Quantum charged fields in Rindler space

We study, using Rindler coordinates, the quantization of a charged scalar field interacting with a constant, external, electric field. First we establish the expression of the Schwinger vacuum decay rate, using the operator formalism. Then we rederive it in the framework of the Feynman path integral method. Our analysis reinforces the conjecture which identifies the zero winding sector of the Minkowski propagator with the Rindler propagator. Moreover we compute the expression of the Unruh's modes that allow to make connection between Minkowskian and Rindlerian quantization scheme by purely algebraic relations. We use these modes to study the physics of a charged two level detector moving in an electric field whose transitions are due to the exchange of charged quanta. In the limit where the Schwinger pair production mechanism of the exchanged quanta becomes negligible we recover the Boltzman equilibrium ratio for the population of the levels of the detector. Finally we explicitly show how the detector can be taken as the large mass and charge limit of an interacting fields system.Comment: 1 Tex file + 5 eps figure

Causality constraints in AdS/CFT from conformal collider physics and Gauss-Bonnet gravity

We explore the relation between positivity of the energy constraints in conformal field theories and causality in their dual gravity description. Our discussion involves CFTs with different central charges whose description, in the gravity side, requires the inclusion of quadratic curvature corrections. It is enough, indeed, to consider the Gauss-Bonnet term. We find that both sides of the AdS/CFT correspondence impose a restriction on the Gauss-Bonnet coupling. In the case of 6d supersymmetric CFTs, we show the full matching of these restrictions. We perform this computation in two ways. First by considering a thermal setup in a black hole background. Second by scrutinizing the scattering of gravitons with a shock wave in AdS. The different helicities provide the corresponding lower and upper bounds. We generalize these results to arbitrary higher dimensions and comment on some hints and puzzles they prompt regarding the possible existence of higher dimensional CFTs and the extent to which the AdS/CFT correspondence would be valid for them.Comment: 31 pages, 5 figures; v2: typos fixed, cosmetic amendments and references adde

Health-related and overall quality of life of patients with chronic hip and knee complaints in general practice

BACKGROUND: Information about quality of life of patients with chronic hip or knee complaints in general practice is scarce. This study describes the health-related and overall quality of life (HRQL) of these complaints. METHODS: Data were obtained from a cohort study in general practice. HRQL at three months follow-up was analysed. HRQL was measured as: symptoms, physical, psychological and social functioning, and general health perceptions, using the Western Ontario and McMaster Universities osteoarthritis index (WOMAC) and the MOS 36-item short-form-health survey (SF-36). Overall quality of life was measured using a 5-point rating scale. RESULTS: The results show that patients with chronic hip or knee complaints have a substantial lower HRQL compared to patients who had recovered from baseline hip or knee complaints. The largest effect was found on symptoms and physical functioning: up to 2.9 standard deviations below patients who had recovered from baseline hip or knee complaints. Scores of patients with both chronic hip and knee complaints were significantly worse than scores of patients with only knee complaints on most subscales. CONCLUSION: In patients with chronic hip or knee complaints the worst scores were seen on scales that measure symptoms and physical functioning, but still a substantially lower score was obtained for overall quality of life. Quality of life was poorer for patients with both chronic hip and knee complaints compared to those with chronic hip or knee complaints onl

Chemical and Physical Environmental Conditions Underneath Mat- and Canopy-Forming Macroalgae, and Their Effects on Understorey Corals

Disturbed coral reefs are often dominated by dense mat- or canopy-forming assemblages of macroalgae. This study investigated how such dense macroalgal assemblages change the chemical and physical microenvironment for understorey corals, and how the altered environmental conditions affect the physiological performance of corals. Field measurements were conducted on macroalgal-dominated inshore reefs in the Great Barrier Reef in quadrats with macroalgal biomass ranging from 235 to 1029 g DW m−2 dry weight. Underneath mat-forming assemblages, the mean concentration of dissolved oxygen was reduced by 26% and irradiance by 96% compared with conditions above the mat, while concentrations of dissolved organic carbon and soluble reactive phosphorous increased by 26% and 267%, respectively. The difference was significant but less pronounced under canopy-forming assemblages. Dissolved oxygen declined and dissolved inorganic carbon and alkalinity increased with increasing algal biomass underneath mat-forming but not under canopy-forming assemblages. The responses of corals to conditions similar to those found underneath algal assemblages were investigated in an aquarium experiment. Coral nubbins of the species Acropora millepora showed reduced photosynthetic yields and increased RNA/DNA ratios when exposed to conditions simulating those underneath assemblages (pre-incubating seawater with macroalgae, and shading). The magnitude of these stress responses increased with increasing proportion of pre-incubated algal water. Our study shows that mat-forming and, to a lesser extent, canopy-forming macroalgal assemblages alter the physical and chemical microenvironment sufficiently to directly and detrimentally affect the metabolism of corals, potentially impeding reef recovery from algal to coral-dominated states after disturbance. Macroalgal dominance on coral reefs therefore simultaneously represents a consequence and cause of coral reef degradation

Doom and Boom on a Resilient Reef: Climate Change, Algal Overgrowth and Coral Recovery

Background: Coral reefs around the world are experiencing large-scale degradation, largely due to global climate change, overfishing, diseases and eutrophication. Climate change models suggest increasing frequency and severity of warming-induced coral bleaching events, with consequent increases in coral mortality and algal overgrowth. Critically, the recovery of damaged reefs will depend on the reversibility of seaweed blooms, generally considered to depend on grazing of the seaweed, and replenishment of corals by larvae that successfully recruit to damaged reefs. These processes usually take years to decades to bring a reef back to coral dominance

Coral larvae move toward reef sounds

Free-swimming larvae of tropical corals go through a critical life-phase when they return from the open ocean to select a suitable settlement substrate. During the planktonic phase of their life cycle, the behaviours of small coral larvae (<1 mm) that influence settlement success are difficult to observe in situ and are therefore largely unknown. Here, we show that coral larvae respond to acoustic cues that may facilitate detection of habitat from large distances and from upcurrent of preferred settlement locations. Using in situ choice chambers, we found that settling coral larvae were attracted to reef sounds, produced mainly by fish and crustaceans, which we broadcast underwater using loudspeakers. Our discovery that coral larvae can detect and respond to sound is the first description of an auditory response in the invertebrate phylum Cnidaria, which includes jellyfish, anemones, and hydroids as well as corals. If, like settlement-stage reef fish and crustaceans, coral larvae use reef noise as a cue for orientation, the alleviation of noise pollution in the marine environment may gain further urgency.Mark J. A. Vermeij, Kristen L. Marhaver, Chantal M. Huijbers, Ivan Nagelkerken and Stephen D. Simpso

Inhibition of IFN-γ-dependent antiviral airway epithelial defense by cigarette smoke

<p>Abstract</p> <p>Background</p> <p>Although individuals exposed to cigarette smoke are more susceptible to respiratory infection, the effects of cigarette smoke on lung defense are incompletely understood. Because airway epithelial cell responses to type II interferon (IFN) are critical in regulation of defense against many respiratory viral infections, we hypothesized that cigarette smoke has inhibitory effects on IFN-γ-dependent antiviral mechanisms in epithelial cells in the airway.</p> <p>Methods</p> <p>Primary human tracheobronchial epithelial cells were first treated with cigarette smoke extract (CSE) followed by exposure to both CSE and IFN-γ. Epithelial cell cytotoxicity and IFN-γ-induced signaling, gene expression, and antiviral effects against respiratory syncytial virus (RSV) were tested without and with CSE exposure.</p> <p>Results</p> <p>CSE inhibited IFN-γ-dependent gene expression in airway epithelial cells, and these effects were not due to cell loss or cytotoxicity. CSE markedly inhibited IFN-γ-induced Stat1 phosphorylation, indicating that CSE altered type II interferon signal transduction and providing a mechanism for CSE effects. A period of CSE exposure combined with an interval of epithelial cell exposure to both CSE and IFN-γ was required to inhibit IFN-γ-induced cell signaling. CSE also decreased the inhibitory effect of IFN-γ on RSV mRNA and protein expression, confirming effects on viral infection. CSE effects on IFN-γ-induced Stat1 activation, antiviral protein expression, and inhibition of RSV infection were decreased by glutathione augmentation of epithelial cells using N-acetylcysteine or glutathione monoethyl ester, providing one strategy to alter cigarette smoke effects.</p> <p>Conclusions</p> <p>The results indicate that CSE inhibits the antiviral effects of IFN-γ, thereby presenting one explanation for increased susceptibility to respiratory viral infection in individuals exposed to cigarette smoke.</p

Scholarship on Gender and Sport in Sex Roles and Beyond

In this paper we critically review how research on girls or women and sport has developed over the last 35 years. We use a post-positivist lens to explore the content of the papers published in Sex Roles in the area of women, gender and sport and examine the shifts in how gender and sport have been conceptualized in these accounts. In order to initiate a broader dialogue about the scholarly analysis of gender and sport, we subsequently explore ideas inspired by feminist theorizing that have dominated/guided related research in other outlets over this time period but have received relatively little attention in papers published in Sex Roles. We conclude by briefly making suggestions for further research in this area

Multiple Means to the Same End: The Genetic Basis of Acquired Stress Resistance in Yeast

In nature, stressful environments often occur in combination or close succession, and thus the ability to prepare for impending stress likely provides a significant fitness advantage. Organisms exposed to a mild dose of stress can become tolerant to what would otherwise be a lethal dose of subsequent stress; however, the mechanism of this acquired stress tolerance is poorly understood. To explore this, we exposed the yeast gene-deletion libraries, which interrogate all essential and non-essential genes, to successive stress treatments and identified genes necessary for acquiring subsequent stress resistance. Cells were exposed to one of three different mild stress pretreatments (salt, DTT, or heat shock) and then challenged with a severe dose of hydrogen peroxide (H2O2). Surprisingly, there was little overlap in the genes required for acquisition of H2O2 tolerance after different mild-stress pretreatments, revealing distinct mechanisms of surviving H2O2 in each case. Integrative network analysis of these results with respect to protein–protein interactions, synthetic–genetic interactions, and functional annotations identified many processes not previously linked to H2O2 tolerance. We tested and present several models that explain the lack of overlap in genes required for H2O2 tolerance after each of the three pretreatments. Together, this work shows that acquired tolerance to the same severe stress occurs by different mechanisms depending on prior cellular experiences, underscoring the context-dependent nature of stress tolerance

Individual Variations in Maternal Care Early in Life Correlate with Later Life Decision-Making and c-Fos Expression in Prefrontal Subregions of Rats

Early life adversity affects hypothalamus-pituitary-adrenal axis activity, alters cognitive functioning and in humans is thought to increase the vulnerability to psychopathology–e.g. depression, anxiety and schizophrenia- later in life. Here we investigated whether subtle natural variations among individual rat pups in the amount of maternal care received, i.e. differences in the amount of licking and grooming (LG), correlate with anxiety and prefrontal cortex-dependent behavior in young adulthood. Therefore, we examined the correlation between LG received during the first postnatal week and later behavior in the elevated plus maze and in decision-making processes using a rodent version of the Iowa Gambling Task (rIGT). In our cohort of male and female animals a high degree of LG correlated with less anxiety in the elevated plus maze and more advantageous choices during the last 10 trials of the rIGT. In tissue collected 2 hrs after completion of the task, the correlation between LG and c-fos expression (a marker of neuronal activity) was established in structures important for IGT performance. Negative correlations existed between rIGT performance and c-fos expression in the lateral orbitofrontal cortex, prelimbic cortex, infralimbic cortex and insular cortex. The insular cortex correlations between c-fos expression and decision-making performance depended on LG background; this was also true for the lateral orbitofrontal cortex in female rats. Dendritic complexity of insular or infralimbic pyramidal neurons did not or weakly correlate with LG background. We conclude that natural variations in maternal care received by pups may significantly contribute to later-life decision-making and activity of underlying brain structures