Radiative transfer through the Intergalactic Medium

We use a probabilistic method to compute the propagation of an ionization front corresponding to the re-ionization of the intergalactic medium in a LCDM cosmology, including both hydrogen and helium. The effects of radiative transfer substantially boost the temperature of the ionized gas over the case of uniform re-ionization. The resulting temperature-density relation of the ionized gas is both non-monotonic and multiple-valued, reflecting the non-local character of radiative transfer and suggesting that a single polytropic relation between local gas density and temperatue is a poor description of the thermodynamic state of baryons in the post-reionization universe.Comment: 5 pages, 7 figures, letter accepted for publication in MNRA

Vultures

Black and turkey vultures cause problems in several ways. The most common problems associated with vultures are structural damage, loss of aesthetic value and property use related to offensive odors and appearance, depredation to livestock and pets, and air traffic safety. Management of these diverse problems often can be addressed by targeting the source of the birds causing the problem, namely the roost where the birds spend the night. Often the roost itself is the problem, such as when birds roost on a communication tower and foul the equipment with their feces or when they roost in a residential area. There, droppings and regurgitations create odors and their presence is perceived as a threat by the homeowners. Several methods are available for roost dispersal. As in many other situations, roost dispersal might best be accomplished through the integrated use of more than one damage management method. The details of the situation will dictate which management approach is the most appropriate, and experience has shown that best results are obtained if the source roost can be dispersed

Radio Signatures of HI at High Redshift: Mapping the End of the ``Dark Ages''

The emission of 21-cm radiation from a neutral intergalactic medium (IGM) at high redshift is discussed in connection with the thermal and ionization history of the universe. The physical mechanisms that make such radiation detectable against the cosmic microwave background include Ly_alpha coupling of the hydrogen spin temperature to the kinetic temperature of the gas and preheating of the IGM by the first generation of stars and quasars. Three different signatures are investigated in detail: (a) the fluctuations in the redshifted 21-cm emission induced by the gas density inhomogeneities that develop at early times in cold dark matter (CDM) dominated cosmologies; (b) the sharp absorption feature in the radio sky due to the rapid rise of the Ly_alpha continuum background that marks the birth of the first UV sources in the universe; and (c) the 21-cm emission and absorption shells that are generated on several Mpc scales around the first bright quasars. Future radio observations with projected facilities like the Giant Metrewave Radio Telescope and the Square Kilometer Array may shed light on the power spectrum of density fluctuations at z>5, and map the end of the "dark ages", i.e. the transition from the post-recombination universe to one populated with radiation sources.Comment: LateX, 19 pages, 5 figures, significantly revised version to be published in the Ap

Are owl pellets good estimators of prey abundance?

Some ecologists have been skeptics about the use of owl pellets to estimate small mammal's fauna. This is due to the assumptions required by this method: (a) that owls hunt at random, and (b) that pellets represent a random sample from the environment. We performed statistical analysis to test these assumptions and to assess the effectiveness of Barn owl pellets as a useful estimator of field abundances of its preys. We used samples collected in the arid Extra-Andean Patagonia along an altitudinal environmental gradient from lower Monte ecoregion to upper Patagonian steppe ecoregion, with a mid-elevation ecotone. To test if owls hunt at random, we estimated expected pellet frequency by creating a distribution of random pellets, which we compared with data using a simulated chi-square. To test if pellets represent a random sample from the environment, differences between ecoregions were evaluated by PERMANOVAs with Bray–Curtis dissimilarities. We did not find evidence that owls foraged non-randomly. Therefore, we can assume that the proportions of the small mammal's species in the diet are representative of the proportions of the species in their communities. Only Monte is different from other ecoregions. The ecotone samples are grouped with those of Patagonian steppes. There are no real differences between localities in the small mammal's abundances in each of these ecoregions and/or Barn owl pellets cannot detect patterns at a smaller spatial scale. Therefore, we have no evidence to invalidate the use of owl pellets at an ecoregional scale.Fil: Andrade, Analia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Centro Nacional Patagónico; ArgentinaFil: Menezes, Jorge Fernando Saraiva de. Universidade Federal do Rio de Janeiro; BrasilFil: Monjeau, Jorge Adrian. Universidade Federal do Rio de Janeiro; Brasil. Fundación Bariloche; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

Quantitative trait locus-specific genotype × alcoholism interaction on linkage for evoked electroencephalogram oscillations

We explored the evidence for a quantitative trait locus (QTL)-specific genotype × alcoholism interaction for an evoked electroencephalogram theta band oscillation (ERP) phenotype on a region of chromosome 7 in participants of the US Collaborative Study on the Genetics of Alcoholism. Among 901 participants with both genotype and phenotype data available, we performed variance component linkage analysis (SOLAR version 2.1.2) in the full sample and stratified by DSM-III-R and Feighner-definite alcoholism categories. The heritability of the ERP phenotype after adjusting for age and sex effects in the combined sample and in the alcoholism classification sub-groups ranged from 40% to 66%. Linkage on chromosome 7 was identified at 158 cM (LOD = 3.8) in the full sample and at 108 in the non-alcoholic subgroup (LOD = 3.1). Further, we detected QTL-specific genotype × alcoholism interaction at these loci. This work demonstrates the importance of considering the complexity of common complex traits in our search for genes that predispose to alcoholism

Food habits, lifestyle factors and mortality among oldest old Chinese: the Chinese longitudinal healthy longevity survey (CLHLS)

There are few studies reporting the association between lifestyle and mortality among the oldest old in developing countries. We examined the association between food habits, lifestyle factors and all-cause mortality in the oldest old (¥80 years) using data from the Chinese Longitudinal Healthy Longevity Survey (CLHLS). In 1998/99, 8959 participants aged 80 years and older took part in the baseline survey. Follow-up surveys were conducted every two to three years until 2011. Food habits were assessed using an in-person interview. Deaths were ascertained from family members during follow-up. Cox and Laplace regression were used to assess the association between food habits, lifestyle factors and mortality risk. There were 6626 deaths during 31,926 person-years of follow-up. Type of staple food (rice or wheat) was not associated with mortality. Daily fruit and vegetable intake was inversely associated with a higher mortality risk (hazard ratios (HRs): 0.85 (95% CI (confidence interval) 0.77–0.92), and 0.74 (0.66–0.83) for daily intake of fruit and vegetables, respectively). There was a positive association between intake of salt-preserved vegetables and mortality risk (consumers had about 10% increase of HR for mortality). Fruit and vegetable consumption were inversely, while intake of salt-preserved vegetables positively, associated with mortality risk among the oldest old. Undertaking physical activity is beneficial for the prevention of premature death.Zumin Shi, Tuohong Zhang, Julie Byles, Sean Martin, Jodie C. Avery and Anne W. Taylo

Anticholinergic drugs and risk of dementia: Time for action?

Evidence suggests that the prescription of bladder anticholinergics is increasing. Recent studies have accentuated concerns about whether certain prescribed medications could increase risk of dementia, including anticholinergic drugs, and specifically anticholinergics used for bladder symptoms. Nevertheless, it can be difficult to draw together the evidence to review the case for possible causation. Recognising this issue in 1965, Bradford-Hill set out nine criteria to help assess whether evidence of a causal relationship could be inferred between a presumed cause and an observed effect. In this commentary, we explore the extent to which associations between anticholinergics and dementia satisfy the Bradford-Hill criteria and examine the potential implications. First, we look at studies that have examined the relationship between anticholinergic drugs with urological properties (bladder drugs) and the onset of dementia, and then present those studies which specifically focus on the cognitive effects of bladder drugs that affect muscarinic receptors in the brain versus the bladder on older people along with suggestions for future research. We also discuss the risks and benefits of these drugs for treating overactive bladder. If it can be shown that certain medications carry a specific risk of dementia, it is possible that initiatives to change prescribing could become a key tool in reducing the risk of dementia and may be easier to implement than some lifestyle changes