337 research outputs found
Algorithmic Based Fault Tolerance Applied to High Performance Computing
We present a new approach to fault tolerance for High Performance Computing
system. Our approach is based on a careful adaptation of the Algorithmic Based
Fault Tolerance technique (Huang and Abraham, 1984) to the need of parallel
distributed computation. We obtain a strongly scalable mechanism for fault
tolerance. We can also detect and correct errors (bit-flip) on the fly of a
computation. To assess the viability of our approach, we have developed a fault
tolerant matrix-matrix multiplication subroutine and we propose some models to
predict its running time. Our parallel fault-tolerant matrix-matrix
multiplication scores 1.4 TFLOPS on 484 processors (cluster jacquard.nersc.gov)
and returns a correct result while one process failure has happened. This
represents 65% of the machine peak efficiency and less than 12% overhead with
respect to the fastest failure-free implementation. We predict (and have
observed) that, as we increase the processor count, the overhead of the fault
tolerance drops significantly
Analyse statistique de la communication par le systÚme perceptif d'un bébé (de 3 à 9 mois) avec sa mÚre
PILE (Programme International pour le Langage de l'Enfant, 2004--2008), s'est donné comme objectif de décrire par des techniques statistiques les processus chez le bébé qui participent à l'émergence de la parole. Une base de données qualitative a été élaborée à partir de séquences vidéo de bébés de 3 mois à 9 mois en interaction avec leur mÚre. Nous présentons une étude statistique de cette base, à l'aide de techniques inférentielles (tests de comparaisons non paramétriques) et d'analyses factorielles. Certains de nos résultats confirment ou précisent les hypothÚses cliniques relativement à l'effet de certains facteurs tels que cohortes, ùge calendaire, sexe des bébés. Les résultats qui décrivent statistiquement le comportement du bébé en interaction avec sa mÚre indiquent que la mise en place du systÚme perceptif chez le bébé est centrale dans la construction des précurseurs du langage
Statistical Analysis of Mother-infant (3 to 9 months) Perceptive System Communication
PILE (Programme International pour le Langage de l'Enfant), the International Program for Child Language aims to describe the processes leading to the emergence of speech in infants thanks to statistic techniques. A qualitative data base was established on the basis of one minute video sequences (the statistical units) of babies aged from 3 to 9 months interacting with their mothers. The phenomenon under study is the process of speech construction. The 110 infants are belonging to seven cohorts: infants without disorders, hospitalized infants, premature infants, infants of visually deficient mothers, infants of blind mothers, infants with neurological disorders. We present a statistical study of this data base through inferential techniques (non parametric comparison tests) and factorial analyses. Some of our findings confirm or bring additional precision to clinical hypotheses concerning the impact of certain factors, such as age cohort, calendar age, infant's sex. The statistical results describing the infant's behavior while interacting with its mother indicate that the development of the baby's perceptive system is central in the construction of language precursors
Herbicide accumulation and evolution in reservoir sediments
The aim of the present study was to understand the effect of reservoir configurations on sediment pesticide
fate. Two dams were selected on the River Garonne, in southwest France: Carbonne and Golfech, both with
reservoirs subject to accumulation of herbicide-contaminated sediment. They are situated upstream and
downstream respectively of an agricultural and urban area: the Mid-Garonne. The results presented include
pesticide concentrations and C/N ratios in the smaller sediment particles (b2 mm) and values of oxygenation
and herbicide concentrations in the water.
The dynamic behaviour of sediment in the reservoirs is discussed. The present study shows that the
theoretical lifespan (weak remanence in vitro) and the results actually observed in the sediment are
conflicting. Pesticide contamination in Carbonne indicates conservation, even accumulation, of herbicide
molecules while in Golfech transformation processes clearly dominate. The hydromorphological position of
Golfech reservoir, i.e. located at the junction of two rivers with contrasting hydrological regimes and very
different oxygenation conditions, leads to accelerated pesticide desorption or degradation. Unfortunately,
this configuration is rare
ApprĂ©hender le Dictionnaire des antiquitĂ©s grecques et romaines par sa table dâauteurs. Les donnĂ©es statistiques comme outil dâanalyse
Ainsi que lâont montrĂ© les Ă©tudes prĂ©cĂ©dentes, toute collaboration au Daremberg a ses raisons propres. Pour prendre de la hauteur et offrir une vue gĂ©nĂ©rale, lâapproche individuelle nâest plus guĂšre opĂ©rante. Lâanalyse statistique peut alors sâavĂ©rer plus rĂ©vĂ©latrice. Ce travail statistique, quoique fastidieux, nâest pas exactement lâexercice Ă©lĂ©mentaire que lâon pourrait imaginer. Les donnĂ©es, en partie au moins, y sont tributaires dâinformations recueillies sur les contributeurs. PrĂ©cisions..
Contribuer au Dictionnaire des antiquités grecques et romaines : quelques cas de figures
La mise en ligne et lâ« actualisation » du Dictionnaire des antiquitĂ©s invitent Ă une « autopsie » historiographique de lâentreprise initiĂ©e par Charles Daremberg (1817-1872), puis rĂ©alisĂ©e par Edmond Saglio (1828-1911) et Edmond Pottier (1855-1934) dans le dernier quart du xixe et le premier quart du xxe siĂšcle . Lors dâun enseignement de master consacrĂ© aux « mĂ©thodes et courants de la recherche en histoire ancienne » Ă lâuniversitĂ© de Toulouse II-Le Mirail, a Ă©tĂ© lancĂ©e en 2004-2005 lâidĂ©e..
Antitrypanosomatid Pharmacomodulation at Position 3 of the 8-Nitroquinolin-2(1H)-one Scaffold Using Palladium-Catalysed Cross-Coupling Reactions
International audienceAn antikinetoplastid pharmacomodulation study at position 3 of the recently described hit molecule 3-bromo-8-nitroquinolin-2(1H)-one was conducted. Twenty-four derivatives were synthesised using the Suzuki-Miyaura cross-coupling reaction and evaluated in vitro on both Leishmania infantum axenic amastigotes and Trypanosoma brucei brucei trypomastigotes. Introduction of a para-carboxyphenyl group at position 3 of the scaffold led to the selective antitrypanosomal hit molecule 3-(4-carboxyphenyl)-8-nitroquinolin-2(1H)-one (21) with a lower reduction potential (-0.56â
V) than the initial hit (-0.45â
V). Compound 21 displays micromolar antitrypanosomal activity (IC50 =1.5â
ÎŒm) and low cytotoxicity on the human HepG2 cell line (CC50 =120â
ÎŒm), having a higher selectivity index (SI=80) than the reference drug eflornithine. Contrary to results previously obtained in this series, hit compound 21 is inactive toward L.â
infantum and is not efficiently bioactivated by T.â
brucei brucei typeâ
I nitroreductase, which suggests the existence of an alternative mechanism of action
Novel 8-nitroquinolin-2(1H)-ones as NTR-bioactivated antikinetoplastid molecules:Synthesis, electrochemical and SAR study
International audienceTo study the antiparasitic 8-nitroquinolin-2(1H)-one pharmacophore, a series of 31 derivatives was synthesized in 1-5 steps and evaluated in vitro against both Leishmania infantum and Trypanosoma brucei brucei. In parallel, the reduction potential of all molecules was measured by cyclic voltammetry. Structure-activity relationships first indicated that antileishmanial activity depends on an intramolecular hydrogen bond (described by X-ray diffraction) between the lactam function and the nitro group, which is responsible for an important shift of the redox potential (+0.3 V in comparison with 8-nitroquinoline). With the assistance of computational chemistry, a set of derivatives presenting a large range of redox potentials (from -1.1 to -0.45 V) was designed and provided a list of suitable molecules to be synthesized and tested. This approach highlighted that, in this series, only substrates with a redox potential above -0.6 V display activity toward L. infantum. Nevertheless, such relation between redox potentials and in vitro antiparasitic activities was not observed in T. b. brucei. Compound 22 is a new hit compound in the series, displaying both antileishmanial and antitrypanosomal activity along with a low cytotoxicity on the human HepG2 cell line. Compound 22 is selectively bioactivated by the type 1 nitroreductases (NTR1) of L. donovani and T. brucei brucei. Moreover, despite being mutagenic in the Ames test, as most of nitroaromatic derivatives, compound 22 was not genotoxic in the comet assay. Preliminary in vitro pharmacokinetic parameters were finally determined and pointed out a good in vitro microsomal stability (half-lifeâŻ>âŻ40âŻmin) and a 92% binding to human albumin
8-Aryl-6-chloro-3-nitro-2-(phenylsulfonylmethyl)imidazo[1,2-a]pyridines as potent antitrypanosomatid molecules bioactivated by type 1 nitroreductases
Based on a previously identified antileishmanial 6,8-dibromo-3-nitroimidazo[1,2-a]pyridine derivative, a Suzuki-Miyaura coupling reaction at position 8 of the scaffold was studied and optimized from a 8-bromo-6-chloro-3-nitroimidazo[1,2-a]pyridine substrate. Twenty-one original derivatives were prepared, screened in vitro for activity against L infantum axenic amastigotes and T. brucei brucei trypomastigotes and evaluated for their cytotoxicity on the HepG2 human cell line. Thus, 7 antileishmanial hit compounds were identified, displaying IC50 values in the 1.1-3 mu M range. Compounds 13 and 23, the 2 most selective molecules (SI = >18 or >17) were additionally tested on both the promastigote and intramacrophage amastigote stages of L donovani. The two molecules presented a good activity (IC50 = 1.2-1.3 mu M) on the promastigote stage but only molecule 23, bearing a 4-pyridinyl substituent at position 8, was active on the intracellular amastigote stage, with a good IC50 value (2.3 mu M), slightly lower than the one of miltefosine (IC50 = 4.3 mu M). The antiparasitic screening also revealed 8 antitrypanosomal hit compounds, including 14 and 20, 2 very active (IC50 = 0.04-0.16 mu M) and selective (SI = >313 to 550) molecules toward T brucei brucei, in comparison with drug-candidate fexinidazole (IC50 = 0.6 & SI > 333) or reference drugs suramin and eflornithine (respective IC50 = 0.03 and 13.3 mu M). Introducing an aryl moiety at position 8 of the scaffold quite significantly increased the antitrypanosomal activity of the pharmacophore. Antikinetoplastid molecules 13, 14, 20 and 23 were assessed for bioactivation by parasitic nitroreductases (either in L donovani or in T. brucei brucei), using genetically modified parasite strains that over-express NTRs: all these molecules are substrates of type 1 nitroreductases (NTRI), such as those that are responsible for the bioactivation of fexinidazole. Reduction potentials measured for these 4 hit compounds were higher than that of fexinidazole (-0.83 V), ranging from -0.70 to -0.64 V
Direct observation of active material concentration gradients and crystallinity breakdown in LiFePO4 electrodes during charge/discharge cycling of lithium batteries
The phase changes that occur during discharge of an electrode comprised of LiFePO4, carbon, and PTFE binder have been studied in lithium half cells by using X-ray diffraction measurements in reflection geometry. Differences in the state of charge between the front and the back of LiFePO4 electrodes have been visualized. By modifying the X-ray incident angle the depth of penetration of the X-ray beam into the electrode was altered, allowing for the examination of any concentration gradients that were present within the electrode. At high rates of discharge the electrode side facing the current collector underwent limited lithium insertion while the electrode as a whole underwent greater than 50% of discharge. This behavior is consistent with depletion at high rate of the lithium content of the electrolyte contained in the electrode pores. Increases in the diffraction peak widths indicated a breakdown of crystallinity within the active material during cycling even during the relatively short duration of these experiments, which can also be linked to cycling at high rate
- âŠ