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Sample records for group v elements

  1. Oxo-group-14-element bond formation in binuclear uranium(V) Pacman complexes.

    PubMed

    Jones, Guy M; Arnold, Polly L; Love, Jason B

    2013-07-29

    Simple and versatile routes to the functionalization of uranyl-derived U(V)-oxo groups are presented. The oxo-lithiated, binuclear uranium(V)-oxo complexes [{(py)3LiOUO}2(L)] and [{(py)3LiOUO}(OUOSiMe3)(L)] were prepared by the direct combination of the uranyl(VI) silylamide "ate" complex [Li(py)2][(OUO)(N")3] (N" = N(SiMe3)2) with the polypyrrolic macrocycle H4L or the mononuclear uranyl (VI) Pacman complex [UO2(py)(H2L)], respectively. These oxo-metalated complexes display distinct U-O single and multiple bonding patterns and an axial/equatorial arrangement of oxo ligands. Their ready availability allows the direct functionalization of the uranyl oxo group leading to the binuclear uranium(V) oxo-stannylated complexes [{(R3Sn)OUO}2(L)] (R = nBu, Ph), which represent rare examples of mixed uranium/tin complexes. Also, uranium-oxo-group exchange occurred in reactions with [TiCl(OiPr)3] to form U-O-C bonds [{(py)3LiOUO}(OUOiPr)(L)] and [(iPrOUO)2(L)]. Overall, these represent the first family of uranium(V) complexes that are oxo-functionalised by Group 14 elements. PMID:23794441

  2. A new structure of two-dimensional allotropes of group V elements.

    PubMed

    Li, Ping; Luo, Weidong

    2016-01-01

    The elemental two-dimensional (2D) materials such as graphene, silicene, germanene, and black phosphorus have attracted considerable attention due to their fascinating physical properties. Structurally they possess the honeycomb or distorted honeycomb lattices, which are composed of six-atom rings. Here we find a new structure of 2D allotropes of group V elements composed of eight-atom rings, which we name as the octagonal tiling (OT) structure. First-principles calculations indicate that these allotropes are dynamically stable and are also thermally stable at temperatures up to 600 K. These allotropes are semiconductors with band gaps ranging from 0.3 to 2.0 eV, thus they are potentially useful in near- and mid-infrared optoelectronic devices. OT-Bi is also a 2D topological insulator (TI) with a band gap of 0.33 eV, which is the largest among the reported elemental 2D TIs, and this gap can be increased further by applying compressive strains. PMID:27150010

  3. A new structure of two-dimensional allotropes of group V elements

    NASA Astrophysics Data System (ADS)

    Li, Ping; Luo, Weidong

    2016-05-01

    The elemental two-dimensional (2D) materials such as graphene, silicene, germanene, and black phosphorus have attracted considerable attention due to their fascinating physical properties. Structurally they possess the honeycomb or distorted honeycomb lattices, which are composed of six-atom rings. Here we find a new structure of 2D allotropes of group V elements composed of eight-atom rings, which we name as the octagonal tiling (OT) structure. First-principles calculations indicate that these allotropes are dynamically stable and are also thermally stable at temperatures up to 600 K. These allotropes are semiconductors with band gaps ranging from 0.3 to 2.0 eV, thus they are potentially useful in near- and mid-infrared optoelectronic devices. OT-Bi is also a 2D topological insulator (TI) with a band gap of 0.33 eV, which is the largest among the reported elemental 2D TIs, and this gap can be increased further by applying compressive strains.

  4. A new structure of two-dimensional allotropes of group V elements

    NASA Astrophysics Data System (ADS)

    Li, Ping; Luo, Weidong

    The elemental two-dimensional (2D) materials such as graphene, silicene, germanene, and black phosphorus have attracted considerable attention due to their fascinating physical properties. Structurally they possess the honeycomb or distorted honeycomb lattices, which are composed of six-atom rings. Here we find a new structure of 2D allotropes of group V elements composed of eight-atom rings, which we name as the octagonal tiling (OT) structure. First-principles calculations indicate that these allotropes are dynamically stable and are also thermally stable at temperatures up to 600 K. These allotropes are semiconductors with band gaps ranging from 0.3 to 2.0 eV, thus they are potentially useful in near- and mid-infrared optoelectronic devices. OT-Bi is also a 2D topological insulator (TI) with a band gap of 0.33 eV, which is the largest among the reported elemental 2D TIs, and this gap can be increased further by applying compressive strains.

  5. A new structure of two-dimensional allotropes of group V elements

    PubMed Central

    Li, Ping; Luo, Weidong

    2016-01-01

    The elemental two-dimensional (2D) materials such as graphene, silicene, germanene, and black phosphorus have attracted considerable attention due to their fascinating physical properties. Structurally they possess the honeycomb or distorted honeycomb lattices, which are composed of six-atom rings. Here we find a new structure of 2D allotropes of group V elements composed of eight-atom rings, which we name as the octagonal tiling (OT) structure. First-principles calculations indicate that these allotropes are dynamically stable and are also thermally stable at temperatures up to 600 K. These allotropes are semiconductors with band gaps ranging from 0.3 to 2.0 eV, thus they are potentially useful in near- and mid-infrared optoelectronic devices. OT-Bi is also a 2D topological insulator (TI) with a band gap of 0.33 eV, which is the largest among the reported elemental 2D TIs, and this gap can be increased further by applying compressive strains. PMID:27150010

  6. Influence of the group V element on the chemical potential and crystal structure of Au-catalyzed III-V nanowires

    SciTech Connect

    Dubrovskii, V. G.

    2014-02-03

    We present a kinetic growth model having a particular emphasis on the influence of the group V element on the preferred crystal structure of Au-catalyzed III-V nanowires. The model circumvents the uncertainty in the group V contribution into the overall liquid chemical potential. We show why the nanowire elongation rate is limited by the group III transport, while the crystal structure depends on the effective group V to III imbalance. Within the model, we are able to explain some important structural trends in Au-catalyzed III-V nanowires. In particular, we show that high group V flux always favors wurtzite structure in molecular-beam epitaxy. This tendency could be inverted in vapor deposition techniques due to suppression of the group III diffusion at high group V flux.

  7. Elementally specific electron-positron annihilation radiation emitted from ion cores of group-V impurity-vacancy complexes in germanium

    NASA Astrophysics Data System (ADS)

    Arutyunov, N. Yu.; Emtsev, V. V.

    2007-12-01

    High-momentum component (HMC) of the electron-positron annihilation has been detected by the angular correlation of annihilation radiation (ACAR) technique in order to obtain elementally specific information about the ion cores of the donor-vacancy complexes (DV) formed by irradiation with 60Co γ-rays at Tirr.≈280 K in oxygen-lean n-Ge doped with group-V donors (D=As, Sb, and Bi). The probability of annihilation of positrons with the core electrons of DV complexes reconstructed from ACAR spectra increases in passing from AsV to SbV and BiV complexes. This increase correlates with the shift of the D atom from its regular position towards the vacancy site predicted by the results of spin-density functional modeling study. The data obtained suggest inward relaxation of the ion cores of DV complexes (including the one directed inward towards the vacancy).

  8. Finite element analysis of stress concentration in Class V restorations of four groups of restorative materials in mandibular premolar

    PubMed Central

    N, Shubhashini; N, Meena; Shetty, Ashish; Kumari, Anitha; DN, Naveen

    2008-01-01

    Aim: To study the concentration of stress in class V restoration of four different restorative materials subjected to occlusal load of 100N, 150N, 200N, 250N and to analyse the obtained data with the listed properties of the restorative material. Materials and Methods: Using FEM analysis the stresses generated in a class V lesion in a mandibular premolar was studied. Results: Within the framework of the aforementioned views, and from the results of the study it can be concluded that microfilled composite is the most suitable restorative material followed by flowable composite, glass ionomer cement and resin modified glass ionomer cement. Conclusion: Restoration of Class V lesions with materials of higher modulus of elasticity will enable better stress distribution. PMID:20142899

  9. On the relation between the microscopic structure and the sound velocity anomaly in elemental melts of groups IV, V, and VI.

    PubMed

    Greenberg, Yaron; Yahel, Eyal; Caspi, El'ad N; Beuneu, Brigitte; Dariel, Moshe P; Makov, Guy

    2010-09-01

    The sound velocity of some liquid elements of groups IV, V, and VI, as reported in the literature, displays anomalous features that set them apart from other liquid metals. In an effort to determine a possible common origin of these anomalies, extensive neutron diffraction measurements of liquid Bi and Sb were carried out over a wide temperature range. The structure factors of liquid Sb and Bi were determined as a function of temperature. The structure of the two molten metals was carefully analyzed with respect to peak locations, widths, and coordination numbers in their respective radial distribution function. The width of the peaks in the radial distribution functions was not found to increase and even decreased within a certain temperature range. This anomalous temperature dependence of the peak widths correlates with the anomalous temperature dependence of the sound velocity. This correlation may be accounted for by increased rigidity of the liquid structure with temperature. A phenomenological correlation between the peak width and the sound velocity is suggested for metallic melts and is found to agree with available data for normal and anomalous elemental liquids in groups IV-VI. PMID:20831323

  10. Metal and metalloid indicator electrodes for the non-aqueous potentiometric titration of weak acids: comparative evaluation of group III, IV and V main-group elements.

    PubMed

    Greenhow, E J; Al-Mudarris, B F

    Indicator electrodes constructed from aluminium, gallium, indium, thallium, carbon, silicon, germanium, tin, lead, arsenic, antimony and bismuth have been evaluated for the potentiometric titration of solutions of benzoic acid in dimethylformamide and 4-methyl-2-pentanone. The aluminium, gallium, silicon and arsenic electrodes have also been evaluated for the determination of 3,5-xylenol in the same two solvents. Aluminium, gallium, indium, silicon, germanium, antimony and bismuth electrodes are superior to, or compare favourably with, a glass electrode for the determination of benzoic acid, when the criterion of efficiency is the sharpness of the end-point inflexion. In non-aqueous titrations of 3,5-xylenol, aluminium and gallium electrodes are similar in efficiency to the glass electrode for determinations in dimethylformamide solution, while the gallium electrode is superior to the glass electrode when 4-methyl-2-pentanone is the solvent. Possible relationships between the properties of the electrode element and the end-point sharpness when it is used as an indicator electrode are briefly considered. PMID:18961658

  11. Platinum-group element geochemistry of the Hongge Fe-V-Ti deposit in the Pan-Xi area, southwestern China

    NASA Astrophysics Data System (ADS)

    Zhong, Hong; Zhou, Xin-Hua; Zhou, Mei-Fu; Sun, Min; Liu, Bing-Guang

    2002-03-01

    Mafic and ultramafic intrusions in the Pan-Xi area along the western margin of the Yangtze block, southwestern China, are spatially associated with the Late Permian Emeishan flood basalts of the Emeishan Large Igneous Province. The Hongge layered intrusion is one of the plutonic bodies of this province and hosts a giant Fe-V-Ti deposit. This intrusion has three zones: a lower, olivine clinopyroxenite zone, a middle, clinopyroxenite zone, and an upper, gabbro zone. Each of these zones consists of one or two compositional cycles, which have distinct Mg# values, TiO2 concentrations and total REE contents. The middle clinopyroxenite zone and upper gabbro zone contain thick (14-84 m) magnetite-mineralized layers. Samples from the lower olivine clinopyroxenite zone and middle clinopyroxenite zone of the Hongge intrusion are enriched in platinum and palladium relative to iridium and ruthenium. Rocks of the lower olivine clinopyroxenite zone have Pd/Ir ratios (1.8-22.3) lower than those of the middle clinopyroxenite zone (6.2 to 83 in its lower part and 3.6 to 49 in its upper part). The Pd/Ir ratios increase progressively upwards in each cyclic unit. Chromite is the major phase controlling concentrations of iridium and ruthenium. The Cu/Pd ratios at the bottom of each cyclic unit are close to that of the mantle and increase upwards. This variation suggests that each cyclic unit represents a new batch of magma, and sulfide mineral segregation removes PGE (platinum-group elements), Ni and Cu. Each cyclic unit in the Hongge layered intrusion might have resulted from crystal fractionation and mixing between a primary and evolved magma. The high Cu/Pd, Ti/Pd, Ni/Pd and Cu/Ir ratios of the intrusion suggest that the sulfide mineral segregation may have played an important role in PGE differentiation. If this interpretation is correct, then there is a potential to find economic PGE-rich horizon in the Hongge-type intrusions in the region.

  12. 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

    SciTech Connect

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

    2013-12-09

    The effect of d{sup 1} 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. Na{sup 1+}/K{sup 1+} doping at Sr{sup 2+}-site is found to be critical to form the d{sup 1} 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 d{sup 1} impurity in SrM should be a main factor for such a substantial improvement of intrinsic coercivity.

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

    SciTech Connect

    Gates, Jacklyn M.

    2008-07-31

    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$+1100\\atop{-760}$ pb was measured at an excitation energy of 16.0 ± 1.8 MeV. For the 2n exit channel, a maximum cross section of 1660$+450\\atop{-370}$ 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$+1730\\atop{-1370}$ 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

  14. Properties of Group Five and Group Seven transactinium elements

    SciTech Connect

    Wilk, Philip A.

    2001-05-01

    The detection and positive identification of the short-lived, low cross section isotopes used in the chemical studies of the heaviest elements are usually accomplished by measuring their alpha-decay, thus the nuclear properties of the heaviest elements must be examined simultaneously with their chemical properties. The isotopes 224 Pa and 266,267 Bh have been studied extensively as an integral part of the investigation of the heaviest members of the groups five and seven of the periodic table. The half-life of 224 Pa was determined to be 855 plus/minus19 ms by measuring its alpha-decay using our rotating wheel, solid state detector system at the Lawrence Berkeley National Laboratory 88-Inch Cyclotron. Protactinium was produced by bombardment of a bismuth target. New neutron rich isotopes, 267 Bh and 266 Bh, were produced in bombardments of a 249 Bk target and their decay was observed using the rotating wheel system. The 266 Bh that was produced decays with a half-life of approximately 1 s by emission of alpha particles with an average energy of 9.25 plus/minus 0.03 MeV. 267 Bh was observed to decay with a 17 s half-life by emission of alpha-particles with an average energy of 8.83 plus/minus 0.03 MeV. The chemical behavior of hafnium, Ha (element 105) was investigated using the fast on-line continuous liquid extraction and detection system SISAK-LISSY. Hafnium was not observed in this experiment following transport and extraction. Protactinium was used as on-line test of the apparatus to determine the experimental efficiency of the entire system. Unfortunately, the amount of protactinium observed after the extraction, compared to the amount produced, was extremely small, only 2.5%. The extraction of the protactinium isotope indicated the efficiency of the apparatus was too low to observe the extraction of hafnium. The chemical behavior of oxychloride compounds of bohrium was investigated by isothermal gas adsorption chromatography in a quartz column at 180, 150

  15. Main-group elements as transition metals.

    PubMed

    Power, Philip P

    2010-01-14

    The last quarter of the twentieth century and the beginning decade of the twenty-first witnessed spectacular discoveries in the chemistry of the heavier main-group elements. The new compounds that were synthesized highlighted the fundamental differences between their electronic properties and those of the lighter elements to a degree that was not previously apparent. This has led to new structural and bonding insights as well as a gradually increasing realization that the chemistry of the heavier main-group elements more resembles that of transition-metal complexes than that of their lighter main-group congeners. The similarity is underlined by recent work, which has shown that many of the new compounds react with small molecules such as H(2), NH(3), C(2)H(4) or CO under mild conditions and display potential for applications in catalysis. PMID:20075912

  16. Thermodynamic Properties of the Group IA Elements

    NASA Astrophysics Data System (ADS)

    Alcock, C. B.; Chase, M. W.; Itkin, V. P.

    1994-05-01

    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 on 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 our previous assessment of the II A group, 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) and the National Institute of Standards and Technology (Washington). 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. §

  17. Non-hydride group V sources for OMVPE

    NASA Astrophysics Data System (ADS)

    Stringfellow, G. B.

    1988-07-01

    A major limitation to the continuing development of organometallic vapor phase epitaxy (OMVPE) for the growth of III/V semiconductor materials is the hazard posed by the hydride sources, AsH3 and PH3, which are virtually universally used, in high pressure cylinders, as the group V source materials for the growth of the highest quality materials. The ideal group V source would be a nontoxic liquid with a moderate vapor pressure (50-500 Torr). To be suitable for OMVPE growth, the molecule must pyrolyze at ordinary growth temperatures, be stable against decomposition in the bottle at room temperature, and not participate in undesirable parasitic reactions with the group III source molecules. The new sources have additional constraints related to purity. They must be easily purified without decomposing and produce no detectable carbon contamination in the resultant epitaxial layers. This set of stringent requirements eliminates most commonly available non-hydride group V sources. Recent research on newly developed sources has shown considerable promise. The entire area of group V sources, including the elemental sources, for OMVPE growth of III/V materials will be reviewed. The sources with no hydrogen atoms attached to the group V atom, the elemental, trimethyl-V, and triethyl-V, sources all appear to give unacceptably high carbon incorporation. Diethylarsine, which has one H attached to the As, produces high quality GaAs but has an inconveniently low vapor pressure. Trimethylphosphine and triethylphosphine o not pyrolyze at low enough temperatures to be useful for conventional OMVPE growth. Tertbutylarsine (TBAs) and tertbutylphosphine (TBP) appear to be promising source materials. TBP has a very low toxicity, a vapor pressure ideal for OMVPE growth, and the pyrolysis occurs at lower temperatures than for PH3, allowing the use of low values of V/III ratio for the growth of high quality material. No carbon contamination can be attributed to the TBP. Control of the As

  18. Colloidal nanocrystals of lithiated group 14 elements.

    PubMed

    Cloud, Jacqueline E; Wang, Yonglong; Yoder, Tara S; Taylor, Lauren W; Yang, Yongan

    2014-12-22

    The synthesis of colloidal nanocrystals (NCs) of lithiated group 14 elements (Z=Si, Ge, and Sn) is reported, which are Li4.4 Si, Li3.75 Si, Li4.4 Ge, and Li4.4 Sn. Lix Z compounds are highly reactive and cannot be synthesized by existing methods. The success relied on separating the surface protection from the crystal formation and using a unique passivating ligand. Bare Lix Z crystals were first produced by milling elemental Li and Z in an argon-filled jar. Then, under the assistance of additional milling, hexyllithium was added to passivate the freshly generated Lix Z NCs. This ball-milling-assisted surface protection method may be generalized to similar systems, such as Nax Z and Kx Z. Moreover, Li4.4 Si and Li4.4 Ge NCs were conformally encapsulated in carbon fibers, providing great opportunities for studying the potential of using Lix Z to mitigate the volume-fluctuation-induced poor cyclability problem confronted by Z anodes in lithium-ion batteries. PMID:25367697

  19. The Heavy Element Abundance in Groups of Galaxies

    NASA Technical Reports Server (NTRS)

    David, Laurence

    2000-01-01

    Over the past few years we have analyzed a sample of clusters observed by the Advanced Spacecraft for Cosmology Astrophysics (ASCA) X-ray satellite. We performed spatially resolved X-ray spectroscopy of a sample of 18 relaxed clusters of galaxies with gas temperatures below 4 keV. The spectral analysis was done using ASCA/SIS (Solid state Imaging Spectrometer) data combined with imaging data from ROSAT/PSPC (German acronym for X-ray satellite/Position Sensitive Proportional Counter) and Einstein/IPC (Imaging Proportional Counter) observations. We derived temperature profiles using single-temperature fits for all of the clusters in the sample, and also corrected for the presence of cold gas in the center of so-called 'cooling flow' clusters. For all of the clusters in the sample we derived Si and Fe abundance profiles. For a few of the clusters we also were able to derive Ne and S abundance profiles. We compared the elemental abundances derived at similar overdensities in all of the clusters in the sample. We also compared element mass-to-light ratios for the entire sample. We concluded that the preferential accretion of low entropy, low abundance gas into the potentials of groups and cold clusters can explain most of the observed trends in metallicity. In addition, we discussed the importance of preheating of the intracluster medium by Type II supernovae on the cluster scaling relations.

  20. How to efficiently select an arbitrary Clifford group element

    SciTech Connect

    Koenig, Robert; Smolin, John A.

    2014-12-15

    We give an algorithm which produces a unique element of the Clifford group on n qubits (C{sub n}) from an integer 0≤i<|C{sub n}| (the number of elements in the group). The algorithm involves O(n{sup 3}) operations and provides, in addition to a canonical mapping from the integers to group elements g, a factorization of g into a sequence of at most 4n symplectic transvections. The algorithm can be used to efficiently select random elements of C{sub n} which are often useful in quantum information theory and quantum computation. We also give an algorithm for the inverse map, indexing a group element in time O(n{sup 3})

  1. Parallel and Serial Grouping of Image Elements in Visual Perception

    ERIC Educational Resources Information Center

    Houtkamp, Roos; Roelfsema, Pieter R.

    2010-01-01

    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…

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

    NASA Technical Reports Server (NTRS)

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

    2000-01-01

    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.

  3. Photochemistry and charge transfer chemistry of the platinum group elements

    SciTech Connect

    Eisenberg, R.

    1991-12-01

    Significant progress has been made on the photochemistry and photophysics of platinum group element dithiolate complexes. The specific systems under investigation are square planar complexes of Pt(II) containing a dithiolate chelate and two other donor groups to complete the coordination sphere. The donor groups may be amines, imines, phosphines, phosphites or olefins, and they can be either monodentate or joined together as part of a chelate ring.

  4. Molecular beam epitaxy of III-P{sub x}As{sub 1−x} solid solutions: Mechanism of composition formation in the sublattice of a group V element

    SciTech Connect

    Emelyanov, E. A. Putyato, M. A.; Semyagin, B. R.; Feklin, D. F.; Preobrazhensky, V. V.

    2015-02-15

    The effect of substrate temperature, As{sub 2} and P{sub 2} molecular flux densities, and growth rate on the composition of III-P{sub x}As{sub 1−x} solid solution layers prepared by molecular beam epitaxy is experimentally investigated. Experimental data in a wide range of growth conditions are analyzed. The results obtained are presented in the form of a kinetic model for describing the process of formation of the composition in the Group V sublattice of the III-P{sub x}As{sub 1−x} solid solution upon molecular beam epitaxy. The model can be used for choosing the growth conditions of the III-P{sub x}As{sub 1−x} (001) solid-solution layers of a specified composition.

  5. Quantum Supergroups V. Braid Group Action

    NASA Astrophysics Data System (ADS)

    Clark, Sean; Hill, David

    2016-05-01

    We construct a braid group action on quantum covering groups. We further use this action to construct a PBW basis for the positive half in finite type which is pairwise-orthogonal under the inner product. This braid group action is induced by operators on the integrable modules; however, these operators satisfy spin braid relations.

  6. A Renormalisation Group Method. V. A Single Renormalisation Group Step

    NASA Astrophysics Data System (ADS)

    Brydges, David C.; Slade, Gordon

    2015-05-01

    This paper is the fifth in a series devoted to the development of a rigorous renormalisation group method applicable to lattice field theories containing boson and/or fermion fields, and comprises the core of the method. In the renormalisation group method, increasingly large scales are studied in a progressive manner, with an interaction parametrised by a field polynomial which evolves with the scale under the renormalisation group map. In our context, the progressive analysis is performed via a finite-range covariance decomposition. Perturbative calculations are used to track the flow of the coupling constants of the evolving polynomial, but on their own perturbative calculations are insufficient to control error terms and to obtain mathematically rigorous results. In this paper, we define an additional non-perturbative coordinate, which together with the flow of coupling constants defines the complete evolution of the renormalisation group map. We specify conditions under which the non-perturbative coordinate is contractive under a single renormalisation group step. Our framework is essentially combinatorial, but its implementation relies on analytic results developed earlier in the series of papers. The results of this paper are applied elsewhere to analyse the critical behaviour of the 4-dimensional continuous-time weakly self-avoiding walk and of the 4-dimensional -component model. In particular, the existence of a logarithmic correction to mean-field scaling for the susceptibility can be proved for both models, together with other facts about critical exponents and critical behaviour.

  7. On spectral synthesis on element-wise compact Abelian groups

    NASA Astrophysics Data System (ADS)

    Platonov, S. S.

    2015-08-01

    Let G be an arbitrary locally compact Abelian group and let C(G) be the space of all continuous complex-valued functions on G. A closed linear subspace \\mathscr H\\subseteq C(G) is referred to as an invariant subspace if it is invariant with respect to the shifts τ_y\\colon f(x)\\mapsto f(xy), y\\in G. By definition, an invariant subspace \\mathscr H\\subseteq C(G) admits strict spectral synthesis if \\mathscr H coincides with the closure in C(G) of the linear span of all characters of G belonging to \\mathscr H. We say that strict spectral synthesis holds in the space C(G) on G if every invariant subspace \\mathscr H\\subseteq C(G) admits strict spectral synthesis. An element x of a topological group G is said to be compact if x is contained in some compact subgroup of G. A group G is said to be element-wise compact if all elements of G are compact. The main result of the paper is the proof of the fact that strict spectral synthesis holds in C(G) for a locally compact Abelian group G if and only if G is element-wise compact. Bibliography: 14 titles.

  8. Platinum-group element abundance patterns in different mantle environments

    SciTech Connect

    Rehkaemper, M.; Halliday, A.N.; Barfod, D.; Fitton, J.G.; Dawson, J.B.

    1997-11-28

    Mantle-derived xenoliths from the Cameroon Line and northern Tanzania display differences in their platinum-group element (PGE) abundance patterns. The Cameroon Line lherzolites have uniform PGE patterns indicating a homogeneous upper mantle over several hundreds of kilometers, with approximately chondritic PGE ratios. The PGE patterns of the Tanzanian peridotites are similar to the PGE systematics of ultramafic rocks from ophiolites. The differences can be explained if the northern Tanzanian lithosphere developed in a fluid-rich suprasubduction zone environment, whereas the Cameroon Line lithosphere only experienced melt extraction from anhydrous periodotites. 32 refs., 2 figs., 1 tab.

  9. Summary of the TeV33 working group

    SciTech Connect

    Bagley, P.P.; Bieniosek, F.M.; Colestock, P.

    1996-10-01

    This summary of the TeV33 working group at Snowmass reports on work in the areas of Tevatron store parameters, the beam-beam interaction, Main Injector intensity (slip stacking), antiproton production, and electron cooling.

  10. Platinum group elements in mantle melts and mantle samples

    NASA Astrophysics Data System (ADS)

    Barnes, Stephen J.; Mungall, James E.; Maier, Wolfgang D.

    2015-09-01

    A large data compilation has been assembled of platinum group element (PGE) analyses in mantle melts and mantle rocks, the latter including an assortment of xenoliths and obducted mantle massifs. The degree of correlation has been investigated among the PGEs and with other major element variables such as Al2O3, TiO2 and Mg number, and the results are considered in the context of the current paradigm for the behaviour of highly siderophile elements in the silicate Earth. Primitive mantle melts have a wide range of PGE contents. Komatiites have the highest abundances of all the PGEs, show the strongest correlations between Pt and Rh, Pt and Pd and between the iridium-group PGEs Ir, Ru and Os (IPGEs). Most basalts of all affinities have lower levels of Pt and Pd and much lower levels of Ir, Ru and Os than komatiites. Within the basalt grouping Rh has stronger affinities with the IPGEs. Picrites and Archaean basalts are intermediate between these two groups. MORBs and a small proportion of continental LIP basalts show strong depletions in all PGEs attributable to retention of sulfide in their mantle source rocks, or sulfide liquid fractionation on ascent. The degree of PGE depletion in other basalts is probably attributable to equilibration with sulfide, but is less than would be expected under conventional models of sulfide extraction, and is instead attributed to mixing of magmas generated at variable depths incorporating both sulfide-saturated and undersaturated components. Basalts with Pt and Pd contents higher than typical komatiites are rare, a notable example being B1-type parent magmas to the Bushveld Complex, which have komatiite-like relative PGE abundances and Pt, Pd and Rh abundances up to a factor of two higher than komatiites for comparable Ti contents. The mantle composition array as a whole is characterized by variable degrees of depletion of Pt, Pd and Rh in Al-poor, melt-depleted harzburgite/dunite lithologies; lack of depletion in these elements in

  11. Platinum group elements in the environment and their health risk.

    PubMed

    Ravindra, Khaiwal; Bencs, László; Van Grieken, René

    2004-01-01

    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 in the last decades in diverse environmental matrices; like airborne particulate matter, soil, roadside dust and vegetation, river, coastal and oceanic environment. Generally, PGEs are referred to behave in an inert manner and to be immobile. However, there is an evidence of spread and bioaccumulation of these elements in the environment. Platinum content of road dusts can be soluble, consequently, it enters the waters, sediments, soil and finally, the food chain. The effect of chronic occupational exposure to Pt compounds is well-documented, and certain Pt species are known to exhibit allergenic potential. However, the toxicity of biologically available anthropogenic Pt is not clear. Hence, there is a need to study the effect on human health of long-term chronic exposure to low levels of Pt compounds. PMID:14654273

  12. Quantitative bioimaging of platinum group elements in tumor spheroids.

    PubMed

    Niehoff, Ann-Christin; Grünebaum, Jonas; Moosmann, Aline; Mulac, Dennis; Söbbing, Judith; Niehaus, Rebecca; Buchholz, Rebecca; Kröger, Sabrina; Wiehe, Arno; Wagner, Sylvia; Sperling, Michael; von Briesen, Hagen; Langer, Klaus; Karst, Uwe

    2016-09-28

    Limited drug penetration into tumor tissue is a significant factor to the effectiveness of cancer therapy. Tumor spheroids, a 3D cell culture model system, can be used to study drug penetration for pharmaceutical development. In this study, a method for quantitative bioimaging of platinum group elements by laser ablation (LA) coupled to inductively coupled plasma mass spectrometry (ICP-MS) is presented. Different matrix-matched standards were used to develop a quantitative LA-ICP-MS method with high spatial resolution. To investigate drug penetration, tumor spheroids were incubated with platinum complexes (Pt(II)acetylacetonate, cisplatin) and the palladium tagged photosensitizer 5,10,15,20-tetrakis(3-hydroxyphenyl)porphyrin (mTHPP). Distribution and accumulation of the pharmaceuticals were determined with the developed method. PMID:27619092

  13. Doping of indium phosphide with group IV elements

    SciTech Connect

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

    1985-06-01

    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.

  14. Cyclic silylated onium ions of group 15 elements.

    PubMed

    Reissmann, Matti; Schäfer, André; Panisch, Robin; Schmidtmann, Marc; Bolte, Michael; Müller, Thomas

    2015-03-01

    Five- and six-membered cyclic silylated onium ions of group 15 elements I were synthesized by intramolecular cyclization of transient silylium ions II. Silylium ions II were prepared by the hydride transfer reaction from silanes III using trityl cation as hydride acceptor. It was found that smaller ring systems could not be obtained by this approach. In these cases tritylphosphonium ions IV were isolated instead. Cations I and IV were isolated in the form of their tetrakispentafluorphenyl borates and characterized by multinuclear NMR spectroscopy and, in two cases, by X-ray diffraction analysis. Cyclic onium ions I showed no reactivity similar to that of isoelectronic intramolecular borane/phosphane frustrated Lewis pairs (FLPs). The results of DFT computations at the M05-2X level suggest that the strength of the newly formed Si-E linkage is the major reason for inertness of I[B(C6F5)4] versus molecular hydrogen. PMID:25664605

  15. Thermodynamic properties of the Group 1A elements

    SciTech Connect

    Alcock, C.B.; Itkin, V.P.; Chase, M.W.

    1994-05-01

    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.

  16. Comprehensive Analyses of the Spectra of Iron-group Elements

    NASA Astrophysics Data System (ADS)

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

    2014-06-01

    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

  17. Determination of the CKM Element V(Ub)

    SciTech Connect

    Fortin, Dominique; /Victoria U.

    2007-04-06

    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.

  18. High resolution photoelectron spectroscopy of clusters of Group V elements

    SciTech Connect

    Wang, Lai-sheng; Niu, B.; Lee, Y.T.; Shirley, D.A.

    1989-07-01

    High resolution HeI (580{angstrom}) photoelectron spectra of As{sub 2}, As{sub 4}, and P{sub 4} were obtained with a newly-built high temperature molecular beam source. Vibrational structure was resolved in the photoelectron spectra of the three cluster species. The Jahn-Teller effect is discussed for the {sup 2}E and {sup 2}T{sub 2} states of P{sub 4}{sup +} and As{sub 4}{sup +}. As a result of the Jahn-Teller effect, the {sup 2}E state splits into two bands, and the {sup 2}T{sub 2} state splits into three bands, in combination with the spin-orbit effect. It was observed that the {nu}{sub 2} normal vibrational mode was involved in the vibronic interaction of the {sup 2}E state, while both the {nu}{sub 2} and {nu}{sub 3} modes were active in the {sup 2}T{sub 2} state. 26 refs., 5 figs., 3 tabs.

  19. Platinum-group elements: so many excellent properties

    USGS Publications Warehouse

    Zientek, Michael L.; Loferski, Patricia J.

    2014-01-01

    The platinum-group elements (PGE) include platinum, palladium, rhodium, ruthenium, iridium, and osmium. These metals have similar physical and chemical properties and occur together in nature. The properties of PGE, such as high melting points, corrosion resistance, and catalytic qualities, make them indispensable to many industrial applications. PGE are strategic and critical materials for many nations because they are essential for important industrial applications but are mined in a limited number of places and have no adequate substitutes. Exploration and mining companies have found approximately 104,000 metric tons of PGE (with minor gold) in mineral deposits around the world that could be developed. For PGE, almost all known production and resources are associated with three geologic features: the Bushveld Complex, a layered mafic-to-ultramafic intrusion in South Africa; the Great Dyke, a layered mafic-to-ultramafic intrusion in Zimbabwe; and sill-like intrusions associated with flood basalts in the Noril’sk-Talnakh area, Russia. To help predict where PGE supplies might be located, USGS scientists study how and where PGE resources are concentrated in the Earth's crust and use that knowledge to assess the likelihood that undiscovered PGE deposits may exist. Techniques used for assessing mineral resources were developed by the USGS to support the stewardship of Federal lands and evaluate mineral resource availability in a global context. The USGS also compiles statistics and information on the worldwide supply, demand, and flow of PGE. These data are all used to inform U.S. national policymakers.

  20. Bioaccessibility of platinum group elements in automotive catalytic converter particulates.

    PubMed

    Turner, Andrew; Price, Simon

    2008-12-15

    The bioaccessibilities of the platinum group elements (PGE): Rh, Pd, and Pt; and the catalyzator poison, Pb, have been determined in particles derived from milled automotive catalytic converters using a physiologically based extraction test (PBET) that simulates, sequentially, the chemical conditions encountered in the human stomach and intestine. PGE accessibility, relative to total metal concentration, was generally less than a few percent, but increased in the stomach with decreasing pH (from 4 to 1) and/or increasing chloride concentration, and with decreasing particle concentration. In most cases, bioaccessibility increased from the acidic stomach to the neutral, carbonate-rich intestine. Bioaccessibility of Pb displayed similar pH and particle concentration dependencies to PGE in the stomach, but this metal exhibited significantly greater mobilization (up to 80%) overall and a reduction in accessibility from the stomach to intestine. Reaction kinetics of PGE dissolution in the stomach at pH 2.5 were modeled using a combined surface reaction-diffusion controlled mechanism with rate constants of 0.068, 0.031, and 0.015 (microg L(-1))(-1) h(-1) for Rh, Pd, and Pt, respectively. For Pb, however, mobilization proceeded via a different mechanism whose time-dependence was fitted with an empirical, logarithmic equation. Overall, PGE bioaccessibility appeared to be controlled by dissolution rates of metallic nanoparticles in the stomach, and solubility and kinetic constraints on inorganic species (chlorides, hydroxychlorides, and carbanatochlorides) and undefined organic complexes formed in the simulated gastrointestinal tract. Further studies are required to elucidate any effects engendered by the long-term oral exposure of small quantities of these species. PMID:19174929

  1. Fe-Group Elements in the Metal-Poor Star HD 84937: Abundances and their Implications

    NASA Astrophysics Data System (ADS)

    Sneden, Chris; Cowan, John J.; Kobayashi, Chiaki; Pignatari, Marco; Lawler, James E.; Den Hartog, Elizabeth; Wood, Michael P.

    2016-01-01

    We have derived accurate relative abundances of the Fe-group elements Sc through Zn in the very metal-poor main-sequence turnoff star HD 84937. For this study we analyzed high resolution, high signal-to-noise HST/STIS and VLT/UVES spectra over a total wavelength range 2300-7000 Å. We employed only recent or newly-applied reliable laboratory transition data for all species. Abundances from more than 600 lines of non-Fe species were combined with about 550 Fe lines in HD 84937 to yield abundance ratios of high precision. From parallel analyses of solar photospheric spectra we also derived new solar abundances of these elements. This in turn yielded internally-consistent relative HD 84937 abundances with respect to the Sun. For seven of the ten Fe-group elements the HD 84937 abundances were from both neutral and ionized transitions. In all of these cases the neutral and ionized species yield the same abundances within the measurement uncertainties. Therefore standard Saha ionization balance appears to hold in the HD 84937 atmosphere. We derived metallicity [Fe/H] = -2.32 with sample standard deviation of 0.06. Solid evidence is seen for departures from the solar abundance mix in HD 84937, for example [Co/Fe] = +0.14, [Cu/Fe] = -0.83, and <[Sc,Ti,V/Fe]> = +0.31. Combining our Sc, Ti, and V abundances for this star with those from large-sample spectroscopic surveys suggests that these elements are positively correlated in stars with [Fe/H] < -2. HD 84937 is unusually enriched in Sc, Ti, and V. Our analysis strongly suggests that different types of supernovae with a large scatter of explosion energies and asymmetries contributed to the creation of the Fe-group elements early in the Galaxy's history.This work has been supported in part by NASA grant NNX10AN93G (J.E.L.), by NSF grants AST-1211055 (J.E.L.), AST-1211585 (C.S.), PHY-1430152 (through JINA, J.J.C. and M.P.), EU MIRGCT-2006-046520 (M.P.), and by the ``Lendlet-2014'' Programme of the Hungarian Academy of

  2. Method of fabricating vertically aligned group III-V nanowires

    DOEpatents

    Wang, George T; Li, Qiming

    2014-11-25

    A top-down method of fabricating vertically aligned Group III-V micro- and nanowires uses a two-step etch process that adds a selective anisotropic wet etch after an initial plasma etch to remove the dry etch damage while enabling micro/nanowires with straight and smooth faceted sidewalls and controllable diameters independent of pitch. The method enables the fabrication of nanowire lasers, LEDs, and solar cells.

  3. New laboratory atomic data for neutral, singly and doubly ionised iron group elements for astrophysics applications

    NASA Astrophysics Data System (ADS)

    Pickering, Juliet C.; Nave, Gillian; Liggins, Florence; Clear, Christian; Ruffoni, Matthew; Sansonetti, Craig

    2015-08-01

    We present new laboratory spectroscopic measurements to produce atomic data for astrophysically important species: neutral, singly and doubly ionised iron group elements.We use high resolution Fourier Transform Spectrometry (FTS) (resolving power up to 2x106 at 200nm) to measure atomic spectra, giving accurate line wavelengths (to a few parts in 108), atomic energy levels, hyperfine structure splitting and log gfs (accurate to a few %) (Ruffoni et al this meeting). These data are vital for astrophysical spectral analyses for: line identification, spectrum synthesis, elemental abundance determinations [eg 1], and disentangling of blends etc. It is not possible to theoretically calculate these atomic data to the accuracy needed for modern astrophysics applications.At Imperial College we have a unique visible-VUV FT spectrometer with short wavelength cut-off of 135nm. We supplement FTS data at shorter wavelengths with spectra recorded on the NIST 10.7m grating spectrograph (with phosphor image or photographic plates) and at longer wavelengths in the IR we use the NIST IR FT spectrometer.An elemental spectrum may contain thousands of spectral lines from the IR to VUV. We use these wavelengths to correct known atomic energy levels, and search for new atomic levels. The result is a classified linelist and accurate atomic energy levels.We present progress on iron group element atomic energy levels and wavelengths for V I and V II [2,3], Co III [4], Cr I, Mn I and Mn II, and Ni II.This work is supported by STFC(UK), The Leverhulme Trust, The Royal Society and NASA.References[1] Bergemann M, Pickering JC & Gehren T,“NLTE analysis of Co I/Co II lines in spectra of cool stars with new laboratory hyperfine splitting constants",MNRAS 401(2) 1334 (2010)[2] Thorne AP, Pickering JC & Semeniuk J,“The spectrum and term analysis of V II”, ApJS 207,13 (2013)[3] Thorne AP, Pickering JC & Semeniuk J,“The spectrum and term analysis of V I",ApJS 192,11 (2011)[4] Smillie DG

  4. The elemental composition of the Sun. II. The iron group elements Sc to Ni

    NASA Astrophysics Data System (ADS)

    Scott, Pat; Asplund, Martin; Grevesse, Nicolas; Bergemann, Maria; Sauval, A. Jacques

    2015-01-01

    We redetermine the abundances of all iron group nuclei in the Sun, based on neutral and singly-ionised lines of Sc, Ti, V, Mn, Fe, Co and Ni in the solar spectrum. We employ a realistic 3D hydrodynamic model solar atmosphere, corrections for departures from local thermodynamic equilibrium (NLTE), stringent line selection procedures and high quality observational data. We have scoured the literature for the best quality oscillator strengths, hyperfine constants and isotopic separations available for our chosen lines. We find log ɛSc = 3.16 ± 0.04, log ɛTi = 4.93 ± 0.04, log ɛV = 3.89 ± 0.08, log ɛCr = 5.62 ± 0.04, log ɛMn = 5.42 ± 0.04, log ɛFe = 7.47 ± 0.04, log ɛCo = 4.93 ± 0.05 and log ɛNi = 6.20 ± 0.04. Our uncertainties factor in both statistical and systematic errors (the latter estimated for possible errors in the model atmospheres and NLTE line formation). The new abundances are generally in good agreement with the CI meteoritic abundances but with some notable exceptions. This analysis constitutes both a full exposition and a slight update of the preliminary results we presented in Asplund et al. (2009, ARA&A, 47, 481), including full line lists and details of all input data we employed. Tables 1-3 are available in electronic form at http://www.aanda.org

  5. Elements of Mathematics, Book 10: Groups and Rings.

    ERIC Educational Resources Information Center

    Exner, Robert; And Others

    One of 12 books developed for use with the core material (Book O) of the Elements of Mathematics Program, this text covers material well beyond the scope of the usual secondary mathematics sequences. These materials are designed for highly motivated students with strong verbal abilities; mathematical theories and ideas are developed through…

  6. The Abundances of the Fe Group Elements in Early B Stars in the Magellanic Clouds and Bridge

    NASA Astrophysics Data System (ADS)

    Peters, Geraldine J.; Adelman, Saul J.

    2016-01-01

    The abundances of three Fe Group elements (V, Cr, and Fe) in 9 early main-sequence band B stars in the LMC, 7 in the SMC , and two in the Magellanic Bridge have been determined from archival FUSE observations and the Hubeny/Lanz NLTE programs TLUSTY/SYNSPEC. Lines from the Fe group elements, except for a few weak multiplets of Fe III, are not observable in the optical spectral region. The best set of lines in the FUSE spectral region are Fe III (UV1), V III 1150 Å, and Cr III 1137 Å. The abundances of these elements in early B stars are a marker for recent SNe Ia activity, as a single exploding white dwarf can deliver 0.5 solar masses of Ni-56 that decays into Fe to the ISM. The Fe group abundances in an older population of stars primarily reflect SNe II activity, in which a single explosion delivers only 0.07 solar masses of Ni-56 to the ISM (the rest remains trapped in the neutron star). The abundances of the Fe group elements in early B stars not only track SNe Ia activity but are also important for computing evolutionary tracks for massive stars. In general, the Fe abundance relative to the sun's value is comparable to the mean abundances for the lighter elements in the Clouds/Bridge but the values of [V,Cr/Fe]sun are smaller. This presentation will discuss the spatial distribution of the Fe Group elements in the Magellanic Clouds, and compare it with our galaxy in which the abundance of Fe declines with radial distance from the center. Support from NASA grants NAG5-13212, NNX10AD66G, STScI HST-GO-13346.22, and USC's Women in Science and Engineering (WiSE) program is greatly appreciated.

  7. Spectroscopy of XY 3Z (C 3 v) radicals with an odd number of electrons: A tensorial formalism adapted to the SU(2)⊗CI⊃C∞vS⊃C3vS group chain

    NASA Astrophysics Data System (ADS)

    El Hilali, A.; Boudon, V.; Loëte, M.

    2006-09-01

    A tensorial formalism adapted to the case of XY 3Z symmetric tops with half integer angular momenta is proposed as an extension of the formalism for the group chain O (3) ⊃ C∞ v ⊃ C3 v developed in a recent paper [A. El Hilali, V. Boudon, M. Loëte, J. Mol. Spectrosc. 234 (2005) 113-121]. We use the chain SU(2)⊗CI⊃C∞vS⊃C3vS, where GS ( G being C∞ v or C3 v) is the G point group with its spinorial representations. Coupling coefficients and formulas for the computation of matrix elements of the tensor operators are derived for this chain. A deduction of coupling coefficients (Clebsch-Gordan, 6 C, 9 C, …) and similar formulas is proposed for the group C3vS itself.

  8. Trace element seasonality in marine macroalgae of different functional-form groups.

    PubMed

    Malea, Paraskevi; Chatziapostolou, Anastasia; Kevrekidis, Theodoros

    2015-02-01

    Novel information on the seasonality of element accumulation in seaweeds is provided. Seasonal patterns of As, Ba, Cd, Co, Cr, Cu, Mn, Mo, Ni, Pb, Se, Sr, U, V and Zn concentrations in macroalgae belonging to different functional-form groups (Ulva intestinalis, Ulva rigida, Codium fragile, Gracilaria gracilis) from the Thessaloniki Gulf, Aegean Sea were determined and compared. Uni- and multivariate data analyses were applied. Element concentrations generally decreased during spring and/or summer, probably due to the growth effect, but a reverse trend, particularly in Ulva species, was also observed. Most elements (Cd, Co, Cr, Cu, Mo, Ni, Pb, Sr) in Ulva species displayed a comparatively low monthly variability, indicating that the extent of seasonal variation is closely related to thallus morphology and growth strategy. In particular, these data suggest that Cd, Co, Cr, Cu, Mo, Ni, Pb and Sr contents in fast-growing, sheet-like macroalgae are less influenced by the season, compared to their contents in coarsely-branched and thick-leathery macroalgae; therefore, sheet-like macroalgae may be more appropriate to be used in biomonitoring of coastal waters. The data presented could be utilized in the development of biomonitoring programmes for the protection of coastal environments. PMID:25460058

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

    USGS Publications Warehouse

    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

    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.

  10. Finding of probable Tunguska Cosmic Body material: anomalies in platinum group elements in peat from the explosion area

    NASA Astrophysics Data System (ADS)

    Kolesnikov, E. M.; Hou, Q. L.; Xie, L. W.; Kolesnikova, N. V.

    2005-04-01

    Further evidencies of a cometary nature of the 1908 Tunguska Cosmic Body (TCB) are presented. Earlier in the event layers of the Sphagnum fuscum peat from the explosion area, anomalies, relative to Earth-materials, of the elements H, C, and N—all abundant in comets—have been found [E.W. Kolesnikov, T. Boettger and N.V. Kolesnikova, Planet. Space Sci. 47 905 (1999); E.M. Kolesnikov, G. Longo, T. Boettger, N.V. Kolesnikova, P. Gioacchini, L. Forlani, R. Giampieri and R. Serra, Icarus 161 235 (2003).]. At the present work we revealed a sharp increase of concentrations of platinum group elements (PGE), REE and other elements in the event layers as well. Their ratios point to a cometary nature of the anomalies observed.

  11. Sandia Higher Order Elements (SHOE) v 0.5 alpha

    SciTech Connect

    2013-09-24

    SHOE is research code for characterizing and visualizing higher-order finite elements; it contains a framework for defining classes of interpolation techniques and element shapes; methods for interpolating triangular, quadrilateral, tetrahedral, and hexahedral cells using Lagrange and Legendre polynomial bases of arbitrary order; methods to decompose each element into domains of constant gradient flow (using a polynomial solver to identify critical points); and an isocontouring technique that uses this decomposition to guarantee topological correctness. Please note that this is an alpha release of research software and that some time has passed since it was actively developed; build- and run-time issues likely exist.

  12. Sandia Higher Order Elements (SHOE) v 0.5 alpha

    Energy Science and Technology Software Center (ESTSC)

    2013-09-24

    SHOE is research code for characterizing and visualizing higher-order finite elements; it contains a framework for defining classes of interpolation techniques and element shapes; methods for interpolating triangular, quadrilateral, tetrahedral, and hexahedral cells using Lagrange and Legendre polynomial bases of arbitrary order; methods to decompose each element into domains of constant gradient flow (using a polynomial solver to identify critical points); and an isocontouring technique that uses this decomposition to guarantee topological correctness. Please notemore » that this is an alpha release of research software and that some time has passed since it was actively developed; build- and run-time issues likely exist.« less

  13. Revised Space Groups for Three Molybdenum(V) Phosphate Compounds

    NASA Astrophysics Data System (ADS)

    Leclaire, A.; Borel, M. M.; Guesdon, A.; Marsh, Richard E.

    2001-06-01

    The space groups of three previously described Mo(V) phosphate structures are revised. (1) δ-KMo2P3O13, originally reported as triclinic, Poverline1, is revised to monoclinic, C2/c; it is identical to the compound previously identified as K4Mo8P12O52. (2) The compound formulated as [Mo12CdP8O50(OH)12]Cd [N(CH3)4]2(H3O)6·5H2O, originally described as monoclinic, Pn, is revised to P21/n (also monoclinic). (3) Rb3O2(MoO)4(PO4)4, originally reported as orthorhombic, C2221, is revised to tetragonal, P43212. The general descriptions of the structures are unchanged; however, for compound 2 the revision involves the addition of a center of symmetry and, as a result, there are significant changes in the interatomic distances and angles.

  14. Platinum group elements in the environment: emissions and exposure.

    PubMed

    Dubiella-Jackowska, Aleksandra; Polkowska, Zaneta; Namieńnik, Jacek

    2009-01-01

    PGEs (Pt, Pd, Ru, Ir, and Os) are a relatively new group of anthropogenic pollutants. Specific useful properties of these metals (high resistance to chemical corrosion over a wide range of temperatures, high melting point, high mechanical resistance, and high plasticity) have fomented rapid growth of new and existing applications in various economic and industrial sectors. These metals are not only used in the chemical, petrochemical, electrical, and electronics industries but also PGE use, in various industries, has dramatically increased emissions of these metals to the environment; emissions from vehicle catalytic converters and hospital wastewater discharges are particularly significant. The environmental benefits of using PGEs in vehicle catalytic converters are clear. These metals catalyze the conversion of toxic constituents of exhaust fumes (CO, HCs, NOxs) to water, CO2, and molecular nitrogen. As a result of adverse physico-chemical and mechanical influences on the catalyst surface, PGEs are released from this layer and are emitted into the environment in exhaust fumes. Research results indicate that the levels of such emissions are rather low (ng km(-1)). However, recent data show that certain chemical forms of PGEs emitted from vehicles are, or may be, bioavailable. Hence, the potential for PGEs to bioaccumulate in different environmental compartments should be studied, and, if necessary, addressed. The use of Pt in anticancerous drug preparations also contributes to environmental burdens. Pt, when administered as a drug, is excreted in a patient's urine and, as a consequence, has been observed in hospital and communal wastewater discharges. Few studies have been published that address bioavailability, mode of penetration into live organisms, or environmental fate of PGEs. The toxic effect of these metals on living organisms, including humans, is still in dispute and incompletely elucidated. Contrary to some chlorine complexes of Pt, which most

  15. On Silicon Group Elements Ejected by Supernovae Type Ia

    NASA Astrophysics Data System (ADS)

    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

    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.

  16. On silicon group elements ejected by supernovae type IA

    SciTech Connect

    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

    There is evidence that the peak brightness of a Type Ia supernova is affected by the electron fraction Y {sub 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 {sub e} at explosion from the abundances recovered from an observed spectra. We show that measurement of {sup 28}Si, {sup 32}S, {sup 40}Ca, and {sup 54}Fe abundances can be used to construct Y {sub e} in the silicon-rich regions of the supernovae. If these four abundances are determined exactly, they are sufficient to recover Y {sub 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 {sup 28}Si abundance is insensitive to Y {sub e}, the {sup 32}S abundance has a nearly linear trend with Y {sub e}, and the {sup 40}Ca abundance has a nearly quadratic trend with Y {sub 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.

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

    USGS Publications Warehouse

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

    1986-01-01

    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.

  18. Integrated learning in practical machine element design course: a case study of V-pulley design

    NASA Astrophysics Data System (ADS)

    Tantrabandit, Manop

    2014-06-01

    To achieve an effective integrated learning in Machine Element Design course, it is of importance to bridge the basic knowledge and skills of element designs. The multiple core learning leads the pathway which consists of two main parts. The first part involves teaching documents of which the contents are number of V-groove formulae, standard of V-grooved pulleys, and parallel key dimension's formulae. The second part relates to the subjects that the students have studied prior to participating in this integrated learning course, namely Material Selection, Manufacturing Process, Applied Engineering Drawing, CAD (Computer Aided Design) animation software. Moreover, an intensive cooperation between a lecturer and students is another key factor to fulfill the success of integrated learning. Last but not least, the students need to share their knowledge within the group and among the other groups aiming to gain knowledge of and skills in 1) the application of CAD-software to build up manufacture part drawings, 2) assembly drawing, 3) simulation to verify the strength of loaded pulley by method of Finite Element Analysis (FEA), 4) the software to create animation of mounting and dismounting of a pulley to a shaft, and 5) an instruction manual. The end product of this integrated learning, as a result of the above 1 to 5 knowledge and skills obtained, the participating students can create an assembly derived from manufacture part drawings and a video presentation with bilingual (English-Thai) audio description of Vpulley with datum diameter of 250 mm, 4 grooves, and type of groove: SPA.

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

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

    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.

  20. Energy spectra of elemental groups of cosmic rays: Update on the KASCADE unfolding analysis

    NASA Astrophysics Data System (ADS)

    Apel, W. D.; Arteaga, J. C.; Badea, A. F.; Bekk, K.; Blümer, J.; Bozdog, H.; Brancus, I. M.; Brüggemann, M.; Buchholz, P.; Cossavella, F.; Daumiller, K.; de Souza, V.; Doll, P.; Engel, R.; Engler, J.; Finger, M.; Fuhrmann, D.; Gils, H. J.; Glasstetter, R.; Grupen, C.; Haungs, A.; Heck, D.; Hörandel, J. R.; Huege, T.; Isar, P. G.; Kampert, K.-H.; Kang, D.; Kickelbick, D.; Klages, H. O.; Kolotaev, Y.; Łuczak, P.; Mathes, H. J.; Mayer, H. J.; Milke, J.; Mitrica, B.; Nehls, S.; Oehlschläger, J.; Ostapchenko, S.; Over, S.; Petcu, M.; Pierog, T.; Rebel, H.; Roth, M.; Schatz, G.; Schieler, H.; Schröder, F.; Sima, O.; Stümpert, M.; Toma, G.; Ulrich, H.; van Buren, J.; Walkowiak, W.; Weindl, A.; Wochele, J.; Wommer, M.; Zabierowski, J.

    2009-03-01

    The KASCADE experiment measures extensive air showers induced by cosmic rays in the energy range around the so-called knee. The data of KASCADE have been used in a composition analysis showing the knee at 3-5 PeV to be caused by a steepening in the light-element spectra [T. Antoni et al., (KASCADE Coll.), Astropart. Phys. 24 (2005) 1-25]. Since the applied unfolding analysis depends crucially on simulations of air showers, different high-energy hadronic interaction models (QGSJet and SIBYLL) were used. The results have shown a strong dependence of the relative abundance of the individual mass groups on the underlying model. In this update of the analysis we apply the unfolding method with a different low energy interaction model (FLUKA instead of GHEISHA) in the simulations. While the resulting individual mass group spectra do not change significantly, the overall description of the measured data improves by using the FLUKA model. In addition data in a larger range of zenith angle are analysed. The new results are completely consistent, i.e. there is no hint to any severe problem in applying the unfolding analysis method to KASCADE data.

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

    SciTech Connect

    Qian, Y.; Bedzyk, M.J. |; Lyman, P.F.

    1997-05-01

    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.

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

    ERIC Educational Resources Information Center

    Thayer, John S.

    2005-01-01

    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.

  3. Marriage of heavy main group elements with π-conjugated materials for optoelectronic applications.

    PubMed

    Parke, Sarah M; Boone, Michael P; Rivard, Eric

    2016-08-01

    This review article summarizes recent progress in the synthesis and optoelectronic properties of conjugated materials containing heavy main group elements from Group 13-16 as integral components. As will be discussed, the introduction of these elements can promote novel phosphorescent behavior and support desirable molecular and polymeric properties such as low optical band gaps and high charge mobilities for photovoltaic and thin film transistor applications. PMID:27344980

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

    USGS Publications Warehouse

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

    1997-01-01

    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.

  5. Modification of radiobiological effects of 171 MeV protons by elements of physical protection

    NASA Astrophysics Data System (ADS)

    Bulinina, Taisia; Shurshakov, Vyacheslav; Ivanov, Alexander; Molokanov, Alexander

    2016-07-01

    Space radiation includes protons of various energies. Physical protection is effective in the case of low energy protons (50-100 MeV) and becomes insufficient for radiation with a high part of high-energy protons. In the experiment performed on outbred mice, the purpose of the study was to evaluate the radiobiological effect of 171 MeV protons and protons modified by elements of physical protection of the spacecraft, on a complex of indicators of the functional condition of the system hematopoiesis and the central nervous system in 24 hours after irradiation at 20 cGy dose. The spacecraft radiation protection elements used in the experiment were a construction of wet hygiene wipes called a «protective curtain», and a glass plate imitating an ISS window. Mass thickness of the " protective curtain" in terms of water equivalent was ̴ 6,2 g/cm2. Physical shielding along the path of 171 MeV protons increases their linear energy transfer leading to the absorbed dose elevation and strengthening of the radiobiological effect. In the experiment, the two types of shielding together raised the absorbed dose from 20 to 23.2 cGy. Chemically different materials (glass and water in the wipes) were found to exert unequal modifying effects on physical and biological parameters of the proton-irradiated mice. There was a distinct dose-dependent reduction of bone marrow cellularity within the dose range from 20 cGy to 23.2 cGy in 24 hours after exposure. No modifying effect of the radiation protection elements on spontaneous motor activity was discovered when compared with entrance protons. The group of animals protected by the glass plate exhibited normal orientative-trying reactions and weakened grip with the forelimbs. The effects observed in the experiment indicate the necessity to carry out comprehensive radiobiological researches (physical, biological and mathematical) in assessing the effects of physical protection, that are actual for ensuring radiation safety of crews in

  6. Fundamental Studies on Donor-acceptor Conjugated Polymers Containing 'Heavy' Group 14 and Group 16 Elements

    NASA Astrophysics Data System (ADS)

    Gibson, Gregory Laird

    One advantage of conjugated polymers as organic materials is that their properties may be readily tuned through covalent modifications. This thesis presents studies on the structure-property relationships resulting from single- and double-atom substitutions on an alternating donor-acceptor conjugated polymer. Specifically, single selenium and tellurium atoms have been incorporated into the acceptor monomer in place of sulfur; silicon and germanium atoms have been substituted in place of carbon at the donor monomer bridge position. The carbon-donor/ tellurium-acceptor polymer was synthesized by a post-polymerization reaction sequence and demonstrated the utility of heavy group 16 atoms to red shift a polymer absorption spectrum. Density functional theory calculations point to a new explanation for this result invoking the lower heavy atom ionization energy and reduced aromaticity of acceptor monomers containing selenium and tellurium compared to sulfur. Absorption and emission experiments demonstrate that both silicon and germanium substitutions in the donor slightly blue shift the polymer absorption spectrum. Polymers containing sulfur in the acceptor are the strongest light absorbers of all polymers studied here. Molecular weight and phenyl end capping studies show that molecular weight appears to affect polymer absorption to the greatest degree in a medium molecular weight regime and that these effects have a significant aggregation component. Solar cell devices containing either the silicon- or germanium-donor/selenium-acceptor polymer display improved red light harvesting or hole mobility relative to their structural analogues. Overall, these results clarify the effects of single atom substitution on donor-acceptor polymers and aid in the future design of polymers containing heavy atoms.

  7. Elemental abundance analyses with DAO spectrograms: XXXII. HR 6455 (A3 III), δ Aqr (A3 V), η Lep (F2 V), and 1 Boo (A1 V)

    NASA Astrophysics Data System (ADS)

    Yüce, K.; Adelman, S. J.; Gulliver, A. F.; Hill, G.

    2011-08-01

    We examine the sharp-lined stars HR 6455 (A3 III, v sin i = 8.7 km s-1) and η Lep (F2 V, v sin i = 13.5 km s-1) as well as δ Aqr (A3 V, v sin i = 81 km s-1) and 1 Boo (A1 V, v sin i = 59 km s-1) to increase the number consistently analyzed A and F stars using high dispersion and high S/N (≥200) spectrograms obtained with CCD detectors at the long Coudé camera of the 1.22-m telescope of the Dominion Astrophysical Observatory. Such studies contribute to understanding systematic abundance differences between normal and non-magnetic main-sequence band chemically peculiar A and early F stars. LTE fine analyses of HR 6455, δ Aqr, and 1 Boo using Kurucz's ATLAS suite programs show the same general elemental abundance trends with differences in the metal richness. Light and iron-peak element abundances are generally solar or overabundant while heavy element and rare earth element abundances are overabundant. HR 6455 is an evolved Am star while δ Aqr and 1 Boo show the phenomenon to different extents. Most derived abundances of η Lep are solar. Table 3 is available at the CDS via http://cdsarc.u-strasbg.fr/cgi-bin/qcat?J/AN/332/681

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

    SciTech Connect

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

    2010-01-01

    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.

  9. Analysis of the trace element content of coals from the Wabaunsee Group southeastern Nebraska

    SciTech Connect

    Kaplan, S.S.; Carr, J.D.; Kelter, P.B.

    1983-01-01

    Eight coal samples obtained from the Honey Creek, Lorton, Wamego, Elmo, and Nodaway coals of the Wabaunsee Group (Upper Pennsylvanian) were analyzed for their concentration of certain trace elements. Analysis of the data suggests (a) a general decrease of trace element concentrations away from the Precambrian Nemaha Arch in a basinward direction, and (b) the post-diagenetic emplacement of lead, zinc and cadmium typical of mid-continent coals.

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

    SciTech Connect

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

    2014-05-01

    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.

  11. Intra- and interspecies variation among Bari-1 elements of the melanogaster species group.

    PubMed Central

    Moschetti, R; Caggese, C; Barsanti, P; Caizzi, R

    1998-01-01

    We have investigated the distribution of sequences homologous to Bari-1, a Tc1-like transposable element first identified in Drosophila melanogaster, in 87 species of the Drosophila genus. We have also isolated and sequenced Bari-1 homologues from D. simulans, D. mauritiana, and D. sechellia, the species constituting with D. melanogaster the melanogaster complex, and from D. diplacantha and D. erecta, two phylogenetically more distant species of the melanogaster group. Within the melanogaster complex the Bari-1 elements are extremely similar to each other, showing nucleotide identity values of at least 99.3%. In contrast, Bari-1-like elements from D. diplacantha and D. erecta are on average only 70% similar to D. melanogaster Bari-1 and are usually defective due to nucleotide deletions and/or insertions in the ORFs encoding their transposases. In D. erecta the defective copies are all located in the chromocenter and on chromosome 4. Surprisingly, while D. melanogaster Bari-1 elements possess 26-bp inverted terminal repeats, their D. diplacantha and D. erecta homologues possess long inverted terminal repeats similar to the terminal structures observed in the S elements of D. melanogaster and in several other Tc1-like elements of different organisms. This finding, together with the nucleotide and amino acid identity level between D. diplacantha and D. erecta elements and Bari-1 of D. melanogaster, suggests a common evolutionary origin and a rapid diversification of the termini of these Drosophila Tc1-like elements. PMID:9725843

  12. Conservation of CD44 exon v3 functional elements in mammals

    PubMed Central

    Vela, Elena; Hilari, Josep M; Delclaux, María; Fernández-Bellon, Hugo; Isamat, Marcos

    2008-01-01

    Background The human CD44 gene contains 10 variable exons (v1 to v10) that can be alternatively spliced to generate hundreds of different CD44 protein isoforms. Human CD44 variable exon v3 inclusion in the final mRNA depends on a multisite bipartite splicing enhancer located within the exon itself, which we have recently described, and provides the protein domain responsible for growth factor binding to CD44. Findings We have analyzed the sequence of CD44v3 in 95 mammalian species to report high conservation levels for both its splicing regulatory elements (the 3' splice site and the exonic splicing enhancer), and the functional glycosaminglycan binding site coded by v3. We also report the functional expression of CD44v3 isoforms in peripheral blood cells of different mammalian taxa with both consensus and variant v3 sequences. Conclusion CD44v3 mammalian sequences maintain all functional splicing regulatory elements as well as the GAG binding site with the same relative positions and sequence identity previously described during alternative splicing of human CD44. The sequence within the GAG attachment site, which in turn contains the Y motif of the exonic splicing enhancer, is more conserved relative to the rest of exon. Amplification of CD44v3 sequence from mammalian species but not from birds, fish or reptiles, may lead to classify CD44v3 as an exclusive mammalian gene trait. PMID:18710510

  13. Mono- and polynucleation, atomistic growth, and crystal phase of III-V nanowires under varying group V flow

    SciTech Connect

    Dubrovskii, V. G.

    2015-05-28

    We present a refined model for the vapor-liquid-solid growth and crystal structure of Au-catalyzed III-V nanowires, which revisits several assumptions used so far and is capable of describing the transition from mononuclear to polynuclear regime and ultimately to regular atomistic growth. We construct the crystal phase diagrams and calculate the wurtzite percentages, elongation rates, critical sizes, and polynucleation thresholds of Au-catalyzed GaAs nanowires depending on the As flow. We find a non-monotonic dependence of the crystal phase on the group V flow, with the zincblende structure being preferred at low and high group V flows and the wurtzite structure forming at intermediate group V flows. This correlates with most of the available experimental data. Finally, we discuss the atomistic growth picture which yields zincblende crystal structure and should be very advantageous for fabrication of ternary III-V nanowires with well-controlled composition and heterointerfaces.

  14. Mono- and polynucleation, atomistic growth, and crystal phase of III-V nanowires under varying group V flow

    NASA Astrophysics Data System (ADS)

    Dubrovskii, V. G.

    2015-05-01

    We present a refined model for the vapor-liquid-solid growth and crystal structure of Au-catalyzed III-V nanowires, which revisits several assumptions used so far and is capable of describing the transition from mononuclear to polynuclear regime and ultimately to regular atomistic growth. We construct the crystal phase diagrams and calculate the wurtzite percentages, elongation rates, critical sizes, and polynucleation thresholds of Au-catalyzed GaAs nanowires depending on the As flow. We find a non-monotonic dependence of the crystal phase on the group V flow, with the zincblende structure being preferred at low and high group V flows and the wurtzite structure forming at intermediate group V flows. This correlates with most of the available experimental data. Finally, we discuss the atomistic growth picture which yields zincblende crystal structure and should be very advantageous for fabrication of ternary III-V nanowires with well-controlled composition and heterointerfaces.

  15. Division Iv/v Working Group on Active B Stars

    NASA Astrophysics Data System (ADS)

    Peters, Geraldine J.; Jones, Carol E.; Townsend, Richard D.; Fabregat, Juan; Bjorkman, Karen S.; McSwain, M. Virginia; Mennickent, Ronald E.; Neiner, Coralie; Stee, Philippe; Fabregat, Juan

    2010-05-01

    The meeting of the Working Group on Active B Stars consisted of a business session followed by a scientific session containing nine talks. The titles of the talks and their presenters are listed below. We plan to publish a series of articles containing summaries of these talks in Issue No. 40 of the Be Star Newsletter. This report contains an account of the announcements made during the business session, an update on a forthcoming IAU Symposium on active B stars, a report on the status of the Be Star Newsletter, the results of the 2009 election of the SOC for the Working Group for 2009-12, a listing of the Working Group bylaws that were recently adopted, and a list of the scientific talks that we presented at the meeting.

  16. Dynamic finite element analysis of third size charpy specimens of V-4Cr-4Ti

    SciTech Connect

    Lansberry, M.R.; Kumar, A.S.; Mueller, G.E.; Kurtz, R.J.

    1997-04-01

    A 2-D finite element analysis was performed on precracked, one third scale CVN specimens to investigate the sensitivity of model results to key material parameters such as yield strength, failure strain and work hardening characteristics. Calculations were carried out at temperatures of -196{degree}C and 50{degree}C. The dynamic finite element analyses were conducted using ABAQUS/Explicit V5.4. The finite element results were compared to experimental results for the production-scale heat of V-4Cr-4Ti (ANL Heat No. 832665) as a benchmark. Agreement between the finite element model and experimental data was very good at -196{degree}C, whereas at 50{degree}C the model predicted a slightly lower absorbed energy than actually measured.

  17. Radiochemical Separation of Group 5 Elements. Model Experiments for Investigation of Dubnium Chemical Behaviour

    SciTech Connect

    Tereshatov, E. E.; Bozhikov, G. A.; Aksenov, N. V.; Starodub, G. Ya.; Vostokin, G. K.; Shishkin, S. V.; Dmitriev, S. N.; Bruchertseifer, H.; Gaeggeler, H. W.

    2007-05-22

    Chemical behaviour of group 5 elements in the aqueous hydrofluoric acid solutions was studied. The radiochemical method for the cation exchange separation of Nb (Pa) and Ta from Zr, Hf and lanthanides is presented. The developed scheme allows excluding of the presence of SF heavy actinides in fractions of separated elements. On the basis of the data of the present work, it is possible to suggest the following order of the stability of the fluoride complexes of group 4 and 5 elements: Nb {approx_equal} Pa > Zr > Hf > Ta. The order of the complex formation is in agreement with theoretical predictions. This analytical procedure can be used in future heavy nuclei synthesis experiments for the separation of dubnium (Db) from other reactions products and for its chemical identification.

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

    USGS Publications Warehouse

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

    2000-01-01

    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.

  19. Levels of platinum group elements and rare-earth elements in wild mushroom species growing in Poland.

    PubMed

    Mleczek, Mirosław; Niedzielski, Przemysław; Kalač, Pavel; Siwulski, Marek; Rzymski, Piotr; Gąsecka, Monika

    2016-01-01

    Due to limited data-describing abilities of mushrooms to accumulate platinum group elements (PGEs) and rare-earth elements (REEs), the aim of this study was to determine, by inductively coupled plasma optical emission spectrometry followed by microwave-assisted sample digestion by nitric acid, the content of these elements in 20 mushroom species (10 above ground and 10 growing on wood), mostly edible, collected near a busy trunk road. The highest content of PGEs in above-ground mushroom species was observed in Lepista gilva and Suillus bovinus fruit bodies (0.38 ± 0.05 and 0.37 ± 0.03 mg kg(-1) DW, respectively), while in mushrooms growing on wood, the highest content was observed in Pleurotus ostreatus (0.35 ± 0.04 mg kg(-1) DW). The mean content of PGEs for both these groups was 0.23 ± 0.08 and 0.26 ± 0.07 mg kg(-1) DW, respectively. The highest content of REEs in Suillus luteus and Tricholoma equestra was 5.03 ± 0.50 and 2.18 ± 0.56 mg kg(-1) DW, respectively, but within mushrooms growing on wood in Ganoderma applanatum fruiting bodies it was 4.19 ± 0.78 mg kg(-1) DW. Mean contents of REEs were 1.39 ± 1.21 and 1.61 ± 0.97 mg kg(-1) DW in above-ground species and species growing on wood, respectively. Generally, the group of mushroom species growing on wood was capable of slightly higher accumulation of both REEs and PGEs. No limits have been established for both the groups until now. PMID:26515437

  20. 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...

  1. New data on platinum group elements in sulfide deposits of the Southern Urals

    NASA Astrophysics Data System (ADS)

    Kovalev, S. G.; Puchkov, V. N.; Salikhov, D. N.

    2015-09-01

    New data on the concentrations of gold and platinum group elements (PGE) in sulfide deposits of the Southern Urals show that a substantial share of Au, Pt, and Pd is concentrated during technological ore processing in their dressing tailings. The behavior of Pt, Pd, and, partly, Au is determined by the size of individual mineral particles.

  2. Voltage-dependent sodium (NaV) channels in group IV sensory afferents

    PubMed Central

    Elmslie, Keith S

    2016-01-01

    Patients with intermittent claudication suffer from both muscle pain and an exacerbated exercise pressor reflex. Excitability of the group III and group IV afferent fibers mediating these functions is controlled in part by voltage-dependent sodium (NaV) channels. We previously found tetrodotoxin-resistant NaV1.8 channels to be the primary type in muscle afferent somata. However, action potentials in group III and IV afferent axons are blocked by TTX, supporting a minimal role of NaV1.8 channels. To address these apparent differences in NaV channel expression between axon and soma, we used immunohistochemistry to identify the NaV channels expressed in group IV axons within the gastrocnemius muscle and the dorsal root ganglia sections. Positive labeling by an antibody against the neurofilament protein peripherin was used to identify group IV neurons and axons. We show that >67% of group IV fibers express NaV1.8, NaV1.6, or NaV1.7. Interestingly, expression of NaV1.8 channels in group IV somata was significantly higher than in the fibers, whereas there were no significant differences for either NaV1.6 or NaV1.7. When combined with previous work, our results suggest that NaV1.8 channels are expressed in most group IV axons, but that, under normal conditions, NaV1.6 and/or NaV1.7 play a more important role in action potential generation to signal muscle pain and the exercise pressor reflex. PMID:27385723

  3. 29 CFR Appendix V to Part 1918 - Basic Elements of a First Aid Training Program (Non-mandatory)

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 29 Labor 7 2014-07-01 2014-07-01 false Basic Elements of a First Aid Training Program (Non.... 1918, App. V Appendix V to Part 1918—Basic Elements of a First Aid Training Program (Non-mandatory... teaching first aid, and the recipients of first aid training. General Program Elements A. Teaching...

  4. 29 CFR Appendix V to Part 1918 - Basic Elements of a First Aid Training Program (Non-mandatory)

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 29 Labor 7 2013-07-01 2013-07-01 false Basic Elements of a First Aid Training Program (Non.... 1918, App. V Appendix V to Part 1918—Basic Elements of a First Aid Training Program (Non-mandatory... teaching first aid, and the recipients of first aid training. General Program Elements A. Teaching...

  5. Contrasting Platinum-Group Element and Chalcophile Element Contents in Pyrrhotite, Pentlandite and Chalcopyrite From Different Environments

    NASA Astrophysics Data System (ADS)

    Barnes, S.-; Dare, S. A.

    2009-05-01

    It is now possible to determine the platinum-group element (PGE) and chalcophile element contents of pyrrhotite (Po), pentlandite (Pn) and chalcopyrite (Ccp). This information may be used to: a) Improve recovery of important economic elements from ore; b) Consider the petrogenesis of the rocks. We have determined the PGE and other chalcophile element contents of Po, Pn and Ccp from a meteorite, a subvolcanic sill, the Merensky Reef Bushveld, Great Dyke, JM Reef Stillwater, AP and PV Reefs Penikat and Creighton Mine at Sudbury. The aims of these studies are to determine which phases host the elements and what implications the host phases have for the petrogenesis of the rocks involved. Sulfides from the meteorite and the subvolcanic sill have been chilled fairly rapidly and experienced very little subsolidus re-equilibration. The Bushveld and Great Dyke sulfides cooled slowly and thus had longer to exsolve. The Stillwater and Penikat sulfides were metamorphosed post-intrusion thus these sulfides have been reheated. The Sudbury sulfides have been deformed and metamorphosed and are the major phases whereas in all other cases the sulfides were minor phases in the rocks. In all cases Pt and Au are not present in the sulfides. Platinum is generally found as Pt-arsenides, Pt-bismuth- tellurides or Pt-alloys as inclusions in the sulfides. Palladium is generally hosted principally by Pn. Osmium and Ru are present in Po and Pn. In the meteorite, the subvolcanic sill and the unmetamorphosed intrusions Re, Ir and Rh are also present in Po and Pn. However in the metamorphosed and deformed sulfides Ir and Rh are present largely as sulfarsenides and as various Re minerals included in the sulfides. Thus in the least metamorphosed and deformed rocks all the PGE except Pt are present in the sulfides. In the metamorphosed rocks Re, Ir and Rh tend to form inclusions in the sulfides. We suggest that this is the result of exsolution during reworking of the sulfides. The concentration of

  6. Divisions Iv-V / Working Group ap & Related Stars

    NASA Astrophysics Data System (ADS)

    Mathys, Gautier; Cunha, Margarida; Dworetsky, Michael; Kochukhov, Oleg; Kupka, Friedrich; LeBlanc, Francis; Monier, Richard; Paunzen, Ernst; Pintado, Olga; Piskunov, Nikolai; Ziznovsky, Jozef

    2012-04-01

    The purpose of the Working Group on Ap and Related Stars (ApWG) is to promote and facilitate research about stars in the spectral type range from B to early F that exhibit surface chemical peculiarities and related phenomena. This is a very active field of research, in which a wide variety of new developments have taken place since 2009, as illustrated by the following selected highlights.

  7. Nonnegative Anisotropic Group Cross Sections: A Hybrid Monte Carlo-Discrete Elements-Discrete Ordinates Approach

    SciTech Connect

    DelGrande, J. Mark; Mathews, Kirk A.

    2001-09-15

    Conventional discrete ordinates transport calculations often produce negative fluxes due to unphysical negative scattering cross sections and/or as artifacts of spatial differencing schemes such as diamond difference. Inherently nonnegative spatial methods, such as the nonlinear, exponential characteristic spatial quadrature, eliminate negative fluxes while providing excellent accuracy, presuming the group-to-group, ordinate-to-ordinate cross sections are all nonnegative. A hybrid approach is introduced in which the flow from spatial cell to spatial cell uses discrete ordinates spatial quadratures, while anisotropic scattering of flux from one energy-angle bin (energy group and discrete element of solid angle) to another such bin is modeled using a Monte Carlo simulation to evaluate the bin-to-bin cross sections. The directional elements tile the sphere of directions; the ordinates for the spatial quadrature are at the centroids of the elements. The method is developed and contrasted with previous schemes for positive cross sections. An algorithm for evaluating the Monte Carlo (MC)-discrete elements (MC-DE) cross sections is described, and some test cases are presented. Transport calculations using MC-DE cross sections are compared with calculations using conventional cross sections and with MCNP calculations. In this testing, the new method is about as accurate as the conventional approach, and often is more accurate. The exponential characteristic spatial quadrature, using the MC-DE cross sections, is shown to provide useful results where linear characteristic and spherical harmonics provide negative scalar fluxes in every cell in a region.

  8. The Element Effect Revisited: Factors Determining Leaving Group Ability in Activated Nucleophilic Aromatic Substitution Reactions

    PubMed Central

    Senger, Nicholas A.; Bo, Bo; Cheng, Qian; Keeffe, James R.; Gronert, Scott; Wu, Weiming

    2012-01-01

    The “element effect” in nucleophilic aromatic substitution reactions (SNAr) is characterized by the leaving group order, F > NO2 > Cl ≈ Br > I, in activated aryl halides. Multiple causes for this result have been proposed. Experimental evidence shows that the element effect order in the reaction of piperidine with 2,4-dinitrophenyl halides in methanol is governed by the differences in enthalpies of activation. Computational studies of the reaction of piperidine and dimethylamine with the same aryl halides using the polarizable continuum model (PCM) for solvation indicate that polar, polarizability, solvation, and negative hyperconjugative effects are all of some importance in producing the element effect in methanol. In addition, a reversal of polarity of the C–X bond from reactant to transition state in the case of ArCl and ArBr compared to ArF also contributes to their difference in reactivity. The polarity reversal, and hyperconjugative influences have received little or no attention in the past. Nor has differential solvation of the different transition states been strongly emphasized. An anionic nucleophile, thiolate, gives very early transition states and negative activation enthalpies with activated aryl halides. The element effect is not established for these reactions. We suggest that the leaving group order in the gas phase will be dependent on the exact combination of nucleophile, leaving group, and substrate framework. The geometry of the SNAr transition state permits useful, qualitative conceptual distinctions to be made between this reaction and other modes of nucleophilic attack. PMID:23057717

  9. Trace-element composition and zoning in clinopyroxene- and amphibole-group minerals: Implications for element partitioning and evolution of carbonatites

    NASA Astrophysics Data System (ADS)

    Reguir, Ekaterina P.; Chakhmouradian, Anton R.; Pisiak, Laura; Halden, Norman M.; Yang, Panseok; Xu, Cheng; Kynický, Jindřich; Couëslan, Chris G.

    2012-01-01

    The present work is a first comprehensive study of the trace-element composition and zoning in clinopyroxene- and amphibole-group minerals from carbonatites, incorporating samples from 14 localities worldwide (Afrikanda, Aley, Alnö, Blue River, Eden Lake, Huayangchuan, Murun, Oka, Ozernaya Varaka, Ozernyi, Paint Lake, Pinghe, Prairie Lake, Turiy Mys). The new electron-microprobe data presented here significantly extend the known compositional range of clinopyroxenes and amphiboles from carbonatites. These data confirm that calcic and sodic clinopyroxenes from carbonatites are not separated by a compositional gap, instead forming an arcuate trend from nearly pure diopside through intermediate aegirine-augite compositions confined to a limited range of CaFeSi 2O 6 contents (15-45 mol%) to aegirine with < 25 mol% of CaMgSi 2O 6 and a negligible proportion of CaFeSi 2O 6. A large set of LA-ICPMS data shows that the clinopyroxenes of different composition are characterized by relatively low levels of Cr, Co and Ni (≤ 40 ppm) and manifold variations in the concentration of trivalent lithophile and some incompatible elements (1-150 ppm Sc, 26-6870 ppm V, 5-550 ppm Sr, 90-2360 ppm Zr, and nil to 150 ppm REE), recorded in some cases within a single crystal. The relative contribution of clinopyroxenes to the whole-rock Rb, Nb, Ta, Th and U budget is negligible. The major-element compositional range of amphiboles spans from alkali- and Al-poor members (tremolite) to Na-Al-rich Mg- or, less commonly, Fe-dominant members (magnesiohastingsite, hastingsite and pargasite), to calcic-sodic, sodic and potassic-sodic compositions intermediate between magnesio-ferrikatophorite, richterite, magnesioriebeckite, ferri-nyböite and (potassic-)magnesio-arfvedsonite. In comparison with the clinopyroxenes, the amphiboles contain similar levels of tetravalent high-field-strength elements (Ti, Zr and Hf) and compatible transition elements (Cr, Co and Ni), but are capable of incorporating

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

    NASA Technical Reports Server (NTRS)

    Buckley, D. H.

    1975-01-01

    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.

  11. Population Signatures in Planetary Nebulae from Abundances of Fe-group and Neutron-Capture Elements

    NASA Astrophysics Data System (ADS)

    Dinerstein, Harriet L.; Geballe, Thomas R.; Sterling, N. C.

    2015-08-01

    There are two categories of elements for which abundances are measured in planetary nebulae (PNe). The first are species whose abundances may be modified by nuclear reactions in the star prior to PN formation, such as He, C, N, and nuclei made by slow neutron captures (Karakas & Lattanzio 2014, PASA, 31, 30). In contrast, elements unaffected by evolution should indicate the star’s initial composition. These include S, Ar, Cl, and (with certain exceptions) O and Ne, most of which are alpha species. A long-missing piece of the puzzle has been the abundances of the Fe-group elements. We cannot determine a meaningful elemental abundance from the gas-phase Fe lines seen in PNe, since Fe is heavily depleted into dust. Another approach is to use a different element as a proxy for Fe. Dinerstein & Geballe (2001, ApJ, 562, 515) identified a line at 3.625 μm as due to Zn, the least refractory Fe-group element. Observations of this line in Milky Way PNe yield -1 ≤ [Zn/H] ≤ 0 (Smith, Zijlstra, & Dinerstein 2014, MNRAS, 441, 3161; Dinerstein et al. 2015, in preparation). Substituting Zn for Fe, PNe can be placed in the [alpha/Fe] vs. [Fe/H] diagram used to characterize stellar populations. Dividing our sample into probable thin and thick disk members using the kinematic criterion of Peimbert’s Type II and III classes (1978, IAU Symp. 76, 215), we find that they occupy similar regions in [alpha/Fe] vs. [Fe/H] phase space as the stars of those populations. Elevated [alpha/Fe] values at subsolar [Fe/H], which tend to be higher for thick than thin disk PNe, cause degeneracies that make alpha species ambiguous metallicity indicators. This is important for self-enrichment studies, since if the initial abundance of an element is lower than projected from an alpha species, internal synthesis may be required to produce even a solar final abundance. Low observed abundances of the n-capture element Se suggest that many Type III PNe may have subsolar initial abundances of n

  12. Influence of main-group element on half-metallic properties in half-Heusler compound

    NASA Astrophysics Data System (ADS)

    Liu, Hongyan; Li, Yushan; Tian, Fuyang; Li, Getian

    2016-04-01

    We investigate the band structure, magnetism and density of states of half-Heusler compounds CoCrZ (Z = Si,Ge,P,As) based on the first-principle calculations. Combined with molecular orbital hybridization theory, we discuss the influence of the main-group element on half-metallic properties of CoCrZ. It is found that the replacement of Ge for Si in CoCrSi can adjust the position of the Fermi level, and while it has no impact on the energy gap width and magnetic structure. However, the substitution of P for Si can effectively adjust the magnetism without disrupting its half-metallicity. Our results demonstrate that the electronic structure of CoCrZ is mainly dependent on the number of valence electrons of the main-group element.

  13. Group V sensitive vapor-liquid-solid growth of Au-catalyzed and self-catalyzed III-V nanowires

    NASA Astrophysics Data System (ADS)

    Dubrovskii, Vladimir G.

    2016-04-01

    We present a new theoretical model that treats the group V sensitive growth rates and structures of Au-catalyzed and self-catalyzed III-V nanowires within a single kinetic picture. It is shown that Au-catalyzed III-V nanowires can grow with a time-independent radius within a wide range of parameters. At high V/III flux ratios, the vapor-liquid-solid growth of Au catalyzed III-V nanowires is controlled by surface diffusion of the group III adatoms, while at low V/III flux ratios it becomes nucleation-limited. Conversely, self-catalyzed III-V nanowires cannot grow with a time-independent droplet size and instead such nanowires may either swell or shrink or converge to a certain stationary radius depending on the V/III flux ratio. Quite importantly, the results are presented in a concise analytical form which is convenient for comparison with experimental data or prior theoretical works. We demonstrate how the model fits the data obtained previously for Au- and Ga-catalyzed GaAs nanowires.

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

    NASA Technical Reports Server (NTRS)

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

    1999-01-01

    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.

  15. Advances in the development of complexes that contain a group 13 element chalcogen multiple bond.

    PubMed

    Franz, Daniel; Inoue, Shigeyoshi

    2016-06-21

    Inorganic group 13 element (M) chalcogenides (E) based on the general formular M2E3 are ubiquitous in synthesis, catalysis and material science. The parent ME fragment which aggregates to form three dimensional networks in the condensed phase can be expected to exhibit multiple bond character between the elements. Low temperature matrix isolation techniques are required to investigate the nature of this elusive species. An alternate approach for respective studies is the synthesis of electron-precise molecular complexes that contain the ME entity and for which isolation at ambient temperature is possible. This is realized by kinetic stabilization with bulky ligands and thermodynamic stabilization using electron donor, as well as acceptor groups attached to the ME functionality (i.e. donor-acceptor stabilization). In this article we revise the literature on complex compounds that exhibit a bonding interaction between a group 13 element atom and a chalcogen atom that is reasonably to be interpreted in terms of a double- or triple bond. PMID:27216700

  16. 29 CFR Appendix V to Part 1918 - Basic Elements of a First Aid Training Program (Non-mandatory)

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 29 Labor 7 2012-07-01 2012-07-01 false Basic Elements of a First Aid Training Program (Non-mandatory) V Appendix V to Part 1918 Labor Regulations Relating to Labor (Continued) OCCUPATIONAL SAFETY AND HEALTH ADMINISTRATION, DEPARTMENT OF LABOR (CONTINUED) SAFETY AND HEALTH REGULATIONS FOR LONGSHORING Pt. 1918, App. V Appendix V to Part...

  17. V1/V2 Neutralizing Epitope is Conserved in Divergent Non-M Groups of HIV-1

    PubMed Central

    Morgand, Marion; Bouvin-Pley, Mélanie; Plantier, Jean-Christophe; Moreau, Alain; Alessandri, Elodie; Simon, François; Pace, Craig S.; Pancera, Marie; Ho, David D.; Poignard, Pascal; Bjorkman, Pamela J.; Mouquet, Hugo; Nussenzweig, Michel C.; Kwong, Peter D.; Baty, Daniel; Chames, Patrick; Braibant, Martine

    2016-01-01

    Background: Highly potent broadly neutralizing monoclonal antibodies (bNAbs) have been obtained from individuals infected by HIV-1 group M variants. We analyzed the cross-group neutralization potency of these bNAbs toward non-M primary isolates (PI). Material and Methods: The sensitivity to neutralization was analyzed in a neutralization assay using TZM-bl cells. Twenty-three bNAbs were used, including reagents targeting the CD4-binding site, the N160 glycan-V1/V2 site, the N332 glycan-V3 site, the membrane proximal external region of gp41, and complex epitopes spanning both env subunits. Two bispecific antibodies that combine the inhibitory activity of an anti-CD4 with that of PG9 or PG16 bNAbs were included in the study (PG9-iMab and PG16-iMab). Results: Cross-group neutralization was observed only with the bNAbs targeting the N160 glycan-V1/V2 site. Four group O PIs, 1 group N PI, and the group P PI were neutralized by PG9 and/or PG16 or PGT145 at low concentrations (0.04–9.39 μg/mL). None of the non-M PIs was neutralized by the bNAbs targeting other regions at the highest concentration tested, except 10E8 that neutralized weakly 2 group N PIs and 35O22 that neutralized 1 group O PI. The bispecific bNAbs neutralized very efficiently all the non-M PIs with IC50 below 1 μg/mL, except 2 group O strains. Conclusion: The N160 glycan-V1/V2 site is the most conserved neutralizing site within the 4 groups of HIV-1. This makes it an interesting target for the development of HIV vaccine immunogens. The corresponding bNAbs may be useful for immunotherapeutic strategies in patients infected by non-M variants. PMID:26413851

  18. RUDI, a short interspersed element of the V-SINE superfamily widespread in molluscan genomes.

    PubMed

    Luchetti, Andrea; Šatović, Eva; Mantovani, Barbara; Plohl, Miroslav

    2016-06-01

    Short interspersed elements (SINEs) are non-autonomous retrotransposons that are widespread in eukaryotic genomes. They exhibit a chimeric sequence structure consisting of a small RNA-related head, an anonymous body and an AT-rich tail. Although their turnover and de novo emergence is rapid, some SINE elements found in distantly related species retain similarity in certain core segments (or highly conserved domains, HCD). We have characterized a new SINE element named RUDI in the bivalve molluscs Ruditapes decussatus and R. philippinarum and found this element to be widely distributed in the genomes of a number of mollusc species. An unexpected structural feature of RUDI is the HCD domain type V, which was first found in non-amniote vertebrate SINEs and in the SINE from one cnidarian species. In addition to the V domain, the overall sequence conservation pattern of RUDI elements resembles that found in ancient AmnSINE (~310 Myr old) and Au SINE (~320 Myr old) families, suggesting that RUDI might be among the most ancient SINE families. Sequence conservation suggests a monophyletic origin of RUDI. Nucleotide variability and phylogenetic analyses suggest long-term vertical inheritance combined with at least one horizontal transfer event as the most parsimonious explanation for the observed taxonomic distribution. PMID:26987730

  19. Partitioning of Si and platinum group elements between liquid and solid Fe-Si alloys

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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).

  20. The measurement of elemental abundances above 10 sup 15 eV at a lunar base

    SciTech Connect

    Swordy, S.P. )

    1990-03-15

    At {approx}10{sup 15} eV the slope of the energy spectrum of cosmic rays becomes significantly steeper than at lower energies. The measurement of relative elemental abundances at these energies is expected to provide a means to resolve the origin of this feature and greatly contribute to the understanding of the sources of cosmic rays. We describe a moon based detector for making well resolved elemental measurements at these energies using hadronic calorimetry. This detector is particularly well suited for a site on the lunar surface because there is no overlying layer of atmosphere and the large mass required can be provided by the lunar regolith.

  1. Reactivity in the periphery of functionalised multiple bonds of heavier group 14 elements.

    PubMed

    Präsang, Carsten; Scheschkewitz, David

    2016-02-21

    Heavier group 14 multiple bonds have intrigued chemists since more than a century. The synthesis of stable compounds with double and triple bonds with silicon, germanium, tin and lead had considerable impact on modern ideas of chemical bonding. These developments were made possible by the use of bulky substituents that provide kinetic and thermodynamic protection. Since about a decade the compatibility of heavier multiple bonds with various functional groups has moved into focus. This review covers multiply bonded group 14 species with at least one additional reactive site. The vinylic functionalities of groups 1 and 17, resulting in nucleophilic and electrophilic disila vinyl groups, respectively, are the most prevalent and well-studied. They have been employed repeatedly for the transfer of heavier multiple bonds to yield low-valent group 14 compounds with novel structural motifs. Vinylic functionalities of groups 2 to 16 and a few σ-bonded transition metal complexes are experimentally known, but their reactivity has been studied to a lesser extent. Donor-coordinated multiple bonds are a relatively new field of research, but the large degree of unsaturation as isomers of alkynes (as well as residual functionality in some cases) offers considerable possibility for further manipulation, e.g. for the incorporation into more extended systems. Heavier allyl halides constitute the major part of heavier multiple bonds with a functional group in allylic position and some examples of successful transformations are given. At present, remote functionalities are basically limited to para-phenylene functionalised disilenes. The reported use of the latter for further derivatisation might encourage investigations in this direction. In summary, the study of peripherally functionalised multiple bonds with heavier group 14 elements is already well beyond its infancy and may be an instrumental factor in awakening the potential of group 14 chemistry for applications in polymers and

  2. Room temperature ferromagnetism in Ist group elements codoped ZnO:Fe nanoparticles by co-precipitation method

    NASA Astrophysics Data System (ADS)

    Pazhanivelu, V.; Paul Blessington Selvadurai, A.; Kannan, R.; Murugaraj, R.

    2016-04-01

    In this paper, we report on the structural, vibrational and magnetic behavior of Ist group elements (Li+, Na+ and K+) codoping effect in ZnO:Fe nanoparticles (NPs) prepared by co-precipitation method. The single crystalline phase of the prepared NPs was identified as Wurtizite structure and the Raman spectra expressed the local structural change and the presence of complex lattice defects such as Zinc interstitial (Zni) and Oxygen vacanvy (V+o) defects in the NPs. The presence of functional groups was confirmed by FT-IR spectral analysis. The optical absorption properties of the prepared NPs were characterised by UV-Drs spectroscopy. The valance state of Zinc ions and the role of Oxygen related defects were analysed from x-ray photoelectron spectroscopy (XPS) spectra. The electron paramagnetic resonance (EPR) spectral line illustrated the presence of complex defects such as Zinc interstitial (Zni) and oxygen vacancy (V+o) defects in the sample. The observed room temperature ferromagnetism (RTFM) in the prepared sample was induced by lattice defects. The observed results are discussed and reported.

  3. Variation of electron-phonon coupling in group IV elemental semiconductors

    NASA Astrophysics Data System (ADS)

    Tandon, Nandan; Pugsley, Lisa; Ram-Mohan, L. R.

    2013-03-01

    Electron-phonon (e-ph) coupling determines the transfer of energy from hot electrons to the lattice, resulting in the heating of devices. In the current treatments, the e-ph coupling is determined within the long-wavelength phonon approximation. In this work, we consider the e-ph coupling and its variation over the entire Brillouin zone (BZ). The electronic structure and the full phonon dispersion are evaluated with the phonon dispersion calculated using the density functional perturbation theory (DFPT). The e-ph coupling is evaluated using maximally localized Wannier functions and generalized Fourier interpolation to generate e-ph matrix elements on arbitrary grids. Examples of specific initial electron momentum both in the valence and in the conduction bands are presented, together with the variation of the e-ph coupling over the entire BZ associated with the specific initial carrier momenta. We observe variations of up to about 400meV in Diamond and 50 - 100 meV in Silicon and Germanium for the evaluated e-ph matrix element. We comment on the consequence of this variation on the carrier lifetimes in these materials. This work was supported by AFRL/DARPA under contract FA8650-10-1-7046

  4. Design of large aperture four group elements mid-wave infrared zoom lens

    NASA Astrophysics Data System (ADS)

    Ji, Yiqun; Shi, Rongbao; He, Hucheng; Shen, Weimin

    2012-10-01

    Zoom lens with variable focal length is well fit for researching objectives far and near. Design of zoom lens working at mid-wave infrared wavelength (7.7-10.3_m) and its view field 10 degrees is presented. Determination of the initial configuration of the variable and the compensate groups are discussed according to the mechanism compensate curves. The compensate group is determined with positive power. Its focal length changes during a large scope, which is from 300mm to 100mm. And the corresponding F number variables from 3.75 to 1.25. So the residual aberration needs to be carefully corrected. The optimized zoom lens is composed of four group elements, and its performance reaches diffraction limited at each focal position.

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

    DOEpatents

    Tom, Glenn M.; McManus, James V.; Luxon, Bruce A.

    1991-08-06

    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.

  6. Trace elements in organisms of different trophic groups in the White Sea

    NASA Astrophysics Data System (ADS)

    Budko, D. F.; Demina, L. L.; Martynova, D. M.; Gorshkova, O. M.

    2015-09-01

    Concentrations of trace elements (Fe, Mn, Cu, Pb, Ni, Cr, Cd, As, Co, and Se) have been studied in different trophic groups of organisms: primary producers (seston, presented mostly by phytoplankton), primary consumers (mesozooplankton, macrozooplankton, and bivalves), secondary consumers (predatory macrozooplankton and starfish), and consumers of higher trophic levels (fish species), inhabiting the coastal zone of Kandalaksha Bay and the White Sea (Cape Kartesh). The concentrations of elements differ significantly for the size groups of Sagitta elegans (zooplankton) and blue mussel Mytilus edulis, as well as for the bone and muscle tissues of studied fish species, Atlantic cod Gadus morhua marisalbi and Atlantic wolffish Anarhichas lupus. The concentrations of all the studied elements were lower among the primary consumers and producers, but increased again at higher trophic levels, from secondary consumers to tertiary consumers ("mesozooplankton → macrozooplankton Sagitta elegans" and "mussels → starfish"). Ni and Pb tended to decline through the food chains seston→…→cod and mesozooplankton→…→stickleback. Only the concentrations of Fe increased in all the trophic chains along with the increase of the trophic level.

  7. 30-Group Neutron, 12-Group Photon Cross Sections from ENDF/B-V in MATSX Format.

    Energy Science and Technology Software Center (ESTSC)

    1985-12-30

    Version: 00 The library was prepared with a fusion + fission + l/E + thermal Maxwellian weight function and has proved useful for many high energy calculations, including criticals such as GODIVA. It works reasonably well for many shielding problems where resonance selfshielding is not too important. The energy group structures for MATXSSA are listed in Table 1, the materials with neutron scattering data in Table 2, those with photon production data in Table 3,more » and those with photon scattering data In Table 4.« less

  8. Determination of copper, scandium, molybdenum, tin, lead, and iron group elements in lunar surface materials

    NASA Technical Reports Server (NTRS)

    Pavlenko, L. I.; Simonova, L. V.; Karyakin, A. V.

    1974-01-01

    Distribution regularities of copper, scandium, molybdenum, tin, lead, and iron group elements were investigated in basaltoid rocks of lunar and terrestrial origin. Samples of various regolith zones taken in the area of the Sea of Fertility were analyzed, along with samples of basic and ultrabasic rocks of the East African Rift for their content of the trace admixtures listed. Data obtained on the abundance of copper, scandium, molybdenum, tin, lead, cobalt, nickel, chromium, and vanadium in Luna 16 lunar surface material were compared with the abundance of these elements in samples of lunar rocks returned by Apollo 11, Apollo 12, and Apollo 14, with the exception of scandium; its content in the latter samples was considerably higher.

  9. The Origin and Distribution of Heavy Elements in the CD Groups MKW 4 and AWM 4

    NASA Technical Reports Server (NTRS)

    Vrtilek, Jan; Mushotzky, Richard (Technical Monitor)

    2003-01-01

    At this point, data for MKW4 have been received and those for AWM4 are still awaited. The MKW4 data have been fully analyzed and a complete manuscript is available and in final review by co-authors before submission for refereed publication. The following is a summary of our principal findings: We examined the distribution and properties of the hot gas which makes up the group halo. The inner halo shows some signs of structure, with circular or elliptical beta-models providing a poor fit to the surface brightness profile. This may be evidence of large-scale motion in the inner halo, but we do not find evidence of sharp fronts or edges in the emission. The temperature of the halo declines in the core, with deprojected spectral fits showing a central temperature of approximately 1.3keV compared to approximately 3keV at 250 arcsec. However, cooling flow models provide poor fits to the inner regions of the group and the estimated cooling time of the gas is long except within the central dominant galaxy, NGC4073. Abundance profiles show a sharp increase in the core of the group. We conclude that MKW4 is a fairly relaxed group, which has developed a strong central temperature gradient but not a large-scale cooling flow.

  10. Verbesserte Elemente der RR-Lyrae-Sterne IQ Bootis, V651 Aurigae und BQ Lyrae

    NASA Astrophysics Data System (ADS)

    Maintz, Gisela

    2015-04-01

    CCD observations of neglected RR Lyrae stars were taken at my private observatory. IQ Boo is a RRab star with a hump in the rising branch. BQ Lyr shows a weak Blazhko effect. The elements of these stars were revised. Star Max period +- JD [d] [d] IQ Boo 2457213.4681 0.535234 0.000001 V651 Aur 2457040.4056 0.617715 0.000003 BQ Lyr 2455703.4120 0.4350488 0.0000002

  11. Multiple complexation of CO and related ligands to a main-group element

    NASA Astrophysics Data System (ADS)

    Braunschweig, Holger; Dewhurst, Rian D.; Hupp, Florian; Nutz, Marco; Radacki, Krzysztof; Tate, Christopher W.; Vargas, Alfredo; Ye, Qing

    2015-06-01

    The ability of an atom or molecular fragment to bind multiple carbon monoxide (CO) molecules to form multicarbonyl adducts is a fundamental trait of transition metals. Transition-metal carbonyl complexes are vital to industry, appear naturally in the active sites of a number of enzymes (such as hydrogenases), are promising therapeutic agents, and have even been observed in interstellar dust clouds. Despite the wealth of established transition-metal multicarbonyl complexes, no elements outside groups 4 to 12 of the periodic table have yet been shown to react directly with two or more CO units to form stable multicarbonyl adducts. Here we present the synthesis of a borylene dicarbonyl complex, the first multicarbonyl complex of a main-group element prepared using CO. The compound is additionally stable towards ambient air and moisture. The synthetic strategy used--liberation of a borylene ligand from a transition metal using donor ligands--is broadly applicable, leading to a number of unprecedented monovalent boron species with different Lewis basic groups. The similarity of these compounds to conventional transition-metal carbonyl complexes is demonstrated by photolytic liberation of CO and subsequent intramolecular carbon-carbon bond activation.

  12. Multiple complexation of CO and related ligands to a main-group element.

    PubMed

    Braunschweig, Holger; Dewhurst, Rian D; Hupp, Florian; Nutz, Marco; Radacki, Krzysztof; Tate, Christopher W; Vargas, Alfredo; Ye, Qing

    2015-06-18

    The ability of an atom or molecular fragment to bind multiple carbon monoxide (CO) molecules to form multicarbonyl adducts is a fundamental trait of transition metals. Transition-metal carbonyl complexes are vital to industry, appear naturally in the active sites of a number of enzymes (such as hydrogenases), are promising therapeutic agents, and have even been observed in interstellar dust clouds. Despite the wealth of established transition-metal multicarbonyl complexes, no elements outside groups 4 to 12 of the periodic table have yet been shown to react directly with two or more CO units to form stable multicarbonyl adducts. Here we present the synthesis of a borylene dicarbonyl complex, the first multicarbonyl complex of a main-group element prepared using CO. The compound is additionally stable towards ambient air and moisture. The synthetic strategy used--liberation of a borylene ligand from a transition metal using donor ligands--is broadly applicable, leading to a number of unprecedented monovalent boron species with different Lewis basic groups. The similarity of these compounds to conventional transition-metal carbonyl complexes is demonstrated by photolytic liberation of CO and subsequent intramolecular carbon-carbon bond activation. PMID:26085273

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

    NASA Astrophysics Data System (ADS)

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

    2014-05-01

    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.

  14. Metallic phases and siderophile elements in main group ureilites: Implications for ureilite petrogenesis

    NASA Astrophysics Data System (ADS)

    Goodrich, Cyrena A.; Ash, Richard D.; Van Orman, James A.; Domanik, Kenneth; McDonough, William F.

    2013-07-01

    Metallic phases and siderophile elements are critical to understanding the petrogenesis of the enigmatic ureilite meteorites. We obtained petrographic, major and minor element, and the first in situ trace element data for metallic phases (metal, sulfides, phosphide, carbide) in 24 main group ureilites of various petrographic types with Fo ˜75-95. The most abundant type of metal (˜1-3 vol.%) occurs as ˜10-40 μm-wide strips along silicate grain boundaries. Ni contents of this metal range from ˜0 to 7.3 wt.% and are correlated with Co among all samples (Ni/Co = 0.64 × CI). A less abundant type of metal occurs as ˜5-150 μm diameter metallic spherules, consisting of cohenite (Fe3C), metal, phosphide and sulfide, enclosed in silicates (preferentially low-Ca pyroxene). Most samples contain 2 types of sulfide: (1) low-Cr (<0.1 wt.%) troilite, and (2) lamellar intergrowths of daubreelite (FeCr2S4) and troilite. Abundances of 17 (mostly siderophile) elements were measured by LA-ICP-MS in grain boundary metal, spherules, graphite, sulfides and silicates. Average compositions of grain boundary metal in 10 samples show decreasing CI-normalized abundance with increasing volatility, interrupted by depletions in W, Mo, Ni and Zn, and enrichments in Au, As, Ga and Ge. CI-normalized Os abundances range from ˜2 to 65, and are correlated with increasing Os/Pt, Os/Ni and Os/Pd ratios. CI-normalized Pt/Os ratios range from ˜0.3 to 1. Bulk cohenite-bearing spherules have siderophile element abundances indistinguishable from those of grain boundary metal in the same sample. CI-normalized patterns of most siderophile elements in the metal are, within error, identical to those of the bulk rock (at 25-40× higher abundances) in each sample. There are no correlations between siderophile element abundances and Fo. We infer that at T ⩾ 1200 °C ureilites contained immiscible Fe-C (3-4 wt.% C) and Fe-S melts, small samples of which were trapped as the spherules within silicates. The

  15. Methods for the determination of platinum group elements originating from the abrasion of automotive catalytic converters

    NASA Astrophysics Data System (ADS)

    Bencs, László; Ravindra, Khaiwal; Van Grieken, René

    2003-10-01

    Anthropogenic emission of platinum group elements (PGEs) from the abrasion of automotive catalytic converters into the environment has significantly increased. However, the concentration level of these PGEs (i.e. Pd, Pt, Rh) is still very low in the nature. Accordingly, their determination and speciation in various environmental compartments appears to be a challenging task for analytical chemists. The present review gives an overview of the analytical procedures documented in this particular field of analytical chemistry with a distinctive emphasis on spectrochemical methodology, it being the most sensitive and robust for accomplishing the above analytical task.

  16. Controlled Synthesis of Polyions of Heavy Main-Group Elements in Ionic Liquids.

    PubMed

    Groh, Matthias F; Wolff, Alexander; Grasser, Matthias A; Ruck, Michael

    2016-01-01

    Ionic liquids (ILs) have been proven to be valuable reaction media for the synthesis of inorganic materials among an abundance of other applications in different fields of chemistry. Up to now, the syntheses have remained mostly "black boxes"; and researchers have to resort to trial-and-error in order to establish a new synthetic route to a specific compound. This review comprises decisive reaction parameters and techniques for the directed synthesis of polyions of heavy main-group elements (fourth period and beyond) in ILs. Several families of compounds are presented ranging from polyhalides over carbonyl complexes and selenidostannates to homo and heteropolycations. PMID:27598123

  17. Theoretical discovery of stable structures of group III-V monolayers: The materials for semiconductor devices

    SciTech Connect

    Suzuki, Tatsuo

    2015-11-23

    Group III-V compounds are very important as the materials of semiconductor devices. Stable structures of the monolayers of group III-V binary compounds have been discovered by using first-principles calculations. The primitive unit cell of the discovered structures is a rectangle, which includes four group-III atoms and four group-V atoms. A group-III atom and its three nearest-neighbor group-V atoms are placed on the same plane; however, these connections are not the sp{sup 2} hybridization. The bond angles around the group-V atoms are less than the bond angle of sp{sup 3} hybridization. The discovered structure of GaP is an indirect transition semiconductor, while the discovered structures of GaAs, InP, and InAs are direct transition semiconductors. Therefore, the discovered structures of these compounds have the potential of the materials for semiconductor devices, for example, water splitting photocatalysts. The discovered structures may become the most stable structures of monolayers which consist of other materials.

  18. Matrix exponentials, SU(N) group elements, and real polynomial roots

    NASA Astrophysics Data System (ADS)

    Van Kortryk, T. S.

    2016-02-01

    The exponential of an N × N matrix can always be expressed as a matrix polynomial of order N - 1. In particular, a general group element for the fundamental representation of SU(N) can be expressed as a matrix polynomial of order N - 1 in a traceless N × N hermitian generating matrix, with polynomial coefficients consisting of elementary trigonometric functions dependent on N - 2 invariants in addition to the group parameter. These invariants are just angles determined by the direction of a real N-vector whose components are the eigenvalues of the hermitian matrix. Equivalently, the eigenvalues are given by projecting the vertices of an (" separators=" N - 1 ) -simplex onto a particular axis passing through the center of the simplex. The orientation of the simplex relative to this axis determines the angular invariants and hence the real eigenvalues of the matrix.

  19. Vertical group III-V nanowires on si, heterostructures, flexible arrays and fabrication

    DOEpatents

    Wang, Deli; Soci, Cesare; Bao, Xinyu; Wei, Wei; Jing, Yi; Sun, Ke

    2015-01-13

    Embodiments of the invention provide a method for direct heteroepitaxial growth of vertical III-V semiconductor nanowires on a silicon substrate. The silicon substrate is etched to substantially completely remove native oxide. It is promptly placed in a reaction chamber. The substrate is heated and maintained at a growth temperature. Group III-V precursors are flowed for a growth time. Preferred embodiment vertical Group III-V nanowires on silicon have a core-shell structure, which provides a radial homojunction or heterojunction. A doped nanowire core is surrounded by a shell with complementary doping. Such can provide high optical absorption due to the long optical path in the axial direction of the vertical nanowires, while reducing considerably the distance over which carriers must diffuse before being collected in the radial direction. Alloy composition can also be varied. Radial and axial homojunctions and heterojunctions can be realized. Embodiments provide for flexible Group III-V nanowire structures. An array of Group III-V nanowire structures is embedded in polymer. A fabrication method forms the vertical nanowires on a substrate, e.g., a silicon substrate. Preferably, the nanowires are formed by the preferred methods for fabrication of Group III-V nanowires on silicon. Devices can be formed with core/shell and core/multi-shell nanowires and the devices are released from the substrate upon which the nanowires were formed to create a flexible structure that includes an array of vertical nanowires embedded in polymer.

  20. 77 FR 43071 - MPS Customer Group v. Maine Public Service Company; Notice of Complaint

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-07-23

    ... Energy Regulatory Commission MPS Customer Group v. Maine Public Service Company; Notice of Complaint Take notice that on July 13, 2012, pursuant to sections 206 and 306 of the Federal Power Act, 16 U.S.C. 824e... Commission (Commission); 18 CFR 385.206, MPS Customer Group (Complainant) filed a formal complaint...

  1. New SSMS Techniques for the Determination of Rhodium and Other Platinum- Group Elements in Carbonaceous Chondrites

    NASA Astrophysics Data System (ADS)

    Jochum, K. P.; Seufert, H. M.

    1995-09-01

    We have developed new spark source mass spectrometric (SSMS) techniques for simultaneous analysis of platinum-group elements (PGE) together with other trace elements in stony meteorites. We have measured elemental abundances of Rh, Ru, Os, Ir, Pt, Au in carbonaceous chondrites of different types including the two CI chondrites Orgueil and Ivuna. These data are relevant for the determination of solar-system abundances. Whereas the solar-system abundances of most PGE are well known, this is not the case for Rh, and no literature data exist for carbonaceous chondrites, mainly because of analytical difficulties. The SSMS techniques include new calibration procedures and the use of a recently developed multi-ion counting (MIC) system [1]. The mono-isotopic element Rh and the other PGE were determined by using internal standard elements (e.g., Nd, U) that were measured by isotope dilution in the same sample electrode material. The data were calibrated with certified standard solutions of PGE which were doped on trace-element poor rock samples. Ion abundances were measured using both the conventional photoplate detection and the ion-counting techniques. The new MIC technique that uses up to 20 small channeltrons for ion counting measurements has the advantage of improved precision, detection limits and analysis time compared to photoplate detection. Tab. 1 shows the Rh analyses for the meteorites Orgueil, Ivuna, Murchison, Allende and Karoonda obtained by conventional photoplate detection. These are the first Rh results for carbonaceous chondrites. The data for the two CI chondrites Orgueil and Ivuna are identical and agree within 4 % with the CI estimate of Anders and Grevesse [2] which was derived indirectly from analyses for H-chondrites. The PGE Os, Ir, Pt, Au and W, Re, Th, U concentrations were determined by both detection systems. Data obtained with the MIC system are more precise (about 4% for concentrations in the ppb range) compared to the photoplate detection

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

    SciTech Connect

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

    1980-10-01

    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.

  3. Transferable tight-binding model for strained group IV and III-V materials and heterostructures

    NASA Astrophysics Data System (ADS)

    Tan, Yaohua; Povolotskyi, Michael; Kubis, Tillmann; Boykin, Timothy B.; Klimeck, Gerhard

    2016-07-01

    It is critical to capture the effect due to strain and material interface for device level transistor modeling. We introduce a transferable s p3d5s* tight-binding model with nearest-neighbor interactions for arbitrarily strained group IV and III-V materials. The tight-binding model is parametrized with respect to hybrid functional (HSE06) calculations for varieties of strained systems. The tight-binding calculations of ultrasmall superlattices formed by group IV and group III-V materials show good agreement with the corresponding HSE06 calculations. The application of the tight-binding model to superlattices demonstrates that the transferable tight-binding model with nearest-neighbor interactions can be obtained for group IV and III-V materials.

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

    NASA Astrophysics Data System (ADS)

    Crisostomo, Christian P.; Yao, Liang-Zi; Huang, Zhi-Quan; Hsu, Chia-Hsiu; Chuang, Feng-Chuan; Lin, Hsin; Albao, Marvin A.; Bansil, Arun

    2015-03-01

    We use first-principles electronic structure calculations to predict a new class of two-dimensional (2D) topological insulators (TIs) in hydrogenated binary compositions of group III elements (B, Al, Ga, In, and Tl) and bismuth (Bi). We identify band inversions in unhydrogenated pristine GaBi, InBi, and TlBi bilayers, with gaps as large as 556 meV for the TlBi case, making these materials suitable for room-temperature applications. Double-sided hydrogenation in which hydrogen was added on opposite sides also exhibited band inversions in the case of GaBi, InBi, and TlBi just as in the unhydrogenated pristine ones. Furthermore, we report the gap to be 885 meV for the hydrogenated TlBi case. Hydrogenation enhace the band gap without changing the band topology. Moreover, our study also aim to demonstrate the possibility of strain engineering in that the topological phase transition in systems whose phase was nontrivial could be driven by suitable strain. Finally, the effect of placing hydrogen to topological edges was also demonstrated. 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. The robustness of III-Bi upon hydrogenation shows that these materials are possible to synthesize by growing on substrates.

  5. 33 CFR 155.5052 - Response plan development and evaluation criteria for nontank vessels carrying group V petroleum...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... requirements of 33 CFR 155.1052. ... evaluation criteria for nontank vessels carrying group V petroleum oil. 155.5052 Section 155.5052 Navigation... Response plan development and evaluation criteria for nontank vessels carrying group V petroleum...

  6. Structures, Bonding, and Energetics of Potential Triatomic Circumstellar Molecules Containing Group 15 and 16 Elements.

    PubMed

    Turner, Walter E; Agarwal, Jay; Schaefer, Henry F

    2015-12-01

    The recent discovery of PN in the oxygen-rich shell of the supergiant star VY Canis Majoris points to the formation of several triatomic molecules involving oxygen, nitrogen, and phosphorus; these are also intriguing targets for main-group synthetic inorganic chemistry. In this research, high-level ab initio electronic structure computations were conducted on the potential circumstellar molecule OPN and several of its heavier group 15 and 16 congeners (SPN, SePN, TePN, OPP, OPAs, and OPSb). For each congener, four isomers were examined. Optimized geometries were obtained with coupled cluster theory [CCSD(T)] using large Dunning basis sets [aug-cc-pVQZ, aug-cc-pV(Q+d)Z, and aug-cc-pVQZ-PP], and relative energies were determined at the complete basis set limit of CCSDT(Q) from focal point analyses. The linear phosphorus-centered molecules were consistently the lowest in energy of the group 15 congeners by at least 6 kcal mol(-1), resulting from double-triple and single-double bond resonances within the molecule. The linear nitrogen-centered molecules were consistently the lowest in energy of the group 16 congeners by at least 5 kcal mol(-1), due to the electronegative central nitrogen atom encouraging electron delocalization throughout the molecule. For OPN, OPP, and SPN, anharmonic vibrational frequencies and vibrationally corrected rotational constants are predicted; good agreement with available experimental data is observed. PMID:26566183

  7. Stabilization of hexa-coordinated P(v) corroles by axial silyloxy groups.

    PubMed

    Chatterjee, Tamal; Lee, Way-Zen; Ravikanth, Mangalampalli

    2016-05-01

    We report the stabilization of the hexa-coordination environment for P(v) corroles by using alkyl/aryl substituted silyloxy groups as axial ligands. The P(v) corroles are highly fluorescent in a hexa-coordination environment compared to in a penta-coordination environment. However, P(v) corroles generally undergo axial ligand dissociation to form a mixture of penta- and hexa-coordinated P(v) corroles in non-coordinating solvents such as toluene, CH2Cl2, CHCl3. The usage of moderately bulkier and electron-donating silyloxy groups helps to restrict the axial ligand dissociation of silyloxy substituted hexa-coordinated P(v) corroles in non-coordinating solvents. The crystal structure confirmed the hexa-coordination geometry for the P(v) corroles. The P(v) corroles strongly absorb and emit in the visible region, with decent quantum yields and singlet state lifetimes. The hexa-coordinated P(v) corroles are highly stable under electrochemical conditions. PMID:27063706

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

    NASA Technical Reports Server (NTRS)

    Lai, Chen-Yao G.

    1996-01-01

    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.

  9. Spatial distribution and sources identification of elements in PM2.5 among the coastal city group in the Western Taiwan Strait region, China.

    PubMed

    Xu, Lingling; Yu, Yanke; Yu, Jianshuan; Chen, Jinsheng; Niu, Zhenchuan; Yin, Liqian; Zhang, Fuwang; Liao, Xu; Chen, Yanting

    2013-01-01

    The main purpose of this study was to investigate the spatial variations of 20 elements (Al, Si, Ti, Ca, Fe, Mg, Cr, Mn, Ni, P, S, K, Cu, Cl, V, Se, Br, As, Zn, and Pb) in PM(2.5) (particle matters ≤ 2.5 μm in aerodynamic diameter) in the coastal city group in the Western Taiwan Strait (WTS) region, China during spring 2011. The average PM(2.5) mass concentration at 13 sites was 77.0 μg/m(3) and the elemental fraction accounted for about 10-20%. Multivariate analyses (principal component analysis and cluster analysis) and a correlation matrix were used to identify the sources of elements in PM(2.5). The results revealed that the elements originated mainly from traffic emissions, coal combustion, pyrometallurgical processes, and crustal sources. Spatially, the concentrations of elements were generally higher in several rapidly growing locations, and the enrichment factors (EFs) for most elements were much higher at the northern sites than those at the southern sites, suggesting that the air quality in the northern part of the study area was strongly affected by anthropogenic activity. Backward wind trajectory analysis during the sampling period indicated that the concentrations of elements in PM(2.5) in the WTS region were greatly impacted by dust particles transported from Northern China in spring. PMID:23178767

  10. [Structure and evolutionary role of the Penelope mobile element in Drosophila species of the virilis group].

    PubMed

    Lezin, G T; Makarova, K V; Velikodvorskaia, V V; Zelentsova, E S; Kechumian, R R; Kidwell, M G; Kunin, E V; Evgen'ev, M B

    2001-01-01

    The mobile element Penelope is activated and mobilizes several other transposons in dysgenic crosses in Drosophila virilis. Its structure proved to be complex and to vary greatly in all examined species of the virilis group. Phylogenetic analysis of the reverse transcriptase (RT) domain assigned Penelope to a new branch, rather than to any known family, of LTR-lacking retroelements. Amino acid sequence analysis showed that the C-terminal domain of the Penelope polyprotein is an active endonuclease, which is related to intron-encoded endonucleases and to bacterial repair endonuclease UrvC, and may act as an integras. Retroelements coding for a putative endonuclease that differs from typical integrase have thus far not been known. The N-terminal domain of the Penelope polyprotein was shown to contain a protease with significant homology to HIV-1 protease. Phylogenetic analysis divided the Penelope copies from several virilis species into two subfamilies, one including virtually identical full-length copies, and the other comprising highly divergent defective copies. The results suggest both vertical and horizontal transfer of the element. Possibly, Penelope invasion recurred during evolution and contributed to genome rearrangement in the virilis species. Chromosome aberrations detected in D. virilis, which is now being invaded by Penelope, is direct evidence for this assumption. PMID:11605533

  11. Tailoring of ZnO with selected group-II elements for LED materials

    NASA Astrophysics Data System (ADS)

    Saleem, Murtaza; Manzoor, Adnan; Zaffar, Mohammed; Hussain, Syed Zajif; Anwar, M. Sabieh

    2016-06-01

    The semiconductor ZnO is a promising candidate for its applications in light-emitting diodes. In this study ZnO nanostructures tailored with selected group-II elements were synthesized using sol-gel-based fuel-agent-assistive chemical technique. Structural studies from X-ray diffraction analysis revealed the presence of wurtzite hexagonal crystal structure in all compositions confirming the stability of the Mg-doped structure while indicating presence of some traces of un-reacted and oxides of Sr and Ba in other compositions. Lattice parameters, crystallite size, lattice strain, density, and cell volume were extracted from X-ray diffraction data. Morphology and elemental composition analysis showed exact correlation with structural arrangements. The size of particles was also observed with dynamic light-scattering measurements. Absorbance and electrical transport studies were performed using UV-Vis spectrophotometry and four-probe measurements, respectively; the former was used to estimate the band gap of nanostructures. Energy-dispersive X-ray analysis was employed for confirming the substitution of Mg, Sr, and Ba atoms at Zn and O sites. Band gap values show strong dependence upon the tailored ZnO compositions.

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

    USGS Publications Warehouse

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

    1985-01-01

    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.

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

    USGS Publications Warehouse

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

    1986-01-01

    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.

  14. Accumulation of platinum group elements by the marine gastropod Littorina littorea.

    PubMed

    Mulholland, Rachel; Turner, Andrew

    2011-04-01

    The accumulation and trophic transfer of the platinum group elements (PGE): Rh, Pd and Pt; have been studied in short-term (5 day) exposures conducted in aquaria containing the marine macroalga, Ulva lactuca, and/or the grazing mollusc, Littorina littorea. Metals added to sea water (to concentrations of 20 μg L⁻¹) were taken up by U. lactuca in the order Rh, Pt > Pd and by L. littorea in the order Pd ≥ Pt ≥ Rh, with greatest metal accumulation in the latter generally occurring in the visceral complex and kidney. When fed contaminated alga, accumulation of Rh and Pd by L. littorea, relative to total available metal, increased by an order of magnitude, while accumulation of Pt was not readily detected. We conclude that the diet is the most important vector for accumulation of Rh and Pd, while accumulation of Pt appears to proceed mainly from the aqueous phase. PMID:21237543

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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

  16. Report of the IAU Working Group on cartographic coordinates and rotational elements: 2009

    USGS Publications Warehouse

    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.

    2010-01-01

    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) Šteins. 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

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

    NASA Astrophysics Data System (ADS)

    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.

    2011-02-01

    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) Šteins. 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

  18. Estimation of the isotope effect on the lattice thermal conductivity of group IV and group III-V semiconductors

    NASA Astrophysics Data System (ADS)

    Morelli, D. T.; Heremans, J. P.; Slack, G. A.

    2002-11-01

    The isotope effect on the lattice thermal conductivity for group IV and group III-V semiconductors is calculated using the Debye-Callaway model modified to include both transverse and longitudinal phonon modes explicitly. The frequency and temperature dependences of the normal and umklapp phonon-scattering rates are kept the same for all compounds. The model requires as adjustable parameters only the longitudinal and transverse phonon Grüneisen constants and the effective sample diameter. The model can quantitatively account for the observed isotope effect in diamond and germanium but not in silicon. The magnitude of the isotope effect is predicted for silicon carbide, boron nitride, and gallium nitride. In the case of boron nitride the predicted increase in the room-temperature thermal conductivity with isotopic enrichment is in excess of 100%. Finally, a more general method of estimating normal phonon-scattering rate coefficients for other types of solids is presented.

  19. The Abundances of the Fe Group Elements in Three Early B Stars in the Large Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Peters, G. J.; Adelman, S. J.

    2005-12-01

    The photospheric abundances of V, Cr, and Fe have been determined for three sharp-lined early B stars in the Large Magellanic Cloud using FUV spectra obtained from the Far Ultraviolet Spectroscopic Explorer (FUSE) and the Kurucz LTE model atmosphere/spectrum synthesis codes ATLAS9/SYNTHE. The program stars include NGC1818/D1, NGC2004/B15, and NGC2004/B30 (star designations are from Robertson 1974, A&AS, 15, 261). The calculations were carried through with model parameters close to those adopted by Korn et al. (2000, A&A, 353, 655). Values of Teff, log g, ξ T, and v sin I are 25000/4.0/0/30, 20000/3.1/6/25, and 23500/3.3/14/30 for NGC1818/D1, NGC2004/B15, and NGC2004/B30, respectively. The abundances quoted below are in sequence for the latter stars. The vanadium abundances, [V/H], determined from V III λ λ 1150,1152 (UV 2), are -0.6, -0.9, and -0.9 dex. Cr was determined from Cr III λ λ 1118,1136. Values of -0.5, -0.8, and -0.7 dex were found. Uncertainties in the V and Cr abundances are ˜0.3 dex. The Fe abundance is primarily from 7 lines of Fe III (UV 1) in the region λ λ 1122-32. Values are -0.8±0.3, ˜-1.1, and -0.4±0.3. Since there is no evidence for N enhancement in the program stars ([N/H] ˜ -0.9, -1.0, and -0.6 from the N III doublet at 1183,1184 Å) the photospheric abundances have probably not been altered by mixing of processed material from the star's interior and the derived abundances represent pristine values for the two young clusters in the LMC. It should be noted that the N and Fe abundances derived for NGC1818/D1 are about 0.5 dex lower than those determined by Korn et al. from much weaker optical lines. We will discuss possible reasons for the discrepancy. The generally low abundances for the Fe group elements in these young cluster B stars imply that supernova activity has been minimal in the regions of the LMC in which the stars were formed. GJP appreciates support from NASA grant NAG5-13212.

  20. Development of metallographic preparation techniques for group IVA and VA elements

    SciTech Connect

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

    2001-01-01

    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, better grain boundary delineation is possible with the new process. Similar results are evident for titanium, zirconium, vanadium, and hafnium. The new preparation stage includes a chemical polish and etchant. The chemical polish was found to eliminate problems associated with the mechanical polish. Specifically, the chemical polish removes the worked surface and eliminates smearing. The etching stage serves to delineate the grain boundaries, and in some cases allows bright field as well as polarized or differential interference contrast (DIC) for optical examination. Finally, optical lighting conditions to enhance the observations available with the optimized procedure will be discussed.

  1. Group velocity of the light pulse in an open V-type system

    NASA Astrophysics Data System (ADS)

    Li, Jingjuan; Fan, Xijun; Tian, Shufen; Liu, Chengpu; Gong, Shangqing; Xu, Zhizhan

    2007-04-01

    We investigate the group velocity of the probe light pulse in an open V-type system with spontaneously generated coherence. We find that, not only varying the relative phase between the probe and driving pulses can but varying the atomic exit rate or incoherent pumping rate also can manipulate dramatically the group velocity, even make the pulse propagation switching from subluminal to superluminal; the subliminal propagation can be companied with gain or absorption, but the superluminal propagation is always companied with absorption.

  2. Elemental copper nanoparticle toxicity to different trophic groups involved in anaerobic and anoxic wastewater treatment processes.

    PubMed

    Gonzalez-Estrella, Jorge; Puyol, Daniel; Gallagher, Sara; Sierra-Alvarez, Reyes; Field, Jim A

    2015-04-15

    Elemental copper nanoparticles (Cu(0) NPs) are potentially inhibitory to the different key microbial trophic groups involved in biological wastewater treatment processes. Cu-based NPs are known to be toxic to methanogens at low concentrations. However, very little is known about the toxic effect of Cu(0) NPs on other microbial groups involved in either upper trophic levels of anaerobic digestion or anoxic nitrogen removal processes. This study evaluated the toxicity of Cu(0) NPs to glucose fermentation, syntrophic propionate oxidation and denitrification in shaken batch bioassays with soluble substrates. Batch experiments were also supplemented with CuCl2 to evaluate the inhibitory impact of soluble Cu(II) ions. Syntrophic propionate oxidation and glucose fermentation were the least and most inhibited processes with inhibition constant (Ki) values of 0.202 and 0.047 mM of added Cu(0) NPs, respectively. Further analyses revealed that the Ki values calculated as a function of the free soluble Cu concentration were <0.003 mM for every biological process tested and most of these Ki values were similar in order of magnitude regardless of whether the Cu source was CuCl2 or Cu(0) NPs. The results taken as a whole indicate that Cu(0) NPs are toxic to all the microbial processes studied. Therefore, Cu(0) NPs can potentially be an important inhibitor of anaerobic wastewater treatment processes that rely on these trophic groups. The evidence suggests that the inhibitory impact of Cu(0) NPs was mainly due to the release of toxic Cu(II) ions originating from the corrosion and dissolution of Cu(0) NPs. PMID:25634735

  3. 20 CFR 655.1115 - Element V-What does “no strike/lockout or layoff” mean?

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    .... If ETA determines that the strike or lockout is covered under USCIS regulation 8 CFR 214.2(h)(17... 20 Employees' Benefits 3 2013-04-01 2013-04-01 false Element V-What does âno strike/lockout or... strike/lockout or layoff” mean? (a) The fifth attestation element requires that the facility attest...

  4. 20 CFR 655.1115 - Element V-What does “no strike/lockout or layoff” mean?

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    .... If ETA determines that the strike or lockout is covered under USCIS regulation 8 CFR 214.2(h)(17... 20 Employees' Benefits 3 2012-04-01 2012-04-01 false Element V-What does âno strike/lockout or... strike/lockout or layoff” mean? (a) The fifth attestation element requires that the facility attest...

  5. 20 CFR 655.1115 - Element V-What does “no strike/lockout or layoff” mean?

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    .... If ETA determines that the strike or lockout is covered under USCIS regulation 8 CFR 214.2(h)(17... 20 Employees' Benefits 3 2014-04-01 2014-04-01 false Element V-What does âno strike/lockout or... strike/lockout or layoff” mean? (a) The fifth attestation element requires that the facility attest...

  6. 20 CFR 655.1115 - Element V-What does “no strike/lockout or layoff” mean?

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    .... If ETA determines that the strike or lockout is covered under USCIS regulation 8 CFR 214.2(h)(17... 20 Employees' Benefits 3 2011-04-01 2011-04-01 false Element V-What does âno strike/lockout or... strike/lockout or layoff” mean? (a) The fifth attestation element requires that the facility attest...

  7. Should an Obsessive-Compulsive Spectrum Grouping of Disorders Be Included in DSM-V?

    PubMed Central

    Phillips, Katharine A.; Stein, Dan J.; Rauch, Scott; 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

    2014-01-01

    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 paper addresses this topic and presents options and preliminary recommendations to be considered for DSM-V. The paper 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

  8. Permissive tracts for nickel, copper, platinum group elements (PGE), and chromium deposits of Mauritania (phase V, deliverable 66): Chapter G1 in Second projet de renforcement institutionnel du secteur minier de la République Islamique de Mauritanie (PRISM-II)

    USGS Publications Warehouse

    Taylor, Cliff D.; Horton, John D.

    2012-01-01

    This report contains the USGS results of the PRISM-II Mauritania Minerals Project and is presented in cooperation with the Ministry of Petroleum, Energy, and Mines of the Islamic Republic of Mauritania. The Report is composed of separate chapters consisting of multidisciplinary interpretive reports with accompanying plates on the geology, structure, geochronology, geophysics, hydrogeology, geochemistry, remote sensing (Landsat TM and ASTER), and SRTM and ASTER digital elevation models of Mauritania. The syntheses of these multidisciplinary data formed the basis for additional chapters containing interpretive reports on 12 different commodities and deposit types known to occur in Mauritania, accompanied by countrywide mineral resource potential maps of each commodity/deposit type. The commodities and deposit types represented include: (1) Ni, Cu, PGE, and Cr deposits hosted in ultramafic rocks; (2) orogenic, Carlin-like, and epithermal gold deposits; (3) polymetallic Pb-Zn-Cu vein deposits; (4) sediment-hosted Pb-Zn-Ag deposits of the SEDEX and Mississippi Valley-type; (5) sediment-hosted copper deposits; ( 6) volcanogenic massive sulfide deposits; (7) iron oxide copper-gold deposits; (8) uranium deposits; (9) Algoma-, Superior-, and oolitic-type iron deposits; (10) shoreline Ti-Zr placer deposits; (11) incompatible element deposits hosted in pegmatites, alkaline rocks, and carbonatites, and; (12) industrial mineral deposits. Additional chapters include the Mauritanian National Mineral Deposits Database are accompanied by an explanatory text and the Mauritania Minerals Project GIS that contains all of the interpretive layers created by USGS scientists. Raw data not in the public domain may be obtained from the Ministry of Petroleum, Energy, and Mines in Nouakchott, Mauritania.

  9. Geophysical Imaging of the Stillwater and Bushveld Complexes and Relation to Platinum-group Element Exploration

    NASA Astrophysics Data System (ADS)

    Finn, C.; Bedrosian, P.; Zientek, M. L.; Cole, J.; Webb, S. J.; Bloss, B. R.

    2015-12-01

    Exploring for platinum-group elements (PGEs) relies on understanding the geophysical signature of the entire magmatic system in which they form, from bottom to top. New potential field and electromagnetic data and methods effectively map internal structures of layered intrusions that host PGE-bearing magmatic ore deposits, the volume of the intrusion and its extent under cover, and locations of sulfide mineralization. High resolution aeromagnetic data can image fine scale linear anomalies related to layering in the Stillwater and Bushveld Complexes. At Stillwater, the aeromagnetic anomalies relate to boundaries between major stratigraphic units and olivine-bearing rock layers altered to a mixture of serpentine and magnetite. The PGE-enriched sulfide mineralization hosted by olivine-bearing rocks in the Stillwater Complex produces a distinct linear magnetic high. In the Upper Zone of the Bushveld Complex, primary magnetite layers generate linear magnetic highs. Electromagnetic (EM) data over the Stillwater Complex highlight contact-type mineralization which contain low resistivity sulfide minerals. Stochastic inversions reveal a low resistivity zone along the southern edge of the Stillwater Complex corresponding to mineralization in banded iron formation or contact-type sulfide mineralization in the Basal zone. Gravity highs characterize the exposed and interpreted buried extent of the Stillwater and Bushveld complexes. A 3D inversion of gravity data of the Sillwater Complex indicates that the complex extends 30 km north and 40 km east of its outcrop beneath Phanerozoic cover. Geophysical models image the 3D geometry of the Bushveld Complex north of the Thabazimbi-Murchison Lineament (TML), critical for understanding the origin of the world's largest layered mafic intrusion and associated platinum- group element deposits, as a ~4 km thick, 160 km x ~125 km body underlying ~1-2 km of cover. Locally thick regions in the TML portion of the model may represent feeders

  10. Report of the IAU Working Group on cartographic coordinates and rotational elements: 2009

    USGS Publications Warehouse

    Archinal, Brent A.; A’Hearn, Michael F.; Bowell, Edward; Conrad, Al; Consolmagno, Guy J.; Courtin, Regis; Fukushima, Toshio; Hestroffer, Daniel; Hilton, James L.; Krasinsky, Georgij A.; Neumann, Gregory; Oberst, Jurgen; Seidelmann, P. Kenneth; Stooke, Philip; Tholen, David J.; Thomas, Peter C.; Williams, Iwan P.

    2010-01-01

    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) Šteins. 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

  11. Measurements of total atomic attenuation cross sections of Tm, Yb, Lu, Hf, Ta, W, Re and Os Elements at 122keV and 136keV

    SciTech Connect

    Kaya, N.; Tirasoglu, E.; Apaydin, G.; Kobya, A. I.

    2007-04-23

    The aim of this study was to measure the total atomic attenuation cross sections ({sigma}t) in eighth elements (69{<=}Z{<=}76) at 122 keV and 136 keV. The experimental values of the cross sections were determined using the transmission geometry. Measurements have been performed using an annular source (Co-57) and Ultra-LEGe solid state detector with a resolution of 150 eV at 5.9 keV. Experimental results have been compared with theoretically calculated values and other available experimental results. Good agreement was observed among the experimental, theoretical and other experimental values.

  12. Re-187-Os-187, Pt-190-Os-186 Isotopic and Highly Siderophile Element Systematics of Group IVA Irons

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

    We have recently completed Re-187-Os-187 and Pt-190-Os-186 isotopic and elemental studies of the two largest magmatic iron meteorite groups, IIAB and IIIAB [1]. These studies revealed closed-system behavior of both isotopic systems, but complex trace element behavior for Re, Pt and Os in group IIIAB. Here we examine isotopic and trace elemental systematics of group IVA irons. The IVA irons are not as extensively fractionated as IIAB and IIIAB and their apparently less complex crystallization history may make for more robust interpretation of the relative partitioning behavior of Re, Pt and Os, as well as the other highly siderophile elements (HSE) measured here; Pd, Ru and Ir [e.g. 2]. An additional goal of our continuing research plan for iron meteorites is to assess the possibility of relating certain ungrouped irons with major groups via trace element modeling. Here, the isotopic and trace element systematics of the ungrouped irons Nedagolla and EET 83230 are compared with the IVA irons.

  13. Graphene challengers: silicene, germanene and stanene, group IV elemental synthetic electronic materials

    NASA Astrophysics Data System (ADS)

    Le Lay, Guy

    Silicene, germanene and stanene, graphene's group IV elemental cousins, have attracted considerable interest since the birth of silicene in 2012. These novel synthetic two-dimensional (2D) Si, Ge and Sn allotropes are artificially created in situ under ultra high vacuum, since, at variance with graphene, which descents from graphite, they have no parent crystal in nature. They are considered as promising candidates for ultimate scaling of nanoelectronic devices. Indeed, the recent fabrication of the first silicene field effect transistors with ambipolar characteristics operating at room temperature demonstrates their potential as emerging 2D electronic materials. In this invited talk, I will present the archetype 3x3 silicene phase formed on a silver (111) substrate, its sister phases and the growth of multilayer silicene, which hosts Dirac fermions and which is stable in ambient air, protected by its ultra-thin native oxide. The recent synthesis of single layer germanene and stanene, near room temperature 2D topological insulators will be also presented, while multilayer germanene will be further addressed. Challenging graphene, silicene, germanene and stanene, which are directly compatible with the current semiconductor industry, could lead to the development of a new class of low energy consumption nanoelectronic devices.

  14. Smoothed particle hydrodynamics and element bending group modeling of flexible fibers interacting with viscous fluids

    NASA Astrophysics Data System (ADS)

    Yang, Xiufeng; Liu, Moubin; Peng, Shiliu

    2014-12-01

    This paper presents a smoothed particle hydrodynamics (SPH) and element bending group (EBG) coupling method for modeling the interaction of flexible fibers with moving viscous fluids. SPH is a well-developed mesh-free particle method for simulating viscous fluid flows. EBG is also a particle method for modeling flexible bodies. The interaction of flexible fibers with moving viscous fluids is rendered through the interaction of EBG particles for flexible fiber and SPH particles for fluid. In numerical simulation, flexible fibers of different lengths are immersed in a moving viscous fluid driven by a body force. The drag force on the fiber obtained from SPH-EBG simulation agrees well with experimental observations. It is shown that the flexible fiber demonstrates three typical bending modes, including the U-shaped mode, the flapping mode, and the closed mode, and that the flexible fiber experiences a drag reduction due to its reconfiguration by bending. It is also found that the U 4/3 drag scaling law for a flexible fiber is only valid for the U-shaped mode, but not valid for the flapping and closed modes. The results indicate that the reconfiguration of a flexible fiber is caused by the fluid force acting on it, while vortex shedding is of importance in the translations of bending modes.

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

    PubMed

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

    2012-06-01

    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

  16. [Pollution characteristics of platinum group elements in road dust in central urban area of Beijing].

    PubMed

    Xu, Ling-Ling; Gao, Bo; Lu, Jin; Zhou, Huai-Dong; Hao, Hong; Wang, Xiao-Jun

    2011-03-01

    In order to survey platinum group elements (PGEs) contamination in central urban area of Beijing, dust samples were collected from the second ring road in December 2009. The road samples were digested with aqua regia and separated and purified with cation exchange resin, and the resulting solutions were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The results showed that the concentrations of Pd, Pt and Rh in road dust ranged from 17.40-458.75 ng x g(-1) (126.66 ng x g(-1)), 10.04-182.89 ng x g(-1) (65.25 ng x g(-1)), 4.00-68.04 ng x g(-1) (22.67 ng x g(-1)) respectively. In comparison with international cities, Pd and Rh concentrations in Beijing road dust were middle level and Pt concentration was lower. Pd concentration was rapidly increased in recent years. The concentrations of PGEs in four locations of the second ring road were arranged in the following order: West approximately East > North > South, which were controlled with the traffic intensity. Size partitioning indicated that the 0.125-0.25 mm fraction had the higher PGEs concentrations than other fractions and the < 0.063 mm fraction had the lower PGEs concentration. These data suggest that autocatalyst PGEs flux estimates into the environment will be significantly underestimated if only a fine grain size fraction (< 0.063 mm) is analyzed. PMID:21634172

  17. Smoothed particle hydrodynamics and element bending group modeling of flexible fibers interacting with viscous fluids.

    PubMed

    Yang, Xiufeng; Liu, Moubin; Peng, Shiliu

    2014-12-01

    This paper presents a smoothed particle hydrodynamics (SPH) and element bending group (EBG) coupling method for modeling the interaction of flexible fibers with moving viscous fluids. SPH is a well-developed mesh-free particle method for simulating viscous fluid flows. EBG is also a particle method for modeling flexible bodies. The interaction of flexible fibers with moving viscous fluids is rendered through the interaction of EBG particles for flexible fiber and SPH particles for fluid. In numerical simulation, flexible fibers of different lengths are immersed in a moving viscous fluid driven by a body force. The drag force on the fiber obtained from SPH-EBG simulation agrees well with experimental observations. It is shown that the flexible fiber demonstrates three typical bending modes, including the U-shaped mode, the flapping mode, and the closed mode, and that the flexible fiber experiences a drag reduction due to its reconfiguration by bending. It is also found that the U4/3 drag scaling law for a flexible fiber is only valid for the U-shaped mode, but not valid for the flapping and closed modes. The results indicate that the reconfiguration of a flexible fiber is caused by the fluid force acting on it, while vortex shedding is of importance in the translations of bending modes. PMID:25615191

  18. Potential mobilization of platinum-group elements by siderophores in surface environments.

    PubMed

    Dahlheimer, Susan R; Neal, Clive R; Fein, Jeremy B

    2007-02-01

    The emission of platinum-group elements (PGEs) from catalytic converters has led to increased environmental abundances of Pt, Pd, and Rh; however, little is known about the environmental effects and fate of these metals. Organic ligands found in soils have the potential to increase the mobility of PGEs and potentially increase the bioavailability of the metals. Here, we assessed the abilities of microbially produced iron-chelating ligands (siderophores) to complex with the PGEs. Batch experiments using the synthetic siderophore desferrioxamine-B (DFO-B) and powdered metal or oxide forms of Pt, Pd, or Rh showed that DFO-B enhances the solubility of Pt and Pd due to the formation of Pt- and Pd-DFO-B aqueous complexes, with estimated minimum stability constants on the order of 10(17-18) and 10(20-24), respectively. Dissolution rates for Pd are comparable to other mineral dissolution rates with DFO-B. DFO-B had little to no effect on the dissolution of Rh metal or Rh2O3. Our results indicate that siderophores have the potential to increase the mobility of Pt and Pd in environments with limited activities of free trivalent cations. These results have implications for the fate of catalytic converter-emitted Pt and Pd, and support the need for further Pt and Pd toxicity and bioaccumulation studies. PMID:17328196

  19. Structure and magnetism in novel group IV element-based magnetic materials

    SciTech Connect

    Tsui, Frank

    2013-08-14

    The project is to investigate structure, magnetism and spin dependent states of novel group IV element-based magnetic thin films and heterostructures as a function of composition and epitaxial constraints. The materials systems of interest are Si-compatible epitaxial films and heterostructures of Si/Ge-based magnetic ternary alloys grown by non-equilibrium molecular beam epitaxy (MBE) techniques, specifically doped magnetic semiconductors (DMS) and half-metallic Heusler alloys. Systematic structural, chemical, magnetic, and electrical measurements are carried out, using x-ray microbeam techniques, magnetotunneling spectroscopy and microscopy, and magnetotransport. The work is aimed at elucidating the nature and interplay between structure, chemical order, magnetism, and spin-dependent states in these novel materials, at developing materials and techniques to realize and control fully spin polarized states, and at exploring fundamental processes that stabilize the epitaxial magnetic nanostructures and control the electronic and magnetic states in these complex materials. Combinatorial approach provides the means for the systematic studies, and the complex nature of the work necessitates this approach.

  20. Photochemistry and charge transfer chemistry of the platinum group elements. Progress report, May 1, 1991--April 30, 1992

    SciTech Connect

    Eisenberg, R.

    1991-12-01

    Significant progress has been made on the photochemistry and photophysics of platinum group element dithiolate complexes. The specific systems under investigation are square planar complexes of Pt(II) containing a dithiolate chelate and two other donor groups to complete the coordination sphere. The donor groups may be amines, imines, phosphines, phosphites or olefins, and they can be either monodentate or joined together as part of a chelate ring.

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

    NASA Technical Reports Server (NTRS)

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

    2002-01-01

    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.

  2. Study on 12kV outdoor vacuum switch with replaceable HRC element drop out fuse

    SciTech Connect

    Wang Jiimei

    1996-12-31

    A new type of vacuum interrupter for 12kV outdoor vacuum switch was experimentally studied, the envelope of which was made of porcelain with petticoat flange for outdoor insulation. In order to produce an axial magnetic field and improve the capacity of transfer current in the vacuum interrupter, an iron plate of horse-shoe construction ingeniously designed was chosen as an electrode. The drop-out fuse with replaceable sand-filled HRC element in series with the vacuum switch is a new conception of design to increase breaking capacity. However, it is a vacuum switch of newly designed to form {open_quotes}a vacuum switch and drop-out type fuse combination{close_quotes}.

  3. On-line gas phase chromatography of the bromides of the group 4, 5, and 6 elements

    SciTech Connect

    Sylwester, E.R.; Gregorich, K.E.; Lee, D.M.; Chung, Y.H.

    1997-12-31

    Gas phase chromatography has been used to determine the volatility of bromides of the group 4, 5, and 6 elements, including the transactinides 104 (Rf) and 105 (Ha). The Heavy Element Volatility Instrument (HEVI) was used to measure the volatilities of the bromides of short-lived isotopes of these elements. Adsorption enthalpy values were calculated from the observed volatilities using a Monte Carlo program. The values for RfBr{sub 4} and HaBr{sub 5} are similar to ZrBr{sub 4} and NbBr{sub 5} rather than to HfBr{sub 4} and TaBr{sub 5}. This deviates from a simple extrapolation from periodic table trends and may indicate the influence of relativistic effects on the electronic level structure of these transactinides. The group 6 element Seaborgium (Sg) has not yet been studied due to the low production cross-section.

  4. High salinity volatile phases in magmatic Ni-Cu-platinum group element deposits

    NASA Astrophysics Data System (ADS)

    Hanley, J. J.; Mungall, J. E.

    2004-12-01

    The role of "deuteric" fluids (exsolved magmatic volatile phases) in the development of Ni-Cu-PGE (platinum group element) deposits in mafic-ultramafic igneous systems is poorly understood. Although considerable field evidence demonstrates unambiguously that fluids modified most large primary Ni-Cu-PGE concentrations, models which hypothesize that fluids alone were largely responsible for the economic concentration of the base and precious metals are not widely accepted. Determination of the trace element composition of magmatic volatile phases in such ore-forming systems can offer considerable insight into the origin of potentially mineralizing fluids in such igneous environments. Laser ablation ICP-MS microanalysis allows researchers to confirm the original metal budget of magmatic volatile phases and quantify the behavior of trace ore metals in the fluid phase in the absence of well-constrained theoretical or experimental predictions of ore metal solubility. In this study, we present new evidence from major deposits (Sudbury, Ontario, Canada; Stillwater Complex, Montana, U.S.A.) that compositionally distinct magmatic brines and halide melt phases were exsolved from crystallizing residual silicate melt and trapped within high-T fluid conduits now comprised of evolved rock compositions (albite-quartz graphic granite, orthoclase-quartz granophyre). Petrographic evidence demonstrates that brines and halide melts coexisted with immiscible carbonic phases at the time of entrapment (light aliphatic hydrocarbons, CO2). Brine and halide melt inclusions are rich in Na, Fe, Mn, K, Pb, Zn, Ba, Sr, Al and Cl, and homogenize by either halite dissolution at high T ( ˜450-700° C) or by melting of the salt phase (700-800° C). LA-ICPMS analyses of single inclusions demonstrate that high salinity volatile phases contained abundant base metals (Cu, Fe, Sn, Bi) and precious metals (Pt, Pd, Au, Ag) at the time of entrapment. Notably, precious metal concentrations in the inclusions

  5. Platinum-group elements: quantification in collected exhaust fumes and studies of catalyst surfaces.

    PubMed

    Palacios, M A; Gómez, M M; Moldovan, M; Morrison, G; Rauch, S; Mcleod, C; Ma, R; Laserna, J; Lucena, P; Caroli, S; Alimonti, A; Petrucci, F; Bocca, B; Schramel, P; Lustig, S; Zischka, M; Wass, U; Stenbom, B; Luna, M; Saenz, J C; Santamaría, J; Torrens, J M

    2000-07-20

    Automotive catalytic converters, in which Pt, Pd and Rh (platinum-group elements; PGEs) are the active components for eliminating several noxious components from exhaust fumes, have become the main source of environmental urban pollution by PGEs. This work reports on the catalyst morphology through changes in catalyst surface by scanning electron microscopy/energy dispersive X-ray spectroscopy (SEM/EDX) and laser-induced breakdown spectrometry (LIBS) from fresh to aged catalytic converters. The distribution of these elements in the fresh catalysts analysed (Pt-Pd-Rh gasoline catalyst) is not uniform and occurs mainly in a longitudinal direction. This heterogeneity seems to be greater for Pt and Pd. PGEs released by the catalysts, fresh and aged 30,000 km, were studied in parallel. Whole raw exhaust fumes from four catalysts of three different types were also examined. Two of these were gasoline catalysts (Pt-Pd Rh and Pd-Rh) and the other two were diesel catalysts (Pt). Samples were collected following the 91,441 EUDC driving cycle for light-duty vehicle testing. The results show that at 0 km the samples collected first have the highest content of particulate PGEs and although the general tendency is for the release to decrease with increasing number of samples taken, exceptions are frequent. At 30,000 km the released PGEs in gasoline and diesel catalysts decreased significantly. For fresh gasoline catalysts the mean of the total amount released was approximately 100, 250 and 50 ng km(-1) for Pt, Pd and Rh, respectively. In diesel catalysts the Pt release varied in the range 400-800 ng km-1. After ageing the catalysts up to 30,000 km, the gasoline catalysts released amounts of Pt between 6 and 8 ng km(-1), Pd between 12 and 16 ng km(-1) and Rh between 3 and 12 ng km(-1). In diesel catalysts the Pt release varied in the range 108-150 ng km(-1). The soluble portion of PGEs in the HNO3 collector solution represented less than 5% of the total amount for fresh catalysts

  6. Photometric elements, apsidal motion, and the third body in the eclipsing binary V974 Cyg

    NASA Astrophysics Data System (ADS)

    Kuznetsov, M. V.; Khaliullin, Kh. F.; Khaliullina, A. I.; Metlov, V. G.; Mossakovskaya, L. V.

    2011-11-01

    We have derived the first photoelectric light curve of the eclipsing binary V974 Cyg from our own photoelectric observations. Analysis of the light curve has yielded the system's photometric elements ( r 1 ≈ r 2 = 0.1192, e = 0.058, L 1 ≈ L 2 = 0.486, and L 3 = 0.028) and absolute parameters ( M 1 ≈ M 2 = 2.2 M ⊙, T eff,1 ≈ T eff,2 = 9500 K, a = 15.0 R ⊙, distance d = 1.29 kpc, age log t = 8.0, t/tMS = 0.11). We have detected apsidal motion with the period U obs = (1140 ± 170) yrs, and the presence of a third body in the system. The orbital parameters derived for the third body are P 3 = 26.5 yrs, e 3 = 0.78, and a 3 sin i 3 = 1.5 AU; and the lower limit for its mass is M 3 > 0.58 M ⊙. The observed apsidal-motion rate is higher than is expected theoretically by a factor of 1.5. The axial rotation of the system's components is not yet synchronized with the orbital motion, probably because V974 Cyg is relatively young and detached.

  7. Calculating three loop ladder and V-topologies for massive operator matrix elements by computer algebra

    NASA Astrophysics Data System (ADS)

    Ablinger, J.; Behring, A.; Blümlein, J.; De Freitas, A.; von Manteuffel, A.; Schneider, C.

    2016-05-01

    Three loop ladder and V-topology diagrams contributing to the massive operator matrix element AQg are calculated. The corresponding objects can all be expressed in terms of nested sums and recurrences depending on the Mellin variable N and the dimensional parameter ε. Given these representations, the desired Laurent series expansions in ε can be obtained with the help of our computer algebra toolbox. Here we rely on generalized hypergeometric functions and Mellin-Barnes representations, on difference ring algorithms for symbolic summation, on an optimized version of the multivariate Almkvist-Zeilberger algorithm for symbolic integration, and on new methods to calculate Laurent series solutions of coupled systems of differential equations. The solutions can be computed for general coefficient matrices directly for any basis also performing the expansion in the dimensional parameter in case it is expressible in terms of indefinite nested product-sum expressions. This structural result is based on new results of our difference ring theory. In the cases discussed we deal with iterative sum- and integral-solutions over general alphabets. The final results are expressed in terms of special sums, forming quasi-shuffle algebras, such as nested harmonic sums, generalized harmonic sums, and nested binomially weighted (cyclotomic) sums. Analytic continuations to complex values of N are possible through the recursion relations obeyed by these quantities and their analytic asymptotic expansions. The latter lead to a host of new constants beyond the multiple zeta values, the infinite generalized harmonic and cyclotomic sums in the case of V-topologies.

  8. Elemente der beiden W-UMa-Sterne GSC 0424-0792 (Brh V62) und GSC 1721-1591 (Brh V127)

    NASA Astrophysics Data System (ADS)

    Bernhard, Klaus; Frank, Peter; Moschner, Wolfgang

    2011-01-01

    CCD observations and ASAS-3 data of GSC 0424-0792 (Brh V62) and GSC 1721-1591 (Brh V127) lead to the following elements and types of variability: GSC 0424-0792: HJD (MinI)= 2453142.489(5)+ E*1.182336(1), type: WUMa GSC 1721-1591: HJD (MinI)= 2455429.5086(4)+E*0.3188963(1), type: WUMa

  9. Therapeutic elements in a self-management approach: experiences from group participation among people suffering from chronic pain

    PubMed Central

    Furnes, Bodil; Natvig, Gerd Karin; Dysvik, Elin

    2014-01-01

    Objective Chronic pain is a complex, multifaceted subjective experience that involves the whole person. Self-management is the dynamic and continuous process of adapting one’s situation to the cognitive, behavioral, and emotional responses necessary to maintain a satisfactory quality of life. Approaches based on cognitive behavioral therapy (CBT) are described as appropriate in assisting people suffering from chronic pain because they challenge maladaptive beliefs and behaviors in relation to pain. This study aimed to explore patients’ experiences of therapeutic elements from group participation in a chronic pain management program. Methods A qualitative research design with a phenomenological hermeneutic approach was used. Six months after participation in the 8-week course, 34 participants formulated and submitted written reports based on open-ended questions related to their group participation and self-help achievement. These reports were analyzed by elements of qualitative content analysis. Results The analysis resulted in two subthemes: “The significance of active involvement in gaining new insight” and “The significance of community and group support.” These were abstracted in the main theme: “Successful self-management is related to several significant contributions in the group.” Conclusion An active role with writing, self-revelation, and exchanges of thoughts and feelings in the group seemed to be the key tools for success. In addition, group support and access to other group members’ experiences were significant therapeutic elements. We suggest that successful self-management requires knowledge of essential therapeutic elements. In a CBT-based group approach, such elements may offer an important health care contribution. PMID:25170253

  10. Bismuth nano-droplets for group-V based molecular-beam droplet epitaxy

    NASA Astrophysics Data System (ADS)

    Li, C.; Zeng, Z. Q.; Fan, D. S.; Hirono, Y.; Wu, J.; Morgan, T. A.; Hu, X.; Yu, S. Q.; Wang, Zh. M.; Salamo, G. J.

    2011-12-01

    Self-assembly of bismuth droplets at nanoscale on GaAs(100) surface using molecular beam epitaxy was demonstrated. Fine control of density and size was achieved by varying growth temperature and total bismuth deposition. Droplet density was tuned by roughly 3 orders of magnitude, and the density-temperature dependence was found to be consistent with classical nucleation theory. These results may extend the flexibility of droplet epitaxy by serving as templates for group V based droplet epitaxy, which is in contrast to conventional group III based droplet epitaxy and may encourage nanostructure formation of bismuth-containing materials.

  11. Airborne particulate matter, platinum group elements and human health: a review of recent evidence.

    PubMed

    Wiseman, Clare L S; Zereini, Fathi

    2009-04-01

    Environmental concentrations of the platinum group elements (PGE) platinum (Pt), palladium (Pd) and rhodium (Rh) have been on the rise, due largely to the use of automobile catalytic converters which employ these metals as exhaust catalysts. It has generally been assumed that the health risks associated with environmental exposures to PGE are minimal. More recent studies on PGE toxicity, environmental bioavailability and concentrations in biologically relevant media indicate however that environmental exposures to these metals may indeed pose a health risk, especially at a chronic, subclinical level. The purpose of this paper is to review the most recent evidence and provide an up-to-date assessment of the risks related to environmental exposures of PGE, particularly in airborne particulate matter (PM). This review concludes that these metals may pose a greater health risk than once thought for several reasons. First, emitted PGE may be easily mobilised and solubilised by various compounds commonly present in the environment, thereby enhancing their bioavailability. Second, PGE may be transformed into more toxic species upon uptake by organisms. The presence of chloride in lung fluids, for instance, may lead to the formation of halogenated PGE complexes that have a greater potential to induce cellular damage. Third, a significant proportion of PGE found in airborne PM is present in the fine fraction that been found to be associated with increases in morbidity and mortality. PGE are also a concern to the extent that they contribute to the suite of metals found in fine PM suspected of eliciting a variety of health effects, especially in vulnerable populations. All these factors highlight the need to monitor environmental levels of PGE and continue research on their bioavailability, behaviour, speciation and associated toxicity to enable us to better assess their potential to elicit health effects in humans. PMID:19181366

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

    PubMed

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

    2004-12-01

    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

  13. [Pollution characteristics of platinum group elements in road rust in Xiamen].

    PubMed

    Hong, Zhen-yu; Hong, You-wei; Yin, Li-qian; Chen, Jin-sheng; Chen, Yan-ting; Xu, Ling-ling

    2015-01-01

    With the potential risks for the environment and human health, the concentration and distribution characteristics of platinum group element(PGEs) in road dust in Xiamen city were investigated. Road dust samples were collected from the traffic trunk road, tunnel, tourism area, and industrial area of Xiamen on October 2012. The samples were digested with aqua regia in a microwave assisted digestion system under high pressure condition, separated and purified with cation exchange resin( Dowex AG50W-X8), and the resulting solutions were analyzed by inductively coupled plasma mass spectrometry (ICP-MS). The results showed that the average concentrations(range) of Pd, Pt and Rh in road dust were 246.82 (58.68-765.52) ng x g(-1), 95.45 (42.14-371.36) ng x g(-1) and 51.76 (21.04-119.72) ng x g(-1), respectively, which were two orders of magnitude higher than the background values. Compared with other cities worldwide, the concentrations of Pd, Pt and Rh in road dust in Xiamen were at higher levels. Theconcentrations of PGEs for different functional areas were listed in the following order: tunnel > urban district > industrial area > tourism area, which indicated that their spatial distributions were mainly affected by the traffic intensity. Correlation analysis results showed that concentration of Pd in the urban traffic artery was significantly correlated with Rh, while Pt was not so correlated with Pd and Rh, suggesting that other sources contributed to PGEs in road dust in addition to the vehicle emission. Although motor vehicle traveling was banned in tourist area, the concentration of PGEs was still at a high level. Some of them might originate from the road dust in surrounding area by atmosphere diffusion. PMID:25898678

  14. [Migration and transformation of anthropogenic platinum group elements in environment: a review].

    PubMed

    Li, Pei-Miao; Gao, Xue-Lu

    2012-12-01

    Anthropogenic platinum group elements (PGEs) are widely applied in vehicle exhaust catalytic converters (VECs), industrial catalysts, and pharmaceutics, making the PGEs, especially Pt, Pd, and Rh, become the newly environmental pollutants in some fields. Given the positive correlations between the Pt/Pd and Pt/Rh ratios in various environmental samples and the active components of VECs, the VECs containing PGEs as catalysts are regarded as the primary source of PGEs pollution. Sufficient reports indicated that in the past three decades, there was a significant increase of PGEs concentrations in diverse environmental matrices like airborne particulate matters, aquatic ecosystem components (e.g., river water, rain water, groundwater, seawater, and sediments), soils, road dusts, and organisms. It was generally assumed that anthropogenic PGEs behave in inert manner, and the health risks associated with the environmental exposures to PGEs are minimal. However, the recent studies on PGEs toxicity and environmental bioavailability indicated that once entering environment, anthropogenic PGEs might easily be mobilized and transformed into more toxic forms under the actions of various biogeochemical processes, and thereby, enhanced their bioavailability and posed potential health risks to human beings through food chain. This paper summarized the research results about the sources, distribution, and biogeochemical behaviors of PGEs in various environmental media, and it was considered that to establish the standards of PGEs for human health risks, to develop standard substances of PGEs for environmental measurements, to study the PGEs in the sediments of marginal seas, and to assess the toxicity of PGEs to marine mollusks, the present contamination status of PGEs in foods, and the risks of PGEs to human health would be the hot research topics in the future. PMID:23479898

  15. Strength of the pnicogen bond in complexes involving group Va elements N, P, and As.

    PubMed

    Setiawan, Dani; Kraka, Elfi; Cremer, Dieter

    2015-03-01

    A set of 36 pnicogen homo- and heterodimers, R3E···ER3 and R3E···E′R′3, involving differently substituted group Va elements E = N, P, and As has been investigated at the ωB97X-D/aug-cc-pVTZ level of theory to determine the strength of the pnicogen bond with the help of the local E···E′ stretching force constants k(a). The latter are directly related to the amount of charge transferred from an E donor lone pair orbital to an E′ acceptor σ* orbital, in the sense of a through-space anomeric effect. This leads to a buildup of electron density in the intermonomer region and a distinct pnicogen bond strength order quantitatively assessed via k(a). However, the complex binding energy ΔE depends only partly on the pnicogen bond strength as H,E-attractions, H-bonding, dipole-dipole, or multipole-multipole attractions also contribute to the stability of pnicogen bonded dimers. A variation from through-space anomeric to second order hyperonjugative, and skewed π,π interactions is observed. Charge transfer into a π* substituent orbital of the acceptor increases the absolute value of ΔE by electrostatic effects but has a smaller impact on the pnicogen bond strength. A set of 10 dimers obtains its stability from covalent pnicogen bonding whereas all other dimers are stabilized by electrostatic interactions. The latter are quantified by the magnitude of the local intermonomer bending force constants XE···E′. Analysis of the frontier orbitals of monomer and dimer in connection with the investigation of electron difference densities, and atomic charges lead to a simple rationalization of the various facets of pnicogen bonding. The temperature at which a given dimer is observable under experimental conditions is provided. PMID:25325889

  16. Extra- and intra-cellular accumulation of platinum group elements by the marine microalga, Chlorella stigmatophora.

    PubMed

    Shams, Leyla; Turner, Andrew; Millward, Geoffrey E; Brown, Murray T

    2014-03-01

    To better understand the marine biogeochemistry of the platinum group elements (PGE), Rh(III), Pd(II) and Pt(IV) were added in combination and at ppb concentrations to cultures of the marine microalga, Chlorella stigmatophora, maintained in sea water at 15 °C and under 60 μmol m(-2) s(-1) PAR. The accumulation of PGE was established in short-term (24-h) exposures, and under varying conditions of algal biomass and PGE concentration, and in a longer-term exposure (156-h) by ICP-MS analysis of sea water and nitric acid digests and EDTA washes of the alga. In short-term exposures, and under all conditions, the extent of accumulation by C. stigmatophora was in the order: Rh > Pd > Pt; and Pd was internalised (or resistant to EDTA extraction) to a considerably greater extent than Rh and Pt. Accumulation isotherms were quasi-linear up to added PGE concentrations of 30 μg L(-1) and all metals displayed a significant reduction in accumulation on a weight-normalised basis with increasing density (biomass) of C. stigmatophora, an effect attributed to the production of exudates able to stabilise metals in sea water through complexation. In the longer-term exposure, kinetic constraints on the reactivities of Rh and, in particular, Pt, resulted in final degrees of accumulation and internalisation by C. stigmatophora that were greatest for Rh and similar between Pd and Pt. Among the PGE, therefore, Rh is predicted to participate in biological removal and transport processes in the marine environment to the greatest extent while decoupling in the biogeochemistries of Pd and Pt is predicted in shorter-term or more transient processes. PMID:24268058

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

    DOEpatents

    Alivisatos, A. Paul; Peng, Xiaogang; Manna, Liberato

    2001-01-01

    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.

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

    NASA Astrophysics Data System (ADS)

    Ishizuka, Shogo; Akimoto, Katsuhiro

    2004-11-01

    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.

  19. Passion, containment, and commitment-essential elements of groups across the lifespan in Bruce Springsteen's work.

    PubMed

    Mangione, Lorraine

    2012-10-01

    The group, with its intensity, interaction, roles and dynamics, is an important unit of experience in everyday life, in psychotherapy groups, and in Bruce Springsteen's music. This paper explores experiences of and ideas about real life groups throughout the lifecycle through Springsteen's music, framed in concepts from a broad group literature including clinical psychology, social psychology, group psychotherapy, sociology, anthropology, and organizational psychology. The lifecycle includes adolescence and the role of the group to contain all its passions; the work world with its excitements and disillusionments; encounters with loss, and the holding power of the group; experiences of dissolution of the group, and possibilities for recommitment; and the passion and support of the group during celebrations. Themes of passion, containment, and commitment weave throughout the narrative. PMID:22974151

  20. Theoretical predictions of properties and gas-phase chromatography behaviour of carbonyl complexes of group-6 elements Cr, Mo, W, and element 106, Sg.

    PubMed

    Pershina, V; Anton, J

    2013-05-01

    Fully relativistic, four-component density functional theory electronic structure calculations were performed for M(CO)6 of group-6 elements Cr, Mo, W, and element 106, Sg, with an aim to predict their adsorption behaviour in the gas-phase chromatography experiments. It was shown that seaborgium hexacarbonyl has a longer M-CO bond, smaller ionization potential, and larger polarizability than the other group-6 molecules. This is explained by the increasing relativistic expansion and destabilization of the (n - 1)d AOs with increasing Z in the group. Using results of the calculations, adsorption enthalpies of the group-6 hexacarbonyls on a quartz surface were predicted via a model of physisorption. According to the results, -ΔHads should decrease from Mo to W, while it should be almost equal--within the experimental error bars--for W and Sg. Thus, we expect that in the future gas-phase chromatography experiments it will be almost impossible--what concerns ΔHads--to distinguish between the W and Sg hexacarbonyls by their deposition on quartz. PMID:23656128

  1. Theoretical predictions of properties and gas-phase chromatography behaviour of carbonyl complexes of group-6 elements Cr, Mo, W, and element 106, Sg

    NASA Astrophysics Data System (ADS)

    Pershina, V.; Anton, J.

    2013-05-01

    Fully relativistic, four-component density functional theory electronic structure calculations were performed for M(CO)6 of group-6 elements Cr, Mo, W, and element 106, Sg, with an aim to predict their adsorption behaviour in the gas-phase chromatography experiments. It was shown that seaborgium hexacarbonyl has a longer M-CO bond, smaller ionization potential, and larger polarizability than the other group-6 molecules. This is explained by the increasing relativistic expansion and destabilization of the (n - 1)d AOs with increasing Z in the group. Using results of the calculations, adsorption enthalpies of the group-6 hexacarbonyls on a quartz surface were predicted via a model of physisorption. According to the results, -ΔHads should decrease from Mo to W, while it should be almost equal - within the experimental error bars - for W and Sg. Thus, we expect that in the future gas-phase chromatography experiments it will be almost impossible - what concerns ΔHads - to distinguish between the W and Sg hexacarbonyls by their deposition on quartz.

  2. ROLE OF SURFACE FUNCTIONAL GROUPS IN THE CAPTURE OF ELEMENTAL MERCURY AND MERCURIC CHLORIDE BY ACTIVATED CARBONS

    EPA Science Inventory

    The paper discusses using a laboratory-scale, fixed bed apparatus to study the role of surface functional groups (SFGs) in the capture of mercuric chloride (HgC12) and elemental mercury (Hgo) in nitrogen (N2) prior to flue gas atmosphere studies. The study focused on two activat...

  3. Finite Element Simulation of Machining of Ti6Al4V Alloy

    SciTech Connect

    Rizzuti, S.; Umbrello, D.

    2011-05-04

    Titanium and its alloys are an important class of materials, especially for aerospace applications, due to their excellent combination of strength and fracture toughness as well as low density. However, these materials are generally regarded as difficult to machine because of their low thermal conductivity and high chemical reactivity with cutting tool materials. Moreover, the low thermal conductivity of Titanium inhibits dissipation of heat within the workpiece causing an higher temperature at the cutting edge and generating for higher cutting speed a rapid chipping at the cutting edge which leads to catastrophic failure. In addition, chip morphology significantly influences the thermo-mechanical behaviour at the workpiece/tool interface, which also affects the tool life.In this paper a finite element analysis of machining of TiAl6V4 is presented. In particular, cutting force, chip morphology and segmentation are taken into account due to their predominant roles to determine machinability and tool wear during the machining of these alloys. Results in terms of residual stresses are also presented. Moreover, the numerical results are compared with experimental ones.

  4. JV Task 94 - Air Quality V: Mercury, Trace Elements, SO3, and Particulate Matter Conference

    SciTech Connect

    Thomas A. Erickson

    2007-01-31

    This final report summarizes the planning, preparation, facilitation and production, and summary of the conference entitled 'Air Quality V: Mercury, Trace Elements, SO{sub 3}, and Particulate Matter,' held September 18-21, 2005, in Arlington, Virginia. The goal of the conference was to build on the discussions of the first four Air Quality Conferences, providing further opportunity for leading representatives of industry, government, research institutions, academia, and environmental organizations to discuss the key interrelationships between policy and science shaping near-term regulations and controls and to assist in moving forward on emerging issues that will lead to acceptable programs and policies to protect human health, the environment, and economic growth. The conference was extremely timely, as it was the last large conference prior to publication of the U.S. Environmental Protection Agency's final regulations for mercury control from coal-fired utilities, and provided a forum to realistically assess the status of mercury controls in relation to the new regulations.

  5. Effects of a Low-Element Challenge Course on Abstinence Self-Efficacy and Group Cohesion

    ERIC Educational Resources Information Center

    Clem, Jamie M.; Smith, Thomas E.; Richards, Kristin V.

    2012-01-01

    Substance abuse researchers identify self-efficacy and group cohesion as important components in alcohol and other drug-dependency treatment. Objectives: The purpose of this single-group, pretest-posttest study is to explore the therapeutic value of a challenge course intervention on the self-efficacy and group cohesion of nine chemically…

  6. Main group redox catalysis: reversible P(III)/P(V) redox cycling at a phosphorus platform.

    PubMed

    Dunn, Nicole L; Ha, Minji; Radosevich, Alexander T

    2012-07-18

    A planar, trivalent phosphorus compound is shown to undergo reversible two-electron redox cycling (P(III)/P(V)) enabling its use as catalyst for a transfer hydrogenation reaction. The trivalent phosphorus compound activates ammonia-borane to furnish a 10-P-5 dihydridophosphorane, which in turn is shown to transfer hydrogen cleanly to azobenzene, yielding diphenylhydrazine and regenerating the initial trivalent phosphorus species. This result constitutes a rare example of two-electron redox catalysis at a main group compound and suggests broader potential for this nonmetal platform to support bond-modifying redox catalysis of the type dominated by transition metal catalysts. PMID:22746974

  7. Chemo-dynamical evolution of the Local Group dwarf galaxies: The origin of r-process elements

    NASA Astrophysics Data System (ADS)

    Hirai, Y.; Ishimaru, Y.; Saitoh, T. R.; Fujii, M. S.; Hidaka, J.; Kajino, T.

    2016-06-01

    The r-process elements such as Au, Eu, and U are observed in the extremely metal-poor stars in the Milky Way halo and the Local Group dwarf galaxies. However, the origin of r-process elements has not yet been identified. The abundance of r-process elements of stars in the Local Group galaxies provides clues to clarify early evolutionary history of galaxies. It is important to understand the chemical evolution of the Local Group dwarf galaxies which would be building blocks of the Milky Way. In this study, we perform a series of N-body/smoothed particle hydrodynamic simulations of dwarf galaxies. We show that neutron star mergers can reproduce the observation of r-process elements. We find that the effects of gas mixing processes including metals in the star-forming region of a typical scale of giant molecular clouds ¥sim 10-100 pc play significant roles in the early chemical enrichment of dwarf galaxies. We also find that the star formation rate of ˜ 10^{-3} M_{⊙}yr^{-1} in early epoch (<1 Gyr) of galactic halo evolution is necessary for these results. Our results suggest that neutron star mergers are a major site of r-process.

  8. Survey of chimeric IStron elements in bacterial genomes: multiple molecular symbioses between group I intron ribozymes and DNA transposons

    PubMed Central

    Tourasse, Nicolas J.; Stabell, Fredrik B.; Kolstø, Anne-Brit

    2014-01-01

    IStrons are chimeric genetic elements composed of a group I intron associated with an insertion sequence (IS). The group I intron is a catalytic RNA providing the IStron with self-splicing ability, which renders IStron insertions harmless to the host genome. The IS element is a DNA transposon conferring mobility, and thus allowing the IStron to spread in genomes. IStrons are therefore a striking example of a molecular symbiosis between unrelated genetic elements endowed with different functions. In this study, we have conducted the first comprehensive survey of IStrons in sequenced genomes that provides insights into the distribution, diversity, origin and evolution of IStrons. We show that IStrons have a restricted phylogenetic distribution limited to two bacterial phyla, the Firmicutes and the Fusobacteria. Nevertheless, diverse IStrons representing two major groups targeting different insertion site motifs were identified. This taken with the finding that while the intron components of all IStrons belong to the same structural class, they are fused to different IS families, indicates that multiple intron–IS symbioses have occurred during evolution. In addition, introns and IS elements related to those that were at the origin of IStrons were also identified. PMID:25324310

  9. Calculations of electron stopping powers for 41 elemental solids over the 50 eV to 30 keV range with the full Penn algorithm

    NASA Astrophysics Data System (ADS)

    Shinotsuka, H.; Tanuma, S.; Powell, C. J.; Penn, D. R.

    2012-01-01

    We present mass collision electron stopping powers (SPs) for 41 elemental solids (Li, Be, graphite, diamond, glassy C, Na, Mg, Al, Si, K, Sc, Ti, V, Cr, Fe, Co, Ni, Cu, Ge, Y, Nb, Mo, Ru, Rh, Pd, Ag, In, Sn, Cs, Gd, Tb, Dy, Hf, Ta, W, Re, Os, Ir, Pt, Au, and Bi) that were calculated from experimental energy-loss-function data with the full Penn algorithm for electron energies between 50 eV and 30 keV. Improved sets of energy-loss functions were used for 19 solids. Comparisons were made of these SPs with SPs calculated with the single-pole approximation, previous SP calculations, and experimental SPs. Generally satisfactory agreement was found with SPs from the single-pole approximation for energies above 100 eV, with other calculated SPs, and with measured SPs.

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

    NASA Technical Reports Server (NTRS)

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

    1989-01-01

    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.

  11. First-principles study of monolayer and bilayer honeycomb structures of group-IV elements and their binary compounds

    NASA Astrophysics Data System (ADS)

    Pan, L.; Liu, H. J.; Wen, Y. W.; Tan, X. J.; Lv, H. Y.; Shi, J.; Tang, X. F.

    2011-01-01

    By using first-principles pseudopotential method, we investigate the structural, vibrational, and electronic properties of monolayer and bilayer honeycomb structures of group-IV elements and their binary compounds. It is found that the honeycomb structures of Si, Ge, and SiGe are buckled for stabilization, while those of binary compounds SiC and GeC containing the first row elements C are planar similar to a graphene sheet. The phonon dispersion relations and electronic band structures are very sensitive to the number of layers, the stacking order, and whether the layers are planar or buckled.

  12. Report of the IAU Working Group on Cartographic Coordinates and Rotational Elements of the Planets and Satellites

    USGS Publications Warehouse

    Davies, M.E.; Abalakin, V.K.; Cross, C.A.; Duncombe, R.L.; Masursky, H.; Morando, B.; Owen, T.C.; Seidelmann, P.K.; Sinclair, A.T.; Wilkins, G.A.; Tjuflin, Y.S.

    1980-01-01

    This paper is the entire report of the IAU Working Group on Cartographic Coordinates and Rotational Elements of the Planets and Satellites, including three annexes. Tables give the recemmended values for the directions of the north poles of rotation and the prime meridians of the planets and satellites. Reference surfaces for mapping these bodies are described. The annexes discuss the guiding principles, given in the body of the report, present explanatory notes, and provide a bibliography of the rotational elements and reference surfaces of the planets and satellites, definitions, and algebraic expressions of relevant parameters. ?? 1980 D. Reidel Publishing Co.

  13. Utilizing Prestructured Art Elements in Brief Group Art Therapy with Adolescents.

    ERIC Educational Resources Information Center

    Vick, Randy M.

    1999-01-01

    A decrease in the average stay in mental health programs has changed the delivery of art therapy services. Article presents strategies for utilizing six prestructured art elements (magazine pictures, magazine words, photocopied images, cut and torn paper, traced shapes, and partial drawings) as a means of addressing these trends. Treatment sources…

  14. Cipollone v. Liggett Group, Inc. strengthens federal preemption defense in pesticide tort litigation

    SciTech Connect

    Stevens, R.W.

    1993-12-31

    When the United States Supreme Court held that the Federal Cigarette Labeling and Advertising Act (Cigarette Act) of 1969 preempted plaintiff`s failure to warn claims in Cipollone v. Liggett Group, Inc., the decision directly affected a far wider range of product liability cases than those involving only cigarettes. This article analyzes how Cipollone affects the defense raised in pesticide injury cases that the Federal Insecticide, Fungicide and Rodenticide Act (FIFRA) preempts state common law failure to warn claims. The Eleventh Circuit in Papas v. Upjohn Co. (Papas I), declining to follow contrary authority, held that FIFRA impliedly preempted state law claims that pesticides were inadequately labeled. On a petition for certiorari, the Supreme Court remanded the case back to the Eleventh Circuit for reconsideration in light of Cipollone. Recently, the Eleventh Circuit in Papas v. Upjohn Co. (Papas II) applied Cipollone to hold that FIFRA expressly preempts the state law claims. This article argues that Papas II correctly held, after Cipollone, that FIFRA preempts the state inadequate labeling and failure to warn claims in pesticide cases. 86 refs.

  15. Classroom Exercise That Incorporates Internet Discussion Groups as an Integral Element in a Communication Course.

    ERIC Educational Resources Information Center

    Bruning, Stephen D.

    Responding to the dramatic changes in the style and form of communication, a communication instructor integrated the Internet into his communication courses at a liberal arts college. Students are required to sign up for a discussion group (listserv) that focuses on the course offering as well as a discussion group in their area of interest. Every…

  16. Threat to Valued Elements of Life: The Experience of Dementia across Three Ethnic Groups

    ERIC Educational Resources Information Center

    Lawrence, Vanessa; Samsi, Kritika; Banerjee, Sube; Morgan, Craig; Murray, Joanna

    2011-01-01

    Purpose: There is a fundamental knowledge gap regarding the experience of dementia within minority ethnic groups in the United Kingdom and elsewhere. The present study examined the subjective reality of living with dementia from the perspective of people with dementia within the 3 largest ethnic groups in the United Kingdom. Design and Methods:…

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

    DOEpatents

    Bell, Zane W.; Huei-Ho, Chuen; Brown, Gilbert M.; Hurlbut, Charles

    2003-04-08

    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.

  18. Measurement of the mass attenuation coefficient from 81 keV to 1333 keV for elemental materials Al, Cu and Pb

    NASA Astrophysics Data System (ADS)

    Gjorgieva, Slavica; Barandovski, Lambe

    2016-03-01

    The mass attenuation coefficients (μ/ρ) for 3 high purity elemental materials Al, Cu and Pb were measured in the γ-ray energy range from 81 keV up to 1333 keV using 22Na, 60Co 133Ba and 133Cs as sources of gamma radiation. Well shielded detector (NaI (Tl) semiconductor detector) was used to measure the intensity of the transmitted beam. The measurements were made under condition of good geometry, assuring that any photon absorbed or deflected appreciably does not reach the detector. The measured values are compared with the theoretical ones obtained by Seltzer (1993).

  19. Structure and optical properties of evaporated films of the Cr- and V-group metals

    NASA Technical Reports Server (NTRS)

    Nestell, J. E., Jr.; Christy, R. W.; Cohen, M. H.; Ruben, G. C.

    1980-01-01

    Thin films of Cr, Mo, and W rapidly evaporated in high vacuum (5 x 10 to the -7th torr) onto room-temperature substrates show anomalously low reflectance (compared to bulk samples). From electron and X-ray diffraction and electron microscopy, the normal bcc crystal structure is found, but with very fine grains. Columnar grains about 100 A in diameter were separated by a less dense grain-boundary network about 10-A wide. The measured optical conductivity agrees with an inhomogeneous-medium model that assumes the normal crystalline conductivity for the grain interiors, with model parameters that correlate to the observed columnar grain size. In contrast, V and Nb films rapidly evaporated onto room-temperature substrates have the reflectance of bulk crystalline material. On liquid-nitrogen temperature substrates, however, V and Nb have normal bcc crystal structure but with small flat-plate grains, and the same model, with appropriate parameters, accounts for the optical conductivity. The difference between these two groups apparently depends on residual gases segregated at the grain boundaries in the Cr-group films.

  20. Effects of the s-process on Fe-group elements in meteorites

    NASA Astrophysics Data System (ADS)

    Trippella, O.; Busso, M.; Wasserburg, G. J.; Palmerini, S.; Frondini, F.; Petrelli, M.; Zucchini, A.

    2016-04-01

    In the present paper we investigate the possible connection between s-process nucleosynthesis occurring during the asymptotic giant branch (AGB) phase of low-mass stars (LMS) and the isotopic anomalies of the “Fe-group” elements observed in several macroscopic samples of meteorites or in grains formed as circumstellar condensates (hereafter CIRCONs). The available measurements of chromium, iron, and nickel are well reproduced by stellar models, which account for the largest shifts in the heaviest isotopes of each element: in particular 54Cr, 58Fe, and 64Ni. Moreover, many circumstellar condensates reflect 50Ti excesses and some production of 46, 47, 49Ti, as predicted by slow-neutron captures in AGB stars. Nevertheless, some difficulties are found in comparing theoretical calculations of s-process nucleosynthesis with calcium, silicon, and zinc isotopic anomalies.

  1. Multigram group separation of actinide and lanthanide elements by LiCl-based anion exchange

    SciTech Connect

    Collins, E.D.; Benker, D.E.; Chattin, F.R.; Orr, P.B.; Ross, R.G.

    1980-01-01

    The laboratory-scale LiCl AIX process has been successfully adapted to the multigram scale and has been used effectively in transuranium element production campaigns to separate the lanthanide fission products from the transplutonium actinides and to partition americium and curium from the heavier elements. Corrosion of the tantalum and glass equipment has been negligible. Although radiolytic gas generation has not caused a problem, radiation exposure of the Dowex 1-X10 anion exchange resin does occur significantly. However, the 1.3-L resin bed can be used successfully to process up to 3 batches, each containing 19 g of /sup 244/Cm (54 W of decay heat). The chromatographic elution process is controlled by use of an alpha detector in the column effluent line and by periodic measurement of the neutron profile of the column. The development and use of feed pretreatment and operating methods has enabled effective and dependable operation.

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

    NASA Technical Reports Server (NTRS)

    Holland, L. R.

    1984-01-01

    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.

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

    SciTech Connect

    David A. Dixon; Anthony J. Arduengo, III

    2010-09-30

    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 σ- or π-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

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

    SciTech Connect

    Barbee, T.W. Jr.

    1981-08-01

    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.

  5. Comparison of Stretching Force Constants in Symmetry Coordinates between Td and C3v Point Groups

    NASA Astrophysics Data System (ADS)

    Julian, Maureen M.

    1999-05-01

    In this paper we consider what happens to the force constants of a silicate moiety (SiO4) when the length of one of its bonds is changed. This situation exists in the molecule O3SiObrSiO3, where Obr is the bridging oxygen atom connecting the two SiO3 moieties. The problem is to present a set of force constants such that when the structure of the more symmetric molecule is perturbed, the relevant force constants are also perturbed. Algebraic expressions are derived for the stretching force constants of SiO4 (tetrahedral point group Td) and ObrSiO3 (point group C3v) in symmetry coordinates. This paper is addressed to students and researchers in applied group theory who wish to compare force constants between similar molecules. We assume the reader has some familarity with the group theoretical methods presented by Wilson et al. (Wilson, E. B. Jr.; Decius, J. C.; Cross, P. C. Molecular Vibrations; Dover: New York, 1980). We cannot apply Wilson's method for obtaining symmetry coordinates from internal coordinates directly, as we demonstrate. Instead we must start with the irreducible representations of the symmetries of the moiety with the higher symmetry and then reduce them to the representations of the symmetries of the moiety with the lower symmetry. The symmetry coordinates are calculated for each species in order to factor the secular equation. The matrix representations of the generators of these point groups are a function of the specific symmetry coordinates. Finally, the symmetry coordinates are applied to the force constant matrix and the algebraic results are compared.

  6. A single aldehyde group can serve as a structural element for recognition by transmembrane protein CD36.

    PubMed

    Tsuzuki, Satoshi; Amitsuka, Takahiko; Okahashi, Tatsuya; Kozai, Yuki; Matsumura, Shigenobu; Inoue, Kazuo; Fushiki, Tohru

    2016-07-01

    Transmembrane protein CD36 is considered to bind its distinct ligands such as long-chain fatty acids primarily by recognizing their terminal carboxyl moiety. In this study, we provide evidence that long-chain fatty aldehydes, such as oleic aldehyde, can be recognized by CD36. We suggest that a single aldehyde group may also serve as one of the structural elements recognizable by CD36. PMID:26923548

  7. Comparison between steady-state and dynamic I-V measurements from a single-cell thermionic fuel element

    SciTech Connect

    Wernsman, B.

    1997-01-01

    A comparison between steady-state and dynamic I-V measurements from a single-cell thermionic fuel element (TFE) is made. The single-cell TFE used in this study is the prototype for the 40kW{sub e} space nuclear power system that is similar to the 6kW{sub e} TOPAZ-II. The steady-state I-V measurements influence the emitter temperature due to electron cooling. Therefore, to eliminate the steady-state I-V measurement influence on the TFE and provide a better understanding of the behavior of the thermionic energy converter and TFE characteristics, dynamic I-V measurements are made. The dynamic I-V measurements are made at various input power levels, cesium pressures, collector temperatures, and steady-state current levels. From these measurements, it is shown that the dynamic I-V{close_quote}s do not change the TFE characteristics at a given operating point. Also, the evaluation of the collector work function from the dynamic I-V measurements shows that the collector optimization is not due to a minimum in the collector work function but due to an emission optimization. Since the dynamic I-V measurements do not influence the TFE characteristics, it is believed that these measurements can be done at a system level to understand the influence of TFE placement in the reactor as a function of the core thermal distribution. {copyright} {ital 1997 American Institute of Physics.}

  8. Comparison between steady-state and dynamic I-V measurements from a single-cell thermionic fuel element

    SciTech Connect

    Wernsman, Bernard

    1997-01-10

    A comparison between steady-state and dynamic I-V measurements from a single-cell thermionic fuel element (TFE) is made. The single-cell TFE used in this study is the prototype for the 40 kW{sub e} space nuclear power system that is similar to the 6 kW{sub e} TOPAZ-II. The steady-state I-V measurements influence the emitter temperature due to electron cooling. Therefore, to eliminate the steady-state I-V measurement influence on the TFE and provide a better understanding of the behavior of the thermionic energy converter and TFE characteristics, dynamic I-V measurements are made. The dynamic I-V measurements are made at various input power levels, cesium pressures, collector temperatures, and steady-state current levels. From these measurements, it is shown that the dynamic I-V's do not change the TFE characteristics at a given operating point. Also, the evaluation of the collector work function from the dynamic I-V measurements shows that the collector optimization is not due to a minimum in the collector work function but due to an emission optimization. Since the dynamic I-V measurements do not influence the TFE characteristics, it is believed that these measurements can be done at a system level to understand the influence of TFE placement in the reactor as a function of the core thermal distribution.

  9. Irradiation and examinations of the second group of thermionic fuel element insulators (UCA-2)

    NASA Astrophysics Data System (ADS)

    Lawrence, Leo A.; Ard, Kevin E.; Veca, Anthony R.; Giraldez, Emilio M.

    1991-01-01

    Thermionic fuel element sheaths, seal and intercell insulators, and end restraints were irradiated in a fast neutron spectrum and examined. Samples were irradiated at temperatures ranging from 1110 K to 1200 K to fast fluences from 3.4×1022 n/cm2 to 6.0×1022 n/cm2. Sample examinations included visual, photographic, dimensional, electrical resistance to temperatures of 1175 K, helium leak rates, and metallography. Examinations of the end restraints and intercell insulators, which were limited to visual and photographic examination, showed no adverse effects from the irradiation. Alumina and yttria have been identified as insulator materials which meet design requirements.

  10. Superlattices of group IV elements, a new possibility to produce direct band gap material

    NASA Astrophysics Data System (ADS)

    Kasper, E.

    1991-01-01

    Consideration is given to the diamond lattice type group IV semiconductors C, SiC, Si and Ge, which exhibit an indirect band gap with the conduction band minimum outside the Brillouin zone center. Ultrathin superlattices are predicted to convert the indirect band gap into a quasi-direct one under certain circumstances. Attention is also given to the growth of Si/Ge strained monolayer superlattices (SMS) by molecular beam epitaxy and experimental results obtained with these structures. The existing investigations of Si/Ge SMS have shown folded quasi-direct conditions in group IV superlattices.

  11. Hybrid in situ replacement for Samson group V Staphylococcus aureus aortic graft infection.

    PubMed

    Karpenko, A A; Ignatenko, P V; Beliaev, A M

    2013-01-01

    Aortic prosthesis replacements including extra-anatomical bypass procedures, in situ revascularisations with the neoaortoiliac system, antibiotic bounded prostheses or allogeneic grafts have high graft reinfection rates. We described a case of a 68-year-old man with Samson group V Staphylococcus aureus infection of his aortobifemoral graft. He underwent an explantation of the infected graft, wound debridement and a hybrid in situ allogeneic aortoiliofemoral replacement. During surgery one of the limbs of the cryopreserved human aortic allogeneic graft was anastomosed with the endarterectomised left common iliac artery, which later was angioplastied and stented. The closed system Jackson-Pratt drains were used to prevent perigraft fluid collection. The groin wound was treated with the vacuum-assisted closure dressing. On review in 6 months he remained symptom free. We conclude that a hybrid management of infected aortic prosthesis may reduce graft reinfection. PMID:23897382

  12. Hybrid in situ replacement for Samson group V Staphylococcus aureus aortic graft infection

    PubMed Central

    Karpenko, A A; Ignatenko, P V; Beliaev, A M

    2013-01-01

    Aortic prosthesis replacements including extra-anatomical bypass procedures, in situ revascularisations with the neoaortoiliac system, antibiotic bounded prostheses or allogeneic grafts have high graft reinfection rates. We described a case of a 68-year-old man with Samson group V Staphylococcus aureus infection of his aortobifemoral graft. He underwent an explantation of the infected graft, wound debridement and a hybrid in situ allogeneic aortoiliofemoral replacement. During surgery one of the limbs of the cryopreserved human aortic allogeneic graft was anastomosed with the endarterectomised left common iliac artery, which later was angioplastied and stented. The closed system Jackson-Pratt drains were used to prevent perigraft fluid collection. The groin wound was treated with the vacuum-assisted closure dressing. On review in 6 months he remained symptom free. We conclude that a hybrid management of infected aortic prosthesis may reduce graft reinfection. PMID:23897382

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

    NASA Technical Reports Server (NTRS)

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

    1979-01-01

    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.

  14. Strain induced topological phase transitions in monolayer honeycomb structures of group-V binary compounds

    PubMed Central

    Nie, Yaozhuang; Rahman, Mavlanjan; Wang, Daowei; Wang, Can; Guo, Guanghua

    2015-01-01

    We present first-principles calculations of electronic structures of a class of two-dimensional (2D) honeycomb structures of group-V binary compounds. Our results show these new 2D materials are stable semiconductors with direct or indirect band gaps. The band gap can be tuned by applying lattice strain. During their stretchable regime, they all exhibit metal-indirect gap semiconductor-direct gap semiconductor-topological insulator (TI) transitions with increasing strain from negative (compressive) to positive (tensile) values. The topological phase transition results from the band inversion at the Γ point which is due to the evolution of bonding and anti-bonding states under lattice strain. PMID:26656257

  15. Multiple bonds between transition metals and main-group elements. 73. Synthetic routes to rhenium(V) alkyl and rhenium(VII) alkylidyne complexes. X-ray crystal structures of (. eta. sup 5 -C sub 5 Me sub 5 )Re( double bond O)(CH sub 3 )(CH sub 2 C(CH sub 3 ) sub 3 ) and (. eta. sup 5 -C sub 5 Me sub 5 )(Br) sub 3 Re triple bond CC(CH sub 3 ) sub 3

    SciTech Connect

    Herrmann, W.A.; Felixberger, J.K.; Anwander, R.; Herdtweck, E.; Kiprof, P.; Riede, J. )

    1990-05-01

    Dialkyloxo({eta}{sup 5}pentamethylcyclopentadienyl)rhenium(V) complexes ({eta}{sup 5}-C{sub 5}Me{sub 5})Re({double bond}O)(CH{sub 3})R{prime}(R{prime} = C{sub 2}H{sub 5}, CH{sub 2}Si(CH{sub 3}){sub 3}, CH{sub 2}C(CH{sub 3}){sub 3}), 1c-e, have become accessible through alkylation of ({eta}{sup 5}-C{sub 5}Me{sub 5})Re({double bond}O)(Cl)(CH{sub 3}) (7) with R{prime}MgCl. 1c-e are the first rhenium complexes containing different alkyl ligands. The neopentyl derivative 1e (R{prime} = CH{sub 2}C(CH{sub 3}){sub 3}) crystallizes in the orthorhombic space group Pbca with a = 960.7 (2), b = 2.844.5 (4), c = 1,260.7 (2) pm, and Z = 8. The X-ray crystal structure was refined to R{sub W} = 3.9%. The chiral molecule shows a distorted tetrahedral geometry around the rhenium center. The tribromide 3b has been structurally characterized. Brown crystals of 3b belong to space group P2{sub 1}/c with unit cell dimensions a = 1,311.5 (2), b = 723.0 (1), c = 1,901.6 (2) pm, {beta} = 92.68 (1){degree}, and Z = 4. The structure exhibits a four-legged piano stool geometry with no trans influence of the neopentylidyne ligand to the bromine atom.

  16. Which Social Elements Are Visible in Virtual Groups? Addressing the Categorization of Social Expressions

    ERIC Educational Resources Information Center

    Perez-Mateo, M.; Guitert, M.

    2012-01-01

    Learning is a social process. That is why it is extremely important to understand how students interact socially in online courses and how it affects the learning process. However, social aspects, understood as those expressions or comments that go beyond strictly academic interaction, i.e. the need to carry out group work, are not clearly…

  17. Crystal Field Theory and the Angular Overlap Model Applied to Hydrides of Main Group Elements.

    ERIC Educational Resources Information Center

    Moore, E. A.

    1990-01-01

    Described is how crystal field theory and the angular overlap model can be applied to very simple molecules which can then be used to introduce such concepts as bonding orbitals, MO diagrams, and Walsh diagrams. The main-group compounds are used as examples and a switch to the transition metal complexes. (KR)

  18. Functionalization of phosphorescent emitters and their host materials by main-group elements for phosphorescent organic light-emitting devices.

    PubMed

    Yang, Xiaolong; Zhou, Guijiang; Wong, Wai-Yeung

    2015-12-01

    Phosphorescent organic light-emitting devices (OLEDs) have attracted increased attention from both academic and industrial communities due to their potential practical application in high-resolution full-color displays and energy-saving solid-state lightings. The performance of phosphorescent OLEDs is mainly limited by the phosphorescent transition metal complexes (such as iridium(III), platinum(II), gold(III), ruthenium(II), copper(I) and osmium(II) complexes, etc.) which can play a crucial role in furnishing efficient energy transfer, balanced charge injection/transporting character and high quantum efficiency in the devices. It has been shown that functionalized main-group element (such as boron, silicon, nitrogen, phosphorus, oxygen, sulfur and fluorine, etc.) moieties can be incorporated into phosphorescent emitters and their host materials to tune their triplet energies, frontier molecular orbital energies, charge injection/transporting behavior, photophysical properties and thermal stability and hence bring about highly efficient phosphorescent OLEDs. So, in this review, the recent advances in the phosphorescent emitters and their host materials functionalized with various main-group moieties will be introduced from the point of view of their structure-property relationship. The main emphasis lies on the important role played by the main-group element groups in addressing the key issues of both phosphorescent emitters and their host materials to fulfill high-performance phosphorescent OLEDs. PMID:26245654

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

    USGS Publications Warehouse

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

    1984-01-01

    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.

  20. Siderophile element systematics of IAB complex iron meteorites: New insights into the formation of an enigmatic group

    NASA Astrophysics Data System (ADS)

    Worsham, Emily A.; Bermingham, Katherine R.; Walker, Richard J.

    2016-09-01

    Siderophile trace element abundances and the 187Re-187Os isotopic systematics of the metal phases of 58 IAB complex iron meteorites were determined in order to investigate formation processes and how meteorites within chemical subgroups may be related. Close adherence of 187Re-187Os isotopic data of most IAB iron meteorites to a primordial isochron indicates that the siderophile elements of most members of the complex remained closed to elemental disturbance soon after formation. Minor, presumably late-stage open-system behavior, however, is observed in some members of the sLM, sLH, sHL, and sHH subgroups. The new siderophile element abundance data are consistent with the findings of prior studies suggesting that the IAB subgroups cannot be related to one another by any known crystallization process. Equilibrium crystallization, coupled with crystal segregation, solid-liquid mixing, and subsequent fractional crystallization can account for the siderophile element variations among meteorites within the IAB main group (MG). The data for the sLM subgroup are consistent with equilibrium crystallization, combined with crystal segregation and mixing. By contrast, the limited fractionation of siderophile elements within the sLL subgroup is consistent with metal extraction from a chondritic source with little subsequent processing. The limited data for the other subgroups were insufficient to draw robust conclusions about crystallization processes involved in their formation. Collectively, multiple formational processes are represented in the IAB complex, and modeling results suggest that fractional crystallization within the MG may have been a more significant process than has been previously recognized.

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

    NASA Astrophysics Data System (ADS)

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

    1986-07-01

    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.

  2. Division IX / Commission 30 / Working Group Catalog of Orbital Elements of Spectroscopic Binaries

    NASA Astrophysics Data System (ADS)

    Pourbaix, Dimitri; Young, Andrew T.; Batten, Alan H.; Fekel, Francis C.; Hartkopf, William I.; Levato, Hugo; Morrell, Nidia I.; Tokovinin, Andrei A.; Torres, Guillermo; Udry, Stepane

    The SB9 Working Group of Commission 30 aims at compiling the 9th Catalogue of Orbits of Spectroscopic Binaries. By definition, this is a never ending task as orbits of newly discovered systems keep appearing in the literature. Despite this, the working group tries to catch up with the delay as nothing was done in between 1989 when the 8th catalogue by Batten et al. and 2000 when the WG was settled. In 2006, at its business meeting, the WG decided to focus on the completeness of systems rather than on completeness of orbits. If the latter is a valuable objective, only the former is useful to any statistical investigation of spectroscopic binaries.

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

    PubMed Central

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

    1997-01-01

    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. PMID:9071584

  4. Transfer of scarlet fever-associated elements into the group A Streptococcus M1T1 clone

    PubMed Central

    Ben Zakour, Nouri L.; Davies, Mark R.; You, Yuanhai; Chen, Jonathan H. K.; Forde, Brian M.; Stanton-Cook, Mitchell; Yang, Ruifu; Cui, Yujun; Barnett, Timothy C.; Venturini, Carola; Ong, Cheryl-lynn Y.; Tse, Herman; Dougan, Gordon; Zhang, Jianzhong; Yuen, Kwok-Yung; Beatson, Scott A.; Walker, Mark J.

    2015-01-01

    The group A Streptococcus (GAS) M1T1 clone emerged in the 1980s as a leading cause of epidemic invasive infections worldwide, including necrotizing fasciitis and toxic shock syndrome123. Horizontal transfer of mobile genetic elements has played a central role in the evolution of the M1T1 clone45, with bacteriophage-encoded determinants DNase Sda16 and superantigen SpeA27 contributing to enhanced virulence and colonization respectively. Outbreaks of scarlet fever in Hong Kong and China in 2011, caused primarily by emm12 GAS8910, led to our investigation of the next most common cause of scarlet fever, emm1 GAS89. Genomic analysis of 18 emm1 isolates from Hong Kong and 16 emm1 isolates from mainland China revealed the presence of mobile genetic elements associated with the expansion of emm12 scarlet fever clones1011 in the M1T1 genomic background. These mobile genetic elements confer expression of superantigens SSA and SpeC, and resistance to tetracycline, erythromycin and clindamycin. Horizontal transfer of mobile DNA conferring multi-drug resistance and expression of a new superantigen repertoire in the M1T1 clone should trigger heightened public health awareness for the global dissemination of these genetic elements. PMID:26522788

  5. Implications of platinum-group element accumulation along U.S. roads from catalytic-converter attrition.

    PubMed

    Ely, J C; Neal, C R; Kulpa, C F; Schneegurt, M A; Seidler, J A; Jain, J C

    2001-10-01

    Automobile catalytic converters are dispersing platinum-group elements (PGEs) Rh, Pt, and Pd into the environment (1-3). This paper represents the first detailed study to assess the PGE content of soils and grasses from U.S. roadsides. These soils were analyzed using cation exchange pretreatment and ultrasonic nebulizer-ICP-MS (4). Highway and several urban sites showed Pt abundances of 64-73 ng/g immediately adjacent to the roadside, with corresponding Pd and Rh abundances of 18-31 ng/g and 3-7 ng/g, respectively. All Pt and most Pd and Rh abundances are statistically above local background soil values. Platinum, Rd, and Rh show positive correlations with traffic-related elements (Ni, Cu, Zn, and Pb) but no correlations with nontraffic-related elements (Y, Ga). Iridium and Ru show no correlations with any of these trace elements. These PGE abundances are comparable to European studies (5-7) and are approaching concentrations that would be economically viable to recover. This study also demonstrates transport of Pt statistically above background more than 50 m from the roadside. Further study is necessary to see how mobile the PGEs are in roadside environments, but these initial data indicate only Pt is taken up by plants. PMID:11642438

  6. Transfer of scarlet fever-associated elements into the group A Streptococcus M1T1 clone.

    PubMed

    Ben Zakour, Nouri L; Davies, Mark R; You, Yuanhai; Chen, Jonathan H K; Forde, Brian M; Stanton-Cook, Mitchell; Yang, Ruifu; Cui, Yujun; Barnett, Timothy C; Venturini, Carola; Ong, Cheryl-lynn Y; Tse, Herman; Dougan, Gordon; Zhang, Jianzhong; Yuen, Kwok-Yung; Beatson, Scott A; Walker, Mark J

    2015-01-01

    The group A Streptococcus (GAS) M1T1 clone emerged in the 1980s as a leading cause of epidemic invasive infections worldwide, including necrotizing fasciitis and toxic shock syndrome. Horizontal transfer of mobile genetic elements has played a central role in the evolution of the M1T1 clone, with bacteriophage-encoded determinants DNase Sda1 and superantigen SpeA2 contributing to enhanced virulence and colonization respectively. Outbreaks of scarlet fever in Hong Kong and China in 2011, caused primarily by emm12 GAS, led to our investigation of the next most common cause of scarlet fever, emm1 GAS. Genomic analysis of 18 emm1 isolates from Hong Kong and 16 emm1 isolates from mainland China revealed the presence of mobile genetic elements associated with the expansion of emm12 scarlet fever clones in the M1T1 genomic background. These mobile genetic elements confer expression of superantigens SSA and SpeC, and resistance to tetracycline, erythromycin and clindamycin. Horizontal transfer of mobile DNA conferring multi-drug resistance and expression of a new superantigen repertoire in the M1T1 clone should trigger heightened public health awareness for the global dissemination of these genetic elements. PMID:26522788

  7. Epitaxial-driven synthesis of group IV element and alloy via designer molecular chemistry

    NASA Astrophysics Data System (ADS)

    Fang, Yanyan

    This dissertation reports a systematic study of device-quality elemental structures based on a new approach of producing high quality Ge films on Si substrates by introducing small concentration of digermylmethane or germylmethane organometallic additives into conventional digermane. Optimized molecular mixtures of these compounds have enabled layer-by-layer growth via facile elimination of extremely stable methane and hydrogen byproducts, consistent-with-calculated chemisorption energies and surface reactivities. The results indicate the additives confer unique pseudosurfactant behavior that profoundly alters the classic Stranski-Krastanov growth mechanism of epitaxial Ge on Si surfaces. Using this approach, atomically flat, carbon-free Ge layers directly on Si with low dislocations densities at unprecedented low temperatures compatible with selective area growth applications have been produced. The new Ge growth processes provide a unique route to extend the utility of elemental Ge into the wider IR optoelectronic domain by tuning its fundamental optical properties using tensile strain as a main parameter. In this study, digermylmethane and digermane have been utilized to produce high quality, thermally stable and tensile strained Ge layers at low temperatures on GeSn/Si or GeSiSn/GeSn/Si heterostructures. As high as 0.43 percent tensile strained Ge film has been demonstrated. Ge/Si(100) systems can serve as perfect templates. Tensile strained pure Si films have been grown on Ge buffered Si (100) via decomposition of trisilane by CVD with an intermediate fully strained thin GeSi layer at Si-Ge interface. These results are significant for Ge-based MOS applications that require a thin Si-layer to isolate the Ge channel from the high permittivity oxide. Furthermore, an entirely new family of GeSiSn/Ge/Si exhibiting tunable direct band gaps at a fixed lattice constant identical to Ge has been developed as a new class of versatile IR semiconductors. In addition, the

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

    NASA Astrophysics Data System (ADS)

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

    2013-04-01

    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.

  9. Multiple magma evolution and ore-forming processes of the Hongge layered intrusion, SW China: Insights from Sr-Nd isotopes, trace elements and platinum-group elements

    NASA Astrophysics Data System (ADS)

    Liao, Mingyang; Tao, Yan; Song, Xieyan; Li, Yubang; Xiong, Feng

    2015-12-01

    The Hongge layered intrusion (259 Ma), which is located in the inner zone of the Emeishan large igneous province (ELIP), is one of the most typical Fe-Ti-V ore deposits in the Pan-Xi area. Mafic-ultramafic layered intrusions of the ELIP have attracted a lot of attention lately because these intrusions host world class Fe-Ti-V oxide deposits plus interesting Cu-Ni-(PGE) mineralization which may have economic potential. This paper, reports new whole-rock major and trace element compositions, PGE abundances and Sr-Nd isotopic data for selected cumulate rocks and basalts. We use these data to investigate the nature of parental magmas and the controls on its evolution from the source mantle en route to the surface involving the Hongge ore-bearing intrusion. Two abrupt changes in Mt/Ilm and trace element ratios such as Ba/Th with depths in the Hongge layered intrusion indicate that this intrusion formed by at least two pluses of relatively primitive magma. The whole rock Sr-Nd isotopic data of basaltic and intrusive rocks plot in the region of Emeishan low-Ti basalts and the compositions of residual liquid (at ∼1260 °C and 1155 °C) calculated by MELTS are similar to our actual high-Ti (BFQ-2) and low-Ti (BC-1) basltic samples, indicate they are co-magmatic rather than derivation from a distinct source. Total PGE abundances in the Hongge samples are extremely low, ranging from 0.5 to 10 ppb. Sulfide-bearing rocks in the Hongge intrusion and the nearby coeval Banfangqing and Baicao basalts have similar mantle-like Pd/Pt ratios (2-6) and extremely high Cu/Pd ratios (3 × 104 to 4 × 105), indicating that sulfide segregation took place at depth prior to emplacement at Hongge and eruption in this region. Sulfide saturation in the Hongge magma may have resulted from such crustal contamination event. Crystallization of silicate minerals under the anhydrous magma, magma hydration plus Fe-Ti enrichments in the parental magma are three critical factors for the formation of Fe

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

    SciTech Connect

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

    1984-01-01

    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.

  11. Efficiency of group implicit concurrent algorithms for transient finite element analysis

    NASA Technical Reports Server (NTRS)

    Ortiz, M.; Sotelino, E. D.; Nour-Omid, B.

    1989-01-01

    The performance of group implicit algorithms is assessed on actual concurrent computers. It is shown that, as the number of subdomains is increased, performance enhancements are derived from two sources: the increased parallelism in the computations; and a reduction in equation solving effort. Moreover, these two performance enhancements are synergistic, in the sense that the corresponding speed-ups are multiplied, rather than merely added. Simulations on a 32-node hypercube are presented for which the interprocessor communications efficiencies obtained are consistently in excess of 90 percent.

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

    SciTech Connect

    Bintinger, D.; Chao, A.; Forest, E.

    1989-02-01

    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.

  13. Formazanido complexes of heavier group 13 elements aluminium, gallium, and indium.

    PubMed

    Schorn, W; Grosse-Hagenbrock, D; Oelkers, B; Sundermeyer, J

    2016-01-21

    The preparation, molecular structures and physical properties of novel heavy group 13 metal formazanido complexes are described. The trimethyl derivatives MMe3 (M = Al, Ga, In) react with 1,3,5-triphenylformazan (Htpf) in a 1 : 1 ratio to give methane and metallacycles of the type [M(tpf)Me2]. While [Al(tpf)Me2] and [Ga(tpf)Me2] are mononuclear compounds with six-membered rings and coordination number 4 in solution and in the crystalline state, indium derivative [In(tpf)Me2] forms oligomers in non-coordinating solvents according to NMR studies, these are probably N-bridged dimers with coordination number 5 at indium. The oligomer is cleaved by addition of one equivalent of pyridine or 4-dimethylaminopyridine (DMAP). The complexes [M(tpf)Me2] (M = Al, Ga) and [In(tpf)Me2(DMAP)] are characterized by XRD analyses. They are unique examples of main group metal formazane ring systems of the third and higher periods. The UV-Vis solution spectra of the neutral ligand Htpf and its metallated compounds [M(tpf)Me2] (M = Al, Ga, In) are discussed. PMID:26658885

  14. 75 FR 11681 - United States v. Daily Gazette Company and Medianews Group, Inc.; Proposed Final Judgment and...

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-11

    ... Interest. J. ``Gazette Company'' means defendant Daily Gazette Company, a privately-held corporation... Justice Antitrust Division United States v. Daily Gazette Company and Medianews Group, Inc.; Proposed... Gazette Company and Medianews Group, Inc.; Proposed Final Judgment and Competitive Impact Statement...

  15. Nitric acid passivation of Ti6Al4V reduces thickness of surface oxide layer and increases trace element release.

    PubMed

    Callen, B W; Lowenberg, B F; Lugowski, S; Sodhi, R N; Davies, J E

    1995-03-01

    Passivation of Ti6Al4V and cpTi implants using methods based on the ASTM-F86 nitric acid protocol are used with the intention of reducing their surface reactivity, and consequently the corrosion potential, in the highly corrosive biologic milieu. The ASTM-F86 passivation protocol was originally developed for surgical implants made of stainless steel and chrome cobalt alloy. Using X-ray photoelectron spectroscopy (XPS) to examine the effect of nitric acid passivation on the surface oxide layer of mill-annealed Ti6Al4V and cpTi, we have found that such treatment actually reduced the oxide thickness on the alloy while having no significant effect on the pure metal. These results correlated with observations obtained using graphite furnace atomic absorption spectrophotometry (GFAAS) to detect trace element release from solid, mill-annealed, Ti6Al4V and cpTi into serum-containing culture medium. We detected significantly greater levels of Ti, Al, and V in the presence of passivated compared to nonpassivated Ti6Al4V. In contrast, nitric acid passivation did not influence Ti release from mill-annealed cpTi. These results, derived from two mill-annealed Ti-based metals, would indicate that re-examination of ASTM-F86-based passivation protocols with respect to Ti6Al4V should be considered in view of the widespread use of this alloy for biomedical devices. PMID:7615579

  16. Simulation of nanoindentation experiment on RF magnetron sputtered nanocolumnar V2O5 film using finite element method

    NASA Astrophysics Data System (ADS)

    Porwal, Deeksha; Gupta, A. K.; Pillai, Anju M.; Sharma, Anand Kumar; Mukhopadhyay, Anoop Kumar; Khan, Kallol; Dey, Arjun

    2016-07-01

    The present work reports the nanomechanical behavior of a pulsed radio frequency (RF) magnetron sputtered vanadium pentoxide (V2O5) film deposited on silicon (Si) substrate using a combination of nanoindentation experiments and a finite element model (FEM). Deposited V2O5 film is characterized by x-ray diffraction (XRD), nanoprofilometry, field emission scanning electron microscopy (FESEM), nanoindentation and FEM. The phase pure 6.16 μm V2O5 film shows a nanocolumnar structure. The film exhibits nanohardness (H) of 0.16 ± 0.013 GPa and Young’s modulus (E) of about 12.05 ± 1.41 GPa. The FEM reproduces experimentally obtained load versus depth (P–h) plot and subsequently give yield stress and strain hardening component data of V2O5 film on Si substrate. Stress–strain behavior and von-Mises stress distribution of the V2O5 film with Si substrate system are also simulated. The FE model confirms the local maximum equivalent stress active underneath the nanoindenters to be nearly twice as high as the yield stress and thereby explains the plastic deformation observed in the V2O5 film.

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

    NASA Technical Reports Server (NTRS)

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

    1992-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

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

    2005-01-01

    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.

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

    NASA Technical Reports Server (NTRS)

    Altshuller, Aubrey P

    1955-01-01

    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.

  20. Adsorption and dynamics of group IV, V atoms and molecular oxygen on semiconductor group IV (0 0 1) surfaces

    NASA Astrophysics Data System (ADS)

    Afanasieva, T.

    2016-08-01

    In this review we address (1) the co-adsorption of group V (As, Sb, Bi) atoms and molecular oxygen on the Si(0 0 1) surface and (2) the adsorption and dynamics of Sb, Bi, Si and Ge ad-dimers on the Si(0 0 1) and Ge(0 0 1) surfaces. The adsorption and diffusion processes of group IV and V atoms on the (0 0 1) surfaces of group IV semiconductor surfaces have been studied using multi-configuration self-consistent field methods and density functional theory calculations. Results obtained by various types of first-principle total energy calculations are mutually compared and discussed. Our results demonstrate the capability of these quantum chemistry methods to provide relevant and reliable information on the interaction between adsorbate and semiconductor surfaces.

  1. Adsorption and dynamics of group IV, V atoms and molecular oxygen on semiconductor group IV (0 0 1) surfaces.

    PubMed

    Afanasieva, T

    2016-08-10

    In this review we address (1) the co-adsorption of group V (As, Sb, Bi) atoms and molecular oxygen on the Si(0 0 1) surface and (2) the adsorption and dynamics of Sb, Bi, Si and Ge ad-dimers on the Si(0 0 1) and Ge(0 0 1) surfaces. The adsorption and diffusion processes of group IV and V atoms on the (0 0 1) surfaces of group IV semiconductor surfaces have been studied using multi-configuration self-consistent field methods and density functional theory calculations. Results obtained by various types of first-principle total energy calculations are mutually compared and discussed. Our results demonstrate the capability of these quantum chemistry methods to provide relevant and reliable information on the interaction between adsorbate and semiconductor surfaces. PMID:27299666

  2. Continuum in the X-Z---Y weak bonds: Z= main group elements.

    PubMed

    Joy, Jyothish; Jose, Anex; Jemmis, Eluvathingal D

    2016-01-15

    The Continuum in the variation of the X-Z bond length change from blue-shifting to red-shifting through zero- shifting in the X-Z---Y complex is inevitable. This has been analyzed by ab-initio molecular orbital calculations using Z= Hydrogen, Halogens, Chalcogens, and Pnicogens as prototypical examples. Our analysis revealed that, the competition between negative hyperconjugation within the donor (X-Z) molecule and Charge Transfer (CT) from the acceptor (Y) molecule is the primary reason for the X-Z bond length change. Here, we report that, the proper tuning of X- and Y-group for a particular Z- can change the blue-shifting nature of X-Z bond to zero-shifting and further to red-shifting. This observation led to the proposal of a continuum in the variation of the X-Z bond length during the formation of X-Z---Y complex. The varying number of orbitals and electrons available around the Z-atom differentiates various classes of weak interactions and leads to interactions dramatically different from the H-Bond. Our explanations based on the model of anti-bonding orbitals can be transferred from one class of weak interactions to another. We further take the idea of continuum to the nature of chemical bonding in general. PMID:26279192

  3. NEUTRONIC REACTOR FUEL ELEMENT

    DOEpatents

    Shackleford, M.H.

    1958-12-16

    A fuel element possessing good stability and heat conducting properties is described. The fuel element comprises an outer tube formed of material selected from the group consisting of stainhess steel, V, Ti. Mo. or Zr, a fuel tube concentrically fitting within the outer tube and containing an oxide of an isotope selected from the group consisting of U/sup 235/, U/sup 233/, and Pu/sup 239/, and a hollow, porous core concentrically fitting within the fuel tube and formed of an oxide of an element selected from the group consisting of Mg, Be, and Zr.

  4. Spontaneous Double Hydrometallation Induced by N→M Coordination in Organometallic Hydrides of Group 14 Elements.

    PubMed

    Novák, Miroslav; Dostál, Libor; Turek, Jan; Alonso, Mercedes; De Proft, Frank; Růžička, Aleš; Jambor, Roman

    2016-04-11

    Our attempts to synthesise N→M intramolecularly coordinated diorganometallic hydrides L2 MH2 [M=Si (4), Ge (5), Sn (6)] containing the CH=N imine group (in which L is C,N-chelating ligand {2-[(2,6-iPr2 C6 H3 )N=CH]C6 H4 }(-) ) yielded 1,1'-bis(2,6-diisopropylphenyl)-2,2'-spriobi[benzo[c][1,2]azasilole] (7), 1,1'-bis(2,6-diisopropylphenyl)-2,2'-spriobi[benzo[c][1,2]azagermole] (8) and C,N-chelated homoleptic stannylene L2 Sn (10), respectively. Compounds 7 and 8 are an outcome of a spontaneous double hydrometallation of the two CH=N imine moieties induced by N→M intramolecular coordination (M=Si, Ge) in the absence of any catalyst. In contrast, the diorganotin hydride L2 SnH2 (6) is redox-unstable and the reduction of the tin centre with the elimination of H2 provided the C,N-chelated homoleptic stannylene L2 Sn (10). Compounds 7 and 8 were characterised by NMR spectroscopy and X-ray diffraction analysis. Because the proposed N→M intramolecularly coordinated diorganometallic hydrides L2 MH2 [M=Si (4), Ge (5), Sn (6)] revealed two different types of reduction reactions, DFT calculations were performed to gain an insight into the structures and bonding of the non-isolable diorganometallic hydrides as well as the products of their subsequent reactions. Furthermore, the thermodynamic profiles of the different reaction pathways with respect to the central metal atom were also investigated. PMID:26934563

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

    USGS Publications Warehouse

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

    1984-01-01

    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.

  6. Transition metal-mediated donor-acceptor coordination of low-oxidation state Group 14 element halides.

    PubMed

    Swarnakar, Anindya K; Ferguson, Michael J; McDonald, Robert; Rivard, Eric

    2016-03-30

    The reactivity of tungsten carbonyl adducts of Group 14 element (Ge, Sn and Pb) dihalides towards the metal-based donors (η(5)-C5H5)Rh(PMe2Ph)2 and Pt(PCy3)2 was examined. When (η(5)-C5H5)Rh(PMe2Ph)2 was treated with the Lewis acid supported Ge(ii) complex, THF·GeCl2·W(CO)5, cyclopentadienyl ring activation occurred, whereas the analogous Lewis acidic units SnCl2·W(CO)5 and PbCl2 form direct adducts with the Rh complex to yield Rh-Sn and Rh-Pb dative bonds. Attempts to prepare metal coordinated element(ii) hydrides by adding hydride sources to the above mentioned rhodium-E(ii) halide complexes were unsuccessful; in each case insoluble products were formed along with regeneration of free (η(5)-C5H5)Rh(PMe2Ph)2. In a parallel study, ECl2·W(CO)5 (E = Ge or Sn) groups were shown to participate in E-Cl oxidation addition chemistry with (Cy3P)2Pt to give the formal Pt(ii) complexes ClPt(PCy3)2ECl·W(CO)5. PMID:26373599

  7. Creep deformation and fracture of a Cr/Mo/V bolting steel containing selected trace-element additions

    NASA Astrophysics Data System (ADS)

    Larouk, Z.; Pilkington, R.

    1999-08-01

    The article reports the creep behavior, at 565 °C, of 1Cr1Mo0.75V (Ti, B) (Durehete D1055) steel, in each of two grain sizes and doped with individual trace elements such as P, As, and Sn, in comparison to a reference cast of the base material containing 0.08 wt pct Ti. The addition of the trace elements P, As, or Sn (each <0.045 wt pct) appears to produce no significant effect on creep strength or creep crack-growth resistance at 565 °C. The fine-grained material shows low creep strength but notch strengthening, while the coarse-grained material shows higher creep strength and exhibits notch weakening for test times up to 2750 hours. From creep crack-growth tests, it appears that the C* parameter is not appropriate for correlating the creep crack-growth rate under the present test conditions. The parameters K I or σ net are found to correlate better, but, from the present data, it is not possible to judge which of these parameters is more appropriate for general use. It is suggested that the presence of Ti in CrMoV steels has an inhibiting effect on trace-element embrittlement.

  8. Compressive Strength Evaluation in Brazed ZrO2/Ti6Al4V Joints Using Finite Element Analysis

    NASA Astrophysics Data System (ADS)

    Sharma, Ashutosh; Kee, Se Ho; Jung, Flora; Heo, Yongku; Jung, Jae Pil

    2016-04-01

    This study aims to synthesize and evaluate the compressive strength of the ZrO2/Ti-6Al-4V joint brazed using an active metal filler Ag-Cu-Sn-Ti, and its application to dental implants assuring its reliability to resist the compressive failure in the actual oral environment. The brazing was performed at a temperature of 750 °C for 30 min in a vacuum furnace under 5 × 10-6 Torr atmosphere. The microstructure of the brazed joint showed the presence of an Ag-rich matrix and a Cu-rich phase, and Cu-Ti intermetallic compounds were observed along the Ti-6Al-4V bonded interface. The compressive strength of the brazed ZrO2/Ti-6Al-4V joint was measured by EN ISO 14801 standard test method. The measured compressive strength of the joint was ~1477 MPa—a value almost five times that of existing dental cements. Finite element analysis also confirmed the high von Mises stress values. The compressive strains in the samples were found concentrated near the Ti-6Al-4V position, matching with the position of the real fractured sample. These results suggest extremely significant compressive strength in ZrO2/Ti-6Al-4V joints using the Ag-Cu-Sn-Ti filler. It is believed that a highly reliable dental implant can be processed and designed using the results of this study.

  9. Compressive Strength Evaluation in Brazed ZrO2/Ti6Al4V Joints Using Finite Element Analysis

    NASA Astrophysics Data System (ADS)

    Sharma, Ashutosh; Kee, Se Ho; Jung, Flora; Heo, Yongku; Jung, Jae Pil

    2016-05-01

    This study aims to synthesize and evaluate the compressive strength of the ZrO2/Ti-6Al-4V joint brazed using an active metal filler Ag-Cu-Sn-Ti, and its application to dental implants assuring its reliability to resist the compressive failure in the actual oral environment. The brazing was performed at a temperature of 750 °C for 30 min in a vacuum furnace under 5 × 10-6 Torr atmosphere. The microstructure of the brazed joint showed the presence of an Ag-rich matrix and a Cu-rich phase, and Cu-Ti intermetallic compounds were observed along the Ti-6Al-4V bonded interface. The compressive strength of the brazed ZrO2/Ti-6Al-4V joint was measured by EN ISO 14801 standard test method. The measured compressive strength of the joint was ~1477 MPa—a value almost five times that of existing dental cements. Finite element analysis also confirmed the high von Mises stress values. The compressive strains in the samples were found concentrated near the Ti-6Al-4V position, matching with the position of the real fractured sample. These results suggest extremely significant compressive strength in ZrO2/Ti-6Al-4V joints using the Ag-Cu-Sn-Ti filler. It is believed that a highly reliable dental implant can be processed and designed using the results of this study.

  10. Platinum group elements and gold in ferromanganese crusts from Afanasiy-Nikitin seamount, equatorial Indian Ocean: Sources and fractionation

    USGS Publications Warehouse

    Banakar, V.K.; Hein, J.R.; Rajani, R.P.; Chodankar, A.R.

    2007-01-01

    The major element relationships in ferromanganese (Fe-Mn) crusts from Afanasiy-Nikitin seamount (ANS), eastern equatorial Indian Ocean, appear to be atypical. High positive correlations (r = 0.99) between Mn/Co and Fe/Co ratios, and lack of correlation of those ratios with Co, Ce, and Ce/Co, indicate that the ANS Fe-Mn crusts are distinct from Pacific seamount Fe-Mn crusts, and reflect region-specific chemical characteristics. The platinum group elements (PGE: Ir, Ru, Rh, Pt, and Pd) and Au in ANS Fe-Mn crusts are derived from seawater and are mainly of terrestrial origin, with a minor cosmogenic component. The Ru/Rh (0.5-2) and Pt/Ru ratios (7-28) are closely comparable to ratios in continental basalts, whereas Pd/Ir ratios exhibit values ( 0.75) correlations between water depth and Mn/Co, Fe/Co, Ce/Co, Co, and the PGEs. Fractionation of the PGE-Au from seawater during colloidal precipitation of the major-oxide phases is indicated by well-defined linear positive correlations (r > 0.8) of Co and Ce with Ir, Ru, Rh, and Pt; Au/Co with Mn/Co; and by weak or no correlations of Pd with water depth, Co-normalized major-element ratios, and with the other PGE (r < 0.5). The strong enrichment of Pt (up to 1 ppm) relative to the other PGE and its positive correlations with Ce and Co demonstrate a common link for the high concentrations of all three elements, which likely involves an oxidation reaction on the Mn-oxide and Fe-oxyhydroxide surfaces. The documented fractionation of PGE-Au and their positive association with redox sensitive Co and Ce may have applications in reconstructing past-ocean redox conditions and water masses.