1,230 research outputs found
Absence of singular superconducting fluctuation corrections to thermal conductivity
We evaluate the superconducting fluctuation corrections to thermal
conductivity in the normal state which diverge as T approaches T_c. We find
zero total contribution for one, two and three-dimensional superconductors for
arbitrary impurity concentration. The method used is diagrammatic many-body
theory, and all contributions -- Aslamazov-Larkin (AL), Maki-Thompson (MT), and
density-of-states (DOS) -- are considered. The AL contribution is convergent,
whilst the divergences of the DOS and MT diagrams exactly cancel.Comment: 4 pages text; 2 figure
The Constraint on FCNC Coupling of the Top Quark with a Gluon from ep Collisions
Using the constraint on the single top production cross-section obtained at
the HERA collider, , we evaluate an upper limit on
oupling constant of the anomalous top quark interaction with a gluon via
flavor-changing neutral current: ,
BRComment: Latex, 3 figures, missed references were adde
Recent Experimental Tests of Special Relativity
We review our recent Michelson-Morley (MM) and Kennedy-Thorndike (KT)
experiment, which tests Lorentz invariance in the photon sector, and report
first results of our ongoing atomic clock test of Lorentz invariance in the
matter sector. The MM-KT experiment compares a cryogenic microwave resonator to
a hydrogen maser, and has set the most stringent limit on a number of
parameters in alternative theories to special relativity. We also report first
results of a test of Lorentz invariance in the SME (Standard Model Extension)
matter sector, using Zeeman transitions in a laser cooled Cs atomic fountain
clock. We describe the experiment together with the theoretical model and
analysis. Recent experimental results are presented and we give a first
estimate of components of the parameters of the SME matter
sector. A full analysis of systematic effects is still in progress, and will be
the subject of a future publication together with our final results. If
confirmed, the present limits would correspond to first ever measurements of
some components, and improvements by 11 and 14 orders of
magnitude on others.Comment: 29 pages. Contribution to Springer Lecture Notes, "Special Relativity
- Will it survive the next 100 years ?", Proceedings, Potsdam, 200
Rotating Resonator-Oscillator Experiments to Test Lorentz Invariance in Electrodynamics
In this work we outline the two most commonly used test theories (RMS and
SME) for testing Local Lorentz Invariance (LLI) of the photon. Then we develop
the general framework of applying these test theories to resonator experiments
with an emphasis on rotating experiments in the laboratory. We compare the
inherent sensitivity factors of common experiments and propose some new
configurations. Finally we apply the test theories to the rotating cryogenic
experiment at the University of Western Australia, which recently set new
limits in both the RMS and SME frameworks [hep-ph/0506074].Comment: Submitted to Lecture Notes in Physics, 36 pages, minor modifications,
updated list of reference
Optimal Fractionation of Products of Refining Straight-run Gasoline on Zeolite Catalyst with Account of its Deactivation
Flowsheet of industrial refining straight-run gasoline on zeolite catalyst includes the necessary stage of fractionation of conversion products to produce commercial gasoline, gas and heavy residue. Changes in qualitative and quantitative compositions of the catalytic conversion products under catalyst deactivation require current parametrical optimization of this stage. Objective functions that take into account catalyst deactivation and the constrains depending on the requirements for product quality and equipment specifications were developed. Optimal conditions were found to differ significantly from those designed for fresh catalyst
Ictal quantitative surface electromyography correlates with postictal EEG suppression.
To test the hypothesis that neurophysiologic biomarkers of muscle activation during convulsive seizures reveal seizure severity and to determine whether automatically computed surface EMG parameters during seizures can predict postictal generalized EEG suppression (PGES), indicating increased risk for sudden unexpected death in epilepsy. Wearable EMG devices have been clinically validated for automated detection of generalized tonic-clonic seizures. Our goal was to use quantitative EMG measurements for seizure characterization and risk assessment.
Quantitative parameters were computed from surface EMGs recorded during convulsive seizures from deltoid and brachial biceps muscles in patients admitted to long-term video-EEG monitoring. Parameters evaluated were the durations of the seizure phases (tonic, clonic), durations of the clonic bursts and silent periods, and the dynamics of their evolution (slope). We compared them with the duration of the PGES.
We found significant correlations between quantitative surface EMG parameters and the duration of PGES (p < 0.001). Stepwise multiple regression analysis identified as independent predictors in deltoid muscle the duration of the clonic phase and in biceps muscle the duration of the tonic-clonic phases, the average silent period, and the slopes of the silent period and clonic bursts. The surface EMG-based algorithm identified seizures at increased risk (PGES ≥20 seconds) with an accuracy of 85%.
Ictal quantitative surface EMG parameters correlate with PGES and may identify seizures at high risk.
This study provides Class II evidence that during convulsive seizures, surface EMG parameters are associated with prolonged postictal generalized EEG suppression
Quantum Interference between Impurities: Creating Novel Many-Body States in s-wave Superconductors
We demonstrate that quantum interference of electronic waves that are
scattered by multiple magnetic impurities in an s-wave superconductor gives
rise to novel bound states. We predict that by varying the inter-impurity
distance or the relative angle between the impurity spins, the states' quantum
numbers, as well as their distinct frequency and spatial dependencies, can be
altered. Finally, we show that the superconductor can be driven through
multiple local crossovers in which its spin polarization, , changes
between and 1.Comment: 4 pages, 4 figure
Deficiency in IκBα in the intestinal epithelium leads to spontaneous inflammation and mediates apoptosis in the gut
The IκB-Kinase (IKK)-NF-κB signalling pathway plays a multifaceted role in inflammatory bowel disease (IBD): on the one hand, it protects from apoptosis; on the other, it activates transcription of numerous inflammatory cytokines and chemokines. Although several murine models of IBD rely on disruption of IKK-NF-κB signalling, these involve either knockouts of a single family-member of NF-κB, or of upstream kinases that are known to have additional, NF-κB-independent, functions. This has made the distinct contribution of NF-κB to homeostasis in intestinal epithelium cells difficult to assess. To examine the role of constitutive NF-κB activation in intestinal epithelial cells, we generated a mouse model with a tissue-specific knockout of the direct inhibitor of NF-κB, Nfkbia/IκBα. We demonstrate that constitutive activation of NF-κB in intestinal epithelial cells induces several hallmarks of IBD including increased apoptosis, mucosal inflammation in both the small intestine and the colon, crypt hyperplasia, and depletion of Paneth cells, concomitant with aberrant Wnt signalling. To determine which NF-κB-driven phenotypes are cell-intrinsic, and which are extrinsic and thus require the immune compartment, we established a long-term organoid culture. Constitutive NF-κB promoted stem-cell proliferation, mis-localisation of Paneth cells, and sensitisation of intestinal epithelial cells to apoptosis in a cell-intrinsic manner. Increased number of stem cells was accompanied by a net increase in Wnt activity in organoids. Because aberrant Wnt signalling is associated with increased risk of cancer in IBD patients and because NFKBIA has recently emerged as a risk locus for IBD, our findings have critical implications for the clinic. In a context of constitutive NF-κB, our findings imply that general anti-inflammatory or immunosuppressive therapies should be supplemented with direct targeting of NF-κB within the epithelial compartment in order to attenuate apoptosis, inflammation, and hyperproliferation
Optical cavity tests of Lorentz invariance for the electron
A hypothetical violation of Lorentz invariance in the electrons' equation of
motion (expressed within the Lorentz-violating extension of the standard model)
leads to a change of the geometry of crystals and thus shifts the resonance
frequency of an electromagnetic cavity. This allows experimental tests of
Lorentz invariance of the electron sector of the standard model. The material
dependence of the effect allows to separate it from an additional shift caused
by Lorentz violation in electrodynamics, and to place independent limits on
both effects. From present experiments, upper limits on Lorentz violation in
the electrons' kinetic energy term are deduced.Comment: 17 pages revte
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