9,435 research outputs found
Methodological Issues in Multistage Genome-Wide Association Studies
Because of the high cost of commercial genotyping chip technologies, many
investigations have used a two-stage design for genome-wide association
studies, using part of the sample for an initial discovery of ``promising''
SNPs at a less stringent significance level and the remainder in a joint
analysis of just these SNPs using custom genotyping. Typical cost savings of
about 50% are possible with this design to obtain comparable levels of overall
type I error and power by using about half the sample for stage I and carrying
about 0.1% of SNPs forward to the second stage, the optimal design depending
primarily upon the ratio of costs per genotype for stages I and II. However,
with the rapidly declining costs of the commercial panels, the generally low
observed ORs of current studies, and many studies aiming to test multiple
hypotheses and multiple endpoints, many investigators are abandoning the
two-stage design in favor of simply genotyping all available subjects using a
standard high-density panel. Concern is sometimes raised about the absence of a
``replication'' panel in this approach, as required by some high-profile
journals, but it must be appreciated that the two-stage design is not a
discovery/replication design but simply a more efficient design for discovery
using a joint analysis of the data from both stages. Once a subset of
highly-significant associations has been discovered, a truly independent
``exact replication'' study is needed in a similar population of the same
promising SNPs using similar methods.Comment: Published in at http://dx.doi.org/10.1214/09-STS288 the Statistical
Science (http://www.imstat.org/sts/) by the Institute of Mathematical
Statistics (http://www.imstat.org
The politics of failure : strategic nuclear arms control, public opinion, and domestic politics in the United States : 1945-1980
Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Political Science, 1989.Includes bibliographical references (leaves 538-560).by Thomas Wallace Graham.Ph.D
Lasing and cooling in a hot cavity
We present a microscopic laser model for many atoms coupled to a single
cavity mode, including the light forces resulting from atom-field momentum
exchange. Within a semiclassical description, we solve the equations for atomic
motion and internal dynamics to obtain analytic expressions for the optical
potential and friction force seen by each atom. When optical gain is maximum at
frequencies where the light field extracts kinetic energy from the atomic
motion, the dynamics combines optical lasing and motional cooling. From the
corresponding momentum diffusion coefficient we predict sub-Doppler
temperatures in the stationary state. This generalizes the theory of cavity
enhanced laser cooling to active cavity systems. We identify the gain induced
reduction of the effective resonator linewidth as key origin for the faster
cooling and lower temperatures, which implys that a bad cavity with a gain
medium can replace a high-Q cavity. In addition, this shows the importance of
light forces for gas lasers in the low-temperature limit, where atoms can
arrange in a periodic pattern maximizing gain and counteracting spatial hole
burning. Ultimately, in the low temperature limit, such a setup should allow to
combine optical lasing and atom lasing in single device.Comment: 11 pages, 6 figure
Muons in supernovae: implications for the axion-muon coupling
The high temperature and electron degeneracy attained during a supernova
allow for the formation of a large muon abundance within the core of the
resulting proto-neutron star. If new pseudoscalar degrees of freedom have large
couplings to the muon, they can be produced by this muon abundance and
contribute to the cooling of the star. By generating the largest collection of
supernova simulations with muons to date, we show that observations of the
cooling rate of SN 1987A place strong constraints on the coupling of axion-like
particles to muons, limiting the coupling to .Comment: 8 pages, 7 figures. v2: Error fixed, results and figures updated;
updated discussion of CMB bounds. v3: Updated references. v4: Updated to
match published versio
Which anthropometric and lower body power variables are predictive of professional and amateur playing status in male rugby union players?
The purpose of this study was to compare anthropometric and lower body power measurements between current professional and amateur male rugby union players. The present study also sought to determine which anthropometric and physical performance variables were predictive of playing standard. Thirty professional and 30 amateur RU players performed Wattbike 6 s maximal effort (WB6S) and countermovement (CMJ) and squat jump (SJ) assessments, anthropometric measures were also taken. Dependant variables recorded and analysed including: body mass, stature, Σ8 site skinfolds, WB6S absolute and relative peak power, CMJ and SJ average concentric force, jump height, peak velocity, time to peak force, rate of force development (RFD) and absolute and relative peak force and power. Professional players were heavier, taller and leaner than their amateur counterparts (p < 0.05). Professional players performed significantly better in all physical performance measures except CMJ and SJ time to peak force, CMJ RFD and SJ relative peak force. Variables which were predictive of playing standard were: Σ8 skinfolds, CMJ peak velocity and WB6S absolute and relative peak power (p < 0.05). These findings indicate that the current body of male professional RU players is anthropometrically and physically superior to their amateur counterparts, although not all variables assessed here were predictive of playing standard. Data presented here indicate that Σ8 skinfolds, WB6S absolute and relative power and CMJ peak velocity are predictive of playing standard, whereas other anthropometric and strength and power variables are not
Novel Reproductive Data on Pealip Redhorse, Moxostoma pisolabrum (Cypriniformes: Catostomidae), from Northeastern Arkansas
Little is known about the natural history of the Pealip Redhorse (Moxostoma pisolabrum), particularly on its reproductive biology in Arkansas. We examined 11 female M. pisolabrum collected in late February 2020 and 2021 from the Black River, Lawrence County. Egg mass (g) represented 9‒14% of the total weight of these gravid females. This is the first time information on female reproduction in this species has been reported from any population of M. pisolabrum in the state
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