| 1. |
- Andersson, V., et al.
(författare)
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Large-Area Balloon-Borne Polarized Gamma Ray Observer (PoGO)
- 2005
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Ingår i: Proceedings of the 22nd Texas Symposium on Relativistic Astrophysics at Stanford. ; , s. 736-743
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Konferensbidrag (refereegranskat)abstract
- We are developing a new balloon-borne instrument (PoGO), to measure polarization of soft gamma rays (30-200 keV) using asymmetry in azimuth angle distribution of Compton scattering. PoGO is designed to detect 10 % polarization in 100mCrab sources in a 6-8 hour observation and bring a new dimension to studies on gamma ray emission/transportation mechanism in pulsars, AGNs, black hole binaries, and neutron star surface. The concept is an adaptation to polarization measurements of well-type phoswich counter consisting of a fast plastic scintillator (the detection part), a slow plastic scintillator (the active collimator) and a BGO scintillator (the bottom anti-counter). PoGO consists of close-packed array of 217 hexagonal well-type phoswich counters and has a narrow field-of-view (~ 5 deg2) to reduce possible source confusion. A prototype instrument has been tested in the polarized soft gamma-ray beams at Advanced Photon Source (ANL) and at Photon Factory (KEK). On the results, the polarization dependence of EGS4 has been validated and that of Geant4 has been corrected.
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| 2. |
- Meszaros, A., et al.
(författare)
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On the origin of the dark gamma-ray bursts
- 2005
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Ingår i: Nuovo cimento della societa italiana de fisica. C, Geophysics and space physics. - 1124-1896 .- 1826-9885. ; 28:3, s. 311-314
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Tidskriftsartikel (refereegranskat)abstract
- The origin of dark bursts-i.e. that have no observed afterglows in X-ray, optical/NIR and radio ranges-is unclear yet. Different possibilities-instrumental biases, very high redshifts, extinction in the host galaxies-are discussed and shown to be important. On the other hand, the dark bursts should not form a new subgroup of long gamma-ray bursts themselves.
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| 3. |
- Royo, Felix, et al.
(författare)
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Effect of repeated confined single housing of young pigs on faecal excreation of cortisol and IgA
- 2005
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Ingår i: Scandinavian Journal of Laboratory Animal Science. - 0901-3393. ; 32:1, s. 33-37
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Tidskriftsartikel (refereegranskat)abstract
- During 48 days four young male, castrated Yorkshire x Landrace pigs (growers) were singly housed alternatively in standard pig pens (4 x 6 days) and metabolic cages (4 x 6 days). The faecal excretion of cortisol metabolites and immunoglobulin A (IgA) was quantified by enzyme-linked immunoabsorbent assays (ELISAs). The first stay in the metabolic cage was associated with an increase in faecal cortisol levels, which may be interpreted as a symptom of acute stress. But when the pigs’ visits to the metabolic cages were repeated, the faecal cortisol generally reverted to fairly low levels. Concomitantly, faecal IgA excretion decreased steadily during the study period suggesting sustained stress. The body weight gain was lower during periods when the pigs were housed in metabolic cages than when they were in pens. These results suggest that metabolic cages caused a continued stress condition in pigs. One pig showed consistent high IgA excretion and a smaller decline in body weight gain during periods in the metabolic cage than the other pigs. This pig thus appeared to be less stressed than the other pigs, but maintained high cortisol levels throughout the study period when housed in the ordinary pen. This indicates that cortisol may have a protective effect against the stress caused by housing in metabolic cages.
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