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1

Cone angles of ligands which are compounds of group-IV and group-V elements  

SciTech Connect

The cone angles theta (a steric characteristic, which expresses the degree of filling of a coordination sphere by a ligand) have been calculated for 610 ligands. The ligands considered have an AB'/sub 3/ or A(OB')/sub 3/ formula and a tetrahedral (with respect to A in an M-AB/sub 3/' fragment of a complex, where M is the coordinating metal) geometry, where A = N, P, As, Sb, Bi, C, Si, Ge, Sn, or Pb, and B' is an alkyl, cycloalkyl, aryl, alkylaryl, or arylalkyl group. The known cone angles of ligands based on phosphorus, which were determined on molecular models, have been corrected, and they have been used to calculate the effect covalent and van der Waals radii of the B' groups. The cone angles were calculated from the effective radii and the M-A internuclear distances. Such a procedure provides for the standardization and comparability of the steric characteristics obtained. The cone angles are identical or close for adjacent elements in groups IV and V (N and C, P and Si, As and Ge, Sb and Sn, Bi and Pb). When A is replaced by lower-lying elements within a group, the cone angles decrease, these decreases being greater, the greater is the size of the ligand. The changes accompanying the transition from nitrogen (or carbon) to phosphorus (or silicon) are especially great. The cone angles of diethylaniline and methyldiphenylamine correspond to that of triphenylphosphine, and the cone angles of dimethylaniline and diphenylamine correspond to that of tributyl-phosphine. The variation of the cone angle as a function of the central metal atom has been examined, and it has been shown that the values of the cone angles established for the compounds of nickel can be used for complexes of all the other transition metals, with the exception of the elements found at the beginning of the transition series.

Imyanitov, N.S.

1986-07-01

2

Comprehensive Ab Initio Study of Doping in Bulk ZnO with Group-V Elements  

NASA Astrophysics Data System (ADS)

Despite the lack of reproducible experimental confirmation, group-V elements have been considered as possible sources of p-type doping in ZnO in the form of simple and complex defects. Using ab initio calculations, based on state-of-the-art hybrid exchange-correlation functional, we study a wide range of defects and defect complexes related with N, P, As, and Sb impurities. We show that none of the candidates for p-type doping can be considered a good source of holes in the valence band due to deep acceptor levels and low formation energies of compensating donor defects. In addition, we discuss the stability of complexes in different regimes.

Petretto, Guido; Bruneval, Fabien

2014-03-01

3

Investigation of magnetic properties induced by group-V element in doped ZnO.  

PubMed

For the potential applications in spintronics, we examine systematically the electronic properties of group-V elements (X) doped ZnO to investigate the magnetic properties induced by X based on density functional theory calculations. Our results indicates that X atoms doped in the form of a substitutional X atom at an O anion site (XO) and at a Zn cation site combining with two Zn vacancies (XZn-2VZn complex) under different circumstances can introduce magnetism. The magnetism comes from the p-p and p-d coupling interaction between the dopant X-p orbitals and the host O-2p and Zn-3d orbitals. The stability of the ferromagnetism (FM) phase induced by XO defects decreases with the increase of dopant atomic number due to the lower electronegativity value, which can be interpreted by the phenomenological band-coupling model. The origin of the magnetism induced by XZn-2VZn is similar to that of the Zn vacancy (VZn) in ZnO and comes from the O-2p orbitals dominantly. The FM stability introduced by XZn-2VZn decreases with the order N < Sb < As < P, which is ascribed to the delocalization of the O-2p orbitals. The results mean that 3p/4p/5p dopants could also make ZnO materials into diluted magnetic semiconductors. PMID:23455330

Lu, Ying-Bo; Dai, Ying; Guo, Meng; Yu, Lin; Huang, Baibiao

2013-04-14

4

Theoretical and Materials Chemistry of Some Group III and V Elements  

NASA Astrophysics Data System (ADS)

The theoretical and material aspects of some group III and V compounds have been investigated. Phosphaborane clusters were investigated by modified neglect of differential overlap semi-empirical molecular orbital calculations (MNDO -SCF) to better understand important structural, electronic, and thermodynamic properties of these experimentally difficult species. The structural, thermodynamic and electronic properties of 111 phosphapentaborane cluster compounds have been calculated via MNDO-SCF. The geometry-optimized, minimum energy structures for all of the known and structurally characterized phosphaborane systems have been calculated. In each case, exceptionally good agreement was observed between the experimentally determined and the calculated structural parameters. Calculations for five classes of phosphapentaborane clusters have been completed and have been related to experimentally proposed structural types. Predictions concerning structural and chemical reactivities for unknown and known phosphapentaborane compounds have been made based on these MO calculations. Production of important thin film materials was discussed relative to chemical vapor deposition (CVD). Advantages of CVD over older thermodynamic deposition techniques were described. The CVD process has been briefly reviewed through seven primary steps. The importance of new source materials which meet stringent industrial requirements have been detailed relative to environmental, occupational safety, and contaminations considerations. Thin films of pure aluminum, aluminum boride and aluminum oxide have been prepared from the chemical vapor deposition (CVD) of rm Al(BH_4)_3, and rm AlH_2(BH_4) cdot N(CH_3)_3, on both single crystals and thermally sensitive substrates. Films were characterized by EDX, AES, SEM, XRD, and resistivity measurements and ranged in thickness from 500 A to 2 mu m. Each type of film was shown by AES to be compositionally uniform in the bulk sample with only very shallow surface contaminations of oxygen and carbon. Both source compounds were, in general, relatively thermally stable, volatile, air-sensitive liquids, thus providing nearly ideal precursor properties for chemical vapor deposition. Organophosphorus sources for the chemical vapor deposition (CVD) of indium phosphide have been examined with MNDO-SCF theoretical calculations in order to predict important depositional parameters such as decomposition temperature and temperature selectivities. Decomposition temperatures and temperature selectivities for the three known organophosphorus sources, t-butyl phosphine (TBP), i-butyl phosphine (IBP) and bisphosphinoethane (BPE), have been shown to match MNDO's predicted values, indicating that MNDO can be used as a first test for the suitability of organophosphorus compounds. Optimized depositional parameters for TBP, IBP and BPE were presented. Alternative phosphorus sources with enhanced depositional properties have been identified and analyzed in terms of decomposition temperature and optimized deposition conditions. Cyclohexyl phosphine (PCH) has been used in conjunction with trimethyl indium (TMI) to deposit polycrystalline indium phosphide with no carbon incorporation. Attempted indium phosphide depositions using dichloro-t-butyl phosphine (DCTBP) and TMI yielded both an etching of the InP(100) surface (73.4 A/sec) and polycrystalline rm Cu_3P. .

Glass, John Arthur, Jr.

5

Computer-learning methods in forecasting crystalline phases in ternary systems containing group V elements  

SciTech Connect

New ABC compounds have been forecast as having structures of TiNiSi, ZrNiAl, MgAgAs and PbFCl types, while AB/sub 2/C/sub 2/ ones have structures of ThCr/sub 2/Si/sub 2/ and CaAl/sub 2/Si/sub 2/ (C = P, As, Sb, or Bi, while A and B are metals or semimetals). Only the fundamental properties of the elements are used. Cybernetic methods and computer training are effective in forecasting new crystalline phases.

Kiseleva, N.N.; Burkhanov, G.S.

1988-05-01

6

Solute trapping of group III, IV, and V elements in silicon by an aperiodic stepwise growth mechanism  

NASA Astrophysics Data System (ADS)

With rapid solidification following pulsed laser melting, we have measured the dependence on interface orientation of the amount of solute trapping of several group III, IV, and V elements (As, Ga, Ge, In, Sb, Sn) in Si. The aperiodic stepwise growth model of Goldman and Aziz accurately fits both the velocity and orientation dependence of solute trapping of all these solutes except Ge. The success of the model implies a ledge structure for the crystal/melt interface and a step-flow mechanism for growth from the melt. In addition, we have observed an empirical inverse correlation between the two free paramters ('diffusive speeds') in this model and the equilibrium solute partition coefficient of a system. This correlation may be used to estimate values of these free paramters for other systems in which solute trapping has not or cannot be measured. The possible microscopic origin of such a correlationis discussed.

Reitano, Riccardo; Smith, Patrick M.; Aziz, Michael J.

1994-08-01

7

Studies on incorporation of As 2 and As 4 in III-V compound semiconductors with two group V elements grown by molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

Under the assumption that one incident As 4 molecule produces one active As 2 molecule before incorporating into epitaxial alloys, a novel thermodynamic model is developed to describe the molecular beam epitaxy (MBE) growth of III-V compound semiconductors with two group V elements using As 4 flux. A parameter ?d representing the activation energy of As 4 dissociation process is introduced in the model. High quality InAs yP 1- y materials were grown on InP substrates using our home made all solid source MBE (SSMBE) system with valved cracker cells under different substrate temperatures and arsenic fluxes with different As 2/As 4 ratios. By taking into account the As 2/As 4 ratio, the model is used to calculate the compositions of the grown samples. The calculated results are in good agreement with the experimental data. Both the experiments and the calculations show the lower incorporation efficiency of As 4 than that of As 2.

Hao, Zhi-Biao; Ren, Zai-Yuan; Guo, Wen-Ping; Luo, Yi

2001-04-01

8

Platinum-group element geochemistry of the Zhuqing Fe-Ti-V oxide ore-bearing mafic intrusions in western Yangtze Block, SW China: control of platinum-group elements by magnetite  

NASA Astrophysics Data System (ADS)

Platinum-group element (PGE) geochemistry combined with elemental geochemistry and magnetite compositions are reported for the Mesoproterozoic Zhuqing Fe-Ti-V oxide ore-bearing mafic intrusions in the western Yangtze Block, SW China. All the Zhuqing gabbros display extremely low concentrations of chalcophile elements and PGEs. The oxide-rich gabbros contain relatively higher contents of Cr, Ni, Ir, Ru, Rh, and lower contents of Pt and Pd than the oxide-poor gabbros. The abundances of whole-rock concentrations of Ni, Ir, Ru, and Rh correlate well with V contents in the Zhuqing gabbros, implying that the distributions of these elements are controlled by magnetite. The fractionation between Ir-Ru-Rh and Pt-Pd in the Zhuqing gabbros is mainly attributed to fractional crystallization of chromite and magnetite, whereas Ru anomalies are mainly due to variable degrees of compatibility of PGE in magnetite. The order of relative incompatibility of PGEs is calculated to be Pd < Pt < Rh < Ir < Ru. The very low PGE contents and Cu/Zr ratios and high Cu/Pd ratios suggest initially S-saturated magma parents that were highly depleted in PGE, which mainly formed due to low degrees of partial melting leaving sulfides concentrating PGEs behind in the mantle. Moreover, the low MgO, Ni, Ir and Ru contents and high Cu/Ni and Pd/Ir ratios for the gabbros suggest a highly evolved parental magma. Fe-Ti oxides fractionally crystallized from the highly evolved magma and subsequently settled in the lower sections of the magma chamber, where they concentrated and formed Fe-Ti-V oxide ore layers at the base of the lower and upper cycles. Multiple episodes of magma replenishment in the magma chamber may have been involved in the formation of the Zhuqing intrusions.

Fan, Hong-Peng; Zhu, Wei-Guang; Zhong, Hong; Bai, Zhong-Jie; He, De-Feng; Ye, Xian-Tao; Chen, Cai-Jie; Cao, Chong-Yong

2014-06-01

9

Electrical activity, mode of incorporation and distribution coefficient of group V elements in Hg 1?x Cd x Te grown from tellurium rich liquid phase epitxial growth solutions  

Microsoft Academic Search

Hg1?xCdxTe films were grown liquid phase epitaxially from tellurium rich solutions containing up to 10 at. % of the group V elements\\u000a P, As, Sb, and Bi. Chemical analysis of the Te growth solutions and the films was carried out in conjunction with extensive\\u000a Hall effect measurements on the films subsequent to various annealing treatments under Hg rich and Te

H. R. Vydyanath; J. A. Ellsworth; C. M. Devaney

1987-01-01

10

Substantial enhancement in intrinsic coercivity on M-type strontium hexaferrite through the increase in magneto-crystalline anisotropy by co-doping of group-V and alkali elements  

NASA Astrophysics Data System (ADS)

The effect of d1 impurity doping in Sr-hexaferrite (SrM) on the magnetic anisotropy is investigated. First-principles calculations revealed that group-V elements (V, Nb) are stabilized with co-doping of alkali elements. Na1+/K1+ doping at Sr2+-site is found to be critical to form the d1 impurities at Fe-site. Experimentally, Na-V doped SrM shows the intrinsic coercivity of ˜5.4 kOe, which is ˜300% enhancement compared to undoped SrM and comparable value to La-Co co-doped SrM. Finally, the spin-orbit coupling from non-vanishing angular momentum of d1 impurity in SrM should be a main factor for such a substantial improvement of intrinsic coercivity.

Ahn, Kyunghan; Ryu, Byungki; Korolev, Dmitry; Jae Kang, Young

2013-12-01

11

Cold Fusion Production and Decay of Neutron-Deficient Isotopes of Dubnium and Development of Extraction Systems for Group V Elements  

SciTech Connect

Excitation functions for the 1n and 2n exit channels of the 208Pb(51V,xn)259-xDb reaction were measured. A maximum cross section of the 1n exit channel of 2070+1100/-760 pb was measured at an excitation energy of 16.0 +- 1.8 MeV. For the 2n exit channel, a maximum cross section of 1660+450/-370 pb was measured at 22.0 +- 1.8 MeV excitation energy. The 1n excitation function for the 209Bi(50Ti,n)258Db reaction was remeasured, resulting in a cross section of 5480+1730/1370 pb at an excitation energy of 16.0 +- 1.6 MeV. Differences in cross section maxima are discussed in terms of the fusion probability below the barrier. The extraction of niobium (Nb) and tantalum (Ta) from hydrochloric acid and mixed hydrochloric acid/lithium chloride media by bis(2-ethylhexyl) hydrogen phosphate (HDEHP) and bis(2-ethylhexyl) hydrogen phosphite (BEHP) was studied. The goal of the experiments was to find a system that demonstrates selectivity among the members of group five of the Periodic Table and is also suitable for the study of dubnium (Db, Z = 105). Experiments with niobium and tantalum were performed with carrier (10-6 M), carrier free (10-10 M) and trace (10-16 M) concentrations of metal using hydrochloric acid solution with concentrations ranging from 1 - 11 M. The extraction of niobium and tantalum from mixed hydrochloric acid/lithium chloride media by HDEHP and BEHP as a function of hydrogen ion (H+) concentration was also investigated. The data obtained are used as the basis to discuss the speciation of niobium and tantalum under the conditions studied and to evaluate possible extraction mechanisms. The 74Se(18O,p3n)88gNb excitation function was measured to determine the best energy for producing the 88Nb used in chemistry experiments. A maximum cross section of 495 +- 5 mb was observed at an 18O energy of 74.0 MeV. The half life of 88gNb was measured and determined to be 14.56 +- 0.11 min.

Gates, Jacklyn M.

2008-07-31

12

Distributed process groups in the V Kernel  

Microsoft Academic Search

The V kernel supports an abstraction of processes, with operations for interprocess communication, process management, and memory management. This abstraction is used as a software base for constructing distributed systems. As a distributed kernel, the V kernel makes intermachine boundaries largely transparent.In this environment of many cooperating processes on different machines, there are many logical groups of processes. Examples include

David R. Cheriton; Willy Zwaenepoel

1985-01-01

13

The Abundances of the Iron Group Elements in IOTA Herculis  

NASA Astrophysics Data System (ADS)

We have determined abundances for the iron group elements Ti, V, Cr, Mn, Co, & Ni in iota Herculis (HD 160762, HR 6588; B3 IV), using coadded IUE spectra in both the long and short-wavelength regions, and the LTE model atmosphere/spectral synthesis codes ATLAS9/SYNTHE. Model parameters were adopted from (Peters & Polidan 1985 (Calibration of Fundamental Stellar Quantities, IAU Symp. 111, p. 417) and Pintado & Adelman 1993 (MNRAS, 264, 63): Teff = 17,500 K, log g = 3.75, vsin i = 5 km s(-1) , and vturb = 2 km s(-1) . Lines of iron group species were carefully chosen to avoid blends, and continua were established by fitting synthetic spectra to observed spectra in an iterative process. Abundances were measured with the profile-fitting technique. We found that Co and Ni appear to be significantly depleted relative to the solar values. Our data suggest a slight depletion of Ti, Cr, and Mn relative to the solar values but the abundance of V appears to be solar. GJP acknowledges partial support for this project from NASA Grant NAG5-3429.

Grigsby, J. A.; Peters, G. J.

1997-05-01

14

Methods for forming group III-V arsenide-nitride semiconductor materials  

NASA Technical Reports Server (NTRS)

Methods are disclosed for forming Group III--arsenide-nitride semiconductor materials. Group III elements are combined with group V elements, including at least nitrogen and arsenic, in concentrations chosen to lattice match commercially available crystalline substrates. Epitaxial growth of these III-V crystals results in direct bandgap materials, which can be used in applications such as light emitting diodes and lasers. Varying the concentrations of the elements in the III-V crystals varies the bandgaps, such that materials emitting light spanning the visible spectra, as well as mid-IR and near-UV emitters, can be created. Conversely, such material can be used to create devices that acquire light and convert the light to electricity, for applications such as full color photodetectors and solar energy collectors. The growth of the III-V crystals can be accomplished by growing thin layers of elements or compounds in sequences that result in the overall lattice match and bandgap desired.

Major, Jo S. (Inventor); Welch, David F. (Inventor); Scifres, Donald R. (Inventor)

2000-01-01

15

Parallel and Serial Grouping of Image Elements in Visual Perception  

ERIC Educational Resources Information Center

The visual system groups image elements that belong to an object and segregates them from other objects and the background. Important cues for this grouping process are the Gestalt criteria, and most theories propose that these are applied in parallel across the visual scene. Here, we find that Gestalt grouping can indeed occur in parallel in some…

Houtkamp, Roos; Roelfsema, Pieter R.

2010-01-01

16

Chemical Etching of Group III - V Semiconductors  

NASA Astrophysics Data System (ADS)

Chemical etching is basically a process used to selectively remove controlled amounts of material from the original substrate. The etch depth can be designed to be just tens of angstroms or up to a few hundred angstroms. The etching process is one of the important stages in the fabrication of micro electronics devices. Errors at this stage will severely impair performance of these devices. Due to the present diadvantages of dry etching, wet chemical etching will still be useful for some time. it is infact one of the standard technique for the processing of Integral Circuits (Ics). This article reviews the chemical etchants used for the reatment of GaAs and others III - V. Semiconductors, the factors involved in their mechanism and the many potential pitfalls, arwillan detects associated with them. The article should present an understandable account for the non-specialist reaser yet it does offer a useful material and information for the specialists readers an well.

Kadhim, Najah J.; Laurie, Stuart H.; Mukherjee, D.

1998-07-01

17

The nature of Group-V acceptor impurities in SnO2  

NASA Astrophysics Data System (ADS)

Group-V elements have long been considered leading candidates for achieving p-type doping in semiconducting oxides. Using first-principles calculations, we investigate the feasibility of achieving ambipolar doping in SnO2 using the Group-V elements N, P, and As. We address the electronic structure of these impurities by performing systematic density functional calculations using hybrid functionals. This approach overcomes the band-gap problems inherent in calculations using the local density approximation or generalized gradient approximation, thus allowing us to accurately determine energies of defect levels. We discuss the stability of the isolated impurities both as substitutional and interstitial defects, based on calculated formation and migration energies. We also investigate their possible passivation by hydrogen and examine binding energies and activation energies of hydrogen-acceptor complexes. We conclude that the Group-V elements are deep acceptors that will not enable p-type doping of SnO2.

Varley, Joel; Janotti, Anderson; van de Walle, Chris

2009-03-01

18

Platinum group elements in the environment and their health risk  

Microsoft Academic Search

Accumulation of platinum group elements (PGEs) in the environment has been increased over the time. Catalytic converters of modern vehicles are considered to be the main sources of PGE pollution, since the correlation is between the Pt:Rh ratios in various environmental compartments and in converter units. The present literature survey shows that the concentration of these metals has increased significantly

Khaiwal Ravindra; László Bencs; René Van Grieken

2004-01-01

19

Working Group on Cartographic Coordinates and Rotational Elements  

NASA Astrophysics Data System (ADS)

The 2003 report of the IAU/IAG Working Group on Cartographic Coordinates and Rotational Elements has appeared in Celestial Mechanics and Dynamical Astronomy(2005)volume 91, part 3-4, pages 203-215. The Working Group continues to maintain and update the information for cartographic coordinates and rotational elements for the Sun, Moon, planets, satellites, asteroids, and comets. A report is published treannually. A web site is maintained at http://extranet.astrogeology.wr.usgs.gov/Projects/WGCCRE with the up-to-date information. It is anticipated that the next report will include updates for Saturn (rotation rate) and all of the Saturnian moons, additions for the newly visited comets and asteroids, and a clarification of the Moon's coordinate systems (the mean Earth/polar axis system needs to be defined more precisely).

Seidelmann, P. Kenneth; Archinal, B. A.; A'Hearn, M. F.; Cruikshank, D. P.; Hilton, J. L.; Keller, H. U.; Oberst, R. J.; Simon, J. L.; Stooke, P.; Tholen, D. J.; Thomas, P. C.

2007-03-01

20

First-principles local pseudopotentials for group-IV elements  

Microsoft Academic Search

A simple scheme is proposed for generating first-principles local pseudopotentials, and applied to group-IV elements. The scheme is based on solving Kohn-Sham equations inversely, using the density from a nonlocal pseudopotential calculation. The generated local pseudopotentials have been applied in the calculations of dimers and solids including diamond and fcc structures of Si, Ge, and Sn. Fairly good results are

Bing Wang; M. J. Stott

2003-01-01

21

Polycomb group response elements in Drosophila and vertebrates.  

PubMed

Polycomb group genes (PcG) encode a group of about 16 proteins that were first identified in Drosophila as repressors of homeotic genes. PcG proteins are present in all metazoans and are best characterized as transcriptional repressors. In Drosophila, these proteins are known as epigenetic regulators because they remember, but do not establish, the patterned expression state of homeotic genes throughout development. PcG proteins, in general, are not DNA binding proteins, but act in protein complexes to repress transcription at specific target genes. How are PcG proteins recruited to the DNA? In Drosophila, there are specific regulatory DNA elements called Polycomb group response elements (PREs) that bring PcG protein complexes to the DNA. Drosophila PREs are made up of binding sites for a complex array of DNA binding proteins. Functional PRE assays in transgenes have shown that PREs act in the context of other regulatory DNA and PRE activity is highly dependent on genomic context. Drosophila PREs tend to regulate genes with a complex array of regulatory DNA in a cell or tissue-specific fashion and it is the interplay between regulatory DNA that dictates PRE function. In mammals, PcG proteins are more diverse and there are multiple ways to recruit PcG complexes, including RNA-mediated recruitment. In this review, we discuss evidence for PREs in vertebrates and explore similarities and differences between Drosophila and vertebrate PREs. PMID:23419717

Kassis, Judith A; Brown, J Lesley

2013-01-01

22

Determination of the CKM Element V(Ub)  

SciTech Connect

The precise determination of the CKM matrix element |V{sub ub}| is crucial in testing the Standard Model mechanism for CP violation. From a sample of 88 million B{bar B} pairs collected with the BABAR detector, charmless semileptonic B decays are selected using simultaneous requirements on the electron energy, E{sub e}, and the invariant mass squared of the electron-neutrino pair, q{sup 2}. The partial branching fraction, unfolded for detector effects, is determined in a region of the q{sup 2}-E{sub e} plane where the dominating semileptonic decays to charm mesons are highly suppressed. Theoretical calculations based on the Heavy Quark Expanion allows for a determination of |V{sub ub}| = (3.95 {+-} 0.27{sub -0.42}{sup +0.58} {+-} 0.25) x 10{sup -3}, where the errors represent experimental, heavy quark parameters and theoretical uncertainties, respectively.

Fortin, Dominique; /Victoria U.

2007-04-06

23

Benchmarking of the 99-group ANSL-V library  

SciTech Connect

The purpose of this paper is to present thermal benchmark data testing results for the BAPL-1, TRX-1, and SEEP-1 lattices, using selected processed cross-sections from the ANSL-V 99-group library. 7 refs., 1 tab.

Wright, R.Q.; Ford, W.E. III; Greene, N.M.; Petrie, L.M.; Primm, R.T. III; Westfall, R.M.

1987-01-01

24

Doping of indium phosphide with group IV elements  

SciTech Connect

This paper studies the doping of single crystals of indium phosphide (InP) with group IV elements using data obtained by measuring the total charge concentration of additives and carriers. Single crystals of indium phosphide were grown by the Czochralski method from liquid melts with a liquid hermetic seal in quartz cubicles. The total impurity concentration was determined by atomic-absorption analysis with + or - 10% error. In order to explain the behavior of germanium and tin in indium phosphide, the authors consider the bond energies of additives in indium phosphide and their tetrahedral radii. The authors conclude that the established higher amphoteric character of germanium with respect to tin is probably explained by the moduli of elasticity of the doped crystal.

Zakharenkov, L.F.; Samorukov, B.E.; Zykov, A.M.

1985-06-01

25

P-element homing is facilitated by engrailed polycomb-group response elements in Drosophila melanogaster.  

PubMed

P-element vectors are commonly used to make transgenic Drosophila and generally insert in the genome in a nonselective manner. However, when specific fragments of regulatory DNA from a few Drosophila genes are incorporated into P-transposons, they cause the vectors to be inserted near the gene from which the DNA fragment was derived. This is called P-element homing. We mapped the minimal DNA fragment that could mediate homing to the engrailed/invected region of the genome. A 1.6 kb fragment of engrailed regulatory DNA that contains two Polycomb-group response elements (PREs) was sufficient for homing. We made flies that contain a 1.5 kb deletion of engrailed DNA (en(?1.5)) in situ, including the PREs and the majority of the fragment that mediates homing. Remarkably, homing still occurs onto the en(?1. 5) chromosome. In addition to homing to en, P[en] inserts near Polycomb group target genes at an increased frequency compared to P[EPgy2], a vector used to generate 18,214 insertions for the Drosophila gene disruption project. We suggest that homing is mediated by interactions between multiple proteins bound to the homing fragment and proteins bound to multiple areas of the engrailed/invected chromatin domain. Chromatin structure may also play a role in homing. PMID:22276200

Cheng, Yuzhong; Kwon, Deborah Y; Arai, Allison L; Mucci, Diane; Kassis, Judith A

2012-01-01

26

Thermodynamic properties of the Group 1A elements  

SciTech Connect

This review describes thermodynamic properties of condensed phases of the alkali metals, excluding francium for which the amount of information is too limited. The properties considered are: heat capacities from 0 to 1600 K, temperatures and enthalpies of fusion and martensitic transformation in Li and Na; discussion of the Debye temperature and electronic heat capacity coefficient at absolute zero temperature is also included. The paper is the second part of a series. Similar to previous assessment of the IIA group [93ALC/CHA], this paper considers original studies, especially with respect to factors which influence the accuracy and reliability of results. Recommendations derived from such analyses are compared with most advanced previous reviews made at the Institute for High Temperatures (Moscow) [70SHP/YAK], [82GUR] and the National Institute of Standards and Technology (Washington) [85JAN]. The properties of individual elements of the group are compared and suggestions are made for experimental studies which should improve poorly measured quantities. The review is supplemented by an IBM PC database which contains references, assessed data, brief description of studies and has facilities for fitting and plotting of data and for adding new information.

Alcock, C.B.; Itkin, V.P. [Univ. of Toronto (Canada); Chase, M.W. [National Institute of Standards and Technology, Gaithersburg, MD (United States)

1994-05-01

27

Comprehensive Analyses of the Spectra of Iron-group Elements  

NASA Astrophysics Data System (ADS)

For many decades, the Atomic Spectroscopy Group at NIST has measured atomic data of vital use to astronomy and other fields using high resolution spectrometers that are found in few other places in the world. These now include the 2-m Fourier transform (FT) spectrometer covering the region 285 nm to 5500 nm, the FT700 vacuum ultraviolet (VUV) FT spectrometer covering the region 143 nm to 900 nm, and a 10.7-m normal incidence spectrograph (NIVS) covering 30 nm to 500 nm. Recent work focused on the measurement and analysis of wavelengths and energy levels of iron-group elements to provide extensive data for the analysis of astrophysical spectra. Our comprehensive linelist for Fe II from 90 nm to 5500 nm contains over 13 600 lines with order of magnitude improvements in the wavelengths compared to previous work [Nave & Johansson, ApJSS 204, 1(2013)]. The spectra were observed in high-current continuous and pulsed hollow cathode (HCL) discharges using FT spectrometers and our NIVS spectrograph. A similar analysis of Cr II contains over 5300 lines and extends the knowledge of this spectrum to the previously unobserved region between 731 nm at 5500 nm [Sansonetti, Nave, Reader & Kerber, ApJSS 202, 15 (2012); Sansonetti & Nave, ApJSS (in prep.)]. Our analysis of the Co III spectrum contains 750 lines observed in Penning discharge lamps and an additional 900 lines compiled from previous work, including Ritz wavelengths, optimized energy levels, and calculated log(gf) values [Smillie, Pickering, Nave & Smith, ApJSS (in prep.)]. NIST and ICL are currently collaborating to complete the measurement and analysis of wavelengths, energy levels, and hyperfine structure parameters for all singly-ionized iron-group elements of astrophysical interest, covering the wavelength range 80 nm to 5500 nm. This project uses archival data from FT spectrometers at NIST, ICL and Kitt Peak National Observatory, with additional spectra of HCL and Penning discharge sources taken using our FT and NIVS spectrometers. Current work includes the spectra of Mn I, Mn II, Ni II, Sc II, and Co III. This work was partially supported by NASA, the STFC and PPARC (UK), the Royal Society of the UK, and the Leverhulme Trust.

Nave, Gillian; Sansonetti, Craig J; Pickering, Juliet C; Liggins, Florence

2014-06-01

28

Investigation of group IVA elements combined with HAXPES and first-principles calculations  

NASA Astrophysics Data System (ADS)

The core level and valence band spectra of group IVA elements were investigated with hard x-ray photoemission spectroscopy (HAXPES) photon energy of 7.939 keV by bulk sensitive manner. The survey and valance band spectra were presented, relative peaks intensity are discussed by thinking about inelastic mean free path (IMFP) and photoionization cross section of photoelectrons (PICS). In order to understand bulk band structures, valence bands are compared with the calculated ones by considering PICS, IMFP and total energy resolution. The calculated results by GGA, HSE06 and GW0 methods are simply discussed by comparing with experiment spectra.

Cui, Y.-T.; Li, G.-L.; Oji, H.; Son, J.-Y.

2014-04-01

29

Fractionation and reactivity of platinum group elements during estuarine mixing.  

PubMed

The fractionation of platinum group elements (PGE) rhodium(III), palladium(II), and platinum(IV), has been studied after their addition in aqueous form to unfiltered river water samples (Tugela river, South Africa) and to mixtures of river water and seawater. The particulate fraction of PGE averaged about 70 (Rh), 50 (Pd), and 25% (Pt) of total metal and was dependent on both particle concentration and salinity. The aqueous (<0.45 microm) pool of PGE was dominated by entities of less than 0.1 microm in diameter, and for Pd and Rh hydrophobic complexes of metal, operationally defined by their retention on a C-18 column, were significant. Distribution coefficients, based on the w/w concentration of metal on particles relative to the corresponding concentration in the aqueous pool, either increased (Rh and Pd) or declined (Pt) with increasing salinity. These observations are interpreted in terms of a number of general and metal-specific mechanisms. Thus, the behavior of Pd appears to be controlled by its association with relatively small (<0.1 microm) dissolved organic ligands, a significant fraction of which is hydrophobic and is subject to salting out upon estuarine mixing. Rhodium may also be partly subject to this mechanism of removal, but kinetic considerations and results of X-ray analysis of filter-retentates suggest that adsorption of cationic hydroxychlorides and the destabilization and precipitation of hydroxy-complexes induced by the rise in pH across the estuarine gradient are more important. Unlike Pd, the binding of Pt by organic ligands is kinetically hindered. Thus, in contrast to Pd, particle-water reactivity of Pt is controlled by electrostatic interactions between the particle surface and inorganic aqueous species. The results of this study improve our understanding of and ability to predict the transport and fate of PGE in estuaries where these metals are mobilized or discharged. PMID:18351078

Cobelo-Garcia, Antonio; Turner, Andrew; Millward, Geoff E

2008-02-15

30

Molecular nitrides with titanium and Group 13-15 elements.  

PubMed

Several heterometallic nitrido complexes were prepared by reaction of the imido-nitrido titanium complex [{Ti(eta(5)-C(5)Me(5))(mu-NH)}(3)(mu(3)-N)] (1) with amido derivatives of Group 13-15 elements. Treatment of 1 with bis(trimethylsilyl)amido [M{N(SiMe(3))(2)}(3)] derivatives of aluminum, gallium, or indium in toluene at 150-190 degrees C affords the single-cube amidoaluminum complex [{(Me(3)Si)(2)N}Al{(mu(3)-N)(2)(mu(3)-NH)Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)}] (2) or the corner-shared double-cube compounds [M(mu(3)-N)(3)(mu(3)-NH)(3){Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)}(2)] [M = Ga (3), In (4)]. Complexes 3 and 4 were also obtained by treatment of 1 with the trialkyl derivatives [M(CH(2)SiMe(3))(3)] (M = Ga, In) at high temperatures. The analogous reaction of 1 with [{Ga(NMe(2))(3)}(2)] at 110 degrees C leads to [{Ga(mu(3)-N)(2)(mu(3)-NH)Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)}(2)] (5), in which two [GaTi(3)N(4)] cube-type moieties are linked through a gallium-gallium bond. Complex 1 reacts with one equivalent of germanium, tin, or lead bis(trimethylsilyl)amido derivatives [M{N(SiMe(3))(2)}(2)] in toluene at room temperature to give cube-type complexes [M{(mu(3)-N)(2)(mu(3)-NH)Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)}] [M = Ge (6), Sn (7), Pb (8)]. Monitoring the reaction of 1 with [Sn{N(SiMe(3))(2)}(2)] and [Sn(C(5)H(5))(2)] by NMR spectroscopy allows the identification of intermediates [RSn{(mu(3)-N)(mu(3)-NH)(2)Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)}] [R = N(SiMe(3))(2) (9), C(5)H(5) (10)] in the formation of 7. Addition of one equivalent of the metalloligand 1 to a solution of lead derivative 8 or the treatment of 1 with a half equivalent of [Pb{N(SiMe(3))(2)}(2)] afford the corner-shared double-cube compound [Pb(mu(3)-N)(2)(mu(3)-NH)(4){Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)}(2)] (11). Analogous antimony and bismuth derivatives [M(mu(3)-N)(3)(mu(3)-NH)(3){Ti(3)(eta(5)-C(5)Me(5))(3)(mu(3)-N)}(2)] [M = Sb (12), Bi (13)] were obtained through the reaction of 1 with the tris(dimethylamido) reagents [M(NMe(2))(3)]. Treatment of 1 with [AlCl(2){N(SiMe(3))(2)}(OEt(2))] affords the precipitation of the singular aluminum-titanium square-pyramidal aggregate [{{(Me(3)Si)(2)N}Cl(3)Al(2)}(mu(3)-N)(mu(3)-NH)(2){Ti(3)(eta(5)-C(5)Me(5))(3)(mu-Cl)(mu(3)-N)}] (14). The X-ray crystal structures of 5, 11, 13, 14, and [AlCl{N(SiMe(3))(2)}(2)] were determined. PMID:19544507

García-Castro, María; Martín, Avelino; Mena, Miguel; Yélamos, Carlos

2009-07-20

31

Design, synthesis, and properties of phthalocyanine complexes with main-group elements showing main absorption and fluorescence beyond 1000 nm.  

PubMed

We present a comprehensive description of the unique properties of newly developed phthalocyanines (Pcs) containing main-group elements that absorb and emit in the near-IR region. Group 16 (S, Se, and Te) elements and group 15 (P, As, and Sb) elements were used as peripheral and central (core) substituents. With the introduction of group 16 elements into free-base Pc, a red-shift of the Q-band was observed, as a result of the electron-donating ability of group 16 elements particularly at the ? positions. An X-ray crystallographic analysis of ?-ArS-, ArSe-, and ArTe-linked free-base Pcs was also successfully performed, and the relationship between structure and optical properties was clarified. When a group 15 element ion was introduced into the center of the Pc ring, the resulting Pcs showed a single Q-band peak beyond 1000 nm (up to 1056 nm in CH2Cl2). In particular, [(ArS)8PcP(OMe)2](+) and [(ArS)8PcAs(OMe)2](+) exhibited a distinct fluorescence in the 960-1400 nm region with moderate quantum yields. The atomic radius of the group 15 element is important for determining the Pc structure, so that this can be controlled by the choice of group 15 elements. Electrochemical data revealed, while MO calculations suggested, that the red-shift of the Q-band is attributable to a decrease of the HOMO-LUMO gap due to significant and moderate stabilization of the LUMO and HOMO, respectively. The effect of peripheral substutuents and a central P(V) ion on the Q-band shift was independently predicted by MO calculations, while the magnitude of the total calculated shift was in good agreement with the experimental observations. The combination of spectral, electrochemical, and theoretical considerations revealed that all of the central group 15 elements, peripheral group 16 elements, and their positions are necessary to shift the Q-band beyond 1000 nm, indicating that the substitution effects of group 15 and 16 elements act synergistically. The Pcs having Q-bands beyond 1000 nm in this study also had stability under aerobic conditions comparative to that of CuPc, which is presently being widely used in consumer products. PMID:24328229

Furuyama, Taniyuki; Satoh, Koh; Kushiya, Tomofumi; Kobayashi, Nagao

2014-01-15

32

Calculations of stopping powers of 100 eV-30 keV electrons in 31 elemental solids  

SciTech Connect

We present calculated electron stopping powers (SPs) for 31 elemental solids (Li, Be, glassy C, graphite, diamond, Na, Mg, K, Sc, Ti, V, Fe, Y, Zr, Nb, Mo, Ru, Rh, In, Sn, Cs, Gd, Tb, Dy, Hf, Ta, W, Re, Os, Ir, and Bi). These SPs were determined with an algorithm previously used for the calculation of electron inelastic mean free paths and from energy-loss functions (ELFs) derived from experimental optical data. The SP calculations were made for electron energies between 100 eV and 30 keV and supplement our earlier SP calculations for ten additional solids (Al, Si, Cr, Ni, Cu, Ge, Pd, Ag, Pt, and Au). Plots of SP versus atomic number for the group of 41 solids show clear trends. Multiple peaks and shoulders are seen that result from the contributions of valence-electron and various inner-shell excitations. Satisfactory agreement was found between the calculated SPs and values from the relativistic Bethe SP equation with recommended values of the mean excitation energy (MEE) for energies above 10 keV. We determined effective MEEs versus maximum excitation energy from the ELFs for each solid. Plots of effective MEE versus atomic number showed the relative contributions of valence-electron and different core-electron excitations to the MEE. For a maximum excitation energy of 30 keV, our effective MEEs agreed well for Be, graphite, Na, Al, and Si with recommended MEEs; a difference for Li was attributed to sample oxidation in the SP measurements for the recommended MEE. Substantially different effective MEEs were found for the three carbon allotropes (graphite, diamond, and glassy C)

Tanuma, S. [Materials Analysis Station, National Institute for Materials Science, 1-2-1 Sengen, Tsukuba, Ibaraki 305-0047 (Japan); Powell, C. J.; Penn, D. R. [National Institute of Standards and Technology, Gaithersburg, Maryland 20899-8370 (United States)

2008-03-15

33

Vapor phase growth of group 3, 4, and 5 compounds by HCl transport of elements  

NASA Technical Reports Server (NTRS)

Technique has been devised for vapor-phase epitaxial growth of group 3, 4, and 5 binary, ternary, or quaternary compounds by HCl transport of the constituent elements or dopants. Technique uses all the constituents of the alloy system in their elemental form. Transport of these elements by an HCl + H2 carrier gas facilitates their transport as subchlorides.

Tyagi, R. C.; Debnam, W. J., Jr.; Mcnear, M. F.; Crouch, R. K.; Breckenridge, R. A.

1973-01-01

34

Bandgap tuning of mono- and bilayer graphene doped with group IV elements  

NASA Astrophysics Data System (ADS)

We report density functional theory band structure calculations of graphene doped with group IV elements. A bandgap as high as 2.13 eV is calculated for a single layer of graphene doped with Si while Ge and Sn doping reduce this bandgap for equal doping concentrations. Bilayers of doped graphene are also studied and it is found that the bandgap of these materials is less than that of the single layer counterparts. Finally, a transverse electric field is applied to the doped bilayers and it is found that the bandgap is inversely proportional to the electric field strength in contrast to what has been observed in the case of pristine bilayers. Carrier effective masses were calculated and in general the effective masses of electrons and holes are found to be similar.

Kaplan, D.; Swaminathan, V.; Recine, G.; Balu, R.; Karna, S.

2013-05-01

35

Report of the IAU/IAG Working Group on cartographic coordinates and rotational elements: 2006  

USGS Publications Warehouse

Every three years the IAU/IAG Working Group on Cartographic Coordinates and Rotational Elements revises tables giving the directions of the poles of rotation and the prime meridians of the planets, satellites, minor planets, and comets. This report introduces improved values for the pole and rotation rate of Pluto, Charon, and Phoebe, the pole of Jupiter, the sizes and shapes of Saturn satellites and Charon, and the poles, rotation rates, and sizes of some minor planets and comets. A high precision realization for the pole and rotation rate of the Moon is provided. The expression for the Sun's rotation has been changed to be consistent with the planets and to account for light travel time ?? 2007 Springer Science+Business Media B.V.

Seidelmann, P. K.; Archinal, B. A.; A'Hearn, M. F.; Conrad, A.; Consolmagno, G. J.; Hestroffer, D.; Hilton, J. L.; Krasinsky, G. A.; Neumann, G.; Oberst, J.; Stooke, P.; Tedesco, E. F.; Tholen, D. J.; Thomas, P. C.; Williams, I. P.

2007-01-01

36

X-ray standing wave investigations of Group III and V metal adsorption on Si(001)  

SciTech Connect

Investigations of atomic bonding, surface reconstruction, surface dynamics, and growth kinetics of group III and V metals on Si(001) are important for understanding the initial growth stage of III-V semiconductors on Si(001). Such studies can also provide valuable information for other important issues such as surfactant-mediated epitaxy, surface passivation and delta-doping layers. X-ray standing waves generated by dynamical Bragg diffraction were used as an element-specific structural probe for investigating Ga and Sb adsorption on Si(001). These high-resolution measurements reveal important quantitative structural information regarding the dimerized surface structures, and provide a stringent test for structural models proposed by various theoretical calculations. An overview of the X-ray standing wave technique and its application to surface structure and dynamics is presented.

Qian, Y.; Bedzyk, M.J. [Northwestern Univ., Evanston, IL (United States)]|[Argonne National Lab., IL (United States). Materials Science Div.; Lyman, P.F. [Northwestern Univ., Evanston, IL (United States)

1997-05-01

37

Fish retroposons related to the Penelope element of Drosophila virilis define a new group of retrotransposable elements.  

PubMed

Poseidon and Neptune are two ancient lineages of retroposons related to the Penelope element from Drosophila virilis. They have been identified in various teleost fish species, including the medakafish (Oryzias latipes), and the pufferfishes Fugu rubripes and Tetraodon nigroviridis, whose genomes are currently being sequenced. Some of these elements are highly reiterated in fish genomes. Penelope-related elements were also identified in blood fluke, shrimp, sea urchin, cichlid fish and frog, showing that they are widespread in animals. Penelope-related retroposons were not detected among sequences from the Drosophila melanogaster and human genome projects, suggesting that they have been lost from certain animal lineages. A sequence encoding a putative Uri (also called GIY-YIG) endonuclease domain was detected downstream from the gene for reverse transcriptase. To the best of our knowledge, this type of endonuclease sequence has previously been identified in group I introns and in genes for prokaryotic excinucleases but not in retrotransposable elements. Penelope-related elements are frequently truncated at their 5' ends and can also be flanked by long terminal repeat-like structures. Phylogenetic analysis of the reverse transcriptase domain failed to assign Penelope-related retroposons to one of the major groups of retroelements. Overall, therefore, the evidence strongly suggests that these sequences represent a new group of retrotransposable elements. PMID:11459192

Volff, J N; Hornung, U; Schartl, M

2001-06-01

38

Platinum-group element resources in podiform chromitites from California and Oregon.  

USGS Publications Warehouse

Assays of Pt, Pd, Rh and Ir from approx 280 podiform chromite deposits in Palaeozoic and Mesozoic ophiolites are statistically analysed to estimate their possible by-product value from mining the chromite. The platinum-group elements occur in discrete platinum-group minerals, and in solid solution in Cu-Ni-Fe sulphides. Low grades and small amounts of total platinum-group elements in podiform chromite deposits imply a small resource. -G.J.N.

Page, N. J.; Singer, D. A.; Moring, B. C.; Carlson, C. A.; McDade, J. M.; Wilson, S. A.

1986-01-01

39

Electronic structures of platinum group elements silicides calculated by a first-principle pseudopotential method using plane-wave basis  

Microsoft Academic Search

The electronic structures of platinum group elements (Ru, Os, Rh, Ir, Pd, and Pt) silicides have been calculated. Ir3Si5 is a semiconductor with the direct gap of 1.14eV. Among monosilicides, RuSi and OsSi with the FeSi-type structure are semiconductors with the gap values of 0.21 and 0.41eV but RhSi, IrSi, PdSi, and PtSi with the MnP-type structure are metals. No

Y. Imai; A. Watanabe

2006-01-01

40

On Silicon Group Elements Ejected by Supernovae Type Ia  

NASA Astrophysics Data System (ADS)

There is evidence that the peak brightness of a Type Ia supernova is affected by the electron fraction Y e at the time of the explosion. The electron fraction is set by the aboriginal composition of the white dwarf and the reactions that occur during the pre-explosive convective burning. To date, determining the makeup of the white dwarf progenitor has relied on indirect proxies, such as the average metallicity of the host stellar population. In this paper, we present analytical calculations supporting the idea that the electron fraction of the progenitor systematically influences the nucleosynthesis of silicon group ejecta in Type Ia supernovae. In particular, we suggest the abundances generated in quasi-nuclear statistical equilibrium are preserved during the subsequent freeze-out. This allows potential recovery of Y e at explosion from the abundances recovered from an observed spectra. We show that measurement of 28Si, 32S, 40Ca, and 54Fe abundances can be used to construct Y e in the silicon-rich regions of the supernovae. If these four abundances are determined exactly, they are sufficient to recover Y e to 6%. This is because these isotopes dominate the composition of silicon-rich material and iron-rich material in quasi-nuclear statistical equilibrium. Analytical analysis shows the 28Si abundance is insensitive to Y e, the 32S abundance has a nearly linear trend with Y e, and the 40Ca abundance has a nearly quadratic trend with Y e. We verify these trends with post-processing of one-dimensional models and show that these trends are reflected in the model's synthetic spectra.

De, Soma; Timmes, F. X.; Brown, Edward F.; Calder, Alan C.; Townsley, Dean M.; Athanassiadou, Themis; Chamulak, David A.; Hawley, Wendy; Jack, Dennis

2014-06-01

41

Spectroscopic and Thermodynamic Investigations of Group V Halides.  

National Technical Information Service (NTIS)

The preparation and spectroscopic characterization of some mixed halogen and mixed halogen-cyanide compounds of phosphorous (V) are reported. Two solid-state forms of PCL5 have been investigated by differential scanning calorimetry. Solution reaction calo...

A. Finch

1977-01-01

42

Determination of 18 siderophile elements including all platinum group elements in chondritic metals and iron meteorites by instrumental neutron activation.  

PubMed

An instrumental neutron activation method is developed to analyze chondritic metals and iron meteorites. By changing irradiation and decay times, and selecting suitable ?-ray and X-ray photopeaks, not only all platinum group elements (Ru, Rh, Pd, Os, Ir, Pt) but also other siderophilic elements (Fe, Co, Ni, Cu, Ga, Ge, As, Mo, Sb, W, Re, Au) can be nondestructively determined in the meteoritic metal samples. To obtain analytical data as accurate as possible, interfering reactions and neutron flux gradients during irradiation are considered. Siderophile elemental abundances measured for the Odessa iron meteorite are highly consistent with the literature values. Rh abundances for bulk H, L, LL, EH, and EL chondrites, which had been scarcely reported in the literature, are derived from Rh/Ni abundance ratios in the metal separates of the corresponding chondritic groups. PMID:21619322

Kong, P; Ebihara, M; Nakahara, H

1996-12-01

43

Re-187 Os-187 Isotopic and Highly Siderophile Element Systematics of Group IVB Irons  

NASA Technical Reports Server (NTRS)

Study of the magmatic iron meteorite groups permits constraints to be placed on the chemical and isotopic composition of parent bodies, and the timing of, and crystal-liquid fractionation processes involved in the crystallization of asteroidal cores. Here we examine Re-Os isotopic and trace elemental systematics of group IVB irons. Compared to most irons, the irons comprising this group are enriched in some of the most refractory siderophile elements, yet highly-depleted in most volatile siderophile elements. These characteristics have been attributed to processes such as high temperature condensation of precursor materials and oxidation in the parent body. Most recently it has been suggested that both processes may be involved in the chemical complexity of the group. Here, high precision isotopic and highly siderophile element (HSE) concentrations are used to further examine these possible origins, and the crystallization history of the group. In addition, we have begun to assess the possibility of relating certain ungrouped irons with major groups via multi-element, trace element modeling. In a companion abstract, the isotopic and trace element systematics of the ungrouped iron Tishomingo are compared with the IVB irons.

Honesto, J.; McDonough, W. F.; Walker, R. J.; McCoy, T. J.; Ash, R. D.

2005-01-01

44

Chapter v: Reports of Divisions, Commissions and Working Groups  

NASA Astrophysics Data System (ADS)

This chapter presents the reports of Business Meeting of IAU Divisions, Commissions, Working Groups and Program Groups, held during the IAU XXVI General Assembly in Prague, 14-25 August 2006. The reports have been written by the out-going presidents and chairpersons.

2007-12-01

45

Conserved structural elements in the V3 crown of HIV1 gp120  

Microsoft Academic Search

Binding of the third variable region (V3) of the HIV-1 envelope glycoprotein gp120 to the cell-surface coreceptors CCR5 or CXCR4 during viral entry suggests that there are conserved structural elements in this sequence-variable region. These conserved elements could serve as epitopes to be targeted by a vaccine against HIV-1. Here we perform a systematic structural analysis of representative human anti-V3

Xunqing Jiang; Valicia Burke; Maxim Totrov; Constance Williams; Timothy Cardozo; Miroslaw K Gorny; Susan Zolla-Pazner; Xiang-Peng Kong

2010-01-01

46

Platinum-Group Elements in Southern Africa: Mineral Inventory and an Assessment of Undiscovered Mineral Resources.  

National Technical Information Service (NTIS)

The platinum-group elements, platinum, palladium, rhodium, ruthenium, iridium, and osmium, possess unique physical and chemical characteristics that make them indispensable to modern technology and industry. However, mineral deposits that are the main sou...

H. L. Parks J. D. Causey M. L. Zientek R. J. Miller

2014-01-01

47

Relativistic Effects and the Chemistry of the Heaviest Main-Group Elements  

ERIC Educational Resources Information Center

The chemical properties of the heaviest main-group elements often show features not found in their lighter counterparts while relativistic effects play an important role in the chemistry of these elements. The unusual properties and their relation to relativistic effects with emphasis on the new research are emphasized.

Thayer, John S.

2005-01-01

48

Report on Intercomparison V-8 of the Determination of Trace Elements in Rye Flour.  

National Technical Information Service (NTIS)

The participants were requested to determine as many elements as they could from among the following 29: As, Be, Ca, Cd, Cl, Co, Cr, Cu, F, Fe, Ga, Hg, I, K, Mg, Mn, Mo, Na, Ni, P, Pb, Sb, Se, Si, Sn, Tl, U, V and Zn. While six of these elements (Be, Ga, ...

L. Pszonicki A. Veglia R. Dybczynski O. Suschny

1982-01-01

49

Concentrations of platinum group elements in 122 U.S. coal samples  

USGS Publications Warehouse

Analysis of more than 13,000 coal samples by semi-quantitative optical emission spectroscopy (OES) indicates that concentrations of the platinum group elements (iridium, palladium, platinum, osmium, rhodium, and ruthenium) are less than 1 ppm in the ash, the limit of detection for this method of analysis. In order to accurately determine the concentration of the platinum group elements (PGE) in coal, additional data were obtained by inductively coupled plasma mass spectroscopy, an analytical method having part-per-billion (ppb) detection limits for these elements. These data indicate that the PGE in coal occur in concentrations on the order of 1 ppb or less.

Oman, C. L.; Finkelman, R. B.; Tewalt, S. J.

1997-01-01

50

Vacancy-assisted diffusion mechanism of group-III elements in ZnO: An ab initio study  

NASA Astrophysics Data System (ADS)

Based on ab initio total energy calculations, the diffusion mechanisms of group-III elements (B, Al, Ga, and In) in ZnO are investigated. The activation energy of vacancy-assisted mechanism consists of formation energy of Zn vacancy (VZn), binding energy between the dopants and VZn, as well as effective diffusion energy barrier of the dopants in ZnO. The effective diffusion energy barriers of B, Al, Ga, and In are estimated to be 1.12, 1.76, 1.45, and 1.06 eV for in-plane diffusion, and 1.12, 2.19, 1.80, and 1.06 eV for out-of-plane diffusion, respectively. The binding energies are estimated to be -0.66, -0.52, -0.48, and -0.43 eV for B-, Al-, Ga-, and In-VZn pairs, showing a size decreasing behavior.

Huang, Gui-Yang; Wang, Chong-Yu; Wang, Jian-Tao

2009-04-01

51

Conserved Structural Elements in the V3 Crown of HIV-1 gp120  

SciTech Connect

Binding of the third variable region (V3) of the HIV-1 envelope glycoprotein gp120 to the cell-surface coreceptors CCR5 or CXCR4 during viral entry suggests that there are conserved structural elements in this sequence-variable region. These conserved elements could serve as epitopes to be targeted by a vaccine against HIV-1. Here we perform a systematic structural analysis of representative human anti-V3 monoclonal antibodies in complex with V3 peptides, revealing that the crown of V3 has four conserved structural elements: an arch, a band, a hydrophobic core and the peptide backbone. These are either unaffected by or are subject to minimal sequence variation. As these regions are targeted by cross-clade neutralizing human antibodies, they provide a blueprint for the design of vaccine immunogens that could elicit broadly cross-reactive protective antibodies.

Jiang, X.; Burke, V; Totrov, M; Williams, C; Cardozo, T; Gorny, M; Zolla-Pazner, S; Kong, X

2010-01-01

52

Acceleration of high resolution temperature based optimization for hyperthermia treatment planning using element grouping.  

PubMed

In regional hyperthermia, optimization is useful to obtain adequate applicator settings. A speed-up of the previously published method for high resolution temperature based optimization is proposed. Element grouping as described in literature uses selected voxel sets instead of single voxels to reduce computation time. Elements which achieve their maximum heating potential for approximately the same phase/amplitude setting are grouped. To form groups, eigenvalues and eigenvectors of precomputed temperature matrices are used. At high resolution temperature matrices are unknown and temperatures are estimated using low resolution (1 cm) computations and the high resolution (2 mm) temperature distribution computed for low resolution optimized settings using zooming. This technique can be applied to estimate an upper bound for high resolution eigenvalues. The heating potential of elements was estimated using these upper bounds. Correlations between elements were estimated with low resolution eigenvalues and eigenvectors, since high resolution eigenvectors remain unknown. Four different grouping criteria were applied. Constraints were set to the average group temperatures. Element grouping was applied for five patients and optimal settings for the AMC-8 system were determined. Without element grouping the average computation times for five and ten runs were 7.1 and 14.4 h, respectively. Strict grouping criteria were necessary to prevent an unacceptable exceeding of the normal tissue constraints (up to approximately 2 degrees C), caused by constraining average instead of maximum temperatures. When strict criteria were applied, speed-up factors of 1.8-2.1 and 2.6-3.5 were achieved for five and ten runs, respectively, depending on the grouping criteria. When many runs are performed, the speed-up factor will converge to 4.3-8.5, which is the average reduction factor of the constraints and depends on the grouping criteria. Tumor temperatures were comparable. Maximum exceeding of the constraint in a hot spot was 0.24-0.34 degree C; average maximum exceeding over all five patients was 0.09-0.21 degree C, which is acceptable. High resolution temperature based optimization using element grouping can achieve a speed-up factor of 4-8, without large deviations from the conventional method. PMID:19746813

Kok, H P; de Greef, M; Bel, A; Crezee, J

2009-08-01

53

sp3-hybridized framework structure of group-14 elements discovered by genetic algorithm  

NASA Astrophysics Data System (ADS)

Group-14 elements, including C, Si, Ge, and Sn, can form various stable and metastable structures. Finding new metastable structures of group-14 elements with desirable physical properties for new technological applications has attracted a lot of interest. Using a genetic algorithm, we discovered a new low-energy metastable distorted sp3-hybridized framework structure of the group-14 elements. It has P42/mnm symmetry with 12 atoms per unit cell. The void volume of this structure is as large as 139.7Å3 for Si P42/mnm, and it can be used for gas or metal-atom encapsulation. Band-structure calculations show that P42/mnm structures of Si and Ge are semiconducting with energy band gaps close to the optimal values for optoelectronic or photovoltaic applications. With metal-atom encapsulation, the P42/mnm structure would also be a candidate for rattling-mediated superconducting or used as thermoelectric materials.

Nguyen, Manh Cuong; Zhao, Xin; Wang, Cai-Zhuang; Ho, Kai-Ming

2014-05-01

54

Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements: 2009  

USGS Publications Warehouse

Every three years the IAU Working Group on Cartographic Coordinates and Rotational Elements revises tables giving the directions of the poles of rotation and the prime meridians of the planets, satellites, minor planets, and comets. This report takes into account the IAU Working Group for Planetary System Nomenclature (WGPSN) and the IAU Committee on Small Body Nomenclature (CSBN) definition of dwarf planets, introduces improved values for the pole and rotation rate of Mercury, returns the rotation rate of Jupiter to a previous value, introduces improved values for the rotation of five satellites of Saturn, and adds the equatorial radius of the Sun for comparison. It also adds or updates size and shape information for the Earth, Mars' satellites Deimos and Phobos, the four Galilean satellites of Jupiter, and 22 satellites of Saturn. Pole, rotation, and size information has been added for the asteroids (21) Lutetia, (511) Davida, and (2867) ??teins. Pole and rotation information has been added for (2) Pallas and (21) Lutetia. Pole and rotation and mean radius information has been added for (1) Ceres. Pole information has been updated for (4) Vesta. The high precision realization for the pole and rotation rate of the Moon is updated. Alternative orientation models for Mars, Jupiter, and Saturn are noted. The Working Group also reaffirms that once an observable feature at a defined longitude is chosen, a longitude definition origin should not change except under unusual circumstances. It is also noted that alternative coordinate systems may exist for various (e. g. dynamical) purposes, but specific cartographic coordinate system information continues to be recommended for each body. The Working Group elaborates on its purpose, and also announces its plans to occasionally provide limited updates to its recommendations via its website, in order to address community needs for some updates more often than every 3 years. Brief recommendations are also made to the general planetary community regarding the need for controlled products, and improved or consensus rotation models for Mars, Jupiter, and Saturn. ?? 2010 Springer Science+Business Media B.V.(outside the USA).

Archinal, B. A.; A'Hearn, M. F.; Bowell, E.; Conrad, A.; Consolmagno, G. J.; Courtin, R.; Fukushima, T.; Hestroffer, D.; Hilton, J. L.; Krasinsky, G. A.; Neumann, G.; Oberst, J.; Seidelmann, P. K.; Stooke, P.; Tholen, D. J.; Thomas, P. C.; Williams, I. P.

2011-01-01

55

Spin-orbit effects in structural and electronic properties for the solid state of the group-14 elements from carbon to superheavy element 114  

NASA Astrophysics Data System (ADS)

Spin-orbit effects approximately scale like Z2 and therefore become very important in the bonding of the heavier p -group elements in the periodic table. Here we show by first-principles density-functional calculations that such effects substantially lower the cohesive energy for solid lead and Uuq (ununquadium, eka-lead, nuclear charge 114), by 2.5 eV/atom for the latter and causing a structural change from face-centered cubic at the scalar relativistic to hexagonal close packed at the spin-orbit coupled level of theory. This implies that unlike lead (cohesive energy Ecoh=2.02eV/atom ), Uuq is weakly bound (Ecoh=0.5eV/atom) , and even less so than solid mercury (Ecoh=0.7eV/atom) , underpinning the original hypothesis by Pitzer in 1975 [K. Pitzer, J. Chem. Phys. 63, 1033 (1975)10.1063/1.431398] that spin-orbit effects lead to chemical inertness of Uuq.

Hermann, Andreas; Furthmüller, Jürgen; Gäggeler, Heinz W.; Schwerdtfeger, Peter

2010-10-01

56

Element-free Galerkin method for a kind of KdV equation  

Microsoft Academic Search

The present paper deals with the numerical solution of the third-order nonlinear KdV equation using the element-free Galerkin (EFG) method which is based on the moving least-squares approximation. A variational method is used to obtain discrete equations, and the essential boundary conditions are enforced by the penalty method. Compared with numerical methods based on mesh, the EFG method for KdV

Ju-Feng Wang; Feng-Xin Sun; Rong-Jun Cheng

2010-01-01

57

Platinum-group elements in the Icelandic rift system: melting processes and mantle sources beneath Iceland  

Microsoft Academic Search

Thirty new platinum-group element (PGE) analyses of various basalt types from Iceland are presented in this study. The analysed samples are divided into three groups based on their Mg-contents, high-Mg tholeiites (10–14 wt.% MgO), composed of primitive olivine tholeiites and picrites, evolved olivine tholeiites (7–10 wt.% MgO) and evolved basalts (4–7 wt.% MgO) consisting of FeTi basalts, quartz tholeiites and

Peter Momme; N??els Óskarsson; Reid R. Keays

2003-01-01

58

Functional groups and elemental analyses of cuticular morphotypes of Cordaites principalis (Germar) Geinitz, Carboniferous Maritimes Basin, Canada  

USGS Publications Warehouse

Well-preserved cuticles were isolated from Cordaites principalis (Germar) Geinitz leaf compressions, i.e., foliage from extinct gymnosperm trees Coniferophyta: Order Cordaitales. The specimens were collected from the Sydney. Stellarton and Bay St. George subbasins of the once extensive Carboniferous Maritimes Basin of Atlantic Canada. Fourier transformation of infrared spectra (FTIR) and elemental analyses indicate that the ca. 300-306-million-year-old fossil cuticles share many of the functional groups observed in modern cuticles. The similarities of the functional groups in each of the three cuticular morphotypes studied support the inclusion into a single cordaite-leaf taxon, i.e., C. principalis (Germar), confirming previous morphological investigations. Vitrinite reflectance measurements on coal seams in close proximity to the fossil-bearing sediments reveal that the Bay St. George sample site has the lowest thermal maturity, whereas the sites in Sydney and Stellarton are more mature. IR absorption and elemental analyses of the cordaite compressions corroborate this trend, which suggests that the coalified mesophyll in the leaves follows a maturation path similar to that of vitrinite. Comparison of functional groups of the cordaite cuticles with those from certain pteridosperms previously studied from the Sydney Subbasin shows that in the cordaite cuticles highly conjugated C-O (1632 cm-1) bands dominate over carbonyl stretch that characterizes the pteridosperm cuticles. The differences demonstrate the potential of chemotaxonomy as a valuable tool to assist distinguishing between Carboniferous plant-fossil groups. Published by Elsevier Science B.V.

Zodrow, E. L.; Mastalerz, M.; Orem, W. H.; Simunek, Z.; Bashforth, A. R.

2000-01-01

59

Methods for the Determination of Platinum Group Elements in Environmental and Biological Materials: A Review  

Microsoft Academic Search

Automobile catalysts are major anthropogenic sources of ultra-traces of platinum group elements (PGEs) in the environment. Nanoparticles of platinum, palladium, and rhodium, the active components of autocatalysts, are being spread into the environment during vehicle operation. Bioaccumulation of the metals can lead to their elevated levels in living organisms. The evaluation of the health risk from PGEs requires the investigation

Maria Balcerzak

2011-01-01

60

Platinum group elements in raptor eggs, faeces, blood, liver and kidney  

Microsoft Academic Search

The increased use of platinum group elements (PGEs) in automobile catalysts and their emission into the environment has led to a concern over environmental and particularly biological accumulation. Specimens of samples from raptors are useful for the investigation of the impact of PGEs because these birds are found in both urban and rural environments and are invariably at the top

Kristine H. Ek; Sebastien Rauch; Gregory M. Morrison; Peter Lindberg

2004-01-01

61

Isomer Shift and Electronegativity in Compounds of Tin and Group-Vi Elements.  

National Technical Information Service (NTIS)

Using the Mossbauer effect in Sn119, measurement was made of the isomer shift in compounds of divalent and tetravalent tin with elements of the VI group. The isomer shift is linearly dependent on the values of electronegativity, in both series of compound...

E. M. Baggio T. Sonnino

1969-01-01

62

IMPORTANCE OF ACTIVATED CARBON'S OXYGEN SURFACE FUNCTIONAL GROUPS ON ELEMENTAL MERCURY ADSORPTION  

EPA Science Inventory

The effect of varying physical and chemical properties of activated carbons on adsorption of elemental mercury [Hg(0)] was studied by treating two activated carbons to modify their surface functional groups and pore structures. Heat treatment (1200 K) in nitrogen (N2), air oxidat...

63

Environmental routes for platinum group elements to biological materials—a review  

Microsoft Academic Search

The increased use of platinum group elements (PGE) in automobile catalysts has led to concern over potential environmental and biological accumulation. Platinum (Pt), palladium (Pd) and rhodium (Rh) concentrations have increased in the environment since the introduction of automobile catalysts. This review summarises current knowledge concerning the environmental mobility, speciation and bioavailability of Pt, Pd and Rh. The greater proportion

Kristine H. Ek; Gregory M. Morrison; Sebastien Rauch

2004-01-01

64

Gene transfer directly demonstrates a role for TCR V alpha elements in superantigen recognition.  

PubMed

Recent structure-function studies of ours and others indicating that regions of the TCR other than V beta are involved in the TCR-superantigen (SAg)-MHC class II trimolecular interaction were correlative; thus, while the conclusions were persuasive, they were not unequivocal. The transfection experiments described in this report show that 1) responsiveness to staphylococcal enterotoxin B in V beta6 T cells was transferred by a V alpha4- but not by V alpha8- and V alpha10-containing alpha-chain cDNA constructs, 2) responsiveness was not transferred by a chimeric alpha-chain construct containing the N and J regions from a responsive T hybrid clone and the V alpha10 V alpha region from a nonresponsive clone, and 3) responsiveness was transferred by a chimeric alpha-chain construct in which most of the V alpha region (from the N terminus to the C-terminal end of the complementarity-determining region 2) was derived from the V alpha4 alpha-chain of a responsive T hybrid and the rest (framework 3, N, and J) from the V alpha8 alpha-chain of a nonresponsive T hybrid. Thus, these data provide the first direct evidence for a specific SAg response facilitating activity in a defined V alpha segment and map this activity N-terminal of framework region 3. Furthermore, the diversity in the alpha- and beta-chain junctional regions of a panel of staphylococcal enterotoxin B-responsive V beta6 T hybrid clones excludes a stringent corequirement for a particular junctional region for the V alpha4 segment to mediate its facilitating activity. Finally, a model postulating a universal role for V alpha elements in TCR recognition of SAg is presented. PMID:9164940

Donson, D; Borrero, H; Rutman, M; Pergolizzi, R; Malhado, N; Macphail, S

1997-06-01

65

Element-free Galerkin method for a kind of KdV equation  

NASA Astrophysics Data System (ADS)

The present paper deals with the numerical solution of the third-order nonlinear KdV equation using the element-free Galerkin (EFG) method which is based on the moving least-squares approximation. A variational method is used to obtain discrete equations, and the essential boundary conditions are enforced by the penalty method. Compared with numerical methods based on mesh, the EFG method for KdV equations needs only scattered nodes instead of meshing the domain of the problem. It does not require any element connectivity and does not suffer much degradation in accuracy when nodal arrangements are very irregular. The effectiveness of the EFG method for the KdV equation is investigated by two numerical examples in this paper.

Wang, Ju-Feng; Sun, Feng-Xin; Cheng, Rong-Jun

2010-06-01

66

Enzymatic properties of rat group IIA and V phospholipases A 2 compared  

Microsoft Academic Search

Group IIA and V phospholipases A2 (PLA2s) are known to play a role in inflammatory responses. We have constructed a bacterial expression vector for rat group IIA and V PLA2s, over-expressed, folded and purified the proteins with the aim to study and compare the properties of the enzymes in detail. For zwitterionic phospholipid micelles, both enzymes display optimum activity at

Marcel J. W. Janssen; Leendert Vermeulen; Hester A. Van der Helm; Anton J. Aarsman; Arend J. Slotboom; Maarten R. Egmond

1999-01-01

67

Development of metallographic preparation techniques for group IVA and VA elements  

Microsoft Academic Search

Existing metallographic preparation techniques for Group IVA\\/VA (e.g. V, Ti, Ta, Hf, Nb, Zr) materials do not reveal all microstructural features inherent to the process history. As a result, new techniques have been developed and compared to existing procedures. For example, in pure tantalum, the new procedure exposes a substructure that is not evident using previously published techniques. In niobium,

S. A. Bingert; T. G. Abeln; D. J. Thoma; J. C. Cooley; W. L. Hults; A. M. Kelly

2001-01-01

68

Quality evaluation of value sets from cancer study common data elements using the UMLS semantic groups  

PubMed Central

Objective The objective of this study is to develop an approach to evaluate the quality of terminological annotations on the value set (ie, enumerated value domain) components of the common data elements (CDEs) in the context of clinical research using both unified medical language system (UMLS) semantic types and groups. Materials and methods The CDEs of the National Cancer Institute (NCI) Cancer Data Standards Repository, the NCI Thesaurus (NCIt) concepts and the UMLS semantic network were integrated using a semantic web-based framework for a SPARQL-enabled evaluation. First, the set of CDE-permissible values with corresponding meanings in external controlled terminologies were isolated. The corresponding value meanings were then evaluated against their NCI- or UMLS-generated semantic network mapping to determine whether all of the meanings fell within the same semantic group. Results Of the enumerated CDEs in the Cancer Data Standards Repository, 3093 (26.2%) had elements drawn from more than one UMLS semantic group. A random sample (n=100) of this set of elements indicated that 17% of them were likely to have been misclassified. Discussion The use of existing semantic web tools can support a high-throughput mechanism for evaluating the quality of large CDE collections. This study demonstrates that the involvement of multiple semantic groups in an enumerated value domain of a CDE is an effective anchor to trigger an auditing point for quality evaluation activities. Conclusion This approach produces a useful quality assurance mechanism for a clinical study CDE repository.

Solbrig, Harold R; Chute, Christopher G

2012-01-01

69

Adhesion and friction behavior of group 4 elements germanium, silicon, tin, and lead  

NASA Technical Reports Server (NTRS)

Adhesion and friction studies were conducted with thin films of the group IV elements silicon, germanium, tin, and lead ion plated on the nickel (011) substrate. The mating surface was gold (111). Contacts were made for the elements in the clean state and with oxygen present. Adhesion and friction experiments were conducted at very light loads of 1 to 10 g. Sliding was at a speed of 0.7 mm/min. Friction results indicate that the more covalently bonded elements silicon and germanium exhibit lower adhesion and friction than the more metallic bonded tin and lead. The adhesion of gold to germanium was observed, and recrystallization of the transferred gold occurred. Plastic flow of germanium was seen with sliding. Oxygen reduced, but did not eliminate, the adhesion observed with germanium and silicon.

Buckley, D. H.

1975-01-01

70

77 FR 43071 - MPS Customer Group v. Maine Public Service Company; Notice of Complaint  

Federal Register 2010, 2011, 2012, 2013

...Commission [Docket No. EL12-84-000] MPS Customer Group v. Maine Public Service...Commission (Commission); 18 CFR 385.206, MPS Customer Group (Complainant) filed a formal...complaint against Maine Public Service Company (MPS or Respondent) seeking an order to...

2012-07-23

71

Proposal for vacuum-ultraviolet anti-Stokes Raman lasers based on the group VI elements  

Microsoft Academic Search

Metastable inversions in the 1S0 state of the group VI elements (oxygen, sulfur, and selenium) are proposed as host media for a new class of anti-Stokes Raman laser. Selective photodissociation of N2O, OCS, or OCSe with appropriate VUV wavelengths can create 1S0 inversion densities in excess of 10 to the 16th atoms\\/cu cm. Using this population inversion to upconvert tunable

J. C. White

1984-01-01

72

Minority carrier device comprising a passivating layer including a Group 13 element and a chalcogenide component  

NASA Technical Reports Server (NTRS)

A minority carrier device includes at least one junction of at least two dissimilar materials, at least one of which is a semiconductor, and a passivating layer on at least one surface of the device. The passivating layer includes a Group 13 element and a chalcogenide component. Embodiments of the minority carrier device include, for example, laser diodes, light emitting diodes, heterojunction bipolar transistors, and solar cells.

Barron, Andrew R. (Inventor); Hepp, Aloysius F. (Inventor); Jenkins, Phillip P. (Inventor); MacInnes, Andrew N. (Inventor)

1999-01-01

73

Distribution of platinum group elements and rhenium between metallic phases of iron meteorites  

Microsoft Academic Search

In situ measurement of the platinum group elements (PGE) and Re by laser ablation-ICPMS allows fractionation patterns to be established between host (kamacite) and Ni-rich exsolved phases (taenite and plessite). Measurements on two IAB iron meteorites (Canyon Diablo and Odessa) show that, for the Ni-rich phases: (a) there is no significant fractionation for Ru and Rh; (b) Pd is enriched;

Takafumi Hirata; Robert W. Nesbitt

1997-01-01

74

A Study of Venus Surface Elemental Composition From 14MeV Neutron Induced Gamma Ray Spectroscopy: Activation Analysis  

Microsoft Academic Search

The surface elemental composition of Venus can be determined by using an artificially pulsed 14 MeV neutron generator (PNG) combined with a gamma ray spectrometer (GRS). The 14 MeV neutrons will interact with the surface materials and generate gamma rays, characteristic of specific elements, whose energy spectrum will be measured by GRS. These characteristic gamma rays are produced mainly through

I. Jun; W. Kim; M. Smith; I. Mitrofanov; M. L. Litvak

2010-01-01

75

Critical magnetic field of V/sub 3/Ga thin films with third element additions  

SciTech Connect

We have made thin films of V-Ga superconductors by electron beam codeposition with approximately one percent additions of Nb, Ta, Sn, Pt or Pb. We have measured the high-magnetic field properties of these films to observe the effect of these impurities on spin-orbit scattering. Although the residual resistivity of the films was affected by the additional elements, the rate of spin-orbit scattering did not appear to increase.

Tedrow, P.M.; Bending, S.J.; Hammond, R.; Meservey, R.; Tkaczyk, J.E.

1985-03-01

76

Finite element simulation of conventional and high speed machining of Ti6Al4V alloy  

Microsoft Academic Search

Titanium alloys are known as difficult-to-machine materials, especially at higher cutting speeds, due to their several inherent properties and their high reactivity with cutting tools, which present a low thermal conductivity. In this paper a finite element analysis (FEA) of machining of TiAl6V4 both for conventional and high speed cutting regimes is presented. In particular, cutting force, chip morphology and

Domenico Umbrello

2008-01-01

77

20 CFR 655.1115 - Element V-What does âno strike/lockout or layoffâ mean?  

Code of Federal Regulations, 2013 CFR

...2013-04-01 2013-04-01 false Element V-What does âno strike/lockout or layoffâ...as Registered Nurses? § 655.1115 Element VâWhat does âno strike/lockout or layoffâ mean? (a) The fifth attestation element requires that the facility...

2013-04-01

78

Partitioning of Si and platinum group elements between liquid and solid Fe–Si alloys  

NASA Astrophysics Data System (ADS)

Crystallization of the Earth's inner core fractionates major and minor elements between the solid and liquid metal, leaving physical and geochemical imprints on the Earth's core. For example, the density jump observed at the Inner Core Boundary (ICB) is related to the preferential partitioning of lighter elements in the liquid outer core. The fractionation of Os, Re and Pt between liquid and solid during inner core crystallization has been invoked as a process that explains the observed Os isotopic signature of mantle plume-derived lavas (Brandon et al., 1998; Brandon and Walker, 2005) in terms of core–mantle interaction. In this article we measured partitioning of Si, Os, Re and Pt between liquid and solid metal. Isobaric (2 GPa) experiments were conducted in a piston-cylinder press at temperatures between 1250 °C and 1600 °C in which an imposed thermal gradient through the sample provided solid–liquid coexistence in the Fe–Si system. We determined the narrow melting loop in the Fe–Si system using Si partitioning values and showed that order–disorder transition in the Fe–Si solid phases can have a large effect on Si partitioning. We also found constant partition coefficients (DOs, DPt, DRe) between liquid and solid metal, for Si concentrations ranging from 2 to 12 wt%. The compact structure of Fe–Si liquid alloys is compatible with incorporation of Si and platinum group elements (PGEs) elements precluding solid–liquid fractionation. Such phase diagram properties are relevant for other light elements such as S and C at high pressure and is not consistent with inter-elemental fractionation of PGEs during metal crystallization at Earth's inner core conditions. We therefore propose that the peculiar Os isotopic signature observed in plume-derived lavas is more likely explained by mantle source heterogeneity (Meibom et al., 2002; Baker and Krogh Jensen, 2004; Luguet et al., 2008).

Morard, G.; Siebert, J.; Badro, J.

2014-05-01

79

Composition, apparatus, and process, for sorption of gaseous compounds of group II-VII elements  

DOEpatents

Scavenger compositions are disclosed, which have utility for effecting the sorptive removal of hazardous gases containing Group II-VII elements of the Periodic Table, such as are widely encountered in the manufacture of semiconducting materials and semiconductor devices. Gas sorption processes including the contacting of Group II-VII gaseous compounds with such scavenger compositions are likewise disclosed, together with critical space velocity contacting conditions pertaining thereto. Further described are gas contacting apparatus, including mesh structures which may be deployed in gas contacting vessels containing such scavenger compositions, to prevent solids from being introduced to or discharged from the contacting vessel in the gas stream undergoing treatment. A reticulate heat transfer structure also is disclosed, for dampening localized exothermic reaction fronts when gas mixtures comprising Group II-VII constituents are contacted with the scavenger compositions in bulk sorption contacting vessels according to the invention.

Tom, Glenn M. (New Milford, CT); McManus, James V. (Danbury, CT); Luxon, Bruce A. (Stamford, CT)

1991-08-06

80

Identification of human DNA helicase V with the far upstream element-binding protein.  

PubMed

The properties of human DNA helicase V (HDH V) were studied in greater detail following an improved purification procedure. From 450 g of cultured cells, <0.1 mg of pure protein was isolated. HDH V unwinds DNA unidirectionally by moving in the 3' to 5' direction along the bound strand in an ATP- and Mg(2+)-dependent fashion. The enzyme is not processive and can also unwind partial RNA-RNA duplexes such as HDH IV and HDH VIII. The M:(r) determined by SDS-PAGE (66 kDa) corresponds to that measured under native conditions, suggesting that HDH V exists as a monomer in the nucleus. Microsequencing of the purified HDH V shows that this enzyme is identical to the far upstream element-binding protein (FBP), a protein that stimulates the activity of the c-myc gene by binding specifically to the 'FUSE' DNA region localized upstream of its promoter. The sequence of HDH V/FBP contains RGG motifs like HDH IV/nucleolin, HDH VIII/G3BP as well as other human RNA and DNA helicases identified by other laboratories. PMID:11222755

Vindigni, A; Ochem, A; Triolo, G; Falaschi, A

2001-03-01

81

Trithorax- and Polycomb-Group Response Elements within an Ultrabithorax Transcription Maintenance Unit Consist of Closely Situated but Separable Sequences  

Microsoft Academic Search

In Drosophila, two classes of genes, the trithorax group and the Polycomb group, are required in concert to maintain gene expression by regulating chromatin structure. We have identified Trithorax protein (TRX) binding elements within the bithorax complex and have found that within the bxd\\/pbx regulatory region these elements are functionally relevant for normal expression patterns in embryos and confer TRX

SERGEI TILLIB; SVETLANA PETRUK; YURII SEDKOV; ALEXANDER KUZIN; MIKI FUJIOKA; TADAATSU GOTO; ALEXANDER MAZO

1999-01-01

82

33 CFR 155.1052 - Response plan development and evaluation criteria for vessels carrying group V petroleum oil as a...  

Code of Federal Regulations, 2013 CFR

...criteria for vessels carrying group V petroleum oil as a primary cargo. 155.1052...criteria for vessels carrying group V petroleum oil as a primary cargo. (a) Owners...operators of vessels that carry group V petroleum oil as a primary cargo must provide...

2013-07-01

83

Nanowires for spintronics: A study of transition-metal elements of groups 8 10  

NASA Astrophysics Data System (ADS)

We have investigated systematically the changes in the electronic structure and magnetic moment of transition-metal elements of groups 8 10 (Fe, Ru, Os; Co, Rh, Ir; Ni, Pd, Pt) as their dimensionality is reduced. Many interesting results are predicted. The importance of spin-orbit interaction for 4-d and 5-d elements is exemplified: by predicting correct magnetic ground state for the linear chains (LC’s) of Pt. Interestingly, all these systems, except Ir, are predicted to be magnetic in one dimension (LC’s). We also show that only one type of carriers are available for conduction in LC’s of Fe, Co, Ni, and Pd, suggesting suitability of nanowires of these for spintronics. Our results are in very good agreement with available experimental data.

Nautiyal, Tashi; Rho, T. H.; Kim, Kwang S.

2004-05-01

84

Recent searches for superheavy elements in deep-inelastic reactions. [Approximately 7 MeV/. mu.  

SciTech Connect

New attempts have been made to synthesize superheavy elements (SHE) by nuclear reactions that may possibly form the products at low excitation energies. Survival of the superheavy elements would then be enhanced because of reduced losses from prompt fission. Classical and diffusion-model calculations of deep-inelastic reactions indicate there should be detectable yields of SHE formed with less than 30 MeV of excitation energy. Accordingly, superheavy elements have been sought in such reactions where targets of /sup 248/Cm and /sup 238/U have been irradiated with /sup 136/Xe and /sup 238/U ions. In the most recent experiments, targets of /sup 248/Cm metal (3.5 to 7 mg-cm/sup -2/) were bombarded with 1.8-GeV /sup 238/U ions from the UNILAC accelerator. The longer-lived SHE and actinides near the target Z were chemically separated, and the yields of a number of isotopes of Bk, Cf, Es, and Fm were measured. An upper limit of 30 nb was obtained for the formation of 1-h /sup 259/No. In addition to the off-line chemical recovery and search for SHE, an on-line experiment was performed to detect volatile SHE with half-lives of a minute or more. All experiments to produce and detect superheavy elements were much less than optimum because of premature failures in the Cm-metal targets. The outcome and status of these experiments and the implications of the actinide yields in estimating the chances for forming superheavy elements in the /sup 248/Cm + /sup 238/U reactions are discussed. 5 figures, 1 table.

Hulet, E.K.; Lougheed, R.W.; Nitschke, J.M.

1980-10-01

85

Depletion of adenosine triphosphate in Desulfovibrio by oxyanions of group VI elements  

Microsoft Academic Search

Oxyanions of elements from group VI of the periodic table, i.e., analogs of SO4\\u000a 2?, destroyed adenosine 5?-triphosphate (ATP) in cells of sulfate-respiring bacteria (Desulfovibrio spp.), probably via the ATP sulfurylase reaction. The approximate order of effectiveness was CrO4\\u000a 2?> MoO4\\u000a 2?=WO4\\u000a 2?>SeO4\\u000a 2?. Cultures of aerobically grown or nitrate-respiring bacteria were less susceptible and with fermentatively grownEscherichia coli the

Barrie F. Taylort; Ronald S. Oremland

1979-01-01

86

pH-dependent release of trace elements including platinum group elements (PGEs) from gasoline and diesel catalysts  

NASA Astrophysics Data System (ADS)

The release of trace metals and platinum group elements (PGEs) from automobile exhaust catalysts represents a remarkable source of higly dispersed environmental contamination. Especially, PGEs have shown increasing research interest due to their possible bioaccessibility. In our research, we focused on leaching behaviour of trace metals from gasoline and diesel automobile catalysts. While catalysts for gasoline engines contain a mixture of Pt-Pd-Rh or Pd-Rh, catalysts for diesel engines are composed only of Pt. We used dust from two crushed gasoline and two crushed diesel catalysts (new and aged). The dust of gasoline catalysts contains significant concentrations of Pt (700 mg.kg-1), Pd (11 000 mg.kg-1) and Rh (700 mg.kg-1). And the dust of diesel catalysts are composed of Pt (3 900 mg.kg-1) and they contains negligible amounts of Pd dan Rh (< 0.5 mg.kg-1, < 0.1 mg.kg-1, respectively). To evaluate leaching of trace metals from dust we used pH-stat leaching test according to the European standard CEN/TS 14997. The concentrations of cations: PGEs (Pt, Pd a Rh), K, Na, Ca, Mg, Al, Ti, Cr, Mn, Fe, Co, Ni, Cu, Zn, Cd, Pb, La and Ce were determined by inductively coupled plasma mass spectrometry (ICP-MS) and atomic absorption spectrometry (AAS), and anions: F-, Cl-, SO42- and NO3- by high-performance liquid chromatography. Although the dusts from catalysts were relatively stable to acid/base influence, the leaching of trace metals from catalysts showed a dependence on pH. Generally, the highest concentrations were released under acidic conditions. The leaching of PGEs was higher for Pt in diesel catalysts and for Pd and Rh in gasoline catalysts. The highest concentrations of Zn and Pb were observed in old catalysts. The rare earth metals were released more from gasoline catalysts. Catalysts particles represent health risk especially with respect to their PGEs contents.

Sucha, Veronika; Mihaljevic, Martin; Ettler, Vojtech; Strnad, Ladislav

2014-05-01

87

Hybridization Trends for Main Group Elements and Expanding the Bent's Rule Beyond Carbon: More than Electronegativity.  

PubMed

Trends in hybridization were systematically analyzed through the combination of DFT calculations with NBO analysis for the five elements X (X = B, C, N, O, and F) in 75 HnX-YHm compounds, where Y spans the groups 13-17 of the periods 2-4. This set of substrates probes the flexibility of the hybridization at five atoms X through variations in electronegativity, polarizability, and orbital size of Y. The results illustrate the scope and limitations of the Bent's rule, the classic correlation between electronegativity and hybridization, commonly used in analyzing structural effects in carbon compounds. The rehybridization effects are larger for fluorine- and oxygen-bonds than they are in the similar bonds to carbon. For bonds with the larger elements Y of the lower periods, trends in orbital hybridization depend strongly on both electronegativity and orbital size. For charged species, the effects of substituent orbital size in the more polarizable bonds to heavier elements show a particularly strong response to the charge introduction at the central atom. In the final section, we provide an example of the interplay between hybridization effects with molecular structure and reactivity. In particular, the ability to change hybridization without changes in polarization provides an alternative way to control structure and reactivity, as illustrated by the strong correlation of strain in monosubstituted cyclopropanes with hybridization in the bond to the substituent. PMID:24773162

Alabugin, Igor V; Bresch, Stefan; Manoharan, Mariappan

2014-05-22

88

REDfly v3.0: toward a comprehensive database of transcriptional regulatory elements in Drosophila  

PubMed Central

The REDfly database of Drosophila transcriptional cis-regulatory elements provides the broadest and most comprehensive available resource for experimentally validated cis-regulatory modules and transcription factor binding sites among the metazoa. The third major release of the database extends the utility of REDfly as a powerful tool for both computational and experimental studies of transcription regulation. REDfly v3.0 includes the introduction of new data classes to expand the types of regulatory elements annotated in the database along with a roughly 40% increase in the number of records. A completely redesigned interface improves access for casual and power users alike; among other features it now automatically provides graphical views of the genome, displays images of reporter gene expression and implements improved capabilities for database searching and results filtering. REDfly is freely accessible at http://redfly.ccr.buffalo.edu.

Gallo, Steven M.; Gerrard, Dave T.; Miner, David; Simich, Michael; Des Soye, Benjamin; Bergman, Casey M.; Halfon, Marc S.

2011-01-01

89

Implementation of Hybrid V-Cycle Multilevel Methods for Mixed Finite Element Systems with Penalty  

NASA Technical Reports Server (NTRS)

The goal of this paper is the implementation of hybrid V-cycle hierarchical multilevel methods for the indefinite discrete systems which arise when a mixed finite element approximation is used to solve elliptic boundary value problems. By introducing a penalty parameter, the perturbed indefinite system can be reduced to a symmetric positive definite system containing the small penalty parameter for the velocity unknown alone. We stabilize the hierarchical spatial decomposition approach proposed by Cai, Goldstein, and Pasciak for the reduced system. We demonstrate that the relative condition number of the preconditioner is bounded uniformly with respect to the penalty parameter, the number of levels and possible jumps of the coefficients as long as they occur only across the edges of the coarsest elements.

Lai, Chen-Yao G.

1996-01-01

90

Should an obsessive-compulsive spectrum grouping of disorders be included in DSM-V?  

PubMed

The obsessive-compulsive (OC) spectrum has been discussed in the literature for two decades. Proponents of this concept propose that certain disorders characterized by repetitive thoughts and/or behaviors are related to obsessive-compulsive disorder (OCD), and suggest that such disorders be grouped together in the same category (i.e. grouping, or "chapter") in DSM. This article addresses this topic and presents options and preliminary recommendations to be considered for DSM-V. The article builds upon and extends prior reviews of this topic that were prepared for and discussed at a DSM-V Research Planning Conference on Obsessive-Compulsive Spectrum Disorders held in 2006. Our preliminary recommendation is that an OC-spectrum grouping of disorders be included in DSM-V. Furthermore, we preliminarily recommend that consideration be given to including this group of disorders within a larger supraordinate category of "Anxiety and Obsessive-Compulsive Spectrum Disorders." These preliminary recommendations must be evaluated in light of recommendations for, and constraints upon, the overall structure of DSM-V. PMID:20533367

Phillips, Katharine A; Stein, Dan J; Rauch, Scott L; Hollander, Eric; Fallon, Brian A; Barsky, Arthur; Fineberg, Naomi; Mataix-Cols, David; Ferrão, Ygor Arzeno; Saxena, Sanjaya; Wilhelm, Sabine; Kelly, Megan M; Clark, Lee Anna; Pinto, Anthony; Bienvenu, O Joseph; Farrow, Joanne; Leckman, James

2010-06-01

91

Heterobimetallic catechol-phosphine complexes with palladium and a group-13 element: structural flexibility and dynamics.  

PubMed

Group-13 metal acetylacetonates [M(acac)3] (M = Al, Ga, In) or Al(OiPr)3 react with a complex [Pd(catphosH)2] that may act as chelating ligand towards a second metal, or with a mixture of catechol phosphine (catphosH2) and [PdCl2(cod)], to give heterometallic complexes featuring either dinuclear M(catphos)2Pd or trinuclear M{(catphos)2Pd}2 motifs. Characterisation of the products by crystallographic and solution NMR studies gives insight into the structural diversity and flexibility of the coordination environments of the group-13 elements and their impact on the stability of the multinuclear complexes. The results indicate that gallium and indium are the most suitable elements for the stabilisation of di- and trinuclear assemblies, respectively. Dynamic NMR spectroscopy allowed to follow the dynamic averaging of the coordination environments of the four distinguishable catechol phosphines in the indium complex [M{(catphos)2Pd}2]H. The results revealed that the isomerisation follows a complicated pathway involving several distinguishable proton transfer steps, and allowed to propose a mechanistic explanation for the observed isomerisation. PMID:24802543

Bauer, G; Nieger, M; Gudat, D

2014-06-21

92

Solid solution softening and hardening in the group-V and group-VI bcc transition metals alloys: First principles calculations and atomistic modeling  

SciTech Connect

The interaction of d transition metal additions with dislocations was studied in bcc alloys by using the atomic row model with ab initio parametrization of the interatomic interactions. Opposite trends were obtained for the solute-dislocation interactions in the group-V (Nb, Ta) and group-VI (Mo, W) bcc metals: while additions with extra valence electrons enhance the double-kink nucleation and result in solid solution softening in the group-VI metals, they cannot cause the intrinsic softening in the group-V metals. Oppositely, additions with fewer valence electrons should lead to an intrinsic softening in the group-V metals and a strong hardening in the group-VI metals. The effect of electronic concentration on the solute-dislocation interaction is less pronounced in the group-V alloys, and other mechanisms may be dominant in their softening and hardening behavior.

Medvedeva, N. I. [Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208-3112 (United States); Institute of Solid State Chemistry, Yekaterinburg (Russian Federation); Gornostyrev, Yu. N. [Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208-3112 (United States); Institute of Metal Physics, Yekaterinburg (Russian Federation); Freeman, A. J. [Department of Physics and Astronomy, Northwestern University, Evanston, Illinois 60208-3112 (United States)

2007-12-01

93

A study of Venus surface elemental composition from 14 MeV neutron induced gamma ray spectroscopy: Activation analysis  

Microsoft Academic Search

The surface elemental composition of Venus can be determined using an artificially pulsed 14MeV neutron generator (PNG) combined with a gamma ray spectrometer (GRS). The 14MeV neutrons will interact with the surface materials and generate gamma rays, characteristic of specific elements, whose energy spectrum will be measured by GRS. These characteristic gamma rays are produced mainly through 3 different neutron

I. Jun; W. Kim; M. Smith; I. Mitrofanov; M. Litvak

2011-01-01

94

Ages, Metallicities, and ?-Element Enhancement for Galaxies in Hickson Compact Groups  

NASA Astrophysics Data System (ADS)

Central velocity dispersions and eight line-strength Lick indices have been determined from 1.3 Å resolution long-slit spectra of 16 elliptical galaxies in Hickson compact groups. These data were used to determine galaxy properties (ages, metallicities, and ?-element enhancements) and allowed a comparison with the parameters determined for a sample of galaxies in lower density environments studied by González. The stellar population parameters were derived by comparison to single stellar population models of Thomas et al. and to a new set of simple stellar population models for the indices Mg2, Fe5270, and Fe5335 based on synthetic spectra. These models, based on an updated version of the fitting functions presented in Barbuy et al., are fully described here. Our main results are (1) the two samples have similar mean values for the metallicities and [?/Fe] ratios and (2) the majority of the galaxies in compact groups seem to be old (median age of 14 Gyr for eight galaxies for which ages could be derived), in agreement with recent work by Proctor et al. These findings support two possible scenarios: compact groups are either young systems whose members have recently assembled and had not enough time to experience any merging yet, or they are old systems that have avoided merging since their time of formation.

Mendes de Oliveira, C.; Coelho, P.; González, J. J.; Barbuy, B.

2005-07-01

95

Micro V-Groove Grinding Technique of Large Germanium Immersion Grating Element for Mid-Infrared Spectrograph  

Microsoft Academic Search

The 8.2m SUBARU large space telescope in Hawaii requires a mid-infrared high dispersion spectrograph with a resolution of 200000 at 10µm which employs a Germanium Immersion Grating (GIG) element. For this, the GIG element with a large number of sharp and smooth micro V-grooves must be fabricated. Previous studies were focused on the fabrication of a prototype GIG element. The

Shaohui Yin; Hitoshi Ohmori; Yoshihiro Uehara; Tomoyuki Shimizu; Weimin Lin

2004-01-01

96

Characterization of the Sukinda and Nausahi ultramafic complexes, Orissa, India by platinum-group element geochemistry  

USGS Publications Warehouse

Samples of 20 chromitite, 14 ultramafic and mafic rock, and 9 laterite and soil samples from the Precambrian Sukinda and Nausahi ultramafic complexes, Orissa, India were analyzed for platinum-group elements (PGE). The maximum concentrations are: palladium, 13 parts per billion (ppb); platinum, 120 ppb; rhodium, 21 ppb; iridium, 210 ppb; and ruthenium, 630 ppb. Comparison of chondrite-normalized ratios of PGE for the chromitite samples of lower Proterozoic to Archean age with similar data from Paleozoic and Mesozoic ophiolite complexes strongly implies that these complexes represent Precambrian analogs of ophiolite complexes. This finding is consistent with the geology and petrology of the Indian complexes and suggests that plate-tectonic and ocean basin developement models probably apply to some parts of Precambrian shield areas. ?? 1985.

Page, N. J.; Banerji, P. K.; Haffty, J.

1985-01-01

97

Platinum-group element geochemistry of zoned ultramafic intrusive suites, Klamath Mountains, California and Oregon.  

USGS Publications Warehouse

Analyses for platinum-group elements of the varied rock suites of three Alaskan-type ultramafic to mafic multi-intrusive bodies are reported. Ir and Ru are less than analytical sensitivities of 100 and 20 ppb; Rh is less than or near 1 ppb. Average Pd assays vary among the rocks within intrusive complexes and between the three complexes (6.3, 13.7, 36.4 ppb); average Pt assays vary little among the same samples (27.9, 60.9, 34.0 ppb). Statistically adjusted Pt/(Pt + Pd) ratios increase in each suite from gabbro through clinopyroxenite to olivine-rich rocks, possibly owing to Pd fractionation.-G.J.N.

Gray, F.; Page, N. J.; Carlson, C. A.; Wilson, S. A.; Carlson, R. R.

1986-01-01

98

Divisions i and III / Working Group: Cartographic Coordinates and Rotational Elements  

NASA Astrophysics Data System (ADS)

As in the past, the primary activity of the IAU Working Group on Cartographic Coordinates and Rotational Elements has been to prepare and publish a triennial (``2009'') report containing current recommendations for models for Solar System bodies (Archinal et al. (2011a)). The authors are B. A. Archinal, M. F. A'Hearn, E. Bowell, A. Conrad, G. J. Consolmagno, R. Courtin, T. Fukushima, D. Hestroffer, J. L. Hilton, G. A. Krasinsky, G. Neumann, J. Oberst, P. K. Seidelmann, P. Stooke, D. J. Tholen, P. C. Thomas, and I. P. Williams. An erratum to the ``2006'' and ``2009'' reports has also been published (Archinal et al. (2011b)). Below we briefly summarize the contents of the 2009 report, a plan to consider requests for new recommendations more often than every three years, three general recommendations by the WG to the planetary community, other WG activities, and plans for our next report.

Archinal, Brent A.; Seidelmann, P. Kenneth; A'Hearn, Michael F.; Conrad, Albert R.; Consolmagno, Guy J.; Courtin, Régis; Fukushima, Toshio; Hestroffer, Daniel; Hilton, James L.; Neumann, Gregory A.; Oberst, Jürgen; Stooke, Philip J.; Tholen, David J.; Thomas, Peter C.; Williams, Iwan P.

2012-04-01

99

CSRL-V ENDF/B-V 227-group neutron cross-section library and its application to thermal-reactor and criticality safety benchmarks  

SciTech Connect

Characteristics and contents of the CSRL-V (Criticality Safety Reference Library based on ENDF/B-V data) 227-neutron-group AMPX master and pointwise cross-section libraries are described. Results obtained in using CSRL-V to calculate performance parameters of selected thermal reactor and criticality safety benchmarks are discussed.

Ford, W.E. III; Diggs, B.R.; Knight, J.R.; Greene, N.M.; Petrie, L.M.; Webster, C.C.; Westfall, R.M.; Wright, R.Q.; Williams, M.L.

1982-01-01

100

Platinum-group element systematics and petrogenetic processing of the continental upper mantle: A review  

NASA Astrophysics Data System (ADS)

The platinum-group element (PGE) systematics of continental mantle peridotites show large variability, reflecting petrogenetic processing of the upper mantle during partial melting and melt/fluid percolation inside the lithosphere. By removing Pd-Cu-Ni rich sulfides, partial melting events that have stabilized the sub-continental mantle lithosphere fractionated PPGEs (Palladium-group PGE; Pt, Pd) relative to IPGEs (Iridium-group PGE; Os, Ir, Ru, Rh). Residual base-metal sulfides (BMS) survive as enclosed IPGE-enriched Monosulfide Solid Solutions (Mss), which otherwise decompose into Ru-Os-Ir-rich refractory platinum-group minerals (PGMs) once the partial melts become S-undersaturated. The small-scale heterogeneous distribution of these microphases may cause extreme nugget effects, as seen in the huge variations in absolute PGE concentrations documented in cratonic peridotites. Magmas fluxing through the lithospheric mantle may change the initial PGE budgets inherited from the melting events, resulting in the great diversity of PGE systematics seen in peridotites from the sub-continental lithosphere. For instance, melt-rock reactions at increasing melt/rock ratios operate as open-system melting processes removing residual BMS/PGMs. Highly percolated peridotites are characterized by extreme PGE depletion, coupled with PGE patterns and Os-isotope compositions that gradually evolve toward that of the percolating melt. Reactions at decreasing melt-rock ratios (usually referred to as «mantle metasomatism») precipitate PPGE-enriched BMS that yield suprachondritic Pd/Ir and occasionally affect Pt/Ir and Rh/Ir ratios as well. Moreover, volatile-rich, small volume melts fractionate Os relative to Ir and S relative to Se, thereby producing rocks with supra-chondritic Os/Ir and S/Se coupled with supra-chondritic Pd/Ir and Pt/Ir. Major magmatic inputs at the lithosphere-asthenosphere boundary may rejuvenate the PGE systematics of the depleted mantle. Integrated studies of «refertilized» peridotites with worldwide provenance provide evidence for mixing between old PGM-rich harzburgitic protoliths and newly-precipitated BMS. Long-lived PGMs carry the Os-isotope compositions of ancient melt-depletion events into seemingly undepleted fertile lherzolites. Another diagnostic feature of major refertilization processes is the increasing modal abundance of Pt-Pd-Te-Bi or Pt-As-S microphases. Due to regional-scale refertilization processes, sizeable (> 100 km) domains of the upper lithospheric mantle are now significantly enriched in Pd, Au, Cu, Se, and other incompatible chalcophile elements that are of considerable importance in PGE-ore forming events.

Lorand, Jean-Pierre; Luguet, Ambre; Alard, Olivier

2013-04-01

101

Adaptive Group Detection Based on the Sort-Descending QR Decomposition for V-BLAST Architectures  

NASA Astrophysics Data System (ADS)

Combining the sphere decoding (SD) algorithm and the sequential detection method, we propose an adaptive group detection (AGD) scheme based on the sort-descending QRD (S-D-QRD) for V-BLAST architectures over an i.i.d. Rayleigh flat fading channel. Simulation results show that the proposed scheme, which encompasses the SD algorithm and the sequential detection method as two extreme cases in a probability sense, can achieve a very flexible tradeoff between the detection performance and computational complexity by adjusting the group parameter.

Jing, Xiaorong; Zhang, Tianqi; Zhou, Zhengzhong

102

Platinum group elements in automobile catalysts: characterization, sources and environmental mobility  

NASA Astrophysics Data System (ADS)

The platinum group elements (PGE) comprise Ru, Rh, Pd, Os, Ir, and Pt. The PGE are extremely siderophile and most of the elements were during the Earth differentiation partitioned into the core. The average natural concentration of PGE in Earth's crust is low and range of 0.X - X0 ?g kg-1. During the magmatic process the PGE are strongly partitioned into sulphides and Ni minerals. The distribution of PGE and increase of their emissions in the environment are mostly related to the use of automobile catalyst (AC) in car engines (in USA since 1975, in Europe since 1986). The ACs consist of a honeycomb support (made from ?-Al2O3 or cordierite with trace element admixtures - mostly lanthanides and Zr) coated with Pt, Pd and Rh in different ratios. While AC for gasoline engines contain a mixture of Pt-Pd-Rh or Pd-Rh, AC for diesel engines are composed only of Pt. New and aged AC of gasoline and diesel engines, AC standard reference materials, tunnel dust from Prague and tunnel dust reference materials were studied using scanning electron microscopy, electron microanalyses, X-ray diffraction and chemical analyses using inductively coupled plasma mass spectrometry. The studied ACs differ in phase and elemental composition and PGE contents. The matrix of the gasoline AC is composed of Al, Zr, Ce, Ba oxides with Rh, Pd and Pt coatings. The support of diesel AC is composed of Mg, Al, Fe, Ti and Ca silicates with Pt coatings. Aged gasoline AC exhibit higher Mg, Mn, Zn and Pb contents compared to the new AC. Aged diesel AC differs in higher Zn and Ba contents compared to the new one. Both aged and new AC does not differ in total PGE contents. Leaching experiments were done with AC, real samples of tunnel dusts and reference materials with inorganic (Cl-, HPO42-) and organic (low and high molecular weight) complexing solutions. The solubility experiments indicate that PGE mobilization from ACs is dependent on particle type, time and complexing medium.

Mihaljevic, Martin; Ettler, Vojtech; Strnad, Ladislav; Sebek, Ondrej; Stedry, Robin; Adamec, Vladimir

2010-05-01

103

K-italic-shell photoelectric cross sections for intermediate-Z-italic elements at 26 keV  

SciTech Connect

Our earlier measurements of K-italic-shell photoelectric cross sections for intermediate Z-italic elements at 74 and 37 keV have been extended to 26 keV using external conversion x rays in Sn. The experimental results are found to show fairly good agreement with the theoretical values of Scofield.

Kumar, S.; Singh, N.; Allawadhi, K.L.; Sood, B.S.

1986-08-01

104

Process for forming shaped group III-V semiconductor nanocrystals, and product formed using process  

DOEpatents

A process for the formation of shaped Group III-V semiconductor nanocrystals comprises contacting the semiconductor nanocrystal precursors with a liquid media comprising a binary mixture of phosphorus-containing organic surfactants capable of promoting the growth of either spherical semiconductor nanocrystals or rod-like semiconductor nanocrystals, whereby the shape of the semiconductor nanocrystals formed in said binary mixture of surfactants is controlled by adjusting the ratio of the surfactants in the binary mixture.

Alivisatos, A. Paul (Oakland, CA); Peng, Xiaogang (Fayetteville, AR); Manna, Liberato (Palo del Colle, IT)

2001-01-01

105

Establishment of Constitutive Model of Titanium Alloy Ti6Al4V and Validation of Finite Element  

Microsoft Academic Search

The quasi-static compressive and dynamic compressive (SHPB) experiments were carried out to investigate the static and dynamic property of titanium alloy Ti6Al4V though analysis and comparison of the experiment results, the Johnson-Cook constitutive model of titanium alloy Ti6Al4V was established. The cutting process of titanium alloy Ti6Al4V was simulated using the orthogonal cutting finite element model. Though the simulation, the

Wu Hong-bing; Xu Chengguang; Jia Zhi-xin; Zhang Xue-chang; Liu Gang

2010-01-01

106

Refractory inclusions from the Leoville, Efremovka, and Vigarano c3v chondrites: Major element differences between types A and B, and extraordinary refractory siderophile element compositions  

Microsoft Academic Search

We have measured the bulk major and trace element compositions of ten CAIs from Leoville, Efremovka, and Vigarano, members of the reduced subgroup of C3V chondrites. by INAA. Like CAls from the reduced subgroup studied previously and unlike CAIs from Allende, a member of the oxidized subgroup, nine of the ten CAIs studied here possess only small amounts of secondary

PAUL J. SYLVESTER; STEVEN B. SIMON; LAWRENCE GROSSMAN

1993-01-01

107

Coronal Element Abundances of the Post-Common Envelope Binary V471 Tauri with ASCA  

NASA Technical Reports Server (NTRS)

We report on ASCA observations of the coronally active companion star in the post-common envelope binary V471 Tau. While it would be prudent to check the following results with grating spectroscopy, we find that a single-temperature plasma model does not fit the data. Two temperature models with variable abundances indicate that Fe is underabundant compared to the Hyades photospheric mean, whereas, the high first ionization potential element Ne is overabundant. This is indicative of the inverse first ionization effect, believed to result from the fractionation of ionized material by the magnetic field in the upper atmosphere of the star. Evolutionary calculations indicate that there should be no peculiar abundances on the companion star resulting from the common envelope epoch. Indeed, we find no evidence for peculiar abundances, although uncertainties are high.

Still, Martin; Hussain, Gaitee; White, Nicholas E. (Technical Monitor)

2002-01-01

108

First-principles calculations of electronic structures and optical properties of group-IIIA elements doped wurtzite CdS  

NASA Astrophysics Data System (ADS)

The electronic structures and optical properties of pure and group-IIIA elements doped wurtzite CdS are investigated using first-principles density-functional approach. The results indicate that when a group-IIIA element is introduced into CdS, the Fermi level moves upward into the conduction band from the band gap of undoped CdS, and the contributions of the s states of cations to the total density of states of CdS near the Fermi level are very large. The calculated optical properties show that absorption peaks located in the visible spectrum appear in group-IIIA doped CdS, but the intensities of the peaks are very weak, especially for the polarization vectors perpendicular to the c axis. Our calculations provide reasonable explanations to the experimental observations of the greatly decrease of resistivity of CdS while retaining high transparency with the doping of group-IIIA element.

Liu, Xin-Dian; Xing, Tao

2014-06-01

109

Prediction of Large-Gap Two-Dimensional Topological Insulators Consisting of Bilayers of Group III Elements with Bi.  

PubMed

We use first-principles electronic structure calculations to predict a new class of two-dimensional (2D) topological insulators (TIs) in binary compositions of group III elements (B, Al, Ga, In, and Tl) and bismuth (Bi) in a buckled honeycomb structure. We identify band inversions in pristine GaBi, InBi, and TlBi bilayers, with gaps as large as 560 meV, making these materials suitable for room-temperature applications. Furthermore, we demonstrate the possibility of strain engineering in that the topological phase transition in BBi and AlBi could be driven at ?6.6% strain. The buckled structure allows the formation of two different topological edge states in the zigzag and armchair edges. More importantly, isolated Dirac-cone edge states are predicted for armchair edges with the Dirac point lying in the middle of the 2D bulk gap. A room-temperature bulk band gap and an isolated Dirac cone allow these states to reach the long-sought topological spin-transport regime. Our findings suggest that the buckled honeycomb structure is a versatile platform for hosting nontrivial topological states and spin-polarized Dirac fermions with the flexibility of chemical and mechanical tunability. PMID:24734779

Chuang, Feng-Chuan; Yao, Liang-Zi; Huang, Zhi-Quan; Liu, Yu-Tzu; Hsu, Chia-Hsiu; Das, Tanmoy; Lin, Hsin; Bansil, Arun

2014-05-14

110

Growth Mechanism of Self-Catalyzed Group III-V Nanowires  

PubMed Central

Group III?V nanowires offer the exciting possibility of epitaxial growth on a wide variety of substrates, most importantly silicon. To ensure compatibility with Si technology, catalyst-free growth schemes are of particular relevance, to avoid impurities from the catalysts. While this type of growth is well-documented and some aspects are described, no detailed understanding of the nucleation and the growth mechanism has been developed. By combining a series of growth experiments using metal?organic vapor phase epitaxy, as well as detailed in situ surface imaging and spectroscopy, we gain deeper insight into nucleation and growth of self-seeded III?V nanowires. By this mechanism most work available in literature concerning this field can be described.

2010-01-01

111

Recent advances in the determination of the platinum group elements and gold.  

PubMed

Accurate determinations of the platinum group elements (PGEs) and gold, known as the precious metals, have always been difficult tasks. The metals are often present at trace levels in sample types of complex composition. This situation has improved recently due to developments of instrumental methods and their applications to analyses of the precious metals in a variety of matrices. Attention has been given to determinations of traces of precious metals in biological, clinical and environmental samples. Foremost in importance is inductively coupled plasma mass spectrometry (ICP-MS) which has provided a sensitive means of simultaneous determination of traces of PGEs and gold. Important extensions and improvements in atomic absorption spectrometry (AAS), nuclear and electrochemical methods have been reported also. More research on sample treatments, especially fire assays, applied to PGEs has been carried out. Chlorination has proven to be a viable alternative to fire assays for preconcentration of PGEs and gold in analyses of geological materials. In addition, the recent availability of some additional reference materials will be of great assistance in research work on precious metals. PMID:18967568

Barefoot, R R; Van Loon, J C

1999-06-01

112

Accumulation and distribution characteristics of platinum group elements in roadside dusts in Beijing, China.  

PubMed

The concentrations, distribution, and accumulation of platinum group elements (PGEs) were investigated in roadside dusts collected in four different foundational areas in Beijing during February to May 2010. The results showed that PGE levels in all samples were above the average upper crust values, with mean concentrations of 57.5 ng · g(-1) Pd, 28.2 ng · g(-1) Pt, and 9.8 ng · g(-1) Rh, respectively. Palladium concentration has increased rapidly in recent years. The rank of PGE levels in four different functional regions for roadside dusts was: heavy density traffic area > residential area > educational area > tourism area. Palladium, Pt, and Rh concentrations in dusts showed strong positive correlations, indicating a common traffic-related source of these metals. Meanwhile, PGEs in these samples were not correlated with other traffic-related metals except for Cr. The average PGE ratios of road dusts from Beijing were consistent with those in Germany and Western Australia, but lower than those in the United States and Mexico, indicating that various catalyst productions were used in different countries. In addition, grain-size partitioning of PGEs in dusts indicated that concentrations of PGEs differed from one particle size to another. The coarse fraction had higher PGE concentrations than the fine fraction in roadside dusts. These results showed that autocatalyst PGE contamination estimates in the environment would be significantly underestimated if only a fine-grain size fraction (<0.063 mm) is analyzed. PMID:22505271

Gao, Bo; Yu, Yanke; Zhou, Huaidong; Lu, Jin

2012-06-01

113

Platinum group elements in raptor eggs, faeces, blood, liver and kidney.  

PubMed

The increased use of platinum group elements (PGEs) in automobile catalysts and their emission into the environment has led to a concern over environmental and particularly biological accumulation. Specimens of samples from raptors are useful for the investigation of the impact of PGEs because these birds are found in both urban and rural environments and are invariably at the top of the food chain. Platinum (Pt), palladium (Pd) and rhodium (Rh) concentrations were determined by quadrupole Inductively Coupled Plasma-Mass Spectrometry (ICP-MS) in eggs of the sparrowhawk (Accipiter nisus) and the peregrine falcon (Falco peregrinus), and in blood, liver and kidney of the peregrine falcon, while only Pt was determined in faeces of the peregrine falcon and the gyrfalcon (Falco rusticolus). PGE concentrations were higher in blood compared to both faeces and eggs, while liver and kidney concentrations were not elevated indicating no bioaccumulation through metallothionein pathways. A significant spatial trend could only be established for Pt in faeces. The general lack of a spatial trend is probably due to the widespread distribution of automobiles and the long-range transport of nanoparticles containing PGEs, and because birds migrate and forage over large areas. No significant temporal trend could be established. Higher relative concentrations of Pd, followed by Rh and Pt, indicate a mobility gradient of Pd>Rh>Pt. PMID:15504501

Ek, Kristine H; Rauch, Sebastien; Morrison, Gregory M; Lindberg, Peter

2004-12-01

114

Volatile transport of platinum-group elements in sulfide-chloride assemblages at 1000°C  

NASA Astrophysics Data System (ADS)

The platinum-group elements (PGE) are appreciably volatile in dry systems in the presence of both Cl and S at 1000°C. The present experiments were conducted in sealed silica-glass tubes, with charges of either pure metals or PGE-bearing Fe-Ni-Cu sulfides and alloys; Na halide (principally NaCl); ± S, Te, As, Bi, C, and basalt powder. Metal transport was detected by visual inspection, XRD, SEM, and neutron activation analysis (NAA). Equivalent partial pressures were estimated from the transport of pure NaCl. For single and binary metal charges, transport occurs in the following sequences: Fe > Cu > Ni > Pd; and Cl > I ? F. In a series of controlled experiments with polymetallic charges and analysis by NAA, the maximum amounts of PGE transported in two days at 1000°C are as follows: Os, 70 ng; Ir, 56 ng; Rh, 150 ng; Pt, 2550 ng; and Pd, 2500 ng on an absolute basis; and Os, 1100 ppm; Ir, 610 ppm; Rh, 860 ppm; Pt, 12,400 ppm; and Pd, 5900 ppm as a proportion of Fe sulfide transported. Platinum and Pd are the dominant PGE transported in experiments with high | s2 and the chondritenormalized amounts exhibit a positively fractionated PGE pattern. The greater volatility of Pt and Pd in S-Cl-bearing systems may point to a general explanation for the positive PGE patterns of mafic rocks and magmatic sulfide and PGE deposits.

Fleet, Michael E.; Wu, Tsai-Way

1993-08-01

115

Origin of the differences in refractory-lithophile-element abundances among chondrite groups  

NASA Astrophysics Data System (ADS)

Chondrite groups can be distinguished on the basis of their abundances of refractory lithophile elements (RLE). These abundances are, in part, functions of the mass fraction of Ca-Al-rich inclusions (CAIs) within the chondrites. Carbonaceous chondrites contain the most CAIs and the highest RLE abundances; they also contain modally abundant fine-grained matrix material that consists largely of modified nebular dust. The amount of dust varied throughout the solar nebula: enstatite and ordinary chondrites formed in low-dust regions in the inner part of the nebula, R chondrites formed in higher-dust zones at somewhat greater heliocentric distances, and carbonaceous chondrites formed in even dustier regions farther from the Sun. The amount of ambient dust peaked in the region where CV and CK chondrites accreted; these chondrites have abundant matrix, the highest modal abundances of CAIs, and the highest bulk RLE contents. Substantial amounts of nebular dust occurred in highly porous multi-millimeter-to-centimeter-size dustballs that were on the order of 100 times more massive than CAIs. Radial drift processes in the nebula affected these dustballs to approximately the same extent as the CAIs; both types of objects were aerodynamically concentrated in the same nebular regions. These regions maintained approximately the same relative amounts of dust through the periods of chondrule formation and chondrite accretion.

Rubin, Alan E.

2011-06-01

116

The nature of the interaction of dimethylselenide with IIIA group element compounds.  

PubMed

The first systematic theoretical study of the nature of intermolecular bonding of dimethylselenide as donor and IIIA group element halides as acceptors was made with the help of the approach of Quantum Theory of Atoms in Molecules. Density Functional Theory with "old" Sapporo triple-? basis sets was used to calculate geometry, thermodynamics, and wave function of Me2Se···AX3 complexes. The analysis of the electron density distribution and the Laplacian of the electron density allowed us to reveal and explain the tendencies in the influence of the central atom (A = B, Al, Ga, In) and halogen (X = F, Cl, Br, I) on the nature of Se···A bonding. Significant changes in properties of the selenium lone pair upon complexation were described by means of the analysis of the Laplacian of the charge density. Charge transfer characteristics and the contributions to it from electron localization and delocalization were analyzed in terms of localization and delocalization indexes. Common features of the complexation and differences in the nature of bonding were revealed. Performed analysis evidenced that gallium and indium halide complexes can be attributed to charge transfer-driven complexes; aluminum halides complexes seem to be mainly of an electrostatic nature. The nature of bonding in different boron halides essentially varies; these complexes are stabilized mainly by covalent Se···B interaction. In all the complexes under study covalence of the Se···A interaction is rather high. PMID:23590617

Madzhidov, Timur I; Chmutova, Galina A

2013-05-16

117

Issues of platinum group element concentration analysis: Do we have solutions?  

NASA Astrophysics Data System (ADS)

When addressing digestion techniques, sample inhomogeneity, reagent blanks and spike sample equilibration are issues of major concern. The issue of complete digestions is often overseen or neglected. Reasons are a) the lack of reference materials certified for PGE concentrations to validate methods, b) too few collaborative trials concerning PGE analysis (proficiency tests), c) assumptions made on complete digestions, d) the lack of alternative digestions method to validate analytical methods and e) large measurement uncertainties that do not allow for detection of bias. Acid digestions in Carius tubes (CT) where originally introduced (ca 1860) to digest organic material for major element analyses. In the 1940 CT were described as effective digestion method of platinum group elements applying temperatures of up to 300° C. In the early 1990s CT heated to about 230° C for silicate rock digestions for the Re-Os isotopic analysis. With the increasing interest in determining PGE with isotope dilution ICP-MS, CT were later on used for sample digestions, partially replacing the classical fire assay technique with NiS. The temperature of 230° C was thought to be sufficient for complete digestion and was not raised due to safety concerns. Recent studies show that CT do not release all the PGE contained in peridotites. It can be demonstrated that higher temperatures (greater 300° C) need to be attained to achieve complete digestions. The use of a high pressure asher (HPA-S) device makes complete PGE digestions of less than 4 g of silicates or chromites at temperatures up to 320° C in a extremely safe environment possible. The recent reintroduction of the original constructions for CT digestions of the 1940s now allow digestions even at 345° C and more. The home made device, which was build after the plan from NIST, is probably as efficient as HPA-S digestions. One advantage of the classical NiS fire assay is the possibility to process large sample amounts which should reduce the sampling effect. Since the results obtained by repeated digestions at high temperature digestions with a HPA-S or with high temperature CT show smaller relative standard deviations and higher concentrations than NiS fire assay digestions. Hence sample inhomogeneity is not the most important source of measurement uncertainty.

Meisel, T.; Becker, H.; Walker, R. J.

2004-05-01

118

Group-V impurities in SnO2 from first-principles calculations  

NASA Astrophysics Data System (ADS)

By means of first-principles calculations we investigate the effects of N, P, As, and Sb impurities on the electrical properties of SnO2 . We find that N prefers to occupy the O site and unexpectedly acts as a very deep acceptor with a level closer to the conduction band than to the valence band. P, As, and Sb prefer the Sn site, where they act as shallow donors. The group-V impurities are therefore not suitable for achieving p -type conductivity in SnO2 , but P, As, and Sb may serve as n -type dopants. We also investigate the interaction between N and H impurities, finding that the binding energy of the N-H complex is much larger than the binding energies found for complexes involving H and group-IIIA impurities in SnO2 .

Varley, J. B.; Janotti, A.; van de Walle, C. G.

2010-06-01

119

Sulfide saturation history of the Stillwater Complex, Montana: chemostratigraphic variation in platinum group elements  

NASA Astrophysics Data System (ADS)

A platinum group element (PGE) investigation of a 5.3 km-thick stratigraphic section of the Stillwater Complex, Montana was undertaken to refine and test a geochemical technique to explore for platiniferous horizons in layered mafic/ultramafic complexes. PGE, Au, major, and trace elements were determined in 92 samples from outcrops along traverses in the Chrome Mountain and Contact Mountain areas in the western part of the Stillwater Complex where the J-M reef occurs ˜1,460 m above the floor of the intrusion. A further 29 samples from a drill hole cored in the immediate vicinity of the J-M reef were analyzed to detail compositional variations directly above and below the J-M reef. Below the J-M reef, background concentrations of Pt (10 ppb) and Pd (7 ppb) are features of peridotites with intermediate S concentrations (mostly 100-200 ppm) and rocks from the Bronzitite, Norite I, and Gabbronorite I zones (mostly <100 ppm S). A sustained increase in S abundance commences at the J-M reef and continues to increase and peaks in the center of the 600 m-thick middle banded series. Over this same interval, Pt, Pd, and Au are initially elevated and then decrease in the order Pd > Pt > Au. Within the middle and upper banded series, S abundances fluctuate considerably, but exhibit an overall upward increase. The behavior of these elements records periodic sulfide saturation during deposition of the Peridotite zone, followed by crystallization under sulfide-undersaturated conditions until saturation is achieved at the base of the J-M reef. Following formation of the reef, sulfide-saturated conditions persisted throughout the deposition of most of the remaining Lower Layered Series. This resulted in a pronounced impoverishment in PGE abundance in the remaining magma, a condition that continued throughout deposition of the remainder of a succession, which is characterized by very low Pt (1.5 ppb) and Pd (0.7 ppb) abundances. Because only unmineralized rock was selected for study in the 5.3 km-thick section, the results provide an unbiased picture of the variation in background PGE levels during crystallization of the Stillwater Complex. In contrast, the variations in the drill core samples through the reef provide a detailed record of ore formation. Plots of Pt, Pd, Pd/S, and Pt + Pd as a function of stratigraphic height in the intrusion show that the location of the J-M reef is defined by an abrupt change in these concentrations and ratios. Although this is the most abrupt change, three other anomalies in PGE abundance and ratios are apparent in the profiles and coincide with known laterally extensive sub-economic sulfide concentrations above the J-M reef. The uppermost of these is the PGE-bearing Picket Pin sulfide horizon. The relative ease with which mineralized horizons can be pinpointed in these diagrams indicates that a similar approach could be used in exploration programs in other ultramafic/mafic intrusions. Our observations exclude the possibilities of either magma mixing within the Stillwater chamber or the fluxing of a volatile-rich fluid as the mechanisms responsible for the genesis of the J-M reef. Rather, our data indicate that the J-M reef formed from a parental magma that was strongly enriched in PGE; this magma likely formed at depth below the Stillwater magma chamber by the interaction of the parental magma with S-rich meta-sedimentary rocks, followed by the re-dissolution of these sulfides in the Stillwater magma.

Keays, Reid R.; Lightfoot, Peter C.; Hamlyn, Paul R.

2012-01-01

120

Exploring cryogenic focused ion beam milling as a Group III-V device fabrication tool  

NASA Astrophysics Data System (ADS)

In this paper, we compare the features observed on a Group III-V strained layer superlattice (SLS) materials system as a result of room temperature Ga+ focused ion beam (FIB) milling to the features observed as a result of cryogenic FIB (cryo-FIB) milling at -135 °C under the same beam conditions (30 kV:1 nA). The features on the cryo-FIB milled material were observed both when the material was still cold and after it returned to room temperature. Although cryo-FIB milling yielded patterned features that were initially cleaner than comparable features defined by FIB milling at room temperature, we found that both room temperature FIB milling and cryo-FIB milling with subsequent sample warm-up resulted in the formation of Group III enriched features. These findings suggest that the structural and chemical properties of features fabricated by cryo-FIB milling are temperature-dependent, which is an important consideration when it comes to device fabrication. These dependencies will need to be better understood and controlled if cryo-FIB milling is to have future applications in this area.

Dolph, Melissa Commisso; Santeufemio, Christopher

2014-06-01

121

Platinum group elements in the feathers of raptors and their prey.  

PubMed

Platinum (Pt), palladium (Pd), and rhodium (Rh) concentrations were determined in the feathers of three raptor species in Sweden, the sparrowhawk ( Accipiter nisus), the peregrine falcon ( Falco peregrinus), and the gyrfalcon ( Falco rusticolus), as well as the main prey of the sparrowhawk (the house sparrow, Passer domesticus) and the gyrfalcon (the willow grouse, Lagopus lagopus). The analysis of feathers from 1917-1999 revealed a clear temporal trend, with significantly higher Rh concentrations in sparrowhawk and peregrine falcon after 1986. There is evidence for increasing platinum group element (PGE) concentrations from 1917 to 1999 in peregrine falcon and sparrowhawk. This suggests that feathers reflect increased PGE concentrations in the environment over this time period. Mean concentrations of PGE in feathers of raptors after 1986 ranged from 0.3 to 1.8 ng x g(-1) for Pt, 0.6 to 2.1 ng x g(-1) for Pd (indicative values), and 0.1 to 0.6 ng x g(-1) for Rh. House sparrows in urban areas had significantly higher Pt and Pd concentrations than urban sparrowhawks. The higher Pd concentrations in relation to Pt and Rh may indicate the greater mobility of Pd in the environment. Although PGE concentrations are generally higher in birds living in urban areas, no significant spatial trend could be established. This is partly due to the widespread distribution of automobiles and partly because birds forage and integrate PGE exposure over large areas. Laser ablation analysis demonstrates that PGE contamination of feathers is predominantly external, consisting of small particles in the nanometer size range. Other indications of external contamination are that Pt and Pd levels are significantly higher in the vane than in the shaft and that PGE relative ratios (except Pd) reflect urban particles. PMID:11910463

Jensen, K H; Rauch, S; Morrison, G M; Lindberg, P

2002-04-01

122

Environmental routes for platinum group elements to biological materials--a review.  

PubMed

The increased use of platinum group elements (PGE) in automobile catalysts has led to concern over potential environmental and biological accumulation. Platinum (Pt), palladium (Pd) and rhodium (Rh) concentrations have increased in the environment since the introduction of automobile catalysts. This review summarises current knowledge concerning the environmental mobility, speciation and bioavailability of Pt, Pd and Rh. The greater proportion of PGE emissions is from automobile catalysts, in the form of nanometer-sized catalyst particles, which deposit on roadside surfaces, as evidenced in samples of road dust, grass and soil. In soil, PGE can be transformed into more mobile species through complexation with organic matter and can be solubilised in low pH rainwater. There are indications that environmentally formed Pd species are more soluble and hence more mobile in the environment than Rh and Pt. PGE can reach waterbodies through stormwater transport and deposition in sediments. Besides external contamination of grass close to roads, internal PGE uptake has been observed for plants growing on soil contaminated with automobile catalyst PGE. Fine particles of PGE were also detected on the surface of feathers sampled from passerines and raptors in their natural habitat, and internal organs of these birds also contained PGE. Uptake has been observed in sediment-dwelling invertebrates, and laboratory studies have shown an uptake of PGE in eel and fish exposed to water containing road dust. The available evidence indicates that the PGE, especially Pd, are transported to biological materials through deposition in roots by binding to sulphur-rich low molecular weight species in plants. PGE uptake to exposed animals have uptake rates in the following order: Pd>Pt>Rh. The liver and kidney accumulate the highest levels of PGE, especially Pd. Urinary Pd and Rh, but not Pt, levels are correlated with traffic intensity. Dental alloys may lead to elevated urinary Pt levels. Platinum is a well-known allergen and Pd also shows a strong sensitisation potential. PMID:15504490

Ek, Kristine H; Morrison, Gregory M; Rauch, Sebastien

2004-12-01

123

Temperature dependent flow softening of titanium alloy Ti6Al4V: An investigation using finite element simulation of machining  

Microsoft Academic Search

Titanium alloy Ti6Al4V is the most commonly used titanium alloy in the aerospace and medical device industries due to its superior properties. There has been a considerable amount of research to better understand the serrated chip formation mechanism of titanium alloy Ti6Al4V by using finite element simulation of machining. An accurate representation of the behavior of the material is important

Yi?it Karpat

2011-01-01

124

Analysis of downdrag on pile groups by the finite element method  

Microsoft Academic Search

The downdrag on friction and endbearing pile groups was investigated, based on a numerical analysis. The emphasis was on quantifying the reduction of downdrag on pile groups, with a flexible pile cap, due to group effect. The case of a single pile and, subsequently, the response of groups were analyzed by developing interaction factors obtained from a three-dimensional nonlinear finite

Sangseom Jeong; Sooil Kim; Jean-Louis Briaud

1997-01-01

125

Control of the growth orientation and electrical properties of polycrystalline Cu2O thin films by group-IV elements doping  

NASA Astrophysics Data System (ADS)

The effects of group-IV element dopants on the structural and electrical properties of Cu2O thin films were studied. Similar dopant-induced behavior was found in the observed variations of the growth orientation and electrical properties of Si- and Ge-doped Cu2O thin films. Ge doping was found to induce electrically active acceptors with an activation energy of 0.18 eV, comparable to the 0.19 eV value of Si-doped Cu2O. These results suggest that locally formed silicate and germanate have the same effect on the structural and electrical properties of Cu2O. On the other hand, Sn and Pb likely act as donors when incorporated substitutionally onto Cu-lattice sites, although further study may be required to suppress self-compensation effects in Cu2O to achieve n-type conductivity.

Ishizuka, Shogo; Akimoto, Katsuhiro

2004-11-01

126

Human Remains from the Moravian Gravettian: Morphology and Taphonomy of Isolated Elements from the Doln?? V?stonice II Site  

Microsoft Academic Search

The excavation and palaeoanthropological analysis of the early Upper Palaeolithic site of Doln?? V?stonice II has yielded a series of incomplete and isolated human remains, comprising cranial vaults, teeth (including a series from an infant), ribs, arm bones, hand phalanges, leg bones, tarsals, metatarsals and pedal phalanges. Morphologically and morphometrically the elements are similar to those from buried individuals at

Erik Trinkaus; Jir ÿõ ´ Svoboda; Dixie L. West; Vladim??r Sládek; Simon W Hillson; Eva Drozdová; Miriam Fišáková

2000-01-01

127

Anionic iron clusters as building blocks for the synthesis of higher nuclearity compounds containing 11- and 12-group elements  

Microsoft Academic Search

Anionic iron clusters have been widely used as building blocks for the formation of mixed metal clusters with 11- and 12- group elements. This review summarizes the results reported in this area, paying special attention to the structural features of the metal core of the species reported.

Montserrat Ferrer; Roser Reina; Oriol Rossell; Miquel Seco

1999-01-01

128

Sniffing for Clues to the Dinosaurs Demise: Measurement of Osmium Isotope Compositions and Platinum Group Element Abundances in Volcanic Emissions  

Microsoft Academic Search

Platinum Group Elements (PGE: Os, Ir, Rh, Ru, Pt, Pd) and osmium isotopes measured in marine and terrestrial sediment, snow and ice records are important paleo-tracers of riverine, hydrothermal, extraterrestrial, volcanic and anthropogenic inputs into the global surficial environment. For instance, the marine Os isotope record across the Cretaceous-Tertiary Boundary (KTB) indicates that the onset of the main phase of

K. W. Sims; B. Peucker-Ehrenbrink; T. Mather; D. Pyle; R. Martin; P. Gauthier; A. Aiuppa

2005-01-01

129

Differences in the promotional effect of the group IA elements on unsupported copper catalysts for carbon monoxide hydrogenation  

Microsoft Academic Search

The differences in promotional effect of the Group IA elements on unsupported copper catalysts for carbon monoxide hydrogenation have been examined. Methanol was selectivity produced on all catalysts at 523 K, 5 MPa, and with a feed gas of molar composition Hâ\\/CO = 2. When normalized with respect to surface area, the methanol synthesis rate was found to increase by

G. R. Sheffer; T. S. King

1989-01-01

130

Superconductivity in quaternary niobium oxynitrides containing main group elements (M=Mg, Al, Si)  

SciTech Connect

Niobium compounds continue to be an interesting family of superconductors, with the recent addition of oxynitrides to it, which can be categorized as low-T{sub c} superconductors (LTS) because they exhibit superconductivity below T{sub c}{approx}17 K. In this paper, we report the superconducting properties of three members of the family of niobium oxynitrides, viz. (Nb{sub 0.89}Al{sub 0.11})(N{sub 0.84}O{sub 0.16}), (Nb{sub 0.95}Mg{sub 0.05})(N{sub 0.92}O{sub 0.08}) and (Nb{sub 0.87}Si{sub 0.09}{open_square}{sub 0.04})(N{sub 0.87}O{sub 0.13}). Low temperature dc and ac magnetization measurements have been performed. In addition, heat capacity has been recorded at low temperature under applied magnetic fields. A detailed analysis of the data is presented. - Graphical abstract: The doped Si oxide accompanied with some amount of cation vacancy in cubic NbN lattice induces relatively large magnetic hysteresis on isothermal hysteresis loops at 5 K of the dc magnetization up to 5 T among the four niobium oxynitrides containing main group elements, Nb{sub 1.00}(N{sub 0.98}O{sub 0.02}); (Nb{sub 0.95}Mg{sub 0.05})(N{sub 0.92}O{sub 0.08}); (Nb{sub 0.89}Al{sub 0.11})(N{sub 0.84}O{sub 0.16}), and (Nb{sub 0.87}Si{sub 0.09}{open_square}{sub 0.04})(N{sub 0.87}O{sub 0.13}). Highlights: Black-Right-Pointing-Pointer Three Nb-oxynitrides doped either with Si, Al, Mg were bulk superconductors below {approx}17 K. Black-Right-Pointing-Pointer The cation vacancies induced by doping silicon act as pinning centers. Black-Right-Pointing-Pointer The Si-doped sample had strong electron correlations.

Ohashi, Y. [Faculty of Engineering, Hokkaido University, N13W8, Kita-ku, Sapporo 060-8628 (Japan); Kikkawa, S., E-mail: kikkawa@eng.hokudai.ac.jp [Faculty of Engineering, Hokkaido University, N13W8, Kita-ku, Sapporo 060-8628 (Japan); Felner, I.; Tsindlekht, M.I. [Racah Institute of Physics, The Hebrew University, Jerusalem 91904 (Israel); Venkateshwarlu, D.; Ganesan, V. [UGC-DAE-Consortium for Scientific Research, Khandwa Rd, Indore (MP) 452001 (India); Yakhmi, J.V. [Bhabha Atomic Research Centre, Mumbai 400085 (India)

2012-04-15

131

Hybridization-based mapping of Neurospora crassa linkage groups II and V.  

PubMed Central

As part of the German Neurospora crassa genome project, physical clone maps of linkage groups II and V of N. crassa were generated by hybridization-based mapping. To this end, two different types of clone library were used: (1) a bacterial artificial clone library of 15-fold genome coverage and an average insert size of 69 kb, and (2) three cosmid libraries--each cloned in a different vector--with 17-fold coverage and 34 kb average insert size. For analysis, the libraries were arrayed on filters. At the first stage, chromosome-specific sublibraries were selected by hybridization of the respective chromosomal DNA fragments isolated from pulsed-field electrophoresis gels. Subsequently, the sublibraries were exhaustively ordered by single clone hybridizations. Eventually, the global libraries were used again for gap filling. By this means, physical maps were generated that consist of 13 and 21 contigs, respectively, and form the basis of the current sequencing effort on the two chromosomes.

Aign, V; Schulte, U; Hoheisel, J D

2001-01-01

132

Phase transitions in Group III-V and II-VI semiconductors at high pressure  

NASA Technical Reports Server (NTRS)

The structures and transition pressures of Group III-V and II-VI semiconductors and of a pseudobinary system (Ga/x/In/1-x/Sb) have been investigated. Results indicate that GaP, InSb, GaSb, GaAs and possible AlP assume Metallic structures at high pressures; a tetragonal, beta-Sn-like structure is adopted by only InSb and GaSb. The rocksalt phase is preferred in InP, InAs, AlSb, ZnO and ZnS. The model of Van Vechten (1973) gives transition pressures which are in good agreement with measured values, but must be refined to account for the occurrence of the ionic rocksalt structure in some compounds. In addition, discrepancies between the theoretical scaling values for volume changes at the semiconductor-to-metal transitions are observed.

Yu, S. C.; Liu, C. Y.; Spain, I. L.; Skelton, E. F.

1979-01-01

133

Synthesis and properties of layered synthetic microstructure (LSM) dispersion elements for 62 eV (200A) to 1. 24 keV (10A) radiation. Final report  

SciTech Connect

The opportunities offered by engineered synthetic multilayer dispersion elements for x-rays have been recognized since the earliest days of x-ray diffraction analysis. In this paper, application of sputter deposition technology to the synthesis of Layered Synthetic Microstructure (LSMs) of sufficient quality for use as x-ray dispersion elements is discussed. It will be shown that high efficiency, controllable bandwidth dispersion elements, with d spacings varying from 15 A to 180 A, may be synthesized onto both mechanically stiff and flexible substrates. Multilayer component materials include tungsten, niobium, molybdenum, titanium, vanadium, and silicon layers separated by carbon layers. Experimental observations of peak reflectivity in first order, integrated reflectivity in first order, and diffraction performance at selected photon energies in the range, 100 to 15,000 eV, will be reported and compared to theory.

Barbee, T.W. Jr.

1981-08-01

134

Minor/major element variation within and among diogenite and howardite orthopyroxenite groups  

NASA Technical Reports Server (NTRS)

Diogenites are orthopyroxenites that may contain chromite and olivine as accessory minerals. Howardite breccias contain orthopyroxenite clasts with similar properties compared to monomict diogenites. We used statistical methods and variation plots of major and minor elements in orthopyroxene and chromite to show whether or not howardite orthopyroxenites are related to monomict diogenites, and to assess their petrogenesis. Our results fail to establish any evidence that monomict diogenites are significantly different from howardite orthopyroxenites in terms of major and minor elements. We also found no differences between Antarctic diogenites and non-Antarctic diogenites. Although element variation plots show compelling evidence that most diogenites originated by igneous fractionation, linear trends among the various diogenites and howardite orthopyroxenite clasts are either non-existent or ill-defined. This militates against an origin from a single magma body, but suggests an origin from multiple magma bodies in the parent planetoid.

Berkley, John L.; Boynton, Nancy J.

1992-01-01

135

Platinum group elements in a 3.5 Ga nickel-iron occurrence - Possible evidence of a deep mantle origin  

NASA Technical Reports Server (NTRS)

This paper reports the results of new field observations and the geochemical analyses for the area of the Bon Accord (BA) (the Kaapvaal craton, South Africa) Ni-Fe deposit, with particular consideration given to the trace element, platinum-group element, and isotopic (Pb, Nd, and Os) compositions. On the basis of these data, an interpretation of BA is suggested, according to which the BA deposit is a siderophile-rich heterogeneity remaining in the deep mantle after a process of incomplete core formation. The implications of such a model for the study of core-mantle segregation and the geochemistry of the lowermost mantle are discussed.

Tredoux, Marian; Hart, Rodger J.; Lindsay, Nicholas M.; De Wit, Maarten J.; Armstrong, Richard A.

1989-01-01

136

STRUCTURAL, ELEMENTAL COMPOSITIONS AND OPTICAL PROPERTIES OF ZnTe:V THIN FILMS  

Microsoft Academic Search

Vanadium doped zinc telluride (ZnTe:V) thin films of various thicknesses for a particular composition of 2.5wt% V were deposited onto glass substrates by e-beam evaporation technique in vacuum at a pressure of 8×10 -4 Pa. The deposition rate of the ZnTe:V films was maintained at 2.05 nms-1. The optical properties of ZnTe:V thin films for different film thicknesses have been

M. S. HOSSAIN; R. ISLAM; K. A. KHAN

137

Group method solutions of the generalized forms of Burgers, Burgers–KdV and KdV equations with time-dependent variable coefficients  

Microsoft Academic Search

Solutions for the generalized forms of Burgers, Burgers–KdV, and KdV equations with time-dependent variable coefficients and\\u000a with initial and boundary conditions are constructed. The analysis rests mainly on the standard group method. Similarity solutions\\u000a are found which reduce the nonlinear system of partial differential equations to systems of ordinary differential equations\\u000a to obtain some exact solutions and others as numerical

Mina B. Abd-el-Malek; Medhat M. Helal

138

Solid solution softening and hardening in the group-V and group-VI bcc transition metals alloys: First principles calculations and atomistic modeling  

Microsoft Academic Search

The interaction of d transition metal additions with dislocations was studied in bcc alloys by using the atomic row model with ab initio parametrization of the interatomic interactions. Opposite trends were obtained for the solute-dislocation interactions in the group-V (Nb, Ta) and group-VI (Mo, W) bcc metals: while additions with extra valence electrons enhance the double-kink nucleation and result in

N. I. Medvedeva; Yu. N. Gornostyrev; A. J. Freeman

2007-01-01

139

Identification of human DNA helicase V with the far upstream element-binding protein  

Microsoft Academic Search

The properties of human DNA helicase V (HDH V) were studied in greater detail following an improved purification procedure. From 450 g of cultured cells, <0.1 mg of pure protein was isolated. HDH V unwinds DNA unidirectionally by moving in the 3' to 5' direction along the bound strand in an ATP- and Mg2+- dependent fashion. The enzyme is not

Alessandro Vindigni; Alexander Ochem; Gianluca Triolo; Arturo Falaschi

2001-01-01

140

DC dissipation current from elements used for lightning protection on 115 kV transmission lines  

Microsoft Academic Search

The Mississippi Power & Light Company is using different elements in transmission lines and towers to protect the electrical system from direct lightning strokes. According to some theories, the objects to be protected against lightning strokes are better protected by using an element from which the charge dissipation current is enhanced. The authors present the results of an experimental study

S. Grzybowski; A. L. Libby; E. B. Jenkins; C. R. Davis

1991-01-01

141

Method of loading organic materials with group III plus lanthanide and actinide elements  

DOEpatents

Disclosed is a composition of matter comprising a tributyl phosphate complex of a group 3, lanthanide, actinide, or group 13 salt in an organic carrier and a method of making the complex. These materials are suitable for use in solid or liquid organic scintillators, as in x-ray absorption standards, x-ray fluorescence standards, and neutron detector calibration standards.

Bell, Zane W. (Oak Ridge, TN) [Oak Ridge, TN; Huei-Ho, Chuen (Oak Ridge, TN) [Oak Ridge, TN; Brown, Gilbert M. (Knoxville, TN) [Knoxville, TN; Hurlbut, Charles (Sweetwater, TX) [Sweetwater, TX

2003-04-08

142

Long-range superexchange in Cu2A2O7 (A= P, As, V) as a key element of the microscopic magnetic model  

NASA Astrophysics Data System (ADS)

A microscopic magnetic model for ?-Cu2P2O7 is evaluated in a combined theoretical and experimental study. Despite a dominant intradimer coupling J1, sizable interdimer couplings enforce long-range magnetic ordering at TN=27 K. The spin model for ?-Cu2P2O7 is compared to the models of the isostructural ?-Cu2V2O7 and ?-Cu2As2O7 systems. As a surprise, coupled dimers in ?-Cu2P2O7 and alternating chains in ?-Cu2As2O7 contrast with a honeycomb lattice in ?-Cu2V2O7. We find that the qualitative difference in the coupling regime of these isostructural compounds is governed by the nature of AO4 side groups: d elements (A=V) hybridize with nearby O atoms forming a Cu-O-A-O-Cu superexchange path, while for p elements (A= P, As) the superexchange is realized via O-O edges of the tetrahedron. Implications for a broad range of systems are discussed.

Janson, O.; Tsirlin, A. A.; Sichelschmidt, J.; Skourski, Y.; Weickert, F.; Rosner, H.

2011-03-01

143

Czochralski growth of heavily indium-doped Si crystals and co-doping effects of group-IV elements  

NASA Astrophysics Data System (ADS)

Heavily indium (In)-doped Si crystals were grown by the Czochralski method under a consideration of the effects of co-doping of electrically neutral group-IV elements (C, Ge or Sn). The In concentration in In-doped Si increased with the amount of In charged into the crucible and reached 3.5×1017 cm?3. The carrier concentration was at most 6×1016 cm?3, limited by the low ionization ratio of ~20% of In. Co-doping of C and Ge effectively enhanced the In concentration while Sn did not, which was examined in terms of the atomistic size, lattice parameter change, mutual bonding energy and solubility of group-IV elements in Si. However, no sufficient increase in carrier concentrations was detected in Si by the co-doping, and formation of some clusters or complexes was suggested.

Inoue, K.; Taishi, T.; Tokumoto, Y.; Kutsukake, K.; Ohno, Y.; Ohsawa, T.; Gotoh, R.; Yonenaga, I.

2014-05-01

144

Combined distillation and normal freezing to purify elements of groups II and VI  

NASA Technical Reports Server (NTRS)

A practical system and its application to the purification of Te and Cd is described. Single crystals are grown directly in vitreous silica ampoules subsequently used for sealed Bridgman growth of (Hg-Cd)Te. The system also prepares the ampoules by heating in high vacuum. Purification of the elements is by the combined effect of distillation and normal freezing. Transport and segregation are discussed.

Holland, L. R.

1984-01-01

145

The behaviour of platinum-group elements in basalts from the East Greenland rifted margin  

Microsoft Academic Search

. The continental flood basalts of the East Greenland volcanic rifted margin were extruded during continental breakup above the ancestral Iceland mantle plume at 55 Ma. Three distinct magma types, the low-Ti, high-Ti and very high-Ti series (LTS, HTS and VHTS respectively), are found intercalated in the ~6-km-thick Plateau Lava sequence. Incompatible trace elements indicate that the LTS are derived

Peter Momme; Christian Tegner; Kent C. Brooks; Reid R. Keays

2002-01-01

146

Measurement of the isotopic composition of the iron-group elements in the galactic cosmic radiation  

NASA Technical Reports Server (NTRS)

With an average mass resolution of approximately 0.65 amu the isotopic composition of Cr, Mn, Fe, and Ni in the galactic cosmic radiation has been measured for energies of about 300 to 600 MeV/amu at the detector. Large deviations from solar-system source composition reported by other workers are not observed.

Tarle, G.; Ahlen, S. P.; Cartwright, B. G.

1978-01-01

147

The chromosomal distributions of Ty1-copia group retrotransposable elements in higher plants and their implications for genome evolution  

Microsoft Academic Search

Retrotransposons make up a major fraction – sometimes more than 40% – of all plant genomes investigated so far. We have isolated\\u000a the reverse transcriptase domains of the Ty1-copia group elements from several species, ranging in genome size from some 100\\u000a Mbp to 23 000 Mbp, and determined the distribution patterns of these retrotransposons on metaphase chromosomes and within\\u000a interphase

Andrea Brandes; Shin Taketa; Thomas Schmidt; Alexander V. Vershinin; Elena G. Alkhimova; Anette Kamm; Robert L. Doudrick; Trude Schwarzacher; Andreas Katsiotis; Sybille Kubis; Amar Kumar; Steven R. Pearce; Andrew J. Flavell; Gill E. Harrison

1997-01-01

148

Deposition of osmium and other platinum-group elements beneath the ultramafic-hosted Rainbow hydrothermal plume  

Microsoft Academic Search

Osmium and other platinum-group elements (PGEs) have been measured in sediments accumulating directly under the Rainbow hydrothermal plume at 36°N on the Mid-Atlantic Ridge. 187Os\\/188Os and PGE concentrations in the sediments of four cores taken 2-25 km from the active vent site reveal evidence of both radiogenic Os scavenged from seawater and, importantly, unradiogenic Os released by hydrothermal venting. The

R. R. Cave; G. E. Ravizza; C. R. German; J. Thomson; R. W. Nesbitt

2003-01-01

149

Environmental risk of particulate and soluble platinum group elements released from gasoline and diesel engine catalytic converters  

Microsoft Academic Search

A comparison of platinum-group element (PGE) emission between gasoline and diesel engine catalytic converters is reported within this work. Whole raw exhaust fumes from four catalysts of three different types were examined during their useful lifetime, from fresh to 80000 km. Two were gasoline engine catalysts (Pt–Pd–Rh and Pd–Rh), while the other two were diesel engine catalysts (Pt). Samples were

M Moldovan; M. A Palacios; M. M Gómez; G Morrison; S Rauch; C McLeod; R Ma; S Caroli; A Alimonti; F Petrucci; B Bocca; P Schramel; M Zischka; C Pettersson; U Wass; M Luna; J. C Saenz; J Santamar??a

2002-01-01

150

Osmium isotopic compositions of Os-rich platinum group element alloys from the Klamath and Siskiyou Mountains  

Microsoft Academic Search

We present new measurements of 186Os\\/188Os and 187Os\\/188Os in 10 Os-rich platinum group element (PGE) alloys from placer deposits formed by the mechanical erosion of peridotite-bearing ophiolites in the Klamath and Siskiyou Mountains in northern California and southwestern Oregon. These data nearly double our database of high-precision 186Os\\/188Os measurements on such samples. Together with previously published data, our new results

Anders Meibom; Robert Frei; Norman H. Sleep

2004-01-01

151

The origin of halide melt phases in layered intrusions, and their significance to platinum-group element mobility  

Microsoft Academic Search

Fluid and melt inclusions are preserved within pegmatite bodies and cumulus minerals within mafic-ultramafic layered intrusions that host economic concentrations of the platinum-group elements (e.g., Bushveld Complex, South Africa; Stillwater Complex, Montana). The inclusions indicate that the earliest volatile phase to have exsolved from the crystallizing intrusions was a relatively anhydrous carbonic fluid (CO2-dominated). As crystallization proceeded, volatiles became increasingly

J. J. Hanley

2007-01-01

152

Vacancy-assisted diffusion mechanism of group-III elements in ZnO: An ab initio study  

Microsoft Academic Search

Based on ab initio total energy calculations, the diffusion mechanisms of group-III elements (B, Al, Ga, and In) in ZnO are investigated. The activation energy of vacancy-assisted mechanism consists of formation energy of Zn vacancy (VZn), binding energy between the dopants and VZn, as well as effective diffusion energy barrier of the dopants in ZnO. The effective diffusion energy barriers

Gui-Yang Huang; Chong-Yu Wang; Jian-Tao Wang

2009-01-01

153

Platinum-group elements of the Meishan Permian–Triassic boundary section: Evidence for flood basaltic volcanism  

Microsoft Academic Search

Permian–Triassic boundary sections record the most severe mass extinction event in geological history. However, there is a long-standing controversy of whether bolide impact and\\/or basaltic flood volcanism triggered the mass extinction. Platinum-group elements (PGEs) are enriched in most extraterrestrial materials, but highly depleted in the terrestrial crust materials. We analyzed Ir, Ru, Rh, Pt and Pd in a set of

Lin Xu; Yangting Lin; Wenjie Shen; Liang Qi; Liewen Xie; Ziyuan Ouyang

2007-01-01

154

Use of 4.7 MeV alpha particles in elemental analysis and fusion reactor materials studies  

NASA Astrophysics Data System (ADS)

The possibilities for using 4.7 MeV alpha particles produced at the U-120 CIP Cyclotron for charged particle induced X- and gamma-ray emission applications (PIXE and PIGE, respectively) and for fast neutron radiation damage simulation are presented. The combined analysis using PIGE and PIXE methods either separately or simultaneously is an excellent means of determining the relative abundances of lighter elements with gamma-ray spectra and of heavier elements ( Z ? 16) with X-ray spectra. Some aspects of surface deformation effects by neutrons were simulated by means of medium-energy helium ions. An investigation of three types of commercial stainless steel (Romanian W 4016, Soviet 12KH18N10T and Japanese W 4541) was started using 3.0 [1], 4.7 and 6.8 MeV helium ions. The main post-irradiation effects observed are discussed.

Constantinescu, B.; Dima, S.; Florescu, V.; Ivanov, E. A.; Plo?tinaru, D.; Sârbu, C.

1986-07-01

155

Mechanical induction of group V phospholipase A2 causes lung inflammation and acute lung injury  

PubMed Central

Ventilation at high tidal volume may cause lung inflammation and barrier dysfunction that culminates in ventilator-induced lung injury (VILI). However, the mechanisms by which mechanical stimulation triggers the inflammatory response have not been fully elucidated. This study tested the hypothesis that onset of VILI is triggered by activation of secretory group V phospholipase A2 (gVPLA2) in pulmonary vascular endothelium exposed to excessive mechanical stretch. High-magnitude cyclic stretch (18% CS) increased expression and surface exposure of gVPLA2 in human pulmonary endothelial cells (EC). CS-induced gVPLA2 activation was required for activation of ICAM-1 expression and polymorphonuclear neutrophil (PMN) adhesion to CS-preconditioned EC. By contrast, physiological CS (5% CS) had no effect on gVPLA2 activation or EC-PMN adhesion. CS-induced ICAM-1 expression and EC-PMN adhesion were attenuated by the gVPLA2-blocking antibody (MCL-3G1), general inhibitor of soluble PLA2, LY311727, or siRNA-induced EC gVPLA2 knockdown. In vivo, ventilator-induced lung leukocyte recruitment, cell and protein accumulation in the alveolar space, and total lung myeloperoxidase activity were strongly suppressed in gVPLA2 mouse knockout model or upon administration of MCL-3G1. These results demonstrate a novel role for gVPLA2 as the downstream effector of pathological mechanical stretch leading to an inflammatory response associated with VILI.

Meliton, Angelo Y.; Munoz, Nilda M.; Meliton, Lucille N.; Birukova, Anna A.; Leff, Alan R.

2013-01-01

156

Final Report: Main Group Element Chemistry in Service of Hydrogen Storage and Activation  

SciTech Connect

Replacing combustion of carbon-based fuels with alternative energy sources that have minimal environmental impact is one of the grand scientific and technological challenges of the early 21st century. Not only is it critical to capture energy from new, renewable sources, it is also necessary to store the captured energy efficiently and effectively for use at the point of service when and where it is needed, which may not be collocated with the collection site. There are many potential storage media but we focus on the storage of energy in chemical bonds. It is more efficient to store energy on a per weight basis in chemical bonds. This is because it is hard to pack electrons into small volumes with low weight without the use of chemical bonds. The focus of the project was the development of new chemistries to enable DOE to meet its technical objectives for hydrogen storage using chemical hydrogen storage systems. We provided computational chemistry support in terms of thermodynamics, kinetics, and properties prediction in support of the experimental efforts of the DOE Center of Excellence for Chemical Hydrogen Storage. The goal of the Center is to store energy in chemical bonds involving hydrogen atoms. Once the hydrogen is stored in a set of X-H/Y-H bonds, the hydrogen has to be easily released and the depleted fuel regenerated very efficiently. This differs substantially from our current use of fossil fuel energy sources where the reactant is converted to energy plus CO2 (coal) or CO2 and H2O (gasoline, natural gas), which are released into the atmosphere. In future energy storage scenarios, the spent fuel will be captured and the energy storage medium regenerated. This places substantial additional constraints on the chemistry. The goal of the computational chemistry work was to reduce the time to design new materials and develop materials that meet the 2010 and 2015 DOE objectives in terms of weight percent, volume, release time, and regeneration ability. This goal was met in terms of reducing the number of costly experiments and helping to focus the experimental effort on the potentially optimal targets. We have used computational chemistry approaches to predict the thermodynamic properties of a wide range of compounds containing boron, nitrogen, hydrogen, and other elements as appropriate including carbon. These calculations were done in most cases with high level molecular orbital theory methods that have small error bars on the order of ± 1 to 2 kcal/mol. The results were used to benchmark more approximate methods such as density functional theory for larger systems and for database development. We predicted reliable thermodynamics for thousands of compounds for release and regeneration schemes to aid/guide materials design and process design and simulation. These are the first reliable computed values for these compounds and for many represent the only available values. Overall, the computational results have provided us with new insights into the chemistry of main group and organic-base chemical hydrogen systems from the release of hydrogen to the regeneration of spent fuel. A number of experimental accomplishments were also made in this project. The experimental work on hydrogen storage materials centered on activated polarized ?- or ?-bonded frameworks that hold the potential for ready dihydrogen activation, uptake, and eventually release. To this end, a large number of non-traditional valence systems including carbenes, cyanocarbons, and C-B and and B-N systems were synthesized and examined. During the course of these studies an important lead arose from the novel valency of a class of stable organic singlet bi-radical systems. A synthetic strategy to an “endless” hydrogen storage polymer has been developed based on our cyanocarbon chemistry. A key issue with the synthetic efforts was being able to link the kinetics of release with the size of the substituents as it was difficult to develop a low molecular weight molecule with the right kinetics. A novel hydrogen activation process has been developed

David A. Dixon; Anthony J. Arduengo, III

2010-09-30

157

Physicochemical Interaction of Rhenium with Elements of the Platinum Group and Properties of Certain Alloys.  

National Technical Information Service (NTIS)

A review is given of the physicochemical interaction of rhenium with the platinum-group metals (ruthenium, osmium, tungsten, palladium, rhodium, iridium, platinum). The solubility of rhenium in these metals and vice versa is illustrated with graphs. Rheni...

I. A. Tsyganova M. A. Tylkina V. P. Polyakova

1969-01-01

158

Use of 4.7 MeV alpha particles in elemental analysis and fusion reactor materials studies  

Microsoft Academic Search

The possibilities for using 4.7 MeV alpha particles produced at the U-120 CIP Cyclotron for charged particle induced X- and gamma-ray emission applications (PIXE and PIGE, respectively) and for fast neutron radiation damage simulation are presented. The combined analysis using PIGE and PIXE methods either separately or simultaneously is an excellent means of determining the relative abundances of lighter elements

B. Constantinescu; S. Dima; V. Florescu; E. A. Ivanov; D. Plostinaru; C. Sârbu

1986-01-01

159

Reduction of light elements loss in polymer foils during MeV-proton irradiation by application of an aluminum coating  

Microsoft Academic Search

Backscattering and forward-scattering spectrometry with 2.2MeV-protons have been applied to detect light elements including H, C, N and O in polymer foils of aromatic polyimide (PI), polyethylene telephthalate (PET) and polyethylene naphthalate (PEN). In the case of PI, no significant loss of H, C, N and O was observed during proton irradiation. In the case of PET and PEN, on

M. Saito; F. Nishiyama; K. Kobayashi; S. Nagata; K. Takahiro

2010-01-01

160

Elemental composition effects on self-absorption for photons below 100 keV in gamma-ray spectrometry  

NASA Astrophysics Data System (ADS)

The influence of elemental composition in the self-absorption phenomenon is observed. The effective atomic number (Zeff) is used to explain this influence for energies below 100 keV. Monte Carlo simulations based on MCNPX and GESPECOR are used to demonstrate the separate impact of Zeff and density ? on the self-absorption for a given extended sample. Results obtained by simulation are in good agreement with those obtained by the transmission method.

Dziri, S.; Nachab, A.; Nourreddine, A.; Sellam, A.; Pape, A.

2014-07-01

161

An element-free Galerkin (EFG) method for numerical solution of the coupled Schrödinger-KdV equations  

NASA Astrophysics Data System (ADS)

The present paper deals with the numerical solution of the coupled Schrödinger-KdV equations using the element-free Galerkin (EFG) method which is based on the moving least-square approximation. Instead of traditional mesh oriented methods such as the finite difference method (FDM) and the finite element method (FEM), this method needs only scattered nodes in the domain. For this scheme, a variational method is used to obtain discrete equations and the essential boundary conditions are enforced by the penalty method. In numerical experiments, the results are presented and compared with the findings of the finite element method, the radial basis functions method, and an analytical solution to confirm the good accuracy of the presented scheme.

Liu, Yong-Qing; Cheng, Rong-Jun; Ge, Hong-Xia

2013-10-01

162

Behavior of EBR-II Mk-V-type fuel elements in simulated loss-of-flow tests  

SciTech Connect

This report discusses three furnace heating tests which were conducted with irradiated, HT9-clad and U-19wt.%Pu-l0wt.%Zr-alloy fuel, Mk-V-type fuel elements in the Alpha-Gamma Hot Cell Facility at Argonne National Laboratory, Illinois. In general, very significant safety margins for fuel-element cladding breaching have been demonstrated in these tests, under conditions that would envelop a bounding unlikely loss-of-flow event in EBR-II. Highlights of the test results will be given, as well as discussions of the cladding breaching mechanisms, axial fuel motion, and fuel surface liquefaction found in high-temperature testing of irradiated metallic fuel elements.

Liu, Y.Y.; Tsai, H.; Billone, M.C.; Holland, J.W.; Kramer, J.M. [Argonne National Lab., IL (United States)

1992-11-01

163

Trace Element Distribution in Organs and Tissues after Implantation of V4A Steels.  

National Technical Information Service (NTIS)

Metallosis, a tissue reaction to metal implants which is caused by corrosion of the implanted metal caused by body liquids, makes activation analysis interesting as a method to determine trace element distributions in tissue and organs. Osteosynthesis of ...

J. Hofmann R. Michel J. Zilkens

1978-01-01

164

Stability and migration of vacancy in V-4Cr-4Ti alloy: Effects of Al, Si, Y trace elements  

NASA Astrophysics Data System (ADS)

Addition of trace amounts of Al, Si and Y into V-4Cr-4Ti alloy is beneficial for the mechanical properties under irradiation. It is thus important to investigate the influence of solute/trace elements on stabilities, energetics and diffusion behaviors of vacancy defects. We performed first-principles calculations to evaluate vacancy-solute/trace interaction inside dilute V-X (X = Ti, Cr, Al, Si, Y) and V-4Cr-4Ti-(Al, Si, Y) alloys. With addition of Si and Y, vacancy-based complexes tend to form near Ti-Si and Ti-Y pairs, while the effect of Al is negligible. Moreover, diffusion coefficients of solute/trace element in vanadium were derived using nine-frequency model. With high binding energy and low diffusion coefficient, Si atom is strongly attractive to vacancy in vanadium matrix. Our theoretical results suggest that the interactions between vacancy and solute/trace elements play some role in the evolution of microstructures inside vanadium alloys.

Zhang, Chong; Zhang, Pengbo; Li, Ruihuan; Zhao, Jijun; Dong, Chuang

2013-11-01

165

The group separation of the rare-earth elements and yttrium from geologic materials by cation-exchange chromatography  

USGS Publications Warehouse

Demand is increasing for the determination of the rare-earth elements (REE) and yttrium in geologic materials. Due to their low natural abundance in many materials and the interferences that occur in many methods of determination, a separation procedure utilizing gradient strong-acid cation-exchange chromatography is often used to preconcentrate and isolate these elements from the host-rock matrix. Two separate gradient strong-acid cation-exchange procedures were characterized and the major elements as well as those elements thought to provide the greatest interference for the determination of the REE in geologic materials were tested for separation from the REE. Simultaneous inductively coupled argon plasma-atomic emission spectroscopy (ICAP-AES) measurements were used to construct the chromatograms for the elution studies, allowing the elution patterns of all the elements of interest to be determined in a single fraction of eluent. As a rock matrix, U.S. Geological Survey standard reference BCR-1 basalt was digested using both an acid decomposition procedure and a lithium metaborate fusion. Hydrochloric and nitric acids were tested as eluents and chromatograms were plotted using the ICAP-AES data; and we observed substantial differences in the elution patterns of the REE and as well as in the solution patterns of Ba, Ca, Fe and Sr. The nitric acid elution required substantially less eluent to elute the REE and Y as a group when compared to the hydrochloric acid elution, and provided a clearer separation of the REE from interfering and matrix elements. ?? 1984.

Crock, J. G.; Lichte, F. E.; Wildeman, T. R.

1984-01-01

166

Groups whose nonlinear irreducible characters separate element orders or conjugacy class sizes  

Microsoft Academic Search

.  A class function ? on a finite group G is said to be an order separator if, for every x and y in G \\\\ {1}, ?(x) = ?(y) is equivalent to x and y being of the same order. Similarly, ? is said to be a class-size separator if, for every x and y in G\\\\ {1}, ?(x) =

Mariagrazia Bianchi; David Chillag; Emanuele Pacifici

2008-01-01

167

Contribution of Exogenous Genetic Elements to the Group A Streptococcus Metagenome  

Microsoft Academic Search

Variation in gene content among strains of a bacterial species contributes to biomedically relevant differences in phenotypes such as virulence and antimicrobial resistance. Group A Streptococcus (GAS) causes a diverse array of human infections and sequelae, and exhibits a complex pathogenic behavior. To enhance our understanding of genotype-phenotype relationships in this important pathogen, we determined the complete genome sequences of

Stephen B. Beres; James M. Musser; Niyaz Ahmed

2007-01-01

168

Group III nitride-arsenide long wavelength lasers grown by elemental source molecular beam epitaxy  

SciTech Connect

Elemental source molecular beam epitaxy was used to grow InGaNAs quantum well samples, edge-emitting laser diodes, and vertical-cavity laser diodes on GaAs substrates. The quantum well samples exhibited an as-grown room temperature photoluminescence peak beyond 1310 nm which both increased dramatically in intensity and blueshifted with thermal annealing. Edge emitting laser diodes had threshold current densities as low as 450 and 750 A/cm{sup 2} for single and triple quantum well active regions, respectively, and emitted light at 1220-1250 nm. The vertical cavity laser diodes emitted light at 1200 nm and had threshold current densities of 3 kA/cm{sup 2} and efficiencies of 0.066 W/A. (c) 2000 American Vacuum Society.

Coldren, C. W. [Solid State and Photonics Laboratory, Stanford University, Via Ortega, Stanford, California 94305 (United States)] [Solid State and Photonics Laboratory, Stanford University, Via Ortega, Stanford, California 94305 (United States); Spruytte, S. G. [Solid State and Photonics Laboratory, Stanford University, Via Ortega, Stanford, California 94305 (United States)] [Solid State and Photonics Laboratory, Stanford University, Via Ortega, Stanford, California 94305 (United States); Harris, J. S. [Solid State and Photonics Laboratory, Stanford University, Via Ortega, Stanford, California 94305 (United States)] [Solid State and Photonics Laboratory, Stanford University, Via Ortega, Stanford, California 94305 (United States); Larson, M. C. [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)] [Lawrence Livermore National Laboratory, Livermore, California 94550 (United States)

2000-05-01

169

Platinum group elements (Pt and Ir) deposition at Dome C (East Antarctica) between 600 kyr BP to 800 kyr BP  

NASA Astrophysics Data System (ADS)

Platinum group elements (PGE: Ir and Pt) concentrations were determined in 42 sections from the EPICA (European Project for Ice Coring in Antarctica) Dome C ice core, covering a period from ~600 kyr BP to ~800 kyr BP, by inductively coupled plasma sector field mass spectrometry (ICP-SFMS) coupled with desolvation nebulizion system and sub-boiling pre-concentration. Our data enable us to extend the previous EPICA Dome C (EDC) records of Ir and Pt covering the past 270 kyr, which corresponds to the last two climatic cycles. Here we discuss the Ir and Pt concentration records coupling with crustal reference element (Ba) and some refractory trace metals (Yb and Hf). Crustal enriched elements (Ba, Yb and Hf) show well defined variations in concentrations in relation to climatic conditions with lower values during the interglacial periods and much increased values by ~10 during the glacial periods. On the other hand, the siderophile elements (Ir and Pt) show a less differences between their concentrations for different climatic conditions. Mean concentrations of Ir and Pt for the glacial periods were approximately two times higher than their mean concentrations for the interglacial periods. Concentration ratios (Ir/Pt) and crustal enrichment factors (EFc) of Ir and Pt indicate that atmospheric PGE in Antarctica may be originated dominantly from non-crustal sources, and the extent of the their contributions were likely regulated by the climatic conditions during the investigated time period.

Soyol-Erdene, Tseren-Ochir; Hur, Soon So; Hong, Sungmin; Hwan, Heejin; Gabrelli, Paolo; Barbante, Carlo; Boutron, Claude F.

2013-04-01

170

Platinum group elements (Pt and Ir) deposition at Dome C (East Antarctica) between 572 kyr BP to 800 kyr BP  

NASA Astrophysics Data System (ADS)

Platinum group elements (PGE: Ir and Pt) concentrations were determined in 42 sections from the EPICA (European Project for Ice Coring in Antarctica) Dome C ice core, covering a period from ~572 kyr BP to ~800 kyr BP, by inductively coupled plasma sector field mass spectrometry (ICP-SFMS) coupled with desolvation nebulizion system and sub-boiling pre-concentration. Our data enable us to extend the previous EPICA Dome C (EDC) records of Ir and Pt covering the past 270 kyr, which corresponds to the last two climatic cycles. Here we discuss the Ir and Pt concentration records coupling with crustal reference element (Ba) and some refractory trace metals (Yb and Hf). Crustal enriched elements (Ba, Yb and Hf) show well defined variations in concentrations in relation to climatic conditions with lower values during the interglacial periods and much increased values by ~10 during the glacial periods. On the other hand, the siderophile elements (Ir and Pt) show a less differences between their concentrations for different climatic conditions. Mean concentrations of Ir and Pt for the glacial periods were approximately two times higher than their mean concentrations for the interglacial periods. Concentration ratios (Ir/Pt) and crustal enrichment factors (EFc) of Ir and Pt indicate that atmospheric PGE in Antarctica originated dominantly from non-crustal source (i.e., extraterrestrial), and the extent of the extraterrestrial contributions were likely regulated by the climatic conditions during the investigated time period.

Soyol-Erdene, T.; Hur, S.; Hong, S.; Hwang, H.; Gabrielli, P.; Barbante, C.; Boutron, C.

2012-12-01

171

Chromosomal Homology and Molecular Organization of Muller's Elements D and E in the Drosophila Repleta Species Group  

PubMed Central

Thirty-three DNA clones containing protein-coding genes have been used for in situ hybridization to the polytene chromosomes of two Drosophila repleta group species, D. repleta and D. buzzatii. Twenty-six clones gave positive results allowing the precise localization of 26 genes and the tentative identification of another nine. The results were fully consistent with the currently accepted chromosomal homologies and in no case was evidence for reciprocal translocations or pericentric inversions found. Most of the genes mapped to chromosomes 2 and 4 that are homologous, respectively, to chromosome arms 3R and 3L of D. melanogaster (Muller's elements E and D). The comparison of the molecular organization of these two elements between D. melanogaster and D. repleta (two species that belong to different subgenera and diverged some 62 million years ago) showed an extensive reorganization via paracentric inversions. Using a maximum likelihood procedure, we estimated that 130 paracentric inversions have become fixed in element E after the divergence of the two lineages. Therefore, the evolution rate for element E is approximately one inversion per million years. This value is comparable to previous estimates of the rate of evolution of chromosome X and yields an estimate of 4.5 inversions per million years for the whole Drosophila genome.

Ranz, J. M.; Segarra, C.; Ruiz, A.

1997-01-01

172

A study of Venus surface elemental composition from 14 MeV neutron induced gamma ray spectroscopy: Activation analysis  

NASA Astrophysics Data System (ADS)

The surface elemental composition of Venus can be determined using an artificially pulsed 14 MeV neutron generator (PNG) combined with a gamma ray spectrometer (GRS). The 14 MeV neutrons will interact with the surface materials and generate gamma rays, characteristic of specific elements, whose energy spectrum will be measured by GRS. These characteristic gamma rays are produced mainly through 3 different neutron interaction mechanisms: capture, inelastic, and activation reactions. Each reaction type has a different neutron energy dependency and different time scale for gamma ray production and transport. Certain elements are more easily identified through one reaction type over the others. Thus, careful analysis of the gamma ray spectra during and after the neutron pulse provides a comprehensive understanding of the surface elemental composition. In this paper, we use a well-tested neutron/gamma transport code, called Monte Carlo N-Particles (MCNP), to investigate the measurement capability of a PNG-GRS detection system through the neutron activation reactions. An activation analysis was performed for a representative soil composition of Venus with a notional operational scenario of PNG and GRS. The analysis shows that the proposed instrument concept can identify most of the modeled surface elements at Venus with sufficient accuracy through the activation mode. Specifically, U, Th, K, Si can be measured to within 1%, Fe within 2%, Al within 10%, Ca within 5%, Mg with 15%, Mn with 20%, and Cl within 6%. Although modeled in the analysis, it is shown that the activation mode alone cannot distinguish the S and Ti peaks.

Jun, I.; Kim, W.; Smith, M.; Mitrofanov, I.; Litvak, M.

2011-02-01

173

A Study of Venus Surface Elemental Composition From 14-MeV Neutron Induced Gamma Ray Spectroscopy: Activation Analysis  

NASA Astrophysics Data System (ADS)

The surface elemental composition of Venus can be determined by using an artificially pulsed 14 MeV neutron generator (PNG) combined with a gamma ray spectrometer (GRS). The 14 MeV neutrons will interact with the surface materials and generate gamma rays, characteristic of specific elements, whose energy spectrum will be measured by GRS. These characteristic gamma rays are produced mainly through 3 different neutron interaction mechanisms: capture, inelastic, and activation reactions. Each reaction type has a different neutron energy dependency and different time scale for gamma ray production and transport. Certain elements are more easily identified through one reaction type over the others. Thus, careful analysis of the gamma ray spectra during and after the neutron pulse provides a comprehensive understanding of the surface elemental composition. In this paper, we use a well-tested neutron/gamma transport code, called Monte Carlo N-Particles (MCNP), to investigate the measurement capability of a PNG-GRS detection system through the neutron activation reactions. An activation analysis was performed for a representative soil composition of Venus with a notional operational scenario of PNG and GRS. The analysis shows that the proposed instrument concept can identify most of the modeled surface elements at Venus with sufficient accuracy through the activation mode. Specifically, U, Th, K, Si can be measured to within 1%, Fe within 2%, Al within 10%, Ca within 5%, Mg with 15%, Mn with 20%, and Cl within 6%. Although modeled in the analysis, it is shown that the activation mode alone cannot distinguish the S and Ti peaks.

Jun, I.; Kim, W.; Smith, M.; Mitrofanov, I.; Litvak, M. L.

2010-12-01

174

Improvement of the electrical impedance tomographic image for the two-phase system with adaptive element grouping technique  

NASA Astrophysics Data System (ADS)

The electrical impedance tomography (EIT) technique is introduced for visualizing two-phase systems. The finite element method is employed to solve the electrical field induced by the currents through electrodes placed along the boundary, and a modified Newton-Raphson iterative method is used to determine the search step minimizing the error between the calculated and the measured voltages at the electrodes. However, even for a two-phase system, the conventional Newton-Raphson method cannot increase the spatial resolution after a certain iteration step. To resolve this problem, an adaptive element grouping technique is introduced. A new image reconstruction algorithm is tested for the synthetic data and phantom experimental data. It seems that the proposed algorithm is useful for the improvement of EIT performance in the application to the visualization of two-phase systems.

Kim, Min Chan; Kim, Sin; Lee, Kyung Jin; Kim, Kyung Youn

2004-07-01

175

Compendation of SSC lattice optics in the presence of dipole field errors: Report of the Correction Element Working Group  

SciTech Connect

The assignment of the Correction Element Working Group (CEWG) is to advance the designs of various candidate correction schemes to a point where they can be compared and distilled down to a single plan. Choosing among, the options often involves consideration of incommensurate factors such as cost, practicality, and theoretical performance. Except for minor issues, the CEWG purpose is to gather and array the facts in a form from which these decisions can be rationally made, but not to make the decisions. The present report analyses various schemes for compensating nonlinear multipole errors in the main arc dipoles of the Superconducting Super Collider. Emphasis is on comparing lumped and distributed compensation, on minimizing the total number of correction elements, and on reducing the sensitivity to closed-orbit errors.

Bintinger, D.; Chao, A.; Forest, E. [and others

1989-02-01

176

Structural and Energetic Analysis of Group V Impurities in p-Type HgCdTe: The Case of As and Sb  

NASA Astrophysics Data System (ADS)

Although molecular beam epitaxy technology-based arsenic-doped Hg1-x Cd x Te has been extensively studied, according to the newly proposed framework of the defect-complex-based p-type doping mechanism, heavier group V elements such as antimony (Sb) should have a different doping behavior because of their larger radius which can cause larger lattice distortion. In this work, we performed first-principles calculations and took As and Sb as examples to study this issue. The substitutional doping, interstitial doping (including split, tetrahedral, and hexagonal interstitial sites), and defect complex doping forms for arsenic and antimony are all investigated. A significant lattice distortion is found in hexagonal and split-site interstitial-Sb-doped Hg0.75Cd0.25Te due to the larger covalent radius of Sb. Compared with As, Sb can lead to a more complicated configuration change in the case of SbHg-V Hg-SbHg tridoping, and the interstitial Sb is found to be stable even with the coupling of Hg vacancies through detailed energetic calculations, indicating that the interstitial Sb has greater ability to form stable defect complexes, and thus great potential to be a more appropriate p-type dopant. This study provides more complementary understanding of the behaviors of group V impurities in HgCdTe.

Wang, Ziyan; Huang, Yan; Lei, Wen; Chen, Xiaoshuang; Zhao, Huxian; Zhou, Xiaohao; Lu, Wei

2014-04-01

177

Elements of a new Global Water Strategy for the Group on Earth Observations  

NASA Astrophysics Data System (ADS)

In order to address the need to review the scope and direction of GEO activities related to water and to provide guidance for the post-2015 GEO planning, the Integrated Global Water Cycle Observations (IGWCO) Community of Practice and the Committee on Earth Observation Satellites (CEOS) are working together to develop a strategy for GEO water activities over the next decade. This presentation will review the elements of the strategy which include topics as comprehensive as user needs and engagement, water cycle observational systems, assessment of water quality, data issues, interoperability and integration of water information systems and capacity building. Impediments in the flow of information and technological capabilities from the providers of new technologies, innovations and data products to the end users will be explored in terms of the nature of these impediments and how they can be overcome. To be successful in GEO's framework of volunteerism, the water strategy should build on activities that are on-going in related programmes at the international and national levels. In addition, implementation of the strategy will need to be supported through new initiatives and policies that promote greater integration. Suggestions for achieving these goals will be outlined at the end of the talk.

Lawford, Richard; Koike, Toshio; Ochiai, Osamu; Cripe, Douglas

2013-04-01

178

Trace element analysis of obsidian artifacts from a classic Maya residential group at Nohmul, Belize  

SciTech Connect

Forty-nine obsidian artifacts from a classic period residential group at Nohmul, northern Belize, have been analyzed by neutron activation analysis. The majority of the samples originated from Ixtepeque, and the remainder from El Chayal. Increasing prominence of the Ixtepeque source from the late Classic into the Terminal Classic (i.e., before and after ca. A.D. 800) suggests greater use of a coastal distribution route known to have originated in the formative and to have remained in use through the colonial period.

Hammond, N.; Neivens, M.D.; Harbottle, G.

1984-01-01

179

Rapid detection by multiplex PCR of Genomic Islands, prophages and Integrative Conjugative Elements in V. cholerae 7th pandemic variants.  

PubMed

Vibrio cholerae poses a threat to human health, and new epidemic variants have been reported so far. Seventh pandemic V. cholerae strains are characterized by highly related genomic sequences but can be discriminated by a large set of Genomic Islands, phages and Integrative Conjugative Elements. Classical serotyping and biotyping methods do not easily discriminate among new variants arising worldwide, therefore the establishment of new methods for their identification is required. We developed a multiplex PCR assay for the rapid detection of the major 7th pandemic variants of V. cholerae O1 and O139. Three specific genomic islands (GI-12, GI-14 and GI-15), two phages (Kappa and TLC), Vibrio Seventh Pandemic Island 2 (VSP-II), and the ICEs of the SXT/R391 family were selected as targets of our multiplex PCR based on a comparative genomic approach. The optimization and specificity of the multiplex PCR was assessed on 5 V. cholerae 7th pandemic reference strains, and other 34 V. cholerae strains from various epidemic events were analyzed to validate the reliability of our method. This assay had sufficient specificity to identify twelve different V. cholerae genetic profiles, and therefore has the potential to be used as a rapid screening method. PMID:22062086

Spagnoletti, Matteo; Ceccarelli, Daniela; Colombo, Mauro M

2012-01-01

180

Coding sequence composition flanking either signal element alters V(D)J recombination efficiency.  

PubMed Central

Lymphoid V(D)J rearrangement is targeted by recombination signal sequences (RSS) bordering V, D or J exons. We demonstrate that the DNA composition of flanking coding positions, particularly poly(A) or poly(T) stretches at one or both RSS, diminishes V(D)J recombination up to 100-fold. Positionally correct cleavages occur in the inhibited reactions, since the junctions formed show the same frequency of precision as uninhibited reactions. Open/shut cleavage/rejoining is not increased at a normal RSS in substrates containing inhibitory A/T homopolymers versus random sequence at a second RSS. Thus recombinase action at both cleavage sites is severely disrupted by modified coding sequences.

Boubnov, N V; Wills, Z P; Weaver, D T

1995-01-01

181

Grouping  

NSDL National Science Digital Library

This interactive Flash applet models the measurement interpretation of division. A child or teacher chooses a total number of objects and a divisor representing the size of equal groups. The applet allows the user to move the objects into equal groups and links the process to jumps on a number line. The applet can be used to introduce children to remainders and to reinforce the language and notation of division. It works well on an interactive white board or projector. A teacher's guide to this collection of applets is cataloged separately.

2006-01-01

182

Finite element modeling of machining of hydrogenated Ti6Al4V alloy  

Microsoft Academic Search

The present study is undertaken to investigate the effect of hydrogen on the cutting performance of Ti-6Al-4V alloy by FEM.\\u000a Mechanical behaviors of hydrogenated Ti-6Al-4V alloy are studied at elevated temperatures and high strain rates with split\\u000a Hopkinson pressure bar. The Johnson–Cook model was developed combined with quasi-static experimental data. A numerical model\\u000a is developed to simulate the cutting process.

S. B. Yang; Jiuhua Xu; Yucan Fu; Weihua Wei

183

Osmium-Isotope and Platinum-Group-Element Systematics of Impact-Melt Rocks, Chesapeake Bay Impact Structure, Virginia, USA  

NASA Technical Reports Server (NTRS)

Osmium (Os) isotopes and platinum-group elements (PGEs) are useful for geochemically identifying a meteoritic component within impact structures, because meteorites are typically characterized by low (187)Os/(188)Os ratios and high PGE concentrations. In contrast, most types of crustal target rocks have high radiogenic Os and very low PGE concentrations. We have examined Os isotope and PGE systematics of impact-melt rocks and pre-impact target rocks from a 2004 test hole in the late Eocene Chesapeake Bay impact structure and from nearby coreholes. Our goal is to determine the proportion of the projectile component in the melt rock Additional information is included in the original extended abstract.

Lee, Seung Ryeol; Wright Horton, J., Jr.; Walker, Richard J.

2005-01-01

184

Distribution of platinum-group elements and Os isotopes in chromite ores from Mayarí-Baracoa Ophiolitic Belt (eastern Cuba)  

Microsoft Academic Search

The Mayarí-Baracoa ophiolitic belt in eastern Cuba hosts abundant chromite deposits of historical economic importance. Among\\u000a these deposits, the chemistry of chromite ore is very variable, ranging from high Al (Cr#=0.43–0.55) to high Cr (Cr#=0.60–0.83)\\u000a compositions. Platinum-group element (PGE) contents are also variable (from 33 ppb to 1.88 ppm) and correlate positively with\\u000a the Cr# of the ore. Bulk PGE abundances correlate

F. Gervilla; J. A. Proenza; R. Frei; J. M. González-Jiménez; C. J. Garrido; J. C. Melgarejo; A. Meibom; R. Díaz-Martínez; W. Lavaut

2005-01-01

185

Average bond energies between boron and elements of the fourth, fifth, sixth, and seventh groups of the periodic table  

NASA Technical Reports Server (NTRS)

The average bond energies D(gm)(B-Z) for boron-containing molecules have been calculated by the Pauling geometric-mean equation. These calculated bond energies are compared with the average bond energies D(exp)(B-Z) obtained from experimental data. The higher values of D(exp)(B-Z) in comparison with D(gm)(B-Z) when Z is an element in the fifth, sixth, or seventh periodic group may be attributed to resonance stabilization or double-bond character.

Altshuller, Aubrey P

1955-01-01

186

Mobilization of the platinum group elements by low-temperature fluids: Implications for mineralization and the iridium controversy  

NASA Technical Reports Server (NTRS)

Geochemical investigations on the widely dispersed Late Proterozoic Acraman impact ejecta horizon and its host marine shales in the Adelaide Geosyncline provide strong evidence for low-temperature mobilization of the platinum group elements (PGE), including Ir. The ejecta horizon was formed when the middle Proterozoic dacitic volcanics in the Gawler Ranges, central South Australia, were impacted by a very large (ca. 4 km) meteorite. The resulting structure, now represented by Lake Acraman, is Australia's largest meteorite impact structure. Debris from the impact was blasted for many hundreds of kilometers, some falling into the shallow sea of the Adelaide Geosyncline, some 300 km to the east of the impact site.

Dowling, Kim; Keays, Reid R.; Wallace, Malcolm W.; Gostin, Victor A.

1992-01-01

187

Chemical fractionations in meteorites. V - Volatile and siderophile elements in achondrites and ocean ridge basalts.  

NASA Technical Reports Server (NTRS)

Eighteen achondrites and 4 terrestrial basalts (3 ocean ridge, 1 continental) were analyzed by radiochemical neutron activation analysis for Ag, Au, Bi, Br, Cd, Co, Cs, Cu, Ga, In, Ir, Rb, Se, Tl and Zn. Samples included 7 eucrites, 5 howardites, 2 nakhlites, 2 shergottites, an angrite, and an aubrite. Light and dark portions of the gas-rich meteorites Kapoeta and Pesyanoe were analyzed separately. Nakhlites and shergottites have volatile element abundances similar to those in ocean ridge basalts; eucrites, howardites, and angrites show greater depletions by an order of magnitude and less similar abundance patterns. In terms of a two-component model of planetary accretion, the parent planets contained the following percentages of low-temperature material: eucrites 0.8, nakhlites 38, shergottites 28. Shergottites may be genetically related to L-chondrites. The siderophile element pattern of achondrites resembles that of the moon, but with less extreme depletions.

Laul, J. C.; Keays, R. R.; Ganapathy, R.; Anders, E.; Morgan, J. W.

1972-01-01

188

Reduction of light elements loss in polymer foils during MeV-proton irradiation by application of an aluminum coating  

NASA Astrophysics Data System (ADS)

Backscattering and forward-scattering spectrometry with 2.2 MeV-protons have been applied to detect light elements including H, C, N and O in polymer foils of aromatic polyimide (PI), polyethylene telephthalate (PET) and polyethylene naphthalate (PEN). In the case of PI, no significant loss of H, C, N and O was observed during proton irradiation. In the case of PET and PEN, on the other hand, all the light elements gradually decreased as irradiation fluence increased and the contents of 15%-H, 14%-C, 47%-O in PET and 7%-H, 5%-C 31%-O in PEN were eventually released up to a fluence of 2.1 × 10 16 protons/cm 2. An aluminum thin film (thickness ˜0.1 ?m) was sputter-deposited on the upper surface of 4 ?m thick PET and PEN foils to prevent the release of light elements. In Al coated PEN foil, for example, the losses of H, C and O were 2%, 0.5% and 22% of the starting contents, respectively, considerably smaller than those found for uncoated PEN. Thus the Al coating was found to be an effective method to suppress the loss of constituent elements.

Saito, M.; Nishiyama, F.; Kobayashi, K.; Nagata, S.; Takahiro, K.

2010-10-01

189

76 FR 45248 - PJM Interconnection, L.L.C., PJM Power Providers Group v. PJM Interconnection, L.L.C...  

Federal Register 2010, 2011, 2012, 2013

...ER11-2875-001, ER11-2875-002; Docket No. EL11-20-001] PJM Interconnection, L.L.C., PJM Power Providers Group v. PJM Interconnection, L.L.C.; Supplemental Notice of Staff Technical Conference On June 13, 2011, the...

2011-07-28

190

Low keV electron probe analysis of silicate minerals for Mg, Al, and Si using pure-element standards  

NASA Technical Reports Server (NTRS)

Accurate electron probe values for Mg, Al, and Si in silicate minerals may be obtained with pure-element standards. Analysis must be done at low (6 kV) accelerating potential and for best results, the average atomic number of the sample should be within about plus or minus 1 of the atomic number of the pure-element standard. This last requirement is automatically fulfilled for most common silicate minerals, as their average atomic numbers usually fall within the 11 to 15 range. Examples studied include a wet-chemically analyzed cordierite containing 17.71 weight percent Al, for which a value of 17.6 plus or minus 0.3 percent was obtained with the electron probe, and a hornblende containing 19.15 percent Si, which gave 19.0 plus or minus 0.3 percent using the probe method.

Cunningham, G. G.

1972-01-01

191

The coupling of thermochemistry and phase diagrams for group III-V semiconductor systems. Final report  

SciTech Connect

The project was directed at linking the thermochemical properties of III-V compound semiconductors systems with the reported phase diagrams. The solid-liquid phase equilibrium problem was formulated and three approaches to calculating the reduced standard state chemical potential were identified and values were calculated. In addition, thermochemical values for critical properties were measured using solid state electrochemical techniques. These values, along with the standard state chemical potentials and other available thermochemical and phase diagram data, were combined with a critical assessment of selected III-V systems. This work was culminated with a comprehensive assessment of all the III-V binary systems. A novel aspect of the experimental part of this project was the demonstration of the use of a liquid encapsulate to measure component activities by a solid state emf technique in liquid III-V systems that exhibit high vapor pressures at the measurement temperature.

Anderson, T.J.

1998-07-21

192

Platinum group element geochemistry of komatiites from the Alexo and Pyke Hill areas, Ontario, Canada  

NASA Astrophysics Data System (ADS)

Thirty-three whole-rock drill core samples and thirteen olivine, chromite, and sulfide separates from three differentiated komatiite lava flows at Alexo and Pyke Hill, Canada, were analyzed for PGEs using the Carius tube digestion ID-ICP-MS technique. The emplaced lavas are Al-undepleted komatiites with ˜27% MgO derived by ˜50% partial melting of LILE-depleted Archean mantle. Major and minor element variations during and after emplacement were controlled by 30 to 50% fractionation of olivine Fo 93-94. The emplaced lavas are characterized by (Pd/Ir) N = 4.0 to 4.6, (Os/Ir) N = 1.07, and Os abundances of ˜2.3 ppb. Variations in PGE abundances within individual flows indicate that Os and Ir were compatible (bulk DOs,Ir = 2.4-7.1) and that Pt and Pd were incompatible (bulk DPt,Pd < 0.2) during lava differentiation, whereas bulk DRu was close to unity. Analyses of cumulus olivine separates indicate that PGEs were incompatible in olivine ( DPGEsOl-Liq = 0.04-0.7). The bulk fractionation trends cannot be accounted for by fractionation of olivine alone, and require an unidentified Os-Ir-rich phase. The composition of the mantle source (Os = 3.9 ppb, Ir = 3.6 ppb, Ru = 5.4 ppb, Pt and Pd = 5.7 ppb) was constrained empirically for Ru, Pt, and Pd; the Os/Ir ratio was taken to be identical to that in the emplaced melt, and the Ru/Ir ratio was taken to be chondritic, so that the absolute IPGE abundances of the source were determined by Ru. This is the first estimate of the PGE composition of a mantle source derived from analyses of erupted lavas. The suprachondritic Pd/Ir and Os/Ir of the inferred Abitibi komatiite mantle source are similar to those in off-craton spinel lherzolites, orogenic massif lherzolites, and enstatite chondrites, and are considered to be an intrinsic mantle feature. Bulk partition coefficients for use in komatiite melting models derived from the source and emplaced melt compositions are: DOs,Ir = 2.3, DRu = 1.0, DPt,Pd = 0.07. Ruthenium abundances are good indicators of absolute IPGE abundances in the mantle sources of komatiite melts with 26 to 29% MgO, as Ru fractionates very little during both high degrees of partial melting and lava differentiation.

Puchtel, Igor S.; Humayun, Munir; Campbell, Andrew J.; Sproule, Rebecca A.; Lesher, C. Michael

2004-03-01

193

Distribution of platinum-group elements in the Bati Kef chromite deposit, Guleman-Elazig area, eastern Turkey.  

USGS Publications Warehouse

The distribution of platinum-group elements (PGE) within chromite deposits from an ophiolite is determined and their geochemistry compared with chromitites from ophiolites and from stratiform layered complexes elsewhere in the world. The Guleman area chromitites are lenses of layered massive to disseminated chromite in dunite or sheared harzburgite along and near the dunite-harzburgite contact. PGE were analysed by a fire assay/spectrographic method. The analyses, in ppb, varied narrowly near the detection limits; only Ir was mostly detected (24-27 ppb) . The data plot as independent, slight variations of individual PGE with crude and irregular spatial distributions, oriented with respect to the land surface. Based on studies elsewhere, the PGE reside mostly in laurite, erlichmanite and Os/Ir alloys included within or interstitial to chromite. Average values for each PGE were normalized with respect to average chondrite concentrations for these elements. All patterns for ophiolite-chromitites (5) show depletion of these elements relative to chondrite average concentrations, with greater depletion in Pt and Pd than in Ir and Ru, to produce patterns with negative slopes. Chromitites from differentiated stratiform complexes (2) yield patterns with positive slopes. -G.J.N.

Page, N. J.; Engin, T.; Singer, D. A.; Haffty, J.

1984-01-01

194

An Instrument to Measure Elemental Energy Spectra of Cosmic Ray Nuclei Up to 10(exp 16) eV  

NASA Technical Reports Server (NTRS)

A longstanding goal of cosmic ray research is to measure the elemental energy spectra of cosmic rays up to and through the "knee" (approx. equal to 3 x 10 (exp 15) eV. It is not currently feasible to achieve this goal with an ionization calorimeter because the mass required to be deployed in Earth orbit is very large (at least 50 tonnes). An alternative method will be presented. This is based on measuring the primary particle energy by determining the angular distribution of secondaries produced in a target layer using silicon microstrip detector technology. The proposed technique can be used over a wide range of energies (10 (exp 11)- 10 (exp 16) eV) and gives an energy resolution of 60% or better. Based on this technique, a design for a new lightweight instrument with a large aperture (KLEM) will be described.

Adams, J.; Bashindzhagyan, G.; Chilingarian, A.; Drury, L.; Egorov, N.; Golubkov,S.; Korotkova, N.; Panasyuk, M.; Podorozhnyi, D.; Procqureur, J.

2000-01-01

195

BRAF-V600E expression in precursor versus differentiated dendritic cells defines clinically distinct LCH risk groups.  

PubMed

Langerhans cell histiocytosis (LCH) is a clonal disorder with elusive etiology, characterized by the accumulation of CD207(+) dendritic cells (DCs) in inflammatory lesions. Recurrent BRAF-V600E mutations have been reported in LCH. In this study, lesions from 100 patients were genotyped, and 64% carried the BRAF-V600E mutation within infiltrating CD207(+) DCs. BRAF-V600E expression in tissue DCs did not define specific clinical risk groups but was associated with increased risk of recurrence. Strikingly, we found that patients with active, high-risk LCH also carried BRAF-V600E in circulating CD11c(+) and CD14(+) fractions and in bone marrow (BM) CD34(+) hematopoietic cell progenitors, whereas the mutation was restricted to lesional CD207(+) DC in low-risk LCH patients. Importantly, BRAF-V600E expression in DCs was sufficient to drive LCH-like disease in mice. Consistent with our findings in humans, expression of BRAF-V600E in BM DC progenitors recapitulated many features of the human high-risk LCH, whereas BRAF-V600E expression in differentiated DCs more closely resembled low-risk LCH. We therefore propose classification of LCH as a myeloid neoplasia and hypothesize that high-risk LCH arises from somatic mutation of a hematopoietic progenitor, whereas low-risk disease arises from somatic mutation of tissue-restricted precursor DCs. PMID:24638167

Berres, Marie-Luise; Lim, Karen Phaik Har; Peters, Tricia; Price, Jeremy; Takizawa, Hitoshi; Salmon, Hélène; Idoyaga, Juliana; Ruzo, Albert; Lupo, Philip J; Hicks, M John; Shih, Albert; Simko, Stephen J; Abhyankar, Harshal; Chakraborty, Rikhia; Leboeuf, Marylene; Beltrão, Monique; Lira, Sérgio A; Heym, Kenneth M; Bigley, Venetia; Collin, Matthew; Manz, Markus G; McClain, Kenneth; Merad, Miriam; Allen, Carl E

2014-04-01

196

A redshift survey of IRAS galaxies. V - The acceleration on the Local Group  

NASA Technical Reports Server (NTRS)

The acceleration on the Local Group is calculated based on a full-sky redshift survey of 5288 galaxies detected by IRAS. A formalism is developed to compute the distribution function of the IRAS acceleration for a given power spectrum of initial perturbations. The computed acceleration on the Local Group points 18-28 deg from the direction of the Local Group peculiar velocity vector. The data suggest that the CMB dipole is indeed due to the motion of the Local Group, that this motion is gravitationally induced, and that the distribution of IRAS galaxies on large scales is related to that of dark matter by a simple linear biasing model.

Strauss, Michael A.; Yahil, Amos; Davis, Marc; Huchra, John P.; Fisher, Karl

1992-01-01

197

Elemental content from 0 to 500 keV neutrons: Lunar Prospector results  

Microsoft Academic Search

Neutron spectroscopy is a new way to study planetary bodies that have sufficiently thin atmospheres. This technique was demonstrated for the first time with Lunar Prospector around the Moon. Here, we report results for moderated neutrons having energies from 0 to 500keV that were measured using the anti-coincidence shield (ACS) of the gamma-ray spectrometer. We describe the detection method, followed

I. Genetay; S. Maurice; W. C. Feldman; O. Gasnault; D. J. Lawrence; R. C. Elphic; C. d'Uston; A. B. Binder

2003-01-01

198

Platinum group element abundances in the upper continental crust revisited - New constraints from analyses of Chinese loess  

NASA Astrophysics Data System (ADS)

Platinum group element (PGE) abundances in the upper continental crust (UCC) are poorly constrained with published values varying by up to an order of magnitude. We evaluated the validity of using loess to estimate PGE abundances in the UCC by measuring these elements in seven Chinese loess samples using a precise method that combines NiS fire assay with isotope dilution. Major and trace elements of the Chinese loess show a typical upper crustal composition and PGE abundances are consistent with literature data on Chinese loess, except for Ru, which is a factor of 10 lowe than published values. We suggest that the high Ru data and RuN/IrN values of Chinese loess reported by Peucker-Ehrenbrink and Jahn (2001) (Geochem. Geophys. Geosys.2, 2001GC000172) are an analytical artifact, rather than a true geochemical characteristic of loess because likely sources of loess are not significantly enriched in Ru and transport and deposition processes cannot preferentially enrich Ru in loess. The effect of eolian fractionation on PGE abundances in loess appears to be limited because Chinese loess from different locations shows similar PGE patterns and concentrations. This conclusion is supported by strong positive correlations between the PGE (except for Pt) and other compatible elements such as Fe2O3, Ni, Cr, Co. Using a compilation of PGE data for loess from China, Argentina and Europe, including our data but excluding one sample with an anomalously high Pt content, we propose average PGE abundances for global loess of Ir = 0.022 ppb (ng/g), Ru = 0.030 ppb, Rh = 0.018 ppb, Pt = 0.599 ppb, and Pd = 0.526 ppb, and suggest that these are the best current estimates for the PGE abundances of the UCC.

Park, Jung-Woo; Hu, Zhaochu; Gao, Shan; Campbell, Ian H.; Gong, Hujun

2012-09-01

199

Search for Platinum-Group Element Nuggets in Terrestrial Rock Samples Using Synchrotron Radiation X-ray Absorption and Fuorescence Imaging  

NASA Astrophysics Data System (ADS)

Concentrations and isotopic ratios of platinum group elements (PGEs) in the Earth's mantle are strongly controlled by chemical differentiation processes involving both silicate and metallic phases, and therefore are instrumental for understanding the differentiation and evolution of the Earth's interior. However, interpretation of the geochemical data of PGEs has been equivocal because the main host phases for PGEs in the mantle are not well constrained. PGEs in mantle rocks are thought to be concentrated in sulfide and metal minerals that consist mainly of PGEs, but such PGE-bearing phases are generally as tiny as 10 ?m or less (so called micronuggets), preventing accurate mineralogical identification or even frequent discovery from mantle-derived samples. In this study, we attempt to develop a novel method for efficient detection of PGE-bearing micronuggets from rock samples by X-ray absorption and fluorescence imaging using the synchrotron radiation beam at BL20XU of SPring-8, Japan. X-ray absorption images of samples with 0.1-3 mm thickness were taken at energies slightly below and above the K-absorption edge of a target element, and distribution maps of the element were obtained from the difference between the high-energy and low-energy images. We successfully detected 5 ?m-size Ru metal grains and 20 ?m Os metal and iridosmine grains from 3 mm-thick pellets of synthetic samples. Also, we found a 50 ?m-size Pt-bearing nugget from nominally homogeneous powder of sulfide concentrate, PTC-1a, reference material issued by CANMET-MMSL. The X-ray fluorescence analyses were operated using an X-ray beam of 15 or 113 keV. The X-ray beam was focused to 2-200 ?m using a slit or sputtered-sliced Fresnel zone plate, and was applied to rock samples with 0.1-3 mm thickness. X-ray emitted from a sample was detected using a solid-state detector. Using a 15-keV beam focused to 10-20 ?m, we successfully detected L lines from several grains of 1-?m Pt particle, even from behind a 100 ?m- thick peridotite slice. Element map images were obtained by scanning the sample, which successfully reproduced the distribution of the Pt particles behind the peridotite slice with 10-?m resolution. We expect that further optimization and combination of these methods will enable detection of ?m-size PGE-bearing micronuggets from natural rock samples.

Kogiso, T.; Suzuki, K.; Suzuki, T.; Uesugi, K.; Takeuchi, A.; Suzuki, Y.

2006-05-01

200

Platinum-group elemental geochemistry of mafic and ultramafic rocks from the Xigaze ophiolite, southern Tibet  

NASA Astrophysics Data System (ADS)

The Xigaze ophiolite in the central part of the Yarlung-Zangbo suture zone, southern Tibet, has a well-preserved sequence of sheeted dykes, basalts, cumulates and mantle peridotites at Jiding and Luqu. Both the basalts and diabases at Jiding have similar compositions with SiO 2 ranging from 45.9 to 53.5 wt%, MgO from 3.1 to 6.8 wt% and TiO 2 from 0.87 to 1.21 wt%. Their Mg #s [100Mg/(Mg + Fe)] range from 40 to 60, indicating crystallization from relatively evolved magmas. They have LREE-depleted, chondrite-normalized REE diagrams, suggesting a depleted mantle source. These basaltic rocks have slightly negative Nb- and Ti-anomalies, suggesting that the Xigaze ophiolite represents a fragment of mature MORB lithosphere modified in a suprasubduction zone environment. The mantle peridotites at Luqu are high depleted with low CaO (0.3-1.2 wt%) and Al 2O 3 (0.04-0.42 wt%). They display V-shaped, chondrite-normalized REE patterns with (La/Gd) N ratios ranging from 3.17 to 64.6 and (Gd/Yb) N from 0.02 to 0.20, features reflecting secondary metasomatism by melts derived from the underlying subducted slab. Thus, the geochemistry of both the basaltic rocks and mantle peridotites suggests that the Xigaze ophiolite formed in a suprasubduction zone. Both the diabases and basalts have Pd/Ir ratios ranging from 7 to 77, similar to MORB. However, they have very low PGE abundances, closely approximating the predicted concentration in a silicate melt that has fully equilibrated with a fractionated immiscible sulfide melt, indicating that the rocks originated from magmas that were S-saturated before eruption. Moderate degrees of partial melting and early precipitation of PGE alloys explain their high Pd/Ir ratios and negative Pt-anomalies. The mantle peridotites contain variable amounts of Pd (5.99-13.5 ppb) and Pt (7.92-20.5 ppb), and have a relatively narrow range of Ir (3.47-5.01 ppb). In the mantle-normalized Ni, PGE, Au and Cu diagram, they are relatively rich in Pd and depleted in Cu. There is a positive correlation between CaO and Pd. The Pd enrichment is possibly due to secondary enrichment by metasomatism. Al 2O 3 and Hf do not correlate with Ir, but show positive variations with Pt, Pd and Au, indicating that some noble metals can be enriched by metasomatic fluids or melts carrying a little Al and Hf. We propose a model in which the low PGE contents and high Pd/Ir ratios of the basaltic rocks reflect precipitation of sulfides and moderate degrees of partial melting. The high Pd mantle peridotites of Xigaze ophiolites were formed by secondary metasomatism by a boninitic melt above a subduction zone.

Chen, Genwen; Xia, Bin

2008-04-01

201

Identification of polycomb and trithorax group responsive elements in the regulatory region of the Drosophila homeotic gene Sex combs reduced  

SciTech Connect

The Drosophilia homeotic gene Sex combs reduced (Scr) is necessary for the establishment and maintenance of the morphological identity of the labial and prothoracic segments. In the early embryo, its expression pattern is established through the activity of several gap and segmentation gene products, as well as other transcription factors. Once established, the Polycomb group (Pc-G) and trithorax group (trx-G) gene products maintain the spatial pattern of Scr expression for the remainder of development. We report the identification of DNA fragments in the Scr regulatory region that may be important for its regulation by Polycomb and trithorax group gene products. When DNA fragments containing these regulatory sequences are subcloned into P-element vectors containing a white minigene, transformants containing these constructs exhibit mosaic patterns of pigmentation in the adult eye, indicating that white minigene expression is repressed in a clonally heritable manner. The size of pigmented and nonpigmented clones in the adult eye suggests that the event determining whether a cell in the eye anlagen will express white occurs at least as early as the first larval instar. The amount of white minigene repression is reduced in some Polycomb group mutants, whereas repression is enhanced in flies mutant for a subset of trithorax group loci. The repressor activity of one fragment, normally located in Scr Intron 2, is increased when it is able to homologously pair, a property consistent with genetic data suggesting that Scr exhibits transvection. Another Scr regulatory fragment, normally located 40 kb upstream of the Scr promoter, silences ectopic expression of an Scr-lacZ fusion gene in the embryo and does so in a Polycomb-dependent manner. We propose that the regulatory sequences located within these DNA fragments may normally mediate the regulation of Scr by proteins encoded by members of Polycomb and trithorax group loci. 98 refs., 6 figs., 4 tabs.

Gindhart, J.G. Jr.; Kaufman, T.C. [Indiana Univ., Bloomington, IN (United States)

1995-02-01

202

Identification of Polycomb and Trithorax Group Responsive Elements in the Regulatory Region of the Drosophila Homeotic Gene Sex Combs Reduced  

PubMed Central

The Drosophila homeotic gene Sex combs reduced (Scr) is necessary for the establishment and maintenance of the morphological identity of the labial and prothoracic segments. In the early embryo, its expression pattern is established through the activity of several gap and segmentation gene products, as well as other transcription factors. Once established, the Polycomb group (Pc-G) and trithorax group (trx-G) gene products maintain the spatial pattern of Scr expression for the remainder of development. We report the identification of DNA fragments in the Scr regulatory region that may be important for its regulation by Polycomb and trithorax group gene products. When DNA fragments containing these regulatory sequences are subcloned into P-element vectors containing a white minigene, transformants containing these constructs exhibit mosaic patterns of pigmentation in the adult eye, indicating that white minigene expression is repressed in a clonally heritable manner. The size of pigmented and nonpigmented clones in the adult eye suggests that the event determining whether a cell in the eye anlagen will express white occurs at least as early as the first larval instar. The amount of white minigene repression is reduced in some Polycomb group mutants, whereas repression is enhanced in flies mutant for a subset of trithorax group loci. The repressor activity of one fragment, normally located in Scr Intron 2, is increased when it is able to homologously pair, a property consistent with genetic data suggesting that Scr exhibits transvection. Another Scr regulatory fragment, normally located 40 kb upstream of the Scr promoter, silences ectopic expression of an Scr-lacZ fusion gene in the embryo and does so in a Polycomb-dependent manner. We propose that the regulatory sequences located within these DNA fragments may normally mediate the regulation of Scr by proteins encoded by members of the Polycomb and trithorax group loci.

Gindhart-Jr., J. G.; Kaufman, T. C.

1995-01-01

203

Optimization of parameters for semiempirical methods V: modification of NDDO approximations and application to 70 elements.  

PubMed

Several modifications that have been made to the NDDO core-core interaction term and to the method of parameter optimization are described. These changes have resulted in a more complete parameter optimization, called PM6, which has, in turn, allowed 70 elements to be parameterized. The average unsigned error (AUE) between calculated and reference heats of formation for 4,492 species was 8.0 kcal mol(-1). For the subset of 1,373 compounds involving only the elements H, C, N, O, F, P, S, Cl, and Br, the PM6 AUE was 4.4 kcal mol(-1). The equivalent AUE for other methods were: RM1: 5.0, B3LYP 6-31G*: 5.2, PM5: 5.7, PM3: 6.3, HF 6-31G*: 7.4, and AM1: 10.0 kcal mol(-1). Several long-standing faults in AM1 and PM3 have been corrected and significant improvements have been made in the prediction of geometries. PMID:17828561

Stewart, James J P

2007-12-01

204

A novel multi-functional magnetic Fe-Ti-V spinel catalyst for elemental mercury capture and callback from flue gas.  

PubMed

A novel magnetic Fe-Ti-V spinel catalyst showed an excellent performance for elemental mercury capture at 100 °C, and the formed HgO can be catalytically decomposed by the catalyst at 300 °C to reclaim elemental mercury and regenerate the catalyst. PMID:20927432

Yang, Shijian; Guo, Yongfu; Yan, Naiqiang; Wu, Daqing; He, Hongping; Xie, Jiangkun; Qu, Zan; Yang, Chen; Jia, Jinping

2010-11-28

205

Comparison of the analytical sensitivities for non-1/ v elements in different neutron beams  

NASA Astrophysics Data System (ADS)

Irregular nuclides such as 113Cd, and some rare-earth isotopes show different analytical sensitivities in PGAA performed at different facilities, because the cross-sections of these nuclides have strong low-energy resonances which partly overlap the energy range of typical neutron beams used for activation. A series of systematic measurements has been performed in the spectrally different cold and thermal neutron beams of the Budapest Research Reactor, Hungary and at the research reactor of NIST, Gaithersburg, USA to quantitatively study the non-1/ v behaviour of irregular nuclides. Samples were prepared that contained one of the irregular nuclides and also a regular one ( 10B, 35Cl and 56Fe) and their activation ratios were compared as measured in five different beams. Theoretical values of the activation ratios were calculated from estimates of the actual neutron spectra and cross-section data, and show a generally good correspondence to the experimental results, although some details are still not reproduced.

Révay, Zsolt

2007-10-01

206

Hyperinfectivity: A Critical Element in the Ability of V. cholerae to Cause Epidemics?  

PubMed Central

Background Cholera is an ancient disease that continues to cause epidemic and pandemic disease despite ongoing efforts to limit its spread. Mathematical models provide one means of assessing the utility of various proposed interventions. However, cholera models that have been developed to date have had limitations, suggesting that there are basic elements of cholera transmission that we still do not understand. Methods and Findings Recent laboratory findings suggest that passage of Vibrio cholerae O1 Inaba El Tor through the gastrointestinal tract results in a short-lived, hyperinfectious state of the organism that decays in a matter of hours into a state of lower infectiousness. Incorporation of this hyperinfectious state into our disease model provides a much better fit with the observed epidemic pattern of cholera. These findings help to substantiate the clinical relevance of laboratory observations regarding the hyperinfectious state, and underscore the critical importance of human-to-human versus environment-to-human transmission in the generation of epidemic and pandemic disease. Conclusions To have maximal impact on limiting epidemic spread of cholera, interventions should be targeted toward minimizing risk of transmission of the short-lived, hyperinfectious form of toxigenic Vibrio cholerae. The possibility of comparable hyperinfectious states in other major epidemic diseases also needs to be evaluated and, as appropriate, incorporated into models of disease prevention.

Hartley, David M; Morris, J. Glenn; Smith, David L

2006-01-01

207

Finite element simulation of conventional and prestressed cutting of Ti6Al4V  

NASA Astrophysics Data System (ADS)

Titanium alloys are known as difficult-to-machine materials, chip morphology plays a predominant role in determining machinability and tool wear during the machining of titanium alloys. Based on the finite element analysis and experimental validation, the cutting processes in conventional cutting and prestressed cutting of titanium alloy ring parts were explored respectively. The Johnson-Cook model expressed by equivalent plastic strain flow stress is utilized to describe the constitutive properties. A ductile fracture criterion based on the strain energy is applied to model the crack initiation and evolution during the chip segmentation. Cutting force as well as distributions of stress, temperature and equivalent plastic strain along cutting time were numerically compared. The results indicate that in conventional cutting and prestressed cutting, chips show the similar characteristic of continuous and regular serrated shape. Initial stress distribution of workpiece was changed by prestress, which correspondingly leads to the alteration of stress distribution in the subsurface layer. Prestress hardly influences the distributions of temperature and equivalent plastic strain on workpiece. The cutting force curves share the same average amplitude and analogous undulating rhythm.

Peng, Ruitao; Tang, Xinzi; Tan, Yuanqiang; Liu, Xiongwei

2013-05-01

208

Platinum-group elements in rocks from the voikar-syninsky ophiolite complex, Polar Urals, U.S.S.R.  

USGS Publications Warehouse

Analyses of platinum-group elements (PGE) in rocks collected from the Voikar-Syninsky ophiolite in the Polar Urals suggest that the distribution and geochemistry of PGE in this Paleozoic ophiolite are similar to those in Mesozoic ophiolites from elsewhere. Chondrite-normalized PGE patterns for chromitite, the tectonite unit, and ultramafic and mafic cumulate unit have negative slopes. These results are similar to those found for chromitites from other ophiolites; stratiform chromities show positive slopes. If the magmas that form both types of chromitite originate from similar mantle source material with respect to PGE content, the processes involved must be quite different. However, the distinct chondrite-normalized PGE patterns may reflect differing source materials. ?? 1983 Springer-Verlag.

Page, N. J.; Aruscavage, P. J.; Haffty, J.

1983-01-01

209

The high mobility group protein 1 enhances binding of the estrogen receptor DNA binding domain to the estrogen response element.  

PubMed

We have examined the ability of the high-mobility group protein 1 (HMG1) to alter binding of the estrogen receptor DNA-binding domain (DBD) to the estrogen response element (ERE). HMG1 dramatically enhanced binding of purified, bacterially expressed DBD to the consensus vitellogenin A2 ERE in a dose-dependent manner. The ability of HMG1 to stabilize the DBD-ERE complex resulted in part from a decrease in the dissociation rate of the DBD from the ERE. Antibody supershift experiments demonstrated that HMG1 was also capable of forming a ternary complex with the ERE-bound DBD in the presence of HMG1-specific antibody. HMG1 did not substantially affect DBD-ERE contacts as assessed by methylation interference assays, nor did it alter the ability of the DBD to induce distortion in ERE-containing DNA fragments. Because HMG1 dramatically enhanced estrogen receptor DBD binding to the ERE, and the DBD is the most highly conserved region among the nuclear receptor superfamily members, HMG1 may function to enhance binding of other nuclear receptors to their respective response elements and act in concert with coactivator proteins to regulate expression of hormone-responsive genes. PMID:9605929

Romine, L E; Wood, J R; Lamia, L A; Prendergast, P; Edwards, D P; Nardulli, A M

1998-05-01

210

Significant Li isotope fractionation in geochemically evolved rare element-bearing pegmatites from the Little Nahanni Pegmatite Group, NWT, Canada  

NASA Astrophysics Data System (ADS)

Lithium isotope signatures of whole rock pegmatite samples and mineral separates from the rare element-bearing Little Nahanni Pegmatite Group, NWT, and whole rock samples from nearby granitic intrusions were measured. Correlation of the Li isotopic values from the pegmatite dikes with whole rock trace element geochemistry, mineralogy and primary textural evidence reflect mechanisms of Li isotopic fractionation during pegmatite formation. The heavier ? 7Li signatures within the broad range measured from whole rock LNPG samples (- 0.94‰ to + 11.36‰) are related to the consolidation of the final ~ 15% melt fraction of a volatile-rich peraluminous magma in the late stages of magmatic fractionation. Rock-forming minerals (quartz, albite, spodumene and mica) display ? 7Li signatures that indicate consolidation of the dikes under variable, non-equilibrium conditions. Lithium isotope signatures of relatively cool, highly evolved peraluminous magmas reflect the build-up of fluxes (e.g., H 2O and F) and provide a qualitative assessment of the state of mineral/melt chemical equilibrium.

Barnes, Elspeth M.; Weis, Dominique; Groat, Lee A.

2012-02-01

211

Comparison of MOVPE grown GaAs solar cells using different substrates and group-V precursors  

Microsoft Academic Search

We have investigated the influence of substrate type (GaAs vs. germanium) and of group-V precursor (AsH3 vs. TBAs) on the epitaxial quality of (In)(Al)GaAs layers. We evaluated these layers in terms of morphology, background contamination and doping characteristics. For final benchmarking of the individually optimised processes, we produced p-on-n single junction GaAs solar cells and compared their relative performance. This

J. Derluyn; K. Dessein; G. Flamand; Y. Mols; J. Poortmans; G. Borghs; I. Moerman

2003-01-01

212

Les Houches Physics at TeV Colliders 2005 Beyond the Standard Model Working Group: Summary Report  

SciTech Connect

The work contained herein constitutes a report of the ''Beyond the Standard Model'' working group for the Workshop ''Physics at TeV Colliders'', Les Houches, France, 2-20 May, 2005. We present reviews of current topics as well as original research carried out for the workshop. Supersymmetric and non-supersymmetric models are studied, as well as computational tools designed in order to facilitate their phenomenology.

Allanach, B.C.; /Cambridge U., DAMTP; Grojean, C.; /Saclay, SPhT /CERN; Skands, P.; /Fermilab; Accomando, E.; Azuelos, G.; Baer, H.; Balazs, C.; Belanger, G.; Benakli, K.; Boudjema, F.; Brelier, B.; Bunichev, V.; Cacciapaglia, G.; Carena, M.; Choudhury, D.; Delsart, P.-A.; De Sanctis, U.; Desch, K.; Dobrescu, B.A.; Dudko, L.; El Kacimi, M.; /Saclay, SPhT /CERN /Fermilab /INFN, Turin /Turin U. /Montreal U. /TRIUMF /Florida State U. /Argonne /Annecy, LAPTH /Paris, LPTHE /Moscow State U. /Cornell U., CIHEP /Delhi U. /Milan U. /INFN, Milan /Freiburg U. /Cadi Ayyad U., Marrakech /Orsay, LPT /Oslo U. /Lancaster U.

2006-03-17

213

Third-order nonlinear optical susceptibilities of group IV and III-V compound semiconductors  

NASA Astrophysics Data System (ADS)

We calculate the third-order nonlinear optical susceptibility ( X(3)) of tetrahedrally coordinated solids by adopting a simple method of linear combination of hybrids developed by us. We have constructed a basis state for the valence bands which is a linear combination of hybrids forming a bond in which their relative phase factor, heretofore neglected, have been properly included. We have also constructed the basis states for the conduction bands which are orthogonal to the valence band functions. We have used our basis states in the expression for the nondispersive part of X(3) at T = 0 K to derive an expression for X(3)xxxx of tetrahedral semiconductors. We have used the Hall-Weaire-Thorpe approximation to calculate the matrix elements between different hybrids and made an average-energy-gap ansatz ( Eg) for the energy gap denominator occurring in the expression for X(3). Our expression for X(3) is obtained in a tractable form in term of matrix elements between intrasite hybrids and between adjacent hybrids forming a bond. We have calculated X(3)xxxx for a large number of tetrahedral semiconductors. Our results yield the correct sign and reasonable agreement in magnitude with experiment, unlike the earlier chemical-bond models.

Nayak, S. K.; Sahu, T.; Mohanty, S. P.

1993-09-01

214

Partitioning of platinum-group elements and Au between sulfide liquid and basalt and the origins of mantle-crust fractionation of the chalcophile elements  

NASA Astrophysics Data System (ADS)

The partitioning of platinum-group elements (PGE; Os, Ir, Ru, Rh, Pt, and Pd) and Au between sulfide melt and silicate melt (i.e., DPGEsul) exerts a critical control on the PGE composition of the Earth's crust and mantle, but previous estimates have been plagued by experimental uncertainties and vary through several orders of magnitude. Here we present direct experimental measurements of DPGEsul, based on in situ microanalysis of the sulfide and silicate melt, with values ranging from ˜4 × 105 (Ru) to ˜2-3 × 106 (Ir, Pt). Our measurements of DPGEsul are >100 times larger than previous results but smaller than anticipated based on comparison of alloy solubilities in sulfide melts and S-free silicate melts. The presence of S in the silicate melt greatly increases alloy solubility. We use our new set of partition coefficients to develop a fully constrained model of PGE behavior during melting which accurately predicts the abundances of PGE in mantle-derived magmas and their restites, including mid-ocean ridge basalts, continental picrites, and the parental magmas of the Bushveld Complex of South Africa. Our model constrains mid-ocean ridge basalt (MORB) to be the products of pooled low and high degree fractional melts. Within-plate picrites are pooled products of larger degrees of fractional melting in columnar melting regimes. A significant control on PGE fractionation in mantle-derived magmas is exerted by residual alloy or platinum group minerals in their source. At low pressures (e.g., MORB genesis) the mantle residual to partial melting retains primitive mantle inter-element ratios and abundances of PGE until sulfide has been completely dissolved but then evolves to extremely high Pt/Pd and low Pd/Ir because Pt and Ir alloys form in the restite. During melting at high pressure to form picrites or komatiites Ir alloy appears as a restite phase but Pt alloy is not stable due to the large effect of pressure on fS2, and of temperature on fO2 along an internal oxygen buffer, which causes large increases in alloy solubility. The magmas parental to the Bushveld Complex of South Africa appear, at least in part, to be partial melts of mantle that has previously been melted to the point of total sulfide exhaustion at low pressure, closely resembling mantle xenoliths of the Kaapvaal craton. Using the new extremely large DPGEsul the world-class Merensky Reef and UG2 Pt deposits of the Bushveld Complex can readily be modeled as the result of sulfide saturation due to mixing of magmas with unremarkable PGE contents, obviating the need to postulate anomalously PGE-rich parent magmas or hydrothermal inputs to the deposits.

Mungall, James E.; Brenan, James M.

2014-01-01

215

Platinum group element behaviour and thermochemical constraints in the ultrabasic basic complex of the Vizcaino Peninsula, Baja California Sur, Mexico  

NASA Astrophysics Data System (ADS)

The Vizcaino complex is characterized by tectonised harzburgites overlain by serpentinized dunite bodies and wherlites layers containing several cumulate chromitite deposits and by fractional crystallization sequences: cyclic repetititons of dunites, pyroxenites with pegmatoidal textures, and gabbros overlain by a succession of gabbronorites to diorites in which olivine is followed by pyroxene and by plagioclase. Enriched sulfide horizons generally associated with pegmatoidal rocks are lacking. The fractionation of platinum-group element (PGE) displays evidence of erratic dispersion throughout the intrusion. PGE patterns of chromitites show high Ir and Ru contents, relatively high Rh content and an unusual Pt-Pd depletion lower than in ophiolitic chromitites. These chromitites do not contain laurite-type sulfides, which are commonly observed in association with Os-Ir-Ru alloys. Dunites show relatively flat patterns and gabbros present typical trends with depletions in the Iridium-group (IPGE) relative to PPGE. Ru, Rh, and especially Ir are very low in these silicate rocks, indicating the precipitation of these elements during the earliest stages of fractional crystallization and their concentration in chromitites. Spilitized dolerite dykes from the metamorphic basement show significant PGE enrichments similar to those of gabbros. Based on our previous thermochemical data, an extremely low fS 2 (<10 -2 atm) was in equilibrium with the silicate melt as indicated by the absence of laurite included in chromitites. In the absence of complexation of Pt (+Pd) by sulfur in the early stage of magmatic differentiation, a complexation of these elements by Cl as chloride complexes in a Cl-rich fluid phase may be expected. This hypothesis is reinforced by the notable absence of any sulfide horizon throughout the intrusion. Part of precious metals (Pt+Pd+Au) may have been remobilized at low temperature and transported as chloride or hydroxide complexes by fluid phases introduced during low-grade metamorphic processes or later during deformation events. In this interpretation, the erratic behaviour of PGE at Vizcaino was partially controlled by solubilities of Pt and Pd as chloride complexes at magmatic temperatures as early as chromite crystallization and the control of local saturation of the magma by variation of fS 2 was overshadowed.

Vatin-Perignon, N.; Amossé, J.; Radelli, L.; Keller, F.; Castro Leyva, T.

2000-07-01

216

Alpha spectroscopy of nuclides produced in the interaction of 5 GeV protons with heavy element targets  

NASA Astrophysics Data System (ADS)

Alpha particle energies were redetermined to an accuracy of 2 to 5 keV for a group of 40 neutron-deficient nuclides with atomic numbers ranging from 65 to 88. Improved half-life values were measured for 10 of these nuclides. Weightless samples containing mixtures of these activities were prepared by use of the helium jet transport technique to remove spallation and fragmentation products recoiling from targets of U, Th, Au, and Ta bombarded with 5 GeV protons. Experimental and calibration techniques are discussed in detail. Implications of the results for the mechanism of reaction of 5 GeV protons with complex targets are briefly discussed. RADIOACTIVITY 5 GeV p + U, Th, Au, Ta; separated recoil products by helium jet; measured E?, t12 151Dy, 154Er, 150Dy, 152Ho, 152Hom, 151Ho, 151Hom, 153Er, 152Er, 154Tm, 154Tmm, 153Tm, 179Pt, 155Yb, 178Pt, 177Pt, 176Pt, 199Pom, 198Po, 212Fr, 197Pom, 213Fr, 212Ra; measured E? 149Tb, 211At, 204Fr, 222Ac, 217At, 218Rn, 219Fr, 211Po, 214Po, 217Rn, 216At, 218Fr, 215At, 213Po, 212Po, 214At, 211Pom; reaction mechanisms discussed.

Bowman, J. David; Eppley, Richard E.; Hyde, Earl K.

1982-02-01

217

Experimental investigation and 3D finite element prediction of the heat affected zone during laser assisted machining of Ti6Al4V alloy  

Microsoft Academic Search

An experimental study was conducted to characterize the heat affected zone produced when laser heating a Ti6Al4V alloy plate workpiece. The emissivity and absorptivity of the Ti6Al4V alloy were determined experimentally. A 3D transient finite element method for a moving Gaussian laser heat source was developed to predict the depth and width of the heat affected zone on the Ti6Al4V

Jihong Yang; Shoujin Sun; Milan Brandt; Wenyi Yan

2010-01-01

218

Inter-Division IV-V / Working Group Ap and Related Stars  

NASA Astrophysics Data System (ADS)

The diversity of physical phenomena embraced by the study of Chemically Peculiar (CP) stars results in an associated research community with interests that are equally diverse. This fact became once more evident during the CP#Ap Workshop that took place in Vienna (Austria) in September 2007, and which gathered over 80 members of this research community. Besides the excellent scientific outcome of the meeting, during the workshop the community had the opportunity to discuss its organization and plans for the future. Following on those plans, the Working Group has submitted a proposal for a Joint Discussion during the IAU XXVII General Assembly, in Rio de Janeiro, which has meanwhile been accepted. Moreover, through an ApN newsletter forum, the Working Group has compiled requests from the community concerning atomic and related data. These requests have been put together and will be shared with Commission 14.

Cunha, Margarida S.; Weiss, Werner W.; Dworetsky, Michael M.; Kochukhov, Oleg; Kupka, Friedrich; Leblanc, Francis; Monier, Richard; Paunzen, Ernst; Piskunov, Nikolai E.; Shibahashi, Hiromoto; Smalley, Barry; Ziznovsky, Jozef

219

Soil-water coupling finite element analysis on seismic enhancement effect of group-pile foundation with ground improvement  

NASA Astrophysics Data System (ADS)

In this paper, soil-water coupling finite element analyses on a real-scale field test of 9-pile foundation subjected to horizontal cyclic loading is conducted at first using a program named as DBLEAVES (Ye, 2007). In the analysis, nonlinear behaviors of ground and piles are described by cyclic mobility model (Zhang et al, 2007) and axial force dependent model (AFD model) proposed by Zhang and Kimura (2002) which can take into consideration of axial-force dependency in the nonlinear moment-curvature relations. After the applicability of the proposed numerical method is verified by comparing the numerical results with the field test results, numerical experiments on seismic enhancement effect of group-pile foundation with ground improvement are conducted both in static loading and dynamic loading. In finding out the optimum pattern of ground improvement around existing pile foundation, three influential factors are considered in the numerical experiments, that is, the size, the location and the shape of ground-improvement zone around the pile group.

Zhang, F.; Jin, Y.; Bao, X.; Kondo, Y.; Nakamura, K.

2010-06-01

220

Vicinal proton-proton coupling constants V. Couplings to methyl groups  

Microsoft Academic Search

A study of the substituent effects upon the vicinal proton-proton coupling 3JMe to methyl groups has been carried out from data sets of experimental and calculated 3JMe couplings in ethane, denoted 3J0Me, monosubstituted ethanes, denoted 3JxMe, and 1, 1-disubstituted ethabes, denoted 3JxyMe, with substituents of the second (C,N O and F), third (Si, P, S and Cl), fourth (Ge, As,

Joaquin Guilleme; Jesus San Fabian; Ernesto Diez

1997-01-01

221

Inter-Division IV-V-IX / Working Group Standard Stars  

NASA Astrophysics Data System (ADS)

The Working Group, created in 1982 during the IAU General Assembly in Patras (Greece), exists to examine, organize, and coordinate the various sets of standard stars for the fields in which they are used: radial velocities, spectral classification, photometry, astrometry, and others. It also provides a forum for discussion and education. All those working with and upon standard stars are considered members of the WG.

Corbally, Christopher J.; Gray, Richard O.

222

“Structural Transformations in Ceramics: Perovskite-like Oxides and Group III, IV, and V Nitrides”  

SciTech Connect

1 Overview of Results and their Significance Ceramic perovskite-like oxides with the general formula (A. A0. ...)(B. B0. ...)O3and titanium-based oxides are of great technological interest because of their large piezoelectric and dielectric response characteristics.[1] In doped and nanoengineered forms, titantium dioxide finds increasing application as an organic and hydrolytic photocatalyst. The binary main-group-metal nitride compounds have undergone recent advancements of in-situ heating technology in diamond anvil cells leading to a burst of experimental and theoretical interest. In our DOE proposal, we discussed our unique theoretical approach which applies ab initio electronic calculations in conjunction with systematic group-theoretical analysis of lattice distortions to study two representative phase transitions in ceramic materials: (1) displacive phase transitions in primarily titanium-based perovskite-like oxide ceramics, and (2) reconstructive phase transitions in main-group nitride ceramics. A sub area which we have explored in depth is doped titanium dioxide electrical/optical properties.

James P. Lewis (PI, former Co-PI), Dorian M. Hatch (Co-PI, former PI), and Harold T. Stokes (Co-PI)

2006-12-31

223

Major and trace element composition of copiapite-group minerals and coexisting water from the Richmond mine, Iron Mountain, California  

USGS Publications Warehouse

Copiapite-group minerals of the general formula AR4 (SO4)6(OH)2??nH2O, where A is predominantly Mg, Fe2+, or 0.67Al3+, R is predominantly Fe3+, and n is typically 20, are among several secondary hydrous Fe sulfates occurring in the inactive mine workings of the massive sulfide deposit at Iron Mountain, CA, a USEPA Superfund site that produces extremely acidic drainage. Samples of copiapite-group minerals, some with coexisting water, were collected from the Richmond mine. Approximately 200 mL of brownish pore water with a pH of -0.9 were extracted through centrifugation from a 10-L sample of moist copiapite-group minerals taken from pyritic muck piles. The pore water is extremely rich in ferric iron (Fe3+=149 g L-1, FeT=162 g L-1 and has a density of 1.52 g mL-1. The composition of the pore water is interpreted in the context of published phase relations in the Fe2O3- SO3-H2O system and previous work on the chemistry of extremely acid mine waters and associated minerals in the Richmond mine. Two distinct members of the copiapite mineral group were identified in the samples with coexisting water: (1) abundant magnesiocopiapite consisting of platy crystals 10 to 50 ??m and (2) minor aluminocopiapite present as smaller platy crystals that form spheroidal aggregates. The average composition (n=5) of the magnesiocopiapite is (Mg0.90Fe0.172+ Zn0.02Cu0.01)???1.10(Fe3.833+Al0.09)???3.92(SO4) 6.00(OH)1.96??20H2O. Bulk compositions determined by digestion and wet-chemical analysis are consistent with the microanalytical results. These results suggest that magnesiocopiapite is the least soluble member of the copiapite group under the prevailing conditions. Micro-PIXE analysis indicates that the copiapite-group minerals in this sample sequester Zn (average 1420 ppm), with lesser amounts of Cu (average 270 ppm) and As (average 64 ppm). ?? 2004 Elsevier B.V. All rights reserved.

Jamieson, H. E.; Robinson, C.; Alpers, C. N.; McCleskey, R. B.; Nordstrom, D. K.; Peterson, R. C.

2005-01-01

224

Porous Silica Sol-Gel Glasses Containing Reactive V2O5 Groups  

NASA Technical Reports Server (NTRS)

Porous silica sol-gel glasses into which reactive vanadium oxide functional groups incorporated exhibit number of unique characteristics. Because they bind molecules of some species both reversibly and selectively, useful as chemical sensors or indicators or as scrubbers to remove toxic or hazardous contaminants. Materials also oxidize methane gas photochemically: suggests they're useful as catalysts for conversion of methane to alcohol and for oxidation of hydrocarbons in general. By incorporating various amounts of other metals into silica sol-gel glasses, possible to synthesize new materials with broad range of new characteristics.

Stiegman, Albert E.

1995-01-01

225

H I Studies of the Sculptor Group Galaxies. V - NGC 253  

NASA Astrophysics Data System (ADS)

A VLA HI map was made of NGC 253. In this study, there is a continuum map (ngc0253.con), an HI data cube (ngc0253.cub), and moment maps (ngc0253.m0 = total HI, ngc0253.m1 = velocity field, and ngc0253.m2 = second moment). These maps have been used in an extensive dynamical and kinematical study of the Sculptor Group galaxies. The images and related TeX file come from the NRAO CDROM "Images From the Radio Universe" (c. 1992 National Radio Astronomy Observatory, used with permission).

Puche, D.; Carignan, C.; van Gorkom, J. H.

1995-07-01

226

Two-step synthesis of multi-substituted amines by using an N-methoxy group as a reactivity control element.  

PubMed

Invited for the cover of this issue is the group of Prof. Noritaka Chida and Dr. Takaaki Sato at Keio University, Japan. The cover illustrates the- N-methoxy group as the reactivity control element to allow for beautiful chemical transformations to blossom in organic synthesis. Read the full text of the article at 10.1002/chem.201402231. PMID:24890036

Yoritate, Makoto; Meguro, Tatsuhiko; Matsuo, Naoya; Shirokane, Kenji; Sato, Takaaki; Chida, Noritaka

2014-06-23

227

v-src induction of the TIS10/PGS2 prostaglandin synthase gene is mediated by an ATF/CRE transcription response element.  

PubMed Central

We recently reported the cloning of a mitogen-inducible prostaglandin synthase gene, TIS10/PGS2. In addition to growth factors and tumor promoters, the v-src oncogene induces TIS10/PGS2 expression in 3T3 cells. Deletion analysis, using luciferase reporters, identifies a region between -80 and -40 nucleotides 5' of the TIS10/PGS2 transcription start site that mediates pp60v-src induction in 3T3 cells. This region contains the sequence CGTCACGTG, which includes overlapping ATF/CRE (CGTCA) and E-box (CACGTG) sequences. Gel shift-oligonucleotide competition experiments with nuclear extracts from cells stably transfected with a temperature-sensitive v-src gene demonstrate that the CGTCACGTG sequence can bind proteins at both the ATF/CRE and E-box sequences. Dominant-negative CREB and Myc proteins that bind DNA, but do not transactivate, block v-src induction of a luciferase reporter driven by the first 80 nucleotides of the TIS10/PGS2 promoter. Mutational analysis distinguishes which TIS10/PGS2 cis-acting element mediates pp60v-src induction. E-box mutation has no effect on the fold induction in response to pp60v-src. In contrast, ATF/CRE mutation attenuates the pp60v-src response. Antibody supershift and methylation interference experiments demonstrate that CREB and at least one other ATF transcription factor in these extracts bind to the TIS10/PGS2 ATF/CRE element. Expression of a dominant-negative ras gene also blocks TIS10/PGS2 induction by v-src. Our data suggest that Ras mediates pp60v-src activation of an ATF transcription factor, leading to induced TIS10/PGS2 expression via the ATF/CRE element of the TIS10/PGS2 promoter. This is the first description of v-src activation of gene expression via an ATF/CRE element. Images

Xie, W; Fletcher, B S; Andersen, R D; Herschman, H R

1994-01-01

228

Red/near-infrared luminescence tuning of group-14 element complexes of dipyrrins based on a central atom.  

PubMed

A dipyrrin complex has been one of the most utilized fluorescent dyes, and a variety of dipyrrin complexes show intriguing functions based on the various coordination structures of the central element. We now report the synthesis, structure, and photophysical properties of germanium and stannane complexes of the N2O2-type tetradentate dipyrrin, L·Ge and L·Sn, which are heavier analogues of the previously reported dipyrrin silicon complex, L·Si. The central group-14 atoms of the monomeric complexes have geometries close to trigonal bipyramidal (TBP), in which the contribution of the square-pyramidal (SP) character becomes higher as the central atom is heavier. Interestingly, L·Sn formed a dimeric structure in the crystal. All complexes L·Si, L·Ge, and L·Sn showed a fluorescence in the red/NIR region. Fluorescence quantum yields of L·Ge and L·Sn are higher than that of L·Si. These results indicated that the central atom on the dipyrrin complexes contributes not only to the geometry difference but also to tuning the fluorescence properties. PMID:24422462

Yamamura, Masaki; Albrecht, Marcel; Albrecht, Markus; Nishimura, Yoshinobu; Arai, Tatsuo; Nabeshima, Tatsuya

2014-02-01

229

The chemistry of the superheavy elements. II. The stability of high oxidation states in group 11 elements: Relativistic coupled cluster calculations for the di-, tetra- and hexafluoro metallates of Cu, Ag, Au, and element 111  

NASA Astrophysics Data System (ADS)

The stability of the high oxidation states +3 and +5 in Group 11 fluorides is studied by relativistic Møller-Plesset (MP) and coupled cluster methods. Higher metal oxidation states are stabilized by relativistic effects. As a result, the hexafluoro complex of the Group 11 element with nuclear charge 111 and oxidation state +5 is the most stable compared to the other congeners. The results also suggest that AgF6- is thermodynamically stable and, therefore, it might be feasable to synthesize this compound. For the copper fluorides we observe very large oscillations in the Møller-Plesset series up to the fourth order. Nonrelativistic calculations lead to the expected trend in the metal-fluorine bond distances for the MF2- compounds, CuF2-

Seth, Michael; Cooke, Fiona; Schwerdtfeger, Peter; Heully, Jean-Louis; Pelissier, Michel

1998-09-01

230

[Transposition of the composite synthetic transposon TnV (Tn5-Rep(pSC101)) is accompanied by the formation of the mini-plasmid pTnV, containing defective Is50-elements].  

PubMed

Using thermoelimination (at 42 degrees C) of the thermoinducible coliphage P1tsCmr omega::TnV (TnV is a Tn5 derivative which contains the replication origin (Rep) of plasmid pSC101), more than 110 KmrCms Escherichia coli K12 clones were selected. It was supposed that the KmrCms phenotype could result only from insertion of TnV (Kmr) into E. coli chromosome and the loss of phage (Cms). It was found that the majority of KmrCms clones (35-90%) contained miniplasmids. Their molecular sizes did not exceed the TnV size (6.1 kb). The formation of miniplasmids called pTnV was observed both in RecA+ cells (C600) and in RecA- (HB101), more often in the latters. Interestingly, that miniplasmids of only several molecular sizes were detected: from 6.1 kb (pTnV60) to 4.35 kb (pTnV43). A restriction analysis showed that DNA of the majority of pTnV plasmids had varying deletions (0.3-1.3 kb) of mainly IS50L element which together with IS50R flank TnV. Very low transposition frequencies (approx. 10(-8) Kmr transconjugants per transferred R388) of all pTnV types (including pTnV60 plasmids containing probably microdeletions of the joining "outside" IS50's ends) suggest that pTnV plasmids are not intermediates in TnV transposition. Possibly the circularized TnV derivatives (pTnV's) are side products of the transposition resulting from the abortive attempts of an excised and autonomous transposon molecule to insert into itself. In the present paper the possible mechanisms of the origin of limited pTnV type numbers are also discussed. PMID:1963206

Borovok, I A

1990-01-01

231

Dust and molecules in the Local Group galaxy NGC 6822. III. The first-ranked HII region complex Hubble V  

NASA Astrophysics Data System (ADS)

We present maps of the first-ranked HII region complex Hubble V in the metal-poor Local Group dwarf galaxy NGC 6822 in the first four transitions of 12CO, the 158 mu m transition of C+, the 21-cm line of HI, the Pabeta line of HII, and the continuum at 21 cm and 2.2 mu m wavelengths. We have also determined various integrated intensities, notably of HCO+ and near-IR H2 emission. Although the second-ranked HII region Hubble X is located in a region of relatively strong HI emission, our mapping failed to reveal any significant CO emission from it. The relatively small CO cloud complex associated with Hubble V is comparable in size to the ionized HII region. The CO clouds are hot (Tkin = 150 K) and have high molecular gas densities (n( H2) ~ 104 cm-3). Molecular hydrogen probably extends well beyond the CO boundaries. C+ column densities are more than an order of magnitude higher than those of CO. The total mass of the complex is about 106 Msun and molecular gas accounts for more than half of this. The complex is excited by luminous stars reddened or obscured at visual, but apparent at near-infrared wavelengths. The total embedded stellar mass may account for about 10% of the total mass, and the mass of ionized gas for half of that. Hubble V illustrates that modest star formation efficiencies may be associated with high CO destruction efficiencies in low-metallicity objects. The analysis of the Hubble V photon-dominated region (PDR) confirms in an independent manner the high value of the CO-to- H2 conversion factor X found earlier, characteristic of starforming low-metallicity regions.

Israel, F. P.; Baas, F.; Rudy, R. J.; Skillman, E. D.; Woodward, C. E.

2003-01-01

232

Effect of isothermal forging on microstructure and fatigue behavior of blended elemental Ti-6Al-4V powder compacts  

NASA Astrophysics Data System (ADS)

The effect of isothermal hot forging (IHF) on microstructure, pore closure, and tensile and fatigue properties of Ti-6A1-4V blended elemental cold pressed and sintered powder compacts was investigated. Two types of sponge fines were used: (a) high chloride produced by the Hunter sodium reduction process (HP) and (b) low chloride produced by the electrolytic process (EP). The as-sintered HP compacts were 99 pct dense while the EP compacts were only 92 pct dense. All sintered preforms were isothermally hot forged below the beta transus temperature and reached almost full density. The microstructure of the HP forged compacts consisted of fine equiaxed alpha, while the EP forged compacts exhibited a coarse lenticular alpha structure after 30 pct reduction and a partially recrystallized structure after 68 pct reduction. It was found that EP compacts forged to a 30 pct reduction exhibited a low fatigue limit of 172 MPa (25 ksi), since the lenticular alpha morphology and the residual porosity resulted in premature fatigue crack initiation. On the other hand, a higher fatigue strength of 485 MPa (70 ksi) was obtained for EP compacts forged to a 78 pct reduction due to the mixed equiaxed/lenticular alpha morphology as well as removal of stress concentration features such as interparticle pore interfaces.

Weiss, I.; Eylon, D.; Toaz, M. W.; Froes, F. H.

1986-03-01

233

Distribution of platinum-group elements and Os isotopes in chromite ores from Mayarí-Baracoa Ophiolitic Belt (eastern Cuba)  

NASA Astrophysics Data System (ADS)

The Mayarí-Baracoa ophiolitic belt in eastern Cuba hosts abundant chromite deposits of historical economic importance. Among these deposits, the chemistry of chromite ore is very variable, ranging from high Al (Cr#=0.43-0.55) to high Cr (Cr#=0.60-0.83) compositions. Platinum-group element (PGE) contents are also variable (from 33 ppb to 1.88 ppm) and correlate positively with the Cr# of the ore. Bulk PGE abundances correlate negatively with the Pd/Ir ratio showing that chromite concentrates mainly Os, Ir and Ru which gives rise to the characteristic negatively sloped, chrondrite-normalized PGE patterns in many chromitites. This is consistent with the mineralogy of PGEs, which is dominated by members of the laurite-erlichmanite solid solution series (RuS2-OsS2), with minor amounts of irarsite (IrAsS), Os-Ir alloys, Ru-Os-Ir-Fe-Ni alloys, Ni-Rh-As, and sulfides of Ir, Os, Rh, Cu, Ni, and/or Pd. Measured 187Os/188Os ratios (from 0.1304 to 0.1230) are among the lower values reported for podiform chromitites. The 187Os/188Os ratios decrease with increasing whole-rock PGE contents and Cr# of chromite. Furthermore, ?Os values of all but one of the chromitite samples are negative indicating a subchondiritc mantle source. ?Os decrease with increasing bulk Os content and decreasing 187Re/188Os ratios. These mineralogical and geochemical features are interpreted in terms of chromite crystallization from melts varying in composition from back-arc basalts (Al-rich chromite) to boninites (Cr-rich chromite) in a suprasubduction zone setting. Chromite crystallization occurs as a consequence of magma mixing and assimilation of preexisting gabbro sills at the mantle-crust transition zone. Cr#, PGE abundances, and bulk Os isotopic composition of chromitites are determined by the combined effects of mantle source heterogeneity, the degree of partial melting, the extent of melt-rock interactions, and the local sulfur fugacity. Small-scale (?m to cm) chemical and isotopic heterogeneities in the platinum-group minerals are controlled by the mechanism(s) of chromite crystallization in a heterogeneous environment created by the turbulent regime generated by successive inputs of different batches of melt.

Gervilla, F.; Proenza, J. A.; Frei, R.; González-Jiménez, J. M.; Garrido, C. J.; Melgarejo, J. C.; Meibom, A.; Díaz-Martínez, R.; Lavaut, W.

2005-12-01

234

Contribution a l'extraction liquide-liquide et a la separation de certains elements du groupe VIII, notamment du ruthenium, par des synergetiques polyimines aromatiques echangeur cationiques micellaires. (Liquid-liquid extraction and separation of VIII group elements, especially ruthenium, by synergic combinations or aromatic polyimines and micellar cationic exchangers).  

National Technical Information Service (NTIS)

This thesis aims to characterize and to quantify the chemical equilibria involved in d-elements liquid-liquid extraction systems, especially elements belonging to the VIII group (Fe, Ni, Co, Ru, Rh, Pd, Pt). These systems are composed of synergic combinat...

X. Vitart

1991-01-01

235

Summary of the 200{times}200 GeV {mu}{sup +}{minus}{mu}{sup {minus}} collider working group  

SciTech Connect

We report the discussions and some preliminary results from the sessions of the 200{times}200 GeV {mu}{sup +}{minus}{mu}{sup {minus}} Collider working group. The physics motivation for such a {open_quote}{open_quote}medium-energy{close_quote}{close_quote} collider is discussed. Possible parameters for such a system are described, and compared with higher-energy systems. Relatively-high luminosities (L{approximately}10{sup 33} cm{sup {minus}2}s{sup {minus}1}) appear possible. Modifications of existing facilities to obtain medium-energy {mu}{sup +}{minus}{mu}{sup {minus}} collisions are discussed. Other discussion topics ({mu}-p colliders, low-energy {mu} sources, etc.) are summarized. {copyright} {ital 1995 American Institute of Physics.}

Neuffer, D.; Whittum, D.; Bombade, P.; Cline, D.; Jackson, G.; McIntyre, P.; Peters, G.; Sasaki, M.; Summers, D.; Yokoya, K.

1996-01-01

236

Sniffing for Clues to the Dinosaurs Demise: Measurement of Osmium Isotope Compositions and Platinum Group Element Abundances in Volcanic Emissions  

NASA Astrophysics Data System (ADS)

Platinum Group Elements (PGE: Os, Ir, Rh, Ru, Pt, Pd) and osmium isotopes measured in marine and terrestrial sediment, snow and ice records are important paleo-tracers of riverine, hydrothermal, extraterrestrial, volcanic and anthropogenic inputs into the global surficial environment. For instance, the marine Os isotope record across the Cretaceous-Tertiary Boundary (KTB) indicates that the onset of the main phase of Deccan volcanism and the transient late Maastrichtian warming preceded the large extraterrestrial impact and the related KTB mass extinction by several hundred thousand years [Ravizza and Peucker-Ehrenbrink, 2003]. Distinguishing extraterrestrial from volcanic PGE sources has been difficult due to the similarity in Os isotopic compositions, complex PGE fractionations, and our lack of knowledge of the Os isotopic composition and PGE abundances in volcanic aerosols. These difficulties have fueled vigorous debate about extraterrestrial vs. volcanic triggers of mass extinctions in the geologic record. To assess the volcanic contribution to the global Re-Os-PGE cycle we have initiated a study of Os isotopic compositions and PGE abundances in volcanic emissions from volcanoes around the globe. Here we report preliminary data on PGE abundances and Os isotopes measured in gas and aerosol filter samples from Vulcan Masaya, Nicaragua and Mt Etna, Italy. Samples were analyzed by ID-ICPMS (ThermoFinnigan ELEMENT 2 and NEPTUNE) at the Woods Hole Oceanographic Institution. Osmium isotope compositions of the filters are unradiogenic (0.1272 to 0.187). Osmium concentrations range from 28 to 97 pg/cubic meter and are 3-4 orders of magnitude lower than those measured by Krahenbuhl et al. [1992] during the spring 1984 eruption of Mauna Loa just after the lava fountaining phase. Normalized PGE abundance patterns are fractionated relative to carbonaceous chondrites and two important features distinguish the pattern from other important PGE sources: 1) Os/Ir is much higher than that of the continental crust, the mantle and extraterrestrial matter; and 2) Pt/Pd is much lower than that of the continental crust, mantle, extraterrestrial matter and catalytic converters. If these PGE patterns from Masaya and Etna are typical of volcanic emissions worldwide they indicate that volcanic emission PGE patterns are distinct from the globally integrated KTB patterns [Tredoux et al. 1989; Evans et al., 1993] and that a volcanic source is not the cause of the elevated PGE abundances across the KTB. The PGE pattern of volcanic emissions is also different from catalytic converters enabling us to distinguish between volcanic sources and contamination from catalytic converters in places such as the Greenland Ice sheet [Barbante et al., 2001]. While these data have important implications for understanding the contribution of volcanic emissions to the global Re-Os-PGE cycles they need to be augmented with further analyses from other volcanoes.

Sims, K. W.; Peucker-Ehrenbrink, B.; Mather, T.; Pyle, D.; Martin, R.; Gauthier, P.; Aiuppa, A.

2005-12-01

237

Search for Platinum-Group Element Nuggets in Terrestrial Rock Samples Using Synchrotron Radiation X-ray Absorption and Fuorescence Imaging  

Microsoft Academic Search

Concentrations and isotopic ratios of platinum group elements (PGEs) in the Earth's mantle are strongly controlled by chemical differentiation processes involving both silicate and metallic phases, and therefore are instrumental for understanding the differentiation and evolution of the Earth's interior. However, interpretation of the geochemical data of PGEs has been equivocal because the main host phases for PGEs in the

T. Kogiso; K. Suzuki; T. Suzuki; K. Uesugi; A. Takeuchi; Y. Suzuki

2006-01-01

238

Distribution of 23 elements in the kidney, liver and lungs of workers from a smeltery and refinery in North Sweden exposed to a number of elements and of a control group.  

PubMed

The levels of antimony, arsenic, cadmium, caesium, chromium, cobalt, copper, gold, iron, lanthanum, lead, manganese, mercury, molybdenum, phosphorus, rubidium, scandium, selenium, silver, tellurium, tin, tungsten and zinc in the kidney, liver and lungs of autopsy specimens from exposed workers in North Sweden, as well as from a control group, have been assayed quantitatively. The workers had been exposed to several elements and their compounds, e.g. lead, mercury, arsenic and cadmium, for long periods in arsenic, lead or selenium plants and in a lead or copper smelter. The chemical analysis was by neutron activation analysis and atomic absorption spectrophotometry. Median levels of antimony, arsenic, cadmium, chromium cobalt, lanthanum, lead or selenium in kidney, liver or lungs in the exposed worker group were found to be about 2 to 16 times as great as the corresponding levels for the control group. Long biological half-life values were observed for these elements, especially in lung tissue. PMID:7433969

Brune, D; Nordberg, G; Wester, P O

1980-09-01

239

Platinum-group element abundance and distribution in chromite deposits of the Acoje Block, Zambales Ophiolite Complex, Philippines  

USGS Publications Warehouse

Platinum-group elements (PGE) occur in ore-grade concentration in some of the chromite deposits related to the ultramafic section of the Acoje Block of the Zambales Ophiolite Complex. The deposits are of three types: Type 1 - associated with cumulate peridotites at the base of the crust; Type 2 - in dunite pods from the top 1 km of mantle harzburgite; and Type 3 - like Type 2, but in deeper levels of the harzburgite. Most of the deposites have chromite compositions that are high in Cr with Cr/(Cr + Al) (expressed as chromium index, Cr#) > 0.6; high-Al (Cr# Pd, thought to be characteristic of PGE-barren deposits) and positive slope (Ir < Pd, characteristic of PGE-rich deposits). Iridium, Ru and Os commonly occur as micron-size laurite (sulfide) inclusions in unfractured chromite. Laurite and native Os are also found as inclusions in interstitial sulfides. Platinum and Pd occur as alloy inclusions (and possibly as solid solution) in interstitial Ni-Cu sulfides and as tellurobismuthides in serpentine and altered sulfides. Variability of PGE distribution may be explained by alteration, crystal fractionation or partial melting processes. Alteration and metamorphism were ruled out, because PGE contents do not correlate with degree of serpentinization or the abundance and type (hydroxyl versus non-hydroxyl) of silicate inclusions in chromite. Preliminary Os isotopic data do not support crustal contamination as a source of the PGEs in the Acoje deposits. The anomalous PGE concentrations in Type 1 high-Cr chromite deposits are attributed to two stages of enrichment: an early enrichment of their mantle source from previous melting events and a later stage of sulfide segregation accompanying chromite crystallization. High-Al chromite deposits which crystallized from basalts derived from relatively low degrees of melting owe their low PGE content to partitioning of PGEs in sulfides and alloys that remain in the mantle. High-Cr deposits crystallized from melts that were previously enriched with PGEs during early melting events of their mantle source; Pt and Pd ore concentrations (ppm levels) are attained by segregation of magmatic sulfides. The Acoje deposits indicate that ophiolites are a potential economic source of the PGEs. ?? 1990.

Bacuta, Jr. , G. C.; Kay, R. W.; Gibbs, A. K.; Lipin, B. R.

1990-01-01

240

Ni, Cu, Au, and platinum-group element contents of sulphides associated with intraplate magmatism: A synthesis  

USGS Publications Warehouse

The tectonic setting of intraplate magmas, typically a plume intersecting a rift, is ideal for the development of Ni - Cu - platinum-group element-bearing sulphides. The plume transports metal-rich magmas close to the mantle - crust boundary. The interaction of the rift and plume permits rapid transport of the magma into the crust, thus ensuring that no sulphides are lost from the magma en route to the crust. The rift may contain sediments which could provide the sulphur necessary to bring about sulphide saturation in the magmas. The plume provides large volumes of mafic magma; thus any sulphides that form can collect metals from a large volume of magma and consequently the sulphides will be metal rich. The large volume of magma provides sufficient heat to release large quantities of S from the crust, thus providing sufficient S to form a large sulphide deposit. The composition of the sulphides varies on a number of scales: (i) there is a variation between geographic areas, in which sulphides from the Noril'sk - Talnakh area are the richest in metals and those from the Muskox intrusion are poorest in metals; (ii) there is a variation between textural types of sulphides, in which disseminated sulphides are generally richer in metals than the associated massive and matrix sulphides; and (iii) the massive and matrix sulphides show a much wider range of compositions than the disseminated sulphides, and on the basis of their Ni/Cu ratio the massive and matrix sulphides can be divided into Cu rich and Fe rich. The Cu-rich sulphides are also enriched in Pt, Pd, and Au; in contrast, the Fe-rich sulphides are enriched in Fe, Os, Ir, Ru, and Rh. Nickel concentrations are similar in both. Differences in the composition between the sulphides from different areas may be attributed to a combination of differences in composition of the silicate magma from which the sulphides segregated and differences in the ratio of silicate to sulphide liquid (R factors). The higher metal content of the disseminated sulphides relative to the massive and matrix sulphides may be due to the fact that the disseminated sulphides equilibrated with a larger volume of magma than massive and matrix sulphides. The difference in composition between the Cu- and Fe-rich sulphides may be the result of the fractional crystallization of monosulphide solid solution from a sulphide liquid, with the Cu-rich sulphides representing the liquid and the Fe-rich sulphides representing the cumulate.

Barnes, S. -J.; Zientek, M. L.; Severson, M. J.

1997-01-01

241

Concentration and distribution of platinum group elements (Pt, Pd, Rh) in airborne particulate matter in Frankfurt am Main, Germany.  

PubMed

The concentrations and distribution of platinum group elements (Pt, Pd, Rh) in airborne particulate matter were studied in a period of one year from August 2001 to July 2002 in urban and in nonurban areas. Airborne dust samples were collected as a total amount (particles with an aerodynamic diameter <22 microm) and classified using an eight-stage Andersen impactor (<10 microm) at three locations with different traffic density roads in the Frankfurt am Main and nonurban areas. Sampling at the three locations was performed simultaneously for total airborne dust and fractionated airborne dust. Pd was determined by total reflection X-ray fluorescence after Hg coprecipitation. Pt and Rh were analyzed by adsorptive striping voltammetry after HPA digestion. The results show that the PGE concentrations in airborne samples depend on the traffic density. The highest PGE concentrations in air were found in the vicinity of major roads with heavy traffic, and the lowest ones were found in the nonurban area. The presence of PGE at the sampling station relatively free of traffic in a nonurban area hints to a transport of some of the emitted PGE from the city to this station by wind. At all three sampling locations, a heterogeneous distribution of the Pd, Pt, and Rh concentrations during the sampling year can be observed. The sum of PGE concentrations in total airborne dust is comparable with the sum of impactor samples. However, the concentration of Pt and Rh in total airborne dust (<22 microm) is on average higher than in impactor samples (<10 microm). On the contrary, Pd concentration is higher in impactor samples in most cases. The airborne PGE distribution is dominated by Pt, followed by Pd and Rh. The impactor samples are dominated by Pd, followed by Pt and Rh. This fact indicates that palladium occurs mainly in relatively fine airborne particles. The main fraction of PGE is found on average in particle sizes between 1.1 and 4.7 microm. Knowledge of the size distribution of particles containing PGE is important with respect to risk assessment of human inhalation. PMID:15074676

Zereini, Fathi; Alt, Friedrich; Messerschmidt, Jürge; von Bohlen, Alex; Liebl, Karlheinz; Püttmann, Wilhelm

2004-03-15

242

Do The Concentrations Of Platinum Group Elements In The Younger Dryas Black Layer Really Support An Extraterrestrial Origin?  

NASA Astrophysics Data System (ADS)

An enigmatic carbon-rich black layer, of possible worldwide occurrence, is interpreted to indicate an extraterrestrial impact around 12.9 ka, a period coeval with the Younger Dryas (YD) environmental changes (Firestone et al. 2007, PNAS 104). This interpretation is based on the possible identification of a series of markers postulated to be of impact origin, such as magnetic grains and microspherules, charcoal, soot, C- spherules, nanodiamonds, fullerenes with extraterrestrial He and elevated concentrations of Ir. Among these markers, only the elevated Ir concentration is a non-ambiguous impact indicator. In early 2007, one of us (PC) measured the concentration of platinum group elements (including Ir) in 4 samples of this black layer. Allen West provided the samples along with their Ir concentrations. The samples originated from Howard Bay, NC (level HB-11D2) and Blackwater Draw, NM (levels BW-DT, D/C and BW-B/A), and were supposed to contain 15 ng/g Ir (<150 micron magnetic fraction), 2.0 ng/g Ir (bulk sediment), 2.25 ng/g Ir (bulk sediment) and <0.1 ng/g Ir (bulk sediment) respectively. In Table 1 of Firestone et al. (2007) the Blackwater Draw sample contains 2.3 ng/g Ir, and the separated magnetic fraction rises up 24 ng/g. The obtained results showed that none of the 4 samples yielded PGE concentrations above 0.5 ng/g. Considering the attention the claim of a possible YD impact has generated in the last year, we are currently reanalyzing these 4 samples of the black layer using high precision NiS fire-assay preconcentration combined with ICP-MS analyses. On proven crater melt rocks or impact layers, the quantitation limits reach: 0.06 ng/g Ru, 0.01 ng/g Rh, 0.14 ng/g Pd, 0.06 ng/g Ir, and 0.1 ng/g Pt, far below the Ir values claimed by Firestone et al. (2007). In addition, these 4 samples are being analyzed for Os isotopes, known to be most sensitive for the detection of minute amounts of extraterrestrial components (%<%%<%0.05 wt%) in impact layers. The results of these new analyses will confirm or not the extraterrestrial origin of the Younger Dryas C-rich black layer.

Claeys, P.; Paquay, F.; Goderis, S.; Vanhaecke, F.

2008-12-01

243

Elements’ important ranking of China drug safety management system: applying the non-structural fuzzy group decision method  

Microsoft Academic Search

Drug safety management is an important issue in China drug management system and attracts great attentions from the whole\\u000a society. In order to reduce drug incident, this study discusses some important elements associated with China drug safety\\u000a management system and analyzes the data collected by questionnaires. Besides, a methodology for rating the important elements\\u000a is described and applied. The non-structural

Xiaoping Zheng; Xiaocui Wang; Tingkuan Zhong

2010-01-01

244

Comparison of the group V and VI transition metal carbides for methane dry reforming and thermodynamic prediction of their relative stabilities  

Microsoft Academic Search

The group V and VI transition metal carbides have been prepared by CH4 TPR, and tested for the dry reforming of methane with carbon dioxide, at elevated pressure. Mo2C and WC were the most stable catalysts, while the group V metal carbides showed the stability order: vanadium \\u000a $${\\\\text{ >}}$$\\u000a niobium \\u000a $${\\\\text{ >}}$$\\u000a tantalum. Catalyst deactivation was due to carbide oxidation

Attila J. Brungs; Andrew P. E. York; Malcolm L. H. Green

1999-01-01

245

Platinum Group Element Distribution and Mineralogy of the Finero Chromitites: How Analytical Results Should be Supported by Mineralogical Observations  

NASA Astrophysics Data System (ADS)

The Finero phlogopite peridotite represents a metasomatized residual mantle harzburgite, ex-posed at the base of the lower-crust section, in the Ivrea Zone (Western Italian Alps). It forms the core of a concentrically zoned sequence of layered gabbro and pyroxenite, amphibole-rich peridotite, and gabbro. The phlogopite peridotite contains small-size podiform chromitites that represent a rare example of chromitites formed by metasomatic processes within the mantle. The available literature data on platinum group elements (PGE) for the Finero chromitites are fragmentary, due to high values of the detection limits for the analytical method. Therefore the trends of chondritic-normalized PGE patterns obtained from these data, remain undefined in most cases. Here we report the results of the Finero chromitites performed with a simple and very effective procedure for the determination of Ru, Rh, Pd, Re, Os, Ir and Pt concentration. Samples are spiked with enriched isotopes and digested in a HNO3/HCl (5+2) acid mixture at 300° C and 125 bar pressure in a high pressure asher (HPA-S, Anton Paar) for 4 to 12 hours. The PGEs are then measured in an ICP-MS after a simple on-line matrix removal determined with an ICP-MS system. The acid digestion procedure does not require an optimization for each chromite composition as it is required for the flux for NiS fire assay digestions. Our results, normalized to the mantle (ca. 0.085 CI chondrite) show a peculiar shape. Osmium, Ir, Ru are unfractionated (5-8 times the mantle concentration), forming flat patterns, whilst the content of Rh is quite high (about 10 times the mantle concentration) giving a positive anomaly in all the analyzed chromitites. Low contents of Pt > Pd (less than the mantle concentration) is reflected in a strong negative slope. Several polished sections, obtained from the same chromites have been investigated by reflected-light microscopy at 250-800x magnification. This "in situ" investigation identified more than 50 Platinum Group Minerals (PGM), that occur, in most cases, as small grains (less than 10 microns) included in the chromite crystals. Most of these PGM have been analyzed by electron microprobe analysis. The most abundant PGM is laurite that is accompanied by abundant cuprorhodsite and cuproiridsite. One alloy of Pt-Cu and one grain of Rh-Sb-S have been also analyzed. Hence, the relatively high Rh concentrations in these chromitites is supported by the presence of Rh bearing minerals, especially cuprorhodsite. The PGM population found in the Finero chromitites is thus consistent with the whole rock PGE analyses, being characterized by the presence of abundant Ru-Os-Ir-Rh minerals and the absence of Pd phases. The combination of mineralogical observations with chemical analytical data make the results credible and thus useful for geochemical interpretations. The distribution and mineralogy of PGE indicate that the chromite-PGE mineralization in the Finero complex significantly differs from that typical of ophiolitic mantle. This difference possibly reflects variations in the chemical and physical conditions of the chromite-forming system within sub-continental upper mantle compared with a sub-oceanic environment.

Meisel, T.; Zaccarini, F.; Garuti, G.; Stumpfl, E. F.

2004-05-01

246

The use of cation exchange matrix separation coupled with ICP-MS to directly determine platinum group element (PGE) and other trace element emissions from passenger cars equipped with diesel particulate filters (DPF)  

Microsoft Academic Search

Inductively coupled plasma-mass spectrometry coupled with cation exchange matrix separation has been optimised for the direct\\u000a determination of platinum group element (PGE) and trace element emissions from a diesel engine car. After matrix separation\\u000a method detection limits of 1.6 ng g?1 for Pd, 0.4 ng g?1 for Rh and 4.3 ng g?1 for Pt were achieved, the method was validated against the certified reference material BCR

Warren R. L. Cairns; Antonella De Boni; Giulio Cozzi; Massimo Asti; Edoardo Merlone Borla; Flavio Parussa; Ezio Moretto; Paolo Cescon; Claude Boutron; Jacopo Gabrieli; Carlo Barbante

2011-01-01

247

Solid-state 207pb nmr studies of lead-group 16 and mixedtransition-metal-lead-group 16 element-containing materials  

SciTech Connect

207Pb solid-state NMR studies have been conducted on binarylead-group 16 and mixed transition-metal/lead group 16 materials,correlating the NMR chemical shifts of the materials with theirstructures. The experimental results show that the 207Pb chemical shiftsare strongly influenced by the local electronic structure. Data arereported for lead selenide, lead selenate, calcium plumbate, strontiumplumbite, barium plumbite, lead borate, lead zirconate, lead tungstate,lead meta-tantalate, lead niobate, lead molybdate, lead meta-vanadate,lead sulfite, and lead sulfate.

Van Bramer, S.E.; Glatfelter, A.; Bai, S.; Dybowksi, C.; GNeue,G.; Perry, D.L.

2005-08-26

248

Synthesis, structures and bonding of superconducting barium vanadium sulfide and intermetallic solid state compounds of group 2, 3, 13, 14 and transition elements  

NASA Astrophysics Data System (ADS)

Superconducting transition is well known for the Chevrel phases M xMo6S8 and MxMo6Se 8 where M is dopant metal such as Pb, In, Tl and La. Not many ternary group 5 transition metal chalcogenides of similar composition, however, are known to be superconductors. The synthesis and observation of superconducting transition of the Ba doped compound BaxV6S8 (x = 0.45--0.48) is discussed. The electronic structure was analyzed using the tight-binding extended Huckel method. Results of Raman-scattering experiments are also discussed. BaGa4 possesses the most popular structure type in solid state chemistry. More than 600 compounds crystallize in this structure. Many compounds of this family exhibit interesting physical properties such as superconductivity, unusual magnetic behavior, valence fluctuation and heavy fermion phenomena. However, little had been reported about the physical properties of BaGa 4 itself. The single crystal growth, structural characterization, computational his, conductivity and AC susceptibility of crystalline BaGa4 is described. V-Ga binary system is of great interest because some compounds in this family are superconductors exhibiting high critical currents and fields. V 2Ga5 has been reported to show a superconducting transition from 2.1 K to 4.2 K,2,6 depending on the preparation procedure and sample quality. However, no single-crystal X-ray structure determination has been reported for this compound, and the full characterization of its superconducting transition has yet to be completed. The single crystal growth, structural determination, and computational study of Ga5V 2 are discussed. Resistivity and magnetization measurement results are also presented. Ternary intermetallic solid-state compounds of lanthanum, transition metal, and germanium have a wide range of technological applications (i.e., rechargeable cells) because of their interesting physical properties. Many compounds of this type with the stoichiometry LnxTyGe z (Ln = lanthanide, T = transition metal) have been synthesized. A few of them crystallize in orthorhombic lattices in which a transition metal forms a square lattice with capping germanium atoms on the square hollows. This structural motif is found in one of the most populous families, the ThCr 2Si2 series that has more than 600 members. LaNiGe2 , is similar in structure with capped square nets. However, there is one very important difference. In this structure, it is the more electronegative element Ge that builds the square lattice. The main structural motif is the NiGe4 pyramid. With computational analysis as the means of exploration, the electronic charge distribution resulting from such a structural arrangement and the changes that occur to this electronic charge distribution when a partial substitution of Si is made to the Ge in the square lattice are described. Two partially substituted compounds with different levels of Si substitution were synthesized. Their synthesis and magnetic susceptibility measurements are also discussed.

Lobring, Kim Carl

249

Differential occurrence of chromosome inversion polymorphisms among Muller's elements in three species of the tripunctata group of Drosophila, including a species with fast chromosomal evolution.  

PubMed

Detailed chromosome maps with reliable homologies among chromosomes of different species are the first step to study the evolution of the genetic architecture in any set of species. Here, we present detailed photo maps of the polytene chromosomes of three closely related species of the tripunctata group (subgenus Drosophila): Drosophila mediopunctata, D. roehrae, and D. unipunctata. We identified Muller's elements in each species, using FISH, establishing reliable chromosome homologies among species and D. melanogaster. The simultaneous analysis of chromosome inversions revealed a distribution pattern for the inversion polymorphisms among Muller's elements in the three species. Element E is the most polymorphic, with many inversions in each species. Element C follows; while the least polymorphic elements are B and D. While interesting, it remains to be determined how general this pattern is among species of the tripunctata group. Despite previous studies showing that D. mediopunctata and D. unipunctata are phylogenetically closer to each other than to D. roehrae, D. unipunctata shows rare karyotypic changes. It has two chromosome fusions: an additional heterochromatic chromosome pair and a pericentric inversion in the X chromosome. This especial conformation suggests a fast chromosomal evolution that deserves further study. PMID:23379335

Brianti, Mitsue T; Ananina, Galina; Klaczko, Louis B

2013-01-01

250

FB-NOF is a non-autonomous transposable element, expressed in Drosophila melanogaster and present only in the melanogaster group.  

PubMed

Most foldback elements are defective due to the lack of coding sequences but some are associated with coding sequences and may represent the entire element. This is the case of the NOF sequences found in the FB of Drosophila melanogaster, formerly considered as an autonomous TE and currently proposed as part of the so-called FB-NOF element, the transposon that would be complete and fully functional. NOF is always associated with FB and never seen apart from the FB inverted repeats (IR). This is the reason why the FB-NOF composite element can be considered the complete element. At least one of its ORFs encodes a protein that has always been considered its transposase, but no detailed studies have been carried out to verify this. In this work we test the hypothesis that FB-NOF is an active transposon nowadays. We search for its expression product, obtaining its cDNA, and propose the ORF and the sequence of its potential protein. We found that the NOF protein is not a transposase as it lacks any of the motifs of known transposases and also shows structural homology with hydrolases, therefore FB-NOF cannot belong to the superfamily MuDR/foldback, as up to now it has been classified, and can be considered as a non-autonomous transposable element. The alignment with the published genomes of 12 Drosophila species shows that NOF presence is restricted only to the 6 Drosophila species belonging to the melanogaster group. PMID:23685284

Badal, Martí; Xamena, Noel; Cabré, Oriol

2013-09-10

251

Behavior of iron-group elements, oxybarometry, and genesis of unique chromite deposits in the Kempirsai massif  

NASA Astrophysics Data System (ADS)

Ultramafic rocks and high-Cr chromite ore from the Almaz-Zhemchuzhina deposit, the largest in the Main ore field of the Kempirsai massif, have been studied. The detailed mineralogical and geochemical examination of deep structure test and exploratory boreholes allowed us to establish the rough stratification of ultramafic rocks and to demonstrate the position of unique chromite deposits in the generalized vertical section of the southeastern Kempirsai massif. From top to bottom, a barren harzburgite-lherzolite series gives way to an ore-bearing dunite-harzburgite complex with the largest chromite deposits, including the unique Almaz-Zhemchuzhina deposit, in its upper portion and then to pyroxene-free dunite densely impregnated with chromite in the upper part and containing sparsely disseminated chromite at its base. The lower unit is composed of a barren lherzolite-harzburgite series transformed into blastomylonites near the contact with dunite, suggesting a tectonically doubled section in the southeastern part of the massif. The synore asymmetric geochemical zoning developed in the course of formation of chromite deposits as a result of removal of oreforming iron-group elements from the underlying and wall ultramafic rocks into the overlying rocks. Host rocks with disturbed initial proportions of Cr, Fe, Ni, and Mn, together with orebodies, made up ore-bearing zones no less than 1 km in thickness and subdivided into supra-, inter-, and subore subzones. The subore and wall rocks are characterized by partial loss (wt %) of Cr2O3(0.1), NiO (0.04), FeOtot(0.5), and MnO (0.02) and their removal into the interore and supraore (0.03 NiO) subzones. Thus, the subore ultramafic rocks served as a source of ore-forming components, while the interore zone with orebodies occurring therein served as a zone of discharge of these components. Using Mössbauer spectroscopy, the crystal chemistry of iron ions was studied in a representative selection of Cr-spinel samples from rocks and ores of the southeastern and western blocks (the Almaz-Zhemchuzhina and Geophysical XII deposits). The degree of iron oxidation in the samples varies from 8 to 33%. In most cases, a difference in degree of iron oxidation is established in stoichiometric approximation and from Mössbauer data. In other words, the integral stoichiometry of ferrous and ferric ions is disturbed. Such a disturbance may be related not only to partial inversion of the Cr-spinel structure but also to local heterogeneity of the mineral at the micro- and nanolevels with clustering of cations and formation of their associates. An empirical correction of the olivine-Cr-spinel geothermometer and oxybarometer has been performed. The inverse correlation between oxygen fugacity and degree of depletion of ultramafic rocks indicates that these rocks were formed in a closed system with participation of a water-methane fluid. Along with stratification of ultramafics, this correlation testifies to a powerful asthenospheric source of reduced fluids. The retention of low oxygen fugacity in central portions of orebodies does not rule out that after a break this source participated in the formation of unique chromite deposits in the Kempirsai massif.

Chashchukhin, I. S.; Votyakov, S. L.

2009-04-01

252

Finite element simulation of high-speed machining of titanium alloy (Ti–6Al–4V) based on ductile failure model  

Microsoft Academic Search

A Johnson–Cook material model with an energy-based ductile failure criterion is developed in titanium alloy (Ti–6Al–4V) high-speed\\u000a machining finite element analysis (FEA). Furthermore, a simulation procedure is proposed to simulate different high-speed\\u000a cutting processes with the same failure parameter (i.e., density of failure energy). With this finite element (FE) model,\\u000a a series of FEAs for titanium alloy in extremely high-speed

Guang Chen; Chengzu Ren; Xiaoyong Yang; Xinmin Jin; Tao Guo

253

Rhenium-osmium isotope and platinum-group elements in the Xinjie layered intrusion, SW China: Implications for source mantle composition, mantle evolution, PGE fractionation and mineralization  

NASA Astrophysics Data System (ADS)

The Xinjie mafic-ultramafic layered intrusion in the Emeishan large igneous province (ELIP) hosts Cu-Ni-platinum group element (PGE) sulfide ore layers within the lower part and Fe-Ti-V oxide-bearing horizons within the middle part. The major magmatic Cu-Ni-PGE sulfide ores and spatially associated cumulate rocks are examined for their PGE contents and Re-Os isotopic systematics. The samples yielded a Re-Os isochron with an age of 262 ± 27 Ma and an initial 187Os/ 188Os of 0.12460 ± 0.00011 ( ?Os( t) = -0.5 ± 0.1). The age is in good agreement with the previously reported U-Pb zircon age, indicating that the Re-Os system remained closed for most samples since the intrusion emplacement. They have near-chondritic ?Os( t) values ranging from -0.7 to -0.2, similar to those of the Lijiang picrites and Song Da komatiites. Exceptionally, two samples from the roof zone and one from upper sequence exhibit radiogenic ?Os( t) values (+0.6 to +8.6), showing minor contamination by the overlying Emeishan basalts. The PGE-rich ores contain relatively high PGE and small amounts of sulfides (generally less than 2%) and the abundance of Cu and PGE correlate well with S, implying that the distribution of these elements is controlled by the segregation and accumulation of a sulfide liquid. Some ore samples are poor in S (mostly <800 ppm), which may due to late-stage S loss caused by the dissolution of FeS from pre-existing sulfides through their interaction with sulfide-unsaturated flowing magma. The combined study shows that the Xinjie intrusion may be derived from ferropicritic magmas. The sharp reversals in Mg#, Cr/FeO T and Cr/TiO 2 ratios immediately below Units 2-4, together with high Cu/Zr ratios decreasing from each PGE ore layer within these cyclic units, are consistent with multiple magma replenishment episodes. The sulfides in the cumulate rocks show little evidence of PGE depletion with height and thus appear to have segregated from successive inputs of fertile magma. This suggests that the Xinjie intrusion crystallized from in an open magma system, e.g., a magma conduit. The compositions of the disseminated sulfides in most samples can be modeled by applying an R factor (silicate-sulfide mass ratio) of between 1000 and 8000, indicating the segregation of only small amounts of sulfide liquid in the parental ferropicritic magmas. Thus, continuous mixing between primitive ferropicritic magma and differentiated resident magma could lead to crystallization of chromite, Cr-bearing magnetite and subsequently abundant Fe-Ti oxides, thereby the segregation of PGE-rich Cu-sulfide. When considered in the light of previous studies on plume-derived komatiites and picrites worldwide, the close-to-chondritic Os isotopic composition for most Xinjie samples, Lijiang picrites and Song Da komatiites suggest that the ferropicritic magma in the ELIP were generated from a plume. This comprised recycled Neoproterozic oceanic lithosphere, including depleted peridotite mantle embedded with geochemically enriched domains. The ascending magmas thereafter interacted with minor (possibly <10%) subducted/altered oceanic crust. This comparison suggests that the komatiitic melts in the ELIP originated from a greater-than normal degree of melting of incompatible trace element depleted, refractory mantle components in the plume source.

Zhong, Hong; Qi, Liang; Hu, Rui-Zhong; Zhou, Mei-Fu; Gou, Ti-Zhong; Zhu, Wei-Guang; Liu, Bing-Guang; Chu, Zhu-Yin

2011-03-01

254

Effects of liquid immiscibility on trace element fractionation in magmatic iron meteorites: A case study of group IIIAB  

Microsoft Academic Search

Magmatic iron meteorites are generally agreed to represent metal that crystallized in asteroidal cores from a large pool of liquid. Estimates suggest that the metallic liquid contained significant amounts of S and P, both of which are incompatible and exert a strong effect on trace-element partitioning. In tandem, S and P are also prone to cause immiscibility between sulfide liquid

Finn Ulff-Moeller

1998-01-01

255

Three Groups of Transposable Elements with Contrasting Copy Number Dynamics and Host Responses in the Maize (Zea mays ssp. mays) Genome.  

PubMed

Most angiosperm nuclear DNA is repetitive and derived from silenced transposable elements (TEs). TE silencing requires substantial resources from the plant host, including the production of small interfering RNAs (siRNAs). Thus, the interaction between TEs and siRNAs is a critical aspect of both the function and the evolution of plant genomes. Yet the co-evolutionary dynamics between these two entities remain poorly characterized. Here we studied the organization of TEs within the maize (Zea mays ssp mays) genome, documenting that TEs fall within three groups based on the class and copy numbers. These groups included DNA elements, low copy RNA elements and higher copy RNA elements. The three groups varied statistically in characteristics that included length, location, age, siRNA expression and 24?22 nucleotide (nt) siRNA targeting ratios. In addition, the low copy retroelements encompassed a set of TEs that had previously been shown to decrease expression within a 24 nt siRNA biogenesis mutant (mop1). To investigate the evolutionary dynamics of the three groups, we estimated their abundance in two landraces, one with a genome similar in size to that of the maize reference and the other with a 30% larger genome. For all three accessions, we assessed TE abundance as well as 22 nt and 24 nt siRNA content within leaves. The high copy number retroelements are under targeted similarly by siRNAs among accessions, appear to be born of a rapid bust of activity, and may be currently transpositionally dead or limited. In contrast, the lower copy number group of retrolements are targeted more dynamically and have had a long and ongoing history of transposition in the maize genome. PMID:24743518

Diez, Concepcion M; Meca, Esteban; Tenaillon, Maud I; Gaut, Brandon S

2014-04-01

256

Three Groups of Transposable Elements with Contrasting Copy Number Dynamics and Host Responses in the Maize (Zea mays ssp. mays) Genome  

PubMed Central

Most angiosperm nuclear DNA is repetitive and derived from silenced transposable elements (TEs). TE silencing requires substantial resources from the plant host, including the production of small interfering RNAs (siRNAs). Thus, the interaction between TEs and siRNAs is a critical aspect of both the function and the evolution of plant genomes. Yet the co-evolutionary dynamics between these two entities remain poorly characterized. Here we studied the organization of TEs within the maize (Zea mays ssp mays) genome, documenting that TEs fall within three groups based on the class and copy numbers. These groups included DNA elements, low copy RNA elements and higher copy RNA elements. The three groups varied statistically in characteristics that included length, location, age, siRNA expression and 24?22 nucleotide (nt) siRNA targeting ratios. In addition, the low copy retroelements encompassed a set of TEs that had previously been shown to decrease expression within a 24 nt siRNA biogenesis mutant (mop1). To investigate the evolutionary dynamics of the three groups, we estimated their abundance in two landraces, one with a genome similar in size to that of the maize reference and the other with a 30% larger genome. For all three accessions, we assessed TE abundance as well as 22 nt and 24 nt siRNA content within leaves. The high copy number retroelements are under targeted similarly by siRNAs among accessions, appear to be born of a rapid bust of activity, and may be currently transpositionally dead or limited. In contrast, the lower copy number group of retrolements are targeted more dynamically and have had a long and ongoing history of transposition in the maize genome.

Diez, Concepcion M.; Meca, Esteban; Tenaillon, Maud I.; Gaut, Brandon S.

2014-01-01

257

Isolation of a novel IS3 group insertion element and construction of an integration vector for Lactobacillus spp.  

PubMed Central

An insertion sequence (IS) element from Lactobacillus johnsonii was isolated, characterized, and exploited to construct an IS-based integration vector. L. johnsonii NCK61, a high-frequency conjugal donor of bacteriocin production (Laf+) and immunity (Lafr), was transformed to erythromycin resistance (Emr) with the shuttle vector pSA3. The NCK61 conjugative functions were used to mobilize pSA3 into a Laf- Lafs EMs recipient. DNA from the Emr transconjugants transformed into Escherichia coli MC1061 yielded a resolution plasmid with the same size as that of pSA3 with a 1.5-kb insertion. The gram-positive replication region of the resolution plasmid was removed to generate a pSA3-based suicide vector (pTRK327) bearing the 1.5-kb insert of Lactobacillus origin. Plasmid pTRK327 inserted randomly into the chromosomes of both Lactobacillus gasseri ATCC 33323 and VPI 11759. No homology was detected between plasmid and total host DNAs, suggesting a Rec-independent insertion. The DNA sequence of the 1.5-kb region revealed the characteristics of an IS element (designated IS1223): a length of 1,492 bp; flanking, 25-bp, imperfect inverted repeats; and two overlapping open reading frames (ORFs). Sequence comparisons revealed 71.1% similarity, including 35.7% identity, between the deduced ORFB protein of the E. coli IS element IS150 and the putative ORFB protein encoded by the Lactobacillus IS element. A putative frameshift site was detected between the overlapping ORFs of the Lactobacillus IS element. It is proposed that, similar to IS150, IS1223 produces an active transposase via translational frameshifting between two tandem, overlapping ORFs. Images

Walker, D C; Klaenhammer, T R

1994-01-01

258

Repression of transcription mediated at a thyroid hormone response element by the v-erb-A oncogene product  

Microsoft Academic Search

SEVERAL recent observations1,2, such as the identification of the cellular homologue of the v-erb-A oncogene as a thyroid-hormone receptor3,4, have strongly implicated nuclear oncogenes in transcriptional control mechanisms. The v-erb-A oncogene blocks the differentiation of erythroid cells, and changes the growth requirements of fibroblasts and erythroblasts5-7. Mutations in v-erb-A protein have led to the loss of its affinity for thyroid

Jan Sap; Alberto Muñoz; Jackie Schmitt; Henk Stunnenberg; Björn Vennström

1989-01-01

259

Platinum-group elements in southern Africa: mineral inventory and an assessment of undiscovered mineral resources: Chapter Q in Global Mineral Resource Assessment  

USGS Publications Warehouse

The platinum-group elements, platinum, palladium, rhodium, ruthenium, iridium, and osmium, possess unique physical and chemical characteristics that make them indispensable to modern technology and industry. However, mineral deposits that are the main sources of these elements occur only in three countries in the world, raising concerns about potential disruption in mineral supply. Using information in the public domain, mineral resource and reserve information has been compiled for mafic and ultramafic rocks in South Africa and Zimbabwe that host most of the world’s platinum-group element resources. As of 2012, exploration and mining companies have delineated more than 20 billion metric tons of mineralized rock containing 42,000 metric tons of platinum, 29,000 metric tons of palladium, and 5,200 metric tons of rhodium, primarily in mafic and ultramafic intrusions of the Bushveld Complex and the Great Dyke, in southern Africa. Additional mineralized rock is likely to occur in extensions to the well-explored and characterized volumes of mineralized rock. Underexplored extensions of stratabound platinum-group element (PGE) deposits in the Bushveld Complex in South Africa may contain 65,000 metric tons of platinum, palladium, and rhodium to a depth of 3 km. Rocks enriched in PGE, which occur near the contact of the Bushveld Complex with older Transvaal Supergroup sedimentary rocks, may contain 1,100 metric tons of platinum and 1,370 metric tons of palladium (mean estimate to a depth of 1 km). A stratabound platinum-group element deposit in the Great Dyke in Zimbabwe may contain 6,900 metric tons of undiscovered platinum, palladium, and rhodium. By comparison, the global net demand for PGE in 2012 was approximately 460 metric tons. Since the 1920s, mining has recovered 7,200 and 107 metric tons of platinum-group elements from the Bushveld Complex and the Great Dyke, respectively. The large layered intrusions in southern Africa—the Bushveld Complex and the Great Dyke—are now and will continue to be a major source of the world’s supply of PGE. Mining will not deplete the identified mineral resources and reserves or potential undiscovered mineral resources for many decades; however, in the near-term, PGE supply could be affected by social, environmental, political, and economic factors.

Zientek, Michael L.; Causey, J. Douglas; Parks, Heather L.; Miller, Robert J.

2014-01-01

260

The phylogeny of nine species of the Drosophila obscura group inferred by the banding homologies of chromosomal regions. III. Element D.  

PubMed

The phylogenetic relationships among nine species belonging to the obscura group of the genus Drosophila were deduced, based on similarities of the banding pattern of their polytene chromosomal element D. These similarities were inferred by the comparison of chromosomal photomaps. The phylogenetic reconstruction was the most parsimonious based on seriation by overlapping inversions and on the principle of conservation/disassociation of nearby located segments. The gene sequences of element D for all species studied were relatively easy to recognize in terms of the map of D. obscura, already found to occupy a relative central position in this group. Thus, three clusters of closely related species could be identified: obscura (D. obscura, D. ambigua, and D. tristis), African (D. kitumensis and D. microlabis), and subobscura (D. subobscura, D. madeirensis and D. guanche), with D. subsilvestris standing apart. The results are in agreement with those from the previously studied elements B and E, but element D was found to be much more conclusive concerning the links among the different clusters. Thus, it is inferred that D. guanche occupies an intermediate position between the other two species of its own cluster and all the others. The gene arrangement of D. obscura, directly related to those of the other species, has been identified. In the phylogenetic tree proposed, both the African cluster and D. subsilvestris derive from a hypothetical gene arrangement, intermediate in the pathway between the subobscura and obscura clusters. PMID:1473723

Brehm, A; Krimbas, C B

1992-12-01

261

Reaction of carboxylic groups containing organic layers with the surface of a ZnSe internal reflection element during high-energy processes  

Microsoft Academic Search

The aim of this FTIR study was to get information about the reactivity of plasma-deposited organic layers on a ZnSe-ATR probe by means of modification experiments using organic layers with carboxyl groups as model compounds. The model layers prepared on ZnSe internal reflection elements were exposed both to a low pressure plasma in a reactor (generation of ultraviolet radiation: ?=100–400

K Sahre; K.-J Eichhorn

1997-01-01

262

Thick target ?-ray yields for light elements measured in the deuteron energy interval of 0.7-3.4 MeV  

NASA Astrophysics Data System (ADS)

With the aim of providing missing basic data for deuteron-induced ?-ray emission (DIGE, or d-PIGE) analysis a completion of our earlier work (Kiss et al., 1994) has been performed. Typical ?-ray spectra, tables for the most suitable ?-ray lines for elemental analysis and a complete series of absolute thick-target yields for the most characteristic ?-rays of elements with Z=3-20 (except for Be, Ne, P and Ar) in the deuteron energy range of 0.7-3.4 MeV are presented. An analytical formula fitting well the measured yield curves is suggested for the yield calculations in elemental analysis, and also for the effective design and operation of low background experiments. The capability of this method is illustrated in the examples by spectra taken on an industrial glass and an obsidian sample.

Elekes, Z.; Kiss, Á. Z.; Biron, I.; Calligaro, T.; Salomon, J.

2000-07-01

263

An accuracy assessment of photo-ionization cross-section datasets for 1-2 keV x-rays in light elements using PIXE  

NASA Astrophysics Data System (ADS)

Proton-induced x-ray emission (PIXE) was used to assess the accuracy of the National Institute of Standards and Technology XCOM and FFAST photo-ionization cross-section databases in the low energy region (1-2 keV) for light elements. Characteristic x-ray yields generated in thick samples of Mg, Al and Si in elemental and oxide form, were compared to fundamental parameters computations of the expected x-ray yields; the database for this computation included XCOM attenuation coefficients. The resultant PIXE instrumental efficiency constant was found to differ by 4-6% between each element and its oxide. This discrepancy was traced to use of the XCOM Hartree-Slater photo-electric cross-sections. Substitution of the FFAST Hartree-Slater cross-sections reduced the effect. This suggests that for 1-2 keV x-rays in light element absorbers, the FFAST predictions of the photo-electric cross-sections are more accurate than the XCOM values.

Heirwegh, C. M.; Pradler, I.; Campbell, J. L.

2013-09-01

264

A measurement of the top quark mass in 1.96 TeV proton-antiproton collisions using a novel matrix element method  

SciTech Connect

A measurement of the top quark mass in t{bar t} {yields} l + jets candidate events, obtained from p{bar p} collisions at {radical}s = 1.96 TeV at the Fermilab Tevatron using the CDF II detector, is presented. The measurement approach is that of a matrix element method. For each candidate event, a two dimensional likelihood is calculated in the top pole mass and a constant scale factor, 'JES', where JES multiplies the input particle jet momenta and is designed to account for the systematic uncertainty of the jet momentum reconstruction. As with all matrix elements techniques, the method involves an integration using the Standard Model matrix element for tt production and decay. however, the technique presented is unique in that the matrix element is modified to compensate for kinematic assumptions which are made to reduce computation time. Background events are dealt with through use of an event observable which distinguishes signal from background, as well as through a cut on the value of an event's maximum likelihood. Results are based on a 955 pb{sup -1} data sample, using events with a high-p{sub T} lepton and exactly four high-energy jets, at least one of which is tagged as coming from a b quark; 149 events pass all the selection requirements. They find M{sub meas} = 169.8 {+-} 2.3(stat.) {+-} 1.4(syst.) GeV/c{sup 2}.

Freeman, John C.; /LBL, Berkeley

2007-12-01

265

A measurement of the top quark mass in 1.96 TeV proton-antiproton collisions using a novel matrix element method  

NASA Astrophysics Data System (ADS)

A measurement of the top quark mass in tt¯ ? l + jets candidate events, obtained from pp¯ collisions at s = 1.96 TeV at the Fermilab Tevatron using the CDF II detector, is presented. The measurement approach is that of a matrix element method. For each candidate event, a two dimensional likelihood is calculated in the top pole mass and a constant scale factor, "JES", where JES multiplies the input particle jet momenta and is designed to account for the systematic uncertainty of the jet momentum reconstruction. As with all matrix element techniques, the method involves an integration using the Standard Model matrix element for tt¯ production and decay. However, the technique presented is unique in that the matrix element is modified to compensate for kinematic assumptions which are made to reduce computation time. Background events are dealt with through use of an event observable which distinguishes signal from background, as well as through a cut on the value of an event's maximum likelihood. Results are based on a 955 pb-1 data sample, using events with a high-pT lepton and exactly four high-energy jets, at least one of which is tagged as coming from a b quark; 149 events pass all the selection requirements. We find Mmeas = 169.8 +/- 2.3 (stat.) +/- 1.4 (syst.) GeV/c2.

Freeman, John

266

A Measurement of the Top Quark Mass in 1.96 TeV Proton-Antiproton Collisions Using a Novel Matrix Element Method  

SciTech Connect

A measurement of the top quark mass in t{bar t} {yields} l + jets candidate events, obtained from p{bar p} collisions at {radical}s = 1.96 TeV at the Fermilab Tevatron using the CDF II detector, is presented. The measurement approach is that of a matrix element method. For each candidate event, a two dimensional likelihood is calculated in the top pole mass and a constant scale factor, 'JES', where JES multiplies the input particle jet momenta and is designed to account for the systematic uncertainty of the jet momentum reconstruction. As with all matrix element techniques, the method involves an integration using the Standard Model matrix element for t{bar t} production and decay. However, the technique presented is unique in that the matrix element is modified to compensate for kinematic assumptions which are made to reduce computation time. Background events are dealt with through use of an event observable which distinguishes signal from background, as well as through a cut on the value of an event's maximum likelihood. Results are based on a 955 pb{sup -1} data sample, using events with a high-p{sub T} lepton and exactly four high-energy jets, at least one of which is tagged as coming from a b quark; 149 events pass all the selection requirements. They find M{sub meas} = 169.8 {+-} 2.3(stat.) {+-} 1.4(syst.) GeV/c{sup 2}.

CDF Collaboration; Freeman, John; Freeman, John

2007-09-30

267

Epitaxy of group IV optical materials and synthesis of IV/III-V semiconductor analogs by designer hydride chemistries  

NASA Astrophysics Data System (ADS)

The thesis studies new methods to fabricate optoelectronic Ge1-y Sny/Si(100) alloys and investigate their photoluminescence (PL) properties for possible applications in Si-based photonics including IR lasers. The work initially investigated the origin of the difference between the PL spectrum of bulk Ge, dominated by indirect gap emission, and the PL spectrum of Ge-on-Si films, dominated by direct gap emission. It was found that the difference is due to the supression of self-absorption effects in Ge films, combined with a deviation from quasi-equilibrium conditions in the conduction band of undoped films. The latter is confirmed by a model suggesting that the deviation is caused by the shorter recombination lifetime in the films relative to bulk Ge. The knowledge acquired from this work was then utilized to study the PL properties of n-type Ge1-ySny/Si (y=0.004-0.04) samples grown via chemical vapor deposition of Ge2H 6/SnD4/P(GeH3)3. It was found that the emission intensity (I) of these samples is at least 10x stronger than observed in un-doped counterparts and that the I dir/Iind ratio of direct over indirect gap emission increases for high-Sn contents due to the reduced gamma-L valley separation, as expected. Next the PL investigation was expanded to samples with y=0.05-0.09 grown via a new method using the more reactive Ge3H 8 in place of Ge2H6. Optical quality, 1-um thick Ge1-ySny/Si(100) layers were produced using Ge 3H10/SnD4 and found to exhibit strong, tunable PL near the threshold of the direct-indirect bandgap crossover. A byproduct of this study was the development of an enhanced process to produce Ge 3H8, Ge4H10, and Ge5H 12 analogs for application in ultra-low temperature deposition of Group-IV semiconductors. The thesis also studies synthesis routes of an entirely new class of semiconductor compounds and alloys described by Si5-2y(III-V) y (III=Al, V= As, P) comprising of specifically designed diamond-like structures based on a Si parent lattice incorporating isolated III-V units. The common theme of the two thesis topics is the development of new mono-crystalline materials on ubiquitous silicon platforms with the objective of enhancing the optoelectronic performance of Si and Ge semiconductors, potentially leading to the design of next generation optical devices including lasers, detectors and solar cells.

Grzybowski, Gordon

268

Human group V secretory phospholipase A2 is associated with lipid rafts and internalized in a flotillin?dependent pathway.  

PubMed

The mechanisms of secretory phospholipase A2 (sPLA2) action are not understood clearly. Previously, it was suggested that sPLA2s are internalized into cells for the targeting of sPLA2 to intracellular action sites. However, the mechanisms for sPLA2 internalization remain to be identified. The present study demonstrated for the first time that human group V sPLA2 (hVPLA2) is associated with lipid rafts and is internalized in a flotillin?dependent pathway. The lipid raft association was probed by cholesterol?sensitive enrichment of hVPLA2 in low?density fractions and co?patching of ganglioside GM1 rafts through cross?linking of hVPLA2 in HEK293 and CHO cells. The hVPLA2 associated with lipid rafts was shown to be internalized into HEK293 cells at a relatively rapid rate (t1/2 =16 min) and this internalization was inhibited by the knockdown of flotillin?1, but not by chlorpromazine, an inhibitor of clathrin?mediated endocytosis. Moreover, internalized hVPLA2 was shown to be colocalized extensively with flotillin?1 in a punctate structure, but not caveolin?1. These data revealed that the internalization of hVPLA2 is mediated by flotillin?1. Attenuation of arachidonic acid release from plasma membrane through the association of hVPLA2 with lipid rafts suggested that this association with lipid rafts may be important in protecting mammalian cells from excessive degradation of plasma membrane and trafficking hVPLA2 into intracellular targets. PMID:24042857

Rhee, Hae Jin; Ji, Liting; Kim, Seung-Hyuk; Lee, Jongho

2013-11-01

269

Group B Streptococci Escape Host Immunity by Deletion of Tandem Repeat Elements of the Alpha C Protein  

Microsoft Academic Search

Group B streptococci (GBS) are the most common cause of neonatal sepsis, pneumonia, and meningitis. The alpha C protein is a surface-associated antigen; the gene (bca) for this protein contains a series of tandem repeats (each encoding 82 aa) that are identical at the nucleotide level and express a protective epitope. We previously reported that GBS isolates from two of

Lawrence C. Madoff; James L. Michel; Elizabeth W. Gong; David E. Kling; Dennis L. Kasper

1996-01-01

270

Results of the Survey of RP Group Members: An Element in Strategic Planning for the Research & Planning Unit.  

ERIC Educational Resources Information Center

This document focuses on a stakeholder survey for a research unit. Although it covers just one part of the overall planning process that the Research & Planning (RP) Unit at the California Community Colleges Chancellor's Office, the researchers did survey other groups in the strategic planning effort. The stakeholder survey focused on four general…

Hom, Willard

271

Molecular characterization of Hor v 9. Conservation of a T-cell epitope among group IX pollen allergens and human VCAM and CD2.  

PubMed

We have cloned, sequenced and expressed a recombinant group IX pollen allergen from barley (Hordeum vulgare). Hor v 9 is a polypeptide of 313 amino acids. The Hor v 9 cDNA clone was engineered into the E. coli protein expression vector pMAL and expressed as a fusion of maltose binding protein and truncated Hor v 9. Polyclonal antibodies to the fusion protein were raised in mice. Cross-reactive proteins, RNA and DNA homologues were found in many agricultural species including wheat, rye, triticale, oats, maize, sunflower and flax. The presence of group IX-like proteins in a variety of agricultural crops may represent a previously uncharacterized aeroallergenic occupational hazard. Sequence comparisons of the barley allergen, Hor v 9, with Poa p 9 and other cloned group IX pollen allergens revealed putative structural domains common to all. These include a signal peptide, two conserved immunoglobulin-like motifs, a 150 amino acid highly conserved carboxyterminal domain and a carboxyterminal transmembrane helix. This structural arrangement is also found in cell adhesion molecules. The highly conserved T-cell epitope previously characterized and mapped in group IX allergens (and present in Hor v 9) was found in several human cell adhesion molecule sequences (VCAM, NCAM and CD2). This T-cell epitope corresponded to the most highly conserved amino acid residues common to all group IX homologues sequenced to date. CD2 and VCAM are known to play a role in allergic inflammation: VCAM is involved in the recruitment of lymphocytes to sites of inflammation, and cross-linking CD2 leads to T-cell activation. We anticipate that the similar structural arrangement of group IX allergens and human cell adhesion molecules, as well as the presence of a T-cell epitope common to group IX pollen allergens and cell adhesion molecules, will have important consequences in the natural history of the atopic immune response. PMID:9095254

Astwood, J D; Hill, R D

1996-01-01

272

Surface organometallic chemistry of main group elements: selective synthesis of silica supported [triple bond Si-OB(C(6)F(5))(3)](-)[HNEt(2)Ph](+).  

PubMed

The reaction of the Lewis acid B(C(6)F(5))(3) with silanol groups of silica surfaces, dehydroxylated at different temperatures (300, 500, 700, and 800 degrees C), has been investigated in presence of the Brønsted base NEt(2)Ph. The structure of the resulting modified silica supports [triple bond Si-OB(C(6)F(5))(3)](-)[HNEt(2)Ph](+) (1) has been carefully identified by IR and multinuclear solid-state NMR spectroscopies, isotopic (2)H and (18)O labeling, elemental analysis, molecular modeling, and comparison with synthesized molecular models. Highly dehydroxylated silica surfaces were required to transform selectively each silanol group into unique [triple bond Si-OB(C(6)F(5))(3)](-)[HNEt(2)Ph](+) fragments. For lower dehydroxylation temperatures, two sorts of surface sites were coexisting on silica: the free silanol groups [triple bond SiOH] and the ionic species 1. PMID:11921228

Millot, Nicolas; Cox, Andrew; Santini, Catherine C; Molard, Yann; Basset, Jean-Marie

2002-03-15

273

Partitioning of platinum-group elements and Au in the Fe-Ni-Cu-S system: experiments on the fractional crystallization of sulfide melt  

NASA Astrophysics Data System (ADS)

Partitioning of platinum-group elements (PGE) between sulfide liquid and monosulfide solid solution ( mss) has been investigated by crystallizing mss from Fe-Ni-Cu sulfide liquid at 1,000 1,040° C, using bulk compositions and PGE contents typical of magmatic sulfides associated with mafic and ultramafic systems. Products were analyzed in situ for PGE and Au using SIMS. Sulfide liquid compositions were more Ni- and Cu-rich than coexisting mss. Liquid/ mss partition coefficients are: Os-0.23±0.04, Ir-0.28±0.11, Ru-0.24±0.05, Rh-0.33±0.06, Pt-4.8±0.7, Pd-4.8±1.9, Au-11.4. Partitioning of PGE is independent of PGE concentration and Ni content in the composition range investigated. Additionally, Henry's law appears to be obeyed up to minor-element contents in the sulfide liquid and mss. Osmium, Ir, Ru, and Rh are compatible elements in the anhydrous Fe-Ni-Cu-S system, whereas Pt, Pd and Au are incompatible elements. These affinities correspond to the partitions of PGE between massive and Cu-rich magmatic sulfides. However, the detailed precious-metal compositions of the Cu-rich sulfides of mafic rock systems, disseminated ores of komatiites and Cu-rich assemblage of droplet ore from the Noril'sk-Talnakh deposits are not consistent with those expected for pristine fractionated sulfide liquids.

Fleet, Michael E.; Chryssoulis, Stephen L.; Stone, William E.; Weisener, Christopher G.

1993-03-01

274

A MODIFIED MATERIAL MODEL FOR THE FINITE ELEMENT SIMULATION OF MACHINING TITANIUM ALLOY Ti6Al4 V  

Microsoft Academic Search

Because of their desirable properties, such as high strength to weight ratio and corrosion resistance, titanium alloys are commonly employed in the aerospace and medical device industries. Titanium alloys are known to be difficult to machine, so the selection of cutting conditions with minimal experimental effort is important for manufacturers. Finite element modeling, which is an indispensable tool to understand

Y. Karpat

2010-01-01

275

Influence of the Third Element of Diffusion in Solid State (Vliyanie Tretego Elementa na Diffuziyu v Tverdom Sostoyanii).  

National Technical Information Service (NTIS)

The influence of Mg and Sb or the diffusion speed of Hg from its Pb alloy is studied in this work. The relationship between the coefficient of diffusion - D, and the quantity of the third element in the alloy, is investigated.

S. Gertsriken I. Dehtyar

1975-01-01

276

New elastic electron scattering factors for the elements for incident energies of 10, 40, 60, and 90 keV  

SciTech Connect

An improved set of scattering factors for all neutral elements has bee completed for inclusion in the new edition of the International Tables of X-ray Crystallography . These calculations are compared with the former electron scattering factors and the deviations between the two are discussed.(AIP)

Ross, A.W.; Fink, M.

1986-12-01

277

The major, trace and rare earth element geochemistry of glauconites from the early Cretaceous Kurnub Group of Jordan  

Microsoft Academic Search

The major, trace and REE geochemistry of glauconites (as members of the trioctahedral micas) from the early Cretaceous Kurnub Group of Jordan are discussed. The investigated glauconites, with 7.1 to 9.2% K2O, are ranked as evolved to highly evolved as defined by Odin and Matter (1981). Al 2O3 contents show a significant inverse relationship with K 2O and Fe2O3. The

GHALEB JARRAR; BELAL AMIREH; DIETER ZACHMANN

278

Re-Os systematics in chondrites and the fractionation of the platinum group elements in the early solar system  

Microsoft Academic Search

We have investigated the Re-Os system for samples of whole rock, metal, and sulfide from ordinary chondrites. Using closed-system analytical techniques, we found complete exchange between sample and tracer isotopes for silicate-containing samples and obtained precise and reliable Re-Os concentration measurements. Results on two Group IVA iron meteorites and on a silicate-rich iron (Steinbach, IVA-AN) are consistent with the IVA-IVB

J. H Chen; D. A Papanastassiou; G. J Wasserburg

1998-01-01

279

Halide interferences in an electrothermal graphite furnace atomic absorption spectrometry with Group IIIB elements as studied by atomic and molecular absorption signal profiles  

NASA Astrophysics Data System (ADS)

Molecular absorptions of monohalides ( MX; X ? F, Cl and Br) of alkali metals, alkaline-earth metals and Group IIIB elements produced in a conventional electrothermal graphite furnace atomizer have been observed by a rapid measurement system. Their characteristic data are summarized as appearance and peak temperatures and the analytical sensitivities. Furthermore, molecular absorptions ofAlF and InF are utilized to study the interference of fluoride with aluminum and indium atomic absorptions. Although the formations of AlF and InF suppress the atomic absorptions ofAl and In, respectively, the time-overlap in signal appearance of atomic absorptions of these two elements and molecular absorptions of their monofluorides is not observed. This is contradictory to pure "vapor phase mechanism", and indicates that processes occurring on the graphite surface are also important. Usefulness of strontium nitrate as a matrix modifier for the determination of indium was also demonstrated.

Tsunoda, K.; Haraguchi, H.; Fuwa, K.

280

Electron stopping powers of some elements and compounds from 0 to 10,000 eV: A compilation  

SciTech Connect

Electron stopping powers of hydrogen, helium, nitrogen, oxygen, aluminum, silicon, silicon dioxide, nickel, copper, silver, tungsten, gold, air, collodion, liquid water, polystyrene, polyethylene, aluminum oxide, kaptan, mylar (polyethylene terephthalate), bakelite, lucite, plexiglas (polymethyl methacrylate), perspex, PMMA resist, melinex, and nylon 6,6 are given from 0 to 10,000 eV where available. Ashley's formulae for the stopping power of some organic solids are included. Iskef and Watt's simple formulae are given. The NBS Bethe stopping powers for 51 materials from 1 to 10 keV are reproduced.

Devaney, J.J.

1989-07-01

281

Modulation of the Activity of a Polycomb-Group Response Element in Drosophila by a Mutation in the Transcriptional Activator Woc  

PubMed Central

Polycomb group response elements (PRE) are cis-regulatory elements that bind Polycomb group proteins. We are studying a 181-bp PRE from the Drosophila engrailed gene. This PRE causes pairing-sensitive silencing of mini-white in transgenes. Here we show that the 181-bp PRE also represses mini-white expression in flies with only one copy of the transgene. To isolate mutations that alter the activity of the 181-bp PRE, we screened for dominant suppressors of PRE-mediated mini-white repression. Dominant suppressors of mini-white repression were rare; we recovered only nine mutations out of 68,274 progeny screened. Two of the nine mutations isolated are due to the same single amino acid change in the transcriptional activator Woc (without children). Reversion experiments show that these are dominant gain-of-function mutations in woc. We suggest that Woc can interfere with the activity of the PRE. Our data have implications for how Polycomb group proteins act to either partially repress or completely silence their target genes.

Noyes, Amanda; Stefaniuk, Catherine; Cheng, Yuzhong; Kennison, James A.; Kassis, Judith A.

2011-01-01

282

III-V arsenide-nitride semiconductor  

NASA Technical Reports Server (NTRS)

III-V arsenide-nitride semiconductor are disclosed. Group III elements are combined with group V elements, including at least nitrogen and arsenic, in concentrations chosen to lattice match commercially available crystalline substrates. Epitaxial growth of these III-V crystals results in direct bandgap materials, which can be used in applications such as light emitting diodes and lasers. Varying the concentrations of the elements in the III-V materials varies the bandgaps, such that materials emitting light spanning the visible spectra, as well as mid-IR and near-UV emitters, can be created. Conversely, such material can be used to create devices that acquire light and convert the light to electricity, for applications such as full color photodetectors and solar energy collectors. The growth of the III-V material can be accomplished by growing thin layers of elements or compounds in sequences that result in the overall lattice match and bandgap desired.

Major, Jo S. (Inventor); Welch, David F. (Inventor); Scifres, Donald R. (Inventor)

2000-01-01

283

Performance of the Vitek MS v2.0 system in distinguishing Streptococcus pneumoniae from nonpneumococcal species of the Streptococcus mitis group.  

PubMed

The Vitek MS v2.0 matrix-assisted laser desorption ionization-time of flight mass spectrometry system accurately distinguished Streptococcus pneumoniae from nonpneumococcal S. mitis group species. Only 1 of 116 nonpneumococcal isolates (<1%) was misidentified as S. pneumoniae. None of 95 pneumococcal isolates was misidentified. This method provides a rapid, simple means of discriminating among these challenging organisms. PMID:23784130

Branda, John A; Markham, Rachelle P; Garner, Cherilyn D; Rychert, Jenna A; Ferraro, Mary Jane

2013-09-01

284

ENVIRONMENTAL TECHNOLOGY VERIFICATION, TEST REPORT OF CONTROL OF BIOAEROSOLS IN HVAC SYSTEMS, FILTRATION GROUP, AEROSTAR FP-98 MINIPLEAT V-BLANK FILTER  

EPA Science Inventory

The Environmental Technology Verification report discusses the technology and performance of the AeroStar FP-98 Minipleat V-Bank Filter air filter for dust and bioaerosol filtration manufactured by Filtration Group. The pressure drop across the filter was 137 Pa clean and 348 Pa ...

285

76 FR 46793 - PJM Interconnection, L.L.C.; PJM Power Providers Group v. PJM Interconnection, L.L.C.; Notice...  

Federal Register 2010, 2011, 2012, 2013

...ER11-2875-001; ER11-2875-002; Docket No. EL11-20-001] PJM Interconnection, L.L.C.; PJM Power Providers Group v. PJM Interconnection, L.L.C.; Notice Establishing Post-Technical Comment Period As indicated in the...

2011-08-03

286

Performance of the Vitek MS v2.0 System in Distinguishing Streptococcus pneumoniae from Nonpneumococcal Species of the Streptococcus mitis Group  

PubMed Central

The Vitek MS v2.0 matrix-assisted laser desorption ionization–time of flight mass spectrometry system accurately distinguished Streptococcus pneumoniae from nonpneumococcal S. mitis group species. Only 1 of 116 nonpneumococcal isolates (<1%) was misidentified as S. pneumoniae. None of 95 pneumococcal isolates was misidentified. This method provides a rapid, simple means of discriminating among these challenging organisms.

Markham, Rachelle P.; Garner, Cherilyn D.; Rychert, Jenna A.; Ferraro, Mary Jane

2013-01-01

287

Synthesis, surface group modification of 3D MnV{sub 2}O{sub 6} nanostructures and adsorption effect on Rhodamine B  

SciTech Connect

Highlights: ? Fabrication of urchin-like MnV{sub 2}O{sub 6} with oxygen-containing surface groups. ? Mn{sub 0.5}V{sub 2}O{sub 5}·nH{sub 2}O as an intermediate product holds the key to the final products. ? 3D architectures of MnV{sub 2}O{sub 6} with oxygen-containing surface groups as sorbent. ? The sorbent shows a good adsorption ability. -- Abstract: Highly uniform 3D MnV{sub 2}O{sub 6} nanostructures modified by oxygen functional groups (-COO-) were successfully prepared in large quantities by an approach involving preparation of vanadyl ethylene glycolate as the precursor. The growth and self-assembly of MnV{sub 2}O{sub 6} nanobelts and nanorods could be readily tuned by additive species and quantities, which brought different morphologies and sizes to the final products. With a focus on the regulation of structure, the formation process of 3D architectures of MnV{sub 2}O{sub 6} by self-assembly of nanobelts was followed by field emission scanning electron microscopy (FE-SEM) and X-ray diffraction (XRD). The consecutive processes of vanadyl ethylene glycolate and benzoyl peroxide assisted formation of layered structure Mn{sub 0.5}V{sub 2}O{sub 5}·nH{sub 2}O, growth of aligned MnV{sub 2}O{sub 6} nanobelts, and oriented assembly were proposed for the growth mechanism. The band gap vs. different morphology was also studied. Optical characterization of these MnV{sub 2}O{sub 6} with different morphologies showed direct bandgap energies at 1.8–1.95 eV. The adsorption properties of 3D MnV{sub 2}O{sub 6} nanostructures synthesized under different conditions were investigated through the removal test of Rhodamine B in aqueous water, and the 3D nanostructures synthesized with 30 g L{sup ?1} benzoyl peroxide showed good adsorption capability of Rhodamine B.

Zhang, Wanqun, E-mail: wqz@ustc.edu.cn [Hefei National Laboratory for Physical Sciences at Micro-scale, University of Science and Technology of China, Hefei, Anhui 230026 (China) [Hefei National Laboratory for Physical Sciences at Micro-scale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Chemical Experimental Teaching Center, University of Science and Technology of China, Hefei, Anhui 230026 (China); Shi, Lei, E-mail: shil@ustc.edu.cn [Hefei National Laboratory for Physical Sciences at Micro-scale, University of Science and Technology of China, Hefei, Anhui 230026 (China)] [Hefei National Laboratory for Physical Sciences at Micro-scale, University of Science and Technology of China, Hefei, Anhui 230026 (China); Tang, Kaibin; Liu, Zhongping [Hefei National Laboratory for Physical Sciences at Micro-scale, University of Science and Technology of China, Hefei, Anhui 230026 (China)] [Hefei National Laboratory for Physical Sciences at Micro-scale, University of Science and Technology of China, Hefei, Anhui 230026 (China)

2012-07-15

288

Platinum Group Element (PGE) Abundances in Lava Flows Generated by the Hawaiian Plume: Insights into Plume Evolution  

NASA Astrophysics Data System (ADS)

Picritic and high-MgO (7.7-24 wt.%) basalt samples from Detroit (/sim81-76 Ma) and Koko (/sim48 Ma) Seamounts along the ESC have been analyzed for PGEs (Ru, Rh, Pd, Ir, and Pt) allowing an examination of how the PGEs in lavas from the Hawaiian plume have changed over time. Major and trace element (including the PGEs) concentrations were quantified by ICP methods at the University of Notre Dame. See Ely et al. (1999, Chem. Geol. 157:219) for the PGE analytical method. Bennett et al. (2000) analyzed Hawaiian picrites and found PGE abundances slightly greater than average MORB and comparable to the low-PGE basaltic komatiites. These authors modeled the PGE abundances of these picrites by using variable amounts of residual sulfide during melting, such that Koolau (low PGE contents) formed from a relatively sulfide-rich source and Loihi (high PGEs) from a sulfide-poor source. Our PGE data from Detroit Seamount show slightly higher PGE abundances than Loihi and Kilauea, suggesting these picrites formed from a source lacking residual sulfide. These results suggest that, if the model of Bennett et al. (2000) is correct, the dilution of plume lava with MORB source, as hypothesized on the basis of depleted isotope ratios and lower trace element abundances than modern Hawaii (Keller et al., 2000, Nature 405:603; Kinman & Neal, 2002, Eos 83:F1282; Regelous et al., 2003, JPet 44:113), was not the controlling factor in PGE abundances. However, since MORB PGE concentrations are not substantially different than low-PGE Hawaiian picrites, incorporation of MORB material within the Hawaiian plume at Detroit Seamount would not have drastically reduced the PGE abundances. Koko Seamount has relatively high PGE concentrations (/sim3-12 times greater than those from Detroit lavas). This may be the result of a lack of residual sulfide facilitated by higher degrees of partial melting. Although our initial data are consistent with variable degrees of partial melting and/or source heterogeneity over the life of the Hawaiian plume, the data from Detroit Seamount can be modeled by, for example, magma mixing between Koko-type "PGE-rich" plume and MORB end members (cf. Kinman & Neal, 2002). The Pt/Ir ratios and PGE abundances of picrites from Detroit and Koko Seamounts and from Hawaii (as analyzed by Bennett et al., 2000) increase in the order: Hawaii (4.8), Detroit (5.8), Koko (8.1). Bennett et al. argued that if more sulfide was retained in the source the PGE profile would be more fractionated and abundances would be lower. Our data suggest the opposite is true. For Koko Seamount to have PGE abundances approximately 3-12 times greater than the high-PGE picrites from Hawaii and yet have a more fractionated profile, the source of the Hawaiian plume must have been relatively PGE-enriched at 48 Ma than it is currently. In addition, the more fractionated profile of Detroit Seamount is consistent with the incorporation of MORB material (Pt/Ir /sim 25.9), thereby raising its Pt/Ir ratio.

Shafer, J. T.; Neal, C. R.

2003-12-01

289

Facile fabrication of amphiphilic gold nanoparticles with V-shaped brushes from block copolymers with a trithiocarbonate group as the junction.  

PubMed

Amphiphilic gold nanoparticles grafted with V-shaped brushes (Au-V-brushes) were prepared by grafting a polystyrene-b-poly(ethylene oxide) (PS-b-PEO) block copolymer with a trithiocarbonate group as the junction to the Au surface. The obtained Au-V-brushes were subjected to solubility test and UV-vis, FT-IR, TEM and DLS characterizations. It is found that the Au-V-brushes are soluble in both water and organic solvents. In the common solvent DMF, the size of the Au-V-brushes is about 17 nm, whereas in selective solvents (toluene and water) aggregates of 70-90 nm are formed. Phase transfer of the Au-V-brushes from the water phase into the toluene phase occurs upon addition of Na(2)SO(4) into water and the Au-V-brushes can also transfer from the toluene phase to the interface of toluene and water phases after addition of citric acid in the water phase. PMID:21596387

Wang, Zhao-Li; Xu, Jun-Ting; Du, Bin-Yang; Fan, Zhi-Qiang

2011-08-15

290

First measurement of the ratio B(t --> Wb)/B(t --> Wq) and associated limit on the Cabibbo-Kobayashi-Maskawa element /V(tb)/.  

PubMed

We present the first measurement of the ratio of branching fractions R identical withB(t-->Wb)/B(t-->Wq) from p_p collisions at sqrt[s] = 1.8 TeV. The data set corresponds to 109 pb(-1) of data recorded by the Collider Detector at Fermilab during the 1992-95 Tevatron run. We measure R = 0.94(+0.31)(-0.24)(stat+syst) or R>0.61 (0.56) at 90% (95)% C.L., in agreement with the standard model predictions. This measurement yields a limit on the Cabibbo-Kobayashi-Maskawa quark mixing matrix element /V(tb)/ under the assumption of three generations and unitarity. PMID:11327939

Affolder, T; Akimoto, H; Akopian, A; Albrow, M G; Amaral, P; Amendolia, S R; Amidei, D; Anikeev, K; Antos, J; Apollinari, G; Arisawa, T; Asakawa, T; Ashmanskas, W; Azfar, F; Azzi-Bacchetta, P; Bacchetta, N; Bailey, M W; Bailey, S; de Barbaro, P; Barbaro-Galtieri, A; Barnes, V E; Barnett, B A; Baroiant, S; Barone, M; Bauer, G; Bedeschi, F; Belforte, S; Bell, W H; Bellettini, G; Bellinger, J; Benjamin, D; Bensinger, J; Beretvas, A; Berge, J P; Berryhill, J; Bevensee, B; Bhatti, A; Binkley, M; Bisello, D; Bishai, M; Blair, R E; Blocker, C; Bloom, K; Blumenfeld, B; Blusk, S R; Bocci, A; Bodek, A; Bokhari, W; Bolla, G; Bonushkin, Y; Bortoletto, D; Boudreau, J; Brandl, A; van den Brink, S; Bromberg, C; Brozovic, M; Bruner, N; Buckley-Geer, E; Budagov, J; Budd, H S; Burkett, K; Busetto, G; Byon-Wagner, A; Byrum, K L; Calafiura, P; Campbell, M; Carithers, W; Carlson, J; Carlsmith, D; Caskey, W; Cassada, J; Castro, A; Cauz, D; Cerri, A; Chan, A W; Chang, P S; Chang, P T; Chapman, J; Chen, C; Chen, Y C; Cheng, M T; Chertok, M; Chiarelli, G; Chirikov-Zorin, I; Chlachidze, G; Chlebana, F; Christofek, L; Chu, M L; Chung, Y S; Ciobanu, C I; Clark, A G; Connolly, A; Conway, J; Cordelli, M; Cranshaw, J; Cronin-Hennessy, D; Cropp, R; Culbertson, R; Dagenhart, D; D'Auria, S; DeJongh, F; Dell'Agnello, S; Dell'Orso, M; Demortier, L; Deninno, M; Derwent, P F; Devlin, T; Dittmann, J R; Donati, S; Done, J; Dorigo, T; Eddy, N; Einsweiler, K; Elias, J E; Engels, E; Erbacher, R; Errede, D; Errede, S; Fan, Q; Feild, R G; Fernandez, J P; Ferretti, C; Field, R D; Fiori, I; Flaugher, B; Foster, G W; Franklin, M; Freeman, J; Friedman, J; Fukui, Y; Furic, I; Galeotti, S; Gallinaro, M; Gao, T; Garcia-Sciveres, M; Garfinkel, A F; Gatti, P; Gay, C; Gerdes, D W; Giannetti, P; Giromini, P; Glagolev, V; Glenzinski, D; Gold, M; Goldstein, J; Gordon, A; Gorelov, I; Goshaw, A T; Gotra, Y; Goulianos, K; Green, C; Grim, G; Gris, P; Groer, L; Grosso-Pilcher, C; Guenther, M; Guillian, G; Da Costa, J G; Haas, R M; Haber, C; Hafen, E; Hahn, S R; Hall, C; Handa, T; Handler, R; Hao, W; Happacher, F; Hara, K; Hardman, A D; Harris, R M; Hartmann, F; Hatakeyama, K; Hauser, J; Heinrich, J; Heiss, A; Herndon, M; Hill, C; Hoffman, K D; Holck, C; Hollebeek, R; Holloway, L; Hughes, R; Huston, J; Huth, J; Ikeda, H; Incandela, J; Introzzi, G; Iwai, J; Iwata, Y; James, E; Jensen, H; Jones, M; Joshi, U; Kambara, H; Kamon, T; Kaneko, T; Karr, K; Kasha, H; Kato, Y; Keaffaber, T A; Kelley, K; Kelly, M; Kennedy, R D; Kephart, R; Khazins, D; Kikuchi, T; Kilminster, B; Kim, B J; Kim, D H; Kim, H S; Kim, M J; Kim, S H; Kim, Y K; Kirby, M; Kirk, M; Kirsch, L; Klimenko, S; Koehn, P; Köngeter, A; Kondo, K; Konigsberg, J; Kordas, K; Korn, A; Korytov, A; Kovacs, E; Kroll, J; Kruse, M; Kuhlmann, S E; Kurino, K; Kuwabara, T; Laasanen, A T; Lai, N; Lami, S; Lammel, S; Lamoureux, J I; Lancaster, J; Lancaster, M; Lander, R; Latino, G; LeCompte, T; Lee, A M; Lee, K; Leone, S; Lewis, J D; Lindgren, M; Liss, T M; Liu, J B; Liu, Y C; Litvintsev, D O; Lobban, O; Lockyer, N; Loken, J; Loreti, M; Lucchesi, D; Lukens, P; Lusin, S; Lyons, L; Lys, J; Madrak, R; Maeshima, K; Maksimovic, P; Malferrari, L; Mangano, M; Mariotti, M; Martignon, G; Martin, A; Matthews, J A; Mayer, J; Mazzanti, P; McFarland, K S; McIntyre, P; McKigney, E; Menguzzato, M; Menzione, A; Mesropian, C; Meyer, A; Miao, T; Miller, R; Miller, J S; Minato, H; Miscetti, S; Mishina, M; Mitselmakher, G; Moggi, N; Moore, E; Moore, R; Morita, Y; Moulik, T; Mulhearn, M; Mukherjee, A; Muller, T; Munar, A; Murat, P; Murgia, S; Nachtman, J; Nagaslaev, V; Nahn, S; Nakada, H; Nakaya, T; Nakano, I; Nelson, C; Nelson, T; Neu, C; Neuberger, D; Newman-Holmes, C; Ngan, C Y; Niu, H; Nodulman, L; Nomerotski, A; Oh, S H; Ohmoto, T; Ohsugi, T; Oishi, R; Okusawa, T; Olsen, J; Orejudos, W; Pagliarone, C; Palmonari, F; Paoletti, R; Papadimitriou, V; Pappas, S P; Partos, D; Patrick, J; Pauletta, G; Paulini, M; Paus, C; Pescara, L; Phillips, T J; Piacentino, G; Pitts, K T; Pompos, A; Pondrom, L; Pope, G; Popovic, M; Prokoshin, F; Proudfoot, J; Ptohos, F; Pukhov, O; Punzi, G; Ragan, K; Rakitine, A; Reher, D; Reichold, A; Ribon, A; Riegler, W; Rimondi, F; Ristori, L; Riveline, M; Robertson, W J; Robinson, A; Rodrigo, T; Rolli, S; Rosenson, L; Roser, R; Rossin, R; Roy, A; Safonov, A; St Denis, R; Sakumoto, W K; Saltzberg, D; Sanchez, C; Sansoni, A; Santi, L; Sato, H; Savard, P; Schlabach, P; Schmidt, E E; Schmidt, M P; Schmitt, M; Scodellaro, L; Scott, A; Scribano, A; Segler, S; Seidel, S; Seiya, Y; Semenov, A; Semeria, F; Shah, T; Shapiro, M D; Shepard, P F; Shibayama, T; Shimojima, M; Shochet, M; Siegrist, J; Sill, A; Sinervo, P; Singh, P; Slaughter, A J; Sliwa, K; Smith, C; Snider, F D; Solodsky, A; Spalding, J; Speer, T; Sphicas, P; Spinella, F; Spiropulu, M; Spiegel, L; Steele, J; Stefanini, A; Strologas, J; Strumia, F; Stuart, D; Sumorok, K; Suzuki, T

2001-04-01

291

A comparative evaluation of substance abuse treatment: V. Substance abuse treatment can enhance the effectiveness of self-help groups.  

PubMed

Affiliation with Alcoholics Anonymous (AA) and other 12-Step self-help groups is becoming more common at the same time as professional substance abuse treatment services are becoming less available and of shorter duration. As a result of these two trends, patients' outcomes may be increasingly influenced by the degree to which professional treatment programs help patients take maximum advantage of self-help groups. The present study of 3018 treated veterans examined how the theoretical orientation of a substance abuse treatment program affects (1) the proportion of its patients that participate in self-help groups, and, (2) the degree of benefit patients derive from participation in self-help groups. Patients treated in 12-Step and eclectic treatment programs had higher rates of subsequent participation in 12-Step self-help groups than did patients treated in cognitive behavioral programs. Furthermore, the theoretical orientation of treatment moderated the outcome of self-help group participation: As the degree of programs' emphasis on 12-Step approaches increased, the positive relationships of 12-Step group participation to better substance use and psychological outcomes became stronger. Hence, it appears that 12-Step oriented treatment programs enhance the effectiveness of 12-Step self-help groups. Findings are discussed in terms of implications for clinical practice and for future evaluations of the combined effects of treatment and self-help groups. PMID:10195833

Humphreys, K; Huebsch, P D; Finney, J W; Moos, R H

1999-03-01

292

Bonds, bands, and band gaps in tetrahedrally bonded ternary compounds: The role of group V lone pairs  

NASA Astrophysics Data System (ADS)

An interesting class of tetrahedrally coordinated ternary compounds has attracted considerable interest because of their potential as good thermoelectrics. These compounds, denoted as I3-V-VI4, contain three monovalent-I (Cu, Ag), one nominally pentavalent-V (P, As, Sb, Bi), and four hexavalent-VI (S, Se, Te) atoms; and can be visualized as ternary derivatives of the II-VI zincblende or wurtzite semiconductors, obtained by starting from four unit cells of (II-VI) and replacing four type II atoms by three type I and one type V atoms. We find that nominally pentavalent-V atoms are effectively trivalent and their lone (ns2) pairs play an active role in opening up a gap. The lowest conduction band is a strongly hybridized anti-bonding combination of the lone pair and chalcogen (VI) p-states. The magnitude of the gap is sensitive to the nature of the exchange interaction (local vs non-local) and the V-VI distance. We also find that the electronic structure near the gap can be reproduced extremely well within a local theory if one can manipulate the position of the filled d bands of Cu and Ag by an effectively large U.

Do, Dat T.; Mahanti, S. D.

2014-04-01

293

L X-ray fluorescence cross sections of some rare earth elements ( Z = 62, 64, 66, 68 and 70) at 17.8, 22.6 and 25.8 keV  

NASA Astrophysics Data System (ADS)

L X-ray fluorescence cross sections of the elements with Z = 62, 64, 66, 68 and 70 have been measured at 17.8, 22.6 and 25.8 keV using an X-ray tube and secondary exciters of Mo, Ag and Sn. The measured cross sections have been compared with the theoretical predictions and with the data of others. Theoretical values calculated using photoionisation cross sections from Scofield [Lawrence Livermore Laboratory, UCRL-51326, 1973], fluorescence yields and Coster-Kronig transition probabilities from Puri et al. [X-ray Spectrom. 22 (1993) 358] and radiative widths from Campbell and Wang [At. Data Nucl. Data Tables 43 (1989) 281] show good agreement with our data. Except two sets of data on L? cross sections, all the data of other groups agree well with those of ours.

Mandal, A. C.; Santra, S.; Mitra, D.; Sarkar, M.; Bhattacharya, D.

2005-06-01

294

M-shell X-ray production cross-sections for elements with 67 {<=} Z {<=} 92 at incident photon energies E{sub M{sub 1}}V  

SciTech Connect

The X-ray production cross-sections for the Mk (k = {xi}, {delta}, {alpha}, {beta}, {zeta}, {gamma}, m{sub 1} and m{sub 2}) groups of X-rays have been evaluated for all the elements with 67 {<=} Z {<=} 92 at incident photon energies ranging E{sub M{sub 1}}V using currently available theoretical data sets of different physical parameters, namely, partial photoionization cross-sections, X-ray emission rates, fluorescence and Coster-Kronig yields, and the K-shell/L{sub j} (j = 1-3) subshell to the M{sub i} (i = 1-5) subshell vacancy transfer probabilities, based on the independent particle models.

Chauhan, Yogeshwar; Kumar, Anil [University College of Engineering, Punjabi University, Patiala 147002, Punjab (India); Puri, Sanjiv [University College of Engineering, Punjabi University, Patiala 147002, Punjab (India)], E-mail: sanjivpurichd@yahoo.com

2009-07-15

295

Ages and sources of components of Zn-Pb, Cu, precious metal, and platinum group element deposits in the goodsprings district, clark county, Nevada  

USGS Publications Warehouse

The Goodsprings district, Clark County, Nevada, includes zinc-dominant carbonate replacement deposits of probable late Paleozoic age, and lead-dominant carbonate replacement deposits, copper ?? precious metal-platinum group element (PGE) deposits, and gold ?? silver deposits that are spatially associated with Late Triassic porphyritic intrusions. The district encompasses ??500 km2 although the distribution of all deposits has been laterally condensed by late Mesozoic crustal contraction. Zinc, Pb, and Cu production from about 90 deposits was ??160,000 metric tons (t) (Zn > Pb >> Cu), 2.1 million ounces (Moz) Ag, 0.09 Moz Au, and small amounts of PGEs-Co, V, Hg, Sb, Ni, Mo, Mn, Ir, and U-were also recovered. Zinc-dominant carbonate replacement deposits (Zn > Pb; Ag ?? Cu) resemble Mississippi Valley Type (MVT) Zn-Pb deposits in that they occur in karst and fault breccias in Mississippian limestone where the southern margin of the regional late Paleozoic foreland basin adjoins Proterozoic crystalline rocks of the craton. They consist of calcite, dolomite, sphalerite, and galena with variably positive S isotope compositions (??34S values range from 2.5-13%), and highly radiogenic Pb isotope compositions (206Pb/204Pb >19), typical of MVT deposits above crystalline Precambrian basement. These deposits may have formed when southward flow of saline fluids, derived from basinal and older sedimentary rocks, encountered thinner strata and pinch-outs against the craton, forcing fluid mixing and mineral precipitation in karst and fault breccias. Lead-dominant carbonate replacement deposits (Pb > Zn, Ag ?? Cu ?? Au) occur among other deposit types, often near porphyritic intrusions. They generally contain higher concentrations of precious metals than zinc-dominant deposits and relatively abundant iron oxides after pyrite. They share characteristics with copper ?? precious metal- PGE and gold ?? silver deposits including fine-grained quartz replacement of carbonate minerals in ore breccias and relatively low S and Pb isotope values (??34S values vary from 0-??4%; 206Pb/204Pb <18.5). Copper ?? precious metal-PGE deposits (Cu, Co, Ag, Au, Pd, and Pt) consist of Cu carbonate minerals (after chalcocite and chalcopyrite) and fine-grained quartz that have replaced breccia clasts and margins of fissures in Paleozoic limestones and dolomites near porphyritic intrusions. Gold ?? silver deposits occur along contacts and within small-volume stocks and dikes of feldspar porphyry, one textural variety of porphyritic intrusions. Lead isotope compositions of copper ?? precious metal-PGE, gold ?? silver, and lead-dominant carbonate replacement deposits are similar to those of Mojave crust plutons, indicating derivation of Pb from 1.7 Ga crystalline basement or from Late Proterozoic siliciclastic sedimentary rocks derived from 1.7 Ga crystalline basement. Four texturally and modally distinctive porphyritic intrusions are exposed largely in the central part of the district: feldspar quartz porphyry, plagioclase quartz porphyry, feldspar biotite quartz porphyry, and feldspar porphyry. Intrusions consist of 64 to 70 percent SiO2 and variable K2O/Na2O (0.14-5.33) that reflect proportions of K-feldspar and albite phenocrysts and megacrysts as well as partial alteration to K-mica; quartz and biotite phenocrysts are present in several subtypes. Albite may have formed during emplacement of magma in brine-saturated basinal strata, whereas hydrothermal alteration of matrix, phenocrystic, and megacrystic feldspar and biotite to K-mica, pyrite, and other hydrothermal minerals occurred during and after intrusion emplacement. Small volumes of garnet-diopside-quartz and retrograde epidote-mica-amphibole skarn have replaced carbonate rocks adjacent to one intrusion subtype (feldspar-quartz porphyry), but alteration of carbonate rocks at intrusion contacts elsewhere is inconsp. Uranium-lead ages of igneous zircons vary inconsistently from ?? 180 to 230

Vikre, P.; Browne, Q. J.; Fleck, R.; Hofstra, A.; Wooden, J.

2011-01-01

296

G2(+)M study on N-alkylamino cation affinities of neutral main-group element hydrides: trends across the periodic table.  

PubMed

We have made an extensive theoretical exploration of gas-phase N-alkylamino cation affinities (NAAMCA), including amino cation affinities (AMCA) and N-dimethylamino cation affinities (NDMAMCA), of neutral main-group element hydrides of groups 15-17 and periods 2-4 in the periodic table by using the G2(+)M method. Some similarities and differences are found between NAAMCA and the corresponding alkyl cation affinities (ACA) of HnX. Our calculations show that the AMCA and NDMAMCA are systematically lower than the corresponding proton affinities (PA) for HnX. In general, there is no linear correlation between NAAMCA and PA of HnX. Instead, the correlations exist only within the central elements X in period 2, or periods 3-4, which is significantly different from the reasonable correlations between ACA and PA for all HnX. NAAMCA (HnX) are weaker than NAAMCA (Hn-1X(-)) by more than 700 kJ/mol and generally stronger than ACA (HnX), with three exceptions: H2ONR2(+)(R = H, Me) and HFNH2(+). These new findings can be rationalized by the negative hyperconjugation and Pauli repulsion. PMID:24738576

Geng, Song; Wu, Ding-Lu; Yang, Jing; Wei, Xi-Guang; Zhu, Jun; Zhang, Hai-Bo; Ren, Yi; Lau, Kai-Chung

2014-05-01

297

LA-ICP-MS zircon geochronology and platinum-group elements characteristics of the Triassic basalts, SW China: Implications for post-Emeishan large igneous province magmatism  

NASA Astrophysics Data System (ADS)

The Triassic post-Emeishan large igneous province (ELIP) basalts, mainly found in the Kaiyuan (KY), Qilinshan (QLS), and Laochang-Kafang (LK) areas, show spatial and geochemical relationships with the Permian ELIP, SW China. Specifically, the post-ELIP basalts are located in the southern part of the intermediate zone of the ELIP. These basalts have major trace element and Sr-Nd isotope features that are similar to those of Permian Emeishan high-Ti basalts. The LA-ICP-MS zircon U-Pb age and whole-rock platinum-group elements (PGE) concentrations of the post-ELIP basalts are reported in this paper. The determined age of 247.7 ± 1.4 Ma for the KY volcanic rocks is almost 10 Ma younger than the termination age of the ELIP magmatism, supporting their origin from post-ELIP magmatism. All the post-ELIP basalts show uniform but significant low PGE contents. Ir and Ru are depleted relative to Rh, Pt, and Pd in the primitive mantle-normalized PGE patterns, suggesting that a low degree of partial melting of the mantle source plays an important role in the PGE characteristics of the post-ELIP basalts. The Ir and Ru contents of the post-ELIP basalts are similar to those of the Emeishan high-Ti basalts. However, the Pt and Pd contents are strikingly depleted. This is consistent with the notion of early extraction of palladium-group PGE during the eruption of the Emeishan basalts.

Zhang, Jiawei; Huang, Zhilong; Luo, Taiyi; Yan, Zaifei

2014-06-01

298

Group B streptococci escape host immunity by deletion of tandem repeat elements of the alpha C protein.  

PubMed Central

Group B streptococci (GBS) are the most common cause of neonatal sepsis, pneumonia, and meningitis. The alpha C protein is a surface-associated antigen; the gene (bca) for this protein contains a series of tandem repeats (each encoding 82 aa) that are identical at the nucleotide level and express a protective epitope. We previously reported that GBS isolates from two of 14 human maternal and neonatal pairs differed in the number of repeats contained in their alpha C protein; in both pairs, the alpha C protein of the neonatal isolate was smaller in molecular size. We now demonstrate by PCR that the neonatal isolates contain fewer tandem repeats. Maternal isolates were susceptible to opsonophagocytic killing in the presence of alpha C protein-specific antiserum, whereas the discrepant neonatal isolates proliferated. An animal model was developed to further study this phenomenon. Adult mice passively immunized with antiserum to the alpha C protein were challenged with an alpha C protein-expressing strain of GBS. Splenic isolates of GBS from these mice showed a high frequency of mutation in bca--most commonly a decrease in repeat number. Isolates from non-immune mice were not altered. Spontaneous deletions in the repeat region were observed at a much lower frequency (6 x 10(-4)); thus, deletions in that region are selected for under specific antibody pressure and appear to lower the organism's susceptibility to killing by antibody specific to the alpha C protein. This mechanism of antigenic variation may provide a means whereby GBS evade host immunity. Images Fig. 1 Fig. 2 Fig. 3 Fig. 4

Madoff, L C; Michel, J L; Gong, E W; Kling, D E; Kasper, D L

1996-01-01

299

The content of selected chemical elements in the hair of young men of the Bantu language group from Tanzania versus environmental and social conditioning.  

PubMed

Research works that would determine the content of chemical elements in black population organisms on the basis of hair analysis are not numerous. There are no studies referring to black populations living in indigenous environment, like the Mafinga region, Iringa District in Tanzania examined by us. The aim of the study performed was to analyse the content of chemical elements Fe, Ca, Mg, Zn and Cu in easily available biological media like hair. The material was collected in October 2005 and March 2006 during anthropological examination, which came from young males (n?=?91), students of a secondary school. Large Ca concentration range was found for the total number of subjects (680.20 to 2,089.70?µg/g d.m.). Mean Fe content in hair for the total number of subjects was 11.19?±?3.70?µg/g d.m., while that of Mg 6.84?±?2.02?µg/g d.m. Mean Zn concentration for the total number of subjects was 91.06?±?39.22?µg/g d.m., being significantly higher in younger group than in older one (p?=?0.039). Mean Cu concentration in hair for the total number of subjects was 7.50?±?2.90?µg/g d.m Body mass index (BMI?=?kg/m²) was calculated for the subjects showing that out of 91 men participating in the study 15.4% was characterised by mediocre nutrition. No statistically significant correlations were found between BMI and the analysed chemical elements. The analysis of the content of trace elements in the hair of the examined young males showed deficiencies in Zn, Cu, Fe and significantly in Mg. PMID:20041314

R?bacz, Ewa; Baranowska-Bosiacka, Irena; Chlubek, Dariusz

2010-12-01

300

Experimental design and optimization of leaching process for recovery of valuable chemical elements (U, La, V, Mo, Yb and Th) from low-grade uranium ore.  

PubMed

The paper deals with experimental design and optimization of leaching process of uranium and associated metals from low-grade, Polish ores. The chemical elements of interest for extraction from the ore were U, La, V, Mo, Yb and Th. Sulphuric acid has been used as leaching reagent. Based on the design of experiments the second-order regression models have been constructed to approximate the leaching efficiency of elements. The graphical illustrations using 3-D surface plots have been employed in order to identify the main, quadratic and interaction effects of the factors. The multi-objective optimization method based on desirability approach has been applied in this study. The optimum condition have been determined as P=5bar, T=120°C and t=90min. Under these optimal conditions, the overall extraction performance is 81.43% (for U), 64.24% (for La), 98.38% (for V), 43.69% (for Yb) and 76.89% (for Mo) and 97.00% (for Th). PMID:24857897

Zakrzewska-Koltuniewicz, Gra?yna; Herdzik-Koniecko, Irena; Cojocaru, Corneliu; Chajduk, Ewelina

2014-06-30

301

The origin and distribution of HAPs elements in relation to maceral composition of the A1 lignite bed (Paleocene, Calvert Bluff Formation, Wilcox Group), Calvert mine area, east-central Texas  

USGS Publications Warehouse

The origin and distribution of twelve potentially Hazardous Air Pollutants (HAPs; As, Be, Cd, Cr, Co, Hg, Mn, Ni, Pb Sb, Se, and U) identified in the 1990 Clean Air Act Amendments were examined in relation to the maceral composition of the A1 bed (Paleocene, Calvert Bluff Formation, Wilcox Group) of the Calvert mine in east-central Texas. The 3.2 m-thick A1 bed was divided into nine incremental channel samples (7 lignite samples and 2 shaley coal samples) on the basis of megascopic characteristics. Results indicate that As, Cd, Cr, Ni, Pb, Sb, and U are strongly correlated with ash yield and are enriched in the shaley coal samples. We infer that these elements are associated with inorganic constituents in the coal bed and may be derived from a penecontemporaneous stream channel located several kilometers southeast of the mining block. Of the HAPs elements studied, Mn and Hg are the most poorly correlated to ash yield. We infer an organic association for Mn; Hg may be associated with pyrite. The rest of the trace elements (Be, Co, and Se) are weakly correlated with ash yield. Further analytical work is necessary to determine the mode of occurrence for these elements. Overall, concentrations of the HAPs elements are generally similar to or less than those reported in previous studies of lignites of the Wilcox Group, east-central region, Texas. Petrographic analysis indicates the following ranges in composition for the seven lignite samples: liptinites (5-8%), huminites (88-95%), and inertinites (trace amounts to 7%). Samples from the middle portion of the A1 bed contain abundant crypto-eugelinite compared to the rest of the samples; this relationship suggests that the degradation of plant material was an important process during the development of the peat mire. With the exception of Hg and Mn, relatively low levels of the HAPs elements studied are found in the samples containing abundant crypto-eugelinite. We infer that the peat-forming environment for this portion of the coal bed was very wet with minimal detrital input. Relatively high concentrations of crypto-humotelinite were found in samples from the top and base of the coal bed. The presence of abundant crypto-humotelinite in this part of the coal bed suggests the accumulation of wood-rich peat under conditions conducive to a high degree of tissue preservation in the peat mire. Although several of the trace elements (Be, Co, Ni, and Sb) exhibit enrichment in these samples, they are not necessarily chemically associated with humotelinite. We infer that these elements, with the exception of Be, are possibly associated with deposition of the roof and floor rock of the coal bed; however, further analytical work would be necessary to confirm this hypothesis. Beryllium may have an organic origin. ?? 1997 Elsevier Science B.V.

Crowley, S. S.; Warwick, P. D.; Ruppert, L. F.; Pontolillo, J.

1997-01-01

302

Practical routes to (SiH?)?P: applications in group IV semiconductor activation and in group III-V molecular synthesis.  

PubMed

The (SiH?)?P hydride is introduced as a practical source for n-doping of group IV semiconductors and as a highly-reactive delivery agent of -(SiH?)?P functionalities in exploratory synthesis. In contrast to earlier methods, the compound is produced here in high purity quantitative yields via a new single-step method based on reactions of SiH?Br and (Me?Sn)?P, circumventing the need for toxic and unstable starting materials. As an initial demonstration of its utility we synthesized monosubstituted Me?M-P(SiH?)? (M = Al, Ga, In) derivatives of Me?M containing the (SiH?)?P ligand for the first time, in analogy to the known Me?M-P(SiMe?)? counterparts. A dimeric structure of Me?M-P(SiH?)? is proposed on the basis of spectroscopic characterizations and quantum chemical simulations. Next, in the context of materials synthesis, the (SiH?)?P compound was used to dope germanium for the first time by building a prototype p(++)Si(100)/i-Ge/n-Ge photodiode structure. The resultant n-type Ge layers contained active carrier concentrations of 3-4 × 10¹? atoms cm?³ as determined by spectroscopic ellipsometry and confirmed by SIMS. Strain analysis using high resolution XRD yielded a Si content of 4 × 10²? atoms cm?³ in agreement with SIMS and within the range expected for incorporating Si?P type units into the diamond cubic Ge matrix. Extensive characterizations for structure, morphology and crystallinity indicate that the Si co-dopant plays essentially a passive role and does not compromise the device quality of the host material nor does it fundamentally alter its optical properties. PMID:20379588

Tice, Jesse B; Chizmeshya, A V G; Tolle, J; D' Costa, V R; Menendez, J; Kouvetakis, J

2010-05-21

303

Revised Energy Spectra for Primary Elements, H - Si, above 50 GeV from the ATIC-2 Science Flight  

NASA Technical Reports Server (NTRS)

The Advanced Thin Ionization Calorimeter (ATIC) long duration balloon experiment had a successful science flight accumulating 18 days of data (12/02 - 1/03) during a single circumnavigation in Antarctica. ATIC measures the energy spectra of elements from H to Fe in primary cosmic rays using a fully active Bismuth Germanate calorimeter preceded by a carbon target, with embedded scintillator hodoscopes, and a silicon matrix charge detector at the top. Preliminary results from ATIC have been reported in previous conferences. The revised results reported here are derived from a new analysis of the data with improved charge resolution, lower background and revised energy calibration. The raw energy deposit spectra are de-convolved into primary energy spectra and extrapolated to the top of the atmosphere. We compare these revised results to previous data and comment upon the astrophysical interpretation of the results.

Wefel, J. P.; Adams, J. H., Jr.; Ahn, H. S.; Bashindzhagyan, G. L.; Chang, J.; Christl, M.; Fazely, A. R.; Ganel, O.; Gunashingha, R. M.; Guzik, T. G.; Isbert, J.; Kim, K. C.; Kouznetsov, E. N.; Panasyuk, M. I.; Panov, A. D.; Schmidt, W. K. H.; Seo, E. S.; Sokolskaya, N. V.; Watts, J. W.; Wu, J.; Zatsepin, V. I.

2007-01-01

304

The Finite Element Sea Ice-Ocean Model (FESOM) v.1.4: formulation of an ocean general circulation model  

NASA Astrophysics Data System (ADS)

The Finite Element Sea Ice-Ocean Model (FESOM) is the first global ocean general circulation model based on unstructured-mesh methods that has been developed for the purpose of climate research. The advantage of unstructured-mesh models is their flexible multi-resolution modelling functionality. In this study, an overview of the main features of FESOM will be given; based on sensitivity experiments a number of specific parameter choices will be explained; and directions of future developments will be outlined. It is argued that FESOM is sufficiently mature to explore the benefits of multi-resolution climate modelling and that its applications will provide information useful for the advancement of climate modelling on unstructured meshes.

Wang, Q.; Danilov, S.; Sidorenko, D.; Timmermann, R.; Wekerle, C.; Wang, X.; Jung, T.; Schröter, J.

2014-04-01

305

Wafer-scale integration of group III-V lasers on silicon using transfer printing of epitaxial layers  

NASA Astrophysics Data System (ADS)

The hard-drive and electronic industries can benefit by using the properties of light for power transfer and signalling. However, the integration of silicon electronics with lasers remains a challenge, because practical monolithic silicon lasers are not currently available. Here, we demonstrate a strategy for this integration, using an elastomeric stamp to selectively release and transfer epitaxial coupons of GaAs to realize III-V lasers on a silicon substrate by means of a wafer-scale printing process. Low-threshold continuous-wave lasing at a wavelength of 824 nm is achieved from Fabry-Pérot ridge waveguide lasers operating at temperatures up to 100 °C. Single and multi-transverse mode devices emit total optical powers of >60 mW and support modulation bandwidths of >3 GHz. This fabrication strategy opens a route to the low-cost integration of III-V photonic devices and circuits on silicon and other substrates.

Justice, John; Bower, Chris; Meitl, Matthew; Mooney, Marcus B.; Gubbins, Mark A.; Corbett, Brian

2012-09-01

306

Cardiovascular and neurohormonal responses to i. v. l-arginine in two groups with primary autonomic failure  

Microsoft Academic Search

Nitric oxide (NO) is synthesised from the amino-acid l-arginine by the enzyme nitric oxide synthetase (NOS) and modulates\\u000a a wide variety of neural, cardiovascular and hormonal processes. Cardiovascular autonomic dysfunction and impaired neurohormonal\\u000a secretion characterise patients with primary chronic autonomic failure (AF). To investigate the role of NO, we studied the\\u000a cardiovascular and neurohormonal effects of intravenous (i. v.) l-arginine

J. Kimber; L. Watson; C. J. Mathias

2001-01-01

307

Influence of Alloying with Elements of Subgroups IV, V, and VI on the Oxidation of Vanadium in Heating in Air  

SciTech Connect

It is established that unalloyed vanadium has the lowest oxidation resistance in air; it is resistant in air up to 523 K. Further heating leads to a marked increase in weight, especially at 737 K, and subsequently at 1000 K. X-ray diffraction analysis of the scale formed (573 - 737 K) indicates the presence on the surface of the oxides VO and V/sub 2/O/sub 3/ or of those close to them stoichometrically. In all cases the layer of metal directly adjoining the scale is characterized by an increased hardness and poor etchability. Composite derivatograms are shown which were obtained in heating of typ VnM-2 unalloyed vanadium and its alloys. It is shown that alloying of vanadium with niobium, tungsten, titanium, chromium, and zirconium increases its scaling resistance but has little influence on the temperature of the transition of the oxidation products to the liquid phase.

Shirokov, V.V.; Kas'yan, I.M.; Stepanishin, V.I; Vengrenovich, R.D.

1986-03-01

308

Interaction of transuranium elements with biologically important molecules: structural and spectroscopic study of NP(V) complexes with imidazole.  

PubMed

New Np(V) complexes with imidazole, [NpO(2)(CH(3)COO)(Im)(2)(H(2)O)], [(NpO(2))(2)(C(2)O(4))(Im)(6)] x 5 Im x H(2)O, and [NpO(2)(NO(2))(Im)(4)], were synthesized. Their crystal structures were determined using X-ray single-crystal diffractometry. The crystal structures are confirmed by IR and UV-vis spectroscopic data. In all three complexes, neptunium coordinates the imidazole molecule through the nitrogen atom. These complexes are the first example of direct bonding of the imidazole molecule to the actinide atom. These results suggest that coordination of histidine residue in proteins or other imidazole-containing biologically important molecules could occur under usual biological conditions. PMID:19166371

Andreev, Grigory B; Budantseva, Nina A; Tananaev, Ivan G; Myasoedov, Boris F

2009-02-01

309

Platinum-group element, Gold, Silver and Base Metal distribution in compositionally zoned sulfide droplets from the Medvezky Creek Mine, Noril'sk, Russia  

USGS Publications Warehouse

Concentrations of Ag, Au, Cd, Co, Re, Zn and Platinum-group elements (PGE) have been determined in sulfide minerals from zoned sulfide droplets of the Noril'sk 1 Medvezky Creek Mine. The aims of the study were; to establish whether these elements are located in the major sulfide minerals (pentlandite, pyrrhotite, chalcopyrite and cubanite), to establish whether the elements show a preference for a particular sulfide mineral and to investigate the model, which suggests that the zonation in the droplets is caused by the crystal fractionation of monosulfide solid solution (mss). Nickel, Cu, Ag, Re, Os, Ir, Ru, Rh and Pd, were found to be largely located in the major sulfide minerals. In contrast, less than 25% of the Au, Cd, Pt and Zn in the rock was found to be present in these sulfides. Osmium, Ir, Ru, Rh and Re were found to be concentrated in pyrrhotite and pentlandite. Palladium and Co was found to be concentrated in pentlandite. Silver, Cd and Zn concentrations are highest in chalcopyrite and cubanite. Gold and platinum showed no preference for any of the major sulfide minerals. The enrichment of Os, Ir, Ru, Rh and Re in pyrrhotite and pentlandite (exsolution products of mss) and the low levels of these elements in the cubanite and chalcopyrite (exsolution products of intermediate solid solution, iss) support the mss crystal fractionation model, because Os, Ir, Ru, Rh and Re are compatible with mss. The enrichment of Ag, Cd and Zn in chalcopyrite and cubanite also supports the mss fractionation model these minerals are derived from the fractionated liquid and these elements are incompatible with mss and thus should be enriched in the fractionated liquid. Gold and Pt do not partition into either iss or mss and become sufficiently enriched in the final fractionated liquid to crystallize among the iss and mss grains as tellurides, bismithides and alloys. During pentlandite exsolution Pd appears to have diffused from the Cu-rich portion of the droplet into pentlandite. ?? Springer-Verlag 2006.

Barnes, S. -J.; Cox, R. A.; Zientek, M. L.

2006-01-01

310

Two-step Synthesis of Multi-Substituted Amines by Using an N-Methoxy Group as a Reactivity Control Element.  

PubMed

The development of a two-step synthesis of multi-substituted N-methoxyamines from N-methoxyamides is reported. Utilization of the N-methoxy group as a reactivity control element was the key to success in this two-step synthesis. The first reaction involves a N-methoxyamide/aldehyde coupling reaction. Whereas ordinary amides cannot condense with aldehydes intermolecularly due to the poor nucleophilicity of the amide nitrogen, the N-methoxy group enhances the nucleophilicity of the nitrogen, enabling the direct coupling reaction. The second reaction in the two-step process was nucleophilic addition to the N-methoxyamides. Incorporation of the N-methoxy group into the amides increased the electrophilicity of the amide carbonyls and promoted the chelation effect. This nucleophilic addition enabled quick diversification of the products derived from the first step. The developed strategy was applicable to a variety of substrates, resulting in the elaboration of multi-substituted piperidines and acyclic amines, as well as a substructure of a complex natural alkaloid. PMID:24862505

Yoritate, Makoto; Meguro, Tatsuhiko; Matsuo, Naoya; Shirokane, Kenji; Sato, Takaaki; Chida, Noritaka

2014-06-23

311

Comparative mitochondrial genomics in zygomycetes: bacteria-like RNase P RNAs, mobile elements and a close source of the group I intron invasion in angiosperms  

PubMed Central

To generate data for comparative analyses of zygomycete mitochondrial gene expression, we sequenced mtDNAs of three distantly related zygomycetes, Rhizopus oryzae, Mortierella verticillata and Smittium culisetae. They all contain the standard fungal mitochondrial gene set, plus rnpB, the gene encoding the RNA subunit of the mitochondrial RNase P (mtP-RNA) and rps3, encoding ribosomal protein S3 (the latter lacking in R.oryzae). The mtP-RNAs of R.oryzae and of additional zygomycete relatives have the most eubacteria-like RNA structures among fungi. Precise mapping of the 5? and 3? termini of the R.oryzae and M.verticillata mtP-RNAs confirms their expression and processing at the exact sites predicted by secondary structure modeling. The 3? RNA processing of zygomycete mitochondrial mRNAs, SSU-rRNA and mtP-RNA occurs at the C-rich sequence motifs similar to those identified in fission yeast and basidiomycete mtDNAs. The C-rich motifs are included in the mature transcripts, and are likely generated by exonucleolytic trimming of RNA 3? termini. Zygomycete mtDNAs feature a variety of insertion elements: (i) mtDNAs of R.oryzae and M.verticillata were subject to invasions by double hairpin elements; (ii) genes of all three species contain numerous mobile group I introns, including one that is closest to an intron that invaded angiosperm mtDNAs; and (iii) at least one additional case of a mobile element, characterized by a homing endonuclease insertion between partially duplicated genes [Paquin,B., Laforest,M.J., Forget,L., Roewer,I., Wang,Z., Longcore,J. and Lang,B.F. (1997) Curr. Genet., 31, 380–395]. The combined mtDNA-encoded proteins contain insufficient phylogenetic signal to demonstrate monophyly of zygomycetes.

Seif, Elias; Leigh, Jessica; Liu, Yu; Roewer, Ingeborg; Forget, Lise; Lang, B. Franz

2005-01-01

312

SWIFT trial of delayed elective intervention v conservative treatment after thrombolysis with anistreplase in acute myocardial infarction. SWIFT (Should We Intervene Following Thrombolysis?) Trial Study Group.  

PubMed Central

OBJECTIVE--To see whether early elective angiography with a view to coronary angioplasty or bypass grafting of a stenosed infarct related vessel would improve outcome in acute myocardial infarction treated by thrombolysis with anistreplase. DESIGN--Randomised study of two treatment strategies with analysis of results over 12 months. SETTING--21 district hospitals and regional cardiac centres in Britain and Ireland. SUBJECTS--800 of 993 patients presenting with clinical and electrocardiographic features of acute myocardial infarction up to three hours after the onset of major symptoms. TREATMENT STRATEGIES--Intravenous anistreplase 30 units followed by a standard regimen of heparin, warfarin, and timolol and (in patients so randomised) early angiography plus appropriate intervention. MAIN OUTCOME MEASURE--Death or reinfarction within 12 months. RESULTS--397 patients were randomised to receive early angiography plus appropriate intervention (coronary angioplasty in 169 cases, coronary grafting in 59) and 403 patients to receive conservative care (of these, 12 had angioplasty and seven bypass grafting during the initial admission). By 12 months mortality (5.8% (23 patients) in the intervention group v 5.0% (20) in the conservative care group; p = 0.6) and rates of reinfarction (15.1% (60 patients) v 12.9% (52); p = 0.4) were similar in the two groups. No significant differences in rates of angina or rest pain were found at 12 months. Left ventricular ejection fraction at three and 12 months was the same in both groups. Median hospital stay was longer in the intervention group (11 days v 10 days; p less than 0.0001). CONCLUSION--For most patients given thrombolytic treatment for acute myocardial infarction a strategy of angiography and intervention is appropriate only when required for clinical indications.

1991-01-01

313

Determination of gold and the platinum group elements in geological samples by ICP-MS after nickel sulphide fire assay: difficulties encountered with different types of geological samples.  

PubMed

Problems involved in the determination of Au and the platinum group elements by the nickel sulphide fire assay (NiS-FA) procedure for black shale samples, samples containing magnetite, and samples containing As, Cu, and Fe were studied. The interference of the graphite in black shale samples was eliminated either by roasting the sample prior to fusion or by adding an oxidant to the fusion flux. Addition of a reducing agent to samples, containing the oxygen-rich mineral magnetite, enabled the NiS-FA procedure to be carried out for this sample type. The interference of Cu on Rh in the ICP-MS determination was corrected by establishing a linear correlation between the interference of Cu on (103)Rh and (105)Pd. PMID:18968787

Juvonen, R; Lakomaa, T; Soikkeli, L

2002-09-12

314

Platinum group elements in gold-sulfide and base-metal ores of the Sayan-Baikal Fold Region and possible platinum and palladium speciation in sulfides  

NASA Astrophysics Data System (ADS)

The concentration levels and distribution features of the platinum group elements (PGE) in quartz-sulfide and base-metal ores in deposits of the Sayan-Baikal Fold Region (SBFR) are discussed. Microfire assay neutron activation analysis (MF-NAA), which enables one to work on a nondestructive basis and allows one to avoid inaccuracies related to chemical sample preparation, was used as the main analytical technique. Three types of hydrothermal mineralization with elevated grades of PGE (especially Pt, Pd, and Ru) have been identified: (1) pyrite-pyrrhotite (massive sulfide) mineralization hosted in black shales of the Il’chir Sequence; (2) gold-sulfide ores of the Zun-Kholba, Tainsky, Kamenny, and some other gold deposits; and (3) silver-basemetal ores of the Dzhida-Vitim Zone. The PGE contents significantly vary, from global average values to tens of grams per ton. An absence of PGE minerals implies that these elements are finely dispersed in sulfide minerals and native gold. Taking into account difficulties in conversion of PGE into analytical forms, their nonuniform distribution in sulfide minerals, their high affinity to coordination compounds, and experimental results, cluster species of Pt and Pd in major minerals are suggested for the gold-sulfide and silver-base-metal ores in deposits, which are related to suprasubduction ophiolites and island-arc and intraplate settings in the SBFR.

Mironov, A. G.; Zhmodik, S. M.; Kolesov, G. M.; Mit'kin, V. N.; Damdinov, B. B.; Zayakina, S. B.

2008-02-01

315

Multireference - M?ller-Plesset Perturbation Theory Results on Levels and Transition Rates in Al-like Ions of Iron Group Elements  

SciTech Connect

Ground configuration and low-lying levels of Al-like ions contribute to a variety of laboratory and solar spectra, but the available information in databases are neither complete not necessarily correct. We have performed multireference Moeller-Plesset perturbation theory calculations that approach spectroscopic accuracy in order to check the information that databases hold on the 40 lowest levels of Al-Like ions of iron group elements (K through Ge), and to provide input for the interpretation of concurrent experiments. Our results indicate problems of the database holdings on the levels of the lowest quartet levels in the lighter elements of the range studied. The results of our calculations of the decay rates of five long-lived levels (3s{sup 2}3p {sup 2}p{sup o}{sub 3/2}, 3s3p{sup 2} {sup 4}P{sup o} J and 3s3p3d {sup 4}F{sup o}{sub 9/2}) are compared with lifetime data from beam-foil, electron beam ion trap and heavy-ion storage ring experiments.

Santana, J A; Ishikawa, Y; Tr?abert, E

2009-02-19

316

U.v.-irradiation of thin films of polystyrene derivatives: formation of carboxylic group and crosslinking from 4-trimethylsilylmethyl substituent  

Microsoft Academic Search

Photoirradiation of thin films of poly(4-trimethylsilylmethylstyrene) (PTMSMS), poly(4-methylstyrene) (P4MS), and polystyrene (PS) at 254 nm with a low-pressure Hg lamp in air made the surfaces hydrophilic through oxygenation. The hydrophilicity estimated from the contact angle with water was in the order of PTMSMS ? P4MS > PS. Formation of carboxylic acid group on the surface and crosslinking in the bulk

Hiroo Inoue; Kazuhiko Mizuno; N ICHINOSE; S KAWANISHI

1996-01-01

317

Ir, Ru, Pt, and Pd in basalts and komatiites: New constraints for the geochemical behavior of the platinum-group elements in the mantle  

SciTech Connect

The concentrations of the platinum-group elements (PGE) Ir, Ru, Pt, and Pd were determined in 18 mantle-derived basalts from a variety of tectonic settings and six komatiites from three locations. All analyses were performed using isotope dilution, Carius tube digestion, and the precise technique of multiple collector inductively coupled plasma mass spectrometry. Multiple analyses of two samples indicate external reproducibilities, based upon separate dissolutions, or approximately 2--9% in the ppt to ppb concentration range. Mid-ocean ridge basalts from the Kolbeinsey Ridge, tholeiites from Iceland and alkali basalts from the Cameroon Line define three individual samples suites that are characterized by distinct major, trace, and platinum-group element systematics. All three-sample suites display correlations of the PGE with MgO, Ni, and Cr. The new analytical results are employed to constrain the geochemical behavior of the PGE during the formation and differentiation of mantle-derived melts. The PGE are inferred to be compatible in sulfides during partial melting with sulfide-silicate melt partition coefficients of {approximately}1 x 10{sup 4}. The fractionated PGE patterns of mantle melts re a consequence of the incompatibility of Pd in nonsulfide phases, whereas Ir and Ru must be compatible in at least one other mantle phase. Model calculations indicate that PGE alloys or spinel may be responsible for the higher compatibility of the latter elements during partial melting. It is further demonstrated that the shape of the melting regime has a profound effect on the PGE systematics of mantle magmas. The systematic trends of the three samples suites in plots of PGE against Ni and Cr are the results of magma differentiation processes that involve fractional crystallization of silicate minerals and the concurrent segregation of an immiscible sulfide liquid. The behavior of the PGE during magma fractionation indicates that the segregated sulfides probably equilibrate with {gt}90% of the silicate magma and that PGE scavenging by sulfides is best described by a combination of batch and fractional equilibrium partitioning.

Rehkaemper, M.; Halliday, A.N.; Fitton, J.G.; Lee, D.C.; Wieneke, M.; Arndt, N.T.

1999-11-01

318

Measurement of L X-ray fluorescence cross-sections for elements with 45 ? Z ? 50 using synchrotron radiation at 8 keV  

NASA Astrophysics Data System (ADS)

The L shell fluorescence cross-sections of the elements in range 45 ? Z ? 50 have been determined at 8 keV using Synchrotron radiation. The individual L X-ray photons, Ll, L?, L?I, L?II, L?I and L?II produced in the target were measured with high resolution Si( Li) detector. The experimental set-up provided a low background by using linearly polarized monoenergetic photon beam, improving the signal-to-noise ratio. The experimental cross-sections obtained in this work were compared with available experimental data from Scofield [1,2] Krause [3,4] and Scofield and Puri et al. [5,6]. These experimental values closely agree with the theoretical values calculated using Scofield and Krause data, except for the case of L?, where values measured of this work are slighter higher.

Bonzi, Edgardo V.; Badiger, Nagappa M.; Grad, Gabriela B.; Barrea, Raúl A.; Figueroa, Rodolfo G.

2011-10-01

319

Elastic scattering of {59.54}-keV ?-rays in elements with {22 ? {Z} ? {92}} at momentum transfer {0.4 ? {x} ? 4.7 {Å}-1}  

NASA Astrophysics Data System (ADS)

Differential cross sections for elastic scattering of the 59.54 keV ?-rays in elements with 22 ?Z ?92 have been measured over the angular range 10?-160?corresponding to the momentum transfer 0.4 ?x ?4.7 Å-1. The measurements at forward and backward angles were performed using the 241Am radioactive point-source, target and the Ge detectors in the transmission and reflection arrangements, respectively. The measured differential scattering cross sections are compared with those based on the form-factor (FF) formalism and state-of-the-art S-matrix calculations to differentiate between their relative efficacies and to check angular-dependence of the anomalous scattering factors (ASF) incorporated as correction to the modified form-factor (MF). The S-matrix values exhibit agreement with the measured data at backward angles and differences ˜10% at forward angles. The scattering cross sections based on the MF including ASF’s are in general lower at various angles by up to 20% for medium- and high-Z elements. The observed deviations being higher at the forward angles infer possibility of angular-dependence of ASF’s.

Kumar, S.; Sharma, V.; Shahi, J. S.; Mehta, D.; Singh, N.

2009-10-01

320

Group V secretory phospholipase A2 is involved in macrophage activation and is sufficient for macrophage effector functions in allergic pulmonary inflammation  

PubMed Central

We reported that Pla2g5-null mice lacking group V secretory phospholipase A2 (gV-sPLA2) showed reduced eosinophilic pulmonary inflammation and Th2 cytokine generation when challenged with an extract (Df) from house dust mite Dermatophagoides farinae, compared to wild-type (WT) controls. Adoptive transfer studies suggested that gV-sPLA2 in dendritic cells (DCs) was necessary for sensitization of Pla2g5-null mice, but was not sufficient to induce the effector phase of pulmonary inflammation. Here, we demonstrate that gV-sPLA2 is inducibly expressed in mouse and human macrophages (M? activated by IL-4, and is required for the acquisition of M? effector functions that facilitate the effector phase of pulmonary inflammation. We demonstrate that gV-sPLA2 expression in M? is sufficient for the development of pulmonary inflammation, even when inflammation is induced by intrapulmonary administration of IL-4. The concentrations of CCL22/CCL17 and effector T-cell recruitment are severely impaired in Pla2g5-null mice. Intratracheal transfers of enriched CD68+ cells isolated from the lungs of Df-challenged WT donor mice induce eosinophilia, chemokine production, and recruitment of T-cells into the lungs of Pla2g5-null recipients previously sensitized by WT Df-loaded DCs. Our studies identified a unique function of gV-sPLA2 in activation of M? and in their capacity to recruit T-cells to amplify the effector phase of pulmonary inflammation.

Ohta, Shin; Imamura, Mitsuru; Xing, Wei; Boyce, Joshua A.; Balestrieri, Barbara

2013-01-01

321

Methods for forming group III-arsenide-nitride semiconductor materials  

NASA Technical Reports Server (NTRS)

Methods are disclosed for forming Group III-arsenide-nitride semiconductor materials. Group III elements are combined with group V elements, including at least nitrogen and arsenic, in concentrations chosen to lattice match commercially available crystalline substrates. Epitaxial growth of these III-V crystals results in direct bandgap materials, which can be used in applications such as light emitting diodes and lasers. Varying the concentrations of the elements in the III-V crystals varies the bandgaps, such that materials emitting light spanning the visible spectra, as well as mid-IR and near-UV emitters, can be created. Conversely, such material can be used to create devices that acquire light and convert the light to electricity, for applications such as full color photodetectors and solar energy collectors. The growth of the III-V crystals can be accomplished by growing thin layers of elements or compounds in sequences that result in the overall lattice match and bandgap desired.

Major, Jo S. (Inventor); Welch, David F. (Inventor); Scifres, Donald R. (Inventor)

2002-01-01

322

First principles DFT study of ferromagnetism in SnO2 induced by doped group 1A and 2A non-magnetic elements X (X=Li, Na, K, Be, Mg, Ca)  

NASA Astrophysics Data System (ADS)

Transition metal - free - ferromagnetism in diluted magnetic semiconductors (DMS) is of much current interest in the search for more efficient DMS materials for spintronic applications. Here, we report the results of our first principles density functional theory (DFT) study on impurity - induced ferromagnetism in non-magnetic SnO2 by a non-magnetic impurity. The impurities considered are sp-type of group 1A and 2A elements X (X = Li, Na, K, Be, Mg, Ca). Even a single atom of the group 1A elements makes the system magnetic, whereas for the group 2A elements Ca and Mg, a higher doping is required to induce ferromagnetism. For all the elements studied, the magnetic moment appears to increase with the doping concentration, at least at certain impurity separations, which is a positive indicator for practical applications.

Chakraborty, Brahmananda; Ramaniah, Lavanya M.

2014-04-01

323

ICEG2D (v2.0) - An Integrated Software Package for Automated Prediction of Flow Fields for Single-Element Airfoils With Ice Accretion  

NASA Technical Reports Server (NTRS)

An integrated geometry/grid/simulation software package, ICEG2D, is being developed to automate computational fluid dynamics (CFD) simulations for single- and multi-element airfoils with ice accretions. The current version, ICEG213 (v2.0), was designed to automatically perform four primary functions: (1) generate a grid-ready surface definition based on the geometrical characteristics of the iced airfoil surface, (2) generate high-quality structured and generalized grids starting from a defined surface definition, (3) generate the input and restart files needed to run the structured grid CFD solver NPARC or the generalized grid CFD solver HYBFL2D, and (4) using the flow solutions, generate solution-adaptive grids. ICEG2D (v2.0) can be operated in either a batch mode using a script file or in an interactive mode by entering directives from a command line within a Unix shell. This report summarizes activities completed in the first two years of a three-year research and development program to address automation issues related to CFD simulations for airfoils with ice accretions. As well as describing the technology employed in the software, this document serves as a users manual providing installation and operating instructions. An evaluation of the software is also presented.

Thompson David S.; Soni, Bharat K.

2001-01-01

324

Batisivite, V8Ti6[Ba(Si2O)]O28, a new mineral species from the derbylite group  

NASA Astrophysics Data System (ADS)

Batisivite has been found as an accessory mineral in the Cr-V-bearing quartz-diopside metamorphic rocks of the Slyudyanka Complex in the southern Baikal region, Russia. A new mineral was named after the major cations in its ideal formula (Ba, Ti, Si, V). Associated minerals are quartz, Cr-V-bearing diopside and tremolite; calcite; schreyerite; berdesinskiite; ankangite; V-bearing titanite; minerals of the chromite-coulsonite, eskolaite-karelianite, dravite-vanadiumdravite, and chernykhite-roscoelite series; uraninite; Cr-bearing goldmanite; albite; barite; zircon; and unnamed U-Ti-V-Cr phases. Batisivite occurs as anhedral grains up to 0.15-0.20 mm in size, without visible cleavage and parting. The new mineral is brittle, with conchoidal fracture. Observed by the naked eye, the mineral is black and opaque, with a black streak and resinous luster. Batisivite is white in reflected light. The microhardness (VHN) is 1220-1470 kg/mm2 (load is 30 g), the mean value is 1330 kg/mm2. The Mohs hardness is near 7. The calculated density is 4.62 g/cm3. The new mineral is weakly anisotropic and bireflected. The measured values of reflectance are as follows (?, nm— R {max/'}/ R {min/'}): 440—17.5/17.0; 460—17.3/16.7; 480—17.1/16.5; 500—17.2/16.6; 520—17.3/16.7; 540—17.4/16.8; 560—17.5/16.8; 580—17.6/16.9; 600—17.7/17.1; 620—17.7/17.1; 640—17.8/17.1; 660—17.9/17.2; 680—18.0/17.3; 700—18.1/17.4. Batisivite is triclinic, space group P overline 1 ; the unit-cell dimensions are: a = 7.521(1) Å, b = 7.643(1) Å, c = 9.572(1) Å, ? = 110.20°(1), ? = 103.34°(1), ? = 98.28°(1), V = 487.14(7) Å3, Z = 1. The strongest reflections in the X-ray powder diffraction pattern [ d, Å ( I, %)( hkl)] are: 3.09(8)(12 overline 2 ); 2.84, 2.85(10)(021, 120); 2.64(8)(21 overline 3 ); 2.12(8)(31 overline 3 ); 1.785(8)(32 overline 4 ), 1.581(10)(24 overline 2 ); 1.432, 1.433(10)(322, 124). The chemical composition (electron microprobe, average of 237 point analyses, wt %) is: 0.26 Nb2O5, 6.16 SiO2, 31.76 TiO2, 1.81 Al2O3, 8.20 VO2, 26.27 V2O3, 12.29 Cr2O3, 1.48 Fe2O3, 0.08 MgO, 11.42 BaO; the total is 99.73. The VO2/V2O3 ratio has been calculated. The simplified empirical formula is (V{4.8/3+}Cr2.2V{0.7/4+}Fe0.3)8.0(Ti5.4V{0.6/4+})6.0[Ba(Si1.4Al0.5O0.9)]O28. An alternative to the title formula could be a variety (with the diorthogroup Si2O7) V8Ti6[Ba(Si2O7)]O22. Batisivite probably pertains to the V{8/3+}Ti{6/4+}[Ba(Si2O)]O28-Cr{8/3+}Ti{6/4+} [Ba(Si2O)]O28 solid solution series. The type material of batisivite has been deposited in the Fersman Mineralogical Museum, Russian Academy of Sciences, Moscow.

Reznitsky, L. Z.; Sklyarov, E. V.; Armbruster, T.; Galuskin, E. V.; Ushchapovskaya, Z. F.; Polekhovsky, Yu. S.; Karmanov, N. S.; Kashaev, A. A.; Barash, I. G.

2008-12-01

325

Proton inelastic mean free path in a group of bioorganic compounds and water in 0.05-10 MeV range - Including higher-order corrections  

NASA Astrophysics Data System (ADS)

The systematic calculations of the inelastic mean free paths (MFP) of 0.05-10 MeV protons in a group of eleven important bioorganic compounds, i.e. DNA, five bases, three fatty acids, cellulose and ?-carotene, have been performed. The expressions for the calculations are derived from the Ashley's optical-data model and from the higher-order correction terms in stopping power calculations. Especially, the Bloch correction for the inelastic MFP is proposed empirically in this work. The inelastic MFPs for energetic protons in water are also evaluated and compared with other theoretical calculations. The proton inelastic MFPs for these 11 bioorganic compounds in the energy range from 0.05 to 10 MeV are presented here for the first time, and might be useful for studies of various radiation effects in these materials.

Tan, Zhenyu; Xia, Yueyuan; Zhao, Mingwen; Liu, Xiangdong

2010-07-01

326

Effects of mother lode-type gold mineralization on 187Os/188Os and platinum group element concentrations in peridotite: Alleghany District, California  

USGS Publications Warehouse

Osmium isotope compositions and concentrations of Re, platinum group elements (PGE), and Au were determined for host peridotites (serpentinites and barzburgites) and hydrothermally altered ultramafic wall rocks associated with Mother Lode-type hydrothermal gold-quartz vein mineralization in the Alleghany district, California. The host peridotites have Os isotope compositions and Re, PGE, and Au abundances typical of the upper mantle at their presumed formation age during the late Proterozoic or early Paleozoic. The hydrothermally altered rocks have highly variable initial Os isotope compositions with ??os, values (% deviation of 187OS/188OS from the chondritic average calculated for the approx. 120 Ma time of mineralization) ranging from -1.4 to -8.3. The lowest Os isotope compositions are consistent with Re depletion of a chondritic source (e.g., the upper mantle) at ca. 1.6 Ga. Most of the altered samples are enriched in Au and have depleted and fractionated abundances of Re and PGE relative to their precursor peridotites. Geoehemical characteristics of the altered samples suggest that Re and some PGE were variably removed from the ultramafic rocks during the mineralization event. In addition to Re, the Pt and Pd abundances of the most intensely altered rocks appear to have been most affected by mineralization. The 187Os-depleted isotopic compositions of some altered rocks are interpreted to be a result of preferential 187Os loss via destruction of Re-rich phases during the event. For these rocks, Os evidently is not a useful tracer of the mineralizing fluids. The results do, however, provide evidence for differential mobility of these elements, and mobility of 187Os relative to the initial bulk Os isotope composition during hydrothermal metasomatic alteration of ultramafic rocks. ?? 2007 Society of Economic Geologists, Inc.

Walker, R. J.; Bohlke, J. K.; McDonough, W. F.; Li, J.

2007-01-01

327

Endothelial protein C receptor-associated invasiveness of rheumatoid synovial fibroblasts is likely driven by group V secretory phospholipase A2  

PubMed Central

Introduction Rheumatoid synovial fibroblasts (RASFs) mediate joint inflammation and destruction in rheumatoid arthritis (RA). Endothelial protein C receptor (EPCR) is a specific receptor for the natural anticoagulant activated protein C (APC). It mediates the cytoprotective properties of APC and is expressed in rheumatoid synovial tissue. A recent report shows that group V secretory phospholipase A2 (sPLA2V) prevents APC from binding to EPCR in endothelium and inhibits EPCR/APC function. The aim of this study was to investigate the expression and function of EPCR on RASFs. Methods Human synovial fibroblasts (SFs) were isolated from RA or osteoarthritis (OA) synovial tissues and treated with control, EPCR, or sPLA2V small interfering RNA (siRNA); recombinant human APC, tumor necrosis factor-alpha (TNF-?), or sPLA2V. RASF viability and migration/invasion were measured by 3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyl tetrazolium bromide (MTT) and collagen gel migration/invasion assays, respectively, and cartilage degradation by 1,9-dimethylmethylene blue (DMMB) assay in the presence of human OA articular cartilage explants. The expression or activation of cytokines, EPCR, cadherin-11, mitogen-activated protein (MAP) kinases, and nuclear factor-kappa-B (NF-?B) or both were detected by enzyme-linked immunosorbent assay, Western blotting, or immunostaining. Results EPCR was expressed by both OASFs and RASFs but was markedly increased in RASFs. When EPCR was suppressed by siRNA or blocking antibody cell viability, cell invasion and cartilage degradation were reduced by more than 30%. Inflammatory mediators interleukin-1-beta (IL-1?), cadherin-11, and NF-?B were significantly reduced by EPCR suppression under control or TNF-?-stimulated conditions. The expression or activation (or both) of MAP kinases ERK, p38, and JNK were also markedly decreased in cells transfected with EPCR siRNA. Further analysis revealed that sPLA2V co-localized with EPCR on RASFs. Suppression of sPLA2V reduced cell viability and cartilage degradation and increased APC binding to RASFs. Conversely, recombinant sPLA2V increased cartilage degradation, blocked APC binding to RASFs, and could not rescue the effects induced by EPCR suppression. Conclusions Our results demonstrate that EPCR is overexpressed by RASFs and mediates the aggressive behavior of RASFs. This function of EPCR is contrary to its cytoprotective role in other settings and is likely driven by sPLA2V.

2014-01-01

328

Minor and trace element abundances in chondritic meteorites  

Microsoft Academic Search

The abundances of the elements Cl, F, P, Mn, Ti, Zn, Ge, Co, Ni, Fe, V, Cu, Sr, Cr, Ba and Sc have been determined in a total of fifty meteorites involving representatives of all chondrite groups. These analyses are discussed in terms of the observed co-variations among the various elements and the chemical fractionation which distinguishes the individual chondrite

L. Greenland; J. F. Lovering

1965-01-01

329

Distribution of platinum-group elements in magmatic and altered ores in the Jinchuan intrusion, China: an example of selenium remobilization by postmagmatic fluids  

NASA Astrophysics Data System (ADS)

The division of platinum-group elements (PGE) between those hosted in platinum-group minerals (PGM) versus those in solid solution in base metal sulfides (BMS) has been determined for ores from the PGE-bearing Ni-Cu-rich Jinchuan intrusion in northwest China. All the BMS are devoid of Pt and Ir, and magmatic BMS are also barren of Rh. These PGE may have been scavenged by arsenic to form PGM during magmatic crystallization of the BMS. Pd, Os, and Ru are recorded in BMS and Pd is predominantly in solid solution in pentlandite. Unlike the fresh magmatic ores, in altered or serpentinized ores, Pd-PGM are present. Froodite is hosted in magnetite, formed during alteration of BMS, accompanied by sulfur loss and liberation of Pd. Michenerite ([Pd,Pt]BiTe), sperrylite (PtAs2), and Au-bearing PGM are located in altered silicates. Irarsite (IrAsS) occurs mainly enclosed in BMS. Padmaite (PdBiSe), identified at the junctions of magnetite and BMS, was the last PGM to form and locally partially replaces earlier non-Se-bearing PGM. We propose that padmaite formed under oxidizing conditions during late local remobilization of Se from the BMS. Se-bearing PGM are rare and our review shows they are frequently associated with carbonate, suggesting that Pd and Se can be mobilized great distances in low pH oxidizing fluids and may be precipitated on contact with carbonate. S/Se ratios are used by researchers of magmatic Ni-Cu-PGE ores to determine sulfur loss, assuming Se is immobile and representative of magmatic sulfur content. This study shows that Se as well as S is potentially mobile and this should be considered in the use of S/Se ratios.

Prichard, Hazel M.; Knight, Robert D.; Fisher, Peter C.; McDonald, Iain; Zhou, Mei-Fu; Wang, Christina Y.

2013-08-01

330

The mineralogy and mineral associations of platinum group elements and gold in the Platreef at Zwartfontein, Akanani Project, Northern Bushveld Complex, South Africa  

NASA Astrophysics Data System (ADS)

The mineralogy of the platinum-group elements (PGE), and gold, in the Platreef of the Bushveld Complex, was investigated using an FEI Mineral Liberation Analyser. Polished sections were prepared from 171 samples collected from two boreholes, for the in-situ examination of platinum group minerals (PGM). PGM and gold minerals encountered include maslovite (PtBiTe, 32 area% of total PGM), kotulskite (Pd(BiTe), 17 %), isoferroplatinum (Pt3Fe, 15 %), sperrylite (PtAs2, 11 %), cooperite (PtS, 5 %), moncheite (PtTe2; 5 %), electrum (AuAg; 5 %), michenerite (PdBiTe; 3 %), Pd alloys (Pd, Sb, Sn; 3 %), hollingworthite ((Rh,Pt)AsS; 2 %), as well as minor (all <1 area% of total PGM) merenskyite (PdBiTe2), laurite (RuS2), rustenburgite (Pt0.4Pd0.4Sn0.2), froodite (PdBi2), atokite (Pd0.5Pt0.3Sn0.2), stumpflite (PtSb), plumbopalladinite (Pd3Pb2), and zvyagintsevite (Pd3Pb). An observed association of all PGM with base metal sulfides (BMS), and a pronounced association of PGE tellurides, arsenides and Pd&Pt alloys with secondary silicates, is consistent with the remobilisation and recrystallisation of some of the PGM's during hydrothermal alteration and serpentinisation subsequent to their initial (primary) crystallisation from BMS (e.g. Godel et al. J Petrol 48:1569-1604, 2007; Hutchinson and McDonald Appl Earth Sci (Trans Inst Min Metall B) 114:B208-224, 2008).

van der Merwe, Frits; Viljoen, Fanus; Knoper, Mike

2012-09-01

331

Pt-Pd reefs in magnetitites of the Stella layered intrusion, South Africa: A world of new exploration opportunities for platinum group elements  

NASA Astrophysics Data System (ADS)

The 3033 Ma Stella layered intrusion of South Africa consists largely of magnetite gabbros and gabbros that are hosted by greenstones of the Kraaipan belt. The intrusion contains a 100-m-thick, platinum group element (PGE) enriched interval that includes a number of laterally continuous PGE reefs constituting the oldest mineralization of this type known on Earth. The richest of the reefs is hosted by magnetitite and contains 10 15 ppm Pt + Pd over 1 m, representing by far the highest PGE grades known up to this time in magnetitite-hosted Pt-Pd reefs. The PGEs are interpreted to have been concentrated by sulfide melt, after S saturation had been reached in the advanced stages of magmatic differentiation, in response to magnetite crystallization. Reaction between sulfide melt and oxides led to late magmatic S loss, causing a paucity of sulfides in most of the PGE mineralized interval. As a result, the reefs cannot be distinguished macroscopically from their unmineralized host rocks, and we suggest that similar mineralization may have been overlooked in the upper parts of other tholeiitic intrusions elsewhere.

Maier, W. D.; Barnes, S.-J.; Gartz, V.; Andrews, G.

2003-10-01

332

Lead isotope study of the late Archean Lac des Iles palladium deposit, Canada: enrichment of platinum group elements by ponded sulfide melt  

NASA Astrophysics Data System (ADS)

Lead isotopic compositions of mineral separates are presented from the mineralized zones (Roby, Twilight, and High Grade zones) of the Lac des Iles palladium deposit (approximately 2.69 Ga) and tonalitic country rocks (approximately 2.727 to 2.775 Ga) in the Wabigoon subprovince of the western Superior Province of Canada. Plagioclase separates show Pb isotope ratios similar to those of the late Archean depleted mantle. Sulfide minerals coexisting with plagioclase have a more radiogenic Pb isotope composition, but very low concentrations of U (<0.2 ppb U) and Th (<0.01 ppb) compared to Pb (?50 ppb). The isotope data are consistent with a model involving the incorporation of radiogenic Pb from country rocks to sulfide melt near the base of the magma chamber or along the conduit of the parental magmas. The proposed interpretation is also supported by decreasing Cu/Pd ratios from earlier barren to late fertile gabbro intrusions in the complex. The ponding sulfide melt became enriched in platinum group elements, as it was interacting with a large magma volume during the evolution of the Lac des Iles igneous complex.

Hinchey, John G.; Hattori, Kéiko H.

2007-08-01

333

Determination of the platinum - Group elements (PGE) and gold (Au) in manganese nodule reference samples by nickel sulfide fire-assay and Te coprecipitation with ICP-MS  

USGS Publications Warehouse

Platinum group elements (PGE) and Au data in polymetallic oceanic ferromanganese nodule reference samples and crust samples obtained by inductively coupled plasma mass spectrometry (ICP-MS), after separation and pre-concentration by nickel sulfide fire-assay and Te coprecipitation, are presented. By optimizing several critical parameters such as flux composition, matrix matching calibration, etc., best experimental conditions were established to develop a method suitable for routine analysis of manganese nodule samples for PGE and Au. Calibrations were performed using international PGE reference materials, WMG-1 and WMS-1. This improved procedure offers extremely low detection limits in the range of 0.004 to 0.016 ng/g. The results obtained in this study for the reference materials compare well with previously published data wherever available. New PGE data arc also provided on some international manganese nodule reference materials. The analytical methodology described here can be used for the routine analysis of manganese nodule and crust samples in marine geochemical studies.

Balaram, V.; Mathur, R.; Banakar, V. K.; Hein, J. R.; Rao, C. R. M.; Gnaneswara, Rao, T.; Dasaram, B.

2006-01-01

334

Distribution and mineralogy of platinum-group elements in altered chromitites of the Campo Formoso layered intrusion (Bahia State, Brazil): control by magmatic and hydrothermal processes  

NASA Astrophysics Data System (ADS)

Polyphase, penetrative hydrothermal metasomatism in chromitites of the Campo Formoso layered intrusion produced spectacular chromite - ferrian chromite zoning and transformed the primary intercumulus silicates into a chlorite - serpentine - carbonate - talc assemblage. Alteration did not substantially modify the composition of chromite cores and the distribution of platinum-group elements (PGE) through the sequence of chromitite layers, which still are consistent with magmatic fractionation processes. Texture and composition of laurite and Os-Ir-Ru alloys included in chromite cores indicate that these PGM were not altered, and are probably magmaticin origin. In contrast, the PGM located in the intergranular chlorite matrix (laurite, Ir-Ru-Rh sulfarsenides and Pt-Pd compounds with Sb, Bi and Te) display evidence of hydrothermal reworking. These PGM are intimately intergrown with low-temperature Ni-sulfides. The paragenesis suggests that the Ni-sulfides-PGM assemblage formed at the expenses of unknown PGM precursors, which must have been originally present in the intercumulus silicate matrix. Mechanism of formation involves a sequence of dissolution-precipitation events controlled by variation of redox conditions during chromite alteration. The presence of a secondary ore mineral assemblage consisting of galena, bismuthinite, native antimony, and various Pb-Sb compounds suggests a possible contribution of fluids derived from the adjacent granite.

Garuti, G.; Proenza, J. A.; Zaccarini, F.

2007-03-01

335

I.v. cocaine induces rapid, transient excitation of striatal neurons via its action on peripheral neural elements: single-cell, iontophoretic study in awake and anesthetized rats.  

PubMed

Cocaine's (COC) direct interaction with the dopamine (DA) transporter is usually considered the most important action underlying the psychomotor stimulant and reinforcing effects of this drug. However, some physiological, behavioral and psycho-emotional effects of COC are very rapid and brief and they remain intact during DA receptor blockade, suggesting possible involvement of peripheral non-DA neural mechanisms. To assess this issue, single-unit recording with microiontophoresis was used to examine changes in impulse activity of dorsal and ventral striatal neurons to i.v. COC (0.25-0.5 mg/kg) in the same rats under two conditions: awake with DA receptor blockade and anesthetized with urethane. In the awake preparation approximately 70% striatal neurons showed rapid and transient (latency approximately 6 s, duration approximately 15 s) COC-induced excitations. These effects were stronger in ventral than dorsal striatum. During anesthesia, these phasic effects were fully blocked and COC slowly decreased neuronal discharge rate. Cocaine-methiodide (COC-M), a derivative that cannot cross the blood-brain barrier, also caused phasic excitations in the awake, but not anesthetized condition. In contrast to regular COC, COC-M had no tonic effect on discharge rate in either preparation. Most striatal neurons that were phasically excited by both COC forms also showed short-latency excitations during tail-touch and tail-pinch in the awake preparation, an effect strongly attenuated during anesthesia. Finally, most striatal neurons that in awake conditions were phasically excited by somato-sensory stimuli and COC salts were also excited by iontophoretic glutamate (GLU). Although striatal neurons were sensitive to GLU in both preparations, the response magnitude at the same GLU current was higher in awake than anesthetized conditions. These data suggest that in awake animals i.v. COC, like somato-sensory stimuli, transiently excites striatal neurons via its action on peripheral neural elements and rapid neural transmission. While the nature of these neuronal elements needs to be clarified using other analytical techniques, they might involve voltage-gated K(+) and Na(+) channels, which have a high affinity for COC and are located on terminals of visceral sensory nerves that densely innervate peripheral vessels. Therefore, along with direct action on specific brain substrates, central excitatory effects of COC may occur via indirect action, involving afferents of visceral sensory nerves and rapid neural transmission. By providing a rapid sensory signal and triggering transient neural activation, such a peripherally triggered action might play a crucial role in the sensory effects of COC, thus contributing to learning and development of drug-taking behavior. PMID:17706878

Kiyatkin, E A; Brown, P L

2007-09-21

336

L-Ficolin and Capsular Polysaccharide-Specific IgG in Cord Serum Contribute Synergistically to Opsonophagocytic Killing of Serotype III and V Group B Streptococci  

PubMed Central

Group B streptococci (GBS; Streptococcus agalactiae) are the most common cause of neonatal sepsis and meningitis. Serotype-specific IgG antibody is known to protect neonates against GBS infections by promoting opsonophagocytosis. The L-ficolin-mediated lectin pathway of the complement is also a potential mechanism for opsonization of GBS, because L-ficolin activates the complement after binding to serotype Ib, III, V, VI, and VIII GBS. In the present study, we investigated how L-ficolin and serotype-specific IgG in cord sera contribute to opsonophagocytic killing of GBS. Neither L-ficolin nor serotype-specific IgG concentrations correlated with C3b deposition on serotype Ib and VI GBS, suggesting L-ficolin- and serotype-specific IgG-independent mechanisms of complement activation. The percentage of serotype VIII GBS killed was high regardless of the concentration of L-ficolin and IgG. In contrast, L-ficolin and serotype-specific IgG can each initiate C3b deposition on serotype III and V GBS and promote phagocytosis by polymorphonuclear leukocytes, but L-ficolin and serotype-specific IgG together promote opsonophagocytic killing to a greater extent than does either alone in vitro. This synergy was observed when serotype III-specific IgG concentrations were between 1 and 6 ?g/ml and when serotype V-specific IgG concentrations were between 2 and 5 ?g/ml. Concentrations of serotype III-specific IgG in cord blood above 7 ?g/ml are considered protective for neonates colonized with GBS, but most neonates with IgG levels of less than 7 ?g/ml do not develop GBS infections. The data presented here suggest that L-ficolin enhances opsonophagocytosis of serotype III and V GBS when serotype-specific IgG alone is suboptimal for protection.

Fujieda, Mioko; Aoyagi, Youko; Matsubara, Kousaku; Takeuchi, Yasuhito; Fujimaki, Wakae; Matsushita, Misao; Bohnsack, John F.

2012-01-01

337

Platinum group elements (Pt, Pd, Rh) in airborne particulate matter in rural vs. urban areas of Germany: concentrations and spatial patterns of distribution.  

PubMed

This study examines platinum group element concentrations (PGE) (i.e. platinum (Pt), palladium (Pd) and rhodium (Rh)) and their spatial distribution in airborne particulate matter fractions (PM) of human health concern in urban and rural areas of Germany. Fractionated airborne dust and PM(10), PM(2.5) and PM(1) samples were collected along a busy road in Frankfurt am Main from July 2008 to April 2010. PM(10) was also sampled in Deuselbach and Neuglobsow between January 2008 and July 2009 to examine their concentrations at rural locations and potential for long-range transport. Pt, Pd and Rh were isolated and pre-enriched in samples using a combination of Te and Hg co-precipitation methods. Concentrations were determined using isotope dilution ICP-Q-MS (in collision mode with He). The highest airborne PGE concentrations were measured in PM(10) from Frankfurt (e.g. 12.4pg Pt/m(3) (mean)), while the rural locations of Deuselbach and Neuglobsow exhibited the lowest levels (e.g. 2pg Pt/m(3) (mean)). PGE concentrations were observed to decline with increasingly smaller PM size fractions from PM(10) to PM(1). All size fractions generally contained higher levels of Pd compared to Pt and Rh, an element of greater concern due to its solubility. PM(2.5) collected in Frankfurt had a mean of 16.1pg Pd/m(3), compared to 9.4pg/m(3) for Pt. PGE concentrations also demonstrated a distinct seasonal relationship, with the greatest levels occurring in winter. Compared to a previous study in 2002, PGE concentrations in fractionated airborne dust have significantly increased over time. Elevated PGE levels were also measured for PM(10) sampled in Neuglobsow and Deuselbach, which could not be attributed to local emission sources. Using the diagnostic meteorological model, CALMET, trajectory analyses confirmed our hypothesis that PGE are being transported over longer distances from other areas of Europe. PMID:22221875

Zereini, Fathi; Alsenz, Heiko; Wiseman, Clare L S; Püttmann, Wilhelm; Reimer, Eberhard; Schleyer, Ruprecht; Bieber, Elke; Wallasch, Markus

2012-02-01

338

Multipole Matrix Elements v for H-Like Atoms and Their Applications (as ? = 1, n ? 4, Enl < 0 ? E ? 1)  

NASA Astrophysics Data System (ADS)

This article deals with the connection between multipole matrix elements ? and ? for H-like atoms, where ? is the so-called "auxiliary" parameter of Heun's differential equation and ˜ {Z}=Z/? is the "effective" nuclear charge, and new properties of Appell's function F2(x,y) to the vicinity of the singular point (1, 1) and in addition, here, first V. A. Fock's idea for the continuous spectrum is taken into consideration. Such an approach allows us to get the explicit expressions for squares of the dipole moments and the certain physical characteristics in atomic physics and also their exact numerical values, e.g., the average oscillator strengths bar {f}(nl,El') and the line intensities J(nl, El'), etc., as n ? 4, l'= l ± 1 and 0 ? E ? 1 (see Tables 1-3). Besides, diagrams of certain radial functions for the discrete-continuous transitions are given here.

Tarasov, V. F.

339

Baseline glutamate levels affect group I and II mGluRs in layer V pyramidal neurons of rat sensorimotor cortex.  

PubMed

Possible functional roles for glutamate that is detectable at low concentrations in the extracellular space of intact brain and brain slices have not been explored. To determine whether this endogenous glutamate acts on metabotropic glutamate receptors (mGluRs), we obtained whole cell recordings from layer V pyramidal neurons of rat sensorimotor cortical slices. Blockade of mGluRs with (+)-alpha-amino-4-carboxy-alpha-methyl-benzeacetic acid (MCPG, a general mGluR antagonist) increased the mean amplitude of spontaneous excitatory postsynaptic currents (sEPSCs), an effect attributable to a selective increase in the occurrence of large amplitude sEPSCs. 2S-2-amino-2-(1S,2S-2-carboxycyclopropyl-1-yl)-3-(xanth-9-yl)propanoic acid (LY341495, a group II antagonist) increased, but R(-)-1-amino-2,3-dihydro-1H-indene-1,5-dicarboxylic acid (AIDA) and (RS)-hexyl-HIBO (group I antagonists) decreased sEPSC amplitude, and (R,S)-alpha-cyclopropyl-4-phosphonophenylglycine (CPPG, a group III antagonist) did not change it. The change in sEPSCs elicited by MCPG, AIDA, and LY341495 was absent in tetrodotoxin, suggesting that it was action potential-dependent. The increase in sEPSCs persisted in GABA receptor antagonists, indicating that it was not due to effects on inhibitory interneurons. AIDA and (S)-3,5-dihydroxyphenylglycine (DHPG, a group I agonist) elicited positive and negative shifts in holding current, respectively. LY341495 and (2S,2'R,3'R)-2-(2',3'-dicarboxycyclopropyl)glycine (DCG-IV, a group II agonist) elicited negative and positive shifts in holding current, respectively. The AIDA and LY341495 elicited currents persisted in TTX. Finally, in current clamp, LY341495 depolarized cells by approximately 2 mV and increased the number of action potentials to a given depolarizing current pulse. Thus ambient levels of glutamate tonically activate mGluRs and regulate cortical excitability. PMID:12626613

Bandrowski, A E; Huguenard, J R; Prince, D A

2003-03-01

340

Estradiol activates group I and II metabotropic glutamate receptor signaling, leading to opposing influences on cAMP response element-binding protein.  

PubMed

In addition to mediating sexual maturation and reproduction through stimulation of classical intracellular receptors that bind DNA and regulate gene expression, estradiol is also thought to influence various brain functions by acting on receptors localized to the neuronal membrane surface. Many intracellular signaling pathways and modulatory proteins are affected by estradiol via this unconventional route, including regulation of the transcription factor cAMP response element-binding protein (CREB). However, the mechanisms by which estradiol acts at the membrane surface are poorly understood. Because both estradiol and CREB have been implicated in regulating learning and memory, we characterized the effects of estradiol on this transcription factor in cultured rat hippocampal neurons. Within minutes of administration, estradiol triggered mitogen-activated protein kinase (MAPK)-dependent CREB phosphorylation in unstimulated neurons. Furthermore, after brief depolarization, estradiol attenuated L-type calcium channel-mediated CREB phosphorylation. Thus, estradiol exhibited both positive and negative influences on CREB activity. These effects of estradiol were sex specific and traced to membrane-localized estrogen receptors that stimulated group I and II metabotropic glutamate receptor (mGluR) signaling. Activation of estrogen receptor alpha (ERalpha) led to mGluR1a signaling, triggering CREB phosphorylation through phospholipase C regulation of MAPK. In addition, estradiol stimulation of ERalpha or ERbeta triggered mGluR2/3 signaling, decreasing L-type calcium channel-mediated CREB phosphorylation. These results not only characterize estradiol regulation of CREB but also provide two putative signaling mechanisms that may account for many of the unexplained observations regarding the influence of estradiol on nervous system function. PMID:15901789

Boulware, Marissa I; Weick, Jason P; Becklund, Bryan R; Kuo, Sidney P; Groth, Rachel D; Mermelstein, Paul G

2005-05-18

341

Compensatory mutations demonstrate that P8 and P6 are RNA secondary structure elements important for processing of a group I intron.  

PubMed Central

Compensatory mutations have been constructed which demonstrate that P8 and P6, two of nine proposed base-pairing interactions characteristic of group I introns, exist within the folded structure of the Tetrahymena thermophila rRNA intervening sequence, and that these secondary structure elements are important for splicing in E. coli and self-splicing in vitro. Two-base mutations in the 5' and 3' segments of P8 are predicted to disrupt P8 and a strong splicing-defective phenotype is observed in each case. A compensatory four-base mutation in P8 is predicted to restore pairing, and results in the restoration of splicing activity to nearly wild type levels. Thus, we conclude that P8 exists and is essential for splicing. In contrast to the strong phenotypes generally exhibited by mutations which disrupt RNA secondary structure, a two-base mutation in L8, the loop between P8[5'] and P8[3'], results in only a slight decrease in splicing activity. We also tested P6, a pairing which is proposed to consist of only two base-pairs in this intron. A two-base mutation in P6[3'] reduces splicing activity to a greater extent than does a two-base mutation in P6[5']. Comparison of the activities of these mutants and a compensatory P6 four-base mutant support the existence of P6, and suggest that the P6 pairing may be particularly important in the exon ligation step of splicing. Images

Williamson, C L; Desai, N M; Burke, J M

1989-01-01

342

Kaposi's sarcoma-associated herpesvirus (human herpesvirus 8) replication and transcription factor activates the K9 (vIRF) gene through two distinct cis elements by a non-DNA-binding mechanism.  

PubMed

The replication and transcription activator (RTA) of Kaposi's sarcoma-associated herpesvirus (KSHV), or human herpesvirus 8, a homologue of Epstein-Barr virus BRLF1 or Rta, is a strong transactivator and inducer of lytic replication. RTA acting alone can induce lytic replication of KSHV in infected cell lines that originated from primary effusion lymphomas, leading to virus production. During the lytic replication process, RTA activates many kinds of genes, including polyadenylated nuclear RNA, K8, K9 (vIRF), ORF57, and so on. We focused here on the mechanism of how RTA upregulates the K9 (vIRF) promoter and identified two independent cis-acting elements in the K9 (vIRF) promoter that responded to RTA. These elements were finally confined to the sequence 5'-TCTGGGACAGTC-3' in responsive element (RE) I-2B and the sequence 5'-GTACTTAAAATA-3' in RE IIC-2, both of which did not share sequence homology. Multiple factors bound specifically with these elements, and their binding was correlated with the RTA-responsive activity. Electrophoretic mobility shift assay with nuclear extract from infected cells and the N-terminal part of RTA expressed in Escherichia coli, however, did not show that RTA interacted directly with these elements, in contrast to the RTA responsive elements in the PAN/K12 promoter region, the ORF57/K8 promoter region. Thus, it was likely that RTA could transactivate several kinds of unique cis elements without directly binding to the responsive elements, probably through cooperation with other DNA-binding factors. PMID:12414946

Ueda, Keiji; Ishikawa, Kayo; Nishimura, Ken; Sakakibara, Shuhei; Do, Eunju; Yamanishi, Koichi

2002-12-01

343

Assessment of Degree of Applicability of Benchmarks for Gadolinium Using KENO V.a and the 238-Group SCALE Cross-Section Library  

SciTech Connect

A review of the degree of applicability of benchmarks containing gadolinium using the computer code KENO V.a and the gadolinium cross sections from the 238-group SCALE cross-section library has been performed for a system that contains {sup 239}Pu, H{sub 2}O, and Gd{sub 2}O{sub 3}. The system (practical problem) is a water-reflected spherical mixture that represents a dry-out condition on the bottom of a sludge receipt and adjustment tank around steam coils. Due to variability of the mixture volume and the H/{sup 239}Pu ratio, approximations to the practical problem, referred to as applications, have been made to envelop possible ranges of mixture volumes and H/{sup 239}Pu ratios. A newly developed methodology has been applied to determine the degree of applicability of benchmarks as well as the penalty that should be added to the safety margin due to insufficient benchmarks.

Goluoglu, S.

2003-12-01

344

A calibration method for group V fluxes and impact of V/III flux ratio on the growth of InAs/InAsSb type-II superlattices by molecular beam epitaxy  

NASA Astrophysics Data System (ADS)

A calibration method for group V fluxes is demonstrated for the growth of InAsxSb1-x alloys and strain-balanced InAs/InAsxSb1-x superlattices on GaSb substrates by molecular beam epitaxy for IR optoelectronic device applications. The structural and optical properties of these structures grown with varying V/III flux ratios are investigated using several characterization methods, including X-ray diffraction (XRD), photoluminescence (PL), and reflection high energy electron diffraction. Samples grown at 450 °C with Sb/In flux ratios from 1.0 to 2.0 and As/In flux ratios from 1.2 to 2.5 lead to Sb mole fractions ranging from 0.078 to 0.34. High structural and optical quality superlattices for Sb mole fractions up to 0.34 are verified by XRD and low-temperature PL measurements. When varying both Sb mole fraction and period, superlattice structures are demonstrated with low-temperature emission wavelengths ranging from 3.6 to 7.1 ?m.

Li, Hua; Liu, Shi; Cellek, Oray O.; Ding, Ding; Shen, Xiao-Meng; Steenbergen, Elizabeth H.; Fan, Jin; Lin, Zhiyuan; He, Zhao-Yu; Zhang, Qiang; Webster, Preston T.; Johnson, Shane R.; Ouyang, Lu; Smith, David J.; Zhang, Yong-Hang

2013-09-01

345

Platinum-group elements (PGE) and Rhenium in Marine Sediments across the Cretaceous-Tertiary Boundary: Constraints on Re-PGE Transport in the Marine Environment  

NASA Technical Reports Server (NTRS)

The nature of Re-platinum-group element (PGE; Pt, Pd, Ir, Os, Ru) transport in the marine environment was investigated by means of marine sediments at and across the Cretaceous-Tertiary boundary (KTB) at two hemipelagic sites in Europe and two pelagic sites in the North and South Pacific. A traverse across the KTB in the South Pacific pelagic clay core found elevated levels of Re, Pt, Ir, Os, and Ru, each of which is approximately symmetrically distributed over a distance of approx. 1.8 m across the KTB. The Re-PGE abundance patterns are fractionated from chondritic relative abundances: Ru, Pt, Pd, and Re contents are slightly subchondritic relative to Ir, and Os is depleted by approx. 95% relative to chondritic Ir proportions. A similar depletion in Os (approx. 90%) was found in a sample of the pelagic KTB in the North Pacific, but it is enriched in Ru, Pt, Pd, and Re relative to Ir. The two hemipelagic KTB clays have near-chondritic abundance patterns. The approx. 1.8-m-wide Re-PGE peak in the pelagic South Pacific section cannot be reconciled with the fallout of a single impactor, indicating that postdepositional redistribution has occurred. The elemental profiles appear to fit diffusion profiles, although bioturbation could have also played a role. If diffusion had occurred over approx. 65 Ma, the effective diffusivities are approx. 10(exp -13)sq cm/s, much smaller than that of soluble cations in pore waters (approx. 10(exp -5) sq cm/s). The coupling of Re and the PGEs during redistribution indicates that postdepositional processes did not significantly fractionate their relative abundances. If redistribution was caused by diffusion, then the effective diffusivities are the same. Fractionation of Os from Ir during the KTB interval must therefore have occurred during aqueous transport in the marine environment. Distinctly subchondritic Os/Ir ratios throughout the Cenozoic in the South Pacific core further suggest that fractionation of Os from Ir in the marine environment is a general process throughout geologic time because most of the inputs of Os and Ir into the ocean have OsAr ratios greater than or = 1. Mass balance calculations show that Os and Re burial fluxes in pelagic sediments account for only a small fraction of the riverine Os (less than 10%) and Re (less than 0.1%) inputs into the oceans. In contrast, burial of Ir in pelagic sediments is similar to the riverine Ir input, indicating that pelagic sediments are a much larger repository for Ir than for Os and Re. If all of the missing Os and Re is assumed to reside in anoxic sediments in oceanic margins, the calculated burial fluxes in anoxic sediments are similar to observed burial fluxes. However, putting all of the missing Os and Re into estuarine sediments would require high concentrations to balance the riverine input and would also fail to explain the depletion of Os at pelagic KTB sites, where at most approx. 25% of the K-T impactor's Os could have passed through estuaries. If Os is preferentially sequestered in anoxic marine environments, it follows that the OsAr ratio of pelagic sediments should be sensitive to changes in the rates of anoxic sediment deposition. There is thus a clear fractionation of Os and Re from Ir in precipitation out of sea water in pelagic sections. Accordingly, it is inferred here that Re and Os are removed from sea water in anoxic marine depositional regimes.

Lee, Cin-Ty Aeolus; Wasserburg, Gerald J.; Kyte, Frank T.

2003-01-01

346

SCALE radiation shielding V and V package  

SciTech Connect

Verification and validation (V and V) are essential elements of software quality assurance (QA) for computer codes that are used for scientific calculations. The sponsors of the SCALE code system have required a QA plan and a V and V plan. For purposes of validating and verifying the SCALE shielding codes, a set of problems has been assembled and tested.

Emmett, M.B.; Bowman, S.M.; Broadhead, B.L.

1997-12-01

347

Platinum-group elements in alpine-type ultramafic rocks and related chromite ores of the main ophiolite belt of the Urals  

NASA Astrophysics Data System (ADS)

On the basis of a representative collection of ultramafic rocks and chromite ores and a series of technological samples from the largest (Central and Western) deposits in the Rai-Iz massif of the Polar Urals and the Almaz-Zhemchuzhina and Poiskovy deposits in the Kempirsai massif of the southern Urals, the distribution and speciation of platinum-group elements (PGE) in various type sections of mafic-ultramafic massifs of the Main ophiolite belt of the Urals have been studied. Spectral-chemical and spectrophotometric analyses were carried out to estimate PGE in 700 samples of ultramafic rocks and chromite ores; 400 analyses of minerals from rocks, ores, and concentrates and 100 analyses of PGE minerals (PGM) in chromite ores and concentrates were performed using an electron microprobe. Near-chondritic and nonchondritic PGE patterns in chromitebearing sections have been identified. PGE mineralization has been established to occur in chromite ore from all parts of the mafic-ultramafic massifs in the Main ophiolite belt of the Urals. The PGE deposits and occurrences discovered therein are attributed to four types (Kraka, Kempirsai, Nurali-Upper Neiva, and Shandasha), which are different in mode of geological occurrence, geochemical specialization, and placer-forming capability. Fluid-bearing minerals of the pargasite-edenite series have been identified for the first time in the matrix of chromite ore of the Kempirsai massif (the Almaz-Zhemchuzhina deposit) and Voikar-Syn’ya massif (the Kershor deposit). The PGE grade in various types of chromite ore ranges from 0.1-0.2 to 1-2 g/t or higher. According to technological sampling, the average PGE grade in the largest deposits of the southeastern ore field of the Kempirsai massif is 0.5-0.7 g/t. Due to the occurrence of most PGE as PGM 10-100 mm in size and the proved feasibility of their recovery into nickel alloys, chromites of the Kempirsai massif can be considered a complex ore with elevated and locally high Os, Ir, and Ru contents. The Nurali-Upper Neiva type of ore is characterized by small-sized primary deposits, which nevertheless are the main source of large Os-Ir placers in the Miass and Nev’yansk districts of the southern and central Urals, respectively.

Volchenko, Yu. A.; Koroteev, V. A.; Neustroeva, I. I.

2009-04-01

348

The Content of Selected Chemical Elements in the Hair of Young Men of the Bantu Language Group from Tanzania Versus Environmental and Social Conditioning  

Microsoft Academic Search

Research works that would determine the content of chemical elements in black population organisms on the basis of hair analysis\\u000a are not numerous. There are no studies referring to black populations living in indigenous environment, like the Mafinga region,\\u000a Iringa District in Tanzania examined by us. The aim of the study performed was to analyse the content of chemical elements

Ewa R?bacz; Irena Baranowska-Bosiacka; Dariusz Chlubek

2010-01-01

349

Platinum Group Elements, 187OS/188OS and 87SR/86SR Isotope Systematics in Depleted Fluid-Modified Mariana Fore-Arc Peridotites  

NASA Astrophysics Data System (ADS)

The serpentine mud volcanoes of the Izu-Bonin-Mariana (IBM) fore-arc, collected during Ocean Drilling Program Leg 195 [1], contain hard-rock clasts of serpentine sampled from close to the décollement, which separates the down-going Pacific slab from the overlying mantle wedge. These clasts preserve evidence for melt depletion (>25 % melt extraction in many instances) in a sub-arc environment, and extensive (40 - 100%) serpentinization due to subsequent fluid / peridotite interaction, e.g. [2]. Platinum-group element (PGE) abundances are not consistent with melt-depletion alone [3]. Fractionation between I-PGE (Os, Ir, Ru) has resulted in groups of IBM serpentinites with either a high chondrite-normalized Os/Ir ratio (OsN/IrN) or a low OsN/IrN ratio. Similarly, fractionation of P-PGE (Pt, Pd) is marked, and distinguishes the IBM serpentinites from worldwide abyssal peridotites. Interaction with high-pH fluids [4] may have partially oxidized mantle sulphide, the major primary host for PGE in these rocks, leading to partial breakdown to sulphate and the selective redistribution of certain PGE (Os, Ru, Pt), a feature normally associated with sub-aerial weathering [5], but which likely prevails in other oxidizing environments. In particular, the Re-Os systematics of the high (OsN/IrN) IBM serpentinites have been disturbed by the addition of Os. Unlike peridotite xenoliths associated with magmatic regions of subduction zones where subduction-related Os-addition is unequivocally radiogenic and derived from crustal material [6][7], where Os has been added to the IBM serpentinites it is unradiogenic and was most likely derived from within the oceanic mantle. IBM serpentinites therefore preserve osmium isotope ratios that are exclusively sub-chondritic (187Os/188Os ? 0.127), as previously reported [8]. These serpentinized peridotites were produced by at least a three-step process: melt depletion, serpentinization, and the mobilization of Os, Ru and Pt to produce low OsN/IrN "donor" and high OsN/IrN "recipient" serpentinites. The distinct chondrite normalized PGE patterns of the low OsN/IrN serpentinites are remarkably similar to those of back-arc basin basalts (BABB) from sites 291, 292, 444A, 450 drilled in the Philippine Sea Plate (PSP) during DSDP Legs 31, 58 and 59 [9]. [1] Fryer, et al. (1992) Proc. ODP Sci. Results 125, Fryer, P., Pearce, J. A., Stokking, L. B., et al., 373-385, Ocean Drilling Program, College Station TX, USA. [2] Savov et al. (2005) Geochem. Geophys. Geosyst. 6, Q04J15, doi:10.1029/2004GC000777 [3] Handler, & Bennett (1999) Geochim. Cosmochim. Acta 63, 3597-3618 [4] Mottl, M.J. (1992) Proc. ODP Sci. Results, 125, Fryer, P., Pearce, J. A., Stokking, L. B., et al., 373-385, Ocean Drilling Program, College Station TX, USA. [5] Lorand, et al. (2003) Geochim. Cosmochim. Acta 67, 4137-4151. [6] Brandon et al. (1999) Chem. Geol. 160, 387-407. [7] Widom et al. (2003) Chem. Geol. 196, 283- 306. [8] Parkinson et al. (1999) Science 281, 211-312 [9] Dale et al. (2008) Chem. Geol. 248, 213-238.

Harvey, J.; Savov, I. P.; Shirey, S. B.; Horan, M. F.; Mock, T. D.

2012-12-01

350

Universal mechanism for ion-induced nanostructure formation on III-V compound semiconductor surfaces  

SciTech Connect

We have examined the formation of nanostructures on ion-irradiated compound semiconductor surfaces. We computed the ion doses needed to fully deplete group V elements from the surfaces. These group V depletion doses are in good agreement with the measured threshold ion doses for nucleation of group III-rich nanostructures on a wide variety of III-V compound semiconductor surfaces. Since the group V depletion doses decrease with increasing sputtering yield, these results suggest a universal nanostructure formation mechanism which depends upon the total sputtering yield of each III-V compound.

Kang, M.; Wu, J. H.; Huang, S.; Warren, M. V.; Jiang, Y.; Robb, E. A.; Goldman, R. S. [Department of Materials Science and Engineering, University of Michigan, Ann Arbor, Michigan 48109-2136 (United States)

2012-08-20

351

Mobilisation of trace elements from as-supplied and additionally cleaned coal: Predictions for Ba, Be, Cd, Co, Mo, Nb, Sb, V and W  

Microsoft Academic Search

The partitioning of the elements antimony, barium, beryllium, cadmium, cobalt, molybdenum and vanadium between the products of combustion of coals containing them burnt as pulverised fuel in excess air has been modelled using the MTDATA thermodynamic equilibrium package with data from the MTOX silicate melt model added to the standard database and trace element data added where necessary. The coals

B. M. Gibbs; D. Thompson; B. B. Argent

2008-01-01

352

The GOAL study: a prospective examination of the impact of factor V Leiden and ABO(H) blood groups on haemorrhagic and thrombotic pregnancy outcomes.  

PubMed

Factor V Leiden (FVL) and ABO(H) blood groups are the common influences on haemostasis and retrospective studies have linked FVL with pregnancy complications. However, only one sizeable prospective examination has taken place. As a result, neither the impact of FVL in unselected subjects, any interaction with ABO(H) in pregnancy, nor the utility of screening for FVL is defined. A prospective study of 4250 unselected pregnancies was carried out. A venous thromboembolism (VTE) rate of 1.23/1000 was observed, but no significant association between FVL and pre-eclampsia, intra-uterine growth restriction or pregnancy loss was seen. No influence of FVL and/or ABO(H) on ante-natal bleeding or intra-partum or postpartum haemorrhage was observed. However, FVL was associated with birth-weights >90th centile [odds ratio (OR) 1.81; 95% confidence interval (CI(95)) 1.04-3.31] and neonatal death (OR 14.79; CI(95) 2.71-80.74). No association with ABO(H) alone, or any interaction between ABO(H) and FVL was observed. We neither confirmed the protective effect of FVL on pregnancy-related blood loss reported in previous smaller studies, nor did we find the increased risk of some vascular complications reported in retrospective studies. PMID:18028481

Clark, Peter; Walker, Isobel D; Govan, Lindsay; Wu, Olivia; Greer, Ian A

2008-01-01

353

Breakout Group 3  

Cancer.gov

Group 3: Standards for database structure, organization and communications- a nd to fulfill regulatory requirements Data Format(s) „„ Standard Format Standard Format „„ Common Data Elements Common Data Elements „„ Annotations (DICOM or other) Annotations

354

Measurement of Ll, L. cap alpha. , L. beta. , and L. gamma. x-ray-production cross sections in some high-Z elements by 60 keV photons  

SciTech Connect

Ll, L..cap alpha.., L..beta.., and L..gamma.. x-ray-production cross sections have been measured in elements Ta, W, Au, Hg, Tl, Pb, Bi, Th, and U for 60-keV photons. The measured values have been interpreted in terms of photoelectric cross sections, fluorescence yields, Coster-Kronig transition probabilities, and radiative decay rates. A fairly good agreement is found between the experimental and calculated values.

Shatendra, K.; Allawadhi, K.L.; Sood, B.S.

1985-05-01

355

Renormgruppa v statisticheskoj fizike - impul'snoe i real'noe prostranstva. (Renormalization group in statistical physics - momentum and real spaces).  

National Technical Information Service (NTIS)

Two variants of the renormalization group approach in statistical physics are considered, the renormalization group in the momentum and the renormalization group in the real spaces. Common properties of these methods and their differences are cleared up. ...

V. I. Yukalov

1988-01-01

356

POST IRRADIATION EXAMINATION OF SEVEN ELEMENT ZIRCALOY-SHEATHED UOâ FUEL BUNDLES IRRADIATED IN PRESSURIZED WATER TEST CR-V-e  

Microsoft Academic Search

Zircaloy-2 sheathed UOâ pellets, enriched to 7.95 wt% U²³⁵ ; in total U, and assembled into seven-rod clusters, were irradiated for 145 days ; in a pressurized water loop. The most highly rated element operated at 505 W\\/cm ; length, and achieved a burn-up ln excess of 7,500 MWd\\/ ton of U. The outer ; elements of each bundle had

A. S. Bain; R. D. MacDonald; J. A. L. Robertson

1961-01-01

357

TE-Locate: A Tool to Locate and Group Transposable Element Occurrences Using Paired-End Next-Generation Sequencing Data  

PubMed Central

Transposable elements (TEs) are common mobile DNA elements present in nearly all genomes. Since the movement of TEs within a genome can sometimes have phenotypic consequences, an accurate report of TE actions is desirable. To this end, we developed TE-Locate, a computational tool that uses paired-end reads to identify the novel locations of known TEs. TE-Locate can utilize either a database of TE sequences, or annotated TEs within the reference sequence of interest. This makes TE-Locate useful in the search for any mobile sequence, including retrotransposed gene copies. One major concern is to act on the correct hierarchy level, thereby avoiding an incorrect calling of a single insertion as multiple events of TEs with high sequence similarity. We used the (super)family level, but TE-Locate can also use any other level, right down to the individual transposable element. As an example of analysis with TE-Locate, we used the Swedish population in the 1,001 Arabidopsis genomes project, and presented the biological insights gained from the novel TEs, inducing the association between different TE superfamilies. The program is freely available, and the URL is provided in the end of the paper.

Platzer, Alexander; Nizhynska, Viktoria; Long, Quan

2012-01-01

358

TE-Locate: A Tool to Locate and Group Transposable Element Occurrences Using Paired-End Next-Generation Sequencing Data.  

PubMed

Transposable elements (TEs) are common mobile DNA elements present in nearly all genomes. Since the movement of TEs within a genome can sometimes have phenotypic consequences, an accurate report of TE actions is desirable. To this end, we developed TE-Locate, a computational tool that uses paired-end reads to identify the novel locations of known TEs. TE-Locate can utilize either a database of TE sequences, or annotated TEs within the reference sequence of interest. This makes TE-Locate useful in the search for any mobile sequence, including retrotransposed gene copies. One major concern is to act on the correct hierarchy level, thereby avoiding an incorrect calling of a single insertion as multiple events of TEs with high sequence similarity. We used the (super)family level, but TE-Locate can also use any other level, right down to the individual transposable element. As an example of analysis with TE-Locate, we used the Swedish population in the 1,001 Arabidopsis genomes project, and presented the biological insights gained from the novel TEs, inducing the association between different TE superfamilies. The program is freely available, and the URL is provided in the end of the paper. PMID:24832231

Platzer, Alexander; Nizhynska, Viktoria; Long, Quan

2012-01-01

359

Platinum-group elements, S, Se and Cu in highly depleted abyssal peridotites from the Mid-Atlantic Ocean Ridge (ODP Hole 1274A): Influence of hydrothermal and magmatic processes  

NASA Astrophysics Data System (ADS)

Highly depleted harzburgites and dunites were recovered from ODP Hole 1274A, near the intersection between the Mid-Atlantic Ocean Ridge and the 15°20'N Fracture Zone. In addition to high degrees of partial melting, these peridotites underwent multiple episodes of melt-rock reaction and intense serpentinization and seawater alteration close to the seafloor. Low concentrations of Se, Cu and platinum-group elements (PGE) in harzburgites drilled at around 35-85 m below seafloor are consistent with the consumption of mantle sulfides after high degrees (>15-20 %) of partial melting and redistribution of chalcophile and siderophile elements into PGE-rich residual microphases. Higher concentrations of Cu, Se, Ru, Rh and Pd in harzburgites from the uppermost and lowest cores testify to late reaction with a sulfide melt. Dunites were formed by percolation of silica- and sulfur-undersaturated melts into low-Se harzburgites. Platinum-group and chalcophile elements were not mobilized during dunite formation and mostly preserve the signature of precursor harzburgites, except for higher Ru and lower Pt contents caused by precipitation and removal of platinum-group minerals. During serpentinization at low temperature (<250 °C) and reducing conditions, mantle sulfides experienced desulfurization to S-poor sulfides (mainly heazlewoodite) and awaruite. Contrary to Se and Cu, sulfur does not record the magmatic evolution of peridotites but was mostly added in hydrothermal sulfides and sulfate from seawater. Platinum-group elements were unaffected by post-magmatic low-temperature processes, except Pt and Pd that may have been slightly remobilized during oxidative seawater alteration.

Marchesi, Claudio; Garrido, Carlos J.; Harvey, Jason; González-Jiménez, José María; Hidas, Károly; Lorand, Jean-Pierre; Gervilla, Fernando

2013-11-01

360

A trace element study of siderite–jasper banded iron formation in the 3.45 Ga Warrawoona Group, Pilbara Craton—Formation from hydrothermal fluids and shallow seawater  

Microsoft Academic Search

Shale-normalised rare earth element and yttrium (REE+Y) patterns for siderite–jasper couples in a banded iron formation of the 3.45Ga Panorama Formation, Warrawoona Group, eastern Pilbara Craton, display distinct positive Y and Eu anomalies and weak positive La and Gd anomalies, combined with depleted light REE relative to middle and heavy REE. Ambient seawater and hydrothermal fluids are identified as major

Robert Bolhar; Martin J. Van Kranendonk; Balz S. Kamber

2005-01-01

361

The Intergroup Rhabdomyosarcoma Study Group (IRSG): Major Lessons From the IRS-I Through IRS-IV Studies as Background for the Current IRS-V Treatment Protocols.  

PubMed

Purpose. To enumerate lessons from studying 4292 patients with rhabdomyosarcoma (RMS) in the Intergroup Rhabdomyosarcoma Study Group (IRSG, 1972-1997).Patients. Untreated patients < 21 years of age at diagnosis received systemic chemotherapy, with or without irradiation (XRT) and/or surgical removal of the tumor.Methods. Pathologic materials and treatment were reviewed to ascertain compliance and to confirm response and relapse status.Results. Survival at 5 years increased from 55 to 71% over the period. Important lessons include the fact that extent of disease at diagnosis affects prognosis. Re-excising an incompletely removed tumor is worthwhile if acceptable form and function can be preserved. The eye, vagina, and bladder can usually be saved. XRT is not necessary for children with localized, completely excised embryonal RMS. Hyperfractionated XRT has thus far not produced superior local control rates compared with conventional, once-daily XRT. Patients with non-metastatic cranial parameningeal sarcoma can usually be cured with localized XRT and systemic chemotherapy, without whole-brain XRT and intrathecal drugs. Adding doxorubicin, cisplatin, etoposide, and ifosfamide has not significantly improved survival of patients with gross residual or metastatic disease beyond that achieved with VAC (vincristine, actinomycin D, cyclophosphamide) and XRT. Most patients with alveolar RMS have a tumor-specific translocation. Mature rhabdomyoblasts after treatment of patients with bladder rhabdomyosarcoma are not necessarily malignant, provided that the tumor has shrunk and malignant cells have disappeared.Discussion. Current IRSG-V protocols, summarized herein, incorporate recommendations for risk-based management. Two new agents, topotecan and irinotecan, are under investigation for patients who have an intermediate or high risk of recurrence. PMID:18521303

Raney, R B; Maurer, H M; Anderson, J R; Andrassy, R J; Donaldson, S S; Qualman, S J; Wharam, M D; Wiener, E S; Crist, W M

2001-01-01

362

The Intergroup Rhabdomyosarcoma Study Group (IRSG): Major Lessons From the IRS-I Through IRS-IV Studies as Background for the Current IRS-V Treatment Protocols  

PubMed Central

Purpose. To enumerate lessons from studying 4292 patients with rhabdomyosarcoma (RMS) in the Intergroup Rhabdomyosarcoma Study Group (IRSG, 1972–1997). Patients. Untreated patients < 21 years of age at diagnosis received systemic chemotherapy, with or without irradiation (XRT) and/or surgical removal of the tumor. Methods. Pathologic materials and treatment were reviewed to ascertain compliance and to confirm response and relapse status. Results. Survival at 5 years increased from 55 to 71% over the period. Important lessons include the fact that extent of disease at diagnosis affects prognosis. Re-excising an incompletely removed tumor is worthwhile if acceptable form and function can be preserved. The eye, vagina, and bladder can usually be saved. XRT is not necessary for children with localized, completely excised embryonal RMS. Hyperfractionated XRT has thus far not produced superior local control rates compared with conventional, once-daily XRT. Patients with non-metastatic cranial parameningeal sarcoma can usually be cured with localized XRT and systemic chemotherapy, without whole-brain XRT and intrathecal drugs. Adding doxorubicin, cisplatin, etoposide, and ifosfamide has not significantly improved survival of patients with gross residual or metastatic disease beyond that achieved with VAC (vincristine, actinomycin D, cyclophosphamide) and XRT. Most patients with alveolar RMS have a tumor-specific translocation. Mature rhabdomyoblasts after treatment of patients with bladder rhabdomyosarcoma are not necessarily malignant, provided that the tumor has shrunk and malignant cells have disappeared. Discussion. Current IRSG-V protocols, summarized herein, incorporate recommendations for risk-based management. Two new agents, topotecan and irinotecan, are under investigation for patients who have an intermediate or high risk of recurrence.

Maurer, Harold M.; Anderson, James R.; Andrassy, Richard J.; Donaldson, Sarah S.; Qualman, Stephen J.; Wharam, Moody D.; Wiener, Eugene S.; Crist, William M.

2001-01-01

363

On Some Algebraic and Combinatorial Properties of Dunkl Elements  

NASA Astrophysics Data System (ADS)

We introduce and study a certain class of nonhomogeneous quadratic algebras together with the special set of mutually commuting elements inside of each, the so-called Dunkl elements. We describe relations among the Dunkl elements. This result is a further generalization of similar results obtained in [S. Fomin and A. N. Kirillov, Quadratic algebras, Dunkl elements and Schubert calculus, in Advances in Geometry (eds. J.-S. Brylinski, V. Nistor, B. Tsygan and P. Xu), Progress in Math. Vol. 172 (Birkhäuser Boston, Boston, 1995), pp. 147-182, A. Postnikov, On a quantum version of Pieri's formula, in Advances in Geometry (eds. J.-S. Brylinski, R. Brylinski, V. Nistor, B. Tsygan and P. Xu), Progress in Math. Vol. 172 (Birkhäuser Boston, 1995), pp. 371-383 and A. N. Kirillov and T. Maenor, A Note on Quantum K-Theory of Flag Varieties, preprint]. As an application we describe explicitly the set of relations among the Gaudin elements in the group ring of the symmetric group, cf. [E. Mukhin, V. Tarasov and A. Varchenko, Bethe Subalgebras of the Group Algebra of the Symmetric Group, preprint arXiv:1004.4248]. Also we describe a few combinatorial properties of some special elements in the associative quasi-classical Yang-Baxter algebra in a connection with the values of the ?-Grothendieck polynomials for some special permutations, and on the other hand, with the Ehrhart polynomial of the Chan-Robbins polytope.

Kirillov, Anatol N.

2013-06-01

364

Batisivite, V 8 Ti 6 [Ba(Si 2 O)]O 28 , a new mineral species from the derbylite group  

Microsoft Academic Search

Batisivite has been found as an accessory mineral in the Cr-V-bearing quartz-diopside metamorphic rocks of the Slyudyanka\\u000a Complex in the southern Baikal region, Russia. A new mineral was named after the major cations in its ideal formula (Ba, Ti,\\u000a Si, V). Associated minerals are quartz, Cr-V-bearing diopside and tremolite; calcite; schreyerite; berdesinskiite; ankangite;\\u000a V-bearing titanite; minerals of the chromite-coulsonite, eskolaite-karelianite,

L. Z. Reznitsky; E. V. Sklyarov; T. Armbruster; E. V. Galuskin; Z. F. Ushchapovskaya; Yu. S. Polekhovsky; N. S. Karmanov; A. A. Kashaev; I. G. Barash

2008-01-01

365

Accelerator measurement of the energy spectra of neutrons emitted in the interaction of 3-GeV protons with several elements  

NASA Technical Reports Server (NTRS)

The application of time of flight techniques for determining the shapes of the energy spectra of neutrons between 20 and 400 MeV is discussed. The neutrons are emitted at 20, 34, and 90 degrees in the bombardment of targets by 3 GeV protons. The targets used are carbon, aluminum, cobalt, and platinum with cylindrical cross section. Targets being bombarded are located in the internal circulating beam of a particle accelerator.

Nalesnik, W. J.; Devlin, T. J.; Merker, M.; Shen, B. S. P.

1972-01-01

366

Plane Groups  

NSDL National Science Digital Library

This is a lengthy PDF document (60 pages+) about plane groups and symmetry. It includes colorful images of each of the 17 plane groups, in several different forms. Additionally, there are some summarizing graphics that show unit cells, lattices, symmetry elements, etc. There is lots here to choose from -- I doubt that anyone will want to use all of the images. Studying plane groups is a good way to introduce crystal systems, point groups, lattices, symmetry operators, etc. All is in 2-D, but it is easy to tell students that the principles are the same in 3-D. For those who like to make changes, the PDF document was created from individual EPS files. This means that the files can be opened in Adobe Illustrator, Corel Draw, etc., and modified to fit your own needs.

Perkins, Dexter

367

Precise Validation of Database (n,γ) Cross Sections Using a Lead-Slowing-Down Spectrometer and Simulation from 0.1 eV to 30 keV: Methodology and Data for a Few Elements  

Microsoft Academic Search

Projects dealing with future reactors based on new fuels and able to incinerate nuclear waste require good knowledge of numerous cross sections. In order to resolve nuclear database discrepancies, capture cross-section profiles between 0.1 eV and 30 keV have been measured for different materials using a lead-slowing-down-time spectrometer in association with a pulsed neutron generator. The measurement of the neutron

L. Perrot; A. Billebaud; R. Brissot; A. Giorni; D. Heuer; J.-M. Loiseaux; O. Meplan; J.-B. Viano

2003-01-01

368

The elemental abundances in interplanetary dust particles  

NASA Astrophysics Data System (ADS)

We compiled a table of all major, minor, and trace-element abundances in 89 interplanetary dust particles (IDPs) that includes data obtained with proton-induced x-ray emission (PIXE), synchroton x-ray fluorescence (SXRF), and secondary ion mass spectrometry (SIMS). For the first time, the reliability of the trace-element abundances in IDPs is tested by various crosschecks. We also report on the results of cluster analyses that we performed on IDP compositions. Because of the incompleteness of the data set, we included only the elements Cr, Mn, Ni, Cu, and Zn, normalized to Fe and CI chondrite abundances, that are determined in 73 IDPs. The data arrange themselves in four rather poorly defined groups that we discuss in relation to CI chondrites following the assumption that on the average CI abundances are most probable. The largest group (chondritic), with 44 members, has close to CI abundances for many refractory and moderately refractory elements (Na, Al, Si, P, K, Sc, Ti, V, Cr, Co, Ge, Sr). It is slightly depleted in Fe and more in Ca and S, while the volatile elements (Cl, Cu, Zn, Ga, Se, Rb) are enriched by =1.7 × CI and Br by 21 × CI. The low-Zn group, with 12 members, is very similar to the chondritic group except for its Zn-depletion, stronger Ca-depletion and Fe-enrichment. The low-Ni group, with 11 members, has Ni/Fe = 0.03 × CI and almost CI-like Ca, but its extraterrestrial origin is not established. The last group (6 members) contains non-systematic particles of unknown origin. We found that Fe is inhomogeneously distributed on a micron scale. Furthermore, the abundances of elements that are measured near their limits of detection are easily overestimated. These biases involved, the incomplete data set and possible contaminating processes prevent us from obtaining information on the specific origin(s) of IDPs from elemental abundances.

Arndt, Peter; Bohsung, Jörg; Maetz, Mischa; Jessberger, Elmar K.

1996-11-01

369

Natural gas plays of the Knox Group in the Appalachian basin: A significant element of the U. S. Department of Energy atlas of major Appalachian gas plays  

Microsoft Academic Search

Oil and gas have been produced from the Knox Group in the Appalachian basin since the early 1990s. However, only since the 1960s have significant volumes of hydrocarbons been produced. Porosity development along the Knox unconformity is the dominant geologic control for hydrocarbon migration and entrapment. Other important controls include stratigraphy, diagenesis, paleokarst, structure, and fractures. Cumulative production is ultimately,

M. T. Baranoski; M. E. Wolfe

1993-01-01

370

Interrelationship between the Content of Some Trace Elements and Vitamins in Food Products (O Vzaimozavisimosti Mezhdu Soderzhaniem Nekotorykh Mikroelementov i Vitaminov v Pishchevykh Produktakh).  

National Technical Information Service (NTIS)

The problem of interrelationships between some trace elements and vitamins has not yet been finally solved and is of great interest. The present work consisted in determining the content of manganese, molybdenum and vitamins B1, B2 and C in food products ...

V. P. Kamchatnov

1973-01-01

371

Microwave-assisted carbohydrohalogenation of first-row transition-metal oxides (M = V, Cr, Mn, Fe, Co, Ni, Cu) with the formation of element halides.  

PubMed

The anhydrous forms of first-row transition-metal chlorides and bromides ranging from vanadium to copper were synthesized in a one-step reaction using the relatively inexpensive element oxides, carbon sources, and halogen halides as starting materials. The reactions were carried out in a microwave oven to give quantitative yields within short reaction times. PMID:24099620

Berger, Matthias; Neumeyer, Felix; Auner, Norbert

2013-10-21

372

Synthesis and characterization of some new Schiff base complexes of group 13 elements, ab initio studies, cytotoxicity and reaction with hydrogen peroxide.  

PubMed

A novel tetradentate Schiff base, naphthabza-H2=N,N'-bis(naphthylidene)-2-aminobenzylamine, and a series of aluminum(III), gallium(III), and indium(III) complexes with general formula, MLNO3, were synthesized and characterized by elemental analysis, 1H NMR, FT-IR, UV-Vis spectroscopy and thermogravimetric method. The product of the reaction of complexes with hydrogen peroxide was characterized by similar techniques. According to the ab initio calculations aluminum and gallium complexes have five-coordinated structures and indium complex is a six-coordinated one. Also, the growth inhibitory effects of the complexes toward K562 cancer cell line were measured and the results for these complexes are as follows: Al>Ga>In. PMID:23143208

Asadi, Mozaffar; Savaripoor, Nooshin; Asadi, Zahra; Ghatee, Mohammad Hadi; Moosavi, Fatemeh; Yousefi, Reza; Jamshidi, Mehrnaz

2013-01-15

373

Basic moments of phonon density of states spectra and characteristic phonon temperatures of group IV, III-V, and II-VI materials  

NASA Astrophysics Data System (ADS)

We have redigitized a large variety of phonon density of states (PDOS) spectra, that have been published by diferent researchers for group IV (diamond, 3C-SiC, Si, and Ge), III-V (BN, BP, BAs, BSb, AlN, AlP, AlAs, AlSb, GaN, GaP, GaAs, GaSb, InN, InP, InAs, and InSb), and II-VI materials (ZnO, ZnS, ZnSe, ZnTe, CdS, and CdTe), including calculations of their moments, , of orders n=-1, 1, 2, and 4. Notwithstanding the obvious differences in concrete shapes of spectra presented for one and the same material by different authors, the respective magnitudes of estimated moments have been found in most cases to be nearly the same (to within uncertainties of some few percent). For most materials under study, the average phonon temperatures of the lower and upper sections of PDOS spectra, ?L and ?U, are found to be by factors of order 0.6 lower or 1.4 higher, respectively, than the average phonon temperature, ?P, of the total PDOS spectra. The estimated high-temperature limits of Debye temperatures, ?D(?), are found to be significantly higher (by factors of order 1.4) than ?P, implying an order-of-magnitude equality, ?D(?)~?U (within differences not exceeding an order of +/-10%, for all materials under study). The phonon temperatures, ?g, that are effective in controlling the observable temperature dependences of fundamental energy gaps, Eg(T), are found to be usually of the same order as the respective average phonon temperatures, ?g~?P. The existing differences between these two qualitatively different types of characteristic phonon temperatures are seen to be limited, for diamond, 3C-SiC, Si, Ge, AlN, GaN, GaP, GaAs, GaSb, InP, InSb, ZnS, ZnSe, ZnTe, and CdTe, to an order of +/-12%. We design an exemplary way for precalculating harmonic parts of isochoric heat capacities on the basis of the estimated quadruplets of PDOS spectra moments. This novel calculation scheme is exemplified for silicon and germanium.

Pässler, Roland

2007-05-01

374

Evaluation of essential trace and toxic elements in biological samples of normal and night blindness children of age groups 3-7 and 8-12 years.  

PubMed

The most common cause of blindness in developing countries is vitamin A deficiency. The World Health Organization estimates 13.8 million children to have some degree of visual loss related to vitamin A deficiency. The causes of night blindness in children are multifactorial, and particular consideration has been given to childhood nutritional deficiency, which is the most common problem found in underdeveloped countries. Such deficiency can result in physiological and pathological processes that in turn influence biological samples composition. Vitamin and mineral deficiency prevents more than two billion people from achieving their full intellectual and physical potential. This study was designed to compare the levels of Zn, Mg, Ca, K, Na, As, Cd, and Pb in scalp hair, blood, and urine of night blindness children age ranged 3-7 and 8-12 years of both genders, comparing them to sex- and age-matched controls. A microwave-assisted wet acid digestion procedure was developed as a sample pretreatment, for the determination of As, Ca, Cd, K, Pb, Mg, Na, and Zn in biological samples of night blindness children. The proposed method was validated by using conventional wet digestion and certified reference samples of hair, blood, and urine. The concentrations of trace and toxic elements were measured by atomic absorption spectrophotometer prior to microwave-assisted acid digestion. The results of this study showed that the mean values of As, Cd, Na, and Pb were significantly higher in scalp hair, blood, and urine samples of male and female night blindness children than in referents (p?elements in biological samples (scalp hair and blood) of night blindness children. PMID:20820941

Afridi, Hassan Imran; Kazi, Tasneem Gul; Kazi, Naveed; Kandhro, Ghulam Abbas; Baig, Jameel Ahmed; Shah, Abdul Qadir; Wadhwa, Sham Kumar; Khan, Sumaira; Kolachi, Nida Fatima; Shah, Faheem; Jamali, Mohammad Khan; Arain, Mohammad Balal; Sirajuddin

2011-10-01

375

Spatial extent of the singlet and triplet excitons in luminescent angular-shaped transition-metal diynes and polyynes comprising non-pi-conjugated group 16 main group elements.  

PubMed

A novel approach based on conjugation interruption has been developed and is presented for a series of luminescent and thermally stable chalcogen-bridged platinum(II) polyyne polymers trans-[{-Pt(PBu3)2C[triple bond]C(C6H4)E(C6H4)C[triple bond]C-}n] (E = O, S, SO, SO2). Particular attention was focused on the photophysical properties of these Group 10 polymetallaynes and comparison was made to their binuclear model complexes trans-[Pt(Ph)(PEt3)2C[triple bond]C(C6H4)E(C6H4)C[triple bond]CPt(Ph)(PEt3)2] and their closest Group 11 gold(I) and Group 12 mercury(II) neighbours, [MC[triple bond]C(C6H4)E(C6H4)C[triple bond]CM] (M = Au(PPh3), HgMe; E = O, S, SO, SO2). The regiochemical structures of these angular-shaped molecules were studied by NMR spectroscopy and single-crystal X-ray structural analyses. Upon photoexcitation, each one has an intense purple-blue fluorescence emission near 400 nm in dilute fluid solutions at room temperature. Harvesting of the organic triplet emissions harnessed through the strong heavy-atom effects of Group 10-12 transition metals was studied in detail. These metal-containing aryleneethynylenes spaced by chalcogen units were found to have large optical gaps and high-energy triplet states. The influence of metal- and chalcogen-based conjugation interrupters on the intersystem crossing rate and on the spatial extent of the lowest singlet and triplet excitons was fully elucidated. We discuss and compare the phosphorescence spectra of these transition-metal diynes and polyynes in terms of the nature of the metal centre, conjugated chain length and Group 16 spacer unit. Our work here indicates that high-energy triplet states in these materials intrinsically give rise to very efficient phosphorescence with fast radiative decays and one could readily observe room-temperature phosphorescence for the platinum polyynes. PMID:16411257

Poon, Suk-Yue; Wong, Wai-Yeung; Cheah, Kok-Wai; Shi, Jian-Xin

2006-03-01

376

Aerobactin iron uptake sequences in plasmid ColV-K30 are flanked by inverted IS1-like elements and replication regions.  

PubMed Central

By using Southern blot hybridization procedures, we found that a specific sequence within a 16.3-kilobase HindIII restriction fragment of pColV-K30 was also present in at least three other pColV-K30 HindIII fragments. Restriction endonuclease mapping of these HindIII fragments indicated that two of these repeated sequences, identified as IS1-like, occur in reverse orientation adjacent to the ends of the aerobactin iron uptake region, also included in the 16.3-kilobase HindIII fragment. There are two distinct replication regions enclosing the IS1-flanked aerobactin genes. A pColV-K30 BamHI restriction endonuclease fragment, carrying one of these replication regions, showed homology with the F plasmid EcoRI fragment f5, which carries the F replication sequences. Images

Perez-Casal, J F; Crosa, J H

1984-01-01

377

The 190Pt186Os Decay System Applied to Dating Platinum-Group Element Mineralization in Layered Intrusions, Ophiolites and Detrital Deposits  

Microsoft Academic Search

Discrete platinum-group minerals (PGM) occur as accessory phases in mafic-ultamafic intrusions and ophiolitic chromitites, as well as numerous detrital deposits globally. The 190Pt-186Os decay system, measured by laser ablation MC-ICPMS (LA-MC-ICPMS) provides a useful geochronometric tool for direct dating of PGM. Here we present two examples that verify the accuracy of the technique in geologically well constrained situations and demonstrate

J. A. Coggon; G. Nowell; G. Pearson; T. Oberthür; J. Lorand; F. Melcher; S. W. Parman

2010-01-01

378

Threshold Group Testing  

Microsoft Academic Search

We introduce a natural generalization of the well-studied group testing prob- lem: A test gives a positive (negative) answer if the pool contains at least u (at most l) positive elements, and an arbitrary answer if the number of positive elements is between these fixed thresholds l and u. We show that the p posi- tive elements can be determined

Peter Damaschke

2006-01-01

379

Testing WIMS-D4M cross sections and the ANL ENDF/B-V 69 group library. Results from global diffusion and Monte Carlo calculations compared with measurements in the Romanian 14-MW TRIGA reactor  

SciTech Connect

The WIMS-D4 code has been modified (WIMS-D4M) to produce microscopic isotopic cross sections in ISOTXS format for use in diffusion and transport calculations. Beginning with 69-group libraries based on ENDF/B-V data, numerous cell calculations have been made to prepare a set of broad group cross sections for use in diffusion calculations. Global calculations have been made for two control rod states of the Romanian steady state TRIGA reactor with 29 fresh HEU fuel clusters. Detailed Monte Carlo calculations also have been performed for the same reactor configurations using data based on ENDF/B-V. Results from these global calculations are compared with each other and with the measured excess reactivities. Although region-averaged macroscopic principal cross sections obtained from WIMS-D4M are in good agreement with the corresponding Monte Carlo values, problems exist with the high energy (E > 10 keV) microscopic hydrogen transport cross sections.

Bretscher, M.M.

1993-12-31

380

How Deep and Hot was Earth's Magma Ocean? Combined Experimental Datasets for the Metal-silicate Partitioning of 11 Siderophile Elements - Ni, Co, Mo, W, P, Mn, V, Cr, Ga, Cu and Pd  

NASA Technical Reports Server (NTRS)

Since approximately 1990 high pressure and temperature (PT) experiments on metal-silicate systems have showed that partition coefficients (D) for siderophile (iron-loving) elements are much different than those measured at low PT conditions. The high PT data have been used to argue for a magma ocean during growth of the early Earth. Initial conclusions were based on experiments and calculations for a small number of elements such as Ni and Co. However, for many elements only a limited number of experimental data were available then, and they only hinted at values of metal-silicate D's at high PT conditions. In the ensuing decades there have been hundreds of new experiments carried out and published on a wide range of siderophile elements. At the same time several different models have been advanced to explain the siderophile elements in the earth's mantle: a) intermediate depth magma ocean; 25-30 GPa, b) deep magma ocean; up to 50 GPa, and c) early reduced and later oxidized magma ocean. Some studies have drawn conclusions based on a small subset of siderophile elements, or a set of elements that provides little leverage on the big picture (like slightly siderophile elements), and no single study has attempted to quantitatively explain more than 5 elements at a time. The purpose of this abstract is to update the predictive expressions outlined by Righter et al. (1997) with new experimental data from the last decade, test the predictive ability of these expressions against independent datasets (there are more data now to do this properly), and to apply the resulting expressions to the siderophile element patterns in Earth's upper mantle. The predictive expressions have the form: lnD = alnfO2 + b/T + cP/T + d(1Xs) + e(1Xc) + SigmafiXi + g These expressions are guided by the thermodynamics of simple metal-oxide equilibria that control each element, include terms that mimic the activity coefficients of each element in the metal and silicate, and quantify the effect of variable oxygen fugacity. Preliminary results confirm that D(Ni) and D(Co) converge at pressures near 25-30 GPa and approximately 2200 K, and show that D(Pd) and D(Cu) become too low at the PT conditions of the deepest models. Furthermore, models which force fit V and Cr mantle concentrations by metal-silicate equilibrium overlook the fact that at early Earth mantle fO2, these elements will be more compatible in Mg-perovskite and (Fe,Mg)O than in metal. Thus an intermediate depth magma ocean, at 25-30 GPa, 2200 K, and at IW-2, can explain more mantle siderophile element concentrations than other models.

Righter, Kevin

2008-01-01

381

A Measurement of the Top Quark Mass with the D0 Detector at s**(1/2) = 1.96-TeV using the Matrix Element Method  

SciTech Connect

Using a data set of 158 and 169 pb{sup -1} of D0 Run-II data in the electron and muon plus jets channel, respectively, the top quark mass has been measured using the Matrix Element Method. The method and its implementation are described. Its performance is studied in Monte Carlo using ensemble tests and the method is applied to the Moriond 2004 data set.

Kroeninger, Kevin Alexander; /Bonn U.

2004-04-01

382

Toxicity of Arsenic (III) and (V) on Plant Growth, Element Uptake, and Total Amylolytic Activity of Mesquite (Prosopis Juliflora x P. Velutina)  

Microsoft Academic Search

The effects of arsenite [As(III)] and arsenate [As(V)] on the growth of roots, stems, and leaves and the uptake of arsenic (As), micro- and macronutrients, and total amylolytic activity were investigated to elucidate the phytotoxicity of As to the mesquite plant (Prosopis juliflora x P. velutina). The plant growth was evaluated by measuring the root and shoot length, and the

Ntebogeng S. Mokgalaka-Matlala; Edith Flores-Tavizón; Hiram Castillo-Michel; Jose R. Peralta-Videa; Jorge L. Gardea-Torresdey

2008-01-01

383

Determination of the Kobayashi-Maskawa-Cabibbo matrix element {ital V}{sub {ital us}} under various flavor-symmetry-breaking models in hyperon semileptonic decays  

SciTech Connect

We study the success to describe hyperon semileptonic decays of four models that incorporate second-order SU(3) symmetry-breaking corrections. The criteria to assess their success is by determining {ital V}{sub {ital us}} in each of the three relevant hyperon semileptonic decays and comparing the values so obtained with one another and also with the one that comes from {ital K}{sub {ital l}3} decays. A strong dependence on the particular symmetry-breaking model is observed. Values of {ital V}{sub {ital us}} which do not agree with the one of {ital K}{sub {ital l}3} are generally obtained. However, in the context of chiral perturbation theory, only the model whose corrections are {ital O}({ital m}{sub {ital s}}) and {ital O}({ital m}{sub {ital s}}{sup 3/2}) is successful. Using its predictions for the {ital f}{sub 1} form factors one can quote a value of {ital V}{sub {ital us}} from this model, namely, {ital V}{sub {ital us}}=0.2176{plus_minus}0.0026, which is in excellent agreement with the {ital K}{sub {ital l}3} one. {copyright} {ital 1996 The American Physical Society.}

Flores-Mendieta, R.; Garcia, A. [Departamento de Fisica, Centro de Investigacion y de Estudios Avanzados del IPN, Apartado Postal 14-740, 07000, Mexico, Distrito Federal (Mexico)] [Departamento de Fisica, Centro de Investigacion y de Estudios Avanzados del IPN, Apartado Postal 14-740, 07000, Mexico, Distrito Federal (Mexico); Sanchez-Colon, G. [Departamento de Fisica Aplicada, Centro de Investigacion y de Estudios Avanzados del IPN, Unidad Merida, Apartado Postal 73, Cordemex 97310, Merida, Yucatan (Mexico)] [Departamento de Fisica Aplicada, Centro de Investigacion y de Estudios Avanzados del IPN, Unidad Merida, Apartado Postal 73, Cordemex 97310, Merida, Yucatan (Mexico)

1996-12-01

384

Natural gas plays of the Knox Group in the Appalachian basin: A significant element of the U. S. Department of Energy atlas of major Appalachian gas plays  

SciTech Connect

Oil and gas have been produced from the Knox Group in the Appalachian basin since the early 1990s. However, only since the 1960s have significant volumes of hydrocarbons been produced. Porosity development along the Knox unconformity is the dominant geologic control for hydrocarbon migration and entrapment. Other important controls include stratigraphy, diagenesis, paleokarst, structure, and fractures. Cumulative production is ultimately, controlled by the reservoir conditions characteristic to each play. The two most significant Knox plays in terms of total cumulative gas production are (1) the Lower Ordovician-Upper Cambrian eroded shelf sandstones known as the Rose Run sandstone in Kentucky, Ohio, and Pennsylvania, and the Theresa sandstone in New York, and (2) the Lower Ordovician-Upper Cambrian paleokarstic carbonates known as the Beekmantown dolomite in Kentucky, Ohio, and Tennessee, and the Copper Ridge (Trempealeau) dolomite in Ohio. Minor volumes of gas have been produced from fracture and paleokarstic carbonate plays in the Know dolomite of Kentucky, Tennessee, and Virginia, and from localized sandstones of the Copper Ridge (Trempealeau) in Ohio. Some individual wells in Ohio have produced more than 1 billion ft[sup 3] of gas from the Beekmantown, Rose Run, or Copper Ridge (Trempealeau). Cumulative gas production from all the Knox plays in the Appalachian basin has been in excess of 60 billion ft[sup 3] of gas. The Knox Group plays are currently the most active exploration targets in the basin.

Baranoski, M.T.; Wolfe, M.E. (Ohio Department of Natural Resources, Columbus, OH (United States))

1993-08-01

385

Measurement of Ll, L. cap alpha. , L. beta. , and L. gamma. x-ray production cross sections in some high-Z elements by 18-, 26-, 33-, and 44-keV photons  

SciTech Connect

The cross sections for the production of Ll, L..cap alpha.., L..beta.., and L..gamma.. x rays in the elements Ta, W, Au, Hg, Tl, Pb, Bi, Th, and U by photons of energies 17.781, 25.770, 32.890, and 43.949 keV have been measured, using a standard double-reflection experimental setup. The measured values have been interpreted in terms of the photoionization cross sections, fluorescence yields, Coster-Kronig transition probabilities, and radiative decay rates. A fairly good agreement is found between the experiment and calculations.

Singh, N.; Mittal, R.; Singh, B.; Allawadhi, K.L.; Sood, B.S.

1986-10-01

386

Complexes of an anionic gallium(I) N-heterocyclic carbene analogue with group 14 element(II) fragments: synthetic, structural and theoretical studies.  

PubMed

The reactions of the anionic gallium(I) N-heterocyclic carbene (NHC) analogue, [K(tmeda)][:Ga{[N(Ar)C(H)]2}], Ar = C6H3Pri2-2,6, with the heavier group 14 alkene analogues, R2E=ER2, E = Ge or Sn, R = -CH(SiMe3)2, have been carried out. In 2:1 stoichiometries, these lead to the ionic [K(tmeda)][R2EGa{[N(Ar)C(H)]2}] complexes which exhibit long E-Ga bonds. The nature of these bonds has been probed by DFT calculations, and the complexes have been compared to neutral NHC adducts of group 14 dialkyls. The 4:1 reaction of [K(tmeda)][:Ga{[N(Ar)C(H)]2}] with R2Sn=SnR2 leads to the digallyl stannate complex, [K(tmeda)][RSn[Ga{[N(Ar)C(H)]2}]2], presumably via elimination of KR. In contrast, the reaction of the gallium heterocycle with PbR2 affords the digallane4, [Ga{[N(Ar)C(H)]2}]2, via an oxidative coupling reaction. For sake of comparison, the reactions of [K(tmeda)][:Ga{[N(Ar)C(H)]2}] with Ar'2E=EAr'2, E = Ge, Sn or Pb, Ar' = C6H2Pri3-2,4,6, were carried out and led to either no reaction (E = Ge), the formation of [K(tmeda)][Ar'2SnGa{[N(Ar)C(H)]2}] (E = Sn), or the gallium(III) heterocycle, [Ar'Ga{[N(Ar)C(H)]2}] (E = Pb). Salt elimination reactions between [K(tmeda)][:Ga{[N(Ar)C(H)]2}] and the guanidinato group 14 complexes [(Giso)ECl], E = Ge or Sn, Giso = [Pri2NC{N(Ar)}2]-, gave the neutral [(Giso)EGa{[N(Ar)C(H)]2}] complexes. All complexes have been characterized by NMR spectroscopy and X-ray crystallographic studies. PMID:16933925

Green, Shaun P; Jones, Cameron; Lippert, Kai-Alexander; Mills, David P; Stasch, Andreas

2006-09-01

387

Extended Affine Weyl Groups  

Microsoft Academic Search

In this paper we study the Weyl groups of reduced extended affine root systems, the root systems of extended affine Lie algebras. We start by describing the extended affine Weyl group as a semidirect product of a finite Weyl group and a Heisenberg-like normal subgroup. This provides a unique expression for the Weyl group elements (in terms of some naturally

Saeid Azam

1999-01-01

388

Computation of activities induced by 14 MeV neutrons for the elemental analysis of human tissues, skin and tooth enamel.  

PubMed

For planning experiments for neutron activation analysis investigations at 14 MeV, suitable induced beta activities in Bq/g/neutron flux have been computed via appropriate reactions for the estimation of 19F, 23Na, 24Mg, 31P, 32S, 35,37Cl, 39K, 40Ca, 55Mn, 56Fe, 66Zn, 63,65Cu, 107,109Ag and 208Pb. The computational work for (n,p); (n, alpha); (n,n') and (n,2n) reactions induced with 14 MeV neutrons are based on the pre-equilibrium emission mechanism and also the compound nucleus theory with otpical model potential and pairing energy corrections. The cross-sections obtained by pre-equilibrium computer codes are reasonable and have been used in the present computations. PMID:8287054

Khanchi, R S; Bansal, S L; Aggarwal, S; Khurana, S; Mohindra, R K

1994-01-01

389

Two-Way Antigenic Cross-Reactivity between Severe Acute Respiratory Syndrome Coronavirus (SARS-CoV) and Group 1 Animal CoVs Is Mediated through an Antigenic Site in the N-Terminal Region of the SARS-CoV Nucleoprotein?  

PubMed Central

In 2002, severe acute respiratory syndrome-associated coronavirus (SARS-CoV) emerged in humans, causing a global epidemic. By phylogenetic analysis, SARS-CoV is distinct from known CoVs and most closely related to group 2 CoVs. However, no antigenic cross-reactivity between SARS-CoV and known CoVs was conclusively and consistently demonstrated except for group 1 animal CoVs. We analyzed this cross-reactivity by an enzyme-linked immunosorbent assay (ELISA) and Western blot analysis using specific antisera to animal CoVs and SARS-CoV and SARS patient convalescent-phase or negative sera. Moderate two-way cross-reactivity between SARS-CoV and porcine CoVs (transmissible gastroenteritis CoV [TGEV] and porcine respiratory CoV [PRCV]) was mediated through the N but not the spike protein, whereas weaker cross-reactivity occurred with feline (feline infectious peritonitis virus) and canine CoVs. Using Escherichia coli-expressed recombinant SARS-CoV N protein and fragments, the cross-reactive region was localized between amino acids (aa) 120 to 208. The N-protein fragments comprising aa 360 to 412 and aa 1 to 213 reacted specifically with SARS convalescent-phase sera but not with negative human sera in ELISA; the fragment comprising aa 1 to 213 cross-reacted with antisera to animal CoVs, whereas the fragment comprising aa 360 to 412 did not cross-react and could be a potential candidate for SARS diagnosis. Particularly noteworthy, a single substitution at aa 120 of PRCV N protein diminished the cross-reactivity. We also demonstrated that the cross-reactivity is not universal for all group 1 CoVs, because HCoV-NL63 did not cross-react with SARS-CoV. One-way cross-reactivity of HCoV-NL63 with group 1 CoVs was localized to aa 1 to 39 and at least one other antigenic site in the N-protein C terminus, differing from the cross-reactive region identified in SARS-CoV N protein. The observed cross-reactivity is not a consequence of a higher level of amino acid identity between SARS-CoV and porcine CoV nucleoproteins, because sequence comparisons indicated that SARS-CoV N protein has amino acid identity similar to that of infectious bronchitis virus N protein and shares a higher level of identity with bovine CoV N protein within the cross-reactive region. The TGEV and SARS-CoV N proteins are RNA chaperons with long disordered regions. We speculate that during natural infection, antibodies target similar short antigenic sites within the N proteins of SARS-CoV and porcine group 1 CoVs that are exposed to an immune response. Identification of the cross-reactive and non-cross-reactive N-protein regions allows development of SARS-CoV-specific antibody assays for screening animal and human sera.

Vlasova, Anastasia N.; Zhang, Xinsheng; Hasoksuz, Mustafa; Nagesha, Hadya S.; Haynes, Lia M.; Fang, Ying; Lu, Shan; Saif, Linda J.

2007-01-01

390

M X-ray cross sections from 75 to 300 keV proton bombardment of selected 5d transition elements  

NASA Astrophysics Data System (ADS)

M X-ray production cross sections for selected thick targets of Hf, W, Re, Pt, Au and Pb impacted by 75-300 keV protons are presented and compared with ECPSSR and RPWBA theories using different atomic data bases, including comparisons with other investigators. The results for the major M X-ray transitions exhibit a universal character with respect to the reduced proton velocity in agreement with expectations from theory.

Cipolla, Sam J.

2014-07-01

391

Rayleigh and Compton scattering cross sections for low, medium and high Z elements in the energy region 23.18 <= E <= 30.85 keV  

Microsoft Academic Search

Using nearly monoenergetic unpolarised Kalpha x-ray photons coherent (Rayleigh) and incoherent (atomic Compton) scattering cross sections in the atomic region 13 <= Z <= 82 have been measured at 23.18, 24.14, 25.19, 26.27 and 30.85 keV. Experimental scattering cross sections in the momentum transfer region 1.322 h Å-1 <= q <= 1.759 h Å-1 [q = sin (theta\\/2)lambda(Å)] were obtained

D. V. Rao; R. Cesareo; G. E. Gigante

1996-01-01

392

Geochemistry of trace elements in coals from the Zhuji Mine, Huainan Coalfield, Anhui, China  

USGS Publications Warehouse

The abundances of nine major elements and thirty-eight trace elements in 520 samples of low sulfur coals from the Zhuji Mine, Huainan Coalfield, Anhui, China, were determined. Samples were mainly collected from 10 minable coal seams of 29 boreholes during exploration. The B content in coals shows that the influence of brackish water decreased toward the top of coal seams; marine transgression and regression occurred frequently in the Lower Shihezi Formation. A wide range of elemental abundances is found. Weighted means of Na, K, Fe, P, Be, B, Co, Ni, Cr, Se, Sb, Ba, and Bi abundances in Zhuji coals are higher, and the remainder elements are either lower or equal to the average values of elements in coals of northern China. Compared to the Chinese coals, the Zhuji coals are higher in Na, K, Be, B, Cr, Co, Se, Sn, Sb, and Bi, but lower in Ti, P, Li, V and Zn. The Zhuji coals are lower only in S, P, V and Zn than average U.S. and world coals. Potassium, Mg, Ca, Mn, Sr, As, Se, Sb and light rare earth elements (LREE) had a tendency to be enriched in thicker coal seams, whereas Fe, Ti, P, V, Co, Ni, Y, Mo, Pb and heavy rare earth elements (HREE) were inclined to concentrate in thinner coal seams. The enrichment of some elements in the Shanxi or Upper Shihezi Formations is related to their depositional environments. The elements are classified into three groups based on their stratigraphic distributions from coal seams 3 to 11-2, and the characteristics of each group are discussed. Lateral distributions of selected elements are also investigated. The correlation coefficients of elemental abundances with ash content show that the elements may be classified into four groups related to modes of occurrence of these elements. ?? 2009 Elsevier B.V. All rights reserved.

Sun, R.; Liu, G.; Zheng, L.; Chou, C. -L.

2010-01-01

393

Joint Analysis Group, Deepwater Horizon Oil Spill: Review of R/V Brooks McCall Data to Examine Subsurface Oil.  

National Technical Information Service (NTIS)

The National Incident Commander for the Deepwater Horizon Oil Spill established the Joint Analysis Group (JAG) to examine the subsurface oceanographic data that was collected through the coordinated sampling efforts of vessels contracted for or owned by B...

2011-01-01

394

Study of cross sections and spin-density matrix elements for two-body reactions in 5 GeV\\/c pi+p two-pronged interactions  

Microsoft Academic Search

Results are presented on differential (total) cross sections and decay parameters for four two-body reactions (pi+p --> ppi+, pi+p --> pvarrho+, pi+p --> Delta++pi0 and pi+p --> Delta++eta0) obtained from a sample of approximately 30 000 two-pronged interactions 5 GeV\\/c incident momentum. In the forward direction the dsigma\\/dt' distribution of reaction pvarrho+, Delta++pi0 and Delta++eta0 show a dip or flat

D. J. Schotanus; C. L. Pols; D. Z. Toet; R. T. van de Walle; J. V. Mayor; G. E. Pearson; B. Chaurand; R. Vanderhaghen; G. Rinaudo; A. E. Werbrouck

1970-01-01

395

L i ( i = 1-3) subshell X-ray production cross sections and fluorescence yields for some elements with 56 ? Z ? 68 at 22.6 keV  

NASA Astrophysics Data System (ADS)

The L k ( k = l, ?, ? 1,4, ? 3,6, ? 2,15,9,10,7, ? 1,5 and ? 2,3,4) X-ray production (XRP) cross sections have been measured for six elements with 56 ? Z ? 68 at 22.6 keV incident photon energy using the EDXRF spectrometer. The incident photon intensity, detector efficiency and geometrical factors have been determined from the K X-ray yields emitted from elemental targets with 22 ? Z ? 42 in the same geometrical setup and from knowledge of the K XRP cross sections. The L 1 and L 2 subshell fluorescence yields have been deduced from the present measured L k XRP cross sections using the relativistic Hartree-Fock-Slater (HFS) model based photoionization cross sections. The present deduced ?1 (exp) values have been found to be, on an average, higher by 15% and 20% than those based on the Dirac-Hartree-Slater (DHS) model and the semi-empirical values compiled by Krause, respectively, for elements with 60 ? Z ? 68.

Chauhan, Yogeshwar; Tiwari, M. K.; Puri, Sanjiv

2008-01-01

396

The 190Pt-186Os Decay System Applied to Dating Platinum-Group Element Mineralization in Layered Intrusions, Ophiolites and Detrital Deposits  

NASA Astrophysics Data System (ADS)

Discrete platinum-group minerals (PGM) occur as accessory phases in mafic-ultamafic intrusions and ophiolitic chromitites, as well as numerous detrital deposits globally. The 190Pt-186Os decay system, measured by laser ablation MC-ICPMS (LA-MC-ICPMS) provides a useful geochronometric tool for direct dating of PGM. Here we present two examples that verify the accuracy of the technique in geologically well constrained situations and demonstrate the potential for using the 190Pt-186Os PGM method to accurately date layered mafic intrusions, ophiolitic chromitites and detrital PGM deposits. Fifty PGM grains from three different horizons within the Bushveld complex yield a Pt-Os isochron age of 2012 ± 47 Ma (2?, MSWD = 1.19, 186Os/188Osi = 0.119818 ± 0.000006). This is consistent with the published U-Pb zircon age of 2054 Ma (Scoates and Friedman, 2008). The younger PGM isochron age is not likely to be a function of difference in blocking temperatures in the different systems. Pt-Os model ages are possible in high pt grains because initial 186Os/188Os can be well constrained. Using this approach we obtained Pt-Os model ages of 2113 ± 106 Ma and 2042 ± 102 Ma for a Bushveld Pt-Fe alloy and sperrylite respectively. Detrital PGM derived from the Meratus ophiolite, southeast Borneo yield a 190Pt-186Os isochron age of 202.5 Ma ± 8.3 Ma (2?, n = 260, MSWD = 0.90, 186Os/188Osi = 0.119830 ± 0.000003), consistent with radiometric and biostratigraphic age constraints (Wakita et al., 1998). We interpret this as the age of formation of the PGM grains in during chromitite genesis in the lower oceanic lithosphere. Our combined data demonstrate the utility of the LA-MC-ICPMS method as a tool for accurate Pt-Os dating of detrital PGM as well as their igneous parent bodies. We can constrain Pt/Os fractionation at the ablation site as being < 2.5%, while within-grain heterogeneity is ultimately one of the strongest controls on isochron and single-grain ages given the partial sampling represented by laser ablation. Scoates, J.S. and Friedman, R.M. 2008. Precise age of the platiniferous Merensky reef, Bushveld Complex, South Africa, by the U-Pb zircon chemical abrasion ID-TIMS technique; Economic Geology 103, p. 465-471. Wakita, K., Miyazaki, K., Zulkarnain, I., Sopaheluwakan, J. and Sanyoto, P. 1998. Tectonic implications of new age data for the Meratus complex of south Kalimantan, Indonesia; Island Arc 7, p. 202-222.

Coggon, J. A.; Nowell, G.; Pearson, G.; Oberthür, T.; Lorand, J.; Melcher, F.; Parman, S. W.

2010-12-01

397

Chemistry of high-oxidation-state groups V and VI complexes: Novel silyl and imido complexes and the reactions of silyl and alkyl alkylidyne complexes with oxygen  

NASA Astrophysics Data System (ADS)

This dissertation describes the synthesis and characterization of the novel early transition metal (especially group VI metals) complexes free of anionic pi-ligands such as cyclopentadienyl (Cp) and studies of their reactions with oxygen and silanes. Our study of Cp-free tungsten silyl chemistry is reported. A novel d 0 tungsten silyl complex 2 [(ButCH 2)W(=CHBut)2(SiButPh2 ) (2a) ? (ButCH2)2W(?CBu t)(SiButPh2) (2b)] and an equilibrium between 2a and 2b are described in Chapter 2. The thermodynamics of this equilibrium [DeltaH° = -0.9(0.2) kcal/mol, DeltaS° = -0.6(0.8) eu] was investigated by 1H NMR. The studies of the alpha-hydrogen exchange between 2a and 2b by 2-D EXSY experiments gave kinetic parameters of the exchange: DeltaH? = 17.9(1.1) kcal/mol, DeltaS? = 1.9(5.7) eu for the forward reaction (2a ? 2b) and Delta H? = 18.6 (1.1) kcal/mol, DeltaS ? = 1.9(5.7) eu for the back reaction (2b ? 2a). The reaction of O2 with silyl alkylidyne 2b [(Bu tCH2)W(=CHBut)2(SiBut Ph2) (2a) ? (ButCH2)2W(?CBu t)(SiButPh2) (2b)] is described in Chapter 3. A silyl migration product (ButCH2) 2W(=O)[=C(But)(SiButPh2)] ( 5) was characterized. A siloxy analog of 2b, (Bu tCH2)2W?CBut(OSiBu tPh2) (6), was prepared and excluded as a possible intermediate in the formation of 5. Ab initio calculations suggested a pathway involving silyl migration in 2b to give a tungsten (IV) intermediate (ButCH 2)2W=C(But)(SiButPh2) (7) prior to the reaction with O2. A crystal structure of (Me3SiCH2)2W(=O)(=CHSiMe3)(O=PMe 3)•(Me3SiCH2)3W?CSiMe 3 (12) was obtained from the reaction of alkyl alkylidyne (Me3SiCH2)3W?CSiMe3 with O2 in the presence of PMe3. In Chapter 4, preparation and characterization of bis(2,6-diisopropylphenylimido)molybdenum(VI) amide and silyl complexes (ArN=)2Mo(NMe2)2 (14), (ArN=)2Mo(NMe2)[Si(SiMe3) 3] (15), (ArN=)2MoCl[N(SiMe3) 2] (16), (ArN=)2Mo(NMe2)[N(SiMe 3)2] (17), and (ArN=)2Mo(NHAr) 2 (18) are reported. In addition, new bis(imido)molybdenum(VI) amine adducts (ArN=)2MoCl2(NHMe2) ( 19), (ArN=)2MoCl2(NHEt2) (20 ), (ArN=)2MoCl2(NHMe2)2 (21), and (ArN=)2MoCl2(NHMe2)•(ArN=) 2MoCl2(DME) (22) and their X-ray structures are reported. Preparation and characterization of Cp-free tantalum(V) amide silyl complexes have been investigated, as reported in Chapter 5. Thermodynamics of interesting equilibria (Me2N)3Ta[Si(SiMe3)3] 2 (25) ? (Me2N)3Ta(SiButPh2)[Si(SiMe 3)3] (27) ? (Me2N)3Ta(SiButPh2) 2 (26) was studied. In the equilibrium 25 + Li(THF)3SiButPh2 ? 27 + Li(THF)3Si(SiMe3)3, Delta H° = -0.54(0.17) kcal/mol and DeltaS° = -0.79(0.65) eu, and in the equilibrium 27 + Li(THF) 3SiButPh2 ? 26 + Li(THF)3Si(SiMe3)3, Delta H° = - 0.56(0.17) kcal/mol and DeltaS° = -1.52(0.65) eu.

Chen, Tianniu

398

Chemical Elements  

NSDL National Science Digital Library

To find quick facts on elements The Photographic Periodic Table of Elements-shows a photograhpic representation of most of the elements (remember some are invisible gases) The Element Song Click on the following links to find quick facts about the elements and peridoic table: Periodic Table of Elements: LANL - Originally this resource, the Periodic Table, was created by Robert Husted at Los Alamos National Laboratory during his time ...