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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
31

ASPECTS OF THE GEOMETRY OF METRICAL CONNECTIONS

Wells, Matthew J. 01 January 2009 (has links)
Differential geometry is about space (a manifold) and a geometric structure on that space. In Riemann’s lecture (see [17]), he stated that “Thus arises the problem, to discover the matters of fact from which the measure-relations of space may be determined...”. It is key then to understand how manifolds differ from one another geometrically. The results of this dissertation concern how the geometry of a manifold changes when we alter metrical connections. We investigate how diverse geodesics are in different metrical connections. From this, we investigate a new class of metrical connections which are dependent on the class of smooth functions. Specifically, we fix a Riemannian metric and investigate the geometry of the manifold when we change the metrical connections associated with the fixed Riemannian metric. We measure the change in the Riemannian curvatures associated with this new class of metrical connections, and then give uniqueness and existence criterion for curvature of compact 2-manifolds. These results depend on the use of Hodge Theory and ultimately on the function f we choose to define a metrical connection.
32

Deep Boltzmann machines as hierarchical generative models of perceptual inference in the cortex

Reichert, David Paul January 2012 (has links)
The mammalian neocortex is integral to all aspects of cognition, in particular perception across all sensory modalities. Whether computational principles can be identified that would explain why the cortex is so versatile and capable of adapting to various inputs is not clear. One well-known hypothesis is that the cortex implements a generative model, actively synthesising internal explanations of the sensory input. This ‘analysis by synthesis’ could be instantiated in the top-down connections in the hierarchy of cortical regions, and allow the cortex to evaluate its internal model and thus learn good representations of sensory input over time. Few computational models however exist that implement these principles. In this thesis, we investigate the deep Boltzmann machine (DBM) as a model of analysis by synthesis in the cortex, and demonstrate how three distinct perceptual phenomena can be interpreted in this light: visual hallucinations, bistable perception, and object-based attention. A common thread is that in all cases, the internally synthesised explanations go beyond, or deviate from, what is in the visual input. The DBM was recently introduced in machine learning, but combines several properties of interest for biological application. It constitutes a hierarchical generative model and carries both the semantics of a connectionist neural network and a probabilistic model. Thus, we can consider neuronal mechanisms but also (approximate) probabilistic inference, which has been proposed to underlie cortical processing, and contribute to the ongoing discussion concerning probabilistic or Bayesian models of cognition. Concretely, making use of the model’s capability to synthesise internal representations of sensory input, we model complex visual hallucinations resulting from loss of vision in Charles Bonnet syndrome.We demonstrate that homeostatic regulation of neuronal firing could be the underlying cause, reproduce various aspects of the syndrome, and examine a role for the neuromodulator acetylcholine. Next, we relate bistable perception to approximate, sampling-based probabilistic inference, and show how neuronal adaptation can be incorporated by providing a biological interpretation for a recently developed sampling algorithm. Finally, we explore how analysis by synthesis could be related to attentional feedback processing, employing the generative aspect of the DBM to implement a form of object-based attention. We thus present a model that uniquely combines several computational principles (sampling, neural processing, unsupervised learning) and is general enough to uniquely address a range of distinct perceptual phenomena. The connection to machine learning ensures theoretical grounding and practical evaluation of the underlying principles. Our results lend further credence to the hypothesis of a generative model in the brain, and promise fruitful interaction between neuroscience and Deep Learning approaches.
33

Water Quality Modeling of Freshwater Diversions in the Pontchartrain Estuary

Roblin, Rachel 16 May 2008 (has links)
A 1-D tidal, salinity and water quality model that analyzes the general effects freshwater diversions have on the water quality of the Pontchartrain Estuary over a 17-year period is presented here. Using the modeled live algae concentrations in conjunction with the algal bloom probability model results produces an accurate prediction of algal bloom occurrences between 1990 and 2006. The model predicts that the addition of freshwater diversions into Maurepas swamp and increases to flow in the Bonnet Carré Spillway may cause more intense and frequent algal blooms to occur around the Pontchartrain Estuary. The model also predicts that high nutrient input events that occur earlier in the year (January/February) will not likely have algal blooms associated with them. When nutrient input events (even small events) occur in the late spring or early summer, algal blooms have a high probability of occurring when the salinity, temperature and light levels are sufficient.
34

Studies On Cloning And Characterization Of GnRH Receptor From The Pituitary Of Bonnet Monkey (Macaca Radiata) And Functional Studies With The Antiserum To GnRH Receptor

Santra, Sumana 01 1900 (has links)
GnRH is a decapeptide hormone, which plays a major role in the process of mammalian reproduction. It is synthesized by the hypothalamus and binds to its cognate receptor on the pituitary, to bring about the release of gonadotropins LH and FSH. The gonadotropin releasing hormone receptor belongs to the family of G-protein coupled receptors that are characterized by the presence of seven putative transmembrane regions linked by extracellular and intracellular loops. It is a glycoprotein made up of 327 amino acids. During the last several years cloning of this receptor from a number of species has provided considerable insight into the molecular basis of interaction between GnRH and its receptor. The GnRH receptor has been cloned and sequenced from a large number of mammalian species such as human, sheep, cow, rat, mouse, etc. GnRH receptor is known to be unique among the G protein coupled receptors by virtue of the fact that it lacks a C terminal tail which has been implicated in coupling to G-proteins in several seven transmembrane domain receptors. Other members of this G-protein coupled receptor family such as the Luetinising hormone receptor, Follicle stimulating hormone receptor contain the characteristic cytoplasmic tail of about 68-72 amino acids, which is believed to possess a plasma membrane targeting signal sequence. Mutation studies carried out revealed that this C terminal sequence may be important in membrane trafficking in other G protein coupled receptors, since mutant forms of the receptor were not expressed on the plasma membrane. In many G-protein coupled receptors, part of the cytoplasmic tail is important for desensitization and internalization. However, the GnRH receptor is an exception in that its G protein coupling and desensitization functions are dependent on regions of the GnRH receptor other than the carboxy terminal cytoplasmic domain. It has been well established that binding of GnRH to its cognate receptor induces conformational change and it is suggested that the entire extracellular loop and transmembrane region are involved in binding and signal transduction. It is pertinent to note in this connection, that the use of both polyclonal and monoclonal antibodies has contributed significantly to the understanding of the interactions between ligands and their cognate receptors. Recent studies have established that there are several extrahypothalamic sites of production of GnRH, which include testes, lymphocytes, human placenta, mammary gland etc. Of these the production of GnRH in the human placenta has attracted attention in view of the demonstration that the placental chorionic gonadotropin production (CG) is regulated by placental GnRH. Our laboratory has been investigating the role of GnRH in regulation of Chorionic Gonadotropin (CG) using both in vitro human placental villi system and pregnant bonnet monkey as models. One important and interesting observation that has been made in our studies as well as by several others is that the affinity of the placental GnRH receptor to its ligand is quite low compared to the pituitary receptor. Available evidence indicates that the hypothalamic and the placental GnRH are similar in structure and consequently the difference in the affinity could be attributed to the differences between the pituitary and the placental GnRH receptor. Considering this, it will be ideal and of interest to compare the GnRH receptor from the pituitary and placenta of a species in which both in vitro and in vivo studies can be carried out. For obvious ethical reasons, in vivo studies cannot be carried out with humans. Since very little information is available on the GnRH receptor in non-human primates, as a first step we undertook the task of characterizing the GnRH receptor from the bonnet monkey pituitary and production of antibodies to it, since all the studies carried out so far with antibodies to GnRH receptor have employed antibodies generated to a small stretch of peptide in the extracellular region. Thus the objective of the present study is to clone and express the GnRH receptor from the pituitary of the bonnet monkey {Macaco radiata), raise antibodies and to characterize them functionally. Chapter 1 provides a general review of information currently available regarding structure of GnRH and its receptor as well as the results of studies using antibodies directed to the GnRH receptor fragments. Chapter 2 deals with the partial cloning of the GnRH receptor from the pituitary of the bonnet monkeys by the technique of RT-PCR. We were able to amplify a PCR fragment of 959bp corresponding to the almost full-length GnRH receptor sequence. Southern blot analysis using the full length human pituitary GnRH receptor cDNA as the probe revealed that the 959 bp product was able to hybridize to the probe, confirming the authenticity of the PCR product. Restriction mapping with three different restriction enzymes also gave the expected pattern. Additional evidence was obtained by cloning of this PCR product into expression vector pGEX 5X-2 and sequencing a number of clones. The sequences obtained were then subjected to homology search with other known GnRH receptor sequences available in the Genebank. The sequence was found to be 97% homologous to the human pituitary GnRH receptor sequence and also showed a high degree of homology with the GnRH receptor from other species. Although antibodies have been raised to the GnRH receptor by immunizing rabbits with synthetic peptides corresponding to extracellular regions of the receptor, most of the antibodies have a very low affinity towards the native receptor. Also results of studies using these antibodies indicated that the peptide antibodies failed to recognize the native receptor. Initially we made efforts to express the full-length receptor in E.coli BL21 cells. However, since we were not successful in our attempts to express the full length, we resorted to express a smaller fragment which corresponded to amino acids 164-266, that encompassed one extracellular, two transmembrane and one intracellular domain. Before we proceeded ahead to express this fragment, the authenticity of this fragment was established by southern hybridization, restriction mapping as well as sequencing. This monkey pituitary GnRH receptor fragment corresponding to 315 bp was cloned in the expression vector pGEX 5X-2 and the protein corresponding to this region was overexpressed as a recombinant fusion protein in E.coli. BL21 plys S strain. Overexpression of the protein was induced using IPTG and the lysate was subjected to electrophoresis on a SDS-PAGE gel A signal corresponding to 37Kda, which is in agreement with the expected size (GST portion of the fusion protein plus the peptide) was observed following induction with IPTG. The overexpressed protein was found to be localized to the inclusion bodies, and this was purified from inclusion bodies by cutting out the band corresponding to the overexpressed protein from the preparative SDS-PAGE gels and the protein was eluted out by electroelution. Sera from the rabbits, which were immunized with the overexpressed protein, were checked for the presence of antibodies by ELISA, using the purified protein as the antigen. After ascertaining the presence of high titre antibodies in the sera of immunized animals, the serum was used to detect the presence of GnRH receptor in the membrane preparations from rat pituitary, monkey pituitary and human placenta using the technique of western blotting. A signal corresponding to 68Kda was found in all the cases and the specificity of this signal was established by preabsorption of the antisemrn with pituitary and placental membrane preparations, which resulted in decrease in the intensity of the signal. . The antiserum was also used to localize the GnRH receptor in different tissues such as first trimester and term human placenta, sheep pituitary, monkey placenta, human pituitary and rat prostate by the technique of immunotlourescence using the confocal microscope. The results of the above studies are presented in Chapter 3. Chapter 4 deals with the functional studies carried out using the antiserum to GnRH receptor in an in vivo system using male and female rats. As discussed earlier, all the reported studies on use of antibodies to GnRH receptor have employed a small region of the extracellular portion of the receptor for the production of antibodies. However, the antibodies in the present study have been directed towards a larger fragment, and considering this, it was of interest to evaluate the effect of these antibodies in in vivo as well as in vitro systems. Two approaches were used to evaluate the effect of antibodies, namely passive and active immunization i.e. administration of antiserum to GnRH receptor fragment raised in rabbits and also immunization with the overexpressed recombinant GnRH receptor protein. This study was carried out in both immature as well as adult male rats and also in the cycling female rats. Several parameters were monitored, which included various androgen dependent parameters in the male reproductive tissue i.e. body weight, testes weight as well as the weight of accessory sex organ-the prostate and also the fertility status. In the female rats the changes in the weight of the ovary, uterus, serum E2 and P4 were monitored. No effect on the body weight, testis weight or prostate weight was noticed in the treated animals compared to the controls. Furthermore, an indication that the hypothalamo-pituitary-gonadal axis was not compromised in the passively immunized animals was obtained from the observation that there was no decrease in the serum and testicular testosterone levels. In fact, there was a significant increase in the serum and testicular testosterone levels. This suggested the possibility that the antibodies are exerting a ßßstimulatory effect. To ascertain this possibility, two androgen dependent parameters namely the levels of mRNA for TGF ß, which is androgen repressed gene and Prostatein Cl, which is an androgen induced gene were monitored. It was observed that there was a significant increase in the steady state mRNA level of Prostatein Cl in GnRH antiserum treated animals and a corresponding decrease in TGFß mRNA levels. Active immunization study with injection of the recombinant protein was also carried out in adult male rats. All immunized animals responded to the immunization by producing high titre antibodies, the presence of which was detected by ELISA using the recombinant protein as the antigen. The results of the study revealed that there was no change in the body weight, testis weight or prostate weight. However, there was a significant increase in the serum and testicular testosterone levels compared to the control animals. Fertility studies indicated that all the animals were fertile. However, as in the case of passive immunization studies, an increase in the mRNA levels of Prostatein Cl was noted although the level of TGFß, which is an androgen repressed gene could not be monitored in this case due to the very high levels of endogenous androgens present in these animals. Thus it appears that the antibodies produced both in rabbits as well as in rats were stimulatory in nature probably indicating some specific characteristic of the region of the receptor to which the antibody has been raised. The results obtained in the present study are of significance considering the fact that studies using the antibodies to LH receptor and TSH receptor, both of which belong to the G-protein coupled family also report production of stimulatory antibodies. Active immunization studies using the GnRH receptor protein in the female rats also revealed that the antibodies were not compromising the hypothalamo-pituitary-gonadal axis. Accordingly, there was no decrease in the serum or ovarian levels of estradiol 17ß and progesterone and there was no difference in the ovarian weight. However, a significant decrease in the uterine weight and difference in the histology of the uterus of the immunized animals was observed. This is of significance, considering the fact that the presence of the GnRH receptor has been reported in the uterus also. In an attempt to develop an in vitro system to monitor the effect of GnRH receptor antibody, an in vitro incubation system with the human placental villi, which is known to produce both GnRH and hCG was standardized. Sensitive ELISA and RIA were developed for GnRH and hCG, respectively to monitor their levels.The results of the studies on the effect of addition of GnRH receptor antibody to the immunoreactive hCG levels in the placental incubation medium are presented in Chapter 5. In addition, advantage was taken of the report of the presence of the specific receptors for GnRH in the Leydig cells of the rats, to evaluate the effect of the GnRH receptor antibodies on the function of leydig cells. Results of studies in which the effect of addition of GnRH receptor antibodies on the testosterone production by purified rat Leydig cells were monitored revealed that there was no inhibitory effect. Finally in the Chapter 6, a general discussion and critical evaluation of the results obtained in the study, in light of similar studies reported in literature are presented.
35

le cauchemar mythique : Etude morphologique de l'oppression nocturne dans les textes médièvaux et les croyances populaires / The mythical nightmare : morphological study of the nocturnal oppression in the medieval texts and the popular beliefs

Zochios, Stamatios 06 December 2012 (has links)
Cette thèse cherche à éclairer les représentations textuelles du « cauchemar », non pas considéré comme un mauvais rêve, mais comme un démon d'origine médiévale. Selon les sources, cet esprit envahit la nuit la chambre de ses victimes. Ensuite, il s'installe sur elles et oppresse leurs poitrines, en provoquant la paralysie, l'étouffement et même la mort des personnes endormies. Cet acte est un motif typique des traditions folkloriques européennes. Dans la tradition gréco-romaine, l' ephialtès et l' incubus semblent agir de la même manière. Notre étude se focalise sur les textes du Moyen Âge, où une abondance de textes divers (ecclésiastiques, littéraires et médicaux) témoigne d'une affinité entre les actions du cauchemar et celles d'un ensemble d'êtres fantastiques, comme les revenants, les elfes, les nains et les sorcières. A la lumière de ces premières constatations, cette étude examine les textes médiévaux en relation avec les traditions antiques, ainsi que les traditions qui apparaissent plus tardivement en Europe. La thèse contient trois parties: dans la première, elle met en évidence un démon -archétypique, qui révèle un substrat étymologique et descriptif commun dans les différents extraits étudiés. Sa relation avec le genius loci, dont le caractère est double, bienveillant et malveillant à la fois, a un intérêt particulier. Les sources dressent le portrait d'un cauchemar qui n'est pas seulement un être démoniaque. En effet, il s'agit également d'un être qui apporte des richesses dans la demeure et à ses habitants. Dans la deuxième partie, la relation du cauchemar avec certaines divinités nocturnes de nature dualiste est démontrée, ainsi que son lien avec les Douze Jours de Noël. Finalement, dans la troisième partie, la thèse étudie un lien général qui apparaît entre le cauchemar, la sorcellerie, le cheval, le carnaval et surtout le Double et les traditions extatiques - chamaniques européennes, afin de signaler en dernier lieu de quelle manière cette entité peut combiner des caractères multiples et différents. / The present Phd Thesis sets to shed light on the topic of the “nightmare”, considered not as a bad dream as it is commonly conceptualized, but instead as a demon of medieval origin. This spirit, said to intrude a room during the night hours, usually sits and exercises pressure on the chest of the alleged victim. This particular act, causing paralysis, drowning, and at times even death to the asleep, is a constant and common narrative motive in the folk stories of Europe. In the Greco-Roman tradition, the “ephialtes” and the “incubus” seem to function in a similar fashion. During the Middle Ages (the period which this study focuses on), an abundance of texts -ecclesiastical, literary, and even medical- suggests a close connection between the nightmare's actions and various super-natural beings, such as revenants, fairies, witches, elves, and dwarves. Drawing from this evidence, this study seeks to examine these texts' relation to the traditions of antiquity, along with the relevant traditions arising later across Europe. The Phd thesis is divided into three main sub-sections: the first part focuses on the relation between different variations of the appearance of an archetypal demon, as revealed by common etymological origins and similar actions. Furthermore, descriptions of the nightmare as a genius loci of two-fold nature, both benevolent and malevolent, are explored. Along with its depiction as a demonic being, the nightmare, is frequently presented as an entity offering treasures to the household and its inhabitants. The second part brings to the forefront nightmare's relation to certain nocturnal deities of dual nature, as well as to the holy season of the Twelve Days of Christmas. During the third and last part of the thesis, I scrutinize the relationship between the nightmare and the horse, the carnival, the witchcraft, and particularly the doppelgänger and the ecstatic-shamanistic practices of Europe.
36

Fenómenos alucinatorios visuales y funcionamiento cognitivo en pacientes con déficit de agudeza visual. A propósito del Síndrome de Charles Bonnet

Sáez Ibañez, María de los Ángeles January 2008 (has links)
Psicólogo / Las alucinaciones visuales son síntomas comunes en cuadros clínicos de diversa etiología. Particularmente en el contexto oftalmológico, el Síndrome de Charles Bonnet (SCB) se ha definido por la presencia de alucinaciones visuales generalmente complejas en sujetos con déficit adquirido en su capacidad visual y psicológicamente normales, pudiendo distinguir la naturaleza irreal de las visiones que experimentan. La presente investigación tiene como objetivo describir alucinaciones visuales y nivel de funcionamiento cognitivo en un grupo de pacientes con agudeza visual deficiente y adquirida con el fin de aportar evidencia sobre las características de las alucinaciones visuales y su presentación con conservación o deterioro de las funciones corticales superiores. Los hallazgos indican que las alucinaciones visuales preponderantes son de tipo elemental y estereotipadas presentándose en asociación a emociones displacenteras. Se observó en el grupo evaluado un nivel intelectual global conservado, destacando disfunción de las capacidades atencionales, mnésicas y de funciones ejecutivas. Se discute si estos déficits cognitivos específicos influyen en la manifestación clínica de alucinaciones visuales
37

Online perception with machine learning for automated driving

Ngo, Quang Thanh 09 December 2020 (has links)
The understanding of the environment is the critical ability not only for the living creature but also for automation fields like the robot, automated car, and intelligent system. Especially for some essential task in the domain of automotive such as autonomous driving, path planning, localization, and object detection, the more information we gather, the better the result we get. Intelligent vehicle technology relies on sensorial perception to understand the surroundings of the vehicle. The objective of the research is developing a cooperative online perception system with semantic segmentation for automated driving and improving the current semantic segmentation framework to make it more robust and more suitable for our future projects.
38

Studie vlivu vlastností materiálu na simulaci nárazu hlavy chodce na kapotu / Study of Material Properties Influence on Pedestrian Head Impact on Bonnet

Coufal, Tomáš January 2009 (has links)
The thesis describes the complex of basic testing procedures conducted by Euro NCAP company with a view to the examination of pedestrian protection in accordance with EEVC WG 17 and topical instruments used at passenger vehicles for pedestrian protection. It includes a detailed procedure of the creation of an adult head impactor including its certification and the formation of its impact on the bonnet of the vehicle. It is specialized in the studies how material properties influence the size of HIC criterion.
39

Homogenní kapota - chování při nárazech impaktorem hlavy / Homogeneous Bonnet - Behavior at Head Impactor Impacts

Kadrmas, Lukáš January 2009 (has links)
This thesis deals with the subject of crash tests Euro NCAP, concretely child-head impact test to the car bonnet. Object of thesis is make homogeneous car bonnet, where will remove stiffness places and also the bonnet global stiffness won´t be worst. The bonnet must carry out limits for pedestrian protection.
40

Projekt montážní dílny závěsů kapoty / Project of bonnet hinges assembly shop

Chadim, Jakub January 2011 (has links)
This thesis deals with the technological project of rear bonnet hinges assembly shop, specifically with desing the layout the of assembly shop in the Edscha Automotive Kamenice s.r.o. company. The thesis shows the basic theory to understanding the problems of assembly workshops. The thesis analyses the present state of the assembly workshop and with reference to the requirements of the company and fundamentals technological projection features three possible solutions. The selected solution becomes the shape of rationalization project. In the end is the variant technical-economic reviewed.

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