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Performance of the CMS missing transverse energy reconstruction in pp data at sqrt(s) = 8 TeV
No full textSubmitted to JINST, see paper for full list of authorsInternational audienceThe performance of missing transverse energy reconstruction algorithms is presented using sqrt(s) = 8 TeV proton-proton (pp) data collected with the CMS detector. Events with anomalous missing transverse energy are studied, and the performance of algorithms used to identify and remove these events is presented. The scale and resolution for missing transverse energy, including the effects of multiple pp interactions (pileup), are measured using events with an identified Z boson or isolated photon, and are found to be well described by the simulation. Novel missing transverse energy reconstruction algorithms developed specifically to mitigate the effects of large numbers of pileup interactions on the missing transverse energy resolution are presented. These algorithms significantly reduce the dependence of the missing transverse energy resolution on pileup interactions. Finally, an algorithm that provides an estimate of the significance of the missing transverse energy is presented, which is used to estimate the compatibility of the reconstructed missing transverse energy with a zero nominal value
Measurement of the Z gamma production cross section in pp collisions at 8 TeV and search for anomalous triple gauge boson couplings
No full textSubmitted to JHEP - see paper for full list of authorsInternational audienceThe cross section for the production of Z gamma in proton-proton collisions at 8 TeV is measured based on data collected by the CMS experiment at the LHC corresponding to an integrated luminosity of 19.5 inverse femtobarns. Events with an oppositely-charged pair of muons or electrons together with an isolated photon are selected. The differential cross section as a function of the photon transverse momentum is measured inclusively and exclusively, where the exclusive selection applies a veto on central jets. The observed cross sections are compatible with the expectations of next-to-next-to-leading-order quantum chromodynamics. Limits on anomalous triple gauge couplings of Z Z gamma and Z gamma gamma are set that improve on previous experimental results obtained with the charged lepton decay modes of the Z boson
A space-averaged model of branched structures
No full textInternational audienceMany biological systems and artificial structures are ramified, and present a high geometric complexity. In this work, we propose a space-averaged model of branched systems for conservation laws. From a one-dimensional description of the system, we show that the space-averaged problem is also one-dimensional, represented by characteristic curves, defined as streamlines of the space-averaged branch directions. The geometric complexity is then captured firstly by the characteristic curves, and secondly by an additional forcing term in the equations. This model is then applied to mass balance in a pipe network and momentum balance in a tree under wind loading
In Vivo Single-Cell Detection of Metabolic Oscillations in Stem Cells
No full textInternational audienceThrough the use of bulk measurements in metabolic organs, the circadian clock was shown to play roles in organismal energy homeostasis. However, the relationship between metabolic and circadian oscillations has not been studied in vivo at a single-cell level. Also, it is unknown whether the circadian clock controls metabolism in stem cells. We used a sensitive, noninvasive method to detect metabolic oscillations and circadian phase within epidermal stem cells in live mice at the single-cell level. We observe a higher NADH/NAD+ ratio, reflecting an increased glycolysis/oxidative phosphorylation ratio during the night compared to the day. Furthermore, we demonstrate that single-cell metabolic heterogeneity within the basal cell layer correlates with the circadian clock and that diurnal fluctuations in NADH/NAD+ ratio are Bmal1 dependent. Our data show that, in proliferating stem cells, the circadian clock coordinates activities of oxidative phosphorylation and glycolysis with DNA synthesis, perhaps as a protective mechanism against genotoxicity
LHC Forward Physics
No full textéditeurs : N. Cartiglia et C. RoyonThe goal of this report is to give a comprehensive overview of the rich field of forward physics, with a special attention to the topics that can be studied at the LHC. The report starts presenting a selection of the Monte Carlo simulation tools currently available, chapter 2, then enters the rich phenomenology of QCD at low, chapter 3, and high, chapter 4, momentum transfer, while the unique scattering conditions of central exclusive production are analyzed in chapter 5. The last two experimental topics, Cosmic Ray and Heavy Ion physics are presented in the chapter 6 and 7 respectively. Chapter 8 is dedicated to the BFKL dynamics, multiparton interactions, and saturation. The report ends with an overview of the forward detectors at LHC. Each chapter is correlated with a comprehensive bibliography, attempting to provide to the interested reader with a wide opportunity for further studies
Conception in silico d'une nouvelle phase de carbure de bore
No full textThe goal of this work is to reinforce the boron carbide B 4 C in its use for shielding.This thesis has been devoted to the theoretical study of new boron carbides using abinitio methods based on the density functional theory (DFT) using the local densityapproximation (LDA) and generalized gradient approximation (GGA). These have firstbeen validated by comparing the calculated results with the experimental data on theboron carbide B 4 C. They were then used to design new materials.The idea was to reinforce C-B-C chains with respect to vacancies formation. In thenew material, (B 11 C p )C-C, chains are C-C. With the help of Wade’s ionic model, I havealso found that increasing the carbon concentration in the icosaedra, (B 10 C 2 )C-C, formsanother metastable phase. The concentration in the latter phase, 28.6% carbon concentra-tion, is however outside the domain of concentration were icosahedral phases are knownto exist.Once the structures were designed, the second step was to chek their (meta)stability.This required the calculation of their formation energies, their elastic constants and ofphonons dispersion curves. The third step was to check mechanical strengthening. To thisend, I have shown that these materials are less subject to vacancy formation, and thatvacancies can withstand a huge hydostatic pressure without a discontinuous change ofvolume, at variance with vacancies in B 4 C. The calculated elastic properties showed alarge increase in the bulk modulus, Young modulus and shear modulus.I have shown that different methods can be used to distinguish materials with C-Cchains, especially (B 11 C p )C-C, from B 4 C. These methods are the X-ray diffraction, Ramanand infrared vibrational spectroscopy. In particular, I have identified all of the modes of(B 11 C p )C-C by projecting their eigenvectors onto those of B 4 C and I have calculatedtheir Raman scattering spectrum in a polycrystalline average. I have also studied theRaman spectrum of B 4 C under pressure, and the results are in excellent agreement withexperiment. This enables me to confirm the mode identifications made at ambiant pressureand to understand the difference between calcultions in a monoclinic symmetry and theexperimental data which exhibit a rhombohedral average.In order to provide a method of synthesis, I then studied the phase transition that canoccur under pressure between the material (B 11 C p )CC ( represents a vacancy) andthe material (B 11 C p )C-C. A synthesis method has been elaborated in order to synthesizethis last material. This method is magnesiothermic reaction under high pressure.Le but de ce travail est de renforcer le carbure de bore à 20% d’atomes de carbone B 4 Cpour son utilisation pour le blindage. Cette thèse a été consacrée à l’étude théorique d’unenouvelle phase de carbure de bore à l’aide des méthodes ab initio basées sur la théoriede la fonctionnelle de la densité (DFT), en utilisant l’approximation de la densité locale(LDA) et du gradient généralisé (GGA). Les méthodes employées ont tout d’abord étévalidées en comparant les résultats calculés aux résultats expérimentaux sur le carbure debore B 4 C. Elles ont ensuite été utilisées pour concevoir de nouveaux matériaux.L’idée a été de renforcer les chaînes C-B-C par rapport à la formation de lacunes. Dansle nouveau matériau, (B 11 C p )C-C, les chaînes sont C-C. En me basant sur le modèle io-nique de Wade, j’ai aussi trouvé qu’augmenter la concentration en carbone sur l’icosaèdre,(B 10 C 2 )C-C, forme une deuxième phase métastable. La concentration obtenue (28% enatomes de carbone) sort toutefois du domaine connu d’existence des phases icosaédriques.Une fois les structures conçues, la deuxième étape a été de vérifier leur (méta)stabilité.Cela a nécessité le calcul de leurs énergies de formation, de leurs constantes élastiques etdes courbes de dispersion des phonons. La troisième étape a été de vérifier le renforcementmécanique. Pour cela, j’ai démontré que ces matériaux sont moins sujets à la formationde lacunes, et que les lacunes qui peuvent se former ne subissent pas de réduction dis-continue de volume sous pression hydrostatique contrairement à ce qu’il se passe pourB 4 C. De plus, les propriétés élastiques calculées ont montré une augmentation du moduled’incompressibilité, du module de Young et du module de cisaillement.J’ai montré que différentes méthodes peuvent permettre de différencier les matériaux àchaînes C-C, et plus particulièrement (B 11 C p )C-C, de B 4 C. Ces méthodes sont la diffrac-tion des rayons X et la spectroscopie vibrationnelle Raman et infrarouge. En particulier,j’ai identifié tous les modes propres de (B 11 C p )C-C en projetant leurs vecteurs propressur ceux de B 4 C et j’ai calculé leur spectre de diffusion Raman en moyenne polycris-talline. J’ai aussi étudié le spectre Raman de B 4 C sous pression et les résultats sont enexcellent accord avec l’expérience. Cela m’a permis de valider les identifications des modesréalisées à pression ambiante et de comprendre la différence entre le calcul en symétriemonoclinique et l’expérience en moyenne rhomboédrique.Dans le but de proposer une méthode de synthèse, j’ai ensuite étudié la transition dephase pouvant se produire sous pression entre le matériau (B 11 C p )CC ( représente unelacune) et le matériau (B 11 C p )C-C. Une méthode de synthèse a été élaborée dans le butde réaliser ce matériau. Cette méthode est une magnésiothermie sous haute pression
Signatures of solar event at middle and low latitudes in the Europe-African sector, during geomagnetic storms, October 2013
No full textInternational audienceThis paper presents the variability of the total electron content, VTEC, the ROTI index (proxy of the scintillation index) and the transient variations of the Earth's magnetic field associated to the impacts of solar events during October 2013. The observations are from middle and low latitudes in European African longitude sector. During October 2013, there are four solar events reaching the Earth. The two first events, on October 2 and October 8 are CME, the third event on October 14, is a jet of fast solar wind flowing from a solar coronal hole, and the last event on October 30 is a slow solar wind with southward excursions of the Bz component of the Interplanetary magnetic field, associated to CME passing near the Earth. For the four events, the variation of VTEC at middle latitudes is the same and presents an increase of VTEC at the time of the impact followed by a decrease of VTEC, lasting one or several days. At low latitudes, no clear common pattern for all the events appears. For the four events the variation of the ROTI index over Africa is different showing the asymmetry between West and East Africa. For the first event, on October 2, the scintillations are not inhibited, for the second and the fourth events on October 8 and 30, the scintillations are inhibited on East Africa and for the third event (high speed solar wind stream), on October 14, the scintillations are inhibited over the whole Africa. The available data allow the full explanation of the observations of October 14, indeed, on this day, there is no post sunset increase of the virtual height h'F2 at Ascension Island. There is no Pre Reversal Enhancement (PRE) of the eastward electric field; it is this electric field which moves up the F layer, the necessary condition for the existence of scintillation. The analysis of the variations of the Earth's magnetic field at low latitudes highlights the presence of the ionospheric disturbance dynamo on October 14, which produces a decrease of the Equatorial Electrojet, several hours after the impact of the high speed solar wind. The disturbance dynamo electric field (DDEF) is westward during the day and till after sunset and turns eastward around 22.30LT. So, on October 14, the westward DDEF inhibits the eastward regular electric field
Modélisation du transport d'oxygène dans le placenta humain
No full textThe efficient functioning of the human placenta is crucial for the favorable outcome of the pregnancy. This thesis aims at developing a mathematical model of respiratory gas exchange in the human placenta, which would improve our understanding of the relation between the structure and the function of the organ. Taking advantage of the precise 2D placental structure provided by the placental histology, we construct a 3D model of oxygen transport in the placenta by extending 2D histological cross-sections along the third dimension. The model simultaneously accounts for both diffusion and convention of oxygen in the intervillous space and allows us to predict the oxygen uptake of a placentone.In the first part of the thesis, the diffusion-convection equation governing oxygen exchange is numerically solved for different densities of circular fetal villi in a placentone. These calculations provide estimations of the oxygen uptake of a placentone with an arbitrary villi density and demonstrate the existence of an optimal villi density maximizing the uptake. This optimality is explained as a trade-off between the incoming oxygen flow and the absorbing villous surface.As a next step, the assumption of circular villi is relaxed and an approximate analytical solution is proposed for the diffusion-convection equation. It is shown that only two geometrical characteristics — the villi density and the effective villi radius — are required to predict the fetal oxygen uptake. Two combinations of physiological parameters that determine oxygen uptake in a given placenta are also identified: (i) the maximal oxygen inflow of a placentone, and (ii) the Damköhler number defined as the ratio of the transit time of the maternal blood through the intervillous space to a characteristic oxygen extraction time in a cross-section. Analytical formulas for fast and simple calculation of oxygen uptake are derived, and two diagrams of oxygen transport efficiency in an arbitrary placental cross-section are provided. The theory also suggests a method of how the results of artificial placenta perfusion experiments performed with no-hemoglobin blood can be recalculated to account for oxygen-hemoglobin dissociation. Finally, an automatic image analysis method is developed allowing one to analyze large histological human placenta cross-sections and to determine areas, perimeters and shapes of villous, intervillous space and fetal capillary compartments. These data can then be used as input data for the model. This method is applied to 25 cross-sections from 22 healthy and 3 pathological pregnancies. By combination of the obtained data with the described efficiency diagrams, it is demonstrated that the villi density of a healthy human placenta lies within 10% of the optimal value. The overall geometry efficiency of a healthy placenta was found to be rather low (around 30–40 %).In a perspective, the presented model can constitute the base of a reliable tool of assessment of oxygen exchange efficiency in the human placenta from histological measurements post partum, or, in a longer term, from non-invasive in utero measurements.L’efficacité de fonctionnement du placenta humain joue un rôle crucial dans la santé du nouveau-né. L’objectif principal de cette thèse est de développer un modèle mathématique de l’échange des gaz respiratoires au sein du placenta humain, afin d’améliorer la compréhension de la relation entre la structure et la fonction de cet organe. En exploitant la structure détaillée du placenta fournie par les méthodes d’histologie placentaire, nous construisons un modèle 3D du transport d’oxygène dans le placenta en prolongeant la géométrie des coupes histologiques 2D le long de la troisième dimension. Ce modèle est capable de prendre en compte simultanément la diffusion et la convection de l’oxygène dans l’espace intervillaire.Dans la première partie de la thèse, l’équation de diffusion-convection qui détermine l’échange d’oxygène est résolue numériquement pour diverses valeurs de densités de villosités à l’intérieur du placentone. Ces calculs fournissent une estimation de l’absorption d’oxygène d’un placentone pour une densité arbitraire de villosités, et permettent de mettre en évidence l’existence d’une densité optimale de villosités maximisant l’absorption d’oxygène. Cette optimalité peut être vue comme le résultat d’un équilibre entre l’arrivée d’oxygène par le flux entrant du sang maternel et l’absorption à la surface des villosités.À l’étape suivante, l’on s’affranchit de l’hypothèse d’une forme circulaire des villosités, et l’on propose une solution analytique approchée de l’équation de la diffusion-convection. Il est ensuite démontré que deux caractéristiques géométriques – la densité de villosités et le rayon efficace de villosités – suffisent à prédire l’absorption fœtale d’oxygène dans une géométrie donnée. La théorie identifie également deux combinaisons de paramètres physiologiques qui déterminent l’absorption d’oxygène : (i) le flux entrant maximal d’oxygène dans un placentone, et (ii) le nombre de Damköhler défini comme le rapport entre le temps de passage du sang maternel dans l’espace intervillaire et un temps caractéristique d’extraction d’oxygène dans une coupe transversale du modèle. Des formules analytiques permettant de calculer l’absorption d’oxygène d’une façon simple et efficace en sont déduites, et deux diagrammes d’efficacité du transport d’oxygène dans une coupe arbitraire de placenta sont tracés. La théorie analytique propose également une méthode permettant d’exploiter les résultats d’expériences sur la perfusion artificielle du placenta par un sang ne contenant pas d’hémoglobine, afin de prédire l’efficacité de transfert en intégrant cette fois l’interaction entre l’oxygène et l’hémoglobine.Au final, nous présentons une méthode d’analyse de grandes coupes histologiques de placenta humain, dans le but de mesurer de façon automatique les aires, les périmètres et la morphologie des régions de villosités, de l’espace intervillaire et des capillaires fœtaux. Ces données peuvent ensuite être introduites dans le modèle afin d’estimer l’efficacité du placenta. La méthode est appliquée à 25 coupes placentaires provenant de 22 grossesses saines et de 3 grossesses pathologiques. La combinaison des données obtenues avec les diagrammes d’efficacité montre que toutes les valeurs mesurées de la densité de villosités se retrouvent en écart relatif à moins de 10% de la valeur optimale. En revanche, l’efficacité globale correspond à une valeur assez basse (autour de 30–40 %).Dans l’avenir, le modèle présenté peut constituer la base d’un outil fiable de l’évaluation de l’efficacité d’échange d’oxygène au sein du placenta humain à partir de mesures histologiques post partum, ou, à plus long terme, à partir de mesures non-invasives in utero
6-Iso-chlortetracycline or keto form of chlortetracycline? Need for clarification for relevant monitoring of chlortetracycline residues in food
No full textInternational audienceChlortetracycline (CTC) is a broad-spectrum antibiotic used in veterinary medicine for pulmonary or digestive infections and having a regulatory maximum residue limit (MRL) necessitating an official analytical control method. The purpose of this study was to clarify the identification of different forms of CTC observed in standard solution, in spiked muscle samples and in naturally incurred muscle samples of pigs analysed by LC-MS/MS and to demonstrate the in vivo formation of 6-iso-chlortetracycline and 4-epi-6-iso-CTC as a metabolite of CTC and 4-epi-CTC in muscle. The six following forms were identified, all being isobaric with a protonated molecule at m/z 479 (precursor ion): the keto-enol forms of CTC and the keto-enol forms of 4-epi-chlortetracycline (4-epi-CTC), 6-iso-chlortetracycline (6-iso-CTC) and 4-epi-6-iso-chlortetracycline (4-epi-6-iso-CTC). The 6-iso-CTC and 4-epi-6-iso-CTC were observed only in incurred pig samples so were identified for the first time as metabolites of CTC and 4-epi-CTC. Identification of the different forms was obtained by comparing incurred muscle samples with standard solutions and with spiked samples. Then the differences between the features of the chromatograms obtained by LC-TQ-MS and the fragmentation study of the different forms of CTC obtained by LC-Q-TOF-MS helped us to support this identification. The extraction steps and the LC-MS/MS conditions developed to analyse muscle tissue samples are described. This clarification concerning the rigorous identification of chromatographic peaks allowed us to evaluate the relevance of our monitoring method with regard to the regulations in place in the European Union and could be of help to laboratories involved in official control of antibiotic residues in food of animal origin. Additional results are also presented highlighting the transformation of the CTC when prepared in a mixture with other antibiotics
X-ray absorption spectroscopy of iron at multimegabar pressures in laser shock experiments
No full textInternational audienceTaking advantage of the new opportunities provided by x-ray free electron laser (FEL) sources when coupled to a long laser pulse as available at the Linear Coherent Light Source (LCLS), we have performed x-ray absorption near-edge spectroscopy (XANES) of laser shock compressed iron up to 420 GPa (±50) and 10 800 K (±1390). Visible diagnostics coupled with hydrodynamic simulations were used to infer the thermodynamical conditions along the Hugoniot and the release adiabat. A modification of the pre-edge feature at 7.12 keV in the XANES spectra is observed above pressures of 260 GPa along the Hugoniot. Comparing with ab initio calculations and with previous laser-heated diamond cell data, we propose that such changes in the XANES pre-edge could be a signature of molten iron. This interpretation then suggests that iron is molten at pressures and temperatures higher than 260 GPa (±29) and 5680 K (±700) along the principal Fe Hugoniot