Calibration and evaluation of nitric acid and ammonia permeation tubes by UV optical absorption

An ultraviolet (UV) optical absorption system has been developed for absolute calibrations of nitric acid (HNO3) and ammonia (NH3) permeation tube emission rates. Using this technique, dilute mixtures containing NH3 or HNO3, both of which interact strongly with many surfaces, are accurately measured at levels below a part per million by volume. This compact and portable instrument operates continuously and autonomously to rapidly (<1 h) quantify the emission of trace gases from permeation devices that are commonly used to calibrate air-monitoring instruments. The output from several HNO3 and NH3 permeation tubes, with emission rates that ranged between 13 and 150 ng/min, was examined as a function of temperature, pressure, and carrier gas flow. Absorptions of 0.015% can be detected which allows a precision (3sigma) of +/-1 ng/min for the HNO3 and NH3 permeation tubes studied here. The accuracy of the measurements, which relies on published UV absorption cross sections, is estimated to be +/-10%. Measurements of permeation tube emission rates using ion chromatography analysis are made to further assess measurement accuracy. The output from the HNO3 and NH3 permeation tubes examined here was stable over the study period, which ranged between 3 months and 1 year for each permeation tube.     

Pharmacological analysis of the contractile role of M2 and M3 muscarinic receptors in smooth muscle

Muscarinic receptors expressed on smooth muscle cells are primarily of the M(2) and M(3) subtypes. The M(3) subtype triggers contraction through an interaction with G(q) proteins to stimulate phosphoinositide hydrolysis and mobilize Ca(2+). In contrast, activation of M(2) receptors modulates contraction by preventing relaxation or by potentiating M(3) receptor-mediated contractions, which enhances heterologous desensitization. These effects can be explained by the coupling of M(2) receptors to G(i) proteins that mediate an inhibition of adenylyl cyclase and calcium-activated potassium channels. The pharmacological antagonism of a response mediated through an interaction between M(2) and M(3) receptors has been shown to resemble the profile of the directly acting receptor (M(3)), primarily, and not that of the conditional receptor (M(2)). Evidence for a contractile role of the M(2) receptor has been obtained by inactivating its signaling pathway with pertussis toxin or by measuring contractile effects of muscarinic agonists after M(3) receptors have been covalently inactivated. Under these conditions, M(2) receptors have been shown to mediate an inhibition of the relaxant effects of agents, like isoproterenol, on the contractile effects of nonmuscarinic spasmogens. Muscarinic M(2) and M(3) receptor knockout mice are useful tools for exploring interactions between these receptors in smooth muscle.     

On-line reoptimization of filter designs for multivariate optical elements

An automated method for producing multivariate optical element (MOE) interference filters that are robust to errors in the reactive magnetron sputtering process is described. Reactive magnetron sputtering produces films of excellent thickness and uniformity. However, small changes in the thickness of individual layers can have severe adverse effects on the predictive ability of the MOE. Adaptive reoptimization of the filter design during the deposition process can maintain the predictive ability of the final filter by changing the thickness of the undeposited layers to compensate for the errors in deposition. The merit function used, the standard error of calibration, is fundamentally different from the standard spectrum matching. This new merit function allows large changes in the transmission spectrum of the filter to maintain performance.     

Detection and discrimination of texture modulations defined by orientation,spatial frequency,and contrast

We sought to determine whether the detection and the identification of texture modulations are mediated by a common mechanism. On each trial two textures were presented, one of which contained a modulation in orientation (OM), spatial frequency (FM), or contrast (CM). Observers were required to indicate whether the modulated texture was presented in the first or the second interval as well as the nature of the texture modulation. The results showed that for two of the three pairwise matchings (OM-FM and OM-CM) detection and identification performance were nearly identical, suggesting a common underlying mechanism. However, when FM and CM textures were paired, discrimination thresholds were significantly higher than detection thresholds. In the context of the filter-rectify-filter model of texture perception, our results suggest that the mechanisms underlying detection are labeled with respect to their first-order input; i.e., the identities of these mechanisms are available to higher levels of processing. Several possible explanations for the misidentification of FM and CM at detection threshold are considered.     

Wind Loads for 19th Century Bridges: Design Evolution, Historic Failures, and Modern Preservation

This paper presents an historical survey of the basis for design wind pressure used by 19th and early 20th century engineers. Events significant to the development of current wind design standards for pedestrian bridges are explored. These include 19th century treatments of wind load, a review of bridge disasters that spurred new thinking, and historical developments of today’s standards.     

The use of background and ability profiles to predict college student outcomes.

To determine whether profiles of predictor variables provide incremental prediction of college student outcomes, the authors 1st applied an empirical clustering method to profiles based on the scores of 2,771 entering college students on a battery of biographical data and situational judgment measures, along with SAT and American College Test scores and high school grade point average, which resulted in 5 student groups. Performance of the students in these clusters was meaningfully different on a set of external variables, including college grade point average, self-rated performance, class absenteeism, organizational citizenship behavior, intent to quit their university, and satisfaction with college. The 14 variables in the profile were all significantly correlated with 1 or more of the outcome measures; however, nonlinear prediction of these outcomes on the basis of cluster membership did not add incrementally to a linear-regression-based combination of these 14 variables as predictors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A randomized controlled trial of goal choice interventions for alcohol use disorders among men who have sex with men.

This study tested the efficacy of behavioral treatments for alcohol use disorders (AUD) among men who have sex with men (MSM) and who are at risk for HIV transmission. HIV-negative MSM with current AUD (N = 198) were recruited, offered treatment focused on reducing drinking and HIV risk, and followed during treatment and 12 months posttreatment. Participants (n = 89) accepted treatment and were randomized to either 4 sessions of motivational interviewing (MI) or 12 sessions of combined MI and coping skills training (MI + CBT). Other participants (n = 109) declined treatment but were followed, forming a non-help-seeking group (NHS). MI yielded significantly better drinking outcomes during the 12-week treatment period than MI + CBT, but posttreatment outcomes were equivalent. NHS participants significantly reduced their drinking as well. Service delivery and treatment research implications are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Biology by design: reduction and synthesis of cellular components and behaviour.

Biological research is experiencing an increasing focus on the application of knowledge rather than on its generation. Thanks to the increased understanding of cellular systems and technological advances, biologists are more frequently asking not only ‘how can I understand the structure and behaviour of this biological system?’, but also ‘how can I apply that knowledge to generate novel functions in different biological systems or in other contexts?’ Active pursuit of the latter has nurtured the emergence of synthetic biology. Here, we discuss the motivation behind, and foundational technologies enabling, the development of this nascent field. We examine some early successes and applications while highlighting the challenges involved. Finally, we consider future directions and mention non-scientific considerations that can influence the field''s growth.     

Investigation of the Double Superconducting Transition and Low-Temperature Specific Heat of Pr(Os1-xRux)4Sb12

The double superconducting transition in PrOs₄Sb₁₂, first observed in specific heat C(T) measurements on single crystal samples, was studied by means of specific heat measurements on PrOs₄Sb₁₂ crystals that had been subjected to applied magnetic fields, substitution of up to 4 Ru for Os, and annealing. The double superconducting transitions of a batch of single crystals were measured before and after annealing for 5 days at 500°C, to remove strains and promote homogeniety, with no observed change. Measurements of C(T) near T_c for PrOs₄Sb₁₂ in several magnetic fields are also presented, detailing the evolution of the double transition up to 1 T. Samples of Pr(Os_1-x Ru_x)Sb₁₂ with 0.01 ≤ x ≤ 0.04 also appear to display a double superconducting transition in specific heat. In addition, samples with the smallest Ru concentration measured (x = 0.01) may even display a more isotropic type of superconductivity than pure PrOs₄Sb₁₂ (x = 0).     

THE UNSOLVED MESSAGES OF PEARL HARBOR

In 1941, the United States Navy intercepted enough Japanese naval messages to predict the attack on Pearl Harbor if the code which protected them had been solved. The messages would have disclosed that, while the Japanese government cynically conducted diplomatic negotiations with the United States, the Japanese Combined Fleet under Admiral Isoroku Yamamoto, beginning as early as September 1941, systematically prepared ships, crews, weapons, tactics, and a complicated fuel supply system for the most ambitious operation ever undertaken by the Japanese navy. Details of Japan's intentions were hidden from Navy cryptanalysts because of limited manpower resources and because all Japanese navy codes were assigned a lower priority than Japanese diplomatic codes and German submarine threat.