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

The Basu measure as an indicator of conditional conservatism: Evidence from U.K. earnings components

Following the work of Basu in 1997, the excess of the sensitivity of accounting earnings to negative share return over its sensitivity to positive share return (the Basu coefficient) has been interpreted as an indicator of conditional accounting conservatism. Although this interpretation is supported by substantial evidence that the Basu coefficient is associated with likely demands for conservatism, concerns have arisen that it may reflect factors not directly related to conservatism, and that this may adversely affect its validity as an indicator of that phenomenon. We argue that evidence on the validity of the Basu coefficient as an indicator of conditional conservatism can be obtained by disaggregating earnings into components, classifying those components by whether or not they are likely to be affected by conditional conservatism, and examining whether the Basu coefficient arises primarily from components likely to be affected by conditional conservatism. We implement this procedure for UK firms reporting under FRS 3: Reporting Financial Performance from 1992 to 2004. Although a substantial proportion of the Basu coefficient emanates from cash flow from operating and investing activities (CFOI), which cannot directly reflect accounting conservatism, its incidence across other components of earnings is predominantly within those components likely to be affected by conditional conservatism. Also, although the bias documented by Patatoukas and Thomas in 2009 is present in all of our aggregate earnings measures, it is heavily concentrated in the CFOI component of earnings and largely absent from components classified as likely to be affected by conditional conservatism. With the important caveat that researchers should test the robustness of their results to the exclusion of the element of the Basu coefficient due to cash flows, our findings are consistent with the conditional conservatism interpretation of the coefficient

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