4,865 research outputs found
The Conformal Willmore Functional: a Perturbative Approach
The conformal Willmore functional (which is conformal invariant in general
Riemannian manifold ) is studied with a perturbative method: the
Lyapunov-Schmidt reduction. Existence of critical points is shown in ambient
manifolds -where is a metric close
and asymptotic to the euclidean one. With the same technique a non existence
result is proved in general Riemannian manifolds of dimension three.Comment: 34 pages; Journal of Geometric Analysis, on line first 23 September
201
Low-velocity transient-field technique with radioactive ion beams: G factor of the first excited 2 + state in 72Zn
A. Illana et al. ; 11 pags. ; 10 figs. ; 3 tabs. ; PACS number(s): 23.20.En, 21.10.Ky, 21.60.Cs, 27.50.+eThe g factor of the first excited 2+ state in 72Zn has been measured using the transient-field (TF) technique in combination with Coulomb excitation in inverse kinematics. This experiment presents only the third successful application of the TF method to a short-lived radioactive beam in 10 y, highlighting the intricacies of applying this technique to present and future isotope separator on-line facilities. The significance of the experimental result, g(21+)=+0.47(14), for establishing the structure of the Zn isotopes near N=40 is discussed on the basis of shell-model and beyond-mean-field calculations, the latter accounting for the triaxial degree of freedom, configuration mixing, and particle number and angular momentum projections. © 2014 American Physical Society.This work has been supported by the Spanish Ministerio de Ciencia e Innovacion under Contracts No. FPA2009-13377- Ž C02 and No. FPA2011-29854-C04 and the Spanish Project MEC Consolider-Ingenio 2010, Project No. CDS2007-00042.Peer Reviewe
Hard X-ray Morphological and Spectral Studies of The Galactic Center Molecular Cloud Sgr B2: Constraining Past Sgr A* Flaring Activity
Galactic Center (GC) molecular cloud Sgr B2 is the best manifestation of an
X-ray reflection nebula (XRN) reprocessing a past giant outburst from the
supermassive black hole Sgr A*. Alternatively, Sgr B2 could be illuminated by
low-energy cosmic ray electrons (LECRe) or protons (LECRp). In 2013, NuSTAR for
the first time resolved Sgr B2 hard X-ray emission on sub-arcminute scales. Two
prominent features are detected above 10 keV - a newly emerging cloud
G0.66-0.13 and the central 90" radius region containing two compact cores Sgr
B2(M) and Sgr B2(N) surrounded by diffuse emission. It is inconclusive whether
the remaining level of Sgr B2 emission is still decreasing or has reached a
constant background level. A decreasing Fe K emission can be best
explained by XRN while a constant background emission can be best explained by
LECRp. In the XRN scenario, the 3-79 keV Sgr B2 spectrum can well constrain the
past Sgr A* outburst, resulting in an outburst spectrum with a peak luminosity
of derived from the
maximum Compton-scattered continuum and the Fe K emission consistently.
The XRN scenario is preferred by the fast variability of G0.66-0.13, which
could be a molecular clump located in the Sgr B2 envelope reflecting the same
Sgr A* outburst. In the LECRp scenario, we derived the required CR ion power
and the CR ionization rate
. The Sgr B2 background level
X-ray emission will be a powerful tool to constrain GC CR population.Comment: 17 pages, 6 figures, submitted to Ap
Boosting search by rare events
Randomized search algorithms for hard combinatorial problems exhibit a large
variability of performances. We study the different types of rare events which
occur in such out-of-equilibrium stochastic processes and we show how they
cooperate in determining the final distribution of running times. As a
byproduct of our analysis we show how search algorithms are optimized by random
restarts.Comment: 4 pages, 3 eps figures. References update
Reward-Sensitive Basal Ganglia Stabilize the Maintenance of Goal-Relevant Neural Patterns in Adolescents
Maturation of basal ganglia (BG) and frontoparietal circuitry parallels developmental gains in working memory (WM). Neurobiological models posit that adult WM performance is enhanced by communication between reward-sensitive BG and frontoparietal regions, via increased stability in the maintenance of goal-relevant neural patterns. It is not known whether this reward-driven pattern stability mechanism may have a role in WM development. In 34 young adolescents (12.16â14.72 years old) undergoing fMRI, reward-sensitive BG regions were localized using an incentive processing task. WM-sensitive regions were localized using a delayed-response WM task. Functional connectivity analyses were used to examine the stability of goal-relevant functional connectivity patterns during WM delay periods between and within reward-sensitive BG and WM-sensitive frontoparietal regions. Analyses revealed that more stable goal-relevant connectivity patterns between reward-sensitive BG and WM-sensitive frontoparietal regions were associated with both greater adolescent age and WM ability. Computational lesion models also revealed that functional connections to WM-sensitive frontoparietal regions from reward-sensitive BG uniquely increased the stability of goal-relevant functional connectivity patterns within frontoparietal regions. Findings suggested (1) the extent to which goal-relevant communication patterns within reward-frontoparietal circuitry are maintained increases with adolescent development and WM ability and (2) communication from reward-sensitive BG to frontoparietal regions enhances the maintenance of goal-relevant neural patterns in adolescentsâ WM. The maturation of reward-driven stability of goal-relevant neural patterns may provide a putative mechanism for understanding the developmental enhancement of WM
NuSTAR Spectroscopy of Multi-Component X-ray Reflection from NGC 1068
We report on observations of NGC1068 with NuSTAR, which provide the best
constraints to date on its ~keV spectral shape. We find no strong
variability over the past two decades, consistent with its Compton-thick AGN
classification. The combined NuSTAR, Chandra, XMM-Newton, and Swift-BAT
spectral dataset offers new insights into the complex reflected emission. The
critical combination of the high signal-to-noise NuSTAR data and a spatial
decomposition with Chandra allow us to break several model degeneracies and
greatly aid physical interpretation. When modeled as a monolithic (i.e., a
single N_H) reflector, none of the common Compton-reflection models are able to
match the neutral fluorescence lines and broad spectral shape of the Compton
reflection. A multi-component reflector with three distinct column densities
(e.g., N_H~1.5e23, 5e24, and 1e25 cm^{-2}) provides a more reasonable fit to
the spectral lines and Compton hump, with near-solar Fe abundances. In this
model, the higher N_H components provide the bulk of the Compton hump flux
while the lower N_H component produces much of the line emission, effectively
decoupling two key features of Compton reflection. We note that ~30% of the
neutral Fe Kalpha line flux arises from >2" (~140 pc), implying that a
significant fraction of the <10 keV reflected component arises from regions
well outside of a parsec-scale torus. These results likely have ramifications
for the interpretation of poorer signal-to-noise observations and/or more
distant objects [Abridged].Comment: Submitted to ApJ; 23 pages (ApJ format); 11 figures and 3 tables;
Comments welcomed
Which outcomes have been measured in hand eczema trials? A systematic review:A systematic review
The considerable heterogeneity of outcomes and measurement instruments in hand eczema trials substantially limits the evidence synthesis concerning therapeutic and preventive interventions. Therefore, the Hand Eczema Core Outcome Set (HECOS) initiative is developing a core outcome set for future trials. The first objective was to identify outcomes that were measured in previous trials, to group them in domains, and to identify their measurement instruments. We conducted a systematic review of controlled and randomized controlled hand eczema trials published since 2000. Sixty-one eligible studies were identified. Each assessed one or more of 47 outcomes in the "skin" domain. Eighteen trials (30%) additionally focused on preventive behaviour in risk occupations. Quality of life was measured in 13 studies (21%). Thirty-two distinct named instruments were applied, but 223 measurements (62%) were conducted with unnamed instruments. Only 32 studies (52%) defined a primary outcome. Twenty-nine trials (48%) provided some information on adverse events, but none gave any references concerning relevant methods. Our review confirms the need to harmonize outcome measurements in hand eczema trials. The findings form the basis for a consensus process to generate a core outcome set to improve the explanatory power and comparability of future hand eczema studies.</p
Mirroring everyday clinical practice in clinical trial design: a new concept to improve the external validity of randomized double-blind placebo-controlled trials in the pharmacological treatment of major depression
Background: Randomized, double-blind, placebo-controlled trials constitute the gold standard in clinical research when testing the efficacy of new psychopharmacological interventions in the treatment of major depression. However, the blinded use of placebo has been found to influence clinical trial outcomes and may bias patient
selection.
Discussion: To improve clinical trial design in major depression so as to reflect clinical practice more closely we propose to present patients with a balanced view of the benefits of study participation irrespective of their assignment to placebo or active treatment. In addition every participant should be given the option to finally
receive the active medication. A research agenda is outlined to evaluate the impact of the proposed changes on the efficacy of the drug to be evaluated and on the demographic and clinical characteristics of the enrollment fraction with regard to its representativeness of the eligible population.
Summary: We propose a list of measures to be taken to improve the external validity of double-blind, placebocontrolled trials in major depression. The recommended changes to clinical trial design may also be relevant for other psychiatric as well as medical disorders in which expectations regarding treatment outcome may affect the
outcome itself
Switching of magnetic domains reveals evidence for spatially inhomogeneous superconductivity
The interplay of magnetic and charge fluctuations can lead to quantum phases
with exceptional electronic properties. A case in point is magnetically-driven
superconductivity, where magnetic correlations fundamentally affect the
underlying symmetry and generate new physical properties. The superconducting
wave-function in most known magnetic superconductors does not break
translational symmetry. However, it has been predicted that modulated triplet
p-wave superconductivity occurs in singlet d-wave superconductors with
spin-density wave (SDW) order. Here we report evidence for the presence of a
spatially inhomogeneous p-wave Cooper pair-density wave (PDW) in CeCoIn5. We
show that the SDW domains can be switched completely by a tiny change of the
magnetic field direction, which is naturally explained by the presence of
triplet superconductivity. Further, the Q-phase emerges in a common
magneto-superconducting quantum critical point. The Q-phase of CeCoIn5 thus
represents an example where spatially modulated superconductivity is associated
with SDW order
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