Measurement of Magnetic Relaxation in the peak regime of V3Si

Magnetization relaxation measurements are carried out in the Peak effect regime of superconducting V3Si crystal, using Quantum Design SQUID magnetometer. Relaxation in the increasing field scan is logarithmic in time, consistent with the theory of flux creep. The relaxation on the decreasing field scan however exhibits athermal behavior which is predominantly governed by the flux avalanches triggered by the small external field perturbation experienced by the superconductor during measurement scan in an inhomogeneous field.Comment: PDF, 17 pages including 9 figure

Stable and Metastable vortex states and the first order transition across the peak effect region in weakly pinned 2H-NbSe_2

The peak effect in weakly pinned superconductors is accompanied by metastable vortex states. Each metastable vortex configuration is characterized by a different critical current density J_c, which mainly depends on the past thermomagnetic history of the superconductor. A recent model [G. Ravikumar, et al, Phys. Rev. B 61, R6479 (2000)] proposed to explain the history dependent J_c postulates a stable state of vortex lattice with a critical current density J_c^{st}, determined uniquely by the field and temperature. In this paper, we present evidence for the existence of the stable state of the vortex lattice in the peak effect region of 2H-NbSe_2. It is shown that this stable state can be reached from any metastable vortex state by cycling the applied field by a small amplitude. The minor magnetization loops obtained by repeated field cycling allow us to determine the pinning and "equilibrium" properties of the stable state of the vortex lattice at a given field and temperature unambiguously. The data imply the occurence of a first order phase transition from an ordered phase to a disordered vortex phase across the peak effect.Comment: 20 pages, 10 figures. Corresponding author: S. Ramakrishna

A study on treatment outcome and adverse drug reactions among extra pulmonary tuberculosis patients treated under DOTS in a tertiary care hospital

Background: Pulmonary tuberculosis being the predominant manifestation of the disease Extra-Pulmonary sites can also involve as a result of dissemination from a chief focus. The present study aims to determine the presentation and outcome of patients with extra-pulmonary tuberculosis treated with category I DOTS and to identify the incidence and pattern of ADRs caused by anti-tubercular drugs and to assess the causality and severity of the reported ADRs.Methods: Data was collected from cases of Tuberculosis patients diagnosed and treated under category I DOTS at Sri Siddhartha Medical College for the period of one year (during 2015). These patients were monitored for ADRs during OPDs and hospital stay. Any Adverse effects observed were recorded in ‘Adverse Drug Event Reporting Form’ prepared by the CDSCO, Govt. of India. The data were evaluated for patient demography, types of TB, incidence of ADRs, onset and outcome of the ADRs. ADRs were also assessed for their causality and severity by using WHO-UMC criteria and Hartwig’s scale.Results: Extra-pulmonary cases accounted for 32.2% of total TB cases. Among 224 cases of extra-pulmonary TB studied, 136 (60.7%) were males and 88 (39.3%) were females. Among these patients 82.2% completed treatment, 7.5% were defaulted, 9.9% died and 0.4% treatment failure. The most common reason for default was irregular treatment (29.5%) followed by alcohol abuse (23.5%). Among 224 patients of EPTB who were started on ATT as per DOTS, we noted ADR in 52 patients and 73 ADRs. Gastritis was the most common ADR (25%) followed by anorexia (14%) and skin reactions (9.6%) and multiple drug therapy was the major predisposing factor for these ADR’s.Conclusions: Extra-pulmonary Tuberculosis accounts for 32.2% of the total cases studied. Treatment irregularities and alcohol abuse are the two most common reasons for default. On evaluation of the causality of ADRs, majority of them were found to be ‘possible’ by WHO-UMC and Naronjo’s causality assessment scale. The severity assessment of ADRs showed that 42% reactions were moderate and 58% were of the ‘mild’ nature

Comparison of History Effects in Magnetization in Weakly pinned Crystals of high-TcT_c and low-Tc_c Superconductors

A comparison of the history effects in weakly pinned single crystals of a high $T_c$ YBa$_2$Cu$_3$O$_{7 - \delta}$ (for H $\parallel$ c) and a low $T_c$ Ca$_3$Rh$_4$Sn$_{13}$, which show anomalous variations in critical current density $J_c(H)$ are presented via tracings of the minor magnetization hysteresis loops using a vibrating sample magnetometer. The sample histories focussed are, (i) the field cooled (FC), (ii) the zero field cooled (ZFC) and (iii) an isothermal reversal of field from the normal state. An understanding of the results in terms of the modulation in the plastic deformation of the elastic vortex solid and supercooling across order-disorder transition is sought.Comment: Presented in IWCC-200