19,844 research outputs found
Electrical modulation of the edge channel transport in topological insulators coupled to ferromagnetic leads
The counterpropagating edge states of a two-dimensional topological insulator
(TI) carry electrons of opposite spins. We investigate the transport properties
of edge states in a two-dimensional TI which is contacted to ferromagnetic
leads. The application of a side-gate voltage induces a constriction or quantum
point contact (QPC) which couples the two edge channels. The transport
properties of the system is calculated via the Keldysh nonequilibrium Green's
function method. We found that inter-edge spin-flip coupling can significantly
enhance (suppress) the charge current when the magnetization of the leads are
anti-parallel (parallel) to one another. On the other hand, spin-conserving
inter-edge coupling generally reduces the current by backscattering regardless
of the magnetization configuration. The charge current and the conductance as a
function of the bias voltage, also exhibit similar trends with respect to
spin-flip coupling strength, for both parallel and anti-parallel
configurations. Hence, gate voltage modulation of edge states via a QPC can
provide a means of modulating the spin or charge current flow in TI-based
spintronics devices.Comment: 6 pages, 3 figures, submitted to J. Appl. Phy
A Global Database of Domestic and International Tourist Numbers at National and Subnational Level
We present a new, global data base on tourist destinations. The data base differs from other data bases in that it includes both domestic and international tourists; and it contains data, for the most important destinations, data at national level as well as at lower administrative levels. Missing observations are interpolated using statistical models. The data are freely accessible on the internet.Tourism, Data
Exact Hybrid Covariance Thresholding for Joint Graphical Lasso
This paper considers the problem of estimating multiple related Gaussian
graphical models from a -dimensional dataset consisting of different
classes. Our work is based upon the formulation of this problem as group
graphical lasso. This paper proposes a novel hybrid covariance thresholding
algorithm that can effectively identify zero entries in the precision matrices
and split a large joint graphical lasso problem into small subproblems. Our
hybrid covariance thresholding method is superior to existing uniform
thresholding methods in that our method can split the precision matrix of each
individual class using different partition schemes and thus split group
graphical lasso into much smaller subproblems, each of which can be solved very
fast. In addition, this paper establishes necessary and sufficient conditions
for our hybrid covariance thresholding algorithm. The superior performance of
our thresholding method is thoroughly analyzed and illustrated by a few
experiments on simulated data and real gene expression data
Preparation and identification of monoclonal antibodies against humanin
To generate and characterize a monoclonal antibody (mAb) against humanin (HN), BALB/c mice were immunized with the purified pet-44a-HN in adjuvant and their splenic lymphocytes were fused with myeloma SP2/0 cells. The hybridoma cell lines were screened for HN-specific antibodies by indirect enzyme-linked immunosorbent assay (ELISA), and anti-HN mAb-producing hybridoma clones were obtained using a limiting dilution assay. The specificity and affinity of the antibodies were characterized by western blot assays and indirect ELISA. Following fusion, screening and cloning, four hybridoma clones were obtained, and the clone 5A8H3 was demonstrated to stably produce anti-HN IgG2a. Further characterization of 5A8H3 revealed that this mAb specifically recognized HN, the fusion proteins of pet- 44a-HN protein and pGEMEX-1-HN, but not control (Escherichia coli proteins). This mAb interacted with HN at an affinity constant (Ka) of 2.0 Ă 108 Mâ1 The HN-specific IgG2a mAb was successfully generated. It interacted with HN specifically and sensitively, providing a valuable tool for further study of the biological functions of HN.Key words: Humanin, monoclonal antibodies, characterizatio
A GLOBAL DATABASE OF DOMESTIC AND INTERNATIONAL TOURIST NUMBERS AT NATIONAL AND SUBNATIONAL LEVEL
We present a new, global data base on tourist destinations. The data base differs from other data bases in that it includes both domestic and international tourists; and it contains data, for the most important destinations, data at national level as well as at lower administrative levels. Missing observations are interpolated using statistical models. The data are freely accessible on the internet.tourism, data
Geochemistry and petrogenesis of the Yishak Volcanic Sequence, Kudi ophiolite, West Kunlun (NW China): Implications for the magmatic evolution in a subduction zone environment
The Yishak Volcanic Series (YVS) is part of the Late Cambrian Kudi ophiolite in the western Kunlun Mountains, NW China, which marks the oldest suture zone in the Tibetan Plateau. The YVS is a well-preserved sequence comprising five conformable units (A to E) of basalts to andesites, with mafic dykes in Units A to D. These rocks are sequentially characterized upward by geochemical features of N-MORB (Unit A), E-MORB (Unit B), island-arc basalt (Unit C), BABB (Unit D and mafic dykes) and boninite series rocks (Unit E), reflecting complex interactions among various source components. The evolution of magma compositions from MORB-dominated to boninite series rocks clearly indicates temporally increasing subduction signatures, which, in combination with the extensional tectonic background, suggests that the Kudi ophiolite most likely formed in a spontaneous nucleation of subduction zone. © Springer-Verlag 2005.postprin
Ticking terahertz wave generation in attoseconds
We perform a joint measurement of terahertz waves and high-order harmonics
generated from noble atoms driven by a fundamental laser pulse and its second
harmonic. By correlating their dependence on the phase-delay of the two pulses,
we determine the generation of THz waves in tens of attoseconds precision.
Compared with simulations and models, we find that the laser-assisted
soft-collision of the electron wave packet with the atomic core plays a key
role. It is demonstrated that the rescattering process, being indispensable in
HHG processes, dominant THz wave generation as well but in a more elaborate
way. The new finding might be helpful for the full characterization of the
rescattering dynamics.Comment: 4 figure
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