Three-dimensional feedback processes in current-driven metal.

Using three-dimensional (3D) magnetohydrodynamic simulations, we study how a pit on a metal surface evolves when driven by intense electrical current density j. Redistribution of j around the pit initiates a feedback loop: j both reacts to and alters the electrical conductivity σ, through Joule heating and hydrodynamic expansion, so that j and σ are constantly in flux. Thus, the pit transforms into larger striation and filament structures predicted by the electrothermal instability theory. Both structures are important in applications of current-driven metal: The striation constitutes a density perturbation that can seed the magneto-Rayleigh-Taylor instability, while the filament provides a more rapid path to plasma formation, through 3D j redistribution. Simulations predict distinctive self-emission patterns, thus allowing for experimental observation and comparison.

Seeding the Electrothermal Instability through a Three-Dimensional, Nonlinear Perturbation.

Electrothermal instability plays an important role in applications of current-driven metal, creating striations (which seed the magneto-Rayleigh-Taylor instability) and filaments (which provide a more rapid path to plasma formation). However, the initial formation of both structures is not well understood. Simulations show for the first time how a commonly occurring isolated defect transforms into the larger striation and filament, through a feedback loop connecting current and electrical conductivity. Simulations have been experimentally validated using defect-driven self-emission patterns.

Experimental observation of the stratified electrothermal instability on aluminum with thickness greater than a skin depth.

A direct observation of the stratified electrothermal instability on the surface of thick metal is reported. Aluminum rods coated with 70µm Parylene-N were driven to 1 MA in 100ns, with the metal thicker than the skin depth. The dielectric coating suppressed plasma formation, enabling persistent observation of discrete azimuthally correlated stratified thermal perturbations perpendicular to the current whose wave numbers, k, grew exponentially with rate γ(k)=0.06ns^{-1}-(0.4ns^{-1}µm^{2}rad^{-2})k^{2} in ∼1g/cm^{3}, ∼7000K aluminum.

Stress, Burnout and Coping among Emergency Physicians at a Major Hospital in Kingston, Jamaica.

OBJECTIVES: The study examined the prevalence of stress, burnout, and coping, and the relationship between these variables among emergency physicians at a teaching hospital in Kingston, Jamaica. METHODS: Thirty out of 41 physicians in the Emergency Department completed the Maslach Burnout Inventory, Perceived Stress Scale, Ways of Coping Questionnaire, and a background questionnaire. Descriptive statistical analyses were conducted. RESULTS: Fifty per cent of study participants scored highly on emotional exhaustion; the scores of 53.3% also indicated that they were highly stressed. Stress correlated significantly with the emotional exhaustion and depersonalization components of burnout. Depersonalization was significantly correlated with two coping strategies: escape-avoidance and accepting responsibility; emotional exhaustion was also significantly correlated with escape-avoidance. CONCLUSION: Emergency physicians at the hospital scored high on stress and components of burnout. Interventions aimed at reducing the occupational contributors to stress and improving levels of coping will reduce the risk of burnout and enhance psychological well-being among emergency physicians.

Integrated assessment of pedestrian head impact protection in testing secondary safety and autonomous emergency braking.

Pedestrian impact testing is used to provide information to the public about the relative level of protection provided by different vehicles to a struck pedestrian. Autonomous Emergency Braking (AEB) is a relatively new technology that aims to reduce the impact speed of such crashes. It is expected that vehicles with AEB will pose less harm to pedestrians, and that the benefit will come about through reductions in the number of collisions and a change in the severity of impacts that will still occur. In this paper, an integration of the assessment of AEB performance and impact performance is proposed based on average injury risk. Average injury risk is calculated using the result of an impact test and a previously published distribution of real world crash speeds. A second published speed distribution is used that accounts for the effects of AEB, and reduced average risks are implied. This principle allows the effects of AEB systems and secondary safety performance to be integrated into a single measure of safety. The results are used to examine the effect of AEB on Euro NCAP and ANCAP assessments using previously published results on the likely effect of AEB. The results show that, given certain assumptions about AEB performance, the addition of AEB is approximately the equivalent of increasing Euro NCAP test performance by one band, which corresponds to an increase in the score of 25% of the maximum.

Dependence of the head injury criterion and maximum acceleration on headform mass and initial velocity in tests simulating pedestrian impacts with vehicles.

Impact testing of pedestrian headforms is usually conducted at one velocity and with one mass of headform, but real impacts occur at a range of velocities and masses. A method is proposed to predict the Head Injury Criterion (HIC) and similar quantities at other velocities from their values observed under test conditions. A specific assumption is made about acceleration during the impact as related to displacement, its differential (instantaneous velocity), mass of headform, and initial velocity: namely, that it is the product of a power function of displacement (representing a possibly nonlinear spring) and a term that includes a type of damping. This equation is not solved, but some properties of the solution are obtained: HIC, maximum acceleration, and maximum displacement are found to be power functions of mass of headform and initial velocity. Expressions for the exponents are obtained in terms of the nonlinearity parameter of the spring. Simple formulae are obtained for the dependence of HIC, maximum acceleration, and maximum displacement on velocity and mass. These are relevant to many types of impact.

Pedestrian headform testing: inferring performance at impact speeds and for headform masses not tested, and estimating average performance in a range of real-world conditions.

OBJECTIVE: Tests are routinely conducted where instrumented headforms are projected at the fronts of cars to assess pedestrian safety. Better information would be obtained by accounting for performance over the range of expected impact conditions in the field. Moreover, methods will be required to integrate the assessment of secondary safety performance with primary safety systems that reduce the speeds of impacts. Thus, we discuss how to estimate performance over a range of impact conditions from performance in one test and how this information can be combined with information on the probability of different impact speeds to provide a balanced assessment of pedestrian safety. METHOD: Theoretical consideration is given to 2 distinct aspects to impact safety performance: the test impact severity (measured by the head injury criterion, HIC) at a speed at which a structure does not bottom out and the speed at which bottoming out occurs. Further considerations are given to an injury risk function, the distribution of impact speeds likely in the field, and the effect of primary safety systems on impact speeds. These are used to calculate curves that estimate injuriousness for combinations of test HIC, bottoming out speed, and alternative distributions of impact speeds. RESULTS: The injuriousness of a structure that may be struck by the head of a pedestrian depends not only on the result of the impact test but also the bottoming out speed and the distribution of impact speeds. Example calculations indicate that the relationship between the test HIC and injuriousness extends over a larger range than is presently used by the European New Car Assessment Programme (Euro NCAP), that bottoming out at speeds only slightly higher than the test speed can significantly increase the injuriousness of an impact location and that effective primary safety systems that reduce impact speeds significantly modify the relationship between the test HIC and injuriousness. CONCLUSIONS: Present testing regimes do not take fully into account the relationship between impact severity and variations in impact conditions. Instead, they assess injury risk at a single impact speed. Hence, they may fail to differentiate risks due to the effects of bottoming out under different impact conditions. Because the level of injuriousness changes across a wide range of HIC values, even slight improvements to very stiff structures need to be encouraged through testing. Indications are that the potential of autonomous braking systems is substantial and needs to be weighted highly in vehicle safety assessments.

From crash test speed to performance in real world conditions: a conceptual model and its application to underhood clearance in pedestrian head tests.

Current safety testing protocols typically evaluate performance at a single test speed, which may have undesirable side effects if vehicles are optimised to perform at that speed without consideration to performance at other speeds. One way of overcoming this problem is by using an evaluation that incorporates the distribution of speeds that would be encountered in real crashes, the relationship between test speed and test performance, and the relationship between test performance and injury risk. Such an evaluation is presented in this paper and is applied to pedestrian headform testing. The applicable distribution of pedestrian impact speeds was compiled from in-depth crash data. Values of the Head Injury Criterion across the speed distribution were imputed from a single test result, taking into account the potential for 'bottoming out' on harder structures beneath the hood. Two different risk functions were used: skull fracture risk and fatal head injury risk. Eight example test locations were evaluated; each had an underhood clearance such that it would perform worse at higher speeds than suggested by its original test result. When the effect of bottoming out was included in the evaluation, the calculated average injury risk was generally higher than it was if bottoming out was ignored. The average risk of fatal head injury was more affected by the inclusion of bottoming out than the average skull fracture risk. The methodology presented in this paper may be extended to other forms of impact testing, although the input functions may be more difficult to derive for more complex tests.

Influence of a collapsed coastal landfill on metal levels in sediments and biota--a portent for the future?

In May 2008 a coastal landslide deposited landfill debris onto the shore near Lyme Regis, UK. Six months later, intertidal sediments and biota from the area were sampled to determine whether the landslip had affected distribution and bioavailability of metals in the area and if there were any biological effects. Highest sediment concentrations for the majority of metals occurred near the landslip zone and in several cases exceeded Threshold Effects or Probable Effects Levels (As, Cu, Hg, Ni, Pb, Zn). The 1 M HCl-extractable fraction of Cd, Pb and Zn in sediments also increased near the landslip. Metal bioaccumulation by intertidal biota showed variability between different species and metals, but there were several instances of increased accumulation near the landslip through increased availability from seawater, sediment and dietary sources. In most cases, metal concentrations in molluscs exceeded Oslo and Paris Commission (OSPAR) background concentrations (BCs) together with background assessment concentrations (BACs) at some sites. Kidney tissues in winkles (Littorina littorea) were measured for evidence of oxidative stress using the Total Oxyradical Scavenging Capacity (TOSC) assay. Responses to peroxynitrite, peroxyl and hydroxyl radicals suggested raised levels of TOSC in animals from the sites close to or east of the landfill waste. There have been very few studies of direct impact of landfills on the marine environment and this study could serve as a practical model for similar events driven by sea level rise.

Immunological function in marine invertebrates: responses to environmental perturbation.

The inception of ecological immunology has led to an increase in the number of studies investigating the impact of environmental stressors on host immune defence mechanisms. This in turn has led to an increased understanding of the importance of invertebrate groups for immunological research. This review discusses the advances made within marine invertebrate ecological immunology over the past decade. By demonstrating the environmental stressors tested, the immune parameters typically investigated, and the species that have received the greatest level of investigation, this review provides a critical assessment of the field of marine invertebrate ecological immunology. In highlighting the methodologies employed within this field, our current inability to understand the true ecological significance of any immune dysfunction caused by environmental stressors is outlined. Additionally, a number of examples are provided in which studies successfully demonstrate a measure of immunocompetence through alterations in disease resistance and organism survival to a realized pathogenic threat. Consequently, this review highlights the potential to advance our current understanding of the ecological and evolutionary significance of environmental stressor related immune dysfunction. Furthermore, the potential for the advancement of our understanding of the immune system of marine invertebrates, through the incorporation of newly emerging and novel molecular techniques, is emphasized.

Road safety mass media campaigns: why are results inconclusive, and what can be done?

Recent research literature on the effectiveness (or otherwise) of promoting road safety via mass media advertising is selectively reviewed. The overall picture from this is inconclusive: effects of substantial size have been rare, but effects of small size cannot be ruled out. It is then argued that attempts to use crash data to establish or disprove the cost-effectiveness of campaigns are, indeed, doomed to failure: the random variability in crash numbers is too great (and even low effectiveness may be sufficient as campaigns are very cheap per person reached). It is suggested that evaluation may need to be based on before and after comparison of behaviours or variables that can be objectively observed and are closely linked to safety - and in order to substantiate the behaviour-safety link, credible theories are needed.

Countermeasures to the problem of accidents to intoxicated pedestrians.

A substantial part of the pedestrian accident problem arises from intoxicated pedestrians. Possible countermeasures are reviewed, organised into: (a) prevention of high levels of intoxication in pedestrians, (b) minimising pedestrian activity in the intoxicated, and (c) minimising risk of injury among intoxicated pedestrians. It is concluded that improved safety of intoxicated pedestrians is most likely to come about by making the environment safer for all pedestrians, drunk or sober. The measure that would be expected to have the greatest effect quickest is a reduced speed limit, especially in locations where traffic is busy and there are many pedestrians.

Effects of a weak oestrogenic active chemical (4-tert-pentylphenol) on pair-breeding and F1 development in the fathead minnow (Pimephales promelas).

A fish full life-cycle (FFLC) is the most comprehensive test to determine reproductive toxicity of chemicals to fish and this is likely to apply equally to endocrine active chemicals (EACs). However, FFLC tests use large numbers of animals, are expensive and time consuming. Alternative chronic tests, to the FFLC, potentially include sensitive life-stage windows of effect, such as sexual differentiation, early gonadal development and reproduction. In this paper, a fish pair-breeding study was applied to assess the biological effects of a weak environmental oestrogen, 4-tert-pentylphenol (4TPP), on reproduction and subsequent development of the F1 generation. The results of this study were then compared with the results for a published FFLC study, with this chemical. Fathead minnows (Pimephales promelas) were held in pairs and their reproductive performance assessed over two concurrent 21-day periods, the first without exposure to the test chemical, followed by the second with exposure to the test chemical, in a flow-through system at 25+/-1 degrees C. Embryos from two pairs, per treatment, were subsequently grown up in clean water until 90 days post-hatch to assess developmental effects of the parental exposure on the F1 generation. Nominal (measured geometric mean, time weighted) test concentrations of 4TPP were 56 (48), 180 (173) and 560 (570) microg l(-1). A significant decrease in fecundity was observed in all 4TPP exposed fish (mean number of eggs spawned per pair and number of spawns per pair) when compared to the solvent control. Vitellogenin (VTG) was significantly elevated in F0 males exposed to 560 microg 4TPPl(-1). Somatic endpoints, secondary sexual characteristics (SSC) and gonadosomatic index (GSI) were not affected by the 4TPP exposure. In the F1 generation, there were no treatment-related effects on hatching success, survival, growth, SSC or GSI. Histological examination of the gonads of the F1 fish revealed no treatment-related effects on sex ratio, sexual differentiation or sexual development. However, plasma VTG concentrations were significantly elevated in F1 male fish, derived from parents that had previously been exposed to 4TPP at concentrations of > or = 180 microg l(-1). These data show that the reproductive performance test is suitable for detecting weak environmental oestrogenic chemicals and that exposure of adult fish to oestrogens can result in altered biomarker expression (VTG) of the F1 generation. Our findings indicate that the reproductive performance test was as sensitive for detecting effects on reproduction when compared with a published FFLC test for 4TPP.

Optimising product advice based on age when design criteria are based on weight: child restraints in vehicles.

The motivation for this paper is the high rate of inappropriate child restraint selection in cars that is apparent in published surveys of child restraint use and how the public health messages promoting child restraints might respond. Advice has increasingly been given solely according to the child's weight, while many parents do not know the weight of their children. A common objection to promoting restraint use based on the age of the child is the imprecision of such advice, given the variation in the size of children, but the magnitude of the misclassification such advice would produce has never been estimated. This paper presents a method for estimating the misclassification of children by weight, when advice is posed in terms of age, and applies it to detailed child growth data published by the Centers for Disease Control and Prevention. In Australia, guidelines instructing all parents to promote their children from an infant restraint to a forward-facing child seat at 6 months, and then to a belt-positioning booster at 4 years, would mean that 5% of all children under the age of 6 years would be using a restraint not suited to their weight. Coordination of aged-based advice and the weight ranges chosen for the Australian Standard on child restraints could reduce this level of misclassification to less than 1%. The general method developed may also be applied to other aspects of restraint design that are more directly relevant to good restraint fit.

Validation of the use of zebrafish larvae in visual safety assessment.

INTRODUCTION: The use of zebrafish (Danio rerio) larvae was investigated to predict adverse visual effects and to establish the potential application of this organism in early drug safety assessment. METHODS: Following a comparison of the effects of 4 compounds in TL and WIK strains of zebrafish larvae, a blinded validation set of 27 compounds was tested on WIK strain of larval zebrafish in the optomotor response (OMR) assay. Selected compounds were also tested in the optokinetic response (OKR) and locomotor assays. Larvae were exposed from 3-8 days post-fertilisation (d.p.f.) by immersion in embryo culture media (E3) containing the compound in 1% DMSO (v/v). At 8 d.p.f. toxicity was assessed and the OMR or OKR assays were undertaken at non-toxic treatment levels. Compounds were then rated as 'red', 'amber' or 'green' according to their effects on visual function prior to unblinding of the identities of the test compounds. RESULTS: Overall, the OMR assay revealed a good concordance between the effects of compounds in WIK strain zebrafish with the data available from other in vivo and in vitro models or the clinic: thirteen out of nineteen positive compounds produced the expected effect while six of the eight negative compounds were correctly predicted. This gave an overall predictivity of 70% with a sensitivity of 68% and a specificity of 75%. The two false positive compounds were further tested in locomotor and optokinetic response assays and it was shown that a motility defect, rather than an effect on vision, had given rise to the positive result in the OMR assays. Therefore, the OMR assay would best be employed with other techniques to identify false positives. Further studies on two of the false negatives at higher concentrations suggested that the initial concentrations tested were too low. Therefore, it should be ensured that the maximum tolerated concentration is tested in the OMR assay. A comparison of four standard compounds in the OMR assay in WIK and TL zebrafish wild type strains revealed no difference in sensitivity between the strains. DISCUSSION: Overall, these results suggest that the OMR assay in zebrafish could be useful in predicting the adverse effects of drugs on visual function in man and would support its potential as a screen for 'frontloading' safety pharmacology assessment of this endpoint in vivo.

Plasma biomarker profiling in the detection of growth promoter use in calves.

The detection of illicit growth promoter use during meat production within the European Union is reliant on residue testing which is a limiting factor on the number of animals which can be tested and consequently compromises the efficacy of testing procedures. The present study examined a novel detection strategy based on the profiling of plasma component concentrations in response to growth promoter administrations. Calves subjected to nortestosterone decanoate, 17beta-oestradiol benzoate and dexamethasone were found to have altered urea, aminoterminal propeptide of type III procollagen and sex hormone binding globulin profiles in response to treatments. These findings demonstrate the potential of using the identification of perturbed profiles within a panel of biomarkers which cover a spectrum of biological activity to reveal growth promoter abuse.