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Sample records for auni aasmaa lya

  1. Solid-state dewetting of Au/Ni bilayers: The effect of alloying on morphology evolution

    SciTech Connect

    Herz, A.; Wang, D. Kups, Th.; Schaaf, P.

    2014-07-28

    The solid-state dewetting of thin Au/Ni bilayers deposited onto SiO{sub 2}/Si substrates is investigated. A rapid thermal treatment is used to induce the dewetting process by an increase in temperature. The evolution of the (111) peaks of X-ray diffraction reveals a characteristic change due to mixing of Au and Ni. At low temperature, the Au-Ni thin film is found to break up at the phase boundaries and growing voids are shown to be surrounded by a Ni-rich phase. Branch-like void growth is observed. Upon annealing at increasing temperatures, Au-Ni solid solutions are formed well above the bulk equilibrium solubility of Au and Ni. It is found that this metastable phase formation makes the Au-Ni thin film less vulnerable to rupturing. Moreover, growth mode of still evolving voids changes into a more regular, faceted one due to alloying. Finally, it is shown that annealing above the miscibility gap forms supersaturated, well-oriented Au-Ni solid solution agglomerates via dewetting.

  2. First passage properties of a generalized Pólya urn

    NASA Astrophysics Data System (ADS)

    Kearney, Michael J.; Martin, Richard J.

    2016-12-01

    A generalized two-component Pólya urn process, parameterized by a variable α , is studied in terms of the likelihood that due to fluctuations the initially smaller population in a scenario of competing population growth eventually becomes the larger, or is the larger after a certain passage of time. By casting the problem as an inhomogeneous directed random walk we quantify this role-reversal phenomenon through the first passage probability that equality in size is first reached at a given time, and the related exit probability that equality in size is reached no later than a given time. Using an embedding technique, exact results are obtained which complement existing results and provide new insights into behavioural changes (akin to phase transitions) which occur at defined values of α .

  3. Oxygen reduction kinetics on Pt monolayer shell highly affected by the structure of bimetallic AuNi cores

    SciTech Connect

    Chen, Guangyu; Kuttiyiel, Kurian A.; Su, Dong; Li, Meng; Wang, Chiu -Hui; Buceta, David; Du, Chunyu; Gao, Yunzhi; Yin, Geping; Sasaki, Kotaro; Vukmirovic, Miomir B.; Adzic, Radoslav R.

    2016-07-12

    Here, we describe pronounced effects of structural changes of the AuNi cores on the oxygen reduction reaction (ORR) activity of a Pt monolayer shell. The study of alloyed AuNi nanoparticles compared with AuNi core–shell structured nanoparticles revealed configurations having different electronic and electrochemical properties. Controlled alloying of Au with Ni was essential to tune the electronic properties of Au interacting with the Pt monolayer shell to achieve suitable adsorption of O2 on Pt for expediting the ORR. The alloyed AuNi nanoparticles made the Pt shell more catalytically active for the ORR than the core–shell structured AuNi nanoparticles. The Pt monolayer supported on the alloyed AuNi nanoparticles showed the Pt mass and specific activities as high as 1.52 A mg–1 and 1.18 mA cm–2, respectively, with almost no loss over 5 000 cycles of stability test. This high ORR activity is ascribed to the role of nonspecific steric configuration of Ni atoms changing the electronic properties of the alloy that affect the oxygen and water interaction with the Pt shell and facilitate increased ORR kinetics.

  4. Oxygen reduction kinetics on Pt monolayer shell highly affected by the structure of bimetallic AuNi cores

    DOE PAGES

    Chen, Guangyu; Kuttiyiel, Kurian A.; Su, Dong; ...

    2016-07-12

    Here, we describe pronounced effects of structural changes of the AuNi cores on the oxygen reduction reaction (ORR) activity of a Pt monolayer shell. The study of alloyed AuNi nanoparticles compared with AuNi core–shell structured nanoparticles revealed configurations having different electronic and electrochemical properties. Controlled alloying of Au with Ni was essential to tune the electronic properties of Au interacting with the Pt monolayer shell to achieve suitable adsorption of O2 on Pt for expediting the ORR. The alloyed AuNi nanoparticles made the Pt shell more catalytically active for the ORR than the core–shell structured AuNi nanoparticles. The Pt monolayermore » supported on the alloyed AuNi nanoparticles showed the Pt mass and specific activities as high as 1.52 A mg–1 and 1.18 mA cm–2, respectively, with almost no loss over 5 000 cycles of stability test. This high ORR activity is ascribed to the role of nonspecific steric configuration of Ni atoms changing the electronic properties of the alloy that affect the oxygen and water interaction with the Pt shell and facilitate increased ORR kinetics.« less

  5. Highly sensitive glucose biosensor based on Au-Ni coaxial nanorod array having high aspect ratio.

    PubMed

    Hsu, Che-Wei; Wang, Gou-Jen

    2014-06-15

    An effective glucose biosensor requires a sufficient amount of GOx immobilizing on the electrode surface. An electrode of a 3D nanorod array, having a larger surface-to-volume ratio than a 2D nanostructure, can accommodate more GOx molecules to immobilize onto the surface of the nanorods. In this study, a highly sensitive Au-Ni coaxial nanorod array electrode fabricated through the integration of nano electroforming and immersion gold (IG) method for glucose detection was developed. The average diameter of the as-synthesized Ni nanorods and that of the Au-Ni nanorods were estimated to be 150 and 250 nm, respectively; both had a height of 30 μm. The aspect ratio was 120. Compared to that of a flat Au electrode, the effective sensing area was enhanced by 79.8 folds. Actual glucose detections demonstrated that the proposed Au-Ni coaxial nanorod array electrode could operate in a linear range of 27.5 μM-27.5mM with a detection limit of 5.5μM and a very high sensitivity of 769.6 μA mM(-1)cm(-2). Good selectivity of the proposed sensing device was verified by sequential injections of uric acid (UA) and ascorbic acid (AA). Long-term stability was examined through successive detections over a period of 30 days.

  6. Low-temperature CO oxidation on Ni(111) and on a Au/Ni(111) surface alloy.

    PubMed

    Knudsen, Jan; Merte, Lindsay R; Peng, Guowen; Vang, Ronnie T; Resta, Andrea; Laegsgaard, Erik; Andersen, Jesper N; Mavrikakis, Manos; Besenbacher, Flemming

    2010-08-24

    From an interplay between scanning tunneling microscopy, temperature programmed desorption, X-ray photoelectron spectroscopy, and density functional theory calculations we have studied low-temperature CO oxidation on Au/Ni(111) surface alloys and on Ni(111). We show that an oxide is formed on both the Ni(111) and the Au/Ni(111) surfaces when oxygen is dosed at 100 K, and that CO can be oxidized at 100 K on both of these surfaces in the presence of weakly bound oxygen. We suggest that low-temperature CO oxidation can be rationalized by CO oxidation on O(2)-saturated NiO(111) surfaces, and show that the main effect of Au in the Au/Ni(111) surface alloy is to block the formation of carbonate and thereby increase the low-temperature CO(2) production.

  7. Improvement of the wear resistance of electroplated Au-Ni coatings by Zr ion bombardment of Ni-B sublayer

    SciTech Connect

    Lyazgin, Alexander Shugurov, Artur Sergeev, Viktor Neufeld, Vasily; Panin, Alexey; Shesterikov, Evgeny

    2015-10-27

    The effect of bombardment of the Ni-B sublayer by Zr ion beams on the surface morphology and tribomechanical properties of Au-Ni coatings was investigated. It was found that the treatment has no significant effect on the surface roughness and grain size of the Au-Ni coatings, while it provides essential reducing of their friction coefficient and improvement of wear resistance. It is shown that increased wear resistance of these coatings was caused by their strain hardening resulted from localization of plastic strain. The optimal Zr fluence were determined that provide the maximum reduction of linear wear of the coatings.

  8. Facet-controlled phase separation in supersaturated Au-Ni nanoparticles upon shape equilibration

    SciTech Connect

    Herz, A. E-mail: dong.wang@tu-ilmenau.de; Rossberg, D.; Hentschel, M.; Theska, F.; Wang, D. E-mail: dong.wang@tu-ilmenau.de; Schaaf, P.; Friák, M.; Holec, D.; Šob, M.; Schneeweiss, O.

    2015-08-17

    Solid-state dewetting is used to fabricate supersaturated, submicron-sized Au-Ni solid solution particles out of thin Au/Ni bilayers by means of a rapid thermal annealing technique. Phase separation in such particles is studied with respect to their equilibrium crystal (or Wulff) shape by subsequent annealing at elevated temperature. It is found that (100) faceting planes of the equilibrated particles are enriched with Ni and (111) faces with Au. Both phases are considered by quantum-mechanical calculations in combination with an error-reduction scheme that was developed to compensate for a missing exchange-correlation potential that would reliably describe both Au and Ni. The observed phase configuration is then related to the minimization of strongly anisotropic elastic energies of Au- and Ni-rich phases and results in a rather unique nanoparticle composite state that is characterized by nearly uniform value of elastic response to epitaxial strains all over the faceted surface. The same conclusion is yielded also by evaluating bi-axial elastic moduli when employing interpolated experimental elastic constants. This work demonstrates a useful route for studying features of physical metallurgy at the mesoscale.

  9. The Pólya-Szegö Principle and the Anisotropic Convex Lorentz-Sobolev Inequality

    PubMed Central

    Liu, Shuai; He, Binwu

    2014-01-01

    An anisotropic convex Lorentz-Sobolev inequality is established, which extends Ludwig, Xiao, and Zhang's result to any norm from Euclidean norm, and the geometric analogue of this inequality is given. In addition, it implies that the (anisotropic) Pólya-Szegö principle is shown. PMID:25136698

  10. Unconventional assembly of bimetallic Au-Ni janus nanoparticles on chemically modified silica spheres.

    PubMed

    Jia, Lei; Pei, Xiaowei; Zhou, Feng; Liu, Weimin

    2014-02-10

    This paper reports that Janus Au-Ni nanoparticles (JANNPs) can self-assemble onto silica spheres in a novel way, which is different from that of single-component isotropic nanoparticles. JANNPs modified with octadecylamine (ODA) assemble onto catechol-modified silica spheres (SiO2-OH) to form a very special core-loop complex structure and finally the core-loop assemblies link each other to form large assemblies through capillary force and the hydrophobic interaction of the alkyl chains of ODA. The nanocomposites disassemble in the presence of vanillin and oleic acid because of the breakage of the catechol-metal link. Vanillin-induced disassembly enables the JANNPs to reassemble into a core-loop structure upon ODA addition. The assembly of SiO2-OH and isotropic Ni or Fe3O4 particles generates traditional core-satellite structures. This unconventional self-assembly can be attributed to the synergistic effect of Janus specificity and capillary force, which is also confirmed by the assembly of thiol-terminated silica spheres (SH-SiO2) with anisotropic JANNPs, isotropic Au, and Ni nanoparticles. These results can guide the development of novel composite materials using Janus nanoparticles as the primary building blocks.

  11. Studying Language Change Using Price Equation and Pólya-urn Dynamics

    PubMed Central

    Gong, Tao; Shuai, Lan; Tamariz, Mónica; Jäger, Gerhard

    2012-01-01

    Language change takes place primarily via diffusion of linguistic variants in a population of individuals. Identifying selective pressures on this process is important not only to construe and predict changes, but also to inform theories of evolutionary dynamics of socio-cultural factors. In this paper, we advocate the Price equation from evolutionary biology and the Pólya-urn dynamics from contagion studies as efficient ways to discover selective pressures. Using the Price equation to process the simulation results of a computer model that follows the Pólya-urn dynamics, we analyze theoretically a variety of factors that could affect language change, including variant prestige, transmission error, individual influence and preference, and social structure. Among these factors, variant prestige is identified as the sole selective pressure, whereas others help modulate the degree of diffusion only if variant prestige is involved. This multidisciplinary study discerns the primary and complementary roles of linguistic, individual learning, and socio-cultural factors in language change, and offers insight into empirical studies of language change. PMID:22427981

  12. Tensile properties of thin Au-Ni brazes between strong base materials

    SciTech Connect

    Tolle, M.C.; Kassner, M.E.

    1991-12-01

    It has long been known that when relatively strong base materials are joined by thin, soft, interlayer metals such as with brazing or various solid state joining processes, the ultimate tensile strength (UTS) of the bond may be several factors higher than the UTS of the bulk, or unconstrained, interlayer metals. However, earlier work reported by the authors confirmed that delayed or ``creep`` failure of the bond may occur at stresses much less than the UTS. It was found that for thin silver interlayers, prepared by brazing and physical vapor deposition (PVD), joining elastically deforming base materials (i.e. no measurable plastic deformation occurs in the base metal at the applied stresses), the ambient (and near-ambient) temperature time to failure is controlled by the creep rate of the silver interlayer which is determined by the effective stress within the interlayer. The plastic deformation within the interlayer causes cavity nucleation which continues until the concentration of nuclei is sufficiently high to lead to instability and eventual failure. The delayed failure may be accelerated by base material creep resulting from the effective stress in the base material. Plastic deformation in the base metal causes corresponding deformation in the interlayer, and cavities nucleate as with elastic base metal case. The delayed failure phenomenon was confirmed by the authors only for silver interlayers; other compositions were not tested. In this study, maraging steel was joined with an Au-Ni braze alloy with 57.5 at. % Au and 42.5 at. % Ni. The microstructure is expected to be a refined two-phase (spinodal) alloy with higher strength than the PVD silver of our previous investigation.

  13. Tensile properties of thin Au-Ni brazes between strong base materials

    SciTech Connect

    Tolle, M.C.; Kassner, M.E. )

    1991-12-01

    It has long been known that when relatively strong base materials are joined by thin, soft, interlayer metals such as with brazing or various solid state joining processes, the ultimate tensile strength (UTS) of the bond may be several factors higher than the UTS of the bulk, or unconstrained, interlayer metals. However, earlier work reported by the authors confirmed that delayed or creep'' failure of the bond may occur at stresses much less than the UTS. It was found that for thin silver interlayers, prepared by brazing and physical vapor deposition (PVD), joining elastically deforming base materials (i.e. no measurable plastic deformation occurs in the base metal at the applied stresses), the ambient (and near-ambient) temperature time to failure is controlled by the creep rate of the silver interlayer which is determined by the effective stress within the interlayer. The plastic deformation within the interlayer causes cavity nucleation which continues until the concentration of nuclei is sufficiently high to lead to instability and eventual failure. The delayed failure may be accelerated by base material creep resulting from the effective stress in the base material. Plastic deformation in the base metal causes corresponding deformation in the interlayer, and cavities nucleate as with elastic base metal case. The delayed failure phenomenon was confirmed by the authors only for silver interlayers; other compositions were not tested. In this study, maraging steel was joined with an Au-Ni braze alloy with 57.5 at. % Au and 42.5 at. % Ni. The microstructure is expected to be a refined two-phase (spinodal) alloy with higher strength than the PVD silver of our previous investigation.

  14. Self-grown Ni(OH)(2) layer on bimodal nanoporous AuNi alloys for enhanced electrocatalytic activity and stability.

    PubMed

    Han, Gao-Feng; Xiao, Bei-Bei; Lang, Xing-You; Wen, Zi; Zhu, Yong-Fu; Zhao, Ming; Li, Jian-Chen; Jiang, Qing

    2014-10-08

    Au nanostructures as catalysts toward electrooxidation of small molecules generally suffer from ultralow surface adsorption capability and stability. Here, we report Ni(OH)2 layer decorated nanoporous (NP) AuNi alloys with a three-dimensional and bimodal porous architecture, which are facilely fabricated by a combination of chemical dealloying and in situ surface segregation, for the enhanced electrocatalytic performance in biosensors. As a result of the self-grown Ni(OH)2 on the AuNi alloys with a coherent interface, which not only enhances adsorption energy of Au and electron transfer of AuNi/Ni(OH)2 but also prohibits the surface diffusion of Au atoms, the NP composites are enlisted to exhibit significant enhancement in both electrocatalytic activity and stability toward glucose electrooxidation. The highly reliable glucose biosensing with exceptional reproducibility and selectivity as well as quick response makes it a promising candidate as electrode materials for the application in nonenzymatic glucose biosensors.

  15. The Enhanced Catalytic Activities of Asymmetric Au-Ni Nanoparticle Decorated Halloysite-Based Nanocomposite for the Degradation of Organic Dyes

    NASA Astrophysics Data System (ADS)

    Jia, Lei; Zhou, Tao; Xu, Jun; Li, Xiaohui; Dong, Kun; Huang, Jiancui; Xu, Zhouqing

    2016-02-01

    Janus particles (JPs) are unique among the nano-/microobjects because they provide asymmetry and can thus impart drastically different chemical or physical properties. In this work, we have fabricated the magnetic halloysite nanotube (HNT)-based HNTs@Fe3O4 nanocomposite (NCs) and then anchored the Janus Au-Ni or isotropic Au nanoparticles (NPs) to the surface of external wall of sulfydryl modified magnetic nanotubes. The characterization by physical methods authenticates the successful fabrication of two different magnetic HNTs@Fe3O4@Au and HNTs@Fe3O4@Au-Ni NCs. The catalytic activity and recyclability of the two NCs have been evaluated considering the degradation of Congo red (CR) and 4-nitrophenol (4-NP) using sodium borohydride as a model reaction. The results reveal that the symmetric Au NPs participated NCs display low activity in the degradation of the above organic dyes. However, a detailed kinetic study demonstrates that the employ of bimetallic Janus Au-Ni NPs in the NCs indicates enhanced catalytic activity, owing to the structurally specific nature. Furthermore, the magnetic functional NCs reported here can be used as recyclable catalyst which can be recovered simply by magnet.

  16. Correlation function for generalized Pólya urns: Finite-size scaling analysis

    NASA Astrophysics Data System (ADS)

    Mori, Shintaro; Hisakado, Masato

    2015-11-01

    We describe a universality class for the transitions of a generalized Pólya urn by studying the asymptotic behavior of the normalized correlation function C (t ) using finite-size scaling analysis. X (1 ),X (2 ),... are the successive additions of a red (blue) ball [X (t )=1 (0 )] at stage t and C (t )≡Cov[X (1 ),X (t +1 )]/Var[X (1 )] . Furthermore, z (t ) =∑s=1tX (s ) /t represents the successive proportions of red balls in an urn to which, at the (t +1 )th stage, a red ball is added [X (t +1 )=1 ] with probability q [z (t )]=(tanh{J [2 z (t )-1 ]+h }+1 )/2 ,J ≥0 , and a blue ball is added [X (t +1 )=0 ] with probability 1 -q [z (t )] . A boundary [Jc(h ) ,h ] exists in the (J ,h ) plane between a region with one stable fixed point and another region with two stable fixed points for q (z ) . C (t ) ˜c +c'.tl -1 with c =0 (>0 ) for J Jc) , and l is the (larger) value of the slope(s) of q (z ) at the stable fixed point(s). On the boundary J =Jc(h ) ,C (t ) ≃c +c'.(lnt) -α' and c =0 (c >0 ) ,α'=1 /2 (1 ) for h =0 (h ≠0 ) . The system shows a continuous phase transition for h =0 and C (t ) behaves as C (t ) ≃(lnt) -α'g [(1 -l ) lnt ] with a universal function g (x ) and a length scale 1 /(1 -l ) with respect to lnt . β =ν||.α' holds with β =1 /2 and ν||=1 .

  17. Reflow soldering and isothermal solid-state aging of Sn-Ag eutectic solder on Au/Ni surface finish

    NASA Astrophysics Data System (ADS)

    Liu, C. M.; Ho, C. E.; Chen, W. T.; Kao, C. R.

    2001-09-01

    The reaction between the eutectic Sn-3.5Ag solder and the Au/Ni surface finish during reflow as well as during isothermal aging was studied. The Au layer was electroplated and had a thickness of the one μm. The peak reflow temperature was fixed at 250 C while the reflow time was varied between 10 sec and one h. Samples that went through 90 sec reflow time were then subjected to 160 C isothermal aging for up to 875 h. It was found that during reflow the Au layer reacted very quickly with the solder to form AuSn4. One μm of Au layer was consumed in less than 10 sec. As the aging time increased, AuSn4 grains began to separate themselves from the Ni layer at the roots of the grains and started to fall into the solder. When, the reflow time reached 30 sec, all the Au intermetallic head left the interface, and Ni3Sn4 started, to form at the interface. The Ni3Sn4 growth rate followed linear kinetics initially (<240 sec), but the growth rate slowed down afterward. During the isothermal aging, only a small amount of (AuxNi1-x)Sn4 resettled back to the interface, and a continuous (Au0.45Ni0.55)Sn4 layer did not form at the interface, unlike the case for the Sn-37Pb solder. This is an important advantage for Sn-3.5 Ag over Sn-37Pb because a continuous (Au0.45Ni0.55)Sn4 layer inevitably will weaken a solder joint. Our observation indicated that many (AuxNi1-x)Sn4 particles were trapped by the Ag3Sn particles, and were hindered from resettling back to the interface.

  18. Effects of alloying and local order in AuNi contacts for Ohmic radio frequency micro electro mechanical systems switches via multi-scale simulation

    NASA Astrophysics Data System (ADS)

    Gaddy, Benjamin E.; Kingon, Angus I.; Irving, Douglas L.

    2013-05-01

    Ohmic RF-MEMS switches hold much promise for low power wireless communication, but long-term degradation currently plagues their reliable use. Failure in these devices occurs at the contact and is complicated by the fact that the same asperities that bear the mechanical load are also important to the flow of electrical current needed for signal processing. Materials selection holds the key to overcoming the barriers that prevent widespread use. Current efforts in materials selection have been based on the material's (or alloy's) ability to resist oxidation as well as its room-temperature properties, such as hardness and electrical conductivity. No ideal solution has yet been found via this route. This may be due, in part, to the fact that the in-use changes to the local environment of the asperity are not included in the selection criteria. For example, Joule heating would be expected to raise the local temperature of the asperity and impose a non-equilibrium thermal gradient in the same region expected to respond to mechanical actuation. We propose that these conditions should be considered in the selection process, as they would be expected to alter mechanical, electrical, and chemical mechanisms in the vicinity of the surface. To this end, we simulate the actuation of an Ohmic radio frequency micro electro mechanical systems switch by using a multi-scale method to model a current-carrying asperity in contact with a polycrystalline substrate. Our method couples continuum solutions of electrical and thermal transport equations to an underlying molecular dynamics simulation. We present simulations of gold-nickel asperities and substrates in order to evaluate the influence of alloying and local order on the early stages of contact actuation. The room temperature response of these materials is compared to the response of the material when a voltage is applied. Au-Ni interactions are accounted for through modification of the existing Zhou embedded atom method

  19. Surface morphology and electrical properties of Au/Ni/ Left-Pointing-Angle-Bracket C Right-Pointing-Angle-Bracket /n-Ga{sub 2}O{sub 3}/p-GaSe Left-Pointing-Angle-Bracket KNO{sub 3} Right-Pointing-Angle-Bracket hybrid structures fabricated on the basis of a layered semiconductor with nanoscale ferroelectric inclusions

    SciTech Connect

    Bakhtinov, A. P. Vodopyanov, V. N.; Netyaga, V. V.; Kudrynskyi, Z. R.; Lytvyn, O. S.

    2012-03-15

    Features of the formation of Au/Ni/ Left-Pointing-Angle-Bracket C Right-Pointing-Angle-Bracket /n-Ga{sub 2}O{sub 3} hybrid nanostructures on a Van der Waals surface (0001) of 'layered semiconductor-ferroelectric' composite nanostructures (p-GaSe Left-Pointing-Angle-Bracket KNO{sub 3} Right-Pointing-Angle-Bracket ) are studied using atomic-force microscopy. The room-temperature current-voltage characteristics and the dependence of the impedance spectrum of hybrid structures on a bias voltage are studied. The current-voltage characteristic includes a resonance peak and a portion with negative differential resistance. The current attains a maximum at a certain bias voltage, when electric polarization switching in nanoscale three-dimensional inclusions in the layered GaSe matrix occurs. In the high-frequency region (f > 10{sup 6} Hz), inductive-type impedance (a large negative capacitance of structures, {approx}10{sup 6} F/mm{sup 2}) is detected. This effect is due to spinpolarized electron transport in a series of interconnected semiconductor composite nanostructures with multiple p-GaSe Left-Pointing-Angle-Bracket KNO{sub 3} Right-Pointing-Angle-Bracket quantum wells and a forward-biased 'ferromagnetic metal-semiconductor' polarizer (Au/Ni/ Left-Pointing-Angle-Bracket C Right-Pointing-Angle-Bracket /n{sup +}-Ga{sub 2}O{sub 3}/n-Ga{sub 2}O{sub 3}). A shift of the maximum (current hysteresis) is detected in the current-voltage characteristics for various directions of the variations in bias voltage.

  20. Discovery of a Giant Lya Emitter Near the Reionization Epoch

    SciTech Connect

    Ouchi, Masami; Ono, Yoshiaki; Egami, Eiichi; Saito, Tomoki; Oguri, Masamune; McCarthy, Patrick J.; Farrah, Duncan; Kashikawa, Nobunari; Momcheva, Ivelina; Shimasaku, Kazuhiro; Nakanishi, Kouichiro; Furusawa, Hisanori; Akiyama, Masayuki; Dunlop, James S.; Mortier, Angela M.J.; Okamura, Sadanori; Hayashi, Masao; Cirasuolo, Michele; Dressler, Alan; Iye, Masanori; Jarvis, Matt.J.

    2008-08-01

    We report the discovery of a giant Ly{alpha} emitter (LAE) with a Spitzer/IRAC counterpart near the reionization epoch at z = 6.595. The giant LAE is found from the extensive 1 deg{sup 2} Subaru narrow-band survey for z = 6.6 LAEs in the Subaru/XMM-Newton Deep Survey (SXDS) field, and subsequently identified by deep spectroscopy of Keck/DEIMOS and Magellan/IMACS. Among our 207 LAE candidates, this LAE is not only the brightest narrow-band object with L(Ly{alpha}) = 3.9 {+-} 0.2 x 10{sup 43} erg s{sup -1} in our survey volume of 10{sup 6} Mpc{sup 3}, but also a spatially extended Ly{alpha} nebula with the largest isophotal area whose major axis is at least {approx_equal} 3-inches. This object is more likely to be a large Ly{alpha} nebula with a size of {approx}> 17-kpc than to be a strongly-lensed galaxy by a foreground object. Our Keck spectrum with medium-high spectral and spatial resolutions suggests that the velocity width is v{sub FWHM} = 251 {+-} 21 km s{sup -1}, and that the line-center velocity changes by {approx_equal} 60 km s{sup -1} in a 10-kpc range. The stellar mass and star-formation rate are estimated to be 0.9-5.0 x 10{sup 10}M{sub {circle_dot}} and > 34 M{sub {circle_dot}}yr{sup -1}, respectively, from the combination of deep optical to infrared images of Subaru, UKIDSS-Ultra Deep Survey, and Spitzer/IRAC. Although the nature of this object is not yet clearly understood, this could be an important object for studying cooling clouds accreting onto a massive halo, or forming-massive galaxies with significant outflows contributing to cosmic reionization and metal enrichment of inter-galactic medium.

  1. Stability of Surface and Subsurface Hydrogen on and in Au/Ni Near-Surface Alloys

    SciTech Connect

    Celik, Fuat E.; Mavrikakis, Manos

    2015-10-01

    Periodic, self-consistent DFT-GGA (PW91) calculations were used to study the interaction of hydrogen atoms with the (111) surfaces of substitutional near-surface alloys (NSAs) of Au and Ni with different surface layer compositions and different arrangements of Au atoms in the surface layer. The effect of hydrogen adsorption on the surface and in the first and second subsurface layers of the NSAs was studied. Increasing the Au content in the surface layer weakens hydrogen binding on the surface, but strengthens subsurface binding, suggesting that the distribution of surface and subsurface hydrogen will be different than that on pure Ni(111). While the metal composition of the surface layer has an effect on the binding energy of hydrogen on NSA surfaces, the local composition of the binding site has a stronger effect. For example, fcc hollow sites consisting of three Ni atoms bind H nearly as strongly as on Ni(111), and fcc sites consisting of three Au atoms bind H nearly as weakly as on Au(111). Sites with one or two Au atoms show intermediate binding energies. The preference of hydrogen for three-fold Ni hollow sites alters the relative stabilities of different surface metal atom arrangements, and may provide a driving force for adsorbate-induced surface rearrangement.

  2. A study of the Au/Ni ohmic contact on p-GaN

    SciTech Connect

    Qiao, D.; Yu, L. S.; Lau, S. S.; Lin, J. Y.; Jiang, H. X.; Haynes, T. E.

    2000-10-01

    The formation mechanism of the ohmic Au/Ni/p-GaN contact has been investigated. We found that it is essential to (i) deposit a structure of Au and Ni in the proper deposition sequence, and (ii) anneal the bilayer structure in an oxygen containing ambient. Our findings indicated that oxygen assists the layer-reversal reactions of the metallized layers to form a structure of NiO/Au/p-GaN. The presence of oxygen during annealing appears to increase the conductivity of the p-GaN. It is further suggested that Ni removes or reduces the surface contamination of the GaN sample before or during layer reversal. In the final contact structure, an Au layer, which has a large work function, is in contact with the p-GaN substrate. The presence of Au in the entire contacting layer improves the conductivity of the contact. An ohmic formation mechanism based on our experimental results is proposed and discussed in this work. (c) 2000 American Institute of Physics.

  3. BRIGHT Lights, BIG City: Massive Galaxies, Giant Ly-A Nebulae, and Proto-Clusters

    SciTech Connect

    van Breugel, W; Reuland, M; de Vries, W; Stanford, A; Dey, A; Kurk, J; Venemans, B; Rottgering, H; Miley, G; De Breuck, C; Dopita, M; Sutherland, R; Bland-Hawthorn, J

    2002-08-01

    High redshift radio galaxies are great cosmological tools for pinpointing the most massive objects in the early Universe: massive forming galaxies, active super-massive black holes and proto-clusters. They report on deep narrow-band imaging and spectroscopic observations of several z > 2 radio galaxy fields to investigate the nature of giant Ly-{alpha} nebulae centered on the galaxies and to search for over-dense regions around them. They discuss the possible implications for our understanding of the formation and evolution of massive galaxies and galaxy clusters.

  4. VizieR Online Data Catalog: 1D Lya forest power spectrum (Palanque-Delabrouille+, 2013)

    NASA Astrophysics Data System (ADS)

    Palanque-Delabrouille, N.; Yeche, C.; Borde, A.; Le Goff, J.-M.; Rossi, G.; Viel, M.; Aubourg, E.; Bailey, S.; Bautista, J.; Blomqvist, M.; Bolton, A.; Bolton, J. S.; Busca, N. G.; Carithers, B.; Croft, R. A. C.; Dawson, K. S.; Delubac, T.; Font-Ribera, A.; Ho, S.; Kirkby, D.; Lee, K.-G.; Margala, D.; Miralda-Escude, J.; Muna, D.; Myers, A. D.; Noterdaeme, P.; Paris, I.; Petitjean, P.; Pieri, M. M.; Rich, J.; Rollinde, E.; Ross, N. P.; Schlegel, D. J.; Schneider, D. P.; Slosar, A.; Weinberg, D. H.

    2013-09-01

    The files contain the data describing the measured 1D power spectrum and the correlations between bins from the BOSS Lyman-alpha data. table4a.dat and table5a.dat: P1D results obtained with the Fourier transform and the likelihood method respectively, for each k and z bin. cct4b*.dat and cct5b*.dat: Correlation matrices between k bins for each z bin, for the Fourier transform and the likelihood method respectively. There are 12 HDUs, one for each redshift bin from =2.2 (HDU 1, table[45]b1.dat) to =4.4 (HDU 12, table[45]b12.dat). Each HDU contains a binary table with 35 bins x 35 entries for the Fourier transform method, and 32 bins x 32 entries for the likelihood method. The tables contain the correlation coefficients. The scale ki corresponding to entry (or bin) i can be read in the corresponding entry of table4a.dat or table5a.dat. (30 data files).

  5. Properties of Lya Emitters Around the Radio Galaxy MRC 0316-257

    SciTech Connect

    Venemans, B; Rottgering, H; Miley, G; Kurk, J; De Breuck, C; van Breugel, W; Carilli, C; Ford, H; Heckman, T; Pentericci, L; McCarthy, P

    2004-08-12

    Observations of the radio galaxy MRC 0316-257 at z = 3.13 and the surrounding field are presented. Using narrow- and broad-band imaging obtained with the VLT*, 92 candidate Ly{alpha} emitters with a rest-frame equivalent width of > 15 AngstromS were selected in a {approx} 7{prime} x 7{prime} field around the radio galaxy. Spectroscopy of 40 candidate emitters resulted in the discovery of 33 emission line galaxies of which 31 are Ly{alpha} emitters with redshifts similar to that of the radio galaxy, while the remaining two galaxies turned out to be [{omicron} II] emitters. The Ly{alpha} profiles had widths (FWHM) corresponding to 120-800 kms{sup -1},with a median of 260 kms{sup -1}. Where the signal-to-noise spectra was large enough, the Ly{alpha} profiles are found to be asymmetric, with apparent absorption troughs blueward of the profile peaks, indicative of absorption along the line of sight of an {Eta}{Iota} mass of 1-5000 {mu}{circle_dot}. Besides that of the radio galaxy and one of the emitters that is an QSO, the continuum of the emitters is faint, with luminosities ranging from 1.3 L{sub *} to < 0.03 L{sub *}.The colors of the confirmed emitters are, on average, very blue. The median UV continuum slope is {beta}=-1.65, bluer than the average slope of LBGs with Ly{alpha} emitters is 2.6 {Mu}{circle_dot}{sup -1} as measured by the Ly{alpha} emission line or < 3.9 {Mu}{circle_dot}{sup -1} as measured by the UV continuum. The properties of the Ly{alpha} galaxies (faint, blue and small) are consistent with young star forming galaxies which are nearly dust free. The density of Ly{alpha} emitting galaxies in the field around MRC 0316-257 is a factor of 3.3{sup +0.5}{sub -0.4} larger compared with the density of Ly{alpha} emitters at that redshift. The velocity distribution of the spectroscopically confirmed emitters has a dispersion of 640 km s{sup -1}, corresponding to a FWHM of 1510 km s{sup -1}, which is substantially smaller than the width of the narrow-band filter (FWHM {approx}3500km s{sup -1}). The peak of the velocity distribution is located with 200 kms{sup -1} of the redshift of the radio galaxy. We conclude the confirmed Ly{alpha} emitters are members of a protocluster of galaxies at z {approx}3.13. The size of the protocluster is unconstraint and is larger than 3.3x3.3 Mpc{sup 2}. The mass of this structure is estimated to be > 3-6 x 10{sup 14}{Mu}{circle_dot} and could be the precursor of a cluster of galaxies similar to e.g. the Virgo cluster.

  6. Huge Inverse Magnetization Generated by Faraday Induction in Nano-Sized Au@Ni Core@Shell Nanoparticles.

    PubMed

    Kuo, Chen-Chen; Li, Chi-Yen; Lee, Chi-Hung; Li, Hsiao-Chi; Li, Wen-Hsien

    2015-08-25

    We report on the design and observation of huge inverse magnetizations pointing in the direction opposite to the applied magnetic field, induced in nano-sized amorphous Ni shells deposited on crystalline Au nanoparticles by turning the applied magnetic field off. The magnitude of the induced inverse magnetization is very sensitive to the field reduction rate as well as to the thermal and field processes before turning the magnetic field off, and can be as high as 54% of the magnetization prior to cutting off the applied magnetic field. Memory effect of the induced inverse magnetization is clearly revealed in the relaxation measurements. The relaxation of the inverse magnetization can be described by an exponential decay profile, with a critical exponent that can be effectively tuned by the wait time right after reaching the designated temperature and before the applied magnetic field is turned off. The key to these effects is to have the induced eddy current running beneath the amorphous Ni shells through Faraday induction.

  7. 75 FR 10793 - FY2010 Supplemental Funding for Brownfields Revolving Loan Fund (RLF) Grantees

    Federal Register 2010, 2011, 2012, 2013, 2014

    2010-03-09

    ...: ECL-112 Seattle, WA 98101, Phone (206) 553-7299 Fax (206) 553-0124. Dated: March 2, 2010. David R... Region 2, Lya Theodoratos, NJ, NY, PR, VI 290 Broadway, 18th Theodoratos.Lya@epa.gov . Floor, New...

  8. The Agatston Urban Nutrition Initiative: Working to Reverse the Obesity Epidemic through Academically Based Community Service

    ERIC Educational Resources Information Center

    Johnston, Francis E.

    2009-01-01

    The Agatston Urban Nutrition Initiative (AUNI) presents a fruitful partnership between faculty and students at a premier research university and members of the surrounding community aimed at addressing the problem of childhood obesity. AUNI uses a problem-solving approach to learning by focusing course activities, including service-learning, on…

  9. The Agatston Urban Nutrition Initiative: working to reverse the obesity epidemic through academically based community service.

    PubMed

    Johnston, Francis E

    2009-01-01

    The Agatston Urban Nutrition Initiative (AUNI) presents a fruitful partnership between faculty and students at a premier research university and members of the surrounding community aimed at addressing the problem of childhood obesity. AUNI uses a problem-solving approach to learning by focusing course activities, including service-learning, on understanding and mitigating the obesity culture.

  10. The Coffee-Milk Mixture Problem Revisited

    ERIC Educational Resources Information Center

    Marion, Charles F.

    2015-01-01

    This analysis of a problem that is frequently posed at professional development workshops, in print, and on the Web--the coffee-milk mixture riddle--illustrates the timeless advice of George Pólya's masterpiece on problem solving in mathematics, "How to Solve It." In his book, Pólya recommends that problems previously solved and put…

  11. Do Lyman-alpha photons escape from star-forming galaxies through dust-holes?

    NASA Astrophysics Data System (ADS)

    Wofford, Aida

    2012-10-01

    The hydrogen Lyman-alpha line is arguably the most important signature of galaxies undergoing their first violent burst of star formation. Although Lya photons are easily destroyed by dust, candidate Lya emitters have been detected at z>5. Thus the line can potentially be used to probe galaxy formation and evolution, as long as the astrophysical processes that regulate the escape of Lya photons from star-forming galaxies are well understood.We request 15 orbits for imaging in Lya and the FUV continuum with ACS/SBC, and in the H-beta/H-alpha ratio {proxy for dust extinction} with WFC3/UVIS, a sample of isolated non-AGN face-on spirals for which our team previously obtained and analyzed COS FUV spectroscopy of the central regions. Each target shows a different Lya profile, i.e., pure absorption, P-Cygni like, and multiple-emission. From the COS data, we already know the starburst phase and H I gas velocity. The images would greatly increase the impact of our spectroscopic study by enabling us to 1} conclusively determine if Lya photons escape through dust-holes, 2} assess the relative importance of dust extinction, ISM kinematics, and starburst phase in regulating the Lya escape, 3} clarify what we can really learn from the Lya equivalent width, and 4} provide constraints on the dust extinction to Lya 3D radiative transfer models. Ultimately this program will inform our understanding of the Lya escape at high redshift by providing spatially resolved views of the local conditions within star-forming galaxies that favor escape.

  12. 77 FR 16030 - FY2012 Supplemental Funding for Brownfields Revolving Loan Fund (RLF) Grantees

    Federal Register 2010, 2011, 2012, 2013, 2014

    2012-03-19

    ..., Phone (617) 918-1424, Fax (617) 918-1291. EPA Region 2, Lya Theodoratos, NJ, NY, PR, VI 290 Broadway... Sixth Avenue, Suite 900, Mailstop: Morales.Susan@epa.gov . ECL-112 Seattle, WA 98101, Phone (206)...

  13. The achievement of low contact resistance to indium phosphide: The roles of Ni, Au, Ge, and combinations thereof

    NASA Technical Reports Server (NTRS)

    Fatemi, Navid S.; Weizer, Victor G.

    1992-01-01

    We have investigated the electrical and metallurgical behavior of Ni, Au-Ni, and Au-Ge-Ni contacts on n-InP. We have found that very low values of contact resistivity rho(sub c) in the E-7 omega-sq cm range are obtained with Ni-only contacts. We show that the addition of Au to Ni contact metallization effects an additional order of magnitude reduction in rho(sub c). Ultra-low contact resistivities in the E-8 omega-sq cm range are obtained with both the Au-Ni and the Au-Ge-Ni systems, effectively eliminating the need for the presence of Ge in the Au-Ge-Ni system. The formation of various nickel phosphides at the metal-InP interface is shown to be responsible for the observed rho(sub c) values in the Ni and Au-Ni systems. We show, finally, that the order in which the constituents of Au-Ni and Au-Ge-Ni contacts are deposited has a significant bearing on the composition of the reaction products formed at the metal-InP interface and therefore on the contact resistivity at that interface.

  14. Lyman Alpha Blobs: Seeds of Galaxy Groups

    NASA Astrophysics Data System (ADS)

    Hall, Agnar; Prescott, Moire

    2017-01-01

    Recently, evidence has been mounting that giant Lyman alpha (Lya) nebulae, or "blobs," at high redshift are coincident with regions of galaxy overdensity and likely the progenitors of galaxy groups. These Lya blobs are rare structures found at roughly 1 < z < 6 which have typical diameters of ~100 kpc and Lya luminosities of ~10^42 to 10^44 erg s^-1. Using Hubble Space Telescope (HST) imaging, we explore the environments of three systematically-selected blobs at 1.5 < z < 2.5. Comparing the total surface density of galaxies in a region centered on the blob to the average surface density of galaxies in the field, we find that all three blobs exhibit significant overdensity (up to a factor of 5-10). After narrowing down which galaxies are most likely to be associated with each Lya blob, we confirm that the raw overdensities are enhanced and find evidence of a luminosity gap in at least one of the three systems studied. These results suggest that Lya blobs offer new insight into the early phases of galaxy group and cluster formation.

  15. Surface Segregation in Ternary Alloys

    NASA Technical Reports Server (NTRS)

    Good, Brian; Bozzolo, Guillermo H.; Abel, Phillip B.

    2000-01-01

    Surface segregation profiles of binary (Cu-Ni, Au-Ni, Cu-Au) and ternary (Cu-Au-Ni) alloys are determined via Monte Carlo-Metropolis computer simulations using the BFS method for alloys for the calculation of the energetics. The behavior of Cu or Au in Ni is contrasted with their behavior when both are present. The interaction between Cu and Au and its effect on the segregation profiles for Cu-Au-Ni alloys is discussed.

  16. Surface-enhanced Raman scattering via entrapment of colloidal plasmonic nanocrystals by laser generated microbubbles on random gold nano-islands

    NASA Astrophysics Data System (ADS)

    Kang, Zhiwen; Chen, Jiajie; Ho, Ho-Pui

    2016-05-01

    Surface-enhanced Raman scattering (SERS) typically requires hot-spots generated in nano-fabricated plasmonic structures. Here we report a highly versatile approach based on the use of random gold nano-island substrates (AuNIS). Hot spots are produced through the entrapment of colloidal plasmonic nano-crystals at the interface between AuNIS and a microbubble, which is generated from the localized plasmonic absorption of a focused laser beam. The entrapment strength is strongly dependent on the shape of the microbubble, which is in turn affected by the surface wetting characteristics of the AuNIS with respect to the solvent composition. The laser power intensity required to trigger microbubble-induced SERS is as low as 200 μW μm-2. Experimental results indicate that the SERS limit of detection (LOD) for molecules of 4-MBA (with -SH bonds) is 10-12 M, R6G or RhB (without -SH bonds) is 10-7 M. The proposed strategy has potential applications in low-cost lab-on-chip devices for the label-free detection of chemical and biological molecules.

  17. Tailoring characteristic thermal stability of Ni-Au binary nanocrystals via structure and composition engineering: theoretical insights into structural evolution and atomic inter-diffusion

    SciTech Connect

    Li, Bangquan; Wang, Hailong; Xing, Guozhong; Wang, Rongming E-mail: rmwang@ustb.edu.cn

    2014-11-15

    We report on the structural evolution and atomic inter-diffusion characteristics of the bimetallic Ni-Au nanocrystals (NCs) by molecular dynamics simulations studies. Our results reveal that the thermal stability dynamics of Ni-Au NCs strongly depends on the atomic configurations. By engineering the structural construction with Ni:Au = 1:1 atomic composition, compared with core-shell Au@Ni and alloy NCs, the melting point of core-shell Ni@Au NCs is significantly enhanced up to 1215 K. Unexpectedly, with atomic ratio of Au:Ni= 1:9, the melting process initiates from the atoms in the shell of Ni@Au and alloy NCs, while starts from the core of Au@Ni NCs. The corresponding features and evolution process of structural motifs, mixing and segregation are illustrated via a series of dynamic simulations videos. Moreover, our results revealed that the face centered cubic phase Au{sub 0.75}Ni{sub 0.25} favorably stabilizes in NCs form but does not exist in the bulk counterpart, which elucidates the anomalies of previously reported experimental results on such bimetallic NCs.

  18. Design and fabrication of an implantable cortical semiconductor integrated circuit electrode array

    NASA Astrophysics Data System (ADS)

    Lefevre, Pierre K.

    1990-12-01

    This research furthered the processing steps of the AFIT 16 by 16 implantable cortical semiconductor integrated circuit electrode array, or brain chip. The areas of interest include the brain chip electronics, metallization, ionic permeation, and implantation. The electronics and metallization are heavily covered. A high speed, single clock divide-by-two circuit was modified with a reset transistor and cascaded to form a ripple counter. This device had stable operation at specific source voltage and clock voltage and frequency. A 7-stage inverter with 10 unmodified divide-by-two circuits cascaded operated between 1.7 and 8 volts, and between 39 KHz and 1 MHz, respectively. The metallization process refers to coating Au/Ni or Pt onto exposed aluminum areas (pads) of a CMOS integrated circuit. Sputtering was used to coat the chip. And an Au/Ni etchant or Pt peel-off technique was used. The Au/Ni etchant used was iodine, potassium iodide, and deionized water solution.

  19. 76 FR 2905 - FY2011 Supplemental Funding for Brownfields Revolving Loan Fund (RLF) Grantees

    Federal Register 2010, 2011, 2012, 2013, 2014

    2011-01-18

    ..., VT. Suite 1100, Boston, MA 02114-2023, Phone (617) 918-1424, Fax (617) 918-1291. EPA Region 2, Lya...: ECL-112 Seattle, WA 98101, Phone (206) 553-7299, Fax (206) 553-0124. Dated: January 10, 2011. David...

  20. Do Lyman-alpha photons escape from star-forming galaxies through dust holes?

    NASA Astrophysics Data System (ADS)

    France, Kevin; Wofford, A.; Leitherer, C.; Fleming, B.; McCandliss, S. R.; Nell, N.

    2014-01-01

    H I Lyman-alpha (LyA) is commonly used as a signpost for the entire galaxy at redshifts z>2, and yet spatially and kinematically resolved views of the local conditions within galaxies that determine the integrated properties of this line are scarce. We obtained Hubble Space Telescope (HST) images in continuum-subtracted LyA, H-alpha, H-beta, and far-UV continuum of three low-inclination spiral star-forming galaxies located at redshifts z=0.02, 0.03, and 0.05. This was accomplished using the UVIS and SBC channels of the Wide Field Camera 3 (WFC3) and the Advanced Camera for Surveys (ACS), respectively. Previous HST spectroscopy obtained by our team with the Cosmic Origins Spectrograph (COS) showed that the galaxies display different integrated LyA profiles within their central few kiloparsecs, i.e., pure absorption, single emission, and double emission, which are representative of what is observed between redshifts 0-3. This data is useful for establishing the relative importance of starburst phase, dust content, and gas kinematics in determining the LyA escape. We present preliminary results that combine our spectroscopic and imaging observations.

  1. Development of an Acculturation Measure for Latino Youth.

    ERIC Educational Resources Information Center

    Pillen, Michelle B.; Hoewing-Roberson, Renee C.

    As part of a substance abuse prevention project, a measure was developed in both English and Spanish to measure levels of acculturation among members of a Latino youth population for later comparison of acculturation with high-risk behaviors. The Latino Youth Acculturation Scale (LYAS) consists of 23 items. Eleven items deal with language use of…

  2. The SMC SNR 1E0102.2-7219 as a calibration standard for X-ray astronomy in the 0.3 - 2.5 keV bandpass

    NASA Astrophysics Data System (ADS)

    Plucinsky, P.

    2009-09-01

    The flight calibration of the spectral response of CCD instruments below 1.5 keV is difficult in general because of the lack of strong lines in the on-board calibration sources typically available. We have been using E0102, the brightest supernova remnant in the Small Magellanic Cloud, to evaluate the response models of the ACIS CCDs on the Chandra X-ray Observatory (CXO), the EPIC CCDs on the XMM-Newton Observatory, the XIS CCDs on the Suzaku Observatory, and the XRT CCD on the Swift Observatory. E0102 has strong lines of O, Ne, and Mg below 1.5 keV and little or no Fe emission to complicate the spectrum. The spectrum of E0102 has been well characterized using high-resolution grating instruments, namely the XMM-Newton RGS and the CXO HETG, through which a consistent spectral model has been developed that can then be used to fit the lower- resolution CCD spectra. Fits with this model are sensitive to any problems with the gain calibration and the spectral redistribution model of the CCD instruments. We have also used the measured intensities of the lines to investigate the consistency of the effective area models for the various instruments around the bright O (570 eV and 654 eV) and Ne (910 eV and 1022 eV) lines. We find that the measured fluxes of the O VII triplet, the O VIII Ly-a line, the Ne IX triplet, and the Ne X Ly-a line generally agree to within +/-10% for all instruments, with 28 of our 32 fitted normalizations within +/-10% of the RGS-determined value. The maximum discrepancies, computed as the percentage difference between the lowest and highest normalization for any instrument pair, are 23% for the O VII triplet, 24% for the O VIII Ly-a line, 13% for the Ne IX triplet, and 19% for the Ne X Ly-a line. If only the CXO and XMM are compared, the maximum discrepancies are 22% for the O VII triplet, 16% for the O VIII Ly-a line, 4% for the Ne IX triplet, and 12% for the Ne X Ly-a line.

  3. The SMC SNR 1E0102.2-7219 as a calibration standard for x-ray astronomy in the 0.3-2.5 keV bandpass

    NASA Astrophysics Data System (ADS)

    Plucinsky, Paul P.; Haberl, Frank; Dewey, Daniel; Beardmore, Andrew P.; DePasquale, Joseph M.; Godet, Olivier; Grinberg, Victoria; Miller, Eric D.; Pollock, A. M. T.; Sembay, Steven; Smith, Randall K.

    2008-07-01

    The flight calibration of the spectral response of CCD instruments below 1.5 keV is difficult in general because of the lack of strong lines in the on-board calibration sources typically available. We have been using E0102, the brightest supernova remnant in the Small Magellanic Cloud, to evaluate the response models of the ACIS CCDs on the Chandra X-ray Observatory (CXO), the EPIC CCDs on the XMM-Newton Observatory, the XIS CCDs on the Suzaku Observatory, and the XRT CCD on the Swift Observatory. E0102 has strong lines of O, Ne, and Mg below 1.5 keV and little or no Fe emission to complicate the spectrum. The spectrum of E0102 has been well characterized using high-resolution grating instruments, namely the XMM-Newton RGS and the CXO HETG, through which a consistent spectral model has been developed that can then be used to fit the lower-resolution CCD spectra. Fits with this model are sensitive to any problems with the gain calibration and the spectral redistribution model of the CCD instruments. We have also used the measured intensities of the lines to investigate the consistency of the effective area models for the various instruments around the bright O (570 eV and 654 eV) and Ne (910 eV and 1022 eV) lines. We find that the measured fluxes of the O VII triplet, the O VIII Ly-a line, the Ne IX triplet, and the Ne X Ly-a line generally agree to within +/-10% for all instruments, with 28 of our 32 fitted normalizations within +/-10% of the RGS-determined value. The maximum discrepancies, computed as the percentage difference between the lowest and highest normalization for any instrument pair, are 23% for the O VII triplet, 24% for the O VIII Ly-a line, 13% for the Ne IX~triplet, and 19% for the Ne X Ly-a line. If only the CXO and XMM are compared, the maximum discrepancies are 22% for the O VII triplet, 16% for the O VIII Ly-a line, 4% for the Ne IX triplet, and 12% for the Ne X Ly-a line.

  4. Lyman-Alpha Observations of High Radial Velocity Stars

    NASA Astrophysics Data System (ADS)

    Bookbinder, Jay

    1990-12-01

    H I LYMAN -ALPHA (LY-A) IS ONE OF THE MOST IMPORTANT LINES EMITTED BY PLASMA IN THE TEMPERATURE RANGE OF 7000 TO 10 TO THE FIFTH POWER K IN LATE-TYPE STARS. IT IS A MAJOR COMPONENT OF THE TOTAL RADIATIVE LOSS RATE, AND IT PLAYS A CRUCIAL ROLE IN DETERMINING THE ATMOSPHERIC STRUCTURE AND IN FLUORESCING OTHER UV LINES. YET IT IS ALSO THE LEAST STUDIED MAJOR LINE IN THE FAR UV, BECAUSE MOST OF THE LINE FLUX IS ABSORBED BY THE ISM ALONG THE LINE OF SIGHT AND BECAUSE IT IS STRONGLY COMTAMINATED BY THE GEOCORONAL BACKGROUND. A KNOWLEDGE OF THE Ly-A PROFILE IS ALSO IMPORTANT FOR STUDIES OF DEUTERIUM IN THE INTERSTELLAR MEDIUM. BY OBSERVING HIGH RADIAL VELOCITY STARS WE WILL OBTAIN FOR THE FIRST TIME HIGH RESOLUTION SPECTRA OF THE CORE OF A STELLAR H I LYMAN-A EMISSION LINE PROFILE.

  5. The COS Absorption Survey of Baryon Harbors (CASBaH): Probing the Circumgalactic Media of Galaxies from z = 0 to z = 1.5

    NASA Astrophysics Data System (ADS)

    Tripp, Todd

    2014-10-01

    In Cycle 17, we obtained high S/N, far-ultraviolet COS spectra of nine QSOs at 0.92 < z(QSO) < 1.47 to study the elusive warm-hot gas (log T = 5 - 6) and multiphase gaseous halos. Program highlights include (a) evidence of massive, multiphase galactic outflows with large spatial extent, (b) detection of pristine and cold gas, possibly in cold-accretion flows, and (c) discovery of a bimodal metallicity distribution in Lyman-limit absorbers. These rich data will be mined for some time, but ultimately the usefulness of the database is limited by the FUV wavelength range of the original observations. To fully exploit these unique HST observations to study the circumgalactic medium during the golden age of star formation (0.5 < z < 1.5), we propose high-resolution near-UV (>1800 A) spectroscopy of the same QSOs with STIS and COS to fully cover the H I Lya and Lyman series from z = 0 out to z = z(QSO) and significantly improve the statistics of far-UV lines and diagnostics. With these data we will (1) obtain precise metallicities of the cool CGM with added coverage of H I Lya and Lyman series lines (often not covered in current data at z > 0.5), (2) constrain the metallicity and mass of the warm-hot gas from, e.g, OVI/NeVIII + broad Lya constraints, (3) measure relative abundances (instead of assuming them) using banks of ions accessible only in the far-UV, (4) study absorber redshift evolution with the expanded samples at 0.5 < z < 1.5, (5) obtain more complete and accurate identification of weak lines, which is difficult without constraints on Lya at 0.5 < z < z(QSO), and (6) investigate statistical absorber-galaxy relationships in the epoch of peak star formation.

  6. Far Infrared Spectroscopy of the Nearby Analogues of High-Redshift Galaxies

    NASA Astrophysics Data System (ADS)

    Hayes, Matthew

    2014-10-01

    We propose far infrared emission line spectroscopy of a sample of 23 local star-forming galaxies, drawn from the Lyman alpha Reference Sample (LARS), for which we have unrivalled high-resolution imaging and spectroscopy from HST, and 21cm HI observations from VLA+GMRT. Moreover the galaxies are selected as the close analogues of the high-redshift Lyman-break galaxies and Spitzer+Herschel selected galaxies found in extragalactic deep fields. The science goal of LARS is to determine what governs the escape of Lyman alpha (Lya) photons from galaxies, and thereby aid interpretation of high-z observations where Lya is the most used spectral probe. However given its clean selection and multiwavelength nature, LARS can equally well improve our understanding of FIR line observations of high-z galaxies. The target emission lines in this proposal are [CII], [OI], and [OIII] at 158, 63, and 88 micron, respectively. The motivations are that these lines: 1. are of increasing interest at high-z as new sensitive submm/radio interferometers come online 2. are proposed quantitative tracers of star formation rates, but their utility must be proven in appropriately analogous well-studied galaxies 3. when combined with models of photodissociation regions, enable estimates of the density and mass of PDR gas and provide vital constraints on our Lya radiative transfer models of galaxies. 4. provide uniquely robust estimates of nebular extinction and metallicity when combined with our optical IFU data. Astrophysical applications are many, especially when combined with the array of existing data. Specifically they will provide vital constraints on ISM structure, that are required for understanding the emission of the cosmologically vital Lya emission line. Moreover, SFR calibrations will be tested in star forming environments that resemble those of early galaxies and the legacy value of the sample is hard to overstate.

  7. Sensitivity Tests of a Surface-Layer Windflow Model to Effects of Stability and Vegetation.

    DTIC Science & Technology

    1985-10-25

    ORGANIZATION [b. OFFICE SYMBOL 7a NAME OF MONITORING ORGANIZATION Air Force Geophysics L.aborator y LYA 6. ADDRESS cis SIdtt..d /11 CIdP 7tb ADDRESSL.1...between 1 " J University 12 reasonably accurate wind and 2 km above speeds and directions while ground level (AGL), incorporating effects of sur- so it is...several reasons why a variational approach is appropriate for this 4modeling application. Ball and Johnson stated that the advection terms of the

  8. Science Data Management for WSO-UV

    NASA Astrophysics Data System (ADS)

    Gomez De Castro, Ana; Sachkov, Mikhail; Marcos-Arenal, Pablo; Belén Perea Abarca, G.; Malkov, Oleg

    2016-07-01

    WSO-UV is a 170 primary space telescope that will work in the ultraviolet range (115-315 nm) of the spectrum providing instrumentation for spectroscopy and imaging. WSO-UV is a cornerstone project of the astronomical program of the Russian Space Agency with launch date 2021. Spain and Mexico participate in the project. Scientific observation with WSO-UV will be open to the world wide scientific community after the 1st year of mission. WSO-UV will handle three scientific programs: core, national and open. The core program will be run during the first two years of the mission and will provide unique results that will affect all branches of astrophysics. WSO-UV will be equipped with a camera for very deep imaging in the Hydrogen Lyman-alpha (Lya) line and will be orbiting in a High Earth Orbit (geosynchronous). As a result, it will provide the deepest images ever obtained in this fundamental tracer (Lya is the strongest spectral line in the Universe). In this talk, we describe the strategy for the Lya survey and the foreseen output products and data distribution policy.

  9. LY-alpha Line Emission in a Field of Super-Clustered Damped LY-alpha Absorbers

    NASA Astrophysics Data System (ADS)

    Møller, Palle; Warren, Stephen J.

    1993-12-01

    The quasar pair Q2138-4427 and Q2139-4434 is separated by 8 arcmin on the sky (~ 6 Mpc), and they have correlated damped \\lya absorption (DLA) at two redshifts, z=2.380 and z=2.853 (Francis, P. J., and Hewett, P. C., 1993, AJ 105, 1633). On three nights in September 1993 we imaged the field of Q2138-4427 in B, I, and a narrow band tuned to the DLA at z=2.853. The observations were carried out with the ESO 3.6m telescope. We find two emission line candidates in the field. The two candidates have line fluxes similar to the three sources found in the field of Q0528-250 (M{\\o}ller, P., and Warren, S. J., 1993, \\aa 270, 43) but they are much brighter in the continuum. The two candidates are lying quite far from the quasar, so even if they are spectroscopically confirmed to be \\lya emitters, they are unlikely to be identified with the absorber. Their continuum fluxes make them more likely to be either OII emitters at low redshift, or high redshift AGNs associated with the super-cluster structure reported by Francis and Hewett. \\lya emission sources similar to the ones detected in the field of Q0528-250 are not seen. A comparison of these new results with our previous detections will allow us to draw general conclusions on the nature of the damped systems.

  10. Resistance to sulfur poisoning of Ni-based alloy with coinage (IB) metals

    NASA Astrophysics Data System (ADS)

    Xu, Xiaopei; Zhang, Yanxing; Yang, Zongxian

    2015-12-01

    The poisoning effects of S atom on the (1 0 0), (1 1 0) and (1 1 1) metal surfaces of pure Ni and Ni-based alloy with IB (coinage) metals (Cu, Ag, Au) are systematically studied. The effects of IB metal dopants on the S poisoning features are analyzed combining the density functional theory (DFT) results with thermodynamics data using the ab initio atomistic thermodynamic method. It is found that introducing IB doping metals into Ni surface can shift the d-band center downward from the Fermi level and weaken the adsorption of S on the (1 0 0) and (1 1 0) surfaces, and the S tolerance ability increases in the order of Ni, Cu/Ni, Ag/Ni and Au/Ni. Nevertheless, on the (1 1 1) surface, the S tolerance ability increases in the order of Ag/Ni (or Cu/Ni), Ni, and Au/Ni. When we increase the coverage of the IB metal dopants, we found that not only Au, but Cu and Ag can increase its S tolerance. We therefore propose that alloying can increase its S tolerance and alloying with Au would be a better way to increase the resistance to sulfur poisoning of the Ni anode as compared with the pure Ni and the Ag- or, Cu-doped Ni materials.

  11. Structures and associated catalytic properties of well-defined nanoparticles produced by laser vaporisation of alloy rods.

    PubMed

    Caps, Valérie; Arrii, Sandrine; Morfin, Franck; Bergeret, Gérard; Rousset, Jean-Luc

    2008-01-01

    Bimetallic clusters, all containing gold, have been produced by laser vaporisation of bulk alloys followed by deposition of the formed clusters onto Al2O3 and TiO2 powders or flat silica supports. This technique allows a narrow size distribution of highly dispersed gold-based nanoparticles on powders and nanocrystalline structured thin films on 2D supports to be obtained. The catalytic performances of the as-obtained AuFe, AuNi, AuTi powdery catalysts have been studied in the PROX reaction and compared with those obtained in the oxidation of CO in the temperature range 25-300 degrees C. By comparing the activities of the different catalysts, it is concluded that the nature of the gold partner directly affects the activity of gold. The following tendency is observed: AuFe and AuNi have rather similar activities, significantly lower than that of AuTi. In this paper, we also present a first attempt to study reactivity of original self-supported systems. We show that significant CO oxidation reactivity can be obtained over unsupported nanoporous AuTi and PdAu thin films. By completely excluding the support effect, unsupported catalysts could provide a way of understanding the relevant catalytic mechanisms more easily.

  12. Morphology, stresses, and surface reactivity of nanoporous gold synthesized from nanostructured precursor alloys

    NASA Astrophysics Data System (ADS)

    Rouya, Eric

    Nanoporous metallic materials (NMMs) are generally synthesized using dealloying, whereby the more reactive component is dissolved from a homogeneous alloy in a suitable electrolyte, and the more noble metal atoms simultaneously diffuse into 3-D clusters, forming a bi-continuous network of interconnected ligaments. Nanoporous gold (NPG) in particular is a well-known NMM; it is inert, bio-compatible, and capable of developing large surface areas with 1--100nm pores. While several studies have demonstrated its potential usefulness in fuel cell and sensing devices, its structural, mechanical, and electrocatalytic properties still require further investigation, particularly if NPG is synthesized from precursor alloy films exhibiting metastable nanostructures. In this dissertation, the electrodeposition (ECD) process, microstrucural characteristics, and metatstability of Au-Ni precursor alloys are investigated. The stresses evolved during Au-Ni alloy nucleation and growth are investigated in situ and correlated with microstructural and electrochemical data in order to identify the various stress-inducing mechanisms. In situ stresses generated during Au-Ni and Au-Ag dealloying were investigated, and additionally correlated with the growth stresses. Finally, the surface area and electrocatalytic properties of NPG are characterized using a variety of electrochemical techniques. Potentiostatically electrodeposited Au1-x-Nix (x: 0--90at%) films form a continuous series of metastable solid solutions and exhibit a nanocrystalline morphology, with ˜10--20 nm grains, the size of which decreases with increasing Ni content. The formation of a metastable structure was interpreted in terms of the limited surface diffusivities of adatoms at the growing interface and atomic volume differences (˜15%). Internal stresses generated during ECD of Ni-rich films can be explained assuming a 3-D Volmer-Weber growth mode, where the stress is initially compressive, then transitions into tension

  13. Lyman alpha emitting galaxies at high redshift: Direct detection of young galaxies in a young universe

    NASA Astrophysics Data System (ADS)

    Dawson, Steven Arthur

    An early result of galaxy formation theory was the prediction that the copious ionizing radiation produced in nascent galaxies undergoing their first starbursts should in turn produce a strong Lya emission line. We report on our efforts to detect and characterize primeval galaxies by searching for this expected Lya signature with two observational techniques: serendipitous slit spectroscopy, and narrowband imaging selection. In Part I, we describe our serendipitous slit spectroscopy survey of the Hubble Deep Field and its environs, which resulted in a catalog of 74 spectroscopic redshifts spanning 0.10 < z < 5.77, including a galaxy cluster at z = 0.85 and five galaxies at z > 5. Follow-up observations at higher resolution resulted in the additional serendipitous detection of a strong Lya-emitting galaxy at z = 5.190 (ES1). At the time of its discovery, ES1 was one of only nine known galaxies at z > 5, and was the sixth most distant known galaxy. The unprecedented spectral purity of the observation offers evidence for a galaxy-scale outflow with a. velocity of v > 300 km s -1 , consistent with wind speeds observed in powerful local starbursts (typically 10 2 to 10 3 km s -1 ), and with simulations of the late- stage evolution of Lya emission in star-forming systems. Our final serendipitous detection is the remarkable source CXOHDFN J123635.6+621424, which is both the highest redshift known spiral galaxy, and a rare example of a high redshift, hard X-ray-emitting Type II AGN. Significantly, all of these results were acquired with no direct allocation of telescope time. In Part II, we report on our implementation of narrowband imaging selection, with which we traded redshift coverage for survey volume, focusing on the systematic study of galaxies at a particular epoch in favor of chasing that rare, most-distant object. This effort resulted in a catalog of 76 z [approximate] 4.5 Lya-emitting galaxies spectroscopically-confirmed in campaigns of Keck/LRIS and Keck

  14. Sliding contacts on printed circuit boards and wear behavior

    NASA Astrophysics Data System (ADS)

    Le Solleu, J.-P.

    2010-04-01

    Automotive suppliers use since decades printed circuit boards (PCB) gold plating pads, as direct contact interface for low current sliding contacts. Several gold plating processes are available on the market, providing various wear behaviour. Some specific galvanic hard gold (AuCo or AuNi). plating was developed on PCB's. This specific plating generates extra costs due to the material quantity and also the process complexity. In a cost driven industry, the challenge is to use a standard low cost PCB for systems requesting high reliability performances. After a brief overview of standard PCB manufacturing processes and especially gold plating processes, the global experimental results of wear behaviour of three different gold plating technologies will be exposed and an explanation of the correlation between surface key parameters and wear out will be provided.

  15. Electrochemical synthesis of multisegmented nanowires

    SciTech Connect

    Kok, Kuan-Ying; Ng, Inn-Khuan; Saidin, Nur Ubaidah

    2012-11-27

    Electrochemical deposition has emerged as a promising route for nanostructure fabrication in recent years due to the many inherent advantages it possesses. This study focuses on the synthesis of high-aspect-ratio multisegmented Au/Ni nanowires using template-directed sequential electrochemical deposition techniques. By selectively removing the Ni segments in the nanowires, high-yield of pure gold nanorods of predetermined lengths was obtained. Alternatively, the sacrificial Ni segments in the nanowires can be galvanically displaced with Bi and Te to form barbells structures with Bi{sub x}Te{sub y} nanotubes attached to neighbouring gold segments. Detailed studies on the nanostructures obtained were carried out using various microscopy, diffraction and probebased techniques for structural, morphological and chemical characterizations.

  16. Enhanced emission and photoconductivity due to photo-induced charge transfer from Au nanoislands to ZnO

    SciTech Connect

    Wu, Shang-Hsuan; Chan, Ching-Hsiang; Liang, Ching-Tarng; Chien, Ching-Hang; Yaseen, Mohammad Tariq; Chang, Yia-Chung

    2016-01-25

    We report systematic studies based on photoluminescence, Hall, and photoconductivity measurements together with theoretical modeling in order to identify mechanisms for the photo-induced charge transfer effects in ZnO thin film incorporated with the Au nano-islands (AuNIs). Significant enhancement of near band edge emission and improvement in conductivity of ZnO/AuNIs samples after illumination are observed, which are attributed to the photo-induced hot electrons in Au which are then transferred into the conduction band of ZnO as long as the excitation energy is higher than the offset between the ZnO conduction-band minimum and Au Fermi level. Our experimental results are consistent with the general features predicted by first principles calculations.

  17. Thermal stability and adhesion of low-emissivity electroplated Au coatings.

    SciTech Connect

    Jorenby, Jeff W.; Hachman, John T., Jr.; Yang, Nancy Y. C.; Chames, Jeffrey M.; Clift, W. Miles

    2010-12-01

    We are developing a low-emissivity thermal management coating system to minimize radiative heat losses under a high-vacuum environment. Good adhesion, low outgassing, and good thermal stability of the coating material are essential elements for a long-life, reliable thermal management device. The system of electroplated Au coating on the adhesion-enhancing Wood's Ni strike and 304L substrate was selected due to its low emissivity and low surface chemical reactivity. The physical and chemical properties, interface bonding, thermal aging, and compatibility of the above Au/Ni/304L system were examined extensively. The study shows that the as-plated electroplated Au and Ni samples contain submicron columnar grains, stringers of nanopores, and/or H{sub 2} gas bubbles, as expected. The grain structure of Au and Ni are thermally stable up to 250 C for 63 days. The interface bonding is strong, which can be attributed to good mechanical locking among the Au, the 304L, and the porous Ni strike. However, thermal instability of the nanopore structure (i.e., pore coalescence and coarsening due to vacancy and/or entrapped gaseous phase diffusion) and Ni diffusion were observed. In addition, the study also found that prebaking 304L in the furnace at {ge} 1 x 10{sup -4} Torr promotes surface Cr-oxides on the 304L surface, which reduces the effectiveness of the intended H-removal. The extent of the pore coalescence and coarsening and their effect on the long-term system integrity and outgassing are yet to be understood. Mitigating system outgassing and improving Au adhesion require a further understanding of the process-structure-system performance relationships within the electroplated Au/Ni/304L system.

  18. Detection and Diagnostics of a Coronal Shock Wave Driven by a Partial-Halo Coronal Mass Ejection on 2000 June 28

    DTIC Science & Technology

    2005-03-10

    densities obtained from type II radio bursts, tons cm- 2 s-I sr-1), Si xii 2520.66 (4.03 x 107 photons cm-2 In the solar corona the Lya andOwvi 21032...Space Sci. Rev., 71, 155 Solar Wind Nine, ed. S. R. Habal et al. (Woodbury: AIP), 685 Vourlidas , A., Wu, S. T., Wang, A. H., Subramanian, P., & Howard...2 AND S. W. KAHLER AFRL/VSBXS, 29 Randolph Road, Hanscom AFB, MA 01731 5; A. VOURLIDAS 0 Naval Research Laboratory, Washington, DC 20375 AND 20060244

  19. Department of the Air Force Justification of Estimates for Fiscal Years 1981 and 1982, Submitted to Congress, March 1981. Amendment

    DTIC Science & Technology

    1981-03-01

    support services, such as laundry service or fire protection at bases that are grouped in the same geographic area. Marginal Programs: $500 Reflects...laundry service or fire protection at bases that are grouped in the same geographic area. Productivity Enhancement Savings: $1,300 Capital investments...SI. .0) - ’itis %,il1 procure z. V.~r icty Of ALi cjuipnlent 1Iu tf. ’ L ICp L:ya. I’OLL, .,f.or titis group Of equipmunts is i coslputcr tot A L o

  20. Understanding frequency distributions of path-dependent processes with non-multinomial maximum entropy approaches

    NASA Astrophysics Data System (ADS)

    Hanel, Rudolf; Corominas-Murtra, Bernat; Thurner, Stefan

    2017-03-01

    Path-dependent stochastic processes are often non-ergodic and observables can no longer be computed within the ensemble picture. The resulting mathematical difficulties pose severe limits to the analytical understanding of path-dependent processes. Their statistics is typically non-multinomial in the sense that the multiplicities of the occurrence of states is not a multinomial factor. The maximum entropy principle is tightly related to multinomial processes, non-interacting systems, and to the ensemble picture; it loses its meaning for path-dependent processes. Here we show that an equivalent to the ensemble picture exists for path-dependent processes, such that the non-multinomial statistics of the underlying dynamical process, by construction, is captured correctly in a functional that plays the role of a relative entropy. We demonstrate this for self-reinforcing Pólya urn processes, which explicitly generalize multinomial statistics. We demonstrate the adequacy of this constructive approach towards non-multinomial entropies by computing frequency and rank distributions of Pólya urn processes. We show how microscopic update rules of a path-dependent process allow us to explicitly construct a non-multinomial entropy functional, that, when maximized, predicts the time-dependent distribution function.

  1. Probing Quasar Winds Using Intrinsic Narrow Absorption Lines

    NASA Astrophysics Data System (ADS)

    Culliton, Christopher S.; Charlton, Jane C.; Eracleous, Michael; Roberts, Amber; Ganguly, Rajib; Misawa, Toru; Muzahid, Sowgat

    2017-01-01

    Quasar outflows are important for understanding the accretion and growth processes of the central black hole. Furthermore, outflows potentially have a role in providing feedback to the galaxy, and halting star formation and infall of gas. The geometry and density of these outflows remain unknown, especially as a function of ionization and velocity. Having searched ultraviolet spectra at both high redshift (VLT/UVES; 1.4Lya and with a separate low ionization gas phase to partially covered NV systems with partially covered Lya and without detected low ionization gas. Additionally, we construct a model describing the spatial distributions, geometries, and varied ionization structures of intrinsic NALs.

  2. An observational study of quasar host galaxies, radio galaxies, and lyman alpha emitters

    NASA Astrophysics Data System (ADS)

    Wold, Isak George Bayard

    In this thesis I provide observational constraints on quasar host galaxies, radio galaxies, and Lyman Alpha Emitters (LAEs). I develop and implement a method to provide stellar age constraints for the host galaxies of nearby (z<0.3) quasars. The observational strategy is to spectroscopically observe quasar host galaxies offset from the bright central point source to maximize the signal-to-noise of the stellar light. The central quasar is also spectroscopically observed, so that any nuclear light scattered into our off-axis spectrum can be efficiently modeled and subtracted. The reliability of my technique is tested via a Monte-Carlo routine in which the correspondence between synthetic spectra with known parameters and the model output is determined. Application of this model to a preliminary sample of 10 objects is presented and compared to previous studies. I present 1.4 GHz catalogs for the cluster fields A370 and A2390 observed with the Very Large Array. These are two of the deepest radio images of cluster fields ever taken. I construct differential number counts for each field and find results consistent with previous studies. I emphasize the need to account for cosmic variance. These high resolution, ultra-deep radio catalogs will be vital to future multiwavelength studies. Finally, I apply a newly developed search method to all of the deep GALEX grism fields, which correspond to some of the most intensively studied regions in the sky. My work provides the first large sample of z=0.67-1.16 LAEs (N=60) that can be used to investigate the physical properties of these galaxies. I catalog the candidate z=1 LAE samples in each field and give optical redshifts from both archival and newly obtained observations. With X-ray, UV, and optical data, I determine the false detection rate (cases where the emission line is either not confirmed or is not Lya) and the AGN contamination rate of my sample. With the remaining LAEs, I compute the LAE galaxy luminosity function

  3. Quantum Simulation of the Factorization Problem

    NASA Astrophysics Data System (ADS)

    Rosales, Jose Luis; Martin, Vicente

    2016-11-01

    Feynman's prescription for a quantum simulator was to find a Hamitonian for a system that could serve as a computer. The Pólya-Hilbert conjecture proposed the demonstration of Riemann's hypothesis through the spectral decomposition of Hermitian operators. Here we study the problem of decomposing a number into its prime factors, N =x y , using such a simulator. First, we derive the Hamiltonian of the physical system that simulates a new arithmetic function formulated for the factorization problem that represents the energy of the computer. This function rests alone on the primes below √{N }. We exactly solve the spectrum of the quantum system without resorting to any external ad hoc conditions, also showing that it obtains, for x ≪√{N }, a prediction of the prime counting function that is almost identical to Riemann's R (x ) function. It has no counterpart in analytic number theory, and its derivation is a consequence of the quantum theory of the simulator alone.

  4. The Golden-Thompson inequality: Historical aspects and random matrix applications

    SciTech Connect

    Forrester, Peter J. Thompson, Colin J.

    2014-02-15

    The Golden-Thompson inequality, Tr (e{sup A+B}) ⩽ Tr (e{sup A}e{sup B}) for A, B Hermitian matrices, appeared in independent works by Golden and Thompson published in 1965. Both of these were motivated by considerations in statistical mechanics. In recent years the Golden-Thompson inequality has found applications to random matrix theory. In this article, we detail some historical aspects relating to Thompson's work, giving in particular a hitherto unpublished proof due to Dyson, and correspondence with Pólya. We show too how the 2 × 2 case relates to hyperbolic geometry, and how the original inequality holds true with the trace operation replaced by any unitarily invariant norm. In relation to the random matrix applications, we review its use in the derivation of concentration type lemmas for sums of random matrices due to Ahlswede-Winter, and Oliveira, generalizing various classical results.

  5. Evolution of HI from Z=5 to the present

    NASA Technical Reports Server (NTRS)

    Storrie-Lombardi, L. J.

    2002-01-01

    Studies of damped Lya systems provide us with a good measure of the evolution of the HI column density distribution function and the contribution to the comoving mass density in neutral gas out to redshifts of z = 5 . The column density distribution function at high redshift steepens for the highest column density HI absorbers, though the contribution to the comoving mass density of neutral gas remains fiat from 2 < z < 5 . Results from studies at z < 2 are finding substantial numbers of damped absorbers identified from MgII absorption, compared to previous blind surveys. These results indicate that the contribution to the comoving mass density in neutral gas may be constant from z 0 to z 5. Details of recent work in the redshift range z < 2 work is covered elsewhere in this volume (see D. Nestor). We review here recent results for the redshift range 2 < z < 5.

  6. Bayesian latent variable models for hierarchical clustered count outcomes with repeated measures in microbiome studies.

    PubMed

    Xu, Lizhen; Paterson, Andrew D; Xu, Wei

    2017-04-01

    Motivated by the multivariate nature of microbiome data with hierarchical taxonomic clusters, counts that are often skewed and zero inflated, and repeated measures, we propose a Bayesian latent variable methodology to jointly model multiple operational taxonomic units within a single taxonomic cluster. This novel method can incorporate both negative binomial and zero-inflated negative binomial responses, and can account for serial and familial correlations. We develop a Markov chain Monte Carlo algorithm that is built on a data augmentation scheme using Pólya-Gamma random variables. Hierarchical centering and parameter expansion techniques are also used to improve the convergence of the Markov chain. We evaluate the performance of our proposed method through extensive simulations. We also apply our method to a human microbiome study.

  7. Erosion by a one-dimensional random walk

    NASA Astrophysics Data System (ADS)

    Chisholm, Rebecca H.; Hughes, Barry D.; Landman, Kerry A.

    2014-08-01

    We consider a model introduced by Baker et al. [Phys. Rev. E 88, 042113 (2013), 10.1103/PhysRevE.88.042113] of a single lattice random walker moving on a domain of allowed sites, surrounded by blocked sites. The walker enlarges the allowed domain by eroding the boundary at its random encounters with blocked boundary sites: attempts to step onto blocked sites succeed with a given probability and convert these sites to allowed sites. The model interpolates continuously between the Pólya random walker on the one-dimensional lattice and a "blind" walker who attempts freely, but always aborts, moves to blocked sites. We obtain some exact results about the walker's location and the rate of erosion.

  8. Symmetry and random sampling of symmetry independent configurations for the simulation of disordered solids.

    PubMed

    D'Arco, Philippe; Mustapha, Sami; Ferrabone, Matteo; Noël, Yves; De La Pierre, Marco; Dovesi, Roberto

    2013-09-04

    A symmetry-adapted algorithm producing uniformly at random the set of symmetry independent configurations (SICs) in disordered crystalline systems or solid solutions is presented here. Starting from Pólya's formula, the role of the conjugacy classes of the symmetry group in uniform random sampling is shown. SICs can be obtained for all the possible compositions or for a chosen one, and symmetry constraints can be applied. The approach yields the multiplicity of the SICs and allows us to operate configurational statistics in the reduced space of the SICs. The present low-memory demanding implementation is briefly sketched. The probability of finding a given SIC or a subset of SICs is discussed as a function of the number of draws and their precise estimate is given. The method is illustrated by application to a binary series of carbonates and to the binary spinel solid solution Mg(Al,Fe)2O4.

  9. Detection of a white dwarf in a visual binary system

    NASA Technical Reports Server (NTRS)

    Boehm-Vitense, Erika

    1992-01-01

    The F6 giant HD 160365 was detected to have a white dwarf companion about 8 arcsec south of the star. The UV energy distribution observed with IUE shows that the white dwarf has an effective temperature of 23,000 +/- 2000 K. If log g = 8 the Lya profile indicates an effective temperature around 24,500 K. Using the theoretical models by Wesemael et al. (1980) one finds a visual magnitude of m(V) about 16.5. For T(eff) = 24,500 K one expects for a white dwarf a luminosity of log L/L(solar) about 1.3 and M(V) about 10.67. This gives a distance modulus for the system of m(V) - M(V) = 5.83 and an absolute magnitude M(V)= 0.3 for the giant.

  10. A Potential Paradigm Shift in our Understanding of Helium Reionization

    NASA Astrophysics Data System (ADS)

    Worseck, Gabor

    2014-10-01

    The advent of GALEX and COS have revolutionized studies of HeII reionization. Observations of the FUV-brightest QSOs have resulted in a order-of-magnitude increase in science-grade HeII Lya absorption spectra in the HST archive. The clear picture emerging is that COS has successfully pinpointed the end of HeII reionization at z~2.7. Based on this, and our team's state-of-the-art radiative transfer simulations, one expects complete Gunn-Peterson absorption at higher redshifts. However, surprisingly, our analysis of the three existing sightlines at z>3.5 reveals high-transmission regions consistent with expectations for a reionized IGM, in striking conflict with the models. Explaining these measurements may require invoking other exotic sources of hard photons at high-z, which would amount to a paradigm shift in our understanding of HeII reionization, with concomitant implications for HI reionization. The unequivocal path forward is COS spectra of more QSOs at z>3.5, deep into the reionization era, to put this tentative result on firm statistical footing. We request 24 orbits to obtain science-grade COS far-UV spectra of the 3 brightest HeII QSOs at z>3.5, which will double the HeII pathlength at high-z and test tantalizing indications that HeII reionization began at z>4 and lasted over 1 Gyr. These spectra are complemented by ancillary data from 8m telescopes, including echelle spectra of the coeval HI Lya forest, and our dedicated survey for QSOs in the foreground of each HeII sightline. Our targets are the only viable sources probing z>3.5 in a reasonable orbit request, and it is critical to HST's legacy to solve this riddle before the mission ends.

  11. 4U 1626-67 as Seen by Suzaku Before and After the 2008 Torque Reversal

    NASA Technical Reports Server (NTRS)

    Camero-Arranz, A.; Pottschmidt, K.; Finger, M. H.; Ikhsanov, N. R.; Wilson-Hodge, C. A.; Marcu, D. M.

    2012-01-01

    Aims. The accretion-powered pulsar 4U 1626-67 experienced a new torque reversal at the beginning of 2008, after about 18 years of steadily spinning down. The main goal of the present work is to study this recent torque reversal that occurred in 2008 February. Methods. We present a spectral analysis of this source using two pointed observations performed by Suzaku in 2006 March and in 2010 September. Results. We confirm with Suzaku the presence of a strong emission-line complex centered on 1 keV, with the strongest line being the hydrogen-like Ne Lya at 1.025(3) keV. We were able to resolve this complex with up to seven emission lines. A dramatic increase of the intensity of the Ne Lya line after the 2008 torque reversal occurred, with the equivalent width of this line reaching almost the same value measured by ASCA in 1993. We also report on the detection of a cyclotron line feature centered at approximately 37 keV. In spite of the fact that an increase of the X-ray luminosity (0.5-100keV) of a factor of approximately 2.8 occurred between these two observations, no significant change in the energy of the cyclotron line feature was observed. However, the intensity of the approximately 1 keV line complex increased by an overall factor of approximately 8. Conclusions. Our results favor a scenario in which the neutron star in 4U 1626-67 accretes material from a geometrically thin disk during both the spin-up and spin-down phases.

  12. Stellar Calibration of the WIC and SI Imagers and the GEO Photometers on IMAGE/FUV

    NASA Technical Reports Server (NTRS)

    Gladstone, R.; Mende, S. B.; Frey, H. U.; Geller, S. P.; Immel, T. J.; Lampton, M.; Gerard, J.-C.; Spann, J.; Habraken, S.; Renotte, E.; Jamar, C.; Rochus, P.; Rose, M. Franklin (Technical Monitor)

    2000-01-01

    The FUV instrument on the IMAGE spacecraft comprises three wide-field imagers, the Wide-Band Imaging Camera (WIC) of observing N2 Lyman-Birge-Hopfield (LBH) (140-190 nm) emissions and the Spectrographic Imager (SI), which has a 121.8 nm channel for observing red-shifted HI Lya photons and a 135.6 run channel for observing 01 135.6 nm emissions. In addition, three HI Lya photometers (GEO) are used to monitor the geocorona. The fields of view are 17 degrees x 17 degrees for the WIC imagers, 15 degrees x 15 degrees for the two SI imagers, and 10 diameter for the three GEO photometers. As the IMAGE spacecraft spins every 120 seconds, the GEO photometers sweep out circles on the sky (at 0 degrees and plus or minus 30 degrees with respect to the spacecraft spin plane), and the WIC and SI imagers use the Time Delay Integration (TDI) method to construct images centered on the Earth. Many FUV-bright stars are seen in the WIC, SI and even the GEO data. WE have used archived International Ultraviolet Explorer (IUE) far-ultraviolet flux spectra for 22 of the brightest of these stars to help refine the FUV instrumental sensitivities. The stars chosen range in spectral type form B0V to A11V, with magnitudes ranging from V- 1.3 (a Cru) to V=4.7 (G Cen) (although many more fainter stars are also seen). The initial results of this stellar calibration will be presented and compared with the pre-flight and dayglow modeling results.

  13. On the use of symmetry in configurational analysis for the simulation of disordered solids.

    PubMed

    Mustapha, Sami; D'Arco, Philippe; De La Pierre, Marco; Noël, Yves; Ferrabone, Matteo; Dovesi, Roberto

    2013-03-13

    The starting point for a quantum mechanical investigation of disordered systems usually implies calculations on a limited subset of configurations, generated by defining either the composition of interest or a set of compositions ranging from one end member to another, within an appropriate supercell of the primitive cell of the pure compound. The way in which symmetry can be used in the identification of symmetry independent configurations (SICs) is discussed here. First, Pólya's enumeration theory is adopted to determine the number of SICs, in the case of both varying and fixed composition, for colors numbering two or higher. Then, De Bruijn's generalization is presented, which allows analysis of the case where the colors are symmetry related, e.g. spin up and down in magnetic systems. In spite of their efficiency in counting SICs, neither Pólya's nor De Bruijn's theory helps in solving the difficult problem of identifying the complete list of SICs. Representative SICs are obtained by adopting an orderly generation approach, based on lexicographic ordering, which offers the advantage of avoiding the (computationally expensive) analysis and storage of all the possible configurations. When the number of colors increases, this strategy can be combined with the surjective resolution principle, which permits the efficient generation of SICs of a problem in |R| colors starting from the ones obtained for the (|R| - 1)-colors case. The whole scheme is documented by means of three examples: the abstract case of a square with C(4v) symmetry and the real cases of the garnet and olivine mineral families.

  14. Mapping Baryons in the Halo of NGC 1097

    NASA Astrophysics Data System (ADS)

    Bowen, David

    2012-10-01

    We propose observing 5 background QSOs whose sightlines pass through the halo of NGC 1097 at impact parameters of 53-183 kpc. NGC 1097 is a bright {-21.1} spiral galaxy that has the highest surface density of background, UV-bright QSOs in the nearby Universe. The galaxy hosts a low luminosity AGN at its core, surrounded by a ring of intense star-forming regions; there is also evidence from stellar tidal streams that the galaxy has recently cannibalized a number of dwarf galaxies, and a companion dwarf elliptical is still clearly merging with the outer disk. We aim to examine the physical conditions of gas that fills the halo of such an active galaxy. We will search primarily for Lya and SiIV absorption lines in the spectra of the background QSOs, as well as weak NV from hot gas. At the lowest impact parameters, we may also be able to find absorption lines from low ionization species. Our goals are to test whether the halo of NGC 1097 contains the same distribution of Lyman-alpha forest clouds seen at higher redshifts out to large distances from galaxies, and determine how the HI column density, covering fraction, and temperature of the gas decline with radius in a single galaxy halo. We will examine whether the velocities of the absorbers are consistent with those expected from gas co-rotating in the dark matter halo of the galaxy, or whether there exists a distribution of velocities that might indicate outflows from the galactic disk or from the central AGN, or, alternatively, from inflows from the IGM. Our map of Lya and SiIV around NGC 1097 will provide an important template for understanding the origin of higher redshift QSO absorption line systems.

  15. Non-Selective Evolution of Growing Populations

    PubMed Central

    Jung, Heinrich; Frey, Erwin

    2015-01-01

    Non-selective effects, like genetic drift, are an important factor in modern conceptions of evolution, and have been extensively studied for constant population sizes (Kimura, 1955; Otto and Whitlock, 1997). Here, we consider non-selective evolution in the case of growing populations that are of small size and have varying trait compositions (e.g. after a population bottleneck). We find that, in these conditions, populations never fixate to a trait, but tend to a random limit composition, and that the distribution of compositions “freezes” to a steady state. This final state is crucially influenced by the initial conditions. We obtain these findings from a combined theoretical and experimental approach, using multiple mixed subpopulations of two Pseudomonas putida strains in non-selective growth conditions (Matthijs et al, 2009) as model system. The experimental results for the population dynamics match the theoretical predictions based on the Pólya urn model (Eggenberger and Pólya, 1923) for all analyzed parameter regimes. In summary, we show that exponential growth stops genetic drift. This result contrasts with previous theoretical analyses of non-selective evolution (e.g. genetic drift), which investigated how traits spread and eventually take over populations (fixate) (Kimura, 1955; Otto and Whitlock, 1997). Moreover, our work highlights how deeply growth influences non-selective evolution, and how it plays a key role in maintaining genetic variability. Consequently, it is of particular importance in life-cycles models (Melbinger et al, 2010; Cremer et al, 2011; Cremer et al, 2012) of periodically shrinking and expanding populations. PMID:26274606

  16. Seventeenth-century European origins of hereditary diseases in the Saguenay population (Quebec, Canada).

    PubMed

    Heyer, E; Tremblay, M; Desjardins, B

    1997-04-01

    For over three decades much research has been devoted to the identification of founders who could have been the first carriers of different deleterious genes in the French Canadian population. In some cases this research led to an investigation of the European origins of these founders. Using up-to-date data on genealogical records of 673 probands (6 hereditary diseases) and 99 control group individuals born in the Saguenay region (Quebec, Canada), we show that it is difficult to identify a precise region where a deleterious gene could have originated. By taking several key factors into consideration (founders' genetic contribution, level of commonness, sex, birth year), we found many possible candidates for each disease, leading to various regions of origin in France (Aunis, Maine, Normandie, Orléanais, Perche, and other provinces) or outside France (British Isles, other European countries). Our results also showed notable differences between the origins of male and female founders. Furthermore, all founders common to at least 95% of the probands of a given disease were also common to 95% of the probands of at least one other disease; among these founders 29 were common to 95% or more of the probands of each group (including the control group).

  17. Microstructure-fracture toughness relationship of vanadium alloy/stainless steel brazed joints

    NASA Astrophysics Data System (ADS)

    Gan, Y. X.; Aglan, H. A.; Steward, R. V.; Chin, B. A.; Grossbeck, M. L.

    2001-11-01

    In this work, brazing V-5Ti-5Cr to 304 stainless steel (SS 304) using Au-18Ni alloy as filler material was conducted under high vacuum condition. Sessile drop technique was used to determine the wettability of filler alloy to the stainless steel and the vanadium alloy substrates upon which the relationship between the contact angles with time was obtained. Tensile tests were performed on unnotched and notched specimens to demonstrate the overloading behavior and the fracture toughness of the base materials and the brazed joint. Fracture surface was examined for both the V-5Ti-5Cr and the joint to identify the failure mechanisms under static loadings. It was found that the Au-18Ni filler material exhibited good wettability with the SS 304 and V-5Ti-5Cr. The ultimate tensile strength of the brazed joint reached 245 MPa. The strain to failure was about 1.3%. Young's modulus was about 351 GPa. The fracture toughness ( KIc) of this joint was 19.1 MPa √ m. The fracture surface of the joint showed well brazed area with good wettability and proper amount of residual filler material which came from the solidification of residual liquid filler alloy of Au-Ni. The failure of the joint occurred along the interface of the vanadium/filler under static load.

  18. Seed-induced growth of flower-like Au-Ni-ZnO metal-semiconductor hybrid nanocrystals for photocatalytic applications.

    PubMed

    Chen, Yuanzhi; Zeng, Deqian; Cortie, Michael B; Dowd, Annette; Guo, Huizhang; Wang, Junbao; Peng, Dong-Liang

    2015-03-25

    The combination of metal and semiconductor components in nanoscale to form a hybrid nanocrystal provides an important approach for achieving advanced functional materials with special optical, magnetic and photocatalytic functionalities. Here, a facile solution method is reported for the synthesis of Au-Ni-ZnO metal-semiconductor hybrid nanocrystals with a flower-like morphology and multifunctional properties. This synthetic strategy uses noble and magnetic metal Au@Ni nanocrystal seeds formed in situ to induce the heteroepitaxial growth of semiconducting ZnO nanopyramids onto the surface of metal cores. Evidence of epitaxial growth of ZnO{0001} facets on Ni {111} facets is observed on the heterojunction, even though there is a large lattice mismatch between the semiconducting and magnetic components. Adjustment of the amount of Au and Ni precursors can control the size and composition of the metal core, and consequently modify the surface plasmon resonance (SPR) and magnetic properties. Room-temperature superparamagnetic properties can be achieved by tuning the size of Ni core. The as-prepared Au-Ni-ZnO nanocrystals are strongly photocatalytic and can be separated and re-cycled by virtue of their magnetic properties. The simultaneous combination of plasmonic, semiconducting and magnetic components within a single hybrid nanocrystal furnishes it multifunctionalities that may find wide potential applications.

  19. Oxygen reduction of several gold alloys in 1-molar potassium hydroxide

    NASA Technical Reports Server (NTRS)

    Miller, R. O.

    1975-01-01

    With rotated disk-and-ring equipment, polarograms and other electrochemical measurements were made of oxygen reduction in 1-molar potassium hydroxide on an equiatomic gold-copper (Au-Cu) alloy and a Au-Cu alloy doped with either indium (In) or cobalt (Co) and on Au doped with either nickel (Ni) or platinum (Pt). The results were compared with those for pure Au and pure Pt. The two-electron reaction dominated on all Au alloys as it did on Au. The polarographic results at lower polarization potentials were compared, assuming exclusively a two-step reduction. A qualified ranking of cathodic electrocatalytic activity on the freshly polished reduced disks was indicated: anodized Au Au-Cu-In Au-Cu Au-Cu-Co is equivalent or equal to Au-Pt Au-Ni. Aging in distilled water improved the electrocatalytic efficiency of Au-Cu-Co, Au-Cu, and (to a lesser extent) Au-Cu-In.

  20. Radiation detector based on 4H-SiC used for thermal neutron detection

    NASA Astrophysics Data System (ADS)

    Zaťko, B.; Šagátová, A.; Sedlačková, K.; Boháček, P.; Sekáčová, M.; Kohout, Z.; Granja, C.; Nečas, V.

    2016-11-01

    In this work we have focused on detection of thermal neutrons generated by 239Pu-Be isotopic neutron source. A high quality liquid phase epitaxial layer of 4H-SiC was used as a detection region. The thickness of the layer was 70 μ m and the diameter of circular Au/Ni Schottky contact was 4.5 mm. Around the Schottky contact two guard rings were created. The detector structure was first examined as a detector of protons and alpha particles for energy calibration. Monoenergetic protons of energies from 300 keV up to 1.9 MeV were used for detector energy calibration and a good linearity was observed. The energy resolution of 35 keV was obtained for 1.9 MeV protons. The 6LiF conversion layer was applied on the detector Schottky contact. In the experiment we used different thicknesses of conversion layers from 5 μ m up to 35 μ m. Measured detected spectra show two parts corresponding to alpha particles detection in lower energy channels and 3H in higher energy channels. We have also performed simulations of thermal neutron detection using MCNPX (Monte Carlo N-particle eXtended) code. The detection efficiency and the detector response to thermal neutrons was calculated with respect to the 6LiF layer thickness. The detection efficiency calculation is found to be in good agreement with the experiment.

  1. Brazing of titanium-vapor-coated silicon nitride

    SciTech Connect

    Santella, M.L. )

    1988-09-01

    A technique for brazing Si{sub 3}N{sub 4} with metallic alloys was evaluated. The process involved vapor coating the ceramic with a 1.0-{mu}-thick layer of titanium before the brazing operation. The coating improved wetting of the Si{sub 3}N{sub 4} surfaces to the extent that strong bonding between the solidified braze filler metal and the ceramic occurred. Braze joints of Si{sub 3}N{sub 4} were made with Ag-Cu, Au-Ni, and Au-Ni-Pd alloys at temperatures of 790{degree}, 970{degree}, and 1,130{degree}C. Silicon nitride specimens were also brazed with a Ag-Cu alloy to the molybdenum alloy TZM, titanium, and A286 steel at 790{degree}C. Residual stresses resulting from mismatch of thermal expansion coefficients between the Si{sub 3}N{sub 4} and the metals caused all of the ceramic-to-metal joints to spontaneously crack in the Si{sub 3}N{sub 4} upon cooling from the brazing temperature.

  2. Label-Free LSPR Detection of Trace Lead(II) Ions in Drinking Water by Synthetic Poly(mPD-co-ASA) Nanoparticles on Gold Nanoislands.

    PubMed

    Qiu, Guangyu; Ng, Siu Pang; Liang, Xiongyi; Ding, Ning; Chen, Xiangfeng; Wu, Chi-Man Lawrence

    2017-02-07

    Using self-assembly gold nanoislands (SAM-AuNIs) functionalized by poly(m-phenylenediamine-co-aniline-2-sulfonic acid) (poly(mPD-co-ASA)) copolymer nanoparticles as specific receptors, a highly sensitive localized surface plasmon resonance (LSPR) optochemical sensor is demonstrated for detection of trace lead cation (Pb(II)) in drinking water. The copolymer receptor is optimized in three aspects: (1) mole ratio of mPD:ASA monomers, (2) size of copolymer nanoparticles, and (3) surface density of the copolymer. It is shown that the 95:5 (mPD:ASA mole ratio) copolymer with size less than 100 nm exhibits the best Pb(II)-sensing performance, and the 200 times diluted standard copolymer solution contributes to the most effective functionalization protocol. The resulting poly(mPD-co-ASA)-functionalized LSPR sensor attains the detection limit to 0.011 ppb toward Pb(II) in drinking water, and the linear dynamic range covers 0.011 to 5000 ppb (i.e., 6 orders of magnitude). In addition, the sensing system exhibits robust selectivity to Pb(II) in the presence of other metallic cations as well as common anions. The proposed functional copolymer functionalized on AuNIs is found to provide excellent Pb(II)-sensing performance using simple LSPR instrumentation for rapid drinking-water inspection.

  3. Selection of Optical Cavity Surface Coatings for 1micron Laser Based Missions

    NASA Technical Reports Server (NTRS)

    Hedgeland, Randy J.; Straka, Sharon; Matsumura, Mark; Hammerbacher, Joseph

    2004-01-01

    The particulate surface cleanliness level on several coatings for aluminum and beryllium substrates were examined for use in the optical cavities of high pulse energy Nd:YAG Q-switched, diode-pumped lasers for space flight applications. Because of the high intensity of the lasers, any contaminants in the laser beam path could damage optical coatings and limit the instrument mission objectives at the operating wavelength of 1 micron (micrometer). Our goal was to achieve an EST-STD-CC1246D Level 100 particulate distribution or better to ensure particulate redistribution during launch would not adversely affect the performance objectives. Tapelifts were performed to quantify the amount of particles using in-house developed procedures. The primary candidate coatings included chromate conversion coating aluminum (Al), uncoated Al electroless Nickel (Ni) on Al, Ni-gold (Au) on Al, anodized Al, and gold (Au)/Ni on Beryllium (Be). The results indicate that there were advantages in Ni and Au coating applications for the two major substrates, Al and Be, when considering applications that need to meet launch environments.

  4. Using multivariate analyses to compare subsets of electrodes and potentials within an electrode array for predicting sugar concentrations in mixed solutions.

    SciTech Connect

    Stork, Christopher Lyle; Steen, William Arthur

    2008-04-01

    A non-selective electrode array is presented for the quantification of fructose, galactose, and glucose in mixed solutions. A unique feature of this electrode array relative to other published work is the wide diversity of electrode materials incorporated within the array, being constructed of 41 different metals and metal alloys. Cyclic voltammograms were acquired for solutions containing a single sugar at varying concentrations, and the correlation between current and sugar concentration was calculated as a function of potential and electrode array element. The correlation plots identified potential regions and electrodes that scaled most linearly with sugar concentration, and the number of electrodes used in building predictive models was reduced to 15. Partial least squares regression models relating electrochemical response to sugar concentration were constructed using data from single electrodes and multiple electrodes within the array, and the predictive abilities of these models were rigorously compared using a non-parametric Wilcoxon test. Models using single electrodes (Pt:Rh (90:10) for fructose, Au:Ni (82:18) for galactose, and Au for glucose) were judged to be statistically superior or indistinguishable from those built with multiple electrodes. Additionally, for each sugar, interval partial least squares regression successfully identified a subset of potentials within a given electrode that generated a model of statistically equivalent predictive ability relative to the full potential model. While including data from multiple electrodes offered no benefit in predicting sugar concentration, use of the array afforded the versatility and flexibility of selecting the best single electrode for each sugar.

  5. Vertically p-n-junctioned GaN nano-wire array diode fabricated on Si(111) using MOCVD.

    PubMed

    Park, Ji-Hyeon; Kim, Min-Hee; Kissinger, Suthan; Lee, Cheul-Ro

    2013-04-07

    We demonstrate the fabrication of n-GaN:Si/p-GaN:Mg nanowire arrays on (111) silicon substrate by metal organic chemical vapor deposition (MOCVD) method .The nanowires were grown by a newly developed two-step growth process. The diameter of as-grown nanowires ranges from 300-400 nm with a density of 6-7 × 10(7) cm(-2). The p- and n-type doping of the nanowires is achieved with Mg and Si dopant species. Structural characterization by X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM) indicates that the nanowires are relatively defect-free. The room-temperature photoluminescence emission with a strong peak at 370 nm indicates that the n-GaN:Si/p-GaN:Mg nanowire arrays have potential application in light-emitting nanodevices. The cathodoluminscence (CL) spectrum clearly shows a distinct optical transition of GaN nanodiodes. The nano-n-GaN:Si/p-GaN:Mg diodes were further completed using a sputter coating approach to deposit Au/Ni metal contacts. The polysilazane filler has been etched by a wet chemical etching process. The n-GaN:Si/p-GaN:Mg nanowire diode was fabricated for different Mg source flow rates. The current-voltage (I-V) measurements reveal excellent rectifying properties with an obvious turn-on voltage at 1.6 V for a Mg flow rate of 5 sccm (standard cubic centimeters per minute).

  6. Plasmon-induced photoelectrochemical biosensor for in situ real-time measurement of biotin-streptavidin binding kinetics under visible light irradiation.

    PubMed

    Guo, Jingchun; Oshikiri, Tomoya; Ueno, Kosei; Shi, Xu; Misawa, Hiroaki

    2017-03-08

    We developed a localized surface plasmon-induced visible light-responsive photoelectrochemical (PEC) biosensor using a titanium dioxide (TiO2) photoelectrode loaded with gold nanoislands (AuNIs) for in situ real-time measurement of biotin-streptavidin association. As a proof of concept, self-assembled thiol-terminated biotin molecules bound on a AuNIs/TiO2 photoelectrode were successfully utilized to explore the photocurrent response to streptavidin-modified gold nanoparticle (STA-AuNP) solutions. This plasmon-induced PEC biosensor is simple and easy to miniaturize. Additionally, the PEC biosensor achieves highly sensitive measurements under only visible light irradiation and prevents the UV-induced damage of samples. Furthermore, a novel approach has been proposed to realize the real-time monitoring of biotin-STA binding affinities and kinetics by analyzing the PEC sensing characteristics. This PEC biosensor and novel analysis method could provide a new approach for the specific electrical detection and real-time kinetic measurements for clinical diagnostics and drug development.

  7. Structure and properties of Ti-Ni-Au shape memory alloys

    NASA Astrophysics Data System (ADS)

    Butler, Todd

    Ternary Ti-Ni-X based alloys, where X = Pt, Pd, Hf, Au or Zr, show promise as high temperature shape memory alloys (HTSMAs). In comparison to binary Ni-Ti alloys, some hypo-stoichiometric versions of these ternary compositions exhibit higher transformation temperatures and better mechanical stability due to the formation of nano-scale precipitates. In this study, a Ti 49Ni26Au25 (at.%) alloy was solution annealed at 1050°C for 3 hours and isothermally aged at 400°C and 550°C. A specimen was also annealed at 1050°C for 3 hours and furnace cooled. Ageing resulted in a very high peak micro-hardness for both temperatures. The structures and chemistries of the phases formed during ageing were characterized by wavelength dispersive x-ray spectroscopy (WDS), scanning electron microscopy (SEM), energy dispersive x-ray spectroscopy (EDS), transmission electron microscopy (TEM), three-dimensional atom probe tomography (3DAP), x-ray diffraction (XRD), and differential scanning calorimetry (DSC). It was found that ageing at both 400°C and 550°C resulted in the formation of two different precipitates. First, two variants of a (Au,Ni)4Ti3 type phase form with SADPs similar to tetragonal D1a. The proposed orientation relationships with the matrix are the following: [001]D1a || [100] B2 with (011)B2 // (310)D1a and [001¯ ]D1a || [100]B2 with {011}B2 || (310) D1a. It is then postulated that the (Au,Ni)-rich phase creates local Ti-rich regions that promote the precipitation of two Ti2(Ni,Au) variants with tetragonal (I4/mmm) type symmetry. Their proposed orientation relationships with the matrix are the following: [100]Ti2(Ni,Au) || [100]B2 with (001)B2 || (001)Ti2(Ni.Au) and (001)B2 || (100)Ti2(Ni,Au). The combination of both phases appears to inhibit martensitic transformation by stabilizing the high temperature austenite phase, as evident by no transformation peaks in the aged specimens via DSC. However, it is interesting to note that the as-cast and 1050°C furnace cooled

  8. A new method of making ohmic contacts to p-GaN

    NASA Astrophysics Data System (ADS)

    Hernández-Gutierrez, C. A.; Kudriavtsev, Yu.; Mota, Esteban; Hernández, A. G.; Escobosa-Echavarría, A.; Sánchez-Resendiz, V.; Casallas-Moreno, Y. L.; López-López, M.

    2016-12-01

    The structural, chemical, and electrical characteristics of In+ ion-implanted Au/Ni, Au/Nb and Au/W ohmic contacts to p-GaN were investigated. After the preparation of Ni, Nb and W electrode on the surface of p-GaN, the metal/p-GaN contact interface was implanted by 30 keV In+ ions with an implantation dose of 5 × 1015 ions/cm2 at room temperature to form a thin layer of InxGa1-xN located at the metal-semiconductor interface, achieved to reduce the specific contact resistance due to the improving quantum tunneling transport trough to the structure. The characterization was carried out by high-resolution X-ray diffraction, scanning electron microscopy, Raman spectroscopy, and secondary ion mass spectrometry to investigate the formation of ternary alloy, re-crystallization by rapid thermal annealing process after In+ implantation, and the redistribution of elements. The specific contact resistance was extracted by current-voltage (I-V) curves using transmission line method; the lowest specific contact resistance of 2.5 × 10-4 Ωcm2 was achieved for Au/Ni/p-InxGa1-xN/p-GaN ohmic contacts.

  9. Resolution of the diffusional paradox predicting infinitely fast kinetics on the nanoscale

    NASA Astrophysics Data System (ADS)

    Beke, D. L.; Erdélyi, Z.

    2006-01-01

    In our paper, we offer a natural resolution for a long-standing paradox in diffusion. We show that the growth rate of the diffusion zone (reaction layer) should not go to infinity with decreasing time (as 1/t ), just because the diffusion permeability of the interface is finite. Expression for the changeover thickness X* between the linear and parabolic regimes of the interface shift in phase separating binary A(B) systems is derived in the framework of a deterministic atomistic model for diffusion. X* lies typically between 0.01 and 300nm , depending on the composition dependence of the diffusion coefficient and the phase separation tendency of the alloy. While in ideal binary alloys with composition independent diffusivity, the deviation from the parabolic law practically cannot be observed, in real systems (where the diffusion coefficient can change several orders of magnitude with the composition), measurable deviations are expected as it was experimentally observed very recently in the Ni/Cu and Au/Ni systems. We also offer an atomistic explanation for the phenomenological interface transfer coefficient K . It measures the finite interface permeability (proportional to the jump frequency across the interface) and thus it controls the shift of the interface at short times (diffusion distances). Although it is almost exclusively accepted in the literature that linear growth kinetics are the result of interface reaction control, our results suggest that the linear or nonparabolic growth of a reaction layer on the nanoscale cannot be automatically interpreted by an interface reaction.

  10. Cosmological implications of baryon acoustic oscillation measurements

    SciTech Connect

    Aubourg, Eric

    2015-12-01

    Here, we derive constraints on cosmological parameters and tests of dark energy models from the combination of baryon acoustic oscillation (BAO) measurements with cosmic microwave background (CMB) data and a recent reanalysis of Type Ia supernova (SN) data. Particularly, we take advantage of high-precision BAO measurements from galaxy clustering and the Lyman-α forest (LyaF) in the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). Treating the BAO scale as an uncalibrated standard ruler, BAO data alone yield a high confidence detection of dark energy; in combination with the CMB angular acoustic scale they further imply a nearly flat universe. Adding the CMB-calibrated physical scale of the sound horizon, the combination of BAO and SN data into an “inverse distance ladder” yields a measurement of H0=67.3±1.1 km s-1 Mpc-1, with 1.7% precision. This measurement assumes standard prerecombination physics but is insensitive to assumptions about dark energy or space curvature, so agreement with CMB-based estimates that assume a flat ΛCDM cosmology is an important corroboration of this minimal cosmological model. For constant dark energy (Λ), our BAO+SN+CMB combination yields matter density Ωm=0.301±0.008 and curvature Ωk=-0.003±0.003. When we allow more general forms of evolving dark energy, the BAO+SN+CMB parameter constraints are always consistent with flat ΛCDM values at ≈1σ. And while the overall χ2 of model fits is satisfactory, the LyaF BAO measurements are in moderate (2–2.5σ) tension with model predictions. Models with early dark energy that tracks the dominant energy component at high redshift remain consistent with our expansion history constraints, and they yield a higher H0 and lower matter clustering amplitude, improving agreement with some low redshift observations. Expansion history alone yields an upper limit on the summed mass of neutrino species,

  11. Cosmological implications of baryon acoustic oscillation measurements

    DOE PAGES

    Aubourg, Eric

    2015-12-01

    Here, we derive constraints on cosmological parameters and tests of dark energy models from the combination of baryon acoustic oscillation (BAO) measurements with cosmic microwave background (CMB) data and a recent reanalysis of Type Ia supernova (SN) data. Particularly, we take advantage of high-precision BAO measurements from galaxy clustering and the Lyman-α forest (LyaF) in the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). Treating the BAO scale as an uncalibrated standard ruler, BAO data alone yield a high confidence detection of dark energy; in combination with the CMB angular acoustic scale they further imply a nearly flat universe. Adding the CMB-calibratedmore » physical scale of the sound horizon, the combination of BAO and SN data into an “inverse distance ladder” yields a measurement of H0=67.3±1.1 km s-1 Mpc-1, with 1.7% precision. This measurement assumes standard prerecombination physics but is insensitive to assumptions about dark energy or space curvature, so agreement with CMB-based estimates that assume a flat ΛCDM cosmology is an important corroboration of this minimal cosmological model. For constant dark energy (Λ), our BAO+SN+CMB combination yields matter density Ωm=0.301±0.008 and curvature Ωk=-0.003±0.003. When we allow more general forms of evolving dark energy, the BAO+SN+CMB parameter constraints are always consistent with flat ΛCDM values at ≈1σ. And while the overall χ2 of model fits is satisfactory, the LyaF BAO measurements are in moderate (2–2.5σ) tension with model predictions. Models with early dark energy that tracks the dominant energy component at high redshift remain consistent with our expansion history constraints, and they yield a higher H0 and lower matter clustering amplitude, improving agreement with some low redshift observations. Expansion history alone yields an upper limit on the summed mass of neutrino species, Σmν<0.56 eV (95% confidence), improving to Σmν<0.25 eV if we include

  12. Micro-Mechanical Voltage Tunable Fabry-Perot Filters Formed in (111) Silicon. Degree awarded by Colorado Univ., Boulder, CO

    NASA Technical Reports Server (NTRS)

    Patterson, James D.

    1997-01-01

    The MEMS (Micro-Electro-Mechanical-Systems) technology is quickly evolving as a viable means to combine micro-mechanical and micro-optical elements on the same chip. One MEMS technology that has recently gained attention by the research community is the micro-mechanical Fabry-Perot optical filter. A MEMS based Fabry-Perot consists of a vertically integrated structure composed of two mirrors separated by an air gap. Wavelength tuning is achieved by applying a bias between the two mirrors resulting in an attractive electrostatic force which pulls the mirrors closer. In this work, we present a new micro-mechanical Fabry-Perot structure which is simple to fabricate and is integratable with low cost silicon photodetectors and transistors. The structure consists of a movable gold coated oxide cantilever for the top mirror and a stationary Au/Ni plated silicon bottom mirror. The fabrication process is single mask level, self aligned, and requires only one grown or deposited layer. Undercutting of the oxide cantilever is carried out by a combination of RIE and anisotropic KOH etching of the (111) silicon substrate. Metallization of the mirrors is provided by thermal evaporation and electroplating. The optical and electrical characteristics of the fabricated devices were studied and show promissing results. A wavelength shift of 120nm with 53V applied bias was demonstrated by one device geometry using 6.27 micrometer air gap. The finesse of the structure was 2.4. Modulation bandwidths ranging from 91KHz to greater than 920KHz were also observed. Theoretical calculations show that if mirror reflectivity, smoothness, and parallelism are improved, a finesse of 30 is attainable. The predictions also suggest that a reduction of the air gap to 1 micrometer results in an increased wavelength tuning range of 175 nm with a CMOS compatible 4.75V.

  13. Detection of fast neutrons from D-T nuclear reaction using a 4H-SiC radiation detector

    NASA Astrophysics Data System (ADS)

    Zatko, Bohumir; Sagatova, Andrea; Sedlackova, Katarina; Necas, Vladimir; Dubecky, Frantisek; Solar, Michael; Granja, Carlos

    2016-09-01

    The particle detector based on a high purity epitaxial layer of 4H-SiC exhibits promising properties in detection of various types of ionizing radiation. Due to the wide band gap of 4H-SiC semiconductor material, the detector can reliably operate at room and also elevated temperatures. In this work we focused on detection of fast neutrons generated the by D-T (deuterium-tritium) nuclear reaction. The epitaxial layer with a thickness of 105 μm was used as a detection part. A circular Schottky contact of a Au/Ni double layer was evaporated on both sides of the detector material. The detector structure was characterized by current-voltage and capacitance-voltage measurements, at first. The results show very low current density (<0.1 nA/cm2) at room temperature and good homogeneity of free carrier concentration in the investigated depth. The fabricated detectors were tested for detection of fast neutrons generated by the D-T reaction. The energies of detected fast neutrons varied from 16.0 MeV to 18.3 MeV according to the acceleration potential of deuterons, which increased from 600 kV up to 2 MV. Detection of fast neutrons in the SiC detector is caused by the elastic and inelastic scattering on the silicon or carbide component of the detector material. Another possibility that increases the detection efficiency is the use of a conversion layer. In our measurements, we glued a HDPE (high density polyethylene) conversion layer on the detector Schottky contact to transform fast neutrons to protons. Hydrogen atoms contained in the conversion layer have a high probability of interaction with neutrons through elastic scattering. Secondary generated protons flying to the detector can be easily detected. The detection properties of detectors with and without the HDPE conversion layer were compared.

  14. DNA content, chromatin supraorganization, nuclear glycoproteins and RNA amounts in hepatocytes of mice expressing insulin-dependent diabetes.

    PubMed

    Mello, Maria Luiza S; Aldrovani, Marcela; Moraes, Alberto Silva; Guaraldo, Ana Maria Aparecida; Vidal, Benedicto de Campos

    2009-01-01

    Chromatin supraorganization and extensibility and nuclear glycoprotein content have been reported to change in hepatocytes from mice during development and aging, as well as under starvation and refeeding conditions. In non-obese diabetic (NOD) mice, the expression of insulin-dependent diabetes may be accompanied by metabolic changes in the liver. These changes are likely to be similar to those involved in the aging processes of non-diabetic animals. Therefore, we hypothesized that the chromatin organization, as well as the physical properties and compositions of hepatocyte nuclei would also be affected in NOD mice in the same way as those in aged non-diabetic mice. Nuclear image parameters were evaluated by image analysis of Feulgen-stained preparations. Chromatin extensibility in response to gravity was observed with polarized light after lysis and toluidine blue staining. The Con-A response of nuclear glycoproteins was evaluated with scanning microspectrophotometry. These characteristics were assessed using hepatocyte imprints from female NOD mice after a 28-day period of diabetes expression. Observations and measurements were made in comparison to healthy BALB/c mice. Total RNA amounts were determined for livers of NOD and BALB/c mice. Enhanced polyploidy levels, a decrease in chromatin higher-order packing states, an increased frequency of extended chromatin fiber formation, and deeper Con-A-responsive chromatin areas were observed in the hepatocytes of the NOD mice expressing insulin-dependent diabetes. Reduced amounts of total RNA were also found in the livers of these mice. Our findings for NOD mice expressing insulin-dependent diabetes are consistent with previously reported data for old-aged mice of the inbred strain A/Uni and may reflect changes in transcriptional activities associated with the stressful physiological demands on the liver during the expression of diabetes.

  15. Simultaneous Ultraviolet Line and Continuum Variability Studies in Seyfert 1 Galaxies and Quasars

    NASA Astrophysics Data System (ADS)

    Honnappa, Vijayakumar; Prabhakar, Vedavvathi

    Simultaneous Ultraviolet Line and Continuum Variability Studies in Seyfert 1 Galaxies and Quasars Vijayakumar H. Doddamani*and P. Vedavathi Department of Physics, Bangalore University, Bangalore-560056, *Corresponding author:drvkdmani@gmail.com, Abstract The line and continuum flux variability is a hallmark phenomenon of Seyfert 1 galaxies and quasars. Large amplitude luminosity variability is observed in AGNs from x-rays through radio waves over a wide-ranging timescales from minutes to years. The combinations of high luminosity and short variability time scales suggests, that the power of AGN is produced by a phenomena more efficient in terms of energy release per unit mass than ordinary stellar processes. The basic structure of AGNs thus developed based on the variability studies consists of a central super massive black hole surrounded by an accretion disk or more generally optically thick plasma radiating brightly at UV and soft X-ray wavelengths. The variability studies have been important tools of understanding the physics of the central regions of AGNs, which in general cannot be resolved with the existing or planned ground and space telescopes. Therefore, we have undertaken a study of the simultaneous ultraviolet line and continuum flux variability studies in MRK501, ESOB113-IG45 (also called as Fairall 9), MRK1506, MRK1095 V*GQCOM, PG1211+143, MRK205, PG1226+023 (also known as 3C273), PG1351+640, MRK 1383, MRK876 and QSO2251-178 as these objects have been repeatedly observed by IUE satellite over several years.. It is observed that Fairall 9, MRK 1095 and 3C273 exhibit the large amplitude variability (» 30 times) over the observed timescale, which spans several years. The remaining nine objects exhibit small amplitude (» 5 times) variability over the long time scale of observations. The highest amplitude variability is observed in Lya with a least in the MgII line. The amplitude of variability decreases in the order of Lya, CIV and Mg II, lines. These

  16. New probes of dark matter and dark energy

    NASA Astrophysics Data System (ADS)

    Kim, Young-Rae

    We use N -body simulations of a LCDM universe to study dark matter and dark energy. First, we examine the possibility of detecting the gravitational effect on the total redshift observed for galaxies. For clusters of mass M ~ 10 15 [Special characters omitted.] , the difference in gravitational redshift between the brightest galaxy and the rest of the cluster members is ~ 10 kms - 1 . The most efficient way to detect gravitational redshifts using information from galaxies only involves using the full gravitational redshift profile of clusters. Test on our simulated clusters show that we need at least ~ 2500 clusters/groups with M > 5 x 10 13 [Special characters omitted.] for a detection of gravitational redshifts at the 2s level. Secondly, we investigate the possibility of probing dark energy by measuring the isotropy of the galaxy cluster autocorrelation function (an Alcock-Paczynski test). We assume that the redshift distortion due to peculiar velocities can be removed by measuring kSZ effect. We use the hydrodynamic simulation results of Nagai et al. (2003) to simulate various kSZ surveys. We find by model fitting that a measurement of the correlation function distortion can be used to recover the cosmological parameters that have been used to generate the simulation. With the simulated SPT and ACT surveys, O L could be measured to within 0.1 and 0.2 respectively at one sigma, but only upper limits on the equation of state parameter w will be possible. Finally, using cosmological hydrodynamic simulations we measure the mean transmitted flux in the Lya forest for quasar sightlines that pass near a foreground quasar. We find that the trend of absorption with pixel- quasar separation distance can be fitted using a simple power law form including the usual correlation function parameters r 0 and g so that ([left angle bracket] F ( r )[right angle bracket] = SUMexp(-t eff (1 + [Special characters omitted.] ))). From the simulations we find the relation between r 0

  17. The problem-solving approach in the teaching of number theory

    NASA Astrophysics Data System (ADS)

    Toh, Pee Choon; Hoong Leong, Yew; Toh, Tin Lam; Dindyal, Jaguthsing; Quek, Khiok Seng; Guan Tay, Eng; Him Ho, Foo

    2014-02-01

    Mathematical problem solving is the mainstay of the mathematics curriculum for Singapore schools. In the preparation of prospective mathematics teachers, the authors, who are mathematics teacher educators, deem it important that pre-service mathematics teachers experience non-routine problem solving and acquire an attitude that predisposes them to adopt a Pólya-style approach in learning mathematics. The Practical Worksheet is an instructional scaffold we adopted to help our pre-service mathematics teachers develop problem-solving dispositions alongside the learning of the subject matter. The Worksheet was initially used in a design experiment aimed at teaching problem solving in a secondary school. In this paper, we describe an application and adaptation of the MProSE (Mathematical Problem Solving for Everyone) design experiment to a university level number theory course for pre-service mathematics teachers. The goal of the enterprise was to help the pre-service mathematics teachers develop problem-solving dispositions alongside the learning of the subject matter. Our analysis of the pre-service mathematics teachers' work shows that the MProSE design holds promise for mathematics courses at the tertiary level.

  18. GMRT HI Imaging of the Ly-α Emitting Starburst Galaxy Tololo 1924-416

    NASA Astrophysics Data System (ADS)

    Mendoza Davila, Cesar I.; Perez Sarmiento, Karen; Cannon, John M.; Hayes, Matthew; Melinder, Jens; Östlin, Göran; Pardy, Stephen; LARS Team

    2017-01-01

    The Lyman Alpha Reference Sample (LARS) and its extension (eLARS) form the most comprehensive effort to date to study the details of Lyman Alpha radiative transfer in galaxies. Direct imaging of Lyman Alpha emission from the Hubble Space Telescope is supplemented by a wealth of multi-wavelength observations designed to probe the complex processes that contribute to the escape or destruction of Lyman Alpha photons as they resonantly scatter in the neutral ISM. The 42 LARS+eLARS galaxies span a range of physical properties, including mass and star formation rate. In companion posters, we present results of HI imaging programs using the VLA and the GMRT. In this work, we present new HI imaging of the Lya-emitting starburst galaxy Tololo 1924-416; this source has a similar complement of HST imaging and spectroscopy as the LARS+eLARS galaxies. Tololo 1924-416 is known to be dramatically tidally interacting with ESO 338-IG04B; HI gas is strewn between the galaxies on scales of ~70 kpc. Our new data provide information on scales of ~2-10 kpc at the adopted distance of Tololo 1924-416 (37.5 Mpc). We study the HI morphology and dynamics of this interacting system.

  19. Superluminal motion (review)

    NASA Astrophysics Data System (ADS)

    Malykin, G. B.; Romanets, E. A.

    2012-06-01

    Prior to the development of Special Relativity, no restrictions were imposed on the velocity of the motion of particles and material bodies, as well as on energy transfer and signal propagation. At the end of the 19th century and the beginning of the 20th century, it was shown that a charge that moves at a velocity faster than the speed of light in an optical medium, in particular, in vacuum, gives rise to impact radiation, which later was termed the Vavilov-Cherenkov radiation. Shortly after the development of Special Relativity, some researchers considered the possibility of superluminal motion. In 1923, the Soviet physicist L.Ya. Strum suggested the existence of tachyons, which, however, have not been discovered yet. Superluminal motions can occur only for images, e.g., for so-called "light spots," which were considered in 1972 by V.L. Ginzburg and B.M. Bolotovskii. These spots can move with a superluminal phase velocity but are incapable of transferring energy and information. Nevertheless, these light spots may induce quite real generation of microwave radiation in closed waveguides and create the Vavilov-Cherenkov radiation in vacuum. In this work, we consider various paradoxes, illusions, and artifacts associated with superluminal motion.

  20. Adaptive urn designs for estimating several percentiles of a dose--response curve.

    PubMed

    Mugno, Raymond; Zhus, Wei; Rosenberger, William F

    2004-07-15

    Dose--response experiments are crucial in biomedical studies. There are usually multiple objectives in such experiments and among the goals is the estimation of several percentiles on the dose--response curve. Here we present the first non-parametric adaptive design approach to estimate several percentiles simultaneously via generalized Pólya urns. Theoretical properties of these designs are investigated and their performance is gaged by the locally compound optimal designs. As an example, we re-investigated a psychophysical experiment where one of the goals was to estimate the three quartiles. We show that these multiple-objective adaptive designs are more efficient than the original single-objective adaptive design targeting the median only. We also show that urn designs which target the optimal designs are slightly more efficient than those which target the desired percentiles directly. Guidelines are given as to when to use which type of design. Overall we are pleased with the efficiency results and hope compound adaptive designs proposed in this work or their variants may prove to be a viable non-parametric alternative in multiple-objective dose--response studies.

  1. Exactly solvable model for cluster-size distribution in a closed system

    NASA Astrophysics Data System (ADS)

    Dubrovskii, V. G.

    2017-01-01

    We obtain an exact solution for the cluster-size distributions in a closed system described by nonlinear rate equations for irreversible homogeneous growth with size-linear agglomeration rates of the form Ks=D (a +s -1 ) for all s ≥1 , where D is the diffusion coefficient, s is the size, and a is a positive constant. The size spectrum is given by the Pólya distribution times a factor that normalizes the first moment of the distribution to unity and zeroes out the monomer concentration at t →∞ . We show that the a value sets a maximum mean size that equals e for large a and tends to infinity only when a →0 . The size distributions are monotonically decreasing in the initial stage, converting to different monomodal shapes with a maximum at s =2 in the course of growth. The variance of the distribution is narrower than Poissonian at large a and broader than Poissonian at small a , with the threshold occurring at a ≅1 . In most cases, the sizes present in the distributions are small and hence can hardly be described by continuum equations.

  2. Quantifying velocity, strain rate and stress distribution in coalescing salt sheets for safer drilling

    NASA Astrophysics Data System (ADS)

    Weijermars, R.; van Harmelen, A.

    2015-03-01

    Reaching sub-salt hydrocarbon targets in the deeper part of the Gulf of Mexico requires drilling through a salt canopy. The suture zones in the salt canopy are potential drilling hazards due to anomalous pressure behaviour of entrapped sediments. The Pólya vector field of coalescing salt sheets inside the canopy is used to explain suture formation and distinguish between upright and inclined suture contacts. Our analytical models, based on complex potentials, provide exact solutions for multiple source flows as they compete for space when spreading into the viscous continuum of the salt canopy. The velocity gradient tensor yields the strain rate tensor, which is used to map the principal strain rate magnitude inside the canopy. Quantification of one of the principal strain rates is sufficient because the plane deformation assumption ensures the two principal strain rates are equal in magnitude (but of opposite sign); the third principal dimension can have neither strain nor deviatoric stress. Visualization of the locations where the principal stress vanishes or peaks (with highs and lows) is useful for pre-drilling plans because such peaks must be avoided and the stress-free locations provide the safer drilling sites. A case study-of the Walker Ridge region-demonstrates the practical application of our new method.

  3. PolyaPeak: detecting transcription factor binding sites from ChIP-seq using peak shape information.

    PubMed

    Wu, Hao; Ji, Hongkai

    2014-01-01

    ChIP-seq is a powerful technology for detecting genomic regions where a protein of interest interacts with DNA. ChIP-seq data for mapping transcription factor binding sites (TFBSs) have a characteristic pattern: around each binding site, sequence reads aligned to the forward and reverse strands of the reference genome form two separate peaks shifted away from each other, and the true binding site is located in between these two peaks. While it has been shown previously that the accuracy and resolution of binding site detection can be improved by modeling the pattern, efficient methods are unavailable to fully utilize that information in TFBS detection procedure. We present PolyaPeak, a new method to improve TFBS detection by incorporating the peak shape information. PolyaPeak describes peak shapes using a flexible Pólya model. The shapes are automatically learnt from the data using Minorization-Maximization (MM) algorithm, then integrated with the read count information via a hierarchical model to distinguish true binding sites from background noises. Extensive real data analyses show that PolyaPeak is capable of robustly improving TFBS detection compared with existing methods. An R package is freely available.

  4. Genomic-Enabled Prediction of Ordinal Data with Bayesian Logistic Ordinal Regression

    PubMed Central

    Montesinos-López, Osval A.; Montesinos-López, Abelardo; Crossa, José; Burgueño, Juan; Eskridge, Kent

    2015-01-01

    Most genomic-enabled prediction models developed so far assume that the response variable is continuous and normally distributed. The exception is the probit model, developed for ordered categorical phenotypes. In statistical applications, because of the easy implementation of the Bayesian probit ordinal regression (BPOR) model, Bayesian logistic ordinal regression (BLOR) is implemented rarely in the context of genomic-enabled prediction [sample size (n) is much smaller than the number of parameters (p)]. For this reason, in this paper we propose a BLOR model using the Pólya-Gamma data augmentation approach that produces a Gibbs sampler with similar full conditional distributions of the BPOR model and with the advantage that the BPOR model is a particular case of the BLOR model. We evaluated the proposed model by using simulation and two real data sets. Results indicate that our BLOR model is a good alternative for analyzing ordinal data in the context of genomic-enabled prediction with the probit or logit link. PMID:26290569

  5. Determining the number of isomers in X-, XY-, XYZ-, and XYZU-substituted D2 d allenes: Additive schemes for calculating enthalpies of vaporization

    NASA Astrophysics Data System (ADS)

    Nilov, D. Yu.; Smolyakov, V. M.

    2015-02-01

    Using Pólya's theorem, cycle indices are derived that identify the chiral and achiral substitution isomers of an allene (1,2-propadiene). Equations of symmetry that allow us to determine the number of isomers in a series and arrange the isomers according to families, depending on the number of substitution sites, are obtained. Eight- and nine-constant additive schemes based on the similarity between subgraphs in the molecular graphs (MGs) of a series of 120 molecules of X-, XY-, XYZ-, and XYZU-substituted allenes and the expansion of polygonal numbers (triangular, tetrahedral, and others) of a Pascal triangle are devised. Enthalpies of vaporization L NBP are calculated for 21 XY- and 120 XYZU-substituted allenes, respectively, not yet studied experimentally. It is shown that each coefficient of the scheme (the number of ways for superpositioning subgraphs with lengths i 1, i 2, ⋯ on molecular graphs of allene) is a result of partitioning triangular, tetrahedral, or four-dimensional tetrahedral numbers of a Pascal triangle.

  6. Mannose-binding lectin genotypes: potential role in tubal damage and adverse IVF outcome.

    PubMed

    Laisk, Triin; Peters, Maire; Salumets, Andres

    2011-12-01

    The innate immune system provides the first-line defence against genital tract pathogens and is also involved in establishing and maintaining a successful pregnancy. Genetic variation of factors regulating immune response can be associated with complications after genital tract infections and may lead to unfavourable pregnancy outcomes. This study focused on four polymorphisms in the mannose binding lectin gene (MBL2) and assessed their significance in tubal damage and female fertility by comparing genotype frequencies among 388 controls and women with tubal factor infertility (n=155) or previous ectopic pregnancy (n=178). The high-producing MBL2 genotype HYA/LYA was found to have a protective effect, while the hyper-producing MBL2 genotype HYA/HYA and low-producing MBL2 genotypes were associated with susceptibility to tubal factor infertility. Also, the low-producing genotypes showed association with early pregnancy loss in IVF treatment. In conclusion, these data suggest that certain MBL2 genotypes can be associated with tubal damage in patients with evidence of Chlamydia trachomatis infection and additionally may contribute to the pathogenesis of early pregnancy loss.

  7. Spectral Energy Distribution Fitting of Hetdex Pilot Survey Ly-alpha Emitters in Cosmos and Goods-N

    NASA Technical Reports Server (NTRS)

    Hagen, Alex; Ciardullo, Robin; Cronwall, Caryl; Acquaviva, Viviana; Bridge, Joanna; Zeimann, Gregory R.; Blanc, Guillermo; Bond, Nicholas; Finkelstein, Steven L.; Song, Mimi; Gawiser, Eric; Fox, Derek B.; Gebhardt, Henry; Malz, A. I; Schneider, Donald P.; Drory, Niv; Gebhardt, Karl; Hill, Gary J.

    2014-01-01

    We use broadband photometry extending from the rest-frame UV to the near-IR to fit the individual spectral energy distributions of 63 bright (L(Ly-alpha) greater than 10(exp 43) erg s(exp -1) Ly-alpha emitting galaxies (LAEs) in the redshift range 1.9 less than z less than 3.6. We find that these LAEs are quite heterogeneous, with stellar masses that span over three orders of magnitude, from 7.5 greater than logM/solar mass less than 10.5. Moreover, although most LAEs have small amounts of extinction, some high-mass objects have stellar reddenings as large as E(B - V ) is approximately 0.4. Interestingly, in dusty objects the optical depths for Ly-alpha and the UV continuum are always similar, indicating that Lya photons are not undergoing many scatters before escaping their galaxy. In contrast, the ratio of optical depths in low-reddening systems can vary widely, illustrating the diverse nature of the systems. Finally, we show that in the star-formation-rate-log-mass diagram, our LAEs fall above the "main-sequence" defined by z is approximately 3 continuum selected star-forming galaxies. In this respect, they are similar to submillimeter-selected galaxies, although most LAEs have much lower mass.

  8. Tail Asymptotics of Free Path Lengths for the Periodic Lorentz Process: On Dettmann's Geometric Conjectures

    NASA Astrophysics Data System (ADS)

    Nándori, Péter; Szász, Domokos; Varjú, Tamás

    2014-10-01

    In the simplest case, consider a -periodic ( d ≥ 3) arrangement of balls of radii < 1/2, and select a random direction and point (outside the balls). According to Dettmann's first conjecture, the probability that the so determined free flight (until the first hitting of a ball) is larger than t > > 1 is , where C is explicitly given by the geometry of the model. In its simplest form, Dettmann's second conjecture is related to the previous case with tangent balls (of radii 1/2). The conjectures are established in a more general setup: for -periodic configuration of—possibly intersecting—convex bodies with being a non-degenerate lattice. These questions are related to Pólya's visibility problem (Arch Math Phys Ser 2:135-142,1918), to theories of Bourgain et al. (Commun Math Phys 190:491-508,1998), and of Marklof-Strömbergsson (Ann Math 172:1949-2033,2010). The results also provide the asymptotic covariance of the periodic Lorentz process assuming it has a limit in the super-diffusive scaling, a fact if d = 2 and the horizon is infinite.

  9. Clasp/SJ Observation of Time Variations of Lyman-Alpha Emissions in a Solar Active Region

    NASA Technical Reports Server (NTRS)

    Ishikawa, S.; Kubo, M.; Katsukawa, Y.; Kano, R.; Narukage, N.; Ishikawa, R.; Bando, T.; Winebarger, A.; Kobayashi, K.; Trujillo Bueno, J.; Auchere, F.

    2016-01-01

    The Chromospheric Lyman-alpha SpectroPolarimeter (CLASP) is a sounding rocket experiment launched on September 3, 2015 to investigate the solar chromosphere, and the slit-jaw (SJ) optical system took Lya images with the high time cadence of 0.6 s. By the CLASP/SJ observation, many time variations in the solar chromosphere with the time scale of <1 minute were discovered (see the poster by Kubo et al., Pa-13). We focused on an active region and investigated the short (<30 s) time variations and relation to the coronal structure observed by SDO/AIA. We compared the Ly(alpha) time variations at footpoints of coronal magnetic fields observed by AIA 211 Å (approx.2 MK) and AIA 171 Å (0.6 MK), and non-loop regions. As the result, we found the <30 s Ly(alpha) time variations had more in the footpoint regions. On the other hand, the <30 s time variations had no dependency on the temperature of the loop.

  10. Quantifying evenly distributed states in exclusion and nonexclusion processes

    NASA Astrophysics Data System (ADS)

    Binder, Benjamin J.; Landman, Kerry A.

    2011-04-01

    Spatial-point data sets, generated from a wide range of physical systems and mathematical models, can be analyzed by counting the number of objects in equally sized bins. We find that the bin counts are related to the Pólya distribution. New measures are developed which indicate whether or not a spatial data set, generated from an exclusion process, is at its most evenly distributed state, the complete spatial randomness (CSR) state. To this end, we define an index in terms of the variance between the bin counts. Limiting values of the index are determined when objects have access to the entire domain and when there are subregions of the domain that are inaccessible to objects. Using three case studies (Lagrangian fluid particles in chaotic laminar flows, cellular automata agents in discrete models, and biological cells within colonies), we calculate the indexes and verify that our theoretical CSR limit accurately predicts the state of the system. These measures should prove useful in many biological applications.

  11. Geographic List of Prime Contract Awards. Oct 1992-Sep 1993. FY 1993. (Akron, New York-Williston, North Dakota). Part 9

    DTIC Science & Technology

    1994-03-01

    47 1 t e Oki cm040O ac 0.- m 0.-’ art. 0(0-4 C c 0(0 * N 0 0 4 0 mom (0(4 II0 P47 -WN (D ~ m0 (00 (0 (00-IN (0 w 0C7.44 ca 1004 II 000 0OO 0 0 0...N P PN.a) YflY G a 0 C1A71) flnLYa ) lcfla)mm0)a) mOa)0) t%ýc C31 II I(0(V I cc 11 1(0V MOM Z0I01 ~If I mOIN 110 411 1I(aON IIU11 < I I( O 1101toC~ t...W0W0W0W0W0W(W(W0W0W0W0M0WDM0W CA 01C I ( 00(0D If 11 1 1:I 00(04II N N N N N N N NN N N N N N N N NN N N ? N N N LJIt 01 W (00 4 v 11 U It ’I- I MOM ’ 11 No il

  12. Stochastic and empirical models of the absolute asymmetric synthesis by the Soai-autocatalysis.

    PubMed

    Barabás, Béla; Zucchi, Claudia; Maioli, Marco; Micskei, Károly; Pályi, Gyula

    2015-02-01

    Absolute asymmetric synthesis (AAS) is the preparation of pure (or excess of one) enantiomer of a chiral compound from achiral precursor(s) by a chemical reaction, without enantiopure chiral additive and/or without applied asymmetric physical field. Only one well-characterized example of AAS is known today: the Soai-autocatalysis. In an attempt at clarification of the mechanism of this particular reaction we have undertaken empirical and stochastic analysis of several parallel AAS experiments. Our results show that the initial steps of the reaction might be controlled by simple normal distribution ("coin tossing") formalism. Advanced stages of the reaction, however, appear to be of a more complicated nature. Symmetric beta distribution formalism could not be brought into correspondence with the experimental observations. A bimodal beta distribution algorithm provided suitable agreement with the experimental data. The parameters of this bimodal beta function were determined by a Pólya-urn experiment (simulated by computer). Interestingly, parameters of the resulting bimodal beta function give a golden section ratio. These results show, that in this highly interesting autocatalysis two or even perhaps three catalytic cycles are cooperating. An attempt at constructing a "designed" Soai-type reaction system has also been made.

  13. 2D Emission Line Galaxies in the Faint Infrared Galaxy Survey

    NASA Astrophysics Data System (ADS)

    Pirzkal, Nor; Ryan, Russell E.; Rothberg, Barry; Meurer, Gerhardt R.; Malhotra, Sangeeta; Rhoads, James E.; Koekemoer, Anton M.; Finkelstein, Steven; Grogin, Norman A.

    2015-08-01

    The Faint Infrared Galaxy Survey (FIGS) provides us with a unique opportunity to identify emission line galaxies. Emission lines such as [OII], [OIII], Hα and Lya lines can be identified in the FIGS slitless spectroscopic observations down to faint line fluxes of a few times 10-17 erg/s/cm2. Crucially, the use of multiple observations, taken at different position angles on the sky allows us to accurately determine the location of these star forming regions within individual galaxies using the Emission Line 2D (EM2D) method. Our ability to detect high equivalent width lines independently of any host galaxies allows us to search for naked emission line objects. Combining this method with the wavelength coverage of the G102 grism, we are able to identify emission line objects using [OII] and [OIII], and Hα over 0.2 < z < 2 and using Lyman alpha from 6 < z < 8. Here, we present the first results on star forming galaxies selected using this method and demonstrate the wealth of data to be expected from the FIGS project.

  14. Characteristics of service requests and service processes of fire and rescue service dispatch centers: analysis of real world data and the underlying probability distributions.

    PubMed

    Krueger, Ute; Schimmelpfeng, Katja

    2013-03-01

    A sufficient staffing level in fire and rescue dispatch centers is crucial for saving lives. Therefore, it is important to estimate the expected workload properly. For this purpose, we analyzed whether a dispatch center can be considered as a call center. Current call center publications very often model call arrivals as a non-homogeneous Poisson process. This bases on the underlying assumption of the caller's independent decision to call or not to call. In case of an emergency, however, there are often calls from more than one person reporting the same incident and thus, these calls are not independent. Therefore, this paper focuses on the dependency of calls in a fire and rescue dispatch center. We analyzed and evaluated several distributions in this setting. Results are illustrated using real-world data collected from a typical German dispatch center in Cottbus ("Leitstelle Lausitz"). We identified the Pólya distribution as being superior to the Poisson distribution in describing the call arrival rate and the Weibull distribution to be more suitable than the exponential distribution for interarrival times and service times. However, the commonly used distributions offer acceptable approximations. This is important for estimating a sufficient staffing level in practice using, e.g., the Erlang-C model.

  15. Interface-enforced complexation between copolymer blocks.

    PubMed

    Steinschulte, Alexander A; Xu, Weinan; Draber, Fabian; Hebbeker, Pascal; Jung, Andre; Bogdanovski, Dimitri; Schneider, Stefanie; Tsukruk, Vladimir V; Plamper, Felix A

    2015-05-14

    Binary diblock copolymers and corresponding ternary miktoarm stars are studied at oil-water interfaces. All polymers contain oil-soluble poly(propylene oxide) PPO, water-soluble poly(dimethylaminoethyl methacrylate) PDMAEMA and/or poly(ethylene oxide) PEO. The features of their Langmuir compression isotherms are well related to the ones of the corresponding homopolymers. Within the Langmuir-trough, PEO-b-PPO acts as the most effective amphiphile compared to the other PPO-containing copolymers. In contrast, the compression isotherms show a complexation of PPO and PDMAEMA for PPO-b-PDMAEMA and the star, reducing their overall amphiphilicity. Such complex formation between the blocks of PPO-b-PDMAEMA is prevented in bulk water but facilitated at the interface. The weakly-interacting blocks of PPO-b-PDMAEMA form a complex due to their enhanced proximity in such confined environments. Scanning force microscopy and Monte Carlo simulations with varying confinement support our results, which are regarded as compliant with the mathematical random walk theorem by Pólya. Finally, the results are expected to be of relevance for e.g. emulsion formulation and macromolecular engineering.

  16. Measurements of K Shell Emission of Highly Charged Ions with the XRS at EBIT

    NASA Technical Reports Server (NTRS)

    Porter, F. Scott; Beiersdorfer, P.; Boyce, K.; Brown, G. V.; Chen, H.; Kahn, S.; Kelley, R.; Kilbourne, C. A.

    2004-01-01

    The XRS/EBIT is a 32 channel microcalorimeter spectrometer operating at the electron beam ion trap (EBIT) facility at Lawrence Livermore National Laboratory. The system contains a flight candidate detector array from the XRS instrument for the Astro-E2 mission. The detector array in the XRS/EBIT is functionally identical to the flight array integrated into the XRS instrument and benefits from the enormous amount of calibration data from the XRS program. Since the XRSEBIT was upgraded with the new detector array in October 2003, the system has been used for a number of experiments including a survey of the K shell emission from He-like and H-like O, Ne, Ar, Fe, Ni and Kr as well as for L shell emission to measure the 3C/3D line ratio in Ni. Here we present some basic operational parameters of the instrument as well as direct excitation and simulated maxwellian spectra of He-like and E-like Fe. We show that the XRS instrument can resolve the Lyal and Lya2 lines from each other as well as from the dielectronic recombination satellites in thermal H-like Fe. We also show exactly how well the XRS instrument on Astro-E2 will resolve the thermal He-like triplet in collisionally excited Fe. This work was funded under NASA's Research Opportunities in Space Science program.

  17. Anisotropic nanomaterials: Synthesis, optical and magnetic properties, and applications

    NASA Astrophysics Data System (ADS)

    Banholzer, Matthew John

    encapsulation on the SPR of these structures. Chapter six focuses on the magnetic properties of Au-Ni heterostructures. In addition to demonstration of nanoconfinement effects based upon the anisotropy of the nanorods/nanodisk structure, the magnetic coupling of rod-disk heterostructures is examined. Subsequent investigations suggest that the magnetic behavior of disks can be influenced by nearby rod segments, leading to the creation of a three-state spin system that may prove useful in device applications.

  18. Nanoscopic Thermodynamics.

    PubMed

    Qi, Weihong

    2016-09-20

    Conventional thermodynamics for bulk substances encounters challenges when one considers materials on the nanometer scale. Quantities such as entropy, enthalpy, free energy, melting temperature, ordering temperature, Debye temperature, and specific heat no longer remain constant but change with the crystal dimension, size, and morphology. Often, one phenomenon is associated with a variety of theories from different perspectives. Still, a model that can reconcile the size and shape dependence of the thermal properties of the nanoscaled substances remains one of the goals of nanoscience and nanotechnology. This Account highlights the nanoscopic thermodynamics for nanoparticles, nanowires, and nanofilms, with particular emphasis on the bond energy model. The central idea is that the atomic cohesive energy determines the thermodynamic performance of a substance and the cohesive energy varies with the atomic coordination environment. It is the cohesive energy difference between the core and the shell that dictates the nanoscopic thermodynamics. This bond energy model rationalizes the following: (i) how the surface dangling bonds depress the melting temperature, entropy, and enthalpy; (ii) how the order-disorder transition of the nanoparticles depends on particle size and how their stability may vary when they are embedded in an appropriate matrix; (iii) predictions of the existence of face-centered cubic structures of Ti, Zr, and Hf at small size; (iv) how two elements that are immiscible in the bulk can form an alloy on the nanoscale, where the critical size can be predicted. The model has enabled us to reproduce the size and shape dependence of a number of physical properties, such as melting temperature, melting entropy, melting enthalpy, ordering temperature, Gibbs free energy, and formation heat, among others, for materials such as Pd, Au, Ag, Cu, Ni, Sn, Pb, In, Bi, Al, Ti, Zr, Hf, In-Al, Ag-Ni, Co-Pt, Cu-Ag, Cu-Ni, Au-Ni, Ag-Pt, and Au-Pt on the nanometer scale

  19. Observing Supernova 1987A with the Refurbished Hubble Space Telescope

    NASA Technical Reports Server (NTRS)

    France, Kevin; McCray, Richard; Heng, Kevin; Kirshner, Robert P.; Challis, Peter; Bouchet, Patrice; Crotts, Arlin; Dwek, Eli; Fransson, Claes; Garnavich, Peter M.; Larsson, Josefin; Lundqvist, Peter; Panagia, Nino; Pun, Chun S. J.; Smith, Nathan; Sollerman, Jesper; Sonneborn, George; Stocke, John T.; Wheeler, J. Craig

    2010-01-01

    The young remnant of supernova 1987A (SN 1987A) offers an unprecedented glimpse into the hydrodynamics and kinetics of fast astrophysical shocks. We have been monitoring SN 1987A with the Hubble Space Telescope (HST) since it was launched. The recent repair of the Space Telescope Imaging Spectrograph (STIS) allows us to compare observations in 2004, just before its demise, with those in 2010, shortly after its resuscitation by NASA astronauts. We find that the Ly-alpha and H-alpha lines from shock emission continue to brighten, while their maximum velocities continue to decrease. We report evidence for nearly coherent, resonant scattering of Lya photons (to blueshifts approximately -12,000 km /s) from hotspots on the equatorial ring. We also report emission to the red of Ly-alpha that we attribute to N v lambda lambda 1239,1243 Angstrom line emission. These lines are detectable because, unlike hydrogen atoms, N4+ ions emit hundreds of photons before they are ionized. The profiles of the N v lines differ markedly from that of H-alpha. We attribute this to scattering of N4+ ions by magnetic fields in the ionized plasma. Thus, N v emission provides a unique probe of the isotropization zone of the collisionless shock. Observations with the recently installed Cosmic Origins Spectrograph (COS) will enable us to observe the N v lambda lambda 1239,1243 Angstrom line profiles with much higher signal-to-noise ratios than possible with STIS and may reveal lines of other highly ionized species (such as C IVlambda lambda 1548,1551 Angstrom) that will test our explanation for the N v emission

  20. Virtual libraries of tetrapyrrole macrocycles. Combinatorics, isomers, product distributions, and data mining.

    PubMed

    Taniguchi, Masahiko; Du, Hai; Lindsey, Jonathan S

    2011-09-26

    A software program (PorphyrinViLiGe) has been developed to enumerate the type and relative amounts of substituted tetrapyrrole macrocycles in a virtual library formed by one of four different classes of reactions. The classes include (1) 4-fold reaction of n disubstituted heterocycles (e.g., pyrroles or diiminoisoindolines) to form β-substituted porphyrins, β-substituted tetraazaporphyrins, or α- or β-substituted phthalocyanines; (2) combination of m aminoketones and n diones to form m × n pyrroles, which upon 4-fold reaction give β-substituted porphyrins; (3) derivatization of an 8-point tetrapyrrole scaffold with n reagents, and (4) 4-fold reaction of n aldehydes and pyrrole to form meso-substituted porphyrins. The program accommodates variable ratios of reactants, reversible or irreversible reaction (reaction classes 1 and 2), and degenerate modes of formation. Pólya's theorem (for enumeration of cyclic entities) has also been implemented and provides validation for reaction classes 3 and 4. The output includes the number and identity of distinct reaction-accessible substituent combinations, the number and identity of isomers thereof, and the theoretical mass spectrum. Provisions for data mining enable assessment of the number of products having a chosen pattern of substituents. Examples include derivatization of an octa-substituted phthalocyanine with eight reagents to afford a library of 2,099,728 members (yet only 6435 distinct substituent combinations) and reversible reaction of six distinct disubstituted pyrroles to afford 2649 members (yet only 126 distinct substituent combinations). In general, libraries of substituted tetrapyrrole macrocycles occupy a synthetically accessible region of chemical space that is rich in isomers (>99% or 95% for the two examples, respectively).

  1. The development of a culture of problem solving with secondary students through heuristic strategies

    NASA Astrophysics Data System (ADS)

    Eisenmann, Petr; Novotná, Jarmila; Přibyl, Jiří; Břehovský, Jiří

    2015-12-01

    The article reports the results of a longitudinal research study conducted in three mathematics classes in Czech schools with 62 pupils aged 12-18 years. The pupils were exposed to the use of selected heuristic strategies in mathematical problem solving for a period of 16 months. This was done through solving problems where the solution was the most efficient if heuristic strategies were used. The authors conducted a two-dimensional classification of the use of heuristic strategies based on the work of Pólya (2004) and Schoenfeld (1985). We developed a tool that allows for the description of a pupil's ability to solve problems. Named, the Culture of Problem Solving (CPS), this tool consists of four components: intelligence, text comprehension, creativity and the ability to use existing knowledge. The pupils' success rate in problem solving and the changes in some of the CPS factors pre- and post-experiment were monitored. The pupils appeared to considerably improve in the creativity component. In addition, the results indicate a positive change in the students' attitude to problem solving. As far as the teachers participating in the experiment are concerned, a significant change was in their teaching style to a more constructivist, inquiry-based approach, as well as their willingness to accept a student's non-standard approach to solving a problem. Another important outcome of the research was the identification of the heuristic strategies that can be taught via long-term guided solutions of suitable problems and those that cannot. Those that can be taught include systematic experimentation, guess-check-revise and introduction of an auxiliary element. Those that cannot be taught (or can only be taught with difficulty) include the strategies of specification and generalization and analogy.

  2. Emergence of q-statistical functions in a generalized binomial distribution with strong correlations

    NASA Astrophysics Data System (ADS)

    Ruiz, G.; Tsallis, C.

    2015-05-01

    We study a symmetric generalization pk ( N ) ( η , α ) of the binomial distribution recently introduced by Bergeron et al., where η ∈ [0, 1] denotes the win probability and α is a positive parameter. This generalization is based on q-exponential generating functions ( eq gen z ≡ [ 1 + ( 1 - qgen ) z ] 1 / ( 1 - q gen ) ; e1 z = e z ) where qgen = 1 + 1/α. The numerical calculation of the probability distribution function of the number of wins k, related to the number of realizations N, strongly approaches a discrete qdisc-Gaussian distribution, for win-loss equiprobability (i.e., η = 1/2) and all values of α. Asymptotic N → ∞ distribution is in fact a qatt-Gaussian eq att - β z 2 , where qatt = 1 - 2/(α - 2) and β = (2α - 4). The behavior of the scaled quantity k/Nγ is discussed as well. For γ < 1, a large-deviation-like property showing a qldl-exponential decay is found, where qldl = 1 + 1/(ηα). For η = 1/2, qldl and qatt are related through 1/(qldl - 1) + 1/(qatt - 1) = 1, ∀α. For γ = 1, the law of large numbers is violated, and we consistently study the large-deviations with respect to the probability of the N → ∞ limit distribution, yielding a power law, although not exactly a qLD-exponential decay. All q-statistical parameters which emerge are univocally defined by (η, α). Finally, we discuss the analytical connection with the Pólya urn problem.

  3. Teaching and Learning Science in Hungary, 1867-1945: Schools, Personalities, Influences

    NASA Astrophysics Data System (ADS)

    Frank, Tibor

    2012-03-01

    The article provides an overview of the development of teaching science in Hungary during both the time of the dual monarchy and the newly established independent Hungary after 1920. The integration of Hungary into the Austro-Hungarian Monarchy (1867-1918) strengthened the effect of German speaking European science, the results of which were quickly channelled into the Hungarian school system at all levels. The Hungarian Academy as well as the University of Budapest (today Eötvös Loránd University) played a leading role in the „nationalization" of European science in the educational system. Scientific developments in Hungary strengthened the position of rational and secular thinking in a highly religious society and contributed to the erosion of the mental power of the church tradition, particularly that of the Roman Catholic Church. Toward World War I, influenced by the Protestant Churches, the Jewish tradition, and agnosticism, the public picture of science became more international, occasionally ready to consider challenges of the accepted world view, and sometimes less dogmatic. Leading Hungarian figures with an international reputation who played a decisive role in making science part of Hungarian thinking included the physicists Baron Loránd Eötvös and Sándor Mikola, the mathematicians László Rácz and George Pólya as well as a host of others in related fields. Emigration, mostly Jewish, after World War I, contributed to the curtailment of efforts to teach science effectively as some of the best people left Hungary for, mostly, Germany, Britain, and the United States. However, the interwar school system, the Hungarian version of the German Gymnasium, continued to disseminate scientific thought in Hungarian education. Much of the information was foreign and appeared simply in translation—but an impressive array of indigeneous scientific results paved the way to a larger educated middle class then in the making.

  4. The Cosmic Origins Spectrograph

    NASA Technical Reports Server (NTRS)

    Green, James C.; Froning, Cynthia S.; Osterman, Steve; Ebbets, Dennis; Heap, Sara H.; Leitherer, Claus; Linsky, Jeffrey L.; Savage, Blair D.; Sembach, Kenneth; Shull, J. Michael; Siegmund, Oswald H. W.; Snow, Theodore P.; Spencer, John; Stern, S. Alan; Stocke, John; Welsh, Barry; Beland, Stephane; Burgh, Eric B.; Danforth, Charles; France, Kevin; Keeney, Brian; McPhate, Jason; Penton, Steven V; Andrews, John; Morse, Jon

    2010-01-01

    The Cosmic Origins Spectrograph (COS) is a moderate-resolution spectrograph with unprecedented sensitivity that was installed into the Hubble Space Telescope (HST) in May 2009, during HST Servicing Mission 4 (STS-125). We present the design philosophy and summarize the key characteristics of the instrument that will be of interest to potential observers. For faint targets, with flux F(sub lambda) approximates 1.0 X 10(exp -14) ergs/s/cm2/Angstrom, COS can achieve comparable signal to noise (when compared to STIS echelle modes) in 1-2% of the observing time. This has led to a significant increase in the total data volume and data quality available to the community. For example, in the first 20 months of science operation (September 2009 - June 2011) the cumulative redshift pathlength of extragalactic sight lines sampled by COS is 9 times that sampled at moderate resolution in 19 previous years of Hubble observations. COS programs have observed 214 distinct lines of sight suitable for study of the intergalactic medium as of June 2011. COS has measured, for the first time with high reliability, broad Lya absorbers and Ne VIII in the intergalactic medium, and observed the HeII reionization epoch along multiple sightlines. COS has detected the first CO emission and absorption in the UV spectra of low-mass circumstellar disks at the epoch of giant planet formation, and detected multiple ionization states of metals in extra-solar planetary atmospheres. In the coming years, COS will continue its census of intergalactic gas, probe galactic and cosmic structure, and explore physics in our solar system and Galaxy.

  5. Exploring the Galactic Damped Lyman alpha Absorber with Antipodal Sight Lines

    NASA Astrophysics Data System (ADS)

    Danforth, Charles

    2011-10-01

    Damped Lya Absorbers {DLAs} are the highest column density systems seen in the spectra of distant quasars. Some DLAs are thought to represent absorption from gas associated with an intervening galaxy disks, halo, tidal tail, etc., along the line of sight and DLAs are a key method of studying star formation, metal abundances, and kinematics at high redshift. These systems are exceedingly rare at low-z where the intervening galaxies can be studied in detail, so the precise nature of these important diagnostics remains poorly-understood. However, there is one DLA present along every extragalactic sight line which we can study in exhaustive detail: the Milky Way DLA! We propose a study of sight lines through the Galactic DLA using archival far-UV spectra from STIS, COS, and GHRS. We will construct 30-40 full-DLA profiles for the Milky Way DLA by combining the absorption spectra of pairs of nearly-antipodal sight lines {within 20 degrees of antipodal}. This will allow us to sample a realistic distribution of physical conditions in a system exhibiting realistic kinematics. Our DLA profiles will intersect the Galaxy at a range of angles and probe a variety of Galactic structures - high-velocity clouds, tidal tails, possible outflows, etc. - the same features which are inferred but rarely confirmed in some external DLAs. This diversity of sight lines through the same galaxy will let us determine if the wide range of observed properties in external DLAs {column density, velocity dispersion, abundances, etc.} could be an effect of the precise details of the line of sight or is inherent to the population of DLA hosts.

  6. The Circumgalactic Medium surrounding =2.3 Star-Forming Galaxies in the Keck Baryonic Structure Survey

    NASA Astrophysics Data System (ADS)

    Rudie, Gwen C.

    2013-01-01

    The gaseous environments of galaxies are a crucial but poorly-constrained component of galaxy formation and evolution and contain vital information about the movement of baryons into and out of galaxies. I will present results from the Keck Baryonic Structure Survey (KBSS), a unique spectroscopic survey designed to explore the connection between galaxies and intergalactic baryons during the cosmic peak of star formation ( 2-3). The KBSS combines Keck/HIRES spectra of 15 hyperluminous QSOs with densely-sampled galaxy redshift surveys surrounding each QSO sightline. Through Voigt profile decomposition of ~6000 HI absorbers within the Lya forest in the QSO spectra, my thesis provides the first measurements of the physical properties of the circumgalactic medium (CGM) of high-redshift galaxies characterizing the distribution, HI column densities (NHI), kinematics, and line widths of the gas within 50 kpc to 3 Mpc of 886 foreground galaxies. We find that the strongest absorbers within 100 kpc of galaxies have 1000 times higher NHI than typical IGM values and that the strongest absorption is found within 300 kpc and 300 km/s of galaxies. The spatial covering fraction, multiplicity, and characteristic NHI remain elevated to transverse distances of 2 Mpc while redshift anisotropies on these scales indicate coherent infall. The Doppler widths of CGM absorbers are ~50% larger than average, suggesting higher temperatures and/or increased turbulence likely caused by accretion shocks and/or galactic winds. Comparison with recent theoretical predictions reveals significant discrepancies suggesting that the current understanding of gas flows remains incomplete. Ongoing analysis of metallic CGM absorption features will provide unique insight into the metallicity and physical state of the CGM. Collectively, these measurements yield the first constraints of the co-evolution of galaxies and the IGM, the nature of baryonic flows, and the effect of star formation on both the IGM and on

  7. Evolution in the Continuum Morphological Properties of Ly alpha-Emitting Galaxies from Z=3.1 to Z=2.1

    NASA Technical Reports Server (NTRS)

    Bond, Nicholas A.; Gawiser, Eric; Guaita, Lucia; Padilla, Nelson; Gronwall, Chile Caryl; Ciardullo, Robin; Lai, Kamson

    2011-01-01

    We present a rest-frame ultraviolet morphological analysis of 108 z = 2.1 Lyman Alpha Emitters (LAEs) in the Extended Chandra Deep Field South (ECDF-S) and compare it to a similar sample of 171 LAEs at z = 3.1 . Using Hubble Space Telescope (HST) images taken as part of the Galaxy Evolution From Morphology and SEDs survey, Great Observatories Origins Deep Survey, and Hubble Ultradeep Field surveys, we measure the size and photometric component distributions, where photo- metric components are defined as distinct clumps of UV-continuum emission. At both redshifts, the majority of LAEs have observed half-light radii < 2 kpc, but the median half-light radius rises from 0.97 kpc at z = 3.1 to 1.41 kpc at z = 2.1. A similar evolution is seen in the sizes of individual rest-UV components, but there is no evidence for evolution in the number of mUlti-component systems. In the z = 2.1 LAE sample, we see clear correlations between the LAE size and other physical properties derived from its SED. LAEs are found to be larger for galaxies with larger stellar mass, larger star formation rate, and larger dust obscuration, but there is no evidence for a trend between equivalent width and half-light radius at either redshift. The presence of these correlations suggests that a wide range of objects are being selected by LAE surveys at that redshift, including a significant fraction of objects for which a massive and moderately extended population of old stars underlies the young starburst giving rise to the Lya emission.

  8. Genetic association study between mbl2 and asthma phenotypes in Chinese children.

    PubMed

    Leung, Ting Fan; Tang, Nelson L S; Sung, Ying Man; Li, Chung Yi; Ma, Suk Ling; Lam, Christopher W K; Wong, Gary W K

    2006-11-01

    Mannose-binding lectin (MBL), a member of the innate immune system, initiates complement deposition on microbial surfaces. MBL deficiency is associated with severe respiratory infections. Polymorphisms in the MBL gene (mbl2) were associated with the susceptibility and severity of autoimmune diseases. This study investigated whether mbl2 polymorphisms at positions -550 and -221 and at codon-54 are associated with asthma phenotypes in Chinese children. Asthmatics aged 5-18 yr and non-allergic controls were eligible, and their plasma total and allergen-specific immunoglobulin E (IgE) concentrations were measured by micro-particle immunoassay and fluorescent enzyme immunoassay. mbl2 polymorphisms were genotyped by restriction fragment length polymorphism. Three hundred and seventeen asthmatic children and 140 controls were recruited, with their mean (s.d.) log-transformed plasma total IgE being 2.61 (0.61) and 1.77 (0.77), respectively (p < 0.0001). Polymorphisms at -550 and codon-54 (p < 0.0001 for both) but not at -221 (p = 0.534) of mbl2 were significantly associated with plasma MBL concentrations. mbl2 genotypes were not associated with asthma, atopy, sensitization to individual aeroallergens or spirometric variable. Subjects with LYB haplotype had the lowest plasma MBL concentrations (p < 0.0001), but two- and three-loci mbl2 haplotypes were also not associated with asthma diagnosis. However, patients with LY and LYB haplotypes were less likely to be atopic (p = 0.006 and 0.031). Subjects with LY and LYA were also less likely to be sensitized to cockroach (p = 0.035 and 0.047). The latter three associations became insignificant when adjusted for multiple comparisons. Despite the importance of MBL in innate immunity, our mbl2 polymorphisms only show weak association with asthma and atopy in children.

  9. Smoking status interacts with the association between mannose-binding lectin serum levels and gene polymorphism and the carriage of oropharyngeal bacteria.

    PubMed

    Jounio, Ulla; Rantala, Aino; Bloigu, Aini; Juvonen, Raija; Lajunen, Taina; Silvennoinen-Kassinen, Sylvi; Peitso, Ari; Vainio, Olli; Harju, Terttu; Saukkoriipi, Annika; Leinonen, Maija

    2010-03-01

    Mannose-binding lectin (MBL) role in the carriage of oropharyngeal bacteria is not known. We investigated the association of smoking, MBL2 polymorphisms, and MBL concentrations with oropharyngeal carriage of respiratory bacteria in young men. Oropharyngeal specimens, MBL concentrations, and MBL2 gene polymorphisms were measured in 124 asthmatic and 394 nonasthmatic Finnish military recruits. The carriage rates of S. pneumoniae (p = 0.002), N. meningitidis (p = 0.005), and beta-hemolytic streptococci (p < 0.001) throughout the military service were significantly higher among smokers than in nonsmokers. An MBL level below the median proved to be a significant risk factor for the carriage of N. meningitidis (odds ratio [OR] = 1.9; 95% confidence interval [CI] 1.0-3.6) and beta-hemolytic streptococci (OR = 2.0; 95% CI 1.2-3.2) in the nonsmokers and a borderline significant risk factor for the carriage of S. pneumoniae (OR = 1.5; 95% CI 0.9-2.6), whereas low MBL levels producing MBL2 haplotypes (LXA/LXA, LXA/O, HYA/O, LYA/O, O/O) seemed to be associated with the carriage of N. meningitidis (OR = 1.8; 95% CI 1.0-3.4) and S. pneumoniae (OR = 1.6; 95% CI 0.9-2.7). Thus, MBL deficiency may predispose nonsmokers to oropharyngeal carriage of these bacteria. We hypothesize that the major factor contributing to elevated bacterial carriage in smokers might be increased bacterial adherence to epithelial cells, which obscures the effect of MBL.

  10. Control of Metal/graphite Interfacial Energy Through the Interfacial Segregation of Alloying Additions.

    NASA Astrophysics Data System (ADS)

    Gangopadhyay, Utpal

    concentration which was determined to be 0.45 monolayers. Crater edge profiling studies also revealed Ni at the interface. A theoretical model based on the nearest neighbor bond-regular solution approximation was developed for estimating the surface concentration of the solute. This model was used in the Au-Ni system to estimate the surface Ni concentration and the consequent reduction in surface energy. The predicted values compared favorably with the corresponding experimental values. A model was also developed using a similar approach to predict interfacial Ni concentration in a metal/graphite system. This model was used to estimate the Ni content at a Au/graphite interface for a Au-0. 15Ni sample at 850^circC. The predicted interfacial atom fraction did not agree very well with the experimentally determined value. Nevertheless, it did yield a qualitatively correct trend and the right kind of temperature dependence.

  11. Hubble/COS Observations of Intergalactic Gas Toward PKS 0405-123

    NASA Astrophysics Data System (ADS)

    Shull, J. Michael; Danforth, C.; Froning, C.; Green, J.; Keeney, B.; Stocke, J.; Yao, Y.; Savage, B.; Narayanan, A.; Sembach, K.

    2010-01-01

    We present an overview of far-UV Hubble Space Telescope observations (1150-1780 A, at 17 km/s resolution) taken by the Cosmic Origins Spectrograph (COS) of the QSO PKS 0405-123 at redshift zem = 0.5726 and FUV flux 3.5x10-14 erg/s/cm2/A. This spectrum illustrates the the power of COS for studying metal-enriched gas between the galaxies, distributed throughout the multiphase intergalactic medium (IGM). We used 7 orbits with 9 FP-split positions, obtained S/N = 35-45 over much of the G130M band (1150-1440 A), and detected numerous absorption features of hydrogen (Lya, Lyb) and heavy-element probes of metallicity. Ions that can be studied include lines (O VI, N V, Ne VIII) sensitive to hot gas produced by strong shocks produced in gravitational inflows to the Cosmic Web, in circumgalactic gas, and in galactic winds. The high S/N allows a search for broad Ly-alpha possibly associated with O VI in hot gas (105 to 106 K). This sight line also intercepts a high-velocity cloud seen in Si III at 110-170 km/s (LSR) and b = -37.55 in the Galactic halo. In the absorption system at z = 0.495, the Ne VIII doublet (770.41, 780.32 A) shifts into the COS band, allowing us to probe the warm-hot IGM at log T = 5.5-6.0, several times deeper than previous (STIS) studies (Prochaska et al. 2004; Howk et al. 2009). In other posters, members of the COS science team describe the detection of O VI absorbers at redshifts z = 0.16710, 0.18292, 0.36156, 0.36332, and 0.49501, including a Lyman Limit system at z = 0.16710 with log N(HI) = 16.45 +/- 0.05. The high S/N observations allow us to measure important ions previously not detected and to evaluate the kinematical relationships and physical conditions among the detected ions.

  12. Espectroscopia infravermelha de núcleos ativos de galáxias: resultados adicionais

    NASA Astrophysics Data System (ADS)

    Rodríguez Ardila, A.; Viegas, S.; Pastoria, M. G.

    2003-08-01

    Apresentamos resultados parciais de um levantamento espectroscópico na região do infravermelho próximo (NIR) realizado em 30 núcleos ativos de galáxias (AGN), incluindo vários objetos selecionados do catálogo PG com z de até 0.55. O objetivo é estudar a natureza do contínuo observado e as condições físicas do gas emissor. Todas as fontes de tipo 1 apresentam uma mudança na inclinação do contínuo na região de 1.2mm, associada ao término da contribuição do contínuo emitido pelo AGN e ao início da contribuição do contínuo emitido pela poeira quente atribuída ao tórus que rodeia a fonte central. O índice espectral associado à segunda contribuição varia apreciavelmente de objeto para objeto. Este resultado é comparado com distribuições espectrais de energia preditas por modelos de toroides para testar a validez do modelo unificado. A partir das linhas de FeII observado nos espectros deriva-se, pela primeira vez nessa região espectral, um template empírico de FeII para estudar a intensidade e a origem dessa emissão. A intensidade do FeII é estudada em conjunto com aquela da região visível e comparada às predições de modelos teóricos que incluem fluorescência de Lya, excitação colisional e auto-fluorescência como mecanismos dominantes de exitação. Encontra-se que os dois primeiros processos dominam na formação do espectro de FeII observado. Indicadores de avermelhamento, entre eles Brg/Pab, Pab/Pag, Pab/Pad e [FeII] 1.257/1.644 mm são utilizados para mapear a distribuição de poeira nas regiões emissoras de linhas. Encontra-se valores de extinção Av~3 associados ao último indicador e valores significativamente menores (Av~1.5) para os restantes, o que sugere que o [FeII] se forma em uma região separada da maior parte do gás emissor de linhas estreitas.

  13. SPHEREx: Understanding the Origin and Evolution of Galaxies Through the Extragalactic Background Light

    NASA Astrophysics Data System (ADS)

    Zemcov, Michael B.; SPHEREx Science Team

    2016-01-01

    The near IR extragalactic background light (EBL) encodes the integrated light production over cosmic history, so traces the total emission from all galaxies along the line of sight up to ancient first-light objects present during the epoch of reionization (EOR). The EBL can be constrained both through direct photometric measurements and through measurements of anisotropies in the EBL which take advantage of the fact that extragalactic populations produce fluctuations with distinct spatial and spectral characteristics from local foregrounds. Because the amplitude of the linear clustering signal is proportional to the total photon emission, large-scale EBL anisotropies are an important tracer of star formation history. In particular, EBL anisotropies trace the underlying clustering of faint emission sources, such as low mass objects present during the EOR, dwarf galaxies, and intra-halo light (IHL), all of which are components not readily detected in point source surveys. The fluctuation amplitude measured independently by a number of recent experiments exceeds that expected from the large-scale clustering of known galaxy populations, indicating the presence of a large integrated brightness from these faint and diffuse components. SPHEREx, a mission in NASA's Small Explorer (SMEX) program that was selected for Phase A in July 2015, is an all-sky survey satellite designed to address all three science goals in NASA's astrophysics division: to probe the origin and destiny of our Universe; to explore whether planets around other stars could harbor life; and to explore the origin and evolution of galaxies. SPHEREx will produce extremely deep maps of the ~200 square degrees around the celestial poles in lambda/d lambda~40 bins. These will be ideal for EBL anisotropy measurements, either by averaging into broad spectral bands, or as a possible science enhancement option, by performing tomography of cosmic large scale structure using line tracers such as Lya, Ha, Hb, O

  14. New Ultraluminous Supersoft Source in the Small Magellanic Cloud: MAXI J0158-744

    NASA Astrophysics Data System (ADS)

    Li, Kwan Lok; Lu, T.; Kong, A.

    2012-05-01

    We present a time-resolved analysis of an ultraluminous supersoft source (SSS) MAXI J0158-744 using 18 consecutive follow-up Swift ToO observations. MAXI J0158-744 is an ultraluminous soft X-ray outburst with a peak luminosity up to 4.3 10^39 erg/s in the energy range of 0.2-2.0 keV located in the Magellanic Bridge region, detected by MAXI/GSC on 11 November 2011. Follow-up Swift observations confirmed that the X-ray emissions are ultra-soft, which could be well fitted by blackbody models of temperatures down to 52 eV. Since the onset, the X-ray emission decreased exponentially dropping from $10^39 to 10^37 erg/s in 15 days (assuming the Small Magellanic Cloud distance) and fell below the detection limit of Swift after 09 December 2011. The earliest Swift X-ray spectra show K-edge absorption (0.88 keV) and a broad Lya (0.65 keV) from OVIII, which indicate that it could be an oxygen rich system. Swift UVOT also caught the outburst in U band with magnitude 13.07 on 12 November 2011 and it returned to quiescence with magnitude 13.6 two days later. During this quiescence, we performed two ATCA radio observations at frequencies 5.5 GHz and 9 GHz with the baseline ranging from 337 m to 6 km and constrained an upper limit of 45 micro-Jansky at the X-ray position. By comparing the object with the close-binary soft source (CBSS) model, we therefore concluded that MAXI J0158-744 could be a slowly accreting O-rich white dwarf binary, with unstable hydrogen burning on the WD surface. Remarkably, ultraluminous SSSs are very rare high-energy phenomena and this nearest one MAXI J0158-744 provided a very unique opportunity for us to understand the underlying physics of such a system.

  15. Meta-Analysis of Suicide-Related Behavior or Ideation in Child, Adolescent, and Adult Patients Treated with Atomoxetine

    PubMed Central

    Wietecha, Linda A.; Wang, Shufang; Buchanan, Andrew S.; Kelsey, Douglas K.

    2014-01-01

    and 9 adult clinical trials completed between 1998 and 2011. Ten pediatric (Studies HFBD, HFBK, LYAC, LYAS, LYAT, LYAW, LYAX, LYBG, LYBI, and LYBP) and two adult trials (Studies LYAA and LYAO) were conducted before the requirement to post trials at initiation (ongoing as of July 1, 2005) and, therefore, do not have a registration number. The registration numbers for the 13 pediatric trials meeting this requirement are: NCT00191698 (LYBX), NCT00486122 (LYCC), NCT00386581 (LYCZ), NCT00485459 (S010), NCT00191542 (LY15), NCT00191295 (LYBC), NCT00191906 (LYCK), NCT00192023 (LYCY), NCT00191945 (LYDM), NCT00546910 (LYDV), NCT00406354 (LYDW), NCT00380692 (S017), and NCT00607919 (LYEB). For the seven adult trials, the registration numbers are: NCT00190931 (LYBV), NCT00190957 (LYBY), NCT00190736 (LYCU), NCT00190775 (LYCW), NCT00190879 (LYDQ), NCT00510276 (LYDZ), and NCT00962104 (LYEE). PMID:25019647

  16. Optical Sensing and Trapping Based on Localized Surface Plasmons

    NASA Astrophysics Data System (ADS)

    Kang, Zhiwen

    PNOTs. The system consists of an array of graded plasmonic nano-disks (NDs) with individual elements coded with different resonant wavelengths according to their dimensions. Thus, by switching the wavelength and rotating the polarization of the excitation source, the target nanoparticles trapped by the device can be manipulated from one ND to another. 3D FDTD simulation and MST calculation are utilized to demonstrate the operation of this idea. Our results reveal that the target experiences a trapping potential strength as high as 5000 kBT/W/microm 2, maximum optical torque of ~336 pN˙nm/W/microm2, and the total active volume may reach ~106 nm3. The potential applications in terms of optical sensing are also discussed. In the final design, for which experimental demonstration has been conducted, we show that PNOTs are achievable with random plasmonic nano-islands. Two laser beams having wavelengths of 633 nm and 785 nm are utilized to stimulate the PNOTs and excite the Raman signals simultaneously. The PNOTs are formed by annealing of a thermal evaporated gold film. This so-called nano-island substrate (Au-NIS) has a resonant peak close to 633 nm. The target is photochemical synthesized silver nanodecadedrons (AgNDs) functionalized with 4-Mercaptobenzoic acid (4-MBA) and the resonant peak of these AgNDs is far away from 633 nm and 785 nm. As the target is trapped to the hot-spots when the PNOTs are active, the near-field intensity is enhanced significantly, which results in the emergence of SERS signals, i.e. confirming the expected outcome of SERS upon nanotrapping by the PNOTs. This process is also elucidated numerically through 3D FDTD simulation and MST calculation. Furthermore, the target can be released as the PNOTs become inactive, i.e. disappearance of the SERS signal. Therefore, this design offers not only a robust avenue for monitoring trapping events in PNOTs, but also a reproducible "trap-and-sense" platform for bio-detection. (Abstract shortened by UMI.)

  17. OVI absorbers in SDSS spectra

    NASA Astrophysics Data System (ADS)

    Frank, Stephan

    with the ubiquitous Lya forest lines, and estimate the success rate of retrieving each individual candidate as a function of its redshift, the emission redshift of the quasar, the strength of the absorber and the measured S/N of the spectrum by modelling typical Ly forest spectra. These correction factors allow us to derive the 'incompleteness and S/N corrected' redshift number densities of O VI absorbers. We can place a secure lower limit for the contribution of O VI to the closure mass density at the redshifts probed here: O OV I (2.8 < z < 3.2) >= 1.9 × 10 - 8 h -1 . We show that the strong lines we probe account for over 65% of the mass in the O VI absorbers; the weak absorbers, while dominant in line number density, do not contribute significantly to the mass density. Making a conservative assumption about the ionisation fraction, [Special characters omitted.] , and adopting the Anders & Grevesse (1989) solar abundance values, we derive the mean metallicty of the gas probed in our search : z(2.8 < z < 3.2) >= 3.6 × 10 -4 h , in good agreement with other studies. These results demonstrate that large spectroscopic datasets such as SDSS can play an important role in QSO absorption line studies, in spite of the relatively low resolution. Lastly, we have performed a stacking analysis whereby we shift individual spectra back to the rest-frame of the absorber candidate, and derive a mean absorption spectrum for various subsamples. Besides further validating the reality of the absorbers themselves, i.e. ruling out spurious interlopers and other misclassifications, we can use these stacked spectra for a variety of purposes. First of all, we can judge the effects of additional cut criteria like a minimal strength for associated CIV absorption, and hence produce cleaner and better defined subsamples, increasing the strength of future proposals for high-resolution studies. Secondly, the stack itself contains valuable information about the gas probed in our search. We have

  18. Physics Computing '92: Proceedings of the 4th International Conference

    NASA Astrophysics Data System (ADS)

    de Groot, Robert A.; Nadrchal, Jaroslav

    1993-04-01

    Transputer Arrays * Distribution of Ions Reflected on Rough Surfaces * The Study of Step Density Distribution During Molecular Beam Epitaxy Growth: Monte Carlo Computer Simulation * Towards a Formal Approach to the Construction of Large-scale Scientific Applications Software * Correlated Random Walk and Discrete Modelling of Propagation through Inhomogeneous Media * Teaching Plasma Physics Simulation * A Theoretical Determination of the Au-Ni Phase Diagram * Boson and Fermion Kinetics in One-dimensional Lattices * Computational Physics Course on the Technical University * Symbolic Computations in Simulation Code Development and Femtosecond-pulse Laser-plasma Interaction Studies * Computer Algebra and Integrated Computing Systems in Education of Physical Sciences * Coordinated System of Programs for Undergraduate Physics Instruction * Program Package MIRIAM and Atomic Physics of Extreme Systems * High Energy Physics Simulation on the T_Node * The Chapman-Kolmogorov Equation as Representation of Huygens' Principle and the Monolithic Self-consistent Numerical Modelling of Lasers * Authoring System for Simulation Developments * Molecular Dynamics Study of Ion Charge Effects in the Structure of Ionic Crystals * A Computational Physics Introductory Course * Computer Calculation of Substrate Temperature Field in MBE System * Multimagnetical Simulation of the Ising Model in Two and Three Dimensions * Failure of the CTRW Treatment of the Quasicoherent Excitation Transfer * Implementation of a Parallel Conjugate Gradient Method for Simulation of Elastic Light Scattering * Algorithms for Study of Thin Film Growth * Algorithms and Programs for Physics Teaching in Romanian Technical Universities * Multicanonical Simulation of 1st order Transitions: Interface Tension of the 2D 7-State Potts Model * Two Numerical Methods for the Calculation of Periodic Orbits in Hamiltonian Systems * Chaotic Behavior in a Probabilistic Cellular Automata? * Wave Optics Computing by a Networked-based Vector

  19. [The "dress" makes the neuron -- different forms of the extracellular matrix in the central nervous system of vertebrates].

    PubMed

    Gáti, Georgina; Lendvai, Dávid

    2013-07-07

    érdestestben. Az eddig még nem vizsgált humán gerincvelőben feltérképezték a mátrix szerkezetét, ami fontos terápiás lehetőségeket rejthet magában a gerincvelőt ért sérülésekben. Megállapították, hogy perineuronalis hálók távoli projekcióval rendelkező idegsejtek körül alakulnak ki, izolált periszinaptikus borítékokban pedig a hátsó szarv bővelkedik. Állatmodelljeikben bizonyították, hogy a differenciált neuronokkal született csirke látórendszerében a mátrixszerkezet kikelés után bejövő fényinger nélkül is azonnali teljes fejlettséget mutat. Patkányagyvelőben pedig azt tapasztalták, hogy az egymással projekciós kapcsolatban lévő köztiagyi-kérgi struktúrák plaszticitásuknak megfelelő mátrixfejlettséget és mintázatot mutatnak. Következtetések: Az ember központi idegrendszerének extracelluláris mátrixa régiónként különböző, funkciófüggő eloszlást és fenotípust mutat. A madár agyi mátrixeloszlása genetikailag és nem ingerfüggően determinált. A patkányelőagy kérgi-köztiagyi struktúrái pálya-, projekció- és funkciófüggően fejlődnek, amely az adott rendszer plaszticitását tükrözi vissza. Orv. Hetil., 2013, 154, 1067–1073.

  20. [Optimal treatment of the axilla after positive sentinel lymph node biopsy in early invasive breast cancer. Early results of the OTOASOR trial].

    PubMed

    Sávolt, Akos; Musonda, Patrick; Mátrai, Zoltán; Polgár, Csaba; Rényi-Vámos, Ferenc; Rubovszky, Gábor; Kovács, Eszter; Sinkovics, István; Udvarhelyi, Nóra; Török, Klára; Kásler, Miklós; Péley, Gábor

    2013-12-08

    Bevezetés: Az emlőrákok regionális nyirokcsomóstátuszának meghatározásában az őrszemnyirokcsomó-biopszia mára rutin emlősebészeti eljárássá vált. A magas szintű bizonyítékon alapuló, minimál invazív sebészi módszer a klinikailag negatív hónalji nyirokcsomók esetén sikerrel váltja ki a diagnosztikus axillaris lymphadenectomiát. Az eljárás fontossága abban rejlik, hogy negatív nyirokcsomóstátusz esetén elkerüli az akár 70%-os morbiditással járó (hónalji fájdalom, vállmerevség, lymphoedema és paraesthesia) teljes hónaljárki lymphadenectomiát. Célkitűzés: Jelenleg az elfogadott eljárás pozitív őrszemnyirokcsomó esetén a teljes komplettáló axillaris blokkdisszekció. Eközben több randomizált klinikai vizsgálat bizonyította, hogy a hónalji nyirokcsomók besugárzása és az elektív axillaris blokkdisszekció között nincs különbség a túlélés tekintetében az emlőrákos betegeknél. Az Országos Onkológiai Intézet Emlősebészeti Osztálya ebben a témában kezdett előretekintő, randomizált, kétkarú összehasonlító klinikai vizsgálatot. Az OTOASOR vizsgálat (Optimal Treatment of The Axilla – Surgery or Radiotherapy) célja korai emlőrákos esetekben, pozitív hónalji őrszemnyirokcsomó-státusz esetén az axilla két különböző kezelési lehetőségének, a hagyományos axillaris lymphadenectomiának és a régió további műtét nélküli célzott besugárzásának hosszú távú eredményeinek összehasonlítása volt. Módszer: A tanulmányba korai stádiumú primer, invazív emlőrákos nőbetegeket vontak be, akiknél a tumor 3 cm-nél kisebb volt és a műtét előtt nem volt klinikai gyanújel axillaris nyirokcsomó-propagációra. A betegeket a műtét előtt két karra randomizálták, vagy hagyományos komplettáló axillaris blokkdisszekció („A” kar – hagyományos kezeléses kar), vagy hónalji nyirokcsomó-besugárzás („B” kar – vizsgálati kar). Az