General Semiparametric Shared Frailty Model Estimation and Simulation with frailtySurv

The R package frailtySurv for simulating and fitting semi-parametric shared frailty models is introduced. Package frailtySurv implements semi-parametric consistent estimators for a variety of frailty distributions, including gamma, log-normal, inverse Gaussian and power variance function, and provides consistent estimators of the standard errors of the parameters' estimators. The parameters' estimators are asymptotically normally distributed, and therefore statistical inference based on the results of this package, such as hypothesis testing and confidence intervals, can be performed using the normal distribution. Extensive simulations demonstrate the flexibility and correct implementation of the estimator. Two case studies performed with publicly available datasets demonstrate applicability of the package. In the Diabetic Retinopathy Study, the onset of blindness is clustered by patient, and in a large hard drive failure dataset, failure times are thought to be clustered by the hard drive manufacturer and model

White holes and eternal black holes

We investigate isolated white holes surrounded by vacuum, which correspond to the time reversal of eternal black holes that do not evaporate. We show that isolated white holes produce quasi- thermal Hawking radiation. The time reversal of this radiation, incident on a black hole precursor, constitutes a special preparation that will cause the black hole to become eternal.Comment: 5 pages, 2 figures, revtex; revised version to appear in Classical and Quantum Gravit

Limiting efficiencies of solar energy conversion and photo-detection via internal emission of hot electrons and hot holes in gold

We evaluate the limiting efficiency of full and partial solar spectrum harvesting via the process of internal photoemission in Au-semiconductor Schottky junctions. Our results based on the ab initio calculations of the electron density of states (e-DOS) reveal that the limiting efficiency of the full-spectrum Au converter based on hot electron injection is below 4%. This value is even lower than previously established limit based on the parabolic approximation of the Au electron energy bands. However, we predict limiting efficiency exceeding 10% for the hot holes collection through the Schottky junction between Au and p-type semiconductor. Furthermore, we demonstrate that such converters have more potential if used as a part of the hybrid system for harvesting high- and low-energy photons of the solar spectrum.Comment: Proc. SPIE 9608, Infrared Remote Sensing and Instrumentation XXIII, 960816 (September 1, 2015) 7 pages, 4 figure

Expert consensus for respiratory physiotherapy management of mechanically ventilated adults with community-acquired pneumonia: A Delphi study

Rationale and aims: Patients with community‐acquired pneumonia (CAP) are frequently admitted to an intensive care unit. Physiotherapy may be provided to optimize respiratory function; however, there is significant variability in clinical practice and limited research directing best practice for this cohort. This study aimed to determine expert consensus for best physiotherapy practice for invasively ventilated adults with CAP. Method: A modified Delphi technique involved an international expert panel completing three rounds of an online questionnaire. The initial 35‐statement questionnaire, based on a systematic literature review and survey of current clinical practice, covered physiotherapy assessment and treatment of intubated patients with CAP. Quantitative data using Likert scales determined level of agreement, with qualitative data collected through open‐ended responses. Consensus threshold was set a priori at 70%. Items not achieving consensus were modified and new items added based on themes from qualitative data. Quantitative data were analysed descriptively, with thematic analysis used on qualitative data. Results: The panel comprised 29 international clinical and academic experts in critical care physiotherapy. Response rate was more than 95% for each round. Outcome achieved was 38 consensus statements covering assessment and treatment, with 28 statements (74%) providing consensus on recommended clinical practice, two consensus disagreement statements (7%) for what practice is not recommended, and eight statements (21%) indicating which treatments may be beneficial. Conclusion: Expert consensus regarding physiotherapy for intubated adults with CAP patients provides an evidence‐based approach to guide clinical practice. The consensus statements can also be used to guide research evaluating physiotherapy interventions for patients with CAP

Instabilities and the null energy condition

We show that violation of the null energy condition implies instability in a broad class of models, including classical gauge theories with scalar and fermionic matter as well as any perfect fluid. When applied to the dark energy, our results imply that $w = p / \rho$ is unlikely to be less than -1.Comment: 5 pages, 1 figure, revtex, presentation improved, minor change

"Minus c" Symmetry in Classical and Quantum Theories

It is shown that the transformations of the charge conjugation in classical electrodynamics and in quantum theory can be interpreted as the consequences of the symmetry of Maxwell and Dirac equations with respect to the inversion of the speed of light: c to -c; t to t; (x,y,z) to (x,y,z), where c is the speed of light; t is the time; x, y, z are the spatial variables. The elements of physical interpretation are given.Comment: 12 pages, LaTeX, Poster at the Fifth International Conference on Squeezed States and Uncertainty Relations, May 27-31, 1997, Balatonfured, Hungar

Quantitative Precipitation Nowcasting: A Lagrangian Pixel-Based Approach

Short-term high-resolution precipitation forecasting has important implications for navigation, flood forecasting, and other hydrological and meteorological concerns. This article introduces a pixel-based algorithm for Short-term Quantitative Precipitation Forecasting (SQPF) using radar-based rainfall data. The proposed algorithm called Pixel- Based Nowcasting (PBN) tracks severe storms with a hierarchical mesh-tracking algorithm to capture storm advection in space and time at high resolution from radar imagers. The extracted advection field is then extended to nowcast the rainfall field in the next 3. hr based on a pixel-based Lagrangian dynamic model. The proposed algorithm is compared with two other nowcasting algorithms (WCN: Watershed-Clustering Nowcasting and PER: PERsistency) for ten thunderstorm events over the conterminous United States. Object-based verification metric and traditional statistics have been used to evaluate the performance of the proposed algorithm. It is shown that the proposed algorithm is superior over comparison algorithms and is effective in tracking and predicting severe storm events for the next few hours. © 2012 Elsevier B.V