5,722 research outputs found
Orbital order in the low-dimensional quantum spin system TiOCl probed by ESR
We present electron spin resonance data of Ti (3) ions in single
crystals of the novel layered quantum spin magnet TiOCl. The analysis of the g
tensor yields direct evidence that the d_{xy} orbital from the t_{2g} set is
predominantly occupied and owing to the occurrence of orbital order a linear
spin chain forms along the crystallographic b axis. This result corroborates
recent theoretical LDA+U calculations of the band structure. The temperature
dependence of the parameters of the resonance signal suggests a strong coupling
between spin and lattice degrees of freedom and gives evidence for a transition
to a nonmagnetic ground state at 67 K.Comment: revised version, accepted for publication in Phys. Rev. B, Rapid Com
Radiative rotational lifetimes and state-resolved relative detachment cross sections from photodetachment thermometry of molecular anions in a cryogenic storage ring
Photodetachment thermometry on a beam of OH in a cryogenic storage ring
cooled to below 10 K is carried out using two-dimensional, frequency and time
dependent photodetachment spectroscopy over 20 minutes of ion storage. In
equilibrium with the low-level blackbody field, we find an effective radiative
temperature near 15 K with about 90% of all ions in the rotational ground
state. We measure the J = 1 natural lifetime (about 193 s) and determine the
OH rotational transition dipole moment with 1.5% uncertainty. We also
measure rotationally dependent relative near-threshold photodetachment cross
sections for photodetachment thermometry.Comment: Manuscript LaTeX with 5 pages, 3 figures, and 1 table plus LaTeX
supplement with 12 pages, 3 figures and 3 tables. This article has been
accepted by Physical Review Letter
Holographic Imaging of Crowded Fields: High Angular Resolution Imaging with Excellent Quality at Very Low Cost
We present a method for speckle holography that is optimised for crowded
fields. Its two key features are an iterativ improvement of the instantaneous
Point Spread Functions (PSFs) extracted from each speckle frame and the
(optional) simultaneous use of multiple reference stars. In this way, high
signal-to-noise and accuracy can be achieved on the PSF for each short
exposure, which results in sensitive, high-Strehl re- constructed images. We
have tested our method with different instruments, on a range of targets, and
from the N- to the I-band. In terms of PSF cosmetics, stability and Strehl
ratio, holographic imaging can be equal, and even superior, to the capabilities
of currently available Adaptive Optics (AO) systems, particularly at short
near-infrared to optical wavelengths. It outperforms lucky imaging because it
makes use of the entire PSF and reduces the need for frame selection, thus
leading to higher Strehl and improved sensitivity. Image reconstruction a
posteriori, the possibility to use multiple reference stars and the fact that
these reference stars can be rather faint means that holographic imaging offers
a simple way to image large, dense stellar fields near the diffraction limit of
large telescopes, similar to, but much less technologically demanding than, the
capabilities of a multi-conjugate adaptive optics system. The method can be
used with a large range of already existing imaging instruments and can also be
combined with AO imaging when the corrected PSF is unstable.Comment: Accepted for publication in MNRAS on 15 Nov 201
Hysteresis of Electronic Transport in Graphene Transistors
Graphene field effect transistors commonly comprise graphene flakes lying on
SiO2 surfaces. The gate-voltage dependent conductance shows hysteresis
depending on the gate sweeping rate/range. It is shown here that the
transistors exhibit two different kinds of hysteresis in their electrical
characteristics. Charge transfer causes a positive shift in the gate voltage of
the minimum conductance, while capacitive gating can cause the negative shift
of conductance with respect to gate voltage. The positive hysteretic phenomena
decay with an increase of the number of layers in graphene flakes. Self-heating
in helium atmosphere significantly removes adsorbates and reduces positive
hysteresis. We also observed negative hysteresis in graphene devices at low
temperature. It is also found that an ice layer on/under graphene has much
stronger dipole moment than a water layer does. Mobile ions in the electrolyte
gate and a polarity switch in the ferroelectric gate could also cause negative
hysteresis in graphene transistors. These findings improved our understanding
of the electrical response of graphene to its surroundings. The unique
sensitivity to environment and related phenomena in graphene deserve further
studies on nonvolatile memory, electrostatic detection and chemically driven
applications.Comment: 13 pages, 6 Figure
Biogenic carbonate mercury and marine temperature records reveal global influence of Late Cretaceous Deccan Traps
Peer Reviewedhttps://deepblue.lib.umich.edu/bitstream/2027.42/155784/1/Meyer_et_al_2019_Biogenic_carbonate_mercury.pd
Maturation of the Language Network: From Inter- to Intrahemispheric Connectivities
Language development must go hand-in-hand with brain maturation. Little is known about how the brain develops to serve language processing, in particular, the processing of complex syntax, a capacity unique to humans. Behavioral reports indicate that the ability to process complex syntax is not yet adult-like by the age of seven years. Here, we apply a novel method to demonstrate that the basic neural basis of language, as revealed by low frequency fluctuation stemming from functional MRI data, differs between six-year-old children and adults in crucial aspects. Although the classical language regions are actively in place by the age of six, the functional connectivity between these regions clearly is not. In contrast to adults who show strong connectivities between frontal and temporal language regions within the left hemisphere, children's default language network is characterized by a strong functional interhemispheric connectivity, mainly between the superior temporal regions. These data indicate a functional reorganization of the neural network underlying language development towards a system that allows a close interplay between frontal and temporal regions within the left hemisphere
Water-Gated Charge Doping of Graphene Induced by Mica Substrates
We report on the existence of water-gated charge doping of graphene deposited
on atomically flat mica substrates. Molecular films of water in units of ~0.4
nm-thick bilayers were found to be present in regions of the interface of
graphene/mica hetero-stacks prepared by micromechanical exfoliation of kish
graphite. The spectral variation of the G and 2D bands, as visualized by Raman
mapping, shows that mica substrates induce strong p-type doping in graphene,
with hole densities of {-2}$. The ultrathin water
films, however, effectively block interfacial charge transfer, rendering
graphene significantly less hole-doped. Scanning Kelvin probe microscopy
independently confirmed a water-gated modulation of the Fermi level by 0.35 eV,
in agreement with the optically determined hole density. The manipulation of
the electronic properties of graphene demonstrated in this study should serve
as a useful tool in realizing future graphene applications.Comment: 15 pages, 4 figures; Nano Letters, accepted (2012
TESLA Technical Design Report Part III: Physics at an e+e- Linear Collider
The TESLA Technical Design Report Part III: Physics at an e+e- Linear
ColliderComment: 192 pages, 131 figures. Some figures have reduced quality. Full
quality figures can be obtained from http://tesla.desy.de/tdr. Editors -
R.-D. Heuer, D.J. Miller, F. Richard, P.M. Zerwa
Authentication of the R06E Fruit Bat Cell Line
Fruit bats and insectivorous bats are believed to provide a natural reservoir for a wide variety of infectious diseases. Several lines of evidence, including the successful isolation of infectious viruses, indicate that Marburg virus and Ravn virus have found a major reservoir in colonies of the Egyptian rousette (Rousettus aegyptiacus). To facilitate molecular studies on virus-reservoir host interactions and isolation of viruses from environmental samples, we established cell lines from primary cells of this animal. The cell lines were given to several laboratories until we realized that a contamination with Vero cells in one of the cultures had occurred. Here we describe a general diagnostic procedure for identification of cross-species contamination with the focus on Vero and Rousettus cell lines, and summarize newly discovered properties of the cell lines that may pertain to pathogen discovery
Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV
A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay
channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7
TeV is presented. The data were collected at the LHC, with the CMS detector,
and correspond to an integrated luminosity of 4.6 inverse femtobarns. No
significant excess is observed above the background expectation, and upper
limits are set on the Higgs boson production cross section. The presence of the
standard model Higgs boson with a mass in the 270-440 GeV range is excluded at
95% confidence level.Comment: Submitted to JHE
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