9,924 research outputs found
Nuclear Equation of State and Internal Structure of Magnetars
Recently, neutron stars with very strong surface magnetic fields have been
suggested as the site for the origin of observed soft gamma repeaters (SGRs).
We investigate the influence of a strong magnetic field on the properties and
internal structure of such strongly magnetized neutron stars (magnetars). The
presence of a sufficiently strong magnetic field changes the ratio of protons
to neutrons as well as the neutron appearance density. We also study the pion
production and pion condensation in a strong magnetic field. We discuss the
pion condensation in the interior of magnetars as a possible source of SGRs.Comment: 5 pages with 3 figures, To appear in the Proceedings of the 5th
Huntsville Gamma Ray Burst Symposium, Huntsville, Alabama, USA, Oct. 18-22,
199
Intermediate-mass black holes in dwarf galaxies out to redshift 2.4 in the Chandra COSMOS Legacy Survey
We present a sample of 40 AGN in dwarf galaxies at redshifts
2.4. The galaxies are drawn from the \textit{Chandra} COSMOS-Legacy survey as
having stellar masses M. Most
of the dwarf galaxies are star-forming. After removing the contribution from
star formation to the X-ray emission, the AGN luminosities of the 40 dwarf
galaxies are in the range erg
s. With 12 sources at , our sample constitutes the
highest-redshift discovery of AGN in dwarf galaxies. The record-holder is
cid\_1192, at and with erg
s. One of the dwarf galaxies has
M and is the least massive galaxy found so far to host an AGN. All
the AGN are of type 2 and consistent with hosting intermediate-mass black holes
(BHs) with masses M and typical Eddington
ratios . We also study the evolution, corrected for completeness, of AGN
fraction with stellar mass, X-ray luminosity, and redshift in dwarf galaxies
out to = 0.7. We find that the AGN fraction for M and erg s is
0.4\% for 0.3 and that it decreases with X-ray luminosity and
decreasing stellar mass. Unlike massive galaxies, the AGN fraction seems to
decrease with redshift, suggesting that AGN in dwarf galaxies evolve
differently than those in high-mass galaxies. Mindful of potential caveats, the
results seem to favor a direct collapse formation mechanism for the seed BHs in
the early Universe.Comment: 16 pages, 10 figures, accepted for publication in MNRA
A quasi-time-dependent radiative transfer model of OH104.9+2.4
We investigate the pulsation-phase dependent properties of the circumstellar
dust shell (CDS) of the OH/IR star OH104.9+2.4 based on radiative transfer
modeling (RTM) using the code DUSTY. Our previous study concerning simultaneous
modeling of the spectral energy distribution (SED) and near-infrared (NIR)
visibilities (Riechers et al. 2004) has now been extended by means of a more
detailed analysis of the pulsation-phase dependence of the model parameters of
OH104.9+2.4. In order to investigate the temporal variation in the spatial
structure of the CDS, additional NIR speckle interferometric observations in
the K' band were carried out with the 6 m telescope of the Special
Astrophysical Observatory (SAO). At a wavelength of 2.12 micron the
diffraction-limited resolution of 74 mas was attained. Several key parameters
of our previous best-fitting model had to be adjusted in order to be consistent
with the newly extended amount of observational data. It was found that a
simple rescaling of the bolometric flux F_bol is not sufficient to take the
variability of the source into account, as the change in optical depth over a
full pulsation cycle is rather high. On the other hand, the impact of a change
in effective temperature T_eff on SED and visibility is rather small. However,
observations, as well as models for other AGB stars, show the necessity of
including a variation of T_eff with pulsation phase in the radiative transfer
models. Therefore, our new best-fitting model accounts for these changes.Comment: 7 pages, including 5 postscript figures and 3 tables. Published in
Astronomy and Astrophysics. (v1: accepted version; v2: published version,
minor grammatical changes
Approximating ReLU on a Reduced Ring for Efficient MPC-based Private Inference
Secure multi-party computation (MPC) allows users to offload machine learning
inference on untrusted servers without having to share their privacy-sensitive
data. Despite their strong security properties, MPC-based private inference has
not been widely adopted in the real world due to their high communication
overhead. When evaluating ReLU layers, MPC protocols incur a significant amount
of communication between the parties, making the end-to-end execution time
multiple orders slower than its non-private counterpart.
This paper presents HummingBird, an MPC framework that reduces the ReLU
communication overhead significantly by using only a subset of the bits to
evaluate ReLU on a smaller ring. Based on theoretical analyses, HummingBird
identifies bits in the secret share that are not crucial for accuracy and
excludes them during ReLU evaluation to reduce communication. With its
efficient search engine, HummingBird discards 87--91% of the bits during ReLU
and still maintains high accuracy. On a real MPC setup involving multiple
servers, HummingBird achieves on average 2.03--2.67x end-to-end speedup without
introducing any errors, and up to 8.64x average speedup when some amount of
accuracy degradation can be tolerated, due to its up to 8.76x communication
reduction
Systems Pharmacological Approach of Pulsatillae Radix
In East Asian traditional medicine, Pulsatillae Radix (PR) is widely used to treat amoebic dysentery and renowned for its anti-inflammatory effects. This study aimed to confirm evidence regarding the potential therapeutic effect of PR on Crohnâs disease using a system network level based in silico approach. Study results showed that the compounds in PR are highly connected to Crohnâs disease related pathways, biological processes, and organs, and these findings were confirmed by compound-target network, target-pathway network, and gene ontology analysis. Most compounds in PR have been reported to possess anti-inflammatory, anticancer, and antioxidant effects, and we found that these compounds interact with multiple targets in a synergetic way. Furthermore, the mRNA expressions of genes targeted by PR are elevated significantly in immunity-related organ tissues, small intestine, and colon. Our results suggest that the anti-inflammatory and repair and immune system enhancing effects of PR might have therapeutic impact on Crohnâs disease
Mass-Radius Relation for Magnetic White Dwarfs
Recently, several white dwarfs with very strong surface magnetic fields have
been observed. In this paper we explore the possibility that such stars could
have sufficiently strong internal fields to alter their structure. We obtain a
revised white dwarf mass-radius relation in the presence of strong internal
magnetic fields. We first derive the equation of state for a fully degenerate
ideal electron gas in a magnetic field using an Euler-MacLaurin expansion. We
use this to obtain the mass-radius relation for magnetic He, C,
and Fe white dwarfs of uniform composition.Comment: 7 pages, 7 figures and 1 table, To appear in Ap
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