22,249 research outputs found
A Reinvestigation of Moving Punctured Black Holes with a New Code
We report on our code, in which the moving puncture method is applied and an
adaptive/fixed mesh refinement is implemented, and on its preliminary
performance on black hole simulations. Based on the BSSN formulation,
up-to-date gauge conditions and the modifications of the formulation are also
implemented and tested. In this work we present our primary results about the
simulation of a single static black hole, of a moving single black hole, and of
the head-on collision of a binary black hole system. For the static punctured
black hole simulations, different modifications of the BSSN formulation are
applied. It is demonstrated that both the currently used sets of modifications
lead to a stable evolution. For cases of a moving punctured black hole with or
without spin, we search for viable gauge conditions and study the effect of
spin on the black hole evolution. Our results confirm previous results obtained
by other research groups. In addition, we find a new gauge condition, which has
not yet been adopted by any other researchers, which can also give stable and
accurate black hole evolution calculations. We examine the performance of the
code for the head-on collision of a binary black hole system, and the agreement
of the gravitational waveform it produces with that obtained in other works. In
order to understand qualitatively the influence of matter on the binary black
hole collisions, we also investigate the same head-on collision scenarios but
perturbed by a scalar field. The numerical simulations performed with this code
not only give stable and accurate results that are consistent with the works by
other numerical relativity groups, but also lead to the discovery of a new
viable gauge condition, as well as clarify some ambiguities in the modification
of the BSSN formulation.Comment: 17 pages, 8 figures, accepted for publication in PR
Bony pelvis dimensions in women with and without stress urinary incontinence
Aims To test the null hypothesis that bony pelvis dimensions are similar in women with and without stress urinary incontinence (SUI), both in the postpartum and midlife periods. Methods Secondary analyses were performed of two case–control studies comparing women with SUI to asymptomatic controls. One study examined primiparas in the first 9–12 months postpartum; the other study involved middle‐aged women. SUI was confirmed by full‐bladder stress test. All subjects underwent pelvic magnetic resonance imaging. The interspinous and intertuberous diameters, subpubic angle, and sacrococcygeal joint‐to‐the inferior pubic point distance were measured from the images independently by two authors. Results In the young cohorts, we compared primiparas with de novo postpartum SUI to both continent primiparas and nulliparas. Postpartum SUI is associated with a wider subpubic angle. There is also a trend towards wider interspinous and intertuberous diameters in the stress‐incontinent primiparas as compared to the continent cohorts, although this did not reach statistical significance with our sample sizes. By contrast, no significant differences in bony pelvis dimensions were identified when comparing middle‐aged women with SUI and their continent controls. Conclusions Bony pelvis dimensions are different in women with SUI than in matched continent controls. However, these differences are only identified in young primiparas in the postpartum period, not in middle‐aged women. Neurourol. Urodynam. 32: 37–42, 2013. © 2012 Wiley Periodicals, Inc.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95230/1/22275_ftp.pd
Towards Uniform Gene Bank Documentation In Europe – The Experience From The EFABISnet Project
In the EFABISnet project, a collaborative effort of EAAP, FAO and partners from 14 European countries, in cooperation with the European Regional Focal Point for Animal Genetic Resources (ERFP), national information systems for monitoring the animal genetic resources on breed level were established in Austria, Cyprus, Estonia, Georgia, Iceland, Ireland, Italy, Netherlands, Slovakia, Slovenia, Switzerland, and United Kingdom. The network was soon extended beyond the project plans, with the establishment of EFABIS databases in Finland, Greece, and Hungary. The network was then complemented by a set of inventories of national gene bank collections to strengthen the documentation of ex situ conservation programmes. These documentation systems were established by the National Focal Points for management of farm animal genetic resources. Here we present the experience gained in establishment of these national inventories of gene banks and their relevance to the Strategic Priority Areas of the Global Plan of Action which could be useful for other areas in the world
Atomic and Electronic Structure of a Rashba - Junction at the BiTeI Surface
The non-centrosymmetric semiconductor BiTeI exhibits two distinct surface
terminations that support spin-split Rashba surface states. Their ambipolarity
can be exploited for creating spin-polarized - junctions at the
boundaries between domains with different surface terminations. We use scanning
tunneling microscopy/spectroscopy (STM/STS) to locate such junctions and
investigate their atomic and electronic properties. The Te- and I-terminated
surfaces are identified owing to their distinct chemical reactivity, and an
apparent height mismatch of electronic origin. The Rashba surface states are
revealed in the STS spectra by the onset of a van Hove singularity at the band
edge. Eventually, an electronic depletion is found on interfacial Te atoms,
consistent with the formation of a space charge area in typical -
junctions.Comment: 5 pages, 4 figure
Southern Massive Stars at High Angular Resolution: Observational Campaign and Companion Detection
Multiplicity is one of the most fundamental observable properties of massive
O-type stars and offers a promising way to discriminate between massive star
formation theories. Nevertheless, companions at separations between 1 and 100
mas remain mostly unknown due to intrinsic observational limitations. [...] The
Southern MAssive Stars at High angular resolution survey (SMASH+) was designed
to fill this gap by providing the first systematic interferometric survey of
Galactic massive stars. We observed 117 O-type stars with VLTI/PIONIER and 162
O-type stars with NACO/SAM, respectively probing the separation ranges 1-45 and
30-250mas and brightness contrasts of Delta H < 4 and Delta H < 5. Taking
advantage of NACO's field-of-view, we further uniformly searched for visual
companions in an 8''-radius down to Delta H = 8. This paper describes the
observations and data analysis, reports the discovery of almost 200 new
companions in the separation range from 1mas to 8'' and presents the catalog of
detections, including the first resolved measurements of over a dozen known
long-period spectroscopic binaries.
Excluding known runaway stars for which no companions are detected, 96
objects in our main sample (DEC < 0 deg; H<7.5) were observed both with PIONIER
and NACO/SAM. The fraction of these stars with at least one resolved companion
within 200mas is 0.53. Accounting for known but unresolved spectroscopic or
eclipsing companions, the multiplicity fraction at separation < 8'' increases
to f_m = 0.91 +/- 0.03. The fraction of luminosity class V stars that have a
bound companion reaches 100% at 30mas while their average number of physically
connected companions within 8'' is f_c = 2.2 +/- 0.3. This demonstrates that
massive stars form nearly exclusively in multiple systems. Additionally, the
nine non-thermal (NT) radio emitters observed by SMASH+ are all resolved [...]Comment: 57 pages, 20 figures, 7 tables; accepted for publication in ApJ
On the well posedness of the Baumgarte-Shapiro-Shibata-Nakamura formulation of Einstein's field equations
We give a well posed initial value formulation of the
Baumgarte-Shapiro-Shibata-Nakamura form of Einstein's equations with gauge
conditions given by a Bona-Masso like slicing condition for the lapse and a
frozen shift. This is achieved by introducing extra variables and recasting the
evolution equations into a first order symmetric hyperbolic system. We also
consider the presence of artificial boundaries and derive a set of boundary
conditions that guarantee that the resulting initial-boundary value problem is
well posed, though not necessarily compatible with the constraints. In the case
of dynamical gauge conditions for the lapse and shift we obtain a class of
evolution equations which are strongly hyperbolic and so yield well posed
initial value formulations
Reference priors for high energy physics
Bayesian inferences in high energy physics often use uniform prior
distributions for parameters about which little or no information is available
before data are collected. The resulting posterior distributions are therefore
sensitive to the choice of parametrization for the problem and may even be
improper if this choice is not carefully considered. Here we describe an
extensively tested methodology, known as reference analysis, which allows one
to construct parametrization-invariant priors that embody the notion of minimal
informativeness in a mathematically well-defined sense. We apply this
methodology to general cross section measurements and show that it yields
sensible results. A recent measurement of the single top quark cross section
illustrates the relevant techniques in a realistic situation
Microscopic correlation between chemical and electronic states in epitaxial graphene on SiC(000-1)
We present energy filtered electron emission spectromicroscopy with spatial
and wave-vector resolution on few layer epitaxial graphene on SiC$(000-1) grown
by furnace annealing. Low energy electron microscopy shows that more than 80%
of the sample is covered by 2-3 graphene layers. C1s spectromicroscopy provides
an independent measurement of the graphene thickness distribution map. The work
function, measured by photoelectron emission microscopy (PEEM), varies across
the surface from 4.34 to 4.50eV according to both the graphene thickness and
the graphene-SiC interface chemical state. At least two SiC surface chemical
states (i.e., two different SiC surface structures) are present at the
graphene/SiC interface. Charge transfer occurs at each graphene/SiC interface.
K-space PEEM gives 3D maps of the k_|| pi - pi* band dispersion in micron scale
regions show that the Dirac point shifts as a function of graphene thickness.
Novel Bragg diffraction of the Dirac cones via the superlattice formed by the
commensurately rotated graphene sheets is observed. The experiments underline
the importance of lateral and spectroscopic resolution on the scale of future
electronic devices in order to precisely characterize the transport properties
and band alignments
A New Constraint on the Escape Fraction in Distant Galaxies Using Gamma-ray Burst Afterglow Spectroscopy
We describe a new method to measure the escape fraction fesc of ionizing
radiation from distant star-forming galaxies using the afterglow spectra of
long-duration gamma-ray bursts (GRBs). Optical spectra of GRB afterglows allow
us to evaluate the optical depth of the host ISM, according to the neutral
hydrogen column density N(HI) observed along the sightlines toward the
star-forming regions where the GRBs are found. Different from previous effort
in searching for faint, transmitted Lyman continuum photons, our method is not
subject to background subtraction uncertainties and does not require prior
knowledge of either the spectral shape of the host galaxy population or the IGM
Lya forest absorption along these GRB sightlines. Because most GRBs occur in
sub-L_* galaxies, our study also offers the first constraint on fesc for
distant low-mass galaxies that dominate the cosmic luminosity density. We have
compiled a sample of 27 GRBs at redshift z>2 for which the underlying N(HI) in
the host ISM are known. These GRBs together offer a statistical sampling of the
integrated optical depth to ionizing photons along random sightlines from
star-forming regions in the host galaxies, and allow us to estimate the mean
escape fraction averaged over different viewing angles. We find
=0.02\pm 0.02 and place a 95% c.l. upper limit <= 0.075 for these
hosts. We discuss possible biases of our approach and implications of the
result. Finally, we propose to extend this technique for measuring at
z~0.2 using spectra of core-collapse supernovae.Comment: Five journal pages, including one figure; ApJL in pres
The patient-physician relationship: an account of the physician's perspective
BACKGROUND: The issue of patient-physician relationships in general, and particularly the trust of patients in their primary care physician has gained much interest in academia and with practitioners in recent years. Most research on this important topic, however, focused on how patients view the relationship and not how the physicians see it. This research strives to bridge this gap, with the resolution of leading to an improved appreciation of this multifaceted relationship. METHODS: A survey of 328 actively practicing physicians from all four health maintenance organizations (HMOs) in Israel resulted in a hierarchical formation of components, indicating both the relative as well as absolute importance of each component in the formation of the patient-physician relationship. The sample conducted was a convenience one. Methodologically, we used two different complementary methods of analysis, with the primary emphasis on the Analytic Hierarchical Processing (AHP), a unique and advanced statistical method. RESULTS: The results provide a detailed picture of physicians' attitudes toward the patient-physician relationship. Research indicates that physicians tend to consider the relationship with the patient in a rather pragmatic manner. To date, this attitude was mostly referred to intuitively, without the required rigorous investigation provided by this paper. Specifically, the results indicate that physicians tend to consider the relationship with the patient in a rather pragmatic manner. Namely, while fairness, reliability, devotion, and serviceability received high scores from physicians, social interaction, friendship, familial, as well as appreciation received the lowest scores, indicating low priority for warmth and sociability in the trust relationship from the physician's perspective. The results showed good consistency between the AHP results and the ANOVA comparable analyses. CONCLUSIONS: In contrast to patients who traditionally stress the importance of interpersonal skills, physicians stress the significance of the technical expertise and knowledge of health providers, emphasizing the role of competence and performance. Physicians evaluate the relationship on the basis of their ability to solve problems through devotion, serviceability, reliability, and trustworthiness and disregard the "softer" interpersonal aspects such as caring, appreciation, and empathy that have been found to be important to their patients. This illustrates a mismatch in the important components of relationship building that can lead to a loss of trust, satisfaction, and repeat purchase. POLICY IMPLICATIONS: We study the impact physicians' incentives have on the tangible relationship and discuss the significance of physician-patient relationship on satisfaction with the health service given. As a result policies leading to a more dynamic role must be given to the patient, who being well informed by the physician, can help in the decision making process. Policy schemes need to be implemented as a way of changing physicians' behavior, forcing them to better construct and utilize this dyadic relationship
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