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Sample records for hastelloy n

  1. Hemispherical total emissivity of Hastelloy N with different surface conditions

    NASA Astrophysics Data System (ADS)

    Gordon, Andrew J.; Walton, Kyle L.; Ghosh, Tushar K.; Loyalka, Sudarshan K.; Viswanath, Dabir S.; Tompson, Robert V.

    2012-07-01

    The hemispherical total emissivity of Hastelloy N (a candidate structural material for Next Generation Nuclear Plants (NGNPs), particularly for the molten fluoride cooled reactors) was measured using an experimental set-up that was constructed in accordance with the standard ASTM C835-06. The material surface conditions included: (i) 'as received' (original) sample from the supplier; (ii) samples with increased surface roughness through sand blasting; (iii) oxidized surface, and (iv) samples coated with graphite powder. The emissivity of the as received samples varied from around 0.22 to 0.28 in the temperature range of 473 K to 1498 K. The emissivity increased when the roughness of the surface increased compared to an as received sample. When Hastelloy N was oxidized in air at 1153 K or coated with graphite powder, its emissivity increased substantially. The sample sand blasted with 60 grit beads and sprinkled with graphite powder showed an increase of emissivity from 0.2 to 0.60 at 473 K and from 0.25 to 0.67 at 1473 K. The oxidized surface showed a similar behavior: an increase in emissivity compared to an unoxidized sample. This increase in emissivity has strong favorable safety implications in terms of decay heat removal in post-accident environments. The data were compared with another Hastelloy family member, Hastelloy X.

  2. TEM investigation on the microstructural evolution of Hastelloy N induced by Ar⁺ ion irradiation.

    PubMed

    Liu, Min; Lu, Yanling; Liu, Renduo; Zhou, Xingtai

    2014-02-01

    Hastelloy N alloy has been selected as the primary structure material for molten salt reactor. In this article, Hastelloy N alloy samples were irradiated to different doses at room temperature using 300 keV Ar(+) ions. The microstructural evolution was investigated by transmission electron microscopy (TEM) and energy-dispersive spectroscopy (EDS). Black dot defects emerged in sample irradiated at low dose (0.4 displacement per atom (dpa)), and they grew up with irradiation doses (0.4-2 dpa). A high density of small dislocation loops (nano meters in size) were observed in the sample irradiated to 4 dpa. When the ion dose increased to 12 dpa, complicated structures with defects (including dislocation lines, larger loops and smaller black dots) were observed. Dislocation networks were detected from high-angle annular dark field (HAADF) images. Larger dislocation loops (size: 30-80 nm) were visible in the sample irradiated to 40 dpa. Irradiation with dose of 120 dpa led to the formation of face-centered cubic nanocrystallites with preferred orientations.

  3. Relation of Engine Turbine-blade Life to Stress-rupture Properties of the Alloys, Stellite 21, Hastelloy B, Cast S-816, Forged S-816, X-40, Nimonic 80, Refractaloy 26, N-155, and Inconel X

    NASA Technical Reports Server (NTRS)

    Garrett, F B; Yaker, C

    1951-01-01

    An investigation was conducted to relate the engine performance of the heat-resistant alloys, Stellite 21, Hastelloy B, cast S-816, forged S-816, X-40, Nimonic 80, Refractory 26, N-155, and Iconel X to their stress-rupture properties. The engine test consisted of the repetition of a 20-minute cycle, 15 minutes at rated speed and approximately 5 minutes at idle. The results of the investigation indicated a direct correlation between stress-rupture life and blade life for the relatively low-strength alloys. The stress-rupture life and blade life for the relatively high-strength alloys did not correlate because of the effects of the vibratory stresses and the corrosive-gas atmosphere.

  4. Effects of room-temperature tensile fatigue on critical current and n-value of IBAD-MOCVD YBa2Cu3O7-x /Hastelloy coated conductor

    NASA Astrophysics Data System (ADS)

    Rogers, Samuel; Kan Chan, Wan; Schwartz, Justin

    2016-08-01

    REBa2Cu3O7-x (REBCO) coated conductors potentially enable a multitude of superconducting applications, over a wide range of operating temperatures and magnetic fields, including high-field magnets, energy storage devices, motors, generators, and power transmission systems (Zhang et al 2013 IEEE Trans. Appl. Supercond. 23 5700704). Many of these are AC applications and thus the fatigue properties may be limiting (Vincent et al 2013 IEEE Trans. Appl. Supercond. 23 5700805). Previous electromechanical studies have determined the performance of REBCO conductors under single cycle loads (Barth et al 2015 Supercond. Sci. Technol. 28 045011), but an understanding of the fatigue properties is lacking. Here the fatigue behavior of commercial ion beam assisted deposition-metal organic chemical vapor deposition REBCO conductors on Hastelloy substrates is reported for axial tensile strains up to 0.5% and up to 100 000 cycles. Failure mechanisms are investigated via microstructural studies. Results show that REBCO conductors retained I c(ɛ)/I c0 = 0.9 for 10 000 cycles at ɛ = 0.35% and ɛ = 0.45% strain, and ɛ = 0.5% for 100 cycles. The main cause of fatigue degradation in REBCO conductors is crack propagation that initiates at the slitting defects that result from the manufacturing process.

  5. Air oxidation and seawater corrosion of Hastelloy S and Hastelloy C-4

    SciTech Connect

    Fullam, H.T.

    1980-03-01

    A program is currently under way at the Pacific Northwest Laboratory (PNL) to develop the data and technology needed to permit the licensing of /sup 90/SrF/sub 2/ as a radioisotope heat source fuel for terrestrial applications. The WESF /sup 90/SrF/sub 2/ storage capsule consists of a Hastelloy C-276 inner capsule (2 in. I.D. x 19 in. long) and a 316L stainless steel outer capsule (2-3/8 in. I.D. x 20 in. long). Preliminary experimental tests and theoretical calculations show that the WESF storage capsule is incapable of meeting current licensing requirements for heat sources that are to be used for terrestrial applications. Therefore, the DOE decision was to develop a new heat source design that would retain the existing WESF Hastelloy C-276 inner capsule and replace the current WESF outer capsule with a new outer capsule capable of meeting current licensing requirements. Based on a number of factors, Hastelloy S was selected as the outer capsule material. Hastelloy C-4 was selected as a backup material in case the Hastelloy S had to be rejected for any reason. This report summarizes the results of studies carried out to determine the effects of both air oxidation at heat source operating temperatures and seawater corrosion on the tensile properties of the outer capsule materials.

  6. Effects of room-temperature tensile fatigue on critical current and n-value of IBAD–MOCVD YBa2Cu3O7‑x /Hastelloy coated conductor

    NASA Astrophysics Data System (ADS)

    Rogers, Samuel; Kan Chan, Wan; Schwartz, Justin

    2016-08-01

    REBa2Cu3O7‑x (REBCO) coated conductors potentially enable a multitude of superconducting applications, over a wide range of operating temperatures and magnetic fields, including high-field magnets, energy storage devices, motors, generators, and power transmission systems (Zhang et al 2013 IEEE Trans. Appl. Supercond. 23 5700704). Many of these are AC applications and thus the fatigue properties may be limiting (Vincent et al 2013 IEEE Trans. Appl. Supercond. 23 5700805). Previous electromechanical studies have determined the performance of REBCO conductors under single cycle loads (Barth et al 2015 Supercond. Sci. Technol. 28 045011), but an understanding of the fatigue properties is lacking. Here the fatigue behavior of commercial ion beam assisted deposition–metal organic chemical vapor deposition REBCO conductors on Hastelloy substrates is reported for axial tensile strains up to 0.5% and up to 100 000 cycles. Failure mechanisms are investigated via microstructural studies. Results show that REBCO conductors retained I c(ε)/I c0 = 0.9 for 10 000 cycles at ε = 0.35% and ε = 0.45% strain, and ε = 0.5% for 100 cycles. The main cause of fatigue degradation in REBCO conductors is crack propagation that initiates at the slitting defects that result from the manufacturing process.

  7. Effects of oxidation on the impact energy of Hastelloy S and Hastelloy C-4 Charpy V-notch specimens heated in air at 600 to 800

    SciTech Connect

    Fullam, H.T.

    1981-01-01

    The /sup 90/SrF/sub 2/ heat source being developed at PNL utilizes a Hastelloy S or Hastelloy C-4 outer capsule having a 0.5-in.-thick wall to contain the Hastelloy C-276 inner capsule. The primary objective of the study was to demonstrate that the air oxidation of the outer capsule that could occur during heat-source service would not degrade the ductility and Charpy impact strength of the capsule below the licensing requirements given in Section 1.1. The /sup 90/SrF/sub 2/ heat source under development is intended for general-purpose use. Compatibility considerations limit the interface temperature between the /sup 90/SrF/sub 2/ and Hastelloy C-276 inner capsule to a maximum of 800/sup 0/C. The outer capsule surface temperature will be somewhat less than 800/sup 0/C, and depending on the service, may be substantially lower. The oxidation tests were therefore carried out at 600/sup 0/ to 800/sup 0/C for exposures up to 10,000h to cover the range of temperature the outer capsule might expect to encounter in service. The results showed that the oxidation of Hastelloy S and Hastelloy C-4 in air at 600/sup 0/ to 800/sup 0/C is very slow, and both alloys form adherent oxide layers that serve to protect the underlying metal. Subsurface attack of Hastelloy S and Hastelloy C-4 due to oxidation was greater than expected, considering the slow oxidation rates of the two alloys at 600/sup 0/ to 800/sup 0/C. Estimates of subsurface attack, determined from micrographs of the oxidized specimens, showed erratic results and it was impossible to assign any type of rate equation to the subsurface attack. A conservative estimate of long-term effects can be made using a linear extrapolation of the test results. There were no significant differences between the room-temperature Charpy impact energy of Hastelloy S and Hastelloy C-4 specimens oxidized in air at 600/sup 0/ to 800/sup 0/C and control specimens heated in vacuum.

  8. Applying Tep Measurements to Assess the Response of Hastelloy to Long Time Aging

    NASA Astrophysics Data System (ADS)

    Ifergane, S.; Gelbstein, Y.; Dahan, I.; Pinkas, M.; Landau, A.

    2009-03-01

    Hastelloy C-276 service temperature is restricted due to precipitation of the intermetallic compound μ. Time-temperature curves indicate that the highest precipitation rate is obtained at about 870° C. Thermoelectric Power (TEP) measurements were applied to monitor the precipitation kinetics during aging at 870° C. The TEP was found to be well correlated with the amount of μ phase formed during aging and with the reduction in impact energy and ductility. It was demonstrated that TEP measurements could be used to monitor aging of Hastelloy C-276.

  9. Creep-rupture tests of internally pressurized Hastelloy-X tubes

    NASA Technical Reports Server (NTRS)

    Gumto, K. H.; Colantino, G. J.

    1973-01-01

    Seamless Hastelloy-X tubes with 0.375-in. outside diameter and 0.025-in. wall thickness were tested to failure at temperatures from 1400 to 1650 F and internal helium pressures from 800 to 1800 psi. Lifetimes ranged from 58 to 3600 hr. The creep-rupture strength of the tubes was from 20 to 40 percent lower than that of sheet specimens. Larson-Miller correlations and photomicrographs of some specimens are presented.

  10. Permeation of hydrogen in hastelloy C-276 alloy at high temperature

    SciTech Connect

    Zhang, D.; Liu, W.; Qian, Y.; Que, J.

    2015-03-15

    Tritium is generated by the interaction of neutrons with the lithium and beryllium in the molten salt reactors (MSRs), which use FLiBe as one of solvents of fluoride fuel. Tritium as by-product in the MSRs is an important safety issue because it could easily diffuse into environment through high temperature heat exchangers. The experimental technique of gas driven permeation has been used to investigate the transport parameter of hydrogen in Hastelloy C-276 which is considered as one of the candidate for structure materials. The measurements were carried out at the temperature range of 400-800 Celsius degrees with hydrogen loading pressures ranging from 5*10{sup 3} to 4*10{sup 4} Pa. The H diffusive transport parameters for Hastelloy C-276 follow an Arrhenius law in this temperature range. Regarding diffusivity and Sieverts' constant, Hastelloy C-276 has lower values compared with Ni201 alloy. The possible reason may be the trapping effects, which were formed by the alloying elements of Mo and Cr in the matrix. At the same time, the thin oxidation layer formed by the high Cr content could lead to a slower dissociation process of H{sub 2} at the surface. (authors)

  11. 2G HTS wires made on 30 μm thick Hastelloy substrate

    NASA Astrophysics Data System (ADS)

    Sundaram, A.; Zhang, Y.; Knoll, A. R.; Abraimov, D.; Brownsey, P.; Kasahara, M.; Carota, G. M.; Nakasaki, R.; Cameron, J. B.; Schwab, G.; Hope, L. V.; Schmidt, R. M.; Kuraseko, H.; Fukushima, T.; Hazelton, D. W.

    2016-10-01

    REBCO (RE = rare earth) based high temperature superconducting (HTS) wires are now being utilized for the development of electric and electromagnetic devices for various industrial, scientific and medical applications. In the last several years, the increasing efforts in using the so-called second generation (2G) HTS wires for some of the applications require a further increase in their engineering current density (J e). The applications are those typically related to high magnetic fields where the higher J e of a REBCO wire, in addition to its higher irreversibility fields and higher mechanical strength, is already a major advantage over other superconducting wires. An effective way to increase the J e is to decrease the total thickness of a wire, for which using a thinner substrate becomes an obvious and attractive approach. By using our IBAD-MOCVD (ion beam assisted deposition-metal organic chemical vapor deposition) technology we have successfully made 2G HTS wires using a Hastelloy® C276 substrate that is only 30 μm in thickness. By using this thinner substrate instead of the typical 50 μm thick substrate and with a same critical current (I c), the J e of a wire can be increased by 30% to 45% depending on the copper stabilizer thickness. In this paper, we report the fabrication and characterization of the 2G HTS wires made on the 30 μm thick Hastelloy® C276 substrate. It was shown that with the optimization in the processing protocol, the surface of the thinner Hastelloy® C276 substrate can be readily electropolished to the quality needed for the deposition of the buffer stack. Same in the architecture as that on the standard 50 μm thick substrate, the buffer stack made on the 30 μm thick substrate showed an in-plane texture with a Δϕ of around 6.7° in the LaMnO3 cap layer. Low-temperature in-field transport measurement results suggest that the wires on the thinner substrate had achieved equivalent superconducting performance, most importantly the I

  12. Hardening mechanisms in a dynamic strain aging alloy, Hastelloy X, during isothermal and thermomechanical cyclic deformation

    NASA Technical Reports Server (NTRS)

    Miner, R. V.; Castelli, M. G.

    1992-01-01

    The relative contributions of the hardening mechanisms in Hastelloy X during cyclic deformation were investigated by conducting isothermal cyclic deformation tests within a total strain range of +/-0.3 pct and at several temperatures and strain rates, and thermomechanical tests within several different temperature limits. The results of the TEM examinations and special constant structure tests showed that the precipitation on dislocations of Cr23C6 contributed to hardening, but only after sufficient time above 500 C. Solute drag alone produced very considerable cyclic hardening. Heat dislocation densities, peaking around 10 exp 11 per sq cm, were found to develop at temperatures producing the greatest cyclic hardening.

  13. Thermomechanical deformation behavior of a dynamic strain aging alloy, Hastelloy X

    NASA Technical Reports Server (NTRS)

    Castelli, Michael G.; Miner, Robert V.; Robinson, David N.

    1992-01-01

    An experimental study was performed to identify the effects of dynamic strain aging (solute drag) and metallurgical instabilities under thermomechanical loading conditions. The study involved a series of closely controlled thermomechanical deformation tests on the solid-solution-strenghened nickel-base superalloy, Hastelloy X. This alloy exhibits a strong isothermal strain aging peak at approximately 600 C, promoted by the effects of solute drag and precipitation hardening. Macroscopic thermomechanical hardening trends are correlated with microstructural characteristics through the use of transmission electron microscopy. These observations are compared and contrasted with isothermal conditions. Thermomechanical behavior unique to the isothermal database is identified and discussed. The microstructural characteristics were shown to be dominated by effects associated with the highest temperature of the thermomechanical cycle. Results indicate that the deformation behavior of Hastelloy X is thermomechanically path dependent. In addition, guidance is given pertaining to deformation modeling in the context of macroscopic unified theory. An internal state variable is formulated to qualitatively reflect the isotropic hardening trends identified in the TMD experiments.

  14. Characterization of Hot Deformation Behavior of Hastelloy C-276 Using Constitutive Equation and Processing Map

    NASA Astrophysics Data System (ADS)

    Zhang, Chi; Zhang, Liwen; Shen, Wenfei; Li, Mengfei; Gu, Sendong

    2015-01-01

    In order to clarify the microstructural evolution and workability of Hastelloy C-276 during hot forming to get excellent mechanical properties, the hot deformation behavior of this superalloy is characterized. The cylindrical specimens were isothermal compressed in the temperature range of 1000-1200 °C and strain rate range of 0.001-5 s-1 on a Gleeble 1500 thermal-mechanical simulator. The flow curves and microstructural investigation indicates that dynamic recrystallization is the prime softening mechanism at the evaluated deformation conditions. The constitutive equation was presented as a function of the deformation temperature, strain rate, and strain, and the deformation activation energy was about 450 kJ/mol. The processing maps based on dynamic materials model at the strains of 0.2, 0.4, 0.6, 0.8, and 1.0 were established, and the processing map at 1.0 strain shows good correspondence to the microstructural observation. The domains in processing map in which the efficiency of power dissipation (η) is higher than 0.25 are corresponding to sufficient dynamic recyrstallization phenomenon, which are suggested to be the optimum working areas for Hastelloy C-276.

  15. The Kinetics of Metadynamic Recrystallization in a Ni-Cr-Mo-Based Superalloy Hastelloy C-276

    NASA Astrophysics Data System (ADS)

    Zhang, Chi; Zhang, Liwen; Shen, Wenfei; Liu, Cuiru; Xia, Yingnan

    2016-02-01

    The metadynamic recrystallization (MDRX) behavior of a typical Ni-Cr-Mo-based superalloy Hastelloy C-276 was investigated using two-stage isothermal compression tests on a Gleeble thermal-mechanical simulator in the temperature range of 1050-1200 °C, the strain rate range of 0.1-5.0 s-1, the strains of 0.32, 0.45, and 0.6 at the first stage of compression, and the interval times of 0.5-30 s. The results show that the microstructure and the stress-strain relation of the studied superalloy vary during the interruption period due to the occurrence of MDRX. The MDRX softening fraction and recrystallized grain size increase rapidly with the increasing of interval time, deformation temperature, and strain rate. The effect of strain at the first stage of compression on MDRX is less pronounced. The kinetics of MDRX softening was established based on the flow stress curves, and the apparent activation energy of MDRX of Hastelloy C-276 is evaluated as 241 kJ/mol.

  16. Development testing of the two-watt RTG heat source and Hastelloy-S/T-111 alloy compatibility studies

    SciTech Connect

    Howell, E.I.; Teaney, P.E.

    1993-09-29

    The two-watt radioisotope thermoelectric generator heat source capsules were tested to determine their survivability under extreme environmental conditions: high external pressure, high impact, and high internal pressure. Test results showed that the capsules could withstand external pressures of 1,000 bars and impacts at velocities near 150 meters per second. However, the results of the internal pressure tests (stress-rupture) were not so favorable, possibly because of copper contamination, leading to a recommendation for additional testing. A material compatibility study examined the use of Hastelloy-S as a material to clad the tantalum strength member of the two-watt radioisotopic heat source. Test capsules were subjected to high temperatures for various lengths of time, then cross sectioned and examined with a scanning electron microscope. Results of the study indicate that Hastelloy-S would be compatible with the underlying alloy, not only at the normal operating temperatures of the heat source, but also when exposed to the much higher temperatures of a credible accident scenario.

  17. Improved corrosion resistance of Hastelloy G-30 in nitric/hydrofluoric acid solutions by welding with Inconel 72 weld wire

    SciTech Connect

    Norby, B.C.

    1992-03-03

    When welding Hastelloy G-30, secondary phases form in the weld metal. These phases cause the weld metal to be preferentially attacked in nitric acid (HN0{sub 3}) solutions contaminated with minor amounts of hydrofluoric acid (HF). A post weld solution anneal and water quench is necessary to assure that these phases redissolve into the solid. When a post weld solution anneal and water quench is not feasible, improved corrosion resistance can be obtained by welding with INCO 72 weld wire. When welding Hastelloy G-30 with INCO 72, there can be a region at the weldmetal/base-metal interface that does not benefit from the INCO 72 weld wire. This region consists of melted and resolidified Hastelloy G-30. This unmixed zone can be preferentially attacked in HN03 solutions contaminated with minor amounts of HF. Long term corrosion immersion tests have shown that the rate of attack at the weld-metal/base-metal interface can be as high as 50 mpy. Welding techniques that increase the mixing of the melted Hastelloy G-30 with the INCO 72 weld wire can reduce the interface corrosion rate.

  18. Thermomechanical cyclic hardening behavior of Hastelloy-X. M.S. Thesis

    NASA Technical Reports Server (NTRS)

    Bartolotta, P. A.

    1985-01-01

    Experimental evidence of thermomechanical history dependence on the cyclic hardening behavior of a representative combustor liner material Hastelloy-X is presented, along with a discussion about the relevant concept of thermomechanical path dependence. Based on the experimental results, a discussion is given on the inadequacy of formulating nonisothermal constitutive equations solely on the basis of isothermal testing. Finally, the essence of a mathematical representation of thermoviscoplasticity is presented that qualitatively accounts for the observed hereditary behavior. This is achieved by formulating the scaler evolutionary equation in an established viscoplastic theory to reflect thermomechanical path dependence. Although the necessary nonisothermal tests for further quantifying the thermoviscoplastic model have been identified, such data are not yet available.

  19. Total hemispherical emissivity of very high temperature reactor (VHTR) candidate materials: Hastelloy X, Haynes 230, and Alloy 617

    NASA Astrophysics Data System (ADS)

    Maynard, Raymond K.

    An experimental system was constructed in accordance with the standard ASTM C835-06 to measure the total hemispherical emissivity of structural materials of interest in Very High Temperature Reactor (VHTR) systems. The system was tested with304 stainless steel as well as for oxidized and un-oxidized nickel, and good reproducibility and agreement with the literature data was found. Emissivity of Hastelloy X was measured under different conditions that included: (i) "as received" (original sample) from the supplier; (ii) with increased surface roughness; (iii) oxidized, and; (iv) graphite coated. Measurements were made over a wide range of temperatures. Hastelloy X, as received from the supplier, was cleaned before additional roughening of the surface and coating with graphite. The emissivity of the original samples (cleaned after received) varied from around 0.18 to 0.28 in the temperature range of 473 K to 1498 K. The apparent emissivity increased only slightly as the roughness of the surface increased (without corrections for the increased surface area due to the increased surface roughness). When Hastelloy X was coated with graphite or oxidized however, its emissivity was observed to increase substantially. With a deposited graphite layer on the Hastelloy, emissivity increased from 0.2 to 0.53 at 473 K and from 0.25 to 0.6 at 1473 K; a finding that has strong favorable safety implications in terms of decay heat removal in post-accident VHTR environments. Although initial oxidation of Hastelloy X increased the emissivity prolonged oxidation did not significantly increase emissivity. However as there is some oxidation of Hastelloy X used in the construction of VHTRs, this represents an essentially neutral finding in terms of the safety implications in post-accident VHTR environments. The total hemispherical emissivity of Haynes 230 alloy, which is regarded as a leading candidate material for heat exchangers in VHTR systems, was measured under various surface

  20. Material Data Representation of Hysteresis Loops for Hastelloy X Using Artificial Neural Networks

    NASA Technical Reports Server (NTRS)

    Alam, Javed; Berke, Laszlo; Murthy, Pappu L. N.

    1993-01-01

    The artificial neural network (ANN) model proposed by Rumelhart, Hinton, and Williams is applied to develop a functional approximation of material data in the form of hysteresis loops from a nickel-base superalloy, Hastelloy X. Several different ANN configurations are used to model hysteresis loops at different cycles for this alloy. The ANN models were successful in reproducing the hysteresis loops used for its training. However, because of sharp bends at the two ends of hysteresis loops, a drift occurs at the corners of the loops where loading changes to unloading and vice versa (the sharp bends occurred when the stress-strain curves were reproduced by adding stress increments to the preceding values of the stresses). Therefore, it is possible only to reproduce half of the loading path. The generalization capability of the network was tested by using additional data for two other hysteresis loops at different cycles. The results were in good agreement. Also, the use of ANN led to a data compression ratio of approximately 22:1.

  1. Fatigue Performance of TBCs on Hastelloy X Substrate During Cyclic Bending

    NASA Astrophysics Data System (ADS)

    Musalek, Radek; Kovarik, Ondrej; Tomek, Libor; Medricky, Jan; Pala, Zdenek; Hausild, Petr; Capek, Jiri; Kolarik, Kamil; Curry, Nicholas; Bjorklund, Stefan

    2016-01-01

    Our previous experiments with low-cost steel substrates confirmed that individual steps of conventional thermal barrier coating (TBC) deposition may influence fatigue properties of the coated samples differently. In the presented study, testing was carried out for TBC samples deposited on industrially more relevant Hastelloy X substrates. Samples were tested after each step of the TBC deposition process: as-received (non-coated), grit-blasted, bond-coated (NiCoCrAlY), and bond-coated + top-coated yttria-stabilized zirconia (YSZ). Conventional atmospheric plasma spraying (APS) was used for deposition of bond coat and top coat. In addition, for one half of the samples, dual-layer bond coat was prepared by combination of high-velocity air-fuel (HVAF) and APS processes. Samples were tested in the as-sprayed condition and after 100 hours annealing at 980 °C, which simulated application-relevant in-service conditions. Obtained results showed that each stage of the TBC manufacturing process as well as the simulated in-service heat exposure may significantly influence the fatigue properties of the TBC coated part. HVAF grit-blasting substantially increased the fatigue performance of the uncoated substrates. This beneficial effect was suppressed by deposition of APS bond coat but not by deposition of dual-layer HVAF + APS bond coat. All heat-treated samples showed again enhanced fatigue performance.

  2. Laser texturing of Hastelloy C276 alloy surface for improved hydrophobicity and friction coefficient

    NASA Astrophysics Data System (ADS)

    Yilbas, B. S.; Ali, H.

    2016-03-01

    Laser treatment of Hastelloy C276 alloy is carried out under the high pressure nitrogen assisting gas environment. Morphological and metallurgical changes in the laser treated layer are examined using the analytical tools including, scanning electron and atomic force microscopes, X-ray diffraction, energy dispersive spectroscopy, and Fourier transform infrared spectroscopy. Microhardness is measured and the residual stress formed in the laser treated surface is determined from the X-ray data. The hydrophibicity of the laser treated surface is assessed using the sessile drop method. Friction coefficient of the laser treated layer is obtained incorporating the micro-tribometer. It is found that closely spaced laser canning tracks create a self-annealing effect in the laser treated layer and lowers the thermal stress levels through modifying the cooling rates at the surface. A dense structure, consisting of fine size grains, enhances the microhardness of the surface. The residual stress formed at the surface is compressive and it is in the order of -800 MPa. Laser treatment improves the surface hydrophobicity significantly because of the formation of surface texture composing of micro/nano-pillars.

  3. Compatibility of aluminide-coated Hastelloy x and Inconel 617 in a simulated gas-cooled reactor environment

    SciTech Connect

    Chin, J.; Johnson, W. R.; Chen, K.

    1982-03-01

    Commercially prepared aluminide coatings on Hastelloy X and Inconel 617 substrates were exposed to controlled-impurity helium at 850/sup 0/ and 950/sup 0/C for 3000 h. Optical and scanning electron (SEM) microscopy, electron microprobe profiles, and SEM X-ray mapping were used to evaluate and compare exposed and unexposed control samples. Four coatings were evaluated: aluminide, aluminide with platinum, aluminide with chromium, and aluminide with rhodium. With extended time at elevated temperature, nickel diffused into the aluminide coatings to form epsilon-phase (Ni/sub 3/Al). This diffusion was the primary cause of porosity formation at the aluminide/alloy interface.

  4. Collect Available Creep-Fatigue Data and Study Existing Creep-Fatigue Evaluation Procedures for Grade 91 and Hastelloy XR

    SciTech Connect

    Tai Asayama; Yukio Tachibana

    2007-09-30

    This report describes the results of investigation on Task 5 of DOE/ASME Materials Project based on a contract between ASME Standards Technology, LLC (ASME ST-LLC) and Japan Atomic Energy Agency (JAEA). Task 5 is to collect available creep-fatigue data and study existing creep-fatigue evaluation procedures for Grade 91 steel and Hastelloy XR. Part I of this report is devoted to Grade 91 steel. Existing creep-fatigue data were collected (Appendix A) and analyzed from the viewpoints of establishing a creep-fatigue procedure for VHTR design. A fair amount of creep-fatigue data has been obtained and creep-fatigue phenomena have been clarified to develop design standards mainly for fast breeder reactors. Following this, existing creep-fatigue procedures were studied and it was clarified that the creep-fatigue evaluation procedure of the ASME-NH has a lot of conservatisms and they were analyzed in detail from the viewpoints of the evaluation of creep damage of material. Based on the above studies, suggestions to improve the ASME-NH procedure along with necessary research and development items were presented. Part II of this report is devoted to Hastelloy XR. Existing creep-fatigue data used for development of the high temperature structural design guideline for High Temperature Gas-cooled Reactor (HTGR) were collected. Creep-fatigue evaluation procedure in the design guideline and its application to design of the intermediate heat exchanger (IHX) for High Temperature Engineering Test Reactor (HTTR) was described. Finally, some necessary research and development items in relation to creep-fatigue evaluation for Gen IV and VHTR reactors were presented.

  5. Low-cycle fatigue of Type 347 stainless steel and Hastelloy alloy X in hydrogen gas and in air at elevated temperatures

    NASA Technical Reports Server (NTRS)

    Jaske, C. E.; Rice, R. C.; Buchheit, R. D.; Roach, D. B.; Porfilio, T. L.

    1976-01-01

    An investigation was conducted to assess the low-cycle fatigue resistance of two alloys, Type 347 stainless steel and Hastelloy Alloy X, that were under consideration for use in nuclear-powered rocket vehicles. Constant-amplitude, strain-controlled fatigue tests were conducted under compressive strain cycling at a constant strain rate of 0.001/sec and at total axial strain ranges of 1.5, 3.0, and 5.0 %, in both laboratory-air and low-pressure hydrogen-gas environments at temperatures from 538 to 871 C. Specimens were obtained from three heats of Type 347 stainless steel bar and two heats of Hastelloy Alloy X. The tensile properties of each heat were determined at 21, 538, 649, and 760 C. The continuous cycling fatigue resistance was determined for each heat at temperatures of 538, 760, and 871 C. The Type 347 stainless steel exhibited equal or superior fatigue resistance to the Hastelloy Alloy X at all conditions of this study.

  6. Reduction in mechanical anisotropy through high temperature heat treatment of Hastelloy X processed by Selective Laser Melting (SLM)

    NASA Astrophysics Data System (ADS)

    Etter, T.; Kunze, K.; Geiger, F.; Meidani, H.

    2015-04-01

    Selective Laser Melting (SLM) is an additive manufacturing technology used to directly produce metallic parts from thin powder layers. To evaluate the anisotropic mechanical properties, tensile test specimens of the Ni-base alloy Hastelloy X were built with the loading direction oriented either parallel (z-specimens) or perpendicular to the build-up direction (xy- specimens). Specimens were investigated in the “as-built” condition and after high temperature heat treatment. Tensile tests at room temperature and at 850°C of “as-built” material have shown different mechanical properties for z- and xy-specimens. The anisotropy is reflected in the Young's modulus, with lower values measured parallel to the build-up direction. It is shown that the anisotropy is significantly reduced by a subsequent recrystallization heat treatment. The characterization of microstructural and textural anisotropy was done by Electron Back Scatter Diffraction (EBSD) analysis. Predictions of Young's modulus calculated from the measured textures compare well with the data from tensile tests.

  7. Chemistry of glass-ceramic to metal bonding for header applications. I. Effect of treatments on Inconel 718 and Hastelloy C-276 metallic surfaces

    SciTech Connect

    Kramer, D P; Craven, S M; Schneider, R E; Moddeman, W E; Brohard, D W

    1984-02-02

    Auger electron spectroscopy and depth Auger profiling were used to study the surfaces of Inconel 718 and Hastelloy C-276. The metal surfaces were processed in the same manner as is presently being used in the manufacturing of glass-ceramic headers. At each step in the process, samples were studied with Auger spectroscopy to determine their resultant elemental surface composition and film thickness. In addition, the effect of a final plasma cleaning operation on the metal surface was examined. The results show that the type and concentration of surface species and the thickness of the surface oxides are dependent on the processing technique.

  8. Creep-fatigue damage evaluation of a nickel-base heat-resistant alloy Hastelloy XR in simulated HTGR helium gas environment

    NASA Astrophysics Data System (ADS)

    Tsuji, Hirokazu; Nakajima, Hajime

    1994-02-01

    The properties of Hastelloy XR, which is a developed alloy as the structural material for high-temperature components of the HTTR, under creep-fatigue interaction conditions were examined by performing a series of axial strain-controlled fully reversed fatigue tests in the simulated HTGR helium gas environment at 700, 800, 900 and 950°C. Two types of evaluation techniques, i.e., the life fraction rule and the ductility exhaustion one, were applied for the evaluation of the creep damage during the strain holding. The fatigue life reduction due to the strain holding is observed even at hold times of 6 s, and the saturation point of the fatigue life reduction shifts to the shorter hold time side with increasing temperature. The life fraction rule predicts an excessively conservative value for the creep damage. The ductility exhaustion rule can predict the fatigue life under the effective creep condition much more successfully than the life fraction one.

  9. High-temperature low-cycle fatigue and tensile properties of Hastelloy X and alloy 617 in air and HTGR-helium

    SciTech Connect

    Strizak, J.P.; Brinkman, C.R.; Rittenhouse, P.L.

    1981-01-01

    Results of strain controlled fatigue and tensile tests are presented for two nickel base solution hardened alloys which are reference structural alloys for use in several high temperature gas cooled reactor concepts. These alloys, Hastelloy X Inconel 617, were tested at temperatures ranging from room temperature to 871/sup 0/C in air and impure helium. Materials were tested in the solution annealed as well as in the pre-aged condition where aging consisted of isothermal exposure at one of several temperatures for periods of up to 20,000 h. Comparisons are also given between the strain controlled fatigue lives of these alloys and several other commonly used alloys all tested at 538/sup 0/C.

  10. Thermodynamic Assessment of Hot Corrosion Mechanisms of Superalloys Hastelloy N and Haynes 242 in Eutectic Mixture of Molten Salts KF and ZrF4

    SciTech Connect

    Michael V. Glazoff

    2012-02-01

    The KF - ZrF4 system was considered for the application as a heat exchange agent in molten salt nuclear reactors (MSRs) beginning with the work carried out at ORNL in early fifties. Based on a combination of excellent properties such as thermal conductivity, viscosity in the molten state, and other thermo-physical and rheological properties, it was selected as one of possible candidates for the nuclear reactor secondary heat exchanger loop.

  11. High-temperature corrosion of UNS N10003 in molten Li2BeF4 (FLiBe) salt

    DOE PAGESBeta

    Zheng, Guiqiu; Kelleher, Brian; He, Lingfeng; Cao, Guoping; Anderson, Mark; Allen, Todd; Sridharan, Kumar

    2015-07-30

    Here, corrosion testing of Hastelloy N in molten fluoride salt was performed in purified molten 27LiF-BeF2 (66-34mol%) (FLiBe) salt at 700°C for 1000 hours, in pure nickel and graphite capsules. In the nickel capsule tests, the near-surface region of the alloy exhibited an about 200 nm porous structure, an approximately 3.5 μm chromium depleted region, and MoSi2 precipitates. In tests performed in graphite capsules, the alloy samples gained weight due to the formation of a variety of Cr3C2, Cr7C3, Mo2C and Cr23C6, carbide phases on the surface and in the subsurface regions of the alloy. A Cr depleted region wasmore » observed in the near-surface region where Mo thermally diffused toward either surface or grain boundary, which induced approximately 1.4 μm Ni3Fe alloy layer in this region. The carbide containing layer extended to about 7 μm underneath the Ni3Fe layer. The presence of graphite dramatically changes the mechanisms of corrosion attack in Hastelloy N in molten FLiBe salt. Evaluated by in terms of the depth of attack, graphite clearly accelerates corrosion, but the results appear to indicate that the formation of Cr23C6 phase might stabilize the Cr and mitigate its dissolution in molten FLiBe salt.« less

  12. Thermomechanical characterization of Hastelloy-X under uniaxial cyclic loading

    NASA Technical Reports Server (NTRS)

    Ellis, J. R.; Bartolotta, P. A.; Allen, G. P.; Robinson, D. N.

    1986-01-01

    In most high-temperature engineering applications, components are subjected to complex combinations of thermal and mechanical loading during service. A number of viscoplastic constitutive models were proposed which potentially can provide mathematical descriptions of material response under such conditions. Implementation of these models into large finite element codes such as MARC has already resulted in much improved inelastic analysis capability for hot-section aircraft engine components. However, a number of questions remain regarding the validity of methods adopted in characterizing these constitutive models for particular high-temperature materials. One area of concern is that the majority of experimental data available for this purpose are determined under isothermal conditions. This is in contrast to service conditions which, as noted above, almost always involve some form of thermal cycling. The obvious question arises as to whether a constitutive model characterized using an isothermal data base can adequately predict material response under thermomechanical conditions. An experimental program was initiated within the HOST program to address this particular concern. The results of the most recent isothermal and thermomechanical experiments are described.

  13. High-temperature corrosion of UNS N10003 in molten Li2BeF4 (FLiBe) salt

    SciTech Connect

    Zheng, Guiqiu; Kelleher, Brian; He, Lingfeng; Cao, Guoping; Anderson, Mark; Allen, Todd; Sridharan, Kumar

    2015-07-30

    Here, corrosion testing of Hastelloy N in molten fluoride salt was performed in purified molten 27LiF-BeF2 (66-34mol%) (FLiBe) salt at 700°C for 1000 hours, in pure nickel and graphite capsules. In the nickel capsule tests, the near-surface region of the alloy exhibited an about 200 nm porous structure, an approximately 3.5 μm chromium depleted region, and MoSi2 precipitates. In tests performed in graphite capsules, the alloy samples gained weight due to the formation of a variety of Cr3C2, Cr7C3, Mo2C and Cr23C6, carbide phases on the surface and in the subsurface regions of the alloy. A Cr depleted region was observed in the near-surface region where Mo thermally diffused toward either surface or grain boundary, which induced approximately 1.4 μm Ni3Fe alloy layer in this region. The carbide containing layer extended to about 7 μm underneath the Ni3Fe layer. The presence of graphite dramatically changes the mechanisms of corrosion attack in Hastelloy N in molten FLiBe salt. Evaluated by in terms of the depth of attack, graphite clearly accelerates corrosion, but the results appear to indicate that the formation of Cr23C6 phase might stabilize the Cr and mitigate its dissolution in molten FLiBe salt.

  14. Much simplified ion-beam assisted deposition-TiN template for high-performance coated conductors

    NASA Astrophysics Data System (ADS)

    Xiong, J.; Matias, V.; Wang, H.; Zhai, J. Y.; Maiorov, B.; Trugman, D.; Tao, B. W.; Li, Y. R.; Jia, Q. X.

    2010-10-01

    A much simplified template, i.e., two nonsuperconducting layers between the superconducting YBa2Cu3O7-δ (YBCO) and the polycrystalline metal substrate, has been developed for high-performance coated conductors by using biaxially aligned TiN as a seed layer. A combination of a thin TiN (˜10 nm by ion-beam assisted deposition) layer and an epitaxial buffer LaMnO3 layer (˜120 nm) allows us to grow epitaxial YBCO films with values of full width at half-maximum around 3.5° and 1.7° for the ϕ-scan of (103) and rocking curve of (005) YBCO, respectively. The YBCO films grown on electropolished polycrystalline Hastelloy using this two-layer template exhibited a superconducting transition temperature of 89.5 K, a critical current density of 1.2 MA/cm2 at 75.5 K, and an α value (proportional factor of critical current density Jc˜H-α) of around 0.33, indicating a high density of pinning centers and an absence of weak links.

  15. N-N-Dimethylaniline

    Integrated Risk Information System (IRIS)

    N - N - Dimethylaniline ; CASRN 121 - 69 - 7 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcin

  16. N,N-Dimethylformamide

    Integrated Risk Information System (IRIS)

    N , N - Dimethylformamide ; CASRN 68 - 12 - 2 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarci

  17. N-Nitrosodi-N-propylamine

    Integrated Risk Information System (IRIS)

    N - Nitrosodi - N - propylamine ; CASRN 621 - 64 - 7 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for N

  18. 1/N

    SciTech Connect

    Coleman, S.

    1980-03-01

    There exist families of field theories with symmetry group SO(N) (or SU(N)) that become simpler as N becomes larger. More precisely, the solutions to these theories possess an expansion in powers of 1/N. This expansion is the subject of these lectures. The 1/N expansion can be used to analyze model field theories. The 1/N expansion is developed for phi/sup 4/ theory and applied to two two-dimensional models with similar combinatoric structures, the Gross-Neveu model and the CP/sup N-1/ model. These models display (in the leading 1/N approximation) such interesting phenomena as asymptotic freedom, dynamical symmetry breaking, dimensional transmutation, and non-perturbative confinement. It is possible that the 1/N expansion, with N the number of colors, might fruitfully be applied to quantum chromodynamics. Unfortunately, it is not possible to make a decisive test of the approximation, because no one knows how to compute even the first term in the expansion in closed form. However, it is possible to argue that this first term, whatever its detailed form, has many properties that are also shared by the real world, and which are otherwise underived from field theory. These include the saturation of scattering amplitudes by an infinite number of narrow resonances, the essential feature of dual-resonance models. (RWR)

  19. N-Nitroso-N-methylethylamine

    Integrated Risk Information System (IRIS)

    N - Nitroso - N - methylethylamine ; CASRN 10595 - 95 - 6 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments

  20. Phenomenology of n - n ¯ oscillations revisited

    DOE PAGESBeta

    Gardner, S.; Jafari, E.

    2015-05-22

    We revisit the phenomenology of n-n¯ oscillations in the presence of external magnetic fields, highlighting the role of spin. We show, contrary to long-held belief, that the n-n¯ transition rate need not be suppressed, opening new opportunities for its empirical study.

  1. Systematics of (n,2n) and (n,3n) Cross Sections.

    1991-10-08

    Version 00 SC2N3N can be used to calculate the (n2n) and (n3n) cross section in the energy region from threshold to about 25 MeV with the systematics parameters which well reproduce the experiment in the mass region of 23.le.A.le.238 (especially between 45 and 197.)

  2. N,N-Di- n-octyl- N,N-dimethyl and N,N-di- n-nonyl- N,N-dimethyl ammonium cholates: 13C and 15N CPMAS NMR, powder X-ray diffraction and thermoanalytical characterization

    NASA Astrophysics Data System (ADS)

    Kolehmainen, Erkki; Lahtinen, Manu; Valkonen, Arto; Behera, Babita; Kauppinen, Reijo

    2009-07-01

    N,N-Di- n-octyl- N,N-dimethyl cholate ( 1) and N,N-di- n-nonyl- N,N-dimethyl ammonium cholate ( 2) have been prepared by crystallization from equimolar mixtures of sodium cholate and quaternary N,N-di- n-alkyl- N,N-dimethyl ( n-octyl or n-nonyl) ammonium bromides. The formed crystalline materials have been structurally characterized by 13C and 15N cross polarization magic angle spinning (CPMAS) NMR, powder X-ray diffraction (PXRD) and thermoanalytical (TGA/DTA and DSC) methods and compared with each other. Powder X-ray diffraction patterns of 1 and 2 reveal clear similarities. Combined with the thermoanalytical data of these structures an existence of two hydrated polymorphs (most probably mono- and dihydrates) can be proposed. This presumption is further supported by 13C CPMAS NMR showing clearly double resonances for the carboxylic and majority of other carbons in these quaternary ammonium cholates. Owing to the endogenous character of cholate anion these ionic structures possess great potential in many pharmaceutical applications such as controlled drug delivery.

  3. Quark dynamics of N anti N annihilation

    SciTech Connect

    Dover, C.B.

    1985-01-01

    It is argued that recent observations of strong L dependence and approximate selection rules in certain N anti N annihilation modes necessitate a description of the reaction mechanism in terms of quark-gluon degrees of freedom.

  4. Study of metal corrosion using ac impedance techniques in the STS launch environment

    NASA Technical Reports Server (NTRS)

    Calle, Luz M.

    1989-01-01

    AC impedance measurements were performed to investigate the corrosion resistance of 19 alloys under conditions similar to the STS launch environment. The alloys were: Zirconium 702, Hastelloy C-22, Inconel 625, Hastelloy C-276, Hastelloy C-4, Inconel 600, 7Mo + N, Ferralium 255, Inco Alloy G-3, 20Cb-3, SS 904L, Inconel 825, SS 304LN, SS 316L, SS 317L, ES 2205, SS 304L, Hastelloy B-2, and Monel 400. AC impedance data were gathered for each alloy after one hour immersion time in each of the following three electrolyte solutions: 3.55 percent NaCl, 3.55 percent NaCl-0.1N HCl, and 3.55 percent NaCl-1.0N HCl. The data were analyzed qualitatively using the Nyquist plot and quantitatively using the Bode plot. Polarization resistance, Rp, values were obtained using the Bode plot. Zirconium 702 was the most corrosion resistant alloy in the three electrolytes. The ordering of the other alloys according the their resistance to corrosion varied as the concentration of hydrochloric acid in the electrolyte increased. The corrosion resistance of Zirconium 702 and Ferralium 255 increased as the concentration of hydrochloric acid in the electrolyte increased. The corrosion resistance of the other 17 alloys decreased as the concentration of the hyrdochloric acid in the electrolyte increased.

  5. Improved InGaN/GaN light-emitting diodes with a p-GaN/n-GaN/p-GaN/n-GaN/p-GaN current-spreading layer.

    PubMed

    Zhang, Zi-Hui; Tan, Swee Tiam; Liu, Wei; Ju, Zhengang; Zheng, Ke; Kyaw, Zabu; Ji, Yun; Hasanov, Namig; Sun, Xiao Wei; Demir, Hilmi Volkan

    2013-02-25

    This work reports both experimental and theoretical studies on the InGaN/GaN light-emitting diodes (LEDs) with optical output power and external quantum efficiency (EQE) levels substantially enhanced by incorporating p-GaN/n-GaN/p-GaN/n-GaN/p-GaN (PNPNP-GaN) current spreading layers in p-GaN. Each thin n-GaN layer sandwiched in the PNPNP-GaN structure is completely depleted due to the built-in electric field in the PNPNP-GaN junctions, and the ionized donors in these n-GaN layers serve as the hole spreaders. As a result, the electrical performance of the proposed device is improved and the optical output power and EQE are enhanced.

  6. Coherent Absorption of N00N States.

    PubMed

    Roger, Thomas; Restuccia, Sara; Lyons, Ashley; Giovannini, Daniel; Romero, Jacquiline; Jeffers, John; Padgett, Miles; Faccio, Daniele

    2016-07-01

    Recent results in deeply subwavelength thickness films demonstrate coherent control and logical gate operations with both classical and single-photon light sources. However, quantum processing and devices typically involve more than one photon and nontrivial input quantum states. Here we experimentally investigate two-photon N00N state coherent absorption in a multilayer graphene film. Depending on the N00N state input phase, it is possible to selectively choose between single- or two-photon absorption of the input state in the graphene film. These results demonstrate that coherent absorption in the quantum regime exhibits unique features, opening up applications in multiphoton spectroscopy and imaging. PMID:27447505

  7. Coherent Absorption of N00N States

    NASA Astrophysics Data System (ADS)

    Roger, Thomas; Restuccia, Sara; Lyons, Ashley; Giovannini, Daniel; Romero, Jacquiline; Jeffers, John; Padgett, Miles; Faccio, Daniele

    2016-07-01

    Recent results in deeply subwavelength thickness films demonstrate coherent control and logical gate operations with both classical and single-photon light sources. However, quantum processing and devices typically involve more than one photon and nontrivial input quantum states. Here we experimentally investigate two-photon N00N state coherent absorption in a multilayer graphene film. Depending on the N00N state input phase, it is possible to selectively choose between single- or two-photon absorption of the input state in the graphene film. These results demonstrate that coherent absorption in the quantum regime exhibits unique features, opening up applications in multiphoton spectroscopy and imaging.

  8. N-Nitroso-di-n-butylamine

    Integrated Risk Information System (IRIS)

    N - Nitroso - di - n - butylamine ; CASRN 924 - 16 - 3 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for

  9. First principles study of the ignition mechanism for hypergolic bipropellants: N,N,N',N'-tetramethylethylenediamine (TMEDA) and N,N,N',N'-tetramethylmethylenediamine (TMMDA) with nitric acid.

    PubMed

    Liu, Wei-Guang; Dasgupta, Siddharth; Zybin, Sergey V; Goddard, William A

    2011-05-26

    We report quantum mechanics calculations (B3LYP flavor of density functional theory) to determine the chemical reaction mechanism underlying the hypergolic reaction of pure HNO(3) with N,N,N',N'-tetramethylethylenediamine (TMEDA) and N,N,N',N'-tetramethylmethylenediamine (TMMDA). TMEDA and TMMDA are dimethyl amines linked by two CH(2) groups or one CH(2) group, respectively, but ignite very differently with HNO(3). We explain this dramatic difference in terms of the role that N lone-pair electrons play in activating adjacent chemical bonds. We identify two key atomistic level factors that affect the ignition delay: (1) The exothermicity for formation of the dinitrate salt from TMEDA or TMMDA. With only a single CH(2) group between basic amines, the diprotonation of TMMDA results in much stronger electrostatic repulsion, reducing the heat of dinitrate salt formation by 6.3 kcal/mol. (2) The reaction of NO(2) with TMEDA or TMMDA, which is the step that releases the heat and reactive species required to propagate the reaction. Two factors of TMEDA promote the kinetics by providing routes with low barriers to oxidize the C: (a) formation of a stable intermediate with a C-C double bond and (b) the lower bond energy for breaking the C-C single bond (by 18 kcal/mol comparing to alkane) between two amines. Both factors would decrease the ignition delay for TMEDA versus TMMDA. The same factors also explain the shorter ignition delay of 1,4-dimethylpiperazine (DMPipZ) versus 1,3,5-trimethylhexahydro-1,3,5-triazine (TMTZ). These results indicate that TMEDA and DMPipZ are excellent green replacements for hydrazines as the fuel in bipropellants.

  10. Thermodynamic characteristics of protolytic equilibria of hexamethylenediamine-N,N,N',N'-tetraacetic acid

    NASA Astrophysics Data System (ADS)

    Gridchin, S. N.; Pyreu, D. F.

    2011-04-01

    The heats of dissociation of betaine groups of hexamethylenediamine-N,N,N',N'-tetraacetic acid (H4L) at 298.15 K and the ionic strengths of 0.1, 0.5, and 1.0 (KNO3) were determined by direct calorimetry. The standard thermodynamic characteristics of the ptotolytic equilidria of H4L were calculated using the results from thermochemical and potentiometric measurements made under identical test conditions.

  11. On the effect of N-GaN/P-GaN/N-GaN/P-GaN/N-GaN built-in junctions in the n-GaN layer for InGaN/GaN light-emitting diodes.

    PubMed

    Kyaw, Zabu; Zhang, Zi-Hui; Liu, Wei; Tan, Swee Tiam; Ju, Zhen Gang; Zhang, Xue Liang; Ji, Yun; Hasanov, Namig; Zhu, Binbin; Lu, Shunpeng; Zhang, Yiping; Sun, Xiao Wei; Demir, Hilmi Volkan

    2014-01-13

    N-GaN/P-GaN/N-GaN/P-GaN/N-GaN (NPNPN-GaN) junctions embedded between the n-GaN region and multiple quantum wells (MQWs) are systematically studied both experimentally and theoretically to increase the performance of InGaN/GaN light emitting diodes (LEDs) in this work. In the proposed architecture, each thin P-GaN layer sandwiched in the NPNPN-GaN structure is completely depleted due to the built-in electric field in the NPNPN-GaN junctions, and the ionized acceptors in these P-GaN layers serve as the energy barriers for electrons from the n-GaN region, resulting in a reduced electron over flow and enhanced the current spreading horizontally in the n- GaN region. These lead to increased optical output power and external quantum efficiency (EQE) from the proposed device.

  12. 40 CFR 721.10056 - Benzenemethanaminium, N-(3-aminopropyl)-N,N-dimethyl-, N-soya acyl derivs., chlorides.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...)-N,N-dimethyl-, N-soya acyl derivs., chlorides. 721.10056 Section 721.10056 Protection of Environment...-aminopropyl)-N,N-dimethyl-, N-soya acyl derivs., chlorides. (a) Chemical substance and significant new uses...-dimethyl-, N-soya acyl derivs., chlorides (PMN P-03-47; CAS No. 90194-13-1) is subject to reporting...

  13. "Zhizneopisanie" astronomia N. N. Pavlova, im samim napisannoe %t Astronomer N. N. Pavlov's autobiography

    NASA Astrophysics Data System (ADS)

    Zhukov, V. Yu.

    This document called by the author "the life story" is written for the human resources department. It is a document intended for the official departmental purposes. At the same time there is something facinating about this documentary testimony about the epoch and the man. This short autobiography describes the early years of the Pulkovo astronomer N. N. Pavlov that fell on hard times of the Civil War. In the years between the World War I and the World War II he was awarded Mendeleyev Prize. He defended his doctorate dissertation after the evacuation from Leningrad. He was one fo the first Pulkovo astronomers to return to Leningrad in order to start reconstruction of the observatory that had been completely ruined during the war. Astronomer N. N. Pavlov renewed the Time Service in the city. N. N. Pavlov was a successful scientist and an outstanding person, all his life was devoted to science.

  14. N fixation versus N uptake in alfalfa

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Fertilizer N is the single most expensive input in nearly all crop-production systems and has been implicated in declining groundwater quality due to nitrate contamination. Commercial alfalfas are highly productive in the absence of nitrogen inputs because of the symbiotic association with soil bact...

  15. "N" is for Now

    ERIC Educational Resources Information Center

    Briggs, Linda L.

    2008-01-01

    The leap in wireless LAN standards to 802.11n is a WiFi upgrade so new it has not yet garnered final approval from the standards committee. Although that approval will not come until next year (vendors are currently building to a "pre-n" standard), there are plenty of notebook computers out there capable of running 802.11n. That means students…

  16. Thermodynamic characteristics of the protolytic equilibria of tetramethylenediamine- N,N,N', N'-tetraacetic acid

    NASA Astrophysics Data System (ADS)

    Gridchin, S. N.; Nikol'skii, V. M.

    2014-04-01

    The stepwise dissociation constants of tetramethylenediamine- N,N,N', N'-tetraacetic acid (H4L) are determined by means of potentiometry at 298.15 K and ionic strength values of 0.1, 0.5, and 1.0 (KNO3). The heat effects of the dissociation of the betaine groups of the complexone are measured by direct calorimetry. The standard thermodynamic characteristics of the protolytic equilibria of H4L are calculated via combined use of the results from thermochemical and potentiometric studies performed under identical experimental conditions. Our results are compared with the corresponding data on relative compounds.

  17. Electron and hole accumulations at GaN/AlInN/GaN interfaces and conductive n-type AlInN/GaN distributed Bragg reflectors

    NASA Astrophysics Data System (ADS)

    Yoshida, Shotaro; Ikeyama, Kazuki; Yasuda, Toshiki; Furuta, Takashi; Takeuchi, Tetsuya; Iwaya, Motoaki; Kamiyama, Satoshi; Akasaki, Isamu

    2016-05-01

    We investigated electron and hole accumulations at GaN/AlInN/GaN interfaces by Hall effect measurement. The InN mole fraction and temperature dependences on the sheet carrier densities at the interfaces reveal that electrons and holes were induced by large positive and negative polarization charges to satisfy the charge neutrality conditions, respectively. On the basis of the above results, we then designed and demonstrated a low-resistity 10-pair Si-doped n-type AlInN/GaN distributed Bragg reflector (DBR) by using high Si doped and graded layers at the GaN/AlInN interfaces. The low-resistity n-type AlInN/GaN DBR will reduce the resistance and the internal loss in blue vertical-cavity surface emitting lasers.

  18. 40 CFR 721.9957 - N-Nitroso-N-methylurethane.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false N-Nitroso-N-methylurethane. 721.9957... Substances § 721.9957 N-Nitroso-N-methylurethane. (a) Chemical substance and significant new use subject to reporting. (1) The chemical substance N-nitroso-N-methylurethane (CAS No. 615-53-2) is subject to...

  19. 40 CFR 721.9957 - N-Nitroso-N-methylurethane.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false N-Nitroso-N-methylurethane. 721.9957... Substances § 721.9957 N-Nitroso-N-methylurethane. (a) Chemical substance and significant new use subject to reporting. (1) The chemical substance N-nitroso-N-methylurethane (CAS No. 615-53-2) is subject to...

  20. Experimental verification of the Neuber relation at room and elevated temperatures. M.S. Thesis; [to predict stress-strain behavior in notched specimens of hastelloy x

    NASA Technical Reports Server (NTRS)

    Lucas, L. J.

    1982-01-01

    The accuracy of the Neuber equation at room temperature and 1,200 F as experimentally determined under cyclic load conditions with hold times. All strains were measured with an interferometric technique at both the local and remote regions of notched specimens. At room temperature, strains were obtained for the initial response at one load level and for cyclically stable conditions at four load levels. Stresses in notched members were simulated by subjecting smooth specimens to he same strains as were recorded on the notched specimen. Local stress-strain response was then predicted with excellent accuracy by subjecting a smooth specimen to limits established by the Neuber equation. Data at 1,200 F were obtained with the same experimental techniques but only in the cyclically stable conditions. The Neuber prediction at this temperature gave relatively accurate results in terms of predicting stress and strain points.

  1. Radiación

    NASA Video Gallery

    Fuera del capullo protector de la atmósfera terrestre, el universo está plagado de radiación dañina. Los astronautas que viven y trabajan en el espacio están expuestos no sólo a los rayos ultraviol...

  2. Crystal structure of N-[3-(di-methyl-aza-nium-yl)prop-yl]-N',N',N'',N''-tetra-methyl-N-(N,N,N',N'-tetra-methyl-form-am-id-in-ium-yl)-guanidinium dibromide hydroxide monohydrate.

    PubMed

    Tiritiris, Ioannis; Kantlehner, Willi

    2015-12-01

    The asymmetric unit of the title hydrated salt, C15H37N6 (3+)·2Br(-)·OH(-)·H2O, contains one cation, three partial-occupancy bromide ions, one hydroxide ion and one water mol-ecule. Refinement of the site-occupancy factors of the three disordered bromide ions converges with occupancies 0.701 (2), 0.831 (2) and 0.456 (2) summing to approximately two bromide ions per formula unit. The structure was refined as a two-component inversion twin with volume fractions 0.109 (8):0.891 (8) for the two domains. The central C3N unit of the bis-amidinium ion is linked to the aliphatic propyl chain by a C-N single bond. The other two bonds in this unit have double-bond character as have the four C-N bonds to the outer NMe2 groups. In contrast, the three C-N bonds to the central N atom of the (di-methyl-aza-nium-yl)propyl group have single-bond character. Delocalization of the two positive charges occurs in the N/C/N and C/N/C planes, while the third positive charge is localized on the di-methyl-ammonium group. The crystal structure is stabilized by O-H⋯O, N-H⋯Br, O-H⋯Br and C-H⋯Br hydrogen bonds, forming a three-dimensional network. PMID:26870507

  3. N = 2 string amplitudes

    SciTech Connect

    Ooguri, H.

    1995-08-01

    In physics, solvable models have played very important roles. Understanding a simple model in detail teaches us a lot about more complicated models in generic situations. Five years ago, C. Vafa and I found that the closed N = 2 string theory, that is a string theory with the N = 2 local supersymmetry on the worldsheet, is classically equivalent to the self-dual Einstein gravity in four spacetime dimensions. Thus this string theory is solvable at the classical level. More recently, we have examined the N = 2 string partition function for spacial compactifications, and computed it to all order in the string perturbation expansion. The fact that such computation is possible at all suggests that the N = 2 string theory is solvable even quantum mechanically.

  4. MOP02N (HDF)

    Atmospheric Science Data Center

    2016-10-03

    MOP02N MOPITT Derived CO (Near Infrared Radiances) News:  MOPITT Science Team (2013), MOPITT/Terra Level 2 CO vertical profiles derived from Near Infrared Radiances, version 6, Hampton, VA, USA:NASA Atmospheric Science Data ...

  5. Paris [ital N[bar N

    SciTech Connect

    Pignone, M.; Lacombe, M.; Loiseau, B.; Vinh Mau, R. Division de Physique Theorique, Institut de Physique Nucleaire, 91406 Orsay Cedex LPTPE, Universite Pierre et Marie Curie, 4 Place Jussieu, 75252 Paris Cedex 05 )

    1994-12-01

    The inner part of the Paris nucleon-antinucleon optical potential has been reanalyzed in view of new experimental constraints. These are mainly provided by accurate measurements of the analyzing power in charge-exchange scattering, [ital [bar p]p][r arrow][ital [bar n]n], together with elastic [ital [bar p]p][r arrow][ital [bar p]p] polarization data, allowing a better determination of the isospin dependence of the short-range forces. The fit is performed with a set of 3632 data. The good quality of the fit is illustrated over a large sample of observables for laboratory momenta from 180 to 910 MeV/[ital c]. Curves of the potentials and of the phase shifts are shown as well as the parameters of the potentials and effective range formula coefficients for the [ital S] and [ital P] waves. The spectrum of resonances and bound states predicted by our potential is also displayed. In particular, a bound state having the [ital AX](1565) quantum numbers is found with the right mass.

  6. Expressing n dimensions as n-1

    NASA Astrophysics Data System (ADS)

    Laubenstein, John

    2009-03-01

    The IWPD Scale Metrics team has explored a different conceptualization of multiple dimensions through a model expressing n dimensions as n -- 1. This is achieved by aligning time and a spatial dimension along the same orientation. We have shown that time and distance along the same axis in combination with a scalar is equivalent to two orthogonal dimensions. Scale Metrics is simply a different conceptualization of multi-dimensions; however, it requires a change in the modeling of gravitation since time is no longer considered to be orthogonal to the three spatial dimensions. A model for Scale Metrics gravity has been developed and in the process a quantum theory of gravitation emerges. Why entertain IWPD Scale Metrics? Because the Standard Model has not been successful in the unification of GR with QT. A new model of gravitation built on a foundation of quantum concepts (as opposed to a quantum fix to an inherently classical geometric theory) may be of benefit in the ultimate search for the unification of gravitation with quantum theory. Further, since Scale Metrics provides nothing more than a different way to conceptualize multiple dimensions in a manner that is equivalent to 4 vectors -- it replaces nothing, but rather serves only to complement past and current achievements while providing a new view of quantum gravitation.

  7. 40 CFR 721.10174 - 1-Propanaminium, 3-amino-N-(carboxymethyl)-N,N-dimethyl-, N-peanut-oil acyl derivs., inner salts.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...-(carboxymethyl)-N,N-dimethyl-, N-peanut-oil acyl derivs., inner salts. 721.10174 Section 721.10174 Protection of...-amino-N-(carboxymethyl)-N,N-dimethyl-, N-peanut-oil acyl derivs., inner salts. (a) Chemical substance...-Propanaminium, 3-amino-N-(carboxymethyl)-N,N-dimethyl-, N-peanut-oil acyl derivs., inner salts (PMN...

  8. 40 CFR 721.10174 - 1-Propanaminium, 3-amino-N-(carboxymethyl)-N,N-dimethyl-, N-peanut-oil acyl derivs., inner salts.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...-(carboxymethyl)-N,N-dimethyl-, N-peanut-oil acyl derivs., inner salts. 721.10174 Section 721.10174 Protection of...-amino-N-(carboxymethyl)-N,N-dimethyl-, N-peanut-oil acyl derivs., inner salts. (a) Chemical substance...-Propanaminium, 3-amino-N-(carboxymethyl)-N,N-dimethyl-, N-peanut-oil acyl derivs., inner salts (PMN...

  9. 40 CFR 721.10174 - 1-Propanaminium, 3-amino-N-(carboxymethyl)-N,N-dimethyl-, N-peanut-oil acyl derivs., inner salts.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...-(carboxymethyl)-N,N-dimethyl-, N-peanut-oil acyl derivs., inner salts. 721.10174 Section 721.10174 Protection of...-amino-N-(carboxymethyl)-N,N-dimethyl-, N-peanut-oil acyl derivs., inner salts. (a) Chemical substance...-Propanaminium, 3-amino-N-(carboxymethyl)-N,N-dimethyl-, N-peanut-oil acyl derivs., inner salts (PMN...

  10. 40 CFR 721.10174 - 1-Propanaminium, 3-amino-N-(carboxymethyl)-N,N-dimethyl-, N-peanut-oil acyl derivs., inner salts.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...-(carboxymethyl)-N,N-dimethyl-, N-peanut-oil acyl derivs., inner salts. 721.10174 Section 721.10174 Protection of...-amino-N-(carboxymethyl)-N,N-dimethyl-, N-peanut-oil acyl derivs., inner salts. (a) Chemical substance...-Propanaminium, 3-amino-N-(carboxymethyl)-N,N-dimethyl-, N-peanut-oil acyl derivs., inner salts (PMN...

  11. 40 CFR 721.10174 - 1-Propanaminium, 3-amino-N-(carboxymethyl)-N,N-dimethyl-, N-peanut-oil acyl derivs., inner salts.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...-(carboxymethyl)-N,N-dimethyl-, N-peanut-oil acyl derivs., inner salts. 721.10174 Section 721.10174 Protection of...-amino-N-(carboxymethyl)-N,N-dimethyl-, N-peanut-oil acyl derivs., inner salts. (a) Chemical substance...-Propanaminium, 3-amino-N-(carboxymethyl)-N,N-dimethyl-, N-peanut-oil acyl derivs., inner salts (PMN...

  12. Marine N inventory sensitivity to atmospheric N deposition

    NASA Astrophysics Data System (ADS)

    Landolfi, Angela; Somes, Chris; Zamora, Lauren; Koeve, Wolfgang; Oschlies, Andreas

    2015-04-01

    The marine inventory of fixed nitrogen (N), an essential nutrient controlling productivity, is determined by the balance between N2 fixation by cyanobacteria and N-loss via microbially-mediated processes under low oxygen conditions. Human-driven perturbations of ocean temperature and atmospheric N deposition impact on the magnitude of N-loss and N-gain with potential effects on oceanic N2O emissions. However, the timescale and the net effect of these changes on the N inventory is not known. This is particularly so since the degree of coupling between the major source and sink of N is debated and the sign of the feedbacks among these two opposite processes is not well defined. Here we use a global biogeochemical model to investigate how projected changes in ocean warming and atmospheric N deposition may impact the marine N inventory and affect future N2O emissions.

  13. 40 CFR 721.7270 - 1-propanaminium, 3-amino-, N,N,N-trimethyl-N-soya acyl derivs., chloride.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...-trimethyl-N-soya acyl derivs., chloride. 721.7270 Section 721.7270 Protection of Environment ENVIRONMENTAL...-soya acyl derivs., chloride. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as 1-propanaminium, 3-amino-, N,N,N-trimethyl-N-soya acyl...

  14. African N Assessment

    NASA Astrophysics Data System (ADS)

    Bekunda, M.; Galford, G. L.; Hickman, J. E.; Palm, C.

    2011-12-01

    Africa's smallholder agricultural systems face unique challenges in planning for reducing poverty, concurrent with adaptation and mitigation to climate change. At continental level, policy seeks to promote a uniquely African Green Revolution to increase crop yields and food production, and improve local livelihoods. However, the consequences on the environment and climate are not clear; these pro-economic development measures should be linked to climate change adaptation and mitigation measures, and research is required to help achieve these policy proposals by identifying options, and testing impacts. In particular, increased nitrogen (N) inputs are essential for increasing food production in Africa, but are accompanied by inevitable increases in losses to the environment. These losses appear to be low at input levels promoted in agricultural development programs, while the increased N inputs both increase current food production and appear to reduce the vulnerability of food production to changes in climate. We present field and remote sensing evidence from Malawi that subsidizing improved seed and fertilizers increases resilience to drought without adding excess N to the environment. In Kenya, field research identified thresholds in N2O losses, where emissions are very low at fertilization rates of less than 200 kg ha-1. Village-scale models have identified potential inefficiencies in the food production process where the largest losses of reactive N occur, and which could be targeted to reduce the amount of N released to the environment. We further review some on-going research activities and progress in Africa that compare different methods of managing resources that target resilience in food production and adaptation to climate change, using nutrient N as an indicator, while evaluating the effects of these resource management practices on ecosystems and the environment.

  15. Electrochemical etching of p-n-GaN/AlGaN photoelectrodes

    NASA Astrophysics Data System (ADS)

    Usikov, A. S.; Helava, H.; Nikiforov, A.; Puzyk, M. V.; Papchenko, B. P.; Kovaleva, Yu. V.; Makarov, Yu. N.

    2016-05-01

    Specific features of etching of GaN/AlGaN p-n structures in a KOH-based electrolyte have been studied. It was found that the corrosion process first passes across p layers through vertical channels associated with threading structural defects. Then, the corrosion process occurs in the lateral direction along n layers of the structure, with local hollows and voids thereby formed. The lateral etching is due to the presence of positive piezoelectric charges at boundaries of n-AlGaN and n-GaN layers and positively charged ionized donors in the space-charge region of the p-n junction.

  16. N-methylated derivatives of tyramine in citrus genus plants: identification of N,N,N-trimethyltyramine (candicine).

    PubMed

    Servillo, Luigi; Giovane, Alfonso; D'Onofrio, Nunzia; Casale, Rosario; Cautela, Domenico; Ferrari, Giovanna; Balestrieri, Maria Luisa; Castaldo, Domenico

    2014-03-26

    The distribution of tyramine and its methylated derivatives, N-methyltyramine and N,N-dimethyltyramine, was investigated in tissue parts (leaves and fruits) of several plants of Citrus genus by liquid chromatography-electrospray ionization tandem mass spectrometry (LC-ESI-MS/MS). In the course of our study we discovered the occurrence of N,N,N-trimethyltyramine in all citrus plants examined. This quaternary ammonium compound, known to act in animals as a neurotoxin, was recognized and characterized by mass spectrometric analysis. The substance, never described before in the Citrus genus, is also known as candicine or maltoxin. Results indicate that N,N,N-trimethyltyramine is consistently expressed in leaves of clementine, bitter orange, and lemon. Conversely, low levels were found in the leaves of orange, mandarin, chinotto (Citrus myrtifolia), bergamot, citron, and pomelo. In the edible part of the fruits, N,N,N-trimethyltyramine was found at trace levels.

  17. Critical Review of N, N+, N+ 2, N++, and N++ 2 Main Production Processes and Reactions of Relevance to Titan's Atmosphere

    NASA Astrophysics Data System (ADS)

    Dutuit, Odile; Carrasco, Nathalie; Thissen, Roland; Vuitton, Véronique; Alcaraz, Christian; Pernot, Pascal; Balucani, Nadia; Casavecchia, Piergiorgio; Canosa, André; Le Picard, Sébastien; Loison, Jean-Christophe; Herman, Zdenek; Zabka, Jan; Ascenzi, Daniela; Tosi, Paolo; Franceschi, Pietro; Price, Stephen D.; Lavvas, Panayotis

    2013-02-01

    This paper is a detailed critical review of the production processes and reactions of N, N+, N+ 2, N++, and N++ 2 of relevance to Titan's atmosphere. The review includes neutral, ion-molecule, and recombination reactions. The review covers all possible active nitrogen species under Titan's atmospheric conditions, specifically N2 (A 3Σ+ u), N (4 S), N (2 D), N (2 P), N+ 2, N+ (3 P), N+ (1 D), N++ 2, and N++ species, and includes a critical survey of the reactions of N, N+, N+ 2, N++, and N++ 2 with N2, H2, D2, CH4, C2H2, C2H4, C2H6, C3H8 and the deuterated hydrocarbon analogs, as well as the recombination reactions of N+ 2, N+, N++ 2, and N++. Production processes, lifetimes, and quenching by collisions with N2 of all reactant species are reviewed. The N (4 S) state is reactive with radicals and its reactions with CH2, CH3, C2H3, and C2H5 are reviewed. Metastable states N2 (A 3Σ+ u), N (2 D), and N (2 P) are either reactive or quenched by collisions with the target molecules reviewed. The reactions of N+ (1 D) have similar rate constants as N+ (3 P), but the product branching ratios differ significantly. Temperature effects and the role of the kinetic energy content of reactants are investigated. In all cases, experimental uncertainties of laboratory data are reported or estimated. Recommended values with uncertainties, or estimated values when no data are available, are given for rate constants and product branching ratios at 300 K and at the atmospheric temperature range of Titan (150-200 K for neutral reactions and 150 K for ion reactions).

  18. N1,N5,N10-Tris(4-hydroxycinnamoyl)spermidines from Microdesmis keayana roots.

    PubMed

    Zamble, Alexis; Sahpaz, Sevser; Hennebelle, Thierry; Carato, Pascal; Bailleul, François

    2006-09-01

    Three new N1,N5,N10-tris(4-hydroxycinnamoyl)spermidines were isolated from a methanolic root extract of Microdesmis keayana. They were identified as N5,N10-di(p-coumaroyl)-N1-feruloylspermidine,N5-(p-coumaroyl)-N1,N10-diferuloylspermidine, and N1,N5,N10-triferuloylspermidine, and were named keayanidines A, B, and C (1-3), respectively. Their structures were established by spectral techniques(electrospray mass spectrometry, one- and two-dimensional NMR). A 4',4'',4'''-trimethylated derivative was prepared by methylation of keayanidine C, and the same compound was synthesized fromspermidine and 3,4-dimethoxycinnamic acid to confirm the spectral attributions of the NMR data of the natural compounds. Radical-scavenging properties of all compounds were evaluated by 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical spectrophotometric assay. PMID:17193330

  19. N-Nitrosopyrrolidine

    Integrated Risk Information System (IRIS)

    N - Nitrosopyrrolidine ; CASRN 930 - 55 - 2 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcino

  20. n-Heptane

    Integrated Risk Information System (IRIS)

    n - Heptane ; CASRN 142 - 82 - 5 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effec

  1. N-Nitrosodiphenylamine

    Integrated Risk Information System (IRIS)

    N - Nitrosodiphenylamine ; CASRN 86 - 30 - 6 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcin

  2. N-Nitrosodimethylamine

    Integrated Risk Information System (IRIS)

    N - Nitrosodimethylamine ; CASRN 62 - 75 - 9 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcin

  3. n-Hexane

    Integrated Risk Information System (IRIS)

    n - Hexane ; CASRN 110 - 54 - 3 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effect

  4. N-Nitrosodiethylamine

    Integrated Risk Information System (IRIS)

    N - Nitrosodiethylamine ; CASRN 55 - 18 - 5 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcino

  5. N-Nitrosodiethanolamine

    Integrated Risk Information System (IRIS)

    N - Nitrosodiethanolamine ; CASRN 1116 - 54 - 7 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncar

  6. n-Butanol

    Integrated Risk Information System (IRIS)

    n - Butanol ; CASRN 71 - 36 - 3 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinogenic Effect

  7. Interaction of immunoglobulin G with N,N,N',N'-ethylenediaminetetramethylenephosphonic acid-modified zirconia.

    PubMed

    Subramanian, Anuradha; Sarkar, Sabyasachi

    2003-03-01

    Zirconia beads (25-38 microm in diameter) were modified with N,N,N'.N'-ethylenediaminetetramethylenephosphonic acid to generate a pseudo-biospecific support, r_PEZ. To better understand the force of interaction between the IgG and the r_PEZ, the equilibrium dissociation constant (Kd) was determined by static binding isotherms, as a function of temperature and by frontal analysis at different linear velocities. Temperature had no significant impact on the maximum static binding capacity (Q(max)) and the equilibrium-binding constant (Kd), whereas pH and the salt concentration had a noticeable impact on both Q(max) and Kd values. Q(max) was found to be in the range of 55-65 mg IgG per ml of beads and unaffected by temperature. The maximum dynamic binding capacity (Qx) was found to be in the range of 20-12 mg IgG per ml of beads. The adsorption rate constant (ka) was determined by a split-peak approach to be between 982 and 32421 mol(-1) s(-1) depending on the linear velocity. Adsorption rate of IgG on r_PEZ was studied as a function of both feed concentration and linear velocity. The standard enthalpy and entropy values were estimated for the interaction of IgG with this novel support. The binding constants were also determined by modeling the batch protein-uptake data. PMID:12641289

  8. 40 CFR 721.10115 - 1-Hexadecanaminium, N,N-dibutyl-N-(2-hydroxyethyl)-, bromide (1:1).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false 1-Hexadecanaminium, N,N-dibutyl-N-(2... New Uses for Specific Chemical Substances § 721.10115 1-Hexadecanaminium, N,N-dibutyl-N-(2... chemical substance identified as 1-hexadecanaminium, N,N-dibutyl-N-(2-hydroxyethyl)-, bromide (1:1) (PMN...

  9. 40 CFR 721.10115 - 1-Hexadecanaminium, N,N-dibutyl-N-(2-hydroxyethyl)-, bromide (1:1).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false 1-Hexadecanaminium, N,N-dibutyl-N-(2... New Uses for Specific Chemical Substances § 721.10115 1-Hexadecanaminium, N,N-dibutyl-N-(2... chemical substance identified as 1-hexadecanaminium, N,N-dibutyl-N-(2-hydroxyethyl)-, bromide (1:1) (PMN...

  10. 40 CFR 721.10056 - Benzenemethanaminium, N-(3-aminopropyl)-N,N-dimethyl-, N-soya acyl derivs., chlorides.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Benzenemethanaminium, N-(3-aminopropyl)-N,N-dimethyl-, N-soya acyl derivs., chlorides. 721.10056 Section 721.10056 Protection of Environment... SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10056 Benzenemethanaminium,...

  11. 40 CFR 721.7270 - 1-propanaminium, 3-amino-, N,N,N-trimethyl-N-soya acyl derivs., chloride.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false 1-propanaminium, 3-amino-, N,N,N-trimethyl-N-soya acyl derivs., chloride. 721.7270 Section 721.7270 Protection of Environment ENVIRONMENTAL... Significant New Uses for Specific Chemical Substances § 721.7270 1-propanaminium, 3-amino-,...

  12. Template syntheses of iron(II) complexes containing chiral P-N-N-P and P-N-N ligands.

    PubMed

    Mikhailine, Alexandre A; Kim, Eunice; Dingels, Carsten; Lough, Alan J; Morris, Robert H

    2008-08-01

    A multicomponent template reaction utilizing an air-stable phosphonium precursor leads initially to the first enantiopure bis-tridentate iron complexes mer-[Fe(P-N-N) 2] (2+) in high yield and then to new tetradentate iron complexes trans-[Fe(MeCN) 2(P-N-N-P)] (2+). PMID:18590327

  13. InAlN/AlN/GaN heterostructures for high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Usov, S. O.; Sakharov, A. V.; Tsatsulnikov, A. F.; Lundin, V. W.; Zavarin, E. E.; Nikolaev, A. E.; Yagovkina, M. A.; Zemlyakov, V. E.; Egorkin, V. I.; Ustinov, V. M.

    2016-08-01

    The results of development of InAlN/AlN/GaN heterostructures, grown on sapphire substrates by metal-organic chemical vapour deposition, and high electron mobility transistors (HEMTs) based on them are presented. The dependencies of the InAlN/AlN/GaN heterostructure properties on epitaxial growth conditions were investigated. The optimal indium content and InAlN barrier layer thicknesses of the heterostructures for HEMT s were determined. The possibility to improve the characteristics of HEMTs by in-situ passivation by Si3N4 thin protective layer deposited in the same epitaxial process was demonstrated. The InAlN/AlN/GaN heterostructure grown on sapphire substrate with diameter of 100 mm were obtained with sufficiently uniform distribution of sheet resistance. The HEMTs with saturation current of 1600 mA/mm and transconductance of 230 mS/mm are demonstrated.

  14. Gate length scaling effect on high-electron mobility transistors devices using AlGaN/GaN and AlInN/AlN/GaN heterostructures.

    PubMed

    Liao, S Y; Lu, C C; Chang, T; Huang, C F; Cheng, C H; Chang, L B

    2014-08-01

    Compared to AlGaN/GaN HEMT with 0.15 μm T-gate length, the AlInN/AlN/GaN one exhibits much higher current density and transconductance of 1558 mA/mm at Vd = 2 V and 330 mS/mm, respectively. The high extrinsic ft and fmax of 82 GHz and 70 GHz are extracted from AlInN/AlN/GaN HEMT. Besides, we find that the transconductance roll-off is significant in AlGaN/GaN, but largely improved in AlInN/AlN/GaN HEMT, suggesting that the high carrier density and lattice-matched epitaxial heterostructure is important to reach both large RF output power and high operation frequency, especially for an aggressively gate length scaling.

  15. N-body models

    NASA Technical Reports Server (NTRS)

    Miller, R. H.

    1990-01-01

    The experimental discovery of an overstability in the central regions of galaxies is briefly discussed, and numerical methods for integrating orbits are briefly addressed. The overstability manifests itself as a growing amplitude in the orbit of a galaxy's nucleus about its mass centroid. This finding may complicate studies of the topological properties of orbits and studies of the bifurcation structure of orbits. A sample problem is used to illustrate the importance of a Liouville theorem in N-body calculations.

  16. .. P .,n - NASA

    NASA Website

    t~~ j~te~r~l aoc~~d b~f~r~ lift-off. ~~~~. zero for tni~ mi••ion ~~ 13~,16:~9;OOGmt. Te.i, r~,0rt has b~"n f~era.ea ~$oppl~ment11 to tn. "fQ110 10 ...

  17. Epitaxial NbN/AlN/NbN tunnel junctions on Si substrates with TiN buffer layers

    NASA Astrophysics Data System (ADS)

    Sun, Rui; Makise, Kazumasa; Zhang, Lu; Terai, Hirotaka; Wang, Zhen

    2016-06-01

    We have developed epitaxial NbN/AlN/NbN tunnel junctions on Si (100) substrates with a TiN buffer layer. A 50-nm-thick (200)-oriented TiN thin film was introduced as the buffer layer for epitaxial growth of NbN/AlN/NbN trilayers on Si substrates. The fabricated NbN/AlN/NbN junctions demonstrated excellent tunneling properties with a high gap voltage of 5.5 mV, a large IcRN product of 3.8 mV, a sharp quasiparticle current rise with a ΔVg of 0.4 mV, and a small subgap leakage current. The junction quality factor Rsg/RN was about 23 for the junction with a Jc of 47 A/cm2 and was about 6 for the junction with a Jc of 3.0 kA/cm2. X-ray diffraction and transmission electron microscopy observations showed that the NbN/AlN/NbN trilayers were grown epitaxially on the (200)-orientated TiN buffer layer and had a highly crystalline structure with the (200) orientation.

  18. Exchange interactions and Curie temperatures of the tetrametal nitrides Cr₄N, Mn₄N, Fe₄N, Co₄N, and Ni₄N.

    PubMed

    Meinert, Markus

    2016-02-10

    The exchange interactions of Cr4N, Mn4N, Fe4N, Co4N, and Ni4N compounds with perovskite structure were calculated to obtain the Curie temperatures for these compounds from Monte Carlo calculations. Contrary to naíve expectation, the exchange interactions vary markedly among these five compounds. In Fe4N, the intra-sublattice interaction of the Fe 3c atoms is strongly negative, leading to a significant reduction of the Curie temperature. The calculated Curie temperatures are 291 K (Cr4N), 710 K (Mn4N), 668 K (Fe4N), 827 K (Co4N), and 121 K (Ni4N), in good agreement with experimental observations where available. The much lower Curie temperature of Ni4N compared to fcc Ni is explained on the basis of the exchange interactions.

  19. Nonlocal N=1 supersymmetry

    NASA Astrophysics Data System (ADS)

    Kimura, Tetsuji; Mazumdar, Anupam; Noumi, Toshifumi; Yamaguchi, Masahide

    2016-10-01

    We construct N=1 supersymmetric nonlocal theories in four dimension. We discuss higher derivative extensions of chiral and vector superfields, and write down generic forms of Kähler potential and superpotential up to quadratic order. We derive the condition in which an auxiliary field remains non-dynamical, and the dynamical scalars and fermions are free from the ghost degrees of freedom. We also investigate the nonlocal effects on the supersymmetry breaking and find that supertrace (mass) formula is significantly modified even at the tree level.

  20. High performance AlGaN/GaN HEMTs with AlN/SiNx passivation

    NASA Astrophysics Data System (ADS)

    Xin, Tan; Yuanjie, Lü; Guodong, Gu; Li, Wang; Shaobo, Dun; Xubo, Song; Hongyu, Guo; Jiayun, Yin; Shujun, Cai; Zhihong, Feng

    2015-07-01

    AlGaN/GaN high electron-mobility transistors (HEMTs) with 5 nm AlN passivation by plasma enhanced atomic layer deposition (PEALD) were fabricated, covered by 50 nm SiNx which was grown by plasma enhanced chemical vapor deposition (PECVD). With PEALD AlN passivation, current collapse was suppressed more effectively and the devices show better subthreshold characteristics. Moreover, the insertion of AlN increased the RF transconductance, which lead to a higher cut-off frequency. Temperature dependence of DC characteristics demonstrated that the degradations of drain current and maximum transconductance at elevated temperatures for the AlN/SiNx passivated devices were much smaller compared with the devices with SiNx passivation, indicating that PEALD AlN passivation can improve the high temperature operation of the AlGaN/GaN HEMTs. Project supported by the National Natural Science Foundation of China (No. 60890192).

  1. Applied N=1 supergravity

    SciTech Connect

    Nath, P.; Arnowitt, R.; Chamseddine, A.H.

    1984-01-01

    A review of recent developments in the applications of N=1 supergravity to the construction of unified models of elementary particle interactions is given. Couplings of N=1 supergravity with matter consisting of an arbitrary set of left handed multiplets and a gauge multiplet are discussed. General formulation of spontaneous symmetry breaking and the criteria for breaking of internal symmetry and of local supersymmetry are described. Construction of specific supergravity GUT models, the gauge hierarchy in GUT models and a deduction of the low energy effective potential are discussed. The phenomena of SU(2)XU(1) electro-weak gauge invariance breakdown by supergravity in tree models and by radiative corrections using renormalization group methods are described. The particle content of supergravity unified theories at low energy is given which includes predictions, for a class of supergravity models, of light gauge fermions, i.e. of a charged Dirac fermion, the Wino, with a mass below the W boson mass and a neutral fermion, the Zino, below the mass of the Z boson mass. ''Direct'' gaugino masses arising from loops for the photino and the gluino, (which are massless at the tree level) are exhibited. Decays of the W and Z into photino, Wino, and Zino modes and their branching ratios into various channels are given.

  2. 40 CFR 721.10193 - 1-Butanaminium, N-(3-aminopropyl)-N-butyl-N-(2-carboxyethyl)-, N-coco acyl derivs., inner salts.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...-butyl-N-(2-carboxyethyl)-, N-coco acyl derivs., inner salts. 721.10193 Section 721.10193 Protection of...-aminopropyl)-N-butyl-N-(2-carboxyethyl)-, N-coco acyl derivs., inner salts. (a) Chemical substance and...-aminopropyl)-N-butyl-N-(2-carboxyethyl)-, N-coco acyl derivs., inner salts (PMN P-06-263, Chemical B; CAS...

  3. 40 CFR 180.1130 - N-(n-octyl)-2-pyrrolidone and N-(n-dodecyl)-2-pyrrolidone; exemptions from the requirement of a...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 23 2010-07-01 2010-07-01 false N-(n-octyl)-2-pyrrolidone and N-(n... EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From Tolerances § 180.1130 N-(n-octyl)-2-pyrrolidone and N-(n-dodecyl)-2-pyrrolidone; exemptions from the requirement of a tolerance....

  4. 40 CFR 180.1130 - N-(n-octyl)-2-pyrrolidone and N-(n-dodecyl)-2-pyrrolidone; exemptions from the requirement of a...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 24 2011-07-01 2011-07-01 false N-(n-octyl)-2-pyrrolidone and N-(n... EXEMPTIONS FOR PESTICIDE CHEMICAL RESIDUES IN FOOD Exemptions From Tolerances § 180.1130 N-(n-octyl)-2-pyrrolidone and N-(n-dodecyl)-2-pyrrolidone; exemptions from the requirement of a tolerance....

  5. Impact ionization in N-polar AlGaN/GaN high electron mobility transistors

    SciTech Connect

    Killat, N. E-mail: Martin.Kuball@bristol.ac.uk; Uren, M. J.; Kuball, M. E-mail: Martin.Kuball@bristol.ac.uk; Keller, S.; Kolluri, S.; Mishra, U. K.

    2014-08-11

    The existence of impact ionization as one of the open questions for GaN device reliability was studied in N-polar AlGaN/GaN high electron mobility transistors. Electroluminescence (EL) imaging and spectroscopy from underneath the device gate contact revealed the presence of hot electrons in excess of the GaN bandgap energy even at moderate on-state bias conditions, enabling impact ionization with hole currents up to several hundreds of pA/mm. The detection of high energy luminescence from hot electrons demonstrates that EL analysis is a highly sensitive tool to study degradation mechanisms in GaN devices.

  6. Developing Superconducting Flux Qubit by Using Epitaxial NbN/AlN/NbN Junction

    NASA Astrophysics Data System (ADS)

    Qiu, Wei; Makise, Kazumasa; Terai, Hirotaka; Wang, Zhen

    In an effort to eliminate the intrinsic noise sources that contained within the superconducting qubit circuits, we successfully fabricate superconducting flux qubit circuits (rf SQUID) with full epitaxially grown NbN/AlN/NbN tunnel junctions. The temperature dependent of magnetic flux shift has been investigated by using a NbN/AlN/NbN dc SQUID magnetometer in the temperature range from 20 mK to 2.5 K. Our results show that the shift of the magnetic flux is in the level of ∼1 mF 0 during the experiment.

  7. Birkhoff's Polytope and Unistochastic Matrices, N = 3 and N = 4

    NASA Astrophysics Data System (ADS)

    Bengtsson, Ingemar; Ericsson, Åsa; Kuś, Marek; Tadej, Wojciech; Życzkowski, Karol

    2005-10-01

    The set of bistochastic or doubly stochastic N×N matrices is a convex set called Birkhoff’s polytope, which we describe in some detail. Our problem is to characterize the set of unistochastic matrices as a subset of Birkhoff’s polytope. For N=3 we present fairly complete results. For N=4 partial results are obtained. An interesting difference between the two cases is that there is a ball of unistochastic matrices around the van der Waerden matrix for N=3, while this is not the case for N=4.

  8. Properties of Si{sub n}, Ge{sub n}, and Si{sub n}Ge{sub n} clusters

    SciTech Connect

    Dong, Yi; Rehman, Habib ur; Springborg, Michael

    2015-01-22

    The structures of Si{sub n}, Ge{sub n}, and Si{sub n}Ge{sub n} clusters with up to 44 atoms have been determined theoretically using an unbiased structure-optimization method in combination with a parametrized, density-functional description of the total energy for a given structure. By analyzing the total energy in detail, particularly stable clusters are identified. Moreover, general trends in the structures are identified with the help of specifically constructed descriptors.

  9. Comparison of trap characteristics between AlGaN/GaN and AlGaN/InGaN/GaN heterostructure by frequency dependent conductance measurement

    SciTech Connect

    Chakraborty, Apurba; Biswas, Dhrubes

    2015-02-23

    Frequency dependent conductance measurement is carried out to observe the trapping effect in AlGaN/InGaN/GaN double heterostructure and compared that with conventional AlGaN/GaN single heterostructure. It is found that the AlGaN/InGaN/GaN diode structure does not show any trapping effect, whereas single heterostructure AlGaN/GaN diode suffers from two kinds of trap energy states in near depletion to higher negative voltage bias region. This conductance behaviour of AlGaN/InGaN/GaN heterostructure is owing to more Fermi energy level shift from trap energy states at AlGaN/InGaN junction compare to single AlGaN/GaN heterostructure and eliminates the trapping effects. Analysis yielded interface trap energy state in AlGaN/GaN is to be with time constant of (33.8–76.5) μs and trap density of (2.38–0.656) × 10{sup 12 }eV{sup −1} cm{sup −2} in −3.2 to −4.8 V bias region, whereas for AlGaN/InGaN/GaN structure no interface energy states are found and the extracted surface trap energy concentrations and time constants are (5.87–4.39) ×10{sup 10} eV{sup −1} cm{sup −2} and (17.8–11.3) μs, respectively, in bias range of −0.8–0.0 V.

  10. Distributed bragg reflector using AIGaN/GaN

    DOEpatents

    Waldrip, Karen E.; Lee, Stephen R.; Han, Jung

    2004-08-10

    A supported distributed Bragg reflector or superlattice structure formed from a substrate, a nucleation layer deposited on the substrate, and an interlayer deposited on the nucleation layer, followed by deposition of (Al,Ga,B)N layers or multiple pairs of (Al,Ga,B)N/(Al,Ga,B)N layers, where the interlayer is a material selected from AlN, Al.sub.x Ga.sub.1-x N, and AlBN with a thickness of approximately 20 to 1000 angstroms. The interlayer functions to reduce or eliminate the initial tensile growth stress, thereby reducing cracking in the structure. Multiple interlayers utilized in an AlGaN/GaN DBR structure can eliminate cracking and produce a structure with a reflectivity value greater than 0.99.

  11. GaN/InGaN avalanche phototransistors

    NASA Astrophysics Data System (ADS)

    Shen, Shyh-Chiang; Kao, Tsung-Ting; Kim, Hee-Jin; Lee, Yi-Che; Kim, Jeomoh; Ji, Mi-Hee; Ryou, Jae-Hyun; Detchprohm, Theeradetch; Dupuis, Russell D.

    2015-03-01

    We report on III-nitride (III-N) avalanche phototransistor (APT) action by illuminating ultraviolet (UV) photons onto a GaN/InGaN npn heterojunction bipolar transistor in an open-base configuration. A high responsivity of >1 A/W was measured for the device operating at a collector-to-emitter voltage (VCE) of <15 V in the phototransistor mode. The carrier multiplication in the reversed biased collector leads to a photocurrent avalanche as VCE increases. At λ = 380 nm, the GaN/InGaN APT shows a responsivity of >68 A/W at VCE = 95 V. The InGaN APT demonstrates the feasibility of using III-N bipolar transistor structures for high-sensitivity UV photodetection applications.

  12. N44C nebula

    NASA Technical Reports Server (NTRS)

    1999-01-01

    Resembling the hair in Botticelli's famous portrait of the birth of Venus, an image from NASA's Hubble Space Telescope has captured softly glowing filaments streaming from hot young stars in a nearby nebula.

    The image, presented by the Hubble Heritage Project, was taken in 1996 by Hubble's Wide Field and Planetary Camera 2, designed and built by NASA's Jet Propulsion Laboratory, Pasadena, Calif. The image is available online at

    http://heritage.stsci.edu , http://oposite.stsci.edu/pubinfo/pr/2002/12 orhttp://www.jpl.nasa.gov/images/wfpc .

    On the top right of the image is a source of its artistic likeness, a network of nebulous filaments surrounding the Wolf-Rayet star. This type of rare star is characterized by an exceptionally vigorous 'wind' of charged particles. The shock of the wind colliding with the surrounding gas causes the gas to glow.

    The Wolf-Rayet star is part of N44C, a nebula of glowing hydrogen gas surrounding young stars in the Large Magellanic Cloud. Visible from the Southern Hemisphere, the Large Magellanic Cloud is a small companion galaxy to the Milky Way.

    What makes N44C peculiar is the temperature of the star that illuminates it. The most massive stars -- those that are 10 to 50 times more massive than the Sun -- have maximum temperatures of 30,000 to 50,000 degrees Celsius (54,000 to 90,000 degrees Fahrenheit). The temperature of this star is about 75,000 degrees Celsius (135,000 degrees Fahrenheit). This unusually high temperature may be due to a neutron star or black hole that occasionally produces X-rays but is now inactive.

    N44C is part of a larger complex that includes young, hot, massive stars, nebulae, and a 'superbubble' blown out by multiple supernova explosions. Part of the superbubble is seen in red at the very bottom left of the Hubble image.

    The Space Telescope Science Institute is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract with the Goddard

  13. 40 CFR 721.10175 - 1-Propanaminium, N-(3-aminopropyl)-2-hydroxy-N,N-dimethyl-3-sulfo-, N-(C12-18 and C18-unsatd...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...-hydroxy-N,N-dimethyl-3-sulfo-, N-(C12-18 and C18-unsatd. acyl) derivs., inner salts. 721.10175 Section 721... 1-Propanaminium, N-(3-aminopropyl)-2-hydroxy-N,N-dimethyl-3-sulfo-, N-(C12-18 and C18-unsatd. acyl... chemical substance identified as 1-Propanaminium, N-(3-aminopropyl)-2-hydroxy-N,N-dimethyl-3-sulfo-,...

  14. Oxycodone N-oxide.

    PubMed

    Sonar, Vijayakumar N; Parkin, Sean; Crooks, Peter A

    2012-11-01

    The title compound, (5R,9R,13S,14S,17R)-14-hydroxy-3-methoxy-17-methyl-4,5-epoxymorphinan-6-one N-oxide, C(18)H(21)NO(5), has been prepared in a diastereomerically pure form by the reaction of oxycodone with 3-chloroperbenzoic acid and subsequent crystallization of the product from chloroform. The crystal packing shows that the molecule exhibits intramolecular O-H···O [D···A = 2.482 (2) Å] hydrogen bonding. In addition, there are weak intermolecular C-H...O interactions which, along with van der Waals forces, stabilize the structure. The new chiral center at the 17-position is demonstrated to be R.

  15. Cyclo-hexyl-methyl-ammonium N,N'-dicyclo-hexyl-N,N'-dimethyl-N''-(2,2,2-trifluoro-acet-yl)phospho-nic triamide).

    PubMed

    Yazdanbakhsh, Mohammad; Eshtiagh-Hosseini, Hossein; Sabbaghi, Fahimeh

    2008-12-10

    In the salt, C(7)H(16)N(+)·C(16)H(28)F(3)N(3)O(2)P(-), the P atom shows tetra-hedral coordination. Two ion pairs are linked by N-H⋯O hydrogen bonds across a center of inversion. The phosphoryl and carbonyl groups are staggered [O-P-N-C = 64.8 (3)°].

  16. Relativistic scalar-vector models of the N-N and N-nuclear interactions

    SciTech Connect

    Green, A.E.S.

    1985-01-01

    This paper for the Proceedings of Conference an Anti-Nucleon and Nucleon-Nucleus Interactions summarizes work by the principal investigator and his collaborators on the nucleon-nucleon (N-N) and nucleon-nuclear (N-eta) interactions. It draws heavily on a paper presented at the Many Body Conference in Rome in 1972 but also includes a brief review of our phenomenological N-eta interaction studies. We first summarize our 48-49 generalized scalar-vector meson field theory model of the N-N interactions. This is followed by a brief description of our phenomenological work in the 50's on the N-eta interaction sponsored by the Atomic Energy Commission (the present DOE). This work finally led to strong velocity dependent potentials with spin orbit and isospin terms for shell and optical model applications. This is followed by a section on the Emergence of One-Boson Exchange Models describing developments in the 60's of quantitative generalized one boson exchange potentials (GOBEP) including our purely relativistic N-N analyses. Then follows a section on the application of this meson field model to the N-eta interaction, in particular to spherical closed shell nuclei. This work was sponsored by AFOSR but funding was halted with the Mansfield amendment. We conclude with a discussion of subsequent collateral work by former colleagues and by others who have converged upon scalar-vector relativistic models of N-N, antiN-N, N-eta and antiN-eta interactions and some lessons learned from this extended endeavor. 61 refs.

  17. Characterization of chronic N,N'-diacetylbenzidine-induced nephropathy.

    PubMed Central

    Zimmerman, S. W.

    1979-01-01

    Rats given N,N'-diacetyl benzidine (N,N'-DAB) by intraperitoneal injections were studied to further characterize the ensuing renal disease. Significant proteinuria and albuminuria occurred at 10 weeks and thereafter and was enhanced by prior unilateral nephrectomy. Glomerular epithelial cell vacuolization and cyst formation were marked in proteinuric rats. Focal glomerular sclerosis and synechia were present, but proliferative crescent formation was not. Glomerular fibrinogen was noted, but no immunoglobulins or C3 was detected by immunofluorescence microscopy. Glomerular epithelial cell cysts and disruption were noted ultrastructurally, but no electron-dense deposits were seen. Tubular basement membrane thickening and wrinkling were noted in N,N'-DAB rats, and maximum urine osmolarlity was decreased. None of the animals developed renal insufficiency. Parenteral N,N'-DAB-induced renal disease is different from crescentic glomerulonephritis noted in rats fed N,N'-DAB and has similarities to an experimental model of aminonucleoside induced focal sclerosis, supporting the theory of primary glomerular epithelial cell injury mediating proteinuria and focal sclerosis. Images Figure 6 Figure 7 Figure 4 Figure 5 Figure 1 Figure 2 Figure 3 PMID:426029

  18. N abundance of nodules as an indicator of N metabolism in n(2)-fixing plants.

    PubMed

    Shearer, G; Feldman, L; Bryan, B A; Skeeters, J L; Kohl, D H; Amarger, N; Mariotti, F; Mariotti, A

    1982-08-01

    This paper expands upon previous reports of (15)N elevation in nodules (compared to other tissues) of N(2)-fixing plants. N(2)-Fixing nodules of Glycine max (soybeans), Vigna unguiculata (cowpea), Phaseolus vulgaris (common bean), Phaseolus coccineus (scarlet runner bean), Prosopis glandulosa (mesquite), and Olneya tesota (desert ironwood) were enriched in (15)N. Nodules of Vicia faba (fava beans), Arachis hypogaea (peanut), Trifolium pratense (red clover), Pisum sativum (pea), Lathyrus sativus (grass pea), Medicago sativa (alfalfa), and Lupinus mutabilis (South American lupine) were not; nor were the nodules of nine species of N(2)-fixing nonlegumes. The nitrogen of ineffective nodules of soybeans and cowpeas was not enriched in (15)N. Thus, (15)N elevation in nodules of these plants depends on active N(2)-fixation. Results obtained so far on the generality of (15)N enrichment in N(2)-fixing nodules suggest that only the nodules of plants which actively fix N(2) and which transport allantoin or allantoic acid exhibit (15)N enrichment. PMID:16662517

  19. Nucleation of GaN/AlN quantum dots

    SciTech Connect

    Adelmann, C; Daudin, B; Oliver, R; Briggs, G; Rudd, R

    2003-10-13

    We study the nucleation of GaN islands grown by plasma-assisted molecular-beam epitaxy on AlN in a Stranski-Krastanov mode. In particular, we assess the variation of their height and density as a function of GaN coverage. We show that the GaN growth passes four stages: initially, the growth is layer-by-layer; subsequently, bidimensional precursor islands form, which transform into genuine three-dimensional islands. During the latter stage, the height and the density of the islands increase with GaN coverage until the density saturates. During further GaN growth, the density remains constant and a bimodal height distribution appears. The variation of island height and density as a function of substrate temperature is discussed in the framework of an equilibrium model for Stranski-Krastanov growth [R. E. Rudd et al., Phys. Rev. Lett. 90, 146101 (2003)].

  20. Characterization of AlInN/AlN/GaN Heterostructures with Different AlN Buffer Thickness

    NASA Astrophysics Data System (ADS)

    Çörekçi, S.; Dugan, S.; Öztürk, M. K.; Çetin, S. Ş.; Çakmak, M.; Özçelik, S.; Özbay, E.

    2016-07-01

    Two AlInN/AlN/GaN heterostructures with 280-nm- and 400-nm-thick AlN buffer grown on sapphire substrates by metal-organic chemical vapor deposition (MOCVD) have been investigated by x-ray diffraction (XRD), atomic force microscopy (AFM), photoluminescence (PL) and Hall-effect measurements. The symmetric (0002) plane with respect to the asymmetric (10bar{1}2) plane in the 280-nm-thick AlN buffer has a higher crystal quality, as opposed to the 400-nm-thick buffer. The thinner buffer improves the crystallinity of both (0002) and (10bar{1}2) planes in the GaN layers, it also provides a sizeable reduction in dislocation density of GaN. Furthermore, the lower buffer thickness leads to a good quality surface with an rms roughness of 0.30 nm and a dark spot density of 4.0 × 108 cm-2. The optical and transport properties of the AlInN/AlN/GaN structure with the relatively thin buffer are compatible with the enhancement in its structural quality, as verified by XRD and AFM results.

  1. Reverse bias leakage current mechanism of AlGaN/InGaN/GaN heterostructure

    NASA Astrophysics Data System (ADS)

    Chakraborty, Apurba; Ghosh, Saptarsi; Mukhopadhyay, Partha; Jana, Sanjay K.; Dinara, Syed Mukulika; Bag, Ankush; Mahata, Mihir K.; Kumar, Rahul; Das, Subhashis; Das, Palash; Biswas, Dhrubes

    2016-03-01

    The reverse bias leakage current mechanism of AlGaN/InGaN/GaN heterostructure is investigated by current-voltage measurement in temperature range from 298 K to 423 K. The Higher electric field across the AlGaN barrier layer of AlGaN/InGaN/GaN double heterostructure due to higher polarization charge is found to be responsible for strong Fowler-Nordheim (FN) tunnelling in the electric field higher than 3.66 MV/cm. For electric field less than 3.56 MV/cm, the reverse bias leakage current is also found to follow the trap assisted Frenkel-Poole (FP) emission in low negative bias region. Analysis of reverse FP emission yielded the barrier height of trap energy level of 0.34 eV with respect to Fermi level. [Figure not available: see fulltext.

  2. New methods for preparing n, n-dialkyltrifluoroacetamides

    NASA Technical Reports Server (NTRS)

    Hsu, L.

    1972-01-01

    The customary preparative methods for N,N-dialkyltrifluoroacetamides involve the acylation of an amine by trifluoroacetic acid or its derivatives. In this report the synthesis of N,N-dialkyltrifluoroacetamides by reacting trifluoroacetic anhydride or acid with disubstituted formamides and acetamides is discussed. These reactions are interpreted with the aid of gas chromatographic analysis. Different reaction mechanisms are proposed for the reactions of formamides and acetamides with trifluoroacetic anhydride or acid. The use of the proposed reaction mechanisms for the synthesis of other fluorinated compounds is discussed.

  3. New methods for preparing N,N-dialkyltrifluoroacetamides

    NASA Technical Reports Server (NTRS)

    Hsu, L.

    1972-01-01

    The customary preparative methods for N,N-dialkyltrifluoroacetamides involve the acylation of an amine by trifluoroacetic acid or its derivatives. The synthesis of N,N-dialkyltrifluoroacetamides by reacting trifluoroacetic anhydride or acid with disubstituted formamides and acetamides is discussed. These reactions were interpreted with the aid of gas chromatographic analysis. Different reaction mechanisms are proposed for the reactions of formamides and acetamides with trifluoroacetic anhydride or acid. The use of the proposed reaction mechanisms for the synthesis of other fluorinated compounds is discussed.

  4. Radiation hardness of n-GaN schottky diodes

    SciTech Connect

    Lebedev, A. A. Belov, S. V.; Mynbaeva, M. G.; Strel’chuk, A. M.; Bogdanova, E. V.; Makarov, Yu. N.; Usikov, A. S.; Kurin, S. Yu.; Barash, I. S.; Roenkov, A. D.; Kozlovski, V. V.

    2015-10-15

    Schottky-barrier diodes with a diameter of ∼10 µm are fabricated on n-GaN epitaxial films grown by hydride vapor-phase epitaxy (HVPE) on sapphire substrates. The changes in the parameters of the diodes under irradiation with 15 MeV protons are studied. The carrier removal rate was found to be 130–145 cm{sup –1}. The linear nature of the dependence N = f(D) (N is the carrier concentration, and D, the irradiation dose) shows that compensation of the material is associated with transitions of electrons from shallow donors to deep acceptor levels which are related to primary radiation defects.

  5. Photoionization and fragmentaton of (N2O)n clusters

    NASA Astrophysics Data System (ADS)

    Kamke, W.; Kamke, B.; Kiefl, H. U.; Hertel, I. V.

    1986-02-01

    A supersonic molecular beam and monochromatized synchrotron radiation are presently used to measure photoionization efficiency curves for (N2O)n, at n = 1-6, in the 55-110 nm wavelength region. By measuring the energy loss of cluster ions which fragment in a field free drift region of the ion source, it becomes possible to detect delayed unimolecular and collision-induced fragmentations of the cluster ions. From a study of the dependence of the 'metastable' signals on background pressure, it appears that only the removal of a single N2O molecule at a time can occur by unimolecular decay.

  6. N Reactor operational safety summary

    SciTech Connect

    Franz, G.R.; Quapp, W.J.; Ogden, D.M.

    1988-08-01

    This report is a safety summary of the N Reactor. Beginning with its conceptual design in the mid-1950`s, and throughout its 23 years of operation, continuous efforts have been made to ensure safe N Reactor operation and protection of the public health and safety. The N Reactor Updated Safety Analysis Report, completed in 1978(UNC1978), and its subsequent amendments document the safety bases of N Reactor. Following the April 1986 Chernobyl accident in the Soviet Union, a major effort to confirm N Reactor safety and further increase its safety margin was initiated. This effort, called the Safety Enhancement Program, reassessed the N Reactor using the latest accepted analysis techniques and commercial light-water reactor guidelines, where applicable. 122 refs., 38 figs., 10 tabs.

  7. Update of ENDL U(n,2n), U(n,gamma), U(n,f) Evaluations

    SciTech Connect

    Beck, B; Brown, D A; McNabb, D P

    2004-02-13

    The authors are in the re-evaluating of all the actinide cross section evaluations in LLNL's ENDL database, starting with uranium and focusing on inventory changing reactions. This article describes their first serious pass at updating the uranium cross section data, including estimates of cross section uncertainties. Furthermore, they are developing new tools to automate the re-evaluation and this article contains some preliminary results from these codes, namely the {sup 235}U(n, 2n) and {sup 238}U(n, 2n) evaluations.

  8. 4,4\\'-Methylene bis(N,N\\'-dimethyl)aniline

    Integrated Risk Information System (IRIS)

    4,4 ' - Methylene bis ( N , N ' - dimethyl ) aniline ; CASRN 101 - 61 - 1 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Haz

  9. N4ITK: improved N3 bias correction.

    PubMed

    Tustison, Nicholas J; Avants, Brian B; Cook, Philip A; Zheng, Yuanjie; Egan, Alexander; Yushkevich, Paul A; Gee, James C

    2010-06-01

    A variant of the popular nonparametric nonuniform intensity normalization (N3) algorithm is proposed for bias field correction. Given the superb performance of N3 and its public availability, it has been the subject of several evaluation studies. These studies have demonstrated the importance of certain parameters associated with the B-spline least-squares fitting. We propose the substitution of a recently developed fast and robust B-spline approximation routine and a modified hierarchical optimization scheme for improved bias field correction over the original N3 algorithm. Similar to the N3 algorithm, we also make the source code, testing, and technical documentation of our contribution, which we denote as "N4ITK," available to the public through the Insight Toolkit of the National Institutes of Health. Performance assessment is demonstrated using simulated data from the publicly available Brainweb database, hyperpolarized (3)He lung image data, and 9.4T postmortem hippocampus data. PMID:20378467

  10. Radiative n 14N capture at astrophysical energies

    NASA Astrophysics Data System (ADS)

    Dubovichenko, S. B.

    2013-06-01

    In the potential cluster model with forbidden states and classification of orbital cluster states according to Young's schemes, the possibility is considered of describing the experimental data for the total cross sections of radiative n 14N capture at energies from 25.0 meV (25•10-3 eV) to 1.0 MeV. It is shown that on the whole it is possible to successfully explain the behavior of these cross sections outside the resonant energy region on the basis of the E1 transition from the 2S1/2 scattering wave with zero phase to the bound 2Р1/2 state of the 15N nucleus in the n14N channel.

  11. Vibrational and multinuclear NMR spectra of anionic mercuriomethanes [CH 4-n(HgX) n] n-

    NASA Astrophysics Data System (ADS)

    Breitinger, D. K.; Krumphanzl, U.; Moll, M.

    1990-03-01

    Vibrational spectra of solid sodium sulfitomercuriomethanates Na n[CH 4-n(HgSO 3) n]·nH 2O (2 ≤ and ≤ 4) exhibit high frequencies of the valence vibrations ν as(SO 3) > ν s(SO 3) (average 1057 cm -1) with big differences ν as - ν s (mean 104 cm -1), and ν(HgS) vibrations in the 200 to 230 cm -1 range, thus indicating S-coordinated sulfite ligands. Force field calculations for the ion [C(HgSO 3) 4] 4- yield high force constants K(S-O) = 605 N/m, K(Hg-S) = 258 N/m, and even K(C-Hg) = 181 N/m.- For thiosulfatomercuriomethanates [CH 4-n(HgS 2O 3] n- (1 ≤ n ≤ 4) in aqueous solutions Raman spectra suggest S-coordination with high ν as(SO 3) and ν s(SO 3) (average 1130 cm -1), and low ν(S-S) (˜420 cm -1) frequencies, and strong ν(Hg-S) bands (˜250 cm -1). From 1H, 13C and 199Hg NMR data is concluded that the CHg bond strengths in the series decrease on a lower level than in other mercuriomethanes.- On the whole, the electronic properties of the peripheral ligands X in the mercuriomethanes CH 4-n(HgX) n seem to be more important for the CHg bond strengths than the total charge.

  12. Band offsets of non-polar A-plane GaN/AlN and AlN/GaN heterostructures measured by X-ray photoemission spectroscopy

    PubMed Central

    2014-01-01

    The band offsets of non-polar A-plane GaN/AlN and AlN/GaN heterojunctions are measured by X-ray photoemission spectroscopy. A large forward-backward asymmetry is observed in the non-polar GaN/AlN and AlN/GaN heterojunctions. The valence-band offsets in the non-polar A-plane GaN/AlN and AlN/GaN heterojunctions are determined to be 1.33 ± 0.16 and 0.73 ± 0.16 eV, respectively. The large valence-band offset difference of 0.6 eV between the non-polar GaN/AlN and AlN/GaN heterojunctions is considered to be due to piezoelectric strain effect in the non-polar heterojunction overlayers. PMID:25258600

  13. Band offsets of non-polar A-plane GaN/AlN and AlN/GaN heterostructures measured by X-ray photoemission spectroscopy.

    PubMed

    Sang, Ling; Zhu, Qin Sheng; Yang, Shao Yan; Liu, Gui Peng; Li, Hui Jie; Wei, Hong Yuan; Jiao, Chun Mei; Liu, Shu Man; Wang, Zhan Guo; Zhou, Xiao Wei; Mao, Wei; Hao, Yue; Shen, Bo

    2014-01-01

    The band offsets of non-polar A-plane GaN/AlN and AlN/GaN heterojunctions are measured by X-ray photoemission spectroscopy. A large forward-backward asymmetry is observed in the non-polar GaN/AlN and AlN/GaN heterojunctions. The valence-band offsets in the non-polar A-plane GaN/AlN and AlN/GaN heterojunctions are determined to be 1.33 ± 0.16 and 0.73 ± 0.16 eV, respectively. The large valence-band offset difference of 0.6 eV between the non-polar GaN/AlN and AlN/GaN heterojunctions is considered to be due to piezoelectric strain effect in the non-polar heterojunction overlayers.

  14. Proof without Words: (1 + 1/n)[superscript n] less than e less than (1 + 1/n)[superscript n+1

    ERIC Educational Resources Information Center

    Khattri, Sanjay Kumar

    2008-01-01

    We present a pictorial proof of the inequation (1 + 1/n)[superscript n] less than e less than (1 + 1/n)[superscript n+1]. The inequation is also confirmed through the Taylor expansion and alternating series theorem.

  15. Analysis of InGaN light-emitting diodes with GaN-AlGaN and AlGaN-GaN composition-graded barriers

    SciTech Connect

    Yang, Yujue; Wang, Junxi; Li, Jinmin; Zeng, Yiping

    2014-06-21

    The effects of InGaN-based light-emitting diodes (LEDs) with Al composition increasing and decreasing GaN-AlGaN barriers along the growth direction are studied numerically. Simulation results suggest that the LEDs with GaN-AlGaN composition-decreased barriers show more significant enhancement of light-output power and internal quantum efficiency than LEDs with composition-increasing GaN-AlGaN barriers when compared with the conventional LED with GaN barriers, due to the improvement in hole injection efficiency and electron blocking capability. Moreover, the optical performance is further improved by replacing GaN-AlGaN barriers with AlGaN-GaN barriers of the same Al composition-decreasing range, which are mainly attributed to the modified band diagrams. In addition, the major causes of the different efficiency droop behaviors for all the designed structures are explained by the electron leakage current and the different increase rates of hole concentration with injection current.

  16. The Ultraviolet Behavior of N

    SciTech Connect

    Bern, Z.; Carrasco, J.J.; Dixon, L.J.; Johansson, H.; Roiban, R.

    2009-05-15

    We describe the construction of the complete four-loop four-particle amplitude of N = 8 supergravity. The amplitude is ultraviolet finite, not only in four dimensions, but in five dimensions as well. The observed extra cancellations provide additional non-trivial evidence that N = 8 supergravity in four dimensions may be ultraviolet finite to all orders of perturbation theory.

  17. 40 CFR 721.8100 - Potassium N,N-bis (hydroxy-ethyl) cocoamine oxide phosphate, and potassium N,N-bis (hy-droxy...

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Potassium N,N-bis (hydroxy-ethyl) cocoamine oxide phosphate, and potassium N,N-bis (hy-droxy-ethyl) tal-lo-wa-mine oxide phos-phate. 721.8100... Substances § 721.8100 Potassium N,N-bis (hydroxy-ethyl) cocoamine oxide phosphate, and potassium N,N-bis...

  18. 40 CFR 721.8100 - Potassium N,N-bis (hydroxy-ethyl) cocoamine oxide phosphate, and potassium N,N-bis (hy-droxy...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Potassium N,N-bis (hydroxy-ethyl) cocoamine oxide phosphate, and potassium N,N-bis (hy-droxy-ethyl) tal-lo-wa-mine oxide phos-phate. 721.8100... Substances § 721.8100 Potassium N,N-bis (hydroxy-ethyl) cocoamine oxide phosphate, and potassium N,N-bis...

  19. 40 CFR 721.8100 - Potassium N,N-bis (hydroxy-ethyl) cocoamine oxide phosphate, and potassium N,N-bis (hy-droxy...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Potassium N,N-bis (hydroxy-ethyl) cocoamine oxide phosphate, and potassium N,N-bis (hy-droxy-ethyl) tal-lo-wa-mine oxide phos-phate. 721.8100... Substances § 721.8100 Potassium N,N-bis (hydroxy-ethyl) cocoamine oxide phosphate, and potassium N,N-bis...

  20. 40 CFR 721.8100 - Potassium N,N-bis (hydroxy-ethyl) cocoamine oxide phosphate, and potassium N,N-bis (hy-droxy...

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Potassium N,N-bis (hydroxy-ethyl) cocoamine oxide phosphate, and potassium N,N-bis (hy-droxy-ethyl) tal-lo-wa-mine oxide phos-phate. 721.8100... Substances § 721.8100 Potassium N,N-bis (hydroxy-ethyl) cocoamine oxide phosphate, and potassium N,N-bis...

  1. 40 CFR 721.8100 - Potassium N,N-bis (hydroxy-ethyl) cocoamine oxide phosphate, and potassium N,N-bis (hy-droxy...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Potassium N,N-bis (hydroxy-ethyl) cocoamine oxide phosphate, and potassium N,N-bis (hy-droxy-ethyl) tal-lo-wa-mine oxide phos-phate. 721.8100... Substances § 721.8100 Potassium N,N-bis (hydroxy-ethyl) cocoamine oxide phosphate, and potassium N,N-bis...

  2. Configuration space Faddeev formalism: Λ + n + n bound state search

    NASA Astrophysics Data System (ADS)

    Suslov, Vladimir; Filikhin, Igor; Vlahovic, Branislav

    2015-04-01

    The HypHI Collaboration has recently reported the evidence for bound state of Λ + n + n system (Phys. Rev. C 88, 041001(R) (2013)). However, the theoretical analysis did not find Λ3n bound state (see, for instance, Phys. Lett. B 736, 93 (2014)). In the present work we will describe our attempt to construct a phenomenological three-body ΛNN force with the spin-isospin dependence that is attractive in the channel T=1, S=1/2. This dependence was tested to reproduce the value of ground state energy for Λ3H hypernuclei. The formalism of the configuration-space Faddeev equations is applied for Λ + n + n and Λ + n + p systems. As Λ + n interaction the s-wave potential simulating model NSC97f is used. This potential reproduces well the hyperon binding energy for Λ3H nuclei (J. Phys. G: 31, 389 (2005)). The details of the model and obtained results will be presented. This work is supported by the NSF (HRD-1345219) and NASA (NNX09AV07A).

  3. O( N) Random Tensor Models

    NASA Astrophysics Data System (ADS)

    Carrozza, Sylvain; Tanasa, Adrian

    2016-11-01

    We define in this paper a class of three-index tensor models, endowed with {O(N)^{⊗ 3}} invariance ( N being the size of the tensor). This allows to generate, via the usual QFT perturbative expansion, a class of Feynman tensor graphs which is strictly larger than the class of Feynman graphs of both the multi-orientable model (and hence of the colored model) and the U( N) invariant models. We first exhibit the existence of a large N expansion for such a model with general interactions. We then focus on the quartic model and we identify the leading and next-to-leading order (NLO) graphs of the large N expansion. Finally, we prove the existence of a critical regime and we compute the critical exponents, both at leading order and at NLO. This is achieved through the use of various analytic combinatorics techniques.

  4. Large N phase transitions in massive N = 2 gauge theories

    SciTech Connect

    Russo, J. G.

    2014-07-23

    Using exact results obtained from localization on S{sup 4}, we explore the large N limit of N = 2 super Yang-Mills theories with massive matter multiplets. In this talk we discuss two cases: N = 2* theory, describing a massive hypermultiplet in the adjoint representation, and super QCD with massive quarks. When the radius of the four-sphere is sent to infinity these theories are described by solvable matrix models, which exhibit a number of interesting phenomena including quantum phase transitions at finite 't Hooft coupling.

  5. H enhancement of N vacancy migration in GaN.

    SciTech Connect

    Wixom, Ryan R.; Wright, Alan Francis

    2005-06-01

    We have used density functional theory to investigate diffusion of V{sub N}{sup +} in the presence of H{sup +}. Optimal migration pathways were determined using the climbing image nudged elastic band and directed dimer methods. Our calculations indicate that the rate-limiting barrier for VN{sub N}{sup +} migration will be reduced by 0.58 eV by interplay with H{sup +}, which will enhance migration by more than an order of magnitude at typical GaN growth temperatures.

  6. Nuclear response functions for the N- N ∗(1440) transition

    NASA Astrophysics Data System (ADS)

    Alvarez-Ruso, L.; Barbaro, M. B.; Donnelly, T. W.; Molinari, A.

    2003-08-01

    Parity-conserving and -violating response functions are computed for the inclusive electroexcitation of the N ∗(1440) (Roper) resonance in nuclear matter modeled as a relativistic Fermi gas. Using various empirical parameterizations and theoretical models of the N- N ∗(1440) transition form factors, the sensitivity of the response functions to details of the structure of the Roper resonance is investigated. The possibility of disentangling this resonance from the contribution of Δ electroproduction in nuclei is addressed. Finally, the contributions of the Roper resonance to the longitudinal scaling function and to the Coulomb sum rule are also explored.

  7. High breakdown voltage in AlGaN/GaN HEMTs using AlGaN/GaN/AlGaN quantum-well electron-blocking layers.

    PubMed

    Lee, Ya-Ju; Yao, Yung-Chi; Huang, Chun-Ying; Lin, Tai-Yuan; Cheng, Li-Lien; Liu, Ching-Yun; Wang, Mei-Tan; Hwang, Jung-Min

    2014-01-01

    In this paper, we numerically study an enhancement of breakdown voltage in AlGaN/GaN high-electron-mobility transistors (HEMTs) by using the AlGaN/GaN/AlGaN quantum-well (QW) electron-blocking layer (EBL) structure. This concept is based on the superior confinement of two-dimensional electron gases (2-DEGs) provided by the QW EBL, resulting in a significant improvement of breakdown voltage and a remarkable suppression of spilling electrons. The electron mobility of 2-DEG is hence enhanced as well. The dependence of thickness and composition of QW EBL on the device breakdown is also evaluated and discussed.

  8. High breakdown voltage in AlGaN/GaN HEMTs using AlGaN/GaN/AlGaN quantum-well electron-blocking layers

    PubMed Central

    2014-01-01

    In this paper, we numerically study an enhancement of breakdown voltage in AlGaN/GaN high-electron-mobility transistors (HEMTs) by using the AlGaN/GaN/AlGaN quantum-well (QW) electron-blocking layer (EBL) structure. This concept is based on the superior confinement of two-dimensional electron gases (2-DEGs) provided by the QW EBL, resulting in a significant improvement of breakdown voltage and a remarkable suppression of spilling electrons. The electron mobility of 2-DEG is hence enhanced as well. The dependence of thickness and composition of QW EBL on the device breakdown is also evaluated and discussed. PMID:25206318

  9. Metal-free functionalization of N,N-dialkylanilines via temporary oxidation to N,N-dialkylaniline N-oxides and group transfer.

    PubMed

    Lewis, Robert S; Wisthoff, Michael F; Grissmerson, J; Chain, William J

    2014-07-18

    A simple set of protocols for the controlled elaboration of anilines is reported allowing access to a diverse array of aminophenols, aminoarylsulfonates, alkylated anilines, and aminoanilines in 29-95% yield in a single laboratory operation from easily isolable, bench-stable N,N-dialkylaniline N-oxides. The introduction of new C-O, C-C, and C-N bonds on the aromatic ring is made possible by a temporary increase in oxidation level and excision of a weak N-O bond.

  10. Technology of integrated self-aligned E/D-mode n++GaN/InAlN/AlN/GaN MOS HEMTs for mixed-signal electronics

    NASA Astrophysics Data System (ADS)

    Blaho, M.; Gregušová, D.; Haščík, Š.; Seifertová, A.; Ťapajna, M.; Šoltýs, J.; Šatka, A.; Nagy, L.; Chvála, A.; Marek, J.; Carlin, J.-F.; Grandjean, N.; Konstantinidis, G.; Kuzmík, J.

    2016-06-01

    We describe the technology and performance of integrated enhancement/depletion (E/D)-mode n++GaN/InAlN/AlN/GaN HEMTs with a self-aligned metal-oxide-semiconductor (MOS) gate structure. An identical starting epi-structure was used for both types of devices without the additional need for a contacts regrowth. The n++GaN cap layer was etched away in the gate trenches of the E-mode HEMT while it was left intact for the D-mode HEMT. The plasma etching process was shown to be highly selective between the cap and the InAlN barrier and also to polish the InAlN surface. However, different GaN etching initiation times inside and outside the mesa region were obtained. Gate contacts were isolated using a dielectric layer deposited at low temperature through an e-beam resist to retain the self-aligned approach. Feasibility of the approach for future fast GaN-based mixed-signal electronic circuits was shown by obtaining alternative HEMT threshold voltage values of +0.8 V and -2.6 V, invariant maximal output current of ˜0.35 A mm-1 despite large source-to-drain distances and by demonstrating a functional logic invertor.

  11. Technology of integrated self-aligned E/D-mode n++GaN/InAlN/AlN/GaN MOS HEMTs for mixed-signal electronics

    NASA Astrophysics Data System (ADS)

    Blaho, M.; Gregušová, D.; Haščík, Š.; Seifertová, A.; Ťapajna, M.; Šoltýs, J.; Šatka, A.; Nagy, L.; Chvála, A.; Marek, J.; Carlin, J.-F.; Grandjean, N.; Konstantinidis, G.; Kuzmík, J.

    2016-06-01

    We describe the technology and performance of integrated enhancement/depletion (E/D)-mode n++GaN/InAlN/AlN/GaN HEMTs with a self-aligned metal-oxide-semiconductor (MOS) gate structure. An identical starting epi-structure was used for both types of devices without the additional need for a contacts regrowth. The n++GaN cap layer was etched away in the gate trenches of the E-mode HEMT while it was left intact for the D-mode HEMT. The plasma etching process was shown to be highly selective between the cap and the InAlN barrier and also to polish the InAlN surface. However, different GaN etching initiation times inside and outside the mesa region were obtained. Gate contacts were isolated using a dielectric layer deposited at low temperature through an e-beam resist to retain the self-aligned approach. Feasibility of the approach for future fast GaN-based mixed-signal electronic circuits was shown by obtaining alternative HEMT threshold voltage values of +0.8 V and ‑2.6 V, invariant maximal output current of ∼0.35 A mm‑1 despite large source-to-drain distances and by demonstrating a functional logic invertor.

  12. NpN-GaN/InxGa1-xN/GaN heterojunction bipolar transistor on free-standing GaN substrate

    NASA Astrophysics Data System (ADS)

    Lochner, Zachary; Jin Kim, Hee; Lee, Yi-Che; Zhang, Yun; Choi, Suk; Shen, Shyh-Chiang; Doug Yoder, P.; Ryou, Jae-Hyun; Dupuis, Russell D.

    2011-11-01

    Data and analysis are presented for NpN-GaN/InGaN/GaN double-heterojunction bipolar transistors (HBTs) grown and fabricated on a free-standing GaN (FS-GaN) substrate in comparison to that on a sapphire substrate to investigate the effect of dislocations in III-nitride HBT epitaxial structures. The performance characteristics of HBTs on FS-GaN exhibit a maximum collector current density of ˜12.3 kA/cm2, dc current gain of ˜90, and maximum differential gain of ˜120 without surface passivation, representing a substantial improvement over similar devices grown on sapphire. This is attributed to the reduction in threading dislocation density afforded by using a homoepitaxial growth on a high-crystalline-quality substrate. The minority carrier diffusion length increases significantly owing to not only a mitigated carrier trap effect via fewer dislocations, but also possibly reduced microscopic localized states.

  13. Molecular and crystal structures of dialkylated adenines ( N6, N9-Me 2Ade, N3, N6-MeBnAde) and cytosines ( N1, N4-Me 2Cyt)

    NASA Astrophysics Data System (ADS)

    Krüger, Thomas; Wagner, Christoph; Bruhn, Clemens; Lis, Tadeusz; Steinborn, Dirk

    2008-11-01

    N6, N9-Dimethyladenine ( N6, N9-Me 2Ade, 1) and N1, N4-dimethylcytosine ( N1, N4-Me 2Cyt, 3) were obtained by conventional methods, whereas the reaction of N6-benzyladenine with MeI/NaOH resulted in the formation of N3, N6-MeBnAde ( 2a) and N6, N9-BnMeAde ( 2b). All compounds were fully characterized by microanalysis, NMR spectroscopy ( 1H, 13C) and 1, 2a·2MeOH and 3 also by single-crystal X-ray diffraction analyses. In single-crystals of 1, obtained from THF solutions, twofold N6-H···N7' hydrogen-bonded dimeric units ( N6, N9-Me 2Ade) 2 (AA1 2 type according to Jeffrey and Saenger, 1991) were found. This proved to be another modification than that obtained by crystallization N6, N9-Me 2Ade from MeOH/PhCl (Sternglanz, 1978). Crystals of 2a·2MeOH exhibited an analogous hydrogen bond pattern as found in 1. The shorter N6···N7' distance in 2a·2MeOH (2.932(2) Å) indicates slightly stronger hydrogen bonds than in 1 (3.078(3) Å). Crystals of 3 are built up from centrosymmetric dimers ( N1, N4-Me 2Cyt) 2 having a twofold N4-H···N3' hydrogen bond, thus exhibiting the CC3 2 hydrogen bond pattern. The hydrogen bonding patterns in the dialkylated nucleobase derivatives are discussed in terms of those found in crystals of the less substituted nucleobases N9-MeAde and Cyt/ N1-MeCyt, respectively.

  14. Electron beam induced current profiling of the p-ZnO:N/n-GaN heterojunction

    SciTech Connect

    Przeździecka, E. Stachowicz, M.; Chusnutdinow, S.; Jakieła, R.; Kozanecki, A.

    2015-02-09

    The high quality p-n structures studied consist of nitrogen doped ZnO:N films grown by plasma assisted molecular beam epitaxy on n-type GaN templates. The nitrogen concentration, determined by secondary ion mass spectroscopy, is about 1 × 10{sup 20} cm{sup −3}. Temperature dependent photoluminescence studies confirm the presence of acceptor centers with an energy level lying approximately 130 meV above the valence band. The maximum forward-to-reverse current ratio I{sub F}/I{sub R} in the obtained p-n diodes is about 10{sup 7} at ±5 V, which is 2–5 orders of magnitude higher than previously reported for this type of heterojunctions. Electron-beam-induced current measurements confirm the presence of a p–n junction, located at the p-ZnO/n-GaN interface. The calculated diffusion length and activation energy of minority carriers are presented. The heterostructures exhibit strong absorption in the UV range with a four orders of magnitude high bright-to-dark current ratio.

  15. Experimental observation of N00N state Bloch oscillations.

    PubMed

    Lebugle, Maxime; Gräfe, Markus; Heilmann, René; Perez-Leija, Armando; Nolte, Stefan; Szameit, Alexander

    2015-09-22

    Bloch oscillations of quantum particles manifest themselves as periodic spreading and relocalization of the associated wave functions when traversing lattice potentials subject to external gradient forces. Albeit this phenomenon is deeply rooted into the very foundations of quantum mechanics, all experimental observations so far have only contemplated dynamics of one and two particles initially prepared in separable local states. Evidently, a more general description of genuinely quantum Bloch oscillations will be achieved on excitation of a Bloch oscillator by nonlocal states. Here we report the observation of Bloch oscillations of two-particle N00N states, and discuss the nonlocality on the ground of Bell-like inequalities. The time evolution of two-photon N00N states in Bloch oscillators, whether symmetric, antisymmetric or partially symmetric, reveals transitions from particle antibunching to bunching. Consequently, the initial states can be tailored to produce spatial correlations akin to those of bosons, fermions and anyons, presenting potential applications in photonic quantum simulation.

  16. Blockade involving high- n, n ~ 300 , strontium Rydberg atoms

    NASA Astrophysics Data System (ADS)

    Yoshida, Shuhei; Burgdörfer, Joachim; Zhang, Xinyue; Dunning, F. Barry

    2016-05-01

    The blockade of high- n strontium n1F3 Rydberg states contained in a hot atomic beam is investigated both theoretically and experimentally. One difficulty in such experiments is that, once created, Rydberg atoms move out of the excitation volume reducing blockade effects. While the effects of such motion are apparent, the data provide strong evidence of blockade, consistent with theoretical predictions. Because of their relatively high angular momentum (L = 3) , a pair of n1F3 Rydberg atoms have many degenerate states whose degeneracy is removed by Rydberg-Rydberg interactions yielding a high density of states near the target energy. To evaluate the effect of blockade not only the energy shifts but also the modification of the oscillator strengths for excitation have to be taken into account. The n-scaling of the interactions and the importance of high-order multipoles will also be discussed. Research supported by the NSF and Robert A. Welch Foundation.

  17. Sustainable development in an N-rich/n-poor world.

    PubMed

    Perrings, Charles; Kinzig, Ann; Halkos, George

    2014-11-01

    Sustainable development requires that per capita inclusive wealth-produced, human, and natural capital-does not decline over time. We investigate the impact of changes in nitrogen on inclusive wealth. There are two sides to the nitrogen problem. Excess use of nitrogen in some places gives rise to N-pollution, which can cause environmental damage. Insufficient replacement of nitrogen in other places gives rise to N-depletion, or loss of nutrient stocks. Neither is explicitly accounted for in current wealth measures, but both affect wealth. We calculate an index of net N-replacement, and investigate its relationship to wealth. In countries with low levels of relative N-loss, we find that the uncompensated loss of soil nitrogen in poorer countries is associated with declining rates of growth of inclusive per capita wealth. What is less intuitive is that increasing fertilizer application in both rich and poor countries can increase per capita inclusive wealth. PMID:24459077

  18. Sustainable development in an N-rich/n-poor world.

    PubMed

    Perrings, Charles; Kinzig, Ann; Halkos, George

    2014-11-01

    Sustainable development requires that per capita inclusive wealth-produced, human, and natural capital-does not decline over time. We investigate the impact of changes in nitrogen on inclusive wealth. There are two sides to the nitrogen problem. Excess use of nitrogen in some places gives rise to N-pollution, which can cause environmental damage. Insufficient replacement of nitrogen in other places gives rise to N-depletion, or loss of nutrient stocks. Neither is explicitly accounted for in current wealth measures, but both affect wealth. We calculate an index of net N-replacement, and investigate its relationship to wealth. In countries with low levels of relative N-loss, we find that the uncompensated loss of soil nitrogen in poorer countries is associated with declining rates of growth of inclusive per capita wealth. What is less intuitive is that increasing fertilizer application in both rich and poor countries can increase per capita inclusive wealth.

  19. Measurement of 235U(n,n'γ) and 235U(n,2nγ) reaction cross sections

    NASA Astrophysics Data System (ADS)

    Kerveno, M.; Thiry, J. C.; Bacquias, A.; Borcea, C.; Dessagne, P.; Drohé, J. C.; Goriely, S.; Hilaire, S.; Jericha, E.; Karam, H.; Negret, A.; Pavlik, A.; Plompen, A. J. M.; Romain, P.; Rouki, C.; Rudolf, G.; Stanoiu, M.

    2013-02-01

    The design of generation IV nuclear reactors and the studies of new fuel cycles require knowledge of the cross sections of various nuclear reactions. Our research is focused on (n,xnγ) reactions occurring in these new reactors. The aim is to measure unknown cross sections and to reduce the uncertainty on present data for reactions and isotopes of interest for transmutation or advanced reactors. The present work studies the 235U(n,n'γ) and 235U(n,2nγ) reactions in the fast neutron energy domain (up to 20 MeV). The experiments were performed with the Geel electron linear accelerator GELINA, which delivers a pulsed white neutron beam. The time characteristics enable measuring neutron energies with the time-of-flight (TOF) technique. The neutron induced reactions [in this case inelastic scattering and (n,2n) reactions] are identified by on-line prompt γ spectroscopy with an experimental setup including four high-purity germanium (HPGe) detectors. A fission ionization chamber is used to monitor the incident neutron flux. The experimental setup and analysis methods are presented and the model calculations performed with the TALYS-1.2 code are discussed.

  20. Oxygen in GaN.

    NASA Astrophysics Data System (ADS)

    van de Walle, Chris G.; Neugebauer, Jörg

    1997-03-01

    Oxygen is commonly present during epitaxial growth of GaN. We have proposed that unintentional incorporation of O, as well as Si, is responsible for the frequently observed n-type conductivity in as-grown GaN. Here we present results from comprehensive density-functional-pseudopotential studies of GaN:O under pressure, and of O interactions with native defects and dopant impurities. We find that the O donor undergoes a DX-like transition under pressure: a large outward relaxation introduces a deep level in the band gap. This behavior explains the carrier freezeout in GaN under pressure.^1 Si donors do not exhibit the transition, consistent with experiment. Results for these impurities in AlGaN will also be discussed. We have also investigated the interaction between O and native defects. Most notably we find a large binding energy between O and the gallium vacancy (V_Ga), which we have proposed to be the source of the yellow luminescence. Finally, we have studied the interaction between O and Mg acceptors. The incorporation of the O donor is significantly enhanced in Mg-doped material. In addition, we calculate a binding energy of 0.6 eV for Mg-O complexes. The presence of O during growth can thus be detrimental to p-type GaN. ^1 C. Wetzel et al., Proc. ICPS-23 (World Scientific, Singapore, 1996), p. 2929.

  1. Groundwater Monitoring Plan for the 1301-N, 1324-N/NA, and 1325-N RCRA Facilities

    SciTech Connect

    Hartman, Mary J.

    2002-06-08

    The 1301-N and 1325-N Liquid Waste Disposal Facilities, the 1324-N Surface Impoundment, and the 1324-NA Percolation Pond, located in the 100 N Area of the Hanford Site, are regulated under the Resource Conservation and Recovery Act of 1976 (RCRA). The closure plans for these facilities stipulate that groundwater is monitored according to the 100-N Pilot Project: Proposed Consolidated Groundwater Monitoring Program (BHI-00725). This document supplements the consolidated plan by providing information on sampling and analysis protocols, quality assurance, data management, and a conceptual model for the RCRA sites. Monitoring well networks, constituents, and sampling frequency remain the same as in the consolidated plan or the previous groundwater monitoring plan (Hartman 1996).

  2. Graphene in ohmic contact for both n-GaN and p-GaN

    SciTech Connect

    Zhong, Haijian; Liu, Zhenghui; Shi, Lin; Xu, Gengzhao; Fan, Yingmin; Huang, Zengli; Wang, Jianfeng; Ren, Guoqiang; Xu, Ke

    2014-05-26

    The wrinkles of single layer graphene contacted with either n-GaN or p-GaN were found both forming ohmic contacts investigated by conductive atomic force microscopy. The local I–V results show that some of the graphene wrinkles act as high-conductive channels and exhibiting ohmic behaviors compared with the flat regions with Schottky characteristics. We have studied the effects of the graphene wrinkles using density-functional-theory calculations. It is found that the standing and folded wrinkles with zigzag or armchair directions have a tendency to decrease or increase the local work function, respectively, pushing the local Fermi level towards n- or p-type GaN and thus improving the transport properties. These results can benefit recent topical researches and applications for graphene as electrode material integrated in various semiconductor devices.

  3. Heteroepitaxial growth of GaN on various powder compounds (AlN, LaN, TiN, NbN, ZrN, ZrB 2 , VN, BeO) by hydride vapor phase epitaxy

    NASA Astrophysics Data System (ADS)

    Park, Jinsub; Ha, Jun-Seok; Hong, Soon-Ku; Lee, Seog Woo; Cho, Meoung Whan; Yao, Takafumi; Lee, Hae Woo; Lee, Sang Hwa; Lee, Sung-Keun; Lee, Hyo-Jong

    2012-04-01

    We investigated the nucleation and growth behavior of GaN on various powders by hydride vapor phase epitaxy. In relative comparison, the nucleation tendency of GaN on each powder can be summarized as AlN > LaN, TiN, NbN > ZrN > ZrB2 > VN, BeO, indicating that the number of nucleation sites increased from right to left. LaN and NbN have not yet been reported as buffer materials for GaN growth. Of these, NbN is expected to be a good buffer material because the interatomic distance on the NbN (111) plane has only 2% difference from that on the GaN (0001) plane.

  4. New metabolic pathway for N,N-dimethyltryptamine

    SciTech Connect

    Hryhorczuk, L.M.; Rainey, J.M. Jr.; Frohman, C.E.; Novak, E.A.

    1986-01-01

    N,N-Dimethyltryptamine (DMT) undergoes a major structural alteration when added to whole human blood or its red blood cells in vitro. A new high-pressure liquid chromatography (HPLC) peak is present in extracts of these treated tissues. The compound responsible for this peak has been identified by ultraviolet spectrophotometry and by mass spectrometry as dimethylkynuramine (DMK). The enzyme responsible for this appears to be different from tryptophan 2,3-dioxygenase and also from indoleamine 2,3-dioxygenase.

  5. Incomplete nested dissection for solving n by n grid problems

    NASA Technical Reports Server (NTRS)

    George, A.; Poole, W. G., Jr.; Voigt, R. G.

    1978-01-01

    Nested dissection orderings are known to be very effective for solving sparse positive definite linear systems which arise from n by n grid problems. In this paper we consider incomplete nested dissection, an ordering which corresponds to the premature termination of nested dissection. Analyses of the arithmetic and storage requirements for incomplete nested dissection are given and the ordering is shown to be competitive with nested dissection with regard to arithmetic operations and superior to that ordering in storage requirements.

  6. Purification of isopenicillin N synthetase.

    PubMed Central

    Pang, C P; Chakravarti, B; Adlington, R M; Ting, H H; White, R L; Jayatilake, G S; Baldwin, J E; Abraham, E P

    1984-01-01

    Isopenicillin N synthetase was extracted from Cephalosporium acremonium and purified about 200-fold. The product showed one major protein band, coinciding with synthetase activity, when subjected to electrophoresis in polyacrylamide gel. An isopenicillin N synthetase from Penicillium chrysogenum was purified about 70-fold by similar procedures. The two enzymes resemble each other closely in their Mr, in their mobility on electrophoresis in polyacrylamide gel and in their requirement for Fe2+ and ascorbate for maximum activity. Preliminary experiments have shown that a similar isopenicillin N synthetase can be extracted from Streptomyces clavuligerus. PMID:6435606

  7. Heats of NF(sub n) (n= 1-3) and NF(sub n)(+)(n = 1-3)

    NASA Technical Reports Server (NTRS)

    Ricca, Alessandra; Arnold, James (Technical Monitor)

    1998-01-01

    Accurate heats of formation are computed for NF(sub n) and NF(sub n)(+), for n = 1-3. The geometries and the vibrational frequencies are determined at the B3LYP level of theory. The energetics are determined at the CCSD(T) level of theory. Basis set limit values are obtained by extrapolation. In those cases where the CCSD(T) calculations become prohibitively large, the basis set extrapolation is performed at the MP2 level. The temperature dependence of the heat of formation, heat capacity, and entropy are computed for the temperature range 300 to 4000 K and fit to a polynomial.

  8. [Effects of irrigation mode and N application rate on cotton field fertilizer N use efficiency and N losses].

    PubMed

    Wang, Xiao-Juan; Wei, Chang-Zhou; Zhang, Jun; Dong, Peng; Wang, Juan; Zhu, Qi-Chao; Wang, Jin-Xin

    2012-10-01

    A field experiment was conducted to study the effects of different irrigation modes (drip irrigation and furrow irrigation) and different N application rates (0, 240, 360 and 480 kg N x hm(-2)) on the fertilizer N use efficiency and N losses in a cotton field in Xinjiang, Northwest China. The main N cycling pathways, such as the N uptake by cotton plant, NO3(-)-N residual in soil, NH3 volatilization, NO3(-)-N leaching, and nitrification-denitrification, were quantitatively monitored. Compared with furrow irrigation, drip irrigation increased the seed cotton yield, plant N uptake, and fertilizer N use efficiency significantly. The NO3(-)-N residual in soil was significantly greater under furrow irrigation than under drip irrigation. With the application of fertilizer N, the N loss from NH3 volatilization under drip irrigation occupied 0.06% -0.14% of applied N, and was significantly greater than that under furrow irrigation. The N loss from NO3(-)-N leaching under drip irrigation and furrow irrigation was 4.4% and 8.8% of the applied N, respectively. Compared with furrow irrigation, drip irrigation could significantly decrease the NO3(-)-N leakage rate in leakage water. The nitrification-dinetrification loss under drip irrigation and furrow irrigation was 17.9% and 16.8% of the applied N, respectively. It was suggested that NO3(-)-N leaching and nitrification-denitrification were the main N losses in the cotton fields of Xinjiang.

  9. In-situ SEM indentation studies of the deformation mechanisms in TiN, CrN and TiN/CrN.

    PubMed

    Rzepiejewska-Malyska, K; Parlinska-Wojtan, M; Wasmer, K; Hejduk, K; Michler, J

    2009-01-01

    In this study, the microstructure and the deformation mechanisms of TiN, CrN and multilayer TiN/CrN thin films on silicon substrates were investigated. Cross-sectional lamellas of nanoindents were prepared by focused ion beam milling to observe by transmission electron microscopy the microstructure of the as-deposited and deformed materials. TiN film exhibits nanocrystalline columns, whereas CrN shows large grains. The TiN/CrN multilayer presents microstructural features typical for both materials. A film hardness of 16.9GPa for CrN, 15.8GPa for TiN and 16.6GPa for TiN/CrN was found by the nanoindentation. Reduced modulus recorded for TiN and CrN reference coatings were 221.54 and 171.1GPa, respectively, and 218.6GPa for the multilayer coating. The deformation mechanisms were observed via in-situ scanning electron microscope nanoindentation. The TiN thin film showed short radial cracks, whereas CrN deformed through pile-up and densification of the material. For TiN/CrN multilayer pile-up and cracks were found. Transmission electron microscopy observations indicated that TiN deforms through grain boundary sliding and CrN via densification and material flow. The deformation mechanism observed in TiN/CrN multilayer was found to be a mixture of both modes.

  10. Laboratory experiments for Titan's ionosphere : the chemistry of N2+, N+, and N2++ nitrogen ions

    NASA Astrophysics Data System (ADS)

    Thissen, R.; Alcaraz, C.; Dutuit, O.; Nicolas, C.; Soldi-Lose, H.; Zabka, J.; Franceschi, P.

    Laboratory experiments for Titan's ionosphere : the chemistry of N+ , N+ , and N2+ nitrogen ions 2 2 R. Thissen (1), C. Alcaraz (1), O. Dutuit (1), C. Nicolas (2), H. Soldi-Lose (3), J. Zabka (4), P. Franceschi (5) (1) LCP, Bât. 350, Centre Universitaire Paris-Sud, F-91405 Orsay Cedex, France, (2) Synchrotron SOLEIL, L'Orme des Merisiers, Saint-Aubin BP 48, 91192 Gif-sur-Yvette, France, (3) Institut für Chemie, Fachgruppe Organische Chemie, Technische Universität Berlin, Straße des 17. Juni 135, D-10623 Berlin, (4) J. Heyrovsky Institute of Physical Chemistry, Dolejskova 3, CZ 18223 Praha 8 - Kobylisy, Czech Republik, (5) Dept. of Physics, University of Trento, Via Sommarive 14, 38050 Povo (TN), Italy (christian.alcaraz@lcp.u-psud.fr) N2 is the major neutral componant of Titan's atmosphere, its ionisation by solar radiation and by magnetospheric electron impact is the most important production of ions in Titan's ionosphere. These primary processes not only lead to N+ molecular 2 monocations but also to N+ atomic ions and to N2+ molecular dications, which can 2 pertain some internal or translational excitation. This contribution will summarize our efforts to caracterize in gaz phase laboratory experiments the reactivity of the nitrogen ions with the most important neutral targets of the Titan's atmosphere [1-3]: • N+ + CH4 , C2 H2 , and C2 H6 2 • N+ (3 P, 1 D) + CH4 , and C2 H4 • N2+ + N2 , CH4 , and C2 H4 2 In this work, particular attention has been paid on the effect of internal and/or translational excitation of the primary nitrogen ions on the rate constant and branching ratio of these ion-molecule reactions. The results from these studies have been compared to the literature values when available and some significant differences have been found. These new values have been used as input data in 1D models of the Titan's ionosphere to show the effect on the final density profiles of the main ions [4] and to demonstrate the existence of a N2+2 dication

  11. Anionic Polymerization of 1,3-Cyclohexadiene with Alkyllithium/Amine Systems. Characteristics of n-Butyllithium/N,N,N',N'-Tetramethylethylenediamine System for Living Anionic Polymerization.

    PubMed

    Natori; Inoue

    1998-07-28

    The n-butyllithium (n-BuLi)/N,N,N',N'-tetramethylethylenediamine (TMEDA) system (with the molar ratio of TMEDA to n-BuLi higher than 4/4) has been found to polymerize 1,3-cyclohexadiene to produce "living" polymer having a narrow molecular weight distribution with well-controlled polymer chain length. The rate of polymerization and polymer yield increased with increasing of the ratio of TMEDA to n-BuLi. The molecular weight distribution of obtained polymers became narrower with the ratio of TMEDA to n-BuLi. The formation of benzene generated by termination reaction was found to decrease with the ratio of TMEDA to n-BuLi. In contrast to 1,3-cyclohexadiene, low yield and broad molecular weight distribution were observed in the polymerization of 1,3-hexadiene and 2,4-hexadiene initiated by the n-BuLi/TMEDA (4/5) system. The microstructure of poly(1,3-cyclohexadiene) was determined by 2D-NMR. A high content of 1,2-units was found in the polymerization initiated by the alkyllithium/TMEDA system, while the high content of 1,4-units was observed in the cases of alkyllithium or alkyllithium/1,4-diazabicyclo[2,2,2]octane system. The 7Li NMR signals of the n-BuLi/TMEDA systems and poly(1,3-cyclohexadienyl)lithium /TMEDA were in higher magnetic field than the signals of n-BuLi and poly(1,3-cyclohexadienyl)lithium, respectively, indicating the disaggregation of the lithium species. PMID:9680400

  12. Fabrication, welding and heat treatment of nickel alloys UNS N08800, N08810, N08811, and N08825

    SciTech Connect

    Tassen, C.S.; Smith, G.D.; Mannan, S.K.; Hinshaw, E.B.

    1996-10-01

    The selection of materials of construction, including the final heat treatment, is a major factor in the success of many processes in an oil refinery. Alloys UNS N08800, N08810, N08811, and N08825 are each used in refinery applications and have the excellent corrosive resistance and mechanical properties required for the demanding service conditions. These materials always undergo some amount of fabrication or welding prior to going into service. In many cases, a post-weld/fabrication heat treatment is not necessary; however, in some cases, it is beneficial to heat treat these alloys after fabrication and welding. This paper will describe guidelines for when a post-weld/fabrication heat treatment should be considered and applicable welding products and heat treat procedures.

  13. N-Consecutive-Phase Encoder

    NASA Technical Reports Server (NTRS)

    Divsalar, Dariush; Lee, Ho-Kyoung; Weber, Charles

    1995-01-01

    N-consecutive-phase encoder (NCPE) is conceptual encoder for generating alphabet of N consecutive full-response continuous-phase-modulation (CPM) signals. Enables use of binary preencoder of higher rate than used with simple continuous-phase encoder (CPE). NCPE makes possible to achieve power efficiencies and bandwidth efficiencies greater than conventional trellis coders with continuous-phase frequency-shift keying (CPFSK).

  14. More on N=8 attractors

    SciTech Connect

    Ceresole, Anna; Ferrara, Sergio; Gnecchi, Alessandra; Marrani, Alessio

    2009-08-15

    We examine a few simple extremal black hole configurations of N=8, d=4 supergravity. We first elucidate the relation between the BPS Reissner-Noerdstrom black hole and the non-BPS Kaluza-Klein dyonic black hole. Their classical entropy, given by the Bekenstein-Hawking formula, can be reproduced via the attractor mechanism by suitable choices of symplectic frame. Then, we display the embedding of the axion-dilaton black hole into N=8 supergravity.

  15. Potential impact of atmospheric N deposition on soil N2O emission varies with different soil N regimes

    NASA Astrophysics Data System (ADS)

    Kim, Y.; Yi, M.; Koike, T.

    2011-12-01

    Future increases in nitrogen (N) deposition has the potential to change belowground nutrient dynamics, especially N cycle, and thereby can alter the soil-atmosphere exchange of nitrous oxide (N2O) which is one of the major greenhouse gases. Moreover, we considered that their effect on soil N2O emission varies with different soil N levels because N2O is a by-product of the biological nitrification process in aerobic soil environments and of the biological denitrification process in anaerobic soil environments. To understand the changes in soil N2O flux under different soil N, we carried out simulated N addition experiment in three-year-old hybrid larch F1 (F1: Larix gmelinii var. japonica × Larix kaempferi) plantation during two growing seasons 2008 - 2009. The hybrid larch F1 was developed to make up for several problems of larch species, e.g. a high susceptibility to disease or grazing damage by insects and fungi, and a large number of this seedlings are planted recently in northern Japan. Based on soil analysis, we selected two sites which have different soil N concentration, i.e. low-N and high-N concentrations. Nitrogen input was initiated at the onset of our experiment, and included four treatments with four replications: Low-N soil + Zero-N control, Low-N soil + 50 kg-N addition, High-N soil + Zero-N control and High-N soil + 50 kg-N addition. The N was added as ammonium nitrate (NH4NO3) solution distributed in four occasions during each growing season. Gas and soil samples were taken from each plot on ten occasions at a time during each growing season. Collected N2O concentrations were determined by a gas chromatograph (GC-14B; Shimadzu, Kyoto, Japan) equipped with an electron capture detector, while total-N and inorganic-N concentrations were obtained by a NC analyzer (Sumigraph NC-1000; Sumica Chemical Analysis Service Ltd., Osaka, Japan) and an auto analyzer (AACS-4; BL-TEC Inc., Osaka, Japan), respectively. Before the N addition, initial total-N in High-N

  16. Enhanced sheet carrier densities in polarization controlled AlInN/AlN/GaN/InGaN field-effect transistor on Si (111)

    SciTech Connect

    Hennig, J. Dadgar, A.; Witte, H.; Bläsing, J.; Lesnik, A.; Strittmatter, A.; Krost, A.

    2015-07-15

    We report on GaN based field-effect transistor (FET) structures exhibiting sheet carrier densities of n = 2.9 10{sup 13} cm{sup −2} for high-power transistor applications. By grading the indium-content of InGaN layers grown prior to a conventional GaN/AlN/AlInN FET structure control of the channel width at the GaN/AlN interface is obtained. The composition of the InGaN layer was graded from nominally x{sub In} = 30 % to pure GaN just below the AlN/AlInN interface. Simulations reveal the impact of the additional InGaN layer on the potential well width which controls the sheet carrier density within the channel region of the devices. Benchmarking the In{sub x}Ga{sub 1−x}N/GaN/AlN/Al{sub 0.87}In{sub 0.13}N based FETs against GaN/AlN/AlInN FET reference structures we found increased maximum current densities of I{sub SD} = 1300 mA/mm (560 mA/mm). In addition, the InGaN layer helps to achieve broader transconductance profiles as well as reduced leakage currents.

  17. Formation of excited states of N,N,N',N'-tetramethyl-p-phenylenediamine in irradiated nonpolar liquids. [Electron beams

    SciTech Connect

    Choi, H.T.; Tweeten, D.W.; Lipsky, S.

    1984-11-22

    The yield of N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) excited states, G/sub s/, has been obtained in irradiated tetramethylsilane, isooctane, cyclopentane, n-hexane, and cyclohexane as a function of TMPD concentration, c, over the range c = 0.5 x 10/sup -3/-50 x 10/sup -3/ M. In tetramethylsilane and isooctane, G/sub s/ is found to be linear on c as would be expected on the basis of a nondiffusional transfer of the solvent ion positive charge to TMPD followed by recombination of TMPD/sup +/ with the geminate electron. In cyclopentane, n-hexane, and cyclohexane, G/sub s/ becomes increasingly concave downward in its depedence on c. This concavity is attributed to an increasing contribution to G/sub s/ from excited states of the solvent that nonradiatively transfer their energy to TMPD. Optical excitation of cyclohexane at 147 nm and measurement of the quenching of its fluorescence by TMPD confirm this view.

  18. Plasma chemistries for dry etching GaN, AlN, InGaN and InAlN

    SciTech Connect

    Pearton, S.J.; Vartuli, C.B.; Lee, J.W.; Donovan, S.M.; MacKenzie, J.D.; Abernathy, C.R.; Shul, R.J.; McLane, G.F.; Ren, F.

    1996-04-01

    Etch rates up to 7,000 {angstrom}/min. for GaN are obtained in Cl{sub 2}/H{sub 2}/Ar or BCl{sub 3}/Ar ECR discharges at 1--3mTorr and moderate dc biases. Typical rates with HI/H{sub 2} are about a factor of three lower under the same conditions, while CH{sub 4}/H{sub 2} produces maximum rates of only {approximately}2,000 {angstrom}/min. The role of additives such as SF{sub 6}, N{sub 2}, H{sub 2} or Ar to the basic chlorine, bromine, iodine or methane-hydrogen plasma chemistries are discussed. Their effect can be either chemical (in forming volatile products with N) or physical (in breaking bonds or enhancing desorption of the etch products). The nitrides differ from conventional III-V`s in that bond-breaking to allow formation of the etch products is a critical factor. Threshold ion energies for the onset of etching of GaN, InGaN and InAlN are {ge} 75 eV.

  19. Preparation and cytotoxicity of N,N,N-trimethyl chitosan/alginate beads containing gold nanoparticles.

    PubMed

    Martins, Alessandro F; Facchi, Suelen P; Monteiro, Johny P; Nocchi, Samara R; Silva, Cleiser T P; Nakamura, Celso V; Girotto, Emerson M; Rubira, Adley F; Muniz, Edvani C

    2015-01-01

    Polyelectrolyte complex beads based on N,N,N-trimethyl chitosan (TMC) and sodium alginate (ALG) were obtained. This biomaterial was characterised by FTIR, TGA/DTG, DSC and SEM analysis. The good properties of polyelectrolyte complex hydrogel beads were associated, for the first time, with gold nanoparticles (AuNPs). Through a straightforward methodology, AuNPs were encapsulated into the beads. The in vitro cytotoxicity assays on the Caco-2 colon cancer cells and healthy VERO cells showed that the beads presented good biocompatibility on both cell lines, whereas the beads loaded with gold nanoparticles (beads/AuNPs) was slightly cytotoxic on the Caco-2 and VERO cells.

  20. Meson-exchange model for πN scattering and γN-->πN reaction

    NASA Astrophysics Data System (ADS)

    Sato, T.; Lee, T.-S. H.

    1996-11-01

    An effective Hamiltonian consisting of bare Δ⇆πN, γN vertex interactions and energy-independent meson-exchange πN⇆πN,γN transition operators is derived by applying a unitary transformation to a model Lagrangian with N,Δ,π, ρ, ω, and γ fields. With appropriate phenomenological form factors and coupling constants for ρ and Δ, the model can give a good description of πN scattering phase shifts up to the Δ excitation energy region. It is shown that the best reproduction of the recent LEGS data of the photon-asymmetry ratios in γp-->π0p reactions provides rather restricted constraints on the coupling strengths GE of the electric E2 and GM of the magnetic M1 transitions of the bare Δ⇆γN vertex and the less well-determined coupling constant gωNN of ω meson. Within the ranges that GM=1.9+/-0.05, GE=0.0+/-0.025, and 7<=gωNN<=10.5, the predicted differential cross sections and photon-asymmetry ratios are in an overall good agreement with the data of γp-->π0p, γp-->π+n, and γn-->π-p reactions from 180 MeV to the Δ excitation region. The predicted M1+ and E1+ multipole amplitudes are also in good agreement with the empirical values determined by the amplitude analyses. The constructed effective Hamiltonian is free of the nucleon renormalization problem and hence is suitable for nuclear many-body calculations. We have also shown that the assumptions made in the K-matrix method, commonly used in extracting empirically the γN-->Δ transition amplitudes from the data, are consistent with our meson-exchange dynamical model. It is found that the helicity amplitudes calculated from our bare γN-->Δ vertex are in good agreement with the predictions of the constituent quark model. The differences between these bare amplitudes and the dressed amplitudes, which are closer to the empirical values listed by the Particle Data Group, are shown to be due to the nonresonant meson exchange mechanisms. Within the range 7<=gωNN<=10.5 of the ω meson coupling

  1. GaN-based ultraviolet light-emitting diodes with AlN/GaN/InGaN multiple quantum wells.

    PubMed

    Chang, Hung-Ming; Lai, Wei-Chih; Chen, Wei-Shou; Chang, Shoou-Jinn

    2015-04-01

    We demonstrate indium gallium nitride/gallium nitride/aluminum nitride (AlN/GaN/InGaN) multi-quantum-well (MQW) ultraviolet (UV) light-emitting diodes (LEDs) to improve light output power. Similar to conventional UV LEDs with AlGaN/InGaN MQWs, UV LEDs with AlN/GaN/InGaN MQWs have forward voltages (V(f)'s) ranging from 3.21 V to 3.29 V at 350 mA. Each emission peak wavelength of AlN/GaN/InGaN MQW UV LEDs presents 350 mA output power greater than that of the corresponding emission peak wavelength of AlGaN/InGaN MQW UV LEDs. The light output power at 350mA of AlN/GaN/InGaN MQWs UV LEDs with 375 nm emission wavelength can reach around 26.7% light output power enhancement in magnitude compared to the AlGaN/InGaN MQWs UV LEDs with same emission wavelength. But 350mA light output power of AlN/GaN/InGaN MQWs UV LEDs with emission wavelength of 395nm could only have light output power enhancement of 2.43% in magnitude compared with the same emission wavelength AlGaN/InGaN MQWs UV LEDs. Moreover, AlN/GaN/InGaN MQWs present better InGaN thickness uniformity, well/barrier interface quality and less large size pits than AlGaN/InGaN MQWs, causing AlN/GaN/InGaN MQW UV LEDs to have less reverse leakage currents at -20 V. Furthermore, AlN/GaN/InGaN MQW UV LEDs have the 2-kV human body mode (HBM) electrostatic discharge (ESD) pass yield of 85%, which is 15% more than the 2-kV HBM ESD pass yield of AlGaN/InGaN MQW UV LEDs of 70%.

  2. Diffusion technique for 15N and inorganic N analysis of low-N aqueous solutions and Kjeldahl digests.

    PubMed

    Chen, Rui Rui; Dittert, Klaus

    2008-06-01

    Diffusion of ammonia is a common sample preparation method for the stable isotope analysis of inorganic nitrogen in aqueous solution. Classical diffusion methods usually require 6-12 days of diffusion and often focus on (15)N/(14)N analysis only. More recent studies have discussed whether complete N recovery was necessary for the precise analysis of stable N isotope ratios. In this paper we present a newly revised diffusion technique that allows correct and simultaneous determination of total N and (15)N at% from aqueous solutions and Kjeldahl digests, with N concentrations down to sub-0.5-mg N L(-1) levels, and it is tested under different conditions of (15)N isotope labelling. With the modification described, the diffusion time was reduced to 72 h, while the ratios of measured and expected (15)N at% were greater than 99% and the simultaneous recovery of total N was >95%. Analysis of soil microbial biomass N and its (15)N/(14)N ratio is one of the most important applications of this diffusion technique. An experiment with soil extracts spiked with (15)N-labelled yeast showed that predigestion was necessary to prevent serious N loss during Kjeldahl digestion of aqueous samples (i.e. soil extracts). The whole method of soil microbial biomass N preparation for (15)N/(14)N analysis included chloroform fumigation, predigestion, Kjeldahl digestion and diffusion. An experiment with soil spiked with (15)N-labelled yeast was carried out to evaluate the method. Results showed a highly significant correlation of recovered and added N, with the same recovery rate (0.21) of both total N and (15)N. A k(N) value of 0.25 was obtained based on the data. In conclusion, the diffusion method works for soil extracts and microbial biomass N determination and hence could be useful in many types of soil/water studies.

  3. Theoretical and experimental studies of electric field distribution in N-polar GaN/AlGaN/GaN heterostructures

    SciTech Connect

    Gladysiewicz, M. Janicki, L.; Kudrawiec, R.; Siekacz, M.; Cywinski, G.

    2015-12-28

    Electric field distribution in N-polar GaN(channel)/AlGaN/GaN(buffer) heterostructures was studied theoretically by solving Schrodinger and Poisson equations in a self-consistent manner for various boundary conditions and comparing results of these calculations with experimental data, i.e., measurements of electric field in GaN(channel) and AlGaN layers by electromodulation spectroscopy. A very good agreement between theoretical calculations and experimental data has been found for the Fermi-level located at ∼0.3 eV below the conduction band at N-polar GaN surface. With this surface boundary condition, the electric field distribution and two dimensional electron gas concentration are determined for GaN(channel)/AlGaN/GaN(buffer) heterostructures of various thicknesses of GaN(channel) and AlGaN layers.

  4. Hepatic microsomal N-oxidation and N-demethylation of N,N-dimethylaniline in red-winged blackbird compared with rat and other birds

    USGS Publications Warehouse

    Pan, H.P.; Fouts, J.R.; Devereux, T.R.

    1975-01-01

    Hepatic microsomes prepared from red-winged blackbirds and albino rats were incubated with N,N-dimethylaniline (DMA)_in complete incubation mixtures at pH 7.9 and 37?C for 10 min. Formaldehyde and N,N-dimethylaniline--oxide produced from DMA were measured. Redwings were found to have significantly lower N-demethylation activities than rats, and redwings had only marginal or no N-oxidation activities. Hepatic microsomes from redwings did not further metabolize the N-oxide. The N-oxidation and N-demethylation activities of brown-headed cowbirds, common grackles, and starlings were similar to those of redwings.

  5. Lipoxygenase-mediated hydrogen peroxide-dependent N-demethylation of N,N-dimethylaniline and related compounds.

    PubMed

    Hover, C G; Kulkarni, A P

    2000-02-01

    To date, studies of xenobiotic N-demethylation have focused on heme-proteins such as P450 and peroxidases. In this study we investigated the ability of non-heme iron proteins, namely soybean lipoxygenase (SLO) and human term placental lipoxygenase (HTPLO) to mediate N-demethylation of N,N-dimethylaniline (DMA) and related compounds in the presence of hydrogen peroxide. In addition to being hydrogen peroxide dependent, the reaction was also dependent on incubation time, concentration of enzyme and DMA and the pH of the medium. Using Nash reagent to estimate formaldehyde production, we determined the specific activity for SLO mediated N-demethylation of DMA to be 200 + 18 nmol HCHO/min per mg protein or 23 +/- 2 nmol/min per nmol of enzyme, while that of HTPLO was 33 +/- 4 nmol HCHO/min per mg protein. Nordihydroguaiaretic acid (NDGA), a classical inhibitor of lipoxygenase (LO), as well as antioxidants and free radical reducing agents, caused a marked reduction in the rate of production of formaldehyde from DMA by SLO. Besides N,N-dimethylaniline, N-methylaniline, N,N,N',N'-tetramethylbenzidine, N,N-dimethyl-p-phenylenediamine, N,N-dimethyl-3-nitroaniline and N,N-dimethyl-p-toluidine were also demethylated by SLO. The formation of a DMA N-oxide was not detected. Preliminary experiments suggested SLO-mediated hydrogen peroxide-dependent S-dealkylation of methiocarb or O-dealkylation of 4-nitroanisole does not occur.

  6. Polarization-induced Zener tunnel diodes in GaN/InGaN/GaN heterojunctions

    SciTech Connect

    Yan, Xiaodong; Li, Wenjun; Islam, S. M.; Pourang, Kasra; Fay, Patrick; Xing, Huili; Jena, Debdeep

    2015-10-19

    By the insertion of thin In{sub x}Ga{sub 1−x}N layers into Nitrogen-polar GaN p-n junctions, polarization-induced Zener tunnel junctions are studied. The reverse-bias interband Zener tunneling current is found to be weakly temperature dependent, as opposed to the strongly temperature-dependent forward bias current. This indicates tunneling as the primary reverse-bias current transport mechanism. The Indium composition in the InGaN layer is systematically varied to demonstrate the increase in the interband tunneling current. Comparing the experimentally measured tunneling currents to a model helps identify the specific challenges in potentially taking such junctions towards nitride-based polarization-induced tunneling field-effect transistors.

  7. GaN High Power Devices

    SciTech Connect

    PEARTON,S.J.; REN,F.; ZHANG,A.P.; DANG,G.; CAO,X.A.; LEE,K.P.; CHO,H.; GILA,B.P.; JOHNSON,J.W.; MONIER,C.; ABERNATHY,C.R.; HAN,JUNG; BACA,ALBERT G.; CHYI,J.-I.; LEE,C.-M.; NEE,T.-E.; CHUO,C.-C.; CHI,G.C.; CHU,S.N.G.

    2000-07-17

    A brief review is given of recent progress in fabrication of high voltage GaN and AlGaN rectifiers, GaN/AlGaN heterojunction bipolar transistors, GaN heterostructure and metal-oxide semiconductor field effect transistors. Improvements in epitaxial layer quality and in fabrication techniques have led to significant advances in device performance.

  8. New data on ({gamma}, n), ({gamma}, 2n), and ({gamma}, 3n) partial photoneutron reactions

    SciTech Connect

    Varlamov, V. V. Ishkhanov, B. S.; Orlin, V. N.; Peskov, N. N.; Stepanov, M. E.

    2013-11-15

    Systematic discrepancies between the results of various experiments devoted to determining cross sections for total and partial photoneutron reactions are analyzed by using objective criteria of reliability of data in terms of the transitional photoneutron-multiplicity function F{sub i} = {sigma}({gamma}, in)/{sigma}({gamma}, xn), whose values for i = 1, 2, 3, ... cannot exceed by definition 1.00, 0.50, 0.33, ..., respectively. It was found that the majority of experimental data on the cross sections obtained for ({gamma}, n), ({gamma}, 2n), and ({gamma}, 3n) reactions with the aid of methods of photoneutron multiplicity sorting do not meet objective criteria (in particular, F{sub 2} > 0.50 for a vast body of data). New data on the cross sections for partial reactions on {sup 181}Ta and {sup 208}Pb nuclei were obtained within a new experimental-theoretical method that was proposed for the evaluation of cross sections for partial reactions and in which the experimental neutron yield cross section {sigma}{sup expt}({gamma}, xn) = {sigma}({gamma}, n) + 2{sigma}({gamma}, 2n) + 3{sigma}({gamma}, 3n) + ..., which is free from problems associated with determining neutron multiplicities, is used simultaneously with the functions F{sub i}{sup theor} calculated within a combined model of photonuclear reactions.

  9. Sturmian function approach and {bar N}N bound states

    SciTech Connect

    Yan, Y.; Tegen, R.; Gutsche, T.; Faessler, A.

    1997-09-01

    A suitable numerical approach based on Sturmian functions is employed to solve the {bar N}N bound state problem for local and nonlocal potentials. The approach accounts for both the strong short-range nuclear potential and the long-range Coulomb force and provides directly the wave function of protonium and {bar N}N deep bound states with complex eigenvalues E=E{sub R}{minus}i({Gamma}/2). The spectrum of {bar N}N bound states has two parts, the atomic states bound by several keV, and the deep bound states which are bound by several hundred MeV. The observed very small hyperfine splitting of the 1s level and the 1s and 2p decay widths are reasonably well reproduced by both the Paris and Bonn potentials (supplemented with a microscopically derived quark annihilation potential), although there are differences in magnitude and level ordering. We present further arguments for the identification of the {sup 13}PF{sub 2} deep bound state with the exotic tensor meson f{sub 2}(1520). Both investigated models can accommodate the f{sub 2}(1520) but differ greatly in the total number of levels and in their ordering. The model based on the Paris potential predicts the {sup 13}P{sub 0} level slightly below 1.1 GeV while the model based on the Bonn potential puts this state below 0.8 GeV. It remains to be seen if this state can be identified with a scalar partner of the f{sub 2}(1520). {copyright} {ital 1997} {ital The American Physical Society}

  10. Quantitative electron microscopy of InN-GaN alloys

    NASA Astrophysics Data System (ADS)

    Bartel, T.; Jinschek, J. R.; Freitag, B.; Specht, P.; Kisielowski, C.

    2006-01-01

    The local element distribution in quantum wells largely affects physical properties of devices made from such materials. In the past, quantitative electron microscopy was developed to access the stoichiometry on an atomic scale as shown on the cover page of this issue's Editor's Choice [1] for the GaN/InxGa1-xN/GaN and the GaAs/AlxGa1-xAs/GaAs system by the application of QUANTITEM and Chemical Imaging, respectively. In case of GaN/InxGa1-xN/GaN local strain mapping allows for extracting similar data and an unusual large indium fluctuation can be observed if compared with the aluminum distribution in GaAs/AlxGa1-xAs/GaAs quantum well structures. However, radiation damage, sample preparation and microscope stability affect the data analyses and it is of essence to monitor and control such effects as outlined in the related paper.The first author Til Bartel is a PhD candidate in physics at the Technical University of Berlin, currently visiting LBNL in California to apply transmission electron microscopy to III-nitride semiconductors. Christian Kisielowski is Staff Scientist and Principle Investigator at the National Center for Electron Microscopy (NCEM) and is responsible for the development and application of high resolution electron microscopy.The present special issue of physica status solidi (a) is a compilation of presentations from the recent symposium on Indium Nitride and Indium Rich Related Alloys at the E-MRS 2005 Fall Meeting in Warsaw.

  11. BOC(n,n) signal multipath mitigation using MEDLL technology

    NASA Astrophysics Data System (ADS)

    Su, Xuan; Zhang, Yanmei; Su, Lianqing; Guo, Haichao

    2015-11-01

    For satellite navigation and positioning receivers are susceptible to the influence of the multipath, this paper used multipath estimating delay lock loop (MEDLL) technology for BOC (n, n) multipath signal tracking. Through the analysis of multipath signal model, it is concluded that all the multipath signal can be expressed by its amplitude, phase and delay. Then in odor to get the accurate direct signal, this paper applied MEDLL algorithm to estimate the received signal. Finally, the simulation show that this algorithm can realize multipath signal track demodulation and accurate data demodulation under a low signal noise ratio environment (SNR= -20db).

  12. 6-Propionyl-2-(N,N-dimethylamino) naphthalene (PRODAN) revisited

    SciTech Connect

    Sun, S. |; Heitz, M.P.; Perez, S.A.; Colon, L.A.; Bruckenstein, S.; Bright, F.V.

    1997-09-01

    The photophysics of 6-propionyl-2-(N,N-dimethylamino) naphthalene (PRODAN) in liquid water are reported. Our results demonstrate that the often mentioned extra blue-edge shoulder seen for PRODAN in liquid water is a result of PRODAN-PRODAN intermolecular interactions in a supersaturated PRODAN solution and not a consequence of impurities in the commercial PRODAN preparations. In all cases where the aqueous PRODAN solution is not supersaturated, there is no detectable blue-edge emission shoulder. {copyright} {ital 1997} {ital Society for Applied Spectroscopy}

  13. Extent of shielding by counterions determines the bactericidal activity of N,N,N-trimethyl chitosan salts.

    PubMed

    Follmann, Heveline D M; Martins, Alessandro F; Nobre, Thatyane M; Bresolin, Joana D; Cellet, Thelma S P; Valderrama, Patrícia; Correa, Daniel S; Muniz, Edvani C; Oliveira, Osvaldo N

    2016-02-10

    In this study, we show that the bactericidal activity of quaternized chitosans (TMCs) with sulfate, acetate, and halide counterions against Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus) correlates with the "availability" of N-quaternized groups [-(+)N(CH3)3] in the TMCs backbones. N,N,N-trimethyl chitosan sulfate (TMCS) and N,N,N-trimethyl chitosan acetate (TMCAc) displayed the highest activities, probably due to their delocalized π system. Among TMCs with halide counterions, activity was higher for N,N,N-trimethyl chitosan chloride (TMCCl), whereas N,N,N-trimethyl chitosan iodide (TMCI) and N,N,N-trimethyl chitosan bromide (TMCBr) exhibited lower, similar values to each other. This is consistent with the shielding of -(+)N(CH3)3 groups inferred from chemical shifts for halide counterions in (1)HNMR spectra. We also demonstrate that TMCs with distinct bactericidal activities can be classified according to their vibrational spectra using principal component analysis. Taken together, these physicochemical characterization approaches represent a predictive tool for the bactericidal activity of chitosan derivatives.

  14. Molecular and component volumes of N,N-dimethyl-N-alkylamine N-oxides in DOPC bilayers.

    PubMed

    Belička, Michal; Klacsová, Mária; Karlovská, Janka; Westh, Peter; Devínsky, Ferdinand; Balgavý, Pavol

    2014-05-01

    The volumetric properties of fluid bilayers formed of dioleoylphosphatidylcholine (DOPC) with incorporated N,N-dimethyl-N-alkylamine N-oxides (CnNO, n=6, 10-18 is the even number of carbons in alkyl chain) were studied by vibrating tube densitometry in the temperature interval from 20°C to 50°C. It was found that the DOPC and CnNO mixed ideally in the investigated composition range and hence the molecular volumes of DOPC (VDOPC) and incorporated CnNO (VCnNO) were constant and additive within error limits. From the temperature dependencies of the molecular volumes of DOPC and CnNO their coefficients of isobaric thermal expansivities in the investigated temperature interval were obtained. The VCnNO volumes of CnNO incorporated into DOPC bilayers showed linear dependencies on the CnNO alkyl chain length at all measured temperatures. This allowed to calculate the component volume of the CnNO methylene group (VCH2) at several temperatures and its coefficient of isobaric thermal expansivity. Using the assumption that the component volume of the CnNO methyl group VCH3 = 2VCH2 we also calculated the component volume and the coefficient of isobaric thermal expansivity of the hydrophilic group of CnNO (VNO). We found that the VCH2 volume increases in the whole temperature interval whereas the VNO volume decreases.

  15. nEDM at SNS

    SciTech Connect

    Clayton, Steven

    2014-07-30

    This PowerPoint presentation covered the following topics: Overview; participants in the collaboration; the experimental method and Free Precession Method descriptions; and then experimental design elements, ending with a summary. A new nEDM experiment is under development with a goal sensitivity 90% CL σd < (3-5) x 10-28 e-cm in 300 live-days; Free precession method: SQUIDS to read out the 3He precession frequency, Scintillation signal for the n relative precession frequency; Dressed spin method: Strong RF field to match n and 3He effective magnetic moments; Modulation/feedback of dressing parameter based on scintillation signal; and, Ongoing development/demonstration of many aspects of the apparatus (a subset was shown here).

  16. Crystal structure of catena-poly[N,N,N',N'-tetra-methyl-guanidinium [(chlorido-cadmate)-di-μ-chlorido

    PubMed

    Ndiaye, Mamadou; Samb, Abdoulaye; Diop, Libasse; Maris, Thierry

    2016-01-01

    In the structure of the title salt, {(C5H14N3)[CdCl3]} n , the Cd(II) atom of the complex anion is five-coordinated by one terminal and four bridging Cl atoms. The corresponding coordination polyhedron is a distorted trigonal bipyramid, with Cd-Cl distances in the range 2.4829 (4)-2.6402 (4) Å. The bipyramids are condensed into a polyanionic zigzag chain extending parallel to [101]. The tetra-methyl-guanidinium cations are situated between the polyanionic chains and are linked to them through N-H⋯Cl hydrogen bonds, forming a layered network parallel to (010). PMID:26870572

  17. Thermoelectric Transport in a ZrN/ScN Superlattice

    NASA Astrophysics Data System (ADS)

    Zebarjadi, Mona; Bian, Zhixi; Singh, Rajeev; Shakouri, Ali; Wortman, Robert; Rawat, Vijay; Sands, Tim

    2009-07-01

    Metal/semiconductor superlattices have the potential for a high thermoelectric figure of merit. The thermopower of these structures can be enhanced by controlling the barrier height using high-energy electron filtering. In addition, phonon scattering at interfaces can reduce the lattice contribution to the thermal conductivity. In this paper, we present theoretical and experimental studies of the thermoelectric transport in ZrN/ScN metal/semiconductor superlattices. Preliminary measurement results show an exponential increase in the cross-plane electrical conductivity with increasing temperature, which indicates the presence of the barrier. Fit of the Boltzmann transport-based model with the data indicates a barrier height of 280 meV. The cross-plane Seebeck coefficient of the sample is also measured by combining Seebeck voltage transient measurements with the thermal imaging technique. A Seebeck coefficient of 820 μV/K at room temperature is extracted, which is in good agreement with the simulation result of 800 μV/K. Theoretical calculations predict that the ZrN/ScN structure can exhibit a ZT of 1.5 at 1300 K assuming lateral momentum is conserved and that a ZT of 3 is achievable if the lateral momentum is not conserved.

  18. Investigation of amber light-emitting diodes based on InGaN/AlN/AlGaN quantum wells

    NASA Astrophysics Data System (ADS)

    Iida, Daisuke; Lu, Shen; Hirahara, Sota; Niwa, Kazumasa; Kamiyama, Satoshi; Ohkawa, Kazuhiro

    2016-05-01

    We investigated InGaN-based amber light-emitting diodes (LEDs) with AlN/(Al)GaN barrier layers grown by metalorganic vapor-phase epitaxy. Tensilely strained AlN/Al0.03Ga0.97N barriers improved the crystalline quality of compressively strained InGaN quantum wells. We found that strain compensation among wells and barriers improves the external quantum efficiency of high-In-content InGaN-based amber LEDs. The amber LEDs with AlN/Al0.03Ga0.97N barriers have shown an electroluminescence (EL) intensity approximately 2.5-fold that of LEDs with the AlN/GaN barriers at 20 mA.

  19. High-n immersion lithography

    NASA Astrophysics Data System (ADS)

    Sewell, Harry; Mulkens, Jan; Graeupner, Paul; McCafferty, Diane; Markoya, Louis; Donders, Sjoerd; Cortie, Rogier; Meijers, Ralph; Evangelista, Fabrizio; Samarakone, Nandarisi

    2008-03-01

    A two-year study on the feasibility of High-n Immersion Lithography shows very promising results. This paper reports the findings of the study. The evaluation shows the tremendous progress made in the development of second-generation immersion fluid technology. Candidate fluids from several suppliers have been evaluated. All the commercial fluids evaluated are viable, so there are a number of options. Life tests have been conducted on bench top fluid-handling systems and the results referenced to full-scale systems. Parameters such as Dose per Laser Pulse, Pulse Rate, Fluid Flow Rate, and Fluid Absorbency at 193nm, and Oxygen/Air Contamination Levels were explored. A detailed evaluation of phenomena such as Last Lens Element (LLE) contamination has been conducted. Lens cleaning has been evaluated. A comparison of High-n fluid-based technology and water-based immersion technology shows interesting advantages of High-n fluid in the areas of Defect and Resist Interaction. Droplet Drying tests, Resist Staining evaluations, and Resist Contrast impact studies have all been run. Defect-generating mechanisms have been identified and are being eliminated. The lower evaporation rate of the High-n fluids compared with water shows the advantages of High-n Immersion. The core issue for the technology, the availability of High-n optical material for use as the final lens element, is updated. Samples of LuAG material have been received from development partners and have been evaluated. The latest status of optical materials and the technology timelines are reported. The potential impact of the availability of the technology is discussed. Synergy with technologies such as Double Patterning is discussed. The prospects for <22nm (hp) are evaluated.

  20. Crystal structure of bis-(N,N,N',N'-tetra-methyl-guanidinium) tetra-chlorido-cuprate(II).

    PubMed

    Ndiaye, Mamadou; Samb, Abdoulaye; Diop, Libasse; Maris, Thierry

    2016-07-01

    In the structure of the title salt, (C5H14N3)2[CuCl4], the Cu(II) atom in the anion lies on a twofold rotation axis. The tetra-chlorido-cuprate(II) anion adopts a flattened tetra-hedral coordination environment and inter-acts electrostatically with the tetra-methyl-guanidinium cation. The crystal packing is additionally consolidated through N-H⋯Cl and C-H⋯Cl hydrogen bonds, resulting in a three-dimensional network structure. PMID:27555960

  1. Gravitational N-Body Simulations

    NASA Astrophysics Data System (ADS)

    Aarseth, Sverre J.

    2010-01-01

    Preface; 1. The N-body problem; 2. Predictor-corrector methods; 3. Neighbour treatments; 4. Two-body regularization; 5. Multiple regularization; 6. Tree codes; 7. Program organization; 8. Initial setup; 9. Decision-making; 10. Neighbour schemes; 11. Two-body algorithms; 12. Chain procedures; 13. Accuracy and performance; 14. Practical aspects; 15. Star clusters; 16. Galaxies; 17. Planetary systems; 18. Small-N experiments; Appendix A. Global regularization algorithms; Appendix B. Chain algorithms; Appendix C. High-order systems; Appendix D. Practical algorithms; Appendix E. KS procedures with GRAPE; Appendix F. Alternative simulation method; Appendix G. Table of symbols; Appendix H. Hermite integration method; References; Index.

  2. Gravitational N-Body Simulations

    NASA Astrophysics Data System (ADS)

    Aarseth, Sverre J.

    2003-10-01

    Preface; 1. The N-body problem; 2. Predictor-corrector methods; 3. Neighbour treatments; 4. Two-body regularization; 5. Multiple regularization; 6. Tree codes; 7. Program organization; 8. Initial setup; 9. Decision-making; 10. Neighbour schemes; 11. Two-body algorithms; 12. Chain procedures; 13. Accuracy and performance; 14. Practical aspects; 15. Star clusters; 16. Galaxies; 17. Planetary systems; 18. Small-N experiments; Appendix A. Global regularization algorithms; Appendix B. Chain algorithms; Appendix C. High-order systems; Appendix D. Practical algorithms; Appendix E. KS procedures with GRAPE; Appendix F. Alternative simulation method; Appendix G. Table of symbols; Appendix H. Hermite integration method; References; Index.

  3. Influence of N2 partial pressure on structural and microhardness properties of TiN/ZrN multilayers deposited by Ar/N2 vacuum arc discharge

    NASA Astrophysics Data System (ADS)

    Naddaf, M.; Abdallah, B.; Ahmad, M.; A-Kharroub, M.

    2016-08-01

    The influence of N2 partial pressure on structural, mechanical and wetting properties of multilayered TiN/ZrN thin films deposited on silicon substrates by vacuum arc discharge of (N2 + Ar) gas mixtures is investigated. X-ray diffraction (XRD) results show that the average texturing coefficient of (1 1 1) orientation and the grain size of both TiN and ZrN individual layers increase with increasing the N2 partial pressure. The Rutherford back scattering (RBS) measurements and analysis reveal that incorporation of the nitrogen in the film increases with increasing the N2 partial pressure and both TiN and ZrN individual layers have a nitrogen over-stoichiometry for N2 partial pressure ⩾50%. The change in the film micro-hardness is correlated to the changes in crystallographic texture, grain size, stoichiometry and the residual stress in the film as a function of the N2 partial pressure. In particular, stoichiometry of ZrN and TiN individual is found to play the vital role in determining the multilayer hardness. The multilayer film deposited at N2 partial pressure of 25% has the best stoichiometric ratio of both TiN and ZrN layers and the highest micro-hardness of about 32 GPa. In addition, water contact angle (WCA) measurements and analysis show a decrease in the work of adhesion on increasing the N2 partial pressure.

  4. Self-assembled GaN quantum wires on GaN/AlN nanowire templates.

    PubMed

    Arbiol, Jordi; Magen, Cesar; Becker, Pascal; Jacopin, Gwénolé; Chernikov, Alexey; Schäfer, Sören; Furtmayr, Florian; Tchernycheva, Maria; Rigutti, Lorenzo; Teubert, Jörg; Chatterjee, Sangam; Morante, Joan R; Eickhoff, Martin

    2012-12-01

    We present a novel approach for self-assembled growth of GaN quantum wires (QWRs) exhibiting strong confinement in two spatial dimensions. The GaN QWRs are formed by selective nucleation on {112[combining macron]0} (a-plane) facets formed at the six intersections of {11[combining macron]00} (m-plane) sidewalls of AlN/GaN nanowires used as a template. Based on microscopy observations we have developed a 3D model explaining the growth mechanism of QWRs. We show that the QWR formation is governed by self-limited pseudomorphic growth on the side facets of the nanowires (NWs). Quantum confinement in the QWRs is confirmed by the observation of narrow photoluminescence lines originating from individual QWRs with emission energies up to 4.4 eV. Time-resolved photoluminescence studies reveal a short decay time (~120 ps) of the QWR emission. Capping of the QWRs with AlN allows enhancement of the photoluminescence, which is blue-shifted due to compressive strain. The emission energies from single QWRs are modelled assuming a triangular cross-section resulting from self-limited growth on a-plane facets. Comparison with the experimental results yields an average QWR diameter of about 2.7 nm in agreement with structural characterization. The presented results open a new route towards controlled realization of one-dimensional semiconductor quantum structures with a high potential both for fundamental studies and for applications in electronics and in UV light generation.

  5. 40 CFR 721.275 - Halogenated-N-(2-propenyl)-N-(substituted phenyl) acetamide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Halogenated-N-(2-propenyl)-N... New Uses for Specific Chemical Substances § 721.275 Halogenated-N-(2-propenyl)-N-(substituted phenyl... identified generically as halogenated-N-(2-propenyl)-N-(substituted phenyl) acetamide (P-83-1085) is...

  6. 40 CFR 721.4090 - Ethanaminium, N-[bis(diethylamino)-methylene]-N-ethyl-, bromide.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Ethanaminium, N- -N-ethyl-, bromide... Substances § 721.4090 Ethanaminium, N- -N-ethyl-, bromide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as ethanaminium, N- -N-ethyl-, bromide (PMN...

  7. 40 CFR 721.10159 - 1-Docosanamine, N,N-dimethyl-.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false 1-Docosanamine, N,N-dimethyl-. 721... Substances § 721.10159 1-Docosanamine, N,N-dimethyl-. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as 1-docosanamine, N,N-dimethyl- (PMN...

  8. 40 CFR 721.275 - Halogenated-N-(2-propenyl)-N-(substituted phenyl) acetamide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Halogenated-N-(2-propenyl)-N... New Uses for Specific Chemical Substances § 721.275 Halogenated-N-(2-propenyl)-N-(substituted phenyl... identified generically as halogenated-N-(2-propenyl)-N-(substituted phenyl) acetamide (P-83-1085) is...

  9. 40 CFR 721.4090 - Ethanaminium, N-[bis(diethylamino)-methylene]-N-ethyl-, bromide.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Ethanaminium, N- -N-ethyl-, bromide... Substances § 721.4090 Ethanaminium, N- -N-ethyl-, bromide. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as ethanaminium, N- -N-ethyl-, bromide (PMN...

  10. 40 CFR 721.10159 - 1-Docosanamine, N,N-dimethyl-.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false 1-Docosanamine, N,N-dimethyl-. 721... Substances § 721.10159 1-Docosanamine, N,N-dimethyl-. (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance identified as 1-docosanamine, N,N-dimethyl- (PMN...

  11. Biomaterials based on N,N,N-trimethyl chitosan fibers in wound dressing applications.

    PubMed

    Zhou, Zhongzheng; Yan, Dong; Cheng, Xiaojie; Kong, Ming; Liu, Ya; Feng, Chao; Chen, Xiguang

    2016-08-01

    In the present work, N,N,N-trimethyl chitosan (TMC) fibers were synthesized successfully and the resulting quaternized materials were characterized by FTIR. The designed TMC fibers with different degree of quaternization achieved high water absorption capability. In antibacterial activity study, TMC fibers showed high antibacterial activity than chitosan fibers against the gram-negative bacteria Escherichia coli (>63%) and gram-positive bacteria Staphylococcus aureus (>99%). TMC fibers exhibited no obvious cytotoxicity to mouse embryo fibroblast cells with low extraction concentrations (<0.05g/mL). In animal wound healing test, TMC2 fibers could significantly enhance wound re-epithelialization and contraction compared with the control (chitosan fibers). In conclusion, TMC fibers have a potential to be used as wound dressing materials.

  12. Two cases of lymphosarcoma in channel catfish exposed to N-methyl-N'-nitro-N-nitrosoguanidine.

    PubMed

    Chen, H H; Brittelli, M R; Muska, C F

    1985-04-01

    Of 158 channel catfish (Ictalurus punctatus) exposed to N-methyl-N'-nitro-N-nitrosoguanidine [(MNNG) CAS:70-25-7] in water for 28 days, 2 developed disseminated lymphosarcoma. One fish was necropsied at 12 months and another at 18 months following exposure. Both fish had a massive neoplastic infiltration of the bilateral pairs of head and trunk kidneys from which the neoplastic cells appeared to originate. The neoplastic infiltration was also observed in the following: thymus, gills, oral mucosa, liver, skin, skeletal muscle of head-neck region, and to a lesser extent spleen and bone marrow. This is probably the first report of lymphosarcoma in channel catfish. Although the occurrence of lymphosarcoma in these 2 catfish appeared to be related to exposure to MNNG, the exact role MNNG played in the tumor formation was not determined. PMID:3857387

  13. A comparative study on the neurotoxicity of n-pentane, n-hexane, and n-heptane in the rat.

    PubMed Central

    Takeuchi, Y; Ono, Y; Hisanaga, N; Kitoh, J; Sugiura, Y

    1980-01-01

    The neurotoxicity of n-pentane, n-hexane, and n-heptane have been studied in Wistar strain male rats after exposure to 3000 ppm of n-pentane, n-hexane, or n-heptane for 12 hours a day for 16 weeks. The nerve conduction velocity and the distal latency were measured before the beginning of the exposure and after exposure for four, eight, 12, and 16 weeks. The experiment showed that n-hexane disturbed the conduction velocity of the motor nerve and the mixed nerve and prolonged the distal latency in the rat's tail, but that n-pentane and n-heptane did not. The light and electron microscopic examination showed that the peripheral nerve, the neuromuscular junction, and the muscle fibre of the rats exposed to n-hexane were severely impaired, but those of the rats exposed to n-pentane or n-heptane showed no particular changes even after 16 weeks of exposure. These results show that n-hexane is far more toxic to the peripheral nerve of the rat than n-pentane or n-heptane. It is necessary to study the neurotoxicity of other petroleum hydrocarbons, since some reports suggest that petroleum solvents might possibly contain neurotoxic hydrocarbons other than n-hexane. Images PMID:7426474

  14. Cover crops and N credits

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Cover crops often provide many short- and long-term benefits to cropping systems. Legume cover crops can significantly reduce the N fertilizer requirement of non-legume cash crops that follow. The objectives of this presentation were to: I) educate stakeholders about the potential benefits of cover ...

  15. The N Program with CLAS

    NASA Astrophysics Data System (ADS)

    Mueller, James A.

    1999-10-01

    The study of excited baryons allows us to probe the internal structure of light quark baryons. The N program at CLAS is a collection of experiments which examine production of N^*'s in both photon and electron beams. These experiments measure the photocouplings to known states over a wide range of Q^2, and search for missing resonances predicted by the quark model. These experiments use the CEBAF Large Acceptance Spectrometer (CLAS). This detector was built by ~ 130 physicists from ~ 30 Universities and National Laboratories, and is located in Hall B, one of three experimental areas at the TJNAF. The CLAS has acceptance covering 80% of the azimuthal angle for polar angles between 8^circ and 150^circ. The large acceptance for exclusive final states as well as its broad kinematic coverage, make it possible to simultaneously measure the production of many N^* resonances in a variety of exclusive final states. We will present an overview of the CLAS N^* physics program, describe the CLAS and its performance, and give some results from the first 1.5 years of operation.

  16. N2O FIELD STUDY

    EPA Science Inventory

    The report gives results of measurements of nitrous oxide (N2O) emissions from coal-fired utility boilers at three electric power generating stations. Six units were tested, two at each site, including sizes ranging from 165 to 700 MW. Several manufacturers and boiler firing type...

  17. Performance improvement of GaN-based LEDs with step stage InGaN/GaN strain relief layers in GaN-based blue LEDs.

    PubMed

    Jia, Chuanyu; Yu, Tongjun; Lu, Huimin; Zhong, Cantao; Sun, Yongjian; Tong, Yuzhen; Zhang, Guoyi

    2013-04-01

    The performance of nitride-based LEDs was improved by inserting dual stage and step stage InGaN/GaN strain relief layer (SRL) between the active layer and n-GaN template. The influences of step stage InGaN/GaN SRL on the structure, electrical and optical characteristics of GaN-based LEDs were investigated. The analysis of strain effect on recombination rate based k·p method indicated 12.5% reduction of strain in InGaN/GaN MQWs by inserting SRL with step stage InGaN/GaN structures. The surface morphology was improved and a smaller blue shift in the electroluminescence (EL) spectral with increasing injection current was observed for LEDs with step stage SRL compared with conventional LEDs. The output power of LEDs operating at 20 mA was about 15.3 mW, increased by more than 108% by using step stage InGaN/GaN SRL, which shows great potential of such InGaN/GaN SRL in modulating InGaN/GaN MQWs optical properties based on its strain relief function.

  18. Influence of internal electric fields on band gaps in short period GaN/GaAlN and InGaN/GaN polar superlattices

    SciTech Connect

    Gorczyca, I. Skrobas, K.; Suski, T.; Christensen, N. E.; Svane, A.

    2015-08-21

    The electronic structures of short period mGaN/nGa{sub y}Al{sub 1−y}N and mIn{sub y}Ga{sub 1-y}N/nGaN superlattices grown along the wurtzite c axis have been calculated for different alloy compositions y and various small numbers m of well- and n of barrier-monolayers. The general trends in gap behavior can, to a large extent, be related to the strength of the internal electric field, E, in the GaN and InGaN quantum wells. In the GaN/GaAlN superlattices, E reaches 4 MV/cm, while in the InGaN/GaN superlattices, values as high as E ≈ 6.5 MV/cm are found. The strong electric fields are caused by spontaneous and piezoelectric polarizations, the latter contribution dominating in InGaN/GaN superlattices. The influence of different arrangements of In atoms (indium clustering) on the band gap values in InGaN/GaN superlattices is examined.

  19. Evaluation of N,N-dialkylamides as promising process extractants

    NASA Astrophysics Data System (ADS)

    Pathak, P. N.; Prabhu, D. R.; Kanekar, A. S.; Manchanda, V. K.

    2010-03-01

    Studies carried out at BARC, India on the development of new extractants for reprocessing of spent fuel suggested that while straight chain N,N-dihexyloctanamide (DHOA) is promising alternative to TBP for the reprocessing of irradiated uranium based fuels, branched chain N,N-di(2-ethylhexyl)isobutyramide (D2EHIBA) is suitable for the selective recovery of 233U from irradiated Th. In advanced fuel cycle scenarios, the coprocessing of U/Pu stream appears attractive particularly with respect to development of proliferation resistant technologies. DHOA extracted Pu(IV) more efficiently than TBP, both at trace-level concentration as well as under uranium/plutonium loading conditions. Uranium extraction behavior of DHOA was however, similar to that of TBP during the extraction cycle. Stripping behavior of U and Pu (without any reductant) was better for DHOA than that of TBP. It was observed during batch studies that whereas 99% Pu is stripped in four stages in case of DHOA, only 89% Pu is stripped in case of TBP under identical experimental conditions. DHOA offered better fission product decontamination than that of TBP. GANEX (Group ActiNide EXtraction) and ARTIST (Amide-based Radio-resources Treatment with Interim Storage of Transuranics) processes proposed for actinide partitioning use branched chain amides for the selective extraction of uranium from spent fuel feed solutions. The branched-alkyl monoamide (BAMA) proposed to be used in ARTIST process is N,N-di-(2-ethylhexyl)butyramide (D2EHBA). In this context, the extraction behavior of U(VI) and Pu(IV) were compared using D2EHIBA, TBP, and D2EHBA under similar concentration of nitric acid (0.5 — 6M) and of uranium (0-50g/L). These studies suggested that D2EHIBA is a promising extractant for selective extraction of uranium over plutonium in process streams. Similarly, D2EHIBA offered distinctly better decontamination of 233U over Th and fission products under THOREX feed conditions. The possibility of simultaneous

  20. PARTITIONING THE RELATIVE INFLUENCE OF SOIL N, MYCORRHIZAE, AND FOLIAR N UPTAKE ON FOLIAR δ15N PATTERNS: CAN WE DETECT FOLIAR UPTAKE OF REACTIVE N?

    NASA Astrophysics Data System (ADS)

    Vallano, D.; Sparks, J. P.

    2009-12-01

    Vegetation is an important sink for atmospheric reactive N in N-limited systems and may be capable of incorporating reactive N compounds directly into leaves through the foliar uptake pathway. A proxy for atmospheric reactive N entering vegetation would be useful to estimate the impact of direct foliar N uptake on plant metabolism. Natural abundance foliar N isotopic composition (δ15N) is a practical tool for this purpose because plant-available N sources often have different isotopic compositions. Current understanding of foliar δ15N suggests these values primarily represent the integration of soil δ15N, direct foliar N uptake, mycorrhizal fractionation, and within-plant fractionations. Using a potted plant mesocosm system, we estimated the influence of mycorrhizae on foliar δ15N patterns in red maple (Acer rubrum) seedlings along an N deposition gradient in New York State. We found that mycorrhizal associations altered foliar δ15N in red maple seedlings from 0.03 - 1.01‰ across sites. Along the same temporal and spatial scales, we examined the influence of soil δ15N, foliar N uptake, and mycorrhizae on foliar δ15N in adult stands of American beech (Fagus grandifolia), black birch (Betula lenta), red maple (A. rubrum), and red oak (Quercus rubra). Using multiple regression models, atmospheric NO2 concentration explained 0%, 69%, 23%, and 45% of the residual variation in foliar δ15N remaining in American beech, red maple, red oak, and black birch, respectively, after accounting for soil δ15N. Our results suggest that foliar δ15N may be used to estimate pollution-derived atmospheric reactive N entering vegetation via the foliar N uptake pathway.

  1. N,N-Dimethyl-N'-[3-(trifluoro-methyl)-phenyl]-urea.

    PubMed

    Yu, Da-Sheng; Li, Fang-Shi; Yao, Wei; Liu, Yin-Hong; Lu, Chui

    2008-06-07

    The title compound, C(10)H(11)F(3)N(2)O, is an important urea-based herbicide. In the crystal structure, the mol-ecular packing is stabilized by two intra-molecular C-H⋯O hydrogen bonds and one inter-molecular N-H⋯O hydrogen bond, generating a C(4) graph-set motif running parallel to the [001] direction. The F atoms are disordered over two sites, with occupancies of 0.176 (9) and 0.824 (9).

  2. Cosmological N-body Simulation

    NASA Astrophysics Data System (ADS)

    Lake, George

    1994-05-01

    .90ex> }}} The ``N'' in N-body calculations has doubled every year for the last two decades. To continue this trend, the UW N-body group is working on algorithms for the fast evaluation of gravitational forces on parallel computers and establishing rigorous standards for the computations. In these algorithms, the computational cost per time step is ~ 10(3) pairwise forces per particle. A new adaptive time integrator enables us to perform high quality integrations that are fully temporally and spatially adaptive. SPH--smoothed particle hydrodynamics will be added to simulate the effects of dissipating gas and magnetic fields. The importance of these calculations is two-fold. First, they determine the nonlinear consequences of theories for the structure of the Universe. Second, they are essential for the interpretation of observations. Every galaxy has six coordinates of velocity and position. Observations determine two sky coordinates and a line of sight velocity that bundles universal expansion (distance) together with a random velocity created by the mass distribution. Simulations are needed to determine the underlying structure and masses. The importance of simulations has moved from ex post facto explanation to an integral part of planning large observational programs. I will show why high quality simulations with ``large N'' are essential to accomplish our scientific goals. This year, our simulations have N >~ 10(7) . This is sufficient to tackle some niche problems, but well short of our 5 year goal--simulating The Sloan Digital Sky Survey using a few Billion particles (a Teraflop-year simulation). Extrapolating past trends, we would have to ``wait'' 7 years for this hundred-fold improvement. Like past gains, significant changes in the computational methods are required for these advances. I will describe new algorithms, algorithmic hacks and a dedicated computer to perform Billion particle simulations. Finally, I will describe research that can be enabled by

  3. Organometallic vapor phase epitaxial growth of GaN on ZrN /AlN/Si substrates

    NASA Astrophysics Data System (ADS)

    Oliver, Mark H.; Schroeder, Jeremy L.; Ewoldt, David A.; Wildeson, Isaac H.; Rawat, Vijay; Colby, Robert; Cantwell, Patrick R.; Stach, Eric A.; Sands, Timothy D.

    2008-07-01

    An intermediate ZrN /AlN layer stack that enables the epitaxial growth of GaN on (111) silicon substrates using conventional organometallic vapor phase epitaxy at substrate temperatures of ˜1000°C is reported. The epitaxial (111) ZrN layer provides an integral back reflector and Ohmic contact to n-type GaN, whereas the (0001) AlN layer serves as a reaction barrier, as a thermally conductive interface layer, and as an electrical isolation layer. Smooth (0001) GaN films less than 1μm thick grown on ZrN /AlN/Si yield 0002 x-ray rocking curve full width at half maximum values as low as 1230arcsec.

  4. Equilibrium among potassium polytellurides in N,N-dimethylformamide solution

    NASA Astrophysics Data System (ADS)

    McAfee, Jason L.; Andreatta, Jeremy R.; Sevcik, Richard S.; Schultz, Linda D.

    2012-08-01

    Reactions between elemental potassium and tellurium in N,N-dimethylformamide (DMF) are monitored using UV-visible spectroscopy and compared with those in liquid ammonia solution. In liquid ammonia, the elements react together, via a step-wise sequence, to form polytellurides, each of which is characterized by a distinctive color, the highest being potassium tritelluride. However, when the elements are combined in DMF, these distinctive color changes are not observed - the solution develops an initial plum color, which gradually darkens to purple as the reaction progresses. UV-visible and Raman spectroscopic studies indicate that equilibrium exists among the mono-, di-, and tritelluride in DMF. This equilibrium is not seen in liquid ammonia solution due to the insolubility of potassium monotelluride in that solvent. Spectral data also indicate that potassium tetratelluride is formed in DMF solution.

  5. The 2NQAM modulations of rate (N-1)/N

    NASA Astrophysics Data System (ADS)

    Duponteil, D.; Ledter, L.

    The use of error-correcting codes leads to efficient M-ary modulations by increasing their noise immunity. The results of the Ungerboeck approach concerning the optimal design of coding by taking account of the modulation are summarized. The method used by Calderbank allows the global definition of families of coded modulations using the same convolutional code. For the 2NQAM (quadrature amplitude modulation) modulations with rate (N-1)/N, the maximum attainable coding gain is related to the trellis complexity, exactly to the number of states in the Viterbi decoder, and is nearly independent of the number of states of the modulation. OQAM with rate 2/3 gives the performances and the optimal receiver structure for all the modulations of the family. The results shows that the receiver can be implemented in two circuits, a preprocessor and a Viterbi decoder, this structure being suited to the reception of modulations with different rates and using the same convolutional code.

  6. A Detailed Chemical Kinetic Reaction Mechanism for n-Alkane Hydrocarbons From n-Octane to n-Hexadecane

    SciTech Connect

    Westbrook, C K; Pitz, W J; Herbinet, O; Curran, H J; Silke, E J

    2008-02-08

    Detailed chemical kinetic reaction mechanisms have been developed to describe the pyrolysis and oxidation of nine n-alkanes larger than n-heptane, including n-octane (n-C{sub 8}H{sub 18}), n-nonane (n-C{sub 9}H{sub 20}), n-decane (n-C{sub 10}H{sub 22}), n-undecane (n-C{sub 11}H{sub 24}), n-dodecane (n-C{sub 12}H{sub 26}), n-tridecane (n-C{sub 13}H{sub 28}), n-tetradecane (n-C{sub 14}H{sub 30}), n-pentadecane (n-C{sub 15}H{sub 32}), and n-hexadecane (n-C{sub 16}H{sub 34}). These mechanisms include both high temperature and low temperature reaction pathways. The mechanisms are based on our previous mechanisms for the primary reference fuels n-heptane and iso-octane, using the reaction class mechanism construction first developed for n-heptane. Individual reaction class rules are as simple as possible in order to focus on the parallelism between all of the n-alkane fuels included in the mechanisms, and these mechanisms will be refined further in the future to incorporate greater levels of accuracy and predictive capability. These mechanisms are validated through extensive comparisons between computed and experimental data from a wide variety of different sources. In addition, numerical experiments are carried out to examine features of n-alkane combustion in which the detailed mechanisms can be used to compare reactivities of different n-alkane fuels. The mechanisms for all of these n-alkanes are presented as a single detailed mechanism, which can be edited to produce efficient mechanisms for any of the n-alkanes included, and the entire mechanism, with supporting thermochemical and transport data, together with an explanatory glossary explaining notations and structural details, will be available for download from our web page.

  7. Neutron capture and (n,2n) measurements on 241Am

    SciTech Connect

    Vieira, D; Jandel, M; Bredeweg, T; Bond, E; Clement, R; Couture, A; Haight, R; O'Donnell, J; Reifarth, R; Ullmann, J; Wilhelmy, J; Wouters, J; Tonchev, A; Hutcheson, A; Angell, C; Crowell, A; Fallin, B; Hammond, S; Howell, C; Karowowski, H; Kelley, J; Pedroni, R; Tornow, W; Macri, R; Agvaanluvsan, U; Becker, J; Dashdorj, D; Stoyer, M; Wu, C

    2007-07-18

    We report on a set of neutron-induced reaction measurements on {sup 241}Am which are important for nuclear forensics and advanced nuclear reactor design. Neutron capture measurements have been performed on the DANCE detector array at the Los Alamos Neutron Scattering CEnter (LANSCE). In general, good agreement is found with the most recent data evaluations up to an incident neutron energy of {approx} 300 keV where background limits the measurement. Using mono-energetic neutrons produced in the {sup 2}H(d,n){sup 3}He reaction at Triangle University Nuclear Laboratory (TUNL), we have measured the {sup 241}Am(n,2n) excitation function from threshold (6.7 MeV) to 14.5 MeV using the activation method. Good agreement is found with previous measurements, with the exception of the three data points reported by Perdikakis et al. around 11 MeV, where we obtain a much lower cross section that is more consistent with theoretical estimates.

  8. Role of Deacetylase Activity of N-Deacetylase/N-Sulfotransferase 1 in Forming N-Sulfated Domain in Heparan Sulfate*

    PubMed Central

    Dou, Wenfang; Xu, Yongmei; Pagadala, Vijayakanth; Pedersen, Lars C.; Liu, Jian

    2015-01-01

    Heparan sulfate (HS) is a highly sulfated polysaccharide that plays important physiological roles. The biosynthesis of HS involves a series of enzymes, including glycosyltransferases (or HS polymerase), epimerase, and sulfotransferases. N-Deacetylase/N-Sulfotransferase isoform 1 (NDST-1) is a critical enzyme in this pathway. NDST-1, a bifunctional enzyme, displays N-deacetylase and N-sulfotransferase activities to convert an N-acetylated glucosamine residue to an N-sulfo glucosamine residue. Here, we report the cooperative effects between N-deacetylase and N-sulfotransferase activities. Using baculovirus expression in insect cells, we obtained three recombinant proteins: full-length NDST-1 and the individual N-deacetylase and N-sulfotransferase domains. Structurally defined oligosaccharide substrates were synthesized to test the substrate specificities of the enzymes. We discovered that N-deacetylation is the limiting step and that interplay between the N-sulfotransferase and N-deacetylase accelerates the reaction. Furthermore, combining the individually expressed N-deacetylase and N-sulfotransferase domains produced different sulfation patterns when compared with that made by the NDST-1 enzyme. Our data demonstrate the essential role of domain cooperation within NDST-1 in producing HS with specific domain structures. PMID:26109066

  9. High-temperature ultraviolet detection based on surface photovoltage effect in SiN passivated n-GaN films

    NASA Astrophysics Data System (ADS)

    Matys, M.; Adamowicz, B.; Zytkiewicz, Z. R.; Taube, A.; Kruszka, R.; Piotrowska, A.

    2016-08-01

    We investigated the surface photovoltage (SPV) effect in n-GaN layers passivated with various insulators, i.e., Al2O3, SiO2, and SiN for ultraviolet (UV) light detection. We revealed that SPV in SiN/GaN shows markedly different behaviour than in oxide/GaN, i.e., the photo-signal exhibited very fast response (1 s) and recovery (2 s) times, contrary to oxide/GaN, and it was thermally stable up to 523 K. Furthermore, SPV spectra for SiN/GaN showed a sharp cut-off edge directly corresponding to the GaN band gap. We explained these results in terms of the different band structure of SiN/GaN and oxide/GaN junctions. All the observed properties of SPV response from SiN/GaN indicate that this relatively simple system can be applied to sensitive high temperature visible-blind UV detection.

  10. Pure AlN layers in metal-polar AlGaN/AlN/GaN and AlN/GaN heterostructures grown by low-temperature ammonia-based molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Kaun, Stephen W.; Mazumder, Baishakhi; Fireman, Micha N.; Kyle, Erin C. H.; Mishra, Umesh K.; Speck, James S.

    2015-05-01

    When grown at a high temperature (820 °C) by ammonia-based molecular beam epitaxy (NH3-MBE), the AlN layers of metal-polar AlGaN/AlN/GaN heterostructures had a high GaN mole fraction (∼0.15), as identified by atom probe tomography in a previous study (Mazumder et al 2013 Appl. Phys. Lett. 102 111603). In the study presented here, growth at low temperature (<740 °C) by NH3-MBE yielded metal-polar AlN layers that were essentially pure at the alloy level. The improved purity of the AlN layers grown at low temperature was correlated to a dramatic increase in the sheet density of the two-dimensional electron gas (2DEG) at the AlN/GaN heterointerface. Through application of an In surfactant, metal-polar AlN(3.5 nm)/GaN and AlGaN/AlN(2.5 nm)/GaN heterostructures grown at low temperature yielded low 2DEG sheet resistances of 177 and 285 Ω/□, respectively.

  11. Registration of N614, A3N615, N616, and N617 Shattercane Genetic Stocks with cytoplasmic or nuclear male-sterility and juicy or dry midribs

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Four shattercane [Sorghum bicolor subsp. drummondii (Nees ex Steud) de Wet & Harlan] genetic stocks, N614, A3N615, N616, N617 (Reg. No. XXX, PI 665683 to 665686), with A3 cytoplasmic male-sterility or nuclear male-sterility gene ms3 containing either juicy (dd) or dry (DD) culms were developed joint...

  12. 40 CFR 721.10193 - 1-Butanaminium, N-(3-aminopropyl)-N-butyl-N-(2-carboxyethyl)-, N-coco acyl derivs., inner salts.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false 1-Butanaminium, N-(3-aminopropyl)-N-butyl-N-(2-carboxyethyl)-, N-coco acyl derivs., inner salts. 721.10193 Section 721.10193 Protection of... CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10193 1-Butanaminium,...

  13. Reactive N emissions from beef cattle feedlots

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Large amounts of nitrogen (N) are fed to meet the nutritional needs of beef cattle in feedlots. However, only from 10 to 15% of fed N is retained in animals. Most N is excreted. Chemical and biological processes transform manure N into ammonia, nitrous oxide and nitrate. These reactive forms of ...

  14. Ion irradiation induced disappearance of dislocations in a nickel-based alloy

    NASA Astrophysics Data System (ADS)

    Chen, H. C.; Li, D. H.; Lui, R. D.; Huang, H. F.; Li, J. J.; Lei, G. H.; Huang, Q.; Bao, L. M.; Yan, L.; Zhou, X. T.; Zhu, Z. Y.

    2016-06-01

    Under Xe ion irradiation, the microstructural evolution of a nickel based alloy, Hastelloy N (US N10003), was studied. The intrinsic dislocations are decorated with irradiation induced interstitial loops and/or clusters. Moreover, the intrinsic dislocations density reduces as the irradiation damage increases. The disappearance of the intrinsic dislocations is ascribed to the dislocations climb to the free surface by the absorption of interstitials under the ion irradiation. Moreover, the in situ annealing experiment reveals that the small interstitial loops and/or clusters induced by the ion irradiation are stable below 600 °C.

  15. "N"-2 Repetition Costs Depend on Preparation in Trials "n"-1 and "n"-2

    ERIC Educational Resources Information Center

    Scheil, Juliane; Kleinsorge, Thomas

    2014-01-01

    In task switching, a common result supporting the notion of inhibitory processes as a determinant of switch costs is the occurrence of "n"-2 repetition costs. Evidence suggests that this effect is not affected by preparation. However, the role of preparation on preceding trials has been neglected so far. In this study, evidence for an…

  16. 100-N Area underground storage tank closures

    SciTech Connect

    Rowley, C.A.

    1993-08-01

    This report describes the removal/characterization actions concerning underground storage tanks (UST) at the 100-N Area. Included are 105-N-LFT, 182-N-1-DT, 182-N-2-DT, 182-N-3-DT, 100-N-SS-27, and 100-N-SS-28. The text of this report gives a summary of remedial activities. In addition, correspondence relating to UST closures can be found in Appendix B. Appendix C contains copies of Unusual Occurrence Reports, and validated sampling data results comprise Appendix D.

  17. Large N model of bose gases

    NASA Astrophysics Data System (ADS)

    Ke, Ke; Radzihovsky, Leo

    2009-10-01

    We construct the large N model of bose gases. Using an artificial parameter 1/N to do the perturbative analysis to study two models: U(N) bose gases and U(1) xO(N) bose gases. We find that for the U(N) model we get the same Bogoliubov spectrum and LHY thermal dynamical relations with ordinary bose gases. For the U(1) xO(N) model, however, we calculate dispersion relation, chemical potential and free energy when N goes to infinity and find that every quantities depends on the ration of two scattering length and √(na^3).

  18. Educación no formal

    NASA Astrophysics Data System (ADS)

    Tignanelli, H.

    Se comentan en esta comunicación, las principales contribuciones realizadas en el campo de la educación en astronomía en los niveles primario, secundario y terciario, como punto de partida para la discusión de la actual inserción de los contenidos astronómicos en los nuevos contenidos curriculares de la EGB - Educación General Básica- y Polimodal, de la Reforma Educativa. En particular, se discuten los alcances de la educación formal y no formal, su importancia para la capacitación de profesores y maestros, y perspectivas a futuro.

  19. A Detailed Chemical Kinetic Reaction Mechanism for n-Alkane Hydrocarbons from n-Octane to n-Hexadecane

    SciTech Connect

    Westbrook, C K; Pitz, W J; Herbinet, O; Silke, E J; Curran, H J

    2007-09-25

    Detailed chemical kinetic reaction mechanisms have been developed to describe the pyrolysis and oxidation of the n-alkanes, including n-octane (n-C{sub 8}H{sub 18}), n-nonane (n-C{sub 9}H{sub 20}), n-decane (n-C{sub 10}H{sub 22}), n-undecane (n-C{sub 11}H{sub 24}), n-dodecane (n-C{sub 12}H{sub 26}), n-tridecane (n-C{sub 13}H{sub 28}), n-tetradecane (n-C{sub 14}H{sub 30}), n-pentadecane (n-C{sub 15}H{sub 32}), and n-hexadecane (n-C{sub 16}H{sub 34}). These mechanisms include both high temperature and low temperature reaction pathways. The mechanisms are based on previous mechanisms for n-heptane, using the same reaction class mechanism construction developed initially for n-heptane. Individual reaction class rules are as simple as possible in order to focus on the parallelism between all of the n-alkane fuels included in the mechanisms, and there is an intent to develop these mechanisms further in the future to incorporate greater levels of accuracy and predictive capability. Several of these areas for improvement are identified and explained in detail. These mechanisms are validated through comparisons between computed and experimental data from as many different sources as possible. In addition, numerical experiments are carried out to examine features of n-alkane combustion in which the detailed mechanisms can be used to compare processes in all of the n-alkane fuels. The mechanisms for all of these n-alkanes are presented as a single detailed mechanism, which can be edited to produce efficient mechanisms for any of the n-alkanes included, and the entire mechanism, with supporting thermochemical and transport data, together with an explanatory glossary explaining notations and structural details, will be available on our web page when the paper is accepted for publication.

  20. Influence of InGaN sub-quantum-well on performance of InAlN/GaN/InAlN resonant tunneling diodes

    NASA Astrophysics Data System (ADS)

    Chen, Haoran; Yang, Lin'an; Hao, Yue

    2014-08-01

    The resonant tunneling mechanism of the GaN based resonant tunneling diode (RTD) with an InGaN sub-quantum-well has been investigated by means of numerical simulation. At resonant-state, Electrons in the InGaN/InAlN/GaN/InAlN RTD tunnel from the emitter region through the aligned discrete energy levels in the InGaN sub-quantum-well and GaN main-quantum-well into the collector region. The implantation of the InGaN sub-quantum-well alters the dominant transport mechanism, increase the transmission coefficient and give rise to the peak current and peak-to-valley current ratio. We also demonstrate that the most pronounced negative-differential-resistance characteristic can be achieved by choosing appropriately the In composition of InxGa1-xN at around x = 0.06.

  1. Influence of InGaN sub-quantum-well on performance of InAlN/GaN/InAlN resonant tunneling diodes

    SciTech Connect

    Chen, Haoran; Yang, Lin'an Hao, Yue

    2014-08-21

    The resonant tunneling mechanism of the GaN based resonant tunneling diode (RTD) with an InGaN sub-quantum-well has been investigated by means of numerical simulation. At resonant-state, Electrons in the InGaN/InAlN/GaN/InAlN RTD tunnel from the emitter region through the aligned discrete energy levels in the InGaN sub-quantum-well and GaN main-quantum-well into the collector region. The implantation of the InGaN sub-quantum-well alters the dominant transport mechanism, increase the transmission coefficient and give rise to the peak current and peak-to-valley current ratio. We also demonstrate that the most pronounced negative-differential-resistance characteristic can be achieved by choosing appropriately the In composition of In{sub x}Ga{sub 1−x}N at around x = 0.06.

  2. Catalytic diamination of olefins via N-N bond activation.

    PubMed

    Zhu, Yingguang; Cornwall, Richard G; Du, Haifeng; Zhao, Baoguo; Shi, Yian

    2014-12-16

    CONSPECTUS: Vicinal diamines are important structural motifs present in various biologically and chemically significant molecules. Direct diamination of olefins provides an effective approach to this class of compounds. Unlike well-established oxidation processes such as epoxidation, dihydroxylation, and aminohydroxylation, direct diamination of olefins had remained a long-standing challenge and had been less well developed. In this Account, we summarize our recent studies on Pd(0)- and Cu(I)-catalyzed diaminations of olefins using di-tert-butyldiaziridinone and its related analogues as nitrogen sources via N-N bond activation. A wide variety of imidazolidinones, cyclic sulfamides, indolines, imidazolinones, and cyclic guanidines can be obtained from conjugated dienes and terminal olefins. For conjugated dienes, the diamination proceeds regioselectively at the internal double bond with the Pd(0) catalyst. Mechanistic studies show that the diamination likely involves a four-membered Pd(II) species resulting from the insertion of Pd(0) into the N-N bond of di-tert-butyldiaziridinone. Interestingly, the Cu(I)-catalyzed process occurs regioselectively at either the terminal or internal double bond depending on the reaction conditions via two mechanistically distinct pathways. The Cu(I) catalyst cleaves the N-N bond of di-tert-butyldiaziridinone to form a Cu(II) nitrogen radical and a four-membered Cu(III) species, which are likely in rapid equilibrium. The Cu(II) nitrogen radical and the four-membered Cu(III) species lead to the terminal and internal diamination, respectively. Terminal olefins are effectively C-H diaminated at the allylic and homoallylic carbons with Pd(0) as catalyst and di-tert-butyldiaziridinone as nitrogen source, likely involving a diene intermediate generated in situ from the terminal olefin via formation of a π-allyl Pd complex and subsequent β-hydride elimination. When di-tert-butylthiadiaziridine 1,1-dioxide is used as nitrogen source

  3. Reflections on the "N" + "k" Queens Problem

    ERIC Educational Resources Information Center

    Chatham, Doug

    2009-01-01

    The "N" queens problem is a classic puzzle. It asks for an arrangement of "N" mutually non-attacking queens on an "N" x "N" chessboard. We discuss a recent variation called the "N" + "k" queens problem, where pawns are added to the chessboard to allow a greater number of non-attacking queens to be placed on it. We describe some of what is known…

  4. N=1 supersymmetric {beta}-functions

    SciTech Connect

    Jones, D. R. T.

    1997-06-15

    Recent results on three-loop, four-loop and large-N{sub f}{beta}-functions in supersymmetric gauge theories are summarised. It is argued that the O(1/N{sub f})-corrected form of {beta}{sub g} in SQCD is consistent with the existence of the conformal window 3N{sub c}/2<N{sub f}<3N{sub c}.

  5. Bootstrapping N=2 chiral correlators

    NASA Astrophysics Data System (ADS)

    Lemos, Madalena; Liendo, Pedro

    2016-01-01

    We apply the numerical bootstrap program to chiral operators in four-dimensional N=2 SCFTs. In the first part of this work we study four-point functions in which all fields have the same conformal dimension. We give special emphasis to bootstrapping a specific theory: the simplest Argyres-Douglas fixed point with no flavor symmetry. In the second part we generalize our setup and consider correlators of fields with unequal dimension. This is an example of a mixed correlator and allows us to probe new regions in the parameter space of N=2 SCFTs. In particular, our results put constraints on relations in the Coulomb branch chiral ring and on the curvature of the Zamolodchikov metric.

  6. Investigation of Gd3N@C2n (40 n 44) family by Raman and inelastic electron tunneling spectroscopy

    SciTech Connect

    Burke, Brian; Chan, Jack; Williams, Keith A; Ge, Jiechao; Shu, Chunying; Fu, Wujun; Dorn, Harry C; Kushmerick, James G; Puretzky, Alexander A; Geohegan, David B

    2010-01-01

    The structure and vibrational spectrum of Gd3N@C80 is studied through Raman and inelastic electron tunneling spectroscopy as well as density-functional theory and universal force eld calculations. Hindered rotations, shown by both theory and experiment, indicate the formation of a Gd3N-C80 bond which reduces the ideal icosahedral symmetry of the C80 cage. The vibrational modes involving the movement of the encapsulated species are a ngerprint of the interaction between the fullerene cage and the core complex. We present Raman data for the Gd3N@C2n 40 n 44 family as well as Y3N@C80, Lu3N@C80, and Y3N@C88 for comparison. Conductance measurements have been performed on Gd3N@C80 and reveal a Kondo effect similar to that observed in C60.

  7. Hole transport in N,N-bis(2,2-diphenylvinyl)-N,N'-diphenylbenzidine- doped poly(styrene)

    NASA Astrophysics Data System (ADS)

    Sinicropi, John A.; Cowdery-Corvan, J. R.; Magin, Edward H.; Borsenberger, Paul M.

    1996-10-01

    Hole mobilities have been measured in poly(styrene) (PS) doped with N,N-bis(2,2-diphenylvinyl)-N,N'-diphenylbenzidine (ENA). ENA is a weakly polar donor molecule with a dipole moment of 0.86 Debye. The mobilities were unexpectedly high, exceeding 10-3 cm2/Vs at high fields. The results are described within the framework of a formalism based on disorder, due to Bassler and coworkers. The formalism is based on the argument that charge transport occurs by hopping through a manifold of localized states that are distributed in energy. The key parameters of the formalism are the energy width of the hoping site manifold, the degree of positional disorder, and the prefactor mobility. For ENA doped PS, the widths are between 0.079 and 0.090 eV, increasing with increasing dilution. The widths are described by an argument based on dipolar disorder. The argument is based on the assumption that the total width is comprised of a dipolar component and a van der Waals component. Due to the very low dipole moment of ENA, the dipolar component is near-zero and the total width determined by the van der Waals component. The degree of positional disorder is between 1.6 and 4.8, increasing with increasing dilution. The prefactor mobilities are between 4.2 multiplied by 10-5 and 1.9 multiplied by 10-2 cm2/Vs, and can be described by a wavefunction decay constant (rho) 0 of 1.0 angstrom.

  8. Microsolvation for the Dicyanamide Anion: [N(CN)2-](H2O)n (n=0-12)

    SciTech Connect

    Jagoda-Cwiklik, Barbra; Wang, Xue B.; Woo, Hin-Koon; Yang, Jie; Wang, Guanjun; Zhou, Mingfei; Jungwirth, Pavel; Wang, Lai S.

    2007-08-16

    Photoelectron spectroscopy is combined with ab initio calculations to study the microsolvation of the dicyanamide anion, N(CN)2 -. Photoelectron spectra of [N(CN)2-] (H2O)n (n = 0-12) have been measured at room temperature and also at low temperature for n= 0-4. Vibrationally resolved photoelectron spectra are obtained for N(CN)2-, allowing the electron affinity of the N(CN)2 radical to be determined accurately as 4.135 ±0.010 eV. The electron binding energies and the spectral width of the hydrated clusters are observed to increase with the number of water molecules. The first five waters are observed to provide significant stabilization to the solute, whereas the stabilization becomes weaker for n > 5. The spectral width, which carries information about the solvent reorganization upon electron detachment in [N(CN)2-](H2O)n, levels off for n > 6. Theoretical calculations reveal several close-lying isomers for n= 1 and 2 due to the fact that the N(CN)2- anion possesses three almost equivalent hydration sites. In all the hydrated clusters, the most stable structures consist of a water cluster solvating one end of the N(CN)2- anion.

  9. Elimination of surface band bending on N-polar InN with thin GaN capping

    SciTech Connect

    Kuzmík, J. Haščík, Š.; Kučera, M.; Kúdela, R.; Dobročka, E.; Adikimenakis, A.; Mičušík, M.; Gregor, M.; Plecenik, A.; Georgakilas, A.

    2015-11-09

    0.5–1 μm thick InN (0001) films grown by molecular-beam epitaxy with N- or In-polarity are investigated for the presence of native oxide, surface energy band bending, and effects introduced by 2 to 4 monolayers of GaN capping. Ex situ angle-resolved x-ray photo-electron spectroscopy is used to construct near-surface (GaN)/InN energy profiles, which is combined with deconvolution of In3d signal to trace the presence of InN native oxide for different types of polarity and capping. Downwards surface energy band bending was observed on bare samples with native oxide, regardless of the polarity. It was found that the In-polar InN surface is most readily oxidized, however, with only slightly less band bending if compared with the N-polar sample. On the other hand, InN surface oxidation was effectively mitigated by GaN capping. Still, as confirmed by ultra-violet photo-electron spectroscopy and by energy band diagram calculations, thin GaN cap layer may provide negative piezoelectric polarization charge at the GaN/InN hetero-interface of the N-polar sample, in addition to the passivation effect. These effects raised the band diagram up by about 0.65 eV, reaching a flat-band profile.

  10. N+CPT clock resonance

    SciTech Connect

    Crescimanno, M.; Hohensee, M.

    2008-12-15

    In a typical compact atomic time standard a current modulated semiconductor laser is used to create the optical fields that interrogate the atomic hyperfine transition. A pair of optical sidebands created by modulating the diode laser become the coherent population trapping (CPT) fields. At the same time, other pairs of optical sidebands may contribute to other multiphoton resonances, such as three-photon N-resonance [Phys. Rev. A 65, 043817 (2002)]. We analyze the resulting joint CPT and N-resonance (hereafter N+CPT) analytically and numerically. Analytically we solve a four-level quantum optics model for this joint resonance and perturbatively include the leading ac Stark effects from the five largest optical fields in the laser's modulation comb. Numerically we use a truncated Floquet solving routine that first symbolically develops the optical Bloch equations to a prescribed order of perturbation theory before evaluating. This numerical approach has, as input, the complete physical details of the first two excited-state manifolds of {sup 87}Rb. We test these theoretical approaches with experiments by characterizing the optimal clock operating regimes.

  11. Quantum algebra of N superspace

    SciTech Connect

    Hatcher, Nicolas; Restuccia, A.; Stephany, J.

    2007-08-15

    We identify the quantum algebra of position and momentum operators for a quantum system bearing an irreducible representation of the super Poincare algebra in the N>1 and D=4 superspace, both in the case where there are no central charges in the algebra, and when they are present. This algebra is noncommutative for the position operators. We use the properties of superprojectors acting on the superfields to construct explicit position and momentum operators satisfying the algebra. They act on the projected wave functions associated to the various supermultiplets with defined superspin present in the representation. We show that the quantum algebra associated to the massive superparticle appears in our construction and is described by a supermultiplet of superspin 0. This result generalizes the construction for D=4, N=1 reported recently. For the case N=2 with central charges, we present the equivalent results when the central charge and the mass are different. For the {kappa}-symmetric case when these quantities are equal, we discuss the reduction to the physical degrees of freedom of the corresponding superparticle and the construction of the associated quantum algebra.

  12. Nitrogen input 15N-signatures are reflected in plant 15N natural abundances of N-rich tropical forest in China

    NASA Astrophysics Data System (ADS)

    Abdisa Gurmesa, Geshere; Lu, Xiankai; Gundersen, Per; Yunting, Fang; Mo, Jiangming

    2016-04-01

    In this study, we tested the measurement of natural abundance of 15N (δ15N) for its ability to assess changes in N cycling due to increased N deposition in two forest types; namely, an old-growth broadleaved forest and a pine forest, in southern China. We measured δ15N values of inorganic N in input and output fluxes under ambient N deposition, and N concentration and δ15N of major ecosystem compartments under ambient and increased N deposition. Our results showed that N deposition to the forests was 15N-depleted, and was dominated by NH4-N. Plants were 15N-depleted due to imprint from the 15N-depleted atmospheric N deposition. The old-growth forest had larger N concentration and was more 15N-enriched than the pine forest. Nitrogen addition did not significantly affect N concentration, but it significantly increased δ15N values of plants, and slightly more so in the pine forest, toward the 15N signature of the added N in both forests. The result indicates that the pine forest may rely more on the 15N-depleted deposition N. Soil δ15N values were slightly decreased by the N addition. Our result suggests that ecosystem δ15N is more sensitive to the changes in ecosystem N status and N cycling than N concentration in N-saturated sub-tropical forests.

  13. On the cytotoxic activity of Pd(II) complexes of N,N-disubstituted-N'-acyl thioureas.

    PubMed

    Plutín, Ana M; Mocelo, Raúl; Alvarez, Anislay; Ramos, Raúl; Castellano, Eduardo E; Cominetti, Marcia R; Graminha, Angelica E; Ferreira, Antonio G; Batista, Alzir A

    2014-05-01

    The rational design of anticancer drugs is one of the most promising strategies for increasing their cytotoxicity and for minimizing their toxicity. Manipulation of the structure of ligands or of complexes represents a strategy for which is possible to modify the potential mechanism of their action against the cancer cells. Here we present the cytotoxicity of some new palladium complexes and our intention is to show the importance of non-coordinated atoms of the ligands in the cytotoxicity of the complexes. New complexes of palladium (II), with general formulae [Pd(PPh3)2(L)]PF6 or [PdCl(PPh3)(L)], where L=N,N-disubstituted-N'-acyl thioureas, were synthesized and characterized by elemental analysis, molar conductivity, melting points, IR, NMR((1)H, (13)C and (31)P{(1)H}) spectroscopy. The spectroscopic data are consistent with the complexes containing an O, S chelated ligand. The structures of complexes with N,N-dimethyl-N'-benzoylthiourea, N,N-diphenyl-N'-benzoylthiourea, N,N-diethyl-N'-furoylthiourea, and N,N-diphenyl-N'-furoylthiourea were determined by X-ray crystallography, confirming the coordination of the ligands with the metal through sulfur and oxygen atoms, forming distorted square-planar structures. The N,N-disubstituted-N'-acyl thioureas and their complexes were screened with respect to their antitumor cytotoxicity against DU-145 (human prostate cancer cells), MDA-MB-231 (human breast cancer cells) and their toxicity against the L929 cell line (health cell line from mouse). PMID:24561278

  14. [Spatial Variation of Ammonia-N, Nitrate-N and Nitrite-N in Groundwater of Dongshan Island].

    PubMed

    Wiu, Hai-yan; Fu, Shi-feng; Cai, Xiao-qiong; Tang, Kun-xian; Cao, Chao; Chen, Qing-hui; Liang, Xiu-yu

    2015-09-01

    In Dongshan Island, groundwater is the main resource of the local residents' drinking water, domestic water, agriculture irrigation and freshwater aquaculture. This study aimed to investigate the spatial distribution characteristic and its variation pattern of ammonia-N, nitrate-N and nitrite-N in groundwater, as well as its pollution source and influence factors. It is very important to understand the pollution level of ammonia-N, nitrate-N and nitrite-N in groundwater of Dongshan Island, the control and prevention of ammonia-N, nitrate-N and nitrite-N pollution, which is of great significance to the residents' health. In this study, the spatial variability characteristics of ammonia-N, nitrate-N and nitrite-N concentration in groundwater of Dongshan Island was analysed by geo- statistic method, the values of the non-observation points were determined by Kriging method, and the pollution characteristics of ammonia-N, nitrate-N and nitrite-N in groundwater of Dongshan Island was also analyzed. Our results showed that the ammonia-N and nitrite-N concentration in groundwater of Dongshan Island were at low levels, but their spatial variability were high, and their autocorrelation were poor; however, the nitrate-N concentration was general high, its spatial variability was moderate, and the autocorrelation was much good. The distribution characteristics of ammonia-N, nitrate-N and nitrite-N in groundwater of Dongshan Island were similar that the high concentration areas were all located in the coastal land. The domestic pollutants and human and animal wastes from towns and villages were the main sources of nitrogen pollution, which would be the first step to control the nitrogen pollution of Dongshan Island. Land use pattern, soil type, groundwater depth, pH, dissolved oxygen, season, and the existence of Fe2+, were the impact factors that influence the distribution and transformation of ammonia-N, nitrate-N and nitrite-N in groundwater, which could be the considerable

  15. Surface donor states distribution post SiN passivation of AlGaN/GaN heterostructures

    SciTech Connect

    Goyal, Nitin; Fjeldly, Tor A.

    2014-07-21

    In this paper, we present a physics based analytical model to describe the effect of SiN passivation on two-dimensional electron gas density and surface barrier height in AlGaN/GaN heterostructures. The model is based on an extraction technique to calculate surface donor density and surface donor level at the SiN/AlGaN interface. The model is in good agreement with the experimental results and promises to become a useful tool in advanced design and characterization of GaN based heterostructures.

  16. [Spatial Variation of Ammonia-N, Nitrate-N and Nitrite-N in Groundwater of Dongshan Island].

    PubMed

    Wiu, Hai-yan; Fu, Shi-feng; Cai, Xiao-qiong; Tang, Kun-xian; Cao, Chao; Chen, Qing-hui; Liang, Xiu-yu

    2015-09-01

    In Dongshan Island, groundwater is the main resource of the local residents' drinking water, domestic water, agriculture irrigation and freshwater aquaculture. This study aimed to investigate the spatial distribution characteristic and its variation pattern of ammonia-N, nitrate-N and nitrite-N in groundwater, as well as its pollution source and influence factors. It is very important to understand the pollution level of ammonia-N, nitrate-N and nitrite-N in groundwater of Dongshan Island, the control and prevention of ammonia-N, nitrate-N and nitrite-N pollution, which is of great significance to the residents' health. In this study, the spatial variability characteristics of ammonia-N, nitrate-N and nitrite-N concentration in groundwater of Dongshan Island was analysed by geo- statistic method, the values of the non-observation points were determined by Kriging method, and the pollution characteristics of ammonia-N, nitrate-N and nitrite-N in groundwater of Dongshan Island was also analyzed. Our results showed that the ammonia-N and nitrite-N concentration in groundwater of Dongshan Island were at low levels, but their spatial variability were high, and their autocorrelation were poor; however, the nitrate-N concentration was general high, its spatial variability was moderate, and the autocorrelation was much good. The distribution characteristics of ammonia-N, nitrate-N and nitrite-N in groundwater of Dongshan Island were similar that the high concentration areas were all located in the coastal land. The domestic pollutants and human and animal wastes from towns and villages were the main sources of nitrogen pollution, which would be the first step to control the nitrogen pollution of Dongshan Island. Land use pattern, soil type, groundwater depth, pH, dissolved oxygen, season, and the existence of Fe2+, were the impact factors that influence the distribution and transformation of ammonia-N, nitrate-N and nitrite-N in groundwater, which could be the considerable

  17. 2-Chloro-N-isopropyl-N-phenyl­acetamide

    PubMed Central

    Yuan, Mao-Sen; Li, Zhi-peng; Wang, Qi

    2010-01-01

    In the title compound, C11H14ClNO, the herbicide propachlor, there are significant differences between the three N—C bond lengths [N—Ccarbon­yl = 1.354 (3) Å, N—Cphen­yl = 1.444 (2) Å and N—Cisoprop­yl = 1.496 (3) Å], indicating the presence of π delocalization involving the carbonyl group. The N atom lies 0.074 (2) Å from the plane defined by the the three bonded C atoms. PMID:21588328

  18. Effects of GaN interlayer on the transport properties of lattice-matched AlInN/AlN/GaN heterostructures

    SciTech Connect

    Wu, F.; Gao, K. H. Li, Z. Q.; Lin, T.; Zhou, W. Z.

    2015-04-21

    We study the effects of GaN interlayer on the transport properties of two-dimensional electron gases confined in lattice-matched AlInN/AlN/GaN heterostructures. It is found that the Hall mobility is evidently enhanced when an additional ultrathin GaN interlayer is introduced between AlInN and AlN layers. The enhancement of the Hall mobility is especially remarkable at low temperature. The high Hall mobility results in a low sheet resistance of 23 Ω/◻ at 2 K. Meanwhile, Shubnikov-de Haas oscillations (SdH) are also remarkably enhanced due to the existence of GaN interlayer. The enhancement of the SdH oscillations is related to the larger quantum mobility μ{sub q} owing to the suppression of the interface roughness, alloy disorder, and ionized impurity scatterings by the GaN interlayer.

  19. Photoactive azoimine dyes: 4-(2-pyridylazo)-N,N-diethylaniline and 4-(2-pyridylazo)-N,N-dimethylaniline: computational and experimental investigation.

    PubMed

    Yoopensuk, Suthirat; Tongying, Pornthip; Hansongnern, Kanidtha; Pakawatchai, Chaveng; Saithong, Saowanit; Tantirungrotechai, Yuthana; Leesakul, Nararak

    2012-02-01

    4-(2-Pyridylazo)-N,N-dimethylaniline and 4-(2-pyridylazo)-N,N-diethylaniline, two photoactive azoimine dyes, were prepared from the reaction of 2-aminopyridine with N,N-dialkyl-1,4-nitrosoaniline at room temperature. Structural characterizations of these dyes using single crystal X-ray diffraction, (1)H NMR, elemental analysis, mass spectroscopy and IR spectroscopy have been carried out. The X-ray structure indicates a trans configuration around the azo group. The photochemical behavior of these compounds differs from that of 2-phenylazopyridine, the non-dialkylamino substituent compound. The synthesized compounds show emission spectra at room temperature while 2-phenylazopyridine does not. The excitation spectra of these compounds differ from their absorption spectra which can be explained on the basis of the trans to cis photoisomerization which is supported by the TD-PBE0/6-31G(d,p) calculations. Both oxidation of the dialkylamino substituents (-NR(2); R=-CH(3) and -C(2)H(5)) and reduction of -N=N-/-N=N-(-) and -N=N-(-)/-N=N-(2-) were observed in the cyclic voltammogram indicating a π-acidity of both dyes. PMID:22137011

  20. 40 CFR Table 1 to Subpart N of... - General Provisions Applicability to Subpart N

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... Subpart N 1 Table 1 to Subpart N of Part 63 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Electroplating and Chromium Anodizing Tanks Pt. 63, Subpt. N, Table 1 Table 1 to Subpart N of Part 63—General...) and (h) of subpart N specify the frequency of periodic reports of monitoring data used to...

  1. 40 CFR 721.520 - Alanine, N-(2-carboxyethyl)-N-alkyl-, salt.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...)(4), (c)(4) (where N = 100). The requirement of 40 CFR 721.91(a)(4) that the amount of the substance... 40 Protection of Environment 31 2014-07-01 2014-07-01 false Alanine, N-(2-carboxyethyl)-N-alkyl... Specific Chemical Substances § 721.520 Alanine, N-(2-carboxyethyl)-N-alkyl-, salt. (a) Chemical...

  2. 40 CFR 721.520 - Alanine, N-(2-carboxyethyl)-N-alkyl-, salt.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...)(4), (c)(4) (where N = 100). The requirement of 40 CFR 721.91(a)(4) that the amount of the substance... 40 Protection of Environment 32 2013-07-01 2013-07-01 false Alanine, N-(2-carboxyethyl)-N-alkyl... Specific Chemical Substances § 721.520 Alanine, N-(2-carboxyethyl)-N-alkyl-, salt. (a) Chemical...

  3. 40 CFR 721.520 - Alanine, N-(2-carboxyethyl)-N-alkyl-, salt.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...)(4), (c)(4) (where N = 100). The requirement of 40 CFR 721.91(a)(4) that the amount of the substance... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Alanine, N-(2-carboxyethyl)-N-alkyl... Specific Chemical Substances § 721.520 Alanine, N-(2-carboxyethyl)-N-alkyl-, salt. (a) Chemical...

  4. 40 CFR 721.520 - Alanine, N-(2-carboxyethyl)-N-alkyl-, salt.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...)(4), (c)(4) (where N = 100). The requirement of 40 CFR 721.91(a)(4) that the amount of the substance... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Alanine, N-(2-carboxyethyl)-N-alkyl... Specific Chemical Substances § 721.520 Alanine, N-(2-carboxyethyl)-N-alkyl-, salt. (a) Chemical...

  5. 40 CFR 721.520 - Alanine, N-(2-carboxyethyl)-N-alkyl-, salt.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...)(4), (c)(4) (where N = 100). The requirement of 40 CFR 721.91(a)(4) that the amount of the substance... 40 Protection of Environment 32 2012-07-01 2012-07-01 false Alanine, N-(2-carboxyethyl)-N-alkyl... Specific Chemical Substances § 721.520 Alanine, N-(2-carboxyethyl)-N-alkyl-, salt. (a) Chemical...

  6. 40 CFR Table 1 to Subpart N of... - General Provisions Applicability to Subpart N

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... Subpart N 1 Table 1 to Subpart N of Part 63 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Electroplating and Chromium Anodizing Tanks Pt. 63, Subpt. N, Table 1 Table 1 to Subpart N of Part 63—General...) No § 63.347(g) and (h) of subpart N specify the frequency of periodic reports of monitoring data...

  7. Eta(') mass and chiral symmetry breaking at large N(c) and N(f).

    PubMed

    Girlanda, L; Stern, J; Talavera, P

    2001-06-25

    We propose a method for implementing the large- N(c), large-N(f) limit of QCD at the effective Lagrangian level. Depending on the value of the ratio N(f)/N(c), different patterns of chiral symmetry breaking can arise, leading in particular to different behaviors of the eta(') mass in the combined large-N limit. PMID:11415379

  8. Variation in internal N efficiency of maize and impact on yield-goal based N recommendations

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Internal N efficiency (IE) is defined as grain dry matter (DM) produced per unit of N in the above-ground plant at physiological maturity (R6). Internal N efficiency defines the target for plant N content at R6 in yield-goal based N rate recommendations (currently used in 30 U.S. states) and several...

  9. Eta(') mass and chiral symmetry breaking at large N(c) and N(f).

    PubMed

    Girlanda, L; Stern, J; Talavera, P

    2001-06-25

    We propose a method for implementing the large- N(c), large-N(f) limit of QCD at the effective Lagrangian level. Depending on the value of the ratio N(f)/N(c), different patterns of chiral symmetry breaking can arise, leading in particular to different behaviors of the eta(') mass in the combined large-N limit.

  10. On the unitary representations of N=2 and N=4 superconformal algebras

    NASA Astrophysics Data System (ADS)

    Eguchi, Tohru; Taormina, Anne

    1988-08-01

    We discuss the relationship between the unitary representations of N=2 and N=4 superconformal algebras. We describe how the N=4 irreducible representations decompose into those of N=2 algebra. We also describe the modular properties of N=4 superconformal characters.

  11. Ntrace a 15N tracing model to analyse gross N transformations and sources of gaseous N emissions

    NASA Astrophysics Data System (ADS)

    Muller, Christoph

    2013-04-01

    Anthropogenically generated reactive nitrogen (N) cascades throughout the global environment ...(Galloway and Cowling, 2002). This reactive N may be lost from ecosystems via leaching, as nitrate (NO3-), or in gaseous forms such as ammonia and nitrous oxide (N2O) and the loss is governed by the N dynamics of the system. Thus, to be rendered environmentally benign NO3- must be reduced to a non-reactive form, dinitrogen (N2) which requires the evaluation of three major biological pathways of NO3- reduction: i) assimilatory NO3- reduction into biomass, ii) dissimilatory NO3- reduction to NH4+ (DNRA) and iii) dissimilatory NO3- reduction to N2 (denitrification) ...(Burger and Jackson, 2004). Advanced techniques based on 15N tracing in combination with suitable model analyses are the method of choice to analyse complex N interactions and simultaneous N transformation process. Techniques are based on dilution - enrichment principles and usually rely on the simultaneous labelling of various N pools. The data sets are then analysed by suitable 15N tracing models which allow the individual N transformation rates to be calculated based on realistic kinetic settings. The 15N tracing model Ntrace has been developed to analyse the simultaneously occurring N transformation rates in soil-plant systems and includes submodels for the evaluation of the processes associated with gaseous N emissions. The 15N tracing model and some typical model results will be presented. Literature cited .Burger, M., and Jackson, L. E. (2004). Plant and microbial use and turnover: rapid conversion of nitrate to ammonium in soil with roots. Plant and Soil 266, 289-301. Galloway, J. N., and Cowling, E. B. (2002). Reactive nitrogen and the world: 200 years of change. Ambio 31, 64-71. .

  12. Characterization of AlInN/GaN structures on AlN templates for high-performance ultraviolet photodiodes

    NASA Astrophysics Data System (ADS)

    Sakai, Yusuke; Khai, Pum Chian; Ichikawa, Junki; Egawa, Takashi; Jimbo, Takashi

    2011-02-01

    The authors characterize AlInN/GaN structures on AlN templates for high-performance ultraviolet photodiodes. AlInN/GaN structures were grown with various growth parameters by metal organic chemical vapor deposition. In the case of nearly lattice-matched to GaN underlying layers, AlInN/GaN structures are found to have smooth interface. AlInN layers grown at the low pressure are confirmed to have high crystal quality from x-ray diffraction measurements and good surface morphology from atomic force microscope images. The noble AlInN-based photodiodes were fabricated. Their performances show the leakage current of 48 nA at a reverse voltage of 5 V and the cutoff wavelength around 260 nm. A cutoff-wavelength responsivity of 21.84 mA/W is obtained, corresponding to quantum efficiency of 10.6%. It may be possible to realize high-performance ultraviolet photodiodes by further optimizing AlInN/GaN structures.

  13. AlN/air distributed Bragg reflector by GaN sublimation from microcracks of AlN

    NASA Astrophysics Data System (ADS)

    Mitsunari, T.; Tanikawa, T.; Honda, Y.; Yamaguchi, M.; Amano, H.

    2013-05-01

    We report the fabrication of a four-period AlN/air distributed Bragg reflector (DBR) by in-situ GaN sublimation from microcracks of AlN. The GaN/AlN multilayer structure was grown on a stripe-patterned and dot-patterned Si substrate, and subsequently annealed at 1200 °C in H2 and NH3 atmosphere. Microcracks were observed on the surface and side face of the A1N/air DBRs. We achieved an AlN/air structure by the decomposition of GaN from the microcracks of AlN. Partially crack-free AlN layers were observed over a 5×5 μm area in the c-plane of AlN/air DBRs. The root mean square (RMS) values of the surface and back surface of stripe-patterned AlN/air DBRs were 0.94 and 3.3 nm, respectively. The relative reflectivity was measured using a He-Cd laser (442 nm). In some areas, stripe-patterned and dot-patterned AlN/air DBRs showed a high reflectivity of 83.7% and 90.7%, respectively, at the wavelength of 442 nm.

  14. Mechanisms of intestinal absorption of the carcinogen MNNG (N-Methyl-N'-nitro-N-nitrosoguanidine)

    SciTech Connect

    Koyama, S.Y.; Hollander, D.; Dadufalza, V.

    1988-06-01

    The authors studied the characteristics and mechanisms of MNNG (N-methyl-N'-nitro-N-nitrosoguanidine) intestinal absorption and the interaction between bile acids and fatty acids and MNNG absorption rat in vivo in male Sprague-Dawley rats. They found that MNNG was absorbed by simple passive diffusion. Transport of MNNG was the highest at pH 6.0. The addition of the bile salt, taurocholate by itself, greatly increased MNNG absorption, while the addition of the long-chain unsaturated fatty acids, oleic and linoleic, decreased the rate of absorption of MNNG. The phospholipid lecithin addition to the perfusate did not change the rate of MNNG absorption. Induction of dietary vitamin A deficiency (serum vitamin A level decreased from 40.9 to 13.7 ..mu..g/dl) did not change the absorption rate of MNNG. These studies demonstrate that bile acids, dietary fatty acids, and the pH of the intestinal content can modify the rate of absorption of this carcinogen by the small intestine. Since initial intestinal absorption determines serum levels and subsequent reabsorption and enterohepatic cycling determines long-term lumenal levels, serum levels, and total body content, factors which modify the rate of intestinal absorption of MNNG could also modify its carcinogenicity.

  15. Regioselective synthesis of cationic 6-deoxy-6-(N,N,N-trialkylammonio)curdlan derivatives.

    PubMed

    Zhang, Ruoran; Liu, Shu; Edgar, Kevin J

    2016-01-20

    Curdlan, a bioactive β-1,3-glucan, is of intense interest for pharmaceutical and biomedical applications. Cationic derivatives of curdlan and other polysaccharides are especially attractive for their potential to interact in controlled fashion with proteins, among many other possible applications, but relatively few methods exist for their synthesis. Herein we report a regioselective method for preparation of cationic, water-soluble 6-(N,N,N-trialkylammonio)-6-deoxycurdlan salts by reaction of 6-bromo-6-deoxycurdlan and its 2,4-O-diesters with trialkylamines. Dimethyl sulfoxide was identified as the optimal solvent for this nucleophilic displacement to produce cationic curdlan derivatives (80 °C, 24h), providing maximum degree of triethylammonium substitution (DS) of 0.89, exclusively at the C-6 position. 6-Bromo-6-deoxycurdlan was also reacted with heterocyclic amines such as pyridine and imidazole, providing ammonium-substituted curdlan derivatives with substantial DS (0.66 and 0.86, respectively). The new combination of regioselective Furuhata bromination and bromine displacement under optimized conditions with tertiary amines provides access to quaternized curdlan derivatives that possess high, permanent positive charge and are readily water-soluble, properties that indicate potential application promise including for mucoadhesion, permeation enhancement, and delivery of genes and anionic drugs. Regioselectivity and DS of those curdlan ammonium derivatives were quantified by means of (1)H NMR, (13)C NMR and FTIR spectroscopic methods and by elemental analysis. PMID:26572378

  16. Controlled synthesis of N,N,N-trimethyl chitosan for modulated bioadhesion and nasal membrane permeability.

    PubMed

    Pardeshi, Chandrakantsing V; Belgamwar, Veena S

    2016-01-01

    In an experiment to explore the bioadhesion, biocompatibility, and membrane permeation properties, the controlled synthesis of N,N,N-trimethyl chitosan (TMC) was carried out by two-step reductive methylation of chitosan (CHT). Methylation was confirmed by (1)H NMR (δ=3.1 ppm) and FTIR analysis (CH stretch at 1,485 cm(-1)). The TMC was further characterized by DSC, TGA, XRD, HR-TEM, SEM, and elemental analysis. Findings revealed improved solubility, enhanced viscosity, increased swelling index and higher molecular weight of TMC over CHT. Comparative evaluation validated increased bioadhesion potential, and improved ex vivo biocompatibility of TMC compared to CHT. Increased bioadhesion of TMC NPs over CHT NPs can be attributed to the strong electrostatic interactions between cationic amino groups with anionic sialic and sulfonic acid moieties contained in the mucin of the nasal mucus. Ex vivo biocompatibility studies suggested that the NP formulations of both biopolymers were biocompatible and could be applied safely on the nasal epithelium. Ex vivo permeation studies executed on excised cattle nasal mucosa illustrated improved permeability of TMC NPs over CHT NPs. In the author's opinion, two-step reductive methylation of CHT could be an attractive strategy to improve its solubility, bioadhesion, and permeation characteristics without affecting biocompatibility across the mucosal surfaces.

  17. Genetic control of sensitivity of rats to gastrocarcinogenesis by N-methyl-N'-nitro-N-nitrosoguanidine.

    PubMed

    Ohgaki, H; Kawachi, T; Matsukura, N; Morino, K; Sugimura, T

    1982-01-01

    The administration of N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) in drinking water induces tumours, mainly adenocarcinomas in the glandular stomach of rats. The sensitivities of different strains of rats to gastrocarcinogenesis induced by MNNG vary: Wistar and ACI strains are sensitive, whereas the Buffalo strain is resistant. Genetic analyses were made on the induction of gastric tumous by MNNG in the ACI and Buffalo strains and their F1 and F2 hybrids. Rats of both sexes, 7-9 weeks old, were given 83 micrograms of MNNG/ml of drinking water for 32 weeks and sacrificed in experimental week 72. The incidences of gastric tumours were as follows: ACI strain, male 80%, female 63%; Buffalo strain, male 29%, female 6%; F1 hybrid, male 35%, female 9%; F2 hybrid, male 65%, female 29%. There were no significant differences in the sensitivities of Buffalo X ACI F1 and ACI X Buffalo F1, or of Buffalo X ACI F2 and ACI X Buffalo F2. These results show that the gene(s) controlling resistance to MNNG is autosomal in the Buffalo strain and is inherited dominantly by F1 and F2 hybrids. In both strains and their hybrids, the incidence of gastric tumours was higher in males than in females.

  18. AlGaN/InGaN Photocathode Development

    SciTech Connect

    Buckley, J. H.; Leopold, D. J.

    2008-12-24

    An increase in quantum efficiency in photodetectors could result in a proportional reduction in the area of atmospheric Cherenkov telescopes and an even larger reduction in cost. We report on the development of high quantum efficiency, high gain, UV/blue photon-counting detectors based on AlGaN/InGaN photocathode heterostructures grown by molecular beam epitaxy. This research could eventually result in nearly ideal light detectors with a number of distinct advantages over existing technologies for numerous applications in high-energy physics and particle astrophysics. Potential advantages include much lower noise detection, better stability and radiation resistance than other cathode structures, high VUV sensitivity and very low radioactive background levels for deep underground experiments, and high detection efficiency for the detection of individual VUV-visible photons. We are also developing photocathodes with intrinsic gain, initially improving the detection efficiency of hybrid semiconductor-vacuum tube devices and eventually leading to a new type of all-solid-state photomultiplier device.

  19. N*(1535) electroproduction at high Q2

    SciTech Connect

    G. Ramalho, M.T. Pena, K. Tsushima

    2012-04-01

    A covariant spectator quark model is applied to study the {gamma}N {yields} N*(1535) reaction in the large Q{sup 2} region. Starting from the relation between the nucleon and N*(1535) systems, the N*(1535) valence quark wave function is determined without the addition of any parameters. The model is then used to calculate the {gamma}N {yields} N*(1535) transition form factors. A very interesting, useful relation between the A{sub 1/2} and S{sub 1/2} helicity amplitudes for Q{sup 2} > GeV{sup 2}, is also derived.

  20. Large N Model of Bose Gas

    NASA Astrophysics Data System (ADS)

    Ke, Ke; Radzihovsky, Leo

    2010-03-01

    We construct the large N model of bose gas. Using an artificial parameter 1/N to do the perturbative analysis to study two models: U(N) bose gas and U(1) xO(N) bose gas. We find that for U(N) bose gas we get Bogoliubov spectrum and LHY thermal dynamical relations which is the same as the usual weak coupling bose gas models. For U(1) xO(N) bose gas model, however, we calculate the non-perturbative quantum correction to the depletion, chemical potential, free energy and dispersion relations.

  1. Mismatch relaxation by stacking fault formation of AlN islands in AlGaN/GaN structures on m-plane GaN substrates

    SciTech Connect

    Smalc-Koziorowska, Julita; Sawicka, Marta; Skierbiszewski, Czeslaw; Grzegory, Izabella

    2011-08-08

    We study the mismatch relaxation of 2-5 nm thin elongated AlN islands formed during growth of AlGaN on bulk m-plane GaN by molecular beam epitaxy. The relaxation of these m-plane AlN layers is anisotropic and occurs through the introduction of stacking faults in [0001] planes during island coalescence, while no relaxation is observed along the perpendicular [1120] direction. This anisotropy in the mismatch relaxation and the formation of stacking faults in the AlN islands are explained by the growth mode of the AlN platelets and their coalescence along the [0001] direction.

  2. N2O and δ15N-N2O and δ18O-N2O from polar ice cores: interpretable data for interglacials

    NASA Astrophysics Data System (ADS)

    Bock, Michael; Schmitt, Jochen; Seth, Barbara; Beck, Jonas; Fischer, Hubertus

    2014-05-01

    Ice cores provide a wealth of information on climate change. For instance, the history of the atmospheric greenhouse gas N2O can be reconstructed using air entrapped in polar ice cores. N2O has several sources in both terrestrial and marine ecosystems, predominantly wetland soils and oxygen minimum zones in the ocean. N2O records generally follow the climatic changes during the glacial-interglacial cycles with higher N2O mixing ratios during warmer climate stages. However, the underlying processes driving these changes are difficult to identify from N2O mixing ratios alone. Additional information on the individual sources and sinks are provided by stable isotope measurements. The emission fluxes of the dominant N2O sources are ascribed to several pathways (nitrification, denitrification), with characteristic fractionation factors for the nitrogen and oxygen isotope signatures of the generated N2O (δ15N-N2O and δ18O-N2O). In the end, the individual proportions of pathways are responsible for distinct δ15N-N2O and δ18O-N2O for the average terrestrial and marine sources. Here, we present new ice core measurements of δ15N-N2O and δ18O-N2O covering the Holocene, MIS 5 and MIS 11. For the past 15 kyrs the δ15N-N2O record shows a continuous decrease starting at 15 kyrs to about 6 kyrs; during the past 6 kyrs δ15N-N2O remains rather constant. The resemblance with a recently published global reconstruction of bulk δ15N is remarkable (McLauchlan et al. 2013, Nature). Taken at face value this could mean that mainly the terrestrial source signature changed rather than a shift in the relative proportions of the terrestrial and marine source. The integrity of N2O ice core records relies on the assumption that the measurements truly represent the past atmosphere. However, comparative analyses of different ice cores from the same age intervals show offsets in the N2O mixing ratios among the records. One likely assumption is that higher mixing ratios are due to in

  3. Electrical properties of GaN-based heterostructures adopting InAlN/AlGaN bilayer barriers

    NASA Astrophysics Data System (ADS)

    Xu, Z. Y.; Xu, F. J.; Huang, C. C.; Wang, J. M.; Zhang, X.; Yang, Z. J.; Wang, X. Q.; Shen, B.

    2016-08-01

    Electrical properties of GaN-based heterostructures adopting InAlN/AlGaN bilayer barriers are investigated by Hall-effect and current-voltage measurements. It is found that this structure possesses both merits of high two-dimensional electron gas (2DEG) density and low gate leakage current density, while maintaining high 2DEG mobility. Furthermore, temperature dependence of the 2DEG density in this structure is verified to follow a combined tendency of InAlN/GaN (increase) and AlGaN/GaN (decrease) heterostructures with increasing temperature from 90 K to 400 K, which is mainly caused by superposition of the effects from carrier thermal activation induced by extrinsic factors in InAlN layer and the reduced conduction-band discontinuity.

  4. Electrically conducting n-type AlGaN/GaN distributed Bragg reflectors grown by metalorganic chemical vapor deposition

    NASA Astrophysics Data System (ADS)

    Liu, Yuh-Shiuan; Haq, A. F. M. Saniul; Kao, Tsung-Ting; Mehta, Karan; Shen, Shyh-Chiang; Detchprohm, Theeradetch; Yoder, P. Douglas; Dupuis, Russell D.; Xie, Hongen; Ponce, Fernando A.

    2016-06-01

    We report an electrically conducting 40-pair silicon doped Al0.12Ga0.88N/GaN distributed Bragg reflector (DBR) grown by metalorganic chemical vapor deposition on a silicon doped n-type GaN template. Due to the relatively small lattice mismatch between AlGaN and GaN, strain managing layers are not required for crack-free n-DBR growth. The DBR demonstrates a peak reflectivity of 91.6% at 368 nm with stopband of 11 nm. In addition, the 40-pair n-DBR shows the vertical resistance of 5.5 Ω, which corresponds to bulk resistivity of 0.52 Ω cm, near the maximum measured current of 100 mA.

  5. Physics of gate leakage current in N-polar InAlN/GaN heterojunction field effect transistors

    SciTech Connect

    Goswami, Arunesh; Trew, Robert J.; Bilbro, Griff L.

    2014-10-28

    A physics based model of the gate leakage current in N-polar InAlN/GaN heterojunction field effect transistors is demonstrated. The model is based on the space charge limited current flow dominated by the effects of deep traps in the InAlN surface layer. The model predicts accurately the gate-leakage measurement data of the N-polar InAlN/GaN device with InAlN cap layer. In the pinch-off state, the gate leakage current conduction through the surface of the device in the drain access region dominates the current flow through the two dimensional electron gas channel. One deep trap level and two levels of shallow traps are extracted by fitting the model results with measurement data.

  6. Production of ArN+ ions in the reactions Ar++N2 and N2++Ar

    NASA Astrophysics Data System (ADS)

    Tosi, Paolo; Correale, Raffaele; Lu, Wenyun; Bassi, Davide

    1999-03-01

    We have studied the production of ArN+ starting from the two symmetric charge-state reactants Ar++N2 and N2++Ar. For both reactions we measured the total cross sections as a function of the relative energy, in the energy range from 5 to 45 eV. Estimates of the reaction thresholds and symmetry considerations suggest that the reaction Ar++N2 produces ArN+ essentially in its first excited state A 3Π, while the reaction N2++Ar produces ground state ArN+ ions. This fact explains the discrepancies between different estimates of the dissociation energy of ArN+ obtained in previous studies.

  7. Tests of N-85, N-86 and N-87 airfoil sections in the 11-inch high speed wind tunnel

    NASA Technical Reports Server (NTRS)

    Stack, John; Lindsey, W F

    1938-01-01

    Three airfoils, the N-85, the N-86, and the N-87, were tested at the request of the Bureau of Aeronautics, Navy Department, to determine the suitability of these sections for use as propeller-blade sections. Further tests of the NACA 0009-64 airfoil were also made to measure the aerodynamic effect of thickening the trailing edge in accordance with current propeller practice. The N-86 and the N-87 airfoils appear to be nearly equivalent aerodynamically and both are superior to the N-85 airfoil. Comparison of those airfoils with the previously developed NACA 2409-34 airfoils indicate that the NACA 2409-34 is superior, particularly at high speeds. Thickening the trailing edge appears to have a detrimental effect, although the effect may be small if the trailing-edge radius is less than 0.5 percent of the cord. The N-86 and the N-87 airfoils appear to be nearly equivalent.

  8. EBAC-DCC Analysis of World Data of pi N, gamma N, and N(e,e') Reactions

    SciTech Connect

    Hiroyuki Kamano,Tsung-Shung Lee

    2012-04-01

    The development, results, and prospect of the Dynamical Coupled-Channels analysis at Excited Baryon Analysis Center (EBAC-DCC) are reported. In this contribution, we report on the development, results, and prospect of EBAC. The EBAC project has three components, as illustrated in Fig. 1. The first task is to perform a dynamical coupled-channels analysis of the world data of {pi}N, {gamma}*N {yields} {pi}N, {eta}N, {pi}{pi}N, K{Lambda}, K{Sigma}, {omega}N, {hor_ellipsis} to determine the meson-baryon partial-wave amplitudes. The second step is to develop a procedure to extract the N* parameters from the determined partial-wave amplitudes. The third step is to investigate the interpretations of the extracted N* properties in terms of the available hadron models and Lattice QCD.

  9. Piezoelectric Franz-Keldysh effect in a GaN/InGaN/AlGaN multilayer structure

    NASA Astrophysics Data System (ADS)

    Hou, Yong T.; Teo, Kie L.; Li, Ming Fu; Uchida, Kazuo; Tokunaga, Hiroki; Akutsu, Nakao; Matsumoto, Koh

    1999-11-01

    Contactless electroreflectance (CER) of a GaN/InGaN/AlGaN multilayer structure grown on sapphire has been measured in the temperature range of 15K and 450K. Except for the GaN exciton structures, well-defined Franz-Keldysh Oscillations are observed above the AlGaN band gap. An electomodulational model based on complex Airy functions is used to analyze the FKOs line shape. The temperature dependence of transition energies is obtained both for GaN and AlGaN. The magnitude of the built in electric field in AlGaN layer is also determined. The temperature dependence of the electric field is found to be consistent with the variation of thermal strain in the epilayer. It is demonstrated that the built-in electric field can be identified to be due to the piezoelectric effect.

  10. N2H+ and N15NH+ toward the prestellar core 16293E in L1689N

    NASA Astrophysics Data System (ADS)

    Daniel, F.; Faure, A.; Pagani, L.; Lique, F.; Gérin, M.; Lis, D.; Hily-Blant, P.; Bacmann, A.; Roueff, E.

    2016-07-01

    Context. Understanding the processes that could lead to an enrichment of molecules in 15N atoms is of particular interest because this may shed light on the relatively strong variations observed in the 14N/15N ratio in various solar system environments. Aims: The sample of molecular clouds where 14N/15N ratios have been measured currently is small and has to be enlarged to allow statistically significant studies. In particular, the N2H+ molecule currently shows the broadest spread of 14N/15N ratios in high-mass star-forming regions. However, the 14N/15N ratio in N2H+ was obtained in only two low-mass star-forming regions (L1544 and B1b). We here extend this sample to a third dark cloud. Methods: We targeted the 16293E prestellar core, where the N15NH+J = 1-0 line was detected. Using a model previously developed for the physical structure of the source, we solved the molecular excitation with a nonlocal radiative transfer code. For this purpose, we computed specific collisional rate coefficients for the N15NH+-H2 collisional system. As a first step of the analysis, the N2H+ abundance profile was constrained by reproducing the N2H+J = 1-0 and 3-2 maps. A scaling factor was then applied to this profile to match the N15NH+J = 1-0 spectrum. Results: We derive a column density ratio N2H+/N15NH. Conclusions: We performed a detailed analysis of the excitation of N2H+ and N15NH+ in the direction of the 16293E core with modern models that solve the radiative transfer and with the most accurate collisional rate coefficients available to date. We obtained the third estimate of the N2H+/N15NH+ column density ratio in the direction of a cold prestellar core. The current estimate ~330 agrees with the typical value of the elemental isotopic ratio in the local interstellar medium. It is lower than in some other cores, however, where values as high as 1300 have been reported.

  11. Stability and aromaticity of nH2@B12N12 (n=1–12) clusters

    PubMed Central

    Giri, Santanab; Chakraborty, Arindam; Chattaraj, Pratim K.

    2011-01-01

    Standard ab initio and density functional calculations are carried out to determine the structure, stability, and reactivity of B12N12 clusters with hydrogen doping. To lend additional support, conceptual DFT-based reactivity descriptors and the associated electronic structure principles are also used. Related cage aromaticity of this B12N12 and nH2@B12N12 are analyzed through the nucleus independent chemical shift values. PMID:22110872

  12. Revisiting {N}=4 superconformal blocks

    NASA Astrophysics Data System (ADS)

    Bissi, Agnese; Łukowski, Tomasz

    2016-02-01

    We study four-point correlation functions of four generic half-BPS supermultiplets of {N}=4 SCFT in four dimensions. We use the two-particle Casimir of four-dimensional superconformal algebra to derive superconformal blocks which contribute to the partial wave expansion of such correlators. The derived blocks are defined on analytic superspace and allow us in principle to find any component of the four-point correlator. The lowest component of the result agrees with the superconformal blocks found by Dolan and Osborn.

  13. Frank N. Bash Symposium 2015

    NASA Astrophysics Data System (ADS)

    The University of Texas at Austin Department of Astronomy and McDonald Observatory will be hosting the sixth biennial Frank N. Bash Symposium on the topic of New Horizons in Astronomy, October 18-20, 2015, on The University of Texas at Austin campus. This meeting will bring together young researchers at the cutting edge of astronomy and astrophysics, to promote the exchange of research ideas and visions for the future of astronomy. The symposium will focus on invited review talks, and will include discussions and contributed poster papers from postdocs and students.

  14. N-(3-ethynylphenyl)maleimide

    NASA Technical Reports Server (NTRS)

    Hergenrother, Paul M. (Inventor); Connell, John W. (Inventor); Havens, Stephen J. (Inventor)

    1990-01-01

    Acetylene terminated aspartimides are prepared using two methods. In the first, an amino-substituted aromatic acetylene is reacted with an aromatic bismaleimide in a solvent of glacial acetic acid and/or m-cresol. In the second method, an aromatic diamine is reacted with an ethynyl containing maleimide, such as N-(3-ethynylphenyl) maleimide, in a solvent of glacial acetic acid and/or m-cresol. In addition, acetylene terminated aspartimides are blended with various acetylene terminated oligomers and polymers to yield composite materials exhibiting improved mechanical properties.

  15. Color tunable monolithic InGaN/GaN LED having a multi-junction structure.

    PubMed

    Kong, Duk-Jo; Kang, Chang-Mo; Lee, Jun-Yeob; Kim, James; Lee, Dong-Seon

    2016-03-21

    In this study, we have fabricated a blue-green color-tunable monolithic InGaN/GaN LED having a multi-junction structure with three terminals. The device has an n-p-n structure consisting of a green and a blue active region, i.e., an n-GaN / blue-MQW / p-GaN / green-MQW / n-GaN / Al2O3 structure with three terminals for independently controlling the two active regions. To realize this LED structure, a typical LED consisting of layers of n-GaN, blue MQW, and p-GaN is regrown on a conventional green LED by using a metal organic chemical vapor deposition (MOCVD) method. We explain detailed mechanisms of three operation modes which are the green, blue, and cyan mode. Moreover, we discuss optical properties of the device. PMID:27136884

  16. Color tunable monolithic InGaN/GaN LED having a multi-junction structure.

    PubMed

    Kong, Duk-Jo; Kang, Chang-Mo; Lee, Jun-Yeob; Kim, James; Lee, Dong-Seon

    2016-03-21

    In this study, we have fabricated a blue-green color-tunable monolithic InGaN/GaN LED having a multi-junction structure with three terminals. The device has an n-p-n structure consisting of a green and a blue active region, i.e., an n-GaN / blue-MQW / p-GaN / green-MQW / n-GaN / Al2O3 structure with three terminals for independently controlling the two active regions. To realize this LED structure, a typical LED consisting of layers of n-GaN, blue MQW, and p-GaN is regrown on a conventional green LED by using a metal organic chemical vapor deposition (MOCVD) method. We explain detailed mechanisms of three operation modes which are the green, blue, and cyan mode. Moreover, we discuss optical properties of the device.

  17. Energy relaxation of hot electrons in lattice-matched AlInN/AlN/GaN heterostructures

    SciTech Connect

    Zhang, J.-Z.; Dyson, A.; Ridley, B. K.

    2013-12-04

    Using the dielectric continuum model, hot-electron power dissipation and energy relaxation times are calculated for a typical lattice-matched AlInN/AlN/GaN heterostructure, including effects of hot phonons and screening from the mobile electrons. The calculated power dissipation and energy relaxation times are very close to the experimental data.

  18. Analysis of current instabilities of thin AlN/GaN/AlN double heterostructure high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Zervos, Ch; Adikimenakis, A.; Bairamis, A.; Kostopoulos, A.; Kayambaki, M.; Tsagaraki, K.; Konstantinidis, G.; Georgakilas, A.

    2016-06-01

    The current instabilities of high electron mobility transistors (HEMTs), based on thin double AlN/GaN/AlN heterostructures (˜0.5 μm total thickness), directly grown on sapphire substrates, have been analyzed and compared for different AlN top barrier thicknesses. The structures were capped by 1 nm GaN and non-passivated 1 μm gate-length devices were processed. Pulsed I-V measurements resulted in a maximum cold pulsed saturation current of 1.4 A mm-1 at a gate-source voltage of +3 V for 3.7 nm AlN thickness. The measured gate and drain lag for 500 ns pulse-width varied between 6%-12% and 10%-18%, respectively. Furthermore, a small increase in the threshold voltage was observed for all the devices, possibly due to the trapping of electrons under the gate contact. The off-state breakdown voltage of V br = 70 V, for gate-drain spacing of 2 μm, was approximately double the value measured for a single AlN/GaN HEMT structure grown on a thick GaN buffer layer. The results suggest that the double AlN/GaN/AlN heterostructures may offer intrinsic advantages for the breakdown and current stability characteristics of high current HEMTs.

  19. 15N Abundance of Nodules as an Indicator of N Metabolism in N2-Fixing Plants 1

    PubMed Central

    Shearer, Georgia; Feldman, Lori; Bryan, Barbara A.; Skeeters, Jerri L.; Kohl, Daniel H.; Amarger, Nöelle; Mariotti, Françoise; Mariotti, André

    1982-01-01

    This paper expands upon previous reports of 15N elevation in nodules (compared to other tissues) of N2-fixing plants. N2-Fixing nodules of Glycine max (soybeans), Vigna unguiculata (cowpea), Phaseolus vulgaris (common bean), Phaseolus coccineus (scarlet runner bean), Prosopis glandulosa (mesquite), and Olneya tesota (desert ironwood) were enriched in 15N. Nodules of Vicia faba (fava beans), Arachis hypogaea (peanut), Trifolium pratense (red clover), Pisum sativum (pea), Lathyrus sativus (grass pea), Medicago sativa (alfalfa), and Lupinus mutabilis (South American lupine) were not; nor were the nodules of nine species of N2-fixing nonlegumes. The nitrogen of ineffective nodules of soybeans and cowpeas was not enriched in 15N. Thus, 15N elevation in nodules of these plants depends on active N2-fixation. Results obtained so far on the generality of 15N enrichment in N2-fixing nodules suggest that only the nodules of plants which actively fix N2 and which transport allantoin or allantoic acid exhibit 15N enrichment. PMID:16662517

  20. 40 CFR Table Jj-7 to Subpart Jj of... - Nitrous Oxide Emission Factors (kg N2O-N/kg Kjdl N)

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 21 2011-07-01 2011-07-01 false Nitrous Oxide Emission Factors (kg N2O-N/kg Kjdl N) JJ Table JJ-7 to Subpart JJ of Part 98 Protection of Environment ENVIRONMENTAL... N2O-N/kg Kjdl N) Manure management system component N2O emission factor Uncovered anaerobic lagoon...

  1. Production of N2O/+/ by reaction of metastable O2/+/ ions with N2

    NASA Technical Reports Server (NTRS)

    Ajello, J. M.; Rayermann, P.

    1975-01-01

    Photoionization mass spectrometry examination of the production of N2O(+) was undertaken to determine whether N2(+) or O2(+) ions are responsible for onset of N2O(+). It appears that the N2(+) ion does not contribute significantly to the production of N2O(+) in this experiment. Therefore, it is clear that excited O2(+) is responsible for the formation of N2O(+) near the appearance potential of these ions.

  2. 40 CFR 721.10173 - Silanamine,1,1,1-triethoxy-N,N-diethyl-.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Silanamine,1,1,1-triethoxy-N,N-diethyl... Specific Chemical Substances § 721.10173 Silanamine,1,1,1-triethoxy-N,N-diethyl-. (a) Chemical substance...,1-triethoxy-N,N-diethyl- (PMN P-03-793; CAS No. 35077-00-0) is subject to reporting under...

  3. 40 CFR 721.10173 - Silanamine,1,1,1-triethoxy-N,N-diethyl-.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Silanamine,1,1,1-triethoxy-N,N-diethyl... Specific Chemical Substances § 721.10173 Silanamine,1,1,1-triethoxy-N,N-diethyl-. (a) Chemical substance...,1-triethoxy-N,N-diethyl- (PMN P-03-793; CAS No. 35077-00-0) is subject to reporting under...

  4. WH(n) under pressure.

    PubMed

    Zaleski-Ejgierd, Patryk; Labet, Vanessa; Strobel, Timothy A; Hoffmann, Roald; Ashcroft, N W

    2012-04-18

    An initial observation of the formation of WH under pressure from W gaskets surrounding hydrogen in diamond anvil cells led to a theoretical study of tungsten hydride phases. At P = 1 atm no stoichiometry is found to be stable with respect to separation into the elements, but as the pressure is raised WH(n) (n = 1-6, 8) stoichiometries are metastable or stable. WH and WH(4) are calculated to be stable at P > 15 GPa, WH(2) becomes stable at P > 100 GPa and WH(6) at P > 150 GPa. In agreement with experiment, the structure computed for WH is anti-NiAs. WH(2) shares with WH a hexagonal arrangement of tungsten atoms, with hydrogen atoms occupying octahedral and tetrahedral holes. For WH(4) the W atoms are in a distorted fcc arrangement. As the number of hydrogens rises, the coordination of W by H increases correspondingly, leading to a twelve-coordinated W in WH(6). In WH(8) H(2) units also develop. All of the hydrides considered should be metallic at high pressure, though the Fermi levels of WH(4) and WH(6) lie in a deep pseudogap. Prodded by these theoretical studies, experiments were then undertaken to seek phases other than WH, exploring a variety of experimental conditions that would favor further reaction. Though a better preparation and characterization of WH resulted, no higher hydrides have as yet been found. PMID:22418444

  5. Disorder in large- N theories

    NASA Astrophysics Data System (ADS)

    Aharony, Ofer; Komargodski, Zohar; Yankielowicz, Shimon

    2016-04-01

    We consider Euclidean Conformal Field Theories perturbed by quenched disorder, namely by random fluctuations in their couplings. Such theories are relevant for second-order phase transitions in the presence of impurities or other forms of disorder. Theories with quenched disorder often flow to new fixed points of the renormalization group. We begin with disorder in free field theories. Imry and Ma showed that disordered free fields can only exist for d > 4. For d > 4 we show that disorder leads to new fixed points which are not scale-invariant. We then move on to large- N theories (vector models or gauge theories in the `t Hooft limit). We compute exactly the beta function for the disorder, and the correlation functions of the disordered theory. We generalize the results of Imry and Ma by showing that such disordered theories exist only when disorder couples to operators of dimension Δ > d/4. Sometimes the disordered fixed points are not scale-invariant, and in other cases they have unconventional dependence on the disorder, including non-trivial effects due to irrelevant operators. Holography maps disorder in conformal theories to stochastic differential equations in a higher dimensional space. We use this dictionary to reproduce our field theory results. We also study the leading 1 /N corrections, both by field theory methods and by holography. These corrections are particularly important when disorder scales with the number of degrees of freedom.

  6. 40 CFR 721.3152 - Ethanaminium, N-ethyl-2-hydroxy-N,N-bis(2-hydroxyethyl)-, diester with C12-18 fatty acids, ethyl...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Ethanaminium, N-ethyl-2-hydroxy-N,N... Ethanaminium, N-ethyl-2-hydroxy-N,N-bis(2-hydroxyethyl)-, diester with C12-18 fatty acids, ethyl sulfates... ethanaminium, N-ethyl-2-hydroxy-N,N-bis(2-hydroxyethyl)-, diester with C12-18 fatty acids, ethyl...

  7. 40 CFR 721.3152 - Ethanaminium, N-ethyl-2-hydroxy-N,N-bis(2-hydroxyethyl)-, diester with C12-18 fatty acids, ethyl...

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Ethanaminium, N-ethyl-2-hydroxy-N,N... Ethanaminium, N-ethyl-2-hydroxy-N,N-bis(2-hydroxyethyl)-, diester with C12-18 fatty acids, ethyl sulfates... ethanaminium, N-ethyl-2-hydroxy-N,N-bis(2-hydroxyethyl)-, diester with C12-18 fatty acids, ethyl...

  8. Cone Penetrometer N Factor Determination Testing Results

    SciTech Connect

    Follett, Jordan R.

    2014-03-05

    This document contains the results of testing activities to determine the empirical 'N Factor' for the cone penetrometer in kaolin clay simulant. The N Factor is used to releate resistance measurements taken with the cone penetrometer to shear strength.

  9. The category of Z2 n -supermanifolds

    NASA Astrophysics Data System (ADS)

    Covolo, Tiffany; Grabowski, Janusz; Poncin, Norbert

    2016-07-01

    In physics and in mathematics Z2 n -gradings, n ≥ 2, appear in various fields. The corresponding sign rule is determined by the "scalar product" of the involved Z2 n -degrees. The Z2 n -supergeometry exhibits challenging differences with the classical one: nonzero degree even coordinates are not nilpotent, and even (respectively, odd) coordinates do not necessarily commute (respectively, anticommute) pairwise. In this article we develop the foundations of the theory: we define Z2 n -supermanifolds and provide examples in the ringed space and coordinate settings. We thus show that formal series are the appropriate substitute for nilpotency. Moreover, the class of Z2 • -supermanifolds is closed with respect to the tangent and cotangent functors. We explain that any n-fold vector bundle has a canonical "superization" to a Z2 n -supermanifold and prove that the fundamental theorem describing supermorphisms in terms of coordinates can be extended to the Z2 n -context.

  10. Coating MCPs with AlN and GaN

    NASA Technical Reports Server (NTRS)

    Bensaoula, Abdelhakim; Starikov, David; Boney, Chris

    2006-01-01

    A development effort underway at the time of reporting the information for this article is devoted to increasing the sensitivity of microchannel plates (MCPs) as detectors of photons and ions by coating the MCPs with nitrides of elements in period III of the periodic table. Conventional MCPs are relatively insensitive to slowly moving, large-mass ions for example, ions of biomolecules under analysis in mass spectrometers. The idea underlying this development is to coat an MCP to reduce its work function (decrease its electron affinity) in order to increase both (1) the emission of electrons in response to impingement of low-energy, large-mass ions and (2) the multiplying effect of secondary electron emission. Of particular interest as coating materials having appropriately low or even negative electron affinities are gallium nitride, aluminum nitride, and ternary alloys of general composition Al(x)Ga(1-x)N (where 0N and GaN both undoped and doped with Si were deposited on commercial MCPs by radio-frequency molecular-beam epitaxy (also known as plasma-assisted molecular-beam epitaxy) at temperatures <200 C. This deposition technique is particularly suitable because (1) MCPs cannot withstand the higher deposition-substrate temperatures used to decompose constituent compounds in some other deposition techniques and (2) in this technique, the constituent Al, Ga, and N

  11. Advanced heat exchanger development for molten salts

    DOE PAGESBeta

    Sabharwall, Piyush; Clark, Denis; Glazoff, Michael; Zheng, Guiqiu; Sridharan, Kumar; Anderson, Mark

    2014-12-01

    This study addresses present work concerned with advanced heat exchanger development for molten salt in nuclear and non nuclear thermal systems. The molten salt systems discussed herein use alloys, such as Hastelloy N and 242, which show corrosion resistance to molten salt at nominal operating temperatures up to 700°C. These alloys were diffusion welded, and the corresponding information is presented. Test specimens were prepared for exposing diffusion welds to molten salt environments. Hastelloy N and 242 were found to be weldable by diffusion welding, with ultimate tensile strengths about 90% of base metal values. Both diffusion welds and sheet materialmore » in Hastelloy N were corrosion tested in?58 mol% KF and 42 mol% ZrF4 at 650, 700, and 850°C for 200, 500, and 1,000 hours. Corrosion rates found were similar between welded and nonwelded materials, typically <10 mils per year. For materials of construction, nickel and alloys with dense nickel coatings are effectively inert to corrosion in fluorides, but not so in chlorides. Hence, additional testing of selected alloys for resistance to intergranular corrosion is needed, as is a determination of corrosion rate as a function of contaminant type and alloy composition with respect to chromium and carbon to better define the optimal chromium and carbon composition, independent of galvanic or differential solubility effects. Also presented is the division of the nuclear reactor and high temperature components per ASME standards, along with design requirements for a subcritical Rankine power cycle heat exchanger that has to overcome pressure difference of about 17 MPa.« less

  12. Advanced heat exchanger development for molten salts

    SciTech Connect

    Sabharwall, Piyush; Clark, Denis; Glazoff, Michael; Zheng, Guiqiu; Sridharan, Kumar; Anderson, Mark

    2014-12-01

    This study addresses present work concerned with advanced heat exchanger development for molten salt in nuclear and non nuclear thermal systems. The molten salt systems discussed herein use alloys, such as Hastelloy N and 242, which show corrosion resistance to molten salt at nominal operating temperatures up to 700°C. These alloys were diffusion welded, and the corresponding information is presented. Test specimens were prepared for exposing diffusion welds to molten salt environments. Hastelloy N and 242 were found to be weldable by diffusion welding, with ultimate tensile strengths about 90% of base metal values. Both diffusion welds and sheet material in Hastelloy N were corrosion tested in?58 mol% KF and 42 mol% ZrF4 at 650, 700, and 850°C for 200, 500, and 1,000 hours. Corrosion rates found were similar between welded and nonwelded materials, typically <10 mils per year. For materials of construction, nickel and alloys with dense nickel coatings are effectively inert to corrosion in fluorides, but not so in chlorides. Hence, additional testing of selected alloys for resistance to intergranular corrosion is needed, as is a determination of corrosion rate as a function of contaminant type and alloy composition with respect to chromium and carbon to better define the optimal chromium and carbon composition, independent of galvanic or differential solubility effects. Also presented is the division of the nuclear reactor and high temperature components per ASME standards, along with design requirements for a subcritical Rankine power cycle heat exchanger that has to overcome pressure difference of about 17 MPa.

  13. Dopant-free GaN/AlN/AlGaN radial nanowire heterostructures as high electron mobility transistors.

    PubMed

    Li, Yat; Xiang, Jie; Qian, Fang; Gradecak, Silvija; Wu, Yue; Yan, Hao; Blom, Douglas A; Lieber, Charles M

    2006-07-01

    We report the rational synthesis of dopant-free GaN/AlN/AlGaN radial nanowire heterostructures and their implementation as high electron mobility transistors (HEMTs). The radial nanowire heterostructures were prepared by sequential shell growth immediately following nanowire elongation using metal-organic chemical vapor deposition (MOCVD). Transmission electron microscopy (TEM) studies reveal that the GaN/AlN/AlGaN radial nanowire heterostructures are dislocation-free single crystals. In addition, the thicknesses and compositions of the individual AlN and AlGaN shells were unambiguously identified using cross-sectional high-angle annular darkfield scanning transmission electron microscopy (HAADF-STEM). Transport measurements carried out on GaN/AlN/AlGaN and GaN nanowires prepared using similar conditions demonstrate the existence of electron gas in the undoped GaN/AlN/AlGaN nanowire heterostructures and also yield an intrinsic electron mobility of 3100 cm(2)/Vs and 21,000 cm(2)/Vs at room temperature and 5 K, respectively, for the heterostructure. Field-effect transistors fabricated with ZrO(2) dielectrics and metal top gates showed excellent gate coupling with near ideal subthreshold slopes of 68 mV/dec, an on/off current ratio of 10(7), and scaled on-current and transconductance values of 500 mA/mm and 420 mS/mm. The ability to control synthetically the electronic properties of nanowires using band structure design in III-nitride radial nanowire heterostructures opens up new opportunities for nanoelectronics and provides a new platform to study the physics of low-dimensional electron gases.

  14. Low-n-6 and low-n-6 plus high-n-3 diets for use in clinical research

    PubMed Central

    MacIntosh, Beth A.; Ramsden, Christopher E.; Faurot, Keturah R.; Zamora, Daisy; Mangan, Margaret; Hibbeln, Joseph R.; Mann, J. Douglas

    2014-01-01

    Few trials have evaluated the metabolic effects and health outcomes of lowering dietary n-6 PUFA. The objectives of the present paper were (1) to report the methods employed to lower dietary n-6 PUFA, while either increasing or maintaining n-3 PUFA intake and (2) to validate our methods with 24 h recalls and erythrocyte fatty acid analyses. A total of sixty-seven subjects were randomised to either (1) an average-n-3 PUFA, low-n-6 PUFA (L6) intervention designed to lower linoleic acid (LA; ≤2·5 % of energy (en%)) and arachidonic acid (≤60 mg/d), while maintaining an average US intake of n-3 PUFA or (2) a high-n-3 PUFA, low-n-6 PUFA (H3-L6) intervention designed to lower n-6 LA, while increasing the n-3 PUFA α-linolenic acid (ALA; ≥1·5 en%) and EPA + DHA (≥1000 mg/d). Pre- and intra-intervention nutrient intakes were estimated with six 24 h dietary recalls per subject. Both groups achieved the targeted reductions in dietary LA to ≤2·5 en% (median LA 2·45 (2·1, 3·1); P<0·001). Intakes of n-3 PUFA did not change for the L6 group. Target increases in n-3 ALA (median 1·6 en%, (1·3, 2·0), P<0·001) and EPA + DHA (1482 mg, (374, 2558), P<0·001) were achieved in the H3-L6 group. Dietary changes were validated by corresponding changes in erythrocyte n-6 and n-3 fatty acid composition. Dietary LA can be lowered to ≤2·5 en%, with or without concurrent increases in dietary n-3 PUFA, in an outpatient clinical trial setting using this integrated diet method. PMID:23328113

  15. Consolidated Fleet N2Y-1

    NASA Technical Reports Server (NTRS)

    1930-01-01

    Consolidated Fleet N2Y-1: The Consolidated Fleet N2Y-1 aircraft were used as trainers for the pilots who would fly the 'parasite' fighters attached to the airships Akron and Macon. This N2Y-1 was turned over to the NACA for research work. Note that the vertical surfaces are instrumented for NACA work. This N2Y was used for landing gear tests.

  16. Hydration and vibrational dynamics of betaine (N,N,N-trimethylglycine)

    NASA Astrophysics Data System (ADS)

    Li, Tanping; Cui, Yaowen; Mathaga, John; Kumar, Revati; Kuroda, Daniel G.

    2015-06-01

    Zwitterions are naturally occurring molecules that have a positive and a negative charge group in its structure and are of great importance in many areas of science. Here, the vibrational and hydration dynamics of the zwitterionic system betaine (N,N,N-trimethylglycine) is reported. The linear infrared spectrum of aqueous betaine exhibits an asymmetric band in the 1550-1700 cm-1 region of the spectrum. This band is attributed to the carboxylate asymmetric stretch of betaine. The potential of mean force computed from ab initio molecular dynamic simulations confirms that the two observed transitions of the linear spectrum are related to two different betaine conformers present in solution. A model of the experimental data using non-linear response theory agrees very well with a vibrational model comprising of two vibrational transitions. In addition, our modeling shows that spectral parameters such as the slope of the zeroth contour plot and central line slope are both sensitive to the presence of overlapping transitions. The vibrational dynamics of the system reveals an ultrafast decay of the vibrational population relaxation as well as the correlation of frequency-frequency correlation function (FFCF). A decay of ˜0.5 ps is observed for the FFCF correlation time and is attributed to the frequency fluctuations caused by the motions of water molecules in the solvation shell. The comparison of the experimental observations with simulations of the FFCF from ab initio molecular dynamics and a density functional theory frequency map shows a very good agreement corroborating the correct characterization and assignment of the derived parameters.

  17. AlN interlayer to improve the epitaxial growth of SmN on GaN (0001)

    NASA Astrophysics Data System (ADS)

    Vézian, S.; Damilano, B.; Natali, F.; Khalfioui, M. Al; Massies, J.

    2016-09-01

    An in situ study of the epitaxial growth of SmN thin films on Ga-polar GaN (0001) templates by molecular beam epitaxy is reported. Using X-ray photoelectron spectroscopy we found that Ga segregates at the surface during the first stages of growth. We showed that the problem related to Ga surface segregation can be simply suppressed by growing a few monolayers of AlN before starting the SmN growth. This results in a significant improvement of the crystallinity of SmN thin films assessed by X-ray diffraction.

  18. Utilisation of GaN and InGaN/GaN with nanoporous structures for water splitting

    SciTech Connect

    Benton, J.; Bai, J.; Wang, T.

    2014-12-01

    We report a cost-effective approach to the fabrication of GaN based nanoporous structure for applications in renewable hydrogen production. Photoelectrochemical etching in a KOH solution has been employed to fabricate both GaN and InGaN/GaN nanoporous structures with pore sizes ranging from 25 to 60 nm, obtained by controlling both etchant concentration and applied voltage. Compared to as-grown planar devices the nanoporous structures have exhibited a significant increase of photocurrent with a factor of up to four times. An incident photon conversion efficiency of up to 46% around the band edge of GaN has been achieved.

  19. Fabrication of low-density GaN/AlN quantum dots via GaN thermal decomposition in MOCVD.

    PubMed

    Zhang, Jin; Li, Senlin; Xiong, Hui; Tian, Wu; Li, Yang; Fang, Yanyan; Wu, Zhihao; Dai, Jiangnan; Xu, Jintong; Li, Xiangyang; Chen, Changqing

    2014-01-01

    With an appropriate high anneal temperature under H2 atmosphere, GaN quantum dots (QDs) have been fabricated via GaN thermal decomposition in metal organic chemical vapor deposition (MOCVD). Based on the characterization of atomic force microscopy (AFM), the obtained GaN QDs show good size distribution and have a low density of 2.4 × 10(8) cm(-2). X-ray photoelectron spectroscopy (XPS) analysis demonstrates that the GaN QDs were formed without Ga droplets by thermal decomposition of GaN.

  20. Ab initio modeling of zincblende AlN layer in Al-AlN-TiN multilayers

    NASA Astrophysics Data System (ADS)

    Yadav, S. K.; Wang, J.; Liu, X.-Y.

    2016-06-01

    An unusual growth mechanism of metastable zincblende AlN thin film by diffusion of nitrogen atoms into Al lattice is established. Using first-principles density functional theory, we studied the possibility of thermodynamic stability of AlN as a zincblende phase due to epitaxial strains and interface effect, which fails to explain the formation of zincblende AlN. We then compared the formation energetics of rocksalt and zincblende AlN in fcc Al through direct diffusion of nitrogen atoms to Al octahedral and tetrahedral interstitials. The formation of a zincblende AlN thin film is determined to be a kinetically driven process, not a thermodynamically driven process.

  1. N-Terminal Acetylation-Targeted N-End Rule Proteolytic System: The Ac/N-End Rule Pathway

    PubMed Central

    Lee, Kang-Eun; Heo, Ji-Eun; Kim, Jeong-Mok; Hwang, Cheol-Sang

    2016-01-01

    Although Nα-terminal acetylation (Nt-acetylation) is a pervasive protein modification in eukaryotes, its general functions in a majority of proteins are poorly understood. In 2010, it was discovered that Nt-acetylation creates a specific protein degradation signal that is targeted by a new class of the N-end rule proteolytic system, called the Ac/N-end rule pathway. Here, we review recent advances in our understanding of the mechanism and biological functions of the Ac/N-end rule pathway, and its crosstalk with the Arg/N-end rule pathway (the classical N-end rule pathway). PMID:26883906

  2. Near infrared electroluminescence from n-InN/p-NiO/GaN light-emitting diode fabricated by PAMBE

    NASA Astrophysics Data System (ADS)

    Zhao, Yang; Wang, Hui; Zhuang, Shiwei; Wu, Guoguang; Leng, Jiyan; Li, Wancheng; Gao, Fubin; Zhang, Baolin; Du, Guotong

    2016-07-01

    The n-InN/p-NiO/GaN heterojunction was fabricated by using plasma-assisted molecular beam epitaxy (PAMBE) combined with radio frequency magnetron sputtering. The device exhibited typical rectification characteristic with a turn-on voltage of ~1.5 V. Under forward bias, a dominant near infrared emission (NIR) peaked around 1565 nm was detected at room temperature. The NIR emission was attributed to the band-edge emission of InN film according to the photoluminescence spectrum of InN layer. Furthermore, the mechanism of the current transport and light emission was tentatively discussed in terms of the band diagrams of the heterojunction.

  3. Hydrogen Generation using non-polar coaxial InGaN/GaN Multiple Quantum Well Structure Formed on Hollow n-GaN Nanowires.

    PubMed

    Park, Ji-Hyeon; Mandal, Arjun; Kang, San; Chatterjee, Uddipta; Kim, Jin Soo; Park, Byung-Guon; Kim, Moon-Deock; Jeong, Kwang-Un; Lee, Cheul-Ro

    2016-08-24

    This article demonstrates for the first time to the best of our knowledge, the merits of InGaN/GaN multiple quantum wells (MQWs) grown on hollow n-GaN nanowires (NWs) as a plausible alternative for stable photoelectrochemical water splitting and efficient hydrogen generation. These hollow nanowires are achieved by a growth method rather not by conventional etching process. Therefore this approach becomes simplistic yet most effective. We believe relatively low Ga flux during the selective area growth (SAG) aids the hollow nanowire to grow. To compare the optoelectronic properties, simultaneously solid nanowires are also studied. In this present communication, we exhibit that lower thermal conductivity of hollow n-GaN NWs affects the material quality of InGaN/GaN MQWs by limiting In diffusion. As a result of this improvement in material quality and structural properties, photocurrent and photosensitivity are enhanced compared to the structures grown on solid n-GaN NWs. An incident photon-to-current efficiency (IPCE) of around ~33.3% is recorded at 365 nm wavelength for hollow NWs. We believe that multiple reflections of incident light inside the hollow n-GaN NWs assists in producing a larger amount of electron hole pairs in the active region. As a result the rate of hydrogen generation is also increased.

  4. 7 CFR 29.2440 - (N Group).

    Code of Federal Regulations, 2012 CFR

    2012-01-01

    ... 7 Agriculture 2 2012-01-01 2012-01-01 false (N Group). 29.2440 Section 29.2440 Agriculture... INSPECTION Standards Grades § 29.2440 (N Group). Extremely common tobacco which does not meet the minimum... Grade names and specifications N1L First quality light colored nondescript, thin to medium body and...

  5. 7 CFR 29.2440 - (N Group).

    Code of Federal Regulations, 2013 CFR

    2013-01-01

    ... 7 Agriculture 2 2013-01-01 2013-01-01 false (N Group). 29.2440 Section 29.2440 Agriculture... INSPECTION Standards Grades § 29.2440 (N Group). Extremely common tobacco which does not meet the minimum... Grade names and specifications N1L First quality light colored nondescript, thin to medium body and...

  6. 7 CFR 29.2440 - (N Group).

    Code of Federal Regulations, 2014 CFR

    2014-01-01

    ... 7 Agriculture 2 2014-01-01 2014-01-01 false (N Group). 29.2440 Section 29.2440 Agriculture... INSPECTION Standards Grades § 29.2440 (N Group). Extremely common tobacco which does not meet the minimum... Grade names and specifications N1L First quality light colored nondescript, thin to medium body and...

  7. Hydrogen Generation using non-polar coaxial InGaN/GaN Multiple Quantum Well Structure Formed on Hollow n-GaN Nanowires.

    PubMed

    Park, Ji-Hyeon; Mandal, Arjun; Kang, San; Chatterjee, Uddipta; Kim, Jin Soo; Park, Byung-Guon; Kim, Moon-Deock; Jeong, Kwang-Un; Lee, Cheul-Ro

    2016-01-01

    This article demonstrates for the first time to the best of our knowledge, the merits of InGaN/GaN multiple quantum wells (MQWs) grown on hollow n-GaN nanowires (NWs) as a plausible alternative for stable photoelectrochemical water splitting and efficient hydrogen generation. These hollow nanowires are achieved by a growth method rather not by conventional etching process. Therefore this approach becomes simplistic yet most effective. We believe relatively low Ga flux during the selective area growth (SAG) aids the hollow nanowire to grow. To compare the optoelectronic properties, simultaneously solid nanowires are also studied. In this present communication, we exhibit that lower thermal conductivity of hollow n-GaN NWs affects the material quality of InGaN/GaN MQWs by limiting In diffusion. As a result of this improvement in material quality and structural properties, photocurrent and photosensitivity are enhanced compared to the structures grown on solid n-GaN NWs. An incident photon-to-current efficiency (IPCE) of around ~33.3% is recorded at 365 nm wavelength for hollow NWs. We believe that multiple reflections of incident light inside the hollow n-GaN NWs assists in producing a larger amount of electron hole pairs in the active region. As a result the rate of hydrogen generation is also increased. PMID:27556534

  8. 40 CFR 721.10055 - 1-Propanaminium, 3-amino-N-(carboxymethyl)-N,N-dimethyl-, N-soya acyl derivs., inner salts.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...-(carboxymethyl)-N,N-dimethyl-, N-soya acyl derivs., inner salts. 721.10055 Section 721.10055 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10055 1-Propanaminium,...

  9. 40 CFR 721.10055 - 1-Propanaminium, 3-amino-N-(carboxymethyl)-N,N-dimethyl-, N-soya acyl derivs., inner salts.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...-(carboxymethyl)-N,N-dimethyl-, N-soya acyl derivs., inner salts. 721.10055 Section 721.10055 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10055 1-Propanaminium,...

  10. 40 CFR 721.10055 - 1-Propanaminium, 3-amino-N-(carboxymethyl)-N,N-dimethyl-, N-soya acyl derivs., inner salts.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...-(carboxymethyl)-N,N-dimethyl-, N-soya acyl derivs., inner salts. 721.10055 Section 721.10055 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10055 1-Propanaminium,...

  11. 40 CFR 721.10055 - 1-Propanaminium, 3-amino-N-(carboxymethyl)-N,N-dimethyl-, N-soya acyl derivs., inner salts.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...-(carboxymethyl)-N,N-dimethyl-, N-soya acyl derivs., inner salts. 721.10055 Section 721.10055 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY (CONTINUED) TOXIC SUBSTANCES CONTROL ACT SIGNIFICANT NEW USES OF CHEMICAL SUBSTANCES Significant New Uses for Specific Chemical Substances § 721.10055 1-Propanaminium,...

  12. 40 CFR 721.10175 - 1-Propanaminium, N-(3-aminopropyl)-2-hydroxy-N,N-dimethyl-3-sulfo-, N-(C12-18 and C18-unsatd...

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...-hydroxy-N,N-dimethyl-3-sulfo-, N-(C12-18 and C18-unsatd. acyl) derivs., inner salts. 721.10175 Section 721...) derivs., inner salts. (a) Chemical substance and significant new uses subject to reporting. (1) The...-18 and C18-unsatd. acyl) derivs., inner salts (PMN P-04-141; CAS No. 691400-36-9) is subject...

  13. H7N9: Frequently Asked Questions

    MedlinePlus

    ... risk from this virus in the United States right now? No cases of human or bird infection with this H7N9 virus have ... considered to be low. Is it possible that human cases of H7N9 flu ... The most likely scenario for this right now would be H7N9 infection in a traveler ...

  14. Hydrogen Generation using non-polar coaxial InGaN/GaN Multiple Quantum Well Structure Formed on Hollow n-GaN Nanowires

    PubMed Central

    Park, Ji-Hyeon; Mandal, Arjun; Kang, San; Chatterjee, Uddipta; Kim, Jin Soo; Park, Byung-Guon; Kim, Moon-Deock; Jeong, Kwang-Un; Lee, Cheul-Ro

    2016-01-01

    This article demonstrates for the first time to the best of our knowledge, the merits of InGaN/GaN multiple quantum wells (MQWs) grown on hollow n-GaN nanowires (NWs) as a plausible alternative for stable photoelectrochemical water splitting and efficient hydrogen generation. These hollow nanowires are achieved by a growth method rather not by conventional etching process. Therefore this approach becomes simplistic yet most effective. We believe relatively low Ga flux during the selective area growth (SAG) aids the hollow nanowire to grow. To compare the optoelectronic properties, simultaneously solid nanowires are also studied. In this present communication, we exhibit that lower thermal conductivity of hollow n-GaN NWs affects the material quality of InGaN/GaN MQWs by limiting In diffusion. As a result of this improvement in material quality and structural properties, photocurrent and photosensitivity are enhanced compared to the structures grown on solid n-GaN NWs. An incident photon-to-current efficiency (IPCE) of around ~33.3% is recorded at 365 nm wavelength for hollow NWs. We believe that multiple reflections of incident light inside the hollow n-GaN NWs assists in producing a larger amount of electron hole pairs in the active region. As a result the rate of hydrogen generation is also increased. PMID:27556534

  15. Neuroblastoma—Versión para pacientes

    Cancer.gov

    Información del Instituto Nacional del Cáncer sobre el tratamiento y los exámenes de detección del neuroblastoma, así como referencias a estudios clínicos, investigación y otros temas relacionados con este tipo de cáncer.

  16. Hydrogen Generation using non-polar coaxial InGaN/GaN Multiple Quantum Well Structure Formed on Hollow n-GaN Nanowires

    NASA Astrophysics Data System (ADS)

    Park, Ji-Hyeon; Mandal, Arjun; Kang, San; Chatterjee, Uddipta; Kim, Jin Soo; Park, Byung-Guon; Kim, Moon-Deock; Jeong, Kwang-Un; Lee, Cheul-Ro

    2016-08-01

    This article demonstrates for the first time to the best of our knowledge, the merits of InGaN/GaN multiple quantum wells (MQWs) grown on hollow n-GaN nanowires (NWs) as a plausible alternative for stable photoelectrochemical water splitting and efficient hydrogen generation. These hollow nanowires are achieved by a growth method rather not by conventional etching process. Therefore this approach becomes simplistic yet most effective. We believe relatively low Ga flux during the selective area growth (SAG) aids the hollow nanowire to grow. To compare the optoelectronic properties, simultaneously solid nanowires are also studied. In this present communication, we exhibit that lower thermal conductivity of hollow n-GaN NWs affects the material quality of InGaN/GaN MQWs by limiting In diffusion. As a result of this improvement in material quality and structural properties, photocurrent and photosensitivity are enhanced compared to the structures grown on solid n-GaN NWs. An incident photon-to-current efficiency (IPCE) of around ~33.3% is recorded at 365 nm wavelength for hollow NWs. We believe that multiple reflections of incident light inside the hollow n-GaN NWs assists in producing a larger amount of electron hole pairs in the active region. As a result the rate of hydrogen generation is also increased.

  17. Semiconducting ZnSnN2 thin films for Si/ZnSnN2 p-n junctions

    NASA Astrophysics Data System (ADS)

    Qin, Ruifeng; Cao, Hongtao; Liang, Lingyan; Xie, Yufang; Zhuge, Fei; Zhang, Hongliang; Gao, Junhua; Javaid, Kashif; Liu, Caichi; Sun, Weizhong

    2016-04-01

    ZnSnN2 is regarded as a promising photovoltaic absorber candidate due to earth-abundance, non-toxicity, and high absorption coefficient. However, it is still a great challenge to synthesize ZnSnN2 films with a low electron concentration, in order to promote the applications of ZnSnN2 as the core active layer in optoelectronic devices. In this work, polycrystalline and high resistance ZnSnN2 films were fabricated by magnetron sputtering technique, then semiconducting films were achieved after post-annealing, and finally Si/ZnSnN2 p-n junctions were constructed. The electron concentration and Hall mobility were enhanced from 2.77 × 1017 to 6.78 × 1017 cm-3 and from 0.37 to 2.07 cm2 V-1 s-1, corresponding to the annealing temperature from 200 to 350 °C. After annealing at 300 °C, the p-n junction exhibited the optimum rectifying characteristics, with a forward-to-reverse ratio over 103. The achievement of this ZnSnN2-based p-n junction makes an opening step forward to realize the practical application of the ZnSnN2 material. In addition, the nonideal behaviors of the p-n junctions under both positive and negative voltages are discussed, in hope of suggesting some ideas to further improve the rectifying characteristics.

  18. An extrinsic fmax > 100 GHz InAlN/GaN HEMT with AlGaN back barrier

    NASA Astrophysics Data System (ADS)

    Bo, Liu; Zhihong, Feng; Shaobo, Dun; Xiongwen, Zhang; Guodong, Gu; Yuangang, Wang; Peng, Xu; Zezhao, He; Shujun, Cai

    2013-04-01

    We report the DC and RF performance of InAlN/GaN high-electron mobility transistors with AlGaN back barrier grown on SiC substrates. These presented results confirm the high performance that is reachable by InAlN-based technology. The InAlN/GaN HEMT sample showed a high 2DEG mobility of 1550 cm2/(V·s) at a 2DEG density of 1.7 × 1013 cm-2. DC and RF measurements were performed on the unpassivated device with 0.2 μm “T“ gate. The maximum drain current density at VGS = 2 V is close to 1.05 A/mm in a reproducible way. The reduction in gate leakage current helps to increase the frequency performance of AlGaN back barrier devices. The power gain cut-off frequency of a transistor with an AlGaN back barrier is 105 GHz, which is much higher than that of the device without an AlGaN back barrier at the same gate length. These results indicate InAlN/GaN HEMT is a promising candidate for millimeter-wave application.

  19. Epitaxial stabilization of cubic-SiN{sub x} in TiN/SiN{sub x} multilayers

    SciTech Connect

    Soederberg, Hans; Oden, Magnus; Larsson, Tommy; Hultman, Lars; Molina-Aldareguia, Jon M.

    2006-05-08

    The formation of cubic-phase SiN{sub x} is demonstrated in TiN/SiN{sub x} multilayers deposited by reactive dual magnetron sputtering. Transmission electron microscopy examination shows a transition from epitaxially stabilized growth of crystalline SiN{sub x} to amorphous growth as the layer thickness increases from 0.3 to 0.8 nm. The observations are supported by ab initio calculations on different polytypes, which show that the NaCl structure has the best lattice match to TiN. Calculations also reveal a large difference in elastic shear modulus between NaCl-SiN{sub x} and TiN. The results for phase structure and shear modulus offer an explanation for the superhardening effect determined by nanoindentation experiments.

  20. Crystal structure of bis-{N-[(di-ethyl-amino)-dimethyl-sil-yl]anilido-κ(2) N,N'}zinc.

    PubMed

    Chen, Juan

    2015-12-01

    The title zinc amide, [Zn(C12H21N2Si)2], was prepared by the metathetical reaction of [LiN(SiMe2NEt2)(C6H5)]2 with zinc dichloride. It is mononuclear and the mol-ecule is generated by twofold rotation symmetry. The central Zn(II) atom is N,N'-chelated by each of the two N-silylated anilide ligands in a highly distorted tetra-hedral environment. Two N-Si-N ligands are arranged in a cis fashion around the Zn(II) atom. The Zn-Namine bonds [2.2315 (12) Å] are much longer than the Zn-Nanilide bonds [1.9367 (11) Å]. PMID:26870447

  1. Effect of feeding system and breed on n-3 and n-6 polyunsaturated fatty acid content of lamb muscles

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Katahdin (KK, n=6), Katahdin x Suffolk (KS, n=6), Suffolk x Katahdin (SK, n=6) and Suffolk (SS, n=6) wethers were used to evaluate omega-3 (n-3) and omega-6 (n-6) polyunsaturated fatty acid content, and the ratio of n-6 to n-3 in muscles of these lambs, raised on concentrate or forage diets. Lambs ...

  2. Technical Note: Simultaneous measurement of sedimentary N2 and N2O production and new 15N isotope pairing technique

    NASA Astrophysics Data System (ADS)

    Hsu, T.-C.; Kao, S.-J.

    2013-04-01

    Dinitrogen (N2) and/or nitrous oxide (N2O) are produced through denitrification, anaerobic ammonium oxidation (anammox) or nitrification in sediments, of which entangled processes obfuscate the absolute rate estimation of gaseous nitrogen production from individual pathway. Recently, the classical isotope pairing technique (IPT), the most common 15N-nitrate enrichment method to quantify denitrification, has been modified by different researchers to (1) discriminate relative contribution of N2 production by denitrification from anammox or to (2) provide more accurate denitrification rate by considering both N2O and N2 productions. Both modified methods, however, have deficiencies such as overlooking N2O production in case 1 and neglecting anammox in case 2. In this paper, a new method was developed to refine previous methods. We installed cryogenic traps to pre-concentrate N2 and N2O separately, thus, allowing simultaneous measurement for two gases generated by one sample. The precision is better than 2% for N2 (m/z 28, m/z 29 and m/z 30), and 1.5% for N2O (m/z 44, m/z 45 and m/z 46). Based on the six m/z peaks of the two gases, we further revised IPT formulae to truthfully resolve the production rates of N2 and N2O contributed from 3 specific nitrogen removal processes, i.e. N2 and N2O from denitrification, N2 from anammox and N2O from nitrification. To validate the applicability of our new method, incubation experiments were conducted using sediment cores taken from the Danshuei estuary in Taiwan. We successfully determined the rates of aforementioned nitrogen removal processes. Moreover, N2O yield was as high as 66%, which no doubt would significantly bias previous IPT approaches when N2O was not considered. Our new method not only complements the previous IPT but also provides more comprehensive information to advance our understanding of nitrogen dynamics through the water-sediment interface.

  3. Modis-N airborne simulator

    NASA Technical Reports Server (NTRS)

    Cech, Steven D.

    1992-01-01

    All required work associated with the above referenced contract has been successfully completed at this time. The Modis-N Airborne Simulator has been developed from existing AB184 Wildfire spectrometer parts as well as new detector arrays, optical components, and associated mechanical and electrical hardware. The various instrument components have been integrated into an operational system which has undergone extensive laboratory calibration and testing. The instrument has been delivered to NASA Ames where it will be installed on the NASA ER-2. The following paragraphs detail the specific tasks performed during the contract effort, the results obtained during the integration and testing of the instrument, and the conclusions which can be drawn from this effort.

  4. Sweetwater, Texas Large N Experiment

    NASA Astrophysics Data System (ADS)

    Sumy, D. F.; Woodward, R.; Barklage, M.; Hollis, D.; Spriggs, N.; Gridley, J. M.; Parker, T.

    2015-12-01

    From 7 March to 30 April 2014, NodalSeismic, Nanometrics, and IRIS PASSCAL conducted a collaborative, spatially-dense seismic survey with several thousand nodal short-period geophones complemented by a backbone array of broadband sensors near Sweetwater, Texas. This pilot project demonstrates the efficacy of industry and academic partnerships, and leveraged a larger, commercial 3D survey to collect passive source seismic recordings to image the subsurface. This innovative deployment of a large-N mixed-mode array allows industry to explore array geometries and investigate the value of broadband recordings, while affording academics a dense wavefield imaging capability and an operational model for high volume instrument deployment. The broadband array consists of 25 continuously-recording stations from IRIS PASSCAL and Nanometrics, with an array design that maximized recording of horizontal-traveling seismic energy for surface wave analysis over the primary target area with sufficient offset for imaging objectives at depth. In addition, 2639 FairfieldNodal Zland nodes from NodalSeismic were deployed in three sub-arrays: the outlier, backbone, and active source arrays. The backbone array consisted of 292 nodes that covered the entire survey area, while the outlier array consisted of 25 continuously-recording nodes distributed at a ~3 km distance away from the survey perimeter. Both the backbone and outlier array provide valuable constraints for the passive source portion of the analysis. This project serves as a learning platform to develop best practices in the support of large-N arrays with joint industry and academic expertise. Here we investigate lessons learned from a facility perspective, and present examples of data from the various sensors and array geometries. We will explore first-order results from local and teleseismic earthquakes, and show visualizations of the data across the array. Data are archived at the IRIS DMC under stations codes XB and 1B.

  5. Method for homogenizing alloys susceptible to the formation of carbide stringers and alloys prepared thereby

    DOEpatents

    Braski, David N.; Leitnaker, James M.

    1980-01-01

    A novel fabrication procedure prevents or eliminates the reprecipitation of segregated metal carbides such as stringers in Ti-modified Hastelloy N and stainless steels to provide a novel alloy having carbides uniformly dispersed throughout the matrix. The fabrication procedure is applicable to other alloys prone to the formation of carbide stringers. The process comprises first annealing the alloy at a temperature above the single phase temperature for sufficient time to completely dissolve carbides and then annealing the single phase alloy for an additional time to prevent the formation of carbide stringers upon subsequent aging or thermomechanical treatment.

  6. Metal-interconnection-free integration of InGaN/GaN light emitting diodes with AlGaN/GaN high electron mobility transistors

    SciTech Connect

    Liu, Chao; Cai, Yuefei; Liu, Zhaojun; Ma, Jun; Lau, Kei May

    2015-05-04

    We report a metal-interconnection-free integration scheme for InGaN/GaN light emitting diodes (LEDs) and AlGaN/GaN high electron mobility transistors (HEMTs) by combining selective epi removal (SER) and selective epitaxial growth (SEG) techniques. SER of HEMT epi was carried out first to expose the bottom unintentionally doped GaN buffer and the sidewall GaN channel. A LED structure was regrown in the SER region with the bottom n-type GaN layer (n-electrode of the LED) connected to the HEMTs laterally, enabling monolithic integration of the HEMTs and LEDs (HEMT-LED) without metal-interconnection. In addition to saving substrate real estate, minimal interface resistance between the regrown n-type GaN and the HEMT channel is a significant improvement over metal-interconnection. Furthermore, excellent off-state leakage characteristics of the driving transistor can also be guaranteed in such an integration scheme.

  7. X-ray photoelectron spectroscopy analysis of GaN/(0001)AlN and AlN/(0001)GaN growth mechanisms

    NASA Astrophysics Data System (ADS)

    King, S. W.; Carlson, E. P.; Therrien, R. J.; Christman, J. A.; Nemanich, R. J.; Davis, R. F.

    1999-11-01

    The mechanisms of growth of GaN on AlN and AlN on GaN via gas source-molecular beam epitaxy with NH3 as the nitrogen source have been investigated using x-ray photoelectron spectroscopy, low energy electron diffraction, and Auger electron spectroscopy. The growth of GaN on AlN at low temperatures (650-750 °C) occurs via a Stranski-Krastanov 2D→3D type mechanism with the transition to 3D growth occurring at ≈10-15 Å. The mechanism changes to Frank van der Merwe (FM)/layer-by-layer growth above 800 °C. The growth of AlN on GaN occurred via a FM layer-by-layer mechanism within the 750-900 °C temperature range investigated. We propose a model based on the interaction of ammonia and atomic hydrogen with the GaN/AlN surfaces which indicates that the surface kinetics of hydrogen desorption and ammonia decomposition are the factors that determine the GaN growth mechanism.

  8. Comparative Study on Intersubband Absorption in AlGaN/GaN and AlInN/GaN Heterostructures Grown on Low-Defect Substrates

    NASA Astrophysics Data System (ADS)

    Edmunds, Colin; Tang, Liang; Shao, Jiayi; Li, Donghui; Gardner, Geoff; Manfra, Michael; Malis, Oana; Grier, Andrew; Ikonic, Zoran; Harrison, Paul; Zakharov, Dimitri

    2013-03-01

    Intersubband (ISB) devices utilizing III-nitrides have attracted attention for near- and far-infrared optoelectronic applications. However, the lattice mismatch between GaN and commonly used substrates results in a high defect density that hinders the vertical transport required for these devices. Furthermore, most devices in the literature utilize AlGaN/GaN heterostructures for which there is no lattice-matched alloy composition. Due to this lattice mismatch, AlGaN is not ideal for the development of complex devices such as quantum cascade lasers that often require active-region thicknesses on the order of microns for efficient operation. Fortunately, exact lattice matching occurs in AlInN/GaN heterostructures at roughly 18% In composition. To investigate the challenges of lattice-matched nitrides, we presents a comparative study of ISB absorption in high-quality AlGaN/GaN and near lattice-matched AlInN/GaN heterostructures grown by molecular-beam epitaxy on low-defect free-standing GaN substrates. Experimental measurements of transition energy, integrated absorbance and linewidth were compared to theoretical predictions that included many-body effects, interface roughness and calculations of the transition lifetime.

  9. Metal-interconnection-free integration of InGaN/GaN light emitting diodes with AlGaN/GaN high electron mobility transistors

    NASA Astrophysics Data System (ADS)

    Liu, Chao; Cai, Yuefei; Liu, Zhaojun; Ma, Jun; Lau, Kei May

    2015-05-01

    We report a metal-interconnection-free integration scheme for InGaN/GaN light emitting diodes (LEDs) and AlGaN/GaN high electron mobility transistors (HEMTs) by combining selective epi removal (SER) and selective epitaxial growth (SEG) techniques. SER of HEMT epi was carried out first to expose the bottom unintentionally doped GaN buffer and the sidewall GaN channel. A LED structure was regrown in the SER region with the bottom n-type GaN layer (n-electrode of the LED) connected to the HEMTs laterally, enabling monolithic integration of the HEMTs and LEDs (HEMT-LED) without metal-interconnection. In addition to saving substrate real estate, minimal interface resistance between the regrown n-type GaN and the HEMT channel is a significant improvement over metal-interconnection. Furthermore, excellent off-state leakage characteristics of the driving transistor can also be guaranteed in such an integration scheme.

  10. N-cadherin prodomain processing regulates synaptogenesis.

    PubMed

    Reinés, Analía; Bernier, Louis-Philippe; McAdam, Robyn; Belkaid, Wiam; Shan, Weisong; Koch, Alexander W; Séguéla, Philippe; Colman, David R; Dhaunchak, Ajit S

    2012-05-01

    Classical cadherins, which are adhesion molecules functioning at the CNS synapse, are synthesized as adhesively inactive precursor proteins in the endoplasmic reticulum (ER). Signal sequence and prodomain cleavage in the ER and Golgi apparatus, respectively, activates their adhesive properties. Here, we provide the first evidence for sorting of nonadhesive precursor N-cadherin (ProN) to the neuronal surface, where it coexists with adhesively competent mature N-cadherin (N-cad), generating a spectrum of adhesive strengths. In cultured hippocampal neurons, a high ProN/N-cad ratio downregulates synapse formation. Neurons expressing genetically engineered uncleavable ProN make markedly fewer synapses. The synapse number can be rescued to normality by depleting surface ProN levels through prodomain cleavage by an exogenous protease. Finally, prodomain processing is developmentally regulated in the rat hippocampus. We conclude that it is the ProN/N-cad ratio and not mature N-cad alone that is critical for regulation of adhesion during synaptogenesis.

  11. Urea-triazone N characteristics and uses.

    PubMed

    Clapp, J G

    2001-11-21

    Urea-triazone nitrogen (N) is a stable solution resulting from a controlled reaction in aqueous medium of urea, formaldehyde, and ammonia which contains at least 25% total N. This N source contains no more than 40%, nor less than 5%, of total N from unreacted urea and not less that 40% from triazone. All other N shall be derived from water-soluble dissolved reaction products of the above reactants. It is a source of slowly available N. The rate of mineralization of urea-triazone is about 66% that of urea after 8 days when incorporated in a Munjor sandy loam. Ammonia volatilization losses of N applied as urea-triazone were about 41% of those from urea on a Cecil sandy loam in the first week after application. N leaching losses through saturated Yolo loam columns of urea-triazone were about two thirds that of urea or nitrate N. This N source has proven to be a safer and more effective material for direct application on plant foliage. Tomato growth was enhanced with foliar application of urea-triazone relative to that obtained from ammonium nitrate or urea. The stability of this N source from potential losses via ammonia volatilization and nitrate leaching when soil applied is also documented by results from university trials. PMID:12805784

  12. CRITICAL REVIEW OF N, N{sup +}, N{sup +} {sub 2}, N{sup ++}, And N{sup ++} {sub 2} MAIN PRODUCTION PROCESSES AND REACTIONS OF RELEVANCE TO TITAN'S ATMOSPHERE

    SciTech Connect

    Dutuit, Odile; Thissen, Roland; Vuitton, Veronique; Canosa, Andre; Picard, Sebastien Le; Loison, Jean-Christophe; Ascenzi, Daniela; Tosi, Paolo; Franceschi, Pietro; Price, Stephen D.; Lavvas, Panayotis

    2013-02-15

    This paper is a detailed critical review of the production processes and reactions of N, N{sup +}, N{sup +} {sub 2}, N{sup ++}, and N{sup ++} {sub 2} of relevance to Titan's atmosphere. The review includes neutral, ion-molecule, and recombination reactions. The review covers all possible active nitrogen species under Titan's atmospheric conditions, specifically N{sub 2} (A {sup 3}{Sigma}{sup +} {sub u}), N ({sup 4} S), N ({sup 2} D), N ({sup 2} P), N{sup +} {sub 2}, N{sup +} ({sup 3} P), N{sup +} ({sup 1} D), N{sup ++} {sub 2}, and N{sup ++} species, and includes a critical survey of the reactions of N, N{sup +}, N{sup +} {sub 2}, N{sup ++}, and N{sup ++} {sub 2} with N{sub 2}, H{sub 2}, D{sub 2}, CH{sub 4}, C{sub 2}H{sub 2}, C{sub 2}H{sub 4}, C{sub 2}H{sub 6}, C{sub 3}H{sub 8} and the deuterated hydrocarbon analogs, as well as the recombination reactions of N{sup +} {sub 2}, N{sup +}, N{sup ++} {sub 2}, and N{sup ++}. Production processes, lifetimes, and quenching by collisions with N{sub 2} of all reactant species are reviewed. The N ({sup 4} S) state is reactive with radicals and its reactions with CH{sub 2}, CH{sub 3}, C{sub 2}H{sub 3}, and C{sub 2}H{sub 5} are reviewed. Metastable states N{sub 2} (A {sup 3}{Sigma}{sup +} {sub u}), N ({sup 2} D), and N ({sup 2} P) are either reactive or quenched by collisions with the target molecules reviewed. The reactions of N{sup +} ({sup 1} D) have similar rate constants as N{sup +} ({sup 3} P), but the product branching ratios differ significantly. Temperature effects and the role of the kinetic energy content of reactants are investigated. In all cases, experimental uncertainties of laboratory data are reported or estimated. Recommended values with uncertainties, or estimated values when no data are available, are given for rate constants and product branching ratios at 300 K and at the atmospheric temperature range of Titan (150-200 K for neutral reactions and 150 K for ion reactions).

  13. The study of near-resonance Raman scattering of AlInN/AlN/GaN heterostructure

    NASA Astrophysics Data System (ADS)

    Liu, Yanli; Yang, Lianhong; Chen, Dunjun; Zhang, Li; Lu, Hai; Zhang, Rong; Zheng, Youdou

    2015-07-01

    The visible and ultraviolet (UV) Raman scattering of an AlInN/AlN/GaN heterostructure were measured under z (x, _) z bar configuration at room temperature. Compared with the visible Raman spectrum, three new peaks at 609, 700, and 840 cm-1 occurred in the UV Raman spectrum and were verified to result from the resonance enhanced Raman effect. The near-resonance Raman scattering is stimulated by the electron transition process between the valence band and subband of triangular quantum well located at the interface of AlN/GaN because this transition process has a near equal energy with the 325 nm excitation light. According to the calculated dispersion relations of interface phonon modes in the AlInN/AlN/GaN heterostructure and the 2DEG-related resonance enhanced effect, these new Raman peaks were mainly attributed to the interface phonon modes and disorder-activated mode. The contributions from the bulk phonon modes of AlN and AlInN layers play a very minor role.

  14. Investigation of the electronic transport in GaN nanowires containing GaN/AlN quantum discs

    NASA Astrophysics Data System (ADS)

    Rigutti, Lorenzo; Jacopin, Gwénolé; De Luna Bugallo, Andres; Tchernycheva, Maria; Warde, Elias; Julien, François H.; Songmuang, Rudeesun; Galopin, Elisabeth; Largeau, Ludovic; Harmand, Jean-Christophe

    2010-10-01

    We report the investigation of electronic transport in GaN nanowires containing GaN/AlN quantum discs (QDiscs). The nanowires were grown by plasma-assisted molecular beam epitaxy and contacted by electron-beam lithography. Three nanowire samples containing QDiscs are analyzed and compared to a reference binary n-i-n GaN nanowire sample. The current-voltage measurements on single nanowires show that if the QDiscs are covered with a lateral GaN shell, the current mainly flows through the shell close to the lateral surface and the wire conductivity is extremely sensitive to the environmental conditions. On the contrary, if no GaN shell is present, the current flows through the QDisc region and a reproducible negative differential resistance related to electron tunneling through the QDiscs can be observed for temperatures up to 250 K. The demonstration of the resonant tunneling in GaN/AlN superlattices is of major importance for the development of nitride-based far-infrared quantum cascade lasers operating at high temperature.

  15. Improved electrical properties of n-n and p-n Si/SiC junctions with thermal annealing treatment

    NASA Astrophysics Data System (ADS)

    Liang, J.; Nishida, S.; Arai, M.; Shigekawa, N.

    2016-07-01

    The effects of annealing process on the electrical properties of n+-Si/n-SiC and p+-Si/n-SiC junctions fabricated by using surface-activated bonding are investigated. It is found by measuring the current-voltage (I-V) characteristics of n+-Si/n-SiC junctions that the reverse-bias current and the ideality factor decreased to 2.0 × 10-5 mA/cm2 and 1.10, respectively, after the junctions annealing at 700 °C. The flat band voltages of n+-Si/n-SiC and p+-Si/n-SiC junctions obtained from capacitance-voltage (C-V) measurements decreased with increasing annealing temperature. Furthermore, their flat band voltages are very close to each other irrespective of the annealing temperature change, which suggests that the Fermi level is still pinned at the bonding interface even for the junctions annealing at high temperature and the interface state density causing Fermi level pinning varies with the junctions annealing. The reverse characteristics of n+-Si/n-SiC junctions are in good agreement with the calculations based on thermionic field emission. In addition, the calculated donor concentration of 4H-SiC epi-layers and flat band voltage is consistent with the values obtained from C-V measurements.

  16. Ionization of sodium and rubidium nS, nP, and nD Rydberg atoms by blackbody radiation

    SciTech Connect

    Beterov, I. I.; Tretyakov, D. B.; Ryabtsev, I. I.; Ekers, A.; Bezuglov, N. N.

    2007-05-15

    Results of theoretical calculations of ionization rates of Rb and Na Rydberg atoms by blackbody radiation (BBR) are presented. Calculations have been performed for nS, nP, and nD states of Na and Rb, which are commonly used in a variety of experiments, at principal quantum numbers n=8-65 and at three ambient temperatures of 77, 300, and 600 K. A peculiarity of our calculations is that we take into account the contributions of BBR-induced redistribution of population between Rydberg states prior to photoionization and field ionization by extraction electric field pulses. The obtained results show that these phenomena affect both the magnitude of measured ionization rates and shapes of their dependences on n. The calculated ionization rates are compared with the results of our earlier measurements of BBR-induced ionization rates of Na nS and nD Rydberg states with n=8-20 at 300 K. A good agreement for all states except nS with n>15 is observed. We also present the useful analytical formulas for the quick estimation of BBR ionization rates of Rydberg atoms.

  17. 49 CFR Appendix - Figures to Subpart N of Part 572

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... Version Test conditions and instrumentation. Pt. 572, Subpt. N, Fig. N1 Figures to Subpart N of Part 572 ER18JY02.000 Pt. 572, Subpt. N, Fig. N2 ER18JY02.001 Pt. 572, Subpt. N, Fig. N3 ER18JY02.002 Pt. 572, Subpt. N, Fig. N4 ER13JA00.005 Pt. 572, Subpt. N, Fig. N5 ER19SE02.000 Pt. 572, Subpt. N, Fig. N6...

  18. 49 CFR Appendix - Figures to Subpart N of Part 572

    Code of Federal Regulations, 2014 CFR

    2014-10-01

    ... Version Test conditions and instrumentation. Pt. 572, Subpt. N, Fig. N1 Figures to Subpart N of Part 572 ER18JY02.000 Pt. 572, Subpt. N, Fig. N2 ER18JY02.001 Pt. 572, Subpt. N, Fig. N3 ER18JY02.002 Pt. 572, Subpt. N, Fig. N4 ER13JA00.005 Pt. 572, Subpt. N, Fig. N5 ER19SE02.000 Pt. 572, Subpt. N, Fig. N6...

  19. 49 CFR Appendix - Figures to Subpart N of Part 572

    Code of Federal Regulations, 2013 CFR

    2013-10-01

    ... Version Test conditions and instrumentation. Pt. 572, Subpt. N, Fig. N1 Figures to Subpart N of Part 572 ER18JY02.000 Pt. 572, Subpt. N, Fig. N2 ER18JY02.001 Pt. 572, Subpt. N, Fig. N3 ER18JY02.002 Pt. 572, Subpt. N, Fig. N4 ER13JA00.005 Pt. 572, Subpt. N, Fig. N5 ER19SE02.000 Pt. 572, Subpt. N, Fig. N6...

  20. Ecosystem N distribution and δ15N during a century of forest regrowth after agricultural abandonment

    USGS Publications Warehouse

    Compton, J.E.; Hooker, T.D.; Perakis, S.S.

    2007-01-01

    Stable isotope ratios of terrestrial ecosystem nitrogen (N) pools reflect internal processes and input–output balances. Disturbance generally increases N cycling and loss, yet few studies have examined ecosystem δ15N over a disturbance-recovery sequence. We used a chronosequence approach to examine N distribution and δ15N during forest regrowth after agricultural abandonment. Site ages ranged from 10 to 115 years, with similar soils, climate, land-use history, and overstory vegetation (white pine Pinus strobus). Foliar N and δ15N decreased as stands aged, consistent with a progressive tightening of the N cycle during forest regrowth on agricultural lands. Over time, foliar δ15N became more negative, indicating increased fractionation along the mineralization–mycorrhizal–plant uptake pathway. Total ecosystem N was constant across the chronosequence, but substantial internal N redistribution occurred from the mineral soil to plants and litter over 115 years (>25% of ecosystem N or 1,610 kg ha−1). Temporal trends in soil δ15N generally reflected a redistribution of depleted N from the mineral soil to the developing O horizon. Although plants and soil δ15N are coupled over millennial time scales of ecosystem development, our observed divergence between plants and soil suggests that they can be uncoupled during the disturbance-regrowth sequence. The approximate 2‰ decrease in ecosystem δ15N over the century scale suggests significant incorporation of atmospheric N, which was not detected by traditional ecosystem N accounting. Consideration of temporal trends and disturbance legacies can improve our understanding of the influence of broader factors such as climate or N deposition on ecosystem N balances and δ15N.

  1. Glacial-Interglacial and Holocene N2O Stable Isotope Changes Constrain Terrestrial N Cycling

    NASA Astrophysics Data System (ADS)

    Schmitt, J.; Spahni, R.; Bock, M.; Seth, B.; Stocker, B. D.; Ri, X.; Schilt, A.; Brook, E.; Otto-Bliesner, B. L.; Liu, Z.; Prentice, I. C.; Fischer, H.; Joos, F.

    2015-12-01

    The land biosphere contributes most to the natural source of the long-lived greenhouse gas nitrous oxide (N2O), with N2O emissions being dependent on the turnover rate of both the terrestrial nitrogen (N) and carbon (C) cycle. The C:N stoichiometry of vegetation and soil organic matter links the cycles intimately. Sustained plant productivity increase must be supported by biological N fixation. Intensified N cycling in turn enhances N loss and thereby N2O emissions. The temporal and spatial dynamics of terrestrial N and C cycles and related terrestrial N2O emissions are poorly constrained over the glacial-interglacial transition and the Holocene. Here we reconstruct increased terrestrial N2O emissions since the Last Glacial Maximum based on N2O concentration and isotope measurements on several ice cores and show that this N2O increase can be explained by N cycle modelling - provided N fixation is allowed to respond dynamically to increasing N demand and turnover. The Ice core reconstructions suggest a deglacial increase of 1.1 ± 0.4 Tg N/yr in terrestrial and 0.6 ± 0.4 Tg/yr in oceanic N2O emissions, but relatively constant terrestrial emissions over the Holocene. Transient simulations with a Dynamic Global Vegetation Model are shown to represent the climate and CO2 induced changes in terrestrial N2O emission, and suggest a deglacial increase in biological N fixation by 20%, independently of its absolute magnitude. Deciphering the response of biological N fixation during climatic changes is an important factor for our understanding of plant growth and the land carbon sink, alongside anthropogenic greenhouse gas emissions.

  2. 40 CFR 180.384 - Mepiquat (N,N-dimethylpip-eridinium); tolerances for residues.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...) Tolerances are established for residues of the plant growth regulator mepiquat (N,N-dimethylpiperidinium) in... byproducts 0.1 Sheep, meat byproducts 0.1 (2) Tolerances are established for residues of the plant growth regulator mepiquat chloride (N,N-dimethylpiperidinium chloride) in or on the following...

  3. Structures, stabilities, and magnetic properties of the Fe n Au (n = 1-12) clusters

    NASA Astrophysics Data System (ADS)

    Jin, Lv; Jiang-Yan, Zhang; Rui-Rui, Liang; Hai-Shun, Wu

    2016-06-01

    The configurations, stabilities, electronic, and magnetic properties of Fe n Au (n = 1-12) clusters are investigated systematically by using the relativistic all-electron density functional theory with the generalized gradient approximation. The substitutional effects of Au in Fe n+1 (n = 1, 2, 4, 5, 10-12) clusters are found in optimized structures which keep the similar frameworks with the most stable Fe n+1 clusters. And the growth way for Fe n Au (n = 6-9) clusters is that the Au atom occupies a peripheral position of Fe n cluster. The peaks appear respectively at n = 6 and 9 for Fe n Au clusters and at n = 5 and 10 for Fe n+1 clusters based on the size dependence of second-order difference of energy, implying that these clusters possess relatively high stabilities. The analysis of atomic net charge Q indicates that the charge always transfers from Fe to Au atom which causes the Au atom to be nearly non-magnetic, and the doped Au atom has little effect on the average magnetic moment of Fe atoms in Fe n Au cluster. Finally, the total magnetic moment is reduced by 3 μB for each of Fe n Au clusters except n = 3, 11, and 12 compared with for corresponding pure Fe n +1 clusters. Project supported by the National Natural Science Foundation of China (Grant No. 21301112) and the Ph. D. Program Foundation of the Education Ministry of China (Grant No. 20131404120001).

  4. Elevated CO2 and O3 modify N turnover rates, but not N2O emissions

    Technology Transfer Automated Retrieval System (TEKTRAN)

    In order to predict and mitigate future climate change, it is essential to understand effects of elevated CO2 (eCO2) and O3 (eO3) on N-cycling, including N2O emissions, due to plant mediated changes. This is of particular interest for agroecosystems, since N-cycling and N2O emissions are responsive ...

  5. 40 CFR 721.1085 - Benzenamine,4,4′-methylenebis[N-ethyl-N-methyl-.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false Benzenamine,4,4â²-methylenebis[N-ethyl-N-methyl-. 721.1085 Section 721.1085 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.1085 Benzenamine,4,4′-methylenebis[N-ethyl-N-methyl-. (a)...

  6. 40 CFR 721.225 - 2-Chloro-N-methyl-N-substituted acetamide (generic name).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false 2-Chloro-N-methyl-N-substituted... Specific Chemical Substances § 721.225 2-Chloro-N-methyl-N-substituted acetamide (generic name). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance...

  7. 40 CFR 721.225 - 2-Chloro-N-methyl-N-substituted acetamide (generic name).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false 2-Chloro-N-methyl-N-substituted... Specific Chemical Substances § 721.225 2-Chloro-N-methyl-N-substituted acetamide (generic name). (a) Chemical substance and significant new uses subject to reporting. (1) The chemical substance...

  8. 40 CFR 721.4080 - MNNG (N-methyl-N′-nitro-N-nitrosoguanidine).

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false MNNG (N-methyl-Nâ²-nitro-N... Specific Chemical Substances § 721.4080 MNNG (N-methyl-N′-nitro-N-nitrosoguanidine). (a) Chemical substance and significant new use subject to reporting. (1) The chemical substance MNNG...

  9. 40 CFR 721.1085 - Benzenamine,4,4′-methylenebis[N-ethyl-N-methyl-.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... 40 Protection of Environment 31 2011-07-01 2011-07-01 false Benzenamine,4,4â²-methylenebis[N-ethyl-N-methyl-. 721.1085 Section 721.1085 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.1085 Benzenamine,4,4′-methylenebis[N-ethyl-N-methyl-. (a)...

  10. 40 CFR 721.4080 - MNNG (N-methyl-N′-nitro-N-nitrosoguanidine).

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ... 40 Protection of Environment 30 2010-07-01 2010-07-01 false MNNG (N-methyl-Nâ²-nitro-N... Specific Chemical Substances § 721.4080 MNNG (N-methyl-N′-nitro-N-nitrosoguanidine). (a) Chemical substance and significant new use subject to reporting. (1) The chemical substance MNNG...

  11. H5N1 Avian Flu (H5N1 Bird Flu)

    MedlinePlus

    ... H5N1 - Avian/Bird Flu H5N1 Avian Flu - H5N1 Bird Flu H5N1 is a highly pathogenic avian (bird) flu virus that has caused serious outbreaks in ... been no reported infections with these viruses in birds, poultry, or people in the United States. You ...

  12. Skewing (n +1) Tensor Indices where the Index Range is n

    ERIC Educational Resources Information Center

    Agacy, R. L.

    2005-01-01

    It is known that any totally skew quantity with (n + 1) indices, each of which ranges over n values, vanishes identically. The aim of this short note is to show that this is equivalent to the simple fact that any (n + 1) vectors in an n-dimensional vector space are linearly dependent.

  13. Copper-catalyzed aminooxygenation of styrenes with N-fluorobenzenesulfonimide and N-hydroxyphthalimide derivatives

    PubMed Central

    Li, Yan; Zhou, Xue; Zheng, Guangfan

    2015-01-01

    Summary A copper-catalyzed aminooxygenation reaction of styrenes with N-fluorobenzenesulfonimide and N-hydroxyphthalimide derivatives has been developed. The aminooxygenation product could be converted into the corresponding alcohol or free amine through the cleavage of the N–O or C–N bond of the N-hydroxyphthalimide moiety. PMID:26877794

  14. 40 CFR 721.3848 - Glycine, N-(carboxymethyl)-N-dodecyl-, monosodium salt.

    Code of Federal Regulations, 2010 CFR

    2010-07-01

    ...-, monosodium salt. 721.3848 Section 721.3848 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.3848 Glycine, N-(carboxymethyl)-N-dodecyl-, monosodium salt. (a... glycine, N-(carboxymethyl)-N-dodecyl-, monosodium salt (PMN P-00-469; CAS No. 141321-68-8) is subject...

  15. 40 CFR 721.3848 - Glycine, N-(carboxymethyl)-N-dodecyl-, monosodium salt.

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ...-, monosodium salt. 721.3848 Section 721.3848 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.3848 Glycine, N-(carboxymethyl)-N-dodecyl-, monosodium salt. (a... glycine, N-(carboxymethyl)-N-dodecyl-, monosodium salt (PMN P-00-469; CAS No. 141321-68-8) is subject...

  16. 40 CFR 721.3848 - Glycine, N-(carboxymethyl)-N-dodecyl-, monosodium salt.

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ...-, monosodium salt. 721.3848 Section 721.3848 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.3848 Glycine, N-(carboxymethyl)-N-dodecyl-, monosodium salt. (a... glycine, N-(carboxymethyl)-N-dodecyl-, monosodium salt (PMN P-00-469; CAS No. 141321-68-8) is subject...

  17. 40 CFR 721.3848 - Glycine, N-(carboxymethyl)-N-dodecyl-, monosodium salt.

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ...-, monosodium salt. 721.3848 Section 721.3848 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.3848 Glycine, N-(carboxymethyl)-N-dodecyl-, monosodium salt. (a... glycine, N-(carboxymethyl)-N-dodecyl-, monosodium salt (PMN P-00-469; CAS No. 141321-68-8) is subject...

  18. 40 CFR 721.3848 - Glycine, N-(carboxymethyl)-N-dodecyl-, monosodium salt.

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...-, monosodium salt. 721.3848 Section 721.3848 Protection of Environment ENVIRONMENTAL PROTECTION AGENCY... Specific Chemical Substances § 721.3848 Glycine, N-(carboxymethyl)-N-dodecyl-, monosodium salt. (a... glycine, N-(carboxymethyl)-N-dodecyl-, monosodium salt (PMN P-00-469; CAS No. 141321-68-8) is subject...

  19. Microbial Potential for Ecosystem N Loss Is Increased by Experimental N Deposition

    PubMed Central

    Upchurch, Rima A.; Zak, Donald R.

    2016-01-01

    Fossil fuel combustion and fertilizer use has increased the amount of biologically available N entering terrestrial ecosystems. Nonetheless, our understanding of how anthropogenic N may alter the physiological mechanisms by which soil microorganisms cycle N in soil is still developing. Here, we applied shotgun metagenomics to a replicated long-term field experiment to determine how two decades of experimental N deposition, at a rate expected by mid-century, has affected the genetic potential of the soil microbial community to cycle N in soils. Experimental N deposition lead to a significant and persistent increase in functional assemblages mediating N cycle transformations associated with ecosystem N loss (i.e., denitrification and nitrification), whereas functional assemblages associated with N input and retention (i.e., N fixation and microbial N assimilation) were less positively affected. Furthermore, the abundance and composition of microbial taxa, as well as functional assemblages involved in housekeeping functions (i.e., DNA replication) were unaffected by experimental N deposition. Taken together, our results suggest that functional genes and gene pathways associated with ecosystem N loss have been favored by experimental N deposition, which may represent a genetic mechanism fostering increased N loss as anthropogenic N deposition increases in the future. PMID:27737013

  20. Self-compensation in highly n-type InN

    SciTech Connect

    Rauch, C.; Tuomisto, F.; King, P. D. C.; Veal, T. D.; Lu, H.; Schaff, W. J.

    2012-07-02

    Acceptor-type defects in highly n-type InN are probed using positron annihilation spectroscopy. Results are compared to Hall effect measurements and calculated electron mobilities. Based on this, self-compensation in n-type InN is studied, and the microscopic origin of compensating and scattering centers in irradiated and Si-doped InN is discussed. We find significant compensation through negatively charged indium vacancy complexes as well as additional acceptor-type defects with no or small effective open volume, which act as scattering centers in highly n-type InN samples.

  1. Engineering of electric field distribution in GaN(cap)/AlGaN/GaN heterostructures: theoretical and experimental studies

    NASA Astrophysics Data System (ADS)

    Gladysiewicz, M.; Janicki, L.; Misiewicz, J.; Sobanska, M.; Klosek, K.; Zytkiewicz, Z. R.; Kudrawiec, R.

    2016-09-01

    Polarization engineering of GaN-based heterostructures opens a way to develop advanced transistor heterostructures, although measurement of the electric field in such heterostructures is not a simple task. In this work, contactless electroreflectance (CER) spectroscopy has been applied to measure the electric field in GaN-based heterostructures. For a set of GaN(d  =  0, 5, 15, and 30 nm)/AlGaN(20 nm)/GaN(buffer) heterostructures a decrease of electric field in the GaN(cap) layer from 0.66 MV cm-1 to 0.27 MV cm-1 and an increase of the electric field in the AlGaN layer from 0.57 MV cm-1 to 0.99 MV cm-1 have been observed with the increase in the GaN(cap) thickness from 5-30 nm. For a set of GaN(20 nm)/AlGaN(d  =  10, 20, 30, and 40 nm)/GaN(buffer) heterostructures a decrease of the electric field in the AlGaN layer from 1.77 MV cm-1 to 0.64 MV cm-1 and an increase of the electric field in the GaN layer from 0.57 MV cm-1 to 0.99 MV cm-1 were observed with the increase in the AlGaN thickness from 10-40 nm. To determine the distribution of the electric field in these heterostructures the Schrödinger and Poisson equations are solved in a self-consistent manner and matched with experimental data. It is shown that the built-in electric field in the GaN(cap) and AlGaN layers obtained from measurements does not reach values of electric field resulting only from polarization effects. The measured electric fields are smaller due to a screening of polarization effects by free carriers, which are inhomogeneously distributed across the heterostructure and accumulate at interfaces. The results clearly demonstrate that CER measurements supported by theoretical calculations are able to determine the electric field distribution in GaN-based heterostructures quantitatively, which is very important for polarization engineering in this material system.

  2. Engineering of electric field distribution in GaN(cap)/AlGaN/GaN heterostructures: theoretical and experimental studies

    NASA Astrophysics Data System (ADS)

    Gladysiewicz, M.; Janicki, L.; Misiewicz, J.; Sobanska, M.; Klosek, K.; Zytkiewicz, Z. R.; Kudrawiec, R.

    2016-09-01

    Polarization engineering of GaN-based heterostructures opens a way to develop advanced transistor heterostructures, although measurement of the electric field in such heterostructures is not a simple task. In this work, contactless electroreflectance (CER) spectroscopy has been applied to measure the electric field in GaN-based heterostructures. For a set of GaN(d  =  0, 5, 15, and 30 nm)/AlGaN(20 nm)/GaN(buffer) heterostructures a decrease of electric field in the GaN(cap) layer from 0.66 MV cm‑1 to 0.27 MV cm‑1 and an increase of the electric field in the AlGaN layer from 0.57 MV cm‑1 to 0.99 MV cm‑1 have been observed with the increase in the GaN(cap) thickness from 5–30 nm. For a set of GaN(20 nm)/AlGaN(d  =  10, 20, 30, and 40 nm)/GaN(buffer) heterostructures a decrease of the electric field in the AlGaN layer from 1.77 MV cm‑1 to 0.64 MV cm‑1 and an increase of the electric field in the GaN layer from 0.57 MV cm‑1 to 0.99 MV cm‑1 were observed with the increase in the AlGaN thickness from 10–40 nm. To determine the distribution of the electric field in these heterostructures the Schrödinger and Poisson equations are solved in a self-consistent manner and matched with experimental data. It is shown that the built-in electric field in the GaN(cap) and AlGaN layers obtained from measurements does not reach values of electric field resulting only from polarization effects. The measured electric fields are smaller due to a screening of polarization effects by free carriers, which are inhomogeneously distributed across the heterostructure and accumulate at interfaces. The results clearly demonstrate that CER measurements supported by theoretical calculations are able to determine the electric field distribution in GaN-based heterostructures quantitatively, which is very important for polarization engineering in this material system.

  3. Computational Chemistry Study on Crystal Growth of InGaN/GaN

    NASA Astrophysics Data System (ADS)

    Inaba, Yusaku; Onozu, Takayuki; Takami, Seiichi; Kubo, Momoji; Miyamoto, Akira; Imamura, Akira

    2001-04-01

    We carried out density functional theory (DFT) calculations and tight-binding quantum chemical molecular dynamics simulations to investigate the crystal growth of InGaN layers on a GaN(0001) surface under periodic boundary conditions. The periodic DFT calculations indicate that the formation of the uniform InGaN thin films is difficult, which leads to the segregation of In atoms in the InGaN thin films. The tight-binding quantum chemical molecular dynamics simulations suggest that the Ga polarity surface of the GaN(0001) is preferable for the construction of the smooth GaN thin films than the N polarity surface of the GaN(0001). Moreover, the formation of the smooth InN thin films was found to be difficult on the GaN(0001) surface.

  4. Internal quantum efficiency in yellow-amber light emitting AlGaN-InGaN-GaN heterostructures

    SciTech Connect

    Ngo, Thi Huong; Gil, Bernard; Valvin, Pierre; Damilano, Benjamin; Lekhal, Kaddour; De Mierry, Philippe

    2015-09-21

    We determine the internal quantum efficiency of strain-balanced AlGaN-InGaN-GaN hetero-structures designed for yellow-amber light emission, by using a recent model based on the kinetics of the photoluminescence decay initiated by Iwata et al. [J. Appl. Phys. 117, 075701 (2015)]. Our results indicate that low temperature internal quantum efficiencies sit in the 50% range and we measure that adding an AlGaN layer increases the internal quantum efficiency from 50% up to 57% with respect to the GaN-InGaN case. More dramatic, it almost doubles from 2.5% up to 4.3% at room temperature.

  5. 40 CFR 721.3152 - Ethanaminium, N-ethyl-2-hydroxy-N,N-bis(2-hydroxyethyl)-, diester with C12-18 fatty acids, ethyl...

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ...-bis(2-hydroxyethyl)-, diester with C12-18 fatty acids, ethyl sulfates (salts). 721.3152 Section 721... Ethanaminium, N-ethyl-2-hydroxy-N,N-bis(2-hydroxyethyl)-, diester with C12-18 fatty acids, ethyl sulfates... ethanaminium, N-ethyl-2-hydroxy-N,N-bis(2-hydroxyethyl)-, diester with C12-18 fatty acids, ethyl...

  6. Soil N and 15N variation with time in a California annual grassland ecosystem

    USGS Publications Warehouse

    Brenner, D.L.; Amundson, Ronald; Baisden, W. Troy; Kendall, C.; Harden, J.

    2001-01-01

    The %N and ??15N values of soils and plants were measured along a chronosequence spanning 3 to 3000 Ky in a California annual grassland. Total soil N decreased with increasing soil age (1.1 to 0.4 kg N m-2) while the mean ?? 15N values of the soil N increased by several ??? from the youngest to oldest sites (+3.5 to +6.2 ???). The ?? 15N values of plants varied along the gradient, reflecting changing soil N pools and differences in the form of N uptake. The decline in total N storage with time is hypothesized to be due to a shift from N to P limitation with increasing soil age. The general increase in ?? 15N values with time is interpreted using a N mass balance model, and appears to reflect a shift toward an increasing proportional losses of inorganic mineral forms of N (vs. organic forms) with increasing soil age. We develop a quantitative index of this trend (mineral vs. organic forms of N loss) using mass balance considerations and parameters. The %N and ?? 15N values along the California age gradient were compared to the published data for a comparably aged chronosequence in Hawaii. Most striking in this comparison is the observation that the California soil and plant ?? 15N values are several ??? greater than those on comparably aged Hawaiian sites. Multiple explanations are plausible, but assuming the sites have a similar range in ?? 15N values of atmospheric inputs, the isotopic differences suggest that N may be, at least seasonally, in greater excess in the strongly seasonal, semi-arid, California grassland. Copyright ?? 2001 Elsevier Science Ltd.

  7. Do Humans Really Learn A[superscript n] B[superscript n] Artificial Grammars from Exemplars?

    ERIC Educational Resources Information Center

    Hochmann, Jean-Remy; Azadpour, Mahan; Mehler, Jacques

    2008-01-01

    An important topic in the evolution of language is the kinds of grammars that can be computed by humans and other animals. Fitch and Hauser (F&H; 2004) approached this question by assessing the ability of different species to learn 2 grammars, (AB)[superscript n] and A[superscript n] B[superscript n]. A[superscript n] B[superscript n] was taken to…

  8. Backreaction and N{sub f} = 2N{sub c} SQCD-like theories

    SciTech Connect

    Caceres, Elena; Flauger, Raphael; Ihl, Matthias; Wrase, Timm

    2009-04-20

    We present new supergravity backgrounds generated by N{sub c} D5-branes, wrapping the S{sup 2} of the resolved conifold, in the presence of N{sub f} = 2N{sub c} smeared flavor D5-branes. The smearing allows us to take their backreaction on the geometry into account. The near horizon geometries are expected to be supergravity duals of SQCD-like theories with N{sub f} = 2N{sub c}.

  9. Synthesis, characterization and antioxidant study of N,N'-bis(2-chlorobenzamidothiocarbonyl)hydrazine

    NASA Astrophysics Data System (ADS)

    Firdausiah, Syadza; Hasbullah, Siti Aishah; Yamin, Bohari M.

    2015-09-01

    N,N'-bis(2-chlorobenzamidothiocarbonyl)hydrazine was synthesized from 2-chlorobenzoylisothiocyanate and hydrazine in acetone. The compound was characterized by infrared, 1H and 13C NMR, and UV-Vis spectroscopies. X-ray crystallography study showed the molecule adopt trans configuration at both N-N and C-N bonds. The compound showed high antioxidant activity, EC50 of 374.89 µM, compared to ascorbic acid (EC50 of 561.36 µM).

  10. Process dependency on threshold voltage of GaN MOSFET on AlGaN/GaN heterostructure

    NASA Astrophysics Data System (ADS)

    Wang, Qingpeng; Jiang, Ying; Miyashita, Takahiro; Motoyama, Shin-ichi; Li, Liuan; Wang, Dejun; Ohno, Yasuo; Ao, Jin-Ping

    2014-09-01

    GaN metal-oxide-semiconductor field-effect transistors (MOSFETs) with recessed gate on AlGaN/GaN heterostructure are reported in which the drain and source ohmic contacts were fabricated on the AlGaN/GaN heterostructure and the electron channel was formed on the GaN buffer layer by removing the AlGaN barrier layer. Negative threshold voltages were commonly observed in all devices. To investigate the reasons of the negative threshold voltages, different oxide thickness, etching gas and bias power of inductively-coupled plasma (ICP) system were utilized in the fabrication process of the GaN MOSFETs. It is found that positive charges of around 1 × 1012 q/cm2 exist near the interface at the just threshold condition in both silane- and tetraethylorthosilicate (TEOS)-based devices. It is also found that the threshold voltages do not obviously change with the different etching gas (SiCl4, BCl3 and two-step etching of SiCl4/Cl2) at the same ICP bias power level (20-25 W) and will become deeper when higher bias power is used in the dry recess process which may be related to the much serious ion bombardment damage. Furthermore, X-ray photoelectron spectroscopy (XPS) experiments were done to investigate the surface conditions. It is found that N 1s peaks become lower with higher bias power of the dry etching process. Also, silicon contamination was found and could be removed by HNO3/HF solution. It indicates that the nitrogen vacancies are mainly responsible for the negative threshold voltages rather than the silicon contamination. It demonstrates that optimization of the ICP recess conditions and improvement of the surface condition are still necessary to realize enhancement-mode GaN MOSFETs on AlGaN/GaN heterostructure.

  11. Evidence for N 2N 3N 45 super coster kronig processes in metallic Nb, Mo, Ru and Rh

    NASA Astrophysics Data System (ADS)

    Nyholm, Ralf; M»rtensson, Nils

    1980-09-01

    The 4p photoelectron spectra of metallic Nb, Mo, Ru and Rh have been recorded. By use of a deconvolution procedure it is shown that the 4p 1/2 spin-orbit component has a linewidth which significantly exceeds that of the 4p 3/2 component. This suggests that N 2N 3N 45 super Coster Kronig processes give a considerable contribution to the decay rata of the 4p 1/2 hole state.

  12. Does elevated N make lignin more recalcitrant?

    NASA Astrophysics Data System (ADS)

    Weintraub, M. N.; Rinkes, Z. L.; Grandy, S.; Wickings, K.; Bertrand, I.

    2014-12-01

    Increases in nitrogen (N) availability are often found to reduce decomposition rates of lignin-rich plant litter. However, the biological and chemical mechanisms that cause this inhibitory effect are still unclear. Our goal was to determine why increased N availability inhibits lignin decomposition. We tested two competing hypotheses: 1) decomposers degrade lignin to obtain protected N compounds and stop producing lignin-degrading enzymes if mineral N is available; or 2) chemical reactions between lignin and mineral N make lignin more recalcitrant, thereby limiting the ability of decomposers to break it down. To test these hypotheses, we followed changes in carbon (C) mineralization, microbial biomass and enzyme activities, litter chemistry, and lignin monomer concentrations over a 478-day laboratory incubation of three genotypes of maize stem internodes varying in litter quality. They were factorially combined with either an acidic or neutral pH sandy soil, with and without added N. Adding N reduced C mineralization, microbial biomass, and lignin-degrading enzyme activities in all treatments. Furthermore, our data on litter chemistry and lignin monomers indicate that N addition did not significantly alter the quantity or quality of lignin in any treatment. These results suggest that abiotic interactions between N and lignin compounds did not alter the ability of decomposers to breakdown lignin. Thus, we conclude that mineral N alters microbial enzyme and biomass dynamics, but not lignin chemistry during maize decomposition.

  13. Antigenic Properties of N Protein of Hantavirus

    PubMed Central

    Yoshimatsu, Kumiko; Arikawa, Jiro

    2014-01-01

    Hantavirus causes two important rodent-borne viral zoonoses, hemorrhagic fever with renal syndrome (HFRS) in Eurasia and hantavirus pulmonary syndrome (HPS) in North and South America. Twenty-four species that represent sero- and genotypes have been registered within the genus Hantavirus by the International Committee on Taxonomy of Viruses (ICTV). Among the viral proteins, nucleocapsid (N) protein possesses an immunodominant antigen. The antigenicitiy of N protein is conserved compared with that of envelope glycoproteins. Therefore, N protein has been used for serological diagnoses and seroepidemiological studies. An understanding of the antigenic properties of N protein is important for the interpretation of results from serological tests using N antigen. N protein consists of about 430 amino acids and possesses various epitopes. The N-terminal quarter of N protein bears linear and immunodominant epitopes. However, a serotype-specific and multimerization-dependent antigenic site was found in the C-terminal half of N protein. In this paper, the structure, function, and antigenicity of N protein are reviewed. PMID:25123683

  14. Growth condition optimization and mobility enhancement through prolonging the GaN nuclei coalescence process of AlGaN/AlN/GaN structure

    NASA Astrophysics Data System (ADS)

    He, Xiao-Guang; Zhao, De-Gang; Jiang, De-Sheng; Zhu, Jian-Jun; Chen, Ping; Liu, Zong-Shun; Le, Ling-Cong; Yang, Jing; Li, Xiao-Jing; Zhang, Shu-Ming; Yang, Hui

    2015-09-01

    AlGaN/AlN/GaN structures are grown by metalorganic vapor phase epitaxy on sapphire substrates. Influences of AlN interlayer thickness, AlGaN barrier thickness, and Al composition on the two-dimensional electron gas (2DEG) performance are investigated. Lowering the V/III ratio and enhancing the reactor pressure at the initial stage of the high-temperature GaN layer growth will prolong the GaN nuclei coalescence process and effectively improve the crystalline quality and the interface morphology, diminishing the interface roughness scattering and improving 2DEG mobility. AlGaN/AlN/GaN structure with 2DEG sheet density of 1.19 × 1013 cm-2, electron mobility of 2101 cm2·V-1·s-1, and square resistance of 249 Ω is obtained. Project support by the National Natural Science Foundation of China (Grant Nos. 61474110, 61377020, 61376089, 61223005, and 61176126), the National Science Fund for Distinguished Young Scholars, China (Grant No. 60925017), the One Hundred Person Project of the Chinese Academy of Sciences, and the Basic Research Project of Jiangsu Province, China (Grant No. BK20130362).

  15. Two-dimensional electron gases in strained quantum wells for AlN/GaN/AlN double heterostructure field-effect transistors on AlN

    SciTech Connect

    Li, Guowang; Song, Bo; Ganguly, Satyaki; Zhu, Mingda; Wang, Ronghua; Yan, Xiaodong; Verma, Jai; Protasenko, Vladimir; Grace Xing, Huili; Jena, Debdeep

    2014-05-12

    Double heterostructures of strained GaN quantum wells (QWs) sandwiched between relaxed AlN layers provide a platform to investigate the quantum-confined electronic and optical properties of the wells. The growth of AlN/GaN/AlN heterostructures with varying GaN quantum well thicknesses on AlN by plasma molecular beam epitaxy (MBE) is reported. Photoluminescence spectra provide the optical signature of the thin GaN QWs. Reciprocal space mapping in X-ray diffraction shows that a GaN layer as thick as ∼28 nm is compressively strained to the AlN layer underneath. The density of the polarization-induced two-dimensional electron gas (2DEG) in the undoped heterostructures increases with the GaN QW thickness, reaching ∼2.5 × 10{sup 13}/cm{sup 2}. This provides a way to tune the 2DEG channel density without changing the thickness of the top barrier layer. Electron mobilities less than ∼400 cm{sup 2}/Vs are observed, leaving ample room for improvement. Nevertheless, owing to the high 2DEG density, strained GaN QW field-effect transistors with MBE regrown ohmic contacts exhibit an on-current density ∼1.4 A/mm, a transconductance ∼280 mS/mm, and a cut off frequency f{sub T}∼104 GHz for a 100-nm-gate-length device. These observations indicate high potential for high-speed radio frequency and high voltage applications that stand to benefit from the extreme-bandgap and high thermal conductivity of AlN.

  16. Effect of buffer structures on AlGaN/GaN high electron mobility transistor reliability

    SciTech Connect

    Liu, L.; Xi, Y. Y.; Ren, F.; Pearton, S. J.; Laboutin, O.; Cao, Yu; Johnson, Wayne J.; Kravchenko, Ivan I

    2012-01-01

    AlGaN/GaN high electron mobility transistors (HEMTs) with three different types of buffer layers, including a GaN/AlGaN composite layer, or 1 or 2 lm GaN thick layers, were fabricated and their reliability compared. The HEMTs with the thick GaN buffer layer showed the lowest critical voltage (Vcri) during off-state drain step-stress, but this was increased by around 50% and 100% for devices with the composite AlGaN/GaN buffer layers or thinner GaN buffers, respectively. The Voff - state for HEMTs with thin GaN and composite buffers were 100 V, however, this degraded to 50 60V for devices with thick GaN buffers due to the difference in peak electric field near the gate edge. A similar trend was observed in the isolation breakdown voltage measurements, with the highest Viso achieved based on thin GaN or composite buffer designs (600 700 V), while a much smaller Viso of 200V was measured on HEMTs with the thick GaN buffer layers. These results demonstrate the strong influence of buffer structure and defect density on AlGaN/GaN HEMT performance and reliability.

  17. Working toward high-power GaN/InGaN heterojunction bipolar transistors

    NASA Astrophysics Data System (ADS)

    Shen, Shyh-Chiang; Dupuis, Russell D.; Lochner, Zachery; Lee, Yi-Che; Kao, Tsung-Ting; Zhang, Yun; Kim, Hee-Jin; Ryou, Jae-Hyun

    2013-07-01

    III-nitride (III-N) heterojunction bipolar transistors (HBTs) are a less-explored electronic device technology due to the myriad research issues in material growth, device design and fabrication associated with these devices. For III-N HBTs, npn-GaN/InGaN heterostructures provide the benefits of mitigating the poor base electrical conductivity of p-type GaN and the problematic magnesium incorporation issues. Consequently, InGaN-base III-N HBTs are promising for next-generation high-power RF III-N systems. This paper will describe the current development status of npn GaN/InGaN HBTs grown either on sapphire or free-standing (FS) GaN substrates using optimized metalorganic chemical vapor deposition (MOCVD) and refined HBT processing techniques. Recombination current paths in GaN/InGaN HBTs are studied and small-signal equivalent circuits are developed. The extracted device model indicates that, with further device fabrication technique development, Johnson's figure of merit (JFOM) of GaN/InGaN HBTs can be as high as 5 THz V.

  18. Optically and thermally detected deep levels in n-type Schottky and p+-n GaN diodes

    NASA Astrophysics Data System (ADS)

    Hierro, A.; Kwon, D.; Ringel, S. A.; Hansen, M.; Speck, J. S.; Mishra, U. K.; DenBaars, S. P.

    2000-05-01

    N-Schottky and p+-n GaN junctions are currently used for different technologies. A comparison of the deep levels found throughout the entire band gap of n-GaN grown by metal-organic chemical vapor deposition under both configurations is presented. Both deep level optical spectroscopy and deep level transient spectroscopy measurements are used allowing the observation of both majority and minority carrier traps. Deep levels at Ec-Et=0.58-0.62, 1.35, 2.57-2.64, and 3.22 eV are observed for both diode configurations, with concentrations in the ˜1014-1016cm-3 range. The 0.58-0.62 eV level appears correlated with residual Mg impurities in the n side of the p+-n diode measured by secondary-ion-mass spectroscopy, while the 1.35 eV level concentration increases by a factor of ˜4 for the Schottky junction possibly correlating with the carbon profile. The 2.57-2.64 eV level is a minority carrier hole trap in n-GaN, likely related to the yellow photoluminescence band, and is detected both optically from the conduction band (2.64 eV) and thermally from the valence band (0.87 eV).

  19. Tuning emission in violet, blue, green and red in cubic GaN/InGaN/GaN quantum wells

    NASA Astrophysics Data System (ADS)

    Orozco Hinostroza, I. E.; Avalos-Borja, M.; Compeán García, V. D.; Zamora, C. Cuellar; Rodríguez, A. G.; López Luna, E.; Vidal, M. A.

    2016-02-01

    Light emission in the three primary colors was achieved in cubic GaN/InGaN/GaN heterostructures grown by molecular beam epitaxy on MgO substrates in a single growth process. A heterostructure with four quantum wells with a width of 10 nm was grown; this quantum wells width decrease the segregation effect of In. Photoluminescence emission produced four different emission signals: violet, blue, green-yellow and red. Thus, we were able to tune energy transitions in the visible spectrum modifying the In concentration in cubic InxGa1-xN ternary alloy.

  20. Analytical modeling of AlGaN/AlN/GaN heterostructures including effects of distributed surface donor states

    SciTech Connect

    Goyal, Nitin; Fjeldly, Tor A.

    2014-07-14

    In this paper, a physics based analytical model is presented for calculation of the two-dimensional electron gas density and the bare surface barrier height of AlGaN/AlN/GaN material stacks. The presented model is based on the concept of distributed surface donor states and the self-consistent solution of Poisson equation at the different material interfaces. The model shows good agreement with the reported experimental data and can be used for the design and characterization of advanced GaN devices for power and radio frequency applications.

  1. Efficient carrier relaxation and fast carrier recombination of N-polar InGaN/GaN light emitting diodes

    SciTech Connect

    Feng, Shih-Wei Liao, Po-Hsun; Leung, Benjamin; Han, Jung; Yang, Fann-Wei; Wang, Hsiang-Chen

    2015-07-28

    Based on quantum efficiency and time-resolved electroluminescence measurements, the effects of carrier localization and quantum-confined Stark effect (QCSE) on carrier transport and recombination dynamics of Ga- and N-polar InGaN/GaN light-emitting diodes (LEDs) are reported. The N-polar LED exhibits shorter ns-scale response, rising, delay, and recombination times than the Ga-polar one does. Stronger carrier localization and the combined effects of suppressed QCSE and electric field and lower potential barrier acting upon the forward bias in an N-polar LED provide the advantages of more efficient carrier relaxation and faster carrier recombination. By optimizing growth conditions to enhance the radiative recombination, the advantages of more efficient carrier relaxation and faster carrier recombination in a competitive performance N-polar LED can be realized for applications of high-speed flash LEDs. The research results provide important information for carrier transport and recombination dynamics of an N-polar InGaN/GaN LED.

  2. The application of poly(N, N'-dibromo-N-ethyl-benzene-1,3-disulfonamide) and N, N, N', N'-tetrabromobenzene-1,3-disulfonamide as catalysts for one-pot synthesis of 2-aryl-1-arylmethyl-1H-1,3-benzimidazoles and 1,5-benzodiazepines, and new reagents for synthesis of benzimidazoles.

    PubMed

    Ghorbani-Vaghei, Ramin; Veisi, Hojat

    2010-05-01

    Poly(N, N'-dibromo-N-ethyl-benzene-1, 3-di-sulfonamide) (PBBS) and N, N, N', N'- tetrabromobenzene-1,3-disulfonamide (TBBDA) are effective catalysts for the one-pot synthesis of 2-aryl-1-arylmethyl-1H-1,3-benzimidazoles and 1,5-benzodiazepines and new reagents for synthesis of benzimidazoles from o-phenylenediamine (OPDA) with aldehydes and ketones at room temperature with good to high yield. PMID:19517262

  3. H1N1 (Originally Referred to As Swine Flu)

    MedlinePlus

    ... Changes H7N9 H3N2v H1N1 - Swine Flu H5N1 - Avian/Bird Flu Planning & Preparedness Business Planning Community Planning School ... Changes H7N9 H3N2v H1N1 - Swine Flu H5N1 - Avian/Bird Flu H1N1 - originally referred to as Swine Flu ...

  4. High N2O emission in an N-saturated subtropical forest, southwest China

    NASA Astrophysics Data System (ADS)

    Dörsch, P.; Zhu, J.; Mulder, J.

    2012-04-01

    Nitrogen (N)-saturated forests in subtropical China are significant N sinks, despite low forest growth rates. In a forested headwater catchment at Tieshanping, Chongqing, SW China, with 4 g N m-2a-1 atmogenic deposition (60% of which as NH4+-N) and leaching of only 0.6 g N m-2 a-1 (NO3--N dominated), we applied state-of-the-art field and laboratory methodologies to investigate the nature of the N sinks. The study included the determination of spatiotemporal patterns of N2O emission, a 15N labeling experiment and laboratory incubations to determine nitrification and denitrification characteristics and their gaseous product stoichiometries. Emission of N2O occurred predominantly during the wet season (summer), driven by rain episodes. N2O emission rates were particularly high along a hill slope (HS) with a thin organic surface layer overlaying an argic B horizon causing transient interflow during storm flow conditions. Lower N2O emission rates were observed at the foot slope in a colluvium-derived groundwater discharge zone (GDZ). Laboratory incubation experiments suggested that the difference in N2O emission rate is primarily due to higher N2O/N2 product ratios of denitrification in the HS topsoil being exposed to frequent drying-rewetting. Lower N2O/N2 product ratios in soils of the GDZ, in turn, could be attributed to more stable anoxia, lower NO3- availability and higher pH as compared with the hillslope, all of which favor the expression of N2O reductase. Estimated annual N2O emission for the relatively dry hydrological year 2009-2010 was 0.4 g N m-2, which is equivalent to approximately 10% of the annual input of reactive N. Measurements during summer 2009 indicated that N2O emissions can be even higher during wet years. A 15NO3- labeling experiment conducted on HS soils during summer revealed that between 75 and 86% of the N2O emission derived from denitrification during the first 6 days after label addition, accounting for 8-15% of the applied NO3--N. Our

  5. Structure effects in the 15N(n ,γ )16N radiative capture reaction from the Coulomb dissociation of 16N

    NASA Astrophysics Data System (ADS)

    Neelam, Shubhchintak, Chatterjee, R.

    2015-10-01

    Background: The 15N(n ,γ )16N reaction plays an important role in red giant stars and also in inhomogeneous big bang nucleosynthesis. However, there are controversies regarding spectroscopic factors of the four low-lying states of 16N, which have direct bearing on the total direct capture cross section and also on the reaction rate. Direct measurements of the capture cross section at low energies are scarce and available only at three energies below 500 keV. Purpose: The aim of this paper is to calculate the 15N(n ,γ )16N radiative capture cross section and its subsequent reaction rate by an indirect method and in that process investigate the effects of spectroscopic factors of different levels of 16N to the cross section. Method: A fully quantum mechanical Coulomb breakup theory under the aegis of post-form distorted wave Born approximation is used to calculate the Coulomb breakup of 16N on Pb at 100 MeV/u . This is then related to the photodisintegration cross section of 16N(γ ,n )15N and subsequently invoking the principle of detailed balance, the 15N(n ,γ )16N capture cross section is calculated. Results: The nonresonant capture cross section is calculated with spectroscopic factors from the shell model and those extracted (including uncertainties) from two recent experiments. The data seem to favor a more single particle nature for the low-lying states of 16N. The total neutron capture rate is also calculated by summing up nonresonant and resonant (significant only at temperatures greater than 1 GK) contributions and comparison is made with other charged particle capture rates. In the typical temperature range of 0.1 -1.2 GK, almost all the contributions to the reaction rate come from capture cross sections below 0.25 MeV. Conclusion: We have attempted to resolve the discrepancy in the spectroscopic factors of low-lying 16N levels and conclude that it would certainly be useful to perform a Coulomb dissociation experiment to find the low energy capture

  6. Luminescence Properties of GaN:Tb, GaN/AlGaN:Eu Superlattice, and AlN:Tb and Eu.

    NASA Astrophysics Data System (ADS)

    Lozykowski, H. J.; Jadwisienczak, W. M.; Brown, I. G.

    2001-03-01

    We report on recent progress in the investigation of cathodoluminescence (CL) of GaN doped with Tb, the visible photoluminescence (PL) and CL of GaN and Al_0.14Ga_0.86N /GaN superlattice doped with Eu, and the CL from AlN doped with Eu and Tb. The CL of GaN:Tb shows sharp emission lines corresponding to Tb^3+ ions transitions resolved in the spectral range from 350 nm to 750 nm, and observed over the temperature range of 7 - 330 K. The luminescence exhibits transitions which originate in the ^5D3 and ^5D4 levels and terminate in the ^7F manifolds. The depth resolved CL spectra analysis show a luminescence surface dead layer thickness of ~20 nm. The decay times for ^5D_3-->^7F5 (423.4nm) and ^5D_4-->^7F5 (551.6nm) transitions at 7 K are ~0.7 and ~1.8 ms, with little change with temperature. The visible PL and CL of GaN and Al_0.14Ga_0.86N/GaN superlattice doped with Eu ions, show sharp characteristic emission lines corresponding to Eu^3+ intra-4f^6-shell transitions. The luminescence shows dominant ^5D_0-->^7F_1,2,3 and weaker ^5D_0-->^7F_4,5,6 and ^5D_1-->^7F1 transitions. The intensity of Eu emission from Al_0.14Ga_0.86N/GaN superlattice annealed in N2 is ~58% stronger than from Eu in the GaN epilayer. Strong CL was observed from AlN thin single crystal films doped with Eu^3+ and Tb^3+ ions. The space group symmetry of the wurtzite AlN is C-P6_3mc and the Al cation occupies the site of point group symmetry C_3v. We assume that those implanted RE ions in AlN occupy relaxed substitutional Al-sites with hexagonal C_3v crystal symmetry. Emission lines corresponding to Eu^3+ and Tb^3+ intra-4f^n-shell transitions are resolved in the spectral range from 300 to 900 nm. The CL kinetics for several transitions of Eu^3+ (^5D_0), Tb^3+ (^5D_3,4) were analyzed. (Electronic mail: lozykows/@bobcat.ent.ohiou.edu)

  7. Theoretical studies on ultraviolet nearly lattice-matched BAlGaN/BAlGaN quantum well structures with quaternary BAlGaN barriers

    NASA Astrophysics Data System (ADS)

    Park, Seoung-Hwan; Ahn, Doyeol

    2016-07-01

    Light emission characteristics of B x Al y Ga1- x - y N/BAlGaN quantum well (QW) structures with quaternary BAlGaN barrier were investigated using the multiband effective-mass theory. The internal field in the BAlGaN well of the BAlGaN/AlN QW structure is shown to be large (˜10 MV/cm) under the lattice-matched condition (ɛ = 0.0%). On the other hand, the internal field is significantly reduced by using BAlGaN barrier and the peak intensity of the spontaneous emission coefficient of the lattice-matched BAlGaN/BAlGaN QW structure is comparable to that of the conventional BAlGaN/AlN QW structure. We observe that the light intensity of the lattice-matched BAlGaN/BAlGaN QW structure is comparable to that of the conventional BAlGaN/AlN QW structure. Also, we observe that the nearly lattice-matched BAlGaN/BAlGaN QW structure with small strain (0.5%) has about 3 times larger peak intensity than the conventional QW AlGaN/AlN structure. Hence, BAlGaN/BAlGaN QW system could be used as a UV light source with a higher light emission and a higher crystal quality, compared to conventional AlGaN/AlN QW structures with larger strain (1.78%).

  8. Dynamical coupled-channels study of {pi}N{yields}{pi}{pi}N reactions

    SciTech Connect

    Kamano, H.; Julia-Diaz, B.; Lee, T.-S. H.; Matsuyama, A.; Sato, T.

    2009-02-15

    As a step toward performing a complete coupled-channels analysis of the world data of {pi}N,{gamma}*N{yields}{pi}N,{eta}N,{pi}{pi}N reactions, the {pi}N{yields}{pi}{pi}N reactions are investigated starting with the dynamical coupled-channels model developed in Phys. Rev. C 76, 065201 (2007). The channels included are {pi}N,{eta}N, and {pi}{pi}N which has {pi}{delta},{rho}N, and {sigma}N resonant components. The nonresonant amplitudes are generated from solving a set of coupled-channels equations with the meson-baryon potentials defined by effective Lagrangians. The resonant amplitudes are generated from 16 bare excited nucleon (N*) states that are dressed by the nonresonant interactions as constrained by the unitarity condition. The data of total cross sections and {pi}N and {pi}{pi} invariant mass distributions of {pi}{sup +}p{yields}{pi}{sup +}{pi}{sup +}n,{pi}{sup +}{pi}{sup 0}p and {pi}{sup -}p{yields}{pi}{sup +}{pi}{sup -}n,{pi}{sup -}{pi}{sup 0}p,{pi}{sup 0}{pi}{sup 0}n reactions from threshold to the invariant mass W=2 GeV can be described to a very large extent. We show the importance of the coupled-channels effects and the strong interference among the contributions from the {pi}{delta},{sigma}N, and {rho}N channels. The large interference between the resonant and nonresonant amplitudes is also demonstrated. Possible future developments are discussed.

  9. N-15 tracing helps explaining N leaching losses from contrasting forest ecosystems

    NASA Astrophysics Data System (ADS)

    Staelens, J.; Rütting, T.; Huygens, D.; Müller, C.; Verheyen, K.; Boeckx, P.

    2009-04-01

    Despite chronically enhanced nitrogen (N) deposition to forest ecosystems in Europe and NE America, considerable N retention by forests has been observed, reducing N leaching losses. Organic and mineral soil layers typically immobilize more N than the aboveground biomass, but it is unclear which factors determine N retention in forest ecoystems. However, this knowledge is crucial to assess the impact of changing anthropogenic N emissions on future N cycling and N loss of forests. For coniferous and deciduous forest stands at comparable sites, it is known that both N deposition onto the forest floor as well as N loss by leaching below the rooting zone are significantly higher in coniferous stands. In addition, the N loss in coniferous stands is often more enhanced than can be explained by the higher N input only. This suggests lower N retention by coniferous stands, and may be related to differences in litter and soil characteristics, microbial activity, and N uptake by plant roots. To test this hypothesis, we studied the effect of forest type on N retention using 15N tracing techniques: a field tracer experiment and a combination of in situ isotope pool dilution and a tracing model. The N dynamics were examined for two adjacent forest stands (pedunculate oak (Quercus robur L.) and Scots pine (Pinus sylvestris L.)) on a well-drained sandy soil and with a similar stand history, located in a region with high N deposition (Belgium). Input-output N budgets were established by quantifying atmospheric deposition and leaching below the rooting zone, and confirmed the above finding of higher N deposition and disproportionately higher N loss for the pine stand compared to the oak stand. First, the fate of inorganic N within the ecosystems was studied by spraying three pulses of dissolved 15N, either as ammonium or as nitrate, onto the forest floor in 12 plots of 25 m2. The organic and mineral soil layers, tree roots, soil water percolate, ferns, and tree foliage were sampled

  10. Some properties of n-dimensional triangulations

    NASA Technical Reports Server (NTRS)

    Lawson, C. L.

    1985-01-01

    A number of mathematical results relevant to the problem of constructing a triangulation, i.e., a simplicial tessellation, of the convex hull of an arbitrary finite set of points in n-space are described. The principal results achieved are: (1) a set of n+2 points in n-space may be triangulated in at most 2 different ways; (2) the sphere test defined in this report selects a preferred one of these two triangulations; (3) a set of parameters is defined that permits the characterization and enumeration of all sets of n+2 points in n-space that are significantly different from the point of view of their possible triangulation; (4) the local sphere test induces a global sphere test property for a triangulation; and (5) a triangulation satisfying the global sphere property is dual to the n-dimensional Dirichlet tesselation, i.e., it is a Delaunay triangulation.

  11. Valence band offsets of Sc x Ga1‑x N/AlN and Sc x Ga1‑x N/GaN heterojunctions

    NASA Astrophysics Data System (ADS)

    Tsui, H. C. L.; Goff, L. E.; Palgrave, R. G.; Beere, H. E.; Farrer, I.; Ritchie, D. A.; Moram, M. A.

    2016-07-01

    The valence band offsets of Sc x Ga1‑x N/AlN heterojunctions were measured by x-ray photoelectron spectroscopy (XPS) and were found to increase from 0.42 eV to 0.95 eV as the Sc content x increased from 0 to 0.15. The increase in valence band offset with increasing x is attributed to the corresponding increase in spontaneous polarization of the wurtzite structure. The Sc x Ga1‑x N/AlN heterojunction is type I, similar to other III-nitride-based heterojunctions. The data also indicate that a type II staggered heterojunction, which can enhance spatial charge separation, could be formed if Sc x Ga1‑x N is grown on GaN.

  12. N95 respirator use during advanced pregnancy

    PubMed Central

    Roberge, Raymond J.; Kim, Jung-Hyun; Powell, Jeffrey B.

    2015-01-01

    Background To determine the physiological and subjective effects of wearing an N95 filtering facepiece respirator (N95 FFR) in advanced stages of pregnancy. Methods Healthy pregnant women (n = 22) and nonpregnant women (n = 22) had physiological and subjective measurements taken with and without wearing an N95 FFR during exercise and postural sedentary activities over a 1-hour period. Results There were no differences between the pregnant and nonpregnant women with respect to heart rate, respiratory rate, oxygen saturation, transcutaneous carbon dioxide level, chest wall temperature, aural temperature, and subjective perceptions of exertion and thermal comfort. No significant effect on fetal heart rate was noted. Conclusions Healthy pregnant women wearing an N95 FFR for 1 hour during exercise and sedentary activities did not exhibit any significant differences in measured physiological and subjective responses compared with nonpregnant women. PMID:25278401

  13. The influences of AlN/GaN superlattices buffer on the characteristics of AlGaN/GaN-on-Si (1 1 1) template

    NASA Astrophysics Data System (ADS)

    Ni, Yiqiang; He, Zhiyuan; Zhou, Deqiu; Yao, Yao; Yang, Fan; Zhou, Guilin; Shen, Zhen; Zhong, Jian; Zhen, Yue; Zhang, Baijun; Liu, Yang

    2015-07-01

    The influence of AlN/GaN superlattices (SL) buffer on the characteristics of AlGaN/GaN-on-Si (1 1 1) template was studied in detail. There existed an optimized Relative AlN Thickness (RAT) in the superlattices buffer which can not only further filtering the edge- and screw-type dislocations to the upper epilayer and lead to a good crystal quality with narrowest (0 0 0 2) and (1 0 -1 2) full width of half maximum (FWHMs), 439″ and 843″, but also improve the surface roughness to enhance the Two dimensional electron gas (2DEG) mobility and superior electrical properties were achieved. Moreover, an optimized RAT in SL can induce a proper compressive stress to the subsequently grown GaN epilayer and protect it from crack during the cooling step, which can also lead to a better wafer bending.

  14. Mechanism of the Fischer reaction. Rearrangement of cyclohexanone N-methylphenylhydrazone and N,N'-dimethyl-N-phenyl-N'-(1-cyclohexenyl)hydrazine to 9-methyl-1,2,3,4-tetrahydrocarbazole

    SciTech Connect

    Przheval'skii, N.M.; Kletskii, M.E.; Grandberg, I.I.; Kostromina, L.Yu.

    1985-12-01

    The kinetics of the thermal and acid-catalyzed Fischer reaction of cyclohexanone N-methylphenylhydrazone and N,N'-dimethyl-N-phenyl-N'-(1-cyclohexenyl)hydrazine were studied by a spectrophotometric method. Formation of the carbon-carbon bond proceeds by a (3,3)-sigmatropic shift mechanism. This conclusion was confirmed by MINDO/3 calculations of the rearrangement of a model divinylhydrazine.

  15. Asymmetric quantum-well structures for AlGaN/GaN/AlGaN resonant tunneling diodes

    NASA Astrophysics Data System (ADS)

    Yang, Lin'an; Li, Yue; Wang, Ying; Xu, Shengrui; Hao, Yue

    2016-04-01

    Asymmetric quantum-well (QW) structures including the asymmetric potential-barrier and the asymmetric potential-well are proposed for AlGaN/GaN/AlGaN resonant tunneling diodes (RTDs). Theoretical investigation gives that an appropriate decrease in Al composition and thickness for emitter barrier as well as an appropriate increase of both for collector barrier can evidently improve the negative-differential-resistance characteristic of RTD. Numerical simulation shows that RTD with a 1.5-nm-thick GaN well sandwiched by a 1.3-nm-thick Al0.15Ga0.85N emitter barrier and a 1.7-nm-thick Al0.25Ga0.75N collector barrier can yield the I-V characteristic having the peak current (Ip) and the peak-to-valley current ratio (PVCR) of 0.39 A and 3.6, respectively, about double that of RTD with a 1.5-nm-thick Al0.2Ga0.8N for both barriers. It is also found that an introduction of InGaN sub-QW into the diode can change the tunneling mode and achieve higher transmission coefficient of electron. The simulation demonstrates that RTD with a 2.8-nm-thick In0.03Ga0.97N sub-well in front of a 2.0-nm-thick GaN main-well can exhibit the I-V characteristic having Ip and PVCR of 0.07 A and 11.6, about 7 times and double the value of RTD without sub-QW, respectively. The purpose of improving the structure of GaN-based QW is to solve apparent contradiction between the device structure and the device manufacturability of new generation RTDs for sub-millimeter and terahertz applications.

  16. Growth and Stress-induced Transformation of Zinc blende AlN Layers in Al-AlN-TiN Multilayers

    PubMed Central

    Li, Nan; Yadav, Satyesh K.; Wang, Jian; Liu, Xiang-Yang; Misra, Amit

    2015-01-01

    AlN nanolayers in sputter deposited {111}Al/AlN/TiN multilayers exhibit the metastable zinc-blende-structure (z-AlN). Based on density function theory calculations, the growth of the z-AlN is ascribed to the kinetically and energetically favored nitridation of the deposited aluminium layer. In situ nanoindentation of the as-deposited {111}Al/AlN/TiN multilayers in a high-resolution transmission electron microscope revealed the z-AlN to wurzite AlN phase transformation through collective glide of Shockley partial dislocations on every two {111} planes of the z-AlN. PMID:26681109

  17. Growth and stress-induced transformation of zinc blende AlN layers in Al-AlN-TiN multilayers

    DOE PAGESBeta

    Li, Nan; Yadav, Satyesh K.; Wang, Jian; Liu, Xiang -Yang; Misra, Amit

    2015-12-18

    We report that AlN nanolayers in sputter deposited {111}Al/AlN/TiN multilayers exhibit the metastable zinc-blende-structure (z-AlN). Based on density function theory calculations, the growth of the z-AlN is ascribed to the kinetically and energetically favored nitridation of the deposited aluminium layer. In situ nanoindentation of the as-deposited {111}Al/AlN/TiN multilayers in a high-resolution transmission electron microscope revealed the z-AlN to wurzite AlN phase transformation through collective glide of Shockley partial dislocations on every two {111} planes of the z-AlN.

  18. Hot-electron real-space transfer and longitudinal transport in dual AlGaN/AlN/{AlGaN/GaN} channels

    NASA Astrophysics Data System (ADS)

    Šermukšnis, E.; Liberis, J.; Matulionis, A.; Avrutin, V.; Ferreyra, R.; Özgür, Ü.; Morkoç, H.

    2015-03-01

    Real-space transfer of hot electrons is studied in dual-channel GaN-based heterostructure operated at or near plasmon-optical phonon resonance in order to attain a high electron drift velocity at high current densities. For this study, pulsed electric field is applied in the channel plane of a nominally undoped Al0.3Ga0.7N/AlN/{Al0.15Ga0.85N/GaN} structure with a composite channel of Al0.15Ga0.85N/GaN, where the electrons with a sheet density of 1.4 × 1013 cm-2, estimated from the Hall effect measurements, are confined. The equilibrium electrons are situated predominantly in the Al0.15Ga0.85N layer as confirmed by capacitance-voltage experiment and Schrödinger-Poisson modelling. The main peak of the electron density per unit volume decreases as more electrons occupy the GaN layer at high electric fields. The associated decrease in the plasma frequency induces the plasmon-assisted decay of non-equilibrium optical phonons (hot phonons) confirmed by the decrease in the measured hot-phonon lifetime from 0.95 ps at low electric fields down below 200 fs at fields of E \\gt 4 kV cm-1 as the plasmon-optical phonon resonance is approached. The onset of real-space transfer is resolved from microwave noise measurements: this source of noise dominates for E \\gt 8 kV cm-1. In this range of fields, the longitudinal current exceeds the values measured for a mono channel reference Al0.3Ga0.7N/AlN/GaN structure. The results are explained in terms of the ultrafast decay of hot phonons and reduced alloy scattering caused by the real-space transfer in the composite channel.

  19. On the Decimal Numbers Base "n"

    ERIC Educational Resources Information Center

    Poon, K.-K.; Yeung, K.-W.; Shiu, W.-C.

    2005-01-01

    This paper focuses on the representation of a proper fraction "a"/"b" by a decimal number base "n" where "n" is any integer greater than 1. The scope is narrowed to look at only fractions where "a","b" are positive integers with "a" less than "b" and "b" not equal to 0 nor equal to 1. Some relationships were found between "b" and "n", which…

  20. Effects of HF content in the (FH)(n)F- anion on the formation of ionic plastic crystal phases of N-ethyl-N-methylpyrrolidinium and N,N-dimethylpyrrolidinium fluorohydrogenate salts.

    PubMed

    Taniki, Ryosuke; Matsumoto, Kazuhiko; Hagiwara, Rika

    2014-01-28

    Fluorohydrogenate salts based on N-ethyl-N-methylpyrrolidinium (EMPyr(FH)nF) and N,N-dimethylpyrrolidinium (DMPyr(FH)nF) cations were synthesized, and the effects of the HF content n in EMPyr(FH)nF (1.0 ≤ n ≤ 2.3) and DMPyr(FH)nF (1.0 ≤ n ≤ 2.0) on their thermal and structural properties were discussed, focusing on the characterization of ionic plastic crystal (IPC) phases. Several solid phases (IPC (I) and IPC (II) phases, and crystal phases of EMPyr(FH)1F, EMPyr(FH)2F, and EMPyr(FH)3F) are observed in the EMPyr(FH)nF system. The IPC (I) phase has an NaCl-type structure and is composed of EMPyr(+) cations and (FH)nF(-) (n = 1, 2, and 3) anions randomly occupying the anion positions in the lattice over a wide range of n values in (FH)nF(-). The melting point of EMPyr(FH)nF in the range 1.8 ≤ n ≤ 2.3 is maximal at n = 2.0, whereas it increases with a decrease in n in the range 1.0 ≤ n ≤ 1.2. Furthermore, in the range 1.3 ≤ n ≤ 1.7, the solid phase is regarded as the IPC phase (IPC (II)), and their melting points are nearly constant (260-270 K). In the DMPyr(FH)nF system, the IPC (I') phase and crystal phases of DMPyr(FH)1F and DMPyr(FH)2F were observed. Although the IPC (I') phase has an NaCl-type structure, similar to the IPC (I) phase of EMPyr(FH)nF, it has higher ordering compared to the IPC (I) phase. The melting point of DMPyr(FH)nF increases monotonously with decreasing n but disappears in the small n region where the salt decomposes below the melting point.

  1. Stranski-Krastanow growth of (112¯2)-oriented GaN/AlN quantum dots

    NASA Astrophysics Data System (ADS)

    Lahourcade, L.; Valdueza-Felip, S.; Kehagias, T.; Dimitrakopulos, G. P.; Komninou, P.; Monroy, E.

    2009-03-01

    Semipolar GaN(112¯2) deposited on AlN(112¯2) by plasma-assisted molecular-beam epitaxy can follow the Frank-Van der Merwe or the Stranski-Krastanow growth mode as a function of the Ga/N ratio. N-rich grown GaN relaxes elastically at a critical thickness but the resulting GaN islands present multiple crystallographic orientations. In contrast, after deposition of a few two-dimensional GaN monolayers under Ga-rich conditions, a growth interruption in vacuum induces (112¯2)-oriented islanding. Applying this latter procedure, we have synthesized GaN/AlN quantum dot superlattices with reduced internal electric field.

  2. Green light emission by InGaN/GaN multiple-quantum-well microdisks

    SciTech Connect

    Hsu, Yu-Chi; Lo, Ikai Shih, Cheng-Hung; Pang, Wen-Yuan; Hu, Chia-Hsuan; Wang, Ying-Chieh; Tsai, Cheng-Da; Chou, Mitch M. C.; Hsu, Gary Z. L.

    2014-03-10

    The high-quality In{sub x}Ga{sub 1−x}N/GaN multiple quantum wells were grown on GaN microdisks with γ-LiAlO{sub 2} substrate by using low-temperature two-step technique of plasma-assisted molecular beam epitaxy. We demonstrated that the hexagonal GaN microdisk can be used as a strain-free substrate to grow the advanced In{sub x}Ga{sub 1−x}N/GaN quantum wells for the optoelectronic applications. We showed that the green light of 566-nm wavelength (2.192 eV) emitted from the In{sub x}Ga{sub 1−x}N/GaN quantum wells was tremendously enhanced in an order of amplitude higher than the UV light of 367-nm wavelength (3.383 eV) from GaN.

  3. More on two-dimensional O (N ) models with N =(0 ,1 ) supersymmetry

    NASA Astrophysics Data System (ADS)

    Peterson, Adam J.; Kurianovych, Evgeniy; Shifman, Mikhail

    2016-03-01

    We study the behavior of two-dimensional supersymmetric connections of n copies of O (N ) models with an N =(0 ,1 ) heterotic deformation generated by a right-moving fermion. We develop the model in analogy with the connected N =(0 ,2 ) C P (N -1 ) models for the case of a single connecting fermionic superfield. We calculate the effective potential in the large-N limit and determine the vacuum field configurations. Similarly to other supersymmetry (SUSY) connected models we find that SUSY is unbroken under certain conditions despite the vanishing of the Witten index. Specifically, this preservation of SUSY occurs when we have an even number n of O (N ) families. As in previous cases we show that this result follows from a Zn symmetry under a particular exchange of the O (N ) families. This leads to a definition of a modified Witten index, which guarantees the preservation of SUSY in this case.

  4. Titanium induced polarity inversion in ordered (In,Ga)N/GaN nanocolumns

    NASA Astrophysics Data System (ADS)

    Kong, X.; Li, H.; Albert, S.; Bengoechea-Encabo, A.; Sanchez-Garcia, M. A.; Calleja, E.; Draxl, C.; Trampert, A.

    2016-02-01

    We report on the formation of polarity inversion in ordered (In,Ga)N/GaN nanocolumns grown on a Ti-masked GaN-buffered sapphire substrate by plasma assisted molecular beam epitaxy. High-resolution transmission electron microscopy and electron energy-loss spectroscopy reveal a stacking fault-like planar defect at the homoepitaxial GaN interface due to Ti incorporation, triggering the generation of N-polar domains in Ga-polar nanocolumns. Density functional theory calculations are applied to clarify the atomic configurations of a Ti monolayer occupation on the GaN (0002) plane and to prove the inversion effect. The polarity inversion leads to an enhanced indium incorporation in the subsequent (In,Ga)N segment of the nanocolumn. This study provides a deeper understanding of the effects of Ti mask in the well-controlled selective area growth of (In,Ga)N/GaN nanocolumns.

  5. Titanium induced polarity inversion in ordered (In,Ga)N/GaN nanocolumns.

    PubMed

    Kong, X; Li, H; Albert, S; Bengoechea-Encabo, A; Sanchez-Garcia, M A; Calleja, E; Draxl, C; Trampert, A

    2016-02-12

    We report on the formation of polarity inversion in ordered (In,Ga)N/GaN nanocolumns grown on a Ti-masked GaN-buffered sapphire substrate by plasma assisted molecular beam epitaxy. High-resolution transmission electron microscopy and electron energy-loss spectroscopy reveal a stacking fault-like planar defect at the homoepitaxial GaN interface due to Ti incorporation, triggering the generation of N-polar domains in Ga-polar nanocolumns. Density functional theory calculations are applied to clarify the atomic configurations of a Ti monolayer occupation on the GaN (0002) plane and to prove the inversion effect. The polarity inversion leads to an enhanced indium incorporation in the subsequent (In,Ga)N segment of the nanocolumn. This study provides a deeper understanding of the effects of Ti mask in the well-controlled selective area growth of (In,Ga)N/GaN nanocolumns.

  6. Structures and stabilities of (OsnN)0,±(n = 7 - 11) clusters

    NASA Astrophysics Data System (ADS)

    Guo, W. L.; Zhang, L. L.; Luo, M.; Zhang, X. R.

    2015-08-01

    Structures and stabilities of (OsnN)0,± clusters have been systematically studied via using density functional theory (DFT) with generalized gradient approximation (GGA). The calculations show that the stable configurations of (OsnN)0,± are such structures with one N atom bonded to the external of the basic constructions consisting of Os atoms. Meanwhile, (OsnN)0,± clusters (n = 7 - 9) represent “magic number” effect, and 8 is the magic number. Additionally, the ground-state structures of (Os8N)0,± clusters have the best stability, while that of Os7N cluster possesses the worst stability. The result of the study on the ionization potential (IP) and the electron affinity (EA) shows that there are not topological differences among the configurations of (OsnN)0,±(n = 7 - 11) clusters.

  7. Parafoveal load of word N+1 modulates preprocessing effectiveness of word N+2 in Chinese reading.

    PubMed

    Yan, Ming; Kliegl, Reinhold; Shu, Hua; Pan, Jinger; Zhou, Xiaolin

    2010-12-01

    Preview benefits (PBs) from two words to the right of the fixated one (i.e., word N + 2) and associated parafoveal-on-foveal effects are critical for proposals of distributed lexical processing during reading. This experiment examined parafoveal processing during reading of Chinese sentences, using a boundary manipulation of N + 2-word preview with low- and high-frequency words N + 1. The main findings were (a) an identity PB for word N + 2 that was (b) primarily observed when word N + 1 was of high frequency (i.e., an interaction between frequency of word N + 1 and PB for word N + 2), and (c) a parafoveal-on-foveal frequency effect of word N + 1 for fixation durations on word N. We discuss implications for theories of serial attention shifts and parallel distributed processing of words during reading.

  8. Stranski-Krastanow growth of (1122)-oriented GaN/AlN quantum dots

    SciTech Connect

    Lahourcade, L.; Monroy, E.; Kehagias, T.; Dimitrakopulos, G. P.; Komninou, P.

    2009-03-16

    Semipolar GaN(1122) deposited on AlN(1122) by plasma-assisted molecular-beam epitaxy can follow the Frank-Van der Merwe or the Stranski-Krastanow growth mode as a function of the Ga/N ratio. N-rich grown GaN relaxes elastically at a critical thickness but the resulting GaN islands present multiple crystallographic orientations. In contrast, after deposition of a few two-dimensional GaN monolayers under Ga-rich conditions, a growth interruption in vacuum induces (1122)-oriented islanding. Applying this latter procedure, we have synthesized GaN/AlN quantum dot superlattices with reduced internal electric field.

  9. The excitation functions of 187Re(n,2n) 186m,gRe reactions

    NASA Astrophysics Data System (ADS)

    Huang, Xiao-Long; Kang, Meng-Xiao; Liu, Li-Le; Wang, Ji-Min; Chen, Xiong-Jun

    2016-08-01

    A new value for the emission probability of 137.144 keV γ-rays from 186gRe decay is recommended to be (9.47±0.03)/%. Using this value the measured cross sections for 187Re(n,2n)186mRe and 187Re(n,2n)186gRe reactions around 14 MeV are analyzed, and the cross section for 187Re(n,2n)186m+gRe reaction at 14.8 MeV is (2213±116) mb. The UNF code was adopted to calculate the cross sections for the 187Re(n,2n)186m+gRe reaction below 20 MeV, fitting to the value (2213±116) mb at 14.8 MeV using a set of optimum neutron optical potential parameters which were obtained based on the relevant experimental data of rhenium. The isomeric cross section ratio for the 187Re(n,2n)186m,gRe reaction was analyzed using the V-H method based on nuclear statistical theory. Combining these calculated results, the excitation functions for the 187Re(n,2n)186mRe and 187Re(n,2n)186gRe reactions were obtained. The obtained results are in good agreement with the available experimental data.

  10. Aqueous complexation of trivalent lanthanide and actinide cations by N,N,N'{sub 2},N'-tetrakis(2-pyridylmethyl)ethylenediamine.

    SciTech Connect

    Beitz, J. V.; Ensor, D. D.; Jensen, M. P.; Morss, L. R.

    1999-06-16

    The aqueous complexation reactions of trivalent lanthanide and actinide cations with the hexadentate ligand N,N,N{prime},N{prime}-tetrakis(2-pyridylmethyl)ethylenediamine (TPEN), have been characterized using potentiometric and spectroscopic techniques in 0.1 M NaClO{sub 4} At 25 C, the stability constant of Am(TPEN){sup 3+} is two orders of magnitude larger than that of Sm(TPEN){sup 3+}, reflecting the stronger interactions of the trivalent actinide cations with softer ligands as compared to lanthanide cations.

  11. Comparative studies on the thermal stability and corrosion resistance of CrN, CrSiN, and CrSiN/AlN coatings

    SciTech Connect

    Kim, Gwang Seok; Kim, Sung Min; Lee, Sang Yul; Lee, Bo Young

    2009-07-15

    In this work, three kinds of Cr-based nitride coatings such as monolithic CrN, CrSiN coatings, and multilayered CrSiN/AlN coating with bilayer period of 3.0 nm were deposited on both Si (100) wafer and AISI H13 steel substrates by unbalanced magnetron sputtering. Thermal stability of these coatings was evaluated by annealing the coatings at temperatures between 600 and 1000 degree sign C for 30 min in air. In addition, the corrosion behaviors of these coatings were investigated by potentiodynamic polarization tests in a deaerated 3.5 wt. % NaCl solution at 40 degree sign C. Results from annealing test show the monolithic CrN and CrSiN coatings were completely oxidized after annealed at 800 and 900 degree sign C, and their cross sectional images and atomic force microscopy showed a loose and very porous morphology due to the oxidation. Also, the hardness values of the monolithic CrN and CrSiN coatings were decreased significantly from 22 and 27 GPa to 8 and 14 GPa, respectively. However, the multilayered CrSiN/AlN coating still exhibited a dense microstructure without visible change after annealed at 1000 degree sign C, and moreover, the relatively high hardness of 25 GPa was maintained. The superior thermal stability of the CrSiN/AlN multilayer coating could be attributed to the formation of the dense and stable oxidation barrier consisted of the Al{sub 2}O{sub 3}, Cr{sub 2}O{sub 3}, and amorphous SiO{sub 2} phases near the surface region, which retard the diffusion of oxygen into the coating. In the potentiodynamic polarization test results, it was found that the significantly improved corrosion resistance of the multilayered CrSiN/AlN coating was observed in comparison with those from the monolithic CrN and CrSiN coatings, and its corrosion current density (i{sub corr}) and protective efficiency were measured to be approximately 4.21 {mu}A/cm{sup 2} and 95%, respectively.

  12. Oxidation of manganese and iron by Leptothrix discophora: Use of N,N,N prime ,N prime -tetramethyl-p-phenylenediamine as an indicator of metal oxidation

    SciTech Connect

    de Vrind-de Jong, E.W.; Corstjens, P.L.A.M.; Kempers, E.S.; Westbroek, P.; de Vrind, J.P.M. )

    1990-11-01

    A new method for the quantification and characterization of manganese-oxidizing activity by spent culture medium of Leptothrix discophora SS-1 was developed. It is based on the formation of the dye Wurster blue from N,N,N{prime},N{prime}-tetramethyl-p-phenylenediamine by oxidized manganese generated in the spent medium. The kinetic parameters thus obtained agreed well with data obtained with other methods. It was also possible to demonstrate iron oxidation by spent culture medium. The kinetics of the process and inhibition by enzyme poisons suggest that iron oxidation is enzymatically catalyzed. Probably two different factors are involved in manganese and iron oxidation.

  13. Oxidation of Manganese and Iron by Leptothrix discophora: Use of N,N,N',N'-Tetramethyl-p-Phenylenediamine as an Indicator of Metal Oxidation.

    PubMed

    de Vrind-de Jong, E W; Corstjens, P L; Kempers, E S; Westbroek, P; de Vrind, J P

    1990-11-01

    A new method for the quantification and characterization of manganese-oxidizing activity by spent culture medium of Leptothrix discophora SS-1 was developed. It is based on the formation of the dye Wurster blue from N,N,N',N'-Tetramethyl-p-phenylenediamine by oxidized manganese generated in the spent medium. The kinetic parameters thus obtained agreed well with data obtained with other methods. It was also possible to demonstrate iron oxidation by spent culture medium. The kinetics of the process and inhibition by enzyme poisons suggest that iron oxidation is enzymatically catalyzed. Probably two different factors are involved in manganese and iron oxidation. PMID:16348351

  14. On four dimensional N = 3 superconformal theories

    NASA Astrophysics Data System (ADS)

    Aharony, Ofer; Evtikhiev, Mikhail

    2016-04-01

    In this note we study four dimensional theories with N = 3 superconformal symmetry, that do not also have N = 4 supersymmetry. No examples of such theories are known, but their existence is also not ruled out. We analyze several properties that such theories must have. We show that their conformal anomalies obey a = c. Using the N = 3 superconformal algebra, we show that they do not have any exactly marginal deformations preserving N = 3 supersymmetry, or global symmetries (except for their R-symmetries). Finally, we analyze the possible dimensions of chiral operators labeling their moduli space.

  15. Residence Time Statistics for N Renewal Processes

    NASA Astrophysics Data System (ADS)

    Burov, S.; Barkai, E.

    2011-10-01

    We present a study of residence time statistics for N renewal processes with a long tailed distribution of the waiting time. Such processes describe many nonequilibrium systems ranging from the intensity of N blinking quantum dots to the residence time of N Brownian particles. With numerical simulations and exact calculations, we show sharp transitions for a critical number of degrees of freedom N. In contrast to the expectation, the fluctuations in the limit of N→∞ are nontrivial. We briefly discuss how our approach can be used to detect nonergodic kinetics from the measurements of many blinking chromophores, without the need to reach the single molecule limit.

  16. Climate impacts on belowground N cycling, N2O fluxes, and N leaching: Development of a mechanistic N reactive transport model in CLM

    NASA Astrophysics Data System (ADS)

    Riley, W. J.; Tang, J.; Koven, C.

    2011-12-01

    Nitrogen (N) availability is a dominant factor controlling the terrestrial carbon response to climate and climate change. Further, N2O from managed and unmanaged ecosystems is an important greenhouse gas that is not, or poorly, represented in global climate models. Here we describe the development, testing, and application of a vertically-resolved, multi-phase reactive transport N cycle model integrated in CLM4, the land-surface model in the Community Earth System Model (CESM). This model development builds on our integration of vertically-resolved soil C dynamics in CLM by including process representations of nitrification, denitrification, microbial activity, leaching, equilibrium partitioning between aqueous and gaseous phases, sorption, and exchanges with the atmosphere. We first present tests of the belowground reactive transport model against several agricultural datasets with varying levels (0 - 250 kg N ha-1) and types (NH4NO3; (NH4)2SO4; CO(NH2)2; KNO3) of fertilizer application, water additions, and plant types. Comparisons are also made to N cycle observations in unmanaged forests and grasslands and to two atmospheric N2O inversions. We analyze the sensitivity of our regional predictions to uncertainty in N deposition and fertilizer application, belowground model parameters, and model representation of plant N processes. Finally, we present an analysis of the impact of incorporation of these N cycling processes on soil C dynamics.

  17. Recombination of N4(+) ions with electrons

    NASA Technical Reports Server (NTRS)

    Cao, Y. S.; Johnsen, R.

    1991-01-01

    Using a modified high-pressure-afterglow/mass spectrometer apparatus similar to that described by Lee and Johnsen (1989), spectroscopic observations of afterglow helium plasmas, with N2 as a minor additive, were carried out in order to verify the mechanism suggested by Bates (1991) for dissociative recombination of electrons with N4(+) ions. It was found that dissociative recombination of electrons with N4(+) ions results in the formation of N2 molecules in the C 3Pi(u) (v = 0,1) state, with the recombination rate coefficient of (2.6 +/- 0.3) x 10 exp -6 cu cm/sec at 300 K.

  18. Simplest N-Sulfonylamine HNSO2.

    PubMed

    Deng, Guohai; Wu, Zhuang; Li, Dingqing; Linguerri, Roberto; Francisco, Joseph S; Zeng, Xiaoqing

    2016-09-14

    The simplest N-sulfonylamine HNSO2 has been generated in the gas phase through flash vacuum pyrolysis of methoxysulfonyl azide CH3OS(O)2N3. Its identification was accomplished by combining matrix-isolation IR spectroscopy and quantum chemical calculations. Both experimental and theoretical evidence suggest a stepwise decomposition of the azide via the methoxysulfonyl nitrene CH3OS(O)2N, observed in the 193 nm laser photolysis of the azide, with concerted fragmentation into CH2O and HNSO2. Upon the 193 nm laser irradiation, HNSO2 isomerizes into the novel N-hydroxysulfinylamine HONSO. PMID:27575523

  19. Use of N immobilization to tighten the N cycle in conventional agroecosystems.

    PubMed

    McSwiney, Claire P; Snapp, Sieglinde S; Gentry, Lowell E

    2010-04-01

    Soils in conventional agroecosystems are purposely held in a nitrogen (N)-saturated state to maximize crop yields. Planting winter annual cover crops when fields are usually fallow has been proposed to ameliorate N losses from soils. In this study we introduced winter annual cover crops into an N rate study with plots fertilized at 0, 34, 67, 101, 134, 168, and 202 kg N/ha in maize (Zea mays L.) to determine how winter annual cover crops affect yields, N2O and NO3- fluxes, and N pools. At the six-leaf stage and during flowering, incorporation of cover crop into soil resulted in a 30% reduction in maize biomass. Three weeks after fertilization, KCl-extractable soil mineral N was 75-87% lower in covercropped soils than in no-cover soils, indicating that N had been immobilized in the covercropped soils. At physiological maturity, there was no difference between cover and no-cover treatments in crop yield, which was maximized at 9 Mg/ha in 2006 and 7 Mg/ha in 2007. Where N rates exceed crop requirements, cover crop incorporation may reduce N exports as NO3- and N2O. Tighter N cycling in conventional agroecosystems could be fostered by matching N rates to the amount of N removed with grain and using N immobilization to retain N and support yields. If N immobilization is viewed as a means for efficient fertilizer N use rather than a process that decreases crop productivity, growers might be more willing to adopt cover-cropping practices.

  20. [Characteristics of ammonium N and nitrate N accumulation in dryland soil in relation with wheat yield].

    PubMed

    Miao, Yan-Fang; Li, Sheng-Xiu; Fu, Yan-Yan; Wang, Zhao-Hui; Xu, Xiao-Feng; Luo, Lai-Chao

    2014-04-01

    A total of eleven field trials in Yongshou, Shaanxi Province and seven in Luoyang, Henan Province were conducted with two treatments (without N as control and with 150 kg N x hm(-2) addition). The wheat biomass and seed yield were determined, and so were the nitrate and ammonium N concentrations in five layers (0-20, 20-40, 40-60, 60-80, 80-100 cm) at each trial site. Results showed that soil ammonium concentrations in the two provinces were very low while nitrate N concentrations were relatively high. Soil nitrate N occupied 91% of the total mineral N, and exhibited the same trend as the total mineral N in reflecting soil N supplying capacity. Without N application, the cumulative nitrate N amounts in the 0-40, 0-60, 0-80 and 0-100 cm layers in Yongshou were significantly correlated with wheat biomass and seed yield while no such correlation existed in Luoyang. With N addition, the relations of cumulative nitrate N of the different layers to wheat biomass and yield were greatly declined in Yongshou whereas those of Luoyang were changed to be negative. The yield increases were significantly correlated with the amount of nitrate N accumulated in the 0-80 and 0-100 cm layers of the two sites under N addition. Wheat mainly depended on nitrate N from the 0-20 cm layer at seedling stage, 0-40 cm at reviving, and 0-60 cm at elongation stages, and could utilize 0-100 cm nitrate N at maturity. After wheat harvest, the concentration of ammonium N was not significantly different from the initial value while that of nitrate N greatly decreased. PMID:25011293

  1. Use of N immobilization to tighten the N cycle in conventional agroecosystems.

    PubMed

    McSwiney, Claire P; Snapp, Sieglinde S; Gentry, Lowell E

    2010-04-01

    Soils in conventional agroecosystems are purposely held in a nitrogen (N)-saturated state to maximize crop yields. Planting winter annual cover crops when fields are usually fallow has been proposed to ameliorate N losses from soils. In this study we introduced winter annual cover crops into an N rate study with plots fertilized at 0, 34, 67, 101, 134, 168, and 202 kg N/ha in maize (Zea mays L.) to determine how winter annual cover crops affect yields, N2O and NO3- fluxes, and N pools. At the six-leaf stage and during flowering, incorporation of cover crop into soil resulted in a 30% reduction in maize biomass. Three weeks after fertilization, KCl-extractable soil mineral N was 75-87% lower in covercropped soils than in no-cover soils, indicating that N had been immobilized in the covercropped soils. At physiological maturity, there was no difference between cover and no-cover treatments in crop yield, which was maximized at 9 Mg/ha in 2006 and 7 Mg/ha in 2007. Where N rates exceed crop requirements, cover crop incorporation may reduce N exports as NO3- and N2O. Tighter N cycling in conventional agroecosystems could be fostered by matching N rates to the amount of N removed with grain and using N immobilization to retain N and support yields. If N immobilization is viewed as a means for efficient fertilizer N use rather than a process that decreases crop productivity, growers might be more willing to adopt cover-cropping practices. PMID:20437954

  2. Regulation of Nitrate-N Release from Temperate Forests: A Test of the N Flushing Hypothesis

    NASA Astrophysics Data System (ADS)

    Creed, I. F.; Band, L. E.; Foster, N. W.; Morrison, I. K.; Nicolson, J. A.; Semkin, R. S.; Jeffries, D. S.

    1996-11-01

    During the past decade, significant spatial and temporal variability in the release of nitrate-nitrogen (N) from catchments in a sugar maple forest in central Ontario was observed. To explain this variability, we tested the flushing hypothesis [Hornberger et al., 1994], where, when the soil saturation deficit is high, N accumulates in the upper layers of the soil and, as the soil saturation deficit decreases, the formation of a saturated subsurface layer flushes N from the upper layers of the soil into the stream. We used the Regional Hydro-Ecological Simulation System to simulate water, carbon, and N dynamics. A N flushing index was modeled as S/S30, the ratio of the current day saturation deficit to the previous 30-day average saturation deficit. A N source index was modeled as the ratio of N supply/demand. The relationship between the simulated N indices and the observed release of N indicated two mechanisms for the release of N from catchments: (1) a N flushing mechanism, where the N-enriched upper layer of the soil is flushed, after a period of low demand for N by the forest (e.g., during spring snowmelt and autumn stormflow, the water table rising into previously unsaturated parts of a N-enriched soil profile) or after a period of high demand for N by the forest (e.g., during summer droughts, the water table rising into previously saturated parts of a N-impoverished soil profile following a period of enhanced rates of nitrification); and (2) a N draining mechanism, where spring snowmelt recharge of the groundwater translocates N from the upper layer of the soil into deeper hydrological flow pathways that are released slowly over the year.

  3. N2-fixing red alder indirectly accelerates ecosystem nitrogen cycling

    USGS Publications Warehouse

    Perakis, Steven S.; Matkins, Joselin J.; Hibbs, David E.

    2012-01-01

    Symbiotic N2-fixing tree species can accelerate ecosystem N dynamics through decomposition via direct pathways by producing readily decomposed leaf litter and increasing N supply to decomposers, as well as via indirect pathways by increasing tissue and detrital N in non-fixing vegetation. To evaluate the relative importance of these pathways, we compared three-year decomposition and N dynamics of N2-fixing red alder leaf litter (2.34 %N) to both low-N (0.68 %N) and high-N (1.21 %N) litter of non-fixing Douglas-fir, and decomposed each litter source in four forests dominated by either red alder or Douglas-fir. We also used experimental N fertilization of decomposition plots to assess elevated N availability as a potential mechanism of N2-fixer effects on litter mass loss and N dynamics. Direct effects of N2-fixing red alder on decomposition occurred primarily as faster N release from red alder than Douglas-fir litter, but direct increases in N supply to decomposers via fertilization did not stimulate decomposition of any litter. Fixed N indirectly influenced detrital dynamics by increasing Douglas-fir tissue and litter N concentrations, which accelerated litter N release without accelerating mass loss. By increasing soil N, tissue N, and the rate of N release from litter of non-fixers, we conclude that N2-fixing vegetation can indirectly foster plant-soil feedbacks that contribute to the persistence of elevated N availability in terrestrial ecosystems.

  4. Continuous field measurement of N2O isotopologues using FTIR spectroscopy following 15N addition

    NASA Astrophysics Data System (ADS)

    Phillips, R. L.; Griffith, D. W.; Dijkstra, F. A.; Lugg, G.; Lawrie, R.; Macdonald, B.

    2012-12-01

    Anthropogenic additions of fertilizer nitrogen (N) have significantly increased the mole fraction of nitrous oxide (N2O) in the troposphere. Tracking the fate of fertilizer N and its transformation to N2O is important to advance knowledge of greenhouse gas emissions from soils. Transport and transformations are frequently studied using 15N labeling experiments, but instruments capable of continuous measurements of 15N-N2O at the surface of soil have only recently come to the fore. Our primary aim was to quantify emissions of N2O and the fraction of 15N emitted as N2O from an agricultural soil following 15N addition using a mobile Fourier Transform Infrared (FTIR) spectrometer. We set up a short-term field experiment on a coastal floodplain site near Nowra, New South Wales. We deployed an automated chamber system connected to a multi-pass cell (optical pathlength 24 m) and low resolution FTIR spectrometer to measure fluxes of all N2O isotopologues collected from five 0.25 m2 chambers every three hours. We measured N2O fluxes pre and post-application of 15N-labeled substrate as potassium nitrate (KNO3) or urea [CO(NH2)2] to the soil surface. Root mean square uncertainties for all isotopologue measurements were less than 0.3 nmol mol-1 for 1 minute average concentration measurements, and minimum detectable fluxes for each isotopologue were <0.1 ng N m-2 s-1. Emissions of all N2O isotopologues were evident immediately following 15N addition. Emissions of 14N15NO, 15N14NO and 15N15NO isotopologues subsided within 10 d, but 14N14NO fluxes were evident over the entire experiment. The figure provides an overview of the emissions. Cumulative 15N-N2O fluxes (sum of the three 15N isotopologues) per chamber for the 14 days following 15N addition ranged from 1.5 to 10.3 mg 15N-N2O m-2. The chambers were destructively sampled after 2 weeks and 15N analyzed in soil and plant material using isotope ratio mass spectrometry. Approximately 1% (range 0.7 - 1.9%) of the total amount of

  5. Microwave spectroscopy of the cold rubidium (n +1 ) d5 /2→n g and n h transitions

    NASA Astrophysics Data System (ADS)

    Lee, Jeonghun; Nunkaew, J.; Gallagher, T. F.

    2016-08-01

    We present an experimental technique that allows us to determine the zero-field intervals between high-ℓ states of Rb in a magneto-optical trap, in spite of the fact that we can only control the stray electric field in one direction. The technique is based on measuring a property of the atom that depends on the field, as opposed to its square. This approach allows the determination of the zero-field intervals and the magnitude of the stray field in the uncontrolled perpendicular direction. We use this technique to observe the microwave transitions of rubidium from the (n +1 ) d5 /2 states to the n g and n h states of 27 ≤n ≤30 . From the observed microwave transitions, we determine the quantum defects of the n g and n h states. Using the quantum defects of the n g and n h states and the adiabatic core polarization theory, we determine the Rb+ ionic dipole and quadrupole polarizabilities to be αd=9.12 (2 ) a03 and αq=14 (3 ) a05 , respectively.

  6. Demonstration of isotype GaN/AlN/GaN heterobarrier diodes by NH{sub 3}-molecular beam epitaxy

    SciTech Connect

    Fireman, Micha N.; Browne, David A.; Mazumder, Baishakhi; Speck, James S.; Mishra, Umesh K.

    2015-05-18

    The results of vertical transport through nitride heterobarrier structures grown by ammonia molecular beam epitaxy are presented. Structures are designed with binary layers to avoid the effects of random alloy fluctuations in ternary nitride barriers. The unintentional incorporation of Ga in the AlN growth is investigated by atom probe tomography and is shown to be strongly dependent on both the NH{sub 3} flowrate and substrate temperature growth parameters. Once nominally pure AlN layer growth conditions are achieved, structures consisting of unintentionally doped (UID) GaN spacer layers adjacent to a nominally pure AlN are grown between two layers of n+ GaN, from which isotype diodes are fabricated. Varying the design parameters of AlN layer thickness, UID spacer layer thickness, and threading dislocation density show marked effects on the vertical transport characteristics of these structures. The lack of significant temperature dependence, coupled with Fowler-Nordheim and/or Milliken-Lauritsen analysis, point to a prevalently tunneling field emission mechanism through the AlN barrier. Once flatband conditions in the UID layer are achieved, electrons leave the barrier with significant energy. This transport mechanism is of great interest for applications in hot electron structures.

  7. Continuous formation of N-chloro-N,N-dialkylamine solutions in well-mixed meso-scale flow reactors

    PubMed Central

    Jolley, Katherine E

    2015-01-01

    Summary The continuous flow synthesis of a range of organic solutions of N,N-dialkyl-N-chloramines is described using either a bespoke meso-scale tubular reactor with static mixers or a continuous stirred tank reactor. Both reactors promote the efficient mixing of a biphasic solution of N,N-dialkylamine in organic solvent, and aqueous sodium hypochlorite to achieve near quantitative conversions, in 72–100% in situ yields, and useful productivities of around 0.05 mol/h with residence times from 3 to 20 minutes. Initial calorimetric studies have been carried out to inform on reaction exotherms, rates and safe operation. Amines which partition mainly in the organic phase require longer reaction times, provided by the CSTR, to compensate for low mass transfer rates in the biphasic system. The green metrics of the reaction have been assessed and compared to existing procedures and have shown the continuous process is improved over previous procedures. The organic solutions of N,N-dialkyl-N-chloramines produced continuously will enable their use in tandem flow reactions with a range of nucleophilic substrates. PMID:26734089

  8. Continuous formation of N-chloro-N,N-dialkylamine solutions in well-mixed meso-scale flow reactors.

    PubMed

    Blacker, A John; Jolley, Katherine E

    2015-01-01

    The continuous flow synthesis of a range of organic solutions of N,N-dialkyl-N-chloramines is described using either a bespoke meso-scale tubular reactor with static mixers or a continuous stirred tank reactor. Both reactors promote the efficient mixing of a biphasic solution of N,N-dialkylamine in organic solvent, and aqueous sodium hypochlorite to achieve near quantitative conversions, in 72-100% in situ yields, and useful productivities of around 0.05 mol/h with residence times from 3 to 20 minutes. Initial calorimetric studies have been carried out to inform on reaction exotherms, rates and safe operation. Amines which partition mainly in the organic phase require longer reaction times, provided by the CSTR, to compensate for low mass transfer rates in the biphasic system. The green metrics of the reaction have been assessed and compared to existing procedures and have shown the continuous process is improved over previous procedures. The organic solutions of N,N-dialkyl-N-chloramines produced continuously will enable their use in tandem flow reactions with a range of nucleophilic substrates.

  9. Continuous formation of N-chloro-N,N-dialkylamine solutions in well-mixed meso-scale flow reactors.

    PubMed

    Blacker, A John; Jolley, Katherine E

    2015-01-01

    The continuous flow synthesis of a range of organic solutions of N,N-dialkyl-N-chloramines is described using either a bespoke meso-scale tubular reactor with static mixers or a continuous stirred tank reactor. Both reactors promote the efficient mixing of a biphasic solution of N,N-dialkylamine in organic solvent, and aqueous sodium hypochlorite to achieve near quantitative conversions, in 72-100% in situ yields, and useful productivities of around 0.05 mol/h with residence times from 3 to 20 minutes. Initial calorimetric studies have been carried out to inform on reaction exotherms, rates and safe operation. Amines which partition mainly in the organic phase require longer reaction times, provided by the CSTR, to compensate for low mass transfer rates in the biphasic system. The green metrics of the reaction have been assessed and compared to existing procedures and have shown the continuous process is improved over previous procedures. The organic solutions of N,N-dialkyl-N-chloramines produced continuously will enable their use in tandem flow reactions with a range of nucleophilic substrates. PMID:26734089

  10. Normally-off p-GaN/AlGaN/GaN high electron mobility transistors using hydrogen plasma treatment

    NASA Astrophysics Data System (ADS)

    Hao, Ronghui; Fu, Kai; Yu, Guohao; Li, Weiyi; Yuan, Jie; Song, Liang; Zhang, Zhili; Sun, Shichuang; Li, Xiajun; Cai, Yong; Zhang, Xinping; Zhang, Baoshun

    2016-10-01

    In this letter, we report a method by introducing hydrogen plasma treatment to realize normally-off p-GaN/AlGaN/GaN HEMT devices. Instead of using etching technology, hydrogen plasma was adopted to compensate holes in the p-GaN above the two dimensional electron gas (2DEG) channel to release electrons in the 2DEG channel and form high-resistivity area to reduce leakage current and increase gate control capability. The fabricated p-GaN/AlGaN/GaN HEMT exhibits normally-off operation with a threshold voltage of 1.75 V, a subthreshold swing of 90 mV/dec, a maximum transconductance of 73.1 mS/mm, an ON/OFF ratio of 1 × 107, a breakdown voltage of 393 V, and a maximum drain current density of 188 mA/mm at a gate bias of 6 V. The comparison of the two processes of hydrogen plasma treatment and p-GaN etching has also been made in this work.

  11. The transformations and fates of deposited N in an N saturated subtropical forested catchment, SW China

    NASA Astrophysics Data System (ADS)

    Zhu, Jing; Mulder, Jan; Dörsch, Peter

    2015-04-01

    Subtropical forests in south China are receiving long-term elevated nitrogen (N) deposition. Previous field observations in the N-saturated forested headwater catchment at Tieshanping (TSP), Chongqing, SW China, found apparent fast NH4+ disappearance in the top soil on the hillslope, but lab incubation for nitrification potentials did not support such disappearance. Meanwhile, large unaccounted N sinks were suggested by fast NO3- disappearance along the flow path in the groundwater discharge zone (GDZ), possibly due to denitrification and subsequent N2 emission. In this study, we investigated the fates of deposited N (mainly in the forms of NH4+ and NO3-) and the nature of the N transformations using isotopic tracer approach. 15N-labeled NH4+ or NO3- (99 atom% 15N) were amended to repacked surface soil columns from the hillslope and GDZ of TSP. The changes of the N forms of NH4+, NO3-, dissolved organic N, microbial biomass N and bulk N in soil were traced in a period of 15 days, representing transient (0.5 hr, 6 hr and 1 day) and mid-term (5 days and 15 days) N transformations. The soil moistures were kept at the typical field conditions (55% and 95% WFPS for hillslope soil and GDZ soil, respectively). Opposite to the field observations, the amount of added NH4+ decreased gradually on hillslope. 85% and 30% of the added 15N-NH4+ kept in the form of NH4+ after 1 day and 15 days. 15N-NO3- was produced gradually on hillslope, up to 26% of added 15N-NH4+ after 15 days incubation. About half of the added 15N-NH4+ was incorporated to organic N. The added 15N-NO3- showed a similar picture, with 55% left in the soil of hillslope after the whole incubation. Interestingly, although soil in GDZ had much higher WFPS, the nitrification rate of it was much higher than that on hillslope. Apparently the added 15N-NH4+ was incorporated immediately into organic matter in GDZ soil and being denitrified gradually along the time. The incorporation of the added 15N-NO3- into soil

  12. SEMICONDUCTOR DEVICES: AlGaN/GaN double-channel HEMT

    NASA Astrophysics Data System (ADS)

    Si, Quan; Yue, Hao; Xiaohua, Ma; Pengtian, Zheng; Yuanbin, Xie

    2010-04-01

    The fabrication of AlGaN/GaN double-channel high electron mobility transistors on sapphire substrates is reported. Two carrier channels are formed in an AlGaN/GaN/AlGaN/GaN multilayer structure. The DC performance of the resulting double-channel HEMT shows a wider high transconductance region compared with single-channel HEMT. Simulations provide an explanation for the influence of the double-channel on the high transconductance region. The buffer trap is suggested to be related to the wide region of high transconductance. The RF characteristics are also studied.

  13. Relative gas diffusivity as a controller of soil N2 and N2O fluxes

    NASA Astrophysics Data System (ADS)

    Clough, Tim; Balaine, Nimlesh; Beare, Mike; Thomas, Steve

    2015-04-01

    Animal grazing may induce soil compaction and has been shown to enhance emissions of the greenhouse gas nitrous oxide (N2O). The dominant substrate for N2O production is urea, supplied to the soil in ruminant urine. While studies have examined the effects of water-filled pore space on N2O emissions there has been less attention paid to the role of soil physical properties, such as relative gas diffusivity (Dp/Do), on N2O emissions and associated emissions of dinitrogen (N2). Three experiments were performed on soil cores maintained at a range of soil bulk densities (1.1 to 1.5 Mg/m3) and soil matric potentials (-10 to -0.2 kPa). These soil cores received urea at 700 kg N/ha to simulate a urine deposition event. Using the 15N tracer technique we measured N2 and N2O fluxes in order to investigate the role of soil Dp/Do as a controlling factor the magnitude of N2 and N2O fluxes and the reduction of N2O. As soil compaction and soil moisture contents increased soil Dp/Do declined. This in turn resulted in slower rates of nitrification. The mean cumulative fluxes of N2O, as a percentage of N applied, ranged from <1 to 16% after 35 days. Cumulative N2 fluxes as a percentage of N applied, ranged from <1 to 60% after 35 days. Soil compaction and soil matric potential interacted to influence Dp/Do which in turn was seen to be a strong determinant of the magnitude of both N2O and N2 fluxes. As Dp/Do values decreased a critical value was reached where N2O fluxes rapidly switched from being at a maximum to a minimum while at the same time N2 production intensified. This was also reflected in the N2:N2O ratios, based on cumulative fluxes, which ranged from <1 to 25. When compared with water-filled pore space the Dp/Do variable proved to be a better predictor of the switch from N2O production to N2 production.

  14. Integrated p-n junction InGaN/GaN multiple-quantum-well devices with diverse functionalities

    NASA Astrophysics Data System (ADS)

    Cai, Wei; Gao, Xumin; Yuan, Wei; Yang, Yongchao; Yuan, Jialei; Zhu, Hongbo; Wang, Yongjin

    2016-05-01

    We propose, fabricate, and demonstrate integrated p-n junction InGaN/GaN multiple-quantum-well devices with diverse functionalities on a GaN-on-silicon platform. Suspended devices with a common n-contact are realized using a wafer-level process. For the integrated devices, part of the light emitted by a light-emitting diode (LED) is guided in-plane through a suspended waveguide and is sensed by another photodiode. The induced photocurrent is tuned by the LED. The integrated devices can act as two independent LEDs to deliver different signals simultaneously for free-space visible light communication. Furthermore, the suspended devices can be used as two separate photodiodes to detect incident light with a distinct on/off switching performance.

  15. Extraction of copper(II) from acid chloride solutions by N-dodecyl- and N,N-dihexylpyridinecarboxamides

    SciTech Connect

    Borowiak-Resterna, A.

    1999-01-01

    N-dodecyl- and N,N-dihexylpyridinecarboxamides with amide group at 2, 3 or 4 position were synthesized. Model individual amides were used to recover copper(II) from chloride solutions at constant water activity and constant total concentration of dissolved species in aqueous solution. It was found, that pyridine-2-carboxamide forms with copper complexes (CuCl{sub 2}){sub x}(Ext){sub 2}. Remaining amides form with copper complexes CuCl{sub 2}(Ext){sub 2}. Monoalkylamides are not suitable for extraction because they and their complexes are slightly soluble in the hydrocarbon diluents. N,N-dialkylpyridinecarboxamides and their copper complexes are sufficiently soluble in the hydrocarbon phase to carry out extraction. However, they are strong extractants and extract efficiently copper already from dilute chloride solutions ([Cl{sup {minus}}] = 0.1 M). They extract also significant amounts of copper from concentrated (3--4 M) nitrate solutions.

  16. Thermal stability and in situ SiN passivation of InAlN/GaN high electron mobility heterostructures

    NASA Astrophysics Data System (ADS)

    Lugani, L.; Carlin, J.-F.; Py, M. A.; Grandjean, N.

    2014-09-01

    We investigate the thermal stability of nearly lattice-matched InAlN layers under metal organic vapor phase epitaxy conditions for temperatures >800 °C and show that they are not fully stable. In particular, InAlN top layers undergo degradation during high temperature annealing due to a surface related process, which causes the loss of crystal quality. This strongly impacts the transport properties of InAlN/GaN HEMT heterostructures; in particular, the mobility is significantly reduced. However, we demonstrate that high thermal stability can be achieved by capping with a GaN layer as thin as 0.5 nm. Those findings enabled us to realize in situ passivated HEMT heterostructures with state of the art transport properties.

  17. Polarization field engineering of GaN/AlN/AlGaN superlattices for enhanced thermoelectric properties

    SciTech Connect

    Sztein, Alexander; Bowers, John E.; DenBaars, Steven P.; Nakamura, Shuji

    2014-01-27

    A novel polarization field engineering based strategy to simultaneously achieve high electrical conductivity and low thermal conductivity in thermoelectric materials is demonstrated. Polarization based electric fields are used to confine electrons into two-dimensional electron gases in GaN/AlN/Al{sub 0.2}Ga{sub 0.8}N superlattices, resulting in improved electron mobilities as high as 1176 cm{sup 2}/Vs and in-plane thermal conductivity as low as 8.9 W/mK. The resulting room temperature ZT values reach 0.08, a factor of four higher than InGaN and twelve higher than GaN, demonstrating the potential benefits of this polarization based engineering strategy for improving the ZT and efficiencies of thermoelectric materials.

  18. Ab initio modeling of zincblende AlN layer in Al-AlN-TiN multilayers

    DOE PAGESBeta

    Yadav, S. K.; Wang, J.; Liu, X. -Y.

    2016-06-13

    An unusual growth mechanism of metastable zincblende AlN thin film by diffusion of nitrogen atoms into Al lattice is established. Using first-principles density functional theory, we studied the possibility of thermodynamic stability of AlN as a zincblende phase due to epitaxial strains and interface effect, which fails to explain the formation of zincblende AlN. We then compared the formation energetics of rocksalt and zincblende AlN in fcc Al through direct diffusion of nitrogen atoms to Al octahedral and tetrahedral interstitials. Furthermore, the formation of a zincblende AlN thin film is determined to be a kinetically driven process, not a thermodynamicallymore » driven process.« less

  19. First-principles calculations for AlN, GaN, and InN: Bulk and alloy properties

    SciTech Connect

    Wright, A.F.; Nelson, J.S.

    1995-02-01

    First-principles density-functional calculations utilizing ab initio pseudopotentials and plane-wave expansions are used to determine lattice parameters, bulk moduli, and band structures for AlN, GaN and InN. It is found that large numbers of plane waves are necessary to resolve the nitrogen 2p wave functions and that explicit treatment of the gallium 3d and indium 4d electrons is important for an accurate description of GaN and InN. Several properties of ternary zinc-blende alloys are determined including their bond-length and bond-angle relaxation and their energy-gap bowing parameters. The similarity of the calculated zinc-blende and wurtzite direct gaps also allows estimates to be made of the energy gap versus composition for wurtzite alloys.

  20. [Bis(quinolin-2-ylcarbon-yl)amido-κ(3) N,N',N'']bromido-(N,N-di-methyl-formamide-κO)copper(II).

    PubMed

    Faizi, Md Serajul Haque; Sen, Pratik

    2014-06-01

    In the mononuclear title complex, [CuBr(C20H12N3O2)(C3H7NO)], synthesized from the quinoline-derived reduced Schiff base 4-(quinolin-2-ylmeth-yl)amino-phenol, the coordination geometry around Cu(2+) is distorted square-pyramidal, comprising a bromide anion at the apex [Cu-Br = 2.4671 (5) Å]. The base of the pyramid is built up from one di-methyl-formamide O-atom donor [Cu-O = 2.078 (2) Å] and three N-atom donors from the monoanionic, tridentate bis-(quinolin-2-ylcarbon-yl)di-imide ligand [Cu-Ndi-imide = 1.941 (3) Å, and Cu-Nquinol-yl = 2.060 (3) and 2.049 (3) Å]. An intra-molecular C-H⋯O occurs. In the crystal, weak methyl and aromatic C-H⋯Br and formyl C-H⋯Ocarbon-yl hydrogen-bonding inter-actions generate an overall layered structure lying parallel to (001). PMID:24940197

  1. Isotopic investigations of dissolved organic N in soils identifies N mineralization as a major sink process

    NASA Astrophysics Data System (ADS)

    Wanek, Wolfgang; Prommer, Judith; Hofhansl, Florian

    2016-04-01

    Dissolved organic nitrogen (DON) is a major component of transfer processes in the global nitrogen (N) cycle, contributing to atmospheric N deposition, terrestrial N losses and aquatic N inputs. In terrestrial ecosystems several sources and sinks contribute to belowground DON pools but yet are hard to quantify. In soils, DON is released by desorption of soil organic N and by microbial lysis. Major losses from the DON pool occur via sorption, hydrological losses and by soil N mineralization. Sorption/desorption, lysis and hydrological losses are expected to exhibit no 15N fractionation therefore allowing to trace different DON sources. Soil N mineralization of DON has been commonly assumed to have no or only a small isotope effect of between 0-4‰, however isotope fractionation by N mineralization has rarely been measured and might be larger than anticipated. Depending on the degree of 15N fractionation by soil N mineralization, we would expect DON to become 15N-enriched relative to bulk soil N, and dissolved inorganic N (DIN; ammonium and nitrate) to become 15N-depleted relative to both, bulk soil N and DON. Isotopic analyses of soil organic N, DON and DIN might therefore provide insights into the relative contributions of different sources and sink processes. This study therefore aimed at a better understanding of the isotopic signatures of DON and its controls in soils. We investigated the concentration and isotopic composition of bulk soil N, DON and DIN in a wide range of sites, covering arable, grassland and forest ecosystems in Austria across an altitudinal transect. Isotopic composition of ammonium, nitrate and DON were measured in soil extracts after chemical conversion to N2O by purge-and-trap isotope ratio mass spectrometry. We found that delta15N values of DON ranged between -0.4 and 7.6‰, closely tracking the delta15N values of bulk soils. However, DON was 15N-enriched relative to bulk soil N by 1.5±1.3‰ (1 SD), and inorganic N was 15N

  2. Electron density and currents of AlN/GaN high electron mobility transistors with thin GaN/AlN buffer layer

    SciTech Connect

    Bairamis, A.; Zervos, Ch.; Georgakilas, A.; Adikimenakis, A.; Kostopoulos, A.; Kayambaki, M.; Tsagaraki, K.; Konstantinidis, G.

    2014-09-15

    AlN/GaN high electron mobility transistor (HEMT) structures with thin GaN/AlN buffer layer have been analyzed theoretically and experimentally, and the effects of the AlN barrier and GaN buffer layer thicknesses on two-dimensional electron gas (2DEG) density and transport properties have been evaluated. HEMT structures consisting of [300 nm GaN/ 200 nm AlN] buffer layer on sapphire were grown by plasma-assisted molecular beam epitaxy and exhibited a remarkable agreement with the theoretical calculations, suggesting a negligible influence of the crystalline defects that increase near the heteroepitaxial interface. The 2DEG density varied from 6.8 × 10{sup 12} to 2.1 × 10{sup 13} cm{sup −2} as the AlN barrier thickness increased from 2.2 to 4.5 nm, while a 4.5 nm AlN barrier would result to 3.1 × 10{sup 13} cm{sup −2} on a GaN buffer layer. The 3.0 nm AlN barrier structure exhibited the highest 2DEG mobility of 900 cm{sup 2}/Vs for a density of 1.3 × 10{sup 13} cm{sup −2}. The results were also confirmed by the performance of 1 μm gate-length transistors. The scaling of AlN barrier thickness from 1.5 nm to 4.5 nm could modify the drain-source saturation current, for zero gate-source voltage, from zero (normally off condition) to 0.63 A/mm. The maximum drain-source current was 1.1 A/mm for AlN barrier thickness of 3.0 nm and 3.7 nm, and the maximum extrinsic transconductance was 320 mS/mm for 3.0 nm AlN barrier.

  3. Variation for N Uptake System in Maize: Genotypic Response to N Supply

    PubMed Central

    Garnett, Trevor; Plett, Darren; Conn, Vanessa; Conn, Simon; Rabie, Huwaida; Rafalski, J. Antoni; Dhugga, Kanwarpal; Tester, Mark A.; Kaiser, Brent N.

    2015-01-01

    An understanding of the adaptations made by plants in their nitrogen (N) uptake systems in response to reduced N supply is important to the development of cereals with enhanced N uptake efficiency (NUpE). Twenty seven diverse genotypes of maize (Zea mays, L.) were grown in hydroponics for 3 weeks with limiting or adequate N supply. Genotypic response to N was assessed on the basis of biomass characteristics and the activities of the nitrate (NO3−) and ammonium (NH4+) high-affinity transport systems. Genotypes differed greatly for the ability to maintain biomass with reduced N. Although, the N response in underlying biomass and N transport related characteristics was less than that for biomass, there were clear relationships, most importantly, lines that maintained biomass at reduced N maintained net N uptake with no change in size of the root relative to the shoot. The root uptake capacity for both NO3− and NH4+ increased with reduced N. Transcript levels of putative NO3− and NH4+ transporter genes in the root tissue of a subset of the genotypes revealed that predominately ZmNRT2 transcript levels responded to N treatments. The correlation between the ratio of transcripts of ZmNRT2.2 between the two N levels and a genotype's ability to maintain biomass with reduced N suggests a role for these transporters in enhancing NUpE. The observed variation in the ability to capture N at low N provides scope for both improving NUpE in maize and also to better understand the N uptake system in cereals. PMID:26617612

  4. Strain-balanced InGaN/GaN multiple quantum wells

    SciTech Connect

    Van Den Broeck, D. M.; Hosalli, A. M.; Bedair, S. M.; Bharrat, D.; El-Masry, N. A.

    2014-07-21

    InGaN/GaN multiple quantum well (MQW) structures suffer from a high amount of compressive strain in the InGaN wells and the accompanied piezoelectric field resulting in both a blue shift in emission and a reduction of emission intensity. We report the growth of In{sub x}Ga{sub 1−x}N/GaN “strain-balanced” multiple quantum wells (SBMQWs) grown on thick In{sub y}Ga{sub 1−y}N templates for x > y by metal organic chemical vapor deposition. SBMQWs consist of alternating layers of In{sub x}Ga{sub 1−x}N wells and GaN barriers under compressive and tensile stress, respectively, which have been lattice matched to a thick In{sub y}Ga{sub 1−y}N template. Growth of the In{sub y}Ga{sub 1−y}N template is also detailed in order to achieve thick, relaxed In{sub y}Ga{sub 1−y}N grown on GaN without the presence of V-grooves. When compared to conventional In{sub x}Ga{sub 1−x}N/GaN MQWs grown on GaN, the SBMQW structures exhibit longer wavelength emission and higher emission intensity for the same InN mole fraction due to a reduction in the well strain and piezoelectric field. By matching the average lattice constant of the MQW active region to the lattice constant of the In{sub y}Ga{sub 1−y}N template, essentially an infinite number of periods can be grown using the SBMQW growth method without relaxation-related effects. SBMQWs can be utilized to achieve longer wavelength emission in light emitting diodes without the use of excess indium and can be advantageous in addressing the “green gap.”.

  5. Point defects stabilise cubic Mo-N and Ta-N

    NASA Astrophysics Data System (ADS)

    Koutná, Nikola; Holec, David; Svoboda, Ondřej; Klimashin, Fedor F.; Mayrhofer, Paul H.

    2016-09-01

    We employ ab initio calculations to investigate energetics of point defects in metastable rocksalt cubic Ta-N and Mo-N. Our results reveal a strong tendency to off-stoichiometry, i.e. defected structures are surprisingly predicted to be more stable than perfect ones with 1:1 metal-to-nitrogen stoichiometry. Despite the similarity of Ta-N and Mo-N systems in exhibiting this unusual behaviour, we also point out their crucial differences. While Ta-N significantly favours metal vacancies, Mo-N exhibits similar energies of formation regardless of the vacancy type (V Mo, V N) as long as their concentration is below ≈ 15~\\text{at}. % . The overall lowest energies of formation were obtained for \\text{T}{{\\text{a}}0.78}\\text{N} and \\text{M}{{\\text{o}}0.91}\\text{N} , which are hence predicted to be the most stable compositions. To account for various experimental conditions during synthesis, we further evaluated the phase stability as a function of chemical potential of individual species. The proposed phase diagrams reveal four stable compositions, \\text{M}{{\\text{o}}0.84}\\text{N} , \\text{M}{{\\text{o}}0.91}\\text{N} , \\text{Mo}{{\\text{N}}0.69} and \\text{Mo}{{\\text{N}}0.44} , in the case of Mo-N and nine stable compositions in the case of Ta-N indicating the important role of metal under-stoichiometry, since \\text{T}{{\\text{a}}0.75}\\text{N} and \\text{T}{{\\text{a}}0.78}\\text{N} significantly dominate the diagram. This is particularly important for understanding and designing experiments using non-equilibrium deposition techniques. Finally, we discuss the role of defect ordering and estimate a cubic lattice parameter as a function of defect contents and put them in the context of existing literature theoretical and experimental data.

  6. Variation for N Uptake System in Maize: Genotypic Response to N Supply.

    PubMed

    Garnett, Trevor; Plett, Darren; Conn, Vanessa; Conn, Simon; Rabie, Huwaida; Rafalski, J Antoni; Dhugga, Kanwarpal; Tester, Mark A; Kaiser, Brent N

    2015-01-01

    An understanding of the adaptations made by plants in their nitrogen (N) uptake systems in response to reduced N supply is important to the development of cereals with enhanced N uptake efficiency (NUpE). Twenty seven diverse genotypes of maize (Zea mays, L.) were grown in hydroponics for 3 weeks with limiting or adequate N supply. Genotypic response to N was assessed on the basis of biomass characteristics and the activities of the nitrate ([Formula: see text]) and ammonium ([Formula: see text]) high-affinity transport systems. Genotypes differed greatly for the ability to maintain biomass with reduced N. Although, the N response in underlying biomass and N transport related characteristics was less than that for biomass, there were clear relationships, most importantly, lines that maintained biomass at reduced N maintained net N uptake with no change in size of the root relative to the shoot. The root uptake capacity for both [Formula: see text] and [Formula: see text] increased with reduced N. Transcript levels of putative [Formula: see text] and [Formula: see text] transporter genes in the root tissue of a subset of the genotypes revealed that predominately ZmNRT2 transcript levels responded to N treatments. The correlation between the ratio of transcripts of ZmNRT2.2 between the two N levels and a genotype's ability to maintain biomass with reduced N suggests a role for these transporters in enhancing NUpE. The observed variation in the ability to capture N at low N provides scope for both improving NUpE in maize and also to better understand the N uptake system in cereals. PMID:26617612

  7. Non-Abelian duality and confinement: From N=2 to N=1 supersymmetric QCD

    SciTech Connect

    Shifman, M.; Yung, A.

    2011-05-15

    Recently, we discovered and discussed non-Abelian duality in the quark vacua of N=2 super-Yang-Mills theory with the U(N) gauge group and N{sub f} flavors (N{sub f}>N). Both theories from the dual pair support non-Abelian strings, which confine monopoles. Now we introduce an N=2-breaking deformation, a mass term {mu}A{sup 2} for the adjoint fields. Starting from a small deformation, we eventually make it large, which enforces complete decoupling of the adjoint fields. We show that the above non-Abelian duality fully survives in the limit of N=1 supersymmetric QCD (SQCD), albeit some technicalities change. For instance, non-Abelian strings which used to be Bogomol'nyi-Prasad-Sommerfield saturated in the N=2 limit, cease to be saturated in N=1 SQCD. Our duality is a distant relative of Seiberg's duality in N=1 SQCD. Both share some common features, but have many drastic distinctions. This is due to the fact that Seiberg's duality apply to the monopole rather than quark vacua. More specifically, in our theory we deal with N{sub f}<(3/2)N massive quark flavors. We consider the vacuum in which N squarks condense. Then we identify a crossover transition from weak to strong coupling. At strong coupling, we find a dual theory, U(N{sub f}-N) SQCD, with N{sub f} light dyon flavors. Dyons condense triggering the formation of non-Abelian strings, which confine monopoles. Screened quarks and gauge bosons of the original theory decay into confined monopole-antimonopole pairs and form stringy mesons.

  8. Accessibility of N-acyl-d-mannosamines to N-acetyl-d-neuraminic acid aldolase

    PubMed Central

    Pan, Yanbin; Ayani, Tiffany; Nadas, Janos; Wen, Shouming; Guo, Zhongwu

    2011-01-01

    N-Acetyl-d-neuraminic acid (NeuNAc) aldolase is an important enzyme for the metabolic engineering of cell surface NeuNAc using chemically modified d-mannosamines. To explore the optimal substrates for this application, eight N-acyl derivatives of d-mannosamine were prepared, and their accessibility to NeuNAc aldolase was investigated quantitatively. The N-propionyl-, N-butanoyl-, N-iso-butanoyl-, N-pivaloyl- and N-phenylacetyl-d-mannosamines proved to be as good substrates as, or even better than, the natural N-acetyl-d-mannosamine, while the N-trifluoropropionyl and benzoyl derivatives were poor. It was proposed that the electronic effects might have a significant influence on the enzymatic aldol condensation reaction of d-mannosamine derivatives, with electron-deficient acyl groups having a negative impact. The results suggest that N-propionyl-, N-butanoyl-, N-iso-butanoyl- and N-phenylacetyl-d-mannosamines may be employed to bioengineer NeuNAc on cells. PMID:15280054

  9. Production of 15N-depleted biomass during cyanobacterial N2-fixation at high Fe concentrations

    NASA Astrophysics Data System (ADS)

    Zerkle, Aubrey L.; Junium, Christopher K.; Canfield, Donald E.; House, Christopher H.

    2008-09-01

    In this study we examine the effects of varying Fe, Mo, and P concentrations on δ15N fractionation during N2 fixation in the cyanobacterium Anabaena variabilis. We show that when grown in Fe-enriched media ([Fe] ≥ 50 nM), this organism produces biomass up to 3‰ lower in δ15N than when grown in Fe-limited media ([Fe] < 50 nM). A compilation of our data with previous measurements of δ15N in N2-fixing cyanobacteria reveals a general trend toward the production of more 15N-depleted biomass at higher Fe concentrations. We discuss our results in the context of negative δ15N values preserved in Archean and some Phanerozoic sediments, generally attributed to the production of marine organic matter with low δ15N by N2 fixation (and potentially NH4+ regeneration) during periods of fluctuating nutrient dynamics. We suggest that enhanced Fe availability during periods of widespread ocean anoxia can further stimulate the production of 15N-depleted biomass by N2-fixing organisms, contributing to the isotopic record.

  10. Influence of AlN thickness on AlGaN epilayer grown by MOCVD

    NASA Astrophysics Data System (ADS)

    Jayasakthi, M.; Juillaguet, S.; Peyre, H.; Konczewicz, L.; Baskar, K.; Contreras, S.

    2016-10-01

    AlGaN/AlN layers were grown by metalorganic chemical vapor deposition (MOCVD) on sapphire substrates. The AlN buffer thickness was varied from 400 nm to 800 nm. The AlGaN layer thickness was 1000 nm. The crystalline quality, thickness and composition of AlGaN were determined using high resolution X-ray diffraction (HRXRD). The threading dislocation density (TDD) was found to decrease with increase of AlN layer thickness. Reciprocal space mapping (RSM) was used to estimate the strain and relaxation between AlGaN and AlN. The optical properties of AlGaN layers were investigated by temperature dependent photoluminescence (PL). PL intensities of AlGaN layers increases with increasing the AlN thickness. The surface morphology of AlGaN was studied by atomic force microscopy (AFM). Root mean square (RMS) roughness values were found to be decreased while increase of AlN thickness.

  11. Alkali metal control over N-N cleavage in iron complexes.

    PubMed

    Grubel, Katarzyna; Brennessel, William W; Mercado, Brandon Q; Holland, Patrick L

    2014-12-01

    Though N2 cleavage on K-promoted Fe surfaces is important in the large-scale Haber-Bosch process, there is still ambiguity about the number of Fe atoms involved during the N-N cleaving step and the interactions responsible for the promoting ability of K. This work explores a molecular Fe system for N2 reduction, particularly focusing on the differences in the results obtained using different alkali metals as reductants (Na, K, Rb, Cs). The products of these reactions feature new types of Fe-N2 and Fe-nitride cores. Surprisingly, adding more equivalents of reductant to the system gives a product in which the N-N bond is not cleaved, indicating that the reducing power is not the most important factor that determines the extent of N2 activation. On the other hand, the results suggest that the size of the alkali metal cation can control the number of Fe atoms that can approach N2, which in turn controls the ability to achieve N2 cleavage. The accumulated results indicate that cleaving the triple N-N bond to nitrides is facilitated by simultaneous approach of least three low-valent Fe atoms to a single molecule of N2. PMID:25412468

  12. Nitrogen fixation in boreal peatlands: the effects of increased N deposition on N2-fixation

    NASA Astrophysics Data System (ADS)

    Popma, J. M.; Wieder, R.; Lamers, L.; Vile, M. A.

    2013-12-01

    Boreal peatlands are of great importance to global carbon and nitrogen cycling. While covering only 3-4 % of the terrestrial surface, they account for 25-30 % of the world's soil C and 9-15 % of the world's soil N. In Western Canada atmospheric dry deposition rates are extremely low: approximately 1 kg N ha-1 yr-1. Though these systems have been functioning as net sinks over the past 11,000 years, natural and anthropogenic disturbances might compromise the historical balance of C and N. Biological N2-fixation has recently been shown to represent a very significant input of N into these systems, contributing to 62% of total N in Western Canada. Interactions between N deposition and biological N2-fixation are as yet, unknown, but the impact of elevated deposition of N-compounds from increased industrial expansion of oil sands mining to peatlands, is concerning. Given that nitrogenase, the enzyme responsible for catalyzing N2-fixation, is energetically costly when active, enhanced inputs of atmospheric N deposition could be a major determinant for enzyme activity and rates of biological N input to these bogs. Understanding interactions between N deposition and N2 fixation in boreal peatlands can aid in predicting the consequences of increased N deposition and setting critical loads. We conducted a field-fertilization experiment in a poor fen in Alberta, Canada, to determine the effects of enhanced N deposition on a dominant fen species Sphagnum angustifolium. The experiment consisted of seven N treatments: Control, 0, 5, 10, 15, 20 and 25 kg N ha-1 y1, n=3. N2-fixation was measured during summer 2012 and 2013 using the acetylene reduction assay (ARA). ARA rates were converted to rates of N2-fixation by calibrating ARA with paired 15N2-incubations. In both 2012 and 2013, with increasing N deposition from 0 kg N ha-1 yr-1 to 25 kg N ha-1 yr-1, rates of N2 fixation decreased, with highest rates in the 0 kg N ha-1 yr-1 treatment mosses (54.2 × 1.40; 48.58 × 7.12 kg N ha

  13. Nanostructure and strain in InGaN/GaN superlattices grown in GaN nanowires.

    PubMed

    Kehagias, Th; Dimitrakopulos, G P; Becker, P; Kioseoglou, J; Furtmayr, F; Koukoula, T; Häusler, I; Chernikov, A; Chatterjee, S; Karakostas, Th; Solowan, H-M; Schwarz, U T; Eickhoff, M; Komninou, Ph

    2013-11-01

    The structural properties and the strain state of InGaN/GaN superlattices embedded in GaN nanowires were analyzed as a function of superlattice growth temperature, using complementary transmission electron microscopy techniques supplemented by optical analysis using photoluminescence and spatially resolved microphotoluminescence spectroscopy. A truncated pyramidal shape was observed for the 4 nm thick InGaN inclusions, where their (0001¯) central facet was delimited by six-fold {101¯l} facets towards the m-plane sidewalls of the nanowires. The defect content of the nanowires comprised multiple basal stacking faults localized at the GaN base/superlattice interface, causing the formation of zinc-blende cubic regions, and often single stacking faults at the GaN/InGaN bilayer interfaces. No misfit dislocations or cracks were detected in the heterostructure, implying a fully strained configuration. Geometrical phase analysis showed a rather uniform radial distribution of elastic strain in the (0001¯) facet of the InGaN inclusions. Depending on the superlattice growth temperature, the elastic strain energy is partitioned among the successive InGaN/GaN layers in the case of low-temperature growth, while at higher superlattice growth temperature the in-plane tensile misfit strain of the GaN barriers is accommodated through restrained diffusion of indium from the preceding InGaN layers. The corresponding In contents of the central facet were estimated at 0.42 and 0.25, respectively. However, in the latter case, successful reproduction of the experimental electron microscopy images by image simulations was only feasible, allowing for a much higher occupancy of indium adatoms at lattice sites of the semipolar facets, compared to the invariable 25% assigned to the polar facet. Thus, a high complexity in indium incorporation and strain allocation between the different crystallographic facets of the InGaN inclusions is anticipated and supported by the results of

  14. A comprehensive detailed chemical kinetic reaction mechanism for combustion of n-alkane hydrocarbons from n-octane to n-hexadecane

    SciTech Connect

    Westbrook, Charles K.; Pitz, William J.; Herbinet, Olivier; Silke, Emma J.; Curran, Henry J.

    2009-01-15

    Detailed chemical kinetic reaction mechanisms have been developed to describe the pyrolysis and oxidation of nine n-alkanes larger than n-heptane, including n-octane (n-C{sub 8}H{sub 18}), n-nonane (n-C{sub 9}H{sub 20}), n-decane (n-C{sub 10}H{sub 22}), n-undecane (n-C{sub 11}H{sub 24}), n-dodecane (n-C{sub 12}H{sub 26}), n-tridecane (n-C{sub 13}H{sub 28}), n-tetradecane (n-C{sub 14}H{sub 30}), n-pentadecane (n-C{sub 15}H{sub 32}), and n-hexadecane (n-C{sub 16}H{sub 34}). These mechanisms include both high temperature and low temperature reaction pathways. The mechanisms are based on previous mechanisms for the primary reference fuels n-heptane and iso-octane, using the reaction classes first developed for n-heptane. Individual reaction class rules are as simple as possible in order to focus on the parallelism between all of the n-alkane fuels included in the mechanisms. These mechanisms are validated through extensive comparisons between computed and experimental data from a wide variety of different sources. In addition, numerical experiments are carried out to examine features of n-alkane combustion in which the detailed mechanisms can be used to compare reactivities of different n-alkane fuels. The mechanisms for these n-alkanes are presented as a single detailed mechanism, which can be edited to produce efficient mechanisms for any of the n-alkanes included, and the entire mechanism, with supporting thermochemical and transport data, together with an explanatory glossary explaining notations and structural details, is available for download from our web page. (author)

  15. New technology N products in alabama

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Because of high fertilizer N prices, growers are interested in using less expensive sources of N and using fertilizer additives to reduce ammonia volatilization losses from urea sources. An experiment on a Lucedale fine sandy loam in Central Alabama (Prattville Research Unit) was conducted in 2007 ...

  16. New technology N products in alabama

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Because of high fertilizer N prices, growers are interested in using less expensive sources of N and using fertilizer additives to reduce ammonia volatilization losses from urea sources. An experiment on a Lucedale fine sandy loam in Central Alabama (Prattville Research Unit) was conducted in 2007 t...

  17. Evaluating Assessment Using N-Dimensional Filtering.

    ERIC Educational Resources Information Center

    Dron, Jon; Boyne, Chris; Mitchell, Richard

    This paper describes the use of the CoFIND (Collaborative Filter in N Dimensions) system to evaluate two assessment styles. CoFIND is a resource database that organizes itself around its users' needs. Learners enter resources, categorize, then rate them using "qualities," aspects of resources which learners find worthwhile, the n dimensions of…

  18. Meson dynamics in large-N limit

    SciTech Connect

    Tan, C.I.

    1983-01-01

    The large-N limit of QCD with matter fields present is considered in a Hamiltonian loop space approach. The semi-classical nature of the large-N limit is clarified where a valence approximation emerges naturally. A pseudospin algebra is introduced for handling fermions.

  19. Leucemia—Versión para pacientes

    Cancer.gov

    Información del Instituto Nacional del Cáncer sobre el tratamiento de la leucemia, así como referencias a estudios clínicos, investigación, estadísticas y otros temas relacionados con este tipo de cáncer.

  20. Thermodynamic and Spectroscopic Studies of Trivalent f -element Complexation with Ethylenediamine- N,N '-di(acetylglycine)- N,N '-diacetic Acid

    DOE PAGESBeta

    Heathman, Colt R.; Grimes, Travis S.; Zalupski, Peter R.

    2016-03-21

    In this study, the coordination behavior and thermodynamic features of complexation of trivalent lanthanides and americium by ethylenediamine-N,N'-di(acetylglycine)-N,N'-diacetic acid (EDDAG-DA) (bisamide-substituted-EDTA) were investigated by potentiometric and spectroscopic techniques. Acid dissociation constants (Ka) and complexation constants (β) of lanthanides (except Pm) were determined by potentiometric analysis. Absorption spectroscopy was used to determine stability constants for the binding of trivalent americium and neodymium by EDDAG-DA under similar conditions. The potentiometry revealed 5 discernible protonation constants and 3 distinct metal–ligand complexes (identified as ML–, MHL, and MH2L+). Time-resolved fluorescence studies of Eu-(EDDAG-DA) solutions (at varying pH) identified a constant inner-sphere hydration number ofmore » 3, suggesting that glycine functionalities contained in the amide pendant arms are not involved in metal complexation and are protonated under more acidic conditions. The thermodynamic studies identified that f-element coordination by EDDAG-DA is similar to that observed for ethylenediamine-N,N,N',N'-tetraacetic acid (EDTA). However, coordination via two amidic oxygens of EDDAG-DA lowers its trivalent f-element complex stability by roughly 3 orders of magnitude relative to EDTA.« less

  1. Ultrafast Exciton Dynamics in InGaN/GaN and Rh/Cr2O3 Nanoparticle-Decorated InGaN/GaN Nanowires.

    PubMed

    Pu, Ying-Chih; Kibria, M G; Mi, Zetian; Zhang, Jin Z

    2015-07-01

    Ultrafast exciton and charge-carrier dynamics in InGaN/GaN nanowires (NWs) with and without Rh/Cr2O3 nanoparticle (NP) decoration have been investigated using femtosecond transient absorption (TA) techniques with excitation at 415 nm and white-light probe (450-700 nm). By comparing the TA profiles between InGaN/GaN and InGaN/GaN-Rh/Cr2O3 NWs, an additional decay component on the medium time scale (∼50 ps) was identified with Rh/Cr2O3 decoration, which is attributed to interfacial charge transfer from InGaN/GaN NWs to Rh/Cr2O3 NPs, desired for light energy conversion applications. This is consistent with reduced photoluminescence (PL) of the NWs by the Rh/Cr2O3 NPs. A kinetic model was developed to explain the TA results and gain further insight into the exciton and charge-carrier dynamics.

  2. The algebras of large N matrix mechanics

    SciTech Connect

    Halpern, M.B.; Schwartz, C.

    1999-09-16

    Extending early work, we formulate the large N matrix mechanics of general bosonic, fermionic and supersymmetric matrix models, including Matrix theory: The Hamiltonian framework of large N matrix mechanics provides a natural setting in which to study the algebras of the large N limit, including (reduced) Lie algebras, (reduced) supersymmetry algebras and free algebras. We find in particular a broad array of new free algebras which we call symmetric Cuntz algebras, interacting symmetric Cuntz algebras, symmetric Bose/Fermi/Cuntz algebras and symmetric Cuntz superalgebras, and we discuss the role of these algebras in solving the large N theory. Most important, the interacting Cuntz algebras are associated to a set of new (hidden!) local quantities which are generically conserved only at large N. A number of other new large N phenomena are also observed, including the intrinsic nonlocality of the (reduced) trace class operators of the theory and a closely related large N field identification phenomenon which is associated to another set (this time nonlocal) of new conserved quantities at large N.

  3. Effect of electron scavengers to reduce the ionization current of photoexcited N,N,N',N'-tetramethyl-p-phenylenediamine in nonpolar organic liquids

    SciTech Connect

    Lee, K.; Lipsky, S.

    1982-05-27

    The effects of perfluoro-n-hexane, perfluoro-n-heptane, perfluoromethylcyclohexane, and perfluorodecalin to reduce the ionization current of photoexcited N,N,N',N'-tetramethyl-p-phenylenediamine (TMPD) have been studied in the solvents tetramethylsilane, 2,2-dimethylbutane (2,2-DMB), isooctane, cyclohexane, n-hexane, and n-pentane. Results are reported over a range of excitation energies from 5.2 to 6.7 eV and, for selected systems, over a temperature range from -78 to 25/sup 0/C. At quencher concentrations, c/sub q/ less than or equal to 0.2 M, the ratio of the photocurrent without quencher, J/sub 0/, to that with quencher, J, is found to be concave upward, linear, or concave downward in its dependence on c/sub q/, depending on the system studied. At higher c/sub q/, J/sub 0//J is always concave upward. Both J/sub 0/ and J increase to about the same extent as the excitation energy increases, thus maintaining J/sub 0//J constant. As the temperature increases, J increases somewhat more rapidly than does J/sub 0/ and increasingly so the larger is c/sub q/. An attempt is made to explain these results with a model based on interaction of the quencher with an epithermal electron.

  4. Restricted Schur polynomials and finite N counting

    SciTech Connect

    Collins, Storm

    2009-01-15

    Restricted Schur polynomials have been posited as orthonormal operators for the change of basis from N=4 SYM to type IIB string theory. In this paper we briefly expound the relationship between the restricted Schur polynomials and the operators forwarded by Brown, Heslop, and Ramgoolam. We then briefly examine the finite N counting of the restricted Schur polynomials.

  5. Thermodynamic and Spectroscopic Studies of Trivalent f-element Complexation with Ethylenediamine-N,N'-di(acetylglycine)-N,N'-diacetic Acid.

    PubMed

    Heathman, Colt R; Grimes, Travis S; Zalupski, Peter R

    2016-03-21

    The coordination behavior and thermodynamic features of complexation of trivalent lanthanides and americium by ethylenediamine-N,N'-di(acetylglycine)-N,N'-diacetic acid (EDDAG-DA) (bisamide-substituted-EDTA) were investigated by potentiometric and spectroscopic techniques. Acid dissociation constants (K(a)) and complexation constants (β) of lanthanides (except Pm) were determined by potentiometric analysis. Absorption spectroscopy was used to determine stability constants for the binding of trivalent americium and neodymium by EDDAG-DA under similar conditions. The potentiometry revealed 5 discernible protonation constants and 3 distinct metal-ligand complexes (identified as ML(-), MHL, and MH2L(+)). Time-resolved fluorescence studies of Eu-(EDDAG-DA) solutions (at varying pH) identified a constant inner-sphere hydration number of 3, suggesting that glycine functionalities contained in the amide pendant arms are not involved in metal complexation and are protonated under more acidic conditions. The thermodynamic studies identified that f-element coordination by EDDAG-DA is similar to that observed for ethylenediamine-N,N,N',N'-tetraacetic acid (EDTA). However, coordination via two amidic oxygens of EDDAG-DA lowers its trivalent f-element complex stability by roughly 3 orders of magnitude relative to EDTA. PMID:26930023

  6. Superconformal SU(1, 1|n) mechanics

    NASA Astrophysics Data System (ADS)

    Galajinsky, Anton; Lechtenfeld, Olaf

    2016-09-01

    Recent years have seen an upsurge of interest in dynamical realizations of the superconformal group SU(1, 1|2) in mechanics. Remarking that SU(1, 1|2) is a particular member of a chain of supergroups SU(1, 1| n) parametrized by an integer n, here we begin a systematic study of SU(1, 1| n) multi-particle mechanics. A representation of the superconformal algebra su(1, 1| n) is constructed on the phase space spanned by m copies of the (1, 2 n, 2 n-1) supermultiplet. We show that the dynamics is governed by two prepotentials V and F, and the Witten-Dijkgraaf-Verlinde-Verlinde equation for F shows up as a consequence of a more general fourth-order equation. All solutions to the latter in terms of root systems reveal decoupled models only. An extension of the dynamical content of the (1, 2 n, 2 n-1) supermultiplet by angular variables in a way similar to the SU(1, 1|2) case is problematic.

  7. 7 CFR 29.2440 - (N Group).

    Code of Federal Regulations, 2011 CFR

    2011-01-01

    ... 7 Agriculture 2 2011-01-01 2011-01-01 false (N Group). 29.2440 Section 29.2440 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... INSPECTION Standards Grades § 29.2440 (N Group). Extremely common tobacco which does not meet the...

  8. 7 CFR 29.2440 - (N Group).

    Code of Federal Regulations, 2010 CFR

    2010-01-01

    ... 7 Agriculture 2 2010-01-01 2010-01-01 false (N Group). 29.2440 Section 29.2440 Agriculture Regulations of the Department of Agriculture AGRICULTURAL MARKETING SERVICE (Standards, Inspections, Marketing... INSPECTION Standards Grades § 29.2440 (N Group). Extremely common tobacco which does not meet the...

  9. Genotoxicology of N-nitroso compounds

    SciTech Connect

    Rao, T.K.; Epler, J.L.; Lijinsky, W.

    1984-01-01

    This book attempts to demonstrate the complexity of the mechanisms of biological action of the toxic N-nitroso compounds. The conclusions presented on genetic toxicology are based on comparative studies of biological assays and a firm foundation of chemical structural relations among N-nitroso compounds. Topics considered include the formation of N-nitroso compounds and their significance, N-nitrosamine mutagenicity using the Salmonella/Mammalian-Microsome Mutagenicity Assay, the structural basis for the mutagenic activity of N-nitrosamines in the Salmonella Histidine Reversion Assay, the effect of pH and structure on the mutagenic activity of N-nitroso compounds, the induction of bacteriophage lambda by N-nitroso compounds, the relationship between the carcinogenicity and mutagenicity of nitrosamines in a Hepatocyte-Mediated Mutagenicity Assay, the mutagenic activity of nitrosamines in mammalian cells (study with the CHO/HGPRT and human leukocyte SCE assays), dimethylnitrosamine demethylase and the mutagenicity of dimethylnitrosamine (effects of rodent liver fractions and dimethylsulfoxide), the relationship between metabolism and mutagenicity of two cyclic nitrosamines, structureactivity relations in carcinogenesis by N-nitroso compounds, and a comparison of mutagenic and carcinogenic properties.

  10. Linfoma—Versión para pacientes

    Cancer.gov

    Información del Instituto Nacional del Cáncer sobre el tratamiento del linfoma, así como referencias a estudios clínicos, investigación, estadísticas y otros temas relacionados con este tipo de cáncer.

  11. Aeronca C-2N Deluxe Scout

    NASA Technical Reports Server (NTRS)

    1936-01-01

    Aeronca C-2N Deluxe Scout: Known as the 'Flying Bathtub,' the portly Aeronca C-2N Deluxe Scout was used during Langley's research into the stability of light planes. Gust structure and intensity at low altitude was also investigated with the C-2. This particular C-2 still exists, as part of the collection of the Experimental Aircraft Association's Museum in Oshkosh, Wisconsin.

  12. Analysis of the auger recombination rate in P+N-n-N-N HgCdTe detectors for HOT applications

    NASA Astrophysics Data System (ADS)

    Schuster, J.; Tennant, W. E.; Bellotti, E.; Wijewarnasuriya, P. S.

    2016-05-01

    Infrared (IR) photon detectors must be cryogenically cooled to provide the highest possible performance, usually to temperatures at or below ~ 150K. Such low operating temperatures (Top) impose very stringent requirements on cryogenic coolers. As such, there is a constant push in the industry to engineer new detector architectures that operate at higher temperatures, so called higher operating temperature (HOT) detectors. The ultimate goal for HOT detectors is room temperature operation. While this is not currently possibly for photon detectors, significant increases in Top are nonetheless beneficial in terms of reduced size, weight, power and cost (SWAP-C). The most common HgCdTe IR detector architecture is the P+n heterostructure photodiode (where a capital letter indicates a wide band gap relative to the active layer or "AL"). A variant of this architecture, the P+N-n-N-N heterostructure photodiode, should have a near identical photo-response to the P+n heterostructure, but with significantly lower dark diffusion current. The P+N-n-N-N heterostructure utilizes a very low doped AL, surrounded on both sides by wide-gap layers. The low doping in the AL, allows the AL to be fully depleted, which drastically reduces the Auger recombination rate in that layer. Minimizing the Auger recombination rate reduces the intrinsic dark diffusion current, thereby increasing Top. Note when we use the term "recombination rate" for photodiodes, we are actually referring to the net generation and recombination of minority carriers (and corresponding dark currents) by the Auger process. For these benefits to be realized, these devices must be intrinsically limited and well passivated. The focus of this proceeding is on studying the fundamental physics of the intrinsic dark currents in ideal P+N-n-N-N heterostructures, namely Auger recombination. Due to the complexity of these devices, specifically the presence of multiple heterojunctions, numerical device modeling techniques must be

  13. Structure and mechanical properties of nanoscale multilayered CrN/ZrSiN coatings

    SciTech Connect

    Zhang, Z. G.; Rapaud, O.; Allain, N.; Baraket, M.; Dong, C.; Coddet, C.

    2009-07-15

    Nanocrystalline/amorphous CrN/ZrSiN multilayer coatings with a bilayer thickness ranging from 11 to 153 nm were prepared by reactive magnetron sputtering technique. The microstructure and mechanical properties of these thin films were characterized by x-ray diffraction (XRD), scanning electron microscopy, transmission electron microscopy (TEM), Fourier transform infrared spectroscopy (FTIR), and nanoindentation. The formation of nanocrystalline CrN and nanocomposite ZiSiN in the single layer coatings was identified by XRD and FTIR. The periodic structure of the as-deposited multilayer coatings was confirmed by TEM observation. Nanoindentation tests showed that both the values of hardness (H) and reduced elastic modulus (E{sub r}) of CrN/ZrSiN multilayers remained almost constant despite varying the bilayer thickness. The multilayer coatings exhibited higher H of 30 GPa and higher resistance to plastic deformation when compared to the single layer CrN and ZrSiN coatings.

  14. Photoelectrochemical corrosion of GaN-based p-n structures

    NASA Astrophysics Data System (ADS)

    Fomichev, A. D.; Kurin, S. Yu; Ermakovi, I. A.; Puzyk, M. V.; Usikov, A. S.; Helava, H.; Nikiforov, A.; Papchenko, B. P.; Makarov, Yu N.; Chernyakov, A. E.

    2016-08-01

    Direct water photoelectrolysis using III-N materials is a promising way for hydrogen production. GaN/AlGaN based p-n structures were used in a photoelectrochemical process to investigate the material etching (corrosion) in an electrolyte. At the beginning, the corrosion performs through the top p-type layers via channels associated with threading defects and can penetrate deep into the structure. Then, the corrosion process occurs in lateral direction in n- type layers forming voids and cavities in the structure. The lateral etching is due to net positive charges at the AlGaN/GaN interfaces arising because of spontaneous and piezoelectric polarization in the structure and positively charged ionized donors in the space charge region of the p-n junction.

  15. NMR Determination of the Rotational Barrier in N,N-Dimethylacetamide

    ERIC Educational Resources Information Center

    Gasparro, Francis P.; Kolodny, Nancy H.

    1977-01-01

    Describes a physical chemistry experiment that uses dynamic nuclear magnetic resonance spectroscopy to determine the barrier to rotation in N,N-dimethylacetamide by measuring changes in line shapes as a function of temperature. (MLH)

  16. 40 CFR Table 1 to Subpart N of... - General Provisions Applicability to Subpart N

    Code of Federal Regulations, 2013 CFR

    2013-07-01

    ... CATEGORIES National Emission Standards for Chromium Emissions From Hard and Decorative Chromium Electroplating and Chromium Anodizing Tanks Pt. 63, Subpt. N, Table 1 Table 1 to Subpart N of Part...

  17. 40 CFR Table 1 to Subpart N of... - General Provisions Applicability to Subpart N

    Code of Federal Regulations, 2012 CFR

    2012-07-01

    ... CATEGORIES National Emission Standards for Chromium Emissions From Hard and Decorative Chromium Electroplating and Chromium Anodizing Tanks Pt. 63, Subpt. N, Table 1 Table 1 to Subpart N of Part...

  18. Stage specific activity of synthetic antimalarial endoperoxides, N-89 and N-251, against Plasmodium falciparum.

    PubMed

    Morita, Masayuki; Koyama, Takahiko; Sanai, Hitomi; Sato, Akira; Hiramoto, Akiko; Masuyama, Araki; Nojima, Masatomo; Wataya, Yusuke; Kim, Hye-Sook

    2015-02-01

    We have reported that two endoperoxides, N-89 and N-251, synthesized in 2001, possess potent antimalarial activities. Aiming at their eventual use for curing malaria in humans, we have been investigating various aspects of their antimalarial actions. Here we show that N-89 and N-251 inhibit the growth of Plasmodium falciparum within human erythrocytes in vitro at its lifecycle stage 'trophozoite' specifically. It is known that artemisinin compounds, which are currently used for curing malaria, have other stage-specificities. Therefore, it is likely that the antimalarial mechanism of N-89 and N-251 differs from those of artemisinin compounds. As malaria parasites resistant to artemisinin-based combination therapy are currently emerging in some tropical regions, N-89 and N-251 are candidates for overcoming these new problems. PMID:25449979

  19. DQO Summary Report for 105-N/109-N Interim Safe Storage Project Waste Characterization

    SciTech Connect

    T. A. Lee

    2005-09-15

    The DQO summary report provides the results of the DQO process completed for waste characterization activities for the 105-N/109-N Reactor Interim Safe Storage Project including decommission, deactivate, decontaminate, and demolish activities for six associated buildings.

  20. 40 CFR Table 1 to Subpart N of... - General Provisions Applicability to Subpart N

    Code of Federal Regulations, 2011 CFR

    2011-07-01

    ... CATEGORIES National Emission Standards for Chromium Emissions From Hard and Decorative Chromium Electroplating and Chromium Anodizing Tanks Pt. 63, Subpt. N, Table 1 Table 1 to Subpart N of Part...