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Orientador: Carlos Alberto dos Reis Filho / Dissertação (mestrado) - Universidade Estadual de Campinas, Faculdade de Engenharia Elétrica e de Computação / Made available in DSpace on 2018-08-16T07:16:47Z (GMT). No. of bitstreams: 1 Lima_JoseErickdeSouza_M.pdf: 6787187 bytes, checksum: 105b3b5aec8638e48cd17d79b4962b1d (MD5) Previous issue date: 2010 / Resumo: Este trabalho descreve um sistema constituído de diversos instrumentos, que se encontram interligados e gerenciados por um aplicativo de software, implementando um ambiente compacto para a caracterização de conversores analógico-digitais, de acordo com os procedimentos descritos nas normas IEEE 1057-1994 e IEEE 1241-2000. O sistema desenvolvido possui limitações quanto aos tipos de conversores analógico-digitais que podem ser testados, devidas às restrições impostas pelos equipamentos disponíveis neste momento. Sua estrutura, no entanto, foi concebida para permitir a expansão destes limites com a troca dos instrumentos limitantes à medida que estes forem adquiridos. A avaliação da sua funcionalidade foi realizada testando dois conversores analógico-digitais que têm características distintas. Enquanto um dos dispositivos testados tem resolução nominal de 10 bits e taxa de conversão de 80 MSPS, o outro tem resolução de 8 bits e taxa de conversão nominal de 8kSPS. A motivação para o desenvolvimento deste sistema está no projeto de conversores analógico-digitais integrados que se encontra em andamento no LPM-FEEC-Unicamp. A disponibilidade de um ambiente de teste com as propriedades do sistema desenvolvido é um requisito importante para o sucesso do projeto, pois viabiliza a verificação imediata dos circuitos construídos, reduzindo o tempo de convergência às metas do projeto / Abstract: This paper describes a system composed of various instruments, which are interconnected and managed by a software application, implementing a compact environment for characterization of analog-digital converters, according to the procedures described in IEEE 1057-1994 and IEEE 1241 -2000. The developed system has limitations on the kinds of analog-digital converters that can be tested due to restrictions imposed by the equipment available at the moment. Its structure, however, was designed to allow the expansion of these limits with the exchange of the limiting instruments as they are acquired. The evaluation of its functionality was performed by testing two analog-digital converters that have distinct characteristics. While one of the tested devices has nominal resolution of 10 bits and conversion rate of 80 MSPS, the other has 8-bit resolution and conversion rate four orders of magnitude below. The motivation for developing this system is the design of integrated analog-digital converters that is being carried on at the LPM-FEEC-Unicamp. The availability of a test environment with the properties of the developed system is an important requisite for the success of the project because it enables the immediate verification of the constructed circuits, thus reducing the convergence time to the project goals / Mestrado / Eletrônica, Microeletrônica e Optoeletrônica / Mestre em Engenharia Elétrica

This master thesies deals about pressure sensors producing by Honeywell and their applications in distributed measuring system. It deals also about base specifications from personal sensors of blood pressure, barometric hypsometer to 500 m, sensors of relative air velocity to 350km/h.

La transmission synaptique dans les corticaux est généralement décrite comme un phénomène de « tout ou rien » ou digital. Un Potentiel d'Action (PA) est émis dans la cellule présynaptique, provoquant le relargage de neurotransmetteurs au niveau du bouton présynaptique et, en conséquence, une dépolarisation transitoire de la cellule postsynaptique (Potentiel Post-Synaptique Excitateur ou PPSE). Cependant, de nombreuses études ont démontrées que la forme du PA présynaptique dépend de l'activité sous liminaire précédant son émission. En effet, si la cellule présynaptique est dépolarisée durant 5 à 10 s avant l'émission du PA, ce dernier s'élargit, ce qui provoque une augmentation du relargage de neurotransmetteurs et de l'amplitude du PPSE. Ainsi, la transmission synaptique dépend d'un phénomène digital, le PA, dont la forme est modulée analogiquement. On parle de transmission Analogique-Digitale. L'élargissement du PA et l'augmentation de la transmission synaptique suite à une longue dépolarisation de la transmission synaptique est nommée Facilitation Analogique-Digital due à la Dépolarisation (FADD). Durant cette thèse, nous nous sommes posé 3 questions principales. Quel est le mécanisme biophysique de la FADD ? Existe-il des Facilitations Analogique Digitale dépendante de modulation de l'amplitude du PA et non de sa largeur ? Les modulations de la forme du PA sont-elles toutes à court terme (de la milliseconde à la seconde) ou existe-t-il des modulations de la forme du PA à long terme (plusieurs jours) ? Pour répondre à la première question, nous avons enregistré des paires de neurones CA3 de l'hippocampe et avons dépolarisé la cellule présynaptique durant 10 s avant l'émission du PA. Nous avons observé une FADD de 30 % qui était supprimée par le blocage pharmacologique des canaux potassiques axonaux Kv1. Ces canaux sont responsables de la phase de repolarisation du PA et ont la propriété de s'inactiver durant de longues dépolarisations. Nous en avons conclu qu'entre les neurones CA3, la FADD était due à l'inactivation des canaux Kv1 pendant la dépolarisation précédant le PA, ce qui provoque un ralentissement de la phase de repolarisation du PA et ainsi un élargissment du PA. Afin de répondre à la seconde question, nous avons enregistré des paires de neurones CA3 dans l'hippocampe. Nous avons observé qu'une courte hyperpolarisation (50 ms) du neurone présynaptique avant l'émission du potentiel d'action provoquait une augmentation de l'amplitude du PA entrainant un accroissement du relargage de neurotransmetteur et de la taille du PPSE. Nous avons nommé ce phénomène FADH pour Facilitation Analogique-Digitale induite par Hyperpolarisation. La FADH est due à récupération de l'inactivation de canaux sodiques responsables de l'amplitude du PA quand le neurone présynaptique est hyperpolarisé, ce qui augmente leur disponibilité. Enfin, pour répondre à la troisième question, nous avons bloqué la transmission synaptique entre les neurones CA3 durant 3 jours. Cela a entrainé une augmentation compensatoire de la transmission synaptique entre les paires de neurones CA3. Il est important de noter que cette augmentation compensatoire est due à la régulation négative des canaux Kv1 entrainant un élargissement du PA. Ainsi, la forme du PA peut-être moduler sur le long terme et participer à la plasticité synaptique. En conclusion, nous avons démontré que le PA n'a pas une forme fixée mais que cette dernière est modulée sur des échelles de temps allant de la dizaine de ms à plusieurs, permettant aux réseaux neuronaux d'élargir leur capacité de transfert d'information. / Generally, the synaptic transmission in cortical networks is described as an « all-or-none » or digital phenomenon. An Action Potential (AP) is emitted in the presynaptic cell entailing the release of neurotransmitters at presynaptic terminal and, consequently, a transient depolarization of the postsynaptic cell (Excitatory Post-Synaptic Potential or EPSP). However, several studies showed that the presynaptic AP shape depend on the subthreshold activity before his occurrence. Indeed, if the presynaptic cell is depolarized during 5 to 10 seconds before the AP emission, the AP is getting broader which leads to an increase in neurotransmitters release and EPSP amplitude. Therefore, the synaptic transmission depends on a digital phenomenon, the AP, whose shape is modulated in an analogic way, the so-called Analog-Digital transmission. The increase in AP width and synaptic transmission following a long depolarization of the presynaptic cell is named Analog Digital Facilitation induced by depolarization (d-ADF). During this thesis, we asked 3 main questions. What is the biophysic mechanism of d-ADF? Are there ADFs depending on AP amplitude modulation? Are the modulations of the AP shape all short term modulations (ms to s) or are there some long term AP shape modulations (days)? To answer the first question, we recorded pairs of hippocampal CA3 neurons and we depolarized the presynaptic cell during 10 ms before AP emission. We observed a d-ADF of 30 % which was suppressed by the phamarcological blockade of axonal potassium channels Kv1. These channels are responsible of the AP repolarization phase and have the property to inactivate during long depolarization. We concluded that the d-ADF at the CA3-CA3 synapse is due to inactivation of Kv1 channels during the depolarization preceding the AP which entails a slowing of the AP repolarization phase and a broadening of the AP. In order to answer the second question, we recorded pairs of hippocampal CA3 neurons. We observed that a short hyperpolarization of the presynaptic neuron (50 ms) before the AP emission entailed an increase of the AP amplitude leading to an increase of neurotransmitters release and EPSP amplitude. We named this phenomenon hyperpolarization induced Analog-Digital Facilitation (h-ADF). The h-ADF is due to the recovery from inactivation of sodium channels responsible of AP amplitude when the presynaptic neuron is hyperpolarized. Finally, to answer the third question, we blocked the synaptic transmission between CA3 neurons for 3 days. This provoked a compensatory increase of synaptic transmission between pairs of CA3 neurons. Interestingly, this compensatory increase is due to the downregulation of Kv1 channels leading to a broadening of the AP. Therefore, the AP shape can be modulated within days and participate to synaptic plasticity. In conclusion, we showed that the AP is not digital but that its shape is modulated within time scales going from the ms to several days, increasing information transfer ability of neuronal networks.

Many problems in early vision can be formulated in terms of minimizing an energy or cost function. Examples are shape-from-shading, edge detection, motion analysis, structure from motion and surface interpolation (Poggio, Torre and Koch, 1985). It has been shown that all quadratic variational problems, an important subset of early vision tasks, can be "solved" by linear, analog electrical or chemical networks (Poggio and Koch, 1985). IN a variety of situateions the cost function is non-quadratic, however, for instance in the presence of discontinuities. The use of non-quadratic cost functions raises the question of designing efficient algorithms for computing the optimal solution. Recently, Hopfield and Tank (1985) have shown that networks of nonlinear analog "neurons" can be effective in computing the solution of optimization problems. In this paper, we show how these networks can be generalized to solve the non-convex energy functionals of early vision. We illustrate this approach by implementing a specific network solving the problem of reconstructing a smooth surface while preserving its discontinuities from sparsely sampled data (Geman and Geman, 1984; Marroquin 1984; Terzopoulos 1984). These results suggest a novel computational strategy for solving such problems for both biological and artificial vision systems.