Effect of PVA doping on flux pinning in Bulk MgB2

The synthesis and characterization of PVA (Poly Vinyl Acetate) doped bulk MgB2 superconductor is reported here. PVA is used as a Carbon source. PVA doping effects made two distinguishable contributions: first enhancement of Jc field performance and second an increase in Hc2 value, both because of carbon incorporation into MgB2 crystal lattice. The susceptibility measurement reveals that Tc decreased from 37 to 36 K. Lattice parameter a decreased from 3.085 A to 3.081 A due to the partial substitution of Carbon at Boron site. PVA doped sample exhibited the Jc values greater than 10^5 A/cm2 at 5 & 10 K at low fields; which is almost 3 times higher than the pure one, while at high fields the Jc is increased by an order of magnitude in comparison to pure MgB2. From R(T)H measurements we found higher Tc values under magnetic field for doped sample; indicating an increase in Hc2. Also the magnetization measurements exhibited a significant enhancement in Hirr value. The improved performance of PVA doped MgB2 can be attributed to the substitution of carbon at boron site in parent MgB2 and the resulting impact on the carrier density and impurity scattering. The improved flux pinning behavior could easily be seen from reduced flux pinning force plots.Comment: 14 Pages of Text + Figs. To appear in Physica

Born Effective Charges and Infrared Response of LiBC

Calculations of the zone center optical mode frequencies (including LO-TO splitting), Born effective charges Z$^*_{\alpha\alpha}$ for each atom, dielectric constants $\epsilon_{0}$ and $\epsilon_{\infty}$, and the dielectric response in the infrared, using density functional linear response theory, are reported. Calculated Raman modes are in excellent agreement with experimental values (170 cm$^{-1}$ and 1170 cm$^{-1}$), while it will require better experimental data to clarify the infrared active mode frequencies. The Born effective charges Z$^*_{\alpha \alpha}$ (i) have surprisingly different values for B and C, and (ii) show considerable anisotropy. Relationships between the effective charges and LO-TO splitting are discussed, and the predicted reflectivity in the range 0 -- 1400 cm$^{-1}$ is presented. These results hold possible implications for Li removal in LiBC, and C substition for B in MgB$_2$.Comment: 6 pages, 3 figure

Retention of Two-Band Superconductivity in Highly Carbon-Doped MgB2

Tunneling data on MgB_{1.8}C_{0.2} show a reduction in the energy gap of the pi-bands by a factor of two from undoped MgB2 that is consistent with the Tc reduction, but inconsistent with the expectations of the dirty limit. Dirty-limit theory for undoped MgB2 predicts a single gap about three times larger than measured and a reduced Tc comparable to that measured. Our heavily-doped samples exhibit a uniform dispersion of C suggestive of significantly enhanced scattering, and we conclude that the retention of two-band superconductivity in these samples is caused by a selective suppression of interband scattering.Comment: 4 pages, 4 figures; added one figure, added one reference, minor changes to the text, manuscript accepted for publication as a Phys. Rev. B Rapid Communicatio

Reversible Pressure-Induced Amorphization in Solid C70 : Raman and Photoluminescence Study

We have studied single crystals of $C_{70}$ by Raman scattering and photoluminescence in the pressure range from 0 to 31.1 GPa. The Raman spectrum at 31.1 GPa shows only a broad band similar to that of the amorphous carbon without any trace of the Raman lines of $C_{70}$. After releasing the pressure from 31.1 GPa, the Raman and the photoluminescence spectra of the recovered sample are that of the starting $C_{70}$ crystal. These results indicate that the $C_{70}$ molecules are stable upto 31.1 GPa and the amorphous carbon high pressure phase is reversible, in sharp contrast to the results on solid $C_{60}$. A qualitative explaination is suggested in terms of inter- versus intra-molecular interactions.Comment: To appear in Phys. Rev. Lett., 12 pages, RevTeX (preprint format), 3 figures available upon reques

Murine model for Fusarium oxysporum invasive fusariosis reveals organ-specific structures for dissemination and long-term persistence

Peer reviewedPublisher PD

11^{11}B NMR study of pure and lightly carbon doped MgB2_2 superconductors

We report a $^{11}$B NMR line shape and spin-lattice relaxation rate ($1/(T_1T)$) study of pure and lightly carbon doped MgB$_{2-x}$C$_{x}$ for $x=0$, 0.02, and 0.04, in the vortex state and in magnetic field of 23.5 kOe. We show that while pure MgB$_2$ exhibits the magnetic field distribution from superposition of the normal and the Abrikosov state, slight replacement of boron with carbon unveils the magnetic field distribution of the pure Abrikosov state. This indicates a considerable increase of $H_{c2}^c$ with carbon doping with respect to pure MgB$_2$. The spin-lattice relaxation rate $1/(T_1T)$ demonstrates clearly the presence of a coherence peak right below $T_c$ in pure MgB$_2$, followed by a typical BCS decrease on cooling. However, at temperatures lower than $\approx 10$K strong deviation from the BCS behavior is observed, probably from residual contribution of the vortex dynamics. In the carbon doped systems both the coherence peak and the BCS temperature dependence of $1/(T_1T)$ weaken, an effect attributed to the gradual shrinking of the $\sigma$ hole cylinders of the Fermi surface with electron doping.Comment: 8 pages, 6 figures, submitted to Phys. Rev.

Survival and Predictors of Mortality in Systemic Sclerosis‐Associated Pulmonary Arterial Hypertension: Outcomes From the Pulmonary Hypertension Assessment and Recognition of Outcomes in Scleroderma Registry

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/106105/1/acr22121.pd

Serum Cortisol level in children with catecholamine dependent shock: A Prospective Observational study

BACKGROUND: Adrenal glucocorticoid cortisol maintains the cardiovascular function, decreases the catabolism and stabilizes the alveolar capillary membrane during inflammatory stress period. AIM OF THE STUDY: To determine the prevalence of adrenal insufficiency by measuring serum cortisol level in children with catecholamine dependent septic shock. METHOD: 49 children admitted with catecholamine dependant septic shock satisfying inclusion criteria recruited in to the study. Random serum cortisol was measured and correlated with various prognostic parameters like duration of inotropic and ventilator support, PICU and hospital stay and mortality. RESULT: The prevalence of adrenal insufficiency (< 18μgm/dl) was 41%. Duration of inotropic support (Median of 3 vs 2 days; P= 0.04), ventilator days (Median of 2.5 vs 1 day; P = 0.001) and proportionately the PICU stays (Median of 5 vs 4 days; P = 0.03) were significantly prolonged in the children with low cortisol when compared to children with normal cortisol level. Whereas the total duration of hospital stay (Median days of 10 vs 7; P=0.07) and the mortality (7 children in each group 35% vs 24%; p=0.304) were comparable between the two groups. CONCLUSION: we concluded that the low serum cortisol was a common finding among children suffering catecholamine dependent septic shock and it was positively correlated with prolonged hemodynamic, respiratory support and ICU care. We require further study to delineate the incidence of absolute and relative adrenal insufficiency by doing a stimulation test and also require controlled randomized trials to analyse the benefits of steroid supplementation on morbidity and mortality of these children

Work-life Balance and Mental Health Among dental and Medical Professionals: Insights into Stress and Burnout- A Cross-sectional Study

Background: The dental profession is inherently demanding, requiring a combination of clinical expertise, patient management skills, and administrative efficiency. While the field of dentistry is highly rewarding, it is also associated with significant stressors that can adversely affect the mental health and overall well-being of practitioners. These stressors include long working hours, patient expectations, financial pressures, and the need for continuous professional development. Furthermore, the growing complexity of dental treatments and advancements in technology add to the challenges faced by dental professionals.Materials and Methods: A cross-sectional survey was conducted among dental professionals in clinical and academic roles. A validated questionnaire, covering demographics, work environment, perceived stress, burnout indicators, and coping strategies, was distributed. Responses were collected and analyzed using statistical tools to identify key stressors and the prevalence of burnout, comparing variations across clinical and academic settings. The study also examined correlations between demographic factors (age, gender, years of experience) and mental health indicators.Results: Findings indicated a high prevalence of stress and burnout among dental professionals, with notable differences between clinical and academic roles. Clinical practitioners reported higher levels of occupational stress due to patient demands and procedural pressures, whereas academic professionals highlighted administrative burdens and workload imbalance as primary stressors. Both groups demonstrated significant burnout markers, including emotional exhaustion and depersonalization. Common coping mechanisms reported included social support, physical activity, and mindfulness practices, though their effectiveness varied across different roles.Conclusion: The study underscores the pressing need for mental health support tailored to the unique demands of dental professionals in clinical and academic settings. Addressing stressors specific to each environment, while promoting effective coping strategies, is essential for enhancing work-life balance and mitigating burnout in dental careers. Organizational policies focused on mental health awareness and supportive work environments are recommended to foster better mental well-being among dental professionals