3,846 research outputs found
Grid Added Value to Address Malaria
Through this paper, we call for a distributed, internet-based collaboration
to address one of the worst plagues of our present world, malaria. The spirit
is a non-proprietary peer-production of information-embedding goods. And we
propose to use the grid technology to enable such a world wide "open source"
like collaboration. The first step towards this vision has been achieved during
the summer on the EGEE grid infrastructure where 46 million ligands were docked
for a total amount of 80 CPU years in 6 weeks in the quest for new drugs.Comment: 7 pages, 1 figure, 6th IEEE International Symposium on Cluster
Computing and the Grid, Singapore, 16-19 may 2006, to appear in the
proceeding
Generating Gowdy cosmological models
Using the analogy with stationary axisymmetric solutions, we present a method
to generate new analytic cosmological solutions of Einstein's equation
belonging to the class of Gowdy cosmological models. We show that the
solutions can be generated from their data at the initial singularity and
present the formal general solution for arbitrary initial data. We exemplify
the method by constructing the Kantowski-Sachs cosmological model and a
generalization of it that corresponds to an unpolarized Gowdy model.Comment: Latex, 15 pages, no figure
Recommended from our members
Continued evaluation of potential for geologic storage of carbon dioxide in the southeastern United States
Southern States Energy Board
Duke Energy
Santee Cooper Power
Southern CompanyBureau of Economic Geolog
Palaeoecology of the Cenomanian amber forest of Sarthe (western France)
Cretaceous ambers have been discovered in France since the beginning of the 18th century. The best known are those from south-western France which are Late Albian-Early Cenomanian in age, but there are other important amber deposits in other regions. Here, we summarise the data on one of these other Cretaceous amber regions, the Sarthe Department. These deposits have been mentioned in the literature since the end of the 18th century, but they have remained relatively unknown. The material, that has been studied during the 1970's and 1980's, yielded a well-diversified arthropod fauna (72 arthropod specimens, including arachnids, cockroaches, bugs, beetles, flies, wasps...) dated to late Early-Middle Cenomanian. In the last decade, 4 types of bacteria, a possible testate amoeba and fungal remains were also found. A re-examination of the historical collections of the Sarthe amber, housed in the "Musée Vert" (Le Mans, France), allows to estimate the geographical extent of the amber deposits in the Sarthe Department. The study of the microfossils of these samples provides new data on their palaeoenvironment
Stress response function of a two-dimensional ordered packing of frictional beads
We study the stress profile of an ordered two-dimensional packing of beads in
response to the application of a vertical overload localized at its top
surface. Disorder is introduced through the Coulombic friction between the
grains which gives some indeterminacy and allows the choice of one constrained
random number per grain in the calculation of the contact forces. The so-called
`multi-agent' technique we use, lets us deal with systems as large as
grains. We show that the average response profile has a double
peaked structure. At large depth , the position of these peaks grows with
, while their widths scales like . and are analogous to
`propagation' and `diffusion' coefficients. Their values depend on that of the
friction coefficient . At small , we get and , with , which means that the peaks get
closer and wider as the disorder gets larger. This behavior is qualitatively
what was predicted in a model where a stochastic relation between the stress
components is assumed.Comment: 7 pages, 7 figures, accepted version to Europhys. Let
Replication and update of molecular biology databases in a grid environment
PCSV, présenté par V. Breton, à paraître dans les proceedingsUpdate of molecular biology databases is a growing burden on the biomedical research community. As the grid allows to share and replicate data, we propose a service to automatically update the biology databases from a single changing reference using web services. In this paper we report the components, the architecture and the deployment of the update service on the french RUGBI grid infrastructure. RUGBI is a computing grid infrastructure based on existing middleware and technologies for the community of scientists in bioinformatics
Large scale deployment of molecular docking application on computational grid infrastructures for combating malaria
PCSVInternational audienceComputational grids are solutions for several biological applications like virtual screening or molecular dynamics where large amounts of computing power and storage are required. The WISDOM project successfully deployed virtual screening at large scale on EGEE grid infrastructures in the summer 2005 and achieved 46 million dockings in 45 days, which is equivalent to 80 CPU years. WISDOM is one good example of a successful deployment of an embarrassingly parallel application. In this paper, we describe the improvements in our deployment. We screened ZINC database against four targets implicated in malaria. During more than 2 months and a half, we have achieved 140 million dockings, representing an average throughput of almost 80,000 dockings per hour. This was made possible by the availability of thousands of CPUs through different infrastructures worldwide. Through the acquired experience, the WISDOM production environment is evolving to enable an easy and fault-tolerant deployment of biological tool
Validation of the GATE Monte Carlo simulation platform for modelling a CsI(Tl) scintillation camera dedicated to small animal imaging
Monte Carlo simulations are increasingly used in scintigraphic imaging to
model imaging systems and to develop and assess tomographic reconstruction
algorithms and correction methods for improved image quantitation. GATE (GEANT
4 Application for Tomographic Emission) is a new Monte Carlo simulation
platform based on GEANT4 dedicated to nuclear imaging applications. This paper
describes the GATE simulation of a prototype of scintillation camera dedicated
to small animal imaging and consisting of a CsI(Tl) crystal array coupled to a
position sensitive photomultiplier tube. The relevance of GATE to model the
camera prototype was assessed by comparing simulated 99mTc point spread
functions, energy spectra, sensitivities, scatter fractions and image of a
capillary phantom with the corresponding experimental measurements. Results
showed an excellent agreement between simulated and experimental data:
experimental spatial resolutions were predicted with an error less than 100 mu
m. The difference between experimental and simulated system sensitivities for
different source-to-collimator distances was within 2%. Simulated and
experimental scatter fractions in a [98-182 keV] energy window differed by less
than 2% for sources located in water. Simulated and experimental energy spectra
agreed very well between 40 and 180 keV. These results demonstrate the ability
and flexibility of GATE for simulating original detector designs. The main
weakness of GATE concerns the long computation time it requires: this issue is
currently under investigation by the GEANT4 and the GATE collaboration
Long Term Study of the Double Pulsar J0737-3039 with XMM-Newton: pulsar timing
The relativistic double neutron star binary PSR J0737-3039 shows clear
evidence of orbital phase-dependent wind-companion interaction, both in radio
and X-rays. In this paper we present the results of timing analysis of PSR
J0737-3039 performed during 2006 and 2011 XMM-Newton Large Programs that
collected ~20,000 X-ray counts from the system. We detected pulsations from PSR
J0737-3039A (PSR A) through the most accurate timing measurement obtained by
XMM-Newton so far, the spin period error being of 2x10^-13 s. PSR A's pulse
profile in X-rays is very stable despite significant relativistic spin
precession that occurred within the time span of observations. This yields a
constraint on the misalignment between the spin axis and the orbital momentum
axis Delta_A ~6.6^{+1.3}_{-5.4} deg, consistent with estimates based on radio
data. We confirmed pulsed emission from PSR J0737-3039B (PSR B) in X-rays even
after its disappearance in radio. The unusual phenomenology of PSR B's X-ray
emission includes orbital pulsed flux and profile variations as well as a loss
of pulsar phase coherence on time scales of years. We hypothesize that this is
due to the interaction of PSR A's wind with PSR B's magnetosphere and
orbital-dependent penetration of the wind plasma onto PSR B closed field lines.
Finally, the analysis of the full XMM-Newton dataset provided evidences of
orbital flux variability (~7%) for the first time, involving a bow-shock
scenario between PSR A's wind and PSR B's magnetosphere.Comment: Comments: 16 Pages, 6 Figures. Accepted for publication in
Astrophysical Journal (Draft Version
- …