| 1. |
- Abazov, V. M., et al.
(författare)
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The upgraded DO detector
- 2006
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Ingår i: Nuclear Instruments and Methods in Physics Research Section A. - : Elsevier BV. - 0168-9002 .- 1872-9576. ; 565:2, s. 463-537
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Tidskriftsartikel (refereegranskat)abstract
- The DO experiment enjoyed a very successful data-collection run at the Fermilab Tevatron collider between 1992 and 1996. Since then, the detector has been upgraded to take advantage of improvements to the Tevatron and to enhance its physics capabilities. We describe the new elements of the detector, including the silicon microstrip tracker, central fiber tracker, solenoidal magnet, preshower detectors, forward muon detector, and forward proton detector. The uranium/liquid -argon calorimeters and central muon detector, remaining from Run 1, are discussed briefly. We also present the associated electronics, triggering, and data acquisition systems, along with the design and implementation of software specific to DO.
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| 2. |
- Abazov, V. M., et al.
(författare)
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Determination of the strong coupling constant from the inclusive jet cross section in pp collisions at s=1.96 TeV
- 2009
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Ingår i: PHYS REV D. - 1550-7998 .- 1550-2368. ; 80, s. 111107-
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Tidskriftsartikel (refereegranskat)abstract
- We determine the strong coupling constant alpha(s) and its energy dependence from the p(T) dependence of the inclusive jet cross section in pp collisions at s=1.96 TeV. The strong coupling constant is determined over the transverse momentum range 50 < p(T)< 145 GeV. Using perturbative QCD calculations to order O(alpha(3)(s)) combined with O(alpha(4)(s)) contributions from threshold corrections, we obtain alpha(s)(M-Z)=0.1161(-0.0048)(+0.0041). This is the most precise result obtained at a hadron-hadron collider.
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| 3. |
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| 5. |
- Ferrie, J E, et al.
(författare)
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Diagnosis-specific sickness absence and all-cause mortality in the GAZEL study.
- 2009
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Ingår i: Journal of epidemiology and community health. - : BMJ. - 1470-2738 .- 0143-005X. ; 63:1, s. 50-5
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Tidskriftsartikel (refereegranskat)abstract
- BACKGROUND: This study aims to examine diagnosis-specific sickness absence as a risk marker for all-cause mortality. METHODS: Prospective occupational cohort (the GAZEL study). Medically certified sickness absence spells >7 days for 15 diagnostic categories, 1990-1992, were examined in relation to all-cause mortality, January 1993-February 2007. The reference group for each diagnostic category was participants with no spell >7 days for that diagnosis. The participants were French public utility workers (5271 women and 13 964 men) aged 37-51 years in 1990, forming the GAZEL study. Over the follow-up period, there were 144 deaths in women and 758 in men. RESULTS: 7875 employees (41.0%) had at least one spell of sickness absence >7 days over the 3-year period. The commonest diagnoses were mental disorders, musculoskeletal diseases, respiratory diseases and external causes in both sexes; genitourinary diseases in women, and digestive and circulatory diseases in men. Of these common diagnoses, mental disorders in women, hazard ratio (95% confidence intervals) 1.24 (1.1 to 1.4), and mental disorders 1.35 (1.3 to 1.5), digestive diseases 1.29 (1.1 to 1.6) and circulatory diseases 1.35 (1.2 to 1.6) in men were associated with mortality after adjustment for age, employment grade and sickness absence in all other diagnostic categories. CONCLUSIONS: Employees with medically certified absence spells of 1 week or more over a 3-year period had a 60% excess risk of early death. In women and men this excess risk was associated with some of the commonest diagnoses of sickness absence, in particular mental disorders. Sickness absence for mental disorders may be a useful early indicator of groups at increased risk of fatal disease.
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| 6. |
- Graves, Genevieve J. M., et al.
(författare)
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Limits from the Hubble Space Telescope on a Point Source in SN 1987A
- 2005
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 629, s. 944-959
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Tidskriftsartikel (refereegranskat)abstract
- We observed supernova 1987A (SN 1987A) with the Space Telescope Imaging Spectrograph (STIS) on the Hubble Space Telescope (HST) in 1999 September and again with the Advanced Camera for Surveys (ACS) on the HST in 2003 November. Our spectral observations cover ultraviolet (UV) and optical wavelengths from 1140 to 10266 Å, and our imaging observations cover UV and optical wavelengths from 2900 to 9650 Å. No point source is observed in the remnant. We obtain a limiting flux of Fopt<=1.6×10-14 ergs s-1 cm-2 in the wavelength range 2900-9650 Å for any continuum emitter at the center of the supernova remnant (SNR). This corresponds to an intrinsic luminosity of Lopt<=5×1033 ergs s-1. It is likely that the SNR contains opaque dust that absorbs UV and optical emission, resulting in an attenuation of ~35% due to dust absorption in the SNR. Correcting for this level of dust absorption would increase our upper limit on the luminosity of a continuum source by a factor of 1.54. Taking into account dust absorption in the remnant, we find a limit of Lopt<=8×1033 ergs s-1. We compare this upper bound with empirical evidence from point sources in other supernova remnants and with theoretical models for possible compact sources. We show that any survivor of a possible binary system must be no more luminous than an F6 main-sequence star. Bright young pulsars such as Kes 75 or the Crab pulsar are excluded by optical and X-ray limits on SN 1987A. Other nonplerionic X-ray point sources have luminosities similar to the limits on a point source in SN 1987A; RCW 103 and Cas A are slightly brighter than the limits on SN 1987A, while Pup A is slightly fainter. Of the young pulsars known to be associated with SNRs, those with ages <=5000 yr are all too bright in X-rays to be compatible with the limits on SN 1987A. Examining theoretical models for accretion onto a compact object, we find that spherical accretion onto a neutron star is firmly ruled out and that spherical accretion onto a black hole is possible only if there is a larger amount of dust absorption in the remnant than predicted. In the case of thin-disk accretion, our flux limit requires a small disk, no larger than 1010 cm, with an accretion rate no more than 0.3 times the Eddington accretion rate. Possible ways to hide a surviving compact object include the removal of all surrounding material at early times by a photon-driven wind, a small accretion disk, or very high levels of dust absorption in the remnant. It will not be easy to improve substantially on our optical-UV limit for a point source in SN 1987A, although we can hope that a better understanding of the thermal infrared emission will provide a more complete picture of the possible energy sources at the center of SN 1987A.
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| 7. |
- Kivimäki, M, et al.
(författare)
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Sickness absence as a prognostic marker for common chronic conditions : analysis of mortality in the GAZEL study.
- 2008
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Ingår i: Occup Environ Med. - : BMJ. - 1470-7926 .- 1351-0711. ; 65:12, s. 820-6
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Tidskriftsartikel (refereegranskat)abstract
- Sickness absence as a prognostic marker for common chronic conditions: analysis of mortality in the GAZEL study.Kivimäki M, Head J, Ferrie JE, Singh-Manoux A, Westerlund H, Vahtera J, Leclerc A, Melchior M, Chevalier A, Alexanderson K, Zins M, Goldberg M.Department of Epidemiology and Public Health, University College London, London, UK. m.kivimaki@ucl.ac.ukOBJECTIVES: To determine whether sickness absence is a prognostic marker in terms of mortality among people with common chronic conditions. METHODS: Prospective occupational cohort study of 13,077 men and 4871 women aged 37-51 from the National Gas and Electricity Company, France. Records of physician-certified sickness absences over a 3-year period were obtained from employers' registers. Chronic conditions were assessed in annual surveys over the same period. The main outcome measure was all-cause mortality (803 deaths, mean follow-up after assessment of sickness absence: 13.9 years). RESULTS: In Cox proportional hazard models adjusted for age, sex, socioeconomic position and co-morbidity, >28 annual sickness-absence days versus no absence days was associated with an excess mortality risk among those with cancer (hazard ratio 5.4, 95% CI 2.2 to 13.1), depression (1.7, 1.1 to 2.8), chronic bronchitis or asthma (2.7, 1.6 to 4.6) and hypertension (1.6, 1.0 to 2.6). The corresponding hazard ratios for more than five long (>14 days) sickness-absence episodes per 10 person-years versus no such episodes were 5.4 (2.2 to 13.1), 1.8 (1.3 to 2.7), 2.0 (1.3 to 3.2) and 1.8 (1.2 to 2.7), respectively. Areas under receiver operating characteristics curves for these absence measures varied between 0.56 and 0.73, indicating the potential of these measures to distinguish groups at high risk of mortality. The findings were consistent across sex, age and socioeconomic groups and in those with and without co-morbid conditions. CONCLUSION: Data on sickness absence may provide useful prognostic information for common chronic conditions at the population level.
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| 8. |
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| 9. |
- Berger, E., et al.
(författare)
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An Intermediate Luminosity Transient in NGC 300 : The Eruption of a Dust-Enshrouded Massive Star
- 2009
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Ingår i: Astrophysical Journal. - 0004-637X .- 1538-4357. ; 699, s. 1850-1865
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Tidskriftsartikel (refereegranskat)abstract
- We present multi-epoch high-resolution optical spectroscopy, UV/radio/X-ray imaging, and archival Hubble and Spitzer observations of an intermediate luminosity optical transient recently discovered in the nearby galaxy NGC 300. We find that the transient (NGC 300 OT2008-1) has a peak absolute magnitude of M bol ≈ -11.8 mag, intermediate between novae and supernovae, and similar to the recent events M85 OT2006-1 and SN 2008S. Our high-resolution spectra, the first for this event, are dominated by intermediate velocity (~200-1000 km s-1) hydrogen Balmer lines and Ca II emission and absorption lines that point to a complex circumstellar environment, reminiscent of the yellow hypergiant IRC+10420. In particular, we detect asymmetric Ca II H&K absorption with a broad red wing extending to ~103 km s-1, indicative of gas inflow at high velocity (possibly the wind of a massive binary companion). The low luminosity, intermediate velocities, and overall similarity to a known eruptive star indicate that the event did not result in a complete disruption of the progenitor. We identify the progenitor in archival Spitzer observations, with deep upper limits from Hubble data. The spectral energy distribution points to a dust-enshrouded star with a luminosity of about 6 × 104 L sun, indicative of a ~10-20 M sun progenitor (or binary system). This conclusion is in good agreement with our interpretation of the outburst and circumstellar properties. The lack of significant extinction in the transient spectrum indicates that the dust surrounding the progenitor was cleared by the outburst. We thus predict that the progenitor should be eventually visible with Hubble if the transient event marks an evolutionary transition to a dust-free state, or with Spitzer if the event marks a cyclical process of dust formation.
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| 10. |
- Fransson, Claes, et al.
(författare)
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Hubble Space Telescope and Ground-based Observations of SN 1993J and SN 1998S : CNO Processing in the Progenitors
- 2005
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Ingår i: Astrophysical Journal. - : American Astronomical Society. - 0004-637X .- 1538-4357. ; 622, s. 991-1007
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Tidskriftsartikel (refereegranskat)abstract
- Ground-based and Hubble Space Telescope observations are presented for SN 1993J and SN 1998S. SN 1998S shows strong, relatively narrow circumstellar emission lines of N III-V and C III-IV, as well as broad lines from the ejecta. Both the broad ultraviolet and optical lines in SN 1998S indicate an expansion velocity of ~7000 km s-1. The broad emission components of Lyα and Mg II are strongly asymmetrical after day 72 past the explosion and differ in shape from Hα. Different models based on dust extinction from dust in the ejecta or shock region, in combination with Hα from a circumstellar torus, are discussed. It is concluded, however, that the double-peaked line profiles are more likely to arise as a result of optical depth effects in the narrow, cool, dense shell behind the reverse shock than in a torus-like region. The ultraviolet lines of SN 1993J are broad, with a boxlike shape, coming from the ejecta and a cool, dense shell. The shapes of the lines are well fitted by a shell with inner velocity ~7000 km s-1 and outer velocity ~10,000 km s-1. For both SN 1993J and SN 1998S a strong nitrogen enrichment is found, with N/C~12.4 in SN 1993J and N/C~6.0 in SN 1998S. From a compilation of all supernovae with determined CNO ratios, we discuss the implications of these observations for the structure of the progenitors of Type II supernovae. Based in part on observations obtained with the Hubble Space Telescope, which is operated by AURA, Inc., under NASA contract NAS 5-26555.
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