Search results for " conduction"
showing 10 items of 373 documents
Early auditory evoked potentials: developmental aspects and validity in neuropaediatric and audiologic disorders.
1984
Auditory evoked potentials and in this context especially five waves in the first 10 ms (early auditory evoked potentials = EAEP) are a diagnostic aid in topodiagnosis of posterior fossa diseases. This is due to waves I to V which arise along the acoustic nerve and in brain stem structures such as medulla, pons and mid-brain. Besides an indication about the site of a lesion in the posterior fossa, wave V allows an objective threshold determination. The present results were gained in normal children aged 1-3 years and in children with neuropaediatric and audiologic disorders.
Diltiazem for Prevention of Acoustical Trauma during Otologic Surgery
1995
100 patients were tested in a prospective, randomized, double-blinded study to assess the perioperative efficacy of a calcium channel blocker (diltiazem) in preventing acoustical trauma during otologic surgery. The patients were randomly divided into a therapy group (diltiazem) and a control group (placebo). Bone conduction hearing thresholds were examined preoperatively and again 1 day and 3 months postoperatively. Frequency-dependent changes in postoperative bone conduction and the number of patients with various degrees of postoperative hearing loss in both groups were statistically analyzed. The results indicated only a small postoperative hearing loss after ear surgery in both groups. …
Impaired refractory periods of peripheral sensory nerves in multiple sclerosis.
1978
Maximum conduction velocity and relative refractory period (RRP) of median nerve sensory fibers were studied in 36 patients diagnosed as having multiple sclerosis (MS) and in 31 controls. Maximum conduction velocity did not differ in the two groups, but the RRP was significantly prolonged in MS patients. Increased RRP is observed mainly when peripheral nerve myelin is abnormal or damaged. Our findings support the assumption that peripheral nerve myelinated fibers are usually involved in MS.
Sympathetic Vasomotor Response of the Radial Artery in Patients With Diabetic Foot Syndrome
2003
OBJECTIVE—Neurophysiological assessment of the peripheral autonomic system is characterized by various limitations. An alternative approach to laser Doppler and venous plethymography is the assessment of the sympathetic vasomotor response of the radial artery obtained by continuous wave Doppler sonography. Nomogram data have been established and demonstrate the temporary disappearance of diastolic flow after coughing or deep inspiration. RESEARCH DESIGN AND METHODS—We assessed the sympathetic vasomotor response in 25 patients (mean age 64 years, range 43–76) with diabetic foot syndrome. The Doppler data were correlated with nerve conduction studies of the median and peroneal nerve, the exte…
Influence of nerve branch of origin and extracanalicular extension of the tumor on hearing after middle fossa removal of vestibular schwannoma
2007
Neither nerve branch of origin nor extracanalicular (up to 1 cm) extension of a vestibular schwannoma (VS) influence the postoperative hearing outcome in patients operated via a middle cranial fossa (MCF) approach.To test whether the nerve branch of tumor origin and an extracanalicular, up to 1 cm, tumor extension influences hearing outcome after MCF VS surgery.This was a retrospective case review of 50 patients with postoperative pure-tone audiogram (PTA) performed later than 90 days after surgery. Twenty patients had a superior vestibular nerve (SVN) tumor and 27 patients had an inferior vestibular nerve (IVN) tumor. In three patients the nerve branch of origin of the VS could not be uneq…
Correlated barrier hopping in NiO films
1991
The ac conduction in NiO films has been investigated in the frequency range 10 Hz < v < 10^9 Hz and at temperatures between 10 and 300 K. The frequency and the temperature dependence of the electrical conductivity can be consistently explained within a model developed for the mechanism of charge transfer in amorphous semiconductors which proposes that charge carriers hop over potential barriers between defect sites, the height of the barriers being correlated with the intersite separation.
Mathematical Model of Solid Food Pasteurization by Ohmic Heating: Influence of Process Parameters
2013
Pasteurization of a solid food undergoing ohmic heating has been analysed by means of a mathematical model, involving the simultaneous solution of Laplace’s equation, which describes the distribution of electrical potential within a food, the heat transfer equation, using a source term involving the displacement of electrical potential, the kinetics of inactivation of microorganisms likely to be contaminating the product. In the model, thermophysical and electrical properties as function of temperature are used. Previous works have shown the occurrence of heat loss from food products to the external environment during ohmic heating. The current model predicts that, when temperature gradient…
Formation of X-ray emitting stationary shocks in magnetized protostellar jets
2016
X-ray observations of protostellar jets show evidence of strong shocks heating the plasma up to temperatures of a few million degrees. In some cases, the shocked features appear to be stationary. They are interpreted as shock diamonds. We aim at investigating the physics that guides the formation of X-ray emitting stationary shocks in protostellar jets, the role of the magnetic field in determining the location, stability, and detectability in X-rays of these shocks, and the physical properties of the shocked plasma. We performed a set of 2.5-dimensional magnetohydrodynamic numerical simulations modelling supersonic jets ramming into a magnetized medium and explored different configurations…
Effects of radiation in accretion regions of classical T Tauri stars
2019
Models and observations indicate that the impact of matter accreting onto the surface of young stars produces regions at the base of accretion columns, in which optically thin and thick plasma components coexist. Thus an accurate description of these impacts requires to account for the effects of absorption and emission of radiation. We study the effects of radiation emerging from shock-heated plasma in impact regions on the structure of the pre-shock downfalling material. We investigate if a significant absorption of radiation occurs and if it leads to a pre-shock heating of the accreting gas. We developed a radiation hydrodynamics model describing an accretion column impacting onto the su…
YSO accretion shocks: magnetic, chromospheric or stochastic flow effects can suppress fluctuations of X-ray emission
2013
Context. Theoretical arguments and numerical simulations of radiative shocks produced by the impact of the accreting gas onto young stars predict quasi-periodic oscillations in the emitted radiation. However, observational data do not show evidence of such periodicity. Aims. We investigate whether physically plausible perturbations in the accretion column or in the chromosphere could disrupt the shock structure influencing the observability of the oscillatory behavior. Methods. We performed local 2D magneto-hydrodynamical simulations of an accretion shock impacting a chromosphere, taking optically thin radiation losses and thermal conduction into account. We investigated the effects of seve…