Evaluando los niveles tróficos de dos tiburones oceánicos del Océano Pacífico suroriental

Indexación: Web of ScienceStable isotope analyses for shortfin mako (Isurus oxyrinchus) and blue sharks (Prionace glauca) were conducted to assess their trophic position in two periods of time (before 1980 and after 2000) in the Southeastern Pacific waters (SEP). Both sharks showed that their trophic position decreased over time (P < 0.05). Many factors could be involved in this change such as dietary shifts, prey availability, or indirect fishing effects in SEP waters.RESUMEN. Para evaluar los niveles tróficos de los tiburones marrajo (Isurus oxyrinchus) y azulejo (Prionace glauca) en dos períodos de tiempo (previo a 1980 y posterior al 2000) en aguas del Pacífico suroriental (SEP), se realizaron análisis de isótopos estables. Ambos tiburones mostraron un descenso del nivel trófico en el tiempo (P < 0,05). Varios son los factores que pueden estar involucrados en este evento, como los cambios dietarios, la disponibilidad de las presas o los efectos indirectos de la pesquería en aguas del Pacífico suroriental.http://www.lajar.cl/pdf/imar/v44n2/Art%C3%ADculo_44_2_25.pd

A possible signature of terrestrial planet formation in the chemical composition of solar analogs

Recent studies have shown that the elemental abundances in the Sun are anomalous when compared to most (about 85%) nearby solar twin stars. Compared to its twins, the Sun exhibits a deficiency of refractory elements (those with condensation temperatures Tc>900K) relative to volatiles (Tc<900K). This finding is speculated to be a signature of the planet formation that occurred more efficiently around the Sun compared with the majority of solar twins. Furthermore, within this scenario, it seems more likely that the abundance patterns found are specifically related to the formation of terrestrial planets. In this work we analyze abundance results from six large independent stellar abundance surveys to determine whether they confirm or reject this observational finding. We show that the elemental abundances derived for solar analogs in these six studies are consistent with the Tc trend suggested as a planet formation signature. The same conclusion is reached when those results are averaged heterogeneously. We also investigate the dependency of the abundances with first ionization potential (FIP), which correlates well with Tc. A trend with FIP would suggest a different origin for the abundance patterns found, but we show that the correlation with Tc is statistically more significant. We encourage similar investigations of metal-rich solar analogs and late F-type dwarf stars, for which the hypothesis of a planet formation signature in the elemental abundances makes very specific predictions. Finally, we examine a recent paper that claims that the abundance patterns of two stars hosting super-Earth like planets contradict the planet formation signature hypothesis. Instead, we find that the chemical compositions of these two stars are fully compatible with our hypothesis.Comment: To appear in Astronomy and Astrophysic

Stellar Chemical Abundances: In Pursuit of the Highest Achievable Precision

The achievable level of precision on photospheric abundances of stars is a major limiting factor on investigations of exoplanet host star characteristics, the chemical histories of star clusters, and the evolution of the Milky Way and other galaxies. While model-induced errors can be minimized through the differential analysis of spectrally similar stars, the maximum achievable precision of this technique has been debated. As a test, we derive differential abundances of 19 elements from high-quality asteroid-reflected solar spectra taken using a variety of instruments and conditions. We treat the solar spectra as being from unknown stars and use the resulting differential abundances, which are expected to be zero, as a diagnostic of the error in our measurements. Our results indicate that the relative resolution of the target and reference spectra is a major consideration, with use of different instruments to obtain the two spectra leading to errors up to 0.04 dex. Use of the same instrument at different epochs for the two spectra has a much smaller effect (~0.007 dex). The asteroid used to obtain the solar standard also has a negligible effect (~0.006 dex). Assuming that systematic errors from the stellar model atmospheres have been minimized, as in the case of solar twins, we confirm that differential chemical abundances can be obtained at sub-0.01 dex precision with due care in the observations, data reduction and abundance analysis.Comment: Accepted for publication in ApJ; 13 pages, 6 figures, 7 table

siRNA knockdown of SPHK1 in vivo protects mice from systemic, type-I Allergy.

Systemic anaphylaxis is considered to be a typical immediate hypersensitivity response, determined by the activation of immune cells,&#xd;&#xa;via antigen-induced aggregation of IgE-sensitized Fc&#x3b5;RI cells. Perhaps most the important cells, in the immediate hypersensitivity responses, are mast cells. We have previously shown that SPHK1 plays a key role in the intracellular signaling pathways triggered by FceRI aggregation on human&#xd;&#xa;mast cells. More recently, we performed a genome-wide gene expression profiling of human mast cells, sensitized with IgE alone, or stimulated by Fc&#x3b5;RI aggregation. We found that sphingosine kinase 1 (SPHK1) was one&#xd;&#xa;of genes activated at the earlier stages of mast cell activation, including during sensitization. Moreover, SPHK1 has been shown, by us and others, to be a key player in the intracellular signaling pathways triggered by&#xd;&#xa;several immune-receptors, including fMLP, C5a, and Fcg- and Fcereceptors. Here we have investigated the in vivo role of SPHK1 in allergy, using a specific siRNA to knockdown SPHK1 in vivo. Our results support a role for&#xd;&#xa;SPHK1 in the inflammatory responses that share clinical, immunological, and histological features of type I hypersensitivity. Thus, mice pretreated with the siRNA for SPHK1 were protected from the IgE mediated allergic&#xd;&#xa;reactions including: temperature changes, histamine release, cytokine production, cell-adhesion molecule expression, and immune cell infiltration into the lungs

On the Change in Surpluses Equivalence: Measuring Benefits from Transport Infrastructure Investments

Reductions in transport costs resulting from infrastructure improvements generate benefits that can be measured as surplus changes either at an economy-wide scale (social welfare changes) or, as is common practice in cost-benefit analysis (CBA), at a transport market level as transport users’ surplus changes. In this paper we look at an economy with spatially separated markets embedded in a transport network (a spatial price equilibrium model) to study the equivalence between these two benefit measures. Three different product market competition arrangements are considered. A similar question and strategy is presented in Jara-Díaz (1986) employing a two-node network and extreme competition assumptions on the production side: perfect competition and monopolistic production with arbitrage. We extend his work by additionally considering perfect collusion (monopoly without resale) and Cournot-Nash oligopoly under flow-dependent transport costs (i.e. congestion in transport). Numerical simulations in a three-node network with and without transshipment nodes, illustrate our main results

Combination methods for HIV prevention in men who have sex with men (MSM)

This is the protocol for a review and there is no abstract. The objectives are as follows: This review seeks to examine the effectiveness of prevention interventions for MSM that combine at least two of the three categories of intervention modality (biomedical, behavioural and structural) compared either to other HIV prevention interventions or to minimal/no HIV prevention. Below, descriptions of the criteria that will be used to categorise intervention components are provided under the heading Types of interventions' and the full list of outcomes of interest are provided in the section Types of outcome measures'. All planned comparisons are detailed in the section Data synthesis', followed by the planned variables of interest for subgroup and meta-regression analyses

HIV, sexual risk and ethnicity among gay and bisexual men in England: survey evidence for persisting health inequalities.

To examine ethnic group differences in HIV testing and sexual behaviours among a large sample of gay and bisexual men (GBM), 13 years after similar observations were made, assess national HIV prevention responses and inform planning priorities. Cross-sectional convenience self-completion online survey in summer 2014, designed and recruited in collaboration with community-based health promoters and gay internet services; comparison with earlier findings reporting on similarly designed survey in 2001. We recruited 15 388 GBM living in England who self-reported as follows: 18.5% from ethnic minorities; 9.0% tested HIV positive (cf. 17.0% and 5.4% in 2001). Compared with the white British, Asian men were no longer less likely to report diagnosed HIV but had an equal probability of doing so (2001 OR=0.32, 95% CI 0.13 to 0.79; 2014 OR=1.04, 95% CI 0.71 to 1.54); black men remained significantly more likely to report diagnosed HIV (2001 OR=2.06, 95% CI 1.56 to 3.29; 2014 OR=1.62, 95% CI 1.10 to 2.36) as did men in the other white group (2001 OR=1.54, 95% CI 1.23 to 1.93; 2014 OR=1.31, 95% CI 1.10 to 1.55). Overall annual incidence of reported HIV diagnoses in 2014 was 1.1%. Black men were significantly more likely to report diagnosis with HIV in the last 12 months than the white British (adjusted odds ratios (AOR) 2.57, 95% CI 1.22 to 5.39). No minority ethnic group was more or less likely to report condom unprotected anal intercourse (CUAI) in the last year but men in the Asian, black and all others groups were more likely than the white British to report CUAI with more than one non-steady partners. Among GBM in England, HIV prevalence continues to be higher among black men and other white men compared with the white British. The protective effect of being from an Asian background appears no longer to pertain. Sexual risk behaviours may account for some of these differences