19 research outputs found
AgapeZ1: a Large Amplification Microlensing Event or an Odd Variable Star Towards the Inner Bulge of M31
AgapeZ1 is the brightest and the shortest duration microlensing candidate
event found in the Agape data. It occured only 42" from the center of M31. Our
photometry shows that the half intensity duration of the event6 is 4.8 days and
at maximum brightness we measure a stellar magnitude of R=18.0 with B-R=0.80
mag color. A search on HST archives produced a single resolved star within the
projected event position error box. Its magnitude is R=22.Comment: 4 pages with 5 figure
Variable stars towards the bulge of M31: the AGAPE catalogue
We present the AGAPE astrometric and photometric catalogue of 1579 variable
stars in a 14'x10' field centred on M31. This work is the first survey devoted
to variable stars in the bulge of M31. The R magnitudes of the objects and the
B-R colours suggest that our sample is dominated by red long-period variable
stars (LPV), with a possible overlap with Cepheid-like type II stars. Twelve
nova candidates are identified. Correlations with other catalogues suggest that
2 novae could be recurrent novae and provide possible optical counterparts for
2 supersoft X-ray sources candidates observed with Chandra.Comment: 11 pages, Latex, accepted for publication in A&
Signalling mechanisms mediating Zn2+-induced TRPM2 channel activation and death cell in microglial cells
Excessive Zn2+ causes brain damage via promoting ROS generation. Here we investigated the role of ROS-sensitive TRPM2 channel in H2O2/Zn2+-induced Ca2+ signalling and cell death in microglial cells. H2O2/Zn2+ induced concentration-dependent increases in cytosolic Ca2+ concentration ([Ca2+]c), which was inhibited by PJ34, a PARP inhibitor, and abolished by TRPM2 knockout (TRPM2-KO). Pathological concentrations of H2O2/Zn2+ induced substantial cell death that was inhibited by PJ34 and DPQ, PARP inhibitors, 2-APB, a TRPM2 channel inhibitor, and prevented by TRPM2-KO. Further analysis indicate that Zn2+ induced ROS production, PARP-1 stimulation, increase in the [Ca2+]c and cell death, which were suppressed by chelerythrine, a protein kinase C inhibitor, DPI, a NADPH-dependent oxidase (NOX) inhibitor, GKT137831, a NOX1/4 inhibitor, and Phox-I2, a NOX2 inhibitor. Furthermore, Zn2+-induced PARP-1 stimulation, increase in the [Ca2+]c and cell death were inhibited by PF431396, a Ca2+-sensitive PYK2 inhibitor, and U0126, a MEK/ERK inhibitor. Taken together, our study shows PKC/NOX-mediated ROS generation and PARP-1 activation as an important mechanism in Zn2+-induced TRPM2 channel activation and, TRPM2-mediated increase in the [Ca2+]c to trigger the PYK2/MEK/ERK signalling pathway as a positive feedback mechanism that amplifies the TRPM2 channel activation. Activation of these TRPM2-depenent signalling mechanisms ultimately drives Zn2+-induced Ca2+ overloading and cell death
Réflectomètre à large spectre EUV pour la métrologie d'optiques
Le Laboratoire Charles Fabry conçoit de nombreuses optiques dont
certaines pour les applications dans le spectre EUV. Pour les
besoins de caractérisation, il est nécessaire de
posséder une métrologie à la longueur d'onde
d'utilisation proche des moyens de fabrication. Ceci permet
d'étudier les composants dès leur conception et de
caractériser les optiques. Nous présentons ici les
performances d'un réflectomètre automatisé EUV large
spectre. Il a été développé dans le cadre de la
centrale CEMOX, initiée par le pôle PRaXO
AGAPE: a search for dark matter towards M31 by microlensing effects on unresolved stars
M31 is a very tempting target for a microlensing search of compact objects in
galactic haloes. It is the nearest large galaxy, it probably has its own dark
halo, and its tilted position with respect to the line of sight provides an
unmistakable signature of microlensing. However most stars of M31 are not
resolved and one has to use the ``pixel method'': monitor the pixels of the
image rather than the stars. AGAPE is the implementation of this idea. Data
have been collected and treated during two autumns of observation at the 2
metre telescope of Pic du Midi. The process of geometric and photometric
alignment, which must be performed before constructing pixel light curves, is
described. Seeing variations are minimised by working with large super-pixels
(2.1) compared with the average seeing. A high level of stability of pixel
fluxes, crucial to the approach, is reached. Fluctuations of super-pixels do
not exceed 1.7 times the photon noise which is 0.1% of the intensity for the
brightest ones. With such stable data, 10 microlensing events are expected for
a full ``standard halo''. With a larger field, a regular and short time
sampling and a long lever arm in time, the pixel method will be a very
efficient tool to explore the halo of M31.Comment: 15 pages, 15 figures. Text and figures with better definition will
also be available at http://cdfinfo.in2p3.fr/Experiences/AGAPE/publis.html
Modified according to the requirement of the referee. To appear in A&
AGAPE: a Microlensing Search for Dark Matter by Monitoring Pixels
AGAPE is an observational search of massive compact halo objects (MACHOs) in
the direction of M31 by means of a novel method: the gravitational microlensing
of unresolved stars. The search consists in examining CCD pixel light curves
for microlensing features. The high level of temporal stability necessary to
detect microlensing events has been achieved, with quiet pixels stable within a
factor of two of the photon noise (the brightest ones down to a level of 0.001
mag). The data analysis is still in progress, but hundreds of variable objects
(cepheids, novae, ...) have already been found. Among them there are several
lightcurves that resemble microlensing events.Comment: presented at the International Conference on "Dark and Visible Matter
in Galaxies" (Sesto Pusteria, Italy, 2-5 July 1996), 8 pages, 7 figures, uses
paspconf.sty, psfig.st
AGAPE : Andromeda Gravitational Amplification Pixel Experiment
This paper presents a collective analytic work on the document in its transition to digital form carried out within a network of researchers of the CNRS Information and Communication Science and Technology (STIC) Department. The collective drafting of a text, carried out with a device of annotations, built an analytical inventory of research in progress. It stressed three topics: the form, the text and the medium which reflect the radical transformations that are taking place and the issues still going on. In particular, the more and more dynamic construction of documents actually transforms their traditional stability. The advance of the collective thought could lead to the development of a theory of the document