368 research outputs found
Lithium Diffusion & Magnetism in Battery Cathode Material LixNi1/3Co1/3Mn1/3O2
We have studied low-temperature magnetic properties as well as
high-temperature lithium ion diffusion in the battery cathode materials
LixNi1/3Co1/3Mn1/3O2 by the use of muon spin rotation/relaxation. Our data
reveal that the samples enter into a 2D spin-glass state below TSG=12 K. We
further show that lithium diffusion channels become active for T>Tdiff=125 K
where the Li-ion hopping-rate [nu(T)] starts to increase exponentially.
Further, nu(T) is found to fit very well to an Arrhenius type equation and the
activation energy for the diffusion process is extracted as Ea=100 meV.Comment: Submitted to Journal of Physics: Conference Series (2014
Spin pseudogap in Ni-doped SrCuO2
The S=1/2 spin chain material SrCuO2 doped with 1% S=1 Ni-impurities is
studied by inelastic neutron scattering. At low temperatures, the spectrum
shows a pseudogap \Delta ~ 8 meV, absent in the parent compound, and not
related to any structural phase transition. The pseudogap is shown to be a
generic feature of quantum spin chains with dilute defects. A simple model
based on this idea quantitatively accounts for the exprimental data measured in
the temperature range 2-300 K, and allows to represent the momentum-integrated
dynamic structure factor in a universal scaling form.Comment: 5 pages, 3 figure
On the Coulomb Branch of a Marginal Deformation of N=4 SUSY Yang-Mills
We determine the exact vacuum structure of a marginal deformation of N=4 SUSY
Yang-Mills with gauge group U(N). The Coulomb branch of the theory consists of
several sub-branches which are governed by complex curves of the form
Sigma_{n_{1}} U Sigma_{n_{2}} U Sigma_{n_{3}} of genus N=n_{1}+n_{2}+n_{3}.
Each sub-branch intersects with a family of Higgs and Confining branches
permuted by SL(2,Z) transformations. We determine the curve by solving a
related matrix model in the planar limit according to the prescription of
Dijkgraaf and Vafa, and also by explicit instanton calculations using a form of
localization on the instanton moduli space. We find that Sigma_{n} coincides
with the spectral curve of the n-body Ruijsenaars-Schneider system. Our results
imply that the theory on each sub-branch is holomorphically equivalent to
certain five-dimensional gauge theory with eight supercharges. This equivalence
also implies the existence of novel confining branches in five dimensions.Comment: LaTeX file. 48 page
Risk factors for delayed presentation and referral of symptomatic cancer: Evidence for common cancers
Background:It has been suggested that the known poorer survival from cancer in the United Kingdom, compared with other European countries, can be attributed to more advanced cancer stage at presentation. There is, therefore, a need to understand the diagnostic process, and to ascertain the risk factors for increased time to presentation.Methods:We report the results from two worldwide systematic reviews of the literature on patient-mediated and practitioner-mediated delays, identifying the factors that may influence these.Results:Across cancer sites, non-recognition of symptom seriousness is the main patient-mediated factor resulting in increased time to presentation. There is strong evidence of an association between older age and patient delay for breast cancer, between lower socio-economic status and delay for upper gastrointestinal and urological cancers and between lower education level and delay for breast and colorectal cancers. Fear of cancer is a contributor to delayed presentation, while sanctioning of help seeking by others can be a powerful mediator of reduced time to presentation. For practitioner delay, ‘misdiagnosis’ occurring either through treating patients symptomatically or relating symptoms to a health problem other than cancer, was an important theme across cancer sites. For some cancers, this could also be linked to inadequate patient examination, use of inappropriate tests or failing to follow-up negative or inconclusive test results.Conclusion:Having sought help for potential cancer symptoms, it is therefore important that practitioners recognise these symptoms, and examine, investigate and refer appropriately. © 2009 Cancer Research UK All rights reserved
Four-loop anomalous dimensions in Leigh-Strassler deformations
We determine the scalar part of the four-loop chiral dilatation operator for
Leigh-Strassler deformations of N=4 super Yang-Mills. This is sufficient to
find the four-loop anomalous dimensions for operators in closed scalar
subsectors. This includes the SU(2) subsector of the (complex)
beta-deformation, where we explicitly compute the anomalous dimension for
operators with a single impurity. It also includes the "3-string null"
operators of the cubic Leigh-Strassler deformation. Our four-loop results show
that the rational part of the anomalous dimension is consistent with a
conjecture made in arXiv:1108.1583 based on the three-loop result of
arXiv:1008.3351 and the N=4 magnon dispersion relation. Here we find additional
zeta(3) terms.Comment: Latex, feynmp, 21 page
Functional oropharyngeal sensory disruption interferes with the cortical control of swallowing
<p>Abstract</p> <p>Background</p> <p>Sensory input is crucial to the initiation and modulation of swallowing. From a clinical point of view, oropharyngeal sensory deficits have been shown to be an important cause of dysphagia and aspiration in stroke patients. In the present study we therefore investigated effects of functional oropharyngeal disruption on the cortical control of swallowing. We employed whole-head MEG to study cortical activity during self-paced volitional swallowing with and without topical oropharyngeal anesthesia in ten healthy subjects. A simple swallowing screening-test confirmed that anesthesia caused swallowing difficulties with decreased swallowing speed and reduced volume per swallow in all subjects investigated. Data were analyzed by means of synthetic aperture magnetometry (SAM) and the group analysis of the individual SAM data was performed using a permutation test.</p> <p>Results</p> <p>The analysis of normal swallowing revealed bilateral activation of the mid-lateral primary sensorimotor cortex. Oropharyngeal anesthesia led to a pronounced decrease of both sensory and motor activation.</p> <p>Conclusion</p> <p>Our results suggest that a short-term decrease in oropharyngeal sensory input impedes the cortical control of swallowing. Apart from diminished sensory activity, a reduced activation of the primary motor cortex was found. These findings facilitate our understanding of the pathophysiology of dysphagia.</p
Engineering a pure Dirac regime in ZrTe
Real-world topological semimetals typically exhibit Dirac and Weyl nodes that
coexist with trivial Fermi pockets. This tends to mask the physics of the
relativistic quasiparticles. Using the example of ZrTe, we show that strain
provides a powerful tool for in-situ tuning of the band structure such that all
trivial pockets are pushed far away from the Fermi energy, but only for a
certain range of Van der Waals gaps. Our results naturally reconcile
contradicting reports on the presence or absence of additional pockets in
ZrTe, and provide a clear map of where to find a pure three-dimensional
Dirac semimetallic phase in the structural parameter space of the material.Comment: 17 page
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Engineering a pure Dirac regime in ZrTe5
Real-world topological semimetals typically exhibit Dirac and Weyl nodes that coexist with trivial Fermi pockets. This tends to mask the physics of the relativistic quasiparticles. Using the example of ZrTe5, we show that strain provides a powerful tool for in-situ tuning of the band structure such that all trivial pockets are pushed far away from the Fermi energy, but only for a certain range of Van der Waals gaps. Our results naturally reconcile contradicting reports on the presence or absence of additional pockets in ZrTe5, and provide a clear map of where to find a pure three-dimensional Dirac semimetallic phase in the structural parameter space of the material
Structure of the string R-matrix
By requiring invariance directly under the Yangian symmetry, we rederive
Beisert's quantum R-matrix, in a form that carries explicit dependence on the
representation labels, the braiding factors, and the spectral parameters u_i.
In this way, we demonstrate that there exist a rewriting of its entries, such
that the dependence on the spectral parameters is purely of difference form.
Namely, the latter enter only in the combination u_1-u_2, as indicated by the
shift automorphism of the Yangian. When recasted in this fashion, the entries
exhibit a cleaner structure, which allows to spot new interesting relations
among them. This permits to package them into a practical tensorial expression,
where the non-diagonal entries are taken care by explicit combinations of
symmetry algebra generators.Comment: 9 pages, LaTeX; typos correcte
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