Dissipative Cylindrical Collapse of a Charged Anisotropic Fluid in f(R)f(R) Gravity

This paper is devoted to investigate the cylindrical collapse of an anisotropic fluid in $f(R)$ gravity. For this purpose, the viscous charged anisotropic fluid dissipating energy with heat flow and shear is assumed. We use the perturbation scheme to develop the dynamical equations for the variables that ultimately lead to the disturbance of the physical variables and the Starobinksy like $f(R)$ model chosen. The evolution of the matter variables is discussed with the help of these equations. It can be concluded that the range of dynamic instabilities depends on the field strength, density distribution, pressure and the curvature term of the $f(R)$ model. We find that our results of Newtonian and post-Newtonian regimes reduce asymptotically to general relativity solutions in the limiting case.Comment: 20 pages, accepted for publication in Canadian Journal of Physic

Wormhole Structures in Logarithmic-Corrected R2R^2 Gravity

This paper is devoted to find the feasible shape functions for the construction of static wormhole geometry in the frame work of logarithmic-corrected $R^2$ gravity model. We discuss the asymptotically flat wormhole solutions sustained by the matter sources with anisotropic pressure, isotropic pressure and barotropic pressure. For anisotropic case, we consider three shape functions and evaluate the null energy conditions and weak energy conditions graphically along with their regions. Moreover, for barotropic and isotropic pressures, we find shape function analytically and discuss its properties. For the formation of traversable wormhole geometries, we cautiously choose the values of parameters involved in $f(R)$ gravity model. We show explicitly that our wormhole solutions violates the non-existence theorem even with logarithmic corrections. We discuss all physical properties via graphical analysis and it is concluded that the wormhole solutions with relativistic formalism can be well justified with logarithmic corrections.Comment: 12 pages, 8 figure

Interleukin-1 alpha variation is associated with the risk of developing preeclampsia

Objective Preeclampsia is a syndrome that affects 5 of all pregnancies, producing substantial maternal and prenatal morbidity and mortality. Several studies have reported that cytokine genes are associated with the persistence of preeclampsia or the severity of the disease. The aim of this study is to investigate the relationships between the polymorphisms of interleukin-1 alpha-889 (IL-1A) gene and preeclampsia. Method Genomic DNA was extracted from the peripheral blood of 305 patients with preeclampsia and 325 normal controls from Sayyad Shirazi Hospital of Golestan University. Then subjected to SSP-PCR amplification. STATA software and the chi square test were used for statistic calculations. Results The frequencies of IL-1A -889 genotypes C/C, T/T and C/T in preeclampsia cases were 34.8, 8.2, 57 and in controls were 20.9, 7.6 and 71.3 respectively. There was a significant 1.5 fold excess frequency in genotype C/C in cases (CI = 1.44-3.07, OR = 2.1, P = 0.0001). There was a significant difference in the frequencies of alleles or genotypes in IL-1A promoter regions between patients with preeclampsia and the control group. Turkomans showed the highest frequency of the C allele and Sistanies had the lowest frequency of the C allele in preeclampsia compared to control groups (CI = 1.5-3.9, OR = 2.48, P = 0.0001). Conclusion Our findings suggest that the IL-1A-899C/C genotype and C allele are associated with susceptibility to preeclampsia. © 2015 Elsevier Ireland Ltd. All rights reserved

SiC power MOSFETs performance, robustness and technology maturity

Relatively recently, SiC power MOSFETs have transitioned from being a research exercise to becoming an industrial reality. The potential benefits that can be drawn from this technology in the electrical energy conversion domain have been amply discussed and partly demonstrated. Before their widespread use in the field, the transistors need to be thoroughly investigated and later validated for robustness and longer term stability and reliability. This paper proposes a review of commercial SiC power MOSFETs state-of-the-art characteristics and discusses trends and needs for further technology improvements, as well as device design and engineering advancements to meet the increasing demands of power electronics

Accidental Leaders: Experiences and Perspectives of Higher Education Leaders in Pakistan

This research explored the experiences and perspectives of university leaders in Pakistan.  Using a qualitative narrative approach, we explored leadership stories, challenges, and opportunities at various positions unique to the Pakistani context.  Findings underscored the accidental nature of higher education leadership in Pakistan, the significance of mentoring provided by teachers and family support for nascent academic leaders, as well as the challenges these academic leaders face ranging from financial barriers to teaching quality issues, to retention of foreign qualified faculty.  The research offers several policy recommendations including institutionalized leadership training and support for promising leaders; transparency in policies regarding leader appointment, promotion, and succession; support for existing universities rather than expansion; and addressing brain drain due to the attrition of foreign qualified faculty members.This research explored the experiences and perspectives of university leaders in Pakistan.  Using a qualitative narrative approach, we explored leadership stories, challenges, and opportunities at various positions unique to the Pakistani context.  Findings underscored the accidental nature of higher education leadership in Pakistan, the significance of mentoring provided by teachers and family support for nascent academic leaders, as well as the challenges these academic leaders face ranging from financial barriers to teaching quality issues, to retention of foreign qualified faculty.  The research offers several policy recommendations including institutionalized leadership training and support for promising leaders; transparency in policies regarding leader appointment, promotion, and succession; support for existing universities rather than expansion; and addressing brain drain due to the attrition of foreign qualified faculty members

Avalanche ruggedness of parallel SiC power MOSFETs

© 2018 Elsevier Ltd The aim of this paper is to investigate the impact of electro-thermal device parameter spread on the avalanche ruggedness of parallel silicon carbide (SiC) power MOSFETs representative of multi-chip layout within an integrated power module. The tests were conducted on second generation 1200 V, 36 A–80 mΩ rated devices. Different temperature-dependent electrical parameters were identified and measured for a number of devices. The influence of spread in measured parameters was investigated experimentally during avalanche breakdown transient switching events and important findings have been highlighted