1,121 research outputs found
Integrable Structure of Interface Dynamics
We establish the equivalence of a 2D contour dynamics to the dispersionless
limit of the integrable Toda hierarchy constrained by a string equation.
Remarkably, the same hierarchy underlies 2D quantum gravity.Comment: 5 pages, no figures, submitted to Phys. Rev. Lett, typos correcte
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Planning Strategically for Regional Development in the Permian Basin
The Survey Research Center and the Center for Economic Development at the University of North Texas were retained by the Permian Basin Regional Planning Commission to assist them in developing a strategic plan for the region
Ultracold collisions of oxygen molecules
Collision cross sections and rate constants between two ground- state oxygen
molecules are investigated theoretically at translational energies below K and in zero magnetic field. We present calculations for elastic and spin-
changing inelastic collision rates for different isotopic combinations of
oxygen atoms as a prelude to understanding their collisional stability in
ultracold magnetic traps. A numerical analysis has been made in the framework
of a rigid- rotor model that accounts fully for the singlet, triplet, and
quintet potential energy surfaces in this system. The results offer insights
into the effectiveness of evaporative cooling and the properties of molecular
Bose- Einstein condensates, as well as estimates of collisional lifetimes in
magnetic traps. Specifically, looks like a good candidate for
ultracold studies, while is unlikely to survive evaporative
cooling. Since is representative of a wide class of molecules that
are paramagnetic in their ground state we conclude that many molecules can be
successfully magnetically trapped at ultralow temperatures.Comment: 15 pages, 9 figure
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Modeling the impact of the 13-valent pneumococcal conjugate vaccine serotype catch-up program using United States claims data
Background: Analysis of US claims data from April 2010 to June 2011 estimated that 39% of the 13-valent pneumococcal conjugate vaccine (PCV13) catch-up eligible cohort would ever receive the catch-up vaccination; a previous analysis assumed 87%. Methods: This updated figure was applied to a previously published 10-year Markov model while holding all other inputs constant. Results: Our model estimated that the catch-up program as currently implemented is estimated to prevent an additional 1.7 million cases of disease in children aged ā¤59 months over a 10-year period, compared with routine PCV13 vaccination with no catch-up program. Conclusions: Because 39% catch-up uptake is less than the level of completion of the 4-dose primary PCV13 series, vaccine-preventable cases of pneumococcal disease and related deaths could be decreased further with additional uptake of catch-up vaccination in the catch-up eligible cohort
Distinguishing Among Strong Decay Models
Two competing models for strong hadronic decays, the and
models, are currently in use.
Attempts to rule out one or the other have been hindered by a poor
understanding of final state interactions and by ambiguities in the treatment
of relativistic effects.
In this article we study meson decays in both models, focussing on certain
amplitude ratios for which the relativistic uncertainties largely cancel out
(notably the ratios in and
), and using a Quark Born Formalism to estimate the
final state interactions.
We find that the model is strongly favoured.
In addition, we predict a amplitude ratio of for the decay
.
We also study the parameter-dependence of some individual amplitudes (as
opposed to amplitude ratios), in an attempt to identify a ``best'' version of
the model.Comment: 20 pages, uuencoded postscript file with 7 figures, MIT-CTP-2295;
CMU-HEP94-1
Molecular Dynamics Simulation of Sympathetic Crystallization of Molecular Ions
It is shown that the translational degrees of freedom of a large variety of
molecules, from light diatomic to heavy organic ones, can be cooled
sympathetically and brought to rest (crystallized) in a linear Paul trap. The
method relies on endowing the molecules with an appropriate positive charge,
storage in a linear radiofrequency trap, and sympathetic cooling. Two
well--known atomic coolant species, and
, are sufficient for cooling the molecular mass range
from 2 to 20,000 amu. The large molecular charge required for simultaneous
trapping of heavy molecules and of the coolant ions can easily be produced
using electrospray ionization. Crystallized molecular ions offer vast
opportunities for novel studies.Comment: Accepted for publication in Phys. Rev.
Multiplexing siRNAs to compress RNAi-based screen size in human cells
Here we describe a novel strategy using multiplexes of synthetic small interfering RNAs (siRNAs) corresponding to multiple gene targets in order to compress RNA interference (RNAi) screen size. Before investigating the practical use of this strategy, we first characterized the gene-specific RNAi induced by a large subset (258 siRNAs, 129 genes) of the entire siRNA library used in this study (ā¼800 siRNAs, ā¼400 genes). We next demonstrated that multiplexed siRNAs could silence at least six genes to the same degree as when the genes were targeted individually. The entire library was then used in a screen in which randomly multiplexed siRNAs were assayed for their affect on cell viability. Using this strategy, several gene targets that influenced the viability of a breast cancer cell line were identified. This study suggests that the screening of randomly multiplexed siRNAs may provide an important avenue towards the identification of candidate gene targets for downstream functional analyses and may also be useful for the rapid identification of positive controls for use in novel assay systems. This approach is likely to be especially applicable where assay costs or platform limitations are prohibitive
HIV Cure Strategies: How Good Must They Be to Improve on Current Antiretroviral Therapy?
Background: We examined efficacy, toxicity, relapse, cost, and quality-of-life thresholds of hypothetical HIV cure interventions that would make them cost-effective compared to life-long antiretroviral therapy (ART). Methods: We used a computer simulation model to assess three HIV cure strategies: Gene Therapy, Chemotherapy, and Stem Cell Transplantation (SCT), each compared to ART. Efficacy and cost parameters were varied widely in sensitivity analysis. Outcomes included quality-adjusted life expectancy, lifetime cost, and cost-effectiveness in dollars/quality-adjusted life year (100,000/QALY. Results: For patients on ART, discounted quality-adjusted life expectancy was 16.4 years and lifetime costs were 54,000. Chemotherapy was cost-effective with efficacy of 88%, relapse rate 0.5%/month, and cost 150,000/procedure, SCT was cost-effective with efficacy of 79% and relapse rate 0.5%/month. Moderate efficacy increases and cost reductions made Gene Therapy cost-saving, but substantial efficacy/cost changes were needed to make Chemotherapy or SCT cost-saving. Conclusions: Depending on efficacy, relapse rate, and cost, cure strategies could be cost-effective compared to current ART and potentially cost-saving. These results may help provide performance targets for developing cure strategies for HIV
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