8,251 research outputs found
Origin of Rashba-splitting in the quantized subbands at Bi2Se3 surface
We study the band structure of the topological
insulator (111) surface using angle-resolved photoemission spectroscopy. We
examine the situation where two sets of quantized subbands exhibiting different
Rashba spin-splitting are created via bending of the conduction (CB) and the
valence (VB) bands at the surface. While the CB subbands are strongly Rashba
spin-split, the VB subbands do not exhibit clear spin-splitting. We find that
CB and VB experience similar band bending magnitudes, which means, a
spin-splitting discrepancy due to different surface potential gradients can be
excluded. On the other hand, by comparing the experimental band structure to
first principles LMTO band structure calculations, we find that the strongly
spin-orbit coupled Bi 6 orbitals dominate the orbital character of CB,
whereas their admixture to VB is rather small. The spin-splitting discrepancy
is, therefore, traced back to the difference in spin-orbit coupling between CB
and VB in the respective subbands' regions
Transmission measurement at 10.6 microns of Te2As3Se5 rib-waveguides on As2S3 substrate
The feasibility of chalcogenide rib waveguides working at lambda = 10.6
microns has been demonstrated. The waveguides comprised a several microns thick
Te2As3Se5 film deposited by thermal evaporation on a polished As2S3 glass
substrate and further etched by physical etching in Ar or CF4/O2 atmosphere.
Output images at 10.6 microns and some propagation losses roughly estimated at
10dB/cm proved that the obtained structures behaved as channel waveguides with
a good lateral confinement of the light. The work opens the doors to the
realisation of components able to work in the mid and thermal infrared up to 20
microns and even more.Comment: The following article appeared in Vigreux-Bercovici et al., Appl.
Phys. Lett. 90, 011110 (2007) and may be found at
http://link.aip.org/link/?apl/90/01111
Microsurgical Technique of Simultaneous Pancreas/Kidney Transplantation in the Rat: Clinical Experience and Review of the Literature
Background: For experimental basic research, standardized transplantation models reflecting technical and immunologic aspects are necessary. This article describes an experimental model of combined pancreas/kidney transplantation (PKTx) in detail. Materials and Methods: Donor rats underwent en bloc pancreatectomy and nephrectomy. Revascularization was performed using the aorta with the superior mesenteric artery and the inferior vena cava with the portal vein. Exocrine drainage of the pancreas took place over a segment of the duodenum which was transplanted side-to-side to the jejunum. The kidney vessels were transplanted end-to-side. The ureter was anastomosed by patch technique. Postoperatively, serum parameters were monitored daily. Biopsies for histopathology were taken on days 5, 8 and 12. Results: All 12 recipients survived the combined PKTx without serious surgical complications. One thrombosis of the portal vein led to organ failure. Blood glucose levels were normal by the 3rd postoperative day. The transplanted duodenal segment showed slight villous atrophy, and the kidneys were well perfused without vascular complications. The anastomosis between ureter and bladder was leakproof. Conclusions: Excellent graft function and survival rates can be achieved due to simplified operation technique and short operation time. It may thus have high clinical relevance to immunologic issues within the scope of basic research. Copyright (C) 2009 S. Karger AG, Base
Quasiparticle Chirality in Epitaxial Graphene Probed at the Nanometer Scale
Graphene exhibits unconventional two-dimensional electronic properties
resulting from the symmetry of its quasiparticles, which leads to the concepts
of pseudospin and electronic chirality. Here we report that scanning tunneling
microscopy can be used to probe these unique symmetry properties at the
nanometer scale. They are reflected in the quantum interference pattern
resulting from elastic scattering off impurities, and they can be directly read
from its fast Fourier transform. Our data, complemented by theoretical
calculations, demonstrate that the pseudospin and the electronic chirality in
epitaxial graphene on SiC(0001) correspond to the ones predicted for ideal
graphene.Comment: 4 pages, 3 figures, minor change
Rapid chemical evolution of tropospheric volcanic emissions from Redoubt Volcano, Alaska, based on observations of ozone and halogen-containing gases
Evidence of reduced surface electron-phonon scattering in the conduction band of Bi_{2}Se_{3} by non-equilibrium ARPES
The nature of the Dirac quasiparticles in topological insulators calls for a
direct investigation of the electron-phonon scattering at the \emph{surface}.
By comparing time-resolved ARPES measurements of the TI Bi_{2}Se_{3} with
different probing depths we show that the relaxation dynamics of the electronic
temperature of the conduction band is much slower at the surface than in the
bulk. This observation suggests that surface phonons are less effective in
cooling the electron gas in the conduction band.Comment: 5 pages, 3 figure
A Combined Digital-Analog Tracker for Terrestrial Applications
A combined Digital-Analog Tracker is suggested to allow maximum efficiency in a solar-electrical energy converter, utilizing a twelve-foot parabolic collector. The analog tracker compares solar beam radiation to ambient (diffuse) light to obtain optimum placement of the collector when the sun is visible. The digital portion of the tracker utilizes a wired program which derives information on solar position from a non-volatile random-access semiconductor memory. This arrangement allows accurate mapping of the sun even when the sun is obscured by atmospheric phenomena which would make mapping impossible
Optical Pulse-Phased Photopolarimetry of PSR B0656+14
We have observed the optical pulse profile of PSR B0656+14 in 10 phase bins
at a high signal-to-noise ratio, and have measured the linear polarization
profile over 30% of the pulsar period with some significance. The pulse profile
is double-peaked, with a bridge of emission between the two peaks, similar to
gamma-ray profiles observed in other pulsars. There is no detectable unpulsed
flux, to a 1-sigma limit of 16% of the pulse-averaged flux. The emission in the
bridge is highly (~ 100%) polarized, with a position angle sweep in excellent
agreement with the prediction of the Rotating Vector Model as determined from
radio polarization observations. We are able to account for the gross features
of the optical light curve (i.e., the phase separation of the peaks) using both
polar cap and outer gap models. Using the polar cap model, we are also able to
estimate the height of the optical emission regions.Comment: 27 pages, 11 figures, accepted by ApJ (scheduled v597 n2, November
10, 2003
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