To see the other types of publications on this topic, follow the link: SNN.
Dissertations / Theses on the topic 'SNN'
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'SNN.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Parana-Liyanage, Krishani. "Outlier detection in spatial data using the m-SNN algorithm." DigitalCommons@Robert W. Woodruff Library, Atlanta University Center, 2013. http://digitalcommons.auctr.edu/dissertations/1299.
Full textAbstract:
Outlier detection is an important topic in data analysis because of its applications to numerous domains. Its application to spatial data, and in particular spatial distribution in path distributions, has recently attracted much interest. This recent trend can be seen as a reflection of the massive amounts of spatial data being gathered through mobile devices, sensors and social networks. In this thesis we propose a nearest neighbor distance based method the Modified-Shared Nearest Neighbor outlier detection (m-SNN) developed for outlier detection in spatial domains. We modify the SNN technique for use in outlier detection, and compare our approach with the widely used outlier detection technique, the LOF Algorithm and a base Gaussian approach. It is seen that the m-SNN compares well with the LOF in simple spatial data distributions and outperforms it in more complex distributions. Experimental results of using buoy data to track the path of a hurricane are also shown.
2
Itani, Aashish. "COMPARISON OF ADVERSARIAL ROBUSTNESS OF ANN AND SNN TOWARDS BLACKBOX ATTACKS." OpenSIUC, 2021. https://opensiuc.lib.siu.edu/theses/2864.
Full textAbstract:
n recent years, the vulnerability of neural networks to adversarial samples has gained wide attention from machine learning and deep learning communities. Addition of small and imperceptible perturbations to the input samples can cause neural network models to make incorrect prediction with high confidence. As the employment of neural networks on safety critical application is rising, this vulnerability of traditional neural networks to the adversarial samples demand for more robust alternative neural network models. Spiking Neural Network (SNN), is a special class of ANN, which mimics the brain functionality by using spikes for information processing. The known advantages of SNN include fast inference, low power consumption and biologically plausible information processing. In this work, we experiment on the adversarial robustness of the SNN as compared to traditional ANN, and figure out if SNN can be a candidate to solve the security problems faced by ANN.
3
Parker, William Chesluk. "CENTRALITY DEPENDENCE OF BULK FIREBALL PROPERTIES IN /Snn=62.4 and 200 GeV." Thesis, The University of Arizona, 2009. http://hdl.handle.net/10150/192559.
Full text
4
Zapata, Rodriguez Mireya. "Arquitectura escalable SIMD con conectividad jerárquica y reconfigurable para la emulación de SNN." Doctoral thesis, Universitat Politècnica de Catalunya, 2017. http://hdl.handle.net/10803/461085.
Full textAbstract:
A biological neural system consists of millions of highly integrated neurons with multiple dynamic functions operating in coordination with each other. Its structural organization is characterized by highly hierarchical assemblies. These assemblies are distinguished by locally dense and globally ispersed connections communicated by spikes traveling through the axon to the target neuron. In the last century, approaching the biological complexity of the cortex by means of hardware architectures has continued to be a challenge still unattainable. This is not only due to the massively parallel processing with support for the communication between neurons in large-scale networks, but also for the need of mechanisms that allow the evolution of the neural network efficiently.
In this context, this thesis contributes to the development of an architecture called HEENS (Hardware Emulator of Evolved Neural System), which supports inter-chip connectivity with a ring topology between a Master Chip (MC) controlling one or more Neuromorphic Chips (NCs). The MC is implemented in a PSoC device that integrates a CPU ARM Dual Core together with programmable logic. The ARM is responsible for setting up the communication ring and executing the software application that controls the data configuration transmission from the algorithm and the neural parameters to all NCs in the network. Besides, the MC is in charge of activating the evolution mode of the network, as well as managing the dispatching of reconfiguration data to any of the nodes during the execution.
Each NC, in turn, consists of a configurable 2D array of Processing Elements (PEs) with a SIMD-like processing scheme implemented on a Kintex7 FPGA. NCs are SNN multiprocessors that support the execution of any neural algorithm based on spikes. A set of custom instructions was designed specifically for this architecture. The NCs support a hierarchical scheme of local and global spikes to mimic the brain structural configuration. Local spikes establish inter-neuronal connectivity within a single chip and the global ones allow inter-modular communication between different chips. The NCs have fixed hub neurons that process local and global spikes, thus allowing inter-modular and intra-modular connectivity. This definition of local and global spikes allows the development of multi-level hierarchical architectures inspired by the brain
topologies, and offers excellent scalability.
The spike propagation through the multi-chip network is supported by an Aurora / AER-SRT protocol stack.
The Aurora protocol encapsulates and de-capsulates the packets transmitted through a high-speed serial link that communicates the platform, while the Synchronous Address Event representation (AER-SRT) protocol manages the data (address events) and controls packets that allow synchronization of the operation of the
neural network. Each event encapsulates the address neuron that fires a spike as result of the neural algorithm execution.
The definition of local and global synaptic topology is implemented using on-chip RAM blocks, which reduces the combinational logic requirements and, in addition to allowing the dynamic connectivity configuration, permits the development of evolutionary applications by supporting the on-line reconfiguration of both the neural algorithm or the neural and synaptic parameters. HEENS also supports axon programmable delays, which incorporates dynamic features to the network.Un sistema neuronal biológico consiste de millones de neuronas altamente integradas con múltiples funciones dinámicas operando en coordinación entre sí. Su organización estructural se caracteriza por contener agrupaciones altamente jerárquicas. Dichas agrupaciones se distinguen por conexiones localmente densas y globalmente dispersas comunicadas a través de pulsos transitorios (spikes) que viajan por el axón hasta la neurona destino. En el último siglo, aproximarse a la complejidad biológica del cortex mediante arquitecturas de hardware continúa siendo un desafío todavía inalcanzable. Esto se debe, no sólo al masivo procesamiento paralelo con soporte para la comunicación entre neuronas en redes de gran escala, sinó también a la necesidad de mecanismos que permitan la evolución de la red neuronal de forma eficiente. En este marco, esta tesis contribuye al desarrollo de una arquitectura denominada HEENS (Emulador de Hardware para Sistemas Neuronales Evolutivos, Hardware Emulator of Evolved Neural System) que soporta conectividad inter-chip con una topología de anillo entre un chip que actúa de master (MC) y uno o más Chips Neuromórficos (NCs). El MC está implementado en un dispositivo PSoC que integra un CPU ARM Dual Core junto con lógica programable. El ARM se encarga de configurar el anillo de comunicación y de ejecutar la aplicación de software que controla el envío de información de configuración del algoritmo y los parámetros neuronales a todos los NCs de la red. Además, el MC es el encargado de activar el modo de evolución de la red, así como de gestionar el envío de datos de reconfiguración a cualquiera de los nodos durante la ejecución. Cada NC a su vez, está compuesto por un arreglo 2D parametrizable de Elementos de Procesamiento (Processing Elements, PEs) con un esquema de procesamiento tipo SIMD implementado sobre una FPGA Kintex7. Los NCs son multiprocesadores SNN que soportan la ejecución de cualquier algoritmo neuronal basado en spikes. Se cuenta con un set de instrucciones personalizadas diseñadas específicamente para esta arquitectura. Imitando la configuración estructural del cerebro los NC soportan un esquema jerárquico con spikes locales y globales. Los spikes locales establecen la conectividad inter-neuronal dentro de un mismo chip, y los globales la comunicación inter-modular entre diferentes chips. Los NC cuentan con neuronas fijas tipo hub que procesan spikes locales y globales que permiten la conectividad inter e intra modulos. La definición de spikes locales y globales permite desarrollar arquitecturas jerárquicas multi-nivel que se inspiran en las topologías del cerebro y ofrecen una escalabilidad excelente. La propagación de spikes a través de la red multi-chip es soportada por una pila de protocolos Aurora/AER-SRT. El protocolo Aurora encapsula y desencapsula los paquetes transmitidos a través del enlace serial de alta velocidad que comunica la plataforma. Mientras que el protocolo Síncrono de Representación de Eventos de Dirección (AER-SRT) gestiona los datos (eventos de dirección) y los paquetes de control que permiten sincronizar la operación de la red neuronal. Cada evento encapsula la dirección de la neurona que genera un spike como resultado del procesamiento del algoritmo neuronal. La definición de topología sináptica local y global es implementada usando bloques de memoria RAM on-chip, lo que reduce los requerimientos de lógica combinacional y, además de facilitar la configuración del conexionado sin modificar el hardware, permite el desarrollo de aplicaciones evolutivas al soportar la reconfiguración on-line tanto del algoritmo neuronal como de los parámetros neuronales y sinápticos. HEENS también admite retardos programables de axón, lo cual incorpora características dinámicas a la red.
5
Johnson, Ian Jeffrey. "Photon and [pi]⁰ production in ¹⁹⁷Au+¹⁹⁷Au collisions at [square root]SNN=130GeV /." For electronic version search Digital dissertations database. Restricted to UC campuses. Access is free to UC campus dissertations, 2002. http://uclibs.org/PID/11984.
Full text
6
Quintero, Amilkar. "MEASUREMENT OF CHARM MESON PRODUCTION IN Au+Au COLLISIONS ATsqrt(SNN) =200 GeV." Kent State University / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=kent1460734511.
Full text
7
Appelt, Eric. "Measurements of Charged-Particle Transverse Momentum Spectra in PbPb Collisions at Square Root of SNN = 2|76 TeV and in pPb Collisions at Square Root of SNN = 5|02 TeV with the CMS Detector." Thesis, Vanderbilt University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3584408.
Full text
8
Ahmed, Samah. "Measurement of Neutral Mesons in p-Pb collisions at √sNN = 8.16TeV with the ALICE detector." Master's thesis, Faculty of Science, 2019. http://hdl.handle.net/11427/31492.
Full textAbstract:
The measured transverse momentum spectra of neutral pion π 0 and η mesons are presented for p-Pb collisions at √ sNN = 8.16 TeV using the photon conversion method for the signal extraction. This method uses the tracking and particle identification capabilities of the central barrel detectors of ALICE. Signal extracted down to 0.3 GeV/c and 0.7 GeV/c for π 0 and η respectively. The resulting spectra are presented and systematic uncertainties have been evaluated. A suppression of the yield compared to pp collisions at the same center of mass energy is observed in RpA for both mesons. Comparisons to theory predictions show consistency with the spectra and RpA.
9
Castillo, Javier. "Production de particules doublement étranges dans les collisions d'ions lourds ultra-relativistes à √SNN = 130 GeV." Paris 7, 2002. http://www.theses.fr/2002PA077043.
Full text
10
Raisig, Pascal [Verfasser], Harald [Gutachter] Appelshäuser, and Christoph [Gutachter] Blume. "J/ψ production in √sNN = 5.02 TeV Pb−Pb collisions / Pascal Raisig ; Gutachter: Harald Appelshäuser, Christoph Blume." Frankfurt am Main : Universitätsbibliothek Johann Christian Senckenberg, 2020. http://d-nb.info/1212509749/34.
Full text
11
Faustino, Bruno Filipe Fernandes Simões Salgueiro. "Implementation for spatial data of the shared nearest neighbour with metric data structures." Master's thesis, Faculdade de Ciências e Tecnologia, 2012. http://hdl.handle.net/10362/8489.
Full text
12
Navarro, Jose Luis La Rosa. "Estudo da multiplicidade de partículas carregadas em colisões centrais Pb+Pb a SNN = 2.76 TeV no experimento ATLAS." Universidade de São Paulo, 2012. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-26032013-152519/.
Full textAbstract:
Dentre os observáveis globais que permitem caracterizar a colisão entre íons pesados relativísticos, a multiplicidade de partículas é uma das variáveis mais fundamentais, diretamente ligada à densidade de energia da colisão. Serão apresentados resultados do estudo de multiplicidade de partículas carregadas para colisões centrais entre íons de chumbo a energias de 2.76 TeV (energia no centro de massa) utilizando o detector ATLAS no Large Hadron Collider (LHC). A multiplicidade na produção de partículas carregadas é medida utilizando dois métodos diferentes entre o intervalo de pseudorapidez || < 2.5 empregando o sistema de detectores semicondutores centrais de trajetórias do ATLAS. A seleção de eventos é crucial para esta análise e é aplicada a dados obtidos através de um trigger de minimum bias, impondo-se a coincidência entre o sinal do calorímetro de zero grau (ZDC) (|| > 8.3) e a coincidência entre o sinal do Minimum Bias Trigger Scintilator (MBTS) (2.1< || <3.8), de forma a remover da amostra de dados os eventos decorrentes da dissociação eletromagnética. Neste trabalho, eventos produzidos pelo gerador de eventos HIJING também foram analisados e os dados simulados reconstruídos utilizando-se os mesmos algoritmos empregados na análise dos dados reais. A multiplicidade e a densidade inclusiva de partículas foram medidas para as colisões mais centrais e estão em bom acordo com os resultados obtidos por outros experimentos.From the global observables that allows the characterization of the heavy ion collisions at relativistic energies, the particle multiplicity is one of the most fundamental observables, directly related to the energy density of the collision. There will be presented results about the study of central collision charged particle multiplicity in Pb - Pb collisions at the 2.76 TeV center of mass energy using the ATLAS detector at the Large Hadron Collider (LHC). The particle multiplicity is measured using two different methods in the || < 2:5 rapidity interval, deploying the ATLAS inner tracker semiconductor system. The event selection plays a crucial role in this analysis and is applied on data acquired using a minimum bias trigger. Imposing the condition of coincidence between the two Zero Degree Calorimeters (ZDC) arms (|| > 8.3) and the coincidence of the Minimum Bias Trigger Scintillator (MBTS) detector (2.1 < || <3.8) the electromagnetic dissociation events are removed from the sample. For this work, events produced by the HIJING event generator were also analyzed and the simulated data was reconstructed using the same algorithms used on data. The multiplicities and inclusive particle density measured for most central collisions are in good agreement with the ones measured by other experiments.
13
Lima, Caio Eduardo Ferreira. "Estudo da energia transversal eletromagnética em colisões Pb-Pb a √SNN = 2.76 TeV com o experimento ALICE." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-04072017-154951/.
Full textAbstract:
A física de altas energias, mais especificamente o estudo de colisões entre de íons pesados relativísticos tem como objetivo o estudo do comportamento de quarks e glúons em condições extremas de temperatura, pressão e densidade. Tais condições levam à formação de um novo estado da matéria chamado Plasma de Quarks e Glúons (QGP, do inglês Quark-Gluon Plasma). Medidas de observáveis globais tem sido usadas como uma importante ferramenta para a caracterização desse novo estado. Entre esses observáveis, a energia transversal por unidade de rapidez (dET/dy) das partículas emitidas em uma colisão entre íons pesados pode ser usada como evidência da formação do QGP. Este trabalho propõe um procedimento para obtenção da energia transversal eletromagnética, que é um importante componente da energia transversal total, em colisões Pb-Pb no experimento ALICE no LHC. O estudo foi feito através de simulações de Monte Carlo e validou o procedimento proposto com uma diferença sistemática em função da centralidade em torno de 2%.High energy physics with heavy ion collisions studies quarks and gluons under extreme conditions of temperature, pressure and density. Such conditions lead to the formation of a new state of matter called the Quark-Gluon Plasma (QGP). The measurement of global observables have been used as an important tool for the characterization of this new state. Among these observables, the transverse energy per unit of rapidity (dET/dy) from particles emitted in a heavy ion collision can be used as evidence of QGP formation. The work proposes a procedure to obtain the transverse electromagnetic energy, an important component of total transverse energy, in Pb-Pb collisions measured by the LHC-ALICE experiment. The study was done using Monte Carlo simulations, and validated the proposed procedure with a systematic difference as function of the centrality around 2%.
14
Ronflette, Lucile. "Isolated photon production in p-Pb collisions at √ sNN = 5.02 TeV with the ALICE experiment at the LHC." Thesis, Nantes, 2016. http://www.theses.fr/2016NANT4062.
Full textAbstract:
La chromodynamique quantique est la théorie associée à l’ interaction forte dans le modèle standard. Elle prédit le confinement des partons (quarks et gluons) à l’ intérieur des hadrons dans des conditions thermodynamiques standards. Lorsque des hautes densités d’énergie sont mises en jeu, un état de déconfinement de la matière hadronique, le plasma de Quarks et Gluons (PQG), est prédit par la théorie. Cet état aurait existé aux premiers instants de l’ Univers. L ’ expérience ALICE (A Large Ion Collider Experiment) au CERN-LHC est dédiée à l’ étude de la matière hadronique dans les collisions pp, p-Pb et dans les collisions Pb-Pb où la formation d’un PQG est attendue. Dans cette thèse, nous présentons l’étude des photons issus des interactions dures entre partons. Leur section efficace de production est calculable dans le cadre de la chromodynamique quantique perturbative. Une telle mesure effectuée dans les collisions p-Pb, permet d’ étudier les effets nucléaires froids. Expérimentalement, les photons prompts sont mesurés en utilisant la méthode de l’isolement. La mesure de la section efficace des photons isolés dans les collisions p-Pb à √ sNN = 5.02 TeV avec le calorimètre EMCal de l’ expérience ALICE est présentée. Les résultats sont consistants avec les calculs théoriques effectués. La comparaison avec la section efficace mesurée dans les collisions pp a été réalisée via la détermination du facteur de modification nucléaire, RpΑ. Ce dernier est compatible avec l’unité et n’indique aucune modification claire, due à des effets nucléaires, de la production de photons prompts dans les collisions p-PbQuantum ChromoDynamics is the theory associated to the strong interaction in the standard model. It predicts that partons (quarks and gluons) are confined into hadrons at standard thermodynamic conditions. A state of deconfined hadronic matter, the Quark-Gluon Plasma (QGP), is predicted for a high energy density and would have existed in the early state of the Universe. ALICE (A Large Ion Collider Experiment) at CERN-LHC (Large Hadron Collider) is dedicated to hadronic matter study in p-p, p-Pb (Pb-p) and in Pb-Pb collisions where QGP formation is expected. In this thesis, we will present the study of photons coming directly from parton-parton hard scatterings, the prompt photons. Their production cross-section is calculable in perturbative Quantum ChromoDynamics theory. Such a measurement in p-Pb collisions enables the study of cold nuclear matter effects whose knowledge is crucial to distinguish key signatures of the QGP from nuclear effects in Pb-Pb collisions. Experimentally, the prompt photon can be discriminated using the isolation analysis method. In this thesis, the measurement of the isolated photon cross-section in p- Pb collisions at √ sNN= 5.02 TeV with the EMCal calorimeter of the ALICE experiment, is presented. The results are consistent, within the uncertainties, with theoretical calculations. The comparison with the measured cross-section in p-p analysis is performed via the determination of the nuclear modification factor RpΑ. The last one is compatible with the unity and does not clearly indicate modification of the prompt photon production due to nuclear effects in p-Pb collisions
15
Asano, Hidemitsu. "Nuclear modification of electron yields from charm and bottom hadrons in Au+Au collisions at √SNN = 200 GeV." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215299.
Full text
16
Onderwaater, Jacobus [Verfasser], Anton [Akademischer Betreuer] Andronic, and Guy [Akademischer Betreuer] Moore. "Charge correlations and collective dynamics in Pb-Pb collisions at √sNN=2.76 TeV / Jacobus Onderwaater ; Anton Andronic, Guy Moore." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2017. http://d-nb.info/1143827449/34.
Full text
17
Bickley, Abigail Anne. "Charged Antiparticle to Particle Ratios Near Midrapidity in d+Au and p+p Collisions at sqrt(sNN) 200 GeV /." College Park, Md. : University of Maryland, 2004. http://hdl.handle.net/1903/1943.
Full textAbstract:
Thesis (Ph. D.)--University of Maryland, College Park, 2004.Thesis research directed by: Chemistry. Title from t.p. of PDF. Includes bibliographical references. Published by UMI Dissertation Services, Ann Arbor, Mich. Also available in paper.
18
Silva, Antonio Carlos Oliveira da. "Medida de produção de Dº em jatos em colisões PbPb a SNN = 5.02 TeV com o ALICE no LHC." Universidade de São Paulo, 2017. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-25022018-102658/.
Full textAbstract:
Quarks charm são criados em estágios iniciais da colisão de íons pesados em processos de espalhamento duro. Portanto eles são sondas ideais para o Plasma de Quarks e Glúons (QGP), que é um estado da matéria em que os partons contidos em hadrons, em condições de alta temperatura (150 MeV) ou densidade (cerca de cinco vezes a densidade da matéria ordinária), passam para um estado livre de quarks e glúons. A fragmentação de quarks charm pode produzir mésons D. Jatos contendo um méson D como um de seus constituentes podem ser identificados como originados de uma fragmentação de quark pesado. Jatos contendo mésons D são valiosas ferramentas para caracterizar interações de quarks charm com o plasma. Jatos de charm podem fornecer informações para o estudo da perda de energia dependente da massa pela medida da modificação da produção de jatos de charm em colisões de núcleos de chumbo com respeito a colisões entre prótons em função do momento transversal dos jatos. Além disso, uma visão mais profunda pode ser obtida com a medida da distribuição da fração de momento, que é de particular interesse para investigar a possível influência do meio na fragmentação de quarks charm em jatos. Mésons D são reconstruídos através da análise de massa invariante de seu canal de decaimento hadrônico, rejeitando uma grande quantidade de fundo combinatório com seleções topológicas e explorando o tempo de vida relativamente longo de mésons D e as capacidades de identificação de partículas do detector ALICE. Jatos são reconstruídos com o algoritmo anti-kT usando candidatos a mésons D e partículas carregadas. A medida do espectro de momento transversal de jatos contendo mésons D em colisões de núcleos de chumbo a energias de sNN = 5.02 TeV será apresentada. Esses resultados levam a novas possibilidades de sondagem das propriedades do QGP quando comparados com medidas de referência. Por fim, os métodos desenvolvidos podem ser empregados no estudo das funções de fragmentação de quarks charm em colisões de íons pesados.Charm quarks are created in the early stages of heavy-ion collisions in hard-scattering processes. Therefore, they are ideal probes of the Quark-Gluon Plasma (QGP), which is a state of matter where partons contained in hadrons, at high temperatures (150 MeV) or density (about five times the density of ordinary matter), change to a deconfined state of quarks and gluons. The fragmentation of charm quarks can produce D mesons. Jets containing a D meson as one of their constituents can be identified as originating from heavy-quark fragmentation. These jets are a valuable tool to characterize the charm interaction with the QGP. Charmed jets can provide information to the study the mass-dependent energy loss by the measurement of the modification of the charm-jet yield in Pb-Pb collisions with respect to pp collisions as a function of the jet transverse momentum. Moreover, a further insight can be obtained with the measurement of the momentum-fraction distribution, which is of particular interest to investigate the possible influence of the medium in the charm-jet fragmentation. D mesons are reconstructed through an invariant mass analysis of their hadronic decay channels, rejecting the large combinatorial background with topological selections exploiting the relatively large lifetime of D mesons and the particle identification capabilities of the ALICE detector. Jets are reconstructed with the anti-kT algorithm using D-meson candidates and charged tracks. The measurement of the transverse momentum spectrum of jets containing D mesons in Pb-Pb collisions at sNN = 5.02 TeV will be presented. These results lead to new possibilities of probing the QGP properties when compared to baseline measurements. Furthermore, the methods developed can be employed in the study of charm-quark fragmentation functions in heavy-ion collisions.
19
Buhry, Laure. "Estimation de paramètres de modèles de neurones biologiques sur une plate-forme de SNN (Spiking Neural Network) implantés "insilico"." Thesis, Bordeaux 1, 2010. http://www.theses.fr/2010BOR14057/document.
Full textAbstract:
Ces travaux de thèse, réalisés dans une équipe concevant des circuits analogiques neuromimétiques suivant le modèle d’Hodgkin-Huxley, concernent la modélisation de neurones biologiques, plus précisément, l’estimation des paramètres de modèles de neurones. Une première partie de ce manuscrit s’attache à faire le lien entre la modélisation neuronale et l’optimisation. L’accent est mis sur le modèle d’Hodgkin- Huxley pour lequel il existait déjà une méthode d’extraction des paramètres associée à une technique de mesures électrophysiologiques (le voltage-clamp) mais dont les approximations successives rendaient impossible la détermination précise de certains paramètres. Nous proposons dans une seconde partie une méthode alternative d’estimation des paramètres du modèle d’Hodgkin-Huxley s’appuyant sur l’algorithme d’évolution différentielle et qui pallie les limitations de la méthode classique. Cette alternative permet d’estimer conjointement tous les paramètres d’un même canal ionique. Le troisième chapitre est divisé en trois sections. Dans les deux premières, nous appliquons notre nouvelle technique à l’estimation des paramètres du même modèle à partir de données biologiques, puis développons un protocole automatisé de réglage de circuits neuromimétiques, canal ionique par canal ionique. La troisième section présente une méthode d’estimation des paramètres à partir d’enregistrements de la tension de membrane d’un neurone, données dont l’acquisition est plus aisée que celle des courants ioniques. Le quatrième et dernier chapitre, quant à lui, est une ouverture vers l’utilisation de petits réseaux d’une centaine de neurones électroniques : nous réalisons une étude logicielle de l’influence des propriétés intrinsèques de la cellule sur le comportement global du réseau dans le cadre des oscillations gammaThese works, which were conducted in a research group designing neuromimetic integrated circuits based on the Hodgkin-Huxley model, deal with the parameter estimation of biological neuron models. The first part of the manuscript tries to bridge the gap between neuron modeling and optimization. We focus our interest on the Hodgkin-Huxley model because it is used in the group. There already existed an estimation method associated to the voltage-clamp technique. Nevertheless, this classical estimation method does not allow to extract precisely all parameters of the model, so in the second part, we propose an alternative method to jointly estimate all parameters of one ionic channel avoiding the usual approximations. This method is based on the differential evolution algorithm. The third chaper is divided into three sections : the first two sections present the application of our new estimation method to two different problems, model fitting from biological data and development of an automated tuning of neuromimetic chips. In the third section, we propose an estimation technique using only membrane voltage recordings – easier to mesure than ionic currents. Finally, the fourth and last chapter is a theoretical study preparing the implementation of small neural networks on neuromimetic chips. More specifically, we try to study the influence of cellular intrinsic properties on the global behavior of a neural network in the context of gamma oscillations
20
Buhry, Laure. "Estimation de paramètres de modèles de neurones biologiques sur une plate-forme de SNN (Spiking Neural Network) implantés "in silico"." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2010. http://tel.archives-ouvertes.fr/tel-00561396.
Full textAbstract:
Ces travaux de thèse, réalisés dans une équipe concevant des circuits analogiques neuromimétiques suivant le modèle d'Hodgkin-Huxley, concernent la modélisation de neurones biologiques, plus précisément, l'estimation des paramètres de modèles de neurones. Une première partie de ce manuscrit s'attache à faire le lien entre la modélisation neuronale et l'optimisation. L'accent est mis sur le modèle d'Hodgkin- Huxley pour lequel il existait déjà une méthode d'extraction des paramètres associée à une technique de mesures électrophysiologiques (le voltage-clamp) mais dont les approximations successives rendaient impossible la détermination précise de certains paramètres. Nous proposons dans une seconde partie une méthode alternative d'estimation des paramètres du modèle d'Hodgkin-Huxley s'appuyant sur l'algorithme d'évolution différentielle et qui pallie les limitations de la méthode classique. Cette alternative permet d'estimer conjointement tous les paramètres d'un même canal ionique. Le troisième chapitre est divisé en trois sections. Dans les deux premières, nous appliquons notre nouvelle technique à l'estimation des paramètres du même modèle à partir de données biologiques, puis développons un protocole automatisé de réglage de circuits neuromimétiques, canal ionique par canal ionique. La troisième section présente une méthode d'estimation des paramètres à partir d'enregistrements de la tension de membrane d'un neurone, données dont l'acquisition est plus aisée que celle des courants ioniques. Le quatrième et dernier chapitre, quant à lui, est une ouverture vers l'utilisation de petits réseaux d'une centaine de neurones électroniques : nous réalisons une étude logicielle de l'influence des propriétés intrinsèques de la cellule sur le comportement global du réseau dans le cadre des oscillations gamma.
21
Winn, Michael [Verfasser], and Johanna [Akademischer Betreuer] Stachel. "Inclusive J/psi production at mid-rapidity in p-Pb collisions at √sNN=5.02 TeV / Michael Winn ; Betreuer: Johanna Stachel." Heidelberg : Universitätsbibliothek Heidelberg, 2016. http://d-nb.info/1180614534/34.
Full text
22
Gaudichet, Ludovic. "Production de [lambda](1520) dans les collisions p+p et Au+Au à √SNN=200 GeV dans l'expérience STAR au RHIC." Nantes, 2003. http://www.theses.fr/2003NANT2046.
Full textAbstract:
Les collisions d'ions lourds ultra-relativistes sont produites dans le but d'observer la matière dense et chaude. Un objectif majeur est de prouver l'existence du plasma de quarks et de gluons (QGP), un état dans lequel les conditions de température et de densité sont suffisamment élevées pour rompre le confinement des quarks à l'intérieur de hadrons. Dans ce but, le RHIC produit des collisions p+p et Au+Au avec une énergie dans le centre de masse de √SNN=200 GeV. Cette thèse porte sur la production des résonances [lambda](1520) dans ces deux systèmes grâce au dispositif expérimental de la collaboration STAR. Les différents rapports [Lambda](1520) indiquent une baisse significative de leur production dans les collisions d'ions lourds. Ces résultats constituent une forte présomption d'un découplement des particules en 2 phases : chimique puis thermique. Cette conclusion est une étape importante dans notre compréhension du comportement de la matière dans les collisions d'ions lourds ultra-relativistes.
23
Klein, Carsten [Verfasser], Henner [Akademischer Betreuer] Büsching, Henner [Gutachter] Büsching, and Harald [Gutachter] Appelshäuser. "Dielectron production in Pb-Pb collisions at √sNN = 5.02 TeV with ALICE / Carsten Klein ; Gutachter: Henner Büsching, Harald Appelshäuser ; Betreuer: Henner Büsching." Frankfurt am Main : Universitätsbibliothek Johann Christian Senckenberg, 2020. http://d-nb.info/1207542156/34.
Full text
24
Faivre, Julien. "Reconstruction et étude des baryons multi-étranges dans les collisions d'ions lourds ultra-relativistes à √snn=200GeV avec l'expérience STAR au RHIC." Université Louis Pasteur (Strasbourg) (1971-2008), 2004. https://publication-theses.unistra.fr/public/theses_doctorat/2004/FAIVRE_Julien_2004.pdf.
Full textAbstract:
L’étude de la production d’étrangeté est essentielle pour la compréhension du scénario des collisions d’ions lourds ultra-relativistes. Elle est donc directement nécessaire à l’étude de la phase de partons déconfinés qui résulterait de ces collisions : le plasma de quarks et de gluons. STAR, l’une des quatre expériences du collisionneur RHIC, constitue un outil idéal pour l’observation des particules multi-étranges Xi et Oméga. Nous avons créé un code de reconstruction des Xi et Oméga utilisant les traces de la chambre à projection temporelle de STAR. Nous avons ensuite mis au point une méthode multivariables de sélection du signal par rapport au fond combinatoire, l’analyse discriminante linéaire, permettant d’optimiser l’efficacité de la sélection et le rapport signal sur bruit en prenant en compte les corrélations entre variables. Nous l’avons appliquée aux données Au-Au prises à 200 GeV dans le centre de masse afin d’améliorer la précision des résultats précédents. Le taux de production de Oméga et anti-Oméga a été obtenu pour trois classes de centralité, ainsi que leur flot radial et leur température de découplage cinétique. Le gain sur l’incertitude relative est de 15 à 30 % selon les observables. Notre analyse permet en outre de distinguer la fonction modélisant le mieux le spectre en masse transverse des Oméga. La vitesse moyenne du flot radial 0,50 ± 0,02 c et la température de découplage cinétique 132 ± 20 MeV ainsi mesurées semblent notamment indiquer que les baryons multi-étranges se découplent plus tôt du milieu hadronique que les particules plus légères que sont le pion, le kaon et le proton. Les barres d’erreur restent cependant trop grandes pour tirer des conclusions fortesThe study of strangeness production is essential for the understanding of the scenario of the ultra-relativistic heavy-ion collisions. It is therefore directly necessary for studying the deconfined partonic phase that is thought to be produced in those collisions : the quark-gluon plasma. STAR, one of the four experiments on the RHIC collider, is an ideal tool for observing the multi-strange particles Xi and Omega. We have created a reconstruction code for the Xi and Omega using the tracks in STAR’s time projection chamber. We have then developped a multi-variable method selecting signal amongst combinatoric background, the linear discriminant analysis, which allows for an optimization of the selection efficiency and of the signal-to-noise ratio by taking the correlations between variables into account. We have used it on the Au-Au data taken at a center of mass energy of 200 GeV, so as to improve the accuracy of the former results. The Omega and anti-Omega yields have been obtained in three centrality classes, as well as their radial flow and their kinetic freeze-out temperature. Depending on the observables, a 15 to 30 % improvement has been reached on the relative uncertainty. Furthermore, our analysis distinguishes the function that best describes the Omega transverse mass spectrum. The measured average velocity of the radial flow 0. 50 ± 0. 02 c and kinetic freeze-out temperature 132 ± 20 MeV seem to indicate that the multi-strange baryons decouple earlier from the hadronic medium than lighter particles such as pions, kaons and protons. Yet, the error bars remain too large to draw strong conclusions
25
Huang, Chun Lu. "Inclusive J/ψ production in pp and Pb-Pb collisions at forward rapidity at √sNN = 5.02 TeV in ALICE at the LHC." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASP036.
Full textAbstract:
Les collisions hadroniques de haute énergie sont considérés comme un outil précieux pour comprendre les mécanismes de production avec l’aide de la théorie de la chromodynamique quantique (QCD). À très haute température et/ou densité, la matière ordinaire subit une transition de phase, prédite par la QCD, et atteint une nouvelle phase de matière pour laquelle les quarks et les gluons sont confinés. Cette nouvelle phase de matière de la QCD est appelée le plasma de quarks et de gluons (PQG). En laboratoire, les collisions d’ions lourds ultra-relativistes sont utilisées pour atteindre les conditions de temperature et de densité pour recréer le PQG. Pour sonder et caractériser les propriétés du PQG, beaucoup d’observables ont été proposées. En particulier, la production de charmonia, constituée d’une paire de quark et d’anti-quark charmés, est une des sondes proposés car la paire ccbar est produite au stade initial de la collision et peut traverser et interagir avec le milieu formé chaud et dense. De plus, la production de charmonia implique des échelles d’énergie dure et molle et permet d’étudier à la fois des aspects de la QCD perturbative et non perturbative. Dans ce document, les productions inclusives de J/psi à rapidité vers l’avant en collisions pp et Pb-Pb mesurées à snn = 5.02 TeV avec l’expérience ALICE (A Large Ion Collider Experiment) sont présentées. Les mesures sont effectuées dans le canal de désintégration du J/psi en dimuon avec le spectromètre à muon d’ALICE. L’échantillon de données de haute statistique pp ainsi que l’ensemble des données Pb-Pb du Run 2 du LHC sont analysés et ces données permettent d’obtenir des résultats plus précis que les données précédemment publiées. La section efficace de production de J/psi en collisions pp qui sert de référence aux mesures en collisions Pb-Pb est présentée en fonction de l’impulsion transverse (pT) et de la rapidité (y). Le facteur de modification nucléaire du J/psi, défini comme le rapport entre le taux de J/psi en collisions Pb-Pb et la section efficace pp, normalisée par la fonction de recoupement nucléaire, est exposé en fonction de pT. Ces mesures étendent le domaine en pt des précédentes mesures jusqu’à 20 GeV/c. La section efficace de production de J/psi mesurée en collisions pp est comparé aux différents calculs théoriques basés sur les modèles NRQCD (non-relativistic QCD) et CEM (colour evaporation model). En collisions Pb-Pb, une comparaison entre les mesures du factor de modification nucléaire du J/psi et les calculs théoriques basés sur des modèles de transport et statistique sont présentésHigh-energy hadron-hadron collisions are considered as a useful tool which helps us to understand particle production mechanisms with the help of the Quantum Chromodynamics (QCD) theory. At extremely high temperature and/or high density, ordinary matter undergoes a phase transition, predicted by QCD, and reaches a new phase of matter in which quarks and gluons are deconfined. This new phase of QCD matter is called quark-gluon plasma (QGP). In laboratory, ultra-relativistic heavy-ion collisions are used to satisfy the temperature and density condition in order to recreate the QGP. To probe and characterize the QGP properties, many observables have been proposed. In particular, charmonium, made of a pair of charm and anticharm quarks, is one of the proposed probes because the ccbar are produced at the initial stage of the heavy-ion collision and can cross and interact with the hot and dense formed medium. Besides, charmonium production involves hard and soft energy scales and therefore provides an opportunity to study both perturbative and non-perturbative aspects of the QCD. In this manuscript, we report on inclusive J/psi production at forward rapidity in pp and Pb-Pb collisions measured at snn = 5.02 TeV in A Large Ion Collider Experiment (ALICE) at the LHC. The measurements are performed in the J/psi dimuon decay channel with the muon spectrometer. The high-statistic pp data sample and the full Pb-Pb data sample of the LHC Run 2 period are analyzed and those datasets permit to obtain more precise results than the earlier published results. The J/psi production cross section in pp collisions that serves as a reference for the measurements in Pb-Pb collisions is presented as a function of the transverse momentum (pT) and of the rapidity (y). The J/psi nuclear modification factor, defined as the ratio of the yield in Pb-Pb collisions to the cross section in pp collisions scaled by the nuclear overlap function, is shown as a function of pT. The measurements are extended in pT, with respect to previous results, up to 20 GeV/c. The J/psi production cross section measured in pp collisions is compared to different theoretical calculations based on non-relativistic QCD (NRQCD) model and on colour evaporation model (CEM). In Pb-Pb collisions, a comparison between the measured J/psi nuclear modification factor and the theoretical calculations based on transport and on statistical model is presented
26
Snook, Benjamin A. "Measurements of the v2 of pi 0 Mesons Produced in Square Root of SNN = 2.76 TeV PbPb Collisions at the Large Hadron Collider." Thesis, Vanderbilt University, 2014. http://pqdtopen.proquest.com/#viewpdf?dispub=3584405.
Full text
27
Francisco, Audrey. "Measurement of the J/ψ elliptic flow in Pb-Pb collisions at √sNN=5.02TeV with the muon spectrometer of ALICE at the LHC." Thesis, Ecole nationale supérieure Mines-Télécom Atlantique Bretagne Pays de la Loire, 2018. http://www.theses.fr/2018IMTA0087/document.
Full textAbstract:
Les conditions extrêmes de température et de densité d'énergie créées lors des collisions d'ions lourds ultra-relativistes au sein du Grand collisionneur de hadrons (LHC) fournissent une occasion unique d'étudier les propriétés de la matière. Une transition de phase de la matière hadronique vers un milieu déconfiné de quarks et de gluons (PQG) est prédite par la chromodynamique quantique et des efforts théoriques et expérimentaux considérables ont été investis pour étudier ses propriétés. Parmi les sondes éminentes du PQG, les quarks lourds jouent un rôle prépondérant car ils sont créés lors des processus durs initiaux, avant la formation du PQG, et leur nombre est conservé durant les phases partoniques et hadroniques de la collision. Les états liés de quarks lourds– quarkonium (charmonium pour cc et bottomonium pour bb), constituent des sondes remarquables du milieu. Les observations expérimentales de quarkonia aux énergies du LHC dans les collisions A-A sont reproduites au travers de deux mécanismes antagonistes : la suppression séquentielle, proposée très tôt comme signature du PQG, et la (re)génération de quarkonia par (re)combinaison de quarks déconfinés. Cependant des incertitudes importantes sont associées aux prédictions théoriques et de nombreuses inconnues demeurent. L'anisotropie azimuthale de l'espace des moments (désignée sous le terme de flot elliptique, v2) de la production de charmonium devrait permettre d'avoir une meilleure vue d'ensemble et de contraindre davantage les paramètres des modèles théoriques. Si les quarks charmés se (re)combinent en paires cc, les J/ψ produits devraient hériter de leur flot. Les études précédentes ont montré des premiers signes d'un v2positif du J/ψ dans les collisions Pb-Pb à √sNN=2.76TeV. Cette thèse porte sur la mesure de l'anisotropie azimuthale du J/ψ dans les collisions Pb-Pb à√sNN=5.02TeV où une (re)combinaison légèrement plus importante est prédite par rapport aux énergies inférieures et une augmentation statistique d'un facteur 3 a été enregistrée. L'étude du flot elliptique du J/ψ fournit des informations clés sur la magnitude et la dynamique des mécanismes de suppression et de (re)génération de charmonia. Par ailleurs elle offre un regard unique sur l'évolution et les interactions des quarks charmés au sein du milieu en expansionExtreme temperatures and energy densities produced in ultra-relativistic heavy-ion collisions at the Large Hadron Collider provide a unique opportunity to study the properties of matter. A phase transition of the hadronic matter to a deconfined medium of quarks and gluons, the Quark-Gluon Plasma (QGP), is predicted by Quantum Chromodynamics and considerable theoretical and experimental efforts have been invested to study its properties. Among the prominent probes of the QGP, heavy quarks play a crucial role since they are created in primary hard-scattering processes, before the QGP formation, and their number is conserved throughout the partonic and hadronic phases of the collision. Bound states of heavyquarks – quarkonium (charmonium for cc and bottomoniumbb) provide remarkable probes of the medium. At LHC energies, experimental observations of quarkonium in A-Acollisions are reproduced through two antagonist mechanisms: a sequential suppression of the quarkonium states, early suggested as a signature of the QGP, and quarkonium (re)generation by (re)combination of deconfined quarks. However, theoretical predictions carry large uncertainties and many unknows remain. The momentum space azimuthal anisotropy of charmonium production (referred as elliptic flow v2) should help to clarify the picture and to constrain the model parameters. If charm quarks (re)combine in the medium into cc pairs, the J/ψ originating from (re)combination should inherit their flow. Previous studies have shown first hints of a positive J/ψ v2 in Pb-Pb collisions at √sNN=2.76TeV. This thesis focuses on the measurement of J/ψ azimuthal anisotropy in Pb-Pb collisions at √sNN=5.02TeV where a slightly stronger (re)generation component is predicted with respect to lower collision energies, and a factor of 3more data were collected. The study of J/ψ v2 provides important information on the magnitude and dynamics of charmonium suppression and (re)generation mechanisms. In addition, it offers a unique insight on charm quark evolution and interactions in the expanding medium
28
Godoy, Denise Aparecida Moreira de. "Anisotropia azimutal elíptica de elétrons de decaimentos de quarks pesados em colisões de Pb-Pb a SNN = 2.76 TeV medida no experimento ALICE." Universidade de São Paulo, 2013. http://www.teses.usp.br/teses/disponiveis/43/43134/tde-07102014-151944/.
Full textAbstract:
Nessa tese serão apresentadas medidas de anisotropia azimutal elíptica de elétrons de decaimentos de quarks pesados feitas no perimento de colisão de íons pesados ALICE (A Large Ion Collider Experiment, em inglês). As medidas foram obtidas em colisões de Pb-Pb com energia de centro de massa por par de nucleons (psNN) igual a 2.76 TeV com o colisor de hadrons LHC (Large Hadron Collider, em inglês). Colisões ultrarelativísticas de íons pesados podem alcançar temperaturas e/ou densidades de energia suficientemente altas para formar o Plasma de Quarks e Gluons (QGP, na sigla em inglês), o estado da matéria onde os partons estão desconfinados dos hadrons. O parâmetro de anisotropia azimutal elíptica é um dos observáveis mais importantes utilizados no estudo da formação do QGP. Esse parâmetro é quantificado pelo segundo harmônico, denominado v2, da distribuição do ângulo azimutal das partículas em relação ao ângulo do plano de reação, o qual é definido pela direção do parâmetro de impacto e pela direção do feixe de partículas. Medidas de anisotropia azimutal elíptica de quarks pesados (charm e beauty) são interessantes, pois os quarks pesados são sondas sensíveis às propriedades do QGP, visto que eles são predominantemente produzidos em processos iniciais de espalhamento duro e interagem com o meio desconfinado. Medidas de v2 de elétrons de decaimentos de quarks pesados em baixos valores de momento transversal indicam movimento coletivo de quarks pesados e possível termalização no QGP. Por outro lado, medidas de v2 de elétrons de decaimentos de quarks pesados em altos valores de momento transversal são interpretadas como uma dependência da geometria do meio por onde os quarks pesados atravessam e perdem energia. Serão mostrados resultados de v2 de elétrons de decaimentos de quarks pesados em função do momento transversal em colisões de Pb-Pb a psNN = 2.76 TeV em eventos com centralidades 20-40% e 30-50%. O resultado é comparado com previsões teóricas e medida obtida em colisões de Au-Au a psNN = 0.2 TeV no experimento RHIC. Resultados preliminares de v2 de elétrons de decaimentos de charm e beauty, separadamente, também serão mostrados em colisões de Pb-Pb a psNN = 2.76 TeV em eventos com centralidade 30-50%.This thesis presents measurements of the elliptic azimuthal anisotropy of electrons from heavy-flavour decays with the A Large Ion Collider Experiment (ALICE). The measurement is performed for the first time in Pb-Pb collisions at center-of-mass energy per colliding nucleon pair psNN = 2.76 TeV at the Large Hadron Collider (LHC). In heavy-ion collisions at ultrarelativistic energies sufficiently high temperature and/or energy density can be achieved to form the Quark-Gluon Plasma (QGP), the state of matter predicted by Quantum Chromodynamics (QCD) in which quarks and gluons are deconfined from hadrons. One of the most important probes of the QGP formation is the elliptic azimuthal anisotropy, which is quantified by the second harmonic v2 of the particle azimuthal angle distribution with respect to the angle of the reaction plane, which is defined by the impact parameter direction and the beam direction. In addition, heavy quarks (charm and beauty) serve as a sensitive probe of the QGP properties since they are predominantly produced in initial hard scattering processes and interact with the deconfined medium. The transverse momentum dependence of the heavy-flavour decay electron v2 can be used to investigate the QGP properties. The measurement of v2 of electrons from heavy-flavour decays at low transverse momentum provides a way to test whether heavy quarks take part in the collective motion in the medium. Whereas, v2 of electrons from heavy-flavour decays at high transverse momentum is interpreted as a path length dependence of heavy-quark energy loss within the created dense medium. Results of the elliptic azimuthal anisotropy of electrons from heavy-flavour decays as a function of tranverse momentum obtained in 20-40% and 30-50% central Pb-Pb collisions at psNN = 2.76 TeV will be shown. The measurement is compared with theoretical predictions and previous measurement at the RHIC experiment. Preliminary measurements of the elliptic azimuthal anisotropy of electrons from charm and beauty as a function of tranverse momentum in 30-50% central Pb-Pb collisions at psNN = 2.76 TeV will be shown as well.
29
Hippolyte, Boris. "Etude de la production d'étrangeté dans les collisions d'ions lourds ultra-relativistes à (racine carré de)√snn=130GeV avec l'expérience STAR au RHIC." Université Louis Pasteur (Strasbourg) (1971-2008), 2002. https://publication-theses.unistra.fr/public/theses_doctorat/2002/HIPPOLYTE_Boris_2002.pdf.
Full textAbstract:
La production d'étrangeté est une composante majeure de la mise enévidence d'une phase de partons déconfinés dans les collisions d'ions lourds ultra-relativistes. Parmi les nouvelles expériences ayant pris place auprès du collisionneur RHIC, STAR (Solenoidal Tracker At RHIC) offre d'importantes possibilités pour la reconstruction de particules multi-étranges comme les Oméga et l'hypothétique dibaryon H0. Nous avons détaillé les principales motivations de ce type d'étude replacées dans le contexte de différents modèles ainsi que des expériences passées. L'analyse des collisions issues des premières prises de données de STAR à 130 GeV par paire de nucléons dans le centre de masse,grâce à la mise au point de sélections spécifiques, nous a permis d'obtenir un signal significatif d'Oméga et d'anti-Oméga. Concernant les deux modes de désintégration envisagés pour les H0,aucun signal significatif n'a pu être observé. A partir de simulations, il a été possible d'estimer l'efficacité de détection de ces particules étranges et de déterminer la sensibilité de détection de STAR pour la reconstruction d'un des modes de désintégration supposés du H0 qui s'élève à 0,39 H0 par événement pour la première année de fonctionnement. De même, la détermination de l'efficacité de notre sélection des Omégas nous a permis d'établir le rapport anti-particule/particule (0. 95 +/- 0. 15) puis de déterminer le taux de production dN/dy= 0. 64 +/- 0. 14 et le paramètre de pente inverse correspondant T= 411 +/- 44 MeV. Ces résultats entachés actuellement d'une grande incertitude statistique restent compatibles avec différentes prédictions théoriques. Ils ne permettent donc pas encore de conclure quant à l'existence d'un plasma de quarks et de gluonsStrangeness production is one of the major probes to identify a deconfined phase of partons in relativistic heavy ion collisions. Among the new experiments which started at RHIC, STAR (Solenoidal Tracker At RHIC) offers important possibilities for what is related to multi-strange particle reconstruction such as Omegas and the hypothetical H0 dibaryon. We have discussed the main motivations of this kind of studies in the context of various models as well as earlier experiments. The analysis of first year data taking of STAR with collisions at 130 GeV per pair of nuclei in the center of mass and the setting of optimized selections has allowed to obtain a relevant signal of Omega and anti-Omega particles. For what is related to the H0 search, no significant signal has been observed so far. Using simulations, it has been possible to estimate the efficiency in the detection of strange particles and establish the sensitivity of STAR for the reconstruction of one of the assumed decay modes of the H0 which is of 0. 39 H0 per event for the set of data taken during the first year. Furthermore, the efficiency of our selections has allowed for the extraction of the anti-particle to particle ratio (0. 95 +/- 0. 15),for the corrected yields dN/dy= 0. 64 +/- 0. 14 and the related inverse slope parameter T= 411 +/- 44 MeV. These results, which have a important statistical uncertainty, are compatible with numerous theoretical predictions. They do not permit to conclude if a quark gluon plasma has been reached or not
30
Fiorini, Anna. "Analisi e sviluppo di modelli per la classificazione di immagini in contesto open set nell’ambito di dispositivi embedded." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021. http://amslaurea.unibo.it/22412/.
Full textAbstract:
L’obiettivo del mio progetto di tesi era quello di aggiungere una funzionalità all’interno del sensore di visione intelligente Smart-VS. Questo dispositivo è in grado di classificare l’oggetto in due classi, Good e No Good, sulla base del set di esempi forniti in fase di training, in ambito industriale è però difficile ottenere un set di campioni che comprenda tutte le situazioni possibili che potrebbero verificarsi. Lo scopo di questo progetto era perciò quello di progettare e implementare dei modelli che fossero in grado di rilevare la presenza di oggetti mai visti prima (Open set). La fase iniziale si è focalizzata sulla scelta dell’estrattore di features delle immagini. Alla fine, si sono utilizzati un descrittore di features ingegnerizzate e la VGG-16 pre-addestrata sul database ImageNet. La prima strategia è stata quella di creare un modello in grado di effettuare una tradizionale classificazione binaria per oggetti Good e No Good e inserire la fase di riconoscimento dell’Open set nella fase di inferenza. La seconda strategia si è focalizzata sull’utilizzo di modelli di Deep Metric Learning che sono in grado di imparare una trasformazione dallo spazio immagine allo spazio delle features, attribuendo alla distanza una misura di similarità semantica tra gli oggetti. In questo modo le classi Good e No Good risulteranno compatte mentre gli oggetti Open, semanticamente diversi, si troveranno lontani. Entrambe le strategie hanno prodotto risultati soddisfacenti, in particolare, nella prima categoria è stata creata una CNN che utilizza le features estratte dalla VGG-16 per eseguire il training per la classificazione binaria e che poi impiega il Classificatore con Processo Gaussiano per identificare gli oggetti Open che raggiunge un livello di accuracy sulle 3 classi del 99,44%. Mentre nella seconda categoria tra i modelli implementati il più performante è risultato essere la Rete Neurale Siamese con le features della VGG-16 che ottiene un accuracy del 99,3
31
Wagner, Jan [Verfasser], Tetyana [Akademischer Betreuer] Galatyuk, and Anton [Akademischer Betreuer] Andronic. "Electrons from decays of open charm and beauty hadrons in p-Pb collisions at sqrt(sNN) = 5.02 TeV / Jan Wagner ; Tetyana Galatyuk, Anton Andronic." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2016. http://d-nb.info/1117797139/34.
Full text
32
Tarhini, Mohamad. "Mesure de la production du boson Z et du J/ψ dans les collisions p-Pb et Pb-Pb à √sNN = 5.02 TeV avec ALICE." Thesis, Université Paris-Saclay (ComUE), 2017. http://www.theses.fr/2017SACLS283/document.
Full textAbstract:
Les collisions d'ions lourds ultra-relativistes sont considérées comme un outil unique pour produire, enlaboratoire, un milieu chaud et dense interagissant fortement, le Plasma de Quarks etde Gluons (PQG). Cette thèse est dédiée à l’étude de deux sondes, les J/ψ et les bosons Z, qui peuvent aider àatteindre une meilleure compréhension des propriétés du PQG.Dans les collisions d’ions lourds, il existe une observable importante pour étudier la formation du PQG, c’est lamesure de la production des J/ψ. L’importance des différents effets qui peuvent augmenter ou supprimer cetteproduction varie avec l’énergie de la collision. Dans cette thèse, la production des J/ψ est mesurée avec lescollisions Pb-Pb à √sNN =5.02 TeV, en utilisant principalement le spectromètre à muons du détecteur ALICE. Lefacteur de modification nucléaire des J/ψ est présenté en fonction de la centralité des collisions, la rapidité etl’impulsion transversale (pT). En outre, les résultats sur le pT moyen du J/ψ sont présentés. La comparaison entreles résultats expérimentaux et divers calculs théoriques suggère que la production du J/ψ est affectée dans le milieupar deux processus concurrents : le dissociation et le régénération.Dans les collisions d’ions lourds, l'état initial de la collision peut aussi affecter les résultats, en l'absence deformation du PQG. La compréhension et la quantification des tels effets est crucial pour les séparer de ceuxprovoqués par la présence du PQG. Un de ces effets est la modification nucléaire des fonctions de distribution despartons (PDFs). La mesure de production du boson Z dans les collisions d’ions lourds est un outil puissant pourétudier la modification nucléaire des PDFs car il n’est pas affectés par la présence d'une matière en forteinteraction. La seconde partie de cette thèse est dévolue à la mesure de la production des bosons Z, pour lapremière fois dans ALICE, avec les collisions p-Pb et Pb-Pb à √sNN =5.02 TeV. Dans les collisions Pb-Pb où laprécision de la mesure est plus élevée, l'accord entre les données et des calculs théoriques est meilleur lorsque cesderniers prennent en compte la modification nucléaire des PDFsUltra relativistic heavy-ion collisions are considered as a unique tool to produce, in the laboratory, thehot and dense strongly-interacting medium, the Quark-Gluon Plasma (QGP). This thesis is dedicated to the studyof two powerful probes, the J/ψ and Z-boson, that can help reaching a better understanding of the properties of theQGP.An important observable to study the QGP formation in heavy-ion collisions is the measurement of the J/ψproduction. The sizes of the different effects that can enhance or suppress this production vary with the collisionenergy. In this thesis, the J/ψ production is measured in Pb-Pb collisions at √sNN = 5.02 TeV using mainly themuon spectrometer of the ALICE detector. The J/ψ nuclear modification factor is presented as a function ofcollision centrality, rapidity and transverse momentum (pT). In addition, results on the J/ψ average pT and squaredaverage pT are also obtained. The comparison between the results and various theoretical calculations suggests thatthe J/ψ production is affected in the medium by an interplay between dissociation and regeneration mechanisms.In heavy-ion collisions, the initial state of the collision can affect the results even in the absence of the QGP.Understanding and quantifying such effects is crucial in order to separate them from the ones caused by thepresence of the QGP. One of these effects is the nuclear modification of the parton distribution functions (PDFs).The measurement of Z-boson production in heavy-ion collisions is a powerful tool to study the nuclearmodification of PDFs since it is not affected by the presence of the strongly-interacting medium. The second partof this thesis is devoted to measure the Z-boson production, for the first time with ALICE, in p-Pb and Pb-Pbcollisions at √sNN = 5.02 TeV. In Pb-Pb collisions where the precision of the measurement is higher, the agreementbetween data and theoretical calculations is better when the latter take into account the nuclear modification of thePDFs
33
Schuchmann, Simone [Verfasser], Harald [Gutachter] Appelshäuser, and Reinhard [Gutachter] Stock. "Modification of K0s and Λ(Λ̄) transverse momentum spectra in Pb-Pb collisions at √sNN=2.76 TeV with ALICE / Simone Schuchmann ; Gutachter: Harald Appelshäuser, Reinhard Stock." Frankfurt am Main : Universitätsbibliothek Johann Christian Senckenberg, 2016. http://d-nb.info/1118731344/34.
Full text
34
Hornung, Sebastian [Verfasser], and Silvia [Akademischer Betreuer] Masciocchi. "Production of (anti-)3He and (anti-)H in p-Pb collisions at √SNN = 5.02 TeV measured with ALICE at the LHC / Sebastian Hornung ; Betreuer: Silvia Masciocchi." Heidelberg : Universitätsbibliothek Heidelberg, 2020. http://d-nb.info/1214056040/34.
Full text
35
Leardini, Lucia [Verfasser], and Johanna [Akademischer Betreuer] Stachel. "Measurement of neutral mesons and direct photons in Pb–Pb collisions at √sNN = 2.76 TeV with the ALICE experiment at the LHC / Lucia Leardini ; Betreuer: Johanna Stachel." Heidelberg : Universitätsbibliothek Heidelberg, 2017. http://d-nb.info/1177689014/34.
Full text
36
Lardeux, Antoine. "Étude de la production inclusive de J/Ψ dans les collisions Pb-Pb à √sNN=2,76 TeV avec le spectromètre à muons de l'expérience ALICE au LHC." Phd thesis, Ecole des Mines de Nantes, 2014. http://tel.archives-ouvertes.fr/tel-01044653.
Full textAbstract:
La théorie de la chromodynamique quantique prédit l'existence d'un état déconfiné de la matière appelé Plasma de Quarks et de Gluons (PQG). Expérimentalement, la formation d'un PQG est attendue sous les conditions extrêmes de température et de densité atteintes lors de collisions d'ions lourds ultra-relativistes. Afin d'observer et de caractériser de manière indirecte un tel état de la matière, de nombreuses observables ont été proposées. En particulier, les phénomènes de suppression et de(re)combinaison du meson J/Ψ dans le PQG sont intensément étudiés. Cette thèse présente l'analyse de la production inclusive de J/Ψ dans les collisions Pb-Pb, à une énergie dans le centre de masse √sNN = 2,76 TeV, détectés avec le spectromètre à muons de l'expérience ALICE au LHC. A partir de la statistique élevée d'événements collectés lors de la prise de données de 2011, le facteur de modification nucléaire du J/Ψ a été mesuré en fonction de son impulsion transverse, de sa rapidité et de la centralité de la collision. L'impulsion transverse moyenne du J/Ψ a également été mesurée en fonction de la centralité. Les prédictions des modèles théoriques, incluant tous une contribution de (re)combinaison, présentent un bon accord avec les données. Enfin, un excès de J/Ψ de très faible impulsion transverse (<300 MeV/c) par rapport à la production hadronique attendue a été observé pour la première fois.
37
Beck, Hans [Verfasser], Christoph [Akademischer Betreuer] Blume, and Harald [Akademischer Betreuer] Appelshäuser. "Femtoscopic Proton-Lambda and Gamma-Gamma Correlations in Pb-Pb Collisions at sqrt(sNN) = 2.76 TeV with ALICE / Hans Beck. Betreuer: Christoph Blume. Gutachter: Christoph Blume ; Harald Appelshäuser." Frankfurt am Main : Univ.-Bibliothek Frankfurt am Main, 2015. http://d-nb.info/1078670269/34.
Full text
38
Greifenhagen, Robert André Heinrich [Verfasser], Burkhard [Gutachter] Kämpfer, Christoph [Gutachter] Blume, and Thomas E. [Gutachter] Cowan. "Two-Pion Intensity-Interferometry in Collisions of Au+Au at √sNN = 2.41 GeV measured with HADES / Robert André Heinrich Greifenhagen ; Gutachter: Burkhard Kämpfer, Christoph Blume, Thomas E. Cowan." Dresden : Technische Universität Dresden, 2021. http://d-nb.info/1231916923/34.
Full text
39
Audurier, Benjamin. "Etude de la production inclusive de J/ψ dans les collisions pp et Pb-Pb √sNN =5.02 TeV avec le spectromètre à muon de l'expérience ALICE au LHC." Thesis, Nantes, 2017. http://www.theses.fr/2017NANT4018/document.
Full textAbstract:
La production des états charmonia (par exemple le J/ψ et le ψ(2S)) est l’une des sondes étudiées pour comprendre les propriétés du Plasma de Quarks et de Gluons (PQG) formé dans les collisions d’ions lourds à très haute énergie. En effet, la présence d’un milieu déconfiné est susceptible de modifier le taux de production des charmonia par effet d’écrantage de couleur de la paire de quarks charme-anti-charme. Une telle suppression fut déjà observée dans les collisions d’ions lourds aux énergies du SPS et du RHIC. Dans les collisions Pb-Pb à √sNN = 2.76 TeV au LHC, une suppression relative du taux de production du J/ψ par rapport à celui mesuré dans les collisions pp normalisé aux nombres de collisions binaires proton-proton (facteur de modification nucléaire RAA) fut aussi mesurée. Cette suppression est cependant moins importante que ce qui fut observé à plus petites énergies dans le centre de masse. Ceci peut s’expliquer par la présence d’un nouveau mécanisme de production, la recombinaison de quarks charme et anticharme déconfinés au moment de l’expansion hydrodynamique du PQG ou durant la phase d’hadronisation. Dans cette thèse, nous présentons les résultats de la production de J/ψ dans les collisions pp et Pb-Pb, mesurée par le détecteur ALICE à √sNN = 5.02 TeV à rapidité avant dans le canal de décroissance dimuonique. La section efficace de production mesurée dans les collisions pp est comparée à différents modèles théoriques et est utilisée pour calculer le RAA en collisions Pb-Pb, lui-même comparé à différentes prédictions théoriques ainsi qu’aux précédentes mesuresThe production of charmonium states (for instance J/ψ and ψ(2S)) is one of the probes studied to investigate the properties of the Quark-Gluon Plasma (QGP) formed in high-energy heavy-ion collisions. Indeed, the presence of a deconfined medium should modify the charmonium production yield, due to the color screening of the charm quark anti-quark potential. Such a suppression was already observed in heavy-ion collisions at SPS and RHIC energies. In Pb-Pb collisions at √sNN = 2.76 TeV at the LHC, a clear suppression of the J/ψ yield with respect to the one measured in binary-scaled pp collisions (nuclear modification factor RAA) was observed, but much smaller than that at lower collision energies. This observation can be explained by the presence of a new production mechanism, the (re)combination of deconfined charm and anti-charm quarks during the hydrodynamical expansion of the QGP or at the hadronization stage. In this thesis, we report on the results of the J/ψ production in pp and Pb-Pb collisions measured with the ALICE detector √sNN = 5.02 TeV at forward rapidity in the dimuon channel. The cross-section in pp collisions is compared to various model calculations, and is used to compute the RAA in Pb-Pb collisions, which is also compared to theoretical predictions as well as to previous measurements
40
Patterson, James Cameron. "Managing a real-time massively-parallel neural architecture." Thesis, University of Manchester, 2012. https://www.research.manchester.ac.uk/portal/en/theses/managing-a-realtime-massivelyparallel-neural-architecture(dfab5ca7-fcd5-4ebe-887b-0a7c330c7206).html.
Full textAbstract:
A human brain has billions of processing elements operating simultaneously; the only practical way to model this computationally is with a massively-parallel computer. A computer on such a significant scale requires hundreds of thousands of interconnected processing elements, a complex environment which requires many levels of monitoring, management and control. Management begins from the moment power is applied and continues whilst the application software loads, executes, and the results are downloaded. This is the story of the research and development of a framework of scalable management tools that support SpiNNaker, a novel computing architecture designed to model spiking neural networks of biologically-significant sizes. This management framework provides solutions from the most fundamental set of power-on self-tests, through to complex, real-time monitoring of the health of the hardware and the software during simulation. The framework devised uses standard tools where appropriate, covering hardware up / down events and capacity information, through to bespoke software developed to provide real-time insight to neural network software operation across multiple levels of abstraction. With this layered management approach, users (or automated agents) have access to results dynamically and are able to make informed decisions on required actions in real-time.
41
Martin, Blanco Javier. "Study of J/Ψ production dependence with the charged particle multiplicity in p-Pb collisions at √sNN = 5. 02 TeV and pp collisions at √s = 8 TeV with the ALICE experiment at the LHC." Nantes, 2015. https://archive.bu.univ-nantes.fr/pollux/show/show?id=730dbcb5-68e6-4f80-b4f0-6de306fe2f6b.
Full textAbstract:
Une suppression de la production de J/ Ψ a été mise en évidence lors des collisions Pb-Pb à √sNN = 2. 76 TeV, fournissant une preuve supplémentaire de la formation d’un milieu déconfiné au cours des collisions d’ions lourds ultra-relativistes, appelé Plasma de Quarks et Gluons. Par ailleurs, les collisions p-Pb à √sNN = 5. 02 TeV ont été étudiées au LHC afin de mesurer les effets de la matière nucléaire froide (p. Ex. écrantage des gluons, perte d’énergie, absorption nucléaire). La compréhension des collisions p-Pb aidera à dissocier les effets de la matière nucléaire chaude et froide dans des collisions Pb-Pb. Cette thèse analyse la production inclusive de J/ Ψ dans les collisions p-Pb et pp avec le spectromètre à muons de l’experience ALICE. Le taux de production de J/ Ψ et son moment transverse moyen, ont été mesurés pour des rapidités à l’avant et à l’arrière en fonction de la multiplicité des particules chargées. Des mesures de la production de particules en fonction de la multiplicité de l’événement dans des systèmes de petite taille permettent de mettre en évidence des effets collectifs de l’état final, comme ceux observés dans les collisions Pb-Pb. L’augmentation observée, avec la multiplicité, de la production de J/ Ψ aux rapidités à l’arrière, est en accord avec celle mise en évidence en collisions pp. Cependant, une déviation de ce comportement pour la production de J/ Ψ aux rapidités à l’avant à haute multiplicité à été mesurée. Une tendance à la saturation du moment transverse moyen du J/ Ψ en collisions p-Pb a aussi été observée. L’origine de ces comportements, qu’ils soient liés aux effets de la matière nucléaire froide ou à la présence d’autres effets dans l’état final, n’est toujours pas connueA suppression of the J/Ψ production was found in Pb- Pb collisions at √sNN = 2. 76 TeV, providing further evidence of the formation of a deconfined medium in ultrarelativistic heavy-ion collisions, the so-called Quark- Gluon Plasma. In addition, p-Pb collisions at √sNN = 5. 02 TeV have been studied at the LHC to measure cold nuclear matter effects (e. G. Gluon shadowing, energy loss, nuclear absorption). Understanding p-Pb collisions will help to disentangle hot and cold nuclear matter effects in Pb-Pb collisions. Surprisingly, some observables in p-Pb collisions behave as in heavy-ion collisions where it is understood as a result of a collective expansion of the medium. This thesis analyses inclusive J/Ψ production in p- Pb and pp collisions with the ALICE muon spectrometer. The J/Ψ production rate, and its mean transverse momentum, have been measured at forward and backward rapidities as a function of the charged particle multiplicity. Measurements of particle production as a function of the event multiplicity in small size systems provide a way to sign the presence of collective final state effects like those observed in Pb-Pb collisions. The observed increase of the J/Ψ production at backward rapidity with multiplicity, is consistent with that observed in pp collisions. However, a deviation from this behaviour in the J/Ψ production at forward rapidity at high multiplicity has been measured. A trend towards saturation has also been observed in the J/Ψ mean transverse momentum in p-Pb collisions. Whether these effects can be explained by cold nuclear matter effects or by the presence of further final state effects is still unresolved
42
Crkovská, Jana. "Study of the J/ψ production in pp collisions at √s = 5.02 TeV and of the J/ ψ production multiplicity dependence in p-Pb collisions at √sNN = 8.16 TeV with ALICE at the LHC." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS343/document.
Full textAbstract:
L’expérience ALICE au CERN examine l’état de la matière QCD chaude et dense créée lors de collisions d’ions lourds ultra-relativistes - le plasma de Quark Gluon (QGP). En raison de sa courte durée de vie, le QGP ne peut être étudié que via ses signatures.La suppression de J/ψ a été proposée comme preuve de la formation du milieu déconfiné.Néanmoins, il est devenu évident que la réalité est bien plus complexe, car il existe d’autres mécanismes concurrents qui affectent la production de J/ψ . Pour comprendre quels effets agissant sur la production de J/ψ dans les collisions noyau-noyau résultent véritablement de la présence du QGP, ALICE étudie également la production de J/ψ en collisions pp et p–Pb. Le QGP ne devrait pas se former dans ces systèmes. De plus, les mesures de la production de J/ψ dans les collisions p–Pb peuvent révéler des informations sur les effets provenant de la liaison des nucléons dans le noyau, appelés effets de la matière nucléaire froide (CNM). L’objectif de cette thèse est d’étudier la production de J/ψ à rapidité vers l’avant avec le spectromètre à muons ALICE. La section efficace de production J/ψ inclusive dans les collisions pp à √s = 5.02 TeV,et sa dépendance en pT et en rapidité, ont été examinées et comparées à des calculs théoriques ainsi qu’ à des mesures à d’autres énergies du LHC. Les données sont bien décrites par la somme des calculs de pQCD pour les J/ψ prompts et de FONLL pour les J/ψ non-prompts. La production différentielle en multiplicité des J/ψ a été étudiée dans les collisions p–Pb et Pb–p à √sNN = 8,16 TeV, ainsi que le moment transvers moyen. La mesure montre un comportement dépendant de la rapidité pour les taux de production relatifs des J/ψ . Le moment transvers moyen des J/ψ est par contre identique dans les deux intervalles de rapidité mesurés. La nouvelle analyse a augmenté la précision et étendu la mesure à des multiplicités plus élevées par rapport à la mesure précédente à √sNN = 5,02 TeV. Nous constatons que les taux de production relatifs et le relatif sont indépendants de l’énergie du centre de masseThe ALICE experiment at CERN probesthe state of hot and dense QCD matter created in ultrarelativisticheavy ion collisions - the Quark GluonPlasma (QGP). Due to its short lifetime, the QGP canbe studied only via its signatures. The suppression ofJ/ ψ was proposed as a proof of formation of the deconfinedmedium. Nevertheless, it became clear thatthe real picture is far more complex as there are othercompeting mechanisms affecting the J/ ψ production.To understand which effects acting on the J/ productionin nucleus-nucleus collisions truly stem fromthe presence of the QGP, ALICE also studies the productionof J/ψ in pp and p–Pb collisions. The QGP isexpected not to form in these systems. Furthermore,measurements of the J/ ψ production in p–Pb collisionscan unveil information on the effects originatingfrom the binding of the nucleons in the nucleus, referredto as the cold nuclear matter effects (CNM).The objective of this thesis is to study the productionof J/ ψ at forward rapidity with the ALICE Muon Spectrometer.The inclusive J/ ψ production cross sectionin pp collisions at √s = 5.02 TeV, and its dependenceon pT and rapidity, were examined and compared withtheoretical calculations as well as measurement atother LHC energies. The data are well described bya sum of pQCD calculations for prompt and FONLLcalculations for non-prompt contribution. The multiplicitydifferential J/ ψ production was studied in p–Pband Pb–p collisions at √sNN = 8.16 TeV, as well asits mean transverse momentum. The measurementshows a rapidity dependent behaviour of relative J/ ψ yields. The J/ ψ mean transverse momentum on theother hand is identical in the two measured rapidityintervals. The new analysis increased the precisionand extended the measurement to higher multiplicitiescompared to previous measurement at √sNN =5.02 TeV. We find that both relative yields and relative are independent of centre-of-mass energy
43
Sanchez, Castro Xitzel. "KOs and lambda production associated to high-p T charged hadrons in Pb-Pb collisions at √sNN = 2.76 TeV with ALICE : comparison between the hard and "soft" processes related to the production of hadrons." Thesis, Strasbourg, 2015. http://www.theses.fr/2015STRAE006/document.
Full textAbstract:
Dans les collisions d'ions lourds ultra-relativistes (A-A), la matière se trouve dans des conditions extrêmes de densité d'énergie; elle forme un plasma de quarks et de gluons déconfinés. Aux énergies du RHIC et du LHC, le rapport baryon sur méson, tel Λ/K0S, prend des valeurs élevées sur une plage d'impulsions transverses intermédiaires pour les collisions centrales A-A. L'objectif de ce travail est de vérifier si la production accrue de baryons est seulement due à des effets collectifs au cœur du système formé ou s'il existe aussi un impact lié à une fragmentation des partons modifiée par le milieu. À l'aide de corrélations angulaires à deux hadrons, les K0S et Λ produits en association avec un hadron de haut pT (processus durs) sont séparés de ceux issus du milieu thermalisé (processus softs). Les rapports Λ/K0S à relier aux mécanismes durs et softs sont établis; les résultats sont obtenus pour les collisions Pb-Pb à √sNN = 2.76 TeV enregistrées en 2011 avec l'expérience ALICEIn ultrarelativistic heavy-ion collisions, the QCD matter is under extreme conditions of energy density, forming a quark-gluon plasma (QGP), in which quarks and gluons are deconfined. At RHIC and LHC energies, a large baryon-to-meson ratio, like Λ/K0S, was observed within the transverse momentum range 2 < pT < 6 GeV/c for central heavy-ion collisions. The goal of this dissertation is to verify if the baryon-to-meson enhancement is only due to collective effects of the bulk of matter, and if there is also a contribution related to in-medium modifications of parton fragmentation.With two-hadron angular correlations, the K0S and Λ produced in association to an energetic hadron (hard processes) are separated from those originated from the thermalised medium (soft processes). The differential Λ/K0S ratios related to the soft or hard production processes are extracted. The results are obtained for the Pb-Pb collisions at √sNN = 2.76 TeV recorded in 2011 with the ALICE experiment
44
Harrod, Steven B., Ryan T. Lacy, Jun Zhu, Benjamin A. Hughes, Marla K. Perna, and Russell W. Brown. "Gestational IV Nicotine Produces Elevated Brain-Derived Neurotrophic Factor in the Mesocorticolimbic Dopamine System of Adolescent Rat Offspring." Digital Commons @ East Tennessee State University, 2011. https://doi.org/10.1002/syn.20975.
Full textAbstract:
Maternal smoking during pregnancy is associated with enduring psychopathology, such as increased likelihood of substance use, in offspring. Various animal models demonstrate that continuous nicotine exposure produces teratogenic effects in offspring, as well. In this experiment, a novel intravenous (IV) exposure model was used to determine if gestational nicotine (GN) treatment produced alterations in methamphetamine-induced sensitization and the expression of brain-derived neurotrophic factor (BDNF) in the mesocorticolimbic dopamine (DA) system of adolescent offspring. Dams were injected with IV saline or nicotine (0.05 mg/kg/injection) three times per day on gestational days 8-21. Habituation was measured on postnatal day (PND) 25-27 and baseline activity on PND 28. On PND 29-35, offspring were injected with saline or methamphetamine (0.3 mg/kg) and locomotor activity was measured after the first and seventh injections. On PND 36, brains were removed, flash frozen, and BDNF protein levels in the nucleus accumbens (NAcc), dorsal striatum (Str), frontal cortex (FC), and hippocampus (Hipp) were analyzed. GN did not affect habituation or the induction of methamphetamine-induced sensitization. Interestingly, GN, but not adolescent methamphetamine treatment, elevated levels of BDNF in the NAcc and Str; however, the GN-induced increase in BDNF in the FC was attenuated by adolescent methamphetamine treatment. Both GN and adolescent methamphetamine treatment increased BDNF in the Hipp. These findings indicate that GN exposure will result in increased levels of BDNF protein throughout the mesocorticolimbic DA system during adolescent development and suggests that methamphetamine abuse will modulate the expression of BDNF in motivational circuitries of adolescent offspring exposed to GN.
45
Cope, Zackary A., Kimberly N. Huggins, A. Brianna Sheppard, Daniel M. Noel, David S. Roane, and Russell W. Brown. "Neonatal Quinpirole Treatment Enhances Locomotor Activation and Dopamine Release in the Nucleus Accumbens Core in Response to Amphetamine Treatment in Adulthood." Digital Commons @ East Tennessee State University, 2010. https://doi.org/10.1002/syn.20729.
Full textAbstract:
Neonatal quinpirole treatment to rats produces long-term increases in D(2) receptor sensitivity that persists throughout the animal's lifetime, a phenomenon referred to as D(2) priming. Male and female Sprague-dawley rats were administered quinpirole (1 mg kg(-1)) or saline from postnatal days (P)1-11. At P60, all animals were given an injection of quinpirole (100 microg kg(-1)), and results showed that rats neonatally treated with quinpirole demonstrated enhanced yawning in response to quinprole, verifying D(2) receptor priming because yawning is a D(2) receptor mediated event. Beginning 1-3 days later, locomotor sensitization was tested through administration of d-amphetamine (1 mg kg(-1)) or saline every other day over 14 days, and horizontal activity and turning behavior were analyzed. Findings indicated that D(2)-priming enhanced horizontal activity in response to amphetamine in females compared to males at Days 1 and 4 of locomotor sensitization testing, and D(2)-priming enhanced turning in response to amphetamine. Seven to ten days after sensitization was complete, microdialysis of the NAcc core was performed using a cumulative dosing regimen of amphetamine (0.1-3.0 mg kg(-1)). D(2)-primed rats administered amphetamine demonstrated a 500% increase in accumbal DA overflow compared to control rats administered amphetamine. Additionally, amphetamine produced a significant increase in NE overflow compared to controls, but this was unaffected by D(2) priming. These results indicate that D(2) receptor priming as is produced by neonatal quinpirole treatment robustly enhances behavioral activation and accumbal DA overflow in response to amphetamine, which may underlie increases in psychostimulant use and abuse within the psychotic population where increased D(2) receptor sensitivity is a hallmark.
46
Correll, Jennifer A., Daniel M. Noel, A. Brianna Sheppard, Kimberly N. Thompson, Yi Li, Deling Yin, and Russell W. Brown. "Nicotine Sensitization and Analysis of Brain-Derived Neurotrophic Factor in Adolescent Beta-Arrestin-2 Knockout Mice." Digital Commons @ East Tennessee State University, 2009. https://doi.org/10.1002/syn.20625.
Full textAbstract:
Nicotine sensitization and levels of brain-derived neurotrophic factor (BDNF) were analyzed in adolescent beta-arrestin-2 knockout (betaA-2 KO) and wild type (WT) mice. The beta-arrestin-2 protein has been shown to be important in G-protein hydrolysis and receptor internalization. Four- to five-week-old adolescent betaA-2 KO and WT C57/Bl6 mice were administered either nicotine (0.5 mg/kg free base) or saline 10 min before being placed into a locomotor arena on each of 7 (Experiment 1) or 14 (Experiment 2) consecutive days. A nicotine challenge was given 7 days after sensitization was complete. In Experiment 1, betaA-2 KO mice administered nicotine or saline and WT mice administered nicotine demonstrated significant hypoactivity during early in testing, and neither WT nor betaA-2 KO mice administered nicotine demonstrated sensitization. On the nicotine challenge, WT mice administered nicotine demonstrated significantly higher activity levels compared to all groups, and this same group demonstrated significantly higher levels of accumbal BDNF compared to all groups. In Experiment 2, betaA-2 KO mice were again hypoactive compared to WT mice, whereas WT mice administered nicotine demonstrated significant hypoactivity during initial testing and significantly higher levels of activity compared to all other groups late in testing. On the nicotine challenge, WT mice that received nicotine demonstrated a significant increase in activity compared to all groups, and showed increased accumbal BDNF compared to all groups. These results show that the beta-arrestin-2 protein is important in induction and expression of nicotine sensitization as well as nicotine's effects on accumbal BDNF.
47
Brown, Russell W., Marla K. Perna, Tori L. Schaefer, and Michael T. Williams. "The Effects of Adulthood Nicotine Treatment on D2-Mediated Behavior and Neurotrophins of Rats Neonatally Treated with Quinpirole." Digital Commons @ East Tennessee State University, 2006. https://doi.org/10.1002/syn.20237.
Full textAbstract:
This study was designed to analyze the effects of nicotine on yawning behavior and neurotrophin content in the hippocampus and frontal cortex of D2-receptor primed female adult Sprague-Dawley rats. Animals were neonatally treated with quinpirole, a dopamine (DA) D2/D3 agonist, from postnatal day 1-21 (P1-21) and raised to P60 and administered nicotine tartarate (0.3 mg/kg free base) or saline twice daily for 14 days. One day after nicotine treatment had ceased, the number of yawns was recorded for 1 h in response to an acute injection of quinpirole (i.p., 100 microg/kg). Yawning is a D2-receptor mediated event. D2-primed rats demonstrated a significant increase in yawning in response to acute quinpirole compared with that of controls, but nicotine did not alleviate this effect. Neonatal quinpirole treatment produced a significant decrease of nerve growth factor (NGF) and brain-derived neurotrophic factor (BDNF) in the hippocampus that was alleviated by adulthood nicotine treatment. Interestingly, nicotine treatment to controls produced a significant increase of NGF in the frontal cortex, but a significant decrease of both NGF and BDNF in the hippocampus and BDNF in the frontal cortex. The decreases shown in NGF and BDNF is contrary to past findings that have shown nicotine to produce significant increases of hippocampal NGF and BDNF, but these past studies utilized male rats or mice or were performed in vitro. This study shows that nicotine has complex interactions with NGF and BDNF in D2-primed and control animals, and emphasizes the importance of gender differences when analyzing nicotine's effects on neurotrophins.
48
Forssell, Melker, and Gustav Janér. "Product Matching Using Image Similarity." Thesis, Uppsala universitet, Institutionen för informationsteknologi, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-413481.
Full textAbstract:
PriceRunner is an online shopping comparison company. To maintain up-todate prices, PriceRunner has to process large amounts of data every day. The processing of the data includes matching unknown products, referred to as offers, to known products. Offer data includes information about the product such as: title, description, price and often one image of the product. PriceRunner has previously implemented a textual-based machine learning (ML) model, but is also looking for new approaches to complement the current product matching system. The objective of this master’s thesis is to investigate the potential of using an image-based ML model for product matching. Our method uses a similarity learning approach where the network learns to recognise the similarity between images. To achieve this, a siamese neural network was trained with the triplet loss function. The network is trained to map similar images closer together and dissimilar images further apart in a vector space. This approach is often used for face recognition, where there is an extensive amount of classes and a limited amount of images per class, and new classes are frequently added. This is also the case for the image data used in this thesis project. A general model was trained on images from the Clothing and Accessories hierarchy, one of the 16 toplevel hierarchies at PriceRunner, consisting of 17 product categories. The results varied between each product category. Some categories proved to be less suitable for image-based classification while others excelled. The model handles new classes relatively well without any, or with briefer, retraining. It was concluded that there is potential in using images to complement the current product matching system at PriceRunner.
49
Massacrier, Laure. "La physique des (di)muons dans ALICE au LHC : analyse en collisions pp (√s = 7 TeV) et Pb-Pb (√sNN = 2.76 TeV) des résonances de basses masses (ρ, ω, ф) et étude d'un trajectographe en pixels de Silicium dans l'ouverture du spectromètre." Phd thesis, Université Claude Bernard - Lyon I, 2011. http://tel.archives-ouvertes.fr/tel-00800827.
Full textAbstract:
L'expérience ALICE au LHC étudie le plasma de quarks gluons (PQG), état de la matière où quarks et gluons existent à l'état déconfinés. Une des sondes utilisée pour explorer cet état est l'étude de plusieurs résonances (ρ, ω, ф, J/ψ et Ƴ) via leur canal de désintégration dimuonique, à l'aide d'un spectromètre à muons couvrant les pseudo-rapidités -4 < η < -2.5. La première partie de la thèse se focalise sur les mésons vecteurs de basses masses (ρ, ω et ф) . Elle concerne l'analyse des données récoltées en 2010 en collisions pp à √s = 7 TeV et Pb-Pb à √sNN = 2.76 TeV. Les mésons vecteurs de basses masses sont des outils intéressants pour sonder le PQG grâce à leurs faibles durées de vie et leur canal de désintégration dimuonique non affecté par les interactions dans l'état final. Les taux de production et fonctions spectrales de ces mésons sont modifiées par le milieu hadronique chaud et le PQG. En collisions pp, les distributions du ф, du (ρ+ω) en fonction de l'impulsion transverse ainsi que les sections efficaces et sections efficaces différentielles de production des différents mésons ont été extraites. L'analyse en collisions Pb-Pb ainsi que ses perspectives sont également présentées. La seconde partie de la thèse concerne le futur de l'expérience ALICE et les plans d'amélioration des détecteurs pour l'horizon 2017. Une étude de faisabilité pour l'ajout d'un trajectographe en pixels de Silicium (MFT) à l'avant de l'absorbeur hadronique dans l'acceptance du spectromètre à muons est présentée. Les performances et améliorations apportées par le MFT dans différents canaux de physique ont été étudiées en simulation
50
Massacrier, Laure. "La physique des (di)muons dans ALICE au LHC : analyse en collisions pp (√s = 7 TeV) et Pb-Pb (√sNN = 2.76 TeV) des résonances de basses masses (ρ, ω, ф) et étude d’un trajectographe en pixels de Silicium dans l’ouverture du spectromètre." Thesis, Lyon 1, 2011. http://www.theses.fr/2011LYO10203/document.
Full textAbstract:
L’expérience ALICE au LHC étudie le plasma de quarks gluons (PQG), état de la matière où quarks et gluons existent à l’état déconfinés. Une des sondes utilisée pour explorer cet état est l’étude de plusieurs résonances (ρ, ω, ф, J/ψ et Ƴ) via leur canal de désintégration dimuonique, à l’aide d’un spectromètre à muons couvrant les pseudo-rapidités -4 < η < -2.5. La première partie de la thèse se focalise sur les mésons vecteurs de basses masses (ρ, ω et ф) . Elle concerne l’analyse des données récoltées en 2010 en collisions pp à √s = 7 TeV et Pb-Pb à √sNN = 2.76 TeV. Les mésons vecteurs de basses masses sont des outils intéressants pour sonder le PQG grâce à leurs faibles durées de vie et leur canal de désintégration dimuonique non affecté par les interactions dans l’état final. Les taux de production et fonctions spectrales de ces mésons sont modifiées par le milieu hadronique chaud et le PQG. En collisions pp, les distributions du ф, du (ρ+ω) en fonction de l’impulsion transverse ainsi que les sections efficaces et sections efficaces différentielles de production des différents mésons ont été extraites. L’analyse en collisions Pb-Pb ainsi que ses perspectives sont également présentées. La seconde partie de la thèse concerne le futur de l’expérience ALICE et les plans d’amélioration des détecteurs pour l’horizon 2017. Une étude de faisabilité pour l’ajout d’un trajectographe en pixels de Silicium (MFT) à l’avant de l’absorbeur hadronique dans l’acceptance du spectromètre à muons est présentée. Les performances et améliorations apportées par le MFT dans différents canaux de physique ont été étudiées en simulationALICE experiment at LHC studies the Quark Gluon Plasma (QGP), a particular state of matter where quarks and gluons are deconfined. A probe to explore this state is the study of several resonances (ρ, ω, ф, J/ψ and Ƴ) through their dimuon decay channel, with a muon spectrometer covering pseudo-rapidity -4 < η < -2.5. In the first part of this thesis, the focus is on light vector mesons (ρ, ω and ф) and their analysis in the 2010 data, in pp collisions at √s = 7 TeV and Pb-Pb collisions at √sNN = 2.76 TeV. Light vector mesons are powerful tools to probe the QGP due to their short lifetime and their dimuon decay channel. Indeed, leptons have negligible final state interactions. Production rates and spectral functions of those mesons are modified by the hot hadronic and QGP medium. In pp collisions, pT distributions, production cross sections and pT-differential cross sections of the different mesons have been extracted. The Pb-Pb analysis and its prospects are also presented. The second part of the thesis concerns ALICE upgrades plans of year 2017. A feasibility study for a Muon Forward Tracker (MFT) in Silicon pixels located upstream of the hadronic absorber, in the spectrometer acceptance, was performed. Performances and improvements brought by the MFT on several physics cases were in simulations