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Sample records for deep boron centers

  1. 2.3 Boron-centered radicals

    NASA Astrophysics Data System (ADS)

    Howard, J. A.

    This document is part of Subvolume A1 `Inorganic Radicals, Metal Complexes and Nonconjugated Carbon Centered Radicals' of Volume 26 `Magnetic Properties of Free Radicals' of Landolt-Börnstein Group II `Molecules and Radicals'.

  2. Usuda Deep Space Center support for ICE

    NASA Technical Reports Server (NTRS)

    Goodwin, J. P.

    1986-01-01

    The planning, implementation and operations that took place to enable the Usuda, Japan, Deep Space Center to support the International Cometary Explorer (ICE) mission are summarized. The results show that even on very short notification our two countries can provide mutual support to help ensure mission success. The data recovery at the Usuda Deep Space Center contributed significantly to providing the required continuity of the experimental data stream at the encounter of the Comet Giacobini-Zinner.

  3. Deep ultraviolet emission in hexagonal boron nitride grown by high-temperature molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Vuong, T. Q. P.; Cassabois, G.; Valvin, P.; Rousseau, E.; Summerfield, A.; Mellor, C. J.; Cho, Y.; Cheng, T. S.; Albar, J. D.; Eaves, L.; Foxon, C. T.; Beton, P. H.; Novikov, S. V.; Gil, B.

    2017-06-01

    We investigate the opto-electronic properties of hexagonal boron nitride grown by high temperature plasma-assisted molecular beam epitaxy. We combine atomic force microscopy, spectroscopic ellipsometry, and photoluminescence spectroscopy in the deep ultraviolet to compare the quality of hexagonal boron nitride grown either on sapphire or highly oriented pyrolytic graphite. For both substrates, the emission spectra peak at 235 nm, indicating the high optical quality of hexagonal boron nitride grown by molecular beam epitaxy. The epilayers on highly oriented pyrolytic graphite demonstrate superior performance in the deep ultraviolet (down to 210 nm) compared to those on sapphire. These results reveal the potential of molecular beam epitaxy for the growth of hexagonal boron nitride on graphene, and more generally, for fabricating van der Waals heterostructures and devices by means of a scalable technology.

  4. Oxygen-Boron Vacancy Defect in Cubic Boron Nitride: A Diamond NV- Isoelectronic Center

    NASA Astrophysics Data System (ADS)

    Abtew, Tesfaye; Gao, Weiwei; Gao, Xiang; Sun, Yiyang; Zhang, Shengbai; Zhang, Peihong

    2015-03-01

    The promises of NV? center in diamond for quantum information application have inspired unprecedented research interests in optical manipulations of defect states, and have stimulated the search for alternative isoelectronic defect systems. In this talk, we present a diamond NV- like color center in c-BN based on first-principles electronic structure calculations using the Heyd-Scuseria-Ernzerhof hybrid functional. The defect consists of an substitutional oxygen and an adjacent boron vacancy (ON -VB). We discuss the electronic and optical properties of this center in comparison with the NV- center GC-2 defect center in c-BN. We acknowledge the computational support provided by the Center for Computational Research at the University at Buffalo, SUNY. This work is supported by the US Department of Energy under Grant No. DE-SC0002623 and by the National Science Foundation under Grant No. DMR-0946404. Work at Beijing CSRC is supported by the National Natural Science Foundation of China (Grant No. 11328401).

  5. Boron

    USDA-ARS?s Scientific Manuscript database

    Boron is an essential micronutrient element required for plant growth. Boron deficiency is wide-spread in crop plants throughout the world especially in coarse-textured soils in humid areas. Boron toxicity can also occur, especially in arid regions under irrigation. Plants respond directly to the...

  6. Dative Bonding between Group 13 Elements Using a Boron-Centered Lewis Base.

    PubMed

    Braunschweig, Holger; Dewhurst, Rian D; Pentecost, Leanne; Radacki, Krzysztof; Vargas, Alfredo; Ye, Qing

    2016-01-04

    An electron-rich monovalent boron compound is used as a Lewis base to prepare adducts with Group 13 Lewis acids using both its boron and nitrogen sites. The hard Lewis acid AlCl3 binds through a nitrogen atom of the Lewis base, while softer Lewis acids GaX3 (Cl, Br, I) bind at the boron atom. The latter are the first noncluster Lewis adducts between a boron-centered Lewis base and a main-group Lewis acid. © 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  7. Boron

    MedlinePlus

    ... body handles other minerals such as magnesium and phosphorus. It also seems to increase estrogen levels in ... happens in men.PhosphorusSupplemental boron might reduce blood phosphorus levels in some people.

  8. Nanoscale structure study of boron nitride nanosheets and development of a deep-UV photo-detector.

    PubMed

    Sajjad, Muhammad; Jadwisienczak, Wojciech M; Feng, Peter

    2014-05-07

    In this communication, we report on the synthesis of few atomic-layer boron nitride nanosheets (BNNSs) and their application for deep ultraviolet photo-detection. Synthesis of BNNSs is carried out by using the short-pulse plasma beam deposition technique. High-resolution tunneling electron microscopy, cathodoluminescence spectroscopy and photo-stimulated measurements are conducted and linked to characterize the BNNS morphology. The obtained BNNSs are flat with a typical size of 50 × 50 μm(2) and are optically transparent down to 210 nm. Nanoscale studies by transmission electron microscopy revealed that these nanosheets are composed of a densely packed honeycomb crystal lattice structure of covalently bonded boron and nitrogen atoms. Cathodoluminescence spectroscopy of these nanosheets revealed a single sharp excitonic peak centered at 233 nm at 300 K. The synthesized BNNSs are used to demonstrate applicability of BNNSs for detecting ultraviolet photons. The initial experimental tests of the developed prototype BNNSs based deep-ultraviolet photo-detector show that it is blind to photons with an energy less than 4 eV. The calculated output power of the detector is approximately 2 μW and the ratio between the output electrical power and the input optical power is ∼1%.

  9. Nanoscale structure study of boron nitride nanosheets and development of a deep-UV photo-detector

    NASA Astrophysics Data System (ADS)

    Sajjad, Muhammad; Jadwisienczak, Wojciech M.; Feng, Peter

    2014-04-01

    In this communication, we report on the synthesis of few atomic-layer boron nitride nanosheets (BNNSs) and their application for deep ultraviolet photo-detection. Synthesis of BNNSs is carried out by using the short-pulse plasma beam deposition technique. High-resolution tunneling electron microscopy, cathodoluminescence spectroscopy and photo-stimulated measurements are conducted and linked to characterize the BNNS morphology. The obtained BNNSs are flat with a typical size of 50 × 50 μm2 and are optically transparent down to 210 nm. Nanoscale studies by transmission electron microscopy revealed that these nanosheets are composed of a densely packed honeycomb crystal lattice structure of covalently bonded boron and nitrogen atoms. Cathodoluminescence spectroscopy of these nanosheets revealed a single sharp excitonic peak centered at 233 nm at 300 K. The synthesized BNNSs are used to demonstrate applicability of BNNSs for detecting ultraviolet photons. The initial experimental tests of the developed prototype BNNSs based deep-ultraviolet photo-detector show that it is blind to photons with an energy less than 4 eV. The calculated output power of the detector is approximately 2 μW and the ratio between the output electrical power and the input optical power is ~1%.

  10. The Deep Impact Network Experiment Operations Center

    NASA Technical Reports Server (NTRS)

    Torgerson, J. Leigh; Clare, Loren; Wang, Shin-Ywan

    2009-01-01

    Delay/Disruption Tolerant Networking (DTN) promises solutions in solving space communications challenges arising from disconnections as orbiters lose line-of-sight with landers, long propagation delays over interplanetary links, and other phenomena. DTN has been identified as the basis for the future NASA space communications network backbone, and international standardization is progressing through both the Consultative Committee for Space Data Systems (CCSDS) and the Internet Engineering Task Force (IETF). JPL has developed an implementation of the DTN architecture, called the Interplanetary Overlay Network (ION). ION is specifically implemented for space use, including design for use in a real-time operating system environment and high processing efficiency. In order to raise the Technology Readiness Level of ION, the first deep space flight demonstration of DTN is underway, using the Deep Impact (DI) spacecraft. Called the Deep Impact Network (DINET), operations are planned for Fall 2008. An essential component of the DINET project is the Experiment Operations Center (EOC), which will generate and receive the test communications traffic as well as "out-of-DTN band" command and control of the DTN experiment, store DTN flight test information in a database, provide display systems for monitoring DTN operations status and statistics (e.g., bundle throughput), and support query and analyses of the data collected. This paper describes the DINET EOC and its value in the DTN flight experiment and potential for further DTN testing.

  11. The Deep Impact Network Experiment Operations Center

    NASA Technical Reports Server (NTRS)

    Torgerson, J. Leigh; Clare, Loren; Wang, Shin-Ywan

    2009-01-01

    Delay/Disruption Tolerant Networking (DTN) promises solutions in solving space communications challenges arising from disconnections as orbiters lose line-of-sight with landers, long propagation delays over interplanetary links, and other phenomena. DTN has been identified as the basis for the future NASA space communications network backbone, and international standardization is progressing through both the Consultative Committee for Space Data Systems (CCSDS) and the Internet Engineering Task Force (IETF). JPL has developed an implementation of the DTN architecture, called the Interplanetary Overlay Network (ION). ION is specifically implemented for space use, including design for use in a real-time operating system environment and high processing efficiency. In order to raise the Technology Readiness Level of ION, the first deep space flight demonstration of DTN is underway, using the Deep Impact (DI) spacecraft. Called the Deep Impact Network (DINET), operations are planned for Fall 2008. An essential component of the DINET project is the Experiment Operations Center (EOC), which will generate and receive the test communications traffic as well as "out-of-DTN band" command and control of the DTN experiment, store DTN flight test information in a database, provide display systems for monitoring DTN operations status and statistics (e.g., bundle throughput), and support query and analyses of the data collected. This paper describes the DINET EOC and its value in the DTN flight experiment and potential for further DTN testing.

  12. Barrier layers as resonators on deep centers

    NASA Astrophysics Data System (ADS)

    Oreshkin, P. T.

    1990-11-01

    A response is given to the paper of L. S. Barman and A. A. Lebedev (Izv. Vyssh. Uchebn. Zaved. SSSR, Fiz., No. 12, 88 90 (1989)), and it is shown that the arguments given there are not satisfactory. New experimental data have been obtained for n+-p junctions in Si, where square reverse-bias pulses U < Ures are observed to shift the DLTS peaks. Here Ures is the magnitude of the pulse for which all activation-drift processes become activation-transit processes and the barrier layer operates as a freshly prepared resonator on deep centers (see the paper by P. T. Oreshkin, Elektronnaya Tekhnika, Ser. 3, Mikroelektronika, No. 4 (128), 12 20 (1988).

  13. First-principles calculation of a negatively charged boron-vacancy center in diamond

    NASA Astrophysics Data System (ADS)

    Kunisaki, Aiko; Muruganathan, Manoharan; Mizuta, Hiroshi; Kodera, Tetsuo

    2017-04-01

    As the boron doping in diamond has been well established, and a negatively charged boron-vacancy (BV) center has an active electron paramagnetic resonance, the BV center is an attractive candidate for spin information devices. Using the first-principles calculation, we report the electronic structure of the BV center in diamond for its various charge states. A geometrically optimized BV center in the diamond supercell exhibited C 3 v symmetry. The BV+1 charge state did not exhibit any spin splitting defect levels, while the BV0 and BV‑2 charge states showed a small energy separation between spin-polarized states. On the other hand, the negatively charged BV‑1 center possesses bound states with a larger separation inside the diamond bandgap. Moreover, it has the spin-triplet ground state and the spin-conserved triplet excited state. These characteristics indicate that the BV‑1 center in diamond is a good candidate for qubit operation.

  14. 193 nm deep-ultraviolet solar-blind cubic boron nitride based photodetectors

    NASA Astrophysics Data System (ADS)

    Soltani, A.; Barkad, H. A.; Mattalah, M.; Benbakhti, B.; De Jaeger, J.-C.; Chong, Y. M.; Zou, Y. S.; Zhang, W. J.; Lee, S. T.; BenMoussa, A.; Giordanengo, B.; Hochedez, J.-F.

    2008-02-01

    Deep-ultraviolet (DUV) solar-blind photodetectors based on high-quality cubic boron nitride (cBN) films with a metal/semiconductor/metal configuration were fabricated. The design of interdigitated circular electrodes enables high homogeneity of electric field between pads. The DUV photodetectors present a peak responsivity at 180nm with a very sharp cutoff wavelength at 193nm and a visible rejection ratio (180 versus 250nm) of more than four orders of magnitude. The characteristics of the photodetectors present extremely low dark current, high breakdown voltage, and high responsivity, suggesting that cBN films are very promising for DUV sensing.

  15. Boron isotopes in deep-sea bamboo corals: pH, vital effects and environmental factors

    NASA Astrophysics Data System (ADS)

    Farmer, J. R.; Hoenisch, B.; Hill, T. M.; LaVigne, M.; Robinson, L. F.

    2011-12-01

    Deep-sea corals are an intriguing archive for reconstructing deep-ocean environmental conditions, in particular with regard to anthropogenic climate change and ocean acidification. However, previous research in deep-sea aragonitic scleractinian corals observed heterogeneity in their geochemical composition that greatly exceeded the magnitude of variability expected from environmental conditions. Here we investigate the boron isotopic composition (δ11B) and B/Ca ratios of the calcitic gorgonian bamboo coral Keratoisis sp. (family Isididae) as potential indicators of seawater-pH at depth. Initial results from a specimen collected alive on Little Joe Seamount, CA (2136m depth) show that the δ11B of surface calcite is within the expected range of aqueous borate-δ11B, based on seawater pH, temperature, pressure and salinity. A radial cross section through an ~5 cm thick internode reveals largely homogeneous δ11B. However, in the centermost 0.5 cm of calcite growth adjacent to the axial core of the coral, a ~2% increase in δ11B corresponds with disequilibrium depletions in δ13C and δ18O, consistent with hypotheses for different growth modes of central calcite perhaps as a result of active calcite deposition along the axial core. Aside from this central region, the geochemical homogeneity and good agreement between coral surface δ11B and seawater borate δ11B suggests that bamboo corals may record deep-ocean carbon chemistry and thus pH. The cosmopolitan distribution of Keratoisis sp. in both living and fossil deep-sea coral communities thus potentially presents the opportunity to reconstruct recent and Holocene deep-water pH at high resolution.

  16. Kinetics and mechanism of the deep electrochemical oxidation of sodium diclofenac on a boron-doped diamond electrode

    NASA Astrophysics Data System (ADS)

    Vedenyapina, M. D.; Borisova, D. A.; Rosenwinkel, K.-H.; Weichgrebe, D.; Stopp, P.; Vedenyapin, A. A.

    2013-08-01

    The kinetics and mechanism of the deep oxidation of sodium diclofenac on a boron-doped diamond electrode are studied to develop a technique for purifying wastewater from pharmaceutical products. The products of sodium diclofenac electrolysis are analyzed using cyclic voltammetry and nuclear magnetic resonance techniques. It is shown that the toxicity of the drug and products of its electrolysis decreases upon its deep oxidation.

  17. The origin of deep-level impurity transitions in hexagonal boron nitride

    SciTech Connect

    Du, X. Z.; Li, J.; Lin, J. Y.; Jiang, H. X.

    2015-01-12

    Deep ultraviolet photoluminescence (PL) emission spectroscopy has been employed to investigate the origin of the widely observed deep level impurity related donor-acceptor pair (DAP) transition with an emission peak near 4.1 eV in hexagonal boron nitride (h-BN). A set of h-BN epilayers were grown by metal-organic chemical vapor deposition (MOCVD) under different ammonia (NH{sub 3}) flow rates to explore the role of nitrogen vacancies (V{sub N}) in the deep-level transitions. The emission intensity of the DAP transition near 4.1 eV was found to decrease exponentially with an increase of the NH{sub 3} flow rate employed during the MOCVD growth, implying that impurities involved are V{sub N}. The temperature-dependent PL spectra were measured from 10 K up to 800 K, which provided activation energies of ∼0.1 eV for the shallow impurity. Based on the measured energy level of the shallow impurity (∼0.1 eV) and previously estimated bandgap value of about 6.5 eV for h-BN, we deduce a value of ∼2.3 eV for the deep impurity involved in this DAP transition. The measured energy levels together with calculation results and formation energies of the impurities and defects in h-BN suggest that V{sub N} and carbon impurities occupying the nitrogen sites, respectively, are the most probable shallow donor and deep acceptor impurities involved in this DAP transition.

  18. Photosynthetic antenna-reaction center mimicry with a covalently linked monostyryl boron-dipyrromethene-aza-boron-dipyrromethene-C60 triad.

    PubMed

    Shi, Wen-Jing; El-Khouly, Mohamed E; Ohkubo, Kei; Fukuzumi, Shunichi; Ng, Dennis K P

    2013-08-19

    An efficient functional mimic of the photosynthetic antenna-reaction center has been designed and synthesized. The model contains a near-infrared-absorbing aza-boron-dipyrromethene (ADP) that is connected to a monostyryl boron-dipyrromethene (BDP) by a click reaction and to a fullerene (C60 ) using the Prato reaction. The intramolecular photoinduced energy and electron-transfer processes of this triad as well as the corresponding dyads BDP-ADP and ADP-C60 have been studied with steady-state and time-resolved absorption and fluorescence spectroscopic methods in benzonitrile. Upon excitation, the BDP moiety of the triad is significantly quenched due to energy transfer to the ADP core, which subsequently transfers an electron to the fullerene unit. Cyclic and differential pulse voltammetric studies have revealed the redox states of the components, which allow estimation of the energies of the charge-separated states. Such calculations show that electron transfer from the singlet excited ADP ((1) ADP*) to C60 yielding ADP(.+) -C60 (.-) is energetically favorable. By using femtosecond laser flash photolysis, concrete evidence has been obtained for the occurrence of energy transfer from (1) BDP* to ADP in the dyad BDP-ADP and electron transfer from (1) ADP* to C60 in the dyad ADP-C60 . Sequential energy and electron transfer have also been clearly observed in the triad BDP-ADP-C60 . By monitoring the rise of ADP emission, it has been found that the rate of energy transfer is fast (≈10(11)  s(-1) ). The dynamics of electron transfer through (1) ADP* has also been studied by monitoring the formation of C60 radical anion at 1000 nm. A fast charge-separation process from (1) ADP* to C60 has been detected, which gives the relatively long-lived BDP-ADP(.+) C60 (.-) with a lifetime of 1.47 ns. As shown by nanosecond transient absorption measurements, the charge-separated state decays slowly to populate mainly the triplet state of ADP before returning to the ground state

  19. Evaluation of processes controlling the geochemical constituents in deep groundwater in Bangladesh: spatial variability on arsenic and boron enrichment.

    PubMed

    Halim, M A; Majumder, R K; Nessa, S A; Hiroshiro, Y; Sasaki, K; Saha, B B; Saepuloh, A; Jinno, K

    2010-08-15

    Forty-six deep groundwater samples from highly arsenic affected areas in Bangladesh were analyzed in order to evaluate the processes controlling geochemical constituents in the deep aquifer system. Spatial trends of solutes, geochemical modeling and principal component analysis indicate that carbonate dissolution, silicate weathering and ion exchange control the major-ion chemistry. The groundwater is dominantly of Na-Cl type brackish water. Approximately 17% of the examined groundwaters exhibit As concentrations higher than the maximum acceptable limit of 10 microg/L for drinking water. Strong correlation (R(2)=0.67) of Fe with dissolved organic carbon (DOC) and positive saturation index of siderite suggests that the reductive dissolution of Fe-oxyhydroxide in presence of organic matter is considered to be the dominant process to release high content of Fe (median 0.31 mg/L) in the deep aquifer. In contrast, As is not correlated with Fe and DOC. Boron concentration in the 26% samples exceeds the standard limit of 500 microg/L, for water intended for human consumption. Negative relationships of B/Cl ratio with Cl and boron with Na/Ca ratio demonstrate the boron in deep groundwater is accompanied by brackish water and cation exchange within the clayey sediments.

  20. Progress to a Gallium-Arsenide Deep-Center Laser

    PubMed Central

    Pan, Janet L.

    2009-01-01

    Although photoluminescence from gallium-arsenide (GaAs) deep-centers was first observed in the 1960s, semiconductor lasers have always utilized conduction-to-valence-band transitions. Here we review recent materials studies leading to the first GaAs deep-center laser. First, we summarize well-known properties: nature of deep-center complexes, Franck-Condon effect, photoluminescence. Second, we describe our recent work: insensitivity of photoluminescence with heating, striking differences between electroluminescence and photoluminescence, correlation between transitions to deep-states and absence of bandgap-emission. Room-temperature stimulated-emission from GaAs deep-centers was observed at low electrical injection, and could be tuned from the bandgap to half-the-bandgap (900–1,600 nm) by changing the electrical injection. The first GaAs deep-center laser was demonstrated with electrical injection, and exhibited a threshold of less than 27 mA/cm2 in continuous-wave mode at room temperature at the important 1.54 μm fiber-optic wavelength. This small injection for laser action was explained by fast depopulation of the lower state of the optical transition (fast capture of free holes onto deep-centers), which maintains the population inversion. The evidence for laser action included: superlinear L-I curve, quasi-Fermi level separations satisfying Bernard-Duraffourg’s criterion, optical gains larger than known significant losses, clamping of the optical-emission from lossy modes unable to reach laser action, pinning of the population distribution during laser action.

  1. The effect of dipole boron centers on the electroluminescence of nanoscale silicon p{sup +}−n junctions

    SciTech Connect

    Bagraev, Nikolay; Klyachkin, Leonid; Kuzmin, Roman; Malyarenko, Anna; Mashkov, Vladimir

    2014-02-21

    Nanoscale silicon p{sup +}−;n junctions with very high concentration of boron, 5 10{sup 21} cm{sup −3}, are found to demonstrate interesting optical properties. Emission band dominated in near-infrared electroluminescence (EL) spectra possesses high degree of the linear polarization along preferred crystallographic axis which can be controlled by the lateral voltage applied in the plane of the p{sup +}−n junction. Such behavior together with the temperature dependence of the EL intensity is attributed to the presence of the self-compensating dipole boron centers, B{sup +}-B{sup −}, with negative correlation energy which are identified using the ESR technique in the nanoscale silicon p{sup +}−n junctions heavily doped with boron. The model of the recombination process though the negative-U dipole boron centers controlling the optical properties of the nanoscale silicon p{sup +}−n junctions is proposed.

  2. Dielectric strength, optical absorption, and deep ultraviolet detectors of hexagonal boron nitride epilayers

    NASA Astrophysics Data System (ADS)

    Li, J.; Majety, S.; Dahal, R.; Zhao, W. P.; Lin, J. Y.; Jiang, H. X.

    2012-10-01

    Hexagonal boron nitride (hBN) epilayers have been synthesized by metal organic chemical vapor deposition and their dielectric strength, optical absorption, and potential as a deep ultraviolet (DUV) detector material have been studied. Based on the graphene optical absorption concept, the estimated band-edge absorption coefficient of hBN is about 7 × 105/cm, which is more than 3 times higher than the value for wurtzite AlN (˜2 × 105 /cm). The dielectric strength of hBN epilayers exceeds that of AlN and is greater than 4.4 MV/cm based on the measured result for an hBN epilayer released from the host sapphire substrate. The hBN epilayer based DUV detectors exhibit a sharp cut-off wavelength around 230 nm, which coincides with the band-edge photoluminescence emission peak and virtually no responses in the long wavelengths. Based on the present study, we have identified several advantageous features of hBN DUV photodetectors: (1) low long wavelength response or high DUV to visible rejection ratio; (2) requiring very thin active layers due to high optical absorption; (3) high dielectric strength and chemical inertness and resistance to oxidation and therefore suitable for applications in extreme conditions; (4) high prospects of achieving flexible devices; and (5) possible integration with graphene optoelectronics due to their similar structures and lattice constants.

  3. Growth of hexagonal boron nitride on (111) Si for deep UV photonics and thermal neutron detection

    NASA Astrophysics Data System (ADS)

    Ahmed, K.; Dahal, R.; Weltz, A.; Lu, J.-Q.; Danon, Y.; Bhat, I. B.

    2016-09-01

    Hexagonal boron nitride (hBN) growth was carried out on (111) Si substrates at a temperature of 1350 °C using a cold wall chemical vapor deposition system. The hBN phase of the deposited films was identified by the characteristic Raman peak at 1370 cm-1 with a full width at half maximum of 25 cm-1, corresponding to the in-plane stretch of B and N atoms. Chemical bonding states and composition of the hBN films were analyzed by X-ray photoelectron spectroscopy; the extracted B/N ratio was 1.03:1, which is 1:1 within the experimental error. The fabricated metal-hBN-metal devices demonstrate a strong deep UV (DUV) response. Further, the hBN growth on the vertical (111) surfaces of parallel trenches fabricated in (110) Si was explored to achieve a thermal neutron detector. These results demonstrate that hBN-based detectors represent a promising approach towards the development of DUV photodetectors and efficient solid-state thermal neutron detectors.

  4. Toward deep blue nano hope diamonds: heavily boron-doped diamond nanoparticles.

    PubMed

    Heyer, Steffen; Janssen, Wiebke; Turner, Stuart; Lu, Ying-Gang; Yeap, Weng Siang; Verbeeck, Jo; Haenen, Ken; Krueger, Anke

    2014-06-24

    The production of boron-doped diamond nanoparticles enables the application of this material for a broad range of fields, such as electrochemistry, thermal management, and fundamental superconductivity research. Here we present the production of highly boron-doped diamond nanoparticles using boron-doped CVD diamond films as a starting material. In a multistep milling process followed by purification and surface oxidation we obtained diamond nanoparticles of 10-60 nm with a boron content of approximately 2.3 × 10(21) cm(-3). Aberration-corrected HRTEM reveals the presence of defects within individual diamond grains, as well as a very thin nondiamond carbon layer at the particle surface. The boron K-edge electron energy-loss near-edge fine structure demonstrates that the B atoms are tetrahedrally embedded into the diamond lattice. The boron-doped diamond nanoparticles have been used to nucleate growth of a boron-doped diamond film by CVD that does not contain an insulating seeding layer.

  5. Chirality Relay in 2,2'-Substituted 1,1'-Binaphthyl: Access to Propeller Chirality of the Tricoordinate Boron Center.

    PubMed

    Wang, Chen; Sun, Zuo-Bang; Xu, Qing-Wen; Zhao, Cui-Hua

    2016-11-14

    It is a challenging issue to achieve propeller chirality for triarylboranes owing to the low transition barrier between the P and M forms of the boron center. Herein, we report a new strategy to achieve propeller chirality of triarylboranes. It was found that the chirality relay from axially chiral 1,1'-binaphthyl to propeller chirality of the trivalent boron center can be realized when a Me2 N and a Mes2 B group (Mes=mesityl) are introduced at the 2,2'-positions of the 1,1'-binaphthyl skeleton (BN-BNaph) owing to the strong π-π interaction between the Me2 N-bonded naphthyl ring and the phenyl ring of one adjacent Mes group, which not only exerts great steric hindrance on the rotation of the two Mes groups but also gives unequal stability to the two configurations of the boron center for a given configuration of the binaphthyl moiety. The stereostructures of the boron center were fully characterized through (1) H NMR spectroscopy, X-ray crystal analyses, and theoretical calculations. Detailed comparisons with the analog BN-Ph-BNaph, in which the Mes2 B group is separated from 1,1'-binaphthyl by a para-phenylene spacer, confirmed the essential role of π-π interaction for the successful chirality relay in BN-BNaph.

  6. Boron desorption and fractionation in Subduction Zone Fore Arcs: Implications for the sources and transport of deep fluids

    NASA Astrophysics Data System (ADS)

    Saffer, Demian M.; Kopf, Achim J.

    2016-12-01

    At many subduction zones, pore water geochemical anomalies at seafloor seeps and in shallow boreholes indicate fluid flow and chemical transport from depths of several kilometers. Identifying the source regions for these fluids is essential toward quantifying flow pathways and volatile fluxes through fore arcs, and in understanding their connection to the loci of excess pore pressure at depth. Here we develop a model to track the coupled effects of boron desorption, smectite dehydration, and progressive consolidation within sediment at the top of the subducting slab, where such deep fluid signals likely originate. Our analysis demonstrates that the relative timing of heating and consolidation is a dominant control on pore water composition. For cold slabs, pore water freshening is maximized because dehydration releases bound water into low porosity sediment, whereas boron concentrations and isotopic signatures are modest because desorption is strongly sensitive to temperature and is only partially complete. For warmer slabs, freshening is smaller, because dehydration occurs earlier and into larger porosities, but the boron signatures are larger. The former scenario is typical of nonaccretionary margins where insulating sediment on the subducting plate is commonly thin. This result provides a quantitative explanation for the global observation that signatures of deeply sourced fluids are generally strongest at nonaccretionary margins. Application of our multitracer approach to the Costa Rica, N. Japan, N. Barbados, and Mediterranean Ridge subduction zones illustrates that desorption and dehydration are viable explanations for observed geochemical signals, and suggest updip fluid migration from these source regions over tens of km.

  7. 2-(2-Hydroxyphenyl)benzimidazole-based four-coordinate boron-containing materials with highly efficient deep-blue photoluminescence and electroluminescence.

    PubMed

    Zhang, Zhenyu; Zhang, Houyu; Jiao, Chuanjun; Ye, Kaiqi; Zhang, Hongyu; Zhang, Jingying; Wang, Yue

    2015-03-16

    Two novel four-coordinate boron-containing emitters 1 and 2 with deep-blue emissions were synthesized by refluxing a 2-(2-hydroxyphenyl)benzimidazole ligand with triphenylborane or bromodibenzoborole. The boron chelation produced a new π-conjugated skeleton, which rendered the synthesized boron materials with intense fluorescence, good thermal stability, and high carrier mobility. Both compounds displayed deep-blue emissions in solutions with very high fluorescence quantum yields (over 0.70). More importantly, the samples showed identical fluorescence in the solution and solid states, and the efficiency was maintained at a high level (approximately 0.50) because of the bulky substituents between the boron atom and the benzimidazole unit, which can effectively separate the flat luminescent units. In addition, neat thin films composed of 1 or 2 exhibited high electron and hole mobility in the same order of magnitude 10(-4), as determined by time-of-flight. The fabricated electroluminescent devices that employed 1 or 2 as emitting materials showed high-performance deep-blue emissions with Commission Internationale de L'Eclairage (CIE) coordinates of (X = 0.15, Y = 0.09) and (X = 0.16, Y = 0.08), respectively. Thus, the synthesized boron-containing materials are ideal candidates for fabricating high-performance deep-blue organic light-emitting diodes.

  8. Clinical trials of boron neutron capture therapy [in humans] [at Beth Israel Deaconess Medical Center][at Brookhaven National Laboratory

    SciTech Connect

    Wallace, Christine

    2001-05-29

    Assessment of research records of Boron Neutron Capture Therapy was conducted at Brookhaven National Laboratory and Beth Israel Deaconess Medical Center using the Code of Federal Regulations, FDA Regulations and Good Clinical Practice Guidelines. Clinical data were collected from subjects' research charts, and differences in conduct of studies at both centers were examined. Records maintained at Brookhaven National Laboratory were not in compliance with regulatory standards. Beth Israel's records followed federal regulations. Deficiencies discovered at both sites are discussed in the reports.

  9. Effects of seawater-pH and biomineralization on the boron isotopic composition of deep-sea bamboo corals

    NASA Astrophysics Data System (ADS)

    Farmer, Jesse R.; Hönisch, Bärbel; Robinson, Laura F.; Hill, Tessa M.

    2015-04-01

    The ocean is currently absorbing excess carbon from anthropogenic emissions, leading to reduced seawater-pH (termed 'ocean acidification'). Instrumental records of ocean acidification are unavailable from well-ventilated areas of the deep ocean, necessitating proxy records to improve spatio-temporal understanding on the rate and magnitude of deep ocean acidification. Here we investigate boron, carbon, and oxygen isotopes on live-collected deep-sea bamboo corals (genus Keratoisis) from a pHtot range of 7.5-8.1. These analyses are used to explore the potential for using bamboo coral skeletons as archives of past deep-sea pH and to trace anthropogenic acidification in the subsurface North Atlantic Ocean (850-2000 m water depth). Boron isotope ratios of the most recently secreted calcite of bamboo coral skeletons are close to the calculated isotopic composition of borate anion in seawater (δ11Bborate) for North Atlantic corals, and 1-2‰ higher than δ11Bborate for Pacific corals. Within individual coral skeletons, carbon and oxygen isotopes correlate positively and linearly, a feature associated with vital effects during coral calcification. δ11B variability of 0.5-2‰ is observed within single specimens, which exceeds the expected anthropogenic trend in modern North Atlantic corals. δ11B values are generally elevated in Pacific corals relative to δ11Bborate, which may reflect pH-driven physiological processes aiding coral calcification in environments unfavorable for calcite precipitation. Elevated δ11B values are also observed proximal to the central axis in multiple Atlantic and Pacific specimens, relative to δ11Bborate, which might reflect ontogenetic variability in calcification rates. Although the observed boron isotope variability is too large to resolve the present anthropogenic ocean acidification signal at the studied depths in the North Atlantic (∼0.03-0.07 pH units), pH changes ⩾0.1 units might still be reconstructed using δ11B measurements in

  10. Deep structure of the Pyatigorsk volcanic center (Northern Caucasus)

    NASA Astrophysics Data System (ADS)

    Zhostkow, R. A.; Masurenkov, Yu. P.; Dudarov, Z. I.; Shevchenko, A. V.; Dolov, S. M.; Danilov, K. B.

    2012-04-01

    Pyatigorsk laccoliths show a perceptible circular arrangement of tectonic and petro-geochemical features that also manifested in specific properties of a hydrothermal system of the Caucasian Mineral Waters and can be described as direct and natural elements of a higher order system, namely, the fluid-magmatic system of the Pyatigorsk volcanic center. It has been shown that mentioned arrangement may be approximated by a system of concentric isolines forming an isometric shape with the center located approximately 10 km west from the top of the Mount Beshtau positioned over the crust-mantle boundary inflection zone, and concentration of hydro-carbonates in the center of the anomalous area is six times more than this concentration at the periphery. On the basis of petro-geochemical and geological studies the hydrothermal system with obvious features of juvenile origin has been outlined. An average lifespan of this system is estimated to be at least several millions of years. The results of geophysical studies at the Beshtau laccolith (Pyatigorsk volcanic center) which were carried out in 2011 using the method of low-frequency microseismic sounding are presented. Vertical geophysical profile down to a depth of 30 km using a modified algorithm for processing the original data that improved the results of the transcripts and outlines the deep geological structure in more detail in the subsequent interpretation are presented and discussed. Thus, relationship of hydro-chemical properties of the Caucasian Mineral Waters with respect to structural and petro-geochemical features of Pyatigorsk volcanic center and its fluid-magmatic system structure has been discovered. Affiliation of the Caucasian Mineral Waters with a hydrothermal element of this system has been proved to be correct. New data on the deep structure of the Beshtau laccolith were obtained, and their combined interpretation with previous results obtained in geological, geophysical and petro-geochemical studies

  11. Annealing kinetics of boron-containing centers in electron-irradiated silicon

    SciTech Connect

    Feklisova, O. V. Yarykin, N. A.; Weber, J.

    2013-02-15

    The annealing kinetics of B{sub i}O{sub i} pairs created by fast-electron irradiation in Si wafers is studied. The wafers are grown by the Czochralski method and doped with boron to different levels. It is found that, at a particular temperature, the annealing rate steadily increases with increasing boron concentration. The results are described with a simple model that takes into consideration the interaction of interstitial boron atoms with oxygen atoms and substitutional boron atoms. In the context of the model, the temperature dependence of the dissociation rate of the B{sub i}O{sub i} complex is calculated.

  12. Electrically active centers formed in silicon during the high-temperature diffusion of boron and aluminum

    SciTech Connect

    Sobolev, N. A.; Loshachenko, A. S.; Poloskin, D. S.; Shek, E. I.

    2013-02-15

    The parameters of electrically active centers formed during the high-temperature diffusion of boron and aluminum into silicon in various media are studied by the Hall method and capacitance spectroscopy. It is found that the variation in the resistivity of the n base of the structures with p-n junctions fabricated in the study is controlled by the formation of three donor levels Q1, E4, and Q3 with the energies E{sub c} - 0.31, E{sub c} - 0.27, and E{sub c} - 0.16 eV. Diffusion in a chlorine-containing atmosphere introduces only a single level E4, but its concentration is 2.5 times lower, compared with diffusion in air. The values of the ionization energy of the Q3 level, measured under equilibrium (Hall effect) and nonequilibrium (capacitance spectroscopy) conditions, almost coincide. The deepest level E1 with an energy of E{sub c} - 0.54 eV, formed upon diffusion in both media, has no effect on the resistivity in the n base of the structures.

  13. Evolution of deep centers in GaN grown by hydride vapor phaseepitaxy

    SciTech Connect

    Fang, Z.-Q.; Look, D.C.; Jasinski, J.; Benamara, M.; Liliental-Weber, Z.; Molnar, R.J.

    2001-04-18

    Deep centers and dislocation densities in undoped n GaN, grown by hydride vapor phase epitaxy (HVPE), were characterized as a function of the layer thickness by deep level transient spectroscopy and transmission electron microscopy, respectively. As the layer thickness decreases, the variety and concentration of deep centers increase, in conjunction with the increase of dislocation density. Based on comparison with electron irradiation induced centers, some dominant centers in HVPE GaN are identified as possible point defects.

  14. Evidence of Northeastern Atlantic Ocean Acidification Recorded by Boron Isotopes on Deep-sea Coral Madrepora oculata

    NASA Astrophysics Data System (ADS)

    Gonzalez-Roubaud, C.; Douville, E.; Bordier, L.; Louvat, P.; Gaillardet, J.; Hall-Spencer, J. M.; Juillet-Leclerc, A.

    2011-12-01

    Ocean acidification is caused by the rising levels of CO2 in the atmosphere since the industrial era. Seawater pH has already decreased 0.1 units in surface waters and will continue to drop as atmospheric CO2 levels increase. Assessing the pH variability during the last decades is essential as survival of calcifying organisms strongly depends on seawater pH. Several studies have shown the potential of boron isotopic composition in tropical corals for reconstructing for sea-surface paleo-pH at low latitudes. For highest latitudes and deeper waters (50-4500 m), cold-water corals are interesting and unique as natural archives not only because they live between 4°C and 12°C under strong currents, recording the parameters of sub-surface or intermediate currents, but also because they build their aragonite skeleton without the photosynthesis process. In order to assess if the seawater acidification has already reached the North Atlantic Ocean at high latitudes, pH reconstruction has been performed on a deep-sea coral Madrepora oculata sample from Rost Reef (67°N, 9°E, 350 m of depth). Boron isotopes have been measured on the Neptune Multi-Collector Inductively Coupled Plasma Mass Spectrometer (MCICP-MS) with direct injection system (d-DIHEN). External reproducibility obtained here for seawater reference NASS-2 was 0.1%. The model age estimates its life-span to 40±3 years (2σ) and the Li/Mg ratio estimates a relative constant seawater temperature during the whole period of growth of the coral (7.0±0.5°C). A drop tendency is observed on boron isotopes, reflecting a potential decrease of seawater pH of approximately 0.06±0.02 pH units during the last 40 years, depending on the isotopic fractionation coefficient employed for calculations. Similarly, seawater acidification rate is 0.0012±0.00015 pH units per year. pH and temperature reconstructions revealed an influence of thermohaline circulation and surface winds on the skeleton geochemistry. Supplementary

  15. Deep Energy Retrofit Guidance for the Building America Solutions Center

    SciTech Connect

    Less, Brennan; Walker, Iain

    2015-01-01

    The U.S. DOE Building America program has established a research agenda targeting market-relevant strategies to achieve 40% reductions in existing home energy use by 2030. Deep Energy Retrofits (DERs) are part of the strategy to meet and exceed this goal. DERs are projects that create new, valuable assets from existing residences, by bringing homes into alignment with the expectations of the 21st century. Ideally, high energy using, dated homes that are failing to provide adequate modern services to their owners and occupants (e.g., comfortable temperatures, acceptable humidity, clean, healthy), are transformed through comprehensive upgrades to the building envelope, services and miscellaneous loads into next generation high performance homes. These guidance documents provide information to aid in the broader market adoption of DERs. They are intended for inclusion in the online resource the Building America Solutions Center (BASC). This document is an assemblage of multiple entries in the BASC, each of which addresses a specific aspect of Deep Energy Retrofit best practices for projects targeting at least 50% energy reductions. The contents are based upon a review of actual DERs in the U.S., as well as a mixture of engineering judgment, published guidance from DOE research in technologies and DERs, simulations of cost-optimal DERs, Energy Star and Consortium for Energy Efficiency (CEE) product criteria, and energy codes.

  16. Boron isotopes and B/Ca in benthic foraminifera: Proxies for the deep ocean carbonate system

    NASA Astrophysics Data System (ADS)

    Rae, James W. B.; Foster, Gavin L.; Schmidt, Daniela N.; Elliott, Tim

    2011-02-01

    Accurate records of the state of the ocean carbonate system are critical for understanding past changes in pCO 2, ocean acidification and climate. The chemical principles underlying the proxy of oceanic pH provided by the boron isotope ratio of foraminiferal carbonate are relatively well understood, but the proxy's reliability has been questioned. We present 76 new Multi-Collector Inductively-Coupled Plasma Mass Spectrometry (MC-ICPMS) δ11B measurements on a range of benthic foraminifera from 23 late-Holocene samples from the Atlantic that reaffirm the utility of the δ11B-pH proxy. Our boron isotope measurements on ~ 10 benthic foraminifera tests typically yield a precision of ~ ± 0.25‰ at 2 s.d. (equivalent to ~ ± 0.03 pH units). δ11B values of epifaunal species are within analytical uncertainty of those predicted from a simple model assuming sole incorporation of B(OH) 4- from seawater and no vital effects, using the independently determined fractionation factor of 1.0272 between 11B/ 10B of aqueous boron species. Infaunal foraminifera are consistent with this model, but record the combined effects of lower pore-water δ11B and pH. No influence of partial dissolution or shell size on δ11B is observed. We have also measured the B/Ca ratios of the same samples. For individual Cibicidoides species, B/Ca shows a good correlation with Δ[CO 32-], but the B/Ca of different co-occurring species morphotypes varies considerably. These effects are not seen in δ11B, which may therefore provide a more robust proxy of the ocean carbonate system. Whilst in theory δ11B and B/Ca can be combined to provide a quantitative reconstruction of alkalinity and dissolved inorganic carbonate (DIC), in practice this is precluded by propagated uncertainties. δ11B data give significant constraints on foraminifera calcification mechanisms, and seem most simply explained by incorporation of B(OH) 4- into a HCO 3- pool, which is then completely incorporated in foraminiferal CaCO 3

  17. Growth and device processing of hexagonal boron nitride epilayers for thermal neutron and deep ultraviolet detectors

    SciTech Connect

    Doan, T. C.; Li, J.; Lin, J. Y.; Jiang, H. X.

    2016-07-15

    Solid-state neutron detectors with high performance are highly sought after for the detection of fissile materials. However, direct-conversion neutron detectors based on semiconductors with a measureable efficiency have not been realized. We report here the first successful demonstration of a direct-conversion semiconductor neutron detector with an overall detection efficiency for thermal neutrons of 4% and a charge collection efficiency as high as 83%. The detector is based on a 2.7 μm thick {sup 10}B-enriched hexagonal boron nitride (h-BN) epitaxial layer. The results represent a significant step towards the realization of practical neutron detectors based on h-BN epilayers. Neutron detectors based on h-BN are expected to possess all the advantages of semiconductor devices including wafer-scale processing, compact size, light weight, and ability to integrate with other functional devices.

  18. High Acidification Rate of Norwegian Sea Revealed by Boron Isotopes in the Deep-Sea Coral Madrepora Oculata

    NASA Astrophysics Data System (ADS)

    Gonzalez, C.; Douville, E.; Hall-Spencer, J.; Montagna, P.; Louvat, P.; Gaillardet, J.; Frank, N.; Bordier, L.; Juillet-Leclerc, A.

    2012-12-01

    Ocean acidification and global warming due to the increase of anthropogenic CO2 are major threats for marine calcifying organisms, such as deep-sea corals, particularly in high-latitude regions. In order to evaluate the current anthropogenic perturbation and to properly assess the impacts and responses of calcifiers to previous changes in pH it is critical to investigate past changes of the seawater carbonate system. Unfortunately, current instrumental records of oceanic pH are limited, covering only a few decades. Scleractinian coral skeletons record chemical parameters of the seawater in which they grow. However, pH variability over multidecadal timescales remains largely unknown in intermediate and deep seawater masses. Here we present a study that highlights the potential of deep-sea-corals to overcome the lack of long-term pH records and that emphasizes a rapid acidification of high latitude subsurface waters of Norwegian Sea during the past decades. We have reconstructed seawater pH and temperature from a well dated deep-sea coral specimen Madrepora oculata collected alive from Røst reef in Norwegian Sea (67°N, 9°E, 340 m depth). This large branching framework forming coral species grew its skeleton over more than four decades determined using AMS 14C and 210Pb dating (Sabatier et al. 2012). B-isotopes and Li/Mg ratios yield an acidification rate of about -0.0030±0.0008 pH-unit.year-1 and a warming of 0.3°C during the past four decades (1967-2007). Overall our reconstruction technique agrees well with previous pH calculations (Hönisch et al., 2007 vs. Trotter et al., 2011 and McCulloch et al., 2012, i.e. the iterative method), but additional corrections are here applied using stable isotope correlations (O, C, B) to properly address kinetic fractionation of boron isotopes used for pH reconstruction. The resulting pH curve strongly anti-correlates with the annual NAO index, which further strengthens our evidence for the ocean acidification rate

  19. Theoretical Investigation of Stabilizing Mechanism by Boron in Body-Centered Cubic Iron Through (Fe,Cr)23(C,B)6 Precipitates

    NASA Astrophysics Data System (ADS)

    Sahara, Ryoji; Matsunaga, Tetsuya; Hongo, Hiromichi; Tabuchi, Masaaki

    2016-05-01

    Small amounts of boron improve the mechanical properties in high-chromium ferritic heat-resistant steels. In this work, the stabilizing mechanism by boron in body-centered cubic iron (bcc Fe) through (Fe,Cr)23(C,B)6 precipitates was investigated by first-principles calculations. Formation energy analysis of (Fe,Cr)23(C,B)6 reveals that the compounds become more stable to elemental solids as the boron concentration increases. Furthermore, the interface energy of bcc Fe(110) || Fe23(C,B)6(111) also decreases with boron concentration in the compounds. The decreased interface energy caused by boron addition is explained by the balance between the change in the phase stability of the precipitates and the change in the misfit parameter for the bcc Fe matrix and the precipitates. These results show that boron stabilizes the microstructure of heat-resistant steels, which is important for understanding the origins of the creep strength in ferritic steels.

  20. A study on the optimum fast neutron flux for boron neutron capture therapy of deep-seated tumors.

    PubMed

    Rasouli, Fatemeh S; Masoudi, S Farhad

    2015-02-01

    High-energy neutrons, named fast neutrons which have a number of undesirable biological effects on tissue, are a challenging problem in beam designing for Boron Neutron Capture Therapy, BNCT. In spite of this fact, there is not a widely accepted criterion to guide the beam designer to determine the appropriate contribution of fast neutrons in the spectrum. Although a number of researchers have proposed a target value for the ratio of fast neutron flux to epithermal neutron flux, it can be shown that this criterion may not provide the optimum treatment condition. This simulation study deals with the determination of the optimum contribution of fast neutron flux in the beam for BNCT of deep-seated tumors. Since the dose due to these high-energy neutrons damages shallow tissues, delivered dose to skin is considered as a measure for determining the acceptability of the designed beam. To serve this purpose, various beam shaping assemblies that result in different contribution of fast neutron flux are designed. The performances of the neutron beams corresponding to such configurations are assessed in a simulated head phantom. It is shown that the previously used criterion, which suggests a limit value for the contribution of fast neutrons in beam, does not necessarily provide the optimum condition. Accordingly, it is important to specify other complementary limits considering the energy of fast neutrons. By analyzing various neutron spectra, two limits on fast neutron flux are proposed and their validity is investigated. The results show that considering these limits together with the widely accepted IAEA criteria makes it possible to have a more realistic assessment of sufficiency of the designed beam. Satisfying these criteria not only leads to reduction of delivered dose to skin, but also increases the advantage depth in tissue and delivered dose to tumor during the treatment time. The Monte Carlo Code, MCNP-X, is used to perform these simulations.

  1. Double aromaticity in transition metal centered double-ring boron clusters M@B2n (M = Ti, Cr, Fe, Ni, Zn; n = 6, 7, 8)

    NASA Astrophysics Data System (ADS)

    Xu, Chang; Cheng, Longjiu; Yang, Jinlong

    2014-09-01

    It is well known that double-ring boron clusters have got the special double aromaticity with delocalized π orbitals in two directions (tangential and radial), which are potential ligands centered by a transition metal. In this article, the transition metal centered double-ring boron clusters M@B2n (M = Ti, Cr, Fe, Ni, Zn; n = 6, 7, 8) are theoretically investigated by density functional theory calculations. These endohedral compounds have also got double aromaticity in both tangential and radial directions. Interestingly, the tangential delocalized π orbitals of boron ligands following the Huckle's (4n + 2) rule do not interact with the central metal, while the radial π orbitals of boron ligands are bonded with the central mental to form spd-π endohedral bonding. The spd-π endohedral bonding follows the 18e-principle in Ni@B14 and Fe@B16. However, due to the flat shape of the compounds, 14e (Cr@B14) and 16e (Ni@B12) can also be electronically very stable where the energy levels of the spd-π orbitals delocalized in z-direction rise up. This intriguing bonding model makes sense in further study of the boron chemistry.

  2. CDGP, the data center for deep geothermal data from Alsace

    NASA Astrophysics Data System (ADS)

    Schaming, Marc; Grunberg, Marc; Jahn, Markus; Schmittbuhl, Jean; Cuenot, Nicolas; Genter, Albert; Dalmais, Eléonore

    2016-04-01

    CDGP (Centre de données de géothermie profonde, deep geothermal data center, http://cdgp.u-strasbg.fr) is set by the LabEX G-EAU-THERMIE PROFONDE to archive the high quality data collected in the Upper Rhine Graben geothermal sites and to distribute them to the scientific community for R&D activities, taking IPR (Intellectual Property Rights) into account. Collected datasets cover the whole life of geothermal projects, from exploration to drilling, stimulation, circulation and production. They originate from the Soultz-sous-Forêts pilot plant but also include more recent projects like the ECOGI project at Rittershoffen, Alsace, France. They are historically separated in two rather independent categories: geophysical datasets mostly related to the industrial management of the geothermal reservoir and seismological data from the seismic monitoring both during stimulations and circulations. Geophysical datasets are mainly up to now from the Soultz-sous-Forêts project that were stored on office's shelves and old digital media. Some inventories have been done recently, and a first step of the integration of these reservoir data into a PostgreSQL/postGIS database (ISO 19107 compatible) has been performed. The database links depths, temperatures, pressures, flows, for periods (times) and locations (geometries). Other geophysical data are still stored in structured directories as a data bank and need to be included in the database. Seismological datasets are of two kinds: seismological waveforms and seismicity bulletins; the former are stored in a standardized way both in format (miniSEED) and in files and directories structures (SDS) following international standard of the seismological community (FDSN), and the latter in a database following the open standard QuakeML. CDGP uses a cataloging application (GeoNetwork) to manage the metadata resources. It provides metadata editing and search functions as well as a web map viewer. The metadata editor supports ISO19115

  3. A pentacoordinate boron-containing π-electron system with Cl-B-Cl three-center four-electron bonds.

    PubMed

    Dou, Chuandong; Saito, Shohei; Yamaguchi, Shigehiro

    2013-06-26

    Tricoordinate boron-containing π-electron systems are an attractive class of compounds with intense fluorescence and strong electron-accepting properties. However, the impact of pentacoordination of the boron atoms on their properties has not been determined. We now disclose a B,B'-bis(1,8-dichloro-9-anthryl)-substituted 9,10-dihydro-9,10-diboraanthracene as a new pentacoordinate organoboron compound. In this skeleton, with the aid of the orthogonal arrangement of the anthryl substituent, the B and Cl atoms can form a three-center four-electron (3c-4e) Cl-B-Cl bond. The pentacoordination of the boron atom significantly perturbs the electronic structure and thereby the photophysical and electrochemical properties.

  4. Deep Energy Retrofit Guidance for the Building America Solutions Center

    SciTech Connect

    Less, Brennan; Walker, Iain

    2015-01-01

    The U.S. DOE Building America program has established a research agenda targeting market-relevant strategies to achieve 40% reductions in existing home energy use by 2030. Deep Energy Retrofits (DERs) are part of the strategy to meet and exceed this goal. DERs are projects that create new, valuable assets from existing residences, by bringing homes into alignment with the expectations of the 21st century. Ideally, high energy using, dated homes that are failing to provide adequate modern services to their owners and occupants (e.g., comfortable temperatures, acceptable humidity, clean, healthy), are transformed through comprehensive upgrades to the building envelope, services and miscellaneous loads into next generation high performance homes. These guidance documents provide information to aid in the broader market adoption of DERs.

  5. Impurity-induced deep centers in Tl6SI4

    DOE PAGES

    Shi, Hongliang; Lin, Wenwen; Kanatzidis, Mercouri G.; ...

    2017-04-13

    Tl6SI4 is a promising material for room-temperature semiconductor radiation detection applications. The history of the development of semiconductor radiation detection materials has demonstrated that impurities strongly affect the carrier transport and that material purification is a critically important step in improving the carrier transport and thereby the detector performance. Here, we report combined experimental and theoretical studies of impurities in Tl6SI4. Impurity concentrations in Tl6SI4 were analyzed by glow discharge mass spectrometry. Purification of the raw material by multi-pass vertical narrow zone refining was found to be effective in reducing the concentrations of most impurities. Density functional theory calculations weremore » also performed to study the trapping levels introduced by the main impurities detected in experiments. We show that, among dozens of detected impurities, most are either electrically inactive or shallow. In the purified Tl6SI4 sample, only Bi has a significant concentration (0.2 ppm wt) and introduces deep electron trapping levels in the band gap. Lastly, improvement of the purification processes is expected to further reduce the impurity concentrations and their impact on carrier transport in Tl6SI4, leading to improved detector performance.« less

  6. Impurity-induced deep centers in Tl6SI4

    NASA Astrophysics Data System (ADS)

    Shi, Hongliang; Lin, Wenwen; Kanatzidis, Mercouri G.; Szeles, Csaba; Du, Mao-Hua

    2017-04-01

    Tl6SI4 is a promising material for room-temperature semiconductor radiation detection applications. The history of the development of semiconductor radiation detection materials has demonstrated that impurities strongly affect the carrier transport and that material purification is a critically important step in improving the carrier transport and thereby the detector performance. Here, we report combined experimental and theoretical studies of impurities in Tl6SI4. Impurity concentrations in Tl6SI4 were analyzed by glow discharge mass spectrometry. Purification of the raw material by multi-pass vertical narrow zone refining was found to be effective in reducing the concentrations of most impurities. Density functional theory calculations were also performed to study the trapping levels introduced by the main impurities detected in experiments. We show that, among dozens of detected impurities, most are either electrically inactive or shallow. In the purified Tl6SI4 sample, only Bi has a significant concentration (0.2 ppm wt) and introduces deep electron trapping levels in the band gap. Improvement of the purification processes is expected to further reduce the impurity concentrations and their impact on carrier transport in Tl6SI4, leading to improved detector performance.

  7. Deep Level Donor-like Centers in MOCVD-grown n-type GaN

    NASA Astrophysics Data System (ADS)

    Ahoujja, Mo; Yeo, Y. K.; Hengehold, R. L.; Johnstone, D. K.

    2002-03-01

    Defects in semiconductors are of high importance because they adversely affect device performance. For example, defects may act as carrier trap and generation centers which may lead to premature current leakage, and they may also act as non-radiative recombination centers that may reduce the quantum efficiency of electro-optical devices. Therefore understanding the dynamical properties of deep level defects is an important step toward improving device performance. In this work, deep level defects in GaN grown on sapphire substrates by metal organic chemical vapor deposition (MOCVD) have been investigated using isothermal capacitance transient spectroscopy (ICTS) and current voltage temperature (IVT) measurements. ICTS analyses show that there are two deep levels of E3 and E4 with emission activation energies of 0.55 and 0.61 eV below the conduction band, respectively, at room temperature. The E4 trap center was found to be the most dominant defect having a larger cross section, smaller capture barrier, and higher concentration. The results from the I-V-T measurements show that this deep center is at about 0.54 eV below the conduction band, and decreases with increasing reverse bias voltage, indicating characteristics of a center with a donor nature. Further analyses of the trap filling dynamics reveal a coupled behavior nature between E3 and E4 traps.

  8. First-principles study of boron oxygen hole centers in crystals: Electronic structures and nuclear hyperfine and quadrupole parameters

    SciTech Connect

    Li Zucheng; Pan Yuanming

    2011-09-15

    The electronic structures, nuclear hyperfine coupling constants, and nuclear quadrupole parameters of fundamental boron oxygen hole centers (BOHCs) in zircon (ZrSiO{sub 4}, I4{sub 1}/amd) and calcite (CaCO{sub 3}, R3c) have been investigated using ab initio Hartree-Fock (HF) and various density functional theory (DFT) methods based on the supercell models with all-electron localized basis sets. Both exact HF exchange and appropriate correlation functionals are important in describing the BOHCs, and the parameter-free hybrid method based on Perdew, Burke, and Ernzerhof density functionals (PBE0) turns out to be the best DFT method in reproducing the electron paramagnetic resonance (EPR) data. Our results reveal three distinct types of simple-spin (S = 1/2) [BO{sub 3}]{sup 2-} centers in calcite: (i) the classic [BO{sub 3}]{sup 2-} radical with the D{sub 3h} symmetry and the unpaired spin equally distributed on the three oxygen atoms (i.e. the O{sub 3}{sup 5-} type); (ii) the previously reported [BO{sub 2}]{sup 0} center with the unpaired spin equally distributed on two of the three oxygen atoms (O{sub 2}{sup 3-}); and (iii) a new variety with {approx}90% of its unpaired spin localized on one (O{sup -}) of the three oxygen atoms with a long B-O bond (1.44 A). Calculations confirm the unusual [BO{sub 4}]{sup 0} center in zircon and show it to arise from a highly distorted configuration with 90% of the unpaired spin on one oxygen atom that has a considerably longer B-O bond (1.68 A) than its three counterparts (1.45 A). The calculated magnitudes and directions of {sup 11}B and {sup 17}O hyperfine coupling constants and nuclear quadrupole constants for the [BO{sub 4}]{sup 0} center in zircon are in excellent agreement with the 15 K EPR experimental data. These BOHCs are all characterized by a small negative spin density on the central B atom arising from spin polarization. Our calculations also demonstrate that the spin densities on BOHCs are affected substantially by

  9. SPECIAL ACTIVITIES SUPPLEMENTAL TO AND RELATED TO THE ART PROGRAM AT DEEP RIVER OUTDOOR EDUCATION CENTER.

    ERIC Educational Resources Information Center

    Gary City Public School System, IN.

    A CURRICULUM GUIDE DEALING WITH VARIOUS SUBJECT AREAS WAS PREPARED FOR POSSIBLE STUDY ACTIVITIES THAT WOULD USE THE LEARNING RESOURCES AVAILABLE AT THE DEEP RIVER OUTDOOR EDUCATION CENTER IN GARY, INDIANA. ACTIVITIES GUIDES ARE PRESENTED FOR (1) ART ACTITIVIES RELATED TO DESIGN, COLOR, LANDSCAPE REPRESENTATION, PAPER CONSTRUCTION, DRAWING, PRINT…

  10. Synthesis, photochromic, and computational studies of dithienylethene-containing β-diketonate derivatives and their near-infrared photochromic behavior upon coordination of a boron(III) center.

    PubMed

    Poon, Chun-Ting; Lam, Wai Han; Yam, Vivian Wing-Wah

    2013-03-04

    A series of dithienylethene-containing 1-thienyl-3-aryl-propane-1,3-diones (aryl = phenyl (Ph), thienyl (Th), and 4,5-bis(2,5-dimethylthiophen-3-yl)thiophen-2-yl (DTE-Th)) and the corresponding boron(III) diketonates, (O^O)BR(2) (R = F, C(6)F(5), and Ph), have been designed and synthesized. Their photophysical, electrochemical, and photochromic properties have been studied. Upon coordination of a boron(III) center, the closed forms of the dithienylethene-containing β-diketonates show near-infrared response and the photochromic behavior was also found to be affected by the aryl substituents at the 3-position of the β-diketonates. Moreover, computational studies have been performed that help to provide an understanding of the effect of substituents on the photophysical and photochromic properties.

  11. Person-Centered Care Practices in Long-Term Care in the Deep South.

    PubMed

    Jacobs, M Lindsey; Snow, A Lynn; Parmelee, Patricia A; Davis, Jullet A

    2016-04-01

    The purpose of this study was to identify structural, market, and administrator factors of nursing homes that are related to the implementation of person-centered care. Administrators of Medicare/Medicaid-certified nursing homes in the Deep South were invited to complete a standardized survey about their facility and their perceptions and attitudes regarding person-centered care practices (PCCPs). Nursing home structural and market factors were obtained from public websites, and these data were matched with administrator data. Consistent with the resource-based theory of competitive advantage, nursing homes with greater resources and more competition were more likely to implement PCCPs. Implementation of person-centered care was also higher in nursing homes with administrators who perceived culture change implementation to be feasible in their facilities. Given that there is a link between resource availability and adoption of person-centered care, future research should investigate the cost of such innovations.

  12. Impulsive and compulsive behaviors in Parkinson Study Group (PSG) centers performing deep brain stimulation surgery.

    PubMed

    Hack, Nawaz; Akbar, Umer; Thompson-Avila, Amanda; Fayad, Sarah M; Hastings, Erin M; Moro, Elena; Nestor, Kelsey; Ward, Herbert; York, Michele; Okun, Michael S

    2014-01-01

    Impulse control disorders (ICDs), dopamine dysregulation syndrome (DDS), and dopamine agonist withdrawal syndrome (DAWS) have been reported commonly in Parkinson's disease (PD) populations. The treatment approaches may be widely variable and there is not much information on these syndromes in the setting of deep brain stimulation (DBS). To evaluate (1) ICDs, DAWS and DDS pre- and post DBS in PD and (2) to investigate pre-DBS treatment strategies regarding these behaviors among Parkinson Study Group (PSG) centers. Forty-eight PSG centers were surveyed on ICDs, DAWS and DDS, as well as on potential relationships to DBS and treatment approaches. Sixty-seven percent of PSG centers reported that they served a population of over 500 PD patients per year, and 94% of centers performed DBS surgery. Most centers (92%) reported screening for ICDs, DAWS and DDS. Of the centers screening for these symptoms, 13% reported always employing a formal battery of pre-operative tests, 46% of sites inconsistently used a formal battery, while 23% of sites reported never using a formal battery to screen for these symptoms. The estimated numbers of centers observing ICDs, DAWS and DDS pre-operatively in individuals with PD were 71%, 69%, and 69%, respectively. PSG DBS centers observing at least one case of a new de novo occurrence of an ICD, DAWS or DDS after DBS surgery were 67%, 65% and 65%, respectively. The results suggest that addiction-like syndromes and withdrawal syndromes are prevalent in expert PSG centers performing DBS. Most centers reported screening for these issues without the use of a formal battery, and there were a large number of centers reporting ICDs, DAWS and DDS post-DBS. A single treatment strategy did not emerge.

  13. Mechanical properties of particulate composites based on a body-centered-cubic Mg-Li alloy containing boron

    NASA Technical Reports Server (NTRS)

    Whalen, R. T.; Gonzalez-Doncel, G.; Robinson, S. L.; Sherby, O. D.

    1989-01-01

    The effect of substituting the Mg metal in Mg-B composites by a Mg-14 wt pct Li solid solution on the ductility of the resulting composite was investigated using elastic modulus measurements on the P/M composite material prepared with a dispersion of B particles (in a vol pct range of 0-30) in a matrix of Mg-14 wt pct Li-1.5 wt pct Al. It was found that the elastic modulus of the composites increased rapidly with increasing boron, with specific stiffness values reaching about two times that of most structural materials. The values of the compression and tensile strengths increased significantly with boron additions. Good tensile ductility was achieved at the level of 10 vol pct B. However, at 20 vol pct B, the Mg-Li composite exhibited only limited tensile ductility (about 2 percent total elongation).

  14. Mechanical properties of particulate composites based on a body-centered-cubic Mg-Li alloy containing boron

    NASA Technical Reports Server (NTRS)

    Whalen, R. T.; Gonzalez-Doncel, G.; Robinson, S. L.; Sherby, O. D.

    1989-01-01

    The effect of substituting the Mg metal in Mg-B composites by a Mg-14 wt pct Li solid solution on the ductility of the resulting composite was investigated using elastic modulus measurements on the P/M composite material prepared with a dispersion of B particles (in a vol pct range of 0-30) in a matrix of Mg-14 wt pct Li-1.5 wt pct Al. It was found that the elastic modulus of the composites increased rapidly with increasing boron, with specific stiffness values reaching about two times that of most structural materials. The values of the compression and tensile strengths increased significantly with boron additions. Good tensile ductility was achieved at the level of 10 vol pct B. However, at 20 vol pct B, the Mg-Li composite exhibited only limited tensile ductility (about 2 percent total elongation).

  15. Utilization of the Usuda Deep Space Center for the United States International Cometary Explorer (ICE)

    NASA Technical Reports Server (NTRS)

    Fanelli, N. A.; Goodwin, J. P.; Petty, S. M.; Hayashi, T.; Nishimura, T.

    1986-01-01

    The Usuda Deep Space Center, which supported the ICE mission by enhancing the telemetry capability, is described. An outline of the comet Giacobini-Zinner observation project is provided. Usuda performance with one receiver channel was comparable to, if not better than, that of the Goldstone 64-m antenna with the two channels combined. The Usuda beam waveguide system is analyzed and found to have many advantages over conventional waveguide systems. It is concluded that this experience with the Usuda beam waveguide will become an integral part of future DSN decision making processes.

  16. A DLTS study of 4H-SiC-based p-n junctions fabricated by boron implantation

    SciTech Connect

    Ivanov, P. A. Potapov, A. S.; Samsonova, T. P.; Korol'kov, O.; Sleptsuk, N.

    2011-10-15

    Deep-level transient spectroscopy (DLTS) has been used to study p-n junctions fabricated by implantation of boron into epitaxial 4H-SiC films with n-type conductivity and the donor concentration (8-9) Multiplication-Sign 10{sup 14} cm{sup -3}. A DLTS signal anomalous in sign is observed; this signal is related to recharging of deep compensating boron-involved centers in the n-type region near the metallurgical boundary of the p-n junction.

  17. DEEP VADOSE ZONE APPLIED FIELD RESEARCH CENTER: TRANSFORMATIONAL TECHNOLOGY DEVELOPMENT FOR ENVIRONMENTAL REMEDIATION

    SciTech Connect

    Wellman, Dawn M.; Triplett, Mark B.; Freshley, Mark D.; Truex, Michael J.; Gephart, Roy E.; Johnson, Timothy C.; Chronister, Glen B.; Gerdes, Kurt D.; Chamberlain, Skip; Marble, Justin; Ramirez, Rosa

    2011-02-27

    DOE-EM, Office of Groundwater and Soil Remediation and DOE Richland, in collaboration with the Hanford site and Pacific Northwest National Laboratory, have established the Deep Vadose Zone Applied Field Research Center (DVZ-AFRC). The DVZ-AFRC leverages DOE investments in basic science from the Office of Science, applied research from DOE EM Office of Technology Innovation and Development, and site operation (e.g., site contractors [CH2M HILL Plateau Remediation Contractor and Washington River Protection Solutions], DOE-EM RL and ORP) in a collaborative effort to address the complex region of the deep vadose zone. Although the aim, goal, motivation, and contractual obligation of each organization is different, the integration of these activities into the framework of the DVZ-AFRC brings the resources and creativity of many to provide sites with viable alternative remedial strategies to current baseline approaches for persistent contaminants and deep vadose zone contamination. This cooperative strategy removes stove pipes, prevents duplication of efforts, maximizes resources, and facilitates development of the scientific foundation needed to make sound and defensible remedial decisions that will successfully meet the target cleanup goals for one of DOE EM's most intractable problems, in a manner that is acceptable by regulators.

  18. Coprecipitation and isotopic fractionation of boron in modern biogenic carbonates

    SciTech Connect

    Vengosh, A. Hebrew Univ., Jerusalem ); Chivas, A.R.; McCulloch, M.T. ); Kolodny, Y.; Starinsky, A. )

    1991-10-01

    The abundances and isotopic composition of boron in modern, biogenic calcareous skeletons from the Gulf of Elat, Israel, the Great Barrier Reef, Australia, and in deep-sea sediments have been examined by negative thermal-ionization mass spectrometry. The selected species (Foraminifera, Pteropoda, corals, Gastropoda, and Pelecypoda) yield large variations in boron concentration that range from 1 ppm in gastropod shells to 80 ppm in corals. The variations of {delta}{sup 11}B may be controlled by isotopic exchange of boron species in which {sup 10}B is preferentially partitioned into the tetrahedral species, and coprecipitation of different proportions of trigonal and tetrahedral species in the calcium carbonates. The B content and {delta}{sup 11}B values of deep-sea sediments, Foraminifera tests, and corals are used to estimate the global oceanic sink of elemental boron by calcium carbonate deposition. As a result of enrichment of B in corals, a substantially higher biogenic sink of 6.4 {plus minus} 0.9 {times} 10{sup 10} g/yr is calculated for carbonates. This is only slightly lower than the sink for desorbable B in marine sediments (10 {times} 10{sup 10} g/yr) and approximately half that of altered oceanic crust (14 {times} 10{sup 10} g/yr). Thus, carbonates are an important sink for B in the oceans being {approximately}20% of the total sinks. The preferential incorporation of {sup 10}B into calcium carbonate results in oceanic {sup 11}B-enrichment, estimated as 1.2 {plus minus} 0.3 {times} 10{sup 12} per mil {center dot} g/yr. The boron-isotope composition of authigenic, well-preserved carbonate skeletons may provide a useful tool to record secular boron-isotope variations in seawater at various times in the geological record.

  19. Boron cosmochemistry

    NASA Technical Reports Server (NTRS)

    Curtis, D. B.; Gladney, E. S.

    1985-01-01

    The abundances of boron, silicon, sulfur, and sodium were determined in 50 pieces of 28 chondritic meteorites. Boron abundances are found to define compositionally distinct domains within type C2M carbonaceous chondrites and petrologic type 5 and 6 ordinary chondrites. These domains may manifest the redistribution of boron within meteorites in response to low-temperature hydrous processes in C2M chondrites and high-temperature metamorphic processes in high petrologic type ordinary chondrites. Assuming that the redistribution was limited to regions comparable in size to the mass of the available meteorites, the boron abundance in unaltered material is determined. The depletion factors for boron in chondritic subgroups correlate with those for sulfur in the same subgroups. This correlation indicates that boron, like sulfur, is a moderately volatile element with a condensation temperature between 400 and 900 K.

  20. Boron supercapacitors

    DOE PAGES

    Zhan, Cheng; Zhang, Pengfei; Dai, Sheng; ...

    2016-11-16

    Supercapacitors based on the electric double-layer mechanism use porous carbons or graphene as electrodes. To move beyond this paradigm, we propose boron supercapacitors to leverage two-dimensional (2D) boron sheets’ metallicity and low weight. Six 2D boron sheets from both previous theoretical design and experimental growth are chosen as test electrodes. By applying joint density functional theory (JDFT) to the electrode–electrolyte system, we examine how the 2D boron sheets charge up against applied potential. JDFT predicts that these 2D boron sheets exhibit specific capacitance on the order of 400 F/g, about four times that of graphene. As a result, our workmore » suggests that 2D boron sheets are promising electrodes for supercapacitor applications.« less

  1. Boron supercapacitors

    SciTech Connect

    Zhan, Cheng; Zhang, Pengfei; Dai, Sheng; Jiang, De -en

    2016-11-16

    Supercapacitors based on the electric double-layer mechanism use porous carbons or graphene as electrodes. To move beyond this paradigm, we propose boron supercapacitors to leverage two-dimensional (2D) boron sheets’ metallicity and low weight. Six 2D boron sheets from both previous theoretical design and experimental growth are chosen as test electrodes. By applying joint density functional theory (JDFT) to the electrode–electrolyte system, we examine how the 2D boron sheets charge up against applied potential. JDFT predicts that these 2D boron sheets exhibit specific capacitance on the order of 400 F/g, about four times that of graphene. As a result, our work suggests that 2D boron sheets are promising electrodes for supercapacitor applications.

  2. Boron reclamation

    SciTech Connect

    Smith, R.M.

    1980-07-01

    A process to recover high purity /sup 10/B enriched crystalline boron powder from a polymeric matrix was developed on a laboratory basis and ultimately scaled up to production capacity. The process is based on controlled pyrolysis of boron-filled scrap followed by an acid leach and dry sieving operation to return the powder to the required purity and particle size specifications. Typically, the recovery rate of the crystalline powder is in excess of 98.5 percent, and some of the remaining boron is recovered in the form of boric acid. The minimum purity requirement of the recovered product is 98.6 percent total boron.

  3. The Deep Impact Network Experiment Operations Center Monitor and Control System

    NASA Technical Reports Server (NTRS)

    Wang, Shin-Ywan (Cindy); Torgerson, J. Leigh; Schoolcraft, Joshua; Brenman, Yan

    2009-01-01

    The Interplanetary Overlay Network (ION) software at JPL is an implementation of Delay/Disruption Tolerant Networking (DTN) which has been proposed as an interplanetary protocol to support space communication. The JPL Deep Impact Network (DINET) is a technology development experiment intended to increase the technical readiness of the JPL implemented ION suite. The DINET Experiment Operations Center (EOC) developed by JPL's Protocol Technology Lab (PTL) was critical in accomplishing the experiment. EOC, containing all end nodes of simulated spaces and one administrative node, exercised publish and subscribe functions for payload data among all end nodes to verify the effectiveness of data exchange over ION protocol stacks. A Monitor and Control System was created and installed on the administrative node as a multi-tiered internet-based Web application to support the Deep Impact Network Experiment by allowing monitoring and analysis of the data delivery and statistics from ION. This Monitor and Control System includes the capability of receiving protocol status messages, classifying and storing status messages into a database from the ION simulation network, and providing web interfaces for viewing the live results in addition to interactive database queries.

  4. Implementation Plan for the Deep Vadose Zone-Applied Field Research Center

    SciTech Connect

    Wellman, Dawn M.; Truex, Michael J.; Freshley, Mark D.; Gephart, Roy E.; Triplett, Mark B.; Johnson, Timothy C.

    2011-02-11

    The Long-Range Deep Vadose Zone Program Plan was published in October 2010. It summarized the U.S. Department of Energy’s (DOE’s) state-of-knowledge about the contaminant remediation challenges facing the deep vadose zone (DVZ) beneath the Central Plateau of the Hanford Site and their approach to solving those challenges. Developing an implementation plan is the next step to address the knowledge and capabilities required to solve DVZ challenges when needed. This multi-year plan (FY-11 through FY-20) identifies the short to long-term research, management, and execution plans required to solve those problems facing the DVZ-Applied Field Research Center (DVZ-AFRC). The schedule supporting implementation overlies existing activities and milestones from Hanford’s DOE-Environmental Management (EM) end-user projects. Success relies upon multi-project teams focused on coordinated subsurface projects undertaken across the DOE Complex combined with facilitated, problem-focused, research investments implemented through the DVZ-AFRC.

  5. Electroextraction of boron from boron carbide scrap

    SciTech Connect

    Jain, Ashish; Anthonysamy, S.; Ghosh, C.; Ravindran, T.R.; Divakar, R.; Mohandas, E.

    2013-10-15

    Studies were carried out to extract elemental boron from boron carbide scrap. The physicochemical nature of boron obtained through this process was examined by characterizing its chemical purity, specific surface area, size distribution of particles and X-ray crystallite size. The microstructural characteristics of the extracted boron powder were analyzed by using scanning electron microscopy and transmission electron microscopy. Raman spectroscopic examination of boron powder was also carried out to determine its crystalline form. Oxygen and carbon were found to be the major impurities in boron. Boron powder of purity ∼ 92 wt. % could be produced by the electroextraction process developed in this study. Optimized method could be used for the recovery of enriched boron ({sup 10}B > 20 at. %) from boron carbide scrap generated during the production of boron carbide. - Highlights: • Recovery of {sup 10}B from nuclear grade boron carbide scrap • Development of process flow sheet • Physicochemical characterization of electroextracted boron • Microscopic examination of electroextracted boron.

  6. Reduction of the linewidths of deep luminescence centers in 28Si reveals fingerprints of the isotope constituents.

    PubMed

    Steger, M; Yang, A; Stavrias, N; Thewalt, M L W; Riemann, H; Abrosimov, N V; Churbanov, M F; Gusev, A V; Bulanov, A D; Kovalev, I D; Kaliteevskii, A K; Godisov, O N; Becker, P; Pohl, H-J

    2008-05-02

    Dramatic reductions of the linewidths of well-known deep centers in 28Si reveal "isotopic fingerprints" of the constituents. The approximately 1014 meV Cu center, thought to be either a Cu pair or an isolated Cu, is shown to contain four Cu atoms, and the approximately 780 meV Ag center is shown to contain four Ag. The approximately 944 meV ;{*}Cu center, thought to be a different configuration of a Cu pair, in fact contains three Cu and one Ag, and a new two-Cu two-Ag center is found. The approximately 735 meV center, previously assigned to Fe, actually contains Au and three Cu. This suggests a family of four-atom (Cu, Ag, Au) centers.

  7. Cost analysis of awake versus asleep deep brain stimulation: a single academic health center experience.

    PubMed

    Jacob, R Lorie; Geddes, Jonah; McCartney, Shirley; Burchiel, Kim J

    2016-05-01

    OBJECT The objective of this study was to compare the cost of deep brain stimulation (DBS) performed awake versus asleep at a single US academic health center and to compare costs across the University HealthSystem Consortium (UHC) Clinical Database. METHODS Inpatient and outpatient demographic and hospital financial data for patients receiving a neurostimulator lead implant (from the first quarter of 2009 to the second quarter of 2014) were collected and analyzed. Inpatient charges included those associated with International Classification of Diseases, Ninth Revision (ICD-9) procedure code 0293 (implantation or replacement of intracranial neurostimulator lead). Outpatient charges included all preoperative charges ≤ 30 days prior to implant and all postoperative charges ≤ 30 days after implant. The cost of care based on reported charges and a cost-to-charge ratio was estimated. The UHC database was queried (January 2011 to March 2014) with the same ICD-9 code. Procedure cost data across like hospitals (27 UHC hospitals) conducting similar DBS procedures were compared. RESULTS Two hundred eleven DBS procedures (53 awake and 158 asleep) were performed at a single US academic health center during the study period. The average patient age ( ± SD) was 65 ± 9 years old and 39% of patients were female. The most common primary diagnosis was Parkinson's disease (61.1%) followed by essential and other forms of tremor (36%). Overall average DBS procedure cost was $39,152 ± $5340. Asleep DBS cost $38,850 ± $4830, which was not significantly different than the awake DBS cost of $40,052 ± $6604. The standard deviation for asleep DBS was significantly lower (p ≤ 0.05). In 2013, the median cost for a neurostimulator implant lead was $34,052 at UHC-affiliated hospitals that performed at least 5 procedures a year. At Oregon Health & Science University, the median cost was $17,150 and the observed single academic health center cost for a neurostimulator lead implant was

  8. Provision of deep procedural sedation by a pediatric sedation team at a freestanding imaging center.

    PubMed

    Emrath, Elizabeth T; Stockwell, Jana A; McCracken, Courtney E; Simon, Harold K; Kamat, Pradip P

    2014-08-01

    Freestanding imaging centers are popular options for health care systems to offer services accessible to local communities. The provision of deep sedation at these centers could allow for flexibility in scheduling imaging for pediatric patients. Our Children's Sedation Services group, comprised of pediatric critical care medicine and pediatric emergency medicine physicians, has supplied such a service for 5 years. However, limited description of such off-site services exists. The site has resuscitation equipment and medications, yet limited staffing and no proximity to hospital support. To describe the experience of a cohort of pediatric patients undergoing sedation at a freestanding imaging center. A retrospective chart review of all sedations from January 2012 to December 2012. Study variables include general demographics, length of sedation, type of imaging, medications used, completion of imaging, adverse events based on those defined by the Pediatric Sedation Research Consortium database and need for transfer to a hospital for additional care. Six hundred fifty-four consecutive sedations were analyzed. Most patients were low acuity American Society of Anesthesiologists physical class ≤ 2 (91.8%). Mean sedation time was 55 min (SD ± 24). The overwhelming majority of patients (95.7%) were sedated for MRI, 3.8% for CT and <1% (three patients) for both modalities. Propofol was used in 98% of cases. Overall, 267 events requiring intervention occurred in 164 patient encounters (25.1%). However, after adjustment for changes from expected physiological response to the sedative, the rate of events was 10.2%. Seventy-five (11.5%) patients had desaturation requiring supplemental oxygen, nasopharyngeal tube or oral airway placement, continuous positive airway pressure or brief bag valve mask ventilation. Eleven (1.7%) had apnea requiring continuous positive airway pressure or bag valve mask ventilation briefly. One patient had bradycardia that resolved with

  9. Computational Studies of Nanostructures of Boron

    NASA Astrophysics Data System (ADS)

    Tandy, P.; Yu, M.; Leahy, C.; Tian, W. Q.; Wu, S. Y.; Jayanthi, C. S.

    2009-03-01

    The goal of this work is to develop a reliable semi-empirical Hamiltonian for boron that may be used to predict nanostructures of boron. It is well known that bonding in boron is complicated as it may form three-center, two-electron bonds. The semi-empirical Hamiltonian used here was recently developed by Leahy et al. in the framework of linear combination of atomic orbitals[1]. The salient feature of this Hamiltonian is that it treats environment dependency and charge redistributions on equal footing. It will be shown that such a parameterized Hamiltonian can predict the B80 cage structure with C1 symmetry as found in a recent first-principles study [2]. Having validated our semi-empirical Hamiltonian for boron with small boron clusters and the B80 cage, we have performed a systematic study of other boron nanostructures: (i) larger cage structures (e.g., B215), (ii) boron clusters cut from the bulk alpha boron, and (iii) boron sheets (triangular sheets with and without holes). We will discuss the ground state structures of these boron nanostructures as well as the energetics and HOMO-LUMO gaps of different families of boron clusters as a function their diameters. 1. C. Leahy et al. Phys. Rev. B74, 155408 (2006). 2. N. G. Szwacki et al. PRL 100, 159901 (2008).

  10. The symmetry of the boron buckyball and a related boron nanotube

    NASA Astrophysics Data System (ADS)

    Gonzalez Szwacki, N.; Tymczak, C. J.

    2010-07-01

    We investigate the symmetry of the boron buckyball and a related boron nanotube. Using large-scale ab initio calculations up to second-order Møller-Plesset perturbation theory, we have determined unambiguously the equilibrium geometry/symmetry of two structurally related boron clusters: the B 80 fullerene and the finite-length (5 0) boron nanotube. The B 80 cluster was found to have the same symmetry, Ih, as the C 60 molecule since its 20 additional boron atoms are located exactly at the centers of the 20 hexagons. Additionally, we also show that the (5 0) boron nanotube does not suffer from atomic buckling and its symmetry is D5d instead of C5v as has been described by previous calculations. Therefore, we predict that all the boron nanotubes rolled from the α-sheet will be free from structural distortions, which has a significant impact on their electronic properties.

  11. Low-energy neutrino search for dark matter in the Galactic Center with IceCube-DeepCore

    SciTech Connect

    Flis, Samuel; Collaboration: IceCube Collaboration

    2014-11-18

    The cubic-kilometer sized IceCube neutrino observatory, constructed in the glacial ice at the South Pole, offers new opportunities for neutrino physics to reach lower neutrino energies with its in-fill array 'DeepCore'. A set of analysis techniques where the outer layers of IceCube are used as a veto makes it possible to reject atmospheric muons and thereby allows low-energy neutrino searches to be performed above the horizon. With these techniques the Galactic Center, an important target in searches for self-annihilating dark matter, becomes accessible for IceCube. In this contribution, we present the status of the Galactic Center dark matter analysis, using more than 10 months of data taken with the 79-string configuration of IceCube-DeepCore, as well as the new veto techniques used in the analysis.

  12. Cost of a genioplasty under deep intravenous sedation in a private office versus general anesthesia in an outpatient surgical center.

    PubMed

    Van Sickels, J E; Tiner, B D

    1992-07-01

    The cases of twenty-four patients who underwent genioplasties either under deep intravenous (IV) sedation in a dental office or under general anesthesia in a surgical center were reviewed. A cost comparison of this operation in these two environments showed that it was twice as expensive to have the same procedure done in an outpatient surgical suite under general anesthesia as it was in a private office under IV sedation.

  13. Studies of deep level transient spectroscopy of DX centers in GaAlAs: Te under uniaxial stress

    SciTech Connect

    Li, Ming-Fu |; Yu, Y.P. |; Weber, E.R.; Haller, E.E. |; Hansen, W.L.; Bauser, E.

    1991-11-01

    DX centers in Al{sub 0.38}Ga{sub 0.62}As doped with Te have been studied by Deep Level Transient Spectroscopy (DLTS) as a function of uniaxial stress. No splitting nor broadening of the DLTS peaks were observed. However, the peak positions and heights depend on the stress and its directions. The results have been analyzed by comparison with existing models and hydrostatic pressure measurements.

  14. Direct current sputtering of boron from boron/boron mixtures

    DOEpatents

    Timberlake, J.R.; Manos, D.; Nartowitz, E.

    1994-12-13

    A method for coating a substrate with boron by sputtering includes lowering the electrical resistance of a boron-containing rod to allow electrical conduction in the rod; placing the boron-containing rod inside a vacuum chamber containing substrate material to be coated; applying an electrical potential between the boron target material and the vacuum chamber; countering a current avalanche that commences when the conduction heating rate exceeds the cooling rate, and until a steady equilibrium heating current is reached; and, coating the substrate material with boron by sputtering from the boron-containing rod. 2 figures.

  15. Correlation of a generation-recombination center with a deep level trap in GaN

    SciTech Connect

    Nguyen, X. S. E-mail: elecsj@nus.edu.sg; Lin, K.; Zhang, Z.; Arehart, A. R.; Ringel, S. A.; McSkimming, B.; Speck, J. S.; Fitzgerald, E. A.; Chua, S. J. E-mail: elecsj@nus.edu.sg

    2015-03-09

    We report on the identification of a deep level trap centre which contributes to generation-recombination noise. A n-GaN epilayer, grown by MOCVD on sapphire, was measured by deep level transient spectroscopy (DLTS) and noise spectroscopy. DLTS found 3 well documented deep levels at E{sub c} − 0.26 eV, E{sub c} − 0.59 eV, and E{sub c} − 0.71 eV. The noise spectroscopy identified a generation recombination centre at E{sub c} − 0.65 ± 0.1 eV with a recombination lifetime of 65 μs at 300 K. This level is considered to be the same as the one at E{sub c} − 0.59 eV measured from DLTS, as they have similar trap densities and capture cross section. This result shows that some deep levels contribute to noise generation in GaN materials.

  16. The role of deep acceptor centers in the oxidation of acceptor-doped wide-band-gap perovskites ABO3

    NASA Astrophysics Data System (ADS)

    Putilov, L. P.; Tsidilkovski, V. I.

    2017-03-01

    The impact of deep acceptor centers on defect thermodynamics and oxidation of wide-band-gap acceptor-doped perovskites without mixed-valence cations is studied. These deep centers are formed by the acceptor-bound small hole polarons whose stabilization energy can be high enough (significantly higher than the hole-acceptor Coulomb interaction energy). It is shown that the oxidation enthalpy ΔHox of oxide is determined by the energy εA of acceptor-bound states along with the formation energy EV of oxygen vacancies. The oxidation reaction is demonstrated to be either endothermic or exothermic, and the regions of εA and EV values corresponding to the positive or negative ΔHox are determined. The contribution of acceptor-bound holes to the defect thermodynamics strongly depends on the acceptor states depth εA: it becomes negligible at εA less than a certain value (at which the acceptor levels are still deep). With increasing εA, the concentration of acceptor-bound small hole polarons can reach the values comparable to the dopant content. The results are illustrated with the acceptor-doped BaZrO3 as an example. It is shown that the experimental data on the bulk hole conductivity of barium zirconate can be described both in the band transport model and in the model of hopping small polarons localized on oxygen ions away from the acceptor centers. Depending on the εA magnitude, the oxidation reaction can be either endothermic or exothermic for both mobility mechanisms.

  17. Crystalline boron nitride aerogels

    DOEpatents

    Zettl, Alexander K.; Rousseas, Michael; Goldstein, Anna P.; Mickelson, William; Worsley, Marcus A.; Woo, Leta

    2017-04-04

    This disclosure provides methods and materials related to boron nitride aerogels. In one aspect, a material comprises an aerogel comprising boron nitride. The boron nitride has an ordered crystalline structure. The ordered crystalline structure may include atomic layers of hexagonal boron nitride lying on top of one another, with atoms contained in a first layer being superimposed on atoms contained in a second layer.

  18. Peculiarities of thermal extinction of deep-center luminescence in cadmium selenide

    SciTech Connect

    Ermolovich, I.B.; Bulakh, B.M.

    1986-10-01

    The authors study the mechanisms of thermal extinction of the luminescence bands in cadmium selenide with lambda mad = 0.92 (band I) and 1.16 um (band II), for which the main photoluminescence centers are responsible. CdSe crystals grown from the gas phase and deliberately not doped were studied. The curves of the intensities of the bands I and II in the layers and single crystals are shown. A model is presented of the configurational coordinates for explaining the internal mechanism of extinction of impurity luminescence in crystal phosphors. A diagram is shown of the recombination transitions for wide-gap crystal phosphors with the anticipation of two luminescence centers and a nonradiative recombination center. This study proves that the corresponding luminescence centers in cadmium selenide single crystals and layers have the same physicochemical structure.

  19. Boron Nitride Nanotubes

    NASA Technical Reports Server (NTRS)

    Smith, Michael W. (Inventor); Jordan, Kevin (Inventor); Park, Cheol (Inventor)

    2012-01-01

    Boron nitride nanotubes are prepared by a process which includes: (a) creating a source of boron vapor; (b) mixing the boron vapor with nitrogen gas so that a mixture of boron vapor and nitrogen gas is present at a nucleation site, which is a surface, the nitrogen gas being provided at a pressure elevated above atmospheric, e.g., from greater than about 2 atmospheres up to about 250 atmospheres; and (c) harvesting boron nitride nanotubes, which are formed at the nucleation site.

  20. Boron nitride nanotubes

    DOEpatents

    Smith, Michael W [Newport News, VA; Jordan, Kevin [Newport News, VA; Park, Cheol [Yorktown, VA

    2012-06-06

    Boron nitride nanotubes are prepared by a process which includes: (a) creating a source of boron vapor; (b) mixing the boron vapor with nitrogen gas so that a mixture of boron vapor and nitrogen gas is present at a nucleation site, which is a surface, the nitrogen gas being provided at a pressure elevated above atmospheric, e.g., from greater than about 2 atmospheres up to about 250 atmospheres; and (c) harvesting boron nitride nanotubes, which are formed at the nucleation site.

  1. Boron nitride composites

    DOEpatents

    Kuntz, Joshua D.; Ellsworth, German F.; Swenson, Fritz J.; Allen, Patrick G.

    2017-02-21

    According to one embodiment, a composite product includes: a matrix material including hexagonal boron nitride and one or more borate binders; and a plurality of cubic boron nitride particles dispersed in the matrix material. According to another embodiment, a composite product includes: a matrix material including hexagonal boron nitride and amorphous boron nitride; and a plurality of cubic boron nitride particles dispersed in the matrix material.

  2. Potential for deep basin-centered gas accumulation in Hanna Basin, Wyoming

    USGS Publications Warehouse

    Wilson, Michael S.; Dyman, Thaddeus S.; Nuccio, Vito F.

    2001-01-01

    The potential for a continuous-type basin-centered gas accumulation in the Hanna Basin in Carbon County, Wyoming, is evaluated using geologic and production data including mud-weight, hydrocarbon-show, formation-test, bottom-hole-temperature, and vitrinite reflectance data from 29 exploratory wells. This limited data set supports the presence of a hypothetical basin-centered gas play in the Hanna Basin. Two generalized structural cross sections illustrate our interpretations of possible abnormally pressured compartments. Data indicate that a gas-charged, overpressured interval may occur within the Cretaceous Mowry, Frontier, and Niobrara Formations at depths below 10,000 ft along the southern and western margins of the basin. Overpressuring may also occur near the basin center within the Steele Shale and lower Mesaverde Group section at depths below 18,000 to 20,000 ft. However, the deepest wells drilled to date (12,000 to 15,300 ft) have not encountered over-pressure in the basin center. This overpressured zone is likely to be relatively small (probably 20 to 25 miles in diameter) and is probably depleted of gas near major basement reverse faults and outcrops where gas may have escaped. Water may have invaded reservoirs through outcrops and fracture zones along the basin margins, creating an extensive normally pressured zone. A zone of subnormal pressure also may exist below the water-saturated, normal-pressure zone and above the central zone of overpressure. Subnormal pressures have been interpreted in the center of the Hanna Basin at depths ranging from 10,000 to 25,000 ft based on indirect evidence including lost-circulation zones. Three wells on the south side of the basin, where the top of the subnormally pressured zone is interpreted to cut across stratigraphic boundaries, tested the Niobrara Formation and recovered gas and oil shows with very low shut-in pressures.

  3. Embedded Ultrathin Cluster Electrodes for Long-Term Recordings in Deep Brain Centers

    PubMed Central

    Thorbergsson, Palmi Thor; Ekstrand, Joakim; Friberg, Annika; Granmo, Marcus; Pettersson, Lina M. E.; Schouenborg, Jens

    2016-01-01

    Neural interfaces which allow long-term recordings in deep brain structures in awake freely moving animals have the potential of becoming highly valuable tools in neuroscience. However, the recording quality usually deteriorates over time, probably at least partly due to tissue reactions caused by injuries during implantation, and subsequently micro-forces due to a lack of mechanical compliance between the tissue and neural interface. To address this challenge, we developed a gelatin embedded neural interface comprising highly flexible electrodes and evaluated its long term recording properties. Bundles of ultrathin parylene C coated platinum electrodes (N = 29) were embedded in a hard gelatin based matrix shaped like a needle, and coated with Kollicoat™ to retard dissolution of gelatin during the implantation. The implantation parameters were established in an in vitro model of the brain (0.5% agarose). Following a craniotomy in the anesthetized rat, the gelatin embedded electrodes were stereotactically inserted to a pre-target position, and after gelatin dissolution the electrodes were further advanced and spread out in the area of the subthalamic nucleus (STN). The performance of the implanted electrodes was evaluated under anesthesia, during 8 weeks. Apart from an increase in the median-noise level during the first 4 weeks, the electrode impedance and signal-to-noise ratio of single-units remained stable throughout the experiment. Histological postmortem analysis confirmed implantation in the area of STN in most animals. In conclusion, by combining novel biocompatible implantation techniques and ultra-flexible electrodes, long-term neuronal recordings from deep brain structures with no significant deterioration of electrode function were achieved. PMID:27159159

  4. Methods of forming boron nitride

    DOEpatents

    Trowbridge, Tammy L; Wertsching, Alan K; Pinhero, Patrick J; Crandall, David L

    2015-03-03

    A method of forming a boron nitride. The method comprises contacting a metal article with a monomeric boron-nitrogen compound and converting the monomeric boron-nitrogen compound to a boron nitride. The boron nitride is formed on the same or a different metal article. The monomeric boron-nitrogen compound is borazine, cycloborazane, trimethylcycloborazane, polyborazylene, B-vinylborazine, poly(B-vinylborazine), or combinations thereof. The monomeric boron-nitrogen compound is polymerized to form the boron nitride by exposure to a temperature greater than approximately 100.degree. C. The boron nitride is amorphous boron nitride, hexagonal boron nitride, rhombohedral boron nitride, turbostratic boron nitride, wurzite boron nitride, combinations thereof, or boron nitride and carbon. A method of conditioning a ballistic weapon and a metal article coated with the monomeric boron-nitrogen compound are also disclosed.

  5. Boron Fullerenes: An Electronic Structure Study

    NASA Astrophysics Data System (ADS)

    Sadrzadeh, Arta; Pupysheva, Olga; Boustani, Ihsan; Yakobson, Boris

    2008-03-01

    Using ab initio calculations, we study electronic structure and frequency modes of B80, a member of boron fullerene family made from boron isomorphs of carbon fullerenes with additional atoms in the centers of hexagons. We also investigate geometrical and electronic structural properties of double-rings with various diameters, which are important as building blocks of boron nanotubes, and as the most stable clusters among the studied isomers with no more than 36 atoms. Double-rings also appear as building blocks of B80. Furthermore, we investigate the possibility of further stabilizing some of fullerenes by depleting them.

  6. Kinetics of photoconductivity in ZnSe crystals upon photoexcitation of deep centers

    SciTech Connect

    Bruk, L.I.; Gorya, O.S.; Korotkov, V.A.

    1995-10-01

    It has long been known that investigation of the spectral characteristics of photoconductivity (PC) in wide-band-gap semiconductors does not provide full information on the position of photosensitive centers in the forbidden band. The broad spectrum of intrinsic and impurity PC consists of several overlapping bands. In the long-wavelength region, impurity photoeffect is superimposed over the falling-off spectrum of intrinsic PC. In addition, measurements of steady-state PC are incapable of revealing photoinsensitive recombination and trapping centers. Those levels that were not excited prior to illumination of the semiconductor may provide no contribution to PC and may appear either photoinsensitive or indistinguishable from dominant channels of recombination and trapping on other centers. Preliminary excitation may alter the state of these levels to such a degree that they will show up as a spike in the PC relaxation curve. In this paper, we report kinetic studies of the PC and the effective cross section for photon capture (CSPC) in the photosensitivity range of zinc selenide single crystals containing trace impurities.

  7. Deep levels of vacancy-hydrogen centers in silicon studied by Laplace DLTS

    NASA Astrophysics Data System (ADS)

    Bonde Nielsen, K.; Dobaczewski, L.; Goscinski, K.; Bendesen, R.; Andersen, Ole; Bech Nielsen, B.

    1999-12-01

    We identify the acceptor levels (-/0) of the VH and V2H defects in silicon from comparison of DLTS and EPR annealing data. The levels are very close to each other and close to the acceptor level of the PV defect (the E-center) as well. In order to separate them, we have applied the high-resolution technique of Laplace DLTS and compared the formation and annealing properties of defects generated by implantation of hydrogen or helium. We further applied Laplace DLTS in combination with uniaxial stress to study the acceptor level at Ec-Et=0.31 eV previously assigned to a vacancy-hydrogen-oxygen defect. We find, in accordance with recent EPR measurements, that the defect displays orthorhombic-I symmetry and rule out that it contains two hydrogen atoms. The defect can be understood as a single hydrogen atom bound inside the A-center, the well-known VO defect of silicon, and we denote it VOH accordingly. The observed orthorhombic-I symmetry arises because the hydrogen atom (at T=160 K) swiftly jumps among two equivalent sites across the (1 1 0) plane that contains the Si-O-Si bond. Previous studies have shown that hydrogenation of oxygen-rich electron-irradiated samples leads to the formation of VOH with simultaneous depletion of the A-center. Our structural data are in accordance with this dynamic behavior.

  8. Cosmic abundance of boron.

    NASA Technical Reports Server (NTRS)

    Cameron, A. G. W.; Colgate, S. A.; Grossman, L.

    1973-01-01

    All abundances are expressed relative to a million atoms of Si. An average abundance of boron in ordinary chondrites is 6.2. The boron abundance in meteorites is highly variable. It has been found that the abundances in carbonaceous chondrites are very much higher than those in ordinary chondrites. The condensation of boron and beryllium from a cooling, low-pressure gas of solar composition is discussed together with the occurrence of boron in the interstellar medium, questions of element abundances in the sun, problems of boron production by cosmic rays, and boron production from supernovae.

  9. Hot-embossing replication of self-centering optical fiber alignment structures prototyped by deep proton writing

    NASA Astrophysics Data System (ADS)

    Ebraert, Evert; Wissmann, Markus; Guttmann, Markus; Kolew, Alexander; Worgull, Matthias; Barié, Nicole; Schneider, Marc; Hofmann, Andreas; Beri, Stefano; Watté, Jan; Thienpont, Hugo; Van Erps, Jürgen

    2016-07-01

    This paper presents the hot-embossing replication of self-centering fiber alignment structures for high-precision, single-mode optical fiber connectors. To this end, a metal mold insert was fabricated by electroforming a polymer prototype patterned by means of deep proton writing (DPW). To achieve through-hole structures, we developed a postembossing process step to remove the residual layer inherently present in hot-embossed structures. The geometrical characteristics of the hot-embossed replicas are compared, before and after removal of the residual layer, with the DPW prototypes. Initial measurements on the optical performance of the replicas are performed. The successful replication of these components paves the way toward low-cost mass replication of DPW-fabricated prototypes in a variety of high-tech plastics.

  10. Investigation to the deep center related properties of low temperature grown InPBi with Hall and photoluminescence

    SciTech Connect

    Wang, Peng; Pan, Wenwu; Wu, Xiaoyan; Wang, Kai; Yue, Li; Gong, Qian; Wang, Shumin

    2015-12-15

    InP{sub 1-x}Bi{sub x} epilayers with bismuth (Bi) concentration x= 1.0% were grown on InP by gas source molecular beam epitaxy (GS-MBE) at low temperature (LT). Bi incorporation decreased the intrinsic free electron concentration of low temperature grown InP indicated by hall analysis. It is concluded that deep level center was introduced by Bi. Influence of Si doping on the InP{sub 1-x}Bi{sub x} films Photoluminescence (PL) was investigated. N-type doping in the InP{sub 1-x}Bi{sub x} epilayers was found to be effective at PL enhancement. Blue shift of InPBi PL emission wavelength was observed as the Si doping concentration increasing. Two independent peaks were fitted and their temperature dependence behavior was observed to be distinct obviously. Two individual radiative recombination processes were expected to be involved.

  11. Deep venous thrombosis in lap band surgery: a single center study.

    PubMed

    Shah, Kavin G; Rajan, Derry; Nicastro, Jeffrey; Molmenti, Ernesto P; Coppa, Gene

    2012-04-01

    Bariatric surgery has been demonstrated to be an effective treatment for morbid obesity. The purpose of this study is to investigate the incidence of pre- and post-operative deep venous thrombosis (DVT) in Lap-Band surgical patients. This study group comprised 56 consecutive patients who underwent Lap-Band surgery. Mean age and body mass index were 38 years (range: 18-64 years) and 50.9 kg/m(2) (range: 53-74 kg/m(2)), respectively. All the patients were screened with duplex ultrasonography pre- and post-operatively. There were no iliac, femoral, or popliteal vein thromboses detected at any given point of time. No patient had any clinical signs or symptoms of DVT post-operatively. There were no observable differences attributable to DVT prophylaxis. This data suggest that in the setting of chemical and mechanical prophylaxis, the incidence of DVT in patients undergoing Lap-Band surgery at an established bariatric centre is minimal.

  12. Hyperbaric oxygen therapy as additional treatment in deep sternal wound infections – a single center's experience

    PubMed Central

    Bryndza, Magdalena; Chrapusta, Anna; Kobielska, Ewa; Kapelak, Bogusław; Grudzień, Grzegorz

    2016-01-01

    Introduction Deep sternal wound infection (DSWI) is one of the most serious complications after cardiac surgery procedures, observed in 5% of patients. Current standard medical therapy for DSWI includes antibiotics, surgical debridement, resuturing or negative pressure wound therapy (NPWT). Unfortunately, in some cases these methods are insufficient, and additional therapeutic options are needed. Aim To assess the effects and usefulness of additional hyperbaric oxygen therapy (HBO2) in patients with DSWI after cardiac surgery procedures. Material and methods A retrospective analysis of 10 patients after cardiac surgery who developed DSWI in the period 2010–2012 was performed. After 3 months of ineffective conventional therapy including targeted antibiotic, surgical sternal debridement and NPWT, patients were qualified for additional HBO2 therapy. A total of 20 sessions of HBO2 therapy were performed, each 92 minutes long. Results After 4 weeks of HBO2 treatment, 7 patients presented complete wound healing with fibrous scar formation. One patient was qualified for the another cycle of HBO2 therapy with 20 additional sessions, and complete wound healing was observed. In 2 cases, after 5 and 19 sessions, HBO2 was interrupted because of improper qualifications. Conclusions The HBO2 as an additional therapy in DSWI was successful in 80% of cases, and no complications were observed. However, due to the small number of published studies with a small number of patients, randomized, clinical trials are needed to assess the clinical results of HBO2 in DSWI after cardiac surgery procedures. PMID:27785131

  13. Creation of deep blue light emitting nitrogen-vacancy center in nanosized diamond

    SciTech Connect

    Himics, L. Tóth, S.; Veres, M.; Koós, M.; Balogh, Z.

    2014-03-03

    This paper reports on the formation of complex defect centers related to the N3 center in nanosized diamond by employing plasma immersion and focused ion beam implantation methods. He{sup +} ion implantation into nanosized diamond “layer” was performed with the aim of creating carbon atom vacancies in the diamond structure, followed by the introduction of molecular N{sub 2}{sup +} ion and heat treatment in vacuum at 750 °C to initiate vacancy diffusion. To decrease the sp{sup 2} carbon content of nanosized diamond formed during the implantation processes, a further heat treatment at 450 °C in flowing air atmosphere was used. The modification of the bonding properties after each step of defect creation was monitored by Raman scattering measurements. The fluorescence measurements of implanted and annealed nanosized diamond showed the appearance of an intensive and narrow emission band with fine structures at 2.98 eV, 2.83 eV, and 2.71 eV photon energies.

  14. Potential for deep basin-centered gas accumulation in Travis Peak (Hosston) Formation, Gulf Coastal Basin

    USGS Publications Warehouse

    Bartberger, Charles E.; Dyman, Thaddeus S.; Condon, Steven M.

    2003-01-01

    The potential of Lower Cretaceous sandstones of the Travis Peak Formation in the northern Gulf Coast Basin to harbor a basin-centered gas accumulation was evaluated by examining (1) the depositional and diagenetic history and reservoir properties of Travis Peak sandstones, (2) the presence and quality of source rocks for generating gas, (3) the burial and thermal history of source rocks and time of gas generation and migration relative to tectonic development of Travis Peak traps, (4) gas and water recoveries from drill-stem and formation tests, (5) the distribution of abnormal pressures based on shut-in-pressure data, and (6) the presence or absence of gas-water contacts associated with gas accumulations in Travis Peak sandstones. The Travis Peak Formation (and correlative Hosston Formation) is a basinward-thickening wedge of terrigenous clastic sedimentary rocks that underlies the northern Gulf Coast Basin from eastern Texas across northern Louisiana to southern Mississippi. Clastic infl ux was focused in two main fl uvial-deltaic depocenters?one located in northeastern Texas and the other in southeastern Mississippi and northeastern Louisiana. Across the main hydrocarbon-productive trend in eastern Texas and northern Louisiana, the Travis Peak Formation is about 2,000 ft thick. Most Travis Peak hydrocarbon production in eastern Texas comes from drilling depths between 6,000 and 10,000 ft. Signifi cant decrease in porosity and permeability occurs through that depth interval. Above 8,000-ft drilling depth in eastern Texas, Travis Peak sandstone matrix permeabilities often are signifi cantly higher than the 0.1-millidarcy (mD) cutoff that characterizes tight-gas reservoirs. Below 8,000 ft, matrix permeability of Travis Peak sandstones is low because of pervasive quartz cementation, but abundant natural fractures impart signifi cant fracture permeability. Although pressure data within the middle and lower Travis Peak Formation are limited in eastern Texas

  15. Deep Space Network (DSN), Network Operations Control Center (NOCC) computer-human interfaces

    NASA Technical Reports Server (NTRS)

    Ellman, Alvin; Carlton, Magdi

    1993-01-01

    The technical challenges, engineering solutions, and results of the NOCC computer-human interface design are presented. The use-centered design process was as follows: determine the design criteria for user concerns; assess the impact of design decisions on the users; and determine the technical aspects of the implementation (tools, platforms, etc.). The NOCC hardware architecture is illustrated. A graphical model of the DSN that represented the hierarchical structure of the data was constructed. The DSN spacecraft summary display is shown. Navigation from top to bottom is accomplished by clicking the appropriate button for the element about which the user desires more detail. The telemetry summary display and the antenna color decision table are also shown.

  16. Deep Space Network (DSN), Network Operations Control Center (NOCC) computer-human interfaces

    NASA Technical Reports Server (NTRS)

    Ellman, Alvin; Carlton, Magdi

    1993-01-01

    The Network Operations Control Center (NOCC) of the DSN is responsible for scheduling the resources of DSN, and monitoring all multi-mission spacecraft tracking activities in real-time. Operations performs this job with computer systems at JPL connected to over 100 computers at Goldstone, Australia and Spain. The old computer system became obsolete, and the first version of the new system was installed in 1991. Significant improvements for the computer-human interfaces became the dominant theme for the replacement project. Major issues required innovating problem solving. Among these issues were: How to present several thousand data elements on displays without overloading the operator? What is the best graphical representation of DSN end-to-end data flow? How to operate the system without memorizing mnemonics of hundreds of operator directives? Which computing environment will meet the competing performance requirements? This paper presents the technical challenges, engineering solutions, and results of the NOCC computer-human interface design.

  17. Deep Space Network (DSN), Network Operations Control Center (NOCC) computer-human interfaces

    NASA Technical Reports Server (NTRS)

    Ellman, Alvin; Carlton, Magdi

    1993-01-01

    The technical challenges, engineering solutions, and results of the NOCC computer-human interface design are presented. The use-centered design process was as follows: determine the design criteria for user concerns; assess the impact of design decisions on the users; and determine the technical aspects of the implementation (tools, platforms, etc.). The NOCC hardware architecture is illustrated. A graphical model of the DSN that represented the hierarchical structure of the data was constructed. The DSN spacecraft summary display is shown. Navigation from top to bottom is accomplished by clicking the appropriate button for the element about which the user desires more detail. The telemetry summary display and the antenna color decision table are also shown.

  18. VLBI Software Correlator at the Interferometric Tracking Center of the China Deep Space Network

    NASA Astrophysics Data System (ADS)

    Han, Songtao; Tang, Geshi; Chen, Lue; Cao, Jianfeng; Ren, Tianpeng; Wang, Mei

    2014-12-01

    With the development of computer techniques, the VLBI software correlator is more and more popular. This article presents the development and performance of the software correlator used in the Interferometric Tracking Center. The software correlator has the ability of VLBI data processing both for spacecraft navigation and VLBI geodesy. Also, the data formats of VSR (VLBI Science Receiver) and VSI (VLBI Standard Interface) are accommodated. The correlator is written modularly in the C programming language and operated by shell script. The complex vector mathematics of the IPP (Intel Integrated Performance Primitive) library is induced because the efficiency of computing can be improved greatly. Parallel algorithm processing is adopted in the software. We present the results of the multi-agency VLBI experiment conducted with the ESA Spacecraft Venus Express in May 2013 and the Chinese Chang'e-3 lunar navigation in December 2013, which verifies the performance of the software correlator.

  19. Boron Nitride Nanoribbons from Exfoliation of Boron Nitride Nanotubes

    NASA Technical Reports Server (NTRS)

    Hung, Ching-Cheh; Hurst, Janet; Santiago, Diana

    2017-01-01

    Two types of boron nitride nanotubes (BNNTs) were exfoliated into boron nitride nanoribbons (BNNR), which were identified using transmission electron microscopy: (1) commercial BNNTs with thin tube walls and small diameters. Tube unzipping was indicated by a large decrease of the sample's surface area and volume for pores less than 2 nm in diameter. (2) BNNTs with large diameters and thick walls synthesized at NASA Glenn Research Center. Here, tube unraveling was indicated by a large increase in external surface area and pore volume. For both, the exfoliation process was similar to the previous reported method to exfoliate commercial hexagonal boron nitride (hBN): Mixtures of BNNT, FeCl3, and NaF (or KF) were sequentially treated in 250 to 350 C nitrogen for intercalation, 500 to 750 C air for exfoliation, and finally HCl for purification. Property changes of the nanosized boron nitride throughout this process were also similar to the previously observed changes of commercial hBN during the exfoliation process: Both crystal structure (x-ray diffraction data) and chemical properties (Fourier-transform infrared spectroscopy data) of the original reactant changed after intercalation and exfoliation, but most (not all) of these changes revert back to those of the reactant once the final, purified products are obtained.

  20. Incidence of Deep Vein Thrombosis in Patients Undergoing Degenerative Spine Surgery onProphylactic Dalteparin; A Single Center Report

    PubMed Central

    Moayer, AlirezaFarid; Mohebali, Navideh; Razmkon, Ali

    2016-01-01

    Objective: To determine the incidence of deep vein thrombosis (DVT)in patients undergoing spinal surgeries receiving prophylactic doses of Deltaparin in a single center in central Iran. Method: This cross-sectional study was conducted in Shariatee hospital of Isfahan during a 12-month period. We included all the patients undergoing elective spinal surgeries in our center during the study period who received prophylactic dosages of subcutaneous Dalteparin (5000unit daily) thefirst postoperative day. Those with absolute contraindications of anticoagulation therapy were not included in the study. Patients were followed for 3 months clinically and the incidence of DVT was recorded. DVT was suspected clinically and was confirmed by color Doppler sonography. Results: Overall we included 120 patients with mean age of 44.8 ± 12.6years among whom there were 54 (45%) men and 66 (55%) women. Lumbar discectomy (32.9%)and laminectomy (20.2%)were the most common performed procedures. DVT was detected in 1 (0.83%) patient in postoperative period. None of the patients developed pulmonary embolism and none hemorrhagic adverse event was recorded. The patient was treated with therapeutic unfractionated heparin and was discharged with warfarin.  Conclusion: Our results shows the efficacy of LMWH (Dalteparin) in reducing the incidence of DVT to 0.83%. These results also show the safety of Dalteparin in spine surgery because of lack of bleeding complication. PMID:27162925

  1. Atomistic study of boron-doped silicon

    SciTech Connect

    Fearn, M.; Pettifor, D.G.; Jefferson, J.H.

    1996-12-31

    Atomistic simulations using both tight-binding and density-functional approaches have been performed to investigate boron-related defects in silicon. In agreement with experiment, the boron interstitial is shown to be a negative-U center in the sense that its neutral charge state, with an associated Jahn-Teller distortion off the ideal tetrahedral site, is never the ground state for any value of the chemical potential in the gap. The possible consequences for an electron-assisted migration of the interstitial are discussed. The authors also find the boron substitutional defect to be a next-nearest neighbor of a silicon vacancy in agreement with EPR spectra. A semi-empirical tight-binding model of the boron-silicon system is validated by direct comparison with the accurate density-functional results and is then used to perform molecular dynamics simulations of boron diffusion at high temperatures. The mobility of the interstitial is found to be strongly charge-state dependent. Termination of the boron interstitial migration path by recombination with a silicon vacancy is shown to be a very likely process with a number of configurations having no barrier to capture when the boron is a near-neighbor of the vacancy.

  2. Boron-Loaded Silicone Rubber Scintillators

    SciTech Connect

    Bell, Z.W.; Maya, L.; Brown, G.M.; Sloop, F.V.Jr

    2003-05-12

    Silicone rubber received attention as an alternative to polyvinyltoluene in applications in which the scintillator is exposed to high doses because of the increased resistance of the rubber to the formation of blue-absorbing color centers. Work by Bowen, et al., and Harmon, et al., demonstrated their properties under gamma/x-ray irradiation, and Bell, et al. have shown their response to thermal neutrons. This last work, however, provided an example of a silicone in which both the boron and the scintillator were contained in the rubber as solutes, a formulation which led to the precipitation of solids and sublimation of the boron component. In the present work we describe a scintillator in which the boron is chemically bonded to the siloxane and so avoids the problem of precipitation and loss of boron to sublimation. Material containing up to 18% boron, by weight, was prepared, mounted on photomultipliers, and exposed to both neutron and gamma fluxes. Pulse height spectra showing the neutron and photon response were obtained, and although the light output was found to be much poorer than from samples in which boron was dissolved, the higher boron concentrations enabled essentially 100% neutron absorption in only a few millimeters' thickness of rubber.

  3. Synthesis and Characterization of a Boron-Nitrogen-Boron Zigzag-Edged Benzo[fg]tetracene Motif.

    PubMed

    Fingerle, Michael; Maichle-Mössmer, Cäcilia; Schundelmeier, Simon; Speiser, Bernd; Bettinger, Holger F

    2017-09-01

    The boron-nitrogen-boron (BNB) zigzag edged benzo[fg]tetracene is accessible from 4-butyl-2,6-diphenylaniline in four steps in good yields. The two mesityl groups stabilize the boron centers toward nucleophilic attack and result in two enantiomeric forms in the solid state. The title compound has a large optical gap, shows blue fluorescence, and is quite resistant toward oxidation and reduction.

  4. Reverse annealing and low-temperature diffusion of boron in boron-implanted silicon

    SciTech Connect

    Huang, J.; Fan, D.; Jaccodine, R.J.

    1988-06-01

    Low-temperature annealing (525 /sup 0/C--800 /sup 0/C) of 50-keV, 1 x 10/sup 15/-cm/sup -2/, boron-implanted silicon was studied with the emphasis on the mechanisms responsible for the reverse annealing as well as the enhanced diffusion of the implanted boron. The electrical properties of boron-implanted silicon were analyzed with Hall measurement. Boron depth profiles were also measured using secondary-ion mass spectrometry. These results were then correlated with cross-section transmission electron microscopy studies and deep-level transient spectroscopy studies. It is shown that reverse annealing is possibly due to boron-silicon interstitial complexes, rather than the formation of the commonly observed rodlike defects or precipitates. On the other hand, the enhanced tail diffusion of boron is found to be most likely associated with self-interstitials. Consequently, vacancy trapping of the silicon interstitial component may account for both the charge carrier recovery and the ending of the enhanced tail diffusion of implanted boron.

  5. Boron nitride converted carbon fiber

    SciTech Connect

    Rousseas, Michael; Mickelson, William; Zettl, Alexander K.

    2016-04-05

    This disclosure provides systems, methods, and apparatus related to boron nitride converted carbon fiber. In one aspect, a method may include the operations of providing boron oxide and carbon fiber, heating the boron oxide to melt the boron oxide and heating the carbon fiber, mixing a nitrogen-containing gas with boron oxide vapor from molten boron oxide, and converting at least a portion of the carbon fiber to boron nitride.

  6. Metagenomic resolution of microbial functions in deep-sea hydrothermal plumes across the Eastern Lau Spreading Center.

    PubMed

    Anantharaman, Karthik; Breier, John A; Dick, Gregory J

    2016-01-01

    Microbial processes within deep-sea hydrothermal plumes affect ocean biogeochemistry on global scales. In rising hydrothermal plumes, a combination of microbial metabolism and particle formation processes initiate the transformation of reduced chemicals like hydrogen sulfide, hydrogen, methane, iron, manganese and ammonia that are abundant in hydrothermal vent fluids. Despite the biogeochemical importance of this rising portion of plumes, it is understudied in comparison to neutrally buoyant plumes. Here we use metagenomics and bioenergetic modeling to describe the abundance and genetic potential of microorganisms in relation to available electron donors in five different hydrothermal plumes and three associated background deep-sea waters from the Eastern Lau Spreading Center located in the Western Pacific Ocean. Three hundred and thirty one distinct genomic 'bins' were identified, comprising an estimated 951 genomes of archaea, bacteria, eukarya and viruses. A significant proportion of these genomes is from novel microorganisms and thus reveals insights into the energy metabolism of heretofore unknown microbial groups. Community-wide analyses of genes encoding enzymes that oxidize inorganic energy sources showed that sulfur oxidation was the most abundant and diverse chemolithotrophic microbial metabolism in the community. Genes for sulfur oxidation were commonly present in genomic bins that also contained genes for oxidation of hydrogen and methane, suggesting metabolic versatility in these microbial groups. The relative diversity and abundance of genes encoding hydrogen oxidation was moderate, whereas that of genes for methane and ammonia oxidation was low in comparison to sulfur oxidation. Bioenergetic-thermodynamic modeling supports the metagenomic analyses, showing that oxidation of elemental sulfur with oxygen is the most dominant catabolic reaction in the hydrothermal plumes. We conclude that the energy metabolism of microbial communities inhabiting rising

  7. Metagenomic resolution of microbial functions in deep-sea hydrothermal plumes across the Eastern Lau Spreading Center

    PubMed Central

    Anantharaman, Karthik; Breier, John A; Dick, Gregory J

    2016-01-01

    Microbial processes within deep-sea hydrothermal plumes affect ocean biogeochemistry on global scales. In rising hydrothermal plumes, a combination of microbial metabolism and particle formation processes initiate the transformation of reduced chemicals like hydrogen sulfide, hydrogen, methane, iron, manganese and ammonia that are abundant in hydrothermal vent fluids. Despite the biogeochemical importance of this rising portion of plumes, it is understudied in comparison to neutrally buoyant plumes. Here we use metagenomics and bioenergetic modeling to describe the abundance and genetic potential of microorganisms in relation to available electron donors in five different hydrothermal plumes and three associated background deep-sea waters from the Eastern Lau Spreading Center located in the Western Pacific Ocean. Three hundred and thirty one distinct genomic ‘bins' were identified, comprising an estimated 951 genomes of archaea, bacteria, eukarya and viruses. A significant proportion of these genomes is from novel microorganisms and thus reveals insights into the energy metabolism of heretofore unknown microbial groups. Community-wide analyses of genes encoding enzymes that oxidize inorganic energy sources showed that sulfur oxidation was the most abundant and diverse chemolithotrophic microbial metabolism in the community. Genes for sulfur oxidation were commonly present in genomic bins that also contained genes for oxidation of hydrogen and methane, suggesting metabolic versatility in these microbial groups. The relative diversity and abundance of genes encoding hydrogen oxidation was moderate, whereas that of genes for methane and ammonia oxidation was low in comparison to sulfur oxidation. Bioenergetic-thermodynamic modeling supports the metagenomic analyses, showing that oxidation of elemental sulfur with oxygen is the most dominant catabolic reaction in the hydrothermal plumes. We conclude that the energy metabolism of microbial communities inhabiting

  8. Persistent urinary retention after surgery for deep infiltrating endometriosis: a multi-center series of 16 cases.

    PubMed

    Azaïs, Henri; Rubod, Chrystèle; Ghoneim, Tarek; Vassilieff, Maud; Bailly, Emmanuel; Boileau, Laurent; Villet, Richard; Collinet, Pierre

    2015-06-01

    Persistent urinary retention (UR) is a complication of 3.5-14.3% of patients having undergone deep pelvic endometriosis (DPE) surgery of posterior compartment, and it is prone to persist. The purpose of this study is to identify surgical procedures and clinical circumstances associated with persistent UR, and consider its treatment. We undertook a multi-center retrospective study studying medical records of patients who had surgery for DPE between January 2005 and December 2012. Patients who suffered from UR defined as a post-void residual (PVR) volume >100 mL needing intermittent self-catheterizations more than 30 days after surgery were included. Preoperative data (functional complaints, clinical examination, imaging, medical treatment) were recorded. Types of surgery and detailed postoperative urinary symptoms were noted. 881 patients had surgery for DPE and 16 patients were included (1.8%). In 93.8% of cases, a lesion of posterior compartment was clinically significant. Mean lesion size was 28.8 ± 7.3 mm. Colorectal resection and colpectomy were necessary in 93.8 and 87.5% of cases, respectively. Loss of bladder sensation and straining during urination were the two most common post-operative symptoms. 11 patients still required self-catheterization up to 1 year after the intervention. Patients with increased risks of UR present with a symptomatic and clinically palpable deep pelvic endometriotic lesion of the posterior compartment. Treatment implies surgery with colorectal resection. Bilateral resection of utero-sacral ligaments and posterior colpectomy tend to increase that risk. Complications due to PVR volume and straining during urination may be prevented by self-catheterization.

  9. Investigation on origin of Z{sub 1/2} center in SiC by deep level transient spectroscopy and electron paramagnetic resonance

    SciTech Connect

    Kawahara, Koutarou; Suda, Jun; Kimoto, Tsunenobu; Thang Trinh, Xuan; Tien Son, Nguyen; Janzen, Erik

    2013-03-18

    The Z{sub 1/2} center in n-type 4H-SiC epilayers-a dominant deep level limiting the carrier lifetime-has been investigated. Using capacitance versus voltage (C-V) measurements and deep level transient spectroscopy (DLTS), we show that the Z{sub 1/2} center is responsible for the carrier compensation in n-type 4H-SiC epilayers irradiated by low-energy (250 keV) electrons. The concentration of the Z{sub 1/2} defect obtained by C-V and DLTS correlates well with that of the carbon vacancy (V{sub C}) determined by electron paramagnetic resonance, suggesting that the Z{sub 1/2} deep level originates from V{sub C}.

  10. Computational assessment of deep-seated tumor treatment capability of the 9Be(d,n)10B reaction for accelerator-based boron neutron capture therapy (AB-BNCT).

    PubMed

    Capoulat, M E; Minsky, D M; Kreiner, A J

    2014-03-01

    The 9Be(d,n)10B reaction was studied as an epithermal neutron source for brain tumor treatment through Boron Neutron Capture Therapy (BNCT). In BNCT, neutrons are classified according to their energies as thermal (<0.5 eV), epithermal (from 0.5 eV to 10 keV) or fast (>10 keV). For deep-seated tumors epithermal neutrons are needed. Since a fraction of the neutrons produced by this reaction are quite fast (up to 5-6 MeV, even for low-bombarding energies), an efficient beam shaping design is required. This task was carried out (1) by selecting the combinations of bombarding energy and target thickness that minimize the highest-energy neutron production; and (2) by the appropriate choice of the Beam Shaping Assembly (BSA) geometry, for each of the combinations found in (1). The BSA geometry was determined as the configuration that maximized the dose deliverable to the tumor in a 1 h treatment, within the constraints imposed by the healthy tissue dose adopted tolerance. Doses were calculated through the MCNP code. The highest dose deliverable to the tumor was found for an 8 μm target and a deuteron beam of 1.45 MeV. Tumor weighted doses ≥40 Gy can be delivered up to about 5 cm in depth, with a maximum value of 51 Gy at a depth of about 2 cm. This dose performance can be improved by relaxing the treatment time constraint and splitting the treatment into two 1-h sessions. These good treatment capabilities strengthen the prospects for a potential use of this reaction in BNCT. Copyright © 2013 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.

  11. Use of the trellis device in the management of deep vein thrombosis: a retrospective single-center experience.

    PubMed

    Chaudhry, Muhammad A; Pappy, Reji; Hennebry, Thomas A

    2013-06-01

    The Trellis thrombectomy system (Covidien) is one of the newer devices that incorporates isolated pharmacomechanical thrombectomy and thrombolysis (PMT) for treatment of deep venous thrombosis (DVT). We conducted a retrospective review of patients with upper- and lower-extremity DVT managed with the Trellis thrombectomy system at our center. All patients with symptomatic DVT who presented to our center between April 2010 and April 2011 who underwent PMT by the Trellis device were included in this retrospective review. Twenty-eight patients (mean age, 46.4 ± 21.2 years) presented with symptoms with a mean duration of 1.3 ± 1.8 months. Eighty-six percent had 100% occlusion on admission, while 14.3% had 70%-90% stenosis. The mean lytic dose used was tPA 20.7 ± 12 mg. The mean Trellis treatment time was 25.1 ± 11.5 minutes. Grade 3 lysis was achieved in 23 of 28 patients (85.8%), while grade 2 lysis was achieved in 14.2%. Mean total hospital stay was 2.6 ± 2.7 days. Postprocedure symptom resolution was 100%, and there was no reocclusion in 78.6% of patients at 1 year. At 12 months, the patency rate (primary or secondary) was 80% as determined by Doppler ultrasound. In patients with DVT involving the ilio-femoral and the upper-extremity vessels, the use of the Trellis device was associated with a high technical success rate as well as a satisfactory 12-month patency rate. Moreover, this strategy was associated with reduced lytic dose, shorter treatment time and hospital stay, and no bleeding complications.

  12. Properties of boron/boron-nitride multilayers

    SciTech Connect

    Jankowski, A.F.; Wall, M.A.; Hayes, J.P.; Alexander, K.B.

    1996-06-01

    Boron-Nitride films are of interest for their high hardness and wear resistance. Large intrinsic stresses and poor adhesion which often accompany high hardness materials can be moderated through the use of a layered structure. Alternate layers of boron (B) and boron-nitride (BN) are formed by modulating the composition of the sputter gas during deposition from a pure B target. The thin films are characterized with TEM to evaluate the microstructure and with nanoindentation to determine hardness. Layer pair spacing and continuity effects on hardness are evaluated for the B/BN films.

  13. Model of boron diffusion from gas phase in silicon carbide

    SciTech Connect

    Aleksandrov, O. V.; Mokhov, E. N.

    2011-06-15

    Boron diffusion from the gas phase in silicon carbide is described on the basis of a two-component model. 'Shallow' boron, i.e., boron at silicon sites, is a slow component with a high surface concentration. Its diffusivity is proportional to the concentration of positively charged intrinsic point defects, which are presumably interstitial silicon atoms. 'Deep' boron, i.e., impurity-defect pairs of boron-carbon vacancy, is a fast component with lower surface concentration. The ratio between the surface concentrations of the components depends on the pressure of silicon or carbon vapors in the gas phase. The diffusion and interaction of components are described by the set of diffusion-reaction equations. The diffusion retardation observed on the concentration-profile tail is related to the capture of impurity-defect pairs and excess vacancies by traps of background impurities and defects.

  14. Violation of the Guiding Center Approximation for Energetic Ions in the Deep Inner Magnetosphere during Magnetic Storms

    NASA Astrophysics Data System (ADS)

    Shibahara, K.; Nose, M.

    2009-12-01

    During a magnetic storm, the ring current is developed in the inner magnetosphere. It is believed that the decrease of Dst index during a strom is mainly due to the development of the ring current. Recent numerical simulations have revealed how the ring current grows and decays (Lemon et al., 2004; Zaharia et al., 2006) in the self-consistent field with the guiding center approximation (GCA). This approximation breaks down if the spatial scale of the magnetic field change is comparable to the gyroradius. From the following two reasons, we suspect an approach to treat motion of ring current oxygen ions with the GCA. (1) During magnetic storms a dominant part of energy density of the ring current is carried by oxygen ions (Daglis at al., 1999) which are 16 times heavier than protons; that is, gyroradius of oxygen ions is 4 times larger than that of protons with the same kinetic energy. (2) Magnetic field configuration becomes far deviated from dipole field even in the deep inner magnetosphere. In this study, we examine whether the GCA is valid for ring current ions, in particular for oxygen ions. We compared energetic ion trajectories computed by the Lorentz equation and those by the GCA equation (Northrop, 1963). We used the TS04 (Tsyganenko and Sitnov, 2005) magnetic field model as well as the Volland-Stern (Volland 1973; Stern 1975) electric field model. In case of integration of the Lorentz equation, we found that some of ions have different trajectories from those of the GCA equation. Most remarkable results can be summarized as follows. First, ions having a pitch angle of ~90 degrees do not conserve the first adiabatic invariant and gradually increase their amplitude of bouncing motion around the magnetic equator. Second, an ion with a large gyroradius (i.e, an energetic oxygen ion) can be accelerated thorough the meandering motion even in the deep inner magnetosphere. Above-mentioned results lead some interest phenomena, for example, pitch angle distribution

  15. Creating the Deep Space Environment for Testing the James Webb Space Telescope (JWST) at NASA Johnson Space Center's Chamber A

    NASA Technical Reports Server (NTRS)

    Homan, Jonathan L.; Cerimele, Mary P.; Montz, Michael E.; Bachtel, Russell; Speed, John; O'Rear, Patrick

    2013-01-01

    Chamber A is the largest thermal vacuum chamber at the Johnson Space Center and is one of the largest space environment chambers in the world. The chamber is 19.8 m (65 ft) in diameter and 36.6 m (120 ft) tall and is equipped with cryogenic liquid nitrogen panels (shrouds) and gaseous helium shrouds to create a simulated space environment. It was originally designed and built in the mid 1960 s to test the Apollo Command and Service Module and several manned tests were conducted on that spacecraft, contributing to the success of the program. The chamber has been used since that time to test spacecraft active thermal control systems, Shuttle DTO, DOD, and ESA hardware in simulated Low Earth Orbit (LEO) conditions. NASA is now moving from LEO towards exploration of locations with environments approaching those of deep space. Therefore, Chamber A has undergone major modifications to enable it to simulate these deeper space environments. Environmental requirements were driven, and modifications were funded by the James Webb Space Telescope program, and this telescope which will orbit Solar/Earth L2, will be the first test article to benefit from the chamber s new capabilities. To accommodate JWST, the Chamber A high vacuum system has been modernized, additional LN2 shrouds have been installed, the liquid nitrogen system has been modified to remove dependency on electrical power and increase its reliability, a new helium shroud/refrigeration system has been installed to create a colder more stable and uniform heat sink, and the controls have been updated to increase the level of automation and improve operator interfaces. Testing of these major modifications was conducted in August of 2012 and this initial test was very successful, with all major systems exceeding their performance requirements. This paper will outline the changes in overall environmental requirements, discuss the technical design data that was used in the decisions leading to the extensive modifications

  16. Creating the Deep Space Environment for Testing the James Webb Space Telescope at NASA Johnson Space Center's Chamber A

    NASA Technical Reports Server (NTRS)

    Homan, Jonathan L.; Cerimele, Mary P.; Montz, Michael E.; Bachtel, Russell; Speed, John; O'Rear, Patrick

    2013-01-01

    Chamber A is the largest thermal vacuum chamber at the Johnson Space Center and is one of the largest space environment chambers in the world. The chamber is 19.8 m (65 ft.) in diameter and 36.6 m (120 ft.) tall and is equipped with cryogenic liquid nitrogen panels (shrouds) and gaseous helium shrouds to create a simulated space environment. It was originally designed and built in the mid 1960 s to test the Apollo Command and Service Module and several manned tests were conducted on that spacecraft, contributing to the success of the program. The chamber has been used since that time to test spacecraft active thermal control systems, Shuttle DTO, DOD, and ESA hardware in simulated Low Earth Orbit (LEO) conditions. NASA is now moving from LEO towards exploration of locations with environments approaching those of deep space. Therefore, Chamber A has undergone major modifications to enable it to simulate these deeper space environments. Environmental requirements were driven, and modifications were funded by the James Webb Space Telescope program, and this telescope, which will orbit Solar/Earth L2, will be the first test article to benefit from the chamber s new capabilities. To accommodate JWST, the Chamber A high vacuum system has been modernized, additional LN2 shrouds have been installed, the liquid nitrogen system has been modified to minimize dependency on electrical power and increase its reliability, a new helium shroud/refrigeration system has been installed to create a colder more stable and uniform heat sink, and the controls have been updated to increase the level of automation and improve operator interfaces. Testing of these major modifications was conducted in August of 2012 and this initial test was very successful, with all major systems exceeding their performance requirements. This paper will outline the changes in overall environmental requirements, discuss the technical design data that was used in the decisions leading to the extensive

  17. Creating the Deep Space Environment for Testing the James Webb Space Telescope at the Johnson Space Center's Chamber A

    NASA Technical Reports Server (NTRS)

    Homan, Jonathan L.; Cerimele, Mary P.; Montz, Michael E.

    2012-01-01

    Chamber A is the largest thermal vacuum chamber at the Johnson Space Center and is one of the largest space environment chambers in the world. The chamber is 19.8 m (65 ft) in diameter and 36.6 m (120 ft) tall and is equipped with cryogenic liquid nitrogen panels (shrouds) and gaseous helium shrouds to create a simulated space environment. It was originally designed and built in the mid 1960's to test the Apollo Command and Service Module and several manned tests were conducted on that spacecraft, contributing to the success of the program. The chamber has been used since that time to test spacecraft active thermal control systems, Shuttle DTO, DOD, and ESA hardware in simulated Low Earth Orbit (LEO) conditions. NASA is now moving from LEO towards exploration of locations with environments approaching those of deep space. Therefore, Chamber A has undergone major modifications to enable it to simulate these deeper space environments. Environmental requirements were driven, and the modifications were funded, by the James Webb Space Telescope program, and this telescope which will orbit Solar/Earth L2, will be the first test article to benefit from the chamber s new capabilities. To accommodate JWST, the Chamber A high vacuum system has been modernized, additional LN2 shrouds have been installed, the liquid nitrogen system has been modified to remove dependency on electrical power and increase its reliability, a new helium shroud/refrigeration system has been installed to create a colder more stable and uniform heat sink and, the controls have been updated to increase the level of automation and improve operator interfaces. Testing of these major modifications was conducted in August 2012 and this initial test was very successful, with all major systems exceeding their performance requirements. This paper will outline the changes in the overall environmental requirements, discuss the technical design data that was used in the decisions leading to the extensive

  18. Fabrication of boron articles

    DOEpatents

    Benton, Samuel T.

    1976-01-01

    This invention is directed to the fabrication of boron articles by a powder metallurgical method wherein the articles are of a density close to the theoretical density of boron and are essentially crackfree. The method comprises the steps of admixing 1 to 10 weight percent carbon powder with amorphous boron powder, cold pressing the mixture and then hot pressing the cold pressed compact into the desired article. The addition of the carbon to the mixture provides a pressing aid for inhibiting the cracking of the hot pressed article and is of a concentration less than that which would cause the articles to possess significant concentrations of boron carbide.

  19. Boron diffusion in nanocrystalline 3C-SiC

    SciTech Connect

    Schnabel, Manuel; Weiss, Charlotte; Rachow, Thomas; Löper, Philipp; Janz, Stefan; Canino, Mariaconcetta; Summonte, Caterina; Mirabella, Salvo; Wilshaw, Peter R.

    2014-05-26

    The diffusion of boron in nanocrystalline silicon carbide (nc-SiC) films with a grain size of 4–7 nm is studied using a poly-Si boron source. Diffusion is found to be much faster than in monocrystalline SiC as it takes place within the grain boundary (GB) network. Drive-in temperatures of 900–1000°C are suitable for creating shallow boron profiles up to 100 nm deep, while 1100°C is sufficient to flood the 200 nm thick films with boron. From the resulting plateau at 1100 °C a boron segregation coefficient of 28 between nc-SiC and the Si substrate, as well as a GB boron solubility limit of 0.2 nm{sup −2} is determined. GB diffusion in the bulk of the films is Fickian and thermally activated with D{sub GB}(T)=(3.1−5.6)×10{sup 7}exp(−5.03±0.16  eV/k{sub B}T) cm{sup 2}s{sup −1}. The activation energy is interpreted in terms of a trapping mechanism at dangling bonds. Higher boron concentrations are present at the nc-SiC surface and are attributed to immobilized boron.

  20. Low-dimensional boron structures based on icosahedron B12

    NASA Astrophysics Data System (ADS)

    Kah, C. B.; Yu, M.; Tandy, P.; Jayanthi, C. S.; Wu, S. Y.

    2015-10-01

    One-dimensional icosahedral boron chains and two-dimensional icosahedral boron sheets (icosahedral α, δ6, and δ4 sheets) that contain icosahedra B12 as their building units have been predicted in a computer simulation study using a state-of-the-art semi-empirical Hamiltonian. These novel low-dimensional icosahedral structures exhibit interesting bonding and electronic properties. Specifically, the three-center, two-electron bonding between icosahedra B12 of the boron bulk (rhombohedral boron) transforms into a two-center bonding in these new allotropes of boron sheets. In contrast to the previously reported stable buckled α and triangular boron monolayer sheets, these new allotropes of boron sheets form a planar network. Calculations of electronic density of states (DOS) reveal a semiconducting nature for both the icosahedral chain and the icosahedral δ6 and δ4 sheets, as well as a nearly gapless (or metallic-like) feature in the DOS for the icosahedral α sheet. The results for the energy barrier per atom between the icosahedral δ6 and α sheets (0.17 eV), the icosahedral δ6 and δ4 sheets (0.38 eV), and the icosahedral α and δ4 sheets (0.27 eV), as indicated in the respective parentheses, suggest that these new allotropes of boron sheets are relatively stable.

  1. Probing deep level centers in GaN epilayers with variable-frequency capacitance-voltage characteristics of Au /GaN Schottky contacts

    NASA Astrophysics Data System (ADS)

    Wang, R. X.; Xu, S. J.; Shi, S. L.; Beling, C. D.; Fung, S.; Zhao, D. G.; Yang, H.; Tao, X. M.

    2006-10-01

    Under identical preparation conditions, Au /GaN Schottky contacts were prepared on two kinds of GaN epilayers with significantly different background electron concentrations and mobility as well as yellow emission intensities. Current-voltage (I-V) and variable-frequency capacitance-voltage (C-V) characteristics show that the Schottky contacts on the GaN epilayer with a higher background carrier concentration and strong yellow emission exhibit anomalous reverse-bias I-V and C-V characteristics. This is attributed to the presence of deep level centers. Theoretical simulation of the low-frequency C-V curves leads to a determination of the density and energy level position of the deep centers.

  2. The structure of boron in boron fibres

    NASA Technical Reports Server (NTRS)

    Bhardwaj, J.; Krawitz, A. D.

    1983-01-01

    The structure of noncrystalline, chemically vapour-deposited boron fibres was investigated by computer modelling the experimentally obtained X-ray diffraction patterns. The diffraction patterns from the models were computed using the Debye scattering equation. The modelling was done utilizing the minimum nearest-neighbour distance, the density of the model, and the broadening and relative intensity of the various peaks as boundary conditions. The results suggest that the fibres consist of a continuous network of randomly oriented regions of local atomic order, about 2 nm in diameter, containing boron atoms arranged in icosahedra. Approximately half of these regions have a tetragonal structure and the remaining half a distorted rhombohedral structure. The model also indicates the presence of many partial icosahedra and loose atoms not associated with any icosahedra. The partial icosahedra and loose atoms indicated in the present model are in agreement with the relaxing sub-units which have been suggested to explain the anelastic behavior of fibre boron and the loosely bound boron atoms which have been postulated to explain the strengthening mechanism in boron fibres during thermal treatment.

  3. Characterization of Dissolved Organic Matter from Deep-sea Floor Hydrothermal Vents in South Mariana Backarc Spreading Center

    NASA Astrophysics Data System (ADS)

    Kitajima, F.; Yamanaka, T.

    2004-12-01

    In South Mariana Backarc Spreading Center, a few active hydrothermal fields are located. We investigated a characterization of dissolved organic matter (DOM) from hydrothermal vents in this area, in order to clarify the biosphere beneath deep-sea floor. Hot water sample was collected from a drilled hole (APM01 located in Fryer site, 12o 55.22fN, 143o 37.16fE, depth 2850m) during the ROPOS/TN167A cruise in March 2004. The hole had been drilled during Hakurei-Maru 2 cruise in January 2004. Another hot water sample was collected from a natural black smoker located in Pika site (12o 55.15fN, 143o 36.96fE, depth 2773m) during YK03-09 cruise. In this investigation, we developed a standalone filtration system in order to collect and enrich dissolved organic matter of quite low concentration. This system was designed to be put near hydrothermal vents for at least 24h. This system has an ODS disk (EmporeTM High Performance Extraction Disk C18 90mmφ) with a pre-filter (Whatman GMF 1 μ)m filter paper) to adsorb dilute organics. We collected DOM from the APM01 casing pipe for about 30h (Tmax = 25-30 o C, the estimated volume of filtrated water is max. 300L) using this filtration system. Adsorbed organics were eluted with methanol for 12h twice and toluene once using soxhlet extractor. Recovered amounts of methanol eluents are 72.8mg for APM01, and 89.7mg for the black smoker. Prior to GCMS analysis, we carried out high resolution 1 H-NMR measurement (400MHz), together with the DOM samples collected from the Suiyo Seamount in July-August 2001 and August 2002. Most of the samples show signals in the region of 3-4 ppm, and the samples from the vents of relatively low temperatures (APM01 and AP04: the natural vent at the Suiyo Seamount, temperature 8-48o C ) show signals also in the region of 0.8-1.6 ppm.

  4. Magnetron sputtered boron films

    DOEpatents

    Makowiecki, D.M.; Jankowski, A.F.

    1998-06-16

    A method is described for the production of thin boron and titanium/boron films by magnetron sputter deposition. The amorphous boron films contain no morphological growth features, unlike those found when thin films are prepared by various physical vapor deposition processes. Magnetron sputter deposition method requires the use of a high density crystalline boron sputter target which is prepared by hot isostatic pressing. Thin boron films prepared by this method are useful for producing hardened surfaces, surfacing machine tools, etc. and for ultra-thin band pass filters as well as the low Z element in low Z/high Z optical components, such as mirrors which enhance reflectivity from grazing to normal incidence. 8 figs.

  5. Magnetron sputtered boron films

    DOEpatents

    Makowiecki, Daniel M.; Jankowski, Alan F.

    1998-01-01

    A method is described for the production of thin boron and titanium/boron films by magnetron sputter deposition. The amorphous boron films contain no morphological growth features, unlike those found when thin films are prepared by various physical vapor deposition processes. Magnetron sputter deposition method requires the use of a high density crystalline boron sputter target which is prepared by hot isostatic pressing. Thin boron films prepared by this method are useful for producing hardened surfaces, surfacing machine tools, etc. and for ultra-thin band pass filters as well as the low Z element in low Z/high Z optical components, such as mirrors which enhance reflectivity from grazing to normal incidence.

  6. Microwave sintering of boron carbide

    DOEpatents

    Blake, R.D.; Katz, J.D.; Petrovic, J.J.; Sheinberg, H.

    1988-06-10

    A method for forming boron carbide into a particular shape and densifying the green boron carbide shape. Boron carbide in powder form is pressed into a green shape and then sintered, using a microwave oven, to obtain a dense boron carbide body. Densities of greater than 95% of theoretical density have been obtained. 1 tab.

  7. Boron and the kidney.

    PubMed

    Pahl, Madeleine V; Culver, B Dwight; Vaziri, Nosratola D

    2005-10-01

    Boron, the fifth element in the periodic table, is ubiquitous in nature. It is present in food and in surface and ocean waters, and is frequently used in industrial, cosmetic, and medical settings. Exposure to boron and related compounds has been recently implicated as a potential cause of chronic kidney disease in Southeast Asia. This observation prompted the present review of the published data on the effects of acute and chronic exposure to boron on renal function and structure in human beings and in experimental animals.

  8. Innovative method for boron extraction from iron ore containing boron

    NASA Astrophysics Data System (ADS)

    Wang, Guang; Wang, Jing-song; Yu, Xin-yun; Shen, Ying-feng; Zuo, Hai-bin; Xue, Qing-guo

    2016-03-01

    A novel process for boron enrichment and extraction from ludwigite based on iron nugget technology was proposed. The key steps of this novel process, which include boron and iron separation, crystallization of boron-rich slag, and elucidation of the boron extraction behavior of boron-rich slag by acid leaching, were performed at the laboratory. The results indicated that 95.7% of the total boron could be enriched into the slag phase, thereby forming a boron-rich slag during the iron and slag melting separation process. Suanite and kotoite were observed to be the boron-containing crystalline phases, and the boron extraction properties of the boron-rich slag depended on the amounts and grain sizes of these minerals. When the boron-rich slag was slowly cooled to 1100°C, the slag crystallized well and the efficiency of extraction of boron (EEB) of the slag was the highest observed in the present study. The boron extraction property of the slow-cooled boron-rich slag obtained in this study was much better than that of szaibelyite ore under the conditions of 80% of theoretical sulfuric acid amount, leaching time of 30 min, leaching temperature of 40°C, and liquid-to-solid ratio of 8 mL/g.

  9. Direct current sputtering of boron from boron/coron mixtures

    DOEpatents

    Timberlake, John R.; Manos, Dennis; Nartowitz, Ed

    1994-01-01

    A method for coating a substrate with boron by sputtering includes lowering the electrical resistance of a boron-containing rod to allow electrical conduction in the rod; placing the boron-containing rod inside a vacuum chamber containing substrate material to be coated; applying an electrical potential between the boron target material and the vacuum chamber; countering a current avalanche that commences when the conduction heating rate exceeds the cooling rate, and until a steady equilibrium heating current is reached; and, coating the substrate material with boron by sputtering from the boron-containing rod.

  10. Boron-Based Drug Design.

    PubMed

    Ban, Hyun Seung; Nakamura, Hiroyuki

    2015-06-01

    The use of the element boron, which is not generally observed in a living body, possesses a high potential for the discovery of new biological activity in pharmaceutical drug design. In this account, we describe our recent developments in boron-based drug design, including boronic acid containing protein tyrosine kinase inhibitors, proteasome inhibitors, and tubulin polymerization inhibitors, and ortho-carborane-containing proteasome activators, hypoxia-inducible factor 1 inhibitors, and topoisomerase inhibitors. Furthermore, we applied a closo-dodecaborate as a water-soluble moiety as well as a boron-10 source for the design of boron carriers in boron neutron capture therapy, such as boronated porphyrins and boron lipids for a liposomal boron delivery system.

  11. Boron nitride composites

    DOEpatents

    Kuntz, Joshua D.; Ellsworth, German F.; Swenson, Fritz J.; Allen, Patrick G.

    2016-02-16

    According to one embodiment, a composite product includes hexagonal boron nitride (hBN), and a plurality of cubic boron nitride (cBN) particles, wherein the plurality of cBN particles are dispersed in a matrix of the hBN. According to another embodiment, a composite product includes a plurality of cBN particles, and one or more borate-containing binders.

  12. Zeolitic Boron Imidazolate Frameworks**

    PubMed Central

    Zhang, Jian; Wu, Tao; Zhou, Cong; Chen, Shumei; Feng, Pingyun; Bu, Xianhui

    2009-01-01

    From porous AlPO4 to porous BIFs Reported here are a family of crystalline materials based on boron imidazolate frameworks (BIFs). It is demonstrated that the synthetic method, which is based on the crosslinking of various pre-synthesized boron imidazolates by monovalent cations (Li+ and Cu+), is capable of generating a large variety of open frameworks ranging from the 4-connected zeolitic sodalite type to the 3-connected chiral (10,3)-a type. PMID:19241428

  13. Phosphine-boronates: efficient bifunctional organocatalysts for Michael addition.

    PubMed

    Baslé, Olivier; Porcel, Susana; Ladeira, Sonia; Bouhadir, Ghenwa; Bourissou, Didier

    2012-05-11

    Phosphine-boronates R(2)P(o-C(6)H(4))B(OR')(2) have been evaluated as bifunctional organocatalysts for the Michael addition of malonate pronucleophiles to methylvinylketone. The presence of the Lewis acidic boron center adjacent to phosphorus significantly improves catalytic performance. Isolation and complete characterization of a key intermediate, namely a β-phosphonium enolate, substantiate the role of the Lewis acidic moiety in the catalytic process.

  14. Suppression of oxidation enhanced boron diffusion in silicon by carbon implantation and characterization of MOSFETs with carbon implanted channels

    SciTech Connect

    Ban, I.; Oeztuerk, M.C.; Demirlioglu, E.

    1996-12-31

    Scaling of MOSFETs into the deep submicron regime requires shallow doping profiles with abrupt doping transitions in the MOSFET active region. In NMOS transistors with boron doped channels, oxidation enhanced diffusion is a key contributor to boron profile broadening. Starting from the arguments presented in several recent reports on the role of carbon in silicon as a sink for self-interstitials, we have explored the feasibility of using carbon in the MOSFET in the active region to retard boron diffusion during gate oxidation. MOSFETs with carbon and boron implanted channels have been fabricated. Boron diffusion, activation, and critical electrical parameters such as subthreshold swing, threshold voltage, and off-state leakage current have been evaluated as a function of the carbon dose. We have shown that carbon can effectively suppress boron diffusion during gate oxidation. However, at dose levels around 10{sup 14}cm{sup -2} carbon results in poor boron activation and degradation in MOSFET performance.

  15. Process for making boron nitride using sodium cyanide and boron

    DOEpatents

    Bamberger, Carlos E.

    1990-02-06

    This a very simple process for making boron nitride by mixing sodium cyanide and boron phosphate and heating the mixture in an inert atmosphere until a reaction takes place. The product is a white powder of boron nitride that can be used in applications that require compounds that are stable at high temperatures and that exhibit high electrical resistance.

  16. Process for making boron nitride using sodium cyanide and boron

    DOEpatents

    Bamberger, Carlos E.

    1990-01-01

    This a very simple process for making boron nitride by mixing sodium cyanide and boron phosphate and heating the mixture in an inert atmosphere until a reaction takes place. The product is a white powder of boron nitride that can be used in applications that require compounds that are stable at high temperatures and that exhibit high electrical resistance.

  17. Understanding boron through size-selected clusters: structure, chemical bonding, and fluxionality.

    PubMed

    Sergeeva, Alina P; Popov, Ivan A; Piazza, Zachary A; Li, Wei-Li; Romanescu, Constantin; Wang, Lai-Sheng; Boldyrev, Alexander I

    2014-04-15

    Boron is an interesting element with unusual polymorphism. While three-dimensional (3D) structural motifs are prevalent in bulk boron, atomic boron clusters are found to have planar or quasi-planar structures, stabilized by localized two-center-two-electron (2c-2e) σ bonds on the periphery and delocalized multicenter-two-electron (nc-2e) bonds in both σ and π frameworks. Electron delocalization is a result of boron's electron deficiency and leads to fluxional behavior, which has been observed in B13(+) and B19(-). A unique capability of the in-plane rotation of the inner atoms against the periphery of the cluster in a chosen direction by employing circularly polarized infrared radiation has been suggested. Such fluxional behaviors in boron clusters are interesting and have been proposed as molecular Wankel motors. The concepts of aromaticity and antiaromaticity have been extended beyond organic chemistry to planar boron clusters. The validity of these concepts in understanding the electronic structures of boron clusters is evident in the striking similarities of the π-systems of planar boron clusters to those of polycyclic aromatic hydrocarbons, such as benzene, naphthalene, coronene, anthracene, or phenanthrene. Chemical bonding models developed for boron clusters not only allowed the rationalization of the stability of boron clusters but also lead to the design of novel metal-centered boron wheels with a record-setting planar coordination number of 10. The unprecedented highly coordinated borometallic molecular wheels provide insights into the interactions between transition metals and boron and expand the frontier of boron chemistry. Another interesting feature discovered through cluster studies is boron transmutation. Even though it is well-known that B(-), formed by adding one electron to boron, is isoelectronic to carbon, cluster studies have considerably expanded the possibilities of new structures and new materials using the B(-)/C analogy. It is

  18. Studies of deep level centers determining the diffusion length in epitaxial layers and crystals of undoped n-GaN

    SciTech Connect

    Lee, In-Hwan; Polyakov, A. Y.; Turutin, A. V.; Shemerov, I. V.; Smirnov, N. B.; Yakimov, E. B.; Tarelkin, S. A.; Pearton, S. J.

    2016-05-28

    A wide variety of parameters were measured for undoped n-GaN grown by hydride vapor phase epitaxy and compared to n-GaN films grown by conventional and lateral overgrowth metalorganic chemical vapor deposition. The parameters included deep level electron and hole trap spectra, microcathodoluminescence, electron beam induced current, diffusion length, and electron capture cross section from the dependence of the low temperature persistent photocapacitance on forward bias injection pulse duration. The results show a prominent role of electron traps with levels near E{sub c}-0.56 eV in limiting the lifetime and diffusion length values in all these materials.

  19. Studies of deep level centers determining the diffusion length in epitaxial layers and crystals of undoped n-GaN

    NASA Astrophysics Data System (ADS)

    Lee, In-Hwan; Polyakov, A. Y.; Smirnov, N. B.; Yakimov, E. B.; Tarelkin, S. A.; Turutin, A. V.; Shemerov, I. V.; Pearton, S. J.

    2016-05-01

    A wide variety of parameters were measured for undoped n-GaN grown by hydride vapor phase epitaxy and compared to n-GaN films grown by conventional and lateral overgrowth metalorganic chemical vapor deposition. The parameters included deep level electron and hole trap spectra, microcathodoluminescence, electron beam induced current, diffusion length, and electron capture cross section from the dependence of the low temperature persistent photocapacitance on forward bias injection pulse duration. The results show a prominent role of electron traps with levels near Ec-0.56 eV in limiting the lifetime and diffusion length values in all these materials.

  20. Boronated liposome development and evaluation

    SciTech Connect

    Hawthorne, M.F.

    1995-11-01

    The boronated liposome development and evaluation effort consists of two separate tasks. The first is the development of new boron compounds and the synthesis of known boron species with BNCT potential. These compounds are then encapsulated within liposomes for the second task, biodistribution testing in tumor-bearing mice, which examines the potential for the liposomes and their contents to concentrate boron in cancerous tissues.

  1. Inverse volt-ampere characteristics of an Ag-n-InP junction with taking account of the resonance tunneling through deep centers in InP

    NASA Astrophysics Data System (ADS)

    Bulyarsky, S. V.; Gaina, A.; Evseyev, E. P.

    Presence of an impurity state in the region of the potential barrier leads to increase of its general transmission probability and, thereafter, to increase of the resonance current through the barrier [1]. Resonance tunnel current could be greater than the over barrier one [2]. We examine the resonance tunneling through deep centers in the region of Space charge with taking account of the phonon ionization of the deep impurity center.The contribution of the electron-phonon interaction in the total value of the current has been calculated. It has been shown that in the region of high temperatures the phonons contribution is dominant. Depending on the position of the deep impurity center on the energies scale E_t three distinct cases could occur: a) Zcenters concentration γ=2hF/4πSqrt(2mE)kT; β=Shω; λ=(Sqrt(1+β+β^2/γ^2 -β/y)^2(Sqrt(1+β+β^2/γ^2+β/2γ); where Shω/2π-heat realise; m*- the effective mass; Δ(γ,β)-weakly dependent on γ and β function, h- Plank constant. b)0ψ_B) J=e^2(h/2π)N_TF(E_T+Shω/2π)^3/2/exp[-(E+Shω/2π)^2/4kTShω

  2. Method for separating boron isotopes

    DOEpatents

    Rockwood, Stephen D.

    1978-01-01

    A method of separating boron isotopes .sup.10 B and .sup.11 B by laser-induced selective excitation and photodissociation of BCl.sub.3 molecules containing a particular boron isotope. The photodissociation products react with an appropriate chemical scavenger and the reaction products may readily be separated from undissociated BCl.sub.3, thus effecting the desired separation of the boron isotopes.

  3. Status of Boron Combustion Research

    DTIC Science & Technology

    1984-10-01

    layer . . . . . . . . . . . . . . . . . . . . . . . . . . 10 5 Vaporization of boron oxide drops In wet and dry .-. environments. From Turns et al . ([1...19 10 SEN photographs of boron slurry agglomerates: a. Oxide layer present: b. Oxide layer absent.From Turns et al . [7...21 -- f- 11 Ignition of boron agglomerates as a function of particle and agglomerate diameters. From Shevahuk et al . [26

  4. Mineral of the month: boron

    USGS Publications Warehouse

    Lyday, Phyllis A.

    2005-01-01

    What does boron have to do with baseball, apple pie, motherhood and Chevrolet? Boron minerals and chemicals are used in the tanning of leather baseballs and gloves; in micro-fertilizer to grow apples and in the glass and enamels of bakewares to cook apple pie; in boron detergents for soaking baby clothes and diapers; and in fiberglass parts for the Chevrolet Corvette.

  5. Boron Nitride Nanotubes for Engineering Applications

    NASA Technical Reports Server (NTRS)

    Hurst, Janet; Hull, David; Gorican, Daniel

    2005-01-01

    Boron nitride nanotubes (BNNT) are of significant interest to the scientific and technical communities for many of the same reasons that carbon nanotubes (CNT) have attracted wide attention. Both materials have potentially unique and important properties for structural and electronic applications. However of even more consequence than their similarities may be the complementary differences between carbon and boron nitride nanotubes While BNNT possess a very high modulus similar to CNT, they also possess superior chemical and thermal stability. Additionally, BNNT have more uniform electronic properties, with a uniform band gap of 5.5 eV while CNT vary from semi-conductive to highly conductive behavior. Boron nitride nanotubes have been synthesized both in the literature and at NASA Glenn Research Center, by a variety of methods such as chemical vapor deposition, arc discharge and reactive milling. Consistent large scale production of a reliable product has proven difficult. Progress in the reproducible synthesis of 1-2 gram sized batches of boron nitride nanotubes will be discussed as well as potential uses for this unique material.

  6. In Vivo Boron Uptake Determination for Boron Neutron Capture Synovectomy

    SciTech Connect

    Binello, Emanuela; Shortkroff, Sonya; Yanch, Jacquelyn C.

    1999-06-06

    Boron neutron capture synovectomy (BNCS) has been proposed as a new application of the boron neutron capture reaction for the treatment of rheumatoid arthritis. In BNCS, a boron compound is injected into the joint space, where it is taken up by the synovium. The joint is then irradiated with neutrons of a desired energy range, inducing the boron neutron capture reaction in boron-loaded cells. Boron uptake by the synovium is an important parameter in the assessment of the potential of BNCS and in the determination of whether to proceed to animal irradiations for the testing of therapeutic efficacy. We present results from an investigation of boron uptake in vivo by the synovium.

  7. Interstitial-boron solution strengthened WB3+x

    NASA Astrophysics Data System (ADS)

    Cheng, Xiyue; Zhang, Wei; Chen, Xing-Qiu; Niu, Haiyang; Liu, Peitao; Du, Kui; Liu, Gang; Li, Dianzhong; Cheng, Hui-Ming; Ye, Hengqiang; Li, Yiyi

    2013-10-01

    By means of variable-composition evolutionary algorithm coupled with density functional theory and in combination with aberration-corrected high-resolution transmission electron microscopy experiments, we have studied and characterized the composition, structure, and hardness properties of WB3+x (x < 0.5). We provide robust evidence for the occurrence of stoichiometric WB3 and non-stoichiometric WB3+x, both crystallizing in the metastable hP16 (P63/mmc) structure. No signs for the formation of the highly debated WB4 (both hP20 and hP10) phases were found. Our results rationalize the seemingly contradictory high-pressure experimental findings and suggest that the interstitial boron atom is located in the tungsten layer and vertically interconnect with four boron atoms, thus forming a typical three-center boron net with the upper and lower boron layers in a three-dimensional covalent network, which thereby strengthen the hardness.

  8. Prevalence of Isolated Asymptomatic Deep Vein Thrombosis in Varicose Vein Patients with Superficial Thrombophlebitis: A Single Center Experience in Japan

    PubMed Central

    Horiguchi, Sadaaki; Shirato, Hiroyuki; Kawakami, Toshimitsu; Ono, Hisako; Yabuki, Shiho; Jojima, Kumiko; Niimi, Masanori

    2015-01-01

    Objective: Prevalence of asymptomatic deep vein thrombosis (DVT) in patients with primary varicose veins remains unclear. Materials and Methods: Here, we conducted a retrospective study to clarify the incidence of asymptomatic DVT in patients with varicose veins, especially focusing on those with superficial thrombophlebitis (STP). Results: Among 431 patients with primary varicose veins with saphenous vein incompetence, 20 (4.64%) had asymptomatic DVT. The presence of STP was a significant risk factor for asymptomatic DVT as 10 of the 24 (41.7%) patients with STP had asymptomatic DVT, and all cases having calf muscle vein thrombosis. In contrast, of the patients with primary varicose veins without STP only 2.46% had asymptomatic DVT. Conclusions: In patients with primary varicose veins with STP, significant risk factors for DVT were being over C3 on the clinical, etiological, anatomical, and pathophysiological (CEAP) classification. (This article is a translation of Jpn J Phlebol 2014; 25: 13–19.) PMID:27087866

  9. A fast parallel imaging rotary phased array head coil with improved sensitivity profile deep in the center of the brain.

    PubMed

    Weber, Ewald; Li, Bing Keong; Liu, Feng; Crozier, Stuart

    2007-01-01

    A new class of a receive-only 2T 4-element rotary phased array head coil has been proposed for MRI brain imaging applications. Coil elements of the rotary phased array head coil have "paddle-like" structures consisting of a pair of main conductors located on opposite sides, inserted equi-angularly around and over the head. Using such a unique design, the proposed rotary head coil can improve the sensitivity deep at the centre of the brain and produces highly homogeneous brain images. The rotary phased array head coil is numerically modeled using a hybrid MoM/FEM method and a prototype was constructed accordingly. In vivo MR brain imaging using the prototype rotary phased array head coil has been undertaken and the acquired brain images show high homogeneity as anticipated. In addition, parallel imaging, VD-GRAPPA, is used in conjunction with the rotary phased array head coil to enable rapid imaging.

  10. Boron isotope exchange in a heterogeneous boron-boron fluoride system

    SciTech Connect

    Begak, O.Yu.; Fedorov, V.V.

    1988-11-01

    Studies have been made on exchange between /sup 10/B and /sup 11/B in heterogeneous systems containing finely divided amorphous boron and BF/sub 3/ gas. The kinetic and thermodynamic parameters have been examined. The self-diffusion coefficient for boron in amorphous boron has been determined at 973-1273 K.

  11. Minerals Yearbook 1989: Boron

    SciTech Connect

    Lyday, P.A.

    1990-08-01

    U.S. production and sales of boron minerals and chemicals decreased during the year. Domestically, glass fiber insulation was the largest use for borates, followed by sales to distributors, textile-grade glass fibers, and borosilicate glasses. California was the only domestic source of boron minerals. The United States continued to provide essentially all of its own supply while maintaining a strong position as a source of sodium borate products and boric acid exported to foreign markets. Supplementary U.S. imports of Turkish calcium borate and calcium-sodium borate ores, borax, and boric acid, primarily for various glass uses, continued.

  12. Boron hydride polymer coated substrates

    DOEpatents

    Pearson, Richard K.; Bystroff, Roman I.; Miller, Dale E.

    1987-01-01

    A method is disclosed for coating a substrate with a uniformly smooth layer of a boron hydride polymer. The method comprises providing a reaction chamber which contains the substrate and the boron hydride plasma. A boron hydride feed stock is introduced into the chamber simultaneously with the generation of a plasma discharge within the chamber. A boron hydride plasma of ions, electrons and free radicals which is generated by the plasma discharge interacts to form a uniformly smooth boron hydride polymer which is deposited on the substrate.

  13. Boron hydride polymer coated substrates

    DOEpatents

    Pearson, R.K.; Bystroff, R.I.; Miller, D.E.

    1986-08-27

    A method is disclosed for coating a substrate with a uniformly smooth layer of a boron hydride polymer. The method comprises providing a reaction chamber which contains the substrate and the boron hydride plasma. A boron hydride feed stock is introduced into the chamber simultaneously with the generation of a plasma discharge within the chamber. A boron hydride plasma of ions, electrons and free radicals which is generated by the plasma discharge interacts to form a uniformly smooth boron hydride polymer which is deposited on the substrate.

  14. Deep level centers and their role in photoconductivity transients of InGaAs/GaAs quantum dot chains

    SciTech Connect

    Kondratenko, S. V. Vakulenko, O. V.; Mazur, Yu. I. Dorogan, V. G.; Marega, E.; Benamara, M.; Ware, M. E.; Salamo, G. J.

    2014-11-21

    The in-plane photoconductivity and photoluminescence are investigated in quantum dot-chain InGaAs/GaAs heterostructures. Different photoconductivity transients resulting from spectrally selecting photoexcitation of InGaAs QDs, GaAs spacers, or EL2 centers were observed. Persistent photoconductivity was observed at 80 K after excitation of electron-hole pairs due to interband transitions in both the InGaAs QDs and the GaAs matrix. Giant optically induced quenching of in-plane conductivity driven by recharging of EL2 centers is observed in the spectral range from 0.83 eV to 1.0 eV. Conductivity loss under photoexcitation is discussed in terms of carrier localization by analogy with carrier distribution in disordered media.

  15. Deep level centers and their role in photoconductivity transients of InGaAs/GaAs quantum dot chains

    NASA Astrophysics Data System (ADS)

    Kondratenko, S. V.; Vakulenko, O. V.; Mazur, Yu. I.; Dorogan, V. G.; Marega, E.; Benamara, M.; Ware, M. E.; Salamo, G. J.

    2014-11-01

    The in-plane photoconductivity and photoluminescence are investigated in quantum dot-chain InGaAs/GaAs heterostructures. Different photoconductivity transients resulting from spectrally selecting photoexcitation of InGaAs QDs, GaAs spacers, or EL2 centers were observed. Persistent photoconductivity was observed at 80 K after excitation of electron-hole pairs due to interband transitions in both the InGaAs QDs and the GaAs matrix. Giant optically induced quenching of in-plane conductivity driven by recharging of EL2 centers is observed in the spectral range from 0.83 eV to 1.0 eV. Conductivity loss under photoexcitation is discussed in terms of carrier localization by analogy with carrier distribution in disordered media.

  16. Fabrication of boron sputter targets

    DOEpatents

    Makowiecki, D.M.; McKernan, M.A.

    1995-02-28

    A process is disclosed for fabricating high density boron sputtering targets with sufficient mechanical strength to function reliably at typical magnetron sputtering power densities and at normal process parameters. The process involves the fabrication of a high density boron monolithe by hot isostatically compacting high purity (99.9%) boron powder, machining the boron monolithe into the final dimensions, and brazing the finished boron piece to a matching boron carbide (B{sub 4}C) piece, by placing aluminum foil there between and applying pressure and heat in a vacuum. An alternative is the application of aluminum metallization to the back of the boron monolithe by vacuum deposition. Also, a titanium based vacuum braze alloy can be used in place of the aluminum foil. 7 figs.

  17. Fabrication of boron sputter targets

    DOEpatents

    Makowiecki, Daniel M.; McKernan, Mark A.

    1995-01-01

    A process for fabricating high density boron sputtering targets with sufficient mechanical strength to function reliably at typical magnetron sputtering power densities and at normal process parameters. The process involves the fabrication of a high density boron monolithe by hot isostatically compacting high purity (99.9%) boron powder, machining the boron monolithe into the final dimensions, and brazing the finished boron piece to a matching boron carbide (B.sub.4 C) piece, by placing aluminum foil there between and applying pressure and heat in a vacuum. An alternative is the application of aluminum metallization to the back of the boron monolithe by vacuum deposition. Also, a titanium based vacuum braze alloy can be used in place of the aluminum foil.

  18. Understanding Boron through Size-Selected Clusters: Structure, Chemical Bonding, and Fluxionality

    SciTech Connect

    Sergeeva, Alina P.; Popov, Ivan A.; Piazza, Zachary A.; Li, Wei-Li; Romanescu, Constantin; Wang, Lai S.; Boldyrev, Alexander I.

    2014-04-15

    Conspectus Boron is an interesting element with unusual polymorphism. While three-dimensional (3D) structural motifs are prevalent in bulk boron, atomic boron clusters are found to have planar or quasi-planar structures, stabilized by localized two-center–two-electron (2c–2e) σ bonds on the periphery and delocalized multicenter–two-electron (nc–2e) bonds in both σ and π frameworks. Electron delocalization is a result of boron’s electron deficiency and leads to fluxional behavior, which has been observed in B13+ and B19–. A unique capability of the in-plane rotation of the inner atoms against the periphery of the cluster in a chosen direction by employing circularly polarized infrared radiation has been suggested. Such fluxional behaviors in boron clusters are interesting and have been proposed as molecular Wankel motors. The concepts of aromaticity and antiaromaticity have been extended beyond organic chemistry to planar boron clusters. The validity of these concepts in understanding the electronic structures of boron clusters is evident in the striking similarities of the π-systems of planar boron clusters to those of polycyclic aromatic hydrocarbons, such as benzene, naphthalene, coronene, anthracene, or phenanthrene. Chemical bonding models developed for boron clusters not only allowed the rationalization of the stability of boron clusters but also lead to the design of novel metal-centered boron wheels with a record-setting planar coordination number of 10. The unprecedented highly coordinated borometallic molecular wheels provide insights into the interactions between transition metals and boron and expand the frontier of boron chemistry. Another interesting feature discovered through cluster studies is boron transmutation. Even though it is well-known that B–, formed by adding one electron to boron, is isoelectronic to carbon, cluster studies have considerably expanded the possibilities of new structures and new materials using the B

  19. Determination of phase stability of elemental boron.

    PubMed

    White, Mary Anne; Cerqueira, Anthony B; Whitman, Catherine A; Johnson, Michel B; Ogitsu, Tadashi

    2015-03-16

    Boron is an important element, used in applications from superhard materials to superconductors. Boron exists in several forms (allotropes) and, surprisingly, it was not known which form (α or β) is stable at ambient conditions. Through experiment, we quantify the relative stability of α-boron and β-boron as a function of temperature. The ground-state energies of α-boron and β-boron are nearly identical. For all temperatures up to 2000 K, the complicated β-boron structure is more stable than the simpler α-boron structure at ambient pressure. Below 1000 K, β-boron is entropically stabilized with respect to α-boron owing to its partially occupied sites, whereas at higher temperatures β-boron is enthalpically stabilized with respect to α-boron. We show that α-boron only becomes stable on application of pressure.

  20. Process for microwave sintering boron carbide

    DOEpatents

    Holcombe, Cressie E.; Morrow, Marvin S.

    1993-01-01

    A method of microwave sintering boron carbide comprises leaching boron carbide powder with an aqueous solution of nitric acid to form a leached boron carbide powder. The leached boron carbide powder is coated with a glassy carbon precursor to form a coated boron carbide powder. The coated boron carbide powder is consolidated in an enclosure of boron nitride particles coated with a layer of glassy carbon within a container for microwave heating to form an enclosed coated boron carbide powder. The enclosed coated boron carbide powder is sintered within the container for microwave heating with microwave energy.

  1. Process for microwave sintering boron carbide

    DOEpatents

    Holcombe, C.E.; Morrow, M.S.

    1993-10-12

    A method of microwave sintering boron carbide comprises leaching boron carbide powder with an aqueous solution of nitric acid to form a leached boron carbide powder. The leached boron carbide powder is coated with a glassy carbon precursor to form a coated boron carbide powder. The coated boron carbide powder is consolidated in an enclosure of boron nitride particles coated with a layer of glassy carbon within a container for microwave heating to form an enclosed coated boron carbide powder. The enclosed coated boron carbide powder is sintered within the container for microwave heating with microwave energy.

  2. Sensing deep extreme environments: the receptor cell types, brain centers, and multi-layer neural packaging of hydrothermal vent endemic worms.

    PubMed

    Shigeno, Shuichi; Ogura, Atsushi; Mori, Tsukasa; Toyohara, Haruhiko; Yoshida, Takao; Tsuchida, Shinji; Fujikura, Katsunori

    2014-01-01

    Deep-sea alvinellid worm species endemic to hydrothermal vents, such as Alvinella and Paralvinella, are considered to be among the most thermotolerant animals known with their adaptability to toxic heavy metals, and tolerance of highly reductive and oxidative stressful environments. Despite the number of recent studies focused on their overall transcriptomic, proteomic, and metabolic stabilities, little is known regarding their sensory receptor cells and electrically active neuro-processing centers, and how these can tolerate and function in such harsh conditions. We examined the extra- and intracellular organizations of the epidermal ciliated sensory cells and their higher centers in the central nervous system through immunocytochemical, ultrastructural, and neurotracing analyses. We observed that these cells were rich in mitochondria and possessed many electron-dense granules, and identified specialized glial cells and serial myelin-like repeats in the head sensory systems of Paralvinella hessleri. Additionally, we identified the major epidermal sensory pathways, in which a pair of distinct mushroom bodies-like or small interneuron clusters was observed. These sensory learning and memory systems are commonly found in insects and annelids, but the alvinellid inputs are unlikely derived from the sensory ciliary cells of the dorsal head regions. Our evidence provides insight into the cellular and system-wide adaptive structure used to sense, process, and combat the deep-sea hydrothermal vent environment. The alvinellid sensory cells exhibit characteristics of annelid ciliary types, and among the most unique features were the head sensory inputs and structure of the neural cell bodies of the brain, which were surrounded by multiple membranes. We speculated that such enhanced protection is required for the production of normal electrical signals, and to avoid the breakdown of the membrane surrounding metabolically fragile neurons from oxidative stress. Such pivotal

  3. Methods of producing continuous boron carbide fibers

    SciTech Connect

    Garnier, John E.; Griffith, George W.

    2015-12-01

    Methods of producing continuous boron carbide fibers. The method comprises reacting a continuous carbon fiber material and a boron oxide gas within a temperature range of from approximately 1400.degree. C. to approximately 2200.degree. C. Continuous boron carbide fibers, continuous fibers comprising boron carbide, and articles including at least a boron carbide coating are also disclosed.

  4. Boron and Compounds

    Integrated Risk Information System (IRIS)

    EPA 635 / 04 / 052 www.epa.gov / iris TOXICOLOGICAL REVIEW OF BORON AND COMPOUNDS ( CAS No . 7440 - 42 - 8 ) In Support of Summary Information on the Integrated Risk Information System ( IRIS ) June 2004 U.S . Environmental Protection Agency Washington , DC DISCLAIMER This document has been reviewed

  5. Nothing Boring About Boron.

    PubMed

    Pizzorno, Lara

    2015-08-01

    The trace mineral boron is a micronutrient with diverse and vitally important roles in metabolism that render it necessary for plant, animal, and human health, and as recent research suggests, possibly for the evolution of life on Earth. As the current article shows, boron has been proven to be an important trace mineral because it (1) is essential for the growth and maintenance of bone; (2) greatly improves wound healing; (3) beneficially impacts the body's use of estrogen, testosterone, and vitamin D; (4) boosts magnesium absorption; (5) reduces levels of inflammatory biomarkers, such as high-sensitivity C-reactive protein (hs-CRP) and tumor necrosis factor α (TNF-α); (6) raises levels of antioxidant enzymes, such as superoxide dismutase (SOD), catalase, and glutathione peroxidase; (7) protects against pesticide-induced oxidative stress and heavy-metal toxicity; (8) improves the brains electrical activity, cognitive performance, and short-term memory for elders; (9) influences the formation and activity of key biomolecules, such as S-adenosyl methionine (SAM-e) and nicotinamide adenine dinucleotide (NAD(+)); (10) has demonstrated preventive and therapeutic effects in a number of cancers, such as prostate, cervical, and lung cancers, and multiple and non-Hodgkin's lymphoma; and (11) may help ameliorate the adverse effects of traditional chemotherapeutic agents. In none of the numerous studies conducted to date, however, do boron's beneficial effects appear at intakes > 3 mg/d. No estimated average requirements (EARs) or dietary reference intakes (DRIs) have been set for boron-only an upper intake level (UL) of 20 mg/d for individuals aged ≥ 18 y. The absence of studies showing harm in conjunction with the substantial number of articles showing benefits support the consideration of boron supplementation of 3 mg/d for any individual who is consuming a diet lacking in fruits and vegetables or who is at risk for or has osteopenia; osteoporosis; osteoarthritis (OA

  6. Fluorine-enhanced boron diffusion in amorphous silicon

    NASA Astrophysics Data System (ADS)

    Jacques, J. M.; Robertson, L. S.; Jones, K. S.; Law, M. E.; Rendon, Mike; Bennett, Joe

    2003-05-01

    Silicon wafers were preamorphized with 70 keV Si+ at a dose of 1×1015atoms/cm2, generating a deep amorphous layer of 1800 Å. Implants of 500 eV 11B+, with and without 6 keV F+, followed at doses of 1×1015 atoms/cm2 and 2×1015 atoms/cm2, respectively. After annealing at 550 °C, secondary ion mass spectroscopy determined that the diffusivity of boron in amorphous silicon is significantly enhanced in the presence of fluorine. Ellipsometry and cross-sectional transmission electron microscopy indicate the enhanced diffusion only occurs in the amorphous layer. Fluorine increases the boron diffusivity by approximately five orders of magnitude at 550 °C. It is proposed that the ability of fluorine to reduce the dangling bond concentration in amorphous silicon may reduce the formation energy for mobile boron, enhancing its diffusivity.

  7. Bosonic Anomalies in Boron-Doped Polycrystalline Diamond

    NASA Astrophysics Data System (ADS)

    Zhang, Gufei; Samuely, Tomas; Kačmarčík, Jozef; Ekimov, Evgeny A.; Li, Jun; Vanacken, Johan; Szabó, Pavol; Huang, Junwei; Pereira, Paulo J.; Cerbu, Dorin; Moshchalkov, Victor V.

    2016-12-01

    Quantum confinement and coherence effects are considered the cause of many specific features for systems which are generally low dimensional, strongly disordered, and/or situated in the vicinity of the metal-insulator transition. Here, we report on the observation of anomalous resistance peak and specific heat peaks superimposed at the superconducting transition of heavily boron-doped polycrystalline bulk diamond, which is a three-dimensional system situated deep on the metallic side of the boron-doping-driven metal-insulator transition in diamond. The anomalous resistance peak and specific heat peaks are interpreted as a result of confinement and coherence effects in the presence of intrinsic and extrinsic granularity. Our data, obtained for superconducting diamond, provide a reference for understanding the superconductivity in other granular disordered systems. Furthermore, our study brings attention to the significant influence of granular disorder on the physical properties of boron-doped diamond, which is considered a promising candidate for electronics applications.

  8. Nature of exciton transitions in hexagonal boron nitride

    SciTech Connect

    Li, J.; Cao, X. K.; Lin, J. Y.; Jiang, H. X.; Hoffman, T. B.; Edgar, J. H.

    2016-03-21

    In contrast to other III-nitride semiconductors GaN and AlN, the intrinsic (or free) exciton transition in hexagonal boron nitride (h-BN) consists of rather complex fine spectral features (resolved into six sharp emission peaks) and the origin of which is still unclear. Here, the free exciton transition (FX) in h-BN bulk crystals synthesized by a solution method at atmospheric pressure has been probed by deep UV time-resolved photoluminescence (PL) spectroscopy. Based on the separations between the energy peak positions of the FX emission lines, the identical PL decay kinetics among different FX emission lines, and the known phonon modes in h-BN, we suggest that there is only one principal emission line corresponding to the direct intrinsic FX transition in h-BN, whereas all other fine features are a result of phonon-assisted transitions. The identified phonon modes are all associated with the center of the Brillouin zone. Our results offer a simple picture for the understanding of the fundamental exciton transitions in h-BN.

  9. Nature of exciton transitions in hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

    Li, J.; Cao, X. K.; Hoffman, T. B.; Edgar, J. H.; Lin, J. Y.; Jiang, H. X.

    2016-03-01

    In contrast to other III-nitride semiconductors GaN and AlN, the intrinsic (or free) exciton transition in hexagonal boron nitride (h-BN) consists of rather complex fine spectral features (resolved into six sharp emission peaks) and the origin of which is still unclear. Here, the free exciton transition (FX) in h-BN bulk crystals synthesized by a solution method at atmospheric pressure has been probed by deep UV time-resolved photoluminescence (PL) spectroscopy. Based on the separations between the energy peak positions of the FX emission lines, the identical PL decay kinetics among different FX emission lines, and the known phonon modes in h-BN, we suggest that there is only one principal emission line corresponding to the direct intrinsic FX transition in h-BN, whereas all other fine features are a result of phonon-assisted transitions. The identified phonon modes are all associated with the center of the Brillouin zone. Our results offer a simple picture for the understanding of the fundamental exciton transitions in h-BN.

  10. Impact of boron dilution accidents on low boron PWR safety

    SciTech Connect

    Papukchiev, A.; Liu, Y.; Schaefer, A.

    2006-07-01

    In conventional pressurized water reactor (PWR) designs, soluble boron is used for reactivity control over core fuel cycle. As an inadvertent reduction of the boron concentration during a boron dilution accident could introduce positive reactivity and have a negative impact on PWR safety, design changes to reduce boron concentration in the reactor coolant are of general interest. In the framework of an investigation into the feasibility of low boron design, a PWR core configuration based on fuel with higher gadolinium (Gd) load has been developed which permits to reduce the natural boron concentration at begin of cycle (BOC) to 518 ppm. For the assessment of the potential safety advantages, a boron dilution accident due to small break loss-of-coolant-accident (SBLOCA) has been simulated with the system code ATHLET for two PWR core designs: a low boron design and a standard core design. The results from the comparative analyses showed that the impact of the boron dilution accident on the new PWR design safety is significantly lower in comparison with the standard design. The new reactor design provided at least 4, 4% higher reactivity margin to recriticality during the whole accident which is equivalent to the negative reactivity worth of additional 63% of all control rods fully inserted in to the core. (authors)

  11. Boronizing protects metals against wear

    SciTech Connect

    Stewart, K.

    1997-03-01

    Boronizing is a thermochemical surface treatment that involves diffusion of boron into a base metal at a high temperature. The resulting metallic boride provides high hardness and resistance to acid corrosion, and lengthens service life by a factor of three to ten. Boronizing fills a gap between conventional surface treatments and the more exotic chemical and physical vapor deposition. In a number of applications, boronizing has replaced such processes as carburizing, nitriding, and nitrocarburizing. It has even replaced hard chrome plating in some cases, while achieving similar service life improvements. Boron can be uniformly applied to irregular surfaces, and can be applied to specific areas of a surface. It is also suitable for high-volume production applications, as first demonstrated in the European automotive industry. This article describes the boronizing process, provides material selection/preparation criteria, and lists industrial applications.

  12. Microstructure Analysis of Boron Nanotubes

    DTIC Science & Technology

    2012-05-01

    figure 1 2 3 High resolution TEM showing very small elongated BNT filaments 3 4 SAED from an area in figure 3 showing exactly the same kind of...scattered large numbers of BNT 4 7 EDAX analyses of boron nitride nano powder showing boron and oxygen 5 8 Low magnification SEM picture of folded 600...Picatinny Arsenal, New Jersey. INTRODUCTION Boron nanotubes ( BNT ) have never been produced in a reliable manner, yet they remain a promising

  13. Structures, stability, mechanical and electronic properties of α-boron and α∗-boron

    NASA Astrophysics Data System (ADS)

    He, Chaoyu; Zhong, J. X.

    2013-04-01

    The structures, stability, mechanical and electronic properties of α-boron and a promising metastable boron phase (α*-boron) have been studied by first-principles calculations. α-boron and α*-boron consist of equivalent icosahedra B12 clusters in different connecting configurations of "3S-6D-3S" and "2S-6D-4S", respectively. The total energy calculations show that α*-boron is less stable than α-boron but more favorable than the well-known β-boron and γ-boron at zero pressure. Both α-boron and α*-boron are confirmed dynamically and mechanically stable. The mechanical and electronic properties of α-boron and α*-boron indicate that they are potential superhard semiconducting phases of element boron.

  14. Boron nitride nanotubes.

    PubMed

    Chopra, N G; Luyken, R J; Cherrey, K; Crespi, V H; Cohen, M L; Louie, S G; Zettl, A

    1995-08-18

    The successful synthesis of pure boron nitride (BN) nanotubes is reported here. Multi-walled tubes with inner diameters on the order of 1 to 3 nanometers and with lengths up to 200 nanometers were produced in a carbon-free plasma discharge between a BN-packed tungsten rod and a cooled copper electrode. Electron energy-loss spectroscopy on individual tubes yielded B:N ratios of approximately 1, which is consistent with theoretical predictions of stable BN tube structures.

  15. Carrier compensation near tail region in aluminum- or boron-implanted 4H-SiC (0001)

    SciTech Connect

    Negoro, Y.; Kimoto, T.; Matsunami, H.

    2005-08-15

    Electrical behavior of implanted Al and B near implant-tail region in 4H-SiC (0001) after high-temperature annealing has been investigated. Depth profiles of Al and B acceptors determined by capacitance-voltage characteristics are compared with those of Al and B atoms measured by secondary-ion-mass spectrometry. For Al{sup +} (aluminum-ion) implantation, slight in-diffusion of Al implants occurred in the initial stage of annealing at 1700 deg. C. The profile of the Al-acceptor concentration in a 'box-profile' region as well as an 'implant-tail' region is in good agreement with that of the Al-atom concentration, indicating that nearly all of the implanted Al atoms, including the in-diffused Al atoms, work as Al acceptors. Several electrically deep centers were formed by Al{sup +} implantation. For B{sup +} (boron-ion) implantation, significant out- and in-diffusion of B implants occurred in the initial stage of annealing at 1700 deg. C. A high density of B-related D centers exists near the tail region. In the tail region, the sum of B-acceptor concentration and D-center concentration corresponds to the B-atom concentration. C{sup +} (carbon-ion) coimplantation with a ten times higher dose than B{sup +} effectively suppressed the B diffusion, but additional deep centers were introduced by C{sup +} coimplantation.

  16. Method of fabricating boron containing coatings

    DOEpatents

    Makowiecki, Daniel M.; Jankowski, Alan F.

    1999-01-01

    Hard coatings are fabricated from boron nitride, cubic boron nitride, and multilayer boron/cubic boron nitride, and the fabrication thereof involves magnetron sputtering in a selected atmosphere. These hard coatings may be applied to tools and engine and other parts, as well to reduce wear on tribological surfaces and electronic devices. These boron coatings contain no morphological growth features. For example, the boron is formed in an inert (e.g. argon) atmosphere, while the cubic boron nitride is formed in a reactive (e.g. nitrogen) atmosphere. The multilayer boron/cubic boron nitride, is produced by depositing alternate layers of boron and cubic boron nitride, with the alternate layers having a thickness of 1 nanometer to 1 micrometer, and at least the interfaces of the layers may be discrete or of a blended or graded composition.

  17. Method of fabricating boron containing coatings

    DOEpatents

    Makowiecki, D.M.; Jankowski, A.F.

    1999-04-27

    Hard coatings are fabricated from boron nitride, cubic boron nitride, and multilayer boron/cubic boron nitride, and the fabrication thereof involves magnetron sputtering in a selected atmosphere. These hard coatings may be applied to tools and engine and other parts, as well to reduce wear on tribological surfaces and electronic devices. These boron coatings contain no morphological growth features. For example, the boron is formed in an inert (e.g. argon) atmosphere, while the cubic boron nitride is formed in a reactive (e.g. nitrogen) atmosphere. The multilayer boron/cubic boron nitride, is produced by depositing alternate layers of boron and cubic boron nitride, with the alternate layers having a thickness of 1 nanometer to 1 micrometer, and at least the interfaces of the layers may be discrete or of a blended or graded composition. 3 figs.

  18. Photoelectron Spectroscopy of Aluminum Doped Boron Clusters

    NASA Astrophysics Data System (ADS)

    Li, Wei-Li; Romanescu, Constantin; Wang, Lai-Sheng

    2012-06-01

    Anionic boron clusters have been shown to be planar or quasi-planar up to B21- from a series of combined photoelectron spectroscopy and theoretical studies. All these boron clusters consist of a peripheral ring characterized by strong two-center-two-electron (2c-2e) B-B bonds and one or more interior atoms. The propensity for planarity is due to σ - and π -electron delocalizations throughout the molecular plane, giving rise to concepts of σ - and π -aromaticity. The quasi-planarity, on the other hand, can be mechanical in nature - the circumference of the cluster is too small to fit the inner atoms - even for doubly aromatic clusters. Two questions arise: firstly, can isoelectronic substitution by a single aluminum atom on the outer ring enhance the planarity of quasi-planar structures, and, secondly, can the interior boron atoms be replaced by aluminum? A series of aluminum isoelectronic substitution of boron clusters have been investigated ranging from B7- to B12-. Aluminum turns out to avoid the central position in the all these clusters and enhance the planarity of AlB6- and AlB11- clusters by expanding the peripheral ring. References: [1] C. Romanescu, A. P. Sergeeva, W. L. Li, A. I. Boldyrev and L. S. Wang, {J. Am. Chem. Soc}. {133} (22), 8646-8653 (2011) [2] T. R. Galeev, C. Romanescu, W. L. Li, L. S. Wang and A. I. Boldyrev, {J. Chem. Phys.} {135}, (8) 104301 (2011) [3] W. L. Li, C. Romanescu, T. R. Galeev, L. S. Wang and A. I. Boldyrev, {J. Phys. Chem. A} {115} (38), 10391-10397 (2011)

  19. Boron isotopic compositions of some boron minerals

    SciTech Connect

    Oi, Takao; Musashi, Masaaki; Ossaka, Tomoko; Kakihana, Hidetake ); Nomura, Masao; Okamoto, Makoto )

    1989-12-01

    Boron minerals that have different structural formulae but are supposed to have the same geologic origin have been collected and analyzed for the {sup 11}B/{sup 10}B isotopic ratio. It has been reconfirmed that minerals of marine origin have higher {sup 11}B/{sup 10}B ratios than those of nonmarine origin. It has been found that the sequence of decreasing {sup 11}B/{sup 10}B values among the minerals with the same geologic origin is; borax, tincal, kernite (Na borates) > ulexite (Na/Ca borate) > colemanite, iyoite, meyerhofferite (Ca borates). This sequence is explainable on the basis of the difference in crystal structure among the minerals. That is, minerals with high BO{sub 3}/BO{sub 4} ratios, (the ratio of the number of the BO{sub 3} triangle units to the number of the BO{sub 4} tetrahedron units in the structural formula of a mineral) have higher {sup 11}B/{sup 10}B ratios.

  20. Boron containing multilayer coatings and method of fabrication

    DOEpatents

    Makowiecki, Daniel M.; Jankowski, Alan F.

    1997-01-01

    Hard coatings are fabricated from multilayer boron/boron carbide, boron carbide/cubic boron nitride, and boron/boron nitride/boron carbide, and the fabrication thereof involves magnetron sputtering in a selected atmosphere. These hard coatings may be applied to tools and engine and other parts, as well to reduce wear on tribological surfaces and electronic devices. These boron coatings contain no morphological growth features. For example, the boron and boron carbide used in forming the multilayers are formed in an inert (e.g. argon) atmosphere, while the cubic boron nitride is formed in a reactive (e.g. nitrogen) atmosphere. The multilayer boron/boron carbide, and boron carbide/cubic boron nitride is produced by depositing alternate layers of boron, cubic boron nitride or boron carbide, with the alternate layers having a thickness of 1 nanometer to 1 micrometer, and at least the interfaces of the layers may be of a discrete or a blended or graded composition.

  1. Boron Clusters Come of Age

    ERIC Educational Resources Information Center

    Grimes, Russell N.

    2004-01-01

    Boron is the only element other than carbon that can build molecules of unlimited size by covalently boding to itself, a property known as catenation. In contrast to the chains and rings favored by carbon, boron arguably adopts a cluster motif that is reflected in the various forms of the pure element and in the huge area of polyhedral borane…

  2. Boron Clusters Come of Age

    ERIC Educational Resources Information Center

    Grimes, Russell N.

    2004-01-01

    Boron is the only element other than carbon that can build molecules of unlimited size by covalently boding to itself, a property known as catenation. In contrast to the chains and rings favored by carbon, boron arguably adopts a cluster motif that is reflected in the various forms of the pure element and in the huge area of polyhedral borane…

  3. Boronate esters: Synthesis, characterization and molecular base receptor analysis

    NASA Astrophysics Data System (ADS)

    Gómez-Jaimes, Gelen; Barba, Victor

    2014-10-01

    The synthesis of three boronate esters obtained by reacting 4-fluorophenylboronic (1), 4-iodophenylboronic (2) and 3,4-chlorophenylboronic (3) acids with 2,4,5-trihidroxybenzaldehyde is reported. The structural characterization was determined by spectroscopic and spectrometric techniques. The boron atom was evaluated to acts as Lewis acid center in the reaction with pyridine (Py), triethylamine (TEA) and fluoride anion (F-). The titration method was followed by UV-Vis and 11B NMR spectroscopy; results indicate the good interaction with the fluoride ion but poor coordination towards pyridine in solution.

  4. Boron Abundances in A and B-type Stars

    NASA Technical Reports Server (NTRS)

    Lambert, David L.

    1997-01-01

    Boron abundances in A- and B-type stars may be a successful way to track evolutionary effects in these hot stars. The light elements - Li, Be, and B - are tracers of exposure to temperatures more moderate than those in which the H-burning CN-cycle operates. Thus, any exposure of surface stellar layers to deeper layers will affect these light element abundances. Li and Be are used in this role in investigations of evolutionary processes in cool stars, but are not observable in hotter stars. An investigation of boron, however, is possible through the B II 1362 A resonance line. We have gathered high resolution spectra from the IUE database of A- and B-type stars near 10 solar mass for which nitrogen abundances have been determined. The B II 1362 A line is blended throughout; the temperature range of this program, requiring spectrum syntheses to recover the boron abundances. For no star could we synthesize the 1362 A region using the meteoritic/solar boron abundance of log e (B) = 2.88; a lower boron abundance was necessary which may reflect evolutionary effects (e.g., mass loss or mixing near the main-sequence), the natal composition of the star forming regions, or a systematic error in the analyses (e.g., non-LTE effects). Regardless of the initial boron abundance, and despite the possibility of non-LTE effects, it seems clear that boron is severely depleted in some stars. It may be that the nitrogen and boron abundances are anticorrelated, as would be expected from mixing between the H-burning and outer stellar layers. If, as we suspect, a residue of boron is present in the A-type supergiants, we may exclude a scenario in which mixing occurs continuously between the surface and the deep layers operating the CN-cycle. Further exploitation of the B II 1362 A line as an indicator of the evolutionary status of A- and B-type stars will require a larger stellar sample to be observed with higher signal-to-noise as attainable with the Hubble Space Telescope.

  5. Applications and perspectives of boron-enriched nanocomposites in cancer therapy.

    PubMed

    Yinghuai, Zhu; Hosmane, Narayan S

    2013-04-01

    Recently, boron compounds have attracted increasing attention both in academic laboratories and in the pharmaceutical industry. Boron, in particular the (10)B isotope, has the unique capability of absorbing a slow neutron to initiate a nuclear reaction with release of energetic particles such as α- and Li-particles, which is not observed in its carbon analogues. The nuclear capture reaction concept has been adopted in radiation therapy and used in boron neutron capture therapy (BNCT). BNCT is a potentially promising treatment for malignant brain tumors as well as other cancers, despite the limitation of a scarcity of neutron sources. There is the need in advanced research centers to construct high boron-containing composites as BNCT agents and develop more efficient drug carriers. This review discusses recent works on the development of boron-based therapeutic nanomaterials as BNCT agents.

  6. Functionalized boron nitride nanotubes

    DOEpatents

    Sainsbury, Toby; Ikuno, Takashi; Zettl, Alexander K

    2014-04-22

    A plasma treatment has been used to modify the surface of BNNTs. In one example, the surface of the BNNT has been modified using ammonia plasma to include amine functional groups. Amine functionalization allows BNNTs to be soluble in chloroform, which had not been possible previously. Further functionalization of amine-functionalized BNNTs with thiol-terminated organic molecules has also been demonstrated. Gold nanoparticles have been self-assembled at the surface of both amine- and thiol-functionalized boron nitride Nanotubes (BNNTs) in solution. This approach constitutes a basis for the preparation of highly functionalized BNNTs and for their utilization as nanoscale templates for assembly and integration with other nanoscale materials.

  7. Boron isotope geochemistry of the oceanic crust from DSDP/ODP Hole 504B

    SciTech Connect

    Ishikawa, Tsuyoshi; Nakamura, Eizo )

    1992-04-01

    Boron contents and boron isotopic compositions were determined for the uppermost 1.3 km section of typical 6.2 Ma oceanic crust from DSDP/ODP Hole 504B, Costa Rica Rift, Galapagos Spreading Center. Both the boron content and the {delta}{sup 11}B value in the oceanic crust are controlled by two types of alteration: (1) low-temperature alteration (0 to 60C; Zones 1 and 2) and (2) high-temperature hydrothermal alteration (200 to 400C; Zones 3 and 4). Basalts subjected to the low-temperature alteration are characterized by their relatively high boron contents (0.69 to 19.3 ppm) and high {delta}{sup 11}B values (+2.2 to +10.6{per thousand}), indicating uptake of boron into secondary phases in equilibrium with seawater or evolved seawater. Hydrothermally altered basalts contain less abundant boron (0.17 to 0.52 ppm) and relatively constant {delta}{sup 11}B values ({minus}0.1 to +1.0{per thousand}). Although basalts from the upper part of these hydrothermal zones (< 1,300 mbsf) show equilibrated boron content and {delta}{sup 11}B value with aqueous fluid, effective leaching of boron from basalt is predominant in the lower part (> 1,300 mbsf). Original boron content and {delta}{sup 11}B value of the Hole 504B MORB were 0.35 ppm and +0.2{per thousand}, respectively. The present data provide fundamental information in understanding of the distribution of boron and boron isotopes in the oceanic crust.

  8. METHOD OF COATING SURFACES WITH BORON

    DOEpatents

    Martin, G.R.

    1949-10-11

    A method of forming a thin coating of boron on metallic, glass, or other surfaces is described. The method comprises heating the article to be coated to a temperature of about 550 d C in an evacuated chamber and passing trimethyl boron, triethyl boron, or tripropyl boron in the vapor phase and under reduced pressure into contact with the heated surface causing boron to be deposited in a thin film.

  9. Boron implanted strontium titanate

    NASA Astrophysics Data System (ADS)

    Cooper, C. J. M.

    Single crystals of strontium titanate implanted with boron were found to have highly conductive surface layers. The effects of varying dose from 10 to the 16th power to 10 to the 17th power ions/sq cm, implantation voltage from 50 to 175 keV and annealing conditions on the room temperature surface resistance and Hall mobility are presented. Variation of the implantation voltage did not have a major effect on the sheet resistances obtained by boron implantation of strontium titanate, while dose and annealing conditions have major effects. Doses of 5 x 10 to the 16th power ions/sq cm required annealing on the order of one hour at 500 K for maximum reduction of the room temperature resistance in the implanted layer. Samples implanted with a dose of 1 x 10 to the 17th power ions/sq cm required slightly higher temperatures (approximately 575 K) to obtain a minimum resistance at room temperature. Long term (several weeks) room temperature annealing was found to occur in high dose samples. After one to two months at room temperature followed by an anneal to 575 K, the surface resistances were found to be lower than those produced by the annealing of a freshly implanted sample to 575 K.

  10. Mathematical modeling and experimental validation of the spatial distribution of boron in the root of Arabidopsis thaliana identify high boron accumulation in the tip and predict a distinct root tip uptake function.

    PubMed

    Shimotohno, Akie; Sotta, Naoyuki; Sato, Takafumi; De Ruvo, Micol; Marée, Athanasius F M; Grieneisen, Verônica A; Fujiwara, Toru

    2015-04-01

    Boron, an essential micronutrient, is transported in roots of Arabidopsis thaliana mainly by two different types of transporters, BORs and NIPs (nodulin26-like intrinsic proteins). Both are plasma membrane localized, but have distinct transport properties and patterns of cell type-specific accumulation with different polar localizations, which are likely to affect boron distribution. Here, we used mathematical modeling and an experimental determination to address boron distributions in the root. A computational model of the root is created at the cellular level, describing the boron transporters as observed experimentally. Boron is allowed to diffuse into roots, in cells and cell walls, and to be transported over plasma membranes, reflecting the properties of the different transporters. The model predicts that a region around the quiescent center has a higher concentration of soluble boron than other portions. To evaluate this prediction experimentally, we determined the boron distribution in roots using laser ablation-inductivity coupled plasma-mass spectrometry. The analysis indicated that the boron concentration is highest near the tip and is lower in the more proximal region of the meristem zone, similar to the pattern of soluble boron distribution predicted by the model. Our model also predicts that upward boron flux does not continuously increase from the root tip toward the mature region, indicating that boron taken up in the root tip is not efficiently transported to shoots. This suggests that root tip-absorbed boron is probably used for local root growth, and that instead it is the more mature root regions which have a greater role in transporting boron toward the shoots. © The Author 2015. Published by Oxford University Press on behalf of Japanese Society of Plant Physiologists.

  11. Mathematical Modeling and Experimental Validation of the Spatial Distribution of Boron in the Root of Arabidopsis thaliana Identify High Boron Accumulation in the Tip and Predict a Distinct Root Tip Uptake Function

    PubMed Central

    Shimotohno, Akie; Sotta, Naoyuki; Sato, Takafumi; De Ruvo, Micol; Marée, Athanasius F.M.; Grieneisen, Verônica A.; Fujiwara, Toru

    2015-01-01

    Boron, an essential micronutrient, is transported in roots of Arabidopsis thaliana mainly by two different types of transporters, BORs and NIPs (nodulin26-like intrinsic proteins). Both are plasma membrane localized, but have distinct transport properties and patterns of cell type-specific accumulation with different polar localizations, which are likely to affect boron distribution. Here, we used mathematical modeling and an experimental determination to address boron distributions in the root. A computational model of the root is created at the cellular level, describing the boron transporters as observed experimentally. Boron is allowed to diffuse into roots, in cells and cell walls, and to be transported over plasma membranes, reflecting the properties of the different transporters. The model predicts that a region around the quiescent center has a higher concentration of soluble boron than other portions. To evaluate this prediction experimentally, we determined the boron distribution in roots using laser ablation-inductivity coupled plasma-mass spectrometry. The analysis indicated that the boron concentration is highest near the tip and is lower in the more proximal region of the meristem zone, similar to the pattern of soluble boron distribution predicted by the model. Our model also predicts that upward boron flux does not continuously increase from the root tip toward the mature region, indicating that boron taken up in the root tip is not efficiently transported to shoots. This suggests that root tip-absorbed boron is probably used for local root growth, and that instead it is the more mature root regions which have a greater role in transporting boron toward the shoots. PMID:25670713

  12. Comparison between proton boron fusion therapy (PBFT) and boron neutron capture therapy (BNCT): a Monte Carlo study

    PubMed Central

    Barraclough, Brendan; Lee, Heui Chang; Suh, Tae Suk; Lu, Bo

    2017-01-01

    The aim of this study is to compare between proton boron fusion therapy (PBFT) and boron neutron capture therapy (BNCT) and to analyze dose escalation using a Monte Carlo simulation. We simulated a proton beam passing through the water with a boron uptake region (BUR) in MCNPX. To estimate the interaction between neutrons/protons and borons by the alpha particle, the simulation yielded with a variation of the center of the BUR location and proton energies. The variation and influence about the alpha particle were observed from the percent depth dose (PDD) and cross-plane dose profile of both the neutron and proton beams. The peak value of the maximum dose level when the boron particle was accurately labeled at the region was 192.4% among the energies. In all, we confirmed that prompt gamma rays of 478 keV and 719 keV were generated by the nuclear reactions in PBFT and BNCT, respectively. We validated the dramatic effectiveness of the alpha particle, especially in PBFT. The utility of PBFT was verified using the simulation and it has a potential for application in radiotherapy. PMID:28427153

  13. Entropy of gaseous boron monobromide

    NASA Astrophysics Data System (ADS)

    Wang, Jian-Feng; Peng, Xiao-Long; Zhang, Lie-Hui; Wang, Chao-Wen; Jia, Chun-Sheng

    2017-10-01

    We present an explicit representation of molar entropy for gaseous boron monobromide in terms of experimental values of only three molecular constants. Fortunately, through comparison of theoretically calculated results and experimental data, we find that the molar entropy of gaseous boron monobromide can be well predicted by employing the improved Manning-Rosen oscillator to describe the internal vibration of boron monobromide molecule. The present approach provides also opportunities for theoretical predictions of molar entropy for other gases with no use of large amounts of experimental spectroscopy data.

  14. A new and effective approach to boron removal by using novel boron-specific fungi isolated from boron mining wastewater.

    PubMed

    Taştan, Burcu Ertit; Çakir, Dilara Nur; Dönmez, Gönül

    2016-01-01

    Boron-resistant fungi were isolated from the wastewater of a boron mine in Turkey. Boron removal efficiencies of Penicillium crustosum and Rhodotorula mucilaginosa were detected in different media compositions. Minimal Salt Medium (MSM) and two different waste media containing molasses (WM-1) or whey + molasses (WM-2) were tested to make this process cost effective when scaled up. Both isolates achieved high boron removal yields at the highest boron concentrations tested in MSM and WM-1. The maximum boron removal yield by P. crustosum was 45.68% at 33.95 mg l(-1) initial boron concentration in MSM, and was 38.97% at 42.76 mg l(-1) boron for R. mucilaginosa, which seemed to offer an economically feasible method of removing boron from the effluents.

  15. Boron and Boron-Rich Solids at High Pressures

    NASA Astrophysics Data System (ADS)

    Polian, Alain; Ovsyannikov, Sergey V.; Gauthier, Michel; Munsch, Pascal; Chervin, Jean-Claude; Lemarchand, Gilles

    Boron seems to be the indispensable ingredient to obtain materials with high hardness. It exists under many different structures. The simplest member of the family, α-boron is based on an arrangement of slightly distorted B12 icosahedra in a rhombohedral unit cell. B12X2 compounds, with X = O, P, As, are based on the α-boron structure, with the X atoms in the inter-icosahedra space. The stability of α-boron has been studied by x-ray diffraction and Raman scattering up to 100 GPa, showing no sign of phase transformation, and by Raman scattering for B12P2 and B12As2 with the observation of phase transformation in the 80 GPa range.

  16. 1. LOOKING SOUTH TO THE CONTROL CENTER FROM THE EAST ...

    Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

    1. LOOKING SOUTH TO THE CONTROL CENTER FROM THE EAST SIDE OF TEST STAND 1-A. - Edwards Air Force Base, Air Force Rocket Propulsion Laboratory, Control Center, Test Area 1-115, near Altair & Saturn Boulevards, Boron, Kern County, CA

  17. Copper passivation of boron in silicon and boron reactivation kinetics

    NASA Astrophysics Data System (ADS)

    Aboelfotoh, M. O.; Svensson, B. G.

    1991-12-01

    Copper passivation of substitutional boron in single-crystal silicon and the reactivation kinetics of the passivated boron have been investigated with the use of Schottky-barrier structures formed by the deposition of copper on boron-doped silicon at room temperature. It is found that passivation of the boron acceptors occurs after copper deposition. The results suggest that the fast-diffusing interstitial Cu+ passivates the boron acceptors by forming neutral B-Cu complexes, rather than by direct compensation. No compensating donor levels associated with Cu are observed. These results are consistent with recent theoretical predictions. The reactivation kinetics are first order with an activation energy of 0.89 eV, and the annealing process is found to be controlled by long-range diffusion, rather than by pure dissociation. The thermal dissociation of the B-Cu complexes is driven by the formation of the copper silicide η'-Cu3Si, indicating the importance of silicide formation in the reactivation of the boron acceptors.

  18. Nothing Boring About Boron

    PubMed Central

    Pizzorno, Lara

    2015-01-01

    The trace mineral boron is a micronutrient with diverse and vitally important roles in metabolism that render it necessary for plant, animal, and human health, and as recent research suggests, possibly for the evolution of life on Earth. As the current article shows, boron has been proven to be an important trace mineral because it (1) is essential for the growth and maintenance of bone; (2) greatly improves wound healing; (3) beneficially impacts the body’s use of estrogen, testosterone, and vitamin D; (4) boosts magnesium absorption; (5) reduces levels of inflammatory biomarkers, such as high-sensitivity C-reactive protein (hs-CRP) and tumor necrosis factor α (TNF-α); (6) raises levels of antioxidant enzymes, such as superoxide dismutase (SOD), catalase, and glutathione peroxidase; (7) protects against pesticide-induced oxidative stress and heavy-metal toxicity; (8) improves the brains electrical activity, cognitive performance, and short-term memory for elders; (9) influences the formation and activity of key biomolecules, such as S-adenosyl methionine (SAM-e) and nicotinamide adenine dinucleotide (NAD+); (10) has demonstrated preventive and therapeutic effects in a number of cancers, such as prostate, cervical, and lung cancers, and multiple and non-Hodgkin’s lymphoma; and (11) may help ameliorate the adverse effects of traditional chemotherapeutic agents. In none of the numerous studies conducted to date, however, do boron’s beneficial effects appear at intakes > 3 mg/d. No estimated average requirements (EARs) or dietary reference intakes (DRIs) have been set for boron—only an upper intake level (UL) of 20 mg/d for individuals aged ≥ 18 y. The absence of studies showing harm in conjunction with the substantial number of articles showing benefits support the consideration of boron supplementation of 3 mg/d for any individual who is consuming a diet lacking in fruits and vegetables or who is at risk for or has osteopenia; osteoporosis

  19. Tomographic image of prompt gamma ray from boron neutron capture therapy: A Monte Carlo simulation study

    SciTech Connect

    Yoon, Do-Kun; Jung, Joo-Young; Suk Suh, Tae; Jo Hong, Key

    2014-02-24

    Purpose of paper is to confirm the feasibility of acquisition of three dimensional single photon emission computed tomography image from boron neutron capture therapy using Monte Carlo simulation. Prompt gamma ray (478 keV) was used to reconstruct image with ordered subsets expectation maximization method. From analysis of receiver operating characteristic curve, area under curve values of three boron regions were 0.738, 0.623, and 0.817. The differences between length of centers of two boron regions and distance of maximum count points were 0.3 cm, 1.6 cm, and 1.4 cm.

  20. Interaction of copper impurity with radiation defects in silicon doped with boron

    SciTech Connect

    Yarykin, N. A.; Weber, J.

    2010-08-15

    The spectrum of deep levels formed in boron-doped Czochralski-grown silicon single crystals as a result of interaction of radiation defects with copper impurity is studied. It is shown that, irrespective of the order of introduction of defects (both in the case of low-temperature copper diffusion into crystals preliminarily irradiated with electrons and in the case of irradiation of the samples contaminated with copper), the same set of deep levels appears. In addition to conventional radiation defects, three types of levels have been detected in the band gap of copper-containing crystals. These levels include the level E{sub v} + 0.49 eV (already mentioned in available publications), the level E{sub v} + 0.51 eV (previously not related to copper), and a level close to the donor level of a vacancy. Based on the analysis of concentration profiles, the interstitial carbonoxygen pair is excluded from possible precursors of the copper-containing center with level E{sub v} + 0.49 eV.

  1. Effect of nitrogen on the growth of boron doped single crystal diamond

    SciTech Connect

    Karna, Sunil; Vohra, Yogesh

    2013-11-18

    Boron-doped single crystal diamond films were grown homoepitaxially on synthetic (100) Type Ib diamond substrates using microwave plasma assisted chemical vapor deposition. A modification in surface morphology of the film with increasing boron concentration in the plasma has been observed using atomic force microscopy. Use of nitrogen during boron doping has been found to improve the surface morphology and the growth rate of films but it lowers the electrical conductivity of the film. The Raman spectra indicated a zone center optical phonon mode along with a few additional bands at the lower wavenumber regions. The change in the peak profile of the zone center optical phonon mode and its downshift were observed with the increasing boron content in the film. Furthermore, sharpening and upshift of Raman line was observed in the film that was grown in presence of nitrogen along with diborane in process gas.

  2. Effect of nitrogen on the growth of boron doped single crystal diamond

    DOE PAGES

    Karna, Sunil; Vohra, Yogesh

    2013-11-18

    Boron-doped single crystal diamond films were grown homoepitaxially on synthetic (100) Type Ib diamond substrates using microwave plasma assisted chemical vapor deposition. A modification in surface morphology of the film with increasing boron concentration in the plasma has been observed using atomic force microscopy. Use of nitrogen during boron doping has been found to improve the surface morphology and the growth rate of films but it lowers the electrical conductivity of the film. The Raman spectra indicated a zone center optical phonon mode along with a few additional bands at the lower wavenumber regions. The change in the peak profilemore » of the zone center optical phonon mode and its downshift were observed with the increasing boron content in the film. Furthermore, sharpening and upshift of Raman line was observed in the film that was grown in presence of nitrogen along with diborane in process gas.« less

  3. Reducing Boron Toxicity by Microbial Sequestration

    SciTech Connect

    Hazen, T.; Phelps, T.J.

    2002-01-01

    While electricity is a clean source of energy, methods of electricity-production, such as the use of coal-fired power plants, often result in significant environmental damage. Coal-fired electrical power plants produce air pollution, while contaminating ground water and soils by build-up of boron, which enters surrounding areas through leachate. Increasingly high levels of boron in soils eventually overcome boron tolerance levels in plants and trees, resulting in toxicity. Formation of insoluble boron precipitates, mediated by mineral-precipitating bacteria, may sequester boron into more stable forms that are less available and toxic to vegetation. Results have provided evidence of microbially-facilitated sequestration of boron into insoluble mineral precipitates. Analyses of water samples taken from ponds with high boron concentrations showed that algae present contained 3-5 times more boron than contained in the water in the samples. Boron sequestration may also be facilitated by the incorporation of boron within algal cells. Experiments examining boron sequestration by algae are in progress. In bacterial experiments with added ferric citrate, the reduction of iron by the bacteria resulted in an ironcarbonate precipitate containing boron. An apparent color change showing the reduction of amorphous iron, as well as the precipitation of boron with iron, was more favorable at higher pH. Analysis of precipitates by X-ray diffraction, scanning electron microscopy, and inductively coupled plasma mass spectroscopy revealed mineralogical composition and biologicallymediated accumulation of boron precipitates in test-tube experiments.

  4. Nano boron nitride flatland.

    PubMed

    Pakdel, Amir; Bando, Yoshio; Golberg, Dmitri

    2014-02-07

    Recent years have witnessed many breakthroughs in research on two-dimensional (2D) nanomaterials, among which is hexagonal boron nitride (h-BN), a layered material with a regular network of BN hexagons. This review provides an insight into the marvellous nano BN flatland, beginning with a concise introduction to BN and its low-dimensional nanostructures, followed by an overview of the past and current state of research on 2D BN nanostructures. A comprehensive review of the structural characteristics and synthetic routes of BN monolayers, multilayers, nanomeshes, nanowaves, nanoflakes, nanosheets and nanoribbons is presented. In addition, electronic, optical, thermal, mechanical, magnetic, piezoelectric, catalytic, ecological, biological and wetting properties, applications and research perspectives for these novel 2D nanomaterials are discussed.

  5. Boron diffusion in silicon devices

    DOEpatents

    Rohatgi, Ajeet; Kim, Dong Seop; Nakayashiki, Kenta; Rounsaville, Brian

    2010-09-07

    Disclosed are various embodiments that include a process, an arrangement, and an apparatus for boron diffusion in a wafer. In one representative embodiment, a process is provided in which a boric oxide solution is applied to a surface of the wafer. Thereafter, the wafer is subjected to a fast heat ramp-up associated with a first heating cycle that results in a release of an amount of boron for diffusion into the wafer.

  6. Neutron detectors comprising boron powder

    DOEpatents

    Wang, Zhehui; Morris, Christopher; Bacon, Jeffrey Darnell; Makela, Mark F; Spaulding, Randy Jay

    2013-05-21

    High-efficiency neutron detector substrate assemblies comprising a first conductive substrate, wherein a first side of the substrate is in direct contact with a first layer of a powder material comprising .sup.10boron, .sup.10boron carbide or combinations thereof, and wherein a conductive material is in proximity to the first layer of powder material; and processes of making said neutron detector substrate assemblies.

  7. Characterization of electrodeposited elemental boron

    SciTech Connect

    Jain, Ashish; Anthonysamy, S. Ananthasivan, K.; Ranganathan, R.; Mittal, Vinit; Narasimhan, S.V.; Vasudeva Rao, P.R.

    2008-07-15

    Elemental boron was produced through electrowinning from potassium fluoroborate dissolved in a mixture of molten potassium fluoride and potassium chloride. The characteristics of the electrodeposited boron (raw boron) as well as the water and acid-leached product (processed boron) were studied. The chemical purity, specific surface area, size distribution of particles and X-ray crystallite size of the boron powders were investigated. The morphology of the deposits was examined using scanning electron microscopy (SEM). The chemical state of the matrix, as well as the impurity phases present in them, was established using X-ray photoelectron spectroscopy (XPS). In order to interpret and understand the results obtained, a thermodynamic analysis was carried out. The gas-phase corrosion in the head space as well as the chemistry behind the leaching process were interpreted using this analysis. The ease of oxidation of these powders in air was investigated using differential thermal analysis (DTA) coupled with thermogravimetry (TG). From the results obtained in this study it was established that elemental boron powder with a purity of 95-99% could be produced using a high temperature molten salt electrowinning process. The major impurities were found to be oxygen, carbon, iron and nickel.

  8. Geologic mapping on the deep seafloor: Reconstructing lava flow emplacement and eruptive history at the Galápagos Spreading Center

    NASA Astrophysics Data System (ADS)

    McClinton, J. T.; White, S.; Colman, A.; Sinton, J. M.; Bowles, J. A.

    2012-12-01

    The deep seafloor imposes significant difficulties on data collection that require the integration of multiple data sets and the implementation of unconventional geologic mapping techniques. We combine visual mapping of geological contacts by submersible with lava flow morphology maps and relative and absolute age constraints to create a spatiotemporal framework for examining submarine lava flow emplacement at the intermediate-spreading, hotspot-affected Galápagos Spreading Center (GSC). We mapped 18 lava flow fields, interpreted to be separate eruptive episodes, within two study areas at the GSC using visual observations of superposition, surface preservation and sediment cover from submersible and towed camera surveys, augmented by high-resolution sonar surveys and sample petrology [Colman et al., Effects of variable magma supply on mid-ocean ridge eruptions: Constraints from mapped lava flow fields along the Galápagos Spreading Center; 2012 G3]. We also mapped the lava flow morphology within the majority of these eruptive units using an automated, machine-learning classification method [McClinton et al., Neuro-fuzzy classification of submarine lava flow morphology; 2012 PE&RS]. The method combines detailed geometric, acoustic, and textural attributes derived from high-resolution sonar data with visual observations and a machine-learning algorithm to classify submarine lava flow morphology as pillows, lobates, or sheets. The resulting lava morphology maps are a valuable tool for interpreting patterns in the emplacement of submarine lava flows at a mid-ocean ridge (MOR). Within our study area at 92°W, where the GSC has a relatively high magma supply, high effusion rate sheet and lobate lavas are more abundant in the oldest mapped eruptive units, while the most recent eruptions mostly consist of low effusion rate pillow lavas. The older eruptions (roughly 400yrs BP by paleomagnetic intensity) extend up to 1km off axis via prominent channels and tubes, while the

  9. Solid state, thermal synthesis of site-specific protein-boron cluster conjugates and their physicochemical and biochemical properties.

    PubMed

    Goszczyński, Tomasz M; Kowalski, Konrad; Leśnikowski, Zbigniew J; Boratyński, Janusz

    2015-02-01

    Boron clusters represent a vast family of boron-rich compounds with extraordinary properties that provide the opportunity of exploitation in different areas of chemistry and biology. In addition, boron clusters are clinically used in boron neutron capture therapy (BNCT) of tumors. In this paper, a novel, in solid state (solvent free), thermal method for protein modification with boron clusters has been proposed. The method is based on a cyclic ether ring opening in oxonium adduct of cyclic ether and a boron cluster with nucleophilic centers of the protein. Lysozyme was used as the model protein, and the physicochemical and biological properties of the obtained conjugates were characterized. The main residues of modification were identified as arginine-128 and threonine-51. No significant changes in the secondary or tertiary structures of the protein after tethering of the boron cluster were found using mass spectrometry and circular dichroism measurements. However, some changes in the intermolecular interactions and hydrodynamic and catalytic properties were observed. To the best of our knowledge, we have described the first example of an application of cyclic ether ring opening in the oxonium adducts of a boron cluster for protein modification. In addition, a distinctive feature of the proposed approach is performing the reaction in solid state and at elevated temperature. The proposed methodology provides a new route to protein modification with boron clusters and extends the range of innovative molecules available for biological and medical testing. Copyright © 2014 Elsevier B.V. All rights reserved.

  10. Influence of Boron Substitution on the Crystal and Electronic Properties of LiCrO2 Battery Cathode

    NASA Astrophysics Data System (ADS)

    Ozkendir, Osman Murat; Ates, Sule; Celik, Gultekin; Klysubun, Wantana

    2017-06-01

    Boron-substituted LiCrO2 battery cathode material samples were investigated by X-ray-based techniques to probe the influence of boron on their crystal and electronic structure properties. Studies were carried on a series of Li-ion battery cathode materials with the general formula LiCr1- x B x O2. Up to 10 pct boron substitution amounts, light boron atoms were determined to sit in Cr coordinations. However, for more substitutions (>10 pct), higher electronegativity of boron was determined to govern the crystal structure by obtaining isolated boron-centered domains and built Li2BO4 structures. Electronic structure studies and further crystal structure analysis were carried by X-ray absorption fine structure technique. In the studied samples, increasing boron concentration in the samples ( i.e., >10 pct substitution) were determined to cause a decrease in oxygen bond distances as a result of boron sitting in some chromium locations. As a result of this study, 10 pct boron substitution was determined as a threshold to protect the LiCrO2 crystal structure.

  11. Hexagonal boron nitride is an indirect bandgap semiconductor

    NASA Astrophysics Data System (ADS)

    Cassabois, G.; Valvin, P.; Gil, B.

    2016-04-01

    Hexagonal boron nitride is a wide bandgap semiconductor with very high thermal and chemical stability that is used in devices operating under extreme conditions. The growth of high-purity crystals has recently revealed the potential of this material for deep ultraviolet emission, with intense emission around 215 nm. In the last few years, hexagonal boron nitride has been attracting even more attention with the emergence of two-dimensional atomic crystals and van der Waals heterostructures, initiated with the discovery of graphene. Despite this growing interest and a seemingly simple structure, the basic questions of the bandgap nature and value are still controversial. Here, we resolve this long-debated issue by demonstrating evidence for an indirect bandgap at 5.955 eV by means of optical spectroscopy. We demonstrate the existence of phonon-assisted optical transitions and we measure an exciton binding energy of about 130 meV by two-photon spectroscopy.

  12. Boronated porhyrins and methods for their use

    DOEpatents

    Miura, Michiko; Shelnutt, John A.; Slatkin, Daniel N.

    1999-03-02

    The present invention covers boronated porphyrins containing multiple carborane cages which selectively accumulate in neoplastic tissue within the irradiation volume and thus can be used in cancer therapies such as boron neutron capture therapy and photodynamic therapy.

  13. Boronated porhyrins and methods for their use

    DOEpatents

    Miura, M.; Shelnutt, J.A.; Slatkin, D.N.

    1999-03-02

    The present invention covers boronated porphyrins containing multiple carborane cages which selectively accumulate in neoplastic tissue within the irradiation volume and thus can be used in cancer therapies such as boron neutron capture therapy and photodynamic therapy. 3 figs.

  14. Synthesis and Utility of Dihydropyridine Boronic Esters**

    PubMed Central

    Panda, Santanu; Coffin, Aaron; Nguyen, Q. Nhu; Tantillo, Dean; Ready, Joseph M.

    2016-01-01

    When activated by an acylating agent, pyridine boronic esters react with organometallic reagents to form a dihydropyridine boronic ester. This intermediate allows access to a number of valuable substituted pyridine, dihydropyridine and piperidine products. PMID:26694785

  15. Synthesis and Utility of Dihydropyridine Boronic Esters.

    PubMed

    Panda, Santanu; Coffin, Aaron; Nguyen, Q Nhu; Tantillo, Dean J; Ready, Joseph M

    2016-02-05

    When activated by an acylating agent, pyridine boronic esters react with organometallic reagents to form a dihydropyridine boronic ester. This intermediate allows access to a number of valuable substituted pyridine, dihydropyridine, and piperidine products.

  16. Processing of boron carbide

    NASA Astrophysics Data System (ADS)

    Cho, Namtae

    The processing of boron carbide powder including sintering optimization, green body optimization and sintering behavior of nano-sized boron carbide was investigated for the development of complex shaped body armor. Pressureless sintered B4C relative densities as high as 96.7% were obtained by optimizing the soak temperature, and holding at that temperature for the minimum time required to reach terminal density. Although the relative densities of pressureless sintered specimens were lower than that of commercially produced hot-pressed B4C, their (Vickers) hardness values were comparable. For 4.45 cm dia. 1.35 cm height disk-shaped specimens, pressureless sintered to at least 93.0% relative density, post-hot isostatic pressing resulted in vast increases in relative densities (e.g. 100.0%) and hardness values significantly greater than that of commercially produced hot-pressed B 4C. The densification behavior of 20-40nm graphite-coated B4C nano-particles was studied using dilatometry, x-ray diffraction and electron microscopy. The higher than expected sintering onset from a nano-scale powder (˜1500°C) was caused by remnant B2O3 not removed by methanol washing, keeping particles separated until volatilization, and the carbon coatings, which imposed particle to particle contact of a substance more refractory than B4C. Solid state sintering (1500-1850°C) was followed by an arrest in contraction attributed to formation of eutectic liquid droplets of size more than 10X the original nano-particles. These droplets, induced to form well below known B4C-graphite eutectic temperatures by the high surface energy of nanoparticles, are interpreted to have quickly solidified to form a vast number of voids in particle packing, which in turn, impeded continued solid state sintering. Starting at 2200°C, a permanent liquid phase formed which facilitated a rapid measured contraction by liquid phase sintering and/or compact slumping.

  17. Analysis of boron carbides' electronic structure

    NASA Technical Reports Server (NTRS)

    Howard, Iris A.; Beckel, Charles L.

    1986-01-01

    The electronic properties of boron-rich icosahedral clusters were studied as a means of understanding the electronic structure of the icosahedral borides such as boron carbide. A lower bound was estimated on bipolaron formation energies in B12 and B11C icosahedra, and the associated distortions. While the magnitude of the distortion associated with bipolaron formation is similar in both cases, the calculated formation energies differ greatly, formation being much more favorable on B11C icosahedra. The stable positions of a divalent atom relative to an icosahedral borane was also investigated, with the result that a stable energy minimum was found when the atom is at the center of the borane, internal to the B12 cage. If incorporation of dopant atoms into B12 cages in icosahedral boride solids is feasible, novel materials might result. In addition, the normal modes of a B12H12 cluster, of the C2B10 cage in para-carborane, and of a B12 icosahedron of reduced (D sub 3d) symmetry, such as is found in the icosahedral borides, were calculated. The nature of these vibrational modes will be important in determining, for instance, the character of the electron-lattice coupling in the borides, and in analyzing the lattice contribution to the thermal conductivity.

  18. PrB7(-) : A Praseodymium-Doped Boron Cluster with a Pr(II) Center Coordinated by a Doubly Aromatic Planar η(7) -B7(3-) Ligand.

    PubMed

    Chen, Teng-Teng; Li, Wan-Lu; Jian, Tian; Chen, Xin; Li, Jun; Wang, Lai-Sheng

    2017-06-06

    The structure and bonding of a Pr-doped boron cluster (PrB7(-) ) are investigated using photoelectron spectroscopy and quantum chemistry. The adiabatic electron detachment energy of PrB7(-) is found to be low [1.47(8) eV]. A large energy gap is observed between the first and second detachment features, indicating a highly stable neutral PrB7 . Global minimum searches and comparison between experiment and theory show that PrB7(-) has a half-sandwich structure with C6v symmetry. Chemical bonding analyses show that PrB7(-) can be viewed as a Pr(II) [η(7) -B7(3-) ] complex with three unpaired electrons, corresponding to a Pr (4f(2) 6s(1) ) open-shell configuration. Upon detachment of the 6s electron, the neutral PrB7 cluster is a highly stable Pr(III) [η(7) -B7(3-) ] complex with Pr in its favorite +3 oxidation state. The B7(3-) ligand is found to be highly stable and doubly aromatic with six delocalized π and six delocalized σ electrons and should exist for a series of lanthanide M(III) [η(7) -B7(3-) ] complexes. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  19. Investigation of structural information for boron-rich solids and aluminates via NMR and NQR studies

    SciTech Connect

    Lee, D.

    1991-01-01

    Along with NMR, Nuclear Quadrupole Resonance (NQR) has become important recently for obtaining structural information from oxide glasses. The NQR studies prove in this thesis that they provide more accurate structural information than the NMR studies have done. This study presents boron and aluminum NMR, and NQR studies for some borate glasses and compounds, icosahedral boron-rich solids, some crystalline aluminosilicates. Various borates were employed to acquire structural information as well as to determine the quadrupole parameters (the quadrupole coupling constant Qcc and the asymmetry parameter {eta}) using NQR under a guidance of NMR or vice versa. By NQR a previously unknown boron site was observed for vitreous Li{sub 2}O{center dot}B{sub 2}O{sub 3}. The NMR and NQR studies were performed on some icosachedral boron-rich solids: {alpha}-rhombohedral boron (B{sub 12}), {beta}-boron (B{sub 105}) and boron carbide (B{sub 12}C{sub 3}). Three different forms of crystalline aluminosilicate (Al{sub 2}SiO{sub 5}) were studied by NQR. The NQR study yielded more accurate values of the quadrupole parameters for {sup 27}Al than the previous NMR single crystal study did.

  20. Methods for boron delivery to mammalian tissue

    DOEpatents

    Hawthorne, M. Frederick; Feaks, Debra A.; Shelly, Kenneth J.

    2003-01-01

    Boron neutron capture therapy can be used to destroy tumors. This treatment modality is enhanced by delivering compounds to the tumor site where the compounds have high concentrations of boron, the boron compounds being encapsulated in the bilayer of a liposome or in the bilayer as well as the internal space of the liposomes. Preferred compounds, include carborane units with multiple boron atoms within the carborane cage structure. Liposomes with increased tumor specificity may also be used.

  1. Methods and compositions for boronizing metallic surfaces

    SciTech Connect

    Reid, D. K.

    1985-11-26

    The present disclosure is directed to methods and compositions for boronizing metal and in particular ferrous surfaces. It has been discovered that if hydrocarbons are processed in metallic equipment which have been previously boronized, that coke formation and deposition which is commonly experienced at high temperatures can be minimized if not totally eliminated. The compositions utilized for this purpose are comprised of boron or boron compounds contained in an organic solvent or carrier together with specific activating materials.

  2. Boron Clusters as Highly Stable Magnesium-Battery Electrolytes**

    PubMed Central

    Carter, Tyler J; Mohtadi, Rana; Arthur, Timothy S; Mizuno, Fuminori; Zhang, Ruigang; Shirai, Soichi; Kampf, Jeff W

    2014-01-01

    Boron clusters are proposed as a new concept for the design of magnesium-battery electrolytes that are magnesium-battery-compatible, highly stable, and noncorrosive. A novel carborane-based electrolyte incorporating an unprecedented magnesium-centered complex anion is reported and shown to perform well as a magnesium-battery electrolyte. This finding opens a new approach towards the design of electrolytes whose likelihood of meeting the challenging design targets for magnesium-battery electrolytes is very high. PMID:24519845

  3. Diffusion of boron in alloys

    SciTech Connect

    Wang, W.; Zhang, S; He, X.

    1995-04-01

    By means of particle tracking autoradiography (PTA), the diffusion coefficients of boron between 900 and 1,200 C were measured in 04MnNbB steel, 25MnTiB steel, Ni-B, Fe-30%Ni-B and Fe-3%Si-B alloys, and the frequency factor D{sub 0} and activation energy Q were obtained respectively. The experiment results indicated that there was an obvious difference between the present result and the result obtained by Busby (in 1953). It was found that the boron diffusivity in {gamma}-Fe increased as Ni was added. The diffusivity of boron in Fe-3%Si-B alloy with b.c.c. structure was much slower than one obtained by Busby in {alpha}-Fe (1954), which, however, was much faster than the results obtained in {gamma}-Fe (with f.c.c. structure). Based on the present data of boron diffusion coefficients, the mechanism of segregation of boron to grain boundaries is discussed.

  4. Wettability of boron carbide

    SciTech Connect

    Torvund, T.; Akselsen, O.M.; Ulvensoeen, J.H.; Grong, O.

    1994-12-31

    The wettability of boron carbide has been examined by means of the sessile drop method, using the following candidate alloys: (96wt%AG-4wt%Ti), (Ag-26.5wt%Cu-3wt%Ti), (Sn-10wt%Ag-4wt%Ti), Sn(99.95wt%) and Al(99.99wt%). The results show that B{sub 4}C is completely wetted by the Ag-based alloys. Sn-10wt%Ag-4wt%Ti alloy and pure Al partly wet the B{sub 4}C surface, while pure Sn does not wet B{sub 4}C at all. For all the alloys used, except pure Sn, a reaction layer was observed at the interface between the ceramic part and the metal drop. Although the spreading kinetics of the Al-drop was much slower compared with the Ti-containing alloys, the reaction rate was considerably higher in the former case. This suggests that aluminium is an attractive candidate material for brazing of B{sub 4}C. Formation of the low melting B{sub 2}O{sub 3} at the B{sub 4}C surface may cause oxidation of the filler metal during joining, which, in turn, leads to a low bond strength.

  5. Boron intake and prostate cancer risk.

    PubMed

    Gonzalez, Alejandro; Peters, Ulrike; Lampe, Johanna W; White, Emily

    2007-12-01

    Experimental studies suggest that boron may prevent prostate cancer. Only one small epidemiological study has been conducted of boron, which found that those in the highest quartile of boron intake had less than half the risk of prostate cancer versus those in the lowest quartile. We evaluated the association between boron intake and prostate cancer within the VITamins And Lifestyle (VITAL) cohort. A total of 35,244 men completed the baseline supplement and food frequency questionnaire (FFQ) in 2000-2002. A boron database was constructed from published sources to estimate boron intake from the FFQ and from multivitamins. A total of 832 men developed prostate cancer from baseline to 31 December 2004. Dietary boron intake and total boron intake from diet plus multivitamins were not associated with prostate cancer risk. The hazard ratio of prostate cancer for those in the highest versus lowest quartile of total boron intake was 1.17 (95% CI 0.85, 1.61). This risk did not vary by prostate cancer stage or Gleason score. Furthermore, none of the foods high in boron content was associated with a decreased risk of prostate cancer. This cohort study provides no evidence for a preventive role of boron intake on prostate cancer. Since few studies exist on this topic, future research is needed to better elucidate any role that boron may play in the prevention of prostate cancer.

  6. Mineral resource of the month: boron

    USGS Publications Warehouse

    Lyday, Phyllis A.

    2005-01-01

    What does boron have to do with baseball, apple pie, motherhood and Chevrolet? Boron minerals and chemicals are used in the tanning of leather baseballs and gloves; in micro-fertilizer to grow apples and in the glass and enamels of bakewares to cook apple pie; in boron detergents for soaking baby clothes and diapers; and in fiberglass parts for the Chevrolet Corvette.

  7. Graphene on hexagonal boron nitride

    NASA Astrophysics Data System (ADS)

    Yankowitz, Matthew; Xue, Jiamin; LeRoy, B. J.

    2014-07-01

    The field of graphene research has developed rapidly since its first isolation by mechanical exfoliation in 2004. Due to the relativistic Dirac nature of its charge carriers, graphene is both a promising material for next-generation electronic devices and a convenient low-energy testbed for intrinsically high-energy physical phenomena. Both of these research branches require the facile fabrication of clean graphene devices so as not to obscure its intrinsic physical properties. Hexagonal boron nitride has emerged as a promising substrate for graphene devices as it is insulating, atomically flat and provides a clean charge environment for the graphene. Additionally, the interaction between graphene and boron nitride provides a path for the study of new physical phenomena not present in bare graphene devices. This review focuses on recent advancements in the study of graphene on hexagonal boron nitride devices from the perspective of scanning tunneling microscopy with highlights of some important results from electrical transport measurements.

  8. Boron doping a semiconductor particle

    DOEpatents

    Stevens, Gary Don; Reynolds, Jeffrey Scott; Brown, Louanne Kay

    1998-06-09

    A method (10,30) of boron doping a semiconductor particle using boric acid to obtain a p-type doped particle. Either silicon spheres or silicon powder is mixed with a diluted solution of boric acid having a predetermined concentration. The spheres are dried (16), with the boron film then being driven (18) into the sphere. A melt procedure mixes the driven boron uniformly throughout the sphere. In the case of silicon powder, the powder is metered out (38) into piles and melted/fused (40) with an optical furnace. Both processes obtain a p-type doped silicon sphere with desired resistivity. Boric acid is not a restricted chemical, is inexpensive, and does not pose any special shipping, handling, or disposal requirements.

  9. Boron doping a semiconductor particle

    DOEpatents

    Stevens, G.D.; Reynolds, J.S.; Brown, L.K.

    1998-06-09

    A method of boron doping a semiconductor particle using boric acid to obtain a p-type doped particle. Either silicon spheres or silicon powder is mixed with a diluted solution of boric acid having a predetermined concentration. The spheres are dried, with the boron film then being driven into the sphere. A melt procedure mixes the driven boron uniformly throughout the sphere. In the case of silicon powder, the powder is metered out into piles and melted/fused with an optical furnace. Both processes obtain a p-type doped silicon sphere with desired resistivity. Boric acid is not a restricted chemical, is inexpensive, and does not pose any special shipping, handling, or disposal requirements. 2 figs.

  10. Determination of boron in materials by cold neutron prompt gamma-ray activation analysis.

    PubMed

    Paul, Rick L

    2005-01-01

    An instrument for cold neutron prompt gamma-ray activation analysis (PGAA), located at the NIST Center for Neutron Research (NCNR), has proven useful for the measurement of boron in a variety of materials. Neutrons, moderated by passage through liquid hydrogen at 20 K, pass through a (58)Ni coated guide to the PGAA station in the cold neutron guide hall of the NCNR. The thermal equivalent neutron fluence rate at the sample position is 9 x 10(8) cm(-2) s(-1). Prompt gamma rays are measured by a cadmium- and lead-shielded high-purity germanium detector. The instrument has been used to measure boron mass fractions in minerals, in NIST SRM 2175 (Refractory Alloy MP-35-N) for certification of boron, and most recently in semiconductor-grade silicon. The limit of detection for boron in many materials is <10 ng g(-1).

  11. Boron oxygen complexes in Si

    NASA Astrophysics Data System (ADS)

    Sanati, M.; Estreicher, S. K.

    2006-04-01

    The carrier lifetime in boron-doped Czochralski Si is strongly reduced by irradiation (space-based solar cells) or illumination (terrestrial cells). The culprits are believed to be boron-oxygen complexes. We use first-principles theory to predict the structure, electrical activity, and stability of complexes involving substitutional or interstitial B and interstitial O or oxygen dimers. Four complexes with comparable binding energies and thermodynamic gap levels are identified and their local vibrational modes predicted. Replacing B with Ga yields complexes with much smaller binding energies.

  12. Boron Derivatives of 3-Methylpyrazole.

    DTIC Science & Technology

    1984-12-01

    AD-A14$ 988 BORON DERIVRTIYES OF 3 -IETHYLPYRRZOLECU) KENTUCKY UNIV i/i LEXINGTON DEPT OF CHEMISTRY K NIEDENZU ET AL. DEC 84 UK/DC/TR- 5 N8@814-83-K...REPORT DOCUMENTATION PAGE BEFORE CO.!?OVE~r;G FORM UK/DC/TR- 5 I - -_ E. ’and Subtitle) OF 21-P R & PZRIOD COVER=~ BORON DERIVATIVES OF 3 -METHYLPYRAZOLE...pathways for the latter process. In addition, the compounds 4 ,4 ,8,8-tetrabromo- and 4 ,4 ,8 ,8-tetrakis( 3 -methylpyrazole-l-yl)-l, 5 (7)-dimethyl

  13. Transition-Metal Planar Boron Clusters: a New Class of Aromatic Compounds with High Coordination

    NASA Astrophysics Data System (ADS)

    Wang, Lai-Sheng

    2012-06-01

    Photoelectron spectroscopy in combination with computational studies over the past decade has shown that boron clusters possess planar or quasi-planar structures, in contrast to that of bulk boron, which is dominated by three-dimensional cage-like building blocks. All planar or quasi-planar boron clusters are observed to consist of a monocyclic circumference with one or more interior atoms. The propensity for planarity has been found to be due to both σ and π electron delocalization throughout the molecular plane, giving rise to concepts of σ and π double aromaticity. We have found further that the central boron atoms can be substituted by transition metal atoms to form a new class of aromatic compounds, which consist of a central metal atom and a monocyclic boron ring (M B_n). Eight-, nine-, and ten-membered rings of boron have been observed, giving rise to octa-, ennea-, and deca-coordinated aromatic transition metal compounds [1-3]. References: [1] ``Aromatic Metal-Centered Monocyclic Boron Rings: Co B_9^- and Ru B_9^-" (Constantin Romanescu, Timur R. Galeev, Wei-Li Li, A. I. Boldyrev, and L. S. Wang), Angew. Chem. Int. Ed. {50}, 9334-9337 (2011). [2] ``Transition-Metal-Centered Nine-Membered Boron Rings: M B_9 and M B_9^- (M = Rh, Ir)" (Wei-Li Li, Constantin Romanescu, Timur R. Galeev, Zachary Piazza, A. I. Boldyrev, and L. S. Wang), J. Am. Chem. Soc. {134}, 165-168 (2012). [3] ``Observation of the Highest Coordination Number in Planar Species: Decacoordinated Ta B10^- and Nb B_9^- Anions" (Timur R. Galeev, Constantin Romanescu, Wei-Li Li, L. S. Wang, and A. I. Boldyrev), Angew. Chem. Int. Ed. {51}, 2101-2105 (2012).

  14. Analytical boron diffusivity model in silicon for thermal diffusion from boron silicate glass film

    NASA Astrophysics Data System (ADS)

    Kurachi, Ikuo; Yoshioka, Kentaro

    2015-09-01

    An analytical boron diffusivity model in silicon for thermal diffusion from a boron silicate glass (BSG) film has been proposed in terms of enhanced diffusion due to boron-silicon interstitial pair formation. The silicon interstitial generation is considered to be a result of the silicon kick-out mechanism by the diffused boron at the surface. The additional silicon interstitial generation in the bulk silicon is considered to be the dissociation of the diffused pairs. The former one causes the surface boron concentration dependent diffusion. The latter one causes the local boron concentration dependent diffusion. The calculated boron profiles based on the diffusivity model are confirmed to agree with the actual diffusion profiles measured by secondary ion mass spectroscopy (SIMS) for a wide range of the BSG boron concentration. This analytical diffusivity model is a helpful tool for p+ boron diffusion process optimization of n-type solar cell manufacturing.

  15. Thermionic properties of the molybdenum boron system

    SciTech Connect

    Storms, E.K.

    1980-01-01

    The thermionic work function has been measured as a function of composition within the various two phase regions between Mo and MoB/sub 2/. Values at the low boron and high boron phase boundaries for the various compounds were obtained by extrapolation. The following effective work functions were obtained: Mo/sub 2/B (low boron) = 3.08 eV; Mo/sub 2/B (high boron) = 3.63 eV; ..cap alpha..-MoB (low boron) = 3.38 eV; ..cap alpha..-MoB (high boron) = 4.30 eV; ..beta..-MoB (low boron) = 2.83 eV; ..beta..-MoB (high boron) = 3.92; Mo/sub 2/B/sub 3/ (low boron) = 4.65 eV; Mo/sub 2/B/sub 3/ (high boron) = 3.85 eV; and MoB/sub 2/ (low boron) = 3.52 eV. Because the composition range of these compounds is very narrow, the work function is very sensitive to the composition within the single phase regions.

  16. Boron analysis and boron imaging in biological materials for Boron Neutron Capture Therapy (BNCT).

    PubMed

    Wittig, Andrea; Michel, Jean; Moss, Raymond L; Stecher-Rasmussen, Finn; Arlinghaus, Heinrich F; Bendel, Peter; Mauri, Pier Luigi; Altieri, Saverio; Hilger, Ralf; Salvadori, Piero A; Menichetti, Luca; Zamenhof, Robert; Sauerwein, Wolfgang A G

    2008-10-01

    Boron Neutron Capture Therapy (BNCT) is based on the ability of the stable isotope 10B to capture neutrons, which leads to a nuclear reaction producing an alpha- and a 7Li-particle, both having a high biological effectiveness and a very short range in tissue, being limited to approximately one cell diameter. This opens the possibility for a highly selective cancer therapy. BNCT strongly depends on the selective uptake of 10B in tumor cells and on its distribution inside the cells. The chemical properties of boron and the need to discriminate different isotopes make the investigation of the concentration and distribution of 10B a challenging task. The most advanced techniques to measure and image boron are described, both invasive and non-invasive. The most promising approach for further investigation will be the complementary use of the different techniques to obtain the information that is mandatory for the future of this innovative treatment modality.

  17. Boron-enhanced diffusion of boron from ultralow-energy boron implantation

    SciTech Connect

    Agarwal, A.; Eaglesham, D.J.; Gossmann, H.J.; Pelaz, L.; Herner, S.B.; Jacobson, D.C.; Haynes, T.E.; Erokhin, Y.E.

    1998-05-03

    The authors have investigated the diffusion enhancement mechanism of BED (boron enhanced diffusion), wherein the boron diffusivity is enhanced three to four times over the equilibrium diffusivity at 1,050 C in the proximity of a silicon layer containing a high boron concentration. It is shown that BED is associated with the formation of a fine-grain polycrystalline silicon boride phase within an initially amorphous Si layer having a high B concentration. For 0.5 keV B{sup +}, the threshold implantation dose which leads to BED lies between 3 {times} 10{sup 14} and of 1 {times} 10{sup 15}/cm{sup {minus}2}. Formation of the shallowest possible junctions by 0.5 keV B{sup +} requires that the implant dose be kept lower than this threshold.

  18. High fluence boron implantation into polyimide

    NASA Astrophysics Data System (ADS)

    Vacík, J.; Hnatowicz, V.; Červená, J.; Peřina, V.; Popok, V.; Odzhaev, V.; Fink, D.

    1999-01-01

    100 keV B + ions are implanted at high fluences into polyimide and the boron depth distributions are measured by the neutron depth profiling technique. Subsequently the implanted samples are annealed isochronally to determine the diffusional, trapping and detrapping behaviour of the boron atoms. The boron depth profiles of as-implanted samples differ significantly from those predicted by TRIM code. Pronounced inward and outward profile tails point at increased mobility and redistribution of boron atoms after implantation. Thermal annealing to the temperatures below 150°C does not change the total boron content in 1 μm thick surface layer and the boron depth profiles as well. For higher annealing temperatures a continuous desorption and significant redistribution of boron atoms is observed.

  19. Estimating the Proportion of Essential Tremor and Parkinson's Disease Patients Undergoing Deep Brain Stimulation Surgery: Five-Year Data From Columbia University Medical Center (2009-2014).

    PubMed

    Kestenbaum, Meir; Ford, Blair; Louis, Elan D

    2015-12-01

    The aim of this study was to estimate, at a tertiary referral center, the proportion of essential tremor (ET) and Parkinson's disease (PD) patients who underwent DBS surgery. DBS surgery is an important treatment for ET and PD. Surprisingly, there are no published data on the precise proportion of such patients who are referred for this procedure. Using the computerized billing database at the Center for Parkinson's Disease and Other Movement Disorders, Columbia University Medical Center, we searched for patients who received the diagnostic codes 333.1 (tremor) and 332.0 (PD) and who were followed by a doctor at the center during the 5-year period from 2009 to 2014. The number of patients who underwent DBS surgery for these diagnoses during this time period was also determined. Seventy-seven patients with these diagnoses (52 PD, 14 ET, and 11 ET + PD) who were followed at the center underwent DBS surgery during this time period. The proportion of ET patients who underwent DBS surgery was 2.90% (95% confidence interval [CI]: 1.78-4.02), and for PD this was 1.38% (95% CI: 1.04-1.72). The difference was significant (P < 0.001). At a tertiary-referral center, 1 in 34 ET patients and 1 in 72 PD patients underwent DBS surgery. Similar studies from other major centers would be of additional value. These data are likely to have utility when planning health care services for patients with these diagnoses.

  20. Structure of boron nitride nanotubes

    NASA Astrophysics Data System (ADS)

    Buranova, Yu. S.; Kulnitskiy, B. A.; Perezhogin, I. A.; Blank, V. D.

    2015-01-01

    The crystallographic structure of boron nitride nanotubes has been investigated. Various defects that may arise during nanotube synthesis are revealed by electron microscopy. Nanotubes with different numbers of walls and different diameters are modeled by molecular dynamics methods. Structural features of single-wall nanotubes are demonstrated. The causes of certain defects in multiwall nanotubes are indicated.

  1. Boron trifluoride coatings for plastics

    NASA Technical Reports Server (NTRS)

    Kubacki, R. M.

    1978-01-01

    Tough, durable coatings of boron triflouride can be deposited on plastic optical components to protect them from destructive effects of abrasion, scratching, and environment. Coating material can be applied simultaneously with organic polymers, using plasma glow-discharge methods, or it can be used as base material for other coatings to increase adhesion.

  2. Method of separating boron isotopes

    DOEpatents

    Jensen, R.J.; Thorne, J.M.; Cluff, C.L.

    1981-01-23

    A method of boron isotope enrichment involving the isotope preferential photolysis of (2-chloroethenyl)-dichloroborane as the feed material. The photolysis can readily by achieved with CO/sub 2/ laser radiation and using fluences significantly below those required to dissociate BCl/sub 3/.

  3. Method of separating boron isotopes

    DOEpatents

    Jensen, Reed J.; Thorne, James M.; Cluff, Coran L.; Hayes, John K.

    1984-01-01

    A method of boron isotope enrichment involving the isotope preferential photolysis of (2-chloroethenyl)dichloroborane as the feed material. The photolysis can readily be achieved with CO.sub.2 laser radiation and using fluences significantly below those required to dissociate BCl.sub.3.

  4. Structure of boron nitride nanotubes

    SciTech Connect

    Buranova, Yu. S. Kulnitskiy, B. A.; Perezhogin, I. A.; Blank, V. D.

    2015-01-15

    The crystallographic structure of boron nitride nanotubes has been investigated. Various defects that may arise during nanotube synthesis are revealed by electron microscopy. Nanotubes with different numbers of walls and different diameters are modeled by molecular dynamics methods. Structural features of single-wall nanotubes are demonstrated. The causes of certain defects in multiwall nanotubes are indicated.

  5. Method of separating boron isotopes

    SciTech Connect

    Jensen, R.J.; Cluff, C.L.; Hayes, J.K.; Thorne, J.M.

    1984-05-08

    A method of boron isotope enrichment involving the isotope preferential photolysis of (2-chloroethenyl)dichloroborane as the feed material. The photolysis can readily be achieved with CO/sub 2/ laser radiation and using fluences significantly below those required to dissociate BCl/sub 3/.

  6. Chronic boron exposure and human semen parameters.

    PubMed

    Robbins, Wendie A; Xun, Lin; Jia, Juan; Kennedy, Nola; Elashoff, David A; Ping, Liu

    2010-04-01

    Boron found as borates in soil, food, and water has important industrial and medical applications. A panel reviewing NTP reproductive toxicants identified boric acid as high priority for occupational studies to determine safe versus adverse reproductive effects. To address this, we collected boron exposure/dose measures in workplace inhalable dust, dietary food/fluids, blood, semen, and urine from boron workers and two comparison worker groups (n=192) over three months and determined correlations between boron and semen parameters (total sperm count, sperm concentration, motility, morphology, DNA breakage, apoptosis and aneuploidy). Blood boron averaged 499.2 ppb for boron workers, 96.1 and 47.9 ppb for workers from high and low environmental boron areas (p<0.0001). Boron concentrated in seminal fluid. No significant correlations were found between blood or urine boron and adverse semen parameters. Exposures did not reach those causing adverse effects published in animal toxicology work but exceeded those previously published for boron occupational groups.

  7. Boron neutron capture therapy for cancer

    SciTech Connect

    Barth, R.E.; Soloway, A.H. ); Fairchild, R.G. State Univ. of New York, Stony Brook )

    1990-10-01

    Boron neutron capture therapy (BNCT) bring together two components that when kept separate have only minor effects on normal cells. The first component is a stable isotope of boron (boron 10) that can be concentrated in tumor cells. The second is a beam of low-energy neutrons that produces short-range radiation when absorbed, or captured, by the boron. The combination of these two conditions at the site of a tumor releases intense radiation that can destroy malignant tissues. BNCT is based on the nuclear reaction that occurs when boron 10 is irradiated with an absorbs neutrons. The neutrons that it takes up are called thermal, or slow, neutrons. They are of such low energy that they cause little tissue damage as compared with other forms of radiation such as protons, gamma rays and fast neutrons. When an atom of boron 10 captures a neutron, an unstable isotope, boron 11, forms. The boron 11 instantly fissions, yielding lithium 7 nuclei and energetic alpha particles. These heavy particles, which carry 2.79 million electron volts of energy, are a highly lethal form of radiation. If the treatment proceeds as intended, the destructive effects of the capture reaction would occur primarily in those cancer cells that have accumulated boron 10. Normal cells with low concentrations of boron would be spared.

  8. Ferromagnetism and semiconducting of boron nanowires

    PubMed Central

    2012-01-01

    More recently, motivated by extensively technical applications of carbon nanostructures, there is a growing interest in exploring novel non-carbon nanostructures. As the nearest neighbor of carbon in the periodic table, boron has exceptional properties of low volatility and high melting point and is stronger than steel, harder than corundum, and lighter than aluminum. Boron nanostructures thus are expected to have broad applications in various circumstances. In this contribution, we have performed a systematical study of the stability and electronic and magnetic properties of boron nanowires using the spin-polarized density functional calculations. Our calculations have revealed that there are six stable configurations of boron nanowires obtained by growing along different base vectors from the unit cell of the bulk α-rhombohedral boron (α-B) and β-rhombohedral boron (β-B). Well known, the boron bulk is usually metallic without magnetism. However, theoretical results about the magnetic and electronic properties showed that, whether for the α-B-based or the β-B-based nanowires, their magnetism is dependent on the growing direction. When the boron nanowires grow along the base vector [001], they exhibit ferromagnetism and have the magnetic moments of 1.98 and 2.62 μB, respectively, for the α-c [001] and β-c [001] directions. Electronically, when the boron nanowire grows along the α-c [001] direction, it shows semiconducting and has the direct bandgap of 0.19 eV. These results showed that boron nanowires possess the unique direction dependence of the magnetic and semiconducting behaviors, which are distinctly different from that of the bulk boron. Therefore, these theoretical findings would bring boron nanowires to have many promising applications that are novel for the boron bulk. PMID:23244063

  9. Geometric and electronic structures of boron(III)-cored dyes tailored by incorporation of heteroatoms into ligands.

    PubMed

    Sun, Lin; Zhang, Fan; Wang, Xinyang; Qiu, Feng; Xue, Minzhao; Tregnago, Giulia; Cacialli, Franco; Osella, Silvio; Beljonne, David; Feng, Xinliang

    2015-03-01

    Complexation of a boron atom with a series of bidentate heterocyclic ligands successfully gives rise to corresponding BF2-chelated heteroarenes, which could be considered as novel boron(III)-cored dyes. These dye molecules exhibit planar structures and expanded π-conjugated backbones due to the locked conformation with a boron center. The geometric and electronic structures of these BF2 complexes can be tailored by embedding heteroatoms in the unique modes to form positional isomer and isoelectronic structures. The structure-property relationship is further elucidated by studying the photophysical properties, electrochemical behavior and quantum-chemical calculations.

  10. Electronic level scheme in boron- and phosphorus-doped silicon nanowires.

    PubMed

    Sato, Keisuke; Castaldini, Antonio; Fukata, Naoki; Cavallini, Anna

    2012-06-13

    We report the first observation of the electronic level scheme in boron (B)- and phosphorus (P)-doped nanowires (NWs). The NWs' morphology dramatically depends on the doping impurity while a few deep electronic levels appear in both kinds of nanowires, independently of the doping type. We demonstrate that the doping impurities induce the same shallow levels as in bulk silicon. The presence of two donor levels in the lower half-bandgap is also revealed. In both kinds of NWs, B- and P-doped, the donor level (0/+) at E(v) + 0.36 eV of the gold-hydrogen complex is observed. This means that the gold diffusion from the NW tip introduces an electronically active level, which might negatively affects the electrical characteristics of the NWs. In P-doped NWs, we observed a further donor level at 0.26 eV above the valence band due to the phosphorus-vacancy pairs, the E-center, well-known in bulk silicon. These findings seriously question both diffusion modeling of impurities in NWs and the technological aspects arising from this.

  11. Reductive Insertion of Elemental Chalcogens into Boron-Boron Multiple Bonds.

    PubMed

    Braunschweig, Holger; Dellermann, Theresa; Ewing, William C; Kramer, Thomas; Schneider, Christoph; Ullrich, Stefan

    2015-08-24

    The syntheses of sulfur- and selenium-bridged cyclic compounds containing boron stabilized by N-heterocyclic carbenes (NHCs) have been achieved by the reductive insertion of elemental chalcogens into boron-boron multiple bonds. The three pairs of bonding electrons between the boron atoms in the triply bonded diboryne enabled six-electron reduction reactions, resulting in the formation of [2.2.1]-bicyclic systems wherein bridgehead boron atoms are spanned by three chalcogen bridges. A similar reaction using a diborene (boron-boron double bond) resulted in the reductive transfer of both pairs of bonding electrons to three sulfur atoms, yielding a NHC-stabilized trisulfidodiborolane. The demonstration of these six- and four-electron reductions lends support to the presence of three and two pairs of bonding electrons between the boron atoms of the diboryne and diborene, respectively, a fact that may be useful in future discussions on bond order.

  12. Jaguar Procedures for Detonation Behavior of Explosives Containing Boron

    NASA Astrophysics Data System (ADS)

    Stiel, L. I.; Baker, E. L.; Capellos, C.

    2009-12-01

    The Jaguar product library was expanded to include boron and boron containing products by analysis of Available Hugoniot and static volumetric data to obtain constants of the Murnaghan relationships for the components. Experimental melting points were also utilized to obtain the constants of the volumetric relationships for liquid boron and boron oxide. Detonation velocities for HMX—boron mixtures calculated with these relationships using Jaguar are in closer agreement with literature values at high initial densities for inert (unreacted) boron than with the completely reacted metal. These results indicate that the boron does not react near the detonation front or that boron mixtures exhibit eigenvalue detonation behavior (as shown by some aluminized explosives), with higher detonation velocities at the initial points. Analyses of calorimetric measurements for RDX—boron mixtures indicate that at high boron contents the formation of side products, including boron nitride and boron carbide, inhibits the detonation properties of the formulation.

  13. Synthesis of boron nitride nanotubes by boron ink annealing

    NASA Astrophysics Data System (ADS)

    Li, Lu Hua; Chen, Ying; Glushenkov, Alexey M.

    2010-03-01

    Ball-milling and annealing is one effective method for the mass production of boron nitride nanotubes (BNNTs). We report that the method has been modified to a boron (B) ink annealing method. In this new process, the nanosize ball-milled B particles are mixed with metal nitrate in ethanol to form an ink-like solution, and then the ink is annealed in nitrogen-containing gas to form nanotubes. The new method greatly enhances the yield of BNNTs, giving a higher density of nanotubes. These improvements are caused by the addition of metal nitrate and ethanol, both of which can strongly boost the nitriding reaction, as revealed by thermogravimetric analysis. The size and structure of BNNTs can be controlled by varying the annealing conditions. This high-yield production of BNNTs in large quantities enables the large-scale application of BNNTs.

  14. Synthesis of boron nitride nanotubes by boron ink annealing.

    PubMed

    Li, Lu Hua; Chen, Ying; Glushenkov, Alexey M

    2010-03-12

    Ball-milling and annealing is one effective method for the mass production of boron nitride nanotubes (BNNTs). We report that the method has been modified to a boron (B) ink annealing method. In this new process, the nanosize ball-milled B particles are mixed with metal nitrate in ethanol to form an ink-like solution, and then the ink is annealed in nitrogen-containing gas to form nanotubes. The new method greatly enhances the yield of BNNTs, giving a higher density of nanotubes. These improvements are caused by the addition of metal nitrate and ethanol, both of which can strongly boost the nitriding reaction, as revealed by thermogravimetric analysis. The size and structure of BNNTs can be controlled by varying the annealing conditions. This high-yield production of BNNTs in large quantities enables the large-scale application of BNNTs.

  15. Head phantom experiment and calculation for boron neutron capture therapy.

    PubMed

    Matsumoto, T; Aizawa, O

    1988-06-01

    Head phantom experiments with various neutron beams and calculations were carried out in order to provide useful information for boron neutron capture therapy (BNCT). Thermal neutron beams for thermal neutron capture therapy were used for phantom experiments with various neutron collimator aperture sizes. The filtered beam neutrons of 24 and 144 keV generated with iron and silicon filters were also used to investigate the possible application of BNCT in the treatment of deep-seated cancers. Thermal neutron fluence and induced capture gamma dose distributions within the phantom were calculated with a transport code DOT 3.5 and compared with the experimental results. The results showed that the calculation used was consistent with the experimental results and provided useful information on BNCT. The filtered beam neutron may be very useful for the treatment of deep or widespread cancer, if there were a high power research reactor constructed for this purpose.

  16. Longitudinal Splitting of Boron Nitride Nanotubes for the Facile Synthesis of High Quality Boron Nitride Nanoribbons

    DTIC Science & Technology

    2011-05-24

    Boron Nitride Nanotubes for the Facile Synthesis of High Quality Boron Nitride Nanoribbons Kris J. Erickson,†,‡,§ Ashley...We report the synthesis of BNNRs through the potassium-intercalation-induced longitudinal splitting of boron nitride nanotubes (BNNTs). This facile...COVERED 00-00-2011 to 00-00-2011 4. TITLE AND SUBTITLE Longitudinal Splitting of Boron Nitride Nanotubes for the Facile Synthesis of High

  17. Mapping Boron Dioxide (BO2) Light Emission During Ballistic Initiation of Boron

    DTIC Science & Technology

    2016-03-03

    ARL-TN-0738 ● FEB 2016 US Army Research Laboratory Mapping Boron Dioxide (BO2) Light Emission During Ballistic Initiation of...ARL-TN-0738 ● FEB 2016 US Army Research Laboratory Mapping Boron Dioxide (BO2) Light Emission During Ballistic Initiation of Boron...Technical Note 3. DATES COVERED (From - To) February 2013–February 2015 4. TITLE AND SUBTITLE Mapping Boron Dioxide (BO2) Light Emission During

  18. Behavior of Boron Doped Graphites and Boron Carbide under Ion Beam and Plasma Irradiation

    NASA Astrophysics Data System (ADS)

    Begrambekov, L. B.; Buzhinsky, O. I.; Zakharovi, A.

    The paper shortly describes the methods of boron carbide coating deposition and presents the experimental results characterizing the properties of boron carbide coatings and of boron doped graphites important to their application as the plasma facing materials of fusion devices and other plasma apparatus dealing with dense and high temperature plasma. Conclusion is made that thick renewable boron carbide coating can successfully be used as the protecting coating of plasma facing elements of ITER.

  19. Prediction of boron carbon nitrogen phase diagram

    NASA Astrophysics Data System (ADS)

    Yao, Sanxi; Zhang, Hantao; Widom, Michael

    We studied the phase diagram of boron, carbon and nitrogen, including the boron-carbon and boron-nitrogen binaries and the boron-carbon-nitrogen ternary. Based on the idea of electron counting and using a technique of mixing similar primitive cells, we constructed many ''electron precise'' structures. First principles calculation is performed on these structures, with either zero or high pressures. For the BN binary, our calculation confirms that a rhmobohedral phase can be stablized at high pressure, consistent with some experimental results. For the BCN ternary, a new ground state structure is discovered and an Ising-like phase transition is suggested. Moreover, we modeled BCN ternary phase diagram and show continuous solubility from boron carbide to the boron subnitride phase.

  20. Method for preparing boron-carbide articles

    DOEpatents

    Benton, S.T.; Masters, D.R.

    1975-10-21

    The invention is directed to the preparation of boron carbide articles of various configurations. A stoichiometric mixture of particulate boron and carbon is confined in a suitable mold, heated to a temperature in the range of about 1250 to 1500$sup 0$C for effecting a solid state diffusion reaction between the boron and carbon for forming the boron carbide (B$sub 4$C), and thereafter the resulting boron-carbide particles are hot-pressed at a temperature in the range of about 1800 to 2200$sup 0$C and a pressure in the range of about 1000 to 4000 psi for densifying and sintering the boron carbide into the desired article.

  1. A new class of boron nanotube.

    PubMed

    Wang, Jing; Liu, Ying; Li, You-Cheng

    2009-12-07

    The configurations, stability and electronic structures of a new class of boron sheet and related boron nanotubes are predicted within the framework of density functional theory. This boron sheet is sparser than those of recent proposals. Our theoretic results show that the stable boron sheet remains flat and is metallic. There are bands similar to the pi-bands in graphite near the Fermi level. Stable nanotubes with various diameters and chiral vectors can be rolled from the sheet. Within our study, only the thin (8, 0) nanotube with a band gap of 0.44 eV is semiconducting, while all the other thicker boron nanotubes are metallic, independent of their chirality. It indicates the possibility, in the design of nanodevices, to control the electronic transport properties of the boron nanotube through the diameter.

  2. Initial boronization of PBX-M using ablation of solid boronized probes

    SciTech Connect

    Kugel, H.W.; Hirooka, Y.; Kaita, R.; Kaye, S.; Khandagle, M.; Timberlake, J.; Bell, R.; England, A.; Isler, R.; Okabayashi, M.; Paul, S.; Takahashi, H.; Tighe, W.; von Goeler, S.; Post-Zwicker, A.P.; Jones, S.

    1993-05-01

    The initial boronization of PBX-M was performed using the sequential ablation of two types of solid target probes. Probe-1 in a mushroom shape consisted of a 10.7% boronized 2-D C-C composite containing 3.6 g of boron in a B{sub 4}C binder. Probe-2 in a rectangular shape consisted of an 86% boronized graphite felt composite containing 19.5 g of 40 {mu} boron particles. After boronization with Probe-1, the loop voltage during 1 MW neutral beam heated plasmas decreased 27% and volt-sec consumption decreased 20%. Strong peripheral spectral lines from low-Z elements decreased by factors of about 5. The central oxygen density decreased 15--20%. The total radiated power during neutral beam injection decreased by 43%. Probe-2 boronization exhibited improved operating conditions similar to Probe-1, but for some parameters, a smaller percentage change occurred due to the residual boron from the previous boronization using Probe-1. The ablation rates of both probes were consistent with front face temperatures at or slightly above the boron melting point. These results confirm the effectiveness of the solid target boronization (STB) technique as a real-time impurity control method for replenishing boron depositions without the use of hazardous borane compounds.

  3. Initial boronization of PBX-M using ablation of solid boronized probes

    SciTech Connect

    Kugel, H.W.; Hirooka, Y.; Kaita, R.; Kaye, S.; Khandagle, M. . Inst. of Plasma and Fusion Research); Timberlake, J.; Bell, R.; England, A.; Isler, R.; Okabayashi, M.; Paul, S.; Takahashi, H.; Tighe, W.; von Goeler, S.; Post-Zwicker, A.P. ); Jones, S. )

    1993-05-01

    The initial boronization of PBX-M was performed using the sequential ablation of two types of solid target probes. Probe-1 in a mushroom shape consisted of a 10.7% boronized 2-D C-C composite containing 3.6 g of boron in a B[sub 4]C binder. Probe-2 in a rectangular shape consisted of an 86% boronized graphite felt composite containing 19.5 g of 40 [mu] boron particles. After boronization with Probe-1, the loop voltage during 1 MW neutral beam heated plasmas decreased 27% and volt-sec consumption decreased 20%. Strong peripheral spectral lines from low-Z elements decreased by factors of about 5. The central oxygen density decreased 15--20%. The total radiated power during neutral beam injection decreased by 43%. Probe-2 boronization exhibited improved operating conditions similar to Probe-1, but for some parameters, a smaller percentage change occurred due to the residual boron from the previous boronization using Probe-1. The ablation rates of both probes were consistent with front face temperatures at or slightly above the boron melting point. These results confirm the effectiveness of the solid target boronization (STB) technique as a real-time impurity control method for replenishing boron depositions without the use of hazardous borane compounds.

  4. Dietary boron, brain function, and cognitive performance.

    PubMed Central

    Penland, J G

    1994-01-01

    Although the trace element boron has yet to be recognized as an essential nutrient for humans, recent data from animal and human studies suggest that boron may be important for mineral metabolism and membrane function. To investigate further the functional role of boron, brain electrophysiology and cognitive performance were assessed in response to dietary manipulation of boron (approximately 0.25 versus approximately 3.25 mg boron/2000 kcal/day) in three studies with healthy older men and women. Within-subject designs were used to assess functional responses in all studies. Spectral analysis of electroencephalographic data showed effects of dietary boron in two of the three studies. When the low boron intake was compared to the high intake, there was a significant (p < 0.05) increase in the proportion of low-frequency activity, and a decrease in the proportion of higher-frequency activity, an effect often observed in response to general malnutrition and heavy metal toxicity. Performance (e.g., response time) on various cognitive and psychomotor tasks also showed an effect of dietary boron. When contrasted with the high boron intake, low dietary boron resulted in significantly poorer performance (p < 0.05) on tasks emphasizing manual dexterity (studies II and III); eye-hand coordination (study II); attention (all studies); perception (study III); encoding and short-term memory (all studies); and long-term memory (study I). Collectively, the data from these three studies indicate that boron may play a role in human brain function and cognitive performance, and provide additional evidence that boron is an essential nutrient for humans. PMID:7889884

  5. Synthesis, Properties, and Applications Of Boron Nitride

    NASA Technical Reports Server (NTRS)

    Pouch, John J.; Alterovitz, Samuel A.

    1993-01-01

    Report describes synthesis, properties, and applications of boron nitride. Especially in thin-film form. Boron nitride films useful as masks in x-ray lithography; as layers for passivation of high-speed microelectronic circuits; insulating films; hard, wear-resistant, protective films for optical components; lubricants; and radiation detectors. Present status of single-crystal growth of boron nitride indicates promising candidate for use in high-temperature semiconductor electronics.

  6. Toxic effects of boron on mallard reproduction

    USGS Publications Warehouse

    Smith, G.J.; Anders, V.P.

    1989-01-01

    Boron, a naturally occurring trace element generally considered environmentally innocuous, was documented to severely impair mallard reproduction. Boron is leached from irrigated agricultural soils and transported in drainage water that contaminates wetlands. Until now, only the selenium accumulated in aquatic food chains has been documented to pose a toxic hazard to wildlife in drainage water wetlands. Management of drainage water-contaminated environments must now also consider the adverse effects of boron, as well as the possible interactions of drainage water contaminants.

  7. Stereodivergent Olefination of Enantioenriched Boronic Esters

    PubMed Central

    Armstrong, Roly J.; García‐Ruiz, Cristina; Myers, Eddie L.

    2016-01-01

    Abstract A stereodivergent coupling reaction between vinyl halides and boronic esters is described. This coupling process proceeds without a transition‐metal catalyst, instead proceeding by electrophilic selenation or iodination of a vinyl boronate complex followed by stereospecific syn or anti elimination. Chiral, nonracemic boronic esters could be coupled with complete enantiospecificity. The process enables the highly stereoselective synthesis of either the E or Z alkene from a single isomer of a vinyl coupling partner. PMID:27958668

  8. Synthesis, Properties, and Applications Of Boron Nitride

    NASA Technical Reports Server (NTRS)

    Pouch, John J.; Alterovitz, Samuel A.

    1993-01-01

    Report describes synthesis, properties, and applications of boron nitride. Especially in thin-film form. Boron nitride films useful as masks in x-ray lithography; as layers for passivation of high-speed microelectronic circuits; insulating films; hard, wear-resistant, protective films for optical components; lubricants; and radiation detectors. Present status of single-crystal growth of boron nitride indicates promising candidate for use in high-temperature semiconductor electronics.

  9. Boron containing multilayer coatings and method of fabrication

    DOEpatents

    Makowiecki, D.M.; Jankowski, A.F.

    1997-09-23

    Hard coatings are fabricated from multilayer boron/boron carbide, boron carbide/cubic boron nitride, and boron/boron nitride/boron carbide, and the fabrication thereof involves magnetron sputtering in a selected atmosphere. These hard coatings may be applied to tools and engine and other parts, as well to reduce wear on tribological surfaces and electronic devices. These boron coatings contain no morphological growth features. For example, the boron and boron carbide used in forming the multilayers are formed in an inert (e.g. argon) atmosphere, while the cubic boron nitride is formed in a reactive (e.g. nitrogen) atmosphere. The multilayer boron/boron carbide, and boron carbide/cubic boron nitride is produced by depositing alternate layers of boron, cubic boron nitride or boron carbide, with the alternate layers having a thickness of 1 nanometer to 1 micrometer, and at least the interfaces of the layers may be of a discrete or a blended or graded composition. 6 figs.

  10. Boron-10 ABUNCL Active Testing

    SciTech Connect

    Kouzes, Richard T.; Ely, James H.; Lintereur, Azaree T.; Siciliano, Edward R.

    2013-07-09

    The Department of Energy Office of Nuclear Safeguards and Security (NA-241) is supporting the project Coincidence Counting With Boron-Based Alternative Neutron Detection Technology at Pacific Northwest National Laboratory (PNNL) for the development of a 3He proportional counter alternative neutron coincidence counter. The goal of this project is to design, build and demonstrate a system based upon 10B-lined proportional tubes in a configuration typical for 3He-based coincidence counter applications. This report provides results from testing of the active mode of the General Electric Reuter-Stokes Alternative Boron-Based Uranium Neutron Coincidence Collar (ABUNCL) at Los Alamos National Laboratory using sources and fuel pins.

  11. Low temperature boron doped diamond

    NASA Astrophysics Data System (ADS)

    Zeng, Hongjun; Arumugam, Prabhu U.; Siddiqui, Shabnam; Carlisle, John A.

    2013-06-01

    Low temperature boron doped diamond (LT-BDD) film deposited under 600 °C (460 °C minimum) has been reported. Study reveals that the deposition temperature and boron dopant cause nanocrystalline diamond (NCD) instead of ultrananocrystalline diamond (UNCD®). Unlike conventional NCD, LT-BDD has faster renucleation rate, which ensures a low surface roughness (approximately 10 nm at 0.6 μm thickness). The overall characteristics of LT-BDD are mixed with the characteristics of conventional NCD and UNCD. Raman spectrum and electrochemical characterization prove that the quality of LT-BDD is similar to those grown under 650-900 °C. LT-BDD enables diamond applications on microelectromechanical systems, bio- and optical technologies.

  12. Mineral resource of the month: boron

    USGS Publications Warehouse

    Crangle, Robert D.

    2012-01-01

    The article offers information on the mineral, boron. Boron compounds, particularly borates, have more commercial applications than its elemental relative which is a metalloid. Making up the 90% of the borates that are used worldwide are colemanite, kernite, tincal, and ulexite. The main borate deposits are located in the Mojave Desert of the U.S., the Tethyan belt in southern Asia, and the Andean belt of South America. Underground and surface mining are being used in gathering boron compounds. INSETS: Fun facts;Boron production and consumption.

  13. Premixed Combustion Model for Boron Clouds

    NASA Astrophysics Data System (ADS)

    Wang, Mengze; Han, Wang; Chen, Zheng

    2015-11-01

    Boron particle is an ideal additive in solid propellants and fuels due to its very high volumetric heat release. In this study, a premixed combustion model for boron clouds is developed based on a previous combustion model for single boron particle. The flame structure is assumed to be composed of three zones: the preheat zone, the ignition zone, and the reaction zone, and analytical solutions are derived from the governing equations. Consequently the influence of the boron clouds' physical properties on the flame propagation process is investigated.

  14. Producing carbon stripper foils containing boron

    SciTech Connect

    Stoner, J. O. Jr.

    2012-12-19

    Parameters being actively tested by the accelerator community for the purpose of extending carbon stripper foil lifetimes in fast ion beams include methods of deposition, parting agents, mounting techniques, support (fork) materials, and inclusion of alloying elements, particularly boron. Specialized production apparatus is required for either sequential deposition or co-deposition of boron in carbon foils. A dual-use vacuum evaporator for arc evaporation of carbon and electron-beam evaporation of boron and other materials has been built for such development. Production of both carbon and boron foils has begun and improvements are in progress.

  15. Boron removal from geothermal waters by electrocoagulation.

    PubMed

    Yilmaz, A Erdem; Boncukcuoğlu, Recep; Kocakerim, M Muhtar; Yilmaz, M Tolga; Paluluoğlu, Cihan

    2008-05-01

    Most of the geothermal waters in Turkey contain extremely high concentration of boron when they are used for irrigation. The use of geothermal waters for irrigation can results in excess amount deposition of boron in soil. On the other hand, a minimal boron concentration is required for irrigational waters. In this study, electrocoagulation (EC) was selected as a treatment process for the removal of boron from thermal waters obtained from Ilica-Erzurum in Turkey. Current density (CD), pH of solution and temperature of solution were selected as operational parameters. The results showed that boron removal efficiency increased from pH 4.0 to 8.0 and decreased at pH 10.0. Although boron removal efficiency was highest at pH 8.0, energy consumption was very high at this pH value compared to other pH intervals. Boron removal efficiency reached to 95% with increasing current density from 1.5 to 6.0 mA/cm(2), but energy consumption was also increased in this interval. At higher temperatures of solution, such as 313 and 333 K, boron removal efficiency increased. At optimum conditions, boron removal efficiency in geothermal water reached up to 95%.

  16. Boron deposition from fused salts. Final report

    SciTech Connect

    Smith, M.L.

    1980-08-01

    A partial evaluation of the feasibility of a process to electrodeposit pure coherent coatings of elemental boron from molten fluorides has been performed. The deposit produced was powdery and acicular, unless the fluoride melt was purified to have very low oxygen concentration. When the oxygen activity was reduced in the melt by addition of crystalline elemental boron, dense, amorphous boron deposit was produced. The boron deposits produced had cracks but were otherwise pure and dense and ranged up to 0.35 mm thick. Information derived during this project suggests that similar deposits might be obtained crack-free up to 1.00 mm thick by process modifications and improvements.

  17. METHOD OF PREPARING POLONIUM-BORON SOURCES

    DOEpatents

    Birden, J.H.

    1959-08-01

    An improved technique is described for preparation of a polonium-boron neutron source. A selected amount of Po-210 is vaporized into a thin walled nickel container, then the desired amcunt of boron powder is added. After sealing the container, it is heated quickly by induction heating to vaporize the Po-210 and deposit it in the still cool boron powder. The unit is then quickly cooled to prevent revaporization of the Po-210 from the boron. The build-up of neutron emission may be followed by means of a neutron counter in order to terminate the heating at the optimum level of neutron yield.

  18. DLTS study of deep centers created by Ar-ion bombardment in n- and p-type MBE AlGaAs

    NASA Astrophysics Data System (ADS)

    Kaniewska, M.; Sadowski, J.; Guziewicz, M.

    2004-07-01

    The thermal emission rate of dominant traps in molecular beam epitaxial n- and p-type AlGaAs subjected to Ar-ion beam etching has been studied by deep level transient spectroscopy. Emission signatures were determined and compared with results obtained by other authors for irradiation induced and grown-in defects in GaAs and AlGaAs. The most significant result of this study is the observation that the process-induced defects in n- as well as p-type AlGaAs exhibit emission signatures, which are characteristic of native defects found in GaAs. The effect is discussed in terms of a compensation effect and related band bending.

  19. Making Microscopic Cubes Of Boron

    NASA Technical Reports Server (NTRS)

    Faulkner, Joseph M.

    1993-01-01

    Production of finely divided cubes of boron involves vacuum-deposition technology and requires making of template. Template supports pattern of checkered squares 25 micrometers on side, which are etched 25 micrometers into template material. Template coasted uniformly with paralyene or some similar vacuum coating with low coefficient of adhesion. Intended application to solid rocket fuels, explosives, and pyrotechnics; process used for other applications, from manufacture of pharmaceuticals to processing of nuclear materials.

  20. Conduction mechanism in boron carbide

    NASA Technical Reports Server (NTRS)

    Wood, C.; Emin, D.

    1984-01-01

    Electrical conductivity, Seebeck-coefficient, and Hall-effect measurements have been made on single-phase boron carbides, B(1-x)C(x), in the compositional range from 0.1 to 0.2 X, and between room temperature and 1273 K. The results indicate that the predominant conduction mechanism is small-polaron hopping between carbon atoms at geometrically inequivalent sites.

  1. Making Microscopic Cubes Of Boron

    NASA Technical Reports Server (NTRS)

    Faulkner, Joseph M.

    1993-01-01

    Production of finely divided cubes of boron involves vacuum-deposition technology and requires making of template. Template supports pattern of checkered squares 25 micrometers on side, which are etched 25 micrometers into template material. Template coasted uniformly with paralyene or some similar vacuum coating with low coefficient of adhesion. Intended application to solid rocket fuels, explosives, and pyrotechnics; process used for other applications, from manufacture of pharmaceuticals to processing of nuclear materials.

  2. Conduction mechanism in boron carbide

    NASA Technical Reports Server (NTRS)

    Wood, C.; Emin, D.

    1984-01-01

    Electrical conductivity, Seebeck-coefficient, and Hall-effect measurements have been made on single-phase boron carbides, B(1-x)C(x), in the compositional range from 0.1 to 0.2 X, and between room temperature and 1273 K. The results indicate that the predominant conduction mechanism is small-polaron hopping between carbon atoms at geometrically inequivalent sites.

  3. Boron-Doped Strontium-Stabilized Bismuth Cobalt Oxide Thermoelectric Nanocrystalline Ceramic Powders Synthesized via Electrospinning

    NASA Astrophysics Data System (ADS)

    Koçyiğit, Serhat; Aytimur, Arda; Çınar, Emre; Uslu, İbrahim; Akdemir, Ahmet

    2014-01-01

    Boron-doped strontium-stabilized bismuth cobalt oxide thermoelectric nanocrystalline ceramic powders were produced by using a polymeric precursor technique. The powders were characterized by using x-ray diffraction (XRD), scanning electron microscopy (SEM), and physical properties measurement system (PPMS) techniques. The XRD results showed that these patterns have a two-phase mixture. The phases are face-centered cubic (fcc) and body-centered cubic (bcc). Values of the crystallite size, dislocation density, and microstrain were calculated by using the Scherrer equation. The lattice parameters were calculated for fcc and bcc phases. The SEM results showed that needle-like grains are formed in boron-undoped composite materials, but the needle-like grains changed to the plate-like grains with the addition of boron. The distribution of the nanofiber diameters was calculated and the average diameter of the boron-doped sample is smaller than the boron-undoped one. PPMS values showed that the electrical resistivity values decreased, but the thermal conductivity values, the Seebeck coefficients, and figure of merit ( ZT) increased with increasing temperature for the two samples.

  4. Boronization in DIII-D

    SciTech Connect

    Jackson, G.L.; Burrell, K.H.; DeBoo, J.C.; Greenfield, C.M.; Groebner, R.J.; Hodapp, T.; Kellman, A.G.; Lee, R.; Lippman, S.I.; Phillips, J.; Taylor, T.S.; West, W.P.; Winter, J.; Moyer, R.; Watkins, J.

    1992-05-01

    A thin boron film has been applied to the DIII-D tokamak plasma facing surfaces to reduce impurity influx, particularly oxygen and carbon. A direct result of this surface modification was the observation of a regime of very high energy confinement, VH-mode, with confinement times from 1.5 to 2 times greater than predicted by H-mode scaling relation for the same set of parameters. VH-mode discharges are characterized by low ohmic target densities, low edge neutral pressure, and reduced cycling. These conditions have reduced the collisionality, {nu}*, in the edge region producing a higher edge pressure gradient and a significant bootstrap current, up to 30% of the total current. We will describe the edge plasma properties after boronization including reductions in recycling inferred from measurements of {tau}{sup p}*. In particular we will discuss the edge plasma conditions necessary for access to VH-mode including the boronization process and properties of the deposited film.

  5. Boron coating on boron nitride coated nuclear fuels by chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Durmazuçar, Hasan H.; Gündüz, Güngör

    2000-12-01

    Uranium dioxide-only and uranium dioxide-gadolinium oxide (5% and 10%) ceramic nuclear fuel pellets which were already coated with boron nitride were coated with thin boron layer by chemical vapor deposition to increase the burn-up efficiency of the fuel during reactor operation. Coating was accomplished from the reaction of boron trichloride with hydrogen at 1250 K in a tube furnace, and then sintering at 1400 and 1525 K. The deposited boron was identified by infrared spectrum. The morphology of the coating was studied by using scanning electron microscope. The plate, grainy and string (fiber)-like boron structures were observed.

  6. Energy Landscape of Fullerene Materials: A Comparison of Boron to Boron Nitride and Carbon

    NASA Astrophysics Data System (ADS)

    de, Sandip; Willand, Alexander; Amsler, Maximilian; Pochet, Pascal; Genovese, Luigi; Goedecker, Stefan

    2011-06-01

    Using the minima hopping global geometry optimization method on the density functional potential energy surface we show that the energy landscape of boron clusters is glasslike. Larger boron clusters have many structures which are lower in energy than the cages. This is in contrast to carbon and boron nitride systems which can be clearly identified as structure seekers. The differences in the potential energy landscape explain why carbon and boron nitride systems are found in nature whereas pure boron fullerenes have not been found. We thus present a methodology which can make predictions on the feasibility of the synthesis of new nanostructures.

  7. Accumulation and loss of arsenic and boron, alone and in combination, in mallard ducks

    USGS Publications Warehouse

    Pendleton, G.W.; Whitworth, M.R.; Olsen, G.H.

    1995-01-01

    Study was conducted at the Patuxent Wildlife Research Center from June to October 1987. Adult mallard ducks were exposed to dietary concentrations of arsenic as sodium arsenate, boron as boric acid, or both; tissue accumulation and loss rates were estimated when the ducks were returned to uncontaminated food.

  8. Investigating controls on boron isotope ratios in shallow marine carbonates

    NASA Astrophysics Data System (ADS)

    Zhang, Shuang; Henehan, Michael J.; Hull, Pincelli M.; Reid, R. Pamela; Hardisty, Dalton S.; Hood, Ashleigh v. S.; Planavsky, Noah J.

    2017-01-01

    The boron isotope-pH proxy has been widely used to reconstruct past ocean pH values. In both planktic foraminifera and corals, species-specific calibrations are required in order to reconstruct absolute values of pH, due to the prevalence of so-called vital effects - physiological modification of the primary environmental signals by the calcifying organisms. Shallow marine abiotic carbonate (e.g. ooids and cements) could conceivably avoid any such calibration requirement, and therefore provide a potentially useful archive for reconstructions in deep (pre-Cenozoic) time. However, shallow marine abiotic carbonates could also be affected by local shifts in pH caused by microbial photosynthesis and respiration, something that has up to now not been fully tested. In this study, we present boron isotope measurements from shallow modern marine carbonates, from the Bahama Bank and Belize to investigate the potential of using shallow water carbonates as pH archives, and to explore the role of microbial processes in driving nominally 'abiogenic' carbonate deposition. For Bahama bank samples, our boron-based pH estimates derived from a range of carbonate types (i.e. ooids, peloids, hardground cements, carbonate mud, stromatolitic micrite and calcified filament micrite) are higher than the estimated modern mean-annual seawater pH values for this region. Furthermore, the majority (73%) of our marine carbonate-based pH estimates fall out of the range of the estimated pre-industrial seawater pH values for this region. In shallow sediment cores, we did not observe a correlation between measured pore water pH and boron-derived pH estimates, suggesting boron isotope variability is a depositional rather than early diagenetic signal. For Belize reef cements, conversely, the pH estimates are lower than likely in situ seawater pH at the time of cement formation. This study indicates the potential for complications when using shallow marine non-skeletal carbonates as marine pH archives

  9. The noble gases adsorption on boron-rich boron nitride nanotubes: A theoretical investigation

    NASA Astrophysics Data System (ADS)

    Wang, Chong; Guo, Chen

    2017-07-01

    In this work, using density functional theory (DFT) calculations, we have systematically explored the noble gases (Ng = He, Ne, Ar, Kr) adsorption on boron-rich boron nitride nanotubes (BNNTs) surface with antisite boron atom. One or two nitrogen atoms of BNNTs are replaced by boron atoms, which are considered as boron-rich BNNTs for Ng adsorption. It is found that the boron-rich BNNTs can adsorb Ng in exothermic process, and the adsorption energies increase in order from He to Kr. The quantum theory of atoms in molecules (QTAIM) and noncovalent interactions (NCIs) calculations show that the interactions between boron-rich BNNTs and Ng are noncovalent, and the interactions for Ar and Kr are obviously larger than those for He and Ne. The charge transfer from Ng to boron-rich BNNTs and the changes of energy gap caused by Ng adsorption demonstrate that the boron-rich BNNTs are expected to become the Ng adsorption and sensing materials. Moreover, the 2B-BNNTs do not decrease the Ng adsorption interactions on boron-rich BNNTs, compared with 1B-BNNTs. It is expected that the present results will provide a useful guide to develop novel boron nitride nanomaterials for storage and application of Ng.

  10. Recruitment of marine invertebrates to hard substrates at deep-sea hydrothermal vents on the East Pacific Rise and Galapagos spreading center

    NASA Astrophysics Data System (ADS)

    Van Dover, Cindy Lee; Berg, Carl J.; Turner, Ruth D.

    1988-10-01

    Recruitment panels were placed at and near hydrothermal vent communities at three sites on the Galapagos spreading center and one site on the East Pacific Rise at 21°N. Deployment periods ranged from 26 days (Clam Acres, 21°N) to 260-320 days (Rose Garden, Garden of Eden, Mussel Bed, GSC) to 1216 days (Clam Acres). Recruitment of gastropod post-larvae and juveniles was observed on arrays deployed at Clam Acres for 26 days. Regardless of length of deployment, populations of polychaetes, mollusks, and barnacles colonizing the panels were predominantly post-larval, juvenile, or sub-adult stages. We suggest that some combination of competition, migration, and predation maintains these populations in immature stages. Size distributions of individuals within a taxon on panels deployed for 1216 days are broad, suggesting intermittent or continuous recruitment in many of the vent-associated species rather than a single episodic recruitment event. Folliculinid and foraminiferan protozoans were the most abundant eucaryotic organisms colonizing long-term deployments at Clam Acres. On the Galapagos spreading center, level of recruitment differed among the vent sites, with Rose Garden > Garden of Eden ≫ Mussel Bed. Recruitment of vent-associated species was greater on panels placed within vent communities compared to panels placed adjacent to these communities. This observation is consistent with the maintenance of vent communities in discrete regions of hydrothermal flux.

  11. Boron Discovered in Ancient Habitable Mars Groundwater

    SciTech Connect

    Gasda, Patrick

    2016-12-13

    Boron was recently discovered in calcium-sulfate veins on Mars using the ChemCam instrument on NASA’s Curiosity Mars Rover. This is the first Mars mission to detect boron on the Red Planet. Los Alamos Post-Doctoral Student Patrick Gasda explains how this discovery helps us better understand the timescale of habitability on Mars.

  12. Boron Carbides As Thermo-electric Materials

    NASA Technical Reports Server (NTRS)

    Wood, Charles

    1988-01-01

    Report reviews recent theoretical and experimental research on thermoelectric materials. Recent work with narrow-band semiconductors demonstrated possibility of relatively high thermoelectric energy-conversion efficiencies in materials withstanding high temperatures needed to attain such efficiencies. Among promising semiconductors are boron-rich borides, especially boron carbides.

  13. Boron chemicals in diagnosis and therapeutics

    PubMed Central

    Das, Bhaskar C; Thapa, Pritam; Karki, Radha; Schinke, Caroline; Das, Sasmita; Kambhampati, Suman; Banerjee, Sushanta K; Van Veldhuizen, Peter; Verma, Amit; Weiss, Louis M; Evans, Todd

    2013-01-01

    Advances in the field of boron chemistry have expanded the application of boron from material use to medicine. Boron-based drugs represent a new class of molecules that possess several biomedical applications including use as imaging agents for both optical and nuclear imaging as well as therapeutic agents with anticancer, antiviral, antibacterial, antifungal and other disease-specific activities. For example, bortezomib (Velcade®), the only drug in clinical use with boron as an active element, was approved in 2003 as a proteasome inhibitor for the treatment of multiple myeloma and non-Hodgkin’s lymphoma. Several other boron-based compounds are in various phases of clinical trials, which illustrates the promise of this approach for medicinal chemists working in the area of boron chemistry. It is expected that in the near future, several boron-containing drugs should become available in the market with better efficacy and potency than existing drugs. This article discusses the current status of the development of boron-based compounds as diagnostic and therapeutic agents in humans. PMID:23617429

  14. Boron chemicals in diagnosis and therapeutics.

    PubMed

    Das, Bhaskar C; Thapa, Pritam; Karki, Radha; Schinke, Caroline; Das, Sasmita; Kambhampati, Suman; Banerjee, Sushanta K; Van Veldhuizen, Peter; Verma, Amit; Weiss, Louis M; Evans, Todd

    2013-04-01

    Advances in the field of boron chemistry have expanded the application of boron from material use to medicine. Boron-based drugs represent a new class of molecules that possess several biomedical applications including use as imaging agents for both optical and nuclear imaging as well as therapeutic agents with anticancer, antiviral, antibacterial, antifungal and other disease-specific activities. For example, bortezomib (Velcade(®)), the only drug in clinical use with boron as an active element, was approved in 2003 as a proteasome inhibitor for the treatment of multiple myeloma and non-Hodgkin's lymphoma. Several other boron-based compounds are in various phases of clinical trials, which illustrates the promise of this approach for medicinal chemists working in the area of boron chemistry. It is expected that in the near future, several boron-containing drugs should become available in the market with better efficacy and potency than existing drugs. This article discusses the current status of the development of boron-based compounds as diagnostic and therapeutic agents in humans.

  15. Porphyrins for boron neutron capture therapy

    DOEpatents

    Miura, Michiko; Gabel, Detlef

    1990-01-01

    Novel compounds for treatment of brain tumors in Boron Neutron Capture Therapy are disclosed. A method for preparing the compounds as well as pharmaceutical compositions containing said compounds are also disclosed. The compounds are water soluble, non-toxic and non-labile boronated porphyrins which show significant uptake and retention in tumors.

  16. Ultratough single crystal boron-doped diamond

    DOEpatents

    Hemley, Russell J [Carnegie Inst. for Science, Washington, DC ; Mao, Ho-Kwang [Carnegie Inst. for Science, Washington, DC ; Yan, Chih-Shiue [Carnegie Inst. for Science, Washington, DC ; Liang, Qi [Carnegie Inst. for Science, Washington, DC

    2015-05-05

    The invention relates to a single crystal boron doped CVD diamond that has a toughness of at least about 22 MPa m.sup.1/2. The invention further relates to a method of manufacturing single crystal boron doped CVD diamond. The growth rate of the diamond can be from about 20-100 .mu.m/h.

  17. DEEP UNDERGROUND NEUTRINO EXPERIMENT

    SciTech Connect

    Wilson, Robert J.

    2016-03-03

    The Deep Underground Neutrino Experiment (DUNE) collaboration will perform an experiment centered on accelerator-based long-baseline neutrino studies along with nucleon decay and topics in neutrino astrophysics. It will consist of a modular 40-kt (fiducial) mass liquid argon TPC detector located deep underground at the Sanford Underground Research Facility in South Dakota and a high-resolution near detector at Fermilab in Illinois. This conguration provides a 1300-km baseline in a megawatt-scale neutrino beam provided by the Fermilab- hosted international Long-Baseline Neutrino Facility.

  18. Subsequent Pulse Generator Replacement Surgery Does Not Increase the Infection Rate in Patients With Deep Brain Stimulator Systems: A Review of 1537 Unique Implants at a Single Center.

    PubMed

    Frizon, Leonardo A; Hogue, Olivia; Wathen, Connor; Yamamoto, Erin; Sabharwal, Navin C; Jones, Jaes; Volovetz, Josephine; Maldonado-Naranjo, Andres L; Lobel, Darlene A; Machado, Andre G; Nagel, Sean J

    2017-07-01

    Deep brain stimulation (DBS) is a well-recognized treatment for patients with movement disorders and other neurological diseases. The implantable pulse generator (IPG) is a fundamental component of the DBS system. Although IPG implantation and replacement surgeries are comparatively minor procedures relative to the brain lead insertion, patients often require multiple IPG replacements during their lifetime with each operation carrying a small but possibly cumulative risk of complications. To better educate our patients and improve surgical outcomes, we reviewed our series of patients at our institution. Using electronic health record data, we retrospectively reviewed all initial and subsequent IPG surgeries from patients who underwent at least one IPG surgery between the years of 2010 and 2015 at the Cleveland Clinic main campus. We calculated infection rates for initial IPG implantation surgeries and the infection rate for subsequent replacements. Fisher's exact tests were used to evaluate the chance of an infection between the initial implantation and replacement. Fisher's exact tests and simple logistic regression analyses were used to determine the predictive ability of selected demographic and clinical variables RESULTS: Our final sample included 697 patients and 1537 surgeries. For all patients, the infection rate at the first surgery was 2.01%; at the second surgery, it was 0.44%; and at the third surgery, it was 1.83%. When considering only patients that underwent at least three replacement surgeries (n = 114) the infection rate did not change in a significant manner with subsequent interventions compared to the first replacement. No other variable of interest was a significant predictor of infection. We did not find increasing rates of infection with subsequent IPG replacement procedures. © 2017 International Neuromodulation Society.

  19. Evaluation of nonpermanent inferior vena cava filter placement in patients with deep venous thrombosis after lower extremity fracture: A single-center retrospective study.

    PubMed

    Pan, Ye; Zhao, Jun; Mei, Jiacai; Shao, Mingzhe; Zhang, Jian; Wu, Haisheng

    2016-09-01

    To investigate nonpermanent inferior vena cava (IVC) filter in the prevention of perioperative pulmonary embolism (PE) in patients of lower extremity and/or pelvic bone fracture with deep vein thrombosis (DVT). Lower extremity or pelvic bone fracture patients with lower extremity DVT hospitalized in our hospital from January 2003 to October 2014 were retrospectively analyzed. Data was analyzed for age, gender, position of fracture, position of proximal of thrombosis, indications of placement, complications, retrieval rate, and rate of entrapped filter clot. Patients who underwent IVC filter placement were selected as the filter group. The patients who did not perform IVC filter placement after 2008 and the cases between January 2003 and December 2007 were selected as control group 1 and control group 2, respectively. The incidence of perioperative symptomatic PE and mortality were analyzed. A total of 2763 cases complicated with DVT underwent orthopedic surgery between January 2003 and October 2014. 823 nonpermanent filters were inserted. All filters were successfully deployed with no major complications. After a mean 14.2 days indwelling time, all of temporary filters were removed. Retrieval was attempted in 556 patients with retrievable filters and was successful in 545 (98%); mean indwelling time was 16.3 days. The total retrieval rate was 90%. The incidence of PE in the filter group was significantly lower compared with the two control groups. Among the patients who received chemical anticoagulant therapy, the incidence of PE in filter group, control group 1 and control group 2 were 0.14%, 1.60% and 2.10%, respectively. The incidence of PE in filter group was also significant lower compared with control groups. Nonpermanent IVC filter placement seems like to be a safe and effective method for preventing perioperative symptomatic and fatal PE in bone fracture patients with DVT in the present retrospective study. © The Author(s) 2015.

  20. Boron clusters as highly stable magnesium-battery electrolytes.

    PubMed

    Carter, Tyler J; Mohtadi, Rana; Arthur, Timothy S; Mizuno, Fuminori; Zhang, Ruigang; Shirai, Soichi; Kampf, Jeff W

    2014-03-17

    Boron clusters are proposed as a new concept for the design of magnesium-battery electrolytes that are magnesium-battery-compatible, highly stable, and noncorrosive. A novel carborane-based electrolyte incorporating an unprecedented magnesium-centered complex anion is reported and shown to perform well as a magnesium-battery electrolyte. This finding opens a new approach towards the design of electrolytes whose likelihood of meeting the challenging design targets for magnesium-battery electrolytes is very high. © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  1. Boron-doped superlattices and Bragg mirrors in diamond

    SciTech Connect

    Fiori, A.; Bousquet, J.; Eon, D.; Omnès, F.; Bustarret, E.; Bellet-Amalric, E.

    2014-08-25

    A periodic modulation of the boron doping level of single crystal diamond multilayers over more than three orders of magnitude during epitaxial growth by microwave plasma-enhanced chemical vapor deposition is shown to yield Bragg mirrors in the visible. The thicknesses and doping level of the individual layers were controlled by in situ spectroscopic ellipsometry, enabling to tune the reflectance peak to the wavelength range of diamond color centers, such as NV{sup 0} or NV{sup −}. The crystalline quality, periodicity, and sharpness of the doping transitions in these doping superlattices over tens of periods were confirmed by high resolution X-ray diffraction.

  2. Primitive boron isotope composition of the mantle.

    PubMed

    Chaussidon, M; Marty, B

    1995-07-21

    Boron isotope ratios are homogeneous in volcanic glasses of oceanic island basalts [-9.9 +/- 1.3 per mil, relative to standard NBS 951 (defined by the National Bureau of Standards)], whereas mid-oceanic ridge basalts (MORBs) and back-arc basin basalts (BABBs) show generally higher and more variable ratios. Melts that have assimilated even small amounts of altered basaltic crust show significant variations in the boron isotope ratios. Assimilation may thus account for the higher boron ratios of MORBs and BABBs. A budget of boron between mantle and crust implies that the primitive mantle had a boron isotope ratio of -10 +/- 2 per mil and that this ratio was not fractionated significantly during the differentiation of the mantle.

  3. Boronated mesophase pitch coke for lithium insertion

    NASA Astrophysics Data System (ADS)

    Frackowiak, E.; Machnikowski, J.; Kaczmarska, H.; Béguin, F.

    Boronated carbons from mesophase pitch have been used as materials for lithium storage in Li/carbon cells. Doping by boron has been realized by co-pyrolysis of coal tar pitch with the pyridine-borane complex. Amount of boron in mesocarbon microbeads (MCMB) varied from 1.4 to 1.8 wt.% affecting the texture of carbon. Optical microscopy and X-ray diffractograms have shown tendency to more disordered structure for boron-doped carbon. The values of specific reversible capacity ( x) varied from 0.7 to 1.1 depending significantly on the final temperature of pyrolysis (700-1150°C). The optimal charge/discharge performance was observed for boronated carbon heated at 1000°C.

  4. Stabilization of boron carbide via silicon doping.

    PubMed

    Proctor, J E; Bhakhri, V; Hao, R; Prior, T J; Scheler, T; Gregoryanz, E; Chhowalla, M; Giulani, F

    2015-01-14

    Boron carbide is one of the lightest and hardest ceramics, but its applications are limited by its poor stability against a partial phase separation into separate boron and carbon. Phase separation is observed under high non-hydrostatic stress (both static and dynamic), resulting in amorphization. The phase separation is thought to occur in just one of the many naturally occurring polytypes in the material, and this raises the possibility of doping the boron carbide to eliminate this polytype. In this work, we have synthesized boron carbide doped with silicon. We have conducted a series of characterizations (transmission electron microscopy, scanning electron microscopy, Raman spectroscopy and x-ray diffraction) on pure and silicon-doped boron carbide following static compression to 50 GPa non-hydrostatic pressure. We find that the level of amorphization under static non-hydrostatic pressure is drastically reduced by the silicon doping.

  5. Stabilization of boron carbide via silicon doping

    NASA Astrophysics Data System (ADS)

    Proctor, J. E.; Bhakhri, V.; Hao, R.; Prior, T. J.; Scheler, T.; Gregoryanz, E.; Chhowalla, M.; Giulani, F.

    2015-01-01

    Boron carbide is one of the lightest and hardest ceramics, but its applications are limited by its poor stability against a partial phase separation into separate boron and carbon. Phase separation is observed under high non-hydrostatic stress (both static and dynamic), resulting in amorphization. The phase separation is thought to occur in just one of the many naturally occurring polytypes in the material, and this raises the possibility of doping the boron carbide to eliminate this polytype. In this work, we have synthesized boron carbide doped with silicon. We have conducted a series of characterizations (transmission electron microscopy, scanning electron microscopy, Raman spectroscopy and x-ray diffraction) on pure and silicon-doped boron carbide following static compression to 50 GPa non-hydrostatic pressure. We find that the level of amorphization under static non-hydrostatic pressure is drastically reduced by the silicon doping.

  6. Ring Enlargement of Three-Membered Boron Heterocycles upon Reaction with Organic π Systems: Implications for the Trapping of Borylenes.

    PubMed

    Krasowska, Małgorzata; Bettinger, Holger F

    2016-07-18

    New low-energy pathways for the reaction between substituted boriranes and borirenes with unsaturated hydrocarbons (ethyne or ethene) were discovered using density functional and coupled cluster theory. The interaction between the π bond of the hydrocarbon and the empty p orbital of the boron center leads to ring expansion of the three-membered to a five-membered boron heterocycle. The reactions are strongly exothermic and have low or even no barriers. They involve intermediates with a pentacoordinate boron center with two hydrocarbon molecules coordinating to boron akin to metal-olefin complexes. These borylene complexes are shallow minima on the potential energy surfaces. But significantly higher barriers for ring formation are computed for 1,5-cyclooctadiene and dibenzocyclooctatetraene complexes of borylenes, making these complexes likely detectable under appropriate experimental conditions. Our computational findings have implications for the interpretation of trapping experiments of thermally generated small borylenes with excess of small π systems. Because of very low barriers for reactions of three-membered boron heterocycles with π systems and the at least locally large excess of the latter under such conditions, formation of five-membered boron heterocycles should be considered.

  7. KENNEDY SPACE CENTER, FLA. - U.S. Senator Bill Nelson (center) and NASA Administrator Sean O’Keefe are deep in conversation as they leave the Central Florida Research Park, near Orlando. Behind Nelson at left is Congressman Tom Feeney. The research park is being proposed as the location for NASA’s new Shared Services Center. Six sites around the U.S. are under consideration for location of the Center, which would centralize NASA’s payroll, accounting, human resources, facilities and procurement offices that are now handled at each field center. The consolidation is part of the One NASA focus. Others attending the presentation included U.S. Representative Ric Keller, Congressman Dave Weldon, Center Director Jim Kennedy and Pamella J. Dana, Ph.D., director, Office of Tourism, Trade, and Economic Development in Florida.

    NASA Image and Video Library

    2004-02-19

    KENNEDY SPACE CENTER, FLA. - U.S. Senator Bill Nelson (center) and NASA Administrator Sean O’Keefe are deep in conversation as they leave the Central Florida Research Park, near Orlando. Behind Nelson at left is Congressman Tom Feeney. The research park is being proposed as the location for NASA’s new Shared Services Center. Six sites around the U.S. are under consideration for location of the Center, which would centralize NASA’s payroll, accounting, human resources, facilities and procurement offices that are now handled at each field center. The consolidation is part of the One NASA focus. Others attending the presentation included U.S. Representative Ric Keller, Congressman Dave Weldon, Center Director Jim Kennedy and Pamella J. Dana, Ph.D., director, Office of Tourism, Trade, and Economic Development in Florida.

  8. Boron isotope systematics of tourmaline formation in the Sullivan Pb-Zn-Ag deposit, British Columbia, Canada

    USGS Publications Warehouse

    Jiang, S.-Y.; Palmer, M.R.; Slack, J.F.; Shaw, D.R.

    1999-01-01

    We report here the results of 54 boron isotope analyses of tourmaline associated with the giant Sullivan Pb-Zn-Ag deposit in southeastern British Columbia, Canada. The ??11B values range from -11.1 to -2.9???, which is almost as great as the range found worldwide in tourmalines from 33 massive sulfide deposits and tourmalinites in dominantly clastic metasedimentary terranes. The major control on the overall ??11B values of the Sullivan tourmalinites is the boron source. Potential controls over the large range of the data also include: (1) differences in formation temperatures of the tourmalinites, (2) different stages of tourmaline formation, (3) variations in the proportions of dissolved boron incorporated into the tourmaline (Rayleigh fractionation), (4) seawater entrainment, and (5) post-depositional metamorphism. The boron isotope data at Sullivan are consistent with boron derivation from leaching of footwall clastic sediments. However, the great abundance of tourmaline in the Sullivan deposit suggests that the local clastic sediments were not the sole source of boron, and we argue that non-marine evaporites, buried deep below the orebody, are the most viable source of this additional boron. It is likely that some of the variation in tourmaline ??11B values reflect mixing of boron from these two sources. Comparison of the potential effects of these controls with geologic and other geochemical evidence suggests that major causes for the wide range of ??11B values measured at Sullivan are seawater entrainment and Rayleigh fractionation, although in places, post-depositional alteration and thermal metamorphism were important in determining ??11B values of some of the recrystallized tourmalinites.

  9. Recombination Activity of Iron in Boron Doped Silicon

    NASA Astrophysics Data System (ADS)

    Yli-Koski, M.; Palokangas, M.; Sokolov, V.; Storgårds, J.; Väinölä, H.; Holmberg, H.; Sinkkonen, J.

    The charge carrier lifetime in iron contaminated boron doped silicon wafers was determined by surface photovoltage, SPV, and microwave photoconductive decay, µPCD, techniques. Our results show that the charge carrier lifetime in boron doped silicon wafers depends on the boron concentration when the lifetime is limited by iron-boron pairs.

  10. Boron enrichment in martian clay.

    PubMed

    Stephenson, James D; Hallis, Lydia J; Nagashima, Kazuhide; Freeland, Stephen J

    2013-01-01

    We have detected a concentration of boron in martian clay far in excess of that in any previously reported extra-terrestrial object. This enrichment indicates that the chemistry necessary for the formation of ribose, a key component of RNA, could have existed on Mars since the formation of early clay deposits, contemporary to the emergence of life on Earth. Given the greater similarity of Earth and Mars early in their geological history, and the extensive disruption of Earth's earliest mineralogy by plate tectonics, we suggest that the conditions for prebiotic ribose synthesis may be better understood by further Mars exploration.

  11. Boron Enrichment in Martian Clay

    PubMed Central

    Nagashima, Kazuhide; Freeland, Stephen J.

    2013-01-01

    We have detected a concentration of boron in martian clay far in excess of that in any previously reported extra-terrestrial object. This enrichment indicates that the chemistry necessary for the formation of ribose, a key component of RNA, could have existed on Mars since the formation of early clay deposits, contemporary to the emergence of life on Earth. Given the greater similarity of Earth and Mars early in their geological history, and the extensive disruption of Earth's earliest mineralogy by plate tectonics, we suggest that the conditions for prebiotic ribose synthesis may be better understood by further Mars exploration. PMID:23762242

  12. Boron foils for RDDS experiment

    NASA Astrophysics Data System (ADS)

    Lipski, A. R.; Rainovski, G.; Pietralla, N.; Dewald, A.

    2008-06-01

    Application of the deposition method based on the vibrational motion of micro particles in an electrostatic field [I. Sugai, Nucl. Instr. and Meth. A 397 (1997) 81] is described for the production of isotopic 11B foils. The method proved suitable for target production of this typically brittle material when a very flat target surface was required. The goal to produce 11B targets of 160-350 μg/cm 2 was achieved by depositing the boron on a thin foil substrate, such as Nb and Sn. The coated foil was stretched flat before it was mounted on a frame.

  13. Improved Boron for Enhanced Combustion

    DTIC Science & Technology

    1990-06-01

    2, p. 74F - 80F, 1955. 11. Perry and Chilton, " Chemical Engineer ’ Handbook," McGraw-Hill, 5th Edition, 1973, and 6th Edition, 1986. 12. Levenspiel ...0., " Chemical Reaction Engineering ," Wiley & Sons, 2nd Edition, 1972. 13. Hern, R. B, and R. G. Sidall, M. W. Thring, "Flow Patterns in a Phase Change...wet chemical method, allows the use of higher solution concentrations of boron than AAS, provides better precision, and allows us to simultaneously

  14. Boron contents and isotopic compositions of the hydrothermally altered oceanic crust from the Troodos ophiolite, Cyprus

    NASA Astrophysics Data System (ADS)

    Matsukura, S.; Yamaoka, K.; Ishikawa, T.; Kawahata, H.

    2010-12-01

    The boron contents and isotopic compositions were determined for the hydrothermally altered oceanic crust through the Troodos ophiolite. The samples were represented by the International Crustal Research Drilling Group (ICRDG) drill-Holes CY1 (479m), CY2A (689m), CY4 (2263m), and selected outcrops along the Akaki river. Hole CY1 was composed upper and lower pillow lava, CY4 constituted sheeted dike complex and gabbro section, and the samples along Akaki river formed from pillow lava to sheeted dike complex. Hole CY2A was composed pillow lava and sheeted dike, drilled near Agrokipia ‘B’ deposit a stockwork type which completely enclosed within the lower pillow lava. The goal of this study is to understand the Boron geochemistry during hydrothermal alteration of the oceanic crust including hydrothermal ore deposit as Agrokipia ‘B’. The average boron contents of each sequence from Troodos ophiolite were pillow lava (63.2ppm), sheeted dike complex (4.5ppm), gabbro section (1.6ppm). But then, those of Oman ophiolite were 7.9ppm, 5.3ppm, 1.7ppm (Yamaoka et al., 2010 submitted). Thus, both of these ophiolites, the vertical profile of boron content decreased with depth, also the boron contents were much richer than fresh-MORB (0.5ppm) (Spivack and Edmond, 1987; Chaussidon and Jambon, 1994). This indicates boron rich of the altered oceanic crust were derived from seawater. And sheeted dike complex and gabbro section were similar value relatively, but pillow lava differed widely. These results may represent the difference of length being submarine, because these ophiolites were generated in deep water of the Tethys sea about 90Ma (Late Cretaceous) (Tilton et al., 1981; Mukasa and Ludden, 1987), and Oman ophiolite was obducted about 70Ma (Lanphere, 1981) but Troodos ophiolite uplifted about 10Ma (Middle Miocene) (Robertson and Woodcock, 1979).

  15. Hydrocarbon analogues of boron clusters - planarity, aromaticity and antiaromaticity

    NASA Astrophysics Data System (ADS)

    Zhai, Hua-Jin; Kiran, Boggavarapu; Li, Jun; Wang, Lai-Sheng

    2003-12-01

    An interesting feature of elemental boron and boron compounds is the occurrence of highly symmetric icosahedral clusters. The rich chemistry of boron is also dominated by three-dimensional cage structures. Despite its proximity to carbon in the periodic table, elemental boron clusters have been scarcely studied experimentally and their structures and chemical bonding have not been fully elucidated. Here we report experimental and theoretical evidence that small boron clusters prefer planar structures and exhibit aromaticity and antiaromaticity according to the Hückel rules, akin to planar hydrocarbons. Aromatic boron clusters possess more circular shapes whereas antiaromatic boron clusters are elongated, analogous to structural distortions of antiaromatic hydrocarbons. The planar boron clusters are thus the only series of molecules other than the hydrocarbons to exhibit size-dependent aromatic and antiaromatic behaviour and represent a new dimension of boron chemistry. The stable aromatic boron clusters may exhibit similar chemistries to that of benzene, such as forming sandwich-type metal compounds.

  16. Theoretical Study of the BF3-Promoted Rearrangement of Oxiranyl N-Methyliminodiacetic Acid Boronates.

    PubMed

    Vallejos, Margarita M; Pellegrinet, Silvina C

    2017-06-02

    The mechanism of the rearrangement of oxiranyl N-methyliminodiacetyl (MIDA) boronates in dicholoromethane has been extensively investigated with density functional theory. Several reaction pathways were examined. Our results revealed that the most-favorable mechanisms for the BF3-promoted rearrangement of 2-phenyl oxiranyl MIDA boronate (1) and 1-phenyl oxiranyl MIDA boronate (24) comprise two steps: ring opening of the epoxide to a carbocation intermediate followed by migration of a MIDA-boryl group (for the reaction of 1) and hydrogen (for the reaction of 24), to give the same BF3-coordinated α-boryl aldehyde in both cases. The first step of the ring opening of the epoxide is the rate-determining step of these reactions. In the rearrangement step for the reaction of 1, the MIDA-boryl group migrates easily, probably because of its electron-rich sp(3)-hybridized boron center. For 24, the most-favorable pathway involves a rare boryl-substituted carbocation. The course of these reactions is mainly controlled by electronic effects, although steric effects are also significant. The higher energy barrier calculated for the unsubstituted oxiranyl MIDA boronate (31) explains the lack of reactivity in the studied BF3-promoted rearrangement.

  17. Fabrication Of Carbon-Boron Reinforced Dry Polymer Matrix Composite Tape

    NASA Technical Reports Server (NTRS)

    Belvin, Harry L.; Cano, Roberto J.; Treasure, Monte; Shahood, Thomas W.

    1999-01-01

    Future generation aerospace vehicles will require specialized hybrid material forms for component structure fabrication. For this reason, high temperature composite prepregs in both dry and wet forms are being developed at NASA Langley Research Center (LaRC). In an attempt to improve compressive properties of carbon fiber reinforced composites, a hybrid carbon-boron tape was developed and used to fabricate composite laminates which were subsequently cut into flexural and compression specimens and tested. The hybrid material, given the designation HYCARB, was fabricated by modifying a previously developed process for the manufacture of dry polymer matrix composite (PMC) tape at LaRC. In this work, boron fibers were processed with IM7/LaRC(TradeMark)IAX poly(amide acid) solution-coated prepreg to form a dry hybrid tape for Automated Tow Placement (ATP). Boron fibers were encapsulated between two (2) layers of reduced volatile, low fiber areal weight poly(amide acid) solution-coated prepreg. The hybrid prepreg was then fully imidized and consolidated into a dry tape suitable for ATP. The fabrication of a hybrid boron material form for tow placement aids in the reduction of the overall manufacturing cost of boron reinforced composites, while realizing the improved compression strengths. Composite specimens were press-molded from the hybrid material and exhibited excellent mechanical properties.

  18. Oxidation of Boron Nitride in Composites

    NASA Technical Reports Server (NTRS)

    Jacobson, Nathan S.

    1998-01-01

    Boron nitride (BN) is a prime candidate for fiber coatings in silicon carbide (SiC) fiber-reinforced SiC matrix composites. The properties of BN allow the fiber to impart beneficial composite properties to the matrix, even at elevated temperatures. The problem with BN is that it is readily attacked by oxygen. Although BN is an internal component of the composite, a matrix crack or pore can create a path for hot oxygen to attack the BN. This type of attack is not well understood. A variety of phenomena have been observed. These include borosilicate glass formation, volatilization of the BN, and under some conditions, preservation of the BN. In this study at the NASA Lewis Research Center, a series of BN materials and BN-containing model composites were methodically examined to understand the various issues dealing with the oxidation of BN in composites. Initial studies were done with a series of monolithic BN materials prepared by hot pressing and chemical vapor deposition (CVD). From these studies, we found that BN showed a strong orientation effect in oxidation and was extremely sensitive to the presence of water vapor in the environment. In addition, CVD material deposited at a high temperature showed much better oxidation behavior than CVD material deposited at a lower temperature.

  19. First-principles simulations of boron diffusion in graphite.

    PubMed

    Suarez-Martinez, I; El-Barbary, A A; Savini, G; Heggie, M I

    2007-01-05

    Boron strongly modifies electronic and diffusion properties of graphite. We report the first ab initio study of boron interaction with the point defects in graphite, which includes structures, thermodynamics, and diffusion. A number of possible diffusion mechanisms of boron in graphite are suggested. We conclude that boron diffuses in graphite by a kick-out mechanism. This mechanism explains the common activation energy, but large magnitude difference, for the rate of boron diffusion parallel and perpendicular to the basal plane.

  20. First-Principles Simulations of Boron Diffusion in Graphite

    SciTech Connect

    Suarez-Martinez, I.; El-Barbary, A. A.; Savini, G.; Heggie, M. I.

    2007-01-05

    Boron strongly modifies electronic and diffusion properties of graphite. We report the first ab initio study of boron interaction with the point defects in graphite, which includes structures, thermodynamics, and diffusion. A number of possible diffusion mechanisms of boron in graphite are suggested. We conclude that boron diffuses in graphite by a kick-out mechanism. This mechanism explains the common activation energy, but large magnitude difference, for the rate of boron diffusion parallel and perpendicular to the basal plane.

  1. On the chemical bonding features in boron containing compounds: a combined QTAIM/ELF topological analysis.

    PubMed

    Alikhani, M Esmaïl

    2013-08-14

    The nature of chemical bonding in four classes of boron-containing compounds has been investigated using two topological approaches: the "quantum theory of atoms in molecules (QTAIM)" and "electron localization function (ELF)". It has been shown that the bonding in these compounds could be described in terms of familiar schemes (covalent single, double or triple bonds, dative bond, etc.) and be rationalized from the QTAIM tools. The ELF analysis is the bridge between two worlds: classical donor-acceptor and delocalization in the one hand, and the quantum chemical concepts obtained from the charge and its Laplacian topology. Particularly, we have shown that: (1) in the case of boron-boron bonding, although the V(B,B) basins are similar to the V(C,C) ones, but the V(B,B) population is always smaller than the corresponding V(C,C). (2) In the planar tetracoordinate boron species, each boron atom is characterized by three chemical bonds despite four neighboring atoms. (3). In the [RuH2(η(2):η(2)-H2BMes)(PCy3)2] compound, the B-Ru bonding belongs to the closed-shell interaction, and there is no BCP between the hydrogen bridge atoms (H(B)) and the ruthenium center despite the close contact of the atoms. (4) In the case of the XH···M···HX hydrogen bonding, we found a complex bonding mode involving not only the two hydrogen atoms, but also the two boron atoms. The presence of an RCP in the center of the B-H-Cr-H-B five-membered cycle confers to the compound the potential to evolve under perturbation.

  2. Autoionizing states of atomic boron

    NASA Astrophysics Data System (ADS)

    Argenti, Luca; Moccia, Roberto

    2016-04-01

    We present a B -spline K -matrix method for three-active-electron atoms in the presence of a polarizable core, with which it is possible to compute multichannel single-ionization scattering states with good accuracy. We illustrate the capabilities of the method by computing the parameters of several autoionizing states of the boron atom, with S2e, 2,o2P and D2e symmetry, up to at least the 2 p2(1S) excitation threshold of the B ii parent ion, as well as selected portions of the photoionization cross section from the ground state. Our results exhibit remarkable gauge consistency, they significantly extend the existing sparse record of data for the boron atom, and they are in good agreement with the few experimental and theoretical data available in the literature. These results open the way to extend to three-active-electron systems the spectral analysis of correlated wave packets in terms of accurate scattering states that has already been demonstrated for two-electron atoms in Argenti and Lindroth [Phys. Rev. Lett. 105, 053002 (2010), 10.1103/PhysRevLett.105.053002].

  3. Composite boron nitride neutron detectors

    NASA Astrophysics Data System (ADS)

    Roth, M.; Mojaev, E.; Khakhan, O.; Fleider, A.; Dul`kin, E.; Schieber, M.

    2014-09-01

    Single phase polycrystalline hexagonal boron nitride (BN) or mixed with boron carbide (BxC) embedded in an insulating polymeric matrix acting as a binder and forming a composite material as well as pure submicron size polycrystalline BN has been tested as a thermal neutron converter in a multilayer thermal neutron detector design. Metal sheet electrodes were covered with 20-50 μm thick layers of composite materials and assembled in a multi-layer sandwich configuration. High voltage was applied to the metal electrodes to create an interspacing electric field. The spacing volume could be filled with air, nitrogen or argon. Thermal neutrons were captured in converter layers due to the presence of the 10B isotope. The resulting nuclear reaction produced α-particles and 7Li ions which ionized the gas in the spacing volume. Electron-ion pairs were collected by the field to create an electrical signal proportional to the intensity of the neutron source. The detection efficiency of the multilayer neutron detectors is found to increase with the number of active converter layers. Pixel structures of such neutron detectors necessary for imaging applications and incorporation of internal moderator materials for field measurements of fast neutron flux intensities are discussed as well.

  4. High fluence boron implantation into polymers

    NASA Astrophysics Data System (ADS)

    Vacik, J.; Cervena, J.; Fink, D.; Klett, R.; Hnatowicz, V.; Popok, V.; Odzhaev, V.

    100 keV B+ ions are implanted at high fluence into three polymers of technological importance and into a polymeric mixture, respectively. The boron depth distributions are measured by the neutron depth profiling technique. It is shown that the boron atoms redistribute after their implantation according to the nuclear (collisional) energy transfer distribution. This contrasts to low fluence implantation, where the boron atoms redistribute according to their electronic energy transfer distributions. Subsequently, the samples are annealed isochronally. The change of the boron depth profiles with annealing temperature is then evaluated to determine the diffusional, trapping and detrapping behavior of the boron atoms. At, or slightly above room temperature, intrinsic boron impurities of the examined polymer foils become mobile and getter in the ion-implanted region. At higher temperatures, the thermal desorption spectra show a nearly continuous desorption of both the implanted and gettered boron, with no pronounced desorption peaks. Due to the high polymeric destruction yield, the different polymers show little difference in their desorption behavior.

  5. Where Boron? Mars Rover Detects It

    NASA Image and Video Library

    2016-12-13

    This map shows the route driven by NASA's Curiosity Mars rover (blue line) and locations where the rover's Chemistry and Camera (ChemCam) instrument detected the element boron (dots, colored by abundance of boron according to the key at right). The main map shows the traverse from landing day (Sol 0) in August 2012 to the rover's location in September 2016, with boron detections through September 2015. The inset at upper left shows a magnified version of the most recent portion of that traverse, with boron detections during that portion. Overlapping dots represent cases when boron was detected in multiple ChemCam observation points in the same target and non-overlapping dots represent cases where two different targets in the same location have boron. Most of the mission's detections of boron have been made in the most recent seven months (about 200 sols) of the rover's uphill traverse. The base image for the map is from the High Resolution Imaging Science Experiment (HiRISE) camera on NASA's Mars Reconnaissance Orbiter. North is up. The scale bar at lower right represents one kilometer (0.62 mile). http://photojournal.jpl.nasa.gov/catalog/PIA21150

  6. Properties of vacuum-evaporated boron films

    NASA Technical Reports Server (NTRS)

    Feakes, F.

    1973-01-01

    The work on the properties of thin boron films made by vacuum evaporation of elemental boron using an electron beam as the energy source is reported. The program aimed at characterizing the properties of vacuum evaporated films. The work was directed toward those variables considered to be important in affecting the tensile strength of the boron films. In general, the thickness of the films was less than 0.002 in. The temperature of the substrate on which the boron was condensed was found to be most important. Three distinctly different forms of boron deposit were produced. Although the transition temperature was not sharply defined, at substrate temperatures of less than approximately 600 deg C the boron deposits were amorphous to X-ray. If the substrate were highly polished, the deposits were black and mirror-like. For substrates with coefficients of thermal expansion close to that of boron, the deposits were then continuous and uncracked. The studies suggest that the potential continues to exist for film-type composites to have both high strength and high modulus.

  7. Combustion synthesis of novel boron carbide

    NASA Astrophysics Data System (ADS)

    Harini, R. Saai; Manikandan, E.; Anthonysamy, S.; Chandramouli, V.; Eswaramoorthy, D.

    2013-02-01

    The solid-state boron carbide is one of the hardest materials known, ranking third behind diamond and cubic boron nitride. Boron carbide (BxCx) enriched in the 10B isotope is used as a control rod material in the nuclear industry due to its high neutron absorption cross section and other favorable physico-chemical properties. Conventional methods of preparation of boron carbide are energy intensive processes accompanied by huge loss of boron. Attempts were made at IGCAR Kalpakkam to develop energy efficient and cost effective methods to prepare boron carbide. The products of the gel combustion and microwave synthesis experiments were characterized for phase purity by XRD. The carbide formation was ascertained using finger-print spectroscopy of FTIR. Samples of pyrolized/microwave heated powder were characterized for surface morphology using SEM. The present work shows the recent advances in understanding of structural and chemical variations in boron carbide and their influence on morphology, optical and vibrational property results discussed in details.

  8. Deep Earthquakes.

    ERIC Educational Resources Information Center

    Frohlich, Cliff

    1989-01-01

    Summarizes research to find the nature of deep earthquakes occurring hundreds of kilometers down in the earth's mantle. Describes further research problems in this area. Presents several illustrations and four references. (YP)

  9. Conductivity of boron-doped polycrystalline diamond films: influence of specific boron defects

    NASA Astrophysics Data System (ADS)

    Ashcheulov, P.; Šebera, J.; Kovalenko, A.; Petrák, V.; Fendrych, F.; Nesládek, M.; Taylor, A.; Vlčková Živcová, Z.; Frank, O.; Kavan, L.; Dračínský, M.; Hubík, P.; Vacík, J.; Kraus, I.; Kratochvílová, I.

    2013-10-01

    The resistivity of boron doped polycrystalline diamond films changes with boron content in a very complex way with many unclear factors. From the large number of parameters affecting boron doped polycrystalline diamond film's conductivity we focused on the role of boron atoms inside diamond grains in terms of boron contribution to the continuum of diamond electronic states. Using a combination of theoretical and experimental techniques (plane-wave Density Functional Theory, Neutron Depth Profiling, resistivity and Hall effect measurements, Atomic Force Microscopy and Raman spectroscopy) we studied a wide range of B defect parameters - the boron concentration, location, structure, free hole concentration and mobility. The main goal and novelty of our work was to find the influence of B defects (structure, interactions, charge localisation and spins) in highly B-doped diamonds - close or above the metal-insulator transition - on the complex material charge transport mechanisms.

  10. JAGUAR Procedures for Detonation Behavior of Explosives Containing Boron

    NASA Astrophysics Data System (ADS)

    Stiel, Leonard; Baker, Ernest; Capellos, Christos

    2009-06-01

    The JAGUAR product library was expanded to include boron and boron containing products. Relationships of the Murnaghan form for molar volumes and derived properties were implemented in JAGUAR. Available Hugoniot and static volumertic data were analyzed to obtain constants of the Murnaghan relationship for solid boron, boron oxide, boron nitride, boron carbide, and boric acid. Experimental melting points were also utilized with optimization procedures to obtain the constants of the volumetric relationships for liquid boron and boron oxide. Detonation velocities for HMX - boron mixtures calculated with these relationships using JAGUAR are in closer agreement with literature values at high initial densities for inert (unreacted) boron than with the completely reacted metal. These results indicate that boron mixtures may exhibit eigenvalue detonation behavior, as observed by aluminized combined effects explosives, with higher detonation velocities than would be achieved by a classical Chapman-Jouguet detonation. Analyses of calorimetric measurements for RDX - boron mixtures indicate that at high boron contents the formation of side products, including boron nitride and boron carbide, inhibits the energy output obtained from the detonation of the formulation.

  11. Thermodynamic limitation on boron energy realization in ramjet propulsion

    NASA Astrophysics Data System (ADS)

    Gany, Alon

    2014-05-01

    This study addresses a specific boron combustion aspect, revealing that thermodynamic conditions associated with highly boron-loaded ramjet combustors, may lead to blockage of the reaction between boron and air, causing termination of the combustion process, incomplete chemical reaction, and only partial realization of the potential boron combustion energy. Sustained boron combustion may take place when the evaporation rate of the protective liquid boron oxide layer B2O3(l) on the boron particles exceeds its generation rate by the oxidation reaction, typically at temperatures above 1900-2000 K. However, if the actual partial pressure of gaseous boron oxide B2O3(g) produced in the combustion process attains the equilibrium vapor pressure of boron oxide at the conditions existing in the combustion chamber, condensation of the boron oxide to form a liquid layer on the boron particle surfaces may take place, extinguishing the particle combustion by blocking the reaction between the boron and the surrounding oxidizing gas. The study predicts conditions for blockage and incomplete boron combustion over a range of chamber pressures and temperatures. This effect may be characteristic to combustors employing boron-containing fuels, but may not be encountered in the combustion of individual boron particles in air.

  12. X-ray diffraction study of boron produced by pyrolysis of boron tribromide

    NASA Astrophysics Data System (ADS)

    Rosenberg, David

    The goal of this research was to determine the composition of boron deposits produced by pyrolysis of boron tribromide, and to use the results to (a) determine the experimental conditions (reaction temperature, etc.) necessary to produce alpha-rhombohedral boron and (b) guide the development/refinement of the pyrolysis experiments such that large, high purity crystals of alpha-rhombohedral boron can be produced with consistency. Developing a method for producing large, high purity alpha-rhombohedral boron crystals is of interest because such crystals could potentially be used to achieve an alpha-rhombohedral boron based neutron detector design (a solid-state detector) that could serve as an alternative to existing neutron detector technologies. The supply of neutron detectors in the United States has been hampered for a number of years due to the current shortage of helium-3 (a gas used in many existing neutron detector technologies); the development of alternative neutron detector technology such as an alpha-rhombohedral boron based detector would help provide a more sustainable supply of neutron detectors in this country. In addition, the prospect/concept of an alpha-rhombohedral boron based neutron detector is attractive because it offers the possibility of achieving a design that is smaller, longer life, less power consuming, and potentially more sensitive than existing neutron detectors. The main difficulty associated with creating an alpha-rhombohedral boron based neutron detector is that producing large, high purity crystals of alpha-rhombohedral boron is extremely challenging. Past researchers have successfully made alpha-rhombohedral boron via a number of methods, but no one has developed a method for consistently producing large, high purity crystals. Alpha-rhombohedral boron is difficult to make because it is only stable at temperatures below around 1100-1200 °C, its formation is very sensitive to impurities, and the conditions necessary for its

  13. Crystallization of Beryllium-Boron Metallic Glasses

    SciTech Connect

    Jankowski, A F; Wall, M A; Nieh, T G

    2002-02-14

    Prior studies of evaporation and sputter deposition show that the grain size of pure beryllium can be dramatically refined through the incorporation of metal impurities. Recently, the addition of boron at a concentration greater than 11% is shown to serve as a glassy phase former in sputter deposited beryllium. Presently, thermally induced crystallization of the beryllium-boron metallic glass is reported. The samples are characterized during an in-situ anneal treatment with bright field imaging and electron diffraction using transmission electron microscopy. A nanocrystalline structure evolves from the annealed amorphous phase and the crystallization temperature is affected by the boron concentration.

  14. Boron-10 Lined Proportional Counter Wall Effects

    SciTech Connect

    Siciliano, Edward R.; Kouzes, Richard T.

    2012-05-01

    The Department of Energy Office of Nuclear Safeguards (NA-241) is supporting the project 'Coincidence Counting With Boron-Based Alternative Neutron Detection Technology' at Pacific Northwest National Laboratory (PNNL) for development of an alternative neutron coincidence counter. The goal of this project is to design, build and demonstrate a boron-lined proportional tube based system in the configuration of a coincidence counter. This report provides information about how variations in proportional counter radius and gas pressure in a typical coincident counter design might affect the observed signal from boron-lined tubes. A discussion comparing tubes to parallel plate counters is also included.

  15. Boron Nitride Nanoribbons: Synthesis and Future Directions

    NASA Astrophysics Data System (ADS)

    Gibb, Ashley; Erikson, Kris; Sinitskii, Alex; Rousseas, Michael; Alem, Nasim; Tour, James; Zettl, Alex

    2012-02-01

    Boron Nitride Nanoribbons (BNNR) have been theorized to have many interesting electrical and magnetic properties and edge states, but these characteristics have not been experimentally verified due to challenges in synthesis and purification. We have produced BNNRs by longitudinally splitting boron nitride nanotubes (BNNT) using potassium vapor as an intercalant. Due to the strong interactions between boron nitride sheets, separation of nanoribbons from their parent tubes is challenging. We have used various solvent systems to assist with separation of the ribbons with the goal of probing their properties.

  16. Boron distribution in sintered silicon carbide

    SciTech Connect

    Carter, W.D.; Holloway, P.H. ); White, C.; Clausing, R. )

    1988-01-01

    Boron concentrations on intergranular and transgranular fracture areas in sintered SiC were measured; {alpha}-SiC grains oriented parallel to the fracture surface would fracture at the {alpha}-{beta} interphase boundary. Auger electron spectroscopy showed that boron does not segregate to these boundaries in sintered SiC. This conclusion was generalized to include the other types of SiC grain boundaries. The absence of boron at grain boundaries suggests that its role in sintering is not to enhance diffusion rates. Chemical reactions and free surface segregation, which may explain the increased densification of SiC when B is present, are discussed.

  17. Developments in boron magnetic resonance imaging (MRI)

    SciTech Connect

    Schweizer, M.

    1995-11-01

    This report summarizes progress during the past year on maturing Boron-11 magnetic resonance imaging (MRI) methodology for noninvasive determination of BNCT agents (BSH) spatially in time. Three major areas are excerpted: (1) Boron-11 MRI of BSH distributions in a canine intracranial tumor model and the first human glioblastoma patient, (2) whole body Boron-11 MRI of BSH pharmacokinetics in a rat flank tumor model, and (3) penetration of gadolinium salts through the BBB as a function of tumor growth in the canine brain.

  18. Characterization of boron tolerant bacteria isolated from a fly ash dumping site for bacterial boron remediation.

    PubMed

    Edward Raja, Chellaiah; Omine, Kiyoshi

    2013-08-01

    Boron is an essential micronutrient for plants, but can above certain concentrations be toxic to living organisms. A major environmental concern is the removal of boron from contaminated water and fly ash. For this purpose, the samples were collected from a fly ash dumping site, Nagasaki prefecture, Japan. The chemical characteristics and heavy metal concentration of the samples were performed by X-ray fluorescent analysis and leaching test. For bacterial analysis, samples were collected in sterile plastic sheets and isolation was carried out by serial dilution method. The boron tolerant isolates that showed values of maximum inhibitory concentration toward boron ranging from 100 to 260 mM level were screened. Based on 16S rRNA sequencing and phylogenetic analysis, the isolates were most closely related to the genera Bacillus, Lysinibacillus, Microbacterium and Ralstonia. The boron tolerance of these strains was also associated with resistant to several heavy metals, such as As (III), Cr (VI), Cd, Cu, Pb, Ni, Se (III) and Zn. Indeed, these strains were arsenic oxidizing bacteria confirmed by silver nitrate test. These strains exhibited their salt resistances ranging from 4 to 15 % were determined in Trypticase soy agar medium. The boron tolerant strains were capable of removing 0.1-2.0 and 2.7-3.7 mg l(-1) boron from the medium and fly ash at 168 h. Thus, we have successfully identified the boron tolerant and removal bacteria from a fly ash dumping site for boron remediation.

  19. Mathematical modeling of boron diffusion from boron oxide glass film sources

    SciTech Connect

    Yeckel, A.; Middleman, S.

    1988-09-01

    Mathematical models are developed to examine two alternative means of boron doping from boron-rich glass films. For the planar source diffusion system, in which boron diffusion and glass film growth occur simultaneously at high temperature (900-1200/sup 0/C), glass film growth rates and the degree of doping achieved are predicted. In most cases, the solubility limit of boron in silicon is attained at the silicon surface. It is found that depletion of the boron source wafers used in this process may be slowed considerably by their removal from the reactor after a short time. Model predictions for an alternative method, in which the glass film is pregrown at low temperature (300/sup 0/C) and the diffusion subsequently performed at high temperature, demonstrate a strong dependence of the boron surface concentration on the initial boron content in the pregrown glass film, for concentrations of boron near the solubility limit. The conditions for which a masking film of SiO/sub 2/ is insufficient to prevent boron diffusion into silicon, known as mask failure, are also predicted by the models.

  20. Borocaptate sodium: a potential boron delivery compound for boron neutron capture therapy evaluated in dogs with spontaneous intracranial tumors.

    PubMed Central

    Kraft, S L; Gavin, P R; DeHaan, C E; Leathers, C W; Bauer, W F; Miller, D L; Dorn, R V

    1992-01-01

    Borocaptate sodium (Na2B12H11SH) is a boron-carrying compound under consideration for use in boron neutron capture therapy. The biodistribution of boron from borocaptate sodium administration will partly determine boron neutron capture therapy efficacy and normal tissue radiation tolerance. The biodistribution of boron was determined in 30 dogs with spontaneous intracranial tumors at 2, 6, or 12 hr after intravenous borocaptate sodium infusion. Blood and tissue boron concentrations were measured using inductively coupled plasma atomic emission spectroscopy. Mean tumor boron concentration (mean +/- standard error) was 35.9 +/- 4.6 (n = 15), 22.5 +/- 6.0 (n = 9), and 7.0 +/- 1.1 micrograms of boron per g (n = 6) at 2, 6, and 12 hr, respectively, after borocaptate sodium infusion. Peritumor boron concentrations were elevated above that of normal brain in half of the dogs. Normal brain boron concentration (mean +/- standard error) was 4.0 +/- 0.5, 2.0 +/- 0.4, and 2.0 +/- 0.3 micrograms of boron per g at 2, 6, and 12 hr after infusion, respectively. Some cranial and systemic tissues, and blood, had high boron concentration relative to tumor tissue. Geometric dose sparing should partly offset these relatively high normal tissue and blood concentrations. Borocaptate sodium biodistribution is favorable because tumor boron concentrations of recommended magnitude for boron neutron capture therapy were obtained and there was a high tumor-to-normal brain boron concentration ratio. PMID:1465427

  1. The Catalog of Event Data of the Operational Deep-ocean Assessment and Reporting of Tsunamis (DART) Stations at the National Data Buoy Center

    NASA Astrophysics Data System (ADS)

    Bouchard, R.; Locke, L.; Hansen, W.; Collins, S.; McArthur, S.

    2007-12-01

    DART systems are a critical component of the tsunami warning system as they provide the only real-time, in situ, tsunami detection before landfall. DART systems consist of a surface buoy that serves as a position locater and communications transceiver and a Bottom Pressure Recorder (BPR) on the seafloor. The BPR records temperature and pressure at 15-second intervals to a memory card for later retrieval for analysis and use by tsunami researchers, but the BPRs are normally recovered only once every two years. The DART systems also transmit subsets of the data, converted to an estimation of the sea surface height, in near real-time for use by the tsunami warning community. These data are available on NDBC's webpages, http://www.ndbc.noaa.gov/dart.shtml. Although not of the resolution of the data recorded to the BPR memory card, the near real-time data have proven to be of value in research applications [1]. Of particular interest are the DART data associated with geophysical events. The DART BPR continuously compares the measured sea height with a predicted sea-height and when the difference exceeds a threshold value, the BPR goes into Event Mode. Event Mode provides an extended, more frequent near real-time reporting of the sea surface heights for tsunami detection. The BPR can go into Event Mode because of geophysical triggers, such as tsunamis or seismic activity, which may or may not be tsunamigenic. The BPR can also go into Event Mode during recovery of the BPR as it leaves the seafloor, or when manually triggered by the Tsunami Warning Centers in advance of an expected tsunami. On occasion, the BPR will go into Event Mode without any associated tsunami or seismic activity or human intervention and these are considered "False'' Events. Approximately one- third of all Events can be classified as "False". NDBC is responsible for the operations, maintenance, and data management of the DART stations. Each DART station has a webpage with a drop-down list of all

  2. Development of Conductive Boron-Doped Diamond Electrode: A microscopic, Spectroscopic, and Voltammetric Study

    PubMed Central

    Bennet, Kevin E.; Lee, Kendall H.; Kruchowski, James N.; Chang, Su-Youne; Marsh, Michael P.; Orsow, Alexander A. Van; Paez, Aurelio; Manciu, Felicia S.

    2013-01-01

    Building on diamond characteristics such as hardness, chemical inertness and low electron emission threshold voltage, the current microscopic, spectroscopic and voltammetric investigations are directed towards improving the properties of electrode coating materials for their future use in clinical studies of deep brain stimulation via fast-scan cyclic voltammetry (FSCV). In this study we combine the capabilities of confocal Raman mapping in providing detailed and accurate analysis of local distributions of material constituents in a series of boron-doped polycrystalline diamond films grown by chemical vapor deposition, with information from the more conventional techniques of scanning electron microscopy (SEM) and infrared absorption spectroscopy. Although SEM images show a uniform distribution of film crystallites, they have the limitation of being unable to differentiate the distribution of boron in the diamond. Values of 1018–1021 atoms/cm3 of boron content have been estimated from the absorption coefficient of the 1290 cm−1 infrared absorption band and from the 500 cm−1 Raman vibration. The observed accumulation of boron atoms and carbon sp2 impurities at the grain boundaries suggests that very high doping levels do not necessarily contribute to improvement of the material’s conductivity, corroborating with voltammetric data. FSCV results also indicate an enhanced stability of analyte detection. PMID:28788420

  3. Development of Conductive Boron-Doped Diamond Electrode: A microscopic, Spectroscopic, and Voltammetric Study.

    PubMed

    Bennet, Kevin E; Lee, Kendall H; Kruchowski, James N; Chang, Su-Youne; Marsh, Michael P; Van Orsow, Alexander A; Paez, Aurelio; Manciu, Felicia S

    2013-12-06

    Building on diamond characteristics such as hardness, chemical inertness and low electron emission threshold voltage, the current microscopic, spectroscopic and voltammetric investigations are directed towards improving the properties of electrode coating materials for their future use in clinical studies of deep brain stimulation via fast-scan cyclic voltammetry (FSCV). In this study we combine the capabilities of confocal Raman mapping in providing detailed and accurate analysis of local distributions of material constituents in a series of boron-doped polycrystalline diamond films grown by chemical vapor deposition, with information from the more conventional techniques of scanning electron microscopy (SEM) and infrared absorption spectroscopy. Although SEM images show a uniform distribution of film crystallites, they have the limitation of being unable to differentiate the distribution of boron in the diamond. Values of 10(18)-10(21) atoms/cm³ of boron content have been estimated from the absorption coefficient of the 1290 cm(-1) infrared absorption band and from the 500 cm(-1) Raman vibration. The observed accumulation of boron atoms and carbon sp² impurities at the grain boundaries suggests that very high doping levels do not necessarily contribute to improvement of the material's conductivity, corroborating with voltammetric data. FSCV results also indicate an enhanced stability of analyte detection.

  4. Influence of oxygen on defect production in electron-irradiated, boron-doped silicon

    NASA Technical Reports Server (NTRS)

    Deangelis, H. M.; Drevinsky, P. J.

    1984-01-01

    Deep level transient spectroscopy (DLTS) measurements were made on float-zone and crucible-grown, boron-doped silicon irradiated with 1-MeV electrons. The minority carrier trap attributed to a boron-related state, was not seen in low-resistivity, float-zone silicon. However, a new majority carrier trap was observed in these samples. In the case of more lightly doped material the minority carrier trap was present, and its introduction rate was lower in float-zone than in crucible-grown silicon. For 1- and 10-ohm-cm float-zone material that was oxidized during processing, the introduction rates for this trap were comparable to those for crucible-grown silicon. This behavior indicates that the minority carrier trap involves oxygen and that it may be due to a boron-oxygen complex. The majority carrier trap seen in heavily doped, float-zone silicon may also involve boron but not oxygen. Observed trap concentrations suggest that oxygen content in the regions examined by DLTS is affected by processing techniques. Other differences were observed in defect production and annealing behavior of electron-irradiated, float-zone and crucible-grown silicon.

  5. Radiation tolerance of boron doped dendritic web silicon solar cells

    NASA Technical Reports Server (NTRS)

    Rohatgi, A.

    1980-01-01

    The potential of dendritic web silicon for giving radiation hard solar cells is compared with the float zone silicon material. Solar cells with n(+)-p-P(+) structure and approximately 15% (AMl) efficiency were subjected to 1 MeV electron irradiation. Radiation tolerance of web cell efficiency was found to be at least as good as that of the float zone silicon cell. A study of the annealing behavior of radiation-induced defects via deep level transient spectroscopy revealed that E sub v + 0.31 eV defect, attributed to boron-oxygen-vacancy complex, is responsible for the reverse annealing of the irradiated cells in the temperature range of 150 to 350 C.

  6. KENNEDY SPACE CENTER, FLA. - Wildflowers resembling petunias stand out against the deep green of the marsh foliage at KSC, which shares a boundary with the National Merritt Island Wildlife Refuge. Approximately one half of the Refuge's 140,000 acres consists of brackish estuaries and marshes. The remaining lands consist of coastal dunes, scrub oaks, pine forests and flatwoods, and palm and oak hammocks.

    NASA Image and Video Library

    2003-07-29

    KENNEDY SPACE CENTER, FLA. - Wildflowers resembling petunias stand out against the deep green of the marsh foliage at KSC, which shares a boundary with the National Merritt Island Wildlife Refuge. Approximately one half of the Refuge's 140,000 acres consists of brackish estuaries and marshes. The remaining lands consist of coastal dunes, scrub oaks, pine forests and flatwoods, and palm and oak hammocks.

  7. Fragment approach to the electronic structure of τ -boron allotrope

    NASA Astrophysics Data System (ADS)

    Karmodak, Naiwrit; Jemmis, Eluvathingal D.

    2017-04-01

    The presence of nonconventional bonding features is an intriguing part of elemental boron. The recent addition of τ boron to the family of three-dimensional boron allotropes is no exception. We provide an understanding of the electronic structure of τ boron using a fragment molecular approach, where the effect of symmetry reduction on skeletal bands of B12 and the B57 fragments are examined qualitatively by analyzing the projected density of states of these fragments. In spite of the structural resemblance to β boron, the reduction of symmetry from a rhombohedral space group to the orthorhombic one destabilizes the bands and reduces the electronic requirements. This suggests the presence of the partially occupied boron sites, as seen for a β boron unit cell, and draws the possibility for the existence of different energetically similar polymorphs. τ boron has a lower binding energy than β boron.

  8. Boron dose determination for BNCT using Fricke and EPR dosimetry

    SciTech Connect

    Wielopolski, L.; Ciesielski, B.

    1995-02-01

    In Boron Neutron Capture Therapy (BNCT) the dominant dose delivered to the tumor is due to {alpha} and {sup 7}Li charged particles resulting from a neutron capture by {sup 10}B and is referred to herein as the boron dose. Boron dose is directly attributable to the following two independent factors, one boron concentration and the neutron capture energy dependent cross section of boron, and two the energy spectrum of the neutrons that interact with boron. The neutron energy distribution at a given point is dictated by the incident neutron energy distribution, the depth in tissue, geometrical factors such as beam size and patient`s dimensions. To account for these factors can be accommodated by using Monte Carlo theoretical simulations. However, in conventional experimental BNCT dosimetry, e.g., using TLDs or ionization chambers, it is only possible to estimate the boron dose. To overcome some of the limitations in the conventional dosimetry, modifications in ferrous sulfate dosimetry (Fricke) and Electron Paramagnetic Resonance (EPR) dosimetry in alanine, enable to measure specifically boron dose in a mixed gamma neutron radiation fields. The boron dose, in either of the dosimeters, is obtained as a difference between measurements with boronated and unboronated dosimeters. Since boron participates directly in the measurements, the boron dosimetry reflects the true contribution, integral of the neutron energy spectrum with boron cross section, of the boron dose to the total dose. Both methods are well established and used extensively in dosimetry, they are presented briefly here.

  9. Lateral carrier confinement of GaN-based vertical-cavity surface-emitting diodes using boron ion implantation

    NASA Astrophysics Data System (ADS)

    Hamaguchi, Tatsushi; Nakajima, Hiroshi; Ito, Masamichi; Mitomo, Jugo; Satou, Susumu; Fuutagawa, Noriyuki; Narui, Hironobu

    2016-12-01

    Boron ion implantation, which is used for confining carriers in gallium nitride (GaN)-based vertical-cavity surface-emitting laser diodes (VCSELs), was studied. Detailed analysis indicated that boron ion implantation of GaN increases GaN’s absorption coefficient from zero to 800 cm-1 and its refractive index from 2.45 to 2.51 at the surface of the wafer at a wavelength of 453 nm. The depth profile of boron obtained by secondary ion mass spectroscopy (SIMS) showed an exponential decrease toward the bottom of the wafer. Assuming that the changes in optical parameters caused by implantation are proportional to the concentration of boron in GaN, the boron ion implantation applied to GaN-VCSELs causes optical absorption of 0.04% per round trip in the cavity and extends the light path of the cavity by 2.2 nm, both of which apparently have negligible impact on the operation of GaN-VCSELs. The implanted boron ions pass through the active regions, introducing non-radiative recombination centers at the edges of those active regions made of InGaN multi-quantum wells, which, however, does not cause significant current injection loss.

  10. Boron-Filled Hybrid Carbon Nanotubes.

    PubMed

    Patel, Rajen B; Chou, Tsengming; Kanwal, Alokik; Apigo, David J; Lefebvre, Joseph; Owens, Frank; Iqbal, Zafar

    2016-07-27

    A unique nanoheterostructure, a boron-filled hybrid carbon nanotube (BHCNT), has been synthesized using a one-step chemical vapor deposition process. The BHCNTs can be considered to be a novel form of boron carbide consisting of boron doped, distorted multiwalled carbon nanotubes (MWCNTs) encapsulating boron nanowires. These MWCNTs were found to be insulating in spite of their graphitic layered outer structures. While conventional MWCNTs have great axial strength, they have weak radial compressive strength, and do not bond well to one another or to other materials. In contrast, BHCNTs are shown to be up to 31% stiffer and 233% stronger than conventional MWCNTs in radial compression and have excellent mechanical properties at elevated temperatures. The corrugated surface of BHCNTs enables them to bond easily to themselves and other materials, in contrast to carbon nanotubes (CNTs). BHCNTs can, therefore, be used to make nanocomposites, nanopaper sheets, and bundles that are stronger than those made with CNTs.

  11. Boron-Filled Hybrid Carbon Nanotubes

    PubMed Central

    Patel, Rajen B.; Chou, Tsengming; Kanwal, Alokik; Apigo, David J.; Lefebvre, Joseph; Owens, Frank; Iqbal, Zafar

    2016-01-01

    A unique nanoheterostructure, a boron-filled hybrid carbon nanotube (BHCNT), has been synthesized using a one-step chemical vapor deposition process. The BHCNTs can be considered to be a novel form of boron carbide consisting of boron doped, distorted multiwalled carbon nanotubes (MWCNTs) encapsulating boron nanowires. These MWCNTs were found to be insulating in spite of their graphitic layered outer structures. While conventional MWCNTs have great axial strength, they have weak radial compressive strength, and do not bond well to one another or to other materials. In contrast, BHCNTs are shown to be up to 31% stiffer and 233% stronger than conventional MWCNTs in radial compression and have excellent mechanical properties at elevated temperatures. The corrugated surface of BHCNTs enables them to bond easily to themselves and other materials, in contrast to carbon nanotubes (CNTs). BHCNTs can, therefore, be used to make nanocomposites, nanopaper sheets, and bundles that are stronger than those made with CNTs. PMID:27460526

  12. Ni doping of semiconducting boron carbide

    SciTech Connect

    Hong, Nina; Liu Jing; Adenwalla, S.; Langell, M. A.; Kizilkaya, Orhan

    2010-01-15

    The wide band gap, temperature stability, high resistivity, and robustness of semiconducting boron carbide make it an attractive material for device applications. Undoped boron carbide is p type; Ni acts as a n-type dopant. Here we present the results of controlled doping of boron carbide with Ni on thin film samples grown using plasma enhanced chemical vapor deposition. The change in the dopant concentration within the thin film as a function of the dopant flow rate in the precursor gas mixture was confirmed by x-ray photoelectron spectroscopy measurements; with increasing dopant concentration, current-voltage (I-V) curves clearly establish the trend from p-type to n-type boron carbide.

  13. Bipolaron Hopping Conduction in Boron Carbides

    SciTech Connect

    ASELAGE, TERRENCE L.; EMIN, D.; MCCREADY, STEVEN S.

    1999-09-20

    The electrical conductivities of boron carbides, B{sub 12+x}C{sub 3{minus}x} with 0.1 < x < 1.7, between 300 and 1200K suggest the hopping of a nearly temperature-independent density of small (bi)polarons. The activation energies of the nobilities are low, {approx} 0.16 eV, and are nearly independent of the composition. At lower temperatures, conductivities have non-Arrhenius temperature dependencies and strong sensitivity to carbon concentration. Percolative aspects of low-temperature hopping are evident in this sensitivity to composition. Boron carbides' Seebeck coefficients are anomalous in that (1) they are much larger than expected from boron carbides' large carrier densities and (2) they depend only weakly on the carrier density. Carrier-induced softening of local vibrations gives contributions to the Seebeck coefficient that mirror the magnitudes and temperature dependencies found in boron carbides.

  14. Boron Neutron Capture Therapy - A Literature Review

    PubMed Central

    Nedunchezhian, Kavitaa; Thiruppathy, Manigandan; Thirugnanamurthy, Sarumathi

    2016-01-01

    Boron Neutron Capture Therapy (BNCT) is a radiation science which is emerging as a hopeful tool in treating cancer, by selectively concentrating boron compounds in tumour cells and then subjecting the tumour cells to epithermal neutron beam radiation. BNCT bestows upon the nuclear reaction that occurs when Boron-10, a stable isotope, is irradiated with low-energy thermal neutrons to yield α particles (Helium-4) and recoiling lithium-7 nuclei. A large number of 10 Boron (10B) atoms have to be localized on or within neoplastic cells for BNCT to be effective, and an adequate number of thermal neutrons have to be absorbed by the 10B atoms to maintain a lethal 10B (n, α) lithium-7 reaction. The most exclusive property of BNCT is that it can deposit an immense dose gradient between the tumour cells and normal cells. BNCT integrates the fundamental focusing perception of chemotherapy and the gross anatomical localization proposition of traditional radiotherapy. PMID:28209015

  15. Boron strengthening in FeAl

    SciTech Connect

    Baker, I.; Li, X.; Xiao, H.; Klein, O.; Nelson, C.; Carleton, R.L.; George, E.P.

    1998-11-01

    The effect of boron on the strength of B2-structured FeAl is considered as a function of composition, grain size and temperature. Boron does not affect the concentrations of antisite atoms or vacancies present, with the former increasing and the latter decreasing with increasing deviation from the stoichiometric composition. When vacancies are absent, the strength increase per at. % B per unit lattice strain, {Delta}{sigma}/({Delta}c x {epsilon}) increases with increasing aluminum concentration, but when vacancies are present (>45 at. % Al), {Delta}{sigma}/({Delta}c x {epsilon}) decreases again. Boron increases grain size strengthening in FeAl. B strengthening is roughly independent of temperature up to the yield strength peak but above the point, when diffusion-assisted deformation occurs, boron strengthening increases dramatically.

  16. New approach to obtain boron selective emitters

    SciTech Connect

    Moehlecke, A.; Luque, A.

    1994-12-31

    Selective emitters, used in high efficiency solar cells, need a series of oxidations and photolithographic steps that render the process more expensive. In this paper, a new way to make selective emitters using boron is presented. The main feature of this approach is to save oxide growths and photolithographic processes and it is based on the property of boron doped silicon surfaces to be resistant to anisotropic etchings like the one performed during the texturization. Using this characteristic of boron emitter surfaces, the authors can obtain a highly doped emitter under metal grid and simultaneously a shield to avoid texture on these surfaces. First cells were processed and short wavelength response of p{sup +}nn{sup +} solar cells was enhanced by using lightly doped boron emitters in the uncovered area.

  17. Enhanced detection of viral diversity using partial and near full-length genomes of HIV-1 provirus deep sequencing data from recently infected donors at four blood centers in Brazil

    PubMed Central

    Pessôa, Rodrigo; Watanabe, Jaqueline Tomoko; Calabria, Paula; Alencar, Cecilia Salete; Loureiro, Paula; Lopes, Maria Esther; Proetti, Anna Barbara; Félix, Alvina Clara; Sabino, Ester C; Busch, Michael P.; Sanabani, Sabri S

    2014-01-01

    Background Here, we report application of high-throughput near-full-length genome (NFLG) and partial HIV-1 proviral genome deep sequencing to characterize HIV in recently infected blood donors at four major blood centers in Brazil. Study Design and Methods From 2007-2011, 341 HIV+ blood donors from 4 blood centers were recruited to participate in a case control study to identify HIV risk factors and motivations to donate. Forty-seven (17 from São Paulo [SP], 8 from Minas Gerais [MG], 11 from Pernambuco [PE] and 11 from Rio de Janeiro [RJ]) were classified as recently infected based on testing by less-sensitive enzyme immunoassays. Five overlapping amplicons spanning the HIV genome were PCR amplified from peripheral blood mononuclear cells (PBMCs). The amplicons were molecularly bar-coded, pooled, and sequenced by an Illumina paired-end protocol. Results Of the 47 recently infected donor samples studied, 39 (82.9%) NFLGs and 6 (12.7%) partial fragments were de novo assembled into contiguous sequences and successfully subtyped. Subtype B was the only non-recombinant virus identified in this study and accounted for 62.2% (28/45) of samples. The remaining 37.8% (17/45) of samples showed various patterns of subtype discordance in different regions of HIV-1 genomes, indicating 2- 4 circulating recombinant subtypes derived from clades B, F and C. Fourteen samples (31.1%) from this study harbored drug resistance mutations, indicating higher rate of drug resistance among Brazilian blood donors. Conclusion Our findings revealed a high proportion of HIV-1 recombinants among recently infected blood donors in Brazil which has implications for future blood screening, diagnosis, therapy and vaccine development. PMID:25413141

  18. Large diameter carbon-boron fiber

    NASA Technical Reports Server (NTRS)

    Veltri, R. D.; Jacob, B. A.; Galasso, F. S.

    1975-01-01

    Investigations concerned with a development of large-diameter carbon fibers are considered, taking into account the employment of vapor deposition techniques. In the experiments a carbon monofilament substrate is used together with reacting gases which consist of combinations of hydrogen, methane, and boron trichloride. It is found that the described approach can be used to obtain a large-diameter carbon filament containing boron. The filament has reasonable strength and modulus properties.

  19. Formose reaction controlled by boronic acid compounds

    PubMed Central

    Imai, Toru; Michitaka, Tomohiro

    2016-01-01

    Formose reactions were carried out in the presence of low molecular weight and macromolecular boronic acid compounds, i.e., sodium phenylboronate (SPB) and a copolymer of sodium 4-vinylphenylboronate with sodium 4-styrenesulfonate (pVPB/NaSS), respectively. The boronic acid compounds provided different selectivities; sugars of a small carbon number were formed favorably in the presence of SPB, whereas sugar alcohols of a larger carbon number were formed preferably in the presence of pVPB/NaSS. PMID:28144337

  20. Boronate-tau mediated uptake in neurons.

    PubMed

    Pérez, Mar; Cuadros, Raquel; Pallas-Bazarra, Noemi; García, Carlos; Langa, Elena; Jurado-Arjona, Jerónimo; Hernández, Félix; Avila, Jesús

    2014-01-01

    We modified tau protein with boronic acid to facilitate its delivery into non neural or neural cultured cells lacking tau protein. Our results indicate that the incorporated tau promotes the formation of cytoplasmic extensions in non-neuronal cells, as well as the appearance of neurites in cultured tau knockout hippocampal neurons. In addition, boronated tau is incorporated into hippocampal neurons of tau knockout mice after intracranial injection in vivo. These findings describe a novel method to deliver exogenous tau protein into cells.

  1. Abrasive slurry composition for machining boron carbide

    DOEpatents

    Duran, E.L.

    1984-11-29

    An abrasive slurry particularly suited for use in drilling or machining boron carbide consists essentially of a suspension of boron carbide and/or silicon carbide grit in a carrier solution consisting essentially of a dilute solution of alkylaryl polyether alcohol in octyl alcohol. The alkylaryl polyether alcohol functions as a wetting agent which improves the capacity of the octyl alcohol for carrying the grit in suspension, yet without substantially increasing the viscosity of the carrier solution.

  2. Abrasive slurry composition for machining boron carbide

    DOEpatents

    Duran, Edward L.

    1985-01-01

    An abrasive slurry particularly suited for use in drilling or machining boron carbide consists essentially of a suspension of boron carbide and/or silicon carbide grit in a carrier solution consisting essentially of a dilute solution of alkylaryl polyether alcohol in octyl alcohol. The alkylaryl polyether alcohol functions as a wetting agent which improves the capacity of the octyl alcohol for carrying the grit in suspension, yet without substantially increasing the viscosity of the carrier solution.

  3. Deep learning

    NASA Astrophysics Data System (ADS)

    Lecun, Yann; Bengio, Yoshua; Hinton, Geoffrey

    2015-05-01

    Deep learning allows computational models that are composed of multiple processing layers to learn representations of data with multiple levels of abstraction. These methods have dramatically improved the state-of-the-art in speech recognition, visual object recognition, object detection and many other domains such as drug discovery and genomics. Deep learning discovers intricate structure in large data sets by using the backpropagation algorithm to indicate how a machine should change its internal parameters that are used to compute the representation in each layer from the representation in the previous layer. Deep convolutional nets have brought about breakthroughs in processing images, video, speech and audio, whereas recurrent nets have shone light on sequential data such as text and speech.

  4. Deep earthquakes

    SciTech Connect

    Frohlich, C.

    1989-01-01

    Earthquakes are often recorded at depths as great as 650 kilometers or more. These deep events mark regions where plates of the earth's surface are consumed in the mantle. But the earthquakes themselves present a conundrum: the high pressures and temperatures at such depths should keep rock from fracturing suddenly and generating a tremor. This paper reviews the research on this problem. Almost all deep earthquakes conform to the pattern described by Wadati, namely, they generally occur at the edge of a deep ocean and define an inclined zone extending from near the surface to a depth of 600 kilometers of more, known as the Wadati-Benioff zone. Several scenarios are described that were proposed to explain the fracturing and slipping of rocks at this depth.

  5. Deep learning.

    PubMed

    LeCun, Yann; Bengio, Yoshua; Hinton, Geoffrey

    2015-05-28

    Deep learning allows computational models that are composed of multiple processing layers to learn representations of data with multiple levels of abstraction. These methods have dramatically improved the state-of-the-art in speech recognition, visual object recognition, object detection and many other domains such as drug discovery and genomics. Deep learning discovers intricate structure in large data sets by using the backpropagation algorithm to indicate how a machine should change its internal parameters that are used to compute the representation in each layer from the representation in the previous layer. Deep convolutional nets have brought about breakthroughs in processing images, video, speech and audio, whereas recurrent nets have shone light on sequential data such as text and speech.

  6. Boron

    SciTech Connect

    Cozen, L.F. )

    1991-05-01

    This paper reports that borate minerals and refined borates are used extensively for the manufacture of vitreous materials such as insulation and textile fiberglasses, borosilicate glass, and porcelain enamels and frits. In North America, these applications are estimated to account for over 54% of the borate consumption. Other substantial uses are in soaps and detergents, metallurgy, fire retardants, industrial biocides, agriculture, and various miscellaneous applications. Reported domestic borate consumption in 1990 was estimated by the U.S. Bureau of Mines to be 320 000 metric tons B{sub 2}O{sub 3} versus 354 000 metric tons B{sub 2}O{sub 3} in 1989. Consumption is projected to remain essentially static in 1991. Imports were estimated by the Bureau to be 50 000 metric tons B{sub 2}O{sub 3} in 1990. Exports of boric acid and refined borates were approximately 650 000 metric tons of product, a 15 000 metric ton increase from the 1989 level. This increase partially offsets the drop in the 1990 consumption level.

  7. Boronization on NSTX using Deuterated Trimethylboron

    SciTech Connect

    W.R. Blanchard; R.C. Gernhardt; H.W. Kugel; P.H. LaMarche

    2002-01-28

    Boronization on the National Spherical Torus Experiment (NSTX) has proved to be quite beneficial with increases in confinement and density, and decreases in impurities observed in the plasma. The boron has been applied to the interior surfaces of NSTX, about every 2 to 3 weeks of plasma operation, by producing a glow discharge in the vacuum vessel using deuterated trimethylboron (TMB) in a 10% mixture with helium. Special NSTX requirements restricted the selection of the candidate boronization method to the use of deuterated boron compounds. Deuterated TMB met these requirements, but is a hazardous gas and special care in the execution of the boronization process is required. This paper describes the existing GDC, Gas Injection, and Torus Vacuum Pumping System hardware used for this process, the glow discharge process, and the automated control system that allows for remote operation to maximize both the safety and efficacy of applying the boron coating. The administrative requirements and the detailed procedure for the setup, operation and shutdown of the process are also described.

  8. Amorphous boron nitride at high pressure

    NASA Astrophysics Data System (ADS)

    Durandurdu, Murat

    2016-06-01

    The pressure-induced phase transformation in hexagonal boron nitrite and amorphous boron nitrite is studied using ab initio molecular dynamics simulations. The hexagonal-to-wurtzite phase transformation is successfully reproduced in the simulation with a transformation mechanism similar to one suggested in experiment. Amorphous boron nitrite, on the other hand, gradually transforms to a high-density amorphous phase with the application of pressure. This phase transformation is irreversible because a densified amorphous state having both sp3 and sp2 bonds is recovered upon pressure release. The high-density amorphous state mainly consists of sp3 bonds and its local structure is quite similar to recently proposed intermediate boron nitrite phases, in particular tetragonal structure (P42/mnm), rather than the known the wurtzite or cubic boron nitrite due to the existence of four membered rings and edge sharing connectivity. On the basis of this finding we propose that amorphous boron nitrite might be best candidate as a starting structure to synthesize the intermediate phase(s) at high pressure and temperature (probably below 800 °C) conditions.

  9. Synthesis of Borophene: Anisotropic, Two-Dimensional Boron Allotrope

    SciTech Connect

    Mannix, Andrew J.; Zhou, Xiang-Feng; Kiraly, Brian T.; Wood, Joshua D.; Alducin, Diego; Meyers, Benjamin; Liu, Xiaolong; Fisher, Brandon L.; Santiago, Ulises; Guest, Jeffrey R.; Yacaman, Miguel; Ponce, Artura; oganov, artem R; Hersam, Mark C.; Guisinger, N. P.

    2015-12-18

    At the atomic-cluster scale, pure boron is markedly similar to carbon, forming simple planar molecules and cage-like fullerenes. Theoretical studies predict that two-dimensional (2D) boron sheets will adopt an atomic configuration similar to that of boron atomic clusters. We synthesized atomically thin, crystalline 2D boron sheets (i.e., borophene) on silver surfaces under ultrahigh-vacuum conditions. Atomic-scale characterization, supported by theoretical calculations, revealed structures reminiscent of fused boron clusters with multiple scales of anisotropic, out-of-plane buckling. Unlike bulk boron allotropes, borophene shows metallic characteristics that are consistent with predictions of a highly anisotropic, 2D metal.

  10. Development of magnetic resonance technology for noninvasive boron quantification

    SciTech Connect

    Bradshaw, K.M.

    1990-11-01

    Boron magnetic resonance imaging (MRI) and spectroscopy (MRS) were developed in support of the noninvasive boron quantification task of the Idaho National Engineering Laboratory (INEL) Power Burst Facility/Boron Neutron Capture Therapy (PBF/BNCT) program. The hardware and software described in this report are modifications specific to a GE Signa{trademark} MRI system, release 3.X and are necessary for boron magnetic resonance operation. The technology developed in this task has been applied to obtaining animal pharmacokinetic data of boron compounds (drug time response) and the in-vivo localization of boron in animal tissue noninvasively. 9 refs., 21 figs.

  11. The effect of boron deficiency on gene expression and boron compartmentalization in sugarbeet

    USDA-ARS?s Scientific Manuscript database

    NIP5, BOR1, NIP6, and WRKY6 genes were investigated for their role in boron deficiency in sugar beet, each with a proposed role in boron use in model plant species. All genes showed evidence of polymorphism in fragment size and gene expression in the target genomic DNA and cDNA libraries, with no co...

  12. Spectromicroscopy of boron for the optimization of boron neutron capture therapy (BNCT) for cancer

    NASA Astrophysics Data System (ADS)

    Gilbert, B.; Redondo, J.; Baudat, P.-A.; Lorusso, G. F.; Andres, R.; Van Meir, E. G.; Brunet, J.-F.; Hamou, M.-F.; Suda, T.; Mercanti, Delio; Ciotti, M. Teresa; Droubay, T. C.; Tonner, B. P.; Perfetti, P.; Margaritondo, M.; DeStasio, Gelsomina

    1998-10-01

    We used synchrotron spectromicroscopy to study the microscopic distribution of boron in rat brain tumour and healthy tissue in the field of boron neutron capture therapy (BNCT). The success of this experimental cancer therapy depends on the preferential uptake of ? in tumour cells after injection of a boron compound (in our case ?, or BSH). With the Mephisto (microscope à emission de photoélectrons par illumination synchrotronique de type onduleur) spectromicroscope, high-magnification imaging and chemical analysis was performed on brain tissue sections from a rat carrying an implanted brain tumour and the results were compared with inductively coupled plasma-atomic emission spectroscopy (ICP-AES) detection of boron in bulk tissue. Boron was found to have been taken up more favourably by regions of tumour rather than healthy tissue, but the resulting boron distribution in the tumour was inhomogeneous. The results demonstrate that Mephisto can perform microchemical analysis of tissue sections, detect and localize the presence of boron with submicron spatial resolution. The application of this technique to boron in brain tissue can therefore be used to evaluate the current efforts to optimize BNC therapy.

  13. Deep Lysimeter

    DOEpatents

    Hubbell, Joel M.; Sisson, James B.

    2004-06-01

    A deep lysimeter including a hollow vessel having a chamber, a fill conduit extending into the chamber through apertures, a semi-permeable member mounted on the vessel and in fluid communication with the fill conduit, and a line connection for retrieving the lysimeter.

  14. Deep Trouble.

    ERIC Educational Resources Information Center

    Popke, Michael

    2002-01-01

    Discusses how the safety-related ruling by the National Federation of State High School Associations to eliminate the option of using 18-inch starting platforms in pools less than 4 feet deep may affect operators of swimming pools and the swim teams who use them. (EV)

  15. Deep Fish.

    PubMed

    Ishaq, Omer; Sadanandan, Sajith Kecheril; Wählby, Carolina

    2017-01-01

    Zebrafish ( Danio rerio) is an important vertebrate model organism in biomedical research, especially suitable for morphological screening due to its transparent body during early development. Deep learning has emerged as a dominant paradigm for data analysis and found a number of applications in computer vision and image analysis. Here we demonstrate the potential of a deep learning approach for accurate high-throughput classification of whole-body zebrafish deformations in multifish microwell plates. Deep learning uses the raw image data as an input, without the need of expert knowledge for feature design or optimization of the segmentation parameters. We trained the deep learning classifier on as few as 84 images (before data augmentation) and achieved a classification accuracy of 92.8% on an unseen test data set that is comparable to the previous state of the art (95%) based on user-specified segmentation and deformation metrics. Ablation studies by digitally removing whole fish or parts of the fish from the images revealed that the classifier learned discriminative features from the image foreground, and we observed that the deformations of the head region, rather than the visually apparent bent tail, were more important for good classification performance.

  16. Boron site preference in ternary Ta and Nb boron silicides

    SciTech Connect

    Khan, Atta U.; Nunes, Carlos A.; Coelho, Gilberto C.; Suzuki, Paulo A.; Grytsiv, Andriy; Bourree, Francoise; Rogl, Peter F.

    2012-06-15

    X-ray single crystal (XSC) and neutron powder diffraction data (NPD) were used to elucidate boron site preference for five ternary phases. Ta{sub 3}Si{sub 1-x}B{sub x} (x=0.112(4)) crystallizes with the Ti{sub 3}P-type (space group P4{sub 2}/n) with B-atoms sharing the 8g site with Si atoms. Ta{sub 5}Si{sub 3-x} (x=0.03(1); Cr{sub 5}B{sub 3}- type) crystallizes with space group I4/mcm, exhibiting a small amount of vacancies on the 4a site. Both, Ta{sub 5}(Si{sub 1-x}B{sub x}){sub 3}, x=0.568(3), and Nb{sub 5}(Si{sub 1-x}B{sub x}){sub 3}, x=0.59(2), are part of solid solutions of M{sub 5}Si{sub 3} with Cr{sub 5}B{sub 3}-type into the ternary M-Si-B systems (M=Nb or Ta) with B replacing Si on the 8h site. The D8{sub 8}-phase in the Nb-Si-B system crystallizes with the Ti{sub 5}Ga{sub 4}-type revealing the formula Nb{sub 5}Si{sub 3}B{sub 1-x} (x=0.292(3)) with B partially filling the voids in the 2b site of the Mn{sub 5}Si{sub 3} parent type. - Graphical abstract: The crystal structures of a series of compounds have been solved from X-ray single crystal diffractometry revealing details on the boron incorporation. Highlights: Black-Right-Pointing-Pointer Structure of a series of compounds have been solved by X-ray single crystal diffractometry. Black-Right-Pointing-Pointer Ta{sub 3}(Si{sub 1-x}B{sub x}) (x=0.112) crystallizes with the Ti{sub 3}P-type, B and Si atoms randomly share the 8g site. Black-Right-Pointing-Pointer Structure of Nb{sub 5}Si{sub 3}B{sub 1-x} (x=0.292; Ti{sub 5}Ga{sub 4}-type) was solved from NPD.

  17. Enhanced diffusion of boron by oxygen precipitation in heavily boron-doped silicon

    NASA Astrophysics Data System (ADS)

    Torigoe, Kazuhisa; Ono, Toshiaki

    2017-06-01

    The enhanced diffusion of boron has been investigated by analyzing out-diffusion profiles in the vicinity of the interface between a lightly boron-doped silicon epitaxial layer and a heavily boron-doped silicon substrate with a resistivity of 8.2 mΩ cm and an oxide precipitate (O.P.) density of 108-1010 cm-3. It is found that the boron diffusion during annealing at 850-1000 °C is enhanced with the increase of the oxide precipitate density. On the basis of a model for boron diffusion mediated by silicon self-interstitials, we reveal that the enhanced diffusion is attributed to self-interstitials supersaturated as a result of the emission from oxide precipitates and the absorption by punched-out dislocations. In addition, the temperature dependence of the fraction of the self-interstitial emission obtained analyzing the diffusion enhancement well explains the morphology changes of oxide precipitates reported in literature.

  18. Ceramic silicon-boron-carbon fibers from organic silicon-boron-polymers

    NASA Technical Reports Server (NTRS)

    Riccitiello, Salvatore R. (Inventor); Hsu, Ming-Ta S. (Inventor); Chen, Timothy S. (Inventor)

    1993-01-01

    Novel high strength ceramic fibers derived from boron, silicon, and carbon organic precursor polymers are discussed. The ceramic fibers are thermally stable up to and beyond 1200 C in air. The method of preparation of the boron-silicon-carbon fibers from a low oxygen content organosilicon boron precursor polymer of the general formula Si(R2)BR(sup 1) includes melt-spinning, crosslinking, and pyrolysis. Specifically, the crosslinked (or cured) precursor organic polymer fibers do not melt or deform during pyrolysis to form the silicon-boron-carbon ceramic fiber. These novel silicon-boron-carbon ceramic fibers are useful in high temperature applications because they retain tensile and other properties up to 1200 C, from 1200 to 1300 C, and in some cases higher than 1300 C.

  19. Feasibility of a boron loaded scintillation detector for dose measurements related to boron neutron capture therapy

    NASA Astrophysics Data System (ADS)

    Kim, Don-Soo; Egan, James J.; Kegel, Gunter H. R.; Desimone, David

    2002-04-01

    The feasibility of the use of a boron loaded scintillation detector in a head phantom for boron neutron capture therapy dose estimates was evaluated. Several monoenergetic neutron groups were produced via the ^7Li(p,n)^7Be reaction in a metallic lithium target using the Van de Graaff accelerator at University of Massachusetts Lowell. The pulse-height spectra were taken from a natural boron loaded (10205-, 304-, 407-, 507-, 570-, 702-, and 780-keV incident neutrons. The results shows that a boron loaded scintillator could be used to distinguish the doses from different radiation sources in boron neutron capture therapy. This detector may be used in the estimation of doses due to fast neutrons, alpha particles and recoil lithium from ^10B(n,α)^7Li, and photons at the same time during neutron irradiation procedures.

  20. Atmospheric contribution to boron enrichment in aboveground wheat tissues.

    PubMed

    Wang, Cheng; Ji, Junfeng; Chen, Mindong; Zhong, Cong; Yang, Zhongfang; Browne, Patrick

    2017-05-01

    Boron is an essential trace element for all organisms and has both beneficial and harmful biological functions. A particular amount of boron is discharged into the environment every year because of industrial activities; however, the effects of environmental boron emissions on boron accumulation in cereals has not yet been estimated. The present study characterized the accumulation of boron in wheat under different ecological conditions in the Yangtze River Delta (YRD) area. This study aimed to estimate the effects of atmospheric boron that is associated with industrial activities on boron accumulation in wheat. The results showed that the concentrations of boron in aboveground wheat tissues from the highly industrialized region were significantly higher than those from the agriculture-dominated region, even though there was no significant difference in boron content in soils. Using the model based on the translocation coefficients of boron in the soil-wheat system, we estimated that the contribution of atmosphere to boron accumulation in wheat straw in the highly industrialized region exceeded that in the agriculture-dominated region by 36%. In addition, from the environmental implication of the model, it was estimated that the development of boron-utilizing industries had elevated the concentration of boron in aboveground wheat tissues by 28-53%. Copyright © 2017 Elsevier Ltd. All rights reserved.

  1. Photon effect on electron-irradiated boron-doped silicon solar cell

    NASA Astrophysics Data System (ADS)

    Roux, M.; Bernard, J.; Reulet, R.; Crabb, R. L.

    1984-07-01

    The correlation between current-voltage-characteristic measurements and deep-level transient-spectroscopy data on boron-doped silicon solar cells irradiated at room temperature by a 1-MeV electron beam, followed or not by an illumination, is presented in this study. From such correlation it is possible to conclude that the additional degradation induced by light is due to the appearance of a defect in oxygen-lean silicon, which should be associated with the vacancy-oxygen-carbon complex. A model based upon the dissociation (enhanced by capture of photogenerated carriers) of the interstitial-boron/interstitial-oxygen complex accounts for these observations: it verifies that the 'photon effect' exists in oxygen-lean cells and is absent in high-oxygen-concentration cells.

  2. Photoacoustically Measured Speeds of Sound of Liquid HBO2: On Unlocking the Fuel Potential of Boron

    SciTech Connect

    Bastea, S; Crowhurst, J; Armstrong, M; ., N T

    2010-03-24

    Elucidation of geodynamic, geochemical, and shock induced processes is often limited by challenges to accurately determine molecular fluid equations of state (EOS). High pressure liquid state reactions of carbon species underlie physiochemical mechanisms such as differentiation of planetary interiors, deep carbon sequestration, propellant deflagration, and shock chemistry. Here we introduce a versatile photoacoustic technique developed to measure accurate and precise speeds of sound (SoS) of high pressure molecular fluids and fluid mixtures. SoS of an intermediate boron oxide, HBO{sub 2} are measured up to 0.5 GPa along the 277 C isotherm. A polarized Exponential-6 interatomic potential form, parameterized using our SoS data, enables EOS determinations and corresponding semi-empirical evaluations of > 2000 C thermodynamic states including energy release from bororganic formulations. Our thermochemical model propitiously predicts boronated hydrocarbon shock Hugoniot results.

  3. Mid-infrared surface phonon polaritons in boron-nitride nanotubes

    NASA Astrophysics Data System (ADS)

    Ghamsari, Behnood G.; Xu, Xiaoji G.; Gilburd, Leonid; Walker, Gilbert C.; Berini, Pierre

    2014-11-01

    Boron-nitride nanotubes (BNNTs) are structural analogs of carbon nanotubes formed from hexagonal boron-nitride (h-BN) sheets. h-BN exhibits strong phonon resonances which result in a negative permittivity band in the mid-infrared (mid-IR) part of the electromagnetic spectrum. Recently, we have experimentally demonstrated that BNNTs can support one-dimensional surface phonon polaritons (SPhPs) in the mid-IR. In this work, we thoroughly study the modal characteristics of the SPhP modes of BNNTs with respect to their structural attributes, such as diameter, hollowness, and ellipticity, as well as dispersion as a function of frequency. As is discussed in detail throughout the paper, the SPhP modes of BNNTs offer deep-subwavelength field confinement and large field enhancement and provide a viable means for nanophotonics, near-field optics, and thermo-optics at mid-IR wavelengths.

  4. Metal impurities in crystallographic voids of beta-rhombohedral boron lattice: Binding energies and electron levels

    NASA Astrophysics Data System (ADS)

    Chkhartishvili, Levan; Murusidze, Ivane; Darchiashvili, Maguli; Tsagareishvili, Otar; Gabunia, Domenti

    2012-11-01

    Applying quasi-classical approach, the binding energies and electron levels of metal impurities (Li, Mg, Al, Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Hf, Ta, and Re) introduced into crystallographic voids of types A, D and E in the beta-rhombohedral boron lattice are calculated. Binding energies are estimated as ˜1 eV-60 eV per bond. The most of the obtained metal-boron bond lengths are very close to the mean radii of voids in the undoped crystal. Relatively light impurities (from Li to Cu) are found to form donor electron states directly inside the conduction band, i.e., they cause metallization of the material being introduced at sufficiently high concentrations. Heavy impurities (from Zr to Re) form shallow or deep donor levels inside the band gap or even valence band depending on dopants and voids of accommodation.

  5. Optoelectronic properties of hexagonal boron nitride epilayers

    NASA Astrophysics Data System (ADS)

    Cao, X. K.; Majety, S.; Li, J.; Lin, J. Y.; Jiang, H. X.

    2013-01-01

    This paper summarizes recent progress primarily achieved in authors' laboratory on synthesizing hexagonal boron nitride (hBN) epilayers by metal organic chemical vapor deposition (MCVD) and studies of their structural and optoelectronic properties. The structural and optical properties of hBN epilayers have been characterized by x-ray diffraction (XRD) and photoluminescence (PL) studies and compared to the better understood wurtzite AIN epilayers with a comparable energy bandgap. These MOCVD grown hBN epilayers exhibit highly efficient band-edge PL emission lines centered at around 5.5 eVat room temperature. The band-edge emission of hBN is two orders of magnitude higher than that of high quality AlN epilayers. Polarization-resolved PL spectroscopy revealed that hEN epilayers are predominantly a surface emission material, in which the band-edge emission with electric field perpendicular to the c-axis (Eemi⊥c) is about 1.7 times stronger than the component along the c-axis (Eemillc). This is in contrast to AIN, in which the band­ edge emission is known to be polarized along the c-axis, (Eemillc). Based on the graphene optical absorption concept, the estimated band-edge absorption coefficient of hBN is about 7x105 cm-1, which is more than 3 times higher than the value for AlN (~2x105 cm-1 . The hBN epilayer based photodetectors exhibit a sharp cut-off wavelength around 230 nm, which coincides with the band-edge PL emission peak and virtually no responses in the long wavelengths. The dielectric strength of hBN epilayers exceeds that of AlN and is greater than 4.5 MV/cm based on the measured result for an hBN epilayer released from the host sapphire substrate.

  6. Boron nitride fibers from polymer precursors

    SciTech Connect

    Wade, B.E.

    1992-12-31

    Conversion of polymer precursors to high performance boron nitride fibers as explored through a fundamental study of the mutually dependent chemical, morphological, and processing requirements in precursor polymer synthesis, formation of continuous precursor fibers, and finally thermochemical conversion to oriented boron nitride fibers. Polyborate and polyborazylene precursors were investigated. method of incorporating polyborazine in polyborate were also explored in order to stabilize the shape of polyborate fibers and to help initiate an orientable boron nitride structure. Polyborazylene, a polyborazine of fused borazine polycyclic structures was chosen for study as a precursor for boron nitride fibers because of the closeness of its structure to that of the desired turbostratic boron nitride. Both poly(ethylene oxide) and poly(methyl methacrylate) were found to be compatible with the monomer, borazine, and polyborazylenesolutions with monoglyme. They could be used to build the viscosity of solutions. However, fibers that were hand-drawn from these solutions were very sticky and quickly hydrolyzed in room atmosphere. Conversion of polyborazylene to oriented boron nitride fibers was not realized. Processable polyborates were produced by polycondensation of trimethoxyboroxine and boric acid and also by disproportionation or trimethyoxyboraxine. It was shown that the rheological characteristics of the polyborate formed could be controlled by an appropriate combination of the conversion of the monomer to polymer and the addition of a linear organic polymer as a rheological aid. Poly(methyl methacrylate) was found to be a suitable rheological aid, with a decomposition temperature that is high enough to facilitate its incorporation in the polymerizing system and low energy to be fugitive during thermochemical conversion of the polyborate to boron nitride.

  7. Boron removal in radioactive liquid waste by forward osmosis membrane

    SciTech Connect

    Doo Seong Hwang; Hei Min Choi; Kune Woo Lee; Jei Kwon Moon

    2013-07-01

    This study investigated the treatment of boric acid contained in liquid radioactive waste using a forward osmosis membrane. The boron permeation through the membrane depends on the type of membrane, membrane orientation, pH of the feed solution, salt and boron concentration in the feed solution, and osmotic pressure of the draw solution. The boron flux begins to decline from pH 7 and increases with an increase of the osmotic driving force. The boron flux decreases slightly with the salt concentration, but is not heavily influenced by a low salt concentration. The boron flux increases linearly with the concentration of boron. No element except for boron was permeated through the FO membrane in the multi-component system. The maximum boron flux is obtained in an active layer facing a draw solution orientation of the CTA-ES membrane under conditions of less than pH 7 and high osmotic pressure. (authors)

  8. Method of manufacture of atomically thin boron nitride

    DOEpatents

    Zettl, Alexander K

    2013-08-06

    The present invention provides a method of fabricating at least one single layer hexagonal boron nitride (h-BN). In an exemplary embodiment, the method includes (1) suspending at least one multilayer boron nitride across a gap of a support structure and (2) performing a reactive ion etch upon the multilayer boron nitride to produce the single layer hexagonal boron nitride suspended across the gap of the support structure. The present invention also provides a method of fabricating single layer hexagonal boron nitride. In an exemplary embodiment, the method includes (1) providing multilayer boron nitride suspended across a gap of a support structure and (2) performing a reactive ion etch upon the multilayer boron nitride to produce the single layer hexagonal boron nitride suspended across the gap of the support structure.

  9. [Minimally invasive cytoselective radiation therapy using boron neutron capture reaction].

    PubMed

    Nakamura, Hiroyuki

    2010-12-01

    The cell-killing effect of boron neutron capture therapy (BNCT) is due to the nuclear reaction of two essentially nontoxic species, boron-10 ((10)B) and thermal neutrons, whose destructive effect is well observed in boron-loaded tissues. High accumulation and selective delivery of boron into tumor tissue are the most important requirements to achieve efficient neutron capture therapy of cancers. This review focuses on liposomal boron delivery system (BDS) as a recent promising approach that meet these requirements for BNCT. BDS involves two strategies: (1) encapsulation of boron in the aqueous core of liposomes and (2) accumulation of boron in the liposomal bilayer. In this review, recent development of liposomal boron delivery system is summarized.

  10. Epoxy resin composition containing metal tetrafluoroborate and boron ester

    SciTech Connect

    Morehead, G.T.

    1990-06-12

    This patent describes a curable composition. It comprises: a polyepoxide; a metal tetrafluoroborate; and at least one boron ester selected from the group consisting of triesters of boric acid and diesters of boronic acid.

  11. Fatigue of boron-aluminum composites bonds and joints

    NASA Technical Reports Server (NTRS)

    Hersh, M. S.

    1973-01-01

    Study examines effects of boron filament diameter on bonds and joints in boron-aluminum composite. Data include static strength, fatigue, and dynamic moduli of elasticity. Manson-Coffin analyses and metallurgical and fracture surface evaluation were also performed.

  12. Purification of boron nitride nanotubes via polymer wrapping

    SciTech Connect

    Choi, Jin-Hyuk; Kim, Jaewoo; Seo, Duckbong; Seo, Young-Soo

    2013-03-15

    Highlights: ► Surface modification of boron nitride nanotubes using polymeric materials. ► Surface-modified BNNT was purified with a simple dilution-centrifugation step. ► Surface-modified BNNT can be directly used for polymer composite fabrication ► Degree of purification was analyzed by Raman spectroscopy. - Abstract: Boron nitride nanotubes (BNNT) synthesized by a ball milling-annealing were surface-modified using three different types of polymeric materials. Those materials were chosen depending on future applications especially in polymer nanocomposite fabrications. We found that the surface-modified BNNT can be purified with a simple dilution-centrifugation step, which would be suitable for large-scale purification. Degree of purification was monitored by means of the center peak position and FWHM of E{sub 2g} mode of BNNT in Raman spectra. As the purification of BNNT develops, the peak position was up-shifted while FWHM of the peak was narrowed.

  13. Boron implanted emitter for n-type silicon solar cell

    NASA Astrophysics Data System (ADS)

    Liang, Peng; Han, Pei-De; Fan, Yu-Jie; Xing, Yu-Peng

    2015-03-01

    The effects of ion doses on the properties of boron implanted Si for n-type solar cell application were investigated with doses ranging from 5× 1014 cm- 2 to 2× 1015 cm- 2 and a subsequent two-step annealing process in a tube furnace. With the help of the TCAD process simulation tool, knowledge on diffusion kinetics of dopants and damage evolution was obtained by fitting SIMS measured boron profiles. Due to insufficient elimination of the residual damage, the implanted emitter was found to have a higher saturation current density (J0e) and a poorer crystallographic quality. Consistent with this observation, Voc, Jsc, and the efficiency of the all-implanted p+-n-n+ solar cells followed a decreasing trend with an increase of the implantation dose. The obtained maximum efficiency was 19.59% at a low dose of 5× 1014 cm- 2. The main efficiency loss under high doses came not only from increased recombination of carriers in the space charge region revealed by double-diode parameters of dark I-V curves, but also from the degraded minority carrier diffusion length in the emitter and base evidenced by IQE data. These experimental results indicated that clusters and dislocation loops had appeared at high implantation doses, which acted as effective recombination centers for photogenerated carriers. Project supported by the National Natural Science Foundation of China (Grant Nos. 61275040, 60976046, and 61021003) and the National Basic Research Program of China (Grant No. 2012CB934200).

  14. A study of the microstructure of a rapidly solidified nickel-base superalloy modified with boron. M.S. Thesis. Final Contractor Report

    NASA Technical Reports Server (NTRS)

    Speck, J. S.

    1986-01-01

    The microstructures of melt-spun superalloy ribbons with variable boron levels have been studied by transmission electron microscopy. The base alloy was of approximate composition Ni-11% Cr-5%Mo-5%Al-4%Ti with boron levels of 0.06, 0.12, and 0.60 percent (all by weight). Thirty micron thick ribbons display an equiaxed chill zone near the wheel contact side which develops into primary dendrite arms in the ribbon center. Secondary dendrite arms are observed near the ribbon free surface. In the higher boron bearing alloys, boride precipitates are observed along grain boundaries. A concerted effort has been made to elucidate true grain shapes by the use of bright field/dark field microscopy. In the low boron alloy, grain shapes are often convex, and grain faces are flat. Boundary faces frequently have large curvature, and grain shapes form concave polygons in the higher boron level alloys. It is proposed that just after solidification, in all of the alloys studied, grain shapes were initially concave and boundaries were wavy. Boundary straightening is presumed to occur on cooling in the low boron alloy. Boundary migration is precluded in the higher boron alloys by fast precipitation of borides at internal interfaces.

  15. A study of the microstructure of a rapidly solidified nickel-base superalloy modified with boron. M.S. Thesis. Final Contractor Report

    NASA Technical Reports Server (NTRS)

    Speck, J. S.

    1986-01-01

    The microstructures of melt-spun superalloy ribbons with variable boron levels have been studied by transmission electron microscopy. The base alloy was of approximate composition Ni-11% Cr-5%Mo-5%Al-4%Ti with boron levels of 0.06, 0.12, and 0.60 percent (all by weight). Thirty micron thick ribbons display an equiaxed chill zone near the wheel contact side which develops into primary dendrite arms in the ribbon center. Secondary dendrite arms are observed near the ribbon free surface. In the higher boron bearing alloys, boride precipitates are observed along grain boundaries. A concerted effort has been made to elucidate true grain shapes by the use of bright field/dark field microscopy. In the low boron alloy, grain shapes are often convex, and grain faces are flat. Boundary faces frequently have large curvature, and grain shapes form concave polygons in the higher boron level alloys. It is proposed that just after solidification, in all of the alloys studied, grain shapes were initially concave and boundaries were wavy. Boundary straightening is presumed to occur on cooling in the low boron alloy. Boundary migration is precluded in the higher boron alloys by fast precipitation of borides at internal interfaces.

  16. Center on Centers.

    ERIC Educational Resources Information Center

    Utah System Approach to Individualized Learning Project.

    Classroom areas organized into centers for specific study purposes are discussed. These centers are used for individual or small group work. The physical arrangement of the area used for a study center is described, including the organization of furniture, materials, and preferred locations. Suggestions are made for the management and stocking of…

  17. The abundance of boron in diffuse interstellar clouds

    NASA Astrophysics Data System (ADS)

    Ritchey, Adam M.

    -resolution ground-based observations of Ca II l3933 and K I l7698, I show that unresolved structure in the UV data has little influence on final boron abundances. Many sight lines exhibit multiple complexes of absorption components well separated in velocity. I interpret such sight lines as tracing both local gas, with velocity components near 0 km s -1 relative to the local standard of rest (LSR), and gas associated with a distant spiral arm, with components at more negative velocities. In these cases, profile templates are created for each complex and fitted to that portion of the B II profile independently, thereby enabling a comparative analysis of boron abundances in distinct physical regions within the Galaxy. With this procedure, I find suggestive evidence for a higher B/O ratio in the inner Sagittarius-Carina spiral arm than in the vicinity of the Sun. Abundances of secondary elements increase relative to those of primary elements toward the Galactic center due to enhanced rates of star formation and stellar nucleosynthesis. The finding that the B/O ratio is elevated toward the inner Galaxy may thus indicate the secondary nature of boron, which in turn would cast doubt on the efficiency of the n-process, a primary production mechanism. Measured line-of-sight abundance ratios of B/H and B/O firmly establish that boron is depleted (relative to the Sun) in diffuse gas. A comparison of these ratios with measures of gas density, namely the average line-of-sight hydrogen density [left angle bracket] n H [right angle bracket] and the fraction of hydrogen in molecular form f (H 2 ), further demonstrates that the depletion increases in high-density sight lines, a trend seen in the abundances of many other elements, including in the oxygen, copper, and gallium results presented here. Elemental depletion onto interstellar dust grains increases with average gas density due to the larger fraction of cold clouds, relative to warm gas, along the line of sight. In the case of boron, this

  18. Boron toxicity in the rare serpentine plant, Streptanthus morrisonii.

    PubMed

    Sage, R F; Ustin, S L; Manning, S J

    1989-01-01

    The release of boron-laden mist from the cooling towers of some geothermal power stations in northern California potentially threatens nearby populations of the rare serpentine plant, Streptanthus morrisonii F. W. Hoffm. To assess the tolerance of S. morrisonii to high levels of boron, the effect of boron on leaf condition, life history, germination rate, growth rate, allocation and photosynthesis was measured on plants grown in a greenhouse. Relative to other species, S. morrisonii was tolerant of excess boron. On serpentine soil, mild to moderate toxicity symptoms (older leaves exhibiting chlorosis and necrosis, but few leaves killed) were apparent when the boron concentration in applied nutrient solutions was 240-650 microm. Severe toxicity symptoms (significant leaf loss, young leaves with toxicity symptoms) were apparent when the applied solution was over 1000 microm boron. Above 1000 microm boron, S. morrisonii appeared unable to complete its life cycle. On a tissue basis, boron toxicity was first observed when leaf boron content was 40-90 micromol g(-1) dry weight. In leaves with severe boron toxicity (> 35% injury), the boron content was generally above 130 micromol g(-1) dry weight. These levels were an order of magnitude above the tissue boron content of plants in the field. Prior to the onset of pronounced boron toxicity symptoms, growth rate, allocation patterns, and photosynthesis were unaffected by high boron. These results indicate that inhibition of growth and photosynthesis occurred because of a loss of viable tissue due to boron injury, rather than a progressive decline as leaf boron levels increased.

  19. Polyethylene/Boron Composites for Radiation Shielding Applications

    SciTech Connect

    Harrison, Courtney; Grulke, Eric; Burgett, Eric; Hertel, Nolan

    2008-01-21

    Multifunctional composites made with boron are absorbers of low energy nuetrons, and could be used for structural shielding materials. Polyethylene/boron carbide composites were fabricated using conventional polymer processing techniques, and were evaluated for mechanical and radiation shielding properties. Addition of neat boron carbide (powder and nanoparticles) to an injection molding grade HPDE showed superior mechanical properties compared to neat HDPE. Radiation shielding measurements of a 2 wt% boron carbide composite were improved over those of the neat polyethylene.

  20. Update on human health effects of boron.

    PubMed

    Nielsen, Forrest H

    2014-10-01

    In vitro, animal, and human experiments have shown that boron is a bioactive element in nutritional amounts that beneficially affects bone growth and central nervous system function, alleviates arthritic symptoms, facilitates hormone action and is associated with a reduced risk for some types of cancer. The diverse effects of boron suggest that it influences the formation and/or activity of substances that are involved in numerous biochemical processes. Several findings suggest that this influence is through the formation of boroesters in biomolecules containing cis-hydroxyl groups. These biomolecules include those that contain ribose (e.g., S-adenosylmethionine, diadenosine phosphates, and nicotinamide adenine dinucleotide). In addition, boron may form boroester complexes with phosphoinositides, glycoproteins, and glycolipids that affect cell membrane integrity and function. Both animal and human data indicate that an intake of less than 1.0mg/day inhibits the health benefits of boron. Dietary surveys indicate such an intake is not rare. Thus, increasing boron intake by consuming a diet rich in fruits, vegetables, nuts and pulses should be recognized as a reasonable dietary recommendation to enhance health and well-being. Published by Elsevier GmbH.

  1. Unilamellar liposomes with enhanced boron content.

    PubMed

    Li, Tiejun; Hamdi, Julie; Hawthorne, M Frederick

    2006-01-01

    A new type of boron-rich, DSPC-free, unilamellar liposomes was formed using the novel dual-chain, ionic, nido-carborane lipid, K[nido-7-(C16H33OCH2)2CHOCH2-7,8-C2B9H11] (DAC-16), and cholesterol for encapsulation of an aqueous buffer core. Since DSPC was not necessary for the formation of stable DAC-16 liposomes, the boron concentration of these vesicles was increased dramatically to approximately 8.8 wt % in the dry lipid; these liposomes had a high bilayer boron incorporation efficiency of 98%. DSPC-free liposomes exhibited a size distribution pattern of 40-60 nm, which was in the range normally associated with selective tumor uptake. This size distribution was maintained throughout storage at room temperature for several months. Additionally, optimized liposome formulations incorporating DAC-16, DSPC, and cholesterol were identified having stable size distribution patterns after storage for more than two months at a variety of temperatures. Although animal studies indicate that DAC-16 liposomes are toxic, this new ionic nido-carborane lipid allows the formation of liposomes of high boron content for in vitro applications that require the delivery of large amounts of boron.

  2. Boron nitride nanotubes and nanosheets.

    PubMed

    Golberg, Dmitri; Bando, Yoshio; Huang, Yang; Terao, Takeshi; Mitome, Masanori; Tang, Chengchun; Zhi, Chunyi

    2010-06-22

    Hexagonal boron nitride (h-BN) is a layered material with a graphite-like structure in which planar networks of BN hexagons are regularly stacked. As the structural analogue of a carbon nanotube (CNT), a BN nanotube (BNNT) was first predicted in 1994; since then, it has become one of the most intriguing non-carbon nanotubes. Compared with metallic or semiconducting CNTs, a BNNT is an electrical insulator with a band gap of ca. 5 eV, basically independent of tube geometry. In addition, BNNTs possess a high chemical stability, excellent mechanical properties, and high thermal conductivity. The same advantages are likely applicable to a graphene analogue-a monatomic layer of a hexagonal BN. Such unique properties make BN nanotubes and nanosheets a promising nanomaterial in a variety of potential fields such as optoelectronic nanodevices, functional composites, hydrogen accumulators, electrically insulating substrates perfectly matching the CNT, and graphene lattices. This review gives an introduction to the rich BN nanotube/nanosheet field, including the latest achievements in the synthesis, structural analyses, and property evaluations, and presents the purpose and significance of this direction in the light of the general nanotube/nanosheet developments.

  3. Study of barrier height and trap centers of Au/n-Hg{sub 3}In{sub 2}Te{sub 6} Schottky contacts by current-voltage (I-V) characteristics and deep level transient spectroscopy

    SciTech Connect

    Li, Yapeng; Fu, Li Sun, Jie; Wang, Xiaozhen

    2015-02-28

    The temperature-dependent electrical characteristics of the Au/n-Hg{sub 3}In{sub 2}Te{sub 6} Schottky contact have been studied at the temperature range of 140 K–315 K. Based on the thermionic emission theory, the ideality factor and Schottky barrier height were calculated to decrease and increase from 3.18 to 1.88 and 0.39 eV to 0.5 eV, respectively, when the temperature rose from 140 K to 315 K. This behavior was interpreted by the lateral inhomogeneities of Schottky barrier height at the interface of Au/n-Hg{sub 3}In{sub 2}Te{sub 6} contact, which was shown by the plot of zero-bias barrier heights Φ{sub bo} versus q/2kT. Meanwhile, it was found that the Schottky barrier height with a Gaussian distribution was 0.67 eV and the standard deviation σ{sub 0} was about 0.092 eV, indicating that the uneven distribution of barrier height at the interface region. In addition, the mean value of Φ{sup ¯}{sub b0} and modified Richardson constant was determined to be 0.723 eV and 62.8 A/cm{sup 2}K{sup 2} from the slope and intercept of the ln(I{sub o}/T{sup 2}) – (qσ{sub 0}{sup 2}/2k{sup 2}T{sup 2}) versus q/kT plot, respectively. Finally, two electron trap centers were observed at the interface of Au/n-Hg{sub 3}In{sub 2}Te{sub 6} Schottky contact by means of deep level transient spectroscopy.

  4. Screening of Wheat Genotypes for Boron Efficiency in Bangladesh

    USDA-ARS?s Scientific Manuscript database

    A number of Bangladeshi wheat genotypes (varieties and advanced lines) have been tested for boron efficiency through sand culture experiments over two years (2007-08 & 2008-09) against two Thai check varieties ‘Fang 60’ (boron efficient) and ‘SW41’ (boron inefficient). Performances of the genotypes ...

  5. Dietary boron: possible roles in human and animal physiology

    USDA-ARS?s Scientific Manuscript database

    Boron is a bioactive element of low molecular weight. Since discovery of the first boron biomolecule, boromycin, in 1967, several other similar biomolecules are now well-characterized. Most recently described was a bacterial cell-to-cell communication signal that requires boron, autoinducer-II. Boro...

  6. Colorimetric Sugar Sensing Using Boronic Acid-Substituted Azobenzenes.

    PubMed

    Egawa, Yuya; Miki, Ryotaro; Seki, Toshinobu

    2014-02-14

    In association with increasing diabetes prevalence, it is desirable to develop new glucose sensing systems with low cost, ease of use, high stability and good portability. Boronic acid is one of the potential candidates for a future alternative to enzyme-based glucose sensors. Boronic acid derivatives have been widely used for the sugar recognition motif, because boronic acids bind adjacent diols to form cyclic boronate esters. In order to develop colorimetric sugar sensors, boronic acid-conjugated azobenzenes have been synthesized. There are several types of boronic acid azobenzenes, and their characteristics tend to rely on the substitute position of the boronic acid moiety. For example, o-substitution of boronic acid to the azo group gives the advantage of a significant color change upon sugar addition. Nitrogen-15 Nuclear Magnetic Resonance (NMR) studies clearly show a signaling mechanism based on the formation and cleavage of the B-N dative bond between boronic acid and azo moieties in the dye. Some boronic acid-substituted azobenzenes were attached to a polymer or utilized for supramolecular chemistry to produce glucose-selective binding, in which two boronic acid moieties cooperatively bind one glucose molecule. In addition, boronic acid-substituted azobenzenes have been applied not only for glucose monitoring, but also for the sensing of glycated hemoglobin and dopamine.

  7. Boron-containing amino carboxylic acid compounds and uses thereof

    DOEpatents

    Kabalka, George W.; Srivastava, Rajiv R.

    2000-03-14

    Novel compounds which are useful for boron neutron capture therapy (BNCT) are disclosed. The compounds comprise a stable boron-containing group and an aminocycloalkane carboxylic acid group or a boronated acyclic hydrocarbon-linked amino carboxylic acid. Methods for synthesis of the compounds and for use of the compounds in BNCT are disclosed.

  8. Mechanical and physical properties of modern boron fibers

    NASA Technical Reports Server (NTRS)

    Dicarlo, J. A.

    1978-01-01

    Measurements of the Young's modulus, flexural modulus, shear modulus and Poisson's ratio for boron fibers prepared by modern deposition techniques are reported. Physical properties of the boron fibers, including density, thermal expansion and resistance, are also surveyed. In addition, prediction of the total deformation strain in an anelastic boron fiber subjected to tensile or flexural stress is discussed.

  9. X-ray diffraction investigation of ultrafine boron nitride powders

    SciTech Connect

    Gurov, S.V.; Chukalin, V.I.; Rezchikova, T.V.; Torbov, V.J.; Troitskii, V.N.

    1986-01-01

    This paper presents an x-ray diffraction analysis of ultrafine boron nitride powders of different mean particle sizes. Diffraction spectra of the ultrafine boron nitride powders were obtained using a DRON-1 apparatus. The experimental facts are indicative of a turbostratic character of deformation of the hexagonal lattice of ultrafinely divided boron nitride.

  10. Tracing recycled volatiles in a heterogeneous mantle with boron isotopes

    NASA Astrophysics Data System (ADS)

    Walowski, Kristina; Kirstein, Linda; de Hoog, Cees-Jan; Elliot, Tim; Savov, Ivan; Devey, Colin

    2016-04-01

    Recycling of oceanic lithosphere drives the chemical evolution of the Earth's mantle supplying both solids and volatiles to the Earth's interior. Yet, how subducted material influences mantle composition remains unclear. A perfect tracer for slab recycling should be only fractionated at the Earth's surface, have a strong influence on mantle compositions but be resistant to perturbations en route back to the surface. Current understanding suggests that boron concentrations linked to B isotope determinations fulfil all these requirements and should be an excellent tracer of heterogeneity in the deep mantle. Here, we present the trace element, volatile and the B isotope composition of basaltic glasses and melt inclusions in olivine from distinct end-member ocean island basalts (OIB) to track the fate of recycled lithosphere and ultimately document how recycling contributes to mantle heterogeneity. The chosen samples represent the different end member OIB compositions and include: EMI (Pitcairn), EMII (MacDonald), HIMU (St. Helena), and FOZO (Cape Verde & Reunion). The data is derived from both submarine and subaerial deposits, with B isotope determination of both basaltic glass and melt inclusions from each locality. Preliminary results suggest OIB have B isotopic compositions that overlap the MORB array (-7.5‰±0.7; Marschall et al., 2015) but extend to both lighter and heavier values. These results suggest that B isotopes will be useful for resolving mantle source heterogeneity at different ocean islands and contribute to our understanding of the volatile budget of the deep mantle.

  11. KENNEDY SPACE CENTER, FLA. - U.S. Senator Bill Nelson (left foreground) and NASA Administrator Sean O’Keefe (right) look deep in conversation as they leave the Central Florida Research Park, near Orlando. Behind Nelson is Congressman Tom Feeney and Center Director Jim Kennedy. The research park is being proposed as the location for NASA’s new Shared Services Center. Six sites around the U.S. are under consideration for location of the Center, which would centralize NASA’s payroll, accounting, human resources, facilities and procurement offices that are now handled at each field center. The consolidation is part of the One NASA focus. Others attending the presentation included U.S. Representative Ric Keller, Congressman Dave Weldon and Pamella J. Dana, Ph.D., director, Office of Tourism, Trade, and Economic Development in Florida.

    NASA Image and Video Library

    2004-02-19

    KENNEDY SPACE CENTER, FLA. - U.S. Senator Bill Nelson (left foreground) and NASA Administrator Sean O’Keefe (right) look deep in conversation as they leave the Central Florida Research Park, near Orlando. Behind Nelson is Congressman Tom Feeney and Center Director Jim Kennedy. The research park is being proposed as the location for NASA’s new Shared Services Center. Six sites around the U.S. are under consideration for location of the Center, which would centralize NASA’s payroll, accounting, human resources, facilities and procurement offices that are now handled at each field center. The consolidation is part of the One NASA focus. Others attending the presentation included U.S. Representative Ric Keller, Congressman Dave Weldon and Pamella J. Dana, Ph.D., director, Office of Tourism, Trade, and Economic Development in Florida.

  12. Longitudinal splitting of boron nitride nanotubes for the facile synthesis of high quality boron nitride nanoribbons.

    PubMed

    Erickson, Kris J; Gibb, Ashley L; Sinitskii, Alexander; Rousseas, Michael; Alem, Nasim; Tour, James M; Zettl, Alex K

    2011-08-10

    Boron nitride nanoribbons (BNNRs), the boron nitride structural equivalent of graphene nanoribbons (GNRs), are predicted to possess unique electronic and magnetic properties. We report the synthesis of BNNRs through the potassium-intercalation-induced longitudinal splitting of boron nitride nanotubes (BNNTs). This facile, scalable synthesis results in narrow (down to 20 nm), few sheet (typically 2-10), high crystallinity BNNRs with very uniform widths. The BNNRs are at least 1 μm in length with minimal defects within the ribbon plane and along the ribbon edges.

  13. Biological Evaluation of Boronated Unnatural Amino Acids as New Boron Carriers

    PubMed Central

    Kabalka, G.W.; Yao, M.-L.; Marepally, S.R.; Chandra, S.

    2010-01-01

    There is a pressing need for new and more efficient boron delivery agents to tumor cells for use in boron neutron capture therapy (BNCT). A class of boronated unnatural cyclic amino acids has demonstrated a remarkable selectivity toward tumors in animal and cell culture models, far superior to currently used agents in clinical BNCT. One of these amino acids, 1-amino-3-boronocyclopentanecarboxylic acid (ABCPC), has shown a tumor to blood ratio of 8 and a tumor to normal brain ratio of nearly 21 in a melanoma bearing mouse model. This work represents further biological characterization of this compound for tumor targeting in an EMT6 murine mammary carcinoma mouse model and a T98G human glioblastoma cell line. Female BALB/c mice bearing EMT6 tumors were injected with the fructose complex form of racemic mixtures of cis- and trans isomers of ABCPC in identical concentrations. Boron concentrations were measured in the tumor, blood, brain, skin, and liver tissues at 1, 3, and 5 hr post injection. These observations revealed a remarkable difference in racemic mixtures of cis and trans isomers in tumor targeting by boron. This implies that further separation of the L and D forms of this compound may enhance tumor targeting to an even higher degree than that provided by the racemic mixtures. Since the uptake measurements were made in homogenized tumor and normal tissues, little is known about the subcellular location of the boron arising from the various isomeric forms of the amino acid. To study subcellular delivery of boron from ABCPC in T98G human glioblastoma cells, we employed secondary ion mass spectrometry (SIMS) based technique of ion microscopy, which is capable of quantitatively imaging isotopic (elemental) gradients in cells and tissues at 500 nm spatial resolution. The T98G cells were exposed to the nutrient medium containing 100 ppm boron equivalent of a mixture of both L and D isomers of ABCPC in the form of a fructose complex for 1 hr. Following this

  14. Conducting Boron Sheets Formed by the Reconstruction of the α-Boron (111) Surface

    NASA Astrophysics Data System (ADS)

    Amsler, Maximilian; Botti, Silvana; Marques, Miguel A. L.; Goedecker, Stefan

    2013-09-01

    Systematic ab initio structure prediction was applied for the first time to predict low energy surface reconstructions by employing the minima hopping method on the α-boron (111) surface. Novel reconstruction geometries were identified and carefully characterized in terms of structural and electronic properties. Our calculations predict the formation of a planar, monolayer sheet at the surface, which is responsible for conductive surface states. Furthermore, the isolated boron sheet is shown to be the ground state 2D structure in vacuum at a hole density of η=1/5 and is therefore a potential candidate as a precursor for boron nanostructures.

  15. Single step synthesis of nanostructured boron nitride for boron neutron capture therapy

    NASA Astrophysics Data System (ADS)

    Singh, Bikramjeet; Singh, Paviter; Kumar, Manjeet; Thakur, Anup; Kumar, Akshay

    2015-05-01

    Nanostructured Boron Nitride (BN) has been successfully synthesized by carbo-thermic reduction of Boric Acid (H3BO3). This method is a relatively low temperature synthesis route and it can be used for large scale production of nanostructured BN. The synthesized nanoparticles have been characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analyzer (DTA). XRD analysis confirmed the formation of single phase nanostructured Boron Nitride. SEM analysis showed that the particles are spherical in shape. DTA analysis showed that the phase is stable upto 900 °C and the material can be used for high temperature applications as well boron neutron capture therapy (BNCT).

  16. Infiltration processing of boron carbide-, boron-, and boride-reactive metal cermets

    DOEpatents

    Halverson, Danny C.; Landingham, Richard L.

    1988-01-01

    A chemical pretreatment method is used to produce boron carbide-, boron-, and boride-reactive metal composites by an infiltration process. The boron carbide or other starting constituents, in powder form, are immersed in various alcohols, or other chemical agents, to change the surface chemistry of the starting constituents. The chemically treated starting constituents are consolidated into a porous ceramic precursor which is then infiltrated by molten aluminum or other metal by heating to wetting conditions. Chemical treatment of the starting constituents allows infiltration to full density. The infiltrated precursor is further heat treated to produce a tailorable microstructure. The process at low cost produces composites with improved characteristics, including increased toughness, strength.

  17. A system to deposit boron films (boronization) in the DIII-D tokamak

    SciTech Connect

    Hodapp, T.R.; Jackson, G.L.; Phillips, J.; Holtrop, K.L.; Petersen, P.I. ); Winter, J. . Inst. fuer Plasmaphysik)

    1991-09-01

    A system has been added to the D3-D tokamak to coat its plasma facing surfaces with a film of boron using diborane gas. The system includes special health and safety equipment for handling the diborane gas which is toxic and inflammable. The purpose of the boron film is to reduce the levels of impurity atoms in the D3-D plasmas. Experiments following the application of the boron film in D3-D have led to significant reductions in plasma impurity levels and the observation of a new, very high confinement regime. 9 refs., 1 fig.

  18. Formation of cubic boron-nitride by the reactive sputter deposition of boron

    SciTech Connect

    Jankowski, A.F.; Hayes, J.P.; Makowiecki, D.W.; McKeman, M.A.

    1997-03-01

    Boron-nitride films are synthesized by RF magnetron sputtering boron targets where the deposition parameters of gas pressure, flow and composition are varied along with substrate temperature and applied bias. The films are analyzed using Auger electron spectroscopy, transmission electron microscopy, nanoindentation, Raman spectroscopy and x-ray absorption spectroscopy. These techniques provide characterization of film composition, crystalline structure, hardness and chemical bonding, respectively. Reactive, rf-sputtering process parameters are established which lead to the growth of crystalline BN phases. The deposition of stable and adherent boron nitride coatings consisting of the cubic phase requires 400 `C substrate heating and the application of a 300 V negative bias.

  19. Lessons from Earth's Deep Time

    ERIC Educational Resources Information Center

    Soreghan, G. S.

    2005-01-01

    Earth is a repository of data on climatic changes from its deep-time history. Article discusses the collection and study of these data to predict future climatic changes, the need to create national study centers for the purpose, and the necessary cooperation between different branches of science in climatic research.

  20. Enhancement and retardation of thermal boron diffusion in silicon from atmospheric pressure chemical vapor deposited boron silicate glass film

    NASA Astrophysics Data System (ADS)

    Kurachi, Ikuo; Yoshioka, Kentaro

    2014-03-01

    Thermal boron diffusion into silicon from boron silicate glass (BSG) prepared by atmospheric pressure CVD (AP-CVD) has been investigated in terms of the BSG boron concentration dependence on diffusion mechanism for N-type solar cell applications. With thermal diffusion at 950 °C in N2 for 20 min, the sheet resistance of the boron-diffused layer decreases with BSG boron concentration up to approximately 4 × 1021 cm-3 at which a boron-rich layer (BRL) is formed at the surface. However, the resistance increases with BSG boron concentration when the BSG boron concentration is higher than 4 × 1021 cm-3. It is also confirmed that the diffusion depth decreases with increasing BSG boron concentration within this BSG concentration region. To clarify this mechanism, the BSG boron concentration dependence on boron diffusivity has also been studied. From extracted diffusivities, the anomalous diffusion can be explained by silicon interstitials formed owing to kick-out by diffused boron atoms and by silicon interstitial generation-degradation due to BRL formation.

  1. Accelerator-driven boron neutron capture therapy

    NASA Astrophysics Data System (ADS)

    Edgecock, Rob

    2014-05-01

    Boron Neutron Capture Therapy is a binary treatment for certain types of cancer. It works by loading the cancerous cells with a boron-10 carrying compound. This isotope has a large cross-section for thermal neutrons, the reaction producing a lithium nucleus and alpha particle that kill the cell in which they are produced. Recent studies of the boron carrier compound indicate that the uptake process works best in particularly aggressive cancers. Most studied is glioblastoma multiforme and a trial using a combination of BNCT and X-ray radiotherapy has shown an increase of nearly a factor of two in mean survival over the state of the art. However, the main technical problem with BNCT remains producing a sufficient flux of neutrons for a reasonable treatment duration in a hospital environment. This paper discusses this issue.

  2. Oxygen radical functionalization of boron nitride nanosheets.

    PubMed

    Sainsbury, Toby; Satti, Amro; May, Peter; Wang, Zhiming; McGovern, Ignatius; Gun'ko, Yurii K; Coleman, Jonathan

    2012-11-14

    The covalent chemical functionalization of exfoliated hexagonal boron-nitride nanosheets (BNNSs) is achieved by the solution-phase oxygen radical functionalization of boron atoms in the h-BN lattice. This involves a two-step procedure to initially covalently graft alkoxy groups to boron atoms and the subsequent hydrolytic defunctionalization of the groups to yield hydroxyl-functionalized BNNSs (OH-BNNSs). Characterization of the functionalized-BNNSs using HR-TEM, Raman, UV-vis, FTIR, NMR, and TGA was performed to investigate both the structure of the BNNSs and the covalent functionalization methodology. OH-BNNSs were used to prepare polymer nanocomposites and their mechanical properties analyzed. The influence of the functional groups grafted to the surface of the BNNSs is investigated by demonstrating the impact on mechanical properties of both noncovalent and covalent bonding at the interface between the nanofiller and polymer matrixes.

  3. On the Mechanism of Boron Ignition

    NASA Technical Reports Server (NTRS)

    Keil, D. G.; Dreizin, E. L.; Felder, W.; Vicenzi, E. P.

    1997-01-01

    Boron filaments were electrically heated in air and argon/oxygen mixtures while their resistance, temperature, and radiation at the wavelengths of BO and BO2 bands were monitored. The filaments 'burned' in two distinct stages. Samples of the filaments were quenched at different times before and during the burning and analyzed using electron microscopy. The beginning of the first stage combustion characterized by a local resistance minimum, a sharp spike in boron oxide radiation emission, and a rapid rise in temperature, occurred at 1500 +/- 70 deg. C, independent of pre-heating history and oxygen content (540%) in the gas environment. The data suggest that a phase transition occurs in the filaments at this temperature that triggers stage one combustion. Significant amounts of oxygen were found inside quenched filaments. Large spherical voids formed in the boron filaments during their second stage combustion which is interpreted to indicate a crucial role for the gas dissolution processes in the combustion scenario.

  4. A small, insertable oven for boronization

    SciTech Connect

    Brouchous, D.A.; Diebold, D.A.; Doczy, M.L.

    1996-04-01

    A small insertable oven for benchmarking the boronizing characteristics of solid compounds, such as decaborane and carborane, has been developed for the Phaedrus-T tokamak. Assembly and installation of the oven are relatively easy as the oven design utilizes a Langmuir probe drive assembly, which is standard equipment on most tokamaks and allows the oven to be inserted into the tokamak without requiring a vent. Films deposited by heating carborane into the vapor state with the oven are found to be spatially nonuniform in both thickness and in the ratio of boron to carbon as compared to films deposited with trimethylboron, a gaseous compound. Overall plasma performance is not found to be greatly affected by whether decaborane, carborane or trimethylboron is used for boronization in Phaedrus-T. {copyright} {ital 1996 American Institute of Physics.} {lt}ii;010512{gt}

  5. Metallicity of boron carbides at high pressure

    NASA Astrophysics Data System (ADS)

    Dekura, Haruhiko; Shirai, Koun; Yanase, Akira

    2010-03-01

    Electronic structure of semiconducting boron carbide at high pressure has been theoretically investigated, because of interests in the positive pressure dependence of resistivity, in the gap closure, and in the phase transition. The most simplest form B12(CCC) is assumed. Under assumptions of hydrostatic pressure and neglecting finite-temperature effects, boron carbide is quite stable at high pressure. The crystal of boron carbide is stable at least until a pressure higher than previous experiments showed. The gap closure occurs only after p=600 GPa on the assumption of the original crystal symmetry. In the low pressure regime, the pressure dependence of the energy gap almost diminishes, which is an exceptional case for semiconductors, which could be one of reasons for the positive pressure dependence of resistivity. A monotonous increase in the apex angle of rhombohedron suggests that the covalent bond continues to increase. The C chain inserted in the main diagonal of rhombohedral structure is the chief reason of this stability.

  6. On the Mechanism of Boron Ignition

    NASA Technical Reports Server (NTRS)

    Keil, D. G.; Dreizin, E. L.; Felder, W.; Vicenzi, E. P.

    1997-01-01

    Boron filaments were electrically heated in air and argon/oxygen mixtures while their resistance, temperature, and radiation at the wavelengths of BO and BO2 bands were monitored. The filaments 'burned' in two distinct stages. Samples of the filaments were quenched at different times before and during the burning and analyzed using electron microscopy. The beginning of the first stage combustion characterized by a local resistance minimum, a sharp spike in boron oxide radiation emission, and a rapid rise in temperature, occurred at 1500 +/- 70 deg. C, independent of pre-heating history and oxygen content (540%) in the gas environment. The data suggest that a phase transition occurs in the filaments at this temperature that triggers stage one combustion. Significant amounts of oxygen were found inside quenched filaments. Large spherical voids formed in the boron filaments during their second stage combustion which is interpreted to indicate a crucial role for the gas dissolution processes in the combustion scenario.

  7. Boron-10 Lined Proportional Counter Model Validation

    SciTech Connect

    Lintereur, Azaree T.; Siciliano, Edward R.; Kouzes, Richard T.

    2012-06-30

    The Department of Energy Office of Nuclear Safeguards (NA-241) is supporting the project “Coincidence Counting With Boron-Based Alternative Neutron Detection Technology” at Pacific Northwest National Laboratory (PNNL) for the development of an alternative neutron coincidence counter. The goal of this project is to design, build and demonstrate a boron-lined proportional tube-based alternative system in the configuration of a coincidence counter. This report discusses the validation studies performed to establish the degree of accuracy of the computer modeling methods current used to simulate the response of boron-lined tubes. This is the precursor to developing models for the uranium neutron coincidence collar under Task 2 of this project.

  8. Boron Nanotubes/Nanofibers in Propellant Material Formulations: Testing and Characterization for Gun Barrel Protection

    DTIC Science & Technology

    2011-01-13

    synthesis of boron nanostructures comprising of a mixture of boron nanotubes ( BNTs ) and nanofibers (BNFs) was developed under this contract. A method of...nitrogen doping the BNTs and BNFs was also demonstrated. A key feature of this work is the use of a solid instead of a gaseous boron precursor for the...synthesis of boron nanotubes and boron nanofibers. A solid boron precursor was chosen for BNT /BNF synthesis because typical gaseous boron precursors

  9. A Metal and Base-Free Chemoselective Primary Amination of Boronic Acids Using Cyanamidyl/Arylcyanamidyl Radical as Aminating Species: Synthesis and Mechanistic Studies by Density Functional Theory.

    PubMed

    Chatterjee, Nachiketa; Arfeen, Minhajul; Bharatam, Prasad V; Goswami, Avijit

    2016-06-17

    An efficient, metal and base-free, chemoselective synthesis of aryl-, heteroaryl-, and alkyl primary amines from the corresponding boronic acids has been achieved at ambient temperature mediated by [bis(trifluoroacetoxy)iodo]benzene (PIFA) and N-bromosuccinimide (NBS) using cyanamidyl/arylcyanamidyl radicals as the aminating species. The primary amine compounds were initially obtained as their corresponding ammonium trifluoroacetate salts which, on treatment with aq NaOH, provide the free amines. Finally, the primary amines were isolated through column chromatography over silica-gel using hexane-EtOAc solvent system as the eluent. The reactions are sufficiently fast, completing within 1 h. Quantum chemical calculations in combination with experimental observations validate that the ipso amination of substituted boronic acids involves the formation of cyanamidyl/arylcyanamidyl radical, followed by regiospecific interaction of its nitrile-N center with boron atom of the boronic acids, leading to chemoselective primary amination.

  10. Chemical and mechanical analysis of boron-rich boron carbide processed via spark plasma sintering

    NASA Astrophysics Data System (ADS)

    Munhollon, Tyler Lee

    Boron carbide is a material of choice for many industrial and specialty applications due to the exceptional properties it exhibits such as high hardness, chemical inertness, low specific gravity, high neutron cross section and more. The combination of high hardness and low specific gravity makes it especially attractive for high pressure/high strain rate applications. However, boron carbide exhibits anomalous behavior when high pressures are applied. Impact pressures over the Hugoniot elastic limit result in catastrophic failure of the material. This failure has been linked to amorphization in cleavage planes and loss of shear strength. Atomistic modeling has suggested boron-rich boron carbide (B13C2) may be a better performing material than the commonly used B4C due to the elimination of amorphization and an increase in shear strength. Therefore, a clear experimental understanding of the factors that lead to the degradation of mechanical properties as well as the effects of chemistry changes in boron carbide is needed. For this reason, the goal of this thesis was to produce high purity boron carbide with varying stoichiometries for chemical and mechanical property characterization. Utilizing rapid carbothermal reduction and pressure assisted sintering, dense boron carbides with varying stoichiometries were produced. Microstructural characteristics such as impurity inclusions, porosity and grain size were controlled. The chemistry and common static mechanical properties that are of importance to superhard materials including elastic moduli, hardness and fracture toughness of the resulting boron-rich boron carbides were characterized. A series of six boron carbide samples were processed with varying amounts of amorphous boron (up to 45 wt. % amorphous boron). Samples with greater than 40 wt.% boron additions were shown to exhibit abnormal sintering behavior, making it difficult to characterize these samples. Near theoretical densities were achieved in samples with

  11. Liposomal boron delivery for neutron capture therapy.

    PubMed

    Nakamura, Hiroyuki

    2009-01-01

    Tumor cell destruction in boron neutron capture therapy (BNCT) is due to the nuclear reaction between (10)B and thermal neutrons. The thermal neutrons have an energy of 0.025 eV, clearly below the threshold energy required to ionize tissue components. However, neutron capture by (10)B produces lithium ion and helium (alpha-particles), which are high linear energy transfer (LET) particles, and dissipate their kinetic energy before traveling one cell diameter (5-9 microm) in biological tissues, ensuring their potential for precise cell killing. BNCT has been applied clinically for the treatment of malignant brain tumors, malignant melanoma, head and neck cancer, and hepatoma using two boron compounds: sodium borocaptate (Na(2)(10)B(12)H(11)SH; Na(2)(10)BSH) and l-p-boronophenylalanine (l-(10)BPA). These low molecular weight compounds are cleared easily from the cancer cells and blood. Therefore, high accumulation and selective delivery of boron compounds into tumor tissues are most important to achieve effective BNCT and to avoid damage of adjacent healthy cells. Much attention has been focused on the liposomal drug delivery system (DDS) as an attractive, intelligent technology of targeting and controlled release of (10)B compounds. Two approaches have been investigated for incorporation of (10)B into liposomes: (1) encapsulation of (10)B compounds into liposomes and (2) incorporation of (10)B-conjugated lipids into the liposomal bilayer. Our laboratory has developed boron ion cluster lipids for application of the latter approach. In this chapter, our boron lipid liposome approaches as well as recent developments of the liposomal boron delivery system are summarized.

  12. Boron removal by electrocoagulation and recovery.

    PubMed

    Isa, Mohamed Hasnain; Ezechi, Ezerie Henry; Ahmed, Zubair; Magram, Saleh Faraj; Kutty, Shamsul Rahman Mohamed

    2014-03-15

    This work investigated the removal of boron from wastewater and its recovery by electrocoagulation and hydrothermal mineralization methods respectively. The experimental design was developed using Box-Behnken Model. An initial study was performed based on four preselected variables (pH, current density, concentration and time) using synthetic wastewater. Response surface methodology (RSM) was used to evaluate the effect of process variables and their interaction on boron removal. The optimum conditions were obtained as pH 6.3, current density 17.4 mA/cm(2), and time 89 min. At these applied optimum conditions, 99.7% boron removal from an initial concentration of 10.4 mg/L was achieved. The process was effectively optimized by RSM with a desirability value of 1.0. The results showed that boron removal efficiency enhanced with increase in current density and treatment time. Removal efficiency also increased when pH was increased from 4 to 7 and subsequently decreased at pH 10. Adsorption kinetics study revealed that the reaction followed pseudo second order kinetic model; evidenced by high correlation and goodness of fit. Thermodynamics study showed that mechanism of boron adsorption was chemisorption and the reaction was endothermic in nature. Furthermore, the adsorption process was spontaneous as indicated by negative values of the adsorption free energy. Treatment of real produced water using electrocoagulation resulted in 98% boron removal. The hydrothermal mineralization study showed that borate minerals (Inyoite, Takadaite and Nifontovite) can be recovered as recyclable precipitate from electrocoagulation flocs of produced water. Copyright © 2013 Elsevier Ltd. All rights reserved.

  13. Deep smarts.

    PubMed

    Leonard, Dorothy; Swap, Walter

    2004-09-01

    When a person sizes up a complex situation and rapidly comes to a decision that proves to be not just good but brilliant, you think, "That was smart." After you watch him do this a few times, you realize you're in the presence of something special. It's not raw brainpower, though that helps. It's not emotional intelligence, either, though that, too, is often involved. It's deep smarts. Deep smarts are not philosophical--they're not"wisdom" in that sense, but they're as close to wisdom as business gets. You see them in the manager who understands when and how to move into a new international market, in the executive who knows just what kind of talk to give when her organization is in crisis, in the technician who can track a product failure back to an interaction between independently produced elements. These are people whose knowledge would be hard to purchase on the open market. Their insight is based on know-how more than on know-what; it comprises a system view as well as expertise in individual areas. Because deep smarts are experienced based and often context specific, they can't be produced overnight or readily imported into an organization. It takes years for an individual to develop them--and no time at all for an organization to lose them when a valued veteran walks out the door. They can be taught, however, with the right techniques. Drawing on their forthcoming book Deep Smarts, Dorothy Leonard and Walter Swap say the best way to transfer such expertise to novices--and, on a larger scale, to make individual knowledge institutional--isn't through PowerPoint slides, a Web site of best practices, online training, project reports, or lectures. Rather, the sage needs to teach the neophyte individually how to draw wisdom from experience. Companies have to be willing to dedicate time and effort to such extensive training, but the investment more than pays for itself.

  14. Fracture behavior of unidirectional boron/aluminum composite laminates

    NASA Technical Reports Server (NTRS)

    Jones, F. W.; Goree, J. G.

    1983-01-01

    An experimental investigation of the fracture behavior of unidirectional boron/aluminum composite laminates was conducted in order to verify the results of mathematical models. These models predict the fiber stresses and displacements and the amount of damage growth in a center-notched lamina as a function of the applied remote stress and the matrix and fiber material properties. A brittle lacquer coating was used to detect the yielding in the matrix while X-ray techniques were used to determine the number of broken fibers in the laminate. The notched strengths and the amounts of damage found in the specimens agreed well with those predicted by the models. It was shown that for thin laminates the amount of damage and the fiber displacements do not depend strongly on the number of plies for a given notch width.

  15. Mode Grüneisen parameters of boron carbide

    NASA Astrophysics Data System (ADS)

    Werheit, Helmut; Manghnani, Murli H.; Kuhlmann, Udo; Hushur, Anwar; Shalamberidze, Sulkhan

    2017-10-01

    IR- and Raman-active phonons of boron carbide and the mode Grüneisen parameters γ related are studied concerning their dependence on chemical composition, temperatures between 30 and 800 K and pressures up to ∼70 GPa. Most bulk phonons yield γ between +1.5 and - 1.5: those related to icosahedra yield γ = 0.8(3). Surface phonons are distinguished by considerably higher γ. Negative γ of chain bending modes supports the assumption that the chain center buckles out under pressure. Some striking specific mode Grüneisen parameters are explained. Pressure-dependent bond lengths suggest the reversible high-pressure phase transition to be second order.

  16. Thermal conductance of graphene/hexagonal boron nitride heterostructures

    NASA Astrophysics Data System (ADS)

    Lu, Simon; McGaughey, Alan J. H.

    2017-03-01

    The lattice-based scattering boundary method is applied to compute the phonon mode-resolved transmission coefficients and thermal conductances of in-plane heterostructures built from graphene and hexagonal boron nitride (hBN). The thermal conductance of all structures is dominated by acoustic phonon modes near the Brillouin zone center that have high group velocity, population, and transmission coefficient. Out-of-plane modes make their most significant contributions at low frequencies, whereas in-plane modes contribute across the frequency spectrum. Finite-length superlattice junctions between graphene and hBN leads have a lower thermal conductance than comparable junctions between two graphene leads due to lack of transmission in the hBN phonon bandgap. The thermal conductances of bilayer systems differ by less than 10% from their single-layer counterparts on a per area basis, in contrast to the strong thermal conductivity reduction when moving from single- to multi-layer graphene.

  17. Thermal conductivity behavior of boron carbides

    NASA Technical Reports Server (NTRS)

    Wood, C.; Zoltan, A.; Emin, D.; Gray, P. E.

    1983-01-01

    Knowledge of the thermal conductivity of boron carbides is necessary to evaluate its potential for high temperature thermoelectric energy conversion applications. The thermal diffusivity of hot pressed boron carbide B/sub 1-x/C/sub x/ samples as a function of composition, temperature and temperature cycling was measured. These data in concert with density and specific heat data yield the thermal conductivities of these materials. The results in terms of a structural model to explain the electrical transport data and novel mechanisms for thermal conduction are discussed.

  18. Proton linacs for boron neutron capture therapy

    SciTech Connect

    Lennox, A.J. |

    1993-08-01

    Recent advances in the ability to deliver boron-containing drugs to brain tumors have generated interest in {approximately}4 MeV linacs as sources of epithermal neutrons for radiation therapy. In addition, fast neutron therapy facilities have been studying methods to moderate their beams to take advantage of the high cross section for epithermal neutrons on boron-10. This paper describes the technical issues involved in each approach and presents the motivation for undertaking such studies using the Fermilab linac. the problems which must be solved before therapy can begin are outlined. Status of preparatory work and results of preliminary measurements are presented.

  19. Boron Nitride Nanotubes-Reinforced Glass Composites

    NASA Technical Reports Server (NTRS)

    Bansal, Narottam; Hurst, Janet B.; Choi, Sung R.

    2005-01-01

    Boron nitride nanotubes of significant lengths were synthesized by reaction of boron with nitrogen. Barium calcium aluminosilicate glass composites reinforced with 4 weight percent of BN nanotubes were fabricated by hot pressing. Ambient-temperature flexure strength and fracture toughness of the glass-BN nanotube composites were determined. The strength and fracture toughness of the composite were higher by as much as 90 and 35 percent, respectively, than those of the unreinforced glass. Microscopic examination of the composite fracture surfaces showed pullout of the BN nanotubes. The preliminary results on the processing and improvement in mechanical properties of BN nanotube reinforced glass matrix composites are being reported here for the first time.

  20. Tight-Binding study of Boron structures

    NASA Astrophysics Data System (ADS)

    McGrady, Joseph W.; Papaconstantopoulos, Dimitrios A.; Mehl, Michael J.

    2014-10-01

    We have performed Linearized Augmented Plane Wave (LAPW) calculations for five crystal structures (alpha, dhcp, sc, fcc, bcc) of Boron which we then fitted to a non-orthogonal tight-binding model following the Naval Research Laboratory Tight-Binding (NRL-TB) method. The predictions of the NRL-TB approach for complicated Boron structures such as R105 (or β-rhombohedral) and T190 are in agreement with recent first-principles calculations. Fully utilizing the computational speed of the NRL-TB method we calculated the energy differences of various structures, including those containing vacancies using supercells with up to 5000 atoms.

  1. Phenylene bridged boron-nitrogen containing dendrimers.

    PubMed

    Proń, Agnieszka; Baumgarten, Martin; Müllen, Klaus

    2010-10-01

    The synthesis and characterization of novel phenylene bridged boron-nitrogen containing π-conjugated dendrimers N3B6 and N3B3, with peripheral boron atoms and 1,3,5-triaminobenzene moiety as a core, are presented. UV-vis absorption and emission measurements reveal that the optical properties of the resulting compounds can be controlled by changing the donor/acceptor ratio: a 1:1 ratio results in a more efficient charge transfer than the 1:2 ratio. This was proven by the red shift of the emission maxima and the stronger solvatochromic effect in N3B3 compared to N3B6.

  2. Reactive sputter deposition of boron nitride

    SciTech Connect

    Jankowski, A.F.; Hayes, J.P.; McKernan, M.A.; Makowiecki, D.M.

    1995-10-01

    The preparation of fully dense, boron targets for use in planar magnetron sources has lead to the synthesis of Boron Nitride (BN) films by reactive rf sputtering. The deposition parameters of gas pressure, flow and composition are varied along with substrate temperature and applied bias. The films are characterized for composition using Auger electron spectroscopy, for chemical bonding using Raman spectroscopy and for crystalline structure using transmission electron microscopy. The deposition conditions are established which lead to the growth of crystalline BN phases. In particular, the growth of an adherent cubic BN coating requires 400--500 C substrate heating and an applied {minus}300 V dc bias.

  3. Can Two-Dimensional Boron Superconduct?

    PubMed

    Penev, Evgeni S; Kutana, Alex; Yakobson, Boris I

    2016-04-13

    Two-dimensional boron is expected to exhibit various structural polymorphs, all being metallic. Additionally, its small atomic mass suggests strong electron-phonon coupling, which in turn can enable superconducting behavior. Here we perform first-principles analysis of electronic structure, phonon spectra, and electron-phonon coupling of selected 2D boron polymorphs and show that the most stable structures predicted to feasibly form on a metal substrate should also exhibit intrinsic phonon-mediated superconductivity, with estimated critical temperature in the range of Tc ≈ 10-20 K.

  4. Titanium reinforced boron-polyimide composite

    NASA Technical Reports Server (NTRS)

    Clark, G. A.; Clayton, K. I.

    1969-01-01

    Processing techniques for boron polyimide prepreg were developed whereby composites could be molded under vacuum bag pressure only. A post-cure cycle was developed which resulted in no loss in room temperature mechanical properties of the composite at any time during up to 16 hours at 650 F. A design utilizing laminated titanium foil was developed to achieve a smooth transition of load from the titanium attachment points into the boron-reinforced body of the structure. The box beam test article was subjected to combined bending and torsional loads while exposed to 650 F. Loads were applied incrementally until failure occurred at 83% design limit load.

  5. Low pressure growth of cubic boron nitride films

    NASA Technical Reports Server (NTRS)

    Ong, Tiong P. (Inventor); Shing, Yuh-Han (Inventor)

    1997-01-01

    A method for forming thin films of cubic boron nitride on substrates at low pressures and temperatures. A substrate is first coated with polycrystalline diamond to provide a uniform surface upon which cubic boron nitride can be deposited by chemical vapor deposition. The cubic boron nitride film is useful as a substitute for diamond coatings for a variety of applications in which diamond is not suitable. any tetragonal or hexagonal boron nitride. The cubic boron nitride produced in accordance with the preceding example is particularly well-suited for use as a coating for ultra hard tool bits and abrasives, especially those intended to use in cutting or otherwise fabricating iron.

  6. Magnetron sputtered boron films and TI/B multilayer structures

    DOEpatents

    Makowiecki, Daniel M.; Jankowski, Alan F.

    1993-01-01

    A method is described for the production of thin boron and titanium/boron films by magnetron sputter deposition. The amorphous boron films contain no morphological growth features, unlike those found when thin films are prepared by various physical vapor deposition processes. Magnetron sputter deposition method requires the use of a high density crystalline boron sputter target which is prepared by hot isostatic pressing. Thin boron films prepared by this method are useful for ultra-thin band pass filters as well as the low Z element in low Z/high Z mirrors which enhance reflectivity from grazing to normal incidence.

  7. Magnetron sputtered boron films and TI/B multilayer structures

    DOEpatents

    Makowiecki, D.M.; Jankowski, A.F.

    1993-04-20

    A method is described for the production of thin boron and titanium/boron films by magnetron sputter deposition. The amorphous boron films contain no morphological growth features, unlike those found when thin films are prepared by various physical vapor deposition processes. Magnetron sputter deposition method requires the use of a high density crystalline boron sputter target which is prepared by hot isostatic pressing. Thin boron films prepared by this method are useful for ultra-thin band pass filters as well as the low Z element in low Z/high Z mirrors which enhance reflectivity from grazing to normal incidence.

  8. Magnetron sputtered boron films and Ti/B multilayer structures

    DOEpatents

    Makowiecki, Daniel M.; Jankowski, Alan F.

    1995-01-01

    A method is described for the production of thin boron and titanium/boron films by magnetron sputter deposition. The amorphous boron films contain no morphological growth features, unlike those found when thin films are prepared by various physical vapor deposition processes. Magnetron sputter deposition method requires the use of a high density crystalline boron sputter target which is prepared by hot isostatic pressing. Thin boron films prepared by this method are useful for ultra-thin band pass filters as well as the low Z element in low Z/high Z mirrors which enhance reflectivity from grazing to normal incidence.

  9. Magnetron sputtered boron films and Ti/B multilayer structures

    DOEpatents

    Makowiecki, D.M.; Jankowski, A.F.

    1995-02-14

    A method is described for the production of thin boron and titanium/boron films by magnetron sputter deposition. The amorphous boron films contain no morphological growth features, unlike those found when thin films are prepared by various physical vapor deposition processes. Magnetron sputter deposition method requires the use of a high density crystalline boron sputter target which is prepared by hot isostatic pressing. Thin boron films prepared by this method are useful for ultra-thin band pass filters as well as the low Z element in low Z/high Z mirrors which enhance reflectivity from grazing to normal incidence. 6 figs.

  10. Dietary boron: progress in establishing essential roles in human physiology.

    PubMed

    Hunt, Curtiss D

    2012-06-01

    This review summarizes the progress made in establishing essential roles for boron in human physiology and assesses that progress in view of criteria for essentiality of elements. The evidence to date suggests that humans and at least some higher animals may use boron to support normal biological functions. These include roles in calcium metabolism, bone growth and maintenance, insulin metabolism, and completion of the life cycle. The biochemical mechanisms responsible for these effects are poorly understood but the nature of boron biochemistry suggests further characterization of the cell signaling molecules capable of complexing with boron. Such characterization may provide insights into the biochemical function(s) of boron in humans.

  11. Deep, zonal subequatorial currents.

    PubMed

    Talley, L D; Johnson, G C

    1994-02-25

    Large-scale, westward-extending tongues of warm (Pacific) and cold (Atlantic) water are found between 2000 and 3000 meters both north and south of the equator in the Pacific and Atlantic oceans. They are centered at 5 degrees to 8 degrees north and 10 degrees to 15 degrees south (Pacific) and 5 degrees to 8 degrees north and 15 degrees to 20 degrees south (Atlantic). They are separated in both oceans by a contrasting eastward-extending tongue, centered at about 1 degrees to 2 degrees south, in agreement with previous helium isotope observations (Pacific). Thus, the indicated deep tropical westward flows north and south of the equator and eastward flow near the equator may result from more general forcing than the hydrothermal forcing previously hypothesized.

  12. Boron Nitride Nanotubes for Spintronics

    PubMed Central

    Dhungana, Kamal B.; Pati, Ranjit

    2014-01-01

    With the end of Moore's law in sight, researchers are in search of an alternative approach to manipulate information. Spintronics or spin-based electronics, which uses the spin state of electrons to store, process and communicate information, offers exciting opportunities to sustain the current growth in the information industry. For example, the discovery of the giant magneto resistance (GMR) effect, which provides the foundation behind modern high density data storage devices, is an important success story of spintronics; GMR-based sensors have wide applications, ranging from automotive industry to biology. In recent years, with the tremendous progress in nanotechnology, spintronics has crossed the boundary of conventional, all metallic, solid state multi-layered structures to reach a new frontier, where nanostructures provide a pathway for the spin-carriers. Different materials such as organic and inorganic nanostructures are explored for possible applications in spintronics. In this short review, we focus on the boron nitride nanotube (BNNT), which has recently been explored for possible applications in spintronics. Unlike many organic materials, BNNTs offer higher thermal stability and higher resistance to oxidation. It has been reported that the metal-free fluorinated BNNT exhibits long range ferromagnetic spin ordering, which is stable at a temperature much higher than room temperature. Due to their large band gap, BNNTs are also explored as a tunnel magneto resistance device. In addition, the F-BNNT has recently been predicted as an ideal spin-filter. The purpose of this review is to highlight these recent progresses so that a concerted effort by both experimentalists and theorists can be carried out in the future to realize the true potential of BNNT-based spintronics. PMID:25248070

  13. Boron nitride nanotubes for spintronics.

    PubMed

    Dhungana, Kamal B; Pati, Ranjit

    2014-09-22

    With the end of Moore's law in sight, researchers are in search of an alternative approach to manipulate information. Spintronics or spin-based electronics, which uses the spin state of electrons to store, process and communicate information, offers exciting opportunities to sustain the current growth in the information industry. For example, the discovery of the giant magneto resistance (GMR) effect, which provides the foundation behind modern high density data storage devices, is an important success story of spintronics; GMR-based sensors have wide applications, ranging from automotive industry to biology. In recent years, with the tremendous progress in nanotechnology, spintronics has crossed the boundary of conventional, all metallic, solid state multi-layered structures to reach a new frontier, where nanostructures provide a pathway for the spin-carriers. Different materials such as organic and inorganic nanostructures are explored for possible applications in spintronics. In this short review, we focus on the boron nitride nanotube (BNNT), which has recently been explored for possible applications in spintronics. Unlike many organic materials, BNNTs offer higher thermal stability and higher resistance to oxidation. It has been reported that the metal-free fluorinated BNNT exhibits long range ferromagnetic spin ordering, which is stable at a temperature much higher than room temperature. Due to their large band gap, BNNTs are also explored as a tunnel magneto resistance device. In addition, the F-BNNT has recently been predicted as an ideal spin-filter. The purpose of this review is to highlight these recent progresses so that a concerted effort by both experimentalists and theorists can be carried out in the future to realize the true potential of BNNT-based spintronics.

  14. Ultrahard nanotwinned cubic boron nitride.

    PubMed

    Tian, Yongjun; Xu, Bo; Yu, Dongli; Ma, Yanming; Wang, Yanbin; Jiang, Yingbing; Hu, Wentao; Tang, Chengchun; Gao, Yufei; Luo, Kun; Zhao, Zhisheng; Wang, Li-Min; Wen, Bin; He, Julong; Liu, Zhongyuan

    2013-01-17

    Cubic boron nitride (cBN) is a well known superhard material that has a wide range of industrial applications. Nanostructuring of cBN is an effective way to improve its hardness by virtue of the Hall-Petch effect--the tendency for hardness to increase with decreasing grain size. Polycrystalline cBN materials are often synthesized by using the martensitic transformation of a graphite-like BN precursor, in which high pressures and temperatures lead to puckering of the BN layers. Such approaches have led to synthetic polycrystalline cBN having grain sizes as small as ∼14 nm (refs 1, 2, 4, 5). Here we report the formation of cBN with a nanostructure dominated by fine twin domains of average thickness ∼3.8 nm. This nanotwinned cBN was synthesized from specially prepared BN precursor nanoparticles possessing onion-like nested structures with intrinsically puckered BN layers and numerous stacking faults. The resulting nanotwinned cBN bulk samples are optically transparent with a striking combination of physical properties: an extremely high Vickers hardness (exceeding 100 GPa, the optimal hardness of synthetic diamond), a high oxidization temperature (∼1,294 °C) and a large fracture toughness (>12 MPa m(1/2), well beyond the toughness of commercial cemented tungsten carbide, ∼10 MPa m(1/2)). We show that hardening of cBN is continuous with decreasing twin thickness down to the smallest sizes investigated, contrasting with the expected reverse Hall-Petch effect below a critical grain size or the twin thickness of ∼10-15 nm found in metals and alloys.

  15. Deep morphea.

    PubMed

    Bielsa, Isabel; Ariza, Aurelio

    2007-06-01

    Deep morphea encompasses a variety of clinical entities in which inflammation and sclerosis are found in the deep dermis, panniculus, fascia, or superficial muscle. Morphea profunda, eosinophilic fasciitis, and disabling pansclerotic morphea of children are included in this group, but overlapping of the extent and depth of cutaneous involvement in these various conditions precludes their distinction on the sole basis of clinical or even histologic examination. Furthermore, the limits between morphea profunda and generalized morphea, which usually are classified outside this group, are not clear. Histologically, all these disorders show similar inflammatory and sclerotic findings, the primary difference being the depth of these changes. Associated clinical findings, including arthralgias, arthritis, contractures, or carpal tunnel syndrome, are frequent. Although visceral complications are uncommon, pulmonary, esophageal, and even cardiac abnormalities have been reported. Eosinophilia, hypergammaglobulinemia, and increased erythrocyte sedimentation rate may be present with disease activity. Laboratory studies may demonstrate autoantibody production. Treatment is nonstandardized but UVA irradiation and antiinflammatory or immunosuppressive drugs (mainly antimalarial agents and corticosteroids) may be beneficial.

  16. Chemical Behaviors of Energetic Deuterium Implanted into Boron Coatings

    SciTech Connect

    Kodama, H.; Morimoto, Y.; Sasaki, M.; Oyaidu, M.; Oya, Y.; Sagara, A.; Noda, N.; Okuno, K.

    2003-09-15

    To study chemical behaviors of energetic deuterium implanted into boron coating deposited by boronization in fusion devices, two types of boron coating film deposited on silicon and IG-430U were prepared by Plasma Chemical Vapor Deposition (PCVD) technique. Boron polycrystal was used as the reference sample. The chemical behavior of deuterium was investigated by XPS (X-ray photoelectron spectroscopy) and TDS (Thermal adsorption spectroscopy).The 1.0 keV D{sub 2}{sup +} ions were implanted into the samples and the deuterium desorption behavior was studied by TDS. The TDS spectra showed that there were two deuterium release peaks at around 550 and 750 K, which were attributed to the release from deuterium trapped by boron and carbon, respectively. It was also found that most of implanted deuterium was trapped in carbon trapping site compared with boron one.In XPS measurements, the chemical shift of B-1s towards positive side was observed in the film on IG-430U after D{sub 2}{sup +} ion implantation. However, no chemical shifts were found in the film on silicon and boron polycrystal. In highly concentrated boron materials, even if deuterium was implanted into the boron materials, the amount of B-D bond was too low to be measured by XPS. This suggests that deuterium implanted into highly pure boron materials wasn't almost trapped, so that the retention of deuterium in the boron materials would be reduced, compared that in carbon materials.

  17. Tremendous spin-splitting effects in open boron nitride nanotubes: application to nanoscale spintronic devices.

    PubMed

    Hao, Shaogang; Zhou, Gang; Duan, Wenhui; Wu, Jian; Gu, Bing-Lin

    2006-07-05

    Our calculations demonstrate that the intrinsic magnetism of boron nitride nanotubes (BNNTs) can be induced by their open ends, and the resulting magnetic moment is sensitive to the chirality of BNNTs. It is found that BNNTs, a pure sp-electron system, present a tremendous spin-splitting larger than 1 eV and that B-rich-ended and N-rich-ended BNNTs exhibit "conjugate", spin-polarized, deep-gap states. Tremendous spin-splitting effects combined with considerable local spin-polarizations at the open ends make BNNTs significant for applications of nanoscale spintronics such as spin-polarized electron emitters.

  18. Tandem-ESQ for Accelerator-Based Boron Neutron Capture Therapy (AB-BNCT)

    SciTech Connect

    Kreiner, A. J.; Kwan, J. W.; Henestroza, E.; Burlon, A. A.; Di Paolo, H.; Minsky, D.; Debray, M.; Valda, A.; Somacal, H. R.

    2007-02-12

    A folded tandem, with 1.25 MV terminal voltage, combined with an ElectroStatic Quadrupole (ESQ) chain is being proposed as a machine for Accelerator-Based Boron Neutron Capture Therapy (AB-BNCT). The machine is shown to be capable of accelerating a 30 mA proton beam to 2.5 MeV. These are the specifications needed to produce sufficiently intense and clean epithermal neutron beams, based on the on the 7Li(p,n)7Be reaction, to perform BNCT treatment for deep seated tumors in less than an hour.

  19. Cell cycle dependence of boron uptake from two boron compounds used for clinical neutron capture therapy.

    PubMed

    Yoshida, F; Matsumura, A; Shibata, Y; Yamamoto, T; Nakauchi, H; Okumura, M; Nose, T

    2002-12-10

    In neutron capture therapy, it is important that the boron is selectively uptaken by tumor cells. In the present study, we used flow cytometry to sort the cells in the G0/G1 phase and those in the G2/M phase, and the boron concentration in each fraction was measured with inductively coupled plasma atomic emission spectroscopy. The results revealed that sodium borocaptate and boronophenylalanine (BPA), were associated with higher rates of boron uptake in the G2/M than in the G0/G1 phase. However, the difference was more prominent in the case of BPA. The G2/M:G0/G1 ratio decreased as a function of exposure time in BPA containing culture medium, thereby indicating the cell cycle dependency of BPA uptake. Such heterogeneity of boron uptake by tumor cells should be considered for microdosimetry.

  20. Hollow boron nitride nanospheres as boron reservoir for prostate cancer treatment

    NASA Astrophysics Data System (ADS)

    Li, Xia; Wang, Xiupeng; Zhang, Jun; Hanagata, Nobutaka; Wang, Xuebin; Weng, Qunhong; Ito, Atsuo; Bando, Yoshio; Golberg, Dmitri

    2017-01-01

    High global incidence of prostate cancer has led to a focus on prevention and treatment strategies to reduce the impact of this disease in public health. Boron compounds are increasingly recognized as preventative and chemotherapeutic agents. However, systemic administration of soluble boron compounds is hampered by their short half-life and low effectiveness. Here we report on hollow boron nitride (BN) spheres with controlled crystallinity and boron release that decrease cell viability and increase prostate cancer cell apoptosis. In vivo experiments on subcutaneous tumour mouse models treated with BN spheres demonstrated significant suppression of tumour growth. An orthotopic tumour growth model was also utilized and further confirmed the in vivo anti-cancer efficacy of BN spheres. Moreover, the administration of hollow BN spheres with paclitaxel leads to synergetic effects in the suppression of tumour growth. The work demonstrates that hollow BN spheres may function as a new agent for prostate cancer treatment.

  1. Hollow boron nitride nanospheres as boron reservoir for prostate cancer treatment.

    PubMed

    Li, Xia; Wang, Xiupeng; Zhang, Jun; Hanagata, Nobutaka; Wang, Xuebin; Weng, Qunhong; Ito, Atsuo; Bando, Yoshio; Golberg, Dmitri

    2017-01-06

    High global incidence of prostate cancer has led to a focus on prevention and treatment strategies to reduce the impact of this disease in public health. Boron compounds are increasingly recognized as preventative and chemotherapeutic agents. However, systemic administration of soluble boron compounds is hampered by their short half-life and low effectiveness. Here we report on hollow boron nitride (BN) spheres with controlled crystallinity and boron release that decrease cell viability and increase prostate cancer cell apoptosis. In vivo experiments on subcutaneous tumour mouse models treated with BN spheres demonstrated significant suppression of tumour growth. An orthotopic tumour growth model was also utilized and further confirmed the in vivo anti-cancer efficacy of BN spheres. Moreover, the administration of hollow BN spheres with paclitaxel leads to synergetic effects in the suppression of tumour growth. The work demonstrates that hollow BN spheres may function as a new agent for prostate cancer treatment.

  2. Hollow boron nitride nanospheres as boron reservoir for prostate cancer treatment

    PubMed Central

    Li, Xia; Wang, Xiupeng; Zhang, Jun; Hanagata, Nobutaka; Wang, Xuebin; Weng, Qunhong; Ito, Atsuo; Bando, Yoshio; Golberg, Dmitri

    2017-01-01

    High global incidence of prostate cancer has led to a focus on prevention and treatment strategies to reduce the impact of this disease in public health. Boron compounds are increasingly recognized as preventative and chemotherapeutic agents. However, systemic administration of soluble boron compounds is hampered by their short half-life and low effectiveness. Here we report on hollow boron nitride (BN) spheres with controlled crystallinity and boron release that decrease cell viability and increase prostate cancer cell apoptosis. In vivo experiments on subcutaneous tumour mouse models treated with BN spheres demonstrated significant suppression of tumour growth. An orthotopic tumour growth model was also utilized and further confirmed the in vivo anti-cancer efficacy of BN spheres. Moreover, the administration of hollow BN spheres with paclitaxel leads to synergetic effects in the suppression of tumour growth. The work demonstrates that hollow BN spheres may function as a new agent for prostate cancer treatment. PMID:28059072

  3. Mechanisms implicated in the effects of boron on wound healing.

    PubMed

    Nzietchueng, Rosine Mayap; Dousset, Brigitte; Franck, Patricia; Benderdour, Mohamed; Nabet, Pierre; Hess, Ketsia

    2002-01-01

    Recently, we demonstrated that boron modulates the turnover of the extracellular matrix and increases TNFalpha release. In the present study, we used an in vitro test to investigate the direct effect of boron on specific enzymes (elastase, trypsin-like enzymes, collagenase and alkaline phosphatase) implicated in extracellular matrix turnover. Boron decreased the elastase and alkaline phosphatase activity, but had no effect on trypsin and collagenase activities. The effect of boron on the enzyme activities was also tested in fibroblasts considered as an in vivo test. In contrast to the results obtained in vitro, boron enhanced the trypsin-like, collagenase, and cathepsin D activities in fibroblasts. Boron did not modify the generation of free radicals compared to the control and did not seem to act on the intracellular alkaline phosphatase activity, However, as it did enhance phosphorylation, it can be hypothesized that boron may affect living cells via a mediator, which could be TNFalpha whose transduction signal involves a cascade of phosphorylations.

  4. Annealing behaviour of boron atoms implanted into polyethyleneterephtalate

    NASA Astrophysics Data System (ADS)

    Vacík, J.; Hnatowicz, V.; Červená, J.; Peřina, V.; Popok, V.; Odzhaev, V.; Švorčík, V.; Rybka, V.; Arenholz, E.; Fink, D.

    2000-05-01

    Hundred keV B+ ions were implanted at high fluences into polyethyleneterephtalate (PET, Mylar) and the boron depth distributions were measured by the neutron depth profiling technique (NDP). Subsequently the implanted samples were annealed isochronally to determine the diffusional, trapping and detrapping behaviour of the boron atoms. The boron depth profiles of as-implanted samples differ significantly from those predicted by TRIM code. Pronounced inward and outward profile tails point at increased mobility and redistribution of boron atoms during the implantation. Thermal annealing to the temperatures below 100°C does not change the total boron content in the 1 μm thick surface layer and the boron depth profiles as well. For higher annealing temperatures a significant redistribution of boron atoms is observed.

  5. Process of Making Boron-Fiber Reinforced Composite Tape

    NASA Technical Reports Server (NTRS)

    Belvin, Harry L. (Inventor); Cano, Roberto J. (Inventor); Johnston, Norman J. (Inventor); Marchello, Joseph M. (Inventor)

    2002-01-01

    The invention is an apparatus and method for producing a hybrid boron reinforced polymer matrix composition from powder pre-impregnated fiber tow bundles and a linear array of boron fibers. The boron fibers are applied onto the powder pre-impregnated fiber tow bundles and then are processed within a processing component having an impregnation bar assembly. After passing through variable-dimension forming nip-rollers, the powder pre-impregnated fiber tow bundles with the boron fibers become a hybrid boron reinforced polymer matrix composite tape. A driving mechanism pulls the powder pre-impregnated fiber tow bundles with boron fibers through the processing line of the apparatus and a take-up spool collects the formed hybrid boron-fiber reinforced polymer matrix composite tape.

  6. The versatility of boron in biological target engagement

    NASA Astrophysics Data System (ADS)

    Diaz, Diego B.; Yudin, Andrei K.

    2017-08-01

    Boron-containing molecules have been extensively used for the purposes of chemical sensing, biological probe development and drug discovery. Due to boron's empty p orbital, it can coordinate to heteroatoms such as oxygen and nitrogen. This reversible covalent mode of interaction has led to the use of boron as bait for nucleophilic residues in disease-associated proteins, culminating in the approval of new therapeutics that work by covalent mechanisms. Our analysis of a wide range of covalent inhibitors with electrophilic groups suggests that boron is a unique electrophile in its chameleonic ability to engage protein targets. Here we review boron's interactions with a range of protein side-chain residues and reveal that boron's properties are nuanced and arise from its uncommon coordination preferences. These mechanistic and structural insights should serve as a guide for the development of selective boron-based bioactive molecules.

  7. Process of Making Boron-Fiber Reinforced Composite Tape

    NASA Technical Reports Server (NTRS)

    Belvin, Harry L. (Inventor); Cano, Roberto J. (Inventor); Johnston, Norman J. (Inventor); Marchello, Joseph M. (Inventor)

    2002-01-01

    The invention is an apparatus and method for producing a hybrid boron reinforced polymer matrix composition from powder pre-impregnated fiber tow bundles and a linear array of boron fibers. The boron fibers are applied onto the powder pre-impregnated fiber tow bundles and then are processed within a processing component having an impregnation bar assembly. After passing through variable-dimension forming nip-rollers, the powder pre-impregnated fiber tow bundles with the boron fibers become a hybrid boron reinforced polymer matrix composite tape. A driving mechanism pulls the powder pre-impregnated fiber tow bundles with boron fibers through the processing line of the apparatus and a take-up spool collects the formed hybrid boron-fiber reinforced polymer matrix composite tape.

  8. Boron gettering on cavities induced by helium implantation in Si

    NASA Astrophysics Data System (ADS)

    Roqueta, F.; Alquier, D.; Ventura, L.; Dubois, Ch.; Jérisian, R.

    2001-10-01

    In this paper, we shed light on the strong interaction between the cavity layer induced by helium implantation and boron. First of all, we evidence the impact of He gettering step on a boron-diffused profile. In order to study the boron-cavity interaction, we had used uniformly boron-doped wafers implanted with helium at high dose and anneal using usual furnace annealing (FA) as well as rapid thermal annealing. Then, to avoid any precipitation phenomena, conditions were chosen to not exceed the boron solid solubility value. Our experimental results exhibit a large trapping of boron within the cavity layer. This trapping occurs since the early stage of the annealing. These results enable us to have better understanding of this He gettering step as well as its interaction with boron atoms, which are of great interest for device.

  9. Effect of low temperature oxidation (LTO) in reducing boron skin in boron spin on dopant diffused emitter

    SciTech Connect

    Singha, Bandana; Solanki, Chetan Singh

    2016-05-06

    Formation of boron skin is an unavoidable phenomenon in p-type emitter formation with boron dopant source. The boron skin thickness is generally less than 100 nm and difficult to remove by chemical and physical means. Low temperature oxidation (LTO) used in this work is useful in removing boron skin thickness up to 30 nm and improves the emitter performance. The effective minority carrier lifetime gets improved by more than 30% after using LTO and leakage current of the emitter gets lowered by 100 times thereby showing the importance of low temperature oxidation in boron spin on dopant diffused emitters.

  10. The geochemical cycle of boron: Constraints from boron isotope partitioning experiments between mica and fluid

    NASA Astrophysics Data System (ADS)

    Wunder, Bernd; Meixner, Anette; Romer, Rolf L.; Wirth, Richard; Heinrich, Wilhelm

    2005-10-01

    The fractionation of boron isotopes between synthetic boromuscovite and fluid was experimentally determined at 3.0 GPa/500 °C and 3.0 GPa/700 °C. For near-neutral fluids Δ 11B (mica-fluid) = δ 11B (mica) - δ 11B (fluid) is - 10.9 ± 1.3‰ at 500 °C, and - 6.5 ± 0.4‰ at 700 °C. This supports earlier assumptions that the main fractionation effect is due to the change from trigonal coordination of boron in neutral fluids to tetrahedrally coordinated boron in micas, clays and melts. The T-dependence of this effect is approximated by the equation Δ 11B (mica,clay,melt-neutral fluid) = - 10.69 · (1000/ T [K]) + 3.88; R2 = 0.992, valid from 25 °C for fluid-clay up to about 1000 °C for fluid-silicate melt. Experiments at 0.4 GPa that used strongly basic fluids produced significantly lower fractionations with Δ 11B (mica-fluid) of - 7.4 ± 1.0‰ at 400 °C, and - 4.8 ± 1.0‰ at 500 °C, showing the reduced fractionation effect when large amounts of boron in basic fluids are tetrahedrally coordinated. Field studies have shown that boron concentrations and 11B/ 10B-ratios in volcanic arcs systematically decrease across the arc with increasing distance from the trench, thus reflecting the thermal structure of the subducting slab. Our experiments show that the boron isotopic signature in volcanic arcs probably results from continuous dehydration of micas along a distinct P- T range. Continuous slab dehydration and boron transport via fluid into the mantle wedge is responsible for the boron isotopic signature in volcanic arcs.

  11. Boron uptake measurements in a rat model for Boron Neutron Capture Therapy of lung tumours.

    PubMed

    Bortolussi, S; Bakeine, J G; Ballarini, F; Bruschi, P; Gadan, M A; Protti, N; Stella, S; Clerici, A; Ferrari, C; Cansolino, L; Zonta, C; Zonta, A; Nano, R; Altieri, S

    2011-02-01

    Lung carcinoma is the leading cause of cancer mortality in the Western countries. Despite the introduction over the last few years of new therapeutic agents, survival from lung cancer has shown no discernible improvement in the last 20 years. For these reasons any efforts to find and validate new effective therapeutic procedures for lung cancer are very timely. The selective boron uptake in the tumour with respect to healthy tissues makes Boron Neutron Capture Therapy a potentially advantageous option in the treatment of tumours that affect whole vital organs, and that are surgically inoperable. To study the possibility of applying BNCT to the treatment of diffuse pulmonary tumours, an animal model for boron uptake measurements in lung metastases was developed. Both healthy and tumour-bearing rats were infused with Boronophenylalanine (BPA) and sacrificed at different time intervals after drug administration. The lungs were extracted, and prepared for boron analysis by neutron autoradiography and α-spectroscopy. The boron concentrations in tumour and normal lung were plotted as a function of the time elapsed after BPA administration. The concentration in tumour is almost constant within the error bars for all the time intervals of the experiment (1-8 h), while the curve in normal lung decreases after 4 h from BPA infusion. At 4 h, the ratio of boron concentration in tumour to boron concentration in healthy lung is higher than 3, and it stays above this level up to 8 h. Also the images of boron distribution in the samples, obtained by neutron autoradiography, show a selective absorption in the metastases. Copyright © 2010 Elsevier Ltd. All rights reserved.

  12. The investigation of physical conditions of boron uptake region in proton boron fusion therapy (PBFT)

    NASA Astrophysics Data System (ADS)

    Jung, Joo-Young; Yoon, Do-Kun; Lee, Heui Chang; Lu, Bo; Suh, Tae Suk

    2016-09-01

    We conducted a quantitative study to identify the effectiveness of proton boron fusion therapy (PBFT). Four simulation scenarios were designed to investigate the escalation in total dose with the proton boron reaction using a Monte Carlo n-particle extended (MCNPX 2.6.0) simulation. The peak integrated dose was obtained for three different physical conditions (i.e., boron uptake region (BUR) thickness, BUR location, and boron concentration) with differing proton beam energy (60-90 MeV). We found that the peak integrated dose was increased by up to 96.62% compared to the pristine proton Bragg-peak. For the synergetic effect to take place with 60-70 MeV proton beam, the BUR had to be at least 0.3 cm thick while spanning the Bragg-peak. Similarly to the thickness, the BUR location needed to be within 0.3 cm from the Bragg-peak when the thickness was maintained at 0.9 cm. An effective proton boron reaction required the boron concentration to be equal to or greater than 14.4 mg/g. These results demonstrate the impact of various physical and beam conditions of the PBFT, which are critical environmental factors for the treatment planning. We envision that this study will advance our understanding of the PBFT, which can be an invaluable treatment method for maximizing the potential of proton therapy.

  13. In vitro and in vivo studies of boron neutron capture therapy: boron uptake/washout and cell death.

    PubMed

    Ferrari, C; Bakeine, J; Ballarini, F; Boninella, A; Bortolussi, S; Bruschi, P; Cansolino, L; Clerici, A M; Coppola, A; Di Liberto, R; Dionigi, P; Protti, N; Stella, S; Zonta, A; Zonta, C; Altieri, S

    2011-04-01

    Boron neutron capture therapy (BNCT) is a binary radiotherapy based on thermal-neutron irradiation of cells enriched with (10)B, which produces α particles and (7)Li ions of short range and high biological effectiveness. The selective uptake of boron by tumor cells is a crucial issue for BNCT, and studies of boron uptake and washout associated with cell survival studies can be of great help in developing clinical applications. In this work, boron uptake and washout were characterized both in vitro for the DHDK12TRb (DHD) rat colon carcinoma cell line and in vivo using rats bearing liver metastases from DHD cells. Despite a remarkable uptake, a large boron release was observed after removal of the boron-enriched medium from in vitro cell cultures. However, analysis of boron washout after rat liver perfusion in vivo did not show a significant boron release, suggesting that organ perfusion does not limit the therapeutic effectiveness of the treatment. The survival of boron-loaded cells exposed to thermal neutrons was also assessed; the results indicated that the removal of extracellular boron does not limit treatment effectiveness if adequate amounts of boron are delivered and if the cells are kept at low temperature. Cell survival was also investigated theoretically using a mechanistic model/Monte Carlo code originally developed for radiation-induced chromosome aberrations and extended here to cell death; good agreement between simulation outcomes and experimental data was obtained. © 2011 by Radiation Research Society

  14. Identification of a Novel System for Boron Transport: Atr1 Is a Main Boron Exporter in Yeast▿ †

    PubMed Central

    Kaya, Alaattin; Karakaya, Huseyin C.; Fomenko, Dmitri E.; Gladyshev, Vadim N.; Koc, Ahmet

    2009-01-01

    Boron is a micronutrient in plants and animals, but its specific roles in cellular processes are not known. To understand boron transport and functions, we screened a yeast genomic DNA library for genes that confer resistance to the element in Saccharomyces cerevisiae. Thirty boron-resistant transformants were isolated, and they all contained the ATR1 (YML116w) gene. Atr1 is a multidrug resistance transport protein belonging to the major facilitator superfamily. C-terminal green fluorescent protein-tagged Atr1 localized to the cell membrane and vacuole, and ATR1 gene expression was upregulated by boron and several stress conditions. We found that atr1Δ mutants were highly sensitive to boron treatment, whereas cells overexpressing ATR1 were boron resistant. In addition, atr1Δ cells accumulated boron, whereas ATR1-overexpressing cells had low intracellular levels of the element. Furthermore, atr1Δ cells showed stronger boron-dependent phenotypes than mutants deficient in genes previously reported to be implicated in boron metabolism. ATR1 is widely distributed in bacteria, archaea, and lower eukaryotes. Our data suggest that Atr1 functions as a boron efflux pump and is required for boron tolerance. PMID:19414602

  15. Prediction of Boron-Boron Triple-Bond Polymers Stabilized by Janus-Type Bis(N-heterocyclic) Carbenes.

    PubMed

    Fantuzzi, Felipe; Chaer Nascimento, Marco A

    2015-05-18

    A class of polymeric compounds containing boron-boron triple bonds stabilized by N-heterocyclic biscarbenes is proposed. Since a triply bonded B2 is related to its third excited state, the predicted macromolecule would be composed by several units of an electronically excited first-row homonuclear dimer. Moreover, it is shown that the replacement of biscarbene with N2 or CO as spacers could change the bonding profile of the boron-boron units to a cumulene-like structure. Based on these results, different types of diboryne polymers are proposed, which could lead to an unprecedented set of boron materials with distinct physical properties. The novel diboryne macromolecules could be synthesized by the reaction of Janus-type biscarbenes with tetrabromodiborane, B2 Br4 , and sodium naphthalenide, [Na(C10 H8 )], similarly to Braunschweig's work on the room temperature stable boron-boron triple bond compounds (Science, 2012, 336, 1420).

  16. Biological activity of N(4)-boronated derivatives of 2'-deoxycytidine, potential agents for boron-neutron capture therapy.

    PubMed

    Nizioł, Joanna; Uram, Łukasz; Szuster, Magdalena; Sekuła, Justyna; Ruman, Tomasz

    2015-10-01

    Boron-neutron capture therapy (BNCT) is a binary anticancer therapy that requires boron compound for nuclear reaction during which high energy alpha particles and lithium nuclei are formed. Unnatural, boron-containing nucleoside with hydrophobic pinacol moiety was investigated as a potential BNCT boron delivery agent. Biological properties of this compound are presented for the first time and prove that boron nucleoside has low cytotoxicity and that observed apoptotic effects suggest alteration of important functions of cancer cells. Mass spectrometry analysis of DNA from cancer cells proved that boron nucleoside is inserted into nucleic acids as a functional nucleotide derivative. NMR studies present very high degree of similarity of natural dG-dC base pair with dG-boron nucleoside system. Copyright © 2015 Elsevier Ltd. All rights reserved.

  17. On the Mechanism of Pd(0)-Catalyzed, Cu(I) Carboxylate-Mediated Thioorganic-Boronic Acid Desulfitative Coupling. A Non-innocent Role for Carboxylate Ligand

    PubMed Central

    Musaev, Djamaladdin G.; Liebeskind, Lanny S.

    2009-01-01

    Computational studies of the mechanism of the Pd-catalyzed, Cu(I)-carboxylate-mediated desulfitative coupling of thioorganics with boronic acids have determined that the requisite Cu(I)-carboxylate plays multiple important roles. The Cu(I)-carboxylate enhances both the transmetalation and the C-C reductive elimination steps: it acts as a reactive transmetalation center and it provides a vital carboxylate ligand. The carboxylate ligand functions not only as an activator for the boronic acid, but it also displaces a phosphine ligand at the palladium center generating a catalytically competent mono-phosphine-palladium intermediate. PMID:20161122

  18. NEW ADVANCES IN BORON SOIL CHEMISTRY

    EPA Science Inventory

    Boron is an essential plant micronutrient for which the range between deficiency and toxicity is narrower than for any other nutrient element. Plants respond directly to the amount of B in soil solution and only indirectly to the amount of B adsorbed on soil particle surfaces. ...

  19. NEW ADVANCES IN BORON SOIL CHEMISTRY

    EPA Science Inventory

    Boron is an essential plant micronutrient for which the range between deficiency and toxicity is narrower than for any other nutrient element. Plants respond directly to the amount of B in soil solution and only indirectly to the amount of B adsorbed on soil particle surfaces. ...

  20. New insight into pecan boron nutrition

    USDA-ARS?s Scientific Manuscript database

    Alternate bearing by individual pecan [Carya illinoinensis (Wangenh.) K. Koch] trees is problematic for nut producers and processors. There are many unknowns regarding alternate bearing physiology, such as the relationship between boron and fruit set, nutmeat quality, and kernel maladies. Evidence...

  1. Boron nitride solid state neutron detector

    DOEpatents

    Doty, F. Patrick

    2004-04-27

    The present invention describes an apparatus useful for detecting neutrons, and particularly for detecting thermal neutrons, while remaining insensitive to gamma radiation. Neutrons are detected by direct measurement of current pulses produced by an interaction of the neutrons with hexagonal pyrolytic boron nitride.

  2. Tetrahedral boron in naturally occurring tourmaline

    SciTech Connect

    Tagg, S.L.; Cho, H.; Dyar, M.D.; Grew, E.S.

    1999-09-01

    Evidence for boron in both trigonal and tetrahedral coordination has been found in {sup 11}B magic-angle-spinning (MAS) nuclear magnetic resonance (NMR) spectra of natural, inclusion-free specimens of aluminum-rich lithian tourmaline from granitic pregmatites.

  3. Axial residual stresses in boron fibers

    NASA Technical Reports Server (NTRS)

    Behrendt, D. R.

    1978-01-01

    The axial residual stress distribution as a function of radius was determined from the fiber surface to the core including the average residual stress in the core. Such measurements on boron on tungsten (B/W) fibers show that the residual stresses for 102, 142, 203, and 366 micron diameter fibers were similar, being compressive at the surface and changing monotonically to a region of tensile within the boron. At approximately 25 percent of the original radius, the stress reaches a maximum tensile stress of about 860 mn/sq.m and then decreases to a compressive stress near the tungsten boride core. Data were presented for 203 micron diameter B/W fibers that show annealing above 900 C reduces the residual stresses. A comparison between 102 micron diameter B/W and boron on carbon (b/C) shows that the residual stresses were similar in the outer regions of the fibers, but that large differences near and in the core were observed. The effects of these residual stresses on the fracture of boron fibers were discussed.

  4. Intrinsic ferromagnetism in hexagonal boron nitride nanosheets

    SciTech Connect

    Si, M. S.; Gao, Daqiang E-mail: xueds@lzu.edu.cn; Yang, Dezheng; Peng, Yong; Zhang, Z. Y.; Xue, Desheng E-mail: xueds@lzu.edu.cn; Liu, Yushen; Deng, Xiaohui; Zhang, G. P.

    2014-05-28

    Understanding the mechanism of ferromagnetism in hexagonal boron nitride nanosheets, which possess only s and p electrons in comparison with normal ferromagnets based on localized d or f electrons, is a current challenge. In this work, we report an experimental finding that the ferromagnetic coupling is an intrinsic property of hexagonal boron nitride nanosheets, which has never been reported before. Moreover, we further confirm it from ab initio calculations. We show that the measured ferromagnetism should be attributed to the localized π states at edges, where the electron-electron interaction plays the role in this ferromagnetic ordering. More importantly, we demonstrate such edge-induced ferromagnetism causes a high Curie temperature well above room temperature. Our systematical work, including experimental measurements and theoretical confirmation, proves that such unusual room temperature ferromagnetism in hexagonal boron nitride nanosheets is edge-dependent, similar to widely reported graphene-based materials. It is believed that this work will open new perspectives for hexagonal boron nitride spintronic devices.

  5. Intrinsic ferromagnetism in hexagonal boron nitride nanosheets.

    PubMed

    Si, M S; Gao, Daqiang; Yang, Dezheng; Peng, Yong; Zhang, Z Y; Xue, Desheng; Liu, Yushen; Deng, Xiaohui; Zhang, G P

    2014-05-28

    Understanding the mechanism of ferromagnetism in hexagonal boron nitride nanosheets, which possess only s and p electrons in comparison with normal ferromagnets based on localized d or f electrons, is a current challenge. In this work, we report an experimental finding that the ferromagnetic coupling is an intrinsic property of hexagonal boron nitride nanosheets, which has never been reported before. Moreover, we further confirm it from ab initio calculations. We show that the measured ferromagnetism should be attributed to the localized π states at edges, where the electron-electron interaction plays the role in this ferromagnetic ordering. More importantly, we demonstrate such edge-induced ferromagnetism causes a high Curie temperature well above room temperature. Our systematical work, including experimental measurements and theoretical confirmation, proves that such unusual room temperature ferromagnetism in hexagonal boron nitride nanosheets is edge-dependent, similar to widely reported graphene-based materials. It is believed that this work will open new perspectives for hexagonal boron nitride spintronic devices.

  6. Intrinsic ferromagnetism in hexagonal boron nitride nanosheets

    NASA Astrophysics Data System (ADS)

    Si, M. S.; Gao, Daqiang; Yang, Dezheng; Peng, Yong; Zhang, Z. Y.; Xue, Desheng; Liu, Yushen; Deng, Xiaohui; Zhang, G. P.

    2014-05-01

    Understanding the mechanism of ferromagnetism in hexagonal boron nitride nanosheets, which possess only s and p electrons in comparison with normal ferromagnets based on localized d or f electrons, is a current challenge. In this work, we report an experimental finding that the ferromagnetic coupling is an intrinsic property of hexagonal boron nitride nanosheets, which has never been reported before. Moreover, we further confirm it from ab initio calculations. We show that the measured ferromagnetism should be attributed to the localized π states at edges, where the electron-electron interaction plays the role in this ferromagnetic ordering. More importantly, we demonstrate such edge-induced ferromagnetism causes a high Curie temperature well above room temperature. Our systematical work, including experimental measurements and theoretical confirmation, proves that such unusual room temperature ferromagnetism in hexagonal boron nitride nanosheets is edge-dependent, similar to widely reported graphene-based materials. It is believed that this work will open new perspectives for hexagonal boron nitride spintronic devices.

  7. Investigating the Boron Requirement of Plants.

    ERIC Educational Resources Information Center

    Bohnsack, Charles W.

    1991-01-01

    This article describes a simple and rapid method for using summer squash to investigate born deficiency in plants. Author asserts that students are likely to feel challenged by laboratory exercises and projects that focus on the role boron plays in plant growth because it is an unresolved problem in biology. (PR)

  8. Annealing studies of highly doped boron superlattices

    SciTech Connect

    Jackman, T. E.; Houghton, D. C.; Jackman, J. A.; Denhoff, M. W.; Kechang, S.; McCaffrey, J.; Rockett, A.

    1989-09-01

    Coevaporation of B/sub 2/ O/sub 3/ during silicon molecular-beam epitaxy at growth temperatures (/ital T//sub /ital G// ) varying from 540 to 800 /degree/C has been used to prepare superlattice structures (/ital pipi/'s) of varying boron concentration (3/times/10/sup 18/ --3/times/10/sup 20/ B cm/sup /minus/3/). The superlattices were subsequently subjected to various annealing procedures and the layers were examined by secondary ion mass spectrometry, electrochemical profiling, and cross-sectional transmission electron microscopy. A significant redistribution of boron was observed even before annealing for /ital T//sub /ital G// /gt/700 /degree/C and high boron concentrations. In addition, significant oxygen was incorporated for /ital T//sub /ital G// /le/700 /degree/C, with a growth rate of 0.5 nm s/sup /minus/1/ and a B/sub 2/ O/sub 3/ flux of 2/times/10/sup 13/ cm/sup /minus/2/ s/sup /minus/1/. After annealing, the boron diffusion coefficients were determined for the layers and found to vary significantly with /ital T//sub /ital G//.

  9. NEW ADVANCES IN BORON SOIL CHEMISTRY - Paper

    EPA Science Inventory

    Boron is an essential plant micronutrient for which the range between deficiency and toxicity is narrower than for any other nutrient element. Plants respond directly to the amount of B in soil solution and only indirectly to the amount of B adsorbed on soil particle surfaces. ...

  10. Powdered Hexagonal Boron Nitride Reducing Nanoscale Wear

    NASA Astrophysics Data System (ADS)

    Chkhartishvili, L.; Matcharashvili, T.; Esiava, R.; Tsagareishvili, O.; Gabunia, D.; Margiev, B.; Gachechiladze, A.

    2013-05-01

    A morphology model is suggested for nano-powdered hexagonal boron nitride that can serve as an effective solid additive to liquid lubricants. It allows to estimate the specific surface, that is a hard-to-measure parameter, based on average size of powder particles. The model can be used also to control nanoscale wear processes.

  11. Composite Reinforcement using Boron Nitride Nanotubes

    DTIC Science & Technology

    2014-05-09

    while retaining the nanotube structure. This project involves the use of computational quantum chemistry to study interactions of aluminium (Al...small clusters of 1–4 metal atoms. The effect of varying the radius of the nanotubes and the size of aluminium and titanium clusters was considered...15. SUBJECT TERMS Boron Nitride Nanotubes, composite materials, Aluminum Alloys , Titanium Alloy , Theoretical Chemistry 16. SECURITY

  12. Monolayer boron-aluminum compacted sheet material

    NASA Technical Reports Server (NTRS)

    Sumner, E. V.

    1973-01-01

    The manufacturing techniques, basic materials used, and equipment required to produce monolayer boron-aluminum composites are described. Tentative materials and process specifications are included. Improvements in bonding and filament spacing obtained through use of brazing powder in the fugitive binder are discussed.

  13. Advances in boronization on NSTX-Upgrade

    NASA Astrophysics Data System (ADS)

    Skinner, C. H.; Blanchard, W.; Cai, D.; Jaworski, M.; Bedoya, F.; Allain, J. P.; Scotti, F.; Koel, B. E.

    2016-10-01

    Boronization has been effective in reducing plasma impurities and enabling access to higher density, higher confinement plasmas in many magnetic fusion devices. The National Spherical Torus eXperiment, NSTX, has recently undergone a major upgrade to NSTX-U in order to develop the physics basis for a ST-based Fusion Nuclear Science Facility (FNSF) with capability for double the toroidal field, plasma current, and NBI heating power and increased pulse duration from 1 - 1.5 s to 5 - 8 s. A new deuterated tri-methyl boron conditioning system was implemented together with a novel surface analysis diagnostic (MAPP). We report on the spatial distribution of the boron deposition versus discharge pressure, gas injection and electrode location. The oxygen concentration of the plasma facing surface was measured by in-vacuo XPS and increased both with plasma exposure and with exposure to trace residual gases. This increase was correlated with the rise of oxygen emission from the plasma. A dedicated experiment is planned to optimize the boronization process including XPS measurements of the plasma facing surface under specific plasma conditions. We will report on the results. Support was provided through DOE Contract Number DE-AC02-09CH11466.

  14. Investigating the Boron Requirement of Plants.

    ERIC Educational Resources Information Center

    Bohnsack, Charles W.

    1991-01-01

    This article describes a simple and rapid method for using summer squash to investigate born deficiency in plants. Author asserts that students are likely to feel challenged by laboratory exercises and projects that focus on the role boron plays in plant growth because it is an unresolved problem in biology. (PR)

  15. Assessment of Boron Steels for Army Use

    DTIC Science & Technology

    1978-11-01

    transform the microstructure from austenite to the lower tempera- ture transformation product martensite (lower bainite may also be satisfactory for... bainite , carbides, or pearlite. Thus, as long as low tem- perature transformation products are desired (martensite and lower bainite ), boron 13

  16. NEW ADVANCES IN BORON SOIL CHEMISTRY - Paper

    EPA Science Inventory

    Boron is an essential plant micronutrient for which the range between deficiency and toxicity is narrower than for any other nutrient element. Plants respond directly to the amount of B in soil solution and only indirectly to the amount of B adsorbed on soil particle surfaces. ...

  17. Energetics of Boron Doping of Carbon Pores

    NASA Astrophysics Data System (ADS)

    Wexler, Carlos; St. John, Alexander; Connolly, Matthew

    2014-03-01

    Carbon-based materials show promise, given their light weight, large surface areas and low cost for storage of hydrogen and other gases, e.g., for energy applications. Alas, the interaction of H2 and carbon, 4-5kJ/mol, is insufficient for room-temperature operation. Boron doping of carbon materials could raise the binding energy of H2 to 12-15kJ/mol. The nature of the incorporation of boron into a carbon structure has not been studied so far. In this talk we will address the energetics of boron incorporation into a carbon matrix via adsorption and decomposition of decaborane by first principles calculations. These demonstrate: (a) A strong adsorption of decaborane to carbon (70-80kJ/mol) resulting in easy incorporation of decaborane, sufficient for up to 10-20% B:C at low decaborane vapour pressures. (b) Identification that boron acts as an electron acceptor when incorporated substitutionally into a graphene-like material, as expected due to its valence. (c) The electrostatic field near the molecule is responsible for ca. 2/3 of the enhancement of the H2-adsorbent interaction in aromatic compounds such as pyrene, coronene and ovalene. Supported by DOE DE-FG36-08GO18142, ACS-PRF 52696-ND5, and NSF 1069091.

  18. Deep blast

    NASA Astrophysics Data System (ADS)

    From southern New Mexico to the Great Slave Lake of Canada, scientists from the United States and Canada recently detonated 10 underground chemical explosions to generate a clearer picture of the Earth's crust and upper mantle. Called Project Deep Probe, the experiment is designed to see through the crust and into the upper mantle to a depth of 300 miles.In the United States, Earth scientists from Rice University, Purdue University, and the University of Oregon are participating in the project. “Researchers hope to get a picture of the upper mantle beneath the Rocky Mountains and the Colorado Plateau, to understand the role the mantle played in formation and uplift,” says Alan Levander of Rice. To enhance that “picture,” 750 portable seismographs were placed along a roughly north-south line extending from Crownpoint, New Mexico to Edmonton, Alberta. The seismic recordings will be used to enhance weak seismic waves that penetrated the upper mantle.

  19. Deep space communication - Past, present, and future

    NASA Technical Reports Server (NTRS)

    Posner, E. C.; Stevens, R.

    1984-01-01

    This paper reviews the progress made in deep space communication from its beginnings until now, describes the development and applications of NASA's Deep Space Network, and indicates directions for the future. Limiting factors in deep space communication are examined using the upcoming Voyager encounter with Uranus, centered on the downlink telemetry from spacecraft to earth, as an example. A link calculation for Voyager at Uranus over Australia is exhibited. Seven basic deep space communication functions are discussed, and technical aspects of spacecraft communication equipment, ground antennas, and ground electronics and processing are considered.

  20. Boron Isotopes in Benthic Foraminifera by MC-ICPMS: Unlocking the Ocean's Carbon Cycle

    NASA Astrophysics Data System (ADS)

    Rae, J. W.; Foster, G. L.; Schmidt, D. N.; Elliott, T. R.

    2008-12-01

    The cause of glacial-interglacial CO2 cycles has been described as the "holy grail" of climate science. All models currently proposed invoke changes in deep ocean carbon storage, but the mechanisms by which this took place remain unclear. Proxies for two components of the ocean carbonate system would allow us to fully reconstruct ocean carbonate equilibria and trace the spatial and temporal pattern of glacial carbon storage, providing valuable constraints on the causal mechanisms of atmospheric CO2 change. The theory behind the boron isotope pH proxy is well understood, but its reliability has been questioned, primarily due to uncertainty in the fractionation factor between boron species in seawater, and analytical difficulties associated with negative thermal ionisation (NTIMS) measurements. We have developed a new technique for boron isotopic analysis by multicollector inductively coupled plasma mass spectrometry (MC- ICPMS), which overcomes many of the problems associated with NTIMS measurements. Our method is precise (better than 0.25%, or ~0.02 pH units, on full procedural replicates at 95% confidence), rapid (allowing duplicate measurement of 10-20 samples per analytical session), and has small sample size requirements of ~10 ng boron (~0.5 mg foraminiferal tests). As MC-ICPMS analysis requires separation of boron prior to measurement, any bias between samples and standards with different matrices is also removed. Recent experimental work has also improved uncertainty in the isotopic fractionation factor (now measured at 1.0272 ±0.0006 [1]), providing a powerful independent means to test the behaviour of the foram-based δ11B proxy, and its ability to provide absolute pH values. We have measured δ11B in several species of benthic foraminifera from a range of core-top samples. In contrast to previous studies, we find a very close match between foraminiferal δ11B values and the δ11B of seawater B(OH)4- - predicted using the recently determined fractionation