Isotope shift of 40,42,44,48Ca in the 4s 2S1/2 → 4p 2P3/2 transition

NASA Astrophysics Data System (ADS)

Gorges, C.; Blaum, K.; Frömmgen, N.; Geppert, Ch; Hammen, M.; Kaufmann, S.; Krämer, J.; Krieger, A.; Neugart, R.; Sánchez, R.; Nörtershäuser, W.

2015-12-01

We report on improved isotope shift measurements of the isotopes {}{40,42,{44,48}}Ca in the 4{{s}}{ }2{{{S}}}1/2\\to 4{{p}}{ }2{{{P}}}3/2 (D2) transition using collinear laser spectroscopy. Accurately known isotope shifts in the 4{{s}}{ }2{{{S}}}1/2\\to 4{{p}}{ }2{{{P}}}1/2(D1) transition were used to calibrate the ion beam energy with an uncertainty of {{Δ }}U≈ +/- 0.25 {{V}}. The accuracy in the D2 transition was improved by a factor of 5-10. A King-plot analysis of the two transitions revealed that the field shift factor in the D2 line is about 1.8(13)% larger than in the D1 transition which is ascribed to relativistic contributions of the 4{{{p}}}1/2 wave function.

Rational synthesis of high nuclearity Mo/Fe/S clusters: the reductive coupling approach in the convenient synthesis of (Cl(4)-cat)(2)Mo(2)Fe(6)S(8)(PR(3))(6) [R = Et, (n)Pr, (n)Bu] and the new [(Cl(4)-cat)(2)Mo(2)Fe(2)S(3)O(PEt(3))(3)Cl]-1/2(Fe(PEt(3))(2)(MeCN)(4)) and (Cl(4)-cat)(2)Mo(2)Fe(3)S(5)(PEt(3))(5) clusters.

PubMed

Han, J; Koutmos, M; Ahmad, S A; Coucouvanis, D

2001-11-05

A general method for the synthesis of high nuclearity Mo/Fe/S clusters is presented and involves the reductive coupling of the (Et(4)N)(2)[(Cl(4)-cat)MoOFeS(2)Cl(2)] (I) and (Et(4)N)(2)[Fe(2)S(2)Cl(4)] (II) clusters. The reaction of I and II with Fe(PR(3))(2)Cl(2) or sodium salts of noncoordinating anions such as NaPF(6) or NaBPh(4) in the presence of PR(3) (R = Et, (n)Pr, or (n)Bu) affords (Cl(4)-cat)(2)Mo(2)Fe(6)S(8)(PR(3))(6) [R = Et (IIIa), (n)Pr (IIIb), (n)Bu (IIIc)], Fe(6)S(6)(PEt(3))(4)Cl(2) (IV) and (PF(6))[Fe(6)S(8)(P(n)Pr(3))(6)] (V) as byproducts. The isolation of (Et(4)N)[Fe(PEt(3))Cl(3)] (VI), NaCl, and SPEt(3) supports a reductive coupling mechanism. Cluster IV and V also have been synthesized by the reductive self-coupling of compound II. The reductive coupling reaction between I and II by PEt(3) and NaPF(6) in a 1:1 ratio produces the (Et(4)N)(2)[(Cl(4)-cat)Mo(L)Fe(3)S(4)Cl(3)] clusters [L = MeCN (VIIa), THF (VIIb)]. The hitherto unknown [(Cl(4)-cat)(2)Mo(2)Fe(2)S(3)O(PEt(3))(3)Cl](+) cluster (VIII) has been isolated as the 2:1 salt of the (Fe(PEt(3))(2)(MeCN)(4))(2+) cation after the reductive self-coupling reaction of I in the presence of Fe(PEt(3))(2)Cl(2). Cluster VIII crystallizes in the monoclinic space group P2(1)/c with a = 11.098(3) A, b = 22.827(6) A, c = 25.855(6) A, beta = 91.680(4) degrees, and Z = 4. The formal oxidation states of metal atoms in VIII have been assigned as Mo(III), Mo(IV), Fe(II), and Fe(III) on the basis of zero-field Mössbauer spectra. The Fe(PEt(3))(2)(MeCN)(4) cation of VIII is also synthesized independently, isolated as the BPh(4)(-) salt (IX), and has been structurally characterized. The reductive coupling of compound I also affords in low yield the new (Cl(4)-cat)(2)Mo(2)Fe(3)S(5)(PEt(3))(5) cluster (X) as a byproduct. Cluster X crystallizes in the monoclinic space group P2(1)/n with a = 14.811(3) A, b = 22.188(4) A, c = 21.864(4) A, beta = 100.124(3) degrees, and Z = 4 and the structure shows very short Mo

Synthesis of the new quaternary sulfides K[sub 2]Y[sub 4]Sn[sub 2]S[sub 11] and BaLnAgS[sub 3] (Ln = Er, Y, Gd) and the structures of K[sub 2]Y[sub 4]Sn[sub 2]S[sub 11] and BaErAgS[sub 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Wu, Ping; Ibers, J.A.

1994-05-01

Several new quarternary sulfides, K[sub 2]Y[sub 4]Sn[sub 2]S[sub 11] and BaLnAgS[sub 3] (Ln = Er, Y, Gd), have been synthesized by the reaction of the constituent binary chalcogenides and elements at 1000[degrees]C. The crystal structures of K[sub 2]Y[sub 4]Sn[sub 2]S[sub 11] and BaErAgS[sub 3] have been determined by single-crystal X-ray diffraction techniques. Crystal data: K[sub 2]Y[sub 4]Sn[sub 2]S[sub 11]-space group D[sup 8][sub 4h] - P4/ncc, M = 1023.88, Z = 4, a = 8.587(1), c = 27.892(4) [angstrom] (T = 115 K), V = 2056.7(4) [angstrom][sup 3], R[sub W](F[sup 2]) = 0.093 for 1965 observations having F[sup 2][sub 0] >more » 2[sigma](F[sup 2][sub 0]); BaEr AgS[sub 3]-space group C[sup 3][sub 2H] - C2/m, M = 508.65, Z = 4, a = 17.340(4), b = 4.014(1), x = 8.509(2) [angstrom], [beta] = 103.23(3)[degrees], (T = 115 K), V = 576.5(2) [angstrom][sup 3], R[sub W](F[sup 2]) = 0.049 for 1404 observations and 48 variables, R(F) = 0.018 for 1299 observations having F[sup 2][sub 0] > 2[sigma](F[sup 2][sub 0]). In both structures, the rare-earth atoms have octahedral coordination and the octahedra form slabs through edge- and corner-sharing. These slabs are separated by K[sup +] Ba[sup 2+] cations, and are crosslinked into three-dimensional frameworks by Sn[sub 2]S[sub 6] units as edge-sharing SnS[sub 4] tetrahedral pairs in K[sub 2]Y[sub 4]Sn[sub 2]S[sub 11], and by Ag[sub 2]S[sub 9] units as corner-sharing trigonal-bipyramidal AgS[sub 5] pairs in BaEr AgS[sub 3]. From their powder diffraction patterns, BaYAgS[sub 3] and Ba GdAgS[sub 3] appear to be isostructural with BaErAgS[sub 3].« less

Structures of Exocyclic R,R- and S,S-N6,N6-(2,3-Dihydroxybutan-1,4-diyl)-2′-Deoxyadenosine Adducts Induced by 1,2,3,4-Diepoxybutane

PubMed Central

2015-01-01

1,3-Butadiene (BD) is an industrial and environmental chemical present in urban air and cigarette smoke, and is classified as a human carcinogen. It is oxidized by cytochrome P450 to form 1,2,3,4-diepoxybutane (DEB); DEB bis-alkylates the N6 position of adenine in DNA. Two enantiomers of bis-N6-dA adducts of DEB have been identified: R,R-N6,N6-(2,3-dihydroxybutan-1,4-diyl)-2′-deoxyadenosine (R,R-DHB-dA), and S,S-N6,N6-(2,3-dihydroxybutan-1,4-diyl)-2′-deoxyadenosine (S,S-DHB-dA) [SeneviratneU., AntsypovichS., DorrD. Q., DissanayakeT., KotapatiS., and TretyakovaN. (2010) Chem. Res. Toxicol.23, 1556−156720873715]. Herein, the R,R-DHB-dA and S,S-DHB-dA adducts have been incorporated into the 5′-d(C1G2G3A4C5X6A7G8A9A10G11)-3′:5′-d(C12T13T14C15T16T17G18T19C20C21G22)-3′ duplex [X6 = R,R-DHB-dA (R6) or S,S-DHB-dA (S6)]. The structures of the duplexes were determined by molecular dynamics calculations, which were restrained by experimental distances obtained from NMR data. Both the R,R- and S,S-DHB-dA adducts are positioned in the major groove of DNA. In both instances, the bulky 3,4-dihydroxypyrrolidine rings are accommodated by an out-of-plane rotation about the C6-N6 bond of the bis-alkylated adenine. In both instances, the directionality of the dihydroxypyrrolidine ring is evidenced by the pattern of NOEs between the 3,4-dihydroxypyrrolidine protons and DNA. Also in both instances, the anti conformation of the glycosyl bond is maintained, which combined with the out-of-plane rotation about the C6-N6 bond, allows the complementary thymine, T17, to remain stacked within the duplex, and form one hydrogen bond with the modified base, between the imine nitrogen of the modified base and the T17 N3H imino proton. The loss of the second Watson–Crick hydrogen bonding interaction at the lesion sites correlates with the lower thermal stabilities of the R,R- and S,S-DHB-dA duplexes, as compared to the corresponding unmodified duplex. The reduced base stacking at the

Transition probabilities for the 3s2 3p(2P0)-3s3p2(4P) intersystem lines of Si II

NASA Technical Reports Server (NTRS)

Calamai, Anthony G.; Smith, Peter L.; Bergeson, S. D.

1993-01-01

Intensity ratios of lines of the spin-changing 'intersystem' multiplet of S II (4P yields 2P0) at 234 nm have been used to determine electron densities and temperatures in a variety of astrophysical environments. However, the accuracy of these diagnostic calculations have been limited by uncertainties associated with the available atomic data. We report the first laboratory measurement, using an ion-trapping technique, of the radiative lifetimes of the three metastable levels of the 3s3p2 4P term of Si II. Our results are 104 +/- 16, 406 +/- 33, and 811 +/- 77 micro-s for lifetimes of the J = 1/2, 5/2, and 3/2 levels, respectively. A-values were derived from our lifetimes by use of measured branching fractions. Our A-values, which differ from calculated values by 30 percent or more, should give better agreement between modeled and observed Si II line ratios.

Band alignments of different buffer layers (CdS, Zn(O,S), and In{sub 2}S{sub 3}) on Cu{sub 2}ZnSnS{sub 4}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Yan, Chang; Liu, Fangyang; Song, Ning

2014-04-28

The heterojunctions of different n-type buffers, i.e., CdS, Zn(O,S), and In{sub 2}S{sub 3} on p-type Cu{sub 2}ZnSnS{sub 4} (CZTS) were investigated using X-ray Photoelectron Spectroscopy (XPS) and Near Edge X-ray Absorption Fine Structure (NEXAFS) Measurements. The band alignment of the heterojunctions formed between CZTS and the buffer materials was carefully measured. The XPS data were used to determine the Valence Band Offsets (VBO) of different buffer/CZTS heterojunctions. The Conduction Band Offset (CBO) was calculated indirectly by XPS data and directly measured by NEXAFS characterization. The CBO of the CdS/CZTS heterojunction was found to be cliff-like with CBO{sub XPS} = −0.24 ± 0.10 eV and CBO{submore » NEXAFS} = −0.18 ± 0.10 eV, whereas those of Zn(O,S) and In{sub 2}S{sub 3} were found to be spike-like with CBO{sub XPS} = 0.92 ± 0.10 eV and CBO{sub NEXAFS} = 0.87 ± 0.10 eV for Zn(O,S)/CZTS and CBO{sub XPS} = 0.41 ± 0.10 eV for In{sub 2}S{sub 3}/CZTS, respectively. The CZTS photovoltaic device using the spike-like In{sub 2}S{sub 3} buffer was found to yield a higher open circuit voltage (Voc) than that using the cliff-like CdS buffer. However, the CBO of In{sub 2}S{sub 3}/CZTS is slightly higher than the optimum level and thus acts to block the flow of light-generated electrons, significantly reducing the short circuit current (Jsc) and Fill Factor (FF) and thereby limiting the efficiency. Instead, the use of a hybrid buffer for optimization of band alignment is proposed.« less

Contribution of S4 segments and S4-S5 linkers to the low-voltage activation properties of T-type CaV3.3 channels.

PubMed

Sanchez-Sandoval, Ana Laura; Herrera Carrillo, Zazil; Díaz Velásquez, Clara Estela; Delgadillo, Dulce María; Rivera, Heriberto Manuel; Gomora, Juan Carlos

2018-01-01

Voltage-gated calcium channels contain four highly conserved transmembrane helices known as S4 segments that exhibit a positively charged residue every third position, and play the role of voltage sensing. Nonetheless, the activation range between high-voltage (HVA) and low-voltage (LVA) activated calcium channels is around 30-40 mV apart, despite the high level of amino acid similarity within their S4 segments. To investigate the contribution of S4 voltage sensors for the low-voltage activation characteristics of CaV3.3 channels we constructed chimeras by swapping S4 segments between this LVA channel and the HVA CaV1.2 channel. The substitution of S4 segment of Domain II in CaV3.3 by that of CaV1.2 (chimera IIS4C) induced a ~35 mV shift in the voltage-dependence of activation towards positive potentials, showing an I-V curve that almost overlaps with that of CaV1.2 channel. This HVA behavior induced by IIS4C chimera was accompanied by a 2-fold decrease in the voltage-dependence of channel gating. The IVS4 segment had also a strong effect in the voltage sensing of activation, while substitution of segments IS4 and IIIS4 moved the activation curve of CaV3.3 to more negative potentials. Swapping of IIS4 voltage sensor influenced additional properties of this channel such as steady-state inactivation, current decay, and deactivation. Notably, Domain I voltage sensor played a major role in preventing CaV3.3 channels to inactivate from closed states at extreme hyperpolarized potentials. Finally, site-directed mutagenesis in the CaV3.3 channel revealed a partial contribution of the S4-S5 linker of Domain II to LVA behavior, with synergic effects observed in double and triple mutations. These findings indicate that IIS4 and, to a lesser degree IVS4, voltage sensors are crucial in determining the LVA properties of CaV3.3 channels, although the accomplishment of this function involves the participation of other structural elements like S4-S5 linkers.

Contribution of S4 segments and S4-S5 linkers to the low-voltage activation properties of T-type CaV3.3 channels

PubMed Central

Sanchez-Sandoval, Ana Laura; Herrera Carrillo, Zazil; Díaz Velásquez, Clara Estela; Delgadillo, Dulce María; Rivera, Heriberto Manuel

2018-01-01

Voltage-gated calcium channels contain four highly conserved transmembrane helices known as S4 segments that exhibit a positively charged residue every third position, and play the role of voltage sensing. Nonetheless, the activation range between high-voltage (HVA) and low-voltage (LVA) activated calcium channels is around 30–40 mV apart, despite the high level of amino acid similarity within their S4 segments. To investigate the contribution of S4 voltage sensors for the low-voltage activation characteristics of CaV3.3 channels we constructed chimeras by swapping S4 segments between this LVA channel and the HVA CaV1.2 channel. The substitution of S4 segment of Domain II in CaV3.3 by that of CaV1.2 (chimera IIS4C) induced a ~35 mV shift in the voltage-dependence of activation towards positive potentials, showing an I-V curve that almost overlaps with that of CaV1.2 channel. This HVA behavior induced by IIS4C chimera was accompanied by a 2-fold decrease in the voltage-dependence of channel gating. The IVS4 segment had also a strong effect in the voltage sensing of activation, while substitution of segments IS4 and IIIS4 moved the activation curve of CaV3.3 to more negative potentials. Swapping of IIS4 voltage sensor influenced additional properties of this channel such as steady-state inactivation, current decay, and deactivation. Notably, Domain I voltage sensor played a major role in preventing CaV3.3 channels to inactivate from closed states at extreme hyperpolarized potentials. Finally, site-directed mutagenesis in the CaV3.3 channel revealed a partial contribution of the S4-S5 linker of Domain II to LVA behavior, with synergic effects observed in double and triple mutations. These findings indicate that IIS4 and, to a lesser degree IVS4, voltage sensors are crucial in determining the LVA properties of CaV3.3 channels, although the accomplishment of this function involves the participation of other structural elements like S4-S5 linkers. PMID:29474447

Photoionization of Cl+ from the 3s23p4 3P2,1,0 and the 3s23p4 1D2,1S0 states in the energy range 19-28 eV

NASA Astrophysics Data System (ADS)

McLaughlin, Brendan M.

2017-01-01

Absolute photoionization cross-sections for the Cl+ ion in its ground and the metastable states, 3s23p4 3P2,1,0 and 3s23p4 1D2,1S0, were measured recently at the Advanced Light Source at Lawrence Berkeley National Laboratory using the merged beams photon-ion technique at a photon energy resolution of 15 meV in the energy range 19-28 eV. These measurements are compared with large-scale Dirac-Coulomb R-matrix calculations in the same energy range. Photoionization of this sulphur-like chlorine ion is characterized by multiple Rydberg series of auto-ionizing resonances superimposed on a direct photoionization continuum. A wealth of resonance features observed in the experimental spectra is spectroscopically assigned, and their resonance parameters are tabulated and compared with the recent measurements. Metastable fractions in the parent ion beam are determined from this study. Theoretical resonance energies and quantum defects of the prominent Rydberg series 3s23p3nd, identified in the spectra as 3p → nd transitions, are compared with the available measurements made on this element. Weaker Rydberg series 3s23p3ns, identified as 3p → ns transitions and window resonances 3s3p4(4P)np features, due to 3s → np transitions, are also found in the spectra.

Heteromorphic NiCo2S4/Ni3S2/Ni Foam as a Self-Standing Electrode for Hydrogen Evolution Reaction in Alkaline Solution.

PubMed

Liu, Hui; Ma, Xiao; Rao, Yuan; Liu, Yang; Liu, Jialiang; Wang, Luyang; Wu, Mingbo

2018-04-04

Considerable works have been devoted on developing high-efficiency nonplatinum electrocatalysts for hydrogen evolution reaction (HER). Herein, 3D heteromorphic NiCo 2 S 4 /Ni 3 S 2 nanosheets network has been constructed on Ni foam (denoted as NiCo 2 S 4 /Ni 3 S 2 /NF) serving as a self-standing electrocatalyst through directly thermal sulfurization of a single-source NiCo-layered double hydroxide precursor. The resultant NiCo 2 S 4 /Ni 3 S 2 /NF electrode exhibits outstanding electrocatalytic HER performance with an extremely low onset overpotential of 15 mV and long-term durability in alkaline solution. Such enhanced HER performance can be credited to (1) the massive exposed active sites provided by mixed transition metal chalcogenides (NiCo 2 S 4 and Ni 3 S 2 ), (2) the strong interfacial interaction at NiCo 2 S 4 /Ni 3 S 2 heterojunction interfaces with the strengthened H binding, and (3) the porous highly conductive Ni foam substrate with accelerated electron transfer. This work opens up a new direction to fabricate effective and non-noble-metal electrodes for water splitting and hydrogen generation.

Investigation of magnetic properties on spin-ordering effects of FeGa2S4 and FeIn2S4

NASA Astrophysics Data System (ADS)

Myoung, Bo Ra; Lim, Jung Tae; Kim, Chul Sung

2017-09-01

We have studied crystal and magnetic properties of chalcogenides FeGa2S4 and FeIn2S4 with X-ray diffractometer (XRD), magnetic property measurement system (MPMS), magnetometer, physical property measurement system (PPMS), and Mössbauer spectrometer. The crystal structure has 2-dimension triangular lattice structure with P-3m1 of FeGa2S4, while FeIn2S4 has inverse spinel with space group Fd3m. The AC magnetic susceptibility measurements show that FeGa2S4 is an insulating spin glass material, exhibiting geometrical frustration, unlike in the antiferromagnetic [AFM] metallic spin glass FeIn2S4. From hysteresis (M-H) curves at 4.2 K, FeGa2S4 has spin-flop behavior with an angle of 120° of triangle, as against linear slope of FeIn2S4 due to anti-parallel spin. The gap energy by splitting of 5T2g, Δ1 and electric quadrupole splitting ΔEQ of FeIn2S4 are much higher than that of FeGa2S4 at 4.2 K because FeGa2S4 is geometrically frustrated magnet having degenerate ground state at low temperature.

Synthesis of ( 2S, 4S)-4-phenylamino-5-oxoproline derivatives.

PubMed

Nizova, I A; Krasnov, V P; Levit, G L; Kodess, M I

2002-01-01

The paper describes the synthesis of ( 2S, 4S)-4-(N-Ts)- and ( 2S, 4S)-4-(N-Boc)-phenylamino-5-oxoprolines (pyroglutamic acid). These derivatives have been shown to be useful for synthesis of their amides and peptides in spite of steric hindrances caused by bulky groups adjacent to the reaction centre. Under the conditions applied no lactam ring opening and no loss of stereochemical integrity of any of the chiral centres were observed, which has been confirmed by NMR techniques.

Determination of the 1s2{\\ell }2{{\\ell }}^{\\prime } state production ratios {{}^{4}P}^{o}/{}^{2}P, {}^{2}D/{}^{2}P and {{}^{2}P}_{+}/{{}^{2}P}_{-} from fast (1{s}^{2},1s2s\\,{}^{3}S) mixed-state He-like ion beams in collisions with H2 targets

NASA Astrophysics Data System (ADS)

Benis, E. P.; Zouros, T. J. M.

2016-12-01

New results are presented on the ratio {R}m={σ }{T2p}( {}4P)/{σ }{T2p}({}2P) concerning the production cross sections of Li-like 1s2s2p quartet and doublet P states formed in energetic ion-atom collisions by single 2p electron transfer to the metastable 1s2s {}3S component of the He-like ion beam. Spin statistics predict a value of R m = 2 independent of the collision system in disagreement with most reported measurements of {R}m≃ 1{--}9. A new experimental approach is presented for the evaluation of R m having some practical advantages over earlier approaches. It also allows for the determination of the separate contributions of ground- and metastable-state beam components to the measured spectra. Applying our technique to zero-degree Auger projectile spectra from 4.5 MeV {{{B}}}3+ (Benis et al 2002 Phys. Rev. A 65 064701) and 25.3 MeV {{{F}}}7+ (Zamkov et al 2002 Phys. Rev. A 65 062706) mixed state (1{s}2 {}1S,1s2s {}3S) He-like ion collisions with H2 targets, we report new values of {R}m=3.5+/- 0.4 for boron and {R}m=1.8+/- 0.3 for fluorine. In addition, the ratios of {}2D/{}2P and {{}2P}+/{{}2P}- populations from either the metastable and/or ground state beam component, also relevant to this analysis, are evaluated and compared to previously reported results for carbon collisions on helium (Strohschein et al 2008 Phys. Rev. A 77 022706) including a critical comparison to theory.

Computational chemistry of modified [MFe3S4] and [M2Fe2S4] clusters: assessment of trends in electronic structure and properties.

PubMed

Jensen, Kasper P; Ooi, Bee-Lean; Christensen, Hans E M

2008-12-18

The aim of this work is to understand the molecular evolution of iron-sulfur clusters in terms of electronic structure and function. Metal-substituted models of biological [Fe(4)S(4)] clusters in oxidation states [M(x)Fe(4-x)S(4)](3+/2+/1+) have been studied by density functional theory (M = Cr, Mn, Fe, Co, Ni, Cu, Zn, and Pd, with x = 1 or 2). Most of these clusters have not been characterized before. For those that have been characterized experimentally, very good agreement is obtained, implying that also the predicted structures and properties of new clusters are accurate. Mean absolute errors are 0.024 A for bond lengths ([Fe(4)S(4)], [NiFe(3)S(4)], [CoFe(3)S(4)]) and 0.09 V for shifts in reduction potentials relative to the [Fe(4)S(4)] cluster. All structures form cuboidal geometries similar to the all-iron clusters, except the Pd-substituted clusters, which instead form highly distorted trigonal and tetragonal local sites in compromised, pseudocuboidal geometries. In contrast to other electron-transfer sites, cytochromes, blue copper proteins, and smaller iron-sulfur clusters, we find that the [Fe(4)S(4)] clusters are very insensitive to metal substitution, displaying quite small changes in reorganization energies and reduction potentials upon substitution. Thus, the [Fe(4)S(4)] clusters have an evolutionary advantage in being robust to pollution from other metals, still retaining function. We analyze in detail the electronic structure of individual clusters and rationalize spin couplings and redox activity. Often, several configurations are very close in energy, implying possible use as spin-crossover systems, and spin states are predicted accurately in all but one case ([CuFe(3)S(4)]). The results are anticipated to be helpful in defining new molecular systems with catalytic and magnetic properties.

Cs 2 Hg 3 S 4 : A Low-Dimensional Direct Bandgap Semiconductor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Islam, Saiful M.; Vanishri, S.; Li, Hao

2015-01-13

Cs2Hg3S4 was synthesized by slowly cooling a melted stoichiometric mixture of Hg and Cs2S4. Cs2Hg3S4 crystallizes in the Ibam spacegroup with a = 6.278(1) angstrom, b = 11.601(2) angstrom, and c = 14.431(3)angstrom; d(calc) = 6.29 g/cm(3). Its crystal structure consists of straight chains of [Hg3S4](n)(2n-) that engage in side-by-side weak bonding interactions forming layers and are charge balanced by Cs+ cations. The thermal stability of this compound was investigated with differential thermal analysis and temperature dependent in situ synchrotron powder diffraction. The thermal expansion coefficients of the a, b, and c axes were assessed at 1.56 x 10(-5), 2.79more » x10(-5), and 3.04 x 10(-5) K-1, respectively. Large single-crystals up to similar to 5 cm in length and similar to 1 cm in diameter were grown using a vertical Bridgman method. Electrical conductivity and photoconductivity measurements on naturally cleaved crystals of Cs2Hg3S4 gave resistivity rho of >= 10(8) Omega.cm and carrier mobility-lifetime (mu tau) products of 4.2 x 10(-4) and 5.82 x 10(-5) cm(2) V-1 for electrons and holes, respectively. Cs2Hg3S4 is a semiconductor with a bandgap E-g similar to 2.8 eV and exhibits photoluminescence (PL) at low temperature. Electronic band structure calculations within the density functional theory (DFT) framework employing the nonlocal hybrid functional within Heyd-Scuseria-Ernzerhof (HSE) formalism indicate a direct bandgap of 2.81 eV at Gamma. The theoretical calculations show that the conduction band minimum has a highly dispersive and relatively isotropic mercury-based s-orbital-like character while the valence band maximum features a much less dispersive and more anisotropic sulfur orbital-based band.« less

(3,3-Difluoro-pyrrolidin-1-yl)-[(2S,4S)-(4-(4-pyrimidin-2-yl-piperazin-1-yl)-pyrrolidin-2-yl]-methanone: A potent, selective, orally active dipeptidyl peptidase IV inhibitor

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ammirati, Mark J.; Andrews, Kim M.; Boyer, David D.

2010-10-01

A series of 4-substituted proline amides was synthesized and evaluated as inhibitors of dipeptidyl pepdidase IV for the treatment of type 2 diabetes. (3,3-Difluoro-pyrrolidin-1-yl)-[(2S,4S)-(4-(4-pyrimidin-2-yl-piperazin-1-yl)-pyrrolidin-2-yl]-methanone (5) emerged as a potent (IC{sub 50} = 13 nM) and selective compound, with high oral bioavailability in preclinical species and low plasma protein binding. Compound 5, PF-00734200, was selected for development as a potential new treatment for type 2 diabetes.

Growth of In/sub 2/S/sub 3/ and CdIn/sub 2/S/sub 4/ single crystals from a solution in a melt

DOE Office of Scientific and Technical Information (OSTI.GOV)

Buzhor, V.P.; Lyalikova, R. Yu.; Radautsan, S.I.

1986-08-01

The authors studied the reaction of In/sub 2/S/sub 3/ and CdIn/sub 2/S/sub 4/ with melts based on cadmium chloride. As the initial materials, they used polycrystalline In/sub 2/S/sub 3/ and CdIn/sub 2/S/sub 4/, cadmium chloride, and cadmium sulfide. The studies were carried out by the method of thermal analysis in sealed quartz ampules on an MOM derivatotograph. The solubility curve of In/sub 2/S/sub 3/ in a cadmium chloride melt is given. Nucleation occurs both within the liquid pahse and on the walls of the reaction container. At cooling rates of 4-5 K/h, with a charge of 100 g in amore » reaction container of diameter 20 mm the authors obtained In/sub 2/S/sub 3/ and CdIn/sub 2/S/sub 4/ crystals measuring 10-12 mm in size.« less

Identification of the 1s2s2p 4P5/2-->1s22s 2S1/2 magnetic quadrupole inner-shell satellite line in the Ar16+ K-shell x-ray spectrum

NASA Astrophysics Data System (ADS)

Beiersdorfer, P.; Bitter, M.; Hey, D.; Reed, K. J.

2002-09-01

We have identified the dipole-forbidden 1s2s2p 4P5/2-->1s22s 2S1/2 transition in lithiumlike Ar15+ in high-resolution K-shell x-ray emission spectra recorded at the Livermore EBIT-II electron-beam ion trap and the Princeton National Spherical Tokamak Experiment. Unlike other Ar15+ satellite lines, which can be excited by dielectronic recombination, the line is exclusively excited by electron-impact excitation. Its predicted radiative rate is comparable to that of the well-known 1s2p 3P1-->1s2 1S0 magnetic quadrupole transition in heliumlike Ar16+. As a result, it can also only be observed in low-density plasma. We present calculations of the electron-impact excitation cross sections of the innershell excited Ar15+ satellite lines, including the magnetic sublevels needed for calculating the linear line polarization. We compare these calculations to the relative magnitudes of the observed 1s2s2p-->1s22s transitions and find good agreement, confirming the identification of the lithiumlike 1s2s2p 4P5/2-->1s22s 2S1/2 magnetic quadrupole line.

IR Li2Ga2GeS6 nanocrystallized GeS2-Ga2S3-Li2S electroconductive chalcogenide glass with good nonlinearity

PubMed Central

Liu, Qiming; Zhang, Peng

2014-01-01

GeS2-Ga2S3-Li2S electroconductive glasses were prepared by the conventional melt-quenching method through carefully controlling the heating rate. Comparing with the reference of glass-forming region, our investigated GeS2-Ga2S3-Li2S system was extended to the cation ratio of 0–20% Li with around 40% Ga. GeS2-Ga2S3-Li2S glass-ceramics containing IR Li2Ga2GeS6 nonlinear nanocrystals were obtained by the more carefully controlled heating rate. Its optical nonlinearity was investigated by the Maker fringe measurements, the maximum second harmonic intensity was observed to be 0.35 of the reference Z-cut quartz. IR Li2Ga2GeS6 nonlinear crystals were directly obtained at the composition of 40GeS2-30GaS1.5-30LiS0.5. PMID:25030713

Influence of the environment on the [4Fe-4S]2+ to [2Fe-2S]2+ cluster switch in the transcriptional regulator FNR.

PubMed

Crack, Jason C; Gaskell, Alisa A; Green, Jeffrey; Cheesman, Myles R; Le Brun, Nick E; Thomson, Andrew J

2008-02-06

In Escherichia coli, the switch between aerobic and anaerobic metabolism is primarily controlled by the fumarate and nitrate reduction transcriptional regulator FNR. In the absence of O2, FNR binds a [4Fe-4S]2+ cluster, generating a transcriptionally active dimeric form. Exposure to O2 results in the conversion of the cluster to a [2Fe-2S]2+ form, leading to dissociation of the protein into transcriptionally inactive monomers. The [4Fe-4S]2+ to [2Fe-2S]2+ cluster conversion proceeds in two steps. Step 1 involves the one-electron oxidation of the cluster, resulting in the release of Fe2+, generating a [3Fe-4S]1+ cluster intermediate, and a superoxide ion. In step 2, the cluster intermediate spontaneously rearranges to form the [2Fe-2S]2+ cluster, with the release of a Fe3+ ion and two sulfide ions. Here, we demonstrate that, in both native and reconstituted [4Fe-4S] FNR, the reaction environment and, in particular, the presence of Fe2+ and/or Fe3+ chelators can influence significantly the cluster conversion reaction. We demonstrate that while the rate of step 1 is largely insensitive to chelators, that of step 2 is significantly enhanced by both Fe2+ and Fe3+ chelators. We show that, for reactions in Fe3+-coordinating phosphate buffer, step 2 is enhanced to the extent that step 1 becomes the rate determining step and the [3Fe-4S]1+ intermediate is no longer detectable. Furthermore, Fe3+ released during this step is susceptible to reduction in the presence of Fe2+ chelators. This work, which may have significance for the in vivo FNR cluster conversion reaction in the cell cytoplasm, provides an explanation for apparently contradictory results reported from different laboratories.

Dielectron widths of the Gamma(1S,2S,3S) resonances.

PubMed

Rosner, J L; Adam, N E; Alexander, J P; Berkelman, K; Cassel, D G; Duboscq, J E; Ecklund, K M; Ehrlich, R; Fields, L; Galik, R S; Gibbons, L; Gray, R; Gray, S W; Hartill, D L; Heltsley, B K; Hertz, D; Jones, C D; Kandaswamy, J; Kreinick, D L; Kuznetsov, V E; Mahlke-Krüger, H; Meyer, T O; Onyisi, P U E; Patterson, J R; Peterson, D; Phillips, E A; Pivarski, J; Riley, D; Ryd, A; Sadoff, A J; Schwarthoff, H; Shi, X; Stroiney, S; Sun, W M; Wilksen, T; Weinberger, M; Athar, S B; Avery, P; Breva-Newell, L; Patel, R; Potlia, V; Stoeck, H; Yelton, J; Rubin, P; Cawlfield, C; Eisenstein, B I; Karliner, I; Kim, D; Lowrey, N; Naik, P; Sedlack, C; Selen, M; White, E J; Wiss, J; Shepherd, M R; Besson, D; Pedlar, T K; Cronin-Hennessy, D; Gao, K Y; Gong, D T; Hietala, J; Kubota, Y; Klein, T; Lang, B W; Poling, R; Scott, A W; Smith, A; Dobbs, S; Metreveli, Z; Seth, K K; Tomaradze, A; Zweber, P; Ernst, J; Arms, K; Severini, H; Dytman, S A; Love, W; Mehrabyan, S; Savinov, V; Aquines, O; Li, Z; Lopez, A; Mendez, H; Ramirez, J; Huang, G S; Miller, D H; Pavlunin, V; Sanghi, B; Shipsey, I P J; Xin, B; Adams, G S; Anderson, M; Cummings, J P; Danko, I; Napolitano, J; He, Q; Insler, J; Muramatsu, H; Park, C S; Thorndike, E H; Coan, T E; Gao, Y S; Liu, F; Stroynowski, R; Artuso, M; Blusk, S; Butt, J; Li, J; Menaa, N; Mountain, R; Nisar, S; Randrianarivony, K; Redjimi, R; Sia, R; Skwarnicki, T; Stone, S; Wang, J C; Zhang, K; Csorna, S E; Bonvicini, G; Cinabro, D; Dubrovin, M; Lincoln, A; Asner, D M; Edwards, K W; Briere, R A; Chen, J; Ferguson, T; Tatishvili, G; Vogel, H; Watkins, M E

2006-03-10

We determine the dielectron widths of the Gamma(1S), Gamma(2S), and Gamma(3S) resonances with better than 2% precision by integrating the cross section of e+e- -->Gamma over the e+e- center-of-mass energy. Using e+e- energy scans of the Gamma resonances at the Cornell Electron Storage Ring and measuring Gamma production with the CLEO detector, we find dielectron widths of 1.252+/-0.004(sigma(stat))+/-0.019(sigma(syst)) keV, 0.581+/-0.004+/-0.009 keV, and 0.413+/-0.004+/-0.006 keV for the Gamma(1S), Gamma(2S), and Gamma(3S), respectively.

Duality invariance of s ≥ 3/2 fermions in AdS

DOE PAGES

Deser, S.; Seminara, D.

2014-09-30

The research show that in D = 4 AdS, s ≥ 3/2 partially massless (PM) fermions retain the duality invariances of their flat space massless counterparts. They have tuned ratios m 2/M 2 ≠ 0 that turn them into sums of effectively massless unconstrained helicity ±(s, ···, 3/2) excitations, shorn of the lowest (non-dual) helicity ±1/2-rung and — more generally — of succeeding higher rung as well. Each helicity mode is separately duality invariant, like its flat space counterpart.

(2R,1'S,2'R)- and (2S,1'S,2'R)-3-[2-Mono(di,tri)fluoromethylcyclopropyl]alanines and their incorporation into hormaomycin analogues

PubMed Central

Kozhushkov, Sergei I; Yufit, Dmitrii S; Grosse, Christian; Kaiser, Marcel

2014-01-01

Summary Efficient and scalable syntheses of enantiomerically pure (2R,1'S,2'R)- and (2S,1'S,2'R)-3-[2-mono(di,tri)fluoromethylcyclopropyl]alanines 9a–c, as well as allo-D-threonine (4) and (2S,3R)-β-methylphenylalanine (3), using the Belokon' approach with (S)- and (R)-2-[(N-benzylprolyl)amino]benzophenone [(S)- and (R)-10] as reusable chiral auxiliaries have been developed. Three new fluoromethyl analogues of the naturally occurring octadepsipeptide hormaomycin (1) with (fluoromethylcyclopropyl)alanine moieties have been synthesized and subjected to preliminary tests of their antibiotic activity. PMID:25550751

Structure and electrochemistry of proteins harboring iron-sulfur clusters of different nuclearities. Part II. [4Fe-4S] and [3Fe-4S] iron-sulfur proteins.

PubMed

Zanello, Piero

2018-06-01

In the context of the plethora of proteins harboring iron-sulfur clusters we have already reviewed structure/electrochemistry of metalloproteins expressing single types of iron-sulfur clusters (namely: {Fe(Cys) 4 }, {[Fe 2 S 2 ](Cys) 4 }, {[Fe 2 S 2 ](Cys) 3 (X)} (X = Asp, Arg, His), {[Fe 2 S 2 ](Cys) 2 (His) 2 }, {[Fe 3 S 4 ](Cys) 3 }, {[Fe 4 S 4 ](Cys) 4 } and {[Fe 4 S 4 ](S γ Cys ) 3 (nonthiolate ligand)} cores) and their synthetic analogs. More recently we are focussing on structure/electrochemistry of metalloproteins harboring iron-sulfur centres of different nuclearities. Having started such a subject with proteins harboring [4Fe-4S] and [2Fe-2S] clusters, we now depict the state of art of proteins containing [4Fe-4S] and [3Fe-4S] clusters. Copyright © 2018 Elsevier Inc. All rights reserved.

H2 S3(1) and S4(1) transitions in the atmospheres of Neptune and Uranus - Observations and analysis

NASA Technical Reports Server (NTRS)

Smith, Wm. Hayden; Baines, Kevin H.

1990-01-01

The present observational results for Neptune's S3(1) and S4(1) H2 lines show the former line's measured equivalent width to be the same as for this feature in Uranus, repeating the equality already established between the two planets for the latter feature. It is also noted that the observed ratio of the H2 S3(0)/S3(1) lines for Neptune's atmosphere is reproduced by models belonging to the family of models created by Baines and Smith (1990); by comparison with the earlier Uranus models of Baines and Bergstrahl (1986), the greater continuum absorption of Neptune is responsible for the increased S3(0)/S3(1) line ratio near 0.82 microns.

Collision-induced dissociation of [4Fe-4S] cubane cluster complexes: [Fe4S4Cl4 - x(SC2H5)x]2-/1- (x = 0-4)

NASA Astrophysics Data System (ADS)

Fu, You-Jun; Laskin, Julia; Wang, Lai-Sheng

2006-09-01

Collision-induced dissociation (CID) experiments on a series of [4Fe-4S] cluster ions, [Fe4S4Cl4 - x(SC2H5)x]2-/1- (x = 0-4), revealed that their fragmentation channels change with the coordination environment. Among the three Coulomb repulsion related channels for the doubly charged species, the collision induced electron detachment channel was found to become more significant from x = 0 to 4 due to the decreasing electron binding energies and the magnitude of repulsion Coulomb barrier, while both the ligand detachment of Cl- and the fission of the [Fe4S4]2+ core became more and more significant with the increase of the Cl- coordination, and eventually became the dominant channel at x = 0. From the parents containing the SC2H5 ligand, neutral losses of HSC2H5 (62 u) and/or HSCHCH2 (60 u) were observed. It was proposed that inter- and intra-ligand proton transfer could happen during the CID process, resulting in hydrogen coordination to the [4Fe-4S] cluster. In the presence of O2, [Fe4S4Cl3(SC2H5)]2- and [Fe4S4Cl4]2- can form the O2-substituted products [Fe4S4Cl2(SC2H5)O2]- and [Fe4S4Cl3O2]-, respectively. It was shown that the O2 complexation occurs by coordination to the empty iron site of the [4Fe-4S] cubane core after dissociation of one Cl- ligand.

Four new chalcohalides, NaBa{sub 2}SnS{sub 4}Cl, KBa{sub 2}SnS{sub 4}Cl, KBa{sub 2}SnS{sub 4}Br and CsBa{sub 2}SnS{sub 4}Cl: Syntheses, crystal structures and optical properties

DOE Office of Scientific and Technical Information (OSTI.GOV)

Li, Chao; Feng, Kai; Tu, Heng

Four new chalcohalides, namely NaBa{sub 2}SnS{sub 4}Cl, KBa{sub 2}SnS{sub 4}Cl, KBa{sub 2}SnS{sub 4}Br, and CsBa{sub 2}SnS{sub 4}Cl, have been synthesized by the conventional high temperature solid-state reactions. They crystallize in three different space groups: space group I4/mcm for NaBa{sub 2}SnS{sub 4}Cl and KBa{sub 2}SnS{sub 4}Cl, Pnma for KBa{sub 2}SnS{sub 4}Br, and P2{sub 1}/c for CsBa{sub 2}SnS{sub 4}Cl. In all four compounds, the X{sup −} halide anions are only connected to six alkali metal or Ba cations, and the Sn atoms are only tetrahedrally enjoined to four S atoms. However, the M–X–Ba pseudo layers and the SnS{sub 4} tetrahedra are arrangedmore » in different ways in the three structural types, which demonstrates the interesting effect of ionic radii on the crystal structures. UV–vis–NIR spectroscopy measurements indicate that NaBa{sub 2}SnS{sub 4}Cl, KBa{sub 2}SnS{sub 4}Cl, KBa{sub 2}SnS{sub 4}Br, and CsBa{sub 2}SnS{sub 4}Cl have band gaps of 2.28, 2.30, 1.95, and 2.06 eV, respectively. - Graphical abstract: A new series of chalcohalides, NaBa{sub 2}SnS{sub 4}Cl, KBa{sub 2}SnS{sub 4}Cl, KBa{sub 2}SnS{sub 4}Br and CsBa{sub 2}SnS{sub 4}Cl have been obtained. They present three different space groups: NaBa{sub 2}SnS{sub 4}Cl and KBa{sub 2}SnS{sub 4}Cl in space group I4/mcm, KBa{sub 2}SnS{sub 4}Br in Pnma and CsBa{sub 2}SnS{sub 4}Cl in space group P2{sub 1}/c. UV–vis–NIR spectroscopy measurements indicate that NaBa{sub 2}SnS{sub 4}Cl, KBa{sub 2}SnS{sub 4}Cl, KBa{sub 2}SnS{sub 4}Br and CsBa{sub 2}SnS{sub 4}Cl have band gaps of 2.28, 2.30 1.95, and 2.06 eV, respectively. - Highlights: • Four new chalcohalides, NaBa{sub 2}SnS{sub 4}Cl, KBa{sub 2}SnS{sub 4}Cl, KBa{sub 2}SnS{sub 4}Br and CsBa{sub 2}SnS{sub 4}Cl were obtained. • They adopt three different structures owing to different ionic radii and elemental electronegativity. • NaBa{sub 2}SnS{sub 4}Cl, KBa{sub 2}SnS{sub 4}Cl, KBa{sub 2}SnS{sub 4}Br and CsBa{sub 2}SnS{sub 4}Cl have

Hierarchical NiCo2 S4 Nanotube@NiCo2 S4 Nanosheet Arrays on Ni Foam for High-Performance Supercapacitors.

PubMed

Chen, Haichao; Chen, Si; Shao, Hongyan; Li, Chao; Fan, Meiqiang; Chen, Da; Tian, Guanglei; Shu, Kangying

2016-01-01

Hierarchical NiCo2 S4 nanotube@NiCo2 S4 nanosheet arrays on Ni foam have been successfully synthesized. Owing to the unique hierarchical structure, enhanced capacitive performance can be attained. A specific capacitance up to 4.38 F cm(-2) is attained at 5 mA cm(-2) , which is much higher than the specific capacitance values of NiCo2 O4 nanosheet arrays, NiCo2 S4 nanosheet arrays and NiCo2 S4 nanotube arrays on Ni foam. The hierarchical NiCo2 S4 nanostructure shows superior cycling stability; after 5000 cycles, the specific capacitance still maintains 3.5 F cm(-2) . In addition, through the morphology and crystal structure measurement after cycling stability test, it is found that the NiCo2 S4 electroactive materials are gradually corroded; however, the NiCo2 S4 phase can still be well-maintained. Our results show that hierarchical NiCo2 S4 nanostructures are suitable electroactive materials for high performance supercapacitors. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Reactivity of Cubane-Type [(OC)(3)MFe(3)S(4)(SR)(3)](3-) Clusters (M = Mo, W): Interconversion with Cuboidal [Fe(3)S(4)](0) Clusters and Electron Transfer.

PubMed

Raebiger, James W.; Crawford, Charles A.; Zhou, Jian; Holm, R. H.

1997-03-12

The title clusters, several examples of which have been reported earlier, have been prepared by two different methods and subjected to structural and reactivity studies. The compounds (Et(4)N)(3)[(OC)(3)MFe(3)S(4)(Smes)(3)].MeCN (M = Mo/W) are isomorphous and crystallize in monoclinic space group P2(1)/n with a = 13.412(1)/13.297(1) Å, b = 19.0380(1)/18.9376(3) Å, c = 26.4210(1)/26.2949(1) Å, beta = 97.87(1)/97.549(1) degrees, and Z = 4. The clusters contain long M-S (2.62/2.59 Å) and M-Fe (3.22/3.19 Å) bonds, consistent with the reported structure of [(OC)(3)MoFe(3)S(4)(SEt)(3)](3-) (3). Reaction of [(OC)(3)MoFe(3)S(4)(LS(3))](3-) (7) with CO in the presence of NaPF(6) affords cuboidal [Fe(3)S(4)(LS(3))](3-) (9), also prepared in this laboratory by another route as a synthetic analogue of protein-bound [Fe(3)S(4)](0) clusters. The clusters [Fe(3)S(4)(SR)(3)](3-) (R = mes, Et), of limited stability, were generated by the same reaction. Treatment of 9 with [M(CO)(3)(MeCN)(3)] affords 7 and its M = W analogue. The clusters [(OC)(3)MFe(3)S(4)(SR)(3)](3-) form a four-member electron transfer series in which the 3- cluster can be once reduced (4-) and twice oxidized (2-, 1-) to afford clusters of the indicated charges. The correct assignment of redox couple to potential in the redox series of six clusters is presented, correcting an earlier misassignment of the redox series of 3. Carbonyl stretching frequencies are shown to be sensitive to cluster oxidation state, showing that the M sites and Fe(3)S(4) fragments are electronically coupled despite the long bond distances. (LS(3) = 1,3,5-tris((4,6-dimethyl-3-mercaptophenyl)thio)-2,4,6-tris(p-tolylthio)benzenate(3-); mes = mesityl.)

Synthesis of novel (2R,4R)- and (2S,4S)-iso dideoxynucleosides with exocyclic methylene as potential antiviral agents.

PubMed

Yoo, Su Jeong; Kim, Hea Ok; Lim, Yoongho; Kim, Jeongmin; Jeong, Lak Shin

2002-01-01

Novel (2R,4R)- and (2S,4S)-iso dideoxynucleosides with exocyclic methylene have been designed and synthesized, based on the lead BMS-200475 (3) which exhibited potent anti-HBV activity. For the synthesis of D types of (2R,4R)-nucleosides, L-xylose was converted to the key intermediate 14. The intermediate 14 was converted to the uracil derivative 4a and the cytosine derivative 4b. Compound 14 was also converted to the purine derivatives such as adenine derivative 4c, hypoxanthine derivative 4d, and guanine derivative 4e. The corresponding L types of (2S,4S)-enantiomers were more efficiently synthesized from the commercially available 1,2-isopropylidene-D-xylose (20) than the synthetic method used in the synthesis of (2R,4R)-nucleosides. The key intermediate 25 was converted to the pyrimidine analogues 5a and 5b and the purine derivatives 5c, 5d, and 5e using the similar method used in the preparation of 4c, 4d, and 4e. The synthesized final (2R,4R)- and (2S,4S)-nucleosides were tested against several viruses such as HIV-1, HSV-1, HSV-2, HCMV and HBV. (2R,4R)-Adenine analogue 4c exhibited potent anti-HBV activity (EC(50)=1.5 microM in 2.2.15 cells) among compounds tested, while (2R,4R)-uracil derivative 4a was the most active against HCMV among compounds tested and (2R,4R)-adenine derivative 4c was found to be moderately active against the same virus. However, the corresponding (2S,4S)-isomers were found to be totally inactive against all tested viruses. Both (2R,4R)-adenine derivative 4c and (2S,4S)-adenine analogue 5c were totally resistant to the adenosine deaminase like iso-ddA (1). From the molecular modeling study the hydroxymethyl side chains of BMS-200475 (3) and 4c were almost overlapped, indicating that 4c may be suitable for phosphorylation by cellular kinases like the lead 3, but some discrepancy between two bases was observed, indicating why 4c is less potent against HBV than 3. It is concluded that discovery of (2R,4R)-adenine analogue 4c as potent

Measurement of the 1s2s ^1S0 - 1s2p ^3P1 interval in helium-like silicon.

NASA Astrophysics Data System (ADS)

Redshaw, M.; Harry, R.; Myers, E. G.; Weatherford, C. A.

2001-05-01

Accurate calculation of the energy levels of helium-like ions is a basic problem in relativistic atomic theory. For the n=3D2 levels at moderate Z, published calculations give all ``structure'' but not all explicit QED contributions to order (Zα)^4 a.u.(D.R. Plante, W.R. Johnson and J. Sapirstein, Phys. Rev. A 49), 3519 (1994).^, (K.T. Cheng, M.H. Chen, W.R. Johnson and J. Sapirstein, Phys. Rev. A 50), 247 (1994).. Measurements of the 1s2p ^3P - 1s2s ^3S transitions, which lie in the vacuum ultra-violet, are barely precise enough to challenge the theory. However, the intercombination 1s2s ^1S0 - 1s2p ^3P1 interval lies in the infra-red for Z<40 and enables precision measurements using laser spectroscopy(E.G. Myers, J.K. Thompson, E.P. Gavathas, N.R. Claussen, J.D. Silver and D.J.H. Howie, Phys. Rev. Lett. 75), 3637 (1995).. We aim to measure this interval in Si^12+ using a foil-stripped 1 MeV/u ion beam from the Florida State Van de Graaff accelerator and a single-mode c.w. Nd:YAG laser at 1.319 μm. To obtain a sufficient transition probability, the Si^12+ beam is merged co-linearly with the laser light inside an ultra-high finesse build-up cavity. The results should provide a clear test of current and developing calculations of QED contributions in two-electron ions.

Fabrication of solar cells based on Cu2ZnSnS4 prepared from Cu2SnS3 synthesized using a novel chemical procedure

NASA Astrophysics Data System (ADS)

Correa, John M.; Becerra, Raúl A.; Ramírez, Asdrubal A.; Gordillo, Gerardo

2016-11-01

Solar cells based on kesterite-type Cu2ZnSnS4 (CZTS) thin films were fabricated using a chemical route to prepare the CZTS films, consisting in sequential deposition of Cu2SnS3 (CTS) and ZnS thin films followed by annealing at 550 °C in nitrogen atmosphere. The CTS compound was prepared in a one-step process using a novel chemical procedure consisting of simultaneous precipitation of Cu2S and SnS2 performed by diffusion membranes assisted CBD (chemical bath deposition) technique. Diffusion membranes were used to optimize the kinetic growth through a moderate control of release of metal ions into the work solution. As the conditions for the formation in one step of the Cu2SnS3 compound have not yet been reported in literature, special emphasis was put on finding the parameters that allow growing the Cu2SnS3 thin films by simultaneous precipitation of Cu2S and SnS2. For that, we propose a methodology that includes numerical solution of the equilibrium equations that were established through a study of the chemical equilibrium of the system SnCl2, Na3C6H5O7·2H2O, CuCl2 and Na2S2O3·5H2O. The formation of thin films of CTS and CZTS free of secondary phases grown with a stoichiometry close to that corresponding to the Cu2SnS3 and Cu2ZnSnS4 phases, was verified through measurements of X-ray diffraction (XRD) and Raman spectroscopy. Solar cell with an efficiency of 4.2%, short circuit current of 16.2 mA/cm2 and open-circuit voltage of 0.49 V was obtained.

Superconductivity in semimetallic B i 3 O 2 S 3

DOE PAGES

Li, L.; Parker, D.; Babkevich, P.; ...

2015-03-12

We report in this paper a further investigation on the thermodynamic and transport properties, and an assessment of theoretical calculations, for the BiS 2-layered Bi 3O 2S 3 superconductor. The polycrystalline sample is synthesized with a superconducting transition temperature of T c onset=5.75K and T c zero=4.03K (≈Tc mag) that drops to 3.3 K by applying a hydrostatic pressure of 6 kbar. Density-of-states (DOS) calculations give substantial hybridization between Bi, O, and S, with Bi the largest component of DOS, which supports the idea that the BiS 2 layer is relevant for producing electron-phonon coupling. An analysis of previously publishedmore » specific heat data for Bi 3O 2S 3 is additionally suggestive of a strong electron-phonon interaction in the Bi-O-S system. The analysis of the Seebeck coefficient results strongly suggests that Bi 3O 2S 3 is a semimetal. In fact, we found the semimetallic or narrow band gap behavior may occur in certain other materials in the BiS 2-layered class of materials, such as Bi 4O 4S 3.« less

Bulk superconductivity in bismuth oxysulfide Bi4O4S3.

PubMed

Singh, Shiva Kumar; Kumar, Anuj; Gahtori, Bhasker; Shruti; Sharma, Gyaneshwar; Patnaik, Satyabrata; Awana, Veer P S

2012-10-10

A very recent report on the observation of superconductivity in Bi(4)O(4)S(3) [Mizuguchi, Y.; http://arxiv.org/abs/1207.3145] could potentially reignite the search for superconductivity in a broad range of layered sulfides. We report here the synthesis of Bi(4)O(4)S(3) at 500 °C by a vacuum encapsulation technique and its basic characterizations. The as-synthesized Bi(4)O(4)S(3) was contaminated with small amounts of Bi(2)S(3) and Bi impurities. The majority phase was found to be tetragonal (space group I4/mmm) with lattice parameters a = 3.9697(2) Å and c = 41.3520(1) Å. Both AC and DC magnetization measurements confirmed that Bi(4)O(4)S(3) is a bulk superconductor with a superconducting transition temperature (T(c)) of 4.4 K. Isothermal magnetization (M-H) measurements indicated closed loops with clear signatures of flux pinning and irreversible behavior. The lower critical field (H(c1)) at 2 K for the new superconductor was found to be ~15 Oe. Magnetotransport measurements showed a broadening of the resistivity (ρ) and a decrease in T(c) (ρ = 0) with increasing magnetic field. The extrapolated upper critical field H(c2)(0) was ~31 kOe with a corresponding Ginzburg-Landau coherence length of ~100 Å . In the normal state, the ρ ~ T(2) dependence was not indicated. Hall resistivity data showed a nonlinear magnetic field dependence. Our magnetization and electrical transport measurements substantiate the appearance of bulk superconductivity in as-synthesized Bi(4)O(4)S(3). On the other hand, Bi heat-treated at the same temperature is not superconducting, thus excluding the possibility of impurity-driven superconductivity in the newly discovered superconductor Bi(4)O(4)S(3).

S3 and S4 abundances and improved chemical kinetic model for the lower atmosphere of Venus

NASA Astrophysics Data System (ADS)

Krasnopolsky, Vladimir A.

2013-07-01

Mixing ratios of S3 and S4 are obtained from reanalysis of the spectra of true absorption in the visible range retrieved by Maiorov et al. (Maiorov, B.S. et al. [2005]. Solar Syst. Res. 39, 267-282) from the Venera 11 observations. These mixing ratios are fS3 = 11 ± 3 ppt at 3-10 km and 18 ± 3 ppt at 10-19 km, fS4 = 4 ± 4 ppt at 3-10 km and 6 ± 2 ppt at 10-19 km, and show a steep decrease in both S3 and S4 above 19 km. Photolysis rates of S3 and S4 at various altitudes are calculated using the Venera 11 spectra and constant photolysis yields as free parameters. The chemical kinetic model for the Venus lower atmosphere (Krasnopolsky, V.A. [2007]. Icarus 191, 25-37) has been improved by inclusion of the S4 cycle from Yung et al. (Yung, Y.L. et al. [2009]. J. Geophys. Res. 114, E00B34), reduction of the H2SO4 and CO fluxes at the upper boundary of 47 km by a factor of 4 in accord with the recent photochemical models for the middle atmosphere, by using a closed lower boundary for OCS instead of a free parameter for this species at the surface, and some minor updates. Our model with the S4 cycle but without the SO3 + 2 OCS reaction suggested by Krasnopolsky and Pollack (Krasnopolsky, V.A., Pollack, J.B. [1994]. Icarus 109, 58-78) disagrees with the observations of OCS, CO, S3, and S4. However, inclusion of the S4 cycle improves the model fit to all observational constraints. The best-fit activation energy of 7800 K for thermolysis of S4 supports the S4 enthalpy from Mills (Mills, K.C. [1974]. Thermodynamic Data for Inorganic Sulfides, Selenides and Tellurides. Butterworths, London). Chemistry of the Venus lower atmosphere is initiated by disequilibrium products H2SO4 and CO from the middle atmosphere, photolysis of S3 and S4, and thermochemistry in the lowest scale height. The chemistry is mostly driven by sulfur that is formed in a slow reaction SO + SO, produces OCS, and results in dramatic changes in abundances of OCS, CO, and free sulfur allotropes. The SX + OCS

Mechanistic studies on the reactions of PhS(-) or [MoS(4)](2)(-) with [M(4)(SPh)(10)](2)(-) (M = Fe or Co).

PubMed

Cui, Zhen; Henderson, Richard A

2002-08-12

Kinetic studies, using stopped-flow spectrophotometry, on the reactions of [M(4)(SPh)(10)](2)(-) (M = Fe or Co) with PhS(-) to form [M(SPh)(4)](2)(-) are described, as are the reactions between [M(4)(SPh)(10)](2)(-) and [MoS(4)](2)(-) to form [S(2)MoS(2)Fe(SPh)(2)](2)(-) or [S(2)MoS(2)CoS(2)MoS(2)](2)(-). The kinetics of the reactions with PhS(-) are consistent with an initial associative substitution mechanism involving attack of PhS(-) at one of the tetrahedral M sites of [M(4)(SPh)(10)](2)(-) to form [M(4)(SPh)(11)](3)(-). Subsequent or concomitant cleavage of a micro-SPh ligand, at the same M, initiates a cascade of rapid reactions which result ultimately in the complete rupture of the cluster and formation of [M(SPh)(4)](2)(-). The kinetics of the reaction between [M(4)(SPh)(10)](2)(-) and [MoS(4)](2)(-) indicate an initial dissociative substitution mechanism at low concentrations of [MoS(4)](2)(-), in which rate-limiting dissociation of a terminal thiolate from [M(4)(SPh)(10)](2)(-) produces [M(4)(SPh)(9)](-) and the coordinatively unsaturated M site is rapidly attacked by a sulfido group of [MoS(4)](2)(-). It is proposed that subsequent chelation of the MoS(4) ligand results in cleavage of an M-micro-SPh bond, initiating a cascade of reactions which lead to the ultimate break-up of the cluster and formation of the products, [S(2)MoS(2)Fe(SPh)(2)](2)(-) or [S(2)MoS(2)CoS(2)MoS(2)](2)(-). With [Co(4)(SPh)(10)](2)(-), at higher concentrations of [MoS(4)](2)(-), a further substitution pathway is evident which exhibits a second order dependence on the concentration of [MoS(4)](2)(-). The mechanistic picture of cluster disruption which emerges from these studies rationalizes the "all or nothing" reactivity of [M(4)(SPh)(10)](2)(-).

Absolute structure and structure-function relationships of 4R,2‧R and 4S,2‧S Pidotimod®

NASA Astrophysics Data System (ADS)

Sarno, Simone; Manzo, Angelo M.; Ferraris, Davide M.; Miggiano, Riccardo; Rizzi, Menico; Palin, Luca; Boccaleri, Enrico; Milanesio, Marco

2017-11-01

Pidotimod® is a dipeptide with widely recognized immunomodulatory properties and with particularly beneficial effects for the treatment of acute respiratory and urinary tract infections. Pidotimod® presents two chiral centres which originate four stereoisomers. (4R,2‧S, 4S,2‧R, 4R,2‧R and 4S,2‧S). To date, only the 4R,2‧S and 4S,2‧R stereoisomers are reported in the literature. We report here the absolute crystal structure of the 4R,2‧R and 4S,2‧S diastereoisomers of Pidotimod®, obtained by crystals grown by slow evaporation of a mixture of water and ethanol. The analysis of the crystal structures revealed the key role of a solvent water molecule in the crystal packing engaged in an extended hydrogen bonds network. This water-assisted H-bond network explained the recalcitrance of 4R,2‧R and 4S,2‧S Pidotimod® to crystallize in pure ethanol, despite their high solubility, and the growth of well-diffracting crystals only in presence of water. Hence, Pidotimod®4R,2‧R and 4S,2‧S stereoisomers markedly differ from the 4R,2‧S and 4S,2‧R ones, which crystallize in absence of water. The molecular and crystal structures of the 4R,2‧R and 4S,2‧S Pidotimod® stereoisomers here presented gave some hints on the differences in bioactivity with respect to the 4R,2‧S stereoisomer. In fact, beyond an expected different dispositions of hydrophilic ligands, 4R,2‧R and 4S,2‧S showed an incremented tendency to intermolecular H-bonds with water.

A novel S-enantioselective amidase acting on 3,3,3-trifluoro-2-hydroxy-2-methylpropanamide from Arthrobacter sp. S-2.

PubMed

Fuhshuku, Ken-ichi; Watanabe, Shunsuke; Nishii, Tetsuro; Ishii, Akihiro; Asano, Yasuhisa

2015-01-01

A novel S-enantioselective amidase acting on 3,3,3-trifluoro-2-hydroxy-2-methylpropanamide was purified from Arthrobacter sp. S-2. The enzyme acted S-enantioselectively on 3,3,3-trifluoro-2-hydroxy-2-methylpropanamide to yield (S)-3,3,3-trifluoro-2-hydroxy-2-methylpropanoic acid. Based on the N-terminal amino acid sequence of this amidase, the gene coding S-amidase was cloned from the genomic DNA of Arthrobacter sp. S-2 and expressed in an Escherichia coli host. The recombinant S-amidase was purified and characterized. Furthermore, the purified recombinant S-amidase with the C-His6-tag, which was expressed in E. coli as the C-His6-tag fusion protein, was used in the kinetic resolution of (±)-3,3,3-trifluoro-2-hydroxy-2-methylpropanamide to obtain (S)-3,3,3-trifluoro-2-hydroxy-2-methylpropanoic acid and (R)-3,3,3-trifluoro-2-hydroxy-2-methylpropanamide.

Facile fabrication of novel BiVO4/Bi2S3/MoS2 n-p heterojunction with enhanced photocatalytic activities towards pollutant degradation under natural sunlight.

PubMed

Wang, Jingzhen; Jin, Jia; Wang, Xiangguo; Yang, Shengnan; Zhao, Yinlan; Wu, Yawen; Dong, Shuying; Sun, Jingyu; Sun, Jianhui

2017-11-01

The novel three-component BiVO 4 /Bi 2 S 3 /MoS 2 heterojunction was successfully fabricated through a facile in-situ hydrothermal method based on the formation of the intermediate Bi 2 S 3 by coupling BiVO 4 and MoS 2 precursor. The Bi 2 S 3 was easily formed attributing to the strong interaction between Bi 3+ and S 2- ions with the aid of the hydrothermal reaction. The photocatalytic performances of samples were systematically investigated via the photocatalytic degradation of Rhodamine B (RhB), methylene blue (MB) and malachite green (MG) under solar light irradiation. As a result, the photocatalytic degradation rate of BM-10 for RhB, MB and MG are 97%, 93% and 94%, respectively. The enhanced photocatalytic activities could be due to the suppression of charge recombination and the enhanced the visible light absorption of BiVO 4 /Bi 2 S 3 /MoS 2 heterojunction. Copyright © 2017 Elsevier Inc. All rights reserved.

S3/S4 Integrated Truss being moved into the Space Shuttle Payloa

NASA Image and Video Library

2007-02-07

In the Space Station Processing Facility, an overhead crane moves the S3/S4 integrated truss to a payload canister. After it is stowed in the canister, the S3/S4 truss will be transported to the launch pad. The truss is the payload on mission STS-117, targeted for launch on March 15.

S3/S4 Integrated Truss being moved into the Space Shuttle Payloa

NASA Image and Video Library

2007-02-07

In the Space Station Processing Facility, an overhead crane settles the S3/S4 integrated truss into the payload canister. After it is stowed in the canister, the S3/S4 truss will be transported to the launch pad. The truss is the payload on mission STS-117, targeted for launch on March 15.

[3Fe-4S] to [4Fe-4S] cluster conversion in Desulfovibrio fructosovorans [NiFe] hydrogenase by site-directed mutagenesis.

PubMed

Rousset, M; Montet, Y; Guigliarelli, B; Forget, N; Asso, M; Bertrand, P; Fontecilla-Camps, J C; Hatchikian, E C

1998-09-29

The role of the high potential [3Fe-4S]1+,0 cluster of [NiFe] hydrogenase from Desulfovibrio species located halfway between the proximal and distal low potential [4Fe-4S]2+,1+ clusters has been investigated by using site-directed mutagenesis. Proline 238 of Desulfovibrio fructosovorans [NiFe] hydrogenase, which occupies the position of a potential ligand of the lacking fourth Fe-site of the [3Fe-4S] cluster, was replaced by a cysteine residue. The properties of the mutant enzyme were investigated in terms of enzymatic activity, EPR, and redox properties of the iron-sulfur centers and crystallographic structure. We have shown on the basis of both spectroscopic and x-ray crystallographic studies that the [3Fe-4S] cluster of D. fructosovorans hydrogenase was converted into a [4Fe-4S] center in the P238 mutant. The [3Fe-4S] to [4Fe-4S] cluster conversion resulted in a lowering of approximately 300 mV of the midpoint potential of the modified cluster, whereas no significant alteration of the spectroscopic and redox properties of the two native [4Fe-4S] clusters and the NiFe center occurred. The significant decrease of the midpoint potential of the intermediate Fe-S cluster had only a slight effect on the catalytic activity of the P238C mutant as compared with the wild-type enzyme. The implications of the results for the role of the high-potential [3Fe-4S] cluster in the intramolecular electron transfer pathway are discussed.

[3Fe-4S] to [4Fe-4S] cluster conversion in Desulfovibrio fructosovorans [NiFe] hydrogenase by site-directed mutagenesis

PubMed Central

Rousset, Marc; Montet, Yael; Guigliarelli, Bruno; Forget, Nicole; Asso, Marcel; Bertrand, Patrick; Fontecilla-Camps, Juan C.; Hatchikian, E. Claude

1998-01-01

The role of the high potential [3Fe-4S]1+,0 cluster of [NiFe] hydrogenase from Desulfovibrio species located halfway between the proximal and distal low potential [4Fe-4S]2+,1+ clusters has been investigated by using site-directed mutagenesis. Proline 238 of Desulfovibrio fructosovorans [NiFe] hydrogenase, which occupies the position of a potential ligand of the lacking fourth Fe-site of the [3Fe-4S] cluster, was replaced by a cysteine residue. The properties of the mutant enzyme were investigated in terms of enzymatic activity, EPR, and redox properties of the iron-sulfur centers and crystallographic structure. We have shown on the basis of both spectroscopic and x-ray crystallographic studies that the [3Fe-4S] cluster of D. fructosovorans hydrogenase was converted into a [4Fe-4S] center in the P238 mutant. The [3Fe-4S] to [4Fe-4S] cluster conversion resulted in a lowering of approximately 300 mV of the midpoint potential of the modified cluster, whereas no significant alteration of the spectroscopic and redox properties of the two native [4Fe-4S] clusters and the NiFe center occurred. The significant decrease of the midpoint potential of the intermediate Fe-S cluster had only a slight effect on the catalytic activity of the P238C mutant as compared with the wild-type enzyme. The implications of the results for the role of the high-potential [3Fe-4S] cluster in the intramolecular electron transfer pathway are discussed. PMID:9751716

Pressure-enhanced superconductivity in Eu 3 Bi 2 S 4 F 4

DOE PAGES

Luo, Yongkang; Zhai, Hui -Fei; Zhang, Pan; ...

2014-12-17

The pressure effect on the newly discovered charge-transferred BiS 2-based superconductor, Eu 3Bi 2S 4F 4, with a T c of 1.5 K at ambient pressure, is investigated by transport and magnetic measurements. Accompanied with the enhancement of metallicity under pressures, the onset superconducting transition temperature increases abruptly around 1.0 GPa, reaching ~10.0 K at 2.26 GPa. Alternating current magnetic susceptibility measurements indicate that a new superconducting phase with a higher T c emerges and dominates at high pressures. In the broad pressure window of 0.68GPa≤p≤2.00 GPa, the high-T c phase coexists with the low-T c phase. Hall effect measurementsmore » reveal a significant difference in electronic structures between the two superconducting phases. As a result, our work devotes the effort to establish the commonality of pressure effect on the BiS 2-based superconductors, and also uncovers the importance of electron carrier density in the high-T c phase.« less

Experimental and theoretical study of pure and doped crystals: Gd2O2S, Gd2O2S:Eu3+ and Gd2O2S:Tb3+

NASA Astrophysics Data System (ADS)

Wang, Fei; Chen, Xiumin; Liu, Dachun; Yang, Bin; Dai, Yongnian

2012-08-01

Quantum chemistry and experimental method were used to study on pure and doped Gd2O2S crystals in this paper. The band structure and DOS diagrams of pure and doped Gd2O2S crystals which calculated by using DFT (Density Functional Theory) method were illustrated to explain the luminescent properties of impurities in crystals. The calculations of the crystal structure were finished by using the program of CASTEP (Cambridge Sequential Total Energy Package). The samples showed the characteristic emissions of Tb3+ ions with 5D4-7FJ transitions and Eu3+ ions with 5D0-7FJ transitions which emit pure green luminescence and red luminescence respectively. The experimental excitation spectra of Tb3+ and Eu3+ doped Gd2O2S are in agreement of the DOS diagrams over the explored energy range, which has allowed a better understanding of different luminescence mechanisms of Tb3+ and Eu3+ in Gd2O2S crystals.

Mass spectrometric identification of intermediates in the O2-driven [4Fe-4S] to [2Fe-2S] cluster conversion in FNR

PubMed Central

Crack, Jason C.; Thomson, Andrew J.

2017-01-01

The iron-sulfur cluster containing protein Fumarate and Nitrate Reduction (FNR) is the master regulator for the switch between anaerobic and aerobic respiration in Escherichia coli and many other bacteria. The [4Fe-4S] cluster functions as the sensory module, undergoing reaction with O2 that leads to conversion to a [2Fe-2S] form with loss of high-affinity DNA binding. Here, we report studies of the FNR cluster conversion reaction using time-resolved electrospray ionization mass spectrometry. The data provide insight into the reaction, permitting the detection of cluster conversion intermediates and products, including a [3Fe-3S] cluster and persulfide-coordinated [2Fe-2S] clusters [[2Fe-2S](S)n, where n = 1 or 2]. Analysis of kinetic data revealed a branched mechanism in which cluster sulfide oxidation occurs in parallel with cluster conversion and not as a subsequent, secondary reaction to generate [2Fe-2S](S)n species. This methodology shows great potential for broad application to studies of protein cofactor–small molecule interactions. PMID:28373574

S3/S4 Integrated Truss being moved into the Space Shuttle Payloa

NASA Image and Video Library

2007-02-07

In the Space Station Processing Facility, an overhead crane lowers the S3/S4 integrated truss into the open bay of the payload canister. After it is stowed in the canister, the S3/S4 truss will be transported to the launch pad. The truss is the payload on mission STS-117, targeted for launch on March 15.

S3/S4 Integrated Truss being moved into the Space Shuttle Payloa

NASA Image and Video Library

2007-02-07

In the Space Station Processing Facility, an overhead crane lowers the S3/S4 integrated truss toward the open doors of the payload canister. After it is stowed in the canister, the S3/S4 truss will be transported to the launch pad. The truss is the payload on mission STS-117, targeted for launch on March 15.

S3/S4 Integrated Truss being moved into the Space Shuttle Payloa

NASA Image and Video Library

2007-02-07

In the Space Station Processing Facility, workers attach an overhead crane to the S3/S4 integrated truss in order to move it to the payload canister. After it is stowed in the canister, the S3/S4 truss will be transported to the launch pad. The truss is the payload on mission STS-117, targeted for launch on March 15.

Protonation and Proton-Coupled Electron Transfer at S-Ligated [4Fe-4S] Clusters

PubMed Central

Morris, Wesley D.; Darcy, Julia W.; Mayer, James M.

2015-01-01

Biological [Fe-S] clusters are increasingly recognized to undergo proton-coupled electron transfer (PCET), but the site of protonation, mechanism, and role for PCET remains largely unknown. Here we explore this reactivity with synthetic model clusters. Protonation of the arylthiolate-ligated [4Fe-4S] cluster [Fe4S4(SAr)4]2- (1, SAr = S-2,4-6-(iPr)3C6H2) leads to thiol dissociation, reversibly forming [Fe4S4(SAr)3L]1- (2) + ArSH (L = solvent, and/or conjugate base). Solutions of 2 + ArSH react with the nitroxyl radical TEMPO to give [Fe4S4(SAr)4]1- (1ox) and TEMPOH. This reaction involves PCET coupled to thiolate association and may proceed via the unobserved protonated cluster [Fe4S4(SAr)3(HSAr)]1-(1-H). Similar reactions with this and related clusters proceed comparably. An understanding of the PCET thermochemistry of this cluster system has been developed, encompassing three different redox levels and two protonation states. PMID:25965413

Superconductivity enhanced by Se doping in Eu3Bi2(S,Se)4F4

NASA Astrophysics Data System (ADS)

Zhang, P.; Zhai, H. F.; Tang, Z. J.; Li, L.; Li, Y. K.; Chen, Q.; Chen, J.; Wang, Z.; Feng, C. M.; Cao, G. H.; Xu, Z. A.

2015-07-01

We investigated the negative-chemical-pressure effect of Eu3Bi2S4-x Se x F4 (0 ≤ x ≤ 2.0) by the partial substitution of S with Se. The crystalline lattice substantially expands as Se is doped, suggesting an effective negative chemical pressure. With Se/S doping, the charge-density-wave-like anomaly is suppressed, and meanwhile the superconducting transition temperature (T_c) is enhanced. For x = 2.0 , T c reaches 3.35 K and bulk superconductivity is confirmed by the strong diamagnetic signal, with shielding volume fraction over 90%. Magnetic-susceptibility, specific-heat and Hall-effect measurements reveal that the Se/S doping increases the carrier density, corresponding to the increase of the average Eu valence. Our work provides a rare paradigm of negative-chemical-pressure effect.

Compilation, design tests: Energetic particles Satellite S-3 including design tests for S-3A, S-3B and S-3C

NASA Technical Reports Server (NTRS)

Ledoux, F. N.

1973-01-01

A compilation of engineering design tests which were conducted in support of the Energetic Particle Satellite S-3, S-3A, and S-3b programs. The purpose for conducting the tests was to determine the adequacy and reliability of the Energetic Particles Series of satellites designs. The various tests consisted of: (1) moments of inertia, (2) functional reliability, (3) component and structural integrity, (4) initiators and explosives tests, and (5) acceptance tests.

Photon transitions in Upsilon(2S) and Upsilon(3S) decays.

PubMed

Artuso, M; Boulahouache, C; Blusk, S; Butt, J; Dambasuren, E; Dorjkhaidav, O; Li, J; Menaa, N; Mountain, R; Muramatsu, H; Nandakumar, R; Redjimi, R; Sia, R; Skwarnicki, T; Stone, S; Wang, J C; Zhang, K; Csorna, S E; Bonvicini, G; Cinabro, D; Dubrovin, M; Bornheim, A; Pappas, S P; Weinstein, A J; Rosner, J L; Briere, R A; Chen, G P; Ferguson, T; Tatishvili, G; Vogel, H; Watkins, M E; Adam, N E; Alexander, J P; Berkelman, K; Cassel, D G; Crede, V; Duboscq, J E; Ecklund, K M; Ehrlich, R; Fields, L; Galik, R S; Gibbons, L; Gittelman, B; Gray, R; Gray, S W; Hartill, D L; Heltsley, B K; Hertz, D; Hsu, L; Jones, C D; Kandaswamy, J; Kreinick, D L; Kuznetsov, V E; Mahlke-Krüger, H; Meyer, T O; Onyisi, P U E; Patterson, J R; Peterson, D; Pivarski, J; Riley, D; Ryd, A; Sadoff, A J; Schwarthoff, H; Shepherd, M R; Stroiney, S; Sun, W M; Thayer, J G; Urner, D; Wilksen, T; Weinberger, M; Athar, S B; Avery, P; Breva-Newell, L; Patel, R; Potlia, V; Stoeck, H; Yelton, J; Rubin, P; Cawlfield, C; Eisenstein, B I; Gollin, G D; Karliner, I; Kim, D; Lowrey, N; Naik, P; Sedlack, C; Selen, M; Thaler, J J; Williams, J; Wiss, J; Edwards, K W; Besson, D; Pedlar, T K; Cronin-Hennessy, D; Gao, K Y; Gong, D T; Kubota, Y; Lang, B W; Li, S Z; Poling, R; Scott, A W; Smith, A; Stepaniak, C J; Dobbs, S; Metreveli, Z; Seth, K K; Tomaradze, A; Zweber, P; Ernst, J; Mahmood, A H; Arms, K; Gan, K K; Severini, H; Asner, D M; Dytman, S A; Love, W; Mehrabyan, S; Mueller, J A; Savinov, V; Li, Z; Lopez, A; Mendez, H; Ramirez, J; Huang, G S; Miller, D H; Pavlunin, V; Sanghi, B; Shibata, E I; Shipsey, I P J; Adams, G S; Chasse, M; Cravey, M; Cummings, J P; Danko, I; Napolitano, J; Park, C S; Park, W; Thayer, J B; Thorndike, E H; Coan, T E; Gao, Y S; Liu, F; Stroynowski, R

2005-01-28

We have studied the inclusive photon spectra in Upsilon(2S) and Upsilon(3S) decays using a large statistics data sample obtained with the CLEO III detector. We present the most precise measurements of electric dipole (E1) photon transition rates and photon energies for Upsilon(2S) --> gammachi(bJ)(1P) and Upsilon(3S) --> gammachi(bJ)(2P) (J = 0, 1, 2). We measure the rate for a rare E1 transition Upsilon(3S) --> gammachi(b0)(1P) for the first time. We also set upper limits on the rates for the hindered magnetic dipole (M1) transitions to the eta(b)(1S) and eta(b)(2S) states.

Improved GaSb surfaces using a (NH4)2S/(NH4)2S04 solution

NASA Astrophysics Data System (ADS)

Murape, D. M.; Eassa, N.; Nyamhere, C.; Neethling, J. H.; Betz, R.; Coetsee, E.; Swart, H. C.; Botha, J. R.; Venter, A.

2012-05-01

Bulk (1 0 0) n-GaSb surfaces have been treated with a sulphur based solution ((NH4)2S/(NH4)2SO4) to which sulphur has been added, not previously reported for the passivation of GaSb surfaces. Au/n-GaSb Schottky barrier diodes (SBDs) fabricated on the treated material show significant improvement compared to that of the similar SBDs on the as-received material as evidenced by the lower ideality factor (n), higher barrier height (ϕb) and lower contact resistance obtained. Additionally, the reverse leakage current, although not saturating, has been reduced by almost an order of magnitude at -0.2 V. The sample surfaces were studied by scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The native oxide, Sb-O, present on the as-received material is effectively removed on treating with ([(NH4)2S/(NH4)2SO4]+S) and (NH4)2S. Analysis of the as-received surface by XPS, prior to and after argon sputtering, suggests that the native oxide layer is ≤8.5 nm.

Suppression of (Υ1S), Υ(2S), and Υ(3S) quarkonium states in PbPb collisions at s NN = 2.76 TeV

DOE PAGES

Khachatryan, V.; Sirunyan, A. M.; Tumasyan, A.; ...

2017-04-19

The production yields of Υ(1S), Υ(2S), and Υ(3S) quarkonium states are measured through their decays into muon pairs in the CMS detector, in PbPb and pp collisions at the centre-of-mass energy per nucleon pair of 2.76 TeV. The data correspond to integrated luminosities of 166μb –1 and 5.4pb –1 for PbPb and pp collisions, respectively. Differential production cross sections are reported as functions of Υ rapidity y up to 2.4, and transverse momentum p T up to 20GeV/c. A strong centrality-dependent suppression is observed in PbPb relative to pp collisions, by factors of up to ≈2 and 8, for themore » Υ(1S) and Υ(2S) states, respectively. No significant dependence of this suppression is observed as a function of y or p T. The Υ(3S) state is not observed in PbPb collisions, which corresponds to a suppression for the centrality-integrated data by at least a factor of ≈7 at a 95% confidence level. As a result, the observed suppression is in agreement with theoretical scenarios modeling the sequential melting of quarkonium states in a quark gluon plasma.« less

Tune-out wavelength for the 1 s 2 s3 S - 1 s 3 p 3 P transition of helium: relativistic effects

NASA Astrophysics Data System (ADS)

Drake, Gordon W. F.; Manalo, Jacob

2017-04-01

The tune-out wavelength is the wavelength at which the frequency dependent polarizability of an atom vanishes. It can be measured to very high precision by means of an interferometric comparison between two beams. This paper is part of a joint theoretical/ experimental project with K. Baldwin et al. (Australian National University) and L.-Y. Tang et al. (Wuhan Institute of Physics and Mathematics) to perform a high precision comparison between theory and experiment as a probe of atomic structure, including relativistic and quantum electrodynamic effects. We will report the results of calculations for the tune-out wavelength that is closest to the 1 s 2 s3 S - 1 s 3 p3 P transition of 4He. Our result for the M = 0 magnetic substate, obtained with a fully correlated Hylleraas basis set, is 413 . 079 958 51 (12) nm. This includes a leading relativistic contribution of - 0 . 059 218 5 (16) nm from the Breit interaction as a perturbation, and a relativistic recoil contribution of - 0 . 000 044 47 (17) nm. The results will be compared with recent relativistic CI calculations. Research supported by tha Natural Sciences and Engineering Research Council of Canada.

Co-variability of S 6+ , S 4+ , and S 2- in apatite as a function of oxidation state: Implications for a new oxybarometer

DOE Office of Scientific and Technical Information (OSTI.GOV)

Konecke, Brian A.; Fiege, Adrian; Simon, Adam C.

In this study, we use micro-X-ray absorption near-edge structures (μ-XANES) spectroscopy at the S K-edge to investigate the oxidation state of S in natural magmatic-hydrothermal apatite (Durango, Mexico, and Mina Carmen, Chile) and experimental apatites crystallized from volatile-saturated lamproitic melts at 1000 °C and 300 MPa over a broad range of oxygen fugacities [( Embedded Image , FMQ+1.2, FMQ+3; FMQ = fayalite-magnetite-quartz solid buffer]. The data are used to test the hypothesis that S oxidation states other than S6+ may substitute into the apatite structure. Peak energies corresponding to sulfate S6+ (~2482 eV), sulfite S4+ (~2478 eV), and sulfide S2-more » (~2470 eV) were observed in apatite, and the integrated areas of the different sulfur peaks correspond to changes in Embedded Image and bulk S content. Here, multiple tests confirmed that the S oxidation state in apatite remains constant when exposed to the synchrotron beam, at least for up to 1 h exposure (i.e., no irradiation damages). To our knowledge, this observation makes apatite the first mineral to incorporate reduced (S2-), intermediate (S4+), and oxidized (S6+) S in variable proportions as a function of the prevailing Embedded Image of the system. Apatites crystallized under oxidizing conditions (FMQ+1.2 and FMQ+3), where the S6+/STotal peak area ratio in the coexisting glass (i.e., quenched melt) is ~1, are dominated by S6+ with a small contribution of S4+, whereas apatites crystallizing at reduced conditions (FMQ) contain predominantly S2-, lesser amounts of S6+, and possibly traces of S4+. A sulfur oxidation state vs. S concentration analytical line transect across hydrothermally altered apatite from the Mina Carmen iron oxide-apatite (IOA) deposit (Chile) demonstrates that apatite can become enriched in S4+ relative to S6+, indicating metasomatic overprinting via a SO2-bearing fluid or vapor phase. This XANES study demonstrates that as the Embedded Image increases from FQM to FMQ+1.2

Electrical conductivity studies in (Ag3AsS3)x(As2S3)1-x superionic glasses and composites

NASA Astrophysics Data System (ADS)

Studenyak, I. P.; Neimet, Yu. Yu.; Kranjčec, M.; Solomon, A. M.; Orliukas, A. F.; Kežionis, A.; Kazakevičius, E.; Šalkus, T.

2014-01-01

Compositional, frequency, and temperature studies of impedance and electrical conductivity in (Ag3AsS3)x(As2S3)1-x superionic glasses and composites were performed. Frequency range from 10 Hz to 3 × 109 Hz and temperature interval 300-400 K were used for the measurements. Compositional dependences of electrical conductivity and activation energy are analyzed; the most substantial changes are observed with the transition from (Ag3AsS3)0.4(As2S3)0.6 glass to (Ag3AsS3)0.5(As2S3)0.5 composite. With increase of Ag3AsS3 content, the investigated materials are found to have crystalline inclusions and show the two-phase composite nature. Addition of Ag3AsS3 leads to the increase of electrical conductivity whereas the activation energy decreases.

Evaluation of anti-melanoma activities of (1S,2E,4R,6E,8R,11S,12R)-8,12-epoxy-2,6-cembradiene-4,11-diol, (1S,2E,4R,6E,8S,11R,12S)-8,11-epoxy-4,12-epoxy-2,6-cembradiene and (1S,4R,13S)-cembra-2E,7E,11E-trien-4,13-diol from the Red Sea soft coral Sarcophyton glaucum.

PubMed

Szymanski, Pawel T; Ahmed, Safwat A; Radwan, Mohamed M; Khalifa, Sherief I; Fahmy, Hesham

2014-08-01

Three natural cembranoids from the Red Sea soft coral Sarcophyton glaucum namely (1S,2E,4R,6E,8R,11S,12R)-8,12-epoxy-2,6-cembradiene-4,11-diol, (1S,2E,4R,6E,8S,11R,12S)-8,11-epoxy-4,12-epoxy-2,6-cembradiene and (1S,4R,13S)-cembra-2E,7E,11E-trien-4,13-diol were evaluated for their inhibitory effects on mouse melanoma B16F10 cell growth. Results show that all the cembranoids strongly inhibit viability of melanoma cells particularly during 48 -72 hrs treatment and also inhibit de novo DNA synthesis and PARP activity and stimulate fragmentation of DNA. (1S,2E,4R,6E,8R,11S,12R)-8,12-epoxy-2,6-cembradiene-4,11-diol was not cytotoxic to monkey kidney CV-1 cells at the concentration that produces the anti-melanoma effects which indicates that this compound may be a good candidate for further development. (1S,2E,4R,6E,8S,11R,12S)-8,11-epoxy-4,12-epoxy-2,6-cembradiene and (1S,4R,13S)-cembra-2E,7E,11E-trien-4,13-diol were found to be cytotoxic to healthy cells.

The ν 3 and 2ν 3 bands of 32S 16O 3, 32S 18O 3, 34S 16O 3, and 34S 18O 3

DOE Office of Scientific and Technical Information (OSTI.GOV)

Sharpe, Steven W.; Blake, Thomas A.; Sams, Robert L.

2003-12-01

The fifth of a series of publications on the high resolution rotation-vibration spectra of sulfur trioxide reports the results of a systematic study of the v3(é) and 2v3(A1'+E') infrared bands of the four symmetric top isotopomers 32S 16O 3, 34S 16O 3, 32S 18O 3, and 34S 18O 3. An internal coupling between the l = 0 and l = +2 levels of the 2v3 (A1'+E') states was observed. This small perturbation results in a level crossing between K-l = 9 and 12, in consequence of which the band origins of the A1', l=0 “ghost” states could be determined tomore » a high degree of accuracy. Ground and upper state rotational as well as vibrational anharmonicity constants are reported. The constants for the center-of-mass substituted species 32S 16O 3 and 34S 16O 3 vary only slightly, as do the constants for the 32S 18O 3, 34S 18O 3 pair. The S-O bond lengths for the vibrational ground states of the species 32S 16O 3, 34S 16O 3, 32S 18O 3 and 34S 18O 3, are, respectively, 141.981992(6), 141.979412(20), 150.605240(73), and 150.602348(73) pm, where the uncertainties, given in parentheses, are two standard deviations and refer to the last digits of the associated quantity.« less

Methods of using (1S,3S)-3-amino-4-difluoromethylenyl-1-cyclopentanoic acid

DOEpatents

Silverman, Richard B; Dewey, Stephen L; Miller, Steven

2015-03-03

(1S,3S)-3-amino-4-difluoromethylenyl-1-cyclopentanoic acid also known as CPP-115 or its pharmaceutically acceptable salts can be used to treat addiction and neurological disorders such as epilepsy without side effects such as visual field defects caused by vigabatrin (Sabril).

MoS2/Ni3S4 composite nanosheets on interconnected carbon shells as an excellent supercapacitor electrode architecture for long term cycling at high current densities

NASA Astrophysics Data System (ADS)

Qin, Shengchun; Yao, Tinghui; Guo, Xin; Chen, Qiang; Liu, Dequan; Liu, Qiming; Li, Yali; Li, Junshuai; He, Deyan

2018-05-01

In this paper, we report an electrode architecture of molybdenum disulfide (MoS2)/nickel sulfide (Ni3S4) composite nanosheets anchored on interconnected carbon (C) shells (C@MoS2/Ni3S4). Electrochemical measurements indicate that the C@MoS2/Ni3S4 structure possesses excellent supercapacitive properties especially for long term cycling at high current densities. A specific capacitance as high as ∼640.7 F g-1 can still be delivered even after 10,000 cycles at a high current density of 20 A g-1. From comparison of microstructures and electrochemical properties of the related materials/structures, the improved performance of C@MoS2/Ni3S4 can be attributed to the relatively dispersedly distributed nanosheet-shaped MoS2/Ni3S4 that provides efficient contact with electrolyte and effectively buffers the volume change during charge/discharge processes, enhanced cycling stability by MoS2, and reduced equivalent series resistance by the interconnected C shells.

Highly efficient hydrogen evolution based on Ni3S4@MoS2 hybrids supported on N-doped reduced graphene oxide

NASA Astrophysics Data System (ADS)

Xu, Xiaobing; Zhong, Wei; Wu, Liqian; Sun, Yuan; Wang, Tingting; Wang, Yuanqi; Du, Youwei

2018-01-01

Hydrogen evolution reaction (HER) through water splitting at low overpotential is an appealing technology to produce renewable energy, wherein the design of stable electrocatalysts is very critical. To achieve optimal electrochemical performance, a highly efficient and stable noble-metal-free HER catalyst is synthesized by means of a facile hydrothermal co-synthesis. It consists of Ni3S4 nanosheets and MoS2 nanolayers supported on N-doped reduced graphene oxide (Ni3S4/MoS2@N-rGO). The optimized sample provides a large amount of active sites that benefit electron transfer in 3D conductive networks. Thanks to the strong synergistic effect in the catalyst network, we achieved a low overpotential of 94 mV, a small Tafel slope of 56 mV/dec and remarkable durability in an acidic medium.

Na 3Cr 2P 3S 12 and K 3Cr 2P 3S 12: Two New One-Dimensional Thiophosphate Compounds with a Novel Structure

NASA Astrophysics Data System (ADS)

Coste, S.; Kopnin, E.; Evain, M.; Jobic, S.; Payen, C.; Brec, R.

2001-12-01

Two new alkali metal chromium thiophosphates, Na3Cr2P3S12 and K3Cr2P3S12, have been synthesized and their structure determined from single-crystal or powder X-ray diffraction analyses. These isostructural compounds, which exhibit a novel structural arrangement, crystallize in the monoclinic system (space group P21/c) with the cell parameters a=17.4076(10) Å, b=11.1723(10) Å, c=19.2502(11) Å, β=149.731(3)° (V=1887.1(2) Å3, Z=4) and a=17.9690(14) Å, b=12.0607(5) Å, c=19.3109(16) Å, β=150.008(3)° (V=2091.98(16) Å3, Z=4) for Na3Cr2P3S12 (I) and K3Cr2P3S12 (II), respectively. For (I), the single-crystal refinement led to R/Rw(F2)=0.0417/0.0650 (for 4125 independent reflections and 182 refined parameters). For (II), the Rietveld refinement led to Rp/Rwp=0.0181/0.0233 (for 90 refined parameters). In both materials, the structures consist of 1∞[Cr2P3S12]3- chains built upon two edge-sharing [CrS6] octahedra capped by two [PS4] tetrahedra defining isolated [Cr2P2S12]-8 entities. These entities are linked to each other through an extra [PS4] tetrahedral group. Magnetic measurements evidence antiferromagnetic coupling between Cr3+ cations. The charge balance of the phase is MI3CrIII2PV3S-II12.

Isothermal sections of the quasi-ternary systems Ag{sub 2}S(Se)–Ga{sub 2}S(Se){sub 3}–In{sub 2}S(Se){sub 3} at 820 K and the physical properties of the ternary phases Ga{sub 5.5}In{sub 4.5}S{sub 15}, Ga{sub 6}In{sub 4}Se{sub 15} and Ga{sub 5.5}In{sub 4.5}S{sub 15}:Er{sup 3+}, Ga{sub 6}In{sub 4}Se{sub 15}:Er{sup 3+}

DOE Office of Scientific and Technical Information (OSTI.GOV)

Ivashchenko, I.A., E-mail: Ivashchenko.Inna@eenu.edu.ua; Danyliuk, I.V.; Gulay, L.D.

Isothermal sections of the quasi-ternary systems Ag{sub 2}S(Se)–Ga{sub 2}S(Se){sub 3}–In{sub 2}S(Se){sub 3} at 820 K were compared. Along the 50 mol% Ag{sub 2}S(Se), both systems feature continuous solid solutions with the chalcopyrite structure. Along the 17 mol% Ag{sub 2}S(Se), the interactions at the AgIn{sub 5}S(Se){sub 8}–'AgGa{sub 5}S(Se){sub 8}' sections are different. In the Ag{sub 2}S–Ga{sub 2}S{sub 3}–In{sub 2}S{sub 3} system the existence of the layered phase AgGa{sub x}In{sub 5–x}S{sub 8}, 2.25≤x≤2.85, was confirmed (S.G. P6{sub 3}mc). The Ag{sub 2}Se–Ga{sub 2}Se{sub 3}–In{sub 2}Se{sub 3} system features the formation of solid solution (up to 53 mol% Ga{sub 2}Se{sub 3}) based on AgIn{submore » 5}Se{sub 8} (S.G. P-42m). Crystal structure, atomic coordinates were determined by powder diffraction method for samples from the homogeneity region of AgIn{sub 5}Se{sub 8}. Specific conductivities of the crystals Ga{sub 6}In{sub 4}Se{sub 15} (1.33·10{sup −6} Ω{sup −1} m{sup −1}), Ga{sub 5.94}In{sub 3.96}Er{sub 0.1}Se{sub 15} (3.17·10{sup −6} Ω{sup −1} m{sup −1}), Ga{sub 5.5}In{sub 4.5}S{sub 15} (7.94·10{sup −6} Ω{sup −1} m{sup −1}), Ga{sub 5.46}In{sub 4.47}Er{sub 0.07}S{sub 15} (1·10{sup −9} Ω{sup −1} m{sup −1}) were measured at room temperature. Optical absorption and photoconductivity spectra were recorded in the range 400–760 nm. The introduction of erbium leads to an increase in the absorption coefficient and to the appearance of absorption bands at 530, 660, 810, 980, 1530 nm. - Highlights: • Nature of solid solutions in Ag{sub 2}S(Se)–Ga{sub 2}S(Se){sub 3}–In{sub 2}S(Se){sub 3} (820 K) were discussed. • Crystal structures of ternary and quaternary compounds were discussed. • Specific conductivity, optical properties of four single crystals were measured. • Photoconductivity of the Ga{sub 5.5}In{sub 4.5}S{sub 15} in the range 400–760 nm were recorded.« less

Measurement of the Υ ( 1 S ) , Υ ( 2 S ) , and Υ ( 3 S ) cross sections in pp collisions at s = 7   TeV

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chatrchyan, S.; Khachatryan, V.; Sirunyan, A. M.

Themore » $$\\Upsilon$$(1S), $$\\Upsilon$$(2S), and $$\\Upsilon$$(3S) production cross sections are measured using a data sample corresponding to an integrated luminosity of 35.8 $$\\pm$$ 1.4 inverse picobarns of proton-proton collisions at $$\\sqrt{s}$$ = 7 TeV, collected with the CMS detector at the LHC. Upsilon resonances are identified through their decays to dimuons. Integrated over the $$\\Upsilon$$ transverse momentum range $$p_{t}^{\\Upsilon} \\lt$$ 50GeV and rapidity range |$$y^\\Upsilon$$| $$\\lt$$ 2.4, and assuming unpolarized Upsilon production, the products of the Upsilon production cross sections and dimuon branching fractions are \\begin{equation*}\\sigma(pp \\to \\Upsilon(1S) X) . B(\\Upsilon(1S) \\to \\mu^+ \\mu^-) = (8.55 \\pm 0.05^{+0.56}_{-0.50} \\pm 0.34) nb,\\end{equation*} \\begin{equation*}\\sigma(pp \\to \\Upsilon(2S) X) . B(\\Upsilon(2S) \\to \\mu^+ \\mu^-) = (2.21 \\pm 0.03^{+0.16}_{-0.14} \\pm 0.09) nb,\\end{equation*} \\begin{equation*}\\sigma(pp \\to \\Upsilon(3S) X) . B(\\Upsilon(3S) \\to \\mu^+ \\mu^-) = (1.11 \\pm 0.02^{+0.10}_{-0.08} \\pm 0.04) nb, \\end{equation*} where the first uncertainty is statistical, the second is systematic, and the third is from the uncertainty in the integrated luminosity. differential cross sections in bins of transverse momentum and rapidity, and the cross section ratios are presented. Cross section measurements performed within a restricted muon kinematic range and not corrected for acceptance are also provided. These latter measurements are independent of Upsilon polarization assumptions. results are compared to theoretical predictions and previous measurements.« less

3-[4-Bromo-α( R*)-methoxybenzyl]-6-chloro-3( S*),4( S*)-dihydroxychroman: X-ray and DFT Studies

NASA Astrophysics Data System (ADS)

Sepay, Nayim; Mondal, Rina; Guha, Chayan; Mallik, Asok K.

2018-05-01

Sodium borohydride reduction of E-3-benzylidenechromanone epoxides in dry methanol has afforded 3( S*), 4( S*)-dihydroxy-3-[α( R*)-methoxybenzyl]chromans as an interesting class of products, the structures of which have been assigned mainly from spectral data and consideration of the mechanistic aspects. X-ray diffraction study of one of them, 3-[4-bromo-α( R*)-methoxybenzyl]-6-chloro-3( S*),4( S*)- dihydroxychroman, is performed. The title compound crystallizes in the monoclinic sp. gr. P21/ n, with a = 13.336(6) Å, b = 10.866(5) Å, c = 27.166(11) Å, β = 95.193(6)°, V = 3920(3) Å3, and Z = 8. Supramolecular construction of the compound involves O-H···O intermolecular hydrogen bonds as well as three other types of non-covalent interactions which are responsible for crystal packing. Density functional theory was applied for geometry optimization, molecular orbital calculations, and prediction of UV spectral features. The geometric parameters (bond lengths, bond angles, and dihedral angles) for the representative compound obtained from density functional theory with B3LY6-31G basis set were in good agreement with experimental values.

Low-temperature solid-state preparation of ternary CdS/g-C3N4/CuS nanocomposites for enhanced visible-light photocatalytic H2-production activity

NASA Astrophysics Data System (ADS)

Cheng, Feiyue; Yin, Hui; Xiang, Quanjun

2017-01-01

Low-temperature solid-state method were gradually demonstrated as a high efficiency, energy saving and environmental protection strategy to fabricate composite semiconductor materials. CdS-based multiple composite photocatalytic materials have attracted increasing concern owning to the heterostructure constituents with tunable band gaps. In this study, the ternary CdS/g-C3N4/CuS composite photocatalysts were prepared by a facile and novel low-temperature solid-state strategy. The optimal ternary CdS/g-C3N4/CuS composite exhibits a high visible-light photocatalytic H2-production rate of 57.56 μmol h-1 with the corresponding apparent quantum efficiency reaches 16.5% at 420 nm with Na2S/Na2SO3 mixed aqueous solution as sacrificial agent. The ternary CdS/g-C3N4/CuS composites show the enhanced visible-light photocatalytic H2-evolution activity comparing with the binary CdS-based composites or simplex CdS. The enhanced photocatalytic activity is ascribed to the heterojunctions and the synergistic effect of CuS and g-C3N4 in promotion of the charge separation and charge mobility. This work shows that the low-temperature solid-state method is efficient and environmentally benign for the preparation of CdS-based multiple composite photocatalytic materials with enhanced visible-light photocatalytic H2-production activity.

Study of dipion transitions among Υ(3S), Υ(2S), and Υ(1S) states

NASA Astrophysics Data System (ADS)

Cronin-Hennessy, D.; Gao, K. Y.; Hietala, J.; Kubota, Y.; Klein, T.; Lang, B. W.; Poling, R.; Scott, A. W.; Smith, A.; Zweber, P.; Dobbs, S.; Metreveli, Z.; Seth, K. K.; Tomaradze, A.; Ernst, J.; Ecklund, K. M.; Severini, H.; Love, W.; Savinov, V.; Lopez, A.; Mehrabyan, S.; Mendez, H.; Ramirez, J.; Huang, G. S.; Miller, D. H.; Pavlunin, V.; Sanghi, B.; Shipsey, I. P. J.; Xin, B.; Adams, G. S.; Anderson, M.; Cummings, J. P.; Danko, I.; Hu, D.; Moziak, B.; Napolitano, J.; He, Q.; Insler, J.; Muramatsu, H.; Park, C. S.; Thorndike, E. H.; Yang, F.; Artuso, M.; Blusk, S.; Khalil, S.; Li, J.; Menaa, N.; Mountain, R.; Nisar, S.; Randrianarivony, K.; Sia, R.; Skwarnicki, T.; Stone, S.; Wang, J. C.; Bonvicini, G.; Cinabro, D.; Dubrovin, M.; Lincoln, A.; Pappas, S. P.; Weinstein, A. J.; Asner, D. M.; Edwards, K. W.; Naik, P.; Briere, R. A.; Ferguson, T.; Tatishvili, G.; Vogel, H.; Watkins, M. E.; Rosner, J. L.; Adam, N. E.; Alexander, J. P.; Cassel, D. G.; Duboscq, J. E.; Ehrlich, R.; Fields, L.; Galik, R. S.; Gibbons, L.; Gray, R.; Gray, S. W.; Hartill, D. L.; Heltsley, B. K.; Hertz, D.; Jones, C. D.; Kandaswamy, J.; Kreinick, D. L.; Kuznetsov, V. E.; Mahlke-Krüger, H.; Mohapatra, D.; Onyisi, P. U. E.; Patterson, J. R.; Peterson, D.; Pivarski, J.; Riley, D.; Ryd, A.; Sadoff, A. J.; Schwarthoff, H.; Shi, X.; Stroiney, S.; Sun, W. M.; Wilksen, T.; Athar, S. B.; Patel, R.; Yelton, J.; Rubin, P.; Cawlfield, C.; Eisenstein, B. I.; Karliner, I.; Kim, D.; Lowrey, N.; Selen, M.; White, E. J.; Wiss, J.; Mitchell, R. E.; Shepherd, M. R.; Besson, D.; Pedlar, T. K.

2007-10-01

We present measurements of decay matrix elements for hadronic transitions of the form Υ(nS)→Υ(mS)ππ, where (n,m)=(3,1),(2,1),(3,2). We reconstruct charged and neutral pion modes with the final state Upsilon decaying to either μ+μ- or e+e-. Dalitz plot distributions for the 12 decay modes are fit individually as well as jointly assuming isospin symmetry, thereby measuring the matrix elements of the decay amplitude. We observe and account for the anomaly previously noted in the dipion invariant mass distribution for the Υ(3S)→Υ(1S)ππ transition and obtain good descriptions of the dynamics of the decay using the most general decay amplitude allowed by partial conservation of the axial-vector current considerations. The fits further indicate that the Υ(2S)→Υ(1S)ππ and Υ(3S)→Υ(2S)ππ transitions also show the presence of terms in the decay amplitude that were previously ignored, although at a relatively suppressed level.

The [4Fe-4S](2+) cluster in reconstituted biotin synthase binds S-adenosyl-L-methionine.

PubMed

Cosper, Michele Mader; Jameson, Guy N L; Davydov, Roman; Eidsness, Marly K; Hoffman, Brian M; Huynh, Boi Hanh; Johnson, Michael K

2002-11-27

The combination of resonance Raman, electron paramagnetic resonance and Mössbauer spectroscopies has been used to investigate the effect of S-adenosyl-l-methionine (SAM) on the spectroscopic properties of the [4Fe-4S]2+ cluster in biotin synthase. The results indicate that SAM interacts directly at a unique iron site of the [4Fe-4S]2+ cluster in BioB and support the hypothesis of a common inner-sphere mechanism for the reductive cleavage of SAM in the radical SAM family of Fe-S enzymes.

One-Pot Synthesis of Tunable Crystalline Ni3 S4 @Amorphous MoS2 Core/Shell Nanospheres for High-Performance Supercapacitors.

PubMed

Zhang, Yu; Sun, Wenping; Rui, Xianhong; Li, Bing; Tan, Hui Teng; Guo, Guilue; Madhavi, Srinivasan; Zong, Yun; Yan, Qingyu

2015-08-12

Transition metal sulfides gain much attention as electrode materials for supercapacitors due to their rich redox chemistry and high electrical conductivity. Designing hierarchical nanostructures is an efficient approach to fully utilize merits of each component. In this work, amorphous MoS(2) is firstly demonstrated to show specific capacitance 1.6 times as that of the crystalline counterpart. Then, crystalline core@amorphous shell (Ni(3)S(4)@MoS(2)) is prepared by a facile one-pot process. The diameter of the core and the thickness of the shell can be independently tuned. Taking advantages of flexible protection of amorphous shell and high capacitance of the conductive core, Ni(3)S(4) @amorphous MoS(2) nanospheres are tested as supercapacitor electrodes, which exhibit high specific capacitance of 1440.9 F g(-1) at 2 A g(-1) and a good capacitance retention of 90.7% after 3000 cycles at 10 A g(-1). This design of crystalline core@amorphous shell architecture may open up new strategies for synthesizing promising electrode materials for supercapacitors. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Treatment for GaSb surfaces using a sulphur blended (NH4)2S/(NH4)2SO4 solution

NASA Astrophysics Data System (ADS)

Murape, D. M.; Eassa, N.; Neethling, J. H.; Betz, R.; Coetsee, E.; Swart, H. C.; Botha, J. R.; Venter, A.

2012-07-01

A sulphur based chemical, [(NH4)2S/(NH4)2SO4] to which S has been added, not previously reported for the treatment of (1 0 0) n-GaSb surfaces, is introduced and benchmarked against the commonly used passivants Na2S·9H2O and (NH4)2S. The surfaces of the treated material were studied by scanning electron microscopy (SEM), Auger electron spectroscopy (AES) and X-ray photoelectron spectroscopy (XPS). It has been found that the native oxides present on the GaSb surface are more effectively removed when treated with ([(NH4)2S/(NH4)2SO4] + S) than with (NH4)2S or Na2S·9H2O, as evidenced by the ratio of the O506 eV to Sb457 eV AES peaks. XPS results reveal that Sb2S3/Sb2S5 "replaces" Sb2O3/Sb2O5, suggesting that sulphur atoms substitute oxygen atoms in Sb2O3/Sb2O5 to form Sbsbnd S. It seems sulphurization only partially removes Ga2O3. Treatment with ([(NH4)2S/(NH4)2SO4] + S) also results in a noteworthy improvement in the current-voltage (I-V) characteristics of Au/n-GaSb Schottky contacts compared to those fabricated on as-received material.

Phase equilibria in the quasiternary system Ag2S-Ga2S3-In2S3 and optical properties of (Ga55In45)2S300, (Ga54.59In44.66Er0.75)2S300 single crystals

NASA Astrophysics Data System (ADS)

Ivashchenko, I. A.; Danyliuk, I. V.; Olekseyuk, I. D.; Pankevych, V. Z.; Halyan, V. V.

2015-07-01

The quasiternary system Ag2S-Ga2S3-In2S3 was investigated by differential thermal, X-ray diffraction analyses. The phase diagram of the Ga2S3-In2S3 system and nine polythermal sections, isothermal section at 820 K and the liquidus surface projection were constructed. The existence of the large solid solutions ranges of binary and ternary compounds was established. The range of the existence of the quaternary phase AgGaxIn5-xS8 (2.25≤x≤2.85) at 820 K was determined. The single crystals (Ga55In45)2S300 and (Ga54.59In44.66Er0.75)2S300 were grown by a directional crystallization method from solution-melt. Optical absorption spectra in the 500-1600 nm range were recorded. The luminescence of the (Ga54.59In44.66Er0.75)2S300 single crystal shows a maximum at 1530 nm for the excitation wavelengths of 532 and 980 nm at 80 and 300 K.

Three-Dimensionally Hierarchical Ni/Ni3S2/S Cathode for Lithium-Sulfur Battery.

PubMed

Li, Zhe; Zhang, Shiguo; Zhang, Jiaheng; Xu, Miao; Tatara, Ryoichi; Dokko, Kaoru; Watanabe, Masayoshi

2017-11-08

Lithium-sulfur (Li-S) batteries have attracted interest as a promising energy-storage technology due to their overwhelming advantages such as high energy density and low cost. However, their commercial success is impeded by deterioration of sulfur utilization, significant capacity fade, and poor cycle life, which are principally originated from the severe shuttle effect in relation to the dissolution and migration of lithium polysulfides. Herein, we proposed an effective and facile strategy to anchor the polysulfides and improve sulfur loading by constructing a three-dimensionally hierarchical Ni/Ni 3 S 2 /S cathode. This self-supported hybrid architecture is sequentially fabricated by the partial sulfurization of Ni foam by a mild hydrothermal process, followed by physical loading of elemental sulfur. The incorporation of Ni 3 S 2 , with high electronic conductivity and strong polysulfide adsorption capability, can not only empower the cathode to alleviate the shuttle effect, but also afford a favorable electrochemical environment with lower interfacial resistance, which could facilitate the redox kinetics of the anchored polysulfides. Consequently, the obtained Ni/Ni 3 S 2 /S cathode with a sulfur loading of ∼4.0 mg/cm 2 demonstrated excellent electrochemical characteristics. For example, at high current density of 4 mA/cm 2 , this thick cathode demonstrated a discharge capacity of 441 mAh/g at the 150th cycle.

Electron Excitation Rate Coefficients for Transitions from the IS21S Ground State to the 1S2S1,3S and 1S2P1,3P0 Excited States of Helium

NASA Astrophysics Data System (ADS)

Aggarwal, K. M.; Kingston, A. E.; McDowell, M. R. C.

1984-03-01

The available experimental and theoretical electron impact excitation cross section data for the transitions from the 1s2 1S ground state to the 1s2s 1,3S and 1s2p 1,3P0 excited states of helium are assessed. Based on this assessed data, excitation rate coefficients are calculated over a wide electron temperature range below 3.0×106K. A comparison with other published results suggests that the rates used should be lower by a factor of 2 or more.

ZnS/Al2S3 Layer as a Blocking Layer in Quantum Dot Sensitized Solar Cells

NASA Astrophysics Data System (ADS)

Vafapoor, Borzoo; Fathi, Davood; Eskandari, Mehdi

2017-12-01

In this research, the effect of treatment of the CdS/CdSe sensitized ZnO photoanode by ZnS, Al2S3, and ZnS/Al2S3 nanoparticles as a barrier layer on the performance of quantum dot sensitized solar cell is investigated. Current density-voltage (J-V) characteristics show that cell efficiency is enhanced from 3.62% to 4.82% with treatment of a CdS/CdSe/ZnS sensitized ZnO photoanode by Al2S3 nanoparticles. In addition, short- circuit current density (J sc) is increased from 11.5 mA/cm2 to 14.8 mA/cm2. The results extracted from electrochemical impedance spectroscopy indicate that charge transfer resistance (R ct) in photoanode/electrolyte interfaces decreases with deposition of Al2S3 nanoparticles on CdS/CdSe/ZnS sensitized ZnO photoanodes, while the chemical capacitance of photoanode (C μ ) and electron lifetime (t n) increase. Also, results revealed that cell performance is considerably decreased with the treatment of the AL2S3 blocking layer incorporated between ZnO nanorods and CdS/CdSe QDs.

ZnS/Al2S3 Layer as a Blocking Layer in Quantum Dot Sensitized Solar Cells

NASA Astrophysics Data System (ADS)

Vafapoor, Borzoo; Fathi, Davood; Eskandari, Mehdi

2018-03-01

In this research, the effect of treatment of the CdS/CdSe sensitized ZnO photoanode by ZnS, Al2S3, and ZnS/Al2S3 nanoparticles as a barrier layer on the performance of quantum dot sensitized solar cell is investigated. Current density-voltage ( J- V) characteristics show that cell efficiency is enhanced from 3.62% to 4.82% with treatment of a CdS/CdSe/ZnS sensitized ZnO photoanode by Al2S3 nanoparticles. In addition, short- circuit current density ( J sc) is increased from 11.5 mA/cm2 to 14.8 mA/cm2. The results extracted from electrochemical impedance spectroscopy indicate that charge transfer resistance ( R ct) in photoanode/electrolyte interfaces decreases with deposition of Al2S3 nanoparticles on CdS/CdSe/ZnS sensitized ZnO photoanodes, while the chemical capacitance of photoanode ( C μ ) and electron lifetime ( t n) increase. Also, results revealed that cell performance is considerably decreased with the treatment of the AL2S3 blocking layer incorporated between ZnO nanorods and CdS/CdSe QDs.

40 CFR 180.1281 - S-Abscisic Acid, (S)-5-(1-hydroxy-2,6,6-trimethyl-4-oxo-1-cyclohex-2-enyl)-3-methyl-penta-(2Z,4E...

Code of Federal Regulations, 2010 CFR

2010-07-01

... 40 Protection of Environment 23 2010-07-01 2010-07-01 false S-Abscisic Acid, (S)-5-(1-hydroxy-2,6... Exemptions From Tolerances § 180.1281 S-Abscisic Acid, (S)-5-(1-hydroxy-2,6,6-trimethyl-4-oxo-1-cyclohex-2... from the requirement of a tolerance is established for residues of S-Abscisic Acid in or on all food...

Electronic structure of silver doped As2S3

NASA Astrophysics Data System (ADS)

Kaur, Veerpal; Khatta, Swati; Tripathi, S. K.; Prakash, S.

2018-04-01

We have studied the band structure, density of states and partial density of states for pure arsenic trisulfide (As2S3) and silver (Ag) doped arsenic trisulfide (As2S3) using DFT based GGA approach. It is observed that with the introduction of silver in As2S3, some extra states are observed in the gap region hence modifying the semiconducting gap in As2S3. These extra states in the gap region are due to 4d-states of silver.

Absolute cross section for electron-impact ionization of He (1 s 2 s 3S)

NASA Astrophysics Data System (ADS)

Génévriez, Matthieu; Jureta, Jozo J.; Defrance, Pierre; Urbain, Xavier

2017-07-01

We present an experimental determination of the electron-impact ionization cross section of the 1 s 2 s 3S state of helium, for which there is a serious long-lasting discrepancy between theory and experiment. A technique for the production of a fast, intense beam of helium in the 1 s 2 s 3S state only has been developed for this purpose, based on photodetachment of the He- anion. The cross section is measured using the animated crossed beam technique. The present results are much lower than the experimental data of Dixon et al. [J. Phys. B 9, 2617 (1976), 10.1088/0022-3700/9/15/013] and are in excellent agreement with the calculation of Fursa and Bray [J. Phys. B 36, 1663 (2003), 10.1088/0953-4075/36/8/317].

Worldsheet scattering in AdS3/CFT2

NASA Astrophysics Data System (ADS)

Sundin, Per; Wulff, Linus

2013-07-01

We confront the recently proposed exact S-matrices for AdS 3/ CFT 2 with direct worldsheet calculations. Utilizing the BMN and Near Flat Space (NFS) expansions for strings on AdS 3 × S 3 × S 3 × S 1 and AdS 3 × S 3 × T 4 we compute both tree-level and one-loop scattering amplitudes. Up to some minor issues we find nice agreement in the tree-level sector. At the one-loop level however we find that certain non-zero tree-level processes, which are not visible in the exact solution, contribute, via the optical theorem, and give an apparent mismatch for certain amplitudes. Furthermore we find that a proposed one-loop modification of the dressing phase correctly reproduces the worldsheet calculation while the standard Hernandez-Lopez phase does not. We also compute several massless to massless processes.

Novel Solution Process for Fabricating Ultra-Thin-Film Absorber Layers in Fe 2SiS 4 and Fe 2GeS 4 Photovoltaics

DOE Office of Scientific and Technical Information (OSTI.GOV)

Orefuwa, Samuel A.; Lai, Cheng-Yu; Dobson, Kevin D.

2014-05-12

Fe 2SiS 4 and Fe 2GeS 4 crystalline materials posses direct bandgaps of ~1.55 and ~1.4 eV respectively and an absorption coefficient larger than 10^5 cm–1; their theoretical potential as solar photovoltaic absorbers has been demonstrated. However, no solar devices that employ either Fe 2SiS 4 or Fe 2GeS 4 have been reported to date. In the presented work, nanoprecursors to Fe 2SiS 4 and Fe 2GeS 4 have been fabricated and employed to build ultra-thin-film layers via spray coating and rod coating methods. Temperature-dependent X-Ray diffraction analyses of nanoprecursors coatings show an unprecedented low temperature for forming crystalline Femore » 2SiS 4 and Fe 2GeS 4. Fabricating of ultra-thin-film photovoltaic devices utilizing Fe 2SiS 4 and Fe 2GeS 4 as solar absorber material is presented.« less

Hadronic Transitions from Upsilon (2S) to Upsilon (1s) and Upsilon Dipion Transitions at Energies Near the Upsilon (4S)

NASA Astrophysics Data System (ADS)

Kotoy, Sergei Anatolievich

This dissertation consists of two closely related analyses, both of which were performed using data collected with the CLEO II detector at the Cornell Electron Storage Ring. In the first analysis, using the world largest data sample of Υ(2 S) events, we have investigated the hadronic transitions between the Υ(2S) and the Υ(1S), i.e. decays of the Υ(2S) into the Υ(1S), plus a pair of pions ( p+p- or p0p0 ), a single η or a single p0 . The dipion transitions U(2S)-->U( 1S)pp were studied most closely, by using two different techniques: ``exclusive'' and ``inclusive''. In these measurements we determine the U(2S)-->U( 1S)pp branching ratios, and, by combining the exclusive and inclusive results, we derive the Υ(1S), leptonic branching ratios Bee and Bmm . Parameters of the ππ system in the dipion transitions (dipion invariant mass spectra, angular distributions) were analyzed and found to be consistent with current theoretical models. Lastly, we searched for the η and single π0 transitions and obtained upper limits on the branching ratios B(U(2S) -->U(1S)h ) and B(U(2S) -->U(1S)p 0) . In the second analysis, the data collected at the center of mass energies near the Υ(4S) were used to search for the dipion transition between pairs of Υ resonances. As a result of this search, we established upper limits on the branching ratios of the dipion transitions post='par'>p+p- and U(4S)-->U( 1S)p+p- , and measured the cross-sections for the radiative production of Υ(3 S) and Υ(2S) resonances e+e--->U(nS) g at the center of mass energies of Ecm = 10.58 GeV and Ecm = 10.52 GeV.

Deletion of the S3–S4 Linker in theShaker Potassium Channel Reveals Two Quenching Groups near the outside of S4

PubMed Central

Sørensen, J.B.; Cha, A.; Latorre, R.; Rosenman, E.; Bezanilla, F.

2000-01-01

When attached outside the voltage-sensing S4 segment of the Shaker potassium channel, the fluorescent probe tetramethylrhodamine (TMRM) undergoes voltage-dependent fluorescence changes (ΔF) due to differential interaction with a pH-titratable external protein-lined vestibule (Cha, A., and F. Bezanilla. 1998. J. Gen. Physiol. 112:391–408.). We attached TMRM at the same sites [corresponding to M356C and A359C in the wild-type (wt) channel] in a deletion mutant of Shaker where all but the five amino acids closest to S4 had been removed from the S3–S4 linker. In the deletion mutant, the maximal ΔF/F seen was diminished 10-fold, and the ΔF at M356C became pH independent, suggesting that the protein-lined vestibule is made up in large part by the S3–S4 linker. The residual ΔF showed that the probe still interacted with two putative quenching groups near the S4 segment. One group was detected by M356C-TMRM (located outside of S3 in the deletion mutant) and reported on deactivation gating charge movement when applying hyperpolarizing voltage steps from a holding potential of 0 mV. During activating voltage steps from a holding potential of −90 mV, the fluorescence lagged considerably behind the movement of gating charge over a range of potentials. Another putative quenching group was seen by probes attached closer to the S4 and caused a ΔF at extreme hyperpolarizations (more negative than −90 mV) only. A signal from the interaction with this group in the wt S3–S4 linker channel (at L361C) correlated with gating charge moving in the hyperpolarized part of the Q-V curve. Probe attached at A359C in the deletion mutant and at L361C in wt channel showed a biphasic ΔF as the probe oscillated between the two groups, revealing that there is a transient state of the voltage sensor in between, where the probe has maximal fluorescence. We conclude that the voltage sensor undergoes two distinct conformational changes as seen from probes attached outside the S4

Measurements of the $$\\Upsilon$$(1S), $$\\Upsilon$$(2S), and $$\\Upsilon$$(3S) differential cross sections in pp collisions at $$\\sqrt{s} =$$ 7 TeV

DOE PAGES

Khachatryan, Vardan

2015-07-22

Differential cross sections as a function of transverse momentum p T are presented for the production of Υ(nS) (n = 1, 2, 3) states decaying into a pair of muons. Thus, data corresponding to an integrated luminosity of 4.9 fb -1 in pp collisions at √s = 7 TeV were collected with the CMS detector at the LHC. The analysis selects events with dimuon rapidity |y| < 1.2 and dimuon transverse momentum in the range 10 < p T < 100 GeV. The measurements show a transition from an exponential to a power-law behavior at p T ≈ 20 GeVmore » for the three Υ states. Above that transition, the Υ(3S) spectrum is significantly harder than that of the Υ(1S). The ratios of the Υ(3S) and Υ(2S) differential cross sections to theγ Υ(1S) cross section show a rise as p T increases at low p T, then become flatter at higher p T.« less

Design and synthesis of highly potent benzodiazepine gamma-secretase inhibitors: preparation of (2S,3R)-3-(3,4-difluorophenyl)-2-(4-fluorophenyl)-4- hydroxy-N-((3S)-1-methyl-2-oxo-5- phenyl-2,3-dihydro-1H-benzo[e][1,4]-diazepin-3-yl)butyramide by use of an asymmetric Ireland-Claisen rearrangement.

PubMed

Churcher, Ian; Williams, Susie; Kerrad, Sonia; Harrison, Timothy; Castro, José L; Shearman, Mark S; Lewis, Huw D; Clarke, Earl E; Wrigley, Jonathan D J; Beher, Dirk; Tang, Yui S; Liu, Wensheng

2003-06-05

Novel benzodiazepine-containing gamma-secretase inhibitors for potential use in Alzheimer's disease have been designed that incorporate a substituted hydrocinnamide C-3 side chain. A syn combination of alpha-alkyl or aryl and beta-hydroxy or hydroxymethyl substituents was shown to give highly potent compounds. In particular, (2S,3R)-3-(3,4-difluorophenyl)-2-(4-fluorophenyl)-4-hydroxy-N-((3S)-2-oxo-5-phenyl-2,3-dihydro-1H-benzo[e][1,4]diazepin-3-yl)butyramide (34) demonstrated excellent in vitro potency (IC(50) = 0.06 nM). 34 could also be selectively methylated to give [(3)H]-28, which is of use in radioligand binding assays.

No Evidence from FTIR Difference Spectroscopy that Glutamate-189 of the D1 Polypeptide Ligates a Mn Ion that Undergoes Oxidation During the S0 to S1, S1 to S2, or S2 to S3 Transitions in Photosystem II†

PubMed Central

Strickler, Melodie A.; Hillier, Warwick; Debus, Richard J.

2008-01-01

In the recent X-ray crystallographic structural models of photosystem II, Glu189 of the D1 polypeptide is assigned as a ligand of the oxygen-evolving Mn4 cluster. To determine if D1-Glu189 ligates a Mn ion that undergoes oxidation during one or more of the S0 → S1, S1 → S2, and S2 → S3 transitions, the FTIR difference spectra of the individual S state transitions in D1-E189Q and D1-E189R mutant PSII particles from the cyanobacterium Synechocystis sp. PCC 6803 were compared with those in wild-type PSII particles. Remarkably, the data show that neither mutation significantly alters the mid-frequency regions (1800 − 1200 cm−1) of any of the FTIR difference spectra. Importantly, neither mutation eliminates any specific symmetric or asymmetric carboxylate stretching mode that might have been assigned to D1-Glu189. The small spectral alterations that are observed are similar in amplitude to those that are observed in wild-type PSII particles that have been exchanged into FTIR analysis buffer by different methods or those that are observed in D2-H189Q mutant PSII particles (the residue D2-His189 is located > 25 Å from the Mn4 cluster and accepts a hydrogen bond from Tyr YD). The absence of significant mutation-induced spectral alterations in the D1-Glu189 mutants shows that the oxidation of the Mn4 cluster does not alter the frequencies of the carboxylate stretching modes of D1-Glu189 during the S0 → S1, S1 → S2, or S2 → S3 transitions. One explanation of these data is that D1-Glu189 ligates a Mn ion that does not increase its charge or oxidation state during any of these S state transitions. However, because the same conclusion was reached previously for D1-Asp170, and because the recent X-ray crystallographic structural models assign D1-Asp170 and D1-Glu189 as ligating different Mn ions, this explanation requires that (1) the extra positive charge that develops on the Mn4 cluster during the S1 → S2 transition be localized on the Mn ion that is ligated

Anticonvulsant activity of a mGlu(4alpha) receptor selective agonist, (1S,3R,4S)-1-aminocyclopentane-1,2,4-tricarboxylic acid.

PubMed

Chapman, A G; Talebi, A; Yip, P K; Meldrum, B S

2001-07-20

The metabotropic Group III agonist, (1S,3R,4S)-1-aminocyclopentane-1,2,4-tricarboxylic acid (ACPT-1), selective for the mGlu(4alpha) receptor, suppresses sound-induced seizures in DBA/2 mice following its intracerebroventricular (i.c.v.) administration (ED(50) 5.6 [2.9-10.7], nmol i.c.v., 15 min, clonic phase) and in genetically epilepsy-prone (GEP) rats following focal administration into the inferior colliculus (ED(50) 0.08 [0.01-0.50], nmol, 60 min, clonic phase). ACPT-1 also protects against clonic seizures induced in DBA/2 mice by the Group I agonist, (RS)-3,5-dihydroxyphenylglycine (3,5-DHPG) (ED(50) 0.60 [0.29-1.2], nmol i.c.v.) and by the Group III antagonist, (RS)-alpha-methylserine-O-phosphate (MSOP) (ED(50) 49.3 [37.9-64.1], nmol i.c.v.). Another Group III agonist, (RS)-4-phosphonophenyl-glycine (PPG), preferentially activating the mGlu(8) receptor, previously shown to protect against sound-induced seizures in DBA/2 mice and GEP rats, also protects against seizures induced in DBA/2 by 3,5-DHPG (ED(50) 3.7 [2.4-5.7], nmol i.c.v.) and by the Group III antagonist, MSOP (ED(50) 40.2 [21.0-77.0], nmol i.c.v.). At very high doses (500 nmol i.c.v. and above), Group III antagonists have pro-convulsant and convulsant activity. The anticonvulsant protection against sound-induced seizures in DBA/2 mice provided by a fully protective dose (20 nmol, i.c.v.) of the mGlu(4) receptor agonist ACPT-1, is partially reversed by the co-administration of the Group III antagonists, MSOP, (RS)-alpha-methyl-4-phosphonophenylglycine (MPPG) or (S)-2-amino-2-methyl-4-phosphonobutanoic acid (MAP4), in the 20-50 nmol dose range. At doses of 50-200 nmol, MPPG and MAP4 cause further reversal of the ACPT-1 anticonvulsant protection, while the MSOP effect on ACPT-1 protection is abolished at higher doses. In contrast, the anticonvulsant protection against sound-induced seizures in DBA/2 mice provided by a fully protective dose (20 nmol, i.c.v.) of the mGlu(8) receptor agonist PPG, is not

Cd-free buffer layer materials on Cu2ZnSn(SxSe1-x)4: Band alignments with ZnO, ZnS, and In2S3

NASA Astrophysics Data System (ADS)

Barkhouse, D. Aaron R.; Haight, Richard; Sakai, Noriyuki; Hiroi, Homare; Sugimoto, Hiroki; Mitzi, David B.

2012-05-01

The heterojunctions formed between Cu2ZnSn(SxSe1-x)4 (CZTSSe) and three Cd-free n-type buffers, ZnS, ZnO, and In2S3, were studied using femtosecond ultraviolet photoemission and photovoltage spectroscopy. The electronic properties including the Fermi level location at the interface, band bending in the CZTSSe substrate, and valence and conduction band offsets were determined and correlated with device properties. We also describe a method for determining the band bending in the buffer layer and demonstrate this for the In2S3/CZTSSe system. The chemical bath deposited In2S3 buffer is found to have near optimal conduction band offset (0.15 eV), enabling the demonstration of Cd-free In2S3/CZTSSe solar cells with 7.6% power conversion efficiency.

F-theory and AdS3/CFT2 (2, 0)

NASA Astrophysics Data System (ADS)

Couzens, Christopher; Martelli, Dario; Schäfer-Nameki, Sakura

2018-06-01

We continue to develop the program initiated in [1] of studying supersymmetric AdS3 backgrounds of F-theory and their holographic dual 2d superconformal field theories, which are dimensional reductions of theories with varying coupling. Imposing 2d N=(0,2) supersymmetry,wederivethegeneralconditionsonthegeometryforTypeIIB AdS3 solutions with varying axio-dilaton and five-form flux. Locally the compact part of spacetime takes the form of a circle fibration over an eight-fold Y_8^{τ } , which is elliptically fibered over a base \\tilde{M}_6 . We construct two classes of solutions given in terms of a product ansatz \\tilde{M}_6}=Σ × {M}_4 , where Σ is a complex curve and \\tilde{M}_4 is locally a Kähler surface. In the first class \\tilde{M}_4 is globally a Kähler surface and we take the elliptic fibration to vary non-trivially over either of these two factors, where in both cases the metrics on the total space of the elliptic fibrations are not Ricci-flat. In the second class the metric on the total space of the elliptic fibration over either curve or surface are Ricci-flat. This results in solutions of the type AdS3 × K3 × ℳ 5 τ , dual to 2d (0, 2) SCFTs, and AdS3 × S 3/Γ × CY 3, dual to 2d (0, 4) SCFTs, respectively. In all cases we compute the charges for the dual field theories with varying coupling and find agreement with the holographic results. We also show that solutions with enhanced 2d N=(2,2) supersymmetry must have constant axio-dilaton. Allowing the internal geometry to be non-compact leads to the most general class of Type IIB AdS5 solutions with varying axio-dilaton, i.e. F-theoretic solutions, that are dual to 4d N=1 SCFTs.

STS-117 S3 and S4 Trusses in the Space Shuttle Atlantis Cargo Bay

NASA Technical Reports Server (NTRS)

2007-01-01

This nadir view of the STS-117 mission Space Shuttle Atlantis, taken by the Expedition 15 crew aboard the International Space Station (ISS), occurred just before the two spacecraft linked up in Earth orbit. Berthed in the cargo bay are the 17.8 ton second and third (S3 and S4) truss segments ready for installment. STS-117 mission objectives included the addition of S3 and S4 with Photovoltaic Radiator (PVR), the deployment of the third set of solar arrays, and the retraction of the P4 starboard solar array wing and one radiator.

Ba{sub 3}GeS{sub 5} and Ba{sub 3}InS{sub 4}Cl: Interesting size effects originated from the tetrahedral anions

DOE Office of Scientific and Technical Information (OSTI.GOV)

Pan, Ming-Yan; Xia, Sheng-Qing, E-mail: shqxia@sdu.edu.cn; Liu, Xiao-Cun

2014-11-15

Two new barium chalcogenides, Ba{sub 3}GeS{sub 5} and Ba{sub 3}InS{sub 4}Cl, were synthesized by using high temperature solid-state reactions and their structures were determined by single-crystal X-ray diffraction technique. Despite the similar chemical formula, the structures of Ba{sub 3}GeS{sub 5} and Ba{sub 3}InS{sub 4}Cl are subtly different due to the size effects originated from the tetrahedral anions. Ba{sub 3}GeS{sub 5} crystallizes in the orthorhombic space group Pnma (no. 62) with cell parameters of a=12.0528(9) Å, b=9.5497(7) Å and c=8.5979(6) Å, while Ba{sub 3}InS{sub 4}Cl adopts a different tetragonal system (space group: I4/mcm, no. 140, a=b=8.3613(6) Å, c=14.3806(18) Å). The measuredmore » optical band gap of Ba{sub 3}GeS{sub 5} is 3.0 eV, a little smaller than the value of 3.42 eV in Ba{sub 3}InS{sub 4}Cl. Theoretical calculations by Wien2k are provided as well in order to better understand these results. - Graphical abstract: The polyhedral structure view for Ba{sub 3}GeS{sub 5} and Ba{sub 3}InS{sub 4}Cl in which Ba, S and Cl atoms are plotted in purple, red and green spheres. - Highlights: • Two new barium chalcogenides, Ba{sub 3}GeS{sub 5} and Ba{sub 3}InS{sub 4}Cl, were synthesized from the BaCl{sub 2}-flux reactions. • Their crystal structures feature discrete [MS{sub 4}] tetrahedra which embody interesting size effects. • Both compounds exhibit a band gap around 3.0 eV. • They are thermally stable up to 1073 K.« less

Temperature-Dependent Kinetics Studies of the Reactions Br((sup 2)P3/2) + H2S yields SH + HBr and Br((sup 2)P3/2) + CH3SH yields CH3S + HBr. Heats of Formation of SH and CH3S Radicals

NASA Technical Reports Server (NTRS)

Nicovich, J. M.; Kreutter, K. D.; vanDijk, C. A.; Wine, P. H.

1997-01-01

Time resolved resonance fluorescence detection of Br(sup 2)P3/2) atom disappearance or appearance following 266-nm laser flash photolysis of CF2Br2/H2S/H2/N2, CF2Br2/CH3SH/H2/N2, Cl2CO/H2S/HBr/N2, and CH3SSCH3/HBr/H2/N2 mixtures has been employed to study the kinetics of the reactions Br((sup 2)P3/2) + H2S = SH + HBr (1,-1) and Br((sup2)P3/2) + CH3SH = CH3S + HBr (2, -2) as a function of temperature over the range 273-431K. Arrhenius expressions in units of 10(exp -12) cu cm/molecule/s which describe the results are k1 = (14.2 +/- 3.4) exp[(-2752 +/- 90)/T],(k-1) = (4.40 +/- 0.92) exp[(-971 +/- 73)/T],k(2) = (9.24 +/- 1.15) exp[(-386 +/- 41)/T], and k(-2) = (1.46 +/-0.21) exp[(-399 +/-41)/T; errors are 2 sigma and represent precision only. By examining Br((sup 2)P3/2) equilibrium kinetics following 355nm laser flash photolysis of Br2/CH3SH/H2/N2 mixtures, a 298 K rate coefficient of (1.7 +/- 0.5) x 10(exp -10) cu cm/molecule/s has been obtained for the reaction CH3S + Br2 yields CH3SBr + Br. To our knowledge, these are the first kinetic data reported for each of the reactions studied. Measured rate coefficients, along with known rate coefficients for similar radical + H2S, CH3SH, HBr,Br2 reactions are considered in terms of possible correlations of reactivity with reaction thermochemistry and with IP - EA, the difference between the ionization potential of the electron donor and the electron affinity of the electron acceptor. Both thermochemical and charge-transfer effects appear to be important in controlling observed reactivities. Second and third law analyses of the equilibrium data for reactions 1 and 2 have been employed to obtain the following enthalpies of reaction in units of kcal/mol: for reaction 1, Delta-H(298) = 3.64 +/- 0.43 and Delta-H(0) = 3.26 +/-0.45; for reaction 2, Delta-H(298) = -0.14 +/- 0.28 and Delta-H(0) = -0.65 +/- 0.36. Combining the above enthalpies of reaction with the well-known heats of formation of Br, HBr, H2S, and CH3SH gives the

Iron-sulfur cluster disassembly in the FNR protein of Escherichia coli by O2: [4Fe-4S] to [2Fe-2S] conversion with loss of biological activity

PubMed Central

Khoroshilova, Natalia; Popescu, Codrina; Münck, Eckard; Beinert, Helmut; Kiley, Patricia J.

1997-01-01

The transcription factor FNR (fumarate nitrate reduction) requires the presence of an iron-sulfur (Fe-S) cluster for its function as a global transcription regulator in Escherichia coli when oxygen becomes scarce. To define the oxidation state and type of Fe-S cluster present in the active form of FNR, we have studied anaerobically purified FNR with Mössbauer spectroscopy. Our data showed that this form of FNR contained a [4Fe-4S]2+ cluster (δ = 0.45 mm/s; ΔEQ = 1.22 mm/s) and that the [4Fe-4S]2+ cluster was rapidly destroyed on exposure of FNR to air. Under these conditions, the yellow–green active form of FNR turned deep red; analysis of sulfide indicated that 70% of the labile sulfide was still present, suggesting that the Fe-S cluster had been converted into a different form. Little [3Fe-4S] cluster was, however, detected by EPR. According to Mössbauer spectroscopy, the [4Fe-4S]2+ cluster was converted in about 60% yield to a [2Fe-2S]2+ cluster (δ = 0.28 mm/s; ΔEQ = 0.58 mm/s) following 17 min of exposure to air. The [2Fe-2S]2+ cluster form of FNR was much more stable to oxygen, but was unable to sustain biological activity (e.g., DNA binding). However, DNA binding and the absorption spectrum characteristic of the [4Fe-4S]2+ cluster could be largely restored from the [2Fe-2S]2+ form when Cys, Fe, DTT, and the NifS protein were added. It has yet to be determined whether the form of FNR containing the [2Fe-2S]2+ cluster has any biological significance, e.g., as an in vivo intermediate that is more rapidly converted to the active form than the apoprotein. PMID:9177174

Cation–Eutectic Transition via Sublattice Melting in CuInP 2S 6/In 4/3P 2S 6 van der Waals Layered Crystals

DOE PAGES

Susner, Michael A.; Chyasnavichyus, Marius; Puretzky, Alexander A.; ...

2017-07-07

Single crystals of the van der Waals layered ferrielectric material CuInP 2S 6 spontaneously phase separate when synthesized with Cu deficiency. In this paper, we identify a route to form and tune intralayer heterostructures between the corresponding ferrielectric (CuInP 2S 6) and paraelectric (In 4/3P 2S 6) phases through control of chemical phase separation. We conclusively demonstrate that Cu-deficient Cu 1–xIn 1+x/3P 2S 6 forms a single phase at high temperature. We also identify the mechanism by which the phase separation proceeds upon cooling. Above 500 K both Cu + and In 3+ become mobile, while P 2S 6 4–more » anions maintain their structure. We therefore propose that this transition can be understood as eutectic melting on the cation sublattice. Such a model suggests that the transition temperature for the melting process is relatively low because it requires only a partial reorganization of the crystal lattice. As a result, varying the cooling rate through the phase transition controls the lateral extent of chemical domains over several decades in size. At the fastest cooling rate, the dimensional confinement of the ferrielectric CuInP 2S 6 phase to nanoscale dimensions suppresses ferrielectric ordering due to the intrinsic ferroelectric size effect. Finally, intralayer heterostructures can be formed, destroyed, and re-formed by thermal cycling, thus enabling the possibility of finely tuned ferroic structures that can potentially be optimized for specific device architectures.« less

Cation–Eutectic Transition via Sublattice Melting in CuInP 2S 6/In 4/3P 2S 6 van der Waals Layered Crystals

DOE Office of Scientific and Technical Information (OSTI.GOV)

Susner, Michael A.; Chyasnavichyus, Marius; Puretzky, Alexander A.

Single crystals of the van der Waals layered ferrielectric material CuInP 2S 6 spontaneously phase separate when synthesized with Cu deficiency. In this paper, we identify a route to form and tune intralayer heterostructures between the corresponding ferrielectric (CuInP 2S 6) and paraelectric (In 4/3P 2S 6) phases through control of chemical phase separation. We conclusively demonstrate that Cu-deficient Cu 1–xIn 1+x/3P 2S 6 forms a single phase at high temperature. We also identify the mechanism by which the phase separation proceeds upon cooling. Above 500 K both Cu + and In 3+ become mobile, while P 2S 6 4–more » anions maintain their structure. We therefore propose that this transition can be understood as eutectic melting on the cation sublattice. Such a model suggests that the transition temperature for the melting process is relatively low because it requires only a partial reorganization of the crystal lattice. As a result, varying the cooling rate through the phase transition controls the lateral extent of chemical domains over several decades in size. At the fastest cooling rate, the dimensional confinement of the ferrielectric CuInP 2S 6 phase to nanoscale dimensions suppresses ferrielectric ordering due to the intrinsic ferroelectric size effect. Finally, intralayer heterostructures can be formed, destroyed, and re-formed by thermal cycling, thus enabling the possibility of finely tuned ferroic structures that can potentially be optimized for specific device architectures.« less

Nitric oxide reactivity of [2Fe-2S] clusters leading to H2S generation.

PubMed

Tran, Camly T; Williard, Paul G; Kim, Eunsuk

2014-08-27

The crosstalk between two biologically important signaling molecules, nitric oxide (NO) and hydrogen sulfide (H2S), proceeds via elusive mechanism(s). Herein we report the formation of H2S by the action of NO on synthetic [2Fe-2S] clusters when the reaction environment is capable of providing a formal H(•) (e(-)/H(+)). Nitrosylation of (NEt4)2[Fe2S2(SPh)4] (1) in the presence of PhSH or (t)Bu3PhOH results in the formation of (NEt4)[Fe(NO)2(SPh)2] (2) and H2S with the concomitant generation of PhSSPh or (t)Bu3PhO(•). The amount of H2S generated is dependent on the electronic environment of the [2Fe-2S] cluster as well as the type of H(•) donor. Employment of clusters with electron-donating groups or H(•) donors from thiols leads to a larger amount of H2S evolution. The 1/NO reaction in the presence of PhSH exhibits biphasic decay kinetics with no deuterium kinetic isotope effect upon PhSD substitution. However, the rates of decay increase significantly with the use of 4-MeO-PhSH or 4-Me-PhSH in place of PhSH. These results provide the first chemical evidence to suggest that [Fe-S] clusters are likely to be a site for the crosstalk between NO and H2S in biology.

Rates of proton transfer to Fe-S-based clusters: comparison of clusters containing {MFe(mu(2)-S)(2)}n+ and {MFe(3)(mu(3)-S)(4)}n+ (M = Fe, Mo, or W) cores.

PubMed

Bates, Katie; Garrett, Brendan; Henderson, Richard A

2007-12-24

The rates of proton transfer from [pyrH]+ (pyr = pyrrolidine) to the binuclear complexes [Fe2S2Cl4]2- and [S2MS2FeCl2]2- (M = Mo or W) are reported. The reactions were studied using stopped-flow spectrophotometry, and the rate constants for proton transfer were determined from analysis of the kinetics of the substitution reactions of these clusters with the nucleophiles Br- or PhS- in the presence of [pyrH]+. In general, Br- is a poor nucleophile for these clusters, and proton transfer occurs before Br- binds, allowing direct measure of the rate of proton transfer from [pyrH]+ to the cluster. In contrast, PhS- is a better nucleophile, and a pathway in which PhS- binds preferentially to the cluster prior to proton transfer from [pyrH]+ usually operates. For the reaction of [Fe2S2Cl4]2- with PhS- in the presence of [pyrH]+ both pathways are observed. Comparison of the results presented in this paper with analogous studies reported earlier on cuboidal Fe-S-based clusters allows discussion of the factors which affect the rates of proton transfer in synthetic clusters including the nuclearity of the cluster core, the metal composition, and the nature of the terminal ligands. The possible relevance of these findings to the protonation sites of natural Fe-S-based clusters, including FeMo-cofactor from nitrogenase, are presented.

Laser-induced breakup of helium 3S 1s2s with intermediate doubly excited states

NASA Astrophysics Data System (ADS)

Simonsen, A. S.; Bachau, H.; Førre, M.

2014-02-01

Solving the time-dependent Schrödinger equation in full dimensionality for two electrons, it is found that in the XUV regime the two-photon double ionization dynamics of He(1s2s) is predominantly dictated by the process of resonance enhanced multiphoton ionization via doubly excited states (DESs). We have studied a pump-probe scenario where the full laser-driven breakup of the 3S 1s2s metastable state is dominated by intermediate quasiresonant excitation to doubly excited (autoionizing) states in the 3Po series. Clear evidence of multipath interference effects is revealed in the resulting angular distributions of the ejected electrons in cases where more than one intermediate DES is populated in the process.

The La{sub 2}S{sub 3}-LaS{sub 2} system: Thermodynamic and kinetic study

DOE Office of Scientific and Technical Information (OSTI.GOV)

Vasilyeva, I.G., E-mail: kamarz@niic.nsc.r; Nikolaev, R.E.

2010-08-15

A detailed thermodynamic study of the LaS{sub 2}-La{sub 2}S{sub 3} system in the temperature range 350-1000 {sup o}C was performed, starting from high quality crystals LaS{sub 2} as the highest polysulfide in the system, and using a sensitive static tensimetric method with a quartz Bourdon gauge and a membrane as a null-point instrument. The p{sub S}-T-x diagram obtained has shown that the phase region covering the composition between LaS{sub 2} and La{sub 2}S{sub 3}, which was previously described as a single grossly nonstoichiometric phase, consists of three discrete stoichiometric phases, LaS{sub 2.00}, LaS{sub 1.91}, and LaS{sub 1.76}, where compositions couldmore » be determined with an accuracy of {+-}0.01 f.u. The thermodynamic characteristics of evaporation of the polysulfides as well as standard heat of LaS{sub 2} formation were calculated. The role of kinetics in the formation of ordered superstructures of sulfur-poorer polysulfides with different formal concentration of vacancies is considered. - Graphical abstract: The p{sub S}-T stability fields for La-polysulfides in the concentration range between LaS{sub 2} and La{sub 2}S{sub 3}.« less

Dirac operators on the S3 and S2 spheres

NASA Astrophysics Data System (ADS)

Cosmo, Fabio Di; Zampini, Alessandro

We describe both the Hodge-de Rham and the spin manifold Dirac operator on the spheres S3 and S2, following the formalism introduced by Kähler, and exhibit a complete spectral resolution for them in terms of suitably globally defined eigenspinors.

Electronic structure and fragmentation properties of [Fe4S4(SEt)4-x(SSEt)x]2-

NASA Astrophysics Data System (ADS)

Fu, You-Jun; Laskin, Julia; Wang, Lai-Sheng

2007-06-01

A limited exposure of (n-Bu4N)2[Fe4S4(SEt)4] solutions in acetonitrile to air was found to produce a new series of [4Fe-4S] cluster complexes, [Fe4S4(SEt)4-x(SSEt)x]2- (x = 1-4), with the original -SEt ligands substituted by -SSEt di-sulfide ligands, which were formed due to partial decomposition of the [4Fe-4S] core in parent [Fe4S4(SEt)4]2-. The products were first observed in the experiments with an ESI-ion Trap-TOF mass spectrometer and were further identified using high resolution Fourier transform ion cyclotron resonance (FTICR) mass spectrometer. Photoelectron spectra of the [Fe4S4(SEt)4-x(SSEt)x]2- dianions revealed that the -SSEt coordination induced little change in the electronic structure of the [4Fe-4S] cluster, but the electron binding energies of [Fe4S4(SEt)4-x(SSEt)x]2- increased from 0.52 to 0.73 eV with increase in x from 0 to 4, suggesting a greater electron withdrawing ability of -SSEt than -SEt. In high resolution MS/MS experiments on [Fe4S4(SEt)3(SSEt)]2-/1-, clusters with both charge states yielded fragment [Fe4S4(SEt)3]-, suggesting that -SSEt could be lost either as a negatively charged ion SSEt- from the doubly charged precursor, or as a radical SSEt from the singly charged species. The biological implication of the interaction between [Fe4S4(SEt)4]2- and O2 is discussed in comparison to the air exposure of [4Fe-4S] proteins to the air.

A novel (S)-(+)-decursin derivative, (S)-(+)-3-(3,4-dihydroxy-phenyl)-acrylic acid 2,2-dimethyl-8-oxo-3,4-dihydro-2H,8H-pyrano[3,2-g]chromen-3-yl-ester, inhibits ovalbumin-induced lung inflammation in a mouse model of asthma.

PubMed

Yang, Eun Ju; Song, Gyu-Yong; Lee, Ji-Sook; Yun, Chi-Young; Kim, In Sik

2009-03-01

(S)-(+)-Decursin is a coumarin compound present in herbal extracts that has various biological activities. (S)-(+)-Decursin attenuates pathophysiologic progression in cancer, bacterial infection and neuropathy. Asthma is an inflammatory disease associated with increased infiltration of leukocytes, especially eosinophils, and secretion of mucus into the airways. Although (S)-(+)-decursin, as well as (S)-(+)-decursin analogues, have various pharmacological properties, the effect of these compounds on asthma is not known. In the present study, we synthesized (S)-(+)-3-(3,4-dihydroxy-phenyl)-acrylic acid 2,2-dimethyl-8-oxo-3,4-dihydro-2H,8H-pyrano[3,2-g]chromen-3-yl-ester (compound 6, C6) from (S)-(+)-decursin and examined if C6 had any inhibitory effects on lung inflammation in a mouse model of ovalbumin-induced asthma. C6 significantly inhibited the leukocytosis (p < 0.01) and eosinophilia (p < 0.05) in bronchoalveolar lavage (BAL) fluid. Examination of lung tissues stained with hematoxylin and eosin and periodic acid Schiff reagents showed that C6 suppressed the increased infiltration of inflammatory cells and elevated mucus hypersecretion. Protein levels of interleukin (IL)-5 (p < 0.05) and eotaxin (p < 0.01) were significantly reduced in BAL fluid by C6. C6 also significantly reduced total and ovalbumin-specific immunoglobulin E (IgE) levels in BAL fluid (p < 0.01) as well as that in serum (p < 0.05). C6 may have pharmacological effects for asthma and may be a potent therapeutic agent for the treatment of allergic airway diseases.

New high-pressure polymorph of In{sub 2}S{sub 3} with defect Th{sub 3}P{sub 4}-type structure

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lai, Xiaojing; Zhu, Feng; Wu, Ye

The high pressure behavior of β-In{sub 2}S{sub 3} (I4{sub 1}/amd and Z=16) has been studied by in situ synchrotron radiation X-ray diffraction combined with diamond anvil cell up to 71.7 GPa. Three pressure-induced phase transitions are evidenced at ∼6.6 GPa, ∼11.1 GPa at room temperature and 35.6 GPa after the high-temperature annealing using a portable laser heating system. The new polymorph of In{sub 2}S{sub 3} at 35.6 GPa is assigned to the denser cubic defect Th{sub 3}P{sub 4} structure (I4¯3d and Z=5.333), whose unit-cell parameters are a=7.557(1) Å and V=431.6(2) Å{sup 3}. The Th{sub 3}P{sub 4}-type phase can be stablemore » at least up to 71.7 GPa and cannot be preserved at ambient pressure. The pressure–volume relationship is well described by the second-order Birch–Murnaghan Equation of State, which yields B{sub 0}=63(3) GPa and B{sub 0}′=4 (fixed) for the β-In{sub 2}S{sub 3} phase and B{sub 0}=87(3) GPa and B{sub 0}′=4 (fixed) for the defect Th{sub 3}P{sub 4}-type phase respectively. - Graphical abstract: The structure and Rietveld refinement of new polymorph the defect Th{sub 3}P{sub 4}-type In{sub 2}S{sub 3}. This structure was observed at 35.6 GPa after laser heating by X-ray diffraction. Display Omitted - Highlights: Three pressure-induced phase transitions of β-In{sub 2}S{sub 3} were observed. β-In{sub 2}S{sub 3} was stable up to 6.6 GPa. The defect Th{sub 3}P{sub 4}-type In{sub 2}S{sub 3} was identified at 35.6 GPa after laser heating and was stable up to 71.7 GPa. Elastic properties of β-In{sub 2}S{sub 3} and Th{sub 3}P{sub 4}-type In{sub 2}S{sub 3} are well presented by Birch–Murnaghan EoS.« less

Crystallographic and optical properties and band diagrams of CuGaS2 and CuGa5S8 phases in Cu-poor Cu2S-Ga2S3 pseudo-binary system

NASA Astrophysics Data System (ADS)

Maeda, Tsuyoshi; Yu, Ying; Chen, Qing; Ueda, Kenta; Wada, Takahiro

2017-04-01

We synthesized Cu-poor Cu-Ga-S samples such, as CuGaS2 and CuGa5S8 with the composition of (1 - x)Cu2S-(x)Ga2S3 with 0.5 ≤ x ≤ 1.0, by a mechanochemical process and sequential heating. The crystal structure changes from tetragonal chalcopyrite-type CuGaS2 (0.5 ≤ x ≤ 0.55) to tetragonal stannite-type CuGa5S8 (x = 0.8). For samples with 0.60 ≤ x ≤ 0.75, the diffraction peaks were identified to be those of a mixed phase of the chalcopyrite- and stannite-type structures. The band-gap energies of Cu-poor Cu-Ga-S samples increase in a stepwise manner with increasing x. The band-gap energy of CuGa5S8 (x = 0.8) with the tetragonal stannite-type structure is approximately 2.66 eV, which is wider than that of chalcopyrite-type CuGaS2 (2.45 eV). The energy levels of valence band maxima (VBMs) were estimated from the ionization energies measured by photoemission yield spectroscopy (PYS). The energy levels of the VBM and conduction band minimum (CBM) of the Cu-poor Cu-Ga-S samples decrease significantly with increasing x (decreasing Cu/Ga ratio). The energy level of the VBM of CuGaS2 (-5.8 eV) is considerably deeper than those of CuInSe2 (-5.2 eV) and CuInS2 (-5.5 eV). The VBM of stannite-type CuGa5S8 with x = 0.8 (-6.4 eV) is much deeper than that of chalcopyrite-type CuGaS2 (-5.8 eV) and stannite-type CuIn3Se5 (-5.6 eV). In order to understand the band structures of chalcopyrite-type CuGaS2 and stannite-type CuGa5S8, we performed first-principles calculations using the Heyd-Scuseria-Ernzerhof (HSE06), nonlocal screened hybrid density functional method. The theoretical band-gap energy of stannite-type CuGa5S8 (2.2 eV) is wider than that of chalcopyrite-type CuGaS2 (2.0 eV). Both the theoretical and experimental band gaps of stannite-type CuGa5S8 are about 0.2 eV wider than those of chalcopyrite-type CuGaS2.

Design and characterization of Au/In4Se3/Ga2S3/C field effect transistors

NASA Astrophysics Data System (ADS)

Khusayfan, Najla M.; Qasrawi, A. F.; Khanfar, Hazem K.

2018-03-01

In the current work, the structural and electrical properties of the In4Se3/Ga2S3 interfaces are investigated. The X-ray analysis which concern the structural evolutions that is associated with the substrate type has shown that the hexagonal κ-In2Se3 and the selenium (rhombohedral) rich orthorhombic In4Se3 phases of InSe are grown onto glass and gold substrates, respectively, at substrate of temperature of 300 °C in a vacuum media. The coating of the κ-In2Se3 and of In4Se3 with amorphous layer of Ga2S3 is accompanied with uniform strain. The In4Se3/Ga2S3 interface is found to be of attractive quantum confinement features as it exhibited a conduction and valence band offsets of 0.20 and 1.86 eV, respectively. When the Au/In4Se3/Ga2S3 interface was contacted with carbon metallic point contact, it reveals a back to back Schottky hybrid device that behaves typically as metal-oxidesemiconductor field effect transition (MOSFET). The depletion capacitance analysis of this device revealed built in voltage values of 1.91 and 1.64 V at the Au and C sides, respectively. The designed MOSFET which is characterized in the frequency domain of 0.01-1.80 GHz is observed to exhibit, resonance-anti-resonance phenomena associated with negative capacitance effect in a wide domain of frequency that nominate it for applications in electronic circuits as parasitic capacitance minimizer, bus switching speed enhancer and low pass/high pass filter at microwave frequencies.

2D double-layer-tube-shaped structure Bi2S3/ZnS heterojunction with enhanced photocatalytic activities

NASA Astrophysics Data System (ADS)

Gao, Xiaoming; Wang, Zihang; Fu, Feng; Li, Xiang; Li, Wenhong

2015-10-01

Bi2S3/ZnS heterojunction with 2D double-layer-tube-shaped structures was prepared by the facile synthesis method. The corresponding relationship was obtained among loaded content to phase, morphology, and optical absorption property of Bi2S3/ZnS composite. The results shown that Bi2S3 loaded could evidently change the crystallinity of ZnS, enhance the optical absorption ability for visible light of ZnS, and improve the morphologies and microstructure of ZnS. The photocatalytic activities of the Bi2S3/ZnS sample were evaluated for the photodegradation of phenol and desulfurization of thiophene under visible light irradiation. The results showed that Bi2S3 loaded greatly improved the photocatalytic activity of ZnS, and the content of loaded Bi2S3 had an impact on the catalytic activity of ZnS. Moreover, the mechanism of enhanced photocatalytic activity was also investigated by analysis of relative band positions of Bi2S3 and ZnS, and photo-generated hole was main active radicals during photocatalytic oxidation process.

Solar Absorber Cu 2 ZnSnS 4 and its Parent Multilayers ZnS/SnS 2 /Cu 2 S Synthesized by Atomic Layer Deposition and Analyzed by X-ray Photoelectron Spectroscopy

DOE Office of Scientific and Technical Information (OSTI.GOV)

Baryshev, Sergey V.; Riha, Shannon C.; Zinovev, Alexander V.

2015-06-01

Presented here are results of x-ray photoelectron spectroscopy (XPS) on multilayers of metal-sulfide binaries ZnS, SnS2, and Cu2S grown by atomic layer deposition (ALD) on Si substrates, and of Cu2ZnSnS4 (CZTS) formed upon 450 °C annealing of the parent multilayer ZnS/SnS2/Cu2S. Survey and detailed spectral analysis of the multilayer ZnS/SnS2/Cu2S are presented step-wise, as each layer was sequentially added by ALD. The set of data is finalized with spectra of the resulting alloy CZTS. XPS analyses indicate significant mixing between SnS2 and Cu2S, which favors CZTS formation within the ALD approach.

(2R,3S,4R)-3,4-Isopropyl­idenedi­oxy-2-(phenyl­sulfonyl­meth­yl)pyrrolidin-1-ol

PubMed Central

Flores, Mari Fe; Garcia, Pilar; M. Garrido, Narciso; Sanz, Francisca; Diez, David

2012-01-01

The title compound, C14H19NO5S, was prepared by nucleophilic addition of the lithium derivative of methyl­phenyl­sulfone to (3S,4R)-3,4-isopropyl­idene­dioxy­pyrroline 1-oxide. There are four mol­ecules in the asymmetric unit. The crystal structure determination confirms the configuration of the chiral centres as 2R,3S,4R. In the crystal, pairs of O—H⋯N hydrogen bonds link the mol­ecules into dimers. PMID:22904989

Facile synthesis of Sb2S3/MoS2 heterostructure as anode material for sodium-ion batteries.

PubMed

Zhang, Zhendong; Zhao, Jiachang; Xu, Meilan; Wang, Hongxia; Gong, Yanmei; Xu, Jingli

2018-05-18

A novel Sb2S3/MoS2 heterostructure in which Sb2S3 nanorods are coated with MoS2 nanosheets to form core-shell structure has been fabricated via a facile two-step hydrothermal process. The Sb2S3/MoS2 heterostructure utilized as anode of sodium-ion batteries (SIBs) shows higher capacity, superior rate capability and better cycling performance compared with individual Sb2S3 nanorods and MoS2 nanosheets. Specifically, the Sb2S3/MoS2 electrode shows an initial reversible capacity of 701 mAh g-1 at the current density of 100 mA g-1, which is remained 80.1% of the initial perforance after 100 cycles at the same current density. This outstanding electrochemical performance indicates Sb2S3/MoS2 heterostructure is a very promising anode material for high-performance SIBs. © 2018 IOP Publishing Ltd.

Hydrolysis and coordination behavior of ferrocenyl-phosphonodithiolate: Synthesis and structure of Cu 4[FcP(OCH 3)( μ-S)( μ3-S)] 4 [Fc = Fe( η5-C 5H 4)( η5-C 5H 5)

NASA Astrophysics Data System (ADS)

Liu, Shu-Lei; Wang, Xi-Ying; Duan, Taike; Leung, Wa-Hung; Zhang, Qian-Feng

2010-02-01

Treatment of the dimeric [FcP(S)( μ-S)] 2 [Fc = Fe( η5-C 5H 4)( η5-C 5H 5)] with the organic base Et 3N in methylene chloride solution resulted in the isolation of a multi-component compound [Et 3NH] 2[(FcPO 2S) 2CH 2][FcPS(OH) 2] 2·CH 2Cl 2 ( 1·CH 2Cl 2). The formation of the [(FcPO 2S) 2CH 2] 2- anion was due to the dechlorination of methylene chloride, it consists of two [FcPO 2S] 2- units bridging by a methylene group. Reaction of Na[FcP(OCH 3)S 2] with equal equivalent of [Cu(MeCN) 4][ClO 4] in methanol afforded a sole tetranuclear copper(I) complex Cu 4[FcP(OCH 3)( μ-S)( μ3-S)] 4 ( 2). The neutral complex 2 consists of a crystallographically centrosymmetric tetramer containing four CuS 3 arrays each of which has one μ-sulfur and two μ3-sulfur bridges.

Synthesis and Luminescence Properties of Novel Ce(3+)- and Eu(2+)-Doped Lanthanum Bromothiosilicate La3Br(SiS4)2 Phosphors for White LEDs.

PubMed

Lee, Szu-Ping; Liu, Shuang-De; Chan, Ting-Shan; Chen, Teng-Ming

2016-04-13

Novel Ce(3+)- and Eu(2+)-doped lanthanum bromothiosilicate La3Br(SiS4)2:Ce(3+)and La3Br(SiS4)2:Eu(2+) phosphors were prepared by solid-state reaction in an evacuated and sealed quartz glass ampule. The La3Br(SiS4)2:Ce(3+) phosphor generates a cyan emission upon excitation at 375 nm, whereas the La3Br(SiS4)2:Eu(2+) phosphor could be excited with extremely broad range from UV to blue region (300 to 600 nm) and generates a reddish-orange broadband emission centered at 640 nm. In addition, thermal luminescence properties of La3Br(SiS4)2:Ce(3+)and La3Br(SiS4)2:Eu(2+) phosphors from 20 to 200 °C were investigated. The combination of a 450 nm blue InGaN-based LED chip with the red-emitting La3Br(SiS4)2:Eu(2+) phosphor, and green-emitting BOSE:Eu(2+) commercial phosphor produced a warm-white light with the CRI value of ∼95 and the CCT of 5,120 K. Overall, these results show that the prepared phosphors may have potential applications in pc-WLED.

Chemistry and properties of poly(arylene ether 1,3,4-oxadiazole)s and poly(arylene ether 1,2,4-triazole)s

NASA Technical Reports Server (NTRS)

Connell, J. W.; Hergenrother, P. M.; Wolf, P.

1992-01-01

Poly(arylene ether)s containing l,3,4-oxadiazole and 1,2,4-triazole units were prepared by the aromatic nucleophilic displacement reaction of bisphenol oxadiazole and bisphenol triazole compounds with activated aromatic dihalides. The polymers exhibited glass transition temperatures (Tg) ranging from 182 to 242 C, and several polymers exhibited melting transitions (Tm) ranging from 265 to 390 C. Inherent viscosities ranged from 1.02 to 3.40 dl/g, indicating relatively high molecular weights. Thin films exhibited tensile strengths, moduli, and elongations at 23 C of 90-110 MPa, 2.7-3.6 GPa, and 4-7 percent, respectively. Titanium-to-titanium tensile shear specimens of a poly(arylene ether 1,3,4-oxadiazole) exhibited tensile shear strengths at 23 and 150 C of 22.1 and 17.9 MPa, respectively.

Faster Electron Injection and More Active Sites for Efficient Photocatalytic H2 Evolution in g-C3 N4 /MoS2 Hybrid.

PubMed

Shi, Xiaowei; Fujitsuka, Mamoru; Kim, Sooyeon; Majima, Tetsuro

2018-03-01

Herein, the structural effect of MoS 2 as a cocatalyst of photocatalytic H 2 generation activity of g-C 3 N 4 under visible light irradiation is studied. By using single-particle photoluminescence (PL) and femtosecond time-resolved transient absorption spectroscopies, charge transfer kinetics between g-C 3 N 4 and two kinds of nanostructured MoS 2 (nanodot and monolayer) are systematically investigated. Single-particle PL results show the emission of g-C 3 N 4 is quenched by MoS 2 nanodots more effectively than MoS 2 monolayers. Electron injection rate and efficiency of g-C 3 N 4 /MoS 2 -nanodot hybrid are calculated to be 5.96 × 10 9 s -1 and 73.3%, respectively, from transient absorption spectral measurement, which are 4.8 times faster and 2.0 times higher than those of g-C 3 N 4 /MoS 2 -monolayer hybrid. Stronger intimate junction between MoS 2 nanodots and g-C 3 N 4 is suggested to be responsible for faster and more efficient electron injection. In addition, more unsaturated terminal sulfur atoms can serve as the active site in MoS 2 nanodot compared with MoS 2 monolayer. Therefore, g-C 3 N 4 /MoS 2 nanodot exhibits a 7.9 times higher photocatalytic activity for H 2 evolution (660 µmol g- 1 h -1 ) than g-C 3 N 4 /MoS 2 monolayer (83.8 µmol g -1 h -1 ). This work provides deep insight into charge transfer between g-C 3 N 4 and nanostructured MoS 2 cocatalysts, which can open a new avenue for more rationally designing MoS 2 -based catalysts for H 2 evolution. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

Hydrazine solution processed Sb2S3, Sb2Se3 and Sb2(S1−xSex)3 film: molecular precursor identification, film fabrication and band gap tuning

PubMed Central

Yang, Bo; Xue, Ding-Jiang; Leng, Meiying; Zhong, Jie; Wang, Liang; Song, Huaibing; Zhou, Ying; Tang, Jiang

2015-01-01

Sb2(S1−xSex)3 (0 ≤ x ≤ 1) compounds have been proposed as promising light-absorbing materials for photovoltaic device applications. However, no systematic study on the synthesis and characterization of polycrystalline Sb2(S1−xSex)3 thin films has been reported. Here, using a hydrazine based solution process, single-phase Sb2(S1−xSex)3 films were successfully obtained. Through Raman spectroscopy, we have investigated the dissolution mechanism of Sb in hydrazine: 1) the reaction between Sb and S/Se yields [Sb4S7]2-/[Sb4Se7]2- ions within their respective solutions; 2) in the Sb-S-Se precursor solutions, Sb, S, and Se were mixed on a molecular level, facilitating the formation of highly uniform polycrystalline Sb2(S1−xSex)3 thin films at a relatively low temperature. UV-vis-NIR transmission spectroscopy revealed that the band gap of Sb2(S1−xSex)3 alloy films had a quadratical relationship with the Se concentration x and it followed the equation , where the bowing parameter was 0.118 eV. Our study provides a valuable guidance for the adjustment and optimization of the band gap in hydrazine solution processed Sb2(S1−xSex)3 alloy films for the future fabrication of improved photovoltaic devices. PMID:26042519

Superconductivity versus structural phase transition in the closely related Bi 2Rh 3.5S 2 and Bi 2Rh 3S 2

DOE PAGES

Kaluarachchi, Udhara S.; Xie, Weiwei; Lin, Qisheng; ...

2015-05-19

Single crystals of Bi 2Rh 3S 2 and Bi 2Rh 3.5S 2 were synthesized by solution growth, and the crystal structures and thermodynamic and transport properties of both compounds were studied. In the case of Bi 2Rh 3S 2, a structural first-order transition at around 165 K is identified by single-crystal diffraction experiments, with clear signatures visible in resistivity, magnetization, and specific heat data. No superconducting transition for Bi 2Rh 3S 2 was observed down to 0.5 K. In contrast, no structural phase transition at high temperature was observed for Bi 2Rh 3.5S 2; however, bulk superconductivity with a criticalmore » temperature, T c ≈ 1.7 K, was observed. The Sommerfeld coefficient γ and the Debye temperature (Θ D) were found to be 9.41 mJ mol –1K –2 and 209 K, respectively, for Bi 2Rh 3S 2, and 22 mJ mol –1K –2 and 196 K, respectively, for Bi 2Rh 3.5S 2. As a result, the study of the specific heat in the superconducting state of Bi 2Rh 3.5S 2 suggests that Bi 2Rh 3.5S 2 is a weakly coupled, BCS superconductor.« less

Periodic perturbations in Shaker K+ channel gating kinetics by deletions in the S3–S4 linker

PubMed Central

Gonzalez, Carlos; Rosenman, Eduardo; Bezanilla, Francisco; Alvarez, Osvaldo; Latorre, Ramon

2001-01-01

Upon depolarization positive charges contained in the transmembrane segment S4 of voltage-dependent channels are displaced from the cytoplasmic to the external milieu. This charge movement leads to channel opening. In Shaker K+ channels four positively charged arginines in the S4 domain are transferred from the internal to the external side of the channel during activation. The distance traveled by the S4 segment during activation is unknown, but large movements should be constrained by the S3–S4 linker. Constructing deletion mutants, we show that the activation time constant and the midpoint of the voltage activation curve of the Shaker K+ channel macroscopic currents becomes a periodic function of the S3–S4 linker length for linkers shorter than 7 aa residues. The periodicity is that typical of α-helices. Moreover, a linker containing only 3 aa is enough to recover the wild-type phenotype. The deletion method revealed the importance of the S3–S4 linker in determining the channel gating kinetics and indicated that the α-helical nature of S4 extends toward its N terminus. These results support the notion that a small displacement of the S4 segment suffices to displace the four gating charges involved in channel opening. PMID:11493701

Resonant photoemission study of pyrite-type NiS2, CoS2 and FeS2

NASA Astrophysics Data System (ADS)

Fujimori, A.; Mamiya, K.; Mizokawa, T.; Miyadai, T.; Sekiguchi, T.; Takahashi, H.; Môri, N.; Suga, S.

1996-12-01

The electronic structure of pyrite-type NiS2, CoS2, and FeS2 has been studied by photoemission spectroscopy. From resonant photoemission studies and configuration-interaction cluster-model analysis of the spectra, NiS2 is found to be a charge-transfer-type insulator, the band gap of which is formed between the occupied S 3p and the empty Ni 3d states. Cluster-model calculations indicate that the short Fe-S distance favors the low-spin (S=0) ground state in FeS2 compared to the high-spin FeS. Resonant photoemission results indicate a sign of electron correlation in the nonmagnetic semiconductor FeS2.

Thin film electroluminescent cells on the basis of Ce-doped CaGa2S4 and SrGa2S4 prepared by flash evaporation method

NASA Astrophysics Data System (ADS)

Gambarov, E.; Bayramov, A.; Kato, A.; Iida, S.

2006-09-01

Ce-doped CaGa2S4 and SrGa2S4 thin film electroluminescent (TFEL) devices were prepared for the first time on the basis of films deposited by flash evaporation method. Significant crystallization, stoichiometry improvement of the films and increase of photoluminescence intensity were found after annealing in H2S and O2 gas stream. EL spectra of the cells exhibited the characteristic double-band emission similar to that seen for Ce3+ activated CaGa2S4 and SrGa2S4 films under photon excitation. Applied voltage and frequency dependences of the electroluminescence were studied. Low voltage operation as low as 20 V was observed for these cells. Luminance of about 4 cd/m2 at 100 V operating voltage with 2.5 kHz frequency was achieved for the TFEL cell with films annealed in O2 gas stream.

Biotransformation of (-)-(1R,4S)-Menthone and (+)-(1S,4R)-Menthone by the Common Cutworm Spodoptera litura Larvae.

PubMed

Marumoto, Shinsuke; Okuno, Yoshiharu; Hagiwara, Yuki; Miyazawa, Mitsuo

2017-08-01

Using biotransformation as a biocatalytic process has the advantage of being able to proceed under mild conditions and with high regio- and enantioselectivity. This study investigated the biotransformation of (-)-(1R,4S)-menthone (1) and (+)-(1S,4R)-menthone (2) by Spodoptera litura larvae. Compound 1 was converted to (-)-(1R,4S)-7-hydroxymenthone (1-1), (+)-(1R,3S,4S)-7-hydroxyneomenthol (1-2) and (-)-(1R,4S,8R)-p-menth-3-one-9-oic acid (1-3). The metabolism of substrate 2 generated three enantiomers of the above metabolites, designated as 2-1 to 2-3, respectively. The C-9 position of (-)-menthone and (+)-menthone was oxidized to carboxylic acid by S. litura, which is a metabolic pathway not observed in any other example of biocatalysis.

12. PIERS 5S AND 4S, SHOWING TRANSITION AT 4S FROM ...

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

12. PIERS 5S AND 4S, SHOWING TRANSITION AT 4S FROM GIRDER SPAN TO 'SUSPENDED' TRUSS SPAN AT U0. VIEW LOOKING WEST. - George P. Coleman Memorial Bridge, Spanning York River at U.S. Route 17, Yorktown, York County, VA

Synthesis of MoS2-reduced graphene oxide/Fe3O4 nanocomposite for enhanced electromagnetic interference shielding effectiveness

NASA Astrophysics Data System (ADS)

Prasad, Jagdees; Singh, Ashwani Kumar; Shah, Jyoti; Kotnala, R. K.; Singh, Kedar

2018-05-01

This article presents a facile two step hydrothermal process for the synthesis of MoS2-reduced graphene oxide/Fe3O4 (MoS2-rGO/Fe3O4) nanocomposite and its application as an excellent electromagnetic interference shielding material. Characterization tools like; scanning electron microscope, transmission electron microscope, x-ray diffraction, and Raman spectroscopy were used to confirm the formation of nanocomposite and found that spherical Fe3O4 nanoparticles are well dispersed over MoS2-rGO composite with average particle size ∼25–30 nm was confirmed by TEM. Structural characterization done by XRD was found inconsistent with the known lattice parameter of MoS2 nanosheet, reduced graphene oxide and Fe3O4 nanoparticles. Electromagnetic shielding effectiveness of MoS2-rGO/Fe3O4 nanocomposite was evaluated and found to be an excellent EMI shielding material in X-band range (8.0–12.0 GHz). MoS2-rGO composite shows poor shielding capacity (SET ∼ 3.81 dB) in entire range as compared to MoS2-rGO/Fe3O4 nanocomposite (SET ∼ 8.27 dB). It is due to interfacial polarization in the presence of EM field. The result indicates that MoS2-rGO/Fe3O4 nanocomposite provide a new stage for the next generation in high-performance EM wave absorption and EMI shielding effectiveness.

Temperature behaviour of optical parameters in (Ag3AsS3)0.3(As2S3)0.7 thin films

NASA Astrophysics Data System (ADS)

Kutsyk, Mykhailo M.; Ráti, Yosyp Y.; Izai, Vitalii Y.; Makauz, Ivan I.; Studenyak, Ihor P.; Kökényesi, Sandor; Komada, Paweł; Zhailaubayev, Yerkin; Smailov, Nurzhigit

2015-12-01

(Ag3AsS3)0.3(As2S3)0.7 thin films were deposited onto a quartz substrate by rapid thermal evaporation. The optical transmission spectra of thin films were measured in the temperature range 77-300 K. It is shown that the absorption edge spectra are described by the Urbach rule. The temperature behaviour of absorption spectra was studied, the temperature dependences of energy position of absorption edge and Urbach energy were investigated. The influence of transition from three-dimensional glass to the two-dimensional thin film as well as influence of Ag3AsS3 introduction into As2S3 on the optical parameters of (Ag3AsS3)0.3(As2S3)0.7 were analysed. The spectral and temperature behaviour or refractive index for (Ag3AsS3)0.3(As2S3)0.7 thin film were studied.

High-pressure polymorphism of As2S3 and new AsS2 modification with layered structure

NASA Astrophysics Data System (ADS)

Bolotina, N. B.; Brazhkin, V. V.; Dyuzheva, T. I.; Katayama, Y.; Kulikova, L. F.; Lityagina, L. V.; Nikolaev, N. A.

2014-01-01

At normal pressure, the As2S3 compound is the most stable equilibrium modification with unique layered structure. The possibility of high-pressure polymorphism of this substance remains questionable. Our research showed that the As2S3 substance was metastable under pressures P > 6 GPa decomposing into two high-pressure phases: As2S3 → AsS2 + AsS. New AsS2 phase can be conserved in the single crystalline form in metastable state at room pressure up to its melting temperature (470 K). This modification has the layered structure with P1211 monoclinic symmetry group; the unit-cell values are a = 7.916(2) Å, b = 9.937(2) Å, c = 7.118(1) Å, β = 106.41° ( Z = 8, density 3.44 g/cm3). Along with the recently studied AsS high-pressure modification, the new AsS2 phase suggests that high pressure polymorphism is a very powerful tool to create new layered-structure phases with "wrong" stoichiometry.

Analysis of the right-handed Majorana neutrino mass in an S U (4 )×S U (2 )L×S U (2 )R Pati-Salam model with democratic texture

NASA Astrophysics Data System (ADS)

Yang, Masaki J. S.

2017-03-01

In this paper, we attempt to build a unified model with the democratic texture, that has some unification between up-type Yukawa interactions Yν and Yu . Since the S3 L×S3 R flavor symmetry is chiral, the unified gauge group is assumed to be Pati-Salam type S U (4 )c×S U (2 )L×S U (2 )R. The breaking scheme of the flavor symmetry is considered to be S3 L×S3 R→S2 L×S2 R→0 . In this picture, the four-zero texture is desirable for realistic masses and mixings. This texture is realized by a specific representation for the second breaking of the S3 L×S3 R flavor symmetry. Assuming only renormalizable Yukawa interactions, type-I seesaw mechanism, and neglecting C P phases for simplicity, the right-handed neutrino mass matrix MR can be reconstructed from low energy input values. Numerical analysis shows that the texture of MR basically behaves like the "waterfall texture." Since MR tends to be the "cascade texture" in the democratic texture approach, a model with type-I seesaw and up-type Yukawa unification Yν≃Yu basically requires fine-tunings between parameters. Therefore, it seems to be more realistic to consider universal waterfall textures for both Yf and MR, e.g., by the radiative mass generation or the Froggatt-Nielsen mechanism. Moreover, analysis of eigenvalues shows that the lightest mass eigenvalue MR 1 is too light to achieve successful thermal leptogenesis. Although the resonant leptogenesis might be possible, it also requires fine-tunings of parameters.

Identification and electrophysiological studies of (4 S,5 S)-5-hydroxy-4-methyl-3-heptanone and 4-methyl-3,5-heptanedione in male lucerne weevils

NASA Astrophysics Data System (ADS)

Unelius, C. R.; Park, K.-C.; McNeill, M.; Wee, S. L.; Bohman, B.; Suckling, D. M.

2013-02-01

An investigation to identify a sex or aggregation pheromone of Sitona discoideus Gyllenhål (Coleoptera: Curculionidae) is presented. Antenna flicking and attraction behaviors evoked by conspecifics of both sexes were recorded in arena bioassays, where attraction of females to males was observed. Air entrainment of both males and females was conducted in separate chambers. Gas chromatographic-mass spectrometric analysis of headspace volatiles revealed that two male-specific compounds, 4-methyl-3,5-heptanedione (major) and (4 S,5 S)-5-hydroxy-4-methyl-3-heptanone (minor), were emitted during the autumnal post-aestivatory flight period. The stereoisomers of the minor component were separated by enantioselective gas chromatography and their absolute configurations assigned by NMR (diastereomers) and the known preference of enantioselective transesterification reactions catalyzed by Candida antarctica lipase B. Electroantennogram and single sensillum recording studies indicate that 4-methyl-3,5-heptanedione as well as all individual stereoisomers of 5-hydroxy-4-methyl-3-heptanone are detected by the antennae of male and female S. discoideus. Further, single sensillum recordings suggest that both sexes of S. discoideus have specialized olfactory receptor neurons (ORNs) for detecting 4-methyl-3,5-heptanedione and different populations of stereoselective ORNs for detecting the stereoisomers of 5-hydroxy-4-methyl-3-heptanone. Some of these stereoselective ORNs appear to be sex-specific in S. discoideus.

Synthesis, crystal structure, and spectroscopic characterization of trans-bis[(mu-1,3-bis(4-pyridyl)propane)(mu-(3-thiopheneacetate-O))(3-thiopheneacetate-O)]dicopper(II), [[Cu2(O2CCH2C4H3S)4mu-(BPP)2

PubMed

Marinho, Maria Vanda; Yoshida, Maria Irene; Guedes, Kassilio J; Krambrock, Klaus; Bortoluzzi, Adailton J; Hörner, Manfredo; Machado, Flávia C; Teles, Wagner M

2004-02-23

From the reaction between a dinuclear paddle-wheel carboxylate, namely [Cu2mu-(O2CCH2C4H3S)4] (1), and the flexible ligand 1,3-bis(4-pyridyl)propane (BPP) a neutral 2-D coordination polymer [[Cu2(O2CCH2C4H3S)4mu-(BPP)2

Super reduced Fe4S4 cluster of Balch's dithiolene series.

PubMed

Begum, Ameerunisha; Moula, Golam; Bose, Moumita; Sarkar, Sabyasachi

2012-03-28

A super reduced Fe(4)S(4) cluster with a sulfur based radical, [NBu(4)](4)[Fe(3)(III)Fe(II)(μ(3)-S)(4)(mnt)(3)(6-)(mnt)(1-)˙](4-)˙, (1) (mnt, maleonitrile dithiolate) which evolves H(2)S gas on treatment with acid under ambient conditions has been synthesized and structurally characterized. The Fe-S distances in 1 are in the range 2.246-2.383 Å, in stark contrast to that of the known n = -2 member of the series based on the [Fe(4)(μ(3)-S)(4)(S(2)C(2)R(2))(4)](n) unit (R = CF(3), Ph) with Fe-S bond lengths of 2.149-2.186 Å. The EPR of 1 displays very weak signals at g, 4.03 and 2.38 along with a strong S-based radical EPR signal at g, 2.003 associated with five structured components tentatively assigned to hyperfine interaction arising out of the naturally abundant (57)Fe with = 88 G. The EPR profile resembles the reduced Fe-S cluster of CO inhibited Clostridium pasteurianum W5 hydrogenase or the Fe(4)S(4) centers of wild-type enzyme, IspH treated with HMBPP or IPP.

Mid-infrared emissions of Pr{sup 3+}-doped GeS{sub 2}–Ga{sub 2}S{sub 3}–CdI{sub 2} chalcohalide glasses

DOE Office of Scientific and Technical Information (OSTI.GOV)

Lu, Chunfeng; Guo, Haitao, E-mail: guoht_001@opt.ac.cn; Xu, Yantao

2014-12-15

Graphical abstract: ∼4.6 μm mid-infrared fluorescence emission from Pr{sup 3+} in the sulfide glass is successfully observed at room temperature excited by a 2.01 μm Tm{sup 3+}:YAG ceramic laser system. - Highlights: • Serial Pr{sup 3+}-doped GeS{sub 2}–Ga{sub 2}S{sub 3}–CdI{sub 2} chalcohalide glasses were synthesized. • ∼4.6 μm mid-infrared fluorescence from Pr{sup 3+} was observed at room temperature. • The compositional dependence of luminescence properties was studied. • Radiative properties have been determined using the Judd–Ofelt theory. - Abstract: For elucidation of the glass composition’s influence on the spectroscopic properties in the chalcohalide system and the discovery of a newmore » material for applications in mid-infrared fiber-lasers, a serial Pr{sup 3+}-doped (100 − x)(0.8GeS{sub 2}·0.2Ga{sub 2}S{sub 3})xCdI{sub 2} (x = 5, 10, 15 and 20) chalcohalide glasses were prepared. ∼4.6 μm mid-infrared fluorescence emission from Pr{sup 3+} in the sulfide glass is successfully observed at room temperature excited by a 2.01 μm Tm{sup 3+}:YAG ceramic laser system, and the effective line-width of fluorescence band is 106–227 nm. Intense compositional dependence of mid-infrared emissions is found. The radiative rates of Pr{sup 3+} ions in these glasses were calculated by using the Judd–Ofelt theory.« less

Magic wavelengths for the 6{s}^{2}{}^{1}{S}_{0}{--}6s6p{}^{3}{P}_{1}^{o} transition in ytterbium atom

NASA Astrophysics Data System (ADS)

Tang, Zhi-Ming; Yu, Yan-Mei; Jiang, Jun; Dong, Chen-Zhong

2018-06-01

The static and dynamic electric dipole polarizabilities of the 6{s}2{}1{S}0 and 6s6p{}3{P}1o states of Yb are calculated by using the relativistic ab initio method. Focusing on the red detuning region to the 6{s}2{}1{S}0{--}6s6p{}3{P}1o transition, we find two magic wavelengths at 1035.7(2) and 612.9(2) nm for the 6{s}2{}1{S}0{--}6s6p{}3{P}1o,{M}J=0 transition and three magic wavelengths at 1517.68(6), 1036.0(3) and 858(12) nm for the 6{s}2{}1{S}0{--}6s6p{}3{P}1o,{M}J=+/- 1 transitions. Such magic wavelengths are of particular interest for attaining the state-insensitive cooling, trapping, and quantum manipulation of neutral Yb atom.

Synthesis, structural characterization and conversion of dinuclear iron-sulfur clusters containing the disulfide ligand: [Cp*Fe(μ-η2:η2-bdt)(cis-μ-η1:η1-S2)FeCp*], [Cp*Fe(μ-S(C6H4S2))(cis-μ-η1:η1-S2)FeCp*], and [{Cp*Fe(bdt)}2(trans-μ-η1:η1-S2)].

PubMed

Ji, Xiaoxiao; Tong, Peng; Yang, Dawei; Wang, Baomin; Zhao, Jinfeng; Li, Yang; Qu, Jingping

2017-03-21

The treatment of [Cp*Fe(μ-η 2 :η 4 -bdt)FeCp*] (1, Cp* = η 5 -C 5 Me 5 , bdt = benzene-1,2-dithiolate) with 1/4 equiv. of elemental sulfur (S 8 ) gave a dinuclear iron-sulfur cluster [Cp*Fe(μ-η 2 :η 2 -bdt)(cis-μ-η 1 :η 1 -S 2 )FeCp*] (2), which contains a cis-1,2-disulfide ligand. When complex 2 further interacted with 1/8 equiv. of S 8 , another sulfur atom inserted into an Fe-S bond to give a rare product [Cp*Fe(μ-S(C 6 H 4 S 2 ))(cis-μ-η 1 :η 1 -S 2 )FeCp*] (3). Unexpectedly, a trans-1,2 disulfide-bridged diiron complex [{Cp*Fe(bdt)} 2 (trans-μ-η 1 :η 1 -S 2 )] (4) was isolated from the reaction of complex 1 with 1/2 equiv. of S 8 , which represents a structural isomer of [2Fe-2S] ferredoxin-type clusters. In addition, cis-1,2-disulfide-bridged complex 3 can slowly convert into trans-1,2-disulfide-bridged complex 4 and the complex [Cp*Fe(μ-η 2 :η 2 -S 2 )(cis-μ-η 1 :η 1 -S 2 )FeCp*] (5) by self-assembly reaction at ambient temperature, which is evidenced by time-dependent 1 H NMR spectroscopy.

Atomic alignment effect on reactivity and on product alignment in the energy-transfer reaction of oriented Ar (3P2, 4s [3/2]2, M(J) = 2) + Kr (4p6, 1S0) → Ar (3p6, 1S0) + Kr (5p [3/2]2).

PubMed

Ohoyama, H

2015-03-12

Steric effect for the formation of Kr (5p [3/2]₂) in the energy transfer reaction of Ar (³P₂, 4s [3/2]₂) + Kr has been studied by using an oriented Ar (³P₂, 4s [3/2]₂, M(J) = 2) beam at a collision energy of ∼0.09 eV. The emission intensity of Kr (5p [3/2]₂) is ca. 2 times enhanced when the angular momentum (J(Ar)) of Ar (³P₂) is aligned perpendicular to the relative velocity vector (v(R)). In addition, the Kr (5p [3/2]₂) emission is highly polarized parallel to v(R) (I(∥)/I(⊥) ∼ 1.2) when JAr is aligned perpendicular to v(R). The observed polarization moments indicate that the alignment of the unpaired Ar (3p) orbital of Ar (³P₂) to v(R), (Σ (|L′| = 0), Π (|L′| = 1)), dominates the energy transfer probability (σ(Π)(∥): σ(Σ)(∥): σ(Π)(⊥): σ(Σ)(⊥) = 0.49:1.33:0.55:1.23) and also the alignment of the Kr (5p) orbital of Kr (5p [3/2]₂) to v(R): the Σ-configuration of the Ar (3p) orbital leads to the parallel alignment (Σ-configuration) of the Kr(5p) orbital to v(R), conversely, the Π-configuration of Ar (3p) orbital leads to the perpendicular alignment (Π-configuration) of the Kr(5p) orbital. In addition, the selectivity of the alignment of the Kr (5p) orbital turns out to vary from perpendicular to parallel as the collision energy increases after a threshold down to 0.03 eV.

Structural and optical properties of annealed and illuminated (Ag3AsS3)0.6(As2S3)0.4 thin films

NASA Astrophysics Data System (ADS)

Studenyak, I. P.; Neimet, Yu. Yu.; Rati, Y. Y.; Stanko, D.; Kranjčec, M.; Kökényesi, S.; Daróci, L.; Bohdan, R.

2014-11-01

(Ag3AsS3)0.6(As2S3)0.4 thin films were deposited upon a quartz substrate by rapid thermal evaporation. Structural studies of the as-deposited, annealed and illuminated films were performed using XRD, scanning electron and atomic force microscopies. Surfaces of all the films were found to be covered with Ag-rich crystalline micrometer sized cones. Thermal annealing leads to mechanical deformation of part of the cones and their detachment from the base film surface while the laser illumination leads to the new formations appearance on the surface of thin films. The spectroscopic studies of optical transmission spectra for as-deposited, annealed and illuminated thin films were carried out. The optical absorption spectra in the region of its exponential behaviour were analysed, the dispersion dependences of refractive index as well as their variation after annealing and illumination were investigated.

Electron Excitation Cross Sections for the 2s(sup 2)2p(sup 3) (sup 4)S -> 2s(sup 2)2p(sup 3) (sup 2d) ->2s2p(sup 4) (sup 4p) (Resonance) Transitions in Oil

NASA Technical Reports Server (NTRS)

Zuo, M.; Smith, S.; Chutjian, A.; Williams, I.; Tayal, S.; McLaughlin, B.

1994-01-01

Experimental and theoretical excitation cross sections are reported for the first forbidden transition xxx and the first allowed (resonance) transition xxx in OII. Use is made of electron-energy loss and merged beams methods. The electron energy range covered is 3.33 eV (threshold) to 15 eV for the S->D transition, and 14.9 eV (threshold) to 40 eV for the S->P transition. Care was taken to assess and minimize the metastable fraction of the OII beam. An electron mirror was designed and tested to reflect inelastically back-scattered electrons into the forward direction to account for the full range of polar scattering angles. Comparisons are made between present experiments and 11-state R-Matrix calculations. Calculations are also presented for the xxx transition.

A simple structure of Cu2ZnSnS4/CdS solar cells prepared by sputtering

NASA Astrophysics Data System (ADS)

Li, Zhishan; Wang, Shurong; Ma, Xun; Yang, Min; Jiang, Zhi; Liu, Tao; Lu, Yilei; Liu, Sijia

2017-12-01

In this work, Cu2ZnSnS4 (CZTS) thin films were grown on Mo-coated Soda-lime-glass (SLG) substrates by annealing of sputtered ZnS/Sn/CuS precursors at 580 ℃ for 15 min. As a try, the CZTS solar cells were fabricated using simple structure of Mo-coated SLG/CZTS/CdS/Al and traditional structure of Mo-coated SLG/CZTS/CdS/i-ZnO/In2O3:SnO2 (ITO)/Al, respectively. The results show that the CZTS device with simple structure can achieve same level of the open circuit voltage (Voc) compared with that of traditional structure. In addition, the power conversion efficiency of 2.95% and 3.59% were obtained with simple structure and traditional structure, respectively. The CZTS solar cell with simple structure provides a promising way and an easy process to prepare high-performance CZTS thin film solar cells which is available to large-scale industrial production in the future.

Observation of Upsilon(2S)-->etaUpsilon(1S) and search for related transitions.

PubMed

He, Q; Insler, J; Muramatsu, H; Park, C S; Thorndike, E H; Yang, F; Artuso, M; Blusk, S; Khalil, S; Li, J; Mountain, R; Nisar, S; Randrianarivony, K; Sultana, N; Skwarnicki, T; Stone, S; Wang, J C; Zhang, L M; Bonvicini, G; Cinabro, D; Dubrovin, M; Lincoln, A; Naik, P; Rademacker, J; Asner, D M; Edwards, K W; Reed, J; Briere, R A; Ferguson, T; Tatishvili, G; Vogel, H; Watkins, M E; Rosner, J L; Alexander, J P; Cassel, D G; Duboscq, J E; Ehrlich, R; Fields, L; Galik, R S; Gibbons, L; Gray, R; Gray, S W; Hartill, D L; Heltsley, B K; Hertz, D; Hunt, J M; Kandaswamy, J; Kreinick, D L; Kuznetsov, V E; Ledoux, J; Mahlke-Krüger, H; Mohapatra, D; Onyisi, P U E; Patterson, J R; Peterson, D; Riley, D; Ryd, A; Sadoff, A J; Shi, X; Stroiney, S; Sun, W M; Wilksen, T; Athar, S B; Patel, R; Yelton, J; Rubin, P; Eisenstein, B I; Karliner, I; Mehrabyan, S; Lowrey, N; Selen, M; White, E J; Wiss, J; Mitchell, R E; Shepherd, M R; Besson, D; Pedlar, T K; Xavier, J V; Cronin-Hennessy, D; Gao, K Y; Hietala, J; Kubota, Y; Klein, T; Lang, B W; Poling, R; Scott, A W; Zweber, P; Dobbs, S; Metreveli, Z; Seth, K K; Tomaradze, A; Libby, J; Martin, L; Powell, A; Wilkinson, G; Ecklund, K M; Love, W; Savinov, V; Mendez, H; Ge, J Y; Miller, D H; Shipsey, I P J; Xin, B; Adams, G S; Anderson, M; Cummings, J P; Danko, I; Hu, D; Moziak, B; Napolitano, J

2008-11-07

We report the first observation of Upsilon(2S)-->etaUpsilon(1S), with a branching fraction B=(2.1(-0.6)+0.7(stat)+/-0.3(syst)) x 10(-4) and a statistical significance 5.3sigma. Data were acquired with the CLEO III detector at the CESR e+e(-) symmetric collider. This is the first process observed involving a b-quark spin flip. For related transitions, 90% confidence limits in units of 10(-4) are B(Upsilon(2S)-->pi0Upsilon(1S)) < 1.8, B(Upsilon(3S)-->etaUpsilon(1S)) < 1.8, B(Upsilon(3S)-->pi0Upsilon(1S)) < 0.7, and B(Upsilon(3S)-->pi0Upsilon(2S)) < 5.1.

Heterogeneous reactions of HNO3(g) + NaCl(s) yields HCl(g) + NaNO3(s) and N2O5(g) + NaCl(s) yields ClNO2(g) + NaNO3(s)

NASA Technical Reports Server (NTRS)

Leu, Ming-Taun; Timonen, Raimo S.; Keyser, Leon F.; Yung, Yuk L.

1995-01-01

The heterogeneous reactions of HNO3(g) + NaCl(s) yields HCl(g) + NaNO3(s) (eq 1) and N2O5(g) + NaCl(s) yields ClNO2(g) + NaNO3(S) (eq 2) were investigated over the temperature range 223-296 K in a flow-tube reactor coupled to a quadrupole mass spectrometer. Either a chemical ionization mass spectrometer (CIMS) or an electron-impact ionization mass spectrometer (EIMS) was used to provide suitable detection sensitivity and selectivity. In order to mimic atmospheric conditions, partial pressures of HNO3 and N2O5 in the range 6 x 10(exp -8) - 2 x 10(exp -6) Torr were used. Granule sizes and surface roughness of the solid NaCl substrates were determined by using a scanning electron microscope. For dry NaCl substrates, decay rates of HNO3 were used to obtain gamma(1) = 0.013 +/- 0.004 (1sigma) at 296 K and > 0.008 at 223 K, respectively. The error quoted is the statistical error. After all corrections were made, the overall error, including systematic error, was estimated to be about a factor of 2. HCl was found to be the sole gas-phase product of reaction 1. The mechanism changed from heterogeneous reaction to predominantly physical adsorption when the reactor was cooled from 296 to 223 K. For reaction 2 using dry salts, gamma(2) was found to be less than 1.0 x 10(exp -4) at both 223 and 296 K. The gas-phase reaction product was identified as ClNO2 in previous studies using an infrared spectrometer. An enhancement in reaction probability was observed if water was not completely removed from salt surfaces, probably due to the reaction of N2O5(g) + H2O(s) yields 2HNO3(g). Our results are compared with previous literature values obtained using different experimental techniques and conditions. The implications of the present results for the enhancement of the hydrogen chloride column density in the lower stratosphere after the El Chichon volcanic eruption and for the chemistry of HCl and HNO3 in the marine troposphere are discussed.

First Principles Investigation of the Geometrical and Electrochemical Properties of Na4P<S6 and Li4P2S6

NASA Astrophysics Data System (ADS)

Rush, Larry E., Jr.; Holzwarth, N. A. W.

First principles simulations are used to examine the structural and physical properties of Na4P2S6 in comparison with its Li4P2S6 analog. Four model structures are considered including the C 2 / m structure recently reported by Kuhn and co-workers from their analysis of single crystals of Na4P2S6, and three structures related to the P63 / mcm structure with P site disorder found in 1982 by Mercier and co-workers from their analysis of single crystals of Li4P2S6. The computational results indicate that both Na4P2S6 and Li4P2S6 have the same disordered ground state structures consistent with the P63 / mcm space group, while the optimized C 2 / m structures have higher energies by 0.1 eV and 0.4 eV per formula unit for Na4P2S6 and Li4P2S6, respectively. Simulations of ion migration suggest that Na4P2S6 may have more favorable ionic conductivity compared to Li4P2S6. Supported by NSF Grant DMR-1105485 and DMR-1507942.

Beneficial Effect of S-Filling on Thermoelectric Properties of S x Co4Sb11.2Te0.8 Skutterudite

NASA Astrophysics Data System (ADS)

Wang, Hongtao; Duan, Bo; Bai, Guanghui; Li, Jialiang; Yu, Yue; Yang, Houjiang; Chen, Gang; Zhai, Pengcheng

2018-06-01

In this work, Te-doped and S-filled S x Co4Sb11.2Te0.8 ( x = 0.1, 0.15, 0.2, 0.25, 0.3, 0.4) skutterudite compounds have been prepared using solid state reaction and spark plasma sintering. Thermoelectric measurements of the consolidated samples were examined in a temperature range of 300-850 K, and the influences of S-addition on the thermoelectric properties of S x Co4Sb11.2Te0.8 skutterudites are systematically investigated. The results indicate that the addition of sulfur and tellurium is effective in reducing lattice thermal conductivity due to the point-defect scattering caused by tellurium substitutions and the cluster vibration brought by S-filling. The solubility of tellurium in skutterudites is enhanced with sulfur addition via charge compensation. The thermal conductivity decreases with increasing sulfur content. The highest figure of merit, ZT = 1.5, was obtained at 850 K for S0.3Co4Sb11.2Te0.8 sample, because of the low lattice thermal conductivity.

Facile Synthesis of 1D/2D Core-Shell Structured Sb2S3@MoS2 Nanorods with Enhanced Photocatalytic Performance

NASA Astrophysics Data System (ADS)

Xu, Meilan; Zhao, Jiachang

2018-07-01

Herein, a novel core-shell heterojunction structure of molybdenum disulfide (MoS2) nanosheets coated antimony trisulfide (Sb2S3) nanorods (Sb2S3@MoS2) are designed and fabricated by a two-step hydrothermal method. The Sb2S3@MoS2 heterostructure consists of one-dimension (1D) Sb2S3 nanorods coated by two-dimension (2D) MoS2 nanosheets. When utilized as a photocatalyst under simulated sunlight, compared with pure Sb2S3 nanorods and MoS2 nanosheets, Sb2S3@MoS2 nanorods perform an enhanced photoactivity in degrading Rhodamine B (RhB) with a decomposition efficiency of 99%. The excellent photocatalytic property is attributed to the properly constructed heterojunction between Sb2S3 and MoS2, which can broaden the photoadsorption range. Furthermore, not only can the unique hybrid 1D/2D core-shell structures possess more reaction active sites, but also the compact interfaces between Sb2S3 and MoS2 provide rapid charge transfer channels for charge separation.

Design and Synthesis of 1-(3-(dimethylamino)propyl)-1-(4-fluorophenyl)-1,3-dihydroisobenzofuran-5-carbonitrile (Citalopram) Analogues as Novel Probes for the Serotonin Transporter S1 and S2 Binding Sites

PubMed Central

Banala, Ashwini K.; Zhang, Peng; Plenge, Per; Cyriac, George; Kopajtic, Theresa; Katz, Jonathan L.; Loland, Claus Juul; Newman, Amy Hauck

2013-01-01

The serotonin transporter (SERT) is the primary target for antidepressant drugs. The existence of a high affinity primary orthosteric binding site (S1) and a low affinity secondary site (S2) has been described and their relation to antidepressant pharmacology has been debated. Herein, structural modifications to the N-, 4, 5, and 4’-positions of (±)citalopram (1) are reported. All of the analogues were SERT-selective and demonstrated that steric bulk was tolerated at the SERT S1 site, including two dimeric ligands (15 and 51.) In addition, 8 analogues were identified with similar potencies to S-1 for decreasing the dissociation of [3H]S-1 from the S1 site, via allosteric modulation at S2. Both dimeric compounds had similar affinities for the SERT S1 site (Ki=19.7 and 30.2 nM, respectively), whereas only the N-substituted analogue, 51, was as effective as S-1 in allosterically modulating the binding of [3H]S-1 via S2. PMID:24237160

Pharmacokinetics of S-3-(4-acetylamino-phenoxy)-2-hydroxy-2-methyl-N-(4-nitro-3-trifluoromethyl-phenyl)-propionamide in rats, a non-steroidal selective androgen receptor modulator

PubMed Central

KEARBEY, J. D.; WU, D.; GAO, W.; MILLER, D. D.; DALTON, J. T.

2007-01-01

1. S-3-(4-acetylamino-phenoxy)-2-hydroxy-2-methyl-N-(4-nitro-3-trifluoromethyl-phenyl)-propionamide (also known as S-4) is a non-steroidal selective androgen receptor modulator demonstrating tissue-selective androgenic and anabolic effects. The purpose of the present study was to examine the systemic pharmacokinetics, elimination and oral bioavailability of S-4 in rats. 2. Thirty-five male Sprague–Dawley rats weighing approximately 250 g were randomly assigned to one of seven treatment groups. Intravenous doses of 0.5, 1, 10, and 30 mg kg−1 were given via a jugular catheter. Oral doses of 1, 10 and 30 mg kg−1 were administered via gavage. Plasma concentrations were determined using a validated high-performance liquid chromatography or by a high-performance liquid chromatography/mass spectrometry method. 3. Clearances ranged between 1.0 and 2.1 ml min−1 kg−1 and varied with dose. The volume of distribution was approximately 0.448 l kg−1 in all treatment groups. Oral bioavailability was also dose dependent, with the lower doses showing complete oral bioavailability. The half-life of S-4 over the dose range tested was between 2.6 and 5.3 h. 4. It was demonstrated that S-4 is rapidly absorbed, slowly cleared, and has a moderate volume of distribution in rats. The pharmacokinetics and oral bioavailability of S-4 indicate that it is an excellent candidate for clinical development. PMID:15204699

Redox non-innocence of thioether crowns: elucidation of the electronic structure of the mononuclear Pd(III) complexes [Pd([9]aneS3)2]3+ and [Pd([18]aneS6)]3+.

PubMed

Stephen, Emma; Blake, Alexander J; Carter, Emma; Collison, David; Davies, E Stephen; Edge, Ruth; Lewis, William; Murphy, Damien M; Wilson, Claire; Gould, Robert O; Holder, Alan J; McMaster, Jonathan; Schröder, Martin

2012-02-06

The Pd(II) complexes [Pd([9]aneS(3))(2)](PF(6))(2)·2MeCN (1) ([9]aneS(3) = 1,4,7-trithiacyclononane) and [Pd([18]aneS(6))](PF(6))(2) (2) ([18]aneS(6) = 1,4,7,10,13,16-hexathiacyclooctadecane) can be oxidized electrochemically or chemically oxidized with 70% HClO(4) to [Pd([9]aneS(3))(2)](3+) and [Pd([18]aneS(6))](3+), respectively. These centers have been characterized by single crystal X-ray diffraction, and by UV/vis and multifrequency electron paramagnetic resonance (EPR) spectroscopies. The single crystal X-ray structures of [Pd(III)([9]aneS(3))(2)](ClO(4))(6)·(H(3)O)(3)·(H(2)O)(4) (3) at 150 K and [Pd([18]aneS(6))](ClO(4))(6)·(H(5)O(2))(3) (4) at 90 K reveal distorted octahedral geometries with Pd-S distances of 2.3695(8), 2.3692(8), 2.5356(9) and 2.3490(6), 2.3454(5), 2.5474(6) Å, respectively, consistent with Jahn-Teller distortion at a low-spin d(7) Pd(III) center. The Pd(II) compound [Pd([9]aneS(3))(2)](PF(6))(2) shows a one-electron oxidation process in MeCN (0.2 M NBu(4)PF(6), 293 K) at E(1/2) = +0.57 V vs. Fc(+)/Fc assigned to a formal Pd(III)/Pd(II) couple. Multifrequency (Q-, X-, S-, and L-band) EPR spectroscopic analysis of [Pd([9]aneS(3))(2)](3+) and [Pd([18]aneS(6))](3+) gives g(iso) = 2.024, |A(iso(Pd))| = 18.9 × 10(-4) cm(-1); g(xx) = 2.046, g(yy) = 2.041, g(zz) = 2.004; |A(xx(Pd))| = 24 × 10(-4) cm(-1), |A(yy(Pd))| = 22 × 10(-4) cm(-1), |A(zz(Pd))| = 14 × 10(-4) cm(-1), |a(xx(H))| = 4 × 10(-4) cm(-1), |a(yy(H))| = 5 × 10(-4) cm(-1), |a(zz(H))| = 5.5 × 10(-4) cm(-1) for [Pd([9]aneS(3))(2)](3+), and g(iso) = 2.015, |A(iso(Pd))| = 18.8× 10(-4) cm(-1); g(xx) = 2.048 g(yy) = 2.036, g(zz) = 1.998; |a(xx(H))| = 5, |a(yy(H))| = 5, |a(zz(H))| = 6 × 10(-4) cm(-1); |A(xx(Pd))| = 23× 10(-4) cm(-1), |A(yy(Pd))| = 22 × 10(-4) cm(-1), |A(zz(Pd))| = 4 × 10(-4) cm(-1) for [Pd([18]aneS(6))](3+). Both [Pd([9]aneS(3))(2)](3+) and [Pd([18]aneS(6))](3+) exhibit five-line superhyperfine splitting in the g(zz) region in their frozen solution EPR

Measurement of the radiative decay and energy of the metastable $${(2{s}^{2}2{p}_{1/2}^{5}3{s}_{1/2})}_{(J=0)}$$ level in Fe XVII

DOE Office of Scientific and Technical Information (OSTI.GOV)

Beiersdorfer, P.; Lopez-Urrutia, J. R. Crespo; Trabert, E.

Measurements at the Livermore electron beam ion trap have been performed in order to infer the energy and the radiative lifetime of themore » $${(1{s}^{2}2{s}^{2}2{p}_{1/2}^{5}3{s}_{1/2})}_{J=0}$$ level in the Fe xvii spectrum. This is the longest-lived level in the neonlike iron ion, and its radiative decay produces the Fe xvii line at 1153 Å, feeding the population of the $${(1{s}^{2}2{s}^{2}2{p}_{3/2}^{5}3{s}_{1/2})}_{J=1}$$ upper level of one of the most prominent lines in the Fe xvii L-shell X-ray spectrum, commonly dubbed $3G$. In the presence of a strong ($$\\geqslant $$ few kG) magnetic field, the $${(1{s}^{2}2{s}^{2}2{p}_{1/2}^{5}3{s}_{1/2})}_{J=0}$$ level has a finite probability to decay directly to the $${(1{s}^{2}2{s}^{2}2{p}^{6})}_{J=0}$$ neonlike ground level via the emission of an L-shell X-ray. Our measurements allow us to observe this X-ray line in the Fe xvii L-shell spectrum and from it to infer the radiative rate for the magnetic dipole decay of the $${(1{s}^{2}2{s}^{2}2{p}_{1/2}^{5}3{s}_{1/2})}_{J=0}$$ level to the $${(1{s}^{2}2{s}^{2}2{p}_{3/2}^{5}3{s}_{1/2})}_{J=1}$$. Our result of $$(1.45\\pm 0.15)\\times {10}^{4}$$ s-1 is in agreement with predictions. We have also measured the wavelength of the associated X-ray line to be 16.804 ± 0.002 Å, which means that the line is displaced 1.20 ± 0.05 eV from the neighboring $${(2{s}^{2}2{p}_{1/2}^{5}3{s}_{1/2})}_{J=1}\\to {(2{s}^{2}2{p}^{6})}_{J=0}$$ transition, commonly labeled $3F$. Furthermore, from our measurement, we infer 5950570 ± 710 cm-1 for the energy of the $${(1{s}^{2}2{s}^{2}2{p}_{1/2}^{5}3{s}_{1/2})}_{J=0}$$ level.« less

Measurement of the radiative decay and energy of the metastable $${(2{s}^{2}2{p}_{1/2}^{5}3{s}_{1/2})}_{(J=0)}$$ level in Fe XVII

DOE PAGES

Beiersdorfer, P.; Lopez-Urrutia, J. R. Crespo; Trabert, E.

2016-01-20

Measurements at the Livermore electron beam ion trap have been performed in order to infer the energy and the radiative lifetime of themore » $${(1{s}^{2}2{s}^{2}2{p}_{1/2}^{5}3{s}_{1/2})}_{J=0}$$ level in the Fe xvii spectrum. This is the longest-lived level in the neonlike iron ion, and its radiative decay produces the Fe xvii line at 1153 Å, feeding the population of the $${(1{s}^{2}2{s}^{2}2{p}_{3/2}^{5}3{s}_{1/2})}_{J=1}$$ upper level of one of the most prominent lines in the Fe xvii L-shell X-ray spectrum, commonly dubbed $3G$. In the presence of a strong ($$\\geqslant $$ few kG) magnetic field, the $${(1{s}^{2}2{s}^{2}2{p}_{1/2}^{5}3{s}_{1/2})}_{J=0}$$ level has a finite probability to decay directly to the $${(1{s}^{2}2{s}^{2}2{p}^{6})}_{J=0}$$ neonlike ground level via the emission of an L-shell X-ray. Our measurements allow us to observe this X-ray line in the Fe xvii L-shell spectrum and from it to infer the radiative rate for the magnetic dipole decay of the $${(1{s}^{2}2{s}^{2}2{p}_{1/2}^{5}3{s}_{1/2})}_{J=0}$$ level to the $${(1{s}^{2}2{s}^{2}2{p}_{3/2}^{5}3{s}_{1/2})}_{J=1}$$. Our result of $$(1.45\\pm 0.15)\\times {10}^{4}$$ s-1 is in agreement with predictions. We have also measured the wavelength of the associated X-ray line to be 16.804 ± 0.002 Å, which means that the line is displaced 1.20 ± 0.05 eV from the neighboring $${(2{s}^{2}2{p}_{1/2}^{5}3{s}_{1/2})}_{J=1}\\to {(2{s}^{2}2{p}^{6})}_{J=0}$$ transition, commonly labeled $3F$. Furthermore, from our measurement, we infer 5950570 ± 710 cm-1 for the energy of the $${(1{s}^{2}2{s}^{2}2{p}_{1/2}^{5}3{s}_{1/2})}_{J=0}$$ level.« less

Transfer of D-phenylalanine from gramicidin S synthetase 1 to gramicidin S synthetase 2 in gramicidin S synthesis.

PubMed

Hori, K; Kanda, M; Miura, S; Yamada, Y; Saito, Y

1983-01-01

The transfer of phenylalanine from gramicidin S synthetase 1 (GS 1) to gramicidin S synthetase 2 (GS 2) was studied by the use of combinations of wild-type GS 1 with various GS 2s from a wild strain and gramicidin S non-producing mutant strains of Bacillus brevis Nagano. The combinations of mutant GS 2s lacking 4'-phosphopantetheine (from BI-4, C-3, E-1, and E-2) did not transfer D-phenylalanine from GS 1, although they could activate all the constituent amino acids. Other mutant GS 2s containing 4'-phosphopantetheine, except GS 2 from BII-3 (proline-activation lacking) accepted D-phenylalanine from intact GS 1. To ascertain more directly whether 4'-phosphopantetheine is involved in the transfer of D-phenylalanine from GS 1 to GS 2, pepsin digests of GS 2 that accepted [14C]phenylalanine were analyzed by Sephadex G-50 column chromatography and thin-layer chromatography (TLC). Radioactivity of [14C]phenylalanine was always associated with a peptide containing 4'-phosphopantetheine. Furthermore, the position of radioactivity was distinct from the position of 4'-phosphopantetheine on TLC after alkaline treatment or performic acid oxidation of the digests.

Improved dehydrogenation performance of LiBH4 by 3D hierarchical flower-like MoS2 spheres additives

NASA Astrophysics Data System (ADS)

Zhao, Yan; Liu, Yongchang; Liu, Huiqiao; Kang, Hongyan; Cao, Kangzhe; Wang, Qinghong; Zhang, Chunling; Wang, Yijing; Yuan, Huatang; Jiao, Lifang

2015-12-01

In this work, 3D hierarchical flower-like MoS2 spheres are successfully fabricated via a hydrothermal method followed by a heat treatment. The obtained product is composed of few-layered MoS2 nanosheets with enlarged interlayer distance (ca. 0.66 nm) of the (002) plane. Meanwhile, the hydrogen storage properties of the as-prepared MoS2 ball milled with LiBH4 are systematically investigated. The results of temperature programmed desorption (TPD) and isothermal measurement suggest that the LiBH4-MoS2 (as-prepared) mixture exhibits favorable dehydrogenation properties in both lowering the hydrogen release temperature and improving kinetics of hydrogen release rate. LiBH4-MoS2 (as-prepared) sample (the preparation mass ratio is 1:1) starts to release hydrogen at 171 °C, and roughly 5.6 wt% hydrogen is released within 1 h when isothermally heated to 320 °C, which presents superior dehydrogenation performance compared to that of the bulk LiBH4. The excellent dehydrogenation performance of the LiBH4-MoS2 (as-prepared) mixture may be attributed to the high active site density and enlarged interlayer distance of the MoS2 nanosheets, 3D architectures and hierarchical structures.

Enhancing visible light photocatalytic activity of direct Z-scheme SnS{sub 2}/Ag{sub 3}PO{sub 4} heterojunction photocatalysts

DOE Office of Scientific and Technical Information (OSTI.GOV)

Luo, Jin, E-mail: lj328520504@126.com; Zhou, Xiaosong; Ma, Lin

Highlights: • Novel direct Z-scheme SnS{sub 2}/Ag{sub 3}PO{sub 4} heterojunction photocatalysts are synthesized. • SnS{sub 2}/Ag{sub 3}PO{sub 4} exhibits much higher photocatalytic activity than pure SnS{sub 2} and Ag{sub 3}PO{sub 4}. • A possible photocatalytic mechanism was discussed in detail. - Abstract: Novel direct Z-scheme SnS{sub 2}/Ag{sub 3}PO{sub 4} heterojunction photocatalysts were successfully fabricated with SnS{sub 2} nanoplates hybridized by Ag{sub 3}PO{sub 4} nanoparticals via a facile hydrothermal and precipitation method and applied for the photocatalytic degradation of methyl orange in aqueous solution under visible light irradiation (λ > 420 nm). It was found that the photocatalytic performance of themore » SnS{sub 2} (2.0 wt%)/Ag{sub 3}PO{sub 4} heterojunction photocatalyst with 2.0 wt% SnS{sub 2} content was much higher than that of individual SnS{sub 2} and Ag{sub 3}PO{sub 4}. The enhanced photocatalytic activity could be ascribed to the efficient separation of photogenerated electrons and holes through the formation of direct Z-scheme system composed of SnS{sub 2} and Ag{sub 3}PO{sub 4}. Furthermore, the recycling experiments revealed that the photocorrosion behavior of Ag{sub 3}PO{sub 4} was strongly inhibited by SnS{sub 2}, it may be due to the photogenerated electrons of Ag{sub 3}PO{sub 4} would be quickly combined with the photogenerated holes of SnS{sub 2}. This work will be useful for the design of other direct Z-scheme visible-light-driven photocatalytic systems for application in energy conversion and environmental remediation.« less

Single crystal growth and physical properties of BiS2-layered compound Eu3Bi2S4F4

NASA Astrophysics Data System (ADS)

Higashinaka, Ryuji; Endo, Hideaki; Kajitani, Joe; Matsuda, Tatsuma D.; Aoki, Yuji

2018-05-01

We have for the first time succeeded in growing single crystals of Eu3Bi2S4F4 by CsCl-flux method and performed magnetic property measurements. Magnetization measurements ascertained that the antiferromagnetic transition appears at TN = 2.2 K. The effective moment estimated from a Curie-Weiss (CW) fitting above 150 K is smaller than the free ion value for Eu2+, indicating that the average valence of Eu ions deviates from divalent. Weak magnetic anisotropy develops below 20 K. From CW fitting at low temperatures, we found the difference in Curie Weiss temperature between H∥ [001] and H ⊥ [ 100 ] , indicating the anisotropy of magnetic interaction between Eu ions. In the magnetization curve at 2 K (below TN), a metamagnetic anomaly appears only for the [001] direction around 0.7 T. Since this anomaly disappears above TN, this transition originates from the spin flip of Eu magnetic moments by applying magnetic field. This finding indicates that the ordered moments in the antiferromagnetic state are parallel to the [001] direction, being consistent with the anisotropic Weiss temperature, which is 20% larger for this direction.

One step hydrothermal synthesis of 3D CoS2@MoS2-NG for high performance supercapacitors

NASA Astrophysics Data System (ADS)

Meng, Qi; Chen, Yizhi; Zhu, Wenkun; Zhang, Ling; Yang, Xiaoyong; Duan, Tao

2018-07-01

A three-dimensional (3D) MoS2 coated CoS2-nitrogen doped graphene (NG) (CoS2@MoS2-NG) hybrid has been synthesized by a one step hydrothermal method as supercapacitor (SC) electrode material for the first time. Such a composite consists of NG embedded with stacked CoS2@MoS2 sheets. With a 3D skeleton, it prevents the agglomeration of CoS2@MoS2 nanoparticles, resulting in sound conductivity, rich porous structures and a large surface area. The results indicate that CoS2@MoS2-NG has higher specific capacitance (198 F g‑1 at 1 A g‑1), better rate performance (with about 56.57% from 1 to 16 A g‑1) and an improved cycle stability (with about 96.97% after 1000 cycles). It is an ideal candidate for SC electrode materials.

One step hydrothermal synthesis of 3D CoS2@MoS2-NG for high performance supercapacitors.

PubMed

Meng, Qi; Chen, Yizhi; Zhu, Wenkun; Zhang, Ling; Yang, Xiaoyong; Duan, Tao

2018-07-20

A three-dimensional (3D) MoS 2 coated CoS 2 -nitrogen doped graphene (NG) (CoS 2 @MoS 2 -NG) hybrid has been synthesized by a one step hydrothermal method as supercapacitor (SC) electrode material for the first time. Such a composite consists of NG embedded with stacked CoS 2 @MoS 2 sheets. With a 3D skeleton, it prevents the agglomeration of CoS 2 @MoS 2 nanoparticles, resulting in sound conductivity, rich porous structures and a large surface area. The results indicate that CoS 2 @MoS 2 -NG has higher specific capacitance (198 F g -1 at 1 A g -1 ), better rate performance (with about 56.57% from 1 to 16 A g -1 ) and an improved cycle stability (with about 96.97% after 1000 cycles). It is an ideal candidate for SC electrode materials.

Photoconductive properties of Bi{sub 2}S{sub 3} nanowires

DOE Office of Scientific and Technical Information (OSTI.GOV)

Andzane, J., E-mail: jana.andzane@lu.lv; Kunakova, G.; Erts, D.

2015-02-14

The photoconductive properties of Bi{sub 2}S{sub 3} nanowires synthesized inside anodized alumina (AAO) membrane have been characterized as a function of illuminating photon energy between the wavelengths of 500 to 900 nm and at constant illumination intensity of 1–4 μW·cm{sup −2}. Photoconductivity spectra, photocurrent values, photocurrent onset/decay times of individual Bi{sub 2}S{sub 3} nanowires liberated from the AAO membrane were determined and compared with those of arrays of as-produced Bi{sub 2}S{sub 3} nanowires templated inside pores of AAO membrane. The alumina membrane was found to significantly influence the photoconductive properties of the AAO-hosted Bi{sub 2}S{sub 3} nanowires, when compared to liberated frommore » the AAO membrane individual Bi{sub 2}S{sub 3} nanowires, possibly due to charge carrier trapping at the interface between the nanowire surface and the pore walls.« less

Calculations of resonances parameters for the ((2s2) 1Se, (2s2p) 1,3P0) and ((3s2) 1Se, (3s3p) 1,3P0) doubly excited states of helium-like ions with Z≤10 using a complex rotation method implemented in Scilab

NASA Astrophysics Data System (ADS)

Gning, Youssou; Sow, Malick; Traoré, Alassane; Dieng, Matabara; Diakhate, Babacar; Biaye, Mamadi; Wagué, Ahmadou

2015-01-01

In the present work a special computational program Scilab (Scientific Laboratory) in the complex rotation method has been used to calculate resonance parameters of ((2s2) 1Se, (2s2p) 1,3P0) and ((3s2) 1Se, (3s3p) 1,3P0) states of helium-like ions with Z≤10. The purpose of this study required a mathematical development of the Hamiltonian applied to Hylleraas wave function for intrashell states, leading to analytical expressions which are carried out under Scilab computational program. Results are in compliance with recent theoretical calculations.

Synthesis, characterization, structural and biological aspects of copper(II) dithiocarbamate complexes - Part II, [Cu{S2CN(Me)(R1)}2], [Cu{S2CN(Me)(R2)}2] and [Cu{S2CN(R3)(R4)}2] {R1 = CH2CH(OMe)2, R2 = 2-methyl-1,3-dioxolane, R3 = CH2(CH2)2NCHPhOCH2Ph and R4 = CH2CH2OH}

NASA Astrophysics Data System (ADS)

Ferreira, Isabella P.; de Lima, Geraldo M.; Paniago, Eucler B.; Takahashi, Jacqueline A.; Krambrock, Klaus; Pinheiro, Carlos B.; Wardell, James L.; Visentin, Lorenzo C.

2013-09-01

Three new copper(II) dithiocarbamates (DTC), [Cu{S2CN(Me)(R1)}2] (1), [Cu{S2CN(Me)(R2)}2] (2) and [Cu{S2CN(R3)(R4)}2] (3) with R1 = CH2CH(OMe)2, R2 = 2-methyl-1,3-dioxolane, R3 = CH2(CH2)2NCHPhOCH2Ph and R4 = CH2CH2OH, have been synthesized and characterized by different spectroscopic techniques. Complexes (1) and (2) display typical EPR spectra for separated Cu(II) centers, and the spectrum of (3) is characteristic of two magnetically coupled Cu(II) ions with S = 1. The X-ray crystallographic determination has shown that complexes (1) and (2) crystallise in the triclinic and monoclinic systems. In addition both complexes are monomers in which the geometry at each Cu(II) is square planar. The in vitro antimicrobial activity of the sodium salts of ligands, and of the Cu(II)-DTC complexes have been screened against Aspergillus flavus, Aspergillus niger, Aspergillus parasiticus, Penicillium citrinum and Curvularia senegalensis, as well as Gram positive and Gram negative bacteria. Finally, the toxic effects of complexes (1)-(3) were performed using Chlorella vulgaris.

Thermal and electrochemical behavior of Cu{sub 4−x}Li{sub x}S{sub 2} (x=1, 2, 3) phases

DOE Office of Scientific and Technical Information (OSTI.GOV)

Chen, Erica M.; Poudeu, Pierre F.P., E-mail: ppoudeup@umich.edu

Several compositions of the Cu{sub 4−x}Li{sub x}S{sub 2} (x=1, 2, 3) series were synthesized via solid-state reaction of the elements. The structural stability at various temperatures and the effect of Li:Cu ratio on the thermal conductivity and the electrochemical performance of Cu{sub 4−x}Li{sub x}S{sub 2}/Li half-cells during charge–discharge process were investigated. Differential scanning calorimetry (DSC) measurements showed a sharp endothermic peak at 140 °C for Cu{sub 4−x}Li{sub x}S{sub 2} samples with x=1 and 2, which is ascribed to a structural phase transition. X-ray diffraction (XRD) measurements on various Cu{sub 4−x}Li{sub x}S{sub 2} samples at temperatures below and above 140 °Cmore » indicated a structural phase transition from the room temperature low-symmetry structure to the high temperature cubic structure of Cu{sub 2}S. The thermal conductivity of Cu{sub 4−x}Li{sub x}S{sub 2} samples decreases with decreasing Cu:Li ratio and with increasing temperature. The thermal conductivity of Cu{sub 4−x}Li{sub x}S{sub 2} samples at room temperature decreases from 1.2 W/m K for Cu:Li=3:1 to 0.7 W/m K for Cu:Li=1:3. Cyclic voltammetry of Cu{sub 4−x}Li{sub x}S{sub 2}/Li half-cells showed that high discharge capacity (165 mA h g{sup −1}) and stable reversible charge–discharge process is observed for Cu:Li=2:2, whereas other Cu:Li ratios lead to low discharge capacity and poor reversibility. The electrochemical behavior of Cu{sub 4−x}Li{sub x}S{sub 2}/Li half-cells is rationalized by taking into account the competing reactions of Li{sup +} ions with CuS and Cu{sub 2}S during discharge. - Graphical abstract: Tuning Li content in Cu{sub 4−x}Li{sub x}S{sub 2}/Li half-cells to maintain a Cu/Li ratio equal to unity affords maximum capacity and high stability of the charge–discharge process. - Highlights: • Cu:Li ratio strongly influenced crystal structure and properties of Cu{sub 4-x}Li{sub x}S{sub 2}. • Compositions with x = 1 and

Mechanism of Inactivation of GABA Aminotransferase by (E)- and (Z)-(1S,3S)-3-Amino-4-fluoromethylenyl-1-cyclopentanoic Acid

PubMed Central

Lee, Hyunbeom; Le, Hoang V.; Wu, Rui; Doud, Emma; Sanishvili, Ruslan; Kellie, John F.; Compton, Phillip D.; Pachaiyappan, Boobalan; Liu, Dali; Kelleher, Neil L.

2015-01-01

When γ-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the mammalian central nervous system, falls below a threshold level, seizures occur. One approach to raise GABA concentrations is to inhibit GABA aminotransferase (GABA-AT), a pyridoxal 5’-phosphate-dependent enzyme that degrades GABA. We have previously developed (1S,3S)-3-amino-4-difluoromethylene-1-cyclopentanoic acid (CPP-115), which is 186 times more efficient in inactivating GABA-AT than vigabatrin, the only FDA-approved inactivator of GABA-AT. We also developed (E)- and (Z)-(1S,3S)-3-amino-4-fluoromethylenyl-1-cyclopentanoic acid (1 and 2, respectively), monofluorinated analogs of CPP-115, which are comparable to vigabatrin in inactivating GABA-AT. Here we report the mechanism of inactivation of GABA-AT by 1 and 2. Both produce a metabolite that induces disruption of the Glu270-Arg445 salt bridge to accommodate interaction between the metabolite formyl group and Arg445. This is the second time that Arg445 has interacted with a ligand and is involved in GABA-AT inactivation, thereby confirming the importance of Arg445 in future inactivator design. PMID:26110556

Mechanism of Inactivation of GABA Aminotransferase by (E)- and (Z)-(1S,3S)-3-Amino-4-fluoromethylenyl-1-cyclopentanoic Acid.

PubMed

Lee, Hyunbeom; Le, Hoang V; Wu, Rui; Doud, Emma; Sanishvili, Ruslan; Kellie, John F; Compton, Phillip D; Pachaiyappan, Boobalan; Liu, Dali; Kelleher, Neil L; Silverman, Richard B

2015-09-18

When γ-aminobutyric acid (GABA), the major inhibitory neurotransmitter in the mammalian central nervous system, falls below a threshold level, seizures occur. One approach to raise GABA concentrations is to inhibit GABA aminotransferase (GABA-AT), a pyridoxal 5'-phosphate-dependent enzyme that degrades GABA. We have previously developed (1S,3S)-3-amino-4-difluoromethylene-1-cyclopentanoic acid (CPP-115), which is 186 times more efficient in inactivating GABA-AT than vigabatrin, the only FDA-approved inactivator of GABA-AT. We also developed (E)- and (Z)-(1S,3S)-3-amino-4-fluoromethylenyl-1-cyclopentanoic acid (1 and 2, respectively), monofluorinated analogs of CPP-115, which are comparable to vigabatrin in inactivating GABA-AT. Here, we report the mechanism of inactivation of GABA-AT by 1 and 2. Both produce a metabolite that induces disruption of the Glu270-Arg445 salt bridge to accommodate interaction between the metabolite formyl group and Arg445. This is the second time that Arg445 has interacted with a ligand and is involved in GABA-AT inactivation, thereby confirming the importance of Arg445 in future inactivator design.