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Sample records for monokristallami bn bpaiiibv

  1. Structure of BN Nanotubes

    Science.gov (United States)

    Celik-Aktas, Ayten; Tao, Jing; Zuo, Jian-Min

    2004-03-01

    Boron nitride (BN) nanotubes have been the subject of intensive scientific study in recent years due to their unique properties. BN nanotubes have uniform wide gap semiconducting properties regardless of their chirality and diameter [1]. On the other hand electrical properties of carbon nanotubes (CNTs) depend on their chirality. This unique difference between BN and CNTs makes BN nanotubes a better candidate for nano electronics and/or other nano technology applications. HRTEM and nano area electron diffraction (NAD) studies have been conducted to better understand the microstructure of BN nanotubes. In addition to TEM analysis we would like to present the results of image simulations and compare the NAD patterns with the simulated diffraction patterns. Preliminary results suggest that the BN nanotubes that have been investigated in this study showed overwhelmingly near zigzag chirality. Average diameter of the BN tubes are about 35-40 nm. Regular patches of perfect crystals have been observed along the length of the tubes except tubes with very large diameters (Dng 150 nm). Other regions of the BN nanotubes were quite defective. CNT templates have been employed in the synthesis of our samples. [1] X. Blasé, A. Rubio, S.G. Louie, M.L. Cohen, Europhysics Letters, 28 (1994) 335.

  2. (Fuzzy Ideals of BN-Algebras

    Directory of Open Access Journals (Sweden)

    Grzegorz Dymek

    2015-01-01

    set to be a fuzzy ideal are given. The relationships between ideals and fuzzy ideals of a BN-algebra are established. The homomorphic properties of fuzzy ideals of a BN-algebra are provided. Finally, characterizations of Noetherian BN-algebras and Artinian BN-algebras via fuzzy ideals are obtained.

  3. (Fuzzy) Ideals of BN-Algebras

    Science.gov (United States)

    Walendziak, Andrzej

    2015-01-01

    The notions of an ideal and a fuzzy ideal in BN-algebras are introduced. The properties and characterizations of them are investigated. The concepts of normal ideals and normal congruences of a BN-algebra are also studied, the properties of them are displayed, and a one-to-one correspondence between them is presented. Conditions for a fuzzy set to be a fuzzy ideal are given. The relationships between ideals and fuzzy ideals of a BN-algebra are established. The homomorphic properties of fuzzy ideals of a BN-algebra are provided. Finally, characterizations of Noetherian BN-algebras and Artinian BN-algebras via fuzzy ideals are obtained. PMID:26125050

  4. Electrical transport properties of (BN)-rich hexagonal (BN)C semiconductor alloys

    OpenAIRE

    2014-01-01

    The layer structured hexagonal boron nitride carbon semiconductor alloys, h-(BN)C, offer the unique abilities of bandgap engineering (from 0 for graphite to ∼6.4 eV for h-BN) and electrical conductivity control (from semi-metal for graphite to insulator for undoped h-BN) through alloying and have the potential to complement III-nitride wide bandgap semiconductors and carbon based nanostructured materials. Epilayers of (BN)-rich h-(BN)1-x(C2)x alloys were synthesized by metal-organic chemical ...

  5. Mechanical properties of metal decorated graphyne, graphyne-BN-yne, and BN-yne sheets

    CERN Document Server

    Ahmadi, Aidin; Nasiri, Mahdi Faghih; Sabeti, Moones

    2016-01-01

    In this paper, the mechanical properties of two-dimensional structures of metal decoration systems of simple graphyne (CC), analogous system of BN sheet (BN-yne), also the graphyne-BN sheet (CC-BN-yne) was investigated. The properties such as Young and Bulk moduli were studied using Energy-Strain correlation. We introduced calculations based on density functional theory (DFT); the generalized gradient approximation (GGA) framework was used in this regard. The results demonstrated very competitive values for Young and Bulk moduli of the Pt decorated CC and BN-yne. However, the CC-BN-yne structure defined around 80% of Young and 77% of Bulk values of that of pure structures. Also Na decorated ones were examined and the results showed the same trend for all three structures. The CC-BN-yne defined the lowest values for either Young or Bulk moduli.

  6. Bias induced modulation of electrical and thermal conductivity and heat capacity of BN and BN/graphene bilayers

    Science.gov (United States)

    Chegel, Raad

    2017-04-01

    By using the tight binding approximation and Green function method, the electronic structure, density of state, electrical conductivity, heat capacity of BN and BN/graphene bilayers are investigated. The AA-, AB1- and AB2- BN/graphene bilayers have small gap unlike to BN bilayers which are wide band gap semiconductors. Unlike to BN bilayer, the energy gap of graphene/BN bilayers increases with external field. The magnitude of the change in the band gap of BN bilayers is much higher than the graphene/BN bilayers. Near absolute zero, the σ(T) is zero for BN bilayers and it increases with temperature until reaches maximum value then decreases. The BN/graphene bilayers have larger electrical conductivity larger than BN bilayers. For both bilayers, the specific heat capacity has a Schottky anomaly.

  7. Bias induced modulation of electrical and thermal conductivity and heat capacity of BN and BN/graphene bilayers

    Energy Technology Data Exchange (ETDEWEB)

    Chegel, Raad, E-mail: Raad.chegel@gmail.com

    2017-04-15

    By using the tight binding approximation and Green function method, the electronic structure, density of state, electrical conductivity, heat capacity of BN and BN/graphene bilayers are investigated. The AA-, AB{sub 1}- and AB{sub 2}- BN/graphene bilayers have small gap unlike to BN bilayers which are wide band gap semiconductors. Unlike to BN bilayer, the energy gap of graphene/BN bilayers increases with external field. The magnitude of the change in the band gap of BN bilayers is much higher than the graphene/BN bilayers. Near absolute zero, the σ(T) is zero for BN bilayers and it increases with temperature until reaches maximum value then decreases. The BN/graphene bilayers have larger electrical conductivity larger than BN bilayers. For both bilayers, the specific heat capacity has a Schottky anomaly.

  8. Cellulose nanofibrils (CNF) filled boron nitride (BN) nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Sulaiman, Hanisah Syed; Hua, Chia Chin; Zakaria, Sarani [School of Applied Physic, Faculty of Science and Technology, Universiti Kebangsaan Malaysia.43600 Bangi, Selangor (Malaysia)

    2015-09-25

    In this study, nanocomposite using cellulose nanofibrils filled with different percentage of boron nitride (CNF-BN) were prepared. The objective of this research is to study the effect of different percentage of BN to the thermal conductivity of the nanocomposite produced. The CNF-BN nanocomposite were characterization by FT-IR, SEM and thermal conductivity. The FT-IR analysis of the CNF-BN nanocomposite shows all the characteristic peaks of cellulose and BN present in all samples. The dispersion of BN in CNF were seen through SEM analysis. The effect of different loading percentage of BN to the thermal conductivity of the nanocomposite were also investigated.

  9. Research Update: Direct conversion of h-BN into pure c-BN at ambient temperatures and pressures in air

    Directory of Open Access Journals (Sweden)

    Jagdish Narayan

    2016-02-01

    Full Text Available We report a direct conversion of hexagonal boron nitride (h-BN into pure cubic boron nitride (c-BN by nanosecond laser melting at ambient temperatures and atmospheric pressure in air. According to the phase diagram, the transformation from h-BN into c-BN can occur only at high temperatures and pressures, as the hBN-cBN-Liquid triple point is at 3500 K/9.5 GPa. Using nanosecond laser melting, we have created super undercooled state and shifted this triple point to as low as 2800 K and atmospheric pressure. The rapid quenching from super undercooled state leads to formation of super undercooled BN (Q-BN. The c-BN phase is nucleated from Q-BN depending upon the time allowed for nucleation and growth.

  10. Research Update: Direct conversion of h-BN into pure c-BN at ambient temperatures and pressures in air

    Energy Technology Data Exchange (ETDEWEB)

    Narayan, Jagdish, E-mail: narayan@ncsu.edu; Bhaumik, Anagh [Department of Materials Science and Engineering, Centennial Campus, North Carolina State University, Raleigh, North Carolina 27695-7907 (United States)

    2016-02-01

    We report a direct conversion of hexagonal boron nitride (h-BN) into pure cubic boron nitride (c-BN) by nanosecond laser melting at ambient temperatures and atmospheric pressure in air. According to the phase diagram, the transformation from h-BN into c-BN can occur only at high temperatures and pressures, as the hBN-cBN-Liquid triple point is at 3500 K/9.5 GPa. Using nanosecond laser melting, we have created super undercooled state and shifted this triple point to as low as 2800 K and atmospheric pressure. The rapid quenching from super undercooled state leads to formation of super undercooled BN (Q-BN). The c-BN phase is nucleated from Q-BN depending upon the time allowed for nucleation and growth.

  11. BN coatings deposition by magnetron sputtering of B and BN targets in electron beam generated plasma

    Science.gov (United States)

    Kamenetskikh, A. S.; Gavrilov, N. V.; Koryakova, O. V.; Cholakh, S. O.

    2017-05-01

    Boron nitride coatings were deposited by reactive pulsed magnetron sputtering of B and BN targets (50 kHz, 10 µs for B; 13.56 MHz for BN) at 2-20 mA/cm2 ion current density on the substrate. The effect of electron beam generated plasma on characteristics of magnetron discharge and phase composition of coatings was studied.

  12. Metals on BN Studied by High Resolution Transmission Electron Microscopy

    Science.gov (United States)

    Bangert, U.; Zan, R.; Ramasse, Q.; Jalil, Rashid; Riaz, Ibstam; Novoselov, K. S.

    2012-07-01

    Metal impurities, gold and nickel, have been deliberately introduced into boron-nitride (BN) sheets. The structural and topographic properties of doped BN have been studied by aberration corrected scanning transmission electron microscopy (STEM). Analysis revealed that metal atoms cluster preferentially in/on contaminated areas. The metal coverage on BN is almost the same for the same evaporated amount of 1 Å.

  13. First-principles study of the crystal structures and physical properties of H18-BN and Rh6-BN

    Science.gov (United States)

    Ren, Xiao-Yan; Zhao, Chun-Xiang; Niu, Chun-Yao; Wang, Jia-Qi; Jia, Yu; Cho, Jun-Hyung

    2016-12-01

    As the analog of carbon allotropes, new three-dimensional (3D) boron nitride (BN) allotropes have attracted much attention of researchers due to their great importance in fundamental sciences and wide practical applications. Here, based on first-principles density-functional theory calculations, we predict two new stable BN allotropes: One is H18-BN with the P 6 bar m 2 (D3h1) symmetry containing eighteen atoms in the hexagonal unit cell and the other is Rh6-BN with the R 3 bar m (C3v5) symmetry containing six atoms in the rhombohedral primitive unit cell. The dynamic stabilities of the two structures are examined through the phonon spectrum analysis as well as molecular dynamics simulations, whereas the mechanical properties are analyzed by elastic constants, bulk modulus and shear modulus. From the analysis of the enthalpy evolution with respect to pressure, we find that h-BN can be transformed into either H18-BN or RH6-BN structure under a higher pressure of ∼ 15 GPa. We also find that both the H18-BN and Rh6-BN allotropes are brittle materials with indirect band gaps of 2.31 and 4.48 eV, respectively. The simulated XRD spectra provide detailed structural information of H18-BN and Rh6-BN for future experimental examinations. Our findings not only greatly enrich the existing structural family of 3D-BN materials but also stimulate further experiments.

  14. Deuterated methanol in Orion BN/KL

    CERN Document Server

    Peng, T -C; Brouillet, N; Parise, B; Baudry, A

    2012-01-01

    Deuterated molecules have been detected and studied toward Orion BN/KL in the past decades, mostly with single-dish telescopes. However, high angular resolution data are critical not only for interpreting the spatial distribution of the deuteration ratio but also for understanding this complex region in terms of cloud evolution involving star-forming activities and stellar feedbacks. We present here the first high angular resolution (1.8 arcsec \\times 0.8 arcsec) images of deuterated methanol CH2DOH in Orion BN/KL observed with the IRAM Plateau de Bure Interferometer from 1999 to 2007 in the 1 to 3 mm range. Six CH2DOH lines were detected around 105.8, 223.5, and 225.9 GHz. In addition, three E-type methanol lines around 101-102 GHz were detected and were used to derive the corresponding CH3OH rotational temperatures and column densities toward different regions across Orion BN/KL. The strongest CH2DOH and CH3OH emissions come from the Hot Core southwest region with an LSR velocity of about 8 km/s. We derive ...

  15. Linear Assembles of BN Nanosheets, Fabricated in Polymer/BN Nanosheet Composite Film

    Directory of Open Access Journals (Sweden)

    Hong-Baek Cho

    2011-01-01

    Full Text Available Linear assembles of BN nanosheets (LABNs were fabricated in polysiloxane/BN nanosheet composite film under a high DC electric field. The hexagonal BN nanosheets were dispersed by sonication in a prepolymer mixture of polysiloxane followed by a high-speed mixing. The homogeneous suspension was cast on a spacer of microscale thickness and applied to a high DC electric field before it became cross-linked. X-ray diffraction, scanning electron microscopy, and digital microscopy revealed that LABNs formed in the polysiloxane matrix and that the BN nanosheets in the LABNs were aligned perpendicular to the film plane with high anisotropy. This is the first time that linear assemblies of nanosheets have been fabricated in an organic-inorganic hybrid film by applying a DC electric field. The enhanced thermal conductivity of the composite film is attributed to the LABNs. The LABN formation and heat conduction mechanisms are discussed. The polysiloxane/BN nanosheet composite film has the potential to be used semiconductor applications that require both a high thermal conductivity and a high electric insulation.

  16. Two BN isosteres of anthracene: synthesis and characterization.

    Science.gov (United States)

    Ishibashi, Jacob S A; Marshall, Jonathan L; Mazière, Audrey; Lovinger, Gabriel J; Li, Bo; Zakharov, Lev N; Dargelos, Alain; Graciaa, Alain; Chrostowska, Anna; Liu, Shih-Yuan

    2014-10-29

    The synthesis of two parental BN anthracenes, 1 and 2, was developed, and their electronic structure and reactivity behavior were characterized in direct comparison with all-carbon anthracene. Gas-phase UV-photoelecton spectroscopy studies revealed the following HOMO energy trend: anthracene, -7.4 eV; BN anthracene 1, -7.7 eV; bis-BN anthracene 2, -8.0 eV. The λmax of the lower energy band in the UV-vis absorption spectrum is as follows: anthracene, 356 nm; BN anthracene 1, 359 nm; bis-BN anthracene 2, 357 nm. Thus, although the HOMO is stabilized with increasing BN incorporation, the HOMO-LUMO band gap remains unchanged across the anthracene series. The emission λmax values for the three investigated anthracene compounds are at 403 nm. The pKa values of the N-H proton for BN anthracene 1 and bis-BN anthracene 2 were determined to be approximately 26. BN anthracenes 1 and 2 do not undergo heat- or light-induced cycloaddition reactions or Friedel-Crafts acylations. Electrophilic bromination of BN anthracene 1 with Br2, however, occurs regioselectively at the 9-position. The reactivity behavior and regioselectivity of bromination of BN anthracenes are consistent with the electronic structure of these compounds; i.e., (1) the lower HOMO energy levels for BN anthracenes stabilize the molecules against cycloaddition and Friedel-Crafts reactions, and (2) the HOMO orbital coefficients are consistent with the observed bromination regioselectivity. Overall, this work demonstrates that BN/CC isosterism can be used as a molecular design strategy to stabilize the HOMO of acene-type structures while the optical band gap is maintained.

  17. Synthesis and Characterization of Hexagonal Boron Nitride (h- BN) Films

    Science.gov (United States)

    2014-01-09

    Synthesis 1. Diborane- ammonia (B2H6-NH3- gases): Early results with these precursors were published in 2012. 5 Briefly, LPCVD growth of h-BN in a hot-wall...Approved for public release; distribution is unlimited. Synthesis and Characterization of Hexagonal Boron Nitride (h- BN) Films. The views, opinions and...1 ABSTRACT Number of Papers published in peer-reviewed journals: Synthesis and Characterization of Hexagonal Boron Nitride (h-BN) Films. Report Title

  18. Photo doping effect in graphene/BN heterostructure

    Science.gov (United States)

    Ju, Long; Velasco, Jairo, Jr.; Hwang, Edwin; Kim, Jonghwan; Wang, Feng

    2013-03-01

    Boron nitride has been demonstrated as an ideal substrate to achieve high mobility in graphene. At the same time We observed strong change of graphene transport properties by shining light on graphene/BN heterostructure. This is attributed to photo doping effect induced by impurity excitation in BN. Optical spectroscopy based on this photo-doping effects enables us to probe impurities in crystalline BN. Such information will be important for potential applications based on graphene/BN heterostructures. The potential of applying similar technique to probe defects in other insulators and semiconductors will also be discussed.

  19. A straightforward strategy toward large BN-embedded π-systems: synthesis, structure, and optoelectronic properties of extended BN heterosuperbenzenes.

    Science.gov (United States)

    Wang, Xiao-Ye; Zhuang, Fang-Dong; Wang, Rui-Bo; Wang, Xin-Chang; Cao, Xiao-Yu; Wang, Jie-Yu; Pei, Jian

    2014-03-12

    A straightforward strategy has been used to construct large BN-embedded π-systems simply from azaacenes. BN heterosuperbenzene derivatives, the largest BN heteroaromatics to date, have been synthesized in three steps. The molecules exhibit curved π-surfaces, showing two different conformations which are self-organized into a sandwich structure and further packed into a π-stacking column. The assembled microribbons exhibit good charge transport properties and photoconductivity, representing an important step toward the optoelectronic applications of BN-embedded aromatics.

  20. Side-gate modulation effects on high-quality BN-Graphene-BN nanoribbon capacitors

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Yang; Chen, Xiaolong; Ye, Weiguang; Wu, Zefei; Han, Yu; Han, Tianyi; He, Yuheng; Cai, Yuan; Wang, Ning, E-mail: phwang@ust.hk [Department of Physics and the William Mong Institute of Nano Science and Technology, The Hong Kong University of Science and Technology, Clear Water Bay, Kowloon, Hong Kong (China)

    2014-12-15

    High-quality BN-Graphene-BN nanoribbon capacitors with double side-gates of graphene have been experimentally realized. The double side-gates can effectively modulate the electronic properties of graphene nanoribbon capacitors. By applying anti-symmetric side-gate voltages, we observed significant upward shifting and flattening of the V-shaped capacitance curve near the charge neutrality point. Symmetric side-gate voltages, however, only resulted in tilted upward shifting along the opposite direction of applied gate voltages. These modulation effects followed the behavior of graphene nanoribbons predicted theoretically for metallic side-gate modulation. The negative quantum capacitance phenomenon predicted by numerical simulations for graphene nanoribbons modulated by graphene side-gates was not observed, possibly due to the weakened interactions between the graphene nanoribbon and side-gate electrodes caused by the Ga{sup +} beam etching process.

  1. Determination of micro structural corrosion by BN

    Energy Technology Data Exchange (ETDEWEB)

    Zergoug, M.; Kamel, G.; Benchaala, A. [Laboratoire d' Electronique et d' Electrotechnique, Centre de soudage et de controle, Route de Dely Ibrahim, B.P:64, Cheraga (Algeria)

    2004-07-01

    The quality control of industrial components requires adaptation and the development of new material characterization and particular non destructive testing techniques. To characterize steel, it would be useful to know its chemical composition, physic-chemical constitution, metallurgical state (annealed, hammered) and other parameters (superficial and chemical processing, etc.). The testing method using Barkhausen noise (B.N.) is a particular method, which can be applied on ferromagnetic materials. It is a magnetic non destructive evaluation (NDE) method and can provide very important information about the material microstructure. The work here presented documents the ability to determine the metallurgical state of steel submitted to the corrosive attack by electrochemical process. The samples are characterized by Barkhausen noise as non destructive methods and are compared with methods as metallography, micro hardness measurement, and toughness determination. (authors)

  2. Effect of pH on the Hydrothermal Synthesis of BN Nanocrystals

    Institute of Scientific and Technical Information of China (English)

    2006-01-01

    Boron nitride (BN) has been synthesized using hydrothermal synthesis method. The experimental results showed that the pH value of the reaction solution has an important effect on the yield and phases of BN samples. As the pH value decreased, the content of cBN increased and the yield improved. The increase in cBN content is resulted from the conversion of oBN into cBN under hydrothermal condition, and the growth of cBN nanocrystals may due to the decrease in the reaction speed, thus the crystalline perfection of BN improved when the pH value decreased.

  3. Synthesis and Oxidation Resistance of h-BN Thin Films

    Science.gov (United States)

    Stewart, David; Meulenberg, Robert; Lad, Robert

    Hexagonal boron nitride (h-BN) is an exciting 2D material for use in sensors and other electronic devices that operate in harsh, high temperature environments. Not only is h-BN a wide band gap material with excellent wear resistance and high temperature stability, but recent reports indicate that h-BN can prevent metallic substrates from oxidizing above 600°C in low O2 pressures. However, the PVD of highly crystalline h-BN films required for this oxidation protection has proven challenging. In this work, we have explored the growth of h-BN thin films by reactive RF magnetron sputtering from an elemental B target in an Ar/N2 atmosphere. The film growth rate is extremely slow and the resulting films are atomically smooth and homogeneous. Using DC biasing during deposition and high temperature annealing treatments, the degree of film crystallinity can be controlled. The oxidation resistance of h-BN films deposited on inert sapphire and reactive metal substrates such as Zr and ZrB2 has been examined by techniques such as XPS, XRD, and SEM after oxidation between 600 and 1200°C under varying oxygen pressures. The success of h-BN as a passivation layer for metallic substrates in harsh environments is shown to depend greatly on its crystalline quality and defects. Supported by the NSF SusChEM program.

  4. Diamond-cBN alloy: A universal cutting material

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Pei [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); High Pressure Science and Engineering Center and Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, Nevada 89154 (United States); He, Duanwei, E-mail: duanweihe@scu.edu.cn; Kou, Zili; Li, Yong; Hu, Qiwei; Xu, Chao; Lei, Li; Wang, Qiming [Institute of Atomic and Molecular Physics, Sichuan University, Chengdu 610065 (China); Wang, Liping; Zhao, Yusheng [High Pressure Science and Engineering Center and Department of Physics and Astronomy, University of Nevada Las Vegas, Las Vegas, Nevada 89154 (United States); Xiong, Lun; Liu, Jing [Institute of High Energy Physics, Chinese Academy of Sciences, Beijing 100049 (China)

    2015-09-07

    Diamond and cubic boron nitride (cBN) as conventional superhard materials have found widespread industrial applications, but both have inherent limitations. Diamond is not suitable for high-speed cutting of ferrous materials due to its poor chemical inertness, while cBN is only about half as hard as diamond. Because of their affinity in structural lattices and covalent bonding character, diamond and cBN could form alloys that can potentially fill the performance gap. However, the idea has never been demonstrated because samples obtained in the previous studies were too small to be tested for their practical performance. Here, we report the synthesis and characterization of transparent bulk diamond-cBN alloy compacts whose diameters (3 mm) are sufficiently large for them to be processed into cutting tools. The testing results show that the diamond-cBN alloy has superior chemical inertness over polycrystalline diamond and higher hardness than single crystal cBN. High-speed cutting tests on hardened steel and granite suggest that diamond-cBN alloy is indeed a universal cutting material.

  5. Toeplitz and composition operators on H~2 (B_n)

    Institute of Scientific and Technical Information of China (English)

    曹广福; 孙顺华

    1997-01-01

    The composition operators with closed range on H2( Bn) are characterized, and the Frcdholmness of products of Toeplitz and composition operators discussed. Moreover, using composition operators, the spectra of Toeplitz operators are studied.

  6. Fabrication and Microstructure of BN Matrix Composites with Electrical Conductivity

    Institute of Scientific and Technical Information of China (English)

    2002-01-01

    BN ceramic is an advanced engineering ceramics with excellent thermal shock resistance, good workability and excellent dielectricity.TiB2 ceramic has excellent electric conductivity,high melting points, and corrosion resistance to molten metal.Therefore,the composite consisting of BN and TiB2 ceramics is expected to have a combination of above-mentioned properties,thereby can be used as self- heating crucible.In this paper,hot pressing technology was used to fabricate the high performance BN-TiB2 composite materials.microstructure and electric conducting mechanism were studied,and the relationship between the microstructure and physical property was discussed.The results show that the microstructure of composites has a great influence on the physical property of composites.The BN-TiB2 composites with excellent mechanical strength and stable resistivity can be obtained by optimizing the processing parameter and controlling the microstructure of composites.

  7. GaN nanorods coated with pure BN

    Science.gov (United States)

    Han, Wei-Qiang; Zettl, A.

    2002-12-01

    We report a method to efficiently synthesize gallium nitride (GaN) nanorods coated with insulating boron nitride (BN) layers. The GaN core is crystalline (with either a cubic zincblende or hexagonal wurtzite structure) and has diameters ranging from 10 to 85 nm and lengths up to 60 μm. The outer encapsulating BN shells with typical thicknesses less than 5 nm extend fully over, and adhere well to, the entire nanorod surface.

  8. h-BN-TiO2 Nanocomposite for Photocatalytic Applications

    Directory of Open Access Journals (Sweden)

    Václav Štengl

    2016-01-01

    Full Text Available h-BN-TiO2 nanocomposites were synthesized by the thermal hydrolysis of titanium peroxo-complexes in the presence of exfoliated h-BN. The bulk h-BN was prepared by annealing mixture of boric acid and urea, and high intensity ultrasound was used for its exfoliation. The prepared samples were characterized by X-ray powder diffraction (XRD, infrared spectroscopy, Raman spectroscopy, electron spin resonance (ESR, high resolution electron microscopy, BET surface area, and BJH porosity measurement. The UV-Vis diffuse reflectance spectroscopy was employed to estimate band-gap energies. The photoinduced charge on the surface of h-BN-TiO2 nanocomposites was visualized using electric force microscopy (EFM. The photocatalytic activity was determined by azo dyes Orange II and Reactive Black 5 photobleaching. The highest rate constant k = 0.0762 min−1 and 0.0164 min−1, under UV and visible light irradiation, respectively, showed sample denoted TiP050BN with moderate concentration of h-BN.

  9. A comparative computational study on the BN ring doped nanographenes

    Science.gov (United States)

    Vessally, E.; Soleimani-Amiri, S.; Hosseinian, A.; Edjlali, L.; Bekhradnia, A.

    2017-02-01

    The electronic, optical, energetic, and structural properties of a HBC (hexa-peri-hexabenzocoronene) nanographene and its central benzene- and coronene-like BN substituted forms, and also full BN analogue were investigated using density functional theory. It was found that a larger number of carbon atoms cause a more negative cohesive energy and, thereby a greater structural stability. Our nucleus independent chemical shift analysis indicates that the aromaticity and Clar's sextet rule determine the relative stability of these structures. The benzene-like or coronene-like doping makes the HBC more insulator or semiconductor. Electron-hole Frenkel type exciton binding energy was predicted and calculated to be nearly identical for all nanographenes in the range of 0.61-0.69 eV. The coronene-like BN-doped HBC (BN2-HBN) shows higher conductivity due to very narrow optical and HOMO-LUMO energy gap. Partial density of states analysis indicates that the BN2-HBC electronically can be assumed a full BN whose peripheral atoms are replaced by carbon atoms. These carbon atoms are responsible for new states which are appeared within the gap.

  10. Energetics and Electronic Structure of h-BN Nanoflakes

    Science.gov (United States)

    Yamanaka, Ayaka; Okada, Susumu

    2016-08-01

    We studied the energetics and electronic structure of hexagonal boron nitride (h-BN) nanoribbons with hydrogenated and clean edges with respect to the detailed edge shapes using density functional theory. Our calculations showed that the stability of h-BN edges strongly depends on the edge termination. In the case of hydrogenated edges, the formation energy is constant for all edge angles ranging from armchair to zigzag, indicating that h-BN may exhibit rich variation in their edge atomic arrangements under static conditions. The hydrogenated h-BN nanoribbons are insulators with an energy gap of 4 eV irrespective of edge shape, in which the lowest branch of the conduction band exhibits nearly free electron states nature distributed in the vacuum region outside the ribbons. In contrast, the formation energy of h-BN nanoribbons with clean edges monotonically increases as the edge angle is changed from armchair to zigzag. Our analysis reveals that the increase of density of states at the Fermi level arising from dangling bond states leads to this monotonic increase of edge formation energy in h-BN nanoribbons with clean edges.

  11. Electronic transport properties and first-principles study of graphene/h-BN and h-BN bilayers

    Science.gov (United States)

    Ashhadi, M.; Hadavi, M. S.; Sarri, Z.

    2017-03-01

    We use a tight binding approach to study of electron transport properties of bilayers of zig-zag graphene/h-BN nanoribbon (GBNNR) and h-BN nanoribbon (BNNR) embedded between two bilayer of zig-zag graphene nanoribbons (GNR), which are considered as electrodes. In this study, the parameters of tight biding hopping and on-site energies are obtained by comparing the tight binding band structure graphene/h-BN and h-BN bilayers with density functional theory (DFT) calculations. We numerically compute the transport properties in terms of transmission and current-voltage characteristic. Our calculations show that the electron transport can open a conduction gap in the GNR/BNNR/GNR structure.

  12. Tunable localized surface plasmon resonances in one-dimensional h-BN/graphene/h-BN quantum-well structure

    Science.gov (United States)

    Kaibiao, Zhang; Hong, Zhang; Xinlu, Cheng

    2016-03-01

    The graphene/hexagonal boron-nitride (h-BN) hybrid structure has emerged to extend the performance of graphene-based devices. Here, we investigate the tunable plasmon in one-dimensional h-BN/graphene/h-BN quantum-well structures. The analysis of optical response and field enhancement demonstrates that these systems exhibit a distinct quantum confinement effect for the collective oscillations. The intensity and frequency of the plasmon can be controlled by the barrier width and electrical doping. Moreover, the electron doping and the hole doping lead to very different results due to the asymmetric energy band. This graphene/h-BN hybrid structure may pave the way for future optoelectronic devices. Project supported by the National Natural Science Foundation of China (Grant Nos. 11474207 and 11374217) and the Scientific Research Fund of Sichuan University of Science and Engineering, China (Grant No. 2014PY07).

  13. Investigation on two abnormal phenomena about thermal conductivity enhancement of BN/EG nanofluids

    OpenAIRE

    Wu Jiangtao; Li Xiaojing; Tung Simon; Schneider Eric; Li Yanjiao; Zhou Jing'en; Luo Zhifeng

    2011-01-01

    Abstract The thermal conductivity of boron nitride/ethylene glycol (BN/EG) nanofluids was investigated by transient hot-wire method and two abnormal phenomena was reported. One is the abnormal higher thermal conductivity enhancement for BN/EG nanofluids at very low-volume fraction of particles, and the other is the thermal conductivity enhancement of BN/EG nanofluids synthesized with large BN nanoparticles (140 nm) which is higher than that synthesized with small BN nanoparticles (70 nm). The...

  14. Substituent Directed Phototransformations of BN-Heterocycles: Elimination vs Isomerization via Selective B-C Bond Cleavage.

    Science.gov (United States)

    Yang, Deng-Tao; Mellerup, Soren K; Peng, Jin-Bao; Wang, Xiang; Li, Quan-Song; Wang, Suning

    2016-09-14

    Electron-rich and -poor BN-heterocycles with benzyl-pyridyl backbones and two bulky aryls on the boron (Ar = tipp, BN-1, Ar = MesF, BN-2) have been found to display distinct molecular transformations upon irradiation by UV light. BN-1 undergoes an efficient photoelimination reaction forming a BN-phenanthrene with ΦPE = 0.25, whereas BN-2 undergoes a thermally reversible, stereoselective, and quantitative isomerization to a dark colored BN-1,3,5-cyclooctatriene (BN-1,3,5-COT, BN-2a). This unusual photoisomerization persists for other BN-heterocycles with electron-deficient aryls such as BN-3 with a benzyl-benzothiazolyl backbone and Mes(F) substituents or BN-4 with a benzyl-pyridyl backbone and two C6F5 groups on the boron. The photoisomerization of BN-4 goes beyond BN-1,3,5-COT (BN-4a), forming a new species (BN-1,3,6-COT, BN-4b) via C-F bond cleavage and [1,3]-F atom sigmatropic migration. Computational studies support that BN-4a is an intermediate in the formation of BN-4b. This work establishes that steric and electronic factors can effectively control the transformations of BN-heterocycles, allowing access to important and previously unknown BN-embedded species.

  15. Investigation on two abnormal phenomena about thermal conductivity enhancement of BN/EG nanofluids

    Directory of Open Access Journals (Sweden)

    Wu Jiangtao

    2011-01-01

    Full Text Available Abstract The thermal conductivity of boron nitride/ethylene glycol (BN/EG nanofluids was investigated by transient hot-wire method and two abnormal phenomena was reported. One is the abnormal higher thermal conductivity enhancement for BN/EG nanofluids at very low-volume fraction of particles, and the other is the thermal conductivity enhancement of BN/EG nanofluids synthesized with large BN nanoparticles (140 nm which is higher than that synthesized with small BN nanoparticles (70 nm. The chain-like loose aggregation of nanoparticles is responsible for the abnormal increment of thermal conductivity enhancement for the BN/EG nanofluids at very low particles volume fraction. And the difference in specific surface area and aspect ratio of BN nanoparticles may be the main reasons for the abnormal difference between thermal conductivity enhancements for BN/EG nanofluids prepared with 140- and 70-nm BN nanoparticles, respectively.

  16. Investigation on two abnormal phenomena about thermal conductivity enhancement of BN/EG nanofluids.

    Science.gov (United States)

    Li, Yanjiao; Zhou, Jing'en; Luo, Zhifeng; Tung, Simon; Schneider, Eric; Wu, Jiangtao; Li, Xiaojing

    2011-07-09

    The thermal conductivity of boron nitride/ethylene glycol (BN/EG) nanofluids was investigated by transient hot-wire method and two abnormal phenomena was reported. One is the abnormal higher thermal conductivity enhancement for BN/EG nanofluids at very low-volume fraction of particles, and the other is the thermal conductivity enhancement of BN/EG nanofluids synthesized with large BN nanoparticles (140 nm) which is higher than that synthesized with small BN nanoparticles (70 nm). The chain-like loose aggregation of nanoparticles is responsible for the abnormal increment of thermal conductivity enhancement for the BN/EG nanofluids at very low particles volume fraction. And the difference in specific surface area and aspect ratio of BN nanoparticles may be the main reasons for the abnormal difference between thermal conductivity enhancements for BN/EG nanofluids prepared with 140- and 70-nm BN nanoparticles, respectively.

  17. Enhancement of surface mechanical properties by using TiN[BCN/BN]{sub n}/c-BN multilayer system

    Energy Technology Data Exchange (ETDEWEB)

    Moreno, H. [Laboratorio de Recubrimientos Duros, CDT-ASTIN SENA, Cali (Colombia); Caicedo, J.C., E-mail: Jcesarca@calima.univalle.edu.co [Grupo de Peliculas Delgadas, Universidad del Valle, Cali (Colombia); Amaya, C. [Grupo de Peliculas Delgadas, Universidad del Valle, Cali (Colombia); Munoz-Saldana, J. [Centro de Investigacion y de Estudios Avanzados del IPN, Unidad Queretaro, Mexico (Mexico); Yate, L.; Esteve, J. [Department de Fisica Aplicada i Optica, Universitat de Barcelona, Catalunya (Spain); Prieto, P. [Grupo de Peliculas Delgadas, Universidad del Valle, Cali (Colombia); Centro de Excelencia en Nuevos Materiales, CENM, Cali (Colombia)

    2010-11-15

    The aim of this work is to improve the mechanical properties of AISI 4140 steel substrates by using a TiN[BCN/BN]{sub n}/c-BN multilayer system as a protective coating. TiN[BCN/BN]{sub n}/c-BN multilayered coatings via reactive r.f. magnetron sputtering technique were grown, systematically varying the length period ({Lambda}) and the number of bilayers (n) because one bilayer (n = 1) represents two different layers (t{sub BCN} + t{sub BN}), thus the total thickness of the coating and all other growth parameters were maintained constant. The coatings were characterized by Fourier transform infrared spectroscopy showing bands associated with h-BN bonds and c-BN stretching vibrations centered at 1400 cm{sup -1} and 1100 cm{sup -1}, respectively. Coating composition and multilayer modulation were studied via secondary ion mass spectroscopy. Atomic force microscopy analysis revealed a reduction in grain size and roughness when the bilayer number (n) increased and the bilayer period decreased. Finally, enhancement of mechanical properties was determined via nanoindentation measurements. The best behavior was obtained when the bilayer period ({Lambda}) was 80 nm (n = 25), yielding the relative highest hardness ({approx}30 GPa) and elastic modulus (230 GPa). The values for the hardness and elastic modulus are 1.5 and 1.7 times greater than the coating with n = 1, respectively. The enhancement effects in multilayered coatings could be attributed to different mechanisms for layer formation with nanometric thickness due to the Hall-Petch effect; because this effect, originally used to explain increased hardness with decreasing grain size in bulk polycrystalline metals, has also been used to explain hardness enhancements in multilayered coatings taking into account the thickness reduction at individual single layers that make up the multilayered system. The Hall-Petch model based on dislocation motion within layered and across layer interfaces has been successfully applied to

  18. Thermal Conductance of the 2D MoS2/h-BN and graphene/h-BN Interfaces

    Science.gov (United States)

    Liu, Yi; Ong, Zhun-Yong; Wu, Jing; Zhao, Yunshan; Watanabe, Kenji; Taniguchi, Takashi; Chi, Dongzhi; Zhang, Gang; Thong, John T. L.; Qiu, Cheng-Wei; Hippalgaonkar, Kedar

    2017-01-01

    Two-dimensional (2D) materials and their corresponding van der Waals heterostructures have drawn tremendous interest due to their extraordinary electrical and optoelectronic properties. Insulating 2D hexagonal boron nitride (h-BN) with an atomically smooth surface has been widely used as a passivation layer to improve carrier transport for other 2D materials, especially for Transition Metal Dichalcogenides (TMDCs). However, heat flow at the interface between TMDCs and h-BN, which will play an important role in thermal management of various electronic and optoelectronic devices, is not yet understood. In this paper, for the first time, the interface thermal conductance (G) at the MoS2/h-BN interface is measured by Raman spectroscopy, and the room-temperature value is (17.0 ± 0.4) MW · m−2K−1. For comparison, G between graphene and h-BN is also measured, with a value of (52.2 ± 2.1) MW · m−2K−1. Non-equilibrium Green’s function (NEGF) calculations, from which the phonon transmission spectrum can be obtained, show that the lower G at the MoS2/h-BN interface is due to the weaker cross-plane transmission of phonon modes compared to graphene/h-BN. This study demonstrates that the MoS2/h-BN interface limits cross-plane heat dissipation, and thereby could impact the design and applications of 2D devices while considering critical thermal management. PMID:28262778

  19. Anisotropy of BN and Be x-ray-emission bands

    Energy Technology Data Exchange (ETDEWEB)

    Mansour, A.; Schnatterly, S.E.

    1987-12-15

    We present measurements of the K emission spectra of hexagonal Be and BN (h-Be and h-BN). The anisotropy of the emission allows us to separate the bands into their sigma and ..pi.. components, enabling us to demonstrate the unambiguous ..pi.. character of the B core exciton. We find that the exciton presents a double-peaked structure which we attribute to phonon ringing. For the first time we are able to separate into ..pi.. and sigma components the doubly ionized K emission bands of B and N in h-BN and of Be in h-Be, revealing the effect of the spectator core hole on the shape of the density of states. Such an effect is in qualitative agreement with the final-state rule, although the local p density of states is distorted more than has previously been reported.

  20. Combustion Synthesis of h-BN-SiC Ceramic Composites

    Institute of Scientific and Technical Information of China (English)

    LI Hong-bo; ZHENG Yong-ting; ZHOU Li-juan; HAN Jie-cai

    2006-01-01

    The feasibility was demonstrated to fabricate h-BN-SiC ceramics through combustion synthesis of the mixture of boron carbide and silicon powders under 100 MPa nitrogen pressure. The mass fraction of BN and SiC in the combustion products were found to be 72 % and 28 % respectively. The thermodynamics of the synthesis reaction and the adiabatic combustion temperature were calculated on the theoretical ground. The bending strengths of the ceramics were measured to be 65.2 MPa at room temperature and 55 MPa at 1350 ℃. The phase composition and microstructure of the combustion products were identified by X-ray diffraction (XRD) and scanning electron microscopy (SEM).

  1. Raman fingerprint of aligned graphene/h-BN superlattices.

    Science.gov (United States)

    Eckmann, Axel; Park, Jaesung; Yang, Huafeng; Elias, Daniel; Mayorov, Alexander S; Yu, Geliang; Jalil, Rashid; Novoselov, Kostya S; Gorbachev, Roman V; Lazzeri, Michele; Geim, Andre K; Casiraghi, Cinzia

    2013-11-13

    Graphene placed on hexagonal-boron nitride (h-BN) experiences a superlattice (Moiré) potential, which leads to a strong reconstruction of graphene's electronic spectrum with new Dirac points emerging at sub-eV energies. Here we study the effect of such superlattices on graphene's Raman spectrum. In particular, the 2D Raman peak is found to be exquisitely sensitive to the misalignment between graphene and h-BN lattices, probably due to the presence of a strain distribution with the same periodicity of the Moiré potential. This feature can be used to identify graphene superlattices with a misalignment angle smaller than 2°.

  2. Fundamental Discovery of New Phases and Direct Conversion of Carbon into Diamond and hBN into cBN and Properties

    Science.gov (United States)

    Narayan, Jagdish; Bhaumik, Anagh

    2016-04-01

    We review the discovery of new phases of carbon (Q-carbon) and BN (Q-BN) and address critical issues related to direct conversion of carbon into diamond and hBN into cBN at ambient temperatures and pressures in air without any need for catalyst and the presence of hydrogen. The Q-carbon and Q-BN are formed as a result of quenching from super undercooled state by using high-power nanosecond laser pulses. We discuss the equilibrium phase diagram ( P vs T) of carbon, and show that by rapid quenching, kinetics can shift thermodynamic graphite/diamond/liquid carbon triple point from 5000 K/12 GPa to super undercooled carbon at atmospheric pressure in air. Similarly, the hBN-cBN-Liquid triple point is shifted from 3500 K/9.5 GPa to as low as 2800 K and atmospheric pressure. It is shown that nanosecond laser heating of amorphous carbon and nanocrystalline BN on sapphire, glass, and polymer substrates can be confined to melt in a super undercooled state. By quenching this super undercooled state, we have created a new state of carbon (Q-carbon) and BN (Q-BN) from which nanocrystals, microcrystals, nanoneedles, microneedles, and thin films are formed depending upon the nucleation and growth times allowed and the presence of growth template. The large-area epitaxial diamond and cBN films are formed, when appropriate planar matching or lattice matching template is provided for growth from super undercooled liquid. The Q-phases have unique atomic structure and bonding characteristics as determined by high-resolution SEM and backscatter diffraction, HRTEM, STEM-Z, EELS, and Raman spectroscopy, and exhibit new and improved mechanical hardness, electrical conductivity, and chemical and physical properties, including room-temperature ferromagnetism and enhanced field emission. The Q-carbon exhibits robust bulk ferromagnetism with estimated Curie temperature of about 500 K and saturation magnetization value of 20 emu g-1. We have also deposited diamond on cBN by using a novel

  3. Band-gap engineering of the h-BN/MoS2/h-BN sandwich heterostructure under an external electric field

    Science.gov (United States)

    Huang, Zongyu; Qi, Xiang; Yang, Hong; He, Chaoyu; Wei, Xiaolin; Peng, Xiangyang; Zhong, Jianxin

    2015-05-01

    Based on first-principles calculations in the framework of van der Waals density functional theory, we investigate the structural, electronic properties and band-gap tuning of the h-BN/MoS2/h-BN sandwich heterostructure under an external electric field. We find that, different from the suspended monolayer MoS2 with a direct band-gap, h-BN/MoS2/h-BN has an indirect band-gap. Particular attention has been focused on the engineering of the band-gap of the h-BN/MoS2/h-BN heterostructure via application of an external electric field. With the increase of electric field, the band-gap of the h-BN/MoS2/h-BN heterostructure undergoes an indirect-to-direct band-gap transition. Once the electric field intensity is larger than 0.1 V Å-1, the gap value of direct band-gap shrinks almost linearly with the field-strength, which indicates that the h-BN/MoS2/h-BN heterostructure is a viable candidate for optoelectronic applications.

  4. Atomic Layer Epitaxy of h-BN(0001) Multilayers on Co(0001) and Molecular Beam Epitaxy Growth of Graphene on h-BN(0001)/Co(0001).

    Science.gov (United States)

    Driver, M Sky; Beatty, John D; Olanipekun, Opeyemi; Reid, Kimberly; Rath, Ashutosh; Voyles, Paul M; Kelber, Jeffry A

    2016-03-22

    The direct growth of hexagonal boron nitride (h-BN) by industrially scalable methods is of broad interest for spintronic and nanoelectronic device applications. Such applications often require atomically precise control of film thickness and azimuthal registry between layers and substrate. We report the formation, by atomic layer epitaxy (ALE), of multilayer h-BN(0001) films (up to 7 monolayers) on Co(0001). The ALE process employs BCl3/NH3 cycles at 600 K substrate temperature. X-ray photoelectron spectroscopy (XPS) and low energy electron diffraction (LEED) data show that this process yields an increase in h-BN average film thickness linearly proportional to the number of BCl3/NH3 cycles, with BN layers in azimuthal registry with each other and with the Co(0001) substrate. LEED diffraction spot profile data indicate an average BN domain size of at least 1900 Å. Optical microscopy data indicate the presence of some domains as large as ∼20 μm. Transmission electron microscopy (TEM) and ambient exposure studies demonstrate macroscopic and microscopic continuity of the h-BN film, with the h-BN film highly conformal to the Co substrate. Photoemission data show that the h-BN(0001) film is p-type, with band bending near the Co/h-BN interface. Growth of graphene by molecular beam epitaxy (MBE) is observed on the surface of multilayer h-BN(0001) at temperatures of 800 K. LEED data indicate azimuthal graphene alignment with the h-BN and Co(0001) lattices, with domain size similar to BN. The evidence of multilayer BN and graphene azimuthal alignment with the lattice of the Co(0001) substrate demonstrates that this procedure is suitable for scalable production of heterojunctions for spintronic applications.

  5. Further delays hit troubled $2bn cosmic-ray detector

    CERN Multimedia

    Cartlidge, Edwin

    2010-01-01

    "A $2bn mission to study cosmic rays will have to wait another few months before being sent to the International Space Station (ISS) after NASA announced last month that it was pushing back the launch of the Space Shuttle Endeavour until 26 February 2011" (0.5 page)

  6. Band-gap control in phosphorene/BN structures from first-principles calculations

    Science.gov (United States)

    Marsoner Steinkasserer, Lukas Eugen; Suhr, Simon; Paulus, Beate

    2016-09-01

    Using both DFT as well as G0W0 calculations, we investigate static and dynamic effects on the phosphorene band gap upon deposition and encapsulation on/in BN multilayers. We demonstrate how competing long- and short-range effects cause the phosphorene band gap to increase at low P -BN interlayer spacings, while the band gap is found to drop below that of isolated phosphorene in the BN/P bilayer at intermediate distances around 4 Å. Subsequent stacking of BN layers, i.e., BN/BN/P and BN/BN/BN/P is found to have a negligible effect at the DFT level while at the G0W0 level, increased screening lowers the band gap as compared to the BN/P bilayer. Encapsulation between two BN layers, on the other hand, is found to further increase the phosphorene band gap with respect to the BN/P bilayer. Lastly we investigate the use of the GLLB-SC functional as a starting point for G0W0 calculations showing it to, in the case of phosphorene, yield results close to those obtained from G W0@P B E .

  7. Refined exposure assessment for Brilliant Black BN (E 151

    Directory of Open Access Journals (Sweden)

    European Food Safety Authority

    2015-01-01

    Full Text Available The European Food Safety Authority (EFSA carried out an exposure assessment of Brilliant Black BN (E 151, taking into account new information on its use as a food additive in foods. In 2010, the EFSA Panel on Food Additives and Nutrient Sources added to Food (ANS adopted a scientific opinion on the re-evaluation of Brilliant Black BN and concluded that dietary exposure in 1- to 10-year-old children at the high level may exceed the Acceptable Daily Intake (ADI for Brilliant Black BN of 5 mg/kg body weight (bw/day at the upper end of the range. Following this conclusion, the European Commission requested that EFSA performs a refined exposure assessment for this food colour. Data on the presence of Brilliant Black BN in foods were requested from relevant stakeholders through a call for usage and concentration data. Usage levels were provided to EFSA for 11 out of 37 food categories in which Brilliant Black is authorised. In addition, 4 337 analytical results were also reported to EFSA, with the majority of values being below the limit of detection (LOD or limit of quantification (LOQ. Exposure assessment was performed using the EFSA Comprehensive Food Consumption Database. Three scenarios were considered: (1 exposure estimates based on Maximum Permitted Levels (MPLs, (2 a refined brand-loyal exposure scenario, and (3 a refined non-brand-loyal exposure scenario. Considering the first scenario, high exposure levels (95th percentile exceeded the ADI for toddlers and children in four dietary surveys. In comparison with the previous assessment, for both children and adults, the current mean exposure estimates are of the same order of magnitude, whereas the 95th percentile exposure is lower, particularly in adults. The mean and high-level exposure estimates of Brilliant Black BN are below the ADI for all population groups when considering the refined scenarios (brand-loyal and non-brand-loyal.

  8. R.F. magnetron sputtering of multilayered c-BN films on cemented carbide tool.

    Science.gov (United States)

    Park, Sungtae; Jeong, Sehoon; Lee, Kwangmin

    2011-02-01

    A c-BN thin film was deposited using a B4C target in a r.f. magnetron sputtering system. The c-BN layer was coated with a TiAIN adhesion layer (approximately 2 microm), boron carbide (approximately 1 microm) and BCN (10 approximately 15 nm) nano-gradient layer system. The c-BN layers with thicknesses of more than 0.5 microm were successfully deposited onto cemented carbide substrates. The high resolution XPS spectra analysis of B1s and N1s revealed that the c-BN film was mainly composed of sp3 BN bonds.

  9. Biological Efficacy of Streptomyces sp. Strain BN1 against the Cereal Head Blight Pathogen Fusarium graminearum

    Directory of Open Access Journals (Sweden)

    Boknam Jung

    2013-03-01

    Full Text Available Fusarium head blight (FHB caused by the filamentous fungus Fusarium graminearum is one of the most severe diseases threatening the production of small grains. Infected grains are often contaminated with mycotoxins such as zearalenone and trichothecences. During survey of contamination by FHB in rice grains, we found a bacterial isolate, designated as BN1, antagonistic to F. graminearum. The strain BN1 had branching vegetative hyphae and spores, and its aerial hyphae often had long, straight filaments bearing spores. The 16S rRNA gene of BN1 had 100% sequence identity with those found in several Streptomyces species. Phylogenetic analysis of ITS regions showed that BN1 grouped with S. sampsonii with 77% bootstrap value, suggesting that BN1 was not a known Streptomyces species. In addition, the efficacy of the BN1 strain against F. graminearum strains was tested both in vitro and in vivo. Wheat seedling length was significantly decreased by F. graminearum infection. However, this effect was mitigated when wheat seeds were treated with BN1 spore suspension prior to F. graminearum infection. BN1 also significantly decreased FHB severity when it was sprayed onto wheat heads, whereas BN1 was not effective when wheat heads were point inoculated. These results suggest that spraying of BN1 spores onto wheat heads during the wheat flowering season can be efficient for plant protection. Mechanistic studies on the antagonistic effect of BN1 against F. graminearum remain to be analyzed.

  10. The electric properties and the current-controlled differential negative resistance of cBN crystal

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The electric properties of nonintentionally doped n-cubic boron nitride(cBN) crystal are investigated.The cBN crystal was transformed from hexagonal-boron nitride(h-BN) under high pressure(HP) and high temperature(HT) using magnesium powder as catalyst.At room temperature,the current-voltage(I-V) characteristics of cBN crystal are measured and found to be nonlinear.When the electric field is in the range of(1―1.5)×105 V/cm,the avalanche breakdown occurs inside the whole cBN crystal.At this same time,the bright blue-violet with the wavelength of 380―400 nm from the cBN crystal is observed.When measuring the I-V curve after breakdown of cBN crystal,the current-controlled differential negative resistance phenomenon is observed.The breakdown is repeatable.

  11. Electrodeposition and characterization of Co–BN (h) nanocomposite coatings

    Energy Technology Data Exchange (ETDEWEB)

    Shahri, Z.; Allahkaram, S.R., E-mail: akaram@ut.ac.ir; Zarebidaki, A.

    2013-07-01

    Co–BN (h) nanocomposite coatings were prepared by means of the conventional electrodeposition in a chloride solution containing different concentrations of hexagonal boron nitride particles, and pure Co coating was also prepared as a comparison. Morphology of the coatings and the effect of incorporated particles on metal matrix structure and composition were investigated via scanning electron microscopy, energy dispersive spectroscopy and X-ray diffraction analysis. Microhardness, roughness, friction coefficient and wear resistance of the coatings were also evaluated using Vickers microhardness, stylus profilometer and pin-on disk machine. The results showed that Co–BN (h) nanocomposite coatings exhibit higher hardness and lower friction coefficient. Roughness and wear resistance compared with that of the pure Co coating obtained under the same electrodeposition condition and the wear mechanism of the coatings were also discussed.

  12. Bandgap oscillation in quasiperiodic carbon-BN nanoribbons

    Science.gov (United States)

    Pedreira, D. O.; Azevedo, S.; Bezerra, C. G.; Viol, A.; Viswanathan, G. M.; Ferreira, M. S.

    2014-02-01

    In this work we address the effects of quasiperiodic disorder on the physical properties of nanoribbons, composed by BN and C, constructed according to the Fibonacci quasiperiodic sequence. We assume BN and C as the building blocks of the resulting quasiperiodic structure. The density of states and energy band gap were obtained through ab-initio calculations based on the density functional theory. We report the effects of the quasiperiodic disorder on the oscillatory behavior of the specific heat, in the low temperature regime, and on the behavior of the energy band gap. In particular, we show that the electronic energy band gap oscillates as a function of the Fibonacci generation index n. Our results suggest that the choice of the building block materials of the quasiperiodic sequence, with appropriate band gap energies, may lead to a tuneable band gap of quasiperiodic nanoribbons.

  13. Identification and Characterization of 1,2-BN Cyclohexene Using Microwave Spectroscopy

    Science.gov (United States)

    Kukolich, Stephen G.; Sun, Ming; Daly, Adam M.; Ishibashi, Jacob S. A.; Liu, Shih-Yuan

    2016-06-01

    1,2-BN Cyclohexene was produced from 1,2-BN Cyclohexane through the loss of H_2 and characterized and identified using a pulsed-beam Fourier-transform microwave spectrometer. The first microwave spectra for 1,2-10BN Cyclohexene 1,2-11BN Cyclohexene have been measured in the frequency range of 5.5-12.5 GHz, providing accurate rotational constants and nitrogen and boron quadrupole coupling strengths for two isotopologues. High-level ab initio calculations provided rotational constants and quadrupole coupling strengths for the precursor 1,2-BN Cyclohexane (C_4H12BN) and 1,2-BN Cyclohexene(C_4H10BN). Calculated molecular properties for 1,2-BN Cyclohexene are in very good agreement with measured parameters. Calculated parameters for the starting material, 1,2-BN Cyclohexane do not agree with the experimental data. Rotational constants for 1,2-11BN Cyclohexene are A = 4702.058(2) MHz, B = 4360.334(1) MHz and C = 2494.407(1) MHz. The inertial defect is Δ_0 = -20.78 amu-Å^2 clearly indicating a nonplanar structure. These microwave experiments show that heating the initial compound, 1,2-BN Cyclohexane, to 60 C in a 1 atm neon stream results in the loss of H_2 and conversion to 1,2-BN Cyclohexene. This appears to be the first characterization of the 1,2-BN Cyclohexene monomer. Supported by the NSF CHE-1057796 and DOE DE-EE-0005658

  14. Electrophoretic Deposition of Chitosan/h-BN and Chitosan/h-BN/TiO2 Composite Coatings on Stainless Steel (316L Substrates

    Directory of Open Access Journals (Sweden)

    Namir S. Raddaha

    2014-03-01

    Full Text Available This article presents the results of an experimental investigation designed to deposit chitosan/hexagonal boron nitride (h-BN and chitosan/h-BN/titania (TiO2 composites on SS316L substrates using electrophoretic deposition (EPD for potential antibacterial applications. The influence of EPD parameters (voltage and deposition time and relative concentrations of chitosan, h-BN and TiO2 in suspension on deposition yield was studied. The composition and structure of deposited coatings were investigated by FTIR, XRD and SEM. It was observed that h-BN and TiO2 particles were dispersed in the chitosan matrix through simultaneous deposition. The adhesion between the electrophoretic coatings and the stainless steel substrates was tested by using tape test technique, and the results showed that the adhesion strength corresponded to 3B and 4B classes. Corrosion resistance was evaluated by electrochemical polarization curves, indicating enhanced corrosion resistance of the chitosan/h-BN/TiO2 and chitosan/h-BN coatings compared to the bare stainless steel substrate. In order to investigate the in-vitro inorganic bioactivity, coatings were immersed in simulated body fluid (SBF for 28 days. FTIR and XRD results showed no formation of hydroxyapatite on the surface of chitosan/h-BN/TiO2 and chitosan/h-BN coatings, which are therefore non bioactive but potentially useful as antibacterial coatings.

  15. Direct Growth of MoS₂/h-BN Heterostructures via a Sulfide-Resistant Alloy.

    Science.gov (United States)

    Fu, Lei; Sun, Yangyong; Wu, Nian; Mendes, Rafael G; Chen, Linfeng; Xu, Zhen; Zhang, Tao; Rümmeli, Mark H; Rellinghaus, Bernd; Pohl, Darius; Zhuang, Lin; Fu, Lei

    2016-02-23

    Improved properties arise in transition metal dichalcogenide (TMDC) materials when they are stacked onto insulating hexagonal boron nitride (h-BN). Therefore, the scalable fabrication of TMDCs/h-BN heterostructures by direct chemical vapor deposition (CVD) growth is highly desirable. Unfortunately, to achieve this experimentally is challenging. Ideal substrates for h-BN growth, such as Ni, become sulfides during the synthesis process. This leads to the decomposition of the pregrown h-BN film, and thus no TMDCs/h-BN heterostructure forms. Here, we report a thoroughly direct CVD approach to obtain TMDCs/h-BN vertical heterostructures without any intermediate transfer steps. This is attributed to the use of a nickel-based alloy with excellent sulfide-resistant properties and a high catalytic activity for h-BN growth. The strategy enables the direct growth of single-crystal MoS2 grains of up to 200 μm(2) on h-BN, which is approximately 1 order of magnitude larger than that in previous reports. The direct band gap of our grown single-layer MoS2 on h-BN is 1.85 eV, which is quite close to that for free-standing exfoliated equivalents. This strategy is not limited to MoS2-based heterostructures and so allows the fabrication of a variety of TMDCs/h-BN heterostructures, suggesting the technique has promise for nanoelectronics and optoelectronic applications.

  16. Ion sputtering erosion mechanisms of h-BN composite ceramics with textured microstructures

    Energy Technology Data Exchange (ETDEWEB)

    Duan, Xiaoming, E-mail: dxm_hit@126.com [Institute for Advanced Ceramics, Harbin Institute of Technology, Harbin 150001 (China); Ding, Yongjie [School of Energy Science and Technology, Harbin Institute of Technology, Harbin 150001 (China); Jia, Dechang; Jing, Nan; Yang, Zhihua; He, Peigang; Tian, Zhuo; Wang, Shengjin; Wang, Yujin; Zhou, Yu [Institute for Advanced Ceramics, Harbin Institute of Technology, Harbin 150001 (China); Yu, Daren [School of Energy Science and Technology, Harbin Institute of Technology, Harbin 150001 (China)

    2014-11-15

    Highlights: • Textured h-BN ceramics were made by hot press sintering using mullite as additives. • Sintering pressures play important role on ions sputtering resistance properties. • Textured microstructures lead to various surface morphologies by ion sputtering. • Sputtering erosion mechanisms include B–N bonds breaking and BN layers delamination. - Abstract: Since the hexagonal boron nitride (h-BN) grain shows typical lamellar structures, textured materials can be obtained by arranging h-BN grains along one direction. In this work, textured h-BN composite ceramics with the c-axis orientation arranged along the pressure direction are manufactured by hot-press sintering using mullite as the sintering additive. The results show that sintering pressures not only play a major role in the density and the textured degrees of composite ceramics, but also influence Xe ion erosion resistance performances. After Xe ion sputtering, compositions of both h-BN and mullite stay stable, while the elemental compositions have changed due to the so-called “preferential sputtering”. Sputtered surfaces along different orientations show diverse morphologies attributed to the textured microstructures. The erosion mechanisms of h-BN grains during Xe ion sputtering are breaking of B–N bonds and delamination of BN layers. While the mass loss of composite ceramics is due to the erosion of h-BN grains and mullite coupled with partial detachment of h-BN grains from the surface.

  17. Tuning band gaps of BN nanosheets and nanoribbons via interfacial dihalogen bonding and external electric field.

    Science.gov (United States)

    Tang, Qing; Bao, Jie; Li, Yafei; Zhou, Zhen; Chen, Zhongfang

    2014-08-07

    Density functional theory computations with dispersion corrections (DFT-D) were performed to investigate the dihalogen interactions and their effect on the electronic band structures of halogenated (fluorinated and chlorinated) BN bilayers and aligned halogen-passivated zigzag BN nanoribbons (BNNRs). Our results reveal the presence of considerable homo-halogen (FF and ClCl) interactions in bilayer fluoro (chloro)-BN sheets and the aligned F (Cl)-ZBNNRs, as well as substantial hetero-halogen (FCl) interactions in hybrid fluoro-BN/chloro-BN bilayer and F-Cl-ZBNNRs. The existence of interfacial dihalogen interactions leads to significant band-gap modifications for the studied BN nanosystems. Compared with the individual fluoro (chloro)-BN monolayers or pristine BNNRs, the gap reduction in bilayer fluoro-BN (B-FF-N array), hybrid fluoro-BN/chloro-BN bilayer (N-FCl-N array), aligned Cl-ZBNNRs (B-ClCl-N alignment), and hybrid F-Cl-ZBNNRs (B-FCl-N alignment) is mainly due to interfacial polarizations, while the gap narrowing in bilayer chloro-BN (N-ClCl-N array) is ascribed to the interfacial nearly-free-electron states. Moreover, the binding strengths and electronic properties of the interactive BN nanosheets and nanoribbons can be controlled by applying an external electric field, and extensive modulation from large-gap to medium-gap semiconductors, or even metals can be realized by adjusting the direction and strength of the applied electric field. This interesting strategy for band gap control based on weak interactions offers unique opportunities for developing BN nanoscale electronic devices.

  18. Effects of Temperature Raising Speed on the Growth of BN Crystals in Hydrothermal Solutions

    Institute of Scientific and Technical Information of China (English)

    YU,Mei-Yan(于美燕); LI,Kai(李凯); CUI,De-Liang(崔得良); DONG,Shou-Yi(董守义); WANG,Qi-Long(王琪珑); JIANG,Min-Hua(蒋民华)

    2004-01-01

    Cubic boron nitride (cBN) and orthorhombic boron nitride (oBN) crystals have been prepared in hydrothermal solutions by reacting H3BO3+NaN3+P and H3BO3+NaN3+N2H4 respectively. The experimental results indicated that, if the temperature was increased rapidly, both the yield and perfectness of BN crystals became poor. On the contrast, the yield and perfectness of BN crystals can be improved very much by slowly increasing the temperature of the reaction mixture. The results of X-ray powder diffraction (XRD), Fourier transform infrared spectrum (FTIR)and high resolution transmission electron microscopy (HRTEM) proved that the samples were composed of oBN and cBN.

  19. First-principles study of the noble metal-doped BN layer

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Yungang; Yang, Ping; Sun, Xin; Wang, Zhiguo; Zu, Xiaotao T.; Gao, Fei

    2011-04-18

    Intriguing electronic and magnetic properties of BN layer with noble metal (Pd, Pt, Ag and Au) doping are obtained by first-principles calculations. Adsorbed Pd (or Pt) reduces the band gap of BN sheet owing to the induction of impurity states. The unpaired electrons in the Ag (or Au)-adsorbed and the Pd (or Pt)-substituted BN layers are polarized, and thus exhibit a magnetic moment of 1.0 µB, leading to these BN configurations to be magnetic semiconductors. The half-metallic feature of the Ag-substituted BN layer, along with the delocalization of spin states, renders this configuration an excellent spin filter material. Thus, these findings offer a unique opportunity for developing BN-based nanoscale devices.

  20. Basic research on mechanism of BN inclusion in improving the machinability of steel

    Energy Technology Data Exchange (ETDEWEB)

    Ya-nan, C.; Yan-ping, B.; Min, W.; Xiao-feng, C.; Lin-jing, W.; Li-hua, Z.

    2014-07-01

    Boron nitride-added eco-friendly free cutting steel has recently drawn more and more attention. But, the mechanisms explaining the role of BN inclusions improving the machinability of steels is not very clear. In this investigation, the material removal mechanism for cutting of BN inclusions in steels is explored, using a combination of theoretical analysis and a series of experiments. First, the actual shape of BN inclusions is observed and the amount and distribution of BN inclusions is quantitatively analyzed. Subsequently, the cutting performance of the steel is determined by cutting experimental tests. Moreover, the micro mechanical properties and the material removal mechanisms for cutting of BN inclusions are investigated by means of nano indentation. The results revealed that the BN inclusions are hexagonal and are uniformly distributed, their average content is 23.2 per unit area and their volume fraction is 0.51% in the steel with 74 ppm B and 180 ppm N. It is shown that BN inclusions can improve the cutting performance of steel significantly, and a model describing the material removal mechanism for cutting of BN inclusions is proposed. BN inclusions act as stress concentration source, lubrication and wrap page of hard particles. (Author)

  1. Parabolic starlike mappings of the unit ball $B^n$

    Directory of Open Access Journals (Sweden)

    Samira Rahrovi

    2016-02-01

    Full Text Available Let $f$ be a locally univalent function on the unit disk $U$. We consider the normalized extensions of $f$ to the Euclidean unit ball $B^nsubseteqmathbb{C}^n$ given by$$Phi_{n,gamma}(f(z=left(f(z_1,(f'(z_1^gammahat{z}right,$$ where $gammain[0,1/2]$, $z=(z_1,hat{z}in B^n$ and$$Psi_{n,beta}(f(z=left(f(z_1,(frac{f(z_1}{z_1}^betahat{z}right,$$in which $betain[0,1]$, $f(z_1neq 0$ and $z=(z_1,hat{z}inB^n$. In the case $gamma=1/2$, the function $Phi_{n,gamma}(f$ reduces to the well known Roper-Suffridge extension operator. By using different methods, we prove that if $f$ is parabolic starlike mapping on $U$ then $Phi_{n,gamma}(f$ and $Psi_{n,beta}(f$ are parabolic starlike mappings on $B^n$.

  2. Bandgap oscillation in quasiperiodic (BN)xCy nanotubes

    Science.gov (United States)

    Freitas, A.; Bezerra, C. G.; Azevedo, S.; Machado, L. D.; Pedreira, D. O.

    2016-12-01

    In the present contribution, we apply first-principles calculations to study the effects of quasiperiodic disorder on the physical properties of BN and C nanotubes. We take BN nanotubes (BNNTs) and C nanotubes (CNTs) as building blocks and construct quasiperiodic BNxCy nanotubes according to the Fibonacci sequence. We studied armchair and zigzag nanotubes of varying diameters. Our results demonstrate that the energy gap oscillates as a function of the n-generation index of the Fibonacci sequence. Moreover, we show that the choice of the BNNTs and CNTs may lead to a quasiperiodic BNxCy nanotube presenting an adjustable energy gap. We obtained a variety of quasiperiodic nanotubes with energy gaps ranging from 0.29 eV to 1.06 eV, which may be of interest for specific technological applications. Finally, it is also demonstrated that the specific heat of the quasiperiodic zigzag and armchair nanotubes presents an oscillatory behavior in the low temperature regime, and that this behavior depends on the curvature of the nanotube.

  3. Effect of the cBN content and sintering temperature on the transverse rupture strength and hardness of cBn/diamond cutting tools

    Directory of Open Access Journals (Sweden)

    Kır Durmuş

    2012-01-01

    Full Text Available The aim of this work was to investigate the effect of cBN content and sintering temperature on the transverse rupture strength (TRS of cBN/diamond cutting tools produced by hot pressing. The segments containing different cBN content were manufactured under 35 MPa pressure at 600, 650 and 700°C with a 3 minutes sintering time. The TRS of segments were determined using three-point bending test. Microstructure and phase composition of fracture surface of segments were determined by scanning electron microscopy (SEM, and X-ray diffraction (XRD analysis. The obtained results show that the TRS of the segments with cBN were higher than that of the segments with diamond.

  4. The BnALMT1 and BnALMT2 genes from rape encode aluminum-activated malate transporters that enhance the aluminum resistance of plant cells.

    Science.gov (United States)

    Ligaba, Ayalew; Katsuhara, Maki; Ryan, Peter R; Shibasaka, Mineo; Matsumoto, Hideaki

    2006-11-01

    The release of organic anions from roots can protect plants from aluminum (Al) toxicity and help them overcome phosphorus (P) deficiency. Our previous findings showed that Al treatment induced malate and citrate efflux from rape (Brassica napus) roots, and that P deficiency did not induce the efflux. Since this response is similar to the malate efflux from wheat (Triticum aestivum) that is controlled by the TaALMT1 gene, we investigated whether homologs of TaALMT1 are present in rape and whether they are involved in the release of organic anions. We isolated two TaALMT1 homologs from rape designated BnALMT1 and BnALMT2 (B. napus Al-activated malate transporter). The expression of these genes was induced in roots, but not shoots, by Al treatment but P deficiency had no effect. Several other cations (lanthanum, ytterbium, and erbium) also increased BnALMT1 and BnALMT2 expression in the roots. The function of the BnALMT1 and BnALMT2 proteins was investigated by heterologous expression in cultured tobacco (Nicotiana tabacum) cells and in Xenopus laevis oocytes. Both transfection systems showed an enhanced capacity for malate efflux but not citrate efflux, when exposed to Al. Smaller malate fluxes were also activated by ytterbium and erbium treatment. Transgenic tobacco cells grew significantly better than control cells following an 18 h treatment with Al, indicating that the expression of BnALMT1 and BnALMT2 increased the resistance of these plant cells to Al stress. This report demonstrates that homologs of the TaALMT1 gene from wheat perform similar functions in other species.

  5. Cubic and hexagonal boron-nitride (c-BN/h-BN) thin films deposited in situ by r.f. magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Caicedo, J.M.; Zambrano, G.; Baca, E.; Moran, O.; Prieto, P. [Departamento de Fisica, Universidad del Valle, A.A. 25360 Cali (Colombia); Bejarano, G. [Laboratorio de Recubrimientos Duros, CDT-ASTIN SENA, Cali (Colombia)

    2005-07-01

    Cubic boron-nitride (c-BN)/hexagonal boron nitride (h-BN) thin films were grown in situ on (100) oriented silicon substrates by r.f. (13.56 MHz) magnetron sputtering technique. In order to obtain the highest fraction of the c-BN phase, a negative d.c bias voltage, varying from 0 to -200 V was applied to the substrate during deposition. Another set of boron nitride thin films was deposited in situ on (100) oriented silicon substrates under r.f. bias voltage. The substrate holder was biased from 0 to -350 V by connecting such to an auxiliary r.f. generator (operated at 13.56 MHz). Films were characterized by Fourier Transformed Infrared Spectroscopy (FTIR) and Atomic Force Microscope (AFM). Well-defined peaks at 787 cm{sup -1}, 1100 cm{sup -1} and 1387 cm{sup -1}, corresponding to the 2{sub Au} (out-plane bending of B-N-B bond) h-BN vibration mode, the F2 (stretching) c-BN Transversal Optical (TO) mode and the E{sub 1u} (in-plane stretching of B-N bond) vibration mode of the h-BN, respectively, were observed in the FTIR spectra. A maximal fraction of the c-BN phase close to 85% was obtained under a bias voltage of -150 V at substrate temperature of 300 C and a total pressure of 4 x 10{sup -2} mbar. (copyright 2005 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  6. An Upper Bound of Essential Norm of Composition Operator on H2(Bn)

    Institute of Scientific and Technical Information of China (English)

    Zhihua CHEN; Liangying JIANG; Qiming YAN

    2012-01-01

    The authors give an upper bound of the essential norm of a composition operator on H2(Bn),which involves the counting function in the higher dimensional value distribution theory defined by S.S.Chern.A criterion is also given to assure that the composition operator on H2(Bn) is bounded or compact.

  7. BnWRI1 coordinates fatty acid biosynthesis and photosynthesis pathways during oil accumulation in rapeseed.

    Science.gov (United States)

    Wu, Xue-Long; Liu, Zhi-Hong; Hu, Zhang-Hua; Huang, Rui-Zhi

    2014-06-01

    Photosynthesis in "green" seeds, such as rapeseed, soybean, and Arabidopsis, plays a substantial role in the improved efficiency of oil accumulation. However, the molecular mechanism underpinning the coordinated expression of fatty acid (FA) biosynthesis- and photosynthesis-related genes in such developing seeds remains to be elucidated. Here, we found that seed-specific overexpression of BnWRI1, a WRI1 homolog from rapeseed (Brassica napus cv. ZGY2), results in enhanced chlorophyll content in developing seeds and increased oil content and seed mass in matured seeds. BnWRI1 was co-expressed with BnBCCP and BnCAB, two marker genes of FA biosynthesis and photosynthesis during seed development, respectively. Overexpression of BnWRI1 increased expression of both marker genes. Further, the nuclear-localized BnWRI1 protein was found to act as a transcription activator. It could bind to the GT1-element and/or GCC-box, which are widespread in the upstream regions of genes involved in FA biosynthesis and photosynthesis pathways. Accordingly, BnWRI1 could interact with promoters of BCCP2 and LHB1B2 in vivo. These results suggested that BnWRI1 may coordinate FA biosynthesis and photosynthesis pathways in developing seeds via directly stimulating expression of GT1-element and/or GCC-box containing genes.

  8. van der Waals Bonded Co/h-BN Contacts to Ultrathin Black Phosphorus Devices.

    Science.gov (United States)

    Avsar, Ahmet; Tan, Jun Y; Luo, Xin; Khoo, Khoong Hong; Yeo, Yuting; Watanabe, Kenji; Taniguchi, Takashi; Quek, Su Ying; Özyilmaz, Barbaros

    2017-09-13

    Because of the chemical inertness of two dimensional (2D) hexagonal-boron nitride (h-BN), few atomic-layer h-BN is often used to encapsulate air-sensitive 2D crystals such as black phosphorus (BP). However, the effects of h-BN on Schottky barrier height, doping, and contact resistance are not well-known. Here, we investigate these effects by fabricating h-BN encapsulated BP transistors with cobalt (Co) contacts. In sharp contrast to directly Co contacted p-type BP devices, we observe strong n-type conduction upon insertion of the h-BN at the Co/BP interface. First-principles calculations show that this difference arises from the much larger interface dipole at the Co/h-BN interface compared to the Co/BP interface, which reduces the work function of the Co/h-BN contact. The Co/h-BN contacts exhibit low contact resistances (∼4.5 kΩ) and are Schottky barrier-free. This allows us to probe high electron mobilities (4,200 cm(2)/(V s)) and observe insulator-metal transitions even under two-terminal measurement geometry.

  9. BnWRI1 coordinates fatty acid biosynthesis and photosynthesis pathways during oil accumulation in rapeseed

    Institute of Scientific and Technical Information of China (English)

    Xue-Long Wu; Zhi-Hong Liu; Zhang-Hua Hu; Rui-Zhi Huang

    2014-01-01

    Photosynthesis in“green”seeds, such as rapeseed, soybean, and Arabidopsis, plays a substantial role in the improved efficiency of oil accumulation. However, the molecular mecha-nism underpinning the coordinated expression of fatty acid (FA) biosynthesis-and photosynthesis-related genes in such develop-ing seeds remains to be elucidated. Here, we found that seed-specific overexpression of BnWRI1, a WRI1 homolog from rapeseed (Brassica napus cv. ZGY2), results in enhanced chlorophyl content in developing seeds and increased oil content and seed mass in matured seeds. BnWRI1 was co-expressed with BnBCCP and BnCAB, two marker genes of FA biosynthesis and photosynthesis during seed development, respectively. Over-expression of BnWRI1 increased expression of both marker genes. Further, the nuclear-localized BnWRI1 protein was found to act as a transcription activator. It could bind to the GT1-element and/or GCC-box, which are widespread in the upstream regions of genes involved in FA biosynthesis and photosynthesis pathways. Accordingly, BnWRI1 could interact with promoters of BCCP2 and LHB1B2 in vivo. These results suggested that BnWRI1 may coordinate FA biosynthesis and photosynthesis pathways in developing seeds via directly stimulating expression of GT1-element and/or GCC-box containing genes.

  10. Microstructure and mechanical properties of SiO2-BN ceramic and Invar alloy joints brazed with Ag–Cu–Ti+TiH2+BN composite filler

    Directory of Open Access Journals (Sweden)

    Y. Wang

    2016-03-01

    Full Text Available Ag–Cu–Ti + TiH2+BN composite filler was prepared to braze SiO2-BN ceramic and Invar alloy. The interfacial microstructure, mechanical properties, and residual stress distribution of the brazed joints were investigated. The results show that a wave-like Fe2Ti–Ni3Ti structure appears in the Invar substrate and a thin TiN–TiB2 reaction layer forms adjacent to the SiO2-BN ceramic. The added BN particles react with Ti to form TiN–TiB fine-particles, which is beneficial to refine the microstructure of the brazing seam and to greatly inhibit the brittle compounds formation. The interfacial microstructure at various brazing temperatures was analyzed, and the mechanism for the interfacial reactions responsible for the bonding was proposed. The maximum shear strength of the joints brazed with the composite filler at 880 °C for 10 min is 39 MPa, which is 30% greater than that brazed with Ag–Cu–Ti alloy. The improvement of the joint strength is attributed to the variation of joint microstructure and the reduction of tensile stresses induced in the SiO2-BN ceramic. The finite element analysis indicates that the peak tensile stress decreases from 230 to 142 MPa due to the addition of BN particles in the ceramic.

  11. Mechanical properties and electronic structures of one BN nanotube under radial compression

    Institute of Scientific and Technical Information of China (English)

    Hai-jun SHEN

    2009-01-01

    The Tersoff-potential based MD (molecular dynamics)method was used to simulate the radial compression of one(10,0)BN nanotube,and its compressive pmpertes was compared with those of one (10,0)carbon nanotube The semi-empirical PM3 QC (Quantum chemistry)method was adopted to calculate the electronic structures of the compressed BN-tube,and the effect of the radial compression on the electronic structures of the BN-tube was discussed. It is shown that(I) BN-tube has comparable radial compressive stiffness to carbon-tube,but lower energy-absorbing,load-support and deformation-support capabilities,and (ii) with the increase of compressive strain,the HOMO energy of the BN-tube lncreases the LUMO energy and the LUMO-HOMOenergy-gap decrease,and its chemical activity and conductance increase.

  12. Decomposition of BN and formation of Nd2Fe14BNx phase prepared by mechanical alloying

    Science.gov (United States)

    Liu, W.; Zhang, Z. D.; Sun, X. K.; He, J. F.; Zhao, X. G.

    1999-07-01

    The decomposition of pyrolytic boron nitride (p-BN) during milling is studied as a function of the milling time. It has been found that the p-BN compound can be partially decomposed by milling until an amorphous p-BN phase is formed so that the content of nitrogen in the p-BN system will not continue to be changed by the milling process. Furthermore, the structure and magnetic properties of Nd2Fe14BNx-based alloys prepared by mechanical alloying using either p-BN or milled p-BN as starting material have been investigated. The Nd2Fe14BNx phase with x up to 0.25 coexists with some amounts of NdN, the Nd-rich phase and icons/Journals/Common/alpha" ALT="alpha" ALIGN="TOP"/>-Fe. A pre-milling process of p-BN favours the formation of the Nd2Fe14BNx phase. The magnetic properties of Nd16Fe76B8Nx alloys prepared by using milled p-BN are better than those made of non-milled p-BN. The Curie temperature of the Nd2Fe14BN0.25 phase is 335 °C, which is slightly higher than that of the Nd2Fe14B compound. A coercivity higher than 20 kOe is achieved for Nd2Fe14BNx-based alloys by adding excess Nd, which is close to the value of Nd16Fe76B8 prepared by using pure B.

  13. High-Pressure Design of Advanced BN-Based Materials

    Directory of Open Access Journals (Sweden)

    Oleksandr O. Kurakevych

    2016-10-01

    Full Text Available The aim of the present review is to highlight the state of the art in high-pressure design of new advanced materials based on boron nitride. Recent experimental achievements on the governing phase transformation, nanostructuring and chemical synthesis in the systems containing boron nitride at high pressures and high temperatures are presented. All these developments allowed discovering new materials, e.g., ultrahard nanocrystalline cubic boron nitride (nano-cBN with hardness comparable to diamond, and superhard boron subnitride B13N2. Thermodynamic and kinetic aspects of high-pressure synthesis are described based on the data obtained by in situ and ex situ methods. Mechanical and thermal properties (hardness, thermoelastic equations of state, etc. are discussed. New synthetic perspectives, combining both soft chemistry and extreme pressure–temperature conditions are considered.

  14. Naphthalene degradation and biosurfactant activity by Bacillus cereus 28BN

    Energy Technology Data Exchange (ETDEWEB)

    Tuleva, B.; Christova, N. [Inst. of Microbiology, Bulgarian Academy of Sciences, Sofia (Bulgaria); Jordanov, B.; Nikolova-Damyanova, B. [Inst. of Organic Chemistry, Sofia (Bulgaria); Petrov, P. [National Center of Infectious and Parasitic Diseases, Sofia (Bulgaria)

    2005-08-01

    Biosurfactant activity and naphthalene degradation by a new strain identified as Bacillus cereus 28BN were studied. The strain grew well and produced effective biosurfactants in the presence of n-alkanes, naphthalene, crude oil and vegetable oils. The biosurfactants were detected by the surface tension lowering of the medium, thin layer chromatography and infrared spectra analysis. With (2%) naphthalene as the sole carbon source, high levels of rhamnolipids at a concentration of 2.3 g l{sup -1} were determined in the stationary growth. After 20 d of incubation 72 {+-} 4% of the initial naphthalene was degraded. This is the first report for a Bacillus cereus rhamnolipid producing strain that utilized naphthalene under aerobic conditions. The strain looks promising for application in environmental technologies. (orig.)

  15. High-Pressure Design of Advanced BN-Based Materials.

    Science.gov (United States)

    Kurakevych, Oleksandr O; Solozhenko, Vladimir L

    2016-10-20

    The aim of the present review is to highlight the state of the art in high-pressure design of new advanced materials based on boron nitride. Recent experimental achievements on the governing phase transformation, nanostructuring and chemical synthesis in the systems containing boron nitride at high pressures and high temperatures are presented. All these developments allowed discovering new materials, e.g., ultrahard nanocrystalline cubic boron nitride (nano-cBN) with hardness comparable to diamond, and superhard boron subnitride B13N₂. Thermodynamic and kinetic aspects of high-pressure synthesis are described based on the data obtained by in situ and ex situ methods. Mechanical and thermal properties (hardness, thermoelastic equations of state, etc.) are discussed. New synthetic perspectives, combining both soft chemistry and extreme pressure-temperature conditions are considered.

  16. Process-Induced Carbon and Sub-Layer in SiC/BN/SiC Composites: Characterization and Consequences

    Science.gov (United States)

    Ogbuji, L. U. J. T; Wheeler, D. R.; McCue, T. R.

    2001-01-01

    Following our detection of films of elemental carbon in the Hi-Nicalon TM/BN/SiC composite and its deleterious effect on oxidative durability, we have examined other SiC/BN/SiC systems. The problem is pervasive, and significant residues of free carbon are confirmed in Sylramic /BN/SiC materials. Effective techniques for routine detection and characterization of adventitious carbon in SiC/BN/SiC composites are discussed.

  17. Optoelectronic properties of higher acenes, their BN analogue and substituted derivatives

    Energy Technology Data Exchange (ETDEWEB)

    Armaković, Stevan, E-mail: stevan.armakovic@df.uns.ac.rs [University of Novi Sad, Faculty of Sciences, Department of Physics, Trg Dositeja Obradovića 4, 21000, Novi Sad (Serbia); Armaković, Sanja J. [University of Novi Sad, Faculty of Sciences, Department of Chemistry, Biochemistry and Environmental Protection, Trg Dositeja Obradovića 3, 21000, Novi Sad (Serbia); Holodkov, Vladimir [Educons University, Faculty of Sport and Tourism - TIMS, Radnička 30a, 21000, Novi Sad (Serbia); Pelemiš, Svetlana [University of East Sarajevo, Faculty of Technology, Karakaj bb, 75400, Zvornik, Republic of Srpska, Bosnia and Herzegovina (Bosnia and Herzegovina)

    2016-02-15

    We have investigated optoelectronic properties of higher acenes: pentacene, hexacene, heptacene, octacene, nonacene, decacene and their boron-nitride (BN) analogues, within the framework of density functional theory (DFT). We have also investigated the optoelectronic properties of acenes modified by BN substitution. Calculated optoelectronic properties encompasses: oxidation and reduction potentials, electron and hole reorganization energies and energy difference between excited first singlet and triplet states ΔE(S{sub 1}−T{sub 1}). Oxidation and reduction potentials indicate significantly better stability of BN analogues, comparing with their all-carbon relatives. Although higher acenes possess lower electron and hole reorganization energies, with both best values much lower than 0.1 eV, their BN analogues also have competitive values of reorganization energies, especially for holes for which reorganization energy is also lower than 0.1 eV. On the other hand ΔE(S{sub 1}−T{sub 1}) is much better for BN analogues, having values that indicate that BN analogues are possible applicable for thermally activated delayed fluorescence. - Highlights: • Optoelectronic properties of structures based on higher acenes have been investigated. • Oxidation and reduction potentials together with reorganization energies are calculated. • TADF is analyzed through calculation of ΔE(S{sub 1}−T{sub 1}), which is much better for BN analogues. • Reorganization energies of acenes improve with the increase of number of benzene rings.

  18. Low frequency Raman spectroscopy of few-atomic-layer thick hBN crystals

    Science.gov (United States)

    Stenger, I.; Schué, L.; Boukhicha, M.; Berini, B.; Plaçais, B.; Loiseau, A.; Barjon, J.

    2017-09-01

    Hexagonal boron nitride (hBN) has recently gained a strong interest as a strategic component in engineering van der Waals heterostructures built with 2D crystals such as graphene. This work reports micro-Raman measurements on hBN flakes made of a few atomic layers, prepared by mechanical exfoliation. The temperature dependence of the Raman scattering in hBN is investigated first such as to define appropriate measurements conditions suitable for thin layers avoiding undesirable heating induced effects. We further focus on the low frequency Raman mode corresponding to the rigid shearing oscillation between adjacent layers, found to be equal to 52.5 cm-1 in bulk hBN. For hBN sheets with thicknesses below typically 4 nm, the frequency of this mode presents discrete values, which are found to decrease down to 46.0(5) cm-1 for a three-layer hBN, in good agreement with the linear-chain model. This makes Raman spectroscopy a relevant tool to quantitatively determine in a non destructive way the number of layers in ultra thin hBN sheets, below 8 L, prior to their integration in van der Waals heterostructures.

  19. Facile synthesis, microstructure and photophysical properties of core-shell nanostructured (SiCN)/BN nanocomposites

    Science.gov (United States)

    Zhang, Qian; Jia, Dechang; Yang, Zhihua; Cai, Delong; Laine, Richard M.; Li, Qian; Zhou, Yu

    2017-01-01

    Increasing structural complexity at nanoscale can permit superior control over photophysical properties in the precursor-derived semiconductors. We demonstrate here the synthesis of silicon carbonitride (SiCN)/boron nitride (BN) nanocomposites via a polymer precursor route wherein the cobalt polyamine complexes used as the catalyst, exhibiting novel composite structures and photophysical properties. High Resolution Transmission Electron Microscopy (HRTEM) analysis shows that the diameters of SiCN-BN core-shell nanocomposites and BN shells are 50‒400 nm and 5‒25 nm, respectively. BN nanosheets (BNNSs) are also observed with an average sheet size of 5‒15 nm. The photophysical properties of these nanocomposites are characterized using the UV-Vis and photoluminescence (PL) analyses. The as-produced composites have emission behavior including an emission lifetime of 2.5 ns (±20 ps) longer observed in BN doped SiCN than that seen for SiC nanoparticles. Our results suggest that the SiCN/BN nanocomposites act as semiconductor displaying superior width photoluminescence at wavelengths spanning the visible to near-infrared (NIR) spectral range (400‒700 nm), owing to the heterojunction of the interface between the SiC(N) nanowire core and the BN nanosheet shell.

  20. Graphene on h-BN: to align or not to align?

    Science.gov (United States)

    Guerra, Roberto; van Wijk, Merel; Vanossi, Andrea; Fasolino, Annalisa; Tosatti, Erio

    2017-06-29

    The contact strength, adhesion and friction, between graphene and an incommensurate crystalline substrate such as h-BN depends on their relative alignment angle θ. The well-established Novaco-McTague (NM) theory predicts for a monolayer graphene on a hard bulk h-BN crystal face a small spontaneous misalignment, here θNM ≃ 0.45 degrees which if realized would be relevant to a host of electronic properties besides the mechanical ones. Because experimental equilibrium is hard to achieve, we inquire theoretically about alignment or misalignment by simulations based on dependable state-of-the-art interatomic force fields. Surprisingly at first, we find compelling evidence for θ = 0, i.e., full energy-driven alignment in the equilibrium state of graphene on h-BN. Two factors drive this deviation from the NM theory. First, graphene is not flat, developing on h-BN a long-wavelength out-of-plane corrugation. Second, h-BN is not hard, releasing its contact stress by planar contractions/expansions that accompany the interface moiré structure. Repeated simulations by artificially forcing graphene to keep flat, and h-BN to keep rigid, indeed yield an equilibrium misalignment similar to θNM as expected. Subsequent sliding simulations show that friction of graphene on h-BN, small and essentially independent of misalignments in the artificial frozen state, strongly increases in the more realistic corrugated, strain-modulated, aligned state.

  1. P-BN/n-Si Heterojunction Prepared by Beryllium ion Implantation

    Institute of Scientific and Technical Information of China (English)

    HE Bin; CHEN Guang-Hua; LI Zhi-Zhong; DENG Jin-Xiang; ZHANG Wun-Jun

    2008-01-01

    A boron nitride(BN)/silicon p-n heterojunction is fabricated by implanting beryllium (Be) ions into the BN films deposited by rf sputtering on n-type Si(111)substrates.The FTIR observations indicate that the films deposited have a mixed phase composition of sp2-and sp3-hybridized BN.Considering the thickness of the BN layer.the ion implantation is conducted at an ion energy of 100ke V with the dose of 5×1015cm-2.After annealing at a high temperature,the surface resistance of the BN film decreases significantly by 6 orders down to 1.2×105Ω.Space-charge-limited current characteristic.which indicates the existence of shallow traps in the film,is observed.Current-voltage measurements across the BN film and the Si substrate reveal a clear rectification feature,demonstrating the achievement of p-type doping of BN films by Be ion implantation.

  2. Development of (Ti, Al)N coated cBN tool for ADI machining; ADI zai kakoyo (Ti, Al) N coated cBN kogu no kaihatsu

    Energy Technology Data Exchange (ETDEWEB)

    Shintani, K.; Sugiyama, H.; Kato, H. [Kanazawa Institute of Technology, Ishikawa (Japan); Goto, M. [Sumitomo Electric Industries, Ltd., Osaka (Japan)

    1998-06-25

    Concerning cBN tools used for machining austempered ductile cast iron (ADI), the effects of difference in the strength of cBN particles themselves on tool life and the tool life extending effects of a (Ti, Al)N coating formed on the tool surface are discussed. In the experiment, three kinds of tool materials, which are C60-F, C60-M, and C60-T, are prepared, which contain 60vol% cBN particles different in strength. The flank abrasion inhibiting effect of the coating is also studied. In this study, C60c and C20c tools are tested, built of parent materials containing 20% 1{mu}m T particles and 60% 3{mu}m T particles and coated by (Ti, Al)N. Some of the conclusions reached are outlined below. The strength of cBN particles present in the specimens exerts virtually no influence on the improvement of flank abrasion characteristics. In a tool provided with a (Ti, Al)N coating, some of the (Ti, Al)N coating is retained between the cutting face near the cutting edge and the flank lower edge, and this suppresses the progress of flank abrasion. A tool provided with a (Ti, Al)N coating has a life which is more than three times the life of uncoated cBN tools. 9 refs., 12 figs., 2 tabs.

  3. Characterization methods dedicated to nanometer-thick hBN layers

    Science.gov (United States)

    Schué, Léonard; Stenger, Ingrid; Fossard, Frédéric; Loiseau, Annick; Barjon, Julien

    2017-03-01

    Hexagonal boron nitride (hBN) has regained interest as a strategic component in graphene engineering and in van der Waals heterostructures built with two dimensional materials. It is crucial then, to handle reliable characterization techniques capable to assess the quality of structural and electronic properties of the hBN material used. We present here characterization procedures based on optical spectroscopies, namely cathodoluminescence and Raman, with the additional support of structural analysis conducted by transmission electron microscopy. We show the capability of optical spectroscopies to investigate and benchmark the optical and structural properties of various hBN thin layers sources.

  4. Microstructure Evolution of Ti/BN Powder Blend during Ball Milling and Heat Treatment

    Institute of Scientific and Technical Information of China (English)

    Jianlin LI; Keao HU; Yong ZHONG

    2001-01-01

    Ball milled Ti/BN composite powder was prepared by high energy ball milling for 40 h, using Ti and BN (the molar ratio of Ti/BN is 3:2) as starting materials. The as-milled composite powder consists of TiN, Ti and amorphous phase. TiN formed while the milled powder was annealed at 400℃. The heat treatment at 700℃ led to the formation of TiB2 and TiB. The nanocrystalline Ti and amorphous phase converted to TiN and TiB2 when the powder was heated to 1300℃.

  5. Sensitivity of BN nano-cages to caffeine and nicotine molecules

    Science.gov (United States)

    Soltani, Alireza; Baei, Mohammad T.; Tazikeh Lemeski, E.; Shahini, Malihe

    2014-12-01

    Adsorption of caffeine and nicotine molecules over B12N12 and B16N16 nano-cages were investigated by using first-principles calculations to define whether BN nano-cages are applicable for filtering or sensing caffeine and nicotine molecules. The chemisorption energy of nicotine molecule on BN nano-cages is very stronger than caffeine molecule. Upon the adsorption of caffeine and nicotine molecules, the electronic properties of the BN nano-cages can be significantly changed, being too much sensitized on the caffeine and nicotine adsorptions.

  6. Basic research on mechanism of BN inclusion in improving the machinability of steel

    Directory of Open Access Journals (Sweden)

    Ya-nan, Chen

    2014-12-01

    Full Text Available Boron nitride-added eco-friendly free cutting steel has recently drawn more and more attention. But, the mechanisms explaining the role of BN inclusions improving the machinability of steels is not very clear. In this investigation, the material removal mechanism for cutting of BN inclusions in steels is explored, using a combination of theoretical analysis and a series of experiments. First, the actual shape of BN inclusions is observed and the amount and distribution of BN inclusions is quantitatively analyzed. Subsequently, the cutting performance of the steel is determined by cutting experimental tests. Moreover, the micro mechanical properties and the material removal mechanisms for cutting of BN inclusions are investigated by means of nanoindentation. The results revealed that the BN inclusions are hexagonal and are uniformly distributed, their average content is 23.2 per unit area and their volume fraction is 0.51% in the steel with 74 ppm B and 180 ppm N. It is shown that BN inclusions can improve the cutting performance of steel significantly, and a model describing the material removal mechanism for cutting of BN inclusions is proposed. BN inclusions act as stress concentration source, lubrication and wrappage of hard particles.Los aceros de fácil mecanizado o corte libre con nitruro de boro agregado han despertado un gran interés. Sin embargo, aún no se han determinado los mecanismos que explican el papel de las inclusiones de BN en la mejora de la maquinabilidad de estos aceros. En este trabajo, se investigan los mecanismos de corte de las inclusiones BN en aceros mediante la combinación de un análisis teórico y una serie de experimentos. En primer lugar, se determina la morfología de las inclusiones BN y se analiza cuantitativamente la cantidad y distribución de las mismas. Posteriormente, el rendimiento de corte del acero se determina mediante ensayos de corte. Por otra parte, las propiedades mecánicas locales y los

  7. BnSGS3 Has Differential Effects on the Accumulation of CMV, ORMV and TuMV in Oilseed Rape

    Directory of Open Access Journals (Sweden)

    Quan Chen

    2015-07-01

    Full Text Available Virus diseases greatly affect oilseed rape (Brassica napus production. Investigating antiviral genes may lead to the development of disease-resistant varieties of oilseed rape. In this study, we examined the effects of the suppressor of gene silencing 3 in Brassica napus (BnSGS3, a putative antiviral gene with different genus viruses by constructing BnSGS3-overexpressing (BnSGS3-Ov and BnSGS3-silenced (BnSGS3-Si oilseed rape (cv. Zhongshuang No. 6 plants. These three viruses are Oilseed rape mosaic virus (ORMV, Turnip mosaic virus (TuMV and Cucumber mosaic virus (CMV. The native BnSGS3 expressed in all examined tissues with the highest expression in siliques. All three viruses induced BnSGS3 expression, but ORMV induced a dramatic increase in the BnSGS3-Ov plants, followed by TuMV and CMV. Upon inoculation with three different viruses, transcript abundance of BnSGS3 gene follows: BnSGS3-Ov > non-transgenic plants > BnSGS3-Si. The accumulation quantities of ORMV and TuMV exhibited a similar trend. However, CMV accumulation showed an opposite trend where virus accumulations were negatively correlated with BnSGS3 expression. The results suggest that BnSGS3 selectively inhibits CMV accumulation but promotes ORMV and TuMV accumulation. BnSGS3 should be used in different ways (up- and down-regulation for breeding virus-resistant oilseed rape varieties.

  8. Density functional theory study of BnC clusters.

    Science.gov (United States)

    Liu, Chunhui; Han, Peilin; Tang, Mingsheng

    2011-05-15

    B(n)C clusters (n = 3-10) were studied at the density functional theory (DFT) (B3LYP)/6-311G** level of theory. The calculations predicted that the most stable configurations of the B(n) C clusters are the (n + 1)-membered cyclic structures. For boron-carbon clusters, the configurations containing greater numbers of three-membered boron rings are more favorable, except for the B(7)C and B(9)C clusters. Through molecular orbital analysis of these B(n)C clusters, we have concluded that π-electron delocalization plays a crucial role in the stability of n + 1-membered cyclic structures. In this paper, the relative stability of each cluster is discussed based on their single atomic-binding energies. The capability of clusters to obtain or lose an electron was also discussed, based on their vertical electron detachment energies (VDEs), adiabatic electron detachment energies (ADEs), vertical electron affinities (VEAs) and adiabatic electron affinities (AEAs). Copyright © 2011 John Wiley & Sons, Ltd.

  9. Sepsis Patient Detection and Monitor Based on Auto-BN.

    Science.gov (United States)

    Jiang, Yu; Sha, Lui; Rahmaniheris, Maryam; Wan, Binhua; Hosseini, Mohammad; Tan, Pengliu; Berlin, Richard B

    2016-04-01

    Sepsis is a life-threatening condition caused by an inappropriate immune response to infection, and is a leading cause of elderly death globally. Early recognition of patients and timely antibiotic therapy based on guidelines improve survival rate. Unfortunately, for those patients, it is often detected late because it is too expensive and impractical to perform frequent monitoring for all the elderly. In this paper, we present a risk driven sepsis screening and monitoring framework to shorten the time of onset detection without frequent monitoring of all the elderly. Within this framework, the sepsis ultimate risk of onset probability and mortality is calculated based on a novel temporal probabilistic model named Auto-BN, which consists of time dependent state, state dependent property, and state dependent inference structures. Then, different stages of a patient are encoded into different states, monitoring frequency is encoded into the state dependent property, and screening content is encoded into different state dependent inference structures. In this way, the screening and monitoring frequency and content can be automatically adjusted when encoding the sepsis ultimate risk into the guard of state transition. This allows for flexible manipulation of the tradeoff between screening accuracy and frequency. We evaluate its effectiveness through empirical study, and incorporate it into existing medical guidance system to improve medical healthcare.

  10. Graphene/h-BN/ZnO van der Waals tunneling heterostructure based ultraviolet photodetector.

    Science.gov (United States)

    Wu, Zhiqian; Li, Xiaoqiang; Zhong, Huikai; Zhang, Shengjiao; Wang, Peng; Kim, Tae-ho; Kwak, Sung Soo; Liu, Cheng; Chen, Hongsheng; Kim, Sang-Woo; Lin, Shisheng

    2015-07-27

    We report a novel ultraviolet photodetector based on graphene/h-BN/ZnO van der Waals heterostructure. Graphene/ZnO heterostructure shows poor rectification behavior and almost no photoresponse. In comparison, graphene/h-BN/ZnO structure shows improved electrical rectified behavior and surprising high UV photoresponse (1350AW(-1)), which is two or three orders magnitude larger than reported GaN UV photodetector (0.2~20AW(-1)). Such high photoresponse mainly originates from the introduction of ultrathin two-dimensional (2D) insulating h-BN layer, which behaves as the tunneling layer for holes produced in ZnO and the blocking layer for holes in graphene. The graphene/h-BN/ZnO heterostructure should be a novel and representative 2D heterostructure for improving the performance of 2D materials/Semiconductor heterostructure based optoelectronic devices.

  11. Fabrication of TiB2 composite powders coated with BN by high speed airflow impact

    Institute of Scientific and Technical Information of China (English)

    FENG Cai-mei; WANG Wei-min; FU Zheng-yi

    2005-01-01

    TiB2 powders coated with BN were prepared by Hybridization System making use of dry impact blending method to achieve powder surface modification. Parameters of coating were analyzed and the most appropriate condition was summarized. Scan electron microscope of JSM-5610LV and transmission electron microscope of H600STEM/EDS were used to observe the microstructure of coated powders. Results show that treatment time, rotation speed, granularity ratio of TiB2 to BN, pretreatment of materials etc influence the coating results evidently.Mixing raw materials and coating with BN under the appropriate condition can get round TiB2/BN composite powder with smooth surface and compact coating layer.

  12. STUDY ON EROSION RESISTANCE PROPERTIES OF O'-SIALON-BN IN MOLTEN STEEL

    Institute of Scientific and Technical Information of China (English)

    Q. Zhen; W.Z. Ding; W.C. Li

    2001-01-01

    The erosion resistance properties of O'-Sialon-BN in molten steel are investigated in this work. According to experimental results and theoretical analysis, BN in O'Sialon-BN plays an important role in molten steel erosion resistance. And the erosion kinetics of the O'-Sialon-BN composites in molten steel is controlled by two stages:the first one is controlled by chemical reaction taking place on the interface; the second one is controlled by diffusion. The erosion surface of the materials is also investigated with fractal theory. The results show that the fractal dimensions of the erosion surface vary with erosion time from a linear way to parabolic way, which relates to the change of erosion mechanism from interface chemical reaction to diffusion.

  13. Probing a General Rule towards Thermodynamic Stabilities of Mono BN-doped Lower Polyenes.

    Science.gov (United States)

    Rouf, Alvi Muhammad; Wu, Jingjing; Zhu, Jun

    2017-03-02

    The BN-doped organic analogues are interesting as aliphatic amineboranes for hydrogen storage, precursors for aromatic borazines and adsorbent cage azaboranes. However, BN-doped aliphatic polyenes remained undeveloped. Herein, we perform theoretical calculations on two mono BN-doped aliphatic lower polyenes, 1,3-butadiene and 1,3,5-hexatriene. A general rule is proposed, i.e., isomers with terminal nitrogen and directly BN-connected, N-B(R), in particular, are of significant thermodynamic stability as compared with their inverse analogues (where boron is at the terminal position). The N-B(R) type isomers are found to be the most stable ones in both polyenes. Isomers with terminal B and N are of intermediate stability. Highly destabilized isomers are those with one terminal methylene group and one terminal heteroatom in the butadiene series, and two terminal methylene groups in the hexatriene series. Rules established here may lead researchers to synthesize isomers with particular thermodynamic stability.

  14. Nanoindentation of ultra-hard cBN films: A molecular dynamics study

    Science.gov (United States)

    Huang, Cheng; Peng, Xianghe; Fu, Tao; Zhao, Yinbo; Feng, Chao; Lin, Zijun; Li, Qibin

    2017-01-01

    Cubic Boron nitride (cBN) exhibits excellent mechanical properties including high strength, hardness and thermal resistance, etc. We optimized the parameters in the Tersoff interatomic potential for cBN based on its cohesive energy, lattice parameter, elastic constants, surface energy and stacking fault energy. We performed with molecular dynamics (MD) simulations the nanoindentation on the (001) and (111) surface of monocrystalline cBN thin films to study the deformation mechanisms and the effects of temperature and substrate orientation. It was found that during the indentation plastic deformation is mainly stress-induced slips of dislocations along {111} orientations. It was also found that the hardness of cBN depends strongly on temperature, and the capability of plastic deformation is enhanced with the increase of temperature.

  15. Ap( Bn,dV)上具有BT符号的Toeplitz算子%Toeplitz operators on Ap (Bn, dV) with symbol in BT

    Institute of Scientific and Technical Information of China (English)

    何莉; 曹广福

    2011-01-01

    研究了高维Bergman空间Ap(Bn,dV)(1 <p<∞)上具有BT符号的Toeplitz算子,利用Toeplitz算子的Berezin变换讨论了Toeplitz算子的有界性,得到了Ap(Bn,dV)上具有BT符号的Toeplitz算子的范数和本性范数的估计,推广了MIAO和ZHENG在Bergman空间LP(D,dA)上对具有BT符号的Toeplitz算子的范数和本性范数进行估计的结论.

  16. Radioactive waste from decommissioning of fast reactors (through the example of BN-800)

    Science.gov (United States)

    Rybin, A. A.; Momot, O. A.

    2017-01-01

    Estimation of volume of radioactive waste from operating and decommissioning of fast reactors is introduced. Preliminary estimation has shown that the volume of RW from decommissioning of BN-800 is amounted to 63,000 cu. m. Comparison of the amount of liquid radioactive waste derived from operation of different reactor types is performed. Approximate costs of all wastes disposal for complete decommissioning of BN-800 reactor are estimated amounting up to approx. 145 million.

  17. Band gap tunning in BN-doped graphene systems with high carrier mobility

    KAUST Repository

    Kaloni, T. P.

    2014-02-17

    Using density functional theory, we present a comparative study of the electronic properties of BN-doped graphene monolayer, bilayer, trilayer, and multilayer systems. In addition, we address a superlattice of pristine and BN-doped graphene. Five doping levels between 12.5% and 75% are considered, for which we obtain band gaps from 0.02 eV to 2.43 eV. We demonstrate a low effective mass of the charge carriers.

  18. Modeling Environmental Degradation of SiC/BN/SiC CMCs (Preprint)

    Science.gov (United States)

    2017-04-28

    display, or disclose the work. 14. ABSTRACT (Maximum 200 words ) Experimental data on the stress rupture behavior of SiC fiber based tows...oxygen and water from the environment through matrix cracks to internal fiber tows, the resulting oxidative loss of BN interphase, the oxidative...stress-rupture behavior of the CMCs or minicomposites. The models for oxidation and/or volatilization of BN and SiC by oxygen and water use

  19. Fabrication of AlN/BN bishell hollow nanofibers by electrospinning and atomic layer deposition

    Directory of Open Access Journals (Sweden)

    Ali Haider

    2014-09-01

    Full Text Available Aluminum nitride (AlN/boron nitride (BN bishell hollow nanofibers (HNFs have been fabricated by successive atomic layer deposition (ALD of AlN and sequential chemical vapor deposition (CVD of BN on electrospun polymeric nanofibrous template. A four-step fabrication process was utilized: (i fabrication of polymeric (nylon 6,6 nanofibers via electrospinning, (ii hollow cathode plasma-assisted ALD of AlN at 100 °C onto electrospun polymeric nanofibers, (iii calcination at 500 °C for 2 h in order to remove the polymeric template, and (iv sequential CVD growth of BN at 450 °C. AlN/BN HNFs have been characterized for their chemical composition, surface morphology, crystal structure, and internal nanostructure using X-ray photoelectron spectroscopy, scanning electron microscopy, transmission electron microscopy, energy dispersive X-ray spectroscopy, and selected area electron diffraction. Measurements confirmed the presence of crystalline hexagonal BN and AlN within the three dimensional (3D network of bishell HNFs with relatively low impurity content. In contrast to the smooth surface of the inner AlN layer, outer BN coating showed a highly rough 3D morphology in the form of BN nano-needle crystallites. It is shown that the combination of electrospinning and plasma-assisted low-temperature ALD/CVD can produce highly controlled multi-layered bishell nitride ceramic hollow nanostructures. While electrospinning enables easy fabrication of nanofibrous template, self-limiting reactions of plasma-assisted ALD and sequential CVD provide control over the wall thicknesses of AlN and BN layers with sub-nanometer accuracy.

  20. Bioinspired modification of h-BN for high thermal conductive composite films with aligned structure.

    Science.gov (United States)

    Shen, Heng; Guo, Jing; Wang, Hao; Zhao, Ning; Xu, Jian

    2015-03-18

    With the development of microelectronic technology, the demand of insulating electronic encapsulation materials with high thermal conductivity is ever growing and much attractive. Surface modification of chemical inert h-BN is yet a distressing issue which hinders its applications in thermal conductive composites. Here, dopamine chemistry has been used to achieve the facile surface modification of h-BN microplatelets by forming a polydopamine (PDA) shell on its surface. The successful and effective preparation of h-BN@PDA microplatelets has been confirmed by SEM, EDS, TEM, Raman spectroscopy, and TGA investigations. The PDA coating increases the dispersibility of the filler and enhances its interaction with PVA matrix as well. Based on the combination of surface modification and doctor blading, composite films with aligned h-BN@PDA are fabricated. The oriented fillers result in much higher in-plane thermal conductivities than the films with disordered structures produced by casting or using the pristine h-BN. The thermal conductivity is as high as 5.4 W m(-1) K(-1) at 10 vol % h-BN@PDA loading. The procedure is eco-friendly, easy handling, and suitable for the practical application in large scale.

  1. Preparation of BN/SiO2 ceramics by PIP method

    Institute of Scientific and Technical Information of China (English)

    WANG Jing; WEN Guang-wu; MENG Qing-chang

    2005-01-01

    The precursor infiltration and pyrolysis(PIP) method for preparation of BN/SiO2 composites was used to improve mechanical properties, dielectric properties and feasibility of high temperature dielectric parts with large dimensions and complex shapes. In the processing procedure, the porous BN ceramic matrix was first successfully prepared by compacting the mixed powders of B and BN and then sintering them at a certain temperature under normal pressure of N2.The polycarbosilane(PCS) solution was vacuum infiltrated into porous BN ceramics at the room temperature and then at 800 ℃ in the air to depolimerize out amorphous SiO2, and sintered further at 1 300 ℃ in N2 to get BN/SiO2 composites. The microstructure of materials was studied by means of X-ray diffraction and electron probe micro analysis. The thermo-decomposition mechanism of PCS was investigated by a TG-DTA and infrared (IR) spectrum analysis. The flexural strengths were measured by the three-point bending method. The dielectric constant and the loss tangent were measured by the wave-guide method. The results show BN/SiO2 composites were fabricated. The obtained composites posses a flexural strength of 61.9693.31 MPa, the dielectric constant in the range of 3.503.78 and the order of magnitude of the loss tangent at 10-3, which are good for the high temperature dielectric parts with large size and complex shapes.

  2. Structural and electronic properties of epitaxial multilayer h-BN on Ni(111) for spintronics applications.

    Science.gov (United States)

    Tonkikh, A A; Voloshina, E N; Werner, P; Blumtritt, H; Senkovskiy, B; Güntherodt, G; Parkin, S S P; Dedkov, Yu S

    2016-03-24

    Hexagonal boron nitride (h-BN) is a promising material for implementation in spintronics due to a large band gap, low spin-orbit coupling, and a small lattice mismatch to graphene and to close-packed surfaces of fcc-Ni(111) and hcp-Co(0001). Epitaxial deposition of h-BN on ferromagnetic metals is aimed at small interface scattering of charge and spin carriers. We report on the controlled growth of h-BN/Ni(111) by means of molecular beam epitaxy (MBE). Structural and electronic properties of this system are investigated using cross-section transmission electron microscopy (TEM) and electron spectroscopies which confirm good agreement with the properties of bulk h-BN. The latter are also corroborated by density functional theory (DFT) calculations, revealing that the first h-BN layer at the interface to Ni is metallic. Our investigations demonstrate that MBE is a promising, versatile alternative to both the exfoliation approach and chemical vapour deposition of h-BN.

  3. Initial stages of growth and the influence of temperature during chemical vapor deposition of sp{sup 2}-BN films

    Energy Technology Data Exchange (ETDEWEB)

    Chubarov, Mikhail; Pedersen, Henrik; Högberg, Hans; Henry, Anne, E-mail: anne.henry@liu.se [Department of Physics, Chemistry and Biology, Linköping University, SE-581 83 Linköping (Sweden); Czigány, Zsolt [Institute of Technical Physics and Materials Science, Centre for Energy Research of Hungarian Academy of Sciences, Konkoly-Thege Miklós út 29-33, H-1121 Budapest (Hungary)

    2015-11-15

    Knowledge of the structural evolution of thin films, starting by the initial stages of growth, is important to control the quality and properties of the film. The authors present a study on the initial stages of growth and the temperature influence on the structural evolution of sp{sup 2} hybridized boron nitride (BN) thin films during chemical vapor deposition (CVD) with triethyl boron and ammonia as precursors. Nucleation of hexagonal BN (h-BN) occurs at 1200 °C on α-Al{sub 2}O{sub 3} with an AlN buffer layer (AlN/α-Al{sub 2}O{sub 3}). At 1500 °C, h-BN grows with a layer-by-layer growth mode on AlN/α-Al{sub 2}O{sub 3} up to ∼4 nm after which the film structure changes to rhombohedral BN (r-BN). Then, r-BN growth proceeds with a mixed layer-by-layer and island growth mode. h-BN does not grow on 6H-SiC substrates; instead, r-BN nucleates and grows directly with a mixed layer-by-layer and island growth mode. These differences may be caused by differences in substrate surface temperature due to different thermal conductivities of the substrate materials. These results add to the understanding of the growth process of sp{sup 2}-BN employing CVD.

  4. Decomposition Pathway of Ammonia Borane on the Surface of nano-BN

    Energy Technology Data Exchange (ETDEWEB)

    Neiner, Doinita; Luedtke, Avery T; Karkamkar, Abhijeet J; Shaw, Wendy J; Wang, Julia; Browning, Nigel; Autrey, Thomas; Kauzlarich, Susan M

    2010-08-19

    Ammonia borane (AB) is under significant investigation as a possible hydrogen storage material. While many chemical additives have been demonstrated to have a significant positive effect on hydrogen release from ammonia borane, many provide additional complications in the regeneration cycle. Mechanically alloyed hexagonal BN (nano-BN) has been shown to facilitate the release of hydrogen from AB at lower temperature, with minimal induction time, less exothermically, and inert nano-BN may be easily removed during any regeneration of the spent AB. The samples were prepared by mechanically alloying AB with nano-BN. Raman spectroscopy indicates that the AB:nano-BN samples are physical mixtures of AB and h-BN. The release of hydrogen from AB:nano-BN mixtures as well as the decomposition products were characterized by 11B magic angle spinning (MAS) solid state NMR, TGA/DSC/MS with 15N labeled AB, and solution 11B NMR spectroscopy. The 11B MAS solid state NMR spectrum shows that diammonate of diborane (DADB) is present in the mechanically alloyed mixture, which drastically shortens the induction period for hydrogen release from AB. Analysis of the TGA/DSC/MS spectra using 15N labeled AB shows that all the borazine (BZ) produced in the reaction comes from AB and that increasing nano-BN surface area results in increased amounts of BZ. However, under high temperature, 150°C, isothermal conditions, the amount of BZ released was the same as for neat AB. High resolution transmission electron microscopy (HRTEM), selected area diffraction (SAD), and electron energy loss spectroscopy (EELS) of the initial and final nano-BN additive provide evidence for crystallinity loss but not significant chemical changes. The higher concentration of BZ observed for low temperature dehydrogenation of AB:nano-BN mixtures versus neat AB is attributed to a surface interaction that favors the formation of precursors which ultimately result in BZ

  5. Ab initio study of the structural, electronic and optical properties of BAs and BN compounds and BN{sub x}As{sub 1−x} alloys

    Energy Technology Data Exchange (ETDEWEB)

    Guemou, M., E-mail: guemoumhamed7@gmail.com [Engineering Physics Laboratory, Ibn Khaldoun University of Tiaret, Postbox 78-Zaaroura, 14000 Tiaret (Algeria); Abdiche, A.; Riane, R. [Applied Materials Laboratory, Research Center, University of Sidi Bel Abbes, 22000 Sidi Bel Abbes (Algeria); Khenata, R. [Laboratoire de Physique Quantique et de Modélisation Mathématique (LPQ3M), Département de Technologie, Université de Mascara, 29000 Mascara (Algeria)

    2014-03-01

    In this work, we present a density-functional theory study of structural, electronic and optical properties of BAs, BN binary compounds and their ternary BN{sub x}As{sub 1−x} solid solutions. The calculations are done by using the all-electron full potential linear augmented plane-wave method (FP-LAPW) as employed in WIEN2k code. For the exchange-correlation potential, local-density approximation (LDA) and generalized gradient approximation (GGA) have been used to calculate theoretical lattice parameters, bulk modulus, and its pressure derivative. The electronic band structure of these compounds have been calculated by using the above two approximations. We have also investigated in this article the density of state and the optical properties such as the dielectric function and the refractive index of BAs, BN and BN{sub 0.25}As{sub 0.75} compounds by using the above method. The results obtained for structural and electronic properties are compared with experimental data and other computational work. It has been found that the energy bands with all these approximations are similar except the band gap values. It has also been found that our results with LDA and GGA are in good agreement with other computational work wherever these are available.

  6. Electrical transport properties of (BN-rich hexagonal (BNC semiconductor alloys

    Directory of Open Access Journals (Sweden)

    M. R. Uddin

    2014-08-01

    Full Text Available The layer structured hexagonal boron nitride carbon semiconductor alloys, h-(BNC, offer the unique abilities of bandgap engineering (from 0 for graphite to ∼6.4 eV for h-BN and electrical conductivity control (from semi-metal for graphite to insulator for undoped h-BN through alloying and have the potential to complement III-nitride wide bandgap semiconductors and carbon based nanostructured materials. Epilayers of (BN-rich h-(BN1-x(C2x alloys were synthesized by metal-organic chemical vapor deposition (MOCVD on (0001 sapphire substrates. Hall-effect measurements revealed that homogeneous (BN-rich h-(BN1-x(C2x alloys are naturally n-type. For alloys with x = 0.032, an electron mobility of about 20 cm2/Vs at 650 °K was measured. X-ray photoelectron spectroscopy (XPS was used to determine the chemical composition and analyze chemical bonding states. Both composition and chemical bonding analysis confirm the formation of alloys. XPS results indicate that the carbon concentration in the alloys increases almost linearly with the flow rate of the carbon precursor (propane (C3H8 employed during the epilayer growth. XPS chemical bonding analysis showed that these MOCVD grown alloys possess more C-N bonds than C-B bonds, which possibly renders the undoped h-(BN1-x(C2x alloys n-type and corroborates the Hall-effect measurement results.

  7. Thermal Conductivity of Epoxy Resin Composites Filled with Combustion Synthesized h-BN Particles.

    Science.gov (United States)

    Chung, Shyan-Lung; Lin, Jeng-Shung

    2016-05-20

    The thermal conductivity of epoxy resin composites filled with combustion-synthesized hexagonal boron nitride (h-BN) particles was investigated. The mixing of the composite constituents was carried out by either a dry method (involving no use of solvent) for low filler loadings or a solvent method (using acetone as solvent) for higher filler loadings. It was found that surface treatment of the h-BN particles using the silane 3-glycidoxypropyltrimethoxysilane (GPTMS) increases the thermal conductivity of the resultant composites in a lesser amount compared to the values reported by other studies. This was explained by the fact that the combustion synthesized h-BN particles contain less -OH or active sites on the surface, thus adsorbing less amounts of GPTMS. However, the thermal conductivity of the composites filled with the combustion synthesized h-BN was found to be comparable to that with commercially available h-BN reported in other studies. The thermal conductivity of the composites was found to be higher when larger h-BN particles were used. The thermal conductivity was also found to increase with increasing filler content to a maximum and then begin to decrease with further increases in this content. In addition to the effect of higher porosity at higher filler contents, more horizontally oriented h-BN particles formed at higher filler loadings (perhaps due to pressing during formation of the composites) were suggested to be a factor causing this decrease of the thermal conductivity. The measured thermal conductivities were compared to theoretical predictions based on the Nielsen and Lewis theory. The theoretical predictions were found to be lower than the experimental values at low filler contents ( 60 vol %).

  8. Thermal Conductivity of Epoxy Resin Composites Filled with Combustion Synthesized h-BN Particles

    Directory of Open Access Journals (Sweden)

    Shyan-Lung Chung

    2016-05-01

    Full Text Available The thermal conductivity of epoxy resin composites filled with combustion-synthesized hexagonal boron nitride (h-BN particles was investigated. The mixing of the composite constituents was carried out by either a dry method (involving no use of solvent for low filler loadings or a solvent method (using acetone as solvent for higher filler loadings. It was found that surface treatment of the h-BN particles using the silane 3-glycidoxypropyltrimethoxysilane (GPTMS increases the thermal conductivity of the resultant composites in a lesser amount compared to the values reported by other studies. This was explained by the fact that the combustion synthesized h-BN particles contain less –OH or active sites on the surface, thus adsorbing less amounts of GPTMS. However, the thermal conductivity of the composites filled with the combustion synthesized h-BN was found to be comparable to that with commercially available h-BN reported in other studies. The thermal conductivity of the composites was found to be higher when larger h-BN particles were used. The thermal conductivity was also found to increase with increasing filler content to a maximum and then begin to decrease with further increases in this content. In addition to the effect of higher porosity at higher filler contents, more horizontally oriented h-BN particles formed at higher filler loadings (perhaps due to pressing during formation of the composites were suggested to be a factor causing this decrease of the thermal conductivity. The measured thermal conductivities were compared to theoretical predictions based on the Nielsen and Lewis theory. The theoretical predictions were found to be lower than the experimental values at low filler contents (< 60 vol % and became increasing higher than the experimental values at high filler contents (> 60 vol %.

  9. Vacuolar iron transporter BnMEB2 is involved in enhancing iron tolerance of Brassica napus

    Directory of Open Access Journals (Sweden)

    Wei Zhu

    2016-09-01

    Full Text Available Iron toxicity is a major nutrient disorder that severely affects crop development and yield. Vacuolar detoxification of metal stress is an important strategy for plants to survive and adapt to this adverse environment. Vacuolar iron transporter (VIT members are involved in this process and play essential roles in iron storage and transport. In this study, a rapeseed VIT gene BnMEB2 (BnaC07g30170D was identified. BnMEB2 is a homolog to Arabidopsis MEB2 (At5g24290 and acts as a detoxifier in vacuolar sequestration of divalent metal. Transient expression analysis revealed that BnMEB2 was localized to the vacuolar membrane. Q-PCR detection showed a high expression of BnMEB2 in mature (60-day-old leaves and could be obviously induced by exogenous iron stress in both roots and leaves. Over-expressed BnMEB2 in both Arabidopsis wild type and meb2 mutant seedlings resulted in greatly improved iron tolerability with no significant changes in the expression level of other vacuolar iron transporter genes. The mutant meb2 grew slowly and its root hair elongation was inhibited under high iron concentration condition while BnMEB2 over-expressed transgenic plants of the mutant restored the phenotypes with apparently higher iron storage in roots and dramatically increased iron content in the whole plant. Taken together, these results suggested that BnMEB2 was a VIT gene in rapeseed which was necessary for safe storage and vacuole detoxification function of excess iron to enhance the tolerance of iron toxicity. This research sheds light on a potentially new strategy for attenuating hazardous metal stress from environment and improving iron biofortification in Brassicaceae crops.

  10. Synthesis and characterization of cBN/WCCo composites obtained by the pulse plasma sintering (PPS) method

    Energy Technology Data Exchange (ETDEWEB)

    Michalski, A; Rosinski, M; Plocinska, M; Szawlowski, J, E-mail: mihalski@inmat.pw.edu.pl [Warsaw University of Technology, Faculty of Materials Science and Engineering, Warsaw (Poland)

    2011-10-29

    The cBN/cemented carbide containing 30vol% of cBN particles was produced using a mixture of a 6wt% Co added-WC powder, with a WC grain size of 0.4 {mu}m and a cBN powder with a grain size ranging from 4 to 40 {mu}m. The mixture was sintered to produce a plate, 20 mm in diameter, 3 mm thick. The sintering processes were conducted at temperature of 1100 deg. C under a load of 100 MPa. The phase composition, density, hardness and micro structure of the sintered parts thus obtained were examined. The fractures through the WCCo/cBN composite showed the cBN particles torn out from the cemented carbide matrix were only few, whereas most of them have cleaved along the fracture plane. This gives evidence that the bond at the WCCo/cBN interface is mechanically strong.

  11. Mechanical characterization of Si-C(O) fiber/SiC (CVI) matrix composites with a BN-interphase

    Energy Technology Data Exchange (ETDEWEB)

    Prouhet, S.; Camus, G.; Labrugere, C.; Guette, A. (Lab. des Composites Thermostructuraux, Pessac (France)); Martin, E. (Univ. de Bordeaux, Talence (France). Lab. de Genie Mechanique de l' IUT A)

    1994-03-01

    The mechanical behavior of three CVI-processed 2D woven SiC/BN/SiC composite materials with different initial BN interphase thicknesses has been investigated by means of tensile and impact tests. The results have established the efficiency of a BN interphase in promoting a nonlinear/noncatastrophic tensile behavior and high impact resistance. The effect of the initial BN interphase thickness on the resulting mechanical behavior has also been demonstrated. AES and TEM has revealed the presence of a SiO[sub 2]/C double layer at the BN/fiber interface, which might result from a decomposition undergone by the Si-C(O) Nicalon fiber during processing. It has been suggested that the influence of the initial BN interphase thickness on the mechanical properties of the composites results from both changes occurring in the composition and morphology of the interfacial zones and modifications of the interfacial forces due to accommodation of the radial residual clamping stress.

  12. Negative Refraction with Superior Transmission in Graphene-Hexagonal Boron Nitride (hBN) Multilayer Hyper Crystal

    OpenAIRE

    Ayed Al Sayem; Md. Masudur Rahman; Mahdy, M. R. C.; Ifat Jahangir; Md. Saifur Rahman

    2016-01-01

    In this article, we have theoretically investigated the performance of graphene-hexagonal Boron Nitride (hBN) multilayer structure (hyper crystal) to demonstrate all angle negative refraction along with superior transmission. hBN, one of the latest natural hyperbolic materials, can be a very strong contender to form a hyper crystal with graphene due to its excellence as a graphene-compatible substrate. Although bare hBN can exhibit negative refraction, the transmission is generally low due to...

  13. Fabrication of high thermal conductive Al-cBN ceramic sinters by high temperature high pressure method

    Science.gov (United States)

    Wang, P. F.; Li, Zh. H.; Zhu, Y. M.

    2011-05-01

    Al-cBN ceramic sinters were fabricated by sintering micro-powder mixture of Al and cBN under high temperature and high pressure condition. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), scanning electronic microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDS) elemental mapping analyses and laser flashing thermal conductivity measurements were performed to investigate the sintering properties and thermal conductivity of the Al-cBN ceramic sinters. XRD analysis revealed these Al-cBN ceramic sinters were composed of a large portion of cBN and of a small portion of AlN, and very little amount of AlB 12 and hBN. Formation of boundary phase resulted in the rapid densification of the sinters, as well as the increase of their relative density with increasing Al additions. The Al-cBN ceramic sinters have a maximum thermal conductivity of about 1.94 W/cm K at room temperature and a much higher value of about 2.04 W/cm K at 200 °C. Their high thermal conductivity over that of AlN-hBN composites promise Al-cBN ceramic sinters favorite candidates as high efficiency heat sink materials for wide band gap semiconductors.

  14. Layered Graphene-Hexagonal BN Nanocomposites: Experimentally Feasible Approach to Charge-Induced Switchable CO2 Capture.

    Science.gov (United States)

    Tan, Xin; Kou, Liangzhi; Smith, Sean C

    2015-09-07

    Recently, inducing negative charge density on hexagonal boron nitride (h-BN) has been predicted as an effective strategy for controllable, selective, and reversible CO2 capture. However, h-BN is a wide-gap semiconductor and it is not clear how to effectively induce the requisite negative charge density. In this paper, we employ first-principle calculations to propose hybrid h-BN-graphene (hybrid BN/G) nanosheets as an experimentally feasible strategy to induce charge on h-BN for charge-controlled CO2 capture. The results indicate that the charge density is effectively transferred from the graphene layer with high electronic mobility into the h-BN layer on the surface, regardless of the thickness of BN layers, such that CO2 capture/release can be simply controlled by switching on/off the charge states of hybrid BN/G system. In addition, these negatively charged hybrid BN/G are highly selective for separating CO2 from mixtures with CH4 , N2 , and/or H2 .

  15. CBT4BN versus CBTF2F: Comparison of Online versus Face-To-FaceTreatment for Bulimia Nervosa

    Science.gov (United States)

    Bulik, Cynthia M.; Marcus, Marsha D.; Zerwas, Stephanie; Levine, Michele D.; Hofmeier, Sara; Trace, Sara E.; Hamer, Robert M.; Zimmer, Benjamin; Moessner, Markus; Kordy, Hans

    2012-01-01

    Cognitive-behavioral therapy (CBT) is currently the “gold standard” for treatment of bulimia nervosa (BN), and is effective for approximately 40–60% of individuals receiving treatment; however, the majority of individuals in need of care do not have access to CBT. New strategies for service delivery of CBT and for maximizing maintenance of treatment benefits are critical for improving our ability to treat BN. This clinical trial is comparing an Internet-based version of CBT (CBT4BN) in which group intervention is conducted via therapeutic chat group with traditional group CBT (CBTF2F) for BN conducted via face-to-face therapy group. The purpose of the trial is to determine whether manualized CBT delivered via the Internet is not inferior to the gold standard of manualized group CBT. In this two-site randomized controlled trial, powered for non-inferiority analyses, 180 individuals with BN are being randomized to either CBT4BN or CBTF2F. We hypothesize that CBT4BN will not be inferior to CBTF2F and that participants will value the convenience of an online intervention. If not inferior, CBT4BN may be a cost-effective approach to service delivery for individuals requiring treatment for BN. PMID:22659072

  16. The Effect of Processing Parameters on the Performance of Spark Plasma Sintered cBN-WC-Co Composites

    Science.gov (United States)

    Mao, Cong; Zhang, Mingjun; Zhang, Jian; Tang, Kun; Gan, Hangyu; Zhang, Gaofeng

    2015-12-01

    Cubic boron nitride (cBN) particles were mixed into superfine tungsten carbide (WC), and then cBN-WC-cobalt (Co) composites were prepared using spark plasma sintering method. The influence of the processing parameters on the microstructures and the mechanical properties of the cBN-WC-Co composites were investigated. The results indicated that the cBN particles arranged uniformly and had an excellent adhesion with WC matrix. There was no evidence of phase transformation from cBN to hBN. With the increasing of the sintering temperature, the liquid-phase Co was increased and entered the micro-pores between WC and cBN particles easily. Correspondingly, the density, the flexural strength, and the hardness of the cBN-WC-Co composites also increased. With the further increasing of the sintering temperature, WC grains grew leading to the reduction of the hardness. Therefore, the hardness of the samples increased to a maximum value of 2978 HV at 1250 °C, and then decreased with the sintering temperature. The experimental results also showed that the density, the flexural strength, and the hardness of cBN-WC-Co composites increased with the holding time, whereas the hardness presented a decreasing tendency when the holding time exceeded 7 min.

  17. Identification of Thylakoid Membrane Protein Complexes by Using a BN-Chip/MS Approach

    Institute of Scientific and Technical Information of China (English)

    Longquan Fan; Yinghong Pan

    2012-01-01

    Thylakoid membrane protein complexes of wheat (Triticum aestivum Linn.)play crucial roles in growth and crop production.Knowledge of the composition and structure of protein complexes,as well as protein interactions,will result in a much deeper understanding of metabolic pathways and cellular processes than protein identities alone,especially if the complexes can be separated in the native forms.Whereas the analysis of membrane protein complexes is a significant challenge due to their hydrophobic properties and relatively low abundance.A rapid and efficient method of identifying membrane protein complexes will greatly facilitate the investigation of agriculture.The present work developed an BN-Chip/MS approach for exhaustive separation and identification of protein complexes,by combining using blue-native polyacrylamide gel electrophoresis (BN-PAGE) and chip-based high-performance liquid chromatography quadruple time-of-flight tandem mass spectrometry (HPLC-Chip/ESI-QT-OF-MS,Chip/MS).By using this approach,seventy-five nonredundant proteins of wheat thylakoid membrane complexes were identified from digested 13 bands of BN-gel.When the protocol of BN separation was not used,only 37 nonredundant proteins had been identified and among of them 9 proteins were uniquely identi? ed.This BN-Chip/MS approach is rapid and efficient for identifying protein complexes in wheat thylakoid membranes,and also providing reliable foundations for further functional research of wheat chloroplast and for identifying protein complexes of other species.

  18. Molecular self-assembly on graphene on SiO2 and h-BN substrates.

    Science.gov (United States)

    Järvinen, Päivi; Hämäläinen, Sampsa K; Banerjee, Kaustuv; Häkkinen, Pasi; Ijäs, Mari; Harju, Ari; Liljeroth, Peter

    2013-07-10

    One of the suggested ways of controlling the electronic properties of graphene is to establish a periodic potential modulation on it, which could be achieved by self-assembly of ordered molecular lattices. We have studied the self-assembly of cobalt phthalocyanines (CoPc) on chemical vapor deposition (CVD) grown graphene transferred onto silicon dioxide (SiO2) and hexagonal boron nitride (h-BN) substrates. Our scanning tunneling microscopy (STM) experiments show that, on both substrates, CoPc forms a square lattice. However, on SiO2, the domain size is limited by the corrugation of graphene, whereas on h-BN, single domain extends over entire terraces of the underlying h-BN. Additionally, scanning tunneling spectroscopy (STS) measurements suggest that CoPc molecules are doped by the substrate and that the level of doping varies from molecule to molecule. This variation is larger on graphene on SiO2 than on h-BN. These results suggest that graphene on h-BN is an ideal substrate for the study of molecular self-assembly toward controlling the electronic properties of graphene by engineered potential landscapes.

  19. Estrellas Bn: discontinuidad de Balmer; parámetros fundamentales y colores infrarrojos

    Science.gov (United States)

    Cochetti, Y. R.; Arias, M. L.; Cidale, L. S.; Granada, A.; Zorec, J.

    2015-08-01

    Bn stars are mainly main sequence objects with B spectral types, that display in their spectra broad hydrogen lines in absorption. This line broadening is originated by high rotational velocities. We know that high rotation is probably an essential factor in the development of the Be phenomenon: B stars with high rotational velocity and hydrogen lines in emission, which present an extended envelope. Thus, it is interesting to analyze Bn stars in a broader context, that includes Be stars, with the purpose of investigating their properties, the link between the formation of the envelopes and rotation, and the conditions which define the presence of emission lines. In this work we study a sample of 62 Bn star and 70 Be star spectra in the Balmer jump region. We analyze the presence and intensity of the second Balmer discontinuity, which reveals the existence of circumstellar material, its correlation with the projected rotational velocity, V sen(i), and the fundamental parameters of the stars. We also study the distribution of both groups in different infrared color-color diagrams, to generate methods to classify them in highly obscured regions. Our study suggests that Bn stars are the late counterpart of Be stars. The high projected rotational velocity, the spectral type distribution in both groups, and the presence of Bn stars with a second Balmer discontinuity in absorption, related with dense material close the photosphere, provide evidence that support this hypothesis.

  20. BN/BNSiO2 sputtering yield shape profiles under stationary plasma thruster operating conditions

    Directory of Open Access Journals (Sweden)

    M. Ranjan

    2016-09-01

    Full Text Available Quartz Crystal Microbalance (QCM is used to measure the volumetric and total sputtering yield of Boron Nitride (BN and Boron Nitride Silicon Dioxide (BNSiO2 bombarded by Xenon ions in the energy range of 100 eV to 550 eV. Sputtering yield shape profiles are reported at various angles of incidence 0-85° with surface normal and compared with modified Zhang model. The yield shape profile is found to be symmetric at normal incidence and asymmetric at oblique incidence. Both the materials show a sudden jump in the sputtering yield above 500 eV and at an angle of incidence in the range of 45-65°. Erosion of BN at as low as 74 eV ion energy is predicted using generalized Bohdansky model. BNSiO2 show a marginally higher sputtering yield compare to BN.

  1. First-Principles Studies on Properties of Boron-Related Impurities in c-BN

    Institute of Scientific and Technical Information of China (English)

    TIAN Fu-Bo; WANG Xiao-Li; MA Yan-Ming; CUI Tian; LIU Bing-Bing; ZOU Guang-Tian

    2009-01-01

    We investigate,by first-principles calculations,the pressure dependence of formation enthalpies and defective geometry and bulk modulus of boron-related impurities (VB,CB,NB,and OB ) with different charged states in cubic boron nitride (c-BN) using a supercell approach.It is found that the nitrogen atoms surrounding the defect relax inward in the case of CB,while the nitrogen atoms relax outward in the other cases.These boron-related impurities become much more stable and have larger concentration with increasing pressure.The impurity C+B1 is found to have the lowest formation enthalpy,make the material exhibit semiconductor characters and have the bulk modulus higher than ideal c-BN and than those in the cases of other impurities.Our results suggest that the hardness of c-BN may be strengthened when a carbon atom substitutes at a B site.

  2. Modulation of the electron transport properties in graphene nanoribbons doped with BN chains

    Directory of Open Access Journals (Sweden)

    Wu Liu

    2014-06-01

    Full Text Available Using density-functional theory and the non-equilibrium Green's function method, the electron transport properties of zigzag graphene nanoribbons (ZGNRs doped with BN chains are studied by systematically calculating the energy band structure, density of states and the transmission spectra for the systems. The BN chains destroyed the electronic transport properties of the ZGNRs, and an energy gap appeared for the ZGNRs, and displayed variations from a metal to a wide-gap semiconductor. With an increase in the number of BN chains, the band gap increased gradually in the band structure and the transmission coefficient decreased near the Fermi surface. Additionally, the doping position had a significant effect on the electronic properties of the ZGNRs.

  3. Interfacial characteristics of mullite fiber/BN coating/mullite matrix composites

    Energy Technology Data Exchange (ETDEWEB)

    Chawla, K.K.; Xu, Z.R.; Ha, J.S. [New Mexico Tech, Socorro, NM (United States)] [and others

    1994-12-31

    The interface in mullite fiber Nextel 480/mullite matrix was engineered by using a thick BN (1 {mu}m) coating on mullite fibers, such that deformation mechanisms conducive to toughness enhancement could be brought to play. Significant improvements in the mechanical properties of these mullite fiber/mullite matrix composites could be achieved by incorporation of BN interfacial coating and by using a colloidal processing route to make dense mullite matrix. An interfacial testing system with a flat-bottomed, diamond indenter was used to obtain the interface characteristics. Using a progressive debonding of the interface model, it was determined that the average interfacial frictional sliding shear stress in this composite was about 50 MPa. Fracture surfaces of these BN coated composites obtained in flexure test showed fiber pullout.

  4. The Stress Distribution and Thermal Behavior of TiBN and TiBN/TiN Coatings in Milling AISI H13 Work Tool Steel

    Institute of Scientific and Technical Information of China (English)

    YAN Hong; HUA Jiang; SHIVPURI Raja

    2005-01-01

    The FEM model of TiBN and TiBN/TiN coated cutting tool in milling of H13 steel was developed. Process variables such as temperature and stress in the coating layer as well as in the substrate were analyzed. The efficacy of the present FEM analysis was verified by conducting controlled milling experiments on AISI H13 to collect the relevant tool life and force data.The results show that the stress in a coated tool can significantly be reduced compared to an uncoated cutting tool,possibly due to surface coatings improving the tribological properties of cutting tools.Coatings with good thermal properties also help to improve the thermal behavior of cutting tool.

  5. Synthesis of O'-SiAlON-BN Composite by Reaction Sintering

    Institute of Scientific and Technical Information of China (English)

    ZHEN Qiang; YAN Kai; ZHANG Dahai; LI Wenchao

    2006-01-01

    By using micron α-Si3N4, SiO2, Al2O3 and h-BN as starting materials, O' -SiAlON-BN ( Si2-ZAlzO1+zN2-z, z = 0.3) composite was synthesized by reaction sintering. According to theoretical proportion ratio:n(SiO2)/n(α-Si3N4) = 1, the effects of two sintering aid comtosites, Y2O3+B2O3 and Y2O3+TiO2 at 1700℃ for 2h, were studied. The results indicate that Y2O3+TiO2 as sintering aid can accelerate reaction sintering of O'-SiAlON-BN more effectively than Y2O3+B2O3, and the relative density of the composites declined with the increase of BN addition (10%, 20% and30% respectively); XRD analysis found that excessive β-Si3N4 existed in the O' -SiAlON-BN composite. Therefore, in order to get more pure O' -SiAlON and BN phases in the composites ore SiO2 is needed. When Y2O3+TiO2 was used as sintering aid and addition of BN was 10%, the result of cross experiment on condition of A n(SiO2)/n(α-Si3N4) was 1.05, 1.1 and1.2; B addition of sintering aid was 2%, 4% and 6%; C firing temperature was 1600℃, 1650℃ and 1700℃ ;D-soaking time was 1h, 2h and 3h, shows that the sintering properties were influenced by factors of firing temperature, soaking time, addition of sintering aid and n(SiO2)/n(α-Si3N4) in order of importance. In addition, the technical parameter A3B3C3D3 can achieve the highest relative density. Besides, using Pattern Recognition method, the optimized parameter range to form pure O' -SiAlON and BN without β-Si3N4 remained was determined as Y > 1024X2 - 230.400X+11.088 ( X =0.9999A-0.0006C-0.0163D, Y =0.0163A +0.0009B -0.0014C+0.9999D).

  6. 单位球Bn上的Bohr不等式%Bohr's Inequality on the Unit Ball Bn

    Institute of Scientific and Technical Information of China (English)

    王建飞; 刘太顺

    2007-01-01

    Bohr's type inequalities are studied in this paper: if / is a holomorphic mapping from the unit ball Bn to B", /(O) = p, then we have ∞∑k=0|Dψp(P)[Dkf(0)(zk)]|k!||Dψp(p)||<1 for |z|< max{1/2+|p|,√1-|p|/2} and ψp ∈ Aut(Bn) such that ψp (p) = 0. As corollaries of theabove estimate, we obtain some sharp Bohr's type modulus inequalities. In particular, whenn=1 and |P| →1, then our theorem reduces to a classical result of Bohr.

  7. Near-band edge optical properties of exfoliated h-BN layers.

    OpenAIRE

    Loyza, J.; Barjon, J; Pierret, A.; Betz, A.; Placais, B.; Ducastelle, F.; Loiseau, A.

    2013-01-01

    Luminescence properties of h-BN are governed, in the energy range 5.5 { 6 eV, by strong Frenkel-type excitonic e ects, highly sensitive to structural defects [1-3]. Nowadays, BN meets a growing interest for graphene engineering. It is therefore highly desirable to better know optical and electronic properties of thin layers, in correlation with their structural properties. We carry out optical and structural characterizations of this material by combining CL at 4K in the UV range and TEM. Thi...

  8. B=N Units as Part of Extended π-Conjugated Oligomers and Polymers.

    Science.gov (United States)

    Helten, Holger

    2016-09-01

    The replacement of C=C units by their isoelectronic and isosteric B=N units (BN/CC isosterism) in π-conjugated organic compounds, as a strategy to produce novel organic-inorganic hybrid materials, has recently been successfully transferred to π-conjugated polymers. This Concept provides an overview of the recent advances in this quickly evolving field, with a focus on synthesis, photophysical and electrochemical properties of the new polymers and related oligomers, as well as possible future applications in organic electronics and optoelectronics.

  9. Exfoliated BN shell-based high-frequency magnetic core-shell materials.

    Science.gov (United States)

    Zhang, Wei; Patel, Ketan; Ren, Shenqiang

    2017-09-14

    The miniaturization of electric machines demands high frequency magnetic materials with large magnetic-flux density and low energy loss to achieve a decreased dimension of high rotational speed motors. Herein, we report a solution-processed high frequency magnetic composite (containing a nanometal FeCo core and a boron nitride (BN) shell) that simultaneously exhibits high electrical resistivity and magnetic permeability. The frequency dependent complex initial permeability and the mechanical robustness of nanocomposites are intensely dependent on the content of BN insulating phase. The results shown here suggest that insulating magnetic nanocomposites have potential for application in next-generation high-frequency electric machines with large electrical resistivity and permeability.

  10. Phonons and electron-phonon coupling in graphene-h-BN heterostructures

    Energy Technology Data Exchange (ETDEWEB)

    Slotman, Guus J.; Wijs, Gilles A. de; Fasolino, Annalisa; Katsnelson, Mikhail I. [Institute for Molecules and Materials, Radboud University Nijmegen (Netherlands)

    2014-10-15

    First principle calculations of the phonons of graphene-h-BN heterostructures are presented and compared to those of the constituents. It is shown that AA and AB' stacking are not only energetically less favoured than AB but also dynamically unstable. Low energy flat phonon branches of h-BN character with out of plane displacement have been identified and their coupling to electrons in graphene has been evaluated. (copyright 2014 by WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  11. Proper Motions of the BN Object and the I Radio Source in Orion: Where and When Did BN Become a Runaway Star?

    CERN Document Server

    Rodríguez, L F; Lizano, S; Allen, C; Rodriguez, Luis F.; Poveda, Arcadio; Lizano, Susana; Allen, Christine

    2005-01-01

    We present absolute astrometry of the core of the Orion molecular cloud, made with Very Large Array archive data taken over the last two decades. Our analysis reveals that both the BN object and the radio source I have proper motions: the BN object has a proper motion of $12.6 \\pm 0.6$ mas yr$^{-1}$ (corresponding to a velocity of $27 \\pm 1$ km s$^{-1}$ at an adopted distance of 450 pc) to the northwest, while the radio source I has a proper motion of $5.6 \\pm 0.7$ mas yr$^{-1}$ (corresponding to a velocity of $12 \\pm 2$ km s$^{-1}$) to the southeast. The motion of the two sources is nearly antiparallel, diverging from a point in between them, where they were located about 500 years ago. These results suggest that the BN object and the radio source I were part of a multiple young stellar system that disintegrated in the recent past.

  12. Divacancy-assisted transition metal adsorption on the BN graphene and its interaction with hydrogen molecules: a theoretical study

    Science.gov (United States)

    Chen, Ying; Wang, Hongmei; Wang, Hongxia; Zhao, Jing-xiang; Cai, Qing-hai; Wang, Xiao-Guang; Ding, Yi-hong

    2013-05-01

    We have performed first-principles calculations to study the chemical functionalization of the BN graphene with divacancy (DV) defect by 12 different transition metal (TM) atoms, including Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pt, and Au. The results indicate that the DV defect can assist the adsorption of TM atoms on BN graphene. Moreover, some impurity bands are induced within the band gap of DV-BN graphene, leading to the modification of its electronic properties in various ways. Interestingly, Ti- and Co-adsorbed DV-BN graphenes are found to possess ferromagnetic characteristic, while antiferromagnetic state is preferred for V-, Mn-, and Fe-functionalized DV-BN graphenes, and the paramagnetic state is the ground state for Sc-, Cr-, Ni-, Cu, Zn-, Pt-, and Au-decorated DV-BN graphenes. Finally, aiming at evaluating the potential of these functionalized BN graphenes in hydrogen storage, we study their interaction with H2 molecules. It is found that the dispersed Sc, V, and Cr on DV-BN graphene are able to adsorb up to three H2 molecules as strongly as 0.25-0.58 eV/H2, suggesting that the three nanomaterials may be suitable candidates for hydrogen storage.

  13. Divacancy-assisted transition metal adsorption on the BN graphene and its interaction with hydrogen molecules: a theoretical study

    Energy Technology Data Exchange (ETDEWEB)

    Chen, Ying; Wang, Hongmei; Wang, Hongxia [Key Laboratory for Photoelectric Bandgap Materials, Ministry of Education, Harbin Normal University, Harbin 150025 (China); Zhao, Jing-xiang, E-mail: xjz_hmily@yahoo.com.cn [Key Laboratory for Photoelectric Bandgap Materials, Ministry of Education, Harbin Normal University, Harbin 150025 (China); Cai, Qing-hai; Wang, Xiao-Guang [Key Laboratory for Photoelectric Bandgap Materials, Ministry of Education, Harbin Normal University, Harbin 150025 (China); Ding, Yi-hong, E-mail: yhdd@jlu.edu.cn [State Key Laboratory of Theoretical and Computational Chemistry, Institute of Theoretical Chemistry, Jilin University, Changchun 130023 (China)

    2013-05-15

    We have performed first-principles calculations to study the chemical functionalization of the BN graphene with divacancy (DV) defect by 12 different transition metal (TM) atoms, including Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Pt, and Au. The results indicate that the DV defect can assist the adsorption of TM atoms on BN graphene. Moreover, some impurity bands are induced within the band gap of DV-BN graphene, leading to the modification of its electronic properties in various ways. Interestingly, Ti- and Co-adsorbed DV-BN graphenes are found to possess ferromagnetic characteristic, while antiferromagnetic state is preferred for V-, Mn-, and Fe-functionalized DV-BN graphenes, and the paramagnetic state is the ground state for Sc-, Cr-, Ni-, Cu, Zn-, Pt-, and Au-decorated DV-BN graphenes. Finally, aiming at evaluating the potential of these functionalized BN graphenes in hydrogen storage, we study their interaction with H{sub 2} molecules. It is found that the dispersed Sc, V, and Cr on DV-BN graphene are able to adsorb up to three H{sub 2} molecules as strongly as 0.25–0.58 eV/H{sub 2}, suggesting that the three nanomaterials may be suitable candidates for hydrogen storage.

  14. Anticorrosive performance of waterborne epoxy coatings containing water-dispersible hexagonal boron nitride (h-BN) nanosheets

    Science.gov (United States)

    Cui, Mingjun; Ren, Siming; Chen, Jia; Liu, Shuan; Zhang, Guangan; Zhao, Haichao; Wang, Liping; Xue, Qunji

    2017-03-01

    Homogenous dispersion of hexagonal boron nitride (h-BN) nanosheets in solvents or in the polymer matrix is crucial to initiate their many applications. Here, homogeneous dispersion of hexagonal boron nitride (h-BN) in epoxy matrix was achieved with a water-soluble carboxylated aniline trimer derivative (CAT-) as a dispersant, which was attributed to the strong π-π interaction between h-BN and CAT-, as proved by Raman and UV-vis spectra. Transmission electron microscopy (TEM) analysis confirmed a random dispersion of h-BN nanosheets in the waterborne epoxy coatings. The deterioration process of water-borne epoxy coating with and without h-BN nanosheets during the long-term immersion in 3.5 wt% NaCl solution was investigated by electrochemical measurements and water absorption test. Results implied that the introduction of well dispersed h-BN nanosheets into waterborne epoxy system remarkably improved the corrosion protection performance to substrate. Moreover, 1 wt% BN/EP composite coated substrate exhibited higher impedance modulus (1.3 × 106 Ω cm2) and lower water absorption (4%) than those of pure waterborne epoxy coating coated electrode after long-term immersion in 3.5 wt% NaCl solution, demonstrating its superior anticorrosive performance. This enhanced anticorrosive performance was mainly ascribed to the improved water barrier property of epoxy coating via incorporating homogeneously dispersed h-BN nanosheets.

  15. 78 FR 28836 - Vulcan/BN Geothermal Power Company; Supplemental Notice That Initial Market-Based Rate Filing...

    Science.gov (United States)

    2013-05-16

    ... From the Federal Register Online via the Government Publishing Office DEPARTMENT OF ENERGY Federal Energy Regulatory Commission Vulcan/BN Geothermal Power Company; Supplemental Notice That Initial Market... in the above-referenced proceeding of Vulcan/BN Geothermal Power Company's application for...

  16. Generated photocatalytic performance of h-BN sheet by coupling with reduced graphene oxide/fluorid: A DFT study

    Science.gov (United States)

    Lu, Baichuan; Jia, Jun; Guo, Fengjuan; Li, Dongyang; Zhao, Yunhao; Zhao, Xian; Gao, Hongtao

    2017-09-01

    First-principles calculation based on density functional theory (DFT) was performed to investigate the enhanced photocatalytic mechanism and electronic properties of hexagonal boron nitride (h-BN) sheet by coupling with reduced graphene oxide (RGO) or reduced graphene fluorid (RGF). It is demonstrated that the combination of h-BN with RGO(F) is thermodynamically favorable. The spatial configurations of O and F atoms played a key role in modifying the electronic structure and properties of h-BN/RGO(F) composites. The interaction between h-BN and RGO(F) sheets caused charge accumulation on the side of h-BN layer and charge depletion on the lower side of RGO(F) sheet. There formed a heterjunction between the interface, which could improve the separation efficiency of photogenerated carriers and inhibit their combination. Both valence band edge and conduction band edge positions of h-BN/RGO(F) composites were characterized to illustrate the enhanced oxidation-reduction performance mechanism. The theoretical investigation could provide valuable information for thoroughly understanding the mechanism of the exceptional performance of h-BN/RGO(F) composites compared to the h-BN sheet.

  17. The modulation of Schottky barriers of metal-MoS2 contacts via BN-MoS2 heterostructures.

    Science.gov (United States)

    Su, Jie; Feng, Liping; Zhang, Yan; Liu, Zhengtang

    2016-06-22

    Using first-principles calculations within density functional theory, we systematically studied the effect of BN-MoS2 heterostructure on the Schottky barriers of metal-MoS2 contacts. Two types of FETs are designed according to the area of the BN-MoS2 heterostructure. Results show that the vertical and lateral Schottky barriers in all the studied contacts, irrespective of the work function of the metal, are significantly reduced or even vanish when the BN-MoS2 heterostructure substitutes the monolayer MoS2. Only the n-type lateral Schottky barrier of Au/BN-MoS2 contact relates to the area of the BN-MoS2 heterostructure. Notably, the Pt-MoS2 contact with n-type character is transformed into a p-type contact upon substituting the monolayer MoS2 by a BN-MoS2 heterostructure. These changes of the contact natures are ascribed to the variation of Fermi level pinning, work function and charge distribution. Analysis demonstrates that the Fermi level pinning effects are significantly weakened for metal/BN-MoS2 contacts because no gap states dominated by MoS2 are formed, in contrast to those of metal-MoS2 contacts. Although additional BN layers reduce the interlayer interaction and the work function of the metal, the Schottky barriers of metal/BN-MoS2 contacts still do not obey the Schottky-Mott rule. Moreover, different from metal-MoS2 contacts, the charges transfer from electrodes to the monolayer MoS2, resulting in an increment of the work function of these metals in metal/BN-MoS2 contacts. These findings may prove to be instrumental in the future design of new MoS2-based FETs with ohmic contact or p-type character.

  18. Dielectric Properties of Boron Nitride-Ethylene Glycol (BN-EG) Nanofluids

    Science.gov (United States)

    Fal, Jacek; Cholewa, Marian; Gizowska, Magdalena; Witek, Adam; ŻyŁa, GaweŁ

    2016-10-01

    This paper presents the results of experimental investigation of the dielectric properties of ethylene glycol (EG) with various load of boron nitride (BN) nanoparticles. The nanofuids were prepared by using a two-step method on the basis of commercially available BN nanoparticles. The measurements were carried out using the Concept 80 System (NOVOCONTROL Technologies GmbH & Co. KG, Montabaur, Germany) in a frequency range from 10 Hz to 10 MHz and temperatures from 278.15 K to 328.15 K. The frequency-dependent real (ɛ ^' } ) and imaginary (ɛ ^' ' } ) parts of the complex permittivity (ɛ ^* ) and the alternating current (AC) conductivity are presented. Also, the effect of temperature and mass concentrations on the dielectric properties of BN-EG nanofluids are demonstrated. The results show that the most significant increase can be achieved for 20 wt.% of BN nanoparticles at 283.15 K and 288.15 K, that is eleven times larger than in the case of pure EG.

  19. Excitonic recombinations in h-BN: From bulk to exfoliated layers

    Science.gov (United States)

    Pierret, A.; Loayza, J.; Berini, B.; Betz, A.; Plaçais, B.; Ducastelle, F.; Barjon, J.; Loiseau, A.

    2014-01-01

    Hexagonal boron nitride (h-BN) and graphite are structurally similar but with very different properties. Their combination in graphene-based devices is now of intense research focus, and it becomes particularly important to evaluate the role played by crystalline defects on their properties. In this paper, the cathodoluminescence (CL) properties of hexagonal boron nitride crystallites are reported and compared to those of nanosheets mechanically exfoliated from them. First, the link between the presence of structural defects and the recombination intensity of trapped excitons, the so-called D series, is confirmed. Low defective h-BN regions are further evidenced by CL spectral mapping (hyperspectral imaging), allowing us to observe new features in the near-band-edge region, tentatively attributed to phonon replicas of exciton recombinations. Second, the h-BN thickness was reduced down to six atomic layers, using mechanical exfoliation, as evidenced by atomic force microscopy. Even at these low thicknesses, the luminescence remains intense and exciton recombination energies are not strongly modified with respect to the bulk, as expected from theoretical calculations, indicating extremely compact excitons in h-BN.

  20. Ab initio study of Mn adsorption on w-BN(0 0 0 1) surface

    Energy Technology Data Exchange (ETDEWEB)

    Perez, W. Lopez [GFMC, Departamento de Matematicas y Fisica, Universidad del Norte, A. A. 1569, Barranquilla (Colombia)], E-mail: wlopez@uninorte.edu.co; Rodriguez Martinez, J.A.; Fajardo, F.; Cardona, R. [GEMA - Grupo de estudio de materiales, Departamento de Fisica, Universidad Nacional de Colombia, A. A. 5997, Bogota (Colombia)

    2008-07-15

    We have carried out total energy calculations to study the adsorption energy of Mn on w-BN(0 0 0 1) surface in a 2x2 structure. The surface is modeled using the repeated slabs approach. The calculation was performed solving the Kohn-Sham equation with a plane wave-pseudopotential approach and the generalized gradient approximation (GGA), using the Quantum-Espresso package. We find that with a Mn adatom, the w-BN(0 0 0 1) lateral surface relaxation was around some hundredth of A. To study the most favorable Mn adsorption configuration we considered T{sub 1}, T{sub 4} and H{sub 3} special points. We predict that the Mn-T{sub 4} structure is the most energetically favorable. We find that the adsorption of a Mn atom on top of a B atom (T{sub 1} site) is totally unfavorable. The calculated potential energy to describe the diffusion of a Mn atom on w-BN(0 0 0 1) shows an energy barrier of 0.708 eV. From the density of states with polarized spin we discuss the magnetic effect of Mn on w-BN(0 0 0 1) surface.

  1. Dielectric Properties of Boron Nitride-Ethylene Glycol (BN-EG) Nanofluids

    Science.gov (United States)

    Fal, Jacek; Cholewa, Marian; Gizowska, Magdalena; Witek, Adam; ŻyŁa, GaweŁ

    2017-02-01

    This paper presents the results of experimental investigation of the dielectric properties of ethylene glycol (EG) with various load of boron nitride (BN) nanoparticles. The nanofuids were prepared by using a two-step method on the basis of commercially available BN nanoparticles. The measurements were carried out using the Concept 80 System (NOVOCONTROL Technologies GmbH & Co. KG, Montabaur, Germany) in a frequency range from 10 Hz to 10 MHz and temperatures from 278.15 K to 328.15 K. The frequency-dependent real (ɛ ^' }) and imaginary (ɛ ^' ' }) parts of the complex permittivity (ɛ ^*) and the alternating current (AC) conductivity are presented. Also, the effect of temperature and mass concentrations on the dielectric properties of BN-EG nanofluids are demonstrated. The results show that the most significant increase can be achieved for 20 wt.% of BN nanoparticles at 283.15 K and 288.15 K, that is eleven times larger than in the case of pure EG.

  2. Using charged defects in BN to create rewritable graphene quantum dots and visualize quantum interference

    Science.gov (United States)

    Velasco, Jairo, Jr.

    Heterostructures of graphene and hexagonal boron nitride (BN) are highly tunable platforms that enable the study of novel physical phenomena and technologically promising nanoelectronic devices. Common control schemes employed in these studies are electrostatic gating and chemical doping. However, these methods have significant drawbacks, such as complicated fabrication processes that introduce contamination and irreversible changes to material properties, as well as a lack of flexible control. To address these problems we have developed a new method that employs light and/or electric field excitation to control defect charge (from the single impurity level to ensembles) in the underlying BN. We have used optoelectronic and scanning tunneling spectroscopy measurements to characterize these BN defects. We find that by manipulating defect charge in BN it is possible to create rewritable tip-induced doping patterns such as gate-tunable graphene pn junctions and quantum dots. This creates new opportunities for mapping the electronic states of confined electrons in graphene and to visualize their quantum interference behavior.

  3. Studies on BN rats model to determine the potential allergenicity of proteins from genetically modified foods

    Institute of Scientific and Technical Information of China (English)

    Xu-Dong Jia; Ning Li; Yong-Ning Wu; Xiao-Guang Yang

    2005-01-01

    AIM: To develop a Brown Norway (BN) rat model to determine the potential allergenicity of novel proteins in genetically modified food.METHODS: The allergenicity of different proteins were compared, including ovalbumin (OVA), a potent respiratory and food allergen, bovine serum albumin (BSA), a protein that is considered to have a lesser allergenic potential,and potato acid phosphatase (PAP), a non-allergenic protein when administered to BN rats via different routes of exposure (intraperitoneally or by gavage). IgG and IgE antibody responses were determined by ELISA and PCA,respectively. An immunoassay kit was used to determine the plasma histamine level. In addition, possible systemic effect of allergens was investigated by monitoring blood pressure.RESULTS: OVA provoked very vigorous protein-specific IgG and IgE responses, low grade protein-specific IgG and IgE responses were elicited by BSA, while by neither route did PAP elicit anything. In either routes of exposure,plasma histamine level in BN rats sensitized with OVA was higher than that of BSA or PAP. In addition, an oral challenge with BSA and PAP did not induce any effect on blood pressure, while a temporary drop in systolic blood pressure in few animals of each routes of exposure was found by an oral challenge with OVA.CONCLUSION: BN rat model might be a useful and predictive animal model to study the potential allergenicity of novel food proteins.

  4. Resolving the Structure and Kinematics of the BN Object at $0\\rlap.{"}2$ Resolution

    CERN Document Server

    Rodr{\\'\\i}guez, Luis F; Ho, Paul T P

    2008-01-01

    We present sensitive 7 mm observations of the H53$\\alpha$ recombination line and adjacent continuum, made toward the Orion BN/KL region. In the continuum we detect the BN object, the radio source I (GMR I) and the radio counterpart of the infrared source n (Orion-n). Comparing with observations made at similar angular resolutions but lower frequency, we discuss the spectral indices and angular sizes of these sources. In the H53$\\alpha$ line we only detect the BN object. This is the first time that radio recombination lines are detected from this source. The LSR radial velocity of BN from the H53$\\alpha$ line, $v_{LSR} = 20.1 \\pm 2.1$ km s$^{-1}$, is consistent with that found from previous studies in near-infared lines. While the continuum emission is expected to have considerable optical depth at 7 mm, the observed H53$\\alpha$ line emission is consistent with an optically-thin nature and we discuss possible explanations for this apparent discrepancy. There is evidence of a velocity gradient, with the NE part...

  5. Negative Refraction with Superior Transmission in Graphene-Hexagonal Boron Nitride (hBN) Multilayer Hyper Crystal

    Science.gov (United States)

    Sayem, Ayed Al; Rahman, Md. Masudur; Mahdy, M. R. C.; Jahangir, Ifat; Rahman, Md. Saifur

    2016-05-01

    In this article, we have theoretically investigated the performance of graphene-hexagonal Boron Nitride (hBN) multilayer structure (hyper crystal) to demonstrate all angle negative refraction along with superior transmission. hBN, one of the latest natural hyperbolic materials, can be a very strong contender to form a hyper crystal with graphene due to its excellence as a graphene-compatible substrate. Although bare hBN can exhibit negative refraction, the transmission is generally low due to its high reflectivity. Whereas due to graphene’s 2D nature and metallic characteristics in the frequency range where hBN behaves as a type-I hyperbolic material, we have found graphene-hBN hyper-crystals to exhibit all angle negative refraction with superior transmission. Interestingly, superior transmission from the whole structure can be fully controlled by the tunability of graphene without hampering the negative refraction originated mainly from hBN. We have also presented an effective medium description of the hyper crystal in the low-k limit and validated the proposed theory analytically and with full wave simulations. Along with the current extensive research on hybridization of graphene plasmon polaritons with (hyperbolic) hBN phonon polaritons, this work might have some substantial impact on this field of research and can be very useful in applications such as hyper-lensing.

  6. Negative Refraction with Superior Transmission in Graphene-Hexagonal Boron Nitride (hBN) Multilayer Hyper Crystal.

    Science.gov (United States)

    Sayem, Ayed Al; Rahman, Md Masudur; Mahdy, M R C; Jahangir, Ifat; Rahman, Md Saifur

    2016-05-05

    In this article, we have theoretically investigated the performance of graphene-hexagonal Boron Nitride (hBN) multilayer structure (hyper crystal) to demonstrate all angle negative refraction along with superior transmission. hBN, one of the latest natural hyperbolic materials, can be a very strong contender to form a hyper crystal with graphene due to its excellence as a graphene-compatible substrate. Although bare hBN can exhibit negative refraction, the transmission is generally low due to its high reflectivity. Whereas due to graphene's 2D nature and metallic characteristics in the frequency range where hBN behaves as a type-I hyperbolic material, we have found graphene-hBN hyper-crystals to exhibit all angle negative refraction with superior transmission. Interestingly, superior transmission from the whole structure can be fully controlled by the tunability of graphene without hampering the negative refraction originated mainly from hBN. We have also presented an effective medium description of the hyper crystal in the low-k limit and validated the proposed theory analytically and with full wave simulations. Along with the current extensive research on hybridization of graphene plasmon polaritons with (hyperbolic) hBN phonon polaritons, this work might have some substantial impact on this field of research and can be very useful in applications such as hyper-lensing.

  7. Recent advances in preparation, properties and device applications of two-dimensional h-BN and its vertical heterostructures

    Science.gov (United States)

    Yang, Huihui; Gao, Feng; Dai, Mingjin; Jia, Dechang; Zhou, Yu; Hu, Pingan

    2017-03-01

    Two-dimensional (2D) layered materials, such as graphene, hexagonal boron nitride (h-BN), molybdenum disulfide (MoS{}2 ), have attracted tremendous interest due to their atom-thickness structures and excellent physical properties. h-BN has predominant advantages as the dielectric substrate in FET devices due to its outstanding properties such as chemically inert surface, being free of dangling bonds and surface charge traps, especially the large-band-gap insulativity. h-BN involved vertical heterostructures have been widely exploited during the past few years. Such heterostructures adopting h-BN as dielectric layers exhibit enhanced electronic performance, and provide further possibilities for device engineering. Besides, a series of intriguing physical phenomena are observed in certain vertical heterostructures, such as superlattice potential induced replication of Dirac points, band gap tuning, Hofstadter butterfly states, gate-dependent pseudospin mixing. Herein we focus on the rapid developments of h-BN synthesis and fabrication of vertical heterostructures devices based on h-BN, and review the novel properties as well as the potential applications of the heterostructures composed of h-BN. Project supported by the National Natural Science Foundation of China (Nos. 61390502, 21373068), the National Basic Research Program of China (No. 2013CB632900), the Foundation for Innovative Research Groups of the National Natural Science Foundation of China (No. 51521003), and the Self-Planned Task of State Key Laboratory of Robotics and System (No. SKLRS201607B).

  8. Predicting crystal structures and physical properties of novel superhard p-BN under pressure via first-principles investigation

    Energy Technology Data Exchange (ETDEWEB)

    Long, Jianping, E-mail: longjianping@cdut.cn [College of Materials and Chemistry & Chemical Engineering, Chengdu University of Technology, Chengdu 610059 (China); Shu, Chaozhu [The Mineral Resources Chemistry Key Laboratory of Sichuan Higher Education Institutions, Chengdu University of Technology, Chengdu 610059 (China); Yang, Lijun; Yang, Mei [College of Materials and Chemistry & Chemical Engineering, Chengdu University of Technology, Chengdu 610059 (China)

    2015-09-25

    Graphical abstract: The minimum thermal conductivity as a function of pressure for p-BN. - Highlights: • First-principles calculations were carried out to investigate the physical properties of novel superhard p-BN under pressure. • The calculated Vicker’s hardness of p-BN was 55.4 GPa, which indicates that it is a superhard material. • The elastic constants, polycrystalline modulus and Debye temperature under pressure are obtained. • A new modified Clarke-type equation is used to calculate the minimum thermal conductivity. - Abstract: The first-principles calculations were carried out to investigate the electronic structure, elastic, hardness and thermodynamics properties of novel superhard p-BN under pressure. The calculated lattice parameters are in good agreement with previous theoretical results. The band structure, the density of states and the partial density of states are analyzed, which reveals the insulator character of p-BN. In addition, the elastic constants, polycrystalline modulus and Debye temperature under pressure are also successfully obtained. It is observed that the p-BN should be classified as brittle materials and possesses elastically anisotropic. The calculated Vicker’s hardness of p-BN was 55.4 GPa, which indicates that it is a superhard material. According to the calculated polycrystalline modulus, a new modified Clarke-type equation is used to calculate the minimum thermal conductivity. This work provides a useful guide for designing novel borides materials having excellent mechanical performance.

  9. Brassica napus L. Homeodomain Leucine-Zipper Gene BnHB6 Responds to Abiotic and Biotic Stresses

    Institute of Scientific and Technical Information of China (English)

    Shun-Wu YU; Li-Da ZHANG; Kai-Jing ZUO; Dong-Qin TANG; Xiao-Fen SUN; Ke-Xuan TANG

    2005-01-01

    Ahomeodomain leucine-zipper(HD-Zip) gene BnHB6 (GenBank accession No. AY336103) was isolated from oilseed rape (Brassica napus L.) following drought treatment through rapid amplification of cDNA ends (RACE). The full-length cDNA of BnHB6 was 1 611 bp and contained a 936-bp open reading frame encoding 311 amino acids. Sequence analysis indicated that BnHB6 belonged to the HD-Zip I subfamily.High-stringency Southern boltting analysis showed that BnHB6 appeared in rape as a single copy but had homologous genes. Semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) analysis revealed that BnHB6 was expressed in several tissues tested under control conditions, but that expression was significantly upregulated in shoots by mannitol, NaCl, cold treatment, anaerobic culture, wounding, H2O2, abscisic acid (ABA), and salicylic acid (SA) treatments, but not by ultraviolet treatment. Further RTPCR analysis revealed that BnHB6 was a late-responsive gene, the expression of which was not activated by NaCl, cold treatment, H2O2, ABA, and SA at an early time point (20 min) of treatment in the shoot. However, after a certain period of treatment, the induced expression culminated and then declined until the next peak occurred. Tissue-specific analysis revealed that BnHB6 was expressed at certain levels in the roots, shoots, and flowers, and the roots were found to respond to the osmotic stimuli more rapidly than shoots to increase the expression of BnHB6. The present study implies that BnHB6 plays a positive role as a regulator of biotic and abiotic stresses on growth during seedling establishment.

  10. BnSIP1-1, a Trihelix Family Gene, Mediates Abiotic Stress Tolerance and ABA Signaling in Brassica napus

    Science.gov (United States)

    Luo, Junling; Tang, Shaohua; Mei, Fengling; Peng, Xiaojue; Li, Jun; Li, Xiaofei; Yan, Xiaohong; Zeng, Xinhua; Liu, Fang; Wu, Yuhua; Wu, Gang

    2017-01-01

    The trihelix family genes have important functions in light-relevant and other developmental processes, but their roles in response to adverse environment are largely unclear. In this study, we identified a new gene, BnSIP1-1, which fell in the SIP1 (6b INTERACTING PROTEIN1) clade of the trihelix family with two trihelix DNA binding domains and a fourth amphipathic α-helix. BnSIP1-1 protein specifically targeted to the nucleus, and its expression can be induced by abscisic acid (ABA) and different stresses. Overexpression of BnSIP1-1 improved seed germination under osmotic pressure, salt, and ABA treatments. Moreover, BnSIP1-1 decreased the susceptibility of transgenic seedlings to osmotic pressure and ABA treatments, whereas there was no difference under salt stress between the transgenic and wild-type seedlings. ABA level in the transgenic seedlings leaves was higher than those in the control plants under normal condition. Under exogenous ABA treatment and mannitol stress, the accumulation of ABA in the transgenic plants was higher than that in the control plants; while under salt stress, the difference of ABA content before treatment was gradually smaller with the prolongation of salt treatment time, then after 24 h of treatment the ABA level was similar in transgenic and wild-type plants. The transcription levels of several general stress marker genes (BnRD29A, BnERD15, and BnLEA1) were higher in the transgenic plants than the wild-type plants, whereas salt-responsive genes (BnSOS1, BnNHX1, and BnHKT) were not significantly different or even reduced compared with the wild-type plants, which indicated that BnSIP1-1 specifically exerted different regulatory mechanisms on the osmotic- and salt-response pathways in seedling period. Overall, these findings suggested that BnSIP1-1 played roles in ABA synthesis and signaling, salt and osmotic stress response. To date, information about the involvement of the Brassica napus trihelix gene in abiotic response is scarce

  11. Formation and Physical Properties of h-BN Atomic Layers: A First-Principles Density-Functional Study

    Directory of Open Access Journals (Sweden)

    Yoshitaka Fujimoto

    2017-01-01

    Full Text Available Hexagonal boron nitride (h-BN atomic layers have attracted much attention as a potential device material for future nanoelectronics, optoelectronics, and spintronics applications. This review aims to describe the recent works of the first-principles density-functional study on h-BN layers. We show physical properties induced by introduction of various kinds of defects in h-BN layers. We further discuss the relationship among the defect size, the strain, and the magnetic as well as the electronic properties.

  12. In-situ epitaxial growth of graphene/h-BN van der Waals heterostructures by molecular beam epitaxy.

    Science.gov (United States)

    Zuo, Zheng; Xu, Zhongguang; Zheng, Renjing; Khanaki, Alireza; Zheng, Jian-Guo; Liu, Jianlin

    2015-10-07

    Van der Waals materials have received a great deal of attention for their exceptional layered structures and exotic properties, which can open up various device applications in nanoelectronics. However, in situ epitaxial growth of dissimilar van der Waals materials remains challenging. Here we demonstrate a solution for fabricating van der Waals heterostructures. Graphene/hexagonal boron nitride (h-BN) heterostructures were synthesized on cobalt substrates by using molecular beam epitaxy. Various characterizations were carried out to evaluate the heterostructures. Wafer-scale heterostructures consisting of single-layer/bilayer graphene and multilayer h-BN were achieved. The mismatch angle between graphene and h-BN is below 1°.

  13. Deposition of B{sub 4}C/BCN/c-BN multilayered thin films by r.f. magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Bejarano, G. [Laboratorio de Recubrimientos Duros del CDT-ASTIN SENA, Cali (Colombia); Caicedo, J.M. [Laboratorio de Recubrimientos Duros del CDT-ASTIN SENA, Cali (Colombia); Baca, E. [Departamento de Fisica, Universidad del Valle, A.A. 25360, Cali (Colombia); Prieto, P. [Departamento de Fisica, Universidad del Valle, A.A. 25360, Cali (Colombia)]. E-mail: pprieto@calima.univalle.edu.co; Balogh, A.G. [Institute for Material Science, Darmstadt University of Technology (Germany); Enders, S. [Max Plank Institute, Department of Material Research, Stuttgart (Germany)

    2006-01-03

    Thin films of cubic boron nitride (c-BN) and B{sub 4}C/BCN/c-BN multilayers, were deposited by r.f. (13.56 MHz) multi-target magnetron sputtering from high-purity (99.99%) h-BN and a (99.5%) B{sub 4}C targets, in an Ar (90%)/N{sub 2} (10%) gas mixture. Films were deposited onto silicon substrates with (100) orientations at 300 {sup o}C, with r.f. power density near 7 W/cm{sup 2}. In order to obtain the highest fraction of the c-BN phase, an r.f. substrate bias voltage between - 100 and - 300 V was applied during the initial nucleation process and - 50 to - 100 V during the film growth. Additionally, B{sub 4}C and BCN films were deposited and analyzed individually. For their deposition, we varied the bias voltage of the B{sub 4}C films between - 50 and - 250 V, and for the BCN coatings, the nitrogen gas flow from 3% to 12%. A 300-nm-thick TiN buffer layer was first deposited to improve the adhesion of all samples. X-ray diffraction patterns revealed the presence of c-BN (111) and h-BN phases. FTIR spectroscopy measurements indicate the presence of a peak at 780 cm{sup -} {sup 1} referred to as 'out-of-plane' h-BN vibration mode; another peak at 1100 cm{sup -} {sup 1} corresponds to the c-BN TO mode and the 'in-plane' vibration mode of the h-BN at 1400 cm{sup -} {sup 1}. BN films deposited at 300 deg. C at a pressure of 4.0 Pa and under - 150 V of nucleation r.f. bias, applied for 35 min, presented the highest c-BN fraction, near 85%. By using 32 layers, it was possible to deposit a 4.6-{mu}m-thick c-BN film with adequate mechanical properties and good adhesion to the substrate.

  14. The Influence of Nitrogen and Boron Implant into Silicon Substrate on the Phase and Internal Stress of c-BN Films

    Institute of Scientific and Technical Information of China (English)

    TAN Jun; CAI Zhi-hai; ZHANG Ping

    2004-01-01

    Cubic boron nitride(c-BN) film was deposited on a Si (100) substrate by the RF-magnetron sputtering.The mainly problems for fabrication of c-BN films are the low purity and high intrinsic compressive stress. In order to solve the two problems, the c-BN film with the buffer interlayer was deposited on the substrate which had been implanted with nitrogen and/or boron ions. The results show: the implantation of nitrogen ions can obviously increase c-BN content and reduce the internal stress slightly; while the implantation of boron shows no obvious improvement to the content of c-BN, which can reduce the internal stress in the film obviously. In addition, it is suggested that the implantation of nitrogen and boron shows the best result, which not only can increase the content of c-BN, but also reduce the internal stress in the c-BN film obviously.

  15. Pi and sigma double conjugations in boronyl polyboroene nanoribbons: Bn(BO)2- and Bn(BO)2 (n = 5-12)

    Science.gov (United States)

    Zhai, Hua-Jin; Chen, Qiang; Bai, Hui; Lu, Hai-Gang; Li, Wei-Li; Li, Si-Dian; Wang, Lai-Sheng

    2013-11-01

    A series of boron dioxide clusters, BxO2- (x = 7-14), have been produced and investigated using photoelectron spectroscopy and quantum chemical calculations. The dioxide clusters are shown to possess elongated ladder-like structures with two terminal boronyl (BO) groups, forming an extensive series of boron nanoribbons, Bn(BO)2- (n = 5-12). The electron affinities of Bn(BO)2 exhibit a 4n periodicity, indicating that the rhombic B4 unit is the fundamental building block in the nanoribbons. Both π and σ conjugations are found to be important in the unique bonding patterns of the boron nanoribbons. The π conjugation in these clusters is analogous to the polyenes (aka polyboroenes), while the σ conjugation plays an equally important role in rendering the stability of the nanoribbons. The concept of σ conjugation established here has no analogues in hydrocarbons. Calculations suggest the viability of even larger boronyl polyboroenes, B16(BO)2 and B20(BO)2, extending the boron nanoribbons to ˜1.5 nm in length or possibly even longer. The nanoribbons form a new class of nanowires and may serve as precursors for a variety of boron nanostructures.

  16. PREFACE: Ultrathin layers of graphene, h-BN and other honeycomb structures Ultrathin layers of graphene, h-BN and other honeycomb structures

    Science.gov (United States)

    Geber, Thomas; Oshima, Chuhei

    2012-08-01

    Since ancient times, pure carbon materials have been familiar in human society—not only diamonds in jewellery and graphite in pencils, but also charcoal and coal which have been used for centuries as fuel for living and industry. Carbon fibers are stronger, tougher and lighter than steel and increase material efficiency because of their lower weight. Today, carbon fibers and related composite materials are used to make the frames of bicycles, cars and even airplane parts. The two-dimensional allotrope, now called graphene, is just a single layer of carbon atoms, locked together in a strongly bonded honeycomb lattice. In plane, graphene is stiffer than diamond, but out-of-plane it is soft, like rubber. It is virtually invisible, may conduct electricity (heat) better than copper and weighs next to nothing. Carbon compounds with two carbon atoms as a base, such as graphene, graphite or diamond, have isoelectronic sister compounds made of boron-nitrogen pairs: hexagonal and cubic boron nitride, with almost the same lattice constant. Although the two 2D sisters, graphene and h-BN, have the same number of valence electrons, their electronic properties are very different: freestanding h-BN is an insulator, while charge carriers in graphene are highly mobile. The past ten years have seen a great expansion in studies of single-layer and few-layer graphene. This activity has been concerned with the π electron transport in graphene, in electric and magnetic fields. More than 30 years ago, however, single-layer graphene and h-BN on solid surfaces were widely investigated. It was noted that they drastically changed the chemical reactivity of surfaces, and they were known to 'poison' heterogeneous catalysts, to passivate surfaces, to prevent oxidation of surfaces and to act as surfactants. Also, it was realized that the controlled growth of h-BN and graphene on substrates yields the formation of mismatch driven superstructures with peculiar template functionality on the

  17. AIS-BN: An Adaptive Importance Sampling Algorithm for Evidential Reasoning in Large Bayesian Networks

    CERN Document Server

    Cheng, J; 10.1613/jair.764

    2011-01-01

    Stochastic sampling algorithms, while an attractive alternative to exact algorithms in very large Bayesian network models, have been observed to perform poorly in evidential reasoning with extremely unlikely evidence. To address this problem, we propose an adaptive importance sampling algorithm, AIS-BN, that shows promising convergence rates even under extreme conditions and seems to outperform the existing sampling algorithms consistently. Three sources of this performance improvement are (1) two heuristics for initialization of the importance function that are based on the theoretical properties of importance sampling in finite-dimensional integrals and the structural advantages of Bayesian networks, (2) a smooth learning method for the importance function, and (3) a dynamic weighting function for combining samples from different stages of the algorithm. We tested the performance of the AIS-BN algorithm along with two state of the art general purpose sampling algorithms, likelihood weighting (Fung and Chang...

  18. Atomistic simulations of pristine and defective hexagonal BN and SiC sheets under uniaxial tension

    Energy Technology Data Exchange (ETDEWEB)

    Le, Minh-Quy, E-mail: quy.leminh@hust.edu.vn [Department of Mechanics of Materials and Structures, School of Mechanical Engineering, Hanoi University of Science and Technology, No. 1, Dai Co Viet Road, Hanoi (Viet Nam); International Institute for Computational Science and Engineering, Hanoi University of Science and Technology, No. 1, Dai Co Viet Road, Hanoi (Viet Nam); Nguyen, Danh-Truong [Department of Mechanics of Materials and Structures, School of Mechanical Engineering, Hanoi University of Science and Technology, No. 1, Dai Co Viet Road, Hanoi (Viet Nam)

    2014-10-06

    The uniaxial tensile mechanical properties of pristine and defective hexagonal boron nitride (BN) and silicon carbide (SiC) sheets are investigated through a molecular dynamics finite element method with Tersoff and Tersoff-like potentials. 2-Atom vacancy and 2 types of Stone–Wales defects are considered. It is found that uniaxial tensile stress–strain curves of defective and pristine sheets are almost identical up to fracture points. A centered single defect reduces significantly fracture stress and fracture strain from those of the corresponding pristine sheet. In contrast, Young's modulus is nearly unchanged by a single defect. One 2-atom vacancy in the sheet's center reduces 15–18% and 16–25% in fracture stress, and 32–34% and 32–48% in fracture strain of BN and SiC sheets, respectively. Reduction in fracture properties depends on the tensile direction as well as the orientation of Stone–Wales defects.

  19. Polarity control of h-BN nanoribbon edges by strain and edge termination.

    Science.gov (United States)

    Yamanaka, Ayaka; Okada, Susumu

    2017-03-29

    We studied the polarity of h-BN nano-flakes in terms of their edge geometries, edge hydrogen termination, and uniaxial strain by evaluating their electrostatic potential using density functional theory. Our calculations have shown that the polarity of the nanoribbons is sensitive to their edge shape, edge termination, and uniaxial tensile strain. Polarity inversion of the ribbons can be induced by controlling the hydrogen concentration at the edges and the uniaxial tensile strain. The polarity inversion indicates that h-BN nanoribbons can exhibit non-polar properties at a particular edge hydrogen concentration and tensile strain, even though the nanoribbons essentially have polarity at the edge. We also found that the edge angle affects the polarity of nanoribbons with hydrogenated edges.

  20. Les collections cartographiques numérisées de la BnF

    Directory of Open Access Journals (Sweden)

    Olivier Loiseaux

    2005-04-01

    Full Text Available Depuis 1997 la Bibliothèque nationale de France (BnF propose en accès libre sur son site internet dans la rubrique Gallica de vastes collections de documents numérisés. Les fonds de Gallica, extraits de la vaste bibliothèque numérique de la BnF ont été choisis de manière à constituer une bibliothèque encyclopédique, centrée sur la culture francophone mais également pour permettre la découverte de ressources culturelles par le grand public. Ces fonds numérisés comprennent actuellement 70.000 ouvrages (21 millions de pages, 80.000 images et 500 documents sonores. Parmi les documents iconographiques, on recense entre 3500 et 4000 documents cartographiques.

  1. Ab initio calculations on twisted graphene/hBN: Electronic structure and STM image simulation

    Science.gov (United States)

    Correa, J. D.; Cisternas, E.

    2016-09-01

    By performing ab initio calculations we obtained theoretical scanning tunneling microscopy (STM) images and studied the electronic properties of graphene on a hexagonal boron-nitrite (hBN) layer. Three different stack configurations and four twisted angles were considered. All calculations were performed using density functional theory, including van der Waals interactions as implemented in the SIESTA ab initio package. Our results show that the electronic structure of graphene is preserved, although some small changes are induced by the interaction with the hBN layer, particularly in the total density of states at 1.5 eV under the Fermi level. When layers present a twisted angle, the density of states shows several van Hove singularities under the Fermi level, which are associated to moiré patterns observed in theoretical STM images.

  2. Effect of Si doping on the electronic properties of BN monolayer.

    Science.gov (United States)

    Gupta, Sanjeev K; He, Haiying; Banyai, Douglas; Si, Mingsu; Pandey, Ravindra; Karna, Shashi P

    2014-05-21

    The effect of Si doping on the stability, electronic structure, and electron transport properties of boron nitride (BN) monolayer has been investigated by density functional theory method. Unique features in the electron transport characteristics consisting of a significant enhancement of current at the Si site, diode-like asymmetric current-voltage response, and negative differential resistance are noted for the doped BN monolayer. These features are found to result from new "tunnel" channels induced by the substitutional Si atom near Fermi level in the band gap. The calculated position-projected tunneling currents providing scanning tunneling micrograph clearly discern the site-dependence of the Si atom and can be used to distinguish substitutional sites of atomic dopants in the monolayer.

  3. Tunable light-matter interaction and the role of hyperbolicity in graphene-hBN system

    CERN Document Server

    Kumar, Anshuman; Fung, Kin Hung; Avouris, Phaedon; Fang, Nicholas X

    2015-01-01

    Hexagonal boron nitride (hBN) is a natural hyperbolic material which can also accommodate highly dispersive surface phonon-polariton modes. In this paper, we examine theoretically the mid-infrared optical properties of graphene-hBN heterostructures derived from their coupled plasmon-phonon modes. We found that the graphene plasmon couples differently with the phonons of the two Reststrahlen bands, owing to their different hyperbolicity. This also leads to distinctively different interaction between an external quantum emitter and the plasmon-phonon modes in the two bands, leading to substantial modification of its spectrum. The coupling to graphene plasmons allows for additional gate tunability in the Purcell factor, and narrow dips in its emission spectra.

  4. Temperature dependence of Raman-active phonons and anharmonic interactions in layered hexagonal BN

    Science.gov (United States)

    Cuscó, Ramon; Gil, Bernard; Cassabois, Guillaume; Artús, Luis

    2016-10-01

    We present a Raman scattering study of optical phonons in hexagonal BN for temperatures ranging from 80 to 600 K. The experiments were performed on high-quality, single-crystalline hexagonal BN platelets. The observed temperature dependence of the frequencies and linewidths of both Raman active E2 g optical phonons is analyzed in the framework of anharmonic decay theory, and possible decay channels are discussed in the light of density-functional theory calculations. With increasing temperature, the E2g high mode displays strong anharmonic interactions, with a linewidth increase that indicates an important contribution of four-phonon processes and a marked frequency downshift that can be attributed to a substantial effect of the four-phonon scattering processes (quartic anharmonicity). In contrast, the E2g low mode displays a very narrow linewidth and weak anharmonic interactions, with a frequency downshift that is primarily accounted for by the thermal expansion of the interlayer spacing.

  5. Clifford groups of quantum gates, BN-pairs and smooth cubic surfaces

    Energy Technology Data Exchange (ETDEWEB)

    Planat, Michel [Institut FEMTO-ST, CNRS, 32 Avenue de l' Observatoire, F-25044 Besancon (France); Sole, Patrick [CNRS I3S, Les Algorithmes, Euclide B, 2000 route des Lucioles, BP 121, 06903 Sophia Antipolis (France)

    2009-01-30

    The recent proposal (Planat and Kibler 2008 arXiv:0807.3650 [quant-ph]) of representing Clifford quantum gates in terms of unitary reflections is revisited. In this communication, the geometry of a Clifford group G is expressed as a BN-pair, i.e. a pair of subgroups B and N that generate G, is such that intersection H = B intersection N is normal in G, the group W = N/H is a Coxeter group and two extra axioms are satisfied by the double cosets acting on B. The BN-pair used in this decomposition relies on the swap and match gates already introduced for classically simulating quantum circuits (Jozsa and Miyake 2008 arXiv:0804.4050 [quant-ph]). The two- and three-qubit cases are related to the configuration with 27 lines on a smooth cubic surface. (fast track communication)

  6. 2D Heterostructure coatings of hBN-MoS2 layers for corrosion resistance

    Science.gov (United States)

    Vandana, Sajith; Kochat, Vidya; Lee, Jonghoon; Varshney, Vikas; Yazdi, Sadegh; Shen, Jianfeng; Kosolwattana, Suppanat; Vinod, Soumya; Vajtai, Robert; Roy, Ajit K.; Sekhar Tiwary, Chandra; Ajayan, P. M.

    2017-02-01

    Heterostructures of atomically thin 2D materials could have improved physical, mechanical and chemical properties as compared to its individual components. Here we report, the effect of heterostructure coatings of hBN and MoS2 on the corrosion behavior as compared to coatings employing the individual 2D layer compositions. The poor corrosion resistance of MoS2 (widely used as wear resistant coating) can be improved by incorporating hBN sheets. Depending on the atomic stacking of the 2D sheets, we can further engineer the corrosion resistance properties of these coatings. A detailed spectroscopy and microscopy analysis has been used to characterize the different combinations of layered coatings. Detailed DFT based calculation reveals that the effect on the electrical properties due to atomic stacking is one of the major reasons for the improvement seen in corrosion resistance.

  7. Energy Bandgap and Edge States in an Epitaxially Grown Graphene/h-BN Heterostructure.

    Science.gov (United States)

    Hwang, Beomyong; Hwang, Jeongwoon; Yoon, Jong Keon; Lim, Sungjun; Kim, Sungmin; Lee, Minjun; Kwon, Jeong Hoon; Baek, Hongwoo; Sung, Dongchul; Kim, Gunn; Hong, Suklyun; Ihm, Jisoon; Stroscio, Joseph A; Kuk, Young

    2016-08-09

    Securing a semiconducting bandgap is essential for applying graphene layers in switching devices. Theoretical studies have suggested a created bulk bandgap in a graphene layer by introducing an asymmetry between the A and B sub-lattice sites. A recent transport measurement demonstrated the presence of a bandgap in a graphene layer where the asymmetry was introduced by placing a graphene layer on a hexagonal boron nitride (h-BN) substrate. Similar bandgap has been observed in graphene layers on metal substrates by local probe measurements; however, this phenomenon has not been observed in graphene layers on a near-insulating substrate. Here, we present bulk bandgap-like features in a graphene layer epitaxially grown on an h-BN substrate using scanning tunneling spectroscopy. We observed edge states at zigzag edges, edge resonances at armchair edges, and bandgap-like features in the bulk.

  8. Energy Bandgap and Edge States in an Epitaxially Grown Graphene/h-BN Heterostructure

    Science.gov (United States)

    Hwang, Beomyong; Hwang, Jeongwoon; Yoon, Jong Keon; Lim, Sungjun; Kim, Sungmin; Lee, Minjun; Kwon, Jeong Hoon; Baek, Hongwoo; Sung, Dongchul; Kim, Gunn; Hong, Suklyun; Ihm, Jisoon; Stroscio, Joseph A.; Kuk, Young

    2016-08-01

    Securing a semiconducting bandgap is essential for applying graphene layers in switching devices. Theoretical studies have suggested a created bulk bandgap in a graphene layer by introducing an asymmetry between the A and B sub-lattice sites. A recent transport measurement demonstrated the presence of a bandgap in a graphene layer where the asymmetry was introduced by placing a graphene layer on a hexagonal boron nitride (h-BN) substrate. Similar bandgap has been observed in graphene layers on metal substrates by local probe measurements; however, this phenomenon has not been observed in graphene layers on a near-insulating substrate. Here, we present bulk bandgap-like features in a graphene layer epitaxially grown on an h-BN substrate using scanning tunneling spectroscopy. We observed edge states at zigzag edges, edge resonances at armchair edges, and bandgap-like features in the bulk.

  9. Modulating the spin transport behaviors in ZBNCNRs by edge hydrogenation and position of BN chain

    Directory of Open Access Journals (Sweden)

    Jun Ouyang

    2016-03-01

    Full Text Available Using the density functional theory and the nonequilibrium Green’s function method, we study the spin transport behaviors in zigzag boron-nitrogen-carbon nanoribbons (ZBNCNRs by modulating the edge hydrogenation and the position of B-N nanoribbons (BNNRs chain. The different edge hydrogenations of the ZBNCNRs and the different position relationships of the BNNRs have been considered systematically. Our results show that the metallic, semimetallic and semiconductive properties of the ZBNCNRs can be modulated by the different edge hydrogenations and different position relationships of BN chains. And our proposaled ZBNCNRs devices act as perfect spin-filters with nearly 100% spin polarization. These effects would have potential applications for boron-nitrogen-carbon-based nanomaterials in spintronics nano-devices.

  10. Formation, structure, and properties of "welded" h-BN/graphene compounds

    Science.gov (United States)

    Chernozatonskii, L. A.; Demin, V. A.; Artyukh, A. A.

    2016-07-01

    Structures of h-BN/graphene with holes where atoms at the edges are bonded to each other by sp 2 hybridized C-B and C-N bonds and form continuous junctions from layer to layer with topological defects inside holes have been considered. Their formation, as well as the moiré-type stable atomic structure of such compounds (with different rotation angles of graphene with respect to the hexagonal boron nitride monolayer) with closed hexagonal holes in the AA centers of packing of the moiré superlattice, has been studied. The stability, as well as the electronic and mechanical properties, of such bilayer BN/graphene nanomeshes has been analyzed within electron density functional theory. It has been shown that they have semiconducting properties. Their electronic band structures and mechanical characteristics differ from the respective properties of separate monolayer nanomeshes with the same geometry and arrangement of holes.

  11. First principles study on defectives BN nanotubes for water splitting and hydrogen storage

    Science.gov (United States)

    Bevilacqua, Andressa C.; Rupp, Caroline J.; Baierle, Rogério J.

    2016-06-01

    First principles calculations within the spin polarized density functional approximation have been addressed to investigate the energetic stability, electronic and optical properties of defective BN nanotubes. Our results show that the presence of carbon impurities interacting with vacancies gives rise to defective electronic levels inside the nanotube band gap. By calculating the absorbance index, we have obtained a strong inter-band optical absorption in the visible region (around 2.1 eV) showing that defective BN nanotubes could be an efficient catalytic semiconductor material to be used within solar energy for water splitting. In addition, we observe that the adsorption energy for one and two H2 molecules on the defective surface is in the desired window for the system to be useful as a hydrogen storage medium.

  12. Role of Plasma Temperature and Residence Time in Stagnation Plasma Synthesis of c-BN Nanopowders

    Science.gov (United States)

    2013-01-01

    critical compressive stress model based off of sub- plantation , which in the energy range of thin film technology, ions loose energy by nuclear...interstitial positions. Lower energy species, however, stick to the outer surface and form sp 2 bonded sites. A thermal spike is seen for a very short ...temperature of 350°C, which produced ~98% c- BN. Uchida et al. 14 used a substrate at room temperature during an IVD process. The substrate was rotated

  13. Preparation and Biological Evaluation of 18F-AlF-NOTA-Bn-c(RGDfK)

    Institute of Scientific and Technical Information of China (English)

    SHI; Cui-yan; JIA; Bing; GUO; Fei-hu; YANG; Yun; CUI; Hai-ping

    2012-01-01

    <正>RGD antagonistie peptide radiolabelled by positron-emitting radionuclides, could be used as a image tracer for tumor diagnosis. The purpose of this research was to synthesis 18F-AlF-NOTA-Bn-c(RGDfK) through one-pot radio-chemical procedure. After that, we investigated the biological evaluation of this conjugate and its imaging feasibility on αvβ3 expressing tumors. The radiochemical purity was measured

  14. Phonovoltaic. III. Electron-phonon coupling and figure of merit of graphene:BN

    Science.gov (United States)

    Melnick, Corey; Kaviany, Massoud

    2016-12-01

    The phonovoltaic cell harvests optical phonons like a photovoltaic harvests photons, that is, a nonequilibrium (hot) population of optical phonons (at temperature Tp ,O) more energetic than the band gap produces electron-hole pairs in a p -n junction, which separates these pairs to produce power. A phonovoltaic material requires an optical phonon mode more energetic than its band gap and much more energetic than the thermal energy (Ep ,O>Δ Ee ,g≫kBT ), which relaxes by generating electrons and power (at rate γ˙e -p) rather than acoustic phonons and heat (at rate γ˙p -p). Graphene (h-C) is the most promising material candidate: when its band gap is tuned to its optical phonon energy without greatly reducing the electron-phonon (e -p ) coupling, it reaches a substantial figure of merit [ZpV=Δ Ee ,gγ˙e -p/Ep ,O(γ˙e -p+γ˙p -p) ≈0.8 ] . A simple tight-binding (TB) model presented here predicts that lifting the sublattice symmetry of graphene in order to open a band gap proscribes the e -p interaction at the band edge, such that γ˙e -p→0 as Δ Ee ,g→Ep ,O . However, ab initio (DFT-LDA) simulations of layered h-C/BN and substitutional h-C:BN show that the e -p coupling remains substantial in these asymmetric crystals. Indeed, h-C:BN achieves a high figure of merit (ZpV≈0.6 ). At 300 K and for a Carnot limit of 0.5 (Tp ,O=600 K) , a h-C:BN phonovoltaic can reach an efficiency of ηpV≈0.2 , double the thermoelectric efficiency (Z T ≈1 ) under similar conditions.

  15. Structure of TiBN coatings deposited onto cemented carbides and sialon tool ceramics

    OpenAIRE

    L.A. Dobrzański; M. Staszuk; J. Konieczny; W. Kwaśny; M. Pawlyta

    2009-01-01

    Purpose: The aim of this paper was investigated structure of sintered carbides WC-Co type and sialon tool ceramics with wear resistance ternary coatings TiBN type deposited by cathodes arc evaporation process (CAE-PVD).Design/methodology/approach: Observation of fracture and topography studied coatings were done by scanning electron microscope. Chemical composition was determine by energy dispersive spectrometry (EDS) method. Thin foils of substrates and coatings by transmission electron micr...

  16. When Harry met Sally: different approaches towards Uber and AirBnB—an Australian and Singapore perspective

    National Research Council Canada - National Science Library

    Tham, Aaron

    2016-01-01

    .... Two of the main organisations, or disruptors, are AirBnB and Uber. These two organisations were examined and compared in terms of how they have featured within two countries, Australia and Singapore...

  17. Fully dry PMMA transfer of graphene on h-BN using a heating/cooling system

    Science.gov (United States)

    Uwanno, T.; Hattori, Y.; Taniguchi, T.; Watanabe, K.; Nagashio, K.

    2015-12-01

    The key to achieve high-quality van der Waals heterostructure devices made of stacking various two-dimensional (2D) layered materials lies in the clean interface without bubbles and wrinkles. Although polymethylmethacrylate (PMMA) is generally used as a sacrificial transfer film due to its strong adhesion property, it is always dissolved in the solvent after the transfer, resulting in the unavoidable PMMA residue on the top surface. This makes it difficult to locate clean interface areas. In this work, we present a fully dry PMMA transfer of graphene onto h-BN using a heating/cooling system which allows identification of clean interface area for high quality graphene/h-BN heterostructure fabrication. The mechanism lies in the utilization of the large difference in thermal expansion coefficients between polymers (PMMA/PDMS) and inorganic materials (graphene/h-BN substrate) to mechanically peel off PMMA from graphene by the thermal shrinkage of polymers, leaving no PMMA residue on the graphene surface. This method can be applied to all types of 2D layered materials.

  18. The Proper Motions of the Double Radio Source n in the Orion BN/KL Region

    Science.gov (United States)

    Rodríguez, Luis F.; Dzib, Sergio A.; Loinard, Laurent; Zapata, Luis; Gómez, Laura; Menten, Karl M.; Lizano, Susana

    2017-01-01

    We have extended the time baseline for observations of the proper motions of radio sources in the Orion BN/KL region from 14.7 to 22.5 years. We present improved determinations for the sources BN and I. In addition, we address the proper motions of the double radio source n, that have been questioned in the literature. We confirm that all three sources are moving away at transverse velocities of tens of kilometers per second from a region in-between them, where they were located about 500 years ago. Source n exhibits a new component that we interpret as due to a one-sided ejection of free–free emitting plasma that took place after 2006.36. We used the highly accurate relative proper motions between sources BN and I to determine that their closest separation took place in the year 1475 ± 6, when they were within ∼100 au or less from each other in the plane of the sky.

  19. Engineering of hydrogenated two-dimensional h-BN/C superlattices as electrostatic substrates.

    Energy Technology Data Exchange (ETDEWEB)

    Liu, Zhun; Zhong, Xiaoliang; Yan, Hui; Wang, Ru-Zhi

    2016-01-14

    Hybridized two-dimensional materials incorporating domains from the hexagonal boron nitride (h-BN) and graphene is an interesting branch of materials science due to their highly tunable electronic properties. In the present study, we investigate the hydrogenated two-dimensional (2D) h-BN/C superlattices (SLs) with zigzag edges using first-principles calculations. We found that the domain width, the phase ratio, and the vertical dipole orientation all have significant influence on the stability of SLs. The electronic reconstruction is associated with the lateral polar discontinuities at the zigzag edges and the vertically polarized (B2N2H4)(m) domains, which modifies the electronic structures and the spatial potential of the SLs significantly. Furthermore, we demonstrate that the hydrogenated 2D h-BN/C SLs can be applied in engineering the electronic structure of graphene: laterally-varying doping can be achieved by taking advantage of the spatial variation of the surface potential of the SLs. By applying an external vertical electric field on these novel bidirectional heterostructures, graphene doping levels and band offsets can be tuned to a wide range, such that the graphene doping profile can be switched from the bipolar (p-n junction) to unipolar (n(+)-n junction) mode. It is expected that such bidirectional heterostructures provide an effective approach for developing novel nanoscale electronic devices and improving our understanding of the fundamentals of low-dimensional materials.

  20. The concerted calculation of the BN-600 reactor for the deterministic and stochastic codes

    Science.gov (United States)

    Bogdanova, E. V.; Kuznetsov, A. N.

    2017-01-01

    The solution of the problem of increasing the safety of nuclear power plants implies the existence of complete and reliable information about the processes occurring in the core of a working reactor. Nowadays the Monte-Carlo method is the most general-purpose method used to calculate the neutron-physical characteristic of the reactor. But it is characterized by large time of calculation. Therefore, it may be useful to carry out coupled calculations with stochastic and deterministic codes. This article presents the results of research for possibility of combining stochastic and deterministic algorithms in calculation the reactor BN-600. This is only one part of the work, which was carried out in the framework of the graduation project at the NRC “Kurchatov Institute” in cooperation with S. S. Gorodkov and M. A. Kalugin. It is considering the 2-D layer of the BN-600 reactor core from the international benchmark test, published in the report IAEA-TECDOC-1623. Calculations of the reactor were performed with MCU code and then with a standard operative diffusion algorithm with constants taken from the Monte - Carlo computation. Macro cross-section, diffusion coefficients, the effective multiplication factor and the distribution of neutron flux and power were obtained in 15 energy groups. The reasonable agreement between stochastic and deterministic calculations of the BN-600 is observed.

  1. High-performance polyimide nanocomposites with core-shell AgNWs@BN for electronic packagings

    Science.gov (United States)

    Zhou, Yongcun; Liu, Feng

    2016-08-01

    The increasing density of electronic devices underscores the need for efficient thermal management. Silver nanowires (AgNWs), as one-dimensional nanostructures, possess a high aspect ratio and intrinsic thermal conductivity. However, high electrical conductivity of AgNWs limits their application for electronic packaging. We synthesized boron nitride-coated silver nanowires (AgNWs@BN) using a flexible and fast method followed by incorporation into synthetic polyimide (PI) for enhanced thermal conductivity and dielectric properties of nanocomposites. The thinner boron nitride intermediate nanolayer on AgNWs not only alleviated the mismatch between AgNWs and PI but also enhanced their interfacial interaction. Hence, the maximum thermal conductivity of an AgNWs@BN/PI composite with a filler loading up to 20% volume was increased to 4.33 W/m K, which is an enhancement by nearly 23.3 times compared with that of the PI matrix. The relative permittivity and dielectric loss were about 9.89 and 0.015 at 1 MHz, respectively. Compared with AgNWs@SiO2/PI and Ag@BN/PI composites, boron nitride-coated core-shell structures effectively increased the thermal conductivity and reduced the permittivity of nanocomposites. The relative mechanism was studied and discussed. This study enables the identification of appropriate modifier fillers for polymer matrix nanocomposites.

  2. Carbon-tuned bonding method significantly enhanced the hydrogen storage of BN-Li complexes.

    Science.gov (United States)

    Deng, Qing-ming; Zhao, Lina; Luo, You-hua; Zhang, Meng; Zhao, Li-xia; Zhao, Yuliang

    2011-11-01

    Through first-principles calculations, we found doping carbon atoms onto BN monolayers (BNC) could significantly strengthen the Li bond on this material. Unlike the weak bond strength between Li atoms and the pristine BN layer, it is observed that Li atoms are strongly hybridized and donate their electrons to the doped substrate, which is responsible for the enhanced binding energy. Li adsorbed on the BNC layer can serve as a high-capacity hydrogen storage medium, without forming clusters, which can be recycled at room temperature. Eight polarized H(2) molecules are attached to two Li atoms with an optimal binding energy of 0.16-0.28 eV/H(2), which results from the electrostatic interaction of the polarized charge of hydrogen molecules with the electric field induced by positive Li atoms. This practical carbon-tuned BN-Li complex can work as a very high-capacity hydrogen storage medium with a gravimetric density of hydrogen of 12.2 wt%, which is much higher than the gravimetric goal of 5.5 wt % hydrogen set by the U.S. Department of Energy for 2015.

  3. Superhydrophobic hBN-Regulated Sponges with Excellent Absorbency Fabricated Using a Green and Facile Method

    Science.gov (United States)

    Zhou, Ying; Wang, Yao; Liu, Tengfei; Xu, Gang; Chen, Guangming; Li, Huayi; Liu, Lichun; Zhuo, Qiqi; Zhang, Jiaoxia; Yan, Chao

    2017-03-01

    The world faces severe environmental, human and ecological problems when major oil spills and organic discharges are released into the environment. And so it is imperative to develop tools and high performance innovative materials that can efficiently absorb these organic discharges. Furthermore, green, facile methods to produce these advanced materials are also needed. In this paper, we demonstrate a novel porous supersponge based on melamine coated with hBN. This superhydrophobic sponge (with a contact angle >150°) exhibits excellent absorption performance for oils and organic solvents, including good selectivity, high capacity (up to 175 g·g-1) and extraordinary recyclability (less than 20% decline after 30 cycles of absorption/squeezing). The synthetic procedure required only ultrasonication and immersion of the sponge in aqueous hBN solution, being a green, cost-effective and scalable production methodology. By virtue of the straightforward and cost-effective fabrication method, along with the excellent absorption performance, hBN-decorated sponges have great promise for real world practical application in the field of oil spills and organic leakage cleanup.

  4. Oxidation of SiC/BN/SiC Composites in Reduced Oxygen Partial Pressures

    Science.gov (United States)

    Opila, Elizabeth J.; Boyd, Meredith

    2010-01-01

    SiC fiber-reinforced SiC composites with a BN interphase are proposed for use as leading edge structures of hypersonic vehicles. The durability of these materials under hypersonic flight conditions is therefore of interest. Thermogravimetric analysis was used to characterize the oxidation kinetics of both the constituent fibers and composite coupons at four temperatures: 816, 1149, 1343, and 1538 C (1500, 2100, 2450, and 2800 F) and in oxygen partial pressures between 5% and 0.1% (balance argon) at 1 atm total pressure. One edge of the coupons was ground off so the effects of oxygen ingress into the composite could be monitored by post-test SEM and EDS. Additional characterization of the oxidation products was conducted by XPS and TOF-SIMS. Under most conditions, the BN oxidized rapidly, leading to the formation of borosilicate glass. Rapid initial oxidation followed by volatilization of boria lead to protective oxide formation and further oxidation was slow. At 1538C in 5% oxygen, both the fibers and coupons exhibited borosilicate glass formation and bubbling. At 1538C in 0.1% oxygen, active oxidation of both the fibers and the composites was observed leading to rapid SiC degradation. BN oxidation at 1538C in 0.1% oxygen was not significant.

  5. Mid-J CO emission from the Orion BN/KL explosive outflow

    CERN Document Server

    Peng, T -C; Wyrowski, F; Güsten, R; Menten, K M; 10.1051/0004-6361/201219937

    2012-01-01

    High spatial resolution low-J 12CO observations have shown that the wide-angle outflow seen in the Orion BN/KL region correlates with the famous H2 fingers. Recently, high-resolution large-scale mappings of mid- and higher-J CO emissions have been reported toward the Orion molecular cloud 1 core region using the APEX telescope. Therefore, it is of interest to investigate this outflow in the higher-J 12CO emission, which is likely excited by shocks. The observations were carried out using the dual-color heterodyne array CHAMP+ on the APEX telescope. The images of the Orion BN/KL region were obtained in the 12CO J=6-5 and J=7-6 transitions with angular resolutions of 8.6 and 7.4 arcsec, respectively. The results show a good agreement between our higher-J 12CO emission and SMA low-J 12CO data, which indicates that this wide-angle outflow in Orion BN/KL is likely the result of an explosive event that is related to the runaway objects from a dynamically decayed multiple system. From our observations, we estimate t...

  6. Superhydrophobic hBN-Regulated Sponges with Excellent Absorbency Fabricated Using a Green and Facile Method

    Science.gov (United States)

    Zhou, Ying; Wang, Yao; Liu, Tengfei; Xu, Gang; Chen, Guangming; Li, Huayi; Liu, Lichun; Zhuo, Qiqi; Zhang, Jiaoxia; Yan, Chao

    2017-01-01

    The world faces severe environmental, human and ecological problems when major oil spills and organic discharges are released into the environment. And so it is imperative to develop tools and high performance innovative materials that can efficiently absorb these organic discharges. Furthermore, green, facile methods to produce these advanced materials are also needed. In this paper, we demonstrate a novel porous supersponge based on melamine coated with hBN. This superhydrophobic sponge (with a contact angle >150°) exhibits excellent absorption performance for oils and organic solvents, including good selectivity, high capacity (up to 175 g·g−1) and extraordinary recyclability (less than 20% decline after 30 cycles of absorption/squeezing). The synthetic procedure required only ultrasonication and immersion of the sponge in aqueous hBN solution, being a green, cost-effective and scalable production methodology. By virtue of the straightforward and cost-effective fabrication method, along with the excellent absorption performance, hBN-decorated sponges have great promise for real world practical application in the field of oil spills and organic leakage cleanup. PMID:28332612

  7. High-performance polyimide nanocomposites with core-shell AgNWs@BN for electronic packagings

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, Yongcun; Liu, Feng, E-mail: liufeng@nwpu.edu.cn [State Key Laboratory of Solidification Processing, Northwestern Polytechnical University, Xi' an Shaanxi 710072 (China)

    2016-08-22

    The increasing density of electronic devices underscores the need for efficient thermal management. Silver nanowires (AgNWs), as one-dimensional nanostructures, possess a high aspect ratio and intrinsic thermal conductivity. However, high electrical conductivity of AgNWs limits their application for electronic packaging. We synthesized boron nitride-coated silver nanowires (AgNWs@BN) using a flexible and fast method followed by incorporation into synthetic polyimide (PI) for enhanced thermal conductivity and dielectric properties of nanocomposites. The thinner boron nitride intermediate nanolayer on AgNWs not only alleviated the mismatch between AgNWs and PI but also enhanced their interfacial interaction. Hence, the maximum thermal conductivity of an AgNWs@BN/PI composite with a filler loading up to 20% volume was increased to 4.33 W/m K, which is an enhancement by nearly 23.3 times compared with that of the PI matrix. The relative permittivity and dielectric loss were about 9.89 and 0.015 at 1 MHz, respectively. Compared with AgNWs@SiO{sub 2}/PI and Ag@BN/PI composites, boron nitride-coated core-shell structures effectively increased the thermal conductivity and reduced the permittivity of nanocomposites. The relative mechanism was studied and discussed. This study enables the identification of appropriate modifier fillers for polymer matrix nanocomposites.

  8. Over-Expression of BnMAPK1 in Brassica napus Enhances Tolerance to Drought Stress

    Institute of Scientific and Technical Information of China (English)

    WENG Chang-mei; LU Jun-xing; WAN Hua-fang; WANG Shu-wen; WANG Zhen; LU Kun; LIANG Ying

    2014-01-01

    Mitogen-activated protein kinases (MAPKs) are a family of Ser/Thr protein kinases widely conserved in all eukaryotes and involved in responses to biotic and abiotic stresses. In this study, two over-expressing BnMAPK1 oilseed rape lines, ov3 and ov11, were used to study the drought-resistant mechanism of BnMAPK1 under natural drought and simulation drought through spraying 10%PEG 8000 in seedlings. Zhongyou 821 (WT) was used as control. Compared with wild type, transgenic seedlings had higher leaf water content, higher root activity, slightly higher peroxidase (POD) and superoxide dismutase (SOD) activity, higher proline content and lower malondialdehyde (MDA) content. The expression of drought-resistant related genes, including P5CSB, PLC, LEA4 and SCE1, have been up-regulated in some degree and the expressed time of transgenic lines were earlier than that of wild type. These results suggested that over-expression of BnMAPK1 can enhance the resistance to drought in oilseed rape (Brassica napus).

  9. The Proper Motions of the Double Radio Source n in the Orion BN/KL Region

    CERN Document Server

    Rodriguez, Luis F; Loinard, Laurent; Zapata, Luis; Gomez, Laura; Menten, Karl M; Lizano, Susana

    2016-01-01

    We have extended the time baseline for observations of the proper motions of radio sources in the Orion BN/KL region from 14.7 to 22.5 years. We present improved determinations for the sources BN and I. In addition, we address the proper motions of the double radio source n, that have been questioned in the literature. We confirm that all three sources are moving away at transverse velocities of tens of km s$^{-1}$ from a region in-between them, where they were located about 500 years ago. Source n exhibits a new component that we interpret as due to a one-sided ejection of free-free emitting plasma that took place after 2006.36. We used the highly accurate relative proper motions between sources BN and I to determine that their closest separation took place in the year 1475$\\pm$6, when they were within $\\sim$100 AU or less from each other in the plane of the sky.

  10. Investigation of dependence of BN-600 reactor sector fuel cladding leak detection system responses on the operation parameters

    Directory of Open Access Journals (Sweden)

    O.I. Albutova

    2015-12-01

    Implemented studies of dependence of background on the reactor operational parameters are of practical importance and are original scientifically - similar types of research have not been done previously. Upon completion of testing and validation of the developed model using extended volume of reactor operation data the issue will be addressed of the implementation of the methodology within the composition of the SFCLDS of BN-600 and BN-800 reactors.

  11. Electron Excess Doping and Effective Schottky Barrier Reduction on the MoS2/h-BN Heterostructure.

    Science.gov (United States)

    Joo, Min-Kyu; Moon, Byoung Hee; Ji, Hyunjin; Han, Gang Hee; Kim, Hyun; Lee, Gwanmu; Lim, Seong Chu; Suh, Dongseok; Lee, Young Hee

    2016-10-12

    Layered hexagonal boron nitride (h-BN) thin film is a dielectric that surpasses carrier mobility by reducing charge scattering with silicon oxide in diverse electronics formed with graphene and transition metal dichalcogenides. However, the h-BN effect on electron doping concentration and Schottky barrier is little known. Here, we report that use of h-BN thin film as a substrate for monolayer MoS2 can induce ∼6.5 × 10(11) cm(-2) electron doping at room temperature which was determined using theoretical flat band model and interface trap density. The saturated excess electron concentration of MoS2 on h-BN was found to be ∼5 × 10(13) cm(-2) at high temperature and was significantly reduced at low temperature. Further, the inserted h-BN enables us to reduce the Coulombic charge scattering in MoS2/h-BN and lower the effective Schottky barrier height by a factor of 3, which gives rise to four times enhanced the field-effect carrier mobility and an emergence of metal-insulator transition at a much lower charge density of ∼1.0 × 10(12) cm(-2) (T = 25 K). The reduced effective Schottky barrier height in MoS2/h-BN is attributed to the decreased effective work function of MoS2 arisen from h-BN induced n-doping and the reduced effective metal work function due to dipole moments originated from fixed charges in SiO2.

  12. Plasma synthesis and HPHT consolidation of BN nanoparticles, nanospheres, and nanotubes to produce nanocrystalline cubic boron nitride

    Science.gov (United States)

    Stout, Christopher

    Plasma methods offer a variety of advantages to nanomaterials synthesis. The process is robust, allowing varying particle sizes and phases to be generated simply by modifying key parameters. The work here demonstrates a novel approach to nanopowder synthesis using inductively-coupled plasma to decompose precursor, which are then quenched to produce a variety of boron nitride (BN)-phase nanoparticles, including cubic phase, along with short-range-order nanospheres (e.g., nano-onions) and BN nanotubes. Cubic BN (c-BN) powders can be generated through direct deposition onto a chilled substrate. The extremely-high pyrolysis temperatures afforded by the equilibrium plasma offer a unique particle growth environment, accommodating long deposition times while exposing resulting powders to temperatures in excess of 5000K without any additional particle nucleation and growth. Such conditions can yield short-range ordered amorphous BN structures in the form of 20nm diameter nanospheres. Finally, when introducing a rapid-quenching counter-flow gas against the plasma jet, high aspect ratio nanotubes are synthesized, which are collected on substrate situated radially. The benefits of these morphologies are also evident in high-pressure/high-temperature consolidation experiments, where nanoparticle phases can offer a favorable conversion route to super-hard c-BN while maintaining nanocrystallinity. Experiments using these morphologies are shown to begin to yield c-BN conversion at conditions as low as 2.0 GPa and 1500°C when using micron sized c-BN seeding to create localized regions of high pressures due to Hertzian forces acting on the nanoparticles.

  13. Substitutional carbon doping of free-standing and Ru-supported BN sheets: a first-principles study

    Science.gov (United States)

    Berseneva, N.; Komsa, H.-P.; Vierimaa, V.; Björkman, T.; Fan, Z.; Harju, A.; Todorović, M.; Krasheninnikov, A. V.; Nieminen, R. M.

    2017-10-01

    The development of spatially homogeneous mixed structures with boron (B), nitrogen (N) and carbon (C) atoms arranged in a honeycomb lattice is highly desirable, as they open the possibility of creating stable two-dimensional materials with tunable band gaps. However, at least in the free-standing form, the mixed BCN system is energetically driven towards phase segregation to graphene and hexagonal BN. It is possible to overcome the segregation when BCN material is grown on a particular metal substrate, for example Ru(0 0 0 1), but the stabilization mechanism is still unknown. With the use of density-functional theory we study the energetics of BN/Ru slabs, with different types of configurations of C substitutional defects introduced to the h-BN overlayer. The results are compared to the energetics of free-standing BCN materials. We found that the substrate facilitates the C substitution process in the h-BN overlayer. Thus, more homogeneous BCN material can be grown, overcoming the segregation into graphene and h-BN. In addition, we investigate the electronic and transport gaps in free-standing BCN structures, and assess their mechanical properties and stability. The band gap in mixed BCN free-standing material depends on the concentration of the constituent elements and ranges from zero in pristine graphene to nearly 5 eV in free-standing h-BN. This makes BCN attractive for application in modern electronics.

  14. BN-350 unattended safeguards system current status and initial fuel movement data

    Energy Technology Data Exchange (ETDEWEB)

    Williams, Richard Brady [Los Alamos National Laboratory; Browne, Michael C [Los Alamos National Laboratory; Parker, Robert F [Los Alamos National Laboratory; Ingegneri, Maurizio [IAEA

    2009-01-01

    The Unattended and Remote Monitoring (UNARM) system at the BN-350 fast breeder reactor facility in Aktau, Kazakhstan continues to provide safeguards monitoring data as the spent fuel disposition project transitions from wet fuel storage to dry storage casks. Qualitative data from the initial cask loading procedures has been released by the International Atomic Energy Agency (IAEA) and is presented here for the first time. The BN-350 fast breeder reactor in Aktau, Kazakhstan, operated as a plutonium-producing facility from 1973 W1til 1999. Kazakhstan signed the Nonproliferation Treaty (NPT) in February 1994, and shortly afterwards the IAEA began safeguarding the reactor facility and its nuclear material. Slnce the cessation of reactor operations ten years ago, the chief proliferation concern has been the spent fuel assemblies stored in the pond on-site. By 2002, all fuel assemblies in wet storage had been repackaged into proliferation-resistant canisters. From the beginning, the IAEA's safeguards campaign at the BN-350 included a constant unattended sensor presence in the form of UNARM which monitors nuclear material activities at the facility in the absence of inspector presence. The UNARM equipment at the BN-350 was designed to be modular and extensible, allowing the system to adapt as the safeguards requirements change. This has been particularly important at the BN-350 due to the prolonged wet storage phase of the project. The primary function of the BN-350 UNARM system is to provide the IAEA with an independent, radiation-centric Containment and Surveillance (C&S) layer in addition to the standard seals and video systems. The UNARM system has provided continuous Continuity of Knowledge (COK) data for the BN-350's nuclear material storage areas in order to ensure the validity of the attended measurements during the lifetime of the project. The first of these attended measurements was characterization of the spent fuel assemblies. This characterization

  15. Preparation of the radiopharmaceutical {sup 99m} Tc-HYNIC-[Lys{sup 3}]-BN; Preparacion del radiofarmaco {sup 99m} Tc-HYNIC-[Lys{sup 3}]-BN

    Energy Technology Data Exchange (ETDEWEB)

    Conde S, E. [Universidad Autonoma del Estado de Mexico, Facultad de Quimica, 50000 Toluca, Estado de Mexico (Mexico)

    2007-07-01

    In accordance with their design, the radiopharmaceuticals can be divided in three generations. The radiopharmaceuticals of third generation are used in nuclear medicine to obtain images of specific molecular targets, and they are only in their capacity to detect in vivo such specific biochemical places as receivers and enzymes. The receivers of regulator peptides are over expressed in numerous carcinogenic cells. Those receivers have been used as molecular targets of radiolabelled peptides to locate cancerous tumors. The small peptide bombesin (BN, 14 amino acids) it was isolated of the frog skin and it belongs to a wide neuropeptides group with many biological functions. The equivalent human is the liberator peptide of the gastrin (GRP, 27 amino acids) and his receivers (r-GRP) that are on expressed in the membranes of the tumor cells. The receiving subtype 2 of bombesin (receiving GRP) it is on expressed in several human tumors including breast, prostate, lung cells and pancreatic cancer. Some radiopharmaceuticals similar of BN has been developed that were prepared to be used in nuclear medicine for the detection of wicked tumors and to evidence prostate cancers, breast and of lymphatic nodules. A technique was developed to allow the conjugation of HYNIC-[Lys3]-BN that allowed to obtain this product with a high purity. The identity was determined by HPLC chromatography. It was necessary the validation of the method and the HPLC system, to assure that the results were reliable. Linearity, specificity, accuracy and precision parameters were analyzed, that are those required by the Mexican pharmacopoeia for chromatographic methods. With this conjugated a formulation for lyophilized kits were analyzed, with the purpose of obtaining a radiochemical purity, after the labelled one with {sup 99m}Tc, bigger to 95%; the components used in the nucleus-equipment should favor the conjugation of the {sup 99m}Tc by means of a ligands exchange between the tricine and the

  16. Mixed europium valence in Eu0.937Ba8[BN2]6 - Structure and spectroscopic behavior

    Science.gov (United States)

    Dierkes, Tobias; Seidel, Stefan; Benndorf, Christopher; Heletta, Lukas; de Oliveira Junior, Marcos; Holtkamp, Michael; Karst, Uwe; Block, Theresa; Jüstel, Thomas; Eckert, Hellmut; Pöttgen, Rainer

    2017-08-01

    Polycrystalline samples of Sr0.95Eu0.05Ba8[BN2]6 and Eu0.937Ba8[BN2]6 were synthesized via conventional solid-state reaction from the binary precursor compounds Sr3N2, EuN, Ba3N2 and BN at 1000 °C. The structure of Eu0.937Ba8[BN2]6 was refined from single crystal X-ray diffractometer data: Eu0.937Ba8[BN2]6 type, Fd 3 barm, a = 1594.54(9) pm, wR2 = 0.0654, 380 F2 values and 23 variables. The 8a europium site shows an occupancy of only 93.7(9) % suggesting partial oxidation of europium to fulfil an electron-precise description, i. e. EuII0.81EuIII0.13Ba8[BN2]6. The mixed europium valence was confirmed by magnetic susceptibility measurements (reduced magnetic moment of 7.28 μB per europium atom) and 151Eu Mössbauer spectroscopy (EuII: EuIII = 82: 18). The nitridoborate anions are coordinated by slightly distorted, mono-capped (europium) square prisms formed by the barium atoms. All metal cations are hexa-coordinated by nitrogen atoms. The EPR spectra of EuxSr1-xBa8[BN2]6 samples (0.001 ≤ x ≤ 0.01) suggest close to cubic local symmetry of the Eu2+ dopant ions and reveal some highly unusual features: Magnetic hyperfine splitting is only observed with one of the Eu nuclear isotopes, and the coupling constant of 243.6 MHz is extremely large compared to values (90-100 MHz) typically observed in the literature for Eu2+ doped crystalline materials.

  17. /sup 3/H-PAF-acether displacement and inhibition of binding in intact human platelets by BN 52021

    Energy Technology Data Exchange (ETDEWEB)

    Korth, R.; Le Couedic, J.P.; Benveniste, J.

    1986-03-05

    Intact washed human platelets incubated at 20/sup 0/C in Tyrode's buffer containing 0.25% (w/v) bovine serum albumin bound /sup 3/H paf-acether in a concentration (0-6.5 nM) and time (0-60 min) dependent manner (n=3). BN 52021 (60 ..mu..M) a chemically defined extract from Ginkgo biloba inhibited the binding of increasing concentrations of /sup 3/H paf-acether. Calculated differences between /sup 3/H paf-acether binding in the presence or absence of BN 52021 (60 ..mu..M) reached nearly a plateau in concentrations higher than 0.65 nM /sup 3/H paf-acether. Increasing concentrations of BN 52021 (0-60 ..mu..M) as well as of unlabelled paf-acether (0-50 nM) prevented within 15 min /sup 3/H paf-acether binding (0.65 nM) to platelets in a concentration-dependent way. Increasing BN 52021 concentrations (0-60 ..mu..M) also displaced platelet-bound /sup 3/H paf-acether (0.65 nM) in a concentration-dependent way. Displacement increased with the time length of platelet incubation with BN 52021 and reached a plateau at 15 min. Platelet-bound /sup 3/H paf-acether displacement of 28.3 +/- 6.3%, 31.1 +/- 4.0% and 26.7 +/- 5.6% was observed using 50 nM unlabelled paf-acether, 60 ..mu..M BN 52021 or both substances together (vs 4.3 +/- 7.2% for vehicle alone). No degradation of /sup 3/H paf-acether occurred as assessed by high pressure liquid chromatography. These results demonstrate that BN 52021 competes directly with paf-acether binding sites on human platelets.

  18. Criticality safety issues in the disposition of BN-350 spent fuel

    Energy Technology Data Exchange (ETDEWEB)

    Schaefer, R. W.; Klann, R. T.; Koltyshev, S. M.; Krechetov, S.

    2000-02-28

    A criticality safety analysis has been performed as part of the BN-350 spent fuel disposition project being conducted jointly by the DOE and Kazakhstan. The Kazakhstan regulations are reasonably consistent with those of the DOE. The high enrichment and severe undermoderation of this fast reactor fuel has significant criticality safety consequences. A detailed modeling approach was used that showed some configurations to be safe that otherwise would be rejected. Reasonable requirements for design and operations were needed, and with them, all operations were found to be safe.

  19. Nanopillar optical antenna nBn detectors for subwavelength infrared pixels

    Science.gov (United States)

    Hung, Chung Hong; Senanayake, Pradeep; Lee, Wook-Jae; Farrell, Alan; Hsieh, Nick; Huffaker, Diana L.

    2015-06-01

    The size, weight and power (SWaP) of state of the art infrared focal plane arrays are limited by the pixel size approaching the diffraction limit. We investigate a novel detector architecture which allows improvements in detectivity by shrinking the absorber volume while maintaining high quantum efficiency and wide field of view (FOV). It has been previously shown that the Nanopillar Optical Antenna (NOA) utilizes 3D plasmonic modes to funnel light into a subwavelength nanopillar absorber. We show detailed electro-optical simulations for the NOA-nBn architecture for overcoming generation recombination current with suitable surface passivation to achieve background limited infrared performance.

  20. Mechanical and Thermal Properties of Polymethyl Methacrylate-BN Nanotube Composites

    Directory of Open Access Journals (Sweden)

    C. Y. Zhi

    2008-01-01

    Full Text Available Polymethyl methacrylate (PMMA-BN nanotube (BNNT composites were fabricated and their mechanical and thermal properties were analyzed. Using a 1 wt.% BNNTs fraction in a polymer, the elastic modulus of PMMA was increased up to 19%. In addition, thermal stability and glass transition temperature of PMMA were also positively affected. The thermal conductivity of PMMA with BNNT additions increased three times. The resultant BNNT-PMMA composites possess the high electrical breakover voltages. Thus our studies clearly indicate that BNNTs are promising nanofillers for improvement of mechanical and thermal conductivity of dielectric polymers under preservation of their electrical insulation.

  1. Effect of Adventitious Carbon on the Environmental Degradation of SiC/BN/SiC Composites

    Science.gov (United States)

    Ogbuji, L. U. J. T.; Yun, H. M.; DiCarlo, J.

    2002-01-01

    Pesting remains a major obstacle to the application of SiC/SiC composites in engine service and selective degradation of the boron nitride interphase at intermediate temperatures is of primary concern. However, significant progress has been made on interphase improvement recently and we now know more about the phenomenon and ways to suppress it. By screening SiC/BN/SiC materials through characterization of strength and microstructures after exposure in a burner rig, some factors that control pesting in these composites have been determined. A key precaution is careful control of elemental carbon presence in the interphase region.

  2. Vacuolar Iron Transporter BnMEB2 Is Involved in Enhancing Iron Tolerance of Brassica napus

    OpenAIRE

    Zhu, Wei; Zuo, Rong; Zhou, Rongfang; Huang, Junyan; Tang, Minqiang; Cheng, Xiaohui; Liu, Yueying; Tong, Chaobo; XIANG, YANG; Dong, Caihua; Liu, Shengyi

    2016-01-01

    Iron toxicity is a nutrient disorder that severely affects crop development and yield in some soil conditions. Vacuolar detoxification of metal stress is an important strategy for plants to survive and adapt to this adverse environment. Vacuolar iron transporter (VIT) members are involved in this process and play essential roles in iron storage and transport. In this study, we identified a rapeseed VIT gene BnMEB2 (BnaC07g30170D) homologs to Arabidopsis MEB2 (At5g24290). Transient expression ...

  3. Elastic and thermodynamic properties of c-BN from first-principles calculations

    Institute of Scientific and Technical Information of China (English)

    Hao Yan-Jun; Cheng Yan; Wang Yan-Ju; Chen Xiang-Rong

    2007-01-01

    The elastic constants and thermodynamic properties of c-BN are calculated using the first-principles plane wave method with the relativistic analytic pseudopotential of the Hartwigen, Goedecker and Hutter (HGH) type in the frame of local density approximation and using the quasi-harmonic Debye model, separately. Moreover, the dependences of the normalized volume V/V0 on pressure P, as well as the bulk modulus B, the thermal expansion α, and the heat capacity CV on pressure P and temperature T are also successfully obtained.

  4. First-Principles Investigations of the Working Mechanism of 2D h-BN as an Interfacial Layer for the Anode of Lithium Metal Batteries.

    Science.gov (United States)

    Shi, Le; Xu, Ao; Zhao, Tianshou

    2017-01-18

    An issue with the use of metallic lithium as an anode material for lithium-based batteries is dendrite growth, causing a periodic breaking and repair of the solid electrolyte interphase (SEI) layer. Adding 2D atomic crystals, such as h-BN, as an interfacial layer between the lithium metal anode and liquid electrolyte has been demonstrated to be effective to mitigate dendrite growth, thereby enhancing the Columbic efficiency of lithium metal batteries. But the underlying mechanism leading to the reduced dendrite growth remains unknown. In this work, with the aid of first-principle calculations, we find that the interaction between the h-BN and lithium metal layers is a weak van der Waals force, and two atomic layers of h-BN are thick enough to block the electron tunneling from lithium metal to electrolyte, thus prohibiting the decomposition of electrolyte. The interlayer spacing between the h-BN and lithium metal layers can provide larger adsorption energies toward lithium atoms than that provided by bare lithium or h-BN, making lithium atoms prefer to intercalate under the cover of h-BN during the plating process. The combined high stiffness of h-BN and the low diffusion energy barriers of lithium at the Li/h-BN interfaces induce a uniform distribution of lithium under h-BN, therefore effectively suppressing dendrite growth.

  5. CdTe nBn photodetectors with ZnTe barrier layer grown on InSb substrates

    Science.gov (United States)

    He, Zhao-Yu; Campbell, Calli M.; Lassise, Maxwell B.; Lin, Zhi-Yuan; Becker, Jacob J.; Zhao, Yuan; Boccard, Mathieu; Holman, Zachary; Zhang, Yong-Hang

    2016-09-01

    We have demonstrated an 820 nm cutoff CdTe nBn photodetector with ZnTe barrier layer grown on an InSb substrate. At room temperature, under a bias of -0.1 V, the photodetector shows Johnson and shot noise limited specific detectivity (D*) of 3 × 1013 cm Hz1/2/W at a wavelength of 800 nm and 2 × 1012 cm Hz1/2/W at 200 nm. The D* is optimized by using a top contact design of ITO/undoped-CdTe. This device not only possesses nBn advantageous characteristics, such as generation-recombination dark current suppression and voltage-bias-addressed two-color photodetection, but also offers features including responsivity enhancements by deep-depletion and by using a heterostructure ZnTe barrier layer. In addition, this device provides a platform to study nBn device physics at room temperature, which will help us to understand more sophisticated properties of infrared nBn photodetectors that may possess a large band-to-band tunneling current at a high voltage bias, because this current is greatly suppressed in the large-bandgap CdTe nBn photodetector.

  6. Mechanical, tribological and corrosion properties of CrBN films deposited by combined direct current and radio frequency magnetron sputtering

    Energy Technology Data Exchange (ETDEWEB)

    Jahodova, Vera [Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, 638075 (Singapore); Koszalin University of Technology, Sniadeckich 2, 75-0453 Koszalin (Poland); Technical University of Liberec, Studentska 1402/2, 461 17 Liberec1 (Czech Republic); Ding, Xing-zhao, E-mail: xzding@SIMTech.a-star.edu.sg [Singapore Institute of Manufacturing Technology, 71 Nanyang Drive, 638075 (Singapore); Seng, Debbie H.L. [Institute of Materials Research and Engineering, 3 Research Link, 117602 (Singapore); Gulbinski, W. [Koszalin University of Technology, Sniadeckich 2, 75-0453 Koszalin (Poland); Louda, P. [Technical University of Liberec, Studentska 1402/2, 461 17 Liberec1 (Czech Republic)

    2013-10-01

    Cr–B–N films were deposited on stainless steel substrates by a combined direct current and radio frequency (RF) reactive unbalanced magnetron sputtering process using two elemental Cr and one compound BN targets. Boron content in the as-deposited films was qualitatively analyzed by time-of-flight secondary ion mass spectroscopy. Films' microstructure, mechanical and tribological properties were characterized by X-ray diffraction, nanoindentation and pin-on-disk tribometer experiments. Corrosion behavior of the Cr–B–N films was evaluated by electrochemical potentiodynamic polarization method in a 3 wt.% NaCl solution. All the films were crystallized into a NaCl-type cubic structure. At lower RF power applied on the BN target (≤ 600 W), films are relatively randomly oriented, and films' crystallinity increased with increasing RF power. With increasing RF power further (≥ 800 W), films became (200) preferentially oriented, and films' crystallinity decreased gradually. With incorporation of a small amount of boron atoms into the CrN films, hardness, wear- and corrosion-resistance were all improved evidently. The best wear and corrosion resistance was obtained for the film deposited with 600 W RF power applied on the BN target. - Highlights: • CrBN films deposited by direct current and radio frequency magnetron sputtering. • CrBN exhibited higher hardness, wear- and corrosion-resistance than pure CrN. • The best wear- and corrosion-resistant film was deposited with 600 W RF power.

  7. Thermal Shock Resistance of Si3N4/h-BN Composites Prepared via Catalytic Reaction-Bonding Route

    Science.gov (United States)

    Yang, Wanli; Peng, Zhigang; Dai, Lina; Shi, Zhongqi; Jin, Zhihao

    2017-08-01

    Si3N4/h-BN ceramic matrix composites were prepared via a catalytic reaction-bonding route by using ZrO2 as nitridation catalyst, and the water quenching (fast cooling) and molten aluminum quenching tests (fast heating) were carried out to evaluate the thermal shock resistance of the composites. The results showed that the thermal shock resistance was improved obviously with the increase in h-BN content, and the critical thermal shock temperature difference (ΔT c) reaches as high as 780 °C when the h-BN content was 30 wt.%. The improvement of thermal shock resistance of the composites was mainly due to the crack tending to quasi static propagating at weak bonding interface between Si3N4 and h-BN with the increase in h-BN content. For the molten aluminum quenching test, the residual strength showed no obvious decrease compared with water quenching test, which could be caused by the mild stress condition on the surface. In addition, a calculated parameter, volumetric crack density (N f), was presented to quantitative evaluating the thermal shock resistance of the composites in contrast to the conventional R parameter.

  8. Modulation of interfacial electronic properties in PbI2 and BN van der Waals heterobilayer via external electric field

    Science.gov (United States)

    Ma, Yaqiang; Zhao, Xu; Niu, Mengmeng; Dai, Xianqi; Li, Wei; Wang, Xiaolong; Zhao, Mingyu; Wang, Tianxing; Tang, Yanan

    2017-07-01

    The interfacial electronic properties of PbI2 and BN van der Waals (vdW) heterobilayer are explored by using density functional theory (DFT) method. An intrinsic type-II heterostructure with a wide bandgap is demonstrated. The spatial separation of the lowest energy electron-hole pairs can be actualised and make PbI2/BN heterostructure as a good candidate for applications in optoelectronics and solar cell. A simulation of Efield is actualized to modify its electronic properties. Band alignment converts from type-II to type-I heterostructure separated by a forward voltage with the value of about 0.07 V/Å. Three regions implying different Efield-sensitive properties are obtained from the variations of bandgap with Efield. The charge redistribution with an Efield is mainly on the surface of PbI2 and BN layers as well as the amount of electrons depends on the strength of Efield. In addition, the PbI2/BN heterobilayer exhibits more outstanding optical conductivity capability. Our results could bring forward a new perspective on sensor and shed light on the design of novel nano- and optoelectronics based on the PbI2/BN vdW heterostructure.

  9. Magnetization distribution and spin transport of graphene/h-BN/graphene nanoribbon-based magnetic tunnel junction

    Science.gov (United States)

    Zhang, Y.; Yan, X. H.; Guo, Y. D.; Xiao, Y.

    2017-09-01

    Motivated by recent electronic transport measurement of boron nitride-graphene hybrid atomic layers, we studied magnetization distribution, transmission and current-bias relation of graphene/h-BN/graphene (C/BN/C) nanoribbon-based magnetic tunnel junctions (MTJ) based on density functional theory and non-equilibrium Green's function methods. Three types of MTJs, i.e. asymmetric, symmetric (S) and symmetric (SS), and two types of lead magnetization alignment, i.e. parallel (PC) and antiparallel (APC), are considered. The results show that the magnetization distribution is closely related to the interface structure. Especially for asymmetric MTJ, the B/N atoms at the C/BN interface are spin-polarized and give finite magnetic moments. More interesting, it is found that the APC transmission of asymmetric MTJ with the thinnest barrier dominates over the PC one. By analyzing the projected density of states, one finds that the unusual higher APC transmission than PC is due to the coupling of electronic states of left ZGNR and right ZGNR. By integrating transmission, we calculate the current-bias voltage relation and find that the APC current is larger than PC current at small bias voltage and therefore reproduces a negative tunnel magnetoresistance. The results reported here will be useful and important for the design of C/BN/C-based MTJ.

  10. Wear resistance and microstructural properties of Ni–Al/h-BN/WC–Co coatings deposited using plasma spraying

    Energy Technology Data Exchange (ETDEWEB)

    Hsiao, W.T. [Materials and Chemical Research Laboratories, Industrial Technology Research Institute, Chutung 310, Taiwan (China); Su, C.Y., E-mail: cysu@ntut.edu.tw [Graduate Institute of Manufacturing Technology, National Taipei University of Technology, Taipei 106, Taiwan (China); Huang, T.S. [China Steel Corporation, Kaohsiung, Taiwan (China); Liao, W.H. [Materials and Chemical Research Laboratories, Industrial Technology Research Institute, Chutung 310, Taiwan (China); Nano Technology Laboratory, Department of Materials Engineering, National Chung Hsing University, Taichung 402, Taiwan (China)

    2013-05-15

    Hexagonal boron nitride (h-BN) and tungsten carbide cobalt (WC–Co) were added to nickel aluminum alloy (Ni–Al) and deposited as plasma sprayed coatings to improve their tribological properties. The microstructure of the coatings was analyzed using a scanning electron microscope (SEM). Following wear test, the worn surface morphologies of the coatings were analyzed using a SEM to identify their fracture modes. The results of this study demonstrate that the addition of h-BN and WC–Co improved the properties of the coatings. Ni–Al/h-BN/WC–Co coatings with high hardness and favorable lubrication properties were deposited. - Highlights: • We mixed Ni–Al, h-BN and WC–Co powders and deposited them as composite coatings. • Adding WC–Co was found to increase the hardness and reduce the wear volume loss. • Adding h-BN was found to decrease the hardness and reduce the friction coefficient. • This composite coating was shown to have improved wear properties at 850 °C.

  11. Creep/Stress Rupture Behavior of 3D Woven SiC/SiC Composites with Sylramic-iBN, Super Sylramic-iBN and Hi-Nicalon-S Fibers at 2700F in Air

    Science.gov (United States)

    Bhatt, R. T.

    2017-01-01

    To determine the influence of fiber types on creep durability, 3D SiC/SiC CMCs were fabricated with Sylramic-iBN, super Sylramic-iBN and Hi-Nicalon-S fibers and the composite specimens were then tested under isothermal tensile creep at 14820C at 69, 103 and 138 MPa for up to 300hrs in air. The failed specimens were examined by scanning electron microscopy (SEM) and computed tomography (CT) for fracture mode analysis. The creep data of these composites are compared with those of other SiC/SiC composites in the literature. The results of this study will be presented.

  12. Ferroelectric Single-Crystal Gated Graphene/Hexagonal-BN/Ferroelectric Field-Effect Transistor.

    Science.gov (United States)

    Park, Nahee; Kang, Haeyong; Park, Jeongmin; Lee, Yourack; Yun, Yoojoo; Lee, Jeong-Ho; Lee, Sang-Goo; Lee, Young Hee; Suh, Dongseok

    2015-11-24

    The effect of a ferroelectric polarization field on the charge transport in a two-dimensional (2D) material was examined using a graphene monolayer on a hexagonal boron nitride (hBN) field-effect transistor (FET) fabricated using a ferroelectric single-crystal substrate, (1-x)[Pb(Mg1/3Nb2/3)O3]-x[PbTiO3] (PMN-PT). In this configuration, the intrinsic properties of graphene were preserved with the use of an hBN flake, and the influence of the polarization field from PMN-PT could be distinguished. During a wide-range gate-voltage (VG) sweep, a sharp inversion of the spontaneous polarization affected the graphene channel conductance asymmetrically as well as an antihysteretic behavior. Additionally, a transition from antihysteresis to normal ferroelectric hysteresis occurred, depending on the V(G) sweep range relative to the ferroelectric coercive field. We developed a model to interpret the complex coupling among antihysteresis, current saturation, and sudden conductance variation in relation with the ferroelectric switching and the polarization-assisted charge trapping, which can be generalized to explain the combination of 2D structured materials with ferroelectrics.

  13. Immobilization of Cesium Traps from the BN-350 Fast Reactor (Aktau, Kazakhstan)

    Energy Technology Data Exchange (ETDEWEB)

    J. A. Michelbacher; C. Knight; O. G. Romanenko; I. L. Tazhibaeva; I. L. Yakovlev; A. V. Rovneyko; V. I. Maev; D. Wells; A. Herrick

    2011-03-01

    During BN-350 reactor operations and also during the initial stages of decommissioning, cesium traps were used to decontaminate the reactor’s primary sodium coolant. Two different types of carbon-based trap were used – the MAVR series, low ash granulated graphite adsorber (LAG) contained in a carrier designed to be inserted into the reactor core during shutdown; and a series of ex-reactor trap accumulators(TAs) which used reticulated vitreous carbon (RVC) to reduce Cs-137 levels in the sodium after final reactor shutdown. In total four MAVRs and seven TAs were used at BN-350 to remove an estimated cumulative 755 TBq of cesium. The traps, which also contain residual sodium, need to be immobilized in an appropriate way to allow them to be consigned as waste packages for long term storage and, ultimately, disposal. The present paper reports on the current status of the implementation phase, with particular reference to the work done to date on the trap accumulators, which have the most similarity with the cesium traps used at other reactors.

  14. GGA-based analysis of the metformin adsorption on BN nanotubes

    Science.gov (United States)

    Chigo Anota, Ernesto; Cocoletzi, Gregorio H.

    2014-02-01

    Density functional theory (DFT) studies are done to investigate structural and electronic properties of (5,5) chirality single walls boron nitride nanotubes (BNNTs) in the armchair model interacting with metformin (MF) on the surface and ends. Our calculations consider the exchange-correlation energies with the Hamprecht-Cohen-Tozer-Handy functional within the generalized gradient approximation (HCTH-GGA) and the double polarized DNP base function. The geometry optimization follows the minimum energy criterion for all six geometries we have considered. Results show that the MF is adsorbed through the groups NH2-NH at one end of the nanotube. The system polarity is increased which indicates the possible dispersion and solubility. Moreover the interaction between these species induces an increase in the chemical reactivity of the order of 0.42 eV. Meanwhile the solvation in water keeps the semiconductor characteristics of both nanotube and MF. The work function of the BNNT-MF is drastically reduced respect to the pristine system when the BN nanotube is doped at its surface and ends with carbon. This means that the functionalized BN nanotube facilitates conditions to improve field emission.

  15. First-principles study on electron transport through BN-dimer embedded zigzag carbon nanotubes

    Science.gov (United States)

    Egami, Yoshiyuki; Akera, Hiroshi

    2017-04-01

    First-principles calculations are performed for electron transmission through a metallic zigzag carbon nanotube with substitutional BN dimers parallel to the nanotube axis. The transmission coefficient is calculated in the energy range (around the charge neutrality point) in which there exist two degenerate subbands for each spin. Wave functions in the circumferential direction of one of the degenerate subbands can be chosen so as to have nodes at the position of a carbon dimer parallel to the nanotube axis. It is shown that the transmission probability of an incident wave with such wave-function nodes depends crucially on positions of BN dimers relative to the nodes. By placing each of dimers at one of the nodes, the transmission probability is substantially enhanced and is well described by the Born approximation in spite of spatially extended scattering potential due to ionized B and N. This suggests that the arrangement in the circumferential direction of various impurities influences transport through metallic zigzag carbon nanotubes.

  16. High-Energy Density and Superhard Nitrogen-Rich B-N Compounds

    Science.gov (United States)

    Li, Yinwei; Hao, Jian; Liu, Hanyu; Lu, Siyu; Tse, John S.

    2015-09-01

    The pressure-induced transformation of diatomic nitrogen into nonmolecular polymeric phases may produce potentially useful high-energy-density materials. We combine first-principles calculations with structure searching to predict a new class of nitrogen-rich boron nitrides with a stoichiometry of B3N5 that are stable or metastable relative to solid N2 and h -BN at ambient pressure. The most stable phase at ambient pressure has a layered structure (h -B3N5 ) containing hexagonal B3N3 layers sandwiched with intercalated freely rotating N2 molecules. At 15 GPa, a three-dimensional C 2 2 21 structure with single N-N bonds becomes the most stable. This pressure is much lower than that required for triple-to-single bond transformation in pure solid nitrogen (110 GPa). More importantly, C 2 2 21-B3N5 is metastable, and can be recovered under ambient conditions. Its energy density of ˜3.44 kJ /g makes it a potential high-energy-density material. In addition, stress-strain calculations estimate a Vicker's hardness of ˜4 4 GPa . Structure searching reveals a new clathrate sodalitelike BN structure that is metastable under ambient conditions.

  17. SN 2015bn: a detailed multi-wavelength view of a nearby superluminous supernova

    CERN Document Server

    Nicholl, M; Smartt, S J; Margutti, R; Kamble, A; Alexander, K D; Chen, T -W; Inserra, C; Arcavi, I; Blanchard, P K; Cartier, R; Chambers, K C; Childress, M J; Chornock, R; Cowperthwaite, P S; Drout, M; Flewelling, H A; Fraser, M; Gal-Yam, A; Galbany, L; Harmanen, J; Holoien, T W -S; Hosseinzadeh, G; Howell, D A; Huber, M E; Jerkstrand, A; Kankare, E; Kochanek, C S; Lin, Z -Y; Lunnan, R; Magnier, E A; Maguire, K; McCully, C; McDonald, M; Metzger, B D; Milisavljevic, D; Mitra, A; Reynolds, T; Saario, J; Shappee, B J; Smith, K W; Valenti, S; Villar, V A; Waters, C; Young, D R

    2016-01-01

    We present observations of SN 2015bn (= PS15ae = CSS141223-113342+004332 = MLS150211-113342+004333), a Type I superluminous supernova (SLSN) at $z=0.1136$. As well as being one of the closest SLSNe, it is intrinsically brighter ($M_U\\approx-23.1$) and in a fainter host ($M_B\\approx-16.0$) than other SLSNe at $z\\sim0.1$. We collected the most extensive dataset for an SLSN I to date, including spectroscopy and UV to NIR photometry from $-$50 to +250 d from maximum light. SN 2015bn is a slowly-declining SLSN, but exhibits surprising undulations in the light curve on a timescale of 30-50 d, which are more pronounced in the UV. The spectrum resembles other SLSNe, but our well-sampled data reveal extraordinarily slow evolution except for a rapid transformation between +7 and +30 d. We detect weak features that we tentatively suggest may be hydrogen and helium. At late times, blue colours and a trio of lines around 6000 \\AA\\ seem to distinguish slowly-declining SLSNe from faster ones. We derive physical properties i...

  18. Dynamic Negative Compressibility of Few-Layer Graphene, h-BN, and MoS2

    Science.gov (United States)

    Neves, Bernardo; Barboza, Ana Paula; Chacham, Helio; Oliveira, Camilla; Fernandes, Thales; Martins Ferreira, Erlon; Archanjo, Braulio; Batista, Ronaldo; Oliveira, Alan

    2013-03-01

    We report a novel mechanical response of few-layer graphene, h-BN, and MoS2 to the simultaneous compression and shear by an atomic force microscope (AFM) tip. The response is characterized by the vertical expansion of these two-dimensional (2D) layered materials upon compression. Such effect is proportional to the applied load, leading to vertical strain values (opposite to the applied force) of up to 150%. The effect is null in the absence of shear, increases with tip velocity, and is anisotropic. It also has similar magnitudes in these solid lubricant materials (few-layer graphene, h-BN, and MoS2), but it is absent in single-layer graphene and in few-layer mica and Bi2Se3. We propose a physical mechanism for the effect where the combined compressive and shear stresses from the tip induce dynamical wrinkling on the upper material layers, leading to the observed flake thickening. The new effect (and, therefore, the proposed wrinkling) is reversible in the three materials where it is observed.[2] Financial support from CNPq, Fapemig, Rede Nacional de Pesquisa em Nanotubos de Carbono and INCT-Nano-Carbono

  19. BN-coated Ca(1-x)Sr(x)S:Eu solid-solution nanowires with tunable red light emission.

    Science.gov (United States)

    Lin, Jing; Huang, Yang; Mi, Jiao; Zhang, Xinghua; Lu, Zunming; Xu, Xuewen; Fan, Ying; Zou, Jin; Tang, Chengchun

    2013-10-11

    We report on the controlled growth of novel BN-coated Ca(1-x)Sr(x)S:Eu nanowires via a solid-liquid-solid process. The Ca(1-x)Sr(x)S solid solution forms as one-dimensional nanowires and has been coated with homogeneous protective BN nanolayers. The structure and luminescence properties of this new nanocomposite have been systematically investigated. High-spatial-resolution cathodoluminescence investigations reveal that effective red color tuning has been achieved by tailoring the composition of the Ca(1-x)Sr(x)S nanowires. Moreover, codoping of Ce(3+) and Eu(2+) in the CaS nanowire can induce energy transfer in the matrix and make it possible to obtain enhanced orange color in the nanowires. The BN-coated Ca(1-x)Sr(x)S:Eu solid-solution nanowires are envisaged to be valuable red-emitting nanophosphors and useful in advanced nanodevices and white LEDs.

  20. Theoretical Study of Midwave Infrared HgCdTe nBn Detectors Operating at Elevated Temperatures

    Science.gov (United States)

    Akhavan, Nima Dehdashti; Jolley, Gregory; Umana-Membreno, Gilberto A.; Antoszewski, Jarek; Faraone, Lorenzo

    2015-09-01

    We report a theoretical study of mercury cadmium telluride (HgCdTe) unipolar n-type/barrier/ n-type (nBn) detectors for midwave infrared (MWIR) applications at elevated temperatures. The results obtained indicate that the composition, doping, and thickness of the barrier layer in MWIR HgCdTe nBn detectors can be optimized to yield performance levels comparable with those of ideal HgCdTe p- n photodiodes. It is also shown that introduction of an additional barrier at the back contact layer of the detector structure (nBnn+) leads to substantial suppression of the Auger generation-recombination (GR) mechanism; this results in an order-of-magnitude reduction in the dark current level compared with conventional nBn or p- n junction-based detectors, thus enabling background-limited detector operation above 200 K.

  1. Electronic structure of transferred graphene/h-BN van der Waals heterostructures with nonzero stacking angles by nano-ARPES

    Science.gov (United States)

    Wang, Eryin; Chen, Guorui; Wan, Guoliang; Lu, Xiaobo; Chen, Chaoyu; Avila, Jose; Fedorov, Alexei V.; Zhang, Guangyu; Asensio, Maria C.; Zhang, Yuanbo; Zhou, Shuyun

    2016-11-01

    In van der Waals heterostructures, the periodic potential from the Moiré superlattice can be used as a control knob to modulate the electronic structure of the constituent materials. Here we present a nanoscale angle-resolved photoemission spectroscopy (nano-ARPES) study of transferred graphene/h-BN heterostructures with two different stacking angles of 2.4° and 4.3° respectively. Our measurements reveal six replicas of graphene Dirac cones at the superlattice Brillouin zone (SBZ) centers. The size of the SBZ and its relative rotation angle to the graphene BZ are in good agreement with Moiré superlattice period extracted from atomic force microscopy (AFM) measurements. Comparison to the epitaxial graphene/h-BN with 0° stacking angles suggests that the interaction between graphene and h-BN decreases with increasing stacking angle.

  2. Diamond and cBN hybrid and nanomodified cutting tools with enhanced performance: Development, testing and modelling

    DEFF Research Database (Denmark)

    Loginov, Pavel; Mishnaevsky, Leon; Levashov, Evgeny

    2015-01-01

    The potential of enhancement of superhard steel and cast iron cutting tool performance on the basis of microstuctural modifications of the tool materials is studied. Hybrid machining tools with mixed diamond and cBN grains, as well as machining tool with composite nanomodified metallic binder...... are developed, and tested experimentally and numerically. It is demonstrated that both combination of diamond and cBN (hybrid structure) and nanomodification of metallic binder (with hexagonal boron nitride/hBN platelets) lead to sufficient improvement of the cast iron machining performance. The superhard tools...... compared to the tool with the original binder. Computational model of hybrid superhard tools is developed, and applied to the analysis of structure-performance relationships of the tools....

  3. Al-doped graphene-like BN nanosheet as a sensor for para-nitrophenol: DFT study

    Science.gov (United States)

    Peyghan, Ali Ahmadi; Noei, Maziar; Yourdkhani, Sirous

    2013-07-01

    We investigated the electronic sensitivity of pristine and Al-doped BN sheets to para-nitrophenol (p-NP) by using density functional calculations. It was found that p-NP adsorption on the pristine sheet is endothermic and unfavorable. By replacing adsorbing boron atom of the sheet surface by an Al atom, the sheet becomes more reactive to p-NP, so energy of 20.4 kcal/mol is released upon adsorption process. Upon p-NP adsorption on the Al-doped BN sheet, HOMO/LUMO energy gap of the sheet is dramatically decreased from 5.39 to 1.23 eV and it becomes a p-type semiconductor. Thus, the Al-doped BN sheet may transform the presence of p-NP molecule into an electrical signal, and it might be potentially used in p-NP sensors.

  4. Impact of graphene and single-layer BN insertion on bipolar resistive switching characteristics in tungsten oxide resistive memory

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jongmin; Kim, Duhwan; Jo, Yongcheol; Han, Jaeseok; Woo, Hyeonseok [Division of Physics and Semiconductor Science, Dongguk University, Seoul 100-715 (Korea, Republic of); Kim, Hyungsang, E-mail: hskim@dongguk.edu [Division of Physics and Semiconductor Science, Dongguk University, Seoul 100-715 (Korea, Republic of); Kim, K.K., E-mail: kkkim@dongguk.edu [Department of Energy and Materials Engineering, Dongguk University, Seoul 100-715 (Korea, Republic of); Hong, J.P. [Department of Physics, Hanyang University, Seoul 133-791 (Korea, Republic of); Im, Hyunsik, E-mail: hyunsik7@dongguk.edu [Division of Physics and Semiconductor Science, Dongguk University, Seoul 100-715 (Korea, Republic of)

    2015-08-31

    The role of the atomic interface in the resistive switching in Al–WO{sub 3}–Al devices is investigated by inserting metallic graphene or insulating hexagonal BN sheet between the top Al electrode and WO{sub 3} film. Clear reversible bipolar-type resistive switching phenomena were observed, regardless of the interface modification. However, endurance and retention properties were affected by the nature of the interface. While the device containing the graphene interface showed significantly improved performance, another device containing the hexagonal BN sheet showed degraded performance. These experimental findings suggest that atomic configuration of the electrode/oxide interface plays a key role in determining the resistive switching characteristics. - Highlights: • We fabricated WO{sub 3}-based non-volatile memories. • Effects of interface on memory performance were studied using graphene and BN. • The graphene-inserted device showed significantly improved performance.

  5. ZnO quantum dot-doped graphene/h-BN/GaN-heterostructure ultraviolet photodetector with extremely high responsivity

    Science.gov (United States)

    Lu, Yanghua; Wu, Zhiqian; Xu, Wenli; Lin, Shisheng

    2016-12-01

    A ZnO quantum dot photo-doped graphene/h-BN/GaN-heterostructure ultraviolet photodetector with extremely high responsivity of more than 1915 A W-1 and detectivity of more than 1.02 × 1013 Jones (Jones = cm Hz1/2 W-1) has been demonstrated. The interfaced h-BN layer increases the barrier height at the graphene/GaN heterojunction, which decreases the dark current and improves the on/off current ratio of the device. The photo-doping effect increases the barrier height and carrier concentration at the graphene/h-BN/GaN heterojunction, thus the responsivity is improved from 1473 A W-1 to 1915 A W-1 and the detectivity is improved from 5.8 × 1012 to 1.0 × 1013 Jones. Moreover, all of the responsivity and detectivity values are the highest values among all the graphene-based ultraviolet photodetectors.

  6. DEPOSITION OF TiBN HARD FILMS ON HOT-WORKING-STEEL DIES FOR ALUMINIUM EXTRUSION VIA A DUPLEX PROCESS

    Institute of Scientific and Technical Information of China (English)

    K. MUller

    2001-01-01

    Hot working steels have been used as die materials for hot extrusion of aluminium.Due to tribological interaction at elevated temperature between the die bearing and thesurface of extruded aluminium profiles, not only the surface quality of the extrudedproduct, but also the lifetime of the dies decreases. Deposition of TiBN hard films onthe die bearing could improve the die performance. Treatment should be done in aduplex process process combining a plasma nitriding pretreatment (PN) and a plasmaassisted chemical vapour deposition (PACVD) of TiBN. In this study the influence ofthe process conditions on the properties of the duplex coatings was investigated. Therelationship between structure and mechanical property was researched. For testingthese TiBN hardfilms under elevated temperature conditions and for comparison withother possible coatings special extrusion dies with different coated bearings were used.The extrusion trials were performed on the 8MN-extrusion press at the research anddevelopment center for extrusion, Technical University of Berlin.

  7. Synthesis and characterisation of the complete series of B-N analogues of triptycene.

    Science.gov (United States)

    Seven, Omer; Popp, Sebastian; Bolte, Michael; Lerner, Hans-Wolfram; Wagner, Matthias

    2014-06-14

    The reaction between the bisborate Li2[o-C6H4(BH3)2] and 2 equivalents of an appropriate pyrazole derivative (Hpz(R)) in the presence of Me3SiCl yields o-phenylene-bridged pyrazaboles HB(μ-pz(R))2(μ-o-C6H4)BH (3a-3e; Hpz(R) = 4-iodopyrazole (3a), 4-(trimethylsilyl)pyrazole (3b), 3,5-dimethylpyrazole (3c), 3,5-di(tert-butyl)pyrazole (3d), 3,5-bis(trifluoromethyl)pyrazole (3e)). The synthesis approach thus provides access to uncharged B-N triptycenes bearing (i) functionalisable groups, (ii) electron-donating or -withdrawing substituents and (iii) pyrazole rings of varying steric demand. Treatment of p-R*C6H4BBr2 with the potassium tris(pyrazol-1-yl)borates K[HBpz3] or K[p-R*C6H4Bpz3] yields cationic pyrazolyl-bridged pyrazaboles [p-BrC6H4B(μ-pz)3BH]Br ([4a]Br) and [p-R*C6H4B(μ-pz)3Bp-C6H4R*]Br (R* = Br ([4b]Br), I ([4c]Br), SiMe3 ([4d]Br)), which can be regarded as full B-N analogues of triptycene. The B-H bonds of 3b and [4a]Br are unreactive towards tBuC[triple bond, length as m-dash]CH even at temperatures of 80 °C, thereby indicating an appreciable thermal stability of the corresponding B-N cage bonds. Most of the cage compounds are sufficiently inert towards water to allow quick aqueous workup. However, NMR spectroscopy in CD3OD solution reveals degradation of 3b or [4a]Br to the corresponding pyrazoles and o-C6H4(B(OCD3)2)2 or p-BrC6H4B(OCD3)2/B(OCD3)3. The diphenylated species [4b]Br is significantly more stable under the same measurement conditions; even after 76 d, most of the material degrades only to the stage of the syn/anti-pyrazaboles p-BrC6H4(CD3O)B(μ-pz)2B(OCD3)p-C6H4Br (11a/11b). A derivatisation of [4c]Br with nBu3SnC≡CtBu through Stille-type coupling reactions furnishes the alkynyl derivative [p-tBuC≡CC6H4B(μ-pz)3Bp-C6H4C≡CtBu]Br ([4e]Br). Larger B-N aggregates are also accessible: treatment of the tetrakisborate Li4[1,2,4,5-C6H2(BH3)4] with 4 equivalents of Hpz(R) in the presence of Me3SiCl leads to the corresponding B-N

  8. Unleashing the quadratic nonlinear optical responses of graphene by confining white-graphene (h-BN) sections in its framework.

    Science.gov (United States)

    Karamanis, Panaghiotis; Otero, Nicolás; Pouchan, Claude

    2014-05-21

    In an attempt to diversify the options in designing graphene-based systems bearing large second order nonlinear optical (NLO) responses of octupolar and/or dipolar character, the subject of the quadratic NLO properties of hybrid boron nitride (BN) graphene flakes is opened up. State of the art ab initio and density functional theory methods applied on a toolbox of book-text octupolar and arbitrary dipolar planar hybrid h-BN-graphene nanosized systems reveal that by confining finite h-BN sections in the internal network of graphene, the capacity of the π-electron network of graphene species in delivering giant second order NLO responses could be fully exploited. Configuration interaction (CIS) and time-dependent density functional (TD) computations, within the sum-overstate (SOS) perturbational approach, expose that the prevailing (hyper)polarization mechanism, lying under the sizable computed octupolar hyperpolarizabilities, is fueled by alternating positive and negative atomic charges located in the internal part of the hybrid flakes, and more precisely at the BN/graphene intersections. This type of charge transfer mechanism distinguishes, in fact, the elemental graphene dipoles/octupoles we report here from other conventional NLO dipoles or octupoles. More interestingly, it is shown that by controlling the shape, size, and covering area of the h-BN domain (or domains), one can effectively regulate "à volonté" both the magnitudes and types of the second order NLO responses switching from dipolar to octupolar and vice versa. Especially in the context of the latter class of NLO properties, this communication brings into surface novel, graphene-based, octupolar planar or quasiplanar motifs. The take home message of this communication is summarized as follows: When the right BN segment is incorporated in the right section of the right graphene flake, systems of giant quadratic NLO octupolar and/or dipolar responses may emerge.

  9. Boosting the adsorption performance of BN nanosheet as an anode of Na-ion batteries: DFT studies

    Energy Technology Data Exchange (ETDEWEB)

    Hosseinian, A. [Department of Engineering Science, College of Engineering, University of Tehran, P.O. Box 11365-4563, Tehran (Iran, Islamic Republic of); Soleimani-amiri, S. [Department of Chemistry, Karaj Branch, Islamic Azad University, Karaj (Iran, Islamic Republic of); Arshadi, S., E-mail: chemistry_arshadi@pnu.ac.ir [Department of Chemistry, Payame Noor University, Tehran (Iran, Islamic Republic of); Vessally, E. [Department of Chemistry, Payame Noor University, Tehran (Iran, Islamic Republic of); Edjlali, L. [Department of Chemistry, Tabriz Branch, Islamic Azad University, Tabriz (Iran, Islamic Republic of)

    2017-06-28

    Despite the high advance in the Li-ion battery technology, there exist great concerns about its lifetime, safety, cost, and low-temperature performance. It is expected that the Li-ion batteries may be replaced by Na-ion batteries (NIB) because of the low cost, nontoxicity, and wide availability of sodium. Here, we investigated the potential application of BN nanosheets in anode of NIBs by means of density functional theory calculation and introduced a strategy to increase their performance. It was shown that the Na and Na{sup +} are mainly adsorbed on the center of a hexagonal ring of BN sheet with adsorption energies of −0.08 and −33.7 kcal/mol, respectively. Replacing three N atoms of the hexagonal ring with larger P atoms significantly increases the performance of the sheet as an anode of a NIB but the replacement of B by Al decreases the performance. The initial cell voltage of LIB is increased by about 0.67 V after the P-doping which causes a high storage performance with long discharge time. The results are discussed based on the energetic, structural, orbital, charge transfer and electronic properties and provide guidelines to build better high-capacity anode materials for NIBs. - Highlights: • Potential use of BN sheet as anode in Na-ion batteries (NIB) is studied by DFT. • The replacement of B by Al decreases the performance. • The cell voltage of LIB is increased by about 0.67 V after by P-doping. • The order of performance is P-BN > BN >> Al-BN.

  10. Structural studies with BnSP-7 reveal an atypical oligomeric conformation compared to phospholipases A2-like toxins.

    Science.gov (United States)

    de Lima, Lino Fernando G; Borges, Rafael J; Viviescas, Maria Alejandra; Fernandes, Carlos A H; Fontes, Marcos R M

    2017-07-24

    There are 2.5 million cases of snakebite per year and approximately 100,000 at 150,000 deaths. Thus, it is considered an important public health problem by the World Health Organization. Snakes from the Bothrops genus may cause severe local effects in the victims, so it is important to develop inhibitors to treat local effects in patients. In addition, approximately 30 different species of bothropic snakes have been described that may present differences in their venom composition. Small structural differences in the venom proteins may result in different ligands binding. Herein, BnSP-7, a PLA2-like protein that causes local myotoxic effects, was analyzed using different biophysical techniques. Crystal structures of BnSP-7 binding to three different cinnamic acid derivates were solved showing that the ligands bind in the membrane-dockage region (MDoS) of the protein. Spectroscopy fluorescence and microscale thermophoresis (MST) assays showed that these ligands also bind to BnSP-7 in solution and provide comparative information about their affinity to BnSP-7. MST experiments also showed that hydroxyl radicals of the ligands, involved in their binding with the MDoS region of BnSP-7, are essential to increase their affinity with the protein. As this region has been indicated as essential for the myotoxic mechanism, the ligands could potentially be used as inhibitors for BnSP-7. These results provide relevant insights to understand the PLA2-like proteins myotoxic mechanism and may eventually lead to design of new inhibitors for these toxins. Furthermore, a comparative structural analysis of BnSP-7 with other PLA2-like proteins showed that BnSP-7 has an atypical quaternary conformation, suggesting an intermediate state that is unlike other PLA2-like proteins. This information, combined with the absence or partial occupancy of molecules in their hydrophobic channel and the misaligned membrane-disruption region, led us to hypothesize that the protein is not able to fully

  11. A High-Performance WSe2 /h-BN Photodetector using a Triphenylphosphine (PPh3 )-Based n-Doping Technique.

    Science.gov (United States)

    Jo, Seo-Hyeon; Kang, Dong-Ho; Shim, Jaewoo; Jeon, Jaeho; Jeon, Min Hwan; Yoo, Gwangwe; Kim, Jinok; Lee, Jaehyeong; Yeom, Geun Young; Lee, Sungjoo; Yu, Hyun-Yong; Choi, Changhwan; Park, Jin-Hong

    2016-06-01

    The effects of triphenylphosphine (PPh3 )-based n-doping and hexagonal boron nitride (h-BN) insertion on a tungsten diselenide (WSe2 ) photodetector are systematically studied, and a very high performance WSe2 /h-BN heterostucture-based photodetector is demonstrated with a record photoresponsivity (1.27 × 10(6) A W(-1) ) and temporal photoresponse (rise time: 2.8 ms, decay time: 20.8 ms) under 520 nm wavelength and 5 pW power laser illumination.

  12. Raman enhancement effect on two-dimensional layered materials: graphene, h-BN and MoS2.

    Science.gov (United States)

    Ling, Xi; Fang, Wenjing; Lee, Yi-Hsien; Araujo, Paulo T; Zhang, Xu; Rodriguez-Nieva, Joaquin F; Lin, Yuxuan; Zhang, Jin; Kong, Jing; Dresselhaus, Mildred S

    2014-06-11

    Realizing Raman enhancement on a flat surface has become increasingly attractive after the discovery of graphene-enhanced Raman scattering (GERS). Two-dimensional (2D) layered materials, exhibiting a flat surface without dangling bonds, were thought to be strong candidates for both fundamental studies of this Raman enhancement effect and its extension to meet practical applications requirements. Here, we study the Raman enhancement effect on graphene, hexagonal boron nitride (h-BN), and molybdenum disulfide (MoS2), by using the copper phthalocyanine (CuPc) molecule as a probe. This molecule can sit on these layered materials in a face-on configuration. However, it is found that the Raman enhancement effect, which is observable on graphene, hBN, and MoS2, has different enhancement factors for the different vibrational modes of CuPc, depending strongly on the surfaces. Higher-frequency phonon modes of CuPc (such as those at 1342, 1452, 1531 cm(-1)) are enhanced more strongly on graphene than that on h-BN, while the lower frequency phonon modes of CuPc (such as those at 682, 749, 1142, 1185 cm(-1)) are enhanced more strongly on h-BN than that on graphene. MoS2 demonstrated the weakest Raman enhancement effect as a substrate among these three 2D materials. These differences are attributed to the different enhancement mechanisms related to the different electronic properties and chemical bonds exhibited by the three substrates: (1) graphene is zero-gap semiconductor and has a nonpolar C-C bond, which induces charge transfer (2) h-BN is insulating and has a strong B-N bond, while (3) MoS2 is semiconducting with the sulfur atoms on the surface and has a polar covalent bond (Mo-S) with the polarity in the vertical direction to the surface. Therefore, the different Raman enhancement mechanisms differ for each material: (1) charge transfer may occur for graphene; (2) strong dipole-dipole coupling may occur for h-BN, and (3) both charge transfer and dipole-dipole coupling may

  13. Investigation of band structure and electrochemical properties of h-BN/rGO composites for asymmetric supercapacitor applications

    Energy Technology Data Exchange (ETDEWEB)

    Saha, Sanjit; Jana, Milan; Samanta, Pranab; Murmu, Naresh C. [Surface Engineering & Tribology Division, CSIR-Central Mechanical Engineering Research Institute, Durgapur, 713209 (India); Academy of Scientific and Innovative Research (AcSIR), CSIR-CMERI Campus, Durgapur, 713209 (India); Kim, Nam H. [Advanced Materials Institute of BIN Convergence Technology (BK21 Plus Global), Dept. of BIN Convergence Technology, Chonbuk National University, Jeonju, Jeonbuk, 54896 (Korea, Republic of); Kuila, Tapas, E-mail: tkuila@gmail.com [Surface Engineering & Tribology Division, CSIR-Central Mechanical Engineering Research Institute, Durgapur, 713209 (India); Academy of Scientific and Innovative Research (AcSIR), CSIR-CMERI Campus, Durgapur, 713209 (India); Lee, Joong H., E-mail: jhl@jbnu.ac.kr [Advanced Materials Institute of BIN Convergence Technology (BK21 Plus Global), Dept. of BIN Convergence Technology, Chonbuk National University, Jeonju, Jeonbuk, 54896 (Korea, Republic of); Carbon Composite Research Centre, Department of Polymer & Nanoscience and Technology, Chonbuk National University, Jeonju, Jeonbuk, 54896 (Korea, Republic of)

    2017-04-01

    The effect of different content of graphene oxide (GO) on the electrical and electrochemical property of h-BN/reduced GO (rGO) hetero-structure is investigated elaborately. The increasing amount of rGO within the h-BN moiety plays fascinating role by reducing the electronic work function while increasing the density of state of the electrode. Furthermore, different h-BN/rGO architecture shows different potential window and the transition from pseudocapacitance to electrochemical double layer capacitance (EDLC) is observed with increasing π-conjugation of C atoms. The rod like h-BN is aligned as sheet while forming super-lattice with rGO. Transmission electron microscopy images show crystalline morphology of the hetero-structure super-lattice. The valance band and Mott-Shotky relationship determined from Mott-Shotky X-ray photoelectron spectroscopy shows that the electronic band structure of super-lattice is improved as compared to the insulating h-BN. The h-BN/rGO super-lattice provides high specific capacitance of ∼960 F g{sup −1}. An asymmetric device configured with h-BN/rGO super-lattice and B, N doped rGO shows very high energy and power density of 73 W h kg{sup −1} and 14,000 W kg{sup −1}, respectively. Furthermore, very low relaxation time constant of ∼1.6 ms and high stability (∼80%) after 10,000 charge-discharge cycles ensure the h-BN/rGO super-lattice as potential materials for the next generation energy storage applications. - Highlights: • Band gap energy of boron nitride decreased with increasing graphene oxide content. • Graphene oxide effectively affected the charge storage mechanism of the composite. • Morphology of boron nitride changed from rod to sheet while forming superlattice. • Highly conducting superlattice showed excellent supercapacitor performance. • Asymmetric device exhibited long stability with high energy and power density.

  14. High hardness BaCb-(BxOy/BN) composites with 3D mesh-like fine grain-boundary structure by reactive spark plasma sintering.

    Science.gov (United States)

    Vasylkiv, Oleg; Borodianska, Hanna; Badica, Petre; Grasso, Salvatore; Sakka, Yoshio; Tok, Alfred; Su, Liap Tat; Bosman, Michael; Ma, Jan

    2012-02-01

    Boron carbide B4C powders were subject to reactive spark plasma sintering (also known as field assisted sintering, pulsed current sintering or plasma assisted sintering) under nitrogen atmosphere. For an optimum hexagonal BN (h-BN) content estimated from X-ray diffraction measurements at approximately 0.4 wt%, the as-prepared BaCb-(BxOy/BN) ceramic shows values of Berkovich and Vickers hardness of 56.7 +/- 3.1 GPa and 39.3 +/- 7.6 GPa, respectively. These values are higher than for the vacuum SPS processed B4C pristine sample and the h-BN -mechanically-added samples. XRD and electronic microscopy data suggest that in the samples produced by reactive SPS in N2 atmosphere, and containing an estimated amount of 0.3-1.5% h-BN, the crystallite size of the boron carbide grains is decreasing with the increasing amount of N2, while for the newly formed lamellar h-BN the crystallite size is almost constant (approximately 30-50 nm). BN is located at the grain boundaries between the boron carbide grains and it is wrapped and intercalated by a thin layer of boron oxide. BxOy/BN forms a fine and continuous 3D mesh-like structure that is a possible reason for good mechanical properties.

  15. Effect of different thickness h-BN coatings on interface shear strength of quartz fiber reinforced Si-O-C-N composite

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Shubin [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); Zheng, Yu, E-mail: shubinwang@buaa.edu.cn [Key Laboratory of Aerospace Materials and Performance (Ministry of Education), School of Materials Science and Engineering, Beihang University, Beijing 100191 (China); International Centre for Bamboo and Rattan, Beijing 100102 (China)

    2014-02-15

    Hexagonal boron nitride (h-BN) coatings with different thickness were prepared on quartz fibers to improve mechanical properties of quartz fiber reinforced Si-O-C-N composite. Scanning electron microscopy (SEM), push-out test and single edge notched beam (SENB) in three point bending test were employed to study morphology, interface shear strength and fracture toughness of the composite. The results showed that h-BN coatings changed the crack growth direction and weaken the interface shear strength efficiently. When the h-BN coating was 308.2 nm, the interface shear strength was about 5.2 MPa, which was about one-quarter of that of the sample without h-BN coatings. After the heating process for obtaining composite, the h-BN nanometer-sized grains would grow up to micron-sized hexagonal grains. Different thickness h-BN coatings had different structure. When the coatings were relatively thin, the hexagonal grains were single layer structure, and when the coatings were thicker, the hexagonal grains were multiple layer structure. This multiple layer interface phase would consume more power of cracks, thus interface shear strength of the composite decreased steadily with the increasing of h-BN coatings thickness. When the coating thickness was 238.8 nm, K{sub IC} reaches the peak value 3.8 MPa m{sup 1/2}, which was more than two times of that of composites without h-BN coatings.

  16. Thick c-BN films deposited by radio frequency magnetron sputtering in argon/nitrogen gas mixture with additional hydrogen gas

    Science.gov (United States)

    Zhao, Yan; Gao, Wei; Xu, Bo; Li, Ying-Ai; Li, Hong-Dong; Gu, Guang-Rui; Yin, Hong

    2016-10-01

    The excellent physical and chemical properties of cubic boron nitride (c-BN) film make it a promising candidate for various industry applications. However, the c-BN film thickness restricts its practical applications in many cases. Thus, it is indispensable to develop an economic, simple and environment-friend way to synthesize high-quality thick, stable c-BN films. High-cubic-content BN films are prepared on silicon (100) substrates by radio frequency (RF) magnetron sputtering from an h-BN target at low substrate temperature. Adhesions of the c-BN films are greatly improved by adding hydrogen to the argon/nitrogen gas mixture, allowing the deposition of a film up to 5-μm thick. The compositions and the microstructure morphologies of the c-BN films grown at different substrate temperatures are systematically investigated with respect to the ratio of H2 gas content to total working gas. In addition, a primary mechanism for the deposition of thick c-BN film is proposed. Project supported by the National Natural Science Foundation of China (Grant Nos. 51572105, 61504046, and 51272224), the Scientific Research Foundation for the Returned Overseas Chinese Scholars, State Education Ministry, China, the Development and Reform Commission of Jilin Province, China (Grant No. 2015Y050), and the Scientific Research Foundation for the Returned Overseas of Jilin Province, China.

  17. First-principles studies of BN sheets with absorbed transition metal single atoms or dimers: stabilities, electronic structures, and magnetic properties.

    Science.gov (United States)

    Ma, Dongwei; Lu, Zhansheng; Ju, Weiwei; Tang, Yanan

    2012-04-11

    BN sheets with absorbed transition metal (TM) single atoms, including Fe, Co, and Ni, and their dimers have been investigated by using a first-principles method within the generalized gradient approximation. All of the TM atoms studied are found to be chemically adsorbed on BN sheets. Upon adsorption, the binding energies of the Fe and Co single atoms are modest and almost independent of the adsorption sites, indicating the high mobility of the adatoms and isolated particles to be easily formed on the surface. However, Ni atoms are found to bind tightly to BN sheets and may adopt a layer-by-layer growth mode. The Fe, Co, and Ni dimers tend to lie (nearly) perpendicular to the BN plane. Due to the wide band gap of the pure BN sheet, the electronic structures of the BN sheets with TM adatoms are determined primarily by the distribution of TM electronic states around the Fermi level. Very interesting spin gapless semiconductors or half-metals can be obtained in the studied systems. The magnetism of the TM atoms is preserved well on the BN sheet, very close to that of the corresponding free atoms and often weakly dependent on the adsorption sites. The present results indicate that BN sheets with adsorbed TM atoms have potential applications in fields such as spintronics and magnetic data storage due to the special spin-polarized electronic structures and magnetic properties they possess.

  18. Edge and substrate-induced bandgap in zigzag graphene nanoribbons on the hexagonal nitride boron 8-ZGNR/h-BN(0001

    Directory of Open Access Journals (Sweden)

    V. V. Ilyasov

    2013-09-01

    Full Text Available The results of DFT (GGA-PBEsol and DFT(PBE-D2 study of the band structure of zigzag graphene nanoribbons on hexagonal nitride boron 8-ZGNR/h-BN(0001 are presented, suitable as potential base for new materials for spintronics. It offers a study of regularities in the changes of the valence band electron structure and the induction of the energy gap in the series 8-ZGNR → 8-ZGNR/h-BN(0001 → graphene/h-BN(0001. The peculiarities of the spin state at the Fermi level, the roles of the edge effect and the effect of substrate in formation of the band gap in 8-ZGNR/h-BN(0001 system are discussed. Our calculations shown that vdW-correction plays an important role in the adsorption of GNR on h-BN and results in reduction of the interplanar distances in equilibrium systems ZGNRs/h-BN(0001. As a result of the structural changes we have obtained new values of the energy gap in the 8-ZGNR-AF and 8-ZGNR-AF/h-BN(0001 systems. The paper demonstrates appearance of 600 meV energy gap in the 8-ZGNR/h-BN(0001 interface. The contributions of nanoribbon edges and the substrate in formation of the gap have been differentiated for the first time. The estimations of local magnetic moments on carbon atoms are made. Shown that in case of ferromagnetic ordering substrate presense causes insignificant splitting of the bands. The splitting reached only (14-28 meV. Since the electronic states of a suspended GNR in point (k=π are degenerate near the Fermi level, we can assume that the above splitting in 8-ZGNR/h-BN(0001 is only determined by the contribution of the h-BN(0001 substrate.

  19. Tuning Electronic Structures of BN and C Double-Wall Hetero-Nanotubes

    Directory of Open Access Journals (Sweden)

    Xueran Liu

    2015-01-01

    Full Text Available First principle calculations based on density functional theory with the generalized gradient approximation were carried out to investigate the energetic and electronic properties of carbon and boron nitride double-wall hetero-nanotubes (C/BN-DWHNTs with different chirality and size, including an armchair (n, n carbon nanotube (CNT enclosed in (m, m boron nitride nanotube (BNNT and a zigzag (n, 0 CNT enclosed in (m, 0 BNNT. The electronic structure of these DWHNTs under a transverse electric field was also investigated. The ability to tune the band gap with changing the intertube distance (di and imposing an external electric field (F of zigzag DWHNTs provides the possibility for future electronic and electrooptic nanodevice applications.

  20. Magnetic, electronic and optical properties of different graphene, BN and BC2N nanoribbons

    Science.gov (United States)

    Guerra, T.; Leite, L.; Azevedo, S.; de Lima Bernardo, B.

    2017-04-01

    Graphene nanoribbons are predicted to be essential components in future nanoelectronics. The size, edge type, form, arrangement of atoms and width of nanoribbons drastically change their properties. However, magnetic, electronic and optical properties of armchair, chevron and sawtooth of graphene, BN and BC2N nanoribbons are not fully understood so far. Here, we make use of first-principles calculations based on the density functional theory (DFT) to investigate the structural, magnetic, electronic and optical properties of nanoribbons of graphene, boron nitride and BC2N with armchair edge, chevron-type and sawtooth forms. The lowest formation energies were found for the armchair and chevron nanoribbons of graphene and boron nitride. We have shown that the imbalance of carbon atoms between different sublattices generates a net magnetic moment. Chevron-type nanoribbons of BC2N and graphene showed a band gap comparable with silicon, and a high light absorption in the visible spectrum when compared to the other configurations.

  1. 3-Methyl-1,2-BN-Cyclopentane: A Promising H2 Storage Material?

    Energy Technology Data Exchange (ETDEWEB)

    Luo, Wei; Neiner, Doinita; Karkamkar, Abhijeet J.; Parab, Kshitij; Garner, Edward B.; Dixon, David A.; Matson, Dean W.; Autrey, Thomas; Liu, Shih-Yuan

    2013-01-21

    We provide detailed characterization of properties for 3-methyl-1,2-BN-cyclopentane 1 that are relevant to H2 storage applications such as viscosity, thermal stability, H2 gas stream purity, and polarity. The viscosity of 1 at room temperature is 25±5 cP, about one fourth the viscosity of olive oil. TGA/MS analysis indicates that liquid carrier 1 is thermally stable at 30 °C but decomposes slowly at 50 °C. RGA data suggest that the H2 desorption from 1 is a clean process, producing relatively pure H2 gas. Compound 1 is a polar zwitterionic type liquid consistent with theoretical predictions and solvatochromic studies. "T.A. acknowledges support from the Fuel Cell Technology Program at U.S. DOE, Office of Energy Efficiency 65 and Renewable Energy. Pacific Northwest National Laboratory is operated by Battelle."

  2. A DFT study of 5-fluorouracil adsorption on the pure and doped BN nanotubes

    Science.gov (United States)

    Soltani, Alireza; Baei, Mohammad T.; Tazikeh Lemeski, E.; Kaveh, Sara; Balakheyli, Hanzaleh

    2015-11-01

    The electronic and adsorption properties of the pristine, Al-, Ga-, and Ge-doped BN nanotubes interacted with 5-fluorouracil molecule (5-FU) were theoretically investigated in the gas phase using the B3LYP density functional theory (DFT) calculations. It was found that the adsorption behavior of 5FU molecule on the pristine (8, 0) and (5, 5) BNNTs are electrostatic in nature. In contrast, the 5FU molecule (O-side) implies strong adsorption on the metal-doped BNNTs. Our results indicate that the Ga-doped presents high sensitivity and strong adsorption with the 5-FU molecule than the Al- and Ge-doped BNNTs. Therefore, it can be introduced as a carrier for drug delivery applications.

  3. Electronic and mechanical properties of hybrid graphene/h-BN nanoribbons

    Energy Technology Data Exchange (ETDEWEB)

    Pooja,, E-mail: j.poojaa1228@gmail.com; Sharma, Munish; Ahluwalia, P. K. [Physics Department, Himachal Pradesh University, Shimla-171005 (India); Kumar, Ashok [Physics Department, Panjab University, Chandigarh-160014 (India); Thakur, Anil [Physics Department, Govt. Collage Solan, Himachal Pradesh-173212 (India)

    2015-06-24

    The electronic and mechanical properties of one-dimensional super lattice which are composed of controlled domain size of graphene and h-BN nanoribbons with saturated and unsaturated edges are studied by means of the first-principles method. The results show that the studied zigzag- nanoribbons (Z-GBNNR) with unsaturated edges are half-metallic, while they transform into non-magnetic semiconductor on hydrogen passivations. On the other hand the band-gap of armchair-edges nanoribbons (A-GBNNR) get enhanced by the edges saturation. Furthermore, unsaturated edges A-GBNNR and saturated edges Z-GBNNR are found mechanically more stable. These results provide a fingerprint for their use in spintronics and electronics devices.

  4. Contribution of neutron-capture reactions in energy release in the fuel core of BN-600

    Science.gov (United States)

    Bahdanovich, R. B.; Romanenko, V. I.; Tikhomirov, G. V.

    2017-01-01

    The use of modern computing powers and calculation methods allows to get closer to reality results of modelling, as well as to explore areas inaccessible to the experiment. Until now, the calculation of the energy released from the capture of neutrons in the reactor core has been given little attention. The method for calculation of the effective energy release components in a nuclear reactor allows to specify the values used by engineering programs for capture energy release in fast reactors. The paper presents improved method and the results of calculation of three models of the reactor BN-600. It is shown that the contribution of capture energy release in effective energy release for fresh fuel is equal to 4%, which is more than for VVER reactors. During the calculation we created a simple calculation model of the fast reactor, considering its features.

  5. Structural and electronic properties of V-doped cubic BN: A density functional theory study

    Science.gov (United States)

    Espitia R, Miguel J.; Díaz F, John H.; Rodríguez Martínez, Jairo Arbey

    2016-10-01

    The structural, electronic, and magnetic properties of c-BN compound doped with V atoms were calculated by means of the pseudopotential method, employed exactly as implemented in computational Quantum ESPRESSO code. For the description of the electron-electron interaction, generalized gradient approximation (GGA) was used. A half-metallic behavior is predicted for the concentrations B0.9375V0.0625N and B0.875V0.125N, because of the fact that the majority spins are metallic and the minority spins are semiconducting. We found magnetic moments of 2.0 and 4.0 μβ per supercell, respectively. The main contribution to the magnetic moment comes from the V atom, with local moments of 1.61 μβ/V-atom. These compounds are good candidates for potential applications in spintronics and as spin injectors.

  6. Comparison of Boron diffused emitters from BN, BSoD and H3BO3 dopants

    Science.gov (United States)

    Singha, Bandana; Singh Solanki, Chetan

    2016-12-01

    In this work, we are comparing different limited boron dopant sources for the emitter formation in n-type c-Si solar cells. High purity boric acid solution, commercially available boron spin on dopant and boron nitride solid source are used for comparison of emitter doping profiles for the same time and temperature conditions of diffusion. The characterizations done for the similar sheet resistance values for all the dopant sources show different surface morphologies and different device parameters. The measured emitter saturation current densities (Joe) are more than 20 fA cm-2 for all the dopant sources. The bulk carrier lifetimes measured for different diffusion conditions and different solar cell parameters for the similar sheet resistance values show the best result for boric acid diffusion and the least for BN solid source. So, different dopant sources result in different emitter and cell performances.

  7. Effects of h-BN addition on microstructures and mechanical properties of β-CaSiO3 bioceramics.

    Science.gov (United States)

    Pan, Ying; Yao, Dongxu; Zuo, Kaihui; Xia, Yongfeng; Yin, Jinwei; Liang, Hanqin; Zeng, Yuping

    2016-09-01

    The main purpose of this study consists in investigating the effects of h-BN addition on the sinterability of β-CaSiO3 (β-CS) bioceramics. β-CS bioceramics with different contents of h-BN were prepared at the sintering temperature ranging from 800°C to 1100°C. The results showed that h-BN can be successfully used as sintering additive by being oxidized to form low melting point B2O3 related glassy phase and enhanced the flexural strength by the formation of rod-like β-CS grains. β-CS bioceramics with 1wt% h-BN sintered at 1000°C revealed flexural strength and fracture toughness of 182.2MPa and 2.4MPam(1/2) respectively, which were much higher than that of pure β-CS bioceramics (30.2MPa, 0.53MPam(1/2)) fabricated in the same processing condition.

  8. Inheritance and expression patterns of BN28, a low temperature induced gene in Brassica napus, throughout the Brassicaceae.

    Science.gov (United States)

    Hawkins, G P; Nykiforuk, C L; Johnson-Flanagan, A M; Boothe, J G

    1996-08-01

    Molecular genetics is becoming an important tool in the breeding and selection of agronomically important traits. BN28 is a low temperature induced gene in Brassicaceae species. PCR and Southern blot analysis indicate that BN28 is polymorphic in the three diploid genomes: Brassica rapa (AA), Brassica nigra (BB), and Brassica oleracea (CC). Of the allotetraploids, Brassica napus (AACC) is the only species to have inherited homologous genes from both parental genomes. Brassica juncea (AABB) and Brassica carinata (BBCC) have inherited homologues from the AA and CC genomes, respectively, while Sinapsis arvensis (SS) contains a single homologue from the BB genome and Sinapsis alba (dd) appears to be different from all the diploid parents. All species show message induction when exposed to low temperature. However, differences in expression were noticed at the protein level, with silencing occurring in the BB genome at the level of translation. Results suggest that silencing is occurring in diploid species where duplication may not have occurred. Molecular characterization and inheritance of BN28 homologues in the Brassicaceae may play an important role in determining their quantitative function during exposure to low temperature. Key words : Brassicaceae, BN28, inheritance, polymorphism.

  9. Analytical Study of the Propagation of Fast Longitudinal Modes along wz-BN/AlN Thin Acoustic Waveguides

    Directory of Open Access Journals (Sweden)

    Cinzia Caliendo

    2015-01-01

    Full Text Available The propagation of the fundamental symmetric Lamb mode S0 along wz-BN/AlN thin composite plates suitable for telecommunication and sensing applications is studied. The investigation of the acoustic field profile across the plate thickness revealed the presence of modes having longitudinal polarization, the Anisimkin Jr. plate modes (AMs, travelling at a phase velocity close to that of the wz-BN longitudinal bulk acoustic wave propagating in the same direction. The study of the S0 mode phase velocity and coupling coefficient (K2 dispersion curves, for different electrical boundary conditions, has shown that eight different coupling configurations are allowable that exhibit a K2 as high as about 4% and very high phase velocity (up to about 16,700 m/s. The effect of the thickness and material type of the metal floating electrode on the K2 dispersion curves has also been investigated, specifically addressing the design of an enhanced coupling device. The gravimetric sensitivity of the BN/AlN-based acoustic waveguides was then calculated for both the AMs and elliptically polarized S0 modes; the AM-based sensor velocity and attenuation shifts due to the viscosity of a surrounding liquid was theoretically predicted. The performed investigation suggests that wz-BN/AlN is a very promising substrate material suitable for developing GHz band devices with enhanced electroacoustic coupling efficiency and suitable for application in telecommunications and sensing fields.

  10. Strain-induced magnetic transitions in half-fluorinated single layers of BN, GaN and graphene

    Science.gov (United States)

    Ma, Yandong; Dai, Ying; Guo, Meng; Niu, Chengwang; Yu, Lin; Huang, Baibiao

    2011-05-01

    Recently, extensive experimental and theoretical studies on single layers of BN, GaN and graphene have stimulated enormous interest in exploring the properties of these sheets by decorating their surfaces. In the present work we discuss half-fluorinated single layers of BN, GaN and graphene, in the context of intercoupling between strain and magnetic property. First-principles calculations reveal that the energy difference between ferromagnetic and antiferromagnetic couplings increases significantly with strain increasing for half-fluorinated BN, GaN and graphene sheets. More surprisingly, the half-fluorinated BN and GaN sheets exhibit intriguing magnetic transitions between ferromagnetism and antiferromagnetism by applying strain, even giving rise to half-metal when the sheets are under compression of 6%. It is found that the magnetic coupling as well as the strain-dependent magnetic transition behavior arise from the combined effects of both through-bond and p-p direct interactions. Our work offers a new avenue to facilitate the design of controllable and tunable spin devices.

  11. The different effects of oxygen and air DBD plasma byproducts on the degradation of methyl violet 5BN.

    Science.gov (United States)

    Chen, Guangliang; Zhou, Mingyan; Chen, Shihua; Chen, Wenxing

    2009-12-30

    Through a novel design of the dielectric barrier discharge (DBD) plasma plume used in fabric-fiber surface modification, its discharge byproducts mainly including downstream gases and ultraviolet light were used to treat the dye solution. The different influence of oxygen and air DBD plasmas on the degradation of methyl violet 5BN (MV-5BN), which is widely used in textile industry, was investigated in this paper. The results showed that the cooperation between ultraviolet light and active species generated by the DBD plasma can decolorize MV-5BN effectively, and the chromophore peaks attributed to the -NN- bonds in MV-5BN molecule disappeared entirely when the azo dye solutions were treated for 25 min by the air and oxygen DBD plasmas. The degradation reaction followed an exponential kinetics over time, and the peak of aromatic derivatives at 209 nm in UV-vis spectra increased nearly 2.7 times when the dye solution was treated for 30 min by air DBD plasma. However, the oxygen DBD plasma could deplete the aromatic derivatives entirely. It is found that the formation of O(3) and NO(x) in the downstream gases of air and oxygen plasmas may be responsible for the different effects on the azo dye degradation.

  12. Low-temperature solid state synthesis and in situ phase transformation to prepare nearly pure cBN.

    Science.gov (United States)

    Lian, Gang; Zhang, Xiao; Tan, Miao; Zhang, Shunjie; Cui, Deliang; Wang, Qilong

    2011-07-14

    Cubic boron nitride (cBN) is synthesized by a low-temperature solid state synthesis and in situ phase transformation route with NH(4)BF(4), B, NaBH(4) and KBH(4) as the boron sources and NaN(3) as the nitrogen source. Furthermore, two new strategies are developed, i.e., applying pressure on the reactants during the reaction process and introducing the structural induction effect. These results reveal that the relative contents of cBN are greatly increased by applying these new strategies. Finally, almost pure cBN (∼90%) crystals are obtained by reacting NH(4)BF(4) and NaN(3) at 250 °C and 450 MPa for 24 h, with NaF as the structural induction material. The heterogeneous nucleation mechanism can commendably illuminate the structure induction effect of NaF with face center cubic structure. In addition, the induction effect results in the cBN nanocrystals presenting obvious oriented growth of {111} planes.

  13. High-temperature compressive deformation of Si{sub 3}N{sub 4}/BN fibrous monoliths.

    Energy Technology Data Exchange (ETDEWEB)

    Routbort, J. L.

    1999-02-04

    Fibrous monolithic Si{sub 3}N{sub 4}/BN ({approx}85 vol.% Si{sub 3}N{sub 4}/15 vol.% BN) and monolithic Si{sub 3}N{sub 4} ceramics were compressed at a nearly constant strain rate ({var_epsilon}) at 1200-1400 C in N{sub 2}. The {var_epsilon} range was {approx}1 x 10{sup {minus}6} to 5 x 10{sup {minus}6} s{sup {minus}1}; the stress ({sigma}) range was 37-202 MPa. The Si{sub 3}N{sub 4} and the unidirectional fibrous monoliths that were oriented with the long axis of the Si{sub 3}N{sub 4} cells parallel to the compression direction exhibited plasticity at 1300 and 1400 C, with {var_epsilon} {proportional_to} {sigma}. A 0/90{degree} cross-ply Si{sub 3}N{sub 4}/BN laminate also exhibited significant plasticity, but it was weaker than the above-mentioned ceramics. The unidirectional fibrous monoliths that were compressed perpendicular to the cell direction fractured at {approx}50 MPa in all tests. A {+-}45{degree} laminate tested at 1300 C fractured at a stress of {approx}40 MPa. Low fracture stress correlated with shear through BN layers.

  14. Bandgap renormalization and work function tuning in MoSe2/hBN/Ru(0001) heterostructures

    Science.gov (United States)

    Zhang, Qiang; Chen, Yuxuan; Zhang, Chendong; Pan, Chi-Ruei; Chou, Mei-Yin; Zeng, Changgan; Shih, Chih-Kang

    2016-12-01

    The van der Waals interaction in vertical heterostructures made of two-dimensional (2D) materials relaxes the requirement of lattice matching, therefore enabling great design flexibility to tailor novel 2D electronic systems. Here we report the successful growth of MoSe2 on single-layer hexagonal boron nitride (hBN) on the Ru(0001) substrate using molecular beam epitaxy. Using scanning tunnelling microscopy and spectroscopy, we found that the quasi-particle bandgap of MoSe2 on hBN/Ru is about 0.25 eV smaller than those on graphene or graphite substrates. We attribute this result to the strong interaction between hBN/Ru, which causes residual metallic screening from the substrate. In addition, the electronic structure and the work function of MoSe2 are modulated electrostatically with an amplitude of ~0.13 eV. Most interestingly, this electrostatic modulation is spatially in phase with the Moiré pattern of hBN on Ru(0001) whose surface also exhibits a work function modulation of the same amplitude.

  15. Translation and validation of the EORTC brain cancer module (EORTC QLQ-BN20) for use in Iran

    NARCIS (Netherlands)

    Khoshnevisan, A.; Yekaninejad, M.S.; Ardakani, S.K.; Pakpour, A.H.; Mardani, A.; Aaronson, N.K.

    2012-01-01

    Background The aim of this study was to translate the EORTC quality of life questionnaire for brain cancer, the QLQ-BN20, into Persian, and to evaluate its psychometric properties when used among brain cancer patients in Iran. Methods A standard backward and forward translation procedure was used to

  16. SN 2015BN: A Detailed Multi-wavelength View of a Nearby Superluminous Supernova

    Science.gov (United States)

    Nicholl, M.; Berger, E.; Smartt, S. J.; Margutti, R.; Kamble, A.; Alexander, K. D.; Chen, T.-W.; Inserra, C.; Arcavi, I.; Blanchard, P. K.; Cartier, R.; Chambers, K. C.; Childress, M. J.; Chornock, R.; Cowperthwaite, P. S.; Drout, M.; Flewelling, H. A.; Fraser, M.; Gal-Yam, A.; Galbany, L.; Harmanen, J.; Holoien, T. W.-S.; Hosseinzadeh, G.; Howell, D. A.; Huber, M. E.; Jerkstrand, A.; Kankare, E.; Kochanek, C. S.; Lin, Z.-Y.; Lunnan, R.; Magnier, E. A.; Maguire, K.; McCully, C.; McDonald, M.; Metzger, B. D.; Milisavljevic, D.; Mitra, A.; Reynolds, T.; Saario, J.; Shappee, B. J.; Smith, K. W.; Valenti, S.; Villar, V. A.; Waters, C.; Young, D. R.

    2016-07-01

    We present observations of SN 2015bn (=PS15ae = CSS141223-113342+004332 = MLS150211-113342+004333), a Type I superluminous supernova (SLSN) at redshift z = 0.1136. As well as being one of the closest SLSNe I yet discovered, it is intrinsically brighter ({M}U≈ -23.1) and in a fainter galaxy ({M}B≈ -16.0) than other SLSNe at z˜ 0.1. We used this opportunity to collect the most extensive data set for any SLSN I to date, including densely sampled spectroscopy and photometry, from the UV to the NIR, spanning -50 to +250 days from optical maximum. SN 2015bn fades slowly, but exhibits surprising undulations in the light curve on a timescale of 30-50 days, especially in the UV. The spectrum shows extraordinarily slow evolution except for a rapid transformation between +7 and +20-30 days. No narrow emission lines from slow-moving material are observed at any phase. We derive physical properties including the bolometric luminosity, and find slow velocity evolution and non-monotonic temperature and radial evolution. A deep radio limit rules out a healthy off-axis gamma-ray burst, and places constraints on the pre-explosion mass loss. The data can be consistently explained by a ≳ 10 M {}⊙ stripped progenitor exploding with ˜ {10}51 erg kinetic energy, forming a magnetar with a spin-down timescale of ˜20 days (thus avoiding a gamma-ray burst) that reheats the ejecta and drives ionization fronts. The most likely alternative scenario—interaction with ˜20 M {}⊙ of dense, inhomogeneous circumstellar material—can be tested with continuing radio follow-up.

  17. Cloning of Glutamine Synthetase BnGS2 Allele Genes from Ramie (Boehmeria nivea L.) and Study on Gene-Transforming Tobacco%苎麻谷氨酰胺合成酶BnGS2等位基因的克隆及其转基因烟草特性

    Institute of Scientific and Technical Information of China (English)

    郑建树; 段叶辉; 熊和平; 喻春明; 陈平; 王延周; 谭龙涛; 陈继康; 朱涛涛; 卢凌霄; 朱娟娟

    2014-01-01

    【目的】克隆谷氨酰胺合成酶BnGS2等位基因,分别构建其超量表达载体,并探讨其在转基因烟草中对氮代谢的影响。【方法】依据苎麻转录组unigenes和RT-PCR技术克隆苎麻BnGS2等位基因,利用内切酶TaqⅠ对目的等位基因在中苎1号自交 F1和亲本中进行酶切鉴定,并利用生物信息学对基因序列和结构特征进行分析;通过同源重组技术分别构建 BnGS2等位基因的超量表达载体,并在农杆菌(Agrobacterium tumefaciens)LBA4404的介导下,通过叶盘法将超量表达载体转入烟草中,通过Kan筛选、转化植株基因组DNA PCR验证获得转基因T0植株;利用qRT-PCR分析BnGS2等位基因在转基因T1植株中的相对表达水平,并测定植株叶片中的GS活性、株高、鲜重、可溶蛋白及总氮含量。【结果】首次从苎麻中克隆了一对GS2等位基因,命名为BnGS2-1和BnGS2-2,等位基因序列全长1340 bp,含有一个1293 bp的ORF区,编码430个氨基酸残基多肽;等位基因核苷酸序列在11个位点上存在差异,导致编码的多肽在195、382位点上的氨基酸残基存在替换现象(BnGS2-1为脯氨酸和天冬酰胺,BnGS2-2为苏氨酸和丝氨酸);NCBI BLASTP分析表明苎麻BnGS2与Pisum sativum、Vigna radiata、Glycine max、Phaseolus vulgaris、Medicago truncatula具有很近的亲缘关系;构建了能分别超量表达BnGS2-1和BnGS2-2的载体,并获得能分别超量表达BnGS2-1和BnGS2-2转基因烟草植株;与野生型烟草植株相比,超量表达BnGS2等位基因(BnGS2-1和BnGS2-2)都能显著性提高转基因植株叶片GS活性、鲜重和可溶性蛋白的含量,株高和总氮含量也有增加,但没有达到显著性水平。另外,超量表达不同BnGS2等位基因(BnGS2-1和BnGS2-2)的转基因烟草植株,在株高、鲜重、叶片可溶性蛋白及总氮含量上并没有显著性差异。【结论】在烟草中分

  18. Single-step synthesis of crystalline h-BN quantum- and nanodots embedded in boron carbon nitride films

    Science.gov (United States)

    Matsoso, Boitumelo J.; Ranganathan, Kamalakannan; Mutuma, Bridget K.; Lerotholi, Tsenolo; Jones, Glenn; Coville, Neil J.

    2017-03-01

    Herein we report on the synthesis and characterization of novel crystalline hexagonal boron nitride (h-BN) quantum- and nanodots embedded in large-area boron carbon nitride (BCN) films. The films were grown on a Cu substrate by an atmospheric pressure chemical vapour deposition technique. Methane, ammonia, and boric acid were used as precursors for C, N and B to grow these few atomic layer thick uniform films. We observed that both the size of the h-BN quantum/nanodots and thickness of the BCN films were influenced by the vaporization temperature of boric acid as well as the H3BO3 (g) flux over the Cu substrate. These growth conditions were easily achieved by changing the position of the solid boric acid in the reactor with respect to the Cu substrate. Atomic force microscope (AFM) and TEM analyses show a variation in the h-BN dot size distribution, ranging from nanodots (∼224 nm) to quantum dots (∼11 nm) as the B-source is placed further away from the Cu foil. The distance between the B-source and the Cu foil gave an increase in the C atomic composition (42 at% C–65 at% C) and a decrease in both B and N contents (18 at% B and 14 at% N to 8 at% B and 7 at% N). UV–vis absorption spectra showed a higher band gap energy for the quantum dots (5.90 eV) in comparison with the nanodots (5.68 eV) due to a quantum confinement effect. The results indicated that the position of the B-source and its reaction with ammonia plays a significant role in controlling the nucleation of the h-BN quantum- and nanodots. The films are proposed to be used in solar cells. A mechanism to explain the growth of h-BN quantum/nanodots in BCN films is reported.

  19. Research Progress of PcBN Materials and Cutting Tools%PcBN材料及其刀具研究进展

    Institute of Scientific and Technical Information of China (English)

    班新星; 谢欢; 纪莲清; 刘书锋

    2012-01-01

    介绍了PcBN材料及其刀具的发展史,给出了制备PcBN的工艺流程及关键技术.通过大量实验数据总结出,作为合成PcBN的基本原料,cBN具有高的硬度和化学惰性.但高的化学惰性阻碍了晶格间的良好烧结,即cBN与cBN晶粒直接键合是十分困难的.分析了不同结合剂对制备PcBN的影响,介绍了金属结合剂及陶瓷结合剂对PcBN性能的影响,如:Al、B、AlN、TiN和WC等.最后对PcBN材料的发展作了展望.%The development status of materials and cutting tools of PcBN were briefly introduced, and the preparation PcBN process and the key technologies were given. Summed up by a large number of experimental data, as synthetic PcBN of basic raw materials, cBN has high hardness and chemical inertness. But high chemical inertness hinders the good sintering between the lattices. cBN and cBN grain direct bonding is very difficult. To solve the problems, the influences of different binders on the preparation of PcBN were analyzed, the metal-binding agents and ceramic-binding agents of PcBN performance were introduced, such as: Al, B, AlN and TiN, WC, etc. Finally, the development of PcBN materials in the future was prospected.

  20. Bombesin receptors and transplanted stem cells in rat brain: High-resolution scan with 99mTc BN1.1

    Science.gov (United States)

    Scopinaro, F.; Paschali, E.; Di Santo, G.; Antonellis, T.; Massari, R.; Trotta, C.; Gourni, H.; Bouziotis, P.; David, V.; Soluri, A.; Varvarigou, A. D.

    2006-12-01

    The aim of this work is to detect the presence of transplanted stem cells (TSC) in rat brain with high-resolution (HR) scintigraphy and labelled bombesin (BN). BN is a morphogen for Central Nervous System (CNS) as well as for other organs: CNS-oriented TSC over-express BN Receptors (BNR). BN is also a neurotransmitter and modulates several functions of CNS. 99mTc labelled BN-like peptide scan of CNS is the ideal method to detect growing TSC once knowing normal distribution of BNRs in CNS. HR Planar and single photon emission computerized tomography (SPECT) images of rat brain were performed with new HR detectors (Li-tech, Italy). Pertechnetate, 99mTc HMPAO and the new 99mTc BN1.1 (patented) were i.v. administered in five rats. HR SPECT of 99mTc BN1.1 detected olfactory tract, fronto-lateral cortex, cerebellum, basal ganglia and amygdale. Results of SPECT were confirmed by bio-distribution study performed after autopsy of three of the five rats. The remaining two rats underwent cerebral lesions followed by transplant of TSC. Three months later, HR scintigraphy was repeated and showed images completely different from previous basal study, with hot spot of 99mTc BN1.1 corresponding to the site of TSC transplant. Immuno-histochemistry confirmed the presence of viable TSC. Not only 99mTc BN1.1 HR scan showed viability of transplanted TSC but also the "background brain" was the still now unknown map of BNR in mammalian brain.

  1. Complexity of the microstructure evolution for optimization cBN growth in a four-step ion-assisted deposition process

    Energy Technology Data Exchange (ETDEWEB)

    Wong, S.F. [Department of Applied Physics and Materials Research Centre, Hong Kong Polytechnic University, Kowloon, Hong Kong (China)]. E-mail: 96586087.sf@polyu.edu.hk; Ong, C.W. [Department of Applied Physics and Materials Research Centre, Hong Kong Polytechnic University, Kowloon, Hong Kong (China); Pang, G.K.H. [Department of Applied Physics and Materials Research Centre, Hong Kong Polytechnic University, Kowloon, Hong Kong (China); Li, Q. [Department of Physics, Chinese University of Hong Kong, Shatin, New Territory, Hong Kong (China); Lau, W.M. [Department of Physics, Chinese University of Hong Kong, Shatin, New Territory, Hong Kong (China)

    2005-10-01

    The changes in microstructure of a specially prepared boron nitride (BN) film as a function of film depth were studied by high resolution transmission electron microscopy (HRTEM) and other materials analysis tools. These changes were then correlated to the changes in processing parameters during film growth. The analyzed film was fabricated by the four-step ion-assisted deposition procedure known to be effective in film-stress engineering for the formation and retention of a thick cubic BN (cBN) layer with a three-step buffer-layer deposition. In this deposition, the energy of the ions assisting cBN formation was increased stepwise from 200 to 280, and then to 360 eV [S.F. Wong, C. W. Ong, G.K.H. Pang, K.Z. Baba-Kishi, W. M. Lau, J. Vac. Sci. Technol. A 22 (2004) 676]. The nominal thickness of the cBN layer was 650 nm and that for each of the three buffer layers was about 160 nm. Both the HRTEM and electron diffraction results confirmed that the top cBN layer, with a thickness of 643 nm, consisted of cBN grains with a preferred orientation of their c-axis along the film growth direction. In comparison, the three-step buffer layer deposition yielded complex and intriguing microstructures. In the first buffer layer adjacent to the substrate, grains containing sp{sup 2} planes with a preferred orientation of their basal planes parallel to the film growth direction were the main constituents. The increase of ion energy from 200 to 280 eV for the formation of the second buffer layer first led to an enrichment of the concentration of these sp{sup 2} grains with the preferred orientation. Then, bending of some of the sp{sup 2} planes into curved microstructures was evident. The microstructure became very complex and displayed multiple phases including some amorphous structures. The presence of a cBN-like phase was indeed detected by electron energy loss spectroscopy. This complex microstructure persisted until it was replaced by the cBN structure, without abrupt change

  2. Energetics of a Li Atom adsorbed on B/N doped graphene with monovacancy

    Energy Technology Data Exchange (ETDEWEB)

    Rani, Babita, E-mail: babitabaghla15@gmail.com [Department of Physics, Panjab University, Chandigarh 160014 (India); Department of Physics, Punjabi University, Patiala 147002 (India); Jindal, V.K. [Department of Physics, Panjab University, Chandigarh 160014 (India); Dharamvir, Keya, E-mail: keya@pu.ac.in [Department of Physics, Panjab University, Chandigarh 160014 (India)

    2016-08-15

    We use density functional theory (DFT) to study the adsorption properties and diffusion of Li atom across B/N-pyridinic graphene. Regardless of the dopant type, B atoms of B-pyridinic graphene lose electron density. On the other hand, N atoms (p-type dopants) have tendency to gain electron density in N-pyridinic graphene. Higher chemical reactivity and electronic conductivity of B/N-pyridinic graphene are responsible for stronger binding of Li with the substrates as compared to pristine graphene. The binding energy of Li with B/N-pyridinic graphene exceeds the cohesive energy of bulk Li, making it energetically unfavourable for Li to form clusters on these substrates. Li atom gets better adsorbed on N-pyridinic graphene due to an additional p-p hybridization of the orbitals while Li on B-pyridinic prefers the ionic bonding. Also, significant distortion of N-pyridinic graphene upon Li adsorption is a consequence of the change in bonding mechanism between Li atom and the substrate. Our results show that bonding character and hence binding energies between Li and graphene can be tuned with the help of B/N doping of monovacancy defects. Further, the sites for most stable adsorption are different for the two types of doped and defective graphene, leading to greater Li uptake capacity of B-pyridinic graphene near the defect. In addition, B-pyridinic graphene offering lower diffusion barrier, ensures better Li kinetics. Thus, B-pyridinic graphene presents itself as a better anode material for LIBs as compared to N-pyridinic graphene. - Graphical abstract: Adsorption and diffusion of Li atom across the B/N doped monovacancy graphene is studied using ab-initio DFT calculations. Our results show that bonding mechanism and binding of Li with graphene can be tuned with the help of N/B doping of defects. Also, B-pyridinic graphene presents itself as a better anode material for lithium ion batteries as compared to N-pyridinic graphene. Display Omitted - Highlights: • Density

  3. BN800: The advance sodium cooled fast reator plant based on dose fuel sycle%BN800:定位于闭式燃料循环的先进钠冷快堆核电站

    Institute of Scientific and Technical Information of China (English)

    吴兴曼

    2011-01-01

    Abstract: As one of the advanced countries with actually fastest reactor technology, Russia has always taken a leading role in the forefront of the development of fast reactor technology. After successful operation of BN600 fast reactor nuclear power station with a capacity of six hundred thousand kilowatts of electric power for nearly 30 years, and after a few decades of several design optimization improved and completed on its basis, it is finally decided to build Unit 4 of Beloyarsk nuclear power station (BN800 fast reactor power station). The BN800 fast reactor nuclear power station is considered to be the project of the world's most advanced fast reactor nuclear power being put into implementation. The fast reactor technology in China has been developed for decades. With the Chinese pilot fast reactor to be put into operation soon, the Chinese model fast reactor power station has been put on the agenda. Meanwhile, the closed fuel cycle development strategy with fast reactor as key aspect has given rise to the concern of experts and decision-making level in relevant areas. Based on the experiences accumulated in many years in dealing the Sino-Russian cooperation in fast reactor technology, with reference to the latest Russian published and authoritative literatures regarding BN800 fast reactor nuclear power station, the author compiled this article into a comprehensive introduction for reference by leaders and experts dealing in the related fields of nuclear fuel cycle strategy and fast reactor technology development researches, etc.%作为实际上快堆技术最先进的国家之一,俄罗斯始终站在快堆技术发展的前沿.在成功运行了电功率为600MW的BN600快堆核电站近30年,以及在其基础上改进并完成数次设计优化数十年后,终于决定建设别洛雅尔斯基核电站4号机组(BN800快堆电站).BN800快堆核电站被认为是世界上正在付诸工程的最为先进的快堆核电机组.我国的快堆技术发展

  4. Near-Infrared Circular Polarimetry and Correlation Diagrams in the Orion BN/KL Region: Contribution of Dichroic Extinction

    CERN Document Server

    Fukue, T; Kandori, R; Kusakabe, N; Hough, J H; Lucas, P W; Bailey, J; Whittet, D C B; Nakajima, Y; Hashimoto, J; Nagata, T

    2009-01-01

    We present a deep circular polarization image of the Orion BN/KL nebula in the Ks band and correlations of circular polarization, linear polarization, and H-Ks color representing extinction. The image of circular polarization clearly reveals the quadrupolar structure around the massive star IRc2, rather than BN. H-Ks color is well correlated with circular polarization. A simple relation between dichroic extinction, color excess, circular and linear polarization is derived. The observed correlation between the Stokes parameters and the color excess agrees with the derived relation, and suggests a major contribution of dichroic extinction to the production of circular polarization in this region, indicating the wide existence of aligned grains.

  5. Mechanical and electronic coupling in few-layer graphene and hBN wrinkles: a first-principles study

    Science.gov (United States)

    Guo, Yufeng; Qiu, Jiapeng; Guo, Wanlin

    2016-12-01

    Wrinkle engineering is an important pathway to develop novel functional devices of two-dimensional materials. By combining first-principles calculations and continuum mechanics modelling, we have investigated the wrinkling of few-layer graphene and hexagonal boron nitride (hBN) and provide a way to estimate their bending stiffness. For few-layer wrinkles under the same strain, the magnitude of structural deformation of each constituent layer gradually decreases from bottom to top layers, while interlayer interaction increases with increasing layer number. Comparing with monolayer wrinkles, the electronic properties of few-layer wrinkles are more sensitive to bending deformation as mechanical and electronic coupling induce charge redistribution at the wrinkles, making few-layer graphene and hBN wrinkles suitable for electromechanical system application.

  6. Auger electron spectroscopy, secondary ion mass spectroscopy and optical characterization of a-C-H and BN films

    Science.gov (United States)

    Pouch, J. J.; Alterovitz, S. A.; Warner, J. D.

    1986-01-01

    The amorphous dielectrics a-C:H and BN were deposited on III-V semiconductors. Optical band gaps as high as 3 eV were measured for a-C:H generated by C4H10 plasmas; a comparison was made with bad gaps obtained from films prepared by CH4 glow discharges. The ion beam deposited BN films exhibited amorphous behavior with band gaps on the order of 5 eV. Film compositions were studied by Auger electron spectroscopy (AES), x-ray photoelectron spectroscopy (XPS) and secondary ion mass spectrometry (SIMS). The optical properties were characterized by ellipsometry, UV/VIS absorption, and IR reflection and transmission. Etching rates of a-C:H subjected to O2 dicharges were determined.

  7. First Science Observations with SOFIA/FORCAST: 6 TO 37 micron Imaging of Orion BN/KL

    CERN Document Server

    De Buizer, James M; Becklin, E E; Zinnecker, Hans; Herter, Terry L; Adams, Joseph D; Shuping, Ralph Y; Vacca, William D

    2012-01-01

    The BN/KL region of the Orion Nebula is the nearest region of high mass star formation in our galaxy. As such, it has been the subject of intense investigation at a variety of wavelengths, which have revealed it to be brightest in the infrared to sub-mm wavelength regime. Using the newly commissioned SOFIA airborne telescope and its 5-40 micron camera FORCAST, images of the entire BN/KL complex have been acquired. The 31.5 and 37.1 micron images represent the highest resolution observations (31.5 microns, and that this distinction goes instead to the source IRc4. It was determined from these images and derived dust color temperature maps that IRc4 is also likely to be self-luminous. A new source of emission has also been identified at wavelengths >31.5 microns that coincides with the northeastern outflow lobe from the protostellar disk associated with radio source I.

  8. Dissimilar laser brazing of h-BN and WC-Co alloy in Ar atmosphere without evacuation process

    Science.gov (United States)

    Sechi, Y.; Nagatsuka, K.; Nakata, K.

    2012-08-01

    Laser brazing with Ti as an active element in Ag-Cu alloy braze metal has been successfully applied to dissimilar joining of h-BN and WC-Co alloy in Ar (99.999% purity) gas flow atmosphere without any evacuation process. Good wettability of the braze metal with h-BN and WC-Co alloy were confirmed by the observation and structural analysis of the interface by electron probe micro-analysis and scanning acoustic microscopy. The oxidation of titanium was not observed and this showed that the laser brazing with titanium as an active element in braze metal could be performed even in an Ar gas flow atmosphere without an evacuation process using a high-vacuum furnace.

  9. A comprehensive investigation on CVD growth thermokinetics of h-BN white graphene

    Science.gov (United States)

    Song, Xiufeng; Li, Qiguang; Ji, Jianping; Yan, Zhong; Gu, Yu; Huo, Chengxue; Zou, Yousheng; Zhi, Chunyi; Zeng, Haibo

    2016-09-01

    As an isomorph of graphene, monolayer hexagonal boron nitride (h-BN), so-called white graphene, has been in the spotlight of two-dimensional materials due to its outstanding properties. However, the growth of large and uniform white graphene monocrystalline with low density of defects is still a great challenge. Here, we present a comprehensive investigation on the growth thermokinetics of white graphene monocrystalline domains via atmospheric pressure chemical vapor deposition with the solid ammonia borane as precursors, which will be more suitable for future industrial production due to the handy process and precursor. The single domain size, coverage on substrate, and thickness of white graphene were taken as targeted parameters of products. And then, their dependences on the flow rate of carrier gas, heating temperature of ammonia borane, growth temperature and time were studied in details. Finally, after optimizing the above conditions, both white graphene monocrystalline domains as large as 80 μm2 and polycrystalline ultrathin film with coverage ratio of 95%-100% can be achieved facilely without using vacuum technique. Such white graphene products would be of great significance for the tunnel barrier for the tunneling transistor and the dielectric layers for nanocapacitor with the graphene based heterostructures.

  10. Discovery of an expanding molecular bubble in Orion BN/KL

    CERN Document Server

    Zapata, Luis A; Schmid-Burgk, Johannes; Rodriguez, Luis F; Ho, Paul; Patel, Nimesh A

    2010-01-01

    During their infancy, stars are well known to expel matter violently in the form of well-defined, collimated outflows. A fairly unique exception is found in the Orion BN/KL star-forming region where a poorly collimated and somewhat disordered outflow composed of numerous elongated ``finger-like'' structures was discovered more than 30 years ago. In this letter, we report the discovery in the same region of an even more atypical outflow phenomenon. Using $^{13}$CO(2-1) line observations made with the Submillimeter Array (SMA), we have identified there a 500 to 1,000 years old, expanding, roughly spherically symmetric bubble whose characteristics are entirely different from those of known outflows associated with young stellar objects. The center of the bubble coincides with the initial position of a now defunct massive multiple stellar system suspected to have disintegrated 500 years ago, and with the center of symmetry of the system of molecular fingers surrounding the Kleinmann-Low nebula. We hypothesize tha...

  11. Creep of Sylramic-iBN Fiber Tows at Elevated Temperature in Air and in Silicic Acid-Saturated Steam

    Science.gov (United States)

    2015-06-01

    Details of manufacturer, cross linking method, composition, and diameter of all three generations of fibers; reproduced from Ishikawa [27], with... Ishikawa [29], with kind permission from Springer Science and Business Media Sylramic-iBN fibers retain their strength better than any available SiC...Berger, "Advances in Ceramic Matrix Composites IX," American Ceramic Society, vol. 153, p. 3, 2003. [29] T. Ishikawa , "Advances in Inorganic Fibers

  12. Impact of diet on ozone-induced pulmonary and systemic effects in female Brown Norway (BN) rats

    Science.gov (United States)

    Impact of diet on ozone-induced pulmonary and systemic effects in female Brown Norway (BN) ratsV.L. Bass1, M.C. Schladweiler2, S. Snow5, C.J. Gordon4, K.A. Jarema4, P. Phillips4, A.D. Ledbetter2, D.B. Miller3, J.E. Richards2, U.P. Kodavanti2. 1. SPH, UNC, Chapel Hill2. EPHD, NHE...

  13. The effect of concentration of H$_2$ physisorption on the current–voltage characteristic of armchair BN nanotubes in CNT–BNNT–CNT set

    Indian Academy of Sciences (India)

    R AZIMIRAD; A H BAYANI; S SAFA

    2016-10-01

    In this research, we have studied physisorption of hydrogen molecules on armchair boron nitride (BN) nanotube (3,3) using density functional methods and its effect on the current–voltage ($I–V$) characteristic of the nanotube as a function of concentration using Green’s function techniques. The adsorption geometries and energies, charge transfer and electron transport are calculated. It is found that H$_2$ physisorption can suppress the $I–V$ characteristic of the BN nanotube, but it has no effect on the band gap of the nanotube. As the H$_2$concentration increases, under the same applied bias voltage, the current through the BN nanotube first increases and then begins to decline. The current–voltage characteristic indicates that H$_2$ molecules can be detected by aBN-based sensor.

  14. Bilayered graphene/h-BN with folded holes as new nanoelectronic materials: modeling of structures and electronic properties

    Science.gov (United States)

    Chernozatonskii, Leonid A.; Demin сtor A., Vi; Bellucci, Stefano

    2016-11-01

    The latest achievements in 2-dimensional (2D) material research have shown the perspective use of sandwich structures in nanodevices. We demonstrate the following generation of bilayer materials for electronics and optoelectronics. The atomic structures, the stability and electronic properties of Moiré graphene (G)/h-BN bilayers with folded nanoholes have been investigated theoretically by ab-initio DFT method. These perforated bilayers with folded hole edges may present electronic properties different from the properties of both graphene and monolayer nanomesh structures. The closing of the edges is realized by C-B(N) bonds that form after folding the borders of the holes. Stable ≪round≫ and ≪triangle≫ holes organization are studied and compared with similar hole forms in single layer graphene. The electronic band structures of the considered G/BN nanomeshes reveal semiconducting or metallic characteristics depending on the sizes and edge terminations of the created holes. This investigation of the new types of G/BN nanostructures with folded edges might provide a directional guide for the future of this emerging area.

  15. Tailoring the electronic properties of a Z-shaped graphene field effect transistor via B/N doping

    Energy Technology Data Exchange (ETDEWEB)

    Gupta, Mohit; Gaur, Nitesh; Kumar, Puneet; Singh, Sangeeta [Nanoelectronics and VLSI Lab., Indian Institute of Information Technology, Design and Manufacturing (IIITDM), Jabalpur 482005 (India); Jaiswal, Neeraj K., E-mail: neeraj@iiitdmj.ac.in [Discipline of Physics, Indian Institute of Information Technology, Design and Manufacturing (IIITDM), Jabalpur 482005 (India); Kondekar, P.N. [Nanoelectronics and VLSI Lab., Indian Institute of Information Technology, Design and Manufacturing (IIITDM), Jabalpur 482005 (India)

    2015-03-20

    We performed first-principles calculations to reveal a viable way for tailoring the electronic properties of Z-shaped double gate graphene field effect transistor (Z-GFET). We used B/N impurities in channel region of Z-GFET. It is revealed that doping of channel region by B/N has a significant effect on its band gap which is directly reflected in the corresponding current–voltage characteristics. A semiconducting to metallic transition is also observed in selected configurations. For B–N co-doping (config. W), direct band gap of 1.84 eV is obtained which is 20% lower than that of pristine channel. Present results are useful for future electronic devices. - Highlights: • Doping of B/N can be used to tailor the electronic properties of graphene based FET. • The band structure is sensitive to doping site as well as doping concentration. • B–N co-doped channel exhibits 20% lower band gap than that of pristine channel. • Configurations with N doped channel show highest current amongst others.

  16. FIRST SCIENCE OBSERVATIONS WITH SOFIA/FORCAST: 6-37 {mu}m IMAGING OF ORION BN/KL

    Energy Technology Data Exchange (ETDEWEB)

    De Buizer, James M.; Becklin, E. E.; Zinnecker, Hans; Shuping, Ralph Y.; Vacca, William D. [SOFIA-USRA, NASA Ames Research Center, MS N211-3, Moffett Field, CA 94035 (United States); Morris, Mark R. [Department of Physics and Astronomy, University of California, Los Angeles, CA 90095-1547 (United States); Herter, Terry L.; Adams, Joseph D., E-mail: jdebuizer@sofia.usra.edu [Center for Radiophysics and Space Research, Cornell University, 208 Space Sciences Building, Ithaca, NY 14853 (United States)

    2012-04-20

    The Becklin-Neugebauer/Kleinmann-Low (BN/KL) region of the Orion Nebula is the nearest region of high-mass star formation in our galaxy. As such, it has been the subject of intense investigation at a variety of wavelengths, which have revealed it to be brightest in the infrared to submillimeter wavelength regime. Using the newly commissioned SOFIA airborne telescope and its 5-40 {mu}m camera FORCAST, images of the entire BN/KL complex have been acquired. The 31.5 and 37.1 {mu}m images represent the highest resolution observations ({approx}<4'') ever obtained of this region at these wavelengths. These observations reveal that the BN object is not the dominant brightness source in the complex at wavelengths {>=} 31.5 {mu}m and that this distinction goes instead to the source IRc4. It was determined from these images and derived dust color temperature maps that IRc4 is also likely to be self-luminous. A new source of emission has also been identified at wavelengths {>=} 31.5 {mu}m that coincides with the northeastern outflow lobe from the protostellar disk associated with radio source I.

  17. Enhancement of thermal neutron attenuation of nano-B{sub 4}C, -BN dispersed neutron shielding polymer nanocomposites

    Energy Technology Data Exchange (ETDEWEB)

    Kim, Jaewoo, E-mail: kimj@kaeri.re.kr [Nuclear Materials Research Division, Korea Atomic Energy Research Institute, 111-989 Daeduck-daero, Yuseong-gu, Daejeon-si 305-353 (Korea, Republic of); WCI Quantum Beam based Radiation Research Center, Korea Atomic Energy Research Institute, 111-989 Daeduck-daero, Yuseong-gu, Daejeon-si 305-353 (Korea, Republic of); Missouri University Research Reactor, University of Missouri-Columbia, Columbia, MO 65211 (United States); Lee, Byung-Chul [Nuclear Reactor Core Design Division, Korea Atomic Energy Research Institute, 111-989 Daeduck-daero, Yuseong-gu, Daejeon-si 305-353 (Korea, Republic of); Uhm, Young Rang [Radioisotopes Research Division, Korea Atomic Energy Research Institute, 111-989 Daeduck-daero, Yuseong-gu, Daejeon-si 305-353 (Korea, Republic of); Miller, William H. [Missouri University Research Reactor, University of Missouri-Columbia, Columbia, MO 65211 (United States)

    2014-10-15

    Highlights: • Preparation of B{sub 4}C and BN nanopowders using a simple ball milling process. • Homogeneous dispersion and strong adhesion of nano-B{sub 4}C and -BN with polymer matrix. • Enhancement of mechanical properties of the nanocomposites compared to their micro counterparts. • Enhancement of thermal neutron attenuation of the nanocomposites. - Abstract: Nano-sized boron carbide (B{sub 4}C) and boron nitride (BN) powder were prepared using ball milling. Micro- and milled nano-powders were melt blended with high density polyethylene (HDPE) using a polymer mixer followed by hot pressing to fabricate sheet composites. The tensile and flexural strengths of HDPE nanocomposites were ∼20% higher than their micro counterparts, while those for latter decreased compared to neat HDPE. Thermal neutrons attenuation of the prepared HDPE nanocomposites was evaluated using a monochromatic ∼0.025 eV neutron beam. Thermal neutron attenuation of the HDPE nanocomposites was greatly enhanced compared to their micro counterparts at the same B-10 areal densities. Monte Carlo n-Particles (MCNP) simulations based on the lattice structure modeling also shows the similar filler size dependent thermal neutron absorption.

  18. Investigation on the key factors in the hydrothermal synthesis of BN:The way of introducing sodium azide

    Institute of Scientific and Technical Information of China (English)

    LI Kai; JIANG HaiHui; LIAN Gang; WANG QiLong; ZHAO Xian; CUI DeLiang; TAO XuTang

    2007-01-01

    The way of introducing sodium azide (NaN3) into the reaction solution played an important role in the preparation of cBN by hydrothermal synthesis method. The results showed that both cBN content and crystalline perfection of the samples improved with increasing RN value,and pure cBN could be obtained at 300℃ and 10 MPa when RN increased to 3:1. Here RN is defined as RN =NaN3(I)/NaN3(II),where NaN3(I) denotes the amount of NaN3 (in molar) that is added into the autoclave at the beginning of the reaction process,and NaN3(II) is the amount of NaN3 (also in molar) introduced into the autoclave at high temperature and high pressure (i.e. 300℃ and 10 MPa). In order to explain the experimental results,a preliminary model was proposed in this paper.

  19. Crystallization behaviors of carbon fiber reinforced BN-Si{sub 3}N{sub 4} matrix composite

    Energy Technology Data Exchange (ETDEWEB)

    Li, Bin; Zhang, Chang-Rui; Wang, Si-Qing; Cao, Feng [State Key Laboratory of Advanced Ceramic Fibers and Composites, College of Aerospace and Materials Engineering, National University of Defense Technology, Changsha 410073 (China)

    2007-07-15

    The crystallization behaviors of a new carbon fiber reinforced composite with a hybrid matrix comprising BN and Si{sub 3}N{sub 4} prepared by precursor infiltration and pyrolysis were investigated by Fourier transform infrared spectroscopy, X-ray diffraction and scanning electron microscopy. The results show that the as-received composite is almost amorphous, and its main composition is BN and Si{sub 3}N{sub 4}. When heat treated at 1600 C, the composite is crystallized and shows a much better crystal form. When heat treated at 2100 C, Si{sub 3}N{sub 4} in the matrix is decomposed, and BN exhibits a relatively complete crystallization. The existence of B{sub 4}C and SiC is detected, which indicates the interfacial chemical reactions between nitride matrices and carbon fibers. The surface morphology of carbon fibers in the composite changed significantly when heated from 1600 to 2100 C, which also proved the occurrence of interfacial chemical reactions. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  20. Large-Scale Graphene on Hexagonal-BN Hall Elements: Prediction of Sensor Performance without Magnetic Field.

    Science.gov (United States)

    Joo, Min-Kyu; Kim, Joonggyu; Park, Ji-Hoon; Nguyen, Van Luan; Kim, Ki Kang; Lee, Young Hee; Suh, Dongseok

    2016-09-27

    A graphene Hall element (GHE) is an optimal system for a magnetic sensor because of its perfect two-dimensional (2-D) structure, high carrier mobility, and widely tunable carrier concentration. Even though several proof-of-concept devices have been proposed, manufacturing them by mechanical exfoliation of 2-D material or electron-beam lithography is of limited feasibility. Here, we demonstrate a high quality GHE array having a graphene on hexagonal-BN (h-BN) heterostructure, fabricated by photolithography and large-area 2-D materials grown by chemical vapor deposition techniques. A superior performance of GHE was achieved with the help of a bottom h-BN layer, and showed a maximum current-normalized sensitivity of 1986 V/AT, a minimum magnetic resolution of 0.5 mG/Hz(0.5) at f = 300 Hz, and an effective dynamic range larger than 74 dB. Furthermore, on the basis of a thorough understanding of the shift of charge neutrality point depending on various parameters, an analytical model that predicts the magnetic sensor operation of a GHE from its transconductance data without magnetic field is proposed, simplifying the evaluation of each GHE design. These results demonstrate the feasibility of this highly performing graphene device using large-scale manufacturing-friendly fabrication methods.

  1. Study on the PcBN cutting tools proprerties during hardened steel machining%PcBN加工淬硬钢刀具材料的研究

    Institute of Scientific and Technical Information of China (English)

    李启泉; 张旺玺

    2011-01-01

    PcBN cutting tool materials were prepared using two kinds of binder and in three different concentrations of cBN . Through cutting experiment on hardened steel , it was found that cBN concentration played a key role on the performances of PcBN. After cutting for the same distance, PcBN tools of low concentration had smaller amount of flank wear. SEM observation revealed that CoAl alloy powder improved the density of the PcBN tool material. Based on the results of wear resistance test , it is suggested that the technical indicators of wear test for PCD is not suitable for PcBN.%介绍了立方氮化硼刀具材料( PcBN)的制备过程,并制备了六种不同配方的样品加工淬硬钢.通过切削实验和性能检测,发现PcBN刀片在加工淬硬钢时cBN浓度起着关键作用,切削同样的路程,低浓度PcBN的后刀面磨损量小.经扫描电镜观察,CoAl合金粉能够提高PcBN烧结刀具材料的致密度.测量耐磨性时,证明用于金刚石复合片PCD性能检测的磨耗比技术指标不适用于PcBN材料的检测.

  2. La "Apología" y el "Fedón" del "Matritensis" BN 4569 (N 32) de Constantino Láscaris

    OpenAIRE

    Ramos Jurado, Enrique Ángel

    2001-01-01

    El autor analiza el texto de la "Apología" y el "Fedón" del "Matritensis" BN 4569 y su relación con la tradición manuscrita del corpus platónico. The author analyses the text of the "Apology" and "Phaedo" in the "Matritensis" BN 4569 and its relationship with the manuscript tradition of the Paltonic "corpus".

  3. Large-roll growth of 25-inch hexagonal BN monolayer film for self-release buffer layer of free-standing GaN wafer

    Science.gov (United States)

    Wu, Chenping; Soomro, Abdul Majid; Sun, Feipeng; Wang, Huachun; Huang, Youyang; Wu, Jiejun; Liu, Chuan; Yang, Xiaodong; Gao, Na; Chen, Xiaohong; Kang, Junyong; Cai, Duanjun

    2016-01-01

    Hexagonal boron nitride (h-BN) is known as promising 2D material with a wide band-gap (~6 eV). However, the growth size of h-BN film is strongly limited by the size of reaction chamber. Here, we demonstrate the large-roll synthesis of monolayer and controllable sub-monolayer h-BN film on wound Cu foil by low pressure chemical vapor deposition (LPCVD) method. By winding the Cu foil substrate into mainspring shape supported by a multi-prong quartz fork, the reactor size limit could be overcome by extending the substrate area to a continuous 2D curl of plane inward. An extremely large-size monolayer h-BN film has been achieved over 25 inches in a 1.2” tube. The optical band gap of h-BN monolayer was determined to be 6.0 eV. The h-BN film was uniformly transferred onto 2” GaN or 4” Si wafer surfaces as a release buffer layer. By HVPE method, overgrowth of thick GaN wafer over 200 μm has been achieved free of residual strain, which could provide high quality homo-epitaxial substrate. PMID:27756906

  4. How to Increase the h-BN Crystallinity of Microfilms and Self-Standing Nanosheets: A Review of the Different Strategies Using the PDCs Route

    Directory of Open Access Journals (Sweden)

    Sheng Yuan

    2016-05-01

    Full Text Available Hexagonal boron nitride (h-BN is a well-known material whose use is almost restricted to lubricating applications in domains ranging from metallurgy to cosmetics. Howover, h-BN displays many other interesting properties, opening new perspectives for other engineering applications, such as as a solid lubricant in aeronautics, as the perfect substrate to graphene for electronic devices, etc. However, all these promising developments require tailored h-BN shapes displaying a high level of crystallization, ensuring its properties for the long term. Here, we developed three strategies, all associated with the Polymer Derived Ceramics (PDCs route, to prepare highly crystallized supported thick coatings and self-standing nanosheets. The first strategy concerns the innovative implementation of a Rapid Thermal Annealing to prepare micrometric h-BN coatings on thermal sensitive substrates. Compared to conventional treatment the crystallization of h-BN has successfully lowered to about 300 °C. The second strategy consists of an additivation of the used polymer precursor. Effect of lithium nitride as a crystallization promoter was investigated lowering the onset crystallization temperature from 1400 °C (traditionally to 1000 °C. This novel synthetic route allows preparing self-standing highly crystallized h-BN nanolayers. Finally, the third strategy is based on a unique combination of the PDCs route with Spark Plasma Sintering to profit of both approaches. This original method leads to large and well-crystallized flakes available for a subsequent exfoliation.

  5. Atomic layer-by-layer deposition of h-BN(0001) on cobalt: a building block for spintronics and graphene electronics

    Science.gov (United States)

    Beatty, John; Cao, Yuan; Tanabe, Iori; Sky Driver, M.; Dowben, Peter A.; Kelber, Jeffry A.

    2014-12-01

    X-ray photoelectron spectroscopy (XPS), low energy electron diffraction (LEED) and Raman measurements demonstrate that macroscopically continuous hexagonal BN(0001) (h-BN) multilayer layer films can be grown by atomic layer deposition on Co(0001) substrates. The growth procedure involves alternating exposures of BCl3 and NH3 at 550 K, followed by annealing in ultrahigh vacuum above 700 K to induce long-range order. XPS data demonstrate that the films have a consistent B:N atomic ratio of 1:1. LEED data show that the BN layers are azimuthally in registry, with an estimated domain size of ˜170 Å. The films are continuous over a macroscopic (1 cm × 1 cm) area as demonstrated by the fact that exposure of a h-BN(0001) bi-layer film to ambient at room temperature yields no observable Co oxidation, although some N oxidation is observed, and long range order is lost. The ability to grow large area, continuous multilayer BN films on Co, with atomic level control of film thickness, makes possible an array of magnetic tunnel junction and spin filter applications.

  6. 高压气-固燃烧合成h-BN-SiO2和h-BN陶瓷材料的研究%Investigation of High Pressure Gas-Solid Combustion Synthesis h-BN-SiO2 and h-BN Ceramics

    Institute of Scientific and Technical Information of China (English)

    陈贵清; 韩杰才; 杜善义

    2001-01-01

    采用高压气-固燃烧合成法制备了密度为1.79g/cm3的h-BN-SiO2陶瓷和密度为1.70g/cm3的h-BN陶瓷,抗弯强度分别为76MPa和42.8MPa,硬度分别为212(HV)和108(HV).分析了氮气压力和初始孔隙率对反应物燃烧和产物的影响,结果发现在适当的初始孔隙率和氮气压力条件下(对于h-BN-SiO2:48%≤ρ≤52%,75MPa≤P≤85MPa;对于h-BN:48%≤ρ≤52%,95MPa≤P≤110MPa)可以得到无裂纹的产物.产物中的片状h-BN颗粒为各向同性,高的氮气压力导致h-BN颗粒尺寸增大,同时发现h-BN-SiO2产物中SiO2以玻璃相的形式存在于晶相B7O的边缘,B7O的产生与原料SiO2及其氧化物杂质有关.

  7. Spontaneous doping on high quality talc-graphene-hBN van der Waals heterostructures

    Science.gov (United States)

    Mania, E.; Alencar, A. B.; Cadore, A. R.; Carvalho, B. R.; Watanabe, K.; Taniguchi, T.; Neves, B. R. A.; Chacham, H.; Campos, L. C.

    2017-09-01

    Steady doping, added to its remarkable electronic properties, would make graphene a valuable commodity in the solar cell market, as energy power conversion could be substantially increased. Here we report a graphene van der Waals heterostructure which is able to spontaneously dope graphene (p-type) up to n ~ 2.2  ×  1013 cm-2 while providing excellent charge mobility (μ ~ 25 000 cm2 V-1 s-1). Such properties are achieved via deposition of graphene on atomically flat layered talc, a natural and abundant dielectric crystal. Raman investigation shows a preferential charge accumulation on graphene-talc van der Waals heterostructures, which are investigated through the electronic properties of talc/graphene/hBN heterostructure devices. These heterostructures preserve graphene’s good electronic quality, verified by the observation of quantum Hall effect at low magnetic fields (B  =  0.4 T) at T  =  4.2 K. In order to investigate the physical mechanisms behind graphene-on-talc p-type doping, we performed first-principles calculations of their interface structural and electronic properties. In addition to potentially improving solar cell efficiency, graphene doping via van der Waals stacking is also a promising route towards controlling the band gap opening in bilayer graphene, promoting a steady n or p type doping in graphene and, eventually, providing a new path to access superconducting states in graphene, predicted to exist only at very high doping.

  8. H2 Velocity Maps of Orion: Destruction of the Environment of the BN-KL Nebula

    Directory of Open Access Journals (Sweden)

    Luis Salas

    2001-01-01

    Full Text Available We present the velocity structure of the 2.12 micron H2 emission in Orion, obtained with an IR Fabry-Perot interferometer with a spectral resolution of 24 km/s and a 2arcsec spatial resolution, covering a region of 3.6´ by 3.6´ (0.46 by 0.46 pc2 that contains the H2 filamentary finger system. A simple model is proposed to explain the observed low velocity structure as described by its radial moments: intensity, velocity centroid, velocity dispersion and skewness. We assume a strong wind of 230 km/s produced by IRc2 interacting with a set of molecular clumps with density of 5.6×105 cm-3. The scenario provides a good match to the observed moments is obtained, gives clues to the development of filaments or fingers and entrainment of the molecular material, and associates the observed high velocity blueshifted emission to the region. The H2 line emission is produced by a slow J-shock (20 km/s in the clumps with an emissivity proportional to v1.8 . Estimates for the total wind mass and clumps mass yield 0.5 Msolar and 15 Msolar inside a radius of 1arcmin (0.1 pc. The individual clumps have masses and sizes of few × 10-3 Msolar and 0.007 pc, respectively. We conclude that the central 0.1 pc region surrounding the BN-KL nebula in front of OMC-1 is in the process of being disrupted by the strong wind of IRc2 on a time scale of 2000 yr.

  9. Fabrication, characterization, and mechanical properties of spark plasma sintered Al–BN nanoparticle composites

    Energy Technology Data Exchange (ETDEWEB)

    Firestein, Konstantin L., E-mail: kosty@firestein.ru [National University of Science and Technology “MISIS”, Leninsky prospect 4, Moscow 119049 (Russian Federation); Steinman, Alexander E.; Golovin, Igor S. [National University of Science and Technology “MISIS”, Leninsky prospect 4, Moscow 119049 (Russian Federation); Cifre, Joan [Universitat de les Illes Balears, Ctra. de Valldemossa, km. 7.5, E-07122 Palma de Mallorca (Spain); Obraztsova, Ekaterina A.; Matveev, Andrei T.; Kovalskii, Andrey M. [National University of Science and Technology “MISIS”, Leninsky prospect 4, Moscow 119049 (Russian Federation); Lebedev, Oleg I. [CRISMAT, UMR 6508, CNRS-ENSICAEN, 6Bd Marechal Juin, 14050 Caen (France); Shtansky, Dmitry V., E-mail: shtansky@shs.misis.ru [National University of Science and Technology “MISIS”, Leninsky prospect 4, Moscow 119049 (Russian Federation); Golberg, Dmitri, E-mail: golberg.dmitri@nims.go.jp [World Premier International Center for Materials Nanoarchitectonics (WPI-MANA) National Institute for Materials Science (NIMS), Namiki 1, Tsukuba, Ibaraki 3050044 (Japan)

    2015-08-26

    Fabrication of high strength yet light and low cost composite materials with good mechanical properties at room and elevated temperatures is a challenge that metallurgy and materials science communities are facing for many years, and no “dream material” has been developed so far. The primary goal of this study was to fabricate, characterize, and to carry out tensile tests on Al-based composite materials strengthened with commercially-available BN nanoparticles (BNNPs). The composites were fabricated by spark plasma sintering (SPS) technique. The structures of powder mixtures and composite materials, as well as their fracture surfaces, were studied by scanning and transmission electron microscopy. The influence of BNNPs content (0.5, 1.5, 3, 4.5, 6, and 7.5 wt%) and holding times (5, 60, and 300 min) at 600 °C during SPS on the tensile strength was investigated. A maximum increase in strength was observed for Al-based composites with 4.5 wt% of BNNPs. The sample demonstrated a 50% increase in tensile strength compared with pristine Al. Although the tensile tests performed at 300 °C revealed that the tensile strength became 20% lower than the strength at room temperature, it was, however, still 75% higher compared with that of the pure Al at 300 °C. In addition, at 300 °C the Al–BNNPs composites demonstrated a much higher value of yield stress, about 115 MPa, which is 190% higher than that of pure Al at the same temperature. The damping properties of Al–BNNPs composites were evaluated by temperature dependent internal friction (TDIF) measurements. The obtained results are discussed based on structural analysis and the TDIF data.

  10. Cloning and characterization of newly isolated lipase from Enterobacter sp. Bn12.

    Science.gov (United States)

    Farrokh, Parisa; Yakhchali, Bagher; Karkhane, Ali Asghar

    2014-01-01

    A mesophilic Enterobacter sp. Bn12 producing an alkaline thermostable lipase was isolated from soil in Tehran, Iran. The lipase gene (ELBn12) was identified from a genomic library. Sequence analysis of the DNA fragment revealed an open reading frame of 879 bp encoding a lipase with a molecular mass of 31.3 kDa. The deduced amino acid sequence showed 96% identity with a lipase of Enterobacter sp. Ag1 and the identity of their DNA sequences was 88.9%. ELBn12 belongs to the lipase subfamily I.1 and its catalytic triad consists of Ser82, Asp237 and His259. The lipase was expressed in Escherichia coli (BL21) pLysS and partially purified by anion exchange chromatography. The maximum activity of ELBn12 was obtained at temperature of 60 °C and pH 8.0 towards tricaprylin (C8) and its specific activity was around 2900 U/mg. ELBn12 was stable within a broad pH range from 6.0 to 11.0. The enzyme showed high stability in both polar and nonpolar organic solvents at 50% (v/v). The lipase activity was enhanced in the presence of 10 mM of Ca(2+), Mg(2+) and K(+), while heavy metals (Fe(3+) and Zn(2+)) had strong inhibitory effect. ELBn12 showed high activity in the presence of 1% (w/v) nonionic surfactants, however ionic surfactants inhibited the lipolytic activity. ELBn12 characteristics show that it has a potential to be used in various industrial processes.

  11. Quality of Life in Patients With Brain Metastases Using the EORTC QLQ-BN20+2 and QLQ-C15-PAL

    Energy Technology Data Exchange (ETDEWEB)

    Caissie, Amanda; Nguyen, Janet; Chen, Emily; Zhang Liying [Rapid Response Radiotherapy Program, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario (Canada); Sahgal, Arjun [Rapid Response Radiotherapy Program, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario (Canada); Department of Radiation Oncology, Princess Margaret Hospital, University of Toronto, Toronto, Ontario (Canada); Clemons, Mark [Department of Medical Oncology, Ottawa Hospital Cancer Centre, Ottawa, Ontario (Canada); Kerba, Marc [Department of Radiation Oncology, Tom Baker Cancer Centre, Calgary, Alberta (Canada); Arnalot, Palmira Foro [Parc de Salut Mar Hospital de l' Esperanca, Barcelona (Spain); Danjoux, Cyril; Tsao, May; Barnes, Elizabeth; Holden, Lori [Rapid Response Radiotherapy Program, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario (Canada); Danielson, Brita [Department of Radiation Oncology, Cross Cancer Institute, Edmonton, Alberta (Canada); Chow, Edward, E-mail: edward.chow@sunnybrook.ca [Rapid Response Radiotherapy Program, Odette Cancer Centre, Sunnybrook Health Sciences Centre, University of Toronto, Toronto, Ontario (Canada)

    2012-07-15

    Purpose: The 20-item European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-Brain Neoplasm (QLQ-BN20) is a validated quality-of-life (QOL) questionnaire for patients with primary brain tumors. The European Organisation for Research and Treatment of Cancer Quality of Life Questionnaire-Core 15 Palliative (QLQ-C15-PAL) core palliative questionnaire is a 15-item version of the core 30-item QLQ-C30 and was developed to decrease the burden on patients with advanced cancer. The combination of the QLQ-BN20 and QLQ-C30 to assess QOL may be too burdensome for patients. The primary aim of this study was to assess QOL in patients before and after treatment for brain metastases using the QLQ-BN20+2 and QLQ-C15-PAL, a version of the QLQ-BN20 questionnaire with 2 additional questions assessing cognitive functioning that were not addressed in the QLQ-C15-PAL. Methods and Materials: Patients with brain metastases completed the QLQ-C15-PAL and QLQ-BN20+2 questionnaires to assess QOL before and 1 month after radiation. Linear regression analysis was used to assess changes in QOL scores over time, as well as to explore associations between the QLQ-BN20+2 and QLQ-C15-PAL scales, patient demographics, and clinical variables. Spearman correlation assessed associations between the QLQ-BN20+2 and QLQ-C15-PAL scales. Results: Among 108 patients, the majority (55%) received whole-brain radiotherapy only, with 65% of patients completing follow-up at 1 month after treatment. The most prominent symptoms at baseline were future uncertainty (QLQ-BN20+2) and fatigue (QLQ-C15-PAL). After treatment, significant improvement was seen for the QLQ-C15-PAL insomnia scale, as well as the QLQ-BN20+2 scales of future uncertainty, visual disorder, and concentration difficulty. Baseline Karnofsky Performance Status was negatively correlated to QLQ-BN20+2 motor dysfunction but positively related to QLQ-C15-PAL physical functioning and QLQ-BN20+2 cognitive functioning at

  12. Effects of the platelet-activating factor receptor antagonist BN 52021 on hematologic variables and blood loss during and after cardiopulmonary bypass.

    Science.gov (United States)

    Nathan, N; Mercury, P; Denizot, Y; Cornu, E; Laskar, M; Arnoux, B; Feiss, P

    1994-08-01

    Cardiopulmonary bypass (CPB)-induced thrombocytopenia and leukopenia is augmented after heparin reversal of protamine. Platelet-activating factor (PAF) might be implicated in these disorders. To evaluate the effects of PAF on the hematologic disorders and blood loss during and after CPB, patients were pretreated with BN 52021, a PAF receptor antagonist, or a placebo. BN 52021 (120 mg) (n = 13) or placebo (n = 15) were infused intravenously before vascular cannulation and before cross-clamp release. Platelet and leukocyte counts were assessed in venous blood before and after the first dose of BN 52021 or placebo, 2 min after the beginning of CPB (at the entry of the oxygenator), at the end of CPB, 1, 15, and 30 min after protamine infusion, and 6 and 24 h after CPB. The decrease in platelet and leukocyte counts were the same between groups during and after CPB and after protamine infusion. Bleeding times were not modified by the pretreatment of patients with BN 52021. During surgery, blood loss reached 1660 +/- 297 mL in the BN 52021 group and 1599 +/- 283 mL in the placebo group (P > 0.05). Forty-eight hours postoperatively, the chest tube outputs were not different between groups (1460 +/- 418 mL vs 1640 +/- 362 mL in the BN 52021 and placebo groups, respectively). This study shows that BN 52021 infusion did not change the hematologic variables studied. Moreover, a PAF antagonist pretreatment did not protect the patients against CPB- or protamine-induced hematologic changes.

  13. 理论研究F2BN3多聚体的结构特色和热力学稳定性%Theoretical studies on structural feature and thermodynamic stability of F2BN3 oligomers

    Institute of Scientific and Technical Information of China (English)

    马登学; 夏其英; 张弛

    2009-01-01

    Density functional theory (DFT) was employed to study on (F2BN3)n (n=1~4) clusters at the B3LYP/6-311+G* level. A set of the structural and thermodynamic properties have been obtained. Trends in structural parameters with oligomerization degree n are discussed. The optimized clusters (F2BN3)2-4 all possess cyclic structure formed by B atoms bridged by the α-nitrogen of the azide groups. The boat-twisting conformation lies 10.54 kJ*mol-1 lower in binding energies than the chair isomer for the trimers. The four tetramers newly gained show greatly binding energy differences in range of 3.1~45.65 kJ*mol-1. The dimerization is thermodynamically unfavorable by the enthalpy. However, the formations of trimers and tetramers are very favorable thermodynamically even at high (1200 K) temperatures. Comparisons of the thermodynamic parameters of subsequent oligomerization are also given.%在密度泛函理论(DFT)B3LYP/6-311+G*水平上计算研究了叠氮二氟硼多聚体(F2BN3)n (n=1~4),获得了它们的结构和热力学性质,讨论了几何参数随聚合度的变化趋势.多聚体(F2BN3)2-4的优化构型均为由不同子体系的叠氮基α-N和B原子相连形成的环状结构.三聚体的船扭式构象比椅式构象的结合能低10.54 kJ*mol-1;四个新获得的四聚体的结合能差异较大,大小为3.1~45.65 kJ*mol-1.由焓变可知,单体形成二聚体在热力学上是不利的,而形成三聚体和四聚体在高达1200 K的温度下是有利的,同时分析比较了后续反应的热力学参数.

  14. MOCVD growth of GaBN on 6H-SiC (0001) substrates[Metal Organic Chemical Vapor Deposition

    Energy Technology Data Exchange (ETDEWEB)

    Wei, C.H.; Xie, Z.Y.; Edgar, J.H.; Zeng, K.C.; Lin, J.Y.; Jiang, H.X.; Chaudhuri, J.; Ignatiev, C.; Braski, D.N.

    2000-04-01

    B{sub x}Ga{sub 1{minus}x}N films were deposited on 6H-SiC (0001) substrates at 1,000 C by low pressure MOVPE using diborane, trimethylgallium, and ammonia as precursors. The presence of boron was detected by Auger scanning microprobe, the shift of the (00.2) x-ray diffraction peak, and low-temperature photoluminescence. A single-phase B{sub x}Ga{sub 1{minus}x}N alloy with x = 1.5% was produced at the gas phase B/Ga ratio of 0.005. Phase separation into wurtzite BGaN and the B-rich phase occurred for a B/Ga ratio in the 0.01--0.2 range. Only BN was formed by B/Ga > 0.2. The B-rich phase was identified as h-BN with sp{sup 2} bonding based on the results of Fourier transform infrared spectroscopy. As the diborane flow exceeds the threshold concentration, the growth rate of GBaN decreases sharply, because the growth of GaN is poisoned by the formation of the slow growing BN phase. The band edge emission of B{sub x}Ga{sub 1{minus}x}N varies from 3.451 eV for x = 0% with FWHM of 39.2 meV to 3.465 eV for x = 1.5% with FWHM of 35.1 meV. The narrower FWHM indicates that the quality of GaN epilayer is improved with a small amount of boron incorporation. The PL line widths become broader as more boron is introduced into the solid solution.

  15. Overexpression of sinapine esterase BnSCE3 in oilseed rape seeds triggers global changes in seed metabolism.

    Science.gov (United States)

    Clauss, Kathleen; von Roepenack-Lahaye, Edda; Böttcher, Christoph; Roth, Mary R; Welti, Ruth; Erban, Alexander; Kopka, Joachim; Scheel, Dierk; Milkowski, Carsten; Strack, Dieter

    2011-03-01

    Sinapine (O-sinapoylcholine) is the predominant phenolic compound in a complex group of sinapate esters in seeds of oilseed rape (Brassica napus). Sinapine has antinutritive activity and prevents the use of seed protein for food and feed. A strategy was developed to lower its content in seeds by expressing an enzyme that hydrolyzes sinapine in developing rape seeds. During early stages of seedling development, a sinapine esterase (BnSCE3) hydrolyzes sinapine, releasing choline and sinapate. A portion of choline enters the phospholipid metabolism, and sinapate is routed via 1-O-sinapoyl-β-glucose into sinapoylmalate. Transgenic oilseed rape lines were generated expressing BnSCE3 under the control of a seed-specific promoter. Two distinct single-copy transgene insertion lines were isolated and propagated to generate homozygous lines, which were subjected to comprehensive phenotyping. Sinapine levels of transgenic seeds were less than 5% of wild-type levels, whereas choline levels were increased. Weight, size, and water content of transgenic seeds were significantly higher than those of wild-type seeds. Seed quality parameters, such as fiber and glucosinolate levels, and agronomically important traits, such as oil and protein contents, differed only slightly, except that amounts of hemicellulose and cellulose were about 30% higher in transgenic compared with wild-type seeds. Electron microscopic examination revealed that a fraction of the transgenic seeds had morphological alterations, characterized by large cavities near the embryonic tissue. Transgenic seedlings were larger than wild-type seedlings, and young seedlings exhibited longer hypocotyls. Examination of metabolic profiles of transgenic seeds indicated that besides suppression of sinapine accumulation, there were other dramatic differences in primary and secondary metabolism. Mapping of these changes onto metabolic pathways revealed global effects of the transgenic BnSCE3 expression on seed metabolism.

  16. Effects of PAF Antagonist BN52021 on Systemic and Renal Oxidative Stress in Experimentally Induced Obstructive Jaundice

    OpenAIRE

    Akyürek, Nusret

    2014-01-01

    The aim of this study is to investigate the effects of PAF antagonist BN52021 on systemic and renal oxidative stress in experimentally induced obstructive jaundice. A total of 30 Wistar-Albino type rats used in the study were divided into sham, control and study groups, each consisting of ten subjects. A laparotomy was performed on the study and control groups, and the choledochus was ligated and dissected. In the sham group, the choledochus was dissected by laparotomy and not ligated. The s...

  17. A Tourist-like MITE insertion in the upstream region of the BnFLC.A10 gene is associated with vernalization requirement in rapeseed (Brassica napus L.

    Directory of Open Access Journals (Sweden)

    Hou Jinna

    2012-12-01

    Full Text Available Abstract Background Rapeseed (Brassica napus L. has spring and winter genotypes adapted to different growing seasons. Winter genotypes do not flower before the onset of winter, thus leading to a longer vegetative growth period that promotes the accumulation and allocation of more resources to seed production. The development of winter genotypes enabled the rapeseed to spread rapidly from southern to northern Europe and other temperate regions of the world. The molecular basis underlying the evolutionary transition from spring- to winter- type rapeseed is not known, however, and needs to be elucidated. Results We fine-mapped the spring environment specific quantitative trait locus (QTL for flowering time, qFT10-4,in a doubled haploid (DH mapping population of rapeseed derived from a cross between Tapidor (winter-type and Ningyou7 (semi-winter and delimited the qFT10-4 to an 80-kb region on chromosome A10 of B. napus. The BnFLC.A10 gene, an ortholog of FLOWERING LOCUS C (FLC in Arabidopsis, was cloned from the QTL. We identified 12 polymorphic sites between BnFLC.A10 parental alleles of the TN-DH population in the upstream region and in intron 1. Expression of both BnFLC.A10 alleles decreased during vernalization, but decreased more slowly in the winter parent Tapidor. Haplotyping and association analysis showed that one of the polymorphic sites upstream of BnFLC.A10 is strongly associated with the vernalization requirement of rapeseed (r2 = 0.93, χ2 = 0.50. This polymorphic site is derived from a Tourist-like miniature inverted-repeat transposable element (MITE insertion/deletion in the upstream region of BnFLC.A10. The MITE sequence was not present in the BnFLC.A10 gene in spring-type rapeseed, nor in ancestral ‘A’ genome species B. rapa genotypes. Our results suggest that the insertion may have occurred in winter rapeseed after B. napus speciation. Conclusions Our findings strongly suggest that (i BnFLC.A10 is the gene underlying qFT10

  18. Resistive switching characteristic and uniformity of low-power HfO x -based resistive random access memory with the BN insertion layer

    Science.gov (United States)

    Su, Shuai; Jian, Xiao-Chuan; Wang, Fang; Han, Ye-Mei; Tian, Yu-Xian; Wang, Xiao-Yang; Zhang, Hong-Zhi; Zhang, Kai-Liang

    2016-10-01

    In this letter, the Ta/HfO x /BN/TiN resistive switching devices are fabricated and they exhibit low power consumption and high uniformity each. The reset current is reduced for the HfO x /BN bilayer device compared with that for the Ta/HfO x /TiN structure. Furthermore, the reset current decreases with increasing BN thickness. The HfO x layer is a dominating switching layer, while the low-permittivity and high-resistivity BN layer acts as a barrier of electrons injection into TiN electrode. The current conduction mechanism of low resistance state in the HfO x /BN bilayer device is space-charge-limited current (SCLC), while it is Ohmic conduction in the HfO x device. Project supported by the National Natural Science Foundation of China (Grant Nos. 61274113, 11204212, 61404091, 51502203, and 51502204), the Tianjin Natural Science Foundation, China (Grant Nos. 14JCZDJC31500 and 14JCQNJC00800), and the Tianjin Science and Technology Developmental Funds of Universities and Colleges, China (Grant No. 20130701).

  19. h-BN Nanosheets as 2D Substrates to Load 0D Fe3O4 Nanoparticles: A Hybrid Anode Material for Lithium-Ion Batteries.

    Science.gov (United States)

    Duan, Zhi-Qiang; Liu, Yi-Tao; Xie, Xu-Ming; Ye, Xiong-Ying; Zhu, Xiao-Dong

    2016-03-18

    h-BN, as an isoelectronic analogue of graphene, has improved thermal mechanical properties. Moreover, the liquid-phase production of h-BN is greener since harmful oxidants/reductants are unnecessary. Here we report a novel hybrid architecture by employing h-BN nanosheets as 2D substrates to load 0D Fe3O4 nanoparticles, followed by phenol/formol carbonization to form a carbon coating. The resulting carbon-encapsulated h-BN@Fe3O4 hybrid architecture exhibits synergistic interactions: 1) The h-BN nanosheets act as flexible 2D substrates to accommodate the volume change of the Fe3O4 nanoparticles; 2) The Fe3O4 nanoparticles serve as active materials to contribute to a high specific capacity; and 3) The carbon coating not only protects the hybrid architecture from deformation but also keeps the whole electrode highly conductive. The synergistic interactions translate into significantly enhanced electrochemical performances, laying a basis for the development of superior hybrid anode materials.

  20. Structures, Bonding, and One-Bond B-N and B-H Spin-Spin Coupling Constants for a Series of Neutral and Anionic Five-Membered Rings Containing BN Bonds.

    Science.gov (United States)

    Yáñez, Manuel; Mó, Otilia; Alkorta, Ibon; Del Bene, Janet E

    2008-11-11

    The structures and bonding of a series of five-membered rings with BN bonds CxNyBzH5 (x + y + z = 5) and their most stable deprotonated anions CxNyBzH4(-) as well as anionic rings CxNyBzH5(-) have been investigated at the MP2/6-311++G(d,p) level of theory. The great majority of these rings present BN bond orders close to that found in borazine, suggesting that there is substantial electron delocalization in these rings. This observation is also supported by both NBO and ELF analyses. Ab initio equation-of-motion coupled-cluster singles and doubles (EOM-CCSD) calculations have also been performed to obtain the (15)N-(11)B and (1)H-(11)B spin-spin coupling constants. For neutral systems, the former range from -10 to -35 Hz, thereby bracketing the value of (1)J(B-N) for borazine, which is -29 Hz. (1)J(B-N) spans an even greater range in the anions, from -3 to -36 Hz. The absolute value of (1)J(B-N) decreases upon deprotonation if coupling involves the deprotonated nitrogen or a boron atom bonded to the deprotonated N. (1)J(B-H) always decreases upon nitrogen deprotonation.

  1. Decolorization and detoxification of Synozol red HF-6BN azo dye, by Aspergillus niger and Nigrospora sp

    Directory of Open Access Journals (Sweden)

    Sidra Ilyas

    2013-01-01

    Full Text Available In the present investigation the fungi, Aspergillus niger and Nigrospora sp. were employed for decolorization of Synazol red HF-6BN. Decolorization study showed that Aspergillus niger and Nigrospora sp. were able to decolorize 88% and 96% Synazol red 6BN, respectively, in 24 days. It was also studied that 86% and 90% Synazol red containing of dye effluent was decolorized by Aspergillus niger and Nigrospora sp. after 28 days of incubation at room temperature. A fungal-based protein with relative molecular mass of 70 kDa was partially purified and examined for enzymatic characteristics. The enzyme exhibited highest activity at temperature ranging from 40-50[degree sign]C and at pH=6.0. The enzyme activity was enhanced in the presence of metal cations. High performance liquid chromatography analysis confirmed that these fungal strains are capable to degrade Synazol red dye into metabolites. No zones of inhibition on agar plates and growth of Vigna radiata in the presence of dye extracted sample, indicated that the fungal degraded dye metabolites are nontoxic to beneficial micro-flora and plant growth. Aspergillus niger and Nigrospora sp. have promising potential in color removal from textile wastewater-containing azo dyes.

  2. Preferred orientation in carbon and boron nitride: Does a thermodynamic theory of elastic strain energy get it right. [C; BN

    Energy Technology Data Exchange (ETDEWEB)

    McCarty, K.F. (Sandia National Laboratories, Livermore, California 94550 (United States))

    1999-09-01

    We address whether the elastic strain-energy theory (minimizing the Gibbs energy of a stressed crystal) of McKenzie and co-workers [D. R. McKenzie and M. M. M. Bilek, J. Vac. Sci. Technol. A [bold 16], 2733 (1998)] adequately explains the preferred orientation observed in carbon and BN films. In the formalism, the Gibbs energy of the cubic materials diamond and cubic boron includes the strain that occurs when the phases form, through specific structural transformations, from graphitic precursors. This treatment violates the requirement of thermodynamics that the Gibbs energy be a path-independent, state function. If the cubic phases are treated using the same (path-independent) formalism applied to the graphitic materials, the crystallographic orientation of lowest Gibbs energy is not that observed experimentally. For graphitic (hexagonal) carbon and BN, an elastic strain approach seems inappropriate because the compressive stresses in energetically deposited films are orders of magnitude higher than the elastic limit of the materials. Furthermore, using the known elastic constants of either ordered or disordered graphitic materials, the theory does not predict the orientation observed by experiment. [copyright] [ital 1999 American Vacuum Society.

  3. Effect of composition and grain size on electrical discharge machining of BN--TiB sub 2 composites

    Energy Technology Data Exchange (ETDEWEB)

    Gadalla, A.M.; Bedi, H.S. (Chemical Engineering Department, Texas A M University, College Station, Texas (USA))

    1991-11-01

    TiB{sub 2} conducts the current and forms a liquid phase at the interface with BN. Neighboring crystals of BN and some TiB{sub 2} spall due to thermal shock. During pause periods parts of the liquid and fragments are flushed out by the dielectric. Composites rich in TiB{sub 2} or with fine TiB{sub 2} grains gave high material removal rates. Increasing the amount of conducting phase by 10% is as effective as decreasing the grain size from 11 to 7 {mu}m. Coarse TiB{sub 2} could withstand high pulse durations before wire breaks. Material removal rate increases with pulse duration, frequency, and current. For the same composition and grain size, increasing the pulse duration or current increased the crater depth (the roughness) up to a certain value, beyond which increasing these parameters yielded a smoother surface. The conductivity of the dielectric was effective only for compositions rich in TiB{sub 2} content. In such cases, higher water conductivity lowered the energy required for material removal.

  4. A new Cu(TiBN x ) alloy film for boosting the per-watt illuminance of high power LEDs

    Science.gov (United States)

    Lin, Chon-Hsin

    2017-01-01

    In this study, a new Cu(TiBN x ) alloy film has been explored and utilized as a flexible heat dissipation layer for the substrate of high power LEDs to boost their per-watt illuminance by reducing the thermal resistance and increasing the thermal conductivity of the substrate. The new film is a Cu-alloy seed layer fabricated by co-sputtering Cu and TiB in an N2 atmosphere on a Ta/polyimide (Ta/PI) substrate. The film was then annealed at 340 °C for 1 h without noticeable Cu oxide formation around the film-substrate interface. The new film exhibits low resistivity, high thermal conductivity and low thermal resistance, rendering a substantially higher per-watt illuminance for LEDs that utilize the film as their additional heat dissipation layer. The experimental results gained in the study appear to confirm the new Cu(TiBN x ) film as a good candidate material, at least, for boosting the per-watt illuminance of high power LEDs.

  5. Tribological behaviors of diamond-like carbon coatings on plasma nitrided steel using three BN-containing lubricants

    Energy Technology Data Exchange (ETDEWEB)

    Jia Zhengfeng [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, 18 Tianshui Middle Road, Lanzhou 73000 (China); College of Materials Science and Engineering, Liaocheng University, Liaocheng 252059 (China); Graduate School of the Chinese Academy of Sciences, Beijing 10039 (China); Wang Peng [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, 18 Tianshui Middle Road, Lanzhou 73000 (China); Xia Yanqiu, E-mail: xiayanqiu@yahoo.com [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, 18 Tianshui Middle Road, Lanzhou 73000 (China); Zhang Haobo; Pang Xianjuan [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, 18 Tianshui Middle Road, Lanzhou 73000 (China); Graduate School of the Chinese Academy of Sciences, Beijing 10039 (China); Li Bin [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, 18 Tianshui Middle Road, Lanzhou 73000 (China)

    2009-04-15

    In this work, diamond-like carbon (DLC) coatings were deposited on plasma nitrided AISI 1045 steel by magnetron sputtering. Three BN-containing additives and molybdenum dithiocarbamate (MoDTC) were added to poly-alpha-olefin (PAO) as additives. The additive content (mass fraction) in PAO was fixed at 0.5 wt%. The friction and wear characters of DLC coatings on nitrided steel discs sliding against AISI 52100 steel balls were tested under the lubricated conditions. It was found that borate esters have a higher load carrying capacity and much better anti-wear and friction-reducing ability than that of MoDTC. X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM) were employed to explore the properties of the worn surface and the mechanism of friction and wear. According to the XPS analysis, the adsorbed organic N-containing compounds and BN are, possibly, the primary reason for the novel borate esters to possess a relatively constant coefficient of friction and lower wear rate. On the other hand, possibly, the MoDTC molecules break down during sliding and produce many Mo-oxides, and then the Mo-oxides destroy the DLC coating because of its sharp edge crystalline solid structure. After destroying the DLC coating, the MoDTC react with metals and form MoS{sub 2} tribofilm, and decrease coefficient of friction of rubbing pairs.

  6. NEW OBSERVATIONS OF THE LARGE PROPER MOTIONS OF RADIO SOURCES IN THE ORION BN/KL REGION

    Directory of Open Access Journals (Sweden)

    L. F. Rodríguez

    2008-01-01

    Full Text Available Presentamos astrometr a absoluta de cuatro fuentes de radio en la regi n de Becklin Neugebauer/Kleinman- Low (BN/KL, derivados de datos de archivo (tomados en 1991, 1995, y 2000 as como de nuevas observaciones (tomadas en 2006. Todos los datos consisten de emisi n de continuo a 3.6 cm tomados con el Very Large Array en su con guraci n A, la de m s alta resoluci n angular. Con rmamos las grandes velocidades transversales del objeto BN, la fuente de radio I (GMR I y la contraparte de radio de la fuente infrarroja n (Orion-n, con valores de 15 a 26 km s-1. Las tres fuentes se alejan de un punto entre ellas de donde parecen haber sido eyectadas hace alrededor de 500 a~nos, probablemente como resultado de la desintegraci on de un sistema estelar m ltiple. La fuente de radio Orion-n aparec a como doble en las tres primeras pocas, pero como sencilla en 2006. La cuarta fuente de la regi n, GMR D, no muestra movimientos propios estad sticamente signi cativos. Tambi n discutimos brevemente un escenario din mico para la regi n.

  7. Comparative study on the spectral properties of boron clusters Bn0/-1(n = 38-40)

    Science.gov (United States)

    Li, Shixiong; Zhang, Zhengping; Long, Zhengwen; Sun, Guangyu; Qin, Shuijie

    2016-04-01

    The all-boron fullerenes B40-1 and B39-1 discovered in recent experiments are characterized and revealed using photoelectron spectroscopy. Except for the photoelectron spectroscopy, one may identify such boron clusters with other spectroscopic techniques, such as infrared spectra and Raman spectra. Insight into the spectral properties of boron clusters is important to understand the boron clusters and find their potential applications. In this work, density functional theory (DFT) and time-dependent density functional theory (TD-DFT) calculations are carried out to comparatively study the vibrational frequencies, infrared spectra, Raman spectra and electronic absorption spectra of boron clusters Bn0/-1(n = 38-40). The numerical simulations show that such boron clusters have different and meaningful spectral features. These spectral features are readily compared with future spectroscopy measurements and can be used as fingerprints to distinguish the boron clusters Bn0/-1 with different structures (cage structure or quasi-planar structure) and with different sizes (n = 38-40).

  8. Characterization of oligomeric forms from mammalian F0F1ATP synthase by BN-PAGE: the role of detergents.

    Science.gov (United States)

    Bisetto, Elena; Giorgio, Valentina; Di Pancrazio, Francesca; Mavelli, Irene; Lippe, Giovanna

    2007-12-01

    It is now widely accepted that F0F1ATPsynthase is present in membrane, beside as monomers, in homo-dimeric and higher homo-oligomeric forms, which probably play critical roles in determining mitochondrial morphology. One-step mild detergent extraction followed by blue native electrophoresis (BN-PAGE) is a very interesting tool for studying the native membrane protein assemblies which can be associated with second/third-dimensional SDS-PAGE, immunoblotting, in-gel enzyme activity staining and mass spectrometry analyses. By combining these techniques, we resolved monomers and higher oligomeric forms of ATPsynthase from bovine heart mitochondria. However, a critical point is the choice of the detergents, which strongly influence the protein pattern of BN-PAGE. By using Triton X-100 we obtained that, in spite of the same subunit composition, monomers have a much lower specific activity than dimers and the two forms have a different pattern of tyrosine phosphorylation, suggesting that monomers and dimers are functionally distinct in membrane. In addition, enzyme self-association appeared to occur independently from the binding to ATPsynthase of the inhibitor protein IF1. Dodecylmaltoside was optimal to extract the enzyme from single biopsy samples, allowing us to demonstrate that IF1 plays a central role in regulating the enzyme activity in heart in vivo. Only low concentration of digitonin maintained significant amounts of ATPsynthase oligomers, which seemed to retain intact their native catalytic properties.

  9. Simple fabrication of air-stable black phosphorus heterostructures with large-area hBN sheets grown by chemical vapor deposition method

    Science.gov (United States)

    Sinha, Sapna; Takabayashi, Yuya; Shinohara, Hisanori; Kitaura, Ryo

    2016-09-01

    We have developed a facile and general method to passivate thin black phosphorus (BP) flakes with large-area high-quality monolayer hexagonal boron nitride (hBN) sheets grown by the chemical vapor deposition (CVD) method. In spite of the one-atom-thick structure, the high-quality CVD-grown monolayer hBN has proven to be useful to prevent the degradation of thin BP flakes exfoliated on substrates. Mechanically exfoliated BP flakes prepared on a Si substrate are covered by the monolayer hBN sheet to preserve (otherwise unstable) atomic layered BP flakes from degradation. The present technique can generally be applied to fabricating BP-based electronic devices with much easiness.

  10. Raman Study of Uncoated and p-BN/SiC-Coated Hi-Nicalon Fiber-Reinforced Celsian Matrix Composites. Part 1; Distribution and Nanostructure of Different Phases

    Science.gov (United States)

    Gouadec, Gwenael; Colomban, Philippe; Bansal, Narottam P.

    2000-01-01

    Hi-Nicalon fiber reinforced celsian matrix composites were characterized by Raman spectroscopy and imaging, using several laser wavelengths. Composite #1 is reinforced by as-received fibers while coatings of p-BN and SiC protect the fibers in composite #2. The matrix contains traces of the hexagonal phase of celsian, which is concentrated in the neighborhood of fibers in composite #1. Some free silicon was evident in the coating of composite #2 which might involve a {BN + SiC yields BNC + Si} "reaction" at the p-BN/SiC interface. Careful analysis of C-C peaks revealed no abnormal degradation of the fiber core in the composites.

  11. Cloning and Characterization of Phospholipids:Diacylglycerol Acyltransferase (BnPDAT1) cDNA from Brassica napus L.%甘蓝型油菜磷脂二酰甘油酰基转移酶(BnPDAT1)cDNA的克隆和功能鉴定

    Institute of Scientific and Technical Information of China (English)

    谭太龙; 冯韬; 罗海燕; 彭烨; 刘睿洋; 官春云

    2016-01-01

    Phospholipids:diacylglycerol acyltransferase (PDAT1) is a key enzyme in triacylglycerol (TAG) biosynthesis of plants. In this study, three novel PDAT1 coding sequences (CDSs) were isolated from cDNA of Brassica napus L. cv. Xiangyou 15 seeds, which were mapped to the chromosomes A02, A10, and C09, and designated as BnPDAT1-A02,BnPDAT1-A10, and BnPDAT1-C09, respectively. Three BnPDAT1 CDSs were 1998, 2002, and 2005 bp in length and encoded predicted proteins with 665, 666, and 667 amino acid residues, respectively. BnPDAT1 proteins were predicted to be located on the cell membrane and have a typical PDAT1 conserved domain. Multiple sequence alignments and phylogenetic analysis showed that the deduced amino acid sequences of BnPDAT1 were highly homologous to previously reported PDAT1 inBrassica oleracea,Arabidopsis thalian, and Eruca sativa. Furthermore, the catalytic enzyme activity of the cloned BnPDAT1 genes was confirmed by the yeast comple-mentary experiment. The expression level of BnPDAT1s increased gradually in seed development and reached the maximum from 25 to 30 days after flowering. However, three BnPDAT1 copies were also found to be different in expression pattern.%磷脂二酰甘油酰基转移酶(phospholipids:diacylglycerol acyltransferase,PDAT1)是植物三酰甘油(triacylgly-cerol,TAG)合成的关键酶.本文在甘蓝型油菜湘油15号cDNA中克隆到3个PDAT1全长编码序列(coding sequence,CDS),经比对分别定位于A02、A10、C09染色体,分别命名为BnPDAT1-A02、BnPDAT1-A10和BnPDAT1-C09,其序列长分别为1998、2002和2005 bp,各自编码665、666、667个氨基酸.预测BnPDAT1基因编码蛋白定位于细胞质膜,具有典型的PDAT1保守结构域.多序列比对和进化分析表明,BnPDAT1基因编码蛋白与甘蓝、拟南芥、亚麻芥PDAT1蛋白具有较高的同源性.酵母互补实验证实,该基因编码蛋白具有PDAT1酶活性.BnPDAT1基因在湘油15号中的表达现先上升后降低趋势,在开花后25

  12. Anti-parasitic effect on Toxoplasma gondii induced by BnSP-7, a Lys49-phospholipase A2 homologue from Bothrops pauloensis venom.

    Science.gov (United States)

    Borges, Isabela Pacheco; Castanheira, Letícia Eulalio; Barbosa, Bellisa Freitas; de Souza, Dayane Lorena Naves; da Silva, Rafaela José; Mineo, José Roberto; Tudini, Kelly Aparecida Yoneyama; Rodrigues, Renata Santos; Ferro, Eloísa Amália Vieira; de Melo Rodrigues, Veridiana

    2016-09-01

    Toxoplasmosis affects a third of the global population and presents high incidence in tropical areas. Its great relevance in public health has led to a search for new therapeutic approaches. Herein, we report the antiparasitic effects of BnSP-7 toxin, a Lys49 phospholipase A2 (PLA2) homologue from Bothrops pauloensis snake venom, on Toxoplasma gondii. In an MTT assay, BnSP-7 presented significant cytotoxicity against host HeLa cells at higher doses (200 μg/mL to 50 μg/mL), whereas lower doses (25 μg/mL to 1.56 μg/mL) produced low cytotoxicity. Furthermore, the toxin showed no effect on T. gondii tachyzoite viability when evaluated by trypan blue exclusion, but decreased both adhesion and parasite proliferation when tachyzoites were treated before infection. We also measured cytokines in supernatants collected from HeLa cells infected with T. gondii tachyzoites previously treated with RPMI or BnSP-7, which revealed enhancement of only MIF and IL-6 cytokines levels in supernatants of HeLa cells after BnSP-7 treatment. Our results showed that the BnSP-7 PLA2 exerts an anti-Toxoplasma effect at a lower dose than that required to induce cytotoxicity in HeLa cells, and also modulates the immune response of host cells. In this sense, the anti-parasitic effect of BnSP-7 PLA2 demonstrated in the present study opens perspectives for use of this toxin as a tool for future studies on toxoplasmosis.

  13. Comparison of B{sub 2}O{sub 3} and BN deposited by atomic layer deposition for forming ultrashallow dopant regions by solid state diffusion

    Energy Technology Data Exchange (ETDEWEB)

    Consiglio, Steven, E-mail: steve.consiglio@us.tel.com; Clark, Robert D.; O' Meara, David; Wajda, Cory S.; Tapily, Kandabara; Leusink, Gert J. [TEL Technology Center, America, LLC, 255 Fuller Rd., Albany, New York 12203 (United States)

    2016-01-15

    In this study, the authors investigated atomic layer deposition (ALD) of B{sub 2}O{sub 3} and BN for conformal, ultrashallow B doping applications and compared the effect of dopant-containing overlayers on sheet resistance (R{sub s}) and B profiles for both types of films subjected to a drive-in thermal anneal. For the deposition of B{sub 2}O{sub 3}, tris(dimethylamido)borane and O{sub 3} were used as coreactants and for the deposition of BN, BCl{sub 3} and NH{sub 3} were used as coreactants. Due to the extreme air instability of B{sub 2}O{sub 3} films, physical analysis was performed on B{sub 2}O{sub 3} films, which were capped in-situ with ∼30 Å ALD grown Al{sub 2}O{sub 3} layers. For the BN films, in-situ ALD grown Si{sub 3}N{sub 4} capping layers (∼30 Å) were used for comparison. From spectroscopic ellipsometry, a thickness decrease was observed after 1000 °C, 30 s anneal for the B{sub 2}O{sub 3} containing stack with 60 ALD cycles of B{sub 2}O{sub 3}, whereas the BN containing stacks showed negligible thickness decrease after the annealing step, regardless of the number of BN cycles tested. The postanneal reduction in film thickness as well as decrease in R{sub s} for the B{sub 2}O{sub 3} containing stack suggests that the solid state diffusion dopant mechanism is effective, whereas for the BN containing stacks this phenomenon seems to be suppressed. Further clarification of the effectiveness of the B{sub 2}O{sub 3} containing layer compared to the film stacks with BN was evidenced in backside secondary ion mass spectrometry profiling of B atoms. Thus, B{sub 2}O{sub 3} formed by an ALD process and subsequently capped in-situ followed by a drive-in anneal offers promise as a dopant source for ultrashallow doping, whereas the same method using BN seems ineffective. An integrated approach for B{sub 2}O{sub 3} deposition and annealing on a clustered tool also demonstrated controllable R{sub s} reduction without the use of a capping layer.

  14. 指数Diophantine方程(bn)x+(2n)y=((b+2)n)z的例外解%The Exceptional Solutions of the Exponential Diophantine Equation (bn)x + (2n)y =((b + 2)n)z

    Institute of Scientific and Technical Information of China (English)

    余亚辉; 李振平

    2014-01-01

    设b是大于3的正奇数.运用初等方法讨论了方程(bn)x+(2n)y=((b+2)n)z适合(x,y,z)≠(1,1,1)的正整数解(x,y,z,n).证明了:i)对于任何给定的正整数N,存在无穷多个b可使该方程有满足min{x,y,z}≥N的正整数解(x,y,z,n);ii)对于任何给定的b,该方程仅有有限多组正整数解(x,y,z,n)满足y>z=x.

  15. 氮化硼/环氧树脂复合材料空间电荷与击穿特性实验研究%Study on Space Charge and Breakdown Characteristics of BN/Epoxy Resin Composites

    Institute of Scientific and Technical Information of China (English)

    2016-01-01

    Nano-BN particles were treated by coupling agent, and the surface treated nano-BN/epoxy resin composites were compared. Their microscope morphology, breakdown strength, and space charge were analyzed and measured. The results show that with the increase of micro-BN content, the breakdown strength of the micro-BN/epoxy resin composite decreases. With the increase of nano-BN content, the breakdown strength of the nano-BN/epoxy resin composite increases at first and then decreases. The addi-tion of micro- and nano-BN can reduce the average space charge density of the BN/epoxy resin composite under DC high voltage electric field. Meanwhile, the coupling agent treatment can decrease the average space charge density of the nano-BN/epoxy resin composite during the polarization and increase the space charge dissipation rate during the depolarization.%采用偶联剂对纳米BN颗粒进行表面处理,制备了经过表面处理的纳米BN/环氧树脂复合材料.对纳米/BN环氧树脂复合材料进行了微观形貌分析、击穿强度和空间电荷测试.结果表明:随着微米BN添加量的增加,微米BN/环氧树脂复合材料的击穿强度随之降低;随着纳米BN添加量的增加,纳米BN/环氧树脂复合材料的击穿强度先升高后降低.微、纳米BN的添加会降低直流高压电场下复合材料内的平均空间电荷密度.同时,偶联剂处理会降低纳米BN/环氧树脂复合材料在加压时的平均空间电荷密度,增加纳米BN/环氧树脂复合材料在短路时空间电荷的消散速率.

  16. Interaction between new synthesized derivative of (E,E)-azomethines and BN(6,6-7) nanotube for medical applications: Geometry optimization, molecular structure, spectroscopic (NMR, UV/Vis, excited state), FMO, MEP and HOMO-LUMO investigations

    Science.gov (United States)

    Sheikhi, Masoome; Shahab, Siyamak; Filippovich, Liudmila; Khaleghian, Mehrnoosh; Dikusar, Evgenij; Mashayekhi, Mahsa

    2017-10-01

    In this present work, first time interaction between new synthesized derivative of the 4-((E)-((4-((E)-phenyldiazenyl)phenyl)imino)methyl)benzoic acid (E-PABA) and the BN(6,6-7) Nanotube for medical applications were studied. The geometries of the compounds E-PABA, the BN(6,6-7) Nanotube and the Complex BN(6,6-7)/E-PABA were optimized by Density Functional Theory (DFT) in the gas phase. The adsorption effect of the compound E-PABA on the electronic properties, chemical shift tensors and natural charge of the BN(6,6-7) Nanotube was investigated and discussed. The electronic spectra of the E-PABA and the Complex BN(6,6-7)/E-PABA in the gas phase carried out by Time Dependent Density Functional Theory (TD-DFT) for the foundation adsorption effect on maximum wavelength of the E-PABA.

  17. The use of waveguide acoustic probes for void fraction measurement in the evaporator of BN-350-Type reactor

    Energy Technology Data Exchange (ETDEWEB)

    Melnikov, V.I.; Nigmatulin, B.I.

    1995-09-01

    The present paper deals with some results of the experimental studies which have been carried out to investigate the steam generation dynamics in the Field tubes of sodium-water evaporators used in the BN-350 reactors. The void fraction measurements have been taken with the aid of waveguide acoustic transducers manufactured in accordance with a specially designed technology (waveguide acoustic transducers-WAT technology). Presented in this paper also the transducer design and calibration methods, as well as the diagram showing transducers arrengment in the evaporator. The transducers under test featured a waveguide of about 4 m in length and a 200-mm long sensitive element (probe). Besides, this paper specifies the void fraction data obtained through measurements in diverse points of the evaporator. The studies revealed that the period of observed fluctuations in the void fraction amounted to few seconds and was largely dependent on the level of water in the evaporator.

  18. Interlayer Excitons and Band Alignment in MoS2/hBN/WSe2 van der Waals Heterostructures

    DEFF Research Database (Denmark)

    Latini, Simone; Winther, Kirsten Trøstrup; Olsen, Thomas

    2017-01-01

    van der Waals heterostructures (vdWH) are ideal systems for exploring light-matter interactions at the atomic scale. In particular, structures with a type-II band alignment can yield detailed insight into carrier-photon conversion processes, which are central to, for example, solar cells and light......-emitting diodes. An important first step in describing such processes is to obtain the energies of the interlayer exciton states existing at the interface. Here we present a general first-principles method to compute the electronic quasi-particle (QP) band structure and excitonic binding energies...... of bilayer MoS2/WSe2 with and without intercalated hBN layers, finding excellent agreement with experimental photoluminescence spectra. A comparison to density functional theory calculations demonstrates the crucial role of self-energy and electron-hole interaction effects....

  19. Combustion Synthesis of Ti-2B-Cu/Ni and 3Ti-2BN-Cu/Ni Bilayered Cermets

    Institute of Scientific and Technical Information of China (English)

    Weiping SHEN; Wenbin CAO; Changchun GE; E.H.Grigoryan; A.E.Sytschev; A.S.Rogachev

    2003-01-01

    The effects of Cu and Ni (x=0, 10, 20 and 40 wt pct) and compaction pressures (12, 24, 84 and 108 MPa)on combustion wave velocity and wave front shape for Ti-2B-Cu/Ni and 3Ti-2BN-Cu/Ni bilayered cermets were investigated by a video camera. Since the boiling point of Cu is lower, the wave velocities of specimens are slower.Due to the higher specific heat of Ni than that of Cu, the wave velocities of specimens was slowed down a lot with increasing the Ni diluent. The wave velocity differences of the specimens containing Ni are more than that of the bilayered specimens containing Cu. Wave velocities of the specimens containing Ni increased more than that of the specimens containing Cu when higher pressure was employed for green mixture. The more the wave velocity difference of the bilayer, the more curved the specimen.

  20. Resonant quantum efficiency enhancement of midwave infrared nBn photodetectors using one-dimensional plasmonic gratings

    Energy Technology Data Exchange (ETDEWEB)

    Nolde, Jill A., E-mail: jill.nolde@nrl.navy.mil; Kim, Chul Soo; Jackson, Eric M.; Ellis, Chase T.; Abell, Joshua; Glembocki, Orest J.; Canedy, Chadwick L.; Tischler, Joseph G.; Vurgaftman, Igor; Meyer, Jerry R.; Aifer, Edward H. [Naval Research Laboratory, 4555 Overlook Ave. SW, Washington, DC 20375 (United States); Kim, Mijin [Sotera Defense Solutions, Inc., 7230 Lee Deforest Dr. Suite 100, Columbia, Maryland 21046 (United States)

    2015-06-29

    We demonstrate up to 39% resonant enhancement of the quantum efficiency (QE) of a low dark current nBn midwave infrared photodetector with a 0.5 μm InAsSb absorber layer. The enhancement was achieved by using a 1D plasmonic grating to couple incident light into plasmon modes propagating in the plane of the device. The plasmonic grating is composed of stripes of deposited amorphous germanium overlaid with gold. Devices with and without gratings were processed side-by-side for comparison of their QEs and dark currents. The peak external QE for a grating device was 29% compared to 22% for a mirror device when the illumination was polarized perpendicularly to the grating lines. Additional experiments determined the grating coupling efficiency by measuring the reflectance of analogous gratings deposited on bare GaSb substrates.

  1. Un recueil liturgique et historique du tournant des années 1200 (Paris, BnF, ms. latin 17716

    Directory of Open Access Journals (Sweden)

    Dominique Iogna-Prat

    2005-11-01

    Full Text Available Entamée il y a une dizaine d’années dans le cadre d’un atelier clunisien réunissant M. Huglo, M. Hillebrandt, D. Iogna-Prat, C. Magne, D. Méhu et P. Stirnemann, l’étude du recueil manuscrit Paris, BnF, latin 17716 doit trouver un terme dans cette ultime rencontre consacrée à un réexamen des problèmes posés par cet ensemble composite mais cohérent de pièces liturgiques, historiographiques et diplomatiques. Une place spéciale sera accordée à la liturgie de la Transfiguration (introduite à Cluny...

  2. From meso-Lactide to Isotactic Polylactide: Epimerization by B/N Lewis Pairs and Kinetic Resolution by Organic Catalysts.

    Science.gov (United States)

    Zhu, Jian-Bo; Chen, Eugene Y-X

    2015-10-07

    B/N Lewis pairs have been discovered to catalyze rapid epimerization of meso-lactide (LA) or LA diastereomers quantitatively into rac-LA. The obtained rac-LA is kinetically polymerized into poly(L-lactide) and optically resolved D-LA, with a high stereoselectivity k(L)/k(D) of 53 and an ee of 91% at 50.6% monomer conversion, by newly designed bifunctional chiral catalyst 4 that incorporates three key elements (β-isocupreidine core, thiourea functionality, and chiral BINAM) into a single organic molecule. The epimerization and enantioselective polymerization can be coupled into a one-pot process for transforming meso-LA directly into poly(L-lactide) and D-LA.

  3. Analysis of metabolites in plasma reveals distinct metabolic features between Dahl salt-sensitive rats and consomic SS.13(BN) rats.

    Science.gov (United States)

    Wang, Le; Hou, Entai; Wang, Zhengjun; Sun, Na; He, Liqing; Chen, Lan; Liang, Mingyu; Tian, Zhongmin

    2014-07-18

    Salt-sensitive hypertension is a major risk factor for cardiovascular disorders. Our previous proteomic study revealed substantial differences in several proteins between Dahl salt-sensitive (SS) rats and salt-insensitive consomic SS.13(BN) rats. Subsequent experiments indicated a role of fumarase insufficiency in the development of hypertension in SS rats. In the present study, a global metabolic profiling study was performed using gas chromatography/mass spectrometry (GC/MS) in plasma of SS rats (n=9) and SS.13(BN) rats (n=8) on 0.4% NaCl diet, designed to gain further insights into the relationship between alterations in cellular intermediary metabolism and predisposition to hypertension. Principal component analysis of the data sets revealed a clear clustering and separation of metabolic profiles between SS rats and SS.13(BN) rats. 23 differential metabolites were identified (PSS rats. Pyruvate, which connects TCA cycle and glycolysis, was also increased in SS rats. Moreover, lower activity levels of fumarase, aconitase, α-ketoglutarate dehydrogenase and succinyl-CoA synthetase were detected in the heart, liver or skeletal muscles of SS rats. The distinct metabolic features in SS and SS.13(BN) rats indicate abnormalities of TCA cycle in SS rats, which may play a role in predisposing SS rats to developing salt-sensitive hypertension.

  4. Tuning the band gaps and work functions via topology and carbon concentration: a first-principles investigation of C(x)(BN)(y) compounds.

    Science.gov (United States)

    Xie, Ying; Yu, Haitao; Zhang, Hongxing; Fu, Honggang

    2012-04-07

    The electronic properties, stabilities, and work functions of C(x)(BN)(y) monolayers were systematically investigated by first-principle techniques. The results indicated that the band gaps of the systems are rather sensitive to the topology and symmetry. However, the formation energies clearly suggested that the BN dimers tend to be grouped to one side and the carbon atoms are grouped to the other side. Such an atomic arrangement has the lowest formation energy and is thermodynamically highly stable, and furthermore their band gaps decrease gradually with an increasing of carbon content. Further analysis revealed that the band gap narrowing of G(I) structures depends on the nature of the C-2p(z) and N-2p(z) states. In contrast to the electronic properties, the variation of work functions as functions of carbon content exhibits an opposite trend. The strong correlation between the positive charge (Q(pos.)(tot.)) :work function (W(C(x)(BN)(y))) ratio and carbon content indicated that the ionicity of C(x)(BN)(y) compounds can be controlled by the carbon content and therefore determine the work functions of the systems.

  5. Unconventional morphologies in ordered melts of symmetric multiblock copolymers A(mN/2)(B(N/2)A(N/2))B-mN/2

    NARCIS (Netherlands)

    Smirnova, YG; ten Brinke, G; Erukhimovich, IY

    2005-01-01

    In the limit of weak segregation, microphase separation in melts of symmetric multiblock copolymers with the structural formula A(mN/2)(B(N/2)A(N/2))(n)B-mN/2 was theoretically analyzed. It was shown for the first time that, in the case of these two-length-scale block copolymers AB, competition betw

  6. A Brief Introduction to the Development of China's cBN Industry%国内立方氮化硼产业发展现状简述

    Institute of Scientific and Technical Information of China (English)

    孔帅斐; 栗正新

    2016-01-01

    Analysis has been given to the development status of China's cBN (Cubic Boron Nitride)industry in the recent years through three aspects:cBN abrasives,cutting tools, and the related enterprise.There has been already a steady improvement in China's re-search and development and manufacturing capacity of cBN abrasives and China has be-come a big producer in the world;cBN cutting tool has also achieved impressive result, while there are still gaps compared to the international advanced level.The future devel-opment direction of cubic boron nitride industry has also been discussed in this article.%从立方氮化硼磨料、刀具及相关企业三个方面分析了近年来我国立方氮化硼产业的发展状况。我国立方氮化硼磨料研究开发和制造能力稳步提高,已成为生产强国;立方氮化硼刀具同样取得了骄人的发展成绩,但距离国际先进水平尚有差距。文章还对立方氮化硼行业未来的发展方向进行了展望。

  7. Translation and pilot validation of Hindi translation of assessing quality of life in patients with primary brain tumours using EORTC brain module (BN-20

    Directory of Open Access Journals (Sweden)

    Budrukkar Ashwini

    2006-01-01

    Full Text Available Aim: To translate and validate the European Organisation for Research and Treatment for Cancer (EORTC brain cancer module (BN-20 into Hindi to make it available for patients and scientific community. Methods and Results: The EORTC BN-20 was translated into Hindi using standard guidelines by EORTC. The process included forward translation by two translators, discussion with the translators in case of discrepancies and formation of first intermediate questionnaire. This questionnaire was then given to two more translators who translated this questionnaire back into English. These 2 questionnaires were then compared with the original EORTC questionnaire and the second intermediate questionnaire was formed. The second intermediate questionnaire was subsequently administered in 10 patients with brain tumors who had never seen the questionnaire before, for pilot-testing. Each of these 10 patients after filling up the questionnaire themselves was then interviewed for any difficulty encountered during the filling up of the questionnaire. These were in the form of specific modules including difficulty in answering, confusion while answering and difficulty to understand, whether the questions were upsetting and if patients would have asked the question in any different way. There were major suggestions in three questions, which were incorporated into the second intermediate questionnaire to form the final Hindi BN-20 questionnaire. Conclusion: The final Hindi BN-20 has been approved by EORTC and can be used in clinical practice and studies for patients with brain tumors.

  8. Aggregation of frog rhodopsin to oligomers and their dissociation to monomer: application of BN- and SDS-PAGE.

    Science.gov (United States)

    Shukolyukov, S A

    2009-06-01

    After solubilization of frog rod outer segments (ROS) with mild detergents (digitonin, n-dodecyl-beta-D-maltoside, Chaps, Triton X-100) and subsequent one-dimensional blue native polyacrylamide gel electrophoresis (1D BN-PAGE), the position of rhodopsin (Rh) on the gradient gel does not match the monomer with molecular weight of 40 kDa but appears self-associated into aggregate of Rh (RhA) with molecular mass varying in different detergents from 85 to 125 kDa. Short-term treatment (~2 h) of the excised BN-PAGE strip containing RhA by denaturing detergent mixture (10% SDS + 1 mM dithiothreitol (DTT)) followed by 2D SDS-PAGE revealed dissociation of the RhA into opsin monomer and unidentified proteins. Long-term treatment (approximately 2 days) of RhA that included extraction, denaturation, concentration, and electrophoresis induced, along with dissociation of RhA into opsin monomer + unidentified proteins, also formation of opsin dimers, trimers, and higher oligomers owing to a secondary aggregation of opsin. Direct solubilization of the ROS by harsh SDS + DTT detergent mixture followed by 1D SDS-PAGE revealed only opsin monomer that upon heating disappeared, transforming into higher oligomers owing to secondary aggregation. The data show that degree of Rh oligomerization depends on specific conditions in which it stays. In the native state in the photoreceptor membrane as well as in mild detergents frog Rh exists mainly as dimers or higher oligomers. After solubilization with denaturing detergents, RhA can dissociate into monomers that then spontaneously self-associate into higher oligomers under the influence of various factors (for example, heating).

  9. Introgression of Brown Norway CYP4A genes on to the Dahl salt-sensitive background restores vascular function in SS-5(BN) consomic rats.

    Science.gov (United States)

    Lukaszewicz, Kathleen M; Falck, John R; Manthati, Vijaya L; Lombard, Julian H

    2013-03-01

    The present study tested the hypothesis that the Dahl SS (salt-sensitive) rat has vascular dysfunction due, in part, to the up-regulation of the CYP4A/20-HETE (cytochrome P450 ω-hydroxylase 4A)/20-hydroxyeicosatetraenoic acid) system. To assess the role of vascular 20-HETE, SS rats were compared with SS-5(BN) consomic rats, carrying CYP4A alleles on chromosome 5 from the normotensive BN (Brown Norway) introgressed on to the SS genetic background. Cerebral arteries from SS-5(BN) rats had less CYP4A protein than arteries from SS rats fed either NS (normal-salt, 0.4% NaCl) or HS (high-salt, 4.0% NaCl) diet. ACh (acetylcholine)-induced dilation of MCAs (middle cerebral arteries) from SS and SS-5(BN) rats was present in SS-5(BN) rats fed on either an NS or HS diet, but absent in SS rats. In SS rats fed on either diet, ACh-induced dilation was restored by acute treatment with the CYP4A inhibitor DDMS (N-methyl-sulfonyl-12,12-dibromododec-11-enamide) or the 20-HETE antagonist 20-HEDE [20-hydroxyeicosa-6(Z),15(Z)-dienoic acid]. The restored response to ACh in DDMS-treated SS rats was inhibited by L-NAME (N(G)nitro-L-arginine methyl ester) and unaffected by indomethacin or MS-PPOH [N-methylsulfonyl-6-(2-propargyloxyphenyl)hexanamide]. Vascular relaxation responses to the NO donor C(5)FeN(6)Na(2)O were intact in both SS and SS-5(BN) rats and unaffected by the acute addition of DDMS, indicating that the vascular dysfunction of the SS rat is due to a reduced bioavailability of NO instead of failure of the VSMCs (vascular smooth muscle cells) to respond to the vasodilator. Superoxide levels in cerebral arteries of SS-5(BN) rats [evaluated semi-quantitatively by DHE (dihydroethidium) fluorescence] were lower than those in the arteries of SS rats. These findings indicate that SS rats have an up-regulation of the CYP4A/20-HETE pathway resulting in elevated ROS (reactive oxygen species) and reduced NO bioavailability causing vascular dysfunction.

  10. Rapid degradation of azo dye Direct Black BN by magnetic MgFe2O4-SiC under microwave radiation

    Science.gov (United States)

    Gao, Jia; Yang, Shaogui; Li, Na; Meng, Lingjun; Wang, Fei; He, Huan; Sun, Cheng

    2016-08-01

    A novel microwave (MW) catalyst, MgFe2O4 loaded on SiC (MgFe2O4-SiC), was successfully synthesized by sol-gel method, and pure MgFe2O4 was used as reference. The MgFe2O4 and MgFe2O4-SiC catalysts were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), N2 adsorption analyzer (BET specific surface area), X-ray photoelectron spectroscopy (XPS). The electromagnetic parameters of the prepared catalysts were measured by vector network analyzer. The reflection loss (RL) based on the electromagnetic parameters calculated in Matlab showed MgFe2O4-SiC attained the maximum absorbing value of 13.32 dB at 2.57 GHz, which reached extremely high RL value at low frequency range, revealing the excellent MW absorption property of MgFe2O4-SiC. MW-induced degradation of Direct Black BN (DB BN) over as-synthesized MgFe2O4-SiC indicated that degradation efficiency of DB BN (20 mg L-1) in 5 min reached 96.5%, the corresponding TOC removal was 65%, and the toxicity of DB BN after degradation by MgFe2O4-SiC obviously decreased. The good stability and applicability of MgFe2O4-SiC on the degradation process were also discovered. Moreover, the ionic chromatogram during degradation of DB BN demonstrated that the C-S, C-N and azo bonds in the DB BN molecule were destroyed gradually. MW-induced rad OH and holes could be responsible for the efficient removal involved in the system. These findings make MgFe2O4-SiC become an excellent MW absorbent as well as an effective MW catalyst with rapid degradation of DB BN. Therefore, it may be promising for MgFe2O4-SiC under MW radiation to deal with various dyestuffs and other toxic organic pollutants.

  11. Zinc-Finger Nuclease Knockout of Dual-Specificity Protein Phosphatase-5 Enhances the Myogenic Response and Autoregulation of Cerebral Blood Flow in FHH.1BN Rats

    Science.gov (United States)

    Fan, Fan; Geurts, Aron M.; Pabbidi, Mallikarjuna R.; Smith, Stanley V.; Harder, David R.; Jacob, Howard; Roman, Richard J.

    2014-01-01

    We recently reported that the myogenic responses of the renal afferent arteriole (Af-Art) and middle cerebral artery (MCA) and autoregulation of renal and cerebral blood flow (RBF and CBF) were impaired in Fawn Hooded hypertensive (FHH) rats and were restored in a FHH.1BN congenic strain in which a small segment of chromosome 1 from the Brown Norway (BN) containing 15 genes including dual-specificity protein phosphatase-5 (Dusp5) were transferred into the FHH genetic background. We identified 4 single nucleotide polymorphisms in the Dusp5 gene in FHH as compared with BN rats, two of which altered CpG sites and another that caused a G155R mutation. To determine whether Dusp5 contributes to the impaired myogenic response in FHH rats, we created a Dusp5 knockout (KO) rat in the FHH.1BN genetic background using a zinc-finger nuclease that introduced an 11 bp frame-shift deletion and a premature stop codon at AA121. The expression of Dusp5 was decreased and the levels of its substrates, phosphorylated ERK1/2 (p-ERK1/2), were enhanced in the KO rats. The diameter of the MCA decreased to a greater extent in Dusp5 KO rats than in FHH.1BN and FHH rats when the perfusion pressure was increased from 40 to 140 mmHg. CBF increased markedly in FHH rats when MAP was increased from 100 to 160 mmHg, and CBF was better autoregulated in the Dusp5 KO and FHH.1BN rats. The expression of Dusp5 was higher at the mRNA level but not at the protein level and the levels of p-ERK1/2 and p-PKC were lower in cerebral microvessels and brain tissue isolated from FHH than in FHH.1BN rats. These results indicate that Dusp5 modulates myogenic reactivity in the cerebral circulation and support the view that a mutation in Dusp5 may enhance Dusp5 activity and contribute to the impaired myogenic response in FHH rats. PMID:25397684

  12. Zinc-finger nuclease knockout of dual-specificity protein phosphatase-5 enhances the myogenic response and autoregulation of cerebral blood flow in FHH.1BN rats.

    Directory of Open Access Journals (Sweden)

    Fan Fan

    Full Text Available We recently reported that the myogenic responses of the renal afferent arteriole (Af-Art and middle cerebral artery (MCA and autoregulation of renal and cerebral blood flow (RBF and CBF were impaired in Fawn Hooded hypertensive (FHH rats and were restored in a FHH.1BN congenic strain in which a small segment of chromosome 1 from the Brown Norway (BN containing 15 genes including dual-specificity protein phosphatase-5 (Dusp5 were transferred into the FHH genetic background. We identified 4 single nucleotide polymorphisms in the Dusp5 gene in FHH as compared with BN rats, two of which altered CpG sites and another that caused a G155R mutation. To determine whether Dusp5 contributes to the impaired myogenic response in FHH rats, we created a Dusp5 knockout (KO rat in the FHH.1BN genetic background using a zinc-finger nuclease that introduced an 11 bp frame-shift deletion and a premature stop codon at AA121. The expression of Dusp5 was decreased and the levels of its substrates, phosphorylated ERK1/2 (p-ERK1/2, were enhanced in the KO rats. The diameter of the MCA decreased to a greater extent in Dusp5 KO rats than in FHH.1BN and FHH rats when the perfusion pressure was increased from 40 to 140 mmHg. CBF increased markedly in FHH rats when MAP was increased from 100 to 160 mmHg, and CBF was better autoregulated in the Dusp5 KO and FHH.1BN rats. The expression of Dusp5 was higher at the mRNA level but not at the protein level and the levels of p-ERK1/2 and p-PKC were lower in cerebral microvessels and brain tissue isolated from FHH than in FHH.1BN rats. These results indicate that Dusp5 modulates myogenic reactivity in the cerebral circulation and support the view that a mutation in Dusp5 may enhance Dusp5 activity and contribute to the impaired myogenic response in FHH rats.

  13. Influence of modulation period and modulation ratio on structure and mechanical properties of TiBN/CrN coatings deposited by multi-arc ion plating

    Energy Technology Data Exchange (ETDEWEB)

    Zhou, S.Y.; Yan, S.J.; Han, B. [Key Laboratory of Artificial Micro- and Nano-Materials of Ministry of Education and School of Physics and Technology, Wuhan University, 430072 Wuhan (China); Yang, B. [School of Power and Mechanical Engineering, Wuhan University, 430072 Wuhan (China); Lin, B.Z.; Zhang, Z.D.; Ai, Z.W. [Key Laboratory of Artificial Micro- and Nano-Materials of Ministry of Education and School of Physics and Technology, Wuhan University, 430072 Wuhan (China); Pelenovich, V.O. [Key Laboratory of Artificial Micro- and Nano-Materials of Ministry of Education and School of Physics and Technology, Wuhan University, 430072 Wuhan (China); Institute of Ion-Plasma and Laser Technologies, Academy of Sciences of Uzbekistan, 700135 Tashkent (Uzbekistan); Fu, D.J., E-mail: djfu@whu.edu.cn [Key Laboratory of Artificial Micro- and Nano-Materials of Ministry of Education and School of Physics and Technology, Wuhan University, 430072 Wuhan (China)

    2015-10-01

    Highlights: • TiBN/CrN multilayers were synthesized with varied modulation period and ratio. • The maximum hardness of 38.6 GPa is observed at Λ = 11.7 nm and R = 5:1. • The lowest multilayer COF of 0.32 is lower than that of CrN (0.56). • The wear rate of the coatings is improved and related to H/E and H{sup 3}/E{sup *2} ratios. - Abstract: TiBN/CrN multilayered superlattice coatings with modulation periods Λ (bilayer thickness) ranging from 22.5 to 4.2 nm and modulation ratio R (the thickness ratio of CrN and TiBN layers) ranging from 6:1 to 3:1 were synthesized using an industrial-scale cathodic arc ion plating system in an Ar–N{sub 2} gas mixture. X-ray diffraction (XRD), transmission electron microscopy (TEM) and nanoindention were employed to investigate the influence of modulation period and ratio on microstructure and mechanical properties of the multilayers. The sharp interfaces and nanoscale multilayered modulation were confirmed by TEM. TiBN/CrN multilayer coatings were crystallized with orientations at the (1 1 1), (2 0 0) and (2 2 0) crystallographic planes and the microstructure was strengthened at (2 0 0) preferred orientation. The maximum hardness of 38.6 GPa and elastic modulus of 477 GPa were obtained at Λ = 11.7 nm and R = 5:1. The lowest value of the friction coefficient at 0.32 sliding against a WC-Co ball was obtained at a bilayer period of 11.7 nm, compared to those of the coatings with other modulation periods and monolithic coatings. The wear rate of the multilayered coatings was also lower than those of the monolithic CrN and TiBN coatings.

  14. 掺杂BnNn(n=12,16,20,24,28)团簇的生成热%Heat of formation of BnNn(n=12,16,20,24,28)clusters with doping elements

    Institute of Scientific and Technical Information of China (English)

    岳锌; 赵纪军; 邱介山; 徐京城

    2013-01-01

    Similar to the carbon cage fullerenes, nanoscale spherical space in the medium-sized boron-nitride fullerene cage should be able to form embedded compound within the embedded atom. The studies of this field are still in a fledging period both theoretical and applied research. Employed the first principles method, we investigated serials of embedded compounds M@BnNn (n = 12, 16, 20, 24, 28) constructed with medium-sized boron-nitride fullerene cage and each M atom in the first, second, third and fourth periods of the Periodic Table. By calculating the binding energy of these embedded compounds, we found that the variation pattern of binding energy is consistent with the laws of the atomic radius, while the diameter of boron-nitride fullerene cage is small. The stability of embedded compounds decreases periodically, with increasing diameter of boron-nitride fullerene cage. In each cycle, the stability of the main group element embedded compounds decreases with increasing atom number. For Sub-group, element embedded compounds, the stability is significantly high when M atom is Mn, Fe, Co, or Ni rather than others.%中等尺寸的硼氮富勒烯笼与碳笼富勒烯相似,具有纳米尺度的球形内包空间,应该可以形成内包原子的笼状包合物,且无论从理论研究,还是从应用研究上讲都还处于起步阶段.我们采用第一性原理方法计算了第一、二、三、四周期内各元素原子作为M原子,分别构建M@BnNn(n=12,16,20)包合物并计算结合能.发现当硼氮富勒烯笼直径较小时,不同元素结合能的大小规律与原子半径的规律相符.副族元素的Mn、Fe、Co和Ni较其它元素的包合物稳定性明显增加.

  15. FIRST-PRINCIPLES CALCULATION OF ELECTRONIC STRUCTURE,BONDING CHARACTERISTIC AND BONDING STRENGTH OF TiN(111)/BN/TiN(111) INTERFACE%第一性原理计算TiN(111)/BN/TiN(111)界面的电子结构、成键特性和结合强度

    Institute of Scientific and Technical Information of China (English)

    牛建钢; 王宝军; 王翠表; 田晓

    2009-01-01

    利用第-性原理计算方法研究了TiN(111)/BN/TiN(111)界面的16个理论界面构型.计算结果表明,最稳定界面构型为top-top-BN构型,此构型中B原子只与周围N原子成键,为四面体配位.同时计算了top-top-BN构型的电子结构和成键特性以及界面结合强度,结果表明,top-top-BN构型界面上的键为较强共价键,其界面结合强度比TiN(111)板层或TiN块体材料的(111)晶面间的结合强度大,说明此构型具有强界面特征.%The nanocomposite 'nc-TiN/a-BN' as a representation of the family of super-hard nitride-based nanocomposites, which is a nanocomposite thin film material, exhibits a significant hardness enhancement as compared with the pure constituents. In this paper, first-principles calcula-tions were performed to investigate the role of interfaces in the nanocomposite 'nc-TiN/a-BN' , to which less attention has been paid up to now. In order to determine theoretically the stable interface configuration in 'nc-TiN/a-BN' , 16 possible theoretical TiN(111)/BN/TiN(111) sandwich interface configurations have been constructed based on the structure characteristic of 'nc-TiN/a-BN' . It is found in this calculation that the most favorable interface configuration is 'top-top-BN' , which is closely related to each B atom covalently bonding to its tetrahedrally coordinated N atoms in it. Its electronic structure is calculated. The calculated results show that the bonds at the interface in 'top-top-BN' configuration are covalent. Its interface bonding strength is higher than that between two 111 crystalline planes in slab TiN or bulk TiN.

  16. Most effective way to improve the hydrogen storage abilities of Na-decorated BN sheets: applying external biaxial strain and an electric field.

    Science.gov (United States)

    Tang, Chunmei; Zhang, Xue; Zhou, Xiaofeng

    2017-02-15

    Density functional calculations were used to investigate the hydrogen storage abilities of Na-atoms-decorated BN sheets under both external biaxial strain and a vertical electric field. The Na atom generally has the weakest binding strength to a given substrate compared with the other elements in the periodic table [PANS, 2016, 113, 3735]. Consequently, it is understudied in comparison to other elements and there are few reports about the hydrogen storage abilities of Na-decorated nanomaterials. We calculated that the average binding energy (Eb) of Na atoms to the pure BN sheet is 1.08 eV, which is smaller than the cohesive energy of bulk Na (1.11 eV). However, the Eb can be increased to 1.15 eV under 15% biaxial strain, and further up to 1.53 eV with the control of both 15% biaxial strain and a 5.14 V nm(-1) electric field (E-field). Therefore, the application of biaxial strain and an external upward E-field can prevent clustering of the Na atoms on the surface of a BN sheet, which is crucial for the hydrogen storage. Each Na atom on the surface of a BN sheet can adsorb only one H2 molecule when no strain or E-field is applied; however, the absorption increases to five H2 molecules under 15% biaxial strain and six H2 molecules under both 15% biaxial strain combined with a 5.14 V nm(-1)E-field. The average adsorption energies for H2 of BN-(Na-mH2) (m = 1-6) are within the range of practical applications (0.2-0.6 eV). The hydrogen gravimetric density of the periodic BN-(Na-6H2)4 structure is 9 wt%, which exceeds the 5.5 wt% value that should be met by 2017 as specified by the US Department of Energy. On the other side, removal of the biaxial strain and E-field can help to desorb the H2 molecule. These findings suggest a new route to design hydrogen storage materials under near-ambient conditions.

  17. Evaluation of the internalization kinetics of the radiopharmaceutical {sup 99m}Tc-N{sub 2}S{sub 2}-Tat(49-57)Lys{sup 3}-Bn with diagnostic purposes, using comet assay; Evaluacion de la cinetica de internalizacion del radiofarmaco {sup 99m}Tc-N{sub 2}S{sub 2}-TAT(49-57)Lys{sup 3}-BN con fines diagnosticos, empleando ensayo cometa

    Energy Technology Data Exchange (ETDEWEB)

    Luna G, M. A.

    2011-07-01

    Gastrin-rea leasing peptide receptors (GRP-r) are over expressed in breast and prostate cancer cells. Bombesin (Bn) binds specifically and strongly to GRP-r and this is the base for to label the Bn with radionuclides by gamma rays. Tat (49-57) is a peptide that across the cell membrane easily so that, when it is conjugated to different proteins, it can works as a Trojan horse, facilitating the drug internalization to the cells. The radiopharmaceutical {sup 99m}Tc-N{sub 2}S{sub 2}-Tat(49-57)-Lys{sup 3}-Bn was prepared for diagnosis and therapy at early stage of breast cancer. The objective of this study was to determine the role of Tat in the internalization kinetics of radiopharmaceuticals measured by DNA damage induced by means of comet assay. Human lymphocytes were treated with the following protocols: a) Tat-Bn, b) {sup 99m}Tc-Bn, or c) {sup 99m}Tc-N{sub 2}S{sub 2}-Tat(49-57)-Lys{sup 3}-Bn, also an untreated group was conformed. The internalization was evaluated at 0, 5, 10, 15, 30 and 60 min after exposure with three repetitions each one, and for radiopharmaceuticals with 2.9, 6.6, 9.0 and 14.8 MBq activities. DNA damage was scored in 100 cells per time and treatment, as tail length and tail moment. A Kruskal-Wallis variance analysis with p{<=} 0.05 was applied for comparison between treatments. The results showed that the damage caused by {sup 99m}Tc-N{sub 2}S{sub 2}-Tat(49-57)-Lys{sup 3}-Bn is significantly higher than that caused by {sup 99m}Tc-Bn and Tat-Bn, showing that Tat favors the internalization of the radiopharmaceutical. (Author)

  18. Thermochemistry and electronic structure of small boron clusters (B(n), n = 5-13) and their anions.

    Science.gov (United States)

    Truong, Ba Tai; Grant, Daniel J; Nguyen, Minh Tho; Dixon, David A

    2010-01-21

    Thermochemical parameters of a set of small-sized neutral (B(n)) and anionic (B(n)(-)) boron clusters, with n = 5-13, were determined using coupled-cluster theory CCSD(T) calculations with the aug-cc-pVnZ (n = D, T, and Q) basis sets extrapolated to the complete basis set limit (CBS) plus addition corrections and/or G3B3 calculations. Enthalpies of formation, adiabatic electron affinities (EA), vertical (VDE), and adiabatic (ADE) detachment energies were evaluated. Our calculated EAs are in good agreement with recent experiments (values in eV): B(5) (CBS, 2.29; G3B3, 2.48; exptl., 2.33 +/- 0.02), B(6) (CBS, 2.59; G3B3, 3.23; exptl., 3.01 +/- 0.04), B(7) (CBS, 2.62; G3B3, 2.67; exptl., 2.55 +/- 0.05), B(8) (CBS, 3.02; G3B3, 3.11; exptl., 3.02 +/- 0.02), B(9) (G3B3, 3.03; exptl., 3.39 +/- 0.06), B(10) (G3B3, 2.85; exptl., 2.88 +/- 0.09), B(11) (G3B4, 3.48;, exptl., 3.43 +/- 0.01), B(12) (G3B3, 2.33; exptl., 2.21 +/- 0.04), and B(13) (G3B3, 3.62; exptl., 3.78 +/- 0.02). The difference between the calculated adiabatic electron affinity and the adiabatic detachment energy for B(6) is due to the fact that the geometry of the anion is not that of the ground-state neutral. The calculated adiabatic detachment energies to the (3)A(u), C(2h) and (1)A(g), D(2h) excited states of B(6), which have geometries similar to the (1)A(g), D(2h) state of B(6)(-), are 2.93 and 3.06 eV, in excellent agreement with experiment. The VDEs were also well reproduced by the calculations. Partitioning of the electron localization functions into pi and sigma components allows probing of the partial and local delocalization in global nonaromatic systems. The larger clusters appear to exhibit multiple aromaticity. The binding energies per atom vary in a parallel manner for both neutral and anionic series and approach the experimental value for the heat of atomization of B. The resonance energies and the normalized resonance energies are convenient indices to quantify the stabilization of a cluster

  19. A novel ionic liquid-tolerant Fusarium oxysporum BN secreting ionic liquid-stable cellulase: consolidated bioprocessing of pretreated lignocellulose containing residual ionic liquid.

    Science.gov (United States)

    Xu, Jiaxing; Wang, Xinfeng; Hu, Lei; Xia, Jun; Wu, Zhen; Xu, Ning; Dai, Benlin; Wu, Bin

    2015-04-01

    In this study, microbial communities from chemicals polluted microhabitats were cultured with the addition of imidazolium-based ionic liquid (IL) to enrich for IL-tolerant microbes. A strain of Fusarium oxysporum BN producing cellulase from these enrichments was capable of growing in 10% (w/v) 1-ethyl-3-methylimidazolium phosphinate, much higher than the normal IL concentrations in the lignocellulose regenerated from ILs. Cellulase secreted by the strain showed high resistance to ILs based on phosphate and sulfate radicals, evidencing of a high conformational stability in relevant media. Gratifyingly, F. oxysporum BN can directly convert IL-pretreated rice straw to bioethanol via consolidated bioprocessing (I-CBP). At optimum fermentation condition, a maximum ethanol yield of 0.125 g ethanol g(-1) of rice straw was finally obtained, corresponding to 64.2% of the theoretical yield. Copyright © 2015 Elsevier Ltd. All rights reserved.

  20. Rapid degradation of azo dye Direct Black BN by magnetic MgFe{sub 2}O{sub 4}-SiC under microwave radiation

    Energy Technology Data Exchange (ETDEWEB)

    Gao, Jia; Yang, Shaogui, E-mail: yangsg@nju.edu.cn; Li, Na; Meng, Lingjun; Wang, Fei; He, Huan; Sun, Cheng

    2016-08-30

    Highlights: • MgFe{sub 2}O{sub 4}-SiC was first successfully synthesized. • MgFe{sub 2}O{sub 4}-SiC attained the maximum absorbing value of 13.32 dB at 2.57 GHz, which reached extremely high RL value at low frequency range. • Fast decolorization and high TOC removal of azo dye Direct Black BN with complicated structure could occur with MgFe{sub 2}O{sub 4}-SiC under MW radiation. • MgFe{sub 2}O{sub 4}-SiC had better MW absorbing property and higher MW catalytic activity than MnFe{sub 2}O{sub 4}-SiC under the same condition. • MgFe{sub 2}O{sub 4}-SiC was of practical use in the wastewater treatment. - Abstract: A novel microwave (MW) catalyst, MgFe{sub 2}O{sub 4} loaded on SiC (MgFe{sub 2}O{sub 4}-SiC), was successfully synthesized by sol-gel method, and pure MgFe{sub 2}O{sub 4} was used as reference. The MgFe{sub 2}O{sub 4} and MgFe{sub 2}O{sub 4}-SiC catalysts were characterized by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Transmission electron microscopy (TEM), N{sub 2} adsorption analyzer (BET specific surface area), X-ray photoelectron spectroscopy (XPS). The electromagnetic parameters of the prepared catalysts were measured by vector network analyzer. The reflection loss (RL) based on the electromagnetic parameters calculated in Matlab showed MgFe{sub 2}O{sub 4}-SiC attained the maximum absorbing value of 13.32 dB at 2.57 GHz, which reached extremely high RL value at low frequency range, revealing the excellent MW absorption property of MgFe{sub 2}O{sub 4}-SiC. MW-induced degradation of Direct Black BN (DB BN) over as-synthesized MgFe{sub 2}O{sub 4}-SiC indicated that degradation efficiency of DB BN (20 mg L{sup −1}) in 5 min reached 96.5%, the corresponding TOC removal was 65%, and the toxicity of DB BN after degradation by MgFe{sub 2}O{sub 4}-SiC obviously decreased. The good stability and applicability of MgFe{sub 2}O{sub 4}-SiC on the degradation process were also discovered. Moreover, the ionic chromatogram during degradation

  1. Numerical investigation of the effect of substrate surface roughness on the performance of zigzag graphene nanoribbon field effect transistors symmetrically doped with BN

    Directory of Open Access Journals (Sweden)

    Majid Sanaeepur

    2014-09-01

    Full Text Available The performance of field effect transistors comprised of a zigzag graphene nanoribbon that is symmetrically doped with boron nitride (BN as a channel material, is numerically studied for the first time. The device merit for digital applications is investigated in terms of the on-, the off- and the on/off-current ratio. Due to the strong effect of the substrate roughness on the performance of graphene devices, three common substrate materials (SiO2, BN and mica are examined. Rough surfaces are generated by means of a Gaussian auto-correlation function. Electronic transport simulations are performed in the framework of tight-binding Hamiltonian and non-equilibrium Green's function (NEGF formalisms. The results show that with an appropriate selection of the substrate material, the proposed devices can meet the on/off-current ratio required for future digital electronics.

  2. Suppression of self-heating effect in AlGaN/GaN high electron mobility transistors by substrate-transfer technology using h-BN

    Energy Technology Data Exchange (ETDEWEB)

    Hiroki, Masanobu, E-mail: hiroki.masanobu@lab.ntt.co.jp; Kumakura, Kazuhide; Kobayashi, Yasuyuki; Akasaka, Tetsuya; Makimoto, Toshiki; Yamamoto, Hideki [NTT Basic Research Laboratories, NTT Corporation 3-1 Morinosato Wakamiya, Atsugi-shi 243-0198 (Japan)

    2014-11-10

    We fabricated AlGaN/GaN high electron mobility transistors (HEMTs) on h-BN/sapphire substrates and transferred them from the host substrates to copper plates using h-BN as a release layer. In current–voltage characteristics, the saturation drain current decreased by about 30% under a high-bias condition before release by self-heating effect. In contrast, after transfer, the current decrement was as small as 8% owing to improved heat dissipation: the device temperature increased to 50 °C in the as-prepared HEMT, but only by several degrees in the transferred HEMT. An effective way to improve AlGaN/GaN HEMT performance by a suppression of self-heating effect has been demonstrated.

  3. The wear, deterioration and transformation phenomena of abradable coating BN-SiAl-bounding organic element, caused by the friction between the blades and the turbine casing

    Energy Technology Data Exchange (ETDEWEB)

    Bounazef, M.; Guessasma, S. [Laboratory of Studies and Research on Materials, Process and Surfaces, Belfort-Montbeliard University (France); Ait Saadi, B. [Physical Materials Laboratory, Oran-University (Algeria)

    2004-11-01

    In modern design of gas turbines, the use of abradable materials for the coating seal of engines is widespread. Indeed, in order to increase efficiency of gas turbines, clearances between rotating blades and the casing should be as small as possible. Therefore, the blades scrape this BN-SiAl seal to form a minimum gap. The aim of this work is to investigate the behaviour of a particular abradable material, the BN-SiAl-bounding organic element, during interreaction with the blades under experimental conditions of operating the rotor blade. For this purpose, we use a Sulzer Metco abradability test. Tests are made with different incursion speeds of blade within the coating seal as well as linear blade velocities. The obtained results are shown in the form of graphs describing how the transfer of coating wear occurs and the different effects are observed on the coating surface.

  4. High-Temperature Characteristics of an InAsSb/AlAsSb n+Bn Detector

    Science.gov (United States)

    Ting, David Z.; Soibel, Alexander; Höglund, Linda; Hill, Cory J.; Keo, Sam A.; Fisher, Anita; Gunapala, Sarath D.

    2016-09-01

    The high-temperature characteristics of a mid-wavelength infrared (MWIR) detector based on the Maimon-Wicks InAsSb/AlAsSb nBn architecture was analyzed. The dark current characteristics are examined in reference to recent minority carrier lifetime results. The difference between the responsivity and absorption quantum efficiency (QE) at shorter wavelengths is clarified in terms of preferential absorption of higher-energy photons in the top contact layer, which cannot provide reverse-bias photo-response due to the AlAsSb electron blocking layer and strong recombination. Although the QE does not degrade when the operating temperature increases to 325 K, the turn-on bias becomes larger at higher temperatures. This behavior was originally attributed to the change in the valence band alignment between the absorber and top contact layers caused by the shift in Fermi level with temperature. In this work, we demonstrated the inadequacy of the original description, and offer a more likely explanation based on temperature-dependent band-bending effects.

  5. MBE growth of Sb-based bulk nBn infrared photodetector structures on 6-inch GaSb substrates

    Science.gov (United States)

    Liu, Amy W. K.; Lubyshev, Dmitri; Qiu, Yueming; Fastenau, Joel M.; Wu, Ying; Furlong, Mark J.; Tybjerg, Marius; Martinez, Rebecca J.; Mowbray, Andrew; Smith, Brian

    2015-06-01

    The GaSb-based 6.1 Å lattice constant family of materials and heterostructures provides rich bandgap engineering possibilities and have received considerable attention for their potential and demonstrated performance in infrared (IR) detection and imaging applications. Mid-wave and long-wave IR photodetectors are progressing toward commercial manufacturing applications. To succeed, they must move from research laboratory settings to general semiconductor production, and high-quality GaSb-based epitaxial wafers with diameter larger than the current standard 3-inch are highly desirable. 4-inch GaSb substrates have been in production for a couple of years and are now commercially available. Recently, epi-ready GaSb substrates with diameter in excess of 6-inch were successfully produced. In this work, we report on the MBE (Molecular Beam Epitaxy) growth of generic MWIR bulk nBn photodetectors on 6-inch diameter GaSb substrates. The surface morphology, optical and structural quality of the epiwafers as evaluated by atomic force microscopy (AFM), Nomarski microscopy, low temperature photoluminescence (PL) spectroscopy, and high-resolution x-ray diffraction (XRD) will be discussed. Current density versus voltage (J-V) and photoresponsivity measurements from large-area mesa diode fabricated will also be reported. Material and device properties of these 6-inch epiwafers will be compared to similar structures grown on commercially available 4-inch diameter GaSb substrates.

  6. Assessing reactor physics codes capabilities to simulate fast reactors on the example of the BN-600 benchmark

    Energy Technology Data Exchange (ETDEWEB)

    Ivanov, Vladimir [Scientific and Engineering Centre for Nuclear and Radiation Safety (SES NRS), Moscow (Russian Federation); Bousquet, Jeremy [Gesellschaft fuer Anlagen- und Reaktorsicherheit (GRS) gGmbH, Garching (Germany)

    2016-11-15

    This work aims to assess the capabilities of reactor physics codes (initially validated for thermal reactors) to simulate fast sodium cooled reactors. The BFS-62-3A critical experiment from the BN-600 Hybrid Core Benchmark Analyses was chosen for the investigation. Monte-Carlo codes (KENO from SCALE and SERPENT 2.1.23) and the deterministic diffusion code DYN3D-MG are applied to calculate the neutronic parameters. It was found that the multiplication factor and reactivity effects calculated by KENO and SERPENT using the ENDF/B-VII.0 continuous energy library are in a good agreement with each other and with the measured benchmark values. Few-groups macroscopic cross sections, required for DYN3D-MG, were prepared in applying different methods implemented in SCALE and SERPENT. The DYN3D-MG results of a simplified benchmark show reasonable agreement with results from Monte-Carlo calculations and measured values. The former results are used to justify DYN3D-MG implementation for sodium cooled fast reactors coupled deterministic analysis.

  7. Oxidation of SiC Fiber-Reinforced SiC Matrix Composites with a BN Interphase

    Science.gov (United States)

    Opila, Elizabeth; Boyd, Meredith K.

    2010-01-01

    SiC-fiber reinforced SiC matrix composites with a BN interphase were oxidized in reduced oxygen partial pressures of oxygen to simulate the environment for hypersonic vehicle leading edge applications. The constituent fibers as well as composite coupons were oxidized in oxygen partial pressures ranging from 1000 ppm O2 to 5% O2 balance argon. Exposure temperatures ranged from 816 C to 1353 C (1500 F to 2450 F). The oxidation kinetics of the coated fibers were monitored by thermogravimetric analysis (TGA). An initial rapid transient weight gain was observed followed by parabolic kinetics. Possible mechanisms for the transient oxidation are discussed. One edge of the composite coupon seal coat was ground off to simulate damage to the composite which allowed oxygen ingress to the interior of the composite. Oxidation kinetics of the coupons were characterized by scanning electron microscopy since the weight changes were minimal. It was found that sealing of the coupon edge by silica formation occurred. Differences in the amount and morphology of the sealing silica as a function of time, temperature and oxygen partial pressure are discussed. Implications for use of these materials for hypersonic vehicle leading edge materials are summarized.

  8. Superluminous supernova 2015bn in the nebular phase: evidence for the engine-powered explosion of a stripped massive star

    CERN Document Server

    Nicholl, M; Margutti, R; Chornock, R; Blanchard, P K; Jerkstrand, A; Smartt, S J; Arcavi, I; Challis, P; Chambers, K C; Chen, T -W; Cowperthwaite, P S; Gal-Yam, A; Hosseinzadeh, G; Howell, D A; Inserra, C; Kankare, E; Magnier, E A; Maguire, K; Mazzali, P A; McCully, C; Milisavljevic, D; Smith, K W; Taubenberger, S; Valenti, S; Wainscoat, R J; Yaron, O; Young, D R

    2016-01-01

    We present nebular-phase imaging and spectroscopy for the hydrogen-poor superluminous supernova SN 2015bn, at redshift z=0.1136, spanning +250-400 d after maximum light. The light curve exhibits a steepening in the decline rate from 1.4 mag/(100 d) to 1.7 mag/(100 d), suggestive of a significant decrease in the opacity. This change is accompanied by a transition from a blue continuum superposed with photospheric absorption lines to a nebular spectrum dominated by emission lines of oxygen, calcium and magnesium. There are no obvious signatures of circumstellar interaction or large nickel mass. We show that the spectrum at +400 d is virtually identical to a number of energetic Type Ic supernovae such as SN 1997dq, SN 2012au, and SN 1998bw, indicating similar core conditions and strengthening the link between `hypernovae'/long gamma-ray bursts and superluminous supernovae. A single explosion mechanism may unify these events that span absolute magnitudes of -22 < M_B < -17. Both the light curve and spectrum...

  9. Ab initio studies of coherent spin transport in Fe-hBN/graphene van der Waals multilayers

    Science.gov (United States)

    Magnus Ukpong, Aniekan

    2017-07-01

    This paper presents the results of ab initio studies of the electronic spin inversion and filtering in a ferromagnetic multilayer heterostructure. Spin-polarized electronic structure calculations are performed based on van der Waals density functional theory to give unique insights in to the generation, manipulation and transport of coherent spin conductance. By using an exact theory of the self-consistent ground state of the Fe-hBN/graphene multilayer as a model of the magnetic tunnel junction, hidden asymmetries are unraveled in the spin-resolved charge densities. It is shown that the injection of spin into the graphene/boron nitride tunnel layer from a ferromagnetic contact gives rise to coherent spin current. The projected Fermi surfaces of the up and down spin channels are analyzed to reveal Fermi arc topologies and spin anisotropies. It is also demonstrated that the coherent transport of pure spin-down current in the topological Weyl semimetal phase is robust. The implications of the results on out-of-plane transport of spin polarized conductance in van der Waals multilayer spintronic devices is discussed. The insights derived from this study are expected to open up prospects for further exploration of van der Waals magnetic multilayer heterostructures as a versatile platform for developing materials for Weyltronic applications.

  10. Effect of Repeated Thermal Shock on Mechanical Properties of ZrB2-SiC-BN Ceramic Composites

    Directory of Open Access Journals (Sweden)

    Gang Li

    2014-01-01

    Full Text Available ZrB2-20 vol.% SiC-10 vol.% h-BN (particles ceramic composites (ZSB were fabricated by hot pressing under inert gas protected. ZSB samples with mean size 75 × 55 × 40 mm3 were heated using current heating method and then cooled down to low temperature by circulating water. ZSB samples repeatedly went through thermal shock with 10–50 times under various conditions, respectively. Diverse effects on residual strength of ZSB at different experiment conditions (temperatures, thermal shock times, and heating rates were investigated. The test results indicated that the residual strength of specimen materials all reached the maximum while the temperature was 1600°C and thermal shock number was less than 50 times. Because ZSB samples could not stand the extremely serious hyperoxidation at very high temperature (1800°C, the residual strength of samples decreased sharply. At 1600°C, when the thermal shock times was 20, ZSB samples’ residual strength reached the maximum, but it decreased to the lowest point while the thermal shock times was 30. So we argued that the sensitive thermal shock number was 30. Finally, we analyzed the influences on samples residual strength generated by different heating rates at the same temperature and thermal shock number; the results showed that when heating rate was equal to cooling rate, the residual strength of specimen materials reached the maximum.

  11. Strength degradation mechanisms in h-BN/NiAl coated sapphire fibres with a reactive Hf or Y interlayer

    Energy Technology Data Exchange (ETDEWEB)

    Hajas, D.E. [Materials Chemistry, RWTH-Aachen University, Kopernikusstr. 16, 52074 Aachen (Germany)], E-mail: hajas@mch.rwth-aachen.de; Kyrsta, S. [Materials Chemistry, RWTH-Aachen University, Kopernikusstr. 16, 52074 Aachen (Germany); Richter, S.; Mayer, J. [Central Facility of Electron Microscopy, RWTH-Aachen University, Ahornstrasse 55, 52074 Aachen (Germany); Schneider, J.M. [Materials Chemistry, RWTH-Aachen University, Kopernikusstr. 16, 52074 Aachen (Germany)

    2008-09-15

    NiAl strengthened with ceramic fibres is considered as a load-bearing component in the combustion zone turbine blades. Sapphire fibres coated with hexagonal-boron nitride (h-BN) and Y (or Hf) interlayers and NiAl were investigated to strengthen the fibre matrix interface by compound formation with the transition metals introduced. Our goal is to identify strength degradation relevant mechanisms active during composite formation and application. Therefore, the tensile strength of coated fibres before and after annealing was measured to simulate the effect of composite fabrication. Strength degradation mechanisms were identified by electron microscopy. Chemical reactions between Y or Hf and Al{sub 2}O{sub 3}, as well as surface diffusion of Al{sub 2}O{sub 3} into irregularities in the adjacent coating, alter the surface morphology and may act as crack initiation sites. Based on these results, future strategies for avoiding or minimizing strength degradation during production of intermetallic matrix composites (IMCs) can be compiled.

  12. Effect of platelet-activating factor antagonists (BN-52021, WEB-2170, and BB-882) on bacterial translocation in acute pancreatitis.

    Science.gov (United States)

    de Souza, L J; Sampietre, S N; Assis, R S; Knowles, C H; Leite, K R; Jancar, S; Monteiro Cunha, J E; Machado, M C

    2001-01-01

    Bacterial translocation is an important source of pancreas infection in acute pancreatitis. The effect of platelet-activating factor (PAF) in the pathogenesis of acute pancreatitis has been proved in various studies. The aim of this study was to determine whether potent PAF antagonists influence bacterial translocation in acute pancreatitis. Acute pancreatitis was induced in 62 Wistar rats by injection of 2.5% sodium taurocholate into the biliopancreatic duct. The rats treated with PAF factor antagonists received intravenous injection of WEB-2170 (10 mg/kg), lexipafant (5 mg/kg), and BN-52021 (5 mg/kg) 30 minutes before induction of acute pancreatitis. Six hours after induction of acute pancreatitis, bacteriologic cultures and histologic scoring of tissues were performed. There was a statistically significant reduction in bacterial translocation to the mesenteric lymph nodes and liver but not to the pancreas of the rats treated with PAF antagonists. No significant increase in the intestinal bacterial population of any group was found. There were no statistical differences between the pancreatic histologic scores of the groups. PAF antagonists reduced bacterial translocation to distant sites other than the pancreas, preventing the bacterial dissemination that occurs in the early phase of acute pancreatitis and may have beneficial effects on the evolution of this disease.

  13. Nascent bipolar outflows associated with the first hydrostatic core candidates Barnard 1b-N and 1b-S

    CERN Document Server

    Gerin, M; Fuente, A; Cernicharo, J; Commerçon, B; Marcelino, N

    2015-01-01

    In the theory of star formation, the first hydrostatic core (FHSC) phase is a critical step in which a condensed object emerges from a prestellar core. This step lasts about one thousand years, a very short time compared with the lifetime of prestellar cores, and therefore is hard to detect unambiguously. We present IRAM Plateau de Bure observations of the Barnard 1b dense molecular core, combining detections of H2CO and CH3OH spectral lines and dust continuum at 2.3" resolution (~ 500 AU). The two compact cores B1b-N and B1b-S are detected in the dust continuum at 2mm, with fluxes that agree with their spectral energy distribution. Molecular outflows associated with both cores are detected. They are inclined relative to the direction of the magnetic field, in agreement with predictions of collapse in turbulent and magnetized gas with a ratio of mass to magnetic flux somewhat higher than the critical value, \\mu ~ 2 - 7. The outflow associated with B1b-S presents sharp spatial structures, with ejection velocit...

  14. Corrugated single layer templates for molecules: From $h$-BN Nanomesh to Graphene based Quantum dot arrays

    CERN Document Server

    Ma, Haifeng; Schmidlin, Jeanette; Roth, Silvan; Morscher, Martin; Greber, Thomas

    2010-01-01

    Functional nano-templates enable self-assembly of otherwise impossible arrangements of molecules. A particular class of such templates is that of sp2 hybridized single layers of hexagonal boron nitride or carbon (graphene) on metal supports. If the substrate and the single layer have a lattice mismatch, superstructures are formed. On substrates like rhodium or ruthenium these superstructures have unit cells with ~3 nm lattice constant. They are corrugated and contain sub-units, which behave like traps for molecules or quantum dots, which are small enough to become operational at room temperature. For graphene on Rh(111) we emphasize a new structural element of small extra hills within the corrugation landscape. For the case of molecules like water it is shown that new phases assemble on such templates, and that they can be used as "nano-laboratories" where many individual processes are studied in parallel. Furthermore, it is shown that the h-BN/Rh(111) nanomesh displays a strong scanning tunneling microscopy ...

  15. Microstructure, Mechanical Properties, and Two-Body Abrasive Wear Behavior of Cold-Sprayed 20 vol.% Cubic BN-NiCrAl Nanocomposite Coating

    Science.gov (United States)

    Luo, Xiao-Tao; Yang, Er-Juan; Shang, Fu-Lin; Yang, Guan-Jun; Li, Chen-Xin; Li, Chang-Jiu

    2014-10-01

    20 vol.% cubic boron nitride (cBN) dispersoid reinforced NiCrAl matrix nanocomposite coating was prepared by cold spray using mechanically alloyed nanostructured composite powders. The as-sprayed nanocomposite coating was annealed at a temperature of 750 °C to enhance the inter-particle bonding. Microstructure of spray powders and coatings was characterized. Vickers microhardness of the coatings was measured. Two-body abrasive wear behavior of the coatings was examined on a pin-on-disk test. It was found that, in mechanically alloyed composite powders, nano-sized and submicro-sized cBN particles are uniformly distributed in nanocrystalline NiCrAl matrix. Dense coating was deposited by cold spray at a gas temperature of 650 °C with the same phases and grain size as those of the starting powder. Vickers hardness test yielded a hardness of 1063 HV for the as-sprayed 20 vol.% cBN-NiCrAl coating. After annealed at 750 °C for 5 h, unbonded inter-particle boundaries were partially healed and evident grain growth of nanocrystalline NiCrAl was avoided. Wear resistance of the as-sprayed 20 vol.% cBN-NiCrAl nanocomposite coating was comparable to the HVOF-sprayed WC-12Co coating. Annealing of the nanocomposite coating resulted in the improvement of wear resistance by a factor of ~33% owing to the enhanced inter-particle bonding. Main material removal mechanisms during the abrasive wear are also discussed.

  16. Coincidence Lattices and Interlayer Twist in van der Waals Heterostructures: Application of the Coincidence Lattice Method on \\hbox {hBN/MoSe}_2 Heterobilayer Systems

    Science.gov (United States)

    Koda, Daniel S.; Bechstedt, Friedhelm; Marques, Marcelo; Teles, Lara K.

    2017-07-01

    Van der Waals heterostructures have great potential in large-scale integration devices and exploration of new physics. Experimental investigations allow flexible combinations of two-dimensional crystals in device fabrications. Theory, however, has limitations of supercell sizes and commensurability, translated into computational effort. In this work, we demonstrate the application of the coincidence lattice method to simulate two \\hbox {hBN/MoSe}_2 heterobilayers taking interlayer twist effects into account. We predict that both systems are stable upon contact and interact via van der Waals dispersions. We found that electronic properties of \\hbox {MoSe}_2 are preserved for both simulated systems, but hBN suffers from the increase of interface interactions, as evidenced by band structures and density of states calculations. Finally, band discontinuities are obtained and charge transfer arguments explain small shifts in band offsets with respect to natural alignments. We conclude that hBN is a reasonable substrate for preserving useful properties of \\hbox {MoSe}_2 for application in electronic and optoelectronic devices, and that interlayer twist angles play a significant role in the physics of van der Waals heterostructures.

  17. New primary pressure calibrants for high pressure and temperature scale: SiC-3C and cBN are possible candidates

    Science.gov (United States)

    Zhuravlev, Kirill; Goncharov, Alexander; Prakapenka, Vitali

    2011-03-01

    Since the invention of a diamond-anvil cell, various high-pressure scales for in situ pressure measurements have been realized. Ruby-based pressure scale (Mao et al., 1986) is the best known and high-pressure scientific community has been using it for over two decades. However, it has limited use at elevated temperatures, due to the weakening and broadening of the ruby fluorescence line. The recent developments in the field of high temperature, high pressure physics and geophysics require some alternative pressure scale, capable of measuring pressures at temperatures up to 3000 K. Cubic boron nitride (cBN) was recently proposed as the possible pressure calibrant. It has been suggested that the simultaneous use of x-ray diffraction to measure density and Brillouin spectroscopy to obtain elastic properties of the crystal can be used to construct the pressure scale independent of any other pressure standards. However, the acoustic velocities of cBN are very close to those of diamond and, therefore, are hard to resolve in experiment in diamond-anvil cell. Another possible primary pressure calibrant is cubic silicon carbide (SiC-3C). We performed single crystal x-ray diffraction and Brillouin spectroscopy up to 1 Mbar in pressure at room temperature in the diamond-anvil cell and show that cBN and SiC-3C, indeed, can be used in constructing reliable and accurate high-pressure, high-temperature scale.

  18. Synthesis of tailored 2D SiC{sub f}/SiC ceramic matrix composites with BN/C interphase through ICVI

    Energy Technology Data Exchange (ETDEWEB)

    Udayakumar, A., E-mail: audayk@yahoo.com [Materials Science Division, National Aerospace Laboratories (Council of Scientific and Industrial Research), Bangalore 560 017, Karnataka (India); Raole, P.M., E-mail: raole@ipr.res.in [Institute for Plasma Research, Gandhinagar 382 044 (India); Balasubramanian, M., E-mail: mbala@iitm.ac.in [Department of Metallurgical and Materials Engineering, Indian Institute of Technology Madras, Chennai 600 036 (India)

    2011-10-01

    Synthesis of 2D SiC{sub f} /SiC composites for applications in fusion reactors is a challenging task due to the stringent specification requirements on various mechanical and thermo-mechanical properties, chemical compatibility (with Pb-Li), oxidation resistance and irradiation resistance. Three types of SiC{sub f}/SiC composites with C interface and BN interface, with and without intermediate heat treatment are prepared through isothermal and isobaric chemical vapor infiltration process. Dense SiC seal coat applied to the composites has improved their oxidation resistance. The tensile, flexural and fracture toughness values of composite with BN interface were found to be improved by stabilizing the BN interface through thermal treatment. The electrical and thermal conductivity values obtained for composites with C interface are in the range of 10-29 S/m and 2.5-3.25 W/mK for the temperature range 500-900 deg. C as required for fusion reactor applications.

  19. Formation of BN Coating on PAN Carbon Fiber%碳纤维表面氮化硼涂层的制备

    Institute of Scientific and Technical Information of China (English)

    黄小忠; 王竹; 段曦东; 杜作娟

    2011-01-01

    By means of precursor conversion method, the turbostratic boron niteide(t-BN) coating was formed on the surface of carbon fiber. The surface morphology, structure of the coating were characterized by SEM, XRD, IR, and the tensile strength was tested. Experiments show that the continuous and uniform t-BN thin coating is successfully deposited on carbon fiber by dip-coating in boric acid; The heat treatment temperature is reduced to 400 ℃ by adding a reducing atmosphere of in nitrogen atmosphere; The tensile strength is almost maitained.%用先驱体转化法,在碳纤维表面制备了涡轮层状氮化硼(t-BN)涂层.用SEM,XRD,IR等测试手段对涂层的结构、形貌进行了表征,并且测试了纤维的单丝拉伸强度.实验证明以硼酸为原料,利用先驱体转化法在碳纤维上成功地制备了连续且均匀的t-BN涂层;在氮气气氛中加入还原性气体,使得氮化硼涂层的热处理温度降低到400℃;碳纤维拉伸度基本得到保持.

  20. Processing and Structural Advantages of the Sylramic-iBN SiC Fiber for SiC/SiC Components

    Science.gov (United States)

    Yun, H. M.; Dicarlo, J. A.; Bhatt, R. T.; Hurst, J. B.

    2008-01-01

    The successful high-temperature application of complex-shaped SiC/SiC components will depend on achieving as high a fraction of the as-produced fiber strength as possible during component fabrication and service. Key issues center on a variety of component architecture, processing, and service-related factors that can reduce fiber strength, such as fiber-fiber abrasion during architecture shaping, surface chemical attack during interphase deposition and service, and intrinsic flaw growth during high-temperature matrix formation and composite creep. The objective of this paper is to show that the NASA-developed Sylramic-iBN SiC fiber minimizes many of these issues for state-of-the-art melt-infiltrated (MI) SiC/BN/SiC composites. To accomplish this, data from various mechanical tests are presented that compare how different high performance SiC fiber types retain strength during formation of complex architectures, during processing of BN interphases and MI matrices, and during simulated composite service at high temperatures.

  1. The role of charge trapping in MoS2/SiO2 and MoS2/hBN field-effect transistors

    Science.gov (United States)

    Illarionov, Yury Yu; Rzepa, Gerhard; Waltl, Michael; Knobloch, Theresia; Grill, Alexander; Furchi, Marco M.; Mueller, Thomas; Grasser, Tibor

    2016-09-01

    The commonly observed hysteresis in the transfer characteristics of MoS2 transistors is typically associated with charge traps in the gate insulator. Since in Si technologies such traps can lead to severe reliability issues, we perform a combined study of both the hysteresis as well as the arguably most important reliability issue, the bias-temperature instability. We use single-layer MoS2 FETs with SiO2 and hBN insulators and demonstrate that both phenomena are indeed due to traps in the gate insulator with time constants distributed over wide timescales, where the faster ones lead to hysteresis and the slower ones to bias-temperature instabilities. Our data show that the use of hBN as a gate insulator considerably reduces the number of accessible slow traps and thus improves the reliability. However, the reliability of hBN insulators deteriorates with increasing temperature due to the thermally activated nature of charge trapping.

  2. Herschel observations of B1-bS and B1-bN: two first hydrostatic core candidates in the Perseus star-forming cloud

    CERN Document Server

    Pezzuto, Stefano; Schisano, E; Strafella, F; Di Francesco, J; Sadavoy, S; André, P; Benedettini, M; Bernard, J P; di Giorgio, A M; Facchini, A; Hennemann, M; Hill, T; Könyves, V; Molinari, S; Motte, F; Nguyen-Luong, Q; Peretto, N; Pestalozzi, M; Polychroni, D; Rygl, K L J; Saraceno, P; Schneider, N; Spinoglio, L; Testi, L; Ward-Thompson, D; White, G J

    2012-01-01

    We report far-IR Herschel observations obtained between 70 $\\mu$m and 500 $\\mu$m of two star-forming dusty condensations, B1-bS and B1-bN, in the B1 region of the Perseus star-forming cloud. In the Western part of the Perseus cloud, B1-bS is the only source detected in all of the 6 PACS and SPIRE photometric bands without being visible in the Spitzer map at 24 $\\mu$m. B1-bN is clearly detected between 100 $\\mu$m and 250 $\\mu$m. We have fitted the spectral energy distributions of these sources to derive their physical properties, and find that a simple greybody model fails to reproduce the observed SEDs. At least a two-component model, consisting of a central source surrounded by a dusty envelope is required. The properties derived from the fit, however, suggest that the central source is not a Class 0 object. We then conclude that while B1-bS and B1-bN appear to be more evolved than a pre-stellar core, the best-fit models suggest that their central objects are younger than a Class 0 source. Hence, they may be...

  3. Inhibition of platelet-activating factor- and zymosan-activated serum-induced chemotaxis of human neutrophils by nedocromil sodium, BN 52021 and sodium cromoglycate.

    Science.gov (United States)

    Bruijnzeel, P. L.; Warringa, R. A.; Kok, P. T.

    1989-01-01

    1. Inflammatory cells such as eosinophils and neutrophils are thought to contribute actively to the pathogenesis of asthma since they infiltrate into the lung tissue. These cells are mobilized by lipid-like and protein-like chemotactic factors. As illustrative examples of both groups, platelet-activating-factor (Paf) and zymosan-activated-serum (ZAS) were used in this study. The inhibitory effects of nedocromil sodium, the Paf antagonist BN 52021 and sodium cromoglycate on Paf- and ZAS-induced neutrophil chemotaxis were evaluated. 2. All tested drugs inhibited Paf-induced neutrophil chemotaxis with approximately the same potency (IC50 approximately 1 nM). 3. Nedocromil sodium and sodium cromoglycate were equally potent in inhibiting ZAS-induced neutrophil chemotaxis (IC50 = 0.1-1 microM), whereas BN 52021 was considerably less potent (IC30 = 10 microM). 4. To find out whether the drugs tested could inhibit early events in cell activation, their capacity to inhibit Paf- and ZAS-induced cytosolic free Ca2+-mobilization was investigated. BN 52021, at a concentration of 100 microM, completely inhibited Paf-induced Ca2+-mobilization and inhibited ZAS-induced Ca2+-mobilization by about 50%. Nedocromil sodium and sodium cromoglycate were ineffective. PMID:2551444

  4. Preparation and characterization of reactively sintered Ni{sub 3}Al-hBN-Ag composite coating on Ni-based superalloy

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Shitang [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Graduate School, Chinese Academy of Sciences, Beijing 100039 (China); Zhou Jiansong [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Guo Baogang [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Graduate School, Chinese Academy of Sciences, Beijing 100039 (China); Zhou Huidi [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Pu Yuping [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Central Iron and Steel Research Institute, Beijing 100081 (China); Chen Jianmin [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China)], E-mail: chenjm@lzb.ac.cn

    2009-04-03

    Ni{sub 3}Al-hBN-Ag intermetallic matrix composite coating was prepared on Ni-based superalloy by reactive sintering. The crystalline phase and microstructure of the coating were examined by means of X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). The results showed that the hBN particles pretreated by electroless nickel plating and hot-dip aluminizing and Ag particles with a size of several micrometers were homogeneously dispersed in the Ni{sub 3}Al matrix, and the composite coating had strong interfacial bonding with a fine and dense microstructure. During the reactive sintering, an exothermic reaction between Ni and Al associated with a transient liquid phase occurred, leading to in situ synthesis of the densified Ni{sub 3}Al matrix in the coating with a high tensile strength of more than 70 MPa. The high-temperature tribological properties evaluated on a ball-on-disc test rig showed that the coating possessed self-lubricating properties from room temperature to 800 deg. C due to a synergetic lubricating action of Ag and hBN.

  5. A DFT study on the functionalization of a BN nanosheet with PCsbnd X, (PC = phenyl carbamate, X = OCH3, CH3, NH2, NO2 and CN)

    Science.gov (United States)

    Beheshtian, Javad; Soleymanabadi, Hamed; Peyghan, Ali Ahmadi; Bagheri, Zargham

    2013-03-01

    By using density functional theory calculations, we investigated the chemical functionalization of a BN nanosheet with different organo-azo derivatives including PCsbnd X, (PC = phenyl carbamate, X = OCH3, CH3, NH2, NO2 and CN) in terms of geometric, energetic, and electronic properties. Reaction energies have been calculated to be in the range of 0.19 to 0.35 eV which is augmented by increasing the electron withdrawing characteristic of the functional groups so that the relative magnitude order is sbnd NO2 > sbnd CN > sbnd OCH3 > sbnd CH3 > sbnd NH2. The chemical functionalization leads to a decrease in HOMO/LUMO energy gap of BN sheet especially after adsorption of PCsbnd NO2 by about 1.88 eV. Conduction level and Fermi level of the BN sheet are shifted to lower energies upon the functionalization of the sheet with PCsbnd NO2 and PCsbnd CN, thus, it leads to an increment in work function of the sheet, impeding the field electron emission.

  6. 沙丁胺醇在离子液体[BnMIM]PF6修饰碳糊电极上的电催化氧化及电分析方法%Electrocatalytic Oxidation of Salbutamol at a [BnMIM]PF6 Modified Carbon Paste Electrode and Its Electrochemical Determination

    Institute of Scientific and Technical Information of China (English)

    吴锐; 马少宁; 张艳梅; 高作宁

    2013-01-01

    The electrocatalytic oxidation and electrochemical kinetic of Salbutamol (SAL) were investigated at a 1-Benzyl-3-Methylimidazole hexafluorophosphate([BnMIM]PF6) modified carbon paste electrode([BnMIM]PF6/CPE).The experimental results showed that the [BnMIM]PF6/CPE showed an excellent electrocatalytic activity toward SAL.The reaction rate constant for catalytic oxidation k was obtained as (2.10± 0.05) × 103 (mol· L-1)-1 · s-1 by chronoamperometry(CA).The catalytic oxidation peak current of SAL and its concentration had a good linear relationship in the range of 6.0× 10-7-1.0×10-3 mol· L-1,with a detection limit of 3.7 × 10-8 mol· L 1 (S/N=3) obtained by differential pulse voltammetry (DPV).The proposed method has been successfully applied in the electrochemical quantitative determination of SAL content in the commercial inhaled salbutamol solution.%研究了沙丁胺醇(Salbutamol,SAL)在离子液体1-苄基-3-甲基咪唑六氟磷酸盐([BnMIM]PF6)修饰碳糊电极([BnMIM]PF6/CPE)上的电催化氧化行为和电化学动力学性质.实验结果表明,[BnMIM]PF6/CPE对SAL的电化学氧化具有良好的催化作用.用计时电流法(CA)测定了SAL在[BnMIM] PF6/CPE上的电催化氧化反应速率常数k为(2.10±0.05)×103(mol·L-1)1·s-1.用微分脉冲伏安法(DPV)测得催化氧化峰电流与SAL的浓度在6.0×10-7~1.0×10-3mol· L-1范围内呈良好线性关系,检测限(S/N=3)为3.27×10-8 mol·L-1,同时运用该方法对吸入用沙丁胺醇溶液中的SAL含量进行了电化学定量测定.

  7. SiBN陶瓷纤维的高温抗氧化性研究%High temperature oxidation resistance of SiBN ceramic fiber

    Institute of Scientific and Technical Information of China (English)

    王会峰; 唐彬彬; 牟世伟; 星禧; 柯盛包; 韩克清; 刘勇; 余木火

    2015-01-01

    The chemical structure and the thermal stability of SiBN ceramic fibers were investigated by FTIR and TG. SiBN ceramic fibers were treated under air atmosphere at 1 400℃. The structure and the element contents along the radius of SiBN ceramic fibers after the air⁃oxidation treatment were characterized by means of SEM,XRD and EDS. The results show that SiBN ceramic fibers exhibit good thermal stability at high temperature,which contain Si⁃N bonds and B⁃N bonds in the back⁃bone of the fiber and low carbon content (0.1%). After the air⁃oxidation treatment,the ceramic fibers show a skin⁃core structure. Oxygen mainly exists in the form of SiO2 in the skin of fiber,which can prevent the air from the interior of the fibers, thus providing the high temperature stability. In addition,after air⁃oxidation treatment,the SiBN ceramic fibers maintain their fiber shape and still show compact structure without micropores and amorphous character.%采用FTIR及TG对SiBN陶瓷纤维的结构及高温稳定性进行分析,在空气气氛中1400℃下对其进行高温氧化处理,并利用SEM、XRD、EDS等手段对高温处理后陶瓷纤维的结构及元素分布情况进行表征。结果表明:SiBN陶瓷纤维具有良好的高温稳定性,Si—N键、B—N键构成了SiBN陶瓷纤维的骨架架构,其碳的质量分数仅为0.1%;经高温氧化处理后SiBN纤维出现明显的皮芯结构,其中O元素以SiO2的形式主要富集在皮层,隔绝了纤维内部与空气的接触,从而保证了纤维的高温稳定性。另外,高温氧化处理后仍保持其纤维形状,结构致密,无明显孔洞,且仍为无定型结构。

  8. Analysis and selection of high pressure heaters design for a new generation of NPP with BN-1200 reactor plant

    Science.gov (United States)

    Yurchenko, A. Yu.; Sukhorukov, Yu. G.; Trifonov, N. N.; Grigor'eva, E. B.; Esin, S. B.; Svyatkin, F. A.; Nikolaenkova, E. K.; Prikhod'ko, P. Yu.; Nazarov, V. V.

    2016-09-01

    In the development of advanced high-power steam-turbine plants (STP), special attention is placed on the design of reliable and economical high-pressure heater (HPH) capable to maintain the specified thermal hydraulic performance during the entire service life. Comparative analysis of the known designs of HPH, such as the spiral-collector HPH, the collector-coiled HPH, the collector-platen HPH, modular HPH, and the chamber HPH, was carried out. The advantages and disadvantages of each design were pointed. For better comparison, the heaters are separated into two groups—horizontal and vertical ones. The weight and dimension characteristics, the materials and features of the basic elements, and operating features of variety HPH are presented. At operating the spiral-collector HPH used in the majority of regenerative schemes of high-pressure STP of thermal and nuclear power plants, the disadvantages reducing the economy and reliability of their operation were revealed. The recommendations directed to the reliability growth of HPH, the decrease of subcooling the feed water, the increase of compactness are stated. Some of these were developed by the specialists of OAO NPO TsKTI and are successfully implemented on the thermal power plants and nuclear power plants. Technical solutions to reduce the cost of regeneration system and the weight of chamber HPH, reduce the thickness of the tube plate of HPH, and reliability assurance of the cooler of steam and condensate built in the HPH casing under all operating conditions were proposed. Three types of feed water chambers for vertical and horizontal chamber HPH are considered in detail, the constructive solutions that have been implemented in HPH of the regeneration system of turbines of 1000 and 1200 MW capacity with water-moderated water-cooled power reactor (WMWCPR) are described. The optimal design of HPH for the regeneration system of high-pressure turbine plant with BN-1200 reactor was selected.

  9. Significance of platelet activating factor receptor expression in pancreatic tissues of rats with severe acute pancreatitis and effects of BN52021

    Institute of Scientific and Technical Information of China (English)

    Shi-Hai Xia; Chun-Xiu Hu; Zhi-Ling Zhao; Guo-Dong Xia; Yao Di

    2007-01-01

    AIM: To investigate the dynamic changes and significance of platelet activating factor receptor (PAF-R)mRNA and protein in pancreatic tissues of rats with severe acute pancreatitis (SAP) and effects of BN52021(Ginkgolide B).METHODS: Wistar male rats were randomly assigned to the negative control group (NC group), SAP model group (SAP group), and BN52051-remedy group (BN group), and each of the groups was divided into 6 subgroups at different time points after operation (1 h,2 h, 3 h, 6 h, 12 h, and 24 h) (n = 10 in each). PT-PCR and Western blot methods were used to detect PAFRmRNA and protein expression in pancreatic tissues of rats respectively. Pathological examination of pancreatic tissues was performed and the serum amylase change was detected.RESULTS: Serum amylase and pathological results showed the that SAP model was successfully prepared,BN52021 was able to decrease serum amylase, and the pathological ratings in BN group at 3 h, 6 h, and 12 h significantly decreased compared with those in the SAP group (8.85 ± 0.39 vs 5.95 ± 0.19, 9.15 ± 0.55 vs 5.55 ± 0.36, 10.10 ± 0.65 vs 6.72 ± 0.30, P < 0.05). The result of PAF-mRNA showed dynamic changes in SAP and BN groups, which increased gradually in early stage,reached a peak at 3 h (0.71 ± 0.14 vs 0.54 ± 0.14,0.69 ± 0.13 vs 0.59 ± 0.04, P < 0.05), and decreased gradually later. There were significant differences at each time point except 1 h and 2 h, when compared with those in the NC group (0.71 ± 0.14 or 0.69 ± 0.13 vs 0.47 ± 0.10, 0.38 ± 0.08 or 0.59 ± 0.04 vs 0.47 ± 0.09, 0.25 ± 0.07 or 0.29 ± 0.05 vs 0.46 ± 0.10, 0.20 ± 0.06 or 0.20 ± 0.04 vs 0.43 ± 0.09, P < 0.05), whereas there was no significant difference between BN and SAP groups at each time point. The result of PAF-R protein showed that the change of PAF-R protein in the SAP group and the BN group was consistent with that of PAF-R mRNA.There were significant differences at each time point except 1 h, when compared with

  10. hBN含量对等离子喷涂NiCr/Cr3C2-hBN复合涂层力学性能的影响%Effect of hBN content on mechanical properties of plasma-sprayed NiCr/Cr3 C2-hBN composite coating

    Institute of Scientific and Technical Information of China (English)

    曹玉霞; 杜令忠; 张伟刚; 兰叶; 黄传兵

    2015-01-01

    Taking hBN and Cr3 C2 as core, NiCr/Cr3 C2-hBN composite powder were prepared with the technologies of spray granulation, chemical and metallurgical coating and solid state alloying. The NiCr/Cr3 C2-hBN composite coating was prepared by plasma-spray technology. Microstructure, phase composition, microhardness and tensile strength of the coating were investigated. The results show that the NiCr/Cr3 C2-hBN composite coating consisted of typical lamellae and exhibited excellent binding strength. Both the microhardness and binding strength of the coating decrease with the increase of hBN content. When the hBN content is 20%, microhardness and tensile strength of the coating are 66% and 50% of these of the NiCr/Cr3 C2 coating, respectively. The peeling occurs inside coating and is typical brittle fracture.%采用化工冶金包覆、喷雾造粒和固相合金化技术以Cr3 C2和hBN为核心制备了NiCr/Cr3 C2-hBN复合粉体,并用等离子喷涂技术制备了NiCr/Cr3 C2-hBN涂层,研究了涂层的显微结构、物相组成、显微硬度和结合强度。研究结果表明,等离子喷涂NiCr/Cr3 C2-hBN复合涂层呈典型的层状结构,各层之间结合良好。涂层的显微硬度和结合强度均随hBN含量的增加逐渐降低,当hBN含量为20%时,涂层的显微硬度和结合强度分别为NiCr/Cr3 C2涂层的66%和50%。涂层断裂位置发生在涂层内部,为典型的脆性断裂。

  11. Influence of bacteriocins produced by Lactobacillus plantarum BN in the shelf-life of refrigerated bovine meat Influência de bacteriocinas produzidas por Lactobacillus plantarum BN na vida útil de carne bovina refrigerada

    Directory of Open Access Journals (Sweden)

    Ângela M. Fiorentini

    2001-03-01

    Full Text Available Sugar cane molasses is a cheap by-product of the sugar cane industry. This product was used for growth and production of bacteriocins by Lactobacillus plantarum BN and evaluated for its potential application in the extension of the shelf-life of raw meat. Bovine meat cubes were dipped in the filtered and neutralized supernatant of the fermented broth (Treatment A and stored at 5ºC. Counts of psychrotrophic and mesophilic aerobic microorganisms, pH determination and total acidity were performed on meat cubes after 0, 3, 6, 9, 12 and 15 days. These determinations were also done in cubes dipped in a 6% lactic acid solution (treatment B and distilled water (treatment C. After 3 days, the counts of psychrotrophic microorganisms in cubes submitted to treatment A, B and C increased 0.38, 1.42 and 2.04 log cycles, respectively. The same happened with mesophilic microorganisms (0.31, 0.33 and 1.04 log cycles increases, respectively. On the sixth day, the psychrotrophic population in samples submitted to treatments A and B were 2.07 and 0.64 log cycles, respectively, lower than in the control samples (treatment C. Mesophilic microorganisms in these samples were 1.58 and 1.12 log cycles, respectively, lower than the controls. On the sixth day, only samples submitted to treatment A presented lower counts than those recommended by ICMSF as quality standards for raw meat (Melaço de cana de açúcar é um sub-produto barato da indústria açucareira. Esse produto foi empregado para o crescimento e produção de bacteriocina de Lactobacillus plantarum BN e avaliado quando a sua aplicação potencial no aumento da vida útil de carne crua. Cubos de carne bovina foram imersos por 5 minutos no sobrenadante filtrado e neutralizado dessa cultura (Tratamento A e mantidos a 5ºC. Contagens de microrganismos psicrotróficos e mesófilos, determinação de pH e de acidez total foram realizadas nas amostras após 0, 3, 6, 9, 12 e 15 dias. Essas determinações foram

  12. Chiral Borated Esters in Asymmetric Synthesis:1.The First Asymmetric Reaction Catalyzed by Chiral Spiroborated Esters with an O3BN Framework

    Institute of Scientific and Technical Information of China (English)

    LIU, De-Jun(刘德军); SHAN, Zi-Xing(单自兴); QIN, Jin-Gui(秦金贵)

    2004-01-01

    The first asymmetric reaction catalyzed by chiral spiroborated esters with an O3BN framework was reported. In the presence of 0.1 equivalent of (R,S)-1 or (S,S)-1, acetophenone was reduced by 0.6 equivalent of borane in THF at 0-5 ℃ for 2 h to give (R)-1-phenylethanol of up to 76% ee and 73% isolated yield. Influence of reaction conditions on the stereoselectivity of the reduction was investigated and a possible catalytic mechanism of the chiral spiroborated esters toward the reduction was also suggested.

  13. Solution structure and stability against digestion of rproBnIb, a recombinant 2S albumin from rapeseed: relationship to its allergenic properties.

    Science.gov (United States)

    Pantoja-Uceda, David; Palomares, Oscar; Bruix, Marta; Villalba, Mayte; Rodríguez, Rosalía; Rico, Manuel; Santoro, Jorge

    2004-12-28

    NMR spectroscopy has been used to determine the solution structure of the precursor form of the recombinant napin BnIb, rproBnIb, a 2S albumin, 109-residue protein from the seeds of Brassica napus. More than 90% of the side-chain proton resonances were unambiguously assigned from the analysis of two-dimensional correlation (COSY), total correlation (TOCSY), and nuclear Overhauser effect (NOESY) spectra. The final structures were computed by using restrained molecular dynamics on the basis of 1316 upper-limit distance constraints derived from NOE cross-correlation intensities. The computed structures exhibited a root-mean-square deviation (RMSD) radius of 0.66 A for the backbone and 1.16 A for the side-chain heavy atoms of the structural core. The resulting structure consists of five amphipathic helices arranged in a right-handed super helix, a folding motif found in other proteins of the prolamin superfamily. As in the case of the mature protein, the recombinant precursor behaves as a plant food allergen. To trace out the origin and characteristics of its allergenic properties, rproBnIb was assayed against simulated gastric fluid and found to be very resistant to proteolysis. Also, heat treatment of the protein followed up to 85 degrees C by circular dichroism showed a very limited unfolding, which was recovered after cooling to 20 degrees C, indicating a high thermal stability. These results suggest that rproBnIb, as other 2S albumins, may be able to reach the gut immune system intact. A comparison of the putative epitopes against IgE antibodies of the three members of the prolamine family [2S albumins, nonspecific lipid transfer proteins (nsLTPs), and alpha-amylase/trypsin inhibitors] indicates that there are not common surfaces of interaction with IgE. Though the epitopes appear to be located in different regions of the proteins, they do comply with the requirements of being solvent-exposed and flexible.

  14. 一种基于KPCA-BN的软测量建模方法%A soft sensing method base on KPCA and BN

    Institute of Scientific and Technical Information of China (English)

    唐苦; 王振雷

    2012-01-01

    A kind of soft sensing modeling method which is combination of kernel principal component analysis (KPCA) with bayesian network (BN) is proposed. The KPCA is used to make the feature extraction, eliminate the correlation of the input sample data and decrease the dimensions of input variable in the network model. Then the BN is applied to build a model. After determining the parameters of the gaussian mixture model by EM algorithm based on the pruning algorithm, the gaussian mixture model is used to approximate the probability density of the variables in the bayesian network and train the bayesian network, which can not only reduce the complexity of model but also improve the generalization ability. Finally the proposed method is used to build soft sensing model of the concentration of ethane in the ethylene distillation, and the results show that KPCA-BN approach has a better prediction and generalization ability, and it is an effective data modeling approach.%本文提出了一种将核主元分析(KPCA)和贝叶斯网络(BN)相结合的软测量建模方法.核主元分析可对样本数据进行特征提取,消除数据之间的相关性,降低网络模型的输入变量维数.然后利用贝叶斯网络进行建模,采用基于剪枝算法的EM算法求解高斯混合模型的参数,再利用高斯混合模型逼近贝叶斯网络中变量的联合概率密度,训练贝叶斯网络,该方法不仅降低了模型的复杂性,而且提高了模型的泛化能力.最后采用该方法建立乙烯精馏塔中乙烷浓度的软测量模型,结果表明基于KPCA-BN方法建立的软测量模型有更好的预测效果和泛化能力,是一种有效的数据建模方法.

  15. Ethylene response factor BnERF2-like (ERF2.4) from Brassica napus L. enhances submergence tolerance and alleviates oxidative damage caused by submergence in Arabidopsis thaliana

    Institute of Scientific and Technical Information of China (English)

    Yanyan Lv; Sanxiong Fu; Song Chen; Wei Zhang; Cunkou Qi

    2016-01-01

    Ethylene response factor proteins play an important role in regulating a variety of stress responses in plants, but their exact functions in submergence stress are not well understood. In this study, we isolated BnERF2.4 from Brassica napus L. to study its function in submergence tolerance. The expression of the BnERF2.4 gene in B. napus and the expression of antioxidant enzyme genes in transgenic Arabidopsis were analyzed by quantitative RT-PCR. The expression of BnERF2.4 was induced by submergence in B. napus and the overexpression of BnERF2.4 in Arabidopsis increased the level of tolerance to submergence and oxidative stress. A histochemical method detected lower levels of H2O2, O2•− and malondialdehyde (MDA) in transgenic Arabidopsis. Compared to the wild type, transgenic lines also had higher soluble sugar content and higher activity of antioxidant enzymes, which helped to protect plants against the oxidative damage caused by submergence. It was concluded that BnERF2.4 increased the tolerance of plants to submergence stress and may be involved in regulating soluble sugar content and the antioxidant system in defense against submergence stress.

  16. Interface structure, chemistry and properties of NiAl composites fabricated from matrix-coated single-crystalline Al{sub 2}O{sub 3} fibres (sapphire) with and without an hBN interlayer

    Energy Technology Data Exchange (ETDEWEB)

    Hu, W. [Institute of Physical Metallurgy and Metal Physics, RWTH Aachen University (Germany)]. E-mail: hu@imm.rwth-aachen.de; Weirich, T. [Central Facility for Electron Microscopy, RWTH Aachen University (Germany); Hallstedt, B. [Materials Chemistry, RWTH Aachen University (Germany); Chen, H. [Institute of Physical Metallurgy and Metal Physics, RWTH Aachen University (Germany)]. E-mail: chen@imm.rwth-aachen.de; Zhong, Y. [Institute of Physical Metallurgy and Metal Physics, RWTH Aachen University (Germany); Gottstein, G. [Institute of Physical Metallurgy and Metal Physics, RWTH Aachen University (Germany)

    2006-05-15

    NiAl composites with and without an hBN interlayer were produced from matrix-coated single-crystalline Al{sub 2}O{sub 3} fibres (sapphire) by diffusion bonding. The evolution of interface structure and chemistry during the fabrication processes (fibre coating, diffusion bonding and embedded casting) was characterized by electron microscopy. The interface shear stress for complete debonding was measured by fibre push-out tests at room temperature. Interface structural analysis by transmission electron microscopy demonstrates that a high interface shear strength (about 230-250 MPa) in the composites without hBN interlayers is achieved by direct contact of NiAl with aluminium oxide (intrinsic coherence). In the composites with hBN interlayers the boron nitride was partially (as-diffusion-bonded composite) or completely (as-cast composite) transformed to AlN owing to a chemical reaction with NiAl at high temperatures. The low interface shear strength (about 70 MPa) of the as-diffusion-bonded composites was caused by sliding of textured hBN basal planes. The low interface shear strength (about 75 MPa) of the as-cast composites was attributed to segregation of aluminium boride to triple junctions and grain boundaries of AlN. The interfacial reactions in the composites with hBN interlayers can be rationalized from thermodynamic calculations.

  17. BN interphase in composite materials with nicalon Si-C-O fibers and with vitro ceramic matrix of MAS type; L`interphase BN dans les materiaux composites a fibres Si-C-O nicalon et a matrice vitroceramique de type MAS

    Energy Technology Data Exchange (ETDEWEB)

    Ricca, N.

    1994-03-14

    BN has been suggested as an interphase in silica-based glass-ceramic matrix composites with a view to use these materials in oxidizing atmospheres at medium or high temperatures. The matrix had a boron-doped MAS (MgO-Al{sub 2}O{sub 3}-SiO{sub 2}) composition and was prepared from an hydrosol precursor. Pseudo-ID composites were prepared according to a sol impregnations/calcination/hot-pressing route. Chemical and microstructural characterizations of the fiber/matrix interfacial area were conducted by mean of TEM/EELS and AES analyses. The efficiency of BN as a coupling interphase for this particular composite system was successfully demonstrated through tensile tests performed on either as-processed or aged specimens (100 hours at 1000 deg C in air or under argon). In addition, composites maintained in air at 600 deg C, 800 deg C and 900 deg C while simultaneously loaded did not fail after 150 hours or more. Thus, a BN interphase appeared to be compatible with an oxidizing environment (i.e. the oxide matrix and/or air from 600 to 1000 deg C) and should therefore successfully replace the usual carbon interphase at least for use at medium temperatures. (author)

  18. The dielectric and dynamical properties of zinc-blende BN,AlN and GaN from first-principle calculation

    Institute of Scientific and Technical Information of China (English)

    2008-01-01

    The ab initio calculations of the electronic structural,dielectric and lattice-dy namical properties of zinc-blende BN,AlN and GaN were presented. The ground-state properties,i.e.,the lattice constant,the bulk modulus and band gap,were calculated using a plane-wave-pseudopotential method within the density-function theory. A linear-response approach to the density-function perturb theory was used to derive the Born effective charge,the high-frequency dielectric constants and interatomic force constants for these materials. The interatomic force contants(IFCs) are useful for interpolating the dynamical matrices through the whole Brillouin zone. Phonon frequencies along high-symmetry lines were also obtained by interpolating the dynamical matrices using the interatomic force constants. In this paper,we discussed the difference of dielectric and dynamical properties among zinc-blende BN,AlN and GaN,and meanwhile,also compared these properties with other experimental data available and theoretical values. Generally,the calculations were in good agreement with the other existing experimental data and theoretical values.

  19. Raman Study of Uncoated and P-bn/sic-coated Hi-nicalon Reinforced Celsian Matrix Composites. Part 2; Residual Stress in the Fibers

    Science.gov (United States)

    Gouadec, Gwenael; Colomban, Philippe; Bansal, Narottam P.

    2000-01-01

    Band shifts on Raman spectra were used to assess, at a microscopic scale, the residual strain existing in Hi-Nicalon fibers reinforcing celsian matrix composites. Uncoated as well as p-BN/SiC- and p-B(Si)N/SiC-coated Hi-Nicalon fibers were used as the reinforcements. We unambiguously conclude that the fibers are in a state of compressive residual stress. Quantitative determination of the residual stress was made possible by taking into account the heating induced by laser probing and by using a reference line, of fixed wavenumber. We found fiber compressive residual stress values between 110 and 960 MPa depending on the fiber/matrix coating in the composite. A stress relaxation-like phenomenon was observed at the surface of p-BN/SiC-coated Hi-Nicalon fibers whereas the uncoated or p-B(Si)N/SiC-coated Hi-Nicalon fibers did not show any stress relaxation in the Celsian matrix composites.

  20. The Origin and Evolution of the Halo PN BoBn 1: From a Viewpoint of Chemical Abundances Based on Multiwavelength Spectra

    CERN Document Server

    Otsuka, M; Hyung, S; Izumiura, H; STScI,; Telescope/NAOJ, Subaru; University, Chungbuk National; Observatory/NAOJ, Okayama Astrophysical

    2010-01-01

    We have performed a comprehensive chemical abundance analysis of the extremely metal-poor ([Ar/H]<-2) halo planetary nebula (PN) BoBn 1 based on IUE archive data, Subaru/HDS spectra, VLT/UVES archive data, and Spitzer/IRS spectra. We have detected over 600 lines in total and calculated ionic and elemental abundances of 13 elements using detected optical recombination lines (ORLs) and collisionally excited lines (CELs). The estimations of C, N, O, and Ne abundances from the ORLs and Kr, Xe, and Ba from the CELs are done the first for this nebula, empirically and theoretically. The C, N, O, and Ne abundances from ORLs are systematically larger than those from CELs. The abundance discrepancies apart from O could be explained by a temperature fluctuation model, and that of O might be by a hydrogen deficient cold component model. We have detected 5 fluorine and several s-process elements. The amounts of [F/H], [Kr/H], and [Xe/H] suggest that BoBn 1 is the most F-rich among F detected PNe and is a heavy s-proces...

  1. Self-hardening effect of CrAlN/BN nanocomposite films deposited by direct current and radio frequency reactive cosputtering

    Energy Technology Data Exchange (ETDEWEB)

    Nose, Masateru, E-mail: nose@tad.u-toyama.ac.jp [Faculty of Art and Design, University of Toyama, 180 Futakami, Takaoka-shi, Toyama 933-8588 (Japan); Chiou, Wen-An [NISP Lab., NanoCenter, University of Maryland, College Park, MD 20742-2831 (United States); Kawabata, Tokimasa [School of Science and Engineering, University of Toyama, Toyama-shi, Toyama 930-8555 (Japan); Hatano, Yuji [Hydrogen Isotope Research Center, University of Toyama, Toyama-shi, Toyama 930-8555 (Japan); Matsuda, Kenji [School of Science and Engineering, University of Toyama, Toyama-shi, Toyama 930-8555 (Japan)

    2012-11-15

    A CrAlN/18 vol.% BN nanocomposite film was deposited on substrate by reactive co-sputtering. The films showed an increase of about 30% in indentation hardness and achieved a maximum hardness of approximately 50 GPa after annealing at 800 Degree-Sign C in air. In contrast, the indentation hardness barely changed when the film sample was annealed at 800 Degree-Sign C in nitrogen and argon atmosphere. High-resolution transmission electron microscopy (HRTEM) images revealed that the uppermost layer was characterized by amorphous materials with embedded nanocrystalline particles (occurring at less than {approx} 50 nm below surface). Energy dispersive X-ray spectroscopy (EDS) line profiles of cross-sectional thin films showed a high concentration of oxygen in the uppermost layer of the annealed sample. The indentation hardness of the air-annealed sample was measured by Ar{sup +} ion sputtering before and after etching to the depth at 200 nm from the annealed surface. The hardness decreased from approximately 48 GPa to 43 GPa, which was the same level as the as-deposited films. These results indicate that oxidization of the film surface could be one of the factors responsible for the self-hardening of the CrAlN/BN film.

  2. New blind adaptive BN-Kalman filtering MUD detector.%一种新的盲自适应拟Newton迭代Kalman滤波MUD检测器

    Institute of Scientific and Technical Information of China (English)

    高维廷; 李辉; 翟海天

    2012-01-01

    针对ISI、MAI并存情况下码分多址系统盲自适应Kalman滤波算法检测稳定性不足的问题进行了研究,结合Newton迭代法提出了一种适于多径信道下DS-CDMA系统的盲自适应拟Newton迭代Kalman滤波MUD算法.该算法能够在进行状态滤波的同时对未知噪声的统计特性进行在线估计,确保算法能够有效收敛于期望用户提高了检测算法在动态条件下的用户跟踪能力.仿真结果表明,BN-Kalman算法具有更好的收敛性和动态性能.%The blind multiuser detection algorithm of CDMA(Code Division Multiple Access) system is studied under the condition with ISI, MAI and FNP. A new BN-Kalman algorithm to multipath CDMA system is proposed. The algorithm can estimate the unknown noise statistics characteristics on-line while conducting state filtering, and an efficient iterative implementation that provides very fast convergence under this representation is presented. Simulation results show that the new algorithm has the better tracking capability under the dynamic environment and convergence ability than Kalman algorithm.

  3. First-principles study of the effect of B/N doping in TiO2 thin films for visible light photo-catalysis

    Science.gov (United States)

    Ovali, Rasim Volga; Uddin, Md. Nizam; Bengu, Erman; Gulseren, Oguz

    2014-05-01

    Anatase phase of titanium dioxide (TiO2) , a non-toxic and biocompatible wide-band gap semiconductor, when irradiated with a suitable wavelength light is known to facilitate chemical processes on its surface including degradation reactions. In addition, TiO2 is one of the most important and widely investigated photo-catalyst materials. In this work several atomic models for B/N doping have been used to investigate the effect of doping on electronic structure and density of states of TiO2 through ab-initio density functional theory calculations. The results showed that doping with B and/or N induced a) band gap narrowing (red shift of the absorbance spectra to the visible light region) and b) formation of midgap states especially in case of N interstitial model. These results also supported the observed synergistic effects of B/N doping for higher photo-degradation activity. These computational findings supported the experimental data by indicating the possible routes that can be responsible for the improvement of the photo-catalytic activity in TiO2 due to B and N doping in our experiments. TUBITAK Grant No: TBAG 112T771, TUBITAK Grant No: TBAG 110T394.

  4. Superluminous Supernova SN 2015bn in the Nebular Phase: Evidence for the Engine-powered Explosion of a Stripped Massive Star

    Science.gov (United States)

    Nicholl, M.; Berger, E.; Margutti, R.; Chornock, R.; Blanchard, P. K.; Jerkstrand, A.; Smartt, S. J.; Arcavi, I.; Challis, P.; Chambers, K. C.; Chen, T.-W.; Cowperthwaite, P. S.; Gal-Yam, A.; Hosseinzadeh, G.; Howell, D. A.; Inserra, C.; Kankare, E.; Magnier, E. A.; Maguire, K.; Mazzali, P. A.; McCully, C.; Milisavljevic, D.; Smith, K. W.; Taubenberger, S.; Valenti, S.; Wainscoat, R. J.; Yaron, O.; Young, D. R.

    2016-09-01

    We present nebular-phase imaging and spectroscopy for the hydrogen-poor superluminous supernova (SLSN) SN 2015bn, at redshift z = 0.1136, spanning +250-400 days after maximum light. The light curve exhibits a steepening in the decline rate from 1.4 mag (100 days)-1 to 1.7 mag (100 days)-1, suggestive of a significant decrease in the opacity. This change is accompanied by a transition from a blue continuum superposed with photospheric absorption lines to a nebular spectrum dominated by emission lines of oxygen, calcium, and magnesium. There are no obvious signatures of circumstellar interaction or large 56Ni mass. We show that the spectrum at +400 days is virtually identical to a number of energetic SNe Ic such as SN 1997dq, SN 2012au, and SN 1998bw, indicating similar core conditions and strengthening the link between “hypernovae”/long gamma-ray bursts and SLSNe. A single explosion mechanism may unify these events that span absolute magnitudes of -22 < M B < -17. Both the light curve and spectrum of SN 2015bn are consistent with an engine-driven explosion ejecting 7-30 M ⊙ of oxygen-dominated ejecta (for reasonable choices in temperature and opacity). A strong and relatively narrow O i λ7774 line, seen in a number of these energetic events but not in normal supernovae, may point to an inner shell that is the signature of a central engine.

  5. Theoretical study of adsorption of amino acids on graphene and BN sheet in gas and aqueous phase with empirical DFT dispersion correction.

    Science.gov (United States)

    Singla, Preeti; Riyaz, Mohd; Singhal, Sonal; Goel, Neetu

    2016-02-21

    Understanding interactions of biomolecules with nanomaterials at the molecular level is crucial to design new materials for practical use. In the present study, adsorption of three distinct types of amino acids, namely, valine, arginine and aspartic acid, over the surface of structurally analogous but chemically different graphene and BN nanosheets has been explored within the formalism of DFT. The explicit dispersion correction incorporated in the computational methodology improves the accuracy of the results by accounting for long range van der Waals interactions and is essential for agreement with experimental values. The real biological environment has been mimicked by re-optimizing all the model structures in an aqueous medium. The study provides ample evidence in terms of adsorption energy, solvation energy, separation distance and charge analysis to conclude that both the nano-surfaces adsorb the amino acids with release of energy and there are no bonded interactions between the two. The polarity of the BN nanosheet provides it an edge over the graphene surface to have more affinity towards amino acids.

  6. Optical absorbance and band-gap engineering of (BN) 1 -x(C2)x two-dimensional alloys: Phase separation and composition fluctuation effects

    Science.gov (United States)

    Guilhon, I.; Marques, M.; Teles, L. K.; Bechstedt, F.

    2017-01-01

    The (BN) 1 -x(C2)x alloys are promising materials for band-gap engineering in two-dimensional electronics. In this work, we provide a complete scenario of statistical possibilities for the distribution of atoms and its influence on electronic and optical properties. Using first-principles calculations combined with the generalized quasichemical approximation to account for disorder effects, we study the properties of these two-dimensional alloys as a function of their average composition. Our results show that atomic arrangements with C-C and B-N bonds are energetically favored over the ones with B-B and N-N bonds, explaining the known tendency to phase separation, verified by a T -x phase diagram. We calculate the energy gap as a function of the composition considering both composition fluctuation and phase separation effects. Experimental data are discussed in this context. Finally, we obtain absorption spectra reproducing a two-peak pattern for intermediate carbon concentrations found experimentally and identified with phase-segregated instead of homogeneous alloys.

  7. Herschel/HIFI Spectral Mapping of C$^+$, CH$^+$, and CH in Orion BN/KL: The Prevailing Role of Ultraviolet Irradiation in CH$^+$ Formation

    CERN Document Server

    Morris, Patrick W; Nagy, Zsofia; Pearson, John C; Ossenkopf-Okada, Volker; Falgarone, Edith; Lis, Dariusz C; Gerin, Maryvonne; Melnick, Gary; Neufeld, David A; Bergin, Edwin A

    2016-01-01

    The CH$^+$ ion is a key species in the initial steps of interstellar carbon chemistry. Its formation in diverse environments where it is observed is not well understood, however, because the main production pathway is so endothermic (4280 K) that it is unlikely to proceed at the typical temperatures of molecular clouds. We investigate the formation of this highly reactive molecule with the first velocity-resolved spectral mapping of the CH$^+$ $J=1-0, 2-1$ rotational transitions, three sets of CH $\\Lambda$-doubled triplet lines, $^{12}$C$^+$ and $^{13}$C$^+$ $^2P_{3/2} - ^2P_{1/2}$, and CH$_3$OH 835 GHz E-symmetry Q branch transitions, obtained with Herschel/HIFI over a $\\approx$12 arcmin$^2$ region centered on the Orion BN/KL source. We present the spatial morphologies and kinematics, cloud boundary conditions, excitation temperatures, column densities, and $^{12}$C$^+$ optical depths. Emission from all of C$^+$, CH$^+$, and CH is indicated to arise in the diluted gas, outside of the explosive, dense BN/KL o...

  8. 苎麻α-amylase基因的克隆与表达%Molecular Cloning and Characterization of Bn-α-amylase Gene from Ramie(Boehmeria nivea)

    Institute of Scientific and Technical Information of China (English)

    余伟林; 钟英丽; 揭雨成; 周清明; 周精华; 朱守晶

    2014-01-01

    α-amylase基因不仅参与植物糖代谢与生物能量的调动,而且与植物抗逆功能相关.为了克隆Bn-α-amylase基因,分析其序列及表达特征,本研究以湘苎3号苎麻(Boehmeria nivea)转录组文库中Unigene4746序列为基础,采用RT-PCR技术克隆该基因的全长编码序列,并进行生物信息学分析;利用Real-time PCR分析该基因在不同组织和不同胁迫条件下的表达特征.研究结果表明,苎麻Bn-α-amylase的编码区序列长2 295 bp,编码765个氨基酸(GenBank登录号:KF860891),推导该蛋白质的等电点和分子量分别为5.685和86.11kD,该蛋白在羧基端含有两个保守的结构域,亚细胞定位预测显示该蛋白位于细胞质中,不存在信号肽和跨膜结构域.与苹果(Malus×domestic)、拟南芥(Arabidopsis thaliana)、猕猴桃(Actinidia chinensis)、蓖麻(Ricinus communis)、大豆(Glycine max)的α-amylase基因的核苷酸序列相似性分别为80%、76%、76%、73%和67%,与之编码的氨基酸序列相似性分别为68%、65%、65%、69%和51%.进化树分析表明Bn-α-amylase与大豆、葡萄、猕猴桃、蓖麻的α-amylase基因亲缘关系较近,与拟南芥、水稻、高粱的α-amylase基因亲缘关系次之,与卷柏的α-amylase基因亲缘关系较远.实时荧光定量PCR分析表明,Bn-α-amylase在苎麻根、茎皮、茎木质部、茎尖、叶片中均有表达,其中,在叶中表达量最高,在根中表达量最低,且受干旱、高盐胁迫表达增强,受ABA胁迫表达降低.本研究获得了Bn-α-amylase基因的编码区序列,其编码的蛋白具有植物α-amylase典型的结构域,且该基因响应ABA、干旱和高盐逆境胁迫,提示该基因可能与苎麻抗逆境机制密切相关.

  9. 双层h-BN/Graphene结构稳定性及其掺杂特性的第一性原理研究∗%First-principles study on the structure stability and doping p erformance of double layer h-BN/Graphene

    Institute of Scientific and Technical Information of China (English)

    陈庆玲; 戴振宏; 刘兆庆; 安玉凤; 刘悦林

    2016-01-01

    Using the firs-principles method based on density functional theory, we study the stability and doping performance of double h-BN/Graphene structure, here the exchange correlation potential is expressed through the local density approximation and the interactions between ions and electrons are described by the projective-augmented wave method. Because double layer h-BN/Graphene represents a kind of epitaxial semiconductor system, which can be applied to tunnel pressure sensor, the research is very meaningful. In order to improve the application of this special double layer structures, we often carry out the dopings of some atoms. Unlike previous research work, in which the dopings of the metals Au, Co, Mn and other atoms were took into account, we now mainly consider the dopings of the active metal atoms, such as the dopings of Li, Na, and K atoms. The band structure, electronic density of states, as well as the charge density and stability are studied on the double h-BN/Graphene structure after alkali metal doping. At the same time, bonding and electronic properties of double h-BN/Graphene are discussed under the different biaxial strain conditions. The results show that for the dopings of Li and K atoms, the structure deformation is very large, and the band structure of double h-BN/Graphene can show a small band gap at the K point in the first Brillouin zone, taking on a linear dispersion relation the same as that of the perfect graphene. We can tune the band gap by applying external strain and dopings of atoms, and find a new level appearing near the Fermi level after doping, which is mainly due to the contribution of N atoms. In addition, there exists charge transfer between Na atom and N and C atoms, and the material is converted into metal. We find obvious charge overlapping in the vicinity of Na atoms, these charge overlaps appearing around the Na and C atoms indicate the existence of covalent bond and this covalent bond also appears around the Na atoms and

  10. Fabrication of high performance 2.5D SiO{sub 2f}/Si{sub 3}N{sub 4}-BN composites for high-temperature application

    Energy Technology Data Exchange (ETDEWEB)

    Jiang, Y.G.; Zhang, C.R.; Cao, F.; Wang, S.Q.; Hu, H.F.; Qi, G.J. [State Key Laboratory of Advanced Ceramic Fibers and Composites, College of Aerospace and Materials Engineering, National University of Defense Technology, Changsha (China)

    2007-01-15

    A radar window for a re-entry vehicle should process critical mechanical properties. Fused silica, BN and Si{sub 3}N{sub 4} ceramics are the three popular materials for such applications, but are limited in some fields for their intrinsic disadvantages. In the present study, 2.5 dimensional silica fiber reinforced Si{sub 3}N{sub 4}-BN matrix composites were prepared by a PIP method through repeated infiltration of hybrid precursor and pyrolysis at high temperature in ammonia atmosphere. (Abstract Copyright [2007], Wiley Periodicals, Inc.)

  11. Ultrahigh energy density Li-ion batteries based on cathodes of 1D metals with –Li–N–B–N– repeating units in α-Li{sub x}BN{sub 2} (1 ⩽ x ⩽ 3)

    Energy Technology Data Exchange (ETDEWEB)

    Németh, Károly, E-mail: nemeth@agni.phys.iit.edu [Physics Department, Illinois Institute of Technology, Chicago, Illinois 60616 (United States)

    2014-08-07

    Ultrahigh energy density batteries based on α-Li{sub x}BN{sub 2} (1 ⩽ x ⩽ 3) positive electrode materials are predicted using density functional theory calculations. The utilization of the reversible LiBN{sub 2} + 2 Li{sup +} + 2 e{sup −} ⇌ Li{sub 3}BN{sub 2} electrochemical cell reaction leads to a voltage of 3.62 V (vs Li/Li{sup +}), theoretical energy densities of 3251 Wh/kg and 5927 Wh/l, with capacities of 899 mAh/g and 1638 mAh/cm{sup 3}, while the cell volume of α-Li{sub 3}BN{sub 2} shrinks only 2.8% per two-electron transfer on charge. These values are far superior to the best existing or theoretically designed intercalation or conversion-based positive electrode materials. For comparison, the theoretical energy density of a Li–O{sub 2}/peroxide battery is 3450 Wh/kg (including the weight of O{sub 2}), that of a Li–S battery is 2600 Wh/kg, that of Li{sub 3}Cr(BO{sub 3})(PO{sub 4}) (one of the best designer intercalation materials) is 1700 Wh/kg, while already commercialized LiCoO{sub 2} allows for 568 Wh/kg. α-Li{sub 3}BN{sub 2} is also known as a good Li-ion conductor with experimentally observed 3 mS/cm ionic conductivity and 78 kJ/mol (≈0.8 eV) activation energy of conduction. The attractive features of α-Li{sub x}BN{sub 2} (1 ⩽ x ⩽ 3) are based on a crystal lattice of 1D conjugated polymers with –Li–N–B–N– repeating units. When some of the Li is deintercalated from α-Li{sub 3}BN{sub 2} the crystal becomes a metallic electron conductor, based on the underlying 1D conjugated π electron system. Thus, α-Li{sub x}BN{sub 2} (1 ⩽ x ⩽ 3) represents a new type of 1D conjugated polymers with significant potential for energy storage and other applications.

  12. In silico carbon molecular beam epitaxial growth of graphene on the h-BN substrate: carbon source effect on van der Waals epitaxy

    Science.gov (United States)

    Lee, Jonghoon; Varshney, Vikas; Park, Jeongho; Farmer, Barry L.; Roy, Ajit K.

    2016-05-01

    Against the presumption that hexagonal boron-nitride (h-BN) should provide an ideal substrate for van der Waals (vdW) epitaxy to grow high quality graphene films, carbon molecular beam epitaxy (CMBE) techniques using solid carbon sublimation have reported relatively poor quality of the graphene. In this article, the CMBE growth of graphene on the h-BN substrate is numerically studied in order to identify the effect of the carbon source on the quality of the graphene film. The carbon molecular beam generated by the sublimation of solid carbon source materials such as graphite and glassy carbon is mostly composed of atomic carbon, carbon dimers and carbon trimers. Therefore, the graphene film growth becomes a complex process involving various deposition characteristics of a multitude of carbon entities. Based on the study of surface adsorption and film growth characteristics of these three major carbon entities comprising graphite vapour, we report that carbon trimers convey strong traits of vdW epitaxy prone to high quality graphene growth, while atomic carbon deposition is a surface-reaction limited process accompanied by strong chemisorption. The vdW epitaxial behaviour of carbon trimers is found to be substantial enough to nucleate and develop into graphene like planar films within a nanosecond of high flux growth simulation, while reactive atomic carbons tend to impair the structural integrity of the crystalline h-BN substrate upon deposition to form an amorphous interface between the substrate and the growing carbon film. The content of reactive atomic carbons in the molecular beam is suspected to be the primary cause of low quality graphene reported in the literature. A possible optimization of the molecular beam composition towards the synthesis of better quality graphene films is suggested.Against the presumption that hexagonal boron-nitride (h-BN) should provide an ideal substrate for van der Waals (vdW) epitaxy to grow high quality graphene films, carbon

  13. BnPME is progressively induced after microspore reprogramming to embryogenesis, correlating with pectin de-esterification and cell differentiation in Brassica napus.

    Science.gov (United States)

    Solís, María-Teresa; Berenguer, Eduardo; Risueño, María C; Testillano, Pilar S

    2016-08-11

    Pectins are one of the main components of plant cell walls. They are secreted to the wall as highly methylesterified forms that can be de-esterified by pectin methylesterases (PMEs). The degree of methylesterification of pectins changes during development, PMEs are involved in the cell wall remodeling that occurs during diverse plant developmental processes. Nevertheless, the functional meaning of pectin-related wall remodeling in different cell types and processes remains unclear. In vivo, the microspore follows the gametophytic pathway and differentiates to form the pollen grain. In vitro, the microspore can be reprogrammed by stress treatments becoming a totipotent cell that starts to proliferate and follows the embryogenic pathway, a process known as microspore embryogenesis. To investigate if the change of developmental programme of the microspore towards embryogenesis involves changes in pectin esterification levels, which would cause the cell wall remodeling during the process, in the present study, dynamics of PME expression and degrees of pectin esterification have been analysed during microspore embryogenesis and compared with the gametophytic development, in Brassica napus. A multidisciplinary approach has been adopted including BnPME gene expression analysis by quantitative RT-PCR, fluorescence in situ hybridization, immuno-dot-blot and immunofluorescence with JIM5 and JIM7 antibodies to reveal low and highly-methylesterified pectins. The results showed that cell differentiation at advanced developmental stages involved induction of BnPME expression and pectin de-esterification, processes that were also detected in zygotic embryos, providing additional evidence that microspore embryogenesis mimics zygotic embryogenesis. By contrast, early microspore embryogenesis, totipotency and proliferation were associated with low expression of BnPME and high levels of esterified pectins. The results show that the change of developmental programme of the microspore

  14. Irradiation creep and stress-enhanced swelling of Fe-16Cr-15Ni-Nb austenitic stainless steel in BN-350

    Energy Technology Data Exchange (ETDEWEB)

    Vorobjev, A.N.; Porollo, S.I.; Konobeev, Yu.V. [Institute of Physics and Power Engineering, Obninsk (Russian Federation)] [and others

    1997-04-01

    Irradiation creep and void swelling will be important damage processes for stainless steels when subjected to fusion neutron irradiation at elevated temperatures. The absence of an irradiation device with fusion-relevant neutron spectra requires that data on these processes be collected in surrogate devices such as fast reactors. This paper presents the response of an annealed austenitic steel when exposed to 60 dpa at 480{degrees}C and to 20 dpa at 520{degrees}C. This material was irradiated as thin-walled argon-pressurized tubes in the BN-350 reactor located in Kazakhstan. These tubes were irradiated at hoop stresses ranging from 0 to 200 MPa. After irradiation both destructive and non-destructive examination was conducted.

  15. AGIL/BN - Aide à la Gestion Intégrée du Littoral en Basse-Normandie - Bilan des travaux 2012

    OpenAIRE

    Le Gendre, Romain; Riou, Philippe

    2013-01-01

    Dans le cadre d’une convention multi partenariale, le Laboratoire Environnement Ressources s’est vu confier la maîtrise d’ouvrage du projet « AGIL BN ». Son objectif est de développer des outils et compétences permettant d’élaborer des aides à la prise de décision en matière d’aménagement et de gestion de l’environnement littoral en Basse-Normandie. Il comprend 2 grands volets : - développement d’un Système d’Information Géographique « environnement littoral », avec mise en ligne d’u...

  16. First-Principles Simulations of Chemical Reactions in an HCl Molecule Embedded inside a C or BN Nanotube Induced by Ultrafast Laser Pulses

    Science.gov (United States)

    Miyamoto, Yoshiyuki; Zhang, Hong; Rubio, Angel

    2010-12-01

    We show by first-principles simulations that ultrafast laser pulses induce different chemical reactions in a molecule trapped inside a nanotube. A strong laser pulse polarized perpendicular to the tube axis induces a giant bond stretch of an encapsulated HCl molecule in semiconducting carbon nanotube or in a BN nanotube. Depending on the initial orientation of the HCl molecule, the subsequent laser-induced dynamics is different: either complete disintegration or rebonding of the HCl molecule. Radial motion of the nanotube is always observed and a vacancy appears on the tube wall when the HCl is perpendicular to the tube axis. Those results are important to analyze confined nanochemistry and to manipulate molecules and nanostructures encapsulated in organic and inorganic nanotubes.

  17. Computational investigation of the electronic and structural properties of CN radical on the pristine and Al-doped (6, 0) BN nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Soltani, Alireza, E-mail: alireza.soltani46@yahoo.com [Young Researchers and Elite Club, Gorgan Branch, Islamic Azad University, Gorgan (Iran, Islamic Republic of); Moradi, Ali Varasteh [Department of Chemistry, Gorgan Branch, Islamic Azad University, Gorgan (Iran, Islamic Republic of); Bahari, Mahsa [Young Researchers and Elite Club, Gorgan Branch, Islamic Azad University, Gorgan (Iran, Islamic Republic of); Masoodi, Anis [Department of Chemistry, Gorgan Branch, Islamic Azad University, Gorgan (Iran, Islamic Republic of); Shojaee, Shamim [Young Researchers and Elite Club, Gorgan Branch, Islamic Azad University, Gorgan (Iran, Islamic Republic of)

    2013-12-01

    We have performed first-principle calculations to investigate the adsorption behavior of the CN radical (CåN) on the external surface of H-capped Al-doped (6, 0) zigzag single-walled BN nanotubes (BNNT). We calculated the bond length, gap energies, dipole moments, and electronic properties of the {sup ·}CN on the exterior surface of SWBNNT. Binding energy corresponding to the most stable configuration of CN radical on Al{sub N}-doped BNNT is found to be −471.73 kJ mol{sup −1}. The calculated density of states (DOS) reveals that there is a significant orbital hybridization between {sup ·}CN and Al-doping species in the adsorption process being evidence of an exothermic process. The results indicate that BNNT could be a suitable sensor.

  18. Preparation of p-n Junction Diode by B-Doped Diamond Film Grown on Si-Doped c-BN

    Institute of Scientific and Technical Information of China (English)

    王成新; 高春晓; 张铁臣; 刘洪武; 李迅; 韩永吴; 骆继峰; 申彩霞

    2002-01-01

    A heterojunction diode has been fabricated by boron-doped p-type diamond thin film grown epitaxially ona silicon-doped n-type cubic boron nitride bulk crystal using the conventional hot tilament chemical vapourdeposition method. The ohmic electrode of Ti (50nm)/Mo (l00nm)/Au (300nm) for the p-type diamond filmand the bulk crystal of the c-BN were deposited by the rf planar magnetron method. Then the device wasannealed at 410°C in air for i h in order to form ohmic metal alloy. The current-voltage characteristics of theheterojunction diode were measured and the result indicated that the rectification ratio reached 10a, and theturn-on voltage and the highest current were 7 V and 0.35 mA, respectively.

  19. New nano-sized Al2O3-BN coating 3Y-TZP ceramic composites for CAD/CAM-produced all-ceramic dental restorations. Part I. Fabrication of powders.

    Science.gov (United States)

    Yang, Se Fei; Yang, Li Qiang; Jin, Zhi Hao; Guo, Tian Wen; Wang, Lei; Liu, Hong Chen

    2009-06-01

    Partially sintered 3 mol % yttria-stabilized tetragonal zirconium dioxide (ZrO(2), zirconia) polycrystal (3Y-TZP) ceramics are used in dental posterior restorations with computer-aided design-computer-aided manufacturing (CAD/CAM) techniques. High strength is acquired after sintering, but shape distortion of preshaped compacts during their sintering is inevitable. The aim of this study is to fabricate new machinable ceramic composites with strong mechanical properties that are fit for all-ceramic dental restorations. Aluminum oxide (Al(2)O(3))-coated 3Y-TZP powders were first prepared by the heterogeneous precipitation method starting with 3Y-TZP, Al(NO(3))(3) . 9H(2)O, and ammonia, then amorphous boron nitride (BN) was produced and the as-received composite powders were coated via in situ reaction with boric acid and urea. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) were used to analyze the status of Al(2)O(3)-BN on the surface of the 3Y-TZP particles. TEM micrographs show an abundance of Al(2)O(3) particles and amorphous BN appearing uniformly on the surface of the 3Y-TZP particles after the coating process. The size of the Al(2)O(3) particles is about 20 nm. The XRD pattern shows clearly the peak of amorphous BN among the peaks of ZrO(2).

  20. Theoretical Investigation of the Interfaces and Mechanisms of Induced Spin Polarization of 1D Narrow Zigzag Graphene- and h-BN Nanoribbons on a SrO-Terminated LSMO(001) Surface.

    Science.gov (United States)

    Avramov, Paul; Kuzubov, Alexander A; Kuklin, Artem V; Lee, Hyosun; Kovaleva, Evgenia A; Sakai, Seiji; Entani, Shiro; Naramoto, Hiroshi; Sorokin, Pavel B

    2017-01-26

    The structure of the interfaces and the mechanisms of induced spin polarization of 1D infinite and finite narrow graphene- and h-BN zigzag nanoribbons placed on a SrO-terminated La1-xSrxMnO3 (LSMO) (001) surface were studied using density functional theory (DFT) electronic structure calculations. It was found that the π-conjugated nanofragments are bonded to the LSMO(001) surface by weak disperse interactions. The types of coordination of the fragments, the strength of bonding, and the rate of spin polarization depend upon the nature of the fragments. Infinite and finite graphene narrow zigzag nanoribbons are characterized by the lift of the spin degeneracy and strong spin polarization caused by interface-induced structural asymmetry and oxygen-mediated indirect exchange interactions with Mn ions of LSMO support. Spin polarization changes the semiconducting nature of infinite graphene nanoribbons to half-metallic state with visible spin-up density of states at the Fermi level. The h-BN nanoribbon binding energy is weaker than graphene nanoribbon ones with noticeably shorter interlayer distance. The asymmetry effect and indirect exchange interactions cause spin polarization of h-BN nanoribbon as well with formation of embedded states inside the band gap. The results show a possibility to use one-atom thick nanofragments to design LSMO-based heterostructures for spintronic nanodevices with h-BN as an inert spacer to develop different potential barriers.

  1. An international validation study of the EORTC brain cancer module (EORTC QLQ-BN20) for assessing health-related quality of life and symptoms in brain cancer patients

    NARCIS (Netherlands)

    Taphoorn, M.J.B.; Claassens, L.; Aaronson, N.K.; Coens, C.; Mauer, M.; Osoba, D.; Stupp, R.; Mirimanoff, R.O.; van den Bent, M.J.; Bottomley, A.

    2010-01-01

    Aims The psychometric properties of the EORTC QLQ-BN20, a brain cancer-specific HRQOL questionnaire, have been previously determined in an English-speaking sample of patients. This study examined the validity and reliability of the questionnaire in a multi-national, multi-lingual study. Methods

  2. Biokinetics and dosimetry of a hybrid formulation of {sup 9{sup m}}Tc-BN and {sup 99m}Tc-RGD{sub 2} starting from optic images in a murine model; Biocinetica y dosimetria de una formulacion hibrida de {sup 99m}Tc-BN y {sup 99m}Tc-RGD{sub 2} a partir de imagenes opticas en un modelo murino

    Energy Technology Data Exchange (ETDEWEB)

    Cornejo A, L. G.

    2015-07-01

    This work has the purpose of evaluate the biokinetics and absorbed dose of radiation of hybrid formulation {sup 99m}Tc-BN /{sup 99m}Tc-RGD{sub 2} in a murine model by optical imaging techniques using the multimodal preclinical in vivo image system Xtreme. The used method were the {sup 99m}Tc-BN, {sup 99m}Tc-RGD{sub 2} and {sup 99m}Tc-BN/{sup 99m}Tc-RGD{sub 2} formulas, with specific recognition for GRPr and the integrin s α(v)β(3) and α(v)β(5) respectively, was injected in the vein tail of three nude mousses with induce breast cancer tumors (cell line T-47-D), by the preclinical multimodal imaging system Xtreme (Bruker), optical images in different times was acquired (5, 10, 20 min, 2 and 24 h), using Images Processing Toolbox of MATLAB these images was transform from RGB format to gray scales and sectioned in five independent images corresponding to heart, kidneys, bladder and tumor areas. The intensity of each images was computed in counts per pixel, then those intensities was corrected for background, attenuation and scattering, using different factors for each phenomena previously calculated. Finally the activity values quantified vs time was fitted into a biokinetic model to obtain the disintegrations number and cumulate activities in each organ. With these data the radiation absorbed dose were calculated using MIRD methodology. Results: The number of disintegration and absorbed dose calculated in MBq h/MBq and mGy/MBq, of injected mouse with the {sup 99m}Tc-BN/{sup 99m}Tc-RGD{sub 2} formulation, was: 0.035 ± 0.65 E-02, 0.25 x 10{sub -5} ± 0.46 E-07; 0.393 ± 0.51 E-1, 2.85 E-05 ± 3.7 E-06; 0.306 ± 0.21 E-01, 2.11 E-05 ± 1.45 E-06 and 0.151 ± 0.19 E-01, 1.09 E-05 ± 1.42 E-06 , in heart, kidneys, bladder and tumor, respectively. The number of disintegration obtained in kidneys is comparable to those reported for Trinidad B. 2014 Conclusions: Our results demonstrated that using optical images and a code for image analyses development in MATLAB, could

  3. Iron stabilizes thylakoid protein-pigment complexes in Indian mustard during Cd-phytoremediation as revealed by BN-SDS-PAGE and ESI-MS/MS.

    Science.gov (United States)

    Qureshi, M Irfan; D'Amici, Gian Maria; Fagioni, Marco; Rinalducci, Sara; Zolla, Lello

    2010-07-01

    Two-dimensional BN-SDS-PAGE, ESI-MS/MS and electron microscopy (EM) were used to study the role of iron (Fe) under cadmium (Cd) stress in retention of thylakoidal multiprotein complexes (MPCs) and chloroplast ultrastructure of Indian mustard, a moderate hyperaccumulator plant. Mustard was grown hydroponically with or without iron for 17 days and then exposed to CdCl2 for 3 days. Fe deficiency led to an increase in oxidative stress and damage to chloroplast/thylakoids accompanied by a decrease in chlorophyll content; exposure of plants to Cd further enhanced the oxidative stress and Cd accumulation (more in -Fe plants). However, the presence of iron aided plants in the suppression of oxidative stress and retention of chloroplasts and chlorophylls under Cd stress. Proteomic analyses by 2D BN-SDS-PAGE and mass spectrometry showed that Fe deficiency considerably decreased the amount of LHCII trimer, ATPase-F1 portion, cyt b6/f and RuBisCO. No or less reduction, was observed for PSI(RCI+LHCI), the PSII-core monomer, and the PSII subcomplex, while an increase in the LHCII monomer was noted. Under iron deficiency, Cd proved to be very deleterious to MPCs, except for the PSII subcomplex, the LHCII monomer and free proteins which were increased. Iron proved to be very protective in retaining almost all the complexes. MPCs showed greater susceptibility to Cd than Fe deficiency, mainly at the level of RuBisCO and cyt b6/f; an increase in the amount of the PSII subcomplex, LHCII monomer and free proteins indicates differences in the mechanisms affected by Fe deficiency and Cd stress when compared to Fe-fed plants. This study furthers our understanding of the sites actually damaged in MPCs under Fe deficiency and Cd stress. A role emerges for iron in the protection of MPCs and, hence, of the chloroplast. The present study also indicates the importance of iron for efficient phytoextraction/phytoremediation.

  4. Chemical segregation in the young protostars Barnard 1b-N and S. Evidence of pseudo-disk rotation in Barnard 1b-S

    Science.gov (United States)

    Fuente, A.; Gerin, M.; Pety, J.; Commerçon, B.; Agúndez, M.; Cernicharo, J.; Marcelino, N.; Roueff, E.; Lis, D. C.; Wootten, H. A.

    2017-10-01

    The extremely young Class 0 object B1b-S and the first hydrostatic core (FSHC) candidate, B1b-N, provide a unique opportunity to study the chemical changes produced in the elusive transition from the prestellar core to the protostellar phase. We present 40″ × 70″ images of Barnard 1b in the 13CO 1 → 0, C18O 1 → 0, NH2D 11,1a→ 10,1s, and SO 32→ 21 lines obtained with the NOEMA interferometer. The observed chemical segregation allows us to unveil the physical structure of this young protostellar system down to scales of 500 au. The two protostellar objects are embedded in an elongated condensation, with a velocity gradient of 0.2-0.4 m s-1 au-1 in the east-west direction, reminiscent of an axial collapse. The NH2D data reveal cold and dense pseudo-disks (R 500 - 1000 au) around each protostar. Moreover, we observe evidence of pseudo-disk rotation around B1b-S. We do not see any signature of the bipolar outflows associated with B1b-N and B1b-S, which were previously detected in H2CO and CH3OH, in any of the imaged species. The non-detection of SO constrains the SO/CH3OH abundance ratio in the high-velocity gas. Based on observations carried out with the IRAM Northern Extended Millimeter Array (NOEMA). IRAM is supported by INSU/ CNRS (France), MPG (Germany), and IGN (Spain).The reduced datacube is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/606/L3

  5. ¹¹¹In-Bn-DTPA-nimotuzumab with/without modification with nuclear translocation sequence (NLS) peptides: an Auger electron-emitting radioimmunotherapeutic agent for EGFR-positive and trastuzumab (Herceptin)-resistant breast cancer.

    Science.gov (United States)

    Fasih, Aisha; Fonge, Humphrey; Cai, Zhongli; Leyton, Jeffrey V; Tikhomirov, Ilia; Done, Susan J; Reilly, Raymond M

    2012-08-01

    Increased expression of epidermal growth factor receptors (EGFR) in breast cancer (BC) is often associated with trastuzumab (Herceptin)-resistant forms of the disease and represents an attractive target for novel therapies. Nimotuzumab is a humanized IgG(1) monoclonal antibody that is in clinical trials for treatment of EGFR-overexpressing malignancies. We show here that nimotuzumab derivatized with benzylisothiocyanate diethylenetriaminepentaacetic acid for labelling with the subcellular range Auger electron-emitter, (111)In and modified with nuclear translocation sequence (NLS) peptides ((111)In-NLS-Bn-DTPA-nimotuzumab) was bound, internalized and transported to the nucleus of EGFR-positive BC cells. Emission of Auger electrons in close proximity to the nucleus caused multiple DNA double-strand breaks which diminished the clonogenic survival (CS) of MDA-MB-468 cells that have high EGFR density (2.4 × 10(6) receptors/cell) to less than 3 %. (111)In-Bn-DTPA-nimotuzumab without NLS peptide modification was sevenfold less effective for killing MDA-MB-468 cells. (111)In-Bn-DTPA-nimotuzumab with/without NLS peptide modification were equivalently cytotoxic to MDA-MB-231 and TrR1 BC cells that have moderate EGFR density (5.4 × 10(5) or 4.2 × 10(5) receptors/cell, respectively) reducing their CS by twofold. MDA-MB-231 cells have intrinsic trastuzumab resistance due to low HER2 density, whereas TrR1 cells have acquired resistance despite HER2 overexpression. Biodistribution and microSPECT/CT imaging revealed that (111)In-NLS-Bn-DTPA-nimotuzumab exhibited more rapid elimination from the blood and lower tumour uptake than (111)In-Bn-DTPA-nimotuzumab. Tumour uptake of the radioimmunoconjugates in mice with MDA-MB-468 xenografts was high (8-16 % injected dose/g) and was blocked by administration of an excess of unlabelled nimotuzumab, demonstrating EGFR specificity. We conclude that (111)In-Bn-DTPA-nimotuzumab with/without NLS peptide modification are promising Auger

  6. İbn Haldun’un Siyaset Teorisi Ve Siyasal Sistem Sınıflandırması Political Theory And Politic System Classification Of Ibn Khaldun

    Directory of Open Access Journals (Sweden)

    Ali ÇİFTÇİ

    2013-09-01

    ı’da yapılan birçok çalışmaların yanı sıra İslam Dünyasında da bu alanda değerli çalışmalar yapılmıştır. İslam Dünyasında siyaset teorisi ve siyasal sistem sınıflandırmaları üzerine çalışma yapan önemli düşünürlerden biri de İbn Haldun’dur. Kendisi siyasal hayatın içinde yer almış birisi olarak deneyim ve gözlemlerinin ışığında dönemi için ileri sayılabilecek siyasal sistem incelemelerinde bulunmuştur. Batı’nın Ortaçağında dini düşüncenin ön plana çıkması ile siyasal sistem sınıflandırmaları en aza inerken İslam Dünyasında salt dini düşünceye bağlı kalmadan İbn Haldun tarafından olanı inceleyerek yapılan siyasal sistemlerin araştırılması makaleyi önemli kılmaktadır. Bu bağlamda makalede öncelikle İbn Haldun’un sosyal bilimler içerisindeki yeri ele alınmaktadır. Daha sonra onun siyaset teorisi için vazgeçilmez olan devlet, asabiyet ve riyaset-mülk gibi temel kavramlar üzerinde durulmaktadır. Son olarak da makalenin temel konusu olan İbn Haldun’un siyasal sistem sınıflandırması ana hatları ile irdelenmektedir. İbn Haldun siyasal sistemleri sınıflandırırken bunları öncelikle mülke dayalı ve dine dayalı siyaset olarak ikiye ayırmaktadır. Mülke dayalı siyaseti de kendi içinde tabii mülk ve siyasi mülk şeklinde iki başlık altında incelemektedir. İbn Haldun’un dine dayalı siyaset olarak adlandırdığı ve idealize ettiği yönetim şekli ise hilafet ya da imamettir.

  7. Wafer-scale controlled exfoliation of metal organic vapor phase epitaxy grown InGaN/GaN multi quantum well structures using low-tack two-dimensional layered h-BN

    Energy Technology Data Exchange (ETDEWEB)

    Ayari, Taha; Li, Xin; Voss, Paul L.; Ougazzaden, Abdallah, E-mail: aougazza@georgiatech-metz.fr [School of Electrical and Computer Engineering, Georgia Institute of Technology, Atlanta, Georgia 30332 (United States); Georgia Tech Lorraine, UMI 2958, Georgia Tech-CNRS, 57070 Metz (France); Sundaram, Suresh; El Gmili, Youssef [Georgia Tech Lorraine, UMI 2958, Georgia Tech-CNRS, 57070 Metz (France); Salvestrini, Jean Paul [Georgia Tech Lorraine, UMI 2958, Georgia Tech-CNRS, 57070 Metz (France); Université de Lorraine, LMOPS, EA 4423, 57070 Metz (France)

    2016-04-25

    Recent advances in epitaxial growth have led to the growth of III-nitride devices on 2D layered h-BN. This advance has the potential for wafer-scale transfer to arbitrary substrates, which could improve the thermal management and would allow III-N devices to be used more flexibly in a broader range of applications. We report wafer scale exfoliation of a metal organic vapor phase epitaxy grown InGaN/GaN Multi Quantum Well (MQW) structure from a 5 nm thick h-BN layer that was grown on a 2-inch sapphire substrate. The weak van der Waals bonds between h-BN atomic layers break easily, allowing the MQW structure to be mechanically lifted off from the sapphire substrate using a commercial adhesive tape. This results in the surface roughness of only 1.14 nm on the separated surface. Structural characterizations performed before and after the lift-off confirm the conservation of structural properties after lift-off. Cathodoluminescence at 454 nm was present before lift-off and 458 nm was present after. Electroluminescence near 450 nm from the lifted-off structure has also been observed. These results show that the high crystalline quality ultrathin h-BN serves as an effective sacrificial layer—it maintains performance, while also reducing the GaN buffer thickness and temperature ramps as compared to a conventional two-step growth method. These results support the use of h-BN as a low-tack sacrificial underlying layer for GaN-based device structures and demonstrate the feasibility of large area lift-off and transfer to any template, which is important for industrial scale production.

  8. Effects of B-N Chain Doping on Electronic Structure of Zigzag Graphene Nanoribbons%B-N链对锯齿型石墨烯纳米带电子结构的影响

    Institute of Scientific and Technical Information of China (English)

    王辉; 徐慧

    2012-01-01

    采用基于密度泛函理论的第一性原理计算方法,研究了边缘对称和反对称的锯齿型石墨烯纳米带的电子结构,考察了BN链掺在不同位置时的影响.研究结果表明:B-N原子链有向边缘迁移的现象,并且其掺杂在石墨烯纳米带中央时对体系电子结构的改变很小,而掺杂在边缘时会使体系在费米能级附近的能带结构发生显著的变化.边缘被B-N链取代的石墨烯纳米带的能隙被打开,并产生了明显的自旋非简并现象.这些现象的出现归因于掺杂体系中边缘电子态的重新分布.%Using first-principles based on density functional theory, the electronic structures of B-N chain doped zigzag graphene nanoribbons (ZGNRs) were studied. The symmetry of ZGNRs and the position of B-N chain were considered. The results show that the B-N chain is apt to be doped at the edge of ZGNRs. There are remarkable effects on the electronic structure for the systems with the doped B-N chain at the edge of ZGNRs. Moreover, the opened band gap and spin nondegenerate phenomenon can be observed on the ZGNRs with B-N chain doped at the edge rather than other positions. This may be attributed to the redistribution of edge electronic states on doped ZGNRs.

  9. Effects of BN & Al2 O3/Epoxy Composites Adhesive Layer on Junction Temperature of LED%BN & Al2 O3/环氧树脂复合材料粘接层对LED灯结温的影响

    Institute of Scientific and Technical Information of China (English)

    吕亚南; 李巧梅; 牟其伍; 文翰颖; 朱玲; 寿梦杰

    2015-01-01

    自制BN/EP(环氧树脂)复合材料和Al2 O3/EP复合材料作为LED灯PCB板和散热铝块之间的粘接层材料,采用精密钻孔的方法用高精度测温仪测量LED灯正常工作时的温度分布,讨论粘接层对结温的影响,并与COMSOL Multiphysics软件模拟结果进行对比分析。实验测量LED结温与模拟结温变化趋势基本一致,结温会随着粘接层厚度的增加而上升、随着粘接层复合材料热导率的增加先快速降低而后趋于平缓。最终得到PCB板和散热铝块间最佳粘接层厚度和粘接层复合材料配比,当BN的质量分数为60%时,BN/EP复合材料粘接层的热导率最高,此时LED结温为75.2℃,比纯环氧树脂粘接层LED的结温降低了27.6℃。而Al2 O3/EP复合材料粘接层LED的最低结温为78.2℃,此时Al2 O3的质量分数为50%。%Homemade BN/EP composites and Al2 O3/EP composites were used as the adhesive layer between PCB and the heat sink of LED, respectively. The temperature distribution of LED working in the normal condition was measured by high-precision thermometers through a small hole. The effect of the adhesive layer composites on the junction temperature of LED was discussed, and was compared with the results from COMSOL simulations. A similar variation trend of junction tempera-ture of LED was observed in both our experiment and COMSOL simulation. The junction temperature of LED raised with the increment of thickness of the adhesive layer. Besides, along with the incre-ment of thermal conductivity of the adhesive layer composites, the junction temperature declined sharply at first, and then gradually decreased to a flat level. At last, we obtained two optimum val-ues of the thickness and the ratio of adhesive layer composites with the best performance. When the mass fraction of BN is 60%, the thermal conductivity of BN/EP composites reaches at the highest level. In this condition, the junction temperature of LED is the lowest (75. 2 ℃) and is

  10. 甘蓝型油菜BnFAD8基因编码序列的克隆和表达谱分析%Cloning and expression characteristics of fatty acid desaturase 8 gene from rape (Brassica napus L.)

    Institute of Scientific and Technical Information of China (English)

    刘绵学; 王茂华; 向俊蓓; 杨毅; 李旭锋

    2011-01-01

    通过比对拟南芥等同源基因,克隆了甘蓝型油菜FAD8基因中的保守序列.以得到的FAD8(Fatty Acid Desaturase 8)保守序列片段为信息探针,在GenBank的EST数据库中检索高度同源的EST,并通过人工拼接及RT-PCR得到油菜该基因的全长为1299 bp的cDNA序列,命名为BnFAD8.序列分析结果中发现该基因符合质体定位的ω3脂肪酸脱饱和酶序列特征.通过比较22℃和8℃处理的甘蓝型油菜的BnFAD8基因表达谱,发现该基因在常温下仅存在痕量表达;而在低温条件下在叶中表达出现较大幅度的升高.推测BnFAD8基因和油菜的低温调控存在联系.%Brassica napus fatty acid desaturase 8 (FAD8) belongs to cold-induced omega 3 fatty acid desaturase.By aligning Arabidopsis FAD8 and other homologous FAD8 genes, one highly conserved sequence of FAD8 from rape was cloned in study.Using the FAD8 conserved sequence as a querying probe, highly homologous EST were obtained from database of GenBank and a putative complete ORF of 1299 bp (named: BnFAD8) was assembled according to the rape clone.Furthermore, the full length cDNA of Brassica napus FAD8 was cloned by RT-PCR with two primers designed based on this assembled cDNA sequence.Features of plasmid-located o3 fatty acid desaturase were found in sequence analysis of cDNA cloned.As shown in expression profile result, BnFAD8 was highly expressed in leaves at 8 ℃, but only trace-level expression in leaves at 22 ℃, which suggested that BnFAD8 involved in the process of rape cold acclimation.

  11. Changes of expression of IL-17 in OVA-induced food allergy model in BN rats%OVA致敏BN大鼠IL-17表达水平的变化

    Institute of Scientific and Technical Information of China (English)

    张丽莉; 杨芷菁; 马雅; 刘志刚; 陈思

    2012-01-01

    Objective To investigate the expression of IL-17 in OVA-induced food allergy in BN rats and to analyze the effect of IL-17 in egg allergies. Methods OVA-induced food allergy models were established. The PBS-treated rats were served as controls. The expression levels of IL-17A mRNA were detected by real-time quantitative PCR. The corresponding protein levels of IL-17 were measured by ELISA. Results The expression level of IL-17A mRNA in OVA-treated BN rats was significantly higher than that in PBS-treated BN rats(P<0. 01). Consistently,the expression of IL-17 protein levels in OVA-treated BN rats was significantly higher than that in PBS-treated BN rats (P<0. 05). Conclusion The expression of IL-17 was significantly increased in OVA-induced food allergy model,which implies that IL-17 may play an important role in the mechanism of food allergy.%目的 研究卵清蛋白(OVA)致敏的Brown Norway(BN)大鼠外周血中白细胞介素(IL)-17表达水平的变化,探讨IL-17在鸡蛋所致食物过敏(FA)中的作用.方法 建立OVA致敏的大鼠模型(OVA组),并以仅给予PBS灌胃的大鼠(PBS组)作为对照,采用实时荧光定量PCR(RT-PCR)检测各组IL-17A mRNA表达水平,采用ELISA法检测各组血浆中IL-17蛋白水平.结果 OVA组IL-17A mRNA表达水平显著高于PBS组,差异有统计学意义(P<0.01),且OVA组IL-17水平也明显高于PBS组,差异有统计学意义(P<0.05).结论 OVA诱发FA动物模型中可检测到外周血IL-17表达水平上升,提示IL-17可能在FA的发病过程中起重要作用.

  12. 钛沉积工艺制备TiN/cBN和TiC/金钢石涂层颗粒%Fabrication of TiN/cBN and TiC/diamond coated particles by titanium deposition process

    Institute of Scientific and Technical Information of China (English)

    Walid M. DAOUSH; Hee S. PARK; Soon H. HONG

    2014-01-01

    Cubic boron nitride particles coated by titanium nitride (TiN/cBN) as well as diamond particles coated by titanium carbide (TiC/diamond) were prepared by Ti molten salt deposition followed by heat-treatment process. cBN or diamond particles were mixed separately with Ti powders and molten salts (KCl, NaCl and K2TiF6). The mixture was heated at 900 °C under argon atmosphere. The produced particles were heat-treated under hydrogen at 1000 °C. The morphologies and chemical compositions of the produced particles were investigated by scanning electron microscopy (SEM), X-ray diffraction (XRD) and focused ion beam (FIB). The results show that the cBN and the diamond particles are coated by nano-sized Ti layers. By heat-treatment of the Ti/cBN and TiC/diamond coated particles under hydrogen atmosphere, the deposited Ti layers were interacted by the in-situ transformation reaction with the surfaces of cBN and diamond particles and converted to titanium compounds (TiN and TiC), respectively.%用钛熔盐沉积及热处理工艺分别制备碳化钛涂覆的立方碳化硼颗粒(TiN/cBN)及碳化钛涂覆的金刚石颗粒(TiC/金刚石)。将cBN或金刚石颗粒分别与钛粉和KCl、NaCl和K2TiF6熔盐混合。将所得混合物在Ar气氛中加热至900°C,然后在H2气氛中于1000°C进行热处理。采用扫描电镜、X射线衍射和聚焦离子束技术对所制得颗粒进行表征。结果表明:cBN和金刚石颗粒表面已覆盖了纳米钛层。对Ti/cBN和TiC/金刚石涂层颗粒进行热处理后,颗粒表面沉积的Ti层与cBN和金刚石颗粒发生了原位化学反应,分别转化为钛化合物TiN和TiC。

  13. Tensile Creep and Fatigue of Sylramic-iBN Melt-Infiltrated SiC Matrix Composites: Retained Properties, Damage Development, and Failure Mechanisms

    Science.gov (United States)

    Morscher, Greg; Gowayed, yasser; Miller, Robert; Ojard, Greg; Ahmad, Jalees; Santhosh, Unni; John, Reji

    2008-01-01

    An understanding of the elevated temperature tensile creep, fatigue, rupture, and retained properties of ceramic matrix composites (CMC) envisioned for use in gas turbine engine applications are essential for component design and life-prediction. In order to quantify the effect of stress, time, temperature, and oxidation for a state-of-the-art composite system, a wide variety of tensile creep, dwell fatigue, and cyclic fatigue experiments were performed in air at 1204 C for the SiC/SiC CMC system consisting of Sylramic-iBN SiC fibers, BN fiber interphase coating, and slurry-cast melt-infiltrated (MI) SiC-based matrix. Tests were either taken to failure or interrupted. Interrupted tests were then mechanically tested at room temperature to determine the residual properties. The retained properties of most of the composites subjected to tensile creep or fatigue were usually within 20% of the as-produced strength and 10% of the as-produced elastic modulus. It was observed that during creep, residual stresses in the composite are altered to some extent which results in an increased compressive stress in the matrix upon cooling and a subsequent increased stress required to form matrix cracks. Microscopy of polished sections and the fracture surfaces of specimens which failed during stressed-oxidation or after the room-temperature retained property test was performed on some of the specimens in order to quantify the nature and extent of damage accumulation that occurred during the test. It was discovered that the distribution of stress-dependent matrix cracking at 1204 C was similar to the as-produced composites at room temperature; however, matrix crack growth occurred over time and typically did not appear to propagate through thickness except at final failure crack. Failure of the composites was due to either oxidation-induced unbridged crack growth, which dominated the higher stress regime (> 179 MPa) or controlled by degradation of the fibers, probably caused by

  14. Research progress in polymer/BN thermal conductive composite%聚合物/BN导热复合材料研究进展

    Institute of Scientific and Technical Information of China (English)

    周文英; 王子君; 董丽娜; 睢雪珍

    2015-01-01

    Compared to other thermal conductive inorganic particles,boron nitride(BN) is a kind of important thermal conductive and insulting filler in preparing polymer with high thermal conductivity and insulation due to its unique structure and good thermal and electrical comprehensive properties. The research progresses in thermal conductive polymers filled with micro- and nano-sized BN particles were summarized,and the effects of physical properties,surface modification,structure and dosage of BN on the thermal,insulating and mechanical properties of the polymers were emphasized.The BN nanotubes and nanosheets reinforced polymers possess high thermal conductivity,high electric breakdown strength,high insulating resistance,low dielectric constant and dielectric loss,and good mechanical properties in comparison with micrometer BN. Solving the contradiction between high thermal conductivity and high electric breakdown strength is the future development direction of polymer/BN thermal conductive composite.%与其他导热无机粒子相比,氮化硼粒子具有的独特结构及良好的热、电综合性能,是制备高导热、高绝缘聚合物的一类重要导热绝缘填料。综述了微、纳米氮化硼粒子填充导热聚合物的研究进展,重点讨论了氮化硼粒子的物理性能、表面改性、结构及用量等对聚合物导热、绝缘及力学性能的影响。与微米氮化硼相比,氮化硼纳米管及纳米片增强的聚合物具有高导热、高电击穿强度、高绝缘电阻、低介电常数及介电损耗、良好的力学性能。解决导热聚合物高导热与高电击穿强度间的矛盾是聚合物/氮化硼导热复合材料未来发展的方向。

  15. The strong influence of displacement rate on void swelling in variants of Fe-16Cr-15Ni-3Mo austenitic stainless steel irradiated in BN-350 and BOR-60

    Energy Technology Data Exchange (ETDEWEB)

    Budylkin, N.I.; Bulanova, T.M.; Mironova, E.G.; Mitrofanova, N.M.; Porollo, S.I.; Chernov, V.M.; Shamardin, V.K.; Garner, F.A. E-mail: frank.garner@pnl.gov

    2004-08-01

    Recent irradiation experiments conducted on a variety of austenitic stainless steels have shown that void swelling appears to be increased when the dpa rate is decreased, primarily by a shortening of the transient regime of swelling. This paper presents results derived from nominally similar irradiations conducted on six Russian steels, all laboratory heat variants of Fe-16Cr-15Ni-3Mo-Nb-B, with each irradiated in two fast reactors, BOR-60 and BN-350. The BN-350 irradiation proceeded at a dpa rate three times higher than that conducted in BOR-60. In all six steels, a significantly higher swelling level was attained in BOR-60, agreeing with the results of earlier studies.

  16. Los Annales martyrum transmitidos por Madrid, BN, 10029 y Madrid, BRAH, 78: edición, estudio y panorámica de su infl uencia en la literatura analística latina de la Hispania medieval

    Directory of Open Access Journals (Sweden)

    Martín, José Carlos

    2011-06-01

    Full Text Available The scholar analyzes and publishes the Latin annals of martyrs transmitted in Madrid, BN, 10029 and, in an unpublished second version, Madrid, BRAH, 78. He also examines the possible date and origin, sources and influence in the Latin annals of Iberian Peninsule. Finally, this paper offers new editions of the so-called Chronicon Rotense alterum and Chronicon paruum Ambrosianum.Se estudian y editan en este artículo unos anales de mártires transmitidos por Madrid, BN, 10029 y, en una segunda redacción inédita, por Madrid, BRAH, 78. Además se examina su posible datación y origen, sus fuentes y su influencia en la literatura analística latina de la Península Ibérica. Se ofrecen asimismo nuevas ediciones de los denominados Chronicon Rotense alterum y Chronicon paruum Ambrosianum.

  17. Bulk InAsxSb1-x nBn photodetectors with greater than 5μm cutoff on GaSb

    Science.gov (United States)

    Baril, Neil; Brown, Alexander; Maloney, Patrick; Tidrow, Meimei; Lubyshev, Dmitri; Qui, Yueming; Fastenau, Joel M.; Liu, Amy W. K.; Bandara, Sumith

    2016-09-01

    Mid-wavelength infrared nBn photodetectors based on bulk InAsxSb1-x absorbers with a greater than 5 μm cutoff grown on GaSb substrates are demonstrated. The extended cutoff was achieved by increasing the lattice constant of the substrate from 6.09 to 6.13 Å using a 1.5 μm thick AlSb buffer layer to enable the growth of bulk InAs0.81Sb0.19 absorber material. Transitioning the lattice to 6.13 Å also enables the use of a simple binary AlSb layer as a unipolar barrier to block majority carrier electrons and reduce dark current noise. Individual test devices with 4 μm thick absorbers displayed 150 K dark current density, cutoff wavelength, and quantum efficiency of 3 × 10-5 A/cm2, 5.31 μm, and 44% at 3.4 μm, respectively. The instantaneous dark current activation energy at a given bias and temperature is determined via Arrhenius analysis from the Dark current vs. temperature and bias data, and a discussion of valence band alignment between the InAsxSb1-x absorber and AlSb barrier layers is presented.

  18. Enhancement of thermal transport in Gel Polymer Electrolytes with embedded BN/Al2O3 nano- and micro-particles

    Science.gov (United States)

    Vishwakarma, Vivek; Jain, Ankur

    2017-09-01

    While Gel Polymer Electrolytes (GPEs) have been widely investigated for use in next-generation Li-ion cells due to the potential for improved thermal safety, thermal transport within a GPE is still poorly understood. Among all materials in a Li-ion cell, the GPE has the lowest thermal conductivity, and hence determines the overall rate of heat flow in a Li-ion cell. This makes it critical to measure and understand thermal transport in a GPE and investigate trade-offs between thermal and ionic transport. This paper presents measurements of thermal and ionic conductivities in a PVdF-based GPE. The effect of incorporating BN/Al2O3 ceramic nano/microparticles in the GPE on thermal and ionic transport is characterized. Measurements indicate up to 2.5X improvement in thermal conductivity of activated GPE membranes, with relatively minor effect on electrochemical performance of GPE-based single-layer cells. The measured enhancement in thermal conductivity is in very good agreement with theoretical calculations based on the effective medium theory that accounts for thermal transport in a dispersed, two-phase medium such as a GPE. The fundamental insights gained in this work on thermal transport in a GPE and the role of nano/microparticle inclusions may facilitate thermal-electrochemical optimization and design of GPEs for safe, high-performance Li-ion cells.

  19. A first-principles study of the adsorption behavior of CO on Al- and Ga-doped single-walled BN nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Peyghan, Ali Ahmadi [Young Researchers Club, Islamshahr Branch, Islamic Azad University, Tehran (Iran, Islamic Republic of); Soltani, Alireza, E-mail: Alireza.soltani46@yahoo.com [Young Researchers Club, Gorgan Branch, Islamic Azad University, Gorgan (Iran, Islamic Republic of); Pahlevani, Amin Allah [Young Researchers Club, Gorgan Branch, Islamic Azad University, Gorgan (Iran, Islamic Republic of); Kanani, Yaser [Department of Chemistry, Gorgan Branch, Islamic Azad University, Gorgan (Iran, Islamic Republic of); Khajeh, Soheila [Department of Chemistry,Payame Noor University, 19395-3697 Tehran, Islamic Republic of Iran (Iran, Islamic Republic of)

    2013-04-01

    First-principles computations have been applied to scrutinize the adsorption behavior of CO molecule on the external surface of H-capped aluminum- and gallium-doped (6, 0), (8, 0) zigzag and (5, 5) armchair single-walled BN nanotubes (SWBNNTs). Binding energy corresponding to the most stable configuration of CO on the gallium-doped (6, 0) BNNT is found to be −0.83 eV, which is high typical sensitivity to CO molecule. Our results indicate that both Al- and Ga-doping can notably enhance the adsorption energy of CO/BNNTs complexes. Our electronic results reveal that there is a notable orbital hybridization among two species in adsorption process being an evidence of strong interaction. For the CO/BNNTs complexes, the energy gaps, NBO, dipole moments, natural atomic orbital occupancies and global indices are computed. Finally, we reported a novel type of toxic gas sensor that can be used for detecting the presence of CO molecule.

  20. Ti6Al4V Blade Wear Behavior During High-Speed Rubbing with NiAl-hBN Abradable Seal Coating

    Science.gov (United States)

    Xue, Weihai; Gao, Siyang; Duan, Deli; Zhang, Jiaping; Liu, Yang; Li, Shu

    2016-12-01

    The high-speed rubbing wear behavior between a Ti6Al4V blade and a NiAl-hBN seal coating was studied with a high-speed rub test rig. Blade wear behavior, which had not received enough attentions, was the key concern of this study. The rub tests conducted at different linear speeds and single-pass depths indicated that although wear distance was constant and rub forces decreased at high linear speed, blade wear increased with the increment of linear speed when single-pass depth was invariable. According to scanning electron microscopy, x-ray diffraction, electron probe microanalysis and microhardness analyses of the wear scars, different blade and coating wear mechanisms were observed when rubbed at different linear speeds. Remarkably, when rubbing was done at high linear speed, there was severe blade oxidation with the generation of oxidation layer full of cracks and high-hardness transfer layer in the coating wear scar, and these were identified as reasons of aggravated blade wear.

  1. Adsorption of carbon dioxide (CO{sub 2}) at S functionalized boron nitride (BN) and aluminum nitride (AlN) nanotubes (9, 0): A quantum chemical investigation

    Energy Technology Data Exchange (ETDEWEB)

    Najafi, Meysam, E-mail: meysamnajafi2016@yahoo.com

    2016-10-30

    Highlights: • AlN-NT has higher potential to CO{sub 2} adsorption in comparison to BN-NT. • S functionalization of studied nanotubes improve the CO{sub 2} adsorption ability of them. • E{sub ad} is suitable scale to propose the novel toxic gas sensor based on nanostructured. • E{sub ad} and E{sub HLG} of studied nanotubes have linear dependences. - Abstract: We employed density functional theory to characterize CO{sub 2} adsorption on BNNT and AlNNT surfaces. The effects of S functionalization on the adsorption of CO{sub 2} gas on BNNT and AlNNT surfaces were investigated. Results reveal that adsorptions of CO{sub 2} on studied nanotubes were exothermic and experimentally possible from the energetic viewpoint. Results show that, E{sub ad} values of CO{sub 2} on AlNNT surface were more negative than corresponding values of BNNT. Results reveal that, S functionalization of studied nanotubes causes an increase in the absolute values of E{sub ad} of CO{sub 2} on surface of studied nanotubes. These results show that, there are good linearity dependencies between E{sub ad} and orbital energy values of studied nanotubes. Therefore we can conclude the E{sub ad} and orbital energy values are highly sensitive to the adsorption process which these may be used for the selection the suitable nanotubes with enhanced CO{sub 2} adsorption potential.

  2. BN 52021 (a platelet activating factor-receptor antagonist decreases alveolar macrophage-mediated lung injury in experimental extrinsic allergic alveolitis

    Directory of Open Access Journals (Sweden)

    J-L. Pérez-Arellano

    1998-01-01

    Full Text Available Several lines of research indirectly suggest that platelet activating factor (PAF may intervene in the pathogenesis of extrinsic allergic alveolitis (EAA. The specific aim of our study was to evaluate the participation of PAF on macrophage activation during the acute phase of EAA in an experimental model of this disease developed in guinea pigs. Initially we measured the concentration of PAF in bronchoalvedar lavage fluid, blood and lung tissue. In a second phase we evaluate the participation of PAF on alveolar macrophage activation and parenchymal lung injury. The effect of PAF on parenchymal lung injury was evaluated by m easuring several lung parenchymatous lesion indices (lung index, bronchoalvedar lavage fluid (BALF lactic hydrogenase activity and BALF alkaline phosphatase activity and parameters of systemic response to the challenge (acute phase reagents. We observed that induction of the experimental EAA gave rise to an increase in the concentration of PAF in blood and in lung tissue. The use of the PAF-receptor antagonist BN52021 decreases the release of lysosomal enzymes (β-glucuronidase and tartrate-sensitive acid phosphatase to the extracellular environment both in vivo and in vitro. Furthermore, antagonism of the PAF receptors notably decreases pulmonary parenchymatous lesion. These data suggest that lung lesions from acute EAA are partly mediated by local production of PAF.

  3. Ti6Al4V Blade Wear Behavior During High-Speed Rubbing with NiAl-hBN Abradable Seal Coating

    Science.gov (United States)

    Xue, Weihai; Gao, Siyang; Duan, Deli; Zhang, Jiaping; Liu, Yang; Li, Shu

    2017-02-01

    The high-speed rubbing wear behavior between a Ti6Al4V blade and a NiAl-hBN seal coating was studied with a high-speed rub test rig. Blade wear behavior, which had not received enough attentions, was the key concern of this study. The rub tests conducted at different linear speeds and single-pass depths indicated that although wear distance was constant and rub forces decreased at high linear speed, blade wear increased with the increment of linear speed when single-pass depth was invariable. According to scanning electron microscopy, x-ray diffraction, electron probe microanalysis and microhardness analyses of the wear scars, different blade and coating wear mechanisms were observed when rubbed at different linear speeds. Remarkably, when rubbing was done at high linear speed, there was severe blade oxidation with the generation of oxidation layer full of cracks and high-hardness transfer layer in the coating wear scar, and these were identified as reasons of aggravated blade wear.

  4. First-principles study of spin transport in BN doped CrO{sub 2}–graphene–CrO{sub 2} magnetic tunnel junction

    Energy Technology Data Exchange (ETDEWEB)

    Choudhary, Sudhanshu, E-mail: sudhanshu@nitkkr.ac.in; Mishra, Pradeep, E-mail: pradeepmshr26@gmail.com; Goyal, Rohit, E-mail: rohit91.goyal@gmail.com

    2016-03-06

    We investigate the spin-dependent electronic transport properties of Magnetic tunnel junction (MTJ) consisting of Boron (B) and Nitrogen (N) doped graphene nanosheet sandwiched between two CrO{sub 2} half-metallic–ferromagnet (HMF) electrodes. A large value of tunnel magnetoresistance (TMR) and perfect spin filtration was obtained as compared to un-doped graphene MTJ structures reported in past. The use of HMF electrodes further raises the TMR and improves the spin filtration in comparison to MTJs with metallic and ferromagnetic (FM) electrodes, which suggest HMF electrodes as a suitable candidate over metallic and FM electrodes for implementing graphene sheet based MTJs. A high value of TMR ∼100% is obtained at zero bias voltage, which remains constantly high at higher bias voltages in the range of 0 V to 1 V. The higher value of TMR and better (near perfect) spin filtration abilities suggest its usefulness in spin-valves and other spintronics based applications. The spin-dependent non-equilibrium transport is also investigated by analyzing the bias dependent transmission coefficients. - Highlights: • Higher TMR was observed in BN doped graphene based MTJ in comparison with undoped structure. • Perfect Spin Filtration Effect was observed in doped structure in comparison with undoped structure. • Use of HMF electrodes further raises TMR and Spin Filtration Effect.

  5. Efecto del ion cloruro sobre las propiedades mecánicas a compresión del concreto reforzado con fibras de acero RC-65/35-BN

    Directory of Open Access Journals (Sweden)

    Julián Carrillo

    2015-01-01

    Full Text Available En este estudio se evalúa la influencia de dos ambientes corrosivos, a corto plazo, y de la dosificación de fibras sobre las propiedades mecánicas a compresión del concreto reforzado con fibras de acero (CRFA RC-65/35- BN. El programa experimental comprendió el ensayo de 54 especímenes de CRFA en forma de cilindros con fibras de acero, caracterizadas por una relación longitud/diámetro con valor de 65, con dosificaciones de fibra de 27.5 y 60 kg/m3. En cuanto a los ambientes de exposición, 18 cilindros fueron sumergidos y sometidos a la acción de un medio acuoso, 18 en un medio de solución NaCl al 3.5 % (ion cloruro y 18 permanecieron en condiciones inalteradas durante 60 días. Para esta fase de iniciación de la corrosión se observó una pérdida aproximada del 2 % en la resistencia a compresión, una disminución del 6 % del módulo de elasticidad y un aumento del 13 % en la relación de Poisson del CRFA. Estos resultados demostraron que a corto plazo los ambientes corrosivos no afectan significativamente las propiedades mecánicas en compresión del CRFA utilizado en este estudio.

  6. Low-Temperature Ohmic Contact to Monolayer MoS2 by van der Waals Bonded Co/h-BN Electrodes.

    Science.gov (United States)

    Cui, Xu; Shih, En-Min; Jauregui, Luis A; Chae, Sang Hoon; Kim, Young Duck; Li, Baichang; Seo, Dongjea; Pistunova, Kateryna; Yin, Jun; Park, Ji-Hoon; Choi, Heon-Jin; Lee, Young Hee; Watanabe, Kenji; Taniguchi, Takashi; Kim, Philip; Dean, Cory R; Hone, James C

    2017-08-09

    Monolayer MoS2, among many other transition metal dichalcogenides, holds great promise for future applications in nanoelectronics and optoelectronics due to its ultrathin nature, flexibility, sizable band gap, and unique spin-valley coupled physics. However, careful study of these properties at low temperature has been hindered by an inability to achieve low-temperature Ohmic contacts to monolayer MoS2, particularly at low carrier densities. In this work, we report a new contact scheme that utilizes cobalt (Co) with a monolayer of hexagonal boron nitride (h-BN) that has the following two functions: modifies the work function of Co and acts as a tunneling barrier. We measure a flat-band Schottky barrier of 16 meV, which makes thin tunnel barriers upon doping the channels, and thus achieve low-T contact resistance of 3 kΩ.μm at a carrier density of 5.3 × 10(12)/cm(2). This further allows us to observe Shubnikov-de Haas oscillations in monolayer MoS2 at much lower carrier densities compared to previous work.

  7. Efficient many-body calculations for two-dimensional materials using exact limits for the screened potential: Band gaps of MoS2, h -BN, and phosphorene

    Science.gov (United States)

    Rasmussen, Filip A.; Schmidt, Per S.; Winther, Kirsten T.; Thygesen, Kristian S.

    2016-10-01

    Calculating the quasiparticle (QP) band structure of two-dimensional (2D) materials within the GW self-energy approximation has proven to be a rather demanding computational task. The main reason is the strong q dependence of the 2D dielectric function around q =0 that calls for a much denser sampling of the Brillouin zone (BZ) than is necessary for similar three-dimensional solids. Here, we use an analytical expression for the small q limit of the 2D response function to perform the BZ integral over the critical region around q =0 . This drastically reduces the requirements on the q -point mesh and implies a significant computational speedup. For example, in the case of monolayer MoS2, convergence of the G0W0 band gap to within ˜0.1 eV is achieved with 12 ×12 q points rather than the 36 ×36 mesh required with discrete BZ sampling techniques. We perform a critical assessment of the band gap of the three prototypical 2D semiconductors, MoS2, h -BN, and phosphorene, including the effect of self-consistency at the GW0 level. The method is implemented in the open source code gpaw.

  8. Hierarchical Cobalt Hydroxide and B/N Co-Doped Graphene Nanohybrids Derived from Metal-Organic Frameworks for High Energy Density Asymmetric Supercapacitors

    Science.gov (United States)

    Tabassum, Hassina; Mahmood, Asif; Wang, Qingfei; Xia, Wei; Liang, Zibin; Qiu, Bin; Zhao, Ruo; Zou, Ruqiang

    2017-02-01

    To cater for the demands of electrochemical energy storage system, the development of cost effective, durable and highly efficient electrode materials is desired. Here, a novel electrode material based on redox active β-Co(OH)2 and B, N co-doped graphene nanohybrid is presented for electrochemical supercapacitor by employing a facile metal-organic frameworks (MOFs) route through pyrolysis and hydrothermal treatment. The Co(OH)2 could be firmly stabilized by dual protection of N-doped carbon polyhedron (CP) and B/N co-doped graphene (BCN) nanosheets. Interestingly, the porous carbon and BCN nanosheets greatly improve the charge storage, wettability, and redox activity of electrodes. Thus the hybrid delivers specific capacitance of 1263 F g‑1 at a current density of 1A g‑1 with 90% capacitance retention over 5000 cycles. Furthermore, the new aqueous asymmetric supercapacitor (ASC) was also designed by using Co(OH)2@CP@BCN nanohybrid and BCN nanosheets as positive and negative electrodes respectively, which leads to high energy density of 20.25 Whkg‑1. This device also exhibits excellent rate capability with energy density of 15.55 Whkg‑1 at power density of 9331 Wkg‑1 coupled long termed stability up to 6000 cycles.

  9. Herschel Far-Infrared Spectral-mapping of Orion BN/KL Outflows: Spatial distribution of excited CO, H2O, OH, O and C+ in shocked gas

    CERN Document Server

    Goicoechea, Javier R; Cernicharo, Jose; Neufeld, David A; Vavrek, Roland; Bergin, Edwin A; Cuadrado, Sara; Encrenaz, Pierre; Etxaluze, Mireya; Melnick, Gary J; Polehampton, Edward

    2014-01-01

    We present ~2'x2' spectral-maps of Orion BN/KL outflows taken with Herschel at ~12'' resolution. For the first time in the far-IR domain, we spatially resolve the emission associated with the bright H2 shocked regions "Peak 1" and "Peak 2" from that of the Hot Core and ambient cloud. We analyze the ~54-310um spectra taken with the PACS and SPIRE spectrometers. More than 100 lines are detected, most of them rotationally excited lines of 12CO (up to J=48-47), H2O, OH, 13CO, and HCN. Peaks 1/2 are characterized by a very high L(CO)/L(FIR)~5x10^{-3} ratio and a plethora of far-IR H2O emission lines. The high-J CO and OH lines are a factor ~2 brighter toward Peak 1 whereas several excited H2O lines are ~50% brighter toward Peak 2. A simplified non-LTE model allowed us to constrain the dominant gas temperature components. Most of the CO column density arises from Tk~200-500 K gas that we associate with low-velocity shocks that fail to sputter grain ice mantles and show a maximum gas-phase H2O/CO~10^{-2} abundance r...

  10. Hierarchical Cobalt Hydroxide and B/N Co-Doped Graphene Nanohybrids Derived from Metal-Organic Frameworks for High Energy Density Asymmetric Supercapacitors

    Science.gov (United States)

    Tabassum, Hassina; Mahmood, Asif; Wang, Qingfei; Xia, Wei; Liang, Zibin; Qiu, Bin; zhao, Ruo; Zou, Ruqiang

    2017-01-01

    To cater for the demands of electrochemical energy storage system, the development of cost effective, durable and highly efficient electrode materials is desired. Here, a novel electrode material based on redox active β-Co(OH)2 and B, N co-doped graphene nanohybrid is presented for electrochemical supercapacitor by employing a facile metal-organic frameworks (MOFs) route through pyrolysis and hydrothermal treatment. The Co(OH)2 could be firmly stabilized by dual protection of N-doped carbon polyhedron (CP) and B/N co-doped graphene (BCN) nanosheets. Interestingly, the porous carbon and BCN nanosheets greatly improve the charge storage, wettability, and redox activity of electrodes. Thus the hybrid delivers specific capacitance of 1263 F g−1 at a current density of 1A g−1 with 90% capacitance retention over 5000 cycles. Furthermore, the new aqueous asymmetric supercapacitor (ASC) was also designed by using Co(OH)2@CP@BCN nanohybrid and BCN nanosheets as positive and negative electrodes respectively, which leads to high energy density of 20.25 Whkg−1. This device also exhibits excellent rate capability with energy density of 15.55 Whkg−1 at power density of 9331 Wkg−1 coupled long termed stability up to 6000 cycles. PMID:28240224

  11. Unveiling Sources of Heating in the Vicinity of the Orion BN/KL Hot Core as Traced by Highly Excited Inversion Transitions of Ammonia

    CERN Document Server

    Goddi, C; Humphreys, E M L; Chandler, C J; Matthews, L D

    2011-01-01

    Using the Expanded Very Large Array, we have mapped the vicinity of the Orion BN/KL Hot Core with sub-arcsecond angular resolution in seven metastable inversion transitions of ammonia: (J,K)=(6,6) to (12,12). This emission comes from levels up to 1500 K above the ground state, enabling identification of source(s) responsible for heating the region. We used this multi-transition dataset to produce images of the rotational/kinetic temperature and the column density of ammonia for ortho and para species separately and on a position-by-position basis. We find rotational temperature and column density in the range 160-490 K and (1-4)x10^17 cm^-2, respectively. Our spatially-resolved images show that the highest (column) density and hottest gas is found in a northeast-southwest elongated ridge to the southeast of Source I. We have also measured the ortho-para ratio of ammonia, estimated to vary in the range 0.9-1.6. Enhancement of ortho with respect to para and the offset of hot ammonia emission peaks from known (p...

  12. Theranostic pretargeted radioimmunotherapy of colorectal cancer xenografts in mice using picomolar affinity {sup 86}Y- or {sup 177}Lu-DOTA-Bn binding scFv C825/GPA33 IgG bispecific immunoconjugates

    Energy Technology Data Exchange (ETDEWEB)

    Cheal, Sarah M.; Lee, Sang-gyu; Punzalan, Blesida; Larson, Steven M. [Memorial Sloan Kettering Cancer Center, Department of Radiology, New York, NY (United States); Memorial Sloan Kettering Cancer Center, Molecular Pharmacology and Chemistry Program, New York, NY (United States); Xu, Hong; Guo, Hong-fen [Memorial Sloan Kettering Cancer Center, Department of Pediatrics, New York, NY (United States); Chalasani, Sandhya; Carrasquillo, Jorge A. [Memorial Sloan Kettering Cancer Center, Department of Radiology, New York, NY (United States); Fung, Edward K. [Memorial Sloan Kettering Cancer Center, Molecular Pharmacology and Chemistry Program, New York, NY (United States); Memorial Sloan Kettering Cancer Center, Department of Medical Physics, New York, NY (United States); Jungbluth, Achim [Memorial Sloan Kettering Cancer Center, Department of Pathology, New York, NY (United States); Zanzonico, Pat B.; O' Donoghue, Joseph [Memorial Sloan Kettering Cancer Center, Department of Medical Physics, New York, NY (United States); Smith-Jones, Peter M. [Stony Brook University, Department of Psychiatry and Behavioral Science, Stony Brook, NY (United States); Stony Brook University, Department of Radiology, Stony Brook, NY (United States); Wittrup, K.D. [Massachusetts Institute of Technology, Department of Chemical Engineering, Cambridge, MA (United States); Massachusetts Institute of Technology, Department of Biological Engineering, Cambridge, MA (United States); Massachusetts Institute of Technology, Koch Institute for Integrative Cancer Research, Cambridge, MA (United States); Cheung, Nai-Kong V. [Memorial Sloan Kettering Cancer Center, Molecular Pharmacology and Chemistry Program, New York, NY (United States); Memorial Sloan Kettering Cancer Center, Department of Pediatrics, New York, NY (United States)

    2016-05-15

    GPA33 is a colorectal cancer (CRC) antigen with unique retention properties after huA33-mediated tumor targeting. We tested a pretargeted radioimmunotherapy (PRIT) approach for CRC using a tetravalent bispecific antibody with dual specificity for GPA33 tumor antigen and DOTA-Bn-(radiolanthanide metal) complex. PRIT was optimized in vivo by titrating sequential intravenous doses of huA33-C825, the dextran-based clearing agent, and the C825 haptens {sup 177}Lu-or {sup 86}Y-DOTA-Bn in mice bearing the SW1222 subcutaneous (s.c.) CRC xenograft model. Using optimized PRIT, therapeutic indices (TIs) for tumor radiation-absorbed dose of 73 (tumor/blood) and 12 (tumor/kidney) were achieved. Estimated absorbed doses (cGy/MBq) to tumor, blood, liver, spleen, and kidney for single-cycle PRIT were 65.8, 0.9 (TI 73), 6.3 (TI 10), 6.6 (TI 10), and 5.3 (TI 12), respectively. Two cycles of PRIT (66.6 or 111 MBq {sup 177}Lu-DOTA-Bn) were safe and effective, with a complete response of established s.c. tumors (100 - 700 mm{sup 3}) in nine of nine mice, with two mice alive without recurrence at >140 days. Tumor log kill in this model was estimated to be 2.1 - 3.0 based on time to 500-mm{sup 3} tumor recurrence. In addition, PRIT dosimetry/diagnosis was performed by PET imaging of the positron-emitting DOTA hapten {sup 86}Y-DOTA-Bn. We have developed anti-GPA33 PRIT as a triple-step theranostic strategy for preclinical detection, dosimetry, and safe targeted radiotherapy of established human colorectal mouse xenografts. (orig.)

  13. Study on BN Particles Reinforced Cyanate Ester Resin Composites%氮化硼粒子增强氰酸酯树脂基复合材料的研究

    Institute of Scientific and Technical Information of China (English)

    安群力

    2012-01-01

    Boron nitride (BN)/cyanate ester resin/glass fiber composites were prepared in order to enhance the properties. The effects of BN particles on the reaction activity of cyanate ester resin, mechanical properties, and heat resistance of the composites were investigated. It was found that BN particle had little influence on reaction activity of cyanate ester resin. Inclusion of 8 % couple agent treated BN particles resulted in 5 % and 36 % increase in the flexural strength and inter- laminar shear strength, respectively. The addition of BN particles to the composites also increased the initial decomposition temperatures, heat resistance index, and thermal stability of cyanate ester resin composites.%在玻璃布增强氰酸酯树脂(cE)基复合材料中加入氮化硼(BN)粒子,制得CE/玻璃布/BN复合材料。研究了BN粒子含量对复合材料性能的影响。结果表明,经偶联剂处理的BN粒子使体系凝胶时间缩短,反应活性略有提高。BN粒子的加入可以明显提高复合材料的弯曲强度和层问剪切强度,在BN加入量为8%时,复合材料的弯曲强度和层间剪切强度达到最大值,分别提高了5%和36%。加入BN粒子后,复合材料的起始热分解温度都较未填充体系有所提高,耐热指数升高,热稳定性相应提高。

  14. 等电子体B、N单壁碳纳米管的比较研究%The Comparable Study of Isoelectronic-bodies of Single-walled B/N Nanotubes

    Institute of Scientific and Technical Information of China (English)

    赵华; 田春华; 王素娜; 孙得志; 张翀

    2012-01-01

    A systematic theoretical investigation on the single-walled C-NTs, BC2N-NTs and BN- NTs of (n, n) (n=3, 4, 5, 6) has been performed using the AM1 semiempirical method. The structures, stabilities, ionization potentials (IP), affinity potentials (AP), HOMO-LUMO energy gaps (Eg), and the strains have been studied. The calculation results show that the diameter of C-NT becomes slightly larger than that of the BC2 N-NT and BN-NT, and the diameter of BN-NT is the smallest one. comparing to that of the C-NTs and BC2N-NTs, the HOMO-LUMO gap Eg of pure BN-NTs is independently of their diameters. Since BC~N-NTs or BN-NTs are made of the three (B, C and N) or two (B and N) kind of atoms, POAV analysis suggest that each of them have their own contributions to rehybridizations and strains.%采用AM1方法,本文系统地研究了扶手椅型单壁碳纳米管(C-NTs),BN杂化碳纳米管(BC2N—NTs)和全BN纳米管(BN—NTs)的结构,热力学稳定性,电离势(IP),电子亲和势(EA),最低非占据轨道(LUM0)和最高占据轨道(HOMO)的能级差(Eg)及张力等性质.计算结果表明:当n值一定时,(n,n)C-NTs(n=3,4,5,6)的直径最大,BN—NTs的直径最小;(n,n)C-NTs和BC2N—NTs的Eg(HOMO—LUM0)和n的数值有关系;而(n,n)BN—NTs的Eg(HO—MO—LUMO)和n值关系不大.POAV分析表明了,不同的杂化原子对组成纳米管原子的杂化方式和纳米管的张力有不同的贡献.

  15. Synthesis, structural characterization and evaluation of floating B-N codoped TiO{sub 2}/expanded perlite composites with enhanced visible light photoactivity

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Xin; Wang, Wei; Wang, Xuejiang, E-mail: wangxj@tongji.edu.cn; Zhang, Jing; Zhao, Jianfu; Gu, Zaoli; Zhou, Lijie

    2015-09-15

    Graphical abstract: - Highlights: • We added expanded perlite as a floating carrier to immobilize B-N codoped TiO{sub 2}. • The photo-reaction occurred on the surface of water and easily utilized the solar energy and O{sub 2} to make photodegradation efficiently. • The composites combined the adsorptivity of expanded perlite and photoactivity of B-N-TiO{sub 2}. • The floating photocatalysts give a simple way to recycle, which is important to the application of photocatalysis technology. - Abstract: Floating photocatalysts of boron-nitrogen codoped TiO{sub 2} grafted on expanded perlite (B-N-TiO{sub 2}/EP) were prepared by a facile sol–gel method. The catalysts were characterized by N{sub 2} adsorption–desorption (BET), scanning electron microscope (SEM), high resolution transmission electron microscopy (HRTEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), X-ray photoelectron spectroscopy (XPS) and UV–vis diffuse reflectance spectroscopy (UV–vis–DRS). The results revealed that the physicochemical properties of the photocatalysts, such as BET surface area, porosity and pore size could be controlled by adjusting the calcination temperature and EP dosage. XRD patterns were mainly influenced by calcination temperature and the transformation of anatase to rutile occurred at 650 °C. Uniform TiO{sub 2} loading, higher surface area and absorption in visible light region were obtained for B-N-TiO{sub 2}/EP calcined at 550 °C with 3.0 g EP addition. Moreover, photocatalytic activity for RhB destruction under visible light irradiation was slightly influenced by TiO{sub 2} loading in the range of 1–3 g EP dosage. BNTEP550 showed the highest photocatalytic activity indicating to be a promising photocatalyst employed to remediate contaminated waters using solar irradiation.

  16. Amoebal endosymbiont Parachlamydia acanthamoebae Bn9 can grow in immortal human epithelial HEp-2 cells at low temperature; an in vitro model system to study chlamydial evolution.

    Directory of Open Access Journals (Sweden)

    Chikayo Yamane

    Full Text Available Ancient chlamydiae diverged into pathogenic and environmental chlamydiae 0.7-1.4 billion years ago. However, how pathogenic chlamydiae adapted to mammalian cells that provide a stable niche at approximately 37 °C, remains unknown, although environmental chlamydiae have evolved as endosymbionts of lower eukaryotes in harsh niches of relatively low temperatures. Hence, we assessed whether an environmental chlamydia, Parachlamydia Bn9, could grow in human HEp-2 cells at a low culture temperature of 30 °C. The assessment of inclusion formation by quantitative RT-PCR revealed that the numbers of bacterial inclusion bodies and the transcription level of 16SrRNA significantly increased after culture at 30 °C compared to at 37 °C. Confocal microscopy showed that the bacteria were located close to HEp-2 nuclei and were actively replicative. Transmission electron microscopy also revealed replicating bacteria consisting of reticular bodies, but with a few elementary bodies. Cytochalasin D and rifampicin inhibited inclusion formation. Lactacystin slightly inhibited bacterial inclusion formation. KEGG analysis using a draft genome sequence of the bacteria revealed that it possesses metabolic pathways almost identical to those of pathogenic chlamydia. Interestingly, comparative genomic analysis with pathogenic chlamydia revealed that the Parachlamydia similarly possess the genes encoding Type III secretion system, but lacking genes encoding inclusion membrane proteins (IncA to G required for inclusion maturation. Taken together, we conclude that ancient chlamydiae had the potential to grow in human cells, but overcoming the thermal gap was a critical event for chlamydial adaptation to human cells.

  17. Amoebal Endosymbiont Parachlamydia acanthamoebae Bn9 Can Grow in Immortal Human Epithelial HEp-2 Cells at Low Temperature; An In Vitro Model System to Study Chlamydial Evolution

    Science.gov (United States)

    Nakamura, Shinji; Matsuo, Junji; Ishida, Kasumi; Yamazaki, Sumire; Oguri, Satoshi; Shouji, Natsumi; Hayashi, Yasuhiro; Yoshida, Mitsutaka; Yimin; Yamaguchi, Hiroyuki

    2015-01-01

    Ancient chlamydiae diverged into pathogenic and environmental chlamydiae 0.7–1.4 billion years ago. However, how pathogenic chlamydiae adapted to mammalian cells that provide a stable niche at approximately 37°C, remains unknown, although environmental chlamydiae have evolved as endosymbionts of lower eukaryotes in harsh niches of relatively low temperatures. Hence, we assessed whether an environmental chlamydia, Parachlamydia Bn9, could grow in human HEp-2 cells at a low culture temperature of 30°C. The assessment of inclusion formation by quantitative RT-PCR revealed that the numbers of bacterial inclusion bodies and the transcription level of 16SrRNA significantly increased after culture at 30°C compared to at 37°C. Confocal microscopy showed that the bacteria were located close to HEp-2 nuclei and were actively replicative. Transmission electron microscopy also revealed replicating bacteria consisting of reticular bodies, but with a few elementary bodies. Cytochalasin D and rifampicin inhibited inclusion formation. Lactacystin slightly inhibited bacterial inclusion formation. KEGG analysis using a draft genome sequence of the bacteria revealed that it possesses metabolic pathways almost identical to those of pathogenic chlamydia. Interestingly, comparative genomic analysis with pathogenic chlamydia revealed that the Parachlamydia similarly possess the genes encoding Type III secretion system, but lacking genes encoding inclusion membrane proteins (IncA to G) required for inclusion maturation. Taken together, we conclude that ancient chlamydiae had the potential to grow in human cells, but overcoming the thermal gap was a critical event for chlamydial adaptation to human cells. PMID:25643359

  18. Cloning and Expression Analysis of Glutathione Reductase Gene (BnGR1) from Ramie (Boehmeria nivea L.)%苎麻谷胱甘肽还原酶基因(BnGR1)的克隆和表达分析

    Institute of Scientific and Technical Information of China (English)

    朱守晶; 余伟林; 石朝燕; 揭雨成

    2015-01-01

    谷胱甘肽还原酶(glutathione reductase,GR)是植物体内一种重要的抗氧化酶类.本研究根据苎麻(Boehmeria nivea (L.) Gaud.)转录组中的相关片段,采用RACE技术克隆到了GR基因的全长cDNA序列,命名为BnGR1(GenBank登录号:KF747758).该基因的cDNA全长为1 977 bp,开放读码框为1 494bp,编码497个氨基酸,推测其蛋白相对分子量为53.7 kD,理论等电点为5.68.氨基酸序列分析表明,该蛋白具有吡啶核苷酸-二硫化物氧化还原酶class Ⅰ活性位点、烟酰胺腺嘌呤二核苷酸磷酸(nicotinamideadenine dinucleotide phosphate,NADP)结合位点、黄素腺嘌呤二核苷酸(flavin adenine dinucletide,FAD)结合位点结合位点、氧化型谷胱甘肽(L-glutathione oxidized,GSSG)结合位点和胞质GR特殊结构域,与可可(Theobroma cacao)的GR蛋白(EOY05332)相似性最高,达到88%.此外,本研究成功构建了原核表达载体pGEX-4T-BnGR1,经异丙基-β-d-硫代半乳糖苷(isopropyl-β-d-thiogalactoside,IPTG)诱导获得了53.7 kD左右蛋白,与理论值一致.qRT-PCR表达分析表明,该基因在苎麻的根、茎、茎尖和叶片中均有表达,其中在成熟叶中表达量最高,茎中表达量最低:同时,受CdCl2、外源脱落酸(abscisic acid,ABA)和水杨酸(salicylic acid,SA)的诱导上调表达.BnGR1可能与苎麻抗逆机制密切相关,研究结果为探寻苎麻对重金属Cd2+的耐受分子机理提供基础资料.

  19. Synthesis of h-BN encapsulated spherical core-shell structured SiO{sub 2}-Sr{sub 2}Si{sub 5}N{sub 8}:Eu{sup 2+} red phosphors

    Energy Technology Data Exchange (ETDEWEB)

    Tang Jiaye; Zhan Cheng; Yang Lixun; Hao Luyuan [Chinese Academy of Sciences Key Laboratory of Materials for Energy Conversion, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026 (China); Xu Xin, E-mail: xuxin@ustc.edu.cn [Chinese Academy of Sciences Key Laboratory of Materials for Energy Conversion, Department of Materials Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026 (China); Simeon, Agathopoulos [Materials Science and Engineering Department, University of Ioannina, GR-451 10 Ioannina (Greece)

    2012-02-15

    Highlights: Black-Right-Pointing-Pointer A facile method to synthesized high stable spherical Sr{sub 2}Si{sub 5}N{sub 8}:Eu{sup 2+} red phosphors. Black-Right-Pointing-Pointer The synthesis temperature is about 200 Degree-Sign C lower than the traditional method. Black-Right-Pointing-Pointer The h-BN protective film prevents the agglomeration between different spherical particles. Black-Right-Pointing-Pointer This spherical phosphor could be used in white LED and other display techniques. - Abstract: A facile method was designed for the successful synthesis of highly stable spherical (oxo)nitridosilicate phosphors with excellent monodispersity, high coating density and improved luminescent properties. The novel h-BN-encapsulated spherical core-shell SiO{sub 2}-Sr{sub 2}Si{sub 5}N{sub 8}:Eu{sup 2+} red-emitting phosphors were successfully synthesized by an interfacial reaction mechanism followed by a subsequent gas reduction and nitridation process. A thin film of hexagonal boron nitride (h-BN) was formed in situ during the synthesis process, leading to core-shell SiO{sub 2}-Sr{sub 2}Si{sub 5}N{sub 8}:Eu{sup 2+} phosphors with a perfectly spherical shape, narrow size distribution, non-agglomeration and a smooth surface. The particles consist of three layers: the outer h-BN film; the middle Sr{sub 2}Si{sub 5}N{sub 8}:Eu{sup 2+} phosphor shell and the amorphous SiO{sub 2} core. Under UV and blue light excitation, the SiO{sub 2}-Sr{sub 2}Si{sub 5}N{sub 8}:Eu{sup 2+} phosphors show intense red emission due to the 4f{sup 6}5d-4f{sup 7} transition of the Eu{sup 2+} ions. Furthermore, this method is superior to the traditional gas reduction and nitridation method because of the lower temperature at which synthesis occurs.

  20. Effect of BN 52021, a specific antagonist of platelet activating factor (PAF-acether), on calcium movements and phosphatidic acid production induced by PAF-acether in human platelets

    Energy Technology Data Exchange (ETDEWEB)

    Simon, M.F.; Chap, H.; Braquet, P.; Douste-Blazy, L.

    1987-02-15

    /sup 32/P-labelled human platelets loaded with quin 2 and pretreated with aspirin were stimulated with 1-100 nM platelet activating factor (PAF-acether or 1-0-alkyl-2-acetyl-sn-glycero-3-phosphocholine) in a medium containing the ADP-scavenging system creatine phosphate/creatine phosphokinase. Under these conditions, PAF-acether evoked a characteristic fluorescence change allowing to quantify elevations in cytoplasmic free Ca/sup 2 +/ from internal stores (Ca/sup 2 +/ mobilization) or from external medium (Ca/sup 2 +/ influx), as well as an increased production of phosphatidic acid, reflecting phospholipase C activation. These effects, which can be attributed to PAF-acether only and not to released products such as ADP or thromboxane A2, were strongly inhibited in a dose-dependent manner by BN 52021, a specific antagonist of PAF-acether isolated from Ginkgo biloba. As the drug remained inactive against the same effects elicited by thrombin, it is concluded that BN 52021 does not interfere directly with the mechanism of transmembrane signalling involving inositol-phospholipids or (and) some putative receptor-operated channels, but rather acts on the binding of PAF-acether to its presumed membrane receptor.

  1. Study of the neutron and proton capture reactions 10,11b(n, g), 11b(p, g), 14c(p, g), and 15n(p, g) at thermal and astrophysical energies

    CERN Document Server

    Dubovichenko, Sergey

    2014-01-01

    We have studied the neutron-capture reactions 10,11B(n, g) and the role of the 11B(n, g) reaction in seeding r-process nucleosynthesis. The possibility of the description of the available experimental data for cross sections of the neutron capture reaction on 10B at thermal and astrophysical energies, taking into account the resonance at 475 keV, was considered within the framework of the modified potential cluster model (MPCM) with forbidden states and accounting for the resonance behavior of the scattering phase shifts. In the framework of the same model the possibility of describing the available experimental data for the total cross sections of the neutron radiative capture on 11B at thermal and astrophysical energies were considered with taking into account the 21 and 430 keV resonances. Description of the available experimental data on the total cross sections and astrophysical S-factor of the radiative proton capture on 11B to the ground state of 12C was treated at astrophysical energies. The possibili...

  2. Effects of heat treatment on microstructure and mechanical properties of Ni60/h-BN self-lubricating anti-wear composite coatings on 304 stainless steel by laser cladding

    Science.gov (United States)

    Lu, Xiao-Long; Liu, Xiu-Bo; Yu, Peng-Cheng; Zhai, Yong-Jie; Qiao, Shi-Jie; Wang, Ming-Di; Wang, Yong-Guang; Chen, Yao

    2015-11-01

    Laser clad Ni60/h-BN self-lubricating anti-wear composite coating on 304 stainless steel were heat treated at 600 °C (stress relief annealing) for 1 h and 2 h, respectively. Effects of the phase compositions, microstructure, microhardness, nano-indentation and tribological properties of the composite coatings with and without heat treatment had been investigated systemically. Results indicated that three coatings mainly consist of the matrix γ-(Ni, Fe) solid solution, the CrB ceramic phases and the h-BN lubricating phases. The maximum microhardness of the coatings was first increased from 667.7 HV0.5 to 765.0 HV0.5 after heat treatment for 1 h, and then decreased to 698.3 HV0.5 after heat treatment for 2 h. The hardness of γ-(Ni, Fe) solid solution without heat treatment and after heat treatment 1 h and 2 h were 5.09 GPa, 7.20 GPa and 3.77 GPa, respectively. Compared with the coating without heat treatment, the friction coefficients of the coating after heat treatment were decreased obviously. Effects of the heat treatment time on friction coefficient were negligible, but were significant on wear volume loss. Comparatively speaking, the laser clad self-lubricating anti-wear composite coating after heat treatment for 1 h presented the best anti-wear and friction reduction properties.

  3. Glutathione peroxidase gene BnGPX1 cloning from rapeseed and expression under abiotic stress%甘蓝型油菜谷胱甘肽过氧化物酶基因和非生物胁迫下的表达

    Institute of Scientific and Technical Information of China (English)

    胡茂龙; 龙卫华; 高建芹; 陈新军; 张洁夫; 陈松; 戚存扣; 浦惠明

    2011-01-01

    A glutathione peroxidases gene,designated as BnGPXl (GenBank assession number HM130680), was a key enzyme protecting plants against oxidative damage generated by reactive oxygen species (ROS) under abiotic stresses. It was cloned from rapeseed cultivar Ningyou 16 ( Brassica napus L. ) by RT - PCR ( reverse transcription PCR). The open reading frame (ORF) of BnGPXl was 711 bp, encoding 236 amino acids with isoelec-tric point (pi) of 9.37 and molecular mass of 26.10 kD. BnGPXl had 3 characteristic domains of plant GPXs and 3 conserved cysteine residues. Its genomic DNA (gDNA) fragment (GenBank assession number HM130681) was isolated by PCR. The sequence of gDNA demonstrated 6 exons separated by 5 introns. All introns were spliced following the consensus sequence with GT and AG at 5' and 3' ends respectively. BnGPXl construction was similar to the Arabidopsis AtGPXl gene. Expression patterns of BnGPXl in rapeseed tissues under different abiotic stresses were obtained by semi - quantitative RT - PCR. Results showed that BnGPXl was constitutively and ubiquitously expressed at high levels in stems, leaves,silliques and flowers, but at lower level in roots. The expression was increased under salt, drought and high temperature condition. It did not respond to cold stress.%利用RT-PCR(reverse transcription PCR)技术从甘蓝型油菜宁油16号(Brassica napus L.)中克隆了一个非生物胁迫下细胞抵御活性氧(reactive oxygen species,ROS)伤害的关键酶GPX(谷胱甘肽过氧化物酶)基因,命名为BnGPX1(GenBank登录号:HM 130680).BnGPX1的开放阅读框长度为711bp,推测编码蛋白含有236个氨基酸,分子量为26.10kD,等电点为9.37.BnGPX1酶具有GPX特有的3个结构域及半胱氨酸残基.通过PCR方法克隆得到BnGPX1基因组序列(GenBank登录号:HM130681).该序列与拟南芥AtGPX1基因相似,由6个外显子和5个内含子组成,内含子的剪切位点符合真核生物GT-AG规则.半定量RT-PCR发现BnGPX1在油菜茎、叶

  4. Seyahatnamelerde Hadîs Kültürü: İbn Battûta Örneği Hadith Culture in Travelogues: The Case of Ibn Battuta

    Directory of Open Access Journals (Sweden)

    Yunus MACİT

    2012-09-01

    Full Text Available Books of Travels are one of the most important sources of Islamichistory and religious life; because they have important functions interms of their transport of the historical, geographical and socio-culturalcharacteristics of a certain time to the present day.Travelling is also an important tradition in Islamic culture;because of travelling is a good way to expand the horizons of knowledgeand experience.As it’s known, Ibn Battuta also known as Shams ad-Din (1304–1368 or 1369, was a Berber Muslim Moroccan explorer, known for hisextensive travels, accounts of which were published in the Rihla. Over aperiod of thirty years, he visited most of the known Islamic world as wellas many non-Muslim lands; his journeys including trips to North Africa,West Africa, Southern Europe and Eastern Europe in the West, and tothe Middle East, South Asia, Central Asia, and China in the East, adistance surpassing threefold his near-contemporary Marco Polo.For this reason Ibn Battuta is considered one of thegreatest travelers of all time.As a devout person Ibn Battuta during his travels tried to learn allof the characteristics of religious and religious organizations whereverhe went and established close contacts with religious people andorganizations, also visited sacred-religious authorities and besides gaveplace to the hadith narrations about this places in his book. In histravelogues, which help as to understand the medieval Islamicgeography his time period, as well as information on socio-cultural andeconomical life of Muslim communities, reflections of Muslim civilizationand sunnah and hadiths of Prophet Muhammad to the religious andgeneral public life and religious persons had narrated. For this reason,İbn Battuta’s works are one of the important sources in terms of hadithand sunnah in studies. Seyahatnameler, İslam tarihi ve dini yaşamı açısından en önemli kaynaklar arasındadır. Bu nedensiz değildir; çünkü seyahatnameler, bir d

  5. Approximation of Sums of Experimental Radiative Strength Functions of Dipole Gamma-Transitions in the Region $E_\\gamma \\approx B_n$ for the Atomic Masses $40 \\leq a \\leq 200$

    CERN Document Server

    Sukhovoj, A M; Khitrov, V A

    2008-01-01

    The sums k(E1)+k(M1) of radiative strength functions of dipole primary gamma-transitions were approximated with high precision in the energy region of $0.5 < E_1 < B_n-0.5$ MeV for nuclei: 40K, 60Co, 71,74Ge, 80Br, 114Cd, 118Sn, 124,125Te, 128I, 137,138,139Ba, 140La, 150Sm, 156,158Gd, 160Tb, 163,164,165Dy, 166Ho, 168Er, 170Tm, 174Yb, 176,177Lu, 181Hf, 182Ta, 183,184,185,187W, 188,190,191,193Os, 192Ir, 196Pt, 198Au, 200Hg by sum of two independent functions. It has been shown that this parameter of gamma-decay are determined by the structure of the decaying and excited levels, at least, up to the neutron binding energy.

  6. Theoretical study of electronic and tribological properties of h-BNC2/graphene, h-BNC2/h-BN and h-BNC2/h-BNC2 bilayers.

    Science.gov (United States)

    Ansari, Narjes; Nazari, Fariba; Illas, Francesc

    2015-05-21

    Density functional theory based methods are used to investigate the interlayer sliding energy landscape (ISEL), binding energy and interlayer spacing between h-BNC2/graphene (I), h-BNC2/h-BN (II) and h-BNC2/h-BNC2 (III) bilayer structures for three, six and fourteen different stacking patterns, respectively. Our results show that, in the studied cases, increasing the atomic variety of the ingredient monolayers leads to an ISEL corrugation increase as well. For the studied bilayers the ISEL is obtained by means of the registry index. For sufficiently large flakes of h-BNC2 on graphene sheets with the largest incommensurability and the least monolayer anisotropy, a robust superlubricity occurs regardless of the relative interlayer orientation. On the other hand, for the h-BNC2/h-BNC2 bilayer exhibiting the least incommensurability and the most monolayer anisotropy, the occurrence of robust superlubricity depends on the relative interlayer orientation.

  7. European offshore wind power in 2015: record €13bn investment, 3 GW new capacity; La eólica marina europea en 2015: record de inversión 13.000 M€, 3 GW de nueva potencia

    Energy Technology Data Exchange (ETDEWEB)

    NONE

    2016-07-01

    Offshore wind investments in Europe doubled in 2015 to €13.3bn in a record year for financing and gridconnected installations. A total of 3,019 MW in new offshore wind capacity came online in European waters in 2015, more than double the capacity connected to the grid in 2014. Europe’s total offshore wind capacity now stands at 11,027 MW. A further 3,034 MW of capacity, spread across ten projects, reached final investment decision last year, a twofold increase on 2014. These are some of the main figures contained in “The European offshore wind industry - key trends and statistics 2015”, a report published by EWEA. (Author)

  8. Synthesis, Structure, and Isomerization of Alkoxycarbonyl(chloro)(cyano)rhodium(III) Complexes, mer-[RhCl(CO2R)(CN)(PMe3)3] (R = Me, Et, nPr, iPr, nBu, and Bn), through C–C Bond Cleavage of Cyanoformates

    National Research Council Canada - National Science Library

    Okuda, Yasuhiro; Okamoto, Takeru; Yamamoto, Arisa; Li, Jing; Nakajima, Kiyohiko; Nishihara, Yasushi

    2014-01-01

    Alkoxycarbonyl(chloro)(cyano)rhodium(III) complexes mer-[RhCl(CO2R)(CN)(PMe3)3] (1: R = Me; 2: R = Et; 3: R = nPr; 4: R = iPr; 5: R = nBu; 6: R = Bn) are prepared via oxidative addition of the corresponding cyanoformates...

  9. Molecular and crystal structures of dialkylated adenines ( N6, N9-Me 2Ade, N3, N6-MeBnAde) and cytosines ( N1, N4-Me 2Cyt)

    Science.gov (United States)

    Krüger, Thomas; Wagner, Christoph; Bruhn, Clemens; Lis, Tadeusz; Steinborn, Dirk

    2008-11-01

    N6, N9-Dimethyladenine ( N6, N9-Me 2Ade, 1) and N1, N4-dimethylcytosine ( N1, N4-Me 2Cyt, 3) were obtained by conventional methods, whereas the reaction of N6-benzyladenine with MeI/NaOH resulted in the formation of N3, N6-MeBnAde ( 2a) and N6, N9-BnMeAde ( 2b). All compounds were fully characterized by microanalysis, NMR spectroscopy ( 1H, 13C) and 1, 2a·2MeOH and 3 also by single-crystal X-ray diffraction analyses. In single-crystals of 1, obtained from THF solutions, twofold N6-H···N7' hydrogen-bonded dimeric units ( N6, N9-Me 2Ade) 2 (AA1 2 type according to Jeffrey and Saenger, 1991) were found. This proved to be another modification than that obtained by crystallization N6, N9-Me 2Ade from MeOH/PhCl (Sternglanz, 1978). Crystals of 2a·2MeOH exhibited an analogous hydrogen bond pattern as found in 1. The shorter N6···N7' distance in 2a·2MeOH (2.932(2) Å) indicates slightly stronger hydrogen bonds than in 1 (3.078(3) Å). Crystals of 3 are built up from centrosymmetric dimers ( N1, N4-Me 2Cyt) 2 having a twofold N4-H···N3' hydrogen bond, thus exhibiting the CC3 2 hydrogen bond pattern. The hydrogen bonding patterns in the dialkylated nucleobase derivatives are discussed in terms of those found in crystals of the less substituted nucleobases N9-MeAde and Cyt/ N1-MeCyt, respectively.

  10. 76 FR 15820 - Airworthiness Directives; B-N Group Ltd. Model BN-2, BN-2A, BN-2A-2, BN-2A-3, BN-2A-6, BN-2A-8...

    Science.gov (United States)

    2011-03-22

    ... power and responsibilities among the various levels of government. For the reasons discussed above, I... following Britten-Norman Ltd. Drawing NB-31-235, Issue 13; Britten-Norman Ltd. Drawing NB-31-873, Issue 2; or Britten-Norman Ltd. Drawing NB-0906, Issue 3, as applicable to airplane models. (ii) If...

  11. 75 FR 79990 - Airworthiness Directives; B-N Group Ltd. Model BN-2, BN-2A, BN-2A-2, BN-2A-3, BN-2A-6, BN-2A-8...

    Science.gov (United States)

    2010-12-21

    ... February 24, 2009; Drawing NB-31-235, Issue 13; Drawing NB-31-873, Issue 2; and Drawing NB-31-0906, Issue 3..., or on the distribution of power and responsibilities among the various levels of government. For the... tip following Britten-Norman Ltd. Drawing NB-31-235, Issue 13; Britten-Norman Ltd. Drawing...

  12. 碳纤维表面h-BN耐高温涂层的制备及表征%Preparation and Characterization of h-BN High-temperature Resistant Coating on the Surface of Carbon Fibers

    Institute of Scientific and Technical Information of China (English)

    龙国宁; 黄小忠; 陈金

    2015-01-01

    Objective Hexagonal boron nitride coatings were prepared on carbon fiber surface, in order to improve the oxidation resistance and high temperature resistant performance of the fiber, so as to broaden its application in the field of high temperature. Methods With boric acid, urea, ammonia and nitrogen gas as raw materials, a mixture of boric acid and urea solution was coated on the carbon fiber surface through impregnating method, and the coating was then placed in the ammonia and nitrogen atmosphere for high temperature pyrolysis. The morphology of the coating was observed by electronic microscope analysis to check whether the coating was well bonded with the carbon fiber. Fourier infrared spectra, X ray electronic energy spectrum and X-ray diffraction ( XRD) were used to characterize the composition and structure of the coating. Results The coating on the surface of the carbon fi-ber was continuous and had good appearance. In the infrared spectrum, B—N key and B—N—B key characteristic peaks occurred at 1399, 799 cm-1 . In the X-ray diffraction pattern, (001) crystal plane and (004) crystal plane characteristic peaks of hexagonal boron nitride appeared at 43. 64. and 53. 93., respectively. X-ray photoelectron analysis showed the existence of the four elements of O, B, C and N, and a B/N atom ratio of close to 1:1. Conclusion H-BN coated carbon fiber was successfully prepared, and the coating was well bonded with the carbon fiber. The h-BN in the coating had good crystallinity and high purity, but the existence of a small amount of oxide had influence on the thermostability improvement of h-BN coated carbon fiber. More works have to be done to study how to further improve the purity of h-BN coatings.%目的:在碳纤维表面制备六方氮化硼涂层,以提高纤维的抗氧化、耐高温性能,拓宽其在高温领域的应用。方法以硼酸、尿素、氨气和氮气作为原始材料,先通过浸渍法在碳纤维表面涂覆硼酸和尿素的混

  13. 钛合金表面激光熔覆h-BN固体润滑涂层%Solid Self-lubricating Coatings on TC4 Titanium Alloy by Laser Cladding with h-BN

    Institute of Scientific and Technical Information of China (English)

    王培; 叶源盛

    2015-01-01

    目的:优化钛合金激光熔覆固体润滑涂层的熔覆工艺参数,提高钛合金表面耐磨性能。方法采用Nd:YAG激光器,分别在高功率和低功率条件下,在TC4钛合金表面制备h-BN固体自润滑涂层。观察分析熔覆陶瓷层的宏观形貌、物相组成、显微组织和硬度,采用摩擦磨损试验仪对熔覆层的摩擦学性能进行研究。结果低激光功率下,熔覆材料上浮流失严重,熔覆层的相成分主要是TiN,TiB,TiB2等硬质相,硬度较高,存在裂纹。高激光功率下,基材的熔化稀释较好地抑制了润滑相h-BN的上浮,减少了溅射损失,发生了包晶反应,生成了单质金属Ti,熔覆层硬度低,但摩擦磨损试验表明,涂层中润滑相h-BN含量的增加使得形成了更好的润滑膜,降低了摩擦系数。结论在输出电流400 A,脉宽5 ms,频率12 Hz,扫描速度120 mm/min,搭接率50%~60%的条件下进行激光熔覆,所得熔覆层的表面状态平整,耐摩擦性能最好。%ABSTRACT:Objective To optimize the process parameters for laser cladding of solid self-lubricating coatings on titanium alloy, and improve the surface wear resistance of titanium alloy. Methods Using the Nd: YAG laser, h-BN ( hexagonal boron nitride) solid self-lubricating coatings were prepared on the surface of TC4 titanium alloy under conditions of high power and low power, re-spectively. The macro morphology, layer phase composition, microstructure, hardness and wear resistance of the ceramic layer were analyzed, and the tribological property of the ceramic layer was studied using a friction and wear tester. Results At low laser power, there was severe floating loss of cladding material, and the phase composition of the cladding layer was mainly composed of TiN, TiB, TiB2 and other hard phase components, the hardness was relatively high, with the presence of cracks. At high laser power, melting of the substrate inhibited the floating of the lubricating phase h-BN, reducing the

  14. 基于贝叶斯网络的不确定环境装备故障推理模型%Applying BN (Bayesian Network) to Establishing a New and Effective Failure Inference Model of Equipment under Uncertainties

    Institute of Scientific and Technical Information of China (English)

    蔡志强; 司书宾; 孙树栋; 王宁

    2011-01-01

    针对不确定环境下装备故障传播及推理问题,提出了一种基于贝叶斯网络的故障推理模型,利用网络结构与概率分布有效表达装备中各部件故障状态、关联关系及传播方式.首先将模型中变量按照其对应部件在装备中所处地位及层次的差别进一步分为故障检测变量、故障原因变量与故障模式变量三个子集.其次,依据维修人员在故障推理过程中的思维方式,提出了一套符合故障推理任务的模型网络结构有向边取向规则.然后,分析故障推理模型中变量条件概率分布特点,明确其在不确定性表达及参数简化中的优势.最后,建立平视显示器的故障推理模型实例,结合贝叶斯网络推理能力进行故障预测及诊断分析,验证模型的有效性.%Aim. The introduction of the full paper reviews some papers in the open literature and points out what we believe to be their shortcomings; then, it reviews some other papers on successful BN applications; finally, it proposes what we believe to be a new and effective application mentioned in the title. Section 1 explains how we established our failure inference model based on the BN; its core consists of; (1) our failure inference model uses the network topology and the probability distributions to represent the components, relationships and propagations in the equipment; (2 ) we divide the variables into failure detection subset, failure cause subset and failure mode subset according to their levels and causalities in the equipment; ( 3) we put forward the network edge orientation rule based on the maintenance engineers' actual failure reasoning processes; (4) we analyze the conditional probability distributions of the variables in the failure inference model to indicate their advantages for uncertainty representations and parameter reductions. Section 2 does the case study of a head-up display failure inference model; the results , given in Tables 4, 5 and 6

  15. HERSCHEL FAR-INFRARED SPECTRAL-MAPPING OF ORION BN/KL OUTFLOWS: SPATIAL DISTRIBUTION OF EXCITED CO, H{sub 2}O, OH, O, AND C{sup +} IN SHOCKED GAS

    Energy Technology Data Exchange (ETDEWEB)

    Goicoechea, Javier R.; Cernicharo, José; Cuadrado, Sara; Etxaluze, Mireya [Instituto de Ciencia de Materiales de Madrid (ICMM-CSIC). Sor Juana Ines de la Cruz 3, E-28049 Cantoblanco, Madrid (Spain); Chavarría, Luis [Centro de Astrobiología, CSIC-INTA, Ctra. de Torrejón a Ajalvir km 4, E-28850 Madrid (Spain); Neufeld, David A. [Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218 (United States); Vavrek, Roland [Herschel Science Center, ESA/ESAC, P.O. Box 78, Villanueva de la Cañada, E-28691 Madrid (Spain); Bergin, Edwin A. [Department of Astronomy, University of Michigan, 500 Church Street, Ann Arbor, MI 48109 (United States); Encrenaz, Pierre [LERMA, UMR 8112 du CNRS, Observatoire de Paris, École Normale Supérieure, F-75014 Paris (France); Melnick, Gary J. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, MS 66, Cambridge, MA 02138 (United States); Polehampton, Edward, E-mail: jr.goicoechea@icmm.csic.es [RAL Space, Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire OX11 0QX (United Kingdom)

    2015-01-20

    We present ∼2' × 2' spectral-maps of Orion Becklin-Neugebauer/Kleinmann-Low (BN/KL) outflows taken with Herschel at ∼12'' resolution. For the first time in the far-IR domain, we spatially resolve the emission associated with the bright H{sub 2} shocked regions ''Peak 1'' and ''Peak 2'' from that of the hot core and ambient cloud. We analyze the ∼54-310 μm spectra taken with the PACS and SPIRE spectrometers. More than 100 lines are detected, most of them rotationally excited lines of {sup 12}CO (up to J = 48-47), H{sub 2}O, OH, {sup 13}CO, and HCN. Peaks 1/2 are characterized by a very high L(CO)/L {sub FIR} ≈ 5 × 10{sup –3} ratio and a plethora of far-IR H{sub 2}O emission lines. The high-J CO and OH lines are a factor of ≈2 brighter toward Peak 1 whereas several excited H{sub 2}O lines are ≲50% brighter toward Peak 2. Most of the CO column density arises from T {sub k} ∼ 200-500 K gas that we associate with low-velocity shocks that fail to sputter grain ice mantles and show a maximum gas-phase H{sub 2}O/CO ≲ 10{sup –2} abundance ratio. In addition, the very excited CO (J > 35) and H{sub 2}O lines reveal a hotter gas component (T {sub k} ∼ 2500 K) from faster (v {sub S} > 25 km s{sup –1}) shocks that are able to sputter the frozen-out H{sub 2}O and lead to high H{sub 2}O/CO ≳ 1 abundance ratios. The H{sub 2}O and OH luminosities cannot be reproduced by shock models that assume high (undepleted) abundances of atomic oxygen in the preshock gas and/or neglect the presence of UV radiation in the postshock gas. Although massive outflows are a common feature in other massive star-forming cores, Orion BN/KL seems more peculiar because of its higher molecular luminosities and strong outflows caused by a recent explosive event.

  16. 按照CLSI EP15-A指南验证BN Prospec特定蛋白仪测定免疫球蛋白的精密度和正确度

    Institute of Scientific and Technical Information of China (English)

    莫扬

    2012-01-01

    目的 利用CLSI EP15-A指南对德灵公司生产的BN Prospec特定蛋白仪测定免疫球蛋白IgG,IgA和IgM的精密度和正确度进行验证.方法 精密度验证试验对2个不同水平的质控品每个每天测定3次,共测定5天,分别计算其批内不精密度和天间不精密度,然后与厂家声明的不精密度进行比较,若小于厂家声明的不精密度则认为该仪器的精密度符合厂家声明的精密度;正确度验证试验使用卫生部临检中心发放的室间质控品作为参考物质,对2个不同水平的室间质控品5天内每个每批测定2次求均值,计算相对偏倚.若相对偏倚在参考物质允许的偏倚范围内,结果为可接受.结果 BNProspec特定蛋白仪测定免疫球蛋白IgG,IgA和IgM的批内和天间不精密度均达到厂家声明的不精密度.2个室间质控品的测定结果与靶值的相对偏倚均小于卫生部临床检验中心室间质评的允许偏倚范围内.结论 BN Prospec特定蛋白仪测定免疫球蛋白IgG,IgA和IgM的精密度和正确度达到厂家声明的性能.

  17. In situ synchrotron X-ray diffraction experiments on Al-15%BN mechanically alloyed powder: Observation of AlN nanoparticles precipitation and enhanced thermal stability of nanostructured Al matrix

    Energy Technology Data Exchange (ETDEWEB)

    Lonardelli, I., E-mail: ivan.lonardelli@ing.unitn.i [Department of Materials Engineering and Industrial Technologies, University of Trento, Via Mesiano 77, Trento 38050 (Italy); Zadra, M.; Ischia, G. [Department of Materials Engineering and Industrial Technologies, University of Trento, Via Mesiano 77, Trento 38050 (Italy); Barreiro, J. Gomez [Earth and Planetary Sciences Dept., University of California at Berkeley, CA 94720 (United States); Department of Geochemistry and Petrology, University of Madrid, Madrid 28040 (Spain); Bortolotti, M.; Molinari, A. [Department of Materials Engineering and Industrial Technologies, University of Trento, Via Mesiano 77, Trento 38050 (Italy)

    2009-11-03

    Two different in situ experiments using high energy X-ray diffraction from synchrotron source were performed in order to understand carefully the phase transformation in nanostructured Al-15%BN mechanically alloyed powder. After milling at room temperature for 10 h, a solid solution of Al, B and N was achieved. During the heating, the formation and the evolution of the metastable trigonal Al{sub 2}B{sub 3} and a very fine precipitation of hexagonal AlN (d < 8 nm) within Al grains were detected quantitatively. We found a stabilization of Al{sub 2}B{sub 3} between 225 deg. C and 550 deg. C and, only around 600 deg. C the hexagonal AlB{sub 2} starts to form. A detectable decreasing of the Al crystallite size between 420 deg. C and 470 deg. C was attributed to the precipitation of AlN nanoparticles that reduce the Al volume fraction and, at the same time, hinder the grain boundary propagation. The powder loses the nanostructure above 600 deg. C exhibiting an exceptional thermal stability at temperatures close to 0.9T{sub m}.

  18. Astrophysical S_{17}(0) factor from a measurement of d(7Be,8B)n reaction at E_{c.m.} = 4.5 MeV

    CERN Document Server

    Das, J J; Sugathan, P; Madhavan, N; Rao, P V M; Jhingan, A; Navin, A; Dhiman, S K; Barua, S; Nath, S; Varughese, T; Sinha, A K; Singh, R; Ray, A; Sastry, D L; Kulkarni, R G; Shyam, R

    2004-01-01

    Angular distribution measurements of d(7Be,7Be)d and d(7Be,8B)n reactions at E_{c.m.} = 4.5 MeV were performed to extract the astrophysical S_{17}(0) factor using the asymptotic normalization coefficient (ANC) method. For this purpose a pure, low emittance 7Be beam was separated from the primary 7Li beam by a recoil mass spectrometer operated in a novel mode. A beam stopper at zero degree allowed the use of a higher 7Be beam intensity. Measurement of the elastic scattering in the entrance channel using kinematic coincidence, facilitated the determination of the optical model parameters needed for the analysis of the transfer data. The present measurements significantly reduces errors in the extracted 7Be(p,gamma) cross section using the ANC method and resulted in S17(0) = 20.7(+-) 1.0 (sys) (+-) 1.4 (stat) eV b. This demonstrates the capability of the ANC method in determining the S-factor of reactions involving short lived nuclei with a precision similar to that of the direct (p,gamma) measurements.

  19. Tweaking subtype-selectivity and agonist efficacy at (S)-2-amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl)propionic acid (AMPA) receptors in a small series of BnTetAMPA analogues

    DEFF Research Database (Denmark)

    Wang, Shuang-Yan; Larsen, Younes; Navarrete, Cristina V.

    2016-01-01

    A series of analogues of the (S)-2-Amino-3-(3-hydroxy-5-methyl-isoxazol-4-yl)propionic acid (AMPA) receptor agonist BnTetAMPA (5b) were synthesized and characterized pharmacologically in radioligand binding assays at native and cloned AMPA receptors and functionally by two-electrode voltage clamp...... electrophysiology at the four homomeric AMPA receptors expressed in Xenopus laevis oocytes. The analogues 6 and 7 exhibit very different pharmacological profiles with binding affinity preference for the subtypes GluA1 and GluA3, respectively. X-ray crystal structures of three ligands (6, 7, and 8) in complex...... with the agonist binding domain (ABD) of GluA2 show that they induce full domain closure despite their low agonist efficacies. Trp767 in GluA2 ABD could be an important determinant for partial agonism of this compound series at AMPA receptors, since agonist efficacy also correlated with the location of the Trp767...

  20. 二维石墨烯/h-BN异质结构负热膨胀性质的理论研究%Theoretical Study of Negative Thermal Expansion in 2D Graphene/h-BN Heterostructure

    Institute of Scientific and Technical Information of China (English)

    武明义; 孙强; 贾瑜; 梁二军

    2015-01-01

    二维材料由于存在“膜效应”,即在垂直于薄膜方向的热涨落,使得沿着二维薄膜面内方向出现反常的负热膨胀现象.这种热效应对薄膜的稳定性及电子性质可产生重要影响.基于第一性原理计算和准谐近似,系统地研究了二维单层石墨烯、h-BN和石墨烯/h-BN异质结构的电子、声子以及热膨胀性质,计算了3种结构不同振动模式的格林奈森参数,讨论了引起这3种结构负热膨胀的振动模式.计算表明,由于垂直薄膜方向的热振动,石墨烯和h-BN在薄膜面内均具有较大的负热膨胀系数;它们形成的异质结构依靠弱的范德瓦尔斯相互作用结合在一起,这种层间弱相互作用对薄膜垂直方向的热振动产生影响,使得形成的异质结构的负膨胀系数介于石墨烯和h-BN之间.通过分析异质结构的振动模式,发现引起面内热收缩的ZA振动模式受到了层间范德瓦尔斯相互作用影响,导致异质结构的负热膨胀系数大于石墨烯而小于h-BN.研究表明,可以在实验中通过范德瓦尔斯相互作用来改变层状结构材料的负热膨胀性质,从而提高薄膜材料结构和电子性质的热稳定性.

  1. CD105shRNA对激光诱导的脉络膜新生血管的干预作用及其机制%The Effects of CD 105 Gene Silencing to Experimental Choroidal Neovascularization in BN Rats

    Institute of Scientific and Technical Information of China (English)

    屈超义; 唐罗生; 曾杰西; 罗静; 陈百华; 魏为

    2011-01-01

    目的:观察CD105shRNA对激光诱导的大鼠脉络膜新生血管的抑制作用,并初步探讨其作用机制.方法:40只BN大鼠单眼采用半导体激光建立CNV模型.随机取20只大鼠于建模后1天使用Pgenesil-eng2转染大鼠视网膜和脉络膜作为实验组.在建模后第14天行FFA检查,观察实验组与对照组视网膜激光斑的渗漏情况.各取5只实验组和5只对照组大鼠,行脉络膜铺片,检测并比较脉络膜新生血管渗漏面积.另32只BN大鼠任取一眼建立CNV模型,其中任取20只大鼠于建模后次日进行Pgenesil-eng2转染,作为实验组.12只建模眼作为对照组,未建模眼作为空白时照组.于基因转染后1w,2w,3w和4w各取5只实验组大鼠和3只对照组大鼠眼球,获取每个时间点实验组、对照组和空白对照组的脉络膜组织.检测各组每个时间点CD105和VEGF在mRNA水平的表达.结果:FFA显示光凝后第14天时,对照组的渗漏率为63.2%,实验组为24.6%.实验组的BN大鼠眼底渗漏点数较对照组少,渗漏强度较弱.两组间比较有显著性差异.脉络膜铺片结果显示:2周时对照组大鼠的CNV面积为(31.22±1.46)x 103μm2,实验组大鼠的CNV渗漏面积为(14.46±0.82)× 103μm2,两组间比较有显著性差异.RT-PCR结果显示:实验组VEGF mRNA及CD105 mRNA的表达变化规律与对照组相似,但各个时间点的表达量较对照组均明显下降,其中实验组VEGF mRNA于2w时的表达约为对照组的36.7%;实验组CD105 mRNA在第2w时约为对照组的21.68%.结论:通过沉默CD105基因的表达可以抑制大鼠CNV的生成,下调VEGF的表达可能是其作用机制之一.CD105基因有望成为CNV的基础研究热点和临床治疗的新靶点.%Objective: To investigate the effect of CD 105 gene silencing on BN rat CNV model. Methods: The effective CD105 shRNA express plasmid was transinfected into BN rat CNV model by subretina injection. The result of CD 105 gene silencing to CNV model

  2. 氮化硼纳米管增强氮化硅复合材料的裂纹扩展阻力行为%Crack propagation resistance behavior of Si3N4 composites reinforced by BN nanotubes

    Institute of Scientific and Technical Information of China (English)

    于航海; 王守仁; 杨丽颖

    2012-01-01

    用氮化硼纳米管(BNNT)增强氮化硅(Si3N4)陶瓷制备了BNNT/Si3N4复合材料,利用三点弯曲强度及单边切口梁(SENB)法测定了BNNT/Si3N4复合材料的弯曲强度和断裂韧性。通过SEM观察了BNNT/Si3N4复合材料微观形貌。基于BNNT增强Si3N4陶瓷复合材料的裂纹扩展阻力计算公式,构建了BNNT对Si3N4陶瓷裂纹屏蔽区的裂纹扩展阻力的数学模型。用该模型的计算结果与Si3N4陶瓷的裂纹扩展阻力进行了对比。结果表明:BNNT/Si3N4复合材料的弯曲强度和断裂韧性明显高于Si3N4陶瓷,说明BNNT对Si3N4陶瓷的裂纹扩展有阻力作用,摩擦拔出是Si3N4陶瓷抗裂纹扩展能力提高的主要原因;BNNT对Si3N4陶瓷有明显的升值阻力曲线行为。通过有限元模拟裂纹尖端应力分布,发现BNNT使Si3N4陶瓷裂纹尖端的最大应力转移到纳米管上,而且BNNT降低了Si3N4陶瓷裂纹尖端的应力,对Si3N4陶瓷尖端的裂纹有屏蔽作用,从而提高了Si3N4陶瓷的裂纹扩展阻力。%BNNT/Si3N4 composites were prepared with Si3N4 ceramics enhanced by BN nanotubes (BNNT). Bending strength and fracture toughness of BNNT/Si3 N4 composites were tested by three point bending strength and SENB method. BNNT/Si3N4 composite microstructures were observed by SEM. The mathematical model of the crack propagation resistance of Si3N4 ceramics crack shielding region enhanced by BNNT was constructed, which was based on the crack propagation resistance formula of BNNT reinforcing Si3N4 ceramics. The calculated results used this model were compared with crack propagation resistance of Si3 N4 ceramics. The results show that bending strength and fracture toughness of BNNT/Si3 N4 composites are obviously higher than those of pure Si3 N4 ceramics and BNNT increases the crack propagation resistance of Si3 N4 ceramics. It can be seen that the friction resistance to pull out is the main reason of reducing the Si3 N4

  3. مقدمة ابن المقفع ل ( كليلة و دمنة : مستويات القارئ / İBN MUKAFFA’NIN (KELİLE VE DİMNE MUKADDİMESİ: OKUYUCU DÜZEYLERİ

    Directory of Open Access Journals (Sweden)

    Walat Mohamad

    2015-01-01

    Full Text Available Bu çalışma, İbn Mukaffâ’nın (Kelime ve Dimne adlı eserinin mukaddimesindeki okuyucu seviyelerini incelemektedir. Bu eserin mukaddimesi, önceki mukaddimelerin aksine, kitabın içeriği ya da müellifine değil, okuyucunun seviyesine yoğunlaşır. İbn Mukaffâ, Kelime ve Dimne okuyucularına farklı seviyeler sunmuştur:  Hayvan resimleriyle eğlence arayanlar, yüzeysel anlamla yetinenler ve anlamda derinlik arayanlar vs. Böylece bu hikâyeler okuyucularına, gerçekleşmesi muhtemel şeyleri düşündürür ve eserdeki sembolleri açıklamaksızın onlara çözümler önerir. Bu çalışma, İbn Mukaffâ’nın bu sembol ve işaretleri açıklamamasının sebeplerini ve okuyucunun bu hikâyelerdeki derin manaları anlamak için şiddetli isteğine rağmen, bu işi neden okuyucuya bıraktığını analiz eder. Bu çalışma, İbn Mukaffâ’nın Kelile ve Dimne hikâyelerini ya da en azından onlardan bazılarını yazdığını iddia eden Arap araştırmacıların bu görüşlerini bir araya getirir. Bu makale İbn Mukaffâ’nın okuyucuya, Kelile ve Dimne hikâyelerini nasıl okuyacaklarını ve yapılması gerekenleri mukaddimede empoze ettiğini açıklayan bir çalışmadır.

  4. Tribochemical Behavior of Si3N4-hBN Ceramic Materials with Water Lubrication%Si3N4与Si3N4-hBN陶瓷配副在水润滑下的摩擦化学行为

    Institute of Scientific and Technical Information of China (English)

    陈威; 高义民; 居发亮; 汪勇

    2009-01-01

    利用MMU-5G销-盘式端面磨损试验机考察了蒸馏水润滑条件下Si3N4-hBN(六方氮化硼)复合陶瓷与Si3N4陶瓷配副时的摩擦磨损性能,并分别采用扫描电子显微镜、激光扫描显微镜、X光电子能谱和X射线能谱分析了摩擦面的形貌和物质组成.结果表明:在滴定法水润滑条件下,Si3N4-hBN/Si3N4配副的摩擦因数随hBN含量的增加而显著降低,当hBN体积分数为20%时,摩擦因数降至0.01,Si3N4-hBN的磨损率接近0;在浸入法水润滑条件下,Si3N4-hBN/Si3N4配副的摩擦因数均降至0.01.在滴定法水润滑条件下,磨屑不易被水带走,当Si3N4-hBN与Si3N4配副摩擦时,由于Si3N4-hBN摩擦面上hBN偏聚区域发生脆性断裂和剥落而形成剥落坑,磨屑在剥落坑中堆积并氧化、水解,反应产物富集于剥落坑中,进而在摩擦表面形成含B2O3和SiO2的摩擦化学反应膜,从而保护了Si3N4-hBN和Si3N4摩擦面,使其变得光滑,为发生流体润滑提供了条件.

  5. Determination of the Influence of c-BN+h-BN Coating Structure on Brittleness

    Institute of Scientific and Technical Information of China (English)

    Maciej Kupczyk; Adam Lejwoda; Przemyslaw Cieszkowski; Przemyslaw Libuda

    2004-01-01

    In the article is presented the brittleness study of boron nitride coatings deposited on cutting edges made of cemented carbides by the pulse-plasma method (PPD). Influences of the structure (density, pores, microcracks) of coating material on the brittleness and on selected technological parameters of boron nitride formation by PPD method particularly taking into account discharge voltage on brittleness are shown. Differences between values of both a1(300) and a1(500)coefficients characterized susceptibility to coatings cracking of investigated coating manufactured using different values of discharge voltage were defined. Results of an investigations have been confirmed usefulness of Palmqvist's method for measurement of coating susceptibility to brittle cracking.

  6. BN and BN oxide nanosheets based nanosensor for paracetamol adsorption: a first principles simulation

    Directory of Open Access Journals (Sweden)

    Miguel Castro

    2014-04-01

    Full Text Available The effects that the adsorption of the paracetamol molecule produce on the structural and electronic properties of boron nitride (hBNNs; B27N27H18 and boron nitride oxide (hBNONs; B27N27H17 + O + (OH3 + COOH hexagonal symmetry nanosheets were studied by means of Density Functional Theory. The generalized gradient approximation proposed by Heyd—Scuseria—Ernzerhof ((HSEh1PBE―GGA was used in concert with 6-31G(d basis sets. Several candidate structures, 9 and 13 for the hBNNs―Paracetamol and BNONs―Paracetamol interactions, respectively, were used for the geometry optimization procedure. The results show that in the lowest energy absorption site the paracetamol molecule reaches a parallel orientation to the surface of the nanosheets, producing physisorption for hBNNs―Paracetamol and chemisorption for BNONs―Paracetamol. Besides, the adsorption process yields an increase of the polarity opening the possibility for the solubility and dispersion of these compounds. The paracetamol molecule promotes also a decrease of the reactivity parameter, which is crucial for biological applications of these systems. Referred to pristine hBNNs and BNONs, the work functions of hBNNs-Paracetamol and BNONs―Paracetamol are diminished. That is, these functionalized 2D systems yields appropriate conditions for field emission and they may be used as sensors of such pharmaceutical compound.

  7. Study of the reduction in detection limits of track detectors used for {sup 10}B(n,α){sup 7}Li reaction rate measure through annealing and chemical etching experiments; Estudo da reducao nos limites de deteccao de detectores de tracos utilizados na medida de taxa de reacao {sup 10}B(n, α){sup 7}Li atraves de experimentos de annealing e ataque quimico

    Energy Technology Data Exchange (ETDEWEB)

    Vasconcellos, Herminiane L.; Smilgys, Barbara; Guedes, Sandro, E-mail: hluizav@ifi.unicamp.br [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Instituto de Fisica Gleb Wataghin; Castro, Vinicius A. [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Engenharia Nuclear

    2013-08-15

    The Boron Neutron Capture Therapy (BNCT) is an experimental radiotherapy for cancer treatment. It is based on {sup 10}B(n, α){sup 7}Li reaction, which can be measured by track detectors capable of recording events that strike them. With this recording, it is possible to determine the number of alpha particles and recoiling Lithium-7 nucleus, reaction products, and from this information, which amount of radiation dose a patient is exposed to. In this work, PADC detectors were characterized, irradiated at the IEA-R1 IPEN/CNEN reactor to assess the contribution of the{sup 10}B(n, α){sup 7}Li reaction and protons from fast neutron scattering with the elements that compounds the tissue. With the aim of reducing the proton background, the detectors were subjected to heating experiments at 80°C for periods in the range 0-100 hours. This was done in order to restore partially modified structure of the detector, causing a reduction in the size and density of tracks. This effect is known as annealing. For the visualization of tracks at microscope, detectors were made three chemical attacks with sodium hydroxide (NaOH) for 30, 60 and 90 minutes at 70°C. It was observed a reduction in the track density achieving a plateau heating time of 50 hours. For detectors that have not undergone annealing and were etched with another etchant, PEW solution, a reduction of 87% in track density was obtained. (author)

  8. 六方-BN对非晶前驱体制备不含添加剂的Si3N4/SiC复合材料相变的影响%Effect of hexagonal-BN on phase transformation of additive-free Si3N4/SiC nanocomposites prepared from amorphous precursor

    Institute of Scientific and Technical Information of China (English)

    Alfian NOVIYANTO; Dang-Hyok YOON; Kyungseok LEE; Young Moon KIM; Doo-In KIM; Young-Keun JEONG; Kwang Ho KIM; Sehun KWON; Young-Hwan HAN

    2013-01-01

    Si3N4/SiC nanocomposites are well known and attractive for advanced ceramic applications due to excellent mechanical and thermal properties, which make them suitable for use in turbine engines,heat exchangers,and other sophisticated applications.However,without the presence of additives,the fabrication of Si3N4/SiC composites is difficult.The additives form a liquid phase during sintering and facilitate the densification of the composite.However,the additives present a drawback at high temperatures since they decrease the mechanical properties of the composites.Recently,Si3N4/SiC composites were fabricated via the polymer precursor route without any additives,using electric field assisted sintering (EFAS).In this study,fully densified Si3N4/SiC nanocomposites incorporating hexagonal-BN were successfully fabricated by hot pressing without any additives at 1700 ℃ for 2 h under vacuum at a pressure of 50 MPa (via the amorphous precursor route).Moreover,the incorporation of additives and h-BN is found to decrease the content of SiC.The phase transformation,densification,microstructure,and mechanical properties were discussed and presented.%Si3N4/SiC纳米复合材料由于具有优良的力学和热性能,广泛应用于涡轮发动机、热交换器和其他复杂情况中.然而,不添加添加剂很难制备出Si3N4/SiC复合材料.添加剂在烧结过程形成液相从而促进复合材料的致密化.然而,添加剂的存在降低了复合材料的高温力学性能.通常在不添加添加剂的情况下,采用电场辅助烧结,利用聚合物前体路线制备Si3N4/SiC复合材料.本研究中,在无添加剂、温度1700℃、真空50MPa条件下,热压烧结2h,利用非晶前体路线成功制备了六方-BN致密化的Si3N4/SiC复合材料.聚合物前驱体和BN的作用减少了的SiC含量.并对相变、致密化、微观组织和力学性能进行了讨论.

  9. Time-varying pattern of postoperative recurrence risk of early-stage (T1a-T2bN0M0) non-small cell lung cancer (NSCLC): results of a single-center study of 994 Chinese patients.

    Science.gov (United States)

    Zhu, Jian-fei; Feng, Xing-yu; Zhang, Xue-wen; Wen, Ying-sheng; Lin, Peng; Rong, Tie-hua; Cai, Ling; Zhang, Lan-jun

    2014-01-01

    The aim of this study was to analyze the time-varying pattern of recurrence risk of early-stage (T1a-T2bN0M0) non-small cell lung cancer (NSCLC) after surgery using the hazard function and identify patients who might benefit from adjuvant chemotherapy. This retrospective study enrolled 994 patients with early-stage NSCLC who underwent radical surgical resection between January 1999 and October 2009. Survival curves were generated using the Kaplan-Meier method, and the annual recurrence hazard was estimated using the hazard function. The median recurrence-free survival (RFS) was 8.8 years. The life table survival analysis showed that the 1-year, 3-year, 5-year and 10-year recurrence rates were 82.0%, 67.0%, 59.0% and 48.0%, respectively. Approximately 256 (25.7%) patients experienced relapse [locoregional: 32 (3.2%) and distant: 224 (22.5%)], and 162 patients died from cancer. The annual recurrence hazard curve for the entire population showed that the first major recurrence surge reached a maximum 1.6 years after surgery. The curve subsequently declined until reaching a nadir at 7.2 years. A second peak occurred at 8.8 years. An analysis of clinical-pathological factors demonstrated that this double-peaked pattern was present in several subgroups. The presence of a double-peaked pattern indicates that there is a predictable temporal distribution of the recurrence hazard of early-stage NSCLC. The annual recurrence hazard may be an effective method of selecting patients at high risk of recurrence, who may benefit from adjuvant therapy.

  10. İBN ÂBİDİN’İN ÖRF ANLAYIŞI (ŞERHU MANZÛMETİ UKÛDİ RESMİ’L-MÜFTÎ VE NEŞRU’L-ARF FÎ BİNÂİ BA’Dİ’L-AHKÂMİ ALE’L-URF ADLI RİSA

    Directory of Open Access Journals (Sweden)

    ayhan hıra

    2011-06-01

    Full Text Available İslam hukukunun bütün müslümanlar tarafından kabul edilen başlıca kaynakları Kur’an, sünnet, icma ve kıyastır. Doğrudan Allah’ın sözü olduğu için birinci ve en önemli kaynak Kur’an’dır. En önemli diğer kaynak, Hz. Peygamber’in sözlerini, fiillerini ve takrirlerini içeren sünnettir. İcma ve kıyas ikinci derece kaynaklar olarak fakihlerin ittifakını ve akıl yürütme sürecini gösterir. Hanefi hukukçuları bunların dışında istihsan, örf, sahabi kavli, seddi zerayi gibi kaynakları kullanmaktadırlar. Yeni bireysel veya sosyal sorunların çözümünde işe yaradığından ötürü bu kaynaklar içinde örfün önemli bir yeri vardır. Bunun en güzel örneklerinden biri İbn Âbidin tarafından verilmiştir. O, mezhep-örf ilişkisini incelemiş, zamanın değişmesiyle hükümlerin değişmesini mezhebin içinde kalarak açıklamıştır.

  11. The sup 1 sup 0 sup , sup 1 sup 1 B(n, p) sup 1 sup 0 sup , sup 1 sup 1 Be reactions at E sub n =96 MeV 24.50.+g; 25.40.-h; 25.40.Kv; 27.20.+n; Nuclear reaction: 10B(n,p), 11B(n,p), E=96 MeV; Measured sigma(Ep,theta); DWBA calculations; Deduced Gamow-Teller strength; Dipole excitations

    CERN Document Server

    Ringbom, A; Conde, H; Elmgren, K; Olsson, N; Rahm, J; Rönnqvist, T; Jonsson, O; Nilsson, L; Renberg, P U; Tibell, G; Bargholtz, C; Fransson, K; Lindh, K; Tegnér, P E; Thörngren-Engblom, P; Van der Werf, S Y

    2001-01-01

    Double-differential cross sections of the sup 1 sup 0 sup , sup 1 sup 1 B(n, p) sup 1 sup 0 sup , sup 1 sup 1 Be reactions have been measured at 96 MeV in the angular range 0 deg. -30 deg. for excitation energies up to 35 MeV. The spectra have been decomposed into different multipolarities using sample angular distributions calculated within the distorted-wave Born approximation. From the identified Gamow-Teller strength, S subbeta sub sup + values were obtained for sup 1 sup 0 B and sup 1 sup 1 B. At higher excitation energies, the spectra are dominated by L=1 strength in broad distributions with maxima around 22 and 12 MeV in sup 1 sup 0 B and sup 1 sup 1 B, respectively.

  12. H-1 Upgrades (4BW/4BN) (H-1 Upgrades)

    Science.gov (United States)

    2015-12-01

    Nautical Miles R&M - Reliability and Maintainability RM - Reference Model TV-1 - Technical Standards Profile Univ . - Universal H-1 Upgrades December 2015...Speed (kts) 165 165 135 139 139 Payload (Hot Day) (lbs) 3500 lbs 3500 lbs 2500 lbs 6 Wing Stations 4 Universal Under Wing Stations 3429 3429 Weapon...Stations Universal Mounts 6 6 4 4 4 Precision Guided Munitions 16 16 12 16 16 Maneuverability/Agility (G’s) -0.5 to +2.5 -0.5 to +2.5 -0.5 to +2.5 -0.5 to

  13. Operation Resettlement, Fort Chafee, Arkansas. 1st Psyop Bn

    Science.gov (United States)

    1981-01-01

    una de las suaursales de la Ofioina de Seguridad Social ( Social Security) para obtener su nAnero de Seguridad Social . Neaesita este rrumero para...sane ;<>. xrea ie vivienda . haata qut Ud. pueda ser ppoaesadc acne nueVcs allegados a lea E i\\ Ecie prcsesc ectu marohandc Dim, sobce unos...fundener.tales que r.an .T, Primero. - l^a limpieza de las area it: vivienda y ti >ampai req cnsatilidad, nc tires papelec c basuras t

  14. CHAH', KF, EZE2, c. A. AND OLUOHAZ, BN

    African Journals Online (AJOL)

    aerobic bacteria isolated from surgical sites in human and animal patients in Nsukka, southeast. Nigeria. .... CHAH 02221: ANTIMICROBIAL RESISTANCE PROFILE OF SURGICAL WOUND GONTAMINANTS ..... Veterinary Nursing, 2nd ed.

  15. Space traveller to see stars born 13bn years ago

    CERN Multimedia

    Radford, T

    2004-01-01

    British scientists are working on the James Webb telescope, successor to tje Hubble space telescope. A supersensitive camera called Miri - mid infrared instrument - being built by an international team, will be a key part of the European and American instrument (1 page)

  16. Radiation induced luminescence processes in c-BN

    DEFF Research Database (Denmark)

    Trinkler, L.; Berzina, B.; Benabdesselam, M.

    2004-01-01

    Spectral properties of cubic boron nitride have been studied using methods of photoluminescence (PL), X-ray excited luminescence (XL), thermoluminescence (TL) and optically stimulated luminescence. It is found that emission of cubic boron nitride is presented by 4 subbands, their relative yield...

  17. Inelastic scattering at the B K edge of hexagonal BN

    Energy Technology Data Exchange (ETDEWEB)

    Jia, J.J.; Callcott, T.A.; Zhou, L. [Univ. of Tennessee, Knoxville, TN (United States)] [and others

    1997-04-01

    Many recent soft x-ray fluorescence (SXF) studies have shown that inelastic scattering processes make important contributions to the observed spectra for excitation near the x-ray threshold. These effects are all attributed to a process, usually called an electronic Raman scattering (ERS) process, in which energy is lost to an electronic excitation. The theory has been described using second order perturbation theory by Tulkki and Aberg. In different materials, the detailed nature of the electronic excitation producing the energy loss may be very different. In crystalline Si, diamond and graphite, changes in spectral shape and dispersion of spectral features with variation of the excitation energy are observed, which are attributed to k conservation between the photoelectron generated in the excitation process and the valence hole remaining after the coupled emission process. Hence the process is strongly localized in k-space. In haxagonal boron nitride, which has a lattice and band structure very similar to graphite, inelastic scattering produces very different effects on the observed spectra. Here, the inelastic losses are coupled to a strong resonant elastic scattering process, in which the intermediate state is a localized core exciton and the final state is a localized valence exciton, so that the electronic excitation is strongly localized in real rather than reciprocal space.

  18. Descenso de los niveles de propéptido natriurético de tipo B-N terminal luego de la reversión de pacientes con fibrilación auricular y función ventricular conservada NT-Pro-BNP levels performance before and after reversion to sinus rhythm in patients with preserved ventricular function

    Directory of Open Access Journals (Sweden)

    Claudio Higa

    2011-04-01

    Full Text Available El objetivo fue comparar los niveles de Pro Péptido Natriurético tipo B-N terminal (Pro-BNP-NT basales y post reversión en pacientes con fibrilación auricular solitaria (FAS de comienzo reciente y con función ventricular izquierda conservada. Se determinaron niveles del Pro BNP NT antes y después de su reversión en treinta pacientes con FAS de comienzo reciente y fracción de eyección de ventrículo izquierdo ≥ 50%. Basalmente, los niveles de Pro BNP NT fueron significativamente más elevados respecto a un grupo control sano: 529 pg/ml (157-1763 versus 31.5 pg/ml (24-76, p Our objective was to evaluate changes of N-terminal pro-BNP (NT-Pro-BNP levels at baseline and after restoration to sinus rhythm in hemodynamic stable patients with lone atrial fibrillation (LAF with preserved left ventricular function. NT-Pro-BNP levels were obtained before and after cardioversion in thirty hemodynamic stable patients with LAF and preserved left ventricular function. At baseline levels of NT-Pro BNP levels were significatively higher than a normal control group. NTPro-BNP levels decreased significantly following cardioversion from 529 (157-1763 to 318 (98-870 pg/ml, p < 0.0001. Decreasing of N-terminal pro-BNP concentrations was observed after any mode of cardioversion: electrical or pharmacologic, 345 (153-1151 pg/ml to 169 (86-407 pg/ml, p: 0.02 and from 1624 (541-4010 pg/ml to 856 (532-1160 pg/ml, p < 0.001, respectively. N-terminal pro-BNP decreasing was observed mainly in patients with length of LAF longer than 8 hours: 1289 (338-2103 to 410 (169-905 pg/ml, p < 0.001 but no difference was detected when such length was less than 8 hours: 274 (137-2300 to 286 (82-1440, p = NS. Our study showed that baseline levels of NT-pro-BNP decreased shortly after reversion of patients with LAF to sinus rhythm. This performance occurs predominantly in patients with LAF length of at least eight hours.

  19. Descenso de los niveles de propéptido natriurético de tipo B-N terminal luego de la reversión de pacientes con fibrilación auricular y función ventricular conservada

    Directory of Open Access Journals (Sweden)

    Claudio Higa

    2011-04-01

    Full Text Available El objetivo fue comparar los niveles de Pro Péptido Natriurético tipo B-N terminal (Pro-BNP-NT basales y post reversión en pacientes con fibrilación auricular solitaria (FAS de comienzo reciente y con función ventricular izquierda conservada. Se determinaron niveles del Pro BNP NT antes y después de su reversión en treinta pacientes con FAS de comienzo reciente y fracción de eyección de ventrículo izquierdo ≥ 50%. Basalmente, los niveles de Pro BNP NT fueron significativamente más elevados respecto a un grupo control sano: 529 pg/ml (157-1763 versus 31.5 pg/ml (24-76, p < 0.0001. Las concentraciones de Pro BNP NT descendieron significativamente luego de la cardioversión de 529 (157-1763 a 318 (98-870 pg/ml, p < 0.001. Los descensos se objetivaron tanto luego de la cardioversión eléctrica como de la obtenida por vía farmacológica, 345 (153-1151 pg/ml a 169 (86-407 pg/ml, p: 0.02 y de 1624 (541-4010 pg/ml a 856 (532-1160 pg/ml, p < 0.001, respectivamente. Este fenómeno se observó fundamentalmente en aquellos con una FAS con duración mayor a 8 horas: 1289 (338-2103 a 410 (169-905 pg/ml, p < 0.001. No se observó correlación entre los cambios de la frecuencia cardíaca y del Pro BNP NT pre y post cardioversión a ritmo sinusal. Se observaron descensos significativos de Pro BNP NT basalmente y post reversión (tanto farmacológica como eléctrica en pacientes con FA de reciente aparición y función ventricular conservada. Estos descensos fueron más ostensibles a partir de las 8 horas de duración de la arritmia.

  20. Suppression of 1/f noise in near-ballistic h-BN-graphene-h-BN heterostructure field-effect transistors

    Energy Technology Data Exchange (ETDEWEB)

    Stolyarov, Maxim A.; Liu, Guanxiong; Balandin, Alexander A., E-mail: balandin@ee.ucr.edu [Nano-Device Laboratory (NDL) and Phonon Optimized Engineered Materials (POEM) Center, Department of Electrical and Computer Engineering, Bourns College of Engineering, University of California – Riverside, Riverside, California 92521 (United States); Rumyantsev, Sergey L. [Departments of Electrical, Computer and Systems Engineering and Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States); Ioffe Physical-Technical Institute, Russian Academy of Sciences, St. Petersburg 194021 (Russian Federation); Shur, Michael [Departments of Electrical, Computer and Systems Engineering and Physics, Applied Physics, and Astronomy, Rensselaer Polytechnic Institute, Troy, New York 12180 (United States)

    2015-07-13

    We have investigated low-frequency 1/f noise in the boron nitride–graphene–boron nitride heterostructure field-effect transistors on Si/SiO{sub 2} substrates (f is a frequency). The device channel was implemented with a single layer graphene encased between two layers of hexagonal boron nitride. The transistors had the charge carrier mobility in the range from ∼30 000 to ∼36 000 cm{sup 2}/Vs at room temperature. It was established that the noise spectral density normalized to the channel area in such devices can be suppressed to ∼5 × 10{sup −9 }μm{sup 2 }Hz{sup −1}, which is a factor of ×5 – ×10 lower than that in non-encapsulated graphene devices on Si/SiO{sub 2}. The physical mechanism of noise suppression was attributed to screening of the charge carriers in the channel from traps in SiO{sub 2} gate dielectric and surface defects. The obtained results are important for the electronic and optoelectronic applications of graphene.

  1. Influence of Heat Treatment Temperature on the Structure and Electrochemical Performance of Asphaltene-Based B/N Co-Doped Porous Carbons%热处理温度对沥青基硼氮共掺杂多孔炭结构与电化学性能的影响

    Institute of Scientific and Technical Information of China (English)

    周颖; 王道龙; 肖南; 侯雨辰; 邱介山

    2014-01-01

    B/N co-doped porous carbons have been synthesized by heat treatment at different temperatures using asphaltene from coal liquefaction residue as a carbon precursor, nitric acid as a nitrogen source, H3BO3 as a boron source and a pore-forming agent. The influence of the heat treatment temperature on the pore-structure and surface chemical properties was investigated, and the electrochemical performance in relation to the pore-structure and surface chemical properties was discussed. The crystal structure, morphology, pore-structure, composition and electrochemical performance were examined using X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), transmission electron microscopy (TEM), nitrogen adsorption, element analysis, inductively coupled plasma-atomic emission spectroscopy (ICP-AES), X-ray photoelectron spectroscopy (XPS), and an electrochemical workstation. The results of these analyses indicated that the crystal structure, pore-structure and surface properties were influenced significantly by the heat treatment process. Increases in the heat treatment temperature led to improvements in the degree of graphitization, as wel as gradual increases in the boron content. In contrast, the nitrogen content decreased and the specific surface area and total pore volume increases gradual y and then decline. The electrochemical performance was found to be dependent on the pore-structure and suitable surface chemical properties. The sample synthesized at 900 °C had a specific surface area of 1103 m2∙g-1, pore volume of 0.921 cm3∙g-1, nitrogen content of 5.256%(w), boron content of 1.703%(w), and a maximal specific capacitance of 349 F∙g-1 at 100 mA∙g-1 in 6 mol∙L-1 aqueous solution of KOH. The sample subjected to a heat treatment at 1000 °C had the best rate capability, with a capacity retention of 75%when the current density increased from 100 mA∙g-1 to 10 A∙g-1.%以煤液化沥青质为碳源、硝酸为氮源、硼酸为

  2. Effects of hydrogen adsorption on the properties of double wall BN and (BN){sub x}C{sub y} nanotubes

    Energy Technology Data Exchange (ETDEWEB)

    Freitas, A. [Departamento de Física, Universidade Federal da Paraíba, Caixa Postal 5008, 58059-900 João Pessoa, PB (Brazil); Azevedo, S., E-mail: sazevedo@fisica.ufpb.br [Departamento de Física, Universidade Federal da Paraíba, Caixa Postal 5008, 58059-900 João Pessoa, PB (Brazil); Kaschny, J.R. [Instituto Federal da Bahia – Campus Vitoria da Conquista, Avenida Amazonas 3150, 45030-220 Vitória da Conquista, BA (Brazil)

    2016-01-15

    In the present contribution, we apply first-principles calculations, based on the density functional theory, to study the effects of hydrogen adsorption on the structural and electronic properties of boron nitride and hybrid carbon–boron nitride double wall nanotubes. The results demonstrate that the hydrogen decoration induces significant structural deformation and an appreciable reduction in the gap energy. When the number of hydrogen atoms introduced on the outer wall is increased, desorption of hydrogen pairs are observed. The calculations indicate that each adsorbed hydrogen atom induces a structural deformation with an energetic cost of about 68 meV/atom. It is also found that the introduction of hydrogen atoms can be applied as an efficient tool for tuning the electronic properties of such structures. - Graphical abstract: Localized density of states of a hydrogenated double wall boron nitride nanotube. Some hydrogen pairs are desorbed, forming H{sub 2} molecules. - Highlights: • Hydrogenation induces structural deformation and reduction in the gap energy. • Each H atom induces a deformation with an energetic cost of about 68 meV/atom. • In some cases, desorption of H pairs from the outer wall is observed.

  3. Tool life of the edges coated with the c-BN+h-BN coatings with different structures during hard machinable steel machining

    Directory of Open Access Journals (Sweden)

    Kupczyk, M.

    2005-12-01

    Full Text Available In the presented paper the experimental results concerning the functional quality (durability during steel machining of thin, superhard coatings produced on the cutting edges are described. Differences among mentioned properties of coatings mainly result from a coating structure. But the structure of coatings results from deposition parameters Superhard boron nitride coatings were deposited on insert cutting edges made of cemented carbides by the pulse-plasma method applying different values of the discharge voltage. The comparative investigations of mentioned coatings have been concerned of tool life of edges during hard machinable material machining (nitriding steel hardened in oil. In these investigations for the purpose of additional increase of coatings adhesion to substrates an interfacial layers were applied.

    En este trabajo se describen los resultados experimentales referentes a la calidad funcional (durabilidad durante el mecanizado del acero de recubrimientos delgados, de elevada dureza del filo de corte. Las diferencias en las propiedades de los recubrimientos se deben, principalmente, a la estructura del recubrimiento. No obstante, la estructura del recubrimiento está relacionada con los parámetros de la deposición. Recubrimientos de nitruro de boro de elevada dureza se depositaron sobre filos de corte insertados, fabricados con carburos cementados mediante el método de pulsos de plasma aplicando diferentes valores de voltaje de descarga. Las investigaciones comparativas de los mencionados recubrimientos han relacionado la vida del filo de la herramienta durante el mecanizado del material (acero nitrurado endurecido en aceite. En estas investigaciones se aplicaron capas interfaciales para aumentar la adherencia del recubrimiento.

  4. Stir zone microstructure of commercial purity titanium friction stir welded using pcBN tool

    Energy Technology Data Exchange (ETDEWEB)

    Zhang Yu [Department of Materials Processing, Graduate School of Engineering, Tohoku University, 6-6-02 Aramaki-aza-Aoba, Aoba-ku, Sendai 980-8579 (Japan)], E-mail: a5td9524@stu.material.tohoku.ac.jp; Sato, Yutaka S.; Kokawa, Hiroyuki [Department of Materials Processing, Graduate School of Engineering, Tohoku University, 6-6-02 Aramaki-aza-Aoba, Aoba-ku, Sendai 980-8579 (Japan); Park, Seung Hwan C.; Hirano, Satoshi [Hitachi Research Laboratory, Hitachi Ltd., Omika 7-1-1, Hitachi 319-1292 (Japan)

    2008-08-15

    In the present study, friction stir welding was applied to commercial purity titanium using a polycrystalline cubic boron nitride tool, and microstructure and hardness in the weld were examined. Additionally, the microstructural evolution during friction stir welding was also discussed. The stir zone consisted of fine equiaxed {alpha} grains surrounded by serrate grain boundaries, which were produced through the {beta} {yields} {alpha} allotropic transformation during the cooling cycle of friction stir welding. The fine {alpha} grains caused higher hardness than that in the base material. A lath-shaped {alpha} grain structure containing Ti borides and tool debris was observed in the surface region of the stir zone, whose hardness was the highest in the weld.

  5. Effect of an electric field on the properties of BN Möbius stripes

    Energy Technology Data Exchange (ETDEWEB)

    Lemos de Melo, J. [Departamento de Física, CCEN, Universidade Federal da Paraíba, Caixa Postal 5008, 58051-900 João Pessoa, PB (Brazil); Azevedo, S., E-mail: sazevedo@fisica.ufpb.br [Departamento de Física, CCEN, Universidade Federal da Paraíba, Caixa Postal 5008, 58051-900 João Pessoa, PB (Brazil); Kaschny, J.R. [Instituto Federal da Bahia, Campus Vitória da Conquista, Av. Amazonas 3150, 45075-265 Vitória da conquista, BA (Brazil)

    2014-09-15

    In the present work, we present a first-principles study on the effects of an external electric field on the structural stability and electronic properties of boron nitride Möbius stripes with armchair and zigzag chirality. The calculation results indicate that the gap energy can be remarkably reduced by the application of an external field. Such reduction is in principle attributed to the occurrence of Stark effect, which significance depends on the orientation of the applied field relative to the stripe axis. Moreover, the electric field produces significant changes on dipole momentum of the structure and induces a negative shift on the calculated total energy, reducing the obtained formation energy. - Highlights: • The gap energy is remarkably reduced by the application of an external field. • The electric field produces significant changes on dipole momentum. • The field induces a negative shift on the total energy due to Stark effect.

  6. Negative Refraction with High Transmission in Graphene-hBN Hyper Crystal

    CERN Document Server

    Sayem, Ayed Al; Jahangir, Ifat; Rahman, Md Saifur

    2015-01-01

    In this article, we have theoretically investigated the performance of graphene-hexagonal Boron Nitride hyper crystals to demonstrate all angle negative refraction.Hexagonal Boron Nitride, the latest natural hyperbolic material; can be a very strong contender to form a hyper crystal with graphene due to its excellence as a graphene-compatible substrate. Although bare hexagonal Boron Nitride can exhibit negative refraction, the transmission is generally low due to its high reflective nature. On the other hand, due to two dimensional nature and metallic characteristics of graphene in the frequency range where hexagonal Boron Nitride behaves as a type-I hyperbolic Metamaterial, we have found that graphene-hexagonal Boron Nitride hyper-crystals exhibit all angle negative refraction with superior transmission. This has been possible because of the strong suppression of reflection from the hyper-crystal without any adverse effect on the negative refraction properties. This finding can prove very useful in applicati...

  7. Negative Refraction with High Transmission in Graphene-hBN Hyper Crystal

    OpenAIRE

    Sayem, Ayed Al; Mahdy, Mahdy Rahman Chowdhury; Jahangir, Ifat; Rahman, Md. Saifur

    2015-01-01

    In this article, we have theoretically investigated the performance of graphene-hexagonal Boron Nitride hyper crystals to demonstrate all angle negative refraction.Hexagonal Boron Nitride, the latest natural hyperbolic material; can be a very strong contender to form a hyper crystal with graphene due to its excellence as a graphene-compatible substrate. Although bare hexagonal Boron Nitride can exhibit negative refraction, the transmission is generally low due to its high reflective nature. O...

  8. Observation of fractional Bloch band quantum Hall states in graphene/h-BN superlattices

    Science.gov (United States)

    Wang, Lei; Gao, Yuanda; Wen, Bo; Hone, James; Dean, Cory

    The Hofstadter energy spectrum provides a uniquely tunable system to study emergent topological order in the regime of strong interactions. Previous experiments, however, have been limited to low Bloch band fillings where only the Landau level index plays a role. Here we report measurements of high mobility graphene superlattices where the complete unit cell of the Hofstadter spectrum is accessible. We observe coexistence of conventional fractional quantum Hall effect (QHE) states together with the integer QHE states associated with the fractal Hofstadter spectrum. At large magnetic field, we observe signatures of another series of states, which appears at fractional Bloch filling index. These fractional Bloch band QHE states are not anticipated by existing theoretical pictures and point towards a distinct type of many-body state.

  9. A new procedure for fast soft staining of BN-PAGEs on photosynthetic complexes.

    Science.gov (United States)

    Farci, Domenica; Kirkpatrick, Joanna; Piano, Dario

    2017-02-01

    We report a fast and sensitive procedure for blue native PAGE staining, in which the conventional staining step with CBB is avoided. After running, a short exposure to a mix of polar protic solvents (ethanol and acetic acid) leads to a fast and selective removal of the dye from the migration front and a specific binding to the protein bands, while the rest undergo a selective and complete background removal, leading to an intense contrast. This single-step staining-destaining technique is useful in protein samples that bind colored cofactors such as photosystems, which can be selectively discerned by their characteristic green color. After the staining of such samples, the green color persists, while the other unpigmented protein complexes and the molecular standard remain CBB stained, creating a useful reference system for the assignment of the bands. The advantages and chemical basis of this staining procedure are discussed. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  10. Dicty_cDB: FC-BN07 [Dicty_cDB

    Lifescience Database Archive (English)

    Full Text Available KYYEVILVDNSHNA IRNDPRYNWICKPVHKHRELRGLTSAGIKARGLRRKGTHRARKTRPSRQANYKRRNTVVF HRYR*tnkh*ysfclcprilikcyifptlkkk...SAGIKARGLRRKGTHRARKTRPSRQANYKRRNTVVF HRYR*tnkh*ysfclcprilikcyifptlkkkkkkkkk Homology vs CSM-cDNA Score E Seq

  11. Measurement of the linear electro-optic coefficient of a minute cBN sample

    Institute of Scientific and Technical Information of China (English)

    DOU; Qingping; MA; Haitao; JIA; Gang; CHEN; Zhanguo; ZHANG

    2005-01-01

    Cubic boron nitride (Cbn) is a kind of artificial (synthetic) crystal. Transverse electro-optic modulation in a minute Cbn sample was carried out. Basing on the practical form of the crystal, we established the theoretical and experimental method according to the sample. For the first time, the linear electro-optic effect was observed in Cbn, and half-wave voltage of the Cbn sample was measured successfully. Furthermore, its linear electro-optic coefficient was calculated at 1.17×10-14 m/V.

  12. Strain-tunable half-metallicity in hybrid graphene-hBN monolayer superlattices

    Energy Technology Data Exchange (ETDEWEB)

    Meng, Fanchao, E-mail: fanchao.meng@mail.mcgill.ca [Department of Mining and Materials Engineering, McGill University, Montréal, QC H3A 0C5 (Canada); Zhang, Shiqi [School of Electrical, Computer and Energy Engineering, Arizona State University, Tempe, AZ 85281 (United States); Lee, In-Ho [Korea Research Institute of Standards and Science, 1 Doryong-Dong, Yuseong-Gu, Daejeon 305-600 (Korea, Republic of); Jun, Sukky [Department of Mechanical Engineering, University of Wyoming, Laramie, WY 82071 (United States); Ciobanu, Cristian V., E-mail: cciobanu@mines.edu [Department of Mechanical Engineering, Colorado School of Mines, Golden, CO 80401 (United States)

    2016-07-01

    Highlights: • Armchair superlattices have a bandgap modulated by the deformed domain widths. • Strain and domain width lead to novel spin-dependent behavior for zigzag boundaries. • Limits for spin-dependent bandgap and half-metallic behavior have been charted. - Abstract: As research in 2-D materials evolves toward combinations of different materials, interesting electronic and spintronic properties are revealed and may be exploited in future devices. A way to combine materials is the formation of spatially periodic domain boundaries in an atom-thick monolayer: as shown in recent reports, when these domains are made of graphene and hexagonal boron nitride, the resulting superlattice has half-metallic properties in which one spin component is (semi)metallic and the other is semiconductor. We explore here the range of spin-dependent electronic properties that such superlattices can develop for different type of domain boundaries, domain widths, and values of tensile strain applied to the monolayer. We show evidence of an interplay between strain and domain width in determining the electronic properties: while for armchair boundaries the bandgap is the same for both spin components, superlattices with zigzag boundaries exhibit rich spin-dependent behavior, including different bandgaps for each spin component, half-metallicity, and reversal of half-metallicity. These findings can lead to new ways of controlling the spintronic properties in hybrid-domain monolayers, which may be exploited in devices based on 2-D materials.

  13. A New nBn IR Detection Concept Using HgCdTe Material

    Science.gov (United States)

    Gravrand, O.; Boulard, F.; Ferron, A.; Ballet, Ph.; Hassis, W.

    2015-09-01

    This paper presents a new HgCdTe-based heterostructure to perform quantum infrared detection. The structure is based on the unipolar barrier concept, introduced by White in the 1980s for HgCdTe. The driving concept is the use of a large gap barrier layer to impede the flow of majority carriers (electrons on the conduction band in the case of n-type material) while fac