WorldWideScience

Sample records for crystals bn bpaiiibv

  1. Direct conversion of h-BN into c-BN and formation of epitaxial c-BN/diamond heterostructures

    International Nuclear Information System (INIS)

    Narayan, Jagdish; Bhaumik, Anagh; Xu, Weizong

    2016-01-01

    We have created a new state of BN (named Q-BN) through rapid melting and super undercooling and quenching by using nanosecond laser pulses. Phase pure c-BN is formed either by direct quenching of super undercooled liquid or by nucleation and growth from Q-BN. Thus, a direct conversion of hexagonal boron nitride (h-BN) into phase-pure cubic boron nitride (c-BN) is achieved by nanosecond pulsed laser melting at ambient temperatures and atmospheric pressure in air. According to the P-T phase diagram, the transformation from h-BN into c-BN under equilibrium processing can occur only at high temperatures and pressures, as the hBN-cBN-Liquid triple point is at 3500 K/9.5 GPa or 3700 K/7.0 GPa with a recent theoretical refinement. Using nonequilibrium 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 the formation of a new phase, named as Q-BN. We present detailed characterization of Q-BN and c-BN layers by using Raman spectroscopy, high-resolution scanning electron microscopy, electron-back-scatter diffraction, high-resolution TEM, and electron energy loss spectroscopy, and discuss the mechanism of formation of nanodots, nanoneedles, microneedles, and single-crystal c-BN on sapphire substrate. We have also deposited diamond by pulsed laser deposition of carbon on c-BN and created c-BN/diamond heterostructures, where c-BN acts as a template for epitaxial diamond growth. We discuss the mechanism of epitaxial c-BN and diamond growth on lattice matching c-BN template under pulsed laser evaporation of amorphous carbon, and the impact of this discovery on a variety of applications.

  2. BN / Graphene / BN RF Transistors

    Science.gov (United States)

    Wang, Han; Taychatanapat, Thiti; Hsu, Allen; Jarillo-Herrero, Pablo; Palacios, Tomas

    2011-03-01

    In this work we demonstrate the first BN/graphene/BN transistor for high frequency RF applications. This sandwich structure allows a significant improvement in the mobility of graphene, which reaches more than 18,000 cm2 /Vs at room temperature. Graphene field effect transistors (GFETs) have been fabricated with LDS = 800 nm and LG = 300 nm. The minimum conduction point of these devices is very close to zero, a result of the negligible substrate doping to the graphene. A current density in excess of 1 A/mm and DC transconductance above 200 mS/mm are achieved for both electron and hole conductions. RF characterization is performed for the first time on this device structure and initial results show a current-gain cut-off frequency fT = 10 GHz. These experimental results have been combined with simulations of the small-signal model to study the scaling potential of these GFETs for high frequency applications. The impact of the access resistances (Rs , Rd) , the capacitances (Cgs , Cgd , Cds) , and the transconductance (g m) on the frequency performance of the GFETs has also been studied. Finally, the fabricated devices have been compared to GFETs fabricated with Si O2 substrate and Al 2 O3 gate dielectrics. The improved performance obtained by the BN/graphene/BN structure is very promising to enable the next generation of high frequency RF electronics.

  3. BN-1200 Safety Concept

    International Nuclear Information System (INIS)

    Ashurko, Y.

    2013-01-01

    Safety concept of the BN-1200 design: • Takes into account experience gained from the BR-5/10, BOR-60, BN-350, BN-600, BN-800 and requirements imposed to the 4th generation advanced reactors; • Provides maximal application of inherent safety features and passive safety systems. Such approach permits: • To excel in safety existing designs, in particular BN-800; • And to meet requirements of the 4th generation

  4. Anisotropy of x-ray reflectivity: chemical and structural effects on K-shell excitations in hexagonal BN crystal

    CERN Document Server

    Filatova, E O

    2002-01-01

    The experimental investigation of the B and N K-reflection spectra using both s-polarized synchrotron radiation and unpolarized radiation for different crystal orientations with respect to the electric field vector E was carried out. The absorption spectra calculated from the reflection spectra using Kramers-Kronig analysis are presented. A strong orientation dependence of both reflection and absorption spectra is exhibited. Analysis of the orientation dependences of the x-ray reflection and absorption spectra near both edges strongly supports a possibility of tracing the role of each excitation canal in the formation of fine structure. The high sensitivity of the reflection spectra fine structure to the vibronic interaction connected with Jahn-Teller distortions as well to the core-hole relaxation is discussed. A very strong dependence of the absolute values of the reflectivity on planar crystal anisotropy was discovered.

  5. Cathodoluminescence of BN films

    International Nuclear Information System (INIS)

    Voitkans, A.; Tale, I.; Jansons, J.

    2005-01-01

    Full text: The development of III-V group nitride materials is of considerable interest for semiconductor electronic and optical device applications. The band gaps of III-V group nitrides range from 1.9 eV for wurtzitic InN to greater than 6.2 eV for cubic BN, making these materials well suited for optical applications throughout the visible and into the near-UV region. Investigation of BN thin film cathodoluminescence has been performed. Thickness of BN thin film received from Rostock colleagues was 0.77 μm, and was grown on Si substrate. Cathodoluminescence of BN thin film characterizes with dominant luminescence band at 330 nm and some other less intensive luminescence bands. The same bands are observed in spectra of photoluminescence and they are typical for hexagonal structures of BN. In further research it is recommendable to perform investigations on thicker BN films to obtain more intensive luminescence for precise and detail determination of luminescence parameters

  6. Spontaneous Self-Assembly of Fully Protected Ester 1:1 [α/α-Nα-Bn-hydrazino] Pseudodipeptides into a Twisted Parallel β-Sheet in the Crystal State.

    Science.gov (United States)

    Romero, Eugénie; Moussodia, Ralph-Olivier; Kriznik, Alexandre; Wenger, Emmanuel; Acherar, Samir; Jamart-Grégoire, Brigitte

    2016-10-07

    Previous studies have demonstrated that amidic α/β-pseudodipeptides, 1:1 [α/α-N α -Bn-hydrazino], have the ability to fold via a succession of γ-turn (C 7 pseudocycle) and hydrazinoturn in CDCl 3 solution, their amide terminals enabling the formation of an intramolecular H-bond network. Despite their lack of a primary amide terminals allowing the formation of the hydrazinoturn, their ester counterparts 1-4 were proven to self-assemble into C 6 and C 7 pseudocycles by intramolecular H-bonds in solution state and into an uncommon twisted parallel β-sheet through intermolecular H-bonding in the crystal state to form a supramolecular helix, with eight molecules needed to complete a full 360° rotation. Such self-organization (with eight molecules) has only been observed in a specific α/α-pseudodipeptide, depsipeptide (Boc-Leu-Lac-OEt). Relying on IR absorption, NMR, X-ray diffraction, and CD analyses, the aim of this study was to demonstrate that stereoisomers of ester 1:1 [α/α-N α -Bn-hydrazino] pseudodipeptides 1-4 are able to self-assemble into this β-helical structure. The absolute configuration of the asymmetric C α -atom of the α-amino acid residue influences the left- or right-handed twist without changing the pitch of the formed helix.

  7. Multi-Functional All BN-BN Composites

    Data.gov (United States)

    National Aeronautics and Space Administration — Development of multifunctional Boron Nitride nanotube-Boron Nitride (BN-BN) composites to provide novel energy transducers, thermal conductors, anti-penetrator/wear...

  8. BN-350 ''Mirror System''

    International Nuclear Information System (INIS)

    Thornton, A.L.; Halbig, J.K.

    2004-01-01

    The BN-350 Unattended Monitoring System plays an important role for the Safeguards Department of the International Atomic Energy Agency (IAEA). In 1998, the Los Alamos National Laboratory, in conjunction with the IAEA and sponsored by the US Department of Energy, designed and installed an integrated multi-instrument safeguards system at the BN-350 reactor in Aktau, Kazakhstan, to monitor spent-fuel and blanket assembly conditioning and canning activities. The purpose of the system was to provide effective safeguards at this facility while reducing the manpower load on the IAEA. The system is composed of many individual nondestructive analysis and surveillance components, each having a unique function and working together to provide fully unattended measurement of spent-fuel assemblies. The BN-350 ''Mirror System'' was built to provide a similar system with like components at the IAEA Headquarters in Vienna to facilitate analysis and/or simulation of problems that might occur in the field and for training inspectors and other technical staff in preparation for their work in the field. In addition, the system is used to test new equipment and qualify new or modified software. This paper describes the main components of the Mirror System, how the components are integrated, and how the Mirror System has benefited the IAEA.

  9. BN600 reactivity definition

    International Nuclear Information System (INIS)

    Zheltyshev, V.; Ivanov, A.

    2000-01-01

    Since 1980, the fast BN600 reactor with sodium coolant has been operated at Beloyarsk Nuclear Power Plant. The periodic monitoring of the reactivity modifications should be implemented in compliance with the standards and regulations applied in nuclear power engineering. The reactivity measurements are carried out in order to confirm the basic neutronic features of a BN600 reactor. The reactivity measurements are aimed to justify that nuclear safety is provided in course of the in-reactor installation of the experimental core components. Two reactivity meters are to be used on BN600 operation: 1. Digital on-line reactivity calculated under stationary reactor operation on power (approximation of the point-wise kinetics is applied). 2. Second reactivity meter used to define the reactor control rod operating components efficiency under reactor startup and take account of the changing efficiency of the sensor, however, this is more time-consumptive than the on-line reactivity meter. The application of two reactivity meters allows for the monitoring of the reactor reactivity under every operating mode. (authors)

  10. Phase stability limit of c-BN under hydrostatic and non-hydrostatic pressure conditions

    International Nuclear Information System (INIS)

    Xiao, Jianwei; Du, Jinglian; Wen, Bin; Zhang, Xiangyi; Melnik, Roderick; Kawazoe, Yoshiyuki

    2014-01-01

    Phase stability limit of cubic boron nitride (c-BN) has been investigated by the crystal structure search technique. It indicated that this limit is ∼1000 GPa at hydrostatic pressure condition. Above this pressure, c-BN turns into a metastable phase with respect to rocksalt type boron nitride (rs-BN). However, rs-BN cannot be retained at 0 GPa owing to its instability at pressure below 250 GPa. For non-hydrostatic pressure conditions, the phase stability limit of c-BN is substantially lower than that under hydrostatic pressure conditions and it is also dramatically different for other pressure mode

  11. Bn and Si-Doped Bn Coatings on Woven Fabrics

    Science.gov (United States)

    Hurwitz, Frances I.; Scott, John M.; Wheeler, Donald R.; Chayka, Paul V.; Gray, Hugh R. (Technical Monitor)

    2002-01-01

    A computer controlled, pulsed chemical vapor infiltration (CVI) system has been developed to deposit BN from a liquid borazine (B3N3H6) source, as well as silicon doped BN coatings using borazine and a silicon source, into 2-D woven ceramic fabric preforms. The coating process was evaluated as a function of deposition temperature, pressure, and precursor flow rate. Coatings were characterized by field emission scanning electron microscopy, electron dispersive spectroscopy and Auger spectroscopy. By controlling the reactant feed ratios, Si incorporation could be controlled over the range of 6-24 atomic percent.

  12. Synthesis and Characterization of Quenched and Crystalline Phases: Q-Carbon, Q-BN, Diamond and Phase-Pure c-BN

    Science.gov (United States)

    Bhaumik, Anagh; Narayan, Jagdish

    2018-01-01

    We report the synthesis and characterization of quenched (Q-carbon and Q-BN) and crystalline (diamond and c-BN) phases using a non-equilibrium technique. These phases are formed as a result of the melting and subsequent quenching of amorphous carbon and nanocrystalline h-BN in a super undercooled state by using high-power nanosecond laser pulses. Pulsed laser annealing also leads to the formation of nanoneedles, microneedles and single-crystal thin films of diamond and c-BN. This formation is dependent on the nucleation and growth times, which are controlled by laser energy density and thermal conductivities of substrate and as-deposited thin film. The diamond nuclei present in the Q-carbon structure ( 80% sp 3) can also be grown to larger sizes using the equilibrium hot filament chemical vapor deposition process. The texture of diamond and c-BN crystals is 〈111〉 under epitaxial growth and 〈110〉 under rapid unseeded crystallization. Our nanosecond laser processing opens up a roadmap to the fabrication of novel phases on heat-sensitive substrates.

  13. Pressure sensing element based on the BN-graphene-BN heterostructure

    Science.gov (United States)

    Li, Mengwei; Wu, Chenggen; Zhao, Shiliang; Deng, Tao; Wang, Junqiang; Liu, Zewen; Wang, Li; Wang, Gao

    2018-04-01

    In this letter, we report a pressure sensing element based on the graphene-boron nitride (BN) heterostructure. The heterostructure consists of monolayer graphene sandwiched between two layers of vertically stacked dielectric BN nanofilms. The BN layers were used to protect the graphene layer from oxidation and pollution. Pressure tests were performed to investigate the characteristics of the BN-graphene-BN pressure sensing element. A sensitivity of 24.85 μV/V/mmHg is achieved in the pressure range of 130-180 kPa. After exposing the BN-graphene-BN pressure sensing element to the ambient environment for 7 days, the relative resistance change in the pressure sensing element is only 3.1%, while that of the reference open-faced graphene device without the BN protection layers is 15.7%. Thus, this strategy is promising for fabricating practical graphene pressure sensors with improved performance and stability.

  14. 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 θ NM ≃ 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 θ NM 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.

  15. Cubic boron nitride (cBN) - A new material for advanced optoelectronic devices. Properties and perspectives

    International Nuclear Information System (INIS)

    Nistor, S.V.; Nistor, L.C.; Dinca, G.

    2001-01-01

    Cubic boron nitride (cBN) exhibits, besides exceptional thermal and mechanical properties similar to diamond, an excellent ability to be n or p doped, which makes it a strong candidate for advanced, high - temperature optical and microelectronic devices. Despite its outstanding characteristics, there are quite a few reports concerning the physical properties of cBN. This is partly due to the absence of natural cBN gems and the extreme difficulties in producing enough large (mm 3 sized) single crystals, or single phase thin films, for physical characterization. The state of the art knowledge concerning the basic properties of crystalline cBN, as well as our recent results of microstructure and defect properties studies will be presented. (authors)

  16. Li{sub 4}Ba[BN{sub 2}]{sub 2} - structure and vibrational spectra

    Energy Technology Data Exchange (ETDEWEB)

    Seidel, Stefan; Rodewald, Ute C.; Poettgen, Rainer [Institut fuer Anorganische und Analytische Chemie, Universitaet Muenster (Germany); Somer, Mehmet; Kiraz, Kamil [Chemistry Department, Koc University, Sariyer-Istanbul (Turkey)

    2017-12-13

    The nitridoborate Li{sub 4}Ba[BN{sub 2}]{sub 2} was synthesized from a 4:1 molar ratio of Li{sub 3}[BN]{sub 2} and Ba{sub 3}[BN{sub 2}]{sub 2} in an arc-welded niobium ampoule at a maximum annealing temperature of 1173 K. The structure was refined from single-crystal X-ray diffractometer data: new type, P1, a = 533.9(2), b = 585.0(3), c = 860.6(4) pm, α = 80.72(3), β = 73.84(6), γ = 89.87(4) , wR{sub 2} = 0.1196, 1429 F{sup 2} values, 50 variables. The Li{sub 4}Ba[BN{sub 2}]{sub 2} structure contains two crystallographically independent [BN{sub 2}]{sup 3-} units with 134 pm B-N distance, which are slightly bent: 178 for N2-B1-N1 and 175 for N4-B2-N3. Due to the high lithium content both [BN{sub 2}]{sup 3-} units have a strongly distorted coordination by 8Li{sup +} + 3Ba{sup 2+}. The four crystallographically independent lithium cations show distorted tetrahedral coordination by [BN{sub 2}]{sup 3-} units with Li-N distances ranging from 195 to 247 pm. IR and Raman spectra show the typical vibrations of the [BN{sub 2}] unit along with a well-resolved splitting of the ν({sup 10}B) and ν({sup 11}B) frequencies. (copyright 2017 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  17. Hydrothermal synthesis of cubic boron nitride crystals

    International Nuclear Information System (INIS)

    Yu Meiyan; Cui Deliang; Kai Li; Yin Yansheng; Wang Qilong; Lei Chu

    2005-01-01

    Cubic boron nitride (cBN) crystals have been successfully synthesized by in situ hydrothermal method. In order to obtain cBN pure phase crystals, two comparative experiments were carried out. The experimental results indicated that compared to one-step in situ hydrothermal method, multi-step in situ hydrothermal method was beneficial to the synthesis of cBN. It is believed that the multi-step in situ hydrothermal method is the optimal route to synthesize pure cBN bulk crystals

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

    International Nuclear Information System (INIS)

    Haider, Ali; Kayaci, Fatma; Uyar, Tamer; Biyikli, Necmi; Ozgit-Akgun, Cagla; Okyay, Ali Kemal

    2014-01-01

    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

  19. Anisotropic Effective Mass, Optical Property, and Enhanced Band Gap in BN/Phosphorene/BN Heterostructures.

    Science.gov (United States)

    Hu, Tao; Hong, Jisang

    2015-10-28

    Phosphorene is receiving great research interests because of its peculiar physical properties. Nonetheless, the phosphorus has a trouble of degradation due to oxidation. Hereby, we propose that the electrical and optical anisotropic properties can be preserved by encapsulating into hexagonal boron nitride (h-BN). We found that the h-BN contributed to enhancing the band gap of the phosphorene layer. Comparing the band gap of the pristine phosphorene layer, the band gap of the phosphorene/BN(1ML) system was enhanced by 0.15 eV. It was further enhanced by 0.31 eV in the BN(1ML)/phosphorene/BN(1ML) trilayer structure. However, the band gap was not further enhanced when we increased the thickness of the h-BN layers even up to 4 MLs. Interestingly, the anisotropic effective mass and optical property were still preserved in BN/phosphorene/BN heterostructures. Overall, we predict that the capping of phosphorene by the h-BN layers can be an excellent solution to protect the intrinsic properties of the phosphorene.

  20. 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.

  1. 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.

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

    International Nuclear Information System (INIS)

    Sulaiman, Hanisah Syed; Hua, Chia Chin; Zakaria, Sarani

    2015-01-01

    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

  3. The reconstructed edges of the hexagonal BN

    Science.gov (United States)

    Zhao, Ruiqi; Gao, Junfeng; Liu, Zhongfan; Ding, Feng

    2015-05-01

    As an important two-dimensional material which shows exceptional mechanical and chemical stability, superior electronic properties, along with broad applications, the hexagonal-BN (h-BN) has drawn great attention recently. Here we report a systematic study on the structural stability, electronic and magnetic properties of various h-BN edges, including both bare and hydrogen-terminated ones. It is found that along the armchair (AC) direction, the pristine edge is the most stable one because of the formation of a triple B\\z.tbd N bond, while, along the zigzag (ZZ) directions, the reconstructed ones, ZZB + N and ZZN57 are more stable. The pristine edges are more stable in bare BN in most cases if saturated with hydrogen. By applying the theory of Wulff construction, we predicted that an unpassivated BN domain prefers the hexagonal shape enclosed with bare AC edges i.e., AC-Ns, AC, AC-Bs if the feedstock varies from N-rich to B-rich. However, the evolution from ZZN edged triangular domain, to hexagonal domain enclosed with AC edges, and ZZB edged triangle may occur if the edges are terminated by hydrogen atoms. Further calculation shows that these edges present rich type-dependent properties and thus are important for various applications. This theoretical study showed that controlling the morphologies of BN domains and BN edges is crucial for various applications.As an important two-dimensional material which shows exceptional mechanical and chemical stability, superior electronic properties, along with broad applications, the hexagonal-BN (h-BN) has drawn great attention recently. Here we report a systematic study on the structural stability, electronic and magnetic properties of various h-BN edges, including both bare and hydrogen-terminated ones. It is found that along the armchair (AC) direction, the pristine edge is the most stable one because of the formation of a triple B\\z.tbd N bond, while, along the zigzag (ZZ) directions, the reconstructed ones, ZZB + N

  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. Spin transport in two-layer-CVD-hBN/graphene/hBN heterostructures

    Science.gov (United States)

    Gurram, M.; Omar, S.; Zihlmann, S.; Makk, P.; Li, Q. C.; Zhang, Y. F.; Schönenberger, C.; van Wees, B. J.

    2018-01-01

    We study room-temperature spin transport in graphene devices encapsulated between a layer-by-layer-stacked two-layer-thick chemical vapor deposition (CVD) grown hexagonal boron nitride (hBN) tunnel barrier, and a few-layer-thick exfoliated-hBN substrate. We find mobilities and spin-relaxation times comparable to that of SiO2 substrate-based graphene devices, and we obtain a similar order of magnitude of spin relaxation rates for both the Elliott-Yafet and D'Yakonov-Perel' mechanisms. The behavior of ferromagnet/two-layer-CVD-hBN/graphene/hBN contacts ranges from transparent to tunneling due to inhomogeneities in the CVD-hBN barriers. Surprisingly, we find both positive and negative spin polarizations for high-resistance two-layer-CVD-hBN barrier contacts with respect to the low-resistance contacts. Furthermore, we find that the differential spin-injection polarization of the high-resistance contacts can be modulated by dc bias from -0.3 to +0.3 V with no change in its sign, while its magnitude increases at higher negative bias. These features point to the distinctive spin-injection nature of the two-layer-CVD-hBN compared to the bilayer-exfoliated-hBN tunnel barriers.

  6. Growth kinetics of white graphene (h-BN) on a planarised Ni foil surface.

    Science.gov (United States)

    Cho, Hyunjin; Park, Sungchan; Won, Dong-Il; Kang, Sang Ook; Pyo, Seong-Soo; Kim, Dong-Ik; Kim, Soo Min; Kim, Hwan Chul; Kim, Myung Jong

    2015-07-09

    The morphology of the surface and the grain orientation of metal catalysts have been considered to be two important factors for the growth of white graphene (h-BN) by chemical vapour deposition (CVD). We report a correlation between the growth rate of h-BN and the orientation of the nickel grains. The surface of the nickel (Ni) foil was first polished by electrochemical polishing (ECP) and subsequently annealed in hydrogen at atmospheric pressure to suppress the effect of the surface morphology. Atmospheric annealing with hydrogen reduced the nucleation sites of h-BN, which induced a large crystal size mainly grown from the grain boundary with few other nucleation sites in the Ni foil. A higher growth rate was observed from the Ni grains that had the {110} or {100} orientation due to their higher surface energy.

  7. 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.

  8. Planning of the BN-350 reactor decommissioning

    International Nuclear Information System (INIS)

    Klepikov, A.Kh.; Tazhibayeva, I.L.; Zhantikin, T.M.; Baldov, A.N.; Nazarenko, P.I.; Koltyshev, S.M.; Wells, P.B.

    2002-01-01

    The experimental and commercial BN-350 NPP equipped with a fast neutron sodium cooled reactor is located in Kazakhstan near the Aktau city on the Caspian Sea coast. It was commissioned in 1973 and intended for weapon-grade plutonium production and as stream supply to a water desalination facility and the turbines of the Mangyshlak Atomic Energy Complex. Taking into account technical, financial and political issues, the Government of Kazakhstan enacted the Decree no. 456 'On Decommissioning of the Reactor BN-350 in the Aktau City of the Mangystau Region'. Because the decision on reactor decommissioning was adopted before the end of scheduled operation (2003), the plan to decommission the BN-350 reactor has not yet been developed. To determine the activities required for ensuring reactor safety and in preparation for decommission in the period prior, the development and ensuring approval by the Republic of Kazakhstan Government of the decommissioning plan, a 'Plan of Priority Actions for BN-350 Reactor Decommissioning' was developed and approved. Actions provided for in the plan include the following: Development of BN-350 Reactor Decommissioning Plan; Accident prevention during the period of transition; Unloading nuclear fuel from reactor and draining the coolant from the heat exchange circuits. Decommission is defined as a complex of administrative and technical actions taken to allow the removal of some or all of regulatory controls over a nuclear facility. These actions involve decontamination, dismantling and removal of radioactive materials, waste, components and structures. They are carried out to achieve a progressive and systematic reduction in radiological hazards and are undertaken on the basis of planning and assessment in order to ensure safety decommissioning operations. In accordance with the decision of Kazakhstan Government, three basic stages for BN-350 reactor decommissioning are envisaged: First stage - Placement of BN-350 into long-term storage

  9. crystal

    Science.gov (United States)

    Yu, Yi; Huang, Yisheng; Zhang, Lizhen; Lin, Zhoubin; Sun, Shijia; Wang, Guofu

    2014-07-01

    A Nd3+:Na2La4(WO4)7 crystal with dimensions of ϕ 17 × 30 mm3 was grown by the Czochralski method. The thermal expansion coefficients of Nd3+:Na2La4(WO4)7 crystal are 1.32 × 10-5 K-1 along c-axis and 1.23 × 10-5 K-1 along a-axis, respectively. The spectroscopic characteristics of Nd3+:Na2La4(WO4)7 crystal were investigated. The Judd-Ofelt theory was applied to calculate the spectral parameters. The absorption cross sections at 805 nm are 2.17 × 10-20 cm2 with a full width at half maximum (FWHM) of 15 nm for π-polarization, and 2.29 × 10-20 cm2 with a FWHM of 14 nm for σ-polarization. The emission cross sections are 3.19 × 10-20 cm2 for σ-polarization and 2.67 × 10-20 cm2 for π-polarization at 1,064 nm. The fluorescence quantum efficiency is 67 %. The quasi-cw laser of Nd3+:Na2La4(WO4)7 crystal was performed. The maximum output power is 80 mW. The slope efficiency is 7.12 %. The results suggest Nd3+:Na2La4(WO4)7 crystal as a promising laser crystal fit for laser diode pumping.

  10. Nano-ice models for the water aggregates observed on the h-BN/Rh(111) nanomesh

    International Nuclear Information System (INIS)

    Ding Yun; Iannuzzi, Marcella; Hutter, Jürg

    2012-01-01

    When a large amount of water is deposited onto a bare h-BN/Rh(111) nanomesh, the formation of ordered and stable nano-ice crystals in the pores has been experimentally observed. The present work proposes different possible models for the structure of the observed clusters, based on density functional theory calculations of two-dimensional water lattices adsorbed on free-standing hexagonal BN. Through the investigation of the electronic properties, the interaction with BN, and the distribution of the molecular dipoles, the most probable two-dimensional arrangement has been identified. Finally, a model is proposed for the nano-ice cluster trapped in the pore of the nanomesh, which constitutes 38 molecules distributed according to the most probable two-dimensional arrangement on free-standing BN. Structural and electronic properties of the optimized nano-ice cluster are also reported, and it is shown that the model is consistent with the experimental observation.

  11. Germany unveils €18bn research plan

    Science.gov (United States)

    Banks, Michael

    2009-07-01

    The German government has unveiled an ambitious plan to inject a total of €18bn into teaching and research over the next decade. The German chancellor Angela Merkel, who has a degree in physics, announced that she was releasing the funds despite concerns from her social-democrat coalition partners that financing the package could be difficult in the economic downturn.

  12. 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.

  13. Complete Genome Sequences of Bovine Parainfluenza Virus Type 3 Strain BN-1 and Vaccine Strain BN-CE.

    Science.gov (United States)

    Ohkura, Takashi; Kokuho, Takehiro; Konishi, Misako; Kameyama, Ken-Ichiro; Takeuchi, Kaoru

    2013-01-01

    Bovine parainfluenza virus type 3 (BPIV3) is associated with upper respiratory disease in cattle in many countries. Here, we report the complete genome sequences of the BPIV3 BN-1 strain, isolated from cattle in Japan, and the BN-CE vaccine strain, derived from the BN-1 strain by passages in chicken embryo fibroblasts.

  14. Study on thermal conductive BN/novolac resin composites

    International Nuclear Information System (INIS)

    Li, Shasha; Qi, Shuhua; Liu, Nailiang; Cao, Peng

    2011-01-01

    Highlights: → Boron nitride (BN) particles were used to modify novolac resin. → BN particles were pretreated by γ-aminopropyltriethoxysilane. → The thermal conductivity trend of composite almost agrees with the predicted data from the Maxwell-Eucken model. → At BN concentration of 80 wt.%, thermal conductivity value of composite is 4.5 times that of pure novolac resin. → Combined use of the larger and smaller particles with a mass ratio of 1:2 provides the composites with the maximum thermal conductivity among the testing systems. → The composite thermal property also increases with an increase in the BN concentration. - Abstract: In this study, γ-aminopropyltriethoxysilane-treated boron nitride (BN) particles were used to modify novolac resin. The effect of varying the BN concentration, particle size, and hybrid BN fillers with the binary particle size distribution on the thermal conductivity of the composites was investigated. Scanning electron microscopy (SEM) imaging showed homogeneously dispersed treated BN particles in the matrix. Furthermore, the thermal conductivity increased as the BN concentration was increased. This behavior was also observed when the filler size was increased. Experimentally obtained thermal conductivity values agree with the predicted data from the Maxwell-Eucken model well at less than 70 wt.% BN loading. A larger particle size BN-filled novolac resin exhibits a higher thermal conductivity than a smaller particle size BN-filled one. The combined use of 0.5 and 15 μm particles with a mass ratio of 2:1 achieved the maximum thermal conductivity among the testing systems. The thermal resistance properties of the composites were also studied.

  15. Tunable magnetotransport in Fe/hBN/graphene/hBN/Pt(Fe) epitaxial multilayers

    Science.gov (United States)

    Magnus Ukpong, Aniekan

    2018-03-01

    Theoretical and computational analysis of the magnetotransport properties and spin-transfer torque field-induced switching of magnetization density in vertically-stacked multilayers is presented. Using epitaxially-capped free layers of Pt and Fe, atom-resolved magnetic moments and spin-transfer torques are computed at finite bias. The calculations are performed within linear response approximation to the spin-density reformulation of the van der Waals density functional theory. Dynamical spin excitations are computed as a function of a spin-transfer torque induced magnetic field along the magnetic easy axis, and the corresponding spin polarization perpendicular to the easy axis is obtained. Bias-dependent giant anisotropic magnetoresistance of up to 3200% is obtained in the nonmagnetic-metal-capped Fe/hBN/graphene/hBN/Pt multilayer architecture. Since this specific heterostructure is not yet fabricated and characterized, the predicted high performance has not been demonstrated experimentally. Nevertheless, similar calculations performed on the Fe/hBN/Co stack show that the tunneling magnetoresistance obtained at the Fermi-level is in excellent agreement with results of recent magnetotransport measurements on magnetic tunnel junctions that contain the monolayer hBN tunnel region. The magnitude of the spin-transfer torque is found to increase as the tunneling spin current increases, and this activates the magnetization switching process due to increased charge accumulation. This mechanism causes substantial spin backflow, which manifests as rapid undulations in the bias-dependent tunneling spin currents. The implication of these findings on the design of nanoscale spintronic devices with spin-transfer torque tunable magnetization density is discussed. Insights derived from this study are expected to enhance the prospects for developing and integrating artificially assembled van der Waals multilayer heterostructures as the preferred material platform for efficient

  16. Calculated carrier mobility of h-BN/γ-InSe/h-BN van der Waals heterostructures

    Science.gov (United States)

    Kang, P.; Michaud-Rioux, V.; Kong, X.-H.; Yu, G.-H.; Guo, H.

    2017-12-01

    Recent experiments reported excellent transport properties of two-dimensional (2D) van der Waals (vdW) heterostructures made of atomically thin InSe layers encapsulated by two hBN capping layers (ISBN). The carrier mobility of the ISBN films exceeded μ ˜ 1.2× {{10}4} \\text{c}{{\\text{m}}2} {{\\text{V}}-1} {{\\text{s}}-1} at low temperature, much higher than that of pristine InSe films. It has been puzzling why the relatively inert hBN capping layer could so drastically enhance mobility of the ISBN composite. Using a state-of-the-art first principles method, we have calculated phonon limited carrier mobility of 18 different ISBN films and 6 pristine InSe films with different thicknesses, the largest system containing 2212 atoms. The hBN capping layer significantly alters the elastic stiffness coefficient as compared with pure InSe—thus the acoustic phonons in the ISBN composite—giving rise to the observed large mobility of ISBN films. Of the 18 calculated ISBN films, the ones with no strain at the hBN/InSe interface possess the highest electron mobility, reaching 4340~\\text{c}{{\\text{m}}2}~{{\\text{V}}-1}~{{\\text{s}}-1} at room temperature, which could easily go over {{10}4}~\\text{c}{{\\text{m}}2}~{{\\text{V}}-1}~{{\\text{s}}-1} at low temperatures. We conclude that the mechanical properties of the composite 2D vdW ISBN material play the crucial role for inducing the large carrier mobility, a principle that could be applied to many other 2D vdW heterostructures.

  17. Chemically stabilized epitaxial wurtzite-BN thin film

    Science.gov (United States)

    Vishal, Badri; Singh, Rajendra; Chaturvedi, Abhishek; Sharma, Ankit; Sreedhara, M. B.; Sahu, Rajib; Bhat, Usha; Ramamurty, Upadrasta; Datta, Ranjan

    2018-03-01

    We report on the chemically stabilized epitaxial w-BN thin film grown on c-plane sapphire by pulsed laser deposition under slow kinetic condition. Traces of no other allotropes such as cubic (c) or hexagonal (h) BN phases are present. Sapphire substrate plays a significant role in stabilizing the metastable w-BN from h-BN target under unusual PLD growth condition involving low temperature and pressure and is explained based on density functional theory calculation. The hardness and the elastic modulus of the w-BN film are 37 & 339 GPa, respectively measured by indentation along direction. The results are extremely promising in advancing the microelectronic and mechanical tooling industry.

  18. 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.

  19. Tribological properties of epoxy composite coatings reinforced with functionalized C-BN and H-BN nanofillers

    Science.gov (United States)

    Yu, Jingjing; Zhao, Wenjie; Wu, Yinghao; Wang, Deliang; Feng, Ruotao

    2018-03-01

    A series of epoxy resin (EP) composite coatings reinforced with functionalized cubic boron nitride (FC-BN) and functionalized hexagonal boron nitride (FH-BN) were fabricated successfully on 316L stainless steel by hand lay-up technique. The structure properties were characterized by Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS) and X-ray diffraction (XRD). The morphologies were characterized by atomic force microscopy (AFM), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Moreover, UMT-3 tribometer and surface profiler were used to investigate tribological behaviors of as-prepared composite coatings under dry friction and seawater conditions respectively. The results demonstrated that the presence of FC-BN or FH-BN fillers could greatly decrease the friction coefficient (COF) and wear rate of epoxy, in addition, composite coatings possess better tribological properties under seawater condition which was attributed to the lubricating effect of seawater. Moreover, FC-BN endows the composite coatings the highest wear resistance, and FH-BN /EP composite coatings exhibited the best friction reduction performance which is attributed to the self-lubricating performance of lamella structure for FH-BN sheet.

  20. Introducing lattice strain to graphene encapsulated in hBN

    Science.gov (United States)

    Tomori, Hikari; Hiraide, Rineka; Ootuka, Youiti; Watanabe, Kenji; Taniguchi, Takashi; Kanda, Akinobu

    Due to the characteristic lattice structure, lattice strain in graphene produces an effective gauge field. Theories tell that by controlling spatial variation of lattice strain, one can tailor the electronic state and transport properties of graphene. For example, under uniaxial local strain, graphene exhibits a transport gap at low energies, which is attractive for a graphene application to field effect devices. Here, we develop a method for encapsulating a strained graphene film in hexagonal boron-nitride (hBN). It is known that the graphene carrier mobility is significantly improved by the encapsulation of graphene in hBN, which has never been applied to strained graphene. We encapsulate graphene in hBN using the van der Waals assembly method. Strain is induced by sandwiching a graphene film between patterned hBN sheets. Spatial variation of strain is confirmed with micro Raman spectroscopy. Transport measurement of encapsulated strained graphene is in progress.

  1. Electronic structure of graphene- and BN-supported phosphorene

    Science.gov (United States)

    Davletshin, Artur R.; Ustiuzhanina, Svetlana V.; Kistanov, Andrey A.; Saadatmand, Danial; Dmitriev, Sergey V.; Zhou, Kun; Korznikova, Elena A.

    2018-04-01

    By using first-principles calculations, the effects of graphene and boron nitride (BN) substrates on the electronic properties of phosphorene are studied. Graphene-supported phosphorene is found to be metallic, while the BN-supported phosphorene is a semiconductor with a moderate band gap of 1.02 eV. Furthermore, the effects of the van der Waals interactions between the phosphorene and graphene or BN layers by means of the interlayer distance change are investigated. It is shown that the interlayer distance change leads to significant band gap size modulations and direct-indirect band gap transitions in the phosphorene-BN heterostructure. The presented band gap engineering of phosphorene may be a powerful technique for the fabrication of high-performance phosphorene-based nanodevices.

  2. Graphene growth on h-BN by molecular beam epitaxy

    OpenAIRE

    García Martínez, Jorge Manuel; Pinczuk, Aron

    2013-01-01

    Graphene growth on dielectric substrates has potential to enable new kinds of devices and applications. We explore graphene growth via direct depositing carbon in a MBE environment on different dielectric substrates, such as h-BN and sapphire. The growth of single layer graphene nanometer size domains by solid carbon source molecular beam epitaxy on hexagonal boron nitride (h-BN) flakes is demonstrated [1]. Formation of single-layer graphene is clearly apparent in Raman spectra which disp...

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

    Energy Technology Data Exchange (ETDEWEB)

    Vessally, E. [Department of Chemistry, Payame Noor University, Tehran (Iran, Islamic Republic of); Soleimani-Amiri, S. [Department of Chemistry, Karaj Branch, Islamic Azad University, Karaj (Iran, Islamic Republic of); Hosseinian, A. [Department of Engineering Science, College of Engineering, University of Tehran, P.O. Box 11365-4563, Tehran (Iran, Islamic Republic of); Edjlali, L., E-mail: l_edjlali@iaut.ac.ir [Department of Chemistry, Tabriz Branch, Islamic Azad University, Tabriz (Iran, Islamic Republic of); Bekhradnia, A. [Pharmaceutical Sciences Research Center, Department of Medicinal Chemistry, Mazandaran University of Medical Sciences, Sari (Iran, Islamic Republic of)

    2017-02-28

    Highlights: • Clar’s sextet rule determine the relative stability of HBC nanographenes. • Coronene-like doping increases the electrical conductivity of the HBC. • Frenkel type exciton binding energy is predicted for HBC nanographenes. - Abstract: 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.

  4. Validation of BN Reactor Plant Long-Term Operation

    International Nuclear Information System (INIS)

    Vilensky, O.; Vasilyev, B.; Kaidalov, V.

    2013-01-01

    The BN RP operation life time is mainly determined by resource of non-replaceable equipment. The new standard (RD) “Procedure of strength analysis for main components of sodium cooled fast neutron reactor plants” was developed to validate structure strength in view of radiation effects and degradation of material properties within the time period up to 300000 hours and under irradiation, as well as development of postulated crack-like defects. Using this RD, the extension of operation life of BN-600 reactor non-replaceable components from 30 to 45 years, as well as strength and durability of the most loaded non-replaceable components of BN-800 RP under construction were validated for the specified 45-year operation life. Wider application of steel 16Cr-11Ni-3Mo refers to new decisions in BN-1200 RP design that allow increasing of operation life of the most loaded non-replaceable components up to 60 years. High-chromium steel 12Cr-Ni-Mo-V-Nb is a new material, which was proposed for SG design to increase the operation life up to 30 years. In addition, the austenitic steels 18Cr-9Ni and 16Cr-11Ni-3Mo are now under upgrading for future application of them in commercial BN-1200 RP. To provide additional long-term reliable and safe operation of BN-1200 RP equipment and pipelines, it is planned to develop and implement the lifetime operational monitoring system

  5. 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

  6. Enhancement of surface mechanical properties by using TiN[BCN/BN]n/c-BN multilayer system

    International Nuclear Information System (INIS)

    Moreno, H.; Caicedo, J.C.; Amaya, C.; Munoz-Saldana, J.; Yate, L.; Esteve, J.; Prieto, P.

    2010-01-01

    The aim of this work is to improve the mechanical properties of AISI 4140 steel substrates by using a TiN[BCN/BN] n /c-BN multilayer system as a protective coating. TiN[BCN/BN] n /c-BN multilayered coatings via reactive r.f. magnetron sputtering technique were grown, systematically varying the length period (Λ) and the number of bilayers (n) because one bilayer (n = 1) represents two different layers (t BCN + t 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 -1 and 1100 cm -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 (Λ) was 80 nm (n = 25), yielding the relative highest hardness (∼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 multilayered coatings to explain this

  7. BN-350 nuclear power plant. Regulatory aspects of decommissioning

    International Nuclear Information System (INIS)

    Shiganakov, S.; Zhantikin, T.; Kim, A.

    2002-01-01

    Full text: The BN-350 reactor is a fast breeder reactor using liquid sodium as a coolant [1]. This reactor was commissioned in 1973 and operated for its design life of 20 years. Thereafter, it was operated on the basis of annual licenses, and the final shutdown was initially planned in 2003. In 1999, however, the Government of the Republic of Kazakhstan adopted Decree on the Decommissioning of BN-350 Reactor. This Decree establishes the conception of the reactor plant decommissioning. The conception envisages three stages of decommissioning. The first stage of decommissioning aims at putting the installation into a state of long term safe enclosure. The main goal is an achievement of nuclear-and radiation-safe condition and industrial safety level. The completion criteria for the stage are as follows: spent fuel is removed and placed in long term storage; radioactive liquid metal coolant is drained from the reactor and processed; liquid and solid radioactive wastes are reprocessed and long-term stored; systems and equipment, that are decommissioned at the moment of reactor safe store, are disassembled; radiation monitoring of the reactor building and environment is provided. The completion criteria of the second stage are as follows: 50 years is up; a decision about beginning of works by realization of dismantling and burial design is accepted. The goal of the third stage is partial or total dismantling of equipment, buildings and structure and burial. Since the decision on the decommissioning of BN-350 Reactor Facility was accepted before end of scheduled service life (2003), to this moment 'The Decommissioning Plan' (which in Kazakhstan is called 'Design of BN-350 reactor Decommission') was not worked out. For realization of the Governmental Decree and for determination of activities by the reactor safety provision and for preparation of its decommission for the period till Design approval the following documents were developed: 1. Special Technical Requirements

  8. 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.

  9. Larvicidal activity of Illicium difengpi BN Chang (Schisandraceae ...

    African Journals Online (AJOL)

    Purpose: To determine the larvicidal activity of the essential oil derived from Illicium difengpi B.N. Chang stem bark (Schisandraceae) and its major constituents against the larvae of Aedes aegypti L. Methods: Essential oil of I. difengpi stem bark was obtained by hydrodistillation and analyzed by gas chromatography (GC) ...

  10. Thermal stratification of sodium in the BN 600 reactor

    International Nuclear Information System (INIS)

    Obmelukhin, J.A.; Obukhov, P.I.; Rinejskij, A.A.; Sobolev, V.A.; Sherbakov, S.I.

    1983-01-01

    The signs of thermal stratification of sodium in the BN 600 reactor upper plenum revealed by the analysis of standard temperature sensors' readings are defined. The initial conditions for existence of different temperature sodium layers are given. Two approaches for realizing on a computer of equations describing sodium motion in the upper plenum of the reactor are presented. (author)

  11. Cobalt-60 production in the BN-350 fast power reactor

    International Nuclear Information System (INIS)

    Zvonarev, A.V.; Korobejnikov, V.V.; Matveenko, I.P.

    1994-01-01

    A possibility of Co-60 isotope production in the BN-350 fast reactor was considered. A special irradiating device, which is an assembly with a central hole, where a container containing cobalt and zirconium hydride is placed. The irradiating device tested permits generating 60 Co with specific activity of 100 Ci/g

  12. On the computation of molecular auxiliary functions An and Bn

    Indian Academy of Sciences (India)

    Department of Physics, Faculty of Arts and Sciences, Onsekiz Mart University, C¸ anakkale, Turkey. Email: guseinov@cheerful.com. Abstract. The Comment 'on the computation of auxiliary functions An(p) and Bn(pt)' (F E Harris,. Pramana – J. Phys. 61, C779 (2003)) is analysed in the arbitrary range of parameters n p and pt.

  13. Monte Carlo Generation of the 2BN Bremsstrahlung Distribution

    CERN Document Server

    Peralta, L; Trindade, A

    2003-01-01

    The 2BN bremsstrahlung cross-section is a well-adapted distribution to describe the radiative processes at low electron kinetic energy (Ek<500 keV). In this work a method to implement this distribution in a Monte Carlo generator is developed.

  14. 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)

  15. REVIEW ARTICLE: Nucleation, growth and characterization of cubic boron nitride (cBN) films

    Science.gov (United States)

    Zhang, W. J.; Chong, Y. M.; Bello, I.; Lee, S. T.

    2007-10-01

    Cubic BN (cBN) has a set of extreme properties similar or even superior to diamond. The advance of science and technology of cBN has however been severely hampered by the poor quality of the material available (random orientation, limited film thickness, poor crystallinity and adhesion with substrates due to a non-cubic BN interlayer). This paper reviews the recent progress in the nucleation, growth and characterization techniques of cBN films. It describes various successful approaches in interface engineering and growth techniques in increasing film thickness, improving crystallinity and adhesion of cBN films to the substrate, which are the major issues hindering cBN films for both mechanical and electronic applications. Based on observations of the surface and interface structures, we further discuss the growth mechanisms of cBN films via physical and chemical routes.

  16. The interaction of phosgene gas with different BN nanocones: DFT studies

    Science.gov (United States)

    Vessally, Esmail; Salary, Mina; Arshadi, Sattar; Hosseinian, Akram; Edjlali, Ladan

    2018-01-01

    We investigated the interaction of a phosgene molecule with four kinds of BN nanocones with 60°, 120°, 180° and 240° disclination angles using density functional theory calculations. Based on the results, the phosgene molecule tends to be adsorbed on the apex of all BN nanocones with adsorption energies of -11.1, -4.6, -16.6, and -14.8 kcal/mol, respectively. It was predicted that both of low coordination B atom, and Bsbnd B antiphase defects stabilize the LUMO level of the BN nanocones, and make them more reactive to phosgene gas. The electrical conductivity of the BN nanocone with 60° disclination angle will not change at the presence of the phosgene; and it cannot be used as a sensor. But the electrical conductivity of the BN nanocones with 120°, 180° and 240° disclination angles significantly increases. Therefore, these nanocones may be promising candidates for application in phosgene sensors. We found that the order of electronic sensitivity of the BN nanocones toward the phosgene gas is as follows: BN-240 > BN-120 > BN-180 » BN-60. The recovery time for the BN nanocones with 60°, 120°, 180° and 240° disclination angles is about 4.5 × 10-5, 7.8 × 10-10, 0.48, and 0.02 s at 298 K, respectively, indicating that the BN nanocones benefit from a short recovery time as chemical sensors.

  17. Solid Oxide Fuel Cell Seal Glass - BN Nanotubes Composites

    Science.gov (United States)

    Bansal, Narottam P.; Choi, Sung R.; Hurst, Janet B.; Garg, Anita

    2005-01-01

    Solid oxide fuel cell seal glass G18 composites reinforced with approx.4 weight percent of BN nanotubes were fabricated via hot pressing. Room temperature strength and fracture toughness of the composite were determined by four-point flexure and single edge V-notch beam methods, respectively. The strength and fracture toughness of the composite were higher by as much as 90% and 35%, respectively, than those of the glass G18. Microscopic examination of the composite fracture surfaces using SEM and TEM showed pullout of the BN nanotubes, similar in feature to fiber-reinforced ceramic matrix composites with weak interfaces. Other mechanical and physical properties of the composite will also be presented.

  18. Synthesis of bulk quantity BN nanotubes with uniform morphology

    International Nuclear Information System (INIS)

    Wen, G.; Zhang, T.; Huang, X.X.; Zhong, B.; Zhang, X.D.; Yu, H.M.

    2010-01-01

    Bulk quantity hexagonal BN nanotubes (h-BNNTs) with uniform morphology were synthesized via an improved ball-milling and annealing method. The sample was characterized by X-ray photoelectron spectrometry, electron energy loss spectroscopy, X-ray diffraction, scanning electron microscopy, conventional transmission electron microscopy (TEM) and high-resolution TEM. The results show that the fabricated BNNTs have a uniform diameter ranging from 80 to 100 nm and a length of about 50-60 μm.

  19. [Volatile metabolites analysis and molecular identification of endophytic fungi bn12 from Cinnamomum camphora chvar. borneol].

    Science.gov (United States)

    Chen, Meilan; Yang, Li; Li, Qin; Shen, Ye; Shao, Aijuan; Lin, Shufang; Huang, Luqi

    2011-12-01

    To identify endophytic fungi bn12 from Cinnamomum camphora chvar, borneol and analysis its volatile metabolites. The endophytic fungi bn12 was identified by morphological observation. volatile metabolites of endophytic fungi bn12 was analyzed by gas chromatography/mass spectrography (GC-MS). Volatile metabolites of endophytic fungi bn12 contain borneol and much indoles. The ITS sequence of endophytic fungi bnl2 is most similar to the ITS sequence of pleosporaceae fungus, particularly C. nisikadoi. Endophytic fungi bn12 is belong to pleosporaceae fungus. It has the ability of producing broneol.

  20. 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.

  1. Adsorption-induced gap states of h-BN on metal surfaces

    Science.gov (United States)

    Preobrajenski, A. B.; Krasnikov, S. A.; Vinogradov, A. S.; Ng, May Ling; Käämbre, T.; Cafolla, A. A.; Mårtensson, N.

    2008-02-01

    The formation of hexagonal boron nitride (h-BN) monolayers on Ni(111), Rh(111), and Pt(111) has been studied by a combination of x-ray emission, angle-resolved valence band photoemission, and x-ray absorption in search for interface-induced gap states of h-BN . A significant density of both occupied and unoccupied gap states with N2p and B2p characters is observed for h-BN/Ni(111) , somewhat less for h-BN/Rh(111) and still less for h-BN/Pt(111) . X-ray emission shows that the h-BN monolayer is chemisorbed strongly on Ni(111) and very weakly on Pt(111). We associate the gap states of h-BN adsorbed on the transition metal surfaces with the orbital mixing and electron sharing at the interface because their density increases with the growing strength of chemisorption.

  2. Densification Behavior of BN-added UO2

    International Nuclear Information System (INIS)

    Rhee, Young Woo; Kim, Keonsik; Kim, Dong Joo; Kim, Jong Hun; Oh, Jang Soo; Yang, Jae Ho

    2013-01-01

    Local wall thinning in pipelines affects the structural integrity of industries like nuclear power plants (NPPs). In the present study a pulsed eddy current (PEC) technology to detect the wall thing of carbon steel pipe covered with insulation is developed. Boron is commercially used as a neutron absorber fuel. A neutron absorber fuel is burned out or depleted during reactor operation. Westinghouse have been produced the Integral Fuel Burnable Absorber (IFBA) which is enriched UO 2 fuel pellets with a thin coating of zirconium diboride (ZrB 2 ) on the outer surface. Standard sintered fuel pellets are sputter coated with ZrB 2 . It is known that IFBA fuel can incur 20% to 30% additional fabrication costs. Boron-dispersed UO 2 fuel pellet made by the conventional pressing and sintering process of a powder mixture of UO 2 and B compound might be more cost-effective than IFBAs. M. G. Andrew et al. tried to sinter boron-dispersed UO 2 green pellet. However, they reported that boron-dispersed UO 2 fuel pellet is very difficult to be fabricated with a sufficient level of boron retention and high sintered density (greater than 90 % of theoretical density) because of the volatilization of boron oxide. We have investigated the densification behavior of mixtures of UO 2 and various boron compounds, such as B 4 C, BN, TiB 2 , ZrB 2 , SiB 6 , and HfB 2 . Boron compounds seemed to act as a sintering additive for UO 2 at a certain low temperature range. In this study, the densification behavior of BN-added UO 2 pellet has been investigated by sintering green pellets of a mixture of UO 2 powder and BN powder in H 2 atmosphere. A high density BN-added UO 2 pellet can be fabricated after sintering at 1200 .deg. C for more than 1 h in a H 2 atmosphere. The sintered density of BN-added UO 2 pellet can be increased up to about 95 %TD

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

    Science.gov (United States)

    Raddaha, Namir S; Cordero-Arias, Luis; Cabanas-Polo, Sandra; Virtanen, Sannakaisa; Roether, Judith A; Boccaccini, Aldo R

    2014-03-04

    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.

  4. 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.

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

    Science.gov (United States)

    Caicedo, J. M.; Bejarano, G.; Zambrano, G.; Baca, E.; Morán, O.; Prieto, P.

    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-1, 1100 cm-1 and 1387 cm-1, corresponding to the 2Au (out-plane bending of B-N-B bond) h-BN vibration mode, the F2 (stretching) c-BN Transversal Optical (TO) mode and the E1u (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 × 10-2 mbar.

  6. Bias induced up to 100% spin-injection and detection polarizations in ferromagnet/bilayer-hBN/graphene/hBN heterostructures

    NARCIS (Netherlands)

    Gurram, Mallikarjuna; Omar, Siddharta; van Wees, Bart

    2017-01-01

    We study spin transport in a fully hBN encapsulated monolayer-graphene van der Waals heterostructure at room temperature. A top-layer of bilayer-hBN is used as a tunnel barrier for spin-injection and detection in graphene with ferromagnetic cobalt electrodes. We report surprisingly large and

  7. Effect of an in-plane ligand on the electronic structures of bromo-bridged nano-wire Ni-Pd mixed-metal complexes, [Ni(1-x)Pd(x)(bn)2Br]Br2 (bn = 2S,3S-diaminobutane).

    Science.gov (United States)

    Sasaki, Mari; Wu, Hashen; Kawakami, Daisuke; Takaishi, Shinya; Kajiwara, Takashi; Miyasaka, Hitoshi; Breedlove, Brian K; Yamashita, Masahiro; Kishida, Hideo; Matsuzaki, Hiroyuki; Okamoto, Hiroshi; Tanaka, Hisaaki; Kuroda, Shinichi

    2009-08-03

    Single crystals of quasi-one-dimensional bromo-bridged Ni-Pd mixed-metal complexes with 2S,3S-diaminobutane (bn) as an in-plane ligand, [Ni(1-x)Pd(x)(bn)(2)Br]Br(2), were obtained by using an electrochemical oxidation method involving mixed methanol/2-propanol (1:1) solutions containing different ratios of [Ni(II)(bn)(2)]Br(2) and [Pd(II)(bn)(2)]Br(2). To investigate the competition between the electron-correlation of the Ni(III) states, or Mott-Hubbard states (MH), and the electron-phonon interaction of the Pd(II)-Pd(IV) mixed valence states, or charge-density-wave states (CDW), in the Ni-Pd mixed-metal compounds, X-ray structure analyses, X-ray oscillation photograph, and Raman, IR, ESR, and single-crystal reflectance spectra were analyzed. In addition, the local electronic structures of Ni-Pd mixed-metal single crystals were directly investigated by using scanning tunneling microscopy (STM) at room temperature and ambient pressure. The oxidation states of [Ni(1-x)Pd(x)(bn)(2)Br]Br(2) changed from a M(II)-M(IV) mixed valence state to a M(III) MH state at a critical mixing ratio (x(c)) of approximately 0.8, which is lower than that of [Ni(1-x)Pd(x)(chxn)(2)Br]Br(2) (chxn = 1R,2R-diaminocyclohexane) (x(c) approximately 0.9) reported previously. The lower value of x(c) for [Ni(1-x)Pd(x)(bn)(2)Br]Br(2) can be explained by the difference in their CDW dimensionalities because the three-dimensional CDW ordering in [Pd(bn)(2)Br]Br(2) observed by using X-ray diffuse scattering stabilizes the Pd(II)-Pd(IV) mixed valence state more than two-dimensional CDW ordering in [Pd(chxn)(2)Br]Br(2) does, which has been reported previously.

  8. UV-photoelectron spectroscopy of BN indoles: experimental and computational electronic structure analysis.

    Science.gov (United States)

    Chrostowska, Anna; Xu, Senmiao; Mazière, Audrey; Boknevitz, Katherine; Li, Bo; Abbey, Eric R; Dargelos, Alain; Graciaa, Alain; Liu, Shih-Yuan

    2014-08-20

    We present a comprehensive electronic structure analysis of two BN isosteres of indole using a combined UV-photoelectron spectroscopy (UV-PES)/computational chemistry approach. Gas-phase He I photoelectron spectra of external BN indole I and fused BN indole II have been recorded, assessed by density functional theory calculations, and compared with natural indole. The first ionization energies of these indoles are natural indole (7.9 eV), external BN indole I (7.9 eV), and fused BN indole II (8.05 eV). The computationally determined molecular dipole moments are in the order: natural indole (2.177 D) > fused BN indole II (1.512 D) > external BN indole I (0.543 D). The λmax in the UV-vis absorption spectra are in the order: fused BN indole II (292 nm) > external BN indole I (282 nm) > natural indole (270 nm). The observed relative electrophilic aromatic substitution reactivity of the investigated indoles with dimethyliminium chloride as the electrophile is as follows: fused BN indole II > natural indole > external BN indole I, and this trend correlates with the π-orbital coefficient at the 3-position. Nucleus-independent chemical shifts calculations show that the introduction of boron into an aromatic 6π-electron system leads to a reduction in aromaticity, presumably due to a stronger bond localization. Trends and conclusions from BN isosteres of simple monocyclic aromatic systems such as benzene and toluene are not necessarily translated to the bicyclic indole core. Thus, electronic structure consequences resulting from BN/CC isosterism will need to be evaluated individually from system to system.

  9. 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.

  10. Nanoindentation measurements of a highly oriented wurtzite-type boron nitride bulk crystal

    Science.gov (United States)

    Deura, Momoko; Kutsukake, Kentaro; Ohno, Yutaka; Yonenaga, Ichiro; Taniguchi, Takashi

    2017-03-01

    We succeeded in synthesizing a bulk crystal of wurtzite-type boron nitride (w-BN) by the direct conversion method. The synthesized crystal was approximately 2 mm wide and 350 µm thick, and highly oriented to the c-axis. We performed nanoindentation measurements on the c-plane of the w-BN crystal at room temperature to evaluate the mechanical properties of w-BN. The hardness and Young’s modulus of w-BN from the obtained curves were simultaneously determined to be 54 ± 2 and 860 ± 40 GPa, respectively. The underlying physical mechanism that dominates the mechanical properties of group-III nitride semiconductors is also examined.

  11. 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.

  12. High thermoelectricpower factor in graphene/hBN devices.

    Science.gov (United States)

    Duan, Junxi; Wang, Xiaoming; Lai, Xinyuan; Li, Guohong; Watanabe, Kenji; Taniguchi, Takashi; Zebarjadi, Mona; Andrei, Eva Y

    2016-12-13

    Fast and controllable cooling at nanoscales requires a combination of highly efficient passive cooling and active cooling. Although passive cooling in graphene-based devices is quite effective due to graphene's extraordinary heat conduction, active cooling has not been considered feasible due to graphene's low thermoelectric power factor. Here, we show that the thermoelectric performance of graphene can be significantly improved by using hexagonal boron nitride (hBN) substrates instead of SiO 2 We find the room temperature efficiency of active cooling in the device, as gauged by the power factor times temperature, reaches values as high as 10.35 W⋅m -1 ⋅K -1 , corresponding to more than doubling the highest reported room temperature bulk power factors, 5 W⋅m -1 ⋅K -1 , in YbAl 3 , and quadrupling the best 2D power factor, 2.5 W⋅m -1 ⋅K -1 , in MoS 2 We further show that the Seebeck coefficient provides a direct measure of substrate-induced random potential fluctuations and that their significant reduction for hBN substrates enables fast gate-controlled switching of the Seebeck coefficient polarity for applications in integrated active cooling devices.

  13. JNC results of BN-600 benchmark calculation (phase 4)

    International Nuclear Information System (INIS)

    Ishikawa, Makoto

    2003-01-01

    The present work is the results of JNC, Japan, for the Phase 4 of the BN-600 core benchmark problem (Hex-Z fully MOX fuelled core model) organized by IAEA. The benchmark specification is based on 1) the RCM report of IAEA CRP on 'Updated Codes and Methods to Reduce the Calculational Uncertainties of LMFR Reactivity Effects, Action 3.12' (Calculations for BN-600 fully fuelled MOX core for subsequent transient analyses). JENDL-3.2 nuclear data library was used for calculating 70 group ABBN-type group constants. Cell models for fuel assembly and control rod calculations were applied: homogeneous and heterogeneous (cylindrical supercell) model. Basic diffusion calculation was three-dimensional Hex-Z model, 18 group (Citation code). Transport calculations were 18 group, three-dimensional (NSHEC code) based on Sn-transport nodal method developed at JNC. The generated thermal power per fission was based on Sher's data corrected on the basis of ENDF/B-IV data library. Calculation results are presented in Tables for intercomparison

  14. Preparation of transparent BN films with superhydrophobic surface

    Science.gov (United States)

    Li, Guo-Xing; Liu, Yi; Wang, Bo; Song, Xue-Mei; Li, Er; Yan, Hui

    2008-06-01

    A novel approach was investigated to obtain the superhydrophobicity on surfaces of boron nitride films. In this method boron nitride films were deposited firstly on Si(1 0 0) and quartz substrate using a radio frequency (RF) magnetron sputtering system, and then using CF 4 plasma treatment, the topmost surface area can be modified systematically. The results have shown that the water contact angle on such surfaces can be tuned from 67° to 159°. The films were observed to be uniform. The surfaces of films consist of micro-features, which were confirmed by Atomic Force Micrograph. The chemical bond states of the films were determined by Fourier Transform Infrared (FTIR) Spectroscopy, which indicate the dominance of B-N binding. According to the X-ray Photoelectron Spectroscopy analysis, the surface of film is mainly in BN phase. The micro-feature induced surface roughness is responsible for the observed superhydrophobic nature. The water contact angles measured on these surfaces can be modeled by the Cassie's formulation.

  15. On the Difference Equation xn=anxn-k/(bn+cnxn-1⋯xn-k

    Directory of Open Access Journals (Sweden)

    Stevo Stević

    2012-01-01

    Full Text Available The behavior of well-defined solutions of the difference equation xn=anxn-k/(bn+cnxn-1⋯xn-k, n∈ℕ0, where k∈ℕ is fixed, the sequences an, bn and cn are real, (bn,cn≠(0,0, n∈ℕ0, and the initial values x-k,…,x-1 are real numbers, is described.

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

    Science.gov (United States)

    2017-04-28

    AFRL-RX-WP-JA-2017-0308 MODELING ENVIRONMENTAL DEGRADATION OF SIC/BN/SIC CMCS (PREPRINT) Craig Przybyla and Michael K Cinibulk...2017 Interim 22 July 2013 – 6 January 2017 4. TITLE AND SUBTITLE MODELING ENVIRONMENTAL DEGRADATION OF SIC/BN/SIC CMCS (PREPRINT) 5a. CONTRACT...91360 Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std. Z39-18 Modeling environmental degradation of SiC/BN/SiC CMCs Triplicane A

  17. On the Stability of c-BN-Reinforcing Particles in Ceramic Matrix Materials

    Directory of Open Access Journals (Sweden)

    Anne-Kathrin Wolfrum

    2018-02-01

    Full Text Available Cubic boron nitride (c-BN composites produced at high pressures and temperatures are widely used as cutting tool materials. The advent of new, effective pressure-assisted densification methods, such as spark plasma sintering (SPS, has stimulated attempts to produce these composites at low pressures. Under low-pressure conditions, however, transformation of c-BN to the soft hexagonal BN (h-BN phase can occur, with a strong deterioration in hardness and wear. In the present work, the influence of secondary phases (B2O3, Si3N4, and oxide glasses on the transformation of c-BN was studied in the temperature range between 1100 °C and 1575 °C. The different heat treated c-BN particles and c-BN composites were analyzed by SEM, X-ray diffraction, and Raman spectroscopy. The transformation mechanism was found to be kinetically controlled solution–diffusion–precipitation. Given a sufficiently low liquid phase viscosity, the transformation could be observed at temperatures as low as 1200 °C for the c-BN–glass composites. In contrast, no transformation was found at temperatures up to 1575 °C when no liquid oxide phase is present in the composite. The results were compared with previous studies concerning the c-BN stability and the c-BN phase diagram.

  18. 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)

  19. BN-C Hybrid Nanoribbons as Gas Sensors

    Science.gov (United States)

    Darvishi Gilan, Mahdi; Chegel, Raad

    2018-02-01

    The effects of carbon monoxide (CO) and ammonia (NH3) molecules adsorption on the various composites of boron nitride and graphene BN-C hybrid nanoribbons are investigated using the non-equilibrium Green's function (NEGF) technique based on density functional theory (DFT). The effects of adsorption with possible random configurations on the average of the density of states (DOS), transmission coefficient, and the current-voltage ( I- V) characteristics are calculated. The results indicate that, by embedding armchair graphene nanoribbon (AGNR) with boron nitride nanoribbon (BNNR), the various electronic properties can be observed after gas molecule adsorption. The electronic structure and gap of hybrids system is modified due to gas adsorption, and the systems act like the n-type semiconductor by NH3 molecule adsorption. The hybrid structures due to their tunable band gap are better candidates for gas detecting compared to the pristine BNNRs and AGNRs.

  20. Licensing Support Experience of the BN-600 Operation

    International Nuclear Information System (INIS)

    Khrennikov, N.; Sintsov, A.

    2013-01-01

    License procedure - Main principle: • All works, including fatigue tests of new types of fuel, are carried out at the unit 3 Beloyarsk nuclear power plants with the BN-600 reactor with the justification of the regulatory body. • Justification procedure is standard for all power units and independent from the reactor types. • The regulatory body and independent experts or technical support organizations, which can be involved in this work by the regulatory body, review SAR, operational manuals and other operator documents. • Safety requirements (i.e. Federal rules and codes). The project and design documents shall meet safety requirements. • The technical and organizational measures for safety guarantee shall meet well-known results of the research investigations or shall be experimental validate

  1. 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.

  2. 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.)

  3. 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.)

  4. Decolourization and degradation of azo Dye, Synozol Red HF6BN ...

    African Journals Online (AJOL)

    Decolourization and degradation of azo Dye, Synozol Red HF6BN, by Pleurotus ostreatus. Sidra Ilyas, Skinder Sultan Sultan, Abdul Rehman. Abstract. The present paper focuses on the use of fungus, Pleurotus ostreatus, to decolorize and degrade azo dye, Synazol Red HF6BN. Decolorization study showed that P.

  5. A comparative DFT study on the interaction of cathinone drug with BN nanotubes, nanocages, and nanosheets

    Science.gov (United States)

    Nejati, Kamellia; Hosseinian, Akram; Vessally, Esmail; Bekhradnia, Ahmadreza; Edjlali, Ladan

    2017-11-01

    Cathinone is an organic stimulant which is classified as psychoactive drug and its abuse has been linked to many deaths worldwide. Here, we studied the electronic sensitivity of a BN cage, a zigzag (6, 0) BN nanotube, and a BN nanosheet toward cathinone using density functional theory calculations. The B3LYP-D functional predicts that the order of magnitude of electrical conductivity of BN nanostructures is as follows tube > sheet > cage. The cathinone drug prefers to be adsorbed on the BN nanostructures via its sbnd NH2 group rather than O-head with adsorption energy about -16.1, -14.0 and -5.0 kcal/mol for cage, tube, and sheet, respectively. Our results indicate that by increasing the p-character of the hybridization of the adsorbing B atom in the BN nanostructures, the interaction is strengthened. Based on the density of states analysis, it was demonstrated that the electrical conductivity of the BN nanostructures is decreased by the drug adsorption, indicating that they can be used in the cathinone sensors. The order of magnitude of the sensitivity is as follows: SCage > STube > SSheet. This trend corresponds to the decrease of the structural curvature in the BN nanostructures. Finally, a short recovery time of about 0.54 s, 0.02 s and 4.4 ns is predicted for cage, tube and sheet, respectively, at 298 K.

  6. Midgap states and band gap modification in defective graphene/h-BN heterostructures

    NARCIS (Netherlands)

    Sachs, B.; Wehling, T.O.; Katsnelson, M.I.; Lichtenstein, A.I.

    2016-01-01

    The role of defects in van der Waals heterostructures made of graphene and hexagonal boron nitride (h-BN) is studied using a combination of ab initio and model calculations. Despite the weak van der Waals interaction between layers, defects residing in h-BN, such as carbon impurities and antisite

  7. BnNHL18A shows a localization change by stress-inducing chemical treatments

    International Nuclear Information System (INIS)

    Lee, Suk-Bae; Ham, Byung-Kook; Park, Jeong Mee; Kim, Young Jin; Paek, Kyung-Hee

    2006-01-01

    The two genes, named BnNHL18A and BnNHL18B, showing sequence homology with Arabidopsis NDR1/HIN1-like (NHL) genes, were isolated from cDNA library prepared with oilseed rape (Brassica napus) seedlings treated with NaCl. The transcript level of BnNHL18A was increased by sodium chloride, ethephon, hydrogen peroxide, methyl jasmonate, or salicylic acid treatment. The coding regions of BnNHL18A and BnNHL18B contain a sarcolipin (SLN)-like sequence. Analysis of the localization of smGFP fusion proteins showed that BnNHL18A is mainly localized to endoplasmic reticulum (ER). This result suggests that the SLN-like sequence plays a role in retaining proteins in ER membrane in plants. In response to NaCl, hydrogen peroxide, ethephon, and salicylic acid treatments, the protein localization of BnNHL18A was changed. Our findings suggest a common function of BnNHL18A in biotic and abiotic stresses, and demonstrate the presence of the shared mechanism of protein translocalization between the responses to plant pathogen and to osmotic stress

  8. A first principle investigation into effect of B and BN doped C60 in ...

    Indian Academy of Sciences (India)

    22

    Abstract. The present paper reports the effect of B and BN doped C60 as catalyst for lowering the dehydrogenation energy in MXH4 clusters (M = Na and Li; X = Al and B) using density functional calculations. MXH4 interacts strongly with B doped C60 and weakly with BN-doped. C60 in comparison to pure C60 with binding ...

  9. A first-principle investigation into effect of B- and BN-doped C60 in ...

    Indian Academy of Sciences (India)

    2017-11-23

    Nov 23, 2017 ... Abstract. The present paper reports the effect of B- and BN-doped C60 as catalysts for lowering the dehydrogenation energy in MXH4 clusters (M = Na and Li, X = Al and B) using density functional calculations. MXH4 interacts strongly with. B-doped C60 and weakly with BN-doped C60 in comparison with ...

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

    Energy Technology Data Exchange (ETDEWEB)

    Huang, Cheng [College of Aerospace Engineering, Chongqing University, Chongqing 400044 (China); Peng, Xianghe, E-mail: xhpeng@cqu.edu.cn [College of Aerospace Engineering, Chongqing University, Chongqing 400044 (China); State Key Laboratory of Coal Mine Disaster Dynamics and Control, Chongqing University, Chongqing 400044 (China); Chongqing Key Laboratory of Heterogeneous Material Mechanics, Chongqing University, Chongqing 400044 (China); Fu, Tao, E-mail: futaocqu@163.com [College of Aerospace Engineering, Chongqing University, Chongqing 400044 (China); Zhao, Yinbo; Feng, Chao; Lin, Zijun [College of Aerospace Engineering, Chongqing University, Chongqing 400044 (China); Li, Qibin [College of Aerospace Engineering, Chongqing University, Chongqing 400044 (China); Chongqing Key Laboratory of Heterogeneous Material Mechanics, Chongqing University, Chongqing 400044 (China)

    2017-01-15

    Highlights: • We optimize tersoff potential to better simulate the BN. • We perform respectively the nanoindentations on the (001) and (111) surface of cBN. • The main slip system of cBN under nanoindentation is {111}<110>. • Temperature has a significant effect on the mechanical properties of cBN. - Abstract: 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}<110> 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.

  11. Unusual occurrences during the whole operation of BN-250 NPP

    International Nuclear Information System (INIS)

    Andropenkov, S.

    2000-01-01

    Unusual occurrences during the whole operation BN-350 NPP. 1. Oil ingress in high pressure receiver for the not reveled reason, 12.05.1994. 2. lncrease of water radioactivity of circulating water supply system due to heat exchanger leak of spent fuel assembly washing out system, 17.09.1993. 3. Lack of passableness of sodium drain header of primary circuit reveled during inspection on scheduled preventative maintenance, 28.11.1996. 4. Destruction of the blow-off line of MCP-6 due to corrosion damage of the pipeline while unit was being operated at rated power, 23.04.1993. 5. Lack of passableness of blow-down pipeline connecting reactor gas cover with gas-type pressurizer while unit was being operated at rated power, 17.11.1994. 6. Sodium ingress in blow-down pipeline of loop-5 intermediate heat exchanger while loop-5 was being fed of sodium during scheduled preventative maintenance, 27.06.1994. 7. Resistance deterioration of electro heating zones of loop-4 due to heat exchanger leak and water ingress in air-pipeline of primary circuit boxes recirculating air system, 02.05.1997. 8. Resistance deterioration of electro heating zones of sodium drain header of secondary circuit was sopped in the water for the extinguishing the fire of blowing ventilation oil-strainer, 23.12.1994. 9. Sodium ingress in gas-type pressurizer through pipeline of primary sodium cleanup system and blow-down pipeline of failed MCP-2 while primary sodium cleanup system was being connected to the primary circuit, 17.08.1976. As a rule, the main reactor systems are scrutinized more carefully than the auxiliary reactor systems and the order actions are existed for eliminating and mitigating of consequences of main reactor system fails. Therefore the auxiliary reactor system fails may impact on the main reactor systems through places of its contact in significant measure. The influence of auxiliary reactor system fails on main reactor systems and its possible consequences for behavior of the main

  12. Controlling the electronic properties of the graphene nanoflakes by BN impurities

    Science.gov (United States)

    Mohammed, Mohammed H.

    2018-01-01

    Electronic properties of the graphene nanoflakes (GNFs) can be controlled by using chemical doping method. First-principle of the density functional theory (DFT) method, which is implemented in the Gaussian 09W program are used to investigate the electronic properties, such as electronic band gap, DOS, total energy, dipole moment, HOMO, and LOMO energies of the GNFs with and without various concentrations of the BN impurities in various sites. There are very significant results. My founding results show that these properties of the GNFs depend on the concentrations of BN impurities and the geometrical pattern of the BN impurities in the GNFs. By increasing the distance between these impurities, the electronic band gap and the shape of the DOS are reduced and altered, respectively. So, the results offer that the electronic band gap value depends on the concentrations of BN impurities and sites of these impurities in the GNFs. The electronic dipole moments value is increased by increased the concentrations of the BN impurities. All structures became more stable due to the total energy is increased, excepted B, BN and B2N impurities, which is reduced and make GNFs structure unstable. Then, GNFs can be used in various applications because the electronic properties of the GNFs are controlled and modified with BN impurities.

  13. 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.

  14. 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.

  15. Proprietes des melanges de poudres d'aciers inoxydables 316L/h-BN et 409L/h-BN frittes sous differentes atmospheres (hydrogen-nitrogen)

    Science.gov (United States)

    Mercier, Thierry

    L'influence de la composition d'atmospheres de frittage "hydrogene---azote" sur les proprietes de specimens produits par metallurgie des poudres a partir de melanges de poudres d'aciers inoxydables 316L et 409L et de poudre de nitrure de bore hexagonal (h-BN) a ete etudiee. Ces proprietes ont ete comparees a celles de specimens sans h-BN frittes simultanement dans la meme atmosphere. Une mince couche dense s'est formee a la surface des echantillons contenant du h-BN frittes dans une atmosphere contenant au moins 50% en volume d'hydrogene. Cette couche dense ameliore generalement les proprietes de l'alliage 316L. Les proprietes de l'alliage 409L montrent une amelioration beaucoup moins significative qui s'amenuise lorsque l'atmosphere s'appauvrit en azote. L'azote favorise la corrosion de specimens de 409L avec ou sans h-BN. Quant au 316L, il demeure resistant a la corrosion malgre la presence d'un peu d'azote au frittage et l'addition de h-BN lui est benefique particulierement lorsque fritte en presence d'une teneur elevee d'azote (jusqu'a 50%vol. N2) qui permet tout de meme la formation d'une couche dense en surface.

  16. UK contributions to the decommissioning of the BN-350 reactor in Kazakhstan: 2002 – 2011

    International Nuclear Information System (INIS)

    Wells, D.

    2011-01-01

    UK assistance with the decommissioning of BN-350 has cost ~£8.9 million over ten years, ~£4 million spent directly in Kazakhstan. The Programme has immobilised key wastes, contributed to irreversible shutdown of the reactor and addressed issues associated with sodium coolant processing. The Programme funded the operations to load spent fuel canisters into casks at BN-350, together with their despatch from site and receipt at the secure storage facility. The Programme also delivered technical and project management training, assisted in the production of the BN-350 Decommissioning Plan and contributed to the radiation survey effort in the STS

  17. 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.

  18. A BN Aromatic Ring Strategy for Tunable Hydroxy Content in Polystyrene.

    Science.gov (United States)

    van de Wouw, Heidi L; Lee, Jae Young; Awuyah, Elorm C; Klausen, Rebekka S

    2018-02-05

    BN 2-vinylnaphthalene, a BN aromatic vinyl monomer, is copolymerized with styrene under free radical conditions. Oxidation yields styrene-vinyl alcohol (SVA) statistical copolymers with tunable hydroxy group content. Comprehensive spectroscopic investigation provides proof of structure. Physical properties that vary systematically with hydroxy content include solubility and glass transition temperature. BN aromatic polymers represent a platform for the preparation of diverse functional polymeric architectures via the remarkable reaction chemistry of C-B bonds. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. 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

  20. The effect of incorporated self-lubricated BN(h) particles on the tribological properties of Ni–P/BN(h) composite coatings

    Energy Technology Data Exchange (ETDEWEB)

    Hsu, Chih-I., E-mail: s1322509@gmail.com [School of Defense Science, Chung Cheng Institute of Technology, National Defense University, Taoyuan, Taiwan (China); Hou, Kung-Hsu, E-mail: khou@ndu.edu.tw [Department of Power Vehicle and Systems Engineering, Chung Cheng Institute of Technology, National Defense University, Taoyuan, Taiwan (China); Ger, Ming-Der, E-mail: mingderger@gmail.com [Department of Chemistry and Material Engineering, Chung Cheng Institute of Technology, National Defense University, Taoyuan, Taiwan (China); Wang, Gao-Liang, E-mail: wanggl@takming.edu.tw [Department of Marketing Management, Takming University of Science and Technology, Taipei, Taiwan (China)

    2015-12-01

    Highlights: • The Ni-P-BN(h) coatings were prepared by electroless plating techniques in this research. • Surfactant CTAB resulting in a uniform dispersion of particles in Ni-P coating. • CTAB with a positive effect on the tribological performance of Ni–P/BN(h) coatings. • Frictional tests results show that optimal friction coefficient would be decreased 75%. • Wear resistance of the Ni-P/BN(h) coating is higher about 10 times Ni–P coatings. - Abstract: Ni–P/BN(h) composite coatings are prepared by means of the conventional electroless plating from the bath containing up to 10.0 g/l of hexagonal boron nitride particles with size 0.5 μm. The Ni–P coating is also prepared as a comparison. Cationic surfactant cetyltrimethylammonium bromide (CTAB) is used to stabilize the electrolyte, and the optimum CTAB concentration resulting in a nonagglomerated dispersion of particles is obtained using a dispersion stability analyzer. Morphology of the coatings and the effect of incorporated particles on coating structure and composition are investigated via scanning electron microscopy, field emission electron probe micro-analyzer and X-ray diffraction analysis. Hardness, roughness, friction coefficient and wear resistance of the coatings are also evaluated using Vickers microhardness tester, atomic force microscopy and ball-on disk machine. The presence of CTAB in the depositing bath has a positive effect on the surface roughness and performance of Ni–P/BN(h) composite coatings. The friction and wear tests results show that incorporation of 14.5 vol% BN(h) particles into the Ni–P coating lowers the coating friction coefficient by about 75% and the wear resistance of the Ni–P composites is approximately 10 times higher than Ni–P coating.

  1. 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.

  2. Self-Assembled BN and BCN Quantum Dots Obtained from High Intensity Ultrasound Exfoliated Nanosheets

    Czech Academy of Sciences Publication Activity Database

    Štengl, Václav; Henych, Jiří; Kormunda, M.

    2014-01-01

    Roč. 6, č. 6 (2014), s. 1106-1116 ISSN 1947-2935 Institutional support: RVO:61388980 Keywords : Ultrasound * Exfoliation * BN * BCN * Quantum Dots Subject RIV: CA - Inorganic Chemistry Impact factor: 2.598, year: 2014

  3. 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.

  4. Low-pressure c-BN deposition - is a CVD process possible?

    International Nuclear Information System (INIS)

    Haubner, R.; Tang, X.

    2001-01-01

    Since the low-pressure diamond deposition was discovered in 1982 there is a high interest to find a similar process for the c-BN synthesis. A review about the c-BN deposition process as well as its characterization is given. Experiments with a simple chemical vapor deposition(CVD) reactor using tris(dimethylamino)borane as precursor were carried out. In a cold-wall reactor substrates were heated up by high-frequency. Argon was used as protecting and carrying the precursor, it was saturated with tris(dimethylamino)borane (precursor) according to its vapor pressure and transports the pressure to the hot substrate, where deposition occurs. WC-Co hardmetal plates containing 6 wt. % Co, Mo and Si were used as substrates. Various BN layers were deposited and characterized. X-ray diffraction, IR-spectroscopy and SIMS indicate that BN-coatings containing c-BN were deposited. However a final verification of c-BN crystallites by TEM investigations was not possible till now. (nevyjel)

  5. Synthesis and Characterization of Large-Area Graphene Directly CVD-Grown on h-BN

    Science.gov (United States)

    Kim, Minwoo; Song, Young; Wang, Min; Jang, Seong-Kyu; Lee, Sungjoo; Jang, Won-Jun; Kahng, Se-Jong; Graphene synthesis Collaboration; Characterization Collaboration

    2013-03-01

    As an ideal substrate for graphene, hexagonal boron nitride (h-BN) has been utilized and studied extensively by transfer technique, which still has a high chance to have impurities at the graphene/h-BN interface. Here we report direct CVD growth of graphene on large area h-BN film. AFM and Raman spectroscopy measurements show that there is only one monolayer of graphene, and whose unperturbed electronic structures are also confirmed by electron transport measurements and scanning tunneling spectroscopy. High resolution TEM images for cross-section taken before and after transferring graphene/h-BN on to SiO2 indicate this CVD-grown hybrid structure is robust enough. Based on this new method, high quality and large area graphene on h-BN film with a clean interface can be synthesized for the application of electronic devices, and can fill the missing steps to grow fully CVD-grown super-structure of graphene and h-BN. This research was supported by Basic Science Research Program through the National Research Foundation of Korea (NRF) funded by the Ministry of Education, Science and Technology (Grant Numbers: 2009-0083540, 2012R1A1A2020089 and 2012R1A1A1041416).

  6. Study of electrical properties of Au/BN/InP MIS structures; Badanie wlasciwosci elektrycznych struktur MIS typu Au/BN/InP

    Energy Technology Data Exchange (ETDEWEB)

    Dmowski, K. [Politechnika Warszawska, Warsaw (Poland); Lepley, B.; Bath, A.; Losson, E.; Thevenin, P.; Nabil, S.A. [Metz Univ., 57 (France)

    1997-12-01

    The electrical properties of multilayer system type metal-insulator-semiconductor (MIS) have been investigated on the example of Au/BN/InP. Current-voltage as well as capacity-voltage characteristics have been measured. The applicability of such systems in microelectronics have been discussed. 7 refs, 4 figs.

  7. 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.

  8. Magnetic properties of graphene/BN/Co(111) and potential spintronics

    International Nuclear Information System (INIS)

    Hashmi, Arqum; Hong, Jisang

    2014-01-01

    Using the Vienna ab initio simulation package (VASP) we have explored structural, adsorption, and magnetic properties of graphene/BN/Co(111) with the help of semi empirical and non-local van der Waals functional methods such as DFT-D2, vdW-DF2, optPBE-vdW, and optB88-vdW. In the most stable optimized structure, one carbon is on top of B atom and the other carbon is on top of hollow site of BN layer. No buckling geometry is found in both graphene and BN layers with vdW-DF2 method. In contrast, all three other approaches show that a buckling feature takes place in BN layer adjacent to Co substrate and due to this buckling an adsorption energy of graphene is significantly enhanced. Very interestingly, the graphene has an energy gap only in one spin band due to the influence of Co and an insulating state in BN layer adjacent to graphene is observed. In addition, the Co layer displays half metallic states as well. This feature suggests that the graphene/BN/Co(111) can be utilized for ideal tunneling magnetoresistance (TMR) structure because a high TMR ratio is expected. - Highlights: • The adsorption energy is greatly enhanced due to buckling of supporting BN layer. • The graphene has a gap only in one spin band. • The Co shows a half metallic state. • Due to the gap in graphene and half metallic feature of Co, a high TMR ratio is expected

  9. 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 %.

  10. 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.

  11. 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 %).

  12. 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.

  13. 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

    with 25% of diamond replaced by cBN grains demonstrate 20% increased performance as compared with pure diamond machining tools, and more than two times higher performance as compared with pure cBN tools. Further, cast iron machining efficiency of the wheels modified by hBN particles was 80% more efficient......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...

  14. Spark plasma sintering of cBN(core/SiO2(shell powder prepared by rotary chemical vapor deposition

    Directory of Open Access Journals (Sweden)

    Jianfeng Zhang

    2014-09-01

    Full Text Available SiO2 nanolayer coated cubic boron nitride (cBN, cBN(core/SiO2(shell powder, was prepared by rotary chemical vapor deposition. The cBN/SiO2 powder was densified by spark plasma sintering at 1873 K for 0.3 ks. The hexagonal boron nitride (hBN phase was not observed in the cBN–SiO2 composites, indicating that the SiO2 nanolayer depressed the phase transformation from cBN to hBN. The relative density of cBN–SiO2 increased with increasing SiO2 content (CSiO2. The highest hardness of the cBN–SiO2 composite was 17.5 GPa at CSiO2=38 wt% and a load of 0.98 N.

  15. 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.

  16. Pulse electric current sintering of cubic boron nitride/tungsten carbide–cobalt (cBN/WC–Co) composites: Effect of cBN particle size and volume fraction on their microstructure and properties

    Energy Technology Data Exchange (ETDEWEB)

    Wang, Bo, E-mail: xiaoboking@gmail.com [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xianning West Road No. 28, Xi' an 710049, Shaanxi Province (China); State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace Engineering, Xi' an Jiaotong University, Xianning West Road No. 28, Xi' an 710049, Shaanxi Province (China); Qin, Yi [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xianning West Road No. 28, Xi' an 710049, Shaanxi Province (China); Jin, Feng [State Key Laboratory for Strength and Vibration of Mechanical Structures, School of Aerospace Engineering, Xi' an Jiaotong University, Xianning West Road No. 28, Xi' an 710049, Shaanxi Province (China); Yang, Jian-Feng, E-mail: yang155@mail.xjtu.edu.cn [State Key Laboratory for Mechanical Behavior of Materials, Xi' an Jiaotong University, Xianning West Road No. 28, Xi' an 710049, Shaanxi Province (China); Ishizaki, Kozo [Department of Mechanical Engineering, Nagaoka University of Technology, Nagaoka 940-2188 (Japan)

    2014-06-01

    Cubic boron nitride/tungsten carbide–cobalt (cBN/WC–Co) composites were fabricated by pulse electric current sintering (PECS), using Ni–P as sintering additives to promote low temperature densification. The effect of cBN particle size and volume fraction on the densification, microstructure and mechanical properties of WC–Co composites was investigated. There was no phase transformation from cBN to hBN (hexagonal BN) with low-hardness due to low sintering temperature (1100–1200 °C) and short sintering time. Smaller cBN particle led to lower sinter-ability of the composites due to its high specific surface area. The 30 vol% 10–14 µm cBN/WC–Co composite (P14V30) exhibited high hardness (18.3 GPa, 1200 °C) and high fracture toughness (15.6 MP·m{sup 1/2}, 1000 °C). The high hardness resulted from the homogeneously dispersed cBN particles, which had a good bonding with the WC matrix. Increased fracture toughness was mainly attributed to crack deflection or bridging and pullout of cBN grains.

  17. Effect of substrate temperature and gas flow ratio on the nanocomposite TiAlBN coating

    Energy Technology Data Exchange (ETDEWEB)

    Rosli, Z. M., E-mail: azmr@utem.edu.my; Kwan, W. L., E-mail: kwailoon86@gmail.com; Juoi, J. M., E-mail: jariah@utem.edu.my [Faculty of Manufacturing Engineering, Universiti Teknikal Malaysia Melaka, Hang Tuah Jaya, 76100 Durian Tunggal, Melaka (Malaysia)

    2016-07-19

    Nanocomposite TiAlBN (nc-TiAlBN) coatings were successfully deposited via RF magnetron sputtering by varying the nitrogen-to-total gas flow ratio (R{sub N}), and substrate temperature (T{sub S}). All coatings were deposited on AISI 316 substrates using single Ti-Al-BN hot-pressed disc as a target. The grain size, phases, and chemical composition of the coatings were evaluated using glancing angle X-ray diffraction analysis (GAXRD) and X-ray photoelectron spectroscopy (XPS). Results showed that the grains size of the deposited nc-TiAlBN coatings were in the range of 3.5 to 5.7 nm and reached a nitride saturation state as early as 15 % R{sub N}. As the nitrogen concentration decreases, boron concentration increased from 9 at.% to 16.17 at.%. and thus, increase the TiB{sub 2} phase within the coatings. The T{sub S}, however, showed no significant effect either on the crystallographic structure, grain size, or in the chemical composition of the deposited nc-TiAlBN coating.

  18. Investigation of structure and mechanical properties of plasma vapor deposited nanocomposite TiBN films

    Science.gov (United States)

    Han, Bin; Neena, D.; Wang, Zesong; Kondamareddy, K. k.; Li, Na; Zuo, Wenbin; Yan, Shaojian; Liu, Chuansheng; Fu, Dejun

    2017-04-01

    TiBN coatings have huge potential applications as they have excellent properties with increasing modern industrial requirements. Nanocomposite TiBN coatings were synthesized on cemented carbide, high speed steel and Si substrates by using cathodic arc plasma ion plating from pure TiB2 ceramic targets. The structure and mechanical properties of the TiBN coatings were significantly influenced by the nitrogen partial pressure. Rutherford backscattering spectrometry demonstrates that the nitrogen content of the coating varied from 2.8% to 34.5% and high-resolution electron microscopy images reveal that all coatings have the characteristic of nanocrystals embedded in an amorphous matrix. The root-mean-square roughness of the coatings increases from 3.73 to 14.64 nm and the coefficients of friction of the coatings at room temperature vary from 0.54 to 0.73 with increasing nitrogen partial pressure. The microhardness of the coating increases up to 35.7 GPa at 10 sccm N2 flow rate. The smallest wear rate is 2.65 × 10-15 m3 N-1 m-1 which indicates that TiBN coatings have excellent wear resistance. The adhesion test revealed that the TiBN coatings have good adhesion at low nitrogen partial pressure.

  19. Graphene hot-electron light bulb: incandescence from hBN-encapsulated graphene in air

    Science.gov (United States)

    Son, Seok-Kyun; Šiškins, Makars; Mullan, Ciaran; Yin, Jun; Kravets, Vasyl G.; Kozikov, Aleksey; Ozdemir, Servet; Alhazmi, Manal; Holwill, Matthew; Watanabe, Kenji; Taniguchi, Takashi; Ghazaryan, Davit; Novoselov, Kostya S.; Fal'ko, Vladimir I.; Mishchenko, Artem

    2018-01-01

    The excellent electronic and mechanical properties of graphene allow it to sustain very large currents, enabling its incandescence through Joule heating in suspended devices. Although interesting scientifically and promising technologically, this process is unattainable in ambient environment, because graphene quickly oxidises at high temperatures. Here, we take the performance of graphene-based incandescent devices to the next level by encapsulating graphene with hexagonal boron nitride (hBN). Remarkably, we found that the hBN encapsulation provides an excellent protection for hot graphene filaments even at temperatures well above 2000 K. Unrivalled oxidation resistance of hBN combined with atomically clean graphene/hBN interface allows for a stable light emission from our devices in atmosphere for many hours of continuous operation. Furthermore, when confined in a simple photonic cavity, the thermal emission spectrum is modified by a cavity mode, shifting the emission to the visible range spectrum. We believe our results demonstrate that hBN/graphene heterostructures can be used to conveniently explore the technologically important high-temperature regime and to pave the way for future optoelectronic applications of graphene-based systems.

  20. Safety Design Criteria and Approaches to Safety Substantiation of the BN-1200

    International Nuclear Information System (INIS)

    Ashurko, I.

    2013-01-01

    Russian experience in SFR area: Activities on development of safety design criteria for SFRs of the 4th generation is carried out within the GIF framework. Although this reactor technology is considered as innovative that is relevant to the 4th generation, however, it has already a certain history. In this relation, it seems to be useful to analyze the corresponding experience that is available in various countries. 4 SFRs have been successfully operated in the USSR and in the Russian Federation: • Experimental reactor BR-5/10; • Research reactor BOR-60; • Prototype BN-350 power reactor; • Commercial BN-600 power unit at the Beloyarsk NPP. Thus, Russia gained a considerable experience of design, construction and operation of SFRs. In particular, a certain experience has been acquired on safety substantiation of reactors of this type and their licensing. Now BOR-60 and BN-600 continue their operation, BN-800 power unit is under construction, development of the commercial BN-1200 power unit, that is considered as the 4th generation reactor, has been started. Due to limited number of operating SFRs in the world, successful Russian experience in this area should be taken into account for further development and improvement of SFR SDC developed by the GIF Task Force. In particular, participation of SFR designers in this activities would be fruitful and useful

  1. Modulation of band gap by an applied electric field in BN-based heterostructures

    Science.gov (United States)

    Luo, M.; Xu, Y. E.; Zhang, Q. X.

    2018-05-01

    First-principles density functional theory (DFT) calculations are performed on the structural and electronic properties of the SiC/BN van der Waals (vdW) heterostructures under an external electric field (E-field). Our results reveal that the SiC/BN vdW heterostructure has a direct band gap of 2.41 eV in the raw. The results also imply that electrons are likely to transfer from BN to SiC monolayer due to the deeper potential of BN monolayer. It is also observed that, by applying an E-field, ranging from -0.50 to +0.65 V/Å, the band gap decreases from 2.41 eV to zero, which presents a parabola-like relationship around 0.0 V/Å. Through partial density of states (PDOS) plots, it is revealed that, p orbital of Si, C, B, and N atoms are responsible for the significant variations of band gap. These obtained results predict that, the electric field tunable band gap of the SiC/BN vdW heterostructures carries potential applications for nanoelectronics and spintronic device applications.

  2. A novel combinatorial approach for the realization of advanced cBN composite coating

    International Nuclear Information System (INIS)

    Russell, W.C.; Yedave, S.N.; Sundaram, N.; Brown, W.D.; Malshe, A.P.

    2001-01-01

    The paper reports a novel coating process for the synthesis of hard material composite coatings. It consists of electrostatic spray coating (ESC) of powder particles (of micron-nanometer size) followed by chemical vapor infiltration (CVI) of a suitable binder phase. This novel approach enables fabrication of unique compositions such as cubic boron nitride (cBN) and titanium nitride (TiN) in a coating form. Recently, we have demonstrated the success of this technology by first coating a uniform over-layer (in excess of ∼ 10 μm) of cBN particles an carbide cutting tool inserts using ESC, followed by infiltration of particulate cBN matrix with TiN from its vapor phase using CVI to synthesize cBN-TiN a composite coating. The composite has shown excellent cBN-to-TiN and composite coating-to-carbide substrate adhesion. One of the main emphases of the paper is to discuss optimization and scale up of the ESC technology to achieve the desired microstructure and tailor the thickness across the cutting tool for better performance. Further, the cutting tools have been successfully tested for advanced machining applications. (author)

  3. Template-free synthesis of functional 3D BN architecture for removal of dyes from water.

    Science.gov (United States)

    Liu, Dan; Lei, Weiwei; Qin, Si; Chen, Ying

    2014-03-25

    Three-dimensional (3D) architectures are of interest in applications in electronics, catalysis devices, sensors and adsorption materials. However, it is still a challenge to fabricate 3D BN architectures by a simple method. Here, we report the direct synthesis of 3D BN architectures by a simple thermal treatment process. A 3D BN architecture consists of an interconnected flexible network of nanosheets. The typical nitrogen adsorption/desorption results demonstrate that the specific surface area for the as-prepared samples is up to 1156 m(2) g(-1), and the total pore volume is about 1.17 cm(3) g(-1). The 3D BN architecture displays very high adsorption rates and large capacities for organic dyes in water without any other additives due to its low densities, high resistance to oxidation, good chemical inertness and high surface area. Importantly, 88% of the starting adsorption capacity is maintained after 15 cycles. These results indicate that the 3D BN architecture is potential environmental materials for water purification and treatment.

  4. Enhanced Thermal Conductivity of Polyimide Composites Filled with Modified h-BN and Nanodiamond Hybrid Filler.

    Science.gov (United States)

    Yang, Xi; Yu, Xiaoyan; Naito, Kimiyoshi; Ding, Huili; Qu, Xiongwei; Zhang, Qingxin

    2018-05-01

    A new thermally conductive and electrically insulative polyimide were prepared by filling different amounts of hexagonal boron nitride (h-BN) particles, and the thermal conductivity of Polyimide (PI) composites were improved with the increasing h-BN content. Based on this, two methods were applied to improve thermal conductivity furtherly at limited filler loading in this paper. One is modifying the h-BN to improve interface interaction, another is fabricating a nano-micro hybrid filler with 2-D h-BN and 0-D nano-scale nanodiamond (ND) to build more effective conductive network. Both surface modification and hybrid system have a positive effect on thermal conductivity. The composites introducing 40 wt% hybrid filler (the weight ratio of ND/modified BN was 1/10) showed the highest thermal conductivity, being up to 0.98 W/(m K) (5.2 times that of PI). In addition, the composites exhibits excellent electrical insulation, thermal stability properties etc.

  5. Electronic structure analyses of BN network materials using high energy-resolution spectroscopy methods based on transmission electron microscopy.

    Science.gov (United States)

    Terauchi, M

    2006-07-01

    Electronic structures of boron-nitride (BN) nanotubes and a BN cone-structure material were studied by using a high energy-resolution electron energy-loss spectroscopy (EELS) microscope. A trial of the whole electronic structure study of hexagonal BN (h-BN), which consists of flat BN honeycomb layers, was conducted by a combination of EELS and X-ray emission spectroscopy (XES) based on transmission electron microscopy (TEM) (TEM-EELS/XES). The pi and pi+sigma plasmon energies of BN nanotubes (BNT) were smaller than those of h-BN. The pi+sigma energy was explained by the surface plasmon excitation. The spectrum of a two-wall BNT of 2.7 nm in diameter showed a new spectral onset at 4 eV. The valence electron excitation spectra obtained from the tip region of the BN cone with an apex angle of 20 degrees showed similar intensity distribution with those of BNTs. The B K-shell electron excitation spectra obtained from the bottom edge region of the BN cone showed additional peak intensity when compared with those of h-BN and BNT. The B K-shell electron excitation spectra and B K-emission spectra of h-BN were compared with a result of a LDA band calculation. It showed that high symmetry points in the band diagram appear as peak and/or shoulder structures in the EELS and XES spectra. Interband transitions appeared in the imaginary part of the dielectric function of h-BN experimentally obtained were assigned in the band diagram. The analysis also presented that the LDA calculation estimated the bandgap energy smaller than the real material by an amount of 2 eV. Those results of TEM-EELS/XES analysis presented that high energy-resolution spectroscopy methods combined with TEM is a promising method to analyze whole electronic structures of nanometer scale materials. Copyright (c) 2006 Wiley-Liss, Inc.

  6. Oxidation of BN-coated SiC fibers in ceramic matrix composites

    International Nuclear Information System (INIS)

    Sheldon, B.W.; Sun, E.Y.

    1996-01-01

    Thermodynamic calculations were performed to analyze the simultaneous oxidation of BN and SiC. The results show that, with limited amounts of oxygen present, the formation of SiO 2 should occur prior to the formation of B 2 O 3 . This agrees with experimental observations of oxidation in glass-ceramic matrix composites with BN-coated SiC fibers, where a solid SiO 2 reaction product containing little or no boron has been observed. The thermodynamic calculations suggest that this will occur when the amount of oxygen available is restricted. One possible explanation for this behavior is that SiO 2 formation near the external surfaces of the composite closes off cracks or pores, such that vapor phase O 2 diffusion into the composite occurs only for a limited time. This indicates that BN-coated SiC fibers will not always oxidize to form significant amounts of a low-melting, borosilicate glass

  7. Controlling the orientation of nucleobases by dipole moment interaction with graphene/h-BN interfaces

    KAUST Repository

    Vovusha, Hakkim

    2018-02-08

    The interfaces in 2D hybrids of graphene and h-BN provide interesting possibilities of adsorbing and manipulating atomic and molecular entities. In this paper, with the aid of density functional theory, we demonstrate the adsorption characteristics of DNA nucleobases at different interfaces of 2D hybrid nanoflakes of graphene and h-BN. The interfaces provide stronger binding to the nucleobases in comparison to pure graphene and h-BN nanoflakes. It is also revealed that the individual dipole moments of the nucleobases and nanoflakes dictate the orientation of the nucleobases at the interfaces of the hybrid structures. The results of our study point towards a possible route to selectively control the orientation of individual molecules in biosensors.

  8. 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.

  9. Novel composite cBN-TiN coating deposition method: structure and performance in metal cutting

    International Nuclear Information System (INIS)

    Russell, W.C.; Malshe, A.P.; Yedave, S.N.; Brown, W.D.

    2001-01-01

    Cubic boron nitride coatings are under development for a variety of applications but stabilization of the pure cBN form and adhesion of films deposited by PVD and ion-based methods has been difficult. An alternative method for depositing a composite cBN-TiN film has been developed for wear related applications. The coating is deposited in a two-stage process utilizing ESC (electrostatic spray coating) and CVI (chemical vapor infiltration). Fully dense films of cBN particles evenly dispersed in a continuous TiN matrix have been developed. Testing in metal cutting has shown an increase in tool life (turning - 4340 steel) of three to seven times, depending of machining parameters, in comparison with CVD deposited TiN films. (author)

  10. Characterization of In-Situ BN Interface Formed by Nitridation of Nextel 312

    Science.gov (United States)

    Hurwitz, Fances I.; Riehl, John; Madsen, John; McCue, Terry R.; Boyd, Darwin L.

    1999-01-01

    Treatment of Nextel (TM) 312 in a reactive environment has been used as a low cost approach to the formation of BN on the fiber surface. Although the BN enriched surface region is extremely thin (less than 40 run), it is effective in providing debonding and composite behavior. Variation in mechanical behavior of Nextel (TM) 312/BN/Blackglas (TM) composites has been noted among panels fabricated with AF-10 cloth treated in different nitridation runs, Understanding this variation became the rationale for undertaking a detailed characterization of the nitrided fiber using field emission scanning electron microscopy, low voltage energy dispersive x-ray and Auger electron spectroscopy. Chemical composition and surface morphology are discussed in relation to observed mechanical behavior of NeXtel (TM) 312/Blackglas (TM) composites tested in bending.

  11. Time-resolved Polarimetry of the Superluminous SN 2015bn with the Nordic Optical Telescope

    DEFF Research Database (Denmark)

    Leloudas, Giorgos; Maund, Justyn R.; Gal-Yam, Avishay

    2017-01-01

    We present imaging polarimetry of the superluminous supernova SN 2015bn, obtained over nine epochs between -20 and +46 days with the Nordic Optical Telescope. This was a nearby, slowly evolving Type I superluminous supernova that has been studied extensively and for which two epochs of spectropol......We present imaging polarimetry of the superluminous supernova SN 2015bn, obtained over nine epochs between -20 and +46 days with the Nordic Optical Telescope. This was a nearby, slowly evolving Type I superluminous supernova that has been studied extensively and for which two epochs...... of spectropolarimetry are also available. Based on field stars, we determine the interstellar polarization in the Galaxy to be negligible. The polarization of SN 2015bn shows a statistically significant increase during the last epochs, confirming previous findings. Our well-sampled imaging polarimetry series allows us...

  12. Crystals in crystals

    DEFF Research Database (Denmark)

    Christensen, Claus H.; Schmidt, I.; Carlsson, A.

    2005-01-01

    A major factor governing the performance of catalytically active particles supported on a zeolite carrier is the degree of dispersion. It is shown that the introduction of noncrystallographic mesopores into zeolite single crystals (silicalite-1, ZSM-5) may increase the degree of particle dispersion...... of the zeolite particles, particularly after thermal treatment. When using mesoporous zeolites, the particles were evenly distributed throughout the mesopore system of the zeolitic support, even after calcination, leading to nanocrystals within mesoporous zeolite single crystals....

  13. Exploring Chemical Space with Alchemical Derivatives: BN-Simultaneous Substitution Patterns in C60.

    Science.gov (United States)

    Balawender, Robert; Lesiuk, Michał; De Proft, Frank; Geerlings, Paul

    2018-02-13

    With the idea of using alchemical derivatives to explore in an efficient, computer- and cost-effective way Chemical Space was launched several years ago. In the context of Conceptual DFT response functions, these energies vs nuclear charge derivatives permit the estimatation of the energy of transmutants of a given starting or reference molecule showing different nuclear compositions. After an explorative study on small and planar molecules ( Balawender et al. J. Chem. Theory Comput. 2013 , 9 , 5327 ) by the present authors of this paper, the present study fully exploits the computational advantages of the alchemical derivatives in larger three-dimensional systems. Starting from a single reference calculation on C 60 , the complete BN substitution pattern, from single substituted C 58 BN via the belt (C 20 (BN) 20 and the ball C 12 (BN) 24 structures to the fully substituted (BN) 30 , is explored. Successive and simultaneous substitution strategies are followed and compared, indicating that both techniques yield identical results up to 13 substitutions but that for higher substitutions the simultaneous approach needs to be taken. Due to the cost-efficiency of the algorithm this path can indeed be followed as opposed to earlier work in the literature where for each step a full SCF calculation was at stake leading to prohibitively large computational demands for adopting the simultaneous approach. Previously formulated rules governing the substitution pattern by Kar and co-workers are scrutinized in this context and reformulated giving chemical insight in the gradual substitution process and the relative energies of the isomers. In its present form the method offers an interesting venue to study BN substitution patterns in higher fullerenes and graphene and in general paves the way for more efficient exploration of the Chemical Space.

  14. The effect of incorporated self-lubricated BN(h) particles on the tribological properties of Ni-P/BN(h) composite coatings

    Science.gov (United States)

    Hsu, Chih-I.; Hou, Kung-Hsu; Ger, Ming-Der; Wang, Gao-Liang

    2015-12-01

    Ni-P/BN(h) composite coatings are prepared by means of the conventional electroless plating from the bath containing up to 10.0 g/l of hexagonal boron nitride particles with size 0.5 μm. The Ni-P coating is also prepared as a comparison. Cationic surfactant cetyltrimethylammonium bromide (CTAB) is used to stabilize the electrolyte, and the optimum CTAB concentration resulting in a nonagglomerated dispersion of particles is obtained using a dispersion stability analyzer. Morphology of the coatings and the effect of incorporated particles on coating structure and composition are investigated via scanning electron microscopy, field emission electron probe micro-analyzer and X-ray diffraction analysis. Hardness, roughness, friction coefficient and wear resistance of the coatings are also evaluated using Vickers microhardness tester, atomic force microscopy and ball-on disk machine. The presence of CTAB in the depositing bath has a positive effect on the surface roughness and performance of Ni-P/BN(h) composite coatings. The friction and wear tests results show that incorporation of 14.5 vol% BN(h) particles into the Ni-P coating lowers the coating friction coefficient by about 75% and the wear resistance of the Ni-P composites is approximately 10 times higher than Ni-P coating.

  15. BN-800 as a new stage in development of fast neutron sodium cooled reactors

    International Nuclear Information System (INIS)

    Poplavskij, V.M.; Chebeskov, A.N.; Matveev, V.I.

    2004-01-01

    The role of fast reactors in the strategy of evolution of the nuclear power of Russia is discussed, BN-800 under construction, where unique technical and construction decisions are used, is viewed. Economical estimations of expenses with regard for all life cycle demonstrate that fast reactors may be no higher-priced than the most popular in the world water moderated reactors. Closing of nuclear fuel cycle of BN-800 makes possible decision of the problem of plutonium and actinide utilization, that makes the fast reactor more safety for the environment [ru

  16. Main results of BN-600 reactor stress-strain state investigations

    International Nuclear Information System (INIS)

    Panov, V.A.

    1983-01-01

    The development of BN-600 fast reactor plant needed the solution of a series of complex engineering problems including ones for confirming integrity of the most vital structural components. The particular attention was given to the main vessel since reactor availability end safe operation of the plant as a whole depend on vessel strength end integrity. The present report deals with the main results of theoretical and experimental investigations of the stress-strain state of BN-600 reactor vessel carried out during design, start-up and initial bringing the reactor to power

  17. Study of vibrational modes and specific heat of wurtzite phase of BN

    Energy Technology Data Exchange (ETDEWEB)

    Singh, Daljit, E-mail: daljit.jt@gmail.com; Sinha, M. M. [Department of Physics, SLIET, Longowal (India)

    2016-05-06

    In these days of nanotechnology the materials like BN is of utmost importance as in hexagonal phase it is among hardest materials. The phonon mode study of the materials is most important factor to find structural and thermodynamcal properties. To study the phonons de launey angular force (DAF) constant model is best suited as it involves many particle interactions. Therefore in this presentation we have studied the lattice dynamical properties and specific heat of BN in wurtzite phase using DAF model. The obtained results are in excellent agreement with existing results.

  18. Study of vibrational modes and specific heat of wurtzite phase of BN

    International Nuclear Information System (INIS)

    Singh, Daljit; Sinha, M. M.

    2016-01-01

    In these days of nanotechnology the materials like BN is of utmost importance as in hexagonal phase it is among hardest materials. The phonon mode study of the materials is most important factor to find structural and thermodynamcal properties. To study the phonons de launey angular force (DAF) constant model is best suited as it involves many particle interactions. Therefore in this presentation we have studied the lattice dynamical properties and specific heat of BN in wurtzite phase using DAF model. The obtained results are in excellent agreement with existing results.

  19. Pure & crystallized 2D Boron Nitride sheets synthesized via a novel process coupling both PDCs and SPS methods

    Science.gov (United States)

    Yuan, Sheng; Linas, Sébastien; Journet, Catherine; Steyer, Philippe; Garnier, Vincent; Bonnefont, Guillaume; Brioude, Arnaud; Toury, Bérangère

    2016-02-01

    Within the context of emergent researches linked to graphene, it is well known that h-BN nanosheets (BNNSs), also referred as 2D BN, are considered as the best candidate for replacing SiO2 as dielectric support or capping layers for graphene. As a consequence, the development of a novel alternative source for highly crystallized h-BN crystals, suitable for a further exfoliation, is a prime scientific issue. This paper proposes a promising approach to synthesize pure and well-crystallized h-BN flakes, which can be easily exfoliated into BNNSs. This new accessible production process represents a relevant alternative source of supply in response to the increasing need of high quality BNNSs. The synthesis strategy to prepare pure h-BN is based on a unique combination of the Polymer Derived Ceramics (PDCs) route with the Spark Plasma Sintering (SPS) process. Through a multi-scale chemical and structural investigation, it is clearly shown that obtained flakes are large (up to 30 μm), defect-free and well crystallized, which are key-characteristics for a subsequent exfoliation into relevant BNNSs.

  20. 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.

  1. 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.

  2. 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.

  3. Effect of magnesium aluminum silicate glass on the thermal shock resistance of BN matrix composite ceramics

    NARCIS (Netherlands)

    Cai, Delong; Jia, Dechang; Yang, Zhihua; Zhu, Qishuai; Ocelik, Vaclav; Vainchtein, Ilia D.; De Hosson, Jeff Th M.; Zhou, Yu

    The effects of magnesium aluminum silicate (MAS) glass on the thermal shock resistance and the oxidation behavior of h-BN matrix composites were systematically investigated at temperature differences from 600 degrees C up to 1400 degrees C. The retained strength rate of the composites rose with the

  4. Cross-plane Thermoelectric and Thermionic Transport across Au/h-BN/Graphene Heterostructures.

    Science.gov (United States)

    Poudel, Nirakar; Liang, Shi-Jun; Choi, David; Hou, Bingya; Shen, Lang; Shi, Haotian; Ang, Lay Kee; Shi, Li; Cronin, Stephen

    2017-10-26

    The thermoelectric voltage generated at an atomically abrupt interface has not been studied exclusively because of the lack of established measurement tools and techniques. Atomically thin 2D materials provide an excellent platform for studying the thermoelectric transport at these interfaces. Here, we report a novel technique and device structure to probe the thermoelectric transport across Au/h-BN/graphene heterostructures. An indium tin oxide (ITO) transparent electrical heater is patterned on top of this heterostructure, enabling Raman spectroscopy and thermometry to be obtained from the graphene top electrode in situ under device operating conditions. Here, an AC voltage V(ω) is applied to the ITO heater and the thermoelectric voltage across the Au/h-BN/graphene heterostructure is measured at 2ω using a lock-in amplifier. We report the Seebeck coefficient for our thermoelectric structure to be -215 μV/K. The Au/graphene/h-BN heterostructures enable us to explore thermoelectric and thermal transport on nanometer length scales in a regime of extremely short length scales. The thermoelectric voltage generated at the graphene/h-BN interface is due to thermionic emission rather than bulk diffusive transport. As such, this should be thought of as an interfacial Seebeck coefficient rather than a Seebeck coefficient of the constituent materials.

  5. Oxidation Behavior of AlN/h-BN Nano Composites at High Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Jin Haiyun; Huang Yinmao; Feng Dawei; He Bo [State Key Laboratory of Electrical Insulation and Power Equipment, Xi' an Jiaotong University, Xi' an, 710049 (China); Yang Jianfeng, E-mail: hebo@mail.xjtu.edu.cn [State Key Laboratory for Mechanical Behaviour of Materials, Xi' an Jiaotong University, Xi' an (China)

    2011-10-29

    Both AlN/ nano h-BN composites and AlN/ micro h-BN composites were fabricated. The high temperature oxidation behaviors were investigated at 1000deg. C and 1300deg. C using a cycle-oxidation method. The results showed that there were little changes of both nano composites and monolithic AlN ceramic at temperature of 1000deg. C. And at 1300deg. C, the oxidation dynamics curve of composites could be divided into two courses: a slowly weight increase and a rapid weight decrease, but the oxidation behavior of nano composites was better than micro composites. It was due to that the uniform distribution of oxidation production (Al{sub 18}B{sub 4}O{sub 33}) surround the AlN grains in nano composites and the oxidation proceeding was retarded. The XRD analysis and SEM observations showed that there was no BN remained in the composites surface after 1300deg. C oxidation and the micropores remain due to the vaporizing of B{sub 2}O{sub 3} oxidized by BN.

  6. Amplification of the active site of BnLIP3 gene of Brassica napus L ...

    African Journals Online (AJOL)

    Lipases are useful enzymes that are responsible for the hydrolysis of triacylglycerides and play an important role in plant growth. In this study, we report a rapid molecular method to amplify a partial sequence of the lipase class 3 family designated BnLIP3 gene of Brassica napus L. in order to follow its expression and ...

  7. Fracture toughness enhancement of h-BN monolayers via hydrogen passivation of a crack edge.

    Science.gov (United States)

    Kumar, Rajesh; Parashar, Avinash

    2017-04-21

    Molecular dynamics-based simulations were performed in conjunction with reactive force-field potential parameters to investigate the effect of crack-edge passivation via hydrogenation on the fracture properties of h-BN nanosheets. In semi-hydrogenated (H is attached to either B or N) and fully hydrogenated (H is attached to both B and N) crack-edge atoms, three hybridisation states-sp 2 , sp 3 and sp 2  + sp 3 -were considered in the simulations. Significant improvement in the fracture toughness of h-BN nanosheets was predicted with semi- and fully hydrogenated crack-edge atoms. An overall improvement in fracture toughness of h-BN in the range of 16%-23% was estimated with the sp 3 or sp 2  + sp 3 hybridisation state of crack-edge atoms. This significant shift in the fracture toughness of h-BN nanosheets was attributed to lowered crack-edge energy, a stress-relieving mechanism and blunting of the crack tip. Semi-hydrogenated crack-edge atoms with hydrogen attached only to N atoms have shown a negative response in terms of fracture toughness.

  8. Stable BC 2N nanostructures: low-temperature production of segregated C/BN layered materials

    Science.gov (United States)

    Kohler-Redlich, Ph.; Terrones, M.; Manteca-Diego, C.; Hsu, W. K.; Terrones, H.; Rühle, M.; Kroto, H. W.; Walton, D. R. M.

    1999-09-01

    Stable filaments of nanometer dimensions with overall chemical stoichiometry close to BC 2N were generated by pyrolysis of CH 3CN·BCl 3 over Co at 1000°C and, for the first time, their structures were investigated, at the nanometer level, using high spatial resolution electron energy-loss spectroscopy. Concentration profiles, along and across the filaments, revealed that B, C and N are not homogeneously distributed within the nanostructures but are separated into pure C and BN domains. Interestingly, pure h-BN layers are always sandwiched between graphite-like shells. A two-stage growth process is proposed involving: (a) initial extrusion of a pure carbon filament from the catalytic particle, followed by (b) subsequent thickening of the BN and C layers precipitated from the gas phase. This pyrolytic technique provides an alternative and efficient route to segregated BN/C nanomaterials, which may prove useful as robust nanocomposites and semiconductor nanodevices with enhanced resistance towards oxidation.

  9. Growth and characterization of thick cBN coatings on silicon and tool substrates

    Energy Technology Data Exchange (ETDEWEB)

    Bewilogua, K. [Fraunhofer Institute for Surface Engineering and Thin Films, D-38108 Braunschweig (Germany)]. E-mail: bew@ist.fraunhofer.de; Keunecke, M. [Fraunhofer Institute for Surface Engineering and Thin Films, D-38108 Braunschweig (Germany); Weigel, K. [Fraunhofer Institute for Surface Engineering and Thin Films, D-38108 Braunschweig (Germany); Wiemann, E. [Institute for Machine Tools and Factory Management, Technical University Berlin (Germany)

    2004-12-22

    Recently some research groups have achieved progress in the deposition of cubic boron nitride (cBN) coatings with a thickness of 2 {mu}m and more, which is necessary for cutting tool applications. In our laboratory, thick cBN coatings were sputter deposited on silicon substrates using a boron carbide target. Following a boron carbide interlayer (few 100 nm thick), a gradient layer with continuously increasing nitrogen content was prepared. After the cBN nucleation, the process parameters were modified for the cBN film growth to a thickness of more than 2 {mu}m. However, the transfer of this technology to technically relevant substrates, like cemented carbide cutting inserts, required some further process modifications. At first, a titanium interlayer had to be deposited followed by a more than 1-{mu}m-thick boron carbide layer. The next steps were identical to those on silicon substrates. The total coating thickness was in the range of 3 {mu}m with a 0.5- to nearly 1-{mu}m-thick cBN top layer. In spite of the enormous intrinsic stress, both the coatings on silicon and on cemented carbide exhibited a good adhesion and a prolonged stability in humid air. Oxidation experiments revealed a stability of the coating system on cemented carbide up to 700 deg. C and higher. Coated cutting inserts were tested in turning operations with different metallic workpiece materials. The test results will be compared to those of well-established cutting materials, like polycrystalline cubic boron nitride (PCBN) and oxide ceramics, considering the wear of coated tools.

  10. Defect sensitive etching of hexagonal boron nitride single crystals

    Science.gov (United States)

    Edgar, J. H.; Liu, S.; Hoffman, T.; Zhang, Yichao; Twigg, M. E.; Bassim, Nabil D.; Liang, Shenglong; Khan, Neelam

    2017-12-01

    Defect sensitive etching (DSE) was developed to estimate the density of non-basal plane dislocations in hexagonal boron nitride (hBN) single crystals. The crystals employed in this study were precipitated by slowly cooling (2-4 °C/h) a nickel-chromium flux saturated with hBN from 1500 °C under 1 bar of flowing nitrogen. On the (0001) planes, hexagonal-shaped etch pits were formed by etching the crystals in a eutectic mixture of NaOH and KOH between 450 °C and 525 °C for 1-2 min. There were three types of pits: pointed bottom, flat bottom, and mixed shape pits. Cross-sectional transmission electron microscopy revealed that the pointed bottom etch pits examined were associated with threading dislocations. All of these dislocations had an a-type burgers vector (i.e., they were edge dislocations, since the line direction is perpendicular to the [ 2 11 ¯ 0 ]-type direction). The pit widths were much wider than the pit depths as measured by atomic force microscopy, indicating the lateral etch rate was much faster than the vertical etch rate. From an Arrhenius plot of the log of the etch rate versus the inverse temperature, the activation energy was approximately 60 kJ/mol. This work demonstrates that DSE is an effective method for locating threading dislocations in hBN and estimating their densities.

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

    Energy Technology Data Exchange (ETDEWEB)

    Cui, Mingjun [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); University of Chinese Academy of Sciences, Beijing 100039 (China); Ren, Siming [Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); University of Chinese Academy of Sciences, Beijing 100039 (China); Chen, Jia; Liu, Shuan [Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Zhang, Guangan [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Zhao, Haichao, E-mail: zhaohaichao@nimte.ac.cn [Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Wang, Liping, E-mail: wangliping@nimte.ac.cn [Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China); Xue, Qunji, E-mail: qjxue@lzb.ac.cn [State Key Laboratory of Solid Lubrication, Lanzhou Institute of Chemical Physics, Chinese Academy of Sciences, Lanzhou 730000 (China); Key Laboratory of Marine Materials and Related Technologies, Zhejiang Key Laboratory of Marine Materials and Protective Technologies, Ningbo Institute of Materials Technology and Engineering, Chinese Academy of Sciences, Ningbo 315201 (China)

    2017-03-01

    Highlights: • Hexagonal boron nitride nanosheets were well dispersed by using water-soluble carboxylated aniline trimer as dispersant. • The best corrosion performance of waterborne epoxy coatings was achieved with the addition of 1 wt% h-BN. • The decrease of the pores and defects of coating matrix inhibits the diffusion and water absorption of corrosive medium in the coating. - Abstract: 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{sup −}) as a dispersant, which was attributed to the strong π-π interaction between h-BN and CAT{sup −}, 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 × 10{sup 6} Ω cm{sup 2}) 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.

  12. 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

  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. Electron scattering in graphene by defects in underlying h-BN layer: First-principles transport calculations

    Science.gov (United States)

    Kaneko, Tomoaki; Ohno, Takahisa

    2018-03-01

    We investigate the electronic structure and the transport properties of graphene adsorbed onto h-BN with carbon impurities or atomic vacancies using density functional theory and the non-equilibrium Green's function method. We find that the transport properties are degraded due to carrier doping and scattering off of localized defect states in h-BN. When graphene is doped by introducing defects in h-BN, the transmission spectra become asymmetric owing to the reduction of the electronic density of states, which contributes significantly to the degradation of graphene transport properties as compared with the effect of defect levels.

  15. Mid-IR Imaging of Orion BN/KL: Modeling of Physical Conditions and Energy Balance

    Science.gov (United States)

    Gezari, Daniel; Varosi, Frank; Dwek, Eli; Danchi, William C.; Tan, Jonathan; Okumura, Shin-ichiro

    2016-01-01

    We have modeled two mid-infrared imaging photometry data sets to determine the spatial distribution of physical conditions in the BN/KL (Becklin-Neugebauer / Kleinmann-Low) infrared complex. We observed the BN/KL region using the 10-meter Keck I telescope and the LWS (Living With a Star) in the direct imaging mode, over a 13 inch by 19 inch field . We also modeled images obtained with COMICS (Cooled Mid-Infrared Camera and Spectrometer, Kataza et al. 2000) at the 8.2-meter SUBARU telescope, over a total field of view [which] is 31 inches by 41 inches in a total of nine bands: 7.8, 8.8, 9.7, 10.5, 11.7, 12.4, 18.5, 20.8 and 24.8 microns with 1-micron bandwidth interference filters.

  16. Structure of boron clusters revisited, Bn with n = 14-20

    Science.gov (United States)

    Tai, Truong Ba; Tam, Nguyen Minh; Nguyen, Minh Tho

    2012-03-01

    We reinvestigate the structures of neutral boron clusters Bn, with n = 14-20. G3B3 calculations confirm that a transition between 2D and 3D shape occurs at B20, which has a tubular form. In disagreement with Boustani et al. (Phys. Rev. B, 83 (2011) 193405), we find a planar B19 cluster. Standard heats of formation are obtained and used to evaluate the clusters stability. The average binding energy tends to increase with increasing size toward a limit. Higher stability is found B14, B16, B18 and B20. All Bn have negative NICS-values. The bonding nature and electron delocalization of B20 are re-examined using CMO and LOL.

  17. 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.

  18. First principles prediction of the third conformer of hydrogenated BN sheet

    International Nuclear Information System (INIS)

    Bhattacharya, A.; Bhattacharya, S.; Das, G.P.; Majumder, C.

    2010-01-01

    We report, using first principles density functional calculations, the relative stabilities, structural and electronic properties of various conformers of hydrogenated BN sheet (BHNH). The already known chair and boat BHNH conformers are structurally similar to those of graphane. We propose a third BHNH conformer called 'stirrup' which turns out to be the most stable one, as also verified by frequency analysis. In this conformer, the B-H and N-H bonds of a hexagon alternate in 3-up and 3-down fashion on either side of the sheet. We also explore that any other alternative hydrogenation of the BN sheet disrupts its periodic puckered geometry and turns out to be energetically less stable. (copyright 2010 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  19. Study of transients in the auxiliary power circuits of the BN-600 power unit

    International Nuclear Information System (INIS)

    Sychev, Yu.P.; Lebedev, A.T.; Elsukov, V.I.; Vitkov, V.M.

    1985-01-01

    To test the efficiency of the generating station auxiliary power (AP) supply circuits of the BN-600 power unit and to develop measures for the increase of their operation reliability, the calculations and experiments on studying the source behaviour and power consumers in various emergency situations have been carried out. The maximum permissible break in power supply for AP section is found to be 1.2 s. The frequency method for the AP mechanisms start up from diesel generators (DG), with preliminary excitation current supply to the rotor winding from an independent source, reduces considerably the time of AP mechanisms entering into productive operation. The use of the running-down energy of 200 MW turboaggregate enables to reliably supply the AP mechanisms in the regime of emergency cool-down of the BN-600 reactor to the moment of transition to power supply from a DG

  20. Characterisation of an Al-BN nanocomposite prepared by ball milling and hot extrusion

    Science.gov (United States)

    Arlic, U.; Drozd, Z.; Trojanová, Z.; Molnárová, O.; Kasakewitsch, A.

    2017-07-01

    Aluminium-matrix-nanocomposites were manufactured by ball milling of microscale aluminium powder with BN nanoparticles in air, followed by subsequent consolidation by hot extrusion. The microstructure of the samples was studied using scanning electron microscopy. Vickers microhardness measurements were used to probe the mechanical properties of the samples. The amplitude dependent damping of the nanocomposites was measured at room temperature after thermal treatment of samples, and the linear thermal expansion was measured over a wide temperature range from room temperature up to 670K in the as-extruded state. The experimental results give a comprehensive picture of the behaviour of this nanocomposite system over the range of thermomechanical treatment conditions examined in this study. Based on these experimental data some possible influences of BN nanoparticles on the anelastic, plastic and thermal properties of microcrystalline aluminium are discussed.

  1. Structural and electronic properties of a single C chain doped zigzag BN nanoribbons

    International Nuclear Information System (INIS)

    Wu, Ping; Wang, Qianwen; Cao, Gengyu; Tang, Fuling; Huang, Min

    2014-01-01

    The effects of single C-chain on the stability, structural and electronic properties of zigzag BN nanoribbons (ZBNNRs) were investigated by first-principles calculations. C-chain was expected to dope at B-edge for all the ribbon widths N z considered. The band gaps of C-chain doped N z -ZBNNR are narrower than that of perfect ZBNNR due to new localized states induced by C-chain. The band gaps of N z -ZBNNR-C(n) are direct except for the case of C-chain position n=2. Band gaps of BN nanoribbons are tunable by C-chain and its position n, which may endow the potential applications of BNNR in electronics.

  2. BN Nanosheet/Polymer Films with Highly Anisotropic Thermal Conductivity for Thermal Management Applications.

    Science.gov (United States)

    Wu, Yuanpeng; Xue, Ye; Qin, Si; Liu, Dan; Wang, Xuebin; Hu, Xiao; Li, Jingliang; Wang, Xungai; Bando, Yoshio; Golberg, Dmitri; Chen, Ying; Gogotsi, Yury; Lei, Weiwei

    2017-12-13

    The development of advanced thermal transport materials is a global challenge. Two-dimensional nanomaterials have been demonstrated as promising candidates for thermal management applications. Here, we report a boron nitride (BN) nanosheet/polymer composite film with excellent flexibility and toughness prepared by vacuum-assisted filtration. The mechanical performance of the composite film is highly flexible and robust. It is noteworthy that the film exhibits highly anisotropic properties, with superior in-plane thermal conductivity of around 200 W m -1 K -1 and extremely low through-plane thermal conductivity of 1.0 W m -1 K -1 , making this material an excellent candidate for thermal management in electronics. Importantly, the composite film shows fire-resistant properties. The newly developed unconventional flexible, tough, and refractory BN films are also promising for heat dissipation in a variety of applications.

  3. 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.

  4. An experience of cleaning and decontamination of the BN-350 reactor components

    International Nuclear Information System (INIS)

    Vasilenko, K.T.; Kochetkov, L.A.; Arkhipov, V.M.; Baklushin, R.P.; Gorlov, A.I.; Kiselev, G.V.; Rezinkin, P.S.; Samarkin, A.A.; Tverdovsky, N.D.

    1978-01-01

    In the course of start-up, adjustment and operation of the BN-350 reactor there arose a need for cleaning from sodium and decontamination of primary and secondary equipment components. Design schemes of the systems provided for this purpose as well as those specially designed for cleaning of steam generator evaporators are considered. Technological processes of cleaning and decontamination for some reactor components (removable parts of circulating pumps, evaporators, valves) are described, the results are presented. (author)

  5. Release of radioactive fission products from BN-600 reactor untight fuel elements

    International Nuclear Information System (INIS)

    Osipov, S.L.; Tsikunov, A.G.; Lisitsin, E.C.

    1996-01-01

    The experimental data on the release of radioactive fission products from BN-600 reactor untight fuel elements are given in the report. Various groups of radionuclides: inert gases Xe, Kr, volatile Cs, J, non-volatile Nb, and La are considered. The results of calculation-experimental study of transfer and distribution of radionuclides in the reactor primary circuit, gas system and sodium coolant are considered. It is shown that some complex radioactivity transfer processes can be described by simple mathematical models. (author)

  6. Modulation effect of hydrogen and fluorine decoration on the surface work function of BN sheets

    Directory of Open Access Journals (Sweden)

    N Jiao

    2012-06-01

    Full Text Available Using first-principles calculations within the framework of density-functional theory, we studied the modulation effect of hydrogen/fluorine chemical decoration on the surface work function of BN sheets. We found that the difference in the work function (ΔWBN between two surfaces of the chair structure varies with the different decoration. Geometric distortion and chemical effects cause opposite modulation effects, and the chemical effect plays a leading role by inducing charge redistribution in the system.

  7. Crystal Systems.

    Science.gov (United States)

    Schomaker, Verner; Lingafelter, E. C.

    1985-01-01

    Discusses characteristics of crystal systems, comparing (in table format) crystal systems with lattice types, number of restrictions, nature of the restrictions, and other lattices that can accidently show the same metrical symmetry. (JN)

  8. Virtual Crystallizer

    Energy Technology Data Exchange (ETDEWEB)

    Land, T A; Dylla-Spears, R; Thorsness, C B

    2006-08-29

    Large dihydrogen phosphate (KDP) crystals are grown in large crystallizers to provide raw material for the manufacture of optical components for large laser systems. It is a challenge to grow crystal with sufficient mass and geometric properties to allow large optical plates to be cut from them. In addition, KDP has long been the canonical solution crystal for study of growth processes. To assist in the production of the crystals and the understanding of crystal growth phenomena, analysis of growth habits of large KDP crystals has been studied, small scale kinetic experiments have been performed, mass transfer rates in model systems have been measured, and computational-fluid-mechanics tools have been used to develop an engineering model of the crystal growth process. The model has been tested by looking at its ability to simulate the growth of nine KDP boules that all weighed more than 200 kg.

  9. Crystal Engineering

    Indian Academy of Sciences (India)

    Nangia (2002). “Today, research areas under the wide umbrella of crystal engineering include: supramolecular synthesis; nanotechnology; separation science and catalysis; supramolecular materials and devices; polymorphism; cocrystals, crystal structure prediction; drug design and ligand–protein binding.”

  10. Strain induced enhancement of perpendicular magnetic anisotropy in Co/graphene and Co/BN heterostructures

    Science.gov (United States)

    Yang, B. S.; Zhang, J.; Jiang, L. N.; Chen, W. Z.; Tang, P.; Zhang, X.-G.; Yan, Y.; Han, X. F.

    2017-05-01

    Perpendicular magnetic tunnel junctions in the next-generation magnetic memory using current induced magnetization switching will likely rely on a material design that can enhance the perpendicular magnetic anisotropy of heterojunctions containing only light elements. Using first-principles calculations, we investigated the effect of compressive and tensile strain on the perpendicular magnetic anisotropy of light element heterostructures of Co films, Co/graphene, and Co/BN. We found that the perpendicular magnetic anisotropy of Co/graphene is greatly enhanced compared to the Co films, while that of Co/BN is reduced compared to the Co films. In addition, tensile strain can further enhance perpendicular magnetic anisotropy of Co/graphene and Co/BN heterojunctions by 48.5% and 80.8%, respectively, compared to the unstrained systems. A density of state analysis, combined with layer and orbital magnetic anisotropy contributions obtained from a second-order perturbation theory of the spin-orbit coupling, reveals that the tensile strain effect arises from the increase of the hybridization between same spin dx y and dx2-y2 states of the surface Co film. Our results suggest that strain engineering is an effective approach to enhance the perpendicular magnetic anisotropy of light element heterostructures.

  11. Becoming Socialized into a New Professional Role: LPN to BN Student Nurses' Experiences with Legitimation

    Directory of Open Access Journals (Sweden)

    Sherri Melrose

    2012-01-01

    Full Text Available This paper presents findings from a qualitative descriptive study that explored the professional socialization experiences of Licensed Practical Nurses (LPNs who attended an online university to earn a Baccalaureate degree in nursing (BN, a prerequisite to writing the Canadian Registered Nurse (RN qualifying exam. The project was framed from a constructivist worldview and Haas and Shaffir’s theory of legitimation. Participants were 27 nurses in a Post-LPN to BN program who came from across Canada to complete required practicums. Data was collected from digital recordings of four focus groups held in different cities. Transcripts were analyzed for themes and confirmed with participants through member checking. Two overarching themes were identified and are presented to explain how these unique adult learners sought to legitimize their emerging identity as Registered Nurses (RNs. First, Post-LPN to BN students need little, if any, further legitimation to affirm their identities as “nurse.” Second, practicum interactions with instructors and new clinical experiences are key socializing agents.

  12. 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.

  13. THE PROPER MOTIONS OF THE DOUBLE RADIO SOURCE n IN THE ORION BN/KL REGION

    Energy Technology Data Exchange (ETDEWEB)

    Rodríguez, Luis F.; Loinard, Laurent; Zapata, Luis; Lizano, Susana [Instituto de Radioastronomía y Astrofísica, UNAM, Apdo. Postal 3-72 (Xangari), 58089 Morelia, Michoacán, México (Mexico); Dzib, Sergio A.; Menten, Karl M. [Max Planck Institut für Radioastronomie, Auf dem Hügel 69, D-53121 Bonn (Germany); Gómez, Laura, E-mail: l.rodriguez@crya.unam.mx [Joint ALMA Observatory, Alonso de Córdoba 3107, Vitacura, Santiago (Chile)

    2017-01-10

    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.

  14. Growth of h-BN on copper (110) in a LEEM

    Science.gov (United States)

    Herrmann, Christoph; Omelchenko, Pavlo; Kavanagh, Karen L.

    2018-03-01

    Hexagonal boron nitride (h-BN) was grown by borazine vapour deposition on single crystalline Cu (110) substrates at 740 °C. The growth was investigated in situ using a Low-Energy Electron Microscope (LEEM). Substrates were prepared ex situ by mechanical and electrochemical methods and once in the LEEM system, by annealing in a H2 atmosphere resulting in a reconstructed surface. Exposure to borazine vapour resulted in the nucleation of well-aligned trigonal h-BN islands, which merged to ribbons along surface steps, and into larger, more irregularly shaped features. A coverage of up to 60% was achieved with an exposure of 3900 L. A diffraction ring in the low energy electron diffraction pattern was observed with a preferential alignment along the Cu 〈 111 〉 directions of the underlying substrate. Low-energy electron reflectivity scans, as well as x-ray photoelectron and Raman spectroscopies, confirmed the presence of a partial monolayer of h-BN on the surface.

  15. THE PROPER MOTIONS OF THE DOUBLE RADIO SOURCE n IN THE ORION BN/KL REGION

    International Nuclear Information System (INIS)

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

    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.

  16. Conjugated π electron engineering of generalized stacking fault in graphene and h-BN

    Science.gov (United States)

    Ouyang, Bin; Chen, Cheng; Song, J.

    2018-03-01

    Generalized-stacking-fault energy (GSFE) serves as an important metric that prescribes dislocation behaviors in materials. In this paper, utilizing first-principle calculations and chemical bonding analysis, we studied the behaviors of generalized stacking fault in graphene and h-BN. It has been shown that the π bond formation plays a critical role in the existence of metastable stacking fault (MSF) in graphene and h-BN lattice along certain slip directions. Chemical functionalization was then proposed as an effective means to engineer the π bond, and subsequently MSF along dislocation slips within graphene and h-BN. Taking hydrogenation as a representative functionalization method, we demonstrated that, with the preferential adsorption of hydrogen along the slip line, π electrons along the slip would be saturated by adsorbed hydrogen atoms, leading to the moderation or elimination of MSF. Our study elucidates the atomic mechanism of MSF formation in graphene-like materials, and more generally, provides important insights towards predictive tuning of mechanic properties in two-dimensional nanomaterials.

  17. Atomically precise semiconductor--graphene and hBN interfaces by Ge intercalation.

    Science.gov (United States)

    Verbitskiy, N I; Fedorov, A V; Profeta, G; Stroppa, A; Petaccia, L; Senkovskiy, B; Nefedov, A; Wöll, C; Usachov, D Yu; Vyalikh, D V; Yashina, L V; Eliseev, A A; Pichler, T; Grüneis, A

    2015-12-07

    The full exploration of the potential, which graphene offers to nanoelectronics requires its integration into semiconductor technology. So far the real-world applications are limited by the ability to concomitantly achieve large single-crystalline domains on dielectrics and semiconductors and to tailor the interfaces between them. Here we show a new direct bottom-up method for the fabrication of high-quality atomically precise interfaces between 2D materials, like graphene and hexagonal boron nitride (hBN), and classical semiconductor via Ge intercalation. Using angle-resolved photoemission spectroscopy and complementary DFT modelling we observed for the first time that epitaxially grown graphene with the Ge monolayer underneath demonstrates Dirac Fermions unaffected by the substrate as well as an unperturbed electronic band structure of hBN. This approach provides the intrinsic relativistic 2D electron gas towards integration in semiconductor technology. Hence, these new interfaces are a promising path for the integration of graphene and hBN into state-of-the-art semiconductor technology.

  18. Atomically precise semiconductor—graphene and hBN interfaces by Ge intercalation

    Science.gov (United States)

    Verbitskiy, N. I.; Fedorov, A. V.; Profeta, G.; Stroppa, A.; Petaccia, L.; Senkovskiy, B.; Nefedov, A.; Wöll, C.; Usachov, D. Yu.; Vyalikh, D. V.; Yashina, L. V.; Eliseev, A. A.; Pichler, T.; Grüneis, A.

    2015-01-01

    The full exploration of the potential, which graphene offers to nanoelectronics requires its integration into semiconductor technology. So far the real-world applications are limited by the ability to concomitantly achieve large single-crystalline domains on dielectrics and semiconductors and to tailor the interfaces between them. Here we show a new direct bottom-up method for the fabrication of high-quality atomically precise interfaces between 2D materials, like graphene and hexagonal boron nitride (hBN), and classical semiconductor via Ge intercalation. Using angle-resolved photoemission spectroscopy and complementary DFT modelling we observed for the first time that epitaxially grown graphene with the Ge monolayer underneath demonstrates Dirac Fermions unaffected by the substrate as well as an unperturbed electronic band structure of hBN. This approach provides the intrinsic relativistic 2D electron gas towards integration in semiconductor technology. Hence, these new interfaces are a promising path for the integration of graphene and hBN into state-of-the-art semiconductor technology. PMID:26639608

  19. 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.

  20. A first-principle investigation into effect of B-and BN-doped C60 in ...

    Indian Academy of Sciences (India)

    The present paper reports the effect of B- and BN-doped C 60 as catalysts for lowering the dehydrogenationenergy inMXH4 clusters (M = Na and Li, X = Al and B) using density functional calculations.MXH4 interacts strongly withB-doped C 60 and weakly with BN-doped C 60 in comparison with pure C 60 with binding ...

  1. 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.

  2. 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

  3. 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

  4. Wear properties of hybrid ABO+BN+CNT/Al-Sn alloy matrix composites for engine bearing materials

    Science.gov (United States)

    Bak, Ji Hyeon; Cho, Dae Hyun; Shin, Sunmi; Park, Jin Young; Park, Ik Min

    2018-01-01

    Engine bearing materials need improved wear resistance to withstand high speeds and heavy loads. To meet the requirements of bearing materials, a new metal matrix composite (MMC) was designed. Here, the hybrid aluminum borate whisker (Al18B4O33, ABO) + hexagonal boron nitride (BN) + carbon nanotubes (CNTs)/Al-5Sn alloy MMCs were fabricated by squeeze infiltration. The wear properties of the hybrid MMCs were evaluated using a ball-on-disk tester. The effect of hybridization of ABO, BN, and CNTs on the wear properties of the Al-Sn MMCs was investigated. The microstructure of the hybrid MMCs showed a uniform distribution of the reinforcements. The wear resistance of the Al-5Sn alloy improved with the addition of ABO. The wear properties of the ABO+BN/ Al-Sn and ABO+CNT/Al-Sn MMCs were considerably enhanced compared to those of the ABO reinforced Al-Sn MMC because of the lubricating characteristic of BN and CNTs, and the CNTs were more effective than BN. The friction coefficient and wear rate of 20ABO+5BN+5CNT/Al-Sn MMC decreased by 1/4 and 1/20, respectively, compared to that of the ABO/Al-Sn MMC.

  5. Cyclosarin nerve agent interaction with the pristine, Stone Wales defected, and Si-doped BN nanosheets: Theoretical study

    Science.gov (United States)

    Nejati, K.; Arshadi, S.; Vessally, E.; Bekhradnia, A.; Hosseinian, A.

    2017-06-01

    Never agent identification and disposal is vital for both civilian and military defense resources. Herein, using density functional theory calculations, the reactivity and electronic sensitivity of pristine, Stone Wales (SW) defected, and Si-doped BN (Si-BN) nanosheets toward cyclosarin nerve agent were investigated. It was found that the interaction of cyclosarin with the pristine BN sheet is very weak and also that is not energetically favorable with SW defected one. Unlike the SW defect, replacing a B atom by Si atom significantly makes the cyclosarin adsorption energetically favorable. Calculations show that the carbonyl and etheric oxygen atoms of cyclosarin attack the Si atom of Si-BN with the adsorption energies of -73.5 and -136.9 kJ/mol, respectively. The cyclosarin nerve agent can be decomposed by the Si-BN sheet which is thermodynamically highly favorable. Upon this process, the HOMO and LUMO levels are significantly unstabilized and the HOMO-LUMO gap significantly changed by about 24.2%. The cyclosarin presence and its decomposition by Si-BN sheet can be recognized because of the electrical conductivity change of the sheet.

  6. Effects of the insertion of a thick sp2 buffer layer on the adhesion of cBN-rich film

    International Nuclear Information System (INIS)

    Wong, S.F.; Ong, C.W.; Pang, G.K.H.; Baba-Kishi, K.Z.; Lau, W.M.

    2004-01-01

    A method was proposed and examined to deposit thick cubic boron nitride (cBN)-rich layer of good adhesion to silicon substrate. The method combined (i) the insertion of a thick sp 2 buffer layer, and (ii) the use of an appropriate assist ion beam energy for the growth of the cBN-rich top layer. The sp 2 -bonded boron nitride buffer layer was deposited under irradiation of ions with energies in the range of 200-360 eV. The buffer layer was found to contain curled graphitic basal planes, and so was supposed to be relatively deformable, and facilitate the relaxation of stresses in the cBN-rich top layer. The ion assist introduced during the growth of the cBN-rich layer was supposed to both create and annihilate defects, and so resulted in the generation and relaxation of internal stresses. Results showed that the insertion of a 492 nm sp 2 buffer layer, and the use of a beam energy of 450 eV for assisting the growth of the top layer can produce a 643-nm-thick cBN-rich top layer with satisfactory adhesion, a high cBN content of 87 vol %, a hardness of 57 GPa, and an elastic modulus of 612 GPa

  7. 44Sc-DOTA-BN[2-14]NH2 in comparison to 68Ga-DOTA-BN[2-14]NH2 in pre-clinical investigation. Is 44Sc a potential radionuclide for PET?

    International Nuclear Information System (INIS)

    Koumarianou, E.; Loktionova, N.S.; Fellner, M.; Roesch, F.; Thews, O.; Pawlak, D.; Archimandritis, S.C.; Mikolajczak, R.

    2012-01-01

    Aim: In the present study we demonstrate the in vitro and in vivo comparison of the 44 Sc and 68 Ga labeled DOTA-BN[2-14]NH 2 . 44 Sc is a positron emitter with a half life of 3.92 h. Hence it could be used for PET imaging with ligands requiring longer observation time than in the case of 68 Ga. Methods: The binding affinity of nat Sc-DOTA-BN[2-14]NH 2 and nat Ga-DOTA-BN[2-14]NH 2 to GRP receptors was studied in competition to [ 125 I-Tyr 4 ]-Bombesin in the human prostate cancer cell line PC-3. A preliminary biodistribution in normal rats was performed, while first microPET images were assessed in male Copenhagen rats bearing the androgen-independent Dunning R-3327-AT-1 prostate cancer tumor. Results: The affinity to GRP receptors in the PC-3 cell line was higher for nat Ga-DOTA-BN[2-14]NH 2 (IC 50 (nM)=0.85±0.06) than that of nat Sc-DOTA-BN[2-14]NH 2 (IC 50 (nM)=6.49±0.13). The internalization rate of 68 Ga labeled DOTA-BN[2-14]NH 2 was slower than that of 44 Sc, but their final internalization percents were comparable. 68 Ga-DOTA-BN[2-14]NH 2 was externalized faster than 44 Sc-DOTA-BN[2-14]NH 2 . The biodistribution of 44 Sc-DOTA-BN[2-14]NH 2 and 68 Ga-DOTA-BN[2-14]NH 2 in normal rats revealed a higher uptake in target organs and tissues of the first one while both excreted mainly through urinary tract. In microPET images both tracers were accumulated in the tumor with similar uptake patterns. Conclusions: Despite the differences in the receptor affinity both the 68 Ga- and the 44 Sc-labeled DOTA-BN[2-14]NH 2 tracers showed comparable distribution and similar time constants of uptake and elimination. Moreover no differences in tumor accumulation (neither in the overall uptake nor in the dynamics) were observed from the microPet imaging. From that perspective the use of either 44 Sc or 68 Ga for detecting tumors with GRP receptors is equivalent. - Highlights: ► In vitro and in vivo evaluation of 44 Sc- and 68 Ga-DOTA-BN[2-14]NH 2 in reference to published

  8. Characterization and crystal structure of a 17-membered macrocyclic Schiff base compound MeO-sal-pn-bn

    Czech Academy of Sciences Publication Activity Database

    Khalaji, A.D.; Ghoran, S.H.; Rohlíček, Jan; Dušek, Michal

    2015-01-01

    Roč. 56, č. 2 (2015), s. 259-265 ISSN 0022-4766 Grant - others:AV ČR(CZ) Praemium Academiae Institutional support: RVO:68378271 Keywords : macrocyclic * Schiff base * spectroscopy * powder diffraction * orthorhombic Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 0.536, year: 2015

  9. Decoding the mechanism of the mechanical transfer of a GaN-based heterostructure via an h-BN release layer in a device configuration

    Science.gov (United States)

    Wang, Gaoxue; Yang, D. Z.; Zhang, Z. Y.; Si, M. S.; Xue, Desheng; He, Haiying; Pandey, Ravindra

    2014-09-01

    Mechanical transfer of GaN-based heterostructures using h-BN as the release layer [Y. Kobayashi, K. Kumakura, T. Akasaka, and T. Makimoto, Nature 484, 223 (2012)] has promising applications for the next-generation optoelectronic devices. We investigate such transfer mechanism by mapping out the interlayer sliding energy landscape at each interface of a model heterostructure composed of GaN/BN/substrate together with the reference case of BN/BN interlayer sliding. The calculated results based on density functional theory find a nearly free sliding path for BN/BN, while a slightly higher energy barrier is predicted for hetero-interfaces of strained GaN/BN and BN/graphene substrate. The unstrained GaN/BN interface facilitates an easier peel-off of GaN from the BN layer. Thus, the sliding mechanism, which can also be described by the registry index model, shows dominance of the electrostatic interaction terms associated with the constituent layers of the system, though the van der Waals interaction term seems to determine the equilibrium interlayer distance for the systems considered.

  10. RNA Crystallization

    Science.gov (United States)

    Golden, Barbara L.; Kundrot, Craig E.

    2003-01-01

    RNA molecules may be crystallized using variations of the methods developed for protein crystallography. As the technology has become available to syntheisize and purify RNA molecules in the quantities and with the quality that is required for crystallography, the field of RNA structure has exploded. The first consideration when crystallizing an RNA is the sequence, which may be varied in a rational way to enhance crystallizability or prevent formation of alternate structures. Once a sequence has been designed, the RNA may be synthesized chemically by solid-state synthesis, or it may be produced enzymatically using RNA polymerase and an appropriate DNA template. Purification of milligram quantities of RNA can be accomplished by HPLC or gel electrophoresis. As with proteins, crystallization of RNA is usually accomplished by vapor diffusion techniques. There are several considerations that are either unique to RNA crystallization or more important for RNA crystallization. Techniques for design, synthesis, purification, and crystallization of RNAs will be reviewed here.

  11. Methodology for Applying Cyber Security Risk Evaluation from BN Model to PSA Model

    International Nuclear Information System (INIS)

    Shin, Jin Soo; Heo, Gyun Young; Kang, Hyun Gook; Son, Han Seong

    2014-01-01

    There are several advantages to use digital equipment such as cost, convenience, and availability. It is inevitable to use the digital I and C equipment replaced analog. Nuclear facilities have already started applying the digital system to I and C system. However, the nuclear facilities also have to change I and C system even though it is difficult to use digital equipment due to high level of safety, irradiation embrittlement, and cyber security. A cyber security which is one of important concerns to use digital equipment can affect the whole integrity of nuclear facilities. For instance, cyber-attack occurred to nuclear facilities such as the SQL slammer worm, stuxnet, DUQU, and flame. The regulatory authorities have published many regulatory requirement documents such as U.S. NRC Regulatory Guide 5.71, 1.152, IAEA guide NSS-17, IEEE Standard, and KINS Regulatory Guide. One of the important problem of cyber security research for nuclear facilities is difficulty to obtain the data through the penetration experiments. Therefore, we make cyber security risk evaluation model with Bayesian network (BN) for nuclear reactor protection system (RPS), which is one of the safety-critical systems to trip the reactor when the accident is happened to the facilities. BN can be used for overcoming these problems. We propose a method to apply BN cyber security model to probabilistic safety assessment (PSA) model, which had been used for safety assessment of system, structure and components of facility. The proposed method will be able to provide the insight of safety as well as cyber risk to the facility

  12. /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.

  13. Stabilization of the O p2x2 phase on Cu(001) sheltered by wrinkled BN over-layer

    Science.gov (United States)

    Kim, Yong-Sung; Ma, Chuanxu; Li, An-Ping; Yoon, Mina

    The 2 √3x √3R45°phase of oxygen (O) on the Cu(001) surface has been observed in scanning tunneling microscopy (STM) measurements. Although the p2x2 phase of O on the Cu(001) surface has been proposed theoretically to be the most stable in O-lean conditions, it has not been observed in experiments for a long time. Recently, the O p2x2 phase has been found in STM on the Cu(001) surface with an overlying BN monolayer. In this theoretical study, we investigate what the role of BN over-layer is to stabilize the O p2x2 phase on the Cu(001) surface. The BN over-layer is lattice-matched with the Cu(001) surface and the BN mono-layer sheet is periodically wrinkled along the BN arm-chair direction and along the [100] or [010] direction on the Cu(001) surface. The interlayer space between the Cu(001) surface and the bulge of the wrinkled BN sheet is found to play as a preferential shelter for O to be adsorbed, and the boundary of the BN inner wall along the [010] or [100] direction makes the p2x2 phase more favorable against the 45°-tilted 2 √3x √3R45°phase of O on the Cu(001) surface. This was supported by Center for Nanophase Materials Sciences, which is a DOE Office of Science User Facility, and the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, maaged by UT-Battelle, LLC, for the U. S. DOE.

  14. 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.

  15. TPDA2 ALGORITHM FOR LEARNING BN STRUCTURE FROM MISSING VALUE AND OUTLIERS IN DATA MINING

    Directory of Open Access Journals (Sweden)

    Benhard Sitohang

    2006-01-01

    Full Text Available Three-Phase Dependency Analysis (TPDA algorithm was proved as most efficient algorithm (which requires at most O(N4 Conditional Independence (CI tests. By integrating TPDA with "node topological sort algorithm", it can be used to learn Bayesian Network (BN structure from missing value (named as TPDA1 algorithm. And then, outlier can be reduced by applying an "outlier detection & removal algorithm" as pre-processing for TPDA1. TPDA2 algorithm proposed consists of those ideas, outlier detection & removal, TPDA, and node topological sort node.

  16. 2D Hexagonal Boron Nitride (2D-hBN) Explored for the Electrochemical Sensing of Dopamine.

    Science.gov (United States)

    Khan, Aamar F; Brownson, Dale A C; Randviir, Edward P; Smith, Graham C; Banks, Craig E

    2016-10-04

    Crystalline 2D hexagonal boron nitride (2D-hBN) nanosheets are explored as a potential electrocatalyst toward the electroanalytical sensing of dopamine (DA). The 2D-hBN nanosheets are electrically wired via a drop-casting modification process onto a range of commercially available carbon supporting electrodes, including glassy carbon (GC), boron-doped diamond (BDD), and screen-printed graphitic electrodes (SPEs). 2D-hBN has not previously been explored toward the electrochemical detection/electrochemical sensing of DA. We critically evaluate the potential electrocatalytic performance of 2D-hBN modified electrodes, the effect of supporting carbon electrode platforms, and the effect of "mass coverage" (which is commonly neglected in the 2D material literature) toward the detection of DA. The response of 2D-hBN modified electrodes is found to be largely dependent upon the interaction between 2D-hBN and the underlying supporting electrode material. For example, in the case of SPEs, modification with 2D-hBN (324 ng) improves the electrochemical response, decreasing the electrochemical oxidation potential of DA by ∼90 mV compared to an unmodified SPE. Conversely, modification of a GC electrode with 2D-hBN (324 ng) resulted in an increased oxidation potential of DA by ∼80 mV when compared to the unmodified electrode. We explore the underlying mechanisms of the aforementioned examples and infer that electrode surface interactions and roughness factors are critical considerations. 2D-hBN is utilized toward the sensing of DA in the presence of the common interferents ascorbic acid (AA) and uric acid (UA). 2D-hBN is found to be an effective electrocatalyst in the simultaneous detection of DA and UA at both pH 5.0 and 7.4. The peak separations/resolution between DA and UA increases by ∼70 and 50 mV (at pH 5.0 and 7.4, respectively, when utilizing 108 ng of 2D-hBN) compared to unmodified SPEs, with a particularly favorable response evident in pH 5.0, giving rise to a

  17. Temperature Dependence of Raman-Active In-Plane E2g Phonons in Layered Graphene and h-BN Flakes

    Science.gov (United States)

    Li, Xiaoli; Liu, Jian; Ding, Kai; Zhao, Xiaohui; Li, Shuai; Zhou, Wenguang; Liang, Baolai

    2018-01-01

    Thermal properties of sp2 systems such as graphene and hexagonal boron nitride (h-BN) have attracted significant attention because of both systems being excellent thermal conductors. This research reports micro-Raman measurements on the in-plane E2g optical phonon peaks ( 1580 cm-1 in graphene layers and 1362 cm-1 in h-BN layers) as a function of temperature from - 194 to 200 °C. The h-BN flakes show higher sensitivity to temperature-dependent frequency shifts and broadenings than graphene flakes. Moreover, the thermal effect in the c direction on phonon frequency in h-BN layers is more sensitive than that in graphene layers but on phonon broadening in h-BN layers is similar as that in graphene layers. These results are very useful to understand the thermal properties and related physical mechanisms in h-BN and graphene flakes for applications of thermal devices.

  18. Crystal Data

    Science.gov (United States)

    SRD 3 NIST Crystal Data (PC database for purchase)   NIST Crystal Data contains chemical, physical, and crystallographic information useful to characterize more than 237,671 inorganic and organic crystalline materials. The data include the standard cell parameters, cell volume, space group number and symbol, calculated density, chemical formula, chemical name, and classification by chemical type.

  19. 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

    2017-09-01

    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 (Δ T 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.

  20. Electronic structure and STM images simulation of defects on hBN/ black-phosphorene heterostructures: A theoretical study

    Science.gov (United States)

    Ospina, D. A.; Cisternas, E.; Duque, C. A.; Correa, J. D.

    2018-03-01

    By first principles calculations which include van der Waals interactions, we studied the electronic structure of hexagonal boron-nitride/black-phosphorene heterostructures (hBN/BP). In particular the role of several kind of defects on the electronic properties of black-phosphorene monolayer and hBN/BP heterostructure was analyzed. The defects under consideration were single and double vacancies, as well Stone-Wale type defects, all of them present in the phosphorene layer. In this way, we found that the electronic structure of the hBN/BP is modified according the type of defect that is introduced. As a remarkable feature, our results show occupied states at the Fermi Level introduced by a single vacancy in the energy gap of the hBN/BP heterostructure. Additionally, we performed simulations of scanning tunneling microscopy images. These simulations show that is possible to discriminate the kind of defect even when the black-phosphorene monolayer is part of the heterostructure hBN/BP. Our results may help to discriminate among several kind of defects during experimental characterization of these novel materials.

  1. 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.

  2. 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.

  3. First-principles study of single-layer C-terminated BN quantum dots

    Science.gov (United States)

    Qu, Li-Hua; Zhang, Jian-Min; Xu, Ke-Wei

    2013-09-01

    We present a first-principles study of the structural, electronic and magnetic properties of single-layer C-terminated BN quantum dots (QDs) under different hydrotreating conditions. The morphologies of QDs with fully hydrogenated edges change slightly. For the fully bared cases, the edged C-C bonds become short and protrudent edged C atoms relax inwards therefore edged zigzag C chain tends to a straight line. The cases of the partially passivated by hydrogen atom at apex, the apex C atom is not relaxed inwards and a new C-C bond is formed. The fully hydrogenated QDs especially N-rich cases are energetically more favorable than those with bared or partially hydrogenated ones. The C-terminated BN-QDs have no magnetic moment when their protrudent edged C atoms are fully passivated by hydrogen atoms, while those with bared or partially hydrogenated edges possess magnetic moments and especially for N-rich cases their magnetic moments increase with increasing QD size n for either bared or partially hydrogenated edges. The band gap of the fully hydrogenated QDs decreases oscillatorily with increasing QD size n. Moreover, for the same size n, the energy gap is wider under N-rich condition than under B-rich condition.

  4. Formation of graphene on BN substrate by vapor deposition method and size effects on its structure

    Science.gov (United States)

    Giang, Nguyen Hoang; Hanh, Tran Thi Thu; Ngoc, Le Nhu; Nga, Nguyen To; Van Hoang, Vo

    2018-04-01

    We report MD simulation of the growth of graphene by the vapor deposition on a two-dimensional hBN substrate. The systems (containing carbon vapor and hBN substrate) are relaxed at high temperature (1500 K), and then it is cooled down to room one (300 K). Carbon atoms interact with the substrate via the Lennard-Jones potential while the interaction between carbon atoms is computed via the Tersoff potential. Depending on the size of the model, different crystalline honeycomb structures have been found. Structural properties of the graphene obtained at 300 K are studied by analyzing radial distribution functions (RDFs), coordination numbers, ring statistics, interatomic distances, bond-angle distributions and 2D visualization of atomic configurations. We find that the models containing various numbers of atoms have a honeycomb structure. Besides, differences in structural properties of graphene formed by the vapor deposition on the substrate and free standing one are found. Moreover, the size effect on the structure is significant.

  5. Time-resolved Polarimetry of the Superluminous SN 2015bn with the Nordic Optical Telescope

    Energy Technology Data Exchange (ETDEWEB)

    Leloudas, Giorgos; Gal-Yam, Avishay [Department of Particle Physics and Astrophysics, Weizmann Institute of Science, Rehovot 7610001 (Israel); Maund, Justyn R. [The Department of Physics and Astronomy, University of Sheffield, Hicks Building, Hounsfield Road, Sheffield S3 7RH (United Kingdom); Pursimo, Tapio [Nordic Optical Telescope, Apartado 474, E-38700 Santa Cruz de La Palma, Santa Cruz de Tenerife (Spain); Hsiao, Eric [Department of Physics, Florida State University, Tallahassee, FL 32306 (United States); Malesani, Daniele; De Ugarte Postigo, Antonio [Dark Cosmology Centre, Niels Bohr Institute, University of Copenhagen, Juliane Maries vej 30, DK-2100 Copenhagen (Denmark); Patat, Ferdinando [European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748 Garching (Germany); Sollerman, Jesper [The Oskar Klein Centre, Department of Astronomy, Stockholm University, AlbaNova, SE-10691 Stockholm (Sweden); Stritzinger, Maximilian D. [Department of Physics and Astronomy, Aarhus University, Ny Munkegade 120, DK-8000 Aarhus C (Denmark); Wheeler, J. Craig [Department of Astronomy, University of Texas at Austin, Austin, TX 78712 (United States)

    2017-03-01

    We present imaging polarimetry of the superluminous supernova SN 2015bn, obtained over nine epochs between −20 and +46 days with the Nordic Optical Telescope. This was a nearby, slowly evolving Type I superluminous supernova that has been studied extensively and for which two epochs of spectropolarimetry are also available. Based on field stars, we determine the interstellar polarization in the Galaxy to be negligible. The polarization of SN 2015bn shows a statistically significant increase during the last epochs, confirming previous findings. Our well-sampled imaging polarimetry series allows us to determine that this increase (from ∼0.54% to ≳1.10%) coincides in time with rapid changes that took place in the optical spectrum. We conclude that the supernova underwent a “phase transition” at around +20 days, when the photospheric emission shifted from an outer layer, dominated by natal C and O, to a more aspherical inner core, dominated by freshly nucleosynthesized material. This two-layered model might account for the characteristic appearance and properties of Type I superluminous supernovae.

  6. 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

  7. Fractional Quantum Hall Effects in Graphene on a h-BN Substrate

    Science.gov (United States)

    Yonaga, Kouki; Shibata, Naokazu

    2018-03-01

    Fractional quantum Hall (FQH) effects in graphene are studied because of their relativistic characteristics and the valley degree of freedom. Recently FQH effects have been observed at various filling factors with graphene on a hexagonal boron nitride (h-BN) substrate. However, it is known that h-BN creates the mass term in the Dirac Hamiltonian that acts as the effective model of graphene. To understand recent experiments, we shall investigate many-body effects in the massive Dirac electron system. In this paper, we study the mass-term effects on the FQH states of Dirac electrons by exact diagonalization. We examine the ground state at filling factor 1/3 in the n = ±1 Landau level. Without the mass term, the ground state in the Laughlin state featuring valley degeneracy and the lowest excitation is characterized by the valley unpolarized state (known as the valley skyrmion state). Conversely, we find that the mass-term lifts the valley degeneracy due to the breaking of the inversion symmetry. We also demonstrate that the valley unpolarized excitation is suppressed and that the fully or partially polarized state appears in the lowest excitation by increasing the mass term. Finally, we discuss the stability of FQH states in the massive Dirac Hamiltonian in experimental situations. We find that our numerical results are in agreement with previous experimental results.

  8. Aristoteles Ve İbn Sînâ’nın Reenkarnasyonu Reddi

    Directory of Open Access Journals (Sweden)

    Hasan Özalp

    2013-06-01

    Full Text Available Bu makalede düşünce tarihinin iki önemli düşünürü Aristoteles ve İbn Sînâ’nın reenkarnasyon/tenasüh hakkındaki görüşlerini inceledik. Her iki düşünürde reenkar-nasyonu reddetmektedir. Konuyu ele almadan önce kaynak olmaları bakımından Aristoteles ve İbn Sînâ’dan önceki bazı filozofların ruh ve reenkarnasyon hakkındaki görüşlerini araştırdık. Daha sonra da her iki filozofun ruh tanımlarım belirledikten sonra reenkarnasyone niçin reddettiklerini ortaya koymaya çalıştık. Nihayetinde görüşlerinde ki benzer ve farklı noktaları tespit için bir karşılaştırma yaptık

  9. Mid-Infrared Imaging of Orion BN/KL With Keck I Telescope

    Science.gov (United States)

    Gezari, Daniel Y.; Danchi, William C.; Greenhill, Lincoln J.; Varosi, Frank

    2003-01-01

    We present new images of the Orion BN/KL infrared complex at 4.8, 8.0, 8.9,9.9, 10.4, 11.7, 12.5, 17.6, 18.1,20.0 and 22.0 um obtained with the 10-meter Keck I telescope, with typically 0.3 arcsec resolution at 12.5 um. The multi-wavelength observational image data is registered in a stack and a dust emission/extinction model is fitted to the resulting spectrum of each pixel to create a diffraction-limited "image" of the temperature, opacity and luminosity of the emitting dust, as well as the circumstellar and line-of-sight dust extinction. New source structure, temperature, opacity and luminosity detail is seen in the vicinity of IRc2-IRc7. The model results are used to develop a more complete picture of the structure and energetics of the BN/KL, infrared complex.

  10. BN-9, a chimeric peptide with mixed opioid and neuropeptide FF receptor agonistic properties, produces nontolerance-forming antinociception in mice.

    Science.gov (United States)

    Li, Ning; Han, Zheng-Lan; Wang, Zi-Long; Xing, Yan-Hong; Sun, Yu-Long; Li, Xu-Hui; Song, Jing-Jing; Zhang, Ting; Zhang, Run; Zhang, Meng-Na; Xu, Biao; Fang, Quan; Wang, Rui

    2016-06-01

    Neuropeptide FF (NPFF) behaves as an endogenous opioid-modulating peptide. In the present study, the opioid and NPFF pharmacophore-containing chimeric peptide BN-9 was synthesized and pharmacologically characterized. Agonist activities of BN-9 at opioid and NPFF receptors were characterized in in vitro cAMP assays. Antinociceptive activities of BN-9 were evaluated in the mouse tail-flick and formalin tests. Furthermore, its side effects were investigated in rotarod, antinociceptive tolerance, reward and gastrointestinal transit tests. BN-9 acted as a novel multifunctional agonist at μ, δ, κ, NPFF1 and NPFF2 receptors in cAMP assays. In the tail-flick test, BN-9 produced dose-related antinociception and was approximately equipotent to morphine; this antinociception was blocked by μ and κ receptor antagonists, but not by the δ receptor antagonist. In the formalin test, supraspinal administration of BN-9 produced significant analgesia. Notably, repeated administration of BN-9 produced analgesia without loss of potency over 8 days. In contrast, repeated i.c.v. co-administration of BN-9 with the NPFF receptor antagonist RF9 produced significant antinociceptive tolerance. Furthermore, i.c.v. BN-9 induced conditioned place preference. When given by the same routes, BN-9 had a more than eightfold higher ED50 value for gastrointestinal transit inhibition compared with the ED50 values for antinociception. BN-9 produced a robust, nontolerance-forming analgesia with limited inhibition of gastrointestinal transit. As BN-9 is able to activate both opioid and NPFF systems, this provides an interesting approach for the development of novel analgesics with minimal side effects. © 2016 The British Pharmacological Society.

  11. Optimization and characterization of bulk hexagonal boron nitride single crystals grown by the nickel-chromium flux method

    Science.gov (United States)

    Hoffman, Tim

    Hexagonal boron nitride (hBN) is a wide bandgap III-V semiconductor that has seen new interest due to the development of other III-V LED devices and the advent of graphene and other 2-D materials. For device applications, high quality, low defect density materials are needed. Several applications for hBN crystals are being investigated, including as a neutron detector and interference-less infrared-absorbing material. Isotopically enriched crystals were utilized for enhanced propagation of phonon modes. These applications exploit the unique physical, electronic and nanophotonics applications for bulk hBN crystals. In this study, bulk hBN crystals were grown by the flux method using a molten Ni-Cr solvent at high temperatures (1500°C) and atmospheric pressures. The effects of growth parameters, source materials, and gas environment on the crystals size, morphology and purity were established and controlled, and the reliability of the process was greatly improved. Single-crystal domains exceeding 1mm in width and 200microm in thickness were produced and transferred to handle substrates for analysis. Grain size dependence with respect to dwell temperature, cooling rate and cooling temperature were analyzed and modeled using response surface morphology. Most significantly, crystal grain width was predicted to increase linearly with dwell temperature, with single-crystal domains exceeding 2mm in at 1700°C. Isotopically enriched 10B and 11B hBN crystal were produced using a Ni-Cr-B flux method, and their properties investigated. 10B concentration was evaluated using SIMS and correlated to the shift in the Raman peak of the E2g mode. Crystals with enrichment of 99% 10B and >99% 11B were achieved, with corresponding Raman shift peaks at 1392.0 cm-1 and 1356.6 cm-1, respectively. Peak FWHM also decreased as isotopic enrichment approached 100%, with widths as low as 3.5 cm-1 achieved, compared to 8.0 cm-1 for natural abundance samples. Defect selective etching was

  12. Hybrid MoS2/h-BN Nanofillers As Synergic Heat Dissipation and Reinforcement Additives in Epoxy Nanocomposites.

    Science.gov (United States)

    Ribeiro, Hélio; Trigueiro, João Paulo C; Silva, Wellington M; Woellner, Cristiano F; Owuor, Peter S; Cristian Chipara, Alin; Lopes, Magnovaldo C; Tiwary, Chandra S; Pedrotti, Jairo J; Villegas Salvatierra, Rodrigo; Tour, James M; Chopra, Nitin; Odeh, Ihab N; Silva, Glaura G; Ajayan, Pulickel M

    2017-09-26

    Two-dimensional (2D) nanomaterials as molybdenum disulfide (MoS 2 ), hexagonal boron nitride (h-BN), and their hybrid (MoS 2 /h-BN) were employed as fillers to improve the physical properties of epoxy composites. Nanocomposites were produced in different concentrations and studied in their microstructure, mechanical and thermal properties. The hybrid 2D mixture imparted efficient reinforcement to the epoxy leading to increases of up to 95% in tensile strength, 60% in ultimate strain, and 58% in Young's modulus. Moreover, an enhancement of 203% in thermal conductivity was achieved for the hybrid composite as compared to the pure polymer. The incorporation of MoS 2 /h-BN mixture nanofillers in epoxy resulted in nanocomposites with multifunctional characteristics for applications that require high mechanical and thermal performance.

  13. Interlayer coupling effects on electronic properties of the phosphorene/h-BN van der Walls heterostructure: A first principles investigation

    Science.gov (United States)

    Luo, Yanwei; Zhang, Shuai; Chen, Weiguang; Jia, Yu

    2018-04-01

    By using first-principles calculations, we systemically investigate the electronic properties of phosphorene/h-BN heterostructure with different interlayer distances. Our results show that the electronic states in the vicinity of the Fermi level are completely dominated by phosphorene, and the system exhibits type-I band alignment consequently. Moreover, we also reveal the variation of the band structure of phosphorene/h-BN heterostructure with different interlayer distances. The band gap undergoes a direct to indirect transition as decreasing the interlayer distance. The mechanism of the band gap transition can be attributed to the different energy levels shifts, according to different electronic orbital characters on the band edge. In specific, the energy level of the P_pz bonding state shifts up while that of the P_px,py bonding state falls down, along with the enhancement of the interactions between phosphorene and h-BN.

  14. 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

    2016-11-09

    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.

  15. Liquid crystal tunable photonic crystal dye laser

    DEFF Research Database (Denmark)

    Buss, Thomas; Christiansen, Mads Brøkner; Smith, Cameron

    2010-01-01

    We present a dye-doped liquid crystal laser using a photonic crystal cavity. An applied electric field to the liquid crystal provides wavelength tunability. The photonic crystal enhances resonant interaction with the gain medium.......We present a dye-doped liquid crystal laser using a photonic crystal cavity. An applied electric field to the liquid crystal provides wavelength tunability. The photonic crystal enhances resonant interaction with the gain medium....

  16. 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.

  17. 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.

  18. Nuclear and Physical Properties of Dielectrics under Neutron Irradiation in Fast (BN-600) and Fusion (DEMO-S) Reactors

    Science.gov (United States)

    Blokhin, D. A.; Chernov, V. M.; Blokhin, A. I.

    2017-12-01

    Nuclear and physical properties (activation and transmutation of elements) of BN and Al2O3 dielectric materials subjected to neutron irradiation for up to 5 years in Russian fast (BN-600) and fusion (DEMO-S) reactors were calculated using the ACDAM-2.0 software complex for different post-irradiation cooling times (up to 10 years). Analytical relations were derived for the calculated quantities. The results may be used in the analysis of properties of irradiated dielectric materials and may help establish the rules for safe handling of these materials.

  19. 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

  20. Molecular Cloning, Recombinant Expression and Antifungal Activity of BnCPI, a Cystatin in Ramie (Boehmeria nivea L.

    Directory of Open Access Journals (Sweden)

    Yongting Yu

    2017-10-01

    Full Text Available Phytocystatins play multiple roles in plant growth, development and resistance to pests and other environmental stresses. A ramie (Boehmeria nivea L. phytocystatin gene, designated as BnCPI, was isolated from a ramie cDNA library and its full-length cDNA was obtained by rapid amplification of cDNA ends (RACE. The full-length cDNA sequence (691 bp consisted of a 303 bp open reading frame (ORF encoding a protein of 100 amino acids with deduced molecular mass of 11.06 kDa and a theoretical isoelectric point (pI of 6.0. The alignment of genome DNA (accession no. MF153097 and cDNA sequences of BnCPI showed that an intron (~104 bp exists in the coding region. The BnCPI protein contains most of the highly conserved blocks including Gly5-Gly6 at the N-terminal, the reactive site motif QxVxG (Q49V50V51S52G53, the L79-W80 block and the [LVI]-[AGT]-[RKE]-[FY]-[AS]-[VI]-x-[EDQV]-[HYFQ]-N (L22G23R24 F25A26V27 D28D29H30 N31 block that is common among plant cystatins. BLAST analysis indicated that BnCPI is similar to cystatins from Glycine max (77%, Glycine soja (76%, Hevea brasiliensis (75% and Ricinus communis (75%. The BnCPI was subcloned into expression vector pSmart-I and then overexpressed in Escherichia coli BL21 (DE3 as a His-tagged recombinant protein. The purified reBnCPI has a molecular mass of 11.4 kDa determined by sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS–PAGE. Purified reBnCPI can efficiently inhibit the protease activity of papain and ficin toward BANA (Nα-benzoyl-L-arginine-2-naphthyamide, as well as the mycelium growth of some important plant pathogenic fungi. The data further contribute to our understanding of the molecular functions of BnCPI.

  1. Electronic structure of BN-aromatics: Choice of reliable computational tools

    Science.gov (United States)

    Mazière, Audrey; Chrostowska, Anna; Darrigan, Clovis; Dargelos, Alain; Graciaa, Alain; Chermette, Henry

    2017-10-01

    The importance of having reliable calculation tools to interpret and predict the electronic properties of BN-aromatics is directly linked to the growing interest for these very promising new systems in the field of materials science, biomedical research, or energy sustainability. Ionization energy (IE) is one of the most important parameters to approach the electronic structure of molecules. It can be theoretically estimated, but in order to evaluate their persistence and propose the most reliable tools for the evaluation of different electronic properties of existent or only imagined BN-containing compounds, we took as reference experimental values of ionization energies provided by ultra-violet photoelectron spectroscopy (UV-PES) in gas phase—the only technique giving access to the energy levels of filled molecular orbitals. Thus, a set of 21 aromatic molecules containing B-N bonds and B-N-B patterns has been merged for a comparison between experimental IEs obtained by UV-PES and various theoretical approaches for their estimation. Time-Dependent Density Functional Theory (TD-DFT) methods using B3LYP and long-range corrected CAM-B3LYP functionals are used, combined with the Δ SCF approach, and compared with electron propagator theory such as outer valence Green's function (OVGF, P3) and symmetry adapted cluster-configuration interaction ab initio methods. Direct Kohn-Sham estimation and "corrected" Kohn-Sham estimation are also given. The deviation between experimental and theoretical values is computed for each molecule, and a statistical study is performed over the average and the root mean square for the whole set and sub-sets of molecules. It is shown that (i) Δ SCF+TDDFT(CAM-B3LYP), OVGF, and P3 are the most efficient way for a good agreement with UV-PES values, (ii) a CAM-B3LYP range-separated hybrid functional is significantly better than B3LYP for the purpose, especially for extended conjugated systems, and (iii) the "corrected" Kohn-Sham result is a

  2. Modeling of BN Lifetime Prediction of a System Based on Integrated Multi-Level Information.

    Science.gov (United States)

    Wang, Jingbin; Wang, Xiaohong; Wang, Lizhi

    2017-09-15

    Predicting system lifetime is important to ensure safe and reliable operation of products, which requires integrated modeling based on multi-level, multi-sensor information. However, lifetime characteristics of equipment in a system are different and failure mechanisms are inter-coupled, which leads to complex logical correlations and the lack of a uniform lifetime measure. Based on a Bayesian network (BN), a lifetime prediction method for systems that combine multi-level sensor information is proposed. The method considers the correlation between accidental failures and degradation failure mechanisms, and achieves system modeling and lifetime prediction under complex logic correlations. This method is applied in the lifetime prediction of a multi-level solar-powered unmanned system, and the predicted results can provide guidance for the improvement of system reliability and for the maintenance and protection of the system.

  3. Development of 50 cm B-N Schmidt telescope at ARIES

    Science.gov (United States)

    Gupta, K. G.; Bangia, T.; Kumar, T. S.; Snehlata; Sharma, N.; Shukla, V.

    A 50/80 cm wide field (4 degree) Baker-Nunn Schmidt telescope with 4k CCD (9 micron pixel) is under development at ARIES for studying optical transients, near-earth objects (up to 20 magnitude) and supplementing ASTROSAT objectives. As a modification of original optical design, a field corrector system consisting of a 235 mm meniscus and a 55 mm field - flattener (near focus) have to be incorporated. Detailed mechanical design has been completed with an equatorial English mount and a passive support system for 796 mm primary mirror with 18 axial and 12 radial supports. Original B-N corrector cell assembly will be used with modifications. The electronics will consist of torque dc motors, absolute and incremental encoders for position and velocity feedback. Matlab will be used for modeling before designing complete electronic feedback control system. The telescope is expected to see first light in March 2008.

  4. 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.

  5. 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.

  6. Preparation of the radiopharmaceutical 99m Tc-HYNIC-[Lys3]-BN

    International Nuclear Information System (INIS)

    Conde S, E.

    2007-01-01

    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 99m Tc, bigger to 95%; the components used in the nucleus-equipment should favor the conjugation of the 99m Tc by means of a ligands exchange between the tricine and the

  7. nBn extended short-wavelength infrared focal plane array.

    Science.gov (United States)

    Dehzangi, Arash; Haddadi, Abbas; Chevallier, Romain; Zhang, Yiyun; Razeghi, Manijeh

    2018-02-01

    An extended short-wavelength nBn InAs/GaSb/AlSb type-II superlattice-based infrared focal plane array imager was demonstrated. A newly developed InAs 0.10 Sb 0.90 /GaSb superlattice design was used as the large-bandgap electron barrier in this photodetector. The large band gap electron-barrier design in this nBn photodetector architecture leads to the device having lower dark current densities. A new bi-layer etch-stop scheme using a combination of InAs 0.91 Sb 0.09 bulk and AlAs 0.1 Sb 0.9 /GaSb superlattice layers was introduced to allow complete substrate removal and a shorter wavelength cut-on. Test pixels exhibit 100% cutoff wavelengths of ∼2.30 and ∼2.48  μm at 150 and 300 K, respectively. The devices achieve saturated quantum efficiency values of 59.7% and 63.8% at 150 and 300 K, respectively, under backside illumination and without any antireflection coating. At 150 K, photodetectors exhibit dark current density of 8.75×10 -8   A/cm 2 under -400  mV applied bias, providing specific detectivity of 2.82×10 12   cm·Hz 1/2 /W at 1.78 μm. At 300 K, the dark current density reaches 4.75×10 -2   A/cm 2 under -200  mV bias, providing a specific detectivity of 8.55×10 9   cm·Hz 1/2 /W 1.78 μm.

  8. Theoretical investigation on the alkali-metal doped BN fullerene as a material for hydrogen storage

    International Nuclear Information System (INIS)

    Venkataramanan, Natarajan Sathiyamoorthy; Belosludov, Rodion Vladimirovich; Note, Ryunosuke; Sahara, Ryoji; Mizuseki, Hiroshi; Kawazoe, Yoshiyuki

    2010-01-01

    Graphical abstract: First-principles calculations have been used to investigate hydrogen adsorption on alkali atom doped B 36 N 36 clusters. Adsorption of alkali atoms involves a charge transfer process, creating positively-charged alkali atoms and this polarizes the H 2 molecules and increases their binding energy. The maximum hydrogen storage capacity of Li doped BN fullerene is 8.9 wt.% in which 60 hydrogen atoms were chemisorbed and 12 H 2 were adsorbed in molecular form. - Abstract: First-principles calculations have been used to investigate hydrogen adsorption on alkali atom doped B 36 N 36 clusters. The alkali atom adsorption takes place near the six tetragonal bridge sites available on the cage, thereby avoiding the notorious clustering problem. Adsorption of alkali atoms involves a charge transfer process, creating positively charged alkali atoms and this polarizes the H 2 molecules thereby, increasing their binding energy. Li atom has been found to adsorb up to three hydrogen molecules with an average binding energy of 0.189 eV. The fully doped Li 6 B 36 N 36 cluster has been found to hold up to 18 hydrogen molecules with the average binding energy of 0.146 eV. This corresponds to a gravimetric density of hydrogen storage of 3.7 wt.%. Chemisorption on the Li 6 B 36 N 36 has been found to be an exothermic reaction, in which 60 hydrogen atoms chemisorbed with an average chemisorption energy of -2.13 eV. Thus, the maximum hydrogen storage capacity of Li doped BN fullerene is 8.9 wt.% in which 60 hydrogen atoms were chemisorbed and 12 hydrogen molecules were adsorbed in molecular form.

  9. Folding two dimensional crystals by swift heavy ion irradiation

    International Nuclear Information System (INIS)

    Ochedowski, Oliver; Bukowska, Hanna; Freire Soler, Victor M.; Brökers, Lara; Ban-d'Etat, Brigitte; Lebius, Henning; Schleberger, Marika

    2014-01-01

    Ion irradiation of graphene, the showcase model of two dimensional crystals, has been successfully applied to induce various modifications in the graphene crystal. One of these modifications is the formation of origami like foldings in graphene which are created by swift heavy ion irradiation under glancing incidence angle. These foldings can be applied to locally alter the physical properties of graphene like mechanical strength or chemical reactivity. In this work we show that the formation of foldings in two dimensional crystals is not restricted to graphene but can be applied for other materials like MoS 2 and hexagonal BN as well. Further we show that chemical vapour deposited graphene forms foldings after swift heavy ion irradiation while chemical vapour deposited MoS 2 does not

  10. Folding two dimensional crystals by swift heavy ion irradiation

    Energy Technology Data Exchange (ETDEWEB)

    Ochedowski, Oliver; Bukowska, Hanna [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany); Freire Soler, Victor M. [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany); Departament de Fisica Aplicada i Optica, Universitat de Barcelona, E08028 Barcelona (Spain); Brökers, Lara [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany); Ban-d' Etat, Brigitte; Lebius, Henning [CIMAP (CEA-CNRS-ENSICAEN-UCBN), 14070 Caen Cedex 5 (France); Schleberger, Marika, E-mail: marika.schleberger@uni-due.de [Fakultät für Physik and CENIDE, Universität Duisburg-Essen, D-47048 Duisburg (Germany)

    2014-12-01

    Ion irradiation of graphene, the showcase model of two dimensional crystals, has been successfully applied to induce various modifications in the graphene crystal. One of these modifications is the formation of origami like foldings in graphene which are created by swift heavy ion irradiation under glancing incidence angle. These foldings can be applied to locally alter the physical properties of graphene like mechanical strength or chemical reactivity. In this work we show that the formation of foldings in two dimensional crystals is not restricted to graphene but can be applied for other materials like MoS{sub 2} and hexagonal BN as well. Further we show that chemical vapour deposited graphene forms foldings after swift heavy ion irradiation while chemical vapour deposited MoS{sub 2} does not.

  11. BnDGAT1s Function Similarly in Oil Deposition and Are Expressed with Uniform Patterns in Tissues of Brassica napus

    Directory of Open Access Journals (Sweden)

    Cuizhu Zhao

    2017-12-01

    Full Text Available As an allotetraploid oilcrop, Brassica napus contains four duplicated Acyl-CoA:diacylglycerol acyltransferase 1 (DGAT1 genes, which catalyze one of the rate-limiting steps in triacylglycerol (TAG biosynthesis in plants. While all four BnDGAT1s have been expressed functionally in yeast, their expression patterns in different germplasms and tissues and also consequent contribution to seed oil accumulation in planta remain to be elucidated. In this study, the coding regions of the four BnDGAT1s were expressed in an Arabidopsis dgat1 mutant. All four BnDGAT1s showed similar effects on oil content and fatty acid composition, a result which is different from that observed in previous studies of their expression in yeast. Expression patterns of BnDGAT1s were analyzed in developing seeds of 34 B. napus inbred lines and in different tissues of 14 lines. Different expression patterns were observed for the four BnDGAT1s, which suggests that they express independently or randomly in different germplasm sources. Higher expression of BnDGAT1s was correlated with higher seed oil content lines. Tissue-specific analyses showed that the BnDGAT1s were expressed in a uniform pattern in different tissues. Our results suggest that it is important to maintain expression of the four BnDGAT1s for maximum return on oil content.

  12. QTL list: PrBn [PGDBj Registered plant list, Marker list, QTL list, Plant DB link and Genome analysis methods[Archive

    Lifescience Database Archive (English)

    Full Text Available QT61662 Brassica napus Brassicaceae PrBn controlling homeologous pairing at metaph...ase I in haploids PrBn gene (homeologous pairing regulator in B. napus) ... LG_DY15 ... 34.9 7.7 ... 10.1534/genetics.106.064071 16951054

  13. 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.

  14. Antimicrobial (BN/PE) film combined with modified atmosphere packaging extends the shelf life of minimally processed fresh-cut iceberg lettuce.

    Science.gov (United States)

    Kang, Sun-Chul; Kim, Min-Jeong; Park, In-Sik; Choi, Ung-Kyu

    2008-03-01

    This study was conducted to investigate the effect of modified atmosphere packaging (MAP) in combination with BN/PE film on the shelf life and quality of fresh-cut iceberg lettuce during cold storage. The total mesophilic population in the sample packed in BN/PE film under MAP conditions was dramatically reduced in comparison with that of PE film, PE film under MAP conditions, and BN/PE film. The O2 concentration in the BN/PE film under MAP conditions decreased slightly as the storage period progressed. The coloration of the iceberg lettuce progressed the slowest when it was packaged in BN/PE film under MAP conditions, followed by BN/PE film, PE film, and PE film under MAP conditions. The shelf life of fresh-cut iceberg lettuce packaged in the BN/PE film under MAP conditions was extended by more than 2 days at 10 degrees as compared with that of the BN/PE film in which the extension effect was more than 2 days longer than that of PE, PET, and OPP films.

  15. 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.

  16. P-type sp3-bonded BN/n-type Si heterodiode solar cell fabricated by laser-plasma synchronous CVD method

    International Nuclear Information System (INIS)

    Komatsu, Shojiro; Nagata, Takahiro; Chikyo, Toyohiro; Sato, Yuhei; Watanabe, Takayuki; Hirano, Daisuke; Takizawa, Takeo; Nakamura, Katsumitsu; Hashimoto, Takuya; Nakamura, Takuya; Koga, Kazunori; Shiratani, Masaharu; Yamamoto, Atsushi

    2009-01-01

    A heterojunction of p-type sp 3 -bonded boron nitride (BN) and n-type Si fabricated by laser-plasma synchronous chemical vapour deposition (CVD) showed excellent rectifying properties and proved to work as a solar cell with photovoltaic conversion efficiency of 1.76%. The BN film was deposited on an n-type Si (1 0 0) substrate by plasma CVD from B 2 H 6 + NH 3 + Ar while doping of Si into the BN film was induced by the simultaneous irradiation of an intense excimer laser with a pulse power of 490 mJ cm -2 , at a wavelength of 193 nm and at a repetition rate of 20 Hz. The source of dopant Si was supposed to be the Si substrate ablated at the initial stage of the film growth. The laser enhanced the doping (and/or diffusion) of Si into BN as well as the growth of sp 3 -bonded BN simultaneously in this method. P-type conduction of BN films was determined by the hot (thermoelectric) probe method. The BN/Si heterodiode with an essentially transparent p-type BN as a front layer is supposed to efficiently absorb light reaching the active region so as to potentially result in high efficiency.

  17. 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.

  18. Electronic Properties of Graphene Encapsulated with Different Two-Dimensional Atomic Crystals

    OpenAIRE

    Kretinin, A. V.; Cao, Y.; Tu, J. S.; Yu, G. L.; Jalil, R.; Novoselov, K. S.; Haigh, S. J.; Gholinia, A.; Mishchenko, A.; Lozada, M.; Georgiou, T.; Woods, C. R.; Withers, F.; Blake, P.; Eda, G.

    2014-01-01

    Hexagonal boron nitride is the only substrate that has so far allowed graphene devices exhibiting micron-scale ballistic transport. Can other atomically flat crystals be used as substrates for making quality graphene heterostructures? Here we report on our search for alternative substrates. The devices fabricated by encapsulating graphene with molybdenum or tungsten disulphides and hBN are found to exhibit consistently high carrier mobilities of about 60,000 cm$^{2}$V$^{-1}$s$^{-1}$. In contr...

  19. A first-principle investigation into effect of B-and BN-doped C60 in ...

    Indian Academy of Sciences (India)

    Annual Meetings · Mid Year Meetings · Discussion Meetings · Public Lectures · Lecture Workshops · Refresher Courses · Symposia · Live Streaming. Home; Journals; Bulletin of Materials Science; Volume 40; Issue 7. A first-principle investigation into effect of B- and BN-doped C 60 in lowering dehydrogenation of MXH 4 ...

  20. Adsorption and possible dissociation of glucose by the [BN fullerene-B6]- magnetic nanocomposite. In silico studies

    Science.gov (United States)

    Anota, E. Chigo; Villanueva, M. Salazar; Shakerzadeh, E.; Castro, M.

    2018-02-01

    The adsorption, activation and possible dissociation of the glucose molecule on the magnetic [BN fullerene-B6]- system is performed by means of density functional theory calculations. Three models of magnetic nanocomposites were inspected: i) pristine BN fullerene, BN fullerene functionalized with a magnetic B6 cluster which generates two structures: ii) pyramidal (P) and iii) triangular (T). Chemical interactions of glucose appear for all these cases; however, for the BNF:B6(T)—glucose system, the interaction generates an effect of dissociation on glucose, due to the magnetic effects, since it has high spin multiplicity. The latter nanocomposite shows electronic behavior like-conductor and like-semi-conductor for the P and T geometries, respectively. Intrinsic magnetism associated to values of 1.0 magneton bohr (µB) for the pyramidal and 5.0 µB for the triangular structure, high polarity, and low-chemical reactivity are found for these systems. These interesting properties make these functionalized fullerenes a good option for being used as nano-vehicles for drug delivery. These quantum descriptors remain invariant when the [BN]-fullerene and [BNF:B6 (P) or (T)]- nanocomposites are interacting with the glucose molecule. According to the determined adsorption energy, chemisorption regimes occur in both the phases: gas and aqueous medium.

  1. Effects of nano-sized boron nitride (BN) reinforcement in expandable graphite based in-tumescent fire retardant coating

    Science.gov (United States)

    Zulkurnain, E. S.; Ahmad, F.; Gillani, Q. F.

    2016-08-01

    The purpose of in-tumescent fire retardant coating (IFRC) is to protect substrate from fire attack by limiting heat transfer. A range of coating formulations have been prepared using Bisphenol A epoxy resin BE-188 and polyamide solidifier H-2310 as two-part binder, ammonium polyphosphate (APP) as acid source, melamine (MEL) as the blowing agent, expandable graphite (EG) as carbon source and nano-boron nitride (BN) as inorganic nano filler. The filler was used to improve the performances of the APP-EG-MEL coating. The effects of nano-BN on the char morphology and thermal degradation were investigated by fire test, thermo gravimetric analysis (TGA), Fourier transform infrared spectroscopy (FTIR), X- ray photoelectron spectroscopy (XPS) and field emission scanning electron microscopy (FESEM). The results showed that by substituting or reinforcing of 4% weight percentage of nano-BN, residual weight of the char increases by 23.82% compared to APP-EG-MEL coating without filler. Higher carbon content was obtained in the char and a more compact char was produced. The results indicated that nano-BN could be used as a filler to improve thermal stability of the APP-EG-MEL coating.

  2. 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

  3. 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.

  4. 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.

  5. Dynamical effects in x-ray absorption spectra of graphene and monolayered h-BN on Ni(111)

    Czech Academy of Sciences Publication Activity Database

    Rusz, Ján; Preobrajenski, A.B.; Ling, M.L.; Vinogradov, N.A.; Martensson, N.; Wessely, O.; Sanyal, B.; Eriksson, O.

    2010-01-01

    Roč. 81, č. 7 (2010), 073402/1-073402/4 ISSN 1098-0121 Institutional research plan: CEZ:AV0Z10100520 Keywords : fine-structure * boron-nitride * hegxagonal BN * K- edge * graphite * excitations * excitons Subject RIV: BM - Solid Matter Physics ; Magnetism Impact factor: 3.772, year: 2010

  6. 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.

  7. The BnGRF2 gene (GRF2-like gene from Brassica napus) enhances seed oil production through regulating cell number and plant photosynthesis.

    Science.gov (United States)

    Liu, Jing; Hua, Wei; Yang, Hong-Li; Zhan, Gao-Miao; Li, Rong-Jun; Deng, Lin-Bin; Wang, Xin-Fa; Liu, Gui-Hua; Wang, Han-Zhong

    2012-06-01

    Seed yield and oil content are two important agricultural characteristics in oil crop breeding, and a lot of functional gene research is being concentrated on increasing these factors. In this study, by differential gene expression analyses between rapeseed lines (zy036 and 51070) which exhibit different levels of seed oil production, BnGRF2 (Brassica napus growth-regulating factor 2-like gene) was identified in the high oil-producing line zy036. To elucidate the possible roles of BnGRF2 in seed oil production, the cDNA sequences of the rapeseed GRF2 gene were isolated. The Blastn result showed that rapeseed contained BnGRF2a/2b which were located in the A genome (A1 and A3) and C genome (C1 and C6), respectively, and the dominantly expressed gene BnGRF2a was chosen for transgenic research. Analysis of 35S-BnGRF2a transgenic Arabidopsis showed that overexpressed BnGRF2a resulted in an increase in seed oil production of >50%. Moreover, BnGRF2a also induced a >20% enlargement in extended leaves and >40% improvement in photosynthetic efficiency because of an increase in the chlorophyll content. Furthermore, transcriptome analyses indicated that some genes associated with cell proliferation, photosynthesis, and oil synthesis were up-regulated, which revealed that cell number and plant photosynthesis contributed to the increased seed weight and oil content. Because of less efficient self-fertilization induced by the longer pistil in the 35S-BnGRF2a transgenic line, Napin-BnGRF2a transgenic lines were further used to identify the function of BnGRF2, and the results showed that seed oil production also could increase >40% compared with the wild-type control. The results suggest that improvement to economically important characteristics in oil crops may be achieved by manipulation of the GRF2 expression level.

  8. Nucleation and crystal growth in batch crystallizers

    NARCIS (Netherlands)

    Janse, A.H.

    1977-01-01

    The aim of the present work is to gain knowledge of the mechanism of formation of the crystal size distribution in batch crystallizers in order to give directives for design and operation of batch crystallizers. The crystal size distribution is important for the separation of crystals and mother

  9. Helium crystals

    International Nuclear Information System (INIS)

    Lipson, S.G.

    1987-01-01

    Hexagonal close-packed helium crystals in equilibrium with superfluid have been found to be one of the few systems in which an anisotropic solid comes into true thermodynamic equilibrium with its melt. The discovery of roughening transitions at the liquid-solid interface have shown this system to be ideal for the study of the statistical mechanics of interface structures. We describe the effect of roughening on the shape and growth of macroscopic crystals from both the theoretical and experimental points of view. (author)

  10. 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

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

    International Nuclear Information System (INIS)

    Rani, Babita; Jindal, V.K.; Dharamvir, Keya

    2016-01-01

    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

  12. Therapeutic Crystals

    Science.gov (United States)

    Bond, Charles S.

    2014-01-01

    Some readers might not fully know what the difference is between crystallography, and the "new age" practice of dangling crystals around the body to capitalise on their healing energy. The latter is often considered to be superstition, while ironically, the former has actually resulted in real rationally-based healing of human diseases…

  13. Ribbon Crystals

    DEFF Research Database (Denmark)

    Bohr, Jakob; Markvorsen, Steen

    2013-01-01

    A repetitive crystal-like pattern is spontaneously formed upon the twisting of straight ribbons. The pattern is akin to a tessellation with isosceles triangles, and it can easily be demonstrated with ribbons cut from an overhead transparency. We give a general description of developable ribbons...

  14. Brillouin zone spin filtering mechanism of enhanced tunneling magnetoresistance and correlation effects in a Co(0001 )/h -BN/Co(0001 ) magnetic tunnel junction

    Science.gov (United States)

    Faleev, Sergey V.; Parkin, Stuart S. P.; Mryasov, Oleg N.

    2015-12-01

    The Brillouin zone spin filtering mechanism of enhanced tunneling magnetoresistance (TMR) is described for magnetic tunnel junctions (MTJs) and studied for an example of the MTJ with hcp Co electrodes and hexagonal BN (h -BN) spacer. Our calculations based on the local density approximation of density-functional theory (LDA-DFT) for Co(0001 )/h -BN/Co(0001 ) MTJ predict high TMR in this device due to Brillouin zone filtering mechanism. Owning to the specific complex band structure of the h -BN the spin-dependent tunneling conductance of the system is ultrasensitive to small variations of the Fermi energy position inside the BN band gap. Doping of the BN and, consequentially, changing the Fermi energy position could lead to variation of the TMR by several orders of magnitude. We show also that taking into account correlation effects on beyond DFT level is required to accurately describe position of the Fermi level and thus transport properties of the system. Our study suggests that new MTJ based on hcp Co-Pt or Co-Pd disordered alloy electrodes and p -doped hexagonal BN spacer is a promising candidate for the spin-transfer torque magnetoresistive random-access memory.

  15. 1D ferromagnetic edge contacts to 2D graphene/h-BN heterostructures

    Science.gov (United States)

    Karpiak, Bogdan; Dankert, André; Cummings, Aron W.; Power, Stephen R.; Roche, Stephan; Dash, Saroj P.

    2018-03-01

    We report the fabrication of one-dimensional (1D) ferromagnetic edge contacts to two-dimensional (2D) graphene/h-BN heterostructures. While aiming to study spin injection/detection with 1D edge contacts, a spurious magnetoresistance signal was observed, which is found to originate from the local Hall effect in graphene due to fringe fields from ferromagnetic edge contacts and in the presence of charge current spreading in the nonlocal measurement configuration. Such behavior has been confirmed by the absence of a Hanle signal and gate-dependent magnetoresistance measurements that reveal a change in sign of the signal for the electron- and hole-doped regimes, which is in contrast to the expected behavior of the spin signal. Calculations show that the contact-induced fringe fields are typically on the order of hundreds of mT, but can be reduced below 100 mT with careful optimization of the contact geometry. There may be an additional contribution from magnetoresistance effects due to tunneling anisotropy in the contacts, which needs further investigation. These studies are useful for optimization of spin injection and detection in 2D material heterostructures through 1D edge contacts.

  16. LIBERAL MEASURES AND STRONG POWER. TO THE 190TH BIRTHDAY OF B.N. CHICHERIN

    Directory of Open Access Journals (Sweden)

    Aleksei Dmitrievich Nikotin

    2017-10-01

    Full Text Available Purpose: Identify the general and special in the views of Boris B. Chicherin, as the brightest representative of Russian liberalism at the turn of the XIX–XX centuries on the problem of Russia’s political system, the prospect of the development of civil and political freedoms. Research methodology: when working with the texts analyzed was used the comparative method, system method. The results of the study: The article examines the political and philosophical views of the greatest theoretician of Russian liberalism at the turn of the XIX–XX centuries B.N. Chicherin. The author, noting the breadth of scientific views of the Russian liberal, concentrated on his ideas about Russia’s preferred form of government and the need to reform Russia’s state and legal system. Particular attention is paid to the views of Boris N. Chicherin on the problem of the exercise of individual freedom of a person, his civil and political rights in the conditions of strong state power, building up the legal system of interaction between the state and civil society. The scope of the results: the results can be applied in scientific politological and social-philosophical studies, and in the course of teaching of social and Humanities disciplines.

  17. Microwave Impedance Spectroscopy and Temperature Effects on the Electrical Properties of Au/BN/C Interfaces

    Directory of Open Access Journals (Sweden)

    Hazem K. Khanfar

    2017-01-01

    Full Text Available In the current study, an Au/BN/C microwave back-to-back Schottky device is designed and characterized. The device morphology and roughness were evaluated by means of scanning electron and atomic force microscopy. As verified by the Richardson–Schottky current conduction transport mechanism which is well fitted to the experimental data, the temperature dependence of the current-voltage characteristics of the devices is dominated by the electric field assisted thermionic emission of charge carriers over a barrier height of ~0.87 eV and depletion region width of ~1.1 μm. Both the depletion width and barrier height followed an increasing trend with increasing temperature. On the other hand, the alternating current conductivity analysis which was carried out in the frequency range of 100–1400 MHz revealed the domination of the phonon assisted quantum mechanical tunneling (hopping of charge carriers through correlated barriers (CBH. In addition, the impedance and power spectral studies carried out in the gigahertz-frequency domain revealed a resonance-antiresonance feature at frequency of  ~1.6 GHz. The microwave power spectra of this device revealed an ideal band stop filter of notch frequency of  ~1.6 GHz. The ac signal analysis of this device displays promising characteristics for using this device as wave traps.

  18. The electronic structure and ferromagnetism of TM (TM=V, Cr, and Mn)-doped BN(5, 5) nanotube: A first-principles study

    International Nuclear Information System (INIS)

    He, K.H.; Zheng, G.; Chen, G.; Wan, M.; Ji, G.F.

    2008-01-01

    We study the electronic structure and ferromagnetism of V-, Cr-, and Mn-doped single-wall BN(5, 5) nanotube by using polarized spin calculations within first principles. The optimized structures show that the transition-metal atoms move outwards and the calculated electronic properties demonstrate that the isolated V-, Cr-, and Mn-doped BN(5, 5) nanotubes show half-metallicity. The total ferromagnetic moments are 2μ B , 3.02μ B , and 3.98μ B for V-, Cr-, and Mn-doped BN(5, 5), respectively. The study suggests that such transition-metal (TM)-doped nanotubes may be useful in spintronics and nanomagnets

  19. Physical, mechanical and neutron shielding properties of h-BN/Gd2O3/HDPE ternary nanocomposites

    Science.gov (United States)

    İrim, Ş. Gözde; Wis, Abdulmounem Alchekh; Keskin, M. Aker; Baykara, Oktay; Ozkoc, Guralp; Avcı, Ahmet; Doğru, Mahmut; Karakoç, Mesut

    2018-03-01

    In order to prepare an effective neutron shielding material, not only neutron but also gamma absorption must be taken into account. In this research, a polymer nanocomposite based novel type of multifunctional neutron shielding material is designed and fabricated. For this purpose, high density polyethylene (HDPE) was compounded with different amounts of hexagonal boron nitride (h-BN) and Gd2O3 nanoparticles having average particle size of 100 nm using melt-compounding technique. The mechanical, thermal and morphological properties of nanocomposites were investigated. As filler content increased, the absorption of both neutron and gamma fluxes increased despite fluctuating neutron absorption curves. Adding h-BN and Gd2O3 nano particles had a significant influence on both neutron and gamma attenuation properties (Σ, cm-1 and μ/ρ, cm-2/g) of ternary shields and they show an enhancement of 200-280%, 14-52% for neutron and gamma radiations, respectively, in shielding performance.

  20. Evaluation of the Lipid Interference for Siemens BN ProSpec Cystatin C Assay Using Pediatric Samples.

    Science.gov (United States)

    Akbas, Neval; Gonzalez, Graciela; Devaraj, Sridevi

    2015-01-01

    Endogenous interferents (lipids, hemoglobin and bilirubin) are a common cause of pre-analytical laboratory errors. We evaluated the effect of lipemia on Siemens cystatin C assay using pediatric samples. Lipemic samples were prepared by adding various concentrations of triglycerides into low and high cystatin C sample pools. Cystatin C concentrations were then measured on Siemens BN ProSpec analyzer and change of the analyte concentrations was determined. Low and high cystatin C sample pools were not affected by additions of lower lipid concentrations (150, 500 and 750 mg/dL), while the negative bias of <10% was seen with additions of higher lipid concentrations (1000 and 1500 mg/dL). Our results suggest that the BN ProSpec assay is a good alternative for cystatin C measurements in our pediatric population with no major interference from lipemia. © 2015 by the Association of Clinical Scientists, Inc.

  1. Enhancement of thermal neutron attenuation of nano-B4C, -BN dispersed neutron shielding polymer nanocomposites

    International Nuclear Information System (INIS)

    Kim, Jaewoo; Lee, Byung-Chul; Uhm, Young Rang; Miller, William H.

    2014-01-01

    Highlights: • Preparation of B 4 C and BN nanopowders using a simple ball milling process. • Homogeneous dispersion and strong adhesion of nano-B 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 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

  2. Spin filter effect of hBN/Co detector electrodes in a 3D topological insulator spin valve

    Science.gov (United States)

    Vaklinova, Kristina; Polyudov, Katharina; Burghard, Marko; Kern, Klaus

    2018-03-01

    Topological insulators emerge as promising components of spintronic devices, in particular for applications where all-electrical spin control is essential. While the capability of these materials to generate spin-polarized currents is well established, only very little is known about the spin injection/extraction into/out of them. Here, we explore the switching behavior of lateral spin valves comprising the 3D topological insulator Bi2Te2Se as channel, which is separated from ferromagnetic Cobalt detector contacts by an ultrathin hexagonal boron nitride (hBN) tunnel barrier. The corresponding contact resistance displays a notable variation, which is correlated with a change of the switching characteristics of the spin valve. For contact resistances below ~5 kΩ, the hysteresis in the switching curve reverses upon reversing the applied current, as expected for spin-polarized currents carried by the helical surface states. By contrast, for higher contact resistances an opposite polarity of the hysteresis loop is observed, which is independent of the current direction, a behavior signifying negative spin detection efficiency of the multilayer hBN/Co contacts combined with bias-induced spin signal inversion. Our findings suggest the possibility to tune the spin exchange across the interface between a ferromagnetic metal and a topological insulator through the number of intervening hBN layers.

  3. Use of a TiBN Multilayer Coating for Wear Reduction

    Science.gov (United States)

    Behrens, Bernd-Arno; Bach, Friedrich-Wilhelm; Moehwald, Kai; Deißer, Todd Alexander; Bistron, Marcus

    2007-05-01

    The near surface area of forging dies is exposed to high mechanical loads. Additionally thermal and chemical stresses occur during the forging process. Depending on the number of forged parts, several kinds of damage develop in the surface area, which lead to failures of forging dies. Die wear is the main reason of failure with a 70% ratio. The abrasion resistance of the surface area of forging dies has to be increased in order to reduce wear. Therefore different methods were examined such as the increase of the abrasion resistance by plasma nitriding and by coating with ceramic layers (TiN, TiCN, TiC, CrN). These layers are applied to the forging die by using PACVD or PAPVD treatment. At the Institute of Metal Forming and Metal-Forming Machines of the University of Hanover a wear reduction by factor 3.5 compared to nitrided forging dies for forging helical gears was achieved. This was possible by using a coating compound of 18 ceramic layers. These excellent results for the multilayer system can be explained through the energy reduction at the inner boundaries and a crack deflection effect at the phase transitions. The layer support of neighboring layers and a stress relaxation through the stacked construction of the layer system are also improving the durability of the coating. This multilayer coating consists of a TiN-TiCN-TiC layer system with an overall thickness of 1.8 μm. This paper presents investigations of this multilayer compound and further research to reduce wear through an additional TiBN coating layer. With this additional top coating an increase of the thermal resistance and the oxidation resistance can be achieved. As a result of this enhancement a further increase of the wear reduction was expected.

  4. 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.

  5. 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.

  6. Dosimetric consequences of 10B(n, alpha)7Li reaction occurring at the cellular membrane.

    Science.gov (United States)

    Kalend, A M; Bloomer, W D; Epperly, M W

    1995-01-01

    Microdosimetric expectations of Boron contents are extracted from a CRAY-Monte Carlo simulation of the nuclear reaction 10B(n, alpha)7Li as it occurs on a boronated membrane of a model cell and as the reaction fragments (alpha and Li) traverse into the cellular nucleus. The present microdosimetry calculation is based upon the assumption that the therapeutic advantage of boron neutron capture therapy (BNCT), while depending upon the RBE and LET of the reaction particles, is equally dependent on the boron carrier preferential localization to tumor tissue, and the boron selectivity to cancerous cells and its specificity within subcellular compartments. In particular, boron fixes to cell membrane as it ought to, using monoclonal antibodies. The present Monte Carlo simulation computes stochastic expectations of alpha/Li energy depositions to the nucleus in a uniformly boronated membrane shell of a spherical cell. Differential energy gain was deduced from the stochastic energy depositions in events of neutron reactions with membrane boron compared against those with natural elements (O, H, N) in the cell. Microdosimetry data are presented in terms of specific energy (keV/micron3) and lineal energy (keV/micron) functions of the nucleus-to-cell volume ratios (NCVR). When folded with the geometric boron content and accounting for background reaction energies, the distributions yield effective energy gain to the cell nucleus per neutron capture event. Boron amount required to yield these energy gains are found to be of the order of picograms of boron per gram of cell mass. The boron content as inferred by the present Monte Carlo microdosimetry compares well with that deliverable by present pharmacokinetic means, but are orders of magnitude (mu-grams) less than those deduced previously from anthropomorphic macrodosimetry.

  7. Quick Maintenance for High Voltage Equipment with the New Not Toxic Boron Nitride Powder (BN100) Superior Thermal Conductive and Lightweight Filler

    National Research Council Canada - National Science Library

    Boer, Fabrizio

    2005-01-01

    .... The BN100 superior thermal conductive and lightweight filler technology is a new filler technology, that not only lets Users a full access for maintenance because cure-free being compounded by loose...

  8. The Evolution of Interfacial Sliding Stresses During Cyclic Push-in Testing of C- and BN-Coated Hi-Nicalon Fiber-Reinforced CMCs

    Science.gov (United States)

    Eldridge, J. I.; Bansal, N. P.; Bhatt, R. T.

    1998-01-01

    Interfacial debond cracks and fiber/matrix sliding stresses in ceramic matrix composites (CMCs) can evolve under cyclic fatigue conditions as well as with changes in the environment, strongly affecting the crack growth behavior, and therefore, the useful service lifetime of the composite. In this study, room temperature cyclic fiber push-in testing was applied to monitor the evolution of frictional sliding stresses and fiber sliding distances with continued cycling in both C- and BN-coated Hi-Nicalon SiC fiber-reinforced CMCs. A SiC matrix composite reinforced with C-coated Hi-Nical on fibers as well as barium strontium aluminosilicate (BSAS) matrix composites reinforced with BN-coated (four different deposition processes compared) Hi-Nicalon fibers were examined. For failure at a C interface, test results indicated progressive increases in fiber sliding distances during cycling in room air but not in nitrogen. These results suggest the presence of moisture will promote crack growth when interfacial failure occurs at a C interface. While short-term testing environmental effects were not apparent for failure at the BN interfaces, long-term exposure of partially debonded BN-coated fibers to humid air resulted in large increases in fiber sliding distances and decreases in interfacial sliding stresses for all the BN coatings, presumably due to moisture attack. A wide variation was observed in debond and frictional sliding stresses among the different BN coatings.

  9. Photonic time crystals.

    Science.gov (United States)

    Zeng, Lunwu; Xu, Jin; Wang, Chengen; Zhang, Jianhua; Zhao, Yuting; Zeng, Jing; Song, Runxia

    2017-12-07

    When space (time) translation symmetry is spontaneously broken, the space crystal (time crystal) forms; when permittivity and permeability periodically vary with space (time), the photonic crystal (photonic time crystal) forms. We proposed the concept of photonic time crystal and rewritten the Maxwell's equations. Utilizing Finite Difference Time Domain (FDTD) method, we simulated electromagnetic wave propagation in photonic time crystal and photonic space-time crystal, the simulation results show that more intensive scatter fields can obtained in photonic time crystal and photonic space-time crystal.

  10. Crystal structure of the bora-benzene-2,6-lutidine adduct.

    Science.gov (United States)

    Kivijärvi, Lauri; Haukka, Matti

    2015-12-01

    In the title compound, C12H14BN, the complete mol-ecule is generated by a crystallographic twofold axis, with two C atoms, the B atom and the N atom lying on the rotation axis. The dihedral angle between the bora-benzene and pyridine rings is 81.20 (6)°. As well as dative electron donation from the N atom to the B atom [B-N = 1.5659 (18) Å], the methyl substituents on the lutidine ring shield the B atom, which further stabilizes the mol-ecule. In the crystal, weak aromatic π-π stacking between the pyridine rings [centroid-centroid separation = 3.6268 (9) Å] is observed, which generates [001] columns of mol-ecules.

  11. Crystal growth of Mg2Si for IR-detector

    Science.gov (United States)

    Tokairin, Toshio; Ikeda, Junya; Udono, Haruhiko

    2017-06-01

    Semiconducting Mg2Si is known as a thermoelectric material and recently attracts increasing attention as a Si-based, low-cost and environmental friendly material for an infrared (IR) sensor. With the aim of producing cost-effective Mg2Si single crystal substrates for the IR sensor, we have investigated single crystal growth of Mg2Si using the vertical Bridgman (VB) and micro-pulling-down (μ-PD) methods in open-system. Since the evaporation of Mg was not suppressed during the μ-PD, the composition of the Mg2Si single crystal grown by this method was not stoichiometric. On the other hand, single crystalline Mg2Si was produced by the VB method using the Si-treated inner carbon seat and BN-coated carbon crucible. The Mg2Si crystals with a diameter of 30 mm were grown at a growth rate of 0.5 mm/min and a temperature gradient of 5 °C/cm. The electron density and mobility of the crystal so obtained were 1.8×1017 cm-3 and 283 cm2V-1s-1 at 300 K, respectively. The high electron density was due to contamination from the impurities presented in the crucible.

  12. Microstructural features and properties of the nano-crystalline SiC/BN(C) composite ceramic prepared from the mechanically alloyed SiBCN powder

    International Nuclear Information System (INIS)

    Zhang Pengfei; Jia Dechang; Yang Zhihua; Duan Xiaoming; Zhou Yu

    2012-01-01

    Highlights: ► As-milled SiBCN powder consists of spherical agglomerates, 6.5 ± 5.4 μm in size. ► Hot pressed SiC/BN(C) ceramic consists of nano β-SiC, α-SiC and BN(C). ► Turbostratic BN(C) is composed of t-carbon, t-BN and B-doped t-carbon layers. ► BN(C) retards grain growth and is responsible for the fine grains. ► The temperature and pressure greatly affect the ceramic density and properties. - Abstract: Nano SiC/BN(C) ceramic was prepared from the mechanically-alloyed amorphous SiBCN powder, hot pressed at 1900 °C under 80 MPa in the nitrogen atmosphere for 30 min. The microstructures and the properties of the prepared ceramic were carefully studied by XRD, TEM (SAED, HRTEM and EFTEM), EELS and property testing. Results show that the ceramic consists of β-SiC, α-SiC and BN(C). SiC has an average grain size of about 78.2 ± 32.4 nm, most of which have numerous stacking faults. BN(C) has small size, no fixed shape and turbostratic structure with heterogeneously distributed t-carbon layers, t-BN layers and B-doped t-carbon layers. It has uniform distribution in the ceramic, retarding the atomic diffusion and being responsible for the fine grains. The ceramic has room-temperature density, flexural strength, Young’s modulus and fracture toughness of 2.6 g/cm 3 , 331.1 MPa, 139.4 GPa and 2.8 MPa m 1/2 , respectively. The detailed investigation of the hot-pressed SiC/BN(C) ceramic is helpful for the further study of this material and other ceramics, targeted for the high-temperature applications.

  13. Photonic Crystal Fibers

    National Research Council Canada - National Science Library

    Kristiansen, Rene E

    2005-01-01

    This report results from a contract tasking Crystal Fibre A/S as follows: Crystal Fibre will conduct research and development of large mode area, dual clad multi-core Yb-doped photonic crystal fiber...

  14. Liquid Crystal Devices.

    Science.gov (United States)

    Bradshaw, Madeline J.

    1983-01-01

    The nature of liquid crystals and several important liquid crystal devices are described. Ideas for practical experiments to illustrate the properties of liquid crystals and their operation in devices are also described. (Author/JN)

  15. Liquid Crystal Inquiries.

    Science.gov (United States)

    Marroum, Renata-Maria

    1996-01-01

    Discusses the properties and classification of liquid crystals. Presents a simple experiment that illustrates the structure of liquid crystals and the differences between the various phases liquid crystals can assume. (JRH)

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

    International Nuclear Information System (INIS)

    Caissie, Amanda; Nguyen, Janet; Chen, Emily; Zhang Liying; Sahgal, Arjun; Clemons, Mark; Kerba, Marc; Arnalot, Palmira Foro; Danjoux, Cyril; Tsao, May; Barnes, Elizabeth; Holden, Lori; Danielson, Brita; Chow, Edward

    2012-01-01

    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

  17. 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

  18. Testing of the dual slab verification detector for attended measurements of the BN-350 dry storage casks

    Energy Technology Data Exchange (ETDEWEB)

    Santi, Peter A [Los Alamos National Laboratory; Browne, Michael C [Los Alamos National Laboratory; Williams, Richard B [Los Alamos National Laboratory; Parker, Robert F [Los Alamos National Laboratory

    2009-01-01

    The Dual Slab Verification Detector (DSVD) has been developed and built by Los Alamos National Laboratory in cooperation with the International Atomic Energy Agency (IAEA) as part of the dry storage safeguards system for the spent fuel from the BN-350 fast reactor. The detector consists of two rows of {sup 3}He tubes embedded in a slab of polyethylene which has been designed to be placed on the outer surface of the dry storage cask. The DSVD will be used to perform measurements of the neutron flux emanating from inside the dry storage cask at several locations around each cask to establish a neutron 'fingerprint' that is sensitive to the contents of the cask. The sensitivity of the fingerprinting technique to the removal of specific amount of nuclear material from the cask is determined by the characteristics of the detector that is used to perform the measurements, the characteristics of the spent fuel being measured, and systematic uncertainties that are associated with the dry storage scenario. MCNPX calculations of the BN-350 dry storage asks and layout have shown that the neutron fingerprint verification technique using measurements from the DSVD would be sensitive to both the amount and location of material that is present within an individual cask. To confirm the performance of the neutron fingerprint technique in verifying the presence of BN-350 spent fuel in dry storage, an initial series of measurements have been performed to test the performance and characteristics of the DSVD. Results of these measurements will be presented and compared with MCNPX results.

  19. Testing of the dual slab verification detector for attended measurements of the BN-350 dry storage casks

    International Nuclear Information System (INIS)

    Santi, Peter A.; Browne, Michael C.; Williams, Richard B.; Parker, Robert F.

    2009-01-01

    The Dual Slab Verification Detector (DSVD) has been developed and built by Los Alamos National Laboratory in cooperation with the International Atomic Energy Agency (IAEA) as part of the dry storage safeguards system for the spent fuel from the BN-350 fast reactor. The detector consists of two rows of 3 He tubes embedded in a slab of polyethylene which has been designed to be placed on the outer surface of the dry storage cask. The DSVD will be used to perform measurements of the neutron flux emanating from inside the dry storage cask at several locations around each cask to establish a neutron 'fingerprint' that is sensitive to the contents of the cask. The sensitivity of the fingerprinting technique to the removal of specific amount of nuclear material from the cask is determined by the characteristics of the detector that is used to perform the measurements, the characteristics of the spent fuel being measured, and systematic uncertainties that are associated with the dry storage scenario. MCNPX calculations of the BN-350 dry storage asks and layout have shown that the neutron fingerprint verification technique using measurements from the DSVD would be sensitive to both the amount and location of material that is present within an individual cask. To confirm the performance of the neutron fingerprint technique in verifying the presence of BN-350 spent fuel in dry storage, an initial series of measurements have been performed to test the performance and characteristics of the DSVD. Results of these measurements will be presented and compared with MCNPX results.

  20. 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.

  1. Control of Nanoplane Orientation in voBN for High Thermal Anisotropy in a Dielectric Thin Film: A New Solution for Thermal Hotspot Mitigation in Electronics.

    Science.gov (United States)

    Cometto, Olivier; Samani, Majid K; Liu, Bo; Sun, Shuangxi; Tsang, Siu Hon; Liu, Johan; Zhou, Kun; Teo, Edwin H T

    2017-03-01

    High anisotropic thermal materials, which allow heat to dissipate in a preferential direction, are of interest as a prospective material for electronics as an effective thermal management solution for hot spots. However, due to their preferential heat propagation in the in-plane direction, the heat spreads laterally instead of vertically. This limitation makes these materials ineffective as the density of hot spots increases. Here, we produce a new dielectric thin film material at room temperature, named vertically ordered nanocrystalline h-BN (voBN). It is produced such that its preferential thermally conductive direction is aligned in the vertical axis, which facilitates direct thermal extraction, thereby addressing the increasing challenge of thermal crosstalk. The uniqueness of voBN comes from its h-BN nanocrystals where all their basal planes are aligned in the direction normal to the substrate plane. Using the 3ω method, we show that voBN exhibits high anisotropic thermal conductivity (TC) with a 16-fold difference between through-film TC and in-plane TC (respectively 4.26 and 0.26 W·m -1 ·K -1 ). Molecular dynamics simulations also concurred with the experimental data, showing that the origin of this anisotropic behavior is due to the nature of voBN's plane ordering. While the consistent vertical ordering provides an uninterrupted and preferred propagation path for phonons in the through-film direction, discontinuity in the lateral direction leads to a reduced in-plane TC. In addition, we also use COMSOL to simulate how the dielectric and thermal properties of voBN enable an increase in hot spot density up to 295% compared with SiO 2 , without any temperature increase.

  2. In situ Ia expression on brain cells in the rat: autoimmune encephalomyelitis-resistant strain (BN) and susceptible strain (Lewis) compared.

    Science.gov (United States)

    Matsumoto, Y; Kawai, K; Fujiwara, M

    1989-01-01

    In order to examine in situ Ia expression on brain cells of various strains of rat, experimental autoimmune encephalomyelitis (EAE) was induced in both EAE-susceptible (LEW) and EAE-resistant (BN) strains. For induction of EAE in the resistant strain, two methods were applied: one was injection of guinea-pig myelin basic protein (GPBP) in complete Freund's adjuvant into LBNF1----BN chimeras; the other was transfer of GPBP-reactive T-line cells from BN rats into syngeneic rats. LBNF----BN chimeras developed clinical EAE, whereas BN rats that received T-line cells did not. However, histological EAE was apparent in both groups. Immunohistochemical examination using two different monoclonal antibodies (OX3 and OX6) against rat Ia antigens revealed that microglia of LEW, BN and chimera rats expressed Ia antigens in the central nervous system (CNS) with EAE. On the other hand, astrocytes were negative for Ia antigens in all the strains. Furthermore, quantitative analysis was undertaken in order to compare the density of Ia-positive microglia in the BN CNS with that in the LEW CNS. It was revealed that the density of Ia-positive microglia in the vicinity of perivascular inflammatory cell aggregates was essentially the same in both strains regardless of the difference in methods of EAE induction or histological severity of the disease. Ia-positive microglia remote from inflammatory cell aggregates were somewhat fewer in rats with mild histological EAE. However, no strain difference was noted in this analysis. Therefore, we concluded that in situ Ia-inducibility on the brain cells of EAE-resistant rats is not different from that of EAE-susceptible rats. Although Ia-positive microglia in both strains may be involved in the immune responses in the CNS, it is unlikely that the difference in Ia-inducibility on brain cells would contribute to strain-specific susceptibility to EAE. Images Figure 1 Figure 2 PMID:2785488

  3. 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

  4. Chemical vapor deposition of graphene single crystals.

    Science.gov (United States)

    Yan, Zheng; Peng, Zhiwei; Tour, James M

    2014-04-15

    deserves more attention in the near future. Following that, recent efforts in fabricating large single-crystal monolayer graphene on other metal substrates, including Ni, Pt, and Ru, are also described. The differences in growth conditions reveal different growth mechanisms on these metals. Another key challenge for graphene growth is to make graphene single crystals on insulating substrates, such as h-BN, SiO2, and ceramic. The recently developed plasma-enhanced CVD method can be used to directly synthesize graphene single crystals on h-BN substrates and is described in this Account as well. To summarize, recent research in synthesizing millimeter-sized monolayer graphene grains with different pretreatments, graphene grain shapes, metal catalysts, and substrates is reviewed. Although great advancements have been achieved in CVD synthesis of graphene single crystals, potential challenges still exist, such as the growth of wafer-sized graphene single crystals to further facilitate the fabrication of graphene-based devices, as well as a deeper understanding of graphene growth mechanisms and growth dynamics in order to make graphene grains with precisely controlled thicknesses and spatial structures.

  5. Low sub-threshold swing realization with contacts of graphene/h-BN/MoS2 heterostructures in MoS2 transistors

    Science.gov (United States)

    Li, Chao; Yan, Xiao; Bao, Wenzhong; Ding, Shijin; Zhang, David Wei; Zhou, Peng

    2017-11-01

    MoS2 and other atomically thin-layered semiconductors have attracted intensive interest for their unique characteristics and have become promising candidates for short-channel transistor devices. In this work, we demonstrate an MoS2 transistor with a graphene/hBN/MoS2 heterostructure contact so as to achieve a low sub-threshold swing (SS) and expand the scope of the drain current with a low SS. By inserting an h-BN tunneling layer between graphene and MoS2, the carrier transport with a tunneling effect across h-BN makes the transistor exhibit a less than 80 mV/dec sub-threshold swing over 4 orders of magnitude of the drain current at room temperature. Meanwhile, the MoS2 transistor achieves a maximum on/off ratio of ˜107, and the heterostructure contact shows fairly good ohmic characteristics. Furthermore, the thickness of the h-BN tunneling layer in the heterostructure is optimized, which is essential for the tunneling current and the performance of an MoS2 transistor. This study of an MoS2 transistor based on a graphene/h-BN/MoS2 heterostructure contact may pave the way for the development of thin-layered semiconductors in low-power electronic applications.

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

    International Nuclear Information System (INIS)

    Jia Zhengfeng; Wang Peng; Xia Yanqiu; Zhang Haobo; Pang Xianjuan; Li Bin

    2009-01-01

    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 2 tribofilm, and decrease coefficient of friction of rubbing pairs.

  7. Cutting tool performance enhancement by using a B{sub 4}C/BCN/C-BN multilayer system

    Energy Technology Data Exchange (ETDEWEB)

    Bejarano Gaitan, G. [Technological Development Center ASTIN-SENA, Cali (Colombia); Group of Corrosion and Protection, University of Antioquia, Medellin (Colombia); Caicedo, J.C. [Technological Development Center ASTIN-SENA, Cali (Colombia); Excellence Center for Novel Materials, Universidad del Valle, Cali (Colombia); Prieto, P. [Excellence Center for Novel Materials, Universidad del Valle, Cali (Colombia); Balogh, Adam G. [Institute of Materials Science, Darmstadt University of Technology (Germany)

    2007-07-01

    Thin films of B{sub 4}C/BCN/c-BN multilayers were deposited on to AISI M2 high speed steel substrates by rf. (13.56 MHz) multi-target magnetron sputtering from high purity (99.99%) h-BN and a (99.5%)B{sub 4}C target, in Ar(90%)/N{sub 2}(10%) gasmixture. 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. Mechanical properties like hardness, elastic Young modulus, and adhesion were determined by nanoindentation and scratch measurements. Finally, cutting tools were carried out. Tool performance was registered as functions of bilayer numbers showed enhancement between 60% and 107% and a surface roughness reduction of 60% for cutting tools coated with 16 bilayers, compared to uncoated tools. (copyright 2007 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim) (orig.)

  8. 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.

  9. Binary colloidal crystals

    NARCIS (Netherlands)

    Christova-Zdravkova, C.G.

    2005-01-01

    Binary crystals are crystals composed of two types of particles having different properties like size, mass density, charge etc. In this thesis several new approaches to make binary crystals of colloidal particles that differ in size, material and charge are reported We found a variety of crystal

  10. Identifying anterior segment crystals.

    OpenAIRE

    Hurley, I W; Brooks, A M; Reinehr, D P; Grant, G B; Gillies, W E

    1991-01-01

    A series of 22 patients with crystals in the anterior segment of the eye was examined by specular microscopy. Of 10 patients with hypermature cataract and hyperrefringent bodies in the anterior chamber cholesterol crystals were identified in four patients and in six of the 10 in whom aspirate was obtained cholesterol crystals were demonstrated in three, two of these having shown crystals on specular microscopy. In 10 patients with intracorneal crystalline deposits, cholesterol crystals were f...

  11. Pressure cryocooling protein crystals

    Science.gov (United States)

    Kim, Chae Un [Ithaca, NY; Gruner, Sol M [Ithaca, NY

    2011-10-04

    Preparation of cryocooled protein crystal is provided by use of helium pressurizing and cryocooling to obtain cryocooled protein crystal allowing collection of high resolution data and by heavier noble gas (krypton or xenon) binding followed by helium pressurizing and cryocooling to obtain cryocooled protein crystal for collection of high resolution data and SAD phasing simultaneously. The helium pressurizing is carried out on crystal coated to prevent dehydration or on crystal grown in aqueous solution in a capillary.

  12. Mechanical Properties and Plasma Erosion Resistance of ZrO{sub 2p}(3Y)/BN-SiO{sub 2} Ceramic Composites under Different Sintering Temperature

    Energy Technology Data Exchange (ETDEWEB)

    Zhou Yu; Duan Xiaoming; Jia Dechang; Yang Zhihua; Meng Qingchang; Yu Yang [Institute for Advanced Ceramics, Harbin Institute of Technology, Harbin, 150001 (China); Yu Daren; Ding Yongjie, E-mail: dxmhit@126.com [School of Energy Science and Technology, Harbin Institute of Technology, Harbin, 150001 (China)

    2011-10-29

    ZrO{sub 2p}(3Y)/BN-SiO{sub 2} ceramic composites were hot pressed under different sintering temperature. The ceramic composites were composed by BN, m-ZrO{sub 2}, t-ZrO{sub 2} and SiO{sub 2}. The relative density, bending strength, elastic modulus and fracture toughness increase with the sintering temperature increasing, the maximum value of which at the sintering temperature of 1800 deg. C are 97.5%, 229.9MPa, 60.8GPa and 3.55MPam{sup 1/2}, respectively. The erosion resistance ability of ZrO{sub 2p}(3Y)/BN-SiO{sub 2} ceramic composites rise gradually with the sintering temperature increasing, and the erosion rate of the ceramic composite sintered at 1800 deg. C is 8.03x10{sup -3}mm/h.

  13. Experimental study of microstructure, mechanical and tribological properties of cBN particulates SS316 alloy based MMCs fabricated by DMLS technique

    Energy Technology Data Exchange (ETDEWEB)

    Hussain, M.; Mandal, V.; Singh, P. K.; Kumar, P.; Kumar, V.; Das, A. K. [Indian Institute of Technology (ISM), Dhanbad (India)

    2017-06-15

    Direct metal laser sintering process (DMLS) was chosen to develop cBN particulates reinforced SS316 based Metal matrix composite (MMC) with 5 %, 7.5 % and 10 % cBN in the nitrogen gas atmosphere using continuous wave fibre laser of 400 W output capacity. Effects of process parameters such as laser power, beam scanning speed and the mixing ratio of powder on different physical properties of the developed MMC were investigated. It was found that the physical and mechanical properties such as friction and wear behavior, micro hardness and density come up with improved results. FESEM images indicate the microstructure of the composite and evidently confirms the presence of cubic boron nitride in the SS316 matrix where chromium nitride acted as a binder in the presence of nitrogen atmosphere. The Vickers hardness values of the developed MMCs with laser power 60 W and 65 W were found in the range of 276-478 HV{sub 0}.2 and 297-460 HV{sub 0}.2, respectively. It was found that Vickers hardness is directly proportional to the % of cBN in the powder mixture and the laser beam power. The wear resistance of the sintered MMCs increased with increasing cBN content in powder mixture and re- sults show that wear of MMCs are much lower than that of SS316. X-Ray diffraction (XRD) analysis of the fabricated MMC confirms the presence of different phases such as cBN, CrN, CrB{sub 2}, Cr{sub 2}N and Fe{sub 3}N as a consequence of a series of chemical reaction between cBN and different elements of SS316 in nitrogen atmosphere.

  14. Surfactant exfoliated 2D hexagonal Boron Nitride (2D-hBN) explored as a potential electrochemical sensor for dopamine: surfactants significantly influence sensor capabilities.

    Science.gov (United States)

    Khan, Aamar F; Brownson, Dale A C; Foster, Christopher W; Smith, Graham C; Banks, Craig E

    2017-05-21

    Surfactant exfoliated 2D hexagonal Boron Nitride (2D-hBN) nanosheets are explored as a potential electrochemical sensing platform and evaluated towards the electroanalytical sensing of dopamine (DA) in the presence of the common interferents, ascorbic acid (AA) and uric acid (UA). Surfactant exfoliated 2D-hBN nanosheets (2-4 layers) fabricated using sodium cholate in aqueous media are electrically wired via a drop-casting modification process onto disposable screen-printed graphite electrodes (SPEs). We critically evaluate the performance of these 2D-hBN modified SPEs and demonstrate the effect of 'mass coverage' towards the detection of DA, AA and UA. Previous studies utilising surfactant-free (pristine) 2D-hBN modified SPEs have shown a beneficial effect towards the detection of DA, AA and UA when compared to the underlying/unmodified graphite-based electrode. We show that the fabrication route utilised to prepare 2D-hBN is a vital experimental consideration, such that the beneficial effect previously reported is considerably reduced when surfactant exfoliated 2D-hBN is utilised. We demonstrate for the first time, through implementation of control experiments in the form of surfactant modified graphite electrodes, that sodium cholate is a major contributing factor to the aforementioned detrimental behaviour. The significance here is not in the material per se, but the fundamental knowledge of the surfactant and surface coverage changing the electrochemical properties of the material under investigation. Given the wide variety of ionic and non-ionic surfactants that are utilised in the manufacture of novel 2D materials, the control experiments reported herein need to be performed in order to de-convolute the electrochemical response and effectively evaluate the 'underlying surface/surfactant/2D materials' electrocatalytic contribution.

  15. Initial measurements of BN-350 spent fuel in dry storage casks using the dual slab verification detonator

    Energy Technology Data Exchange (ETDEWEB)

    Santi, Peter Angelo [Los Alamos National Laboratory; Browne, Michael C [Los Alamos National Laboratory; Freeman, Corey R [Los Alamos National Laboratory; Parker, Robert F [Los Alamos National Laboratory; Williams, Richard B [Los Alamos National Laboratory

    2010-01-01

    The Dual Slab Verification Detector (DSVD) has been developed, built, and characterized by Los Alamos National Laboratory in cooperation with the International Atomic Energy Agency (IAEA) as part of the dry storage safeguards system for the spent fuel from the BN-350 fast reactor. The detector consists of two rows of 3He tubes embedded in a slab of polyethylene which has been designed to be placed on the outer surface of the dry storage cask. By performing DSVD measurements at several different locations around the outer surface of the DUC, a signature 'fingerprint' can be established for each DUC based on the neutron flux emanating from inside the dry storage cask. The neutron fingerprint for each individual DUC will be dependent upon the spatial distribution of nuclear material within the cask, thus making it sensitive to the removal of a certain amount of material from the cask. An initial set of DSVD measurements have been performed on the first set of dry storage casks that have been loaded with canisters of spent fuel and moved onto the dry storage pad to both establish an initial fingerprint for these casks as well as to quantify systematic uncertainties associated with these measurements. The results from these measurements will be presented and compared with the expected results that were determined based on MCNPX simulations of the dry storage facility. The ability to safeguard spent nuclear fuel is strongly dependent on the technical capabilities of establishing and maintaining continuity of knowledge (COK) of the spent fuel as it is released from the reactor core and either reprocessed or packaged and stored at a storage facility. While the maintenance of COK is often done using continuous containment and surveillance (C/S) on the spent fuel, it is important that the measurement capabilities exist to re-establish the COK in the event of a significant gap in the continuous CIS by performing measurements that independently confirm the presence

  16. Mussel-inspired immobilization of BN nanosheets onto poly(p-phenylene benzobisoxazole) fibers: Multifunctional interface for photothermal self-healing

    Science.gov (United States)

    Shao, Qing; Hu, Zhen; Xu, Xirong; Yu, Long; Zhang, Dayu; Huang, Yudong

    2018-05-01

    The composites with interfacial self-healing ability are smart and promising materials in the future. Although some approaches have been used to heal the micro-cracks in composite materials, it is still a great challenge to develop a versatile strategy to fabricate multifunctional interface for self-healing. Here, boron nitride nanosheets (BN) are immobilized onto PBO fibers by facile polydopamine (PDA) chemistry. Benefiting from the photothermal effect of BN-PDA, the obtained surface layer displays interfacial self-healing properties under Xenon light irradiation.

  17. Modernization of RTC for fabrication of MOX fuel, Vibropac fuel pins and BN-600 FA with weapon grade plutonium

    International Nuclear Information System (INIS)

    Grachyov, A.F.; Kalygin, V.V.; Skiba, O.V.; Mayorshin, A. A.; Bychkov, A.V.; Kisly, V.A.; Ovsyannikov, Y.F.; Bobrov, D.A.; Mamontov, S.I.; Tsyganov, A.N.; Churutkin, E.I.; Davydov, P.I.; Samosenko, E.A; Shalak, A.R.; Ojima, Hisao

    2004-01-01

    Since mid 70's RIAR has been performing activities on plutonium involvement in fuel cycle. These activities are considered a stage within the framework of the closed fuel cycle development. Developed at RIAR fuel cycle is based on two technologies: 'dry' process of fuel reprocessing and vibro-packing method for fuel pin fabrication. Due to the available scientific capabilities and a gained experience in operating the technological facilities (ORYOL, SIC) for plutonium (various grade) blending into fuel for fast reactors, RIAR is a participant of the activities aimed at solving these tasks. Under international program RIAR with financial support of JNC (Japan) is modernizing the facility for granulated fuel production, vibro-pac fuel pins and FA fabrication to provide the BN-600 'hybrid' core. In order to provide 'hybrid' core it is necessary to produce (per year): - 1775 kg of granulated MOX-fuel, 6500 fuel pins, 50 fuel assemblies. Potential output of the facility under construction is as follows: - 1800 kg of granulated MOX-fuel per year, 40 fuel pins per shift, 200 FAs for the BN-600 reactor per year. Taking into account domestic and foreign experience in MOX-fuel production, different options were discussed of the equipment layouts in the available premises of chemical technological division of RIAR: - in the shielded manipulator boxes, in the existing hot cells. During construction of the facility in the building under operation the following requirements should be met: - facility must meet all standards and regulations set for nuclear facilities, installation work at the facility must not influence other production programs implemented in the building, engineering supply lines of the facility must be connected to the existing service lines of the building, cost of the activities must not exceed amount of JNC funding. The paper presents results of comparison between two options of the process equipment layout: in boxes and hot cells. This equipment is intended

  18. Crystallization In Multicomponent Glasses

    International Nuclear Information System (INIS)

    Kruger, A.A.; Hrma, P.R.

    2009-01-01

    In glass processing situations involving glass crystallization, various crystalline forms nucleate, grow, and dissolve, typically in a nonuniform temperature field of molten glass subjected to convection. Nuclear waste glasses are remarkable examples of multicomponent vitrified mixtures involving partial crystallization. In the glass melter, crystals form and dissolve during batch-to-glass conversion, melter processing, and product cooling. Crystals often agglomerate and sink, and they may settle at the melter bottom. Within the body of cooling glass, multiple phases crystallize in a non-uniform time-dependent temperature field. Self-organizing periodic distribution (the Liesegnang effect) is common. Various crystallization phenomena that occur in glass making are reviewed.

  19. CRYSTALLIZATION IN MULTICOMPONENT GLASSES

    Energy Technology Data Exchange (ETDEWEB)

    KRUGER AA; HRMA PR

    2009-10-08

    In glass processing situations involving glass crystallization, various crystalline forms nucleate, grow, and dissolve, typically in a nonuniform temperature field of molten glass subjected to convection. Nuclear waste glasses are remarkable examples of multicomponent vitrified mixtures involving partial crystallization. In the glass melter, crystals form and dissolve during batch-to-glass conversion, melter processing, and product cooling. Crystals often agglomerate and sink, and they may settle at the melter bottom. Within the body of cooling glass, multiple phases crystallize in a non-uniform time-dependent temperature field. Self-organizing periodic distribution (the Liesegnang effect) is common. Various crystallization phenomena that occur in glass making are reviewed.

  20. 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.

  1. Resonant quantum efficiency enhancement of midwave infrared nBn photodetectors using one-dimensional plasmonic gratings

    International Nuclear Information System (INIS)

    Nolde, Jill A.; 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.; Kim, Mijin

    2015-01-01

    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

  2. Slip Casting of {alpha}-Sialon/AlN/BN Powder Carbothermally Prepared by Boron-rich Slag-based Mixture

    Energy Technology Data Exchange (ETDEWEB)

    Wu Junbin; Xue Xiangxin; Jiang Tao; Zhang Qing [School of Materials and Metallurgy, Northeastern University, Shenyang 110004 (China)

    2011-10-29

    With boron-rich slag, silica fume, bauxite chalmette and carbon black as starting materials, {alpha}-Sialon/AlN/BN powder was prepared by carbothermal reduction-nitridation. The powder was attrition milled to submicron size and suspended in water. The effects of yttrium oxide as a sintering aid, pH, and addition of deflocculant on the suspensions were study. Optimum slip casting properties, i.e. lowest viscosity values, the highest absolute zeta potential values, the smallest floc size and sediment volume were found at pH 10 for the powder. The suspensions were used to slip cast discs which were sintered in a nitrogen atmosphere at 1700 deg. C for 2h. The strength was about 230MPa, the toughness 3.6 MPa{center_dot}m{sup 1/2} and the hardness about 13.8GPa.

  3. Effect of 10B(n, α)7Li irradiation on the structure of a sodium borosilicate glass

    Science.gov (United States)

    Peuget, S.; Fares, T.; Maugeri, E. A.; Caraballo, R.; Charpentier, T.; Martel, L.; Somers, J.; Janssen, A.; Wiss, T.; Rozenblum, F.; Magnin, M.; Deschanels, X.; Jégou, C.

    2014-05-01

    The effects of the nuclear reaction 10B(n, α)7Li on the properties and structure of a sodium borosilicate glass were analysed by density, hardness and fracture toughness measurements, Raman and Nuclear Magnetic Resonance spectroscopy and Transmission Electronic Microscopy (TEM) characterization. The TEM observations showed a homogeneous irradiated glass structure up to the nanometer scale. Modifications of the local order around the main cations were noticed, mainly a slight decrease of the mean boron coordination number and an increase of non-bridging oxygen concentrations. At the glass medium range order, the appearance of the D2 Raman band and a modification of the Si-O-Si angle distribution were also observed after irradiation.

  4. Crystal structure of the borabenzene–2,6-lutidine adduct

    Directory of Open Access Journals (Sweden)

    Lauri Kivijärvi

    2015-12-01

    Full Text Available In the title compound, C12H14BN, the complete molecule is generated by a crystallographic twofold axis, with two C atoms, the B atom and the N atom lying on the rotation axis. The dihedral angle between the borabenzene and pyridine rings is 81.20 (6°. As well as dative electron donation from the N atom to the B atom [B—N = 1.5659 (18 Å], the methyl substituents on the lutidine ring shield the B atom, which further stabilizes the molecule. In the crystal, weak aromatic π–π stacking between the pyridine rings [centroid–centroid separation = 3.6268 (9 Å] is observed, which generates [001] columns of molecules.

  5. The difference between the crystallization processes induced by mechanical milling and annealing under normal and high pressure in amorphous Fe-N alloy

    CERN Document Server

    LiuLi; Guo Xing Yuan; Zhao Xu Dong; Yao Bin; Su Wen Hui

    2002-01-01

    An amorphous Fe-N alloy was prepared by ball milling a mixture of Fe and h-BN. Its crystallization processes induced by mechanical milling (MM) and annealing under normal and high pressure were studied. The crystallization product of the amorphous Fe-N alloy induced by MM and annealing at temperatures between 690 and 800 K under pressures of 3-4 GPa is epsilon-Fe sub x N, while the thermal crystallization product under normal pressure is gamma'-Fe sub 4 N. The difference between the crystallization products produced by mechanical and thermal crystallization is attributed to the effects of local pressure and local temperature produced by ball collisions.

  6. Photonic Crystal Nanocavity Arrays

    National Research Council Canada - National Science Library

    Altug, Hatice; Vuckovic, Jelena

    2006-01-01

    We recently proposed two-dimensional coupled photonic crystal nanocavity arrays as a route to achieve a slow-group velocity of light in all crystal directions, thereby enabling numerous applications...

  7. Growth of dopamine crystals

    Energy Technology Data Exchange (ETDEWEB)

    Patil, Vidya, E-mail: vidya.patil@ruparel.edu; Patki, Mugdha, E-mail: mugdha.patki@ruparel.edu [D. G. Ruparel College, Senapati Bapat Marg, Mahim, Mumbai – 400 016 (India)

    2016-05-06

    Many nonlinear optical (NLO) crystals have been identified as potential candidates in optical and electro-optical devices. Use of NLO organic crystals is expected in photonic applications. Hence organic nonlinear optical materials have been intensely investigated due to their potentially high nonlinearities, and rapid response in electro-optic effect compared to inorganic NLO materials. There are many methods to grow organic crystals such as vapor growth method, melt growth method and solution growth method. Out of these methods, solution growth method is useful in providing constraint free crystal. Single crystals of Dopamine have been grown by evaporating the solvents from aqueous solution. Crystals obtained were of the size of orders of mm. The crystal structure of dopamine was determined using XRD technique. Images of crystals were obtained using FEG SEM Quanta Series under high vacuum and low KV.

  8. Crystal structure and prediction.

    Science.gov (United States)

    Thakur, Tejender S; Dubey, Ritesh; Desiraju, Gautam R

    2015-04-01

    The notion of structure is central to the subject of chemistry. This review traces the development of the idea of crystal structure since the time when a crystal structure could be determined from a three-dimensional diffraction pattern and assesses the feasibility of computationally predicting an unknown crystal structure of a given molecule. Crystal structure prediction is of considerable fundamental and applied importance, and its successful execution is by no means a solved problem. The ease of crystal structure determination today has resulted in the availability of large numbers of crystal structures of higher-energy polymorphs and pseudopolymorphs. These structural libraries lead to the concept of a crystal structure landscape. A crystal structure of a compound may accordingly be taken as a data point in such a landscape.

  9. Photonic crystal pioneer

    Science.gov (United States)

    Anscombe, Nadya

    2011-08-01

    Over the past ten years, Crystal Fiber, now part of NKT Photonics, has been busy commercializing photonic crystal fibre. Nadya Anscombe finds out about the evolution of the technology and its applications.

  10. ALICE photon spectrometer crystals

    CERN Multimedia

    Maximilien Brice

    2006-01-01

    Members of the mechanical assembly team insert the last few crystals into the first module of ALICE's photon spectrometer. These crystals are made from lead-tungstate, a crystal as clear as glass but with nearly four times the density. When a high-energy particle passes through one of these crystals it will scintillate, emitting a flash of light allowing the energy of photons, electrons and positrons to be measured.

  11. A DFT study on graphene, SiC, BN, and AlN nanosheets as anodes in Na-ion batteries.

    Science.gov (United States)

    Hosseinian, A; Khosroshahi, E Saedi; Nejati, K; Edjlali, E; Vessally, E

    2017-11-25

    A great concern exists about the lifetime, cost, low-temperature performance, and safety of Li-ion batteries. Na-ion batteries (NIB) are an alternative to the Li-ion batteries due to the wide availability of sodium, its low cost, and nontoxicity. Here, we examined the Na and Na + adsorption on nanosheets of carbon (graphene), AlN, BN, and SiC to explore their potential use as an anode in NIBs. The interaction of atomic Na was found to play the main role in producing different nanosheet cell voltages. Unlike the graphene and SiC nanosheets, the lone pairs on the surface of the AlN and BN nanosheets hinder the Na adsorption and significantly increase the cell voltage. The order of magnitude of the nanosheet cell voltage as an anode in NIBs is as follows: AlN (1.49 V) > BN (1.46 V) > > C (0.69 V) > SiC (0.61 V). The AlN and BN nanosheets may be appropriate compounds for NIBs and their cell voltages are comparable with carbon nanotubes.

  12. Comparison of the worth of control and protection system rods of different design on the basis of the measurements in BN-600 reactor

    International Nuclear Information System (INIS)

    Vasilyev, B.A.; Roslyakov, V.F.; Farakshin, M.R.

    1988-01-01

    The results of the worth measurements of the basic and experimental absorbing rods of BN-600 reactor are presented. The procedure used for the rods worth comparison on the basis of calculated and experimental data interpretation is described here. Basic and experimental rods relative worth is also presented. (author). 5 refs, 3 figs, 2 tabs

  13. Maximum forseeable accident analysis made by a sodium leak on the BN-800 primary circuit and the more constraining accident development scenario

    International Nuclear Information System (INIS)

    Ivanenko, V.N.; Zybin, V.A.

    1988-01-01

    In this paper the different ways of development for the BN-800 maximum credible accident in case of loss and fire of primary sodium are examined. The more constraining scenario is presented. During the scenario analysis the accidental release of radioactive materials in the environment has been studied. These releases are below the authorized values [fr

  14. 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.

  15. Analysis of liquid crystal properties for photonic crystal fiber devices

    DEFF Research Database (Denmark)

    Weirich, Johannes; Lægsgaard, Jesper; Wei, Lei

    2009-01-01

    We analyze the bandgap structure of Liquid Crystal infiltrated Photonic Crystal Fibers depending on the parameters of the Liquid Crystals by means of finite element simulations. For a biased Liquid Crystal Photonic Crystal Fiber, we show how the tunability of the bandgap position depends...... on the Liquid Crystal parameters....

  16. Modulation of interfacial electronic properties in PbI{sub 2} and BN van der Waals heterobilayer via external electric field

    Energy Technology Data Exchange (ETDEWEB)

    Ma, Yaqiang [College of Physics and Materials Science, Henan Normal University, Xinxiang 453007 (China); Zhao, Xu, E-mail: zhaoxu@htu.cn [College of Physics and Materials Science, Henan Normal University, Xinxiang 453007 (China); Niu, Mengmeng [College of Physics and Materials Science, Henan Normal University, Xinxiang 453007 (China); Dai, Xianqi, E-mail: xqdai@htu.cn [College of Physics and Materials Science, Henan Normal University, Xinxiang 453007 (China); School of Physics and Electronic Engineering, Zhengzhou Normal University, Zhengzhou, Henan 450044 (China); Li, Wei [College of Physics and Materials Science, Henan Normal University, Xinxiang 453007 (China); Wang, Xiaolong [College of Physics and Materials Science, Henan Normal University, Xinxiang 453007 (China); State Key Laboratory of Information Photonics and Optical Communication, Beijing University Posts and Telecommunications, Beijing 100876 (China); Zhao, Mingyu; Wang, Tianxing [College of Physics and Materials Science, Henan Normal University, Xinxiang 453007 (China); Tang, Yanan [School of Physics and Electronic Engineering, Zhengzhou Normal University, Zhengzhou, Henan 450044 (China)

    2017-07-31

    Highlights: • An atomically type-II heterobilayer which is suitable for optoelectronics and solar cell with wide bandgap was formed. • The charge redistribution is mainly on the surface and the amount of electrons depends on the strength of E{sub field}. • The bandgaps varying with E{sub field} can be divided into three ranges indicating different E{sub field}-sensitive which may possess potential in sensor. • Increasing the E{sub field} upon 0.07 V/Å, the band alignment converts from type-II to type-I heterojunction. - Abstract: The interfacial electronic properties of PbI{sub 2} 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 PbI{sub 2}/BN heterostructure as a good candidate for applications in optoelectronics and solar cell. A simulation of E{sub field} 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 E{sub field}-sensitive properties are obtained from the variations of bandgap with E{sub field}. The charge redistribution with an E{sub field} is mainly on the surface of PbI{sub 2} and BN layers as well as the amount of electrons depends on the strength of E{sub field}. In addition, the PbI{sub 2}/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 PbI{sub 2}/BN vdW heterostructure.

  17. Photonic crystal light source

    Science.gov (United States)

    Fleming, James G [Albuquerque, NM; Lin, Shawn-Yu [Albuquerque, NM; Bur, James A [Corrales, NM

    2004-07-27

    A light source is provided by a photonic crystal having an enhanced photonic density-of-states over a band of frequencies and wherein at least one of the dielectric materials of the photonic crystal has a complex dielectric constant, thereby producing enhanced light emission at the band of frequencies when the photonic crystal is heated. The dielectric material can be a metal, such as tungsten. The spectral properties of the light source can be easily tuned by modification of the photonic crystal structure and materials. The photonic crystal light source can be heated electrically or other heating means. The light source can further include additional photonic crystals that exhibit enhanced light emission at a different band of frequencies to provide for color mixing. The photonic crystal light source may have applications in optical telecommunications, information displays, energy conversion, sensors, and other optical applications.

  18. Macromolecular Crystallization in Microgravity

    Science.gov (United States)

    Snell, Edward H.; Helliwell, John R.

    2004-01-01

    The key concepts that attracted crystal growers, macromolecular or solid state, to microgravity research is that density difference fluid flows and sedimentation of the growing crystals are greatly reduced. Thus, defects and flaws in the crystals can be reduced, even eliminated, and crystal volume can be increased. Macromolecular crystallography differs from the field of crystalline semiconductors. For the latter, crystals are harnessed for their electrical behaviors. A crystal of a biological macromolecule is used instead for diffraction experiments (X-ray or neutron) to determine the three-dimensional structure of the macromolecule. The better the internal order of the crystal of a biological macromolecule then the more molecular structure detail that can be extracted. This structural information that enables an understanding of how the molecule functions. This knowledge is changing the biological and chemical sciences with major potential in understanding disease pathologies. Macromolecular structural crystallography in general is a remarkable field where physics, biology, chemistry, and mathematics meet to enable insight to the basic fundamentals of life. In this review, we examine the use of microgravity as an environment to grow macromolecular crystals. We describe the crystallization procedures used on the ground, how the resulting crystals are studied and the knowledge obtained from those crystals. We address the features desired in an ordered crystal and the techniques used to evaluate those features in detail. We then introduce the microgravity environment, the techniques to access that environment, and the theory and evidence behind the use of microgravity for crystallization experiments. We describe how ground-based laboratory techniques have been adapted to microgravity flights and look at some of the methods used to analyze the resulting data. Several case studies illustrate the physical crystal quality improvements and the macromolecular structural

  19. Crystallization and crystal properties of squid rhodopsin

    International Nuclear Information System (INIS)

    Murakami, Midori; Kitahara, Rei; Gotoh, Toshiaki; Kouyama, Tsutomu

    2007-01-01

    Truncated rhodopsin from the retina of the squid Todarodes pacificus was extracted and crystallized by the sitting-drop vapour-diffusion method. Hexagonal crystals grown in the presence of octylglucoside and ammonium sulfate diffracted to 2.8 Å resolution. Rhodopsin, a photoreceptor membrane protein in the retina, is a prototypical member of the G-protein-coupled receptor family. In this study, rhodopsin from the retina of the squid Todarodes pacificus was treated with V8 protease to remove the C-terminal extension. Truncated rhodopsin was selectively extracted from the microvillar membranes using alkyl glucoside in the presence of zinc ions and was then crystallized by the sitting-drop vapour-diffusion method. Of the various crystals obtained, hexagonal crystals grown in the presence of octylglucoside and ammonium sulfate diffracted to 2.8 Å resolution. The diffraction data suggested that the crystal belongs to space group P6 2 , with unit-cell parameters a = b = 122.1, c = 158.6 Å. Preliminary crystallographic analysis, together with linear dichroism results, suggested that the rhodopsin dimers are packed in such a manner that their transmembrane helices are aligned nearly parallel to the c axis

  20. Experience and results of material science research conducted on spent fuel assemblies from the BN-350 fast reactor

    Energy Technology Data Exchange (ETDEWEB)

    Maksimkin, O.; Gusev, M.; Turubarova, L.G.; Tsai, K.V.; Yarovchuk, A.V. [Institute of Nuclear Physics, Almaty (Kazakhstan)

    2007-07-01

    Full text of publication follows: The BN-350 fast reactor was commissioned in 1973, ran successfully for many years and is now in the decommission stage. Its unique operational parameters (low temperature of sodium at the input, wide range of damage rates, etc. ) allowed the investigation of a number of new radiation effects on both austenitic and ferritic-martensitic steels. The latter class of steel was extensively employed as wrappers for fuel assemblies. Much of the accumulated experience in BN-350 is relevant to development of fusion devices. Results are presented on post-operational research of steels 12Cr18Ni10Ti, 08Cr16Ni11Mo3, and 12Cr13Mo2BFR, all serving as hexagonal shrouds of fuel assemblies. Structural materials in the active core zone operated at temperatures of 280-430 deg. C, and were irradiated the range of 0.25-83 dpa with damage rates of 10{sup -9} - 10{sup -6} dpa/s). Investigations of irradiated hexagonal shroud materials were performed with using traditional techniques of transmission and scanning electron microscopy, metallography, mechanical tests, hydrostatic weighing, magnetometry, etc. Additionally, new techniques have been developed and employed with great success on these highly irradiated materials, such as optical computer extensometry, and magnetization cartography. Typical results to be covered in this presentation are: a) In 12Cr18Ni10Ti steel irradiated at a low dose rate of 0.12 x 10{sup -8} dpa/s voids were found at 281 deg. C after only 0.65 dpa, demonstrating once again the acceleration of swelling at low dpa rates observed in other steels. b) Data on helium release during annealing of highly irradiated sample are presented. c) Differences in deformation-induced hardening between the shroud's corners and faces leads to post-irradiation differences in swelling and mechanical properties. d) During room temperature mechanical tests of 12Cr18Ni10Ti steel at {approx}56 dpa at 350 deg. C it was found that ductility lost at

  1. Turning into carbonate the residual sodium left in BN-350 circuits may alleviate concerns over their long term safe confinement

    International Nuclear Information System (INIS)

    Rahmani, L

    2000-01-01

    After the coolant is drained from the reactor vessel and from the primary and secondary circuits of the BN-350 nuclear power plant, what sodium is left in ponds and films may amount to hundreds of kilograms. For the long term safe storage period which is to follow, preliminary safety analyses (e.g. derived from those made for French sodium cooled reactors) might show that the risks incurred through loss of leaktightness are significant. The ingress of moisture into the circuits would generate, by reaction with the sodium, two undesirable products : sodium hydroxide and hydrogene. Even when considering that water would enter the circuits progressively, so that the heat of the reaction does not give rise to over-pressure, some main risk factors remain. The most promising solution to this challenge appears to be the carbonation of the sodium residues, by progressive diffusion of an appropriate association of carbon dioxyde and water vapour through the inert gaseous medium which fills the circuits. The desired product is porous sodium hydrogenocarbonate

  2. Strain-Engineering of Giant Pseudo-Magnetic Fields in Graphene/Boron Nitride (BN) Periodic Nanostructures

    Science.gov (United States)

    Hsu, Chen-Chih; Wang, Jiaqing; Teague, Marcus; Chen, Chien-Chang; Yeh, Nai-Chang

    2015-03-01

    Ideal graphene is strain-free whereas non-trivial strain can induce pseudo-magnetic fields as predicted theoretically and manifested experimentally. Here we employ nearly strain-free single-domain graphene, grown by plasma-enhanced chemical vapor deposition (PECVD) at low temperatures, to induce controlled strain by placing the PECVD-graphene on substrates containing engineered nanostructures. We fabricate periodic pyramid nanostructures (typically 100 ~ 200 nm laterally and 10 ~ 60 nm in height) on Si substrates by focused ion beam, and determine the topography of these nanostructures using atomic force microscopy and scanning electron microscopy after we transferred monolayer h-BN followed by PECVD-graphene onto these substrates. We find both layers conform well to the nanostructures so that we can control the size, arrangement, separation, and shape of the nanostructures to generate desirable pseudo-magnetic fields. We also employ molecular dynamics simulation to determine the displacement of carbon atoms under a given nanostructure. The pseudo-magnetic field thus obtained is ~150T in the center, relatively homogeneous over 50% of the area, and drops off precipitously near the edge. These findings are extended to arrays of nanostructures and compared with topographic and spectroscopic studies by STM. Supported by NSF.

  3. Large spin relaxation anisotropy and valley-Zeeman spin-orbit coupling in WSe2/graphene/h -BN heterostructures

    Science.gov (United States)

    Zihlmann, Simon; Cummings, Aron W.; Garcia, Jose H.; Kedves, Máté; Watanabe, Kenji; Taniguchi, Takashi; Schönenberger, Christian; Makk, Péter

    2018-02-01

    Large spin-orbital proximity effects have been predicted in graphene interfaced with a transition-metal dichalcogenide layer. Whereas clear evidence for an enhanced spin-orbit coupling has been found at large carrier densities, the type of spin-orbit coupling and its relaxation mechanism remained unknown. We show an increased spin-orbit coupling close to the charge neutrality point in graphene, where topological states are expected to appear. Single-layer graphene encapsulated between the transition-metal dichalcogenide WSe2 and h -BN is found to exhibit exceptional quality with mobilities as high as 1 ×105 cm2 V-1 s-1. At the same time clear weak antilocalization indicates strong spin-orbit coupling, and a large spin relaxation anisotropy due to the presence of a dominating symmetric spin-orbit coupling is found. Doping-dependent measurements show that the spin relaxation of the in-plane spins is largely dominated by a valley-Zeeman spin-orbit coupling and that the intrinsic spin-orbit coupling plays a minor role in spin relaxation. The strong spin-valley coupling opens new possibilities in exploring spin and valley degree of freedom in graphene with the realization of new concepts in spin manipulation.

  4. Evaluation of the internalization kinetics of the radiopharmaceutical 99mTc-N2S2-Tat(49-57)Lys3-Bn with diagnostic purposes, using comet assay

    International Nuclear Information System (INIS)

    Luna G, M. A.

    2011-01-01

    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 99m Tc-N 2 S 2 -Tat(49-57)-Lys 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) 99m Tc-Bn, or c) 99m Tc-N 2 S 2 -Tat(49-57)-Lys 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 99m Tc-N 2 S 2 -Tat(49-57)-Lys 3 -Bn is significantly higher than that caused by 99m Tc-Bn and Tat-Bn, showing that Tat favors the internalization of the radiopharmaceutical. (Author)

  5. CMS lead tungstate crystals

    CERN Multimedia

    Laurent Guiraud

    2000-01-01

    These crystals are made from lead tungstate, a crystal that is as clear as glass yet with nearly four times the density. They have been produced in Russia to be used as scintillators in the electromagnetic calorimeter on the CMS experiment, part of the LHC project at CERN. When an electron, positron or photon passes through the calorimeter it will cause a cascade of particles that will then be absorbed by these scintillating crystals, allowing the particle's energy to be measured.

  6. Macromolecular crystallization in microgravity

    International Nuclear Information System (INIS)

    Snell, Edward H; Helliwell, John R

    2005-01-01

    Density difference fluid flows and sedimentation of growing crystals are greatly reduced when crystallization takes place in a reduced gravity environment. In the case of macromolecular crystallography a crystal of a biological macromolecule is used for diffraction experiments (x-ray or neutron) so as to determine the three-dimensional structure of the macromolecule. The better the internal order of the crystal then the greater the molecular structure detail that can be extracted. It is this structural information that enables an understanding of how the molecule functions. This knowledge is changing the biological and chemical sciences, with major potential in understanding disease pathologies. In this review, we examine the use of microgravity as an environment to grow macromolecular crystals. We describe the crystallization procedures used on the ground, how the resulting crystals are studied and the knowledge obtained from those crystals. We address the features desired in an ordered crystal and the techniques used to evaluate those features in detail. We then introduce the microgravity environment, the techniques to access that environment and the theory and evidence behind the use of microgravity for crystallization experiments. We describe how ground-based laboratory techniques have been adapted to microgravity flights and look at some of the methods used to analyse the resulting data. Several case studies illustrate the physical crystal quality improvements and the macromolecular structural advances. Finally, limitations and alternatives to microgravity and future directions for this research are covered. Macromolecular structural crystallography in general is a remarkable field where physics, biology, chemistry and mathematics meet to enable insight to the fundamentals of life. As the reader will see, there is a great deal of physics involved when the microgravity environment is applied to crystallization, some of it known, and undoubtedly much yet to

  7. A crystal barrel

    CERN Multimedia

    2007-01-01

    The production of crystals for the barrel of the CMS electromagnetic calorimeter has been completed. This is an important milestone for the experiment, which received the last of its 62,960 crystals on 9 March. The members of the team responsible for the crystal acceptance testing at CERN display the last crystal for the CMS electromagnetic calorimeter barrel. From left to right: Igor Tarasov, Etiennette Auffray and Hervé Cornet.One of the six machines specially developed to measure 67 different parameters on each crystal. Igor Tarasov is seen inserting the last batch of crystals into the machine. The last of the 62,960 CMS barrel crystals arrived at CERN on 9 March. Once removed from its polystyrene protection, this delicate crystal, like thousands of its predecessors, will be inserted into the last of the 36 supermodules of the barrel electromagnetic calorimeter in a few days' time. This marks the end of an important chapter in an almost 15-year-long journey by the CMS crystals team, some of whose member...

  8. Automation in biological crystallization.

    Science.gov (United States)

    Stewart, Patrick Shaw; Mueller-Dieckmann, Jochen

    2014-06-01

    Crystallization remains the bottleneck in the crystallographic process leading from a gene to a three-dimensional model of the encoded protein or RNA. Automation of the individual steps of a crystallization experiment, from the preparation of crystallization cocktails for initial or optimization screens to the imaging of the experiments, has been the response to address this issue. Today, large high-throughput crystallization facilities, many of them open to the general user community, are capable of setting up thousands of crystallization trials per day. It is thus possible to test multiple constructs of each target for their ability to form crystals on a production-line basis. This has improved success rates and made crystallization much more convenient. High-throughput crystallization, however, cannot relieve users of the task of producing samples of high quality. Moreover, the time gained from eliminating manual preparations must now be invested in the careful evaluation of the increased number of experiments. The latter requires a sophisticated data and laboratory information-management system. A review of the current state of automation at the individual steps of crystallization with specific attention to the automation of optimization is given.

  9. Crystallization Formulation Lab

    Data.gov (United States)

    Federal Laboratory Consortium — The Crystallization Formulation Lab fills a critical need in the process development and optimization of current and new explosives and energetic formulations. The...

  10. 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)

  11. The passive nondestructive assay of the plutonium content of spent-fuel assemblies from the BN-350 fast-breeder reactor in the city of Aqtau, Kazakhstan

    CERN Document Server

    Lestone, J P; Rennie, J A; Sprinkle, J K; Staples, P; Grimm, K N; Hill, R N; Cherradi, I; Islam, N; Koulikov, J; Starovich, Z

    2002-01-01

    The International Atomic Energy Agency is presently interested in developing equipment and techniques to measure the plutonium content of breeder reactor spent-fuel assemblies located in storage ponds before they are relocated to more secure facilities. We present the first quantitative nondestructive assay of the plutonium content of fast-breeder reactor spent-fuel assemblies while still underwater in their facility storage pond. We have calibrated and installed an underwater neutron coincidence counter (Spent Fuel Coincidence Counter (SFCC)) in the BN-350 reactor spent-fuel pond in Aqtau, Kazakhstan. A procedure has been developed to convert singles and doubles (coincidence) neutron rates observed by the SFCC into the total plutonium content of a given BN-350 spent-fuel assembly. The plutonium content has been successfully determined for spent-fuel assemblies with a contact radiation level as high as approx 10 sup 5 Rads/h. Using limited facility information and multiple measurements along the length of spe...

  12. Channeling through Bent Crystals

    Energy Technology Data Exchange (ETDEWEB)

    Mack, Stephanie; /Ottawa U. /SLAC

    2012-09-07

    Bent crystals have demonstrated potential for use in beam collimation. A process called channeling is when accelerated particle beams are trapped by the nuclear potentials in the atomic planes within a crystal lattice. If the crystal is bent then the particles can follow the bending angle of the crystal. There are several different effects that are observed when particles travel through a bent crystal including dechanneling, volume capture, volume reflection and channeling. With a crystal placed at the edge of a particle beam, part of the fringe of the beam can be deflected away towards a detector or beam dump, thus helping collimate the beam. There is currently FORTRAN code by Igor Yazynin that has been used to model the passage of particles through a bent crystal. Using this code, the effects mentioned were explored for beam energy that would be seen at the Facility for Advanced Accelerator Experimental Tests (FACET) at a range of crystal orientations with respect to the incoming beam. After propagating 5 meters in vacuum space past the crystal the channeled particles were observed to separate from most of the beam with some noise due to dechanneled particles. Progressively smaller bending radii, with corresponding shorter crystal lengths, were compared and it was seen that multiple scattering decreases with the length of the crystal therefore allowing for cleaner detection of the channeled particles. The input beam was then modified and only a portion of the beam sent through the crystal. With the majority of the beam not affected by the crystal, most particles were not deflected and after propagation the channeled particles were seen to be deflected approximately 5mm. After a portion of the beam travels through the crystal, the entire beam was then sent through a quadrupole magnet, which increased the separation of the channeled particles from the remainder of the beam to a distance of around 20mm. A different code, which was developed at SLAC, was used to

  13. An algorithm for the determination of emergency process parameters at water-into-sodium leaks in the BN-800 NPP steam generator

    International Nuclear Information System (INIS)

    Poplavsky, V.M.; Baklushin, R.P.

    1990-01-01

    The paper presents calculation relationships for the determination of parameters characterizing a sodium circuit state under water-into-sodium leak emergency conditions (mass of water penetrating into sodium, the leak size, amount of impurities in coolant, the size of expected heat-exchange surface damage). An approximation of some parameters as applied to the BN-800 NPP steam generator is presented. (author). 1 ref., 2 figs

  14. Island shape, size and interface dependency on electronic and magnetic properties of graphene hexagonal-boron nitride (h-BN) in-plane hybrids

    Science.gov (United States)

    Akman, Nurten; Özdoğan, Cem

    2018-04-01

    We systematically investigate the energetics of ion implantation, stability, electronic, and magnetic properties of graphene/hexagonal boron nitrate (h-BN) in-plane hybrids through first principle calculations. We consider hexagonal and triangular islands in supercells of graphene and h-BN layouts. In the case of triangular islands, both phases mix with each other by either solely Csbnd N or Csbnd B bonds. We also patterned triangles with predominating Csbnd N or Csbnd B bonds at their interfaces. The energetics of island implantation is discussed in detail. Formation energies point out that the island implantation could be even exothermic for all hybrids studied in this work. Effects of size and shape of the island, and dominating bonding sort at the island-layout interfaces on the stability, band gap, and magnetic properties of hybrids are studied particularly. The hybrids become more stable with increasing island size. Regardless of the layout, hybrids with hexagonal islands are all non-magnetic and semiconducting. One can thus open a band gap in the semimetallic graphene by mixing it with the h-BN phase. In general, hybrids containing graphene triangles show metallic property and exhibit considerable amount of magnetic moments for possible localized spin utilizations. Total magnetic moment of hybrids with both graphene and h-BN layouts increases with growing triangle island as well. The spin densities of magnetic hybrids are derived from interfaces of the islands and diminish towards their center. We suggest that the increase in stability and magnetic moment depend on the number of atoms at the interfaces rather than the island size.

  15. Metal insulator semiconductor solar cell devices based on a Cu2O substrate utilizing h-BN as an insulating and passivating layer

    International Nuclear Information System (INIS)

    Ergen, Onur; Gibb, Ashley; Vazquez-Mena, Oscar; Zettl, Alex; Regan, William Raymond

    2015-01-01

    We demonstrate cuprous oxide (Cu 2 O) based metal insulator semiconductor Schottky (MIS-Schottky) solar cells with efficiency exceeding 3%. A unique direct growth technique is employed in the fabrication, and hexagonal boron nitride (h-BN) serves simultaneously as a passivation and insulation layer on the active Cu 2 O layer. The devices are the most efficient of any Cu 2 O based MIS-Schottky solar cells reported to date

  16. Substrate-Controlled Diastereoselectivity Reversal in NHC-Catalyzed Cross-Benzoin Reactions Using N-Boc-N-Bn-Protected α-Amino Aldehydes.

    Science.gov (United States)

    Haghshenas, Pouyan; Quail, J Wilson; Gravel, Michel

    2016-12-16

    The effectiveness of utilizing N-Bn-N-Boc-α-amino aldehydes in cross-benzoin reactions with heteroaromatic aldehydes is demonstrated. The reaction is both chemoselective and syn-selective, making it complementary to the anti-selective cross-benzoin reaction of NHBoc-α-amino aldehydes. Good diastereoselectivity is obtained for a variety of amino aldehydes, including nonhindered ones. A Felkin-Anh model can be used to rationalize the observed diastereoselectivity.

  17. 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.

  18. 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.

  19. Wetting Behavior and Reactivity of Molten Silicon with h-BN Substrate at Ultrahigh Temperatures up to 1750 °C

    Science.gov (United States)

    Polkowski, Wojciech; Sobczak, Natalia; Nowak, Rafał; Kudyba, Artur; Bruzda, Grzegorz; Polkowska, Adelajda; Homa, Marta; Turalska, Patrycja; Tangstad, Merete; Safarian, Jafar; Moosavi-Khoonsari, Elmira; Datas, Alejandro

    2017-12-01

    For a successful implementation of newly proposed silicon-based latent heat thermal energy storage systems, proper ceramic materials that could withstand a contact heating with molten silicon at temperatures much higher than its melting point need to be developed. In this regard, a non-wetting behavior and low reactivity are the main criteria determining the applicability of ceramic as a potential crucible material for long-term ultrahigh temperature contact with molten silicon. In this work, the wetting of hexagonal boron nitride (h-BN) by molten silicon was examined for the first time at temperatures up to 1750 °C. For this purpose, the sessile drop technique combined with contact heating procedure under static argon was used. The reactivity in Si/h-BN system under proposed conditions was evaluated by SEM/EDS examinations of the solidified couple. It was demonstrated that increase in temperature improves wetting, and consequently, non-wetting-to-wetting transition takes place at around 1650 °C. The contact angle of 90° ± 5° is maintained at temperatures up to 1750 °C. The results of structural characterization supported by a thermodynamic modeling indicate that the wetting behavior of the Si/h-BN couple during heating to and cooling from ultrahigh temperature of 1750 °C is mainly controlled by the substrate dissolution/reprecipitation mechanism.

  20. Irradiation Creep of Ferritic-Martensitic Steels EP-450, EP-823 and EI-852 Irradiated in the BN-350 Reactor over Wide Ranges of Irradiation Temperature and Dose

    International Nuclear Information System (INIS)

    Porollo, S.I.; Konobeev, Y.V.; Ivanov, A.A.; Shulepin, S.V.; Garner, F.

    2007-01-01

    Full text of publication follows: Ferritic/martensitic (F/M) steels appear to be the most promising materials for advanced nuclear systems, especially for fusion reactors. Their main advantages are higher resistance to swelling and lower irradiation creep rate as has been repeatedly demonstrated in examinations of these materials after irradiation. Nevertheless, available experimental data on irradiation resistance of F/M steels are insufficient, with the greatest deficiency of data for high doses and for both low and high irradiation temperatures. From the very beginning of operation the BN-350 fast reactor has been used for irradiation of specimens of structural materials, including F/M steels. The most unique feature of BN-350 was its low inlet sodium temperature, allowing irradiation at temperatures over a very wide range of temperatures compared with the range in other fast reactors. In this paper data are presented on swelling and irradiation creep of three Russian F/M steels EP-450, EP-823 and EI-852, irradiated in experimental assemblies of the BN-350 reactor at temperatures in the range of 305-700 deg. C to doses ranging from 20 to 89 dpa. The investigation was performed using gas-pressurized creep tubes with hoop stresses in the range of 0 - 294 MPa. (authors)

  1. Silencing of BnTT1 family genes affects seed flavonoid biosynthesis and alters seed fatty acid composition in Brassica napus.

    Science.gov (United States)

    Lian, Jianping; Lu, Xiaochun; Yin, Nengwen; Ma, Lijuan; Lu, Jing; Liu, Xue; Li, Jiana; Lu, Jun; Lei, Bo; Wang, Rui; Chai, Yourong

    2017-01-01

    TRANSPARENT TESTA1 (TT1) is a zinc finger protein that contains a WIP domain. It plays important roles in controlling differentiation and pigmentation of the seed coat endothelium, and can affect the expression of early biosynthetic genes and late biosynthetic genes of flavonoid biosynthesis in Arabidopsis thaliana. In Brassica napus (AACC, 2n=38), the functions of BnTT1 genes remain unknown and few studies have focused on their roles in fatty acid (FA) biosynthesis. In this study, BnTT1 family genes were silenced by RNA interference, which resulted in yellow rapeseed, abnormal testa development (a much thinner testa), decreased seed weight, and altered seed FA composition in B. napus. High-throughput sequencing of genes differentially expressed between developing transgenic B. napus and wild-type seeds revealed altered expression of numerous genes involved in flavonoid and FA biosynthesis. As a consequence of this altered expression, we detected a marked decrease of oleic acid (C18:1) and notable increases of linoleic acid (C18:2) and α-linolenic acid (C18:3) in mature transgenic B. napus seeds by gas chromatography and near-infrared reflectance spectroscopy. Meanwhile, liquid chromatography-mass spectrometry showed reduced accumulation of flavonoids in transgenic seeds. Therefore, we propose that BnTT1s are involved in the regulation of flavonoid biosynthesis, and may also play a role in FA biosynthesis in B. napus. Copyright © 2016 Elsevier Ireland Ltd. All rights reserved.

  2. Thermotropic Ionic Liquid Crystals

    Science.gov (United States)

    Axenov, Kirill V.; Laschat, Sabine

    2011-01-01

    The last five years’ achievements in the synthesis and investigation of thermotropic ionic liquid crystals are reviewed. The present review describes the mesomorphic properties displayed by organic, as well as metal-containing ionic mesogens. In addition, a short overview on the ionic polymer and self-assembled liquid crystals is given. Potential and actual applications of ionic mesogens are also discussed. PMID:28879986

  3. Walkout in Crystal City

    Science.gov (United States)

    Barrios, Greg

    2009-01-01

    When students take action, they create change that extends far beyond the classroom. In this article, the author, who was a former teacher from Crystal City, Texas, remembers the student walkout that helped launch the Latino civil rights movement 40 years ago. The Crystal City student walkout remains a high point in the history of student activism…

  4. Demonstration of Crystal Structure.

    Science.gov (United States)

    Neville, Joseph P.

    1985-01-01

    Describes an experiment where equal parts of copper and aluminum are heated then cooled to show extremely large crystals. Suggestions are given for changing the orientation of crystals by varying cooling rates. Students are more receptive to concepts of microstructure after seeing this experiment. (DH)

  5. Photonic crystal fibers

    DEFF Research Database (Denmark)

    Lægsgaard, Jesper; Hansen, K P; Nielsen, M D

    2003-01-01

    Photonic crystal fibers having a complex microstructure in the transverse plane constitute a new and promising class of optical fibers. Such fibers can either guide light through total internal reflection or the photonic bandgap effect, In this paper, we review the different types and applications...... of photonic crystal fibers with particular emphasis on recent advances in the field....

  6. Crystal growth and crystallography

    Science.gov (United States)

    Chernov, A. A.

    1998-01-01

    Selected topics that may be of interest for both crystal-structure and crystal-growth communities are overviewed. The growth of protein crystals, along with that of some other compounds, is one of the topics, and recent insights into related phenomena are considered as examples of applications of general principles. The relationship between crystal growth shape and structure is reviewed and an attempt to introduce semiquantitative characterization of binding for proteins is made. The concept of kinks for complex structures is briefly discussed. Even at sufficiently low supersaturations, the fluctuation of steps may not be sufficient to implement the Gibbs-Thomson law if the kink density is low enough. Subsurface ordering of liquids and growth of rough interfaces from melts is discussed. Crystals growing in microgravity from solution should be more perfect if they preferentially trap stress-inducing impurities, thus creating an impurity-depleted zone around themselves. Evidently, such a zone is developed only around the crystals growing in the absence of convection. Under terrestrial conditions, the self-purified depleted zone is destroyed by convection, the crystal traps more impurity and grows stressed. The stress relief causes mosaicity. In systems containing stress-inducing but poorly trapped impurities, the crystals grown in the absence of convection should be worse than those of their terrestrial counterparts.

  7. Thermotropic Ionic Liquid Crystals.

    Science.gov (United States)

    Axenov, Kirill V; Laschat, Sabine

    2011-01-14

    The last five years' achievements in the synthesis and investigation of thermotropic ionic liquid crystals are reviewed. The present review describes the mesomorphic properties displayed by organic, as well as metal-containing ionic mesogens. In addition, a short overview on the ionic polymer and self-assembled liquid crystals is given. Potential and actual applications of ionic mesogens are also discussed.

  8. Thermotropic Ionic Liquid Crystals

    OpenAIRE

    Axenov, Kirill V.; Laschat, Sabine

    2011-01-01

    The last five years’ achievements in the synthesis and investigation of thermotropic ionic liquid crystals are reviewed. The present review describes the mesomorphic properties displayed by organic, as well as metal-containing ionic mesogens. In addition, a short overview on the ionic polymer and self-assembled liquid crystals is given. Potential and actual applications of ionic mesogens are also discussed.

  9. Crystals in the LHC

    CERN Multimedia

    Antonella Del Rosso

    2012-01-01

    Bent crystals can be used to deflect charged particle beams. Their use in high-energy accelerators has been investigated for almost 40 years. Recently, a bent crystal was irradiated for the first time in the HiRadMat facility with an extreme particle flux, which crystals would have to withstand in the LHC. The results were very encouraging and confirmed that this technology could play a major role in increasing the beam collimation performance in future upgrades of the machine.   UA9 bent crystal tested with a laser. Charged particles interacting with a bent crystal can be trapped in channelling states and deflected by the atomic planes of the crystal lattice (see box). The use of bent crystals for beam manipulation in particle accelerators is a concept that has been well-assessed. Over the last three decades, a large number of experimental findings have contributed to furthering our knowledge and improving our ability to control crystal-particle interactions. In modern hadron colliders, su...

  10. SYMMETRY OF COMPOSITE CRYSTALS

    NARCIS (Netherlands)

    VANSMAALEN, S

    1991-01-01

    Composite crystals are crystals that consist of two or more subsystems, in first approximation each one having its own three-dimensional periodicity. The symmetry of these subsystems is then characterized by an ordinary space group. Due to their mutual interaction the true structure consists of a

  11. Active Photonic Crystal Waveguides

    DEFF Research Database (Denmark)

    Ek, Sara

    This thesis deals with the fabrication and characterization of active photonic crystal waveguides, realized in III-V semiconductor material with embedded active layers. The platform offering active photonic crystal waveguides has many potential applications. One of these is a compact photonic...... crystal semiconductor optical amplier. As a step towards such a component, photonic crystal waveguides with a single quantum well, 10 quantum wells and three layers of quantum dots are fabricated and characterized. An experimental study of the amplied spontaneous emission and a implied transmission...... are presented in this thesis. A variation of photonic crystal design parameters are used leading to a spectral shift of the dispersion, it is veried that the observed effects shift accordingly. An enhancement of the amplified spontaneous emission was observed close to the band edge, where light is slowed down...

  12. Progress on photonic crystals

    CERN Document Server

    Lecoq, P; Gundacker, S; Hillemanns, H; Jarron, P; Knapitsch, A; Leclercq, J L; Letartre, X; Meyer, T; Pauwels, K; Powolny, F; Seassal, C

    2010-01-01

    The renewal of interest for Time of Flight Positron Emission Tomography (TOF PET) has highlighted the need for increasing the light output of scintillating crystals and in particular for improving the light extraction from materials with a high index of refraction. One possible solution to overcome the problem of total internal reflection and light losses resulting from multiple bouncing within the crystal is to improve the light extraction efficiency at the crystal/photodetector interface by means of photonic crystals, i.e. media with a periodic modulation of the dielectric constant at the wavelength scale. After a short reminder of the underlying principles this contribution proposes to present the very encouraging results we have recently obtained on LYSO pixels and the perspectives on other crystals such as BGO, LuYAP and LuAG. These results confirm the impressive predictions from our previously published Monte Carlo simulations. A detailed description of the sample preparation procedure is given as well ...

  13. Optically Anomalous Crystals

    CERN Document Server

    Shtukenberg, Alexander; Kahr, Bart

    2007-01-01

    Optical anomalies in crystals are puzzles that collectively constituted the greatest unsolved problems in crystallography in the 19th Century. The most common anomaly is a discrepancy between a crystal’s symmetry as determined by its shape or by X-ray analysis, and that determined by monitoring the polarization state of traversing light. These discrepancies were perceived as a great impediment to the development of the sciences of crystals on the basis of Curie’s Symmetry Principle, the grand organizing idea in the physical sciences to emerge in the latter half of the 19th Century. Optically Anomalous Crystals begins with an historical introduction covering the contributions of Brewster, Biot, Mallard, Brauns, Tamman, and many other distinguished crystallographers. From this follows a tutorial in crystal optics. Further chapters discuss the two main mechanisms of optical dissymmetry: 1. the piezo-optic effect, and 2. the kinetic ordering of atoms. The text then tackles complex, inhomogeneous crystals, and...

  14. Organic semiconductor crystals.

    Science.gov (United States)

    Wang, Chengliang; Dong, Huanli; Jiang, Lang; Hu, Wenping

    2018-01-22

    Organic semiconductors have attracted a lot of attention since the discovery of highly doped conductive polymers, due to the potential application in field-effect transistors (OFETs), light-emitting diodes (OLEDs) and photovoltaic cells (OPVs). Single crystals of organic semiconductors are particularly intriguing because they are free of grain boundaries and have long-range periodic order as well as minimal traps and defects. Hence, organic semiconductor crystals provide a powerful tool for revealing the intrinsic properties, examining the structure-property relationships, demonstrating the important factors for high performance devices and uncovering fundamental physics in organic semiconductors. This review provides a comprehensive overview of the molecular packing, morphology and charge transport features of organic semiconductor crystals, the control of crystallization for achieving high quality crystals and the device physics in the three main applications. We hope that this comprehensive summary can give a clear picture of the state-of-art status and guide future work in this area.

  15. Bioengineered magnetic crystals

    International Nuclear Information System (INIS)

    Kasyutich, O; Sarua, A; Schwarzacher, W

    2008-01-01

    In this paper we report on the successful application of a protein crystallization technique to fabricate a three-dimensionally ordered array of magnetic nanoparticles, i.e. a novel type of metamaterial with unique magnetic properties. We utilize ferritin protein cages for the template-constrained growth of superparamagnetic nanoparticles of magnetite/maghemite Fe 3 O 4 -γ-Fe 2 O 3 (magnetoferritin), followed by thorough nanoparticle bioprocessing and purification, and finally by protein crystallization. Protein crystallization is driven by the natural response of proteins to the supersaturation of the electrolyte, which leads to spontaneous nucleation and 3D crystal growth. Within a short period of time (hours to days) we were able to grow functional crystals on the meso-scale, with sizes of the order of tens, up to a few hundred micrometres. We present initial magnetic and Raman spectroscopy characterization results for the obtained 3D arrays of magnetic nanoparticles

  16. Crystallization phenomena of isotactic polystyrene

    NARCIS (Netherlands)

    Lemstra, Peter Jan

    1975-01-01

    In this thesis the crystallization behavior of isotactic polystyrene has been described. The kinetics of the crystallization process and the crystalline structure were studied both for crystallization in the bulk and from dilute solutions. ... Zie Summary

  17. Metal-free ferromagnetic metal and intrinsic spin semiconductor: two different kinds of SWCNT functionalized BN nanoribbons.

    Science.gov (United States)

    Lou, Ping

    2015-03-28

    Two different kinds of SWCNT functionalized zigzag edge BN nanoribbons with n chains (n-ZBNNRs), namely, (a) B-edge functionalized by (m,m)SWCNT and N-edge modified with H (nZBNNR-B-(m,m)SWCNTs); and (b) the B-edge modified with H and the N-edge functionalized by (m,m)SWCNT (nZBNNR-N-(m,m)SWCNTs), have been predicted. Amazingly, we find that unlike the semiconducting and nonmagnetic H-modified n-ZBNNRs, the nZBNNR-B-(m,m)SWCNTs are intrinsic ferromagnetic metals, regardless of ribbon widths n and tube diameters (m,m). At a given (m,m), their local magnetic moments, at first, exhibit oscillation with increasing n, whereas when n is larger than 5, they are independent of n. In contrast, unlike the metallic and nonmagnetic (m,m)SWCNTs, the nZBNNR-N-(m,m)SWCNTs are ferromagnetic intrinsic spin-semiconductors with direct band gaps, regardless of n and (m,m). Their local magnetic moments and band gaps are independent of n and (m,m). The DFT calculations reveal that the process of SWCNT functionalization of the n-ZBNNRs does not need any activation energy. Moreover, the formation energies of the SWCNT functionalized n-ZBNNRs are always less than zero. Therefore, the SWCNT functionalized n-ZBNNRs are not only stable, but can also be spontaneously formed. Furthermore, compared with n-ZBNNRs, the SWCNT functionalized n-ZBNNRs show significant improvements in their thermal and mechanical stabilities. Thus, (m,m)SWCNT functionalization of n-ZBNNRs may open new routes toward practical nanoelectronic and optoelectronic as well as spintronic devices based on BNC-based materials.

  18. Crystals, inflammation, and osteoarthritis.

    Science.gov (United States)

    Rosenthal, Ann K

    2011-03-01

    Calcium pyrophosphate dihydrate (CPPD) and basic calcium phosphate (BCP) crystals are common components of osteoarthritic joint fluids and tissues. Why these crystals form and how they contribute to joint damage in osteoarthritis remain unclear. With renewed interest in inflammation as a key component of osteoarthritis the role of calcium-containing crystals in this common disease warrants re-examination. There is ample evidence supporting a pathogenic role for inflammation in osteoarthritis, and the innate immune system likely participates in this inflammatory process. Recent work reinforces the almost universal existence of calcium-containing crystals in tissues from patients with end-stage osteoarthritis. Calcium-containing crystals may contribute to inflammation in osteoarthritis tissues through their direct interactions with components of the innate immune system, as well as by inducing or amplifying other inflammatory signals. There is increasing evidence that calcium-containing crystals contribute to osteoarthritis and their inflammatory properties may mediate detrimental effects through innate immunity signals. Calcium-containing crystals may thus represent important therapeutic targets in osteoarthritis.

  19. Quartz crystal growth

    Science.gov (United States)

    Baughman, Richard J.

    1992-01-01

    A process for growing single crystals from an amorphous substance that can undergo phase transformation to the crystalline state in an appropriate solvent. The process is carried out in an autoclave having a lower dissolution zone and an upper crystallization zone between which a temperature differential (.DELTA.T) is maintained at all times. The apparatus loaded with the substance, solvent, and seed crystals is heated slowly maintaining a very low .DELTA.T between the warmer lower zone and cooler upper zone until the amorphous substance is transformed to the crystalline state in the lower zone. The heating rate is then increased to maintain a large .DELTA.T sufficient to increase material transport between the zones and rapid crystallization. .alpha.-Quartz single crystal can thus be made from fused quartz in caustic solvent by heating to 350.degree. C. stepwise with a .DELTA.T of 0.25.degree.-3.degree. C., increasing the .DELTA.T to about 50.degree. C. after the fused quartz has crystallized, and maintaining these conditions until crystal growth in the upper zone is completed.

  20. Hypersonic phononic crystals.

    Science.gov (United States)

    Gorishnyy, T; Ullal, C K; Maldovan, M; Fytas, G; Thomas, E L

    2005-03-25

    In this Letter we propose the use of hypersonic phononic crystals to control the emission and propagation of high frequency phonons. We report the fabrication of high quality, single crystalline hypersonic crystals using interference lithography and show that direct measurement of their phononic band structure is possible with Brillouin light scattering. Numerical calculations are employed to explain the nature of the observed propagation modes. This work lays the foundation for experimental studies of hypersonic crystals and, more generally, phonon-dependent processes in nanostructures.

  1. Magnetic ions in crystals

    CERN Document Server

    Stevens, K W

    2014-01-01

    There have been many demonstrations, particularly for magnetic impurity ions in crystals, that spin-Hamiltonians are able to account for a wide range of experimental results in terms of much smaller numbers of parameters. Yet they were originally derived from crystal field theory, which contains a logical flaw; electrons on the magnetic ions are distinguished from those on the ligands. Thus there is a challenge: to replace crystal field theory with one of equal or greater predictive power that is based on a surer footing. The theory developed in this book begins with a generic Hamiltonian, on

  2. Hydrodynamics of superfluid crystals

    International Nuclear Information System (INIS)

    Vardanyan, G.A.; Papoyan, K.V.; Sedrakyan, D.M.

    1984-01-01

    It is shown that three-velocity hydrodynamics equations describing the properties of a two-condensate crystal determine the low-frequency spectrum with allowance for superfluid drag. The drag on one superfluid component of density rho/sup( s/) 12 from another component of density rho/sup( s/) 22 , gives rise to two branches of vibrations of frequencies ω 1 and ω 2 , unlike the case of a one-condensate crystal. The absorption coefficient for transverse sound in a one-condensate crystal is expressed in terms of the quantum-mechanical characteristic quantity that describes the tunneling of atoms

  3. 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

  4. Nonlinear Photonic Crystal Fibers

    DEFF Research Database (Denmark)

    Hansen, Kim Per

    2004-01-01

    Despite the general recession in the global economy and the collapse of the optical telecommunication market, research within specialty fibers is thriving. This is, more than anything else, due to the technology transition from standard all-glass fibers to photonic crystal fibers, which, instead...... of doping, use a microstructure of air and glass to obtain a refractive index difference between the core and the cladding. This air/glass microstructure lends the photonic crystal fibers a range of unique and highly usable properties, which are very different from those found in solid standard fibers......, leading to reduced mode confinement and dispersion flexibility. In this thesis, we treat the nonlinear photonic crystal fiber – a special sub-class of photonic crystal fibers, the core of which has a diameter comparable to the wavelength of the light guided in the fiber. The small core results in a large...

  5. Crystal-Clear Technology.

    Science.gov (United States)

    Ondris-Crawford, Renate J.; And Others

    1993-01-01

    Provides diagrams to aid in discussing polymer dispersed liquid crystal (PDLC) technology. Equipped with a knowledge of PDLC, teachers can provide students with insight on how the gap between basic science and technology is bridged. (ZWH)

  6. Creep of crystals

    International Nuclear Information System (INIS)

    Poirier, J.-P.

    1988-01-01

    Creep mechanisms for metals, ceramics and rocks, effect of pressure and temperature on deformation processes are considered. The role of crystal defects is analysed, different models of creep are described. Deformation mechanisms maps for different materials are presented

  7. Crystal engineering: structure, property and beyond

    OpenAIRE

    Desiraju, Gautam R.

    2017-01-01

    Crystal engineering, which was considered to be crystal structure engineering, is now transforming into crystal property engineering. The same or similar crystal structures could have different properties while different crystal structures could have similar properties.

  8. Thermotropic Ionic Liquid Crystals

    Directory of Open Access Journals (Sweden)

    Sabine Laschat

    2011-01-01

    Full Text Available The last five years’ achievements in the synthesis and investigation of thermotropic ionic liquid crystals are reviewed. The present review describes the mesomorphic properties displayed by organic, as well as metal-containing ionic mesogens. In addition, a short overview on the ionic polymer and self-assembled liquid crystals is given. Potential and actual applications of ionic mesogens are also discussed.

  9. Macromolecular Crystal Quality

    Science.gov (United States)

    Snell, Edward H.; Borgstahl, Gloria E. O.; Bellamy, Henry D.; Curreri, Peter A. (Technical Monitor)

    2001-01-01

    There are many ways of judging a good crystal. Which we use depends on the qualities we seek. For gemstones size, clarity and impurity levels (color) are paramount. For the semiconductor industry purity is probably the most important quality. For the structural crystallographer the primary desideratum is the somewhat more subtle concept of internal order. In this chapter we discuss the effect of internal order (or the lack of it) on the crystal's diffraction properties.

  10. Building a crystal palace

    CERN Multimedia

    2007-01-01

    The end-caps of the CMS electromagnetic calorimeter (ECAL) take shape as the first quadrant was completed on Wednesday 3 October. 1831 crystals, organised into five by five blocks named ‘supercrystals’, make up the first quadrant of Dee 1.With the 61,200-crystal barrel of its electromagnetic calorimeter (ECAL) complete, CMS is now building the endcaps, on the tenth anniversary of their initial design. Crystals for the endcaps were the last to be made, so the race is now on to have them all in place and ready for the turn-on of the LHC next year. Assembly of the first of eight quadrants began in June and crystal mounting was completed on Wednesday 3 October. Each crystal is transparent, has a volume just larger than a CERN coffee cup yet weighs a huge 1.5kg. 1831 of these lead tungstate crystals went into the first quadrant from a total 14,648 in the endcaps. The lead and tungsten account for 86% of each crystal’s weight, but as project leader Dave Cockerill expl...

  11. Overexpression of Sinapine Esterase BnSCE3 in Oilseed Rape Seeds Triggers Global Changes in Seed Metabolism1[W][OA

    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

    2011-01-01

    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. PMID

  12. Electronic properties of graphene encapsulated with different two-dimensional atomic crystals.

    Science.gov (United States)

    Kretinin, A V; Cao, Y; Tu, J S; Yu, G L; Jalil, R; Novoselov, K S; Haigh, S J; Gholinia, A; Mishchenko, A; Lozada, M; Georgiou, T; Woods, C R; Withers, F; Blake, P; Eda, G; Wirsig, A; Hucho, C; Watanabe, K; Taniguchi, T; Geim, A K; Gorbachev, R V

    2014-06-11

    Hexagonal boron nitride is the only substrate that has so far allowed graphene devices exhibiting micrometer-scale ballistic transport. Can other atomically flat crystals be used as substrates for making quality graphene heterostructures? Here we report on our search for alternative substrates. The devices fabricated by encapsulating graphene with molybdenum or tungsten disulfides and hBN are found to exhibit consistently high carrier mobilities of about 60 000 cm(2) V(-1) s(-1). In contrast, encapsulation with atomically flat layered oxides such as mica, bismuth strontium calcium copper oxide, and vanadium pentoxide results in exceptionally low quality of graphene devices with mobilities of ∼1000 cm(2) V(-1) s(-1). We attribute the difference mainly to self-cleansing that takes place at interfaces between graphene, hBN, and transition metal dichalcogenides. Surface contamination assembles into large pockets allowing the rest of the interface to become atomically clean. The cleansing process does not occur for graphene on atomically flat oxide substrates.

  13. Biokinetics and dosimetry of a hybrid formulation of 9mTc-BN and 99mTc-RGD2 starting from optic images in a murine model

    International Nuclear Information System (INIS)

    Cornejo A, L. G.

    2015-01-01

    This work has the purpose of evaluate the biokinetics and absorbed dose of radiation of hybrid formulation 99m Tc-BN / 99m Tc-RGD 2 in a murine model by optical imaging techniques using the multimodal preclinical in vivo image system Xtreme. The used method were the 99m Tc-BN, 99m Tc-RGD 2 and 99m Tc-BN/ 99m Tc-RGD 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 99m Tc-BN/ 99m Tc-RGD 2 formulation, was: 0.035 ± 0.65 E-02, 0.25 x 10 -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 achieve comparable quantitative results as the conventional

  14. Cykl apokaliptycznych egzegez wizji proroka Daniela w kontekście doktrynalnego sporu wschodniego chrześcijaństwa z judaizmem (na materiale kodeksu BN 12245

    Directory of Open Access Journals (Sweden)

    Jan Stradomski

    2017-10-01

    Full Text Available Series of eschatological exegeses in prophet Daniel’s visions in the context of the doctrinal dispute of Eastern Christianity and Judaism (about the manuscript BN 12245 The Bible’s Book of Daniel, along with commentaries of St. Hippolytus of Rome, belongs to the most important sources of Christian knowledge about the end of the world and the Final Judgment. In the medieval Old Church Slavonic literature, the Book of Daniel functions not only as a part of the Old Testament canon (separately or with comments, but it is also present in historiography, and in particular in apocryphal literature. Prophet Daniel and his vision of four beasts are also the basis for preparation of new eschatological texts where the threads of the doctrinal dispute with Judaism are noticeable. Such writings include a series of visions of Prophet Daniel with commentaries, rarely encountered in Cyrillic manuscripts, featured in Codex BN 12245. The article presents a textological, historical and literary analysis of the text.   Cykl apokaliptycznych egzegez wizji proroka Daniela w kontekście doktrynalnego sporu wschodniego chrześcijaństwa z judaizmem (na materiale kodeksu BN 12245 Biblijna Księga Daniela, wraz z komentarzami św. Hipolita Rzymskiego, należy do ważniejszych źródeł wiedzy chrześcijan na temat końca świata i Sądu Ostatecznego. W średniowiecznej literaturze cerkiewnosłowiańskiej materiał Księgi Daniela funkcjonuje nie tylko jako część korpusu kanonicznych pism Starego Testamentu (osobno lub z komentarzami, ale obecny jest też w historiografii, a zwłaszcza w literaturze apokryficznej. Postać proroka Daniela i jego wizja czterech bestii są też bazą opracowywania nowych tekstów o tematyce eschatologicznej, w których widoczne są wątki doktrynalnego sporu z judaizmem. Do takich pism zalicza się rzadko spotykany w rękopisach cyrylickich cykl komentowanych wizji proroka Daniela, jaki znajduje się w kodeksie BN 12245. W artykule

  15. 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

    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....... of incommensurate vdWHs. The method combines our quantum electrostatic heterostructure (QEH) model for obtaining the dielectric function with the many-body GW approximation and a generalized 2D Mott-Wannier exciton model. We calculate the level alignment together with intra- and interlayer exciton binding energies...

  16. Steering a crystallization process to reduce crystal polydispersity; case study of insulin crystallization

    Science.gov (United States)

    Nanev, Christo N.; Petrov, Kostadin P.

    2017-12-01

    The use of the classical nucleation-growth-separation principle (NGSP) was restricted hitherto to nucleation kinetics studies only. A novel application of the NGSP is proposed. To reduce crystal polydispersity internal seeding of equally-sized crystals is suggested, the advantage being avoidance of crystal grinding, sieving and any introduction of impurities. In the present study, size distributions of grown insulin crystals are interpreted retrospectively to select the proper nucleation stage parameters. The conclusion is that when steering a crystallization process aimed at reducing crystal polydispersity, the shortest possible nucleation stage duration has to be chosen because it renders the closest size distribution of the nucleated crystal seeds. Causes of inherent propensity to increasing crystal polydispersity during prolonged growth are also explored. Step sources of increased activity, present in some crystals while absent in others, are pointed as the major polydispersity cause. Insulin crystal morphology is also considered since it determines the dissolution rate of a crystalline medicine.

  17. Crystallization phenomena in slags

    Science.gov (United States)

    Orrling, Carl Folke

    2000-09-01

    The crystallization of the mold slag affects both the heat transfer and the lubrication between the mold and the strand in continuous casting of steel. In order for mold slag design to become an engineering science rather than an empirical exercise, a fundamental understanding of the melting and solidification behavior of a slag must be developed. Thus it is necessary to be able to quantify the phenomena that occur under the thermal conditions that are found in the mold of a continuous caster. The double hot thermocouple technique (DHTT) and the Confocal Laser Scanning Microscope used in this study are two novel techniques for investigating melting and solidification phenomena of transparent slags. Results from these techniques are useful in defining the phenomena that occur when the slag film infiltrates between the mold and the shell of the casting. TTT diagrams were obtained for various slags and indicated that the onset of crystallization is a function of cooling rate and slag chemistry. Crystal morphology was found to be dependent upon the experimental temperature and four different morphologies were classified based upon the degree of melt undercooling. Continuous cooling experiments were carried out to develop CCT diagrams and it was found that the amount and appearance of the crystalline fraction greatly depends on the cooling conditions. The DHTT can also be used to mimic the cooling profile encountered by the slag in the mold of a continuous caster. In this differential cooling mode (DCT), it was found that the details of the cooling rate determine the actual response of the slag to a thermal gradient and small changes can lead to significantly different results. Crystal growth rates were measured and found to be in the range between 0.11 mum/s to 11.73 mum/s depending on temperature and slag chemistry. Alumina particles were found to be effective innoculants in oxide melts reducing the incubation time for the onset of crystallization and also extending

  18. Introduction to protein crystallization

    Science.gov (United States)

    McPherson, Alexander; Gavira, Jose A.

    2014-01-01

    Protein crystallization was discovered by chance about 150 years ago and was developed in the late 19th century as a powerful purification tool and as a demonstration of chemical purity. The crystallization of proteins, nucleic acids and large biological complexes, such as viruses, depends on the creation of a solution that is supersaturated in the macromolecule but exhibits conditions that do not significantly perturb its natural state. Supersaturation is produced through the addition of mild precipitating agents such as neutral salts or polymers, and by the manipulation of various parameters that include temperature, ionic strength and pH. Also important in the crystallization process are factors that can affect the structural state of the macromolecule, such as metal ions, inhibitors, cofactors or other conventional small molecules. A variety of approaches have been developed that combine the spectrum of factors that effect and promote crystallization, and among the most widely used are vapor diffusion, dialysis, batch and liquid–liquid diffusion. Successes in macromolecular crystallization have multiplied rapidly in recent years owing to the advent of practical, easy-to-use screening kits and the application of laboratory robotics. A brief review will be given here of the most popular methods, some guiding principles and an overview of current technologies. PMID:24419610

  19. Crystallization in polymer nanocomposites

    Science.gov (United States)

    Chrissopoulou, Kyriakh; Perivolari, Helena; Leisch, Stefanos; Papananou, Hellen; Anastasiadis, Spiros H.

    Polymer crystallization is a very interesting topic since it is responsible for the final properties of the materials. On the other hand, addition of inorganic nanomaterials has been recently widely used to optimize polymer properties. In this work, the effect of the presence of surfaces and of the severe confinement on polymer morphology and crystallization are investigated in hydrophilic nanohybrids of poly(ethylene oxide) and silica nanoparticles of different sizes; hybrids with different ratios of the two kinds of nanoparticles were synthesized as well, to achieve the highest confinement. Differential Scanning Calorimetry (DSC) and X-Ray Diffraction (XRD) were utilized to investigate the behavior and showed that the polymer chains that were able to crystallize showed a different crystalline behavior in the hybrids with lower Tm and lower crystallinity. Under severe confinement polymer crystallization was completely suppressed. Moreover, the crystallization kinetics was investigated with Isothermal Polarized Optical Microscopy (POM) and Isothermal Differential Scanning Calorimetry (DSC) showing different characteristics in the hybrids compared to that of the neat polymer depending on the silica content. Sponsored by the Greek GSRT (AENAO research project, Action KRIPIS)

  20. 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)

  1. Photonic Crystal Fibres

    DEFF Research Database (Denmark)

    Bjarklev, Anders Overgaard; Broeng, Jes; Sanchez Bjarklev, Araceli

    Photonic crystal fibres represent one of the most active research areas today in the field of optics. The diversity of applications that may be addressed by these fibres and their fundamental appeal, by opening up the possibility of guiding light in a radically new way compared to conventional...... optical fibres, have spun an interest from almost all areas of optics and photonics. The aim of this book is to provide an understanding of the different types of photonic crystal fibres and to outline some of the many new and exciting applications that these fibres offer. The book is intended for both...... readers with a general interest in photonic crystals, as well as for scientists who are entering the field and desire a broad overview as well as a solid starting point for further specialized stuides. Teh book, therefore, covers bothe general aspects such as the link from classical optics to photonic...

  2. Frequency doubling crystals

    Science.gov (United States)

    Wang, Francis; Velsko, Stephan P.

    1989-01-01

    A systematic approach to the production of frequency conversion crystals is described in which a chiral molecule has attached to it a "harmonic generating unit" which contributes to the noncentrosymmetry of the molecule. Certain preferred embodiments of such harmonic generating units include carboxylate, guanadyly and imidazolyl units. Certain preferred crystals include L-arginine fluoride, deuterated L-arginine fluoride, L-arginine chloride monohydrate, L-arginine acetate, dithallium tartrate, ammonium N-acetyl valine, N-acetyl tyrosine and N-acetyl hydroxyproline. Chemical modifications of the chiral molecule, such as deuteration, halogenation and controlled counterion substitution are available to adapt the dispersive properties of a crystal in a particular wavelength region.

  3. 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.

  4. Fast-ICCD photography and gated photon counting measurements of blackbody emission from particulates generated in the KrF-laser ablation of BN and YBCO

    Energy Technology Data Exchange (ETDEWEB)

    Geohegan, D.B.

    1992-11-01

    Fast intensified CCD photography and gated photon counting following KrF-laser irradiation of YBCO and BN targets reveals the first observations of very weak emission from slow-moving ejecta up to 2 cm from the target and times extending to {approx}1.5 ms. Time-of-flight velocities inferred from the emission measurements indicate velocities (v {approximately} (0.45--1.2) {times} 10{sup 4} cm s{sup {minus}1}) comparable to those measured for the large particles which often accompany the pulsed laser deposition process. Gated photon counting is employed to obtain temporally resolved spectra of this weak emission. The spectral shape is characteristic of blackbody emission, which shifts to longer wavelengths as the particles cool during flight in vacuum. Estimates of the temperature of the particles are made based on the emissivity of a perfect blackbody and range from 2200 K to 3200 K for both BN and YBCO when irradiated at ({Phi}{sub 248} = 3.5 J cm{sup {minus}2} and 1.5 J cm{sup {minus}2}, respectively. The temperature decrease of the particles in vacuum is compared to a radiative cooling model which gives estimates of the initial surface temperature and radii of the particles.

  5. One-Step Synthesis of B/N Co-doped Graphene as Highly Efficient Electrocatalyst for the Oxygen Reduction Reaction: Synergistic Effect of Impurities.

    Science.gov (United States)

    Mazánek, Vlastimil; Matějková, Stanislava; Sedmidubský, David; Pumera, Martin; Sofer, Zdeněk

    2018-01-19

    In the last decade, numerous studies of graphene doping by various metal and nonmetal elements have been done in order to obtain tailored properties, such as non-zero band gap, electrocatalytic activity, or controlled optical properties. From nonmetal elements, boron and nitrogen were the most studied dopants. Recently, it has been shown that in some cases the enhanced electrocatalytic activity of graphene and its derivatives can be attributed to metal impurities rather than to nonmetal elements. In this paper, we investigated the electrocatalytical properties of B/N co-doped graphene with respect to the content of metallic impurities introduced by the synthesis procedures. For this purpose, a permanganate (Hummers) and a chlorate (Hofmann) route were used for the preparation of the starting graphene oxides (GO). The GO used for the synthesis of B/N co-doped graphene had significantly difference compositions of oxygen functionalities as well as metallic impurities introduced by the different synthetic procedures. We performed a detailed structural and chemical analysis of the doped graphene samples to correlate their electrocatalytic activity with the concentration of incorporated boron and nitrogen as well as metallic impurities. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  6. Thermodynamics of Crystals

    Science.gov (United States)

    Navrotsky, Alexandra

    Thermodynamics of Crystals is a gold mine of a references bargain with more derivations of useful equations per dollar, or per page, than almost any other book I know. Useful to whom? To the solid state physicist, the solid state chemist working the geophysicist, the rock mechanic, the mineral physicist. Useful for what? For lattice dynamics, crystal potentials, band structure. For elegant, rigorous, and concise derivations of fundamental equations. For comparison of levels of approximation. For some data and physical insights, especially for metals and simple halides. This book is a reissue, with some changes and additions, of a 1970 treatise. It ages well, since the fundamentals do not change.

  7. FRACTIONAL CRYSTALLIZATION FEED ENVELOPE

    International Nuclear Information System (INIS)

    HERTING DL

    2008-01-01

    Laboratory work was completed on a set of evaporation tests designed to establish a feed envelope for the fractional crystallization process. The feed envelope defines chemical concentration limits within which the process can be operated successfully. All 38 runs in the half-factorial design matrix were completed successfully, based on the qualitative definition of success. There is no feed composition likely to be derived from saltcake dissolution that would cause the fractional crystallization process to not meet acceptable performance requirements. However, some compositions clearly would provide more successful operation than other compositions

  8. Time crystals: a review

    Science.gov (United States)

    Sacha, Krzysztof; Zakrzewski, Jakub

    2018-01-01

    Time crystals are time-periodic self-organized structures postulated by Frank Wilczek in 2012. While the original concept was strongly criticized, it stimulated at the same time an intensive research leading to propositions and experimental verifications of discrete (or Floquet) time crystals—the structures that appear in the time domain due to spontaneous breaking of discrete time translation symmetry. The struggle to observe discrete time crystals is reviewed here together with propositions that generalize this concept introducing condensed matter like physics in the time domain. We shall also revisit the original Wilczek’s idea and review strategies aimed at spontaneous breaking of continuous time translation symmetry.

  9. Protein Crystal Malic Enzyme

    Science.gov (United States)

    1992-01-01

    Malic Enzyme is a target protein for drug design because it is a key protein in the life cycle of intestinal parasites. After 2 years of effort on Earth, investigators were unable to produce any crystals that were of high enough quality and for this reason the structure of this important protein could not be determined. Crystals obtained from one STS-50 were of superior quality allowing the structure to be determined. This is just one example why access to space is so vital for these studies. Principal Investigator is Larry DeLucas.

  10. The Crystal Hotel: A Microfluidic Approach to Biomimetic Crystallization.

    Science.gov (United States)

    Gong, Xiuqing; Wang, Yun-Wei; Ihli, Johannes; Kim, Yi-Yeoun; Li, Shunbo; Walshaw, Richard; Chen, Li; Meldrum, Fiona C

    2015-12-02

    A "crystal hotel" microfluidic device that allows crystal growth in confined volumes to be studied in situ is used to produce large calcite single crystals with predefined crystallographic orientation, microstructure, and shape by control of the detailed physical environment, flow, and surface chemistry. This general approach can be extended to form technologically important, nanopatterned single crystals. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  11. The CMS crystal calorimeter

    CERN Document Server

    Lustermann, W

    2004-01-01

    The measurement of the energy of electrons and photons with very high accuracy is of primary importance far the study of many physics processes at the Large Hadron Collider (LHC), in particular for the search of the Higgs Boson. The CMS experiment will use a crystal calorimeter with pointing geometry, almost covering 4p, as it offers a very good energy resolution. It is divided into a barrel composed of 61200 lead tungstate crystals, two end-caps with 14648 crystals and a pre-shower detector in front of the end-cap. The challenges of the calorimeter design arise from the high radiation environment, the 4 Tesla magnetic eld, the high bunch crossing rate of 40 MHz and the large dynamic range, requiring the development of fast, radiation hard crystals, photo-detectors and readout electronics. An overview of the construction and design of the calorimeter will be presented, with emphasis on some of the details required to meet the demanding performance goals. 19 Refs.

  12. Hardness of metallic crystals

    Indian Academy of Sciences (India)

    This paper presents a new formula for calculating the hardness of metallic crystals, resulted from the research on the critical grain size with stable dislocations. The formula is = 6 /[(1 – )], where is the hardness, the coefficient, the shear modulus, the Poisson's ratio, a function of the radius of an atom () ...

  13. Thermoelectricity in liquid crystals

    Science.gov (United States)

    Mohd Said, Suhana; Nordin, Abdul Rahman; Abdullah, Norbani; Balamurugan, S.

    2015-09-01

    The thermoelectric effect, also known as the Seebeck effect, describes the conversion of a temperature gradient into electricity. A Figure of Merit (ZT) is used to describe the thermoelectric ability of a material. It is directly dependent on its Seebeck coefficient and electrical conductivity, and inversely dependent on its thermal conductivity. There is usually a compromise between these parameters, which limit the performance of thermoelectric materials. The current achievement for ZT~2.2 falls short of the expected threshold of ZT=3 to allow its viability in commercial applications. In recent times, advances in organic thermoelectrics been significant, improving by over 3 orders of magnitude over a period of about 10 years. Liquid crystals are newly investigated as candidate thermoelectric materials, given their low thermal conductivity, inherent ordering, and in some cases, reasonable electrical conductivity. In this work the thermoelectric behaviour of a discotic liquid crystal, is discussed. The DLC was filled into cells coated with a charge injector, and an alignment of the columnar axis perpendicular to the substrate was allowed to form. This thermoelectric behavior can be correlated to the order-disorder transition. A reasonable thermoelectric power in the liquid crystal temperature regime was noted. In summary, thermoelectric liquid crystals may have the potential to be utilised in flexible devices, as a standalone power source.

  14. The Crystal Set

    Science.gov (United States)

    Greenslade, Thomas B., Jr.

    2014-01-01

    In past issues of this journal, the late H. R. Crane wrote a long series of articles under the running title of "How Things Work." In them, Dick dealt with many questions that physics teachers asked themselves, but did not have the time to answer. This article is my attempt to work through the physics of the crystal set, which I thought…

  15. Positrons in ionic crystals

    International Nuclear Information System (INIS)

    Pareja, R.

    1988-01-01

    Positron annihilation experiments in ionic crystals are reviewed and their results are arranged. A discussion about the positron states in these materials is made in the light of these results and the different proposed models. The positronium in alkali halides is specially considered. (Author)

  16. Soap Bubbles and Crystals

    Indian Academy of Sciences (India)

    Jean Taylor is Professor. Emerita at Rutgers. University and currently a. Visitor at the Courant. Institute, NYU. She works on problems related to soap bubble froths, crystals, and how they evolve under various physical laws. Much of her recent research has been interdisciplinary, joint work with materials scientists ...

  17. Rhombohedrel Hybrid Crystal Semiconductor Device

    Data.gov (United States)

    National Aeronautics and Space Administration — Development of a new high speed and high efficiency hybrid crystal structure semiconductor device based on the the recent invention of rhombohedral hybrid crystal...

  18. İbn Haldun'un mukaddimequot123sinde toplumun yasalarını keşfeden bir düşünce etkinliği olarak tarih

    OpenAIRE

    KARACA, Çağlar

    2011-01-01

    ÖZET Bu çalıĢmada, Ġbn Haldun‟un tarih anlayıĢı ve toplumun yasalarını keĢfeden bir tarih bilimine katkısı incelenmiĢtir. Ġbn Haldun, kendinden sonraki birçok tarih görüĢüne esin kaynağı olmuĢtur. Ancak onun ününün yanında, Mukaddime‟deki fikirlerin ve tarihsel etkinliğin kuramsal bir değerlendirmesi sönük kalmıĢtır. Ġbn Haldun, kurucusu olduğu umran biliminde tarihsel zorunlulukları, toplumun hal ve tavırlarını keĢfetmeyi amaçlamaktadır. Bir Ġslam bilgini olarak, Aristoteles‟ten et...

  19. Electrical properties of molecular crystals

    International Nuclear Information System (INIS)

    Barraud, A.

    1968-01-01

    This literature survey summarizes the electrical properties of molecular crystals: molecular crystal structure, transport and excitation mechanisms of charge-carriers, and differences compared to inorganic semi-conductors. The main results concerning the electrical conductivity of the most-studied molecular crystals are presented, together with the optical and photo-electrical properties of these crystals. Finally the different types of electrical measurements used are reviewed, as well as the limits of each method. (author) [fr

  20. 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

  1. Surface properties of HMX crystal

    Science.gov (United States)

    Yee, R. Y.; Adicoff, A.; Dibble, E. J.

    1980-01-01

    The surface properties of Beta-HMX crystals were studied. The surface energies of three principal crystal faces were obtained by measuring contact angles with several reference liquids. The surface energies and polarity of the three crystal faces are found to be different.

  2. Optimization of photonic crystal cavities

    DEFF Research Database (Denmark)

    Wang, Fengwen; Sigmund, Ole

    2017-01-01

    We present optimization of photonic crystal cavities. The optimization problem is formulated to maximize the Purcell factor of a photonic crystal cavity. Both topology optimization and air-hole-based shape optimization are utilized for the design process. Numerical results demonstrate...... that the Purcell factor of the photonic crystal cavity can be significantly improved through optimization....

  3. Small Business Innovations (Crystal Components)

    Science.gov (United States)

    1991-01-01

    Scientific Materials Corporation, Bozeman, MT developed the SciMax line of improved Nd:Yag crystals under an Small Business Innovation Research (SBIR) contract with Langley Research Center. They reduced the amount of water trapped in the crystals during growth to improve the optical quality and efficiency. Applications of the crystals include fiber optics, telecommunications, welding, drilling, eye surgery and medical instrumentation.

  4. A Few Good Crystals Please

    Science.gov (United States)

    Judge, Russell A.; Snell, Edward H.

    1999-01-01

    Part of the challenge of macromolecular crystal growth for structure determination is obtaining an appropriate number of crystals with a crystal volume suitable for X-ray analysis. In this respect an understanding of the effect of solution conditions on macromolecule nucleation rates is advantageous. This study investigated the effects of solution conditions on the nucleation rate and final crystal size of two crystal systems; tetragonal lysozyme and glucose isomerase. Batch crystallization plates were prepared at given solution concentration and incubated at set temperatures over one week. The number of crystals per well with their size and axial ratios were recorded and correlated with solution conditions. Duplicate experiments indicate the reproducibility of the technique. Results for each system showing the effect of supersaturation, incubation temperature and solution pH on nucleation rates will be presented and discussed. In the case of lysozyme, having optimized solution conditions to produce an appropriate number of crystals of a suitable size, a batch of crystals were prepared under exactly the same conditions. Fifty of these crystals were analyzed by x-ray techniques. The results indicate that even under the same crystallization conditions, a marked variation in crystal properties exists.

  5. Crystal engineering: A brief overview

    Indian Academy of Sciences (India)

    Crystal engineering demands a detailed and thorough knowledge of intermolecular interactions, which act as the supramolecular glue that binds molecules into crystals. It also requires systematic strategies for the design of a crystal, the architectural blueprint as it were. Finally, this enterprise needs to be geared towards a ...

  6. Design studies on staffing requirements for the new generation nuclear power units of WWER-640 and BN-800 reactor types

    International Nuclear Information System (INIS)

    Solovyov, D.F.

    2001-01-01

    The paper outlines the main staffing requirements for the new generation power units with nuclear reactors. These requirements were developed taking into account IAEA recommendations. NPP staffing structure is described, including the main and auxiliary personnel. The main principles of personnel number determination are given. Special attention is taken to the issues of personnel skill and training, including both theoretical education and practical work on the power units in operation. The use of simulators, system of knowledge control and structure of training are considered. ''Shopless'' staffing structure approach is proposed for the NPP, assuming that the main scope of repair work is performed by the central repair organization, thus increasing the quality of repair and decreasing the number of personnel on the plant. Data are given on the personnel number for the WWER-640 and the BN-800 reactor designs. Specialists of the ''ATOMENERGOPROJECT'' Institute started their work on staffing on the early development stage of the basic design of WWER-640 reactor power unit which is the forerunner of the new generation reactors. This work was based on the approaches taken by the chief engineers of NPPs in operation during their meeting held in 1989 in Kalinin NPP. At this meeting definite decision was taken on changing over to involving manufacturer in the repair work of NPP components using manufacturer's technology. In 1992 the meeting of representatives of suppliers of the main components was held where representatives of ''ATOMENERGOREMONT'' and ''LENENERGOREMONT'' were present. The suppliers agreed on carrying out repair works on the components they produced. For this purpose special departments were set up having some experience. This repair work is already carried out by ''ATOMENERGOREMONT'' on some nuclear power plants. ''LENENERGOREMONT'' has gained considerable experience in this kind of repair work on the turbines of LO-1 and LO-2 NPP in Finland. Within the

  7. Negishi Cross-Coupling Is Compatible with a Reactive B-Cl Bond: Development of a Versatile Late-Stage Functionalization of 1,2-Azaborines and Its Application to the Synthesis of New BN Isosteres of Naphthalene and Indenyl.

    Science.gov (United States)

    Brown, Alec N; Li, Bo; Liu, Shih-Yuan

    2015-07-22

    The compatibility of the Negishi cross-coupling reaction with the versatile B-Cl functionality has been demonstrated in the context of late-stage functionalization of 1,2-azaborines. Alkyl-, aryl-, and alkenylzinc reagents have been utilized for the functionalization of the triply orthogonal precursor 3-bromo-1-(tert-butyldimethylsilyl)-2-chloro-1,2-dihydro-1,2-azaborine (2) to furnish new 2,3-substituted monocyclic 1,2-azaborines. This methodology has enabled the synthesis of previously elusive BN-naphthalene and BN-indenyl structures from a common intermediate.

  8. The influence of additives on crystallization of blends based on polylactid acid

    Science.gov (United States)

    Perd’ochová, D.; Tomanová, K.; Alexy, P.; Bočkaj, J.; Feranc, J.; Plavec, R.; Omaníková, L.; Jurkovič, P.; Prikřyl, R.

    2017-11-01

    The sustainable development consists of the effort of replacing commonly used polymer materials for the biodegradable ones. They do not have sufficient physical and mechanical properties, therefore they have to be modified by producing various ratio mixtures or with the additives. Improving their processability and properties is an important challenge to be afforded before using these materials on the market. One way to improve the properties of these materials is to prepare their blends [1]. The most common way of the preparation of packaging materials is the injection moulding, where the crystallization of material is very important. That is the reason the crystallization has become one of the most studied characteristics of biodegradable blends based on PLA / PHB. The work is a contribution to works that deal with the description of the structure of PLA / PHB blends, which have been modified by the addition of various types of additives, mainly nucleating agents and plasticizers [2]. The films of these blends keep approximately unchanged mechanical properties after two weeks of storage. The presence of plasticizer (ATBC) and nucleating agent (BN) has no significant impact on the processing stability of PLA/PHB blends. The results show that the combination of the plasticizer and nucleating agent greatly affects the process of crystallization of PLA/PHB blends as well as the ratio of polymers and the heat treatment process.

  9. Crystal Engineering of Hand-Twisted Helical Crystals.

    Science.gov (United States)

    Saha, Subhankar; Desiraju, Gautam R

    2017-02-08

    A strategy is outlined for the design of hand-twisted helical crystals. The starting point in the exercise is the one-dimensional (1D) plastic crystal, 1,4-dibromobenzene, which is then changed to a 1D elastic crystal, exemplified by 4-bromophenyl 4'-chlorobenzoate, by introduction of a molecular synthon -O-CO- in lieu of the supramolecular synthon Br···Br in the precursor. The 1D elastic crystals are next modified to two-dimensional (2D) elastic crystals, of the type 4-bromophenyl 4'-nitrobenzoate where the halogen bonding and C-H···O hydrogen bonding are well-matched. Finally, varying the interaction strengths in these 2D elastic crystals gives plastic crystals with two pairs of bendable faces but without slip planes. Typical examples are 4-chlorophenyl and 4-bromophenyl 4'-nitrobenzoate. This type of 2D plasticity represents a new type of bendable crystals in which plastic behavior is seen with a fair degree of isotropic character in the crystal packing. The presence of two sets of bendable faces, generally orthogonal to each other, allows for the possibility of hand-twisting of the crystals to give grossly helical morphologies. Accordingly, we propose the name hand-twisted helical crystals for these substances.

  10. Graphene-based photonic crystal

    International Nuclear Information System (INIS)

    Berman, Oleg L.; Boyko, Vladimir S.; Kezerashvili, Roman Ya.; Kolesnikov, Anton A.; Lozovik, Yurii E.

    2010-01-01

    A novel type of photonic crystal formed by embedding a periodic array of constituent stacks of alternating graphene and dielectric discs into a background dielectric medium is proposed. The photonic band structure and transmittance of such photonic crystal are calculated. The graphene-based photonic crystals can be used effectively as the frequency filters and waveguides for the far infrared region of electromagnetic spectrum. Due to substantial suppression of absorption of low-frequency radiation in doped graphene the damping and skin effect in the photonic crystal are also suppressed. The advantages of the graphene-based photonic crystal are discussed.

  11. Progress of Pharmaceutical Continuous Crystallization

    Directory of Open Access Journals (Sweden)

    Dejiang Zhang

    2017-06-01

    Full Text Available Crystallization is an important unit operation in the pharmaceutical industry. At present, most pharmaceutical crystallization processes are performed in batches. However, due to product variability from batch to batch and to the low productivity of batch crystallization, continuous crystallization is gaining increasing attention. In the past few years, progress has been made to allow the products of continuous crystallization to meet different requirements. This review summarizes the progress in pharmaceutical continuous crystallization from a product engineering perspective. The advantages and disadvantages of different types of continuous crystallization are compared, with the main difference between the two main types of crystallizers being their difference in residence time distribution. Approaches that use continuous crystallization to meet different quality requirements are summarized. Continuous crystallization has advantages in terms of size and morphology control. However, it also has the problem of a process yield that may be lower than that of a batch process, especially in the production of chirality crystals. Finally, different control strategies are compared.

  12. Liquid crystals in tribology.

    Science.gov (United States)

    Carrión, Francisco-José; Martínez-Nicolás, Ginés; Iglesias, Patricia; Sanes, José; Bermúdez, María-Dolores

    2009-09-18

    Two decades ago, the literature dealing with the possible applications of low molar mass liquid crystals, also called monomer liquid crystals (MLCs), only included about 50 references. Today, thousands of papers, conference reports, books or book chapters and patents refer to the study and applications of MLCs as lubricants and lubricant additives and efforts are made to develop new commercial applications. The development of more efficient lubricants is of paramount technological and economic relevance as it is estimated that half the energy consumption is dissipated as friction. MLCs have shown their ability to form ordered boundary layers with good load-carrying capacity and to lower the friction coefficients, wear rates and contact temperature of sliding surfaces, thus contributing to increase the components service life and to save energy. This review includes the use of MLCs in lubrication, and dispersions of MLCs in conventional polymers (PDMLCs). Finally, new lubricating system composed of MLC blends with surfactants, ionic liquids or nanophases are considered.

  13. Liquid crystal dimers

    CERN Document Server

    Kumar Pal, Santanu

    2017-01-01

    This book covers in-depth discussion of design principles, synthesis and thermal behavior of all types of liquid crystal (LC) dimers. The text presents recent advances in the field of LC dimers consisting of different mesogenic units such as calamitic, discotic and bent-core molecules. It starts with a chapter on the introduction of liquid crystal dimers, including their odd-even behavior, basic classification of dimers and common mesophases in dimers. The text shows how the molecular architectures are being used to develop new materials to study a range of interesting phenomena such as the biaxial nematic phase containing rod-like and disc-like mesogenic units. Finally, the text presents perspectives related to technological relevance of these dimers such as dopants in LC display mixtures exhibiting faster relaxation time, strong flexoelectric coupling and others to effect control over the properties of these materials.

  14. Liquid crystal colloids

    CERN Document Server

    Muševič, Igor

    2017-01-01

    This book brings together the many concepts and discoveries in liquid crystal colloids contributed over the last twenty years and scattered across numerous articles and book chapters. It provides both a historical overview of the development of the field and a clear perspective on the future applications in photonics. The book covers all phenomena observed in liquid crystal colloids with an emphasis on experimental tools and applications of topology in condensed matter, as well as practical micro-photonics applications. It includes a number of spectacular manifestations of new topological phenomena not found or difficult to observe in other systems. Starting from the early works on nematic colloids, it explains the basics of topological defects in ordered media, charge and winding, and the elastic forces between colloidal particles in nematics. Following a detailed description of experimental methods, such as optical tweezing and particle tracking, the book eases the reader into the theoretical part, which de...

  15. Phononic crystals fundamentals and applications

    CERN Document Server

    Adibi, Ali

    2016-01-01

    This book provides an in-depth analysis as well as an overview of phononic crystals. This book discusses numerous techniques for the analysis of phononic crystals and covers, among other material, sonic and ultrasonic structures, hypersonic planar structures and their characterization, and novel applications of phononic crystals. This is an ideal book for those working with micro and nanotechnology, MEMS (microelectromechanical systems), and acoustic devices. This book also: Presents an introduction to the fundamentals and properties of phononic crystals Covers simulation techniques for the analysis of phononic crystals Discusses sonic and ultrasonic, hypersonic and planar, and three-dimensional phononic crystal structures Illustrates how phononic crystal structures are being deployed in communication systems and sensing systems.

  16. 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.

  17. Radiation thermal processes in Cr13Mo2NbVB steel - the material of the fuel assembly shell in reactor BN-350 under mechanical tests

    Science.gov (United States)

    Larionov, A. S.; Dikov, A. S.; Poltavtseva, V. P.; Kislitsin, S. B.; Kuimova, M. V.; Chernyavskii, A. V.

    2015-04-01

    Regularities of changes of structural-phase state and mechanical properties of steel 13Mo2NbVB - the material of the fuel assembly shell in reactor BN-350 after various mechanical tests at 350°C are experimentally studied. The formation of microprecipitations FeMo, enriched or depleted with molybdenum was found in the short-time mechanical tests, which is the cause of thermal hardening of irradiated Cr13Mo2NbVB steel and its destruction by the ductile-brittle mechanism. On the basis of long-time creep tests it was shown that the material of the spent fuel assembly shell has sufficient resource for long-time storage in the temperature and force conditions simulating long-time storage of spent nuclear fuel.

  18. Cubic (BN)xC2(1-x) ordered alloys: a first-principles study of the structural, electronic, and effective mass properties

    International Nuclear Information System (INIS)

    Paiva, R de; Azevedo, S

    2006-01-01

    We apply a first-principles method based on the density functional theory within the generalized gradient approximation, and the full-potential linear augmented plane-wave method, to calculate the structural and electronic properties of cubic (BN) x C 2(1-x) ordered alloys. We investigate the equilibrium lattice parameters, the bulk moduli, the density of states, the band-gap energies and the effective masses of the conduction and valence bands along the [111],[100] and [110] directions. The obtained results are used to provide effective-mass and Luttinger parameters, and to give an important guideline to the material's design for optoelectronic devices, we link the first-principles band calculations with effective mass theory

  19. Computational investigation of the electronic and structural properties of CN radical on the pristine and Al-doped (6, 0) BN nanotubes

    International Nuclear Information System (INIS)

    Soltani, Alireza; Moradi, Ali Varasteh; Bahari, Mahsa; Masoodi, Anis; Shojaee, Shamim

    2013-01-01

    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 · CN on the exterior surface of SWBNNT. Binding energy corresponding to the most stable configuration of CN radical on Al N -doped BNNT is found to be −471.73 kJ mol −1 . The calculated density of states (DOS) reveals that there is a significant orbital hybridization between · 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

  20. Magnetic photonic crystals

    Energy Technology Data Exchange (ETDEWEB)

    Lyubchanskii, I L [Donetsk Physical and Technical Institute of the National Academy of Sciences of Ukraine, 72, R. Luxemburg St., 83114 Donetsk (Ukraine); Dadoenkova, N N [Donetsk Physical and Technical Institute of the National Academy of Sciences of Ukraine, 72, R. Luxemburg St., 83114 Donetsk (Ukraine); Lyubchanskii, M I [Donetsk Physical and Technical Institute of the National Academy of Sciences of Ukraine, 72, R. Luxemburg St., 83114 Donetsk (Ukraine); Shapovalov, E A [Department of Physics, Donetsk National University, 24, Universitetskaya St., 83055 Donetsk (Ukraine); Rasing, Th [NSRIM Institute, University of Nijmegen, 6525 ED, Nijmegen (Netherlands)

    2003-09-21

    In this paper we outline a new direction in the area of photonic crystals (PCs), or photonic band gap materials, i.e. one-, two-, or three-dimensional superstructures with periods that are comparable with the wavelengths of electromagnetic radiation. The main (and principal) characteristic of this new class of PCs is the presence of magnetically ordered components (or external magnetic field). The linear and nonlinear optical properties of such magnetic PCs are discussed. (topical review)

  1. LEAR Crystal Barrel Detector

    Energy Technology Data Exchange (ETDEWEB)

    Braune, K.; Keh, S.; Montanet, L.; Zoll, J.; Beckmann, R.; Friedrich, J.; Heinsius, H.; Kiel, T.; Lewendel, B.; Pegel, C.; and others

    1988-11-20

    The features of the Crystal Barrel Detector which is in preparation for LEAR at CERN, are discussed. The physics aims include q-barq- and exotics-spectroscopy and a detailed investigation of yet unknown p-barp-anihilation channels. An eventual later use on the PSI-B-Meson-Factory is discussed. The paper finishes with a description of the present status of the project.

  2. Rare earths crystal chemistry

    International Nuclear Information System (INIS)

    Wells, A.F.

    1988-01-01

    From the viewpoint of general crystal chemistry principles and on the basis of modern data the structural chemistry of rare earth compounds in different oxidation degrees (2,3,4) is briefly presented. The change of the structure type of oxides, halides and some other compounds of rare earths, as well as the coordination number of the central atom from lanthanide ionic radius is considered

  3. Dosimetry for Crystals Irradiation

    CERN Document Server

    Lecomte, Pierre

    2005-01-01

    Before shipment to CMS, all PbWO4 crystals produced in China are irradiated there with 60 Co , in order to insure that the induced absorption coefficient is within specifications. Acceptance tests at CERNand at ENEA also include irradiation with gamma rays from 60 Co sources. There were initially discrepancies in quoted doses and doserates as well as in induced absorption coefficients. The present work resolves the discrepancies in irradiation measurements and defines common dosimetry methods for consistency checks between irradiation facilities.

  4. Crystals against cancer

    CERN Multimedia

    2009-01-01

    This is a remarkable example of direct technology transfer from particle physics to medicine. Clinical trials have begun in Portugal on a new medical imaging system for the diagnosis of breast cancer, which uses positron emission tomography (PET). The system, developed by a Portuguese consortium in collaboration with CERN and laboratories participating in the Crystal Clear collaboration, will detect even the smallest tumours and thus help avoid unnecessary biopsies.

  5. Dynamics of Vortex Crystals.*

    Science.gov (United States)

    Jin, D. Z.; Dubin, D. H. E.

    1997-11-01

    We discuss the linear and nonlinear 2D dynamics of vortex crystals observed in experiments on pure electron plasmas [1]. Vortex crystals are rods of intense vorticity that form stable geometrical patterns in a low vorticity background. We consider a system consisting of several point vortices inside an initially circular background of constant vorticity. When the point vorticities have sufficiently small circulation compared to the background, there exist two time scales in the dynamics: a slow time scale associated with the motion of the point vortices and the driven response in the background; and a fast time scale associated with freely streaming Kelvin waves on the edge of the background vorticity profile. On the slow time scale, we show that the linear dynamics of the point vortices is equivalent to the classical problem of point vortices inside a circular conducting boundary, with the boundary radius equal to that of the background. However, filamentation involving both slow and fast time scales and subsequent wave breaking eventually occurs due to the nonlinear processes. This causes turbulent mixing of the background, and may be responsible for the irreversible ``cooling'' of the point vortex motions toward the vortex crystal state. Supported by NSF grant PHY94-21318. [1] K.S. Fine et al., Phys. Rev. Lett. 75, 3277 (1995).

  6. Dynamics of Vortex Crystals

    Science.gov (United States)

    Jin, D. Z.; Dubin, D. H. E.

    1997-11-01

    This poster discusses the linear and nonlinear dynamics of vortex crystals observed in experiments on pure electron plasmas [1]. Vortex crystals are rods of intense density that form stable geometrical patterns in a low density background. We consider a system consisting of several line charges inside an initially circular background of constant density. When the line charges have sufficiently small charge per unit length compared to the background, there exist two time scales in the dynamics: a slow time scale associated with the motion of the line charges and the driven response in the background; and a fast time scale associated with freely streaming diocotron waves on the edge of the background density profile. On the slow time scale, we show that the linear dynamics of the line charges is equivalent to the classical problem of line charges inside a circular conducting wall, with the wall radius equal to that of the background. However, filamentation involving both slow and fast time scales and subsequent wave breaking eventually occurs due to the nonlinear processes. This causes turbulent mixing of the background, and may be responsible for the irreversible ``cooling'' of the line charge motions toward the vortex crystal state. Supported by NSF grant PHY94-21318. [1] K.S. Fine et al., Phys. Rev. Lett. 75, 3277 (1995).

  7. Slotted Photonic Crystal Sensors

    Science.gov (United States)

    Scullion, Mark G.; Krauss, Thomas F.; Di Falco, Andrea

    2013-01-01

    Optical biosensors are increasingly being considered for lab-on-a-chip applications due to their benefits such as small size, biocompatibility, passive behaviour and lack of the need for fluorescent labels. The light guiding mechanisms used by many of them results in poor overlap of the optical field with the target molecules, reducing the maximum sensitivity achievable. This review article presents a new platform for optical biosensors, namely slotted photonic crystals, which provide higher sensitivities due to their ability to confine, spatially and temporally, the optical mode peak within the analyte itself. Loss measurements showed values comparable to standard photonic crystals, confirming their ability to be used in real devices. A novel resonant coupler was designed, simulated, and experimentally tested, and was found to perform better than other solutions within the literature. Combining with cavities, microfluidics and biological functionalization allowed proof-of-principle demonstrations of protein binding to be carried out. Higher sensitivities were observed in smaller structures than possible with most competing devices reported in the literature. This body of work presents slotted photonic crystals as a realistic platform for complete on-chip biosensing; addressing key design, performance and application issues, whilst also opening up exciting new ideas for future study. PMID:23503295

  8. The fluid phenomena in the crystallization of the protein crystal

    International Nuclear Information System (INIS)

    Duan Li; Kang Qi

    2008-01-01

    This paper reports that an optical diagnostic system consisting of Mach–Zehnder interferometer with a phase shift device and image processor has been used for study of the kinetics of protein crystal growing process. The crystallization process of protein crystal by vapour diffusion is investigated. The interference fringes are observed in real time. The present experiment demonstrates that the diffusion and the sedimentation influence the crystallization of protein crystal which grows in solution, and the concentration capillary convection associated with surface tension occurs at the vicinity of free surface of the protein mother liquor, and directly affects on the outcome of protein crystallization. So far the detailed analysis and the important role of the fluid phenomena in protein crystallization have been discussed a little in both space- and ground-based crystal growth experiments. It is also found that these fluid phenomena affect the outcome of protein crystallization, regular growth, and crystal quality. This may explain the fact that many results of space-based investigation do not show overall improvement. (cross-disciplinary physics and related areas of science and technology)

  9. SUPERLUMINOUS SUPERNOVA SN 2015bn IN THE NEBULAR PHASE: EVIDENCE FOR THE ENGINE-POWERED EXPLOSION OF A STRIPPED MASSIVE STAR

    Energy Technology Data Exchange (ETDEWEB)

    Nicholl, M.; Berger, E.; Blanchard, P. K.; Challis, P.; Cowperthwaite, P. S. [Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA 02138 (United States); Margutti, R. [Center for Cosmology and Particle Physics, New York University, 4 Washington Place, New York, NY 10003 (United States); Chornock, R. [Astrophysical Institute, Department of Physics and Astronomy, 251B Clippinger Lab, Ohio University, Athens, OH 45701 (United States); Jerkstrand, A.; Smartt, S. J.; Inserra, C.; Kankare, E.; Maguire, K. [Astrophysics Research Centre, School of Mathematics and Physics, Queens University Belfast, Belfast BT7 1NN (United Kingdom); Arcavi, I.; Hosseinzadeh, G.; Howell, D. A. [Las Cumbres Observatory Global Telescope, 6740 Cortona Drive, Suite 102, Goleta, CA 93111 (United States); Chambers, K. C.; Magnier, E. A. [Institute for Astronomy, University of Hawaii at Manoa, Honolulu, HI 96822 (United States); Chen, T.-W. [Max-Planck-Institut für Extraterrestrische Physik, Giessenbachstraße 1, D-85748, Garching (Germany); Gal-Yam, A. [Benoziyo Center for Astrophysics, Weizmann Institute of Science, Rehovot 76100 (Israel); Mazzali, P. A., E-mail: matt.nicholl@cfa.harvard.edu [Astrophysics Research Institute, Liverpool John Moores University, IC2, Liverpool Science Park, 146 Brownlow Hill, Liverpool L3 5RF (United Kingdom); and others

    2016-09-10

    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){sup −1} to 1.7 mag (100 days){sup −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 {sup 56}Ni 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 {sub B} < −17. Both the light curve and spectrum of SN 2015bn are consistent with an engine-driven explosion ejecting 7–30 M {sub ⊙} of oxygen-dominated ejecta (for reasonable choices in temperature and opacity). A strong and relatively narrow O i λ 7774 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.

  10. 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

  11. DDA Computations of Porous Aggregates with Forsterite Crystals: Effects of Crystal Shape and Crystal Mass Fraction

    Science.gov (United States)

    Wooden, Diane H.; Lindsay, Sean S.; Harker, David; Woodward, Charles; Kelley, Michael S.; Kolokolova, Ludmilla

    2015-01-01

    Porous aggregate grains are commonly found in cometary dust samples and are needed to model cometary IR spectral energy distributions (SEDs). Models for thermal emissions from comets require two forms of silicates: amorphous and crystalline. The dominant crystal resonances observed in comet SEDs are from Forsterite (Mg2SiO4). The mass fractions that are crystalline span a large range from 0.0 25 AU at 1E6 yr) by inner disk materials (crystals) are challenged to yield the highend-range of cometary crystal mass fractions. However, in current thermal models, Forsterite crystals are not incorporated into larger aggregate grains but instead only are considered as discrete crystals. A complicating factor is that Forsterite crystals with rectangular shapes better fit the observed spectral resonances in wavelength (11.0-11.15 microns, 16, 19, 23.5, 27, and 33 microns), feature asymmetry and relative height (Lindley et al. 2013) than spherically or elliptically shaped crystals. We present DDA-DDSCAT computations of IR absorptivities (Qabs) of 3 micron-radii porous aggregates with 0.13 crystals. We can produce crystal resonances with similar appearance to the observed resonances of comet Hale- Bopp. Also, a lower mass fraction of crystals in aggregates can produce the same spectral contrast as a higher mass fraction of discrete crystals; the 11micron and 23 micron crystalline resonances appear amplified when crystals are incorporated into aggregates composed otherwise of spherically shaped amorphous Fe-Mg olivines and pyroxenes. We show that the optical properties of a porous aggregate is not linear combination of its monomers, so aggregates need to be computed. We discuss the consequence of lowering comet crystal mass fractions by modeling IR SEDs with aggregates with crystals, and the implications for radial transport models of our protoplanetary disk.

  12. Cross section measurement for the 10B(n ,t 2 α ) three-body reaction at 4.0, 4.5, and 5.0 MeV. II. Experimental setup and results

    Science.gov (United States)

    Wang, Zhimin; Bai, Huaiyong; Zhang, Luyu; Jiang, Haoyu; Lu, Yi; Chen, Jinxiang; Zhang, Guohui; Gledenov, Yu. M.; Sedysheva, M. V.; Khuukhenkhuu, G.

    2017-10-01

    Cross sections of the 10B(n ,t 2 α ) three-body reaction were measured at En=4.0 , 4.5, and 5.0 MeV using a twin gridded ionization chamber and a thin-film 10B sample. The present paper is the second part of the work. A digital data-acquisition system was developed for the gridded ionization chamber based on the waveform digitizer. A thin-film 10B sample was designed and prepared. The number of 10B atoms in the sample was determined by the relative method using the thermal neutron induced 10B(nt h,α )7Li and 6Li(nt h,t )4He reactions with a 6LiF sample as the reference. The measurement of the 10B(n ,t 2 α ) reaction was performed at the 4.5 MV Van de Graaff accelerator of Peking University. In the measurement, the double-coincidence technique was used, which involves the forward-backward and the grid-anode coincidence. In the data processing, the effective event area in the forward two-dimensional spectrum and the time window in the drift-time spectrum were employed to reject the background events. Cross sections of the 10B(n ,t 2 α ) and 10B(n ,α )7Li reactions were obtained. The present results are compared with the data of existing measurements and evaluations.

  13. 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

  14. 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...

  15. Principles of crystallization, and methods of single crystal growth

    International Nuclear Information System (INIS)

    Chacra, T.

    2010-01-01

    Most of single crystals (monocrystals), have distinguished optical, electrical, or magnetic properties, which make from single crystals, key elements in most of technical modern devices, as they may be used as lenses, Prisms, or grating sin optical devises, or Filters in X-Ray and spectrographic devices, or conductors and semiconductors in electronic, and computer industries. Furthermore, Single crystals are used in transducer devices. Moreover, they are indispensable elements in Laser and Maser emission technology.Crystal Growth Technology (CGT), has started, and developed in the international Universities and scientific institutions, aiming at some of single crystals, which may have significant properties and industrial applications, that can attract the attention of international crystal growth centers, to adopt the industrial production and marketing of such crystals. Unfortunately, Arab universities generally, and Syrian universities specifically, do not give even the minimum interest, to this field of Science.The purpose of this work is to attract the attention of Crystallographers, Physicists and Chemists in the Arab universities and research centers to the importance of crystal growth, and to work on, in the first stage to establish simple, uncomplicated laboratories for the growth of single crystal. Such laboratories can be supplied with equipment, which are partly available or can be manufactured in the local market. Many references (Articles, Papers, Diagrams, etc..) has been studied, to conclude the most important theoretical principles of Phase transitions,especially of crystallization. The conclusions of this study, are summarized in three Principles; Thermodynamic-, Morphologic-, and Kinetic-Principles. The study is completed by a brief description of the main single crystal growth methods with sketches, of equipment used in each method, which can be considered as primary designs for the equipment, of a new crystal growth laboratory. (author)

  16. Crystal heating on the JUMBO double crystal monochromator at SSRL

    International Nuclear Information System (INIS)

    Rowen, M.; Waldhauer, A.; Pianetta, P.

    1986-01-01

    Heating by intense synchrotron radiation causes the lattice of the first crystal in the JUMBO double crystal monochromator at SSRL to expand. Because the two crystals no longer have the same lattice spacing, they diffract X-rays of the same wavelength at different angles. This causes shifts in energy calibration and beam movement at the sample with change in photon energy or as the current in the storage ring decays. A simple thermal model that predicts the change in wavelength and angle of the monochromatic beam is described. These shifts are proportional to I sin theta tan theta, where I is the SPEAR ring current and theta is the angle of the beam incident on the first crystal. Heating experiments were conducted with Ge(111), quartz(10anti 10), and InSb(111) crystals. Bragg angle shifts of up to 0.25 0 were measured with high precision encoders mounted directly on the crystal goniometers. Photon energy calibration shifts of up to 3.5 eV (at 1700 eV) were measured. Preliminary results show good agreement with the model for Ge and quartz crystals, but not for InSb crystals. Further study is needed to refine the model for Ge and quartz crystals and to determine a better one for InSb. (orig.)

  17. Trial by fire: are the crystals macromolecules?

    Science.gov (United States)

    Raghunathan, Kannan; Harris, Paul T; Arvidson, Dennis N

    2010-05-01

    Protein crystallization screens frequently yield salt crystals as well as protein crystals. A simple method for determining whether a crystal is composed of salt or macromolecules is suggested. A drop containing one or more crystals is transferred to a glass cover slip and the cover slip is then passed through the flame of a Bunsen burner. Macromolecule crystals are destroyed by this treatment, while salt crystals generally remain. The test can be performed after other commonly used tests such as crushing and staining.

  18. 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.

  19. Crystal structure of pseudoguainolide

    Directory of Open Access Journals (Sweden)

    Noureddine Beghidja

    2015-03-01

    Full Text Available The lactone ring in the title molecule, C15H22O3 (systematic name: 3,4a,8-trimethyldodecahydroazuleno[6,5-b]furan-2,5-dione, assumes an envelope conformation with the methine C atom adjacent to the the methine C atom carrying the methyl substituent being the flap atom. The other five-membered ring adopts a twisted conformation with the twist being about the methine–methylene C—C bond. The seven-membered ring is based on a twisted boat conformation. No specific interactions are noted in the the crystal packing.

  20. Photonic crystal optofluidic biolaser

    Science.gov (United States)

    Mozaffari, Mohammad Hazhir; Ebnali-Heidari, Majid; Abaeiani, Gholamreza; Moravvej-Farshi, Mohammad Kazem

    2017-09-01

    Optofluidic biolasers are recently being considered in bioanalytical applications due to their advantages over the conventional biosensing methods Exploiting a photonic crystal slab with selectively dye-infiltrated air holes, we propose a new optofluidic heterostructure biolaser, with a power conversion efficiency of 25% and the spectral linewidth of 0.24 nm. Simulations show that in addition to these satisfactory lasing characteristics, the proposed lab-on-a-chip biolaser is highly sensitive to the minute biological changes that may occur in its cavity and can detect a single virus with a radius as small as 13 nm.

  1. Inorganic Crystal Structure Database (ICSD)

    Science.gov (United States)

    SRD 84 FIZ/NIST Inorganic Crystal Structure Database (ICSD) (PC database for purchase)   The Inorganic Crystal Structure Database (ICSD) is produced cooperatively by the Fachinformationszentrum Karlsruhe(FIZ) and the National Institute of Standards and Technology (NIST). The ICSD is a comprehensive collection of crystal structure data of inorganic compounds containing more than 140,000 entries and covering the literature from 1915 to the present.

  2. Physical Properties of Liquid Crystals

    CERN Document Server

    Gray, George W; Spiess, Hans W

    1999-01-01

    This handbook is a unique compendium of knowledge on all aspects of the physics of liquid crystals. In over 500 pages it provides detailed information on the physical properties of liquid crystals as well as the recent theories and results on phase transitions, defects and textures of different types of liquid crystals. An in-depth understanding of the physical fundamentals is a prerequisite for everyone working in the field of liquid crystal research. With this book the experts as well as graduate students entering the field get all the information they need.

  3. Preventing Crystal Agglomeration of Pharmaceutical Crystals Using Temperature Cycling and a Novel Membrane Crystallization Procedure for Seed Crystal Generation

    Directory of Open Access Journals (Sweden)

    Elena Simone

    2018-01-01

    Full Text Available In this work, a novel membrane crystallization system was used to crystallize micro-sized seeds of piroxicam monohydrate by reverse antisolvent addition. Membrane crystallization seeds were compared with seeds produced by conventional antisolvent addition and polymorphic transformation of a fine powdered sample of piroxicam form I in water. The membrane crystallization process allowed for a consistent production of pure monohydrate crystals with narrow size distribution and without significant agglomeration. The seeds were grown in 350 g of 20:80 w/w acetone-water mixture. Different seeding loads were tested and temperature cycling was applied in order to avoid agglomeration of the growing crystals during the process. Focused beam reflectance measurement (FBRM; and particle vision and measurement (PVM were used to monitor crystal growth; nucleation and agglomeration during the seeded experiments. Furthermore; Raman spectroscopy was used to monitor solute concentration and estimate the overall yield of the process. Membrane crystallization was proved to be the most convenient and consistent method to produce seeds of highly agglomerating compounds; which can be grown via cooling crystallization and temperature cycling.

  4. Aluminum-air battery crystallizer

    Science.gov (United States)

    Maimoni, A.

    1987-01-01

    A prototype crystallizer system for the aluminum-air battery operated reliably through simulated startup and shutdown cycles and met its design objectives. The crystallizer system allows for crystallization and removal of the aluminium hydroxide reaction product; it is required to allow steady-state and long-term operation of the aluminum-air battery. The system has to minimize volume and maintain low turbulence and shear to minimize secondary nucleation and energy consumption while enhancing agglomeration. A lamella crystallizer satisfies system constraints.

  5. Crystal face temperature determination means

    Science.gov (United States)

    Nason, D.O.; Burger, A.

    1994-11-22

    An optically transparent furnace having a detection apparatus with a pedestal enclosed in an evacuated ampule for growing a crystal thereon is disclosed. Temperature differential is provided by a source heater, a base heater and a cold finger such that material migrates from a polycrystalline source material to grow the crystal. A quartz halogen lamp projects a collimated beam onto the crystal and a reflected beam is analyzed by a double monochromator and photomultiplier detection spectrometer and the detected peak position in the reflected energy spectrum of the reflected beam is interpreted to determine surface temperature of the crystal. 3 figs.

  6. Liquid Crystals in Tribology

    Directory of Open Access Journals (Sweden)

    María-Dolores Bermúdez

    2009-09-01

    Full Text Available Two decades ago, the literature dealing with the possible applications of low molar mass liquid crystals, also called monomer liquid crystals (MLCs, only included about 50 references. Today, thousands of papers, conference reports, books or book chapters and patents refer to the study and applications of MLCs as lubricants and lubricant additives and efforts are made to develop new commercial applications. The development of more efficient lubricants is of paramount technological and economic relevance as it is estimated that half the energy consumption is dissipated as friction. MLCs have shown their ability to form ordered boundary layers with good load-carrying capacity and to lower the friction coefficients, wear rates and contact temperature of sliding surfaces, thus contributing to increase the components service life and to save energy. This review includes the use of MLCs in lubrication, and dispersions of MLCs in conventional polymers (PDMLCs. Finally, new lubricating system composed of MLC blends with surfactants, ionic liquids or nanophases are considered.

  7. Tunable Topological Phononic Crystals

    KAUST Repository

    Chen, Zeguo

    2016-05-27

    Topological insulators first observed in electronic systems have inspired many analogues in photonic and phononic crystals in which remarkable one-way propagation edge states are supported by topologically nontrivial band gaps. Such band gaps can be achieved by breaking the time-reversal symmetry to lift the degeneracy associated with Dirac cones at the corners of the Brillouin zone. Here, we report on our construction of a phononic crystal exhibiting a Dirac-like cone in the Brillouin zone center. We demonstrate that simultaneously breaking the time-reversal symmetry and altering the geometric size of the unit cell result in a topological transition that we verify by the Chern number calculation and edge-mode analysis. We develop a complete model based on the tight binding to uncover the physical mechanisms of the topological transition. Both the model and numerical simulations show that the topology of the band gap is tunable by varying both the velocity field and the geometric size; such tunability may dramatically enrich the design and use of acoustic topological insulators.

  8. Electron spectroscopy of crystals

    CERN Document Server

    Nemoshkalenko, V V

    1979-01-01

    This book is conceived as a monograph, and represents an up-to-date collection of information concerning the use of the method of X-ray photoelectron spec­ troscopy in the study of the electron structure of crystals, as well as a personal interpretation of the subject by the authors. In a natural way, the book starts in Chapter 1 with a recapitulation of the fundamentals of the method, basic relations, principles of operation, and a com­ parative presentation of the characteristics and performances of the most com­ monly used ESCA instruments (from the classical ones-Varian, McPherson, Hewlett Packard, and IEEE-up to the latest model developed by Professor Siegbahn in Uppsala), and continues with a discussion of some of the difficult problems the experimentalist must face such as calibration of spectra, prepara­ tion of samples, and evaluation of the escape depth of electrons. The second chapter is devoted to the theory of photoemission from crystal­ line solids. A discussion of the methods of Hartree-Fo...

  9. Reconfigurable topological photonic crystal

    Science.gov (United States)

    Shalaev, Mikhail I.; Desnavi, Sameerah; Walasik, Wiktor; Litchinitser, Natalia M.

    2018-02-01

    Topological insulators are materials that conduct on the surface and insulate in their interior due to non-trivial topology of the band structure. The edge states on the interface between topological (non-trivial) and conventional (trivial) insulators are topologically protected from scattering due to structural defects and disorders. Recently, it was shown that photonic crystals (PCs) can serve as a platform for realizing a scatter-free propagation of light waves. In conventional PCs, imperfections, structural disorders, and surface roughness lead to significant losses. The breakthrough in overcoming these problems is likely to come from the synergy of the topological PCs and silicon-based photonics technology that enables high integration density, lossless propagation, and immunity to fabrication imperfections. For many applications, reconfigurability and capability to control the propagation of these non-trivial photonic edge states is essential. One way to facilitate such dynamic control is to use liquid crystals (LCs), which allow to modify the refractive index with external electric field. Here, we demonstrate dynamic control of topological edge states by modifying the refractive index of a LC background medium. Background index is changed depending on the orientation of a LC, while preserving the topology of the system. This results in a change of the spectral position of the photonic bandgap and the topological edge states. The proposed concept might be implemented using conventional semiconductor technology, and can be used for robust energy transport in integrated photonic devices, all-optical circuity, and optical communication systems.

  10. Amine free crystal structure: The crystal structure of d(CGCGCG)2 and methylamine complex crystal

    International Nuclear Information System (INIS)

    Ohishi, Hirofumi; Tsukamoto, Koji; Hiyama, Yoichi; Maezaki, Naoyoshi; Tanaka, Tetsuaki; Ishida, Toshimasa

    2006-01-01

    We succeeded in the crystallization of d(CGCGCG) 2 and methylamine Complex. The crystal was clear and of sufficient size to collect the X-ray crystallographic data up to 1.0 A resolution using synchrotron radiation. As a result of X-ray crystallographic analysis of 2F o - F c map was much clear and easily traced. It is First time monoamine co-crystallizes with d(CGCGCG) 2 . However, methylamine was not found from the complex crystal of d(CGCGCG) 2 and methylamine. Five Mg ions were found around d(CGCGCG) 2 molecules. These Mg ions neutralized the anion of 10 values of the phosphate group of DNA with five Mg 2+ . DNA stabilized only by a metallic ion and there is no example of analyzing the X-ray crystal structure like this. Mg ion stabilizes the conformation of Z-DNA. To use monoamine for crystallization of DNA, we found that we can get only d(CGCGCG) 2 and Mg cation crystal. Only Mg cation can stabilize the conformation of Z-DNA. The method of using the monoamine for the crystallization of DNA can be applied to the crystallization of DNA of long chain of length in the future like this

  11. İbn Kesīr’in İsrā’īliyyāta Yaklaşımı

    Directory of Open Access Journals (Sweden)

    Harun SAVUT

    2012-03-01

    Full Text Available Kitap ehline dayanan bilgilerin güvenilirliği ilk asırlardan itibaren İslam âlimlerinin gündemini meşgul etmiştir. İsrā’īliyyāt kavramı etrafında şekillenen tartışmalar günümüzde de devam etmektedir. İsrā’īliyyāt konusunda öne çıkan âlimlerden birisi belki de en önemlisi İbn Kes̠īr’dir (ö.774/1373. O, seleften gelen rivayet ve değerlendirmeleri göz önünde bulundurarak İsrā’īliyyātı belli kriterler çerçevesinde ele almıştır. İbn Kes̠īr İsrā’īliyyātı toptan reddetmemiş, meseleyi İslam’a uyup uymaması açısından değerlendirmiş, tek tek rivayetler üzerinde uyguladığı tahlil ve analizlerle hangi nakillerin alınıp hangilerinin alınamayacağını hükme bağlamıştır. Onun İsrā’īlî haberler karşısındaki tutumunun bilinmesi, günümüzde konu üzerinden yürütülen tartışmaları sağlam bir zemine oturtabilmek açısından önemlidir. Çünkü onun Tefsīru’l-Ḳur’āni’l-‘aẓīm adlı eseri, İsrā’īliyyāt başlığı altında yapılan çalışmalarda müracaat edilen en önemli kaynaklardan birisidir. Onun konuya yaklaşımı anlaşıldığı oranda önceki âlimlerin İsrā’īliyyāt ile neyi kastettikleri, karşı çıktıkları rivayetlerin neler olduğu, bu tür materyalleri nerelerde kullanma ihtiyacı hissettikleri netleşecektir.

  12. High-dose-rate iridium-192 afterloading therapy combined with external beam radiotherapy for T1c-T3bN0M0 prostate cancer.

    Science.gov (United States)

    Jo, Yoshimasa; Hiratsuka, Junichi; Fujii, Tomohiro; Takenaka, Atsushi; Fujisawa, Masato

    2004-09-01

    To determine the efficacy of radiotherapy (RT) for T1c-T3bN0M0 prostate cancer in a prospective clinical trial of concurrent external beam RT and fractionated iridium-192 high-dose-rate brachytherapy. Included in the study were 98 patients with T1c-T3bN0M0 prostate cancer who were diagnosed between October 1997 and September 2002 and underwent high-dose-rate brachytherapy with external beam RT. Treatment consisted of external beam RT (four ports) to the prostate of 16 fractions of 2.3 Gy to a total dose of 36.8 Gy and high-dose-rate brachytherapy of 4 fractions of 6.0 Gy within 30 hours to a total dose of 24.0 Gy. No patient received adjuvant hormonal therapy after RT. The most recent prostate-specific antigen level was 0.0 to 3.9 ng/mL (median 0.4). Seven patients (7.1%) developed recurrence and treatment was considered a failure (bone metastasis in two and biochemical failure in five). The overall biochemical disease-free survival (bDFS) rate was 95.9% at 2 years and 92.9% at 5 years. The bDFS rate by T stage was 98.6% at 2 years and 95.9% at 5 years for Stage T1c-T2b and 88.0% and 84.0% for Stage T3a-b, respectively (P = 0.047). The 2-year and 5-year bDFS rate was better in patients with an initial prostate-specific antigen level of less than 20 ng/mL compared with 20 ng/mL or greater (98.6% and 97.1% versus 93.1% and 82.8%, respectively, P = 0.0261). Acute toxicity was mild to moderate (Radiation Therapy Oncology Group grade 1-2) and consisted of cystourethritis or proctitis in 29 (29.6%) of 98 patients. With a low complication rate and satisfactory bDFS rates, this combination therapy can be considered an alternative method for clinical Stage T1c-T3b prostate cancer and is expected to improve patient quality of life. Additional long-term follow-up is needed to confirm this treatment.

  13. THEORY OF INCOMMENSURATE CRYSTAL FACETS

    NARCIS (Netherlands)

    VANSMAALEN, S

    1993-01-01

    The morphology of incommensurately modulated crystals is considered. A surface free energy model is constructed which interprets the stabilization of the incommensurate facets as due to surface pinning of the phase of the modulation wave. The stepped nature of the true crystal surface restricts the

  14. Photoelastic sphenoscopic analysis of crystals

    Science.gov (United States)

    Montalto, L.; Rinaldi, D.; Scalise, L.; Paone, N.; Davı, F.

    2016-01-01

    Birefringent crystals are at the basis of various devices used in many fields, from high energy physics to biomedical imaging for cancer detection. Since crystals are the main elements of those devices, a great attention is paid on their quality and properties. Here, we present a methodology for the photoelastic analysis of birefringent crystals, based on a modified polariscope. Polariscopes using conoscopic observation are used to evaluate crystals residual stresses in a precise but time consuming way; in our methodology, the light beam shape, which impinges on the crystal surface, has been changed from a solid cone (conoscopy) to a wedge (sphenoscopy). Since the polarized and coherent light is focused on a line rather than on a spot, this allows a faster analysis which leads to the observation, at a glance, of a spatial distribution of stress along a line. Three samples of lead tungstate crystals have been observed using this technique, and the obtained results are compared with the conoscopic observation. The samples have been tested both in unloaded condition and in a loaded configuration induced by means of a four points bending device, which allows to induce a known stress distribution in the crystal. The obtained results confirm, in a reliable manner, the sensitivity of the methodology to the crystal structure and stress.

  15. Photoelastic sphenoscopic analysis of crystals

    Energy Technology Data Exchange (ETDEWEB)

    Montalto, L. [DIISM, Dip. Di Ingegneria Industriale e Scienze Matematiche—Università Politecnica delle Marche, Ancona (Italy); SIMAU, Dip. Di Scienze e Ingegneria della Materia, dell’ambiente ed Urbanistica—Università Politecnica delle Marche, Ancona (Italy); Rinaldi, D. [SIMAU, Dip. Di Scienze e Ingegneria della Materia, dell’ambiente ed Urbanistica—Università Politecnica delle Marche, Ancona (Italy); Scalise, L.; Paone, N. [DIISM, Dip. Di Ingegneria Industriale e Scienze Matematiche—Università Politecnica delle Marche, Ancona (Italy); Davì, F. [DICEA, Dip. Di Ingegneria Civile, Edile e Architettura—Università Politecnica delle Marche, Ancona (Italy)

    2016-01-15

    Birefringent crystals are at the basis of various devices used in many fields, from high energy physics to biomedical imaging for cancer detection. Since crystals are the main elements of those devices, a great attention is paid on their quality and properties. Here, we present a methodology for the photoelastic analysis of birefringent crystals, based on a modified polariscope. Polariscopes using conoscopic observation are used to evaluate crystals residual stresses in a precise but time consuming way; in our methodology, the light beam shape, which impinges on the crystal surface, has been changed from a solid cone (conoscopy) to a wedge (sphenoscopy). Since the polarized and coherent light is focused on a line rather than on a spot, this allows a faster analysis which leads to the observation, at a glance, of a spatial distribution of stress along a line. Three samples of lead tungstate crystals have been observed using this technique, and the obtained results are compared with the conoscopic observation. The samples have been tested both in unloaded condition and in a loaded configuration induced by means of a four points bending device, which allows to induce a known stress distribution in the crystal. The obtained results confirm, in a reliable manner, the sensitivity of the methodology to the crystal structure and stress.

  16. Growing Crystals on the Ceiling.

    Science.gov (United States)

    Christman, Robert A.

    1980-01-01

    Described is a method of studying growing crystals in a classroom utilizing a carrousel projector standing vertically. A saturated salt solution is placed on a slide on the lens of the projector and the heat from the projector causes the water to evaporate and salt to crystalize. (Author/DS)

  17. Supramolecular chemistry and crystal engineering

    Indian Academy of Sciences (India)

    recognition and binding, ice structures, and supramolecular chemistry. The traditional view is .... pair-wise leads to synthon control and crystal design in multifunctional molecules. ..... Crystal structure of Na(sac)•1.875H2O (Na pink, O red, N blue, S yellow, C gray, H cream). The regular region on the left side has 10 sac. −.

  18. MyCrystals - a simple visual data management program for laboratory-scale crystallization experiments

    DEFF Research Database (Denmark)

    Løvgreen, Monika Nøhr; Løvgreen, Mikkel; Christensen, Hans Erik Mølager

    2009-01-01

    MyCrystals is designed as a user-friendly program to display crystal images and list crystallization conditions. The crystallization conditions entry fields can be customized to suit the experiments. MyCrystals is also able to sort the images by the entered crystallization conditions, which...

  19. Lamella settler crystallizer

    Science.gov (United States)

    Maimoni, Arturo

    1990-01-01

    A crystallizer which incorporates a lamella settler and which is particularly applicable for use in batteries and power cells for electric vehicles or stationary applications. The lamella settler can be utilized for coarse particle separation or for agglomeration, and is particularly applicable to aluminum-air batteries or power cells for solving the hydrargillite (aluminum-hydroxide) removal problems from such batteries. This invention provides the advantages of very low energy consumption, turbulence, shear, cost and maintenance. Thus, due to the low shear and low turbulence of this invention, it is particularly effective in the control of aluminum hydroxide particle size distribution in the various sections of an aluminum-air system, as well as in other electrochemical systems requiring separation for phases of different densities.

  20. Natural photonic crystals

    Science.gov (United States)

    Vigneron, Jean Pol; Simonis, Priscilla

    2012-10-01

    Photonic structures appeared in nature several hundred millions years ago. In the living world, color is used for communication and this important function strongly impacts the individual chances of survival as well as the chances to reproduce. This has a statistical influence on species populations. Therefore, because they are involved in evolution, natural color-generating structures are - from some point of view - highly optimized. In this short review, a survey is presented of the development of natural photonic crystal-type structures occurring in insects, spiders, birds, fishes and other marine animals, in plants and more, from the standpoint of light-waves propagation. One-, two-, and three-dimensional structures will be reviewed with selected examples.

  1. Diffraction. Single crystal, magnetic

    International Nuclear Information System (INIS)

    Heger, G.

    1999-01-01

    The analysis of crystal structure and magnetic ordering is usually based on diffraction phenomena caused by the interaction of matter with X-rays, neutrons, or electrons. Complementary information is achieved due to the different character of X-rays, neutrons and electrons, and hence their different interactions with matter and further practical aspects. X-ray diffraction using conventional laboratory equipment and/or synchrotron installations is the most important method for structure analyses. The purpose of this paper is to discuss special cases, for which, in addition to this indispensable part, neutrons are required to solve structural problems. Even though the huge intensity of modern synchrotron sources allows in principle the study of magnetic X-ray scattering the investigation of magnetic structures is still one of the most important applications of neutron diffraction. (K.A.)

  2. Lamella settler crystallizer

    Science.gov (United States)

    Maimoni, A.

    1990-12-18

    A crystallizer is described which incorporates a lamella settler and which is particularly applicable for use in batteries and power cells for electric vehicles or stationary applications. The lamella settler can be utilized for coarse particle separation or for agglomeration, and is particularly applicable to aluminum-air batteries or power cells for solving the hydrargillite (aluminum-hydroxide) removal problems from such batteries. This invention provides the advantages of very low energy consumption, turbulence, shear, cost and maintenance. Thus, due to the low shear and low turbulence of this invention, it is particularly effective in the control of aluminum hydroxide particle size distribution in the various sections of an aluminum-air system, as well as in other electrochemical systems requiring separation for phases of different densities. 3 figs.

  3. Crystal Ball at PEP

    International Nuclear Information System (INIS)

    Bartel, W.; Bulos, F.; Luke, D.; Peck, C.; Strauch, K.

    1975-01-01

    The modifications to the SPEAR version of the Crystal Ball required by the higher energies at PEP are discussed. Since the hadron multiplicity is expected to rise as log s, their average energy must rise. On the other hand, if the hadrons are produced in jets, the low energy part of their spectrum is not heavily depleted. This implies that modifications for high energy particles should not deteriorate low energy performance. An external iron calorimeter for measuring the high energy hadrons, charged and neutral, is considered. To improve the angular resolution on γ's, an active internal converter has been studied, estimates have been made of its expected performance, and difficulties requiring further study have been outlined

  4. Between Smoke and Crystal

    DEFF Research Database (Denmark)

    Morsing, Mette; Christensen, Lars Thøger; Thyssen, Ole

    Responsible corporate behavior is not defined once and for all. Rather it develops as society and organizations interact, learn and change. It has convincingly been argued that in the area of CSR, there is a particular need for organizations to keep the definition of CSR open and inclusive to new...... on the CSR form rather than the CSR function, i.e. critiquing the organizational work to achieve a desirable CSR image rather than achieving the CSR substance. We argue that this dichotomy is misplaced and misses the point. In this paper we attempt to demonstrate that CSR is about a continued balancing act...... between image and substance and most importantly it is a balancing act in which ”image” and public relations may drive organizations to improved “substance”. With reference to Odysseus, we label this a balancing act between the Scylla of crystal and the Charybdis of smoke....

  5. Photonic crystals in epitaxial semiconductors

    CERN Document Server

    La Rue, R M de

    1998-01-01

    The title of the paper uses the expression "photonic crystals". By photonic crystals, we mean regular periodic structures with a substantial refractive index variation in one-, two- or three- dimensional space. Such crystals can $9 exist naturally, for example natural opal, but are more typically fabricated by people. Under sufficiently strong conditions, i.e., sufficiently large refractive index modulation, correct size of structural components, and $9 appropriate rotational and translational symmetry, these crystals exhibit the characteristics of a photonic bandgap (PBG) structure. In a full photonic bandgap structure there is a spectral stop band for electromagnetic waves $9 propagating in any direction through the structure and with an arbitrary state of polarization. This behavior is of interest both from a fundamental viewpoint and from the point of view of novel applications in photonic devices. The $9 paper gives an outline review of work on photonic crystals carried out by the Optoelectronics Researc...

  6. Prediction of molecular crystal structures

    CERN Document Server

    Beyer, T

    2001-01-01

    The ab initio prediction of molecular crystal structures is a scientific challenge. Reliability of first-principle prediction calculations would show a fundamental understanding of crystallisation. Crystal structure prediction is also of considerable practical importance as different crystalline arrangements of the same molecule in the solid state (polymorphs)are likely to have different physical properties. A method of crystal structure prediction based on lattice energy minimisation has been developed in this work. The choice of the intermolecular potential and of the molecular model is crucial for the results of such studies and both of these criteria have been investigated. An empirical atom-atom repulsion-dispersion potential for carboxylic acids has been derived and applied in a crystal structure prediction study of formic, benzoic and the polymorphic system of tetrolic acid. As many experimental crystal structure determinations at different temperatures are available for the polymorphic system of parac...

  7. General crystal in prebiotic context

    International Nuclear Information System (INIS)

    Simon, I.

    1993-09-01

    General crystal is an extension of the crystal concept to any form of matter which exhibit neighbour structure determination. This extension makes many results of solid state physics applicable to heterogeneous matter. Among other it includes the description of phase transition from random to unique structure. The advantage of the general crystal approach is demonstrated on globular protein, on of the most important macromolecules of life, which are capable to adopt unique 3D structure spontaneously, regardless of the heterogeneous character of their chemical structure and conformation. It is suggested that the use of general crystal concept may help to find candidates among heterogeneous matters capable to spontaneous self-organization in the same way as crystallization results in unique structure of homogeneous matter, and to apply some of the results of solid state physics to describe the phase transition and other behaviour of this matter. (author). 10 refs

  8. Springer Handbook of Crystal Growth

    CERN Document Server

    Dhanaraj, Govindhan; Prasad, Vishwanath; Dudley, Michael

    2010-01-01

    Over the years, many successful attempts have been made to describe the art and science of crystal growth. Most modern advances in semiconductor and optical devices would not have been possible without the development of many elemental, binary, ternary, and other compound crystals of varying properties and large sizes. The objective of the Springer Handbook of Crystal Growth is to present state-of-the-art knowledge of both bulk and thin-film crystal growth. The goal is to make readers understand the basics of the commonly employed growth processes, materials produced, and defects generated. Almost 100 leading scientists, researchers, and engineers from 22 different countries from academia and industry have been selected to write chapters on the topics of their expertise. They have written 52 chapters on the fundamentals of bulk crystal growth from the melt, solution, and vapor, epitaxial growth, modeling of growth processes and defects, techniques of defect characterization as well as some contemporary specia...

  9. Growth of emerald single crystals

    International Nuclear Information System (INIS)

    Bukin, G.V.; Godovikov, A.A.; Klyakin, V.A.; Sobolev, V.S.

    1986-01-01

    In addition to its use for jewelry, emerald can also be used in low-noise microwave amplifiers. The authors discuss flux crystallization of emerald and note that when emerald is grown by this method, it is desirable to use solvents which dissolve emerald with minimum deviations from congruence but at the same time with sufficient high efficiency. Emerald synthesis and crystal growth from slowly cooled solutions is discussed as another possibility. The techniques are examined. Vapor synthesis and growht of beryl crystals re reviewed and the authors experimentally study the seeded CVD crystallization of beryl from BeO, Al 2 O 3 and SiO 2 oxides, by using complex compounds as carrier agents. The color of crystals of emerald and other varieties of beryl is detemined by slelective light absorption in teh visible part of the spectrum and depends on the density and structural positions of chromphore ions: chromium, iron, vanadium, nickel, manganese and cobalt

  10. Crystallization of glycine with ultrasound

    DEFF Research Database (Denmark)

    Louhi-Kultanen, Marjatta; Karjalainen, Milja; Rantanen, Jukka

    2006-01-01

    Sonocrystallization has proved to be an efficient tool to influence the external appearance and structure of a crystalline product obtained by various crystallization methods. The present work focuses on high intensity sonocrystallization of glycine by varying amplitude of ultrasound with an ultr......Sonocrystallization has proved to be an efficient tool to influence the external appearance and structure of a crystalline product obtained by various crystallization methods. The present work focuses on high intensity sonocrystallization of glycine by varying amplitude of ultrasound...... with an ultrasound frequency of 20kHz at two temperature ranges 40-50 and 20-30 degrees C in a jacketed 250-ml cooling crystallizer equipped with a stirrer. The polymorph composition of the obtained crystals was analyzed with a temperature variable X-ray powder diffractometer (XRPD). XRPD results showed that...... ultrasound power. This study also showed, the higher the ultrasound amplitude the smaller the crystals obtained....

  11. Nanoparticles in liquid crystals, and liquid crystals in nanoparticles

    Science.gov (United States)

    de Pablo, Juan

    2015-03-01

    Liquid crystals are remarkably sensitive to interfacial interactions. Small perturbations at a liquid crystal interface, for example, can be propagated over relatively long length scales, thereby providing the basis for a wide range of applications that rely on amplification of molecular events into macroscopic observables. Our recent research efforts have focused on the reverse phenomenon; that is, we have sought to manipulate the interfacial assembly of nanoparticles or the organization of surface active molecules by controlling the structure of a liquid crystal. This presentation will consist of a review of the basic principles that are responsible for liquid crystal-mediated interactions, followed by demonstrations of those principles in the context of two types of systems. In the first, a liquid crystal is used to direct the assembly of nanoparticles; through a combination of molecular and continuum models, it is found that minute changes in interfacial energy and particle size lead to liquid-crystal induced attractions that can span multiple orders of magnitude. Theoretical predictions are confirmed by experimental observations, which also suggest that LC-mediated assembly provides an effective means for fabrication of plasmonic devices. In the second type of system, the structure of a liquid crystal is controlled by confinement in submicron droplets. The morphology of the liquid crystal in a drop depends on a delicate balance between bulk and interfacial contributions to the free energy; that balance can be easily perturbed by adsorption of analytes or nanoparticles at the interface, thereby providing the basis for development of hierarchical assembly of responsive, anisotropic materials. Theoretical predictions also indicate that the three-dimensional order of a liquid crystal can be projected onto a two-dimensional interface, and give rise to novel nanostructures that are not found in simple isotropic fluids.

  12. DFT investigation of the influence of ordered vacancies on elastic and magnetic properties of graphene and graphene-like SiC and BN structures

    International Nuclear Information System (INIS)

    Fedorov, A.S.; Popov, Z.I.; Fedorov, D.A.; Eliseeva, N.S.; Serjantova, M.V.; Kuzubov, A.A.

    2012-01-01

    Influence of ordered monovacancies on elastic properties of graphene is theoretically investigated by density functional theory (DFT) calculations. Inverse linear dependence of the graphene Young's modulus on the concentration of vacancies has been revealed and migration rate of the vacancies has been calculated as a function of applied strain. It is shown that the migration rate can be controlled by applying various strains or temperatures. The influence of ordered monovacancies on magnetic properties of graphene as well as graphene-like hexagonal carbon silicide (2D-SiC) and the boron nitride (h-BN) structures is investigated. It is established that the presence of vacancies in all systems yields the appearance of local magnetic moment. However, in 2D-SiC structure the magnetic moment occurs only in the case of a Si vacancy. Influence of the distance between vacancies on the ferromagnetic or anti-ferromagnetic ordering for all structures is established. (Copyright copyright 2012 WILEY-VCH Verlag GmbH and Co. KGaA, Weinheim)

  13. İbn Hazm'ın Gâliyye'ye (İtidal Çizgisini Aşanlara Eleştirisi Üzerine

    Directory of Open Access Journals (Sweden)

    Ömer Faruk Teber

    2015-11-01

    Full Text Available Ibn Hazm takes care of the social, geographical environments where the extremist groups (ghulât flourished. Thus, he discusses the places where the extremist groups appeared most extensively. Above all, he should have regarded the formation of the Islamic sects a sociological fact that he gives information, unlike other heresiographical works, about the regions where the sects considered outside Islam lived most intensively. According to Ibn Hazm, the groups deserving to be called ghulat had come out within Persian people, since the Shiism which gained prevalence primarily in Iran and Iraq as well as Southeast Asia developed within the Greek, Persian and Indian climate of culture. In this connection, the Ghaliya is divided into two. 'The first one comprised those who required the advent of another prophet after the Prophet Muhammad. The second group was consisting of those holding, aside from God, the divinity of another being. In İbn Hazm’s opinion, the latter joint with Jews and Christians and went down a beastly infidelity

  14. Understanding the anchoring effect of Graphene, BN, C2N and C3N4 monolayers for lithium-polysulfides in Li-S batteries

    Science.gov (United States)

    Zheng, Yanping; Li, Huanhuan; Yuan, Haiyan; Fan, Honghong; Li, Wenliang; Zhang, Jingping

    2018-03-01

    Recently, Li-S batteries with a high theoretical specific energy have attracted significant attention. However, their practical application is still seriously hindered by the shuttling effect of lithium polysulfides (LiPSs) in the Li-S batteries system. Introducing anchoring materials into the cathode or separator, which can strongly attract LiPSs because of advisable binding energies, has been demonstrated as an effective strategy to alleviate the shuttling effect for achieving the excellent cycling performance of Li-S batteries. In this work, the complete mechanistic understanding of the interaction between non-metallic monolayer materials (N-MMLMs, including Graphene, BN, C2N and C3N4) and LiPSs is given in detail with the aid of density functional theory. The calculation results show that N-MMLM can combine the chemical interaction and the physical entrapment of sulfur species to suppress the shuttling effect. C3N4 and C2N are predicted to trap LiPSs via stronger interfacial interaction and alleviate the interactions between LiPSs and solvents as well as the consequent dissolution. The strong anchoring effect of C3N4/C2N comes from the bonding of Li-N/C-S and charge transfer. Further charge transfer study reveals that the C3N4/C2N can serve as an electrocatalyst, which effectively accelerates the kinetics of LiPSs redox reactions.

  15. Infection of the upper respiratory tract of hamsters by the bovine parainfluenza virus type 3 BN-1 strain expressing enhanced green fluorescent protein.

    Science.gov (United States)

    Ohkura, Takashi; Minakuchi, Moeko; Sagai, Mami; Kokuho, Takehiro; Konishi, Misako; Kameyama, Ken-Ichiro; Takeuchi, Kaoru

    2015-02-01

    Bovine parainfluenza virus type 3 (BPIV3) is an important pathogen associated with bovine respiratory disease complex (BRDC). We have generated a recombinant BPIV3 expressing enhanced green fluorescent protein (rBPIV3-EGFP) based on the BN-1 strain isolated in Japan. After intranasal infection of hamsters with rBPIV3-EGFP, EGFP fluorescence was detected in the upper respiratory tract including the nasal turbinates, pharynx, larynx, and trachea. In the nasal turbinates, rBPIV3-EGFP attained high titers (>10(6) TCID50/g of tissue) 2-4 days after infection. Ciliated epithelial cells in the nasal turbinates and trachea were infected with rBPIV3-EGFP. Histopathological analysis indicated that mucosal epithelial cells in bronchi were shed by 6 days after infection, leaving non-ciliated cells, which may have increased susceptibility to bacterial infection leading to the development of BRDC. These data indicate that rBPIV3-EGFP infection of hamsters is a useful small animal model for studying the development of BPIV3-associated BRDC. Copyright © 2014 Elsevier Inc. All rights reserved.

  16. Spontaneous release of fluoride during the dioxygenolytic cleavage of 5-fluorosalicylate by the salicylate 1,2-dioxygenase from Pseudaminobacter salicylatoxidans BN12.

    Science.gov (United States)

    Eppinger, Erik; Bürger, Sibylle; Stolz, Andreas

    2016-01-01

    The alpha-Proteobacterium Pseudaminobacter salicylatoxidans BN12 forms a peculiar gentisate 1,2-dioxygenase (SDO) that oxidatively cleaves gentisate (2,5-dihydroxybenzoate) and additionally 1-hydroxy-2-naphthoate, salicylate and various amino-, chloro-, fluoro-, hydroxy- and methylsalicylates. In the present study, the conversion of 5-fluorosalicylate by this enzyme was analysed using various analytical techniques. Spectrophotometric assays showed that the conversion of 5-fluorosalicylate by the purified enzyme resulted in the formation of a new unstable intermediate showing an absorbance maximum at λmax = 292 nm. The analysis of the enzymatic reaction by HPLC showed that two main products with absorbance maxima at λmax = 292-296 nm were formed from 5-fluorosalicylate. The same two products (although in different relative proportions) were also formed when the SDO transformed 5-chlorosalicylate or when a purified 5-nitrosalicylate 1,2-dioxygenase from Bradyrhizobium sp. JS329 oxidized 5-nitrosalicylate. A whole cell system with recombinant Escherichia coli cells overexpressing the SDO activity was established in order to produce larger amounts of the reaction products. The reaction products were subsequently identified by (1)H-NMR and mass spectrometry as stereoisomers of 2-oxo-3-(5-oxofuran-2-ylidine)propanoic acid. The release of fluoride in the course of the dioxygenolytic cleavage reaction was confirmed by ion-chromatography and (19)F-NMR. © FEMS 2015. All rights reserved. For permissions, please e-mail: journals.permissions@oup.com.

  17. Isolation of thylakoid membrane complexes from rice by a new double-strips BN/SDS-PAGE and bioinformatics prediction of stromal ridge subunits interaction.

    Directory of Open Access Journals (Sweden)

    Jinzhen Shao

    Full Text Available Thylakoid membrane complexes of rice (Oryza sativa L. play crucial roles in growth and crop production. Understanding of protein interactions within the complex would provide new insights into photosynthesis. Here, a new "Double-Strips BN/SDS-PAGE" method was employed to separate thylakoid membrane complexes in order to increase the protein abundance on 2D-gels and to facilitate the identification of hydrophobic transmembrane proteins. A total of 58 protein spots could be observed and subunit constitution of these complexes exhibited on 2D-gels. The generality of this new approach was confirmed using thylakoid membrane from spinach (Spinacia oleracea and pumpkin (Cucurita spp. Furthermore, the proteins separated from rice thylakoid membrane were identified by the mass spectrometry (MS. The stromal ridge proteins PsaD and PsaE were identified both in the holo- and core- PSI complexes of rice. Using molecular dynamics simulation to explore the recognition mechanism of these subunits, we showed that salt bridge interactions between residues R19 of PsaC and E168 of PasD as well as R75 of PsaC and E91 of PsaD played important roles in the stability of the complex. This stromal ridge subunits interaction was also supported by the subsequent analysis of the binding free energy, the intramolecular distances and the intramolecular energy.

  18. Effect of {sup 10}B(n, α){sup 7}Li irradiation on the structure of a sodium borosilicate glass

    Energy Technology Data Exchange (ETDEWEB)

    Peuget, S., E-mail: sylvain.peuget@cea.fr [CEA, DEN, Laboratoire d’Étude des Matériaux et Procédés Actif, 30207 Bagnols-sur-Cèze (France); Fares, T.; Maugeri, E.A.; Caraballo, R. [CEA, DEN, Laboratoire d’Étude des Matériaux et Procédés Actif, 30207 Bagnols-sur-Cèze (France); Charpentier, T. [CEA, IRAMIS, SIS2M, Laboratoire de Structure et Dynamique par Résonance Magnétique, UMR CEA/CNRS 3299, 91191 Gif-sur-Yvette (France); Martel, L.; Somers, J.; Janssen, A.; Wiss, T. [European Commission, JRC, Institute for Transuranium Elements (ITU), Hermann-von-Helmholtz Platz 1, PO Box 2340, DE-76125 Karlsruhe (Germany); Rozenblum, F. [CEA, DEN, DANS/DRSN/SIREN/LECSI, 91191 Gif-sur-Yvette (France); Magnin, M. [CEA, DEN, Laboratoire d’Étude des Matériaux et Procédés Actif, 30207 Bagnols-sur-Cèze (France); Deschanels, X. [Marcoule Institute of Separation Chemistry, LNAR, 30207 Bagnols-sur-Cèze Cedex (France); Jégou, C. [CEA, DEN, Laboratoire d’Étude des Matériaux et Procédés Actif, 30207 Bagnols-sur-Cèze (France)

    2014-05-01

    The effects of the nuclear reaction {sup 10}B(n, α){sup 7}Li on the properties and structure of a sodium borosilicate glass were analysed by density, hardness and fracture toughness measurements, Raman and Nuclear Magnetic Resonance spectroscopy and Transmission Electronic Microscopy (TEM) characterization. The TEM observations showed a homogeneous irradiated glass structure up to the nanometer scale. Modifications of the local order around the main cations were noticed, mainly a slight decrease of the mean boron coordination number and an increase of non-bridging oxygen concentrations. At the glass medium range order, the appearance of the D2 Raman band and a modification of the Si–O–Si angle distribution were also observed after irradiation. A comparison with other irradiation conditions with Swift Heavy Ions (Kr with 74 MeV) and Gold irradiation (with energies ranging from 1 to 7 MeV) is presented. Raman spectroscopy showed a similar final structure for irradiation conditions under which the glass evolutions are controlled by electronic energy loss in the ion tracks formation regime or nuclear energy loss. Despite important differences in energy deposition regimes, the similarities observed between the final glass structures suggest that structural evolutions are controlled by the glass relaxation mechanisms during the high quenching rate step that follows the energy deposition step.

  19. Manufacturing of thin films of boron for the measurement of the {sup 10}B(n, {alpha}){sup 7} Li reaction used in BNCT

    Energy Technology Data Exchange (ETDEWEB)

    Smilgys, Barbara; Oliveira, Sandro Guedes de; Hadler Neto, Julio Cesar; Vellame, Igor Alencar [Universidade Estadual de Campinas (UNICAMP), SP (Brazil). Inst. de Fisica Gleb Wataghin; Soares, Cleber Jose; Salim, Leonardo Alfredo [Universidade Estadual Paulista (UNESP), Rio Claro, SP (Brazil). Inst. de Geociencias e Ciencias Exatas; Coelho, Paulo Rogerio Pinto [Instituto de Pesquisas Energeticas e Nucleares (IPEN/CNEN-SP), Sao Paulo, SP (Brazil). Centro de Engenharia Nuclear

    2011-07-01

    Full text: The Boron Neutron Capture Therapy (BNCT) is considered to be a possible treatment for different types of aggressive cancers located in areas of difficult access or which already have metastasis. The working principle of this therapy is the selective delivery of a greater amount of boron to the tumor cells than to the healthy ones, followed by the neutron irradiation that will induce the emission of {alpha} particles through the {sup 10}B(n, {alpha}){sup 7} Li reaction used in BNCT reaction. The high energy deposition of the product particles causes the death of the cells and this therapy becomes much effective if the healthy tissue is less exposed to this radiation. The objective of this work is to develop a method for measuring the rate of this reaction by using thin films of boron. We have manufactured thin films with different concentrations of boron deposited on mica and the thin films were exposed to different irradiation time intervals at the reactor IEA-R1 located at IPEN, Sao Paulo. Here we show our first results on the density and uniformity of the thin films, where the detection of the particles is made using plastic track detectors (CR-39) which have their structures damaged by the passage of ions. (author)

  20. 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.

  1. Fahreddin er-Râzî’nin İbn Sînâ Yorumu ve Eleştirisi

    OpenAIRE

    ALTAŞ, EŞREF

    2016-01-01

    tasdik, beş tümel, tanım, kategoriler, burhan ve kıyasın maddeleri ele alınmıştır. Buna göre, mantığın sistematiğinde Râzî’nin yaptığı değişiklikler tablo ile verilmiş, İbn Sinâ’nın mantık sistematiği ile karşılaştırılmış ve başarılı bir şekilde aradaki fark ortaya konmuş- tur. Tasavvur ve tasdikle ilgili Râzî’nin epistemolojik tavrı oldukça ayrıntılı olarak ele alınmış ve Râzî’nin tasavvur ve tasdiklerin tama- mını bedihî olarak kabul ettiği sonucuna varılmıştır. Bu bağlamda tanım eleşt...

  2. Pressure sensor using liquid crystals

    Science.gov (United States)

    Parmar, Devendra S. (Inventor); Holmes, Harlan K. (Inventor)

    1994-01-01

    A pressure sensor includes a liquid crystal positioned between transparent, electrically conductive films (18 and 20), that are biased by a voltage (V) which induces an electric field (E) that causes the liquid crystal to assume a first state of orientation. Application of pressure (P) to a flexible, transparent film (24) causes the conductive film (20) to move closer to or farther from the conductive film (18), thereby causing a change in the electric field (E'(P)) which causes the liquid crystal to assume a second state of orientation. Polarized light (P.sub.1) is directed into the liquid crystal and transmitted or reflected to an analyzer (A or 30). Changes in the state of orientation of the liquid crystal induced by applied pressure (P) result in a different light intensity being detected at the analyzer (A or 30) as a function of the applied pressure (P). In particular embodiments, the liquid crystal is present as droplets (10) in a polymer matrix (12) or in cells (14) in a polymeric or dielectric grid (16) material in the form of a layer (13) between the electrically conductive films (18 and 20). The liquid crystal fills the open wells in the polymer matrix (12) or grid (16) only partially.

  3. Crystal ball single event display

    International Nuclear Information System (INIS)

    Grosnick, D.; Gibson, A.; Allgower, C.; Alyea, J.; Argonne National Lab., IL

    1997-01-01

    The Single Event Display (SED) is a routine that is designed to provide information graphically about a triggered event within the Crystal Ball. The SED is written entirely in FORTRAN and uses the CERN-based HICZ graphing package. The primary display shows the amount of energy deposited in each of the NaI crystals on a Mercator-like projection of the crystals. Ten different shades and colors correspond to varying amounts of energy deposited within a crystal. Information about energy clusters is displayed on the crystal map by outlining in red the thirteen (or twelve) crystals contained within a cluster and assigning each cluster a number. Additional information about energy clusters is provided in a series of boxes containing useful data about the energy distribution among the crystals within the cluster. Other information shown on the event display include the event trigger type and data about π o 's and η's formed from pairs of clusters as found by the analyzer. A description of the major features is given, along with some information on how to install the SED into the analyzer

  4. Dichroic Liquid Crystal Displays

    Science.gov (United States)

    Bahadur, Birendra

    The following sections are included: * INTRODUCTION * DICHROIC DYES * Chemical Structure * Chemical and Photochemical Stability * THEORETICAL MODELLING * DEFECTS CAUSED BY PROLONGED LIGHT IRRADIATION * CHEMICAL STRUCTURE AND PHOTOSTABILITY * OTHER PARAMETERS AFFECTING PHOTOSTABILITY * CELL PREPARATION * DICHROIC PARAMETERS AND THEIR MEASUREMENTS * Order Parameter and Dichroic Ratio Of Dyes * Absorbance, Order Parameter and Dichroic Ratio Measurements * IMPACT OF DYE STRUCTURE AND LIQUID CRYSTAL HOST ON PHYSICAL PROPERTIES OF A DICHROIC MIXTURE * Order Parameter and Dichroic Ratio * EFFECT OF LENGTH OF DICHROIC DYES ON THE ORDER PARAMETER * EFFECT OF THE BREADTH OF DYE ON THE ORDER PARAMETER * EFFECT OF THE HOST ON THE ORDER PARAMETER * TEMPERATURE VARIATION OF THE ORDER PARAMETER OF DYES IN A LIQUID CRYSTAL HOST * IMPACT OF DYE CONCENTRATION ON THE ORDER PARAMETER * Temperature Range * Viscosity * Dielectric Constant and Anisotropy * Refractive Indices and Birefringence * solubility43,153-156 * Absorption Wavelength and Auxochromic Groups * Molecular Engineering of Dichroic Dyes * OPTICAL, ELECTRO-OPTICAL AND LIFE PARAMETERS * Colour And CIE Colour space120,160-166 * CIE 1931 COLOUR SPACE * CIE 1976 CHROMATICITY DIAGRAM * CIE UNIFORM COLOUR SPACES & COLOUR DIFFERENCE FORMULAE120,160-166 * Electro-Optical Parameters120 * LUMINANCE * CONTRAST AND CONTRAST RATIO * SWITCHING SPEED * Life Parameters and Failure Modes * DICHROIC MIXTURE FORMULATION * Monochrome Mixture * Black Mixture * ACHROMATIC BLACK MIXTURE FOR HEILMEIER DISPLAYS * Effect of Illuminant on Display Colour * Colour of the Field-On State * Effect of Dye Linewidth * Optimum Centroid Wavelengths * Effect of Dye Concentration * Mixture Formulation Using More Than Three Dyes * ACHROMATIC MIXTURE FOR WHITE-TAYLOR TYPE DISPLAYS * HEILMEIER DISPLAYS * Theoretical Modelling * Threshold Characteristic * Effects of Dye Concentration on Electro-optical Parameters * Effect of Cholesteric Doping * Effect of Alignment

  5. Current trends in protein crystallization.

    Science.gov (United States)

    Gavira, José A

    2016-07-15

    Proteins belong to the most complex colloidal system in terms of their physicochemical properties, size and conformational-flexibility. This complexity contributes to their great sensitivity to any external change and dictate the uncertainty of crystallization. The need of 3D models to understand their functionality and interaction mechanisms with other neighbouring (macro)molecules has driven the tremendous effort put into the field of crystallography that has also permeated other fields trying to shed some light into reluctant-to-crystallize proteins. This review is aimed at revising protein crystallization from a regular-laboratory point of view. It is also devoted to highlight the latest developments and achievements to produce, identify and deliver high-quality protein crystals for XFEL, Micro-ED or neutron diffraction. The low likelihood of protein crystallization is rationalized by considering the intrinsic polypeptide nature (folded state, surface charge, etc) followed by a description of the standard crystallization methods (batch, vapour diffusion and counter-diffusion), including high throughput advances. Other methodologies aimed at determining protein features in solution (NMR, SAS, DLS) or to gather structural information from single particles such as Cryo-EM are also discussed. Finally, current approaches showing the convergence of different structural biology techniques and the cross-methodologies adaptation to tackle the most difficult problems, are presented. Current advances in biomacromolecules crystallization, from nano crystals for XFEL and Micro-ED to large crystals for neutron diffraction, are covered with special emphasis in methodologies applicable at laboratory scale. Copyright © 2015 Elsevier Inc. All rights reserved.

  6. Crystal extraction: Alignment of crystal with respect to the beam

    CERN Document Server

    Gyr, Marcel

    1992-01-01

    The program CRYSTAL.BAS allows to calculate the exact alignment of the crystal with respect to thebeam. It is written in QBasic and installed on server USRV_865 connected to the PC network. This note describes how to access and to run this program from any PC which is connected to the network NICE. The angle of the two crystals actually installed has been scanned over a relatively wide range and at different positions with respect to the ideal closed orbit, thereafter referred to as beam center line. The signal (Volt) produced by the position sensitive detectors (PSD) intercepting the reflected laser beams used to monitor the crystal alignment, is plotted in the attached figures.

  7. Size effects in crystal plasticity

    DEFF Research Database (Denmark)

    Borg, Ulrik

    2007-01-01

    Numerical analyses of plasticity size effects have been carried out for different problems using a developed strain gradient crystal plasticiy theory. The theory employs higher order stresses as work conjugates to slip gradients and uses higher order boundary conditions. Problems on localization...... of plastic flow in a single crystal, grain boundary effects in a bicrystal, and grain size effects in a polycrystal are studied. Single crystals containing micro-scale voids have also been analyzed at different loading conditions with focus on the stress and deformation fields around the voids, on void...

  8. Crystal structure determination of Efavirenz

    International Nuclear Information System (INIS)

    Popeneciu, Horea; Dumitru, Ristoiu; Tripon, Carmen; Borodi, Gheorghe; Pop, Mihaela Maria

    2015-01-01

    Needle-shaped single crystals of the title compound, C 14 H 9 ClF 3 NO 2 , were obtained from a co-crystallization experiment of Efavirenz with maleic acid in a (1:1) ratio, using methanol as solvent. Crystal structure determination at room temperature revealed a significant anisotropy of the lattice expansion compared to the previously reported low-temperature structure. In both low- and room temperature structures the cyclopropylethynyl fragment in one of the asymmetric unit molecules is disordered. While at low-temperature only one C atom exhibits positional disorder, at room temperature the disorder is present for two C atoms of the cyclopropane ring

  9. Crystal plasticity study of single crystal tungsten by indentation tests

    International Nuclear Information System (INIS)

    Yao, Weizhi

    2012-01-01

    Owing to its favorable material properties, tungsten (W) has been studied as a plasma-facing material in fusion reactors. Experiments on W heating in plasma sources and electron beam facilities have shown an intense micro-crack formation at the heated surface and sub-surface. The cracks go deep inside the irradiated sample, and often large distorted areas caused by local plastic deformation are present around the cracks. To interpret the crack-induced microscopic damage evolution process in W, one needs firstly to understand its plasticity on a single grain level, which is referred to as crystal plasticity. In this thesis, the crystal plasticity of single crystal tungsten (SCW) has been studied by spherical and Berkovich indentation tests and the finite element method with a crystal plasticity model. Appropriate values of the material parameters included in the crystal plasticity model are determined by fitting measured load-displacement curves and pile-up profiles with simulated counterparts for spherical indentation. The numerical simulations reveal excellent agreement with experiment. While the load-displacement curves and the deduced indentation hardness exhibit little sensitivity to the indented plane at small indentation depths, the orientation of slip directions within the crystals governs the development of deformation hillocks at the surface. It is found that several factors like friction, indentation depth, active slip systems, misoriented crystal orientation, misoriented sample surface and azimuthal orientation of the indenter can affect the indentation behavior of SCW. The Berkovich indentation test was also used to study the crystal plasticity of SCW after deuterium irradiation. The critical load (pop-in load) for triggering plastic deformation under the indenter is found to depend on the crystallographic orientation. The pop-in loads decrease dramatically after deuterium plasma irradiation for all three investigated crystallographic planes.

  10. Crystals and liquid crystals confined to curved geometries

    OpenAIRE

    Koning, Vinzenz; Vitelli, Vincenzo

    2014-01-01

    This review introduces the elasticity theory of two-dimensional crystals and nematic liquid crystals on curved surfaces, the energetics of topological defects (disclinations, dislocations and pleats) in these ordered phases, and the interaction of defects with the underlying curvature. This chapter concludes with two cases of three-dimensional nematic phases confined to spaces with curved boundaries, namely a torus and a spherical shell.

  11. 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.)

  12. Crystal Adaptronics: Mechanically Reconfigurable Elastic and Superelastic Molecular Crystals.

    Science.gov (United States)

    Ahmed, Ejaz; Karothu, Durga Prasad; Naumov, Pance

    2018-04-06

    Mechanically reconfigurable molecular crystals-ordered materials that can adapt to variable operating and environmental conditions by deformation, whereby they attain motility or perform work-are quickly shaping up a new research direction in materials science, crystal adaptronics. Properties such as elasticity, superelasticity and ferroelasticity that are normally related to inorganic materials, and phenomena such as shape-memory and self-healing effects which are well established for soft materials, are increasingly reported for molecular crystals, yet their mechanism, quantification, and relation to the crystal structure in organic crystals are not immediately intelligible to the chemistry and materials science research communities. This Minireview provides a condensed topical overview of the elastic, superelastic and ferroelastic molecular crystals, emerging new classes of materials that bridge the gap between the soft matter and inorganic materials. The occurrence and detection of these unconventional properties, and the underlying structural features of the related molecular materials are discussed and highlighted together with selected prominent recent examples. © 2018 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  13. Crystal structure of pymetrozine

    Directory of Open Access Journals (Sweden)

    Youngeun Jeon

    2015-07-01

    Full Text Available The title compound, C10H11N5O {systematic name: 6-methyl-4-[(E-(pyridin-3-ylmethylideneamino]-4,5-dihydro-1,2,4-triazin-3(2H-one}, C10H11N5O, is used as an antifeedant in pest control. The asymmetric unit comprises two independent molecules, A and B, in which the dihedral angles between the pyridinyl and triazinyl ring planes [r.m.s. deviations = 0.0132 and 0.0255 ] are 11.60 (6 and 18.06 (4°, respectively. In the crystal, N—H...O, N—H...N, C—H...N and C—H...O hydrogen bonds, together with weak π–π interactions [ring-centroid separations = 3.5456 (9 and 3.9142 (9 Å], link the pyridinyl and triazinyl rings of A molecules, generating a three-dimensional network.

  14. Patterned Colloidal Photonic Crystals.

    Science.gov (United States)

    Hou, Jue; Li, Mingzhu; Song, Yanlin

    2018-03-01

    Colloidal photonic crystals (PCs) have been well developed because they are easy to prepare, cost-effective, and versatile with regards to modification and functionalization. Patterned colloidal PCs contribute a novel approach to constructing high-performance PC devices with unique structures and specific functions. In this review, an overview of the strategies for fabricating patterned colloidal PCs, including patterned substrate-induced assembly, inkjet printing, and selective immobilization and modification, is presented. The advantages of patterned PC devices are also discussed in detail, for example, improved detection sensitivity and response speed of the sensors, control over the flow direction and wicking rate of microfluidic channels, recognition of cross-reactive molecules through an array-patterned microchip, fabrication of display devices with tunable patterns, well-arranged RGB units, and wide viewing-angles, and the ability to construct anti-counterfeiting devices with different security strategies. Finally, the perspective of future developments and challenges is presented. © 2018 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  15. Single Crystal Surfaces

    Science.gov (United States)

    Aguilar-Santillan, Joaquin

    2014-06-01

    The present work studies (0001) Al2O3 and (111) Al2MgO4 wetting with pure molten Al by the sessile drop technique from 1073 K to 1473 K (800 °C to 1200 °C) under Ar at PO2 10-15 Pa. Al pure liquid wets a smooth and chemically homogeneous surface of an inert solid, the wetting driving force ( t, T) can be readily studied when surface solid roughness increases in the system. Both crystals planes (0001) Al2O3 and (111) Al2MgO4 have crystallographic surfaces with identical O-2 crystalline positions however considering Mg2+ content in Al2MgO4 structure may influence a reactive mode. Kinetic models results under similar experimental conditions show that Al wetting on (0001) Al2O3 is less reactive than (111) Al2MgO4, however at >1273 K (1000 °C) (0001) Al2O3 transformation occurs and a transition of wetting improves. The (111) Al2MgO4 and Al system promotes interface formations that slow its wetting process.

  16. Thermography using cholesteric liquid crystals

    International Nuclear Information System (INIS)

    Elberg, S.; Mathonnet, P.

    1975-05-01

    After a brief recall of the optical characteristics of liquid crystals, the performances the cholesteric films can reach as temperature sensors are reviewed. Several examples are then given in thermography as well as in thermal non-destructive testing [fr

  17. Absence of Quantum Time Crystals

    Science.gov (United States)

    Watanabe, Haruki; Oshikawa, Masaki

    2015-06-01

    In analogy with crystalline solids around us, Wilczek recently proposed the idea of "time crystals" as phases that spontaneously break the continuous time translation into a discrete subgroup. The proposal stimulated further studies and vigorous debates whether it can be realized in a physical system. However, a precise definition of the time crystal is needed to resolve the issue. Here we first present a definition of time crystals based on the time-dependent correlation functions of the order parameter. We then prove a no-go theorem that rules out the possibility of time crystals defined as such, in the ground state or in the canonical ensemble of a general Hamiltonian, which consists of not-too-long-range interactions.

  18. PREPARATION OF REFRACTORY OXIDE CRYSTALS

    Science.gov (United States)

    Grimes, W.R.; Shaffer, J.H.; Watson, G.M.

    1962-11-13

    A method is given for preparing uranium dioxide, thorium oxide, and beryllium oxide in the form of enlarged individual crystals. The surface of a fused alkali metal halide melt containing dissolved uranium, thorium, or beryllium values is contacted with a water-vapor-bearing inert gas stream at a rate of 5 to 10 cubic centimeters per minute per square centimeter of melt surface area. Growth of individual crystals is obtained by prolonged contact. Beryllium oxide-coated uranium dioxide crystals are prepared by disposing uranium dioxide crystals 5 to 20 microns in diameter in a beryllium-containing melt and contacting the melt with a water-vapor-bearing inert gas stream in the same manner. (AEC)

  19. SHORT COMMUNICATION SYNTHESIS AND CRYSTAL ...

    African Journals Online (AJOL)

    Preferred Customer

    -2-cyano-3-methylthioacrylyl)- N'-(substituted phenyl)ureas. Their NMR analysis, mass spectrum analysis and crystal structure have been investigated. RESULTS AND DISCUSSION. The preparation route of target compounds is shown in ...

  20. Nanoparticles Doped, Photorefractive Liquid Crystals

    National Research Council Canada - National Science Library

    Kaczmarek, Malgosia

    2005-01-01

    ...: The main objectives of this exploratory, short project will concern the study of the quality of liquid crystal cells with diluted suspensions of ferroelectric nanoparticles and their photorefractive properties...