The Effect of Heat Treatment on the Oxidation Mechanism of Blended Powder Cr3C2-NiCr Coatings

The advantageous oxidation and wear properties of Cr₃C₂-NiCr thermal spray coatings have resulted in them being extensively applied to combat erosion at high temperatures. Under these conditions, oxide layers take on an ever more significant role in determining the composite response. The response of blended powder-based carbide coatings for erosion applications has formed the basis for application of cermet-based coatings at elevated temperature. In this study, the oxidation mechanisms of as-sprayed and heat-treated Cr₃C₂-NiCr blended powder-based coatings are characterized. Interdiffusion between the coating phases with long-term exposure increased the Cr content of the matrix phase. This had a significant effect on the oxidation mechanism. The implications of the change in oxidation mechanism and oxide morphology on the coating response to high-temperature erosion are discussed.     

Blood lead (Pb) levels: Further evidence for an environmental mechanism explaining the association between socioeconomic status and psychophysiological dysregulation in children.

Objective: The authors recently reported that blood lead (Pb) was a significant mediator for the positive association between socioeconomic status (SES) and peripheral vascular responses to acute stress in children (B. B. Gump et al., 2007). The present study considers the possibility that Pb may also mediate an association between SES and cortisol responses to acute stress. Design: Early childhood Pb exposure was tested as a mediator for cross-sectional associations between SES and cortisol responses. Main Outcome Measures: The primary outcome was cortisol responses to acute stress in 9.5-year-old children (N = 108). Results: Lower family income was associated with significantly greater cortisol levels following an acute stress task. A mediational analysis confirmed that Pb was a significant mediator for this association. Conclusion: These results reaffirm the importance of considering the chemical environment as well as social and psychological environment when evaluating psychophysiological effects of low SES. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Challenges to Bayesian decision support using morphological matrices for design: empirical evidence

A novel Bayesian design support tool is empirically investigated for its potential to support the early design stages. The design support tool provides dynamic guidance with the use of morphological design matrices during the conceptual or preliminary design stages. This paper tests the appropriateness of adopting a stochastic approach for supporting the early design phase. The rationale for the stochastic approach is based on the uncertain nature of the design during this part of the design process. The support tool is based on Bayesian belief networks (BBNs) and uses a simple but effective information content–based metric to learn or induce the model structure. The dynamically interactive tool is assessed with two empirical trials. First, the laboratory-based trial with novice designers illustrates a novel emergent design search methodology. Second, the industrial-based trial with expert designers illustrates the hurdles that are faced when deploying a design support tool in a highly pressurised industrial environment. The conclusion from these trials is that there is a need for designers to better understand the stochastic methodology for them to both be able to interpret and trust the BBN model of the design domain. Further, there is a need for a lightweight domain-specific front end interface is needed to enable a better fit between the generic support tool and the domain-specific design process and associated tools.     

Divergent thinking ability is related to faster relatedness judgments.

Creativity is commonly defined as the novel and useful combination of concepts previously thought to be unrelated. Fundamentally, this process rests on the ability to judge relatedness between concepts. The authors conducted an experiment to test the connection between divergent thinking ability and the speed of judging relatedness. Our results demonstrated that people with higher divergent thinking ability are faster in judging whether two concepts are related or unrelated. In real life, this can lead to a substantial advantage in the number of potentially useful relationships that could be assessed per unit of time. Equally important, there was no link between IQ and speed of judging relatedness. These results are interpreted in relation to a recently proposed model of creative cognition suggesting that creative people are faster in information processing under conditions of low ambiguity. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Integration of superconducting magnets with cryogen-free dilution refrigerator systems

There has been much recent research interest into “cryogen-free” dilution refrigerators. Cryogen-free systems have some advantages from a safety and convenience point of view as liquid cryogens are unnecessary. However, this also makes integrating the low-temperature system with a high magnetic field environment much more challenging. Here we shall describe recent successes of integrating superconducting magnets and dilution refrigerators into one system requiring a single pulse tube cooler. The resulting environment provides experimental temperatures between 7 mK and 30 K and magnetic fields up to 12 T. We shall describe the effects of AC loss heating in such systems on the pulse tube refrigerator when the field is ramped and also the effects of eddy current heating on the mixing chamber in sweeping fields.     

Effect of the initial dose of foot-and-mouth disease virus on the early viral dynamics within pigs

This paper investigates the early viral dynamics of foot-and-mouth disease (FMD) within infected pigs. Using an existing within-host model, we investigate whether individual variation can be explained by the effect of the initial dose of FMD virus. To do this, we consider the experimental data on the concentration of FMD virus genomes in the blood (viral load). In this experiment, 12 pigs were inoculated with one of three different doses of FMD virus: low; medium; or high. Measurements of the viral load were recorded over a time course of approximately 11 days for every 8 hours. The model is a set of deterministic differential equations with the following variables: viral load; virus in the interstitial space; and the proportion of epithelial cells available for infection, infected and uninfected. The model was fitted to the data for each animal individually and also simultaneously over all animals varying only the initial dose. We show that the general trend in the data can be explained by varying only the initial dose. The higher the initial dose the earlier the development of a detectable viral load.     

Design issues in a mandatory greenhouse gas emissions registry for the United States

On March 10, 2009, the US Environmental Protection Agency (EPA) proposed a new rule, Mandatory Reporting of Greenhouse Gases. When final, the rule would compel most large sources of greenhouse gases (GHGs) to report their emissions to EPA as well as fossil fuel suppliers and vehicle engine manufacturers to report their fuel sales and engine emissions rates, respectively. We suggest a number of improvements to the rule that would enhance compatibility with expected future climate legislation and enable a broader range of policies and analysis: (1) lower the threshold for reporting to a level more consistent with expected future legislation, (2) require reporting of electricity use along with direct emissions, (3) require reporting of emissions per unit output for a small number of selected sectors, (4) include a system of identifying corporate ownership of reporting facilities, and (5) identify a path toward coverage for sectors that were left out of the proposal due to underdeveloped reporting protocols.     

Effect of irrigation method on transmission to and persistence of Escherichia coli O157:H7 on lettuce

In this study, the transmission of Escherichia coli O157:H7 to lettuce plants through spray and surface irrigation was demonstrated. For all treatments combined, the number of plants testing positive following a single exposure to E. coli O157: H7 through spray irrigation (29 of 32 plants) was larger than the number testing positive following surface irrigation (6 of 32 plants). E. coli O157:H7 persisted on 9 of 11 plants for 20 days following spray irrigation with contaminated water. Immersion of harvested lettuce heads for 1 min in a 200 ppm chlorine solution did not eliminate all E. coli O157:H7 cells. The results of this study suggest that regardless of the irrigation method used, crops can become contaminated; therefore, the irrigation of food crops with water of unknown microbial quality should be avoided.     

Cardiorespiratory and thermoregulatory response of working in fire-fighter protective clothing in a temperate environment

The cardiorespiratory and thermal responses of two intensities of treadmill exercise were compared for brief periods (12 min) in fire ensemble (FE) but without self contained breathing apparatus, and sports ensemble (SE), in a temperature environment. A further experiment explored the responses of subjects exercising in FE over a prolonged period (60 min). Eighteen male fire-fighters wearing either FE or SE walked on a level treadmill for 6 min at 5 km x h(-1) increasing to 7 km x h(-1) for 6 min. Following a recovery interval of 1 h, the exercise protocol was repeated in the second ensemble; the order of ensemble was balanced. Heart rate (HR), rectal temperature (Tre), VO2 max and rating of perceived exertion (RPE) were monitored continuously under both ensembles. At 7 km x h(-1), VO2 was significantly higher (p<0.05) in FE (36.1 and 39.9 ml x kg(-1) x min(-1)) than in SE and represented 74% VO2 max. There were no changes Tre. In experiment 2, following a rest interval of at least 36 h, eight subjects in FE walked on the treadmill at 6 km x h (gradient 10%) for 60 min also in temperate conditions, where HR, Tre and RPE were recorded at 10-min intervals. During the 60-min exercise in FE, HR reached 161 beats x min(-1) and Tre increased to 38.3 degrees C. Despite considerable subject discomfort, Tre remained below dangerous levels (38.4 degrees C). When RPE were compared with a physiological strain index (PSI) calculated from Tre and HR data over 60 min, there was no significant difference (p<0.05) with a correlation coefficient (r) of 0.98. The results suggest that RPE and PSI are closely related when exercise is sufficiently prolonged or intense to elevate Tre and HR in fire-fighters wearing FE in temperate conditions. If further investigation confirms this relationship for hot humid conditions in which fire-fighters operate, then with training, it may provide individuals with a valid measure of dangerous levels of perceived heat strain.     

Observation of transient disorder during myosin subfragment-1 binding to actin by stopped-flow fluorescence and millisecond time resolution electron cryomicroscopy: evidence that the start of the crossbridge power stroke in muscle has variable geometry

The mechanism of binding of myosin subfragment-1 (S1) to actin in the absence of nucleotides was studied by a combination of stopped-flow fluorescence and ms time resolution electron microscopy. The fluorescence data were obtained by using pyrene-labeled actin and exhibit a lag phase. This demonstrates the presence of a transient intermediate after the collision complex and before the formation of the stable "rigor" complex. The transient intermediate predominates 2-15 ms after mixing, whereas the rigor complex predominates at time >50 ms. Electron microscopy of acto-S1 frozen 10 ms after mixing revealed disordered binding. Acto-S1 frozen at 50 ms or longer showed the "arrowhead" appearance characteristic of rigor. The most likely explanation of the disorder of the transient intermediate is that the binding is through one or more flexible loops on the surfaces of the proteins. The transition from disordered to ordered binding is likely to be part of the force-generating step in muscle.