Excitabilité et solitons temporels de phase dans un système laser neuromorphique

In this thesis, I report the results of studies performed during these last three years at Institut Non Linéaire de Nice. First, I present results on perturbing a neuron-like excitable system build from a simple laser with an injected signal experiment. Excitability, that comes in this case from the proximity of a Saddle-node bifurcation, is defined as an all or-nothing response to an external perturbation. The excitable response, that arises from perturbation larger than a certain threshold, corresponds to the unlocking between the two lasers for one period. Triggering of such excitable responses, that shape do not dependent on the perturbation (kind, strength), is demonstrated applying perturbations. In a second part, I analyze the influence of the connection between one of this neuron and its own axon. Experimentally we add a feedback mirror building a laser submitted to injection and feedback. Under certain conditions, the previous excitable response is found to regenerate in the external cavity, exhibiting a memory behavior where the information is coded in the time spiking pattern. Analytically, this corresponds to the addition of a linear delay term that acts as a space-like coordinate allowing the storage of many "excitable responses", and their interpretation in terms of Sine-Gordon topological solitons. Application of appropriate perturbations could lead to the control of "information" present. Many interesting behaviors of this new structures are observed and analyzed numerically with appropriate models, like collisions, clustering, particle-like diffusion, locking to periodic additional forcing...Dans cette thèse, je reporte les résultats d'études développées durant ces trois dernières années à l'Institut Non-Linéaire de Nice. Premièrement, je présente des résultats sur l'application de perturbation à un système excitable, obtenus à partir d'un simple laser à signal injecté. L'excitabilité, qui vient dans ce cas de la proximité d'une bifurcation noeudselle sur un cercle, et est définit comme une réponse tout-ou-rien à une perturbation. La réponse excitable, présente pour des perturbations supérieures à un certain seuil, correspond au décrochage des deux lasers pour une période. Le déclenchement de tels réponses excitable, dont la forme ne dépend pas de la perturbation (type, amplitude), est démontré par l'application de perturbation. Dans un deuxième temps, j'analyse l'influence de la connexion entre un neurone et son propre axone. Expérimentalement nous ajoutons un miroir de rétroaction fabriquant ainsi un laser injecté et réinjecté. Sous certaines conditions, la précédente réponse excitable se régénère dans la cavité externe, exhibant une propriété de mémorisation, où l'information est codée dans la phase du faisceau. Analytiquement, cela correspond à l'addition d'un terme de retard linéaire qui joue le rôle d'un "quasi-espace" permettant la coexistence de plusieurs "réponse excitable", et leur interprétation en terme de solitons topologique de Sine-Gordon. L'application de perturbations appropriées peut mener au contrôle de l'information présente. De nombreux comportements ont ainsi été observés et reproduits numériquement avec des modèles appropriés, comme les collisions, le groupement, la diffusion, l'accrochage à une modulation périodique, ..

Análise paramétrica da influência da combustão interturbinas num Turbofan de muito alta razão de bypass

Nos últimos anos as viagens aéreas têm vindo a aumentar exponencialmente, levando à construção de aeronaves maiores e mais potentes. A crescente necessidade de conseguir obter trações mais elevadas e consumos menores, levou a que a razão de bypass dos motores começasse a aumentar significativamente. Esse aumento traduz-se em uma diminuição de TSFC mas acompanhado também por uma diminuição da tração. O principal fator seria a falta de energia disponível, visto que o aumento da fan leva também ao aumento da sua necessidade energética mas a energia disponibilizada pela turbina continua a ser a mesma. Assim após toda a energia ter sido retirada das turbinas para o funcionamento da fan e dos compressores, a energia restante que serve para a produção de tração, começa a tender para níveis extremamente baixos. A combustão sequencial surgiu há alguns anos como uma possível solução a esse problema. Através da introdução entre as turbinas, consegue-se gerar energia extra. Essa queima é efetuada a pressões mais elevadas do que no caso do afterburner, obtendo um maior rendimento e menor consumo quando comparado ao mesmo. O foco deste trabalho está na verificação da viabilidade da implementação de um ITB em um turbofan de muito alta razão de bypass, mais especificamente num turbofan 3 eixos sem mistura de caudais, tendo sido escolhido um motor já implementado no mercado. O ITB (Câmara de combustão entre turbinas) é implementado no ducto entre a turbina de pressões intermédias e a turbina de baixas pressões. Os resultados obtidos são comparados aos do motor base de modo a verificar se os níveis de tração e de consumo específicos são favoráveis.In recent years, airline travel has been increasing exponentially, leading to the manufacturing of larger and more powerful aircraft. The growing need to achieve higher thrust and lower consumption led to the significantly increase in engine bypass ratio. That increase translates into a decrease of TSFC but also accompanied by a decrease in thrust. The main factor is the lack of available energy, since the increase in the fan also leads to their increased energy requirement but the energy available from the turbine remains the same. Therefore, after all the energy withdrawn from the turbine for operation of the fan and the compressor, the remaining power that serves to produce thrust begins to tend to extremely low levels. The sequential combustion emerged a few years ago as a possible solution to this problem. The introduction of a second combustion chamber between turbines may provide extra power. This combustion is conducted at higher pressures than in the case of afterburner, obtaining a higher yield and lower consumption compared to the same. The focus of this work is in checking the viability (thrust and consumption) of implementing an ITB in a turbofan of very high bypass ratio, more specifically in a turbofan 3-shafts unmixed flows, having chosen an engine already implemented in the market. The ITB (Interstage Turbine Burner) is implemented in the duct between the intermediate pressure turbine and low pressure turbine. The results are compared to the base engine in order to verify if the specific traction and consumption levels are favorable

Self-medication with antibiotics: identification of risk factors and analysis of the brazilian population’s lifestyle.

Objectives:Measure the prevalence of adult and elderly users of the Brazilian primary healthcare system who self-medicated with antibiotics and identified its association with risk factors for self-medication and lifestyle. Materials and Methods:This is a quantitative, epidemiological study carried out in the Brazilian primary healthcare system. We used a semi-structured questionnaire and the Fantastic Lifestyle Checklist. We carried out a bivariate analysis, a binomial logistic regression, and the Mann-Whitney nonparametric test.Results: Out of the total sample (537 participants), 40.6% used antibiotics without medical prescription in the last 12 months. The dependent variable was associated with the presence of pain (OR=2.390, CI95, 1.414-4.041); storage of leftover antibiotics in the home (OR=2.124 CI95, 1.122-4.021); and use of medicines on someone’s recommendation (OR=1.722, CI95, 1.127-2.631). The group of individuals who used antibiotics without prescription in the last year had the lowest values in all domains assessed by the Fantastic Lifestyle Checklist and had the highest proportions in the final score of “Fair" and "Needs improvement”.Conclusions: A significant proportion of primary health care users in Brazil used antibiotics without medical prescription. Therefore, the population should receive better guidance on the use of antibiotics and greater incentive to develop healthy habits and lifestyle

A cross-sectional study on dental surgeons’ immune status against hepatitis B virus in the Public Health System

Hepatitis B is a severe public health problem. The main world health centers have discussed it due to its pandemic proportion, high pathogenicity and infectivity. This study aimed to determine the immunization profile of dental surgeons - against hepatitis B virus (HBV) in the Public Health System (PHS) through the detection of anti-HBsAg antibodies by immunochromatography and associations with dental surgeons’ social and educational profile, factors related to professional knowledge and practices. This is a cross-sectional study on the prevalence of vaccination and immune status to HBV in dentists of Sao Paulo State PHS. Data collection occurred in three stages: questionnaire application, analysis of adhesion to the vaccination protocol and anti-HBsAg tests. Statistical analysis used the Bivariate Analysis and the Binary Logistic Regression. From the total of 219 interviewees, 74.9% reported having received three doses of the vaccine, but 35.6% were not immune to HBV. The dependent variable was associated with years in the public service (years) (OR [Odds Ratio]=1.04; 95% CI 1.00-1.08); knowledge on the subject (OR=6.93; 95% CI 1.39-34.40); incorrect answer concerning the etiological agent of the disease (OR=2.60; 95% CI 1.30-5.22); ignorance on the number of vaccine doses that have been administered (OR=3.43; 95% CI 1.14-10.30); and less than three doses of the vaccine in the immunization schedule (OR=8.76; 95% CI 3.50-21.91). A considerable portion of professionals non-immune to the HBV were found. We concluded that knowledge, years of practice and completion of the vaccination schedule (three doses) affected dental surgeons’ immune status to HBV

Non-Hermitian zero mode laser in a nanophotonic trimer

Symmetry-protected zero modes in arrays of coupled optical elements have attracted considerable attention because they are expected to be robust against coupling disorders. In the Hermitian limit, zero modes are dark ones, i.e. the intensity in one sublattice vanishes; yet, in a non-Hermitian counterpart, zero modes can be bright and feature {\pi}/2 phase difference between sublattices. In this work, we report on the direct observation of a lasing zero mode in a non-Hermitian three coupled nanocavity array. We show efficient excitation for nearly equal pump power in the two extreme cavities. Furthermore, its efficiency can be dynamically controlled by pumping the center cavity. The realization of zero mode lasing in large arrays of coupled nanolasers has potential applications in laser-mode engineering and it opens up promising avenues in optical computing.Comment: 5 pages, 4 figure