47 research outputs found
The effects of handling and group size on welfare of pigs in lairage and their influence on stomach weight, carcass microbial contamination and meat quality
At unloading and on the way to stunning, 800 barrows were exposed to either gentle handling (GH: slowly with a plastic board or whip) or rough handling (RH: quickly with an electric prod). Pigs were kept in large or small groups (30 or 10 pigs) during lairage. Compared with GH, RH increased climbing (P < 0.05), slipping (P < 0.01) and turning around (P < 0.001) behaviours during unloading, and climbing (P < 0.05) on the way to stunning. RH also reduced drinking behaviour during lairage (P < 0.01). Pigs kept in large groups were observed more often standing (P < 0.05) and fighting (P < 0.001) than pigs kept in small groups, but, in contrast, had a slightly lower level of urinary cortisol at slaughter. Stomach weight and microbial contamination at slaughter were not affected by treatments. RH tended to increase skin bruise score on the carcass (P < 0.06) and produced more exudative meat (P < 0.05). In conclusion, the response of pigs to the two specific stressors applied prior to slaughter in this study did not seem to contribute to stomach weight variation at slaughter, but it did influence pork quality. Key words: Pigs, pre-slaughter handling, group size, stress, stomach weight, microbial contamination, behaviour, meat qualit
The clustering of Luminous Red Galaxies around MgII absorbers
We study the cross-correlation between 212 MgII quasar absorption systems and
\~20,000 Luminous Red Galaxies (LRGs) selected from the Sloan Digital Sky
Survey Data Release 1 in the redshift range 0.4<z<0.8. The MgII systems were
selected to have 2796 & 2803 rest-frame equivalent widths >=1.0 Angstrom and
identifications confirmed by the FeII 2600 or MgI 2852 lines. Over comoving
scales 0.05--13 h^-1 Mpc, the MgII--LRG cross-correlation has an amplitude
0.69+/-0.09 times that of the LRG--LRG auto-correlation. Since LRGs have
halo-masses greater than 3.5 x 10^12 solar masses for M_R<-21, this relative
amplitude implies that the absorber host-galaxies have halo-masses greater than
2--8 x 10^11 Msun. For 10^13 Msun LRGs, the absorber host-galaxies have
halo-masses 0.5--2.5 x 10^12 Msun. Our results appear consistent with those of
Steidel et al. (1994) who found that MgII absorbers with W_r>=0.3 Angstrom are
associated with ~0.7 L^*_B galaxies.Comment: 7 pages, 3 figs; Accepted for publication in MNRAS Letters; Extended
version with Appendix; Text version of MgII absorber catalogue (Table 1) can
be found at http://www.ast.cam.ac.uk/~mim/pub.html. Minor changes to match
the published tex
Four quasars above redshift 6 discovered by the Canada-France High-z Quasar Survey
The Canada-France High-z Quasar Survey (CFHQS) is an optical survey designed
to locate quasars during the epoch of reionization. In this paper we present
the discovery of the first four CFHQS quasars at redshift greater than 6,
including the most distant known quasar, CFHQS J2329-0301 at z=6.43. We
describe the observational method used to identify the quasars and present
optical, infrared, and millimeter photometry and optical and near-infrared
spectroscopy. We investigate the dust properties of these quasars finding an
unusual dust extinction curve for one quasar and a high far-infrared luminosity
due to dust emission for another. The mean millimeter continuum flux for CFHQS
quasars is substantially lower than that for SDSS quasars at the same redshift,
likely due to a correlation with quasar UV luminosity. For two quasars with
sufficiently high signal-to-noise optical spectra, we use the spectra to
investigate the ionization state of hydrogen at z>5. For CFHQS J1509-1749 at
z=6.12, we find significant evolution (beyond a simple extrapolation of lower
redshift data) in the Gunn-Peterson optical depth at z>5.4. The line-of-sight
to this quasar has one of the highest known optical depths at z~5.8. An
analysis of the sizes of the highly-ionized near-zones in the spectra of two
quasars at z=6.12 and z=6.43 suggest the IGM surrounding these quasars was
substantially ionized before these quasars turned on. Together, these
observations point towards an extended reionization process, but we caution
that cosmic variance is still a major limitation in z>6 quasar observations.Comment: 15 pages, 9 figures, AJ, in press, minor changes to previous versio
New perspectives on strong z=0.5 MgII absorbers: are halo-mass and equivalent width anti-correlated?
We measure the mean halo-mass of z=0.5 MgII absorbers using the
cross-correlation (over co-moving scales 0.05-13h^{-1}Mpc) between 1806 MgII
quasar absorption systems and ~250,000 Luminous Red Galaxies (LRGs), both
selected from the SDSS DR3. The MgII systems have rest-frame equivalent widths
W_r(2796)>=0.3A. From the ratio of the MgII-LRG cross-correlation to the
LRG-LRG auto-correlation, we find that the bias ratio between MgII absorbers
and LRGs is 0.65+/-0.08, which implies that the absorber host-galaxies have a
mean halo-mass 20-40 times smaller than that of the LRGs; the MgII absorbers
have halos of mean mass =11.94+/-0.31(stat)+/-0.25(sys). We
demonstrate that this statistical technique, which does not require any
spectroscopic follow-up, does not suffer from contaminants such as stars or
foreground and background galaxies. Finally, we find that the absorber
halo-mass is anti-correlated with the equivalent width. If MgII absorbers were
virialized in galaxy halos a positive M_h-W_r correlation would have been
observed since W_r(2796) is a direct measure of the velocity spread of the MgII
sub-components. Thus, our results demonstrate that the individual clouds of a
MgII system are not virialized in the gaseous halos of the host-galaxies. We
review past results in the literature on the statistics of MgII absorbers and
find that they too require an M_h-W_r anti-correlation. When combined with
measurements of the equivalent width distribution, the M_h-W_r anti-correlation
naturally explains why absorbers with W_r(2796)>=2A are not seen at large
impact parameters. We interpret the M_h-W_r anti-correlation within the
starburst scenario where strong MgII absorbers are produced by
supernovae-driven winds.Comment: 18 pages, 12 EPS figures, Accepted by MNRAS. Full table of MgII
absorbers available at http://www.ast.cam.ac.uk/~mim/pub.html, minor changes
to match the published tex
The Canada-France High-z Quasar Survey: nine new quasars and the luminosity function at redshift 6
We present discovery imaging and spectroscopy for nine new z ~ 6 quasars
found in the Canada-France High-z Quasar Survey (CFHQS) bringing the total
number of CFHQS quasars to 19. By combining the CFHQS with the more luminous
SDSS sample we are able to derive the quasar luminosity function from a sample
of 40 quasars at redshifts 5.74 < z < 6.42. Our binned luminosity function
shows a slightly lower normalisation and flatter slope than found in previous
work. The binned data also suggest a break in the luminosity function at M_1450
approx -25. A double power law maximum likelihood fit to the data is consistent
with the binned results. The luminosity function is strongly constrained (1
sigma uncertainty < 0.1 dex) over the range -27.5 < M_1450 < -24.7. The
best-fit parameters are Phi(M_1450^*) = 1.14 x 10^-8 Mpc^-3 mag^-1, break
magnitude M_1450^* = -25.13 and bright end slope beta = -2.81. However the
covariance between beta and M_1450^* prevents strong constraints being placed
on either parameter. For a break magnitude in the range -26 < M_1450^* < -24 we
find -3.8 < beta < -2.3 at 95% confidence. We calculate the z = 6 quasar
intergalactic ionizing flux and show it is between 20 and 100 times lower than
that necessary for reionization. Finally, we use the luminosity function to
predict how many higher redshift quasars may be discovered in future near-IR
imaging surveys.Comment: 15 pages, 9 figures, AJ in pres
Symposium on Obesity and Asthma-November 2006
Lâasthme et lâobĂ©sitĂ© sont frĂ©quemment associĂ©s et lâobĂ©sitĂ© est considĂ©rĂ©e comme un facteur impliquĂ© tant dans lâaugmentation de la sĂ©vĂ©ritĂ© que dans le dĂ©veloppement de lâasthme. Ce document est un compte-rendu des prĂ©sentations effectuĂ©es dans le cadre dâun symposium du RĂ©seau en santĂ© respiratoire du Fonds de la recherche en santĂ© du QuĂ©bec qui a eu lieu Ă MontrĂ©al le 2 novembre 2006, en collaboration avec le McGill University â Strauss Severe Asthma Program, lâUniversitĂ© Laval (QuĂ©bec) et lâUniversitĂ© de MontrĂ©al. Au cours de cette rencontre, divers aspects de la relation entre obĂ©sitĂ© et asthme ont Ă©tĂ© abordĂ©s, en regard des modĂšles animaux, des influences gĂ©nĂ©tiques, hormonales et physiologiques, de lâinfluence des comorbiditĂ©s (ex : syndrome dâapnĂ©e du sommeil), de lâĂ©pidĂ©miologie, des aspects cliniques et psychologiques et, enfin, du traitement de lâasthme chez la personne obĂšse.Asthma and obesity are frequently associated, and obesity has been considered a factor contributing to both an increase in severity of asthma and to its development. The present document summarizes the proceedings of a symposium held in Montreal, Quebec, on November 2, 2006, under the auspices of the RĂ©seau en santĂ© respiratoire du Fonds de la recherche en santĂ© du QuĂ©bec in collaboration with the McGill University - Strauss Severe Asthma Program, UniversitĂ© Laval (Quebec City) and UniversitĂ© de MontrĂ©al. It includes an overview of the various aspects of the relationships between asthma and obesity with regard to animal models; genetic, hormonal and physiological determinants; influence of comorbidities (eg, sleep apnea syndrome); epidemiology; clinical and psychological features; and management of asthma in the obese population
Eddington-limited accretion and the black hole mass function at redshift 6
We present discovery observations of a quasar in the Canada-France High-z
Quasar Survey (CFHQS) at redshift z=6.44. We also use near-IR spectroscopy of
nine CFHQS quasars at z~6 to determine black hole masses. These are compared
with similar estimates for more luminous Sloan Digital Sky Survey (SDSS)
quasars to investigate the relationship between black hole mass and quasar
luminosity. We find a strong correlation between MgII FWHM and UV luminosity
and that most quasars at this early epoch are accreting close to the Eddington
limit. Thus these quasars appear to be in an early stage of their life cycle
where they are building up their black hole mass exponentially. Combining these
results with the quasar luminosity function, we derive the black hole mass
function at z=6. Our black hole mass function is ~10^4 times lower than at z=0
and substantially below estimates from previous studies. The main uncertainties
which could increase the black hole mass function are a larger population of
obscured quasars at high-redshift than is observed at low-redshift and/or a low
quasar duty cycle at z=6. In comparison, the global stellar mass function is
only ~10^2 times lower at z=6 than at z=0. The difference between the black
hole and stellar mass function evolution is due to either rapid early star
formation which is not limited by radiation pressure as is the case for black
hole growth or inefficient black hole seeding. Our work predicts that the black
hole mass - stellar mass relation for a volume-limited sample of galaxies
declines rapidly at very high redshift. This is in contrast to the observed
increase at 4<z<6 from the local relation if one just studies the most massive
black holes.Comment: 16 pages, 10 figures, AJ in pres
Early-onset Amyloid Deposition and Cognitive Deficits in Transgenic Mice Expressing a Double Mutant Form of Amyloid Precursor Protein 695
n/
Foraging Fidelity as a Recipe for a Long Life: Foraging Strategy and Longevity in Male Southern Elephant Seals
Identifying individual factors affecting life-span has long been of interest for biologists and demographers: how do some individuals manage to dodge the forces of mortality when the vast majority does not? Answering this question is not straightforward, partly because of the arduous task of accurately estimating longevity in wild animals, and of the statistical difficulties in correlating time-varying ecological covariables with a single number (time-to-event). Here we investigated the relationship between foraging strategy and life-span in an elusive and large marine predator: the Southern Elephant Seal (Mirounga leonina). Using teeth recovered from dead males on Ăźles Kerguelen, Southern Ocean, we first aged specimens. Then we used stable isotopic measurements of carbon () in dentin to study the effect of foraging location on individual life-span. Using a joint change-point/survival modelling approach which enabled us to describe the ontogenetic trajectory of foraging, we unveiled how a stable foraging strategy developed early in life positively covaried with longevity in male Southern Elephant Seals. Coupled with an appropriate statistical analysis, stable isotopes have the potential to tackle ecological questions of long standing interest but whose answer has been hampered by logistic constraints
Portrait du programme d'informatique : la clientĂšle Ă©tudiante, de l'inscription Ă l'emploi /
Glossaire: p. ix-xiiBibliogr.: p. 53-5