9,540 research outputs found
Avoided level crossings in the quantization of a mixed regular-chaotic system
The study of avoided level crossings in the spectra of quantum Hamiltonians whose classical counterparts exhibit mixed regular-chaotic dynamics reveals important information about the quantum signatures of such dynamics. Among other topics, one can study delocalization phenomena and exchange of structure in Husimi distributions and compare the quantum dynamics one observes to the dynamics of corresponding classical systems at the same parameter values
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Band-collision gel electrophoresis.
Electrophoretic mobility shift assays are widely used in gel electrophoresis to study binding interactions between different molecular species loaded into the same well. However, shift assays can access only a subset of reaction possibilities that could be otherwise seen if separate bands of reagent species might instead be collisionally reacted. Here, we adapt gel electrophoresis by fabricating two or more wells in the same lane, loading these wells with different reagent species, and applying an electric field, thereby producing collisional reactions between propagating pulse-like bands of these species, which we image optically. For certain pairs of anionic and cationic dyes, propagating bands pass through each other unperturbed; yet, for other pairs, we observe complexing and precipitation reactions, indicating strong attractive interactions. We generalize this band-collision gel electrophoresis (BCGE) approach to other reaction types, including acid-base, ligand exchange, and redox, as well as to colloidal species in passivated large-pore gels
The Bowl Championship Series: A Mathematical Review
We discuss individual components of the college football Bowl Championship
Series, compare with a simple algorithm defined by random walks on a biased
graph, attempt to predict whether the proposed changes will truly lead to
increased BCS bowl access for non-BCS schools, and conclude by arguing that the
true problem with the BCS Standings lies not in the computer algorithms, but
rather in misguided addition.Comment: 12 pages, 2 figures, submitted to Notices of the AM
A Method Based on Total Variation for Network Modularity Optimization using the MBO Scheme
The study of network structure is pervasive in sociology, biology, computer
science, and many other disciplines. One of the most important areas of network
science is the algorithmic detection of cohesive groups of nodes called
"communities". One popular approach to find communities is to maximize a
quality function known as {\em modularity} to achieve some sort of optimal
clustering of nodes. In this paper, we interpret the modularity function from a
novel perspective: we reformulate modularity optimization as a minimization
problem of an energy functional that consists of a total variation term and an
balance term. By employing numerical techniques from image processing
and compressive sensing -- such as convex splitting and the
Merriman-Bence-Osher (MBO) scheme -- we develop a variational algorithm for the
minimization problem. We present our computational results using both synthetic
benchmark networks and real data.Comment: 23 page
A survey of compensatory mitigation within the tidal wetlands of Virginia
This study has as its primary purpose an examination of how compensatory mitigation has worked as a wetlands management tool to date in Virginia (i.e. how well theory has been put into practice). Our approach was to look at the overall use of compensation in coastal Virginia based on regulatory records and to examine as many existing created wetlands as possible within the tidal area of the state to determine how closely these projects have come, collectively, to fulfilling the compensatory goal of wetland replacement. Secondary objectives includes an examination of the literature regarding wetland compensation concept evaluation and to construct a comprehensive lists of wetland compensation sites in Virginia. --p.
70 Years of Human Rights in Global Health: Drawing on a Contentious Past to Secure a Hopeful Future
The Universal Declaration of Human Rights, adopted on Dec 10, 1948, established a modern human rights foundation that has become a cornerstone of global health, central to public health policies, programmes, and practices. To commemorate the 70th anniversary of this seminal declaration, we trace the evolution of human rights in global health, linking the past, present, and future of health as a human right. This future remains uncertain. As contemporary challenges imperil continuing advancements, threatening both human rights protections and global health governance, the future will depend, as it has in the past, on sustained political engagement to realise human rights in global health
On Estimating the High-Energy Cutoff in the X-ray Spectra of Black Holes via Reflection Spectroscopy
The fundamental parameters describing the coronal spectrum of an accreting
black hole are the slope of the power-law continuum and the energy
at which it rolls over. Remarkably, this parameter can be accurately
measured for values as high as 1 MeV by modeling the spectrum of X-rays
reflected from a black hole accretion disk at energies below 100 keV. This is
possible because the details in the reflection spectrum, rich in fluorescent
lines and other atomic features, are very sensitive to the spectral shape of
the hardest coronal radiation illuminating the disk. We show that fitting
simultaneous NuSTAR (3-79 keV) and low-energy (e.g., Suzaku) data with the most
recent version of our reflection model RELXILL, one can obtain reasonable
constraints on at energies from tens of keV up to 1 MeV, for a source
as faint as 1 mCrab in a 100 ks observation.Comment: Accepted for publication in ApJL, 6 pages, 5 figure
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