3,854 research outputs found
Graphene with adatoms: tuning the magnetic moment with an applied voltage
We show that, in graphene with a small concentration of adatoms, the total
magnetic moment can be switched on and off by varying the Fermi energy
, either by applying a gate voltage or by suitable chemical doping. Our
calculation is carried out using a simple tight-binding model described
previously, combined with a mean-field treatment of the electron-electron
interaction on the adatom. The values of at which the moment is turned on
or off are controlled by the strength of the hopping between the graphene sheet
and the adatom, the on-site energy of the adatom, and the strength of the
electron-electron correlation energy U. Our result is in qualitatively
consistent with recent experiments by Nair {\it et al.} [Nat.\ Commun.\ {\bf
4}, 2010 (2013)].Comment: 4 Pages, 1 Figur
Alien Registration- Pike, Annie N. (Portland, Cumberland County)
https://digitalmaine.com/alien_docs/26641/thumbnail.jp
Centriole assembly and the role of Mps1: defensible or dispensable?
The Mps1 protein kinase is an intriguing and controversial player in centriole assembly. Originally shown to control duplication of the budding yeast spindle pole body, Mps1 is present in eukaryotes from yeast to humans, the nematode C. elegans being a notable exception, and has also been shown to regulate the spindle checkpoint and an increasing number of cellular functions relating to genomic stability. While its function in the spindle checkpoint appears to be both universally conserved and essential in most organisms, conservation of its originally described function in spindle pole duplication has proven controversial, and it is less clear whether Mps1 is essential for centrosome duplication outside of budding yeast. Recent studies of Mps1 have identified at least two distinct functions for Mps1 in centriole assembly, while simultaneously supporting the notion that Mps1 is dispensable for the process. However, the fact that at least one centrosomal substrate of Mps1 is conserved from yeast to humans down to the phosphorylation site, combined with evidence demonstrating the exquisite control exerted over centrosomal Mps1 levels suggest that the notion of being essential may not be the most important of distinctions
Analytical Fitting of Gamma-ray Photopeaks in Germanium Cross Strip Detectors
In an ideal germanium detector, fully-absorbed monoenergetic gamma-rays will
appear in the measured spectrum as a narrow peak, broadened into a Gaussian of
width determined only by the statistical properties of charge cloud generation
and the electronic noise of the readout electronics. Multielectrode detectors
complicate this picture. Broadening of the charge clouds as they drift through
the detector will lead to charge sharing between neighboring electrodes and,
inevitably, low-energy tails on the photopeak spectra. We simulate charge
sharing in our germanium cross strip detectors in order to reproduce the
low-energy tails due to charge sharing. Our goal is to utilize these simulated
spectra to develop an analytical fit (shape function) for the spectral lines
that provides a robust and high-quality fit to the spectral profile, reliably
reproduces the interaction energy, noise width, and the number of counts in
both the true photopeak and the low-energy tail, and minimizes the number of
additional parameters. Accurate modeling of the detailed line profiles is
crucial for both calibration of the detectors as well as scientific
interpretation of measured spectra.Comment: Submitted to NIM
Proceedings of the Spacecraft Charging Technology Conference: Executive Summary
Aerospace environments are reviewed in reference to spacecraft charging. Modelling, a theoretical scheme which can be used to describe the structure of the sheath around the spacecraft and to calculate the charging currents within, is discussed. Materials characterization is considered for experimental determination of the behavior of typical spacecraft materials when exposed to simulated geomagnetic substorm conditions. Materials development is also examined for controlling and minimizing spacecraft charging or at least for distributing the charge in an equipotential manner, using electrical conductive surfaces for materials exposed to space environment
Current limiting and negative differential resistance in indium oxide based ceramics
Indium oxide based ceramics with bismuth oxide addition were sintered in air in the temperature range 800-1300 ÂşC. Current-voltage characteristics of In2O3-Bi2O3 ceramics sintered at different temperatures are weakly nonlinear. After an additional heat treatment in air at about 200 ÂşC samples sintered at a temperature within the narrow range of about 1050-1100 ÂşC exhibit a current-limiting effect accompanied by low-frequency current oscillations. It is shown that the observed electrical properties are controlled by the grain-boundary barriers and the heat treatment in air at 200 ÂşC leads to the decrease in the barrier height. Electrical measurements, scanning electron microscopy and X-ray photoelectron spectroscopy results suggest that the current-limiting effect observed in In2O3-Bi2O3 may be explained in terms of a modified barrier model; the observed current-limiting effect is the result of an increase of barrier height with increasing electric field, due to additional oxygen absorption. It is found that In2O3-Bi2O3-Co3O4-Cr2O3 ceramic exhibits current-voltage characteristics with negative differential resistance due to Joule micro heating.This study was performed in part in the frames of the project SEP-2003-C02-42821, CONACYT, MĂ©xico. Funding from the Royal Society, United Kingdom (2007R1/R26999) is gratefully acknowledged
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