This dissertation presents an experimental and analytical study of the Vision Based Navigation system (VisNav). VisNav is a novel intelligent optical sensor system invented by Texas A&M University recently for autonomous proximity operations. This dissertation is focused on system calibration techniques and navigation algorithms. This dissertation is composed of four parts. First, the fundamental hardware and software design configuration of the VisNav system is introduced. Second, system calibration techniques are discussed that should enable an accurate VisNav system application, as well as characterization of errors. Third, a new six degree-of-freedom navigation algorithm based on the Gaussian Least Squares Differential Correction is presented that provides a geometrical best position and attitude estimates through batch iterations. Finally, a dynamic state estimation algorithm utilizing the Extended Kalman Filter (EKF) is developed that recursively estimates position, attitude, linear velocities, and angular rates. Moreover, an approach for integration of VisNav measurements with those made by an Inertial Measuring Unit (IMU) is derived. This novel VisNav/IMU integration technique is shown to significantly improve the navigation accuracy and guarantee the robustness of the navigation system in the event of occasional dropout of VisNav data.

Under 20 års tid har Perimed AB utvecklat och tillverkat LDPM- och LDPI-instrument som är baserade på en analog filterkonstruktion. De analoga komponenterna i konstruktionen är komplexa och icke-linjära med hänsyn till frekvens och de driver även med temperaturen. Funktionen hos konstruktionen beror också kraftigt av att de analoga komponenterna trimmas in under produktionen. Det här examensarbetet syftar till att ta fram en alternativ design baserad kring en digital signal processor. Den digitala signalbehandlingsmetod som beskrivs baseras på väl förankrade laser-Doppler perfusionsteorier. Den implementerade signalbehandlingsalgoritmen beräknar perfusionen ur en samplad fotodetektorström, som har filtrerats till AC- och DC-komponenter med hjälp av ett analogt detektorkort. Algoritmen producerar en råperfusionssignal genom att beräkna en frekvensviktad summa av fotodetektorströmmens effektspektrum. Kompensation för detektorns brus och normalisering med ljusintensitet har också implementerats. Den presenterade implementationen har verifierats mot ett exemplar av LDPM-enheten PF 5010 som har använts som referensinstrument vid alla mätningar. Mätningar in vitro har påvisat liknande mätresultat som referensinstrumentet för en referensvätska med hög perfusion och även för ett statiskt mätobjekt. Vidare har implementationen verifierats med mätningar in vivo på hud, vilket har påvisat nära nog identiska signalnivåer och gensvar på värmeprovokationer som referensinstrumentet. Den demonstrerade uppfinningen förenklar tillverkningen av instrumenten eftersom antalet komponenter reduceras avsevärt och därmed antalet produktionstester. Användandet av en DSP reducerar dessutom instrumentets temperaturkänslighet eftersom den ersätter flera temperaturkänsliga komponenter. / For 20 years Perimed AB have been developing and manufacturing LDPM and LDPI instruments based on an analog filter construction. The analog components in the construction are complex and suffer from non-linear frequency dependency and temperature drifts. The functionality of the design is also heavily depending on analog components which need to be trimmed in the production. In this thesis, an alternative design employing a digital signal processor is presented. The signal processing method used is based on well established laser Doppler perfusion theories. The implemented signal processing algorithm calculates the perfusion from a sampled photodetector current, pre-filtered into AC and DC components by an analog detector card. The algorithm produces a raw perfusion signal by calculating a frequency weighted sum of the power spectral density, PSD, of the photocurrent. Detector noise compensation and light intensity normalization of the signal has also been implemented. The presented digital implementation has been verified using the PF 5010 LDPM unit as a reference. In vitro measurements have shown similar behaviour as the reference in a highly perfused reference fluid as well as for a static scatterer. Furthermore, the DSP implementation has been verified on in vivo measurements of skin, showing nearly identical signal levels and response to heat provocation as the reference. The demonstrated invention improves the manufacturability of the instruments since it reduces the number of electronic components significantly and thus, the amount of manufacturing tests. The DSP also reduces the temperature sensitivity of the instrument since it replaces several analog components sensitive to temperature changes.

This dissertation presents an experimental and analytical study of the Vision Based Navigation system (VisNav). VisNav is a novel intelligent optical sensor system invented by Texas A&M University recently for autonomous proximity operations. This dissertation is focused on system calibration techniques and navigation algorithms. This dissertation is composed of four parts. First, the fundamental hardware and software design configuration of the VisNav system is introduced. Second, system calibration techniques are discussed that should enable an accurate VisNav system application, as well as characterization of errors. Third, a new six degree-of-freedom navigation algorithm based on the Gaussian Least Squares Differential Correction is presented that provides a geometrical best position and attitude estimates through batch iterations. Finally, a dynamic state estimation algorithm utilizing the Extended Kalman Filter (EKF) is developed that recursively estimates position, attitude, linear velocities, and angular rates. Moreover, an approach for integration of VisNav measurements with those made by an Inertial Measuring Unit (IMU) is derived. This novel VisNav/IMU integration technique is shown to significantly improve the navigation accuracy and guarantee the robustness of the navigation system in the event of occasional dropout of VisNav data.

No description available.

No description available.

No description available.

PSD-95 is an abundant scaffolding protein found in the postsynaptic densities (PSDs) of excitatory synapses throughout the mammalian brain, and plays a critical role in innate and learned behaviours. PSD-95 assembles with numerous other proteins, including glutamate receptors, adhesion molecules and signalling proteins, into postsynaptic supercomplexes that are then organised into nanoclusters that comprise the postsynaptic density of excitatory synapses. While the subcellular localisation of PSD-95 has been widely studied, much less is known about its turnover. In this thesis, I present novel insights into PSD-95 synthesis and degradation at synapses of cultured primary neurons gained using the HaloTag technology. The HaloTag consists of an engineered bacterial protein domain that covalently binds synthetic ligands labelled with fluorescent and affinity moieties. Hence, cells expressing proteins fused to the HaloTag can be used to study protein levels, complexes and turnover using these different ligands. This project was based upon a knock-in mouse line expressing the HaloTag fused to endogenous PSD-95 using gene targeting. After demonstrating that these mice were phenotypically normal and that PSD95-HaloTag fusion proteins normally assembled into supercomplexes in the PSD, hippocampal primary cultures were grown from this mouse line. Fluorescent HaloTag ligands were then used to label live neurons, allowing for the visualisation of PSD-95 at synapses by confocal microscopy. Next, I established a pulse-chase labelling method, where one ligand is used to label all existing PSD-95 first, before a second ligand can then be used to label any newly synthesised PSD-95. This allows for the identification and characterisation of subpopulations of PSD-95, which can be separately analysed. I find that PSD-95 has a half-life of 36 hours at synapses, consistent with previous literature. I was also able to observe synaptic heterogeneity in PSD-95 turnover, and classify synapses into types according to their PSD-95 expression profile. Finally, a range of chemical compounds known to modulate protein turnover and neuronal activity was applied over a 24-hour period, and their effects on PSD-95 turnover analysed. It was found that inhibiting either the proteasome or protein synthesis led to significant reductions in PSD-95 degradation as well as inhibiting PSD-95 synthesis. Thus, this project established a method offering a unique way of investigating the turnover of a specific, tagged protein, as well as gaining novel insights into the turnover of PSD-95 at individual synapses.

The dissertation is divided into two separate experiments that explore the effects of visual-spatial learning on PSD-95 dorsal hippocampal expression. Specifically, the aim of these studies was to explore the effect of learning an assay, the Hebb-Williams mazes, on the protein expression of PSD-95 in Fmr1 KO mice. PSD-95 is an important scaffolding protein hypothesized to be involved in learning and memory. In cellular models of Fragile X Syndrome it has been shown to be dysregulated but it has never been measured following behavioural learning. Establishment of a deficit using an ecologically valid behavioural assay could lead to the development of novel interventions. Study one employed a subset of the Hebb-Williams mazes of various levels of difficulty to evaluate PSD-95 protein expression in Fmrp intact and Fmr1 KO mice following learning. The results revealed significant increases in PSD-95 protein expression in control runners when compared to Fmr1 KO mice. There was a negative correlation between PSD-95 protein levels and mean total errors on the mazes meaning that as expression was increased, errors were decreased. The goals of study two were to reverse the molecular and behavioural deficits using pharmacological antagonist treatment shown to be effective in cellular models of Fragile X Syndrome. Fmr1 KO mice were treated with either saline or 20 mg/kg of a metabotropic glutamate receptor antagonist, 2-Methyl-6-(phenylethynyl) pyridine (MPEP). Relative to saline treated controls, drug treated Fmr1 KO mice made fewer errors on the same subset of Hebb-Williams mazes used in study one. Latency to complete these mazes did not differ between groups, indicating that MPEP treatment does not adversely affect motor functioning. Protein assessment revealed that PSD-95 was selectively rescued in MPEP treated mice and not saline controls. Similar to study one, a negative correlation between PSD-95 protein levels and mean total errors was observed. When taken together, these studies indicate that protein deficits are associated with a deficit of learning that can be reversed with a selective glutamate receptor antagonist. One of the strengths of the Hebb-Williams mazes is that performance is measurable without floor or ceiling effects, which plague other common behavioural assays. These data further suggest that pharmacological antagonist treatments may be promising in correcting the learning deficits in human Fragile X Syndrome patients.

Le sujet de cette thèse est né de l'observation de phénomènes incompris des mécanismes à l'origine des très faibles efficacités de discrimination neutron/gamma (n/g) dans les scintillateurs plastiques en comparaison à leurs homologues liquides. Le flash lumineux qu'ils génèrent suite à une interaction avec un rayonnement ionisant (majoritairement des protons de recul dans le cas des neutrons et des électrons dans le cas des gamma) présente des caractéristiques temporelles qui dépendent de la nature de la particule détectée (type et énergie). C'est sur la forme du signal que la séparation peut être réalisée (PSD). Les scintillateurs liquides ont largement été étudiés. C'est seulement récemment qu'il a été démontré qu'une séparation nette pouvait être réalisée à l'aide de plastiques spécialement conçus. L'étude de ces systèmes et la compréhension des processus photophysiques en plastique par rapport à leur efficacité de PSD est toujours d'actualité. Ce travail est dédié à la compréhension des phénomènes en amont des émissions de luminescence, juste après l'interaction rayonnement/matière. Dans un premier temps un état de l'art qui s'étend de 1960 à nos jours a été réalisé. Une deuxième partie est consacrée à la caractérisation des matériaux scintillants mis en jeu pour définir leurs propriétés de fluorescence et de scintillation sous rayonnement. La troisième partie se focalise sur la simulation de traces neutrons via un faisceau de protons pour quantifier dans des conditions contrôlées leur dépôt spécifique d'énergie dans notre plastique présentant des capacités de discrimination n/g-. Une quatrième partie est dévolue à la détermination de leur efficacité de PSD en fonction de leurs paramètres de structure moléculaire. Ces travaux ont conduit à la préparation d'un plastique dans notre laboratoire présentant des propriétés de PSD considérées efficaces, ce qui a donné lieu à un dépôt de brevet. Enfin une étude photophysique conclut ce travail à l'aide d'un laser femtoseconde pour simuler de façon purement optique des interactions neutron avec la matière donnant lieu à de la fluorescence retardée. Nous tentons ainsi de définir la nature des transferts d'énergie mis en jeu. Nous concluons enfin sur la corrélation structure/propriétés de discrimination. Ces avancées permettront de guider le potentiel en termes d'applications industrielles et le développement de nouveaux matériaux.Ce travail est dédié à la compréhension des phénomènes en amont des émissions de luminescence, juste après l'interaction rayonnement/matière. Dans un premier temps un état de l'art qui s'étend de 1960 à nos jours a été investigué. Une deuxième partie est consacrée à la caractérisation complète des matériaux scintillants mis en jeu pour définir leurs propriétés de fluorescence et de scintillation sous rayonnement. Une troisième partie est dévolue à la détermination de leur efficacité en termes de discrimination neutron/gamma en fonction de leurs paramètres de structure moléculaire. Ces travaux ont menés à la préparation d'un plastique dans notre laboratoire présentant des propriétés de PSD considérées efficaces, ce qui a donné lieu à un brevet. La quatrième partie se focalise sur la simulation de traces neutrons via un faisceau de protons pour quantifier dans des conditions contrôlées leur dépôt spécifique d'énergie dans notre plastique, présentant des capacités de discrimination neutron/gamma. Enfin une étude photophysique conclut ce travail à l'aide d'un laser femtoseconde pour simuler de façon purement optique des interactions neutron ou gamma avec la matière donnant lieu à de la fluorescence retardée, et tenter de définir ainsi la nature des transferts d'énergie mis en jeu. Nous concluons enfin sur la corrélation structure / propriétés de discrimination. Ces avancées permettront de guider le potentiel en termes d'applications industrielles et le développement de nouveaux matériaux. / This PhD topic was born from misunderstandings and incomplete knowledge of the mechanism and relative effectiveness of neutron and gamma-ray (n/g) discrimination between plastic scintillators compared to liquid scintillators. The shape of the light pulse these materials generate following interaction with an ionizing particle (predominantly recoil protons in the case of neutrons and electrons in the case of gamma-rays) is different in time in a way that depends on the detected particle (nature and energy). It is this fact that enables separation (PSD). The behavior in liquid scintillators has been extensively studied experimentally for practical applications. Only recently has it been shown that a weak separation can also be achieved using specially prepared plastics. The study of this system presents an open field and the understanding of both liquids and plastics with respect to their PSD properties is far from complete. This work is dedicated to exploring the fundamental photophysical phenomena at play in the generation of luminescence emission, following the interaction of ionizing radiation with organic scintillators. For this purpose, firstly a detailed literature review of the state-of-the-art has been conducted extending from 1960 to the present day. Secondly a complete characterization of the main scintillating materials has been conducted to define their fluorescence properties and the characteristics of their scintillation under irradiation. Thirdly a proton beam has been used to simulate recoil protons to quantify under controlled laboratory conditions their specific energy deposition in a plastic scintillator with PSD properties. The fourth part of this thesis is devoted to the study of PSD efficiency of scintillators as a function of their molecular structure. This investigation has led to a plastic scintillator prepared in our laboratory with good PSD properties and a patent submission. Finally, photophysical experiments were performed using a femtosecond laser to simulate, purely optically, neutron/matter interactions giving rise to delayed fluorescence. This technique was chosen so as to examine the fundamental energy transfers involved. Overall this work led to an improved understanding and greater insight about the correlation between the chemical structure of organic scintillating materials and their n/g- discrimination properties. This will guide both applications and future materials development.

The goal of this diploma thesis is to verify the practical applicability of the Raspberry Pi platform in control applications. The work consists of choosing a suitable operating system and implementing a discrete PID algorithm. An important part of the work was the Linux OS modification and compilation. Measurement has demonstrated the usability of the platform in control applications. The result of this work is a discreet PID controller implemented as a Linux kernel module. The solution also includes a web interface as a human-machine interface.