Medium energy proton radiation damage to (AlGa)As-GaAs solar cells

The performance of (AlGa)As-GaAs solar cells irradiated by medium energy 2, 5, and 10 MeV protons was evaluated. The Si cells without coverglass and a number of GaAs solar cells with 12 mil coverglass were irradiated simultaneously with bare GaAs cells. The cell degradation is directly related to the penetration of depth of protons with GaAs. The influence of periodic and continuous thermal annealing on the GaAs solar cells was investigated

GaAs solar cells for concentrator systems in space

Cells for operation in space up to more than 100 suns were made, and an AMO efficiency of 21% at 100 suns with these cells was obtained. The increased efficiency resulted not only from the higher open circuit voltage associated with the higher light intensity (higher short circuit current); it also benefitted from the increase in fill factor caused by the lower relative contribution of the generation recombination current to the forward bias current when the cell's operating current density is increased. The experimental cells exhibited an AMO efficiency close to 16% at 200 C. The prospect of exploiting this capability for the continuous annealing of radiation damage or for high temperature missions (e.g., near Sun missions) remains therefore open. Space systems with concentration ratios on the order of 100 suns are presently under development. The tradeoff between increased concentration ratio and increased loss due to the cell's series resistance remains attractive even for space applications at a solar concentrator ratio of 100 suns. In the design of contact configuration with low enough series resistance for such solar concentration ratios, the shallow junction depth needed for good radiation hardness and the thin AlGaAs layer thickness needed to avoid excessive optical absorption losses have to be retained

Theory of Light Emission in Sonoluminescence as Thermal Radiation

Based on the model proposed by Hilgenfeldt {\it at al.} [Nature {\bf 398}, 401 (1999)], we present here a comprehensive theory of thermal radiation in single-bubble sonoluminescence (SBSL). We first invoke the generalized Kirchhoff's law to obtain the thermal emissivity from the absorption cross-section of a multilayered sphere (MLS). A sonoluminescing bubble, whose internal structure is determined from hydrodynamic simulations, is then modelled as a MLS and in turn the thermal radiation is evaluated. Numerical results obtained from simulations for argon bubbles show that our theory successfully captures the major features observed in SBSL experiments.Comment: 17 pages, 20 figure

Development of a pyramidal magneto-optical trap for pressure sensing application

Here, we report the development and working of a compact rubidium (Rb) atom magneto-optical trap (MOT) operated with a hollow pyramidal mirror and a single laser beam. This type of compact MOT is suitable for developing portable atom-optic devices, as it works with less number of optical components as compared to conventional MOT setup. The application of this compact MOT setup for pressure sensing has been demonstrated

Optimisation problems and replica symmetry breaking in finite connectivity spin-glasses

A formalism capable of handling the first step of hierarchical replica symmetry breaking in finite-connectivity models is introduced. The emerging order parameter is claimed to be a probability distribution over the space of field distributions (or, equivalently magnetisation distributions) inside the cluster of states. The approach is shown to coincide with the previous works in the replica symmetric case and in the two limit cases m=0,1 where m is Parisi's break-point. As an application to the study of optimization problems, the ground-state properties of the random 3-Satisfiability problem are investigated and we present a first RSB solution improving replica symmetric results.Comment: 16 pages Revtex file, 1 figure; amended version with two new appendices; to be published in J.Phys.

Validating a novel score based on interaction between ACLF grade and MELD score to predict waitlist mortality

Background and Aim: Among candidates listed for liver transplant (LT), MELD score may not capture acute on chronic liver failure (ACLF) severity. Data on interaction between ACLF and MELD score in predicting waitlist (WL) mortality are scanty. / Methods: UNOS database (01/2002 to 06/2018) on LT listings for adults with cirrhosis and ACLF (without HCC) was analyzed. ACLF grades 1, 2, 3a, and 3b- were defined using modified EASL-CLIF criteria. / Results: Of 18,416 candidates with ACLF at listing (mean age 54 years, 69% males, 63% Caucasians), 90-d WL mortality (patient death or being too sick for LT) was 21.6% (18%, 20%, 25%, and 39% for ACLF grades 1, 2, 3a, and 3b respectively). Fine and Gray regression model identified interaction between MELD and ACLF grade, with higher impact of ACLF at lower MELD score. Other variables included candidate’s age, gender, liver disease etiology, listing MELD, ACLF grade, obesity, and performance status. A score developed using parameter estimates from the interaction model on the derivation cohort (N=9181) stratified the validation cohort (N=9235) to four quartiles Q1 (score 15.50). WL mortality increased with each quartile from 13%, 18%, 23%, and 36% respectively. Observed versus expected deciles on WL mortality in validation cohort showed good calibration (goodness of fit P=0.98) and correlation (R=0.99). / Conclusion: Among selected candidates who are in ACLF at listing, MELD score and ACLF interact in predicting cumulative risk of 90-d WL mortality, with higher impact of ACLF grade at lower listing MELD score. Validating these findings in large prospective studies will support to factor in both MELD and ACLF in prioritizing transplant candidates and allocation of liver grafts

Genetically Determined Platelet Count and Risk of Cardiovascular Disease.

Objective- Cardiovascular disease, including coronary artery disease (CAD) and ischemic stroke, is the leading cause of death worldwide. This Mendelian randomization study uses genetic variants as instruments to investigate whether there is a causal effect of genetically determined platelet count on CAD and ischemic stroke risk. Approach and Results- A genome-wide association study of 166 066 subjects was used to identify instruments and genetic association estimates for platelet count. Genetic association estimates for CAD and ischemic stroke were obtained from genome-wide association studies, including 60 801 CAD cases and 123 504 controls, and 60 341 ischemic stroke cases and 454 450 controls, respectively. The inverse-variance weighted meta-analysis of ratio method Mendelian randomization estimates was the main method used to obtain estimates for the causal effect of genetically determined platelet count on risk of cardiovascular outcomes. We found no significant Mendelian randomization effect of genetically determined platelet count on risk of CAD (odds ratio of CAD per SD unit increase in genetically determined platelet count, 1.01; 95% CI, 0.98-1.04; P=0.60). However, higher genetically determined platelet count was causally associated with an increased risk of ischemic stroke (odds ratio, 1.07; 95% CI, 1.04-1.11; P<1×10-5), including all major ischemic stroke subtypes. Similar results were obtained in sensitivity analyses more robust to the inclusion of pleiotropic genetic variants. Conclusions- This Mendelian randomization study found evidence that higher genetically determined platelet count is causally associated with higher risk of ischemic stroke