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  • Electronic Resource  (2)
  • Rabbit penicillin epilepsy  (1)
  • ergodic theorem  (1)
  • 1
    ISSN: 1572-9125
    Keywords: Toeplitz matrix ; generating function ; ergodic theorem ; preconditioning ; conjugate gradient method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract It is well known that the generating function f ∈ L 1([−π, π], ℜ) of a class of Hermitian Toeplitz matrices A n(f) n describes very precisely the spectrum of each matrix of the class. In this paper we consider n × n Hermitian block Toeplitz matrices with m × m blocks generated by a Hermitian matrix-valued generating function f ∈ L 1([−π, π], C m×m ). We extend to this case some classical results by Grenander and Szegö holding when m = 1 and we generalize the Toeplitz preconditioning technique introduced in the scalar case by R. H. Chan and F. Di Benedetto, G. Fiorentino and S. Serra. Finally, concerning the spectra of the preconditioned matrices, some asymptotic distribution properties are demonstrated and, in particular, a Szegö-style theorem is proved. A few numerical experiments performed at the end of the paper confirm the correctness of the theoretical analysis.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Springer
    Neurological sciences 7 (1986), S. 413-420 
    ISSN: 1590-3478
    Keywords: Rabbit penicillin epilepsy ; spikes ; spindles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Description / Table of Contents: Sommario Sono stati studiati gli effetti della penicillina G-sodica (1.000.000 I.U./Kg.i.v.) in 28 conigli impiantati con elettrodi di superficie e con elettrodi profondi nel corno di Ammone dorsale (CAd) e nei nuclei talamici laterali (lT) e mediali (mT). In particolare sono stati esaminati l'attività di “spiking” intercritico, l'attività corticale di “spindling” e le relazioni spikes-spindles. In 20 animali la penicillina ha indotto un pattern EEG intercritico multifocale con spikes presenti a livello corticale e talamico. A livello corticale le spikes erano quasi sempre associate a spindles. Inoltre le spindles, dopo penicillina, presentavano un significativo aumento della durata media, senza modificazioni della frequenza. Il pattern EEG da somministrazione sistemica di penicillina nel coniglio appare più simile al pattern descritto nel ratto che a quello del gatto. Le variazioni della attività di “spindles” e l'attività parossistica di “spikes” potrebbero essere due fenomeni indipendenti indotti dalla penicillina e presenti durante periodi di aumentata eccitabilità corticale.
    Notes: Abstract The effects of Na-penicillin G (1,000,000 I.U./kg i.v.) were studied in 28 rabbits implanted with surface and deep electrodes in the medial (mT) and lateral (lT) nuclei of the thalamus and in the cornu Ammonis dorsalis (CAd). Attention was focused on interictal spike activity, cortical spindle activity and spikes-spindles relationship. A multifocal interictal EEG pattern, represented by cortical and thalamic spikes, was observed in 20 animals. A clear association between cortical spikes and spindles occurred almost constantly. Moreover a statistically significant increase in the average duration of spindles without changes in the average frequency was noticed. Seizure discharges had always a focal start and secondary generalization. The EEG features of parenteral penicillin epilepsy in the rabbit appeared to be more similar to those of the rat than to those of the cat. The spindle activity changes and the paroxysmal spike activity can be interpreted as two independent penicillin induced features appearing during raised cortical excitability periods.
    Type of Medium: Electronic Resource
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