1,001 research outputs found
Weak Gravitational Lensing of High-Redshift 21 cm Power Spectra
We describe the effects of weak gravitational lensing by cosmological large
scale structure on the diffuse emission of 21 centimeter radiation from neutral
hydrogen at high redshifts during the era of reionization. The ability to
observe radial information through the frequency, and thus three-dimensional
regions of the background radiation at different redshifts, suggests that 21 cm
studies may provide a useful context for studying weak lensing effects. We
focus on the gravitational lensing effects on both the angular power spectra
and the intrinsic, three-dimensional power spectra. We present a new approach
for calculating the weak lensing signature based on integrating differential
Fourier-space shells of the deflection field and approximating the
magnification matrix. This method is applied to reionization models of the 21
cm spectra up to small angular scales over a range in redshift. The effect on
the angular power spectrum is typically < 1% on small angular scales, and very
small on scales corresponding to the feature imprinted by reionization bubbles,
due to the near-scale invariance of the angular power spectrum of the 21 cm
signal on these scales. We describe the expected effect of weak lensing on
three-dimensional 21 cm power spectra, and show that lensing creates aspherical
perturbations to the intrinsic power spectrum which depend on the polar angle
of the wavevector. The effect on the 3D power spectrum is < 1% on scales k <
0.1 h/Mpc, but can be > 1% for highly inclined modes for k > 1 h/Mpc. The
angular variation of the lensing effect on these scales is well described by a
quartic polynomial in the cosine of the polar angle. The detection of the
gravitational lensing effects on 21 cm power spectra will require very
sensitive, high resolution observations by future low-frequency radio arrays.Comment: 18 pages, 10 figures; submitting to Ap
Associations between social support, psychological well-being, decision making, empowerment, infant and young child feeding, and nutritional status in Ugandan children ages 0 to 24months
Maternal capabilitiesqualities of mothers that enable them to leverage skills and resources into child healthhold potential influence over mother\u27s adoption of child caring practices, including infant and young child feeding. We developed a survey (n=195) that assessed the associations of 4 dimensions of maternal capabilities (social support, psychological health, decision making, and empowerment) with mothers\u27 infant and young child feeding practices and children\u27s nutritional status in Uganda. Maternal responses were converted to categorical subscales and an overall index. Scale reliability coefficients were moderate to strong ( range=0.49 to 0.80). Mothers with higher social support scores were more likely to feed children according to the minimum meal frequency (odds ratio [OR] [95% confidence interval (CI)]=1.38 [1.10, 1.73]), dietary diversity (OR [95% CI]=1.56 [1.15, 2.11]), iron rich foods, (OR [95% CI]=1.47 [1.14, 1.89]), and minimally acceptable diet (OR [95% CI]=1.55 [1.10, 2.21]) indicators. Empowerment was associated with a greater likelihood of feeding a minimally diverse and acceptable diet. The maternal capabilities index was significantly associated with feeding the minimum number of times per day (OR [95% CI]=1.29 [1.03, 1.63]), dietary diversity (OR [95% CI]=1.44 [1.06, 1.94]), and minimally acceptable diet (OR [95% CI]=1.43 [1.01, 2.01]). Mothers with higher psychological satisfaction were more likely to have a stunted child (OR [95% CI]=1.31 [1.06, 1.63]). No other associations between the capabilities scales and child growth were significant. Strengthening social support for mothers and expanding overall maternal capabilities hold potential for addressing important underlying determinants of child feeding in the Ugandan context
Entanglement of bosonic modes of nonplanar molecules
Entanglement of bosonic modes of material oscillators is studied in the
context of two bilinearly coupled, nonlinear oscillators. These oscillators are
realizable in the vibrational-cum-bending motions of C-H bonds in
dihalomethanes. The bilinear coupling gives rise to invariant subspaces in the
Hilbert space of the two oscillators. The number of separable states in any
invariant subspace is one more than the dimension of the space. The dynamics of
the oscillators when the initial state belongs to an invariant subspace is
studied. In particular, the dynamics of the system when the initial state is
such that the total energy is concentrated in one of the modes is studied and
compared with the evolution of the system when the initial state is such
wherein the modes share the total energy. The dynamics of quantities such as
entropy, mean of number of quanta in the two modes and variances in the
quadratures of the two modes are studied. Possibility of generating maximally
entangled states is indicated.Comment: 21 pages, 6 figure
On the maximum stellar rotation to form a black hole without an accompanying luminous transient
The collapse of a massive star with low angular momentum content is commonly
argued to result in the formation of a black hole without an accompanying
bright transient. Our goal in this Letter is to understand the flow in and
around a newly-formed black hole, involving accretion and rotation, via general
relativistic hydrodynamics simulations aimed at studying the conditions under
which infalling material can accrete without forming a centrifugally supported
structure and, as a result, generate no effective feedback. If the feedback
from the black hole is, on the other hand, significant, the collapse would be
halted and we suggest that the event is likely to be followed by a bright
transient. We find that feedback is only efficient if the specific angular
momentum of the infalling material at the innermost stable circular orbit
exceeds that of geodesic circular flow at that radius by at least . We use the results of our simulations to constrain the maximal stellar
rotation rates of the disappearing massive progenitors PHL293B-LBV and
N6946-BH1, and to provide an estimate of the overall rate of disappearing
massive stars. We find that about a few percent of single O-type stars with
measured rotational velocities are expected to spin below the critical value
before collapse and are thus predicted to vanish without a trace.Comment: 9 pages, 5 figures, accepted at ApJ Letter
Entanglement production in a chaotic quantum dot
It has recently been shown theoretically that elastic scattering in the Fermi
sea produces quantum mechanically entangled states. The mechanism is similar to
entanglement by a beam splitter in optics, but a key distinction is that the
electronic mechanism works even if the source is in local thermal equilibrium.
An experimental realization was proposed using tunneling between two edge
channels in a strong magnetic field. Here we investigate a low-magnetic field
alternative, using multiple scattering in a quantum dot. Two pairs of
single-channel point contacts define a pair of qubits. If the scattering is
chaotic, a universal statistical description of the entanglement production
(quantified by the concurrence) is possible. The mean concurrence turns out to
be almost independent on whether time-reversal symmetry is broken or not. We
show how the concurrence can be extracted from a Bell inequality using
low-frequency noise measurements, without requiring the tunneling assumption of
earlier work.Comment: 12 pages, 2 figures, Kluwer style file include
Management of Thyroid Dysfunction during Pregnancy and Postpartum: An Endocrine Society Clinical Practice Guideline
Objective: The aim was to update the guidelines for the management of thyroid dysfunction during pregnancy and postpartum published previously in 2007. A summary of changes between the 2007 and 2012 version is identified in the Supplemental Data (published on The Endocrine Society\u27s Journals Online web site at http://jcem.endojournals.org).
Evidence: This evidence-based guideline was developed according to the U.S. Preventive Service Task Force, grading items level A, B, C, D, or I, on the basis of the strength of evidence and magnitude of net benefit (benefits minus harms) as well as the Grading of Recommendations, Assessment, Development, and Evaluation (GRADE) system to describe both the strength of recommendations and the quality of evidence.
Consensus Process: The guideline was developed through a series of e-mails, conference calls, and one face-to-face meeting. An initial draft was prepared by the Task Force, with the help of a medical writer, and reviewed and commented on by members of The Endocrine Society, Asia and Oceania Thyroid Association, and the Latin American Thyroid Society. A second draft was reviewed and approved by The Endocrine Society Council. At each stage of review, the Task Force received written comments and incorporated substantive changes.
Conclusions: Practice guidelines are presented for diagnosis and treatment of patients with thyroid-related medical issues just before and during pregnancy and in the postpartum interval. These include evidence-based approaches to assessing the cause of the condition, treating it, and managing hypothyroidism, hyperthyroidism, gestational hyperthyroidism, thyroid autoimmunity, thyroid tumors, iodine nutrition, postpartum thyroiditis, and screening for thyroid disease. Indications and side effects of therapeutic agents used in treatment are also presented
Sialadenosis in Patients with Advanced Liver Disease
Sialadenosis (sialosis) has been associated most often with alcoholic liver disease and alcoholic cirrhosis, but a number of nutritional deficiencies, diabetes, and bulimia have also been reported to result in sialadenosis. The aim of this study was to determine the prevalence of sialadenosis in patients with advanced liver disease. Patients in the study group consisted of 300 candidates for liver transplantation. Types of liver disease in subjects with clinical evidence of sialadenosis were compared with diagnoses in cases who had no manifestations of sialadenosis. The data were analyzed for significant association. Sialadenosis was found in 28 of the 300 subjects (9.3%). Among these 28 cases, 11 (39.3%) had alcoholic cirrhosis. The remaining 17 (60.7%) had eight other types of liver disease. There was no significant association between sialadenosis and alcoholic cirrhosis (P = 0.389). These findings suggest that both alcoholic and non-alcoholic cirrhosis may lead to the development of sialadenosis. Advanced liver disease is accompanied by multiple nutritional deficiencies which may be exacerbated by alcohol. Similar metabolic abnormalities may occur in patients with diabetes or bulimia. Malnutrition has been associated with autonomic neuropathy, the pathogenic mechanism that has been proposed for sialadenosis
Massive Black Hole Binary Inspirals: Results from the LISA Parameter Estimation Taskforce
The LISA Parameter Estimation (LISAPE) Taskforce was formed in September 2007
to provide the LISA Project with vetted codes, source distribution models, and
results related to parameter estimation. The Taskforce's goal is to be able to
quickly calculate the impact of any mission design changes on LISA's science
capabilities, based on reasonable estimates of the distribution of
astrophysical sources in the universe. This paper describes our Taskforce's
work on massive black-hole binaries (MBHBs). Given present uncertainties in the
formation history of MBHBs, we adopt four different population models, based on
(i) whether the initial black-hole seeds are small or large, and (ii) whether
accretion is efficient or inefficient at spinning up the holes. We compare four
largely independent codes for calculating LISA's parameter-estimation
capabilities. All codes are based on the Fisher-matrix approximation, but in
the past they used somewhat different signal models, source parametrizations
and noise curves. We show that once these differences are removed, the four
codes give results in extremely close agreement with each other. Using a code
that includes both spin precession and higher harmonics in the
gravitational-wave signal, we carry out Monte Carlo simulations and determine
the number of events that can be detected and accurately localized in our four
population models.Comment: 14 pages, 2 figures, 5 tables, minor changes to match version to be
published in the proceedings of the 7th LISA Symposium. For more information
see the Taskforce's wiki at http://www.tapir.caltech.edu/dokuwiki/lisape:hom
- …