730 research outputs found
From the Feynman-Schwinger representation to the non-perturbative relativistic bound state interaction
We write the 4-point Green function in QCD in the Feynman-Schwinger
representation and show that all the dynamical information are contained in the
Wilson loop average. We work out the QED case in order to obtain the usual
Bethe-Salpeter kernel. Finally we discuss the QCD case in the non-perturbative
regime giving some insight in the nature of the interaction kernel.Comment: 25 pages, RevTex, 3 figures included, typos corrected, to appear in
Phys. Rev. D 5
"Dark" GRB 080325 in a Dusty Massive Galaxy at z ~ 2
We present optical and near infrared observations of GRB 080325 classified as
a "Dark GRB". Near-infrared observations with Subaru/MOIRCS provided a clear
detection of afterglow in Ks band, although no optical counterpart was
reported. The flux ratio of rest-wavelength optical to X-ray bands of the
afterglow indicates that the dust extinction along the line of sight to the
afterglow is Av = 2.7 - 10 mag. This large extinction is probably the major
reason for optical faintness of GRB 080325. The J - Ks color of the host
galaxy, (J - Ks = 1.3 in AB magnitude), is significantly redder than those for
typical GRB hosts previously identified. In addition to J and Ks bands, optical
images in B, Rc, i', and z' bands with Subaru/Suprime-Cam were obtained at
about one year after the burst, and a photometric redshift of the host is
estimated to be z_{photo} = 1.9. The host luminosity is comparable to L^{*} at
z \sim 2 in contrast to the sub-L^{*} property of typical GRB hosts at lower
redshifts. The best-fit stellar population synthesis model for the host shows
that a large dust extinction (Av = 0.8 mag) attributes to the red nature of the
host and that the host galaxy is massive (M_{*} = 7.0 \times 10^{10} Msun)
which is one of the most massive GRB hosts previously identified. By assuming
that the mass-metallicity relation for star-forming galaxies at z \sim 2 is
applicable for the GRB host, this large stellar mass suggests the high
metallicity environment around GRB 080325, consistent with inferred large
extinction.Comment: 22 pages, 10 figures, accepted for publication in The Astrophysical
Journa
A participatory physical and psychosocial intervention for balancing the demands and resources among industrial workers (PIPPI): study protocol of a cluster-randomized controlled trial
Background: Need for recovery and work ability are strongly associated with high employee turnover, well-being and sickness absence. However, scientific knowledge on effective interventions to improve work ability and decrease need for recovery is scarce. Thus, the present study aims to describe the background, design and protocol of a cluster randomized controlled trial evaluating the effectiveness of an intervention to reduce need for recovery and improve work ability among industrial workers. Methods/Design: A two-year cluster randomized controlled design will be utilized, in which controls will also receive the intervention in year two. More than 400 workers from three companies in Denmark will be aimed to be cluster randomized into intervention and control groups with at least 200 workers (at least 9 work teams) in each group. An organizational resources audit and subsequent action planning workshop will be carried out to map the existing resources and act upon initiatives not functioning as intended. Workshops will be conducted to train leaders and health and safety representatives in supporting and facilitating the intervention activities. Group and individual level participatory visual mapping sessions will be carried out allowing team members to discuss current physical and psychosocial work demands and resources, and develop action plans to minimize strain and if possible, optimize the resources. At all levels, the intervention will be integrated into the existing organization of work schedules. An extensive process and effect evaluation on need for recovery and work ability will be carried out via questionnaires, observations, interviews and organizational data assessed at several time points throughout the intervention period. Discussion: This study primarily aims to develop, implement and evaluate an intervention based on the abovementioned features which may improve the work environment, available resources and health of industrial workers, and hence their need for recovery and work ability
Spectrum and Variability of Mrk501 as observed by the CAT Imaging Telescope
The CAT Imaging Telescope has observed the BL Lac object Markarian 501
between March and August 1997. We report here on the variability over this time
including several large flares. We present also preliminary spectra for all
these data, for the low emission state, and for the largest flare.Comment: 4 pages, 4 figures, Late
Observation of the Crab Nebula Gamma-Ray Emission Above 220 Gev by the Cat Cherenkov Imaging Telescope
The CAT imaging telescope, recently built on the site of the former solar
plant Themis (French Pyrenees), observed gamma-rays from the Crab nebula from
October 1996 to March 1997. This steady source, often considered as the
standard candle of very-high-energy gamma-ray astronomy, is used as a test-beam
to probe the performances of the new telescope, particularly its energy
threshold (220 GeV at 20 degrees zenith angle) and the stability of its
response. Due to the fine-grain camera, an accurate analysis of the
longitudinal profiles of shower images is performed, yielding the source
position in two dimensions for each individual shower.Comment: 5 pages, 3 figures, Tex, contribution to 25th ICRC Durba
Detection of Vhe Gamma-Rays from MRK 501 with the Cat Imaging Telescope
The CAT imaging telescope on the site on the former solar plant Themis has
been observing gamma-rays from Mrk501 above 220 GeV in March and April 1997.
This source is shown to be highly variable and the light curve is presented.
The detected gamma-ray rate for the most intense flare is in excess of 10 per
minute.Comment: 5 pages, 4 figures, Tex, contribution to 25th ICRC Durba
BioMaPS: A Roadmap for Success
The manuscript outlines the impact that our National Science Foundation Interdisciplinary Training for Undergraduates in Biological and Mathematical Sciences program, BioMaPS, has had on the students and faculty at Murray State University. This interdisciplinary program teams mathematics and biology undergraduate students with mathematics and biology faculty and has produced research insights and curriculum developments at the intersection of these two disciplines. The goals, structure, achievements, and curriculum initiatives are described in relation to the effects they have had to enhance the study of biomathematics
The CAT Imaging Telescope for Very-High-Energy Gamma-Ray Astronomy
The CAT (Cherenkov Array at Themis) imaging telescope, equipped with a
very-high-definition camera (546 fast phototubes with 0.12 degrees spacing
surrounded by 54 larger tubes in two guard rings) started operation in Autumn
1996 on the site of the former solar plant Themis (France). Using the
atmospheric Cherenkov technique, it detects and identifies very high energy
gamma-rays in the range 250 GeV to a few tens of TeV. The instrument, which has
detected three sources (Crab nebula, Mrk 421 and Mrk 501), is described in
detail.Comment: 24 pages, 15 figures. submitted to Elsevier Preprin
Association of the coronary artery disease risk gene GUCY1A3 with ischaemic events after coronary intervention
Aim:
A common genetic variant at the GUCY1A3 coronary artery disease locus has been shown to influence platelet aggregation. The risk of ischaemic events including stent thrombosis varies with the efficacy of aspirin to inhibit platelet reactivity. This study sought to investigate whether homozygous GUCY1A3 (rs7692387) risk allele carriers display higher on-aspirin platelet reactivity and risk of ischaemic events early after coronary intervention.
Methods and results:
The association of GUCY1A3 genotype and on-aspirin platelet reactivity was analysed in the genetics substudy of the ISAR-ASPI registry (nâ=â1678) using impedance aggregometry. The clinical outcome cardiovascular death or stent thrombosis within 30âdays after stenting was investigated in a meta-analysis of substudies of the ISAR-ASPI registry, the PLATO trial (nâ=â3236), and the Utrecht Coronary Biobank (nâ=â1003) comprising a total 5917 patients. Homozygous GUCY1A3 risk allele carriers (GG) displayed increased on-aspirin platelet reactivity compared with non-risk allele (AA/AG) carriers [150 (interquartile range 91â209) vs. 134 (85â194) AUâ
min, Pâ203âAUâ
min; 29.5 vs. 24.2%, Pâ=â0.02). Homozygous risk allele carriers were also at higher risk for cardiovascular death or stent thrombosis (hazard ratio 1.70, 95% confidence interval 1.08â2.68; Pâ=â0.02). Bleeding risk was not altered.
Conclusion:
We conclude that homozygous GUCY1A3 risk allele carriers are at increased risk of cardiovascular death or stent thrombosis within 30âdays after coronary stenting, likely due to higher on-aspirin platelet reactivity. Whether GUCY1A3 genotype helps to tailor antiplatelet treatment remains to be investigated
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