2,468 research outputs found
A format for phylogenetic placements
We have developed a unified format for phylogenetic placements, that is,
mappings of environmental sequence data (e.g. short reads) into a phylogenetic
tree. We are motivated to do so by the growing number of tools for computing
and post-processing phylogenetic placements, and the lack of an established
standard for storing them. The format is lightweight, versatile, extensible,
and is based on the JSON format which can be parsed by most modern programming
languages. Our format is already implemented in several tools for computing and
post-processing parsimony- and likelihood-based phylogenetic placements, and
has worked well in practice. We believe that establishing a standard format for
analyzing read placements at this early stage will lead to a more efficient
development of powerful and portable post-analysis tools for the growing
applications of phylogenetic placement.Comment: Documents version 3 of the forma
A wide scalar neutrino resonance and b\bar{b} production at LEP
In supersymmetric models with R-parity violation, scalar neutrinos may be
produced as s-channel resonances in e^+e^- colliders. We note that within
current constraints, the scalar neutrino may have a width of several GeV into
b\bar{b} and be produced with large cross section, leading to a novel
supersymmetry discovery signal at LEP II. In addition, if the scalar neutrino
mass approximately equals m_Z, such a resonance necessarily increases R_b and
reduces A_{FB}(b), significantly improving the fit to electroweak data. Bounds
from B meson and top quark decays are leading constraints, and we stress the
importance of future measurements.Comment: 8 pages. LaTex + RevTex. Revised to include a discussion of ISR
effects. Version to appear in Phys. Rev. Let
Adaptive Mesh Refinement for Characteristic Grids
I consider techniques for Berger-Oliger adaptive mesh refinement (AMR) when
numerically solving partial differential equations with wave-like solutions,
using characteristic (double-null) grids. Such AMR algorithms are naturally
recursive, and the best-known past Berger-Oliger characteristic AMR algorithm,
that of Pretorius & Lehner (J. Comp. Phys. 198 (2004), 10), recurses on
individual "diamond" characteristic grid cells. This leads to the use of
fine-grained memory management, with individual grid cells kept in
2-dimensional linked lists at each refinement level. This complicates the
implementation and adds overhead in both space and time.
Here I describe a Berger-Oliger characteristic AMR algorithm which instead
recurses on null \emph{slices}. This algorithm is very similar to the usual
Cauchy Berger-Oliger algorithm, and uses relatively coarse-grained memory
management, allowing entire null slices to be stored in contiguous arrays in
memory. The algorithm is very efficient in both space and time.
I describe discretizations yielding both 2nd and 4th order global accuracy.
My code implementing the algorithm described here is included in the electronic
supplementary materials accompanying this paper, and is freely available to
other researchers under the terms of the GNU general public license.Comment: 37 pages, 15 figures (40 eps figure files, 8 of them color; all are
viewable ok in black-and-white), 1 mpeg movie, uses Springer-Verlag svjour3
document class, includes C++ source code. Changes from v1: revised in
response to referee comments: many references added, new figure added to
better explain the algorithm, other small changes, C++ code updated to latest
versio
In Situ Probes of the First Galaxies and Reionization: Gamma-ray Bursts
The first structures in the Universe formed at z>7, at higher redshift than
all currently known galaxies. Since GRBs are brighter than other cosmological
sources at high redshift and exhibit simple power-law afterglow spectra that is
ideal for absorption studies, they serve as powerful tools for studying the
early universe. New facilities planned for the coming decade will be able to
obtain a large sample of high-redshift GRBs. Such a sample would constrain the
nature of the first stars, galaxies, and the reionization history of the
Universe.Comment: 8 pages, 3 figures, science white paper submitted to the US Astro2010
Decadal Surve
Kentucky Labor Supply and Demand Surveys
Excerpt from the executive summary:
The Center for Business and Economic Research at the University of Kentucky (CBER), along with its partners, the Survey Research Center at the University of Kentucky (UK-SRC), the Survey Research Center in the Urban Studies Institute at the University of Louisville (UL-SRC), and the Department of Economics at the University of Louisville, is pleased to present this final report on the findings of the Kentucky labor supply and demand surveys sponsored by the Kentucky Cabinet for Workforce Development. The two universities have put together a consortium including some of the best scholars in the region in the areas of labor economics, local economic development, and survey design and administration
Large-scale identification of genetic design strategies using local search
In the past decade, computational methods have been shown to be well suited to unraveling the complex web of metabolic reactions in biological systems. Methods based on fluxâbalance analysis (FBA) and bi-level optimization have been used to great effect in aiding metabolic engineering. These methods predict the result of genetic manipulations and allow for the best set of manipulations to be found computationally. Bi-level FBA is, however, limited in applicability because the required computational time and resources scale poorly as the size of the metabolic system and the number of genetic manipulations increase. To overcome these limitations, we have developed Genetic Design through Local Search (GDLS), a scalable, heuristic, algorithmic method that employs an approach based on local search with multiple search paths, which results in effective, low-complexity search of the space of genetic manipulations. Thus, GDLS is able to find genetic designs with greater in silico production of desired metabolites than can feasibly be found using a globally optimal search and performs favorably in comparison with heuristic searches based on evolutionary algorithms and simulated annealing.Hertz Foundatio
A Plan for a Long-Term, Automated, Broadband Seismic Monitoring Network on the Global Seafloor
Establishing an extensive and highly durable, longâterm, seafloor network of autonomous broadband seismic stations to complement the landâbased Global Seismographic Network has been a goal of seismologists for decades. Seismic signals, chiefly the vibrations from earthquakes but also signals generated by storms and other environmental processes, have been processed from landâbased seismic stations to build intriguing but incomplete images of the Earthâs interior. Seismologists have mapped structures such as tectonic plates and other crustal remnants sinking deep into the mantle to obtain information on their chemical composition and physical state; but resolution of these structures from land stations is not globally uniform. Because the global surface is twoâthirds ocean, increasing the number of seismic stations located in the oceans is critical for better resolution of the Earthâs interior and tectonic structures. A recommendation for a longâterm seafloor seismic station pilot experiment is presented here. The overarching instrumentation goal of a pilot experiment is performance that will lead to the installation of a large number of longâterm autonomous oceanâbottom seismic stations. The payoff of a network of stations separated from one another by a few hundred kilometers under the global oceans would be greatly refined resolution of the Earthâs interior at all depths. A second prime result would be enriched understanding of largeâearthquake rupture processes in both oceanic and continental plates. The experiment would take advantage of newly available technologies such as robotic wave gliders that put an affordable autonomous prototype within reach. These technologies would allow data to be relayed to satellites from seismometers that are deployed on the seafloor with longâlasting, rechargeable batteries. Two regions are presented as promising arenas for such a prototype seafloor seismic station. One site is the central North Atlantic Ocean, and the other highâinterest locale is the central South Pacific Ocean
Opicapone, a Novel Catechol-O-methyl Transferase Inhibitor, for Treatment of Parkinson\u27s Disease Off Episodes
Parkinson\u27s Disease (PD) is a common neurodegenerative disorder and the leading cause of disability. It causes significant morbidity and disability through a plethora of symptoms, including movement disorders, sleep disturbances, and cognitive and psychiatric symptoms. The traditional pathogenesis theory of PD involves the loss of dopaminergic neurons in the substantia nigra (SN). Classically, treatment is pursued with an assortment of medications that are directed at overcoming this deficiency with levodopa being central to most treatment plans. Patients taking levodopa tend to experience off episodes with decreasing medication levels, causing large fluctuations in their symptoms. These off episodes are disturbing and a source of morbidity for these patients. Opicapone is a novel, peripherally acting Catechol-O-methyl transferase (COMT) inhibitor that is used as adjunctive therapy to carbidopa/levodopa for treatment and prevention of off episodes. It has been approved for use as an adjunct to levodopa since 2016 in Europe and has recently (April 2020) gained FDA approval for use in the USA. By inhibiting COMT, opicapone slows levodopa metabolism and increases its availability. Several clinical studies demonstrated significant improvement in treatment efficacy and reduction in duration of off episodes. The main side effect demonstrated was dyskinesia, mostly with the 100mg dose, which is higher than the approved, effective dose of 50mg. Post-marketing surveillance and analysis are required to further elucidate its safety profile and contribute to patient selection. This paper reviews the seminal and latest evidence in the treatment of PD off episodes with the novel drug Opicapone, including efficacy, safety, and clinical indications
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