Tesis: "Branching rate"

1

Blauth, Jérôme [Verfasser]. "Infinite rate mutually catalytic branching driven by alpha-stable Lévy processes / Jérôme Blauth". Mainz : Universitätsbibliothek Mainz, 2017. http://d-nb.info/1125910283/34.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

2

Buras, Zachary J. (Zachary James). "Measuring rate constants and product branching for reactions relevant to combustion and atmospheric chemistry". Thesis, Massachusetts Institute of Technology, 2018. http://hdl.handle.net/1721.1/117862.

Texto completo

Resumen

Thesis: Ph. D., Massachusetts Institute of Technology, Department of Chemical Engineering, 2018.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages [383]-406).
Over the last century there have been countless experimental measurements of the overall reaction kinetics of gas-phase radicals, often with the aid of lasers. In more recent decades, ab initio predictions of product branching using quantum chemical calculations combined with modem rate theories have become common. However, there are few experimental measurements against which to validate predicted product branching, even for an important reaction system such as hydroxyl radical addition to acetylene that is critical to oxidation chemistry both in the atmosphere and in combustion. As a result, many of the kinetic parameters that appear in commonly used combustion mechanisms are based purely on predictions. The few experiments that do attempt to quantify product branching generally fall into two categories, each with unique advantages/disadvantages: crossed molecular beams (CMB) that simulate single collision conditions, or end-product analysis of a complex, thermalized process, such as pyrolysis. Laser flash photolysis (LFP) with molecular beam mass spectrometry (MBMS) offers a compromise between CMB and end-product experiments: the reaction conditions are thermalized but still simple enough that primary products can be quantified with confidence. This thesis describes a unique apparatus, and the improvements made to it, that combines LFP and MBMS for primary product branching quantification, as well as multiple-pass laser absorbance spectrometry (LAS) for accurate measurements of overall kinetics. The full capability of this LFP/MBMS/LAS apparatus is demonstrated for the chemically interesting phenyl radical + propene reaction system, which has been implicated as a potential source of second aromatic ring formation under combustion conditions. Overall kinetic measurements are also reported in this work either for systems that involve a newly discovered reactive species (various cycloaddition reactions of the simplest Criegee Intermediate formed in atmospheric ozonolysis) or that was disputed in the literature (vinyl radical + 1,3-butadiene, which has been implicated as a potential source of benzene in combustion). Finally, this thesis shows how detailed chemical insights made either experimentally or theoretically can be translated into applications via the Reaction Mechanism Generator (R4G). The application discussed is natural gas high temperature pyrolysis for the production of C2 commodity chemicals.
by Zachary J. Buras.
Ph. D.

Los estilos APA, Harvard, Vancouver, ISO, etc.

3

Pucheu, Mathilde. "Dimensional/Viscosimetric properties and branching rate of poly(sodium 2-acrylamido-2-methylpropane sulfonate) of high molar mass used for Enhanced Oil Recovery". Electronic Thesis or Diss., Pau, 2022. http://www.theses.fr/2022PAUU3077.

Texto completo

Resumen

Le pétrole est à la base du développement de notre société moderne, offrant accès à une source d'énergie abondante, bon marché et facilement transportable. Il est utilisé aussi bien pour la production d'électricité que pour les transports et représente la première source de matières premières pour l'industrie chimique. La production de pétrole est généralement assurée par des réservoirs matures exploités par injection d'eau dans un but de maintien de pression ou de balayage du réservoir. Pour améliorer l'efficacité de balayage du réservoir par l'eau injectée, la technique d'injection de polymères hydrosolubles a été développée. L'addition de polymère augmente la viscosité de l'eau injectée du pétrole par un balayage plus efficace du réservoir. Il est ainsi possible d'augmenter la production de pétrole tout en diminuant l'emprunte carbone. Les principaux polymères utilisés pour cette application sont de la famille des polyacrylamides. L'optimisation du procédé requiert une connaissance précise des relations structures-propriétés des polymères utilisés afin de mieux appréhender leurs propriétés viscosifiantes et de transport en milieu poreux. L'objectif est de mettre en place des méthodes analytiques pour la détermination de la distribution en masse molaire et du taux de ramification des polymères étudiés afin de pouvoir corréler les résultats obtenus aux propriétés rhéologiques et au comportement en filtration de leurs solutions. C'est pourquoi, dans le cadre de la thèse, quatre volets (WP pour work packaging) sont abordés afin de répondre au mieux à cette problématique concernant sa structure. Le premier volet (WP1) consiste à caractériser les différents polymères industriels à travers différents outils analytiques qui sont la Chromatographie d'Exclusion Stérique (Size Exclusion Chromatography (SEC)) couplée à un détecteur de diffusion de lumière multi-angle (Multi-Angle Light Scattering (MALS)) pour la taille (masse molaire, Mw, et rayon de giration, Rg), et la rhéologie capillaire pour la viscosité intrinsèque et les courbes d'écoulement (rhéogramme). Ensuite, vient le second volet (WP2) qui a pour but d'étudier le taux de ramification des polymères. Pour ce faire, deux approches analytiques vont être utilisées. La première est la Py-GC/MS, la pyrolyse (Py) couplée à la Chromatographie en Phase Gazeuse (Gaz Chromatography (GC)) couplée elle aussi à la Spectrométrie de Masse (Mass Spectrometry (MS)) afin d'évaluer la microstructure du polymère. La deuxième partie de ce volet est la comparaison des paramètres structuraux (Mw, Rg et viscosité intrinsèque) obtenus par analyses SEC-MALS, diffusion de la lumière (MALS) et rhéologie capillaire. Un système de mélange continu automatique (Automatic Continuous Mixing (ACM)) couplé au rhéomètre capillaire et au MALS sera développé pour faire des analyses en ligne de viscosité intrinsèque et de masse molaire. Ce développement instrumental fait l'objet du troisième volet (WP3). Pour finir, le quatrième volet (WP4) consiste à étudier les propriétés des polymères pendant la filtration
The knowledge of the dimensional properties (Mw, Rg, and the distributions), the viscosimetric properties ([η]), as well as, the branching rate of polymers is primordial for the implementation of a satisfactory Enhanced Oil Recovery (EOR) via polymer flooding. The principal objective of this thesis was to develop analytical methods in order to determine the characteristics of an optimized macromolecule developed by the SNF company, the poly(sodium 2-acrylamido-2-methylpropane sulfonate) (P(ATBS)). Two categories of P(ATBS) were studied: the models and the industrials. The models of high molar masses (1-6 million g/mol) were synthetized by Controlled Radical Polymerization (CRP), for which the branching was controlled by the addition of a crosslinking agent. While the industrials of higher molar masses (8-19 million g/mol) were obtained by Radical Polymerization (RP), for which the branching could be induced by chain transfer reactions. The characterization of the dimensional/viscosimetric properties and the branching rate for both P(ATBS) categories was performed by Size Exclusion Chromatography (SEC), Frit-Inlet Asymmetric Flow Field-Flow Fractionation (FIA4F), capillary viscometry and Multi-Angle Light Scattering (MALS). A correlation of the physico-chemical properties was done to understand the behaviour of the P(ATBS) in solution. A related study was done by Pyrolysis coupled to a Gaz Chromatography and a Mass Spectrometer (Py-GC/MS) for the qualitative and quantitative analyses of the P(ATBS). To this day, the P(ATBS) has never been studied by this technique

Los estilos APA, Harvard, Vancouver, ISO, etc.

4

Heyne, Joshua S. "Direct and Indirect Determinations of Elementary Rate Constants H + O2| Chain Branching; the Dehydration of tertiary-Butanol; the Retro Diels-Alder Reaction of Cyclohexene; the Dehydration of Isopropanol". Thesis, Princeton University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3642091.

Texto completo

Resumen

Due to growing environmental concern over the continued use of fossil fuels, methods to limit emissions and partially replace fossil fuel use with renewable biofuels are of considerable interest. Developing chemical kinetic models for the chemistry that affects combustion properties is important to understanding how new fuels affect combustion energy conversion processes in transportation devices. This thesis reports the experimental study of several important reactions (the H + O₂ branching reaction, the key decomposition reactions of tertiary-butanol, the dehydration reaction of isopropanol, and the retro Diels-Alder reaction of cyclohexene) and develops robust analysis methods to estimate the absolute uncertainties of specific elementary rate constants derived from the experimental data. In the study of the above reactions, both a direct and indirect rate constant determination technique with associated uncertainty estimation methodologies are developed.

In the study of the decomposition reactions, a direct determination technique is applied to experimental data gathered in preparation of this thesis. In the case of the dehydration reaction of tertiary-butanol and the retro Diels-Alder reaction of cyclohexene, both of which are used as internal standards for relative rate studies (Herzler et al. 1997) and chemical thermometry (Rosado-Reyes et al. 2013) , analysis showed an ∼20 K difference in the reaction rate between the reported results and the previous recommendations. In light of these discrepancies, an uncertainty estimation of previous recommendations illuminated an uncertainty of at least 20 K for the dehydration reaction of tertiary-butanol and the retro Diels-Alder reaction of cyclohexene, thus resolving the discrepancies.

The determination of the H + O₂ branching reaction and decomposition reactions of isopropanol used an indirect determination technique. The uncertainty of the H + O₂ branching reaction rate is shown to be underestimated by previous analysis (Hong et al. 2011, Turányi, et al. 2012), and the dehydration reaction of isopropanol is shown to be four times faster than theoretical predictions. Analyses of uncertainties for these reactions show that a linearized local sensitivity analysis does not completely capture uncertainties.

Appendix B in this thesis includes additional work conducted during the preparation of this thesis, namely the measurement of derived cetane numbers for jet fuel surrogates.

Los estilos APA, Harvard, Vancouver, ISO, etc.

5

Niclasen, Rune. "Measuring the branching ratio of the rare decay neutral pion going to electron-positron". Diss., Connect to online resource, 2006. http://gateway.proquest.com/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:3207725.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

6

Meyer, Anne. "Étude expérimentale des réactions ¹³N(a,p)¹⁶O et ³⁰P(p,g)³¹S, et impact sur les abondances isotopiques extrêmes en ¹³C, ¹⁵N et ³⁰Si dans les grains pré-solaires". Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS013.

Texto completo

Resumen

On retrouve dans les météorites primitives des grains qui se sont condensés dans différents environnements stellaires et sont restés intacts après la formation du système solaire. L'identification du site d'origine de ces grains pré-solaires est effectuée grâce à la comparaison entre les abondances isotopiques mesurées et celles prédites par les modèles stellaires. Nous présentons dans ce manuscrit les analyses de deux expériences effectuées à l'installation ALTO avec le spectromètre magnétique split-pole, visant à réduire les incertitudes associées à deux réactions jouant un rôle dans la production des isotopes utilisés pour identifier les grains de novæ. Ces derniers sont caractérisés par des abondances extrêmes en ¹³C, ¹⁵N et ³⁰Si, mais la découverte dans certains grains d'isotopes caractéristiques de la nucléosynthèse dans les supernovæ à effondrement de coeur (CCSN) a remis en question cette origine. La première étude concerne l'impact du taux de la réaction ¹³N(a,p)¹⁶O sur les abondances en ¹³C prédites par de récents modèles de CCSN. Nous procédons à une ré-évaluation du taux de cette réaction en utilisant une méthode Monte Carlo pour obtenir des incertitudes statistiques. Les largeurs partielles alpha des états du noyau composé ¹⁷F sont déterminées en se basant sur les propriétés des états analogues du noyau miroir ¹⁷O qui ont été mesurées en utilisant la réaction de transfert alpha ¹³C(7Li,t)¹⁷O. Nous nous intéressons ensuite à la réaction ³⁰P(p,g)³¹S, qui est une des dernières réactions dont l'incertitude du taux a un impact important sur les prédictions faites par les modèles de novæ classiques, notamment des abondances en ³⁰Si. Pour réduire les incertitudes sur les propriétés spectroscopiques du noyau composé ³¹S, une étude de la réaction ³¹P(³He,t)³¹S a été effectuée. Les tritons et les protons de décroissance venant des états peuplés du ³¹S ont été détectés simultanément à l'aide du spectromètre et de détecteurs silicium à pistes. L'étude des corrélations angulaires proton est présentée et les rapports de branchement extraits
Primitive meteorites contain several types of dust grains that condensed in different stellar environments and survived destruction in the early Solar System. The stellar sources where these presolar grains come from are identified through comparisons between measurements of isotopic abundances and predictions by stellar models. In this manuscript is presented a detailed analysis of two experiments performed at the ALTO facility, using the split-pole magnetic spectrometer, aiming at reducing the nuclear uncertainties associated to two reactions which rate uncertainty affects the synthesis of isotopes used to identify putative novae grains. These grains are characterised by extremely high ¹³C, ¹⁵N and ³⁰Si isotopic abundances, but isotopic signatures found in a few grains indicate also a possible core-collapse supernovae (CCSN) origin. We first study the impact of the ¹³N(a,p)¹⁶O reaction rate uncertainty on ¹³C abundances predicted by recent CCSN models. We perform a re-evaluation of this reaction rate using a Monte Carlo approach to obtain meaningful statistical uncertainties. Alpha partial widths of states in the ¹⁷F compound nucleus are determined using the spectroscopic informations of the analog states in the ¹⁷O mirror nucleus that were measured using the ¹³C(7Li,t)¹⁷O alpha-transfer reaction. We then study the ³⁰P(p,g)³¹S reaction, which is one of the few remaining reactions which rate uncertainty has a strong impact on classical novae model predictions, in particular for ³⁰Si abundances. To reduce the nuclear uncertainties associated to this reaction, we studied the ³¹P(³He,t)³¹S reaction. Triton and proton decays from the populated states in ³¹S were detected simultaneously using the spectrometer and silicon strip detectors. The study of the angular correlations of proton decays is presented and branching ratios are extracted

Los estilos APA, Harvard, Vancouver, ISO, etc.

7

Lavin, Dominic. "Branching fraction measurements of the rare B decays B°→K*⁺s⁻ and B°→K*⁰s⁰". Thesis, University of Edinburgh, 2004. http://hdl.handle.net/1842/11832.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

8

Redford, Sophie Eleanor. "The branching fraction and CP asymmetry of B±→Ψπ± and B±→π±μ+μ− decays". Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:5e903d02-9fd1-426f-a4ca-b1bad46b83ec.

Texto completo

Resumen

Two analyses are performed using data collected by the LHCb experiment during 2011. Both consider decays of charged B mesons reconstructed in the π±μ+μ− final state. Decays involving dimuons provide an experimentally clean signature, even in the high-background environment of the √s = 7 TeV proton-proton collisions at the LHC. The first analysis measures the CP asymmetry of B±→Ψπ± decays using 0.37 fb-1 of data, where the dimuon decays of two resonances are considered, J/ψ→μ+μ− and ψ(2S)→μ+μ−. The branching fraction is measured relative to the Cabibbo favoured B±→ΨK± mode. The second analysis uses 1 fb-1 of data to make the first observation of the non-resonant B±→π±μ+μ− decay. The branching fraction is measured relative to that of B±→K±μ+μ−, and measurements of the CP asymmetry and the ratio of CKM matrix elements Vtd/Vts are obtained. The branching fractions of the decays of interest are found to be B(B±→J/ψ π±) = (3.88 ± 0.11 ± 0.15) x 10-5, B(B±→ψ(2S) π±) = (2.52 ± 0.26 ± 0.15) x 10-5 and B(B±→π±μ+μ−) = (2.48 + 0.57 −0.52 ± 0.17) x 10-8, where the first uncertainty is related to the statistical size of the sample and the second quantifies systematic effects. The measured CP asymmetries in these modes are A CP (J/ψ π) = 0.005 ± 0.027 ± 0.011, A CP (ψ(2S) π) = 0.048 ± 0.090 ± 0.011 and A CP (μμπ) = -0.045 ± 0.220 ± 0.066, with no evidence of direct CP violation seen. The ratio of matrix elements is measured as Vtd/Vts = 0.274 + 0.031 − 0.028 ± 0.008, which is in agreement with previous results.

Los estilos APA, Harvard, Vancouver, ISO, etc.

9

Morin, Julien. "Etudes expérimentales des réactions des radicaux OH et des atomes d’oxygène d’intérêt pour l’atmosphère et la combustion". Thesis, Orléans, 2016. http://www.theses.fr/2016ORLE2034/document.

Texto completo

Resumen

L’objectif de ce travail consiste à étudier, d’une part, les réactions des nitrates d’alkyles avec OH qui ont un intérêt atmosphérique, et d’autre part, les réactions des radicaux OH avec les alcanes et des atomes d’oxygène avec les oléfines qui ont un intérêt pour la combustion. Toutes les réactions ont été étudiées dans des réacteurs à écoulement à basse pression, y compris le réacteur à écoulement à haute température mis en place dans le cadre de la thèse, couplés à un spectromètre de masse quadripolaire à ionisation par impact électronique. Pour les réactions OH + nitrate d’alkyle, la dépendance en température de la constante de vitesse a été mesurée pour dix nitrates d'alkyles, dont pour huit nitrates pour la première fois, sur une large plage de température. Pour six nitrates, les produits de la voie réactionnelle menant au recyclage direct de NO₂, arrachement d’atome H de carbone α, ont été observés et leur rendements mesurés. La grande quantité de données obtenues dans ce travail a été utilisée pour une mise à jour de la relation structure-activité (SAR) pour les réactions d'alkyles nitrates avec OH et a permis d'améliorer les modèles atmosphériques actuels. Les études de réactions de radicaux OH avec les trois alcanes et de l'atome O avec l’éthylène et le propène ont permis de déterminer les constantes de vitesse respectives sur une large gamme de température allant de 220 à 900 K. De plus, la distribution des produits de réactions multivoies O + oléfine en fonction de la température a été déterminée pour la première fois. Ces résultats permettront d’améliorer les modèles de combustion actuellement utilisés
The objective of this work was to study the reactions of alkyl nitrates with OH radicals relevant to atmosphere and reactions of OH radical with alkanes and oxygen atoms with olefins of interest for combustion chemistry. All reactions were studied in low pressure flow reactors (including high temperature flow reactor developed during the thesis) coupled to a quadrupole mass spectrometer with electron impact ionization. For OH reaction with nitrates, the temperature dependence of the rate constant was measured in an extended temperature range for ten alkyl nitrates, for eight of them for the first time. For six nitrates, the products of reaction pathway leading to direct recycling of NO₂ (H atom abstraction from α carbon) were observed and their yields were measured. The large amount of data obtained in this work has been used for an update of the structure-activity relation (SAR) for the reactions of alkyl nitrates with OH and will improve existing atmospheric models. For the reactions of OH radicals with three alkanes and O atoms with ethene and propene the rate constants were measured over a wide temperature range, 220-900 K. Moreover, the distribution of the products of the multichannel reactions O + olefin was determined as a function of temperature for the first time. These results are expected to improve current combustion models

Los estilos APA, Harvard, Vancouver, ISO, etc.

10

Griffith, Peter Noel. "First observation and branching fraction measurement of the rare decay ∧⁰b → pKμ⁺μ⁻ at the LHCb experiment, CERN". Thesis, University of Birmingham, 2017. http://etheses.bham.ac.uk//id/eprint/7446/.

Texto completo

Resumen

The analysis for the first observation and branching fraction measurement of the rare decay ∧$^0$$_b$ → pKμ$^+$μ$^-$ with respect to the control channel ∧$^0$$_b$ → J/ψ pK was performed. The analysis was kept blind in ∧$^0$$_b$ → pKμ$^+$μ$^-$ to avoid selection bias as this decay is unobserved. The data is from proton-proton collisions recorded by the LHCb experiment in 2011 and 2012, corresponding to an integrated luminosity of 1 fb$^-$$^1$ at 7 TeV and 2 fb$^-$$^1$ at 8 TeV respectively. A corrected yield of (7.83 ± 0.131 ± 0.648) x 10$^6$ ∧$^0$$_b$ → J/ψ Pk candidates was measured for the full 3 fb$^-$$^1$ and the analysis is currently under review by the LHCb Collaboration, awaiting approval to un-blind for the branching fraction measurement of ∧$^0$$_b$ → pKμ$^+$μ$^-$.

Los estilos APA, Harvard, Vancouver, ISO, etc.

11

Cakmak, Kerim Mehmet. "Model Independent Analysis Of Rare Exlusive B-meson Decays". Phd thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12604763/index.pdf.

Texto completo

Resumen

Using the general, model indepenent form of the effective Hamiltonian, the general expressions of the longitudinal, normal and transversal polarization asymmetries for l+ and l- for the effective B ->
K(K*)l+l- decays has been calculated. Existence of regions of Wilson coefficients for which the branching ratio coincides with the Standard Model result, while the lepton polarizations differ from the standard model prediction is expected. Hence, studying lepton polarizations in these regions of Wilson coefficients may be helpful in establishing new physics beyond standard model.

Los estilos APA, Harvard, Vancouver, ISO, etc.

12

Wang, Li [Verfasser]. "Impacts of genotypic variations in sulfur distribution and branching characteristics on nitrogen efficiency of oilseed rape (Brassica napus L.) / Li Wang". Kiel : Universitätsbibliothek Kiel, 2015. http://d-nb.info/1074870867/34.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

13

Sipica, Valentin [Verfasser]. "Prospects for measuring the branching ratio of the rare B 0 s my + my - decay with the ATLAS experiment / Valentin Sipica". Siegen : Universitätsbibliothek der Universität Siegen, 2011. http://d-nb.info/1023156768/34.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

14

MARTINI, MATTEO. "Measurement of the Ks->gg branching ratio using a pure Ks beam in the KLOE detector". Doctoral thesis, Università degli Studi di Roma "Tor Vergata", 2008. http://hdl.handle.net/2108/433.

Texto completo

Resumen

La ricerca del canale raro Ks->gg è stata eseguita con un campione di 2x10^9 decadimenti phi->KsKl collezionati a Dafne, con una luminosità integrata di 1.9fb^-1.I decadimenti del Ks vengono taggati attraverso le interazioni del Kl nel calorimentor elettromagnetico. Constraints cinemantici sono richiesti per ridurre l'iniziale campione di 6x10^5 eventi a 2740 candidati, da cui un segnale corrispondente a 711+/-35 eventi è estratto. Normalizzando il campione con i decadimenti del Ks->2p0 contati nello stesso campione di dati, misuriamo: BR(Ks->gg)=(2.26+/-0.12+/-0.06)x10^-6, in accordo con la predizione O(p^4) della ChPT
We have searched for the decay Ks->gg in a sample of 2x10^9 phi->KsKl decays collected at Dafne, with an integrated luminosity of 1.9fb^-1. Ks are tagged by the Kl interaction in the calorimeter. Two prompt photons must also be detected. Kinematic constraints reduce the initial 6x10^5 events to 2740 candidates, from which a signal of 711+/-35 events is extracted. By normalizing to the Ks->2p0 decays counted in the same sample, we measure: BR(Ks->gg)=(2.26+/-0.12+/-0.06)x10^-6, in agreement with O(p^4) ChPT prediction.

Los estilos APA, Harvard, Vancouver, ISO, etc.

15

Olivier, Adelaïde. "Analyse statistique des modèles de croissance-fragmentation". Thesis, Paris 9, 2015. http://www.theses.fr/2015PA090047/document.

Texto completo

Resumen

Cette étude théorique est pensée en lien étroit avec un champ d'application : il s'agit de modéliser la croissance d'une population de cellules qui se divisent selon un taux de division inconnu, fonction d’une variable dite structurante – l’âge et la taille des cellules étant les deux exemples paradigmatiques étudiés. Le champ mathématique afférent se situe à l'interface de la statistique des processus, de l’estimation non-paramétrique et de l’analyse des équations aux dérivées partielles. Les trois objectifs de ce travail sont les suivants : reconstruire le taux de division (fonction de l’âge ou de la taille) pour différents schémas d’observation (en temps généalogique ou en temps continu) ; étudier la transmission d'un trait biologique général d'une cellule à une autre et étudier le trait d’une cellule typique ; comparer la croissance de différentes populations de cellules à travers le paramètre de Malthus (après introduction de variabilité dans le taux de croissance par exemple)
This work is concerned with growth-fragmentation models, implemented for investigating the growth of a population of cells which divide according to an unknown splitting rate, depending on a structuring variable – age and size being the two paradigmatic examples. The mathematical framework includes statistics of processes, nonparametric estimations and analysis of partial differential equations. The three objectives of this work are the following : get a nonparametric estimate of the division rate (as a function of age or size) for different observation schemes (genealogical or continuous) ; to study the transmission of a biological feature from one cell to an other and study the feature of one typical cell ; to compare different populations of cells through their Malthus parameter, which governs the global growth (when introducing variability in the growth rate among cells for instance)

Los estilos APA, Harvard, Vancouver, ISO, etc.

16

Smith, Abraham Jeffrey. "Tissue Loss Syndromes in Acropora cervicornis off Broward County, Florida: Transmissibility, Rates of Skeletal Extension and Tissue Loss". NSUWorks, 2013. http://nsuworks.nova.edu/occ_stuetd/154.

Texto completo

Resumen

The high latitude thickets of Acropora cervicornis off Broward County flourish despite the presence of natural and anthropogenic impacts. These populations provided a unique study area in contrast to disease-stricken populations of the Florida Keys. This study used time-sequenced photographs to examine how A. cervicornis was affected by tissue loss attributed to white-band disease during 2007–2008. Variables monitored included healthy colony skeletal extension rates, diseased colony skeletal extension rates, and tissue loss. The transmissibility of the three white-band syndromes found in the Scooter and Oakland thickets was examined through tissue grafting experiments. Skeletal extension rates of healthy and diseased colonies were generally not significantly different. Mean skeletal extension for A. cervicornis colonies in Broward County was observed to be 9.6 cm/y (SD=3.95, Range: 1.02–19.9). Mean linear tissue loss from disease signs was 2.6 mm/d (SD=4.3, Range: 0.023–16.8). Although the majority of active disease lesions caused severe tissue loss upon contact with healthy branches, in 25% of the cases there was no tissue loss. Disease signs were also observed in 10% of the control grafting trials. A. cervicornis thickets in Broward County were growing at rates similar to those observed in this species elsewhere in Florida, but faster than other areas of the Western Atlantic. Tissue loss rate from disease lesions was lower than reported elsewhere. White-band disease and/or other tissue loss syndromes are always present in Broward County, but the low prevalence of affected colonies, inconsistent transmission of a presumptive agent that causes the disease signs, and optimum branch skeletal extension seems to limit effects on the thickets. Results of this research are significant as the current protected status of acroporid corals no longer allows manipulative research such as coral grafting for transmissibility of potential disease pathogens.

Los estilos APA, Harvard, Vancouver, ISO, etc.

17

Karyagina, Marina. "Life cycle cost modelling for fault-tolerant CNC architectures". Thesis, Queensland University of Technology, 1998.

Buscar texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

18

Lagnoux, Agnès. "Analyse des modeles de branchement avec duplication des trajectoires pour l'étude des événements rares". Toulouse 3, 2006. http://www.theses.fr/2006TOU30231.

Texto completo

Resumen

Nous étudions, dans cette thèse, le modèle de branchement avec duplication des trajectoires d'abord introduit pour l'étude des événements rares destiné à accélérer la simulation. Dans cette technique, les échantillons sont dupliqués en R copies à différents niveaux pendant la simulation. L'optimisation de l'algorithme à coût fixé suggère de prendre les probabilités de transition entre les niveaux égales à une constante et de dupliquer un nombre égal à l'inverse de cette constante, nombre qui peut être non entier. Nous étudions d'abord la sensibilité de l'erreur relative entre la probabilité d'intérêt P(A) et son estimateur en fonction de la stratégie adoptée pour avoir des nombres de retirage entiers. Ensuite, puisqu'en pratique les probabilités de transition sont généralement inconnues (et de même pour les nombres de retirages), nous proposons un algorithme en deux étapes pour contourner ce problème. Des applications numériques et comparaisons avec d'autres modèles sont proposés
This thesis deals with the splitting method first introduced in rare event analysis in order to speed-up simulation. In this technique, the sample paths are split into R multiple copies at various stages during the simulation. Given the cost, the optimization of the algorithm suggests to take the transition probabilities between stages equal to some constant and to resample the inverse of that constant subtrials, which may be non-integer and even unknown but estimated. First, we study the sensitivity of the relative error between the probability of interest P(A) and its estimator depending on the strategy that makes the resampling numbers integers. Then, since in practice the transition probabilities are generally unknown (and so the optimal resampling umbers), we propose a two-steps algorithm to face that problem. Several numerical applications and comparisons with other models are proposed

Los estilos APA, Harvard, Vancouver, ISO, etc.

19

Silva, Maria Alice Melo Rosa Tavares. ""Efeitos do tabagismo sobre o sistema cardiovascular: hemodinâmica e propriedades elásticas arteriais"". Universidade de São Paulo, 2005. http://www.teses.usp.br/teses/disponiveis/5/5159/tde-12012006-160621/.

Texto completo

Resumen

Objetivo Avaliar os efeitos do tabagismo sobre o sistema cardiovascular, através de metodologia não invasiva, analisando as alterações hemodinâmicas clínicas e propriedades elásticas arteriais, após exposição ao fumo. Métodos Estudo realizado em 45 voluntários sendo 18 (F) e 27 (M), fumantes T (n = 25, idade 40 ± 9 anos) e não fumantes NT (n = 20, idade 39 ± 9 anos), que foram submetidos a determinação do monóxido de carbono (CO) e avaliação das propriedades elásticas arteriais por ultrassonografia e teste de função endotelial (hiperemia reativa - HR) antes (B1) e após (B2) a exposição por 20 minutos a um cigarro ou à degustação de uma bala. Resultados Os grupos NT e T mostraram-se homogêneos. A concentração de CO no grupo T era maior do que no grupo NT em condições basais. A concentração de CO no grupo NT não variou antes e após à exposição proposta (bala) mas no grupo T aumentou de maneira significante após o cigarro. A pressão arterial sistólica (PAS) foi igual no B1 nos dois grupos, mas significativamente maior no B2 para o Gr T. A pressão arterial diastólica (PAD) no B1 e B2 não mostrou variação estatísticamente significante nos dois grupos. A freqüência cardíaca (FC) apresentou comportamento estatisticamente diferente nos dois grupos (NT apresentou redução e T apresentou aumento). Em relação às propriedades elásticas arteriais e resposta do fluxo regional: a complacência e a distensibilidade já se mostraram diferentes (p < 0,001) no período basal sendo maior no grupo NT comparado ao grupo T; mas após a HR 1 e 2, o grupo T mostrou elevação estatísticamente significante destas duas propriedades, sendo que o grupo NT não mostrou tais achados. O diâmetro máximo da artéria braquial mostrou-se aumentado em relação ao basal tanto após HR1 como após HR2 apenas no grupo T. O índice de fluxo total (IFT) não era diferente nos dois grupos no B1 e B2, mas após HR 1 e 2 ambos mostraram aumentos significantes (p < 0,001). Houve correlação positiva entre variáveis CO com PAD e FC no grupo T. No grupo NT não houve correlação do CO com PAS, PAD ou FC. Conclusão O tabagismo altera as propriedades elásticas das artérias e tem papel na hemodinâmica com provável participação do monóxido de carbono.
Objective to evaluate the effects of cigarette smoking on cardiovascular system, with non-invasive methodology, analysing hemodynamic disturbs and arterial elastic properties after being exposed to tobacco. METHODS This study was realized in 45 volunteers, 18 female and 27 male smokers T (n=25, age 40 ± 9 years) and non-smokers NT (n=20, age 39 ± 9 years), who were submitted to the determination of carbon monoxide (CO) to the evaluation of the arterial elastic properties by ultrassonography and test endotelial function (reactive hyperemia - HR) before (B1) and after (B2) the exposition for 20 minutes to a cigarette or a candy. RESULTS Both NT and T groups were similar.The CO concentration in the T group was higher than in the NT group on basal conditions. The CO concentration in the NT group have not changed before and after the proposed exposition (candy) but in the T group it was significant in creased after the cigarette exposition.The systolic blood pressure (PAS) was similar on B1 for both groups, but it was significantly higher on B2 for the T group. The diastolic blood pressure (PAD) on B1 and B2 didn´t exposition significant statistical variation on both groups. The cardiac frequency (FC) presented a different result for both groups with statistical significance ( NT had decrease and T had improved). Regarding the arterial elastic properties and the regional flux response: the complacence and the distensibility were different (p < 0,001) in the basal period and they were higher in the NT group compared to the T group. After HR 1 and 2, the T group showed a significant statistical increase of those two properties and the NT group didn´t show those results. The righest diameter of the brachial artery was increased in relation to the basal diameter after HR1 as well as after HR2 only in the T group. The total flux index (IFT) were not different in both groups in B1 and B2, but after HR1 and 2 both showed significant increase (p < 0,001). There was a positive correlation between the CO variations in relation to PAD and FC in the T group. In the NT group there was a no correlation of CO with PAS, PAD or FC. CONCLUSION Cigarette smoking changes the arterial elastic properties and it has a role in the hemodynamic with possible participation of the carbon monoxide

Los estilos APA, Harvard, Vancouver, ISO, etc.

20

Buridon, Victor. "Application de la spectrométrie de masse COINTOF à l'étude de la dissociation de petits agrégats d'eau protonés par collision sur un atome d'argon : développement d'une cible de nano-gouttes de gaz rare". Phd thesis, Université Claude Bernard - Lyon I, 2013. http://tel.archives-ouvertes.fr/tel-00994146.

Texto completo

Resumen

L'étude de l'irradiation dans le système moléculaire à l'échelle du nanomètre est un domaine d'investigation innovant des sciences des radiations. Le Dispositif d'Irradiation d'Agrégats Moléculaires (DIAM) est conçu en vue les conséquences de l'irradiation dans des petits systèmes moléculaires modèles comme les agrégats d'eau protonés. L'irradiation provoque la fragmentation en plusieurs fragments neutres ou chargés. La technique de spectrométrie de masse COINTOF (Correlated Ion and Neutral Time of Flight) permet la détection corrélées des fragments neutres et chargés issus de la dissociation d'un système moléculaire préalablement sélectionné en masse et en vitesse. Les données collectées sont traitées et structurées pour permettre l'analyse statistique des corrélations sur un grand nombre d'événements de fragmentation. Parallèlement à l'identification des canaux de fragmentation, la technique COINTOF permet la mesure de leur rapport de branchement et de leur section efficace. La méthode est présentée pour la dissociation induite par collision sur un atome d'argon, d'agrégats d'eau protonés H+(H2O)n:[2;7], accélérés à 8keV. L'efficacité de détection, information déterminante pour la production de données quantitatives, est mesurée à partir des données et étudiée en fonction de la distribution l'amplitude des signaux de détection. Enfin, un nouveau système de cible constituée de nanogouttes de gaz rares a été développé

Los estilos APA, Harvard, Vancouver, ISO, etc.

21

Oeler, Mario [Verfasser]. "Mutually catalytic branching at infinite rate / Mario Oeler". 2008. http://d-nb.info/991696964/34.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

22

Shaffer, W. K. Alex. "Kinetic modeling of catalyzed olefin polymerization with investigation of hydrogen & comonomer rate effects and branching via internal & terminal double bond polymerization". 1995. http://catalog.hathitrust.org/api/volumes/oclc/35112372.html.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

23

WANG, GUANG-CHANG y 王光昌. "Photodissication of potassium iodide by 193 nm excimer laser:studies on branching ratio of nascent potassium fragment in fine-structure states and their collisional mixing rate". Thesis, 1991. http://ndltd.ncl.edu.tw/handle/75034411017253488835.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

24

Mathis, Michelle. "Search for the Rare Decay $B_s^0 \to \mu^+ \mu^-$ at D0". Thesis, 2013. http://hdl.handle.net/1911/71999.

Texto completo

Resumen

Results of the search for the rare decay $B_s^0 \to \mu^+ \mu^-$ using data collected by the D0 detector at the Fermilab Tevatron collider are presented. This analysis covers the full Run II data set, corresponding to approximately 10.4~fb$^{-1}$ of integrated luminosity in $p\bar{p}$ collisions at a center of mass energy of 1.96 TeV. The analysis used new variables and a multivariate technique to improve the background reduction. After seeing fewer events than expected from background, a new Tevatron best observed limit was set on the branching fraction of the decay at $\cal{B}$($B_s^0 \to \mu^+ \mu^-$) $< 15 \times 10^{-9}$ ($12 \times 10^{-9}$) at the 95\% (90\%) C.L.

Los estilos APA, Harvard, Vancouver, ISO, etc.

25

Nahler, Nils Hendrik. "Photodissoziation von Halogenwasserstoff- und orientierten Wasserstoff-Edelgas-Halogen-Molekülen in Clusterumgebungen". Doctoral thesis, 2002. http://hdl.handle.net/11858/00-1735-0000-0006-B431-7.

Texto completo

Los estilos APA, Harvard, Vancouver, ISO, etc.

Tesis sobre el tema "Branching rate"

Crea una cita precisa en los estilos APA, MLA, Chicago, Harvard y otros