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  • American Institute of Physics (AIP)  (329)
  • Nature Publishing Group  (102)
  • American Geophysical Union (AGU)
  • 1995-1999  (341)
  • 1980-1984  (74)
  • 1930-1934  (16)
  • 1
    Electronic Resource
    Electronic Resource
    Structure of the nucleosome core particle at 7 Å resolution (1984)
    [s.l.] : Nature Publishing Group
    Nature 311 (1984), S. 532-537 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The crystal structure of the nucleosome core particle has been solved to 7 Å resolution. The right-handed B-DNA superhelix on the outside contains several sharp bends and makes numerous interactions with the histone octamer within. The central turn of superhelix and H3 · H4 tetramer ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/311532a0
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  • 2
    Electronic Resource
    Electronic Resource
    Photovoltaic effects in porphyrin polymer films and heterojunctions (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 3381-3389 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Electropolymerized porphyrin films on indium–tin–oxide substrates have been characterized using Rutherford backscattering spectrometry, absorption spectroscopy, electrical characterization methods and with step profiling. With these methods the density of the films (ρ=1.35 g/cm3) and the absorption coefficients α(λ) have been determined. For film thicknesses exceeding 40 nm, silver electrical contacts without shunts are achieved by evaporation. The dark conductivity of the films amounts to 10−13–10−12 Ω−1 cm−1. When applying a band model for the conduction in the films, the dark space charge limited current and the exponent in the relation between photoconductivity and illumination intensity (σ∼Iγ, γ=0.65±0.05) indicate an exponential trap distribution in the band gap of the films. From the action spectra, filter effects of the photoconductance and low mobilities are inferred. Spin coating of acceptor layers on top of the polymer films results in the formation of heterojunctions showing photovoltaic behavior, with an open-circuit voltage 0.4–0.6 V. The short-circuit current is controlled by electron transfer at the donor/acceptor interface only and is limited by filter effects in the bulk and by the low conductivity of the materials. The optoelectrical properties of the layers are different if analyzed using a mercury contact (higher dark conductivity, no photoconductivity) which is attributed to the intro- duction of dopants from ambient air in this case. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363203
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  • 3
    Electronic Resource
    Electronic Resource
    Highly reflective, long wavelength AlAsSb/GaAsSb distributed Bragg reflector grown by molecular beam epitaxy on InP substrates (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 66 (1995), S. 329-331 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Surface normal optoelectronic devices operating at long wavelengths ((approximately-greater-than)1.3 μm), require distributed Bragg reflectors (DBRs) with a practical number (≤50) of mirror layers. This requirement implies a large refractive index difference between the mirror layers, which is difficult to achieve in the traditionally used phosphide compounds. We demonstrate a highly reflective AlAsSb/GaAsSb DBR grown nominally lattice matched to an InP substrate by molecular beam epitaxy. Reflectivity measurements indicate a stop band centered at 1.74 μm with maximum reflectivity exceeding 98%, which is well fitted by our theoretical predictions. Atomic force microscopy and transmission electron microscopy indicate reasonable crystal quality with some defects due to an unintentional lattice mismatch to the substrate. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.114202
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  • 4
    Electronic Resource
    Electronic Resource
    Modelling radioactive waste disposal by penetrator experiments in the abyssal Atlantic Ocean (1984)
    [s.l.] : Nature Publishing Group
    Nature 310 (1984), S. 130-133 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The GME area lies in the southwestern distal part of the Madeira Abyssal Plain (Fig. 1). Extensive geological and geophysical studies have been carried out there by the Rijks Geologische Dienst of the Netherlands and by the UK Institute of Ocanographie Sciences7"11. The sediments found there ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/310130a0
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  • 5
    Electronic Resource
    Electronic Resource
    Diacylglycerol and phorbol ester stimulate secretion without raising cytoplasmic free calcium in human platelets (1983)
    [s.l.] : Nature Publishing Group
    Nature 305 (1983), S. 317-319 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The methods for incorporating quin2 into intact cells and using its fluorescence to monitor [Ca2*! have been detailed elsewhere, together with evidence that the trapped indicator is largely confined to the cytoplasm and measures cytoplasmic free calcium17'18. Shape-change and aggregation were ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/305317a0
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  • 6
    Electronic Resource
    Electronic Resource
    Dynamics of a high-power aluminum-wire array Z-pinch implosion (1997)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 4 (1997), S. 2188-2203 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Annular Al-wire Z-pinch implosions on the Saturn accelerator [D. D. Bloomquist et al., Proceedings, 6th Pulsed Power Conference (Institute of Electrical and Electronics Engineers, New York, 1987), p. 310] that have high azimuthal symmetry exhibit both a strong first and weaker second x-ray burst that correlate with strong and weaker radial compressions, respectively. Measurements suggest that the observed magnetic Rayleigh–Taylor (RT) instability prior to the first compression seeds an m=0 instability observed later. Analyses of axially averaged spectral data imply that, during the first compression, the plasma is composed of a hot core surrounded by a cooler plasma halo. Two-dimensional (2-D) radiation magnetohydrodynamic computer simulations show that a RT instability grows to the classic bubble and spike structure during the course of the implosion. The main radiation pulse begins when the bubble reaches the axis and ends when the spike finishes stagnating on axis and the first compression ends. These simulations agree qualitatively with the measured characteristics of the first x-ray pulse and the overall energetics, and they provide a 2-D view into the plasma hydrodynamics of the implosion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872382
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  • 7
    Electronic Resource
    Electronic Resource
    Improved large diameter wire array implosions from increased wire array symmetry and on-axis mass participation (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 2431-2441 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Aluminum wire array, Z-pinch experiments have been performed on an 8 MA generator using arrays consisting of 24, 30, and 42 wires. These experiments were designed to scan through a region of (array mass, implosion velocity) space in which greater than 30% conversion of the implosion kinetic energy into K-shell x rays was predicted to occur [Thornhill et al., Phys. Plasmas 1, 321 (1994)]. Array masses between 120 and 2050 μg/cm were used in these experiments. An analysis of the x-ray data taken using 24 wire arrays, shows a one-to-one correspondence between the observed kilo-electron-volt yields (5–64 kJ) and the fraction of initial array mass (0.3%–60%) that is radiating from the K shell. The 30 and 42 wire experiments demonstrated that tighter pinches with increased radiated powers were achieved with these larger wire number, improved symmetry arrays. In addition, increases in the implosion mass and array diameter in the 30 and 42 wire number cases resulted in increases in the radiated yield over the corresponding 24 wire shots, up to 88 kJ, which can be interpreted as due to improved coupling and thermalization of the kinetic energy. Moreover, spectroscopic analyses of the 30 and 42 wire experiments have shown that the increased wire numbers also resulted in K-shell radiating mass fractions of greater than 50%. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872919
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  • 8
    Electronic Resource
    Electronic Resource
    Improvement of surface properties by modification and alloying with high-power ion beams : The 39th annual meeting of division of plasma physics of APS (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 2144-2150 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Surface treatment and alloying experiments with Al, Fe, and Ti-based metals as well as Si wafers were conducted on the Repetitive High Energy Pulsed Power-I (RHEPP-I) accelerator [0.8 MV, 20 Ω, 80 ns full width at half maximum (FWHM) pulse width, up to 1 Hz repetition rate] at Sandia National Laboratories. Ions are generated by the magnetically confined anode plasma (MAP) gas-breakdown active anode, which can yield a number of different beam species including H, C, N, O, Kr, and Xe, depending upon the injected gas. Enhanced hardness and wear resistance have been produced by treatment of 440C stainless steel, by the mixing of a thin-film Pt coating into Ti-6Al-4V alloy, and of a Si coating into Al 6061-T6 alloy (Al-1.0Mg-0.6Si). Mixing of a thin-film Hf layer into Al 6061-T6 has improved its corrosion resistance by as much as four orders of magnitude in electrochemical testing, compared with untreated and uncoated Al6061. Processing of Si was used to validate simulation codes. When treated with nitrogen ions, melt and full epitaxial growth was observed to depths of 4–6 μm. Experiments are ongoing to further understand the microstructural basis for these surface improvements. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.872887
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  • 9
    Electronic Resource
    Electronic Resource
    Current-vortex filament model of nonlinear Alfvén perturbations in a finite-pressure plasma (1998)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 5 (1998), S. 3833-3848 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A low-β, two-fluid model is shown to possess solutions in the form of current-vortex filaments. The model can be viewed as that of reduced magnetohydrodynamics, extended with electron inertia, the Hall term and parallel electron pressure. These drift-Alfvén filaments are the plasma analogs of point vortices in the two-dimensional Euler and the Charney–Hasegawa–Mima equations. The discrete system has the same global and local invariants as the original, continuous system. In an unbounded plasma, systems of two and three filaments are integrable. When the global linear momenta vanish, the four filament problem is also integrable. Stationary equilibria of a dipole, tripole, and of von Kármán streets are presented. The phase-space of two interacting, balanced pairs of filaments is analyzed in detail. New periodic four filament configurations are identified in plasma cases that do not exist in Euler systems. It is also shown that a collapse of the four vortices can occur in a finite time. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.873103
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  • 10
    Electronic Resource
    Electronic Resource
    Modeling of sawtooth destabilization during radio-frequency heating experiments in tokamak plasmas (1996)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Plasmas 3 (1996), S. 2994-3003 
    Details
    ISSN: 1089-7674
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Sawtooth oscillations in tokamaks have been stabilized using ion cyclotron resonance heating (ICRH), but often reappear while ICRH continues. It is shown that the reappearance of sawteeth during one particular ICRH discharge in the Joint European Torus (JET) [Campbell et al., Phys. Rev. Lett. 60, 2148 (1988)] was correlated with a change of sign in the energy δW associated with m=1 internal kink displacements. To compute δW, a new analytical model is used for the distribution function of heated minority ions, which is consistent with Fokker–Planck simulations of ICRH. Minority ions have a stabilizing influence, arising from third adiabatic invariant conservation, but also contribute to a destabilizing shift of magnetic flux surfaces. As the minor radius of the q=1 surface rises, the stabilizing influence of minority ions diminishes, and the shape of the plasma cross section becomes increasingly important. It is shown that an increase in ICRH power can destabilize the kink mode: this is consistent with observations of sawteeth in JET discharges with varying levels of ICRH. It is suggested that the sawtooth-free period could be prolonged by minimizing the vertical extent of the ICRH power deposition profile.1996 American Institute of Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.871629
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