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Understanding of semiconductor breakdown under high electric fields is an important aspect of materials’ properties, particularly for the design of power devices. For decades, a power-law has been used to describe the dependence of material-specific critical electrical field ($${\mathcal{E}}_{\text{crit}}$$ E crit ) at which the material breaks down and bandgap (Eg). The relationship is often used to gauge tradeoffs of emerging materials whose properties haven’t yet been determined. Unfortunately, the reported dependencies of $${\mathcal{E}}_{\text{crit}}$$ E crit on Eg cover a surprisingly wide range in the literature. Moreover, $${\mathcal{E}}_{\text{crit}}$$ E crit is a function of material doping. Further, discrepancies arise in $${\mathcal{E}}_{\text{crit}}$$ E crit values owing to differences between punch-through and non-punch-through device structures. We report a new normalization procedure that enables comparison of critical electric field values across materials, doping, and different device types. An extensive examination of numerous references reveals that the dependence $${\mathcal{E}}_{\text{crit}}$$ E crit ∝ Eg1.83 best fits the most reliable and newest data for both direct and indirect semiconductors. Graphical abstract

The regular Cauchy--Born method is a useful and efficient tool for analyzing bulk properties of materials in the absence of defects. However, the method normally fails to capture surface effects, which are essential to determining material properties at small length scales. In this paper, we present a corrector method that improves upon the prediction for material behavior from the Cauchy--Born method over a small boundary layer at the surface of a 1D material by capturing the missed surface effects. We justify the separation of the problem into a bulk response and a localized surface correction by establishing an error estimate, which vanishes in the long wavelength limit., Comment: 28 pages, 5 figures

Phosphodiesterase 5 inhibitors are cardioprotective against myocardial reperfusion ischemic injury in animal models but are contraindicated in patients with coronary disease who take nitrates because of a risk for hypotension. We investigated the safety of vardenafil in patients undergoing coronary artery bypass grafting (CABG) surgery. A single dose of vardenafil was given to 10 patients before CABG surgery. The postoperative course of these 10 patients was compared with the postoperative course of 47 patients who did not receive vardenafil before CABG surgery. There were no perioperative deaths and no episodes of hypotension in the group receiving vardenafil. The clinical and operative characteristics of the 2 study groups were similar. There were no significant differences in postoperative serum troponin levels (9.1 ± 8.3 vs 12.5 ± 9.3 ng/mL; P = 0.29, respectively), duration of postoperative intubation (21.4 ± 10.1 vs 27.4 ± 15.2 hours; P = 0.14, respectively), or length of hospital stay (11.1 ± 13.2 vs 10.0 ± 4.7 days; P = 0.8, respectively) between the group receiving vardenafil and the control group. This pilot study of 10 patients suggests that vardenafil use is safe in patients before CABG surgery. A larger study is needed to explore the myocardial protective effect of the drug.

Effective primary and secondary prevention and advances in cardiac surgery have significantly improved the care and outcomes of patients with myocardial ischemia. While timely reperfusion has proved to be an invaluable tool, ischemia–reperfusion injury represents a mechanism that may limit its effectiveness. Numerous experimental studies have shown effective protection from ischemia–reperfusion injury in animal models, but translation into clinical practice has been less successful. This article summarizes the role of ischemia–reperfusion injury in the pathophysiology of ischemic heart disease and gives an overview of the various modalities that have been developed in order to provide myocardial protection from reperfusion injury in clinical practice.

Metastability is a common obstacle to performing long molecular dynamics simulations. Many numerical methods have been proposed to overcome it. One method is parallel replica dynamics, which relies on the rapid convergence of the underlying stochastic process to a quasi-stationary distribution. Two requirements for applying parallel replica dynamics are knowledge of the time scale on which the process converges to the quasi-stationary distribution and a mechanism for generating samples from this distribution. By combining a Fleming-Viot particle system with convergence diagnostics to simultaneously identify when the process converges while also generating samples, we can address both points. This variation on the algorithm is illustrated with various numerical examples, including those with entropic barriers and the 2D Lennard-Jones cluster of seven atoms., 24 pages, 15 figures, 6 tables

This chapter discusses the conceptualization and development of a methodological tool for conducting classroom research and teacher evaluations with application to the analysis of the Trends in International Mathematics and Science Study (TIMSS) classroom data. The development process involved the creation of a structured video observation system (called the Synchronized Video Observation System, SIVOS) built on top of a database application. The concept applies the integration of an on-screen video frame containing classroom-teaching episodes alongside a structured teaching evaluation rubric. The conceptualization and development of such an application leverages rapid application development techniques. The application is of significance because it allows for the fine-grained and iterative analysis of classroom teaching episodes. It leverages the storing, searching, and retrieval capacity of a database application to code video segments with a structured observation tool. The tool offers an opportunity to enhance the fairness, accuracy, and transparency of teacher evaluations. The approach values low-inference, low-learning curve design. It allows for data to be quickly and easily analyzed. With such tools, teachers, researchers, and administrators have the ability to examine teaching behaviors for continuous improvement.

Spatial multiscale methods have established themselves as useful tools for extending the length scales accessible by conventional statics (i.e., zero temperature molecular dynamics). Recently, extensions of these methods, such as the finite-temperature quasicontinuum (hot-QC) or Coarse-Grained Molecular Dynamics (CGMD) methods, have allowed for multiscale molecular dynamics simulations at finite temperature. Here, we assess the quality of the long-time dynamics these methods generate by considering canonical transition rates. Specifically, we analyze the transition state theory (TST) rates in CGMD and compare them to the corresponding TST rate of the fully atomistic system. The ability of such an approach to reliably reproduce the TST rate is verified through a relative error analysis, which is then used to highlight the major contributions to the error and guide the choice of degrees of freedom. Finally, our analytical results are compared with numerical simulations for the case of a 1-D chain., Comment: 25 pages, 7 figures

Objectives Advances in cardiac surgery have significantly improved the outcomes for patients with myocardial ischemia. However, ischemia/ reperfusion injury represents a mechanism that continues to limit the effectiveness of coronary bypass graft surgery (CABG). Phosphodiesterase 5 inhibitors have been shown to exhibit powerful cardioprotective effects in animal models of ischemia-reperfusion injury. We evaluated the safety of vardenafil in patients undergoing cardiac surgery. Methods 10 male patients undergoing CABG with or without valve surgery were enrolled in the study. Subjects were given a onetime dose of 10 mg oral vardenafil on the morning of surgery. They were monitored for adverse events and left ventricular ejection fraction changes; pertinent clinical parameters were also recorded. Their postoperative parameters and outcomes were also compared with 47 patients who underwent CABG in the same period of time (control group). Results The study drug was tolerated well. There were no episodes of hypotension or deaths in the group receiving vardenafil. The left ventricular ejection fraction did not change significantly after surgery (0.54±0.08 vs 0.53±0.09; P=0.76) in the vardenafil group. The vardenafil group and the control group were similar in terms of clinical characteristics. The type of operation and operative parameters were also similar between the two groups. Peak troponinT levels were not significantly lower in the vardenafil group compared to the control group (9.1 ± 8.3 vs 12.5 ± 9.3 ng/mL; P = 0.26, respectively). The median duration of intubation was not significantly different in the vardenafil group compared to the control group (21.4 ± 10.1 vs 27.4 ± 15.2 h; P = 0.14). The length of hospital stay was also not significantly different between the vardenafil group and the control group (11.1 ± 13.2 vs 10.0 ± 4.7 days; P=0.80, respectively). Conclusions Vardenafil is well tolerated when given to patients immediately prior to CABG surgery and appears safe especially in the setting of the intensive care unit where blood pressure and other vital signs are closely monitored. A larger trial is needed to document the cardioprotective effects of the drug in these patients.

Brain natriuretic peptide (BNP) is secreted by cardiomyocytes in response to excessive stretching. BNP plasma levels are useful for diagnosis in patients with dyspnea [1] predicting heart failure better than clinical assessment alone [2]. Therefore, determination of BNP when heart failure is suspected has become standard of care [3]. However, for patients with established heart failure who undergo an exacerbation, it is unknown whether BNP determination adds any clinical value. Although studies have shown an association between greater BNP levels and adverse events [4,5], the additive value of its determination on top of known predictors for heart failure prognosis has not been tested. We performed a systematic review and meta-analysis of all studies inwhich BNP levels were used for prognosis in patients admitted with decompensated heart failure in order to assess the predictive value of an above median BNP level for all cause mortality, and to determine the discriminative value of elevated BNP levels. Two trained investigators (A.B., A.A.) independently performed a systematic search for studies using PubMed and The Cochrane Collaboration CENTRAL database from January 1990 to December 2009. Proceedings from the American College of Cardiology, American Heart Association, the European Society of Cardiology and the Heart Failure Society of America annual meeting were also searched for the prior 3 years. Potentially relevant studieswere recovered as completemanuscripts and assessed for compliance to inclusion and exclusion criteria. Cross examination of the reference lists was performed to collect additional relevant studies. Inclusion criteria were: a) determination of BNP values within the first 24 h of hospitalization, b) subjects admitted with decompensated heart failure, c) studies that had reported all cause mortality, and d) enrolling N10 subjects. Studies that employed NT pro-BNP were excluded. When uncertain about published data, the principal investigator was contacted by correspondence at least two times. Eventually, in case of unobtainable data, the study was excluded. All cause mortality was chosen as the endpoint of interest. A fixedeffect model, computing relative risks (RRs) with 95% confidence

Heparin-coated surfaces exhibit prolonged compatibility with blood in vitro and in vivo. Deposition of platelets occurs on heparinized surfaces and results in thrombocytopenia, if the surface area is sufficient. Interaction of platelets with heparin-coated materials appears to depend on a protein intermediate. Precoating of heparinized surfaces with fibrinogen solutions, platelet-free plasma, serum, or exhausted or bentonite-adsorbed plasma does not protect against platelet interaction but incubation in albumin reduces platelet adsorption. The behavior of platelets in respect to protein-coated heparinized surfaces parallels the selective adsorption of specific proteins by platelets in suspension.