ABSTRACT
The impact of temperature on the pulsed magnetization of a high-temperature superconductor (HTS) has been numerically studied. The resulting trapped field (TF) and its distribution over the HTS have been calculated for samples with random and periodic pinning (a regular triangular lattice). The increasing ambient temperature (within the considered values) has been shown to improve the field-trapping efficiency and lead to the possibility of pumping more flux into the sample with each consecutive pulse (contrary to the low-temperature case). Various pulse shapes produced different results at high temperatures. Trapezoidal pulses showed the highest efficiency owing to the constant-field segments during which the vortices continued to enter the sample. The critical (activation) field of flux jumps has been shown to decrease with the rising temperature. At the highest considered temperature (30 K), the flux jumps occurred during the TF relaxation. To the best of our knowledge, such calculations have been done for the first time.
ABSTRACT
By means of the Monte Carlo method, a numerical study of the vortex system in a high-temperature superconductor under the impact of pulses of magnetic field has been conducted. Various shapes and amplitudes of pulses have been considered. Samples with random and regular distributions of three different numbers of defects have been compared from the viewpoint of efficiency of flux trapping. The low-temperature behavior of vortices and their penetration into samples have been shown to be independent of the pulse shape but strongly dependent of the type of pinning distribution. Saturating dependences of density of trapped magnetic flux on the pulse amplitude have been obtained. The samples with random pinning demonstrated higher efficiency of flux trapping at lower pulse amplitudes, and the samples with a triangular lattice of defects-at higher amplitudes. If the amplitude exceeded the saturation field of both samples, the trapped field was almost equal. The increasing number of defects has lead to an increase in trapped field within the considered range of concentrations.
ABSTRACT
The neuroparalytic syndrome induced by ammonia was compared with the X-radiation-induced cerebral syndrome. It is suggested that the accumulation of ammonia in the brain and liver of rats is one of the reasons for the similarity of the studied syndromes. The fact that ammonia is bound by glutamic acid indicates that the latter is involved in the mechanisms of ammonia utilization and in the radioprotective properties manifestation.
