12,383 research outputs found
Covariant gaussian approximation in Ginzburg - Landau model
Condensed matter systems undergoing second order transition away from the
critical fluctuation region are usually described sufficiently well by the mean
field approximation. The critical fluctuation region, determined by the
Ginzburg criterion, , is narrow even
in high superconductors and has universal features well captured by the
renormalization group method. However recent experiments on magnetization,
conductivity and Nernst effect suggest that fluctuations effects are large in a
wider region both above and below . In particular some "pseudogap"
phenomena and strong renormalization of the mean field critical temperature
can be interpreted as strong fluctuations effects that are
nonperturbative (cannot be accounted for by "gaussian fluctuations"). The
physics in a broader region therefore requires more accurate approach. Self
consistent methods are generally "non - conserving" in the sense that the Ward
identities are not obeyed. This is especially detrimental in the symmetry
broken phase where, for example, Goldstone bosons become massive. Covariant
gaussian approximation remedies these problems. The Green's functions obey all
the Ward identities and describe the fluctuations much better. The results for
the order parameter correlator and magnetic penetration depth of the Ginzburg -
Landau model of superconductivity are compared with both Monte Carlo
simulations and experiments in high cuprates.Comment: 24 pages, 7 figure
Accurate 3D Cell Segmentation using Deep Feature and CRF Refinement
We consider the problem of accurately identifying cell boundaries and
labeling individual cells in confocal microscopy images, specifically, 3D image
stacks of cells with tagged cell membranes. Precise identification of cell
boundaries, their shapes, and quantifying inter-cellular space leads to a
better understanding of cell morphogenesis. Towards this, we outline a cell
segmentation method that uses a deep neural network architecture to extract a
confidence map of cell boundaries, followed by a 3D watershed algorithm and a
final refinement using a conditional random field. In addition to improving the
accuracy of segmentation compared to other state-of-the-art methods, the
proposed approach also generalizes well to different datasets without the need
to retrain the network for each dataset. Detailed experimental results are
provided, and the source code is available on GitHub.Comment: 5 pages, 5 figures, 3 table
Scheduling soft real-time jobs over dual non-real-time servers
In this paper, we consider soft real-time systems with redundant off-the-shelf processing components (e.g., CPU, disk, network), and show how applications can exploit the redundancy to improve the system's ability of meeting response time goals (soft deadlines). We consider two scheduling policies, one that evenly distributes load (Balance), and one that partitions load according to job slackness (Chop). We evaluate the effectiveness of these policies through analysis and simulation. Our results show that by intelligently distributing jobs by their slackness amount the servers, Chop can significantly improve real-time performance. ©1996 IEEE.published_or_final_versio
Signature of Schwinger's pair creation rate via radiation generated in graphene by strong electric current
Electron - hole pairs are copuously created by an applied electric field near
the Dirac point in graphene or similar 2D electronic systems. It was shown
recently that for sufficiently large electric fields and ballistic times the
I-V characteristics become strongly nonlinear due to Schwinger's pair creation.
Since there is no energy gap the radiation from the pairs' annihilation is
enhanced. The spectrum of radiation is calculated. The angular and polarization
dependence of the emitted photons with respect to the graphene sheet is quite
distinctive. For very large currents the recombination rate becomes so large
that it leads to the second Ohmic regime due to radiation friction.Comment: 9 pages, 7 figure
The Two-Boson-Exchange Correction to Parity-Violating Elastic Electron-Proton Scattering
We calculate the two-boson-exchange (TBE) corrections to the parity-violating
asymmetry of the elastic electron-proton scattering in a simple hadronic model
including the nucleon and the intermediate states. We find that
contribution is, in general, comparable with the
nucleon contribution and the current experimental measurements of
strange-quark effects in the proton neutral weak current. The total TBE
corrections to the current extracted values of
in recent experiments are found to lie in the
range of .Comment: 3 pages, 2 figs, 1 table, talk given at International Conference of
Particle and Nuclei (PANIC08) Eilat, Israel, 9-14 Nov,200
Identifying effective leadership practices for implementing a new mathematics curriculum in Taipei
This study explores successful junior high school principals’ leadership practices for implementing the reformed mathematics curriculum in Taipei. Avolio and Bass’s (2002) full range leadership theory was used to record data through interviews and observations of five Taipei “Grade A” junior high school principals. Findings revealed that specific leadership practices linked to management by exception-active and contingent reward (transaction leadership), and individualised consideration and idealised influence (transformational) were considered effective for implementing reform measures. Ensuring principals are aware of effective measures may further assist reform agendas
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