NGC 6738: not a real open cluster

A photometric, astrometric and spectroscopic investigation of the poorly studied open cluster NGC 6738 has been performed in order to ascertain its real nature. NGC 6738 is definitely not a physical stellar ensemble: photometry does not show a defined mean sequence, proper motions and radial velocities are randomly distributed, spectro-photometric parallaxes range between 10 and 1600 pc, and the apparent luminosity function is identical to that of the surrounding field. NGC 6738 therefore appears to be an apparent concentration of a few bright stars projected on patchy background absorption.Comment: A&A, in press (compared with first submission to astro-ph, now Table 2 and Figure 4 are replaced with corrected versions

Effects of climate change on vascular plant species from the southernmost Central Andes : a case study in north-western Argentina (NOA)

La región de los Andes Tropicales es considerada como una región muy vulnerable al cambio climático porque presenta una alta diversidad y endemismo y porque posee una gran variabilidad altitudinal. Si bien se ha efectuado un gran número de predicciones sobre los cambios que ocurrirán en el clima, pocos estudios evaluaron el impacto que éste tendrá sobre las distribuciones de las especies. En este estudio se estima el efecto del cambio climático sobre la distribución y la conservación de especies endémicas en los años 2050 y 2080, bajo dos escenarios futuros (A2 y B1), para la región del noroeste argentino, coincidente con la porción sur de los Andes Centrales. Los resultados indican que desde el presente al 2080, el cambio climático en la región del NOA ocasionará un único evento de extinción y modificaciones en los rangos de distribución de las especies endémicas. Además, se observa un desplazamiento generalizado de las especies endémicas hacia zonas de mayor altitud y hacia zonas subtropicales. En consecuencia, se estima que los impactos del cambio climático futuro serán mayores para eco-regiones bajas y menos áridas. Asimismo, el sistema de áreas protegidas del NOA no representará de forma adecuada a la flora endémica en el futuro, bajo ningún escenario, según el objetivo de conservación establecido en el presente trabajo. Estos resultados ponen de manifiesto la necesidad de concentrar los esfuerzos de conservación en las especies y ecosistemas identificados como más vulnerables, con objeto de asegurar la conservación futura de la flora endémica de la parte más sur de los Andes Centrales.The Tropical Andes region has been indicated as a highly vulnerable region to climate change for its high diversity and endemism and its great altitudinal variability. While there have been an important number of predictions about the changing climate in the region, few studies have evaluated the impact this will have on the distribution of species. In this paper, we estimated the effect of climate change on the distribution and conservation of endemic species from north-western Argentina (southernmost Central Andes) for the years 2050 and 2080 and under two future scenarios (A2 and B1). According to the results, from the present to 2080, climate change in the region will cause a single extinction event, and changes in all distributional ranges of endemic species. Moreover, a widespread displacement of endemic species towards higher altitudes and subtropical areas is predicted, indicating that the impacts of future climate change will be greater for low and less arid ecoregions. Moreover, the NOA system of protected areas would not be able to represent adequately the endemic flora in the future under any scenario, according to the established target in the present study. These results highlight the need to concentrate conservation efforts on those species and ecosystems identified here as the most vulnerable in order to ensure the future conservation of the endemic flora of the most southern part of the Central Andes

Testing for Chlamydia trachomatis: time trends in positivity rates in the canton of Basel-Stadt, Switzerland

National health statistics report a 2·5-fold increase in laboratory-confirmed Chlamydia trachomatis (CT) cases over the last decade in Switzerland where no CT screening programme exists. We obtained essential denominator information to describe the epidemiology of CT in the canton of Basel-Stadt, an urban canton in north-western Switzerland. Laboratories reporting at least two CT infections from Basel-Stadt residents to the SFOPH in 2010 provided demographic and test-related data. CT positivity rates were calculated for 2002-2010. The influences of test year, age, sex and laboratory on CT positivity were investigated in a multivariable model. Positivity differed between sexes and age groups. In our sample of 32 034 records, female and male CT positivity rates were 4·7% and 11·1%, respectively. Test year was significantly associated with test outcome in the multivariable analysis but no time trend was observed. CT positivity did not change over the past 9 years in Basel-Stadt. In contrast to other European countries without CT screening, we found no evidence that the observed increase of Chlamydia cases in the national notification system represents an epidemiological trend, but rather results from an increased testing frequenc

Radii and Distances of Cepheids, I., Method and Measurement Errors

We develop a formulation of the Baade-Wesselink method which uses the Fourier coefficients of the observables. We derive an explicit, analytic expression to determine the mean radius from each Fourier order. The simplicity of this method allows us to derive the uncertainty in the mean radius due to measurement errors. Using simulations and a recent dataset we demonstrate that the precision of the radius measurement with optical magnitudes is in most cases limited by the accuracy of the measurement of the phase difference between the light and the color index curve. In this case it is advantageous to determine the inverse radius, because it has normal errors.Comment: 18 pages, postscript, accepted for publication in Ap

Comparative Study of Contact Repulsion in Control and Mutant Macrophages Using a Novel Interaction Detection

In this paper, a novel method for interaction detection is presented to compare the contact dynamics of macrophages in the Drosophila embryo. The study is carried out by a framework called macrosight, which analyses the movement and interaction of migrating macrophages. The framework incorporates a segmentation and tracking algorithm into analysing the motion characteristics of cells after contact. In this particular study, the interactions between cells is characterised in the case of control embryos and Shot mutants, a candidate protein that is hypothesised to regulate contact dynamics between migrating cells. Statistical significance between control and mutant cells was found when comparing the direction of motion after contact in specific conditions. Such discoveries provide insights for future developments in combining biological experiments with computational analysis

Molecular weight of hydroxyethyl starch: is there an effect on blood coagulation and pharmacokinetics?

Background. The development of hydroxyethyl starches (HES) with low impact on blood coagulation but higher volume effect compared with the currently used HES solutions is of clinical interest. We hypothesized that high molecular weight, low-substituted HES might possess these properties. Methods. Thirty pigs were infused with three different HES solutions (20 ml kg−1) with the same degree of molar substitution (0.42) but different molecular weights (130, 500 and 900 kDa). Serial blood samples were taken over 24 h and blood coagulation was assessed by Thromboelastograph® analysis and analysis of plasma coagulation. In addition, plasma concentration and in vivo molecular weight were determined and pharmacokinetic data were computed based on a two-compartment model. Results. Thromboelastograph analysis and plasma coagulation tests did not reveal a more pronounced alteration of blood coagulation with HES 500 and HES 900 compared with HES 130. In contrast, HES 500 and HES 900 had a greater area under the plasma concentration-time curve [1542 (142) g min litre−1, P<0.001, 1701 (321) g min litre−1, P<0.001] than HES 130 [1156 (223) g min litre−1] and alpha half life (\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} $\mathrm{t}_{{\alpha}}^{{\frac{1}{2}}}$ \end{document}) was longer for HES 500 [53.8 (8.6) min, P<0.01] and HES 900 [57.1 (12.3) min, P<0.01] than for HES 130 [39.9 (10.7) min]. Beta half life (\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} $\mathrm{t}_{{\beta}}^{{\frac{1}{2}}}$ \end{document}), however, was similar for all three types of HES [from 332 (100) to 381 (63) min]. Conclusions. In low-substituted HES, molecular weight is not a key factor in compromising blood coagulation. The longer initial intravascular persistence of high molecular weight low-substituted HES might result in a longer lasting volume effec

The night-sky at the Calar Alto Observatory

We present a characterization of the main properties of the night-sky at the Calar Alto observatory for the time period between 2004 and 2007. We use optical spectrophotometric data, photometric calibrated images taken in moonless observing periods, together with the observing conditions regularly monitored at the observatory, such as atmospheric extinction and seeing. We derive, for the first time, the typical moonless night-sky optical spectrum for the observatory. The spectrum shows a strong contamination by different pollution lines, in particular from Mercury lines, which contribution to the sky-brightness in the different bands is of the order of ~0.09 mag, ~0.16 mag and ~0.10 mag in B, V and R respectively. The zenith-corrected values of the moonless night-sky surface brightness are 22.39, 22.86, 22.01, 21.36 and 19.25 mag arcsec^-2 in U, B, V, R and I, which indicates that Calar Alto is a particularly dark site for optical observations up to the I-band. The fraction of astronomical useful nights at the observatory is ~70%, with a ~30% of photometric nights. The typical extinction at the observatory is k_V~0.15 mag in the Winter season, with little dispersion. In summer the extinction has a wider range of values, although it does not reach the extreme peaks observed at other sites. The median seeing for the last two years (2005-6) was ~0.90", being smaller in the Summer (~0.87") than in the Winter (~0.96"). We conclude in general that after 26 years of operations Calar Alto is still a good astronomical site, being a natural candidate for future large aperture optical telescopes.Comment: 16 pages, 5 figures, accepted for publishing in the Publications of Astronomical Society of the Pacific (PASP

Electronic property analysis of O-doped Cu3SbS3

The ternary Cu-Sb-S semiconductors are considered to be sustainable and potential alternative absorber materials in thin film photovoltaic applications. In these compounds, several phases may coexist, albeit in different proportions depending on experimental growth conditions. Additionally, the photovoltaic efficiency could be increased with isoelectronic doping. In this work we analyze the electronic properties of O-doped Cu3SbS3 in two structures: the wittichenite and the skinnerite. We use first-principles within the density functional formalism with two different exchange-correlation potentials. In addition, we estimate the potential of these compounds for photovoltaic applications

Calibrating the projection factor for Galactic Cepheids

The projection factor (p), which converts the radial velocity to pulsational velocity, is an important parameter in the Baade-Wesselink (BW) type analysis and distance scale work. The p-factor is either adopted as a constant or linearly depending on the logarithmic of pulsating periods. The aim of this work is to calibrate the p-factor if a Cepheid has both the BW distance and an independent distance measurement, and examine the p-factor for delta Cephei -- the prototype of classical Cepheids. We calibrated the p-factor for several Galactic Cepheids that have both the latest BW distances and independent distances either from Hipparcos parallaxes or main-sequence fitting distances to Cepheid-hosted stellar clusters. Based on 25 Cepheids, the calibrated p-factor relation is consistent with latest p-factor relation in literature. The calibrated p-factor relation also indicates that this relation may not be linear and may exhibit an intrinsic scatter. We also examined the discrepancy of empirical p-factors for delta Cephei, and found that the reasons for this discrepancy include the disagreement of angular diameters, the treatment of radial velocity data, and the phase interval adopted during the fitting procedure. Finally, we investigated the impact of the input p-factor in two BW methodologies for delta Cephei, and found that different p-factors can be adopted in these BW methodologies and yet result in the same angular diameters.Comment: 6 pages, 6 figures and 2 tables. A&A accepte