15,167 research outputs found
The Magnetic Topology of the Weak-Lined T Tauri Star V410 - A Simultaneous Temperature and Magnetic Field Inversion
We present a detailed temperature and magnetic investigation of the T Tauri
star V410 Tau by means of a simultaneous Doppler- and Zeeman-Doppler Imaging.
Moreover we introduce a new line profile reconstruction method based on a
singular value decomposition (SVD) to extract the weak polarized line profiles.
One of the key features of the line profile reconstruction is that the SVD line
profiles are amenable to radiative transfer modeling within our Zeeman-Doppler
Imaging code iMap. The code also utilizes a new iterative regularization scheme
which is independent of any additional surface constraints. To provide more
stability a vital part of our inversion strategy is the inversion of both
Stokes I and Stokes V profiles to simultaneously reconstruct the temperature
and magnetic field surface distribution of V410 Tau. A new image-shear analysis
is also implemented to allow the search for image and line profile distortions
induced by a differential rotation of the star. The magnetic field structure we
obtain for V410 Tau shows a good spatial correlation with the surface
temperature and is dominated by a strong field within the cool polar spot. The
Zeeman-Doppler maps exhibit a large-scale organization of both polarities
around the polar cap in the form of a twisted bipolar structure. The magnetic
field reaches a value of almost 2 kG within the polar region but smaller fields
are also present down to lower latitudes. The pronounced non-axisymmetric field
structure and the non-detection of a differential rotation for V410 Tau
supports the idea of an underlying -type dynamo, which is predicted
for weak-lined T Tauri stars.Comment: Accepted for A&A, 18 pages, 10 figure
Heterogeneous responses of dorsal root ganglion neurons in neuropathies induced by peripheral nerve trauma and the antiretroviral drug stavudine
© 2014 The Authors. European Journal of Pain published by John Wiley & Sons Ltd on behalf of European Pain Federation - EFIC®. Funding sources E.K.B. was funded by a BBSRC PhD studentship. A.N., A.S.C.R. and T.P. were funded by a Wellcome Trust Strategic Award (London Pain Consortium; ref. 083259). A.S.C.R. and W.H. were funded by the Innovative Medicines Initiative Joint Undertaking (Europain; grant agreement no. 115007). We thank Pfizer for providing stavudine. Conflicts of interest None declared. Funded by BBSRC PhD studentship Wellcome Trust Strategic Award. Grant Number: 083259 Innovative Medicines Initiative Joint Undertaking. Grant Number: 115007Peer reviewedPublisher PD
Rotational Symmetry Breaking in Sodium Doped Cuprates
For reasonable parameters a hole bound to a Na^{+} acceptor in
Ca_{2-x}Na_{x}CuO_{2}Cl_{2} has a doubly degenerate ground state whose
components can be represented as states with even (odd) reflection symmetry
around the x(y) -axes. The conductance pattern for one state is anisotropic as
the tip of a tunneling microscope scans above the Cu-O-Cu bonds along the
x(y)-axes. This anisotropy is pronounced at lower voltages but is reduced at
higher voltages. Qualitative agreement with recent experiments leads us to
propose this effect as an explanation of the broken local rotational symmetry.Comment: 10 pages, 4 figure
Enhanced Coherence of Antinodal Quasiparticles in a Dirty d-wave Superconductor
Recent ARPES experiments show a narrow quasiparticle peak at the gap edge
along the antinodal [1,0]-direction for the overdoped cuprate superconductors.
We show that within weak coupling BCS theory for a d-wave superconductor the
s-wave single-impurity scattering cross section vanishes for energies of the
gap edge. This coherence effect occurs through multiple scattering off the
impurity. For small impurity concentrations the spectral function has a
pronounced increase of the (scattering) lifetime for antinodal quasiparticles
but shows a very broad peak in the nodal direction, in qualitative agreement
with experiment and in strong contrast to the behavior observed in underdoped
cuprates.Comment: 4 pages, 3 figures, submitte
Determination of differential elastic and vibrational excitation cross sections for e-H sub 2 scattering
Elastic scattering of electrons by hydroge
Anisotropic superexchange of a 90 degree Cu-O-Cu bond
The magnetic anisotropy af a rectangular Cu-O-Cu bond is investigated in
second order of the spin-orbit interaction. Such a bond is characteristic for
cuprates having edge sharing CuO_2 chains, and exists also in the Cu_3O_4 plane
or in ladder compounds. For a ferromagnetic coupling between the copper spins
an easy axis is found perpendicular to the copper oxygen plaquettes in
agreement with the experimental spin structure of Li_2CuO_2. In addition, a
pseudo-dipolar interaction is derived. Its estimation in the case of the
Cu_3O_4 plane (which is present for instance in Ba_2Cu_3O_4Cl_2 or
Sr_2Cu_3O_4Cl_2) gives a value which is however two orders of magnitude smaller
than the usual dipole-dipole interaction.Comment: 6 pages, 2 figures, improved referenc
Time-dependent density functional theory: Past, present, and future
Time-dependent density functional theory (TDDFT) is presently enjoying
enormous popularity in quantum chemistry, as a useful tool for extracting
electronic excited state energies. This article discusses how TDDFT is much
broader in scope, and yields predictions for many more properties. We discuss
some of the challenges involved in making accurate predictions for these
properties.Comment: 12 pages, 4 figure
Magnon Dispersion in the Field-Induced Magnetically Ordered Phase of TlCuCl3
The magnetic properties of the interacting dimer system TlCuCl3 are
investigated within a bond-operator formulation. The observed field-induced
staggered magnetic order perpendicular to the field is described as a Bose
condensation of magnons which are linear combinations of dimer singlet and
triplet modes. This technique accounts for the magnetization curve and for the
field dependence of the magnon dispersion curves observed by high-field neutron
scattering measurements.Comment: 4 pages, 4 figures, REVTeX
Land use change detection with LANDSAT-2 data for monitoring and predicting regional water quality degradation
The author has identified the following significant results. Comparison between LANDSAT 1 and 2 imagery of Arkansas provided evidence of significant land use changes during the 1972-75 time period. Analysis of Arkansas historical water quality information has shown conclusively that whereas point source pollution generally can be detected by use of water quality data collected by state and federal agencies, sampling methodologies for nonpoint source contamination attributable to surface runoff are totally inadequate. The expensive undertaking of monitoring all nonpoint sources for numerous watersheds can be lessened by implementing LANDSAT change detection analyses
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