11,095 research outputs found
The Upsilon spectrum and m_b from full lattice QCD
We show results for the Upsilon spectrum calculated in lattice QCD including
for the first time vacuum polarization effects for light u and d quarks as well
as s quarks. We use gluon field configurations generated by the MILC
collaboration. The calculations compare the results for a variety of u and d
quark masses, as well as making a comparison to quenched results (in which
quark vacuum polarisation is ignored) and results with only u and d quarks. The
b quarks in the Upsilon are treated in lattice Nonrelativistic QCD through NLO
in an expansion in the velocity of the b quark. We concentrate on accurate
results for orbital and radial splittings where we see clear agreement with
experiment once u, d and s quark vacuum polarisation effects are included. This
now allows a consistent determination of the parameters of QCD. We demonstrate
this consistency through the agreement of the Upsilon and B spectrum using the
same lattice bare b quark mass. A one-loop matching to continuum QCD gives a
value for the b quark mass in full lattice QCD for the first time. We obtain
m_b^{\bar{MS}}(m_b^{\bar{MS}}) = 4.4(3) GeV. We are able to give physical
results for the heavy quark potential parameters, r_0 = 0.469(7) fm and r_1 =
0.321(5) fm. Results for the fine structure in the spectrum and the Upsilon
leptonic width are also presented. We predict the Upsilon - eta_b splitting to
be 61(14) MeV, the Upsilon^{\prime} - eta_b^{\prime} splitting as 30(19) MeV
and the splitting between the h_b and the spin-average of the chi_b states to
be less than 6 MeV. Improvements to these calculations that will be made in the
near future are discussed.Comment: 24 pages, 19 figures. Version to be published. Minor changes made and
typographical errors corrected. Experimental leptonic widths updated in
section
Chapter: âHealth Law and Ethicsâ
Law and ethics are both essential attributes of a high-functioning health care system and powerful explainers of why the existing system is so difficult to improve. U.S. health law is not seamless; rather, it derives from multiple sources and is based on various theories that may be in tension with one another. There are state laws and federal laws, laws setting standards and laws providing funding, laws reinforcing professional prerogatives, laws furthering social goals, and laws promoting market competition. Complying with law is important, but health professionals also should understand that the legal and ethical constraints under which health systems operate must themselves adapt if health systems science is to advance
On a new class of tests for the Pareto distribution using Fourier methods
We propose new classes of tests for the Pareto type I distribution using the
empirical characteristic function. These tests are and statistics based
on a characterisation of the Pareto distribution involving the distribution of
the sample minimum. In addition to deriving simple computational forms for the
proposed test statistics, we prove consistency against a wide range of fixed
alternatives. A Monte Carlo study is included in which the newly proposed tests
are shown to produce high powers. These powers include results relating to
fixed alternatives as well as local powers against mixture distributions. The
use of the proposed tests is illustrated using an observed data set
Detection of a Substantial Molecular Gas Reservoir in a brightest cluster galaxy at z = 1.7
We report the detection of CO(2-1) emission coincident with the brightest
cluster galaxy (BCG) of the high-redshift galaxy cluster SpARCS1049+56, with
the Redshift Search Receiver (RSR) on the Large Millimetre Telescope (LMT). We
confirm a spectroscopic redshift for the gas of z = 1.7091+/-0.0004, which is
consistent with the systemic redshift of the cluster galaxies of z = 1.709. The
line is well-fit by a single component Gaussian with a RSR resolution-corrected
FWHM of 569+/-63 km/s. We see no evidence for multiple velocity components in
the gas, as might be expected from the multiple image components seen in
near-infrared imaging with the Hubble Space Telescope. We measure the
integrated flux of the line to be 3.6+/-0.3 Jy km/s and, using alpha_CO = 0.8
Msun (K km s^-1 pc^2)^-1 we estimate a total molecular gas mass of
1.1+/-0.1x10^11 Msun and a M_H2/M_star ~ 0.4. This is the largest gas reservoir
detected in a BCG above z > 1 to date. Given the infrared-estimated star
formation rate of 860+/-130 Msun/yr, this corresponds to a gas depletion
timescale of ~0.1Gyr. We discuss several possible mechanisms for depositing
such a large gas reservoir to the cluster center -- e.g., a cooling flow, a
major galaxy-galaxy merger or the stripping of gas from several galaxies -- but
conclude that these LMT data are not sufficient to differentiate between them.Comment: accepted for publication in ApJ Letter
Simulation and analysis of solenoidal ion sources
We present a detailed analysis and simulation of solenoidal, magnetically confined electron bombardment ion sources, aimed at molecular beam detection. The aim is to achieve high efficiency for singly ionized species while minimizing multiple ionization. Electron space charge plays a major role and we apply combined ray tracing and finite element simulations to determine the properties of a realistic geometry. The factors controlling electron injection and ion extraction are discussed. The results from simulations are benchmarked against experimental measurements on a prototype source
Avian oncogenesis induced by lymphoproliferative disease virus: a neglected or emerging retroviral pathogen?
Lymphoproliferative disease virus (LPDV) is an exogenous oncogenic retrovirus that induces lymphoid tumors in some galliform species of birds. Historically, outbreaks of LPDV have been reported from Europe and Israel. Although the virus has previously never been detected in North America, herein we describe the widespread distribution, genetic diversity, pathogenesis, and evolution of LPDV in the United States. Characterization of the provirus genome of the index LPDV case from North America demonstrated an 88% nucleotide identity to the Israeli prototype strain. Although phylogenetic analysis indicated that the majority of viruses fell into a single North American lineage, a small subset of viruses from South Carolina were most closely related to the Israeli prototype. These results suggest that LPDV was transferred between continents to initiate outbreaks of disease. However, the direction (New World to Old World or vice versa), mechanism, and time frame of the transcontinental spread currently remain unknown
Theory of periodic swarming of bacteria: application to Proteus mirabilis
The periodic swarming of bacteria is one of the simplest examples for pattern
formation produced by the self-organized collective behavior of a large number
of organisms. In the spectacular colonies of Proteus mirabilis (the most common
species exhibiting this type of growth) a series of concentric rings are
developed as the bacteria multiply and swarm following a scenario periodically
repeating itself. We have developed a theoretical description for this process
in order to get a deeper insight into some of the typical processes governing
the phenomena in systems of many interacting living units. All of our
theoretical results are in excellent quantitative agreement with the complete
set of available observations.Comment: 11 pages, 8 figure
The art and science of searching MEDLINE to answer clinical questions. Finding the right number of articles
The current medical environment makes information retrieval a matter of practical importance for clinicians. Many avenues present themselves to the clinician, but here we focus on MEDLINE by summarizing the current state of the art and providing an innovative approach for skill enhancement. Because new search engines appear rapidly, we focus on generic principles that can be easily adapted to various systems, even those not yet available. We propose an idealized classification system for the results of a MEDLINE search. Type A searches produce a few articles of high quality that are directly focused on the immediate question. Type B searches yield a large number of articles, some more relevant than others. Type C searches produce few or no articles, and those that are located are not germane. Providing that relevant, high-quality articles do exist, type B and C searches may often be improved with attention to search technique. Problems stem from poor recall and poor precision. The most daunting task lies in achieving the balance between too few and too many articles. By providing a theoretical framework and several practical examples, we prepare the searcher to overcome the following barriers: a) failure to begin with a well-built question; b) failure to use the Medical Subject Headings; c) failure to leverage the relationship between recall and precision; and d) failure to apply proper limits to the search. Thought and practice will increase the utility and enjoyment of searching MEDLINE
Operation of a 1-Liter-Volume Gaseous Argon Scintillation Counter
We have built a gas-phase argon ionization detector to measure small nuclear
recoil energies (< 10 keVee). In this paper, we describe the detector response
to X-ray and gamma calibration sources, including analysis of pulse shapes,
software triggers, optimization of gas content, and energy- and
position-dependence of the signal. We compare our experimental results against
simulation using a 5.9-keV X-ray source, as well as higher-energy gamma sources
up to 1332 keV. We conclude with a description of the detector, DAQ, and
software settings optimized for a measurement of the low-energy nuclear
quenching factor in gaseous argon. This work was performed under the auspices
of the U.S. Department of Energy by Lawrence Livermore National Laboratory in
part under Contract W-7405-Eng-48 and in part under Contract DE-AC52-07NA27344.
Funded by Lab-wide LDRD. LLNL-JRNL-415990-DRAFT.Comment: 29 pages, single-column, double-spaced, 21 figure
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