Non-grey dimming events of KIC 8462852 from GTC spectrophotometry

We report ground-based spectrophotometry of KIC 8462852, during its first dimming events since the end of the Kepler mission. The dimmings show a clear colour-signature, and are deeper in visual blue wavelengths than in red ones. The flux loss' wavelength dependency can be described with an \AA ngstr\"om absorption coefficient of $2.19\pm0.45$, which is compatible with absorption by optically thin dust with particle sizes on the order of 0.0015 to 0.15 $\mu$m. These particles would be smaller than is required to be resistant against blow-out by radiation pressure when close to the star. During occultation events, these particles must be replenished on time-scales of days. If dust is indeed the source of KIC 8462852's dimming events, deeper dimming events should show more neutral colours, as is expected from optically thick absorbers.Comment: 5 pages, accepted for A&A letter

Educational attainment and women's environmental mastery in midlife: findings from a British Birth Cohort Study

Using data from 1,184 women in the MRC National Survey of Health and Development, we estimated associations between education and Ryff's environmental mastery scale scores at age 52. Confirmatory factor analysis indicated two subscales, here termed mastery skills and mastery accomplishments. Low education was associated with higher mastery skills. This was partly explained by childhood socioeconomic position, as mastery was lower among those with fathers in the most and least advantaged occupational classes. Education was not associated with mastery accomplishments in unadjusted models. Lower ambitions for family/home were associated with higher mastery accomplishments and may have partly suppressed as an association between education and mastery accomplishments. This study highlights childhood as well as adult correlates of mastery and adds to mounting evidence that higher mastery is not universally found among those who are more educated

Theory of Magnetic Short--Range Order for High-T_c Superconductors

A theory of magnetic short--range order for high--$T_c$ cuprates is presented on the basis of the one--band $t$--$t^{\prime}$--Hubbard model combining the four--field slave--boson functional integral technique with the Bethe cluster method. The ground--state phase diagram evaluated self--consistently at the saddle--point and pair--approximation levels shows the experimentally observed suppression of magnetic long--range order in the favour of a paraphase with antiferromagnetic short--range order. In this phase the uniform static spin susceptibility consists of interrelated itinerant and local parts and increases upon doping up to the transition to the Pauli paraphase. Using realistic values of the Hubbard interaction we obtain the cusp position and the doping dependence of the zero--temperature susceptibility in reasonable agreement with experiments on $\rm La_{2-\delta}Sr_{\delta}CuO_4$.Comment: 3 pages, 2 Postscript figure, Proc. Int. Conf. SCES Zuerich Switzerland Aug. 96, to appear in Physica

Retinal glycoprotein enrichment by concanavalin a enabled identification of novel membrane autoantigen synaptotagmin-1 in equine recurrent uveitis.

Complete knowledge of autoantigen spectra is crucial for understanding pathomechanisms of autoimmune diseases like equine recurrent uveitis (ERU), a spontaneous model for human autoimmune uveitis. While several ERU autoantigens were identified previously, no membrane protein was found so far. As there is a great overlap between glycoproteins and membrane proteins, the aim of this study was to test whether pre-enrichment of retinal glycoproteins by ConA affinity is an effective tool to detect autoantigen candidates among membrane proteins. In 1D Western blots, the glycoprotein preparation allowed detection of IgG reactions to low abundant proteins in sera of ERU patients. Synaptotagmin-1, a Ca2+-sensing protein in synaptic vesicles, was identified as autoantigen candidate from the pre-enriched glycoprotein fraction by mass spectrometry and was validated as a highly prevalent autoantigen by enzyme-linked immunosorbent assay. Analysis of Syt1 expression in retinas of ERU cases showed a downregulation in the majority of ERU affected retinas to 24%. Results pointed to a dysregulation of retinal neurotransmitter release in ERU. Identification of synaptotagmin-1, the first cell membrane associated autoantigen in this spontaneous autoimmune disease, demonstrated that examination of tissue fractions can lead to the discovery of previously undetected novel autoantigens. Further experiments will address its role in ERU pathology

Drude weight and total optical weight in a t-t'-J model

We study the Drude weight D and the total optical weight K for a t-t'-J model on a square lattice that exhibits a metallic phase-modulated antiferromagnetic ground state close to half-filling. Within a suitable 1/N expansion that includes leading quantum-fluctuation effects, D and K are found to increase linearly with small hole doping away from the Mott metal-insulator transition point at half-filling. The slow zero-sound velocity near the latter transition identifies with the velocity of the lower-energy branch of the twofold excitation spectrum. At higher doping values, D and K eventually saturate and then start to decrease. These features are in qualitative agreement with optical conductivity measurements in doped antiferromagnets.Comment: 7 pages, REVTEX file (3 Postscript figures). To appear in J. Phys.: Condens. Mattte

A cool starspot or a second transiting planet in the TrES-1 system?

We investigate the origin of a flux increase found during a transit of TrES-1, observed with the HST. This feature in the HST light curve cannot be attributed to noise and is supposedly a dark area on the stellar surface of the host star eclipsed by TrES-1 during its transit. We investigate the likeliness of two possible hypothesis for its origin: A starspot or a second transiting planet. We made use of several transit observations of TrES-1 from space with the HST and from ground with the IAC-80 telescope. On the basis of these observations we did a statistical study of flux variations in each of the observed events, to investigate if similar flux increases are present in other parts of the data set. The HST observation presents a single clear flux rise during a transit whereas the ground observations led to the detection of two such events but with low significance. In the case of having observed a starspot in the HST data, assuming a central impact between the spot and TrES-1, we would obtain a lower limit for the spot radius of 42000 km. For this radius the spot temperature would be 4690 K, 560 K lower then the stellar surface of 5250 K. For a putative second transiting planet we can set a lower limit for its radius at 0.37 R$_J$ and for periods of less than 10.5 days, we can set an upper limit at 0.72 R$_J$. Assuming a conventional interpretation, then this HST observation constitutes the detection of a starspot. Alternatively, this flux rise might also be caused by an additional transiting planet. The true nature of the origin can be revealed if a wavelength dependency of the flux rise can be shown or discarded with a higher certainty. Additionally, the presence of a second planet can also be detected by radial velocity measurements.Comment: 8 pages, 6 figures, accepted for publication in A&

Blue Dots Team Transits Working Group Review

Transiting planet systems offer an unique opportunity to observationally constrain proposed models of the interiors (radius, composition) and atmospheres (chemistry, dynamics) of extrasolar planets. The spectacular successes of ground-based transit surveys (more than 60 transiting systems known to-date) and the host of multi-wavelength, spectro-photometric follow-up studies, carried out in particular by HST and Spitzer, have paved the way to the next generation of transit search projects, which are currently ongoing (CoRoT, Kepler), or planned. The possibility of detecting and characterizing transiting Earth-sized planets in the habitable zone of their parent stars appears tantalizingly close. In this contribution we briefly review the power of the transit technique for characterization of extrasolar planets, summarize the state of the art of both ground-based and space-borne transit search programs, and illustrate how the science of planetary transits fits within the Blue Dots perspective.Comment: 9 pages, 3 figures, to be published in the proceedings (ASP Conf. Ser.) of the "Pathways Towards Habitable Planets" conference, held in Barcelona (14-18 Sep 2009