The recent discovery of a pathogenic fungus (
Batrachochytrium dendrobatidis) associated with declines of frogs in the American and Australian tropics, suggests that at least the proximate cause, may ...be known for many previously unexplained amphibian declines. We have monitored boreal toads in Colorado since 1991 at four sites using capture–recapture of adults and counts of egg masses to examine the dynamics of this metapopulation. Numbers of male toads declined in 1996 and 1999 with annual survival rate averaging 78% from 1991 to 1994, 45% in 1995 and 3% between 1998 and 1999. Numbers of egg masses also declined. An etiological diagnosis of chytridiomycosis consistent with infections by the genus
Batrachochytrium was made in six wild adult toads. Characteristic histomorphological features (i.e. intracellular location, shape of thalli, presence of discharge tubes and rhizoids) of chytrid organisms, and host tissue response (acanthosis and hyperkeratosis) were observed in individual toads. These characteristics were indistinguishable from previously reported mortality events associated with chytrid fungus. We also observed epizootiological features consistent with mortality events associated with chytrid fungus: an increase in the ratio of female:male toads captured, an apparent spread of mortalities within the metapopulation and mortalities restricted to post metamorphic animals. Eleven years of population data suggest that this metapopulation of toads is in danger of extinction, pathological and epizootiological evidence indicates that
B. dendrobatidis has played a proximate role in this process
Polymer matrix composites with liquid metal droplet and solid particle fillers are promising candidates for thermal interface materials (TIMs) used in electronics thermal management. To achieve good ...thermal transport, the particle and droplet fillers must be interconnected to form thermally conductive percolation pathways in the polymer matrix. This in turn requires displacement of the polymer between fillers as well as rupture of the oxide shell on the liquid metal droplets. This study demonstrates a multipronged strategy to achieve extensive filler bridging and a high thermal conductivity polymer TIM pad. The strategy synergistically employs reactive solid and liquid microscale fillers, a polymer matrix with tuned precure viscosity, and mechanical compression during thermal curing of the composite. The data demonstrate that the viscosity of the precursor polymer solution prior to curing plays a major role in the resulting thermal conductivity. More specifically, samples made with low viscosity ≈100 cSt solutions achieve a high thermal conductivity of ≈15 W m−1 K−1 at a curing pressure of 2 MPa. This thermal conductivity is double that achieved with high viscosity ≈2300 cSt solutions. Since many polymer systems employed in industry and research have a high precure viscosity, this insight has important implications for next‐generation TIMs.
High thermal conductivities in elastomeric composites are achieved by applying compression to improve bridging between thermally conductive fillers. Importantly, i) this compression should be applied when the matrix is in its noncured state and ii) the precure matrix viscosity should be low. Elastomeric composites with high thermal conductivities of ≈15 W m−1 K−1 are achieved using this approach.
A range of bubble and sea spray aerosol generators has been tested in the laboratory and compared with oceanic measurements from the literature. We have shown that the method of generation has a ...significant influence on the properties of the aerosol particles produced. Hence, the validity of a generation system to mimic atmospheric aerosol is dependent on its capacity for generating bubbles and particles in a realistic manner. A bubble-bursting aerosol generator which produces bubbles by water impingement was shown to best reproduce the oceanic bubble spectral shapes, which confirms previous findings. Two porous bubblers and a plunging-water jet system were tested as bubble-bursting aerosol generators for comparison with a standard nebulizer. The methods for aerosol production were evaluated by analysing the bubble spectrum generated by the bubble-bursting systems and the submicron size distribution, hygroscopicity and cloud condensation nucleus activity of the aerosols generated by the different techniques. Significant differences in the bubble spectrum and aerosol properties were observed when using different aerosol generators. The aerosols generated by the different methods exhibited similar hygroscopicity and cloud condensation nucleus activity behaviour when a sample of purely inorganic salts was used as a parent seawater solution; however, significant differences in the aerosol properties were found when using samples of filtered natural seawater enriched with biogenic organics. The presence of organics in the aerosol caused suppression of the growth factor at humidities above 75% RH and an increase in the critical supersaturation with respect to the generation from artificial seawater devoid of organics. The extent of the effect of organics on the aerosol properties varied depending on the method of particle production. The results of this work indicate that the aerosol generation mechanism affects the particles organic enrichment, thus the behaviour of the produced aerosols strongly depends on the laboratory aerosol generator employed. Comparison between bubble lifetimes in several laboratory simulations and the oceanic conditions indicated that it would require a considerable extension of the dimensions of the currently used bubble-bursting laboratory systems in order to replicate the characteristic oceanic bubble lifetimes. We analyzed the implications derived from the reduced bubble residence times in scaled systems, regarding marine surfactants adsorption on rising bubbles, and found that adsorption equilibrium is reached on a timescale much shorter than the bubble lifetime in small-scale laboratory generators. This implies that adsorption of marine surface-active material is not limited by surfactant transport to the bubble surface.
Dietary interventions are effective ways to extend or shorten lifespan. By examining midlife hepatic gene expressions in mice under different dietary conditions, which resulted in different lifespans ...and aging-related phenotypes, we were able to identify genes and pathways that modulate the aging process. We found that pathways transcriptionally correlated with diet-modulated lifespan and physiological changes were enriched for lifespan-modifying genes. Intriguingly, mitochondrial gene expression correlated with lifespan and anticorrelated with aging-related pathological changes, whereas peroxisomal gene expression showed an opposite trend. Both organelles produce reactive oxygen species, a proposed causative factor of aging. This finding implicates a contribution of peroxisome to aging. Consistent with this hypothesis, lowering the expression levels of peroxisome proliferation genes decreased the cellular peroxide levels and extended the lifespan of Drosophila melanogaster and Caenorhabditis elegans. These findings show that transcriptional changes resulting from dietary interventions can effectively reflect causal factors in aging and identify previously unknown or under-appreciated longevity pathways, such as the peroxisome pathway.
The low Ca(2+) concentration (Ca(2+)) of mammalian endolymph in the inner ear is required for normal hearing and balance. We reported (Yamauchi et al., Biochem Biophys Res Commun 331: 1353-1357, ...2005) that the epithelial Ca(2+) channels TRPV5 and TRPV6 (transient receptor potential types 5 and 6) are expressed in the vestibular system and that TRPV5 expression is stimulated by 1,25-dihydroxyvitamin D(3), as also reported in kidney. TRPV5/6 channels are known to be inhibited by extracellular acidic pH. Endolymphatic pH, Ca(2+), and transepithelial potential of the utricle were measured in Cl(-)/HCO(3)(-) exchanger pendrin (SLC26A4) knockout mice in vivo. Slc26a4(-/-) mice exhibit reduced pH and utricular endolymphatic potential and increased Ca(2+). Monolayers of primary cultures of rat semicircular canal duct cells were grown on permeable supports, and cellular uptake of (45)Ca(2+) was measured individually from the apical and basolateral sides. Net uptake of (45)Ca(2+) was greater after incubation with 1,25-dihydroxyvitamin D(3). Net (45)Ca(2+) absorption was dramatically inhibited by low apical pH and was stimulated by apical alkaline pH. Gadolinium, lanthanum, and ruthenium red reduced apical uptake. These observations support the notion that one aspect of vestibular dysfunction in Pendred syndrome is a pathological elevation of endolymphatic Ca(2+) due to luminal acidification and consequent inhibition of TRPV5/6-mediated Ca(2+) absorption.
Throughout history, poor quality medicines have been a persistent problem, with periodical crises in the supply of antimicrobials, such as fake cinchona bark in the 1600s and fake quinine in the ...1800s. Regrettably, this problem seems to have grown in the last decade, especially afflicting unsuspecting patients and those seeking medicines via on-line pharmacies. Here we discuss some of the challenges related to the fight against poor quality drugs, and counterfeits in particular, with an emphasis on the analytical tools available, their relative performance, and the necessary workflows needed for distinguishing between genuine, substandard, degraded and counterfeit medicines.
ABSTRACT We present the COPS-DIGIT-FOOSH (CDF) Herschel spectroscopy data product archive, and related ancillary data products, along with data fidelity assessments, and a user-created archive in ...collaboration with the Herschel-PACS and SPIRE ICC groups. Our products include datacubes, contour maps, automated line fitting results, and best 1D spectra products for all protostellar and disk sources observed with PACS in RangeScan mode for two observing programs: the DIGIT Open Time Key Program (KPOT_nevans_1 and SDP_nevans_1; PI: N. Evans), and the FOOSH Open Time Program (OT1_jgreen02_2; PI: J. Green). In addition, we provide our best SPIRE-FTS spectroscopic products for the COPS Open Time Program (OT2_jgreen02_6; PI: J. Green) and FOOSH sources. We include details of data processing, descriptions of output products, and tests of their reliability for user applications. We identify the parts of the data set to be used with caution. The resulting absolute flux calibration has improved in almost all cases. Compared to previous reductions, the resulting rotational temperatures and numbers of CO molecules have changed substantially in some sources. On average, however, the rotational temperatures have not changed substantially (<2%), but the number of warm (Trot ∼ 300 K) CO molecules has increased by about 18%.
We present Spitzer Infrared Spectrograph (IRS) spectra of 28 Class I protostars in the Taurus star-forming region. The 5-36 mu m spectra reveal excess emission from the inner regions of the envelope ...and accretion disk surrounding these predecessors of low-mass stars, as well as absorption features due to silicates and ices. Together with shorter and longer wavelength data from the literature, we construct spectral energy distributions and fit envelope models to 22 protostars of our sample, most of which are well constrained due to the availability of the IRS spectra. We infer that the envelopes of the Class I objects in our sample cover a wide range in parameter space, particularly in density and centrifugal radius, implying different initial conditions for the collapse of protostellar cores.
The neural systems underlying translation and language switching were investigated using PET. Proficient German–English adult bilinguals were scanned whilst either translating or reading visually ...presented words in German (L1), English (L2) or alternating L1/L2. We refer to alternating L1/L2 as `switching'. The results revealed contrasting patterns of activation for translation and switching, suggesting at least partially independent mechanisms. Translation, but not switching, increased activity in the anterior cingulate and subcortical structures whilst decreasing activation in several other temporal and parietal language areas associated with the meaning of words. Translation also increased activation in regions associated with articulation (the anterior insula, cerebellum and supplementary motor area) arguably because the reading response to the stimulus must be inhibited whilst a response in a different language is activated. In contrast, switching the input language resulted in activation of Broca's area and the supramarginal gyri, areas associated with phonological recoding. The results are discussed in terms of the cognitive control of language processes.
Abstract Background Studies showing that adolescents are more likely to smoke if they have friends who smoke typically infer that this is the result of peer influence. However, it may also be due to ...adolescents choosing friends who have smoking behaviors similar to their own (i.e., selection). One of the most influential studies of influence and selection effects on smoking concluded that these processes contribute about equally to peer group homogeneity in adolescent smoking ( Ennett and Bauman, 1994 ). The goal of this study was to conduct a partial replication of these findings. Methods Data are from 1223 participants in the National Longitudinal Study of Adolescent Health. Spectral decomposition techniques identified friendship cliques, which were then used as the unit of analysis to examine influence and selection effects over a one-year period. Results Non-smokers were more likely to become smokers if they initially belonged to a smoking (vs. non-smoking) group, and smokers were more likely to become non-smokers if they initially belonged to a non-smoking (vs. smoking) group, indicating an influence effect on both initiation and cessation. Further, group members who changed groups between waves were more likely to select groups with smoking behavior congruent to their own, providing evidence of a selection effect. Conclusions While our results generally replicate the group analyses reported by Ennett and Bauman (1994) , they suggest that peer influence and selection effects on adolescent smoking may be much weaker than assumed based on this earlier research.
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