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  • 1
    Electronic Resource
    Electronic Resource
    Approximation with generalized hyperexponential distributions: Weak convergence results (1986)
    Springer
    Queueing systems 1 (1986), S. 169-190 
    Details
    ISSN: 1572-9443
    Keywords: Approximation ; convergence in distribution ; denseness, Erlang distribution ; generalized hyperexponential distribution ; method of stages ; weak convergence
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract Generalized hyperexponential (GH) distributions are linear combinations of exponential CDFs with mixing parameters (positive and negative) that sum to unity. The denseness of the class GH with respect to the class of all CDFs defined on [0, ∞) is established by showing that a GH distribution can be found that is as close to a given CDF as desired, with respect to a suitably defined metric. The metric induces the usual topology of weak convergence so that, equivalently, there exists a sequence of GH CDFs that converges weakly to a given CDF. This result is established by using a similar result for weak convergence of Erlang mixtures. Various set inclusion relations are also obtained relating the GH distributions to other commonly used classes of approximating distributions, including generalized Erlang (GE), mixed generalized Erlang (MGE), those with reciprocal polynomial Laplace transforms (K n ), those with rational Laplace transforms (R n ), and phase-type (PH) distributions. A brief survey of the history and use of approximating distributions in queueing theory is also included.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01536187
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  • 2
    Electronic Resource
    Electronic Resource
    Withdrawal from chronic nicotine substitutes partially for the interoceptive stimulus produced by pentylenetetrazol (PTZ) (1986)
    Springer
    Psychopharmacology 90 (1986), S. 85-89 
    Details
    ISSN: 1432-2072
    Keywords: Pentylenetetrazol ; Drug dependence ; Withdrawal ; Mecamylamine ; Discrimination ; Diazepam ; Nicotine ; Anxiety
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Rats were trained on an FR10 schedule of food reinforcement to press one lever after pentylenetetrazol (PTZ), 20 mg/kg, IP, and an alternate lever after saline. After acute nicotine, 0.64 mg/kg, SC, 35% of the rats pressed the PTZ-lever. Diazepam, 5 mg/kg, IP, blocked the stimulus produced by PTZ, and mecamylamine, 5 mg/kg, IP, blocked the stimulus produced by nicotine. Training was then suspended and rats were treated with nicotine, at 8-h intervals, 0.64 mg/kg on the 1st day, and 1.25 mg/kg on subsequent days, for 21 days. To determine whether nicotine withdrawal substitutes for the stimulus produced by PTZ, rats were tested with saline at various times after chronic nicotine injections. Data from this part of the study were replicated in another group given nicotine for 15 days. Saline at 8 h after nicotine (five determinations each group) produced a small but stable degree of PTZ lever selection (35±4%). At 48 h after termination of nicotine treatment, the percentage of rats selecting the PTZ lever (50%) was greater than that in a control group tested after an equivalent period without training. The PTZ-like stimulus detected after chronic nicotine was not altered by mecamylamine, was additive with PTZ, and was blocked by diazepam. These data suggest that withdrawal from chronic nicotine produces a weak PTZ-like stimulus, which can be antagonized by an anxiolytic drug.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00172876
    Library Location Call Number Volume/Issue/Year Availability
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    Paper (German National Licenses)
    Fulltext
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