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Biomedical subjects

Y Kaufman

Publications and source records attributed to Y Kaufman.

4 recordsLinked to original sources

Long-term sleep disturbances in adolescents after minor head injury.

It has been demonstrated that patients in the acute phase after minor head injury (MHI) complain of sleep disturbances. The purpose of the present study was to characterize the long-term effects of MHI on sleep in adolescents. Nineteen adolescents who had suffered MHI 3 years before the study and had complained of sleep disturbances completed a sleep questionnaire and were investigated in the sleep laboratory by whole-night polysomnographic recordings and were actigraphically monitored for 5 days at home. Questionnaire results revealed severe complaints regarding sleep behavior. Polysomnographic recordings revealed that in comparison with controls, MHI was associated with lower sleep efficiency (79.8 +/- [9.8]% vs 87.7 +/- [6.8]%; P < 0.005), with more wake time (10.6 +/- [9.0]% vs 3.4 +/- [4.4]%; P < 0.005), and with more awakenings lasting more than 3 minutes (2.1 +/- [1.5] vs 0.6 +/- [0.8]; P < 0.005). These findings were confirmed by actigraphic monitoring that revealed lower sleep efficiency (90 +/- [5]% vs 94 +/- [3]%; P < 0.05), more minutes of wake time (49 +/- [21] min vs 28 +/- [15] min; P < 0.05), and a trend toward more awakenings longer than 5 minutes (1.8 +/- [0.8] vs 1.2 +/- [0.8]; P = 0.063). Our data demonstrated that 3 years after MHI without any discernible clinical sequel, adolescents still complain of sleep disturbances that could be confirmed by both polysomnographic and actigraphic monitoring.

Adolescent↗

Bilateral focal motor status epilepticus with retained consciousness after stroke.

Bilateral motor seizures with retained consciousness are rare and often mistaken for pseudoseizures. In the few reported cases, the seizures were brief and the underlying lesion usually was a tumor. Here the authors describe a patient with bilateral focal motor status epilepticus with retained consciousness after a stroke. A seizure should be considered as the possible cause of continuous bilateral limb movements with retained consciousness.

Aged↗

Ionization waves in electron-beam-assisted, shielded capillary discharge

A theory of propagation of cathode-directed ionization waves during the early stages of an electrical breakdown in a shielded, low-pressure capillary is developed. The discharge process occurs due to the ionization of the low-density gas in the capillary by an electron beam that is emanating from a hollow cathode. Due to the strong electric field in the capillary the electrons are in the fast acceleration regime. Consequently, the full momentum equation for the electrons is employed, rather than the electron drift velocity approach. The smallness of the ratio of the capillary radius to the characteristic length of the electric potential variation in the axial direction allows the construction of a quasi-one-dimensional model. The latter retains the important two-dimensional nature of the electron flow as well as the electrodynamic boundary conditions at the capillary wall and the conducting shield and results in a set of one-dimensional, time-dependent partial differential equations for the on-axis distributions of the physical quantities. It is shown that those equations admit self-similar solutions that represent ionization waves propagating with constant velocities. The resulting set of ordinary differential equations is solved numerically for various initial conditions representing a nonperturbed steady state ahead of the ionization front and the resulting features of the ionization waves are investigated and discussed. The obtained solutions describe both ionization growth and virtual anode propagation and represent fast ionization waves in plasma waveguides, for which the maximum value of the mean electron velocity is much higher than the wave velocity. The space-charge distribution associated with the ionization waves is found in the form of plasma oscillations with a continuously increasing frequency and a solitary envelope. The calculated wave velocity increases with the gas pressure and this tendency is in agreement with corresponding experimental observations.

Journal Article↗