sulfides coexisting with (Cu, Ag) 10Zn 2(Sb,As) 4S 13 fahlore sulfosalts. It was found that the thermodynamics of mixing of bcc- and hcp-(Ag,Cu) 2S solutions, which are fast-ion conductors, may be described by using site multiplicities of metals α Ag,Cu > 2 and temperature-dependent regular solution parameters. We obtained estimates for the Gibbs energies of formation for Ag 16Sb 2S 11 and Cu 16Sb 2S 11 polybasite endmembers from the simple sulfides (Ag 2S, Cu 2S, and Sb 2S 3) of -30.79 and -4.07 kJ/gfw at 200°C, and -32.04 and -0.59 kJ/gfw at 400°C, respectively, that are about one half kJ/gfw more positive and about 6 kJ/gfw more negative than those estimated by Harlov and Sack (1995b). The corresponding estimates for formation energies of Ag 10Zn 2Sb 4S 13 and Cu 10Zn 2Sb 4S 13 fahlores (-20.29 and -105.29 kJ/gfw at 200°C and -23.72 and -105.76 kJ/gfw at 400°C) are comparable to, and roughly 110 kJ/gfw more positive than, the corresponding estimates of Ebel and Sack (1994). We also determined that the Gibbs energies of the As-Sb exchange reactions: 1/4Ag 10Zn2Sb4S13+1/2Ag 16As2S11=1/2Ag 16Sb2S11+1/4Ag 10Zn2As4S13Sb-fahlorepearceitepolybasiteAs-fahlore and Ag3SbS3+1/2Ag 16As2S11=1/2Ag 16Sb2S11+Ag3AsS3pyrargyritepearceitepolybasiteproustite are, respectively, 8.75 and 0.40 kJ/gfw in the range 150-350°C, and these predictions are consistent with As-Sb partitioning relations

  6. Ternary eutectic growth of Ag-Cu-Sb alloy within ultrasonic field

    NASA Astrophysics Data System (ADS)

    Zhai, Wei; Hong, Zhenyu; Wei, Bingbo

    2007-08-01

    The liquid to solid transformation of ternary Ag42.4Cu21.6Sb36 eutectic alloy was accomplished in an ultrasonic field with a frequency of 35 kHz, and the growth mechanism of this ternary eutectic was examined. Theoretical calculations predict that the sound intensity in the liquid phase at the solidification interface increases gradually as the interface moves up from the sample bottom to its top. The growth mode of ( ɛ + θ + Sb) ternary eutectic exhibits a transition of “divorced eutectic—mixture of anomalous and regular structures—regular eutectic” along the sample axis due to the inhomogeneity of sound field distribution. In the top zone with the highest sound intensity, the cavitation effect promotes the three eutectic phases to nucleate independently, while the acoustic streaming efficiently suppresses the coupled growth of eutectic phases. In the meantime, the ultrasonic field accelerates the solute transportation at the solid-liquid interface, which reduces the solute solubility of eutectic phases.

  7. Viscosity of liquid Ag-In-Sb-Te: Evidence of a fragile-to-strong crossover.

    PubMed

    Orava, J; Weber, H; Kaban, I; Greer, A L

    2016-05-21

    The temperature-dependent viscosity η(T) is measured for the equilibrium liquid of the chalcogenide Ag-In-Sb-Te (AIST), the first time this has been reported for a material of actual interest for phase-change memory. The measurements, in the range 829-1254 K, are made using an oscillating-crucible viscometer, and show a liquid with high fragility and low viscosity, similar to liquid pure metals. Combining the high-temperature viscosity measurements with values inferred from crystal growth rates in the supercooled liquid allows the form of η(T) to be estimated over the entire temperature range from above the melting point down to the glass transition. It is then clear that η(T) for liquid AIST cannot be described with a single fragility value, unlike other phase-change chalcogenides such as liquid Ge-Sb-Te. There is clear evidence for a fragile-to-strong crossover on cooling liquid AIST, similar to that analyzed in Te85Ge15. The change in fragility associated with the crossover in both these cases is rather weak, giving a broad temperature range over which η(T) is near-Arrhenius. We discuss how such behavior may be beneficial for the performance of phase-change memory. Consideration of the fragile-to-strong crossover in liquid chalcogenides may be important in tuning compositions to optimize the device performance. PMID:27208954

  8. Viscosity of liquid Ag-In-Sb-Te: Evidence of a fragile-to-strong crossover

    NASA Astrophysics Data System (ADS)

    Orava, J.; Weber, H.; Kaban, I.; Greer, A. L.

    2016-05-01

    The temperature-dependent viscosity η(T) is measured for the equilibrium liquid of the chalcogenide Ag-In-Sb-Te (AIST), the first time this has been reported for a material of actual interest for phase-change memory. The measurements, in the range 829-1254 K, are made using an oscillating-crucible viscometer, and show a liquid with high fragility and low viscosity, similar to liquid pure metals. Combining the high-temperature viscosity measurements with values inferred from crystal growth rates in the supercooled liquid allows the form of η(T) to be estimated over the entire temperature range from above the melting point down to the glass transition. It is then clear that η(T) for liquid AIST cannot be described with a single fragility value, unlike other phase-change chalcogenides such as liquid Ge-Sb-Te. There is clear evidence for a fragile-to-strong crossover on cooling liquid AIST, similar to that analyzed in Te85Ge15. The change in fragility associated with the crossover in both these cases is rather weak, giving a broad temperature range over which η(T) is near-Arrhenius. We discuss how such behavior may be beneficial for the performance of phase-change memory. Consideration of the fragile-to-strong crossover in liquid chalcogenides may be important in tuning compositions to optimize the device performance.

  9. Martensitic transformation behavior in Ti–Ni–X (Ag, In, Sn, Sb, Te, Tl, Pb, Bi) ternary alloys

    SciTech Connect

    Jang, Jai-young; Chun, Su-jin; Kim, Nam-suk; Cho, Jeung-won; Kim, Jae-hyun; Yeom, Jong-taek; Kim, Jae-il; Nam, Tae-hyun

    2013-12-15

    Graphical abstract: - Highlights: • Ag, In and Sn were soluble in TiNi matrix, while Sb, Te, Tl, Pb and Bi were not. • The B2-R-B19′transformation occurred in Ti-Ni-(Ag, In, Sn) alloys. • Solid solution hardening was essential for inducing the B2-R transformation. - Abstract: The microstructures and transformation behaviors of Ti–Ni–X (Ag, In, Sn, Sb, Te, Tl, Pb, Bi) ternary alloys were investigated using electron probe micro-analysis (EPMA), X-ray diffraction (XRD), differential scanning calorimetry (DSC) and Micro Vickers hardness tests. All specimens consisted of Ti–Ni matrices and second phase particles. Ag, In and Sn were soluble in Ti–Ni matrices with a limited solubility (≤1.0 at%), while Sb, Te, Tl, Pb and Bi were not soluble. Two-stage B2-R-B19′ transformation occurred in Ti–48.8Ni–1.2Ag, Ti–49.0Ni–1.0In and Ti–49.0Ni–1.0Sn alloys, while one-stage B2-B19′ transformation occurred in Ti–49.0Ni–1.0Ag, Ti–49.0Ni–1.0Sb, Ti–49.0Ni–1.0Te, Ti–49.0Ni–1.0Pb and Ti–49.0Ni–1.0Bi alloys. Micro Vickers hardness of the alloys displaying the B2-R-B19′ transformation (Hv 250–368) was much larger than that (

  10. Synthesis and high temperature thermoelectric properties of Yb0.25Co4Sb12-(Ag2Te)x(Sb2Te3)1−x nanocomposites

    PubMed Central

    Zheng, Jin; Peng, Jiangying; Zheng, Zhexin; Zhou, Menghan; Thompson, Emily; Yang, Junyou; Xiao, Wanli

    2015-01-01

    Nanocomposites are becoming a new paradigm in thermoelectric study: by incorporating nanophase(s) into a bulk matrix, a nanocomposite often exhibits unusual thermoelectric properties beyond its constituent phases. To date most nanophases are binary, while reports on ternary nanoinclusions are scarce. In this work, we conducted an exploratory study of introducing ternary (Ag2Te)x(Sb2Te3)1−x inclusions in the host matrix of Yb0.25Co4Sb12. Yb0.25Co4Sb12-4wt% (Ag2Te)x(Sb2Te3)1−x nanocomposites were prepared by a melting-milling-hot-pressing process. Microstructural analysis showed that poly-dispersed nanosized Ag-Sb-Te inclusions are distributed on the grain boundaries of Yb0.25Co4Sb12 coarse grains. Compared to the pristine nanoinclusion-free sample, the electrical conductivity, Seebeck coefficient, and thermal conductivity were optimized simultaneously upon nanocompositing, while the carrier mobility was largely remained. A maximum ZT of 1.3 was obtained in Yb0.25Co4Sb12-4wt% (Ag2Te)0.42(Sb2Te3)0.58 at 773 K, a ~ 40% increase compared to the pristine sample. The electron and phonon mean-free-path were estimated to help quantify the observed changes in the carrier mobility and lattice thermal conductivity. PMID:26389111

  11. Effects of Cu and Ag as ternary and quaternary additions on some physical properties of SnSb7 bearing alloy

    NASA Astrophysics Data System (ADS)

    El-Bediwi, A. B.

    2004-02-01

    The structure, electrical resistivity, and elastic modulus of SnSb7 and SnSb7X (X = Cu , Ag, or Cu and Ag) rapidly solidified alloys have been investigated using X-ray diffractometer, double bridge, and dynamic resonance techniques. Copper and silver additions to SnSb result in the formation of a eutectic matrix containing embedded crystals (intermetallic phases) of SnCu, SnAg, and SnSb. The hard crystals SnCu, SnAg, and SnSb increase the overall hardness and wear resistance of SnSb bearing alloys. Addition of copper and silver improves internal friction, electrical conductivity, and elastic modulus values of SnSb rapidly solidified bearing alloys. The internal friction, elastic modulus, and electrical resistivity values are relatively sensitive to the composition of the intermediate phases in the matrix. The SbSb(7)Cu(2)g(2) has better properties (lowest internal friction, cost, adequate elastic modulus, and electrical resistivity) for bearing alloys as compared to cast iron and bronzes.

  12. Rb(16)Cd(25.39(3))sb(36): an electron-deficient zintl phase containing infinite dodecahedron chains.

    PubMed

    Zheng, Wu-Zui; Wang, Peng; Wu, Li-Ming; Liu, Yi; Chen, Ling

    2010-07-01

    A novel ternary antimonide Rb(16)Cd(25.39(3))Sb(36) has been synthesized by a solid-state reaction of the appropriate amount of elements in a welded niobium tube at 530 degrees C. The compound crystallizes in orthorhombic space group Cmcm (No. 63) with a = 16.499(5) A, b = 12.391(4) A, c = 12.400(4) A, and Z = 1. The structure features a new 3D network constructed of chains of Rb(+)-centered dodecahedra running along [001]. The atomic distribution of the Cd(8)Sb(12) dodecahedron presents an energetically favored pattern without any Cd-Cd bonding. The formation of the phase and the occurrence of a very narrow phase width of Rb(16)Cd(24+x)Sb(36) [0.94(2) < or = x < or = 1.47(3)] have been studied in detail. The Fermi level of the title compound is expected to be located between those of the hypothetical models of "[Rb(16)Cd(24)Sb(36)](0)" (I, poor metallic) and "[Rb(16)Cd(24)Sb(36)] + 4e" (II, narrow-band-gap semiconductor), which agrees well with the experimental measurements. In the temperature range of 300-473 K, the as-synthesized Rb(16)Cd(25.39(3))Sb(36) exhibits p-type semiconductor behavior and shows temperature-independent thermal conductivities (around 0.49 W/m.K). The electrical conductivity, Seebeck coefficient, and figure of merit (ZT) of Rb(16)Cd(25.39(3))Sb(36) are temperature-dependent; these values are 57.4 S/cm, +81.4 microV/K, and 0.04, respectively, at 466 K. PMID:20509601

  13. Soft chemical synthesis of Ag{sub 3}SbS{sub 3} with efficient and recyclable visible light photocatalytic properties

    SciTech Connect

    Gusain, Meenakshi; Rawat, Pooja; Nagarajan, Rajamani

    2014-12-15

    Highlights: • Highly crystalline Ag{sub 3}SbS{sub 3} synthesized using soft chemical approach. • First time report of photocatalytic activity of Ag{sub 3}SbS{sub 3}. • Ag{sub 3}SbS{sub 3} degraded the harmful organic dyes rapidly under visible radiation. • Pseudo first order kinetics have been followed in these sets of reactions. • Up to 90% of Methylene Blue degraded even after 4th cycle of catalyst reuse. • Structure of catalyst is intact after reuse. • As the catalyst is heavy, its separation after use is quite simple. - Abstract: Application of Ag{sub 3}SbS{sub 3}, obtained by soft chemical approach involving rapid reaction of air stable metal–thiourea complexes in ethylene glycol medium, as visible light photocatalyst for the degradation of dye solutions was investigated. Ag{sub 3}SbS{sub 3} was confirmed by high resolution powder X-ray diffraction pattern and its no defined morphology was present in SEM images. From UV–vis spectroscopy measurements, optical band gap of 1.77 eV was deduced for Ag{sub 3}SbS{sub 3}. Rapid degradation kinetics and recyclability was exhibited by Ag{sub 3}SbS{sub 3} towards Methylene Blue, Methyl Orange, Malachite Green, and Rhodamine 6G dye solutions under visible radiation. All these processes followed pseudo first order kinetics. High surface area (6.39 m{sup 2}/g), with mesopores (3.81 nm), arising from solvent mediated synthesis of Ag{sub 3}SbS{sub 3} has been correlated to its catalytic activity.

  14. Thermoelectric Inhomogeneities in (Ag(sub 1-y)SbTe2)(sub x)(PbTe)(sub 1-x)

    NASA Technical Reports Server (NTRS)

    Snyder, G. Jeffrey; Chen, Nancy; Gascoin, Franck; Mueller, Eckhard; Karpinski, Gabriele; Stiewe, Christian

    2006-01-01

    A document presents a study of why materials of composition (Ag1 ySbTe2)0.05 (PbTe)0.95 [0< or = y < or = 1] were previously reported to have values of the thermoelectric figure of merit [ZT (where Z = alpha(sup 2)/rk, alpha is the Seebeck coefficient, r is electrical resistivity, k is thermal conductivity, and T is absolute temperature)] ranging from <1 to >2. In the study, samples of (AgSbTe2)0.05(PbTe)0.95, (Ag0.67SbTe2)0.05 (PbTe)0.95, and (Ag0.55SbTe2)0.05(PbTe)0.95 were prepared by melting followed, variously, by slow or rapid cooling. Analyses of these samples by x-ray diffraction, electron microscopy, and scanning-microprobe measurements of the Seebeck coefficient led to the conclusion that these materials have a multiphase character on a scale of the order of millimeters, even though they appear homogeneous in x-ray diffraction and electron microscopy. The Seebeck measurements showed significant variations, including both n-type and p-type behavior in the same sample. These variations were found to be consistent with observed variations of ZT. The rapidly quenched samples were found to be less inhomogeneous than were the furnace-cooled ones; hence, rapid quenching was suggested as a basis of research on synthesizing more nearly uniform high-ZT samples.

  15. Enhanced thermoelectric performance and novel nanopores in AgSbTe{sub 2} prepared by melt spinning

    SciTech Connect

    Du, Baoli; Li, Han; Xu, Jingjing; Tang, Xinfeng; Uher, Ctirad

    2011-01-15

    We report a melt-spinning spark-plasma-sintering synthesis process of the polycrystalline p-type material composed of AgSbTe{sub 2} coarse grains and evenly formed 5-10 nm pores that occur primarily on the surface of matrix grains. The formation mechanism of nanopores and their influences on the thermoelectric properties have been studied and correlated. Microstructure analysis shows that the as-prepared sample can be regarded as a nanocomposite of matrix and in situ generated nanopores evenly coated on matrix grains. For the single-phase component and the possible energy-filter effect caused by the nanopores, the electrical transport properties are improved. Moreover, the thermal conductivity is significantly reduced by strong phonon scattering effect resulted from the nanopores. The thermoelectric performance of the as prepared sample enhances greatly and a ZT of 1.65 at 570 K is achieved, increasing{approx}200% compared with the sample prepared by traditional melt and slow-cooling method. -- Graphical abstract: Representative nanostructure of AgSbTe{sub 2} sample (a) ribbons obtained after melt spinning (b) bulk AgSbTe{sub 2} material obtained after spark plasma sintering. Display Omitted

  16. From local structure to nanosecond recrystallization dynamics in AgInSbTe phase-change materials

    NASA Astrophysics Data System (ADS)

    Matsunaga, Toshiyuki; Akola, Jaakko; Kohara, Shinji; Honma, Tetsuo; Kobayashi, Keisuke; Ikenaga, Eiji; Jones, Robert O.; Yamada, Noboru; Takata, Masaki; Kojima, Rie

    2011-02-01

    Phase-change optical memories are based on the astonishingly rapid nanosecond-scale crystallization of nanosized amorphous ‘marks’ in a polycrystalline layer. Models of crystallization exist for the commercially used phase-change alloy Ge2Sb2Te5 (GST), but not for the equally important class of Sb-Te-based alloys. We have combined X-ray diffraction, extended X-ray absorption fine structure and hard X-ray photoelectron spectroscopy experiments with density functional simulations to determine the crystalline and amorphous structures of Ag3.5In3.8Sb75.0Te17.7 (AIST) and how they differ from GST. The structure of amorphous (a-) AIST shows a range of atomic ring sizes, whereas a-GST shows mainly small rings and cavities. The local environment of Sb in both forms of AIST is a distorted 3+3 octahedron. These structures suggest a bond-interchange model, where a sequence of small displacements of Sb atoms accompanied by interchanges of short and long bonds is the origin of the rapid crystallization of a-AIST. It differs profoundly from crystallization in a-GST.

  17. Effects of Ge replacement in GeTe by Ag or Sb on the Seebeck coefficient and carrier concentration modified by local electron imbalance

    NASA Astrophysics Data System (ADS)

    Levin, E. M.; Howard, A.; Straszheim, W. E.

    2015-03-01

    XRD, SEM, EDS, 125Te NMR, Seebeck coefficient, and electrical resistivity of AgxGe50-xTe50 and SbxGe50-xTe50 alloys have been studied. Replacement of Ge in GeTe by Sb significantly increases the Seebeck coefficient, while replacement by Ag decreases it. These effects can be attributed to a change in carrier concentration observed via 125Te NMR spin-lattice relaxation measurements and NMR signal position, which mostly depends on the Knight shift. Variation in carrier concentration in AgxGe50-xTe50 and SbxGe50-xTe50 can be attributed to different electron configurations of valence electrons of Ag (4d105s1) and Sb (5s25p3) compared to that of Ge (4s24p2) resulting in local electron imbalances and changing the concentration of charge carrier (holes) generated by Ge vacancies. In contrast, our 125Te NMR and Seebeck coefficient data for Ag2Sb2Ge46Te50 are similar to those observed for GeTe. This shows that effects from Ag and Sb compensate each other and indicates the existence of [Ag +Sb] pairs. The effects of Ge replacement in GeTe by Ag, Sb, or [Ag +Sb] on rhombohedral lattice distortion also have been analyzed. Interplay between the Seebeck coefficient and electrical resistivity in these alloys results in variation of power factor; the value of 45 mW/cm K2, the highest among known tellurides, was found for Sb2Ge48Te50.

  18. Internal self-ordering in In(Sb,As), (In,Ga)Sb, and (Cd,Zn,Mn)Se nano-agglomerates/quantum dots

    SciTech Connect

    Moeck, P.; Topuria, T.; Browning, N. D.; Booker, G. R.; Mason, N. J.; Nicholas, R. J.; Dobrowolska, M.; Lee, S.; Furdyna, J. K.

    2001-08-13

    Nano-agglomerates of In(Sb,As) in InAs, (In,Ga)Sb in GaSb, and (Cd,Zn,Mn)Se in (Zn,Mn)Se are classified by transmission electron microscopy. In scanning transmission electron microscopy, atomic resolution Z-contrast images reveal different modes of internal compositional modulation on the atomic length scale, resulting for all three material systems in nano-agglomerates of an appropriate size that may constitute a new type of quantum dot. For other nano-agglomerates of In(Sb,As) in InAs and (In,Ga)Sb in GaSb, we observed a second type of nanoscale ordering that results in nano-agglomerates with an internal compositional modulation on a length scale of a few nm. Both types of compositional modulation are discussed as having arisen from a rather long-term structural response to a combination of internal and external strains. {copyright} 2001 American Institute of Physics.

  19. Bioaccessibility of As, Cd, Cu, Ni, Pb, and Sb in toys and low-cost jewelry.

    PubMed

    Guney, Mert; Zagury, Gerald J

    2014-01-21

    Children can be exposed to toxic elements in toys and jewelry following ingestion. As, Cd, Cu, Ni, Pb, and Sb bioavailability was assessed (n = 24) via the in vitro gastrointestinal protocol (IVG), the physiologically based extraction test (PBET), and the European Toy Safety Standard protocol (EN 71-3), and health risks were characterized. Cd, Cu, Ni, and Pb were mobilized from 19 metallic toys and jewelry (MJ) and one crayon set. Bioaccessible Cd, Ni, or Pb exceeded EU migratable concentration limits in four to six MJ, depending on the protocol. Using two-phase (gastric + intestinal) IVG or PBET might be preferable over EN 71-3 since they better represent gastrointestinal physiology. Bioaccessible and total metal concentrations were different and not always correlated, indicating that bioaccessibility measurement may provide more accurate risk characterization. More information on impacts of multiple factors affecting metals mobilization from toys and jewelry is needed before recommending specific tests. Hazard index (HI) for Cd, Ni, or Pb were >1 for all six MJ exceeding the EU limits. For infants (6-12 mo old), 10 MJ had HI > 1 for Cd, Cu, Ni, or Pb (up to 75 for Cd and 43 for Pb). Research on prolonged exposure to MJ and comprehensive risk characterization for toys and jewelry exposure is recommended. PMID:24345102

  20. Electrostatic assembles and optical properties of Au CdTe QDs and Ag/Au CdTe QDs

    NASA Astrophysics Data System (ADS)

    Yang, Dongzhi; Wang, Wenxing; Chen, Qifan; Huang, Yuping; Xu, Shukun

    2008-09-01

    Au-CdTe and Ag/Au-CdTe assembles were firstly investigated through the static interaction between positively charged cysteamine-stabilized CdTe quantum dots (QDs) and negatively charged Au or core/shell Ag/Au nano-particles (NCs). The CdTe QDs synthesized in aqueous solution were capped with cysteamine which endowed them positive charges on the surface. Both Au and Ag/Au NCs were prepared through reducing precursors with gallic acid obtained from the hydrolysis of natural plant poly-phenols and favored negative charges on the surface of NCs. The fluorescence spectra of CdTe QDs exhibited strong quenching with the increase of added Au or Ag/Au NCs. Railey resonance scattering spectra of Au or Ag/Au NCs increased firstly and decreased latter with the concentration of CdTe QDs, accompanied with the solution color changing from red to purple and colorless at last. Experimental results on the effects of gallic acid, chloroauric acid tetrahydrate and other reagents demonstrated the static interaction occurred between QDs and NCs. This finding reveals the possibilities to design and control optical process and electromagnetic coupling in hybrid structures.

  1. Microstructure analyses and thermoelectric properties of Ag{sub 1-x}Pb{sub 18}Sb{sub 1+y}Te{sub 20}

    SciTech Connect

    Perlt, S.; Hoeche, Th.; Dadda, J.; Mueller, E.; Bauer Pereira, P.; Hermann, R.; Sarahan, M.; Pippel, E.; Brydson, R.

    2012-09-15

    This study reports microstructural investigations of long-term annealed Ag{sub 1-x}Pb{sub m}Sb{sub 1+y}Te{sub 2+m} (m=18, x=y=0, hereinafter referred to as AgPb{sub 18}SbTe{sub 20}) (Lead-Antimony-Silver-Tellurium, LAST-18) as well as of Ag{sub 1-x}Pb{sub 18}Sb{sub 1+y}Te{sub 20}, i.e. Ag-deficient and Sb-excess LAST-18 (x{ne}0,y{ne}0), respectively. Two different length scales are explored. The micrometer scale was evaluated by SEM to analyze the volume fraction and the number of secondary phases as well as the impact of processing parameters on the homogeneity of bulk samples. For AgPb{sub 18}SbTe{sub 20}, site-specific FIB liftout of TEM lamellae from thermoelectrically characterized samples was accomplished to investigate the structure on the nanometer scale. High-resolution TEM and energy-filtered TEM were performed to reveal shape and size distribution of nanoprecipitates, respectively. A hypothesis concerning the structure-property relationship is set out within the frame of a gradient annealing experiment. This study is completed by results dealing with inhomogeneities on the micrometer scale of Ag{sub 1-x}Pb{sub 18}Sb{sub 1+y}Te{sub 20} and its electronic properties. Highlights: Black-Right-Pointing-Pointer SEM and TEM microstructure investigation of long-term annealed AgPb{sub 18}SbTe{sub 20}. Black-Right-Pointing-Pointer SEM and thermoelectric studies on Ag{sub 1-x}Pb{sub 18}Sb{sub 1+y}Te{sub 20}. Black-Right-Pointing-Pointer Discussion concerning structure-property relationship in long-term annealed AgPb{sub 18}SbTe{sub 20}. Black-Right-Pointing-Pointer Correlation between Ag{sub 1-x}Pb{sub 18}Sb{sub 1+y}Te{sub 20} microscale structure and electronic properties.

  2. Geospatial Mapping of Pb, Cr, Cu, Zn, Cd, and Sb in Urban Soil, Cd. Juarez, Chihuahua, Mexico

    NASA Astrophysics Data System (ADS)

    Amaya, M. A.; Grimida, S. E.; Elkekli, A. R.; Aldouri, R. K.; Benedict, B. A.; Pingitore, N. E., Jr.

    2015-12-01

    Population-based random stratified sampling of the city of Cd. Juarez, Chihuahua, Mexico provided 500 city blocks for study. We collected soil from the public space (where present) in front of each house on a selected block; equal measured small volumes of these were combined to produce a composite sample for analysis. Such composite samples (1) decrease, by an order of magnitude, laboratory processing and analysis costs, and (2) smooth the data to represent blocks as averages of individual houses. Retention of the unanalyzed samples of the individual houses permits their later analysis should the composites suggest further study of individual houses on an anomalous block. Elemental analysis of 10 mg pressed powders was performed on a Panalytical Epsilon5 EDS-XRF, via 8 secondary targets and 12 USGS and NIST multi-element rock standards. The mean and (range) of concentration for Pb was 43 (13-550) ppm; for Cr, 31 (1.8-76); for Cu, 22 (6-550); for Zn 84 (42-415) ppm; for Cd, 1.9 (0.1-6.2); and for Sb, 5.9 (2.7-29). The old urban core of Cd. Juarez was marked by high levels of Pb, Cr, Cu, and Zn, and, to a smaller degree, of Cd and Sb. This pattern mirrors that of contiguous El Paso, Texas, USA, directly across the narrow Rio Grande. Businesses, industrial facilities, transportation (both railroads and highways), traditional "downtown" shopping, and old residential districts cluster in this urban core. A Pb-Cu-Zn smelter, which operated for more than a century until 1999, is present in the US adjacent to the Rio Grande, about two km away from downtown Cd. Juarez. Thus the city has been subject to both traditional metal sources (e.g., leaded gasoline, highway debris) and smelter emissions. The poplation of Cd. Juarez has exploded in the last few decades to some 1.5 million inhabitants due both to natural growth and in-migration from rural districts for economic opportunity. Most of this growth has been accommodated by radial expansion of the city into the surrounding

  3. Structural analysis of quaternary Se{sub 85−x}Sb{sub 10}In{sub 5}Ag{sub x} bulk glassy alloys

    SciTech Connect

    Sharma, Rita Sharma, Shaveta; Kumar, Praveen; Chander, Ravi; Thangaraj, R.; Mian, M.

    2015-08-28

    The physical properties of chalcogenide semiconductor have attracted much attention recently due to their applications in optical recording media and inorganic resist due to photo induced structural transformations observed in these materials. The bulk samples of Se{sub 85-x}Sb{sub 10}In{sub 5}Ag{sub x} system are prepared by melt-quenching technique. X-ray diffraction technique and RAMAN spectroscopy have been used to study the role of Ag additive on the amorphous/crystalline nature and molecular structure of Se{sub 85}Sb{sub 10}In{sub 5} glassy alloys. The phases Sb{sub 2}Se{sub 3}, In-Sb and In{sub 2}Se{sub 3} has been observed by X-ray diffraction. The formation of AgInSe{sub 2} phase along with the enhancement in intensity has been observed with the Ag addition.Three bands observed by raman spectroscopy for Se85Sb10In5 are at 70 cm-1, 212cm-1 and 252cm-1. The formation of small bands up to wavenumber 188cm{sup -1} and shifting in second band along with the increase in intensity up to sample x=5 has been observed with the Ag addition. The enhancement in intensity in third band with Ag content has been observed.

  4. Influence of Ag doping concentration on structural and optical properties of CdS thin film

    SciTech Connect

    Kumar, Pragati; Saxena, Nupur; Gupta, Vinay; Agarwal, Avinash

    2015-05-15

    This work shows the influence of Ag concentration on structural properties of pulsed laser deposited nanocrystalline CdS thin film. X-ray photoelectron spectroscopy (XPS) studies confirm the dopant concentration in CdS films and atomic concentration of elements. XPS studies show that the samples are slightly sulfur deficient. GAXRD scan reveals the structural phase transformation from cubic to hexagonal phase of CdS without appearance of any phase of CdO, Ag{sub 2}O or Ag{sub 2}S suggesting the substitutional doping of Ag ions. Photoluminescence studies illustrate that emission intensity increases with increase in dopant concentration upto 5% and then decreases for higher dopant concentration.

  5. Loading Ag nanoparticles on Cd(II) boron imidazolate framework for photocatalysis

    NASA Astrophysics Data System (ADS)

    Liu, Min; Zhang, De-Xiang; Chen, Shumei; Wen, Tian

    2016-05-01

    An amine-functionalized Cd(II) boron imidazolate framework (BIF-77) with three-dimensional open structure has been successfully synthesized, which can load Ag nanoparticles (NPs) for photocatalytic degradation of methylene blue (MB).

  6. Polar Noncentrosymmetric ZnMoSb2O7 and Nonpolar Centrosymmetric CdMoSb4O10: d(10) Transition Metal Size Effect Influencing the Stoichiometry and the Centricity.

    PubMed

    Jo, Hongil; Ok, Kang Min

    2016-06-20

    Two new quaternary molybdenum(VI) antimony(III) oxides, ZnMoSb2O7 and CdMoSb4O10, have been synthesized in phase-pure form. The title compounds consist of highly polarizable cations, i.e., d(0) (Mo(6+)) and d(10) (Zn(2+) or Cd(2+)), and lone-pair cations (Sb(3+)). ZnMoSb2O7 exhibits a three-dimensional framework with ZnO4, MoO4, and SbO4 polyhedra in the polar space group P21, whereas CdMoSb4O10 exhibits one-dimensional tubule structures with CdO6, MoO4, and SbO3 polyhedra in the space group P21/m. Several synthetic efforts suggest that the the dissimilar radii of Zn(2+) and Cd(2+) that can accommodate polyhedra of Sb(3+) cations influence the stoichiometry as well as the centricity for the reported materials. Spectroscopic, thermal, and elemental analyses are reported along with dipole moment calculations. Nonlinear optical properties and their structural origin are examined for polar ZnMoSb2O7 as well. PMID:27228083

  7. A new silver ion conducting SbI3-Ag4P2O7 nanocomposite solid electrolyte

    NASA Astrophysics Data System (ADS)

    Suthanthiraraj, S. Austin; Sarumathi, R.

    2013-12-01

    This paper presents an investigation on a new series of silver ion conducting nanocomposite materials of silver pyrophosphate-based solid electrolytes with various amounts of antimony iodide. The detailed electrical conductivity studies carried out by impedance spectroscopic analysis in the frequency range from 20 Hz to 1 MHz have shown that silver ionic conductivity attains a maximum value of 4.1 × 10-4 S cm-1 at room temperature for the typical composition having 60 mol% of SbI3. Powder samples characterized by X-ray diffraction, Fourier transform infrared spectroscopy, differential scanning calorimetric analysis and silver ionic transport studies were identified to indicate the existence of AgI, in addition to certain new phases in all the different compositions of the system. The conduction channel for Ag+ ions across phosphate network was found to get expanded by the presence of iodide ion. The formation of P-O-M (M=Sb3+) within the crystal structure is also favoured, where Sb3+ ions may serve as ionic cross-links between non-bridging oxygen of different phosphate groups. The field emission scanning electron microscopic investigations of their microstructures have suggested the presence of nanocomposites, leading to the observed electrical conductivity data coupled with many interesting features closely related to the particle size and practical application as solid electrolyte for the fabrication of solid-state battery at ambient conditions.

  8. Viscoelastic behavior over a wide range of time and frequency in tin alloys: SnCd and SnSb

    SciTech Connect

    Quackenbush, J.; Brodt, M.; Lakes, R.S.

    1996-08-01

    All materials exhibit some viscoelastic response, which can manifest itself as creep, relaxation, or, if the load is sinusoidal in time, a phase angle {delta} between stress and strain. Recently, a study of pure elements with low melting points, Cd, In, Pb, and Sn disclosed that cadmium exhibited a substantial loss tangent of 0.03 to 0.04 over much of the audio range of frequencies, combined with a moderate stiffness G = 20.7 GPa. Lead, by contrast, exhibited tan {delta} of 0.005 to 0.016 in the audio range. Indium exhibited a high loss tangent exceeding 0.1 at very low frequency. A eutectic alloy of indium and tin was found to exhibit substantial damping exceeding 0.1 below 0.1 Hz, and this alloy was used to make a composite exhibiting high stiffness and high damping. It is the purpose of this communication to present viscoelastic properties of two additional low melting point alloys, SnCd and SnSb. Both InSn and SnSb are used as solders. Although the melting point of Sb is 630.74 C, T{sub H} > 0.55 at ambient temperature for the alloy of SnSb (95 wt% Sn/5 wt% Sb) which melts near 240 C. Eutectic SnCd melts at 177 C so T{sub H} {approx} 0.65 at room temperature.

  9. Structure of CdTe-Cd1 - xMnxTe multiple quantum wells grown on (001) InSb substrates by molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Williams, G. M.; Cullis, A. G.; Whitehouse, C. R.; Ashenford, D. E.; Lunn, B.

    1989-09-01

    Molecular beam epitaxy has been used to prepare multiple quantum well structures of CdTe/Cd1-xMnxTe on (001) InSb substrates. The growth of such a system on InSb allows the use of particularly low growth temperatures, hence minimizing interdiffusion effects. This study presents the first transmission electron microscope investigation of this multilayer system grown on InSb. The work clearly demonstrates that multiple quantum wells of high structural quality can be grown reproducibly over a wide range of layer thicknesses. The importance of efficient substrate surface cleaning prior to growth is demonstrated. In order to grow high structural quality multilayers, the choice of buffer layer is also important and a possible explanation for this observation is given.

  10. Growth, steady-state, and time-resolved photoluminescence study of CdTe/MgCdTe double heterostructures on InSb substrates using molecular beam epitaxy

    SciTech Connect

    DiNezza, Michael J.; Liu, Shi; Kirk, Alexander P.; Zhang, Yong-Hang; Zhao, Xin-Hao

    2013-11-04

    CdTe/MgCdTe double heterostructures (DHs) are grown on InSb substrates using molecular beam epitaxy and reveal strong photoluminescence with over double the intensity of a GaAs/AlGaAs DH with an identical layer structure design grown on GaAs. Time-resolved photoluminescence of the CdTe/MgCdTe DH gives a Shockley-Read-Hall recombination lifetime of 86 ns, which is more than one order of magnitude longer than that of typical polycrystalline CdTe films. These findings indicate that monocrystalline CdTe/MgCdTe DHs effectively reduce surface recombination, have limited nonradiative interface recombination, and are promising for solar cells that could reach power conversion efficiencies similar to that of GaAs.

  11. Ambient CdCl{sub 2} treatment on CdS buffer layer for improved performance of Sb{sub 2}Se{sub 3} thin film photovoltaics

    SciTech Connect

    Wang, Liang; Luo, Miao; Qin, Sikai; Liu, Xinsheng; Chen, Jie; Yang, Bo; Leng, Meiying; Xue, Ding-Jiang; Zhou, Ying; Gao, Liang; Song, Haisheng; Tang, Jiang

    2015-10-05

    Antimony selenide (Sb{sub 2}Se{sub 3}) is appealing as a promising light absorber because of its intrinsically benign grain boundaries, suitable band gap (∼1.1 eV), strong absorption coefficient, and relatively environmentally friendly constituents. Recently, we achieved a certified 5.6% efficiency Sb{sub 2}Se{sub 3} thin film solar cell with the assistance of ambient CdCl{sub 2} treatment on the CdS buffer layer. Here, we focused on investigating the underlying mechanism from a combined materials and device physics perspective applying current density-voltage (J-V) fitting analysis, atomic force microscope, X-ray photoelectron spectroscopy, fluorescence, and UV–Vis transmission spectroscopy. Our results indicated that ambient CdCl{sub 2} treatment on CdS film not only improved CdS grain size and quality, but also incorporated Cl and more O into the film, both of which can significantly improve the heterojunction quality and device performance of CdS/Sb{sub 2}Se{sub 3} solar cells.

  12. Accumulation of Sb, Pb, Cu, Zn and Cd by various plants species on two different relocated military shooting range soils.

    PubMed

    Evangelou, Michael W H; Hockmann, Kerstin; Pokharel, Rasesh; Jakob, Alfred; Schulin, Rainer

    2012-10-15

    Annually, more than 400 t Pb and 10 t Sb enter Swiss soils at some 2000 military shooting ranges. After the decommission of military shooting ranges, heavily contaminated soils (>2000 mg kg(-1) Pb) are landfilled or processed by soil washing, whereas for soils with less contamination, alternate strategies are sought. Although the use of military shooting ranges for grazing in Switzerland is common practice, no assessment has been done about the uptake of Sb in plants and its subsequent potential intake by grazing animals. We determined the uptake of Sb, Pb, Cu, Zn and Cd in the aboveground biomass of nine plant species growing on a calcareous (Chur) and a weakly acidic (Losone) military shooting range soil in order to assess if grazing would be safe to employ on decommissioned military shooting ranges. The two soils did not differ in their total concentrations of Cu, Zn, Sb and Cd, they differed however in the total concentration of Pb. Additionally, their physical and chemical properties were significantly different. The accumulation of Zn, Cu, Cd and Pb in the shoots of all nine plant species remained below the Swiss tolerance values for fodder plants (150 mg kg(-1) Zn, 15-35 mg kg(-1) Cu, 40 mg kg(-1) Pb, and 1 mg kg(-1) Cd DW), with the only exception of Pb in Chenopodium album shoots which reached a concentration of 62 mg kg(-1) DW. Antimony concentrations were 1.5-2.6-fold higher in plants growing on the calcareous soil than on the weakly acidic soil. Considering Cu, Zn, Pb, Sb and Cd, all plants, with the exception C. album, would be suitable for grazing on similar shooting range soils. PMID:22659605

  13. Structure and Thermoelectric Properties of Te-Ag-Ge-Sb (TAGS) Materials Obtained by Reduction of Melted Oxide Substrates

    NASA Astrophysics Data System (ADS)

    Kusz, B.; Miruszewski, T.; Bochentyn, B.; Łapiński, M.; Karczewski, J.

    2016-02-01

    Ge0.77Ag0.1Sb0.13Te1 alloy was fabricated by a novel two-step route. Firstly, oxide reagents were melted at high temperature and quenched into pellets. The pellets were milled to powder and then reduced in hydrogen at various temperatures for various periods of time. Energy-dispersive x-ray analysis indicated the possibility of successful fabrication of stoichiometric thermoelectric materials from the Te-Ag-Ge-Sb system. The electrical conductivity and Seebeck coefficient have been determined over the temperature range from 20°C to 340°C in argon atmosphere. It was also shown that, for most of the fabricated samples, the crystallite size as well as electrical parameters such as the electrical conductivity, Seebeck coefficient, and figure of merit ( ZT) increased with increasing reduction time. The highest value of ZT (˜1.0 at 340°C) was obtained for samples reduced in hydrogen atmosphere at 400°C for 20 h and 40 h.

  14. Anomalous temperature-dependent Young's modulus of a cast LAST (Pb-Sb-Ag-Te) thermoelectric material

    SciTech Connect

    Ren, Fei; Case, Eldon D; Timm, Edward J; Lara-Curzio, Edgar; Trejo, Rosa M

    2010-01-01

    Thermomechanical characterization is important to material evaluation and device design in the development of thermoelectric technology. In this study, we utilize the resonant ultrasound spectroscopy (RUS) technique to examine the elastic behavior of a cast LAST (Pb Sb Ag Te) material with a composition of Ag0.86Pb19Sb1.0Te20 between room temperature and 823 K. The temperature-dependent Young s modulus exhibits a monotonically decreasing trend with increasing temperature. However, an abnormal slope change in the Young s modulus temperature curve around 500 K is observed. In addition, hysteresis between heating and cooling data in the temperature range of 450 550 K is observed, which appears to be dependent on the heating/cooling rate during the RUS experiments such that the hysteresis disappears when the heating/cooling rate was decreased from 5 to 2 K min 1. In this study we propose an order disorder transition model for the anomalous temperature-dependent Young s modulus behavior observed in this study.

  15. Self-regulated route to ternary hybrid nanocrystals of Ag-Ag2S-CdS with near-infrared photoluminescence and enhanced photothermal conversion

    NASA Astrophysics Data System (ADS)

    Zhu, Guoxing; Bao, Chunlin; Liu, Yuanjun; Shen, Xiaoping; Xi, Chunyan; Xu, Zheng; Ji, Zhenyuan

    2014-09-01

    Developing hybrid nanocrystals is a hot topic in materials science. Herein, a ternary hybrid nanocrystal, Ag-Ag2S-CdS, combining near infrared emission and photothermal conversion properties was demonstrated. The ternary Ag-Ag2S-CdS hybrid nanocrystals with cubic shape and uniform size were synthesized by a simple one-pot and one-step colloidal method. The growth process is self-regulated with the formation order of Ag2S, Ag, and CdS, sequentially. The formation of Ag originates from the partial reduction of Ag2S, while the formation of CdS is through an Ag2S catalytic mechanism based on its superionic feature. The obtained ternary hybrid nanocrystals show near infrared emission and photothermal conversion properties in a lab-on-a-particle system. Importantly, an enhanced effect is observed for the photothermal conversion, which is mainly due to the presence of heterointerfaces among the crystals. This work will not only advance the synthesis chemistry of multi-component hybrid nanocrystals but also provide a possible route for the design of advanced multi-model materials used in bio-related fields.Developing hybrid nanocrystals is a hot topic in materials science. Herein, a ternary hybrid nanocrystal, Ag-Ag2S-CdS, combining near infrared emission and photothermal conversion properties was demonstrated. The ternary Ag-Ag2S-CdS hybrid nanocrystals with cubic shape and uniform size were synthesized by a simple one-pot and one-step colloidal method. The growth process is self-regulated with the formation order of Ag2S, Ag, and CdS, sequentially. The formation of Ag originates from the partial reduction of Ag2S, while the formation of CdS is through an Ag2S catalytic mechanism based on its superionic feature. The obtained ternary hybrid nanocrystals show near infrared emission and photothermal conversion properties in a lab-on-a-particle system. Importantly, an enhanced effect is observed for the photothermal conversion, which is mainly due to the presence of

  16. Reducing Lattice Thermal Conductivity of the Thermoelectric Compound AgSbTe2 (P4/mmm) by Lanthanum Substitution: Computational and Experimental Approaches

    NASA Astrophysics Data System (ADS)

    Amouyal, Yaron

    2014-10-01

    In this study we performed lattice dynamics first-principles calculations for the promising thermoelectric (TE) compound AgSbTe2, and estimated the stability of its three polymorphs over a wide temperature range from 0 to 600 K. We calculated the vibrational density of states of the AgSbTe2 (P4/mmm) phase. The results suggested that formation of substitutional defects at Ag-sublattice sites impedes lattice vibrations, thereby reducing lattice thermal conductivity. We focused on calculations based on the Debye approximation for the compound La0.125Ag0.875SbTe2, and predicted reduction of the average sound velocity from 1684 to 1563 m s-1 as a result of La doping. This is manifested as a ca. 14% reduction in thermal conductivity. To confirm the results from computation we produced two Ag-Sb-Te-based alloys, a ternary alloy without La addition and a quaternary alloy containing La. We measured the thermal conductivity of both alloys by use of the laser flash analysis method, and, as a result of La alloying, observed a reduction in thermal conductivity from 0.92 to 0.71 W m-1 K-1 at 573 K, as calculated from first principles.

  17. Cluster Chemistry in Electron-Poor Ae-Pt-Cd Systems (Ae=Ca, Sr, Ba): (Sr,Ba)Pt2Cd4, Ca6Pt8Cd16, and Its Known Antitype Er6Pd16Sb8

    SciTech Connect

    Samal, Saroj L.; Gulo, Fakhili; Corbett, John D.

    2013-02-18

    Three new ternary polar intermetallic compounds, cubic Ca6Pt8Cd16, and tetragonal (Sr, Ba)Pt2Cd4 have been discovered during explorations of the Ae–Pt–Cd systems. Cubic Ca6Pt8Cd16 (Fm-3m, Z = 4, a = 13.513(1) Å) contains a 3D array of separate Cd8 tetrahedral stars (TS) that are both face capped along the axes and diagonally bridged by Pt atoms to generate the 3D anionic network Cd8[Pt(1)]6/2[Pt(2)]4/8. The complementary cationic surface of the cell consists of a face-centered cube of Pt(3)@Ca6 octahedra. This structure is an ordered ternary variant of Sc11Ir4 (Sc6Ir8Sc16), a stuffed version of the close relative Na6Au7Cd16, and a network inverse of the recent Er6Sb8Pd16 (compare Ca6Pt8Cd16). The three groups of elements each occur in only one structural version. The new AePt2Cd4, Ae = Sr, Ba, are tetragonal (P42/mnm,Z = 2, a ≈ 8.30 Å, c ≈ 4.47 Å) and contain chains of edge-sharing Cd4 tetrahedra along c that are bridged by four-bonded Ba/Sr. LMTO-ASA and ICOHP calculation results and comparisons show that the major bonding (Hamilton) populations in Ca6Pt8Cd16 and Er6Sb8Pd16 come from polar Pt–Cd and Pd–Sb interactions, that Pt exhibits larger relativistic contributions than Pd, that characteristic size and orbital differences are most evident for Sb 5s, Pt8, and Pd16, and that some terms remain incomparable, Ca–Cd versus Er–Pd.

  18. Ag adsorption on Cd-terminated CdS (0 0 0 1) and S-terminated CdS (0 0 0 1-bar) surfaces: First-principles investigations

    SciTech Connect

    Ma, Yandong; Dai, Ying; Wei, Wei; Liu, Xianghong; Huang, Baibiao

    2011-04-15

    First-principles calculations are performed to study the adsorption of Ag at Cd-terminated CdS (0 0 0 1) and S-terminated CdS (0 0 0 1-bar) surfaces as a function of Ag coverage. Our results reveal that Ag adsorption at Cd-terminated (0 0 0 1) has a large binging energy than at S-terminated (0 0 0 1-bar) surface. For Ag adsorption at Cd-terminated (0 0 0 1) surface, T4 structure is more favorable and the Ag-Cd bond posses an ionic-like character. While for Ag adsorption at S-terminated (0 0 0 1-bar) surface, the H3 structure is most stable and the bonding between Ag-S is covalent. It is found that the magnitude and the sign of surface dipole moment are partly determined by the difference between the electronegativities of Ag and the host atom bonding with Ag. The adsorption energy changes as a function of Ag coverage. In addition, related properties of Ag cluster adsorption at Cd-terminated (0 0 0 1) surface are also discussed. -- Graphical abstract: We studied the adsorption of Ag at Cd-terminated CdS (0 0 0 1) and S-terminated CdS (0 0 0 1-bar) surfaces as a function of Ag coverage by means of the first-principles calculations. In addition, related properties of Ag cluster adsorption at Cd-terminated (0 0 0 1) surface are also discussed. Our ab initio calculations are useful complement to the intense experimental studies for Ag-CdS interface. Display Omitted Research highlights: {yields} Ag adsorption effects on electronic structure and associated physics properties of CdS is systemically studied. {yields} The surface dipole moment is partly determined by the difference between the electronegativities of silver and the host atom bonding with silver. {yields} The characteristic of Ag cluster (Ag{sub 2}, Ag{sub 4}, and Ag{sub 7}) adsorption on the CdS (0 0 0 1) surface is discussed.

  19. Enhanced visible light photocatalytic performance of ZnO nanowires integrated with CdS and Ag2S.

    PubMed

    Chen, Chienhua; Li, Zhengcao; Lin, Hehnan; Wang, Guojing; Liao, Jiecui; Li, Mingyang; Lv, Shasha; Li, Wei

    2016-02-18

    A series of ZnO-CdS-Ag2S ternary nanostructures with different amounts of Ag2S were prepared using simple and low-cost successive ionic layer adsorption and reaction (SILAR) and a chemical precipitation method. The ZnO nanowires, with a diameter of ∼100 nm and a length of ∼1 μm, were modified by coating CdS and Ag2S. CdS has a high absorption coefficient and can efficiently match with the energy levels of ZnO, which can enhance the light absorption ability of the nanostructures. In addition, Ag2S with a narrow band gap was used as the main light absorber and played an important role in increasing the light absorption in the visible light region. The photocatalytic activity of the ZnO-CdS-Ag2S ternary nanostructures was investigated using the degradation of methyl orange (MO) in an aqueous solution under visible light. The ZnO-CdS-Ag2S ternary nanostructures were found to be more efficient than ZnO nanowires, ZnO-CdS nanowires, and ZnO-Ag2S nanowires. There is 7.68 times more photocatalytic activity for MO degradation in terms of the rate constant for ZnO-CdS-Ag2S 15-cycle ternary nanostructure compared to the as-grown ZnO. Furthermore, the effect of the amount of Ag2S and CdS on the ZnO surface on the photocatalytic activity was analyzed. The superior photo-absorption properties and photocatalytic performance of the ZnO-CdS-Ag2S ternary nanostructures can be ascribed to the heterostructure, which enhanced the separation of the photo-induced electron-hole pairs. In addition, visible light could be absorbed by ZnO-CdS-Ag2S ternary nanostructures rather than by ZnO. PMID:26815888

  20. Understanding nanostructures in thermoelectric materials: an electron microscopy study of AgPb{sub 18}SbSe{sub 20} crystals.

    SciTech Connect

    Lioutas, C. B.; Frangis, N.; Todorov, I.; Chung, D. Y.; Kanatzidis, M. G.; Materials Science Division; Aristotle Univ. Thessaloniki; Northwestern Univ.

    2010-01-01

    The characterization and understanding of the presence of nanostructuring in bulk thermoelectric materials requires real space atomic level information. We report electron diffraction and high-resolution transmission electron microscopy studies of crystals of the system AgPb{sub 18}SbSe{sub 20} (=18PbSe + AgSbSe{sub 2}) which reveal that this system is nanostructured rather than a solid solution. Nanocrystals of varying sizes are found, endotaxially grown in the matrix of PbSe (phase A), and consist of two phases, a cubic one (phase B) and a tetragonal one (phase C). Well-defined coherent interfaces between the phases in the same nanocrystals are observed. On the basis of the results of combined electron crystallography techniques, we propose reasonable structural models for the phases B and C. There are significant differences in the nanostructuring chemistry between AgPb{sub 18}SbSe{sub 20} and the telluride analog AgPb{sub 18}SbTe{sub 20} (LAST-18).

  1. Effect of Zn and Sb Additions on the Impression Creep Behavior of Lead-Free Sn-3.5Ag Solder Alloy

    NASA Astrophysics Data System (ADS)

    Pourmajidian, M.; Mahmudi, R.; Geranmayeh, A. R.; Hashemizadeh, S.; Gorgannejad, S.

    2016-01-01

    The effect of separate additions of 1.5 wt.% Zn and 1.5 wt.% Sb on the creep behavior of Sn-3.5 wt.% Ag lead-free solder alloy was investigated by impression testing. The tests were carried out under constant punching stresses in the range of 60-120 MPa and at temperatures in the range of 298-370 K. Both of the ternary alloys showed creep resistances higher than that of the eutectic binary Sn-3.5Ag alloy. The superior creep resistance of the ternary Sn-3.5Ag-1.5Sb alloy is attributed to the strong solid solutioning effect of antimony in the tin matrix, while the formation of AgZn particles and refinement of the Ag3Sn precipitates account for the higher creep resistance of the Sn-3.5Ag-1.5Zn alloy. The average stress exponents of 8.2, 8.5, and 8.6 and activation energies of 47.4 kJ mol-1, 45.3 kJ mol-1, , and 43.3 kJ mol-1 were obtained for Sn-3.5Ag, Sn-3.5Ag-1.5Zn, and Sn-3.5Ag-1.5Sb, respectively. These activation energies are close to 46 kJ mol-1 for dislocation pipe diffusion of tin. This, together with the stress exponents of 8.2-8.6, suggests that dislocation climb controlled by dislocation pipe diffusion is the predominant creep mechanism in these alloys.

  2. Nanoscale nuclei in phase change materials: Origin of different crystallization mechanisms of Ge{sub 2}Sb{sub 2}Te{sub 5} and AgInSbTe

    SciTech Connect

    Lee, Bong-Sub Bogle, Stephanie N.; Darmawikarta, Kristof; Abelson, John R.; Shelby, Robert M.; Retter, Charles T.; Burr, Geoffrey W.; Raoux, Simone

    2014-02-14

    Phase change memory devices are based on the rapid and reversible amorphous-to-crystalline transformations of phase change materials, such as Ge{sub 2}Sb{sub 2}Te{sub 5} and AgInSbTe. Since the maximum switching speed of these devices is typically limited by crystallization speed, understanding the crystallization process is of crucial importance. While Ge{sub 2}Sb{sub 2}Te{sub 5} and AgInSbTe show very different crystallization mechanisms from their melt-quenched states, the nanostructural origin of this difference has not been clearly demonstrated. Here, we show that an amorphous state includes different sizes and number of nanoscale nuclei, after thermal treatment such as melt-quenching or furnace annealing is performed. We employ fluctuation transmission electron microscopy to detect nanoscale nuclei embedded in amorphous materials, and use a pump-probe laser technique and atomic force microscopy to study the kinetics of nucleation and growth. We confirm that melt-quenched amorphous Ge{sub 2}Sb{sub 2}Te{sub 5} includes considerably larger and more quenched-in nuclei than its as-deposited state, while melt-quenched AgInSbTe does not, and explain this contrast by the different ratio between quenching time and nucleation time in these materials. In addition to providing insights to the crystallization process in these technologically important devices, this study presents experimental illustrations of temperature-dependence of nucleation rate and growth speed, which was predicted by theory of phase transformation but rarely demonstrated.

  3. Ag2S/CdS/TiO2 Nanotube Array Films with High Photocurrent Density by Spotting Sample Method.

    PubMed

    Sun, Hong; Zhao, Peini; Zhang, Fanjun; Liu, Yuliang; Hao, Jingcheng

    2015-12-01

    Ag2S/CdS/TiO2 hybrid nanotube array films (Ag2S/CdS/TNTs) were prepared by selectively depositing a narrow-gap semiconductor-Ag2S (0.9 eV) quantum dots (QDs)-in the local domain of the CdS/TiO2 nanotube array films by spotting sample method (SSM). The improvement of sunlight absorption ability and photocurrent density of titanium dioxide (TiO2) nanotube array films (TNTs) which were obtained by anodic oxidation method was realized because of modifying semiconductor QDs. The CdS/TNTs, Ag2S/TNTs, and Ag2S/CdS/TNTs fabricated by uniformly depositing the QDs into the TNTs via the successive ionic layer adsorption and reaction (SILAR) method were synthesized, respectively. The X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS) results demonstrated that the Ag2S/CdS/TNTs prepared by SSM and other films were successfully prepared. In comparison with the four films of TNTs, CdS/TNTs, Ag2S/TNTs, and Ag2S/CdS/TNTs by SILAR, the Ag2S/CdS/TNTs prepared by SSM showed much better absorption capability and the highest photocurrent density in UV-vis range (320~800 nm). The cycles of local deposition have great influence on their photoelectric properties. The photocurrent density of Ag2S/CdS/TNTs by SSM with optimum deposition cycles of 6 was about 37 times that of TNTs without modification, demonstrating their great prospective applications in solar energy utilization fields. PMID:26428017

  4. CD226 as a genetic adjuvant to enhance immune efficacy induced by Ag85A DNA vaccination.

    PubMed

    Li, Yan; Yang, Fangli; Zhu, Junfeng; Sang, Lixuan; Han, Xue; Wang, Danan; Shan, Fengping; Li, Shengjun; Sun, Xun; Lu, Changlong

    2015-03-01

    Antigen-85A (Ag85A) is one of the major proteins secreted by Mycobacterium tuberculosis. Many studies on animal models have shown that vaccination with the recombinant Ag85A-DNA or Ag85A protein induces powerful immune response. However, these vaccines cannot generate sufficient protective immunity in the systemic compartment. CD226, a member of the immunoglobulin superfamily, is expressed in the majority of NK cells, T cells, monocytes, and platelets, and can be served as a co-stimulator that contributes to multiple innate and adaptive responses. However, there has been no study where either CD226 protein or DNA has been used as an adjuvant for vaccine development. The aim of this study was to develop a novel Ag85A DNA vaccine with CD226 as the genetic adjuvant to increase the immune efficacy induced by Ag85A. Oral vaccination with pcDNA3.1-Ag85A-CD226 DNA induced potent immune responses in mice. CD226 was an effective genetic adjuvant that improved the immune efficacy induced by Ag85A and enhanced the activity of cytotoxic T lymphocytes (CTL) and NK cells in mice. Th1 dominant cytokines (i.e. IL-2, IFN-γ and TNF-α), cellular immunity (i.e. CD4(+)IFN-γ(+)T cells and CD8(+)IFN-γ(+)T cells in splenocytes) and MLNs were also significantly elevated by pcDNA3.1-Ag85A-CD226 DNA vaccination. Our results suggest that CD226 is an effective adjuvant to enhance the immune efficacy induced by Ag85A. Our findings provide a new strategy for the development of a DNA vaccine co-expressing Ag85A and CD226. PMID:25582686

  5. Ag2S/CdS/TiO2 Nanotube Array Films with High Photocurrent Density by Spotting Sample Method

    NASA Astrophysics Data System (ADS)

    Sun, Hong; Zhao, Peini; Zhang, Fanjun; Liu, Yuliang; Hao, Jingcheng

    2015-10-01

    Ag2S/CdS/TiO2 hybrid nanotube array films (Ag2S/CdS/TNTs) were prepared by selectively depositing a narrow-gap semiconductor—Ag2S (0.9 eV) quantum dots (QDs)—in the local domain of the CdS/TiO2 nanotube array films by spotting sample method (SSM). The improvement of sunlight absorption ability and photocurrent density of titanium dioxide (TiO2) nanotube array films (TNTs) which were obtained by anodic oxidation method was realized because of modifying semiconductor QDs. The CdS/TNTs, Ag2S/TNTs, and Ag2S/CdS/TNTs fabricated by uniformly depositing the QDs into the TNTs via the successive ionic layer adsorption and reaction (SILAR) method were synthesized, respectively. The X-ray powder diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectrum (XPS) results demonstrated that the Ag2S/CdS/TNTs prepared by SSM and other films were successfully prepared. In comparison with the four films of TNTs, CdS/TNTs, Ag2S/TNTs, and Ag2S/CdS/TNTs by SILAR, the Ag2S/CdS/TNTs prepared by SSM showed much better absorption capability and the highest photocurrent density in UV-vis range (320~800 nm). The cycles of local deposition have great influence on their photoelectric properties. The photocurrent density of Ag2S/CdS/TNTs by SSM with optimum deposition cycles of 6 was about 37 times that of TNTs without modification, demonstrating their great prospective applications in solar energy utilization fields.

  6. Development of aluminum (Al5083)-clad ternary Ag In Cd alloy for JSNS decoupled moderator

    NASA Astrophysics Data System (ADS)

    Teshigawara, M.; Harada, M.; Saito, S.; Oikawa, K.; Maekawa, F.; Futakawa, M.; Kikuchi, K.; Kato, T.; Ikeda, Y.; Naoe, T.; Koyama, T.; Ooi, T.; Zherebtsov, S.; Kawai, M.; Kurishita, H.; Konashi, K.

    2006-09-01

    To develop Ag (silver)-In (indium)-Cd (cadmium) alloy decoupler, a method is needed to bond the decoupler between Al alloy (Al5083) and the ternary Ag-In-Cd alloy. We found that a better HIP condition was temperature, pressure and holding time at 803 K, 100 MPa and 10 min. for small test pieces ( ϕ22 mm in dia. × 6 mm in height). Hardened layer due to the formation of AlAg 2 was found in the bonding layer, however, the rupture strength of the bonding layer is more than 30 MPa, the calculated design stress. Bonding tests of a large size piece (200 × 200 × 30 mm 3), which simulated the real scale, were also performed according to the results of small size tests. The result also gave good bonding and enough required-mechanical-strength.

  7. High frequency of circulating HBcAg-specific CD8 T cells in hepatitis B infection: a flow cytometric analysis

    PubMed Central

    Matsumura, S; Yamamoto, K; Shimada, N; Okano, N; Okamoto, R; Suzuki, T; Hakoda, T; Mizuno, M; Higashi, T; Tsuji, T

    2001-01-01

    Viral antigen-specific T cells are important for virus elimination. We studied the hepatitis B virus (HBV)-specific T cell response using flow cytometry. Three phases of HBV infection were studied: Group A, HBeAg (+) chronic hepatitis; Group B, HBeAb (+) HBV carrier after seroconversion; and Group C, HBsAb (+) phase. Peripheral T cells were incubated with recombinant HB core antigen (HBcAg), and intracytoplasmic cytokines were analysed by flow cytometry. HBcAg-specific CD4 and CD8 T cells were identified in all three groups and the number of IFN-γpositive T cells was greater than TNF-α-positive T cells. The frequency of IFN-γ-positive CD4 and CD8 T cells was highest in Group C, compared with Groups A and B. No significant difference in the HBcAg-specific T cell response was observed between Group A and Group B. The HBcAg-specific CD8 T cell response was diminished by CD4 depletion, addition of antibody against human leucocyte antigen (HLA) class I, class II or CD40L. Cytokine-positive CD8 T cells without HBcAg stimulation were present at a high frequency (7 of 13 cases) in Group B, but were rare in other groups. HBcAg-specific T cells can be detected at high frequency by a sensitive flow cytometric analysis, and these cells are important for controlling HBV replication. PMID:11472405

  8. Forming-free, bi-directional polarity conductive-bridge memory devices with Ge2Sb2Te5 solid-state electrolyte and Ag active electrode

    NASA Astrophysics Data System (ADS)

    Huang, Yin-Hsien; Chen, Hsuan-An; Wu, Hsin-Han; Hsieh, Tsung-Eong

    2015-01-01

    Preparation and characteristics of conductive-bridge random access memory devices containing Ge2Sb2Te5 (GST) chalcogenide as the solid-state electrolyte, Ag as the active electrode, and W-Ti as the counter electrode are presented. As revealed by the electrical measurement, only the samples containing crystalline GST exhibited the resistive switching behaviors. With an insertion of ZnS-SiO2 dielectric layer at the Ag/GST interface and a postannealing at 100 °C for 1 min, the sample exhibited the best electrical performance with satisfactory cycleability and retention properties. Moreover, the forming-free and bi-directional polarity features were observed in such a sample type. Microstructure and composition analyses found the finely dispersed nano-scale Ag clusters in GST and, when electrical bias is applied, the migrating Ag ions may build up the connections in between neighboring Ag clusters. Moreover, grain boundaries in polycrystalline GST might be the main paths for Ag migration. The thread-like conduction channels in GST hence form, leading to the low resistance state of sample. On the contrary, the depletion of Ag in GST broke the connections in between Ag clusters when the electrical bias is reversed. This led to the rupture of conduction channels and, hence, the high resistance state of sample. The low operational voltage, forming-free, and bi-directional polarity features observed in (AZGW)T sample might also originated from the fine dispersion of Ag clusters in GST electrolyte.

  9. Preparation, characterization, and bacteriostasis of AgNP-coated β-CD grafting cellulose beads.

    PubMed

    Wang, Ting; Li, Bin; Lin, Li

    2013-03-01

    A novel functional material of β-cyclodextrin (β-CD) grafting cellulose beads containing immobilized silver nanoparticles (AgNPs) is presented in this paper. The morphology was characterized by scanning electron microscopy, energy-dispersive X-ray, and X-ray photoelectron spectroscopy. Phenolphthalein probe molecule technique was used to detect the activity of the grafting β-CD, and the results demonstrated that the deposition of AgNPs had no influence on its encapsulation ability. Acid resistance of the AgNPs on the bead material was studied by atomic absorption spectrometry. The stability of the AgNPs was enhanced due to the grafting of β-CD. Tube dilution method was applied to study the bacteriostatic effect, and the minimal inhibitory doses of the novel material against Escherichia coli and Staphylococcus aureus were 12.5 and 25 mg, respectively. The minimal bactericidal doses for the two bacteria were 25 and 25 mg, respectively. PMID:23340866

  10. Towards defect-free epitaxial CdTe and MgCdTe layers grown on InSb (001) substrates

    NASA Astrophysics Data System (ADS)

    Lu, Jing; DiNezza, Michael J.; Zhao, Xin-Hao; Liu, Shi; Zhang, Yong-Hang; Kovacs, Andras; Dunin-Borkowski, Rafal E.; Smith, David J.

    2016-04-01

    A series of three CdTe/MgxCd1-xTe (x~0.24) double heterostructures grown by molecular beam epitaxy on InSb (001) substrates at temperatures in the range of 235-295 °C have been studied using conventional and advanced electron microscopy techniques. Defect analysis based on bright-field electron micrographs indicates that the structure grown at 265 °C has the best structural quality of the series, while structures grown at 30 °C lower or higher temperature show highly defective morphology. Geometric phase analysis of the CdTe/InSb interface for the sample grown at 265 °C reveals minimal interfacial elastic strain, and there is no visible evidence of interfacial defect formation in aberration-corrected electron micrographs of this particular sample. Such high quality CdTe epitaxial layers should provide the basis for applications such as photo-detectors and multi-junction solar cells.

  11. The relationship between electrical and structural characteristics of CdTe and CdMnTe layers grown on InSb

    NASA Astrophysics Data System (ADS)

    Ashenford, D.; Hogg, J. H. C.; Lunn, B.; Scott, C. G.

    1991-06-01

    CdTe and CdMnTe layers with thickness in the range 1-2 μm have been grown by MBE on (001) InSb substrates. Measurements of the free-carrier concentration as a function of depth through these layers have revealed non-unformities attributed to the presence of extended defects arising from the relief of lattice strain resulting from the epilayer-substrate lattice mismatch. Evidence for the existence of such structural non-uniformity has been provided by DCXRD rocking curve measurements. Detailed analysis of these curves also indicates the presence of a thin interfacial layer of a different phase. The use of an excess Cd flux during growth has been found to lead to increased and more uniform carrier densities in both undoped and In doped layers.

  12. Synthesis of Structurally Diverse 2,3-Fused Indoles via Microwave-Assisted AgSbF6-Catalysed Intramolecular Difunctionalization of o-Alkynylanilines

    PubMed Central

    Huang, Yuanqiong; Yang, Yan; Song, Hongjian; Liu, Yuxiu; Wang, Qingmin

    2015-01-01

    2,3-Fused indoles are found in numerous natural products and drug molecules. Although several elegant methods for the synthesis of this structural motif have been reported, long reaction times and harsh conditions are sometimes required, and the yields tend to be low. Herein, we report a microwave method for straightforward access to various types of 2,3-fused indoles via AgSbF6-catalysed intramolecular difunctionalization of o-alkynylanilines. AgSbF6 played a role in both the hydroamination step and the imine-formation step. This method, which exhibited excellent chemoselectivity (no ring-fused 1,2-dihydroquinolines were formed), was used for formal syntheses of the natural products conolidine and ervaticine and the antihistamine drug latrepirdine. PMID:26310858

  13. Measurements of L-shell X-ray production cross-sections of Ag and Sb by low-energy electron impact

    NASA Astrophysics Data System (ADS)

    Zhao, J. L.; An, Z.; Zhu, J. J.; Tan, W. J.; Liu, M. T.

    2016-05-01

    The total L-shell X-ray production cross-sections of Ag and Sb elements were measured by detecting the characteristic X-rays induced by the electron impact in the energy range of 6-28 keV. In this experiment, the thin films with thick aluminum substrates were used as the targets, and the experimental setup was improved. The influence of multiple scattering of electrons penetrating the targets films, electrons reflected from the thick aluminum substrates and bremsstrahlung photons produced when incident electrons impacted the targets were corrected by using the Monte Carlo method. The experimental results determined in this paper were compared with some theoretical models and other available experimental data in the literature. It was shown that the L-shell X-ray production cross-sections of Ag and Sb elements measured in this paper were in good agreement with the theoretical predictions within the uncertainties.

  14. Synthesis of Structurally Diverse 2,3-Fused Indoles via Microwave-Assisted AgSbF6-Catalysed Intramolecular Difunctionalization of o-Alkynylanilines

    NASA Astrophysics Data System (ADS)

    Huang, Yuanqiong; Yang, Yan; Song, Hongjian; Liu, Yuxiu; Wang, Qingmin

    2015-08-01

    2,3-Fused indoles are found in numerous natural products and drug molecules. Although several elegant methods for the synthesis of this structural motif have been reported, long reaction times and harsh conditions are sometimes required, and the yields tend to be low. Herein, we report a microwave method for straightforward access to various types of 2,3-fused indoles via AgSbF6-catalysed intramolecular difunctionalization of o-alkynylanilines. AgSbF6 played a role in both the hydroamination step and the imine-formation step. This method, which exhibited excellent chemoselectivity (no ring-fused 1,2-dihydroquinolines were formed), was used for formal syntheses of the natural products conolidine and ervaticine and the antihistamine drug latrepirdine.

  15. Effects of Ge substitution in GeTe by Ag or Sb on the Seebeck coefficient and carrier concentration derived from 125Te NMR

    NASA Astrophysics Data System (ADS)

    Levin, E. M.

    2016-01-01

    GeTe, a self-doping p -type semiconductor where the high free hole concentration is determined by Ge vacancies is a well-known base for high-efficiency A gxS bxG e50 -2 xT e50 (a tellurium-antimony-germanium-silver series) thermoelectric materials. Here it is shown that the replacement of Ge by Ag in GeTe (a A gxG e50 -xT e50 system) significantly decreases the Seebeck coefficient, whereas the replacement by Sb (S bxG e50 -xT e50 ) increases it. These effects can be attributed to a change in carrier concentration and consistent with 125Te NMR spin-lattice relaxation measurements and NMR signal position, which is mostly dependent on the Knight shift. Opposite changes in carrier concentration in A gxG e50 -xT e50 and S bxG e50 -xT e50 can be explained by different valence electron configurations of Ag and Sb compared to that of Ge, which results in a different local electron imbalance and/or in a change in Ge vacancy formation energy and affects the total carrier concentration. Comparison of our data for GeTe, A g2G e48T e50 , and S b2G e48T e50 with those for A g2S b2G e46T e50 shows that the effects from Ag and Sb compensate for each other and supports the formation of [Ag +Sb ] atomic pairs suggested earlier based on theoretical calculations.

  16. Pressure-induced semimetal-semiconductor transition and enhancement of thermoelectric performance in α-MgAgSb

    NASA Astrophysics Data System (ADS)

    Miao, Naihua; Zhou, Jian; Sa, Baisheng; Xu, Bin; Sun, Zhimei

    2016-05-01

    Comparable to bismuth telluride, α-MgAgSb-based materials (α-MAS) have been investigated recently as promising candidates for room-temperature thermoelectric energy harvesting and thus various efforts have been devoted to the enhancement of their thermoelectric performance. By utilizing first-principles density functional calculations and Boltzmann transport theory, we report that the thermoelectric properties of α-MAS can be dramatically improved with the application of hydrostatic pressure. This is attributed to a pressure-induced semimetal to semiconductor transition in α-MAS. With the benefit of this pressure-tunable behaviour, the Seebeck coefficient of α-MAS can be manipulated flexibly. Furthermore, we found that, through the combination of applying pressure and p-type doping, the optimal thermoelectric power factor and figure of merit of α-MAS can be enhanced remarkably by 110% at 550 K compared with the intrinsic case. Our results provide an interesting insight and a feasible guideline for the improvement of the thermoelectric properties of α-MAS related materials.

  17. Structure of the quantum spin Hall states in HgTe/CdTe and InAs/GaSb/AlSb quantum wells

    NASA Astrophysics Data System (ADS)

    Klipstein, P. C.

    2015-01-01

    A solution of the k . p model is presented for bulk and quantum spin hall (QSH) edge states in semiconductor topological insulator (TI) quantum wells (QWs), bounded at the edge by an infinite wall potential. The edge states are exponentially localized, with a nonzero amplitude at the QW edge, and obey standard boundary conditions for the wave function and its derivative. Single helical edge states with spin locked to the direction of motion are found in the TI band gap (ETI) of QWs with both strong (HgTe/CdTe) and weak (InAs/GaSb/AlSb) s -p hybridization, but in the second case only below a small critical band gap, Ecrit˜1.6 meV . For ETI>Ecrit , there appear to be two degenerate states for each spin direction. It is suggested that Z2-like topological properties can still be maintained if one of these states is spurious or suppressed by disorder. The effect of interface band mixing, and band mixing due to structural inversion asymmetry and bulk inversion asymmetry is also considered. Simple model Hamiltonians are developed for the bulk and edge states which are calibrated against a bulk eight-band k . p calculation close to the TI transition. At the transition, the zero gap bulk states exhibit a spin splitting, essentially changing the Dirac point to a circle. In the TI phase, there is a small change in the dispersion of the QSH edge states. These results confirm the robustness of the QSH edge states to spatial symmetry breaking interactions.

  18. Approaching the N=82 shell closure with mass measurements of Ag and Cd isotopes

    SciTech Connect

    Breitenfeldt, M.; Baruah, S.; Rosenbusch, M.; Schweikhard, L.; Borgmann, Ch.; Boehm, Ch.; George, S.; Audi, G.; Lunney, D.; Minaya-Ramirez, E.; Naimi, S.; Beck, D.; Dworschak, M.; Herfurth, F.; Savreux, R.; Yazidjian, C.; Blaum, K.; Cakirli, R. B.; Casten, R. F.; Delahaye, P.

    2010-03-15

    Mass measurements of neutron-rich Cd and Ag isotopes were performed with the Penning trap mass spectrometer ISOLTRAP. The masses of {sup 112,114-124}Ag and {sup 114,120,122-124,126,128}Cd, determined with relative uncertainties between 2x10{sup -8} and 2x10{sup -7}, resulted in significant corrections and improvements of the mass surface. In particular, the mass of {sup 124}Ag was previously unknown. In addition, other masses that had to be inferred from Q values of nuclear decays and reactions have now been measured directly. The analysis includes various mass differences, namely the two-neutron separation energies, the applicability of the Garvey-Kelson relations, double differences of masses deltaV{sub pn}, which give empirical proton-neutron interaction strengths, as well as a comparison with recent microscopic calculations. The deltaV{sub pn} results reveal that for even-even nuclides around {sup 132}Sn the trends are similar to those in the {sup 208}Pb region.

  19. β-CD Dimer-immobilized Ag Assembly Embedded Silica Nanoparticles for Sensitive Detection of Polycyclic Aromatic Hydrocarbons

    NASA Astrophysics Data System (ADS)

    Hahm, Eunil; Jeong, Daham; Cha, Myeong Geun; Choi, Jae Min; Pham, Xuan-Hung; Kim, Hyung-Mo; Kim, Hwanhee; Lee, Yoon-Sik; Jeong, Dae Hong; Jung, Seunho; Jun, Bong-Hyun

    2016-05-01

    We designed a β-CD dimer on silver nanoparticles embedded with silica nanoparticles (Ag@SiO2 NPs) structure to detect polycyclic aromatic hydrocarbons (PAHs). Silica NPs were utilized as a template for embedding silver NPs to create hot spot structures and enhance the surface-enhanced Raman scattering (SERS) signal, and a thioether-bridged dimeric β-CD was immobilized on Ag NPs to capture PAHs. The assembled Ag NPs on silica NPs were confirmed by TEM and the presence of β-CD dimer on Ag@SiO2 was confirmed by UV-vis and attenuated total reflection-Fourier transform infrared spectroscopy. The β-CD dimer@Ag@SiO2 NPs were used as SERS substrate for detecting perylene, a PAH, directly and in a wide linearity range of 10‑7 M to 10‑2 M with a low detection limit of 10‑8 M. Also, the β-CD dimer@Ag@SiO2 NPs exhibited 1000-fold greater sensitivity than Ag@SiO2 NPs in terms of their perylene detection limit. Furthermore, we demonstrated the possibility of detecting various PAH compounds using the β-CD dimer@Ag@SiO2 NPs as a multiplex detection tool. Various PAH compounds with the NPs exhibited their distinct SERS bands by the ratio of each PAHs. This approach of utilizing the assembled structure and the ligands to recognize target has potential for use in sensitive analytical sensors.

  20. β-CD Dimer-immobilized Ag Assembly Embedded Silica Nanoparticles for Sensitive Detection of Polycyclic Aromatic Hydrocarbons.

    PubMed

    Hahm, Eunil; Jeong, Daham; Cha, Myeong Geun; Choi, Jae Min; Pham, Xuan-Hung; Kim, Hyung-Mo; Kim, Hwanhee; Lee, Yoon-Sik; Jeong, Dae Hong; Jung, Seunho; Jun, Bong-Hyun

    2016-01-01

    We designed a β-CD dimer on silver nanoparticles embedded with silica nanoparticles (Ag@SiO2 NPs) structure to detect polycyclic aromatic hydrocarbons (PAHs). Silica NPs were utilized as a template for embedding silver NPs to create hot spot structures and enhance the surface-enhanced Raman scattering (SERS) signal, and a thioether-bridged dimeric β-CD was immobilized on Ag NPs to capture PAHs. The assembled Ag NPs on silica NPs were confirmed by TEM and the presence of β-CD dimer on Ag@SiO2 was confirmed by UV-vis and attenuated total reflection-Fourier transform infrared spectroscopy. The β-CD dimer@Ag@SiO2 NPs were used as SERS substrate for detecting perylene, a PAH, directly and in a wide linearity range of 10(-7) M to 10(-2) M with a low detection limit of 10(-8) M. Also, the β-CD dimer@Ag@SiO2 NPs exhibited 1000-fold greater sensitivity than Ag@SiO2 NPs in terms of their perylene detection limit. Furthermore, we demonstrated the possibility of detecting various PAH compounds using the β-CD dimer@Ag@SiO2 NPs as a multiplex detection tool. Various PAH compounds with the NPs exhibited their distinct SERS bands by the ratio of each PAHs. This approach of utilizing the assembled structure and the ligands to recognize target has potential for use in sensitive analytical sensors. PMID:27184729

  1. β-CD Dimer-immobilized Ag Assembly Embedded Silica Nanoparticles for Sensitive Detection of Polycyclic Aromatic Hydrocarbons

    PubMed Central

    Hahm, Eunil; Jeong, Daham; Cha, Myeong Geun; Choi, Jae Min; Pham, Xuan-Hung; Kim, Hyung-Mo; Kim, Hwanhee; Lee, Yoon-Sik; Jeong, Dae Hong; Jung, Seunho; Jun, Bong-Hyun

    2016-01-01

    We designed a β-CD dimer on silver nanoparticles embedded with silica nanoparticles (Ag@SiO2 NPs) structure to detect polycyclic aromatic hydrocarbons (PAHs). Silica NPs were utilized as a template for embedding silver NPs to create hot spot structures and enhance the surface-enhanced Raman scattering (SERS) signal, and a thioether-bridged dimeric β-CD was immobilized on Ag NPs to capture PAHs. The assembled Ag NPs on silica NPs were confirmed by TEM and the presence of β-CD dimer on Ag@SiO2 was confirmed by UV-vis and attenuated total reflection-Fourier transform infrared spectroscopy. The β-CD dimer@Ag@SiO2 NPs were used as SERS substrate for detecting perylene, a PAH, directly and in a wide linearity range of 10−7 M to 10−2 M with a low detection limit of 10−8 M. Also, the β-CD dimer@Ag@SiO2 NPs exhibited 1000-fold greater sensitivity than Ag@SiO2 NPs in terms of their perylene detection limit. Furthermore, we demonstrated the possibility of detecting various PAH compounds using the β-CD dimer@Ag@SiO2 NPs as a multiplex detection tool. Various PAH compounds with the NPs exhibited their distinct SERS bands by the ratio of each PAHs. This approach of utilizing the assembled structure and the ligands to recognize target has potential for use in sensitive analytical sensors. PMID:27184729

  2. Metal-Semiconductor Hybrid Aerogels: Evolution of Optoelectronic Properties in a Low-Dimensional CdSe/Ag Nanoparticle Assembly.

    PubMed

    Nahar, Lamia; Esteves, Richard J Alan; Hafiz, Shopan; Özgür, Ümit; Arachchige, Indika U

    2015-10-27

    Hybrid nanomaterials composed of metal-semiconductor components exhibit unique properties in comparison to their individual counterparts, making them of great interest for optoelectronic applications. Theoretical and experimental studies suggest that interfacial interactions of individual components are of paramount importance to produce hybrid electronic states. The direct cross-linking of nanoparticles (NPs) via controlled removal of the surfactant ligands provides a route to tune interfacial interactions in a manner that has not been thoroughly investigated. Herein, we report the synthesis of CdSe/Ag heteronanostructures (aerogels) via oxidation induced self-assembly of thiol-coated NPs and the evolution of optical properties as a function of composition. Three hybrid systems were investigated, where the first and second excitonic energies of CdSe were matched with plasmonic energy of Au or Ag NPs and Ag hollow NPs. Physical characterization of the aerogels suggests the presence of an interconnected network of hexagonal CdSe and cubic Ag NPs. The optical properties of hybrids were systematically examined through UV-vis, photoluminescence (PL), and time-resolved (TR) PL spectroscopic studies that indicate the generation of alternate radiative decay pathways. A new emission (640 nm) from CdSe/Ag aerogels emerged at Ag loading as low as 0.27%, whereas absorption band tailing and PL quenching effects were observed at higher Ag and Au loading, respectively. The TRPL decay time of the new emission (∼600 ns) is markedly different from those of the band-edge (1.83 ± 0.03 ns) and trap-state (1190 ± 120 ns) emission maxima of phase pure CdSe, supporting the existence of alternate radiative relaxation pathways in sol-gel derived CdSe/Ag hybrids. PMID:26389642

  3. New chalcogenide glasses in the CdTe-AgI-As{sub 2}Te{sub 3} system

    SciTech Connect

    Kassem, M.; Le Coq, D.; Boidin, R.; Bychkov, E.

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer Determination of the glass-forming region in the pseudo-ternary CdTe-AgI-As{sub 2}Te{sub 3} system. Black-Right-Pointing-Pointer Characterization of macroscopic properties of the new CdTe-AgI-As{sub 2}Te{sub 3} glasses. Black-Right-Pointing-Pointer Characterization of the total conductivity of CdTe-AgI-As{sub 2}Te{sub 3} glasses. Black-Right-Pointing-Pointer Comparison between the selenide and telluride equivalent systems. -- Abstract: Chalcogenide glasses in the pseudo-ternary CdTe-AgI-As{sub 2}Te{sub 3} system were synthesized and the glass-forming range was determined. The maximum content of CdTe in this glass system was found to be equal to 15 mol.%. The macroscopic characterizations of samples have consisted in Differential Scanning Calorimetry, density, and X-ray diffraction measurements. The cadmium telluride addition does not generate any significant change in the glass transition temperature but the resistance of binary AgI-As{sub 2}Te{sub 3} glasses towards crystallisation is estimated to be decreasing on the base of {Delta}T = T{sub x} - T{sub g} parameter. The total electrical conductivity {sigma} was measured by complex impedance spectroscopy. First, the CdTe additions in the (AgI){sub 0.5}(As{sub 2}Te{sub 3}){sub 0.5} host glass, (CdTe){sub x}(AgI){sub 0.5-x/2}(As{sub 2}Te{sub 3}){sub 0.5-x/2} lead to a conductivity decrease at x {<=} 0.05. Then, the behaviour is reversed at 0.05 {<=} x {<=} 0.15. The obtained results are discussed by comparison with the equivalent selenide system.

  4. Metal coordination study at Ag and Cd sites in crown thioether complexes through DFT calculations and hyperfine parameters.

    PubMed

    do Nascimento, Rafael R; Lima, Filipe C D A; Gonçalves, Marcos B; Errico, Leonardo A; Rentería, Mario; Petrilli, Helena M

    2015-04-01

    Structural and electronic properties of [C12H24S6X], [C13H26S6OX], and [C14H28S6OX] (X: Ag(+), Cd(2+)) crown thioether complexes were investigated within the framework of the density functional theory (DFT) using the projector augmented wave (PAW) method. The theoretical results were compared with time-differential perturbed γ-γ angular correlations (TDPAC) experiments reported in the literature using the (111)Ag→(111)Cd probe. In the case of X=Ag(+), a refinement of the structure was performed and the predicted equilibrium structures compared with available X-ray diffraction experimental data. Structural distortions induced by replacing Ag(+) with Cd(2+) were investigated as well as the electric-field gradient (EFG) tensor at the Cd(2+) sites. Our results suggest that the EFG at Cd(2+) sites corresponds to the Ag(+) coordination sphere structure, i.e., before the structural relaxations of the molecule with X=Cd(2+) are completed. The results are discussed in terms of the characteristics of the TDPAC (111)Ag→(111)Cd probe and the time window of the measurement, and provide an interesting tool with which to probe molecular relaxations. PMID:25814377

  5. CdS and AgBr sensitized eriochrome black T (EBT) dye solar cells

    NASA Astrophysics Data System (ADS)

    Sharma, G. D.; Dube, D. C.; Mathur, S. C.

    1985-11-01

    The photovoltaic and rectification properties of CdS- and AgBr-sensitized Eriochrome Black T dye solar cells have been studied. The dependence of the short-circuit current and the open-circuit voltage on light intensity and electrode material are examined and the variations with electrode material are explained on the basis of the built-in potential developed at the metal-semiconductor interface. Conversion efficiency, fill factor, diode factor and reverse saturation current are also calculated for each cell.

  6. Volume dependence of Anderson hybridization in cubic CeCd and CeAg

    SciTech Connect

    Monachesi, P. ); Andreani, L.C. ); Continenza, A. ); McMahan, A.K. )

    1993-05-15

    We have undertaken a first-principles theoretical study of the Anderson hybridization in cubic CeCd and CeAg as a function of volume reduction. We present results for the hybridization width [Delta]([epsilon]) in both the [ital J]=5/2 multiplet and in the [Gamma][sub 8], [Gamma][sub 7] crystal field states of the [ital f][sup 1] Ce configuration. We also calculate the hybridization contribution to the magnetic transition temperature. This is found to increase with pressure but is smaller than the experimental values, indicating that the Coulomb exchange contribution to the magnetic coupling is not negligible in these compounds.

  7. Volume dependence of Anderson hybridization in cubic CeCd and CeAg

    SciTech Connect

    Monachesi, P.; Continenza, A. . Dipt. di Fisica); Andreani, L.C. ); McMahan, A.K. )

    1992-09-01

    We have undertaken a first-principles theoretical study of the Anderson hybridization in cubic CeCd and CeAg as a function of volume reduction. We present results for the hybridization width [Delta]([epsilon]) in both the J = 5/2 multiplet and in the [Gamma][sub 8], [Gamma][sub 7] crystal field states of the f[sup 1] Ce configuration. We also calculate the hybridization contribution to the magnetic transition temperature. This is found to increase with pressure but is smaller than the experimental values, indicating that the Coulomb exchange contribution to the magnetic coupling is not negligible in these compounds.

  8. Volume dependence of Anderson hybridization in cubic CeCd and CeAg

    SciTech Connect

    Monachesi, P.; Continenza, A.; Andreani, L.C.; McMahan, A.K.

    1992-09-01

    We have undertaken a first-principles theoretical study of the Anderson hybridization in cubic CeCd and CeAg as a function of volume reduction. We present results for the hybridization width {Delta}({epsilon}) in both the J = 5/2 multiplet and in the {Gamma}{sub 8}, {Gamma}{sub 7} crystal field states of the f{sup 1} Ce configuration. We also calculate the hybridization contribution to the magnetic transition temperature. This is found to increase with pressure but is smaller than the experimental values, indicating that the Coulomb exchange contribution to the magnetic coupling is not negligible in these compounds.

  9. Internally consistent database for sulfides and sulfosalts in the system Ag 2S-Cu 2S-ZnS-FeS-Sb 2S 3-As 2S 3: Update

    NASA Astrophysics Data System (ADS)

    Sack, Richard O.

    2005-03-01

    The thermodynamic database for Ag 2S-Cu 2S-ZnS-FeS-Sb 2S 3-As 2S 3 sulfides and sulfosalts applicable to temperatures above 119°C has been updated based on the results of recent petrologic, experimental, and theoretical studies. Solution and end-member properties of fahlore [˜(Ag,Cu) 10(Fe,Zn) 2(Sb,As) 4S 13] have been adjusted to allow for (1) revisions of the description of Fe-Zn partitioning with sphalerite that incorporate sphalerite activity-composition relations derived from the cluster variation method (CVM) model of a previous study, (2) the assumption that the miscibility gaps observed in high-Ag fahlores from the Husky Mine (Yukon, Canada) approximate a temperature of 170°C, and (3) an increase in the Ag-Cu partitioning between fahlore and polybasite (Ag,Cu) 16(Sb,As) 2S 11 required to reproduce compositions of fahlore in the polybasite + Sb-fahlore + ZnS sphalerite assemblage reported in previous experimental studies. The resulting minor parameter adjustments produce a database that demonstrably reproduces the composition data reported for a wide-range of sulfide ore deposits. They result in revised estimates for the Gibbs energies of formation of end-member fahlore components from the simple sulfides that, except for Cu 10Zn 2Sb 4S 13, are less temperature dependent than those previously inferred (at 200 and 400°C: -23.27 and -24.84 kJ/gfw for Ag 10Zn 2Sb 4S 13, -115.18 and -116.57 kJ/gfw for Cu 10Zn 2Sb 4S 13, -85.14 and -75.20 kJ/gfw for Cu 10Fe 2Sb 4S 13, and -3.81 and 9.10 kJ/gfw for Ag 10Fe 2Sb 4S 13). The database is extended to PbS-bearing supersystems containing the galena + fahlore + sphalerite assemblage. Predicted initial Ag-contents of galena calculated from this database agree with those inferred from petrological studies of Ag-Pb-Zn ores from the Coeur d'Alene district, Idaho, USA and Julcani, Peru.

  10. Influence of reactive sulfide (AVS) and supplementary food on Ag, Cd and Zn bioaccumulation in the marine polychaete Neanthes arenaceodentata

    USGS Publications Warehouse

    Lee, J.-S.; Lee, B.-G.; Yoo, H.; Koh, C.-H.; Luoma, S.N.

    2001-01-01

    A laboratory bioassay determined the relative contribution of various pathways of Ag, Cd and Zn bioaccumulation in the marine polychaete Neanthes arenaceodentata exposed to moderately contaminated sediments. Juvenile worms were exposed for 25 d to experimental sediments containing 5 different reactive sulfide (acid volatile sulfides, AVS) concentrations (1 to 30 ??mol g-1), but with constant Ag, Cd, and Zn concentrations of 0.1, 0.1 and 7 ??mol g-1, respectively. The sediments were supplemented with contaminated food (TetraMin??) containing 3 levels of Ag-Cd-Zn (uncontaminated, 1?? or 5??1 metal concentrations in the contaminated sediment). The results suggest that bioaccumulation of Ag, Cd and Zn in the worms occurred predominantly from ingestion of contaminated sediments and contaminated supplementary food. AVS or dissolved metals (in porewater and overlying water) had a minor effect on bioaccumulation of the 3 metals in most of the treatments. The contribution to uptake from the dissolved source was most important in the most oxic sediments, with maximum contributions of 8% for Ag, 30% for Cd and 20% for Zn bioaccumulation. Sediment bioassays where uncontaminated supplemental food is added could seriously underestimate metal exposures in an equilibrated system; N. arenaceodentata feeding on uncontaminated food would be exposed to 40-60% less metal than if the food source was equilibrated (as occurs in nature). Overall, the results show that pathways of metal exposure are dynamically linked in contaminated sediments and shift as external geochemical characteristics and internal biological attributes vary.

  11. Development of CdO-graphite-Ag coatings for gas bearings to 427 C

    NASA Technical Reports Server (NTRS)

    Bhushan, B.

    1981-01-01

    Graphite is one of the most commonly known lubricants. Its effectiveness in a range between room temperature (RT) and 540 C is reportedly improved by adding cadmium oxide. CdO-graphite powder in a gas carrier has been used in numerous applications that rely on dry lubrication. A coating of this composition was developed and successfully tested in foil air bearings for long periods up to a temperature of 427 C and at a normal contacting load (during starting and stopping) of 14 kPa based on bearing projected area. The addition of ultra-fine silver to the CdO-graphite has improved the coating endurance. At 427 C, the CdO-graphite-Ag coating performed better than CdO-graphite without silver, both for extended periods at 14 kPa loading and for limited periods at 35 kPa. At 288 C, the coating was tested for an extended period up to 28 kPa and has also successfully completed high-speed shock tests to an acceleration level of 100g.

  12. Data on metal contents (As, Ag, Sr, Sn, Sb, and Mo) in sediments and shells of Trachycardium lacunosum in the northern part of the Persian Gulf.

    PubMed

    Karbasdehi, Vahid Noroozi; Dobaradaran, Sina; Nabipour, Iraj; Arfaeinia, Hossein; Mirahmadi, Roghayeh; Keshtkar, Mozhgan

    2016-09-01

    In this data article, by using inductively coupled plasma optical spectrometry (ICP-OES), we aimed to (1) determine the concentration levels of As, Ag, Sr, Sn, Sb, and Mo in the sediments and the shells of Trachycardium lacunosum simultaneously in two separated areas (unpolluted and polluted areas) (2) comparison between the metal contents of sediments in the unpolluted and polluted areas as well as shells. Analysis of data showed that sediment as well as shell samples in polluted area contained significantly higher concentration levels of all measured metals compared with unpolluted area. PMID:27508251

  13. Biological interaction between transition metals (Ag, Cd and Hg), selenide/sulfide and selenoprotein P.

    PubMed

    Sasakura, C; Suzuki, K T

    1998-09-01

    The interaction between transition metals (Ag+, Cd2+ and Hg2+) and selenium (Se) in the bloodstream was studied in vitro by means of the HPLC--inductively coupled argon plasma-mass spectrometry (ICP MS) method. Transition metal ions and selenide (produced in vitro from selenite in the presence of glutathione) or sulfide (Na2S) formed a (metal-Se/S) complex, which then bound to a plasma protein, selenoprotein P (Sel P), to form a ternary complex, (metal-Se/S)-Sel P. The molar ratios of metals to Se were 1:1 for Hg/Se and Cd/Se, but either 1:1 or 2:1 for Ag/Se, depending on the ratio of their doses. The results indicate that the interaction between transition metals and Se occurs through the general mechanism, i.e., transition metal ions and selenide form the unit complex (metal-Se)n, and then the complex binds to selenoprotein P to form the ternary complex ¿(metal-Se)n¿m--seleno-protein P in the bloodstream. PMID:9833321

  14. Availability of sediment-bound Cd, Co, and Ag to mussels

    SciTech Connect

    Gagnon, C.; Fisher, N.S.

    1995-12-31

    Ingested sediment is one potentially important source of metals for benthic organisms. The influence of physical and chemical properties of oxidized sediments on the bioavailability of metals to marine filter feeders is largely unknown. The authors examined the relative importance of specific sedimentary components that may exert control on the uptake of Cd, Co, and Ag in the mussel Mytilus edulis. Iron and manganese oxides, montmorillonite clay, silica, and natural sediment particles were triple labeled with the gamma emitters {sup 109}Cd, {sup 57}Co, and {sup 110m}Ag. Some particles were also coated with fulvic acid (FA) to simulate the influence of organic coating on metal bioavailability. Metals associated with FA-coated particles were generally absorbed by mussels to a greater extent than metals associated with uncoated particles. Desorption experiments with labeled particles at pH 5 were performed in parallel to simulate the behavior of food-bound metals in the acidic gut of bivalves. High correlations (r > 0.97) between the amount of desorbed metal under these conditions and the assimilation efficiency for metals from FA-coated particles were noted among coated particles but not uncoated particles (r < 0.6). These results suggest that the relation between metal partitioning to sediments and biological availability of the metal is not obvious, since the organic coatings and the acidic digestion process influence assimilation of sediment-bound metals.

  15. Band bending at Al, In, Ag, and Pt interfaces with CdTe and ZnTe (110)

    NASA Technical Reports Server (NTRS)

    Wahi, A. K.; Miyano, K.; Carey, G. P.; Chiang, T. T.; Lindau, I.

    1990-01-01

    UV and X-ray photoelectron spectroscopic methods are presently used to study the band-bending behavior and interfacial chemistry of Al, In, Ag, and Pt overlayers on vacuum-cleaved p-CdTe and p-ZnTe (110). All four metals are found to yield Schottky barriers on CdTe and ZnTe. The metal-induced gap states model prediction of a difference in barrier heights for two semiconductors which is dependent on their band lineup is borne out by the results for Ag, Pt, and Al, but not for In. Reaction and intermixing for Al, Ag, and Pt overlayers on CdTe and ZnTe indicate that these interfaces are not ideal.

  16. Multistage hydrothermal silicification and Fe-Tl-As-Sb-Ge-REE enrichment in the Red Dog Zn-Pb-Ag district, northern Alaska: Geochemistry, origin, and exploration applications

    USGS Publications Warehouse

    Slack, J.F.; Kelley, K.D.; Anderson, V.M.; Clark, J.L.; Ayuso, R.A.

    2004-01-01

    Geochemical analyses of major, trace, and rare earth elements (REE) in more than 200 samples of variably silicified and altered wall rocks, massive and banded sulfide, silica rock, and sulfide-rich and unmineralized barite were obtained from the Main, Aqqaluk, and Anarraaq deposits in the Red Dog Zn-Pb-Ag district of northern Alaska. Detailed lithogeochemical profiles for two drill cores at Aqqaluk display an antithetic relationship between SiO2/Al2O3 and TiO2/Zr which, together with textural information, suggest preferential silicification of carbonate-bearing sediments. Data for both drill cores also show generally high Tl, Sb, As, and Ge and uniformly positive Eu anomalies (Eu/Eu* > 1.0). Similar high Tl, Sb, As, Ge, and Eu/Eu* values are present in the footwall and shallow hanging wall of Zn-Pb-Ag sulfide intervals at Anarraaq but are not as widely dispersed. Net chemical changes for altered wall rocks in the district, on the basis of average Al-normalized data relative to unaltered black shales of the host Kuna Formation, include large enrichments (>50%) of Fe, Ba, Eu, V, S, Co, Zn, Pb, Tl, As, Sb, and Ge at both Red Dog and Anarraaq, Si at Red Dog, and Sr, U, and Se at Anarraaq. Large depletions (>50%) are evident for Ca at both Red Dog and Anarraaq, for Mg, P, and Y at Red Dog, and for Na at Anarraaq. At both Red Dog and Anarraaq, wall-rock alteration removed calcite and minor dolomite during hydrothermal decarbonation reactions and introduced Si, Eu, and Ge during silicification. Sulfidation reactions deposited Fe, S, Co, Zn, Pb, Tl, As, and Sb; barite mineralization introduced Ba, S, and Sr. Light REE and U were mobilized locally. This alteration and mineralization occurred during Mississippi an hydrothermal events that predated the Middle Jurassic-Cretaceous Brookian orogeny. Early hydrothermal silicification at Red Dog took place prior to or during massive sulfide mineralization, on the basis of the dominantly planar nature of Zn-Pb veins, which suggests

  17. Slurry sampling flow injection chemical vapor generation inductively coupled plasma mass spectrometry for the determination of trace Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions.

    PubMed

    Chen, Wei-Ni; Jiang, Shiuh-Jen; Chen, Yen-Ling; Sahayam, A C

    2015-02-20

    A slurry sampling inductively coupled plasma mass spectrometry (ICP-MS) method has been developed for the determination of Ge, As, Cd, Sb, Hg and Bi in cosmetic lotions using flow injection (FI) vapor generation (VG) as the sample introduction system. A slurry containing 2% m/v lotion, 2% m/v thiourea, 0.05% m/v L-cysteine, 0.5 μg mL(-1) Co(II), 0.1% m/v Triton X-100 and 1.2% v/v HCl was injected into a VG-ICP-MS system for the determination of Ge, As, Cd, Sb, Hg and Bi without dissolution and mineralization. Because the sensitivities of the analytes in the slurry and that of aqueous solution were quite different, an isotope dilution method and a standard addition method were used for the determination. This method has been validated by the determination of Ge, As, Cd, Sb, Hg and Bi in GBW09305 Cosmetic (Cream) reference material. The method was also applied for the determination of Ge, As, Cd, Sb, Hg and Bi in three cosmetic lotion samples obtained locally. The analysis results of the reference material agreed with the certified value and/or ETV-ICP-MS results. The detection limit estimated from the standard addition curve was 0.025, 0.1, 0.2, 0.1, 0.15, and 0.03 ng g(-1) for Ge, As, Cd, Sb, Hg and Bi, respectively, in original cosmetic lotion sample. PMID:25682241

  18. Fully epitaxial C1b-type NiMnSb half-Heusler alloy films for current-perpendicular-to-plane giant magnetoresistance devices with a Ag spacer

    PubMed Central

    Wen, Zhenchao; Kubota, Takahide; Yamamoto, Tatsuya; Takanashi, Koki

    2015-01-01

    Remarkable magnetic and spin-dependent transport properties arise from well-designed spintronic materials and heterostructures. Half-metallic Heusler alloys with high spin polarization exhibit properties that are particularly advantageous for the development of high-performance spintronic devices. Here, we report fully (001)-epitaxial growth of a high-quality half-metallic NiMnSb half-Heusler alloy films, and their application to current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices with Ag spacer layers. Fully (001)-oriented NiMnSb epitaxial films with very flat surface and high magnetization were prepared on Cr/Ag-buffered MgO(001) single crystalline substrates by changing the substrate temperature. Epitaxial CPP-GMR devices using the NiMnSb films and a Ag spacer were fabricated, and room-temperature (RT) CPP-GMR ratios for the C1b-type half-Heusler alloy were determined for the first time. A CPP-GMR ratio of 8% (21%) at RT (4.2 K) was achieved in the fully epitaxial NiMnSb/Ag/NiMnSb structures. Furthermore, negative anisotropic magnetoresistance (AMR) ratio and small discrepancy of the AMR amplitudes between RT and 10 K were observed in a single epitaxial NiMnSb film, indicating robust bulk half metallicity against thermal fluctuation in the half-Heusler compound. The modest CPP-GMR ratios could be attributed to interface effects between NiMnSb and Ag. This work provides a pathway for engineering a new class of ordered alloy materials with particular emphasis on spintronics. PMID:26672482

  19. Fully epitaxial C1b-type NiMnSb half-Heusler alloy films for current-perpendicular-to-plane giant magnetoresistance devices with a Ag spacer

    NASA Astrophysics Data System (ADS)

    Wen, Zhenchao; Kubota, Takahide; Yamamoto, Tatsuya; Takanashi, Koki

    2015-12-01

    Remarkable magnetic and spin-dependent transport properties arise from well-designed spintronic materials and heterostructures. Half-metallic Heusler alloys with high spin polarization exhibit properties that are particularly advantageous for the development of high-performance spintronic devices. Here, we report fully (001)-epitaxial growth of a high-quality half-metallic NiMnSb half-Heusler alloy films, and their application to current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices with Ag spacer layers. Fully (001)-oriented NiMnSb epitaxial films with very flat surface and high magnetization were prepared on Cr/Ag-buffered MgO(001) single crystalline substrates by changing the substrate temperature. Epitaxial CPP-GMR devices using the NiMnSb films and a Ag spacer were fabricated, and room-temperature (RT) CPP-GMR ratios for the C1b-type half-Heusler alloy were determined for the first time. A CPP-GMR ratio of 8% (21%) at RT (4.2 K) was achieved in the fully epitaxial NiMnSb/Ag/NiMnSb structures. Furthermore, negative anisotropic magnetoresistance (AMR) ratio and small discrepancy of the AMR amplitudes between RT and 10 K were observed in a single epitaxial NiMnSb film, indicating robust bulk half metallicity against thermal fluctuation in the half-Heusler compound. The modest CPP-GMR ratios could be attributed to interface effects between NiMnSb and Ag. This work provides a pathway for engineering a new class of ordered alloy materials with particular emphasis on spintronics.

  20. Fully epitaxial C1b-type NiMnSb half-Heusler alloy films for current-perpendicular-to-plane giant magnetoresistance devices with a Ag spacer.

    PubMed

    Wen, Zhenchao; Kubota, Takahide; Yamamoto, Tatsuya; Takanashi, Koki

    2015-01-01

    Remarkable magnetic and spin-dependent transport properties arise from well-designed spintronic materials and heterostructures. Half-metallic Heusler alloys with high spin polarization exhibit properties that are particularly advantageous for the development of high-performance spintronic devices. Here, we report fully (001)-epitaxial growth of a high-quality half-metallic NiMnSb half-Heusler alloy films, and their application to current-perpendicular-to-plane giant magnetoresistance (CPP-GMR) devices with Ag spacer layers. Fully (001)-oriented NiMnSb epitaxial films with very flat surface and high magnetization were prepared on Cr/Ag-buffered MgO(001) single crystalline substrates by changing the substrate temperature. Epitaxial CPP-GMR devices using the NiMnSb films and a Ag spacer were fabricated, and room-temperature (RT) CPP-GMR ratios for the C1b-type half-Heusler alloy were determined for the first time. A CPP-GMR ratio of 8% (21%) at RT (4.2 K) was achieved in the fully epitaxial NiMnSb/Ag/NiMnSb structures. Furthermore, negative anisotropic magnetoresistance (AMR) ratio and small discrepancy of the AMR amplitudes between RT and 10 K were observed in a single epitaxial NiMnSb film, indicating robust bulk half metallicity against thermal fluctuation in the half-Heusler compound. The modest CPP-GMR ratios could be attributed to interface effects between NiMnSb and Ag. This work provides a pathway for engineering a new class of ordered alloy materials with particular emphasis on spintronics. PMID:26672482

  1. High-Temperature Thermoelectric Properties of the Solid–Solution Zintl Phase Eu11Cd6Sb12–xAsx (x < 3)

    SciTech Connect

    Kazem, Nasrin; Xie, Weiwei; Ohno, Saneyuki; Zevalkink, Alexandra; Miller, Gordon J; Snyder, G Jeffrey; Kauzlarich, Susan M

    2014-02-11

    Zintl phases are compounds that have shown promise for thermoelectric applications. The title solid–solution Zintl compounds were prepared from the elements as single crystals using a tin flux for compositions x = 0, 1, 2, and 3. Eu11Cd6Sb12–xAsx (x < 3) crystallize isostructurally in the centrosymmetric monoclinic space group C2/m (no. 12, Z = 2) as the Sr11Cd6Sb12 structure type (Pearson symbol mC58). Efforts to make the As compositions for x exceeding ~3 resulted in structures other than the Sr11Cd6Sb12 structure type. Single-crystal X-ray diffraction indicates that As does not randomly substitute for Sb in the structure but is site specific for each composition. The amount of As determined by structural refinement was verified by electron microprobe analysis. Electronic structures and energies calculated for various model structures of Eu11Cd6Sb10As2 (x = 2) indicated that the preferred As substitution pattern involves a mixture of three of the six pnicogen sites in the asymmetric unit. In addition, As substitution at the Pn4 site opens an energy gap at the Fermi level, whereas substitution at the other five pnicogen sites remains semimetallic with a pseudo gap. Thermoelectric properties of these compounds were measured on hot-pressed, fully densified pellets. Samples show exceptionally low lattice thermal conductivities from room temperature to 775 K: 0.78–0.49 W/mK for x = 0; 0.72–0.53 W/mK for x = 1; and 0.70–0.56 W/mK for x = 2. Eu11Cd6Sb12 shows a high p-type Seebeck coefficient (from +118 to 153 μ V/K) but also high electrical resistivity (6.8 to 12.8 mΩ·cm). The value of zT reaches 0.23 at 774 K. The properties of Eu11Cd6Sb12–xAsx are interpreted in discussion with the As site substitution.

  2. Optical and electrical properties and phonon drag effect in low temperature TEP measurements of AgSbSe2 thin films

    NASA Astrophysics Data System (ADS)

    Namitha Asokan, T.; Urmila, K. S.; Jacob, Rajani; Reena Philip, Rachel; Okram, G. S.; Ganesan, V.; Pradeep, B.

    2014-05-01

    Polycrystalline thin films of silver antimony selenide have been deposited using a reactive evaporation technique onto an ultrasonically cleaned glass substrate at a vacuum of 10-5 torr. The preparative parameters, like substrate temperature and incident fluxes, have been properly controlled in order to get stoichiometric, good quality and reproducible thin film samples. The samples are characterized by XRD, SEM, AFM and a UV—vis—NIR spectrophotometer. The prepared sample is found to be polycrystalline in nature. From the XRD pattern, the average particle size and lattice constant are calculated. The dislocation density, strain and number of crystallites per unit area are evaluated using the average particle size. The dependence of the electrical conductivity on the temperature has also been studied and the prepared AgSbSe2 samples are semiconducting in nature. The AgSbSe2 thin films exhibited an indirect allowed optical transition with a band gap of 0.64 eV. The compound exhibits promising thermoelectric properties, a large Seebeck coefficient of 30 mV/K at 48 K due to strong phonon electron interaction. It shows a strong temperature dependence on thermoelectric properties, including the inversion of a dominant carrier type from p to n over a low temperature range 9-300 K, which is explained on the basis of a phonon drag effect.

  3. Hybrid Au-CdSe and Ag-CdSe nanoflowers and core-shell nanocrystals via one-pot heterogeneous nucleation and growth.

    PubMed

    AbouZeid, Khaled M; Mohamed, Mona B; El-Shall, M Samy

    2011-12-01

    A general approach, based on heterogeneous nucleation and growth of CdSe nanostructures on Au or Ag nanocrystals, for the synthesis of Au-CdSe and Ag-CdSe hybrid nanostructures is developed. The new approach provides a versatile one-pot route for the synthesis of hybrid nanoflowers consisting of a gold or silver core and multipod CdSe rods or an intact CdSe shell with controlled thickness, depending on the nucleation and growth parameters. At lower growth temperatures such as 150 °C, the CdSe clusters are adsorbed on the surface of the metal cores in their surface defects, then multiple arms and branches form, resulting in nanoflower-shaped hybrid structures. Increasing the size of the metal core through the choice of the reducing and capping agents results in an improvement of the interface between the metal and CdSe domains, producing core-shell structures. The growth temperature appears to be the most important factor determining the nature of the interface between the metal and CdSe domains. At relatively high temperatures such as 300 °C, the formation of large, faceted Au cores creates preferential growth sites for the CdSe nanocrystalline shell, thus resulting in well-defined Au-CdSe core-shell structures with large interfaces between the Au and CdSe domains. The present approach is expected to foster systematic studies of the electronic structures and optical properties of the metal-semiconductor hybrid materials for potential applications in photovoltaic and nanoelectronic devices. PMID:21994186

  4. Low-energy electron elastic scattering from Mn, Cu, Zn, Ni, Ag, and Cd atoms

    SciTech Connect

    Felfli, Z.; Msezane, A. Z.; Sokolovski, D.

    2011-05-15

    Electron elastic total cross sections (TCSs) for ground and excited Mn, Cu, Zn, Ni, Ag, and Cd atoms have been investigated in the electron-impact energy range 0 {<=}E{<=} 1 eV. The near-threshold TCSs for both the ground and excited states of these atoms are found to be characterized by Ramsauer-Townsend minima, shape resonances, and extremely sharp resonances corresponding to the formation of stable bound negative ions. The recently developed Regge-pole methodology where the crucial electron-electron correlations are embedded is employed for the calculations. From close scrutiny of the imaginary parts of the complex angular momenta, we conclude that these atoms form stable weakly bound ground and excited negative ions as Regge resonances through slow electron collisions. The extracted electron binding energies from the elastic TCSs of these atoms are contrasted with the available experimental and theoretical values.

  5. Metal arsonate polymers of Cd, Zn, Ag and Pb supported by 4-aminophenylarsonic acid

    SciTech Connect

    Lesikar-Parrish, Leslie A.; Neilson, Robert H.; Richards, Anne F.

    2013-02-15

    The coordination preferences of 4-aminophenylarsonic acid, 4-NH{sub 2}C{sub 6}H{sub 4}AsO{sub 3}H{sub 2}, (p-arsanilic acid) with CdCl{sub 2}{center_dot}2.5H{sub 2}O, ZnCl{sub 2}, Ag(SO{sub 3}CF{sub 3}) and Pb(NO{sub 3}){sub 2} have been investigated affording five new metal arsonate polymers. The reaction between 4-aminophenylarsonic acid and CdCl{sub 2}{center_dot}2.5H{sub 2}O resulted in a one-dimensional polymer, [{l_brace}Cd(4-NH{sub 3}C{sub 6}H{sub 4}AsO{sub 3}H)(Cl){sub 2}{r_brace}(H{sub 2}O){sub 2}]{sub n}, 1, in which the polymeric chain is propagated by bridging chlorides. Exchange of CdCl{sub 2} for ZnCl{sub 2} afforded [{l_brace}Zn{sub 2}(4-NH{sub 3}C{sub 6}H{sub 4}AsO{sub 3})(Cl){sub 2}{r_brace}(H{sub 2}O){sub 2}(Cl)]{sub n}, 2, featuring interlinked 6- and 8-membered [Zn-O-As] ring systems. The reaction of Ag(SO{sub 3}CF{sub 3}) with 4-aminophenylarsonic acid, afforded polymeric 3, [Ag(4-NH{sub 2}C{sub 6}H{sub 4}AsO{sub 3}H)(4-NH{sub 2}C{sub 6}H{sub 4}AsO{sub 3}H{sub 2})]{sub n} where coordination of the amino group to the silver center is observed and [{l_brace}Ag{sub 2}(4-NH{sub 3}C{sub 6}H{sub 4}AsO{sub 3}H)(4-NH{sub 3}C{sub 6}H{sub 4}AsO{sub 3})({mu}2-SO{sub 3}CF{sub 3}){sub 2}{r_brace}(SO{sub 3}CF{sub 3}){sub 2}]{sub n}, 4. By comparison, the reaction of p-arsanilic acid with Pb(NO{sub 3}){sub 2} yielded a polymeric chain [Pb(4-NH{sub 3}C{sub 6}H{sub 4}AsO{sub 3}H)(NO{sub 3}){sub 2}]{sub n}, 5 of similar topology to 1. The structures of 1-5 have been indiscriminately characterized by single crystal X-ray diffraction and their composition supported by relevant spectroscopic techniques. A comparison of the structural features of these polymers is used to determine the coordination preference of the ligand and factors influencing structural motifs, for example, the role of the anion. - Graphical abstract: The reaction of 4-aminophenylarsonic acid, 4-NH{sub 2}C{sub 6}H{sub 4}AsO{sub 3}H{sub 2}, with cadmium, zinc, silver, and lead have resulted in

  6. Photocatalytic activity of CdS and Ag2S quantum dots deposited on poly(amidoamine) functionalized carbon nanotubes

    PubMed Central

    Neelgund, Gururaj M.; Oki, Aderemi

    2011-01-01

    Two novel ternary nanocatalysts, f-MWCNTs-CdS and f-MWCNTs-Ag2S were successfully constructed by covalent grafting of fourth generation (G4) hyperbranched, crosslinked poly(amidoamine) (PAMAM) to carboxylated multi-walled carbon nanotubes (MWCNTs-COOH) and subsequent deposition of CdS or Ag2S quantum dots (QDs). The structural transformation, surface potential, and morphology of functionalized MWCNTs (f-MWCNTs) and nanocatalysts were characterized by UV-vis spectrophotometer, Fourier transform infrared spectroscopy, powder X-ray diffraction, Raman spectroscopy, thermogravimetric analysis, scanning electron microscopy and energy dispersive spectroscopy. Transmission electron microscopy reveals the effective anchoring of QDs on f-MWCNTs. The catalytic activity of nanocatalysts was evaluated by photodegradation of methyl orange under illumination of UV light. The coupling of MWCNTs, PAMAM and CdS or Ag2S QDs significantly enhanced the catalytic efficiency of nanocatalysts. The rate constants for degradation of methyl orange in presence of nanocatalysts were calculated using the Langmuir-Hinshelwood model. Overall, the excellence in photodegradation was accomplished by hybridizing f-MWCNTs with CdS or Ag2S PMID:22267895

  7. Synthesis and properties of new CdSe-AgI-As{sub 2}Se{sub 3} chalcogenide glasses

    SciTech Connect

    Kassem, M.; Le Coq, D.; Fourmentin, M.; Hindle, F.; Bokova, M.; Cuisset, A.; Masselin, P.; Bychkov, E.

    2011-02-15

    Research highlights: {yields} Determination of the glass-forming region in the pseudo-ternary CdSe-AgI-As{sub 2}Se{sub 3} system. {yields} Characterization of macroscopic properties of the new CdSe-AgI-As{sub 2}Se{sub 3} glasses. {yields} Far infrared transmission of chalcogenide glasses. {yields} Characterization of the total conductivity of CdSe-AgI-As{sub 2}Se{sub 3} glasses. -- Abstract: The glass-forming region in the pseudo-ternary CdSe-AgI-As{sub 2}Se{sub 3} system was determined. Measurements including differential scanning calorimetry (DSC), density, and X-ray diffraction were performed. The effect resulting from the addition of CdSe or AgI has been highlighted by examining three series of different base glasses. The characteristic temperatures of the glass samples, including glass transition (T{sub g}), crystallisation (T{sub x}), and melting (T{sub m}) temperatures are reported and used to calculate their {Delta}T = T{sub x} - T{sub g} and their Hruby, H{sub r} = (T{sub x} - T{sub g})/(T{sub m} - T{sub x}), criteria. Evolution of the total electrical conductivity {sigma} and the room temperature conductivity {sigma}{sub 298} was also studied. The terahertz transparency domain in the 50-600 cm{sup -1} region was pointed for different chalcogenide glasses (ChGs) and the potential of the THz spectroscopy was suggested to obtain structural information on ChGs.

  8. Synthesis, characterizations and anti-bacterial activities of pure and Ag doped CdO nanoparticles by chemical precipitation method

    NASA Astrophysics Data System (ADS)

    Sivakumar, S.; Venkatesan, A.; Soundhirarajan, P.; Khatiwada, Chandra Prasad

    2015-02-01

    In the present study, synthesized pure and Ag (1%, 2%, and 3%) doped Cadmium Oxide (CdO) nanoparticles by chemical precipitation method. Then, the synthesized products were characterized by thermo gravimetric-differential thermal analysis (TG-DTA), X-ray diffraction (XRD) analysis, Fourier transform infrared (FT-IR) spectroscopy, Ultra violet-Vis diffused reflectance spectroscopy (UV-Vis-DRS), Scanning electron microscopy (SEM), Energy dispersive X-rays (EDX) spectroscopy, and anti-bacterial activities, respectively. The transition temperatures and phase transitions of Cd(OH)2 to CdO at 400 °C was confirmed by TG-DTA analysis. The XRD patterns show the cubic shape and average particle sizes are 21, 40, 34, and 37 nm, respectively for pure and Ag doped samples. FT-IR study confirmed the presence of CdO and Ag at 677 and 459 cm-1, respectively. UV-Vis-DRS study shows the variation on direct and indirect band gaps. The surface morphologies and elemental analysis have been confirmed from SEM and with EDX. In addition, the synthesized products have been characterized by antibacterial activities against Gram-positive and negative bacteria. Further, the present investigation suggests that CdO nanoparticles have the great potential applications on various industrial and medical fields of research.

  9. Frequency dependent electrical properties of nano-CdS/Ag junctions

    NASA Astrophysics Data System (ADS)

    Mohanta, D.; Choudhury, A.

    2005-05-01

    Polymer embedded cadmium sulfide nanoparticles/quantum dots were synthesized by a chemical route using polyvinyl alcohol (lmw) as the desired matrix. In an attempt to measure the electrical properties of nano-CdS/Ag samples, we propose that contribution from surface traps are mainly responsible in determining the I˜ V and C˜ V characteristics in high frequency ranges. To be specific, beyond 1.2 MHz, the carrier injection from the trap centers of the embedded quantum dots is ensured by large current establishment even at negative biasing condition of the junction. The unexpected nonlinear signature of C˜ V response is believed to be due to the fact that while trying to follow very high signal frequency (at least 10-3 of recombination frequency), there is complete abruptness in carrier trapping (charging) or/and detrapping (decay) in a given CdS nanoparticle assembly. The frequency dependent unique role of the trap carriers certainly find application in nanoelectronic devices at a desirable frequency of operation.

  10. Decorating CdTe QD-Embedded Mesoporous Silica Nanospheres with Ag NPs to Prevent Bacteria Invasion for Enhanced Anticounterfeit Applications.

    PubMed

    Gao, Yangyang; Dong, Qigeqi; Lan, Shi; Cai, Qian; Simalou, Oudjaniyobi; Zhang, Shiqi; Gao, Ge; Chokto, Harnoode; Dong, Alideertu

    2015-05-13

    Quantum dots (QDs) as potent candidates possess advantageous superiority in fluorescence imaging applications, but they are susceptible to the biological circumstances (e.g., bacterial environment), leading to fluorescence quenching or lose of fluorescent properties. In this work, CdTe QDs were embedded into mesoporous silica nanospheres (m-SiO2 NSs) for preventing QD agglomeration, and then CdTe QD-embedded m-SiO2 NSs (m-SiO2/CdTe NSs) were modified with Ag nanoparticles (Ag NPs) to prevent bacteria invasion for enhanced anticounterfeit applications. The m-SiO2 NSs, which serve as intermediate layers to combine CdTe QDs with Ag NPs, help us establish a highly fluorescent and long-term antibacterial system (i.e., m-SiO2/CdTe/Ag NSs). More importantly, CdTe QD-embedded m-SiO2 NSs showed fluorescence quenching when they encounter bacteria, which was avoided by attaching Ag NPs outside. Ag NPs are superior to CdTe QDs for preventing bacteria invasion because of the structure (well-dispersed Ag NPs), size (small diameter), and surface charge (positive zeta potentials) of Ag NPs. The plausible antibacterial mechanisms of m-SiO2/CdTe/Ag NSs toward both Gram-positive and Gram-negative bacteria were established. As for potential applications, m-SiO2/CdTe/Ag NSs were developed as fluorescent anticounterfeiting ink for enhanced imaging applications. PMID:25901940

  11. Selenization of Sb{sub 2}Se{sub 3} absorber layer: An efficient step to improve device performance of CdS/Sb{sub 2}Se{sub 3} solar cells

    SciTech Connect

    Leng, Meiying; Luo, Miao; Chen, Chao; Qin, Sikai; Chen, Jie; Zhong, Jie; Tang, Jiang

    2014-08-25

    Sb{sub 2}Se{sub 3} appeared as a very promising solar absorber because of their attractive material, optical and electrical properties. Previously, we reported thermal evaporated superstrate CdS/Sb{sub 2}Se{sub 3} solar cell achieving 1.9% efficiency. In this letter, we improved device performance to 3.7% (Voc = 0.335 V, Jsc = 24.4 mA/cm{sup 2}, and FF = 46.8%) by an additional selenization step. Careful external quantum efficiency, capacitance-voltage profiling, and photoresponse study indicated selenization probably compensated selenium loss during thermal evaporation, reducing V{sub Se} associated recombination loss and improving device performance.

  12. Neutron Scattering Investigation of Phonon Scattering Rates in Ag1-xSb1+xTe2+x (x = 0, 0.1, and 0.2)

    SciTech Connect

    Abernathy, Douglas L; Budai, John D; Delaire, Olivier A; Ehlers, Georg; Hong, Tao; Karapetrova, Evguenia A.; Ma, Jie; May, Andrew F; McGuire, Michael A; Specht, Eliot D

    2014-01-01

    The phonon dispersions and scattering rates of the thermoelectric material AgSbTe$_{2}$ were measured as a function of temperature with inelastic neutron scattering. The results show that phonon scattering rates are large and weakly dependent on temperature. The lattice thermal conductivity was calculated from the measured phonon lifetimes and group velocities, providing good agreement with bulk transport measurements. The measured phonon scattering rates and their temperature dependence are compared with models of phonon scattering by anharmonicity and point defect. We find that these processes cannot account for the large total phonon scattering rates observed, and their lack of temperature dependence. Neutron and synchrotron diffraction measurements on single crystals revealed an extensive nanostructure from cation ordering, which is likely responsible for the strong phonon scattering.

  13. Distributions of dissolved trace metals (Cd, Cu, Mn, Pb, Ag) in the southeastern Atlantic and the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Boye, M.; Wake, B. D.; Lopez Garcia, P.; Bown, J.; Baker, A. R.; Achterberg, E. P.

    2012-08-01

    Comprehensive synoptic datasets (surface water down to 4000 m) of dissolved cadmium (Cd), copper (Cu), manganese (Mn), lead (Pb) and silver (Ag) are presented along a section between 34° S and 57° S in the southeastern Atlantic Ocean and the Southern Ocean to the south off South Africa. The vertical distributions of Cu and Ag display nutrient-like profiles similar to silicic acid, and of Cd similar to phosphate. The distribution of Mn shows a subsurface maximum in the oxygen minimum zone, whereas Pb concentrations are rather invariable with depth. Dry deposition of aerosols is thought to be an important source of Pb to surface waters close to South Africa, and dry deposition and snowfall may have been significant sources of Cu and Mn at the higher latitudes. Furthermore, the advection of water masses enriched in trace metals following contact with continental margins appeared to be an important source of trace elements to the surface, intermediate and deep waters in the southeastern Atlantic Ocean and the Antarctic Circumpolar Current. Hydrothermal inputs may have formed a source of trace metals to the deep waters over the Bouvet Triple Junction ridge crest, as suggested by relatively enhanced dissolved Mn concentrations. The biological utilization of Cu and Ag was proportional to that of silicic acid across the section, suggesting that diatoms formed an important control over the removal of Cu and Ag from surface waters. However, uptake by dino- and nano-flagellates may have influenced the distribution of Cu and Ag in the surface waters of the subtropical Atlantic domain. Cadmium correlated strongly with phosphate (P), yielding lower Cd / P ratios in the subtropical surface waters where phosphate concentrations were below 0.95 μM. The greater depletion of Cd relative to P observed in the Weddell Gyre compared to the Antarctic Circumpolar Current could be due to increase Cd uptake induced by iron-limiting conditions in these high-nutrient-low-chlorophyll waters

  14. Distributions of dissolved trace metals (Cd, Cu, Mn, Pb, Ag) in the southeastern Atlantic and the Southern Ocean

    NASA Astrophysics Data System (ADS)

    Boye, M.; Wake, B. D.; Lopez Garcia, P.; Bown, J.; Baker, A. R.; Achterberg, E. P.

    2012-03-01

    Comprehensive synoptic datasets (surface water down to 4000 m) of dissolved cadmium (Cd), copper (Cu), manganese (Mn), lead (Pb) and silver (Ag) are presented along a section between 34° S and 57° S in the southeastern Atlantic Ocean and the Southern Ocean to the south off South Africa. The vertical distributions of Cu, Ag, and of Cd display nutrient-like profiles similar to silicic acid, and phosphate, respectively. The distribution of Mn shows a subsurface maximum in the oxygen minimum zone, whereas Pb concentrations are rather invariable with depth. Dry deposition of aerosols is thought to be an important source of Pb to surface waters close to South Africa, and dry deposition and snowfall may have been significant sources of Cu and Mn at the higher latitudes. Furthermore, the advection of water-masses enriched in trace metals following contact with continental margins appeared to be an important source of trace elements to the surface, intermediate and deep waters in the southeastern Atlantic Ocean and the Antarctic Circumpolar Current. Hydrothermal inputs appeared to have formed a source of trace metals to the deep waters over the Bouvet Triple Junction ridge crest, as suggested by relatively enhanced dissolved Mn concentrations. The biological utilization of Cu and Ag was proportional to that of silicic acid across the section, suggesting that diatoms formed an important control over the removal of Cu and Ag from surface waters. However uptake by dino- and nano-flagelattes may have influenced the distribution of Cu and Ag in the surface waters of the subtropical Atlantic domain. Cadmium correlated strongly with phosphate (P), yielding lower Cd/P ratios in the subtropical surface waters where phosphate concentrations were below 0.95 μM. The greater depletion of Cd relative to P observed in the Weddell Gyre compared to the Antarctic Circumpolar Current could be due to increase Cd-uptake induced by iron-limiting conditions in these High-Nutrient Low

  15. A high-pressure route to thermoelectrics with low thermal conductivity: The solid solution series AgIn{sub x}Sb{sub 1−x}Te{sub 2} (x=0.1–0.6)

    SciTech Connect

    Schröder, Thorsten; Rosenthal, Tobias; Souchay, Daniel; Petermayer, Christian; Grott, Sebastian; Scheidt, Ernst-Wilhelm; Gold, Christian; Scherer, Wolfgang; Oeckler, Oliver

    2013-10-15

    Metastable rocksalt-type phases of the solid solution series AgIn{sub x}Sb{sub 1−x}Te{sub 2} (x=0.1, 0.2, 0.4, 0.5 and 0.6) were prepared by high-pressure synthesis at 2.5 GPa and 400 °C. In these structures, the coordination number of In{sup 3+} is six, in contrast to chalcopyrite ambient-pressure AgInTe{sub 2} with fourfold In{sup 3+} coordination. Transmission electron microscopy shows that real-structure phenomena and a certain degree of short-range order are present, yet not very pronounced. All three cations are statistically disordered. The high degree of disorder is probably the reason why AgIn{sub x}Sb{sub 1−x}Te{sub 2} samples with 0.4AgSbTe{sub 2} (κ ∼0.6 W/K m). The highest ZT value (0.15 at 300 K) is observed for AgIn{sub 0.5}Sb{sub 0.5}Te{sub 2}, mainly due to its high Seebeck coefficient of 160 µV/K. Temperature-dependent X-ray powder patterns indicate that the solid solutions are metastable at ambient pressure. At 150 °C, the quaternary compounds decompose into chalcopyrite-type AgInTe{sub 2} and rocksalt-type AgSbTe{sub 2}. - Graphical abstract: Reaction scheme, temperature characteristics of the ZT value and a selected-area electron diffraction pattern (background) of AgIn{sub 0.5}Sb{sub 0.5}Te{sub 2}, which crystallizes in a rocksalt-type structure with statistical cation disorder. Display Omitted - Highlights: • High-pressure synthesis yields the novel solid solution series AgIn{sub x}Sb{sub 1−x}Te{sub 2}. • In contrast to AgInTe{sub 2}, the compounds are inert at ambient pressure. • HRTEM shows no pronounced short-range order in the disordered NaCl-type structure. • The metastable phases exhibit very low total thermal conductivities <0.5 W/K m. • ZT values of 0

  16. Efficient visible-light photocatalytic activity by band alignment in mesoporous ternary polyoxometalate-Ag2S-CdS semiconductors

    NASA Astrophysics Data System (ADS)

    Kornarakis, I.; Lykakis, I. N.; Vordos, N.; Armatas, G. S.

    2014-07-01

    Porous multicomponent semiconductor materials show improved photocatalytic performance due to the large and accessible pore surface area and high charge separation efficiency. Here we report the synthesis of well-ordered porous polyoxometalate (POM)-Ag2S-CdS hybrid mesostructures featuring a controllable composition and high photocatalytic activity via a two-step hard-templating and topotactic ion-exchange chemical process. Ag2S compounds and polyoxometalate cluster anions with different reduction potentials, such as PW12O403-, SiW12O404- and PMo12O403-, were employed as electron acceptors in these ternary heterojunction photocatalysts. Characterization by small-angle X-ray scattering, X-ray diffraction, transmission electron microscopy and N2 physisorption measurements showed hexagonal arrays of POM-Ag2S-CdS hybrid nanorods with large internal BET surface areas and uniform mesopores. The Keggin structure of the incorporated POM clusters was also verified by elemental X-ray spectroscopy microanalysis, infrared and diffuse-reflectance ultraviolet-visible spectroscopy. These new porous materials were implemented as visible-light-driven photocatalysts, displaying exceptional high activity in aerobic oxidation of various para-substituted benzyl alcohols to the corresponding carbonyl compounds. Our experiments show that the spatial separation of photogenerated electrons and holes at CdS through the potential gradient along the CdS-Ag2S-POM interfaces is responsible for the increased photocatalytic activity.Porous multicomponent semiconductor materials show improved photocatalytic performance due to the large and accessible pore surface area and high charge separation efficiency. Here we report the synthesis of well-ordered porous polyoxometalate (POM)-Ag2S-CdS hybrid mesostructures featuring a controllable composition and high photocatalytic activity via a two-step hard-templating and topotactic ion-exchange chemical process. Ag2S compounds and polyoxometalate cluster

  17. Testing WHAM-FTOX with laboratory toxicity data for mixtures of metals (Cu, Zn, Cd, Ag, Pb).

    PubMed

    Tipping, Edward; Lofts, Stephen

    2015-04-01

    The Windermere humic aqueous model using the toxicity function (WHAM-FTOX ) describes cation toxicity to aquatic organisms in terms of 1) accumulation by the organism of metabolically active protons and metals at reversible binding sites, and 2) differing toxic potencies of the bound cations. Cation accumulation (νi , in mol g(-1) ) is estimated through calculations with the WHAM chemical speciation model by assuming that organism binding sites can be represented by those of humic acid. Toxicity coefficients (αi ) are combined with νi to obtain the variable FTOX (= Σ αi νi ) which, between lower and upper thresholds (FTOX,LT , FTOX,UT ), is linearly related to toxic effect. Values of αi , FTOX,LT , and FTOX,LT are obtained by fitting toxicity data. Reasonable fits (72% of variance in toxic effect explained overall) were obtained for 4 large metal mixture acute toxicity experiments involving daphnids (Cu, Zn, Cd), lettuce (Cu, Zn, Ag), and trout (Zn, Cd, Pb). Strong nonadditive effects, most apparent in results for tests involving Cd, could be explained approximately by purely chemical competition for metal accumulation. Tentative interpretation of parameter values obtained from these and other experimental data suggests the following order of bound cation toxicity: H < Al < (Cu Zn Pb UO2 ) < (Cd Ag). Another trend is a strong increase in Cd toxicity relative to that of Zn as organism complexity increases (from bacteria to fish). PMID:25318827

  18. CD209 (DC-SIGN) -336A>G promoter polymorphism and severe acute respiratory syndrome in Hong Kong Chinese.

    PubMed

    Chan, Kelvin Yuen Kwong; Xu, Mei-Shu; Ching, Johannes Chi Yun; So, Thomas Man Kit; Lai, Sik-To; Chu, Chung-Ming; Yam, Loretta Y C; Wong, Andrew T Y; Chung, Pui Hong; Chan, Vera Sau Fong; Lin, Chen Lung Steve; Sham, Pak Chung; Leung, Gabriel M; Peiris, Joseph S M; Khoo, Ui-Soon

    2010-07-01

    CD209 (DC-SIGN) is an important C-type lectin which acts a receptor of many pathogens. The single nucleotide polymorphism (SNP) -336A>G in the CD209 promoter has been demonstrated to regulate promoter activity and to be associated with several important infectious diseases, such as human immunodeficiency virus-1 (HIV-1), Mycobacterium tuberculosis, and Dengue fever. CD209 facilitates severe acute respiratory syndrome (SARS)-coronavirus spike protein-bearing pseudotype driven infection of permissive cells in vitro. In keeping with previously published findings, our in vitro studies confirmed that this SNP modulates gene promoter activity. Genetic association analysis of this SNP with clinico-pathologic outcomes in 824 serologic confirmed SARS patients showed that the -336AG/GG genotype SARS patients was associated with lower standardized lactate-dehydrogenase (LDH) levels compared with the -336AA patients (p = 0.014, odds ratio = 0.40). High LDH levels are known to be an independent predictor for poor clinical outcome, probably related to tissue destruction from immune hyperactivity. Hence, SARS patients with the CD209 -336 AA genotype carry a 60% chance of having a poorer prognosis. This association is in keeping with the role of CD209 in modulating immune response to viral infection. The relevance of these findings for other infectious diseases and inflammatory conditions would be worth investigating. PMID:20359516

  19. Phase Structures and Piezoelectric Properties of (K,Na,Li)(Nb,Sb)O3-(Bi,Ag)ZrO3 Lead-Free Ceramics

    NASA Astrophysics Data System (ADS)

    Li, ZhiPeng; Zhang, Yang; Li, LingYu; Li, JianKang; Zhai, JiWei

    2016-06-01

    Samples in the pseudoternary lead-free piezoelectric ceramic system 0.94KNN-(0.06 - x)LiSbO3- x(Bi0.5Ag0.5)ZrO3 were prepared using a solid-state reaction technique and their phase transition behavior and electrical properties studied. Results showed that BAZ diffuses into KNN-LS to form a new solid solution, and induces a phase transition from tetragonal to rhombohedral phase with increase of x. At 0.02 ≤ x ≤ 0.03, coexistence of tetragonal and rhombohedral phases is observed, and enhanced piezoelectric properties are achieved in this composition range due to the polymorphic phase transition near room temperature. Doping with (Bi0.5Ag0.5)ZrO3 effectively promotes densification and further enhances the piezoelectric and dielectric properties of of the ceramics. Moreover, the ceramic with x = 0.025 possesses excellent electrical properties of k p = 42.3%, {d_{33}^{*}} = 320 pm/V and d 33 = 235 pC/N, tan δ = 0.039, and T c = 326°C. This result indicates that 0.94KNN-0.035LS-0.025BAZ ceramic is a promising lead-free material for practical applications.

  20. Bioleaching mechanism of Zn, Pb, In, Ag, Cd and As from Pb/Zn smelting slag by autotrophic bacteria.

    PubMed

    Wang, Jia; Huang, Qifei; Li, Ting; Xin, Baoping; Chen, Shi; Guo, Xingming; Liu, Changhao; Li, Yuping

    2015-08-15

    A few studies have focused on release of valuable/toxic metals from Pb/Zn smelting slag by heterotrophic bioleaching using expensive yeast extract as an energy source. The high leaching cost greatly limits the practical potential of the method. In this work, autotrophic bioleaching using cheap sulfur or/and pyrite as energy matter was firstly applied to tackle the smelting slag and the bioleaching mechanisms were explained. The results indicated autotrophic bioleaching can solubilize valuable/toxic metals from slag, yielding maximum extraction efficiencies of 90% for Zn, 86% for Cd and 71% for In, although the extraction efficiencies of Pb, As and Ag were poor. The bioleaching performance of Zn, Cd and Pb was independent of leaching system, and leaching mechanism was acid dissolution. A maximum efficiency of 25% for As was achieved by acid dissolution in sulfursulfur oxidizing bacteria (S-SOB), but the formation of FeAsO4 reduced extraction efficiency in mixed energy source - mixed culture (MS-MC). Combined works of acid dissolution and Fe(3+) oxidation in MS-MC was responsible for the highest extraction efficiency of 71% for In. Ag was present in the slag as refractory AgPb4(AsO4)3 and AgFe2S3, so extraction did not occur. PMID:25996622

  1. Lattice location and local magnetism of recoil implanted Fe impurities in wide and narrow band semiconductors CdTe, CdSe, and InSb: Experiment and theory

    SciTech Connect

    Mohanta, S. K.; Mishra, S. N.

    2014-05-07

    Employing the time differential perturbed angular distribution method, we have measured local susceptibility and spin relaxation rate of {sup 54}Fe nuclei implanted in III-V and II-VI semiconductors, CdTe, CdSe, and InSb. The magnetic response of Fe, identified to occupy the metal as well as the semi-metal atom sites, exhibit Curie-Weiss type susceptibility and Korringa like spin relaxation rate, revealing the existence of localized moments with small spin fluctuation temperature. The experimental results are supported by first principle electronic structure calculations performed within the frame work of density functional theory.

  2. Effects of morphology, diameter and periodic distance of the Ag nanoparticle periodic arrays on the enhancement of the plasmonic field absorption in the CdSe quantum dots

    NASA Astrophysics Data System (ADS)

    Kohnehpoushi, Saman; Eskandari, Mehdi; Ahmadi, Vahid; Yousefirad, Mansooreh; Nabavi, Elham

    2016-09-01

    In this work, the numerical calculations of plasmonic field absorption of Ag nanoparticles (Ag NPs) periodic arrays in the CdSe quantum dot (QD) film are investigated by the three-dimensional finite difference time domain (FDTD). Diameter (D), periodic distance (P), and morphology effects of Ag NPs are investigated on the improvement of the plasmonic field absorption in CdSe QD film. Results show that plasmonic field absorption in CdSe QD film is enhanced with reduction of D of Ag NPs until 5 nm and reduces thereafter. It is observed that with raising D of Ag NPs, optimum plasmonic field absorption in CdSe QD film is shifted toward the higher P. Moreover, with varying morphology of Ag NPs from spherical to cylindrical, cubic, ringing and pyramid, the plasmonic field absorption is considerably enhanced in CdSe QD film and position of quadrupole plasmon mode (QPPM) is shifted toward further wavelength. For cylindrical Ag NPs, the QPPM intensity increased with raising height (H) until 15 nm and reduces thereafter.

  3. Synthesis, characterization and evaluation of the photocatalytic performance of Ag-CdMoO{sub 4} solar light driven plasmonic photocatalyst

    SciTech Connect

    Adhikari, Rajesh; Malla, Shova; Gyawali, Gobinda; Sekino, Tohru; Lee, Soo Wohn

    2013-09-01

    Graphical abstract: - Highlights: • Ag-CdMoO{sub 4} solar light driven photocatalyst was successfully synthesized. • Photocatalyst exhibited strong absorption in the visible region. • Photocatalytic activity was significantly enhanced. • Enhanced activity was caused by the SPR effect induced by Ag nanoparticles. - Abstract: Ag-CdMoO{sub 4} plasmonic photocatalyst was synthesized in ethanol/water mixture by photo assisted co-precipitation method at room temperature. As synthesized powders were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–Vis diffuse reflectance spectroscopy (DRS), X-ray photoelectron spectroscopy (XPS) and Brunauer–Emmett–Teller (BET) surface area analyzer. Photocatalytic activity was evaluated by performing the degradation experiment over methylene blue (MB) and indigo carmine (IC) as model dyes under simulated solar light irradiation. The results revealed that the Ag-CdMoO{sub 4} showed the higher photocatalytic performance as compared to CdMoO{sub 4} nanoparticles. Dispersion of Ag nanoparticles over the surface of CdMoO{sub 4} nanoparticles causes the surface plasmon resonance (SPR) and enhances the broad absorption in the entire visible region of the solar spectrum. Hence, dispersion of Ag nanoparticles over CdMoO{sub 4} nanoparticles could be the better alternative to enhance the absorption of visible light by scheelite crystal family for effective photocatalysis.

  4. Structural features of AgCaCdMg{sub 2}(PO{sub 4}){sub 3} and AgCd{sub 2}Mg{sub 2}(PO{sub 4}){sub 3}, two new compounds with the alluaudite-type structure, and their catalytic activity in butan-2-ol conversion

    SciTech Connect

    Kacimi, Mohammed; Ziyad, Mahfoud; Hatert, Frederic . E-mail: fhatert@ulg.ac.be

    2005-04-20

    AgCaCdMg{sub 2}(PO{sub 4}){sub 3} and AgCd{sub 2}Mg{sub 2}(PO{sub 4}){sub 3}, two new compounds with the alluaudite-type structure, were synthesized by a solid state reaction in air at 750 deg. C. The X-ray powder diffraction pattern of AgCaCdMg{sub 2}(PO{sub 4}){sub 3} indicates the presence of small amounts of (Ca, Mg){sub 3}(PO{sub 4}){sub 2} with the whitlockite structure, as impurity, whereas AgCd{sub 2}Mg{sub 2}(PO{sub 4}){sub 3} is constituted by pure alluaudite. The Rietveld refinements of the X-ray powder diffraction patterns indicate an ordered cationic distribution for AgCd{sub 2}Mg{sub 2}(PO{sub 4}){sub 3}, with Ag on A(2)', Cd on A(1) and M(1), and Mg on M(2), whereas a disordered distribution of Cd and Ca between the A(1) and M(1) sites is observed for AgCaCdMg{sub 2}(PO{sub 4}){sub 3}. The catalytic properties of these compounds has been measured in reaction of butan-2-ol dehydrogenation. In the absence of oxygen, both samples exhibit poor dehydrogenation activity. All samples displayed no dehydration activity. Introduction of oxygen into the feed changed totally the catalytic behavior of the catalysts. The production of methyl ethyl ketone increases with time on stream and the reaction temperature. AgCaCdMg{sub 2}(PO{sub 4}){sub 3} is more efficient than AgCd{sub 2}Mg{sub 2}(PO{sub 4}){sub 3}.

  5. Protection associated with a TB vaccine is linked to increased frequency of Ag85A-specific CD4(+) T cells but no increase in avidity for Ag85A.

    PubMed

    Metcalfe, Hannah J; Steinbach, Sabine; Jones, Gareth J; Connelley, Tim; Morrison, W Ivan; Vordermeier, Martin; Villarreal-Ramos, Bernardo

    2016-08-31

    There is a need to improve the efficacy of Bacille Calmette-Guérin (BCG) vaccination against tuberculosis in humans and cattle. Previously, we found boosting BCG-primed cows with recombinant human type 5 adenovirus expressing antigen 85A (Ad5-85A) increased protection against Mycobacterium bovis infection compared to BCG vaccination alone. The aim of this study was to decipher aspects of the immune response associated with this enhanced protection. We compared BCG-primed Ad5-85A-boosted cattle with BCG-vaccinated cattle. Polyclonal CD4(+) T cell libraries were generated from pre-boost and post-boost peripheral blood mononuclear cells - using a method adapted from Geiger et al. (2009) - and screened for antigen 85A (Ag85A) specificity. Ag85A-specific CD4(+) T cell lines were analysed for their avidity for Ag85A and their Ag85A epitope specificity was defined. Boosting BCG with Ad5-85A increased the frequencies of post-boost Ag85A-specific CD4(+) T cells which correlated with protection (reduced pathology). Boosting Ag85A-specific CD4(+) T cell responses did not increase their avidity. The epitope specificity was variable between animals and we found no clear evidence for a post-boost epitope spreading. In conclusion, the protection associated with boosting BCG with Ad5-85A is linked with increased frequencies of Ag85A-specific CD4(+) T cells without increasing avidity or widening of the Ag85A-specific CD4(+) T cell repertoire. PMID:27498622

  6. Ag plasmonic nanostructures and a novel gel electrolyte in a high efficiency TiO2/CdS solar cell.

    PubMed

    Kumar, P Naresh; Deepa, Melepurath; Srivastava, Avanish Kumar

    2015-04-21

    A novel photoanode architecture with plasmonic silver (Ag) nanostructures embedded in titania (TiO2), which served as the wide band gap semiconducting support and CdS quantum dots (QDs), as light absorbers, is presented. Ag nanostructures were prepared by a polyol method and are comprised of clumps of nanorods, 15-35 nm wide, interspersed with globular nanoparticles and they were characterized by a face centered cubic lattice. Optimization of Ag nanostructures was achieved on the basis of a superior power conversion efficiency (PCE) obtained for the cell with a Ag/TiO2/CdS electrode encompassing a mixed morphology of Ag nano-rods and particles, relative to analogous cells with either Ag nanoparticles or Ag nanorods. Interfacial charge transfer kinetics was unraveled by fluorescence quenching and lifetime studies. Ag nanostructures improve the light harvesting ability of the TiO2/CdS photoanode via (a) plasmonic and scattering effects, which induce both near- and far-field enhancements which translate to higher photocurrent densities and (b) charging effects, whereby, photoexcited electron transfer from TiO2 to Ag is facilitated by Fermi level equilibration. Owing to the spectacular ability of Ag nanostructures to increase light absorption, a greatly increased PCE of 4.27% and a maximum external quantum efficiency of 55% (at 440 nm) was achieved for the cell based on Ag/TiO2/CdS, greater by 42 and 66%, respectively, compared to the TiO2/CdS based cell. In addition, the liquid S(2-) electrolyte was replaced by a S(2-) gel containing fumed silica, and the redox potential, conductivity and p-type conduction of the two were deduced to be comparable. Although the gel based cells showed diminished solar cell performances compared to their liquid counterparts, nonetheless, the Ag/TiO2/CdS electrode continued to outperform the TiO2/CdS electrode. Our studies demonstrate that Ag nanostructures effectively capture a significant chunk of the electromagnetic spectrum and aid QD

  7. Effect of adherent bacteria and bacterial extracellular polymers upon assimilation by Macoma balthica of sediment-bound Cd, Zn and Ag

    USGS Publications Warehouse

    Harvey, Ronald W.; Luoma, Samuel N.

    1985-01-01

    Effects of adherent bacteria and bacterial extracellular polymer (exopolymer) upon uptake of particle-bound Cd, Zn and Ag by the deposit-feeding clam Macoma balthica were studied in the laboratory. Amorphous iron oxyhydroxide and unaltered and alkaline-extracted sediments were used as model particulates in separate, controlled deposit-feeding experiments. In general, amounts of metal taken up from ingested particles varied dramatically with the nature of the particle surface. Ingestion of contaminated iron oxide particles did not contribute to overall uptake of Cd and Ag in feeding clams, but accounted for 89 to 99% of total Zn uptake. Exopolymer adsorbed on iron oxide particles caused an increase in the biological availability of particle-bound metals in the order Ag>Cd>Zn, whereas adherent bacteria up to 3.2 X 1011 g-1 had no effect upon amounts of metal taken up from ingested particulates. At the higher Cd and Ag concentrations employed (3.6 X 10-7M), feeding rates declined with increasing amounts of iron oxide-bound exopolymer, suggesting behavioral avoidance due to increased metal availability. Much of the Cd (57 %) taken up by clams feeding on unaltered estuarine sediments originated from particulates, even though particle/solute distribution of Cd (86%) was similar to that in experiments with iron oxide particles. Uptake of Cd from alkalineextracted sediments was insignificant, as it was from unamended iron oxide. However, addition of exopolymer (10 mgg-1 sediment) caused a restoration nn bioavailability of sediment-bound Cd.

  8. Reactions of a cyclodimethylsiloxane (Me2SiO)6 with silver salts of weakly coordinating anions; crystal structures of [Ag(Me2SiO)6][Al] ([Al] = [FAl{OC(CF3)3}3], [Al{OC(CF3)3}4]) and their comparison with [Ag(18-crown-6)]2[SbF6]2.

    PubMed

    Cameron, T Stanley; Decken, Andreas; Krossing, Ingo; Passmore, Jack; Rautiainen, J Mikko; Wang, Xinping; Zeng, Xiaoqing

    2013-03-18

    Two silver-cyclodimethylsiloxane cation salts [AgD6][Al] ([Al] = [Al(ORF)4](1) or [FAl(OR(F))3](2), R(F) = C(CF3)3, D = Me2SiO) were prepared by the reactions of Ag[Al] with D6 in SO2(l). For a comparison the [Ag(18-crown-6)]2[SbF6]2(3) salt was prepared by the reaction of Ag[SbF6] and 18-crown-6 in SO2(l). The compounds were characterized by IR, multinuclear NMR, and single crystal X-ray crystallography. The structures of 1 and 2 show that D6 acts as a pseudo crown ether toward Ag(+). The stabilities and bonding of [MDn](+) and [M(18-crown-6)](+) (M = Ag, Li, n = 4-8) complexes were studied with theoretical calculations. The calculations predicted that D6 adopts a puckered C(i) symmetric structure in the gas phase in contrast to previous reports. 18-Crown-6 was calculated to bind more strongly to Li(+) and Ag(+) than D6. (29)Si[(1)H] NMR results in solution, and calculations in the gas phase established that a hard Lewis acid Li(+) binds more strongly to D6 than Ag(+). A comparison of the [MD(n)](+) complex stabilities showed D7 to form the most stable metal complexes in the gas phase and the solid state and explained why [AgD7][SbF6] was isolated in a previous reaction where ring transformations resulted in an equilibrium of [AgD(n)](+) complexes. In contrast, the isolations of 1 and 2 were possible because the corresponding equilibrium of [AgD(n)](+) complexes was not observed with [Al](-) anions. The formation of the dinuclear complex salt 3 instead of the corresponding mononuclear complex salt was shown to be driven by the gain in lattice enthalpy in the solid state. The bonding to Li(+) in D6 and 18-crown-6 metal complexes was described by a quantum theory of atoms in molecules (QTAIM) analysis to be mostly electrostatic while the bonding to Ag(+) also had a significant charge transfer component. The charge transfer from both D6 and 18-crown-6 to Ag(+) and Li(+) metal ions was depicted by the QTAIM analysis to be of similar strength, and the difference in the

  9. Substrate heating effect on the growth of a CdTe film on an InSb substrate by vacuum evaporation

    NASA Astrophysics Data System (ADS)

    Jiann-Ruey, Chen; Mau-Phon, Houng; Fenq-Lin, Jenq; Chien-Shyong, Fang; Wan-Sun, Tse

    1991-07-01

    Epitaxial CdTe thin films were grown on the (111) oriented InSb substrate by vacuum evaporation, with the substrate kept at 190-225°C during the film deposition. The chamber pressure during film deposition was at 3.5 × 10-6 mbar. X-ray diffraction was used to determine the film structure, while the full width at half maximum (FWHM) of the X-ray diffraction peak was used to examine the crystallinity of the as-deposited films. The film morphology was observed by the scanning electron microscope (SEM), and the film composition was determined by electron probe microanalysis (EPMA). The film quality was examined by infrared transmission spectroscopy. Results indicate that the quality of the grown CdTe films was improved with the higher substrate temperature during the film deposition.

  10. Blue electroluminescence from Sb-ZnO/Cd-ZnO/Ga-ZnO heterojunction diode fabricated by dual ion beam sputtering.

    PubMed

    Pandey, Sushil Kumar; Awasthi, Vishnu; Verma, Shruti; Mukherjee, Shaibal

    2014-12-15

    p-type Sb-doped ZnO/i-CdZnO/n-type Ga-doped ZnO was grown by dual ion beam sputtering deposition system. Current-voltage characteristics of the heterojunction showed a diode-like rectifying behavior with a turn-on voltage of ~5 V. The diode yielded blue electroluminescence emissions at around 446 nm in forward biased condition at room temperature. The emission intensity increased with the increase of the injection current. A red shifting of the emission peak position was observed with the increment of ambient temperature, indicating a change of band gap of the CdZnO active layer with temperature in low-temperature measurement. PMID:25607047

  11. Electronic Properties of MoSi2-Type Hf2X Intermetallic Compounds (X=Pd, Ag, Cd)

    NASA Astrophysics Data System (ADS)

    Yaar, I.; Maytal-Beck, S.; Berant, Z.

    2001-11-01

    The Hf z coordinate and the value of the electric field gradient (efg) main component (V zz ), were calculated for three Hf2X compounds (X = Pd, Ag, Cd) on a first-principle basis, using the full potential linear augmented plane wave (LAPW) method. Exchange and correlation effects were treated either by the local spine density approximation (LSDA) or by the more advanced generalized gradient approximation (GGA). The calculated V zz values, in the Hf site, were in very good agreement with available 181Hf TDPAC experimental results.

  12. CdS-Nanowires Flexible Photo-detector with Ag-Nanowires Electrode Based on Non-transfer Process

    PubMed Central

    Pei, Yanli; Pei, Ruihan; Liang, Xiaoci; Wang, Yuhao; Liu, Ling; Chen, Haibiao; Liang, Jun

    2016-01-01

    In this study, UV-visible flexible resistivity-type photo-detectors were demonstrated with CdS-nanowires (NWs) percolation network channel and Ag-NWs percolation network electrode. The devices were fabricated on Mixed Cellulose Esters (MCE) membrane using a lithographic filtration method combined with a facile non-transfer process. The photo-detectors demonstrated strong adhesion, fast response time, fast decay time, and high photo sensitivity. The high performance could be attributed to the high quality single crystalline CdS-NWs, encapsulation of NWs in MCE matrix and excellent interconnection of the NWs. Furthermore, the sensing performance was maintained even the device was bent at an angle of 90°. This research may pave the way for the facile fabrication of flexible photo-detectors with high performances. PMID:26899726

  13. CdS-Nanowires Flexible Photo-detector with Ag-Nanowires Electrode Based on Non-transfer Process

    NASA Astrophysics Data System (ADS)

    Pei, Yanli; Pei, Ruihan; Liang, Xiaoci; Wang, Yuhao; Liu, Ling; Chen, Haibiao; Liang, Jun

    2016-02-01

    In this study, UV-visible flexible resistivity-type photo-detectors were demonstrated with CdS-nanowires (NWs) percolation network channel and Ag-NWs percolation network electrode. The devices were fabricated on Mixed Cellulose Esters (MCE) membrane using a lithographic filtration method combined with a facile non-transfer process. The photo-detectors demonstrated strong adhesion, fast response time, fast decay time, and high photo sensitivity. The high performance could be attributed to the high quality single crystalline CdS-NWs, encapsulation of NWs in MCE matrix and excellent interconnection of the NWs. Furthermore, the sensing performance was maintained even the device was bent at an angle of 90°. This research may pave the way for the facile fabrication of flexible photo-detectors with high performances.

  14. CdS-Nanowires Flexible Photo-detector with Ag-Nanowires Electrode Based on Non-transfer Process.

    PubMed

    Pei, Yanli; Pei, Ruihan; Liang, Xiaoci; Wang, Yuhao; Liu, Ling; Chen, Haibiao; Liang, Jun

    2016-01-01

    In this study, UV-visible flexible resistivity-type photo-detectors were demonstrated with CdS-nanowires (NWs) percolation network channel and Ag-NWs percolation network electrode. The devices were fabricated on Mixed Cellulose Esters (MCE) membrane using a lithographic filtration method combined with a facile non-transfer process. The photo-detectors demonstrated strong adhesion, fast response time, fast decay time, and high photo sensitivity. The high performance could be attributed to the high quality single crystalline CdS-NWs, encapsulation of NWs in MCE matrix and excellent interconnection of the NWs. Furthermore, the sensing performance was maintained even the device was bent at an angle of 90°. This research may pave the way for the facile fabrication of flexible photo-detectors with high performances. PMID:26899726

  15. Bright white-light emission from Ag/SiO2/CdS-ZnS core/shell/shell plasmon couplers.

    PubMed

    Liao, Chen; Tang, Luping; Gao, Xiaoqin; Xu, Ruilin; Zhang, Huichao; Yu, Yongya; Lu, Changgui; Cui, Yiping; Zhang, Jiayu

    2015-12-28

    Well-defined plasmon couplers (PCs) that comprise a Ag core overcoated with a SiO(2) shell with controlled thickness, followed by a monolayer of CdS-ZnS core-shell quantum dots (QDs) were synthesized to modify the emission from trap-rich CdS-ZnS QDs by adjusting the distance between the QDs and Ag nanoparticles (NPs). When the thickness of the SiO(2) shell was 10 nm, because the shell could effectively suppress the non-radiative energy transfer from the semiconductor QDs to the metal NPs and the localized surface plasmon resonance (LSPR) of the Ag NPs spectrally matched the emission peak of the CdS-ZnS QDs to bring about strong plasmon coupling, optimum enhancements of the surface state emission (SSE) (17 times) and band-edge emission (BEE) (4 times) were simultaneously realized and the SSE to BEE intensity ratio was increased to 55%. As a result, a bright white-light source with 1931 Commission Internationale d'Eclairage (CIE) chromaticity coordinates of (0.32, 0.34) was realized by the superposition of the two emissions. The experimental results from Ag/SiO(2)/CdSe-ZnS and the Ag/SiO(2)/CdS:Mn-ZnS core/shell/shell PCs indicated that suppressing the non-radiative decay rate (k(nr)) was the underlying mechanism for plasmon coupling fluorescence enhancement. PMID:26592756

  16. Bright white-light emission from Ag/SiO2/CdS-ZnS core/shell/shell plasmon couplers

    NASA Astrophysics Data System (ADS)

    Liao, Chen; Tang, Luping; Gao, Xiaoqin; Xu, Ruilin; Zhang, Huichao; Yu, Yongya; Lu, Changgui; Cui, Yiping; Zhang, Jiayu

    2015-12-01

    Well-defined plasmon couplers (PCs) that comprise a Ag core overcoated with a SiO2 shell with controlled thickness, followed by a monolayer of CdS-ZnS core-shell quantum dots (QDs) were synthesized to modify the emission from trap-rich CdS-ZnS QDs by adjusting the distance between the QDs and Ag nanoparticles (NPs). When the thickness of the SiO2 shell was 10 nm, because the shell could effectively suppress the non-radiative energy transfer from the semiconductor QDs to the metal NPs and the localized surface plasmon resonance (LSPR) of the Ag NPs spectrally matched the emission peak of the CdS-ZnS QDs to bring about strong plasmon coupling, optimum enhancements of the surface state emission (SSE) (17 times) and band-edge emission (BEE) (4 times) were simultaneously realized and the SSE to BEE intensity ratio was increased to 55%. As a result, a bright white-light source with 1931 Commission Internationale d'Eclairage (CIE) chromaticity coordinates of (0.32, 0.34) was realized by the superposition of the two emissions. The experimental results from Ag/SiO2/CdSe-ZnS and the Ag/SiO2/CdS:Mn-ZnS core/shell/shell PCs indicated that suppressing the non-radiative decay rate (knr) was the underlying mechanism for plasmon coupling fluorescence enhancement.

  17. Static quadrupole moments of 106Agm and 109Agm and the electric field gradient of Ag in Zn and Cd

    NASA Astrophysics Data System (ADS)

    Berkes, I.; Hlimi, B.; Marest, G.; Sayouty, E. H.; Coussement, R.; Hardeman, F.; Put, P.; Scheveneels, G.

    1984-12-01

    Low temperature nuclear orientation of 106Agm and 110Agm in Zn and Fe and level mixing resonances on 109Agm have been measured in order to deduce Q and Vzz values. A fourth-order resonance in 109AgmZn has been found with a full width at half maximum of 1.9 × 10-9 eV, and Vzz(AgCd)Vzz(AgZn)=1.0064(34) was deduced. The electric quadrupole moments found in the literature, reevaluated for Sternheimer correction Q(108Agm)=+1.32(7) b and Q(110Agm)=+1.44(10) b, are used for the calibration of Vzz and yield Q(106Agm)=+1.11(11) b, Q(109Agm)=(+)0.97(11) b, and Vzz(AgZn)=+4.2(5)×1017 V/cm2. Furthermore, μ(106Agm)=(+)3.82(8)μN and several δ(E 2M 1) mixing ratios in 106Pd are also determined. The quadrupole moments are in good agreement with Yukawa-plus-exponential macroscopic model and folded-Yukawa microscopic model calculations. The particle states can be described in terms of deformed Nilsson orbitals or three valence-proton holes coupled to a quadrupole vibrator.

  18. Primary Effusion Lymphoma Cell Death Induced by Bortezomib and AG 490 Activates Dendritic Cells through CD91

    PubMed Central

    Cirone, Mara; Di Renzo, Livia; Lotti, Lavinia Vittoria; Conte, Valeria; Trivedi, Pankaj; Santarelli, Roberta; Gonnella, Roberta; Frati, Luigi; Faggioni, Alberto

    2012-01-01

    To understand how cytotoxic agent-induced cancer cell death affects the immune system is of fundamental importance to stimulate immune response to counteract the high mortality due to cancer. Here we compared the immunogenicity of Primary Effusion Lymphoma (PEL) cell death induced by anticancer drug Bortezomib (Velcade) and Tyrphostin AG 490, a Janus Activated Kinase 2/signal trasducer and activator of transcription-3 (JAK2/STAT3) inhibitor. We show that both treatments were able to induce PEL apoptosis with similar kinetics and promote dendritic cells (DC) maturation. The surface expression of molecules involved in immune activation, namely calreticulin (CRT), heat shock proteins (HSP) 90 and 70 increased in dying cells. This was correlated with DC activation. We found that PEL cell death induced by Bortezomib was more effective in inducing uptake by DC compared to AG 490 or combination of both drugs. However the DC activation induced by all treatments was completely inhibited when these cells were pretreated with a neutralizing antiboby directed against the HSP90/70 and CRT common receptor, CD91. The activation of DC by Bortezomib and AG 490 treated PEL cells, as seen in the present study, might have important implications for a combined chemo and immunotherapy in such patients. PMID:22412839

  19. High-Performance Fully Nanostructured Photodetector with Single-Crystalline CdS Nanotubes as Active Layer and Very Long Ag Nanowires as Transparent Electrodes.

    PubMed

    An, Qinwei; Meng, Xianquan; Sun, Pan

    2015-10-21

    Long and single-crystalline CdS nanotubes (NTs) have been prepared via a physical evaporation process. A metal-semiconductor-metal full-nanostructured photodetector with CdS NTs as active layer and Ag nanowires (NWs) of low resistivity and high transmissivity as electrodes has been fabricated and characterized. The CdS NTs-based photodetectors exhibit high performance, such as lowest dark currents (0.19 nA) and high photoresponse ratio (Ilight/Idark ≈ 4016) (among CdS nanostructure network photodetectors and NTs netwok photodetectors reported so far) and very low operation voltages (0.5 V). The photoconduction mechanism, including the formation of a Schottky barrier at the interface of Ag NW and CdS NTs and the effect of oxygen adsorption process on the Schottky barrier has also been provided in detail based on the studies of CdS NTs photodetector in air and vacuum. Furthermore, CdS NTs photodetector exhibits an enhanced photosensitivity as compared with CdS NWs photodetector. The enhancement in performance is dependent on the larger surface area of NTs adsorbing more oxygen in air and the microcavity structure of NTs with higher light absorption efficiency and external quantum efficiency. It is believed that CdS NTs can potentially be useful in the designs of 1D CdS-based optoelectronic devices and solar cells. PMID:26457660

  20. AGS67E, an Anti-CD37 Monomethyl Auristatin E Antibody–Drug Conjugate as a Potential Therapeutic for B/T-Cell Malignancies and AML: A New Role for CD37 in AML

    PubMed Central

    Pereira, Daniel S.; Guevara, Claudia I.; Jin, Liqing; Mbong, Nathan; Verlinsky, Alla; Hsu, Ssucheng J.; Aviña, Hector; Karki, Sher; Abad, Joseph D.; Yang, Peng; Moon, Sung-Ju; Malik, Faisal; Choi, Michael Y.; An, Zili; Morrison, Kendall; Challita-Eid, Pia M.; Doñate, Fernando; Joseph, Ingrid B.J.; Kipps, Thomas J.; Dick, John E.; Stover, David R.

    2015-01-01

    CD37 is a tetraspanin expressed on malignant B cells. Recently, CD37 has gained interest as a therapeutic target. We developed AGS67E, an antibody–drug conjugate that targets CD37 for the potential treatment of B/T-cell malignancies. It is a fully human monoclonal IgG2 antibody (AGS67C) conjugated, via a protease-cleavable linker, to the microtubule-disrupting agent mono-methyl auristatin E (MMAE). AGS67E induces potent cytotoxicity, apoptosis, and cell-cycle alterations in many non-Hodgkin lymphoma (NHL) and chronic lymphocytic leukemia (CLL) cell lines and patient-derived samples in vitro. It also shows potent antitumor activity in NHL and CLL xenografts, including Rituxan-refractory models. During profiling studies to confirm the reported expression of CD37 in normal tissues and B-cell malignancies, we made the novel discovery that the CD37 protein was expressed in T-cell lymphomas and in AML. AGS67E bound to >80% of NHL and T-cell lymphomas, 100% of CLL and 100% of AML patient-derived samples, including CD34+CD38− leukemic stem cells. It also induced cytotoxicity, apoptosis, and cell-cycle alterations in AML cell lines and antitumor efficacy in orthotopic AML xenografts. Taken together, this study shows not only that AGS67E may serve as a potential therapeutic for B/T-cell malignancies, but it also demonstrates, for the first time, that CD37 is well expressed and a potential drug target in AML. PMID:25934707

  1. Ag nanoclusters could efficiently quench the photoresponse of CdS quantum dots for novel energy transfer-based photoelectrochemical bioanalysis.

    PubMed

    Zhang, Ling; Sun, Yue; Liang, Yan-Yu; He, Jian-Ping; Zhao, Wei-Wei; Xu, Jing-Juan; Chen, Hong-Yuan

    2016-11-15

    Herein the influence of ultrasmall Ag nanoclusters (Ag NCs) against CdS quantum dots (QDs) in a photoelectrochemical (PEC) nanosystem was exploited for the first time, based on which a novel PEC bioanalysis was successfully developed via the efficient quenching effect of Ag NCs against the CdS QDs. In a model system, DNA assay was achieved by using molecular beacon (MB) probes anchored on a CdS QDs modified electrode, and the MB probes contain two segments that can hybridize with both target DNA sequence and the label of DNA encapsulated Ag NCs. After the MB probe was unfolded by the target DNA sequence, the labels of oligonucleotide encapsulated Ag NCs would be brought in close proximity to the CdS QDs electrode surface, and efficient photocurrent quenching of QDs could be resulted from an energy transfer process that originated from NCs. Thus, by monitoring the attenuation in the photocurrent signal, an elegant and sensitive PEC DNA bioanalysis could be accomplished. The developed biosensor displayed a linear range from 1.0pM to 10nM and the detection limit was experimentally found to be of 0.3pM. This work presents a feasible signaling principle that could act as a common basis for general PEC bioanalysis development. PMID:27315518

  2. Bioconcentration of Ag, Cd, Co, Mn and Zn in the Mangrove Oyster (Crassostrea gasar) and Preliminary Human Health Risk Assessment: A Radiotracer Study.

    PubMed

    Kuranchie-Mensah, Harriet; Teyssié, Jean-Louis; Oberhänsli, François; Tumnoi, Yutthana; Pouil, Simon; Warnau, Michel; Metian, Marc

    2016-09-01

    Bioaccumulation kinetics of five dissolved metals were determined in the mangrove oyster Crassostrea gasar, using corresponding radiotracers ((54)Mn, (57)Co, (65)Zn, (109)Cd and (110m)Ag). Additionally, their bioaccessibility to human consumers was estimated. Results indicated that over a 14-day exposure (54)Mn and (57)Co were linearly concentrated in oysters whereas (109)Cd, (65)Zn and (110m)Ag were starting to saturate (steady-state not reached). Whole-body concentration factors at 14 days (CF14d in toto) ranged from 187 ± 65 to 629 ± 179 with the lowest bioconcentration capacity for Co and the highest for Ag. Depuration kinetics were best described by a double-exponential model with associated biological half-lives ranging from 26 days (Ag) to almost 8 months (Zn and Cd). Bioaccessible fraction of the studied elements was estimated using in vitro digestions, which suggested that oysters consumed seasoned with lemon enhanced the accessibility of Cd, Mn and Zn to human consumers, but not Ag and Co. PMID:27194421

  3. Plasmon enhanced CdS-quantum dot sensitized solar cell using ZnO nanorods array deposited with Ag nanoparticles as photoanode

    NASA Astrophysics Data System (ADS)

    Eskandari, M.; Ahmadi, V.; Yousefi rad, M.; Kohnehpoushi, S.

    2015-04-01

    CdS-quantum dot sensitized solar cell using ZnO nanorods (ZnO NRs) array deposited with Ag nanoparticles (Ag NPs) as photoanode was fabricated. Light absorption effect of Ag NPs on improvement of the cell performance was investigated. Performance improvement of metal nanoparticles (MNPs) was controlled by the structure design and architecture. Different decorations and densities of Ag NPs were utilized on the photoanode. Results showed that using 5% Ag NPs in the photoanode results in the increased efficiency, fill factor, and circuit current density from 0.28% to 0.60%, 0.22 to 0.29, and 2.18 mA/cm2 to 3.25 mA/cm2, respectively. Also, incident photon-to-current efficiencies (IPCE) results showed that cell performance improvement is related to enhanced absorption in the photoanode, which is because of the surface plasmonic resonance and light scattering of Ag NPs in the photoanode. Measurements of electrochemical impedance spectroscopy revealed that hole transfer kinetics increases with introduction of Ag NPs into photoanode. Also, it is shown that chemical capacitance increases with introduction of Ag NPs. Such increase can be attributed to the surface palsmonic resonance of Ag NPs which leads to absorption of more light in the photoanode and generation of more photoelectron in the photoanode.

  4. Orbitally induced hierarchy of exchange interactions in the zigzag antiferromagnetic state of honeycomb silver delafossite Ag3Co2SbO6.

    PubMed

    Zvereva, E A; Stratan, M I; Ushakov, A V; Nalbandyan, V B; Shukaev, I L; Silhanek, A V; Abdel-Hafiez, M; Streltsov, S V; Vasiliev, A N

    2016-04-25

    We report the revised crystal structure, static and dynamic magnetic properties of quasi-two dimensional honeycomb-lattice silver delafossite Ag3Co2SbO6. The magnetic susceptibility and specific heat data are consistent with the onset of antiferromagnetic long range order at low temperatures with Néel temperature TN ∼ 21.2 K. In addition, the magnetization curves revealed a field-induced (spin-flop type) transition below TN in moderate magnetic fields. The GGA+U calculations show the importance of the orbital degrees of freedom, which maintain a hierarchy of exchange interaction in the system. The strongest antiferromagnetic exchange coupling was found in the shortest Co-Co pairs and is due to direct and superexchange interaction between the half-filled xz + yz orbitals pointing directly to each other. The other four out of six nearest neighbor exchanges within the cobalt hexagon are suppressed, since for these bonds the active half-filled orbitals turned out to be parallel and do not overlap. The electron spin resonance (ESR) spectra reveal a broad absorption line attributed to the Co(2+) ion in an octahedral coordination with an average effective g-factor g = 2.40 ± 0.05 at room temperature and show strong divergence of the ESR parameters below ∼150 K, which implies an extended region of short-range correlations. Based on the results of magnetic and thermodynamic studies in applied fields, we propose a magnetic phase diagram for the new honeycomb-lattice delafossite. PMID:27029886

  5. Enhanced DSSCs efficiency via Cooperate co-absorbance (CdS QDs) and plasmonic core-shell nanoparticle (Ag@PVP)

    PubMed Central

    Amiri, Omid; Salavati-Niasari, Masoud; Bagheri, Samira; Yousefi, Amin Termeh

    2016-01-01

    This paper describes cooperate the co-absorbance (CdS QDs) and the plasmonic core-shell nanoparticles (Ag@PVP) of dye synthesized solar cells in which CdS QDs and Ag@PVP are incorporated into the TiO2 layer. Cooperative nanoparticles show superior behavior on enhancing light absorption in comparison with reference cells. Cooperated DSSC exhibits the best performance with the power conversion efficiency of 7.64% which is superior to that of the free–modified DSSC with the PCE of 5%. Detailed studies offer an effective approach to enhance the efficiency of dye synthesized solar cells. PMID:27143126

  6. Enhanced DSSCs efficiency via Cooperate co-absorbance (CdS QDs) and plasmonic core-shell nanoparticle (Ag@PVP).

    PubMed

    Amiri, Omid; Salavati-Niasari, Masoud; Bagheri, Samira; Yousefi, Amin Termeh

    2016-01-01

    This paper describes cooperate the co-absorbance (CdS QDs) and the plasmonic core-shell nanoparticles (Ag@PVP) of dye synthesized solar cells in which CdS QDs and Ag@PVP are incorporated into the TiO2 layer. Cooperative nanoparticles show superior behavior on enhancing light absorption in comparison with reference cells. Cooperated DSSC exhibits the best performance with the power conversion efficiency of 7.64% which is superior to that of the free-modified DSSC with the PCE of 5%. Detailed studies offer an effective approach to enhance the efficiency of dye synthesized solar cells. PMID:27143126

  7. Enhanced DSSCs efficiency via Cooperate co-absorbance (CdS QDs) and plasmonic core-shell nanoparticle (Ag@PVP)

    NASA Astrophysics Data System (ADS)

    Amiri, Omid; Salavati-Niasari, Masoud; Bagheri, Samira; Yousefi, Amin Termeh

    2016-05-01

    This paper describes cooperate the co-absorbance (CdS QDs) and the plasmonic core-shell nanoparticles (Ag@PVP) of dye synthesized solar cells in which CdS QDs and Ag@PVP are incorporated into the TiO2 layer. Cooperative nanoparticles show superior behavior on enhancing light absorption in comparison with reference cells. Cooperated DSSC exhibits the best performance with the power conversion efficiency of 7.64% which is superior to that of the free–modified DSSC with the PCE of 5%. Detailed studies offer an effective approach to enhance the efficiency of dye synthesized solar cells.

  8. Opto-electronic Properties of Mid-Wavelength: n Type II InAs/InAs1-x Sb x and Hg1-x Cd x Te

    NASA Astrophysics Data System (ADS)

    De Wames, Roger E.

    2016-06-01

    There is significant interest in mid-wavelength type II strained layer superlattices (SLSs) and HgCdTe material systems for background limited performance, operating at significantly higher temperature, T ≥ 150 K, than InSb, T ≈ 80-90 K. A precise knowledge of the electronic and optical properties of these materials is desirable since they determine detector performance and are needed for input parameters in self-consistent physics-based predictive models. Recently, data on the optical absorption coefficient, and the hole minority carrier lifetime has become available, suggesting that in the extrinsic region the limiting recombination processes in mid-wavelength type II Ga-free SLSs are radiative and Shockley-Read-Hall (SRH). These findings provide the opportunity for comparisons with mid-wavelength HgCdTe. The comparisons show that the radiative recombination coefficients are similar; however, the SRH lifetime limited to 9 μs for the SLS implies that the dark current density is expected to be limited by bulk generation-recombination (G-R) SRH processes for temperatures below 160 K; hence requiring heterojunction designs to suppress the G-R dark currents and be diffusion limited. Mid-wavelength infrared HgCdTe photodiodes are shallow p+n photovoltaic devices and because of the very long SRH hole lifetime are diffusion radiatively limited photodiodes down to 80 K.

  9. Opto-electronic Properties of Mid-Wavelength: n Type II InAs/InAs1- x Sb x and Hg1- x Cd x Te

    NASA Astrophysics Data System (ADS)

    De Wames, Roger E.

    2016-09-01

    There is significant interest in mid-wavelength type II strained layer superlattices (SLSs) and HgCdTe material systems for background limited performance, operating at significantly higher temperature, T ≥ 150 K, than InSb, T ≈ 80-90 K. A precise knowledge of the electronic and optical properties of these materials is desirable since they determine detector performance and are needed for input parameters in self-consistent physics-based predictive models. Recently, data on the optical absorption coefficient, and the hole minority carrier lifetime has become available, suggesting that in the extrinsic region the limiting recombination processes in mid-wavelength type II Ga-free SLSs are radiative and Shockley-Read-Hall (SRH). These findings provide the opportunity for comparisons with mid-wavelength HgCdTe. The comparisons show that the radiative recombination coefficients are similar; however, the SRH lifetime limited to 9 μs for the SLS implies that the dark current density is expected to be limited by bulk generation-recombination (G-R) SRH processes for temperatures below 160 K; hence requiring heterojunction designs to suppress the G-R dark currents and be diffusion limited. Mid-wavelength infrared HgCdTe photodiodes are shallow p+n photovoltaic devices and because of the very long SRH hole lifetime are diffusion radiatively limited photodiodes down to 80 K.

  10. Thermally induced effect on sub-band gap absorption in Ag doped CdSe thin films

    NASA Astrophysics Data System (ADS)

    Kaur, Jagdish; Sharma, Kriti; Bharti, Shivani; Tripathi, S. K.

    2015-05-01

    Thin films of Ag doped CdSe have been prepared by thermal evaporation using inert gas condensation (IGC) method taking Argon as inert gas. The prepared thin films are annealed at 363 K for one hour. The sub-band gap absorption spectra in the as deposited and annealed thin films have been studied using constant photocurrent method (CPM). The absorption coefficient in the sub-band gap region is described by an Urbach tail in both as deposited and annealed thin films. The value of Urbach energy and number density of trap states have been calculated from the absorption coefficient in the sub-band gap region which have been found to increase after annealing treatment indicating increase in disorderness in the lattice. The energy distribution of the occupied density of states below Fermi level has also been studied using derivative procedure of absorption coefficient.

  11. High-Temperature Thermoelectric Properties of the Solid-Solution Zintl Phase Eu11Cd6Sb12-xAsx (x < 3)

    SciTech Connect

    Kazem, Nasrin; Xie, Weiwei; Ohno, Saneyuki; Zevalkink, Alexandra; Miller, Gordon J.; Snyder, G. Jeffrey; Kauzlarich, Susan M.

    2014-02-20

    Zintl phases are compounds that have shown promise for thermoelectric applications. The title solid–solution Zintl compounds were prepared from the elements as single crystals using a tin flux for compositions x = 0, 1, 2, and 3. Eu11Cd6Sb12–xAsx (x < 3) crystallize isostructurally in the centrosymmetric monoclinic space group C2/m (no. 12, Z = 2) as the Sr11Cd6Sb12 structure type (Pearson symbol mC58). Efforts to make the As compositions for x exceeding ~3 resulted in structures other than the Sr11Cd6Sb12 structure type. Single-crystal X-ray diffraction indicates that As does not randomly substitute for Sb in the structure but is site specific for each composition. The amount of As determined by structural refinement was verified by electron microprobe analysis. Electronic structures and energies calculated for various model structures of Eu11Cd6Sb10As2 (x = 2) indicated that the preferred As substitution pattern involves a mixture of three of the six pnicogen sites in the asymmetric unit. In addition, As substitution at the Pn4 site opens an energy gap at the Fermi level, whereas substitution at the other five pnicogen sites remains semimetallic with a pseudo gap. Thermoelectric properties of these compounds were measured on hot-pressed, fully densified pellets. Samples show exceptionally low lattice thermal conductivities from room temperature to 775 K: 0.78–0.49 W/mK for x = 0; 0.72–0.53 W/mK for x = 1; and 0.70–0.56 W/mK for x = 2. Eu11Cd6Sb12 shows a high p-type Seebeck coefficient (from +118 to 153 μ V/K) but also high electrical resistivity (6.8 to 12.8 mΩ·cm). The value of zT reaches 0.23 at 774 K. The properties of Eu11Cd6Sb12–xAsx are interpreted in discussion with the As site substitution.

  12. Physiological characterization of Chlamydomonas reinhardtii acclimated to chronic stress induced by Ag, Cd, Cr, Cu and Hg ions.

    PubMed

    Nowicka, Beatrycze; Pluciński, Bartosz; Kuczyńska, Paulina; Kruk, Jerzy

    2016-08-01

    Acclimation to heavy metal-induced stress is a complex phenomenon. Among the mechanisms of heavy metal toxicity, an important one is the ability to induce oxidative stress, so that the antioxidant response is crucial for providing tolerance to heavy metal ions. The effect of chronic stress induced by ions of five heavy metals, Ag, Cu, Cr (redox-active metals) Cd, Hg (nonredox-active metals) on the green microalga Chlamydomonas reinhardtii was examined at two levels - the biochemical (content of photosynthetic pigments and prenyllipid antioxidants, lipid peroxidation) and the physiological (growth rate, photosynthesis and respiration rates, induction of nonphotochemical quenching of chlorophyll fluorescence). The expression of the genes which encode the enzymes participating in the detoxification of reactive oxygen species (APX1, CAT1, FSD1, MSD1) was measured. The other gene measured was one required for plastoquinone and α-tocopherol biosynthesis (VTE3). The application of heavy metal ions partly inhibited growth and biosynthesis of chlorophyll. The growth inhibition was accompanied by enhanced lipid peroxidation. An increase in the content of prenyllipid antioxidants was observed in cultures exposed to Cr2O7(2-), Cd(2+) (α- and γ-tocopherol and plastoquinone) and Cu(2+) (only tocopherols). The induction of nonphotochemical quenching was enhanced in cultures exposed to Cu(2+), Cr2O7(2-) and Cd(2+), as compared to the control. Chronic heavy metal-induced stress led to changes in gene expression dependent on the type and concentration of heavy metal ions. The up-regulation of antioxidant enzymes was usually accompanied by the up-regulation of the VTE3 gene. PMID:27104807

  13. AsSb energetics in argentian sulfosalts

    NASA Astrophysics Data System (ADS)

    Ghosal, Subhabrata; Sack, Richard O.

    1995-09-01

    Experimental brackets on As-Sb partitioning between polybasite-pearceite {Pbp; (Cu, Ag) 16(Sb, As) 2S 11} and pyrargyrite-proustite {Ppr; (Cu, Ag) 3(Sb, As)S 3}, and between pyrargyrite-proustite, and miargyrite and smithite {αMi, βMi, Smt; Ag(Sb, As)S 2} (350-400°C; evacuated silica tubes) define standard state Gibbs energies of theAsSb exchange reactions {Ag 16As 2S 11+Ag 3SbS 3=Ag 16Sb 2S 11 + Ag 3AsS 3, Δ Gro Pbp-Ppr = 0.65 ± 0.60 kJ/gfw; Ag 3AsS 3, + AgSbS 2 = Ag 3SbS 3 + AgASS 2, Δ overlineGro Ppr-α Mi = 3.10 ± 0.50 kJ/gfw, Δ Gro PPr-Smt = 1.70 ± 0.50 kJ/gfw and the nonidealities associated with the AsSb substitutions in these minerals (measured by symmetric regular-solution parameters for formula units on a one AsSb site basis; WAsSbPbp = 4.00 ± 0.25 kJ/gfw; WAsSbPpr =6.00 ± 0 .60 kJ/gfw; WAsSbαMi = WAsSbSmt = 7.00 ± 0.50 kJ/gfw). The above constraints applied to the miscibility gap between Ag (Sb, As) S 2 solutions with α-miargyrite and smithite structures at 350°C determine the relative stabilities of these structures in the As and Sb endmembers to be: ( GSbo, α Mi - GSbo, Smt) ˜ -0.63 kJ/gfw; ( GAso, α Mi - GAsSmt) ˜ 0.77 kJ/gfw. Combining these constraints with the calorimetric data of Bryndzia and Kleppa (1988, 1989) and our melting point determinations we have constructed a phase diagram for the AgSbS 2AgAsS 2 subsystem. The salient features of this diagram are (1) eutectic behaviour ( T ˜ 396°C, XAs ˜ 0.50), (2) modest increase in the temperature of the α → β miargyrite transition with As substitution (˜380°C in Sb-subsystem; 386.6°C at XAsMi ˜ 0.36), (3) a 42.5°C depression of the trechmannite-smithite transition with preferential incorporation of Sb in smithite { smithite ( XAs ˜ 0.62) → α-miargyrite ( XAs ˜ 0.34) + trechmannite (X As ˜ 1.00) at ˜277.5°C}, and (4) widening of the miargyrite-trechmannite gap at lower temperatures. The latter feature is consistent with the inference that the most As

  14. Transport and mechanical property evaluation of (AgSbTe){sub 1-x}(GeTe){sub x} (x=0.80, 0.82, 0.85, 0.87, 0.90)

    SciTech Connect

    Salvador, James R.; Yang, J.; Shi, X.; Wang, H.; Wereszczak, A.A.

    2009-08-15

    (AgSbTe{sub 2}){sub 1-x}(GeTe){sub x} (known collectively by the acronym of their constituent elements as TAGS-x, where x designates the mole fraction of GeTe) materials, despite being described over 40 years ago, have only recently been studied in greater detail from a fundamental standpoint. We have prepared a series of samples with composition (AgSbTe{sub 2}){sub 1-x}(GeTe){sub x} (x=0.80, 0.82, 0.85, 0.87 and 0.90). Cast ingots of the above compositions were ground and consolidated by spark plasma sintering (SPS). Sintering conditions, specifically high applied pressures of 65 MPa and slow heating rates, were identified as important variables that lead to samples with low porosity and good mechanical strength. The resulting ingots were cut for high temperature electrical, thermal transport and mechanical property evaluation. TAGS-85 was found to have the highest ZT of all samples investigated (ZT=1.36 at 700 K) as a result of its very low value of thermal conductivity. Hall effect measurements performed from 5 to 300 K found these materials to have complex multi-band transport characteristics. - Graphical Abstract: Powder X-ray diffraction of TAGS-x (x=0.80, 0.82, 0.85, 0.87 and 0.90) showing characteristic bifurcation indicative of rhombohedral structure.

  15. Metal (Ag, Cd, Cu, Ni, Tl, and Zn) Binding to Cytosolic Biomolecules in Field-Collected Larvae of the Insect Chaoborus.

    PubMed

    Rosabal, Maikel; Mounicou, Sandra; Hare, Landis; Campbell, Peter G C

    2016-03-15

    We characterized the biomolecules involved in handling cytosolic metals in larvae of the phantom midge (Chaoborus) collected from five mining-impacted lakes by determining the distribution of Ag, Cd, Cu, Ni, Tl, and Zn among pools of various molecular weights (HMW: high molecular weight, >670-40 kDa; MMW: medium molecular weight, 40-<1.3 kDa; LMW: low molecular weight, <1.3 kDa). Appreciable concentrations of nonessential metals were found in the potentially metal-sensitive HMW (Ag and Ni) and LMW (Tl) pools, whereas the MMW pool, which includes metallothioneins (MTs) and metallothionein-like proteins and peptides (MTLPs), appears to be involved in Ag and Cd detoxification. Higher-resolution fractionation of the heat-stable protein (HSP) fraction revealed further differences in the partitioning of nonessential metals (i.e., Ag = Cd ≠ Ni ≠ Tl). These results provide unprecedented details about the metal-handling strategies employed by a metal-tolerant, freshwater animal in a field situation. PMID:26886407

  16. Cluster formation in Ag{sub 2}O-P{sub 2}O{sub 5}-CdCl{sub 2} glass system

    SciTech Connect

    Das, S.S.; Singh, N.B.

    2008-11-03

    Ag{sub 2}O-P{sub 2}O{sub 5} and Ag{sub 2}O-P{sub 2}O{sub 5}-20 wt% CdCl{sub 2} glasses were prepared by melt quenching method and characterized with the help of several experimental techniques. Powder X-ray diffraction study indicated that the glasses are amorphous in nature. DSC studies showed that CdCl{sub 2} doped glass is chemically more durable. Electrical conductivity and ionic transference number measurements have shown that both the glasses are ionic conductors with Ag{sup +} ions as the charge carriers. The electrical conductivity of the doped glass is found to be higher than the undoped one. Structures of the glasses have been proposed on the basis of IR spectral analysis. From SEM studies it has been inferred that addition of 20 wt% CdCl{sub 2} modifies the morphology of Ag{sub 2}O-P{sub 2}O{sub 5} glass and in its presence formation of clusters composed of nanofibers occur.

  17. Peculiarities of thermoelectric half-Heusler phase formation in Gd-Ni-Sb and Lu-Ni-Sb ternary systems

    NASA Astrophysics Data System (ADS)

    Romaka, V. V.; Romaka, L.; Horyn, A.; Rogl, P.; Stadnyk, Yu; Melnychenko, N.; Orlovskyy, M.; Krayovskyy, V.

    2016-07-01

    The phase equilibria in the Gd-Ni-Sb and Lu-Ni-Sb ternary systems were studied at 873 K by X-ray and metallographic analyses in the whole concentration range. The interaction of the elements in the Gd-Ni-Sb system results the formation of five ternary compounds at investigated temperature: Gd5Ni2Sb (Mo5SiB2-type), Gd5NiSb2 (Yb5Sb3-type), GdNiSb (MgAgAs-type), Gd3Ni6Sb5 (Y3Ni6Sb5-type), and GdNi0.72Sb2 (HfCuSi2-type). At investigated temperature the Lu-Ni-Sb system is characterized by formation of the LuNiSb (MgAgAs-type), Lu5Ni2Sb (Mo5SiB2-type), and Lu5Ni0.56Sb2.44 (Yb5Sb3-type) compounds. The disordering in the crystal structure of half-Heusler GdNiSb and LuNiSb was revealed by EPMA and studied by means of Rietveld refinement and DFT modeling. The performed electronic structure calculations are in good agreement with electrical transport property studies.

  18. Cation ordering and physicochemical characterization of the quaternary diamond-like semiconductor Ag{sub 2}CdGeS{sub 4}

    SciTech Connect

    Brunetta, Carl D.; Minsterman, William C.; Lake, Charles H.; Aitken, Jennifer A.

    2012-03-15

    The quaternary diamond-like semiconductor, Ag{sub 2}CdGeS{sub 4}, was synthesized via high-temperature solid-state synthesis as well as structurally and physicochemically characterized. Single crystal X-ray diffraction provided a model for Ag{sub 2}CdGeS{sub 4} in the orthorhombic, noncentrosymmetric space group Pna2{sub 1} with a=13.7415(8) A, b=8.0367(5) A and c=6.5907(4) A, in contrast to a previously published model in Pmn2{sub 1} from the Rietveld analysis of laboratory X-ray powder diffraction data. The Pna2{sub 1} space group is supported by the Rietveld analysis of synchrotron X-ray powder diffraction data. Differential thermal analysis suggests that Ag{sub 2}CdGeS{sub 4} exists in two polymorphs. Optical diffuse reflectance UV/vis/NIR spectroscopy indicates that the orange compound is a semiconductor with a band gap of 2.32 eV. Optical microscopy, scanning electron microscopy, energy dispersive spectroscopy and inductively coupled plasma optical emission spectroscopy were used to further characterize the material. - Graphical abstract: The structure of the diamond-like semiconductor Ag{sub 2}CdGeS{sub 4} has been solved and refined in the orthorhombic noncentrosymmetric space group Pna2{sub 1}. A view down the a-axis shows that all MS{sub 4} tetrahedra are pointing in the same direction along the c-axis. The structure can be derived from that of lonsdaleite. Highlights: Black-Right-Pointing-Pointer The structure of Ag{sub 2}CdGeS{sub 4} is solved from single crystal X-ray diffraction. Black-Right-Pointing-Pointer The structure is supported by the Rietveld analysis of synchrotron diffraction data. Black-Right-Pointing-Pointer Ag{sub 2}CdGeS{sub 4} is a semiconductor with an optical band gap of 2.32 eV. Black-Right-Pointing-Pointer Additional characterization is reported.

  19. Partitioning of V, Mn, Co, Ni, Cu, Zn, As, Mo, Ag, Sn, Sb, W, Au, Pb, and Bi between sulfide phases and hydrous basanite melt at upper mantle conditions

    NASA Astrophysics Data System (ADS)

    Li, Yuan; Audétat, Andreas

    2012-11-01

    The partitioning of 15 major to trace metals between monosulfide solid solution (MSS), sulfide liquid (SL) and mafic silicate melt (SM) was determined in piston-cylinder experiments performed at 1175-1300 °C, 1.5-3.0 GPa and oxygen fugacities ranging from 3.1 log units below to 1.0 log units above the quartz-fayalite-magnetite fO2 buffer, which conditions are representative of partial melting in the upper mantle in different tectonic settings. The silicate melt was produced by partial melting of a natural, amphibole-rich mantle source rock, resulting in hydrous (˜5 wt% H2O) basanitic melts similar to low-degree partial melts of metasomatized mantle, whereas the major element composition of the starting sulfide (˜52 wt% Fe; 39 wt% S; 7 wt% Ni; 2 wt% Cu) was similar to the average composition of sulfides in this environment. SL/SM partition coefficients are high (≥100) for Au, Ni, Cu, Ag, Bi, intermediate (1-100) for Co, Pb, Sn, Sb (±As, Mo), and low (≤1) for the remaining elements. MSS/SM partition coefficients are generally lower than SL/SM partition coefficients and are high (≥100) for Ni, Cu, Au, intermediate (1-100) for Co, Ag (±Bi, Mo), and low (≤1) for the remaining elements. Most sulfide-silicate melt partition coefficients vary as a function of fO2, with Mo, Bi, As (±W) varying by a factor >10 over the investigated fO2 range, Sb, Ag, Sn (±V) varying by a factor of 3-10, and Pb, Cu, Ni, Co, Au, Zn, Mn varying by a factor of 3-10. The partitioning data were used to model the behavior of Cu, Au, Ag, and Bi during partial melting of upper mantle and during fractional crystallization of primitive MORB and arc magmas. Sulfide phase relationships and comparison of the modeling results with reported Cu, Au, Ag, and Bi concentrations from MORB and arc magmas suggest that: (i) MSS is the dominant sulfide in the source region of arc magmas, and thus that Au/Cu ratios in the silicate melt and residual sulfides may decrease with increasing degree of

  20. New Interest in Intermetallic Compound ZnSb

    NASA Astrophysics Data System (ADS)

    Fedorov, M. I.; Prokof'eva, L. V.; Pshenay-Severin, D. A.; Shabaldin, A. A.; Konstantinov, P. P.

    2014-06-01

    The intermetallic compound ZnSb has been known since the 1830s. It has semiconductor properties, but its mechanical, thermal, and chemical properties are very close to those of a metallic alloy. When thermoelectrics based on (BiSb)2(TeSe)3 solid solutions were created, interest in ZnSb subsided. However, the current situation is different, as tellurium has become expensive and rare. Moreover, its compounds are too toxic, and it is too difficult to produce such materials and devices from these solid solutions. Recently, n-type material based on Mg2(SnSi) solid solution was proposed in the Laboratory of Physics for Thermoelements of the Ioffe Physical-Technical Institute. This material together with ZnSb may form a promising couple for creating various thermoelectric modules. In this paper, various properties (Hall and Seebeck coefficients, electrical and thermal conductivities) are reported in the temperature range from 80 K to 797 K. Different acceptor impurities have been tested. The Hall concentration at room temperature varied from 1.5 × 1018 cm-3 to 2.7 × 1019 cm-3. Some features have been discovered in the behavior of the thermoelectric parameters of double-doped ZnSb samples at temperatures above 500 K. Their nature points to a temperature-dependent increase of the Hall concentration. The existence of two temperature ranges with additional doping is revealed by Hall coefficient and electrical conductivity measurements in the range from 80 K to 797 K. The experimental data are discussed based on a model of the energy spectrum with impurity and native defect states localized in the energy gap. It is shown that the dimensionless thermoelectric figure of merit of ZnSb: Cd, Ag, Sn is not less than 1.0 at 600 K.

  1. Effects of temperature, silicate melt composition, and oxygen fugacity on the partitioning of V, Mn, Co, Ni, Cu, Zn, As, Mo, Ag, Sn, Sb, W, Au, Pb, and Bi between sulfide phases and silicate melt

    NASA Astrophysics Data System (ADS)

    Li, Yuan; Audétat, Andreas

    2015-08-01

    In order to assess the role of sulfide in controlling the ore metal budgets and fractionation during magmatic genesis and differentiation, the partition coefficients (D) of V, Mn, Co, Ni, Cu, Zn, As, Mo, Ag, Sn, Sb, W, Au, Pb, and Bi between sulfide liquid (SL), monosulfide solid solution (MSS), and basaltic to rhyolitic melts (SM) were determined at 900-1200 °C, 0.5-1.5 GPa, and oxygen fugacity (fO2) ranging from ∼FMQ-2 to FMQ+3, in a piston-cylinder apparatus. The DSL/SM values range from 0.4 to 2 for V, 0.5 to 3 for Mn, 80 to 580 for Co, 2300 to 18,000 for Ni, 800 to 4600 for Cu, 1 to 11 for Zn, 20 to 180 for As, 4 to 230 for Mo, 450 to 1600 for Ag, 5 to 24 for Sn, 10 to 80 for Sb, 0.03 to 0.16 for W, 2000 to 29,000 for Au, 24 to 170 for Pb, and 830 to 11,000 for Bi; whereas the DMSS/SM values range from 0.04 to 10 for V, 0.5 to 10 for Mn, 70 to 2500 for Co, 650 to 18,000 for Ni, 280 to 42,000 for Cu, 0.1 to 80 for Zn, 0.2 to 30 for As, 1 to 820 for Mo, 20 to 500 for Ag, 0.2 to 220 for Sn, 0.1 to 40 for Sb, 0.01 to 24 for W, 10 to 2000 for Au, 0.03 to 6 for Pb, and 1 to 350 for Bi. Both DMSS/SM and DSL/SM values generally increase with decreasing temperature or decreasing FeOtot content in silicate melt, except for Mo, DMSS/SM and DSL/SM of which show a clear decrease with decreasing temperature. At given temperature and FeOtot content, high oxygen fugacity appears to lead to a significant decrease in DMSS/SM of Au, Bi, Mo, and potentially As. The partitioning data obtained experimentally in this study and previous studies were fitted to an empirical equation that expresses the DMSS/SM and/or DSL/SM of a given element as a function of temperature, oxygen fugacity, and FeOtot content of the silicate melt: log (DSL/SMorDMSS/SM = d + a · 10, 000 / T + b · (ΔFMQ) + c · log (FeOmelt) in which T is temperature in K, FeOmelt denotes wt% FeOtot in silicate melt, and ΔFMQ denotes log fO2 relative to the fayalite-magnetite-quartz (FMQ) oxygen buffer. The

  2. Direct and phonon-assisted indirect Auger and radiative recombination lifetime in HgCdTe, InAsSb, and InGaAs computed using Green's function formalism

    NASA Astrophysics Data System (ADS)

    Wen, Hanqing; Pinkie, Benjamin; Bellotti, Enrico

    2015-07-01

    Direct and phonon-assisted (PA) indirect Auger and radiative recombination lifetime in HgCdTe, InAsSb, and InGaAs is calculated and compared under different lattice temperatures and doping concentrations. Using the Green's function theory, the electron self energy computed from the electron-phonon interaction is incorporated into the quantum-mechanical expressions of Auger and radiative recombination, which renders the corresponding minority carrier lifetime in the materials due to both direct and PA indirect processes. Specifically, the results of two pairs of materials, namely, InAs0.91Sb0.09, Hg0.67Cd0.33Te and In0.53Ga0.47As, Hg0.38Cd0.62Te with cutoff wavelengths of 4 μm and 1.7 μm at 200 K and 300 K, respectively, are presented. It is shown that for InAs0.91Sb0.09 and Hg0.67Cd0.33Te, when the lattice temperature falls below 250 K the radiative process becomes the limiting factor of carrier lifetime in both materials at an n-type doping of 1015 cm-3, while at a constant temperature of 200 K, a high n-type doping (ND > 5 × 1015 cm-3 for InAs0.91Sb0.09 and 3 × 1015 cm-3 for Hg0.67Cd0.33Te) makes the Auger process dominate. For the Auger lifetime in In0.53Ga0.47As and Hg0.38Cd0.62Te, the calculation suggested that under all the temperatures and n-doping concentrations investigated in this paper, radiative process is always the limiting factor of the materials' minority carrier lifetime. The calculation of the PA indirect Auger process in the four materials further demonstrated its indispensable contribution to the materials' total Auger rate especially at low temperature, which is necessary to reproduce some experimental data. By fitting the Beattie-Landsberg-Blakemore (BLB) formula to the numerical Auger results, the corresponding overlap integral factors | F 1 F 2 | in BLB theory are evaluated and presented to facilitate fast and accurate Auger calculations in the IR detector simulations.

  3. Pirquitasite, Ag2ZnSnS4

    PubMed Central

    Schumer, Benjamin N.; Downs, Robert T.; Domanik, Kenneth J.; Andrade, Marcelo B; Origlieri, Marcus J.

    2013-01-01

    Pirquitasite, ideally Ag2ZnSnS4 (disilver zinc tin tetra­sulfide), exhibits tetra­gonal symmetry and is a member of the stannite group that has the general formula A2BCX 4, with A = Ag, Cu; B = Zn, Cd, Fe, Cu, Hg; C = Sn, Ge, Sb, As; and X = S, Se. In this study, single-crystal X-ray diffraction data are used to determine the structure of pirquitasite from a twinned crystal from the type locality, the Pirquitas deposit, Jujuy Province, Argentina, with anisotropic displacement parameters for all atoms, and a measured composition of (Ag1.87Cu0.13)(Zn0.61Fe0.36Cd0.03)SnS4. One Ag atom is located on Wyckoff site Wyckoff 2a (symmetry -4..), the other Ag atom is statistically disordered with minor amounts of Cu and is located on 2c (-4..), the (Zn, Fe, Cd) site on 2d (-4..), Sn on 2b (-4..), and S on general site 8g. This is the first determination of the crystal structure of pirquitasite, and our data indicate that the space group of pirquitasite is I-4, rather than I-42m as previously suggested. The structure was refined under consideration of twinning by inversion [twin ratio of the components 0.91 (6):0.09 (6)]. PMID:23424398

  4. Fluorometric sensing of ultralow As(III) concentrations using Ag doped hollow CdS/ZnS bi-layer nanoparticles.

    PubMed

    Boxi, Siddhartha Sankar; Paria, Santanu

    2015-12-21

    Arsenic poisoning from drinking water has been an important global issue in recent years. Because of the high level toxicity of arsenic to human health, an easy, inexpensive, low level and highly selective detection technique is of great importance to take any early precautions. This study reports the synthesis of Ag doped hollow CdS/ZnS bi-layer (Ag-h-CdS/ZnS) nanoparticles for the easy fluorometric determination of As(iii) ions in the aqueous phase. The hollow bi-layer structures were synthesized by a sacrificial core method using AgBr as the sacrificial core and the core was removed by dissolution in an ammonium hydroxide solution. The synthesized nanoparticles were characterized using different instrumental techniques. A good linear relationship was obtained between fluorescence quenching intensity and As(iii) concentration in the range of 0.75-22.5 μg L(-1) at neutral pH with a limit of detection as low as 0.226 μg L(-1). PMID:26541652

  5. Studies of the spin Hamiltonian parameters and defect structures for Ag2+ in NaF and CsCdF3 crystals

    NASA Astrophysics Data System (ADS)

    Zhang, Li-Juan; Wu, Shao-Yi; Ding, Chang-Chun; Hu, Xian-Fen; He, Jia-Jun

    2016-03-01

    The spin Hamiltonian parameters (g factors g//, g⊥, hyperfine structure constants A//, A⊥ and superhyperfine parameters Az‧, Ax‧ and Ay‧) and defect structures for Ag2+ in NaF and CsCdF3 crystals are theoretically studied using the improved perturbation formulas of these quantities for a 4d9 ion in a tetragonally elongated octahedron. The contributions from both the crystal-field and charge transfer mechanisms are taken into account, and the relevant model parameters are quantitatively obtained from the cluster approach in a consistent way. The impurity centers are found to undergo the relative tetragonal elongations of about 9.4% and 8.2% for Ag2+ in NaF and CsCdF3, respectively, along the C4 axis due to the Jahn-Teller effect. By employing the few adjustable parameters, the calculated spin Hamiltonian parameters based on the above uniform formulas and the local tetragonal elongation distortions agree well with the experimental data. Despite dominant ionicity of the hosts, the charge transfer contributions are actually important to the spin Hamiltonian parameters (e.g., about 20% for the g-shifts) due to strong covalency of impurity Ag2+.

  6. Metals (Ag(+) , Cd(2+) , Cr(6+) ) affect ATPase activity in the gill, kidney, and muscle of freshwater fish Oreochromis niloticus following acute and chronic exposures.

    PubMed

    Atli, Gülüzar; Canli, Mustdafa

    2013-12-01

    Freshwater fish Oreochromis niloticus were individually acutely exposed to different concentrations (0, 0.1, 0.5, 1.0, and 1.5 μg/mL) of Cd(2+) , Cr(6+) , and Ag(+) for 96 h and 0.05 μg/mL concentration of the same metals for different periods (0, 5, 10, 20, and 30 days) chronically. Following each experimental protocol, Na(+) /K(+) -ATPase, Mg(2+) -ATPase, and Ca(2+) -ATPase activities were measured in the gill, kidney, and muscle of O. niloticus. In vitro experiments were also performed to determine the direct effects of metal ions (0, 0.1, 0.5, 1.0, and 1.5 μg/mL) on ATPases. Except Ag(+) , none of the metals caused fish mortality within 30 days. Silver killed all the fishes within 16 days. Metal exposures generally decreased Na(+) /K(+) -ATPase and Ca(2+) -ATPase activities in the tissues of O. niloticus, although there were some fluctuations in Mg(2+) -ATPase activity. Ag(+) and Cd(2+) were found to be more toxic to ATPase activities than Cr(6+) . It was also observed that metal efficiency was higher in the gill than in the other tissues. Results indicated that the response of ATPases varied depending on metals, exposure types, and tissues. Because ATPases are sensitive to metal toxicity, their activity can give valuable data about fish physiology. Therefore, they may be used as a sensitive biomarker in environmental monitoring in contaminated waters. PMID:21901811

  7. Electronic and optical properties of the LiCdX (X = N, P, As and Sb) filled-tetrahedral compounds with the Tran–Blaha modified Becke–Johnson density functional

    SciTech Connect

    Bouhemadou, A.; Bin-Omran, S.; Allali, D.; Al-Otaibi, S.M.; Khenata, R.; Al-Douri, Y.; Chegaar, M.; Reshak, A.H.

    2015-04-15

    Highlights: • Electronic and optical properties of the LiCdX compounds have been predicted. • Tran–Blaha-modified Becke–Johnson functional significantly improves the band gap. • We predict a direct band gap in all of the considered LiCdX compounds. • Origin of the peaks in the optical spectra is determined. - Abstract: The structural, electronic and optical properties of the LiCdN, LiCdP, LiCdAs and LiCdSb filled-tetrahedral compounds have been explored from first-principles. The calculated structural parameters are consistent with the available experimental results. Since DFT with the common LDA and GGA underestimates the band gap, we use a new developed functional able to accurately describe the electronic structure of semiconductors, namely the Tran–Blaha-modified Becke–Johnson potential. The four investigated compounds demonstrate semiconducting behavior with direct band gap ranging from about 0.32 to 1.65 eV. The charge-carrier effective masses are evaluated at the topmost valence band and at the bottommost conduction band. The evolution of the value and nature of the energy band gap under pressure effect is also investigated. The frequency-dependent complex dielectric function and some macroscopic optical constants are estimated. The microscopic origins of the structures in the optical spectra are determined in terms of the calculated energy band structures.

  8. Effects of metal-bearing nanoparticles (Ag, Au, CdS, ZnO, SiO2) on developing zebrafish embryos.

    PubMed

    Lacave, José María; Retuerto, Ander; Vicario-Parés, Unai; Gilliland, Douglas; Oron, Miriam; Cajaraville, Miren P; Orbea, Amaia

    2016-08-12

    Due to the increasing commercialization of consumer and industrial products containing nanoparticles (NPs), an increase in the introduction of these materials into the environment is expected. NP toxicity to aquatic organisms depends on multiple biotic and abiotic factors, resulting in an unlimited number of combinations impossible to test in practice. The zebrafish embryo model offers a useful screening tool to test and rank the toxicity of nanomaterials according to those diverse factors. This work aims to study the acute and sublethal toxicity of a set of metal-bearing NPs displaying different properties, in comparison to that of the ionic and bulk forms of the metals, in order to establish a toxicity ranking. Soluble NPs (Ag, CdS and ZnO) showed the highest acute and sublethal toxicity, with LC50 values as low as 0.529 mg Ag l(-1) for Ag NPs of 20 nm, and a significant increase in the malformation prevalence in embryos exposed to 0.1 mg Cd l(-1) of CdS NPs of ∼4 nm. For insoluble NPs, like SiO2 NPs, acute effects were not observed during early embryo development due to the protective effect of the chorion. But effects on larvae could be expected, since deposition of fluorescent SiO2 NPs over the gill lamella and excretion through the intestine were observed after hatching. In other cases, such as for gold NPs, the toxicity could be attributed to the presence of additives (sodium citrate) in the NP suspension, as they displayed a similar toxicity when tested separately. Overall, the results indicated that toxicity to zebrafish embryos depends primarily on the chemical composition and, thus, the solubility of the NPs. Other characteristics, such as size, played a secondary role. This was supported by the observation that ionic forms of the metals were always more toxic than the nano forms, and bulk forms were the least toxic to the developing zebrafish embryos. PMID:27363512

  9. Effects of metal-bearing nanoparticles (Ag, Au, CdS, ZnO, SiO2) on developing zebrafish embryos

    NASA Astrophysics Data System (ADS)

    María Lacave, José; Retuerto, Ander; Vicario-Parés, Unai; Gilliland, Douglas; Oron, Miriam; Cajaraville, Miren P.; Orbea, Amaia

    2016-08-01

    Due to the increasing commercialization of consumer and industrial products containing nanoparticles (NPs), an increase in the introduction of these materials into the environment is expected. NP toxicity to aquatic organisms depends on multiple biotic and abiotic factors, resulting in an unlimited number of combinations impossible to test in practice. The zebrafish embryo model offers a useful screening tool to test and rank the toxicity of nanomaterials according to those diverse factors. This work aims to study the acute and sublethal toxicity of a set of metal-bearing NPs displaying different properties, in comparison to that of the ionic and bulk forms of the metals, in order to establish a toxicity ranking. Soluble NPs (Ag, CdS and ZnO) showed the highest acute and sublethal toxicity, with LC50 values as low as 0.529 mg Ag l‑1 for Ag NPs of 20 nm, and a significant increase in the malformation prevalence in embryos exposed to 0.1 mg Cd l‑1 of CdS NPs of ∼4 nm. For insoluble NPs, like SiO2 NPs, acute effects were not observed during early embryo development due to the protective effect of the chorion. But effects on larvae could be expected, since deposition of fluorescent SiO2 NPs over the gill lamella and excretion through the intestine were observed after hatching. In other cases, such as for gold NPs, the toxicity could be attributed to the presence of additives (sodium citrate) in the NP suspension, as they displayed a similar toxicity when tested separately. Overall, the results indicated that toxicity to zebrafish embryos depends primarily on the chemical composition and, thus, the solubility of the NPs. Other characteristics, such as size, played a secondary role. This was supported by the observation that ionic forms of the metals were always more toxic than the nano forms, and bulk forms were the least toxic to the developing zebrafish embryos.

  10. The effect of TiO{sub 2} and Ag nanoparticles on reproduction and development of Drosophila melanogaster and CD-1 mice

    SciTech Connect

    Philbrook, Nicola A.; Winn, Louise M.; Afrooz, A.R.M. Nabiul; Saleh, Navid B.; Walker, Virginia K.

    2011-12-15

    In the last two decades, nanoparticles (NPs) have found applications in a wide variety of consumer goods. Titanium dioxide (TiO{sub 2}) and silver (Ag) NPs are both found in cosmetics and foods, but their increasing use is of concern due to their ability to be taken up by biological systems. While there are some reports of TiO{sub 2} and Ag NPs affecting complex organisms, their effects on reproduction and development have been largely understudied. Here, the effects of orally administered TiO{sub 2} or Ag NPs on reproduction and development in two different model organisms were investigated. TiO{sub 2} NPs reduced the developmental success of CD-1 mice after a single oral dose of 100 or 1000 mg/kg to dams, resulting in a statistically significant increase in fetal deformities and mortality. Similarly, TiO{sub 2} NP addition to food led to a significant progeny loss in the fruit fly, Drosophila, as shown by a decline in female fecundity. Ag NP administration resulted in an increase in the mortality of fetal mice. Similarly in Drosophila, Ag NP feeding led to a significant decrease in developmental success, but unlike TiO{sub 2} NP treatment, there was no decline in fecundity. The distinct response associated with each type of NP likely reflects differences in NP administration as well as the biology of the particular model. Taken together, however, this study warns that these common NPs could be detrimental to the reproductive and developmental health of both invertebrates and vertebrates.

  11. Geochemistry of the Patricia Zn-Pb-Ag Deposit (paguanta, NE Chile)

    NASA Astrophysics Data System (ADS)

    Chinchilla Benavides, D.; Merinero Palomares, R.; Piña García, R.; Ortega Menor, L.; Lunar Hernández, R.

    2013-12-01

    The Patricia Zn-Pb-Ag ore deposit is located within the Paguanta mining project, situated at the northern end of the Andean Oligocene Porphyry Copper Belt of Chile. The sulfide mineralization occurs as W-E oriented veins hosted in volcanic rocks, mainly andesite (pyroclastic, ash and lavas), of Upper Cretaceous to Middle Tertiary age. The ore mineralogy (obtained by EMPA analyses) comprises in order of abundance, pyrite, sphalerite (5.5 - 10.89 wt % Fe, 9.8-19 % molar FeS and 0.52 wt % Cd), galena, arsenopyrite, chalcopyrite and Ag-bearing sulfosalts. The veins show a zoned and banded internal structure with pyrite at the edges and sphalerite in the center. The Ag occurs mostly as Ag-Cu-Sb sulfosalts, in order of abundance: series freibergite - argentotennantite -polybasite and stephanite. Other minor Ag phases such as argentite, pyrargirite and diaphorite were also identified. These Ag phases are typically associated with the base-metal sulfides. Freibergite occurs filling voids within sphalerite, chalcopyrite and at the contact between sphalerite and galena. Polybasite, stephanite, pyrargirite and argentite are mostly in close association with freibergite. In the case of diaphorite, it commonly occurs filling voids between galena crystals or as inclusions within galena. Some minor Ag-bearing sulfosalts are also identified between pyrite crystals. The alteration minerals are dominated by chlorite, illite and kaolinite. The gangue minerals consist of quartz and carbonates identified by XRD as kutnahorite. We obtained linear correlation statistically significant only for Ag, As Au, Cd, Cu, Pb, Sb and Zn and therefore we generated an enhanced scatter plot matrix of these elements. Bulk rock analyses (ICP/MS and XRF) of drill cores show that Ag is strongly and positively correlated with Pb and As, moderately with Cd, Sb, Au and Zn and weakly with Cu, while Au is moderately and positively correlated with Ag, As, Cd, Sb and Zn and weakly with Cu and Pb. These results

  12. Influence of technological defects on the optical and photoelectric properties of AgCd{sub 2-x}Mn{sub x}GaSe{sub 4} alloys

    SciTech Connect

    Tretyak, A. P. Davydyuk, H. Ye.; Bozhko, V. V.; Bulatetska, L. V.; Parasyuk, O. V.

    2012-03-15

    The study is concerned with the photoelectric and optical properties of a AgCd{sub 2-x}Mn{sub x}GaSe{sub 4} alloy with a Mn {yields} Cd isovalent substitution. The positions of the photoconductivity and photoluminescence peaks are determined, and the band gap of the alloy is estimated, based on compositional analysis. The influence of technological defects on specific features of the alloy's photoelectric and optical properties is analyzed. It is established that the centers controlling the alloy crystals' photosensitivity are cation vacancies. The photoluminescence centers responsible for emission at awavelengths from 0.77 to 0.88 {mu}m (dependent on the relation between components in the alloy) are defect complexes consisting of cation and anion vacancies. A physically consistent model is proposed to interpret the effects observed in the alloy.

  13. Influence of metal (Cd and Zn) waterborne exposure on radionuclide (134Cs, 110Ag, and 57Co) bioaccumulation by rainbow trout (Oncorhynchus mykiss): a field and laboratory study.

    PubMed

    Ausseil, Olivier; Adam, Christelle; Garnier-Laplace, Jacqueline; Baudin, Jean-Pierre; Casellas, Claude; Porcher, Jean-Marc

    2002-03-01

    Field and laboratory experiments were carried out to assess the influence of Cd and Zn on the contamination levels of 110Ag, 57Co, and 134Cs in rainbow trout. During a four-week prior exposure phase, two fish groups were held in tanks in the Lot River (France) at a reference (<0.05 microg Cd/L and 68 microg Zn/L) and at a polluted site (1.5 microg Cd/L and 152 microg Zn/L). During a subsequent phase, organisms were brought back to the laboratory, where the radionuclide accumulation and depuration were studied for 14 and 7 d, respectively. During this second phase, the water used in the experiments was brought back from the two sites on the Lot River in order to work under the same chemical conditions. The potential effect of chronic exposure to stable metals on several biomarkers has been explored: Plasma analysis indicated the disruption of certain variables linked to the energetic metabolism and to the maintenance of the ionic balance. In contrast, no significant disruption of the measured enzyme activities was observed. With regard to the bioaccumulation of radionuclides, concentrations in fish exposed to metals are much lower than those in fish from the control group. Various hypotheses are proposed to link fish metabolic profiles due to metal exposure to the radiocontamination of organisms. PMID:11878476

  14. FAS -670 A/G polymorphism may be associated with the depletion of CD4(+) T lymphocytes in HIV-1 infection.

    PubMed

    Hermes, Renata Bezerra; Santana, Bárbara Brasil; Lima, Sandra Souza; Neris Martins Feitosa, Rosimar; de Oliveira Guimarães Ishak, Marluísa; Ishak, Ricardo; Vallinoto, Antonio Carlos Rosário

    2015-10-01

    In this study, the polymorphisms in the FAS and FASL genes was investigated in a sample of 198 HIV-1-seropositive individuals and 191 seronegative controls to evaluate a possible association between polymorphisms and the infection. The identification of the A and G alleles of the FAS -670 polymorphism was accomplished through polymerase chain reaction assays followed by digestion with the restriction enzyme MvaI. The identification of the A and G alleles of the FAS -124 polymorphism and the T and delT alleles of the FAS -169 polymorphism were performed using the amplification-created restriction site method followed by restriction fragment length polymorphism reactions. The comparative analysis of allelic and genotypic frequencies between the groups did not reveal any significant differences. However, the quantitative analysis of CD4(+) T lymphocytes suggests that the G allele of the FAS -670 A/G polymorphism can be a protective factor against the depletion of these cells in the course of an HIV-1 infection. Polymorphisms in the FAS and FASL genes were not associated with the number of CD8(+) T lymphocytes or the plasma viral load. Our findings suggest that the FAS -670 polymorphism may be associated with apoptosis of CD4(+) T lymphocytes after infection by HIV-1. PMID:26429326

  15. Flowing Liquid Anode Atmospheric Pressure Glow Discharge as an Excitation Source for Optical Emission Spectrometry with the Improved Detectability of Ag, Cd, Hg, Pb, Tl, and Zn.

    PubMed

    Greda, Krzysztof; Swiderski, Krzysztof; Jamroz, Piotr; Pohl, Pawel

    2016-09-01

    A novel atmospheric pressure glow discharge generated in contact with a flowing liquid anode (FLA-APGD) was developed as the efficient excitation source for the optical emission spectrometry (OES) detection. Differences in the appearance and the electrical characteristic of the FLA-APGD and a conventional system operated with a flowing liquid cathode (FLC-APGD) were studied in detail and discussed. Under the optimal operating conditions for the FLA-APGD, the emission from the analytes (Ag, Cd, Hg, Pb, Tl, and Zn) was from 20 to 120 times higher as compared to the FLC-APGD. Limits of detections (LODs) established with a novel FLA-APGD system were on average 20 times better than those obtained for the FLC-APGD. A further improvement of the LODs was achieved by reducing the background shift interferences and, as a result, the LODs for Ag, Cd, Hg, Pb, Tl, and Zn were 0.004, 0.040, 0.70, 1.7, 0.035, and 0.45 μg L(-1), respectively. The precision of the FLA-APGD-OES method was evaluated to be within 2-5% (as the relative standard deviation of the repeated measurements). The method found its application in the determination of the content of Ag, Cd, Hg, Pb, Tl, and Zn in a certified reference material (CRM) of Lobster hepatopancreas (TORT-2), four brass samples as well as mineral water and tea leaves samples spiked with the analytes. In the case of brass samples, a reference method, i.e., inductively coupled plasma optical emission spectrometry (ICP-OES) was used. A good agreement between the results obtained with FLA-APGD-OES and the certified values for the CRM TORT-2 as well as the reference values obtained with ICP-OES for the brass samples was revealed, indicating the good accuracy of the proposed method. The recoveries obtained for the spiked samples of mineral water and tea leaves were within the range of 97.5-102%. PMID:27476678

  16. Photovoltaic p-n structure of MoSb2‑xCuxSe4/CdS absorber films obtained via chemical bath deposition

    NASA Astrophysics Data System (ADS)

    Vijila, J. J. J.; Mohanraj, K.; Sivakumar, G.

    2016-07-01

    In this work, a novel mixed metal chalcogenide MoSb2‑xCuxSe4 nanocrystalline thin film was deposited for different copper concentrations (x = 0.0 M, 0.1 M, 0.2 M & 0.3 M) on glass substrate by chemical bath deposition method at room temperature. XRD patterns revealed the incorporation of copper content by the conversion of orthorhombic Sb2Se3 into Cu3SbSe3 with a shift to lower angles. Average crystallite was found to be 69 nm, 17 nm, 10 nm and 9 nm for the deposited films. FTIR spectra confirm the presence of functional groups of Trisodium citrate (TSC) and the metal oxide vibrations. FESEM analysis depicted the morphological changes with the addition of Cu content. UV–vis analysis shows higher absorption in the visible region and the band gap values are found to be 2.16–1.76 eV. Hall effect analysis confirms the p-type nature of the material. The photo-current analysis shows higher photo-conversion efficiency of 1.86% for 0.3 M copper content.

  17. A comparative computational study on hydrogen adsorption on the Ag(+), Cu(+), Mg(2+), Cd(2+), and Zn(2+) cationic sites in zeolites.

    PubMed

    Kozyra, Paweł; Piskorz, Witold

    2016-05-14

    In this article the interaction between H2 and Ag(+), Cu(+), Mg(2+), Cd(2+), and Zn(2+) cations in cluster models of several sizes has been studied computationally. Depending on the changes imposed by the adsorption process on the H2 molecule the activation can vary in a wide range - from only slight weakening of the H-H bond to complete dissociation of the H2 molecule. The NOCV (Natural Orbitals for Chemical Valence) analysis allowed for decomposition of the electron density distortion into contributions easier for interpretation. Three essential factors have been identified (i-iii). In the case of bare cations the main contribution is a donation from σH2 to the cation (i). When a zeolite framework surrounding the cation is introduced, it hinders σ-donation and enhances π-backdonation from the cation to the antibonding orbital of the molecule (ii). For Cu(i) and Ag(i) sites π-backdonation becomes dominant, while for Mg(ii), Cd(ii), and Zn(ii) cations, the σ-donation, albeit diminished, still remains a dominant contribution. Calculations showed that the localization and coordination of Zn(ii) have crucial influence on its interaction with H2. We identified a Zn(2+) position at which the H2 molecule dissociates - here the interaction between H2 and oxygen framework (iii) plays a crucial role. Based on the calculations the mechanism of H2 transformation has been proposed. Upon heterolytic dissociation of H2 the Zn(0) moiety and two OH groups can be formed. Eventually, in two elementary steps, the H2 molecule can be restored. In this case, the ability of the site to activate/dissociate hydrogen is caused by the low coordination number of the zinc cation and the geometry of the site which allows positively charged H2 to interact with framework oxygen what enhances the formation of OH and Z-O-(ZnH)(+) groups. PMID:27092373

  18. Fluorometric selective detection of fluoride ions in aqueous media using Ag doped CdS/ZnS core/shell nanoparticles.

    PubMed

    Boxi, Siddhartha Sankar; Paria, Santanu

    2016-01-14

    The presence of fluoride ions in drinking water plays an important role in human health. For that reason, maintaining the optimum concentration of fluoride ions in drinking water is essential, as both low and excess (above the permissible level) concentrations can cause different health problems, such as fluorosis, urolithiasis, kidney failure, cancer, and can even lead to death. So, development of a simple and low cost method for the detection of fluoride ions in water is highly desirable. In this study, a fluorometric method based on Ag-CdS/Ag-ZnS core/shell nanoparticles is developed for fluoride ion detection. The method was tested in aqueous solution at different pH values. The selectivity and sensitivity of the fluorescence probe was checked in the presence of other anions (Cl(-), Br(-), I(-), NO3(-) SO4(2-), HCO3(-), HPO4(2-), CH3COO(-), and H2PO4(-)) and found there is no significant interference of these associated ions. The fluoride ion concentration was varied in the range 190-22 800 μg L(-1) and a lower detection limit was obtained as 99.7 μg L(-1). PMID:26645767

  19. Photocatalytic removal of M(2+) (Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+) and Ag(+)) over new catalyst CuCrO(2).

    PubMed

    Ketir, W; Bouguelia, A; Trari, M

    2008-10-30

    The metal ions M(2+) (Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+) and Ag(+)) are potentially toxic. Their electro deposition has been carried out in aqueous air-equilibrated CuCrO(2) suspension upon visible illumination. The delafossite CuCrO(2) is p-type semiconductor characterized by a low band gap (1.28 eV) and a long-term chemical stability. The corrosion rate is found to be 10(-2) micromol m(-2)month(-1) in aqua regia. The oxide has been elaborated through nitrate route where the specific surface area is increased via the surface/bulk ratio. A correlation exists between the dark M(2+) adsorption, the redox potential of M(2+/0) couple and the conduction band of CuCrO(2) positioned at -1.06 V(SCE). Ag(+) cannot be photoreduced because of its positive potential located far above the valence band. By contrast, Zn(2+) is efficiently deposited due to the large driving force at the interface. The improved photoactivity of copper with a deposition percentage (90%) is attributed to the strong dark adsorption onto the surface catalyst. The results indicate a competitive effect with the water reduction; it has been observed that the M(2+) deposition goes parallel with the hydrogen evolution. Such behavior is attributed to the low H(2) over voltage when ultra fine aggregate of M islands are photodeposited onto CuCrO(2) substrate. PMID:18384943

  20. Subcellular partitioning of non-essential trace metals (Ag, As, Cd, Ni, Pb, and Tl) in livers of American (Anguilla rostrata) and European (Anguilla anguilla) yellow eels.

    PubMed

    Rosabal, Maikel; Pierron, Fabien; Couture, Patrice; Baudrimont, Magalie; Hare, Landis; Campbell, Peter G C

    2015-03-01

    We determined the intracellular compartmentalization of the trace metals Ag, As, Cd, Ni, Pb, and Tl in the livers of yellow eels collected from the Saint Lawrence River system in Canada (Anguilla rostrata) and in the area of the Gironde estuary in France (Anguilla anguilla). Differential centrifugation, NaOH digestion and thermal shock were used to separate eel livers into putative "sensitive" fractions (heat-denatured proteins, mitochondria and microsomes+lysosomes) and detoxified metal fractions (heat-stable peptides/proteins and granules). The cytosolic heat-stable fraction (HSP) was consistently involved in the detoxification of all trace metals. In addition, granule-like structures played a complementary role in the detoxification of Ni, Pb, and Tl in both eel species. However, these detoxification mechanisms were not completely effective because increasing trace metal concentrations in whole livers were accompanied by significant increases in the concentrations of most trace metals in "sensitive" subcellular fractions, that is, mitochondria, heat-denatured cytosolic proteins and microsomes+lysosomes. Among these "sensitive" fractions, mitochondria were the major binding sites for As, Cd, Pb, and Tl. This accumulation of non-essential metals in "sensitive" fractions likely represents a health risk for eels inhabiting the Saint Lawrence and Gironde environments. PMID:25635611

  1. Atomic-level observation of Ag-ion hopping motion in AgI

    NASA Astrophysics Data System (ADS)

    Sato, W.; Komatsuda, S.; Mizuuchi, R.; Irioka, N.; Kawata, S.; Ohkubo, Y.

    2015-04-01

    Applicability of the 111mCd(→111Cd) and 111In(→111Cd) probes to the study of dynamics in polycrystalline silver iodide (AgI) was examined by means of the time-differential perturbed angular correlation technique. It was found that the 111mCd(→111Cd) probe occupies a unique site in γ-AgI and exhibits nuclear relaxation caused by dynamic perturbation arising from Ag + hopping motion in α-AgI; while the residential sites of 111In(→111Cd) vary, suggesting that 111In ions can not settle themselves in a fixed site in the AgI crystal structure. We here demonstrate that 111mCd(→111Cd) can be a potential nucleus to probe the Ag +-ion dynamic motion in α-AgI.

  2. Assessing metal contamination from construction and demolition (C&D) waste used to infill wetlands: using Deroceras reticulatum (Mollusca: Gastropoda).

    PubMed

    Staunton, John A; Mc Donnell, Rory J; Gormally, Michael J; Williams, Chris D; Henry, Tiernan; Morrison, Liam

    2014-11-01

    Large quantities of construction and demolition waste (C&D) are produced globally every year, with little known about potential environmental impacts. In the present study, the slug, Deroceras reticulatum (Mollusca: Gastropoda) was used as the first biomonitor of metals (Ag, As, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Sb, Se, Ti, Tl, V and Zn) on wetlands post infilling with construction and demolition (C&D) waste. The bioaccumulation of As, Ba, Cd, Co, Sb, Se and Tl were found to be significantly elevated in slugs collected on C&D waste when compared to unimproved pastures (control sites), while Mo, Se and Sr had significantly higher concentrations in slugs collected on C&D waste when compared to known contaminated sites (mining locations), indicating the potential hazardous nature of C&D waste to biota. Identifying exact sources for these metals within the waste can be problematic, due to its heterogenic nature. Biomonitors are a useful tool for future monitoring and impact studies, facilitating policy makers and regulations in other countries regarding C&D waste infill. In addition, improving separation of C&D waste to allow increased reuse and recycling is likely to be effective in reducing the volume of waste being used as infill, subsequently decreasing potential metal contamination. PMID:25298023

  3. Thermally deposited Ag-doped CdS thin film transistors with high-k rare-earth oxide Nd{sub 2}O{sub 3} as gate dielectric

    SciTech Connect

    Gogoi, P.

    2013-03-15

    The performance of thermally deposited CdS thin film transistors doped with Ag has been reported. Ag-doped CdS thin films have been prepared using chemical method. High dielectric constant rare earth oxide Nd{sub 2}O{sub 3} has been used as gate insulator. The thin film trasistors are fabricated in coplanar electrode structure on ultrasonically cleaned glass substrates with a channel length of 50 {mu}m. The thin film transistors exhibit a high mobility of 4.3 cm{sup 2} V{sup -1} s{sup -1} and low threshold voltage of 1 V. The ON-OFF ratio of the thin film transistors is found as 10{sup 5}. The TFTs also exhibit good transconductance and gain band-width product of 1.15 Multiplication-Sign 10{sup -3} mho and 71 kHz respectively.

  4. Direct detection of Pb in urine and Cd, Pb, Cu, and Ag in natural waters using electrochemical sensors immobilized with DMSA functionalized magnetic nanoparticles

    SciTech Connect

    Yantasee, Wassana; Hongsirikarn, Kitiya; Warner, Cynthia L.; Choi, Daiwon; Sangvanich, Thanapon; Toloczko, Mychailo B.; Warner, Marvin G.; Fryxell, Glen E.; Addleman, Raymond S.; Timchalk, Chuck

    2008-03-01

    Urine is universally recognized as one of the best non-invasive matrices for biomonitoring exposure to a broad range of xenobiotics including toxic metals. For direct, simple, and field-deployable monitoring of urinary Pb, electrochemical sensors employing superparamagnetic iron oxide (Fe3O4) nanoparticles with a surface functionalization of dimercaptosuccinic acid (DMSA) has been developed. The metal detection involves rapid collection of dispersed metal-bound nanoparticles from a sample solution at a magnetic or electromagnetic electrode, followed by the stripping voltammetry of the metal in acidic medium. The sensors were evaluated as a function of solution pH, the binding affinity of Pb to DMSA-Fe3O4, the ratio of nanoparticles per sample volume, preconcentration time, and Pb concentrations. The effect of binding competitions between the DMSA-Fe3O4 and urine constituents for Pb on the sensor responses was studied. After 90s of preconcentration in samples containing 25 vol.% of rat urine and 0.1 g/L of DMSA-Fe3O4, the sensor could detect background level of Pb (< 1 ppb) and yielded linear responses from 0 to 50 ppb of Pb, excellent reproducibility (%R.S.D of 5.3 for seven measurements of 30 ppb Pb), and Pb concentrations comparable to those measured by ICP-MS. The sensor could also simultaneously detect background levels (< 1 ppb) of Cd, Pb, Cu, and Ag in river and seawater.

  5. Effects of increased pCO2 and temperature on trace element (Ag, Cd and Zn) bioaccumulation in the eggs of the common cuttlefish, Sepia officinalis

    NASA Astrophysics Data System (ADS)

    Lacoue-Labarthe, T.; Martin, S.; Oberhänsli, F.; Teyssié, J.-L.; Markich, S.; Jeffree, R.; Bustamante, P.

    2009-05-01

    Cephalopods play a key role in many marine trophic networks and constitute alternative fisheries resources, especially given the ongoing decline in finfish stocks. Along the European coast, the eggs of the cuttlefish Sepia officinalis are characterized by an increasing permeability of the eggshell during development, which leads to selective accumulation of essential and non-essential elements in the embryo. Temperature and pH are two critical factors that affect the metabolism of marine organisms in the coastal shallow waters. In this study, we are testing the effects of pH and temperature through a crossed (3×2) laboratory experiment. Seawater pH showed a strong effect on the egg weight and non-significant impact on the hatchlings weight at the end of development implying egg swelling process and embryo growth disturbances. The lower pH of incubation seawater of eggs, the more the hatchlings accumulated 110m Ag in their tissues. The 109Cd CF decreased with increasing pH and 65Zn CF reached the maximal values pH 7.85, independent of temperature. Our results suggest that pH and temperature affected both the permeability properties of the eggshell and the embryo metabolism. To the best of our knowledge, this is one of the first studies on the ocean acidification and ocean warming consequences on the metal uptake in marine organisms, stimulating further interest to evaluate the likely ecotoxicological impact of the global change on the early-life stage of the cuttlefish.

  6. Erratum to: "From Ag2Sb2O6 to Cd2Sb2O7: Investigations on an anion-deficient to ideal pyrochlore solid solution" [J. Solid State Chem. 210(1) (2014) 65-73

    NASA Astrophysics Data System (ADS)

    Laurita, Geneva; Vielma, Jason; Winter, Florian; Berthelot, Romain; Largeteau, Alain; Pöttgen, Rainer; Schneider, G.; Subramanian, M. A.

    2015-09-01

    On page 65, the fourth sentence of paragraph four should read "This cubic structure is described symmetrically by the space group Fd3¯m, and is often represented with the formula A2B2O7" instead of "This cubic structure is described symmetrically by the space group Fd3m, and is often represented with the formula A2B2O7".

  7. Ion conduction in the Ag{sub 2}HgI{sub 4}-Cu{sub 2}HgI{sub 4} systems doped with Cd{sup 2+}, K{sup +}, and Na{sup +}

    SciTech Connect

    Nair, S.M.; Yahya, A.I.; Ahmad, A.

    1996-03-01

    Ion conductivities of face centered cubic Ag{sub 2}HgI{sub 4}-Cu{sub 2}HgI{sub 4} systems doped with Cd{sup 2+}, K{sup +}, and Na{sup +} were measured. In 67 mol% Ag{sub 2}HgI{sub 4} solid solution doped with Cd{sup 2+} ions, the phase transition occurs at a lower temperature than in the parent compounds and the system shows higher conductivity. The increase in conductivity is discussed in terms of vacancies produced. K{sup +} doped Ag{sub 2}HgI{sub 4} exhibits higher conductivity prior to the phase transition, which is attributed to lattice loosening. A decrease in conductivity is observed above 140{degrees}C. This is interpreted in terms of anion framework collapse. Na{sup +} doped Ag{sub 2}HgI{sub 4} shows high conductivity for the high temperature phase because of the small size of Na{sup +} ions. The activation energy for ionic motion for all the samples is calculated from the graph of log({delta}T) versus 1/T.

  8. Charged Defects-Induced Resistive Switching in Sb2Te3 Memristor

    NASA Astrophysics Data System (ADS)

    Zhang, J. J.; Liu, N.; Sun, H. J.; Yan, P.; Li, Y.; Zhong, S. J.; Xie, S.; Li, R. J.; Miao, X. S.

    2016-02-01

    Resistive switching (RS) characteristics of Ta/Sb2Te3/Ta and Ag/Sb2Te3/Ta memory devices have been investigated. The I- V curves show the bipolar RS at room temperature. We have demonstrated that the redistribution and migration of charged defects are responsible for the memristive switching. By using Ag electrode instead of Ta, more defects can be created near the Ag/Sb2Te3 interface, which is a feasible method to eliminate the electroforming process.

  9. Effects of increased pCO2 and temperature on trace element (Ag, Cd and Zn) bioaccumulation in the eggs of the common cuttlefish, Sepia officinalis

    NASA Astrophysics Data System (ADS)

    Lacoue-Labarthe, T.; Martin, S.; Oberhänsli, F.; Teyssié, J.-L.; Markich, S.; Ross, J.; Bustamante, P.

    2009-11-01

    Cephalopods play a key role in many marine trophic networks and constitute alternative fisheries resources, especially given the ongoing decline in finfish stocks. Along the European coast, the eggs of the cuttlefish Sepia officinalis are characterized by an increasing permeability of the eggshell during development, which leads to selective accumulation of essential and non-essential elements in the embryo. Temperature and pH are two critical factors that affect the metabolism of marine organisms in the coastal shallow waters. In this study, we investigated the effects of pH and temperature through a crossed (3×2; pH 8.1 (pCO2, 400 ppm), 7.85 (900 ppm) and 7.6 (1400 ppm) at 16 and 19°C, respectively) laboratory experiment. Seawater pH showed a strong effect on the egg weight and non-significant impact on the weight of hatchlings at the end of development implying an egg swelling process and embryo growth disturbances. The lower the seawater pH, the more 110 mAg was accumulated in the tissues of hatchlings. The 109Cd concentration factor (CF) decreased with decreasing pH and 65Zn CF reached maximal values pH 7.85, independently of temperature. Our results suggest that pH and temperature affected both the permeability properties of the eggshell and embryonic metabolism. To the best of our knowledge, this is one of the first studies on the consequences of ocean acidification and ocean warming on metal uptake in marine organisms, and our results indicate the need to further evaluate the likely ecotoxicological impact of the global change on the early-life stages of the cuttlefish.

  10. The − 5 A/G single-nucleotide polymorphism in the core promoter region of MT2A and its effect on allele-specific gene expression and Cd, Zn and Cu levels in laryngeal cancer

    SciTech Connect

    Starska, Katarzyna; Krześlak, Anna; Forma, Ewa; Morawiec-Sztandera, Alina; Aleksandrowicz, Paweł; Lewy-Trenda, Iwona; and others

    2014-10-15

    Metallothioneins (MTs) are low molecular weight, cysteine-rich heavy metal-binding proteins which participate in the mechanisms of Zn homeostasis, and protect against toxic metals. MTs contain metal-thiolate cluster groups and suppress metal toxicity by binding to them. The aim of this study was to determine the − 5 A/G (rs28366003) single-nucleotide polymorphism (SNP) in the core promoter region of the MT2A gene and to investigate its effect on allele-specific gene expression and Cd, Zn and Cu content in squamous cell laryngeal cancer (SCC) and non-cancerous laryngeal mucosa (NCM) as a control. The MT2A promoter region − 5 A/G SNP was determined by restriction fragment length polymorphism using 323 SCC and 116 NCM. MT2A gene analysis was performed by quantitative real-time PCR. The frequency of A allele carriage was 94.2% and 91.8% in SCC and NCM, respectively, while G allele carriage was detected in 5.8% and 8.2% of SCC and NCM samples, respectively. As a result, a significant association was identified between the − 5 A/G SNP in the MT2A gene with mRNA expression in both groups. Metal levels were analyzed by flame atomic absorption spectrometry. The significant differences were identified between A/A and both the A/G and G/G genotypes, with regard to the concentration of the contaminating metal. The Spearman rank correlation results showed that the MT2A expression and Cd, Zn, Cu levels were negatively correlated. Results obtained in this study suggest that − 5 A/G SNP in MT2A gene may have an effect on allele-specific gene expression and accumulation of metal levels in laryngeal cancer. - Highlights: • MT2A gene expression and metal content in laryngeal cancer tissues • Association between SNP (rs28366003) and expression of MT2A • Significant associations between the SNP and Cd, Zn and Cu levels • Negative correlation between MT2A gene expression and Cd, Zn and Cu levels.

  11. Syntheses, crystal structures and fluorescent properties of Cd(II), Hg(II) and Ag(I) coordination polymers constructed from 1H-1,2,4-triazole-1-acetic acid

    SciTech Connect

    Ding Degang; Xie Lixia; Fan Yaoting; Hou Hongwei; Xu Yan

    2009-06-15

    Three new d{sup 10} coordination polymers, namely [Cd(taa)Cl]{sub n}1, [Hg(taa)Cl]{sub n}2, and [Ag{sub 1.5}(taa)(NO{sub 3}){sub 0.5}]{sub n}3 (taa=1H-1,2,4-triazole-1-acatate anion) have been prepared and characterized by elemental analysis, IR, and single crystal X-ray diffraction. Compound 1 consists of two-dimensional layers constructed by carboxyl-linked helical chains, which are further linked through carboxyl group to generate a unique 3D open framework. Topological analysis reveals that the structure of 1 can be classified as an unprecedented (3,8)-connected network with the Schlaefli symbol (4.5{sup 2}){sub 2}(4{sup 2}.5{sup 8}.6{sup 14}.7{sup 3}.8). Compound 2 manifests a doubly interpenetrated decorated alpha-polonium cubic network with the Schlaefli symbol of (4{sup 10}.6{sup 2}.8{sup 3}). Compound 3 consists of 2D puckered layers made up of Ag centers and taa{sup -} bridges. In addition, all of these compounds are photoluminescent in the solid state with spectra that closely resemble those of the ligand precursor. - Graphical abstract: Three new compounds based on 1H-1,2,4-triazole-1-acetic acid and Cd(II), Hg(II) and Ag(I) salts display luminescent properties and may be potential candidates for luminescent materials.

  12. Thermoelectric properties of homogeneously and non-homogeneously doped CdTe15/16M1/16 (M=N, P, As, Sb) and Cd15/16TeM1/16 (M=Na, K, Rb, Cs)

    NASA Astrophysics Data System (ADS)

    Yang, X. H.; Qin, X. Y.; Li, D.; Zhang, J.; Song, C. J.; Liu, Y. F.; Wang, L.; Xin, H. X.

    2015-11-01

    The electrical transport properties of p-doped semiconductors CdTe15/16M1/16 (M=N, P, As, Sb) and Cd15/16TeM1/16 (M=Na, K, Rb, Cs) with two configurations are investigated through first-principles calculations combined with Boltzmann transport theory under the relaxation time approximation. It is found that N and Cs atoms in the homogeneous structure induce much sharper electron densities of states (DOSs) and flatter energy bands at the valence band edges than the rest of doped elements, resulting in much larger Seebeck coefficients. The calculations reveal that most of the Seebeck coefficients and electrical conductivities are impacted unfavorably by the conglomeration of impurity atoms considered. Though the power factors for homogeneous doping of N and Cs are comparatively smaller, the electronic figures of merit are much larger at 800-1000 K than the rest ones due to much smaller electronic thermal conductivities, therefore probably enhancing the thermoelectric figures of merit. The results show that doping the elements with electronegativities distinct from the host atoms can enhance the Seebeck coefficients and the thermoelectric performances of bulk semiconductors efficiently if the energy levels of doped atoms resonate with those of host atoms and the arrangement of doped atoms is modulated appropriately to avoid deteriorating the sharpness of the DOS (or transport distribution).

  13. The first example of a mixed valence ternary compound of silver with random distribution of Ag(I) and Ag(II) cations.

    PubMed

    Mazej, Zoran; Michałowski, Tomasz; Goreshnik, Evgeny A; Jagličić, Zvonko; Arčon, Iztok; Szydłowska, Jadwiga; Grochala, Wojciech

    2015-06-28

    The reaction between colourless AgSbF6 and sky-blue Ag(SbF6)2 (molar ratio 2 : 1) in gaseous HF at 323 K yields green Ag3(SbF6)4, a new mixed-valence ternary fluoride of silver. Unlike in all other Ag(I)/Ag(II) systems known to date, the Ag(+) and Ag(2+) cations are randomly distributed on a single 12b Wyckoff position at the 4̄ axis of the I4̄3d cell. Each silver forms four short (4 × 2.316(7) Å) and four long (4 × 2.764(6) Å) contacts with the neighbouring fluorine atoms. The valence bond sum analysis suggests that such coordination would correspond to a severely overbonded Ag(I) and strongly underbonded Ag(II). Thorough inspection of thermal ellipsoids of the fluorine atoms closest to Ag centres reveals their unusual shape, indicating that silver atoms must in fact have different local coordination spheres; this is not immediately apparent from the crystal structure due to static disorder of fluorine atoms. The Ag K-edge XANES analysis confirmed that the average oxidation state of silver is indeed close to +1⅓. The optical absorption spectra lack features typical of a metal thus pointing out to the semiconducting nature of Ag3(SbF6)4. Ag3(SbF6)4 is magnetically diluted and paramagnetic (μ(eff) = 1.9 μ(B)) down to 20 K with a very weak temperature independent paramagnetism. Below 20 K weak antiferromagnetism is observed (Θ = -4.1 K). Replacement of Ag(I) with potassium gives K(I)2Ag(II)(SbF6)4 which is isostructural to Ag(I)2Ag(II)(SbF6)4. Ag3(SbF6)4 is a genuine mixed-valence Ag(I)/Ag(II) compound, i.e. Robin and Day Class I system (localized valences), despite Ag(I) and Ag(II) adopting the same crystallographic position. PMID:25815902

  14. Collective and noncollective states in 116Sb

    NASA Astrophysics Data System (ADS)

    Wang, S. Y.; Sun, D. P.; Qi, B.; Chen, Z. Q.; Hu, X. B.; Wang, G.; Liu, C.; Xu, C. J.; Liu, L.; Zhang, P.; Li, Z. Q.; Guo, M. Z.; Cai, Y. Y.; Li, Y. Q.; Liu, S. Y.; Wyngaardt, S. M.; Zhu, L. H.; Wu, X. G.; He, C. Y.; Zheng, Y.; Li, G. S.

    2012-12-01

    Excited states of 116Sb were investigated using in-beam γ-ray spectroscopy techniques with the 114Cd(7Li, 5n) reaction. About 25 new states and 35 new transitions were added into the level scheme of 116Sb. The previously known two rotational bands based on the πg9/2-1⊗νh11/2 and πg9/2-1⊗νd5/2 configurations have been extended up to (16)- and (13)+ states, respectively. A new ΔI=1 band was identified, and interpreted in terms of the triaxial particle rotor model calculations.

  15. Solid Liquid Interdiffusion Bonding of Zn4Sb3 Thermoelectric Material with Cu Electrode

    NASA Astrophysics Data System (ADS)

    Lin, Y. C.; Lee, K. T.; Hwang, J. D.; Chu, H. S.; Hsu, C. C.; Chen, S. C.; Chuang, T. H.

    2016-06-01

    The ZnSb intermetallic compound may have thermoelectric applications because it is low in cost and environmentally friendly. In this study, a Zn4Sb3 thermoelectric element coated with a Ni barrier layer and a Ag reaction layer was bonded with a Ag-coated Cu electrode using a Ag/Sn/Ag solid-liquid interdiffusion bonding process. The results indicated that a Ni5Zn21 intermetallic phase formed easily at the Zn4Sb3/Ni interface, leading to sound adhesion. In addition, Sn film was found to react completely with the Ag layer to form a Ag3Sn intermetallic layer having a melting point of 480°C. The resulting Zn4Sb3 thermoelectric module can be applied at the optimized operation temperature (400°C) of Zn4Sb3 material as a thermoelectric element. The bonding strengths ranged from 14.9 MPa to 25.0 MPa, and shear tests revealed that the Zn4Sb3/Cu-joints fractured through the interior of the thermoelectric elements.

  16. A first-principles study on the negative thermal expansion material: Mn3(A0.5B0.5)N (A=Cu, Zn, Ag, or Cd; B=Si, Ge, or Sn)

    NASA Astrophysics Data System (ADS)

    Qu, Bingyan; He, Haiyan; Pan, Bicai

    2016-07-01

    In this paper, using the first-principles calculations, we systemically study the magnetic and the negative thermal expansion (NTE) properties of Mn3(A0.5B0.5)N (A = Cu, Zn, Ag, or Cd; B = Si, Ge, or Sn). From the calculated results, except Mn3(Cu0.5Si0.5)N, all the doped compounds considered would exhibit the NTE. For the dopants at B sites, the working temperature of the NTE shifts to higher temperature range from Si to Sn, and among the compounds with these dopants, Mn3(A0.5Ge0.5)N has the largest amplitude of the NTE coefficient. As to the dopants at A sites, compared to Mn3(Cu0.5B0.5)N, Mn3(A0.5B0.5)N (A = Ag or Cd) exhibit the NTE with higher temperature ranges and lower coefficient of the thermal expansion. In a word, these compounds would have different working temperatures and coefficients of the NTE, which is important for the applications in different conditions.

  17. Complexation of Cd2+, Ni2+, and Ag+ metal ions with 4,13-didecyl-l,7,10,16-tetraoxa-4,13-diazacyclooctadecane in acetonitrile-ethylacetate binary mixtures

    NASA Astrophysics Data System (ADS)

    Izadyar, M.; Rounaghi, G. H.; Tarahomi, S.; Mohajeri, M.

    2013-12-01

    Conductometric titrations have been performed in acetonitrile-ethylacetate (AN-EtOAc) binary solutions at 288, 298, 308, and 318 K to obtain the stoichiometry, the complex stability constants and the standard thermodynamic parameters for the complexation of Cd2+, Ni2+, and Ag+ cations with 4,13-didecyl-1,7,10,16-tetraoxa-4,13-diazacyclooctadecane (cryptand 22DD). The stability constants of the resulting 1: 1 complexes formed between the metal cations and the ligand were determined by computer fitting of the conductance-mole ratio data. There is a non-linear relationship between the log K f values of complexes and the mole fraction of ethylacetate in the mixed solvent system. In addition, the conductometric data show that the stoichiometry of the complexes formed between the Cd2+, Ni2+, and Ag+ cations with the ligand changes with the nature of the solvent. The standard enthalpy and entropy values for the 1: 1 [ML] complexation reactions were evaluated from the temperature dependence of the formation constants. Thermodynamically, the complexation processes of the metal cations with the C22DD, is mainly entropy governed and the values of thermodynamic parameters are influenced by the nature and composition of the binary mixed solvent solutions.

  18. GaInSb and GaInAsSb thermophotovoltaic device fabrication and characterization

    SciTech Connect

    Hitchcock, C.; Gutmann, R.; Borrego, J.; Ehsani, H.; Bhat, I.; Freeman, M.; Charache, G.

    1997-05-01

    Thermophotovoltaic (TPV) devices have been fabricated using epitaxial ternary and quaternary layers grown on GaSb substrates. The GaInSb layers were grown by organometallic vapor phase epitaxy (OMVPE) and the InGaAsSb lattice-matched layers were grown by liquid phase epitaxy (LPE). Device fabrication steps include unannealed p-type ohmic contacts, annealed Sn/Au n-type ohmic contacts, and a thick Ag top-surface contact using a lift-off process. Devices are characterized primarily by dark I-V, photo I-V, and quantum efficiency measurements, which are correlated to microscopic and macroscopic material properties. Particular emphasis has been on material enhancements to increase quantum efficiency and decrease dark saturation current density. TPV device performance is presently limited by the base diffusion length, typically 1 to 2 microns.

  19. Impacts of anthropogenic pressures on the water quality of the Gironde Estuary (SW France) from the Urban Agglomeration of Bordeaux: spatial characterization and inputs of trace metal elements (Ag, As, Cd, Cu, Pb and Zn)

    NASA Astrophysics Data System (ADS)

    Kessaci, Kahina; Coynel, Alexandra; Blanc, Gérard; Deycard, Victoria N.; Derriennic, Hervé; Schäfer, Jörg

    2014-05-01

    Recent European legislation (2000/60/CE) has listed eight trace metal elements as priority toxic substances for water quality. Urban metal inputs into hydrosystems are of increasing interest to both scientists and managers facing restrictive environmental protection policies, population increase and changing metal applications. The Gironde Estuary (SW France; 625 km2) is known for its metal/metalloid pollution originating from industrial (e.g. Cd, Zn, Cu, As, Ag, Hg) or agricultural sources (e.g. Cu) in the main fluvial tributaries (Garonne and Dordogne Rivers). However, little peer-reviewed scientific work has addressed the impact of urban sources on the Gironde Estuary, especially the Urban Agglomeration of Bordeaux (~1 million inhabitants) located on the downstream branch of the Garonne River. In this study, a snapshot sampling campaign was performed in 2011 for characterizing the spatial distribution of dissolved and particulate metal/metalloid (As, Ag, Cd, Pb, Zn, Cu) concentrations in three suburban watersheds: the Jalle of Blanquefort (330 km2), Eau Bourde (140 km2), and Peugue (112 km2). Furthermore, particulate metal Enrichment Factors (EF) were calculated using local geochemical background measured at the bottom of a sediment core (492 cm). Results indicated that metal concentrations displayed a high spatial variability depending on the suburban watershed and the studied element. Local concentrations anomalies were observed for: (i) As in the Eau Bourde River in dissolved (4.2 μg/l) and particulate phases (246 mg/kg; EF= 20) and attributed to a nearby industrial incinerator; (ii) Zn in the Peugue River with maximum dissolved and particulate concentrations of 87 μg/l and 1580 mg/kg (EF=17), respectively, probably due to urban habitation runoff; (iii) Ag in the Jalle of Blanquefort River with high dissolved (74 ng/l) and particulate concentrations (33.7 mg/kg; EF=117) due to industrial activities in the downstream part. Based on hydro

  20. Characterization of silver photodiffusion in Ge{sub 8}Sb{sub 2}Te{sub 11} thin films

    SciTech Connect

    Kumar, Sandeep; Singh, D.; Sandhu, S.; Thangaraj, R.

    2015-06-24

    Silver-doped amorphous Ge{sub 8}Sb{sub 2}Te{sub 11} thin films have been prepared by photodiffusion at room-temperature; the Ge{sub 8}Sb{sub 2}Te{sub 11}/Ag bilayer was deposited by vacuum thermal evaporation. Photodiffusion of Ag into the amorphous Ge{sub 8}Sb{sub 2}Te{sub 11} thin films has been carried out by illuminating the prepared Ge{sub 8}Sb{sub 2}Te{sub 11}/Ag bilayer with halogen lamp. The photodiffused silver depth profile was traced by means of time of flight secondary ion mass spectroscopy. The film remains amorphous after Ag photodiffusion. The crystallization temperature of the films was evaluated by temperature dependent sheet resistance measurement. The amorphous nature and crystalline phases of the films have been identified by using X-ray diffraction.

  1. Rujevac Sb-Pb-Zn-As polymetallic deposit, Boranja orefield, Western Serbia: native arsenic and arsenic mineralization

    NASA Astrophysics Data System (ADS)

    Radosavljević, Slobodan A.; Stojanović, Jovica N.; Radosavljević-Mihajlović, Ana S.; Vuković, Nikola S.

    2014-02-01

    Rujevac is a low-temperature hydrothermal polymetallic Sb-Pb-Zn-As vein-type ore deposit, hosted within a volcanogenic-sedimentary zone situated in the Rujevac-Crvene Stene-Brezovica Diabase-Chert Formation (DCF) of the Podrinje Metallogenic District (PMD), Serbia. It is located several kilometers SE from the Boranja contact aureole, which is an integral part of the PMD in Western Serbia. Genetically related to the Tertiary granodioritic magma, the mineral assemblages are characterized by specific features. The mineral association of this deposit consists of sulfides, Pb-Sb(As) sulfosalts, native metals, oxides, hydroxides and gangue minerals. Chemical composition of the ore is very complex, where contents of valuable metals range as follows: Sb (0.17-24.31 wt.%), Zn (0.21-6.29 wt.%), Pb (0.15-6.33 wt.%), As (0.06-1.28 wt.%), Cd (25-747 ppm), Ag (7-408 ppm), Hg (13-473 ppm), and Tl (<1-29 ppm). Electron Probe Microanalyses (EPMA) of native arsenic from both the Rujevac and Stragari deposits showed contents of As up to 98.8 and 97.1 wt.%, with impurity contents of Sb up to 1.3 and 6.6 wt.%, and Tl up to 2 and 1.3 wt.%, respectively. Rhombohedral unit-cell parameters for native arsenic from Rujevac and Stragari deposits amount to: a = 3.760(2), c = 10.555(3) Å, V = 129.23(7) Å3 and a = 3.763(1), c = 10.560(5) Å, V = 129.48(8) Å3, respectively. Mineral assemblages, deposition order and genesis of the Rujevac polymetallic deposit were also discussed in detail. Native arsenic mineralization here has been additionally compared with similar well-known global deposits.

  2. Rujevac Sb-Pb-Zn-As polymetallic deposit, Boranja orefield, Western Serbia: native arsenic and arsenic mineralization

    NASA Astrophysics Data System (ADS)

    Radosavljević, Slobodan A.; Stojanović, Jovica N.; Radosavljević-Mihajlović, Ana S.; Vuković, Nikola S.

    2013-05-01

    Rujevac is a low-temperature hydrothermal polymetallic Sb-Pb-Zn-As vein-type ore deposit, hosted within a volcanogenic-sedimentary zone situated in the Rujevac-Crvene Stene-Brezovica Diabase-Chert Formation (DCF) of the Podrinje Metallogenic District (PMD), Serbia. It is located several kilometers SE from the Boranja contact aureole, which is an integral part of the PMD in Western Serbia. Genetically related to the Tertiary granodioritic magma, the mineral assemblages are characterized by specific features. The mineral association of this deposit consists of sulfides, Pb-Sb(As) sulfosalts, native metals, oxides, hydroxides and gangue minerals. Chemical composition of the ore is very complex, where contents of valuable metals range as follows: Sb (0.17-24.31 wt.%), Zn (0.21-6.29 wt.%), Pb (0.15-6.33 wt.%), As (0.06-1.28 wt.%), Cd (25-747 ppm), Ag (7-408 ppm), Hg (13-473 ppm), and Tl (<1-29 ppm). Electron Probe Microanalyses (EPMA) of native arsenic from both the Rujevac and Stragari deposits showed contents of As up to 98.8 and 97.1 wt.%, with impurity contents of Sb up to 1.3 and 6.6 wt.%, and Tl up to 2 and 1.3 wt.%, respectively. Rhombohedral unit-cell parameters for native arsenic from Rujevac and Stragari deposits amount to: a = 3.760(2), c = 10.555(3) Å, V = 129.23(7) Å3 and a = 3.763(1), c = 10.560(5) Å, V = 129.48(8) Å3, respectively. Mineral assemblages, deposition order and genesis of the Rujevac polymetallic deposit were also discussed in detail. Native arsenic mineralization here has been additionally compared with similar well-known global deposits.

  3. Analytical performance of a lab-made concomitant metal analyzer to generate volatile species of Ag, Au, Cd, Cu, Ni, Sn and Zn using 8-hydroxyquinoline as a reaction media.

    PubMed

    Villanueva-Alonso, Julia; Peña-Vázquez, Elena; Bermejo-Barrera, Pilar

    2012-10-15

    This study evaluated the main parameters affecting Ag, Au, Cd, Cu, Ni, Sn and Zn vapor generation using a lab-made concomitant metal analyzer (CMA) as a reaction chamber and gas-liquid separator. The modifier used in the reaction media was 8-hydroxyquinoline, and Inductively-Coupled Plasma Optical Emission Spectrometry was used as detection technique. The performance of the lab-made concomitant analyzer was compared with the performance of a continuous flow gas-liquid separator and of a cyclonic spray chamber. Standards were prepared in acid media and included 1 mg L(-1) of Co as a catalyzer. The optimum concentrations of the reagents in the standards were: 450 mg L(-1) of 8-hydroxyquinoline and 0.4 M nitric acid. The optimum concentration of sodium borohydride to generate the vapors was 2.25% (w/v) (prepared in 0.4% (w/v) NaOH). The volatile species were swept from the CMA to the torch by an argon flow of 0.6 mL min(-1). The use of the CMA led to an improvement of the detection limits for some elements compared to conventional nebulization: 1.1 μg L(-1) for Ag, 7.0 μg L(-1) for Au and 4.3 μg L(-1) for Sn. The limit of detection for Cu was 1.4 μg L(-1) and for Ni 22.5 μg L(-1). The direct mixing of the reagents on the spray chamber was not effective for Cd and Zn; a deviation of the linearity was observed for these elements. PMID:23141310

  4. Syntheses, crystal structures and fluorescent properties of Cd(II), Hg(II) and Ag(I) coordination polymers constructed from 1H-1,2,4-triazole-1-acetic acid

    NASA Astrophysics Data System (ADS)

    Ding, De-Gang; Xie, Li-Xia; Fan, Yao-Ting; Hou, Hong-Wei; Xu, Yan

    2009-06-01

    Three new d10 coordination polymers, namely [Cd(taa)Cl] n1, [Hg(taa)Cl] n2, and [Ag 1.5(taa)(NO 3) 0.5] n3 (taa=1H-1,2,4-triazole-1-acatate anion) have been prepared and characterized by elemental analysis, IR, and single crystal X-ray diffraction. Compound 1 consists of two-dimensional layers constructed by carboxyl-linked helical chains, which are further linked through carboxyl group to generate a unique 3D open framework. Topological analysis reveals that the structure of 1 can be classified as an unprecedented (3,8)-connected network with the Schläfli symbol (4.5 2) 2(4 2.5 8.6 14.7 3.8). Compound 2 manifests a doubly interpenetrated decorated α-polonium cubic network with the Schläfli symbol of (4 10.6 2.8 3). Compound 3 consists of 2D puckered layers made up of Ag centers and taa - bridges. In addition, all of these compounds are photoluminescent in the solid state with spectra that closely resemble those of the ligand precursor.

  5. Preparation and thermoelectric properties of sintered iodine-containing clathrate compounds Ge38Sb8I8 and Sn38Sb8I8

    NASA Astrophysics Data System (ADS)

    Kishimoto, Kengo; Arimura, Shuntaro; Koyanagi, Tsuyoshi

    2006-05-01

    The iodine-containing cationic type-I clathrates Ge38Sb8I8 and Sn38Sb8I8 were prepared and their thermodynamic properties as well as their thermoelectric properties were investigated. Their atomic displacement parameters were as large as those of anionic clathrates such as Ba8Ga16Ge30 and Cs8Cd4Sn42. The room temperature thermal conductivities of Ge38Sb8I8 and Sn38Sb8I8 were 7 and 12mWcm-1K-1, respectively; these values were as low as that of the above anionic clathrates. Both cationic clathrates had negative Seebeck coefficients; the band gap energies of Ge38Sb8I8 and Sn38Sb8I8 were 1.16 and 0.80eV, respectively.

  6. Structural analysis of quaternary Se85-xSb10In5Agx bulk glassy alloys

    NASA Astrophysics Data System (ADS)

    Sharma, Rita; Sharma, Shaveta; Kumar, Praveen; Chander, Ravi; Thangaraj, R.; Mian, M.

    2015-08-01

    The physical properties of chalcogenide semiconductor have attracted much attention recently due to their applications in optical recording media and inorganic resist due to photo induced structural transformations observed in these materials. The bulk samples of Se85-xSb10In5Agx system are prepared by melt-quenching technique. X-ray diffraction technique and RAMAN spectroscopy have been used to study the role of Ag additive on the amorphous/crystalline nature and molecular structure of Se85Sb10In5 glassy alloys. The phases Sb2Se3, In-Sb and In2Se3 has been observed by X-ray diffraction. The formation of AgInSe2 phase along with the enhancement in intensity has been observed with the Ag addition.Three bands observed by raman spectroscopy for Se85Sb10In5 are at 70 cm-1, 212cm-1 and 252cm-1. The formation of small bands up to wavenumber 188cm-1 and shifting in second band along with the increase in intensity up to sample x=5 has been observed with the Ag addition. The enhancement in intensity in third band with Ag content has been observed.

  7. Diameter-Controlled and Surface-Modified Sb2Se3 Nanowires and Their Photodetector Performance

    NASA Astrophysics Data System (ADS)

    Choi, Donghyeuk; Jang, Yamujin; Lee, Jeehee; Jeong, Gyoung Hwa; Whang, Dongmok; Hwang, Sung Woo; Cho, Kyung-Sang; Kim, Sang-Wook

    2014-10-01

    Due to its direct and narrow band gap, high chemical stability, and high Seebeck coefficient (1800 μVK-1), antimony selenide (Sb2Se3) has many potential applications, such as in photovoltaic devices, thermoelectric devices, and solar cells. However, research on the Sb2Se3 materials has been limited by its low electrical conductivity in bulk state. To overcome this challenge, we suggest two kinds of nano-structured materials, namely, the diameter-controlled Sb2Se3 nanowires and Ag2Se-decorated Sb2Se3 nanowires. The photocurrent response of diameter-controlled Sb2Se3, which depends on electrical conductivity of the material, increases non-linearly with the diameter of the nanowire. The photosensitivity factor (K = Ilight/Idark) of the intrinsic Sb2Se3 nanowire with diameter of 80-100 nm is highly improved (K = 75). Additionally, the measurement was conducted using a single nanowire under low source-drain voltage. The dark- and photocurrent of the Ag2Se-decorated Sb2Se3 nanowire further increased, as compared to that of the intrinsic Sb2Se3 nanowire, to approximately 50 and 7 times, respectively.

  8. Diameter-Controlled and Surface-Modified Sb2Se3 Nanowires and Their Photodetector Performance

    PubMed Central

    Choi, Donghyeuk; Jang, Yamujin; Lee, JeeHee; Jeong, Gyoung Hwa; Whang, Dongmok; Hwang, Sung Woo; Cho, Kyung-Sang; Kim, Sang-Wook

    2014-01-01

    Due to its direct and narrow band gap, high chemical stability, and high Seebeck coefficient (1800 μVK−1), antimony selenide (Sb2Se3) has many potential applications, such as in photovoltaic devices, thermoelectric devices, and solar cells. However, research on the Sb2Se3 materials has been limited by its low electrical conductivity in bulk state. To overcome this challenge, we suggest two kinds of nano-structured materials, namely, the diameter-controlled Sb2Se3 nanowires and Ag2Se-decorated Sb2Se3 nanowires. The photocurrent response of diameter-controlled Sb2Se3, which depends on electrical conductivity of the material, increases non-linearly with the diameter of the nanowire. The photosensitivity factor (K = Ilight/Idark) of the intrinsic Sb2Se3 nanowire with diameter of 80–100 nm is highly improved (K = 75). Additionally, the measurement was conducted using a single nanowire under low source-drain voltage. The dark- and photocurrent of the Ag2Se-decorated Sb2Se3 nanowire further increased, as compared to that of the intrinsic Sb2Se3 nanowire, to approximately 50 and 7 times, respectively. PMID:25336056

  9. In Situ Binding Sb Nanospheres on Graphene via Oxygen Bonds as Superior Anode for Ultrafast Sodium-Ion Batteries.

    PubMed

    Wan, Fang; Guo, Jin-Zhi; Zhang, Xiao-Hua; Zhang, Jing-Ping; Sun, Hai-Zhu; Yan, Qingyu; Han, Dong-Xue; Niu, Li; Wu, Xing-Long

    2016-03-30

    Graphene incorporation should be one effective strategy to develop advanced electrode materials for a sodium-ion battery (SIB). Herein, the micro/nanostructural Sb/graphene composite (Sb-O-G) is successfully prepared with the uniform Sb nanospheres (∼100 nm) bound on the graphene via oxygen bonds. It is revealed that the in-situ-constructed oxygen bonds play a significant role on enhancing Na-storage properties, especially the ultrafast charge/discharge capability. The oxygen-bond-enhanced Sb-O-G composite can deliver a high capacity of 220 mAh/g at an ultrahigh current density of 12 A/g, which is obviously superior to the similar Sb/G composite (130 mAh/g at 10 A/g) just without Sb-O-C bonds. It also exhibits the highest Na-storage capacity compared to Sb/G and pure Sb nanoparticles as well as the best cycling performance. More importantly, this Sb-O-G anode achieves ultrafast (120 C) energy storage in SIB full cells, which have already been shown to power a 26-bulb array and calculator. All of these superior performances originate from the structural stability of Sb-O-C bonds during Na uptake/release, which has been verified by ex situ X-ray photoelectron spectroscopies and infrared spectroscopies. PMID:26960386

  10. Theoretical studies on the bonding and electron structures of a [Au3Sb6](3-) complex and its oligomers.

    PubMed

    Li, Wan-Lu; Xu, Cong-Qiao; Hu, Shu-Xian; Li, Jun

    2016-08-01

    Recently an all-metal aromatic sandwich compound of a [Sb3Au3Sb3](3-) ion has been synthesized and characterized experimentally, which indicates that there might exist a variety of stable all-metal sandwich complexes. The intralayer and interlayer chemical bonding interaction in this system plays significant roles in their stability, chemical properties and functionalities. Here we report a systematic theoretical study on the geometries, electronic structures, and chemical bonding of the [Sb3Au3Sb3](3-) ion and its congeners of [X3Au3X3](3-) (X = N, P, As, Sb, Bi, Uup) as well as [X3M3X3](3-) (M, X = Cu, As; Ag, Bi; Au, Sb; Rg, Uup) to understand the special stabilities of these species. Additional studies are also performed on the oligomers [Sb3(Au3Sb3)n](3-) (n = 1-4) to explore whether the sandwich compound can form stable extended systems. Through extensive theoretical analyses, we have shown that among the [Au3X6](3-) (X = N, P, As, Sb, Bi, Uup) species, [Sb3Au3Sb3](3-) is most stable due to superb matching of Sb3 and Au3 in both geometric size and fragment orbital energies. The significant stability of the [Au3Sb6](3-) ion is determined by the interlayer (p-d-p)σ interactions between the vertical Au 5d6s hybrid orbitals of Au3 and Sb 5pπ orbitals of the Sb3 rings. Each Sb3 ring demonstrates unique σ aromaticity, which remains when the complex is extended to oligomers. The results suggest that it is likely that there might exist other stable [ApMpAp](x-) (M = transition metals, A = main group elements, p = 3, 4, 5, …) sandwich ions and oligomers. PMID:27010416

  11. Probabilistic distribution coefficients (K(d)s) in freshwater for radioisotopes of Ag, Am, Ba, Be, Ce, Co, Cs, I, Mn, Pu, Ra, Ru, Sb, Sr and Th: implications for uncertainty analysis of models simulating the transport of radionuclides in rivers.

    PubMed

    Ciffroy, P; Durrieu, G; Garnier, J-M

    2009-09-01

    The objective of this study was to provide operational probability density functions (PDFs) for distribution coefficients (K(d)s) in freshwater, representing the partition of radionuclides between the particulate and the dissolved phases respectively. Accordingly, the K(d) variability should be considered in uncertainty analysis of transport and risk assessment models. The construction of PDFs for 8 elements (Ag, Am, Co, Cs, I, Mn, Pu and Sr) was established according to the procedure already tested in Durrieu et al. [2006. A weighted bootstrap method for the determination of probability density functions of freshwater distribution coefficients (K(d)s) of Co, Cs, Sr and I radioisotopes. Chemosphere 65 (8), 1308-1320]: (i) construction of a comprehensive database where K(d)s values obtained under various environments and parametric conditions were collected; (ii) scoring procedure to account for the 'quality' of each datapoint (according to several criteria such as the presentation of data (e.g. raw data vs mean with or without replicates), contact time, pH, solid-to-liquid ratio, expert judgement) in the construction of the PDF; (iii) weighted bootstrapping procedure to build the PDFs, in order to give more importance to the most relevant datapoints. Two types of PDFs were constructed: (i) non-conditional, usable when no knowledge about the site of concern is available; (ii) conditional PDFs corresponding to a limited range of parameters such as pH or contact time; conditional PDFs can thus be used when some parametric information is known on the site under study. For 7 other radionuclides (Ba, Be, Ce, Ra, Ru, Sb and Th), a simplified procedure was adopted because of the scarcity of data: only non-conditional PDFs were built, without incorporating a scoring procedure. PMID:19114288

  12. Studies on structural & optical properties of CdS0.2Se0.8: Ag nanocomposite thin film for photosensor application

    NASA Astrophysics Data System (ADS)

    Chaudhari, J. B.; Patil, R. S.; Patil, I. J.; Jagtap, P. P.; Sharma, Ramphal

    2012-06-01

    Silver doped CdS0.2Se0.8 thin films of different concentrations were grown by simple and economical chemical bath deposition technique and later on characterized for optoelectronic and physicochemical properties. The X-ray diffraction (XRD) patterns of undoped and doped sample indicates polycrystalline nature with hexagonal structure. Scanning electron microscopy (SEM) micrograph showed uniform morphology with cabbage type structure for undoped film and leaf-like structure for doped films over the entire glass substrate. Room temperature absorbance for 1 wt% doping concentration of silver showed an excitonic peak which confirms the size quantization of the particle. I-V characteristic for undoped and doped film shows ohmic and Schottky junction behavior.

  13. Effects of annealing and additions on dynamic mechanical properties of SnSb quenched alloy

    NASA Astrophysics Data System (ADS)

    El-Bediwi, A. B.

    2004-08-01

    The elastic modulus, internal friction and stiffness values of quenched SnSb bearing alloy have been evaluated using the dynamic resonance technique. Annealing for 2 and 4 h at 120, 140 and 160degreesC caused variations in the elastic modulus. internal friction and stiffness values. This is due to structural changes in the SnSb matrix during isothermal annealing such as coarsening in the phases (Sn, Sb or intermetallic compounds), recrystallization and stress relief. In addition, adding a small amount (1 wt.%) of Cu or Ag improved the bearing mechanical properties of the SnSb bearing alloy. The SnSbCu1 alloy has the best bearing mechanical properties with thermo-mechanical stability for long time at high temperature.

  14. Solidification of InSb-GaSb alloy and InSb with vibration

    NASA Technical Reports Server (NTRS)

    Yuan, Weijun

    1992-01-01

    The objective of this project is to determine the influence of vibration on the composition homogeneity and microstructure of alloy semiconductors solidified with the Vertical Bridgman-Stockbarger (VBS) technique. InSb-GaSb and InSb were directionally solidified in a VBS apparatus with axial vibration of the ampoule.

  15. Valence Fluctuations Revealed by Magnetic Field and Pressure Scans: Comparison with Experiments in YbXCu4 (X=In, Ag, Cd) and CeYIn5 (Y=Ir, Rh)

    NASA Astrophysics Data System (ADS)

    Watanabe, Shinji; Tsuruta, Atsushi; Miyake, Kazumasa; Flouquet, Jacques

    2009-10-01

    The mechanism of how critical end points of the first-order valence transition (FOVT) are controlled by a magnetic field is discussed. We demonstrate that critical temperature is suppressed to be a quantum critical point (QCP) by a magnetic field. This results explain the field dependence of the isostructural FOVT observed in Ce metal and YbInCu4. Magnetic field scan can make the system reenter in a critical valence fluctuation region. Even in intermediate-valence materials, the QCP is induced by applying a magnetic field, at which magnetic susceptibility also diverges. The driving force of the field-induced QCP is shown to be a cooperative phenomenon of the Zeeman effect and the Kondo effect, which creates a distinct energy scale from the Kondo temperature. The key concept is that the closeness to the QCP of the FOVT is vital in understanding Ce- and Yb-based heavy-fermions. This explains the peculiar magnetic and transport responses in CeYIn5 (Y=Ir, Rh) and metamagnetic transition in YbXCu4 for X=In as well as the sharp contrast between X=Ag and Cd.

  16. Hierarchical active factors to band gap and nonlinear optical response in Ag-containing quaternary-chalcogenide compounds

    NASA Astrophysics Data System (ADS)

    Huang, Jun-ben; Mamat, Mamatrishat; Pan, Shilie; Yang, Zhihua

    2016-07-01

    In this research work, Ag-containing quaternary-chalcogenide compounds KAg2TS4 (T=P, Sb) (I-II) and RbAg2SbS4 (III) have been studied by means of Density Functional Theory as potential IR nonlinear optical materials. The origin of wide band gap, different optical anisotropy and large SHG response is explained via a combination of density of states, electronic density difference and bond population analysis. It is indicated that the different covalent interaction behavior of P-S and Sb-S bonds dominates the band gap and birefringence. Specifically, the Ag-containing chalcogenide compound KAg2PS4 possesses wide band gap and SHG response comparable with that of AgGaS2. By exploring the origin of the band gap and NLO response for compounds KAg2TS4 (T=P, Sb), we found the determination factor to the properties is different, especially the roles of Ag-d orbitals and bonding behavior of P-S or Sb-S. Thus, the compounds KAg2TS4 (T=P, Sb) and RbAg2SbS4 can be used in infrared (IR) region.

  17. Liquidus projection of the Ag-Ba-Ge system and melting points of clathrate type-I compounds

    SciTech Connect

    Zeiringer, I.; Grytsiv, A.; Broz, P.

    2012-12-15

    The liquidus and solidus projection has been constructed for the Ag-Ba-Ge system up to 33.3 at% Ba, using electron micro probe analysis (EPMA), X-ray powder diffraction (XRD) and differential thermal analysis (DSC/DTA). Eight different primary crystallization regions were found: (Ge), Ba{sub 8}Ag{sub x}Ge{sub 46-x-y}{open_square}{sub y} ({kappa}{sub I}) ({open_square} is a vacancy), Ba{sub 6}Ag{sub x}Ge{sub 25-x} ({kappa}{sub Ix}), BaGe{sub 2}, Ba(Ag{sub 1-x}Ge{sub x}){sub 2} ({tau}{sub 1}), BaAg{sub 2-x}Ge{sub 2+x} ({tau}{sub 2}) BaAg{sub 5} and (Ag). The ternary invariant reactions have been determined for the region investigated and are the basis for a Schulz-Scheil diagram. The second part of this work provides a comprehensive compilation of melting points of ternary A{sub 8}T{sub x}M{sub 46-x} and quaternary (A=Sr, Ba, Eu; T=Ni, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga; M=Si, Ge, Sn) clathrate type-I compounds and decomposition temperatures of inverse clathrate type-I Ge{sub 38}{l_brace}P,As,Sb{r_brace}{sub 8}{l_brace}Cl,Br,I{r_brace}{sub 8}, Si{sub 46-x}P{sub x}Te{sub y} and tin based compounds. - Graphical Abstract: Partial liquidus projection of the Ag-Ba-Ge system. Highlights: Black-Right-Pointing-Pointer The liquidus and solidus projection has been constructed for the Ag-Ba-Ge system up to 33.33 at% Ba. Black-Right-Pointing-Pointer Eight different primary crystallization fields have been found. Black-Right-Pointing-Pointer All the ternary compounds form congruently from the melt. Black-Right-Pointing-Pointer The ternary invariant reactions have been determined and are the basis for a Schulz-Scheil diagram.

  18. Solution-processed solar cells based on environmentally friendly AgBiS2 nanocrystals

    NASA Astrophysics Data System (ADS)

    Bernechea, María; Miller, Nichole Cates; Xercavins, Guillem; So, David; Stavrinadis, Alexandros; Konstantatos, Gerasimos

    2016-08-01

    Solution-processed inorganic solar cells are a promising low-cost alternative to first-generation solar cells. Solution processing at low temperatures combined with the use of non-toxic and abundant elements can help minimize fabrication costs and facilitate regulatory acceptance. However, at present, there is no material that exhibits all these features while demonstrating promising efficiencies. Many of the candidates being explored contain toxic elements such as lead or cadmium (perovskites, PbS, CdTe and CdS(Se)) or scarce elements such as tellurium or indium (CdTe and CIGS(Se)/CIS). Others require high-temperature processes such as selenization or sintering, or rely on vacuum deposition techniques (Sb2S(Se)3, SnS and CZTS(Se)). Here, we present AgBiS2 nanocrystals as a non-toxic, earth-abundant material for high-performance, solution-processed solar cells fabricated under ambient conditions at low temperatures (≤100 °C). We demonstrate devices with a certified power conversion efficiency of 6.3%, with no hysteresis and a short-circuit current density of ∼22 mA cm‑2 for an active layer thickness of only ∼35 nm.

  19. Performance of thin-film CdS/CdTe solar cells

    NASA Astrophysics Data System (ADS)

    Hussain, O. M.; Reddy, P. J.

    1991-07-01

    A polycrystalline thin-film CdS/CdTe solar cell has been fabricated by means of a laser evaporation of CdTe onto thermally-evaporated CdS films. The cell has demonstrated a maximum efficiency of about 8.25 percent, in conjunction with a quantum efficiency of about 80 percent. The In-doped CdS 0.5-micron thick films were deposited onto conducting glass substrates at 473 K and annealed at 673 K in a hydrogen atmosphere; the Sb-doped CdTe 5-micron thickness films were deposited and then heat-treated in air at 673 K.

  20. Structural transformation of Sb-based high-speed phase-change material.

    PubMed

    Matsunaga, Toshiyuki; Kojima, Rie; Yamada, Noboru; Kubota, Yoshiki; Kifune, Kouichi

    2012-12-01

    The crystal structure of a phase-change recording material (the compound Ag(3.4)In(3.7)Sb(76.4)Te(16.5)) enclosed in a vacuum capillary tube was investigated at various temperatures in a heating process using a large Debye-Scherrer camera installed in BL02B2 at SPring-8. The amorphous phase of this material turns into a crystalline phase at around 416 K; this crystalline phase has an A7-type structure with atoms of Ag, In, Sb or Te randomly occupying the 6c site in the space group. This structure was maintained up to around 545 K as a single phase, although thermal expansion of the crystal lattice was observed. However, above this temperature, phase separation into AgInTe(2) and Sb-Te transpired. The first fragment, AgInTe(2), reliably maintained its crystal structure up to the melting temperature. On the other hand, the atomic configuration of the Sb-Te gradually varied with increasing temperature. This gradual structural transformation can be described as a continuous growth of the modulation period γ. PMID:23165592

  1. In situ STM studies of Sb(111) electrodes in aqueous electrolyte solutions

    NASA Astrophysics Data System (ADS)

    Grozovski, V.; Kallip, S.; Lust, E.

    2013-07-01

    The in situ STM studies of Sb(111), which was cleaved at the temperature of liquid nitrogen inside the glove box, and of Sb(111), which was electrochemically polished in the KI + HCl aqueous solution, have been performed under negative polarizations from - 0.8 to - 0.15 V (versus Ag|AgCl in sat. KCl aqueous solution) in the 0.5 M Na2SO4 + 0.0003 M H2SO4 aqueous solution. The atomic resolution has been achieved. The in situ STM data show that there are no quick surface reconstruction processes and the surface structure of cleaved and electrochemically polished Sb(111) is stable within the potential region investigated, similarly for Bi(111) single crystal electrode, previously studied [S. Kallip, E. Lust, Electrochem. Comm. 7 (2005) 863].

  2. Large magnetoresistance in the antiferromagnetic semimetal NdSb

    NASA Astrophysics Data System (ADS)

    Wakeham, N.; Bauer, E. D.; Neupane, M.; Ronning, F.

    2016-05-01

    There has been considerable interest in topological semimetals that exhibit extreme magnetoresistance (XMR). These have included materials lacking inversion symmetry such as TaAs, as well Dirac semimetals such as Cd3As2 . However, it was reported recently that LaSb and LaBi also exhibit XMR, even though the rocksalt structure of these materials has inversion symmetry, and the band-structure calculations do not show a Dirac dispersion in the bulk. Here, we present magnetoresistance and specific-heat measurements on NdSb, which is isostructural with LaSb. NdSb has an antiferromagnetic ground state and, in analogy with the lanthanum monopnictides, is expected to be a topologically nontrivial semimetal. We show that NdSb has an XMR of ˜104% , even within the antiferromagnetic state, illustrating that XMR can occur independently of the absence of time-reversal symmetry breaking in zero magnetic field. The persistence of XMR in a magnetic system offers the promise of new functionality when combining topological matter with electronic correlations. We also find that in an applied magnetic field below the Néel temperature there is a first-order transition, consistent with evidence from previous neutron scattering work.

  3. AGS II

    SciTech Connect

    Palmer, R.B.

    1984-01-01

    Interest in rare K decays, neutrino oscillations and other fields have generated an increasing demand for running, and improved intensity and duty cycle, at the AGS. Current projects include acceleration of polarized protons and light ions (up to mass 32). Future plans are for a booster to increase intensity and allow heavy ions (up to mass 200), and a stretcher to give 100% duty cycle. A later upgrade could yield an average current of 32 ..mu.. amps. 6 figures, 2 tables.

  4. Optical properties of cadmium implanted GaSb

    NASA Astrophysics Data System (ADS)

    Pandey, S. D.; Dubey, R. L.; Dubey, S. K.

    2013-06-01

    Single crystal, n-type GaSb (gallium antimonide) was implanted with 300 keV 112Cd (cadmium) ions for various ion fluences varying from 1 × 1013 to 1 × 1016 cm-2. Fourier Transform Infra-red studies revealed that the optical absorbance and defect density increased but optical band gap decreased with increase in ion fluence. Rapid thermal annealing of sample implanted with ion fluence 1 × 1013 cm-2 showed significant damage recovery.

  5. Synthesis and Crystal Structures of Hg 6Sb 5Br 7, Hg 6As 4BiCl 7, and Hg 6Sb 4BiBr 7, Built of a Polycationic Mercury-Pnictide Framework with Trapped Anions

    NASA Astrophysics Data System (ADS)

    Beck, Johannes; Hedderich, Sylvia; Neisel, Udo

    2000-11-01

    Hg6Sb5Br7, Hg6As4BiCl7, and Hg6Sb4BiBr7 were prepared from stoichiometric mixtures of Hg2X2, HgX2 (X=Cl, Br), As, Sb, and Bi in sealed, evacuated glass ampoules in temperature gradients 260→240°C for Hg6Sb5Br7, 340→320°C for Hg6As4BiCl7, and 290→270°C for Hg6Sb4BiBr7. All compounds crystallize in the cubic space group Paoverline3 with Z=4 and the lattice constants a=13.003(1) Å for Hg6Sb5Br7, a=12.178(2) Å for Hg6As4BiCl7, and a=12.998(4) Å for Hg6Sb4BiBr7. The structures have been solved based on single-crystal X-ray diffraction data and refined to R(F)=0.0431, 666 Fo for Hg6Sb5Br7, R(F)=0.0478, 690 Fo for Hg6As4BiCl7, and R(F)=0.0444, 840 Fo for Hg6Sb4BiBr7 with 30 parameters for each refinement. The structures are characterized by a three-dimensional polycationic framework of pnictide dumb-bells (As-As distance 2.43 Å, Sb-Sb distance 2.78 Å), each connected by six mercury atoms to six neighbored As2/Sb2 groups. There are two different cages in the framework; one type is occupied by nearly regular MX6 octahedra (M=Sb,Bi; X=Cl, Br), the other by halide ions. The three compounds crystallize closely related to Cd7P4Cl6, which contains a similar polycationic framework of P2 dumb-bells connected by Cd, but with only one type of cage occupied by octahedral [CdCl6]4- ions. The interactions between the atoms of the polycationic framework and the anions are very weak. The observed diamagnetism of all three compounds is in agreement with the ionic formulas (Hg6Sb4)4+[SbBr6]3-Br-, (Hg6As4)4+[BiCl6]3-Cl-, and (Hg6Sb4)4+[BiBr6]3-Br-.

  6. Molar and excess volumes of liquid In-Sb, Mg-Sb, and Pb-Sb alloys

    SciTech Connect

    Hansen, A.R.; Kaminski, M.A. ); Eckert, C.A. )

    1990-04-01

    By a direct Archimedes' technique, volumetric data were obtained for liquid In, Mg, Pb, and Sb and mixtures of In-Sb, Mg-Sb, and Pb-Sb. In this paper the excess volumes for the alloys studied are presented and discussed.

  7. Defect investigations in InAs/GaSb type-II strained layer superlattice

    NASA Astrophysics Data System (ADS)

    Klein, Brianna

    InAs/GaSb type-II strained layer superlattices are a material used for infrared detection. By adjusting the thickness of the InAs and GaSb layers, the material bandgap can be tuned to absorb photons from 3-30 mum. Compared to competing materials such as HgCdTe and InSb, InAs/GaSb superlattices are more mechanically robust, have reduced tunneling currents, and can use strain to suppress Auger recombination. In spite of these advantages, this material still faces several challenges, including low minority carrier lifetime, resulting from trap levels that cause Schockley-Read-Hall recombination. These low lifetimes lead to reduced signal-to-noise ratio and higher dark current. Therefore, increasing the lifetime is important for improving this material's performance. However, to increase the carrier lifetimes, the origin of the traps must first be understood. In this work, several key suspect causes of the "killer" defect were evaluated. A commonly explored suspect in literature, the interfaces, was studied using time-resolved photoluminescence for three different samples. This characterization method was also used to determine if the doping atom and its layer placement significantly impacted the minority carrier lifetime. There is a substantial amount of evidence that the presence of gallium, or the GaSb layer itself harbors the defect. Thus, the rest of the study focused on aspects of GaSb. Layer intermixing of the In and As atoms into the GaSb layer was studied by intentionally incorporating In and As in bulk GaSb and using photocapacitance characterization to observe any possible defect level formation. In addition, trap level formation for different GaSb growth temperatures was also explored with this characterization technique. Finally, in an attempt to reduce trap densities, GaSb was grown with an increased level of Sb monomers rather than dimers. This material was characterized using dark current density measurements and photoluminescence.

  8. Vought SB2U-2 Vindicator

    NASA Technical Reports Server (NTRS)

    1939-01-01

    Vought SB2U-2 Vindicator: The Navy was in the transition from biplanes to monoplanes when it ordered the SB2U. Used for diving tests, this Vought SB2U-2 Vindicator was one of approximately 169 SB2Us built.

  9. Solution-Processed hybrid Sb2 S3 planar heterojunction solar cell

    NASA Astrophysics Data System (ADS)

    Huang, Wenxiao; Borazan, Ismail; Carroll, David

    Thin-film solar cells based on inorganic absorbers permit a high efficiency and stability. Among or those absorber candidates, recently Sb2S3 has attracted extensive attention because of its suitable band gap (1.5eV ~1.7 eV) , strong optical absorption, low-cost and earth-abundant constituents. Currently high-efficiency Sb2S3 solar cells have absorber layer deposited on nanostructured TiO2 electrodes in combination with organic hole transport material (HTM) on top. However it's challenging to fill the nanostructured TiO2 layer with Sb2S3 and subsequently by HTM, this leads to uncovered surface permits charge recombination. And the existing of Sb2S3/TiO2/HTM triple interface will enhance the recombination due to the surface trap state. Therefore, a planar junction cell would not only have simpler structure with less steps to fabricate but also ideally also have a higher open circuit voltage because of less interface carrier recombination. By far there is limited research focusing on planar Sb2S3 solar cell, so the feasibility is still unclear. Here, we developed a low-toxic solution method to fabricate Sb2S3 thin film solar cell, then we studied the morphology of the Sb2S3 layer and its impact to the device performance. The best device with a structure of FTO/TiO2/Sb2S3/P3HT/Ag has PCE over 5% which is similar or higher than yet the best nanostructure devices with the same HTM. Furthermore, based on solution engineering and surface modification, we improved the Sb2S3 film quality and achieved a record PCE. .

  10. Ag(I)-binding to phytochelatins.

    PubMed

    Mehra, R K; Tran, K; Scott, G W; Mulchandani, P; Saini, S S

    1996-02-01

    Phytochelatins (PCs) are glutathione-derived peptides with the general structure (gamma-Glu-Cys)nGly, where n varies from 2 to 11. A variety of metal ions such as Cu(II), Cd(II), Pb(II), Zn(II), and Ag(I) induce PC synthesis in plants and some yeasts. It has generally been assumed that the inducer metals also bind PCs. However, very little information is available on the binding of metals other than Cu(I) and Cd(II) to PCs. In this paper, we describe the Ag(I)-binding characteristics of PCs with the structure (gamma-Glu-Cys)2Gly, (gamma-Glu-Cys)3Gly, and (gamma-Glu-Cys)4Gly. The Ag(I)-binding stoichiometries of these three peptides were determined by (i) UV/VIS spectrophotometry, (ii) luminescence spectroscopy at 77 K, and (iii) reverse-phase HPLC. The three techniques yielded similar results. ApoPCs exhibit featureless absorption in the 220-340 nm range. The binding of Ag(I) to PCs induced the appearance of specific absorption shoulders. The titration end point was indicated by the flattening of the characteristic absorption shoulders. Similarly, luminescence at 77 K due to Ag(I)-thiolate clusters increased with the addition of graded Ag(I) equivalents. The luminescence declined when Ag(I) equivalents in excess of the saturating amounts were added to the peptides. At neutral pH, (gamma-Glu-Cys)2Gly, (gamma-Glu-Cys)3Gly, and (gamma-Glu-Cys)4Gly bind 1.0, 1.5, and 4.0 equivalents of Ag(I), respectively. The Ag(I)-binding capacity of (gamma-Glu-Cys)2Gly and (gamma-Glu-Cys)3Gly was increased at pH 5.0 and below so that Ag(I)/-SH ratio approached 1.0. A similar pH-dependent binding of Ag(I) to glutathione was also observed. The increased Ag(I)-binding to PCs at lower pH is of physiological significance as these peptides accumulate in acidic vacuoles. We also report lifetime data on Ag(I)-PCs. The relatively long decay-times (approximately 0.1-0.3 msec) accompanied with a large Stokes shift in the emission band are indicative of spin-forbidden phosphorescence. PMID

  11. Better CD4+ T cell recovery in Brazilian HIV-infected individuals under HAART due to cumulative carriage of SDF-1-3'A, CCR2-V64I, CCR5-D32 and CCR5-promoter 59029A/G polymorphisms.

    PubMed

    Rigato, Paula O; Hong, Marisa A; Casseb, Jorge; Ueda, Mirthes; de Castro, Isac; Benard, Gil; Duarte, Alberto J S

    2008-09-01

    Polymorphisms of chemokines and chemokine-receptors genes have been shown to influence the rate of progression to AIDS; however, their influence on response to HAART remains unclear. We investigated the frequency of the SDF-1-3'A, CCR2-64I, CCR5-D32 and CCR5-Promoter-59029-A/G polymorphisms in Brazilian HIV-1-infected and uninfected individuals and their influence on CD4+ T-cell evolution HIV-1 infected individuals before and during HAART. Polymorphism detection was done in a transversal study of 200 HIV-1-infected and 82 uninfected individuals. The rate of CD4+ T cell increase or decrease was studied in a cohort of 155 HIV-1 infected individuals on pre and post-HAART. Polymorphisms were determined by PCR associated with RFLP. The rate of CD4+ T-cell decline or increase was also determined. HIV-1 infected and uninfected subjects showed, respectively, frequencies of 0.193 and 0.220 for SDF-1-3'A, of 0.140 and 0.110 for CCR2-V64I, of 0.038 and 0.055 for CCR5-D32, and of 0.442 and 0.390 for CCR5-P-59029-A/G. HIV-1-infected subjects carrying one, two or three of these four polymorphisms showed better CD4+ T-cell recovery than HIV-1-infected subjects carrying the four wild-type alleles (+2.7, +1.6, +3.5, and -0.9 lymphocytes/microl/month, respectively). Regression logistic analysis showed that the CCR5-D32/CCR2-V64I association was predictor of positive CD4+ T cell slope after HAART. The distribution of polymorphisms did not differ between HIV-1-infected and uninfected individuals, but differed from more homogenous ethnic groups probably reflecting the miscegenation of the Brazilian population. We add further evidence of the role of these polymorphisms by showing that the CD4 gain was influenced by carriage of one or more of the polymorphisms studied here. These results highlight the possibility that these genetic traits can be useful to identify patients at risk for faster progression to AIDS or therapeutic failure. PMID:18855658

  12. Thermal and vibrational properties of thermoelectric ZnSb: Exploring the origin of low thermal conductivity

    NASA Astrophysics Data System (ADS)

    Fischer, A.; Scheidt, E.-W.; Scherer, W.; Benson, D. E.; Wu, Y.; Eklöf, D.; Häussermann, U.

    2015-06-01

    The intermetallic compound ZnSb is an interesting thermoelectric material largely due to its low lattice thermal conductivity. The origin of the low thermal conductivity has so far been speculative. Using multitemperature single crystal x-ray diffraction (9-400 K) and powder x-ray diffraction (300-725 K) measurements, we characterized the volume expansion and the evolution of structural properties with temperature and identified an increasingly anharmonic behavior of the Zn atoms. From a combination of Raman spectroscopy and first principles calculations of phonons, we consolidate the presence of low-energy optic modes with wave numbers below 60 cm-1 . Heat capacity measurements between 2 and 400 K can be well described by a Debye-Einstein model containing one Debye and two Einstein contributions with temperatures ΘD=195 K , ΘE 1=78 K , and ΘE 2=277 K as well as a significant contribution due to anharmonicity above 150 K. The presence of a multitude of weakly dispersed low-energy optical modes (which couple with the acoustic, heat carrying phonons) combined with anharmonic thermal behavior provides an effective mechanism for low lattice thermal conductivity. The peculiar vibrational properties of ZnSb are attributed to its chemical bonding properties, which are characterized by multicenter bonded structural entities. We argue that the proposed mechanism to explain the low lattice thermal conductivity of ZnSb might also control the thermoelectric properties of other electron poor semiconductors, such as Zn4Sb3 , CdSb, Cd4Sb3 , Cd13 -xInyZn10 , and Zn5Sb4In2 -δ .

  13. Preparation, characterization, and photocatalytic activity of porous AgBr@Ag and AgBrI@Ag plasmonic photocatalysts

    NASA Astrophysics Data System (ADS)

    Yang, Fan; Tian, Baozhu; Zhang, Jinlong; Xiong, Tianqing; Wang, Tingting

    2014-02-01

    Porous AgBr@Ag and AgBrI@Ag plasmonic photocatalysts were synthesized by a multistep route, including a dealloying method to prepare porous Ag, a transformation from Ag to AgBr and AgBrI, and a photo-reduction process to form Ag nanoparticles on the surface of AgBr and AgBrI. It was found that the porous structure kept unchanged during Ag was transferred into AgBr, AgBrI, AgBr@Ag, and AgBrI@Ag. Both porous AgBr@Ag and porous AgBrI@Ag showed much higher visible-light photocatalytic activity than cubic AgBr@Ag for the degradation of methyl orange, which is because the interconnected pore channels not only provide more reactive sites but also favor the transportation of photo-generated electrons and holes. For AgBrI@Ag, AgBrI solid solution formed at the interface of AgBr and AgI, and the phase junction can effectively separate the photo-generated electrons and holes, favorable to the improvement of photocatalytic activity. The optimal I content for obtaining the highest activity is ∼10 at.%.

  14. Cellular and molecular requirements for the recall of IL-4-producing memory CD4(+)CD45RO(+)CD27(-) T cells during protection induced by attenuated Plasmodium falciparum sporozoites.

    PubMed

    Palmer, Dupeh R; Krzych, Urszula

    2002-03-01

    The requirements for maintenance of antigen (Ag)-specific memory T cells in protection to malaria is poorly understood. We have previously demonstrated a recall of IL-4-producing memory CD4(+)CD45RO(+) T cells with parasitized red blood cells (pRBC) in persons protected by radiation-attenuated Plasmodium falciparum sporozoites (gamma-spz). Using the CD27 marker, we have now identified two subsets of CD4(+)CD45RO(+) T cells: CD4(+)CD45RO(+)CD27(+) T cells representing an early memory and CD4(+)CD45RO(+)CD27() T cells representing a terminally differentiated memory cells. A small subset of CD4(+)CD45RO(+)CD27(-) T cells also expressed CD70, the CD27 ligand. The addition of anti-CD70 monoclonal antibody (mAb) to pRBC-stimulated cultures significantly inhibited the conversion of CD27(+) to CD27(-) subset without profoundly affecting IL-4 production. In contrast, the inclusion of anti-CD27 mAb in parallel cultures abrogated IL-4 production without interfering with conscription of T cells into the CD27(-) T cell set. We propose that the persistence of memory CD4(+) T cells depends on Ag-driven conscription of a mature memory phenotype through co-ligation of CD27 and CD70 expressed, respectively, on CD27(+) and CD27(-) T cells. Hence, protracted protection in malaria depends in part on memory CD4(+) T cells that require specific Ag presumably from the repositories of liver-and blood-stage antigens and the delivery of a second signal from the CD27:CD70 interaction. PMID:11857339

  15. Levels of human platelet-derived soluble CD40 ligand depend on haplotypes of CD40LG-CD40-ITGA2

    PubMed Central

    Aloui, Chaker; Prigent, Antoine; Tariket, Sofiane; Sut, Caroline; Fagan, Jocelyne; Cognasse, Fabrice; Chakroun, Tahar; Garraud, Olivier; Laradi, Sandrine

    2016-01-01

    Increased circulating soluble CD40 ligand (sCD40L) is commonly associated with inflammatory disorders. We aimed to investigate whether gene polymorphisms in CD40LG, CD40 and ITGA2 are associated with a propensity to secrete sCD40L; thus, we examined this issue at the level of human platelets, the principal source of sCD40L. We performed single polymorphism and haplotype analyses to test for the effect of twelve polymorphisms across the CD40LG, CD40 and ITGA2 genes in blood donors. ITGA2 presented a positive association with rs1126643, with a significant modification in sCD40L secretion (carriers of C allele, P = 0.02), unlike the investigated CD40LG and CD40 polymorphisms. One CD40LG haplotype (TGGC) showing rs975379 (C/T), rs3092952 (A/G), rs3092933 (A/G) and rs3092929 (A/C) was associated with increased sCD40L levels (1.906 μg/L (95% CI: 1.060 to 2.751); P = 0.000009). The sCD40L level was associated with the inter-chromosomal CD40LG/CD40/ITGA2 haplotype (ATC), displaying rs3092952 (A/G), rs1883832 (C/T) and rs1126643 (C/T), with increased sCD40L levels (P = 0.0135). Our results help to decipher the genetic role of CD40LG, CD40 and ITGA2 with regard to sCD40L levels found in platelet components. Given the crucial role of sCD40L, this haplotype study in a transfusion model may be helpful to further determine the role of haplotypes in inflammatory clinical settings. PMID:27094978

  16. DWPF SB6 INITIAL CPC FLOWSHEET TESTING SB6-1 TO SB6-4L TESTS OF SB6-A AND SB6-B SIMULANTS

    SciTech Connect

    Lambert, D.; Pickenheim, B.; Best, D.

    2009-09-09

    The Defense Waste Processing Facility (DWPF) will transition from Sludge Batch 5 (SB5) processing to Sludge Batch 6 (SB6) processing in late fiscal year 2010. Tests were conducted using non-radioactive simulants of the expected SB6 composition to determine the impact of varying the acid stoichiometry during the Sludge Receipt and Adjustment Tank (SRAT) and Slurry Mix Evaporator (SME) processes. The work was conducted to meet the Technical Task Request (TTR) HLW/DWPF/TTR-2008-0043, Rev.0 and followed the guidelines of a Task Technical and Quality Assurance Plan (TT&QAP). The flowsheet studies are performed to evaluate the potential chemical processing issues, hydrogen generation rates, and process slurry rheological properties as a function of acid stoichiometry. These studies were conducted with the estimated SB6 composition at the time of the study. This composition assumed a blend of 101,085 kg of Tank 4 insoluble solids and 179,000 kg of Tank 12 insoluble solids. The current plans are to subject Tank 12 sludge to aluminum dissolution. Liquid Waste Operations assumed that 75% of the aluminum would be dissolved during this process. After dissolution and blending of Tank 4 sludge slurry, plans included washing the contents of Tank 51 to {approx}1M Na. After the completion of washing, the plan assumes that 40 inches on Tank 40 slurry would remain for blending with the qualified SB6 material. There are several parameters that are noteworthy concerning SB6 sludge: (1) This is the second batch DWPF will be processing that contains sludge that has had a significant fraction of aluminum removed through aluminum dissolution; (2) The sludge is high in mercury, but the projected concentration is lower than SB5; (3) The sludge is high in noble metals, but the projected concentrations are lower than SB5; and(4) The sludge is high in U and Pu - components that are not added in sludge simulants. Six DWPF process simulations were completed in 4-L laboratory-scale equipment using

  17. Short-wave infrared barriode detectors using InGaAsSb absorption material lattice matched to GaSb

    SciTech Connect

    Craig, A. P.; Percy, B.; Marshall, A. R. J.; Jain, M.; Wicks, G.; Hossain, K.; Golding, T.; McEwan, K.; Howle, C.

    2015-05-18

    Short-wave infrared barriode detectors were grown by molecular beam epitaxy. An absorption layer composition of In{sub 0.28}Ga{sub 0.72}As{sub 0.25}Sb{sub 0.75} allowed for lattice matching to GaSb and cut-off wavelengths of 2.9 μm at 250 K and 3.0 μm at room temperature. Arrhenius plots of the dark current density showed diffusion limited dark currents approaching those expected for optimized HgCdTe-based detectors. Specific detectivity figures of around 7×10{sup 10} Jones and 1×10{sup 10} Jones were calculated, for 240 K and room temperature, respectively. Significantly, these devices could support focal plane arrays working at higher operating temperatures.

  18. [Sb4Au4Sb4]2-: A designer all-metal aromatic sandwich

    NASA Astrophysics Data System (ADS)

    Tian, Wen-Juan; Guo, Jin-Chang; Li, Da-Zhi; You, Xue-Rui; Wang, Ying-Jin; Sun, Zhong-Ming; Zhai, Hua-Jin

    2016-07-01

    We report on the computational design of an all-metal aromatic sandwich, [Sb4Au4Sb4]2-. The triple-layered, square-prismatic sandwich complex is the global minimum of the system from Coalescence Kick and Minima Hopping structural searches. Following a standard, qualitative chemical bonding analysis via canonical molecular orbitals, the sandwich complex can be formally described as [Sb4]+[Au4]4-[Sb4]+, showing ionic bonding characters with electron transfers in between the Sb4/Au4/Sb4 layers. For an in-depth understanding of the system, one needs to go beyond the above picture. Significant Sb → Au donation and Sb ← Au back-donation occur, redistributing electrons from the Sb4/Au4/Sb4 layers to the interlayer Sb-Au-Sb edges, which effectively lead to four Sb-Au-Sb three-center two-electron bonds. The complex is a system with 30 valence electrons, excluding the Sb 5s and Au 5d lone-pairs. The two [Sb4]+ ligands constitute an unusual three-fold (π and σ) aromatic system with all 22 electrons being delocalized. An energy gap of ˜1.6 eV is predicted for this all-metal sandwich. The complex is a rare example for rational design of cluster compounds and invites forth-coming synthetic efforts.

  19. Realization of Dirac Cones in Few Bilayer Sb(111) Films by Surface Modification.

    PubMed

    Pan, Hui; Wang, Xue-Sen

    2015-12-01

    We report the first-principle study on the recovery and linearization of Dirac cones in the electronic band structures of a few bilayer Sb(111) films (n-BL Sb) by surface modification. Due to the interaction between the surface states on the two surfaces of a free-standing film, the distorted Dirac cone in n-BL Sb(111) (n < 5) disappears. We demonstrate that the Dirac cone can be restored by functionalizing one surface with certain atoms including H, Ag, and Au, to reduce the inter-surface interaction. We further show that an ideal Dirac cone with linear dispersion of topological surface states near the zone center can be realized by functionalizing both surfaces of the film with oxygen, which enhances spin-orbital coupling. The realization of Dirac cone by surface functionalization shows promise for applications of topologic materials to spintronic devices and their operation in complicated conditions. PMID:26293493

  20. The Role of Crop Cd Bioavailability in Potential for Transfer of Soil Cd Risk to Humans and Wildlife

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cd is a common contaminant in soils affected by mining and smelting of Zn, Pb, Cu and Ag ores and where biosolids, composts and manures are applied. Zn is usually present at 100-200 times higher concentrations than Cd. Because of this relationship of Cd and Zn in ores and contaminated soils, Zn is...

  1. The first trialkylphosphane telluride complexes of Ag(I): molecular, ionic and supramolecular structural alternatives.

    PubMed

    Daniliuc, Constantin; Druckenbrodt, Christian; Hrib, Cristian G; Ruthe, Frank; Blaschette, Armand; Jones, Peter G; du Mont, Wolf-W

    2007-05-28

    The structures of the first phosphane telluride complexes of silver(I), obtained from i-Pr3PTe (1) with AgNMs2 [Ms = SO2CH3] and with AgSbF6, reveal the superior coordinating ability of 1, particularly as a bridging ligand, compared with related i-Pr3PS and i-Pr3PSe ligands. PMID:17713078

  2. Anisotropic magnetoresistance and current-perpendicular-to-plane giant magnetoresistance in epitaxial NiMnSb-based multilayers

    NASA Astrophysics Data System (ADS)

    Kwon, B.; Sakuraba, Y.; Sukegawa, H.; Li, S.; Qu, G.; Furubayashi, T.; Hono, K.

    2016-01-01

    We fabricated (001)-oriented C1b-NiMnSb epitaxial films on MgO substrate by a magnetron sputtering system and systematically investigated the structure, magnetic property, and anisotropic magnetoresistance (AMR) effect. NiMnSb film was deposited using a stoichiometric NiMnSb target which has Mn-deficient (Mn ˜ 28.7 at. %) off-stoichiometric composition ratio. We have investigated bulk spin-polarization in NiMnSb films by measuring AMR on the basis of recent study for half-metallic L21-Heusler compounds. Although the negative sign of AMR ratio, which is indicative of half-metallic nature, was observed in the single layer NiMnSb films, the magnitude of AMR ratio (-0.10% at RT) was about half of the largest value reported for half-metallic L21-Heusler compounds. The current-perpendicular-to-plane (CPP) giant magnetoresistance (GMR) devices of NiMnSb/Ag/NiMnSb show MR ratio of 13.2% at 10 K and 4.2% at 300 K, which is higher than the previous result for NiMnSb/Cu/NiMnSb CPP-GMR devices [Caballero et al., J. Magn. Magn. Mater. 198-199, 55 (1999)], but much less than the CPP-GMR using L21-Heusler electrodes. The reduction of intrinsic bulk spin-polarization originating from the Mn-deficiency in NiMnSb layer is expected to be the main reason for small MR values.

  3. One-step synthesis of size-tunable Ag nanoparticles incorporated in electrospun PVA/cyclodextrin nanofibers.

    PubMed

    Celebioglu, Asli; Aytac, Zeynep; Umu, Ozgun C O; Dana, Aykutlu; Tekinay, Turgay; Uyar, Tamer

    2014-01-01

    One-step synthesis of size-tunable silver nanoparticles (Ag-NP) incorporated into electrospun nanofibers was achieved. Initially, in situ reduction of silver salt (AgNO3) to Ag-NP was carried out in aqueous solution of polyvinyl alcohol (PVA). Here, PVA was used as reducing agent and stabilizing polymer as well as electrospinning polymeric matrix for the fabrication of PVA/Ag-NP nanofibers. Afterwards, hydroxypropyl-beta-cyclodextrin (HPβCD) was used as an additional reducing and stabilizing agent in order to control size and uniform dispersion of Ag-NP. The size of Ag-NP was ∼8 nm and some Ag-NP aggregates were observed for PVA/Ag-NP nanofibers, conversely, the size of Ag-NP decreased from ∼8 nm down to ∼2 nm within the fiber matrix without aggregation were attained for PVA/HPβCD nanofibers. The PVA/Ag-NP and PVA/HPβCD/Ag-NP nanofibers exhibited surface enhanced Raman scattering (SERS) effect. Moreover, antibacterial properties of PVA/Ag-NP and PVA/HPβCD/Ag-NP nanofibrous mats were tested against Gram-negative (Escherichia coli) and Gram-positive (Staphylococcus aureus) bacteria. PMID:24274573

  4. First-Principles Study of Back Contact Effects on CdTe Thin Film Solar Cells

    SciTech Connect

    Du, Mao-Hua

    2009-01-01

    Forming a chemically stable low-resistance back contact for CdTe thin-film solar cells is critically important to the cell performance. This paper reports theoretical study of the effects of the back-contact material, Sb{sub 2}Te{sub 3}, on the performance of the CdTe solar cells. First-principles calculations show that Sb impurities in p-type CdTe are donors and can diffuse with low diffusion barrier. There properties are clearly detrimental to the solar-cell performance. The Sb segregation into the grain boundaries may be required to explain the good efficiencies for the CdTe solar cells with Sb{sub 2}Te{sub 3} back contacts.

  5. InAs/GaSb type II superlattices for advanced 2nd and 3rd generation detectors

    NASA Astrophysics Data System (ADS)

    Walther, Martin; Rehm, Robert; Schmitz, Johannes; Fleissner, Joachim; Rutz, Frank; Kirste, Lutz; Scheibner, Ralf; Wendler, Joachim; Ziegler, Johann

    2010-01-01

    InAs/GaSb short-period superlattices (SL) based on GaSb, InAs and AlSb have proven their great potential for high performance infrared detectors. Lots of interest is currently focused on the development of short-period InAs/GaSb SLs for advanced 2nd and 3rd generation infrared detectors between 3 - 30 μm. For the fabrication of mono- and bispectral thermal imaging systems in the mid-wavelength infrared region (MWIR) a manufacturable technology for high responsivity thermal imaging systems has been developed. InAs/GaSb short-period superlattices can be fabricated with up to 1000 periods in the intrinsic region without revealing diffusion limited behavior. This enables the fabrication of InAs/GaSb SL camera systems with high responsivity comparable to state of the art CdHgTe and InSb detectors. The material system is also ideally suited for the fabrication of dual-color MWIR/MWIR InAs/GaSb SL camera systems with high quantum efficiency for missile approach warning systems with simultaneous and spatially coincident detection in both spectral channels.

  6. Metal dispersion and mobility in soils from the Lik Zn-Pb-Ag massive sulphide deposit, NW Alaska: Environmental and exploration implications

    USGS Publications Warehouse

    Kelley, K.D.; Kelley, D.L.

    2003-01-01

    The Lik deposit in northern Alaska is a largely unexposed shale-hosted Zn-Pb-Ag massive sulphide deposit that is underlain by continuous permafrost. Residual soils overlying the mineralized zone have element enrichments that are two to six times greater than baseline values. The most prominent elements are Ag, Mo, P, Se, Sr, V by total 4-acid digestion and Tl by a weak partial digestion (Enzyme Leach or EL) because they show multi-point anomalies that extend across the entire mineralized zone, concentration ranges are 0.5-2.6 ppm Ag, 4-26 ppm Mo, 0.1-0.3% P, 3-22 ppm Se, 90-230 ppm Sr, 170-406 ppm V, and 1.6-30 ppb Tl. Lead, Sb, and Hg are also anomalous (up to 178 ppm, 30 ppm, and 1.9 ppm, respectively), but all are characterized by single point anomalies directly over the mineralized zone, with only slightly elevated concentrations over the lower mineralized section. Zinc (total) has a consistent baseline response of 200 ppm, but it is not elevated in soils overlying the mineralized zone. However, Zn by EL shows a distinct single-point anomaly over the ore zone that suggests it was highly mobile and partly adsorbed on oxides or other secondary phases during weathering. In situ analyses (by laser ablation ICP-MS) of pyrite and sphalerite from drill core suggest that sphalerite is the primary residence for Ag, Cd, and Hg in addition to Zn, and pyrite contains As, Fe, Sb, and Tl. The level and degree of oxidation, and the proportion of reacting pyrite and carbonate minerals are two factors that affected the mobility and transport of metals. In oxidizing conditions, Zn is highly mobile relative to Hg and Ag, perhaps explaining the decoupling of Zn from the other sphalerite-hosted elements in the soils. Soils are acidic (to 3.9 pH) directly over the deposit due to the presence of acid-producing pyrite, but acid-neutralizing carbonate away from the mineralized zone yield soils that are near neutral. The soils therefore formed in a complex system involving oxidation and

  7. MOVPE of GaSb/InGaAsSb Multilayers and Fabrication of Dual Band Photodetectors

    NASA Technical Reports Server (NTRS)

    Xiao, Ye-Gao; Bhat, Ishwara; Refaat, Tamer F.; Abedin, M. Nurul; Shao, Qing-Hui

    2005-01-01

    Metalorganic vapor phase epitaxy (MOVPE) of GaSb/InGaAsSb multilayer thin films and fabrication of bias-selectable dual band photodetectors are reported. For the dual band photodetectors the short wavelength detector, or the upper p- GaSb/n-GaSb junction photodiode, is placed optically ahead of the long wavelength one, or the lower photodiode. The latter is based on latticed-matched In0.13Ga0.87As0.11Sb0.89 with bandgap near 0.6 eV. Specifically, high quality multilayer thin films are grown sequentially from top to bottom as p+-GaSb/p-GaSb/n-GaSb/n-InGaAsSb/p-InGaAsSb/p-GaSb on undoped p-type GaSb substrate, and as n-GaSb/p-GaSb/p-InGaAsSb/n-InGaAsSb/n-GaSb on Te-doped n-type GaSb substrate respectively. The multilayer thin films are characterized by optical microscope, atomic force microscope (AFM), electron microprobe analyses etc. The photodiode mesa steps are patterned by photolithography with wet chemical etching and the front metallization is carried out by e-beam evaporation with Pd/Ge/Au/Ti/Au to give ohmic contact on both n- and p-type Sb based layer surfaces. Dark I-V measurements show typical diode behavior for both the upper and lower photodiodes. The photoresponsivity measurements indicate that both the upper and lower photodiodes can sense the infrared illumination corresponding to their cutoff wavelengths respectively, comparable with the simulation results. More work is underway to bring the long wavelength band to the medium infrared wavelength region near 4 micrometers.

  8. Ball Aerospace Advances in 35 K Cooling-The SB235E Cryocooler

    NASA Astrophysics Data System (ADS)

    Lock, J. S.; Glaister, D. S.; Gully, W.; Hendershott, P.; Marquardt, E.

    2008-03-01

    This paper describes the design, development, testing and performance of the Ball Aerospace & Technologies Corp. SB235E, a 2-stage long life space cryocooler optimized for 2 cooling loads. The SB235E model is designed to provide simultaneous cooling at 35 K (typically for HgCdTe detectors) and 85 K (typically for optics). The SB235E is a higher capacity model derivative of the SB235. Initial testing of the SB235E has shown performance of 2.13 W at 35 K and 8.14 W at 85 K for 200 W power at 289 K rejection temperature. These data equate to Carnot efficiency of 0.175 or nearly twice that of other published space cryocooler data. Qualification testing has been completed including full performance mapping and vibration export. Performance mapping with the cold-stage temperature varying from 20 K to 80 K and mid-stage temperature varying from 85 K to 175 K are presented. Two engineering models of the SB235E are currently in build.

  9. TANK 40 FINAL SB7B CHEMICAL CHARACTERIZATION RESULTS

    SciTech Connect

    Bannochie, C.

    2012-03-15

    /free OH{sup -}/other base, total inorganic carbon/total organic carbon (TIC/TOC) analyses, and Cs-137 gamma scan. Weighted dilutions of slurry were submitted for IC, TIC/TOC, and total base/free OH{sup -}/other base analyses. Activities for U-233, U-235, and Pu-239 were determined from the ICP-MS data for the aqua regia digestions of the Tank 40 WAPS slurry using the specific activity of each isotope. The Pu-241 value was determined from a Pu-238/-241 method developed by SRNL AD and previously described. The following conclusions were drawn from the analytical results reported here: (1) The ratios of the major elements for the SB7b WAPS sample are different from those measured for the SB7a WAPS sample. There is less Al and Mn relative to Fe than the previous sludge batch. (2) The elemental composition of this sample and the analyses conducted here are reasonable and consistent with DWPF batch data measurements in light of DWPF pre-sample concentration and SRAT product heel contributions to the DWPF SRAT receipt analyses. The element ratios for Al/Fe, Ca/Fe, Mn/Fe, and U/Fe agree within 10% between this work and the DWPF Sludge Receipt and Adjustment Tank (SRAT) receipt analyses. (3) Sulfur in the SB7b WAPS sample is 82% soluble, slightly less than results reported for SB3, SB4, and SB6 samples but unlike the 50% insoluble sulfur observed in the SB5 WAPS sample. In addition, 23% of the soluble sulfur is not present as sulfate in SB7b. (4) The average activities of the fissile isotopes of interest in the SB7b WAPS sample are (in {mu}Ci/g of total dried solids): 4.22E-02 U-233, 6.12E-04 U-235, 1.08E+01 Pu-239, and 5.09E+01 Pu-241. The full radionuclide composition will be reported in a future document. (5) The fission product noble metal and Ag concentrations appear to have largely peaked in previous DWPF sludge batches, with the exception of Ru, which still shows a slight increase in SB7b.

  10. Growth of InAs/Ga 1-xIn xSb infrared superlattices

    NASA Astrophysics Data System (ADS)

    Chow, D. H.; Miles, R. H.; Nieh, C. W.; McGill, T. C.

    1991-05-01

    A set of InAs/Ga 1-xIn xSb superlattices has been grown by molecular beam epitaxy. The superlattices are deposited on thick, stress-relaxed buffer layers of GaSb on (100)-oriented GaAs substrates. A short-period, heavily strained superlattice has been inserted at the GaAs/GaSb interface. Transmission electron microscope (TEM) images reveal that a dense network of dislocations forms at this interface, with the vast majority of threading dislocations propagating no further than the first 1000 Å of the GaSb buffer layer. Planar superlattice layers are observed, with ni evidence of stress relaxation between the layers or between the InAs/Ga 1- x In xSb superlattice and GaSb buffer. Analysis of X-ray diffraction satellites reveals that cross-incorporation of As in GaSb and Ga 1-xIn xSb layers is virtually eliminated at low growth temperatures. Photoconductivity spectra from the superlattices display sharp photocurrent threshold energies, in agreement with previously published energy gaps derived from calculations and photoluminescence data. Thresholds in the 8-14 μm range are obtained from superlattices with very thin layers ( ≈ 40 Å), which are necessary for strong optical absorption in a type II superlattice. Finally, an absorption coefficient of ≈ 2000 cm -1 is measured at 10 μm from a superlattice with an energy gap of 11.4 μm. This value is comparable to that of bulk Hg 1-xCd xTe, the current industry standard for infrared detectors in the 8-14 μm range.

  11. AlSb/InAs/AlSb quantum wells

    NASA Technical Reports Server (NTRS)

    Kroemer, Herbert

    1990-01-01

    Researchers studied the InAs/AlSb system recently, obtaining 12nm wide quantum wells with room temperature mobilities up to 28,000 cm(exp 2)/V center dot S and low-temperature mobilities up to 325,000 cm(exp 2)/V center dot S, both at high electron sheet concentrations in the 10(exp 12)/cm(exp 2) range (corresponding to volume concentrations in the 10(exp 18)/cm(exp 2) range). These wells were not intentionally doped; the combination of high carrier concentrations and high mobilities suggest that the electrons are due to not-intentional modulation doping by an unknown donor in the AlSb barriers, presumably a stoichiometric defect, like an antisite donor. Inasmuch as not intentionally doped bulk AlSb is semi-insulating, the donor must be a deep one, being ionized only by draining into the even deeper InAs quantum well. The excellent transport properties are confirmed by other observations, like excellent quantum Hall effect data, and the successful use of the quantum wells as superconductive weak links between Nb electrodes, with unprecendentedly high critical current densities. The system is promising for future field effect transistors (FETs), but many processing problems must first be solved. Although the researchers have achieved FETs, the results so far have not been competitive with GaAs FETs.

  12. Synthesis, Characterization and Photocatalytic Activity of New Photocatalyst ZnBiSbO4 under Visible Light Irradiation

    PubMed Central

    Luan, Jingfei; Chen, Mengjing; Hu, Wenhua

    2014-01-01

    In this paper, ZnBiSbO4 was synthesized by a solid-state reaction method for the first time. The structural and photocatalytic properties of ZnBiSbO4 had been characterized by X-ray diffraction, scanning electron microscopy, X-ray photoelectron spectroscopy, Fourier-transform infrared spectroscopy, transmission electron microscope and UV-visible spectrometer. ZnBiSbO4 crystallized with a pyrochlore-type structure and a tetragonal crystal system. The band gap of ZnBiSbO4 was estimated to be 2.49 eV. The photocatalytic degradation of indigo carmine was realized under visible light irradiation with ZnBiSbO4 as a catalyst compared with nitrogen-doped TiO2 (N-TiO2) and CdBiYO4. The results showed that ZnBiSbO4 owned higher photocatalytic activity compared with N-TiO2 or CdBiYO4 for the photocatalytic degradation of indigo carmine under visible light irradiation. The reduction of the total organic carbon, the formation of inorganic products, SO42− and NO3−, and the evolution of CO2 revealed the continuous mineralization of indigo carmine during the photocatalytic process. One possible photocatalytic degradation pathway of indigo carmine was obtained. The phytotoxicity of the photocatalytic-treated indigo carmine (IC) wastewater was detected by examining its effect on seed germination and growth. PMID:24879521

  13. Sequential and simultaneous adsorption of Sb(III) and Sb(V) on ferrihydrite: Implications for oxidation and competition.

    PubMed

    Qi, Pengfei; Pichler, Thomas

    2016-02-01

    Antimony (Sb) is a naturally occurring element of growing environmental concern whose toxicity, adsorption behavior and other chemical properties are similar to that of arsenic (As). However, less is known about Sb compared to As. Individual and simultaneous adsorption experiments with Sb(III) and Sb(V) were conducted in batch mode with focus on the Sb speciation of the remaining liquid phase during individual Sb(III) adsorption experiments. The simultaneous adsorption and oxidation of Sb(III) was confirmed by the appearance of Sb(V) in the solution at varying Fe/Sb ratios (500, 100 and 8) and varying pH values (3.8, 7 and 9). This newly formed Sb(V) was subsequently removed from solution at a Fe/Sb ratio of 500 or at a pH of 3.8. However, more or less only Sb(V) was observed in the liquid phase at the end of the experiments at lower Fe/Sb ratios and higher pH, indicating that competition took place between the newly formed Sb(V) and Sb(III), and that Sb(III) outcompeted Sb(V). This was independently confirmed by simultaneous adsorption experiments of Sb(III) and Sb(V) in binary systems. Under such conditions, the presence of Sb(V) had no influence on the adsorption of Sb(III) while Sb(V) adsorption was significantly inhibited by Sb(III) over a wide pH range (4-10). Thus, in the presence of ferrihydrite and under redox conditions, which allow the presence of both Sb species, Sb(V) should be the dominant species in aquatic environments, since Sb(III) is adsorbed preferentially and at the same time oxidized to Sb(V). PMID:26688239

  14. AGS experiments - 1994, 1995, 1996

    SciTech Connect

    Depken, J.C.

    1997-01-01

    This report contains the following information on the Brookhaven AGS Accelerator complex: FY 1996 AGS schedule as run; FY 1997 AGS schedule (working copy); AGS beams 1997; AGS experimental area FY 1994 physics program; AGS experimental area FY 1995 physics program; AGS experimental area FY 1996 physics program; AGS experimental area FY 1997 physics program (in progress); a listing of experiments by number; two-phage summaries of each experiment begin here, also ordered by number; listing of publications of AGS experiments begins here; and listing of AGS experimenters begins here.

  15. Genetic Pd, Pt, Au, Ag, and Rh mineralogy in Noril'sk sulfide ores

    NASA Astrophysics Data System (ADS)

    Spiridonov, E. M.; Kulagov, E. A.; Serova, A. A.; Kulikova, I. M.; Korotaeva, N. N.; Sereda, E. V.; Tushentsova, I. N.; Belyakov, S. N.; Zhukov, N. N.

    2015-09-01

    The undeformed ore-bearing intrusions of the Noril'sk ore field (NOF) cut through volcanic rocks of the Late Permian-Early Triassic trap association folded in brachysynclines. Due to the nonuniform load on the roof of intrusive bodies, most sulfide melts were squeezed, up to the tops of ore-bearing intrusions; readily fusible Ni-Fe-Cu sulfide melts were almost completely squeezed. In our opinion, not only one but two stages of mineralization developed at the Noril'sk deposits: (i) syntrap magmatic and (ii) epigenetic post-trap metamorphic-hydrothermal. All platinum-group minerals (PGM) and minerals of gold are metasomatic in the Noril'sk ores. They replaced sulfide solid solutions and exsolution structures. All types of PGM and Au minerals occur in the ores, varying in composition from pyrrhotite to chalcopyrite, talnakhite, mooihoekite, and rich in galena; they are localized in the inner and outer contact zones and differ only in the quantitative proportions of ore minerals. The aureoles of PGM and Au-Ag minerals are wider than the contours of sulfide bodies and coincide with halos of fluid impact on orebodies and adjacent host rocks. The pneumatolytic PGM and Au-Ag minerals are correlated in abundance with the dimensions of sulfide bodies. Their amounts are maximal in veins of late fusible ore composed of eutectic PbS ss and iss intergrowths, as well as at their contacts. The Pd and Pt contents in eutectic sulfide ores of NOF are the world's highest. In the process of noble-metal mineral formation, the fluids supply Pd, Pt, Au, As, Sb, Sn, Bi, and a part of Te, whereas Fe, Ni, Cu, Pb, Ag, Rh, a part of Te and Pd are leached from the replaced sulfide minerals. The pneumatolytic PGM of the early stage comprises Pd and Pt intermetallic compounds enriched in Au along with Pd-Pt-Fe-Ni-Cu-Sn-Pb(As) and (Pd,Pt,Au)(Sn,Sb,Bi,Te,As) solid solutions. Pneumatolytic PGM and Au minerals of the middle stage are products of solid-phase transformation and recrystallization of

  16. Lattice-Matched GaInAsSb/A1GaAsSb/GaSb Materials for Thermophotovoltaic Devices

    SciTech Connect

    C.A. Wang; C.J. Vineis; H.K. Choi; M.K. Connors; R.H. Huang; L.R. Daielson; G. Nichols; G.W. Charache; D. Donetsky; S. Anikeef; G. Belenky

    2002-09-19

    High-performance GaInAsSb/AlGaAsSb/GaSb thermophotovoltaic (TPV) devices with quantum efficiency and fill factor near theoretical limits and open-circuit voltage within about 15% of the limit can be routinely fabricated. To achieve further improvements in TPV device performance, detailed materials studies of GaInAsSb epitaxial growth, the microstructure, and minority carrier lifetime, along with device structure considerations are reported. This paper discusses the materials and device issues, and their implications on TPV device performance. In addition, improvements in TPV performance with integrated distributed Bragg reflectors and back-surface reflectors are discussed.

  17. Anisotropic interface induced formation of Sb nanowires on GaSb(111)A substrates.

    PubMed

    Proessdorf, A; Grosse, F; Perumal, K; Braun, W; Riechert, H

    2012-06-15

    The growth of Sb nanowires on GaSb(111)A substrates is studied by in situ azimuthal scan reflection high-energy electron diffraction (ARHEED). Bulk and layer contributions can be distinguished in the ARHEED transmission pattern through the Sb nanowires. The three-dimensional structure of the growing Sb nanowires is identified by post-growth atomic force microscopy (AFM) and x-ray diffraction (XRD). The lattice match of the Sb crystal along the [Formula: see text] and the GaSb crystal along [Formula: see text] directions lead to a preferential orientation of the Sb nanowires. The Sb adsorption and desorption kinetics is studied by thermal desorption spectroscopy. PMID:22595679

  18. Anisotropic interface induced formation of Sb nanowires on GaSb(111)A substrates

    NASA Astrophysics Data System (ADS)

    Proessdorf, A.; Grosse, F.; Perumal, K.; Braun, W.; Riechert, H.

    2012-06-01

    The growth of Sb nanowires on GaSb(111)A substrates is studied by in situ azimuthal scan reflection high-energy electron diffraction (ARHEED). Bulk and layer contributions can be distinguished in the ARHEED transmission pattern through the Sb nanowires. The three-dimensional structure of the growing Sb nanowires is identified by post-growth atomic force microscopy (AFM) and x-ray diffraction (XRD). The lattice match of the Sb crystal along the \\langle \\bar {2}10\\rangle and the GaSb crystal along \\langle \\bar {1}10\\rangle directions lead to a preferential orientation of the Sb nanowires. The Sb adsorption and desorption kinetics is studied by thermal desorption spectroscopy.

  19. Structural Characterization of Doped GaSb Single Crystals by X-ray Topography

    SciTech Connect

    Honnicke, M.G.; Mazzaro, I.; Manica, J.; Benine, E.; M da Costa, E.; Dedavid, B. A.; Cusatis, C.; Huang, X. R.

    2009-09-13

    We characterized GaSb single crystals containing different dopants (Al, Cd and Te), grown by the Czochralski method, by x-ray topography and high angular resolution x-ray diffraction. Lang topography revealed dislocations parallel and perpendicular to the crystal's surface. Double-crystal GaSb 333 x-ray topography shows dislocations and vertical stripes than can be associated with circular growth bands. We compared our high-angular resolution x-ray diffraction measurements (rocking curves) with the findings predicted by the dynamical theory of x-ray diffraction. These measurements show that our GaSb single crystals have a relative variation in the lattice parameter ({Delta}d/d) on the order of 10{sup -5}. This means that they can be used as electronic devices (detectors, for example) and as x-ray monochromators.

  20. Refinement of the canine CD1 locus topology and investigation of antibody binding to recombinant canine CD1 isoforms.

    PubMed

    Schjaerff, Mette; Keller, Stefan M; Fass, Joseph; Froenicke, Lutz; Grahn, Robert A; Lyons, Leslie; Affolter, Verena K; Kristensen, Annemarie T; Moore, Peter F

    2016-03-01

    CD1 molecules are antigen-presenting glycoproteins primarily found on dendritic cells (DCs) responsible for lipid antigen presentation to CD1-restricted T cells. Despite their pivotal role in immunity, little is known about CD1 protein expression in dogs, notably due to lack of isoform-specific antibodies. The canine (Canis familiaris) CD1 locus was previously found to contain three functional CD1A genes: canCD1A2, canCD1A6, and canCD1A8, where two variants of canCD1A8, canCD1A8.1 and canCD1A8.2, were assumed to be allelic variants. However, we hypothesized that these rather represented two separate genes. Sequencing of three overlapping bacterial artificial chromosomes (BACs) spanning the entire canine CD1 locus revealed canCD1A8.2 and canCD1A8.1 to be located in tandem between canCD1A7 and canCD1C, and canCD1A8.1 was consequently renamed canCD1A9. Green fluorescent protein (GFP)-fused canine CD1 transcripts were recombinantly expressed in 293T cells. All proteins showed a highly positive GFP expression except for canine CD1d and a splice variant of canine CD1a8 lacking exon 3. Probing with a panel of anti-CD1 monoclonal antibodies (mAbs) showed that Ca13.9H11 and Ca9.AG5 only recognized canine CD1a8 and CD1a9 isoforms, and Fe1.5F4 mAb solely recognized canine CD1a6. Anti-CD1b mAbs recognized the canine CD1b protein, but also bound CD1a2, CD1a8, and CD1a9. Interestingly, Ca9.AG5 showed allele specificity based on a single nucleotide polymorphism (SNP) located at position 321. Our findings have refined the structure of the canine CD1 locus and available antibody specificity against canine CD1 proteins. These are important fundamentals for future investigation of the role of canine CD1 in lipid immunity. PMID:26687789

  1. MoOx modified Ag anode for top-emitting organic light-emitting devices

    NASA Astrophysics Data System (ADS)

    Cao, Jin; Jiang, XueYin; Zhang, ZhiLin

    2006-12-01

    Efficient top-emitting organic light-emitting devices (TOLEDs) using a thin MoOx layer modified Ag as the effective hole-injection anode are demonstrated. With tris-(8-hydroxy quinoline)aluminum as emitting layer and trilayer LiF /Al/Ag as semitransparent cathode, the Ag /MoOx based TOLED shows a tune-on voltage of 2.67V and a maximum current efficiency of 7.27cd/A, which are much better than those (3.92V, 6.12cd/A) obtained from Ag /Ag2O based TOLED and those (5.25V, 3.5cd/A) obtained from the corresponding bottom-emitting organic light-emitting devices. Contact potential difference measurement shows that the work function of Ag /MoOx is higher than those of Ag /Ag2O and ozone-treated indium tin oxide, leading to a stronger hole injection. The good performance of Ag /MoOx based TOLED is attributed to the efficient hole injection from the Ag /MoOx anode as well as a microcavity effect.

  2. Method of making an InAsSb/InAsSbP diode lasers

    DOEpatents

    Razeghi, Manijeh

    1997-01-01

    InAsSb/InAsSbP/InAs Double Heterostructures (DH) and Separate Confinement Heterostructure Multiple Quantum Well (SCH-MQW) structures are taught wherein the ability to tune to a specific wavelength within 3 .mu.m to 5 .mu.m is possible by varying the ratio of As:Sb in the active layer.

  3. Transport properties in AlInSb/InAsSb heterostructures

    SciTech Connect

    Zhang, Yuwei; Zhang, Yang Wang, Chengyan; Zeng, Yiping

    2013-12-28

    Based on theoretical studies of transport properties in InAsSb-based quantum well heterostructures, we propose a material design for InAsSb quantum well with AlInSb barrier. Variation of electron mobility and two-dimensional electron gas concentration in Al{sub y}In{sub 1−y}Sb/InAs{sub 1−x}Sb{sub x} heterostructures over the compositional range of which InAsSb is fully strained to AlInSb are investigated, where impact from dislocation scattering could be minimized. In comparison with InAs and InSb based quantum well heterostructures, InAsSb is advantageous in achieving the highest electron mobility despite of alloy disorder scattering. The maximum mobility of 37 000 cm{sup 2}/V s is attainable in 15 nm InAs{sub 0.2}Sb{sub 0.8} quantum well with Al{sub 0.24}In{sub 0.76}Sb barrier and there is great potential for further improvement. Our InAsSb based quantum well heterostructure is proved to be a robust structure for high-speed applications.

  4. Method of making an InAsSb/InAsSbP diode lasers

    DOEpatents

    Razeghi, M.

    1997-08-19

    InAsSb/InAsSbP/InAs Double Heterostructures (DH) and Separate Confinement Heterostructure Multiple Quantum Well (SCH-MQW) structures are taught wherein the ability to tune to a specific wavelength within 3 {micro}m to 5 {micro}m is possible by varying the ratio of As:Sb in the active layer. 9 figs.

  5. Ternary CaCu{sub 4}P{sub 2}-type pnictides AAg{sub 4}Pn{sub 2} (A=Sr, Eu; Pn=As, Sb)

    SciTech Connect

    Stoyko, Stanislav S.; Khatun, Mansura; Scott Mullen, C.; Mar, Arthur

    2012-08-15

    Four ternary pnictides AAg{sub 4}Pn{sub 2} (A=Sr, Eu; Pn=As, Sb) were prepared by reactions of the elements at 850 Degree-Sign C and their crystal structures were determined from single-crystal X-ray diffraction studies. These silver-containing pnictides AAg{sub 4}Pn{sub 2} adopt the trigonal CaCu{sub 4}P{sub 2}-type structure (Pearson symbol hR21, space group R3-bar m, Z=3; a=4.5555(6) A, c=24.041(3) A for SrAg{sub 4}As{sub 2}; a=4.5352(2) A, c=23.7221(11) A for EuAg{sub 4}As{sub 2}; a=4.7404(4) A, c=25.029(2) A for SrAg{sub 4}Sb{sub 2}; a=4.7239(3) A, c=24.689(2) A for EuAg{sub 4}Sb{sub 2}), which can be derived from the trigonal CaAl{sub 2}Si{sub 2}-type structure of the isoelectronic zinc-containing pnictides AZn{sub 2}Pn{sub 2} by insertion of additional Ag atoms into trigonal planar sites within [M{sub 2}Pn{sub 2}]{sup 2-} slabs built up of edge-sharing tetrahedra. Band structure calculations on SrAg{sub 4}As{sub 2} and SrAg{sub 4}Sb{sub 2} revealed that these charge-balanced Zintl phases actually exhibit no gap at the Fermi level and are predicted to be semimetals. - Graphical abstract: SrAg{sub 4}As{sub 2} and related pnictides adopt a CaCu{sub 4}P{sub 2}-type structure in which additional Ag atoms enter trigonal planar sites within slabs built from edge-sharing tetrahedra. Highlights: Black-Right-Pointing-Pointer AAg{sub 4}Pn{sub 2} are the first Ag-containing members of the CaCu{sub 4}P{sub 2}-type structure. Black-Right-Pointing-Pointer Ag atoms are stuffed in trigonal planar sites within CaAl{sub 2}Si{sub 2}-type slabs. Black-Right-Pointing-Pointer Ag-Ag bonding develops through attractive d{sup 10}-d{sup 10} interactions.

  6. Investigation of photoelectrochemical-oxidized p-GaSb films

    NASA Astrophysics Data System (ADS)

    Lee, Hsin-Ying; Huang, Hung-Lin; Lee, Ching-Ting; Petrovich Pchelyakov, Oleg; Andreevich Pakhanov, Nikolay

    2012-12-01

    GaSb oxide films were directly formed on the p-GaSb films using the bias-assisted photoelectrochemical (PEC) oxidation method. X-ray photoelectron spectroscopy analysis indicated that the resulting GaSb oxide films consisted of Ga2O3, Sb2O3, and Sb2O5. Different from the non-PEC oxides, the PEC derived oxide contained much more Sb2O5 than Sb2O3. Besides, the interface state density between the PEC oxide and p-GaSb was lower than that of the ordinary oxide/p-GaSb interface. The high quality of the PEC-oxidized GaSb films was attributed to the increase of the stable Sb2O5 content and decrease of the elemental Sb content in the films.

  7. Astronomical imaging with InSb arrays

    NASA Astrophysics Data System (ADS)

    Pipher, Judith L.

    Ten years ago, Forrest presented the first astronomical images with a Santa Barbara Research Center (SBRC) 32 x 32 InSb array camera at the first NASA-Ames Infrared Detector Technology Work-shop. Soon after, SBRC began development of 58 x 62 InSb arrays, both for ground-based astronomy and for the Space Infrared Telescope Facility (SIRTF). By the time of the 1987 Hilo workshop 'Ground-based Astronomical Observations with Infrared Array Dectectors' astronomical results from cameras based on SBRC 32 x 32 and 58 x 62 InSb arrays, a CE linear InSb array, and a French 32 x 32 InSb charge injection device (CID) array were presented. And at the Tucson 1990 meeting 'Astrophysics with Infrared Arrays', it was clear that this new technology was no longer the province of 'IR pundits', but provided a tool for all astronomers. At this meeting, the first astronomical observations with SBRC's new, gateless passivation 256 x 256 InSb arrays will be presented: they perform spectacularly] In this review, I can only broadly brush on the interesting science completed with InSb array cameras. Because of the broad wavelength coverage (1-5.5 micrometer) of InSb, and the extremely high performance levels throughout the band, InSb cameras are used not only in the near IR, but also from 3-5.5 micrometer, where unique science is achieved. For example, the point-like central engines of active galactic nuclei (AGN) are delineated at L' and M', and Bra and 3.29 micrometer dust emission images of galactic and extragalactic objects yield excitation conditions. Examples of imaging spectroscopy, high spatial resolution imaging, as well as deep, broad-band imaging with InSb cameras at this meeting illustrate the power of InSb array cameras.

  8. Conductance oscillations in quantum point contacts of InAs/GaSb heterostructures

    NASA Astrophysics Data System (ADS)

    Papaj, Michał; Cywiński, Łukasz; Wróbel, Jerzy; Dietl, Tomasz

    2016-05-01

    We study quantum point contacts in two-dimensional topological insulators by means of quantum transport simulations for InAs/GaSb heterostructures and HgTe/(Hg,Cd)Te quantum wells. In InAs/GaSb, the density of edge states shows an oscillatory decay as a function of the distance to the edge. This is in contrast to the behavior of the edge states in HgTe quantum wells, which decay into the bulk in a simple exponential manner. The difference between the two materials is brought about by spatial separation of electrons and holes in InAs/GaSb, which affects the magnitudes of the parameters describing the particle-hole asymmetry and the strength of intersubband coupling within the Bernevig-Hughes-Zhang model. We show that the character of the wave-function decay impacts directly the dependence of the point contact conductance on the constriction width and the Fermi energy, which can be verified experimentally and serves to accurately determine the values of the relevant parameters. In the case of InAs/GaSb heterostructures, the conductance magnitude oscillates as a function of the constriction width following the oscillations of the edge state penetration, whereas in HgTe/(Hg,Cd)Te quantum wells a single switching from transmitting to reflecting contact is predicted.

  9. Anisotropic magnetization and transport properties of RAgSb{sub 2} (R=Y, La-Nd, Sm, Gd-Tm)

    SciTech Connect

    Myers, Kenneth D.

    1999-11-08

    This study of the RAgSb{sub 2} series of compounds arose as part of an investigation of rare earth intermetallic compounds containing antimony with the rare earth in a position with tetragonal point symmetry. Materials with the rare earth in a position with tetragonal point symmetry frequently manifest strong anisotropies and rich complexity in the magnetic properties, and yet are simple enough to analyze. Antimony containing intermetallic compounds commonly possess low carrier densities and have only recently been the subject of study. Large single grain crystals were grown of the RAgSb{sub 2} (R=Y, La-Nd, Sm, Gd-Tm) series of compounds out of a high temperature solution. This method of crystal growth, commonly known as flux growth is a versatile method which takes advantage of the decreasing solubility of the target compound with decreasing temperature. Overall, the results of the crystal growth were impressive with the synthesis of single crystals of LaAgSb{sub 2} approaching one gram. However, the sample yield diminishes as the rare earth elements become smaller and heavier. Consequently, no crystals could be grown with R=Yb or Lu. Furthermore, EuAgSb{sub 2} could not be synthesized, likely due to the divalency of the Eu ion. For most of the RAgSb{sub 2} compounds, strong magnetic anisotropies are created by the crystal electric field splitting of the Hund's rule ground state. This splitting confines the local moments to lie in the basal plane (easy plane) for the majority of the members of the series. Exceptions to this include ErAgSb{sub 2} and TmAgSb{sub 2}, which have moments along the c-axis (easy axis) and CeAgSb{sub 2}, which at intermediate temperatures has an easy plane, but exchange coupling at low temperatures is anisotropic with an easy axis. Additional anisotropy is also observed within the basal plane of DyAgSb{sub 2}, where the moments are restricted to align along one of the {l_angle}110{r_angle} axes. Most of the RAgSb{sub 2} compounds

  10. Positive selection of self-antigen-specific CD8+ T cells by hematopoietic cells.

    PubMed

    Yamada, Hisakata; Shibata, Kensuke; Sakuraba, Koji; Fujimura, Kenjiro; Yoshikai, Yasunobu

    2013-08-01

    In contrast to thymic epithelial cells, which induce the positive selection of conventional CD8(+) T cells, hematopoietic cells (HCs) select innate CD8(+) T cells whose Ag specificity is not fully understood. Here we show that CD8(+) T cells expressing an H-Y Ag-specific Tg TCR were able to develop in mice in which only HCs expressed MHC class I, when HCs also expressed the H-Y Ag. These HC-selected self-specific CD8(+) T cells resemble innate CD8(+) T cells in WT mice in terms of the expression of memory markers and effector functions, but are phenotypically distinct from the thymus-independent CD8(+) T-cell population. The peripheral maintenance of H-Y-specific CD8(+) T cells required presentation of the self-Ag and IL-15 on HCs. HC-selected CD8(+) T cells in mice lacking the Tg TCR also showed these features. Furthermore, by using MHC class I tetramers with a male Ag peptide, we found that self-Ag-specific CD8(+) T cells in TCR non-Tg mice could develop via HC-induced positive selection, supporting results obtained from H-Y TCR Tg mice. These findings indicate the presence of self-specific CD8(+) T cells that are positively selected by HCs in the peripheral T-cell repertoire. PMID:23636825

  11. Dissimilatory Sb(V) reduction by microorganisms isolated from Sb-contaminated sediment

    NASA Astrophysics Data System (ADS)

    Dovick, M. A.; Kulp, T. R.

    2013-12-01

    Mining and smelting are major sources of trace metal contamination in freshwater systems. Arsenic (As) is a common contaminant derived from certain mining operations and is a known toxic metalloid and carcinogen. Antimony (Sb) is listed as a pollutant of priority interest by the EPA and is presumed to share similar geochemical and toxicological properties with arsenic. Both elements can occur in four different oxidation states (V, III, 0, and -III) under naturally occurring conditions. In aqueous solutions As(V) and Sb(V) predominate in oxygenated surface waters whereas As(III) and Sb(III) are stable in anoxic settings. Numerous studies have examined microbiological redox pathways that utilize As(V) as a terminal electron acceptor for anaerobic respiration, however there have been few studies on microbial mechanisms that may affect the biogeochemical cycling of Sb in the environment. Here we report bacterial reduction of Sb(V) to Sb(III) in anoxic enrichment cultures and bacterial isolates grown from sediment collected from an Sb contaminated pond at a mine tailings site in Idaho (total pond water Sb concentration = 235.2 +/- 136.3 ug/L). Anaerobic sediment microcosms (40 mL) were established in artificial freshwater mineral salt medium, amended with millimolar concentrations of Sb(V), acetate or lactate, and incubated at 27°C for several days. Antimony(V), lactate, and acetate concentrations were monitored during incubation by High Performance Liquid Chromatography (HPLC) and Ion Chromatography (IC). Live sediment microcosms reduced millimolar amendments of Sb(V) to Sb(III) coupled to the oxidation of acetate and lactate, while no activity occurred in killed controls. Enrichment cultures were established by serially diluting Sb(V)-reducing microcosms in mineral salt medium with Sb(V) and acetate, and a Sb(V)-reducing bacterial strain was isolated by plating on anaerobic agar plates amended with millimolar Sb(V) and acetate. Direct cell counting demonstrated that

  12. TANK 40 FINAL SB4 CHEMICAL CHARACTERIZATION RESULTS

    SciTech Connect

    Best, J

    2008-01-30

    supernate phase from a settled sample. This decant was not filtered prior to performing a warm nitric acid digestion of the material in order to measure the Si content by ICP-AES. Three Si standards, a blank, and a matrix standard were prepared and submitted along with the Tank 40 samples. The following conclusions were drawn from the analytical results reported here: (1) The elemental composition of this sample and the analyses conducted here are reasonable and consistent with DWPF batch data measurements; (2) There was no measurable Si in samples of Tank 40 decant; and (3) Ag and the Ru, Rh, and Pd noble metal concentrations agree well with the estimate used for the SB4 70/30 blend of SB3 and Tank 51 performed in the SRNL Shielded Cells.

  13. AlInAsSb/GaSb staircase avalanche photodiode

    NASA Astrophysics Data System (ADS)

    Ren, Min; Maddox, Scott; Chen, Yaojia; Woodson, Madison; Campbell, Joe C.; Bank, Seth

    2016-02-01

    Over 30 years ago, Capasso and co-workers [IEEE Trans. Electron Devices 30, 381 (1982)] proposed the staircase avalanche photodetector (APD) as a solid-state analog of the photomultiplier tube. In this structure, electron multiplication occurs deterministically at steps in the conduction band profile, which function as the dynodes of a photomultiplier tube, leading to low excess multiplication noise. Unlike traditional APDs, the origin of staircase gain is band engineering rather than large applied electric fields. Unfortunately, the materials available at the time, principally AlxGa1-xAs/GaAs, did not offer sufficiently large conduction band offsets and energy separations between the direct and indirect valleys to realize the full potential of the staircase gain mechanism. Here, we report a true staircase APD operation using alloys of a rather underexplored material, AlxIn1-xAsySb1-y, lattice-matched to GaSb. Single step "staircase" devices exhibited a constant gain of ˜2×, over a broad range of applied bias, operating temperature, and excitation wavelengths/intensities, consistent with Monte Carlo calculations.

  14. Effect of MnSb clusters recharge on ferromagnetism in GaSb-MnSb thin films

    NASA Astrophysics Data System (ADS)

    Talantsev, A.; Koplak, O.; Morgunov, R.

    2016-07-01

    The concentration effect of charge carriers on the magnetic moment of ferromagnetic MnSb nanoclusters embedded in GaSbMn thin films is reported. High concentration of holes enhances the probability of their tunneling through the barrier between the semiconductor matrix and the MnSb nanocluster. Enrichment of the MnSb clusters by Mn2+ ions instead of Mn3+ enhances their ferromagnetism. Dynamics of magnetization relaxation of the MnSb clusters under applied magnetic field has been studied in the 8-300 K temperature range. Magnetic anisotropy constant ∼3.2·104 erg/cm3 has been determined. The fluctuation field HF = 7 Oe and the activation volume VA = 1.7·10-16 cm3 have been extracted from magnetic viscosity data.

  15. InAs/GaSb quantum wells: quantum spin Hall effect and topological superconductivity

    NASA Astrophysics Data System (ADS)

    Sitte, Matthias; Everschor-Sitte, Karin; MacDonald, Allan

    2014-03-01

    In recent years, topological insulators (TIs) have attracted great attention as a new quantum state of matter. The first experimental 2D TIs were HgTe/CdTe quantum well heterostructures. Recently, another semiconducting system - the InAs/GaSb quantum well heterostructure - was shown to be a 2D TI as well. These semiconducting heterojunctions have many advantages compared to HgTe/CdTe systems, including continuously tunable band structure via electric fields and stronger proximity coupling to superconductors. Proximity coupling of a 2D TI and an ordinary superconductor gives rise to one-dimensional topological superconductivity which supports non-local excitations known as Majoranas that can be used for topologically protected quantum computing. We perform empirical tight-binding calculations on these systems, studying the topological phases and their properties. With this knowlegde, we then extend our theory to study the proximity effects when InAs/GaSb quantum wells are coupled to a superconductor.

  16. Vought SB2U-1 Vindicator

    NASA Technical Reports Server (NTRS)

    1937-01-01

    Vought SB2U-1 Vindicator: The graceful lines of an airplane were aided by a concerted effort in drag reduction. Here a Vought SB2U-1 Vindicator is studied in Langley's 30 x 60 Full Scale Tunnel. This evaluation took place in September 1937.

  17. Characterization of CdS thin film in high efficient CdS/CdTe solar cells

    NASA Astrophysics Data System (ADS)

    Tsuji, Miwa; Aramoto, Tetsuya; Ohyama, Hideaki; Hibino, Takeshi; Omura, Kuniyoshi

    2000-06-01

    Cadmium sulfide (CdS) thin film is the most commonly used window material for high-efficient cadmium telluride (CdTe) thin-film photovoltaic devices. High-efficient CdS/CdTe solar cells have been developed using ultra-thin CdS films having a thickness of below 0.1 μm. CdS film is deposited on transparent conductive oxide (TCO) film coated glass substrates by the metal organic chemical vapor deposition (MOCVD) technique, CdTe film is subsequently deposited by the close-spaced sublimation (CSS) technique. Finally, carbon and Ag-In electrodes are fabricated by the screen printing and sintering method. Cell performance depends primarily on the electrical and optical properties of CdS film, and hence we started to develop higher quality CdS film and found out clear differences between high- and low-quality CdS films from various analyses: SEM, AFM, SIMS, TDS and FT-IR. As a result of controlling qualities of CdS films, photovoltaic conversion efficiency of 10.5% has been achieved for a size of 1376 cm 2 of the solar module under air mass (AM) 1.5 conditions by the Japan Quality Assurance Organization (JQA).

  18. 2.4 Micrometer Cutoff Wavelength AlGaAsSb/InGaAsSb Phototransistors

    NASA Technical Reports Server (NTRS)

    Sulima, O. V.; Swaminathan, K.; Refaat, T. F.; Faleev, N. N.; Semenov, A. N.; Solov'ev, V. A.; Ivanov, S. V.; Abedin, M. N.; Singh, U. N.; Prather, D.

    2006-01-01

    We report the first AlGaAsSb/InGaAsSb phototransistors with a cutoff wavelength (50% of peak responsivity) of 2.4 micrometers operating in a broad range of temperatures. These devices are also the first AlGaAsSb/InGaAsSb heterojunction phototransistors (HPT) grown by molecular beam epitaxy (MBE). This work is a continuation of a preceding study, which was carried out using LPE (liquid phase epitaxy)-grown AlGaAsSb/InGaAsSb/GaSb heterostructures. Although the LPE-related work resulted in the fabrication of an HPT with excellent parameters [1-4], the room temperature cutoff wavelength of these devices (approximately 2.15 micrometers) was determined by fundamental limitations implied by the close-to-equilibrium growth from Al-In-Ga-As-Sb melts. As the MBE technique is free from the above limitations, AlGaAsSb/InGaAsSb/GaSb heterostructures for HPT with a narrower bandgap of the InGaAsSb base and collector - and hence sensitivity at longer wavelengths (lambda) - were grown in this work. Moreover, MBE - compared to LPE - provides better control over doping levels, composition and width of the AlGaAsSb and InGaAsSb layers, compositional and doping profiles, especially with regard to abrupt heterojunctions. The new MBE-grown HPT exhibited both high responsivity R (up to 2334 A/W for lambda=2.05 micrometers at -20 deg C.) and specific detectivity D* (up to 2.1 x 10(exp 11) cmHz(exp 1/2)/W for lambda=2.05 micrometers at -20 deg C).

  19. The Synthesis of Ag-Doped Mesoporous TiO2

    SciTech Connect

    Li, Xiaohong S.; Fryxell, Glen E.; Wang, Chong M.; Engelhard, Mark H.

    2008-04-15

    Ag-doped mesoporous titanium oxide was prepared using non-ionic surfactants and easily handled titanium precursors, under mild reaction conditions. In contrast to the stabilizing effect of Cd-doping on mesoporous TiO2, Ag-doping was found to significantly destabilize the mesoporous structure.

  20. CD Recorders.

    ERIC Educational Resources Information Center

    Falk, Howard

    1998-01-01

    Discussion of CD (compact disc) recorders describes recording applications, including storing large graphic files, creating audio CDs, and storing material downloaded from the Internet; backing up files; lifespan; CD recording formats; continuous recording; recording software; recorder media; vulnerability of CDs; basic computer requirements; and…

  1. CD Rainbows

    ERIC Educational Resources Information Center

    Ouseph, P. J.

    2007-01-01

    Several papers have been published on the use of a CD as a grating for undergraduate laboratories and/or for high school and college class demonstrations. Four years ago "The Physics Teacher" had a spectacular cover picture showing emission spectrum as viewed through a CD with no coating. That picture gave the impetus to develop a system that can…

  2. The AgNORs.

    PubMed

    Derenzini, M

    2000-04-01

    The structure and the function of interphase AgNORs and the importance of the "AgNOR" parameter in tumor pathology have been reviewed. Interphase AgNORs are structural-functional units of the nucleolus in which all the components necessary for ribosomal RNA synthesis are located. Two argyrophilic proteins involved in rRNA transcription and processing, nucleolin and nucleophosmin, are associated with interphase AgNORs and are responsible for their stainability with silver methods, thus allowing interphase AgNORs to be visulaized at light microscopic level, also in routine cyto-histopathological preparations. The number of interphase AgNORs is strictly related to rRNA transcriptional activity and, in continuously proliferating cells, to the rapidity of cell proliferation. Evaluation of the quantitative distribution of interphase AgNORs has been applied in tumor pathology both for diagnostic and prognostic purposes. The "AgNOR" parameter has been proved to represent a reliable tool for defining the clinical outcome of cancer disease, being an independent prognostic factor in many types of tumors. PMID:10588056

  3. AgRISTARS

    NASA Technical Reports Server (NTRS)

    1984-01-01

    An introduction to the overall AgRISTARS program, a general statement on progress, and separate summaries of the activities of each project, with emphasis on the technical highlights are presented. Organizational and management information on AgRISTARS is included in the appendices, as is a complete bibliography of publication and reports.

  4. Dendritic Cell Migration and Antigen Presentation Are Coordinated by the Opposing Functions of the Tetraspanins CD82 and CD37.

    PubMed

    Jones, Eleanor L; Wee, Janet L; Demaria, Maria C; Blakeley, Jessica; Ho, Po Ki; Vega-Ramos, Javier; Villadangos, Jose A; van Spriel, Annemiek B; Hickey, Michael J; Hämmerling, Günther J; Wright, Mark D

    2016-02-01

    This study supports a new concept where the opposing functions of the tetraspanins CD37 and CD82 may coordinate changes in migration and Ag presentation during dendritic cell (DC) activation. We have previously published that CD37 is downregulated upon monocyte-derived DC activation, promotes migration of both skin and bone marrow-derived dendritic cells (BMDCs), and restrains Ag presentation in splenic and BMDCs. In this article, we show that CD82, the closest phylogenetic relative to CD37, appears to have opposing functions. CD82 is upregulated upon activation of BMDCs and monocyte-derived DCs, restrains migration of skin and BMDCs, supports MHC class II maturation, and promotes stable interactions between T cells and splenic DCs or BMDCs. The underlying mechanism involves the rearrangement of the cytoskeleton via a differential activation of small GTPases. Both CD37(-/-) and CD82(-/-) BMDCs lack cellular projections, but where CD37(-/-) BMDCs spread poorly on fibronectin, CD82(-/-) BMDCs are large and spread to a greater extent than wild-type BMDCs. At the molecular level, CD82 is a negative regulator of RhoA, whereas CD37 promotes activation of Rac-1; both tetraspanins negatively regulate Cdc42. Thus, this study identifies a key aspect of DC biology: an unactivated BMDC is CD37(hi)CD82(lo), resulting in a highly motile cell with a limited ability to activate naive T cells. By contrast, a late activated BMDC is CD37(lo)CD82(hi), and thus has modified its migratory, cytoskeletal, and Ag presentation machinery to become a cell superbly adapted to activating naive T cells. PMID:26729805

  5. Performance of Graphite Pastes Doped with Various Materials as Back Contact for CdS/CdTe Solar Cell

    NASA Astrophysics Data System (ADS)

    Hanafusa, Akira; Aramoto, Tetsuya; Morita, Akikatsu

    2001-12-01

    To date the problem of developing a suitable back contact for CdS/CdTe solar cells has yet to be resolved. The Cu-doped graphite paste that is widely used as a back contact is associated with degradation problems due to possible Cu diffusion across the CdS/CdTe junction. This study was designed to find ways to improve the graphite paste for superior electrical contacts. Mixtures of graphite paste with various material constituents and dopants consisting of silver-, lead-, nickel-, antimony-, bismuth-, or phosphor-based compounds, were studied. Results show that the performances of solar cells fabricated from these graphite pastes vary with the change in the composition. In the cases of Ag2Te and Ni2P, we studied their relationship with the solar cell characteristics with regard to dopant quantity, and furthermore in the case of Ag2Te, with regard to the sintering temperature of the graphite electrode. A fill factor (F.F.) of over 0.65 and efficiencies over 13% were obtained with Ag2Te, Ag3PO4, Ag2MoO4, and NiTe, and efficiencies over 12% were obtained with AgF, AgCl, Ni2P, and Ni3P.

  6. AGS experiments: 1993 - 1994 - 1995

    SciTech Connect

    Depken, J.C.

    1996-04-01

    This report contains: FY 1995 AGS Schedule as Run; FY 1996-97 AGE Schedule (working copy); AGS Beams 1995; AGS Experimental Area FY 1993 Physics Program; AGS Experimental Area FY 1994 Physics Program; AGS Experimental Area FY 1995 Physics Program; AGS Experimental Area FY 1996 Physics Program (In progress); A listing of experiments by number; Two-page summaries of each experiment begin here, also ordered by number; Listing of publications of AGS experiments begins here; and Listing of AGS experimenters begins here. This is the twelfth edition.

  7. Selective decrease of CD26 expression in T cells from HIV-1-infected individuals.

    PubMed

    Blazquez, M V; Madueño, J A; Gonzalez, R; Jurado, R; Bachovchin, W W; Peña, J; Muñoz, E

    1992-11-01

    The decrease of CD4+ cells in AIDS patients is widely documented, although the selective loss within different subsets of CD4+ cells and the mechanisms involved in this phenomenon are controversial. In the present report we have analyzed the proliferative response to Ag and mitogen of peripheral blood T lymphocytes from HIV-infected individuals, the phenotype profile of CD26+ and CD26- subset of cells and their infectivity by the HIV. The expression of CD26 Ag, either in CD4+ or CD8+ cells, was clearly diminished in all the patients tested. On the other hand, the expression of CD29 seems not to be affected, nevertheless T cells from these patients were unable to generate a proliferative response against soluble Ag. In 11 out of 13 patients, polymerase chain reaction studies demonstrated that the CD26- subset of CD4+ cells was the main reservoir for HIV-1 in infected individuals and HIV-1 virus preferentially infected in vitro CD4+/CD26- subpopulation. This capacity for preferential infectivity, together with the selective loss of cells expressing CD26 Ag, helps to explain the progressive impairment in the immune system of these patients and sheds new light on our understanding of the AIDS pathophysiology. PMID:1357035

  8. Pattern of distribution of selected trace elements in the marine brown alga, Sargassum filipendula Ag. from Sri Lanka.

    PubMed

    Jayasekera, R

    1994-06-01

    Baseline concentrations together with biological variations of 29 trace elements (Ag, As, Au, Ba, Br, Cd, Ce, Co, Cr, Cs, Eu, Fe, Hf, I, Mn, Mo, Ni, Pb, Rb, Sb, Sc, Se, Sm, Sr, Tb, Th, Yb, Zn and Zr) were investigated in the brown alga, Sargassum filipendula collected from the western coast of Sri Lanka. Several elements (Co, Cr, Fe, Hf, Ni, Sc, Se, Th, Zr and the rare earth elements) were found to be enriched in S. filipendula compared to NIES No. 9 Sargasso reference material. Concentration of strontium in S. filipendula was highest at all sites. Chemical abundance of the rare earth elements decreased approximately linearly with increasing atomic numbers. The pattern of elemental distribution appears to be due to the fact that S. filipendula seems capable of concentrating high levels of trace elements under conditions of their very low availability in sea water. Concentration factors for elements in S. filipendula lie in a higher range compared with those reported in the literaure for brown algae. PMID:24197034

  9. Breeding Value of the qSB9b and qSB12a QTLs in RiceBreeding Value of the qSB9b and qSB12a QTLs in Rice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Sheath blight (SB) caused by Rhizoctonia solani Kuhn is a serious rice disease worldwide. The results of 123 TeQing-into-Lemont (TILs) showed those with introgressions containing qSB9b and/or qSB12a were among the most SB resistant TILs. TIL:615, TIL:642 and TIL:567 have consistently appeared modera...

  10. A novel "dual-potential" electrochemiluminescence aptasensor array using CdS quantum dots and luminol-gold nanoparticles as labels for simultaneous detection of malachite green and chloramphenicol.

    PubMed

    Feng, Xiaobin; Gan, Ning; Zhang, Huairong; Yan, Qing; Li, Tianhua; Cao, Yuting; Hu, Futao; Yu, Hongwei; Jiang, Qianli

    2015-12-15

    A novel type of "dual-potential" electrochemiluminescence (ECL) aptasensor array was fabricated on a homemade screen-printed carbon electrode (SPCE) for simultaneous detection of malachite green (MG) and chloramphenicol (CAP) in one single assay. The SPCE substrate consisted of a common Ag/AgCl reference electrode, carbon counter electrode and two carbon working electrodes (WE1 and WE2). In the system, CdS quantum dots (QDs) were modified on WE1 as cathode ECL emitters and luminol-gold nanoparticles (L-Au NPs) were modified on WE2 as anode ECL emitters. Then the MG aptamer complementary strand (MG cDNA) and CAP aptamer complementary strand (CAP cDNA) were attached on CdS QDs and L-Au NPs, respectively. The cDNA would hybridize with corresponding aptamer that was respectively tagged with cyanine dye (Cy5) (as quenchers of CdS QDs) and chlorogenic acid (CA) (as quenchers of l-Au NPs) using poly(ethylenimine) (PEI) as a bridging agent. PEI could lead to a large number of quenchers on the aptamer, which increased the quenching efficiency. Upon MG and CAP adding, the targets could induce strand release due to the highly affinity of analytes toward aptamers. Meanwhile, it could release the Cy5 and CA, which recovered cathode ECL of CdS QDs and anode ECL of L-Au NPs simultaneously. This "dual-potential" ECL strategy could be used to detect MG and CAP with the linear ranges of 0.1-100 nM and 0.2-150 nM, with detection limits of 0.03 nM and 0.07 nM (at 3sB), respectively. More importantly, this designed method was successfully applied to determine MG and CAP in real fish samples and held great potential in the food analysis. PMID:26190470

  11. Relation between the magnetization and the electrical properties of alloy GaSb-MnSb films

    SciTech Connect

    Koplak, O. V.; Polyakov, A. A.; Davydov, A. B.; Morgunov, R. B.; Talantsev, A. D.; Kochura, A. V.; Fedorchenko, I. V.; Novodvorskii, O. A.; Parshina, L. S.; Khramova, O. D.; Shorokhova, A. V.; Aronzon, B. A.

    2015-06-15

    The influence of the charge carrier concentration on the magnetic properties of GaSb-MnSb alloys is studied. The ferromagnetism of GaSb-MnSb films is caused by the presence of MnSb granules and manifests itself in both magnetometric measurements and the presence of an anisotropic magnetoresistance and the anomalous Hall effect. Electric conduction is executed by charge carriers (holes) in a GaSb matrix. The magnetization of clusters depends on stoichiometry and the concentration of Mn{sup 2+} and Mn{sup 3+} ions, which is specified by the film growth conditions. At high film growth temperatures, ferromagnetic clusters containing Mn{sup 2+} ions mainly form. At low growth temperatures, an antiferromagnetic phase containing Mn{sup 3+} ions forms.

  12. T Cell-Extrinsic CD18 Attenuates Antigen-Dependent CD4+ T cell Activation In Vivo1

    PubMed Central

    Wu, Xingxin; Lahiri, Amit; Sarin, Ritu; Abraham, Clara

    2015-01-01

    The β2 integrins (CD11/CD18) are heterodimeric leukocyte adhesion molecules expressed on hematopoietic cells. The role of T cell-intrinsic CD18 in trafficking of naïve T cells to secondary lymphoid organs, and in antigen-dependent T cell activation in vitro and in vivo has been well-defined. However, the T cell-extrinsic role for CD18, including on antigen presenting cells (APC), in contributing to T cell activation in vivo is less well understood. We examined the role for T cell-extrinsic CD18 in the activation of WT CD4+ T cells in vivo through the adoptive transfer of DO11.10 Ag-specific CD4+ T cells into CD18−/− mice. We found that T cell-extrinsic CD18 was required for attenuating OVA-induced T cell proliferation in peripheral lymph nodes (PLN). The increased proliferation of WT DO11.10 CD4+ T cells in CD18−/− PLN was associated with a higher percentage of APC, and these APC demonstrated an increased activation profile and increased Ag-uptake, in particular in F4/80+ APC. Depletion of F4/80+ cells both reduced and equalized antigen-dependent T cell proliferation in CD18−/− relative to littermate control PLN, demonstrating that these cells play a critical role in the enhanced T cell proliferation in CD18−/− mice. Consistently, CD11b blockade, which is expressed on F4/80+ macrophages, enhanced the proliferation of DO11.10+ T cells in CD18+/− PLN. Thus, in contrast to the T cell-intrinsic essential role for CD18 in T cell activation, T cell-extrinsic expression of CD18 attenuates antigen-dependent CD4+ T cell activation in PLN in vivo. PMID:25801431

  13. Growth mechanisms of GaSb heteroepitaxial films on Si with an AlSb buffer layer

    SciTech Connect

    Vajargah, S. Hosseini; Botton, G. A.; Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario L8S 4M1; Canadian Centre for Electron Microscopy, McMaster University, Hamilton, Ontario L8S 4M1 ; Ghanad-Tavakoli, S.; Preston, J. S.; Kleiman, R. N.; Centre for Emerging Device Technologies, McMaster University, Hamilton, Ontario L8S 4L7; Department of Engineering Physics, McMaster University, Hamilton, Ontario L8S 4L7

    2013-09-21

    The initial growth stages of GaSb epilayers on Si substrates and the role of the AlSb buffer layer were studied by high-angle annular dark-field scanning transmission electron microscopy (HAADF-STEM). Heteroepitaxy of GaSb and AlSb on Si both occur by Volmer-Weber (i.e., island mode) growth. However, the AlSb and GaSb islands have distinctly different characteristics as revealed through an atomic-resolution structural study using Z-contrast of HAADF-STEM imaging. While GaSb islands are sparse and three dimensional, AlSb islands are numerous and flattened. The introduction of 3D island-forming AlSb buffer layer facilitates the nucleation of GaSb islands. The AlSb islands-assisted nucleation of GaSb islands results in the formation of drastically higher quality planar film at a significantly smaller thickness of films. The interface of the AlSb and GaSb epilayers with the Si substrate was further investigated with energy dispersive X-ray spectrometry to elucidate the key role of the AlSb buffer layer in the growth of GaSb epilayers on Si substrates.

  14. Choice of Substrate Material for Epitaxial CdTe Solar Cells

    SciTech Connect

    Song, Tao; Kanevce, Ana; Sites, James R.

    2015-06-14

    Epitaxial CdTe with high quality, low defect density, and high carrier concentration should in principle yield high-efficiency photovoltaic devices. However, insufficient effort has been given to explore the choice of substrate for high-efficiency epitaxial CdTe solar cells. In this paper, we use numerical simulations to investigate three crystalline substrates: silicon (Si), InSb, and CdTe each substrate material are generally discussed.

  15. SEMICONDUCTOR MATERIALS: AlGaSb/GaSb quantum wells grown on an optimized AlSb nucleation layer

    NASA Astrophysics Data System (ADS)

    Hanchao, Gao; Cai, Wen; Wenxin, Wang; Zhongwei, Jiang; Haitao, Tian; Tao, He; Hui, Li; Hong, Chen

    2010-05-01

    Five-period AlGaSb/GaSb multiple quantum wells (MQW) are grown on a GaSb buffer. Through optimizing the AlSb nucleation layer, the low threading dislocation density of the MQW is found to be (2.50 ± 0.91) × 108 cm-2 in 1-μm GaSb buffer, as determined by plan-view transmission election microscopy (TEM) images. High resolution TEM clearly shows the presence of 90° misfit dislocations with an average spacing of 5.4 nm at the AlSb/GaAs interface, which effectively relieve most of the strain energy. In the temperature range from T = 26 K to 300 K, photoluminescence of the MQW is dominated by the ground state electron to ground state heavy hole (e1-hh1) transition, while a high energy shoulder clearly seen at T > 76 K can be attributed to the ground state electron to ground state light hole (e1-lh1) transition.

  16. Sb-induced phase control of InAsSb nanowires grown by molecular beam epitaxy.

    PubMed

    Zhuang, Q D; Anyebe, Ezekiel A; Chen, R; Liu, H; Sanchez, Ana M; Rajpalke, Mohana K; Veal, Tim D; Wang, Z M; Huang, Y Z; Sun, H D

    2015-02-11

    For the first time, we report a complete control of crystal structure in InAs(1-x)Sb(x) NWs by tuning the antimony (Sb) composition. This claim is substantiated by high-resolution transmission electron microscopy combined with photoluminescence spectroscopy. The pure InAs nanowires generally show a mixture of wurtzite (WZ) and zinc-blende (ZB) phases, where addition of a small amount of Sb (∼2-4%) led to quasi-pure WZ InAsSb NWs, while further increase of Sb (∼10%) resulted in quasi-pure ZB InAsSb NWs. This phase transition is further evidenced by photoluminescence (PL) studies, where a dominant emission associated with the coexistence of WZ and ZB phases is present in the pure InAs NWs but absent in the PL spectrum of InAs0.96Sb0.04 NWs that instead shows a band-to-band emission. We also demonstrate that the Sb addition significantly reduces the stacking fault density in the NWs. This study provides new insights on the role of Sb addition for effective control of nanowire crystal structure. PMID:25559370

  17. ACCELERATED PROCESSING OF SB4 AND PREPARATION FOR SB5 PROCESSING AT DWPF

    SciTech Connect

    Herman, C

    2008-12-01

    The Defense Waste Processing Facility (DWPF) initiated processing of Sludge Batch 4 (SB4) in May 2007. SB4 was the first DWPF sludge batch to contain significant quantities of HM or high Al sludge. Initial testing with SB4 simulants showed potential negative impacts to DWPF processing; therefore, Savannah River National Laboratory (SRNL) performed extensive testing in an attempt to optimize processing. SRNL's testing has resulted in the highest DWPF production rates since start-up. During SB4 processing, DWPF also began incorporating waste streams from the interim salt processing facilities to initiate coupled operations. While DWPF has been processing SB4, the Liquid Waste Organization (LWO) and the SRNL have been preparing Sludge Batch 5 (SB5). SB5 has undergone low-temperature aluminum dissolution to reduce the mass of sludge for vitrification and will contain a small fraction of Purex sludge. A high-level review of SB4 processing and the SB5 preparation studies will be provided.

  18. Native point defects in GaSb

    SciTech Connect

    Kujala, J.; Segercrantz, N.; Tuomisto, F.; Slotte, J.

    2014-10-14

    We have applied positron annihilation spectroscopy to study native point defects in Te-doped n-type and nominally undoped p-type GaSb single crystals. The results show that the dominant vacancy defect trapping positrons in bulk GaSb is the gallium monovacancy. The temperature dependence of the average positron lifetime in both p- and n-type GaSb indicates that negative ion type defects with no associated open volume compete with the Ga vacancies. Based on comparison with theoretical predictions, these negative ions are identified as Ga antisites. The concentrations of these negatively charged defects exceed the Ga vacancy concentrations nearly by an order of magnitude. We conclude that the Ga antisite is the native defect responsible for p-type conductivity in GaSb single crystals.

  19. Vought SB2U-1 Vindicator

    NASA Technical Reports Server (NTRS)

    1938-01-01

    Vought SB2U-1 Vindicator: This Vought SB2U-1 Vindicator was acquired for one month in late 1938 from NAS Anacostia, Washington, D. C. Anacostia was the source of many of the naval aircraft flown by the NACA, in part due to its proximity and in part became it was the Navy's flight test base. The nose slot cowling was aimed at improving engine cooling.

  20. Photoluminescence studies of type-II CdSe/CdTe superlattices

    SciTech Connect

    Li Jingjing; Johnson, Shane R.; Wang Shumin; Ding Ding; Ning Cunzheng; Zhang Yonghang; Yin Leijun; Skromme, B. J.; Liu Xinyu; Furdyna, Jacek K.

    2012-08-06

    CdSe/CdTe type-II superlattices grown on GaSb substrates by molecular beam epitaxy are studied using time-resolved and steady-state photoluminescence (PL) spectroscopy at 10 K. The relatively long carrier lifetime of 188 ns observed in time-resolved PL measurements shows good material quality. The steady-state PL peak position exhibits a blue shift with increasing excess carrier concentration. Self-consistent solutions of the Schroedinger and Poisson equations show that this effect can be explained by band bending as a result of the spatial separation of electrons and holes, which is critical confirmation of a strong type-II band edge alignment between CdSe and CdTe.

  1. Sb2Se3 under pressure

    PubMed Central

    Efthimiopoulos, Ilias; Zhang, Jiaming; Kucway, Melvin; Park, Changyong; Ewing, Rodney C.; Wang, Yuejian

    2013-01-01

    Selected members of the A2B3 (A = Sb, Bi; B = Se, Te) family are topological insulators. The Sb2Se3 compound does not exhibit any topological properties at ambient conditions; a recent high-pressure study, however, indicated that pressure transforms Sb2Se3 from a band insulator into a topological insulator above ~2 GPa; in addition, three structural transitions were proposed to occur up to 25 GPa. Partly motivated by these results, we have performed x-ray diffraction and Raman spectroscopy investigations on Sb2Se3 under pressure up to 65 GPa. We have identified only one reversible structural transition: the initial Pnma structure transforms into a disordered cubic bcc alloy above 51 GPa. On the other hand, our high-pressure Raman study did not reproduce the previous results; we attribute the discrepancies to the effects of the different pressure transmitting media used in the high-pressure experiments. We discuss the structural behavior of Sb2Se3 within the A2B3 (A = Sb, Bi; B = Se, Te) series. PMID:24045363

  2. Air dispersion of heavy metals in the vicinity of the As-Sb-Tl abounded mine and responsiveness of moss as a biomonitoring media in small-scale investigations.

    PubMed

    Bačeva, Katerina; Stafilov, Trajče; Šajn, Robert; Tănăselia, Claudiu

    2013-12-01

    A systematic study was carried out to investigate air deposition and to explore the natural distribution and enrichment (contamination) with trace elements in the small area (cca. 13 km(2)) of an antimony-arsenic-thallium mineralization outcrop at an abandoned mine "Allchar." The mine is located on the northwestern part of Kožuf Mount, Republic of Macedonia. The locality of Allchar is unique in its mineral composition; besides a very intriguing mineral, lorandite, there are 45 other minerals, some of which are rare. The distribution of 53 elements (with special attention to As, Sb, and Tl) were detected in 69 moss samples from eight various species collected from this area. Moss samples were analyzed following microwave digestion by inductively coupled plasma-mass spectrometry and inductively coupled plasma-atomic emission spectrometry. It was found that the atmospheric deposition for As in the moss samples on or around the Allchar mine is >6.5 times higher and for Tl is 19 times higher compared to values for the samples from the rest of the Allchar area. By the application of multivariate cluster and R-mode factor analyses (FA), five geochemical associations were determined. Cluster and R-mode FA were used to identify and characterize element associations, and five associations of elements were determined by the method of multivariate statistics. F1 (Co, Cr, Fe, Sc, Li, V, Ga, Y, Ni, Mn, Al, La-Lu, Cu, Ge, Be, Bi, and Hf); F2 (As, Tl, Sb, and Mg); F3 (Rb, Cs, and Mo); F4 (Sr, Ba, Hf, Zr, La-Lu, and Bi), and F5 (Cd, Zn, Ag, and Cu). PMID:23729028

  3. Ideal mode operation of an InSb charge injection device

    NASA Astrophysics Data System (ADS)

    Wei, C.-Y.; Woodbury, H. H.

    1984-12-01

    Unlike Si or HgCdTe CID (charge injection device) arrays, which normally operate at 1 MHz with the presence of a less than 10 percent fat zero (i.e., ideal mode), current InSb CID arrays fabricated on InSb CID arrays fabricated on InSb substrates can operate either at a much lower clock frequency of 10 kHz (i.e., slow charge transfer mode), or when both row and column potential wells are partially filled with a large bias charge (i.e., charge sharing mode). The slow charge transfer mode is very ineffective in reading out signal charge from a large-area array and the charge sharing mode exhibits difficulties such as reduced readout efficiency, increased line capacitance, and a large photocurrent effect. By contrast, the ideal mode is free of these problems. This paper describes the design and fabrication of an InSb CID array, which for the first time, successfully demonstrates the ideal mode operation.

  4. Longitudinal Requirement for CD4+ T Cell Help for Adenovirus Vector–Elicited CD8+ T Cell Responses

    PubMed Central

    Provine, Nicholas M.; Larocca, Rafael A.; Penaloza-MacMaster, Pablo; Borducchi, Erica N.; McNally, Anna; Parenteau, Lily R.; Kaufman, David R.

    2014-01-01

    Despite the widespread use of replication-incompetent recombinant adenovirus (Ad) vectors as candidate vaccine platforms, the mechanism by which these vectors elicit CD8+ T cell responses remains poorly understood. Our data demonstrate that induction and maintenance of CD8+ T cell responses by Ad vector immunization is longitudinally dependent on CD4+ T cell help for a prolonged period. Depletion of CD4+ T cells in wild type mice within the first 8 d following Ad immunization resulted in dramatically reduced induction of Ag-specific CD8+ T cells, decreased T-bet and eomesodermin expression, impaired KLRG1+ effector differentiation, and atypical expression of the memory markers CD127, CD27, and CD62L. Moreover, these CD8+ T cells failed to protect against a lethal recombinant Listeria monocytogenes challenge. Depletion of CD4+ T cells between weeks 1 and 4 following immunization resulted in increased contraction of memory CD8+ T cells. These data demonstrate a prolonged temporal requirement for CD4+ T cell help for vaccine-elicited CD8+ T cell responses in mice. These findings have important implications in the design of vaccines aimed at eliciting CD8+ T cell responses and may provide insight into the impaired immunogenicity of vaccines in the context of AIDS and other CD4+ T cell immune deficiencies. PMID:24778441

  5. Controlled CVD growth of Cu-Sb alloy nanostructures

    NASA Astrophysics Data System (ADS)

    Chen, Jing; Yin, Zongyou; Sim, Daohao; Tay, Yee Yan; Zhang, Hua; Ma, Jan; Hng, Huey Hoon; Yan, Qingyu

    2011-08-01

    Sb based alloy nanostructures have attracted much attention due to their many promising applications, e.g. as battery electrodes, thermoelectric materials and magnetic semiconductors. In many cases, these applications require controlled growth of Sb based alloys with desired sizes and shapes to achieve enhanced performance. Here, we report a flexible catalyst-free chemical vapor deposition (CVD) process to prepare Cu-Sb nanostructures with tunable shapes (e.g. nanowires and nanoparticles) by transporting Sb vapor to react with copper foils, which also serve as the substrate. By simply controlling the substrate temperature and distance, various Sb-Cu alloy nanostructures, e.g. Cu11Sb3 nanowires (NWs), Cu2Sb nanoparticles (NPs), or pure Sb nanoplates, were obtained. We also found that the growth of Cu11Sb3 NWs in such a catalyst-free CVD process was dependent on the substrate surface roughness. For example, smooth Cu foils could not lead to the growth of Cu11Sb3 nanowires while roughening these smooth Cu foils with rough sand papers could result in the growth of Cu11Sb3 nanowires. The effects of gas flow rate on the size and morphology of the Cu-Sb alloy nanostructures were also investigated. Such a flexible growth strategy could be of practical interest as the growth of some Sb based alloy nanostructures by CVD may not be easy due to the large difference between the condensation temperature of Sb and the other element, e.g. Cu or Co.

  6. High thermopower and ultra low thermal conductivity in Cd-based Zintl phase compounds.

    PubMed

    Pandey, Tribhuwan; Singh, Abhishek K

    2015-07-14

    By combining first principles density functional theory and electronic as well as lattice Boltzmann transport calculations, we unravel the excellent thermoelectric properties of Zintl phase compounds ACd2Sb2 (where, A = Ca, Ba, Sr). The calculated electronic structures of these compounds show charge carrier pockets and heavy light bands near the band edge, which lead to a large power factor. Furthermore, we report large Grüneisen parameters and low phonon group velocity indicating essential strong anharmonicity in these compounds, which resulted in low lattice thermal conductivity. The combination of low thermal conductivity and the excellent transport properties give a high ZT value of ∼1.4-1.9 in CaCd2Sb2 and BaCd2Sb2 at moderate p and n-type doping. Our results indicate that well optimized Cd-based Zintl phase compounds have the potential to match the performance of conventional thermoelectric materials. PMID:26060054

  7. Growth of Lattice-Matched ZnTeSe Alloys on (100) and (211)B GaSb

    NASA Astrophysics Data System (ADS)

    Chai, J.; Lee, K.-K.; Doyle, K.; Dinan, J. H.; Myers, T. H.

    2012-10-01

    A key issue with the current HgCdTe/Si system is the high dislocation density due to the large mismatch between HgCdTe and Si. An alternative system that has superior lattice matching is HgCdSe/GaSb. A buffer layer to mitigate issues with direct nucleation of HgCdSe on GaSb is ZnTe1- x Se x . We have performed preliminary studies into the growth of lattice-matched ZnTe1- x Se x on both (100) and (211)B GaSb. The effects of substrate orientation, substrate temperature, and growth conditions on the morphology and crystallography of ZnTe0.99Se0.01 alloys were investigated. The lattice-matching condition yielded minimum root-mean-square (rms) roughness of 1.1 nm, x-ray rocking curve full-width at half-maximum (FWHM) value of ~29 arcsec, and density of nonradiative defects of mid-105 cm-2 as measured by imaging photoluminescence.

  8. Low-Temperature Bonding of Bi0.5Sb1.5Te3 Thermoelectric Material with Cu Electrodes Using a Thin-Film In Interlayer

    NASA Astrophysics Data System (ADS)

    Lin, Yan-Cheng; Yang, Chung-Lin; Huang, Jing-Yi; Jain, Chao-Chi; Hwang, Jen-Dong; Chu, Hsu-Shen; Chen, Sheng-Chi; Chuang, Tung-Han

    2016-09-01

    A Bi0.5Sb1.5Te3 thermoelectric material electroplated with a Ni barrier layer and a Ag reaction layer was bonded with a Ag-coated Cu electrode at low temperatures of 448 K (175 °C) to 523 K (250 °C) using a 4- μm-thick In interlayer under an external pressure of 3 MPa. During the bonding process, the In thin film reacted with the Ag layer to form a double layer of Ag3In and Ag2In intermetallic compounds. No reaction occurred at the Bi0.5Sb1.5Te3/Ni interface, which resulted in low bonding strengths of about 3.2 MPa. The adhesion of the Bi0.5Sb1.5Te3/Ni interface was improved by precoating a 1- μm Sn film on the surface of the thermoelectric element and preheating it at 523 K (250 °C) for 3 minutes. In this case, the bonding strengths increased to a range of 9.1 to 11.5 MPa after bonding at 473 K (200 °C) for 5 to 60 minutes, and the shear-tested specimens fractured with cleavage characteristics in the interior of the thermoelectric material. The bonding at 448 K (175 °C) led to shear strengths ranging from 7.1 to 8.5 MPa for various bonding times between 5 and 60 minutes, which were further increased to the values of 10.4 to 11.7 MPa by increasing the bonding pressure to 9.8 MPa. The shear strengths of Bi0.5Sb1.5Te3/Cu joints bonded with the optimized conditions of the modified solid-liquid interdiffusion bonding process changed only slightly after long-term exposure at 473 K (200 °C) for 1000 hours.

  9. Low-Temperature Bonding of Bi0.5Sb1.5Te3 Thermoelectric Material with Cu Electrodes Using a Thin-Film In Interlayer

    NASA Astrophysics Data System (ADS)

    Lin, Yan-Cheng; Yang, Chung-Lin; Huang, Jing-Yi; Jain, Chao-Chi; Hwang, Jen-Dong; Chu, Hsu-Shen; Chen, Sheng-Chi; Chuang, Tung-Han

    2016-07-01

    A Bi0.5Sb1.5Te3 thermoelectric material electroplated with a Ni barrier layer and a Ag reaction layer was bonded with a Ag-coated Cu electrode at low temperatures of 448 K (175 °C) to 523 K (250 °C) using a 4-μm-thick In interlayer under an external pressure of 3 MPa. During the bonding process, the In thin film reacted with the Ag layer to form a double layer of Ag3In and Ag2In intermetallic compounds. No reaction occurred at the Bi0.5Sb1.5Te3/Ni interface, which resulted in low bonding strengths of about 3.2 MPa. The adhesion of the Bi0.5Sb1.5Te3/Ni interface was improved by precoating a 1-μm Sn film on the surface of the thermoelectric element and preheating it at 523 K (250 °C) for 3 minutes. In this case, the bonding strengths increased to a range of 9.1 to 11.5 MPa after bonding at 473 K (200 °C) for 5 to 60 minutes, and the shear-tested specimens fractured with cleavage characteristics in the interior of the thermoelectric material. The bonding at 448 K (175 °C) led to shear strengths ranging from 7.1 to 8.5 MPa for various bonding times between 5 and 60 minutes, which were further increased to the values of 10.4 to 11.7 MPa by increasing the bonding pressure to 9.8 MPa. The shear strengths of Bi0.5Sb1.5Te3/Cu joints bonded with the optimized conditions of the modified solid-liquid interdiffusion bonding process changed only slightly after long-term exposure at 473 K (200 °C) for 1000 hours.

  10. Magnetothermoelectrical and adhesive properties of commutation contacts of thermoelements on the basis of extruded samples of Bi85Sb15 solid solution

    NASA Astrophysics Data System (ADS)

    Tagiyev, M. M.

    2003-09-01

    A study of electrical and adhesive properties of transient contacts for extruded samples of Bi85Sb15 solid solutions have been conducted with alloys: 25Bi + 50Pb + 12.5Cd + 12.5Sn with Tm = 343 K (Wood"s alloy) and 57Bi + 45Sn with Tm =412 K in temperature range ~77-300 K and magnetic field intensity (H) up to ~74x104 A/m. It is shown that resistance of transient contacts (rk) of the extruded of Bi85Sb15 solid solution with the specified contact alloys at ~77K is determined by the resistance of the structure the solid solution Bi85Sb15-solid solution Bi85Sb15, heavily doped by Pb and Sn atoms, diffused from contact alloy into near-contact area of the Bi85Sb15 solid solution. It is established, that by doping extruded samples of Bi85Sb15 solid solution with Pb atoms it is possible to achieve reduction of a transient contact resistance rk in Bi85Sb15 solid solution - contact alloy interface.

  11. Growth of InSb on GaAs Using InAlSb Buffer Layers

    SciTech Connect

    BIEFELD, ROBERT M.; PHILLIPS, JAMIE D.

    1999-09-20

    We report the growth of InSb on GaAs using InAlSb buffers of high interest for magnetic field sensors. We have grown samples by metal-organic chemical vapor deposition consisting of {approximately} 0.55 {micro}m thick InSb layers with resistive InAlSb buffers on GaAs substrates with measured electron nobilities of {approximately}40,000 cm{sup 2}/V.s. We have investigated the In{sub 1{minus}x}Al{sub x}Sb buffers for compositions x{le}0.22 and have found that the best results are obtained near x=0.12 due to the tradeoff of buffer layer bandgap and lattice mismatch.

  12. Lattice-matched epitaxial GaInAsSb/GaSb thermophotovoltaic devices

    SciTech Connect

    Wang, C.A.; Choi, H.K.; Turner, G.W.; Spears, D.L.; Manfra, M.J.; Charache, G.W.

    1997-05-01

    The materials development of Ga{sub 1{minus}x}In{sub x}As{sub y}Sb{sub 1{minus}y} alloys for lattice-matched thermophotovoltaic (TPV) devices is reported. Epilayers with cutoff wavelength 2--2.4 {micro}m at room temperature and lattice-matched to GaSb substrates were grown by both low-pressure organometallic vapor phase epitaxy and molecular beam epitaxy. These layers exhibit high optical and structural quality. For demonstrating lattice-matched thermophotovoltaic devices, p- and n-type doping studies were performed. Several TPV device structures were investigated, with variations in the base/emitter thicknesses and the incorporation of a high bandgap GaSb or AlGaAsSb window layer. Significant improvement in the external quantum efficiency is observed for devices with an AlGaAsSb window layer compared to those without one.

  13. ``Quasi-direct'' narrow GaSb-AlSb (100) quantum wells

    NASA Astrophysics Data System (ADS)

    Brar, Berinder; Kroemer, Herbert; English, John

    1993-02-01

    In GaSb-AlSb quantum wells, GaSb is expected to make a transition to an X-valley semiconductor for well widths less than 2 nm. For narrow X-valley quantum wells the unassisted radiative transitions are no longer forbidden, allowing for the possibility of a "quasi-direct" transition from the X conduction band to the Γ valence band. Photoluminescence characterization of such narrow well GaSb-AlSb multi-quantum well structures has been performed. Spectra from wells as thin as a few monolayers were observed. A comparison of the measured transition energy with a simple calculation supports the idea that the observed transitions are indeed quasi-direct transitions.

  14. Performance improvement of Ge-Sb-Te material by GaSb doping for phase change memory

    NASA Astrophysics Data System (ADS)

    Lu, Yegang; Zhang, Zhonghua; Song, Sannian; Shen, Xiang; Wang, Guoxiang; Cheng, Limin; Dai, Shixun; Song, Zhitang

    2013-06-01

    Effects of GaSb doping on phase change characteristics of Ge-Sb-Te material are investigated by in situ resistance and x-ray diffraction measurement, optical spectroscopy, and x-ray photoelectron spectroscopy. The crystallization temperature and data retention of Ge-Sb-Te material increase significantly by the addition of GaSb, which results from the high thermal stability of amorphous GaSb. In addition, GaSb-doped Ge-Sb-Te material exhibits faster crystallization speed due to the change in electronic states as a result of the formation of chemical bonds with Ga element. Incorporation of GaSb is highly effective way to enhance the comprehensive performance of Ge-Sb-Te material for phase change memory.

  15. Performance improvement of Ge-Sb-Te material by GaSb doping for phase change memory

    SciTech Connect

    Lu, Yegang; Zhang, Zhonghua; Song, Sannian; Cheng, Limin; Song, Zhitang; Shen, Xiang; Wang, Guoxiang; Dai, Shixun

    2013-06-17

    Effects of GaSb doping on phase change characteristics of Ge-Sb-Te material are investigated by in situ resistance and x-ray diffraction measurement, optical spectroscopy, and x-ray photoelectron spectroscopy. The crystallization temperature and data retention of Ge-Sb-Te material increase significantly by the addition of GaSb, which results from the high thermal stability of amorphous GaSb. In addition, GaSb-doped Ge-Sb-Te material exhibits faster crystallization speed due to the change in electronic states as a result of the formation of chemical bonds with Ga element. Incorporation of GaSb is highly effective way to enhance the comprehensive performance of Ge-Sb-Te material for phase change memory.

  16. Growth of CdS Nanorods and Deposition of Silver Nanoparticles.

    PubMed

    Zhao, Jie; Yang, Fanghong; Yang, Ping

    2015-05-01

    Systematic investigations have been done to deposit silver nanoparticles on seeded CdS nanorods. The CdS nanorods were synthesized by using CdS nanocrystals as seeds being indexed to the cubic structure (zinc-blende) and tetradecylphosphonic acid as surfactants to enable preferential growth on the reactive {001} facets. Ostwald ripening process occurred during the growth of CdS nanorods. Ag/CdS heterostructures were obtained through a facile method in which oleylamine was employed as reducing agents under an elevated temperature. Exposing CdS nanorods to Ag+ ions resulted in Ag domains depositing on the tips of the nanorods or defected sites embedding in the nanorod surfaces. Ag domains formed separate nuclei and grew quickly at a high concentration of AgNO3 solution. We further focused on discussing the morphology formation mechanism and optical properties of the heterostructures and the nanorods. The as-synthesized Ag/CdS heterostructures can facilitate charge separation at the metal-semiconductor interface. Herein, it opens up an application possibility of enhancing photocatalytic processes and other devices. PMID:26505026

  17. Isolation and Characterization of Salmonid CD4+ T Cells.

    PubMed

    Maisey, Kevin; Montero, Ruth; Corripio-Miyar, Yolanda; Toro-Ascuy, Daniela; Valenzuela, Beatriz; Reyes-Cerpa, Sebastián; Sandino, Ana María; Zou, Jun; Wang, Tiehui; Secombes, Christopher J; Imarai, Mónica

    2016-05-15

    This study reports the isolation and functional characterization of rainbow trout (Oncorhynchus mykiss) CD4-1(+) T cells and the establishment of an IL-15-dependent CD4-1(+) T cell line. By using Abs specific for CD4-1 and CD3ε it was possible to isolate the double-positive T cells in spleen and head kidney. The morphology and the presence of transcripts for T cell markers in the sorted CD4-1(+)CD3ε(+) cells were studied next. Cells were found to express TCRα, TCRβ, CD152 (CTLA-4), CD154 (CD40L), T-bet, GATA-3, and STAT-1. The sorted CD4-1(+) T cells also had a distinctive functional attribute of mammalian T lymphocytes, namely they could undergo Ag-specific proliferation, using OVA as a model Ag. The OVA-stimulated cells showed increased expression of several cytokines, including IFN-γ1, IL-4/13A, IL-15, IL-17D, IL-10, and TGF-β1, perhaps indicating that T cell proliferation led to differentiation into distinct effector phenotypes. Using IL-15 as a growth factor, we have selected a lymphoid cell line derived from rainbow trout head kidney cells. The morphology, cell surface expression of CD4-1, and the presence of transcripts of T cell cytokines and transcription factors indicated that this is a CD4-1(+) T cell line. To our knowledge, this is the first demonstration of the presence of CD4-1(+)CD3ε(+) T cells in salmonids. As in mammals, CD4-1(+) T cells may be the master regulators of immune responses in fish, and therefore these findings and the new model T cell line developed will contribute to a greater understanding of T cell function and immune responses in teleost fish. PMID:27053758

  18. DWPF simulant CPC studies for SB8

    SciTech Connect

    Koopman, D. C.; Zamecnik, J. R.

    2013-06-25

    The Savannah River National Laboratory (SRNL) accepted a technical task request (TTR) from Waste Solidification Engineering to perform simulant tests to support the qualification of Sludge Batch 8 (SB8) and to develop the flowsheet for SB8 in the Defense Waste Processing Facility (DWPF). These efforts pertained to the DWPF Chemical Process Cell (CPC). Separate studies were conducted for frit development and glass properties (including REDOX). The SRNL CPC effort had two primary phases divided by the decision to drop Tank 12 from the SB8 constituents. This report focuses on the second phase with SB8 compositions that do not contain the Tank 12 piece. A separate report will document the initial phase of SB8 testing that included Tank 12. The second phase of SB8 studies consisted of two sets of CPC studies. The first study involved CPC testing of an SB8 simulant for Tank 51 to support the CPC demonstration of the washed Tank 51 qualification sample in the SRNL Shielded Cells facility. SB8-Tank 51 was a high iron-low aluminum waste with fairly high mercury and moderate noble metal concentrations. Tank 51 was ultimately washed to about 1.5 M sodium which is the highest wash endpoint since SB3-Tank 51. This study included three simulations of the DWPF Sludge Receipt and Adjustment Tank (SRAT) cycle and Slurry Mix Evaporator (SME) cycle with the sludge-only flowsheet at nominal DWPF processing conditions and three different acid stoichiometries. These runs produced a set of recommendations that were used to guide the successful SRNL qualification SRAT/SME demonstration with actual Tank 51 washed waste. The second study involved five SRAT/SME runs with SB8-Tank 40 simulant. Four of the runs were designed to define the acid requirements for sludge-only processing in DWPF with respect to nitrite destruction and hydrogen generation. The fifth run was an intermediate acid stoichiometry demonstration of the coupled flowsheet for SB8. These runs produced a set of processing

  19. The SbMT-2 Gene from a Halophyte Confers Abiotic Stress Tolerance and Modulates ROS Scavenging in Transgenic Tobacco

    PubMed Central

    Chaturvedi, Amit Kumar; Patel, Manish Kumar; Mishra, Avinash; Tiwari, Vivekanand; Jha, Bhavanath

    2014-01-01

    Heavy metals are common pollutants of the coastal saline area and Salicornia brachiata an extreme halophyte is frequently exposed to various abiotic stresses including heavy metals. The SbMT-2 gene was cloned and transformed to tobacco for the functional validation. Transgenic tobacco lines (L2, L4, L6 and L13) showed significantly enhanced salt (NaCl), osmotic (PEG) and metals (Zn++, Cu++ and Cd++) tolerance compared to WT plants. Transgenic lines did not show any morphological variation and had enhanced growth parameters viz. shoot length, root length, fresh weight and dry weight. High seed germination percentage, chlorophyll content, relative water content, electrolytic leakage and membrane stability index confirmed that transgenic lines performed better under salt (NaCl), osmotic (PEG) and metals (Zn++, Cu++ and Cd++) stress conditions compared to WT plants. Proline, H2O2 and lipid peroxidation (MDA) analyses suggested the role of SbMT-2 in cellular homeostasis and H2O2 detoxification. Furthermore in vivo localization of H2O2 and O2−; and elevated expression of key antioxidant enzyme encoding genes, SOD, POD and APX evident the possible role of SbMT-2 in ROS scavenging/detoxification mechanism. Transgenic lines showed accumulation of Cu++ and Cd++ in root while Zn++ in stem under stress condition. Under control (unstressed) condition, Zn++ was accumulated more in root but accumulation of Zn++ in stem under stress condition suggested that SbMT-2 may involve in the selective translocation of Zn++ from root to stem. This observation was further supported by the up-regulation of zinc transporter encoding genes NtZIP1 and NtHMA-A under metal ion stress condition. The study suggested that SbMT-2 modulates ROS scavenging and is a potential candidate to be used for phytoremediation and imparting stress tolerance. PMID:25340650

  20. InAs/GaInSb strained layer superlattice as an infrared detector material: an overview

    NASA Astrophysics Data System (ADS)

    Johnson, Jeffrey L.

    2000-04-01

    The investigation of the InAs/Ga1-xInxSb strained layer superlattice (SLS) has been largely motivated by the promise of overcoming limitations of current mature high-performance IR detectors, such as those using HgCdTe and extrinsic silicon. It also offers fundamentally superior performance over other newly emerging III-V bandgap- engineered materials such as QWIPs. The inherent properties of the InAs/GaInSb SLS have identified it as an attractive alternative for niche VLWIR applications requiring high performance under low backgrounds at operating temperatures > 40K. If this material system proves to meet the stringent demands of VLWIR applications, it will most certainly play a significant role as an alternative materials for photovoltaic focal pane arrays operating in the LWIR and MWIR regimes as well. This paper is an overview of SLS technology development, and focuses on critical development needs as seen from the perspective of the IR detector industry.

  1. Adsorption of Sb(III) and Sb(V) on Freshly Prepared Ferric Hydroxide (FeOxHy)

    PubMed Central

    He, Zan; Liu, Ruiping; Liu, Huijuan; Qu, Jiuhui

    2015-01-01

    Abstract This study prepared fresh ferric hydroxide (in-situ FeOxHy) by the enhanced hydrolysis of Fe3+ ions, and investigates its adsorptive behaviors toward Sb(III) and Sb(V) through laboratory and pilot-scale studies. A contact time of 120-min was enough to achieve adsorption equilibrium for Sb(III) and Sb(V) on the in-situ FeOxHy, and the Elovich model was best to describe the adsorption kinetics of Sb(III) and Sb(V). The Freundlich model was better than Langmuir model to describe the adsorption of Sb(III) and Sb(V) on the in-situ FeOxHy, and the maximum adsorption capacity of Sb(III) and Sb(V) was determined to be 12.77 and 10.21 mmol/g the in-situ FeOxHy as Fe, respectively. Adsorption of Sb(V) decreased whereas that of Sb(III) increased with elevated pH over pH 3–10, owing to the different electrical properties of Sb(III) and Sb(V). Adsorption of Sb(III) and Sb(V) was slightly affected by ionic strength, and thus indicated the formation of inner sphere complexes between Sb and the adsorbent. Sulfate and carbonate showed little effect on the adsorption of Sb(III) and Sb(V). Phosphate significantly inhibited the adsorption of Sb(V), whereas slightly effected that of Sb(III) due to its similar chemical structure to Sb(V). Pilot-scale continuous experiment indicated the feasibility of using in-situ FeOxHy to remove Sb(V), and equilibrium adsorption capacity at the equilibrium Sb(V) concentration of 10 μg/L was determined to be 0.11, 0.07, 0.07, 0.11, and 0.12 mg/g the in-situ FeOxHy as Fe at equilibrium pH of 7.5–7.7, 6.9–7.0, 6.3–6.6, 5.9–6.4, and 5.2–5.9, respectively. PMID:25741175

  2. Sb (111) Abnormal Behavior under Ion Etching

    NASA Astrophysics Data System (ADS)

    Smirnov, A. A.; Bozhko, S. I.; Ionov, A. M.; Protasova, S. G.; Chekmazov, S. V.; Kapustin, A. A.

    Due to a strong spin-orbit interaction (SOI), the surface states of Sb (111) are similar to those for topological insulators (TI) Sugawara et al. (2006). The surface states are protected by time-reversal symmetry and energy dispersion is a linear function of momentum. Defects in crystal structure lead to a local break of the surface translational symmetry and can modify surface states. It is the primary reason to study defects of Sb crystal structure and their effect on the surface states dispersion. Etching of the Sb (111) surface using Ar+ ions is a common way to create defects both in a bulk and on the surface of the crystal. Sb (111) ion etching at room temperature reveals anomalous behavior of surface crystal structure. It results in formation of flat terraces of 2 nm in size. Investigation of electronic structure of the etched Sb (111) surface has demonstrated increase of density of states (DOS) at the Fermi level. The results are discussed in terms of local break of conditions of Peierls transition.

  3. Defect density reduction in InAs/GaSb type II superlattice focal plane array infrared detectors

    NASA Astrophysics Data System (ADS)

    Walther, Martin; Rehm, Robert; Schmitz, Johannes; Niemasz, Jasmin; Rutz, Frank; Wörl, Andreas; Kirste, Lutz; Scheibner, Ralf; Wendler, Joachim; Ziegler, Johann

    2011-01-01

    InAs/GaSb short-period superlattices (SL) have proven their large potential for high performance focal plane array infrared detectors. Lots of interest is focused on the development of short-period InAs/GaSb SLs for mono- and bispectral infrared detectors between 3 - 30 μm. InAs/GaSb short-period superlattices can be fabricated with up to 1000 periods in the intrinsic region without revealing diffusion limited behavior. This enables the fabrication of InAs/GaSb SL camera systems with very high responsivity, comparable to state of the art CdHgTe and InSb detectors. The material system is also well suited for the fabrication of dual-color mid-wavelength infrared InAs/GaSb SL camera systems. These systems exhibit high quantum efficiency and offer simultaneous and spatially coincident detection in both spectral channels. An essential point for the performance of two-dimensional focal plane infrared detectors in camera systems is the number of defective pixel on the matrix detector. Sources for pixel outages are manifold and might be caused by the dislocation in the substrate, the epitaxial growth process or by imperfections during the focal plane array fabrication process. The goal is to grow defect-free epitaxial layers on a dislocation free large area GaSb substrate. Permanent improvement of the substrate quality and the development of techniques to monitor the substrate quality are of particular importance. To examine the crystalline quality of 3" and 4" GaSb substrates, synchrotron white beam X-ray topography (SWBXRT) was employed. In a comparative defect study of different 3" GaSb and 4" GaSb substrates, a significant reduction of the dislocation density caused by improvements in bulk crystal growth has been obtained. Optical characterization techniques for defect characterization after MBE growth are employed to correlate epitaxially grown defects with the detector performance after hybridization with the read-out integrated circuit.

  4. Electronic and thermoelectric properties of CoSbS and FeSbS

    SciTech Connect

    Parker, David S; Singh, David J; Sales, Brian C; McGuire, Michael A; May, Andrew F; Wang, Hsin

    2013-01-01

    We present a combined theoretical and experimental study of the potential thermoelectric performance of three transition metal antimonide sulfides, CoSbS, FeSbS and NiSbS. From theory we find that NiSbS is metallic and hence of little interest regarding thermoelectric performance. CoSbS and FeSbS are both semiconductors with rather heavy valence and conduction bands, whose thermopower can exceed 200 $\\mu$V/K at temperatures of 900 K and carrier concentrations of 10$^{21}$cm$^{-3}$, which is similar to the $n$-type high performance thermoelectric filled skutterudites. The experimental results on several non-optimized $n$-type CoSbS samples confirm its semiconducting nature and indicate a potential for good high temperature thermoelectric performance, finding a ZT for two of the samples of 0.35 at 773 K. Substantially higher ZT values may be possible if the lattice thermal conductivity can be reduced by alloying and the effects of extrinsic scattering, which appear to be substantial in the experimental results, are reduced.

  5. An All-Metal Aromatic Sandwich Complex [Sb3Au3Sb3](3-).

    PubMed

    Pan, Fu-Xing; Li, Lei-Jiao; Wang, Ying-Jin; Guo, Jin-Chang; Zhai, Hua-Jin; Xu, Li; Sun, Zhong-Ming

    2015-09-01

    A sandwich complex, as exemplified by ferrocene in the 1950s, usually refers to one metal center bound by two arene ligands. The subject has subsequently been extended to carbon-free aromatic ligands and multiple-metal-atom "monolayered" center, but not to an all-metal species. Here, we describe the synthesis of an unprecedented all-metal aromatic sandwich complex, [Sb3Au3Sb3](3-), which was isolated as K([2.2.2]crypt)(+) salt and identified by single-crystal X-ray diffraction. Quantum chemical calculations indicate that intramolecular electron transfers for the three metallic layers (Sb → Au donation and Sb ← Au back-donation) markedly redistribute the valence electrons from the cyclo-Sb3 ligands and Au3 interlayer to the Au-Sb bonds, which hold the complex together via σ bonding. Each cyclo-Sb3 possesses aromaticity with delocalized three-center three-electron (3c-3e) π bonds, which are essentially equivalent to a 3c-4e ππ* triplet system, following the reversed 4n Hückel rule for aromaticity in a triplet state. PMID:26275027

  6. Determination of traces of Sb(III) using ASV in Sb-rich water samples affected by mining.

    PubMed

    Cidu, Rosa; Biddau, Riccardo; Dore, Elisabetta

    2015-01-01

    Chemical speciation [Sb(V) and Sb(III)] affects the mobility, bioavailability and toxicity of antimony. In oxygenated environments Sb(V) dominates whereas thermodynamically unstable Sb(III) may occur. In this study, a simple method for the determination of Sb(III) in non acidic, oxygenated water contaminated with antimony is proposed. The determination of Sb(III) was performed by anodic stripping voltammetry (ASV, 1-20 μg L(-1) working range), the total antimony, Sb(tot), was determined either by inductively coupled plasma mass spectrometry (ICP-MS, 1-100μgL(-1) working range) or inductively coupled plasma optical emission spectrometry (ICP-OES, 100-10,000 μg L(-1) working range) depending on concentration. Water samples were filtered on site through 0.45 μm pore size filters. The aliquot for determination of Sb(tot) was acidified with 1% (v/v) HNO3. Different preservatives, namely HCl, L(+) ascorbic acid or L(+) tartaric acid plus HNO3, were used to assess the stability of Sb(III) in synthetic solutions. The method was tested on groundwater and surface water draining the abandoned mine of Su Suergiu (Sardinia, Italy), an area heavily contaminated with Sb. The waters interacting with Sb-rich mining residues were non acidic, oxygenated, and showed extreme concentrations of Sb(tot) (up to 13,000 μg L(-1)), with Sb(III) <10% of total antimony. The stabilization with L(+) tartaric acid plus HNO3 appears useful for the determination of Sb(III) in oxygenated, Sb-rich waters. Due to the instability of Sb(III), analyses should be carried out within 7 days upon the water collection. The main advantage of the proposed method is that it does not require time-consuming preparation steps prior to analysis of Sb(III). PMID:25479865

  7. Lattice dynamics in the FeSb[subscript 3] skutterudite

    SciTech Connect

    Moechel, A.; Sergueev, I.; Nguyen, N.; Long, Gary J.; Grandjean, Fernande; Johnson, D.C.; Hermann, R.P.

    2011-11-17

    Thin films of FeSb{sub 3} were characterized by electronic transport, magnetometry, x-ray diffraction, {sup 57}Fe and {sup 121}Sb nuclear inelastic scattering, and {sup 57}Fe Moessbauer spectroscopy. Resistivity and magnetometry measurements reveal semiconducting behavior with a 16.3(4) meV band gap and an effective paramagnetic moment of 0.57(6) {mu}B, respectively. A systematic comparison of the lattice dynamics with CoSb{sub 3} and EuFe{sub 4}Sb{sub 12} reveals that the Fe{sub 4}Sb{sub 12} framework is softer than the Co{sub 4}Sb{sub 12} framework, and that the observed softening and the associated lowering of the lattice thermal conductivity in the RFe{sub 4}Sb{sub 12} filled skutterudites are not only related to the filler but also to the Fe{sub 4}Sb{sub 12} framework.

  8. TANK 40 FINAL SB5 CHEMICAL CHARACTERIZATION RESULTS PRIOR TO NP ADDITION

    SciTech Connect

    Bannochie, C.; Click, D.

    2010-01-06

    -252, and cold vapor atomic absorption (CV-AA) analysis for Hg. Equivalent dilutions of the peroxide fusion digestions and blank were submitted to AD for ICP-AES analysis. Tank 40 SB5 supernate was collected from a mixed slurry sample in the SRNL Shielded Cells and submitted to AD for ICP-AES. Weighted dilutions of slurry were submitted for ion chromatography (IC), total inorganic carbon/total organic carbon (TIC/TOC), and total base analyses. The following conclusions were drawn from the analytical results reported here: (1) The elemental ratios of the major elements for the SB5 WAPS sample, whose major Tank 51 Qualification sample component underwent Al dissolution, are similar to those measured for the SB4 WAPS sample. (2) The elemental composition of this sample and the analyses conducted here are reasonable and consistent with DWPF batch data measurements in light of DWPF pre-sample concentration and SRAT product heel contributions to the DWPF SRAT receipt analyses. (3) Fifty percent of the sulfur in the SB5 WAPS sample is insoluble, and this represents a significantly larger fraction than that observed in previous sludge batches. (4) The noble metal and Ag concentrations predicted from the measured values for the Tank 51 Confirmation sample and Tank 40 SB4 WAPS sample using a two-thirds Tank 51, one-third Tank 40 heel blend ratio used to arrive at the final SB5 composition, agree with the values for the Tank 40 SB5 WAPS sample measured for this report.

  9. TANK 40 FINAL SB5 CHEMICAL CHARACTERIZATION RESULTS PRIOR TO NP ADDITION

    SciTech Connect

    Bannochie, C; Damon Click, D

    2009-02-26

    -252, and cold vapor atomic absorption (CV-AA) analysis for Hg. Equivalent dilutions of the peroxide fusion digestions and blank were submitted to AD for ICP-AES analysis. Tank 40 SB5 supernate was collected from a mixed slurry sample in the SRNL Shielded Cells and submitted to AD for ICP-AES. Weighted dilutions of slurry were submitted for ion chromatography (IC), total inorganic carbon/total organic carbon (TIC/TOC), and total base analyses. The following conclusions were drawn from the analytical results reported here: (1) The elemental ratios of the major elements for the SB5 WAPS sample, whose major Tank 51 Qualification sample component underwent Al dissolution, are similar to those measured for the SB4 WAPS sample. (2) The elemental composition of this sample and the analyses conducted here are reasonable and consistent with DWPF batch data measurements in light of DWPF pre-sample concentration and SRAT product heel contributions to the DWPF SRAT receipt analyses. (3) Fifty percent of the sulfur in the SB5 WAPS sample is insoluble, and this represents a significantly larger fraction than that observed in previous sludge batches. (4) The noble metal and Ag concentrations predicted from the measured values for the Tank 51 Confirmation sample and Tank 40 SB4 WAPS sample using a two-thirds Tank 51, one-third Tank 40 heel blend ratio used to arrive at the final SB5 composition, agree with the values for the Tank 40 SB5 WAPS sample measured for this report.

  10. Controllable synthesis of metal selenide heterostructures mediated by Ag2Se nanocrystals acting as catalysts.

    PubMed

    Zhou, Jiangcong; Huang, Feng; Xu, Ju; Wang, Yuansheng

    2013-10-21

    Ag2Se nanocrystals were demonstrated to be novel semiconductor mediators, or in other word catalysts, for the growth of semiconductor heterostructures in solution. This is a result of the unique feature of Ag2Se as a fast ion conductor, allowing foreign cations to dissolve and then to heterogrow the second phase. Using Ag2Se nanocrystals as catalysts, dimeric metal selenide heterostructures such as Ag2Se-CdSe and Ag2Se-ZnSe, and even multi-segment heterostructures such as Ag2Se-CdSe-ZnSe and Ag2Se-ZnSe-CdSe, were successfully synthesized. Several interesting features were found in the Ag2Se based heterogrowth. At the initial stage of heterogrowth, a layer of the second phase forms on the surface of an Ag2Se nanosphere, with a curved junction interface between the two phases. With further growth of the second phase, the Ag2Se nanosphere tends to flatten the junction surface by modifying its shape from sphere to hemisphere in order to minimize the conjunct area and thus the interfacial energy. Notably, the crystallographic relationship of the two phases in the heterostructure varies with the lattice parameters of the second phase, in order to reduce the lattice mismatch at the interface. Furthermore, a small lattice mismatch at the interface results in a straight rod-like second phase, while a large lattice mismatch would induce a tortuous product. The reported results may provide a new route for developing novel selenide semiconductor heterostructures which are potentially applicable in optoelectronic, biomedical, photovoltaic and catalytic fields. PMID:24056899

  11. SbF(5)-mediated reactions of oxafluorodiazirines.

    PubMed

    Moss, R A; Fedé, J M; Yan, S

    2001-07-26

    [reaction: see text] The reaction of benzyloxyfluorodiazirine (3) with SbF(5) in benzene gives PhCH(2)OCF, which undergoes SbF(5)-mediated fragmentation to PhCH(2)(+), CO, and SbF(6)(-); the benzyl cation alkylates benzene to yield diphenylmethane. Phenoxyfluorodiazirine (4) reacts with SbF(5) in benzene to give PhOCF and (ultimately) triphenylmethane by a pathway that avoids fragmentation. PMID:11463302

  12. Electrical performance of InAs/AlSb/GaSb superlattice photodetectors

    NASA Astrophysics Data System (ADS)

    Tansel, T.; Hostut, M.; Elagoz, S.; Kilic, A.; Ergun, Y.; Aydinli, A.

    2016-03-01

    Temperature dependence of dark current measurements is an efficient way to verify the quality of an infrared detector. Low dark current density values are needed for high performance detector applications. Identification of dominant current mechanisms in each operating temperature can be used to extract minority carrier lifetimes which are highly important for understanding carrier transport and improving the detector performance. InAs/AlSb/GaSb based T2SL N-structures with AlSb unipolar barriers are designed for low dark current with high resistance and detectivity. Here we present electrical and optical performance of such N-structure photodetectors.

  13. Activation of cord T lymphocytes. IV. Analysis of surface expression and functional role of 1F7 (CD26) molecule.

    PubMed

    Gerli, R; Agea, E; Muscat, C; Ercolani, R; Bistoni, O; Tognellini, R; Mariggió, M A; Spinozzi, F; Bertotto, A

    1994-04-15

    A role for CD26 surface antigen (Ag) in both CD3- and CD2-mediated T cell activation has been previously demonstrated. To analyze the functional role of CD26 in the CD3- and CD2-induced activation pathways of cord T cells, which represent the most reliable source of Ag-unprimed T cells, we employed a newly developed anti-CD26 monoclonal antibody, termed anti-1F7, anti-CD3 and anti-CD2 in activating T lymphocytes. The results showed that CD26 Ag is expressed on the surface of almost all resting cord T cells and that its fluorescence intensity is enhanced by activation. The binding of anti-1F7 induced a decrease in CD26 membrane expression, with no detectable effect on the surface expression of other cord T cell-related molecules. Moreover, the modulation of CD26 resulted in an increase in anti-CD3-mediated cord T cell activation through an enhancement in intracellular calcium levels, IL-2 receptor expression, and IL-2 synthesis, whereas it had no effect on cord T cell activation induced by anti-CD2 or anti-CD2 plus exogenous IL-2. The fact that the selective involvement of CD26 in the activation pathway triggered by anti-CD3, but not anti-CD2, could be reversed by prior stimulation of cord T cells with anti-CD3 suggests that this functional feature, which resembles that of mature thymocytes, may be linked to the Ag-unprimed cell phenotype of cord T lymphocytes. PMID:7909498

  14. Resistivity plateau and extreme magnetoresistance in LaSb

    NASA Astrophysics Data System (ADS)

    Tafti, F. F.; Gibson, Q. D.; Kushwaha, S. K.; Haldolaarachchige, N.; Cava, R. J.

    2016-03-01

    Time reversal symmetry (TRS) protects the metallic surface modes of topological insulators (TIs). The transport signature of such surface states is a plateau that arrests the exponential divergence of the insulating bulk with decreasing temperature. This universal behaviour is observed in all TI candidates ranging from Bi2Te2Se to SmB6. Recently, extreme magnetoresistance (XMR) has been reported in several topological semimetals which exhibit TI universal resistivity behaviour only when breaking time reversal symmetry, a regime where TIs theoretically cease to exist. Among these materials, TaAs and NbP are nominated as Weyl semimetals owing to their lack of inversion symmetry, Cd3As2 is known as a Dirac semimetal owing to its linear band crossing at the Fermi level, and WTe2 is termed a resonant compensated semimetal owing to its perfect electron-hole symmetry. Here we introduce LaSb, a simple rock-salt structure material that lacks broken inversion symmetry, perfect linear band crossing, and perfect electron-hole symmetry yet exhibits all the exotic field-induced behaviours of these more complex semimetals. It shows a field-induced universal TI resistivity with a plateau at roughly 15 K, ultrahigh mobility of carriers in the plateau region, quantum oscillations with the angle dependence of a two-dimensional Fermi surface, and XMR of about one million percent at 9 T. Owing to its structural simplicity, LaSb represents an ideal model system to formulate a theoretical understanding of the exotic consequences of breaking time reversal symmetry in topological semimetals.

  15. Antigen targeting reveals splenic CD169+ macrophages as promoters of germinal center B-cell responses.

    PubMed

    Veninga, Henrike; Borg, Ellen G F; Vreeman, Kyle; Taylor, Philip R; Kalay, Hakan; van Kooyk, Yvette; Kraal, Georg; Martinez-Pomares, Luisa; den Haan, Joke M M

    2015-03-01

    Ag delivery to specific APCs is an attractive approach in developing strategies for vaccination. CD169(+) macrophages in the marginal zone of the spleen represent a suitable target for delivery of Ag because of their strategic location, which is optimal for the capture of blood-borne Ag and their close proximity to B cells and T cells in the white pulp. Here we show that Ag targeting to CD169(+) macrophages in mice resulted in strong, isotype-switched, high-affinity Ab production and the preferential induction and long-term persistence of Ag-specific GC B cells and follicular Th cells. In agreement with these observations, CD169(+) macrophages retained intact Ag, induced cognate activation of B cells, and increased expression of costimulatory molecules upon activation. In addition, macrophages were required for the production of cytokines that promote B-cell responses. Our results identify CD169(+) macrophages as promoters of high-affinity humoral immune responses and emphasize the value of CD169 as target for Ag delivery to improve vaccine responses. PMID:25487358

  16. Identification of dominant recombination mechanisms in narrow-bandgap InAs/InAsSb type-II superlattices and InAsSb alloys

    NASA Astrophysics Data System (ADS)

    Boggess, Thomas

    InAs/Ga(In)Sb type-II superlattices (T2SL) have been extensively studied for both advanced emitter and detector technologies associated with mid-wave (MWIR), long-wave (LWIR), and very-long-wave (VLWIR) infrared applications. The type-II band alignment, together with control of both the layer thicknesses and the alloy composition, provide a rich environment for band structure engineering, including band gap tuning and suppression of Auger recombination. Unfortunately, the InAs/Ga(In)Sb MWIR T2SLs have been found to have minority carrier lifetimes persistently below 100 ns, even at cryogenic temperatures. Such short lifetimes are problematic for detector applications and suggest that this material system will not compete with HgCdTe for IR detector applications. On the other hand, the report by Steenbergen, et al., of much longer minority carrier recombination lifetimes (>412 ns at 77K) in a longwave (8.2 µm) InAs/InAsSb T2SL suggests that the ``Ga-free'' superlattices could be competitive for IR detector applications. We will discuss all-optical measurements of carrier lifetimes as a function of temperature and injected carrier density in InAs/InAsSb T2SLs with a broad range of sample designs based on variations in alloy composition and/or layer thickness. Minority carrier lifetimes ranging from 4.5 µs for a 9.2 µm-band-gap T2SL to 18 µs for a 4.2 µm-band-gap T2SL have been measured at 77 K. This research was performed in collaboration with Y. Aytac, B.V. Olson, J.K. Kim, E.A. Shaner, J.F. Klem, S.D. Hawkins, and M.E. Flatté.

  17. In-situ monitoring of GaSb, GaInAsSb, and AlGaAsSb

    SciTech Connect

    Vineis, C.J. |; Wang, C.A.; Jensen, K.F.; Breiland, W.G.

    1998-06-01

    Suitability of silicon photodiode detector arrays for monitoring the spectral reflectance during epitaxial growths of GaSb, AlGaAsSb, and GaInAsSb, which have cutoff wavelengths of 1.7, 1.2, and 2.3 {micro}m, respectively, is demonstrated. These alloys were grown lattice matched to GaSb in a vertical rotating-disk reactor, which was modified to accommodate near normal reflectance without affecting epilayer uniformity. By using a virtual interface model, the growth rate and complex refractive index at the growth temperature are extracted for these alloys over the 600 to 950 nm spectral range. Excellent agreement is obtained between the extracted growth rate and that determined by ex-situ measurement. Optical constants are compared to theoretical predictions based on an existing dielectric function model for these materials. Furthermore, quantitative analysis of the entire reflectance spectrum yields valuable information on the approximate thickness of overlayers on the pregrowth substrate.

  18. Efficacy evaluation of two synthetic lysine lipidated tripeptides as vaccine adjuvants against HBsAg.

    PubMed

    Sidiq, Tabasum; Khajuria, Anamika; Shafi, Syed; Ismail, Tabasum; Sampath Kumar, Halmathur; Kannappa Srinivas, Vellimedu; Krishna, Ella; Kamal Johri, Rakesh

    2013-04-01

    In the present investigation, adjuvant potential of two novel lipidated tripeptide lysine derivatives (KKSM and KKSMB) was evaluated using various in vitro and animal-derived models of humoral and cell-mediated immune events in response to hepatitis B surface antigen (HBsAg). The results were compared with alum adjuvanted with HBsAg. Both these molecules were found to stimulate anti-HBsAg IgG and neutralizing (IgG1 and IgG2a) antibody titres in mice sera. The two molecules stimulated the proliferation of T-lymphocyte sub-sets (CD4/CD8) as well as the production of soluble mediators of Th1 (IL-2 and IFN-γ) and Th2 response (IL-4) in spleen cell culture supernatant. Furthermore, the two lipidated tripeptides enhanced the CD4, CD8, CD3 and CD19 cell populations as well as CD4/CD8 derived IL-2, IL-4, IFN-γ and TNF-α in whole blood of treated mice. There was found to be the significant enhancement in the release of IL-12, IFN-γ and nitrite content in macrophage supernatant. Moreover, the two lipidated tripeptides enhanced the population of CD80 and CD86 in spleen-derived macrophages and did not show any hemolytic effect on rabbit RBCs. Taken together, these results suggest that both these molecules are the potent enhancers of anti-HBsAg immune response via augmenting Th1/Th2 response in a dose dependent manner. PMID:23474022

  19. Freeze-dried PVP-Ag+ precursors to novel AgBr/AgCl-Ag hybrid nanocrystals for visible-light-driven photodegradation of organic pollutants

    NASA Astrophysics Data System (ADS)

    Chen, Deliang; Chen, Qianqian; Zhang, Wenjie; Ge, Lianfang; Shao, Gang; Fan, Bingbing; Lu, Hongxia; Zhang, Rui; Yang, Daoyuan; Shao, Guosheng

    2015-04-01

    AgBr/AgCl-Ag nanocrystals with various molar Br-to-Ag ratios (RBr/Ag = 0, 1/3, 1/2, 2/3, 1) and different photoreduction times (0-20 min) were synthesized via stepwise liquid-solid reactions using the freeze-dried PVP-Ag+ hybrid as the Ag source, followed by a photoreduction reaction. The AgBr/AgCl-Ag7.5(1:2) nanocrystals obtained take on a spherical morphology with a particle-size range of 58 ± 15 nm. The photocatalytic performance of AgBr/AgCl-Ag nanocrystals was evaluated by photodegrading organic dyes, 4-chlorophenol and isopropanol under artificial visible light (λ ⩾ 420 nm, 100 mW cm-2). For the decomposition of rhodamine B, the AgBr/AgCl-Ag7.5(1:2) nanocrystals has a photodegradation rate of ∼0.87 min-1, ∼159 times higher than that (∼0.0054 min-1) of TiO2 (P25), whereas the AgCl-Ag and AgBr-Ag nanocrystals have photodegradation rates of 0.35 min-1 and 0.45 min-1, respectively. The efficient separation of photogenerated electron-hole pairs in the ternary system consisting of AgBr, AgCl and Ag species plays a key role in the enhancement of photocatalytic performance.

  20. IgE-mediated enhancement of CD4+ T cell responses requires antigen presentation by CD8α− conventional dendritic cells

    PubMed Central

    Ding, Zhoujie; Dahlin, Joakim S.; Xu, Hui; Heyman, Birgitta

    2016-01-01

    IgE, forming an immune complex with small proteins, can enhance the specific antibody and CD4+ T cell responses in vivo. The effects require the presence of CD23 (Fcε-receptor II)+ B cells, which capture IgE-complexed antigens (Ag) in the circulation and transport them to splenic B cell follicles. In addition, also CD11c+ cells, which do not express CD23, are required for IgE-mediated enhancement of T cell responses. This suggests that some type of dendritic cell obtains IgE-Ag complexes from B cells and presents antigenic peptides to T cells. To elucidate the nature of this dendritic cell, mice were immunized with ovalbumin (OVA)-specific IgE and OVA, and different populations of CD11c+ cells, obtained from the spleens four hours after immunization, were tested for their ability to present OVA. CD8α− conventional dendritic cells (cDCs) were much more efficient in inducing specific CD4+ T cell proliferation ex vivo than were CD8α+ cDCs or plasmacytoid dendritic cells. Thus, IgE-Ag complexes administered intravenously are rapidly transported to the spleen by recirculating B cells where they are delivered to CD8α− cDCs which induce proliferation of CD4+ T cells. PMID:27306570

  1. IgE-mediated enhancement of CD4(+) T cell responses requires antigen presentation by CD8α(-) conventional dendritic cells.

    PubMed

    Ding, Zhoujie; Dahlin, Joakim S; Xu, Hui; Heyman, Birgitta

    2016-01-01

    IgE, forming an immune complex with small proteins, can enhance the specific antibody and CD4(+) T cell responses in vivo. The effects require the presence of CD23 (Fcε-receptor II)(+) B cells, which capture IgE-complexed antigens (Ag) in the circulation and transport them to splenic B cell follicles. In addition, also CD11c(+) cells, which do not express CD23, are required for IgE-mediated enhancement of T cell responses. This suggests that some type of dendritic cell obtains IgE-Ag complexes from B cells and presents antigenic peptides to T cells. To elucidate the nature of this dendritic cell, mice were immunized with ovalbumin (OVA)-specific IgE and OVA, and different populations of CD11c(+) cells, obtained from the spleens four hours after immunization, were tested for their ability to present OVA. CD8α(-) conventional dendritic cells (cDCs) were much more efficient in inducing specific CD4(+) T cell proliferation ex vivo than were CD8α(+) cDCs or plasmacytoid dendritic cells. Thus, IgE-Ag complexes administered intravenously are rapidly transported to the spleen by recirculating B cells where they are delivered to CD8α(-) cDCs which induce proliferation of CD4(+) T cells. PMID:27306570

  2. Encapsulating Sn(x)Sb Nanoparticles in Multichannel Graphene-Carbon Fibers As Flexible Anodes to Store Lithium Ions with High Capacities.

    PubMed

    Tang, Xuan; Yan, Feilong; Wei, Yuehua; Zhang, Ming; Wang, Taihong; Zhang, Tianfang

    2015-10-01

    SnxSb intermetallic composites as high theoretical capacities anodes for lithium ion batteries (LIBs) suffer from the quick capacity fading owing to their huge volume change. In this study, flexible mats made up of SnxSb-graphene-carbon porous multichannel nanofibers are fabricated by an electrospinning method and succedent annealing treatment at 700 °C. The flexible mats as binder-free anodes show a specific capacity of 729 mA h/g in the 500th cycle at a current density of 0.1 A/g, which is much higher than those of graphene-carbon nanofibers, pure carbon nanofibers, and SnxSb-graphene-carbon nanofibers at the same cycle. The flexible mats could provide a reversible capacity of 381 mA h/g at 2 A/g, also higher than those of nanofibers, graphene-carbon nanofibers, and SnxSb-carbon nanofibers. It is found that the suitable nanochannels could accommodate the volume expansion to achieve a high specific capacity. Besides, the graphene serves as both conductive and mechanical-property additives to enhance the rate capacity and flexibility of the mats. The electrospinning technique combined with graphene modification may be an effective method to produce flexible electrodes for fuel cells, lithium ion batteries, and super capacitors. PMID:26371535

  3. Ag K- and L3-edge XAFS study on Ag species in Ag/Ga2O3 photocatalysts

    NASA Astrophysics Data System (ADS)

    Yamamoto, M.; Yoshida, T.; Yamamoto, N.; Nomoto, T.; Yamamoto, A.; Yoshida, H.; Yagi, S.

    2016-05-01

    Ag loaded Ga2O3 (Ag/Ga2O3) shows photocatalytic activity for reduction of CO2 with water. Ag L3-edge XANES and K-edge EXAFS spectra were measured for various Ag/Ga2O3 samples, which suggested that structural and chemical states of Ag species varied with the loading amount of Ag and the preparation method. The Ag species were metallic Ag particles with an AgGaO2-like interface structure in the sample with high loading amount of Ag while predominantly Ag metal clusters in the sample with low loading amount of Ag. The XANES feature just above the edge represented the interaction between the Ag species and the Ga2O3 surface, showing that the Ag metal clusters had more electrons in the d-orbitals by interacting with the Ga2O3 surface, which would contribute the high photocatalytic activity.

  4. AGS experiments -- 1995, 1996 and 1997

    SciTech Connect

    Depken, J.C.; Presti, P.L.

    1997-12-01

    This report contains (1) FY 1995 AGS schedule as run; (2) FY 1996 AGS schedule as run; (3) FY 1997 AGS schedule as run; (4) FY 1998--1999 AGS schedule (proposed); (5) AGS beams 1997; (6) AGS experimental area FY 1995 physics program; (7) AGS experimental area FY 1996 physics program; (8) AGS experimental area FY 1997 physics program; (9) AGS experimental area FY 1998--1999 physics program (proposed); (10) a listing of experiments by number; (11) two-page summaries of each experiment, in order by number; and (12) listing of publications of AGS experiments.

  5. AGS experiments -- 1991, 1992, 1993. Tenth edition

    SciTech Connect

    Depken, J.C.

    1994-04-01

    This report contains: (1) FY 1993 AGS schedule as run; (2) FY 1994--95 AGS schedule; (3) AGS experiments {ge} FY 1993 (as of 30 March 1994); (4) AGS beams 1993; (5) AGS experimental area FY 1991 physics program; (6) AGS experimental area FY 1992 physics program; (7) AGS experimental area FY 1993 physics program; (8) AGS experimental area FY 1994 physics program (planned); (9) a listing of experiments by number; (10) two-page summaries of each experiment; (11) listing of publications of AGS experiments; and (12) listing of AGS experiments.

  6. 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.

  7. 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.

  8. Phase equilibria, formation, crystal and electronic structure of ternary compounds in Ti-Ni-Sn and Ti-Ni-Sb ternary systems

    SciTech Connect

    Romaka, V.V.; Rogl, P.; Romaka, L.; Stadnyk, Yu.; Melnychenko, N.; Grytsiv, A.; Falmbigl, M.; Skryabina, N.

    2013-01-15

    The phase equilibria of the Ti-Ni-Sn and Ti-Ni-Sb ternary systems have been studied in the whole concentration range by means of X-ray and EPM analyses at 1073 K and 873 K, respectively. Four ternary intermetallic compounds TiNiSn (MgAgAs-type), TiNi{sub 2-x}Sn (MnCu{sub 2}Al-type), Ti{sub 2}Ni{sub 2}Sn (U{sub 2}Pt{sub 2}Sn-type), and Ti{sub 5}NiSn{sub 3} (Hf{sub 5}CuSn{sub 3}-type) are formed in Ti-Ni-Sn system at 1073 K. The TiNi{sub 2}Sn stannide is characterized by homogeneity in the range of 50-47 at% of Ni. The Ti-Ni-Sb ternary system at 873 K is characterized by formation of three ternary intermetallic compounds, Ti{sub 0.8}NiSb (MgAgAs-type), Ti{sub 5}Ni{sub 0.45}Sb{sub 2.55} (W{sub 5}Si{sub 3}-type), and Ti{sub 5}NiSb{sub 3} (Hf{sub 5}CuSn{sub 3}-type). The solubility of Ni in Ti{sub 0.8}NiSb decreases number of vacancies in Ti site up to Ti{sub 0.91}Ni{sub 1.1}Sb composition. - Graphical abstract: Isothermal section of the Ti-Ni-Sn phase diagram and DOS distribution in hypothetical TiNi{sub 1+x}Sn solid solution. Highlights: Black-Right-Pointing-Pointer Ti-Ni-Sn phase diagram was constructed at 1073 K. Black-Right-Pointing-Pointer Four ternary compounds are formed: TiNiSn, TiNi{sub 2-x}Sn, Ti{sub 2}Ni{sub 2}Sn, and Ti{sub 5}NiSn{sub 3}. Black-Right-Pointing-Pointer Three ternary compounds exist in Ti-Ni-Sb system at 873 K. Black-Right-Pointing-Pointer The TiNi{sub 2}Sb compound is absent.

  9. Destabilization of Ag nanoislands on Ag(100) by adsorbed sulfur

    SciTech Connect

    Shen, Mingmin; Russell, Selena M.; Liu, Da-Jiang; Thiel, Patricia A.

    2011-10-17

    Sulfur accelerates coarsening of Ag nanoislands on Ag(100) at 300 K, and this effect is enhanced with increasing sulfur coverage over a range spanning a few hundredths of a monolayer, to nearly 0.25 monolayers. We propose that acceleration of coarsening in this system is tied to the formation of AgS{sub 2} clusters primarily at step edges. These clusters can transport Ag more efficiently than can Ag adatoms (due to a lower diffusion barrier and comparable formation energy). The mobility of isolated sulfur on Ag(100) is very low so that formation of the complex is kinetically limited at low sulfur coverages, and thus enhancement is minimal. However, higher sulfur coverages force the population of sites adjacent to step edges, so that formation of the cluster is no longer limited by diffusion of sulfur across terraces. Sulfur exerts a much weaker effect on the rate of coarsening on Ag(100) than it does on Ag(111). This is consistent with theory, which shows that the difference between the total energy barrier for coarsening with and without sulfur is also much smaller on Ag(100) than on Ag(111).

  10. Antimony bonding in Ge-Sb-Te phase change materials

    NASA Astrophysics Data System (ADS)

    Bobela, David C.; Taylor, P. Craig; Kuhns, Phillip; Reyes, Arneil; Edwards, Arthur

    2011-01-01

    The amorphous phase in some technologically important Ge-Sb-Te systems is still not well understood despite many models that exist to explain it. Using nuclear magnetic resonance, we demonstrate that Sb bonding in these systems follows the 8-Nrule for chemical bonding in amorphous solids. We find that the Sb atoms preferentially bond to three atoms in a pyramidal configuration analogous to the sites occurring in Sb-S or Sb-Se systems. The data we present should be used as a guide for structural modeling of the amorphous phase.

  11. Shortened Intervals during Heterologous Boosting Preserve Memory CD8 T Cell Function but Compromise Longevity.

    PubMed

    Thompson, Emily A; Beura, Lalit K; Nelson, Christine E; Anderson, Kristin G; Vezys, Vaiva

    2016-04-01

    Developing vaccine strategies to generate high numbers of Ag-specific CD8 T cells may be necessary for protection against recalcitrant pathogens. Heterologous prime-boost-boost immunization has been shown to result in large quantities of functional memory CD8 T cells with protective capacities and long-term stability. Completing the serial immunization steps for heterologous prime-boost-boost can be lengthy, leaving the host vulnerable for an extensive period of time during the vaccination process. We show in this study that shortening the intervals between boosting events to 2 wk results in high numbers of functional and protective Ag-specific CD8 T cells. This protection is comparable to that achieved with long-term boosting intervals. Short-boosted Ag-specific CD8 T cells display a canonical memory T cell signature associated with long-lived memory and have identical proliferative potential to long-boosted T cells Both populations robustly respond to antigenic re-exposure. Despite this, short-boosted Ag-specific CD8 T cells continue to contract gradually over time, which correlates to metabolic differences between short- and long-boosted CD8 T cells at early memory time points. Our studies indicate that shortening the interval between boosts can yield abundant, functional Ag-specific CD8 T cells that are poised for immediate protection; however, this is at the expense of forming stable long-term memory. PMID:26903479

  12. AGS preinjector improvement

    SciTech Connect

    Alessi, J.G.; Brennan, J.M.; Brown, H.N.; Brodowski, J.; Gough, R.; Kponou, A.; Prelec, K.; Staples, J.; Tanabe, J.; Witkover, R.

    1987-01-01

    In 1984, a polarized H/sup -/ source was installed to permit the acceleration of polarized protons in the AGS, using a low current, 750 keV RFQ Linear Accelerator as the preinjector. This RFQ was designed by LANL and has proved to be quite satisfactory and reliable. In order to improve the reliability and simplify maintenance of the overall AGS operations, it has been decided to replace one of the two 750 keV Cockcroft-Waltons (C-W) with an RFQ. The design of a new high current RFQ has been carried out by LBL and is also being constructed there. This paper describes the preinjector improvement project, centered around that RFQ, which is underway at BNL.

  13. Retrogenic ICOS Expression Increases Differentiation of KLRG-1hiCD127loCD8+ T Cells during Listeria Infection and Diminishes Recall Responses.

    PubMed

    Liu, Danya; Burd, Eileen M; Coopersmith, Craig M; Ford, Mandy L

    2016-02-01

    Following T cell encounter with Ag, multiple signals are integrated to collectively induce distinct differentiation programs within Ag-specific CD8(+) T cell populations. Several factors contribute to these cell fate decisions, including the amount and duration of Ag, exposure to inflammatory cytokines, and degree of ligation of cosignaling molecules. The ICOS is not expressed on resting T cells but is rapidly upregulated upon encounter with Ag. However, the impact of ICOS signaling on programmed differentiation is not well understood. In this study, we therefore sought to determine the role of ICOS signaling on CD8(+) T cell programmed differentiation. Through the creation of novel ICOS retrogenic Ag-specific TCR-transgenic CD8(+) T cells, we interrogated the phenotype, functionality, and recall potential of CD8(+) T cells that receive early and sustained ICOS signaling during Ag exposure. Our results reveal that these ICOS signals critically impacted cell fate decisions of Ag-specific CD8(+) T cells, resulting in increased frequencies of KLRG-1(hi)CD127(lo) cells, altered BLIMP-1, T-bet, and eomesodermin expression, and increased cytolytic capacity as compared with empty vector controls. Interestingly, however, ICOS retrogenic CD8(+) T cells also preferentially homed to nonlymphoid organs and exhibited reduced multicytokine functionality and reduced ability to mount secondary recall responses upon challenge in vivo. In sum, our results suggest that an altered differentiation program is induced following early and sustained ICOS expression, resulting in the generation of more cytolyticly potent, terminally differentiated effectors that possess limited capacity for recall response. PMID:26729800

  14. Pb-Bi-Ag-Cu-(Hg) chemistry of galena and some associated sulfosalts. A review and some new data from Colorado California and Pennsylvania

    USGS Publications Warehouse

    Foord, Eugene E.; Shawe, Daniel R.

    1989-01-01

    Galena, associated with Pb-Bi-Ag sulfosalts and simple sulfides, contains varied amounts of Ag and Bi in the Dandy vein system, Idarado mine, Ouray, Colorado; the Jackass mine, Darwin District, California; and the Leadville district, Colorado. Silver- and bismuth-bearing galena associated with minor amounts of pyrite, chalcopyrite and sphalerite occur at the Pequea mine, Lancaster County, Pennsylvania. Ag and Bi contents in the Dandy suite of galena range from about 1.4 to 3.4 and 2.5 to 6.5 wt.% respectively, and are comparable or lower in galena from the other localities. Exsolved matildite is present in galena from the Dandy, Jackass and Leadville localities. The presence in significant amounts of both Ag and Bi in a Pb-rich sulfide system is necessary for formation of PbSss (galena solid-solution). If Ag (especially) and Bi (to a lesser extent) are absent, the galena formed will be essentially pure PbS. Some minor Sb may substitute for Bi. Compositional data for all of the galena samples are in agreement with a previously proposed linear relationship between a and Ag-Bi(Sb) content. Matildite and seven additional Pb-Bi-Ag-Cu sulfosalts have been identified from the Dandy vein system, based on electron-microprobe analyses and some X-ray powder-diffraction data.

  15. A new Schiff base based on vanillin and naphthalimide as a fluorescent probe for Ag+ in aqueous solution

    NASA Astrophysics Data System (ADS)

    Zhou, Yanmei; Zhou, Hua; Ma, Tongsen; Zhang, Junli; Niu, Jingyang

    2012-03-01

    A new Schiff base based on vanillin and naphthalimide was designed and synthesized as fluorescent probe. The probe showed high selectivity for Ag+ over other metal ions such as Pb2+, Na+, K+, Cd2+, Ba2+, Cr3+, Zn2+, Cu2+, Ni2+, Ca2+, Al3+ and Mg2+ in aqueous solution. A new fluorescence emission was observed at 682 nm in the presence of Ag+ ion. The fluorescence intensity quenched with increasing the concentration of Ag+ at 682 nm. The method of job's plot confirmed the 1:2 complex between Ag+ and probe, and the mechanism was proposed.

  16. Electron g-factor in bulk Ga1-xInxAsySb1-y/GaSb quaternary alloy and in GaSb/Ga1-xInxAsySb1-y/GaSb Spherical quantum dots

    NASA Astrophysics Data System (ADS)

    Sánchez-Cano, R.; Porras-Montenegro, N.

    2011-12-01

    Secure quantum communications require an entanglement-preserving photo-detector in which quantum information is transmitted by photon polarization through an mid infrared optical fiber system and then transferred to electron spin in a optoelectronic semiconductor device. Using interpolation scheme we have investigated the electron g-factor in bulk Ga1-xInxAsySb1-y quaternary alloy matched to GaSb as a function of Indium and Arsenic concentration on the complete range 0≤x,y≤1. A specific g-factor as a function of the radius in a spherical GaSb/Ga1-xInxAsySb1-y/GaSb quantum dot heterostructure is calculated. Furthermore, we present calculations of the energy states including the Zeeman effect on the electrons confined in quaternary heterostructure quantum dots, with a parabolic confining potential under applied magnetic fields. Our calculations have been worked out by using interpolating methods to find the band gap as a function of the Indium concentration in order to determine the conduction band-offset at room temperature in GaSb/Ga1-xInxAsySb1-y/GaSb heterostructure, within the effective-mass approximation. Experimental or theoretical electron g-factor, spin-orbit splitting Δso, and coupling matrix elements Ep = (2/m0)||2 value between the states of the lowest conduction band Γ6 and the upper valence bands Γ8 for Ga1-xInxAsySb1-y/GaSb quaternary alloy are not readily available. Our predictions show that electron g-factor values are in the range between the electron g-factor measured in bulk GaSb when x→0 (g = -9.25) and that measured in InAs when x→1 (g = -18.08), but there is a remarkable minimum in the g-factor value (g≃-23.14) at x≃0.67.

  17. Activation of cord T lymphocytes. III. Role of LFA-1/ICAM-1 and CD2/LFA-3 adhesion molecules in CD3-induced proliferative response.

    PubMed

    Gerli, R; Agea, E; Muscat, C; Tognellini, R; Fiorucci, G; Spinozzi, F; Cernetti, C; Bertotto, A

    1993-04-15

    As cord T cells, a model of antigen (Ag)-unprimed cell, display a functional defect when stimulated through the CD3 molecule, the role of lymphocyte function-associated antigen 1(LFA-1)/intercellular adhesion molecule 1 (ICAM-1) and CD2/lymphocyte function-associated antigen 3 (LFA-3) receptor-ligand pairs in cord CD3-triggered T-cell activation was analyzed using specific monoclonal antibodies (mAb) against each adhesion molecule. The addition of anti-CD11a, anti-CD18, or anti-CD2 to both adult and cord peripheral blood mononuclear cells (PBMC) cultures led to a decrease in CD3-induced proliferation. In contrast, CD3-stimulated cord, but not adult, PBMC proliferation was markedly enhanced when anti-CD54 or anti-CD58 were added. Despite the fact that ICAM-1 and LFA-3 molecules were virtually absent on cord resting T cells, mAb against these two molecules boosted both mitogenesis of and interleukin (IL)-2 production by purified cord T cells stimulated with plastic immobilized anti-CD3. Cord T-cell supernatant levels of interferon-gamma (IFN-gamma) were undetectable with CD3 stimulation, slightly raised with CD58/CD3 costimulation, but normal when T cells were preincubated with IL-2 for 24 hr before being costimulated with anti-CD3/CD58. Evidence that IL-2 and IFN-gamma play a pivotal role in fully activating cord T cells came from the demonstration that IL-2 and IFN-gamma are able to bypass the CD3-proliferative defect through differential up-regulation of the adhesion molecules. It would, therefore, seem that ICAM-1 and LFA-3 molecules are crucially implicated in the CD3-activation pathway of Ag-unprimed T cells. PMID:7684326

  18. Syntheses, crystal structures, and NLO properties of the quaternary sulfides RE{sub 3}Sb{sub 0.33}SiS{sub 7} (RE=La, Pr)

    SciTech Connect

    Zhao, Hua-Jun

    2015-07-15

    Two quaternary sulfides RE{sub 3}Sb{sub 0.33}SiS{sub 7} (RE=La, Pr) have been prepared from stoichiometric mixtures of elements at 1223 K in an evacuated silica tube. They are the first examples of chalcogenides in the quaternary RE/Si/Sb/Q (RE=rare earth metal; Q=S, Se, Te) system. These two isostructural materials crystallize in the Ce{sub 3}Al{sub 1.67}S{sub 7} structure type in the hexagonal space group P6{sub 3}. Their structure features one-dimensional chains of face-sharing SbS{sub 6} octahedra running parallel to the c direction surrounded by the discrete SiS{sub 4} tetrahedra and RE cations. The La{sub 3}Sb{sub 0.33}SiS{sub 7} exhibits a SHG signal about 0.5 times that of the commercially used IR NLO material AgGaS{sub 2} at 2.05 μm laser. The optical gap of 1.92 eV for La{sub 3}Sb{sub 0.33}SiS{sub 7} was deduced from UV/Vis reflectance spectroscopy. - Graphical abstract: The RE{sub 3}Sb{sub 0.33}SiS{sub 7} (RE=La, Pr), crystalling in the Ce{sub 3}Al{sub 1.67}S{sub 7} structure type, have been prepared. The La{sub 3}Sb{sub 0.33}SiS{sub 7} exhibits a SHG signal about 0.5 times that of the IR NLO material AgGaS{sub 2}. - Highlights: • The RE{sub 3}Sb{sub 0.33}SiS{sub 7} (RE=La, Pr), crystalling in the Ce{sub 3}Al{sub 1.67}S{sub 7} structure type, have been prepared. • The La{sub 3}Sb{sub 0.33}SiS{sub 7} exhibits a SHG signal about 0.5 times that of the IR NLO material AgGaS{sub 2}. • The optical gap of 1.92 eV for La{sub 3}Sb{sub 0.33}SiS{sub 7} was deduced from UV/Vis reflectance spectroscopy.

  19. Controlled CVD growth of Cu-Sb alloy nanostructures.

    PubMed

    Chen, Jing; Yin, Zongyou; Sim, Daohao; Tay, Yee Yan; Zhang, Hua; Ma, Jan; Hng, Huey Hoon; Yan, Qingyu

    2011-08-12

    Sb based alloy nanostructures have attracted much attention due to their many promising applications, e.g. as battery electrodes, thermoelectric materials and magnetic semiconductors. In many cases, these applications require controlled growth of Sb based alloys with desired sizes and shapes to achieve enhanced performance. Here, we report a flexible catalyst-free chemical vapor deposition (CVD) process to prepare Cu-Sb nanostructures with tunable shapes (e.g. nanowires and nanoparticles) by transporting Sb vapor to react with copper foils, which also serve as the substrate. By simply controlling the substrate temperature and distance, various Sb-Cu alloy nanostructures, e.g. Cu(11)Sb(3) nanowires (NWs), Cu(2)Sb nanoparticles (NPs), or pure Sb nanoplates, were obtained. We also found that the growth of Cu(11)Sb(3) NWs in such a catalyst-free CVD process was dependent on the substrate surface roughness. For example, smooth Cu foils could not lead to the growth of Cu(11)Sb(3) nanowires while roughening these smooth Cu foils with rough sand papers could result in the growth of Cu(11)Sb(3) nanowires. The effects of gas flow rate on the size and morphology of the Cu-Sb alloy nanostructures were also investigated. Such a flexible growth strategy could be of practical interest as the growth of some Sb based alloy nanostructures by CVD may not be easy due to the large difference between the condensation temperature of Sb and the other element, e.g. Cu or Co. PMID:21757793

  20. Consequences of breaking time reversal symmetry in LaSb: a resistivity plateau and extreme magnetoresistance

    NASA Astrophysics Data System (ADS)

    Tafti, Fazel; Gibson, Quinn; Kushwaha, Satya; Haldolaarachchige, Neel; Cava, Robert; Cava Lab Team

    Time reversal symmetry protects the metallic surface modes of topological insulators (TIs). The transport signature of robust metallic surface modes of TIs is a plateau that arrests the exponential divergence of the insulating bulk with decreasing temperature. This universal behavior is observed in all TI candidates ranging from Bi2Te2Se to SmB6. Recently, several topological semimetals (TSMs) have been found that exhibit extreme magnetoresistance (XMR) and TI universal resistivity behavior revealed only when breaking TRS, a regime where TIs theoretically cease to exist. Amongst these new materials, TaAs and NbP are nominated for Weyl semimetal due to their lack of inversion symmetry, Cd3As2 is nominated for Dirac semimetal due to linear band crossing, and WTe2 is nominated for resonant compensated semimetal due to perfect electron-hole symmetry. Here we introduce LaSb, a simple rock-salt structure material without broken inversion symmetry, without perfect linear band crossing, and without perfect electron-hole symmetry. Yet LaSb portrays all the exotic field induced behaviors of the aforementioned semimetals. It shows the universal TI resistivity with a plateau at 15 K, revealed by a magnetic field, ultrahigh mobility of carriers, quantum oscillations with 2D Fermi surface, and XMR of about one million percent. Due to its dramatic simplicity, LaSb is the ideal model system to formulate a theoretical understanding of the exotic consequences of breaking TRS in TSMs.

  1. Study of advanced InSb arrays for SIRTF (Space Infrared Telescope Facility)

    NASA Technical Reports Server (NTRS)

    Hoffman, Alan; Feitt, Robert

    1989-01-01

    The Santa Barbara Research Center has completed a study leading to the development of advanced Indium Antimonide detector arrays for the Space Infrared Telescope Facility (SIRTF) Focal Plane Array Detector (FPAD) Subsystem of the Infrared Array Camera (IRAC) Band 1. The overall goal of the study was to perform design tradeoff studies, analysis and research to develop a Direct Readout Integrated Circuit to be hybridized to an advanced, high performance InSb detector array that would satisfy the technical requirements for Band 1 as specified in the IRAC Instrument Requirements Document (IRD), IRAC-202. The overall goal of the study was divided into both a near-term goal and a far-term goal. The near-term goal identifies current technology available that approaches, and in some cases meets the program technological goals as specified in IRAC-202. The far-term goal identifies technology development required to completely achieve SIRTF program goals. Analyses of potential detector materials indicates that InSb presently meets all Band 1 requirements and is considered to be the baseline approach due to technical maturity. The major issue with regard to photovoltaic detectors such as InSb and HgCdTe is to achieve a reduction in detector capacitance.

  2. Growth of InSb and InAs(1-x)Sb(x) by OM-CVD

    NASA Technical Reports Server (NTRS)

    Chiang, P. K.; Bedair, S. M.

    1984-01-01

    Organometallic chemical vapor deposition (OM-CVD) growth of InSb and InAs(1-x)Sb(x) has been obtained using triethylindium (TEI), trimethylantimony (TMS), and arsine (AsH3) on (100) GaAs, (100) InSb, and (111)-B InSb substrates. InSb with excellent morphology was achieved on both (100) InSb and (111)-B InSb substrates. The measured electron mobility at 300 K of undoped InSb grown on (100) GaAs semi-insulating substrates was 40,000 sq cm/V-s at a carrier concentration of ND-NA = 2.0 x 10 to the 16th per cu cm. Carrier concentration of ND-NA = 1.2 x 10 to the 15th per cu cm has been measured at 77 K. InAs(1-x)Sb(x) (x = 0.07-0.75) with mirror-like surfaces have been grown on (100) InSb and InAs substrates. This composition range of x between 0.55 and 0.75 (Eg = 0.1 eV) has been successfully achieved for the first time. Solid composition variations as a function of growth temperature and InSb substrate orientations are also discussed.

  3. Determination of Sb(III) and Sb(V) by HPLC-Online isotopic dilution-ICP MS.

    PubMed

    Fontanella, Maria Chiara; Beone, Gian Maria

    2016-01-01

    This work provides a method with application of valid techniques to extract and determinate inorganic species of antimony (Sb) for water. The procedure involves•the simultaneous accumulation of Sb(III) and Sb(V) on passive samplers like Diffusive Gradient in Thin Films (DGT) with iron (Fe) oxide gel, eliminating the risk of speciation changes due to transport and storage;•application of less concentrated acid (50 mM Na2EDTA) for elution and preservation of Sb species from DGT resin;•subsequent analytical determination of inorganic species with High Performance Liquid Chromatography-Isotopic Dilution-Inductively Coupled Plasma Mass Spectrometer (HPLC-ID-ICP MS) based on determination of the isotope ratio ((123)Sb/(121)Sb) of isotopes in the samples after spiking with 123Sb enriched standard solution, reducing the effect of signal drift and matrix effect on the final value. PMID:27408828

  4. Hydrothermal crystal growth and structure determination of double hydroxides LiSb(OH)₆, BaSn(OH)₆, and SrSn(OH)₆.

    PubMed

    Mizoguchi, Hiroshi; Bhuvanesh, Nattamai S P; Kim, Young-Il; Ohara, Satoshi; Woodward, Patrick M

    2014-10-01

    Colorless single crystals of LiSb(OH)6, SrSn(OH)6, and BaSn(OH)6, which are useful as precursors for the synthesis of LiSbO3, SrSnO3, and BaSnO3, were synthesized by a low-temperature hydrothermal method using a Teflon-lined autoclave at 380 K. The crystal structures were determined by single-crystal X-ray diffraction measurements. LiSb(OH)6 crystallizes in the trigonal space group P3̅1m with a = 5.3812(3)A, c = 9.8195(7)A, V = 246.25(3)A(3), Z = 2. In this layered structure, [Li2Sb(OH)6](+) and [Sb(OH)6](-) layers are alternately stacked along the c-direction. The [Li2Sb(OH)6](+) layer can be regarded as a cation-ordered CdCl2 layer. The [Sb(OH)6)](-) layer is built up from isolated [Sb(OH)6](-) octahedra, which are linked to each other via hydrogen bonding within the layer. BaSn(OH)6 and SrSn(OH)6 crystallize with monoclinic P21/n space group symmetry. The monoclinic structure possesses a CsCl-type packing of Ba(2+)/Sr(2+) cations and [Sn(OH)6](2-) anions. The [Sn(OH)6](2-) polyhedra are connected to each other through hydrogen bonding to form a three-dimensional framework. The factors that favor these hitherto unknown crystal structures are discussed using a structure map that compares various M(OH)3 and M'M″(OH)6 compounds. PMID:25208245

  5. Recent progress in InGaAsSb/GaSb TPV devices

    SciTech Connect

    Shellenbarger, Z.A.; Mauk, M.G.; DiNetta, L.C.; Charache, G.W.

    1996-05-01

    AstroPower is developing InGaAsSb thermophotovoltaic (TPV) devices. This photovoltaic cell is a two-layer epitaxial InGaAsSb structure formed by liquid-phase epitaxy on a GaSb substrate. The (direct) bandgap of the In{sub 1{minus}x}Ga{sub x}As{sub 1{minus}y}Sb{sub y} alloy is 0.50 to 0.55 eV, depending on its exact alloy composition (x,y); and is closely lattice-matched to the GaSb substrate. The use of the quaternary alloy, as opposed to a ternary alloy--such as, for example InGaAs/InP--permits low bandgap devices optimized for 1,000 to 1,500 C thermal sources with, at the same time, near-exact lattice matching to the GaSb substrate. Lattice matching is important since even a small degree of lattice mismatch degrades device performance and reliability and increases processing complexity. Internal quantum efficiencies as high as 95% have been measured at a wavelength of 2 microns. At 1 micron wavelengths, internal quantum efficiencies of 55% have been observed. The open-circuit voltage at currents of 0.3 A/cm{sup 2} is 0.220 volts and 0.280 V for current densities of 2 A/cm{sup 2}. Fill factors of 56% have been measured at 60 mA/cm{sup 2}. However, as current density increases there is some decrease in fill factor. The results to date show that the GaSb-based quaternary compounds provide a viable and high performance energy conversion solution for thermophotovoltaic systems operating with 1,000 to 1,500 C source temperatures.

  6. Fabrication of Cu-Ag core-shell bimetallic superfine powders by eco-friendly reagents and structures characterization

    SciTech Connect

    Zhao Jun; Zhang Dongming; Zhao Jie

    2011-09-15

    Superfine bimetallic Cu-Ag core-shell powders were synthesized by reduction of copper sulfate pentahydrate and silver nitrate with eco-friendly ascorbic acid as a reducing agent and cyclodextrins as a protective agent in an aqueous system. The influence of Ag/Cu ratio on coatings was investigated. Ag was homogeneously distributed on the surface of Cu particles at a mole ratio of Ag/Cu=1. FE-SEM showed an uniformity of Ag coatings on Cu particles. Antioxidation of Cu particles was improved by increasing Ag/Cu ratio. TEM-EDX and UV-vis spectra also revealed that Cu cores were covered by Ag nanoshells on the whole. The surface composition analysis by XPS indicated that only small parts of Cu atoms in the surface were oxidized. It was noted that the hindrance of cyclodextrins chemisorbed on particles plays an important role in forming high quality and good dispersity Cu-Ag (Cu-Ag) core-shell powders. - Graphical abstract: Mechanism of fabricating Cu-Ag particles with good dispersibility using {beta}-CDs as a protective agent was studied because of its special structure. Highlights: > Green supramolecular {beta}-CD used as a protective agent and ascorbic acid(Vc) as a reducing agent to fabricate Cu-Ag powders. > Particles are monodisperse and the diameter is close to nanoscale(100-150 nm). > Resistance of Cu particles to oxidation was higher. > Formation mechanism explained.

  7. Antigen targeting reveals splenic CD169+ macrophages as promoters of germinal center B‐cell responses

    PubMed Central

    Veninga, Henrike; Borg, Ellen G. F.; Vreeman, Kyle; Taylor, Philip R.; Kalay, Hakan; van Kooyk, Yvette; Kraal, Georg; Martinez‐Pomares, Luisa

    2015-01-01

    Ag delivery to specific APCs is an attractive approach in developing strategies for vaccination. CD169+ macrophages in the marginal zone of the spleen represent a suitable target for delivery of Ag because of their strategic location, which is optimal for the capture of blood‐borne Ag and their close proximity to B cells and T cells in the white pulp. Here we show that Ag targeting to CD169+ macrophages in mice resulted in strong, isotype‐switched, high‐affinity Ab production and the preferential induction and long‐term persistence of Ag‐specific GC B cells and follicular Th cells. In agreement with these observations, CD169+ macrophages retained intact Ag, induced cognate activation of B cells, and increased expression of costimulatory molecules upon activation. In addition, macrophages were required for the production of cytokines that promote B‐cell responses. Our results identify CD169+ macrophages as promoters of high‐affinity humoral immune responses and emphasize the value of CD169 as target for Ag delivery to improve vaccine responses. PMID:25487358

  8. Influence of dopant concentration on the electrical properties of the CdSe-PMMA nanocomposite

    NASA Astrophysics Data System (ADS)

    Kaur, Ramneek; Tripathi, S. K.

    2016-05-01

    This paper reports the synthesis and electrical characterization of CdSe-PMMA nanocomposite. CdSe-PMMA nanocomposite has been prepared by ex-situ technique through chemical route. The influence of three different Ag doping concentrations on the electrical properties has been studied in the temperature range ˜ 303-353 K. Transmission electron micrograph reveals the spherical morphology of the CdSe nanoparticles and their proper dispersion in the PMMA matrix. The electrical conduction of the polymer nanocomposites is through thermally activated process with single activation energy. With Ag doping, initially the activation energy increases upto 0.2 % Ag doping concentration but with further increase in Ag concentration, it decreases. This behavior has been discussed on the basis of randomly oriented grain boundaries and defect states. Thus, the results indicate that the transport properties of the polymer nanocomposites can be tailored by controlled doping concentration.

  9. Chemical state of Ag in Conducting Bridge Random Access Memory cells: a depth resolved X-ray Absorption Spectroscopy investigation.

    NASA Astrophysics Data System (ADS)

    d'Acapito, F.; Souchier, E.; Noe, P.; Blaise, P.; Bernard, M.; Jousseaume, V.

    2016-05-01

    Conducting Bridge Random Access Memories (CBRAM) are a promising substitute for FLASH technology but problems with limited retention of the low resistance ON state still hamper their massive deployment. Depth resolved X-ray Absorption Spectroscopy has been used to describe the chemical state of the atoms of the active electrode (in this case Ag) and to reveal the role of Sb as stabilizer of the metallic state.

  10. Microbiological reduction of Sb(V) in anoxic freshwater sediments.

    PubMed

    Kulp, Thomas R; Miller, Laurence G; Braiotta, Franco; Webb, Samuel M; Kocar, Benjamin D; Blum, Jodi S; Oremland, Ronald S

    2014-01-01

    Microbiological reduction of millimolar concentrations of Sb(V) to Sb(III) was observed in anoxic sediments from two freshwater settings: (1) a Sb- and As-contaminated mine site (Stibnite Mine) in central Idaho and 2) an uncontaminated suburban lake (Searsville Lake) in the San Francisco Bay Area. Rates of Sb(V) reduction in anoxic sediment microcosms and enrichment cultures were enhanced by amendment with lactate or acetate as electron donors but not by H2, and no reduction occurred in sterilized controls. Addition of 2-(14)C-acetate to Stibnite Mine microcosms resulted in the production of (14)CO2 coupled to Sb(V) reduction, suggesting that this process proceeds by a dissimilatory respiratory pathway in those sediments. Antimony(V) reduction in Searsville Lake sediments was not coupled to acetate mineralization and may be associated with Sb-resistance. The microcosms and enrichment cultures also reduced sulfate, and the precipitation of insoluble Sb(III)-sulfide complexes was a major sink for reduced Sb. The reduction of Sb(V) by Stibnite Mine sediments was inhibited by As(V), suggesting that As(V) is a preferred electron acceptor for the indigenous community. These findings indicate a novel pathway for anaerobic microbiological respiration and suggest that communities capable of reducing high concentrations of Sb(V) commonly occur naturally in the environment. PMID:24274659

  11. Ba2Sb4GeS10

    PubMed Central

    Geng, Lei

    2013-01-01

    The title quaternary compound, dibarium tetra­anti­mony germanium deca­sulfide, Ba2Sb4GeS10, crystallizes in a novel three-dimensional ∞ 3[Sb4GeS10]4− network structure, which is composed of triangular pyramidal SbS3 (site symmetry m..), distorted SbS5 (m..) polyhedra and regular GeS4 (-4..) tetra­hedra. The SbS3 and SbS5 units are connected with each other through corner- and edge-sharing, forming a Sb4S10 layer in the ab plane. The GeS4 tetra­hedra further bridge two neighbouring Sb4S10 layers, forming a three-dimensional ∞ 3[Sb4GeS10]4− network. The Ba2+ cation (..2) is located between two Sb4S10 layers and is coordinated by ten S atoms with Ba—S bond lengths in the range 3.2505 (9)–3.4121 (2) Å. PMID:23723748

  12. Microbiological reduction of Sb(V) in anoxic freshwater sediments

    USGS Publications Warehouse

    Oremland, Ronald S.; Kulp, Thomas R.; Miller, Laurence G.; Braiotta, Franco; Webb, Samuel M.; Kocar, Benjamin D; Blum, Jodi S.

    2013-01-01

    Microbiological reduction of millimolar concentrations of Sb(V) to Sb(III) was observed in anoxic sediments from two freshwater settings: (1) a Sb- and As-contaminated mine site (Stibnite Mine) in central Idaho and 2) an uncontaminated suburban lake (Searsville Lake) in the San Francisco Bay Area. Rates of Sb(V) reduction in anoxic sediment microcosms and enrichment cultures were enhanced by amendment with lactate or acetate as electron donors but not by H2, and no reduction occurred in sterilized controls. Addition of 2-14C-acetate to Stibnite Mine microcosms resulted in the production of 14CO2 coupled to Sb(V) reduction, suggesting that this process proceeds by a dissimilatory respiratory pathway in those sediments. Antimony(V) reduction in Searsville Lake sediments was not coupled to acetate mineralization and may be associated with Sb-resistance. The microcosms and enrichment cultures also reduced sulfate, and the precipitation of insoluble Sb(III)-sulfide complexes was a major sink for reduced Sb. The reduction of Sb(V) by Stibnite Mine sediments was inhibited by As(V), suggesting that As(V) is a preferred electron acceptor for the indigenous community. These findings indicate a novel pathway for anaerobic microbiological respiration and suggest that communities capable of reducing high concentrations of Sb(V) commonly occur naturally in the environment.

  13. Preparation and antibacterial activities of Ag/Ag+/Ag3+ nanoparticle composites made by pomegranate (Punica granatum) rind extract

    NASA Astrophysics Data System (ADS)

    Yang, Hui; Ren, Yan-yu; Wang, Tao; Wang, Chuang

    Nano-silver and its composite materials are widely used in medicine, food and other industries due to their strong conductivity, size effect and other special performances. So far, more microbial researches have been applied, but a plant method is rarely reported. In order to open up a new way to prepare AgNP composites, pomegranate peel extract was used in this work to reduce Ag+ to prepare Ag/Ag+/Ag3+ nanoparticle composites. UV-Vis was employed to detect and track the reduction of Ag+ and the forming process of AgNPs. The composition, structure and size of the crystal were analyzed by XRD and TEM. Results showed that, under mild conditions, pomegranate peel extract reacted with dilute AgNO3 solution to produce Ag/Ag+/Ag3+ nanoparticle composites. At pH = 8 and 10 mmol/L of AgNO3 concentration, the size of the achieved composites ranged between 15 and 35 nm with spherical shapes and good crystallinity. The bactericidal experiment indicated that the prepared Ag/Ag+/Ag3+ nanoparticles had strong antibacterial activity against gram positive bacteria and gram negative bacteria. FTIR analysis revealed that biological macromolecules with groups of sbnd NH2, sbnd OH, and others were distributed on the surface of the newly synthesized Ag/Ag+/Ag3+ nanoparticles. This provided a useful clue to further study the AgNP biosynthesis mechanism.

  14. Coherent transient grating effects and auger inhibition in InAsSb systems

    SciTech Connect

    Murdin, B.N.; Pidgeon, C.R.; Ciesla, C.M.

    1995-12-31

    Pump-probe measurements of interband recombination lifetimes have been performed with the Free Electron Laser (CLIO) at room temperature undoped bulk InSb. Significant bleaching near and below the fundamental absorption edge at 7{mu}m was seen near the excitation frequency, with recovery times in the range 0.2-5 ns which were found to be strongly dependent on the pump photon energy. The scattering is dominated by Auger processes, which have rates following quadratic or linear carrier density dependence in low excitation and highly degenerate regimes respectively. The coefficients for Auger recombination in InSb at room temperature were found to be 1.1{+-}0.5x10{sup -26} cm{sup 6}s{sup -1} and 4.0{+-}0.5x 10{sup -9} cm{sup 3}s{sup -1} in these two regimes. These experiments also reveal associated coherent transient grating effects for the first time in these systems. A parametric scattering of the pump pulse into the probe beam is observed at delay times smaller than the coherence length of the FEL which allows us to determine the third-order nonlinear susceptibility and the coherence length of the laser system. A preliminary bleaching experiment on an undoped strained layer superlattice (SLS) sample of InAs/InAs{sub 0.61} Sb{sub 0.39} is also reported. It is well known that the narrower the bandgap in HgCdTe alloys the easier energy and momentum conservation becomes. This SLS structure (band edge 11I{mu}m) shows strong inhibition of the Auger recombination process with lifetimes up to 30 times longer than even the bulk InSb sample (7{mu}m). This opens the possibility of a major leap into the IR for III-V semiconductor light-emitting and detection device applications.

  15. Immediate Dysfunction of Vaccine-Elicited CD8+ T Cells Primed in the Absence of CD4+ T Cells.

    PubMed

    Provine, Nicholas M; Larocca, Rafael A; Aid, Malika; Penaloza-MacMaster, Pablo; Badamchi-Zadeh, Alexander; Borducchi, Erica N; Yates, Kathleen B; Abbink, Peter; Kirilova, Marinela; Ng'ang'a, David; Bramson, Jonathan; Haining, W Nicholas; Barouch, Dan H

    2016-09-01

    CD4(+) T cell help is critical for optimal CD8(+) T cell memory differentiation and maintenance in many experimental systems. In addition, many reports have identified reduced primary CD8(+) T cell responses in the absence of CD4(+) T cell help, which often coincides with reduced Ag or pathogen clearance. In this study, we demonstrate that absence of CD4(+) T cells at the time of adenovirus vector immunization of mice led to immediate impairments in early CD8(+) T cell functionality and differentiation. Unhelped CD8(+) T cells exhibited a reduced effector phenotype, decreased ex vivo cytotoxicity, and decreased capacity to produce cytokines. This dysfunctional state was imprinted within 3 d of immunization. Unhelped CD8(+) T cells expressed elevated levels of inhibitory receptors and exhibited transcriptomic exhaustion and anergy profiles by gene set enrichment analysis. Dysfunctional, impaired effector differentiation also occurred following immunization of CD4(+) T cell-deficient mice with a poxvirus vector. This study demonstrates that following priming with viral vectors, CD4(+) T cell help is required to promote both the expansion and acquisition of effector functions by CD8(+) T cells, which is accomplished by preventing immediate dysfunction. PMID:27448585

  16. Immediate Dysfunction of Vaccine-Elicited CD8+ T Cells Primed in the Absence of CD4+ T Cells

    PubMed Central

    Provine, Nicholas M.; Larocca, Rafael A.; Aid, Malika; Penaloza-MacMaster, Pablo; Badamchi-Zadeh, Alexander; Borducchi, Erica N.; Yates, Kathleen B.; Abbink, Peter; Kirilova, Marinela; Ng’ang’a, David; Bramson, Jonathan; Haining, W. Nicholas

    2016-01-01

    CD4+ T cell help is critical for optimal CD8+ T cell memory differentiation and maintenance in many experimental systems. In addition, many reports have identified reduced primary CD8+ T cell responses in the absence of CD4+ T cell help, which often coincides with reduced Ag or pathogen clearance. In this study, we demonstrate that absence of CD4+ T cells at the time of adenovirus vector immunization of mice led to immediate impairments in early CD8+ T cell functionality and differentiation. Unhelped CD8+ T cells exhibited a reduced effector phenotype, decreased ex vivo cytotoxicity, and decreased capacity to produce cytokines. This dysfunctional state was imprinted within 3 d of immunization. Unhelped CD8+ T cells expressed elevated levels of inhibitory receptors and exhibited transcriptomic exhaustion and anergy profiles by gene set enrichment analysis. Dysfunctional, impaired effector differentiation also occurred following immunization of CD4+ T cell–deficient mice with a poxvirus vector. This study demonstrates that following priming with viral vectors, CD4+ T cell help is required to promote both the expansion and acquisition of effector functions by CD8+ T cells, which is accomplished by preventing immediate dysfunction. PMID:27448585

  17. Transport Measurements on Sb doped Silicon Nanowires

    NASA Astrophysics Data System (ADS)

    Nukala, Prathyusha; Zare, Marzieh; Sapkota, Gopal; Gali, Pradeep; Philipose, Usha

    2011-03-01

    Semiconductor nanowires (NWs) present an alternative approach for device scaling. N-type Si NWs are generally grown with silane as source with phosphine and arsenic as dopants, all of which are toxic in nature. We present a safe, cost-effective approach for synthesis of n- doped Si NWs using Sb. Structural and compositional characterization using electron microscopy and X-ray spectroscopy will be presented for crystallographic information on the quality and morphology. Ohmic contacts established to a single and on an array of doped and undoped NWs in an FET type of device configuration will provide information on several parameters such as type of majority carriers, mobility and concentration. We will highlight the promise of Sb doped Si NWs for electronic applications such as nano-scale field effect transistors and sensors.

  18. Carrier spin relaxation in GaInNAsSb/GaNAsSb/GaAs quantum well

    SciTech Connect

    Asami, T.; Nosho, H.; Tackeuchi, A.; Li, L. H.; Harmand, J. C.; Lu, S. L.

    2011-12-23

    We have investigated the carrier spin relaxation in GaInNAsSb/GaNAsSb/GaAs quantum well (QW) by time-resolved photoluminescence (PL) measurement. The sample consists of an 8-nm-thick GaIn{sub 0.36}N{sub 0.006}AsSb{sub 0.015} well, 5-nm-thick GaN{sub 0.01}AsSb{sub 0.11} intermediate barriers and 100-nm-thick GaAs barriers grown by molecular beam epitaxy on a GaAs(100) substrate. The spin relaxation time and recombination lifetime at 10 K are measured to be 228 ps and 151 ps, respectively. As a reference, we have also obtained a spin relaxation time of 125 ps and a recombination lifetime of 63 ps for GaInNAs/GaNAs/GaAs QW. This result shows that crystal quality is slightly improved by adding Sb, although these short carrier lifetimes mainly originate from a nonradiative recombination. These spin relaxation times are longer than the 36 ps spin relaxation time of InGaAs/InP QWs and shorter than the 2 ns spin relaxation time of GaInNAs/GaAs QW.

  19. Growth and characterization of epitaxial NiMnSb/ZnTe/NiMnSb magnetic multilayers

    NASA Astrophysics Data System (ADS)

    Gerhard, F.; Naydenova, T.; Baussenwein, M.; Schumacher, C.; Gould, C.; Molenkamp, L. W.

    2016-02-01

    The half-metal ferromagnet NiMnSb, with its high spin polarization, low magnetic damping and tunable magnetic anisotropy, is a promising material for applications in spin torque devices. We develop the epitaxial growth of NiMnSb/ZnTe/NiMnSb heterostructures, aiming towards the realization of an all-NiMnSb based magnetic tunneling junction (MTJ). Layers are grown in situ by Molecular Beam Epitaxy (MBE) and Atomic Layer Epitaxy (ALE) methods. By tuning Mn content, the magnetic anisotropy of each of the two NiMnSb layers is adjusted in order to achieve mutually orthogonal uniaxial anisotropies. SQUID measurements of the magnetization along orthogonal crystal directions [110] and [ 1 1 bar 0] confirm that the two layers have mutually orthogonal anisotropy. High Resolution X-Ray Diffraction measurements and simulations confirm the nominal layer stack and demonstrate the high crystalline quality of the individual layers. Such layer stacks provide a potential basis for TMR-based spin-torque devices such as spin-torque oscillators.

  20. Lattice-matched epitaxial GaInAsSb/GaSb thermophotovoltaic devices

    SciTech Connect

    Wang, C.A.; Choi, H.K.; Turner, G.W.; Spears, D.L.; Manfra, M.J.; Charache, G.W.

    1997-03-01

    The materials development of Ga{sub 1{minus}x}In{sub x}As{sub y}Sb{sub 1{minus}y} alloys for lattice-matched thermophotovoltaic (TPV) devices is reported. Epilayers with cutoff wavelength 2{endash}2.4 {mu}m at room temperature and lattice-matched to GaSb substrates were grown by both low-pressure organometallic vapor phase epitaxy and molecular beam epitaxy. These layers exhibit high optical and structural quality. For demonstrating lattice-matched TPV devices, p- and n-type doping studies were performed. Several TPV device structures were investigated, with variations in the base/emitter thicknesses, and some with the incorporation of a high-bandgap GaSb or AlGaAsSb window layer. Significant improvement in the external quantum efficiency and open circuit voltage is observed for devices with an AlGaAsSb window layer compared to those without one. {copyright} {ital 1997 American Institute of Physics.}

  1. Nearly massless Dirac fermions hosted by Sb square net in BaMnSb2

    PubMed Central

    Liu, Jinyu; Hu, Jin; Cao, Huibo; Zhu, Yanglin; Chuang, Alyssa; Graf, D.; Adams, D. J.; Radmanesh, S. M. A.; Spinu, L.; Chiorescu, I.; Mao, Zhiqiang

    2016-01-01

    Layered compounds AMnBi2 (A = Ca, Sr, Ba, or rare earth element) have been established as Dirac materials. Dirac electrons generated by the two-dimensional (2D) Bi square net in these materials are normally massive due to the presence of a spin-orbital coupling (SOC) induced gap at Dirac nodes. Here we report that the Sb square net in an isostructural compound BaMnSb2 can host nearly massless Dirac fermions. We observed strong Shubnikov-de Haas (SdH) oscillations in this material. From the analyses of the SdH oscillations, we find key signatures of Dirac fermions, including light effective mass (~0.052m0; m0, mass of free electron), high quantum mobility (1280 cm2V−1S−1) and a π Berry phase accumulated along cyclotron orbit. Compared with AMnBi2, BaMnSb2 also exhibits much more significant quasi two-dimensional (2D) electronic structure, with the out-of-plane transport showing nonmetallic conduction below 120 K and the ratio of the out-of-plane and in-plane resistivity reaching ~670. Additionally, BaMnSb2 also exhibits a G-type antiferromagnetic order below 283 K. The combination of nearly massless Dirac fermions on quasi-2D planes with a magnetic order makes BaMnSb2 an intriguing platform for seeking novel exotic phenomena of massless Dirac electrons. PMID:27466151

  2. Nearly massless Dirac fermions hosted by Sb square net in BaMnSb2

    NASA Astrophysics Data System (ADS)

    Liu, Jinyu; Hu, Jin; Cao, Huibo; Zhu, Yanglin; Chuang, Alyssa; Graf, D.; Adams, D. J.; Radmanesh, S. M. A.; Spinu, L.; Chiorescu, I.; Mao, Zhiqiang

    2016-07-01

    Layered compounds AMnBi2 (A = Ca, Sr, Ba, or rare earth element) have been established as Dirac materials. Dirac electrons generated by the two-dimensional (2D) Bi square net in these materials are normally massive due to the presence of a spin-orbital coupling (SOC) induced gap at Dirac nodes. Here we report that the Sb square net in an isostructural compound BaMnSb2 can host nearly massless Dirac fermions. We observed strong Shubnikov-de Haas (SdH) oscillations in this material. From the analyses of the SdH oscillations, we find key signatures of Dirac fermions, including light effective mass (~0.052m0 m0, mass of free electron), high quantum mobility (1280 cm2V‑1S‑1) and a π Berry phase accumulated along cyclotron orbit. Compared with AMnBi2, BaMnSb2 also exhibits much more significant quasi two-dimensional (2D) electronic structure, with the out-of-plane transport showing nonmetallic conduction below 120 K and the ratio of the out-of-plane and in-plane resistivity reaching ~670. Additionally, BaMnSb2 also exhibits a G-type antiferromagnetic order below 283 K. The combination of nearly massless Dirac fermions on quasi-2D planes with a magnetic order makes BaMnSb2 an intriguing platform for seeking novel exotic phenomena of massless Dirac electrons.

  3. Nearly massless Dirac fermions hosted by Sb square net in BaMnSb2.

    PubMed

    Liu, Jinyu; Hu, Jin; Cao, Huibo; Zhu, Yanglin; Chuang, Alyssa; Graf, D; Adams, D J; Radmanesh, S M A; Spinu, L; Chiorescu, I; Mao, Zhiqiang

    2016-01-01

    Layered compounds AMnBi2 (A = Ca, Sr, Ba, or rare earth element) have been established as Dirac materials. Dirac electrons generated by the two-dimensional (2D) Bi square net in these materials are normally massive due to the presence of a spin-orbital coupling (SOC) induced gap at Dirac nodes. Here we report that the Sb square net in an isostructural compound BaMnSb2 can host nearly massless Dirac fermions. We observed strong Shubnikov-de Haas (SdH) oscillations in this material. From the analyses of the SdH oscillations, we find key signatures of Dirac fermions, including light effective mass (~0.052m0; m0, mass of free electron), high quantum mobility (1280 cm(2)V(-1)S(-1)) and a π Berry phase accumulated along cyclotron orbit. Compared with AMnBi2, BaMnSb2 also exhibits much more significant quasi two-dimensional (2D) electronic structure, with the out-of-plane transport showing nonmetallic conduction below 120 K and the ratio of the out-of-plane and in-plane resistivity reaching ~670. Additionally, BaMnSb2 also exhibits a G-type antiferromagnetic order below 283 K. The combination of nearly massless Dirac fermions on quasi-2D planes with a magnetic order makes BaMnSb2 an intriguing platform for seeking novel exotic phenomena of massless Dirac electrons. PMID:27466151

  4. Ag-Air Service

    NASA Technical Reports Server (NTRS)

    1981-01-01

    Econ, Inc.'s agricultural aerial application, "ag-air," involves more than 10,000 aircraft spreading insecticides, herbicides, fertilizer, seed and other materials over millions of acres of farmland. Difficult for an operator to estimate costs accurately and decide what to charge or which airplane can handle which assignment most efficiently. Computerized service was designed to improve business efficiency in choice of aircraft and determination of charge rates based on realistic operating cost data. Each subscriber fills out a detailed form which pertains to his needs and then receives a custom-tailored computer printout best suited to his particular business mix.

  5. β-Cyclodextrin coated SiO₂@Au@Ag core-shell nanoparticles for SERS detection of PCBs.

    PubMed

    Lu, Yilin; Yao, Guohua; Sun, Kexi; Huang, Qing

    2015-09-01

    A new type of surface-enhanced Raman scattering (SERS) substrate consisting of β-cyclodextrin (β-CD) coated SiO2@Au@Ag nanoparticles (SiO2@Au@Ag@CD NPs) has been achieved. Our protocol was a simplified approach as the fabrication and modification of the silver shell were realized in a single-step reaction by taking advantage of β-CD as both the reducing and stabilizing agents. The as-synthesized SiO2@Au@Ag@CD NPs were uniform in size and demonstrated high SERS activity and reproducibility. The substrates consisting of the SiO2@Au@Ag@CD NPs were employed for SERS detection of polychlorinated biphenyls (PCBs) including PCB-3, PCB-29 and PCB-77. The SERS detection sensitivity was significantly improved due to enrichment of more PCB molecules captured by β-CD on the substrate surface, as confirmed by the appearance of the new Raman bands which are attributed to the complexes between β-CD and PCBs according to the theoretical simulation. Therefore, this work presents a novel approach to the fabrication of effective SERS substrates that can be employed for rapid determination of trace amounts of PCBs in the environment with high detection sensitivity and recognition selectivity. PMID:25478906

  6. FAST TRACK COMMUNICATION: Emission wavelength extension of mid-infrared InAsSb/InP nanostructures using InGaAsSb sandwich layers

    NASA Astrophysics Data System (ADS)

    Lei, W.; Tan, H. H.; Jagadish, C.

    2010-08-01

    This paper presents a study on the emission wavelength extension of InAsSb nanostructures using InGaAsSb sandwich layers. Due to the reduced lattice mismatch between InAsSb nanostructure layer and buffer/capping layer, the introduction of InGaAsSb sandwich layers leads to larger island size, reduced compressive strain and lower confinement barrier for InAsSb nanostructures, thus resulting in a longer emission wavelength. For InGaAsSb sandwich layers with nominal Sb concentration higher than 10%, type II band alignment is observed for the InAsSb/InGaAsSb heterostructure, which also contributes to the extension of emission wavelength. The InGaAsSb sandwich layers provide an effective approach to extend the emission wavelength of InAsSb nanostructures well beyond 2 µm, which is very useful for device applications in the mid-infrared region.

  7. Thin-film Sb2Se3 photovoltaics with oriented one-dimensional ribbons and benign grain boundaries

    NASA Astrophysics Data System (ADS)

    Zhou, Ying; Wang, Liang; Chen, Shiyou; Qin, Sikai; Liu, Xinsheng; Chen, Jie; Xue, Ding-Jiang; Luo, Miao; Cao, Yuanzhi; Cheng, Yibing; Sargent, Edward H.; Tang, Jiang

    2015-06-01

    Solar cells based on inorganic absorbers, such as Si, GaAs, CdTe and Cu(In,Ga)Se2, permit a high device efficiency and stability. The crystals’ three-dimensional structure means that dangling bonds inevitably exist at the grain boundaries (GBs), which significantly degrades the device performance via recombination losses. Thus, the growth of single-crystalline materials or the passivation of defects at the GBs is required to address this problem, which introduces an added processing complexity and cost. Here we report that antimony selenide (Sb2Se3)—a simple, non-toxic and low-cost material with an optimal solar bandgap of ˜1.1 eV—exhibits intrinsically benign GBs because of its one-dimensional crystal structure. Using a simple and fast (˜1 μm min-1) rapid thermal evaporation process, we oriented crystal growth perpendicular to the substrate, and produced Sb2Se3 thin-film solar cells with a certified device efficiency of 5.6%. Our results suggest that the family of one-dimensional crystals, including Sb2Se3, SbSeI and Bi2S3, show promise in photovoltaic applications.

  8. Cutting edge: Failure of antigen-specific CD4+ T cell recruitment to the kidney during systemic candidiasis.

    PubMed

    Drummond, Rebecca A; Wallace, Carol; Reid, Delyth M; Way, Sing Sing; Kaplan, Daniel H; Brown, Gordon D

    2014-12-01

    Candida albicans is the leading cause of systemic candidiasis, a fungal disease associated with high mortality and poor treatment options. The kidney is the target organ during infection and whose control is largely dependent on innate immunity, because lymphocytes appear redundant for protection. In this article, we show that this apparent redundancy stems from a failure of Ag-specific CD4(+) T cells to migrate into infected kidneys. In contrast, Ag-specific CD8(+) T cells are recruited normally. Using Ag-loaded immunoliposomes to artificially reverse this defective migration, we show that recruited Ag-specific CD4(+) T cells polarize toward a Th17 phenotype in the kidney and are protective during fungal infection. Therefore, our data explain the redundancy of CD4(+) T cells for defense against systemic infection with C. albicans and have important implications for our understanding of antifungal immunity and the control of renal infections. PMID:25344471

  9. InAs/GaSb quantum wells: quantum spin Hall effect and topological superconductivity

    NASA Astrophysics Data System (ADS)

    Sitte, Matthias; Everschor-Sitte, Karin; MacDonald, Allan

    2015-03-01

    Topological insulators have attracted a great deal of attention as a new quantum state of matter in the last decade. The first realizations of 2D TIs were HgTe/CdTe quantum well heterostructures, but in recent years another class of semiconductor heterostructures -- namely InAs/GaSb quantum wells -- was shown to yield 2D TIs as well. Compared to the HgTe/CdTe-based systems they have many advantages, most prominently a continuously tunable band structure via external electric fields and stronger proximity coupling to superconductors. We perform empirical tight-binding calculations on these systems to study how topological properties are changed by varying external control parameters such as electric fields or well thicknesses. Since proximity coupling of a 2D TI and an ordinary s-wave superconductor gives rise to 1D topological superconductivity, these systems also support Majorana fermions as non-local excitations. We will present preliminary results on the proximity effects when InAs/GaSb quantum wells are coupled to a superconductor.

  10. NSOM/QD-Based Direct Visualization of CD3-Induced and CD28-Enhanced Nanospatial Coclustering of TCR and Coreceptor in Nanodomains in T Cell Activation

    PubMed Central

    Lu, Xiaoxu; Wang, Richard C.; Gong, Guangming; Yan, Lin; Huang, Dan; Chen, Zheng W.

    2009-01-01

    Direct molecular imaging of nano-spatial relationship between T cell receptor (TCR)/CD3 and CD4 or CD8 co-receptor before and after activation of a primary T cell has not been reported. We have recently innovated application of near-field scanning optical microscopy (NSOM) and immune-labeling quantum dots (QD) to image Ag-specific TCR response during in vivo clonal expansion, and now up-graded the NSOM/QD-based nanotechnology through dipole-polarization and dual-color imaging. Using this imaging system scanning cell-membrane molecules at a best-optical lateral resolution, we demonstrated that CD3, CD4 or CD8 molecules were distinctly distributed as single QD-bound molecules or nano-clusters equivalent to 2–4 QD fluorescence-intensity/size on cell-membrane of un-stimulated primary T cells, and ∼6–10% of CD3 were co-clustering with CD4 or CD8 as 70–110 nm nano-clusters without forming nano-domains. The ligation of TCR/CD3 on CD4 or CD8 T cells led to CD3 nanoscale co-clustering or interaction with CD4 or CD8 co-receptors forming 200–500 nm nano-domains or >500 nm micro-domains. Such nano-spatial co-clustering of CD3 and CD4 or CD3 and CD8 appeared to be an intrinsic event of TCR/CD3 ligation, not purely limited to MHC engagement, and be driven by Lck phosphorylation. Importantly, CD28 co-stimulation remarkably enhanced TCR/CD3 nanoscale co-clustering or interaction with CD4 co-receptor within nano- or micro-domains on the membrane. In contrast, CD28 co-stimulation did not enhance CD8 clustering or CD3–CD8 co-clustering in nano-domains although it increased molecular number and density of CD3 clustering in the enlarged nano-domains. These nanoscale findings provide new insights into TCR/CD3 interaction with CD4 or CD8 co-receptor in T-cell activation. PMID:19536289

  11. NSOM/QD-based direct visualization of CD3-induced and CD28-enhanced nanospatial coclustering of TCR and coreceptor in nanodomains in T cell activation.

    PubMed

    Zhong, Liyun; Zeng, Gucheng; Lu, Xiaoxu; Wang, Richard C; Gong, Guangming; Yan, Lin; Huang, Dan; Chen, Zheng W

    2009-01-01

    Direct molecular imaging of nano-spatial relationship between T cell receptor (TCR)/CD3 and CD4 or CD8 co-receptor before and after activation of a primary T cell has not been reported. We have recently innovated application of near-field scanning optical microscopy (NSOM) and immune-labeling quantum dots (QD) to image Ag-specific TCR response during in vivo clonal expansion, and now up-graded the NSOM/QD-based nanotechnology through dipole-polarization and dual-color imaging. Using this imaging system scanning cell-membrane molecules at a best-optical lateral resolution, we demonstrated that CD3, CD4 or CD8 molecules were distinctly distributed as single QD-bound molecules or nano-clusters equivalent to 2-4 QD fluorescence-intensity/size on cell-membrane of un-stimulated primary T cells, and approximately 6-10% of CD3 were co-clustering with CD4 or CD8 as 70-110 nm nano-clusters without forming nano-domains. The ligation of TCR/CD3 on CD4 or CD8 T cells led to CD3 nanoscale co-clustering or interaction with CD4 or CD8 co-receptors forming 200-500 nm nano-domains or >500 nm micro-domains. Such nano-spatial co-clustering of CD3 and CD4 or CD3 and CD8 appeared to be an intrinsic event of TCR/CD3 ligation, not purely limited to MHC engagement, and be driven by Lck phosphorylation. Importantly, CD28 co-stimulation remarkably enhanced TCR/CD3 nanoscale co-clustering or interaction with CD4 co-receptor within nano- or micro-domains on the membrane. In contrast, CD28 co-stimulation did not enhance CD8 clustering or CD3-CD8 co-clustering in nano-domains although it increased molecular number and density of CD3 clustering in the enlarged nano-domains. These nanoscale findings provide new insights into TCR/CD3 interaction with CD4 or CD8 co-receptor in T-cell activation. PMID:19536289

  12. Electrochemically Synthesized Sb/Sb2O3 Composites as High-Capacity Anode Materials Utilizing a Reversible Conversion Reaction for Na-Ion Batteries.

    PubMed

    Hong, Kyung-Sik; Nam, Do-Hwan; Lim, Sung-Jin; Sohn, DongRak; Kim, Tae-Hee; Kwon, HyukSang

    2015-08-12

    Sb/Sb2O3 composites are synthesized by a one-step electrodeposition process from an aqueous electrolytic bath containing a potassium antimony tartrate complex. The synthesis process involves the electrodeposition of Sb simultaneously with the chemical deposition of Sb2O3, which allows for the direct deposition of morula-like Sb/Sb2O3 particles on the current collector without using a binder. Structural characterization confirms that the Sb/Sb2O3 composites are composed of approximately 90 mol % metallic Sb and 10 mol % crystalline Sb2O3. The composite exhibits a high reversible capacity (670 mAh g(-1)) that is higher than the theoretical capacity of Sb (660 mAh g(-1)). The high reversible capacity results from the conversion reaction between Na2O and Sb2O3 that occurs additionally to the alloying/dealloying reaction of Sb with Na. Moreover, the Sb/Sb2O3 composite shows excellent cycle performance with 91.8% capacity retention over 100 cycles, and a superior rate capability of 212 mAh g(-1) at a high current density of 3300 mA g(-1). The outstanding cycle performance is attributed to an amorphous Na2O phase generated by the conversion reaction, which inhibits agglomeration of Sb particles and acts as an effective buffer against volume change of Sb during cycling. PMID:26185914

  13. Bimetallic Pt-Ag and Pd-Ag nanoparticles

    SciTech Connect

    Lahiri, Debdutta; Bunker, Bruce; Mishra, Bhoopesh; Zhang, Zhenyuan; Meisel, Dan; Doudna, C. M.; Bertino, M. F.; Blum, Frank D.; Tokuhiro, A. T.; Chattopadhyay, Soma; Shibata, Tomohiro; Terry, Jeff

    2005-04-19

    We report studies of bimetallic nanoparticles with 15%–16% atomic crystal parameters size mismatch. The degree of alloying was also probed in a 2-nm Pt core ssmallest attainable core sized of Pt–Ag nanoparticles scompletely immiscible in bulkd and 20-nm-diameter Pd–Ag nanowires scompletely miscible in bulkd. Particles were synthesized radiolytically, and depending on the initial parameters, they assume spherical or cylindrical snanowired morphologies. In all cases, the metals are seen to follow their bulk alloying characteristics. Also, Pt and Ag segregate in both spherical and wire forms, which indicates that strain due to crystallographic mismatch overcomes the excess surface free energy in the small particles. The Pd–Ag nanowires alloy similar to previously reported spherical Pd–Ag particles of similar diameter and composition

  14. Bimetallic Pt-Ag and Pd-Ag nanoparticles

    SciTech Connect

    Lahiri, Debdutta; Bunker, Bruce; Mishra, Bhoopesh; Zhang, Zhenyuan; Meisel, Dan; Doudna, C.M.; Bertino, M. F.; Blum, Frank D.; Tokuhiro, A.T.; Chattopadhyay, Soma; Shibata, Tomohiro; Terry, Jeff

    2005-05-01

    We report studies of bimetallic nanoparticles with 15%-16% atomic crystal parameters size mismatch. The degree of alloying was probed in a 2-nm Pt core (smallest attainable core size) of Pt-Ag nanoparticles (completely immiscible in bulk) and 20-nm-diameter Pd-Ag nanowires (completely miscible in bulk). Particles were synthesized radiolytically, and depending on the initial parameters, they assume spherical or cylindrical (nanowire) morphologies. In all cases, the metals are seen to follow their bulk alloying characteristics. Pt and Ag segregate in both spherical and wire forms, which indicates that strain due to crystallographic mismatch overcomes the excess surface free energy in the small particles. The Pd-Ag nanowires alloy similar to previously reported spherical Pd-Ag particles of similar diameter and composition.

  15. CD83 Modulates B Cell Activation and Germinal Center Responses.

    PubMed

    Krzyzak, Lena; Seitz, Christine; Urbat, Anne; Hutzler, Stefan; Ostalecki, Christian; Gläsner, Joachim; Hiergeist, Andreas; Gessner, André; Winkler, Thomas H; Steinkasserer, Alexander; Nitschke, Lars

    2016-05-01

    CD83 is a maturation marker for dendritic cells. In the B cell lineage, CD83 is expressed especially on activated B cells and on light zone B cells during the germinal center (GC) reaction. The function of CD83 during GC responses is unclear. CD83(-/-) mice have a strong reduction of CD4(+) T cells, which makes it difficult to analyze a functional role of CD83 on B cells during GC responses. Therefore, in the present study we generated a B cell-specific CD83 conditional knockout (CD83 B-cKO) model. CD83 B-cKO B cells show defective upregulation of MHC class II and CD86 expression and impaired proliferation after different stimuli. Analyses of GC responses after immunization with various Ags revealed a characteristic shift in dark zone and light zone B cell numbers, with an increase of B cells in the dark zone of CD83 B-cKO mice. This effect was not accompanied by alterations in the level of IgG immune responses or by major differences in affinity maturation. However, an enhanced IgE response was observed in CD83 B-cKO mice. Additionally, we observed a strong competitive disadvantage of CD83-cKO B cells in GC responses in mixed bone marrow chimeras. Furthermore, infection of mice with Borrelia burgdorferi revealed a defect in bacterial clearance of CD83 B-cKO mice with a shift toward a Th2 response, indicated by a strong increase in IgE titers. Taken together, our results show that CD83 is important for B cell activation and modulates GC composition and IgE Ab responses in vivo. PMID:26983787

  16. Determination of CdTe bulk carrier lifetime and interface recombination velocity of CdTe/MgCdTe double heterostructures grown by molecular beam epitaxy

    SciTech Connect

    Zhao, Xin-Hao; Campbell, Calli M.; DiNezza, Michael J.; Liu, Shi; Zhao, Yuan; Zhang, Yong-Hang

    2014-12-22

    The bulk Shockley-Read-Hall carrier lifetime of CdTe and interface recombination velocity at the CdTe/Mg{sub 0.24}Cd{sub 0.76}Te heterointerface are estimated to be around 0.5 μs and (4.7 ± 0.4) × 10{sup 2 }cm/s, respectively, using time-resolved photoluminescence (PL) measurements. Four CdTe/MgCdTe double heterostructures (DHs) with varying CdTe layer thicknesses were grown on nearly lattice-matched InSb (001) substrates using molecular beam epitaxy. The longest lifetime of 179 ns is observed in the DH with a 2 μm thick CdTe layer. It is also shown that the photon recycling effect has a strong influence on the bulk radiative lifetime, and the reabsorption process affects the measured PL spectrum shape and intensity.

  17. Detection of Foreign Antigen-specific CD4+Foxp3+ Regulatory T Cells by MHC Class II Tetramer and Intracellular CD154 Staining

    PubMed Central

    Choi, Jin Young

    2013-01-01

    The unrestricted population of CD4+Foxp3+ regulatory T (Treg) cells, which have been known to control the expression of autoimmune diseases and protective immunity to inflammatory reactions, has led to greater appreciation of functional plasticity. Detecting and/or isolating Ag-specific CD4+Foxp3+ Tregs at the single cell level are required to study their function and plasticity. In this study, we established and compared both MHC class II tetramer and intracellular CD154 staining, in order to detect CD4+Foxp3+ Treg specific for foreign Ag in acute and chronic infections with lymphocytic choriomeningitis virus (LCMV). Our results revealed that MHC class II tetramer staining showed a lower detection rate of LCMV GP66-77-specific CD4+ T cells because most of MHC class II tetramers were unbound and unstable when combined staining was performed with intracellular cytokines. In contrast, intracellular CD154 staining was revealed to be easier and simple for detecting LCMV GP66-77-specific CD4+ T cells, compared to MHC class II tetramer staining. Subsequently, we employed intracellular CD154 staining to detect LCMV GP66-77-specific CD4+Foxp3+ Tregs using Foxp3GFP knock-in mouse, and found that LCMV GP66-77-specific CD4+Foxp3+ Tregs and polyclonal CD4+Foxp3+ Tregs showed differential expansion in mice infected with LCMV Arms or Cl13 at acute (8 and 13 days pi) and chronic phases (35 days pi). Therefore, our results provide insight into the valuable use of intracellular CD154 staining to detect and characterize foreign Ag-specific CD4+Foxp3+ Treg in various models. PMID:24385945

  18. Materials Data on AgSbTe2 (SG:166) by Materials Project

    SciTech Connect

    Kristin Persson

    2015-02-09

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  19. Materials Data on AgSbF6 (SG:206) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2014-11-02

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  20. Materials Data on SrAgSb (SG:194) by Materials Project

    SciTech Connect

    Kristin Persson

    2015-02-09

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  1. Materials Data on BaAgSb (SG:194) by Materials Project

    SciTech Connect

    Kristin Persson

    2015-02-09

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  2. Materials Data on CaAgSb (SG:62) by Materials Project

    SciTech Connect

    Kristin Persson

    2015-02-09

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  3. Materials Data on Li2AgSb (SG:216) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-11-02

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  4. Materials Data on AgSbTe2 (SG:123) by Materials Project

    DOE Data Explorer

    Kristin Persson

    2015-02-09

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  5. Materials Data on AgHg3SbO6 (SG:167) by Materials Project

    SciTech Connect

    Kristin Persson

    2014-11-02

    Computed materials data using density functional theory calculations. These calculations determine the electronic structure of bulk materials by solving approximations to the Schrodinger equation. For more information, see https://materialsproject.org/docs/calculations

  6. DWPF Simulant CPC Studies For SB8

    SciTech Connect

    Newell, J. D.

    2013-09-25

    Prior to processing a Sludge Batch (SB) in the Defense Waste Processing Facility (DWPF), flowsheet studies using simulants are performed. Typically, the flowsheet studies are conducted based on projected composition(s). The results from the flowsheet testing are used to 1) guide decisions during sludge batch preparation, 2) serve as a preliminary evaluation of potential processing issues, and 3) provide a basis to support the Shielded Cells qualification runs performed at the Savannah River National Laboratory (SRNL). SB8 was initially projected to be a combination of the Tank 40 heel (Sludge Batch 7b), Tank 13, Tank 12, and the Tank 51 heel. In order to accelerate preparation of SB8, the decision was made to delay the oxalate-rich material from Tank 12 to a future sludge batch. SB8 simulant studies without Tank 12 were reported in a separate report.1 The data presented in this report will be useful when processing future sludge batches containing Tank 12. The wash endpoint target for SB8 was set at a significantly higher sodium concentration to allow acceptable glass compositions at the targeted waste loading. Four non-coupled tests were conducted using simulant representing Tank 40 at 110-146% of the Koopman Minimum Acid requirement. Hydrogen was generated during high acid stoichiometry (146% acid) SRAT testing up to 31% of the DWPF hydrogen limit. SME hydrogen generation reached 48% of of the DWPF limit for the high acid run. Two non-coupled tests were conducted using simulant representing Tank 51 at 110-146% of the Koopman Minimum Acid requirement. Hydrogen was generated during high acid stoichiometry SRAT testing up to 16% of the DWPF limit. SME hydrogen generation reached 49% of the DWPF limit for hydrogen in the SME for the high acid run. Simulant processing was successful using previously established antifoam addition strategy. Foaming during formic acid addition was not observed in any of the runs. Nitrite was destroyed in all runs and no N2O was detected

  7. Thermal instability of GaSb surface oxide

    NASA Astrophysics Data System (ADS)

    Tsunoda, K.; Matsukura, Y.; Suzuki, R.; Aoki, M.

    2016-05-01

    In the development of InAs/GaSb Type-II superlattice (T2SL) infrared photodetectors, the surface leakage current at the mesa sidewall must be suppressed. To achieve this requirement, both the surface treatment and the passivation layer are key technologies. As a starting point to design these processes, we investigated the GaSb oxide in terms of its growth and thermal stability. We found that the formation of GaSb oxide was very different from those of GaAs. Both Ga and Sb are oxidized at the surface of GaSb. In contrast, only Ga is oxidized and As is barely oxidized in the case of GaAs. Interestingly, the GaSb oxide can be formed even in DI water, which results in a very thick oxide film over 40 nm after 120 minutes. To examine the thermal stability, the GaSb native oxide was annealed in a vacuum and analyzed by XPS and Raman spectroscopy. These analyses suggest that SbOx in the GaSb native oxide will be reduced to metallic Sb above 300°C. To directly evaluate the effect of oxide instability on the device performance, a T2SL p-i-n photodetector was fabricated that has a cutoff wavelength of about 4 μm at 80 K. As a result, the surface leakage component was increased by the post annealing at 325°C. On the basis of these results, it is possible to speculate that a part of GaSb oxide on the sidewall surface will be reduced to metallic Sb, which acts as an origin of additional leakage current path.

  8. What Is Ag-Ed?

    ERIC Educational Resources Information Center

    Lindley, Judy

    Ag-Ed is an agricultural education project aimed at upper primary students, held in conjunction with the Toowoomba Show (similar to a county fair) in Queensland, Australia. The program achieves its purpose of helping children understand the impact and relevance that agriculture has on their everyday lives through two components, an Ag-Ed day and a…

  9. AGS Experiments: 1989, 1990, 1991

    SciTech Connect

    Depken, J.C.

    1992-02-01

    This report contains: Experimental areas layout; table of beam parameters and fluxes; experiment schedule ``as run``; proposed 1992 schedule; a listing of experiments by number; two-page summaries of each experiment begin here, also ordered by number; publications of AGS Experiments begin here; and list of AGS Experimenters begins here.

  10. AGS Experiments: 1989, 1990, 1991

    SciTech Connect

    Depken, J.C.

    1992-02-01

    This report contains: Experimental areas layout; table of beam parameters and fluxes; experiment schedule as run''; proposed 1992 schedule; a listing of experiments by number; two-page summaries of each experiment begin here, also ordered by number; publications of AGS Experiments begin here; and list of AGS Experimenters begins here.

  11. Dendritic cell vaccine modified by Ag85A gene enhances anti-tumor immunity against bladder cancer.

    PubMed

    Zhang, Pei; Wang, Jinyan; Wang, Danan; Wang, Huan; Shan, Fengping; Chen, Liudan; Hou, Ying; Wang, Enhua; Lu, Chang-Long

    2012-11-01

    The ability of dendritic cells to provide all the signals required for T-cell activation makes them an ideal cancer vaccine platform. With the use of established DC2.4 cell line, originated from C57BL/6 mice and developed by superinfecting GM-CSF transduced bone marrow cells with myc and raf oncogenes, we investigated whether the DC 2.4 cell line transfected with Ag85A gene could enhance immunity against bladder cancer. Both phenotypic and functional analyses of Ag85A-DCs were done with use of FCM and T cell proliferation test. The cytotoxicity of Ag85A-DCs loaded with tumor cell lysate was verified by LDH. Finally, the production of interferon gamma was assayed by both ELISA and FCM. The immunotherapeutic effect of DC vaccine on murine bladder cancer was assessed pharmacologically and pathologically. Our results showed that Ag85A gene transfected DCs expressed high levels of key surface markers such as CD80, CD86 and MHC-II. The CTL primed with MB49 lysate-pulsed Ag85A-DCs elicits higher activity against MB49 tumor cells and upregulated level of IFN-γ production. Furthermore, the significant inhibitive effect on tumor growth in mice was found in the group of Ag85A-DC vaccine. The infiltration of CD4(+) or CD8(+) T cell within established tumor treated by Ag85A-DC vaccine significantly increased as compared with control groups. It is therefore concluded that DCs engineered by Ag85A gene exerts enhanced anti-tumor immunity against bladder cancer and this study might provide a meaningful mode of action with the use of Ag85A engineered DC vaccination in anti-cancer immunotherapy. PMID:22884511

  12. Magnesium and cadmium containing Heusler phases REPd2Mg, REPd2Cd, REAg2Mg, REAu2Mg and REAu2Cd

    NASA Astrophysics Data System (ADS)

    Johnscher, Michael; Stein, Sebastian; Niehaus, Oliver; Benndorf, Christopher; Heletta, Lukas; Kersting, Marcel; Höting, Christoph; Eckert, Hellmut; Pöttgen, Rainer

    2016-02-01

    Twenty-eight new Heusler phases REPd2Mg, REPd2Cd, REAg2Mg, REAu2Mg and REAu2Cd with different rare earth elements were synthesized from the elements in sealed niobium ampoules in a water-cooled sample chamber of an induction furnace. The samples were characterized by powder X-ray diffraction. The cell volumes show the expected lanthanide contraction. The structures of YPd2Cd, GdPd2Cd, GdAu2Cd, Y1.12Ag2Mg0.88 and GdAg2Mg were refined based on single crystal diffractometer data. The magnetic properties were determined for fifteen phase pure samples. LuAu2Mg is a weak Pauli paramagnet with a susceptibility of 1.0(2) × 10-5 emu mol-1 at room temperature. The remaining samples show stable trivalent rare earth ions and most of them order magnetically at low temperatures. The ferromagnet GdAg2Mg shows the highest ordering temperature of TC = 98.3 K. 113Cd and 89Y MAS NMR spectra of YAu2Cd and YPd2Cd confirm the presence of unique crystallographic sites. The resonances are characterized by large Knight shifts, whose magnitude can be correlated with electronegativity trends.

  13. Gut Microbial Membership Modulates CD4 T Cell Reconstitution and Function after Sepsis.

    PubMed

    Cabrera-Perez, Javier; Babcock, Jeffrey C; Dileepan, Thamotharampillai; Murphy, Katherine A; Kucaba, Tamara A; Badovinac, Vladimir P; Griffith, Thomas S

    2016-09-01

    Transient lymphopenia is one hallmark of sepsis, and emergent data indicate the CD4 T cell compartment in sepsis survivors is numerically and functionally altered (when examined at the Ag-specific level) compared with nonseptic control subjects. Previous data from our laboratory demonstrated Ag-independent, lymphopenia-induced homeostatic proliferation to be a contributing mechanism by which CD4 T cells numerically recover in sepsis survivors. However, we reasoned it is also formally possible that some CD4 T cells respond directly to Ag expressed by gut-resident microbes released during polymicrobial sepsis. The effect of gut microbiome leakage on CD4 T cells is currently unknown. In this study, we explored the number and function of endogenous CD4 T cells specific for segmented filamentous bacterium (SFB) after cecal ligation and puncture (CLP)-induced sepsis using mice that either contained or lacked SFB as a normal gut-resident microbe. Interestingly, SFB-specific CD4 T cells underwent Ag-driven proliferation in CLP-treated SFB(+), but not in SFB(-), mice. Moreover, CLP-treated SFB(+) mice showed resistance to secondary lethal infection with recombinant SFB Ag-expressing virulent Listeria (but not wild-type virulent Listeria), suggesting the CLP-induced polymicrobial sepsis primed for a protective response by the SFB-specific CD4 T cells. Thus, our data demonstrate that the numerical recovery and functional responsiveness of Ag-specific CD4 T cells in sepsis survivors is, in part, modulated by the intestinal barrier's health discreetly defined by individual bacterial populations of the host's microbiome. PMID:27448587

  14. Thermal Treatment Improvement of CuSbS2 Absorbers

    SciTech Connect

    de Souza Lucas, Francisco Willian; Welch, Adam W.; Baranowski, Lauryn L.; Dippo, Patricia C.; Mascaro, Lucia H.; Zakutayev, Andriy

    2015-06-14

    Thermal treatment in Sb2S3 vapor was used to improve the quality of CuSbS2 thin films, a promising non-toxic and earth-abundant absorber. A change in the CuSbS2 crystallographic texture and a decrease in the lattice stress were observed, as well as increases in the grain size, photoluminescence intensity and photoconductivity. To eliminate the influence of the possible Sb2S3 rich surface layer on photovoltaic performance, a selective chemical etching with KOH was developed.

  15. Intrinsic interface states in InAs-AlSb heterostructures.

    PubMed

    Raouafi, F; Benchamekh, R; Nestoklon, M O; Jancu, J-M; Voisin, P

    2016-02-01

    We examine the formation of intrinsic interface states bound to the plane of In-Sb chemical bonds at InAs-AlSb interfaces. Careful parameterization of the bulk materials in the frame of the extended-basis spds (*)tight-binding model and recent progress in predictions of band offsets severely limit the span of tight-binding parameters describing this system. We find that a heavy-hole-like interface state bound to the plane of In-Sb bonds exists for a large range of values of the InSb-InAs band offset. PMID:26732184

  16. Dual effect of CD85/leukocyte Ig-like receptor-1/Ig-like transcript 2 and CD152 (CTLA-4) on cytokine production by antigen-stimulated human T cells.

    PubMed

    Saverino, Daniele; Merlo, Andrea; Bruno, Silvia; Pistoia, Vito; Grossi, Carlo E; Ciccone, Ermanno

    2002-01-01

    The functional outcome of a T cell response to Ag is the result of a balance between coactivation and inhibitory signals. In this study we have investigated the effects of the CD85/leukocyte Ig-like receptor (LIR)-1/Ig-like transcript (ILT) 2 and of CD152 (CTLA-4) inhibitory receptors on the modulation of cell-mediated immune responses to specific Ags, both at the effector and at the resting/memory cell level. Proliferation and cytokine production of CD4+ T lymphocytes stimulated by recall Ags have been evaluated. Cross-linking of CD85/LIR-1/ILT2 or CD152 molecules on cultured T cells using specific mAb and goat anti-mouse antiserum inhibits Ag-specific T cell proliferation. This inhibition is always paralleled by increased production of cytokines that down-regulate immune responses, e.g., IL-10 and TGF-beta. In contrast, the production of cytokines that support T cell expansion and function (e.g., IL-2, IFN-gamma, and IL-13) is significantly decreased. A long-term effect of CD85/LIR-1/ILT2 and of CD152 occurs during Ag-specific T cell activation and expansion. T cells, primed in the presence of anti-CD85/LIR-1/ILT2 and anti-CD152 blocking mAb (but in the absence of cross-linking), proliferate at higher rates and produce higher amounts of IL-2, IFN-gamma, and IL-13, in comparison with T cells stimulated with the Ag alone. We also show that the inhibitory receptors exert a similar effect during Ag activation of specific CD4+ effector T cells. Ag-specific polyclonal CD4+ T cell lines exhibit increased proliferation and IL-2, IFN-gamma, and IL-13 production when the CD85/LIR-1/ILT2 receptor is blocked by specific mAb. In contrast, cross-linking of this receptor down-regulates Ag-specific CD4+ T cell proliferation and increases IL-10 and TGF-beta production. PMID:11751964

  17. Numerical analysis of InSb parameters and InSb 2D infrared focal plane arrays

    NASA Astrophysics Data System (ADS)

    Zhang, Xiaolei; Zhang, Hongfei; Sun, Weiguo; Zhang, Lei; Meng, Chao; Lu, Zhengxiong

    2012-10-01

    Accurate and reliable numerical simulation tools are necessary for the development of advanced semiconductor devices. InSb is using the MATLAB and TCAD simulation tool to calculatet the InSb body bandstructure, blackbody's radiant emittance and simultaneously solve the Poisson, Continuity and transport equations for 2D detector structures. In this work the material complexities of InSb, such as non-parabolicity, degenergcy, mobility and Auger recombination/generation are explained, and physics based models are developed. The Empirical Tight Binding Method (ETBM) was been using to calculate the bandstructure for InSb at 77 K by Matlab. We describe a set of systematic experiments performed in order to calibrate the simulation to semiconductor devices backside illuminated InSb focal plane arrays realized with planar technology. The spectral photoresponse and crosstalk characteristic for mid-wavelength InSb infrared focal plane arrays have been numerically studied.

  18. In situ synthesis of CdS/CdWO4/WO3 heterojunction films with enhanced photoelectrochemical properties

    NASA Astrophysics Data System (ADS)

    Zhan, Faqi; Li, Jie; Li, Wenzhang; Yang, Yahui; Liu, Wenhua; Li, Yaomin

    2016-09-01

    CdS/CdWO4/WO3 heterojunction films on fluorine-doped tin oxide (FTO) substrates are for the first time prepared as an efficient photoanode for photoelectrochemical (PEC) hydrogen generation by an in situ conversion process. The samples are characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), ultraviolet visible spectrometry (UV-vis) and X-ray photoelectron spectroscopy (XPS). The CdS hollow spheres (∼80 nm) sensitized WO3 plate film with a CdWO4 buffer-layer exhibits increased visible light absorption and a significantly improved photoelectrochemical performance. The photocurrent density at 0 V (vs. Ag/AgCl) of the CdS/CdWO4/WO3 anode is ∼3 times higher than that of the CdWO4/WO3 anode, and ∼9 times higher than that of pure WO3 under illumination. The highest incident-photon-to-current-efficiency (IPCE) value increased from 16% to 63% when the ternary heterojunction was formed. This study demonstrates that the synthesis of ternary composite photocatalysts by the in situ conversion process may be a promising approach to achieve high photoelectric conversion efficiency.

  19. Antigen-dependent and –independent contributions to primary memory CD8 T cell activation and protection following infection

    PubMed Central

    Martin, Matthew D.; Badovinac, Vladimir P.

    2015-01-01

    Memory CD8 T-cell activation, including expression of IFN-γ and granzymeB, can be induced by antigen (Ag)-dependent signals through the T-cell-receptor, or by pathogen-derived inflammatory cytokines in an Ag-independent manner. Recent studies have come to conflicting results regarding the contributions of Ag and/or inflammation to memory CD8 T-cell activation. Additionally, research has indicated that inflammation-driven CD8 T-cell responses during un-related infections (bystander activation) have the potential to provide protection, but whether protection occurs in immuno-competent hosts is unclear. To investigate these questions, we examined activation of virus-specific memory CD8 T-cells following infection with L. monocytogenes either expressing or not cognate Ag. We show that Ag and inflammation act synergistically in vitro to induce memory activation. In vivo, we found that when memory CD8 T-cells significantly contribute to clearance of infection, early activation and continued responses by these cells are enhanced by cognate Ag recognition. Mechanistically, we show that bystander responses by memory are dependent upon the dose of infection and the amount of inflammation elicited following infection and are able to provide protection in IFN-γ deficient mice, but not in immuno-competent hosts. The data elucidate the requirements for memory CD8 T-cell activation and the protective role of bystander responses. PMID:26658291

  20. NaAg(2)Mo(3)O(9)AsO(4).

    PubMed

    Hamza, Hamadi; Zid, Mohamed Faouzi; Driss, Ahmed

    2010-01-01

    The title compound, sodium disilver arsenatotrimolybdate, Na(0.93 (1))Ag(2.07 (1))Mo(3)AsO(13), was prepared by a solid-state reaction. In the crystal structure, isolated AsO(4) tetra-hedra share corners with groups of three edge-sharing MoO(6) octa-hedra. This arrangement leads to the formation of anionic (1) (∞)[Mo(3)AsO(13)](n) ribbons extending parallel to [100]. The three metal sites show occupational disorder by Ag(I) and Na(I) cations, each with a different Ag:Na ratio. The metal cations are situated in the space between the ribbons and are surrounded by terminal O atoms of the ribbons in the form of distorted MO(7) polyhedra (M = Ag, Na) for distances < 3.0 Å. The title compound shows weak ionic conductivity. Structural relationships between different compounds in the quaternary systems M-Sb-P-O, M-Nb-P-O and M-Mo-As-O (M is Ag or an alkali metal) are also discussed. PMID:21587345

  1. Spurious and realistic solutions for the quantum spin Hall edge states in InAs/GaSb/AlSb quantum wells.

    PubMed

    Klipstein, P C

    2016-09-21

    A solution of the 4  ×  4 k · p Hamiltonian for the quantum spin Hall (QSH) edge states in ideal semiconductor topological insulator (TI) quantum wells (QWs) was recently demonstrated by the author using standard boundary conditions for the wave function and its derivative, in order to address unphysical behavior associated with open boundary conditions (Klipstein 2015 Phys. Rev. B 91 035310). For HgTe/CdTe QWs which have strong s-p hybridization, there are two non-degenerate solutions in each spin direction with a finite amplitude at the edge, one of which was shown to be spurious. For the case of weakly hybridized InAs/GaSb/AlSb QWs, the solutions near the zone center are degenerate, and the question is now settled of which solution is spurious. The physical solutions for the ideal QW are then used as the basis for a perturbation treatment of the edge state dispersions in realistic QWs, where interface, bulk and structural asymmetries are also present. Interactions are included with more remote states than considered previously, as required for a consistent treatment of the TI bulk states, where a large difference exists in the spin splittings of the conduction and valence band edges. The asymmetry perturbations induce only minor changes to the edge state dispersions, which no longer merge smoothly with the bulk band extrema. PMID:27420636

  2. Spurious and realistic solutions for the quantum spin Hall edge states in InAs/GaSb/AlSb quantum wells

    NASA Astrophysics Data System (ADS)

    Klipstein, P. C.

    2016-09-01

    A solution of the 4  ×  4 k · p Hamiltonian for the quantum spin Hall (QSH) edge states in ideal semiconductor topological insulator (TI) quantum wells (QWs) was recently demonstrated by the author using standard boundary conditions for the wave function and its derivative, in order to address unphysical behavior associated with open boundary conditions (Klipstein 2015 Phys. Rev. B 91 035310). For HgTe/CdTe QWs which have strong s-p hybridization, there are two non-degenerate solutions in each spin direction with a finite amplitude at the edge, one of which was shown to be spurious. For the case of weakly hybridized InAs/GaSb/AlSb QWs, the solutions near the zone center are degenerate, and the question is now settled of which solution is spurious. The physical solutions for the ideal QW are then used as the basis for a perturbation treatment of the edge state dispersions in realistic QWs, where interface, bulk and structural asymmetries are also present. Interactions are included with more remote states than considered previously, as required for a consistent treatment of the TI bulk states, where a large difference exists in the spin splittings of the conduction and valence band edges. The asymmetry perturbations induce only minor changes to the edge state dispersions, which no longer merge smoothly with the bulk band extrema.

  3. Producing CD-ROMs.

    ERIC Educational Resources Information Center

    Hyams, Peter, Ed.

    1992-01-01

    This issue presents 11 articles that address issues relating to the production of CD-ROMs. Highlights include current uses of CD-ROM; standards; steps involved in producing CD-ROMs, including data capture, conversion, and tagging, product design, and indexing; authoring; selecting indexing and retrieval software; costs; multimedia CD-ROMs; and…

  4. CD14+CD16+ and CD14+CD163+ monocyte subpopulations in kidney allograft transplantation

    PubMed Central

    2014-01-01

    Background Monocytes represent a heterogeneous population of cells subdivided according to the expression level of membrane antigens. A pro-inflammatory (intermediate/nonclassical) subpopulation of monocytes is defined by expression of CD16. CD163 seems to be characteristically preferentially expressed by immunosuppressive monocytes. The aim of our study was to evaluate the distribution of monocyte subpopulations in 71 patients with kidney allograft transplantation. Results The phenotype was evaluated by flow cytometry in defined time points. The proportions of peripheral CD14+CD16+ monocytes were downregulated immediately after the kidney transplantation and basiliximab treatment partially attenuated this trend. The transient downregulation of the CD14+CD16+ subpopulation was adjusted to basal values in two months. The proportions of CD14+CD163+ monocytes were transiently upregulated early after the kidney transplantation and remained higher during the first month in most patients. In ATG treated patients, the expansion of CD14+CD163+ monocytes was delayed but their upregulation lasted longer. In vitro data showed the direct effect of ATG and methylprednisolone on expression of CD16 and CD163 molecules while basiliximab did not affect the phenotype of cultured monocytes. Conclusions We assume from our data that kidney allograft transplantation is associated with modulation of monocyte subpopulations (CD14+CD16+ and CD14+CD163+) partially affected by an immunosuppressive regime used. PMID:24499053

  5. Investigation of linear-mode photon-counting HgCdTe APDs for astronomical observations

    NASA Astrophysics Data System (ADS)

    Bryan, Marta L.; Chapman, George; Hall, Donald N. B.; Jack, Michael D.; Jacobson, Shane M.; Wehner, Justin

    2012-07-01

    The unique linear avalanche properties of HgCdTe preserve the Poisson statistics of the incoming photons, opening up new opportunities for GHz bandwidth LADAR and space communications applications. Raytheon has developed and previously reported (1) unique linear mode photon counting arrays based on combining advanced HgCdTe linear mode APDs with their high gain SB415B readout. Their use of HgCdTe APDs preserves the Poisson statistics of the incoming photons, enabling (noiseless) photon counting. This technology is of great potential interest to infrared astronomy but requires extension of noiseless linear HgCdTe avalanching down to much lower bandwidths (100 to 0.001 Hz) with corresponding reductions in dark count rate. We have hybridized the SB415B readout to SWIR HgCdTe APDs optimized for low dark count rate and have characterized their photon counting properties at bandwidths down to 1 KHz. As bandwidth is reduced, the performance becomes limited by the intrinsic properties of the SB415B readout, particularly readout glow, stability and 1/f noise. We report the results of these measurements and the status of hybrid arrays utilizing a newly developed readout which draws on Raytheon’s astronomical readout heritage, specifically the Virgo charge integrating source follower, as a path to much lower dark count rate photon counting operation.

  6. THE AGS ELECTROSTATIC SEPTUM.

    SciTech Connect

    HOCK,J.RUSSO,T.GLEN,J.BROWN,K.

    2003-05-12

    The previous slow beam extraction electro static septum in the AGS was designed in 1981. Research documented at the Fermi Laboratory was used as the base line for this design. The septum consisted of a ground plane of .002 inch diameter wire tungsten-rhenium alloy (75%W 25%Re) with a hollow welded titanium cathode assembly. The vacuum chamber is stationary and the septum is moved with a pair of high vacuum linear feed throughs. After years of beam time, the frequency of failures increased. The vacuum system design was poor by today's standards and resulted in long pump down times after repairs. The failures ranged from broken septum wires to a twisted cathode. In addition to the failures, the mechanical drive system had too much backlash, making the operating position difficult to repeat. The new septum needed to address all of these issues in order to become a more reliable septum.

  7. EPIDAUROS Biotechnologie AG.

    PubMed

    Arnold, Hans-Peter; Kluge, Peter; Mauch, Simon

    2005-07-01

    EPIDAUROS Biotechnologie AG is a leading provider of pharmacogenetic consulting, genotyping and research services to the international pharmaceutical and biotechnology industries, contract research organizations and healthcare providers. The company's mission is to improve safety, efficacy and predictability in drug development and drug therapy. EPIDAUROS determines its customers' needs in the field of pharmacogenetics using an in-depth consultancy process. The development and conduct of genotyping assays for drug-metabolizing enzymes, drug transporters and drug targets (for example, receptors)--all performed under stringent quality standards--are a major activity at EPIDAUROS. The company offers its research services to academic and industrial partners for the development of innovative diagnostic solutions by using its intellectual property. PMID:16014003

  8. Numerical Simulation of the Dissolution Process of GaSb into InSb Melt under Normal and Microgravity Conditions

    NASA Astrophysics Data System (ADS)

    Takagi, Youhei; Suzuki, Natsuki; Okano, Yasunori; Tanaka, Akira; Hayakawa, Yasuhiro; Dost, Sadik

    Temperature Gradient Growth experiments of InxGa1-xSb will be performed on the International Space Station (ISS) in 2012. In the GaSb/InSb/GaSb-sandwich system used, before growth, the dissolution process of GaSb into InSb takes place during the formation of the growth solution (melt). Solutal mass transport occurring during dissolution plays a significant role. In crystal growth on Earth, the large difference between the densities of InSb and GaSb leads to gravitational segregation in the melt and axial non-uniformity in crystal composition. In addition, the large separation between the liquidus and solidus curves in the phase diagram of this system further contributes to compositional non-uniformity. In order to have a better understanding for the effect of gravity on solutal transport during in this system, the dissolution process was numerically simulated under both Earth’s gravity and a microgravity level on the ISS. Numerical simulations showed that under Earth’s gravity, dissolution of the GaSb seed was enhanced due to the contribution of solutal natural convection. However, under microgravity diffusion mass transport was dominant in the melt, and the contribution of natural convection was not significant.

  9. Sb/Cu2Sb-TiC-C Composite Anode for High-Performance Sodium-Ion Batteries.

    PubMed

    Chae, Seung Chul; Hur, Jaehyun; Kim, Il Tae

    2016-02-01

    A novel nanostructure consisting of copper-antimony alloy (Cu2Sb) particles dispersed in a conductive hybrid matrix of titanium carbide (TiC) and carbon (C) has been developed by high energy mechanical milling (HEMM) and explored for use as an anode in sodium-ion batteries. By controlling the molar ratio of Cu and Sb, Cu2Sb and Sb are able to co-exist in a matrix. The (Sb)/Cu2Sb-TiC-C samples have been characterized by X-ray diffraction and by high-resolution transmission electron microscopy. Specifically, the Cu2Sb-TiC-C composite anode demonstrates better cyclic performance as well as better rate-capability compared to Sb/Cu2Sb-TiC-C. Addition- ally, the introduction of the fluoroethylene carbonate (FEC) additive into the electrolyte leads to improved electrochemical performance even at high-rate current densities, when compared to the electrodes without the FEC additive, owing to the formation of a stable and thin SEI layer. PMID:27433694

  10. Investigation of interfaces in AlSb/InAs/Ga₀.₇₁In₀.₂₉Sb quantum wells by photoluminescence

    SciTech Connect

    Junliang, Xing; Yu, Zhang; Yongping, Liao; Juan, Wang; Wei, Xiang; Hongyue, Hao; Yingqiang, Xu; Zhichuan, Niu

    2014-09-28

    We have investigated excitation power and temperature dependent PL spectra to systematically study the influences of the interfaces in the both InAs/Ga₀.₇₁In₀.₂₉Sb and InAs/AlSb on the optical properties of AlSb/Ga₀.₇₁In₀.₂₉Sb/InAs quantum wells (QWs). The localized states as well as the activation energy were analyzed to discuss the possible thermal quenching and non-radiative recombination mechanisms. We found two non-radiative recombination processes were involved in the thermal quenching of radiative emission for the QW structures. The GaAs-like interface in InAs/Ga₀.₇₁In₀.₂₉Sb with higher activation energy (62.7 meV) in high temperature region (70 K–300 K) supplies a deeper hole confinement and less roughness than the InSb-like one, which suppress non-radiative recombination process and promote the optical qualities of the quantum wells. The peak energy of the InSb-like sample exhibited “step-curve” behavior with increase temperature. Neither InSb-like nor AlAs-like interface in InAs/AlSb favored the radiative emission efficiency.

  11. AgH, Ag/sub 2/, and AgO revisited: Basis set extensions

    SciTech Connect

    Martin, R.L.

    1987-05-01

    An extended basis set has been developed for Ag which significantly improves the agreement between theoretical and experimental spectroscopic parameters for AgH, AgO, and Ag/sub 2/. The major improvement comes about as a result of the improved treatment of electron correlation in the Ag d shell upon the introduction of f functions. Their inclusion produces very slight differences at the SCF level, but significant reductions in r/sub e/ and increases in ..omega../sub e/ and D/sub e/ in the Mo-dash-barller--Plesset perturbation theory expansion. At the MP4(SDTQ) level, typical results are 0.02 A too long for r/sub e/, 4% too low for ..omega../sub e/, and 10 kcal too small for D/sub e/. From a pragmatic standpoint, MP2 give results very similar to this at a much reduced level of effort.

  12. Stable core/shell CdTe/Mn-CdS quantum dots sensitized three-dimensional, macroporous ZnO nanosheet photoelectrode and their photoelectrochemical properties.

    PubMed

    Li, Weili; Sheng, Pengtao; Feng, Hongyan; Yin, Xuehua; Zhu, Xuewei; Yang, Xu; Cai, Qingyun

    2014-08-13

    A novel photoelectrode based on ZnS/CdTe/Mn-CdS/ZnS-sensitized three-dimensional macroporous ZnO nanosheet (NS) has been prepared by electrodeposition and successive ion layer adsorption and reaction (SILAR) method. The photoelectrode performances were significantly improved through the coupling of the core/shell CdTe/Mn-CdS quantum dots (QDs) with ZnO NS, and the introduction of the ZnS layer as a potential barrier. The photocurrent density systematically increases from ZnO NS (0.45 mA/cm(2)), CdTe/Mn-CdS/ZnO NS (4.98 mA/cm(2)), to ZnS/CdTe/Mn-CdS/ZnS/ZnO (6.23 mA/cm(2)) under the irradiation of AM 1.5G simulated sunlight. More important, the ZnS/CdTe/Mn-CdS/ZnS-sensitized ZnO NS photoelectrode provides a remarkable photoelectrochemical cell efficiency of 4.20% at -0.39 V vs Ag/AgCl. PMID:25010851

  13. Heterologous vaccination against human tuberculosis modulates antigen-specific CD4+ T-cell function.

    PubMed

    Dintwe, One B; Day, Cheryl L; Smit, Erica; Nemes, Elisa; Gray, Clive; Tameris, Michele; McShane, Helen; Mahomed, Hassan; Hanekom, Willem A; Scriba, Thomas J

    2013-09-01

    Heterologous prime-boost strategies hold promise for vaccination against tuberculosis. However, the T-cell characteristics required for protection are not known. We proposed that boost vaccines should induce long-lived functional and phenotypic changes to T cells primed by Bacille Calmette Guerin (BCG) and/or natural exposure to mycobacteria. We characterized changes among specific CD4(+) T cells after vaccination with the MVA85A vaccine in adults, adolescents, and children. CD4(+) T cells identified with Ag85A peptide-bearing HLA class II tetramers were characterized by flow cytometry. We also measured proliferative potential and cytokine expression of Ag85A-specific CD4(+) T cells. During the effector phase, MVA85A-induced specific CD4(+) T cells coexpressed IFN-γ and IL-2, skin homing integrins, and the activation marker CD38. This was followed by contraction and a transition to predominantly IL-2-expressing, CD45RA(-) CCR7(+) CD27(+) or CD45RA(+) CCR7(+) CD27(+) specific CD4(+) T cells. These surface phenotypes were similar to Ag85A-specific T cells prior to MVA85A. However, functional differences were observed postvaccination: specific proliferative capacity was markedly higher after 6-12 months than before vaccination. Our data suggest that MVA85A vaccination may modulate Ag85A-specific CD4(+) T-cell function, resulting in greater recall potential. Importantly, surface phenotypes commonly used as proxies for memory T-cell function did not associate with functional effects of vaccination. PMID:23737382

  14. Strained InGaSb/AlGa(As)Sb Quantum Wells for p-Channel Transistors

    NASA Astrophysics Data System (ADS)

    Bennett, Brian R.; Podpirka, Adrian A.; Boos, J. B.; Kumar, Satvika L.

    2016-06-01

    Quantum wells of InGaSb clad by AlGa(As)Sb were grown by molecular beam epitaxy. Well and barrier compositions were chosen to yield biaxial compressive strain and enhanced hole mobility in the InGaSb. Wells with thickness of 7.5 nm exhibited room-temperature mobilities of 1000 cm2/V s to 1100 cm2/V s, with the surface-layer material influencing two-dimensional hole densities. The introduction of As into the barrier material allows a wider range of p-channel well/barrier combinations and lattice constants. These could be compatible with n-channel InGaAs wells for complementary field-effect transistor circuits which utilize a common buffer layer. InGaSb wells with thicknesses of 20 nm to 30 nm and compressive strains of 1.0% to 1.5% exhibited hole mobilities of 700 cm2/V s to 900 cm2/V s.

  15. Layer-resolved spin polarization in Sb overlayers on NiMnSb

    SciTech Connect

    Skomski, R.; Komesu, T.; Borca, C. N.; Jeong, H.-K.; Dowben, P. A.; Ristoiu, D.; Nozi {grave e}res, J. P.

    2001-06-01

    The magnetism of antimony overlayers on a ferromagnetic substrate is investigated by spin-polarized inverse photoemission and explained in terms of a spin-dependent envelope-function approximation (SDEFA). The atomic structure of the films, which were deposited by sputtering Sb onto a NiMnSb(001) substrate, is characterized by a unique combination of three features: (i) NiMnSb is a highly spin-polarized semi-Heusler alloy predicted to be halfmetallic, (ii) antimony is a semimetal, exhibiting a band structure reminiscent of indirect-gap semiconductors, and (iii) the small lattice mismatch ensures a well-controlled interface. Combined x-ray absorption spectroscopy and spin-polarized inverse photoemission yield a layer-resolved spin polarization decaying on a length scale of the order of 1 nm. The unusual range of the spin polarization in the paramagnetic overlayer is explained by considering the alloy{endash}antimony interface as a spin-dependent perturbation potential and taking into account the low effective masses of the Sb conduction electrons (only about 0.1 for both electrons and holes). {copyright} 2001 American Institute of Physics.

  16. The AGS-Booster lattice

    SciTech Connect

    Lee, Y.Y.; Barton, D.S.; Claus, J.; Cottingham, J.G.; Courant, E.D.; Danby, G.T.; Dell, G.F.; Forsyth, E.B.; Gupta, R.C.; Kats, J.

    1987-01-01

    The AGS Booster has three objectives. They are to increase the space charge limit of the AGS, to increase the intensity of the polarized proton beam by accumulating many linac pulses (since the intensity is limited by the polarized ion source), and to reaccelerate heavy ions from the BNL Tandem Van de Graaff before injection into the AGS. The machine is capable of accelerating protons at 7.5 Hertz from 200 MeV to 1.5 GeV or to lower final energies at faster repetition rates. The machine will also be able to accelerate heavy ions from as low as 1 MeV/nucleon to a magnetic rigidity as high as 17.6 Tesla-meters with a one second repetition rate. As an accumulator for polarized protons, the Booster should be able to store the protons at 200 MeV for several seconds. We expect that the Booster will increase the AGS proton intensity by a factor of four, polarized proton intensity by a factor of twenty to thirty, and will also enable the AGS to accelerate all species of heavy ions (at present the AGS heavy ion program is limited to the elements lighter than sulfur because it can only accelerate fully stripped ions). The construction project started in FY 1985 and is expected to be completed in 1989. The purpose of this paper is to provide a future reference for the AGS Booster lattice.

  17. K2CsSb Cathode Development

    SciTech Connect

    Smedley,J.; Rao, T.; Wang, E.

    2008-10-01

    K{sub 2}CsSb is an attractive photocathode for high current applications. With a quantum efficiency of >4% at 532nm and >10% at 355nm, it is the only cathode to have demonstrated an average current of 35mA in an accelerator environment We describe ongoing cathode development work. for the energy recovery linac being constructed at BNL Several cathodes have been created on both copper and stainless steel substrates, and their spatial uniformity and spectral response have been characterized. Preliminary lifetime measurements have been performed at high average current densities (>1 mA/mm{sup 2}).

  18. InAs/GaSb superlattice technology

    NASA Astrophysics Data System (ADS)

    Rutz, Frank; Rehm, Robert; Walther, Martin; Schmitz, Johannes; Kirste, Lutz; Wörl, Andreas; Masur, Jan-Michael; Scheibner, Ralf; Ziegler, Johann

    2011-05-01

    We present the InAs/GaSb type-II superlattice dual-color technology developed at Fraunhofer IAF. This includes insights into some of the test methodologies employed at various stages during the fabrication process, which ensure that the basic requirements for achieving high detector performance are met. Much effort is put in improving and monitoring the quality of the substrate and the epilayers. We also present performance data from a dual-color mid-wavelength infrared (MWIR) camera which incorporates the latest backside process technology.

  19. Distribution of chemical elements in soils and stream sediments in the area of abandoned Sb-As-Tl Allchar mine, Republic of Macedonia.

    PubMed

    Bačeva, Katerina; Stafilov, Trajče; Šajn, Robert; Tănăselia, Claudiu; Makreski, Petre

    2014-08-01

    The aim of this study was to investigate the distribution of some toxic elements in topsoil and subsoil, focusing on the identification of natural and anthropogenic element sources in the small region of rare As-Sb-Tl mineralization outcrop and abandoned mine Allchar known for the highest natural concentration of Tl in soil worldwide. The samples of soil and sediments after total digestion were analyzed by inductively coupled plasma-mass spectrometry (ICP-MS) and inductively coupled plasma-atomic emission spectrometry (ICP-AES). Factor analysis (FA) was used to identify and characterize element associations. Six associations of elements were determined by the method of multivariate statistics: Rb-Ta-K-Nb-Ga-Sn-Ba-Bi-Li-Be-(La-Eu)-Hf-Zr-Zn-In-Pd-Ag-Pt-Mg; Tl-As-Sb-Hg; Te-S-Ag-Pt-Al-Sc-(Gd-Lu)-Y; Fe-Cu-V-Ge-Co-In; Pd-Zr-Hf-W-Be and Ni-Mn-Co-Cr-Mg. The purpose of the assessment was to determine the nature and extent of potential contamination as well as to broadly assess possible impacts to human health and the environment. The results from the analysis of the collected samples in the vicinity of the mine revealed that As and Tl elements have the highest median values. Higher median values for Sb are obviously as a result of the past mining activities and as a result of area surface phenomena in the past. PMID:24906071

  20. NK Cells Help Induce Anti-Hepatitis B Virus CD8+ T Cell Immunity in Mice.

    PubMed

    Zheng, Meijuan; Sun, Rui; Wei, Haiming; Tian, Zhigang

    2016-05-15

    Although recent clinical studies demonstrate that NK cell function is impaired in hepatitis B virus (HBV)-persistent patients, whether or how NK cells play a role in anti-HBV adaptive immunity remains to be explored. Using a mouse model mimicking acute HBV infection by hydrodynamic injection of an HBV plasmid, we observed that although serum hepatitis B surface Ag and hepatitis B envelope Ag were eliminated within 3 to 4 wk, HBV might persist for >8 wk in CD8(-/-) mice and that adoptive transfer of anti-HBV CD8(+) T cells restored the ability to clear HBV in HBV-carrier Rag1(-/-) mice. These results indicate that CD8(+) T cells are critical in HBV elimination. Furthermore, NK cells increased IFN-γ production after HBV plasmid injection, and NK cell depletion led to significantly increased HBV persistence along with reduced frequency of hepatitis B core Ag-specific CD8(+) T cells. Adoptive transfer of IFN-γ-sufficient NK cells restored donor CD8(+) T cell function, indicating that NK cells positively regulated CD8(+) T cells via secreting IFN-γ. We also observed that NK cell depletion correlated with decreased effector memory CD8(+) T cell frequencies. Importantly, adoptive transfer experiments showed that NK cells were involved in anti-HBV CD8(+) T cell recall responses. Moreover, DX5(+)CD49a(-) conventional, but not DX5(-)CD49a(+) liver-resident, NK cells were involved in improving CD8(+) T cell responses against HBV. Overall, the current study reveals that NK cells, especially DX5(+)CD49a(-) conventional NK cells, promote the antiviral activity of CD8(+) T cell responses via secreting IFN-γ in a mouse model mimicking acute HBV infection. PMID:27183639

  1. Antimony (Sb) and arsenic (As) in Sb mining impacted paddy soil from Xikuangshan, China: differences in mechanisms controlling soil sequestration and uptake in rice.

    PubMed

    Okkenhaug, Gudny; Zhu, Yong-Guan; He, Junwen; Li, Xi; Luo, Lei; Mulder, Jan

    2012-03-20

    Foods produced on soils impacted by antimony (Sb) mining activities are a potential health risk due to plant uptake of the contaminant metalloids (Sb) and arsenic (As). Here we report for the first time the chemical speciation of Sb in soil and porewater of flooded paddy soil, impacted by active Sb mining, and its effect on uptake and speciation in rice plants (Oryza sativa L. cv Jiahua). Results are compared with behavior and uptake of As. Pot experiments were conducted under controlled conditions in a climate chamber over a period of 50 days. In pots without rice plants, flooding increased both the concentration of dissolved Sb (up to ca. 2000 μg L(-1)) and As (up to ca. 1500 μg L(-1)). When rice was present, Fe plaque developing on rice roots acted as a scavenger for both As and Sb, whereby the concentration of As, but not Sb, in porewater decreased substantially. Dissolved Sb in porewater, which occurred mainly as Sb(V), correlated with Ca, indicating a solubility governed by Ca antimonate. No significant differences in bioaccumulation factor and translocation factor between Sb and As were observed. Greater relative concentration of Sb(V) was found in rice shoots compared to rice root and porewater, indicating either a preferred uptake of Sb(V) or possibly an oxidation of Sb(III) to Sb(V) in shoots. Adding soil amendments (olivine, hematite) to the paddy soil had no effect on Sb and As concentrations in porewater. PMID:22309044

  2. PathCase-SB architecture and database design

    PubMed Central

    2011-01-01

    Background Integration of metabolic pathways resources and regulatory metabolic network models, and deploying new tools on the integrated platform can help perform more effective and more efficient systems biology research on understanding the regulation in metabolic networks. Therefore, the tasks of (a) integrating under a single database environment regulatory metabolic networks and existing models, and (b) building tools to help with modeling and analysis are desirable and intellectually challenging computational tasks. Description PathCase Systems Biology (PathCase-SB) is built and released. The PathCase-SB database provides data and API for multiple user interfaces and software tools. The current PathCase-SB system provides a database-enabled framework and web-based computational tools towards facilitating the development of kinetic models for biological systems. PathCase-SB aims to integrate data of selected biological data sources on the web (currently, BioModels database and KEGG), and to provide more powerful and/or new capabilities via the new web-based integrative framework. This paper describes architecture and database design issues encountered in PathCase-SB's design and implementation, and presents the current design of PathCase-SB's architecture and database. Conclusions PathCase-SB architecture and database provide a highly extensible and scalable environment with easy and fast (real-time) access to the data in the database. PathCase-SB itself is already being used by researchers across the world. PMID:22070889

  3. Memristive Switching in Bi(1-x)Sb(x) Nanowires.

    PubMed

    Han, Nalae; Park, Myung Uk; Yoo, Kyung-Hwa

    2016-04-13

    We investigated the memristive switching behavior in bismuth-antimony alloy (Bi(1-x)Sb(x)) single nanowire devices at 0.1 ≤ x ≤ 0.42. At 0.15 ≤ x ≤ 0.42, most Bi(1-x)Sb(x) single nanowire devices exhibited bipolar resistive switching (RS) behavior with on/off ratios of approximately 10(4) and narrow variations in switching parameters. Moreover, the resistance values in the low-resistance state (LRS) were insensitive to x. On the other hand, at 0.1 ≤ x ≤ 0.15, some Bi(1-x)Sb(x) single nanowire devices showed complementary RS-like behavior, which was ascribed to asymmetric contact properties. Transmission electron microscopy and elemental mapping images of Bi, Sb, and O obtained from the cross sections of the Bi(1-x)Sb(x) single nanowire devices, which were cut before and after RS, revealed that the mobile species was Sb ions, and the migration of the Sb ions to the nanowire surface brought the switch to LRS. In addition, we demonstrated that two types of synaptic plasticity, namely, short-term plasticity and long-term potentiation, could be implemented in Bi(1-x)Sb(x) nanowires by applying a sequence of voltage pulses with different repetition intervals. PMID:27042861

  4. Collaborative interactions between type 2 innate lymphoid cells and antigen-specific CD4+ Th2 cells exacerbate murine allergic airway diseases with prominent eosinophilia.

    PubMed

    Liu, Bo; Lee, Jee-Boong; Chen, Chun-Yu; Hershey, Gurjit K Khurana; Wang, Yui-Hsi

    2015-04-15

    Type-2 innate lymphoid cells (ILC2s) and the acquired CD4(+) Th2 and Th17 cells contribute to the pathogenesis of experimental asthma; however, their roles in Ag-driven exacerbation of chronic murine allergic airway diseases remain elusive. In this study, we report that repeated intranasal rechallenges with only OVA Ag were sufficient to trigger airway hyperresponsiveness, prominent eosinophilic inflammation, and significantly increased serum OVA-specific IgG1 and IgE in rested mice that previously developed murine allergic airway diseases. The recall response to repeated OVA inoculation preferentially triggered a further increase of lung OVA-specific CD4(+) Th2 cells, whereas CD4(+) Th17 and ILC2 cell numbers remained constant. Furthermore, the acquired CD4(+) Th17 cells in Stat6(-/-)/IL-17-GFP mice, or innate ILC2s in CD4(+) T cell-ablated mice, failed to mount an allergic recall response to OVA Ag. After repeated OVA rechallenge or CD4(+) T cell ablation, the increase or loss of CD4(+) Th2 cells resulted in an enhanced or reduced IL-13 production by lung ILC2s in response to IL-25 and IL-33 stimulation, respectively. In return, ILC2s enhanced Ag-mediated proliferation of cocultured CD4(+) Th2 cells and their cytokine production, and promoted eosinophilic airway inflammation and goblet cell hyperplasia driven by adoptively transferred Ag-specific CD4(+) Th2 cells. Thus, these results suggest that an allergic recall response to recurring Ag exposures preferentially triggers an increase of Ag-specific CD4(+) Th2 cells, which facilitates the collaborative interactions between acquired CD4(+) Th2 cells and innate ILC2s to drive the exacerbation of a murine allergic airway diseases with an eosinophilic phenotype. PMID:25780046

  5. Investigation on the interaction of nanoAg with Cu-Zn SOD.

    PubMed

    Zhang, Bin; Yu, Lei; Zhang, Ruijing; Liu, Yang; Liu, Rutao

    2015-12-01

    Silver nanoparticles (nanoAg) are used more and more widely, particularly because of their antimicrobial properties. The effect of exposure to nanoAg on the structure of superoxide dismutase (SOD) was thoroughly investigated using fluorescence measurements, synchronous fluorescence spectroscopy, steady-state and time-resolved fluorescence quenching measurements, UV/Vis absorption spectroscopy, resonance light scattering (RLS), circular dichroism (CD), isothermal titration calorimetry (ITC) and high-resolution transmission electron microscopy (HRTEM). Through van der Waal's force, nanoAg interacted with Cu-Zn SOD and influenced the active site by inducing structural changes, which influenced the function of SOD. The fluorescence studies show that both static and dynamic quenching processes occur. This paper provides reference data for toxicological studies of nanoAg, which are important in the future development of nanotechnology. PMID:25754791

  6. An overwhelmingly selective colorimetric sensor for Ag(+) using a simple modified polyacrylonitrile fiber.

    PubMed

    Xing, Xiaoli; Yang, Huixiao; Tao, Minli; Zhang, Wenqin

    2015-10-30

    A carboxymethyl-dithiocarbamate immobilized polyacrylonitrile fiber colorimetric sensor has been synthesized. This fiber sensor exhibits excellent selectivity and sensitivity for Ag(+) in aqueous solution with a remarkable color change from light pink to red-brown over a wide pH range of 2-12. The sensor responds selectively to Ag(+) in the presence of other ions, including Mg(2+), Al(3+), Ca(2+), Cr(3+), Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+), Cd(2+), Hg(2+) and Pb(2+). The colorimetric sensor has an extremely fast response time (10s) and a low visual limit of detection (5.53×10(-12) mol/L). The fiber sensor also undergoes an obvious color change in the presence of Ag(+) solutions containing EDTA, NaCl or NaBr. Density functional theory optimization reveals that the sensor and Ag(+) interact via a seven-membered ring complexation mechanism. PMID:25967097

  7. A novel rosamine based fluorescent sensor for Ag+ recognition

    NASA Astrophysics Data System (ADS)

    Li, Lian-Qing; Gao, Le-Jun

    2016-01-01

    Rosamine derivative, N-(9-(4-(bis(2-(ethylthio)ethyl)amino)phenyl)-6-(diethylamino)-3H-xanthen-3-ylidene)-N-ethylethanaminium hexafluorophosphate, L, bearing an NS2 group as receptor, was synthesized as a turn on chemosensor for silver ion in ethanol solution. Sensor L exhibited high selectivity toward Ag+ in comparison to other metal cations (Cd2+, Cu2+, Hg2+, Na+, Mg2+, Ni2+, Pb2+, Fe3+, and Zn2+). The detection limit for Ag+ was in 10-7 level. The binding properties between silver ion and L were further studied by 1HNMR titration experiments. The chemosensor L can be used as a potential material for silver recognition.

  8. Fragile structural transition in Mo3Sb7

    DOE PAGESBeta

    Yan, Jiaqiang -Q.; McGuire, Michael A; May, Andrew F; Parker, David S.; Mandrus, D. G.; Sales, Brian C.

    2015-08-10

    Mo3Sb7 single crystals lightly doped with Cr, Ru, or Te are studied in order to explore the interplay between superconductivity, magnetism, and the cubic-tetragonal structural transition. The structural transition at 53 K is extremely sensitive to Ru or Te substitution which introduces additional electrons, but robust against Cr substitution. We observed no sign of a structural transition in superconducting Mo2.91Ru0.09Sb7 and Mo3Sb6.975Te0.025. In contrast, 3 at.% Cr doping only slightly suppresses the structural transition to 48 K while leaving no trace of superconductivity above 1.8 K. Analysis of magnetic properties suggests that the interdimer interaction in Mo3Sb7 is near amore » critical value and essential for the structural transition. Futhermore, all dopants suppress the superconductivity of Mo3Sb7. The tetragonal structure is not necessary for superconductivity.« less

  9. Anomalous transport of Sb in laser irradiated Ge

    SciTech Connect

    Bruno, E.; Scapellato, G. G.; Boninelli, S.; Priolo, F.; Privitera, V.; La Magna, A.; Cuscuna, M.; Fortunato, G.; Napolitani, E.

    2012-10-22

    Excimer laser annealing is shown to be very promising to promote Sb incorporation in Ge up to concentrations as high as 1 Multiplication-Sign 10{sup 21} at./cm{sup 3}. However, we demonstrate that when Ge is melted by laser irradiation, a high excess of vacancies is generated in the molten region. These vacancies induce Sb electrical deactivation at the melt depth through the formation of Sb{sub m}-V{sub n} complexes that act as a sink for further Sb atoms, even leading Sb to back-diffuse towards the surface, against the concentration gradient. These results are fundamental for the realization of new generation Ge-based micro and optoelectronic devices.

  10. Thermally induced native defect transform in annealed GaSb

    NASA Astrophysics Data System (ADS)

    Jie, Su; Tong, Liu; Jing-Ming, Liu; Jun, Yang; Yong-Biao, Bai; Gui-Ying, Shen; Zhi-Yuan, Dong; Fang-Fang, Wang; You-Wen, Zhao

    2016-07-01

    Undoped p-type GaSb single crystals were annealed at 550–600 °C for 100 h in ambient antimony. The annealed GaSb samples were investigated by Hall effect measurement, glow discharge mass spectroscopy (GDMS), infrared (IR) optical transmission and photoluminescence (PL) spectroscopy. Compared with the as-grown GaSb single crystal, the annealed GaSb samples have lower hole concentrations and weak native acceptor related PL peaks, indicating the reduction of the concentration of gallium antisite related native acceptor defects. Consequently, the below gap infrared transmission of the GaSb samples is enhanced after the thermal treatment. The mechanism about the reduction of the native defect concentration and its influence on the material property were discussed. Project supported by the National Natural Science Foundation of China (Grant Nos. 61474104 and 61504131).

  11. Fragile structural transition in Mo3Sb7

    NASA Astrophysics Data System (ADS)

    Yan, J.-Q.; McGuire, M. A.; May, A. F.; Parker, D.; Mandrus, D. G.; Sales, B. C.

    2015-08-01

    Mo3Sb7 single crystals lightly doped with Cr, Ru, or Te are studied in order to explore the interplay between superconductivity, magnetism, and the cubic-tetragonal structural transition. The structural transition at 53 K is extremely sensitive to Ru or Te substitution which introduces additional electrons, but robust against Cr substitution. No sign of a structural transition was observed in superconducting Mo2.91Ru0.09Sb7 and Mo3Sb6.975Te0.025 . In contrast, 3 at.% Cr doping only slightly suppresses the structural transition to 48 K while leaving no trace of superconductivity above 1.8 K. Analysis of magnetic properties suggests that the interdimer interaction in Mo3Sb7 is near a critical value and essential for the structural transition. All dopants suppress the superconductivity of Mo3Sb7 . The tetragonal structure is not necessary for superconductivity.

  12. Recent progress in MBE grown HgCdTe materials and devices at UWA

    NASA Astrophysics Data System (ADS)

    Gu, R.; Lei, W.; Antoszewski, J.; Madni, I.; Umana-Menbreno, G.; Faraone, L.

    2016-05-01

    HgCdTe has dominated the high performance end of the IR detector market for decades. At present, the fabrication costs of HgCdTe based advanced infrared devices is relatively high, due to the low yield associated with lattice matched CdZnTe substrates and a complicated cooling system. One approach to ease this problem is to use a cost effective alternative substrate, such as Si or GaAs. Recently, GaSb has emerged as a new alternative with better lattice matching. In addition, implementation of MBE-grown unipolar n-type/barrier/n-type detector structures in the HgCdTe material system has been recently proposed and studied intensively to enhance the detector operating temperature. The unipolar nBn photodetector structure can be used to substantially reduce dark current and noise without impeding photocurrent flow. In this paper, recent progress in MBE growth of HgCdTe infrared material at the University of Western Australia (UWA) is reported, including MBE growth of HgCdTe on GaSb alternative substrates and growth of HgCdTe nBn structures.

  13. Spin dynamics simulations at AGS

    SciTech Connect

    Huang, H.; MacKay, W.W.; Meot, F.; Roser, T.

    2010-05-23

    To preserve proton polarization through acceleration, it is important to have a correct model of the process. It has been known that with the insertion of the two helical partial Siberian snakes in the Alternating Gradient Synchrotron (AGS), the MAD model of AGS can not deal with a field map with offset orbit. The stepwise ray-tracing code Zgoubi provides a tool to represent the real electromagnetic fields in the modeling of the optics and spin dynamics for the AGS. Numerical experiments of resonance crossing, including spin dynamics in presence of the snakes and Q-jump, have been performed in AGS lattice models, using Zgoubi. This contribution reports on various results so obtained.

  14. NMR investigation of Ag nanoparticles

    NASA Astrophysics Data System (ADS)

    Son, Kwanghyo; Jang, Zeehoon

    2013-01-01

    109Ag nuclear magnetic resonance (NMR) and relaxation measurements have been performed on two powder samples of Ag nanoparticles with average sizes of 20 nm and 80 nm. The measurements have been done in an external field of 9.4 T and in the temperature range 10 K < T < 280 K. The 109Ag NMR spectra for both samples have close to Lorentzian shapes and turn out to be mixtures of homogeneous and inhomogeneous lines. The linewidth Δ ν at room temperature is 1.3 kHz for both samples and gradually increases with decreasing temperature. Both the Knight shift ( K) and the nuclear spin-lattice relaxation rate (1/ T 1) are observed to be almost identical to the values reported for the bulk Ag metal, whereby the Korringa ratio R(= K 2 T 1 T/S) is found to be 2.0 for both samples in the investigated temperature range.

  15. Near-surface depletion of antimony during the growth of GaAsSb and GaAs/GaAsSb nanowires

    SciTech Connect

    Kauko, H.; Helvoort, A. T. J. van; Fimland, B. O.; Munshi, A. M.; Grieb, T.; Müller, K.; Rosenauer, A.

    2014-10-14

    The near-surface reduction of the Sb mole fraction during the growth of GaAsSb nanowires (NWs) and GaAs NWs with GaAsSb inserts has been studied using quantitative high-angle annular dark field scanning transmission electron microscopy (STEM). A model for diffusion of Sb in the hexagonal NWs was developed and employed in combination with the quantitative STEM analysis. GaAsSb NWs grown by Ga-assisted molecular beam epitaxy (MBE) and GaAs/GaAsSb NWs grown by Ga- and Au-assisted MBE were investigated. At the high temperatures employed in the NW growth, As-Sb exchange at and outward diffusion of Sb towards the surface take place, resulting in reduction of the Sb concentration at and near the surface in the GaAsSb NWs and the GaAsSb inserts. In GaAsSb NWs, an increasing near-surface depletion of Sb was observed towards the bottom of the NW due to longer exposure to the As beam flux. In GaAsSb inserts, an increasing change in the Sb concentration profile was observed with increasing post-insert axial GaAs growth time, resulting from a combined effect of radial GaAs overgrowth and diffusion of Sb. The effect of growth temperature on the diffusion of Sb in the GaAsSb inserts was identified. The consequences of these findings for growth optimization and the optoelectronic properties of GaAsSb are discussed.

  16. Thermoelectric Performance of Bi0.5Sb1.5Te3/Sb Composites Fabricated by Electroless Plating and Spark Plasma Sintering

    NASA Astrophysics Data System (ADS)

    Sie, F. R.; Hwang, C. S.; Kuo, C. H.; Chou, Y. W.; Yeh, C. H.; Ho, H. Y.; Lin, Y. L.; Lan, C. H.

    2015-06-01

    This study reports semi-metal/semi-conductor composites with enhanced thermoelectric performance that results from interface effects between Sb clusters and the Bi0.5Sb1.5Te3 matrix. The Sb clusters were dispersed on the surface of Bi0.5Sb1.5Te3 powders by electroless plating and then the powders were rapidly compacted by spark plasma sintering at 673 K and 50 MPa. The thermoelectric properties for Bi0.5Sb1.5Te3 and Bi0.5Sb1.5Te3/Sb bulk samples were measured in the temperature range of 300 K to 500 K. The electrical conductivity of Bi0.5Sb1.5Te3/Sb composites was enhanced at room temperature due to the increase in carrier concentration with increasing Sb content. The enhancement in the power factor of Bi0.5Sb1.5Te3/Sb composites was due to a high Seebeck coefficient at high measured temperature. Moreover, the Sb clusters acted as effective phonon scattering centers, which decreased the lattice thermal conductivity at high temperature. In comparison with Bi0.5Sb1.5Te3, the maximum value of ZT for Bi0.5Sb1.5Te3/Sb (2.8 wt.%) samples was enhanced from 0.21 to 0.54 at 500 K. Consequently, the optimal operation temperature of Bi0.5Sb1.5Te3/Sb composites shifted to higher temperature compared to that for Bi0.5Sb1.5Te3 bulk.

  17. Demonstration of Sn-seeded GaSb homo- and GaAs-GaSb heterostructural nanowires

    NASA Astrophysics Data System (ADS)

    Tornberg, Marcus; Mårtensson, Erik K.; Zamani, Reza R.; Lehmann, Sebastian; Dick, Kimberly A.; Gorji Ghalamestani, Sepideh

    2016-04-01

    The particle-assisted epitaxial growth of antimonide-based nanowires has mainly been realized using gold as the seed material. However, the Au-seeded epitaxial growth of antimonide-based nanowires such as GaSb nanowires presents several challenges such as for example direct nucleation issues and crystal structure tuning. Therefore, it is of great importance to understand the role of seed material choice and properties in the growth behavior of antimonide-based nanowires to obtain a deeper understanding and a better control on their formation processes. In this report, we have investigated the epitaxial growth of GaSb and GaAs-GaSb nanowires using in situ-formed tin seeds by means of metalorganic vapor phase epitaxy technique. This comprehensive report covers the growth of in situ-formed tin seeds and Sn-seeded GaSb nanowires on both GaAs and GaSb (111)B substrates, as well as GaAs-GaSb nanowires on GaAs (111)B substrates. The growth behavior and structural properties of the obtained GaSb nanowires are further investigated and compared with the Au-seeded counterparts. The results provided by this study demonstrate that Sn is a promising seed material for the growth of GaSb nanowires.

  18. Mannose-Capped Lipoarabinomannan from Mycobacterium tuberculosis Induces CD4+ T Cell Anergy via GRAIL.

    PubMed

    Sande, Obondo J; Karim, Ahmad F; Li, Qing; Ding, Xuedong; Harding, Clifford V; Rojas, Roxana E; Boom, W Henry

    2016-01-15

    Mycobacterium tuberculosis cell wall glycolipid, lipoarabinomannan, can inhibit CD4(+) T cell activation by downregulating the phosphorylation of key proximal TCR signaling molecules: Lck, CD3ζ, ZAP70, and LAT. Inhibition of proximal TCR signaling can result in T cell anergy, in which T cells are inactivated following an Ag encounter, yet remain viable and hyporesponsive. We tested whether mannose-capped lipoarabinomannan (LAM)-induced inhibition of CD4(+) T cell activation resulted in CD4(+) T cell anergy. The presence of LAM during primary stimulation of P25 TCR-transgenic murine CD4(+) T cells with M. tuberculosis Ag85B peptide resulted in decreased proliferation and IL-2 production. P25 TCR-transgenic CD4(+) T cells primed in the presence of LAM also exhibited decreased response upon restimulation with Ag85B. The T cell anergic state persisted after the removal of LAM. Hyporesponsiveness to restimulation was not due to apoptosis, generation of Foxp3-positive regulatory T cells, or inhibitory cytokines. Acquisition of the anergic phenotype correlated with upregulation of gene related to anergy in lymphocytes (GRAIL) protein in CD4(+) T cells. Inhibition of human CD4(+) T cell activation by LAM also was associated with increased GRAIL expression. Small interfering RNA-mediated knockdown of GRAIL before LAM treatment abrogated LAM-induced hyporesponsiveness. In addition, exogenous IL-2 reversed defective proliferation by downregulating GRAIL expression. These results demonstrate that LAM upregulates GRAIL to induce anergy in Ag-reactive CD4(+) T cells. Induction of CD4(+) T cell anergy by LAM may represent one mechanism by which M. tuberculosis evades T cell recognition. PMID:26667170

  19. A Brucella spp. Protease Inhibitor Limits Antigen Lysosomal Proteolysis, Increases Cross-Presentation, and Enhances CD8+ T Cell Responses.

    PubMed

    Coria, Lorena M; Ibañez, Andrés E; Tkach, Mercedes; Sabbione, Florencia; Bruno, Laura; Carabajal, Marianela V; Berguer, Paula M; Barrionuevo, Paula; Schillaci, Roxana; Trevani, Analía S; Giambartolomei, Guillermo H; Pasquevich, Karina A; Cassataro, Juliana

    2016-05-15

    In this study, we demonstrate that the unlipidated (U) outer membrane protein (Omp) 19 from Brucella spp. is a competitive inhibitor of human cathepsin L. U-Omp19 inhibits lysosome cathepsins and APC-derived microsome activity in vitro and partially inhibits lysosomal cathepsin L activity within live APCs. Codelivery of U-Omp19 with the Ag can reduce intracellular Ag digestion and increases Ag half-life in dendritic cells (DCs). U-Omp19 retains the Ag in Lamp-2(+) compartments after its internalization and promotes a sustained expression of MHC class I/peptide complexes in the cell surface of DCs. Consequently, U-Omp19 enhances Ag cross-presentation by DCs to CD8(+) T cells. U-Omp19 s.c. delivery induces the recruitment of CD11c(+)CD8α(+) DCs and monocytes to lymph nodes whereas it partially limits in vivo Ag proteolysis inside DCs. Accordingly, this protein is able to induce CD8(+) T cell responses in vivo against codelivered Ag. Antitumor responses were elicited after U-Omp19 coadministration, increasing survival of mice in a murine melanoma challenge model. Collectively, these results indicate that a cysteine protease inhibitor from bacterial origin could be a suitable component of vaccine formulations against tumors. PMID:27084100

  20. Systemic immunological tolerance to ocular antigens is mediated by TNF-related apoptosis-inducing ligand (TRAIL)-expressing CD8+ T cells*

    PubMed Central

    Griffith, Thomas S.; Brincks, Erik L.; Gurung, Prajwal; Kucaba, Tamara A.; Ferguson, Thomas A.

    2010-01-01

    Systemic immunological tolerance to Ag encountered in the eye restricts the formation of potentially damaging immune responses that would otherwise be initiated at other anatomical locations. We previously demonstrated that tolerance to Ag administered via the anterior chamber (AC) of the eye required FasL-mediated apoptotic death of inflammatory cells that enter the eye in response to the antigenic challenge. Moreover, the systemic tolerance induced after AC injection of Ag was mediated by CD8+ regulatory T cells. The present study examined the mechanism by which these CD8+ regulatory T cells mediate tolerance after AC injection of Ag. AC injection of Ag did not prime CD4+ T cells, and led to increased TRAIL expression by splenic CD8+ T cells. Unlike wildtype mice, Trail−/− or Dr5−/− mice did not develop tolerance to Ag injected into the eye, even though responding lymphocytes underwent apoptosis in the AC of the eyes of these mice. CD8+ T cells from Trail−/− mice that were first injected AC with Ag were unable to transfer tolerance to naïve recipient wildtype mice, but CD8+ T cells from AC-injected wildtype or Dr5−/− mice could transfer tolerance. Importantly, the transferred wildtype (Trail+/+) CD8+ T cells were also able to decrease the number of infiltrating inflammatory cells into the eye; however, Trail−/− CD8+ T cells were unable to limit the inflammatory cell ingress. Together, our data suggest that “helpless” CD8+ regulatory T cells generated after AC injection of Ag enforce systemic tolerance in a TRAIL-dependent manner to inhibit inflammation in the eye. PMID:21169546

  1. Thermal fuse for high-temperature batteries

    DOEpatents

    Jungst, Rudolph G.; Armijo, James R.; Frear, Darrel R.

    2000-01-01

    A thermal fuse, preferably for a high-temperature battery, comprising leads and a body therebetween having a melting point between approximately 400.degree. C. and 500.degree. C. The body is preferably an alloy of Ag--Mg, Ag--Sb, Al--Ge, Au--In, Bi--Te, Cd--Sb, Cu--Mg, In--Sb, Mg--Pb, Pb--Pd, Sb--Zn, Sn--Te, or Mg--Al.

  2. CD103+ dendritic cells suppress Helminth-driven Type 2 immunity through constitutive expression of IL-12

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Batf3-dependent CD103+ and CD8alpha+ dendritic cells (DCs) play a central role in the development of type 1 immune responses. However, their role in type 2 immunity remains unclear. We found that Th2 cell responses were enhanced in Batf3-/- mice responding to helminth parasite antigens (Ag). As a r...

  3. Ge2Sb2Te5/Sb superlattice-like thin film for high speed phase change memory application

    NASA Astrophysics Data System (ADS)

    Hu, Yifeng; Zou, Hua; Zhang, Jianhao; Xue, Jianzhong; Sui, Yongxing; Wu, Weihua; Yuan, Li; Zhu, Xiaoqin; Song, Sannian; Song, Zhitang

    2015-12-01

    In order to improve the operation speed of phase change memory (PCM), superlattice-like Ge2Sb2Te5/Sb (SLL GST/Sb) thin films were prepared in a sputtering method to explore the suitability as an active material for PCM application. Compared with GST, SLL GST/Sb thin film has a lower crystallization temperature, crystallization activation energy, thermal conductivity, and smaller crystalline grain size. A faster SET/RESET switching speed (10 ns) and a lower operation power consumption (the energy for RESET operation 9.1 × 10-13 J) are obtained. In addition, GST/Sb shows a good endurance of 8.3 × 104 cycles.

  4. Effect of antimony nano-scale surface-structures on a GaSb/AlAsSb distributed Bragg reflector

    SciTech Connect

    Husaini, S.; Shima, D.; Ahirwar, P.; Rotter, T. J.; Hains, C. P.; Dang, T.; Bedford, R. G.; Balakrishnan, G.

    2013-02-11

    Effects of antimony crystallization on the surface of GaSb during low temperature molecular beam epitaxy growth are investigated. The geometry of these structures is studied via transmission electron and atomic force microscopies, which show the surface metal forms triangular-shaped, elongated nano-wires with a structured orientation composed entirely of crystalline antimony. By depositing antimony on a GaSb/AlAsSb distributed Bragg reflector, the field is localized within the antimony layer. Polarization dependent transmission measurements are carried out on these nano-structures deposited on a GaSb/AlAsSb distributed Bragg reflector. It is shown that the antimony-based structures at the surface favor transmission of light polarized perpendicular to the wires.

  5. Ohmic Contacts to n-type GaSb and n-type GaInAsSb

    SciTech Connect

    R.K. Huang; C.A. Wang; C.T. Harris; M.K. Connors; D.A. Shiau

    2003-06-16

    An investigation with the objective of improving n-type ohmic contacts to GaSb-based devices is described. This study involves a series of n-GaInAsSb and n-GaSb samples with varying doping, grown on both n-GaSb and semi-insulating GaAs substrates. These samples were fabricated into mesa-etched TLM structures, and the specific contact resistivity and sheet resistance of these layers as a function of majority electron concentration were measured. Extremely low specific contact resistivities of about 2 x 10{sup -6} {Omega}-cm{sup 2} and sheet resistances of about 4 {Omega}/{open_square} are found for n-type GaInAsSb doped at about 3 x 10{sup 18} cm{sup -3}.

  6. Ag@Au core-shell dendrites: a stable, reusable and sensitive surface enhanced Raman scattering substrate

    NASA Astrophysics Data System (ADS)

    Jun Yin, Hong; Yang Chen, Zhao; Mei Zhao, Yong; Yang Lv, Ming; An Shi, Chun; Long Wu, Zheng; Zhang, Xin; Liu, Luo; Li Wang, Ming; Jun Xu, Hai

    2015-09-01

    Surface enhanced Raman scattering (SERS) substrate based on fabricated Ag@Au core-shell dendrite was achieved. Ag dendrites were grown on Si wafer by the hydrothermal corrosion method and Au nanofilm on the surface of Ag dendritic nanostructure was then fabricated by chemical reduction. With the help of sodium borohydride in water, Au surface absorbates such as thiophene, adenine, rhodamine, small anions (Br- and I-), and a polymer (PVP, poly(N-vinylpyrrolidone)) can be completely and rapidly removed. After four repeatable experiments, the substrate SERS function did not decrease at all, indicating that the Ag@Au dendrite should be of great significance to SERS application because it can save much resource. Six-month-duration stability tests showed that the Ag@Au core-shell dendrite substrate is much more stable than the Ag dendrite substrates. We have also experimented on fast detection of Cd2+ at 10-8  M concentration by decorating single-stranded DNA containing adenine and guanine bases on the surface of this Ag@Au dendrite. Finite-difference time-domain simulations were carried out to investigate the influence of Au nanolayer on Ag dendrites, which showed that the local electric fields and enhancement factor are hardly affected when a 4 nm Au nanolayer is coated on Ag dendrite surface.

  7. Ag@Au core-shell dendrites: a stable, reusable and sensitive surface enhanced Raman scattering substrate.

    PubMed

    Yin, Hong Jun; Chen, Zhao Yang; Zhao, Yong Mei; Lv, Ming Yang; Shi, Chun An; Wu, Zheng Long; Zhang, Xin; Liu, Luo; Wang, Ming Li; Xu, Hai Jun

    2015-01-01

    Surface enhanced Raman scattering (SERS) substrate based on fabricated Ag@Au core-shell dendrite was achieved. Ag dendrites were grown on Si wafer by the hydrothermal corrosion method and Au nanofilm on the surface of Ag dendritic nanostructure was then fabricated by chemical reduction. With the help of sodium borohydride in water, Au surface absorbates such as thiophene, adenine, rhodamine, small anions (Br(-) and I(-)), and a polymer (PVP, poly(N-vinylpyrrolidone)) can be completely and rapidly removed. After four repeatable experiments, the substrate SERS function did not decrease at all, indicating that the Ag@Au dendrite should be of great significance to SERS application because it can save much resource. Six-month-duration stability tests showed that the Ag@Au core-shell dendrite substrate is much more stable than the Ag dendrite substrates. We have also experimented on fast detection of Cd(2+) at 10(-8) M concentration by decorating single-stranded DNA containing adenine and guanine bases on the surface of this Ag@Au dendrite. Finite-difference time-domain simulations were carried out to investigate the influence of Au nanolayer on Ag dendrites, which showed that the local electric fields and enhancement factor are hardly affected when a 4 nm Au nanolayer is coated on Ag dendrite surface. PMID:26412773

  8. Ag@Au core-shell dendrites: a stable, reusable and sensitive surface enhanced Raman scattering substrate

    PubMed Central

    Jun Yin, Hong; Yang Chen, Zhao; Mei Zhao, Yong; Yang Lv, Ming; An Shi, Chun; Long Wu, Zheng; Zhang, Xin; Liu, Luo; Li Wang, Ming; Jun Xu, Hai

    2015-01-01

    Surface enhanced Raman scattering (SERS) substrate based on fabricated Ag@Au core-shell dendrite was achieved. Ag dendrites were grown on Si wafer by the hydrothermal corrosion method and Au nanofilm on the surface of Ag dendritic nanostructure was then fabricated by chemical reduction. With the help of sodium borohydride in water, Au surface absorbates such as thiophene, adenine, rhodamine, small anions (Br– and I–), and a polymer (PVP, poly(N-vinylpyrrolidone)) can be completely and rapidly removed. After four repeatable experiments, the substrate SERS function did not decrease at all, indicating that the Ag@Au dendrite should be of great significance to SERS application because it can save much resource. Six-month-duration stability tests showed that the Ag@Au core-shell dendrite substrate is much more stable than the Ag dendrite substrates. We have also experimented on fast detection of Cd2+ at 10−8  M concentration by decorating single-stranded DNA containing adenine and guanine bases on the surface of this Ag@Au dendrite. Finite-difference time-domain simulations were carried out to investigate the influence of Au nanolayer on Ag dendrites, which showed that the local electric fields and enhancement factor are hardly affected when a 4 nm Au nanolayer is coated on Ag dendrite surface. PMID:26412773

  9. Inductively Coupled Plasma Reactive Ion Etching of AlGaAsSb and InGaAsSb for Quaternary Antimonide MIM Thermophotovoltaics

    SciTech Connect

    Palmisiano, M. N.; Peake, G. M.; Shul, R. J.; Ashby, C. I.; Cederberg, J. G.; Hafich, M. J.; Biefeld, R. M.

    2002-10-01

    In this letter we report on the inductively coupled plasma reactive ion etching (ICP-RIE) of InGaAsSb and AlGaAsSb for the fabrication of quaternary monolithic interconnected module (MIM) thermophotovoltaic (TPV) devices. A rapid dry etch process is described that produces smooth surfaces using BCl[sub]3 for AlGaAsSb and InGaAsSb capped with GaSb. Uncapped InGaAsSb was etched by adding an H[sub]2 plasma preclean to reduce surface oxides. InGaAsSb etch rate was studied as a function of accelerating voltage, RF power, temperature and pressure. The etch conditions found for InGaAsSb were used for AlGaAsSb etching to determine the effectiveness for isolation of the MIM cells.

  10. Enhanced separation efficiency of photoinduced charges for antimony-doped tin oxide (Sb-SnO2)/TiO2 heterojunction semiconductors with varied Sb doping concentration

    NASA Astrophysics Data System (ADS)

    Zhang, Zhen-Long; Ma, Wen-Hai; Mao, Yan-Li

    2014-09-01

    In this paper, antimony-doped tin oxide (Sb-SnO2) nanoparticles were synthesized with varied Sb doping concentration, and the Sb-SnO2/TiO2 heterojunction semiconductors were prepared with Sb-SnO2 and TiO2. The separation efficiency of photoinduced charges was characterized with surface photovoltage (SPV) technique. Compared with Sb-SnO2 and TiO2, Sb-SnO2/TiO2 presents an enhanced separation efficiency of photoinduced charges, and the SPV enhancements were estimated to be 1.40, 1.43, and 1.99 for Sb-SnO2/TiO2 composed of Sb-SnO2 with the Sb doping concentration of 5%, 10%, and 15%, respectively. To understand the enhancement, the band structure of Sb-SnO2 and TiO2 in the heterojunction semiconductor was determined, and the conduction band offsets (CBO) between Sb-SnO2 and TiO2 were estimated to be 0.56, 0.64, and 0.98 eV for Sb-SnO2/TiO2 composed of Sb-SnO2 with the Sb doping concentration of 5%, 10%, and 15%, respectively. These results indicate that the separation efficiency enhancement is resulting from the energy level matching, and the increase of enhancement is due to the rising of CBO.

  11. Maximizing SB3 Waste Throughput Melt Rate Tests

    SciTech Connect

    Smith, M. E.; Miller, D. H.

    2005-09-01

    The Defense Waste Processing Facility (DWPF) is presently vitrifying Sludge Batch 3 (SB3) and preparing to process Sludge Batch 4 (SB4) in late 2006 or early 2007. Previous laboratory testing and DWPF operational experience has indicated that the maximum waste throughput peak for the Sludge Batch 2 (SB2) system occurs at a waste loading in the mid-30's. This trend has been shown as well for SB3 on a lab-scale basis. These SB3 tests used SRAT product that targeted a REDuction/OXidation (REDOX) of 0.2 and an acid stoichiometry of 135%. Acid stoichiometry, however, has been shown to impact melt rate of MRF tests at one waste loading (35%). Due to the impact of acid stoichiometry on melt rate, it is possible that the current target acid stoichiometry (155%) with SB3 may not exhibit the same maximum waste throughput peak, or there may not even be a discernable peak. In fact, current DWPF operational experience with SB3 and Frit 418 has not shown the same drop off in melt rate and hence waste throughput as was observed with SB2 and Frit 320. The objective of this testing is to determine if increasing the overall alkali content in the feed (via using the higher alkali Frit 320 versus Frit 418) will either result in a shift in the waste throughput to higher waste loadings or an increase in the overall waste throughput at waste loadings of interest (31 to 41%). For these tests, the target Sludge Receipt and Adjustment Tank (SRAT) product REDOX was 0.2 and the target acid stoichiometry was 155%. The incentive for this series of tests stems from a previous Slurry-Fed Melt Rate Furnace (SMRF) test with SB3/Frit 320 feed which showed an increase in melt rate versus SB3/Frit 418 at 35% waste loading. This single data point suggests that overall waste throughput for the SB3/Frit 320 system is higher at 35% waste loading (i.e., the melt rate versus waste loading curve has potentially shifted upward). To address the potential shift in waste throughput, the strategy was to fully

  12. Strong magnetization damping induced by Ag nanostructures in Ag/NiFe/Ag trilayers

    NASA Astrophysics Data System (ADS)

    Ley Domínguez, D.; da Silva, G. L.; Rodríguez-Suárez, R. L.; Rezende, S. M.; Azevedo, A.

    2013-07-01

    Ferromagnetic resonance has been used to investigate the magnetization relaxation in trilayers of Ag(t)/NiFe(10 nm)/Ag(t), sputter deposited on Si(001) where the thickness of the Ag layer varied from 0 nm to 24 nm. In the first stages of formation, the Ag layers form islands that work as mold to imprint defects or inhomogeneities on the NiFe film surface. The magnetic inhomogeneities and defects imprinted on the surface of the NiFe film act as extrinsic sources of magnetization relaxation in addition to the intrinsic Gilbert damping mechanism. Weak inhomogeneities are associated to the two-magnon scattering source and the strong inhomogeneities are associated to the fluctuations of the local magnetization. By adding the three different sources of magnetization damping, we were able to explain the azimuthal dependence of the ferromagnetic resonance linewidth.

  13. CD8+ CD28− and CD8+ CD57+ T cells and their role in health and disease

    PubMed Central

    Strioga, Marius; Pasukoniene, Vita; Characiejus, Dainius

    2011-01-01

    Chronic antigenic stimulation leads to gradual accumulation of late-differentiated, antigen-specific, oligoclonal T cells, particularly within the CD8+ T-cell compartment. They are characterized by critically shortened telomeres, loss of CD28 and/or gain of CD57 expression and are defined as either CD8+CD28− or CD8+CD57+ T lymphocytes. There is growing evidence that the CD8+CD28− (CD8+CD57+) T-cell population plays a significant role in various diseases or conditions, associated with chronic immune activation such as cancer, chronic intracellular infections, chronic alcoholism, some chronic pulmonary diseases, autoimmune diseases, allogeneic transplantation, as well as has a great influence on age-related changes in the immune system status. CD8+CD28− (CD8+CD57+) T-cell population is heterogeneous and composed of various functionally competing (cytotoxic and immunosuppressive) subsets thus the overall effect of CD8+CD28− (CD8+CD57+) T-cell-mediated immunity depends on the predominance of a particular subset. Many articles claim that CD8+CD28− (CD8+CD57+) T cells have lost their proliferative capacity during process of replicative senescence triggered by repeated antigenic stimulation. However recent data indicate that CD8+CD28− (CD8+CD57+) T cells can transiently up-regulate telomerase activity and proliferate under certain stimulation conditions. Similarly, conflicting data is provided regarding CD8+CD28− (CD8+CD57+) T-cell sensitivity to apoptosis, finally leading to the conclusion that this T-cell population is also heterogeneous in terms of its apoptotic potential. This review provides a comprehensive approach to the CD8+CD28− (CD8+CD57+) T-cell population: we describe in detail its origins, molecular and functional characteristics, subsets, role in various diseases or conditions, associated with persistent antigenic stimulation. PMID:21711350

  14. Targeting with bovine CD154 enhances humoral immune responses induced by a DNA vaccine in sheep.

    PubMed

    Manoj, Sharmila; Griebel, Philip J; Babiuk, Lorne A; van Drunen Littel-van den Hurk, Sylvia

    2003-01-15

    CD40-CD154 interactions play an important role in regulating humoral and cell-mediated immune responses. Recently, these interactions have been exploited for the development of therapeutic and preventive treatments. The objective of this study was to test the ability of bovine CD154 to target a plasmid-encoded Ag to CD40-expressing APCs. To achieve this, a plasmid coding for bovine CD154 fused to a truncated secreted form of bovine herpesvirus 1 glycoprotein D (tgD), pSLIAtgD-CD154, was constructed. The chimeric tgD-CD154 was expressed in vitro in COS-7 cells and reacted with both glycoprotein D- and CD154-specific Abs. Both tgD and tgD-CD154 were capable of binding to epithelial cells, whereas only tgD-CD154 bound to B cells. Furthermore, dual-labeling of ovine PBMCs revealed that tgD-CD154 was bound by primarily B cells. The functional integrity of the tgD-CD154 chimera was confirmed by the induction of both IL-4-dependent B cell proliferation and tgD-specific lymphoproliferative responses in vitro. Finally, sheep immunized with pSLIAtgD-CD154 developed a more rapid primary tgD-specific Ab response and a significantly stronger tgD-specific secondary response when compared with animals immunized with pSLIAtgD and control animals. Similarly, virus-neutralizing Ab titers were significantly higher after secondary immunization with pSLIAtgD-CD154. These results demonstrate that using CD154 to target plasmid-expressed Ag can significantly enhance immune responses induced by a DNA vaccine. PMID:12517965

  15. Photoelectrochemical Properties of Nanocrystalline Sb6O13, MgSb2O6, and ZnSb2O6-Based Electrodes for Dye-Sensitized Solar Cells

    NASA Astrophysics Data System (ADS)

    Jang, Jiyeon; Kim, Seung-Joo

    2012-10-01

    Three kinds of antimony compounds - Sb6O13, MgSb2O6 and ZnSb2O6 - were prepared in the form of nanocrystalline film and their photo-electrochemical properties were investigated. The preparation of Sb6O13 was based on thermolysis of a colloidal Sb2O5·4H2O suspension. MgSb2O6 and ZnSb2O6 were prepared via low-temperature hydrothermal methods. All the compounds exhibited semiconducting properties applicable to dye-sensitized solar cell (DSSC). The energy band gaps were estimated to be 3.39 eV for Sb6O13, 3.60 eV for MgSb2O6, and 3.31 eV for ZnSb2O6, respectively. After sensitization with a conventional ruthenium-dye (N719), Sb6O13-based solar cell exhibited the highest open circuit voltage (Voc = 0.76 V) whereas the Voc values (0.44-0.46 V) of MgSb2O6 and ZnSb2O6 are relatively low. The Voc values were proven to be related to the flat band potentials of the antimony compounds. The overall solar-to-electric energy conversion efficiencies were in the range of 0.7-1.0% under AM 1.5, 100 mW/cm2 illumination.

  16. The reaction mechanism of SnSb and Sb thin film anodes for Na-ion batteries studied by X-ray diffraction, 119Sn and 121Sb Mössbauer spectroscopies

    DOE PAGESBeta

    Baggetto, Loïc; Hah, Hien-Yoong; Jumas, Jean-Claude; Johnson, Charles E.; Johnson, Jacqueline A.; Keum, Jong K.; Bridges, Craig A.; Veith, Gabriel M.

    2014-06-01

    The electrochemical reaction of Sb and SnSb anode materials with Na results in the formation of amorphous materials. To understand the resulting phases and electrochemical capacities we studied the reaction products local order using 119Sn and 121Sb Mössbauer spectroscopies in conjunction with measurements performed on model powder compounds of Na-Sn and Na-Sb to further clarify the reactions steps. For pure Sb the discharge (sodiation) starts with the formation of an amorphous phase composed of atomic environments similar to those found in NaSb, and proceeds further by the formation of environments similar to that present in Na3Sb. The reversible reaction takesmore » place during a large portion of the charge process. At full charge the anode material still contains a substantial fraction of Na, which explains the lack of recrystallization into crystalline Sb. The reaction of SnSb yields Na3Sb crystalline phase at full discharge at higher temperatures (65 and 95°C) while the room temperature reaction yields amorphous compounds. The electrochemically-driven, solid-state amorphization reaction occurring at room temperature is governed by the simultaneous formation of Na-coordinated Sn and Sb environments, as monitored by the decrease (increase) of the 119Sn (121Sb) Mössbauer isomer shifts. Overall, the monitoring of the hyperfine parameters enables to correlate the changes in Na content to the individual Sn and Sb local chemical environments.« less

  17. Synthesis of Ag(2) S-Ag nanoprisms and their use as DNA hybridization probes.

    PubMed

    Liu, Bing; Ma, Zhanfang

    2011-06-01

    A simple synthetic route to prepare Ag(2) S-Ag nanoprisms consists of the facile addition of Na(2) S to a solution of triangular Ag nanoprisms. The resulting Ag(2) S-Ag nanoparticles are more stable in solution than the original Ag nanoprisms, and two surface plasmon resonance (SPR) bands of the original Ag nanoprisms still remain. In addition, the SPR bands of the Ag(2) S-Ag nanoprisms are tunable over a wide range. The Ag(2) S-Ag nanoprisms can be directly bioconjugated via well-established stable Ag(2) S surface chemistry with readily available sulfur coupling agents. The nanoprisms are used in the hybridization of functionalized oligonucleotides, and show promise as probes for future biosensing applications. PMID:21538868

  18. Ag(I)-Catalyzed Indolization/C3-Functionalization Cascade of 2-Ethynylanilines via Ring Opening of Donor-Acceptor Cyclopropanes.

    PubMed

    Karmakar, Raju; Suneja, Arun; Singh, Vinod K

    2016-06-01

    A AgSbF6-catalyzed cascade involving the ring opening of donor-acceptor cyclopropanes (DACs) preceded by the cyclization of N-protected 2-ethynylaniline is described. The method discloses a step-economy route to 2,3-disubstituted indole, where a Ag catalyst is found to trigger the cascade by activating both alkyne and DACs. Various functionalities at different ends of both substrates offer rapid access to 2,3-disubstituted indole derivatives in one pot in good to excellent yields. Elaboration of the cascade product to useful intermediates is also depicted. PMID:27186903

  19. Subthreshold behavior of AlInSb/InSb high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Theodore Chandra, S.; B. Balamurugan, N.; G. Lakshmi, Priya; Manikandan, S.

    2015-07-01

    We propose a scaling theory for single gate AlInSb/InSb high electron mobility transistors (HEMTs) by solving the two-dimensional (2D) Poisson equation. In our model, the effective conductive path effect (ECPE) is taken into account to overcome the problems arising from the device scaling. The potential in the effective conducting path is developed and a simple scaling equation is derived. This equation is solved to obtain the minimum channel potential Φdeff,min and the new scaling factor α to model the subthreshold behavior of the HEMTs. The developed model minimizes the leakage current and improves the subthreshold swing degradation of the HEMTs. The results of the analytical model are verified by numerical simulation with a Sentaurus TCAD device simulator. Project supported by the Council of Scientific & Industrial Research (CSIR), Government of India under the SRF Scheme (Sanction Letter No: 08/237(0005)/2012-EMR-I).

  20. Lattice thermal conductivity of Bi, Sb, and Bi-Sb alloy from first principles

    NASA Astrophysics Data System (ADS)

    Lee, Sangyeop; Esfarjani, Keivan; Mendoza, Jonathan; Dresselhaus, Mildred S.; Chen, Gang

    2014-02-01

    Using first principles, we calculate the lattice thermal conductivity of Bi, Sb, and Bi-Sb alloys, which are of great importance for thermoelectric and thermomagnetic cooling applications. Our calculation reveals that the ninth-neighbor harmonic and anharmonic force constants are significant; accordingly, they largely affect the lattice thermal conductivity. Several features of the thermal transport in these materials are studied: (1) the relative contributions from phonons and electrons to the total thermal conductivity as a function of temperature are estimated by comparing the calculated lattice thermal conductivity to the measured total thermal conductivity, (2) the anisotropy of the lattice thermal conductivity is calculated and compared to that of the electronic contribution in Bi, and (3) the phonon mean free path distributions, which are useful for developing nanostructures to reduce the lattice thermal conductivity, are calculated. The phonon mean free paths are found to range from 10 to 100 nm for Bi at 100 K.