1,016 research outputs found
Trace Anomaly of Dilaton Coupled Scalars in Two Dimensions
Conformal scalar fields coupled to the dilaton appear naturally in
two-dimensional models of black hole evaporation. We calculate their trace
anomaly. It follows that an RST-type counterterm appears naturally in the
one-loop effective action.Comment: 11 pages, LaTeX2e; submitted to Phys. Rev. Lett., minor change
High-Energy X-ray Imaging of the Pulsar Wind Nebula MSH~15-52: Constraints on Particle Acceleration and Transport
We present the first images of the pulsar wind nebula (PWN) MSH 15-52 in the
hard X-ray band (>8 keV), as measured with the Nuclear Spectroscopic Telescope
Array (NuSTAR). Overall, the morphology of the PWN as measured by NuSTAR in the
3-7 keV band is similar to that seen in Chandra high-resolution imaging.
However, the spatial extent decreases with energy, which we attribute to
synchrotron energy losses as the particles move away from the shock. The
hard-band maps show a relative deficit of counts in the northern region towards
the RCW 89 thermal remnant, with significant asymmetry. We find that the
integrated PWN spectra measured with NuSTAR and Chandra suggest that there is a
spectral break at 6 keV which may be explained by a break in the
synchrotron-emitting electron distribution at ~200 TeV and/or imperfect cross
calibration. We also measure spatially resolved spectra, showing that the
spectrum of the PWN softens away from the central pulsar B1509-58, and that
there exists a roughly sinusoidal variation of spectral hardness in the
azimuthal direction. We discuss the results using particle flow models. We find
non-monotonic structure in the variation with distance of spectral hardness
within 50" of the pulsar moving in the jet direction, which may imply particle
and magnetic-field compression by magnetic hoop stress as previously suggested
for this source. We also present 2-D maps of spectral parameters and find an
interesting shell-like structure in the NH map. We discuss possible origins of
the shell-like structure and their implications.Comment: 15 pages, 9 figures, accepted for publication in Ap
Resolution of the clinical features of tyrosinemia following orthotopic liver transplantation for hepatoma
The clinical history before transplantation and subsequent clinical and biochemical course of 3 children and one adult with hereditary tyrosinemia treated by orthotopic hepatic transplantation is described. All four patients are now free of their previous dietary restrictions and appear to be cured of both their metabolic disease and their hepatic neoplasm. © 1986 Elsevier Science Publishers B.V. All rights reserved
The effects of preeclampsia on signaling to hematopoietic progenitor cells
Background: The role of the microenvironment is important in cell differentiation. The effect of placental disease on the growth and differentiation and hematopoietic stem cells has not been well-studied.
Methods: Enzyme linked immunoassay was used to measure erythropoietin and osteopontin in plasma from umbilical cord blood of children born to normotensive and preeclamptic women. Additionally, CD34+ cells were isolated from umbilical cord blood and grown in complete methylcellulose media. Colony types were identified and enumerated.
Results: Differences in the concentration of erythropoietin in the cord blood between the controls and the preeclamptics approached significance (P = 0.067) using a Mann-Whitney U test. In the plasma of cord blood from children born to normotensive women, the median erythropoietin was 0.186 mIU/mL compared to 1.986 mIU/mL in children of preeclamptic women. We did not find any significant differences in the number and types of colonies; however, there was a trend toward increased BFU-E in the preeclamptic samples. Furthermore, this trend for increased BFU-E colonies was also seen from CD34+ cells isolated from umbilical cord blood of severe preeclamptics compared to mild.
Conclusion: Our preliminary studies suggest that abnormalities in the placenta, such as those found when the mother experiences preeclampsia, may affect the ability of hematopoietic stem cells to grow and differentiate
A first comparison of search methods for gravitational wave bursts using LIGO and Virgo simulated data
We present a comparative study of 6 search methods for gravitational wave
bursts using simulated LIGO and Virgo noise data. The data's spectra were
chosen to follow the design sensitivity of the two 4km LIGO interferometers and
the 3km Virgo interferometer. The searches were applied on replicas of the data
sets to which 8 different signals were injected. Three figures of merit were
employed in this analysis: (a) Receiver Operator Characteristic curves, (b)
necessary signal to noise ratios for the searches to achieve 50 percent and 90
percent efficiencies, and (c) variance and bias for the estimation of the
arrival time of a gravitational wave burst.Comment: GWDAW9 proceeding
First NuSTAR Limits on Quiet Sun Hard X-Ray Transient Events
We present the first results of a search for transient hard X-ray (HXR)
emission in the quiet solar corona with the \textit{Nuclear Spectroscopic
Telescope Array} (\textit{NuSTAR}) satellite. While \textit{NuSTAR} was
designed as an astrophysics mission, it can observe the Sun above 2~keV with
unprecedented sensitivity due to its pioneering use of focusing optics.
\textit{NuSTAR} first observed quiet Sun regions on 2014 November 1, although
out-of-view active regions contributed a notable amount of background in the
form of single-bounce (unfocused) X-rays. We conducted a search for quiet Sun
transient brightenings on time scales of 100 s and set upper limits on emission
in two energy bands. We set 2.5--4~keV limits on brightenings with time scales
of 100 s, expressed as the temperature T and emission measure EM of a thermal
plasma. We also set 10--20~keV limits on brightenings with time scales of 30,
60, and 100 s, expressed as model-independent photon fluxes. The limits in both
bands are well below previous HXR microflare detections, though not low enough
to detect events of equivalent T and EM as quiet Sun brightenings seen in soft
X-ray observations. We expect future observations during solar minimum to
increase the \textit{NuSTAR} sensitivity by over two orders of magnitude due to
higher instrument livetime and reduced solar background.Comment: 11 pages, 7 figures; accepted for publication in The Astrophysical
Journa
Defining normal IgG changes throughout pregnancy
Immunoglobulin G (IgG) is the major serum immunoglobulin, accounting for roughly 75% of all immunoglobulin. IgG is the only class of immunoglobulin that crosses the placenta and it serves as the main immunologic barrier between the fetus and external environments. There has not been a clear consensus on what the normal values of IgG are throughout pregnancy. The aim of this study is to measure serum immunoglobulin G in each trimester of the pregnant female to determine a normal IgG profile throughout all trimesters in normal pregnancy
The First Focused Hard X-ray Images of the Sun with NuSTAR
We present results from the the first campaign of dedicated solar
observations undertaken by the \textit{Nuclear Spectroscopic Telescope ARray}
({\em NuSTAR}) hard X-ray telescope. Designed as an astrophysics mission, {\em
NuSTAR} nonetheless has the capability of directly imaging the Sun at hard
X-ray energies (3~keV) with an increase in sensitivity of at least two
magnitude compared to current non-focusing telescopes. In this paper we
describe the scientific areas where \textit{NuSTAR} will make major
improvements on existing solar measurements. We report on the techniques used
to observe the Sun with \textit{NuSTAR}, their limitations and complications,
and the procedures developed to optimize solar data quality derived from our
experience with the initial solar observations. These first observations are
briefly described, including the measurement of the Fe K-shell lines in a
decaying X-class flare, hard X-ray emission from high in the solar corona, and
full-disk hard X-ray images of the Sun.Comment: 11 pages, accepted to Ap
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