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Time of Flight Measurements for Neutrons Produced in Reactions Driven by Laser-Target Interactions at Petawatt level
No full textInternational audienceShort intense pulses of fast neutrons were produced in a two stage laser-driven experiment. Protons were accelerated by means of the Target Normal Sheath Acceleration (TNSA) method using the TITAN facility at the Lawrence Livermore National Laboratory. Neutrons were obtained following interactions of the protons with a secondary lithium fluoride (LiF) target. The properties of the neutron flux were studied using BC-400 plastic scintillation detectors and the neutron time of flight (nTOF) technique. The detector setup and the experimental conditions were simulated with the Geant4 toolkit. The effects of different components of the experimental setup on the nTOF were studied. Preliminary results from a comparison between experimental and simulated nTOF distributions are presented
A simple paradigm for nooconomics, the economy of knowledge
No full textInternational audienceThe human noosphere and its inner dynamic are forming a fascinating yet poorly understood multiscale complex system, in which one may represent the interaction of individual knowledge holders and their collective dynamic. Here I propose a simple, improvable paradigm for noodynamics (the study of knowledge flows) and nooconomics at large (the economy of knowledge) based on two intrinsic properties of knowledge-its prolificity and collegiality-and on three simple transfer laws capturing some fundamental differences between material and immaterial economics, namely 1) that knowledge exchanges , unlike property exchanges, are flows, and thus time-dependent, 2) that knowledge exchanges are positive sum, unlike material exchanges and 3) that combinations of knowledge are non linear. I then make a suggestion for a basic knowledge flow equation, namely that transferred knowledge is proportional to the product of spent attention and time, and discuss some of its social and political implications. keywords: knowledge economy, noosphere, multiscale dynamic, knowledge flow, noodynam-ics The purpose of this article is to outline a simple and improvable paradigm for noody-namics, the study of knowledge flows. If we endow this paradigm with an economic perspective, and consider its agents buyers and sellers, it can then also be considered an early working paradigm, or more precisely, an early building block towards a working paradigm, for nooconomics, the economy of knowledge. I thus attempt to demonstrate that noodynamics can be codified extremely simply, although not entirely , and will leave the many exceptions to the present paradigm to discussion
Adaptive kernel estimation of the baseline function in the Cox model with high-dimensional covariates
No full textWe propose a novel kernel estimator of the baseline function in a general high-dimensional Cox model, for which we derive non-asymptotic rates of convergence. To construct our estimator, we first estimate the regression parameter in the Cox model via a LASSO procedure. We then plug this estimator into the classical kernel estimator of the baseline function, obtained by smoothing the so-called Breslow estimator of the cumulative baseline function. We propose and study an adaptive procedure for selecting the bandwidth, in the spirit of Goldenshluger and Lepski [14]. We state non-asymptotic oracle inequalities for the final estimator, which leads to a reduction in the rate of convergence when the dimension of the covariates grows
L'ajustement microéconomique des prix des carburants en France
No full textEn utilisant des millions de relevés individuels de prix entre 2007 et 2009, cette étude décrit plusieurs faits stylisés sur l’ajustement des prix des carburants en France : ils changent en moyenne une fois par semaine ; ils sont plus souvent modifiés le mardi et le vendredi ; la concurrence accroît la fréquence des changements de prix ; la distribution des tailles de changements de prix présente peu de changements inférieurs à 2% ; taille des changements de prix et durée des prix sont corrélées ; l’inflation des prix des carburants est surtout déterminée par la part relative des stations-service augmentant ou baissant leur prix. Les modèles de coût d’ajustement incluant des rigidités informationnelles reproduisent le mieux ces faits stylisés
Search for supersymmetry in the vector-boson fusion topology in proton-proton collisions at sqrt(s) = 8 TeV
No full textSubmitted to JHEP ; see paper for full list of authorsInternational audienceThe first search for supersymmetry in the vector-boson fusion topology is presented. The search targets final states with at least two leptons, large missing transverse momentum, and two jets with a large separation in rapidity. The data sample corresponds to an integrated luminosity of 19.7 inverse femtobarns of proton-proton collisions at sqrt(s) = 8 TeV collected with the CMS detector at the CERN LHC. The observed dijet invariant mass spectrum is found to be consistent with the expected standard model prediction. Upper limits are set on the cross sections for chargino and neutralino production with two associated jets, assuming the supersymmetric partner of the tau lepton to be the lightest slepton and the lightest slepton to be lighter than the charginos. For a so-called compressed-mass-spectrum scenario in which the mass difference between the lightest supersymmetric particle and the next lightest, mass-degenerate, gaugino particles is 50 GeV, a mass lower limit of 170 GeV is set for these latter two particles
Certifying trajectories of dynamical systems
No full textThis paper concerns the reliable integration of dynamical systems with a focus on the computation of one specific trajectory for a given initial condition at high precision. We describe several algorithmic tricks which allow for faster parallel computations and better error estimates. We also introduce so called "Lagrange models". These serve a similar purpose as the more classical Taylor models, but we will show that they allow for larger step sizes, especially when the truncation orders get large
Lipoic acid decreases Mcl-1, Bcl-xL and up regulates Bim on ovarian carcinoma cells leading to cell death
No full textInternational audienceOvarian carcinoma is the leading cause of death from gynecological cancer because there is risk of chemoresistance. As previously demonstrated in our laboratory, Alpha-lipoic acid (LA), a co-factor for metabolic enzymes, suppresses the tumor growth. In this study, we have researched the mechanisms that are responsible for the activity of LA. We have studied the mechanisms of LA in two ovarian cancer cell lines, a cisplatin sensitive one, IGROV1 and its resistant counterpart, IGROV1-R10. These cells have been exposed to lipoic acid at various concentrations. Cell proliferation, cell cycle repartition and nuclear staining with DAPI were recorded. Western blot analyses were performed to detect various proteins implied in apoptotic cell death pathways. To investigate the formation of ROS, the oxidation of CM-DCFH2-DA were also determined. LA suppressed growth proliferation and induced apoptosis in both ovarian cell lines. Moreover, LA provoked a down regulation of two anti-apoptotic proteins, Mcl-1 and Bcl-xL protein and a strong induction of the BH3-only protein Bim. Furthermore, LA induced ROS generation which could be involved in the CHOP induction which is known to activate the Bim translation. Our results reveal novel actions of LA which could explain the anti-tumoral effects of the LA. Therefore, LA seems to be a promising compound for ovarian cancer treatment
Measurement of ISR-FSR interference in the processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi- gamma
No full textSee paper for full list of authors - 32 pages,29 figures, to be submitted to Phys. Rev. DInternational audienceCharge asymmetry in processes e+ e- --> mu+ mu- gamma and e+ e- --> pi+ pi- gamma is measured using 232 fb-1 of data collected with the BABAR detector at center-of-mass energies near 10.58 GeV. An observable is introduced and shown to be very robust against detector asymmetries while keeping a large sensitivity to the physical charge asymmetry that results from the interference between initial and final state radiation. The asymmetry is determined as afunction of the invariant mass of the final-state tracks from production threshold to a few GeV/c2. It is compared to the expectation from QED for e+ e- --> mu+ mu- gamma and from theoretical models for e+ e- --> pi+ pi- gamma. A clear interference pattern is observed in e+ e- --> pi+ pi- gamma, particularly in the vicinity of the f_2(1270) resonance. The inferred rate of lowest order FSR production is consistent with the QED expectation for e+ e- --> mu+ mu- gamma, and is negligibly small for e+ e- --> pi+ pi- gamma
Détermination de faibles quantités de terres rares dans une matrice inorganique par une méthode de RMN
No full textDetermine the doping level is essential to optimize the properties of materials, e.g. luminescence. We present an original high-accuracy method based on the 31P solid-state NMR relaxation to determine low concentrations (< 1 %) of paramagnetic lanthanide ions. Our method was first applied to a model compound, LaPO4, within the incorporation of the dopant is known. NMR experiments under static and MAS (15 kHz) conditions reveal that the 31P relaxation time T1 is strongly affected by the presence of paramagnetic ions in the vicinity of the phosphorous nuclei. A linear variation of 1 / T1 as a function of neodymium (Nd3+) or gadolinium (Gd3+) concentration is shown in the 0-10 at.% range for a homogeneous distribution of the doping ions in the matrix. In the case of a solid-state synthesis at 1450 °C, relaxation measurements show that the homogeneous distribution of doping ions is ensured when the mixing of oxide precursors is performed mechanically, in contrast with the manual grinding. The electronic relaxation times of Gd3+ and Nd3+ have been evaluated by ESR measurements under saturation conditions. This allows us to provide a semi-quantitative interpretation of the nuclear 31P relaxation measurements both in Nd and Gd doped LaPO4. In addition, the comparison between nuclear and electronic relaxation suggests that Nd-Gd codoping may improve the efficiency of Gd3+ ions, interesting for the development of relaxing agents in MRI techniques. In a last part, we generalize our method to crystalline or amorphous materials.Évaluer le taux de dopage d’un matériau est indispensable pour optimiser ses propriétés, en particulier de luminescence. Nous proposons une technique originale, la relaxation nucléaire par RMN, pour la détermination de faibles concentrations en ions lanthanides, paramagnétiques. Cet outil, basé sur la RMN du solide de 31P, a été testé sur un matériau modèle (LaPO4) pour lequel l’incorporation homogène du dopant est connue. Les expériences de RMN ont été faites en statique et en rotation à l’angle magique à 15 kHz. Elles ont montré que le temps de relaxation T1 est très fortement modifié par la présence des ions paramagnétiques voisins du phosphore. Pour une distribution homogène en dopants inférieures à 10 %, la variation de 1 / T1 en fonction du taux de néodyme (Nd3+) ou de gadolinium (Gd3+) est linéaire. Dans le cas d’une synthèse par voie solide, ces mesures indiquent que la distribution homogène est assurée quand les précurseurs oxydes sont mélangés mécaniquement mais pas lors d’un broyage manuel. Les temps de relaxation électronique de Gd3+ et de Nd3+ ont été estimés par RPE en saturation. Cela nous a permis d’établir une interprétation semi-quantitative des mesures de relaxation nucléaire du phosphore dans LaPO4. Par ailleurs, une étude similaire dans le cas d’un codopage Nd3+/Gd3+ a montré que la relaxation de Gd3+ gagnait en efficacité à être associé à Nd3+, ce qui peut être intéressant pour les techniques d’imagerie par résonance magnétique (IRM). Enfin, cette méthode a été généralisée à d’autres matériaux, cristallins ou amorphes
