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  • 1
    Electronic Resource
    Electronic Resource
    Calculations of energy losses due to atomic processes in tokamaks with applications to the International Thermonuclear Experimental Reactor divertor (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2328-2336 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Reduction of the peak heat loads on the plasma facing components is essential for the success of the next generation of high fusion power tokamaks such as the International Thermonuclear Experimental Reactor (ITER) [Rebut et al., Plasma Physics and Controlled Nuclear Fusion Research (International Atomic Energy Agency, Vienna, in press)]. Many present concepts for accomplishing this involve the use of atomic processes to transfer the heat from the plasma to the main chamber and divertor chamber walls and much of the experimental and theoretical physics research in the fusion program is directed toward this issue. The results of these experiments and calculations depend upon a complex interplay of many processes. In order to identify the key features of these experiments and calculations and the relative role of the primary atomic processes, simple quasianalytic models and the latest atomic physics rate coefficients and cross sections have been used to assess the relative roles of central radiation losses through bremsstrahlung, impurity radiation losses from the plasma edge, charge exchange and hydrogen radiation losses from the scrape-off layer, and divertor plasma and impurity radiation losses from the divertor plasma. This analysis indicates that bremsstrahlung from the plasma center and impurity radiation from the plasma edge and divertor plasma can each play a significant role in reducing the power to the divertor plates, and identifies many of the factors which determine the relative role of each process. For instance, for radiation losses in the divertor to be large enough to radiate the power in the divertor for high power experiments, a neutral fraction of 10−3 to 10−2 and an impurity recycling rate of neτrecycle of ∼1016 s m−3 will be required in the divertor. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871257
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  • 2
    Electronic Resource
    Electronic Resource
    Tests of local transport theory and reduced wall impurity influx with highly radiative plasmas in the Tokamak Fusion Test Reactor (1999)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 6 (1999), S. 877-884 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electron temperature (Te) profile in neutral beam-heated supershot plasmas (Te0∼6–7 keV ion temperature Ti0∼15–20 keV, beam power Pb∼16 MW) was remarkably invariant when radiative losses were increased significantly through gas puffing of krypton and xenon in the Tokamak Fusion Test Reactor [McGuire et al., Phys. Plasmas 2, 2176 (1995)]. Trace impurity concentrations (nz/ne∼10−3) generated almost flat and centrally peaked radiation profiles, respectively, and increased the radiative losses to 45%–90% of the input power (from the normal ∼25%). Energy confinement was not degraded at radiated power fractions up to 80%. A 20%–30% increase in Ti, in spite of an increase in ion–electron power loss, implies a factor of ∼3 drop in the local ion thermal diffusivity. These experiments form the basis for a nearly ideal test of transport theory, since the change in the beam heating power profile is modest, while the distribution of power flow between (1) radiation and (2) conduction plus convection changes radically and is locally measurable. The decrease in Te was significantly less than predicted by two transport models and may provide important tests of more complete transport models. At input power levels of 30 MW, the increased radiation eliminated the catastrophic carbon influx (carbon "bloom") and performance (energy confinement and neutron production) was improved significantly relative to that of matched shots without impurity gas puffing. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873327
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  • 3
    Electronic Resource
    Electronic Resource
    K-shell radiation physics in the ultrahigh optical depth pinches of the Z generator (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 4476-4483 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Al:Mg alloy wire arrays of mass loads 1.3–3.6 mg/cm have been imploded with peak currents of 19 MA on the 60 TW Z generator [R. B. Spielman et al., Phys. Plasmas 5, 2105 (1998)] at Sandia National Laboratories. The large mass loads have resulted in the highest K-shell x-ray line optical depths (∼103) produced to date in Z-pinches. Analysis of the time-resolved spectrum of a 2.1 mg/cm shot near the time of peak compression has yielded a temperature–density profile of the pinch that approximately reproduces all features of the x-ray data except the continuum above 5 keV, which is underpredicted. The Ly α/He α ratio for Al is shown to be enhanced relative to that of Mg by two mechanisms: photopumped ladder ionization and absorption of the Al He-like line in a cool outer halo. This analysis and comparisons to some Ti shots demonstrates that the K-shell yield of Al is significantly reduced by line and continuum self-absorption, but that of Ti is not. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873185
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  • 4
    Electronic Resource
    Electronic Resource
    X-ray lasing in colliding plasmas (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 3718-3724 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Conditions favorable for the achievement of population inversion and large gains in short-pulse laser-heated selenium have been reported on previously [K. G. Whitney et al., Phys. Rev. E50, 468 (1994)]. However, the required density profiles to minimize refraction and amplification losses can be difficult to achieve in conventional laser heated blowoff plasmas. The feasibility of accelerating plasma with a laser, and letting it collide with a solid density wall plasma has been explored. The density of the resulting shocked plasma can be controlled and refraction can be reduced in this design. A radiation hydrodynamics model is used to simulate the collision of the laser produced selenium plasma with the wall plasma. The heating of the stagnated plasma with a short-pulse laser is then simulated, providing the hydrodynamic response of the selenium plasma and detailed configuration nonequilibrium atomic populations. From the results of these calculations, it appears feasible to create an x-ray lasing selenium plasma with gains in the J=0–1 line at 182 Å in excess of100 cm−1. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872559
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  • 5
    Electronic Resource
    Electronic Resource
    Measurement instrumentation for electrical transport experiments in extreme pulsed magnetic fields generated by flux compression (1997)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 3843-3860 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: We describe purpose-built instrumentation that has proved successful in making transport measurements of materials in ultrahigh magnetic fields generated by explosive-driven flux compression. The experimental arrangement minimizes severe problems of heating and pick-up associated with the microsecond pulsed field, for which dB/dt can be as large as 109 T/s. Electrical connection to multiple samples in the high field region is via long, lithographically-defined, nested coplanar transmission lines. Contactless measurements by capacitive coupling, as well as resistively coupled measurements, are made at frequencies of order 1 GHz so that pick-up from the microsecond pulse can be effectively filtered. We demonstrate our technique with data on semiconductor samples taken to 450 T using Russian MC-1 type flux compression generators combined with U.S. explosives at the Ancho Canyon firing point, Los Alamos National Laboratory. We discuss the obstacles encountered during these experiments, and outline improvements and refinements of our technique that should enable transport measurements to be made in the highest obtainable magnetic fields (∼1000 T) in samples at temperatures not exceeding a few kelvin. This technology may also be valuable for transport measurements in nondestructive pulsed fields of millisecond duration, now available in many laboratories worldwide. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1148037
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  • 6
    Electronic Resource
    Electronic Resource
    Functional Wild-Type and Carboxy-Terminal-Tagged Rat Substance P Receptors Expressed in Baculovirus-Infected Insect Sf9 Cells (1995)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 64 (1995), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The rat substance P (SP) receptor (SPR) was expressed in insect Sf9 cells by infection with recombinant baculovirus. The receptor bound SP with high affinity (KD = 360 pM) and had a rank order of affinity of SP 〉 neurokinin A 〉 neurokinin B. Ligand activation of the receptor resulted in an increase in both inositol lipid hydrolysis and intracellular Ca2+ concentration ([Ca2+]i). However, high-level expression of the receptor, in the absence of ligand, was correlated with increased basal turnover of inositol lipids and an elevated rate of Ca2+ influx. These results demonstrate that the Sf9 cells provide a suitable environment for the high-level expression of a functionally active SPR. Two carboxy-terminal epitope-tagged receptors (SPR-KT3 = SPR-TPPPEPET, COOH; SPR-Glu = SPR-EEEEYMPME, COOH) were also expressed. The affinity of the KT3-tagged receptor for ligand was similar to that of the wild-type receptor (KD = 405 pM), and that of the Glu-tagged receptor was slightly lower (KD = 1,082 pM). The high-affinity SP binding site of all three receptors was sensitive to guanosine 5′-O-(3-thiotriphosphate) pretreatment. The maximal signal-transducing ability of the epitope-tagged receptors was comparable to that of the wild-type receptor ([Ca2+]i rise as a percentage of wild-type: SPR-KT3, 80–100%; SPR-Glu, 88–100%). These data show that heterologous expression in the baculovirus system results in high expression of functional wild-type and tagged receptors.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1995.64041622.x
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  • 7
    Electronic Resource
    Electronic Resource
    Identification of Lectin-Purified Neural Glycoproteins, GPs 180, 116, and 110, with NMDA and AMPA Receptor Subunits: Conservation of Glycosylation at the Synapse (1998)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 70 (1998), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: The postsynaptic apparatus is associated with a number of glycoproteins with apparent molecular masses of 180, 116, and 110 kDa, which are highly concentrated in and may be uniquely associated with this structure. These glycoproteins, purified by concanavalin A lectin-affinity chromatography, showed immunoreactivity in the present study with subunit-specific antibodies to glutamate receptors as follows: GP 180, NMDA receptor subunits NR2A/NR2B; GP 116, NMDA receptor NR1 (1a); and GP 110, pan-α-amino-3-hydroxy-5-methylisoxazole-4-propionate (pan-AMPA) receptors. Sensitivities to the glycosidases peptide N-glycosidase F and endo-β-N-acetylglucosaminidase H on both western blots and silver-stained gels suggested that the glutamate receptors were at least major constituents of the glycoprotein bands. Similar detailed glycosylation was observed for all three glycoproteins, with neutral oligosaccharides being dominant. Oligomannosidic glycans (with from five to nine mannoses) accounted for ∼50% of the neutral sugars, with Man 5 (at almost 20% of the neutral sugars) always the major glycan. Other abundant neutral oligosaccharides were of the complex type. Similar sensitivities to peptide N-glycosidase F and endo-β-N-acetylglucosaminidase H were observed for cell line-expressed NMDA receptor subunits, suggesting that irrespective of the glycosylation processing available, the least highly processed oligosaccharides will be expressed. This may be indicative of glycosylation sites in these receptors that are inaccessible to the later processing enzymes and favours the oligomannosidic class of glycans in functional roles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1998.70062594.x
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  • 8
    Electronic Resource
    Electronic Resource
    Quantized conductance in quantum wires with gate-controlled width and electron density (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 72 (1998), S. 3506-3508 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We describe quantum wires and point contacts fabricated in GaAs/AlxGa1−xAs heterostructures that are free of the disorder introduced by modulation doping and in which the electron density and the confining potential are separately adjustable by lithographically defined gates. We observe conductance plateaus quantized near even multiples of e2/h in 2 μm wires and up to 15 conductance steps in 5 μm wires at temperatures below 1 K. Near the conductance threshold the quantum point contact and the 2 μm wire both show additional structure below 2e2/h. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.121642
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  • 9
    Electronic Resource
    Electronic Resource
    Making Sense of the Shapes of Simple Metal Hydrides (1995)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 117 (1995), S. 1859-1860 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00111a036
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  • 10
    Electronic Resource
    Electronic Resource
    Synthesis and Spectroscopic Characterization of the d0 Transition Metal-Alkyl-Alkene Complex Cp*2YCH2CH2C(CH3)2CH:CH2 (1995)
    s.l. : American Chemical Society
    Journal of the American Chemical Society 117 (1995), S. 9770-9771 
    Details
    ISSN: 1520-5126
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/ja00143a026
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