1,929 research outputs found
PCA Beyond The Concept of Manifolds: Principal Trees, Metro Maps, and Elastic Cubic Complexes
Multidimensional data distributions can have complex topologies and variable
local dimensions. To approximate complex data, we propose a new type of
low-dimensional ``principal object'': a principal cubic complex. This complex
is a generalization of linear and non-linear principal manifolds and includes
them as a particular case. To construct such an object, we combine a method of
topological grammars with the minimization of an elastic energy defined for its
embedment into multidimensional data space. The whole complex is presented as a
system of nodes and springs and as a product of one-dimensional continua
(represented by graphs), and the grammars describe how these continua transform
during the process of optimal complex construction. The simplest case of a
topological grammar (``add a node'', ``bisect an edge'') is equivalent to the
construction of ``principal trees'', an object useful in many practical
applications. We demonstrate how it can be applied to the analysis of bacterial
genomes and for visualization of cDNA microarray data using the ``metro map''
representation. The preprint is supplemented by animation: ``How the
topological grammar constructs branching principal components
(AnimatedBranchingPCA.gif)''.Comment: 19 pages, 8 figure
Study of the Potts Model on the Honeycomb and Triangular Lattices: Low-Temperature Series and Partition Function Zeros
We present and analyze low-temperature series and complex-temperature
partition function zeros for the -state Potts model with on the
honeycomb lattice and on the triangular lattice. A discussion is given
as to how the locations of the singularities obtained from the series analysis
correlate with the complex-temperature phase boundary. Extending our earlier
work, we include a similar discussion for the Potts model with on the
honeycomb lattice and with on the kagom\'e lattice.Comment: 33 pages, Latex, 9 encapsulated postscript figures, J. Phys. A, in
pres
On the frequentist coverage of Bayesian credible intervals for lower bounded means
For estimating a lower bounded location or mean parameter for a symmetric and
logconcave density, we investigate the frequentist performance of the
Bayesian HPD credible set associated with priors which are
truncations of flat priors onto the restricted parameter space. Various new
properties are obtained. Namely, we identify precisely where the minimum
coverage is obtained and we show that this minimum coverage is bounded between
and ; with
the lower bound improving (for ) on the
previously established ([9]; [8]) lower bound .
Several illustrative examples are given.Comment: Published in at http://dx.doi.org/10.1214/08-EJS292 the Electronic
Journal of Statistics (http://www.i-journals.org/ejs/) by the Institute of
Mathematical Statistics (http://www.imstat.org
HDL-Associated Estradiol Stimulates Endothelial NO Synthase and Vasodilation in an SR-BIâDependent Manner
Cardiovascular diseases remain the leading cause of death in the United States. Two factors associated with a decreased risk of developing cardiovascular disease are elevated HDL levels and sex â specifically, a decreased risk is found in premenopausal women. HDL and estrogen stimulate eNOS and the production of nitric oxide, which has numerous protective effects in the vascular system including vasodilation, antiadhesion, and anti-inflammatory effects. We tested the hypothesis that HDL binds to its receptor, scavenger receptor class B type I (SR-BI), and delivers estrogen to eNOS, thereby stimulating the enzyme. HDL isolated from women stimulated eNOS, whereas HDL isolated from men had minimal activity. Studies with ovariectomized and ovariectomized/estrogen replacement mouse models demonstrated that HDL-associated estradiol stimulation of eNOS is SR-BI dependent. Furthermore, female HDL, but not male HDL, promoted the relaxation of muscle strips isolated from C57BL/6 mice but not SR-BI null mice. Finally, HDL isolated from premenopausal women or postmenopausal women receiving estradiol replacement therapy stimulated eNOS, whereas HDL isolated from postmenopausal women did not stimulate eNOS. We conclude that HDL-associated estrodial is capable of the stimulating eNOS. These studies establish a new paradigm for examining the cardiovascular effects of HDL and estrogen
Consistent model of magnetism in ferropnictides
The discovery of superconductivity in LaFeAsO introduced the ferropnictides
as a major new class of superconducting compounds with critical temperatures
second only to cuprates. The presence of magnetic iron makes ferropnictides
radically different from cuprates. Antiferromagnetism of the parent compounds
strongly suggests that superconductivity and magnetism are closely related.
However, the character of magnetic interactions and spin fluctuations in
ferropnictides, in spite of vigorous efforts, has until now resisted
understanding within any conventional model of magnetism. Here we show that the
most puzzling features can be naturally reconciled within a rather simple
effective spin model with biquadratic interactions, which is consistent with
electronic structure calculations. By going beyond the Heisenberg model, this
description explains numerous experimentally observed properties, including the
peculiarities of the spin wave spectrum, thin domain walls, crossover from
first to second order phase transition under doping in some compounds, and
offers new insight in the occurrence of the nematic phase above the
antiferromagnetic phase transition.Comment: 5 pages, 3 figures, revtex
Search for Axionlike and Scalar Particles with the NA64 Experiment
We carried out a model-independent search for light scalar (s) and
pseudoscalar axionlike (a) particles that couple to two photons by using the
high-energy CERN SPS H4 electron beam. The new particles, if they exist, could
be produced through the Primakoff effect in interactions of hard bremsstrahlung
photons generated by 100 GeV electrons in the NA64 active dump with virtual
photons provided by the nuclei of the dump. The a(s) would penetrate the
downstream HCAL module, serving as shielding, and would be observed either
through their decay in the rest of the HCAL detector or
as events with large missing energy if the a(s) decays downstream of the HCAL.
This method allows for the probing the a(s) parameter space, including those
from generic axion models, inaccessible to previous experiments. No evidence of
such processes has been found from the analysis of the data corresponding to
electrons on target allowing to set new limits on the
-coupling strength for a(s) masses below 55 MeV.Comment: This publication is dedicated to the memory of our colleague Danila
Tlisov. 7 pages, 5 figures, revised version accepted for publication in Phys.
Rev. Let
HDL-Associated Estradiol Stimulates Endothelial NO Synthase and Vasodilation in an SR-BIâDependent Manner
Cardiovascular diseases remain the leading cause of death in the United States. Two factors associated with a decreased risk of developing cardiovascular disease are elevated HDL levels and sex â specifically, a decreased risk is found in premenopausal women. HDL and estrogen stimulate eNOS and the production of nitric oxide, which has numerous protective effects in the vascular system including vasodilation, antiadhesion, and anti-inflammatory effects. We tested the hypothesis that HDL binds to its receptor, scavenger receptor class B type I (SR-BI), and delivers estrogen to eNOS, thereby stimulating the enzyme. HDL isolated from women stimulated eNOS, whereas HDL isolated from men had minimal activity. Studies with ovariectomized and ovariectomized/estrogen replacement mouse models demonstrated that HDL-associated estradiol stimulation of eNOS is SR-BI dependent. Furthermore, female HDL, but not male HDL, promoted the relaxation of muscle strips isolated from C57BL/6 mice but not SR-BI null mice. Finally, HDL isolated from premenopausal women or postmenopausal women receiving estradiol replacement therapy stimulated eNOS, whereas HDL isolated from postmenopausal women did not stimulate eNOS. We conclude that HDL-associated estrodial is capable of the stimulating eNOS. These studies establish a new paradigm for examining the cardiovascular effects of HDL and estrogen
Dark sectors 2016 Workshop: community report
This report, based on the Dark Sectors workshop at SLAC in April 2016,
summarizes the scientific importance of searches for dark sector dark matter
and forces at masses beneath the weak-scale, the status of this broad
international field, the important milestones motivating future exploration,
and promising experimental opportunities to reach these milestones over the
next 5-10 years
First observation of Bs -> D_{s2}^{*+} X mu nu decays
Using data collected with the LHCb detector in proton-proton collisions at a
centre-of-mass energy of 7 TeV, the semileptonic decays Bs -> Ds+ X mu nu and
Bs -> D0 K+ X mu nu are detected. Two structures are observed in the D0 K+ mass
spectrum at masses consistent with the known D^+_{s1}(2536) and
$D^{*+}_{s2}(2573) mesons. The measured branching fractions relative to the
total Bs semileptonic rate are B(Bs -> D_{s2}^{*+} X mu nu)/B(Bs -> X mu nu)=
(3.3\pm 1.0\pm 0.4)%, and B(Bs -> D_{s1}^+ X munu)/B(Bs -> X mu nu)= (5.4\pm
1.2\pm 0.5)%, where the first uncertainty is statistical and the second is
systematic. This is the first observation of the D_{s2}^{*+} state in Bs
decays; we also measure its mass and width.Comment: 8 pages 2 figures. Published in Physics Letters
Search for the standard model Higgs boson in the H to ZZ to 2l 2nu channel in pp collisions at sqrt(s) = 7 TeV
A search for the standard model Higgs boson in the H to ZZ to 2l 2nu decay
channel, where l = e or mu, in pp collisions at a center-of-mass energy of 7
TeV is presented. The data were collected at the LHC, with the CMS detector,
and correspond to an integrated luminosity of 4.6 inverse femtobarns. No
significant excess is observed above the background expectation, and upper
limits are set on the Higgs boson production cross section. The presence of the
standard model Higgs boson with a mass in the 270-440 GeV range is excluded at
95% confidence level.Comment: Submitted to JHE
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