Interstellar 12C/13C from CH+ absorption lines: Results from an extended survey

The 12C/13C isotope ratio in the interstellar medium (ISM), and its evolution with time, is an important tracer of stellar yields. Spatial variations of this ratio can be used to study mixing in the ISM. We want to determine this ratio and its spatial variations in the local ISM from CH+ absorption lines in the optical towards early-type stars. The aim is to determine the average value for the local ISM and study possible spatial variations. We observed a large number of early-type stars with Feros to extend the sample of suitable target stars for CH+ isotope studies. The best suited targets were observed with Uves with higher signal-to-noise ratio and spectral resolution to determine the isotope ratio from the interstellar CH+ lines. This study significantly expands the number of 13CH+ detections. We find an average ratio of = 76.27 +- 1.94 or, for f = 1/R, = (120.46 +- 3.02) 10^{-4}. The scatter in f is 6.3 sigma(). This findings strengthens the case for chemical inhomogeneity in the local ISM, with important implications for the mixing in the ISM. Given the large scatter, the present-day value in the ISM is not significantly larger than the solar value, which corresponds to the local value 4.5 Gyr ago.Comment: 11 pages, 16 figures, 2 tables, A&A submitte

SN 2005 gj: Evidence for LBV supernovae progenitors?

There has been mounting observational evidence in favour of Luminous Blue Variables (LBVs) being the direct progenitors of supernovae. Here we present possibly the most convincing evidence yet for such progenitors. We find multiple absorption component P-Cygni profiles of hydrogen and helium in the spectrum of SN 2005gj, which we interpret as being an imprint of the progenitors mass-loss history. Such profiles have previously only been detected in Luminous Blue Variables. This striking resemblance of the profiles, along with wind velocities and periods consistent with LBV's leads us to connect SN 2005gj to an LBV progenitor.Comment: Accepted as a letter to A&A, 4 pages,3 figure

Using eye movements to assess brain function in mice

AbstractExamining eye movements is an important part of the neurological evaluation of humans; the distribution of the neural circuits that control these movements is such that they are disrupted—often in highly characteristic fashions—by many disease processes. Technical advances have made it possible to measure accurately the eye movements of mice, so it is now possible to use the detective power of eye movement recording to characterize neurological dysfunction in genetically altered strains. Here we introduce analytical tools used in ocular motor research and demonstrate their ability to reveal disorders of the visual pathways, inner ear, and cerebellum

The (B0+?)+O6 system FN CMa: A case for tidal-pulsational interaction?

FN CMa is visually double with a separation of about 0.6arcsec. Sixty high-cadence VLT/UVES spectra permit the A and B components to be disentangled, as the relative contribution of each star to the total light entering the spectrograph fluctuates between exposures due to changes in seeing. Component A exhibits rapid line-profile variations, leading us to attribute the photometric variability seen by HIPPARCOS (with a derived P=0.08866d) to this component. From a total of 122 archival and new echelle spectra it is shown that component A is an SB1 binary with an orbital period of 117.55 days. The eccentricity of 0.6 may result in tidal modulation of the pulsation(s) of component Aa.Comment: 2 pages, 1 figure, IAUS 272 - Active OB Stars: Structure, Evolution, Mass Loss and Critical Limit

Calculation of electrostatic fields using quasi-Green's functions: application to the hybrid Penning trap.

Penning traps offer unique possibilities for storing, manipulating and investigating charged particles with high sensitivity and accuracy. The widespread applications of Penning traps in physics and chemistry comprise e.g. mass spectrometry, laser spectroscopy, measurements of electronic and nuclear magnetic moments, chemical sample analysis and reaction studies. We have developed a method, based on the Green's function approach, which allows for the analytical calculation of the electrostatic properties of a Penning trap with arbitrary electrodes. The ansatz features an extension of Dirichlet's problem to nontrivial geometries and leads to an analytical solution of the Laplace equation. As an example we discuss the toroidal hybrid Penning trap designed for our planned measurements of the magnetic moment of the (anti)proton. As in the case of cylindrical Penning traps, it is possible to optimize the properties of the electric trapping fields, which is mandatory for high-precision experiments with single charged particles. Of particular interest are the anharmonicity compensation, orthogonality and optimum adjustment of frequency shifts by the continuous SternGerlach effect in a quantum jump spectrometer. The mathematical formalism developed goes beyond the mere design of novel Penning traps and has potential applications in other fields of physics and engineering

SOFT: A synthetic synchrotron diagnostic for runaway electrons

Improved understanding of the dynamics of runaway electrons can be obtained by measurement and interpretation of their synchrotron radiation emission. Models for synchrotron radiation emitted by relativistic electrons are well established, but the question of how various geometric effects -- such as magnetic field inhomogeneity and camera placement -- influence the synchrotron measurements and their interpretation remains open. In this paper we address this issue by simulating synchrotron images and spectra using the new synthetic synchrotron diagnostic tool SOFT (Synchrotron-detecting Orbit Following Toolkit). We identify the key parameters influencing the synchrotron radiation spot and present scans in those parameters. Using a runaway electron distribution function obtained by Fokker-Planck simulations for parameters from an Alcator C-Mod discharge, we demonstrate that the corresponding synchrotron image is well-reproduced by SOFT simulations, and we explain how it can be understood in terms of the parameter scans. Geometric effects are shown to significantly influence the synchrotron spectrum, and we show that inherent inconsistencies in a simple emission model (i.e. not modeling detection) can lead to incorrect interpretation of the images.Comment: 24 pages, 12 figure

What do web-use skill differences imply for online health information searches?

BACKGROUND: Online health information is of variable and often low scientific quality. In particular, elderly less-educated populations are said to struggle in accessing quality online information (digital divide). Little is known about (1) how their online behavior differs from that of younger, more-educated, and more-frequent Web users, and (2) how the older population may be supported in accessing good-quality online health information. OBJECTIVE: To specify the digital divide between skilled and less-skilled Web users, we assessed qualitative differences in technical skills, cognitive strategies, and attitudes toward online health information. Based on these findings, we identified educational and technological interventions to help Web users find and access good-quality online health information. METHODS: We asked 22 native German-speaking adults to search for health information online. The skilled cohort consisted of 10 participants who were younger than 30 years of age, had a higher level of education, and were more experienced using the Web than 12 participants in the less-skilled cohort, who were at least 50 years of age. We observed online health information searches to specify differences in technical skills and analyzed concurrent verbal protocols to identify health information seekers’ cognitive strategies and attitudes. RESULTS: Our main findings relate to (1) attitudes: health information seekers in both cohorts doubted the quality of information retrieved online; among poorly skilled seekers, this was mainly because they doubted their skills to navigate vast amounts of information; once a website was accessed, quality concerns disappeared in both cohorts, (2) technical skills: skilled Web users effectively filtered information according to search intentions and data sources; less-skilled users were easily distracted by unrelated information, and (3) cognitive strategies: skilled Web users searched to inform themselves; less-skilled users searched to confirm their health-related opinions such as “vaccinations are harmful.” Independent of Web-use skills, most participants stopped a search once they had found the first piece of evidence satisfying search intentions, rather than according to quality criteria. CONCLUSIONS: Findings related to Web-use skills differences suggest two classes of interventions to facilitate access to good-quality online health information. Challenges related to findings (1) and (2) should be remedied by improving people’s basic Web-use skills. In particular, Web users should be taught how to avoid information overload by generating specific search terms and to avoid low-quality information by requesting results from trusted websites only. Problems related to finding (3) may be remedied by visually labeling search engine results according to quality criteria