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  • Wiley-Blackwell  (9)
  • American Institute of Physics (AIP)  (5)
  • 2000-2004
  • 1985-1989  (12)
  • 1925-1929  (2)
  • 1989  (6)
  • 1985  (6)
  • 1928  (2)
  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 90 (1989), S. 3071-3080 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A simple model for the coupling of two chemical oscillators is proposed. The model consists of twotwo-variable subsystems, each of which gives rise to a "cross-shaped phase diagram'' containing two different steady states plus regions of bistability and of oscillation. The subsystems are coupled by diffusion of both species. Extensive numerical simulations reveal that when one subsystem is in the bistable and the other in the oscillatory region of the parameter space, coupling can result in birhythmicity, period doubling, and chaos. When both subsystems are in the oscillatory region, the coupled behavior is even richer, including quasiperiodicity, entrainment, chaos, and phase death (cessation of oscillations), with various hysteresis phenomena between these modes of behavior. The relation of these observations to behavior found experimentally in coupled chemical oscillators is discussed.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 2461-2463 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Many studies have been devoted in recent years to the experimental determination of the diffusion length of the minority carriers in hydrogenated amorphous silicon. The most popular method for this purpose was the surface photovoltage technique while the most novel method is the photocarrier grating technique. In the present work we report the first experimental comparison of the two methods. It is found that the first method yields values which are typically twice as large as those of the second method. This disagreement can be explained by the recent theoretical studies of the two methods. On the other hand, the present results seem to indicate how some more information on the electronic structure of the above material can be derived by future comparisons between theoretical and experimental results.
    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 65 (1989), S. 969-977 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A series of thermal transport experiments using spectral-line signature and ion expansion measurements has been performed in spherical geometry using the 24 UV-converted beams of the Omega laser system at the Laboratory for Laser Energetics of the University of Rochester. Comparison with previous experiments employing only six beams shows a much better agreement in the mass ablation rate, when using 24 beams, between experimental results obtained from charge collectors and code simulations using a flux limiter of 0.1. The influence of nonuniformities in the irradiation, x-ray line reabsorption, and ionization time lag (non-LTE effects) were studied with the help of a collisional-radiative model. These processes were found to alter the falloff rates (determined mainly by the radical profile of the temperature) of the relative x-ray line intensity with overcoat thickness. With these effects included, agreement between calculated and measured burnthrough curves is greatly improved.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY : American Institute of Physics (AIP)
    Physics of Fluids 1 (1989), S. 214-220 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Recent evidence for amplification of the Balmer-alpha line of hydrogenlike carbon in a recombining plasma [Opt. Commun. 54, 289 (1985)] raises the question of the relative importance of radiative cooling in this experiment and of the role of radiative cooling in optimizing future experiments. This paper approaches this question using results from hydrodynamic and atomic-kinetic simulations of this experiment and some hypothetical variations. A new feature of these simulations is the use of an explicit nonlocal treatment of the Doppler-enhanced escape probability of resonance radiation to take into account opacity effects that are an important limitation of this and many other extreme-ultraviolet and x-ray laser schemes. It is shown that short-pulse (∼100 psec) illumination and cylindrical expansion are very important. Mixing is required for effective cooling of the carbon by a radiative coolant, but the resulting dilution of the lasant reduces the gain coefficient. It is found that amplification cannot be obtained with the prolonged heating caused by long (600 psec) pulses, even with radiative cooling. Gain results comparable to those of other workers have been obtained in simulations of hypothetical cases.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 82 (1985), S. 53-57 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Experimental and model studies are reported of nucleation induced transitions between bistable states of a chemical reaction in a stirred tank reactor. In both systems studied, BrO−3–Br−–Mn2+ and ClO2−–I−, the rate of stirring has a marked effect upon the transition in one direction but not in the other. In both cases, good qualitative agreement is found between the experimental results and those of a simple, two-compartment reactor model.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 0362-2525
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The surface ultrastructure of the gill arches of the killifish, Fundulus heteroclitus, adapted to seawater or freshwater, was found to be similar to that reported for other euryhaline teleosts. Two rows of gill filaments (about 42 filaments per row) extended posterolaterally, and two rows of gill rakers (about 10 rakers per row) extended anteromedially from each arch. Leaf-like respiratory lamellae protruded along both sides of each filament, from its base to its apex. The distributions, sizes, and numbers of various surface cells and structures were also determined. All surfaces were covered by a mosaic of pavement cells, which measured about 7 × 4 μm and exhibited concentrically arranged surface ridges. Taste buds were especially prominent on the rakers and the pharyngeal surfaces of the first and second gill arches, but were often replaced by horny spines on the third and fourth gill arches. Apical crypts of chloride cells occurred mostly on the surfaces of the gill filaments adjacent to the afferent artery of the filament. In seawater adapted killifish, crypts resembled narrow, deep holes along the borders of adjacent pavement cells, had openings of about 2 μm2, and occurred at a frequency of about 1 per 70 μ2 of surface area. In freshwater fish, the crypts usually had larger openings (about 10 μ2), occurred less frequently (1 per 123 μ2), and exhibited many cellular projections in their interiors. Changes in crypt morphology may be related to the ion transport function of chloride cells.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 23 (1989), S. 253-266 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: We report the biocompatibility in the rat brain of a controlled-release, biodegradable polymer, the polyanhydride poly-[bis(p-carboxyphenoxy)propane-sebacic acid] copolymer (PCPP-SA) in a 20:80 formulation. The biodegradable polyanhydride can be used for drug delivery directly into the brain, circumventing the difficulties posed by the blood - brain barrier and avoiding the consequences of having to administer toxic doses systemically to reach therapeutic doses in the central nervous system. The tissue reaction in the presence of PCPP-SA was compared to that seen with other standard neurosurgical implants. Fifty-six adult Sprague-Dawley rats were assigned to one of seven groups and underwent bilateral frontal lobe implantation of PCPP-SA (42 hemispheres), Surgicel (oxidized regenerated cellulose) (35 hemispheres), or Gelfoam (absorbable gelatin sponge) (35 hemispheres). None of the animals showed any behavioral changes or neurological deficits suggestive of either systemic or localized toxicity from the biodegradable polyanhydride, all surviving to the scheduled data of sacrifice. PCPP-SA evoked a well localized inflammatory reaction, comparable to that of Surgicel, which resolved as the PCPP-SA polymer degraded over five weeks. The biodegradable polyanhydride has been shown in this study to be nontoxic and biocompatible in the rat brain, when compared to standard neurosurgical implants.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    BioEssays 10 (1989), S. 44-48 
    ISSN: 0265-9247
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: The recent dramatic development of molecular neurobiology has focused almost entirely on biological events in individual brain cells, and it seems that many of the goals of such work will soon be attained. Yet, when we attain those goals, we will still have to ask how this information will enable us to understand the properties of brain cell collectivities and their presumptive roles in higher brain functions. Even general ideas about those functions are not yet well defined. Therefore, it seems worthwhile to start studying correlations of the molecular events to these higher functions to help delineate the molecular aspects that need study.It is readily appreciated that we cannot tell what other animal species see, hear, taste, smell and feel when touching something, though we can foresee the time when we will be able to detail the biochemical and biophysical consequences of all inputs to those senses. Thus, however deep our understanding of the biology of those species, we are unable to establish relations between their biological responses to inputs and their presumptive mental perceptions. Even though humans can use language to talk about those perceptions, we cannot even verify whether someone else's perceptions are the same as our own, as with the old question of whether two individuals see the same thing when viewing something blue. Questions about still higher mental functions of human brains are even less accessible to analysis and can be approached at best, by using correlations. In this article are a number of such questions and their current correlation-level answers.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Chemical Kinetics 17 (1985), S. 345-354 
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Calculations are performed to model several phenomena observed when a photosensitive oscillating chemical reaction, the Briggs-Rauscher (BR) reaction, is subject to irradiation in a continuous-flow stirred-tank reactor. The BR mechanism proposed earlier by De Kepper and Epstein is supplemented by additional steps involving the photogeneration and subsequent reaction of iodine atoms. The calculations show qualitative agreement with the following experimentally observed phenomena: (a) change in the period and amplitude of oscillation as a function of the intensity of constant illumination, (b) synchronization between periodically varying illumination and the period of chemical oscillation, (c) phase shifts induced by single light pulses, and (d) dark steady states which are excitable by single light pulses and become oscillatory at appropriate levels of constant illumination.
    Additional Material: 5 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Plant/Operations Progress 4 (1985), S. 200-206 
    ISSN: 0278-4513
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 8 Ill.
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