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Unprecedented directed lateral lithiations of tertiary carbons on NHC platforms
No full textInternational audienceUnexpected and unprecedented directed remote lateral lithiation at one CH(CH3)2 of the 3-(2,6-di-isopropylphenyl) wingtip took place upon the reaction of functionalised N-heterocyclic carbene-type molecules with excess of LiCH2SiMe3, leading to dilithiated dianionic 4-amido-N-heterocyclic carbenes. DFT calculations show that the nature of the isolated species are under thermodynamic control
Motion of proximal histidine and structural allosteric transition in soluble guanylate cyclase
No full textInternational audienceWe investigated the changes of heme coordination in purified soluble guanylate cyclase (sGC) by time-resolved spectroscopy in a time range encompassing 11 orders of magnitude (from 1 ps to 0.2 s). After dissociation, NO either recombines geminately to the 4-coordinate (4c) heme (τG1 = 7.5 ps; 97 ± 1% of the population) or exits the heme pocket (3 ± 1%). The proximal His rebinds to the 4c heme with a 70-ps time constant. Then, NO is distributed in two approximately equal populations (1.5%). One geminately rebinds to the 5c heme (τG2 = 6.5 ns), whereas the other diffuses out to the solution, from where it rebinds bimolecularly (τ = 50 μs with [NO] = 200 μM) forming a 6c heme with a diffusion-limited rate constant of 2 × 10(8) M(-1)⋅s(-1). In both cases, the rebinding of NO induces the cleavage of the Fe-His bond that can be observed as an individual reaction step. Saliently, the time constant of bond cleavage differs depending on whether NO binds geminately or from solution (τ5C1 = 0.66 μs and τ5C2 = 10 ms, respectively). Because the same event occurs with rates separated by four orders of magnitude, this measurement implies that sGC is in different structural states in both cases, having different strain exerted on the Fe-His bond. We show here that this structural allosteric transition takes place in the range 1-50 μs. In this context, the detection of NO binding to the proximal side of sGC heme is discussed
Efficiently Summarizing Distributed Data Streams over Sliding Windows
No full textGDD_HCERES2020Estimating the frequency of any piece of information in large-scale distributed data streams became of utmost importance in the last decade (\emph{e.g.}, in the context of network monitoring, big data, \emph{etc.}). If some elegant solutions have been proposed recently, their approximation is computed from the inception of the stream. In a runtime distributed context, one would prefer to gather information only about the recent past. This may be led by the need to save resources or by the fact that recent information is more relevant. In this paper, we consider the \emph{sliding window} model and propose two different (on-line) algorithms that approximate the items frequency in the active window. More precisely, we determine a -approximation meaning that the error is greater than only with probability . These solutions use a very small amount of memory with respect to the size of the window and the number of distinct items of the stream, namely, and bits of space, where is a parameter limiting memory usage. We also provide their distributed variant, \emph{i.e.}, considering the \emph{sliding window functional monitoring} model, with a communication cost of bits per window (where is the number of nodes). We compared the proposed algorithms to each other and also to the state of the art through extensive experiments on synthetic traces and real data sets that validate the robustness and accuracy of our algorithms
Measurement of jet quenching with semi-inclusive hadron-jet distributions in central Pb-Pb collisions at = 2.76 TeV
No full text37 pages, 12 captioned figures, 2 tables, authors from page 32, submitted to JHEP, figures at http://aliceinfo.cern.ch/ArtSubmission/node/1630 ; see paper for full list of authorsInternational audienceWe report the measurement of a new observable of jet quenching in central Pb-Pb collisions at TeV, based on the semi-inclusive rate of charged jets recoiling from a high transverse momentum (high-) charged hadron trigger. Jets are measured using collinear-safe jet reconstruction with infrared cutoff for jet constituents of 0.15 GeV/, for jet resolution parameters , 0.4 and 0.5. Underlying event background is corrected at the event-ensemble level, without imposing bias on the jet population. Recoil jet spectra are reported in the range GeV/. Reference distributions for pp collisions at TeV are calculated using Monte Carlo and NLO pQCD methods, which are validated by comparing with measurements in pp collisions at TeV. The recoil jet yield in central Pb-Pb collisions is found to be suppressed relative to that in pp collisions. No significant medium-induced broadening of the intra-jet energy profile is observed within 0.5 radians relative to the recoil jet axis. The angular distribution of the recoil jet yield relative to the trigger axis is found to be similar in central Pb-Pb and pp collisions, with no significant medium-induced acoplanarity observed. Large-angle jet deflection, which may provide a direct probe of the nature of the quasi-particles in hot QCD matter, is explored
Search for Violation of and Lorentz invariance in meson oscillations
No full text8 pages, 3 figures ; see paper for full list of authorsInternational audienceWe present the first search for CPT-violating effects in the mixing of mesons using the full Run II data set with an integrated luminosity of 10.4 fb of proton-antiproton collisions collected using the D0 detector at the Fermilab Tevatron Collider. We measure the CPT-violating asymmetry in the decay as a function of celestial direction and sidereal phase. We find no evidence for CPT-violating effects and place limits on the direction and magnitude of flavor-dependent CPT- and Lorentz-invariance violating coupling coefficients. We find 95\% confidence intervals of GeV and GeV
Comparison of the Z/gamma*+jets to gamma+jets cross sections in pp collisions at sqrt(s)= 8 TeV
No full textsee paper for full list of authorsInternational audienceA comparison of the differential cross sections for the processes Z/gamma*+jets and photon (gamma)+jets is presented. The measurements are based on data collected with the CMS detector at sqrt(s) = 8 TeV corresponding to an integrated luminosity of 19.7 inverse femtobarns. The differential cross sections and their ratios are presented as functions of pt. The measurements are also shown as functions of the jet multiplicity. Differential cross sections are obtained as functions of the ratio of the Z/gamma* pt to the sum of all jet transverse momenta and of the ratio of the Z/gamma* pt to the leading jet transverse momentum. The data are corrected for detector effects and are compared to simulations based on several QCD calculations
Arbres de régression et de classification (CART)
No full textNational audienceCes outils fournissent de nouvelles méthodes pour répondre aux problématiques des assureurs, notamment pour l'analyse des comportements des assurés et des prospects. Ils permettent de construire des classes de risques
Electrostatic free energies in translational GTPases: Classic allostery and the rest
No full textInternational audienceGTPases typically switch between an inactive, OFF conformation and an active, ON conformation when a GDP ligand is replaced by GTP. Their ON/OFF populations and activity thus depend on the stabilities of four protein complexes, two apo-protein forms, and GTP/GDP in solution. A complete characterization is usually not possible experimentally and poses major challenges for simulations. We review the most important methodological challenges and we review thermodynamic data for two GTPases involved in translation of the genetic code: archaeal Initiation Factors 2 and 5B (aIF2, aIF5B). One main challenge is the multiplicity of states and conformations, including those of GTP/GDP in solution. Another is force field accuracy, especially for interactions of GTP/GDP with co-bound divalent Mg2 + ions. The calculation of electrostatic free energies also poses specific challenges, and requires careful protocols. For aIF2, experiments and earlier simulations showed that it is a “classic” GTPase, with distinct ON/OFF conformations that prefer to bind GTP and GDP, respectively. For aIF5B, we recently proposed a non-classic mechanism, where the ON/OFF states differ only in the protonation state of Glu81 in the nucleotide binding pocket. This model is characterized here using free energy simulations. The methodological analysis should help future studies, while the aIF2, aIF5B examples illustrate the diversity of ATPase/GTPase mechanisms. This article is part of a Special Issue entitled Recent developments of molecular dynamics
Passerini/Tsuji-Trost strategies towards achieving lactams and cyclopentane derivatives.
No full textInternational audienceThe Passerini reaction of α,β-unsaturated aldehydes affords suitable substrates for the Tsuji-Trost reaction with various carbon based-nucleophiles. The resulting α,β-unsaturated amides may be cyclized to lactams or converted into cyclopentane derivatives if bis-nucleophiles are used in the Tsuji-Trost step
The effective confining potential of quantum states in disordered media
No full textThe amplitude of localized quantum states in random or disordered media may exhibit long range exponential decay. We present here a theory that unveils the existence of an effective potential which finely governs the confinement of these states. In this picture, the boundaries of the localization subregions for low energy eigenfunctions correspond to the barriers of this effective potential, and the long range exponential decay characteristic of Anderson localization is explained as the consequence of multiple tunneling in the dense network of barriers created by this effective potential. Finally, we show that the Weyl's formula based on this potential turns out to be a remarkable approximation of the density of states for a large variety of 1D systems, periodic or random