1,475 research outputs found
Local Gromov-Witten Invariants are Log Invariants
We prove a simple equivalence between the virtual count of rational curves in
the total space of an anti-nef line bundle and the virtual count of rational
curves maximally tangent to a smooth section of the dual line bundle. We
conjecture a generalization to direct sums of line bundles.Comment: 15 pages, version accepted for publication in Advances in Mathematic
Multi-conjugated adaptive optics imaging of distant galaxies -- A comparison of Gemini/GSAOI and VLT/HAWK-I data
Multi-conjugated adaptive optics (MCAO) yield nearly diffraction-limited
images at 2m wavelengths. Currently, GeMS/GSAOI at Gemini South is the
only MCAO facility instrument at an 8m telescope. Using real data and for the
first time, we investigate the gain in depth and S/N when MCAO is employed for
-band observations of distant galaxies. Our analysis is based on the
Frontier Fields cluster MACS J0416.1-2403, observed with GeMS/GSAOI (near
diffraction-limited) and compared against VLT/HAWK-I (natural seeing) data.
Using galaxy number counts, we show that the substantially increased thermal
background and lower optical throughput of the MCAO unit are fully compensated
for by the wavefront correction, because the galaxy images can be measured in
smaller apertures with less sky noise. We also performed a direct comparison of
the signal-to-noise ratios (S/N) of sources detected in both data sets. For
objects with intrinsic angular sizes corresponding to half the HAWK-I image
seeing, the gain in S/N is 40 per cent. Even smaller objects experience a boost
in S/N by a up to a factor of 2.5 despite our suboptimal natural guide star
configuration. The depth of the near diffraction limited images is more
difficult to quantify than that of seeing limited images, due to a strong
dependence on the intrinsic source profiles. Our results emphasize the
importance of cooled MCAO systems for -band observations with
future, extremely large telescopes.Comment: 7 pages, 7 figures. Accepted for publication in MNRA
Log BPS numbers of log Calabi-Yau surfaces
Let be a log Calabi-Yau surface pair with a smooth divisor. We
define new conjecturally integer-valued counts of -curves in
. These log BPS numbers are derived from genus 0 log Gromov-Witten
invariants of maximal tangency along via a formula analogous to the
multiple cover formula for disk counts. A conjectural relationship to genus 0
local BPS numbers is described and verified for del Pezzo surfaces and curve
classes of arithmetic genus up to 2. We state a number of conjectures and
provide computational evidence.Comment: 49 pages, 2 figure
Extra-adrenal regeneration of glucocorticoids by 11beta-hydroxysteroid dehydrogenase type 1:physiological regulator and pharmacological target for energy partitioning
The major glucocorticoid in man, cortisol, plays important roles in regulating fuel metabolism, energy partitioning and body fat distribution. In addition to the control of cortisol levels in blood by the hypothalamic-pituitary-adrenal axis, intracellular cortisol levels within target tissues can be controlled by local enzymes. 11Beta-hydroxysteroid dehydrogenase type 1 (11beta-HSD1) catalyses the regeneration of active cortisol from inert cortisone, thereby amplifying cortisol levels and glucocorticoid receptor activation in adipose tissue, liver and other tissues. 11Beta-HSD1 is under complex tissue-specific regulation and there is evidence that it adjusts local cortisol concentrations independently of the plasma cortisol concentrations, e.g. in response to changes in diet. In obesity 11beta-HSD1 mRNA and activity in adipose tissue are increased. The mechanism of this up-regulation remains uncertain; polymorphisms in the HSD11B1 gene have been associated with metabolic complications of obesity, including hypertension and type 2 diabetes, but not with obesity per se. Extensive data have been obtained in mice with transgenic over-expression of 11beta-HSD1 in liver and adipocytes, targeted deletion of 11beta-HSD1, and using novel selective 11beta-HSD1 inhibitors; these data support the use of 11beta-HSD1 inhibitors to lower intracellular glucocorticoid levels and treat both obesity and its metabolic complications. Moreover, in human subjects the non-selective 'prototype' inhibitor carbenoxolone enhances insulin sensitivity. Results of clinical studies with novel potent selective 11beta-HSD1 inhibitors are therefore eagerly awaited. The present article focuses on the physiological role of glucocorticoids in regulating energy partitioning, and the evidence that this process is modulated by 11beta-HSD1 in human subjects
The conceptus induces a switch in protein expression and activities of superoxide dismutase 1 and 2 in the sheep endometrium during early pregnancy
Acknowledgements We thank Philippe Bolifraud (INRA, France), Krawiec Angele, Sandra Grange, Laurence Puillet-Anselme (CHU Grenoble, France) and Margaret Fraser (Aberdeen, UK) for their expert technical assistance. The authors also thank the staff of the sheep sheds of Jouy-en-Josas (INRA, France). The authors would also like to thank the anonymous reviewers for their close examination of this article and their useful comments. Funding This research did not receive any specific grant from any funding agency in the public, commercial or not-for-profit sector.Peer reviewedPostprin
First performance of the gems + gmos system. Part1. Imaging
During the commissioning of the Gemini MCAO System (GeMS), we had the
opportunity to obtain data with the Gemini Multi-Object Spectrograph (GMOS),
the most utilised instrument at Gemini South Observatory, in March and May
2012. Several globular clusters were observed in imaging mode that allowed us
to study the performance of this new and untested combination. GMOS is a
visible instrument, hence pushing MCAO toward the visible.We report here on the
results with the GMOS instruments, derive photometric performance in term of
Full Width Half Maximum (FWHM) and throughput. In most of the cases, we
obtained an improvement factor of at least 2 against the natural seeing. This
result also depends on the Natural Guide Star constellation selected for the
observations and we then study the impact of the guide star selection on the
FWHM performance.We also derive a first astrometric analysis showing that the
GeMS+GMOS system provide an absolute astrometric precision better than 8mas and
a relative astrometric precision lower than 50 mas.Comment: 13 pages, 11 figures, accepted for publication in MNRAS on March 23rd
201
Coronagraphic Low Order Wave Front Sensor : post-processing sensitivity enhancer for high performance coronagraphs
Detection and characterization of exoplanets by direct imaging requires a
coronagraph designed to deliver high contrast at small angular separation. To
achieve this, an accurate control of low order aberrations, such as pointing
and focus errors, is essential to optimize coronagraphic rejection and avoid
the possible confusion between exoplanet light and coronagraphic leaks in the
science image. Simulations and laboratory prototyping have shown that a
Coronagraphic Low Order Wave-Front Sensor (CLOWFS), using a single defocused
image of a reflective focal plane ring, can be used to control tip-tilt to an
accuracy of 10^{-3} lambda/D. This paper demonstrates that the data acquired by
CLOWFS can also be used in post-processing to calibrate residual coronagraphic
leaks from the science image. Using both the CLOWFS camera and the science
camera in the system, we quantify the accuracy of the method and its ability to
successfully remove light due to low order errors from the science image. We
also report the implementation and performance of the CLOWFS on the Subaru
Coronagraphic Extreme AO (SCExAO) system and its expected on-sky performance.
In the laboratory, with a level of disturbance similar to what is encountered
in a post Adaptive Optics beam, CLOWFS post-processing has achieved speckle
calibration to 1/300 of the raw speckle level. This is about 40 times better
than could be done with an idealized PSF subtraction that does not rely on
CLOWFS.Comment: 10 pages, 7 figures, accepted for publication in PAS
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