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  • Oxford University Press  (68)
  • American Institute of Physics (AIP)  (34)
  • American Chemical Society (ACS)  (33)
  • 2015-2019  (90)
  • 1990-1994  (42)
  • 1955-1959  (3)
  • 1
    Publication Date: 2015-07-07
    Description: Journal of Proteome Research DOI: 10.1021/acs.jproteome.5b00307
    Print ISSN: 1535-3893
    Electronic ISSN: 1535-3907
    Topics: Chemistry and Pharmacology
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 5753-5755 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The effect of such medium properties as magnetic unit size, film thickness, and strength of anisotropy, dipolar, and exchange interactions on the storage capacity limit of a thin-film recording medium is investigated. Relationships are derived for media with different properties that have equivalent capacity. The physically realizable range of material properties and their effect on the capacity bound are explored. Results on edge effects for capacity bound computations are presented. The results indicate that media for which anisotropy is the dominant source of magnetic energy have the greatest potential for information storage.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 76 (1994), S. 1956-1958 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The nitrogen donor levels have been studied by admittance spectroscopy between 20 and 200 K in Schottky barriers made on lightly n-type epitaxial 6H-SiC layers. Measurements at different frequencies yield different freezeout temperatures which in turn are used to determine the donor level energies. Two electron traps at Ec−0.082 eV and at Ec−0.140 eV were detected. These levels are associated with nitrogen, respectively, at the hexagonal sites for the former and at the cubic sites for the latter level.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 70 (1991), S. 2926-2938 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experiments are described in which a high-purity, high-power (0.15 TW, 1 MeV) proton beam is generated from an ion source consisting of H2 gas frozen onto a liquid-helium-cooled copper anode at 4.2 K in a series-field-coil extraction diode on the 0.7 TW HydraMITE-II accelerator. Peak anode proton current densities of 2 kA/cm2 were measured. This current density is a factor of 100 higher than those obtained in previous liquid-helium-cooled cryogenic diode experiments on small accelerators and is in the range required for high-power ion beam applications. Thomson parabola, Faraday cup, and carbon activation measurements indicate an ion beam proton fraction close to 100% for the cryogenic source, compared to 50–70% for the standard hydrocarbon anode tested. The cryogenic proton source is believed to consist of no more than a few monolayers of molecular hydrogen. The hydrogen-coated cryogenic anode shows a faster initial anode turn-on than other materials. However, source-limited emission from the thin hydrogen layer results in a somewhat longer current risetime, reduced ion diode efficiency, lower proton current enhancement over the Child–Langmuir limit, and a proton spectrum of lower average energy than for the hydrocarbon anode. Techniques to overcome these limitations are discussed. Cryogenic ion sources consisting of frozen N2, CH4, and Ne have also been studied. In each case, high intensity beams consisting predominantly of components of the refrigerated gas were produced.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 68 (1990), S. 4917-4928 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Accurate modeling of load behavior in Z-pinch plasma radiation sources driven by high-current generators requires the measurement of fast-rise-time multimegampere currents close to the load. Conventional current diagnostics mounted in inductive cavities (such as B-dot loops and Rogowski coils) fail at small radius because of electrical breakdown produced by high dI/dt. In this paper, we describe the use of large-signal, nanosecond-time-resolution lithium niobate piezoelectric stress gauges to directly measure the magnetic pressure B2/2μ0=μ0I2/8π2r2 generated at radius r by a current I flowing in a radial transmission line. Current measurements have been performed at radius r=2.54×10−2 m on Sandia National Laboratories' Proto-II (10 TW) and SATURN (30 TW) gas puff Z-pinch experiments with maximum currents of 10.1 MA and dI/dt to 2.1×1014 A/s. Comparisons with Faraday rotation and B-dot current diagnostic measurements at large radius are presented. Bremsstrahlung noise problems unique to the SATURN gas puff source are discussed. For a Y-cut lithium niobate stress gauge on a pure tungsten electrode, current densities up to I/2πr=78 MA/m can be measured before the electrode yield strength and the piezoelectric operating stress limit are exceeded. Above the Hugoniot elastic limit of the electrode material, the dynamic range and accuracy of the diagnostic are greatly reduced, but it appears that the technique can be extended to higher current densities using an X-cut quartz piezoelectric element and a tungsten-sapphire electrode impedance stack.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 1639-1642 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Previous measurements of the stopping power of Kapton and Havar for 1.1–4.4-MeV protons have been analyzed with modified Bethe–Bloch theory in order to extract some of the parameters required in the formalism. Results suggest the possibility of systematic errors, in that the Havar data appear to have been slightly high and the Kapton data quite low when compared with other reported measurements. Currently recommended values of the mean excitation energy and Barkas-effect parameter are, respectively, 79 eV and 1.34 (Kapton) and 296 eV and 1.36 (Havar). The need for further accurate measurements for Kapton in particular is emphasized.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 5761-5761 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Since the discovery of the high-Tc superconductors, there is a great interest in the magnetic properties of copper oxides due to the possibility of a magnetic origin of the pairing mechanism. With this perspective, we decide to reinvestigate the structure and the magnetic properties of Bi2CuO4, a compound we use successfully as precursor of the Bi-Sr-Ca-Cu high-Tc superconductors. A neutron powder diffraction experiment allowed us to resolve the ambiguity in the structure, and revealed the existence of a magnetic phase transition to a 3D antiferromagnetic ordered state below 50 K. The nuclear structure can be described as formed by stacks of CuO4 units in the c-axis direction, linked in the stacks and with units in other stacks by BiO2 chains, so each stack is connected with four stacks. The space group was confirmed to be P4/ncc. The magnetic space group is P4/n'cc. There is a ferromagnetic ordering of the magnetic moments on Cu atoms along the stacks, and an antiferromagnetic ordering between the stacks. We present an interpretation of the magnetic properties of this compound, at the light of our previous results, and a discussion of a calorimetric experiment.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 6613-6620 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The low-velocity Barkas-effect correction term for the Bethe–Bloch stopping-power formula has been calculated with each of the three extant formalisms for targets with atomic numbers from 1 to 18 and for projectile velocities from 0.025c to 0.3c. Comparison of each with measurements on aluminum revealed which formalism provided the best fit over three different projectile velocity intervals. The method yielding the generally superior agreement was used to calculate the stopping power of each element (except Li, F, Na, Mg, P, and Cl) for protons and alpha particles with energies between 0.5 and 5.0 MeV. Results corresponded very closely to those of an existing fit to most known experimental data.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Experiments to explore the long-time evolution of noninductive, high βp plasmas in the DIII-D tokamak [Plasma Physics and Controlled Nuclear Fusion Research, 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. 1, p. 159], have identified a new, quiescent, high performance regime. The experiments were carried out at low current (400–800 kA) with medium power neutral beam injection (3–10 MW). This regime is characterized by high q0 ((approximately-greater-than)2) and moderate li(∼1.3). It is reached by slow relaxation of the current profile, on the resistive time scale. As the profiles relax, q0 rises and li falls. When q0 goes above 2 (approximately), magnetohydrodynamic (MHD) activity disappears, and the stored energy rises. Most dramatic is the strong peaking of the central density, which increases by as much as a factor of 2. The improved central confinement appears similar to the PEP/reversed central shear/second stable core modes seen in tokamak experiments, but in this case without external intervention or transient excitation. At high current, a similar, but slower relaxation is seen. Also notable in connection with these discharges is the behavior of the edge and scrape-off layer (SOL). The edge localized modes (ELM's) as seen previously, are small and very rapid (to 1 kHz). The SOL exhibits high density (≥1×1019 m−3), which shows little or no falloff with radius. Also the power deposition at the divertor surface is very broad, up to four times the width usually seen. This regime is of particular interest for the development of steady-state tokamak operating scenarios, for the Tokamak Physics Experiment (TPX), and following reactors.
    Type of Medium: Electronic Resource
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 5 (1993), S. 2165-2175 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this paper an investigation of the particle confinement for beam-heated single-null discharges in the open divertor configuration of Doublet III-D (DIII-D) [E. J. Doyle et al., Phys. Fluids B 3, 2300 (1991)] is described. Results are based on a Monte Carlo neutral transport model with a relatively simple plasma model that utilizes experimental data on density, temperature, and heat flux profiles in the edge plasma. For a typical discharge, it is found that the particle confinement time in the quiescent H-mode phase is only about a factor of 2 larger than during the L-mode phase, an increase comparable to the energy confinement time increase. For both H-mode and L-mode phases the particle confinement time is about a factor of 4 larger than the energy confinement time. It is also found that the core plasma fueling rate is higher in the H mode due to the increased transparency of a thinner scrape-off layer. The longer particle confinement time and the increased fueling rate both contribute to the observed density rise during the quiescent period following the L–H transition. Flux surface-averaged transport modeling of the time evolution for the core plasma density profile during H mode suggests that a strong inward particle pinch is necessary near the separatrix.
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