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  • 1
    Electronic Resource
    Electronic Resource
    Diastereoselective Diels-Alder Reactions via Cyclic Vinyloxocarbenium Ions (1995)
    s.l. : American Chemical Society
    The @journal of organic chemistry 60 (1995), S. 6652-6653 
    Details
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/jo00126a001
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  • 2
    Electronic Resource
    Electronic Resource
    Formation and sustainment of a low-aspect ratio tokamak by coaxial helicity injection (1995)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 2 (1995), S. 2337-2341 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Low-aspect-ratio tokamaks with toroidal currents, Ip, up to 250 kA are formed and sustained in the Helicity Injected Tokamak experiment [Nelson et al., Phys. Rev. Lett. 72, 3666 (1994)] using coaxial helicity injection. These plasmas are produced without use of a current drive transformer. Average toroidal currents are sustained at high values, 〈Ip〉=225 kA for 2 ms, where electron thermal energies are measured up to 80 eV with spectroscopy data suggesting burnthrough to the higher ionization states of oxygen. Currents can also be sustained for longer periods at lower values, 〈Ip〉=138 kA for 7 ms. These tokamaks are characterized by a rotating, n=1 distortion, with poloidal distortions approximately following the field line pitch, which only occur on the outer bad-curvature region. Equilibrium reconstructions show these plasmas have a tokamak q profile (q0=5 – 8, q95=10 – 12, qcyl(approximately-equal-to)3.6), with a hollow toroidal current profile and up to 170 kA of closed field toroidal current in a low-aspect-ratio, A=1.68 configuration. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871258
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  • 3
    Electronic Resource
    Electronic Resource
    Sample load-lock and manipulation system with heating capacity (1995)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 66 (1995), S. 267-268 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: An apparatus consisting basically of a fast entry load-lock system with sample manipulation and heating capacity is described. Special attention is paid to the differential pumping details and the sample heating. This low-cost system is within the possibilities of tradesmen and workshops. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1145271
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  • 4
    Electronic Resource
    Electronic Resource
    Angiotensin-II Biochemistry and Physiology: Update on Angiotensin-II Receptor Blockers (1997)
    Oxford, UK : Blackwell Publishing Ltd
    Cardiovascular drug reviews 15 (1997), S. 0 
    Details
    ISSN: 1527-3466
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1527-3466.1997.tb00325.x
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  • 5
    Electronic Resource
    Electronic Resource
    Varistor Behavior at Twin Boundaries in ZnO (1999)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 82 (1999), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The electrical behavior of commercial ZnO varistor devices has been examined with voltage contrast microscopy and point contact dc electrical measurements. Nonlinear voltage-dependent behavior has been observed across both of the major crystalline boundary types present in the system: Bi2O3 layer containing ZnO grain boundaries (or grain boundaries) and antimony spinel layer internal ZnO inversion twin boundaries (or twin boundaries). Twin boundaries, which bisect practically every grain in a typical commercial device, possess potential barriers with higher average breakdown voltages than do grain boundaries. Certain zinc antimonate spinel (Zn7Sb2O12) grains are electrically isolated from the matrix, whereas others are conductive within the matrix.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.1999.tb02048.x
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  • 6
    Electronic Resource
    Electronic Resource
    Species Heterogeneity Between Gerbils and Rats: Quinolinate Production by Microglia and Astrocytes and Accumulations in Response to Ischemic Brain Injury and Systemic Immune Activation (1997)
    Oxford, UK : Blackwell Science Ltd
    Journal of neurochemistry 69 (1997), S. 0 
    Details
    ISSN: 1471-4159
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: Abstract: Quinolinic acid is an excitotoxic kynurenine pathway metabolite, the concentration of which increases in human brain during immune activation. The present study compared quinolinate responses to systemic and brain immune activation in gerbils and rats. Global cerebral ischemia in gerbils, but not rats, increased hippocampus indoleamine-2,3-dioxygenase activity and quinolinate levels 4 days postinjury. In a rat focal ischemia model, small increases in quinolinate concentrations occurred in infarcted regions on days 1, 3, and 7, although concentrations remained below serum values. In gerbils, systemic immune activation by an intraperitoneal injection of endotoxin (1 mg/kg of body weight) increased quinolinate levels in brain, blood, lung, liver, and spleen, with proportional increases in lung indoleamine-2,3-dioxygenase activity at 24 h postinjection. In rats, however, no significant quinolinate content changes occurred, whereas lung indoleamine-2,3-dioxygenase activity increased slightly. Gerbil, but not rat, brain microglia and peritoneal monocytes produced large quantities of [13C6]-quinolinate from l-[13C6]tryptophan. Gerbil astrocytes produced relatively small quantities of quinolinate, whereas rat astrocytes produced no detectable amounts. These results demonstrate that the limited capacity of rats to replicate elevations in brain and blood quinolinic acid levels in response to immune activation is attributable to blunted increases in local indoleamine-2,3-dioxygenase activity and a low capacity of microglia, astrocytes, and macrophages to convert l-tryptophan to quinolinate.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1471-4159.1997.69041519.x
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  • 7
    Electronic Resource
    Electronic Resource
    Bounds upon grain boundary effects in minority carrier semiconductor devices: A rigorous "perturbation'' approach with application to silicon solar cells (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 1515-1521 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Rigorous bounds upon the effects of grain boundaries upon minority carrier semiconductor devices such as solar cells are calculated. These bounds can be formulated in terms of an effective lifetime parameter as for spatially uniformly distributed defects. The value of this lifetime parameter depends on grain boundary geometry and activity. This concept applies to grain boundary effects in both bulk quasineutral and depletion regions. The electrostatic enhancement of grain boundary recombination in depletion regions is less severe than in bulk regions near thermal equilibrium. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363022
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  • 8
    Electronic Resource
    Electronic Resource
    Generalized relationship between dark carrier distribution and photocarrier collection in solar cells (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 81 (1997), S. 268-271 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A recently identified relationship between the probability of collection of a photogenerated carrier in a solar cell and the dark minority-carrier concentration at the point of generation is generalized to three-dimensional geometries with arbitrary doping profile and variable band gap including abrupt compositional changes, grain boundaries, and floating junctions. The proof of the resulting relationship is simpler and more transparent than in earlier work with more restricted geometries. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.364108
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  • 9
    Electronic Resource
    Electronic Resource
    Junction recombination current in abrupt junction diodes under forward bias (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 3083-3090 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A new, analytical method is presented for calculating the depletion-region recombination current for abrupt-junction diodes under forward bias. The method is appropriate when the recombination current is dominated by recombination through Shockley–Read–Hall centers at a single energy level whose density does not vary strongly with position through the device. The new model is systematically compared with earlier models and with the results of finite-element analyses using PC-1D. If it is reasonably assumed that PC-1D is the most accurate of the methods considered here, the others may be ranked according to their proximity to the PC-1D result. It is shown that the new method, despite its simplicity, yields results closer to PC-1D than the earlier models for many practical situations. In addition, it is shown that one existing model may be brought into agreement with the finite-element analysis by a simple modification of the limits of integration. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363168
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  • 10
    Electronic Resource
    Electronic Resource
    Rear surface passivation of high-efficiency silicon solar cells by a floating junction (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 3574-3586 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The passivated emitter, rear locally diffused (PERL) cells, fabricated in our laboratory, reach an efficiency of 24.0%, the highest value for any silicon-based solar cell under terrestrial illumination. In an attempt to improve the rear surface passivation, which is usually obtained by a thermally grown oxide, we add a floating (i.e., noncontacted) p–n junction at the rear surface, resulting in the passivated emitter, rear floating p–n junction (PERF) cell design. Although these cells exhibit record 1-sun open-circuit voltages of up to 720 mV, their efficiency is degraded by nonlinearities ("shoulders'') in the logarithmic I–V curves. In order to understand and manipulate such nonlinearities, this paper presents a detailed investigation of the internal operation of PERF cells by means of numerical modelling based on experimentally determined device parameters. From the model, we derive design rules for optimum cell performance and develop a generalized argumentation that is suitable to compare the passivation properties of different surface structures. For example, the oxidized rear surface of the PERL cell is treated as an electrostatically induced floating junction in this approach and analogies to the diffused floating p–n junction are drawn. Our simulations indicate that optimum rear surface passivation can be obtained in three different ways. (i) The floating junction of the PERF cell should be very lightly doped, resulting in a sheet resistivity of 5000 Ω/(D'Alembertian), and losses due to shunt leaking paths between the p–n junction and the rear metal contacts must be avoided. (ii) The rear surface of the PERL cell should be passivated by chemical vapor deposition of a silicon nitride film containing a larger positive interface charge density than exists in thermally grown oxides. (iii) An external gate can be added at the rear with low leakage currents and gate voltages of around 15 V. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363231
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