A Global Positioning System (GPS) can be used to estimate an objects position,given that the object has a GPS antenna. However, the system requires informationfrom at least four independent satellites in order to be able to give a positionestimate. If two GPS antennas and a carrier-phase GPS measurement unit is usedan estimate of the objects heading can be calculated by determine the baselinebetween the two antennas. The method is called GPS Attitude Determination(GPSAD) and requires that an Integer Ambiguity Problem (IAP) is solved. Thismethod is cheaper than more traditional methods to calculate the heading butis dependent on undisturbed GPS-reception. Through support from an InertialMeasurement Unit (IMU), containing accelerometers and gyroscopes, the systemcan be enhanced. In Thorstenson [2012] data from GPS, GPSAD and IMU wasintegrated in an Extended Kalman Filter (EKF) to enhance the performance. Thisthesis is an extension on Thorstensons work and is divided into two separate problems:enhancement of positioning when less than four satellites are available andthe possibility to integrate the EKF with the search of the correct integers for theIAP in order to enhance the estimation of attitude. For both problems an implementationhas been made and the performance has been enhanced for simulateddata. For the first problem it has been possible to enhance the performance onreal data while that has not been possible for the second problem. A number ofproposals is given on how to enhance the performance for the second problemusing real data.

Zugl.: Marburg, Univ., Diss., 2008

No description available.

Abstract All neurons and macroglial cells of vertebrates derive from the neuroepithelium. Neuroepithelial (NE) cells first proliferate and, after closure of the neural tube, some cells start generating neurons. It is still unclear what triggers differentiation but apparently there is interplay between extrinsic (secreted or transmembrane signals) and intrinsic factors. Diriving from the embryonic ectoderm, the NE cells inherit epithelial characteristics. It has been shown in other developmental systems that epithelial determinants, such as cell-cell contacts and contact to basal laminar components can guide differentiation. The key epithelial features include cell polarity, and tight junctions. We studied these in the NE at two developmental stages, the neural plate, a proliferative stage and the neural tube, a differentiative stage. The polarity of membrane proteins in NE cells was studied with polarly budding viruses. Mouse embryos were infected with Fowl plague- and vesicular stomatitis viruses and cultured in a whole embryo culture system. Viral envelope proteins (HA and G-protein) were localized by indirect immunofluorescence and immunoelectron microscopy. HA was polarized in the plate stage neuroepithelial cells, whereas in the tube it was not polarized anymore. It is also shown by penetrance of apically injected horseradish peroxidase that in the neural plate, NE cells have functional tight junctions. At this stage, they also express occludin, a transmembrane protein of tight junctions, as shown by indirect immunofluorescence. In the neural tube, the paracellular barrier is lost and there is no occludin expression. In contrast, expression of ZO-1, a cytoplasmic protein binding to occiudin, is upregulated. The downregulation of these epithelial features occurs in all NE cells, irrespective of their mode of division and before any neurons are generated in the NE. The change is initiated already at the plate stage and coincides with the switch from E- to N-cadherin. Later, with birth of neurons, the proliferative cell layer also looses contact to basal lamina. This is probably an important step in the regulation of neurogenesis. Furthermore, lack of apico-basolateral polarity of non-anchored membrane proteins may contribute to the mechanism of rapid neuron generation. Until now, it has been impossible to distinguish a neuroepithelial cell preparing for neuron generation from the surrounding cells that give rise to two precursor cells. In this study, the immediate neuron precursors are shown to express the antiproliferative gene TIS2 1. Using this new marker and ISH in serial sections, we show that the switch to differentiation is initiated in single NE cells.

Tesis de Doctorado para optar al grado de Doctor en Ciencias con mención en Física. / Los aisladores topológicos a grandes rasgos son aisladores en el bulto y presentan estados de borde metálicos que están protegidos por alguna simetría del sistema, mediciones ARPES han logrado detectar estos estados, mientras que en experimentos de transporte, estos estados son empañados por una contribución debido a los defectos e impurezas del bulto. El objetivo de esta tesis es proponer un modelo teórico, que sea capaz de entregar una mayor robustez a los estados de superficies de los aisladores topológicos. Para este fin, usaremos una geometría de heteroestructuras o super-redes, ya que dada la gran experiencia experimental en el crecimiento de este tipo de sistema, su realización experimental es factible. Debido el vertiginoso avance del área de los aisladores topológicos, comenzaremos con una breve reseña histórica de el surgimiento de este tipo de materiales (capítulo 1), para luego explicar la física subyacente de los aisladores topológicos en uno de los modelos de aislador topológico mas sencillos, el modelo SSH (capítulo 2) y un modelo mas interesante, el modelo BHZ (capítulo 4), este último fue comprobado experimentalmente. Luego, pasaremos a implementar la estrategia de super-redes para generar nuevos estados de borde topológicamente protegidos, que tienen como base el modelo SSH (capítulo 3) y el modelo BHZ (capítulo 5). En esta tesis, mediante el método tight-binding y los modelos sencillos anteriormente mencionados, logramos diseñar exitosamente nuevos estados de borde topológicos, los que son mucho más resistentes al desorden atómico que sus estructuras base (SSH o BHZ), incluso cuando este desorden destruye la simetría que permite la existencia del orden topológico.

There is a growing interest in autonomous driving systems that can safely rely on multiple sensors including GNSS, IMU, Radar and LiDAR to navigate with high accuracy, integrity, continuity, and availability in complex urban environments. Many existing data sets, collected with multi-sensor platforms, focus on validating different variations of visual localization algorithms like SLAM, place recognition, object detection and visual odometry that help navigate in sky-obstructed and GNSS-denied environments. However, GNSS still plays a vital role in providing the most assured navigation solution. In this thesis, we develop a robust system intended for collecting data sets that will support the design of tightly integrated navigation algorithms and the analysis of integrity risk using GNSS coupled with IMU, Radar, and LiDAR in challenging automotive environments. GNSS pseudorange, doppler, and carrier phase and IMU acceleration and angular velocities are measurements that the system is specifically designed to collect for sensor-fusion algorithm refinement. In addition, time synchronization between sensors is crucial in data sets validating tightly integrated navigation, especially in applications with high dynamics. However, there is no widely accepted accurate and stable method for synchronizing clocks between different sensor types. We implement a common-clock synchronization and a hardware-trigger clock synchronization between multiple sensors. We then collect a preliminary data set to compare the accuracy and stability of sensor time-tagging using a GNSS-receiver-generated hardware trigger versus using a local-clock ROS-based time stamping. We evaluate the impact of these synchronization methods on mapping accuracy performance. / Master of Science / There is a growing interest in vehicles that can drive themselves without human intervention. Typically, these vehicles must rely on different types of sensors that perceive the environment in different ways and complement each other to navigate complex environments. Many algorithms have been developed to use the measurements from these sensors to accurately determine the vehicle position, velocity and orientation with high accuracy. Many existing data sets intended to validate these algorithms focus on sensors that use visual perception to navigate. In this thesis, we develop a robust data collection system to support (a) the validation of innovative navigation system design that make full use of complementary sensor properties and (b) the quantification of how much trust we can put into the navigation solution. In addition, tight integration of these sensors requires accurate timing of the measurements across multiple sensors. However, there is no widely accepted method of synchronizing clocks between multiple sensor types. We implement a first method in which all sensor information is time-stamped using a common clock, and a second method in which one sensor sends a pulse to another to synchronize their two clocks. To compare the accuracy and stability of these synchronization methods, we collect a preliminary data set.

Utilizando a Dinâmica Molecular Tight Binding (TBMD), parametrizada para sistemas de carbono e hidrogênio, simulamos com condições periódicas de contorno e modelos de fatia, superfícies de diamante (100) puras e hidrogenadas em modelos de reconstruções ideais usualmente presentes na literatura, analisando o seu comportamento geométrico e eletrônico. Em seguida abordamos o comportamento morfológico e eletrônico, em simulações com temperaturas que variam entre 100K e 2000K de dois modelos de superfícies monohidrogenadas, que apresentam dois domínios em torno de uma estrutura de depressão local, característica de filmes de alta rugosidade. Em oposição à grande estabilidade térmica exibida pelo modelo monohidrogenado ideal e pelas colunas contínuas de dímeros, os modelos com depressão apresentaram significativa migração de átomos de hidrogênio para regiões subsuperficiais. Em nossas simulações os átomos de hidrogênio ficaram confinados nas regiões subsuperficiais, introduzindo uma desordem morfológica na superfície e nas regiões internas à fatia, induzindo estados eletrônicos nesta região, que levam ao fechamento do gap, passando a caracterizar uma fase quase-metálica. / By using the Tight Binding Molecular Dynamics (TBMD), parametrized to describe carbon and hydrogen atoms composed of systems, we apply periodic boundary conditions, slab models in order to simulate (100) clean and hydrogenated diamond surfaces. We study first the standard models used in the literature, analyzing their geometrical and eletronic behavior. We then focus on the morphological and electronic properties, in simulations under finite temperature dynamics ranging from 100K up to 2000K, of two distinct models of monohydride surfaces; Each model exhibits two distincts domains in the surface pattern characterized by a local depression, characteristic of rough surfaces. In opposition to the high thermal stability observed for ideal monohydrogenated surfaces and the extended dimer rows, these models showed an expressive hydrogen migration to the subsurface regions. In our simulations the hydrogen atoms remain in the subsurface regions, but introduce morphological disorder at the surface and in the slab internal regions. These hydrogen atoms induce electronic states mostly localized in the subsurface region, which are responsible for closing the gap, and leading the system to exhibit a quasi-metallic phase.

Utilizando a Dinâmica Molecular Tight Binding (TBMD), parametrizada para sistemas de carbono e hidrogênio, simulamos com condições periódicas de contorno e modelos de fatia, superfícies de diamante (100) puras e hidrogenadas em modelos de reconstruções ideais usualmente presentes na literatura, analisando o seu comportamento geométrico e eletrônico. Em seguida abordamos o comportamento morfológico e eletrônico, em simulações com temperaturas que variam entre 100K e 2000K de dois modelos de superfícies monohidrogenadas, que apresentam dois domínios em torno de uma estrutura de depressão local, característica de filmes de alta rugosidade. Em oposição à grande estabilidade térmica exibida pelo modelo monohidrogenado ideal e pelas colunas contínuas de dímeros, os modelos com depressão apresentaram significativa migração de átomos de hidrogênio para regiões subsuperficiais. Em nossas simulações os átomos de hidrogênio ficaram confinados nas regiões subsuperficiais, introduzindo uma desordem morfológica na superfície e nas regiões internas à fatia, induzindo estados eletrônicos nesta região, que levam ao fechamento do gap, passando a caracterizar uma fase quase-metálica. / By using the Tight Binding Molecular Dynamics (TBMD), parametrized to describe carbon and hydrogen atoms composed of systems, we apply periodic boundary conditions, slab models in order to simulate (100) clean and hydrogenated diamond surfaces. We study first the standard models used in the literature, analyzing their geometrical and eletronic behavior. We then focus on the morphological and electronic properties, in simulations under finite temperature dynamics ranging from 100K up to 2000K, of two distinct models of monohydride surfaces; Each model exhibits two distincts domains in the surface pattern characterized by a local depression, characteristic of rough surfaces. In opposition to the high thermal stability observed for ideal monohydrogenated surfaces and the extended dimer rows, these models showed an expressive hydrogen migration to the subsurface regions. In our simulations the hydrogen atoms remain in the subsurface regions, but introduce morphological disorder at the surface and in the slab internal regions. These hydrogen atoms induce electronic states mostly localized in the subsurface region, which are responsible for closing the gap, and leading the system to exhibit a quasi-metallic phase.

In the intensive care units, hyperglycaemia among the critically ill is associated with poor outcomes. Many studies have been done on managing hyperglycaemia in the critically ill. Patients in the ICU continue to benefit from the outcome of extensive studies including several randomized clinical trials on glycaemic control with intensive insulin therapy. Tight glycaemic control has now emerged as a major research focus in critical care due to its potential to simultaneously reduce both mortality and cost. Although the debate on tight glycaemic control is on going, managing glycaemic level in ICUs is gaining widespread acceptance as the adverse effects are well known. However, in the less acute wards, to date there have only been a single randomized, controlled study to examine the benefit of glycaemic control. Patients in the less acute wards do not receive the same level of care, as glycaemic control is not regarded as important and not a priority. Glycaemic goals in the less acute wards are often judged based on clinical experience rather than adhering to a standard protocol or a treatment guideline. It is important that patients in the less acute wards received the level of care as practised in the ICU. If hyperglycaemia worsens outcome in the ICU, a similar effect is seen within less acute wards. Hence, tight glycaemic control needs to be extended in the less critical setting as well. To support the establishment of a control protocol for patients in less acute wards, a method that has been successful in the critical care and can be adapted to the less acute wards, is the model based or model-derived control protocol. Model-based protocol can deliver a safe and effective patient-specific control, which means the glycaemic control protocol can be devised to each individual patient. Hence, a physiological model that represents the glucose-insulin regulatory system is presented in this thesis. The developed model, Intensive Control Insulin-Nutrition-Glucose (ICING) is based on the best aspects of two previous clinically-validated glucose-insulin models.

Hyperglycemia is prevalent in critical care, as patients experience stress-induced hyperglycemia, even with no history of diabetes. Hyperglycemia has a significant impact on patient mortality and other negative clinical outcomes such as severe infection, sepsis and septic shock. Tight glycemic control can significantly reduce these negative outcomes by reducing hyperglycemic episode, but achieving it remains clinically elusive, particularly with regard to what constitutes tight control and what protocols are optimal in terms of results and clinical effort. The model used in this thesis is validated using an independent data and readily be used for different clinical interventions. Moreover, this model also able to accurately predict clinical intervention outcomes given that the model prediction error is very small, which is better than any other reported model. In particular, model-based glycemic control methods is used to capture patient-specific physiological dynamics, such as insulin sensitivity, SI. To date, sepsis diagnosis has been a great challenge despite advancement in technologies and medical research. Critically, septic patients are often classified by practitioners according to their experience before standard test results can be assessed, as to avoid delay in treatment. Moreover, several scoring systems have also been widely used to represent sepsis condition and better standardization of sepsis definition across different centers. In this thesis, insulin sensitivity, SI, a model-based metric is used to identify sepsis condition based on the finding that SI represents metabolic condition of a patient. Additionally, several clinical and physiological variables obtained during patient’s stay in critical care are also investigated using mathematical computation and statistical analysis to identify relevant metric which can be accurately use for sepsis interventions. Even though information on SI, clinical and physiological variables of a patient are insufficient to determine the sepsis status, these informations have brought to a different perspective of diagnosing sepsis. Microcirculation dysfunction is very common in sepsis. Tracking of microcirculation state among septic patient enable better tracking of patient state particularly sepsis status. The tracking can potentially be done by using a pulse oximeter that can extract additional information related to oxygen extraction level. The processed signals are therefore represent relative absorption of oxyhemoglobin and reduced hemoglobin that can be used to assess microcirculation status. In addition, this thesis focus on the real challenge of early treatment of sepsis and sepsis diagnosis where several potential metabolic markers are investigated. Microcirculation conditions are assessed using a non-invasive method that is generally used in typical ICU settings. In particular, the concept and method used to assess microcirculation and metabolic conditions are developed in this thesis. Finally, the work presented in this thesis can act as a starting point for many other glycemic control problems in other environments. These areas include cardiac critical care and neonatal critical care that share most similarities to the environment studied in this thesis, to general diabetes where the population is growing exponentially world wide. Eventually, this added knowledge can lead clinical developments from protocol simulations to better clinical decision making.