10,603 research outputs found
WMAP constraints on the Intra-Cluster Medium
We devise a Monte-Carlo based, optimized filter match method to extract the
thermal Sunyaev-Zel'dovich (SZ) signature of a catalog of 116 low-redshift
X-ray clusters from the first year data release of the Wilkinson Microwave
Anisotropy Probe (WMAP). We detect an over-all amplitude for the SZ signal at
the ~ 8-sigma level, yielding a combined constraint of f_{gas}h = 0.08 +/- 0.01
(ran) +/- 0.01 (sys) on the gas mass fraction of the Intra-Cluster Medium. We
also compile X-ray estimated gas fractions from the literature for our sample,
and find that they are consistent with the SZ estimates at the 2-sigma level,
while both show an increasing trend with X-ray temperature. Nevertheless, our
SZ estimated gas fraction is 30-40% smaller than the concordance LCDM cosmic
average. We also express our observations in terms of the SZ flux-temperature
relation, and compare it with other observations, as well as numerical studies.
Based on its spectral and spatial signature, we can also extract the
microwave point source signal of the clusters at the 3-sigma level, which puts
the average microwave luminosity (at ~ 41 GHz) of bright cluster members (M_K <
-21) at (2.4 +/- 0.8) x 10^{27} h^{-2} erg/s/Hz. Furthermore, we can constrain
the average dark matter halo concentration parameter to c_{vir}=3.4+0.6-0.9,
for clusters with T_x > 5 kev.
Our work serves as an example for how correlation of SZ surveys with cluster
surveys in other frequencies can significantly increase our physical
understanding of the intra-cluster medium.Comment: 34 pages, 6 ps figures, Extended discussion of theoretical
uncertainties, radio sources, and future prospects, Accepted for Publication
in Ap
Impurity-induced Local Density of States in a D-wave Superconductor Carrying a Supercurrent
The local density of states (LDOS) and its Fourier component induced by a
unitary impurity in a supercurrent-carrying d-wave superconductor are
investigated. Both of these quantities possess a reflection symmetry about the
line passing through the impurity site and along the supercurrent if it is
applied along the antinodal or nodal direction. With increasing supercurrent,
both the coherence and resonant peaks in the LDOS are suppressed and slightly
broadened. Under a supercurrent along the antinodal direction, the coherence
peaks split into double peaks. The modulation wavevectors associated with
elastic scatterings of quasiparticles by the defect from one constant-energy
piece of the Fermi surface to another are displayed as bright or dark spots in
the Fourier space of the LDOS image, and they may be suppressed or enhanced,
and shifted depending on the applied current and the bias voltage.Comment: 5 pages, 6 figure
Perturbed Three Vortex Dynamics
It is well known that the dynamics of three point vortices moving in an ideal
fluid in the plane can be expressed in Hamiltonian form, where the resulting
equations of motion are completely integrable in the sense of Liouville and
Arnold. The focus of this investigation is on the persistence of regular
behavior (especially periodic motion) associated to completely integrable
systems for certain (admissible) kinds of Hamiltonian perturbations of the
three vortex system in a plane. After a brief survey of the dynamics of the
integrable planar three vortex system, it is shown that the admissible class of
perturbed systems is broad enough to include three vortices in a half-plane,
three coaxial slender vortex rings in three-space, and `restricted' four vortex
dynamics in a plane. Included are two basic categories of results for
admissible perturbations: (i) general theorems for the persistence of invariant
tori and periodic orbits using Kolmogorov-Arnold-Moser and Poincare-Birkhoff
type arguments; and (ii) more specific and quantitative conclusions of a
classical perturbation theory nature guaranteeing the existence of periodic
orbits of the perturbed system close to cycles of the unperturbed system, which
occur in abundance near centers. In addition, several numerical simulations are
provided to illustrate the validity of the theorems as well as indicating their
limitations as manifested by transitions to chaotic dynamics.Comment: 26 pages, 9 figures, submitted to the Journal of Mathematical Physic
Restraints and enablers of green initiative-taking among hospitality employees:a mixed-methods approach
Green initiative-taking, an employee’s self-starting opportunity-seeking action to improve environmental performance is a desirable outcome of organizations’ green policies. Given prior inattention to this area of study, it is unclear what fosters green initiative-taking, and why. This study attempts to answer these questions using a mixed-methods approach. First, an exploratory qualitative study was conducted. Green human resource management, eco-silence, supervisor bottom-line mentality, and co-worker voice emerged as the major themes of employees’ experiences when seeking to engage in green initiative-taking. Second, building on social information processing and social learning theories, a quantitative study proposes a conceptual model of the inter-relationships between the themes that emerged from the first study. Results from a multinational multisource time-lagged quantitative study support most of the hypotheses and shed light on avenues for future research. It suggests that supervisor bottom-line mentality inhibiting green initiative-taking might be standard procedure bottom-line mentality rather than profit bottom-line mentality. Post-hoc, to enhance the study’s applicability, a fuzzy-set analysis was conducted to offer managers the configurations that best yield green initiative-taking among hospitality employees
Non-Markovian Fermionic Stochastic Schr\"{o}dinger Equation for Open System Dynamics
In this paper we present an exact Grassmann stochastic Schr\"{o}dinger
equation for the dynamics of an open fermionic quantum system coupled to a
reservoir consisting of a finite or infinite number of fermions. We use this
stochastic approach to derive the exact master equation for a fermionic system
strongly coupled to electronic reservoirs. The generality and applicability of
this Grassmann stochastic approach is justified and exemplified by several
quantum open system problems concerning quantum decoherence and quantum
transport for both vacuum and finite-temperature fermionic reservoirs. We show
that the quantum coherence property of the quantum dot system can be profoundly
modified by the environment memory.Comment: 10.5 pages, 3 figure
Experimental observation of negative differential resistance from an InAs/GaSb interface
We have observed negative differential resistance at room temperature from devices consisting of a single interface between n-type InAs and p-type GaSb. InAs and GaSb have a type II staggered band alignment; hence, the negative differential resistance arises from the same mechanism as in a p+-n+ tunnel diode. Room-temperature peak current densities of 8.2×10^4 A/cm^2 and 4.2×10^4 A/cm^2 were measured for structures with and without undoped spacer layers at the heterointerface, respectively
The complex morphology of the young disk MWC 758: Spirals and dust clumps around a large cavity
We present Atacama Large Millimeter Array (ALMA) observations at an angular
resolution of 0.1-0.2" of the disk surrounding the young Herbig Ae star MWC
758. The data consist of images of the dust continuum emission recorded at 0.88
millimeter, as well as images of the 13CO and C18O J = 3-2 emission lines. The
dust continuum emission is characterized by a large cavity of roughly 40 au in
radius which might contain a mildly inner warped disk. The outer disk features
two bright emission clumps at radii of about 47 and 82 au that present
azimuthal extensions and form a double-ring structure. The comparison with
radiative transfer models indicates that these two maxima of emission
correspond to local increases in the dust surface density of about a factor 2.5
and 6.5 for the south and north clumps, respectively. The optically thick 13CO
peak emission, which traces the temperature, and the dust continuum emission,
which probes the disk midplane, additionally reveal two spirals previously
detected in near-IR at the disk surface. The spirals seen in the dust continuum
emission present, however, a slight shift of a few au towards larger radii and
one of the spirals crosses the south dust clump. Finally, we present different
scenarios in order to explain the complex structure of the disk.Comment: 15 pages, 11 figures. The paper has been published in ApJ. References
added and typos correcte
Targeting translation initiation by synthetic rocaglates for treating MYC-driven lymphomas.
MYC-driven lymphomas, especially those with concurrent MYC and BCL2 dysregulation, are currently a challenge in clinical practice due to rapid disease progression, resistance to standard chemotherapy, and high risk of refractory disease. MYC plays a central role by coordinating hyperactive protein synthesis with upregulated transcription in order to support rapid proliferation of tumor cells. Translation initiation inhibitor rocaglates have been identified as the most potent drugs in MYC-driven lymphomas as they efficiently inhibit MYC expression and tumor cell viability. We found that this class of compounds can overcome eIF4A abundance by stabilizing target mRNA-eIF4A interaction that directly prevents translation. Proteome-wide quantification demonstrated selective repression of multiple critical oncoproteins in addition to MYC in B-cell lymphoma including NEK2, MCL1, AURKA, PLK1, and several transcription factors that are generally considered undruggable. Finally, (-)-SDS-1-021, the most promising synthetic rocaglate, was confirmed to be highly potent as a single agent, and displayed significant synergy with the BCL2 inhibitor ABT199 in inhibiting tumor growth and survival in primary lymphoma cells in vitro and in patient-derived xenograft mouse models. Overall, our findings support the strategy of using rocaglates to target oncoprotein synthesis in MYC-driven lymphomas.P30 CA036727 - NCI NIH HHS; R24 GM111625 - NIGMS NIH HHS; R35 GM118173 - NIGMS NIH HHS; LB506 - Nebraska Department of Health and Human Services (Nebraska DHHS)Accepted manuscriptSupporting documentatio
Finite-Time Disentanglement via Spontaneous Emission
We show that under the influence of pure vacuum noise two entangled qubits
become completely disentangled in a finite time, and in a specific example we
find the time to be given by times the
usual spontaneous lifetime.Comment: revtex, 4 pages, 2 figure
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