Analysis of Current–Voltage Measurements on Long-Wavelength HgCdTe Photodiodes Fabricated on Si Composite Substrates

We have performed a detailed study of dark current versus voltage to understand existing limitations in dark current and address the nonuniformity of dark current in devices fabricated on HgCdTe grown on silicon substrates. One interesting observation is that trap-assisted tunneling, g-r currents, are not found close to zero bias in certain devices. Devices from the low end of the R ₀ A distribution show heavy shunting paths close to zero bias. We believe that these shunting paths may be the limiting cause of tail distributions in fabricated focal plane array tail distributions. Possible causes for these shunting paths are surface charges associated with dislocation cores and impurity gettering at dislocation cores. The measured non-anti-reflection (AR)-coated quantum efficiency (QE) was 0.576 at 78 K and displays the classical response versus wavelength. The measured QE on isolated single devices is consistent with the 256 × 256 focal-plane array mean QE. Obtained average dark currents are on the order of mid 10⁻⁵ A cm^–2, which is one order of magnitude higher than dark currents obtained from arrays on lattice-matched substrates. On average, arrays on lattice-mismatched substrates show performance characteristics inferior to those of arrays fabricated on lattice-matched substrates. This inferior performance is due to array pixel operability, as can be seen from the tail of the distribution and the average dark currents, which are one order of magnitude higher than those obtained on lattice-matched substrates.     

Comments on a meta-analysis of the relation between dietary calcium intake and blood pressure

The role of dietary calcium in the etiology of hypertension is controversial. In 1995, Cappuccio et al. (American Journal of Epidemiology,1995;142:935-45) examined this issue in a meta-analysis of observational studies published between 1983 and 1993. The author of the present paper reviewed the original studies underlying this meta-analysis and discovered that data from one study had been inappropriately extracted and converted, leading to an understatement of the calcium-blood pressure relation by a factor of about 30. This review also raised questions about the extraction and conversion of data from several other studies and about the statistical methods used. The author repeated the meta-analyses and discovered an unadjusted regression slope between dietary calcium and systolic blood pressure of -0.34 mmHg/100 mg per day (95% confidence interval (CI) -0.46 to -0.22) for men, -0.15 mmHg/100 mg per day (95% CI -0.19 to -0.11) for women, and -0.39 mmHg/100 mg per day (95% CI -0.47 to -0.31) for men and women. For diastolic blood pressure, the pooled regression slope for men was -0.22 mmHg/100 mg per day (95% CI -0.32 to -0.13), while for women it was -0.051 mmHg/100 mg per day (95% CI -0.090 to -0.012); for men and women it was -0.35 mmHg/100 mg per day (95% CI -0.67 to -0.02). These slopes are still modest but are larger than those reported in the original analysis. However, since all of these analyses were based on zero-order correlations or regressions, extreme caution must be exercised in interpreting the results.     

High-entropy boride–carbide ceramics by sequential boro/carbothermal synthesis

A dual-phase high-entropy boride (HEB)/carbide (HEC) ceramic with a fine grain size was synthesized by a sequential boro/carbothermal process. In the first step, an Hf–Nb–Ta–Ti–Zr-containing carbide was synthesized by a carbothermal reduction of oxides followed by the reaction of the carbide with B₄C and ZrH₂ to convert part of the carbide to boride. The resulting composition was ∼29 vol% HEB with an average grain size of ∼1.1 μm. Solid solution formation occurred at the densification temperature of 1900°C resulting in a relative density higher than 99%. The Vickers hardness was 26.5 ± 1.4 GPa. This is the first report of synthesizing dual-phase boride–carbide high-entropy ceramics from carbothermally synthesized, HEC powders.     

Pathogenesis of oleic acid-induced lung injury in the rat: Distribution of oleic acid during injury and early endothelial cell changes

Oleic acid-induced lung injury, a well-described laboratory model for acute pulmonary injury in the rat and other species, causes morphologic and cellular changes similar to human adult respiratory distress syndrome (ARDS). Experiments were performed to test the hypothesis that the initial event of oleic acid lung injury is damage of the pulmonary vascular endothelium by oleic acid, with subsequent pulmonary damage and inflammation. Oleic acid levels were followed in the lung and other tissues by measuring accumulation of¹⁴C-oleic acid; the direct effects of oleic acid and other fatty acids on rat endothelial cells, alveolar type II cells, and hepatocytes in culture were determined. Lung tissue from treated rats was also examined by light and electron microscopy for evidence of endothelial cell damage. At 30 min after injury, oleic acid reached high concentrations in lung tissue as demonstrated by presence of radiolabel (3.24×10⁻⁶ moles per gram of tissue), with counts in the lung nearly an order of magnitude greater than in any other organ measured. Oleic acid was present in the lung mostly as free fatty acid (85%), and was also present in the alveolar fluid supernatans, rather than being cell-associated (1.7×10⁻⁷ moles vs. 1.1×10⁻⁸ moles at 30 min). Oleic acid was toxic to endothelial cells after one minute of exposure at concentrations of 5×10⁻⁴M and above. Electron microscopy showed endothelial cell changes as early as 10 min after induction of injuryin vivo, including the presence of endothelial cell blebbing. The results of these studies suggest that the initial event in oleic acid lung injury is damage to the pulmonary vascular endothelial cell.     

Peat filter performance under changing environmental conditions

Peat is a candidate filter material for in situ treatment of urban runoff, contaminated groundwater and landfill leachates. Until now research has focused on peat sorption in batch experiments and there is a lack of knowledge on peat performance in filter beds. In this project column tests were carried out to evaluate the capacity of peat to remove As, Cd, Cu, Cr, Ni, Pb and Zn in multi-metal solution under a range of environmental conditions that may be encountered in real-life applications (draining, water stagnation, freezing, change in pH and metal concentrations, input of NaCl and elevated DOC). The removal capacity was 91–98% for Cd, Cu, Zn, Ni and Pb and the efficiency was unaffected by the changes of physical factors, but temporarily inhibited for solutions containing NaCl. Leaching of DOC from peat was detected in the initial samples and temporarily decreased metal removal. The peat filters showed high removal rates for Cd, Cu, Zn, Ni and Pb under all experimental conditions and are recommended for treatment of waters containing these elements. In contrast, peat was not found to be efficient for treatment of As and Cr in the multi-metal contaminated water at the pH range (6.7–8.0) studied.     

Effective components of TORDIA cognitive–behavioral therapy for adolescent depression: Preliminary findings.

In this report, we conducted a secondary analysis of the Treatment of SSRI-Resistant Depression in Adolescents (TORDIA) study to explore the impact of specific cognitive–behavioral therapy (CBT) treatment components on outcome. In TORDIA, 334 youths (ages 12 to 18 years) with major depressive disorder who had failed to respond to an adequate course of selective serotonin reuptake inhibitor (SSRI) medication were randomized to a medication switch (either to an alternative SSRI or venlafaxine) with or without 12 weeks of adjunctive CBT. Participants who had more than 9 CBT sessions were 2.5 times more likely to have adequate treatment response than those who had 9 or fewer sessions. CBT participants who received problem-solving and social skills treatment components, controlling for number of sessions and other confounding variables, were 2.3 and 2.6 times, respectively, more likely to have a positive response. These preliminary findings underscore the importance of receiving an adequate number of sessions to attain an adequate clinical response. Finally, social skills and problem solving may be active elements in CBT for adolescent depression and should be considered in treatment by those working with seriously depressed youths. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Review of Creative leadership: Skills that drive change.

Reviews the book, Creative leadership: Skills that drive change by Gerard J. Puccio, Mary C. Murdock, and Marie Mance (2007). The introduction and opening chapter provide the overarching theme of the book, which is to connect the constructs of creativity and leadership and to make a case why the two go hand-in-hand. Both constructs involve dealing with change. The main focus of the book is the creative problem solving (CPS) approach to generating optimal problem solutions. Much of the book is spent illustrating the benefits of applying divergent and convergent thinking skills to each of the six process steps in the CPS model. The book is an easy, enjoyable read with plenty of empirical support for many of the propositions and tenets put forth. Puccio, Murdock, and Mance do a good job of pointing out that creative leadership is not just for the chosen few, but rather can be practiced by anyone. Plenty of practical advice is offered with numerous real-world examples. The book is a good choice even for individuals without any formal education in creativity or leadership. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Implicit Riquier Bases for PDAE and their semi-discretizations

Complicated nonlinear systems of pde with constraints (called pdae) arise frequently in applications. Missing constraints arising by prolongation (differentiation) of the pdae need to be determined to consistently initialize and stabilize their numerical solution. In this article we review a fast prolongation method, a development of (explicit) symbolic Riquier Bases, suitable for such numerical applications. Our symbolic-numeric method to determine Riquier Bases in implicit form, without the unstable eliminations of the exact approaches, applies to square systems which are dominated by pure derivatives in one of the independent variables.     

High resolution time integration for SN radiation transport

First-order, second-order, and high resolution time discretization schemes are implemented and studied for the discrete ordinates (S_N) equations. The high resolution method employs a rate of convergence better than first-order, but also suppresses artificial oscillations introduced by second-order schemes in hyperbolic partial differential equations. The high resolution method achieves these properties by nonlinearly adapting the time stencil to use a first-order method in regions where oscillations could be created. We employ a quasi-linear solution scheme to solve the nonlinear equations that arise from the high resolution method. All three methods were compared for accuracy and convergence rates. For non-absorbing problems, both second-order and high resolution converged to the same solution as the first-order with better convergence rates. High resolution is more accurate than first-order and matches or exceeds the second-order method.     

Speed and safety effect of photo radar enforcement on a highway corridor in British Columbia

This study evaluates the effect of the photo radar program on traffic speed and collisions at photo radar (PRP) influence locations (PRP location) and interleaving non-PRP locations on the Vancouver Island portion of Highway 17 (Pat Bay Highway) in British Columbia (BC). Simple before-after comparison was used to summarize the speed effect while observational before- after method was employed to estimate the safety effect. To control for regression to the mean and time effect, Empirical Bayes (EB) method with comparison groups was employed in collision analysis. The study found a 2.8-km/h reduction in mean speed and a 0.5-km/h reduction in speed standard deviation at a monitoring site 2 km south of the treatment area. Corresponding to speed reduction. the study revealed a 14%+/-11% reduction in expected collisions at the PRP locations, a 19%+/-10% reduction at the non-PRP locations, and a 16%+/-7% reduction along the study corridor as a whole. No evidence was found for a localized effect in a 2-km range of the photo radar direct influence area, over and above those at the interleaving non-PRP locations. The results support the hypothesis of a distance spillover effect--that the program not only improved safety at the PRP locations, but along the entire enforcement corridor as well. It suggests that the unpredictable nature of the deployments lead drivers to modify their behavior along the length of the corridor because they could not discern 'safe' from 'unsafe' segments.