1,636 research outputs found
Types sérologiques de Pasteurella multocida rencontrés en France chez le lapin et la poule
Perreau Pierre, Renault Lucien, Vallée A. Types sérologiques de Pasteurella multocida rencontrés en France chez le lapin et la poule. In: Bulletin de l'Académie Vétérinaire de France tome 115 n°8, 1962. pp. 295-298
Identification en France d’Arizona arizonae chez le dindon
Renault Lucien, Vaissaire Josée, Maire Cl., Motte P. Identification en France d’Arizona arizonae chez le dindon . In: Bulletin de l'Académie Vétérinaire de France tome 125 n°1, 1972. pp. 53-55
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
Cosmic Background dipole measurements with Planck-High Frequency Instrument
This paper discusses the Cosmic Background (CB) dipoles observations in the
framework of the Planck mission. Dipoles observations can be used in three
ways: (i) It gives a measurement of the peculiar velocity of our Galaxy which
is an important observation in large scale structures formation model. (ii)
Measuring the dipole can give unprecedent information on the monopole (that can
be in some cases hard to obtain due to large foreground contaminations). (iii)
The dipole can be an ideal absolute calibrator, easily detectable in
cosmological experiments. Following the last two objectives, the main goal of
the work presented here is twofold. First, we study the accuracy of the
Planck-HFI calibration using the Cosmic Microwave Background (CMB) dipole
measured by COBE as well as the Earth orbital motion dipole. We show that we
can reach for HFI, a relative calibration between rings of about 1% and an
absolute calibration better than 0.4% for the CMB channels (in the end, the
absolute calibration will be limited by the uncertainties on the CMB
temperature). We also show that Planck will be able to measure the CMB dipole
direction at better than 1.7 arcmin and improve on the amplitude. Second, we
investigate the detection of the Cosmic Far-Infrared Background (FIRB) dipole.
Measuring this dipole could give a new and independent determination of the
FIRB for which a direct determination is quite difficult due to Galactic dust
emission contamination. We show that such a detection would require a Galactic
dust emission removal at better than 1%, which will be very hard to achieve.Comment: 10 pages, 13 figures, submitted to A&A, uses aa.sty V5.
Very High Energy Gamma-ray spectral properties of Mrk 501 from CAT Cerenkov telescope observations in 1997
The BL Lac object Mrk 501 went into a very high state of activity during
1997, both in VHE gamma-rays and X-rays. We present here results from
observations at energies above 250 GeV carried out between March and October
1997 with the CAT Cerenkov imaging Telescope. The average differential spectrum
between 30 GeV and 13 TeV shows significant curvature and is well represented
by phi_0 * E_TeV^{-(alpha + beta*log10(E_TeV))}, with: phi_0 = 5.19 +/- 0.13
{stat} +/- 0.12 {sys-MC} +1.66/-1.04 {sys-atm} * 10^-11 /cm^2/s/TeV alpha =
2.24 +/- 0.04 {stat} +/- 0.05 {sys} beta = 0.50 +/- 0.07 {stat} (negligible
systematics). The TeV spectral energy distribution of Mrk 501 clearly peaks in
the range 500 GeV-1 TeV. Investigation of spectral variations shows a
significant hardness-intensity correlation with no measurable effect on the
curvature. This can be described as an increase of the peak TeV emission energy
with intensity. Simultaneous and quasi-simultaneous CAT VHE gamma-ray and
BeppoSAX hard X-ray detections for the highest recorded flare on 16th April and
for lower-activity states of the same period show correlated variability with a
higher luminosity in X-rays than in gamma-rays. The observed spectral energy
distribution and the correlated variability between X-rays and gamma-rays, both
in amplitude and in hardening of spectra, favour a two-component emission
scheme where the low and high energy components are attributed to synchrotron
and inverse Compton (IC) radiation, respectively.Comment: Submitted to Astronomy and Astrophysics, 8 pages including 6 figures.
Published with minor change
The effect of metallicity on the Cepheid distance scale and its implications for the Hubble constant () determination
Recent HST determinations of the expansion's rate of the Universe (the Hubble
constant, H_0) assumed that the Cepheid Period-Luminosity relation at V and I
are independent of metallicity (Freedman, et al., 1996, Saha et al., 1996,
Tanvir et al., 1995). The three groups obtain different vales for H_0. We note
that most of this discrepancy stems from the asumption (by both groups) that
the Period-Luminosity relation is independent of metallicity. We come to this
conclusion as a result of our study of the Period-Luminosity relation of 481
Cepheids with 3 millions two colour measurements in the Large Magellanic Cloud
and the Small Magellanic Cloud obtained as a by-product of the EROS
microlensing survey. We find that the derived interstellar absorption
corrections are particularly sensitive to the metallicity and when our result
is applied to recent estimates based on HST Cepheids observations it makes the
low-H_0 values higher and the high-H_0 value lower, bringing those discrepant
estimates into agrement around .Comment: 4 pages, Latex, with 2 .ps accepted for publication astronomy and
astrophysics Letter
EROS Variable Stars : Discovery of Beat Cepheids in the Small Magellanic Cloud and the effect of metallicity on pulsation
We report the discovery of eleven beat Cepheids in the Small Magellanic
Cloud, using data obtained by the EROS microlensing survey. Four stars are
beating in the fundamental and first overtone mode (F/1OT), seven are beating
in the first and second overtone (1OT/2OT). The SMC F/1OT ratio is
systematically higher than the LMC F/1OT, while the 1OT/2OT period ratio in the
SMC Cepheids is the same as the LMC one.Comment: 4 pages, Latex file with 4 .ps figures. accepted for publication in A
A Letter
A combined structural and biochemical approach reveals translocation and stalling of UvrB on the DNA lesion as a mechanism of damage verification in bacterial nucleotide excision repair
Nucleotide excision repair (NER) is a DNA repair pathway present in all domains of life. In bacteria, UvrA protein localizes the DNA lesion, followed by verification by UvrB helicase and excision by UvrC double nuclease. UvrA senses deformations and flexibility of the DNA duplex without precisely localizing the lesion in the damaged strand, an element essential for proper NER. Using a combination of techniques, we elucidate the mechanism of the damage verification step in bacterial NER. UvrA dimer recruits two UvrB molecules to its two sides. Each of the two UvrB molecules clamps a different DNA strand using its \u3b2-hairpin element. Both UvrB molecules then translocate to the lesion, and UvrA dissociates. The UvrB molecule that clamps the damaged strand gets stalled at the lesion to recruit UvrC. This mechanism allows UvrB to verify the DNA damage and identify its precise location triggering subsequent steps in the NER pathway
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