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Modular Approach to Substituted Boc-Protected 4-(Aminomethyl)pyrroles
No full textInternational audienceThe radical addition of various α-xanthyl ketones to Boc-protected azetine gives adducts which, when treated with ammonia or primary amines, furnish 2,4-disubstituted, 2,3,4-trisubstituted, and polycyclic pyrroles having a protected aminomethyl group at position 4. An unusual ring-opening was observed in the case of a cyclobutanone precursor
Positron annihilation spectroscopy investigation of vacancy clusters in silicon carbide: Combining experiments and electronic structure calculations
No full textInternational audienceThe temperature dependence of the point defects in 6H-SiC induced by 12-MeV proton irradiation was studied by means of isochronal annealing followed by both positron annihilation spectroscopy and electron paramagnetic resonancemeasurements. The formation energies and positron lifetimes of various vacancy clusters were calculated to help in the interpretation of the experiments. The combination of the experiments and calculations enabled the identification of a negative silicon vacancy, with the lifetime of 218 ps, which is annealed between 400 degrees C and 700 degrees C. This process involves vacancy migration and formation of the V-C + V-Si cluster, with a lifetime of 235 ps. In addition, our calculations confirm the identification of several clusters proposed in previous experimental studies
Nucleation stage in supersaturated vapor with inhomogeneities due to nonstationary diffusion onto growing droplets
No full textInternational audienceAn analytical description of the nucleation stage in a supersaturated vapor with instantly created supersaturation is given with taking into account the vapor concentration inhomogeneities arising as a result of depletion due to nonstationary diffusion onto growing droplets. This description is based on the fact, that the intensity of the nucleation of new droplets is suppressed in spherical diffusion regions of a certain size surrounding previously nucleated droplets, and remains at the initial level in the remaining volume of the vapor gas medium. The value of the excluded volume (excluded from nucleation) depends on the explicit form of the vapor concentration profile in the space around the growing droplet, and we use for that the unsteady self-similar solution of the time-dependent diffusion equation with a convective term describing the flow of the gas-vapor mixture caused by the moving surface of the single growing droplet. The main characteristics of the phase transition at the end of the nucleation stage are found and compared with those in the theory of nucleation with homogeneous vapor consumption (the theory of mean-field vapor supersaturation). It is shown that applicability of the mean-field approach depends on smallness of the square root of the ratio of the densities of metastable and stable phases. With increasing the temperature of the supersaturated vapor or for liquid or solid solutions, this smallness weakens, and then it would be more correct to use the excluded volume approach. (C) 2014 Elsevier B.V. All rights reserved
Synthesis of Poly(vinyl pyrrolidone)/Silver Nanoprism Composites through Simultaneous Photoinduced Polymerization and Electron Transfer Processes
No full textInternational audienceAn investigation into the in situ preparation of polymer/silver nanoprism composites is described. Photoinitiated polymerizations of N-vinyl pyrrolidone (NVP) in water using 2-hydroxy-2-methyl-1-phenyl propanone as photoinitiator under nitrogen and simultaneous redox reactions of AgNO3 resulted in the formation of poly(N-vinyl pyrrolidone) (PNVP)/silver nanocomposites. Prolonged irradiations at low photoinitiator concentration and equimolar concentrations of AgNO3 and NVP produced only spherical silver nanoparticles. The nanocomposites produced at high silver and photoiniatiator concentrations with short irradiation times e.g. 5 min contain polygonal (mainly triangular) silver nanoprisms as evidenced by spectral and TEM analysis
Search for excited quarks in the photon+jet final state in proton-proton collisions at sqrt(s) = 8 TeV
No full textSubmitted to Phys. Lett. B ; see paper for full list of authorsA search for excited quarks decaying into the photon+jet final state is presented. The analysis is based on data corresponding to an integrated luminosity of 19.7 inverse femtobarns collected by the CMS experiment in proton-proton collisions at sqrt(s)=8 TeV at the LHC. Events with photons and jets with high transverse momenta are selected and the photon+jet invariant mass distribution is studied to search for a resonance peak. The 95% confidence level upper limits on the product of cross section and branching fraction are evaluated as a function of the excited quark mass. Limits on excited quarks are presented as a function of their mass and coupling strength; masses below 3.5 TeV are excluded at 95% confidence level for unit couplings to their standard model partners
Generalized differential privacy: regions of priors that admit robust optimal mechanisms
No full textInternational audienceDifferential privacy is a notion of privacy that was initially designed for statistical databases, and has been recently extended to a more general class of domains. Both differential privacy and its generalized version can be achieved by adding random noise to the reported data. Thus, privacy is obtained at the cost of reducing the data's accuracy, and therefore their utility. In this paper we consider the problem of identifying optimal mechanisms for gen- eralized differential privacy, i.e. mechanisms that maximize the utility for a given level of privacy. The utility usually depends on a prior distribution of the data, and naturally it would be desirable to design mechanisms that are universally optimal, i.e., optimal for all priors. However it is already known that such mechanisms do not exist in general. We then characterize maximal classes of priors for which a mechanism which is optimal for all the priors of the class does exist. We show that such classes can be defined as convex polytopes in the priors space. As an application, we consider the problem of privacy that arises when using, for instance, location-based services, and we show how to define mechanisms that maximize the quality of service while preserving the desired level of geo- indistinguishability
TIR retrievals of CO<sub>2</sub>, N<sub>2</sub>O and CH<sub>4</sub> over the Arctic ocean from TANSO-FTS and comparison with IASI
No full textThe TANSO-FTS thermal infrared (TIR) spectra of GOSAT in band B4 are quite interesting to provide additional atmospheric information on what is available from the SWIR (B3 and B2) and NIR bands (B1). In this presentation the retrieval scheme based on the LARA radiative transfer and inversion algorithm will be presented for the determination of XCO2, XN2O and XCH4 from spectra recorded over the Arctic ocean during summer. This choice was made to characterize the TANSO-FTS performances in rather difficult conditions (large solar zenith angle (SZA) and cold surface), pushing the performances of TIR sounders to the limit. It also allows us to compare the performances of TANSO-FTS (high spectral resolution for the nominal L1B product of ~ 0.25 cm-1) with those of the lesser resolved Fourier transform space instrument IASI (L1C product of ~ 0.5 cm-1 resolution), which has a better noise figure. Comparisons of the two sounders are possible at high latitude where simultaneous off-nadir observations (SONO) are possible. Comparisons of the expected theoretical performances will be presented together with the actual performances on nearly coinciding SONO footprints (or IFOVs) of the two TIR sounders over water. The IFOVs where carefully filtered for clouds and the choice of Arctic ocean observations is reducing the uncertainties related to IFOV homogeneity. The retrieved surface temperatures Tsurf is used as a common diagnostic and is also compared to the L2 Eumetsat IASI product. A progress report on the issues related to the knowledge of the TANSO-FTS noise and instrument line shape (ILS) as well as spectroscopic issues with line-by-line parameters or heavy molecule cross-sections will be presented. Results will be presented for 2010 (the period of the SCORE-MIP exercises) and possibly for 2013 (to demonstrate that trends are indeed detectable with TANSO-FTS on GOSAT)
Infinitesimal invariants for cycles modulo algebraic equivalence and 1-cycles on Jacobians
No full textInternational audienceWe construct an infinitesimal invariant for cycles in a family with cohomology class in the total space lying in a given level of the Leray filtration. This infinitesimal invariant detects cycles modulo algebraic equivalence in the fibers. We apply this construction to the Ikeda family, which gives optimal results for the Beauville decomposition of the 1-cycle of a very general plane curve in its Jacobian
Ionospheric disturbance dynamo associated to a coronal hole: Case study of 5-10 April 2010
No full textInternational audienceIn this paper we study the planetary magnetic disturbance during the magnetic storm occurring on 5 April 2010 associated with high-speed solar wind stream due to a coronal hole following a coronal mass ejection. We separate the magnetic disturbance associated to the ionospheric disturbance dynamo (Ddyn) from the magnetic disturbance associated to the prompt penetration of magnetospheric electric field (DP2). This event exhibits different responses of ionospheric disturbance dynamo in the different longitude sectors (European-African, Asian, and American). The strongest effect is observed in the European-African sector. The Ddyn disturbance reduces the amplitude of the daytime H component at low latitudes during four consecutive days in agreement with the Blanc and Richmond's model of ionospheric disturbance dynamo. The amplitude of Ddyn decreased with time during the 4 days. We discuss its diverse worldwide effects. The observed signature of magnetic disturbance process in specific longitude sector is strongly dependent on which Earth's side faces the magnetic storms (i.e., there is a different response depending on which longitude sector is at noon when the SSC hits). Finally, we determined an average period of 22 h for Ddyn using wavelet analysis