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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.
161

HANDICAP FAVU / HANDICAP FAVU

Máčalová, Naděžda Unknown Date (has links)
I try to create a discussion about barrier-free of Faculty of Fine arts VUT Brno. Then i made a symbolic elevator and collection to rebuild a buildings of FaVU. My target is change a attitude of school leaders, employer and students of FaVU, to make a barrier-free school.
162

Blood brain barrier dysfunction and a role for inflammation in age-dependent salt-sensitive hypertension

Nist, Kayla Marie 28 July 2020 (has links)
Hypertension is the principal risk factor for chronic kidney disease, myocardial infarction, and stroke, and is responsible for 10% of deaths globally. Normal aging and elevated dietary sodium intake have both been identified as contributors to hypertension, the salt sensitivity of blood pressure, and elevations in sympathetic tone. Normal aging has also been identified as a contributor to vascular dysfunction and inflammation. We hypothesize that normal aging and increased dietary sodium intake contribute to the development and maintenance of age-related salt-sensitive hypertension. We anticipate with age that there are elevations in sympathetic tone, decreases in the vascular integrity of the blood brain barrier, and an increase in the inflammatory response of the innate immune system of the brain by astrocytes and microglia. Using male Sprague-Dawley (SD) rats aged 3-, 8- and 16-months-old as a model of normal aging, rodents were randomly assigned to a normal salt (NS; 0.6% NaCl) or high salt (HS; 4% NaCl) diet. We then assessed the development of hypertension, the salt sensitivity of blood pressure, changes in central vascular integrity, and a role for central inflammation in age-dependent hypertension. We observed a robust age-dependent increase in blood pressure in rodents on a NS diet suggesting male SD rats develop age-dependent hypertension. We also observed that aged rats develop the salt sensitivity of blood pressure. We saw significant elevations in global sympathetic tone, sympathetic tone to the vasculature, and sympathetic tone to the kidney in response to normal aging. Further, there was a dramatic extravasation of intravascularly infused dextrans in the paraventricular nucleus of the hypothalamus (PVN) with age, suggesting a loss in vascular integrity of the blood brain barrier, regardless of dietary sodium intake. Astrocytic density in the PVN was maintained in animals on a NS diet. In rodents on a HS diet, both young and middle aged rats, but not in aged rats showed increased levels of astrocytic density. There was no difference in interstitial astrocyte densities, which excluded perivascular astrocytes, compared to total astrocyte density, suggesting that perivascular astrocytes did not play a significant role in astrocyte activation. Microglial branching complexity was maintained in all groups regardless of salt intake, suggesting that microglial activation was the same through all groups. However, microglial morphology showed a trending increase in activation level on a NS with age. On a HS diet, there is an increase in activation state at 8-months-old. Overall, normal aging and increases in dietary sodium intake contribute to increases in blood pressure, elevations in sympathetic tone, and ultimately a loss in vascular integrity of the blood brain barrier. Importantly, the following studies reveal a novel breakdown in the blood brain barrier in a normal aging model of hypertension by which increased blood pressure and aging evokes an increase in blood brain barrier permeability.
163

Diffusion of silver in 6H-SiC

Hlatshwayo, Thulani Thokozani 18 June 2011 (has links)
SiC is used as the main diffusion barrier in the fuel spheres of the pebble bed modular reactor (PBMR). The PBMR is a modern high temperature nuclear reactor. However, the release of silver from the fuel spheres has raised some doubts about the effectiveness of this barrier, which has led to many studies on the possible migration paths of silver. The reported results of these studies have shown largely differing results concerning the magnitude and temperature dependence of silver being transported through the fuel particle coatings. Results from earlier investigations could be interpreted as a diffusion process governed by an Arrhenius type temperature dependence. In this study, the silver diffusion in 6H-SiC was investigated using two methods. In the first method a thin silver layer was deposited on 6H-SiC by vapour deposition while in the second method silver was implanted in 6H-SiC at room temperature, 350°C and 600°C to a fluence of 2×1016 silver ions cm-2. Finally the effect of neutron irradiation on the diffusion of silver was investigated for the samples implanted at 350°C and 600°C. Silver depth profiles before and after annealing were determined by Rutherford backscattering (RBS). Both isothermal and isochronal annealing were used in this study. Diffusion coefficients as well as detection limits were extracted by comparing the silver depth profiles before and after annealing. The radiation damage after implantation and their recovery after isothermal and isochronal annealing were analysed by Rutherford backscattering spectroscopy combined with channelling. The results of in-diffusion of silver into 6H-SiC at temperatures below the melting point (960°C) using un-encapsulated 6H-SiC samples with 100 nm deposited silver indicated no in-diffusion of silver; however, disappearance of silver occurred at these temperatures. For the encapsulated samples, no in-diffusion of silver was observed at 800°C, 900°C and 1000°C but silver disappeared from the samples’ surface and was found on the walls of the quartz glass ampoule. This disappearance of silver was established to be due to the wetting problem that existed between silver and SiC. The room temperature implantation resulted in a completely amorphous surface layer of approximately 270 nm thick. Epitaxial re-growth from the bulk was already taking place during annealing at 700°C and the crystalline structure seemed to be fully recovered at 1600°C, for samples that were sequentially isochronally annealed from 700°C in steps of 100°C up to 1600°C. However, no silver signal was detected at this temperature, which left certain doubts regarding the crystalline structure of the samples at this temperature. This was speculated to be due to thermal etching of the top original amorphous layer while the deeper amorphous layer was epitaxial re-growth from the bulk. The decomposition of SiC, giving rise to a carbon peak in the RBS spectra due to evaporation of Si, was clearly observed on the same samples at 1600°C. Isothermal annealing at 1300°C for 10 h cycles up to 80h caused epixatial re-growth from the bulk during the first annealing cycle (10h). No further epitaxial re-growth from the bulk was observed up to 80h. This was believed to be due to the amorphous layer re-crystallising into crystals that were randomly oriented to the 6H-SiC substrate. No diffusion of silver was observed at temperatures below 1300°C but silver seemed to form precipitates at these temperatures. Diffusion of silver towards the surface accompanied by silver loss from the surface began at 1300°C and was very high at 1400°C, with silver profiles becoming asymmetric and closer to the surface. The loss of silver was already taking place at 1100°C. This loss was found to be due to the following: diffusion of silver towards the surface; the mass flow of silver via holes that were observed to be becoming larger with higher annealing temperatures on SiC surfaces and thermal etching of SiC. Isothermal annealing at 1300°C for 10h up to 80h caused diffusion of silver during the first annealing cycle, while no further diffusion was observed for any further annealing at the same temperature up to 80 h. The diffusion coefficient was not calculated due to the lack of information on the structural evolution of SiC during the first annealing cycle. Isothermal annealing at 1300°C and 1350°C for 30 minute cycles up to 120 minutes caused high diffusion during the first cycle and reduced diffusion during the second cycle, while no diffusion was observed for any further annealing longer than the second cycle. The higher diffusion during the first 30 minutes was due to ion induced amorphization. The diffusion of silver in amorphised SiC was measured at different temperatures in the range 1300°C to 1385°C and yielded to Do ~ 1.4 × 10-12 m2s-1 and Ea ~ 3.3 × 10-19 J. These values were found to be approximately the same as the values of silver diffusion in polycrystalline CVD-grown SiC found by our group which were due to grain boundary diffusion: Do ~ 4×10-12 m2 s-1 and Ea ~ 4×10-19 J. Implantation of silver at 600°C retained crystallinity although distortions occurred in the implanted region while implantation at 350°C also retained crystallinity but more distortions occurred as compared to silver implanted at 600°C. This was caused by the fact that at 600°C, the displaced atoms were more mobile because of their higher thermal energy than at 350°C. The higher thermal energy increased the probability of the displaced atoms combining with their original lattice sites. Annealing of these samples at 1300°C, 1350°C and 1500°C caused the annihilation of some defects but certain others were retained. No diffusion of silver was observed during annealing of the samples (implanted at 350°C and at 600°C) at 1300°C, 1350°C and 1500°C but silver moved towards the surface at 1500°C. The upper limit of the diffusion coefficient of D < 10-21 m2s-1 was obtained at 1300°C. The movement of silver towards the surface was found to be due to thermal etching at 1500°C. Neutron irradiation of these samples caused no silver diffusion but silver -110mAg, due to -109Ag capturing a neutron during neutron irradiation, was detected in the samples. / Thesis (PhD)--University of Pretoria, 2010. / Physics / unrestricted
164

WORKING CANINE DECONTAMINATION: EFFECT OF CLEANSER & SERIAL DECONTAMINATION ON DERMAL BARRIER FUNCTION

Discepolo, Dakota Rose 01 June 2021 (has links)
Working canines provide a key service to society. During their work, they may be exposed to various environmental contaminants. Unfortunately, previous work has shown that current working canine decontamination protocols are lacking in efficacy (Venable et al., 2017). Furthermore, little work has been done to explore cleanser options and serial decontamination. Therefore, we designed two studies to investigate the impact of cleanser on contaminant removal, and the impact of serial cleanser application on canine dermal health and skin barrier function when applied daily for 14 days. Both studies were approved by the Southern Illinois University Institutional Animal Use and Care Committee (#15-032, #19-031) prior to initiation of the work. Treatments for analysis of cleansers for canine decontamination included Dawn, povidone surgical scrub, chlorohexidine surgical Scrub, or water. Each treatment was balanced by coat type (long; short). A fluorescent marker was used to determine efficacy in contaminant reduction. Significant decreases associated with coat type (P < 0.0082) and cleanser (P < 0.0001) were measured for dermal pH. Additionally, treatment impacted TEWL (P = 0.0049). Yet, TEWL was unaffected by coat type (P = 0.4881). Visual scoring of images revealed that all cleansers were more successful at reduction when compared to control (P < 0.0001). However, software analysis software, yielded no differences in treatment (P = 0.5567). Interestingly, we found a significant correlation between the visual scores and the Image J (P = 0.0006). Repeated decontamination on 8 (n= 8) Labrador retrievers significantly increased TEWL (P< 0.0001) through day 21 and then decreasing the remainder of the study. Similarly, sebum data was also impacted by repeated daily decontamination efforts, decreasing during bathing and then increasing (P =0.0387). Higher sebum values are seen later in the study and may be associated with recovery. In contrast, moisture content (P = 0.3842) and pH (P = 0.7462), were unaffected by repeated decontamination. Interestingly, dander scores assessed on the back were worsened by repeated decontamination (P = 0.0222) but dander scores assessed across the whole body were unaffected (P = 0.1804). Coat shine was unaffected by decontamination (P = 0.1156) similar to coat softness (P = 0.3418). Overall coat condition remained unchanged as a result of repeated decontamination efforts (P= 0.9466). These data reveal that daily decontamination impacts dermal function, potentially increasing the animal’s health risk.
165

The Impact of Cerebral Microinfarction on Blood-Brain Barrier Permeability and Behaviour in Mice

Filadelfi, Melissa 17 September 2020 (has links)
From mid- to late-life aging, many individuals acquire hundreds or even thousands of tiny strokes, known as microinfarcts. These lesions are not apparent using conventional neuroimaging and are therefore primarily detected through histopathological analysis. Notably, clinical and preclinical researchers are unsure of how cerebral microinfarction impacts the brain’s vasculature and its effect on motor output. This thesis aims to characterize a mouse model of cerebral microinfarction to assess the impact of these microscopic lesions on blood-brain barrier (BBB) integrity and motor behaviour. For the first experiment, mice were unilaterally injected through the left common carotid artery with GFP microspheres (20 µm) and were sacrificed at different time points post-surgery (days 1, 3, 7, 14, and 21). All mice received an intravascular injection of Evans Blue dye (100 µl) through the tail vein thirty minutes prior to being transcardially perfused in order to evaluate BBB extravasation, a measurement of BBB disruption. To evaluate motor performance post-microinfarction, sham and microinfarct mice underwent a battery of behavioural tasks prior to and post-surgery. Cerebral microinfarction resulted in acute BBB disruption, where albumin leakage was most prominent one day following surgery. With our microinfarct mouse model, a Python script was developed to semi-automatically detect and register the microspheres to specific brain regions using the Allen Mouse Brain Atlas (version 3). Additionally, using several gross and fine motor behavioural tasks, analyses performed across both experimental groups revealed no significant motor impairments. Having a better insight into how these microscopic lesions affect brain structure and function in preclinical models would increase our understanding of how cerebral microinfarction impacts the human brain.
166

Assessing the Potential for Seepage Barrier Defects to Propagate into Seepage Erosion Mechanisms

Van Leuven, Ryan G. 01 May 2011 (has links)
Seepage barriers have been used extensively to mitigate seepage problems in dams and levees. Although the design of many of these dams and levees has been based on intact barriers, seepage barriers have been shown to be susceptible to deformation and cracking when high differential hydraulic pressures act across the barrier. Under certain conditions, these cracks can lead to serious seepage problems, which could potentially lead to the development of a low-resistance seepage pathway. Three scenarios have been identified where there is the potential for erosion to occur adjacent to a crack in a barrier: 1) erosion at the interface between a fine-grained soil and a course-grained soil, 2) erosion of overlying soil due to flow along a joint in bedrock, and 3) erosion of the barrier material. The objective of this study is to investigate the first mode of erosion and identify the conditions at which more serious seepage problems can develop. The research has been performed using a laboratory model to simulate conditions near a seepage barrier crack under the scenarios described above. The results from the laboratory testing were compared to finite element seepage models for each scenario to estimate the flow velocities near the crack. The flow velocities were compared to estimated critical velocities of the soil to asses where erosion is likely to occur. A comparison was made between the observed behavior in the model and the behavior predicted with the computer model. The results of the research will be used to develop a method to assess the potential for erosion to occur and develop into a failure mode based on conditions near seepage barrier cracks.
167

Evaluation of the Effectiveness of Flexible Debris Flow Barriers for Control of Huaycos Using Satellite Images and GIS, in the Basin of Rímac River, Perú

Pareja Dominguez, Marco Antonio, Pascual Figueroa, Henry Douglas, Silva Dávila, Marisa Rosana 01 January 2022 (has links)
El texto completo de este trabajo no está disponible en el Repositorio Académico UPC por restricciones de la casa editorial donde ha sido publicado. / Recurrent economic and human losses occur in populated areas caused by the debris flow, known in Peru as “huayco” and for which there is little information. To determine the effectiveness of debris flow barriers installed in 2016 in three high-risk creeks with slopes ranging from 29 to 35%, it was analyzed satellite images with the Geographical Information System (GIS). For that, it is necessary to obtain the volumes of both soil erosion in the upper basin transported by the debris flow and the retained solids by the barriers. Topographic, geological, geomorphological, and hydrological characteristics were evaluated, as well as the evolution of the population in the dejection cone. It was no possible to obtain results for all the destructive events because there are no cartographies, and the available satellite images do not have enough temporal or spatial resolution or present cloudiness greater than 20%. The field investigations after the ENSO 2017 occurrence made it possible to verify that the debris flow barriers allowed to avoid the loss of human life and material damage. The field measured volumes of the solids retained by the barriers and the previously estimated volumes of erosion were compared, and retention efficiency of 80–90% was obtained. It recommends continuing with this research because it is necessary to know debris flow characteristics for analyzing the convenience and technical requirements for the implementation of retention barriers in other dangerous streams that are difficult to access.
168

Identification of Nonlinear Constitutive Properties of Damping Coatings

Tidball, Mackenzie E. January 2018 (has links)
No description available.
169

Spatial Correlation Between Framework Geology And Shoreline Morphology In Grand Bay, Mississippi

Mullennex, Asa J 12 August 2016 (has links)
The Grand Bay National Estuarine Research Reserve (GBNERR) adjoins two costal embayments in the eastern Mississippi Sound, Grand Bay and Point Aux Chenes Bay, which encompass a late Pleistocene/ Holocene delta of the Pascagoula-Escatawpa fluvial system. Historical maps and aerial imagery indicate that the GBNERR shoreline has experienced long-term retreat at spatially variable rates. The research presented here investigates the relationship between the coastal geomorphological evolution of GBNERR and the underlying geological framework. Coastal morphology and stratigraphy were characterized by analyzing 85 km of chirp sonar sub-bottom seismic profiles and 45 sediment cores. Shoreline retreat rates were determined through geospatial regression analysis of 11 historical shorelines surveyed between 1850 and 2015. Results indicate that Pleistocene paleochannels in the underlying fluvial distributary ravinement surfaces are spatially correlated with shoreline segments that exhibit elevated retreat rates and should be accounted for in future models of local as well as regional coastal evolution.
170

Considerations for Optimization of the Pharmacokinetic Analysis of Blood-Brain Barrier Permeability

Gilbank, Ashley January 2021 (has links)
Dynamic contrast enhanced MR imaging (DCE-MRI) has commonly been used to investigate disruptions in microvascular capillary permeability in pathologies such as tumours, and in brain diseases such as multiple sclerosis. This imaging technique involves intravenous injection of a contrast agent, which can modulate MR signal contrast, while frequently acquiring images (i.e. every few seconds) as the agent perfuses through the tissue of interest. Microvascular permeability, and other parameters such as blood volume and flow (perfusion) can be quantified through application of a pharmacokinetic model on the data acquired from the MRI scan. The model requires input from both the biological (e.g. pharmacokinetic rate constants) as well as physical (i.e. scanner settings) parameters. As there are a great many variables and different biophysical models (e.g. high blood flow, high permeability tissues, etc.) there needs to be considerations made for situations where the permeability may be only slightly different from normal. In the brain the blood-brain barrier (BBB) is a highly selective barrier that restricts most bulk diffusion/permeability of solutes. Changes in BBB permeability is likely only subtle in diseases such as depression or bipolar disorder, especially when compared against hypervascular-hypermemeable cancers that are void of a BBB altogether. The problem is however, to decide which model of BBB permeability is best suited for differentiating subtle changes. Thus the intention of this project was to investigate multiple pharmacokinetic models for the tracking of MRI contrast agent in regions of the brain with an intact BBB. In the brain, where there is strict regulation of molecules passing through the microvasculature into the extracellular space, and where more subtle disruptions might be of interest, different assumptions may be necessary. Four models were investigated: the Tofts model, the modified Tofts model, the two-compartment exchange model, and the uptake model. Scans of eight healthy subjects were analyzed, and permeability was quantified using each model. The accuracy of each model, quantified by the R\textsuperscript{2} value, were compared. Analysis found that the Tofts model performed significantly worse than the modified Tofts and Uptake models when fitting regions of the brain with a blood-brain barrier, with a p-value of 0.006. The analysis did not reveal any significant difference between the modified Tofts, Uptake or 2CX models, although perhaps it was obscured due to the limited number of data points. Further investigation is needed to determine any differences between the three top-performing models. / Thesis / Master of Applied Science (MASc)

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