2,531 research outputs found
Improvements to the analysis chain and empirical modelling of infrared absorption spectra for the TApIR experiment
Witten Diagrams for Torus Conformal Blocks
We give a holographic description of global conformal blocks in two
dimensional conformal field theory on the sphere and on the torus. We show that
the conformal blocks for one-point functions on the torus can be written as
Witten diagrams in thermal AdS. This is accomplished by deriving a general
conformal Casimir equation for global conformal blocks, and showing that Witten
diagrams obey the same equation. We study the semi-classical limit of n-point
conformal blocks, and show that these equal the action of a network of bulk
world-lines obeying appropriate geodesic equations. We give an alternate
description in the Chern-Simons formulation of 3D gravity, where the conformal
blocks are described by networks of Wilson lines, and argue that these
formulations are equivalent.Comment: 32 pages, 6 figure
A Closer Look at the LkCa 15 Protoplanetary Disk
We present 870 micron observations of dust continuum emission from the LkCa
15 protoplanetary disk at high angular resolution (with a characteristic scale
of 0.25" = 35 AU), obtained with the IRAM Plateau de Bure interferometer and
supplemented by slightly lower resolution observations from the Submillimeter
Array. We fit these data with simple morphological models to characterize the
spectacular ring-like emission structure of this disk. Our analysis indicates
that a small amount of 870 micron dust emission (~5 mJy) originates inside a
large (40-50 AU radius) low optical depth cavity. This result can be
interpreted either in the context of an abrupt decrease by a factor of ~5 in
the radial distribution of millimeter-sized dust grains or as indirect evidence
for a gap in the disk, in agreement with previous inferences from the
unresolved infrared spectrum and scattered light images. A preliminary model
focused on the latter possibility suggests the presence of a low-mass
(planetary) companion, having properties commensurate with those inferred from
the recent discovery of LkCa 15b.Comment: in press at ApJ Letter
Test validation, method comparison and reference range for the measurement of β-hydroxybutyrate in peripheral blood samples
Introduction: The measurement of β-hydroxybutyrate (βOHB) concentrations is a corner stone of the diagnosis of diabetic ketoacidosis and other ketonic states. The aim of this study was to perform a validation of a peripheral blood βOHB assay (Randox) on a Roche cobas c502 analyser and to establish a βOHB reference range for the validated assay.
Materials and methods: Precision, linearity and limit of detection and blank (LoD, LoB) were determined according to Clinical and Laboratory
Standards Institute (CLSI) EP05-A3, EP 06-A and EP17-A2 guidelines, using commercial control material and residual patient sample pools. As method comparison, for 190 semi-quantitative measurements of urine ketones we determined the corresponding βOHB blood concentration. The reference range was based on the CLSI C28-A3 guideline, using 304 randomly selected serum samples from population based German National Cohort (GNC) study.
Results: Coefficients of variation for the validated assay ranged from 1.5% for high concentrations (3.1 mmol/L) to 6.5% for low concentrations (0.1 mmol/L). Detection capacity was LoB = 0.011 mmol/L and LoD = 0.037 mmol/L. Linearity of the assay ranged from 0.10 to 3.95 mmol/L. The agreement between the semi-quantitative urine ketone test and the βOHB blood test was moderate (Kappa = 0.66). The obtained 95% serum reference range was estimated as 0.02 to 0.28 mmol/l βOHB.
Conclusions: The Ranbut βOHB assay showed good precision and analytical performance. Our results confirm that βOHB measurement in peripheral blood is indeed a preferable alternative to the semi-quantitative measurement of urine ketones
Nuclear ashes and outflow in the eruptive star Nova Vul 1670
CK Vulpeculae was observed in outburst in 1670-16721, but no counterpart was
seen until 1982, when a bipolar nebula was found at its location. Historically,
CK Vul has been considered to be a nova (Nova Vul 1670), but a similarity to
'red transients', which are more luminous than classical nova and thought to be
the result of stellar collisions, has re-opened the question of CK Vul's
status. Red transients cool to resemble late M-type stars, surrounded by
circumstellar material rich in molecules and dust. No stellar source has been
seen in CK Vul, though a radio continuum source was identified at the expansion
centre of the nebula. Here we report CK Vul is surrounded by chemically rich
molecular gas with peculiar isotopic ratios, as well as dust. The chemical
composition cannot be reconciled with a nova or indeed any other known
explosion. In addition, the mass of the surrounding gas is too high for a nova,
though the conversion from observations of CO to a total mass is uncertain. We
conclude that CK Vul is best explained as the remnant of a merger of two stars.Comment: an older version of an article that appeared in Nature; published in
Nature, online version, 23 March 201
Optimization and quantification of the systematic effects of a rolling circle filter for spectral pre-processing
Gas dynamics in the inner few AU around the Herbig B[e] star MWC297: Indications of a disk wind from kinematic modeling and velocity-resolved interferometric imaging
We present near-infrared AMBER (R = 12, 000) and CRIRES (R = 100, 000)
observations of the Herbig B[e] star MWC297 in the hydrogen Br-gamma-line.
Using the VLTI unit telescopes, we obtained a uv-coverage suitable for aperture
synthesis imaging. We interpret our velocity-resolved images as well as the
derived two-dimensional photocenter displacement vectors, and fit kinematic
models to our visibility and phase data in order to constrain the gas velocity
field on sub-AU scales. The measured continuum visibilities constrain the
orientation of the near-infrared-emitting dust disk, where we determine that
the disk major axis is oriented along a position angle of 99.6 +/- 4.8 degrees.
The near-infrared continuum emission is 3.6 times more compact than the
expected dust-sublimation radius, possibly indicating the presence of highly
refractory dust grains or optically thick gas emission in the inner disk. Our
velocity-resolved channel maps and moment maps reveal the motion of the
Br-gamma-emitting gas in six velocity channels, marking the first time that
kinematic effects in the sub-AU inner regions of a protoplanetary disk could be
directly imaged. We find a rotation-dominated velocity field, where the blue-
and red-shifted emissions are displaced along a position angle of 24 +/- 3
degrees and the approaching part of the disk is offset west of the star. The
visibility drop in the line as well as the strong non-zero phase signals can be
modeled reasonably well assuming a Keplerian velocity field, although this
model is not able to explain the 3 sigma difference that we measure between the
position angle of the line photocenters and the position angle of the dust
disk. We find that the fit can be improved by adding an outflowing component to
the velocity field, as inspired by a magneto-centrifugal disk-wind scenario.Comment: 15 pages, 13 Figure
On the nature of the Herbig B[e] star binary system V921 Scorpii: Geometry and kinematics of the circumprimary disk on sub-AU scales
V921 Scorpii is a close binary system (separation 0.025") showing the
B[e]-phenomenon. The system is surrounded by an enigmatic bipolar nebula, which
might have been shaped by episodic mass-loss events, possibly triggered by
dynamical interactions between the companion and the circumprimary disk (Kraus
et al. 2012a). In this paper, we investigate the spatial structure and
kinematics of the circumprimary disk, with the aim to obtain new insights into
the still strongly debated evolutionary stage. For this purpose, we combine,
for the first time, infrared spectro-interferometry (VLTI/AMBER, R=12,000) and
spectro-astrometry (VLT/CRIRES, R=100,000), which allows us to study the
AU-scale distribution of circumstellar gas and dust with an unprecedented
velocity resolution of 3 km*s^-1. Using a model-independent photocenter
analysis technique, we find that the Br-gamma-line emission rotates in the same
plane as the dust disk. We can reproduce the wavelength-differential
visibilities and phases and the double-peaked line profile using a
Keplerian-rotating disk model. The derived mass of the central star is
5.4+/-0.4 M_sun*(d/1150 pc), which is considerably lower than expected from the
spectral classification, suggesting that V921 Sco might be more distant (d
approx 2kpc) than commonly assumed. Using the geometric information provided by
our Br-gamma spectro-interferometric data and Paschen, Brackett, and Pfund line
decrement measurements in 61 hydrogen recombination line transitions, we derive
the density of the line-emitting gas (N_e=2...6*10^19 m^-3). Given that our
measurements can be reproduced with a Keplerian velocity field without
outflowing velocity component and the non-detection of age-indicating
spectroscopic diagnostics, our study provides new evidence for the
pre-main-sequence nature of V921 Sco.Comment: 17 pages, 11 figures, 3 tables, accepted by Ap
General unifying features of controlled quantum phenomena
Many proposals have been put forth for controlling quantum phenomena,
including open-loop, adaptive feedback, and real-time feedback control. Each of
these approaches has been viewed as operationally, and even physically,
distinct from the others. This work shows that all such scenarios inherently
share the same fundamental control features residing in the topology of the
landscape relating the target physical observable to the applied controls. This
unified foundation may provide a basis for development of hybrid control
schemes that would combine the advantages of the existing approaches to achieve
the best overall performance.Comment: The published version (includes the supplementary material
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