2,218 research outputs found
Limits to the presence of transiting circumbinary planets in CoRoT data
The CoRoT mission during its flight-phase 2007-2012 delivered the
light-curves for over 2000 eclipsing binaries. Data from the Kepler mission
have proven the existence of several transiting circumbinary planets. Albeit
light-curves from CoRoT have typically lower precision and shorter coverage,
CoRoT's number of targets is similar to Kepler, and some of the known
circumbinary planets could potentially be detected in CoRoT data as well. The
aim of this work has been a revision of the entire CoRoT data-set for the
presence of circumbinary planets, and the derivation of limits to the
abundances of such planets. We developed a code which removes the light curve
of the eclipsing binaries and searches for quasi-periodic transit-like features
in a light curve after removal of binary eclipses and instrumental features.
The code needs little information on the sample systems and can be used for
other space missions as well, like Kepler, K2, TESS and PLATO. The code is
broad in the requirements leading to detections, but was tuned to deliver an
amount of detections that is manageable in a subsequent, mainly visual,
revision about their nature. In the CoRoT sample we identified three planet
candidates whose transits would have arisen from a single pass across the
central binary. No candidates remained however with transit events from
multiple planetary orbits. We calculated the upper limits for the number of
Jupiter, Saturn and Neptune sized planets in co-planar orbits for different
orbital period ranges. We found that there are much less giant planets in
short-periodic orbits around close binary systems than around single stars.Comment: Accepted for publication in A&A, 11 pages, 4 figures and 4 tables.
Updated to fix error in acknowledgemen
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
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 and for periods of less than 10.5 days, we
can set an upper limit at 0.72 R. 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&
Health and mortality of the elderly: the grade of membership method, classification and determination
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 short-range magnetic order for the t-J model
We present a self-consistent theory of magnetic short-range order based on a
spin-rotation-invariant slave-boson representation of the 2D t-J model. In the
functional-integral scheme, at the nearest-neighbour pair-approximation level,
the bosonized t-J Lagrangian is transformed to a classical Heisenberg model
with an effective (doping-dependent) exchange interaction which takes into
account the interrelation of ``itinerant'' and ``localized'' magnetic
behaviour. Evaluating the theory in the saddle-point approximation, we find a
suppression of antiferromagnetic and incommensurate spiral long-range-ordered
phases in the favour of a paramagnetic phase with pronounced antiferromagnetic
short-range correlations.Comment: 2 pages, 1 Postscript figure, LTpaper.sty, Proc. XXI Int. Conf. on
Low Temp. Phys. Prague 9
Novel potential interacting partners of fibronectin in spontaneous animal model of interstitial cystitis
Feline idiopathic cystitis (FIC) is the only spontaneous animal model for human interstitial cystitis (IC), as both possess a distinctive chronical and relapsing character. Underlying pathomechanisms of both diseases are not clearly established yet. We recently detected increased urine fibronectin levels in FIC cases. The purpose of this study was to gain further insight into the pathogenesis by assessing interacting partners of fibronectin in urine of FIC affected cats. Several candidate proteins were identified via immunoprecipitation and mass spectrometry. Considerable changes in FIC conditions compared to physiological expression of co-purified proteins were detected by Western blot and immunohistochemistry. Compared to controls, complement C4a and thioredoxin were present in higher levels in urine of FIC patients whereas loss of signal intensity was detected in FIC affected tissue. Galectin-7 was exclusively detected in urine of FIC cats, pointing to an important role of this molecule in FIC pathogenesis. Moderate physiological signal intensity of galectin-7 in transitional epithelium shifted to distinct expression in transitional epithelium under pathophysiological conditions. I-FABP expression was reduced in urine and urinary bladder tissue of FIC cats. Additionally, transduction molecules of thioredoxin, NF-κB p65 and p38 MAPK, were examined. In FIC affected tissue, colocalization of thioredoxin and NF-κB p65 could be demonstrated compared to absent coexpression of thioredoxin and p38 MAPK. These considerable changes in expression level and pattern point to an important role for co-purified proteins of fibronectin and thioredoxin-regulated signal transduction pathways in FIC pathogenesis. These results could provide a promising starting point for novel therapeutic approaches in the future
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
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