A "fast growth" method of computing free energy differences

Let Delta F be the free energy difference between two equilibrium states of a system. An established method of numerically computing Delta F involves a single, long ``switching simulation'', during which the system is driven reversibly from one state to the other (slow growth, or adiabatic switching). Here we study a method of obtaining the same result from numerous independent, irreversible simulations of much shorter duration (fast growth). We illustrate the fast growth method, computing the excess chemical potential of a Lennard-Jones fluid as a test case, and we examine the performance of fast growth as a practical computational tool.Comment: 17 pages + 4 figures, accepted for publication in J.Chem.Phy

Directional solidification of flake and nodular cast iron during KC-135 low-g maneuvers

Alloys solidified in a low-gravity environment can, due to the elimination of sedimentation and convection, form unique and often desirable microstructures. One method of studying the effects of low-gravity (low-g) on alloy solidification was the use of the NASA KC-135 aircraft flying repetitive low-g maneuvers. Each maneuver gives from 20 to 30 seconds of low-g which is between about 0.1 and 0.001 gravity. A directional solidification furnace was used to study the behavior of off eutectic composition case irons in a low-g environment. The solidification interface of hypereutectic flake and spheroidal graphite case irons was slowly advanced through a rod sample, 5 mm in diameter. Controlled solidification was continued through a number of aircraft parabolas. The known solidification rate of the sample was then correlated with accelerometer data to determine the gravity level during solidification for any location of the sample. The thermal gradient and solidification rate were controlled independently. Samples run on the KC-135 aircraft exhibited bands of coarser graphite or of larger nodules usually corresponding to the regions solidified under low-g. Samples containing high phosphorous (used in order to determine the eutectic cell) exhibited larger eutectic cells in the low-g zone, followed by a band of coarser graphite

Preliminary science report on the directional solidification of hypereutectic cast iron during KC-135 low-G maneuvers

An ADSS-P directional solidification furnace was reconfigured for operation on the KC-135 low-g aircraft. The system offers many advantages over quench ingot methods for study of the effects of sedimentation and convection on alloy formation. The directional sodification furnace system was first flown during the September 1982 series of flights. The microstructure of the hypereutectic cast iron sample solidified on one of these flights suggests a low-g effect on graphite morphology. Further experiments are needed to ascertain that this effect is due to low-gravity and to deduce which of the possible mechanisms is responsible for it

Energy spectrum of turbulent fluctuations in boundary driven reduced magnetohydrodynamics

The nonlinear dynamics of a bundle of magnetic flux ropes driven by stationary fluid motions at their endpoints is studied, by performing numerical simulations of the magnetohydrodynamic (MHD) equations. The development of MHD turbulence is shown, where the system reaches a state that is characterized by the ratio between the Alfven time (the time for incompressible MHD waves to travel along the field lines) and the convective time scale of the driving motions. This ratio of time scales determines the energy spectra and the relaxation toward different regimes ranging from weak to strong turbulence. A connection is made with phenomenological theories for the energy spectra in MHD turbulence.Comment: Published in Physics of Plasma

EUREGIO MRSA-net Twente/Munsterland - a Dutch-German cross-border network for the prevention and control of infections caused by methicillin-resistant Staphylococcus aureus

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Formation of Hydrogen, Oxygen, and Hydrogen Peroxide in Electron Irradiated Crystalline Water Ice

Water ice is abundant both astrophysically, for example in molecular clouds, and in planetary systems. The Kuiper belt objects, many satellites of the outer solar system, the nuclei of comets and some planetary rings are all known to be water-rich. Processing of water ice by energetic particles and ultraviolet photons plays an important role in astrochemistry. To explore the detailed nature of this processing, we have conducted a systematic laboratory study of the irradiation of crystalline water ice in an ultrahigh vacuum setup by energetic electrons holding a linear energy transfer of 4.3 +/- 0.1 keV mm-1. The irradiated samples were monitored during the experiment both on line and in situ via mass spectrometry (gas phase) and Fourier transform infrared spectroscopy (solid state). We observed the production of hydrogen and oxygen, both molecular and atomic, and of hydrogen peroxide. The likely reaction mechanisms responsible for these species are discussed. Additional formation routes were derived from the sublimation profiles of molecular hydrogen (90-140 K), molecular oxygen (147 -151 K) and hydrogen peroxide (170 K). We also present evidence on the involvement of hydroxyl radicals and possibly oxygen atoms as building blocks to yield hydrogen peroxide at low temperatures (12 K) and via a diffusion-controlled mechanism in the warming up phase of the irradiated sample.Comment: ApJ, March 2006, v639 issue, 43 pages, 7 figure

The Relationship between Real-Time EEG Engagement, Distraction and Workload Estimates and Simulator-Based Driving Performance

Identifying potentially impaired drivers is often dependent upon using cognitive testing from a controlled environment (clinic, laboratory) to predict behavior in a dynamic and unpredictable real world driving environment. The goal of this study was to determine the feasibility, and validity, of using a wireless EEG system to ultimately differentiate between impaired and unimpaired drivers. We utilized the B-Alert X10 portable wireless EEG/ECG system and applied previously validated EEG algorithms estimating engagement, workload, and distraction within a sample of normal control (n = 10) and HIV seropositive individuals (n = 14). Participants underwent a 30-minute fully interactive driving simulation. Overall, the HIV+ group evidenced significantly higher distraction during the simulation. When grouped according to poor and good performers on the simulation (regardless of HIV serostatus), those performing worse on the simulation had higher distraction, with a trend for lower workload, levels. We then examined EEG profiles immediately preceding a crash. Prior to a crash, participants evidenced a significant increase in distraction ~ 10-14 seconds leading up to the crash; the greatest increase was seen in the HIV+ group. These preliminary data support the potential utility of using EEG data in patient populations to identify individuals who might be at risk for impaired drivin

Interacting effects of temperature, habitat and phenotype on predator avoidance behaviour in <i>Diadema antillarum</i>: implications for restorative conservation

Caribbean long-spined sea urchin Diadema antillarum populations crashed following a mass mortality event in 1983-1984 with cascading effects on reef health. Population restoration efforts may be hampered by unknown effects of short- and long-term elevated sea surface temperature (SST). We investigated how a key behavioural trait, predator avoidance behaviour (PAB; percentage of long defensive spines that moved in response to shadow stimuli), was affected by elevated SST in 180 individuals from 2 contrasting Honduran reefs: Utila (flattened reef structure, dearth of predation refugia) and Banco Capiro (complex reef structure, abundant refugia). Initiation of PAB is mediated by melanin, which breaks down at elevated water temperatures; thus, as SST rises, D. antillarum may become vulnerable to predation. We compared local current SST (CSST; 29.7°C) with 2 IPCC predicted long-term climate change scenarios under laboratory conditions. PAB decreased by 13.98-15.37% at CSST +1.4°C and 31.67-42.44% at CSST +3.1°C. Trial temperatures were similar to maxima recorded in the Caribbean during the 2016 El Niño, so our results also represent likely responses to worst-case short-term acute temperature anomalies. Juveniles maintained higher PAB than adults, indicating increased reliance on anti-predation behaviours. White-spined phenotypes from Utila’s flattened reef maintained higher PAB than black-spined counterparts, likely due to increased conspicuousness to visual predators. Habitat complexity may mitigate temperature-driven losses in natural behavioural defences. D. antillarum may be resilient to near-term (D. antillarum populations must be coupled to augmented reef complexity to improve future resilience

Ethics and Childhood Vaccination Policy in the United States

Childhood immunization involves a balance between parents' autonomy in deciding whether to immunize their children and the benefits to public health from mandating vaccines. Ethical concerns about pediatric vaccination span several public health domains, including those of policymakers, clinicians, and other professionals. In light of ongoing developments and debates, we discuss several key ethical issues concerning childhood immunization in the United States and describe how they affect policy development and clinical practice. We focus on ethical considerations pertaining to herd immunity as a community good, vaccine communication, dismissal of vaccine-refusing families from practice, and vaccine mandates. Clinicians and policymakers need to consider the nature and timing of vaccine-related discussions and invoke deliberative approaches to policy-making

Impact of Brown Midrib Trait on the Decomposition Rate of Sorghum-Sudangrass Residue in Pastures

Sorghum-sudangrass (Sorghum bicolor var. bicolor x bicolor var. sudanense) can provide high quality summer grazing. Some varieties possess the brown midrib (BMR) trait which results in reduced lignin resulting in higher digestibility and animal performance. If microbes in the rumen can digest BMR sorghum-sudangrass more completely, then soil macro/micro flora and fauna may do so as well. This could result in nutrients being returned to the soil faster from plants containing the BMR trait. The objective of this study was to determine the decomposition rate of BMR and non-BMR sorghumsudangrass. The experimental design was a random complete with four replications. Sorghum-sudangrass with and without the BMR trait was placed in litter decomposition bags as whole plants or divided into leaves and stems. A composite sample was taken when bags were loaded to determine initial dry matter. Loaded bags were then placed on the soil surface in a pasture and collected at 1, 2, 3, 4, 6, 8, 10, 12, 14, or 16 weeks after placement. Upon collection plant material was dried for 3-days at 55°C in a forced air oven. Dry weights at each collection date were subtracted from the initial dry weight to determine total DM loss. The BMR trait did not impact dry matter loss in the leaves. Stems possessing the BMR trait lost dry matter at a greater rate resulting in dry matter losses at 14 weeks of 78 and 68% and 59 and 47% for the BMR and non-BMR varieties in trials 1 and 2, respectively. Whole plants showed limited differences in dry matter loss at 14 weeks after placement