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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.
141

Inflammatory cytokines and NFκB in Alzheimer’s disease

Fisher, Linda January 2006 (has links)
Alzheimer’s disease is the most common form of dementia. It is a neurodegenerative disorder characterized by extracellular senile plaques and intracellular neurofibrillary tangles. The main constituent of the senile plaques is the neurotoxic β-amyloid peptide. Surrounding the senile plaques are activated astrocytes and microglia, believed to contribute to neurotoxicity through secretion of proinflammatory cytokines, like interleukin-1β and interleukin-6. For many inflammatory actions, including the cytokine induction in glial cells, the transcription factor NFκB plays a key role. This suggests that therapeutical strategies aimed to control the development of Alzheimer’s disease could include administration of drugs that hinder NFκB activation. The major aim of this thesis was to examine the effects of β-amyloid together with interleukin-1β on cytokine expression as well as NFκB activation in glial cells. The possibility to block NFκB activation, and downstream effects like interleukin-6 expression, by using an NFκB decoy was investigated. The possibility to improve the cellular uptake of the decoy by linking it to a cell-penetrating peptide was also investigated. The results obtained provide supportive evidence that inflammatory cytokines are induced by β-amyloid, and that they can indeed potentiate its effects. The results further demonstrate that by blocking NFκB activation, the induction of interleukin-6 expression can be inhibited. By using an improved cellular delivery system, the uptake of the NFκB decoy and hence the downstream cytokine inhibition could be increased. In conclusion, these results demonstrate the possibility to decrease the inflammatory reactions taken place in Alzheimer’s disease brains, which may ultimately lead to a possible way of controlling this disorder.
142

Nonparametric Bayesian Context Learning for Buried Threat Detection

Ratto, Christopher Ralph January 2012 (has links)
<p>This dissertation addresses the problem of detecting buried explosive threats (i.e., landmines and improvised explosive devices) with ground-penetrating radar (GPR) and hyperspectral imaging (HSI) across widely-varying environmental conditions. Automated detection of buried objects with GPR and HSI is particularly difficult due to the sensitivity of sensor phenomenology to variations in local environmental conditions. Past approahces have attempted to mitigate the effects of ambient factors by designing statistical detection and classification algorithms to be invariant to such conditions. These methods have generally taken the approach of extracting features that exploit the physics of a particular sensor to provide a low-dimensional representation of the raw data for characterizing targets from non-targets. A statistical classification rule is then usually applied to the features. However, it may be difficult for feature extraction techniques to adapt to the highly nonlinear effects of near-surface environmental conditions on sensor phenomenology, as well as to re-train the classifier for use under new conditions. Furthermore, the search for an invariant set of features ignores that possibility that one approach may yield best performance under one set of terrain conditions (e.g., dry), and another might be better for another set of conditions (e.g., wet).</p><p>An alternative approach to improving detection performance is to consider exploiting differences in sensor behavior across environments rather than mitigating them, and treat changes in the background data as a possible source of supplemental information for the task of classifying targets and non-targets. This approach is referred to as context-dependent learning. </p><p>Although past researchers have proposed context-based approaches to detection and decision fusion, the definition of context used in this work differs from those used in the past. In this work, context is motivated by the physical state of the world from which an observation is made, and not from properties of the observation itself. The proposed context-dependent learning technique therefore utilized additional features that characterize soil properties from the sensor background, and a variety of nonparametric models were proposed for clustering these features into individual contexts. The number of contexts was assumed to be unknown a priori, and was learned via Bayesian inference using Dirichlet process priors.</p><p>The learned contextual information was then exploited by an ensemble on classifiers trained for classifying targets in each of the learned contexts. For GPR applications, the classifiers were trained for performing algorithm fusion For HSI applications, the classifiers were trained for performing band selection. The detection performance of all proposed methods were evaluated on data from U.S. government test sites. Performance was compared to several algorithms from the recent literature, several which have been deployed in fielded systems. Experimental results illustrate the potential for context-dependent learning to improve detection performance of GPR and HSI across varying environments.</p> / Dissertation
143

Quantification of Changes for the Milne Ice Shelf, Nunavut, Canada, 1950 - 2009

Mortimer, Colleen Adel 10 February 2011 (has links)
This study presents a comprehensive overview of the current state of the Milne Ice Shelf and how it has changed over the last 59 years. The 205 ±1 km2 ice shelf experienced a 28% (82 ±0.8 km2) reduction in area between 1950 – 2009, and a 20% (2.5 ±0.9km3 water equivalent (w.e.)) reduction in volume between 1981 – 2008/2009, suggesting a long-term state of negative mass balance. Comparison of mean annual specific mass balances (up to -0.34 m w.e. yr-1) with surface mass balance measurements for the nearby Ward Hunt Ice Shelf suggest that basal melt is a key contributor to total ice shelf thinning. The development and expansion of new and existing surface cracks, as well as ice-marginal and epishelf lake development, indicate significant ice shelf weakening. Over the next few decades it is likely that the Milne Ice Shelf will continue to deteriorate.
144

Dynamics and Historical Changes of the Petersen Ice Shelf and Epishelf Lake, Nunavut, Canada, since 1959

White, Adrienne 07 December 2012 (has links)
This study presents the first comprehensive assessment of the Petersen Ice Shelf and the Petersen Bay epishelf lake, and examines their current characteristics and changes to their structure between 1959 and 2012. The surface of the Petersen Ice Shelf is characterized by a rolling topography of ridges and troughs, which is balanced by a rolling basal topography, with thicker ice under the surface ridges and thinner ice under the surface troughs. Based on thickness measurements collected in 2011 and area measurements from August 2012, the Petersen Ice Shelf has a surface area of 19.32 km2 and a mean thickness of 29 m, with the greatest thicknesses (>100 m) occurring at the fronts of tributary glaciers feeding into the ice shelf. The tributary glaciers along the northern coast of Petersen Bay contributed an estimated area-averaged 7.89 to 13.55 cm yr-1 of ice to the ice shelf between 2011 and 2012. This input is counteracted by a mean surface ablation of 1.30 m yr-1 between 2011 and 2012, suggesting strongly negative current mass balance conditions on the ice shelf. The Petersen Ice Shelf remained relatively stable until 2005 when the first break-up in recent history occurred, removing >8 km2 of ice shelf surface area. This break-up led to the drainage of the epishelf lake once the ice shelf separated from the southern coast, providing a conduit through which the freshwater from the lake escaped. More break-ups occurred in summers 2008, 2011 and 2012, which resulted in a >31.2 km2 loss in surface area (~63% of June 2005 area). While ephemeral regions of freshwater have occurred along the southern coast of Petersen Bay since 2005 (with areas ranging from 0.32-0.53 km2), open water events and a channel along the southern coast have prevented the epishelf lake from reforming. Based on these past and present observations it is unlikely that Petersen Ice Shelf will continue to persist long into the future.
145

Mitochondria-targeted Doxorubicin is Active and Resistant to Drug Efflux

Chamberlain, Graham Ross 21 November 2012 (has links)
Several families of highly effective anticancer drugs are selectively toxic to cancer cells because they interfere with nucleic acids synthesis. Many such drugs are pumped out of cells faster than they can reach their targets, which limits efficacy and renders many tumors drug-resistant. By delivering a drug to the mitochondria of mammalian cells – an organelle where nucleic acids synthesis also occurs – efflux could be prevented through sequestration. Doxorubicin, a topoisomerase II inhibitor, was used as proof-of-principle for this concept due to its susceptibility to resistance. When doxorubicin is attached to a peptide that specifically targets mitochondria, its efficacy is not attenuated by various resistance mechanisms to which doxorubicin is normally susceptible. These results indicate that targeting drugs to the mitochondria provides a means to evade the most common mechanism of drug resistance.
146

Mitochondria-targeted Doxorubicin is Active and Resistant to Drug Efflux

Chamberlain, Graham Ross 21 November 2012 (has links)
Several families of highly effective anticancer drugs are selectively toxic to cancer cells because they interfere with nucleic acids synthesis. Many such drugs are pumped out of cells faster than they can reach their targets, which limits efficacy and renders many tumors drug-resistant. By delivering a drug to the mitochondria of mammalian cells – an organelle where nucleic acids synthesis also occurs – efflux could be prevented through sequestration. Doxorubicin, a topoisomerase II inhibitor, was used as proof-of-principle for this concept due to its susceptibility to resistance. When doxorubicin is attached to a peptide that specifically targets mitochondria, its efficacy is not attenuated by various resistance mechanisms to which doxorubicin is normally susceptible. These results indicate that targeting drugs to the mitochondria provides a means to evade the most common mechanism of drug resistance.
147

Evaluating Vadose Zone Moisture Dynamics using Ground-Penetrating Radar

Steelman, Colby Michael 09 February 2012 (has links)
Near-surface sediments in the vadose zone play a fundamental role in the hydrologic system. The shallow vadose zone can act as a buffer to delay or attenuate surface contaminants before they reach the water table. It also acts as a temporary soil moisture reservoir for plant and atmospheric uptake, and regulates the seasonal groundwater recharge process. Over the past few decades, geophysical methods have received unprecedented attention as an effective vadose zone characterization tool offering a range of non-invasive to minimally invasive techniques with the capacity to provide detailed soil moisture information at depths typically unattainable using conventional point-measurement sensors. Ground-penetrating radar (GPR) has received much of this attention due to its high sensitivity to the liquid water phase in geologic media. While much has been learned about GPR soil moisture monitoring and characterization techniques, it has not been evaluated across highly dynamic natural soil conditions. Consequently, GPR’s capacity to characterize a complete range of naturally occurring vadose zone conditions including wetting/drying and freeze/thaw cycles, is not yet fully understood. Further, the nature of GPR response during highly dynamic moisture periods has not been thoroughly investigated. The objective of this thesis is to examine the capacity of various surface GPR techniques and methodologies for the characterization of soil moisture dynamics in the upper few meters of vadose zone, and to develop measurement strategies capable of providing quantitative information about the current and future state of the shallow hydrologic system. To achieve this, an exhaustive soil moisture monitoring campaign employing a range of GPR antenna frequencies and survey acquisition geometries was initiated at three different agricultural field sites located in southern Ontario, Canada, between May 2006 and October 2008. This thesis represents the first attempt to evaluate multiple annual cycles of soil conditions and associated hydrological processes using high-frequency GPR measurements. Summaries of the seven major works embodied in this thesis are provided below. Direct ground wave (DGW) measurements obtained with GPR have been used in a number of previous studies to monitor volumetric water content changes in the root zone; however, these studies have involved controlled field experiments or measurements collected across limited ranges in soil moisture. To further investigate the capacity of the DGW method, multi-frequency (i.e., 225 MHz, 450 MHz and 900 MHz) common-midpoint (CMP) measurements were used to monitor a complete annual cycle of soil water content variations at three sites with different soil textures (i.e., sand, sandy loam and silt loam). CMP surveys permitted characterization of the nature and evolution of the near-surface electromagnetic wavefields, and their subsequent impact on DGW velocity measurements. GPR results showed significant temporal variations in both the near-surface wavefield and multi-frequency DGW velocities corresponding to both seasonal and shorter term variations in soil conditions. While all of the measurement sites displayed similar temporal responses, the rate and magnitude of these velocity variations corresponded to varying soil water contents which were primarily controlled by the soil textural properties. Overall, the DGW measurements obtained using higher frequency antennas were less impacted by near-surface wavefield interference due to their shorter signal pulse duration. The estimation of soil water content using GPR velocity requires an appropriate petrophysical relationship between the dielectric permittivity and volumetric water content of the soil. The ability of various empirical relationships, volumetric mixing formulae and effective medium approximations were evaluated to predict near-surface volumetric soil water content using high-frequency DGW velocity measurements obtained from CMP soundings. Measurements were collected using 225, 450 and 900 MHz antennas across sand, sandy loam and silt loam soil textures over a complete annual cycle of soil conditions. A lack of frequency dependence in the results indicated that frequency dispersion had minimal impact on the data set. However, the accuracy of soil water content predictions obtained from the various relationships ranged considerably. The best fitting relationships did exhibit some degree of textural bias that should be considered in the choice of petrophysical relationship for a given data set. Further improvements in water content estimates were obtained using a field calibrated third-order polynomial relationship and three-phase volumetric mixing formula. While DGW measurements provide valuable information within the root zone, the characterization of vertical moisture distribution and dynamics requires a different approach. A common approach utilizes normal-moveout (NMO) velocity analysis of CMP sounding data. To further examine this approach, an extensive field study using multi-frequency (i.e., 225 MHz, 450 MHz, 900 MHz) CMP soundings was conducted to monitor a complete annual cycle of vertical soil moisture conditions at the sand, sandy loam and silt loam sites. The use of NMO velocity analysis was examined for monitoring highly dynamic vertical soil moisture conditions consisting of wetting/drying and freeze/thaw cycles with varying degrees of magnitude and vertical velocity gradient. NMO velocity analysis was used to construct interval-velocity-depth models at a fixed location collected every 1 to 4 weeks. Time-lapse models were combined to construct temporal interval-velocity fields, which were converted into soil moisture content. These moisture fields were used to characterize the vertical distribution, and dynamics of soil moisture in the upper few meters of vadose zone. Although the use of multiple antenna frequencies provided varying investigation depths and vertical resolving capabilities, optimal characterization of soil moisture conditions was obtained with 900 MHz antennas. The integration of DGW and NMO velocity data from a single CMP sounding could be used to assess the nature of shallow soil moisture coupling with underlying vadose zone conditions; however, a more quantitative analyses of the surface moisture dynamics would require definitive knowledge of GPR sampling depth. Although surface techniques have been used by a number of previous researchers to characterize soil moisture content in the vadose zone, limited temporal sampling and low resolution near the surface in these studies impeded the quantitative analysis of vertical soil moisture distribution and its associated dynamics within the shallow subsurface. To further examine the capacity of surface GPR, an extensive 26 month field study was undertaken using concurrent high-frequency (i.e., 900 MHz) reflection profiling and CMP soundings to quantitatively monitor soil moisture distribution and dynamics within a sandy vadose zone environment. An analysis on the concurrent use of reflection and CMP measurements was conducted over two contrasting annual cycles of soil conditions. Reflection profiles provided high resolution traveltime data between four stratigraphic reflection events while cumulative results of the CMP sounding data set produced precise depth estimates for those reflecting interfaces, which were used to convert interval traveltime data into soil water content estimates. The downward propagation of episodic infiltration events associated with seasonal and transient conditions were well resolved by the GPR data. The GPR data also revealed variations in the nature of these infiltration events between contrasting annual cycles. The use of CMP soundings also permitted the determination of DGW velocities, which enabled better characterization of short-duration wetting/drying and freezing/thawing processes. This higher resolution information can be used to examine the nature of the coupling between shallow and deep moisture conditions. High-resolution surface GPR measurements were used to examine vertical soil moisture distribution and its associated dynamics within the shallow subsurface over a 26 month period. While the apparent ability of surface GPR methods to give high quality estimates of soil moisture distribution in the upper 3 meters of the vadose zone was demonstrated, the nature of these GPR-derived moisture data needed to be assessed in the context of other hydrological information. As a result, GPR soil moisture estimates were compared with predictions obtained from a well-accepted hydrological modeling package, HYDRUS-1D (Simunek et al., 2008). The nature of transient infiltration pulses, evapotranspiration episodes, and deep drainage patterns were examined by comparing them with vertical soil moisture flow simulations. Using laboratory derived soil hydraulic property information from soil samples and a number of simplifying assumptions about the system, very good agreement was achieved between measured and simulated soil moisture conditions without model calibration. The overall good agreement observed between forward simulations and field measurements over the vertical profile validated the capacity of surface GPR to provide detailed information about hydraulic state conditions in the upper few meters of vadose zone. A unique DGW propagation phenomenon was observed during early soil frost formation. High-frequency DGW measurements were used to monitor the seasonal development of a thin, high velocity frozen soil layer over a wet low velocity unfrozen substratum. During the freezing process, the progressive attenuation of a low velocity DGW and the subsequent development of a high velocity DGW were observed. Numerical simulations using GPRMAX2D (Giannopoulos, 2005) showed that low velocity DGW occurring after freezing commenced was due to energy leaking across the frozen layer from the spherical body wave in the unfrozen half space. This leaky phase progressively dissipated until the frozen layer reached a thickness equivalent to one quarter of the dominant wavelength in the frozen ground. The appearance of the high velocity DGW was governed by its destructive interference with the reflection events from the base of the frozen layer. This interference obscured the high velocity DGW until the frozen layer thickness reached one half of the dominant wavelength in the frozen ground. While GPR has been extensively used to study frozen soil conditions in alpine environments, its capacity to characterize highly dynamic shallow freeze-thaw processes typically observed in temperate environments is not well understood. High-frequency reflection profiles and CMP soundings were used to monitor the freezing and thawing process during the winter seasonal period at the sand and silt loam sites. Reflection profiles revealed the long-term development of a very shallow (<0.5 m) soil frost zone overlying unfrozen wet substratum. During the course of the winter season, long-term traveltime analysis yielded physical properties of the frozen and unfrozen layers as well as the spatial distribution of the base of the soil frost zone. Short-term shallow thawing events overlying frozen substratum formed a dispersive waveguide for both the CMP and reflection profile surveys. Inversion of the dispersive wavefields for the CMP data yielded physical property estimates for the thawed and frozen soils and thawed layer thickness. It was shown that GPR can be used to monitor very shallow freezing and thawing events by responding to changes in the relative dielectric permittivity of the soil water phase. The works embodied in this thesis demonstrate the effectiveness of high-frequency GPR as a non-invasive soil moisture monitoring tool under a full range of naturally occurring moisture conditions with the temporal and vertical resolution necessary to quantitatively examine shallow vadose zone moisture dynamics. Because this study encompassed an unprecedented range of naturally occurring soil conditions, including numerous short and long duration wetting/drying and freezing/thawing cycles, complex geophysical responses were observed during highly dynamic soil moisture processes. Analysis and interpretation of these geophysical responses yielded both qualitative and quantitative information about the state of the hydrologic system, and hence, provided a non-invasive means of characterizing soil moisture processes in shallow vadose zone environments. In the future, these GPR soil moisture monitoring strategies should be incorporated into advanced land-surface hydrological modeling studies to improve our understanding of shallow hydrologic systems and its impacts on groundwater resources.
148

Quantification of Changes for the Milne Ice Shelf, Nunavut, Canada, 1950 - 2009

Mortimer, Colleen Adel 10 February 2011 (has links)
This study presents a comprehensive overview of the current state of the Milne Ice Shelf and how it has changed over the last 59 years. The 205 ±1 km2 ice shelf experienced a 28% (82 ±0.8 km2) reduction in area between 1950 – 2009, and a 20% (2.5 ±0.9km3 water equivalent (w.e.)) reduction in volume between 1981 – 2008/2009, suggesting a long-term state of negative mass balance. Comparison of mean annual specific mass balances (up to -0.34 m w.e. yr-1) with surface mass balance measurements for the nearby Ward Hunt Ice Shelf suggest that basal melt is a key contributor to total ice shelf thinning. The development and expansion of new and existing surface cracks, as well as ice-marginal and epishelf lake development, indicate significant ice shelf weakening. Over the next few decades it is likely that the Milne Ice Shelf will continue to deteriorate.
149

Radar de subsuelo.Evaluación para aplicaciones en arqueología y en patrimonio histórico-artístico

Pérez Gracia, María de la Vega 26 October 2001 (has links)
.El georradar es una herramienta cada vez más utilizada en diferentes ámbitos geológicos, medioambientales y de Ingeniería Civil, así como en estudios de caracterización de yacimientos arqueológicos y de diagnóstico de daños en edificios del patrimonio histórico y cultural.En esta tesis se abordan aspectos metodológicos de calibración de la instrumentación y de caracterización de las propiedades electromagnéticas que rigen la propagación y atenuación de ondas electromagnéticas en los suelos. Por otra parte, se estudian aplicaciones en monumentos históricos, yacimientos arqueológicos y diagnóstico de daños.Concretamente, en esta tesis se calibran cuatro antenas, caracterizadas por su frecuencia central de emisión: 200, 500, 900 y 1000 MHz. En cada caso se obtiene la señal sólo con el ruido interno de la antena (sin reflexiones). De dicho ruido, el de mayor amplitud es la señal inicial; su longitud determina la distancia mínima entre la antena y la primera superficie reflectora del medio para que no se produzca acoplamiento entre la reflexión y la señal inicial. Se analiza también el origen de tiempos de la señal para cada antena (cero de la antena) y se estudia la atenuación producida en la señal durante su propagación por el aire (medio no absorbente), que, por lo tanto, se produce por expansión geométrica, siendo la amplitud inversamente proporcional a la distancia. Se ensaya un procedimiento para caracterizar medios electromagnéticamente, relacionando sus propiedades físicas: granulometría, peso específico, porosidad y saturación, con la conductividad, la permitividad y la frecuencia. Se analizan tres medios formados por un mismo material, modificándose tres propiedades: peso específico aparente, compactación y saturación. En cada caso se obtiene la velocidad de propagación, la permitividad dieléctrica, el espectro de frecuencias y la atenuación. Al aumentar la saturación la velocidad es menor, se produce un desplazamiento hacia las bajas frecuencias, se estrecha el ancho de banda y la atenuación por absorción aumenta. Asimismo se analizan y discuten diferentes métodos para obtener la velocidad: tiempos y espesores conocidos, análisis de hipérbolas, comparación de amplitudes, dromocrónicas de un CMP, modelos geotécnicos, contraste de capacitancias y perfiles de estratigrafía conocida. Los mejores resultados obtenidos son los que proporcionan los ensayos de laboratorio con muestras de espesor conocido y el análisis de reflexiones hiperbólicas. De la comparación de los resultados obtenidos con los que proporciona la literatura se deduce la conveniencia de realizar una caracterización en laboratorio en casos que requieran una resolución fina de las anomalías superficiales o de profundidad intermedia.Relacionados con estas investigaciones (caracterización de medios y calibración de antenas), se han ejecutado y estudiado aplicaciones a casos reales que han permitido resolver problemas prácticos y, al mismo tiempo, han permitido también observar las ventajas de la aplicación de los avances de la investigación, así como avanzar en las técnicas de identificación y cancelación de ruidos introducidos por reflexiones externas o múltiples. Los principales casos resueltos hacen referencia a: control de intervenciones de restauración y rehabilitación en monumentos o en construcciones históricas (casos del teatro romano de Sagunto y de los puentes góticos sobre el río Turia), estudio de daños en edificios del patrimonio cultural (casos de la Catedral de Valencia e Iglesia de San Jorge de Paiporta), caracterización de yacimientos arqueológicos (casos del subsuelo de la Catedral de Valencia, de la Iglesia de San Jorge y de la fortaleza romana y convento en Alcántara).Algunos resultados y casos relevantes se sintetizan en fichas monográficas que presentan en forma esquemática las claves referentes al problema estudiado, lugar y herramienta empleada. Estas fichas serán de gran utilidad en el estudio de casos similares y se espera que constituyan el inicio de un catálogo de casos y soluciones. / The Ground-Penetrating Radar (GPR) is a tool more and more used in different geological, Environmental Engineering and Civil Engineering research, as well as in studies of characterisation of archaeological locations and in the diagnosis of the damages in buildings of the historical and cultural heritage. In this thesis, methodological aspects of calibration of the instrumentation are performed. Also, methodological aspects of the soils characterisation by using its electromagnetic properties are analysed. These properties govern the propagation and attenuation of electromagnetic waves in the soils. On the other hand, several applications to the study of historical monuments, archaeological locations and diagnosis of damages are investigated.Particularly, in this thesis four antennae are gauged. These antennae are characterised by their central frequency of emission: 200, 500, 900 and 1000 MHz. For each case, the internal noise of the antenna (radar record without reflections) is obtained;the highest noise is the initial signal (usually the direct wave); its longitude determines the minimum distance between the antenna and the first reflective surface to obtain a radar data where the two events (direct wave and reflected wave) are clearly separated. It is also analysed the time origin of the traces for each antenna (zero of the antenna). The attenuation of the traces during the wave propagation in the air (non-absorbent medium) is also studied. Therefore, in that case, the attenuation is caused by the geometric spreading, and the wave amplitude is inversely proportional to the distance. A procedure is tested to characterise media using its electromagnetic properties: the conductivity, the permitivity and the frequency, relating them with its physical properties: grain size, specific weight, porosity and saturation. Three different media are analysed, formed by the same solid material and modifying three physical properties: the apparent specific weight, the compactation (and, therefore, the porosity) and the saturation. In each case, the wave propagation velocity, the dielectric permitivity, the spectrum of frequencies and the attenuation are obtained. When the saturation increases, the velocity decreases, a displacement takes place toward the low frequencies, the band width is narrowed and the attenuation caused by absorption increases. In addition, different methods to obtain the wave velocity are analysed and discussed: times and well-known thickness, analysis of hyperbolas, comparison of amplitude, radar records obtained in a CMP, geotechnical models, contrast of capacitancy and profiles of well-known stratigraphy. The best results are obtained from the laboratory measurements using samples of well-known thickness and from the analysis of hyperbolic reflections. Comparison of these results and the values provide by the literature is performed. This comparison shows the convenience of carrying out a characterisation of the medium in laboratory in the cases when a fine resolution of the superficial anomalies or of intermediate depth is required. Related with these investigations (characterisation of means and calibration of antennas), several applications to real cases have been performed and studied. These applications have allowed to solve practical problems and, at the same time, to observe the advantages of applying the advances of the investigation, as well as to make progress in the identification techniques and suppression of noise introduced by external or multiple reflections. The main cases resolved make reference to: control of restoration, interventions and rehabilitation in monuments or in historical buildings (cases of the Roman theatre of Sagunto and the Gothic bridges on the river Turia), study of damages in buildings of the cultural heritage (cases of the Cathedral of Valencia and the Church of San Jorge, in Paiporta), characterisation of archaeological locations (cases of the underground of the Cathedral of Valencia, Church of San Jorge and the Roman fortress and the convent in Alcántara). Some results and the best cases cases are synthesised in monographic cards. These cards present, in schematic form, all the information about the studied problem, the emplacement and the used tool. These cards will be very useful in the study of similar cases, and it is expected that they constitute the beginning of a catalogue of cases and solutions.
150

Construction and evaluation of a magnetoresistive ground penetrating radar system

Blomqvist, Mikael January 2011 (has links)
This Master Thesis examines the possibility to apply a magnetometer developed by the Ångstöm space technology center to a small magnetic ground penetrating radar system with dimension in the order of one dm³. The magnetometer is broadband (DC-1GHz) and miniaturized. Loop antennas are used to transmit the signal.    A series of experiments have been performed in order to characterize the system, mainly examining the ability to determine distance to a target, using continuous sine wave signals and pulse trains. Standing wave patterns are formed between antenna and target and can be used for determining distance in the continuous case. When using a pulse train, the echo from the target could not be resolved using the current experiment set up, distance could therefore not be determined.

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