3,913 research outputs found
Chandra Observation of a Weak Shock in the Galaxy Cluster A2556
Based on a 21.5 ks \chandra\ observation of A2556, we identify an edge on the
surface brightness profile (SBP) at about 160 kpc northeast of the
cluster center, and it corresponds to a shock front whose Mach number
is calculated to be . No prominent
substructure, such as sub-cluster, is found in either optical or X-ray band
that can be associated with the edge, suggesting that the conventional
super-sonic motion mechanism may not work in this case. As an alternative
solution, we propose that the nonlinear steepening of acoustic wave, which is
induced by the turbulence of the ICM at the core of the cluster, can be used to
explain the origin of the shock front. Although nonlinear steepening weak shock
is expected to occur frequently in clusters, why it is rarely observed still
remains a question that requires further investigation, including both deeper
X-ray observation and extensive theoretical studies.Comment: 15 pages, 4 figures, accepted by Ap
Poly[diaqua-μ2-oxalato-di-μ4-succinato-diyttrium(III)]
In the title compound, [Y2(C4H4O4)2(C2O4)(H2O)2]n, the flexible succinate anion assumes a gauche conformation and bridges the eight-coordinated Y atoms, generating two-dimensional layers parallel to (010). The coordination polymer layers are linked into a three-dimensional framework by the rigid oxalate ligands. The oxalate ions are located on a center of inversion. InterÂmolecular O—H⋯O hydrogen bonds help to stabilize the crystal structure
Targeting Acid-Sensing Ion Channels by Peptide Toxins
Acid-sensing ion channels (ASICs) are proton-gated ion channels that are highly expressed in the nervous system and play important roles in physiological and pathological conditions. They are also expressed in non-neuronal tissues with different functions. The ASICs rapidly respond to a reduction in extracellular pH with an inward current that is quickly inactivated despite the continuous presence of protons. Recently, protons have been identified as neurotransmitters in the brain. Until now, six different isoforms (ASIC1a, 1b, 2a, 2b, 3 and 4) in rodents have been discovered and they can be assembled into homotrimers or heterotrimers to form an ion channel. Peptide toxins targeting ASICs have been found from the venoms of spider Psalmotoxin-1 (PcTx1), sea anemones (APETx2 and PhcrTx1) and snakes (MitTx and mambalgins). They reveal different pharmacological properties and are selective blockers of ASICs, except for MitTx, which is a potent activator of ASICs. In this mini review, the structure, pharmacology and effects of peptide toxins on ASICs will be introduced and their therapeutic potentials for neurological and psychological diseases will be discussed
QC-ODKLA: Quantized and Communication-Censored Online Decentralized Kernel Learning via Linearized ADMM
This paper focuses on online kernel learning over a decentralized network.
Each agent in the network receives continuous streaming data locally and works
collaboratively to learn a nonlinear prediction function that is globally
optimal in the reproducing kernel Hilbert space with respect to the total
instantaneous costs of all agents. In order to circumvent the curse of
dimensionality issue in traditional online kernel learning, we utilize random
feature (RF) mapping to convert the non-parametric kernel learning problem into
a fixed-length parametric one in the RF space. We then propose a novel learning
framework named Online Decentralized Kernel learning via Linearized ADMM
(ODKLA) to efficiently solve the online decentralized kernel learning problem.
To further improve the communication efficiency, we add the quantization and
censoring strategies in the communication stage and develop the Quantized and
Communication-censored ODKLA (QC-ODKLA) algorithm. We theoretically prove that
both ODKLA and QC-ODKLA can achieve the optimal sublinear regret
over time slots. Through numerical experiments, we
evaluate the learning effectiveness, communication, and computation
efficiencies of the proposed methods
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