2,129 research outputs found
A New Kilohertz Gravitational-Wave Feature from Rapidly Rotating Core-Collapse Supernovae
We present self-consistent three-dimensional core-collapse supernova
simulations of a rotating progenitor model with various initial
angular velocities from to rad s using a smoothed particle
hydrodynamics code, SPHYNX, and a grid-based hydrodynamics code, FLASH. We
identify two strong gravitational-wave features, with peak frequencies of
Hz and kHz in the first ms postbounce. We demonstrate
that these two features are associated with the deformation from the
proto-neutron star (PNS) modulation induced by the low- instability,
regardless of the simulation code. The Hz feature is present in models
with an initial angular velocity between and rad s, while
the kHz feature is present only in a narrower range, from to
rad s. We show that the kHz signal originates from the
high-density inner core of the PNS, and the deformation triggers a strong
asymmetric distribution of electron anti-neutrinos. In addition to the Hz
and kHz features, we also observe one weaker but noticeable
gravitational-wave feature from higher-order modes in the range between
and rad s. Its peak frequency is around Hz initially and
gradually increases to Hz. Therefore, in addition to the
gravitational bounce signal, the detection of the Hz, kHz, the
higher-order mode, and even the related asymmetric emission of neutrinos, could
provide additional diagnostics to estimate the initial angular velocity of a
collapsing core.Comment: 20 pages, 14 figures,. Accepted for publication in the Astrophysical
Journa
Autoantibodies against the Catalytic Domain of BRAF Are Not Specific Serum Markers for Rheumatoid Arthritis
BACKGROUND: Autoantibodies to the catalytic domain of v-raf murine sarcoma viral oncogene homologue B1 (BRAF) have been recently identified as a new family of autoantibodies involved in rheumatoid arthritis (RA). The objective of this study was to determine antibody responses to the catalytic domain of BRAF in RA and other autoimmune diseases. The association between RA-related clinical indices and these antibodies was also assessed. METHODOLOGY/PRINCIPAL FINDINGS: The presence of autoantibodies to the catalytic domain of BRAF (anti-BRAF) or to peptide P25 (amino acids 656-675 of the catalytic domain of BRAF; anti-P25) was determined in serum samples from patients with RA, primary Sjögren's syndrome (pSS), systemic lupus erythematosus (SLE), and healthy controls by using indirect enzyme-linked immunosorbent assays (ELISAs) based on the recombinant catalytic domain of BRAF or a synthesized peptide, respectively. Associations of anti-BRAF or anti-P25 with disease variables of RA patients were also evaluated. Our results show that the BRAF-specific antibodies anti-BRAF and anti-P25 are equally present in RA, pSS, and SLE patients. However, the erythrocyte sedimentation rate (ESR) used to detect inflammation was significantly different between patients with and without BRAF-specific antibodies. The anti-BRAF-positive patients were found to have prolonged disease, and active disease occurred more frequently in anti-P25-positive patients than in anti-P25-negative patients. A weak but significant correlation between anti-P25 levels and ESRs was observed (r = 0.319, p = 0.004). CONCLUSIONS/SIGNIFICANCE: The antibody response against the catalytic domain of BRAF is not specific for RA, but the higher titers of BRAF-specific antibodies may be associated with increased inflammation in RA
A model for the simultaneous prediction of the flexural and shear deflections of statically determinate and indeterminate RC structures
The deformability of the major part of reinforced concrete (RC) structures is the result of the flexural and shear deformations mainly caused by bending and shear diagonal cracking, respectively. However, the evaluation of the shear deformation contribution is relatively difficult due to the complexities involving the shear behavior of cracked RC elements. These complexities are even more complicated when structures are statically indeterminate, since the external and internal forces cannot be determined from direct application of the equilibrium equations. To address these issues, the current study aims to develop a novel simplified analytical model based on the flexibility (force) method to predict the deflections of statically indeterminate RC structures up to their failure, which can be in bending or in shear. This analytical model considers the influence of flexural cracks on the shear stiffness degradation of a RC structure after concrete cracking initiation, and has a format adjusted for design practice. The good predictive performance of the analytical model is demonstrated by simulating experimental tests with RC elements where shear deformation has different level of contribution for the total deflection registered in these tests.Marie Curie Initial Training Networks - "endure" European Network for Durable Reinforcement and Rehabilitation Solutions, project no: 607851.info:eu-repo/semantics/publishedVersio
FAST Globular Cluster Pulsar Survey: Twenty-Four Pulsars Discovered in Fifteen Globular Clusters
We present the discovery of 24 pulsars in 15 Globular Clusters (GCs) using
the Five-hundred-meter Aperture Spherical radio Telescope (FAST). These include
the first pulsar discoveries in M2, M10, and M14. Most of the new systems are
either confirmed or likely members of binary systems. M53C, NGC6517H and I are
the only three pulsars confirmed to be isolated. M14A is a black widow pulsar
with an orbital period of 5.5 hours and a minimum companion mass of 0.016 \Ms.
M14E is an eclipsing binary pulsar with an orbital period of 20.3 hours. With
the other 8 discoveries that have been reported elsewhere, in total 32 GC
pulsars have been discovered by FAST so far. In addition, We detected M3A
twice. This was enough to determine that it is a black widow pulsar with an
orbital period of 3.3 hours and a minimum companion mass of 0.0125 \Ms.Comment: 12 pages, 2 figures, accepted by ApJL, comments are always welcomed
PSR J1926-0652: A Pulsar with Interesting Emission Properties Discovered at FAST
We describe PSR J1926-0652, a pulsar recently discovered with the
Five-hundred-meter Aperture Spherical radio Telescope (FAST). Using sensitive
single-pulse detections from FAST and long-term timing observations from the
Parkes 64-m radio telescope, we probed phenomena on both long and short time
scales. The FAST observations covered a wide frequency range from 270 to 800
MHz, enabling individual pulses to be studied in detail. The pulsar exhibits at
least four profile components, short-term nulling lasting from 4 to 450 pulses,
complex subpulse drifting behaviours and intermittency on scales of tens of
minutes. While the average band spacing P3 is relatively constant across
different bursts and components, significant variations in the separation of
adjacent bands are seen, especially near the beginning and end of a burst. Band
shapes and slopes are quite variable, especially for the trailing components
and for the shorter bursts. We show that for each burst the last detectable
pulse prior to emission ceasing has different properties compared to other
pulses. These complexities pose challenges for the classic carousel-type
models.Comment: 13pages with 12 figure
Synthesis Mechanism of Low-Voltage Praseodymium Oxide Doped Zinc Oxide Varistor Ceramics Prepared Through Modified Citrate Gel Coating
High demands on low-voltage electronics have increased the need for zinc oxide (ZnO) varistors with fast response, highly non-linear current-voltage characteristics and energy absorption capabilities at low breakdown voltage. However, trade-off between breakdown voltage and grain size poses a critical bottle-neck in the production of low-voltage varistors. The present study highlights the synthesis mechanism for obtaining praseodymium oxide (Pr6O11) based ZnO varistor ceramics having breakdown voltages of 2.8 to 13.3 V/mm through employment of direct modified citrate gel coating technique. Precursor powder and its ceramics were examined by means of TG/DTG, FTIR, XRD and FESEM analyses. The electrical properties as a function of Pr6O11 addition were analyzed on the basis of I-V characteristic measurement. The breakdown voltage could be adjusted from 0.01 to 0.06 V per grain boundary by controlling the amount of Pr6O11 from 0.2 to 0.8 mol%, without alteration of the grain size. The non-linearity coefficient, α, varied from 3.0 to 3.5 and the barrier height ranged from 0.56 to 0.64 eV. Breakdown voltage and α lowering with increasing Pr6O11 content were associated to reduction in the barrier height caused by variation in O vacancies at grain boundary
The FAST discovery of an Eclipsing Binary Millisecond Pulsar in the Globular Cluster M92 (NGC 6341)
We report the discovery of an eclipsing binary millisecond pulsar in the
globular cluster M92 (NGC6341) with the Five-hundred-meter Aperture Spherical
radio Telescope (FAST). PSR J1717+4308A, or M92A, has a pulse frequency of
316.5~Hz (3.16~ms) and a dispersion measure of 35.45 pc cm. The pulsar
is a member of a binary system with an orbital period of 0.20~days around a
low-mass companion which has a median mass of 0.18~\Ms. From observations
so far, at least two eclipsing events have been observed in each orbit. The
longer one lasted for ~5000~s in the orbital phase range 0.1--0.5. The other
lasted for ~500~s and occurred between 1000--2000~s before or after the longer
eclipsing event. The lengths of these two eclipsing events also change. These
properties suggest that J1717+4308A is a ``red-back'' system with a low-mass
main sequence or sub-giant companion. Timing observations of the pulsar and
further searches of the data for additional pulsars are ongoing.Comment: 9 pages, 2 figures, submitted to ApJL, comments are welcomed
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