4,714 research outputs found
Empirical studies on the network of social groups: the case of Tencent QQ
Participation in social groups are important but the collective behaviors of
human as a group are difficult to analyze due to the difficulties to quantify
ordinary social relation, group membership, and to collect a comprehensive
dataset. Such difficulties can be circumvented by analyzing online social
networks. In this paper, we analyze a comprehensive dataset obtained from
Tencent QQ, an instant messenger with the highest market share in China.
Specifically, we analyze three derivative networks involving groups and their
members -- the hypergraph of groups, the network of groups and the user network
-- to reveal social interactions at microscopic and mesoscopic level. Our
results uncover interesting behaviors on the growth of user groups, the
interactions between groups, and their relationship with member age and gender.
These findings lead to insights which are difficult to obtain in ordinary
social networks.Comment: 18 pages, 9 figure
Neuroprotective effects of α-lipoic acid against hypoxic– ischemic brain injury in neonatal rats
Purpose: To explore the neuroprotective efficacy of α-lipoic acid (ALA) against hypoxic-ischemic encephalopathy (HIE) in neonatal rats.Methods: Forty-eight rats (P7-pups) were randomly assigned to one of four groups: group I received saline; group II (HI) underwent unilateral carotid artery ligation and hypoxia (92 % N2 and 8 % O2) for 2.5 h; and groups III and IV (ALA 50 and 100) were treated with 50 or 100 mg ALA/kg for 7 days prior to against hypoxic-ischemic (HI) insult. Cerebral antioxidant status, edema, and the levels of inflammatory markers were determined.Results: ALA administration substantially (p < 0.01) attenuated both cerebral infarct area and degree of edema while decreasing the levels of several inflammatory markers (TNF-α, NF-p65, IL-1β, IL-6). In addition, in the ALA groups, antioxidant enzyme (SOD, CAT, GSH) activities were significantly elevated,while the expressions of TNF-α and IL-1β protein were significantly (p < 0.01) down-regulated.Conclusion: The neuroprotective efficacy of ALA in HIE can be attributed to its suppression of both oxidative stress and the levels of inflammatory markers.Keywords: Hypoxic–ischemic brain injury, α-Lipoic acid, Cerebral infarct area, Edema, Antioxidants, Inflammatory marker
Stability of Phase-modulated Quantum Key Distribution System
Phase drift and random fluctuation of interference visibility in double
unbalanced M-Z QKD system are observed and distinguished. It has been found
that the interference visibilities are influenced deeply by the disturbance of
transmission fiber. Theory analysis shows that the fluctuation is derived from
the envioronmental disturbance on polarization characteristic of fiber,
especially including transmission fiber. Finally, stability conditions of
one-way anti-disturbed M-Z QKD system are given out, which provides a
theoretical guide in pragmatic anti-disturbed QKD.Comment: 9 pages, 3 figue
Probing Transverse Momentum Broadening via Dihadron and Hadron-jet Angular Correlations in Relativistic Heavy-ion Collisions
Dijet, dihadron, hadron-jet angular correlations have been reckoned as
important probes of the transverse momentum broadening effects in relativistic
nuclear collisions. When a pair of high-energy jets created in hard collisions
traverse the quark-gluon plasma produced in heavy-ion collisions, they become
de-correlated due to the vacuum soft gluon radiation associated with the
Sudakov logarithms and the medium-induced transverse momentum broadening. For
the first time, we employ the systematical resummation formalism and establish
a baseline calculation to describe the dihadron and hadron-jet angular
correlation data in and peripheral collisions where the medium effect
is negligible. We demonstrate that the medium-induced broadening and the so-called jet quenching parameter can be
extracted from the angular de-correlations observed in collisions. A
global analysis of dihadron and hadron-jet angular correlation data
renders the best fit for a
quark jet at RHIC top energy. Further experimental and theoretical efforts
along the direction of this work shall significantly advance the quantitative
understanding of transverse momentum broadening and help us acquire
unprecedented knowledge of jet quenching parameter in relativistic heavy-ion
collisions.Comment: 6 pages, 3 figure
Intrinsic-Stabilization Uni-Directional Quantum Key Distribution Between Beijing and Tianjin
Quantum key distribution provides unconditional security for communication.
Unfortunately, current experiment schemes are not suitable for long-distance
fiber transmission because of instability or backscattering. We present a
uni-directional intrinsic-stabilization scheme that is based on
Michelson-Faraday interferometers, in which reflectors are replaced with 90
degree Faraday mirrors. With the scheme, key exchange from Beijing to Tianjin
over 125 kilometers with an average error rate is below 6% has been achieved
and its limited distance exceeds 150 kilometers. Experimental result shows the
system is insensitive to environment and can run over day and night without any
break even in the noise workshop.Comment: 7 pages,4 figure
Anti-proliferation and radiosensitization effects of chitooligosaccharides on human lung cancer line HepG2
AbstractObjectiveTo observe the anti-proliferation and radiosensitization effect of chitooligosaccharides (COS) on human lung cancer cell line HepG2.MethodsCCK-8 assay was employed to obtain the inhibition ratio of COS on HepG2 cells at 24Â h after treatment. The clonogenic assay was used to analyze the cell viability of RAY group and RAYÂ +Â COS group with X-ray of 0, 1, 2, 4, 6 and 8Â Gy, and the cell survival curve was used to analyze the sensitization ratio of COS. Flow cytometry was employed to detect cell cycle and apoptosis rate in control group, RAY group and RAYÂ +Â COS group after 24Â h treatment.ResultsCOS inhibited the proliferation of HepG2 cells, and the inhibition rate positively correlated with the concentration of COS. The cell viability decreased with increasing exposure dose in RAY group and RAYÂ +Â COS group. The cell viabilities of RAYÂ +Â COS group were lower than those of RAY group at the dose of 4, 6 and 8Â Gy (PÂ <Â 0.05), and the sensitization ratio of COS was 1.19. There were higher percentage at G2/M phase and apoptosis rate, and lower percentage at S phase in RAYÂ +Â COS group versus the other two groups (PÂ <Â 0.01).ConclusionsCOS can inhibit the proliferation of HepG2 cells, and enhance the radiosensitization of HepG2 cells, induce apoptosis and G2/M phase arrest
Holographic Storage of Biphoton Entanglement
Coherent and reversible storage of multi-photon entanglement with a multimode
quantum memory is essential for scalable all-optical quantum information
processing. Although single photon has been successfully stored in different
quantum systems, storage of multi-photon entanglement remains challenging
because of the critical requirement for coherent control of photonic
entanglement source, multimode quantum memory, and quantum interface between
them. Here we demonstrate a coherent and reversible storage of biphoton
Bell-type entanglement with a holographic multimode atomic-ensemble-based
quantum memory. The retrieved biphoton entanglement violates Bell's inequality
for 1 microsecond storage time and a memory-process fidelity of 98% is
demonstrated by quantum state tomography.Comment: 5 pages, 4 figures, accepted by Phys. Rev. Let
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