Self-bearing machines for kinetic energy storage have the advantage of integrating the magnetic bearing in the stator/rotor configuration, which reduces the number of mechanical components needed compared with using separated active magnetic bearings. This master's thesis focus on building a MATLAB/Simulink simulation model for a self-bearing cone-shaped Lorenz-type electrical machine. The concept has already been verified analytically but no dynamic simulations have been made. The system was modeled as a negative feedback system with PID controllers to balance the rotor. Disturbances as signal noise, external forces and torques were added to the system to estimate system robustness. Simulations showed stability and promising dynamics, the next step would be to build a prototype.

Climate change is predicted to increase rates of fire activity in boreal forests. A shortened fire return interval may result in different outcomes of community structure in the northern boreal forest, since the age of a forest influences seed production and potential post-fire regeneration. With two closely timed fires, dominant boreal conifers such as black spruce (Picea mariana) may be vulnerable to regeneration failures after fire because of the long time required to reach reproductive maturity. I report on the relationship between stand age and seed productivity of black spruce in northern Yukon Territory and central Alaska. I used fire history maps to select sites of various stand ages, including stand ages that would occur in a short fire return interval (less than 80 years) versus longer fire intervals (up to 200 years). At each site, I measured stand density and basal area using the point-center-quarter method. Ten black spruce trees were randomly selected for cone surveys and age analysis. I also selected a subset of five trees for detailed analyses of cone and seed production within yearly cohorts. The results of this study illustrate the strong relationships between stand age and stand basal area with cone and seed production of northern black spruce. The resulting equations can be used to predict the seed capacity and regeneration potential of black spruce stands with known stand basal area or stand age. I estimate, along with the number of seeds required to produce a two year old black spruce seedling on high quality seedbeds, stands burned at an age less than 50 years will likely have reduced black spruce post-fire density. On low quality seedbeds, black spruce forests are more vulnerable to regeneration failures and fire cycles less than 150 years are likely to result in reduced recruitment. Under a shortened fire return interval these northern black spruce forests are likely to have reduced post-fire density.

Flexible polyurethane foam (PUF) is a very versatile material ever created. The material is used for various applications and consumer end-use products such as upholstered furniture and mattresses. The increased use of these polymeric materials causes fire safety concerns. This has led to the development of various regulations and flammability test standards aimed at addressing the hazards associated with polyurethane foam fires. Several fire protection engineering correlations and thermal models have also been developed for the simulation of fire growth behaviour of polyurethane foams. Thus, the overall objective of this research project is to investigate the laboratory test behaviour of this material and then use finer modeling techniques to predict the heat release rate of the specimens, based on information obtained from cone calorimeter tests.<p> Full-scale fire tests of 10 cm thick polyurethane foams of different sizes were conducted using center and edge-ignition locations. Flame spread and heat release rates were compared. For specimens of the same size, center-ignition tests produced flame areas and peak heat release rates which were respectively 10 and 20% larger compared to edge-ignition tests. Average flame spread rates for horizontal and vertical spread were determined, and results showed excellent agreement with literature. Cone calorimeter tests of the specimens were performed using steel edge frame and open durarock board. Results indicate that different test arrangements and heat sources have significant effects on the fire behaviour of the specimens.<p> Predictions using the integral convolution model and other fire protection engineering correlations were compared with the full-scale tests results. Results show that the model was more efficient in predicting the heat release rates for edge-ignition tests than the center-ignition tests. The model also was more successful in predicting the heat release rates during the early part of the growth phase than during the later stages of the fire. The predicted and measured peak heat release rates and total heat release were within 10-15% of one another. Flame spread and t-squared fire models also gave satisfactory predictions of the full-scale fire behaviour of the specimens.

During the development of the nervous system, neurons migrate to their final location and extend neurites that navigate long distances in the extracellular environment to reach their synaptic targets. The proper functioning of the nervous system depends on correct connectivity, and mistakes in the wiring of the nervous system lead to brain abnormalities and mental illness. Growth cones are motile structures located at the tip of extending neurites that sense and respond to guidance cues encountered along the path toward their targets. Binding of these cues to receptors located on growth cone filopodia and lamellipodia triggers intracellular signaling pathways that regulate growth cone cytoskeletal dynamics. Although studies on extracellular cues and their effects on neuronal guidance are well documented, less is known about the intracellular signaling mechanisms that regulate growth cone motility. This dissertation focuses on two signaling pathways and describes how they might be involved in determining growth cone morphology during neuronal development. The specific aims of this work address: (1) the role of phosphatidylinositol-3-kinase (PI-3K) and its downstream signaling pathway in regulating growth cone motility, and (2) the effect of nitric oxide (NO) release from a single cell on growth cone morphology of neighboring neurons. This study employs defined neurons from the pond snail, Helisoma trivolvis, to demonstrate that inhibition of PI-3K induces a concomitant increase in filopodial length and a decrease in the rate at which neurites advance. These effects are mediated through the lipid and protein kinase activities of PI-3K, and filopodial elongation is due to an increase in the rate at which filopodia elongate and the time that individual filopodia spend extending. Additionally, this study demonstrates that NO release from a single cell can affect growth cone dynamics on neighboring neurons via soluble guanylyl cyclase (sGC), and that NO has a physiological effect up to a distance of 100 ìm. Overall this study provides new information on cellular mechanisms regulating growth cone motility, and suggests a potential role of PI-3K and NO in neuronal pathfinding in vivo.

Due to lack of soil sampling during a conventional cone penetration testing (CPT), it is necessary to classify soils based on recorded tip and sleeve friction and pore pressure (if available) values. However, currently available soil classification models are based on deterministic and judgemental determination of soil classification boundaries which do not address the uncertainties intristic to the problem. Moreover, size and quality of databases used in the development of these soil classification models are undocumented and thus questionable. Similar limitations do also exist in the development of SPT-CPT correlations which are widely used in SPT dominated design such as soil liquefaction triggering. To eliminate these discussed limitations, within the confines of this study it is attempted to present (1) a new probabilistic CPT- based soil classification methodology, and (2) new SPT-CPT correlations which address the uncertainties intrinsic to the problems. For these purposes, a database composed of 400 CPT/SPT boring data pairs was compiled. It is intended to develop probabilistic models, which will correlate CPT tip and sleeve friction values to actual soil classification and CPT tip resistance to SPT blow count N. The new set of correlations, model parameters of which estimated by implementing maximum likelihood methodology, presented herein are judged to represent a robust and defensible basis for (1) prediction of soil type based on CPT data and, (2) estimation of SPT-N value for given CPT data.

No description available.

Sensory-motile cells fulfill various biological functions ranging from immune activity or wound healing to the formation of the highly complex nervous systems of vertebrates. In the case of neurons, a dynamic structure at the tip of outgrowing processes navigates towards target cells or areas during the generation of neural networks. These fan shaped growth cones are equipped with a highly complex molecular machinery able to detect various external stimuli and to translate them into directed motion. Receptor and adhesion molecules trigger signaling cascades that regulate the dynamics of an internal polymeric scaffold, the cytoskeleton. It plays a crucial role in morphology maintenance as well as in the generation and distribution of growth cone forces. The two major components, actin and microtubules (MTs) connect on multiple levels through interwoven biochemical and mechanical interactions. Actin monomers assemble into semiflexible filaments (F-actin) which in turn are either arranged in entangled networks in the flat outer region of the growth cone (lamellipodium) or in radial bundles termed filopodia. The dynamic network of actin filaments extends through polymerization at the front edge of the lamellipodium and is simultaneously moving towards the center (C-domain) of the growth cone. This retrograde flow (RF) of the actin network is driven by the polymerizing filaments themselves pushing against the cell membrane and the contractile activity of motor proteins (myosins), mainly in the more central transition zone (T-zone). Through transmembrane adhesion molecules, a fraction of the retrograde flow forces is mechanically transmitted to the cellular substrate in a clutch-like mechanism generating traction and moving the GC forward. MTs are tubular polymeric structures assembled from two types of tubulin protein subunits. They are densely bundled in the neurite and at the growth cone “neck” (where the neurite opens out into the growth cone) they splay apart entering the C-domain and more peripheral regions (P-domain). Their advancement is driven by polymerization and dynein motor protein activity. The two subsystems, an extending array of MTs and the centripetal moving actin network are antagonistic players regulating GC morphology and motility. Numerous experimental findings suggest that MTs pushing from the rear interact with actin structures and contribute to GC advancement. Nevertheless, the amount of force generated or transmitted through these rigid structures has not been investigated yet. In the present dissertation, the deformation of MTs under the influence of intracellular load is analyzed with fluorescence microscopy techniques to estimate these forces. RF mechanically couples to MTs in the GC periphery through friction and molecular cross-linkers. This leads to MT buckling which in turn allows the calculation of the underlying force. It turns out that forces of at least act on individual MT filaments in the GC periphery. Compared to the relatively low overall protrusion force of neuronal GCs, this is a substantial contribution. Interestingly, two populations of MTs buckle under different loads suggesting different buckling conditions. These could be ascribed to either the length-dependent flexural rigidity of MTs or local variations in the mechanical properties of the lamellipodial actin network. Furthermore, the relation between MT deformation levels and GC morphology and advancement was investigated. A clear trend evolves that links higher MT deformation in certain areas to their advancement. Interactions between RF and MTs also influence flow velocity and MT deformation. It is shown that transient RF bursts are related to higher MT deformation in the same region. An internal molecular clutch mechanism is proposed that links MT deformation to GC advancement. When focusing on GC dynamics it is often neglected that the retraction of neurites and the controlled collapse of GCs are as important for proper neural network formation as oriented outgrowth. Since erroneous connections can cause equally severe malfunctions as missing ones, the pruning of aberrant processes or the transient stalling of outgrowth at pivotal locations are common events in neuronal growth. To date, mainly short term pausing with minor cytoskeletal rearrangements or the full detachment and retraction of neurite segments were described. It is likely that these two variants do not cover the full range of possible events during neuronal pathfinding and that pausing on intermediate time scales is an appropriate means to avoid the misdetection of faint or ambiguous external signals. In the NG108-15 neuroblastoma cells investigated here, a novel type of collapse was observed. It is characterized by the degradation of actin network structures in the periphery while radial filopodia and the C-domain persist. Actin bundles in filopodia are segmented at one or multiple breaking points and subsequently fold onto the edge of the C-domain where they form an actin-rich barrier blocking MT extension. Due to this characteristic, this type of collapse was termed fold collapse. Possible molecular players responsible for this remarkable process are discussed. Throughout fold collapse, GC C-domain area and position remain stable and only the turnover of peripheral actin structures is abolished. At the same time, MT driven neurite elongation is hindered, causing the GC to stall on a time scale of several to tens of minutes. In many cases, new lamellipodial structures emerge after some time, indicating the transient nature of this collapse variant. From the detailed description of the cytoskeletal dynamics during collapse a working model including substrate contacts and contractile actin-myosin activity is derived. Within this model, the known and newly found types of GC collapse and retraction can be reduced to variations in local adhesion and motor protein activity. Altogether the results of this work indicate a more prominent role of forward directed MT-based forces in neuronal growth than previously assumed. Their regulation and distribution during outgrowth has significant impact on neurite orientation and advancement. The deformation of MT filaments is closely related to retrograde actin flow which in turn is a regulator of edge protrusion. For the stalling of GCs it is not only required that actin dynamics are decoupled from the environment but also that MT pushing is suppressed. In the case of fold collapse, this is achieved through a robust barrier assembled from filopodial actin bundles.

This research focuses on the nanoscopic investigation of the three-dimensional surface morphology of the neural growth cones from the snail Helisoma trivolvis, and InN and InGaN semiconductor material systems using Atomic Force Microscopy (AFM). In the analysis of the growth cones, the results obtained from AFM experiments have been used to construct a 3D architecture model for filopodia. The filopodia from B5 and B19 neurons have exhibited different tapering mechanisms. The volumetric analysis has been used to estimate free Ca2+ concentration in the filopodium. The Phase Contrast Microscopy (PCM) images of the growth cones have been corrected to thickness provided by AFM in order to analyze the spatial refractive index variations in the growth cone. AFM experiments have been carried out on InN and InGaN epilayers. Ternary InGaN alloys are promising for device applications tunable from ultraviolet (Eg[GaN]=3.4 eV) to near-infrared (Eg [InN]=0.7 eV). The real-time optical characteristics and ex-situ material properties of InGaN epilayers have been analyzed and compared to the surface morphological properties in order to investigate the relation between the growth conditions and overall physical properties. The effects of composition, group V/III molar ratio and temperature on the InGaN material characteristics have been studied and the growth of high quality indium-rich InGaN epilayers are demonstrated.

Only 6 autochthonous cases of human Chagas disease have been documented in the U.S.A., however, as many as 5% of immigrants from Latin America may be infected with the etiologic agent, Trypanosoma cruzi. The parasite has been isolated from a variety of wild mammals, particularly in the southeastern region of the U.S.A. The goal of our study was to determine if the sylvatic cycle of T. cruzi infection occurs in Kentucky, and, if present, to assess the prevalence of infection in Warren and Barren counties. Raccoons and opossums were live-trapped between June and December, 2007. Animals were anesthetized with isoflurane, and blood samples were collected using a vacutainer system. Sera were frozen at -80oC for subsequent analysis, and whole blood samples were inoculated, in duplicate, into liver infusion tryptose (LIT) medium and cultured at 27oC. Seventeen T. cruzi isolates from raccoons have been positively identified by hemoculture. A total of 25/44 (57%) raccoon samples were found to be positive by hemoculture or serological analysis. In Warren County 18/25 (72%) of raccoons tested positive for T. cruzi and 7/19 raccoons (37%) in Barren County were positive for the parasite. Eighteen of 43 (42%) of the sera collected from opossums in Warren County and 3 of 5 (60%) from Barren County were judged to be positive by either enzyme-linked immunosorbent assay (ELISA) or indirect immunofluorescence assay tests (IFAT). There were no positive hemoculture results for the opossum samples. The infection rates found in the current study for raccoons were slightly higher than those reported in previous studies in the U.S.A. However, the overall prevalence of T. cruzi in opossums (determined by serological analysis) was consistent with previous studies performed in the southeast. To our knowledge, this is the first report of T. cruzi from the state of Kentucky.

Flexible polyurethane foam (PUF) is a very versatile material ever created. The material is used for various applications and consumer end-use products such as upholstered furniture and mattresses. The increased use of these polymeric materials causes fire safety concerns. This has led to the development of various regulations and flammability test standards aimed at addressing the hazards associated with polyurethane foam fires. Several fire protection engineering correlations and thermal models have also been developed for the simulation of fire growth behaviour of polyurethane foams. Thus, the overall objective of this research project is to investigate the laboratory test behaviour of this material and then use finer modeling techniques to predict the heat release rate of the specimens, based on information obtained from cone calorimeter tests.<p> Full-scale fire tests of 10 cm thick polyurethane foams of different sizes were conducted using center and edge-ignition locations. Flame spread and heat release rates were compared. For specimens of the same size, center-ignition tests produced flame areas and peak heat release rates which were respectively 10 and 20% larger compared to edge-ignition tests. Average flame spread rates for horizontal and vertical spread were determined, and results showed excellent agreement with literature. Cone calorimeter tests of the specimens were performed using steel edge frame and open durarock board. Results indicate that different test arrangements and heat sources have significant effects on the fire behaviour of the specimens.<p> Predictions using the integral convolution model and other fire protection engineering correlations were compared with the full-scale tests results. Results show that the model was more efficient in predicting the heat release rates for edge-ignition tests than the center-ignition tests. The model also was more successful in predicting the heat release rates during the early part of the growth phase than during the later stages of the fire. The predicted and measured peak heat release rates and total heat release were within 10-15% of one another. Flame spread and t-squared fire models also gave satisfactory predictions of the full-scale fire behaviour of the specimens.