Population coding—the transmission of information by the combined activity of many neurons—is a feature of many neural systems. Identifying the role played by individual neurons within a population code is vital for the understanding of neural codes. In this thesis I examine which stimuli are best encoded by a given neuron within a population and how this depends on the informational measure used, on commonly-measured neuronal properties, and on the population size and the spacing between stimuli. I also show how correlative measures of topography can be used to test for significant topography in the anatomical arrangement of arbitrary neuronal properties. The neurons involved in a population code are generally clustered together in one region of the brain, and moreover their response selectivity is often reflected in their anatomical arrangement within that region. Although such topographic maps are an often-encountered feature in the brains of many species, there are no standard, objective procedures for quantifying topography. Topography in neural maps is typically identified and described subjectively, but in cases where the scale of the map is close to the resolution limit of the measurement technique, identifying the presence of a topographic map can be a challenging subjective task. In such cases, an objective statistical test for detecting topography would be advantageous. To address these issues, I assess seven measures by quantifying topography in simulated neural maps, and show that all but one of these are effective at detecting statistically significant topography even in weakly topographic maps. The precision of the neural code is commonly investigated using two different families of statistical measures: (i) Shannon mutual information and derived quantities when investigating very small populations of neurons and (ii) Fisher information when studying large populations. The Fisher information always predicts that neurons convey most information about stimuli coinciding with the steepest regions of the tuning curve, but it is known that information theoretic measures can give very different predictions. Using a Monte Carlo approach to compute a stimulus-specific decomposition of the mutual information (the stimulus-specific information, or SSI) for populations up to hundreds of neurons in size, I address the following questions: (i) Under what conditions can Fisher information accurately predict the information transmitted by a neuron within a population code? (ii) What are the effects of level of trial-to-trial variability (noise), correlations in the noise, and population size on the best-encoded stimulus? (iii) How does the type of task in a behavioural experiment (i.e. fine and coarse discrimination, classification) affect the best-encoded stimulus? I show that, for both unimodal and monotonic tuning curves, the shape of the SSI is dependent upon trial-to-trial variability, population size and stimulus spacing, in addition to the shape of the tuning curve. It is therefore important to take these factors into account when assessing which stimuli a neuron is informative about; just knowing the tuning curve may not be sufficient.

A caracterização da topografia de superfícies de engenharia é muito importante em aplicações envolvendo atrito, lubrificação e desgaste. Esta prática teve inicio na década de 30 e até os dias atuais vários esforços são desprendidos no sentido de desenvolver novos métodos para avaliação de superfícies. Embora a grande maioria das superfícies seja especificada por parâmetros 2D tais como Ra (rugosidade média) muitas vezes eles não são suficientes para controlar e caracterizar uma superfície. Novos parâmetros foram desenvolvidos onde engenheiros e processistas de manufatura não são somente capazes de ver as superfícies com muito mais detalhes, mas também são capazes de desenvolver e testar superfícies visando a sua funcionabilidade, ou seja, serem produzidas, controladas e testadas de acordo com a função que irão desempenhar na aplicação. O presente trabalho analisa os parâmetros atuais largamente utilizados pela indústria mostrando as suas vantagens e suas limitações. Testes experimentais foram realizados utilizando estes parâmetros na caracterização de superfícies de mancais após a sua fabricação bem como o seu desempenho em teste de vida acelerado. Foram utilizados um perfilômetro mecânico e um perfilômetro óptico para a medição dos parâmetros de superfície. É mostrado que os parâmetros de rugosidade Ra, Rsk, Rk, Sbi, Sci e Svi podem ser usados para caracterizar um processo de fabricação de uma superfície bem como a sua evolução topográfica num teste de vida acelerado. / The topographic characterization of engineering surfaces is very important in applications involving friction, wear and lubrication. This practice started in the 1930s and until now great efforts have been put to developing new methods for engineering surfaces. Although most of the surfaces are specified using 2D (two dimensions) parameters as Ra (average roughness), sometimes they are not enough to control and characterize the surface. A new group of parameters were developed which engineering and process designers are not only able to view their surfaces in much greater details, but they are also able to design and test surfaces with an eye toward functionality, i. e., to be produced, controlled and tested according to its application. The present work analyzes the present parameters widely used by the industry showing their advantages and their limitations. Experimental tests were carried out utilizing these parameters in the characterization of bearing surfaces after manufacturing as well its performance in the accelerated life test. Mechanical and optical profilers were used to make the measurements. It is shown that the parameters Ra, Rsk, Rk, Sbi, Sci and Svi can be used to characterize the surface manufacturing process as well its topographic evolution in an accelerated life test.

A caracterização da topografia de superfícies de engenharia é muito importante em aplicações envolvendo atrito, lubrificação e desgaste. Esta prática teve inicio na década de 30 e até os dias atuais vários esforços são desprendidos no sentido de desenvolver novos métodos para avaliação de superfícies. Embora a grande maioria das superfícies seja especificada por parâmetros 2D tais como Ra (rugosidade média) muitas vezes eles não são suficientes para controlar e caracterizar uma superfície. Novos parâmetros foram desenvolvidos onde engenheiros e processistas de manufatura não são somente capazes de ver as superfícies com muito mais detalhes, mas também são capazes de desenvolver e testar superfícies visando a sua funcionabilidade, ou seja, serem produzidas, controladas e testadas de acordo com a função que irão desempenhar na aplicação. O presente trabalho analisa os parâmetros atuais largamente utilizados pela indústria mostrando as suas vantagens e suas limitações. Testes experimentais foram realizados utilizando estes parâmetros na caracterização de superfícies de mancais após a sua fabricação bem como o seu desempenho em teste de vida acelerado. Foram utilizados um perfilômetro mecânico e um perfilômetro óptico para a medição dos parâmetros de superfície. É mostrado que os parâmetros de rugosidade Ra, Rsk, Rk, Sbi, Sci e Svi podem ser usados para caracterizar um processo de fabricação de uma superfície bem como a sua evolução topográfica num teste de vida acelerado. / The topographic characterization of engineering surfaces is very important in applications involving friction, wear and lubrication. This practice started in the 1930s and until now great efforts have been put to developing new methods for engineering surfaces. Although most of the surfaces are specified using 2D (two dimensions) parameters as Ra (average roughness), sometimes they are not enough to control and characterize the surface. A new group of parameters were developed which engineering and process designers are not only able to view their surfaces in much greater details, but they are also able to design and test surfaces with an eye toward functionality, i. e., to be produced, controlled and tested according to its application. The present work analyzes the present parameters widely used by the industry showing their advantages and their limitations. Experimental tests were carried out utilizing these parameters in the characterization of bearing surfaces after manufacturing as well its performance in the accelerated life test. Mechanical and optical profilers were used to make the measurements. It is shown that the parameters Ra, Rsk, Rk, Sbi, Sci and Svi can be used to characterize the surface manufacturing process as well its topographic evolution in an accelerated life test.

Made available in DSpace on 2017-07-10T17:31:02Z (GMT). No. of bitstreams: 1 Lucileia.pdf: 4845527 bytes, checksum: 03df89e1eb72d5a4ebab7665eca47e9a (MD5) Previous issue date: 2010-04-13 / This paper presents characteristics of the surface coverage found in bedside drainage developed on volcanic substrate, in the Upper Rio Sergento Course (Campo Erê - SC). The descriptions of the materials were made by sampling along five transects, and the opening of three trenches. The physical attributes of materials associated with the analysis of particle size and volume compared with the topography point to allow pedogenesis as the main factor in the evolution of bedside drainage, mainly over the nose and side slope. In the hollow were identified two deposits of colluvium. The association of physical and chemical properties of surface coverage to classify the soil at the head of this drainage as oxic soils, from red to dark reddish nose to bruno on side slope. The clay minerals as revealed by X-ray diffraction in surface coverage over the nose and side slope of bedside drainage geochemical study indicate hydrolysis intense situation in the area. The largest number of peaks of kaolinite shows an environmental geochemist with a predominance of monossialitization process. Less intense, the process also occurs alitização, being filed by gibbsite. Considering the role of geochemical processes, as well as the occurrence of kaolinite dominant on clay less frequent as vermiculite and gibbsite, the indices obtained and disclosed by routine chemistry, the surface coverage of the nose and side slope, at the bedsiders of drainage studied fits as ferruginous desaturated. / Este trabalho apresenta características da cobertura superficial encontrada em cabeceira de drenagem desenvolvida sobre substrato vulcânico, no Alto Curso do Rio Sargento (Campo Erê - SC). As descrições dos materiais foram efetuadas por meio de sondagens ao longo de cinco transectos, bem como da abertura de três trincheiras. Os atributos físicos dos materiais, associados à análises da granulometria e relação dos volumes com a topografia permitem apontar a pedogênese como principal fator na evolução da cabeceira de drenagem, principalmente ao longo do nose e side slope. No hollow foram identificados dois depósitos de colúvio. A associação de atributos físicos e químicos da cobertura superficial permitem classificar o solo presente na cabeceira de drenagem como latossólico distrófico, passando de vermelho no nose à bruno avermelhado escuro no side slope. Os argilominerais revelados pelos difratogramas de raio-X na cobertura superficial ao longo do nose e side slope da cabeceira de drenagem estudada indicam situação geoquímica de hidrólise intensa na área. A maior quantidade de picos de caulinita mostra um ambiente geoquímico com predomínio do processo de monossialitização. Menos intenso, o processo de alitização também ocorre, sendo registrado pela gibbsita. Considerando a atuação dos processos geoquímicos, bem como a ocorrência dominante da caolinita sobre argilominerais menos freqüentes como a vermiculita e a gibbsita, e os índices obtidos revelados pela química de rotina, a cobertura superficial do nose e side slope, na cabeceira de drenagem estudada, enquadra-se como ferruginoso dessaturado.

Background – Previous reports of abnormal auditory N2 and P3 event-related potentials (ERPs) suggest impaired discrimination, evaluation or context updating for infrequent target stimuli in post-traumatic stress disorder (PTSD). This study examines each of these processes by investigating high-resolution ERP topography during target detection for visual word stimuli. Method – ERPs were recorded at 124 electrodes from 10 PTSD patients and 10 matched controls. Target detection tasks comprised blocks of equally probable red and blue words, with low probability target events. Detection of fixed target words in one color provided the basis for measurement of selective attention for color, stimulus evaluation and target detection processing. Alternative task instructions, with the same stimuli, required detection of any consecutive word repeats in an attended color, which demands working memory updating for nontarget words. Comparison of attended non-target words from each task indicates the extra activity for updating working memory representations of target attributes. Thus, specific condition comparisons provide measures of stimulus discrimination and evaluation, working memory updating and target detection. Results – PTSD patients had slower and less accurate motor responses in both tasks, with greater inaccuracy during the variable target task. There was abnormal ERP activity in PTSD at 200-300 ms in the left posterior temporal region during stimulus discrimination and target recognition. During evaluation of attended non-target words, PTSD patients demonstrate deficits in frontal and parietal regions at 400-500 ms. During working memory updating, at 400-600 ms, there was a delay in frontal activation, followed by smaller activity in parietal areas in PTSD. During target word recognition, PTSD patients demonstrate deficits in frontal activity, with greater occipital and parietal activity. Conclusions – These findings indicate impaired evaluation and integration of new information in working memory. In particular, the results suggest failure in frontal executive systems, with greater dependence on visual processing for effective target detection. The current findings are consistent with neuropsychology studies that identify deficits of attention and memory for verbal information in PTSD. This study provides insight into the temporal components of attention and working memory in PTSD. It is proposed that working memory deficits arise from disruption to synchronized activity in distributed networks engaged in working memory processes.

Central southern Fiordland, New Zealand, is underlain extensively by metasediments and associated metavolcanics. These are mapped in three lithostratigraphic units, from west to east Edgecumbe Group, Cameron Group and Cumbrae Supergroup. Lower Cameron Group units lithocorrelate with Central Fiordland Belt lithological associations and with those of Fraser Complex, Westland. Eastern Fiordland Belt metavolcanics and lacustrine metasediments are tectonostratigraphically unrelated to Cameron Group, from which they are separated by the Grebe Fault. They instead have affiliations with the Loch Burn Formation, Largs Volcanics, Drumduan Group and Paterson Group. These units (collectively, "Cumbrae Supergroup") represent remnants of a Triassic-Jurassic calc-alkaline arc. Six deformational episodes are identified in central southern Fiordland. The earliest, D₁, is obliterated by D₂ and M₂ metamorphism. D₃ is restricted to the Southwest Fiordland Block. D₄ occupied a brief interval of M₃ time. D₄ of the Central and Western Fiordland Belts corresponds to earliest deformation in Eastern Fiordland Belt metavolcanics. The Grebe Fault is a left-lateral reverse D₄ fault; now vertical, it previously dipped eastward. The Dusky Fault, a reactivated D₅ left-lateral transfer structure, accommodated the dip-slip component of displacement at low-angle normal faults during mid-Cretaceous extension. Open folds represent D₆. Post-glacial scarps mark the post-D₆ Kilcoy and Vincent Faults. Their merged northward continuation is intersected by the tailrace tunnel of the Manapouri Hydroelectric Power Station. Southwest Fiordland Block pelites were metamorphosed at 665 �C, c. 3 kbar during M₂. Early M₃ is of contact metamorphic aspect. Late M₃ is distinctively polybaric: Central Fiordland Belt kyanite-garnet pelites recrystallised at c. 8.5 kbar after metamorphism in the sillimanite field at c. 3.5 kbar. Western Fiordland Orthogneiss 12 kbar granulite assemblages formed during late M₃. South of the Dusky Fault, late M₃ is almost asymptomatic. The M₃ field gradient is continuous across the Grebe Fault: in the Eastern Fiordland Belt, late M₃ staurolite and garnet supersede chloritoid in lacustrine (meta-)sapropel-silts. The Grebe Fault is an important tectonostratigraphic break; it may separate New Zealand�s Western and Eastern Provinces. Its relationship to any "Median Tectonic Zone" is unclear, as no such zone has been found in southeastern Fiordland. Cumbrae Supergroup rocks within the "Median Tectonic Zone" represent the arc that nourished the Eastern Province�s Barretts Formation, Murihiku Supergroup and Stephens Subgroup. The Cumbrae arc was �obducted� westwards during Early Cretaceous continent-arc collision. This event simultaneously halted Eastern Province volcanogenic sedimentation and tectonically buried Fiordland, imposing late M₃ pressure increments. Drumduan Group lawsonite is coeval. Cretaceous collision induced glaciation. Late Cretaceous climatic deterioration and extensional tectonism caused icecap development. The Otago "Peneplain" is a Late Cretaceous subglacial floor. Accumulation of voluminous perennial Cretaceous ice on Earth has hitherto not been inferred. Facultative psychrophily in New Zealand�s ancient endemics and their preference for dark conditions reflect passage through a hitherto-unsuspected evolutionary bottleneck: prolonged winter darkness and harsh climate of near-polar Late Cretaceous New Zealand exerted extraordinary evolutive pressures on ancestral forms after biotic links with Gondwana were severed. New Zealand�s ancient endemics are the evolutionary derivatives of a Late Cretaceous near-polar fauna.

Look ahead cruise control deals with the concept of using recorded topographic road data combined with a GPS to control vehicle speed. The purpose of this is to save fuel without a change in travel time for a given road. This thesis explores the sensitivity of different disturbances for look ahead systems. Two different systems are investigated, one using a simple precalculated speed trajectory without feedback and the second based upon a model predictive control scheme with dynamic programming as optimizing algorithm. Defect input data like bad positioning, disturbed angle data, faults in mass estimation and wrong wheel radius are discussed in this thesis. Also some investigations of errors in the environmental model for the systems are done. Simulations over real road profiles with two different types of quantization of the road slope data are done. Results from quantization of the angle data in the system are important since quantization will be unavoidable in an implementation of a topographic road map. The results from the simulations shows that disturbance of the fictive road profiles used results in quite large deviations from the optimal case. For the recorded real road sections however the differences are close to zero. Finally conclusions of how large deviations from real world data a look ahead system can tolerate are drawn.

<p>Look ahead cruise control deals with the concept of using recorded topographic road data combined with a GPS to control vehicle speed. The purpose of this is to save fuel without a change in travel time for a given road. This thesis explores the sensitivity of different disturbances for look ahead systems. Two different systems are investigated, one using a simple precalculated speed trajectory without feedback and the second based upon a model predictive control scheme with dynamic programming as optimizing algorithm.</p><p>Defect input data like bad positioning, disturbed angle data, faults in mass estimation and wrong wheel radius are discussed in this thesis. Also some investigations of errors in the environmental model for the systems are done. Simulations over real road profiles with two different types of quantization of the road slope data are done. Results from quantization of the angle data in the system are important since quantization will be unavoidable in an implementation of a topographic road map.</p><p>The results from the simulations shows that disturbance of the fictive road profiles used results in quite large deviations from the optimal case. For the recorded real road sections however the differences are close to zero. Finally conclusions of how large deviations from real world data a look ahead system can tolerate are drawn.</p>

No description available.

This thesis investigates several aspects of stratified flow over isolated topography in ocean, lake, and atmospheric settings. Three major sub-topics are addressed: steady, inviscid internal waves trapped over topography in a pycnocline stratification, topographically generated internal waves and their interaction with the viscous bottom boundary layer, and flow over large-scale crater topography in the atmosphere. The first topic examines the conditions that lead to very large internal waves trapped over topography in a fluid with a pycnocline stratification. This type of stratification is connected to ocean or lake settings. The steady-state Euler equations of motion are used to derive a single partial differential equation for the isopycnal displacement in supercritical flows under two conditions: a vertically varying background current under the Boussinesq approximation and a constant background current under non-Boussinesq conditions. A numerical method is developed to solve these equations for an efficient exploration of parameter space. Very large waves are found over depression topography when the background flow speed is close to a limiting value. Variations in the background current are examined, as well as comparisons between Boussinesq and non-Boussinesq results. The second topic aims to extend the above subject by considering unsteady, viscous flows. Once again, supercritical flow over topography in a pycnocline stratification generates internal waves. These internal waves interact with the viscous bottom boundary layer to produce bottom boundary instabilities. The three-dimensional aspects of these instabilities are studied under changes in viscosity. The boundary layer instabilities have important implications for sediment transport in the coastal oceans or lakes. Lastly, the final topic is motivated by the connection between dust streaks on the Martian surface and crater topography. Flow over a large 100-km diameter crater is examined with numerical simulations conducted using the Weather Research and Forecasting model. Modifications to the stratification and topography are applied. It is found that a large hydraulic structure of amplitude comparable to the crater depth forms in many cases. This structure may have important implications for dust transport in the atmosphere. In addition, Martian atmospheric parameters are used to study the flow properties under Mars-like conditions.