237 research outputs found
Effects of Geometrical Symmetry on the Vortex Nucleation and Penetration in Mesoscopic Superconductors
We investigate how the geometrical symmetry affects the penetration and
arrangement of vortices in mesoscopic superconductors using self-consistent
Bogoliubov-de Gennes equations. We find that the entrance of the vortex happens
when the current density at the hot spots reaches the depairing current
density. Through determining the spatial distribution of hot spots, the
geometrical symmetry of the superconducting sample influences the nucleation
and entrance of vortices. Our results propose one possible experimental
approach to control and manipulate the quantum states of mesoscopic
superconductors with their topological geometries, and they can be easily
generalized to the confined superfluids and Bose-Einstein condensates
Generalized Two-Dimensional Quaternion Principal Component Analysis with Weighting for Color Image Recognition
A generalized two-dimensional quaternion principal component analysis
(G2DQPCA) approach with weighting is presented for color image analysis. As a
general framework of 2DQPCA, G2DQPCA is flexible to adapt different constraints
or requirements by imposing norms both on the constraint function and
the objective function. The gradient operator of quaternion vector functions is
redefined by the structure-preserving gradient operator of real vector
function. Under the framework of minorization-maximization (MM), an iterative
algorithm is developed to obtain the optimal closed-form solution of G2DQPCA.
The projection vectors generated by the deflating scheme are required to be
orthogonal to each other. A weighting matrix is defined to magnify the effect
of main features. The weighted projection bases remain the accuracy of face
recognition unchanged or moving in a tight range as the number of features
increases. The numerical results based on the real face databases validate that
the newly proposed method performs better than the state-of-the-art algorithms.Comment: 15 pages, 15 figure
(6aS,11aR,11cS)-8-Sulfanylidene-2,3,5,6,6a,7,11,11a,11b,11c-decahydro-3a,7a-diaza-1H,4H-benzo[de]anthracen-3a-ium chloride hemihydrate
The title compound, C15H23N2S+·Cl−·0.5H2O, was prepared from (6aS,11aR,11cS)-2,3,5,6,6a,7,11,11a,11b,11c-decahydro-3a,7a-diaza-1H,4H-benzo[de]anthracene-8-one (sophocarpine) and Lawesson’s reagent. The thione-substituted ring is in an envelope conformation and the three other six-membered rings are in chair conformations. In the crystal, anions and cations are linked by N—H⋯Cl and weak C—H⋯Cl hydrogen bonds. One 0.5-occupancy solvent water molecule lies on a twofold rotation axis and another 0.25-occupancy solvent water molecule is in a general position. The H atoms of these water molecules were not located or included in the refinement
Tunable boson-assisted finite-range interaction and engineering Majorana corner modes in optical lattices
Nonlocal interaction between ultracold atoms trapped in optical lattices can
give rise to interesting quantum many-body phenomena. However, its realization
usually demands unconventional techniques, for example the artificial gauge
fields or higher-orbit Feshbach resonances, and is not highly controllable.
Here, we propose a valid and feasible scheme for realizing a tunable
finite-range interaction for spinless fermions immersed into the bath of
bosons. The strength of the effective interaction for the fermionic subsystem
is artificially tunable by manipulating bosons, ranging from the repulsive to
attractive regime. And the interaction distance is locked to the hopping of
bosons, making the finite-range interaction perfectly clean for the fermionic
subsystem. Specifically we find that, by introducing an additional staggered
hopping of bosons, the proposal is readily applied to search the Majorana
corner modes in such a spinless system, without implementation of complex
artificial gauge fields, which is totally distinct from existing results
reported in spinful systems. Therefore this scheme provides a potential
platform for exploring the unconventional topological superfluids and other
nontrivial phases induced by long-range interactions in ultracold atoms.Comment: 11 pages, 6 figure
Abnormal magnetoresistance behavior in Nb thin film with rectangular antidot lattice
Abnormal magnetoresistance behavior is found in superconducting Nb films
perforated with rectangular arrays of antidots (holes). Generally
magnetoresistance were always found to increase with increasing magnetic field.
Here we observed a reversal of this behavior for particular in low temperature
or current density. This phenomenon is due to a strong 'caging effect' which
interstitial vortices are strongly trapped among pinned multivortices.Comment: 4 pages, 2 figure
Prevalence of syphilis infection in different tiers of female sex workers in China: implications for surveillance and interventions
<p>Abstract</p> <p>Background</p> <p>Syphilis has made a dramatic resurgence in China during the past two decades and become the third most prevalent notifiable infectious disease in China. Female sex workers (FSWs) have become one of key populations for the epidemic. In order to investigate syphilis infection among different tiers of FSWs, a cross-sectional study was conducted in 8 sites in China.</p> <p>Methods</p> <p>Serum specimens (n = 7,118) were collected to test for syphilis and questionnaire interviews were conducted to obtain socio-demographic and behavioral information among FSWs recruited from different types of venues. FSWs were categorized into three tiers (high-, middle- and low-tier FSWs) based on the venues where they solicited clients. Serum specimens were screened with enzyme-linked immunosorbent assay (ELISA) for treponemal antibody followed by confirmation with non-treponemal toluidine red unheated serum test (TRUST) for positive ELISA specimens to determine syphilis infection. A logistic regression model was used to determine factors associated with syphilis infection.</p> <p>Results</p> <p>Overall syphilis prevalence was 5.0% (95%CI, 4.5-5.5%). Low-tier FSWs had the highest prevalence (9.7%; 95%CI, 8.3-11.1%), followed by middle-tier (4.3%; 95%CI, 3.6-5.0%, <it>P </it>< 0.001) and high-tier FSWs (2.2%; 95%CI, 1.6-2.9%, <it>P </it>< 0.001). Factors independently associated with syphilis infection included older age, lower education level, geographic location, lower tier of typology, and injection drug use.</p> <p>Conclusions</p> <p>This multi-site survey showed a high prevalence of syphilis infection among FSWs and substantial disparities in syphilis prevalence by the tier of FSWs. The difference in syphilis prevalence is substantial between different tiers of FSWs, with the highest rate among low-tier FSWs. Thus, current surveillance and intervention activities, which have low coverage in low-tier FSWs in China, should be further examined.</p
Abnormal magnetoresistance behavior in Nb thin film with rectangular antidot lattice
Abnormal magnetoresistance behavior is found in superconducting Nb films
perforated with rectangular arrays of antidots (holes). Generally
magnetoresistance were always found to increase with increasing magnetic field.
Here we observed a reversal of this behavior for particular in low temperature
or current density. This phenomenon is due to a strong 'caging effect' which
interstitial vortices are strongly trapped among pinned multivortices.Comment: 4 pages, 2 figure
Ultrafast Photoinduced Band Splitting and Carrier Dynamics in Chiral Tellurium Nanosheets
Trigonal tellurium (Te) is a chiral semiconductor that lacks both mirror and
inversion symmetries, resulting in complex band structures with Weyl crossings
and unique spin textures. Detailed time-resolved polarized reflectance
spectroscopy is used to investigate its band structure and carrier dynamics.
The polarized transient spectra reveal optical transitions between the
uppermost spin-split H4 and H5 and the degenerate H6 valence bands (VB) and the
lowest degenerate H6 conduction band (CB) as well as a higher energy transition
at the L-point. Surprisingly, the degeneracy of the H6 CB (a proposed Weyl
node) is lifted and the spin-split VB gap is reduced upon photoexcitation
before relaxing to equilibrium as the carriers decay. Using ab initio density
functional theory (DFT) calculations we conclude that the dynamic band
structure is caused by a photoinduced shear strain in the Te film that breaks
the screw symmetry of the crystal. The band-edge anisotropy is also reflected
in the hot carrier decay rate, which is a factor of two slower along c-axis
than perpendicular to it. The majority of photoexcited carriers near the
band-edge are seen to recombine within 30 ps while higher lying transitions
observed near 1.2 eV appear to have substantially longer lifetimes, potentially
due to contributions of intervalley processes in the recombination rate. These
new findings shed light on the strong correlation between photoinduced carriers
and electronic structure in anisotropic crystals, which opens a potential
pathway for designing novel Te-based devices that take advantage of the
topological structures as well as strong spin-related properties.Comment: 42 pages, 13 figure
A simulation study on the measurement of D0-D0bar mixing parameter y at BES-III
We established a method on measuring the \dzdzb mixing parameter for
BESIII experiment at the BEPCII collider. In this method, the doubly
tagged events, with one decays to
CP-eigenstates and the other decays semileptonically, are used to
reconstruct the signals. Since this analysis requires good separation,
a likelihood approach, which combines the , time of flight and the
electromagnetic shower detectors information, is used for particle
identification. We estimate the sensitivity of the measurement of to be
0.007 based on a fully simulated MC sample.Comment: 6 pages, 7 figure
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