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  • Articles  (33)
  • Springer  (21)
  • American Institute of Physics (AIP)  (6)
  • Wiley-Blackwell  (6)
  • 1990-1994  (27)
  • 1970-1974  (6)
  • 1920-1924
  • 1905-1909
  • 1994  (20)
  • 1990  (7)
  • 1972  (6)
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  • Articles  (33)
Years
  • 1990-1994  (27)
  • 1970-1974  (6)
  • 1920-1924
  • 1905-1909
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  • 1
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 61 (1990), S. 385-388 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: Sources producing beams of spin-polarized atoms and ions are now widely used in nuclear physics. Modern systems are increasingly expensive and complex. They provide a variety of species and beam polarizations with intensities often sufficient for experimental needs. The laboratory seeking such a device for its program must evaluate a variety of options and match them to its accelerator, experimental program, and expected resources. The major systems and techniques used are surveyed and criteria dictating the choice of source for particular experimental applications are discussed briefly.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7087-7089 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Optimization of tri- or quadrilayer magneto-optic recording media requires knowledge of the optical and/or magneto-optical constants for all of the individual active or passive layers that together comprise the complete disk structure. The optical (n+ik) and first-order magneto-optical (Q1+iQ2) constants for two series (i) (Tb23Fe72.5Co4.5)100−xPrx, (ii) (Tb27Fe65Co8)100−xPrx of Pr substituted TbFeCo films, for which x varies between 0 and 30, have been determined by a combination of ellipsometry and Kerr polarimetry. Ellipsometry has also been used to determine independently the optical constants of the optimized SiN passivation layers developed to protect these samples. Using constants determined experimentally on thick samples, the variation of the polar Kerr rotation and ellipticity as a function of magnetic film thickness has been calculated for light incident from both the air and substrate side of a typical trilayer magneto-optic disk structure in which material from the above series, the magnetic and thermomagnetic properties of which have been previously reported [Carey et al., J. Magn. Magn. Mater. (to be published)], forms the active storage layer. The agreement obtained with measurements demonstrates the self-consistency of the modeling process and the validity of the determined constants.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 7081-7083 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Nonstoichiometric, Pt deficient, PtMnSb films have been investigated for evidence of the increase in coercivity suggested by the work of Marinero [Appl. Surf. Sci. 43, 117 (1989)]. Structural, magnetic, and magneto-optic properties of thin PtMnSb films of different compositions annealed in under 30 s using a rapid thermal processing (RTP) system [Carey et al., IEEE Meeting on Current Topics in Applied Magnetism, Keele University, 4 November 1992 (unpublished), Paper 15; J. Magn. Soc. Jpn. 17, 290 (1993)], have been determined. It is shown that the crystalline texture of the films can be controlled by adjustments in composition and RTP time and that Pt deficiency produces increases in coercivity. The production of coercivity does not correlate with the marked changes in texture but appears to be associated with the development of MnSb phases within the PtMnSb microstructure.
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  • 4
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Using rapid thermal processing (RTP) we recently demonstrated the production of high quality well ordered barium ferrite films in times much shorter than those required by a conventional annealing process. Influence over the magnetic and structural properties developed in annealed samples was also achieved by variation of the RTP heating profile (R. Carey, P. A. Gago-Sandoval, D. M. Newman, and B. W. J. Thomas, presented at Intermag-93, Stockholm, April 13–16, 1993). It is known that the magneto-optic properties of barium ferrite can be enhanced by selective substitution of some of the Fe by Co2+ and Ti4+ albeit at the expense of reducing the magnetic anisotropy. A multitarget scanning cosputtering process has been used in conjunction with rapid thermal processing to produce a series of barium ferrite films in which Co, Cr, Mn, Ni are selectively introduced to substitute for between 5 and 20 at. % of the Fe. A corresponding percentage of Ti is also added to maintain charge compensation. The magnetic and magneto-optic properties of these films are presented and discussed with reference to their composition and treatment respect to the properties of barium ferrite.
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  • 5
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 6 (1994), S. 662-673 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Some characteristic features of supersonic/supersonic, laminar, variable-density shear layers are studied by examining the self-similar behavior of five nitrogen/hydrogen streams. With the Levy–Lees transformation, the flow-field variables, which include the transverse velocity and dilatation, are obtained through the solution of the coupled set of nonlinear conservation equations. The issue of the appropriate "third boundary condition,'' first given for the supersonic/supersonic case by Ting [J. Math. Phys. 28, 153 (1959)], is addressed and implemented in the present formulation. Expressions for the thermal conductivity, viscosity, specific heat, and binary diffusion coefficients of an arbitrary mixture are utilized so that the Prandtl and Lewis numbers and the Chapman–Rubesin parameter can vary freely across the shear layer. In the particular cases considered, these three quantities varied by factors of approximately 3, 7, and 22, respectively. The region of high vorticity moves toward the less-dense hydrogen stream for large density ratios (∼9:1), and becomes nearly decoupled from the density profile. Because the vorticity is responsible for the kinematic mixing of the two streams, this mixing of the two laminar streams is likely to be inhibited. Even though laminar flows are considered here, this effect is consistent with the experimental observation that as density ratios become very large, further increases in the density ratio have no effect on the turbulent shear layer growth rate. The density and hydrogen mass-fraction profiles are quite elongated in the transverse direction. An increase in the velocity ratio exaggerates both of these effects. Results obtained in this work are compatible with earlier work on incompressible, variable-density flows; more importantly, these results qualitatively resemble those from experiments of compressible and incompressible turbulent flows.
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  • 6
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 2 (1990), S. 1678-1684 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A variety of turbulence models, including five second-order closures and four two-equation models, are tested for the problem of homogeneous turbulent shear flow in a rotating frame. The model predictions for the time evolution of the turbulent kinetic energy and dissipation rate, as well as those for the equilibrium states, are compared with the results of physical and numerical experiments. Most of the two-equation models predict the same results for all rotation rates, in which there is an exponential time growth of the turbulent kinetic energy and dissipation rate. The second-order closures are qualitatively superior since, consistent with physical and numerical experiments, they only predict this type of unstable flow for intermediate rotation rates in the range −0.1≤Ω/S≤0.6. For rotation rates outside this range, there is an exchange of stabilities with a solution whose kinetic energy and dissipation rate decay with time. Although the second-order closures are superior to the two-equation models, there are still problems with the quantitative accuracy of their predictions.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Journal of industrial microbiology and biotechnology 6 (1990), S. 53-59 
    ISSN: 1476-5535
    Keywords: Bituminous coal ; Biosolubilization ; Penicillium sp. ; Surface colonization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary APenicillium sp. previously shown to grow on lignite coals degraded an air-oxidized bituminous coal (Illinois #6) to a material that was more than 80% soluble in 0.5 N NaOH. Scanning electron microscopy of the oxidized Illinois #6 revealed colonization of the surface by thePenicillium sp., production of conidia, and erosion of the coal surface. The average molecular weight (MW) of Illinois #6 degraded by the fungus and base-solubilized was approximately 1000 Da. The average MW for base-solubilized Illinois #6 that was not exposed to the fungus was 6000 Da, suggesting solubilizing mechanisms other than base catalysis. A spectrophotometric assay to quantify the microbial conversion of biosolubilized coal was developed. Standard curves were constructed based on the absorbance at 450 nm of different quantities of microbe-solubilized coal. An acid precipitation step was necessary to remove medium and/or microbial metabolites from solubilized coal to prevent overestimation of the extent of coal biosolubilization. Furthermore, the absorption spectra for different coal products varied, necessitating construction of standard curves for individual coals.
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Bulletin of environmental contamination and toxicology 44 (1990), S. 260-267 
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 70 (1994), S. 397-405 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract. An important step in visual processing is the segregation of objects in a visual scene from one another and from the embedding background. According to current theories of visual neuroscience, the different features of a particular object are represented by cells which are spatially distributed across multiple visual areas in the brain. The segregation of an object therefore requires the unique identification and integration of the pertaining cells which have to be “bound” into one assembly coding for the object in question. Several authors have suggested that such a binding of cells could be achieved by the selective synchronization of temporally structured responses of the neurons activated by features of the same stimulus. This concept has recently gained support by the observation of stimulus-dependent oscillatory activity in the visual system of the cat, pigeon and monkey. Furthermore, experimental evidence has been found for the formation and segregation of synchronously active cell assemblies representing different stimuli in the visual field. In this study, we investigate temporally structured activity in networks with single and multiple feature domains. As a first step, we examine the formation and segregation of cell assemblies by synchronizing and desynchronizing connections within a single feature module. We then demonstrate that distributed assemblies can be appropriately bound in a network comprising three modules selective for stimulus disparity, orientation and colour, respectively. In this context, we address the principal problem of segregating assemblies representing spatially overlapping stimuli in a distributed architecture. Using synchronizing as well as desynchronizing mechanisms, our simulations demonstrate that the binding problem can be solved by temporally correlated responses of cells which are distributed across multiple feature modules.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Biological cybernetics 70 (1994), S. 397-405 
    ISSN: 1432-0770
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Computer Science , Physics
    Notes: Abstract An important step in visual processing is the segregation of objects in a visual scene from one another and from the embedding background. According to current theories of visual neuroscience, the different features of a particular object are represented by cells which are spatially distributed across multiple visual areas in the brain. The segregation of an object therefore requires the unique identification and integration of the pertaining cells which have to be “bound” into one assembly coding for the object in question. Several authors have suggested that such a binding of cells could be achieved by the selective synchronization of temporally structured responses of the neurons activated by features of the same stimulus. This concept has recently gained support by the observation of stimulus-dependent oscillatory activity in the visual system of the cat, pigeon and monkey. Furthermore, experimental evidence has been found for the formation and segregation of synchronously active cell assemblies representing different stimuli in the visual field. In this study, we investigate temporally structured activity in networks with single and multiple feature domains. As a first step, we examine the formation and segregation of cell assemblies by synchronizing and desynchronizing connections within a single feature module. We then demonstrate that distributed assemblies can be appropriately bound in a network comprising three modules selective for stimulus disparity, orientation and colour, respectively. In this context, we address the principal problem of segregating assemblies representing spatially overlapping stimuli in a distributed architecture. Using synchronizing as well as desynchronizing mechanisms, our simulations demonstrate that the binding problem can be solved by temporally correlated responses of cells which are distributed across multiple feature modules.
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