4,055 research outputs found
Metastable States in High Order Short-Range Spin Glasses
The mean number of metastable states in higher order short-range spin
glasses is estimated analytically using a variational method introduced by
Tanaka and Edwards for very large coordination numbers. For lattices with small
connectivities, numerical simulations do not show any significant dependence on
the relative positions of the interacting spins on the lattice, indicating thus
that these systems can be described by a few macroscopic parameters. As an
extremely anisotropic model we consider the low autocorrelated binary spin
model and we show through numerical simulations that its landscape has an
exceptionally large number of local optima
Qualification model spacecraft tests for DEMP, SGEMP, and ESD effects
The development of a satellite design demonstration test program is described. The test approach is comprehensive in that it includes the effects from electrostatic discharge (ESD), system generated electromagnetic pulse (SGEMP), as well as dispersed electromagnetic pulses (DEMP). The comprehensive test concept is based on the similarity of the satellite's response to several environments
Application of the Covariant Spectator Theory to the study of heavy and heavy-light mesons
As an application of the Covariant Spectator Theory (CST) we calculate the
spectrum of heavy-light and heavy-heavy mesons using covariant versions of a
linear confining potential, a one- gluon exchange, and a constant interaction.
The CST equations possess the correct one-body limit and are therefore
well-suited to describe mesons in which one quark is much heavier than the
other. We find a good fit to the mass spectrum of heavy-light and heavy-heavy
mesons with just three parameters (apart from the quark masses). Remarkably,
the fit parameters are nearly unchanged when we fit to experimental
pseudoscalar states only or to the whole spectrum. Because pseudoscalar states
are insensitive to spin-orbit interactions and do not determine spin-spin
interactions separately from central interactions, this result suggests that it
is the covariance of the kernel that correctly predicts the spin-dependent
quark-antiquark interaction
A covariant constituent-quark formalism for mesons
Using the framework of the Covariant Spectator Theory (CST) [1] we are
developing a covariant model formulated in Minkowski space to study mesonic
structure and spectra. Treating mesons as effective states, we
focused in [2] on the nonrelativistic bound-state problem in momentum space
with a linear confining potential. Although integrable, this kernel has
singularities which are difficult to handle numerically. In [2] we reformulate
it into a form in which all singularities are explicitely removed. The
resulting equations are then easier to solve and yield accurate and stable
solutions. In the present work, the same method is applied to the relativistic
case, improving upon the results of the one-channel spectator equation (1CSE)
given in [3].Comment: 6 pages, 5 figures, Presented at EEF70, Workshop on Unquenched Hadron
Spectroscopy: Non-Perturbative Models and Methods of QCD vs. Experimen
Relativistic phenomenology of meson spectra with a covariant quark model in Minkowski space
In this work, we perform a covariant treatment of quark-antiquark systems. We
calculate the spectra and wave functions using a formalism based on the
Covariant Spectator Theory (CST). Our results not only reproduce very well the
experimental data with a very small set of global parameters, but they also
allow a direct test of the predictive power of covariant kernels
Protection of personal information Act No. 4 of 2013: Implications for biobanks
The Protection of Personal Information Act (POPIA) No. 4 of 2013 is the first comprehensive data-protection regulation to be passed in South Africa (SA). Its objectives include giving effect to the constitutional right to privacy by regulating the way in which personal information must be processed, balancing the right to privacy against other rights, and establishing an Information Regulator to ensure that the rights protected by POPIA are respected. POPIA will have an impact on health research, including biobanks. As sharing of samples and data is a central feature of biobanks, POPIA could change the way in which data are obtained, shared and exported. In particular, the provisions regarding data minimisation, requirements pertaining to the transfer of data abroad, consent provisions and identification of the 'responsible person' will impact the operation of biobanks in SA. With POPIA soon to come into force, it is now time to consider its implications for biobanks in SA
Quark model with chiral-symmetry breaking and confinement in the Covariant Spectator Theory
We propose a model for the quark-antiquark interaction in Minkowski space
using the Covariant Spectator Theory. We show that with an equal-weighted
scalar-pseudoscalar structure for the confining part of our interaction kernel
the axial-vector Ward-Takahashi identity is preserved and our model complies
with the Adler-zero constraint for pi-pi-scattering imposed by chiral symmetry.Comment: 4 pages, 2 figures; 21st International Conference on Few-Body
Problems in Physics, May 18 - 22, 2015, Chicago, US
What is the best treatment for plantar fasciitis?
Mechanical therapies -- such as taping, tension night splinting, and rigid arch support -- are the most effective treatment for plantar fasciitis (strength of recommendation: A, based on randomized controlled trials). If limited or no improvement is observed after 6 months of mechanical therapy, extracorporeal shock wave therapy (Orthotripsy) is the next treatment of choice (strength of recommendation [SOR]: A, based on meta-analysis of randomized controlled trials). When mechanical therapies and extracorporeal shock wave therapy have failed for more than 1 year, surgical treatment may be considered (SOR: C, based on a case-series study)
Evidence for a single hydrogen molecule connected by an atomic chain
Stable, single-molecule conducting-bridge configurations are typically
identified from peak structures in a conductance histogram. In previous work on
Pt with H at cryogenic temperatures it has been shown that a peak near 1
identifies a single molecule Pt-H-Pt bridge. The histogram shows
an additional structure with lower conductance that has not been identified.
Here, we show that it is likely due to a hydrogen decorated Pt chain in contact
with the H molecular bridge.Comment: 4 pages, 4 figure
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Dynamic multifactor hubs interact transiently with sites of active transcription in Drosophila embryos.
The regulation of transcription requires the coordination of numerous activities on DNA, yet how transcription factors mediate these activities remains poorly understood. Here, we use lattice light-sheet microscopy to integrate single-molecule and high-speed 4D imaging in developing Drosophila embryos to study the nuclear organization and interactions of the key transcription factors Zelda and Bicoid. In contrast to previous studies suggesting stable, cooperative binding, we show that both factors interact with DNA with surprisingly high off-rates. We find that both factors form dynamic subnuclear hubs, and that Bicoid binding is enriched within Zelda hubs. Remarkably, these hubs are both short lived and interact only transiently with sites of active Bicoid-dependent transcription. Based on our observations, we hypothesize that, beyond simply forming bridges between DNA and the transcription machinery, transcription factors can organize other proteins into hubs that transiently drive multiple activities at their gene targets.Editorial noteThis article has been through an editorial process in which the authors decide how to respond to the issues raised during peer review. The Reviewing Editor's assessment is that all the issues have been addressed (see decision letter)
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