595 research outputs found
Signatures of Topological Defects
We argue that due to various restrictions cosmic strings and monopole-string
networks are not likely to produce the observed flux of ultra-high energy
cosmic rays (UHECR). Among the topological defects studied so far, the most
promising UHECR sources are necklaces and monopolonia. Other viable sources
which are similar to topological defects are relic superheavy particles. All
these sources have an excess of pions (and thus photons) over nucleons at
production. We demonstrate that in the case of necklaces the diffuse proton
flux can be larger than photon flux, due to absorption of the latter on
radiobackground, while monopolonia and relic particles are concentrated in the
Galactic halo, and the photon flux dominates. Another signature of the latter
sources is anisotropy imposed by asymmetric position of the sun in the Galactic
halo. In all cases considered so far, including necklaces, photons must be
present in ultra-high energy radiation observed from topological defects, and
experimental discrimination between photon-induced and proton-induced extensive
air showers can give a clue to the origin of ultra-high energy cosmic rays.Comment: version accepted for publication in Phys. Rev. D. No changes in the
conclusions and in figure
Genetic association study of childhood aggression across raters, instruments, and age
GenĂČmica; Comportament humĂ GenĂłmica; Comportamiento humanoGenomics; Human behaviourChildhood aggressive behavior (AGG) has a substantial heritability of around 50%. Here we present a genome-wide association meta-analysis (GWAMA) of childhood AGG, in which all phenotype measures across childhood ages from multiple assessors were included. We analyzed phenotype assessments for a total of 328 935 observations from 87 485 children aged between 1.5 and 18 years, while accounting for sample overlap. We also meta-analyzed within subsets of the data, i.e., within rater, instrument and age. SNP-heritability for the overall meta-analysis (AGGoverall) was 3.31% (SEâ=â0.0038). We found no genome-wide significant SNPs for AGGoverall. The gene-based analysis returned three significant genes: ST3GAL3 (Pâ=â1.6Eâ06), PCDH7 (Pâ=â2.0Eâ06), and IPO13 (Pâ=â2.5Eâ06). All three genes have previously been associated with educational traits. Polygenic scores based on our GWAMA significantly predicted aggression in a holdout sample of children (variance explained = 0.44%) and in retrospectively assessed childhood aggression (variance explained = 0.20%). Genetic correlations (rg) among rater-specific assessment of AGG ranged from rgâ=â0.46 between self- and teacher-assessment to rgâ=â0.81 between mother- and teacher-assessment. We obtained moderate-to-strong rgs with selected phenotypes from multiple domains, but hardly with any of the classical biomarkers thought to be associated with AGG. Significant genetic correlations were observed with most psychiatric and psychological traits (range |rg|: 0.19â1.00), except for obsessive-compulsive disorder. Aggression had a negative genetic correlation (rgâ=â~â0.5) with cognitive traits and age at first birth. Aggression was strongly genetically correlated with smoking phenotypes (range |rg|: 0.46â0.60). The genetic correlations between aggression and psychiatric disorders were weaker for teacher-reported AGG than for mother- and self-reported AGG. The current GWAMA of childhood aggression provides a powerful tool to interrogate the rater-specific genetic etiology of AGG.We very warmly thank all participants, their parents, and teachers for making this study possible. The project was supported by the âAggression in Children: Unraveling gene-environment interplay to inform Treatment and InterventiON strategiesâ project (ACTION). ACTION received funding from the European Union Seventh Framework Program (FP7/2007-2013) under grant agreement no 602768. Cohort-specific acknowledgements and funding information may be found in the Supplementary text
The Extremely High Energy Cosmic Rays
Experimental results from Haverah Park, Yakutsk, AGASA and Fly's Eye are
reviewed. All these experiments work in the energy range above 0.1 EeV. The
'dip' structure around 3 EeV in the energy spectrum is well established by all
the experiments, though the exact position differs slightly. Fly's Eye and
Yakutsk results on the chemical composition indicate that the cosmic rays are
getting lighter over the energy range from 0.1 EeV to 10 EeV, but the exact
fraction is hadronic interaction model dependent, as indicated by the AGASA
analysis. The arrival directions of cosmic rays are largely isotropic, but
interesting features may be starting to emerge. Most of the experimental
results can best be explained with the scenario that an extragalactic component
gradually takes over a galactic population as energy increases and cosmic rays
at the highest energies are dominated by particles coming from extragalactic
space. However, identification of the extragalactic sources has not yet been
successful because of limited statistics and the resolution of the data.Comment: The review paper including 21 figures. 39 pages: To be published in
Journal of Physics
Measurement of the charm structure function F_{2,c)^{Îł} of the photon at LEP
The production of charm quarks is studied in deep-inelastic electronâphoton scattering using data recorded by the OPAL detector at LEP at nominal eâșeâ» centre-of-mass energies from 183 to 209 GeV. The charm quarks have been identified by full reconstruction of charged D* mesons using their decays into Dâ°Ï with the Dâ° observed in two decay modes with charged particle final states, KÏ and KÏÏÏ. The cross-section Ï^{D*} for production of charged D* in the reaction eâșeâ»âeâșeâ»D*Χ is measured in a restricted kinematical region using two bins in Bjorken x, 0.00140.1 the perturbative QCD calculation at next-to-leading order agrees perfectly with the measured cross-section. For x<0.1 the measured cross-section is 43.8±14.3±6.3±2.8 pb with a next-to-leading order prediction of 17.0âșÂČ·âč_â.â pb
Nasal continuous positive airway pressure improves myocardial perfusion reserve and endothelial-dependent vasodilation in patients with obstructive sleep apnea
<p>Abstract</p> <p>Background</p> <p>Obstructive sleep apnea (OSA) has been associated with cardiovascular disease (CVD), but whether OSA is an independent risk factor for CVD is controversial. The purpose of this study is to determine if patients with OSA have subclinical cardiovascular disease that is detectable by multi-modality cardiovascular imaging and whether these abnormalities improve after nasal continuous positive airway pressure (nCPAP).</p> <p>Results</p> <p>Of the 35 consecutive subjects with newly diagnosed moderate to severe OSA recruited from the Stanford Sleep Disorders Clinic, 20 patients were randomized to active vs. sham nCPAP. Active nCPAP was titrated to pressures that would prevent sleep disordered breathing based on inpatient polysomnography. OSA patients had baseline vascular function abnormalities including decreased myocardial perfusion reserve (MPR), brachial flow mediated dilation (FMD) and nitroglycerin-induced coronary vasodilation. Patients randomized to active nCPAP had improvement of MPR (1.5 ± 0.5 vs. 3.0 ± 1.3, p = 0.02) and brachial FMD (2.5% ± 5.7% vs. 9.0% ± 6.5%, p = 0.03) after treatment, but those randomized to sham nCPAP showed no significant improvement. There were no significant changes seen in chamber sizes, systolic and diastolic function, valvular function and coronary vasodilation to nitroglycerin.</p> <p>Conclusions</p> <p>Patients with moderate to severe OSA had decreased MPR and brachial FMD that improved after 3 months of nCPAP. These findings suggest that relief of apnea in OSA may improve microvascular disease and endothelial dysfunction, which may prevent the development of overt cardiovascular disease. Further study in a larger patient population may be warranted.</p
Watching People Making Decisions: A Gogglebox on Online Consumer Interaction
This paper presents a research study, using eye tracking technology, to measure participant cognitive load when encountering micro-decision. It elaborates and improves on a pilot study that was used to test the experiment design. Prior research that led to a taxonomy of decision constructs faced in online transactional processes is discussed. The main findings relate to participantsâ subjective cognitive load and task error rates
Observation of the Charmed Baryon at CLEO
The CLEO experiment at the CESR collider has used 13.7 fb of data to
search for the production of the (css-ground state) in
collisions at {\rm GeV}. The modes used to
study the are ,
, , , and
. We observe a signal of 40.49.0(stat) events
at a mass of 2694.62.6(stat)1.9(syst) {\rm MeV/}, for all modes
combined.Comment: 10 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
Hadronic Mass Moments in Inclusive Semileptonic B Meson Decays
We have measured the first and second moments of the hadronic mass-squared
distribution in B -> X_c l nu, for P(lepton) > 1.5 GeV/c. We find <M_X^2 -
M_D[Bar]^2> = 0.251 +- 0.066 GeV^2, )^2 > = 0.576 +- 0.170
GeV^4, where M_D[Bar] is the spin-averaged D meson mass.
From that first moment and the first moment of the photon energy spectrum in
b -> s gamma, we find the HQET parameter lambda_1 (MS[Bar], to order 1/M^3 and
beta_0 alpha_s^2) to be -0.24 +- 0.11 GeV^2. Using these first moments and the
B semileptonic width, and assuming parton-hadron duality, we obtain |V_cb| =
0.0404 +- 0.0013.Comment: 11 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLNS, submitted to PR
Measurement of the Relative Branching Fraction of to Charged and Neutral B-Meson Pairs
We analyze 9.7 x 10^6 B\bar{B}$ pairs recorded with the CLEO detector to
determine the production ratio of charged to neutral B-meson pairs produced at
the Y(4S) resonance. We measure the rates for B^0 -> J/psi K^{(*)0} and B^+ ->
J/psi K^{(*)+} decays and use the world-average B-meson lifetime ratio to
extract the relative widths f+-/f00 = Gamma(Y(4S) -> B+B-)/Gamma(Y(4S) ->
B0\bar{B0}) = = 1.04 +/- 0.07(stat) +/- 0.04(syst). With the assumption that
f+- + f00 = 1, we obtain f00 = 0.49 +/- 0.02(stat) +/- 0.01(syst) and f+- =
0.51 +/- 0.02(stat) +/- 0.01(syst). This production ratio and its uncertainty
apply to all exclusive B-meson branching fractions measured at the Y(4S)
resonance.Comment: 11 pages postscript, also available through
http://w4.lns.cornell.edu/public/CLN
- âŠ