Diffusion of tungsten in chromium: Experiments and atomistic modeling

The solute diffusion of tungsten at low concentrations in chromium has been investigated both by experiments and computational methods. From finite-source diffusion experiments measured with an Electron Probe Micro Analyzer at temperatures from 1526 to 1676 K, it was found that the diffusivity of tungsten in chromium follows the Arrhenius relationship D=D[subscript 0]exp(-Q[over]RT), where the activation energy was found to be Q = 386 ± 33 kJ/mol. Diffusion of tungsten in chromium was investigated computationally with both the activation–relaxation technique (ART) and molecular dynamics (MD) using a hybrid potential. From ART, the effective diffusion activation energy was determined to be Q = 315 ± 20 kJ/mol based on a multi-frequency model for a monovacancy mechanism. From MD, the square displacement of tungsten was analyzed at temperatures between 1200 and 1700 K, and the diffusion activation energy was determined to be Q = 310 ± 18 kJ/mol. In spite of possible complications arising due to experimental compositions away from the dilute limit, the agreement between experiments and simulations falls within the calculated uncertainties, supporting a monovacancy mechanism for diffusion of tungsten in chromium.United States. Defense Threat Reduction Agency (Grant No. HDTRA1-11-1-0062)United States. Army Research Office (Grant No. W911NF-09-1-0422)Kwanjeong Educational Foundation (Korea)United States. Dept. of Energy (DOE Computational Science Graduate Fellowship, Grant No. DE-FG02-97ER25308)Hertz Foundatio

THYMUS-DERIVED LYMPHOCYTES PRODUCE AN IMMUNOLOGICALLY SPECIFIC MACROPHAGEARMING FACTOR

Spleen cells from mice immunized with an allogeneic tumor when cultured with the specific tumor cells release into the supernatant a specific macrophage-arming factor(s) (SMAF) which binds nonspecifically to macrophages from both mice and rats and renders these cytotoxic to the specific tumor cells. SMAF also binds in an immunologically specific way to the target cells. SMAF-treated target cells grow normally in the absence of macrophages but are killed in the presence of normal macrophages. Thymus-derived cells are necessary for the production of SMAF since (a) after treatment with anti-θ serum immune spleen cells fail to release SMAF; (b) spleen cells from immunized T cell-deprived mice (thymectomized as adults followed by whole body irradiation and restored with bone marrow) fail to produce SMAF on stimulation with the specific target cells. While SMAF has the properties of a cytophilic antibody, it does not belong to one of the established classes of immunoglobulin since high activity is found after column separation in a fraction having a molecular weight between 50,000–60,000 daltons

Mandatory seat belt laws in eight states: a time-series evaluation

We examined state-specific and aggregate effects of U.S. legislation requiring the use of seat belts among front-seat motor vehicle occupants. Effects of compulsory seat belt use on the number of occupants fatally injured in traffic crashes were examined in the first eight states adopting such laws. Monthly data on crash fatalities between January 1976 and June 1986 were analyzed using Box-Tiao intervention analysis time-series methods. Because the new laws apply only to front-seat occupants, front-seat occupant fatalities were compared with: (1) rear-seat fatalities; (2) nonoccupant fatalities (motorcyclists, pedalcyclists, pedestrians); and (3) fatalities among front-seat occupants in neighboring states without compulsory seat belt use. Exposure to risk of crash involvement was controlled by analyzing fatality rates per vehicle mile traveled. Results revealed a statistically significant decline of 8.7% in the rate of front-seat fatalities in the first eight states with seat belt laws. The fatality rate declined 9.9% in states with primary enforcement laws and 6.8% in states with secondary enforcement only. Rates of rear-seat and non-occupant fatalities did not change when the belt laws were implemented.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/27229/1/0000236.pd

Prevention of siderophore- mediated gut-derived sepsis due to P. aeruginosa can be achieved without iron provision by maintaining local phosphate abundance: role of pH

<p>Abstract</p> <p>Background</p> <p>During extreme physiological stress, the intestinal tract can be transformed into a harsh environment characterized by regio- spatial alterations in oxygen, pH, and phosphate concentration. When the human intestine is exposed to extreme medical interventions, the normal flora becomes replaced by pathogenic species whose virulence can be triggered by various physico-chemical cues leading to lethal sepsis. We previously demonstrated that phosphate depletion develops in the mouse intestine following surgical injury and triggers intestinal <it>P. aeruginosa </it>to express a lethal phenotype that can be prevented by oral phosphate ([Pi]) supplementation.</p> <p>Results</p> <p>In this study we examined the role of pH in the protective effect of [Pi] supplementation as it has been shown to be increased in the distal gut following surgical injury. Surgically injured mice drinking 25 mM [Pi] at pH 7.5 and intestinally inoculated with <it>P. aeruginosa </it>had increased mortality compared to mice drinking 25 mM [Pi] at pH 6.0 (p < 0.05). This finding was confirmed in <it>C. elegans</it>. Transcriptional analysis of <it>P. aeruginosa </it>demonstrated enhanced expression of various genes involved in media alkalization at pH 6.0 and a global increase in the expression of all iron-related genes at pH 7.5. Maintaining the pH at 6.0 via phosphate supplementation led to significant attenuation of iron-related genes as demonstrated by microarray and confirmed by QRT-PCR analyses.</p> <p>Conclusion</p> <p>Taken together, these data demonstrate that increase in pH in distal intestine of physiologically stressed host colonized by <it>P. aeruginosa </it>can lead to the expression of siderophore-related virulence in bacteria that can be prevented without providing iron by maintaining local phosphate abundance at pH 6.0. This finding is particularly important as provision of exogenous iron has been shown to have untoward effects when administered to critically ill and septic patients. Given that phosphate, pH, and iron are near universal cues that dictate the virulence status of a broad range of microorganisms relevant to serious gut origin infection and sepsis in critically ill patients, the maintenance of phosphate and pH at appropriate physiologic levels to prevent virulence activation in a site specific manner can be considered as a novel anti-infective therapy in at risk patients.</p

Autonomous Fruit Harvester with Machine Vision

This study presents an autonomous fruit harvester with a machine vision capable of detecting and picking or cutting an orange fruit from a tree. The system of is composed of a six-degrees of freedom (6-DOF) robotic arm mounted on a four-wheeled electric kart. The kart uses ZED stereo camera for depth estimation of a target. It can also be used to detect trees using the green detection algorithm. Image processing is done using Microsoft Visual Studio and OpenCV library. The x &amp; y coordinates and distance of the tree are passed on to Arduino microcontroller as inputs to motor control of the wheels. When the kart is less than 65cm to the tree, the kart stops and the robotic arm system takes over to search and harvest orange fruits. The robotic arm has a webcam and ultrasonic sensor attached at its end-effector. The webcam is used for orange fruit detection while ultrasonic sensor is used to provide feedback on the distance of the orange fruit to end-effector. Multiple fruit harvesting is successfully done. The success rate of harvesting and putting fruit into the basket is 80% and 85% for the gripper end-effector and cutter end-effector respectively

Selective molecular recognition by nanoscale environments in a supported iridium cluster catalyst

The active sites of enzymes are contained within nanoscale environments that exhibit exquisite levels of specificity to particular molecules. The development of such nanoscale environments on synthetic surfaces, which would be capable of discriminating between molecules that would nominally bind in a similar way to the surface, could be of use in nanosensing, selective catalysis and gas separation. However, mimicking such subtle behaviour, even crudely, with a synthetic system remains a significant challenge. Here, we show that the reactive sites on the surface of a tetrairidium cluster can be controlled by using three calixarene–phosphine ligands to create a selective nanoscale environment at the metal surface. Each ligand is 1.4 nm in length and envelopes the cluster core in a manner that discriminates between the reactivities of the basal-plane and apical iridium atoms. CO ligands are initially present on the clusters and can be selectively removed from the basal-plane sites by thermal dissociation and from the apical sites by reactive decarbonylation with the bulky reactant trimethylamine-N-oxide. Both steps lead to the creation of metal sites that can bind CO molecules, but only the reactive decarbonylation step creates vacancies that are also able to bond to ethylene, and catalyse its hydrogenation

Leadership Reconsidered: Engaging Higher Education in Social Change

Colleges and universities can provide effective environments for the development of future leaders. This book addresses the application of transformative leadership to higher education, identifies resources to use in the process, and..