Relative Flux Calibration of Keck HIRES Echelle Spectra

We describe a new method to calibrate the relative flux levels in spectra from the HIRES echelle spectrograph on the Keck-I telescope. Standard data reduction techniques that transfer the instrument response between HIRES integrations leave errors in the flux of 5 - 10%, because the effective response varies. The flux errors are most severe near the ends of each spectral order, where there can be discontinuous jumps. The source of these errors is uncertain, but may include changes in the vignetting connected to the optical alignment. Our new flux calibration method uses a calibrated reference spectrum of each target to calibrate individual HIRES integrations. We determine the instrument response independently for each integration, and hence we avoid the need to transfer the instrument response between HIRES integrations. The procedure can be applied to any HIRES spectrum, or any other spectrum. While the accuracy of the method depends upon many factors, we have been able to flux calibrate a HIRES spectrum to 1% over scales of 200 A that include order joins. We illustrate the method with spectra of Q1243+3047 towards which we have measured the deuterium to hydrogen abundance ratio.Comment: 24 pages, 17 figures, submitted to PAS

Rap1 is a main regulator of Adherens junction remodelling in the fly retina

During epithelial cell polarisation, the conserved apical and lateral polarity proteins set up the position of the Zonula Adherens (ZA), which consists of a circumferential belt of Adherens Junction (AJ) material, and thus define the apical and lateral domains of the cell. During my thesis, I have tried to uncover the genes that are involved in the transcriptional control of polarity remodelling and ZA morphogenesis during development. To this end, I used the genetically amenable Drosophila retina to carry out transcriptional profiling at the onset of photoreceptor polarity remodelling. With this approach, I was able to uncover several genes that seem to be regulated during polarity remodelling, including the zinc finger transcription factor ovo, which might regulate photoreceptor morphogenesis through regulation of the actin cytoskeleton. In addition to the transcriptional control of epithelial polarity, I made use of the fly photoreceptor to uncover new cellular and molecular pathways that promote AJ morphogenesis during ZA assembly. Using a candidate-based approach, I identified the small GTPase protein Rap1 as an important regulator of AJ morphogenesis, through stabilisation of DE-Cad at the developing ZA. In this context, I found that rap1 functions with the p21-activated kinase pak4 to promote AJ material accumulation at the developing ZA. Finally, in order to discover new genes and mechanisms that might link rap1 to the epithelial gene network, I made use of rap1 RNAi, to conduct a large-scale genetic modifier screen. This genetic screen led to the identification of several ubiquitin-related genes that genetically interact with rap1 and therefore might be involved in rap1-dependent polarity remodelling and ZA morphogenesis

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

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

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

Individual tracking reveals long-distance flight-path control in a nocturnally migrating moth

Each year, trillions of insects make long-range seasonal migrations. These movements are relatively well understood at a population level, but how individual insects achieve them remains elusive. Behavioral responses to conditions en route are little studied, primarily owing to the challenges of tracking individual insects. Using a light aircraft and individual radio tracking, we show that nocturnally migrating death's-head hawkmoths maintain control of their flight trajectories over long distances. The moths did not just fly with favorable tailwinds; during a given night, they also adjusted for head and crosswinds to precisely hold course. This behavior indicates that the moths use a sophisticated internal compass to maintain seasonally beneficial migratory trajectories independent of wind conditions, illuminating how insects traverse long distances to take advantage of seasonal resources

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