1,189 research outputs found
Using double radio relics to constrain galaxy cluster mergers: A model of double radio relics in CIZA J2242.8+5301
Galaxy clusters grow by mergers with other clusters and galaxy groups. These
mergers create shock waves within the intracluster medium (ICM) that can
accelerate particles to extreme energies. In the presence of magnetic fields,
relativistic electrons form large regions emitting synchrotron radiation,
so-called radio relics. Behind the shock front, synchrotron and inverse Compton
(IC) losses cause the radio spectral index to steepen away from the shock
front. An example of such a cluster is CIZA J2242.8+5301, where very clear
spectral steepening in the downstream region is observed. Here we present
hydrodynamical simulations of idealized binary cluster mergers with the aim of
constraining the merger scenario for this cluster. From our simulations, we
find that CIZA J2242.8+5301 is probably undergoing a merger in the plane of the
sky (less then 10 deg from edge-on) with a mass ratio of about 2:1, and an
impact parameter < 400 kpc. We find that the core passage of the clusters
happened about 1 Gyr ago. We conclude that double relics relics can set
constraints on the mass ratios, impact parameters, timescales, and viewing
geometry of binary cluster mergers, which is particularly useful when detailed
X-ray observations are not available. In addition, the presence of large radio
relics can be used to constrain the degree of clumping in the outskirts of the
ICM, which is important to constrain the baryon fraction, density and entropy
profiles, around the virial radius and beyond. We find that the amplitude of
density fluctuations, with sizes of < 200 kpc, in the relic in CIZA
J2242.8+5301 is not larger than 30%. [abridged]Comment: 14 pages, 8 figures, accepted for publication in MNRAS on July 20,
201
Constraining ultralight vector dark matter with the Parkes Pulsar Timing Array second data release
Composed of ultralight bosons, fuzzy dark matter provides an intriguing
solution to challenges that the standard cold dark matter model encounters on
sub-galactic scales. The ultralight dark matter with mass will induce a periodic oscillation in gravitational potentials with a
frequency in the nanohertz band, leading to observable effects in the arrival
times of radio pulses from pulsars. Unlike scalar dark matter, pulsar timing
signals induced by the vector dark matter are dependent on the oscillation
direction of the vector fields. In this work, we search for ultralight vector
dark matter in the mass range of through its gravitational effect in the Parkes Pulsar
Timing Array (PPTA) second data release. Since no statistically significant
detection is made, we place upper limits on the local dark matter
density as for . As no preferred direction is found for the vector dark
matter, these constraints are comparable to those given by the scalar dark
matter search with an earlier 12-year data set of PPTA.Comment: 9 pages, 3 figures, 2 tables; accepted for publication as a Letter in
Phys. Rev.
Polypyrrole/TiO2 nanotube arrays with coaxial heterogeneous structure as sulfur hosts for lithium sulfur batteries
The lithium-sulfur cell has shown great prospects for future energy conversion and storage systems due to the high theoretical specific capacity of sulfur, 1675 mAh g−1. However, it has been hindered by rapid capacity decay and low energy efficiency. In this work, polypyrrole (PPy)/TiO2 nanotubes with coaxial heterogeneous structure as the substrate of the cathode is prepared and used to improve the electrochemical performance of sulfur electrodes. TiO2 nanotubes decorated with PPy provide a highly ordered conductive framework for Li+ ion diffusion and reaction with sulfur. This architecture also is helpful for trapping the produced polysulfides, and as a result attenuates the capacity decay. Furthermore, the heat treatment temperature used in the sulfur loading process has been confirmed to have an important impact on the overall performance of the resultant cell. The as-designed S/PPy/TiO2 nanotube cathode using an elevated heating temperature shows excellent cycling stability with a high discharge capacity of 1150 mAh g−1 and average coulombic efficiency of 96% after 100 cycles
Intranasal Delivery of MVA Vector Vaccine Induces Effective Pulmonary Immunity Against SARS-CoV-2 in Rodents
Antigen-specific tissue-resident memory T cells (Trms) and neutralizing IgA antibodies provide the most effective protection of the lungs from viral infections. To induce those essential components of lung immunity against SARS-CoV-2, we tested various immunization protocols involving intranasal delivery of a novel Modified Vaccinia virus Ankara (MVA)-SARS-2-spike vaccine candidate. We show that a single intranasal MVA-SARS-CoV-2-S application in mice strongly induced pulmonary spike-specific CD8+ T cells, albeit restricted production of neutralizing antibodies. In prime-boost protocols, intranasal booster vaccine delivery proved to be crucial for a massive expansion of systemic and lung tissue-resident spike-specific CD8+ T cells and the development of Th1 - but not Th2 - CD4+ T cells. Likewise, very high titers of IgG and IgA anti-spike antibodies were present in serum and broncho-alveolar lavages that possessed high virus neutralization capacities to all current SARS-CoV-2 variants of concern. Importantly, the MVA-SARS-2-spike vaccine applied in intramuscular priming and intranasal boosting treatment regimen completely protected hamsters from developing SARS-CoV-2 lung infection and pathology. Together, these results identify intramuscular priming followed by respiratory tract boosting with MVA-SARS-2-S as a promising approach for the induction of local, respiratory as well as systemic immune responses suited to protect from SARS-CoV-2 infections
Comparison of Double Kissing Crush Versus Culotte Stenting for Unprotected Distal Left Main Bifurcation Lesions Results From a Multicenter, Randomized, Prospective DKCRUSH-III Study
ObjectivesThe study aimed to investigate the difference in major adverse cardiac event (MACE) at 1-year after double kissing (DK) crush versus Culotte stenting for unprotected left main coronary artery (UPLMCA) distal bifurcation lesions.BackgroundDK crush and Culotte stenting were reported to be effective for treatment of coronary bifurcation lesions. However, their comparative performance in UPLMCA bifurcation lesions is not known.MethodsA total of 419 patients with UPLMCA bifurcation lesions were randomly assigned to DK (n = 210) or Culotte (n = 209) treatment. The primary endpoint was the occurrence of a MACE at 1 year, including cardiac death, myocardial infarction, and target vessel revascularization (TVR). In-stent restenosis (ISR) at 8 months was secondary endpoint, and stent thrombosis (ST) served as a safety endpoint. Patients were stratified by SYNTAX (Synergy between Percutaneous Coronary Intervention with Taxus and Cardiac Surgery) and NERS (New Risk Stratification) scores.ResultsPatients in the Culotte group had significant higher 1-year MACE rate (16.3%), mainly driven by increased TVR (11.0%), compared with the DK group (6.2% and 4.3%, respectively; all p < 0.05). ISR rate in side branch was 12.6% in the Culotte group and 6.8% in the DK group (p = 0.037). Definite ST rate was 1.0% in the Culotte group and 0% in the DK group (p = 0.248). Among patients with bifurcation angle ≥70°, NERS score ≥20, and SYNTAX score ≥23, the 1-year MACE rate in the DK group (3.8%, 9.2%, and 7.1%, respectively) was significantly different to those in the Culotte group(16.5%, 20.4%, and 18.9%, respectively; all p < 0.05).ConclusionsCulotte stenting for UPLMCA bifurcation lesions was associated with significantly increased MACEs, mainly due to the increased TVR. (Double Kissing [DK] Crush Versus Culotte Stenting for the Treatment of Unprotected Distal Left Main Bifurcation Lesions: DKCRUSH-III, a Multicenter Randomized Study Comparing Double-Stent Techniques; ChiCTR-TRC-00000151
Cosmological Constraints from the Large Scale Weak Lensing of SDSS MaxBCG Clusters
We derive constraints on the matter density \Om and the amplitude of matter
clustering \sig8 from measurements of large scale weak lensing (projected
separation R=5-30\hmpc) by clusters in the Sloan Digital Sky Survey MaxBCG
catalog. The weak lensing signal is proportional to the product of \Om and the
cluster-mass correlation function \xicm. With the relation between optical
richness and cluster mass constrained by the observed cluster number counts,
the predicted lensing signal increases with increasing \Om or \sig8, with mild
additional dependence on the assumed scatter between richness and mass. The
dependence of the signal on scale and richness partly breaks the degeneracies
among these parameters. We incorporate external priors on the richness-mass
scatter from comparisons to X-ray data and on the shape of the matter power
spectrum from galaxy clustering, and we test our adopted model for \xicm
against N-body simulations. Using a Bayesian approach with minimal restrictive
priors, we find \sig8(\Om/0.325)^{0.501}=0.828 +/- 0.049, with marginalized
constraints of \Om=0.325_{-0.067}^{+0.086} and \sig8=0.828_{-0.097}^{+0.111},
consistent with constraints from other MaxBCG studies that use weak lensing
measurements on small scales (R<=2\hmpc). The (\Om,\sig8) constraint is
consistent with and orthogonal to the one inferred from WMAP CMB data,
reflecting agreement with the structure growth predicted by GR for an LCDM
cosmological model. A joint constraint assuming LCDM yields \Om=0.298 +/- 0.020
and \sig8=0.831 +/- 0.020. Our cosmological parameter errors are dominated by
the statistical uncertainties of the large scale weak lensing measurements,
which should shrink sharply with current and future imaging surveys.Comment: 20 pages, 12 figures, MNRAS Submitted. For a brief video explaining
the key result of this paper, see http://www.youtube.com/user/OSUAstronomy,
or http://v.youku.com/v_show/id_XNDI3ODA3NzY4.html in countries where YouTube
is not accessibl
Measurement of the cross-section and charge asymmetry of bosons produced in proton-proton collisions at TeV with the ATLAS detector
This paper presents measurements of the and cross-sections and the associated charge asymmetry as a
function of the absolute pseudorapidity of the decay muon. The data were
collected in proton--proton collisions at a centre-of-mass energy of 8 TeV with
the ATLAS experiment at the LHC and correspond to a total integrated luminosity
of 20.2~\mbox{fb^{-1}}. The precision of the cross-section measurements
varies between 0.8% to 1.5% as a function of the pseudorapidity, excluding the
1.9% uncertainty on the integrated luminosity. The charge asymmetry is measured
with an uncertainty between 0.002 and 0.003. The results are compared with
predictions based on next-to-next-to-leading-order calculations with various
parton distribution functions and have the sensitivity to discriminate between
them.Comment: 38 pages in total, author list starting page 22, 5 figures, 4 tables,
submitted to EPJC. All figures including auxiliary figures are available at
https://atlas.web.cern.ch/Atlas/GROUPS/PHYSICS/PAPERS/STDM-2017-13
Search for new phenomena in final states with an energetic jet and large missing transverse momentum in pp collisions at √ s = 8 TeV with the ATLAS detector
Results of a search for new phenomena in final states with an energetic jet and large missing transverse momentum are reported. The search uses 20.3 fb−1 of √ s = 8 TeV data collected in 2012 with the ATLAS detector at the LHC. Events are required to have at least one jet with pT > 120 GeV and no leptons. Nine signal regions are considered with increasing missing transverse momentum requirements between Emiss T > 150 GeV and Emiss T > 700 GeV. Good agreement is observed between the number of events in data and Standard Model expectations. The results are translated into exclusion limits on models with either large extra spatial dimensions, pair production of weakly interacting dark matter candidates, or production of very light gravitinos in a gauge-mediated supersymmetric model. In addition, limits on the production of an invisibly decaying Higgs-like boson leading to similar topologies in the final state are presente
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