A Link Between the Semi-Major Axis of Extrasolar Gas Giant Planets and Stellar Metallicity

The fact that most extrasolar planets found to date are orbiting metal-rich stars lends credence to the core accretion mechanism of gas giant planet formation over its competitor, the disc instability mechanism. However, the core accretion mechanism is not refined to the point of explaining orbital parameters such as their unexpected semi-major axes and eccentricities. We propose a model, which correlates the metallicity of the host star with the original semi-major axis of its most massive planet, prior to migration, considering that the core accretion scenario governs giant gas planet formation. The model predicts that the optimum regions for planetary formation shift inward as stellar metallicity decreases, providing an explanation for the observed absence of long period planets in metal-poor stars. We compare our predictions with the available data on extrasolar planets for stars with masses similar to the mass of the Sun. A fitting procedure produces an estimate of what we define as the Zero Age Planetary Orbit (ZAPO) curve as a function of the metallicity of the star. The model also hints that the lack of planets circling metal-poor stars may be partly caused by an enhanced destruction probability during the migration process, since the planets lie initially closer to the central stars.Comment: Nature of the replacement: According to recent simulations, the temperature profile, T, is more adequately reproduced by beta = 1 rather than beta = 2. We have introduced a distance scale factor that solves the very fast drop of T for low metallicity and introduces naturally the inferior distance limit of our ZAPO. Under this modification all the fitting process was altere

Antocianinas em uvas de variedades viníferas.

Estudou-se, neste trabalho, na vindima de 1979, a ocorrência das antocianinas em variedades de uvas tintas, Bonarda, Merlot, Barbera O'ASTI, Gamay-Beaujolais, Cabernet Franc, Pinot Noir e Canaiolo, cultivadas na região vitivin ícola de Bento Gonçalves, RS. A separação das antocianinas foi estudada por cromatografia em camada delgada unidimensional, e as concentrações, expressas em malvidina-3 monoglicosídeo (rng/l). As variedades estudadas somente apresentaram antocianinas-3-monoglicosídeos, comprovando, portanto, pertencerem à espécie Vitis vinifera. Essa identificação é de grande valia para a detecção de fraudes em vinhos finos tintos. A variedade "Pinot Noir" apresentou maior concentração, 764,12 mg/l; e a Canaiolo, 501,49 mg/l, a de menor concentração. Houve, contudo, uma variação entre as variedades estudadas, o que indica a possibilidade de seleção de variedades pela intensidade de cor, para a elaboração de vinhos tintos

Orbital Magnetism in Ensembles of Parabolic Potentials

We study the magnetic susceptibility of an ensemble of non-interacting electrons confined by parabolic potentials and subjected to a perpendicular magnetic field at finite temperatures. We show that the behavior of the average susceptibility is qualitatively different from that of billiards. When averaged over the Fermi energy the susceptibility exhibits a large paramagnetic response only at certain special field values, corresponding to comensurate classical frequencies, being negligible elsewhere. We derive approximate analytical formulae for the susceptibility and compare the results with numerical calculations.Comment: 4 pages, 4 figures, REVTE

Gene duplication, modularity and adaptation in the evolution of the aflatoxin gene cluster

<p>Abstract</p> <p>Background</p> <p>The biosynthesis of aflatoxin (AF) involves over 20 enzymatic reactions in a complex polyketide pathway that converts acetate and malonate to the intermediates sterigmatocystin (ST) and <it>O</it>-methylsterigmatocystin (OMST), the respective penultimate and ultimate precursors of AF. Although these precursors are chemically and structurally very similar, their accumulation differs at the species level for Aspergilli. Notable examples are <it>A</it>. <it>nidulans </it>that synthesizes only ST, <it>A</it>. <it>flavus </it>that makes predominantly AF, and <it>A</it>. <it>parasiticus </it>that generally produces either AF or OMST. Whether these differences are important in the evolutionary/ecological processes of species adaptation and diversification is unknown. Equally unknown are the specific genomic mechanisms responsible for ordering and clustering of genes in the AF pathway of <it>Aspergillus</it>.</p> <p>Results</p> <p>To elucidate the mechanisms that have driven formation of these clusters, we performed systematic searches of aflatoxin cluster homologs across five <it>Aspergillus </it>genomes. We found a high level of gene duplication and identified seven modules consisting of highly correlated gene pairs (<it>aflA/aflB, aflR/aflS, aflX/aflY</it>, <it>aflF/aflE, aflT/aflQ</it>, <it>aflC/aflW</it>, and <it>aflG/aflL</it>). With the exception of <it>A. nomius</it>, contrasts of mean <it>Ka/Ks </it>values across all cluster genes showed significant differences in selective pressure between section <it>Flavi </it>and non-section <it>Flavi </it>species. <it>A. nomius </it>mean <it>Ka/Ks </it>values were more similar to partial clusters in <it>A. fumigatus </it>and <it>A. terreus</it>. Overall, mean <it>Ka/Ks </it>values were significantly higher for section <it>Flavi </it>than for non-section <it>Flavi </it>species.</p> <p>Conclusion</p> <p>Our results implicate several genomic mechanisms in the evolution of ST, OMST and AF cluster genes. Gene modules may arise from duplications of a single gene, whereby the function of the pre-duplication gene is retained in the copy (<it>aflF</it>/<it>aflE</it>) or the copies may partition the ancestral function (<it>aflA/aflB</it>). In some gene modules, the duplicated copy may simply augment/supplement a specific pathway function (<it>aflR/aflS </it>and <it>aflX/aflY</it>) or the duplicated copy may evolve a completely new function (<it>aflT/aflQ </it>and <it>aflC/aflW</it>). Gene modules that are contiguous in one species and noncontiguous in others point to possible rearrangements of cluster genes in the evolution of these species. Significantly higher mean <it>Ka/Ks </it>values in section <it>Flavi </it>compared to non-section <it>Flavi </it>species indicate increased positive selection acting in the evolution of genes in OMST and AF gene clusters.</p

Sex Differences in Change in Skin Temperature When Exercising in a Hot, Humid Environment

The risk for heat-related illness is increased when exercising in a hot, humid environment. In an effort to protect the athlete, body temperature is measured continuously while exercising in extreme environments. Currently, researchers and laboratory personnel employ the use of mean skin temperature to monitor athlete safety; however, this measurement fails to consider localized changes in temperature that may arise as a function of sex and exercise time. Therefore, the purpose of this study was to examine potential sex differences in the change in skin temperature at 17 different upper body locations while exercising in a hot, humid environment. Young men and women were recruited and completed a 60-min walk/jog interval protocol in a hot (34.1 ± 1 °C), humid (64 ± 8%) environment while skin temperature was continuously measured. To account for differences that may have arisen due to differing workloads between men and women, energy expenditure and metabolic heat production were calculated after the completion of exercise. Data was analyzed either a repeated-measures ANOVA (change in skin temperature) or t-test­ (energy expenditure and metabolic heat production). Location of interaction effects was determined using a Fisher’s Least Significant Difference test. Significance was set a p\u3c0.05 for all statistical testing. There was no difference between men and women in total energy expenditure; however, men were found to have a higher metabolic heat production. Women had a higher change in skin temperature at three locations on the back (left upper, right upper, and right mid-back). Conversely, there were no differences at any time point between men and women in the change in core temperature from baseline measurements. This study highlights the need to further investigate sex differences in cooling mechanisms while exercising in a hot, humid environment

Stochastic stabilization of cosmological photons

The stability of photon trajectories in models of the Universe that have constant spatial curvature is determined by the sign of the curvature: they are exponentially unstable if the curvature is negative and stable if it is positive or zero. We demonstrate that random fluctuations in the curvature provide an additional stabilizing mechanism. This mechanism is analogous to the one responsible for stabilizing the stochastic Kapitsa pendulum. When the mean curvature is negative it is capable of stabilizing the photon trajectories; when the mean curvature is zero or positive it determines the characteristic frequency with which neighbouring trajectories oscillate about each other. In constant negative curvature models of the Universe that have compact topology, exponential instability implies chaos (e.g. mixing) in the photon dynamics. We discuss some consequences of stochastic stabilization in this context.Comment: 4 pages, 3 postscript figures in color which are also appropriate for black and white printers; v2 emphasizes relevance to flat as well as negatively curved cosmologies; to appear in J. Phys.

Consumption of a high-fat meal increased monocyte adhesion molecule expression and oxLDL phagocytosis: implications for cardiovascular disease risk?

Macrophage-derived foam cells are the predominant component of arterial plaques in the early stages of atherosclerosis. The deposition of arterial plaques is effected by several factors that are influenced by a person’s daily nutritional habits. One factor that poses a major risk for plaque development is high levels of plasma LDL resulting from the consumption of a high-fat meal. In order to understand how an individuals’ diet effects arterial plaque deposition via the process of foam cell formation, we measured the acute response in circulating monocyte activity after consuming a high-fat meal. Samples were acquired on a FlowSight (EMD Millipore) equipped with 405, 488, 642, and 785 nm lasers. Samples were analyzed in IDEAS software to identify pro-inflammatory (CD14+/16+) and classic (CD14+/16-) monocytes. We measured monocyte concentration, adhesion molecule expression, scavenger R expression, and oxLDL phagocytosis for 5 h postprandial. We found that consuming a high-fat meal caused an increase in pro-inflammatory monocyte concentration, adhesion molecule expression, monocyte phagocytosis of oxLDL, and CD36 expression in pro-inflammatory monocytes. These results suggest that consuming a high-fat meal increases the potential of monocytes to become foam cells for at least 5 h postprandial