416 research outputs found
Identifying vital edges in Chinese air route network via memetic algorithm
Due to its rapid development in the past decade, air transportation system
has attracted considerable research attention from diverse communities. While
most of the previous studies focused on airline networks, here we
systematically explore the robustness of the Chinese air route network, and
identify the vital edges which form the backbone of Chinese air transportation
system. Specifically, we employ a memetic algorithm to minimize the network
robustness after removing certain edges hence the solution of this model is the
set of vital edges. Counterintuitively, our results show that the most vital
edges are not necessarily the edges of highest topological importance, for
which we provide an extensive explanation from the microscope of view. Our
findings also offer new insights to understanding and optimizing other
real-world network systems
The Study of Dust Formation of Six Tidal Disruption Events
This paper investigates eleven (UV-)optical-infrared (IR) spectral energy
distributions (SEDs) of six tidal disruption events (TDEs), which are
ASASSN-14li, ASASSN-15lh, ASASSN-18ul, ASASSN-18zj, PS18kh, and ZTF18acaqdaa.
We find that all the SEDs show evident IR excesses. We invoke the blackbody
plus dust emission model to fit the SEDs, and find that the model can account
for the SEDs. The derived masses of the dust surrounding ASASSN-14li,
ASASSN-15lh, ASASSN-18ul, ASASSN-18zj, PS18kh, and ZTF18acaqdaa are
respectively ,
,
,
,
, and , if the dust is graphite (silicate). The
temperature of the graphite (silicate) dust of the six TDEs are respectively
\,K, \,K,
\,K, \,K, \,K, and
\,K. By comparing the derived temperatures to the
vaporization temperature of graphite (\,K) and silicate (\,K), we suggest that the IR excesses of PS18kh can be explained by
both the graphite and silicate dust, the rest five TDEs favor the graphite dust
while the silicate dust model cannot be excluded. Moreover, we demonstrate the
lower limits of the radii of the dust shells surrounding the six TDEs are
significantly larger than those of the radii of the photospheres at the first
epochs of SEDs, indicating that the dust might exist before the the TDEs
occurred.Comment: 13 pages, 4 figures, 4 tables, submitted to Ap
An intrinsic link between long-term UV/optical variations and X-ray loudness in quasars
Observations have shown that UV/optical variation amplitude of quasars depend
on several physi- cal parameters including luminosity, Eddington ratio, and
likely also black hole mass. Identifying new factors which correlate with the
variation is essential to probe the underlying physical processes. Combining
~ten years long quasar light curves from SDSS stripe 82 and X-ray data from
Stripe 82X, we build a sample of X-ray detected quasars to investigate the
relation between UV/optical variation amplitude () and X-ray
loudness. We find that quasars with more intense X-ray radiation (com- pared to
bolometric luminosity) are more variable in UV/optical. Such correlation
remains highly significant after excluding the effect of other parameters
including luminosity, black hole mass, Ed- dington ratio, redshift, rest-frame
wavelength (i.e., through partial correlation analyses). We further find the
intrinsic link between X-ray loudness and UV/optical variation is gradually
more prominent on longer timescales (up to 10 years in the observed frame), but
tends to disappear at timescales < 100 days. This suggests a slow and long-term
underlying physical process. The X-ray reprocessing paradigm, in which
UV/optical variation is produced by a variable central X-ray emission
illuminating the accretion disk, is thus disfavored. The discovery points to an
interesting scheme that both the X-ray corona heating and UV/optical variation
is quasars are closely associated with magnetic disc turbulence, and the
innermost disc turbulence (where corona heating occurs) correlates with the
slow turbulence at larger radii (where UV/optical emission is produced).Comment: 9 pages, 4 figures, 1 table, accepted by Ap
Quantum Computing for MIMO Beam Selection Problem: Model and Optical Experimental Solution
Massive multiple-input multiple-output (MIMO) has gained widespread
popularity in recent years due to its ability to increase data rates, improve
signal quality, and provide better coverage in challenging environments. In
this paper, we investigate the MIMO beam selection (MBS) problem, which is
proven to be NP-hard and computationally intractable. To deal with this
problem, quantum computing that can provide faster and more efficient solutions
to large-scale combinatorial optimization is considered. MBS is formulated in a
quadratic unbounded binary optimization form and solved with Coherent Ising
Machine (CIM) physical machine. We compare the performance of our solution with
two classic heuristics, simulated annealing and Tabu search. The results
demonstrate an average performance improvement by a factor of 261.23 and 20.6,
respectively, which shows that CIM-based solution performs significantly better
in terms of selecting the optimal subset of beams. This work shows great
promise for practical 5G operation and promotes the application of quantum
computing in solving computationally hard problems in communication.Comment: Accepted by IEEE Globecom 202
A Single Cluster Covering for Dodecagonal Quasiperiodic Structure
Single cluster covering approach provides a plausible mechanism for the
formation and stability of octagonal and decagonal quasiperiodic structures.
For dodecagonal quasiperiodic pattern such a single cluster covering scheme is
still unavailable. Here we demonstrated that the ship tiling, one of the
dodecagonal quasiperioidic structures, can be constructed from one single
prototile with matching rules. A deflation procedure is devised by assigning
proper orientations to the tiles present in the ship tiling including regular
triangle, 30{\deg}-rhombus and square, and fourteen types of vertical
configurations have been identified in the deflated pattern, which fulfill the
closure condition under deflation and all result in a T-cluster centered at
vertex. This result can facilitate the study of physical properties of
dodecagonal quasicrystals.Comment: 5 pigs ;11page
The association between S100A13 and HMGA1 in the modulation of thyroid cancer proliferation and invasion
Additional file 5: Figure S3. Lentivirus-mediated S100A13 knockdown was utilized to detect the effect on migration capability with scratch-wound assays in TPC1 cell
Fundamental mechanism underlying subwavelength optics of metamaterials: Charge oscillation-induced light emission and interference
Interactions between light and conducting nanostructures can result in a
variety of novel and fascinating phenomena. These properties may have wide
applications, but their underlying mechanisms have not been completely
understood. From calculations of surface charge density waves on conducting
gratings and by comparing them with classical surface plasmons, we revealed a
general yet concrete picture about coupling of light to free electron
oscillation on structured conducting surfaces that can lead to oscillating
subwavelength charge patterns (i.e., spoof surface plasmons but without the
dispersion property of classical surface plasmons). New wavelets emitted from
these light sources then destructively interfere to form evanescent waves. This
principle, usually combined with other mechanisms (e.g. resonance), is mainly a
geometrical effect that can be universally involved in light scattering from
all periodic and nonperiodic structures containing free electrons, including
perfect conductors. The spoof surface plasmon picture may provide clear
guidelines for developing metamaterial-based nano-optical devices.Comment: 11 pages, 9 figures, submitted to PRB (2009
Isolation and characterization of a novel arenavirus harbored by Rodents and Shrews in Zhejiang province, China
AbstractTo determine the biodiversity of arenaviruses in China, we captured and screened rodents and shrews in Wenzhou city, Zhejiang province, a locality where hemorrhagic fever diseases are endemic in humans. Accordingly, arenaviruses were detected in 42 of 351 rodents from eight species, and in 12 of 272 Asian house shrews (Suncus murinus), by RT-PCR targeting the L segment. From these, a single arenavirus was successfully isolated in cell culture. The virion particles exhibited a typical arenavirus morphology under transmission electron microscopy. Comparison of the S and L segment sequences revealed high levels of nucleotide (>32.2% and >39.6%) and amino acid (>28.8% and >43.8%) sequence differences from known arenaviruses, suggesting that it represents a novel arenavirus, which we designated Wenzhou virus (WENV). Phylogenetic analysis revealed that all WENV strains harbored by both rodents and Asian house shrews formed a distinct lineage most closely related to Old World arenaviruses
Molecular and Functional Characterization of a c-type lysozyme from the Asian Corn Borer, Ostrinia furnacalis
Some lepidopteran lysozymes have been reported to display activity against Gram-positive and Gram-negative bacteria, in contrast to most lysozymes that are active only against Gram-positive bacteria. OstrinLysC, a c-type lysozyme, was purified from the Asian corn borer, Ostrinia furnacalis Guenée (Lepidoptera: Pyralidae), and shows activity against Gram-positive and Gram-negative bacteria. The NH2-terminal amino acid sequence was determined by Edman degradation and used in a homology cloning strategy. The gene coding for OstrinLysC contains three exons and two introns. The expression profile of the OstrinlysC gene was examined by quantitative real-time PCR. Following injection of the larvae with bacteria, the OstrinlysC gene is strongly up-regulated in immune tissues. Transcripts were also detected in gut tissue. After feeding the larvae with bacteria, OstrinlysC transcripts increased in immune tissues. A very low level of transcript abundance was also detected in gut tissue. These results suggested that the OstrinlysC gene is involved in immune responses. The three dimensional structure of OstrinLysC was predicted. Based on comparison of the 3-D structure of OstrinLysC with that of silkworm lysozyme and chicken lysozyme, we hypothesize that the positive charge-rich surface and the short loop-2, which is close to the cluster of hydrophobic residues, may play important roles in the interaction with the outer membrane of Gram-negative bacterial cell walls
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