Representations of molecular force fields. I. Ethane: Ab initio and model, harmonic and anharmonic

The quadratic and selected cubic force constants for ethane have been computed, using single determinant molecular orbital wavefunctions at the 4‐31G level, with a view to testing and extending model consistent force fields (CFF) for ’’molecular mechanics’’ calculations. Results agree semiquantitatively with experiment, but experimental force constants of sufficient reliability to provide a definitive comparison are not yet available. In a comparison with the most rational general CFF available, that of Ermer and Lifson, the most significant discrepancies found to occur are those for certain stretch–bend couplings assumed to be zero in the CFF but shown to be appreciable by quantum calculation. It is observed that these couplings, but not the stretch–stretch couplings, are well accounted for by a steric interaction model. The ab initio cubic constants examined display the same pattern of conformity with a steric model. Bend–bend–bend and bend–bend–stretch but not all stretch–stretch–stretch interactions agree with those of the steric model. The partial success of the steric model shows that it is possible to represent a large number of interaction constants, quadratic and higher order, by a small number of parameters in molecular mechanics. The failure of the steric model to account for predominantly stretching interactions confirms that ’’classical’’ nonbonded interactions as embodied in conventional Urey–Bradley fields are not the only major contributors to off‐diagonal force constants. An alternative model, the anharmonic model of Warshel, as modified by Kirtman et al., was found to account well for pure stretches but not for bends or stretch–bend interactions.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/70643/2/JCPSA6-63-11-4750-1.pd

Development and Validation of a Military Training Mental Toughness Inventory

Three studies were conducted in order to develop and validate a mental toughness instrument for use in military training environments. Study 1 (n = 435) focused on item generation and testing the structural integrity of the Military Training Mental Toughness Inventory (MTMTI). The measure assessed ability to maintain optimal performance under pressure from a range of different stressors experienced by recruits during infantry basic training. Study 2 (n = 104) examined the concurrent validity, predictive validity, and test-retest reliability of the measure. Study 3 (n = 106) confirmed the predictive validity of the measure with a sample of more specialized infantry recruits. Overall, the military training mental toughness inventory demonstrated sound psychometric properties and structural validity. Furthermore, it was found to possess good test-retest reliability, concurrent validity, and predicted performance in two different training contexts with two separate samples

Restoration of normal blood flow in atherosclerotic arteries promotes plaque stabilization

Blood flow is a key regulator of atherosclerosis. Disturbed blood flow promotes atherosclerotic plaque development, whereas normal blood flow protects against plaque development. We hypothesized that normal blood flow is also therapeutic, if it were able to be restored within atherosclerotic arteries. Apolipoprotein E-deficient (ApoE-/-) mice were initially instrumented with a blood flow-modifying cuff to induce plaque development and then five weeks later the cuffwas removed to allowrestoration of normal blood flow. Plaques in decuffed mice exhibited compositional changes that indicated increased stability compared to plaques in mice with the cuff maintained. The therapeutic benefit of decuffingwas comparable to atorvastatin and the combination had an additive effect. In addition, decuffing allowed restoration of lumen area, blood velocity, and wall shear stress to near baseline values, indicating restoration of normal blood flow. Our findings demonstrate that the mechanical effects of normal blood flow on atherosclerotic plaques promote stabilization

Weddell Sea Export Pathways from Surface Drifters

The complex export pathways that connect the surface waters of the Weddell Sea with the Antarctic Circumpolar Current influence water mass modification, nutrient fluxes, and ecosystem dynamics. To study this exchange, 40 surface drifters, equipped with temperature sensors, were released into the northwestern Weddell Sea’s continental shelf and slope frontal system in late January 2012. Comparison of the drifter trajectories with a similar deployment in early February 2007 provides insight into the interannual variability of the surface circulation in this region. Observed differences in the 2007 and 2012 drifter trajectories are related to a variable surface circulation responding to changes in wind stress curl over the Weddell Gyre. Differences between northwestern Weddell Sea properties in 2007 and 2012 include 1) an enhanced cyclonic wind stress forcing over the Weddell Gyre in 2012; 2) an acceleration of the Antarctic Slope Current (ASC) and an offshore shift of the primary drifter export pathway in 2012; and 3) a strengthening of the Coastal Current (CC) over the continental shelf in 2007. The relationship between wind stress forcing and surface circulation is reproduced over a longer time period in virtual drifter deployments advected by a remotely sensed surface velocity product. The mean offshore position and speed of the drifter trajectories are correlated with the wind stress curl over the Weddell Gyre, although with different temporal lags. The drifter observations are consistent with recent modeling studies suggesting that Weddell Sea boundary current variability can significantly impact the rate and source of exported surface waters to the Scotia Sea, a process that determines regional chlorophyll distributions

Health care use among latinx children after 2017 executive actions on immigration

BACKGROUND: US immigration policy changes may affect health care use among Latinx children. We hypothesized that January 2017 restrictive immigration executive actions would lead to decreased health care use among Latinx children. METHODS: We used controlled interrupted time series to estimate the effect of executive actions on outpatient cancellation or no-show rates from October 2016 to March 2017 (“immigration action period”) among Latinx children in 4 health care systems in North Carolina. We included control groups of (1) non-Latinx children and (2) Latinx children from the same period in the previous year (“control period”) to account for natural trends such as seasonality. RESULTS: In the immigration action period, 114 627 children contributed 314 092 appointments. In the control period, 107 657 children contributed 295 993 appointments. Relative to the control period, there was an immediate 5.7% (95% confidence interval [CI]: 0.40%-10.9%) decrease in cancellation rates among all Latinx children, but no sustained change in trend of cancellations and no change in no-show rates after executive immigration actions. Among uninsured Latinx children, there was an immediate 12.7% (95% CI: 2.3%-23.1%) decrease in cancellations; however, cancellations then increased by 2.4% (95% CI: 0.89%-3.9%) per week after immigration actions, an absolute increase of 15.5 cancellations per 100 appointments made. CONCLUSIONS: There was a sustained increase in cancellations among uninsured Latinx children after immigration actions, suggesting decreased health care use among uninsured Latinx children. Continued monitoring of effects of immigration policy on child health is needed, along with measures to ensure that all children receive necessary health care

The Restyled Federal Rules of Evidence

A lightly edited transcript of the Symposium held at the William & Mary School of Law on October 28, 2011

The Restyled Federal Rules of Evidence

A lightly edited transcript of the Symposium held at the William & Mary School of Law on October 28, 2011

Aptamer-based multiplexed proteomic technology for biomarker discovery

Interrogation of the human proteome in a highly multiplexed and efficient manner remains a coveted and challenging goal in biology. We present a new aptamer-based proteomic technology for biomarker discovery capable of simultaneously measuring thousands of proteins from small sample volumes (15 [mu]L of serum or plasma). Our current assay allows us to measure ~800 proteins with very low limits of detection (1 pM average), 7 logs of overall dynamic range, and 5% average coefficient of variation. This technology is enabled by a new generation of aptamers that contain chemically modified nucleotides, which greatly expand the physicochemical diversity of the large randomized nucleic acid libraries from which the aptamers are selected. Proteins in complex matrices such as plasma are measured with a process that transforms a signature of protein concentrations into a corresponding DNA aptamer concentration signature, which is then quantified with a DNA microarray. In essence, our assay takes advantage of the dual nature of aptamers as both folded binding entities with defined shapes and unique sequences recognizable by specific hybridization probes. To demonstrate the utility of our proteomics biomarker discovery technology, we applied it to a clinical study of chronic kidney disease (CKD). We identified two well known CKD biomarkers as well as an additional 58 potential CKD biomarkers. These results demonstrate the potential utility of our technology to discover unique protein signatures characteristic of various disease states. More generally, we describe a versatile and powerful tool that allows large-scale comparison of proteome profiles among discrete populations. This unbiased and highly multiplexed search engine will enable the discovery of novel biomarkers in a manner that is unencumbered by our incomplete knowledge of biology, thereby helping to advance the next generation of evidence-based medicine

Biogeochemical cycling of dissolved zinc along the GEOTRACES South Atlantic transect GA10 at 40°S

The biogeochemical cycle of zinc (Zn) in the South Atlantic, at 40°S, was investigated as part of the UK GEOTRACES program. To date there is little understanding of the supply of Zn, an essential requirement for phytoplankton growth, to this highly productive region. Vertical Zn profiles displayed nutrient-like distributions with distinct gradients associated with the watermasses present. Surface Zn concentrations are among the lowest reported for theworld’s oceans (<50 pM). A strong Zn-Si linear relationshipwas observed (Zn (nM)= 0.065 Si (μM), r2=0.97, n = 460). Our results suggest that the use of a global Zn-Si relationship would lead to an underestimation of dissolved Zn in deeper waters of the South Atlantic. By utilizing Si* and a new tracer Zn* our data indicate that the preferential removal of Zn in the Southern Ocean prevented a direct return path for dissolved Zn to the surface waters of the South Atlantic at 40°S and potentially the thermocline waters of the South Atlantic subtropical gyre. The importance of Zn for phytoplankton growth was evaluated using the Zn-soluble reactive phosphorus (SRP) relationship. We hypothesize that the low Zn concentrations in the South Atlantic may select for phytoplankton cells with a lower Zn requirement. In addition, a much deeper kink at ~ 500m in the Zn:SRP ratio was observed compared to other oceanic regions