6,946 research outputs found
Measurement of statistical evidence on an absolute scale following thermodynamic principles
Statistical analysis is used throughout biomedical research and elsewhere to
assess strength of evidence. We have previously argued that typical outcome
statistics (including p-values and maximum likelihood ratios) have poor
measure-theoretic properties: they can erroneously indicate decreasing evidence
as data supporting an hypothesis accumulate; and they are not amenable to
calibration, necessary for meaningful comparison of evidence across different
study designs, data types, and levels of analysis. We have also previously
proposed that thermodynamic theory, which allowed for the first time derivation
of an absolute measurement scale for temperature (T), could be used to derive
an absolute scale for evidence (E). Here we present a novel
thermodynamically-based framework in which measurement of E on an absolute
scale, for which "one degree" always means the same thing, becomes possible for
the first time. The new framework invites us to think about statistical
analyses in terms of the flow of (evidential) information, placing this work in
the context of a growing literature on connections among physics, information
theory, and statistics.Comment: Final version of manuscript as published in Theory in Biosciences
(2013
Improved AURA k-Nearest Neighbour approach
The k-Nearest Neighbour (kNN) approach is a widely-used technique for pattern classification. Ranked distance measurements to a known sample set determine the classification of unknown samples. Though effective, kNN, like most classification methods does not scale well with increased sample size. This is due to their being a relationship between the unknown query and every other sample in the data space. In order to make this operation scalable, we apply AURA to the kNN problem. AURA is a highly-scalable associative-memory based binary neural-network intended for high-speed approximate search and match operations on large unstructured datasets. Previous work has seen AURA methods applied to this problem as a scalable, but approximate kNN classifier. This paper continues this work by using AURA in conjunction with kernel-based input vectors, in order to create a fast scalable kNN classifier, whilst improving recall accuracy to levels similar to standard kNN implementations
On Lorentz Invariance, Spin-Charge Separation And SU(2) Yang-Mills Theory
Previously it has been shown that in spin-charge separated SU(2) Yang-Mills
theory Lorentz invariance can become broken by a one-cocycle that appears in
the Lorentz boosts. Here we study in detail the structure of this one-cocycle.
In particular we show that its non-triviality relates to the presence of a
(Dirac) magnetic monopole bundle. We also explicitely present the finite
version of the cocycle.Comment: 4 page
Structure and Mass of a Young Globular Cluster in NGC 6946
Using the Wide Field Planetary Camera 2 on board the Hubble Space Telescope,
we have imaged a luminous young star cluster in the nearby spiral galaxy NGC
6946. The cluster has an absolute visual magnitude M(V)=-13.2, comparable to
the brightest young `super-star clusters' in the Antennae merger galaxy. UBV
colors indicate an age of about 15 Myr. The cluster has a compact core (core
radius = 1.3 pc), surrounded by an extended envelope. We estimate that the
effective radius (Reff) = 13 pc, but this number is uncertain because the outer
parts of the cluster profile gradually merge with the general field. Combined
with population synthesis models, the luminosity and age of the cluster imply a
mass of 8.2x10^5 Msun for a Salpeter IMF extending down to 0.1 Msun, or
5.5x10^5 Msun if the IMF is log-normal below 0.4 Msun. Depending on model
assumptions, the central density of the cluster is between 5300 Msun pc^-3 and
17000 Msun pc^-3, comparable to other high-density star forming regions. We
also estimate a dynamical mass for the cluster, using high-dispersion spectra
from the HIRES spectrograph on the Keck I telescope. The velocity dispersion is
10.0 +/- 2.7 km/s, implying a total cluster mass within 65 pc of (1.7 +/- 0.9)
x 10^6 Msun. Comparing the dynamical mass with the mass estimates based on the
photometry and population synthesis models, the mass-to-light ratio is at least
as high as for a Salpeter IMF extending down to 0.1 Msun, although a turn-over
in the IMF at 0.4 Msun is still possible within the errors. The cluster will
presumably remain bound, evolving into a globular cluster-like object.Comment: 33 pages, including 10 figures and 3 tables. Accepted for publication
in the Astrophysical Journa
Strong founder effect in Drosophila pseudoobscura colonizing New Zealand from North America
The North American native species Drosophila pseudoobscura was first identified in New Zealand in the last few decades. Here, we have studied the genetic consequences of its spread across the Pacific Ocean. Using 10 microsatellites that are highly variable in North American populations, we found that the New Zealand population has substantially fewer alleles, a much lower average heterozygosity, and significantly different allele frequencies at these loci. We have discussed the relative sensitivity of these parameters for detecting the founding event. X-linked loci were more strongly differentiated between continents than autosomal loci, as reflected by larger changes in allele frequencies and greater reductions in numbers of alleles and average heterozygosity. The severity of the genetic diversity loss supports a scenario of a few D. pseudoobscura females being introduced to New Zealand from North America
A Theory for steady and self-sustained premixed combustion waves
Based on the compressible Navier – Stokes equations for reactive flow problems, an eigenvalue problem for the steady and self-sustained premixed combustion wave propagation is developed. The eigenvalue problem is analytically solved and a set of analytic formulae for description of the wave propagation is found out. The analytic formulae are actually the exact solution of the eigenvalue problem in the form of integration, based on which author develops an iterative and numerical algorithm for calculation of the steady and self-sustained premixed combustion wave propagation and its speed. In order to explore the mathematical model and test the computational method developed in this paper, three groups of combustion wave propagation modes are calculated. The computational results show that the non-trivial modes of the combustion wave propagation exist and their distribution is not continuous but discrete
An HST/WFPC2 Survey of Bright Young Clusters in M31 III. Structural Parameters
Surface brightness profiles for 23 M31 star clusters were measured using
images from the Wide Field Planetary Camera 2 on the Hubble Space Telescope,
and fit to two types of models to determine the clusters' structural
properties. The clusters are primarily young (~10^8 yr) and massive (~10^4.5
solar masses), with median half-light radius 7 pc and dissolution times of a
few Gyr. The properties of the M31 clusters are comparable to those of clusters
of similar age in the Magellanic Clouds. Simulated star clusters are used to
derive a conversion from statistical measures of cluster size to half-light
radius so that the extragalactic clusters can be compared to young massive
clusters in the Milky Way. All three sets of star clusters fall approximately
on the same age-size relation. The young M31 clusters are expected to dissolve
within a few Gyr and will not survive to become old, globular clusters.
However, they do appear to follow the same fundamental plane relations as old
clusters; if confirmed with velocity dispersion measurements, this would be a
strong indication that the star cluster fundamental plane reflects universal
cluster formation conditions.Comment: AJ in press; 37 pages, 12 figure
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The JAK inhibitor tofacitinib suppresses synovial JAK1-STAT signalling in rheumatoid arthritis.
ObjectiveTofacitinib is an oral Janus kinase (JAK) inhibitor for the treatment of rheumatoid arthritis (RA). The pathways affected by tofacitinib and the effects on gene expression in situ are unknown. Therefore, tofacitinib effects on synovial pathobiology were investigated.MethodsA randomised, double-blind, phase II serial synovial biopsy study (A3921073; NCT00976599) in patients with RA with an inadequate methotrexate response. Patients on background methotrexate received tofacitinib 10 mg twice daily or placebo for 28 days. Synovial biopsies were performed on Days -7 and 28 and analysed by immunoassay or quantitative PCR. Clinical response was determined by disease activity score and European League Against Rheumatism (EULAR) response on Day 28 in A3921073, and at Month 3 in a long-term extension study (A3921024; NCT00413699).ResultsTofacitinib exposure led to EULAR moderate to good responses (11/14 patients), while placebo was ineffective (1/14 patients) on Day 28. Tofacitinib treatment significantly reduced synovial mRNA expression of matrix metalloproteinase (MMP)-1 and MMP-3 (p<0.05) and chemokines CCL2, CXCL10 and CXCL13 (p<0.05). No overall changes were observed in synovial inflammation score or the presence of T cells, B cells or macrophages. Changes in synovial phosphorylation of signal transducer and activator of transcription 1 (STAT1) and STAT3 strongly correlated with 4-month clinical responses (p<0.002). Tofacitinib significantly decreased plasma CXCL10 (p<0.005) at Day 28 compared with placebo.ConclusionsTofacitinib reduces metalloproteinase and interferon-regulated gene expression in rheumatoid synovium, and clinical improvement correlates with reductions in STAT1 and STAT3 phosphorylation. JAK1-mediated interferon and interleukin-6 signalling likely play a key role in the synovial response.Trial registration numberNCT00976599
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